by Keyword: Action

By year:[ 2019 | 2018 | 2017 | 2016 | 2015 | 2014 | 2013 | 2012 | 2011 | 2010 | 2009 | 2008 | 2007 | 2006 | 2005 ]

Moulin-Frier, C., Fischer, T., Petit, M., Pointeau, G., Puigbo, J., Pattacini, U., Low, S. C., Camilleri, D., Nguyen, P., Hoffmann, M., Chang, H. J., Zambelli, M., Mealier, A., Damianou, A., Metta, G., Prescott, T. J., Demiris, Y., Dominey, P. F., Verschure, P. F. M. J., (2018). DAC-h3: A proactive robot cognitive architecture to acquire and express knowledge about the world and the self IEEE Transactions on Cognitive and Developmental Systems 10, (4), 1005-1022

This paper introduces a cognitive architecture for a humanoid robot to engage in a proactive, mixed-initiative exploration and manipulation of its environment, where the initiative can originate from both the human and the robot. The framework, based on a biologically-grounded theory of the brain and mind, integrates a reactive interaction engine, a number of state-of-the art perceptual and motor learning algorithms, as well as planning abilities and an autobiographical memory. The architecture as a whole drives the robot behavior to solve the symbol grounding problem, acquire language capabilities, execute goal-oriented behavior, and express a verbal narrative of its own experience in the world. We validate our approach in human-robot interaction experiments with the iCub humanoid robot, showing that the proposed cognitive architecture can be applied in real time within a realistic scenario and that it can be used with naive users.

Keywords: Autobiographical Memory., Biology, Cognition, Cognitive Robotics, Computer architecture, Distributed Adaptive Control, Grounding, Human-Robot Interaction, Humanoid robots, Robot sensing systems, Symbol Grounding

Blancas-Muñoz, M., Vouloutsi, Vasiliki, Zucca, R., Mura, Anna, Verschure, P., (2018). Hints vs distractions in intelligent tutoring systems: Looking for the proper type of help ARXIV Computer Science, (Human-Computer Interaction), 1-4

The kind of help a student receives during a task has been shown to play a significant role in their learning process. We designed an interaction scenario with a robotic tutor, in real-life settings based on an inquiry-based learning task. We aim to explore how learners' performance is affected by the various strategies of a robotic tutor. We explored two kinds of(presumable) help: hints (which were specific to the level or general to the task) or distractions (information not relevant to the task: either a joke or a curious fact). Our results suggest providing hints to the learner and distracting them with curious facts as more effective than distracting them with humour.

Keywords: Computer Science, Human-Computer Interaction

Fischer, Tobias, Puigbò, Jordi-Ysard, Camilleri, Daniel, Nguyen, Phuong D. H., Moulin-Frier, Clément, Lallée, Stéphane, Metta, Giorgio, Prescott, Tony J., Demiris, Yiannis, Verschure, P., (2018). iCub-HRI: A software framework for complex human-robot interaction scenarios on the iCub humanoid robot Frontiers in Robotics and AI , 5, (22), Article 22

Generating complex, human-like behaviour in a humanoid robot like the iCub requires the integration of a wide range of open source components and a scalable cognitive architecture. Hence, we present the iCub-HRI library which provides convenience wrappers for components related to perception (object recognition, agent tracking, speech recognition, touch detection), object manipulation (basic and complex motor actions) and social interaction (speech synthesis, joint attention) exposed as a C++ library with bindings for Java (allowing to use iCub-HRI within Matlab) and Python. In addition to previously integrated components, the library allows for simple extension to new components and rapid prototyping by adapting to changes in interfaces between components. We also provide a set of modules which make use of the library, such as a high-level knowledge acquisition module and an action recognition module. The proposed architecture has been successfully employed for a complex human-robot interaction scenario involving the acquisition of language capabilities, execution of goal-oriented behaviour and expression of a verbal narrative of the robot's experience in the world. Accompanying this paper is a tutorial which allows a subset of this interaction to be reproduced. The architecture is aimed at researchers familiarising themselves with the iCub ecosystem, as well as expert users, and we expect the library to be widely used in the iCub community.

Keywords: Robotics, iCub Humanoid, YARP, Software architecture, C++, Python, Java, Human-robot interaction

González-García, C., Cantini, M., Ballester-Beltrán, J., Altankov, G., Salmerón-Sánchez, M., (2018). The strength of the protein-material interaction determines cell fate Acta Biomaterialia 77, 74-84

Extracellular matrix (ECM) proteins are key mediators of cell/material interactions. The surface density and conformation of these proteins adsorbed on the material surface influence cell adhesion and the cellular response. We have previously shown that subtle variations in surface chemistry lead to drastic changes in the conformation of adsorbed fibronectin (FN). On poly(ethyl acrylate) (PEA), FN unfolds and displays domains for cell adhesion and FN-FN interaction, whereas on poly(methyl acrylate) (PMA) – with only one methyl group less – FN remains globular as it is in solution. The effect of the strength of the protein/material interaction in cell response, and its relation to protein density and conformation, has received limited attention so far. In this work, we used FN-functionalized AFM cantilevers to evaluate, via force spectroscopy, the strength of interaction between fibronectin and the underlying polymer which controls FN conformation (PEA and PMA). We found that the strength of FN/PEA interaction is significantly higher than FN/PMA, which limits the mobility of FN layer on PEA, reduces the ability of cells to mechanically reorganize FN and then leads to enhanced proteolysis and degradation of the surrounding matrix with compromised cell viability. By contrast, both PEA and PMA support cell adhesion when FN density is increased and also in the presence of serum or other serum proteins, including vitronectin (VN) and bovine serum albumin (BSA), which provide a higher degree of mobility to the matrix. Statement of Significance: The identification of parameters influencing cell response is of paramount importance for the design of biomaterials that will act as synthetic scaffolds for cells to anchor, grow and, eventually, become specialised tissues. Cells interact with materials through an intermediate layer of proteins adsorbed on the material surface. It is known that the density and conformation of these proteins determine cell behaviour. Here we show that the strength of protein/material interactions, which has received very limited attention so far, is key to understand the cellular response to biomaterials. Very strong protein/material interactions reduce the ability of cells to mechanically reorganize proteins at the material interface which results in enhanced matrix degradation, leading ultimately to compromised cell viability.

Keywords: Fibronectin adsorption, Fibronectin remodeling, Protein mobility, Protein-material interaction strength

Solórzano, A., Rodríguez-Pérez, R., Padilla, M., Graunke, T., Fernandez, L., Marco, S., Fonollosa, J., (2018). Multi-unit calibration rejects inherent device variability of chemical sensor arrays Sensors and Actuators B: Chemical , 265, 142-154

Inherent sensor variability limits mass-production applications for metal oxide (MOX) gas sensor arrays because calibration for replicas of a sensor array needs to be performed individually. Recently, calibration transfer strategies have been proposed to alleviate calibration costs of new replicas, but they still require the acquisition of transfer samples. In this work, we present calibration models that can be extended to uncalibrated replicas of sensor arrays without acquiring new samples, i.e., general or global calibration models. The developed methodology consists in including multiple replicas of a sensor array in the calibration process such that sensor variability is rejected by the general model. Our approach was tested using replicas of a MOX sensor array in the classification task of six gases and synthetic air, presented at different background humidity and concentration levels. Results showed that direct transfer of individual calibration models provides poor classification accuracy. However, we also found that general calibration models kept predictive performance when were applied directly to new copies of the sensor array. Moreover, we explored, through feature selection, whether particular combinations of sensors and operating temperatures can provide predictive performances equivalent to the calibration model with the complete array, favoring thereby the existence of more robust calibration models.

Keywords: Gas sensor array, MOX sensor, Robust calibration, Calibration transfer, Machine olfaction

Fernandez, L., Yan, J., Fonollosa, J., Burgués, J., Gutierrez, A., Marco, S., (2018). A practical method to estimate the resolving power of a chemical sensor array: Application to feature selection Frontiers in Chemistry , 6, Article 209

A methodology to calculate analytical figures of merit is not well established for detection systems that are based on sensor arrays with low sensor selectivity. In this work, we present a practical approach to estimate the Resolving Power of a sensory system, considering non-linear sensors and heteroscedastic sensor noise. We use the definition introduced by Shannon in the field of communication theory to quantify the number of symbols in a noisy environment, and its version adapted by Gardner and Barlett for chemical sensor systems. Our method combines dimensionality reduction and the use of algorithms to compute the convex hull of the empirical data to estimate the data volume in the sensor response space. We validate our methodology with synthetic data and with actual data captured with temperature-modulated MOX gas sensors. Unlike other methodologies, our method does not require the intrinsic dimensionality of the sensor response to be smaller than the dimensionality of the input space. Moreover, our method circumvents the problem to obtain the sensitivity matrix, which usually is not known. Hence, our method is able to successfully compute the Resolving Power of actual chemical sensor arrays. We provide a relevant figure of merit, and a methodology to calculate it, that was missing in the literature to benchmark broad-response gas sensor arrays.

Keywords: Gas sensor array, MOX sensors, Resolving Power, Sensor resolution, Dimensionality reduction, Machine olfaction

Verschure, P., (2018). The architecture of mind and brain Living machines: A handbook of research in biomimetics and biohybrid systems (ed. Prescott, T. J., Lepora, Nathan, Verschure, P.), Oxford Scholarship (Oxford, UK) , 338-345

The components of a Living Machine must be integrated into a functioning whole, which requires a detailed understanding of the architecture of living machines. This chapter starts with a conceptual and historical analysis which from Plato brings us to nineteenth-century neuroscience and early concepts of the layered structure of nervous systems. These concepts were further captured in the cognitive behaviorism of Tolman and came to full fruition in the cognitive revolution of the second half of the twentieth century. Verschure subsequently describes the most relevant proposals of cognitive architectures followed by an overview of the few proposals stemming from modern neuroscience on the architecture of the brain. Subsequently, we will look at contemporary contenders that mediate between cognitive and brain architecture. An important challenge to any model of cognitive architectures is how to benchmark it. Verschure proposes the Unified Theories of Embodied Minds (UTEM) benchmark which advances from Newell’s classic Unified Theories of Cognition benchmark.

Keywords: Architecture, Mind, Brain, Organization, System, Virtualization, Abstraction layers

Vouloutsi, Vasiliki, Verschure, P., (2018). Emotions and self-regulation Living Machines: A Handbook of Research in Biomimetic and Biohybrid Systems (ed. Prescott, T. J., Lepora, Nathan, Verschure, P.), Oxford Scholarship (Oxford, UK) , 327-337

This chapter takes the view that emotions of living machines can be seen from the perspective of self-regulation and appraisal. We will first look at the pragmatic needs to endow machines with emotions and subsequently describe some of the historical background of the science of emotions and its different interpretations and links to affective neuroscience. Subsequently, we argue that emotions can be cast in terms of self-regulation where they provide for a descriptor of the state of the homeostatic processes that maintain the relationship between the agent and its internal and external environment. We augment the notion of homeostasis with that of allostasis which signifies a change from stability through a fixed equilibrium to stability through continuous change. The chapter shows how this view can be used to create complex living machines where emotions are anchored in the need fulfillment of the agent, in this case considering both utilitarian and epistemic needs.

Keywords: Emotion, Motivation, Needs, Appraisal, Self-regulation, Homeostasis, Allostasis, Human–robot interaction, James–Lange theory

Verschure, P., (2018). Capabilities Living machines: A handbook of research in biomimetics and biohybrid systems (ed. Prescott, T. J., Lepora, Nathan, Verschure, P.), Oxford Scholarship (Oxford, UK) , 211-217

This chapter introduces the “Capabilities” section of the Handbook of Living Machines. Where the previous section considered building blocks, we recognize that components or modules do not automatically make systems. Hence, in the remainder of this handbook, the emphasis is toward the capabilities of living systems and their emulation in artifacts. Capabilities often arise from the integration of multiple components and thus sensitize us to the need to develop a system-level perspective on living machines. Here we summarize and consider the 14 contributions in this section which cover perception, action, cognition, communication, and emotion, and the integration of these through cognitive architectures into systems that can emulate the full gamut of integrated behaviors seen in animals including, potentially, our own capacity for consciousness.

Keywords: Action, Cognition, Cognitive architecture, Communication, Consciousness, Emotion, Perception

Venkova, Tatiana, Juárez, Antonio, Espinosa, Manuel, (2017). Editorial: Modulating prokaryotic lifestyle by DNA-binding proteins: Learning from (apparently) simple systems Frontiers in Molecular Biosciences , 3, Article 86

Within the research in Molecular Biology, one important field along the years has been the analyses on how prokaryotes regulate the expression of their genes and what the consequences of these activities are. Prokaryotes have attracted the interests of researchers not only because the processes taking place in their world are important to cells, but also because many of the effects often can be readily measured, both at the single cell level and in large populations. Contributing to the interest of the present topic is the fact that modulation of gene activity involves the sensing of intra- and inter-cellular conditions, DNA binding and DNA dynamics, and interaction with the replication/transcription machinery of the cell. All of these processes are fundamental to the operation of a biological entity and they condition its lifestyle. Further, the discoveries achieved in the bacterial world have been of ample use in eukaryotes. In addition to the fundamental interest of understanding modulation of prokaryotic lifestyle by DNA-binding proteins, there is an added interest from the healthcare point of view. As it is well-known the antibiotic-resistance strains of pathogenic bacteria are a major world problem, so that there is an urgent need of innovative approaches to tackle it. Human and animal infectious diseases impose staggering costs worldwide in terms of loss of human life and livestock, diminished productivity, and the heavy economic burden of disease. The global dimension of international trade, personal travel, and population migration expands at an ever-accelerating rate. This increasing mobility results in broader and quicker dissemination of bacterial pathogens and in rapid spread of antibiotic resistance. The majority of the newly acquired resistances are horizontally spread among bacteria of the same or different species by processes of lateral (horizontal) gene transfer, so that discovery of new antibiotics is not the definitive solution to fighting infectious diseases. There is an absolute need of finding novel alternatives to the “classical” approach to treat infections by bacterial pathogens, and these new ways must include the exploration and introduction of novel antibacterials, the development of alternative strategies, and the finding of novel bacterial targets. However, all these approaches will result in a stalemate if we, researchers, are not able to achieve a better understanding of the mechanistic processes underlying bacterial gene expression. It is, then, imperative to continue gaining insight into the basic mechanisms by which bacterial cells regulate the expression of their genes. That is why our Research Topic hosted by Frontiers in Molecular Biosciences was timely, and the output of it offers novel and up-to-date points of view to the “simple” bacterial world.

Keywords: DNA-protein interactions, Gene regulation in Prokaryotes, Replication control, Regulation of Bacterial Gene Expression, Global Regulatory Networks

Parmar, J., Villa, K., Vilela, D., Sánchez, S., (2017). Platinum-free cobalt ferrite based micromotors for antibiotic removal Applied Materials Today , 9, 605-611

Self-propelled micromotors have previously shown to enhance pollutant removal compared to non-motile nano-micro particles. However, these systems are expensive, difficult to scale-up and require surfactant for efficient work. Efficient and inexpensive micromotors are desirable for their practical applications in water treatment technologies. We describe cobalt-ferrite based micromotors (CFO micromotors) fabricated by a facile and scalable synthesis, that produce hydroxyl radicals via Fenton-like reaction and take advantage of oxygen gas generated during this reaction for self-propulsion. Once the reaction is complete, the CFO micromotors can be easily separated and collected due to their magnetic nature. The CFO micromotors are demonstrated for highly efficient advanced oxidative removal of tetracycline antibiotic from the water. Furthermore, the effects of different concentrations of micromotors and hydrogen peroxide on the antibiotic degradation were studied, as well as the generation of the highly reactive hydroxyl radicals responsible for the oxidation reaction.

Keywords: Degradation, Fenton reaction, Microbots, Nanomotors, Self-propelled Micromotors, Water treatment

Obiols-Rabasa, M., Oncins, G., Sanz, F., Tadros, T. F., Solans, C., Levecke, B., Booten, K., Esquena, J., (2017). Investigation of the elastic and adhesion properties of adsorbed hydrophobically modified inulin films on latex particles using Atomic Force Microscopy (AFM) Colloids and Surfaces A: Physicochemical and Engineering Aspects , 524, 185-192

Graft polymer surfactants provide very good colloidal stability because of strong steric repulsions between adsorbed surfactant films. The elastic and adhesion properties of adsorbed hydrophobically modified inulin polymer surfactant (INUTEC NRA) have been directly measured using Atomic Force Microscopy (AFM) measurements. For this purpose, poly(methyl methacrylate/butyl acrylate), P(MMA/BuA), latexes prepared in the presence of the hydrophobically modified inulin (INUTEC NRA) were used. These latexes (diameter 118 nm and polydispersity index of 1.05) showed a very high colloidal stability in water and in the presence of electrolyte (up to 0.2 mol dm−3 KBr). The latexes were deposited on mica, which was silanated to enhance the adhesion of the latex particles to the surface. A silicon nitride tip with approximately 10 nm diameter that also contained an adsorbed layer of surfactant was used in the AFM apparatus. The tip was allowed to approach, contact thereafter the particles with an applied force of 12.5 nN, and finally detach from the film. Both elastic (Young’s) modulus of the film and adhesion force were studied. The results showed that the adsorbed surfactant films are highly elastic and their elastic modulus and adhesion force did not change significantly with the presence of Na2SO4 up to 0.05 mol dm−3. The high elastic contribution to the steric interaction ensures strong repulsion between the latex particles both in water and at high electrolyte concentrations. In addition, the lack of dependence of adhesion force on electrolyte concentration ensures uniform deposition of the latex particles on a flat substrate as for example in coating applications. These results show the advantages of using a graft polymer surfactant for enhancing the stability of particle suspensions, as illustrated in previous investigations.

Keywords: AFM, Colloidal stability, Interaction forces, Steric repulsion

Pomareda, V., Magrans, R., Jiménez-Soto, J., Martínez, D., Tresánchez, M., Burgués, J., Palacín, J., Marco, S., (2017). Chemical source localization fusing concentration information in the presence of chemical background noise Sensors 17, (4), 904

We present the estimation of a likelihood map for the location of the source of a chemical plume dispersed under atmospheric turbulence under uniform wind conditions. The main contribution of this work is to extend previous proposals based on Bayesian inference with binary detections to the use of concentration information while at the same time being robust against the presence of background chemical noise. For that, the algorithm builds a background model with robust statistics measurements to assess the posterior probability that a given chemical concentration reading comes from the background or from a source emitting at a distance with a specific release rate. In addition, our algorithm allows multiple mobile gas sensors to be used. Ten realistic simulations and ten real data experiments are used for evaluation purposes. For the simulations, we have supposed that sensors are mounted on cars which do not have among its main tasks navigating toward the source. To collect the real dataset, a special arena with induced wind is built, and an autonomous vehicle equipped with several sensors, including a photo ionization detector (PID) for sensing chemical concentration, is used. Simulation results show that our algorithm, provides a better estimation of the source location even for a low background level that benefits the performance of binary version. The improvement is clear for the synthetic data while for real data the estimation is only slightly better, probably because our exploration arena is not able to provide uniform wind conditions. Finally, an estimation of the computational cost of the algorithmic proposal is presented.

Keywords: Machine olfaction, Odor robots, Chemical sensors, Bayesian inference

Solorzano, A., Fonollosa, J., Fernandez, L., Eichmann, J., Marco, S., (2017). Fire detection using a gas sensor array with sensor fusion algorithms IEEE Conference Publications ISOCS/IEEE International Symposium on Olfaction and Electronic Nose (ISOEN) , IEEE (Montreal, Canada) , 1-3

Conventional fire alarms are based on smoke detection. Nevertheless, in some fire scenarios volatiles are released before smoke. Fire detectors based only on chemical sensors have already been proposed as they may provide faster response, but they are still prone to false alarms in the presence of nuisances. These systems rely heavily on pattern recognition techniques to discriminate fires from nuisances. In this context, it is important to test the systems according to international standards for fires and testing the system against a diversity of nuisances. In this work, we investigate the behavior of a gas sensor array coupled to sensor fusion algorithms for fire detection when exposed to standardized fires and several nuisances. Results confirmed the ability to detect fires (97% Sensitivity), although the system still produces a significant rate of false alarms (35%) for nuisances not presented in the training set.

Keywords: Fire alarm, Gas sensor array, Machine Olfaction, Multisensor system, Sensor fusion

Planell, J. A., Navarro, M., Engel, E., (2017). Developing targeted biocomposites in tissue engineering and regenerative medicine Biomedical Composites (ed. Ambrosio, L.), Woodhead Publishing (Duxfor, UK) Biomaterials, 569-587

Regenerative medicine is a relatively new field with new requirements for smart materials, where composites will have a strong role to play. The new paradigm of regenerative medicine and tissue engineering requires biomaterials with high specificity, where physical and chemical properties are duly tailored and combined with appropriate mechanical and degradation features in order to trigger specific cell events and functions involved in the regenerative process. In this chapter, the chemical, physical, and biological elements that have to be targeted by biocomposites in regenerative medicine are described.

Keywords: Biocomposite, Regenerative medicine, Tissue engineering, Scaffolds, Cell/material interactions

Klein, S., Schierwagen, R., Uschner, F. E., Trebicka, J., (2017). Mouse and rat models of induction of hepatic fibrosis and assessment of portal hypertension Fibrosis (Methods in Molecular Biology) (ed. Rittié, L.), Humana Press (New York, USA) 1627, 91-116

Portal hypertension either develops due to progressive liver fibrosis or is the consequence of vascular liver diseases such as portal vein thrombosis or non-cirrhotic portal hypertension. This chapter focuses on different rodent models of liver fibrosis with portal hypertension and also in few non-cirrhotic portal hypertension models. Importantly, after the development of portal hypertension, the proper assessment of drug effects in the portal and systemic circulation should be discussed. The last part of the chapter is dedicated in these techniques to assess the in vivo hemodynamics and the ex vivo techniques of the isolated liver perfusion and vascular contractility.

Keywords: Aortic ring contraction, Bile duct ligation, Carbon tetrachloride, Colored microsphere technique, High-fat diet, Isolated in situ liver perfusion, Methionine-choline-deficient diet, Partial portal vein ligation, Portal hypertension

Solano-Collado, Virtu, Hüttener, Márrio, Espinosa, Manuel, Juárez, Antonio, Bravo, Alicia, (2016). MgaSpn and H-NS: Two unrelated global regulators with similar DNA-binding properties Frontiers in Molecular Biosciences , 3, Article 60

Global regulators play an essential role in the adaptation of bacterial cells to specific niches. Bacterial pathogens thriving in the tissues and organs of their eukaryotic hosts are a well-studied example. Some of the proteins that recognize local DNA structures rather than specific nucleotide sequences act as global modulators in many bacteria, both Gram-negative and -positive. To this class of regulators belong the H-NS-like proteins, mainly identified in γ-Proteobacteria, and the MgaSpn-like proteins identified in Firmicutes. H-NS and MgaSpn from Escherichia coli and Streptococcus pneumoniae, respectively, neither have sequence similarity nor share structural domains. Nevertheless, they display common features in their interaction with DNA, namely: (i) they bind to DNA in a non-sequence-specific manner, (ii) they have a preference for intrinsically curved DNA regions, and (iii) they are able to form multimeric complexes on linear DNA. Using DNA fragments from the hemolysin operon regulatory region of the E. coli plasmid pHly152, we show in this work that MgaSpn is able to recognize particular regions on extended H-NS binding sites. Such regions are either located at or flanked by regions of potential bendability. Moreover, we show that the regulatory region of the pneumococcal P1623B promoter, which is recognized by MgaSpn, contains DNA motifs that are recognized by H-NS. These motifs are adjacent to regions of potential bendability. Our results suggest that both regulatory proteins recognize similar structural characteristics of DNA.

Keywords: Global transcriptional regulators, Nucleoid-associated proteins, Mga/AtxA family, Protein-DNA interactions, DNA bendability

Fernanda, Andrade, Pedro, Fonte, Ana, Costa, Cassilda Cunha, Reis, Rute, Nunes, Andreia, Almeida, Domingos, Ferreira, Mireia, Oliva, Bruno, Sarmento, (2016). Pharmacological and toxicological assessment of innovative self-assembled polymeric micelles as powders for insulin pulmonary delivery Nanomedicine 11, (17), 2305-2317

Aim: Explore the use of polymeric micelles in the development of powders intended for pulmonary delivery of biopharmaceuticals, using insulin as a model protein. Materials & methods: Formulations were assessed in vitro for aerosolization properties and in vivo for efficacy and safety using a streptozotocin-induced diabetic rat model. Results: Powders presented good aerosolization properties like fine particle fraction superior to 40% and a mass median aerodynamic diameter inferior of 6 μm. Endotracheally instilled powders have shown a faster onset of action than subcutaneous administration of insulin at a dose of 10 IU/kg, with pharmacological availabilities up to 32.5% of those achieved by subcutaneous route. Additionally, micelles improved the hypoglycemic effect of insulin. Bronchoalveolar lavage screening for toxicity markers (e.g., lactate dehydrogenase, cytokines) revealed no signs of lung inflammation and cytotoxicity 14 days postadministration. Conclusion: Developed powders showed promising safety and efficacy characteristics for the systemic delivery of insulin by pulmonary administration.

Keywords: Fine particle fraction, Inhalation, Insulin, In vivo, Pharmacological availability, Polymeric micelles, Pulmonary toxicity

Przybyla, L., Lakins, J. N., Sunyer, R., Trepat, X., Weaver, V. M., (2016). Monitoring developmental force distributions in reconstituted embryonic epithelia Methods , 94, 101-113

The way cells are organized within a tissue dictates how they sense and respond to extracellular signals, as cues are received and interpreted based on expression and organization of receptors, downstream signaling proteins, and transcription factors. Part of this microenvironmental context is the result of forces acting on the cell, including forces from other cells or from the cellular substrate or basement membrane. However, measuring forces exerted on and by cells is difficult, particularly in an in vivo context, and interpreting how forces affect downstream cellular processes poses an even greater challenge. Here, we present a simple method for monitoring and analyzing forces generated from cell collectives. We demonstrate the ability to generate traction force data from human embryonic stem cells grown in large organized epithelial sheets to determine the magnitude and organization of cell-ECM and cell-cell forces within a self-renewing colony. We show that this method can be used to measure forces in a dynamic hESC system and demonstrate the ability to map intracolony protein localization to force organization.

Keywords: Epiblast, Human embryonic stem cells, Mechanotransduction, Monolayer stress microscopy, Self-organization, Traction force

Lozano-Garcia, M., Fiz, J. A., Jané, R., (2016). Automatic differentiation of normal and continuous adventitious respiratory sounds using ensemble empirical mode decomposition and instantaneous frequency IEEE Journal of Biomedical and Health Informatics 20, (2), 486-497

Differentiating normal from adventitious respiratory sounds (RS) is a major challenge in the diagnosis of pulmonary diseases. Particularly, continuous adventitious sounds (CAS) are of clinical interest because they reflect the severity of certain diseases. This study presents a new classifier that automatically distinguishes normal sounds from CAS. It is based on the multi-scale analysis of instantaneous frequency (IF) and envelope (IE) calculated after ensemble empirical mode decomposition (EEMD). These techniques have two major advantages over previous techniques: high temporal resolution is achieved by calculating IF-IE and a priori knowledge of signal characteristics is not required for EEMD. The classifier is based on the fact that the IF dispersion of RS signals markedly decreases when CAS appear in respiratory cycles. Therefore, CAS were detected by using a moving window to calculate the dispersion of IF sequences. The study dataset contained 1494 RS segments extracted from 870 inspiratory cycles recorded from 30 patients with asthma. All cycles and their RS segments were previously classified as containing normal sounds or CAS by a highly experienced physician to obtain a gold standard classification. A support vector machine classifier was trained and tested using an iterative procedure in which the dataset was randomly divided into training (65%) and testing (35%) sets inside a loop. The SVM classifier was also tested on 4592 simulated CAS cycles. High total accuracy was obtained with both recorded (94.6% ± 0.3%) and simulated (92.8% ± 3.6%) signals. We conclude that the proposed method is promising for RS analysis and classification.

Keywords: Diseases, Dispersion, Empirical mode decomposition, Feature extraction, Informatics, Support vector machines

Arcentales, A., Rivera, P., Caminal, P., Voss, A., Bayés-Genís, A., Giraldo, B. F., (2016). Analysis of blood pressure signal in patients with different ventricular ejection fraction using linear and non-linear methods Engineering in Medicine and Biology Society (EMBC) 38th Annual International Conference of the IEEE , IEEE (Orlando, USA) , 2700-2703

Changes in the left ventricle function produce alternans in the hemodynamic and electric behavior of the cardiovascular system. A total of 49 cardiomyopathy patients have been studied based on the blood pressure signal (BP), and were classified according to the left ventricular ejection fraction (LVEF) in low risk (LR: LVEF>35%, 17 patients) and high risk (HR: LVEF≤35, 32 patients) groups. We propose to characterize these patients using a linear and a nonlinear methods, based on the spectral estimation and the recurrence plot, respectively. From BP signal, we extracted each systolic time interval (STI), upward systolic slope (BPsl), and the difference between systolic and diastolic BP, defined as pulse pressure (PP). After, the best subset of parameters were obtained through the sequential feature selection (SFS) method. According to the results, the best classification was obtained using a combination of linear and nonlinear features from STI and PP parameters. For STI, the best combination was obtained considering the frequency peak and the diagonal structures of RP, with an area under the curve (AUC) of 79%. The same results were obtained when comparing PP values. Consequently, the use of combined linear and nonlinear parameters could improve the risk stratification of cardiomyopathy patients.

Keywords: Feature extraction, Blood pressure, Heart rate, Estimation, Data mining, Covariance matrices, Hospitals

Argerich, S., Herrera, S., Benito, S., Giraldo, J., (2016). Evaluation of periodic breathing in respiratory flow signal of elderly patients using SVM and linear discriminant analysis Engineering in Medicine and Biology Society (EMBC) 38th Annual International Conference of the IEEE , IEEE (Orlando, USA) , 4276-4279

Aging population is a major concern that is reflected in the increase of chronic diseases. Heart Failure (HF) is one of the most common chronic diseases of elderly people that is punctuated with acute episodes, which result in hospitalization. The periodic modulation of the amplitude of the breathing pattern is proved to be one of the multiple symptoms of an acute episode, and thus, the features extracted from its characterization contribute in the improvement of the first diagnosis of the clinical practice. The main objective of this study is to evaluate if the features extracted from the breathing pattern along with common clinical variables are reliable enough to detect Periodic Breathing (PB). A dataset of 44 elderly patients containing clinical information and a short record of electrocardiogram and respiratory flow signal was used to train two machine learning classification methods: Support Vector Machine (SVM) and Linear Discriminant Analysis (LDA). All the available clinical parameters within the dataset along with the parameters characterizing the respiratory pattern were used to classify the observations into two groups. SVM classification was optimized and performed using a = -8 and C = 10.04 giving an accuracy of 88.2 % sensitivity of 90 % and specificity of 85.7 % Similar results were achieved with LDA classifying with an accuracy of 82.4 %, a sensitivity of 81.8% and specificity of 83.3 % PB has been accurately detected using both classifiers.

Keywords: Support vector machines, Feature extraction, Training, Senior citizens, Standards, Training data, Hospitals

Brask, J. B., Singla-Buxarrais, G., Uroz, M., Vincent, R., Trepat, X., (2015). Compressed sensing traction force microscopy Acta Biomaterialia 26, 286-294

Adherent cells exert traction forces on their substrate, and these forces play important roles in biological functions such as mechanosensing, cell differentiation and cancer invasion. The method of choice to assess these active forces is traction force microscopy (TFM). Despite recent advances, TFM remains highly sensitive to measurement noise and exhibits limited spatial resolution. To improve the resolution and noise robustness of TFM, here we adapt techniques from compressed sensing (CS) to the reconstruction of the traction field from the substrate displacement field. CS enables the recovery of sparse signals at higher resolution from lower resolution data. Focal adhesions (FAs) of adherent cells are spatially sparse implying that traction fields are also sparse. Here we show, by simulation and by experiment, that the CS approach enables circumventing the Nyquist-Shannon sampling theorem to faithfully reconstruct the traction field at a higher resolution than that of the displacement field. This allows reaching state-of-the-art resolution using only a medium magnification objective. We also find that CS improves reconstruction quality in the presence of noise. Statement of Significance A great scientific advance of the past decade is the recognition that physical forces determine an increasing list of biological processes. Traction force microscopy which measures the forces that cells exert on their surroundings has seen significant recent improvements, however the technique remains sensitive to measurement noise and severely limited in spatial resolution. We exploit the fact that the force fields are sparse to boost the spatial resolution and noise robustness by applying ideas from compressed sensing. The novel method allows high resolution on a larger field of view. This may in turn allow better understanding of the cell forces at the multicellular level, which are known to be important in wound healing and cancer invasion.

Keywords: Compressed sensing, High resolution, Traction force microscopy

Reginensi, Diego, Carulla, Patricia, Nocentini, Sara, Seira, Oscar, Serra-Picamal, Xavier, Torres-Espín, Abel, Matamoros-Angles, Andreu, Gavín, Rosalina, Moreno-Flores, María Teresa, Wandosell, Francisco, Samitier, Josep, Trepat, Xavier, Navarro, Xavier, del Río, José Antonio, (2015). Increased migration of olfactory ensheathing cells secreting the Nogo receptor ectodomain over inhibitory substrates and lesioned spinal cord Cellular and Molecular Life Sciences , 72, (14), 2719-2737

Olfactory ensheathing cell (OEC) transplantation emerged some years ago as a promising therapeutic strategy to repair injured spinal cord. However, inhibitory molecules are present for long periods of time in lesioned spinal cord, inhibiting both OEC migration and axonal regrowth. Two families of these molecules, chondroitin sulphate proteoglycans (CSPG) and myelin-derived inhibitors (MAIs), are able to trigger inhibitory responses in lesioned axons. Mounting evidence suggests that OEC migration is inhibited by myelin. Here we demonstrate that OEC migration is largely inhibited by CSPGs and that inhibition can be overcome by the bacterial enzyme Chondroitinase ABC. In parallel, we have generated a stable OEC cell line overexpressing the Nogo receptor (NgR) ectodomain to reduce MAI-associated inhibition in vitro and in vivo. Results indicate that engineered cells migrate longer distances than unmodified OECs over myelin or oligodendrocyte-myelin glycoprotein (OMgp)-coated substrates. In addition, they also show improved migration in lesioned spinal cord. Our results provide new insights toward the improvement of the mechanisms of action and optimization of OEC-based cell therapy for spinal cord lesion.

Keywords: Olfactory ensheathing cells, Traction force microscopy, Chondroitin sulphate proteoglycans, Cell migration, Nogo receptor ectodomain

Mrkonji, Garcia-Elias, A., Pardo-Pastor, C., Bazellières, E., Trepat, X., Vriens, J., Ghosh, D., Voets, T., Vicente, R., Valverde, M. A., (2015). TRPV4 participates in the establishment of trailing adhesions and directional persistence of migrating cells Pflugers Archiv European Journal of Physiology , 467, (10), 2107-2119

Calcium signaling participates in different cellular processes leading to cell migration. TRPV4, a non-selective cation channel that responds to mechano-osmotic stimulation and heat, is also involved in cell migration. However, the mechanistic involvement of TRPV4 in cell migration is currently unknown. We now report that expression of the mutant channel TRPV4-121AAWAA (lacking the phosphoinositide-binding site 121KRWRK125 and the response to physiological stimuli) altered HEK293 cell migration. Altered migration patterns included periods of fast and persistent motion followed by periods of stalling and turning, and the extension of multiple long cellular protrusions. TRPV4-WT overexpressing cells showed almost complete loss of directionality with frequent turns, no progression, and absence of long protrusions. Traction microscopy revealed higher tractions forces in the tail of TRPV4-121AAWAA than in TRPV4-WT expressing cells. These results are consistent with a defective and augmented tail retraction in TRPV4-121AAWAA- and TRPV4-WT-expressing cells, respectively. The activity of calpain, a protease implicated in focal adhesion (FA) disassembly, was decreased in TRPV4-121AAWAA compared with TRPV4-WT-expressing cells. Consistently, larger focal adhesions were seen in TRPV4-121AAWAA compared with TRPV4-WT-expressing HEK293 cells, a result that was also reproduced in T47D and U87 cells. Similarly, overexpression of the pore-dead mutant TRPV4-M680D resumed the TRPV4-121AAWAA phenotype presenting larger FA. The migratory phenotype obtained in HEK293 cells overexpressing TRPV4-121AAWAA was mimicked by knocking-down TRPC1, a cationic channel that participates in cell migration. Together, our results point to the participation of TRPV4 in the dynamics of trailing adhesions, a function that may require the interplay of TRPV4 with other cation channels or proteins present at the FA sites.

Keywords: Calcium, Calpain, Focal adhesion, Migration, Traction forces, TRPV4

Fonollosa, J., Neftci, E., Huerta, R., Marco, S., (2015). Evaluation of calibration transfer strategies between Metal Oxide gas sensor arrays Procedia Engineering EUROSENSORS 2015 , Elsevier (Freiburg, Germany) 120, 261-264

Abstract Inherent variability of chemical sensors makes necessary individual calibration of chemical detection systems. This shortcoming has traditionally limited usability of systems based on Metal Oxide (MOX) sensor arrays and prevented mass-production for some applications. Here, aiming at exploring transfer calibration between electronic nose systems, we exposed five identical 8-sensor detection units to controlled gas conditions. Our results show that a calibration model provides more accurate predictions when the tested board is included in the calibration dataset. However, we show that previously built calibration models can be extended to other units using a reduced number of measurements. While baseline correction seems imperative for successful baseline correction, among the different tested strategies, piecewise direct standardization provides more accurate predictions.

Keywords: Electronic nose, Calibration, MOX sensor, Machine Olfaction

Serra-Picamal, Xavier, Conte, Vito, Sunyer, Raimon, Muñoz, José J., Trepat, Xavier, (2015). Mapping forces and kinematics during collective cell migration Methods in Cell Biology - Biophysical Methods in Cell Biology (ed. Wilson, L., Tran, P.), Academic Press (Santa Barbara, USA) 125, 309-330

Abstract Fundamental biological processes including morphogenesis and tissue repair require cells to migrate collectively. In these processes, epithelial or endothelial cells move in a cooperative manner coupled by intercellular junctions. Ultimately, the movement of these multicellular systems occurs through the generation of cellular forces, exerted either on the substrate via focal adhesions (cell–substrate forces) or on neighboring cells through cell–cell junctions (cell–cell forces). Quantitative measurements of multicellular forces and kinematics with cellular or subcellular resolution have become possible only in recent years. In this chapter, we describe some of these techniques, which include particle image velocimetry to map cell velocities, traction force microscopy to map forces exerted by cells on the substrate, and monolayer stress microscopy to map forces within and between cells. We also describe experimental protocols to perform these measurements. The combination of these techniques with high-resolution imaging tools and molecular perturbations will lead to a better understanding of the mechanisms underlying collective cell migration in health and disease.

Keywords: Collective cell migration, Monolayer stress microscopy, Traction force microscopy

Vinagre, M., Aranda, J., Casals, A., Aranda, J., Casals, A., (2015). A new relational geometric feature for human action recognition Lecture Notes in Electrical Engineering (ed. Ferrier, J.L., Gusikhin, O., Madani, K., Sasiadek, J.), Springer (Lausanne, Switzerland) 325, 263-278

Pose-based features have demonstrated to outperform low-levelappearance features in human action recognition. New RGB-D cameras provide locations of human joints with which geometric correspondences can be easily calculated. In this article, a new geometric correspondence between joints called Trisarea feature is presented. It is defined as the area of the triangle formed by three joints. Relevant triangles describing human pose are identified and it is shown how the variation over time of the selected Trisarea features constitutes a descriptor of human action. Experimental results show a comparison with other methods and demonstrate how this Trisarea-based representation can be applied to human action recognition.

Keywords: Action descriptor, Action recognition, Pose-based feature

Cuervo, A., Dans, P. D., Carrascosa, J. L., Orozco, M., Gomila, G., Fumagalli, L., (2014). Direct measurement of the dielectric polarization properties of DNA Proceedings of the National Academy of Sciences of the United States of America 111, (35), E3624-E3630

The electric polarizability of DNA, represented by the dielectric constant, is a key intrinsic property that modulates DNA interaction with effector proteins. Surprisingly, it has so far remained unknown owing to the lack of experimental tools able to access it. Here, we experimentally resolved it by detecting the ultraweak polarization forces of DNA inside single T7 bacteriophages particles using electrostatic force microscopy. In contrast to the common assumption of low-polarizable behavior like proteins (εr ~ 2–4), we found that the DNA dielectric constant is ~ 8, considerably higher than the value of ~ 3 found for capsid proteins. State-of-the-art molecular dynamic simulations confirm the experimental findings, which result in sensibly decreased DNA interaction free energy than normally predicted by Poisson–Boltzmann methods. Our findings reveal a property at the basis of DNA structure and functions that is needed for realistic theoretical descriptions, and illustrate the synergetic power of scanning probe microscopy and theoretical computation techniques.

Keywords: Atomic force microscopy, Atomistic simulations, DNA packaging, DNA-ligand binding, Poisson-Boltzmann equation, capsid protein, DNA, double stranded DNA, amino acid composition, article, atomic force microscopy, bacteriophage, bacteriophage T7, dielectric constant, dipole, DNA binding, DNA packaging, DNA structure, electron microscopy, ligand binding, nonhuman, polarization, priority journal, protein analysis, protein DNA interaction, scanning probe microscopy, static electricity, virion, virus capsid, virus particle, atomic force microscopy, atomistic simulations, DNA packaging, DNA-ligand binding, Poisson-Boltzmann equation, Bacteriophage T7, Capsid, Cations, Dielectric Spectroscopy, DNA, DNA, Viral, DNA-Binding Proteins, Electrochemical Techniques, Ligands, Microscopy, Atomic Force, Models, Chemical, Nuclear Proteins

Fresco-Cala, B., Jimenez-Soto, J. M., Cardenas, S., Valcarcel, M., (2014). Single-walled carbon nanohorns immobilized on a microporous hollow polypropylene fiber as a sorbent for the extraction of volatile organic compounds from water samples Microchimica Acta , 181, (9-10), 1117-1124

We have evaluated the behavior of single-walled carbon nanohorns as a sorbent for headspace and direct immersion (micro)solid phase extraction using volatile organic compounds (VOCs) as model analytes. The conical carbon nanohorns were first oxidized in order to increase their solubility in water and organic solvents. A microporous hollow polypropylene fiber served as a mechanical support that provides a high surface area for nanoparticle retention. The extraction unit was directly placed in the liquid sample or the headspace of an aqueous standard or a water sample to extract and preconcentrate the VOCs. The variables affecting extraction have been optimized. The VOCs were then identified and quantified by GC/MS. We conclude that direct immersion of the fiber is the most adequate method for the extraction of VOCs from both liquid samples and headspace. Detection limits range from 3.5 to 4.3 ng L-1 (excepted for toluene with 25 ng L-1), and the precision (expressed as relative standard deviation) is between 3.9 and 9.6 %. The method was applied to the determination of toluene, ethylbenzene, various xylene isomers and styrene in bottled, river and tap waters, and the respective average recoveries of spiked samples are 95.6, 98.2 and 86.0 %.

Keywords: (Micro)solid phase extraction, Nanotechnology, Oxidized single-walled carbon nanohorns, Volatiles compounds, Waters

Rajzer, I., Menaszek, E., Kwiatkowski, R., Planell, J. A., Castaño, O., (2014). Electrospun gelatin/poly(ε-caprolactone) fibrous scaffold modified with calcium phosphate for bone tissue engineering Materials Science and Engineering: C 44, 183-190

In this study gelatin (Gel) modified with calcium phosphate nanoparticles (SG5) and polycaprolactone (PCL) were used to prepare a 3D bi-layer scaffold by collecting electrospun PCL and gelatin/SG5 fibers separately in the same collector. The objective of this study was to combine the desired properties of PCL and Gel/SG5 in the same scaffold in order to enhance mineralization, thus improving the ability of the scaffold to bond to the bone tissue. The scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and the wide angle X-ray diffraction (WAXD) measurements confirmed that SG5 nanoparticles were successfully incorporated into the fibrous gelatin matrix. The composite Gel/SG5/PCL scaffold exhibited more enhanced mechanical properties than individual Gel and Gel/SG5 scaffolds. The presence of SG5 nanoparticles accelerated the nucleation and growth of apatite crystals on the surface of the composite Gel/SG5/PCL scaffold in simulated body fluid (SBF). The osteoblast response in vitro to developed electrospun scaffolds (PCL and Gel/SG5/PCL) was investigated by using normal human primary NHOst cell lines. NHOst cell culture studies showed that higher alkaline phosphatase (ALP) activity and better mineralization were obtained in the case of composite materials than in pure PCL scaffolds. The mechanically strong PCL scaffold served as a skeleton, while the Gel/SG5 fibers facilitated cell spreading and mineralization of the scaffold.

Keywords: Bilayer fibrous scaffold, Ceramic nanoparticles, Electrospinning, Gelatin, Polycaprolactone, Biomechanics, Bone, Calcium phosphate, Cell culture, Electrospinning, Fourier transform infrared spectroscopy, Mechanical properties, Mineralogy, Nanoparticles, Phosphatases, Polycaprolactone, Scanning electron microscopy, X ray diffraction, Polycaprolactone, Alkaline phosphatase activity, Bone tissue engineering, Calcium phosphate nanoparticles, Ceramic nanoparticles, Fibrous scaffolds, Gelatin, Simulated body fluids, Wide-angle x-ray diffraction, Electrospuns, Scaffolds (biology), Electrospinning

Vinagre, M., Aranda, J., Casals, A., (2014). An interactive robotic system for human assistance in domestic environments Computers Helping People with Special Needs (ed. Miesenberger, K., Fels, D., Archambault, D., Pe, Zagler), Springer International Publishing 8548, 152-155

This work introduces an interactive robotic system for assistance, conceived to tackle some of the challenges that domestic environments impose. The system is organized into a network of heterogeneous components that share both physical and logical functions to perform complex tasks. It consists of several robots for object manipulation, an advanced vision system that supplies in-formation about objects in the scene and human activity, and a spatial augmented reality interface that constitutes a comfortable means for interacting with the system. A first analysis based on users' experiences confirms the importance of having a friendly user interface. The inclusion of context awareness from visual perception enriches this interface allowing the robotic system to become a flexible and proactive assistant.

Keywords: Accessibility, Activity Recognition, Ambient Intelligence, Human-Robot Interaction, Robot Assistance, Augmented reality, Complex networks, Computer vision, User interfaces, Accessibility, Activity recognition, Ambient intelligence, Domestic environments, Heterogeneous component, Interactive robotics, Robot assistance, Spatial augmented realities, Human assistance, Robotics

Nevola, L., Martín-Quirós, A., Eckelt, K., Camarero, N., Tosi, S., Llobet, A., Giralt, E., Gorostiza, P., (2013). Light-regulated stapled peptides to inhibit protein-protein interactions involved in clathrin-mediated endocytosis Angewandte Chemie - International Edition , 52, (30), 7704-7708

Control of membrane traffic: Photoswitchable inhibitors of protein-protein interactions were applied to photoregulate clathrin-mediated endocytosis (CME) in living cells. Traffic light (TL) peptides acting as "stop" and "go" signals for membrane traffic can be used to dissect the role of CME in receptor internalization and in cell growth, division, and differentiation.

Keywords: Clathrin-mediated endocytosis, Optopharmacology, Peptides, Photoswitches, Protein-protein interactions

Montufar, E. B., Maazouz, Y., Ginebra, M. P., (2013). Relevance of the setting reaction to the injectability of tricalcium phosphate pastes Acta Biomaterialia 9, (4), 6188-6198

The aim of the present work was to analyze the influence of the setting reaction on the injectability of tricalcium phosphate (TCP) pastes. Even if the injection was performed early after mixing powder and liquid, powder reactivity was shown to play a significant role in the injectability of TCP pastes. Significant differences were observed between the injection behavior of non-hardening β-TCP pastes and that of self-hardening α-TCP pastes. The differences were more marked at low liquid-to-powder ratios, using fine powders and injecting through thin needles. α-TCP was, in general, less injectable than β-TCP and required higher injection loads. Moreover, clogging was identified as a mechanism hindering or even preventing injectability, different and clearly distinguishable from the filter-pressing phenomenon. α-TCP pastes presented transient clogging episodes, which were not observed in β-TCP pastes with equivalent particle size distribution. Different parameters affecting powder reactivity were also shown to affect paste injectability. Thus, whereas powder calcination resulted in an increased injectability due to lower particle reactivity, the addition of setting accelerants, such as hydroxyapatite nanoparticles, tended to reduce the injectability of the TCP pastes, especially if adjoined simultaneously with a Na2HPO4 solution. Although, as a general trend, faster-setting pastes were less injectable, some exceptions to this rule were found. For example, whereas in the absence of setting accelerants fine TCP powders were more injectable than the coarse ones, in spite of their shorter setting times, this trend was inverted when setting accelerants were added, and coarse powders were more injectable than the fine ones.

Keywords: Calcium phosphate cement, Hydroxyapatite, Injectability, Setting reaction, Tricalcium phosphate

Garde, Ainara, Voss, Andreas, Caminal, Pere, Benito, Salvador, Giraldo, Beatriz F., (2013). SVM-based feature selection to optimize sensitivity-specificity balance applied to weaning Computers in Biology and Medicine , 43, (5), 533-540

Classification algorithms with unbalanced datasets tend to produce high predictive accuracy over the majority class, but poor predictive accuracy over the minority class. This problem is very common in biomedical data mining. This paper introduces a Support Vector Machine (SVM)-based optimized feature selection method, to select the most relevant features and maintain an accurate and well-balanced sensitivity–specificity result between unbalanced groups. A new metric called the balance index (B) is defined to implement this optimization. The balance index measures the difference between the misclassified data within each class. The proposed optimized feature selection is applied to the classification of patients' weaning trials from mechanical ventilation: patients with successful trials who were able to maintain spontaneous breathing after 48 h and patients who failed to maintain spontaneous breathing and were reconnected to mechanical ventilation after 30 min. Patients are characterized through cardiac and respiratory signals, applying joint symbolic dynamic (JSD) analysis to cardiac interbeat and breath durations. First, the most suitable parameters (C+,C−,σ) are selected to define the appropriate SVM. Then, the feature selection process is carried out with this SVM, to maintain B lower than 40%. The best result is obtained using 6 features with an accuracy of 80%, a B of 18.64%, a sensitivity of 74.36% and a specificity of 82.42%.

Keywords: Support vector machines, Balance index, Sensitivity-specificity balance, Cardiorespiratory interaction, Joint symbolic dynamics, Feature selection, Weaning procedure

Giraldo, B. F., Tellez, J. P., Herrera, S., Benito, S., (2013). Analysis of heart rate variability in elderly patients with chronic heart failure during periodic breathing CinC 2013 Computing in Cardiology Conference (CinC) , IEEE (Zaragoza, Spain) , 991-994

Assessment of the dynamic interactions between cardiovascular signals can provide valuable information that improves the understanding of cardiovascular control. Heart rate variability (HRV) analysis is known to provide information about the autonomic heart rate modulation mechanism. Using the HRV signal, we aimed to obtain parameters for classifying patients with and without chronic heart failure (CHF), and with periodic breathing (PB), non-periodic breathing (nPB), and Cheyne-Stokes respiration (CSR) patterns. An electrocardiogram (ECG) and a respiratory flow signal were recorded in 36 elderly patients: 18 patients with CHF and 18 patients without CHF. According to the clinical criteria, the patients were classified into the follow groups: 19 patients with nPB pattern, 7 with PB pattern, 4 with Cheyne-Stokes respiration (CSR), and 6 non-classified patients (problems with respiratory signal). From the HRV signal, parameters in the time and frequency domain were calculated. Frequency domain parameters were the most discriminant in comparisons of patients with and without CHF: PTot (p = 0.02), PLF (p = 0.022) and fpHF (p = 0.021). For the comparison of the nPB vs. CSR patients groups, the best parameters were RMSSD (p = 0.028) and SDSD (p = 0.028). Therefore, the parameters appear to be suitable for enhanced diagnosis of decompensated CHF patients and the possibility of developed periodic breathing and a CSR pattern.

Keywords: cardiovascular system, diseases, electrocardiography, frequency-domain analysis, geriatrics, medical signal processing, patient diagnosis, pneumodynamics, signal classification, Cheyne-Stokes respiration patterns, ECG, autonomic heart rate modulation mechanism, cardiovascular control, cardiovascular signals, chronic heart failure, decompensated CHF patients, dynamic interaction assessment, elderly patients, electrocardiogram, enhanced diagnosis, frequency domain parameters, heart rate variability analysis, patient classification, periodic breathing, respiratory flow signal recording, Electrocardiography, Frequency modulation, Frequency-domain analysis, Heart rate variability, Senior citizens, Standards

Marco, S., Gutiérrez-Gálvez, A., Lansner, A., Martinez, D., Rospars, J. P., Beccherelli, R., Perera, A., Pearce, T., Vershure, P., Persaud, K., (2013). Biologically inspired large scale chemical sensor arrays and embedded data processing Proceedings of SPIE - The International Society for Optical Engineering Smart Sensors, Actuators, and MEMS VI , SPIE Digital Library (Grenoble, France) 8763, 1-15

Biological olfaction outperforms chemical instrumentation in specificity, response time, detection limit, coding capacity, time stability, robustness, size, power consumption, and portability. This biological function provides outstanding performance due, to a large extent, to the unique architecture of the olfactory pathway, which combines a high degree of redundancy, an efficient combinatorial coding along with unmatched chemical information processing mechanisms. The last decade has witnessed important advances in the understanding of the computational primitives underlying the functioning of the olfactory system. EU Funded Project NEUROCHEM (Bio-ICT-FET- 216916) has developed novel computing paradigms and biologically motivated artefacts for chemical sensing taking inspiration from the biological olfactory pathway. To demonstrate this approach, a biomimetic demonstrator has been built featuring a large scale sensor array (65K elements) in conducting polymer technology mimicking the olfactory receptor neuron layer, and abstracted biomimetic algorithms have been implemented in an embedded system that interfaces the chemical sensors. The embedded system integrates computational models of the main anatomic building blocks in the olfactory pathway: The olfactory bulb, and olfactory cortex in vertebrates (alternatively, antennal lobe and mushroom bodies in the insect). For implementation in the embedded processor an abstraction phase has been carried out in which their processing capabilities are captured by algorithmic solutions. Finally, the algorithmic models are tested with an odour robot with navigation capabilities in mixed chemical plumes.

Keywords: Antennal lobes, Artificial olfaction, Computational neuroscience, Olfactory bulbs, Plume tracking, Abstracting, Actuators, Algorithms, Biomimetic processes, Chemical sensors, Conducting polymers, Data processing, Flavors, Odors, Robots, Smart sensors, Embedded systems

Arcentales, A., Voss, A., Caminal, P., Bayes-Genis, A., Domingo, M. T., Giraldo, B. F., (2013). Characterization of patients with different ventricular ejection fractions using blood pressure signal analysis CinC 2013 Computing in Cardiology Conference (CinC) , IEEE (Zaragoza, Spain) , 795-798

Ischemic and dilated cardiomyopathy are associated with disorders of myocardium. Using the blood pressure (BP) signal and the values of the ventricular ejection fraction, we obtained parameters for stratifying cardiomyopathy patients as low- and high-risk. We studied 48 cardiomyopathy patients characterized by NYHA ≥2: 19 patients with dilated cardiomyopathy (DCM) and 29 patients with ischemic cardiomyopathy (ICM). The left ventricular ejection fraction (LVEF) percentage was used to classify patients in low risk (LR: LVEF > 35%, 17 patients) and high risk (HR: LVEF ≤ 35%, 31 patients) groups. From the BP signal, we extracted the upward systolic slope (BPsl), the difference between systolic and diastolic BP (BPA), and systolic time intervals (STI). When we compared the LR and HR groups in the time domain analysis, the best parameters were standard deviation (SD) of 1=STI, kurtosis (K) of BPsl, and K of BPA. In the frequency domain analysis, very low frequency (VLF) and high frequency (HF) bands showed statistically significant differences in comaprisons of LR and HR groups. The area under the curve of power spectral density was the best parameter in all classifications, and particularly in the very-low-and high- frequency bands (p <; 0.001). These parameters could help to improve the risk stratification of cardiomyopathy patients.

Keywords: blood pressure measurement, cardiovascular system, diseases, medical disorders, medical signal processing, statistical analysis, time-domain analysis, BP signal, HR groups, LR groups, blood pressure signal analysis, cardiomyopathy patients, diastolic BP, dilated cardiomyopathy, frequency domain analysis, high-frequency bands, ischemic cardiomyopathy, left ventricular ejection fraction, low-frequency bands, myocardium disorders, patient characterization, power spectral density curve, standard deviation, statistical significant differences, systolic BP, systolic slope, systolic time intervals, time domain analysis, ventricular ejection fraction, Abstracts, Databases, Parameter extraction, Telecommunication standards, Time-frequency analysis

Giraldo, B. F., Chaparro, J. A., Caminal, P., Benito, S., (2013). Characterization of the respiratory pattern variability of patients with different pressure support levels Engineering in Medicine and Biology Society (EMBC) 35th Annual International Conference of the IEEE , IEEE (Osaka, Japan) , 3849-3852

One of the most challenging problems in intensive care is still the process of discontinuing mechanical ventilation, called weaning process. Both an unnecessary delay in the discontinuation process and a weaning trial that is undertaken too early are undesirable. In this study, we analyzed respiratory pattern variability using the respiratory volume signal of patients submitted to two different levels of pressure support ventilation (PSV), prior to withdrawal of the mechanical ventilation. In order to characterize the respiratory pattern, we analyzed the following time series: inspiratory time, expiratory time, breath duration, tidal volume, fractional inspiratory time, mean inspiratory flow and rapid shallow breathing. Several autoregressive modeling techniques were considered: autoregressive models (AR), autoregressive moving average models (ARMA), and autoregressive models with exogenous input (ARX). The following classification methods were used: logistic regression (LR), linear discriminant analysis (LDA) and support vector machines (SVM). 20 patients on weaning trials from mechanical ventilation were analyzed. The patients, submitted to two different levels of PSV, were classified as low PSV and high PSV. The variability of the respiratory patterns of these patients were analyzed. The most relevant parameters were extracted using the classifiers methods. The best results were obtained with the interquartile range and the final prediction errors of AR, ARMA and ARX models. An accuracy of 95% (93% sensitivity and 90% specificity) was obtained when the interquartile range of the expiratory time and the breath duration time series were used a LDA model. All classifiers showed a good compromise between sensitivity and specificity.

Keywords: autoregressive moving average processes, feature extraction, medical signal processing, patient care, pneumodynamics, signal classification, support vector machines, time series, ARX, autoregressive modeling techniques, autoregressive models with exogenous input, autoregressive moving average model, breath duration time series, classification method, classifier method, discontinuing mechanical ventilation, expiratory time, feature extraction, final prediction errors, fractional inspiratory time, intensive care, interquartile range, linear discriminant analysis, logistic regression analysis, mean inspiratory flow, patient respiratory volume signal, pressure support level, pressure support ventilation, rapid shallow breathing, respiratory pattern variability characterization, support vector machines, tidal volume, weaning trial, Analytical models, Autoregressive processes, Biological system modeling, Estimation, Support vector machines, Time series analysis, Ventilation

Santano-Martínez, R., Leiva-González, R., Avazbeigi, M., Gutiérrez-Gálvez, A., Marco, S., (2013). Identification of molecular properties coding areas in rat's olfactory bulb by rank products Proceedings of the International Conference on Bio-Inspired Systems and Signal Processing BIOSIGNALS 2013 , SciTePress (Barcelona, Spain) , 383-387

Neural coding of chemical information is still under strong debate. It is clear that, in vertebrates, neural representation in the olfactory bulb is a key for understanding a putative odour code. To explore this code, in this work we have studied a public dataset of radio images of 2-Deoxyglucose uptake (2-DG) in the olfactory bulb of rats in response to diverse odorants using univariate pixel selection algorithms: rank-products and Mann-Whitney U (MWU) test. Initial results indicate that some chemical properties of odorants preferentially activate certain areas of the rat olfactory bulb. While non-parametric test (MWU) has difficulties to detect these regions, rank-product provides a higher power of detection.

Keywords: 2-Deoxyglucose uptake, Chemotopy, Feature selection, Odour coding, Olfaction, Olfactory bulb

Hernando, D., Alcaine, A., Pueyo, E., Laguna, P., Orini, M., Arcentales, A., Giraldo, B., Voss, A., Bayes-Genis, A., Bailon, R., (2013). Influence of respiration in the very low frequency modulation of QRS slopes and heart rate variability in cardiomyopathy patients CinC 2013 Computing in Cardiology Conference (CinC) , IEEE (Zaragoza, Spain) , 117-120

This work investigates the very low frequency (VLF) modulation of QRS slopes and heart rate variability (HRV). Electrocardiogram (ECG) and respiratory flow signal were acquired from patients with dilated cardiomyopathy and ischemic cardiomyopathy. HRV as well as the upward QRS slope (IUS) and downward QRS slope (IDS) were extracted from the ECG. The relation between HRV and QRS slopes in the VLF band was measured using ordinary coherence in 5-minute segments. Partial coherence was then used to remove the influence that respiration simultaneously exerts on HRV and QRS slopes. A statistical threshold was determined, below which coherence values were considered not to represent a linear relation. 7 out of 276 segments belonging to 5 out of 29 patients for IUS and 10 segments belonging to 5 patients for IDS presented a VLF modulation in QRS slopes, HRV and respiration. In these segments spectral coherence was statistically significant, while partial coherence decreased, indicating that the coupling HRV and QRS slopes was related to respiration. 4 segments had a partial coherence value below the threshold for IUS, 3 segments for IDS. The rest of the segments also presented a notable decrease in partial coherence, but still above the threshold, which means that other non-linearly effects may also affect this modulation.

Keywords: diseases, electrocardiography, feature extraction, medical signal processing, pneumodynamics, statistical analysis, ECG, QRS slopes, cardiomyopathy patients, dilated cardiomyopathy, electrocardiogram, feature extraction, heart rate variability, ischemic cardiomyopathy, ordinary coherence, partial coherence value, respiration, respiratory flow signal acquisition, spectral coherence, statistical threshold, time 5 min, very low frequency modulation, Coherence, Educational institutions, Electrocardiography, Frequency modulation, Heart rate variability

Fernandez, L., Gutierrez-Galvez, A., Marco, S., (2013). Multi-way analysis of diversity and redundancy factors in large MOX gas sensor data Metal Oxide-based Sensors 14th International Meeting on Chemical Sensors - IMCS 2012 , AMA Science Portal (Nuremberg, Germany) P2.07, 1279-1280

We propose the use of multi-way methods to analyze the contribution of diversity and redundancy to odor identification and concentration estimation in a large chemical sensor array. We use a chemical sensing system based on a large array of metal oxide sensors (MOX) and inspired on the diversity and redundancy of the olfactory epithelium. In order to analyze the role of diversity (different sensor type and temperature modulation) and redundancy (replicates of sensors and different load resistors) in odor quantification and discrimination tasks, we have acquired two datasets and modeled the data using multi-way techniques.

Keywords: Artificial Olfaction, Large array, MOX gas sensor, Multi-way methods

Giraldo, B. F., Tellez, J. P., Herrera, S., Benito, S., (2013). Study of the oscillatory breathing pattern in elderly patients Engineering in Medicine and Biology Society (EMBC) 35th Annual International Conference of the IEEE , IEEE (Osaka, Japan) , 5228-5231

Some of the most common clinical problems in elderly patients are related to diseases of the cardiac and respiratory systems. Elderly patients often have altered breathing patterns, such as periodic breathing (PB) and Cheyne-Stokes respiration (CSR), which may coincide with chronic heart failure. In this study, we used the envelope of the respiratory flow signal to characterize respiratory patterns in elderly patients. To study different breathing patterns in the same patient, the signals were segmented into windows of 5 min. In oscillatory breathing patterns, frequency and time-frequency parameters that characterize the discriminant band were evaluated to identify periodic and non-periodic breathing (PB and nPB). In order to evaluate the accuracy of this characterization, we used a feature selection process, followed by linear discriminant analysis. 22 elderly patients (7 patients with PB and 15 with nPB pattern) were studied. The following classification problems were analyzed: patients with either PB (with and without apnea) or nPB patterns, and patients with CSR versus PB, CSR versus nPB and PB versus nPB patterns. The results showed 81.8% accuracy in the comparisons of nPB and PB patients, using the power of the modulation peak. For the segmented signal, the power of the modulation peak, the frequency variability and the interquartile ranges provided the best results with 84.8% accuracy, for classifying nPB and PB patients.

Keywords: cardiovascular system, diseases, feature extraction, geriatrics, medical signal processing, oscillations, pneumodynamics, signal classification, time-frequency analysis, Cheyne-Stokes respiration, apnea, cardiac systems, chronic heart failure, classification problems, discriminant band, diseases, elderly patients, feature selection process, frequency variability, interquartile ranges, linear discriminant analysis, nonperiodic breathing, oscillatory breathing pattern, periodic breathing, respiratory How signal, respiratory systems, signal segmentation, time 5 min, time-frequency parameters, Accuracy, Aging, Frequency modulation, Heart, Senior citizens, Time-frequency analysis

Nocentini, S., Reginensi, D., Garcia, S., Carulla, P., Moreno-Flores, Wandosell, F., Trepat, X., Bribian, A., Del Rí, (2012). Myelin-associated proteins block the migration of olfactory ensheathing cells: an in vitro study using single-cell tracking and traction force microscopy Cellular and Molecular Life Sciences , 69, (10), 1689-1703

Newly generated olfactory receptor axons grow from the peripheral to the central nervous system aided by olfactory ensheathing cells (OECs). Thus, OEC transplantation has emerged as a promising therapy for spinal cord injuries and for other neural diseases. However, these cells do not present a uniform population, but instead a functionally heterogeneous population that exhibits a variety of responses including adhesion, repulsion, and crossover during cell–cell and cell–matrix interactions. Some studies report that the migratory properties of OECs are compromised by inhibitory molecules and potentiated by chemical gradients. Here, we demonstrated that rodent OECs express all the components of the Nogo receptor complex and that their migration is blocked by myelin. Next, we used cell tracking and traction force microscopy to analyze OEC migration and its mechanical properties over myelin. Our data relate the decrease of traction force of OEC with lower migratory capacity over myelin, which correlates with changes in the F-actin cytoskeleton and focal adhesion distribution. Lastly, OEC traction force and migratory capacity is enhanced after cell incubation with the Nogo receptor inhibitor NEP1-40.

Keywords: Ensheathing glia, Traction force, microscopy, Migration, Myelin-associated inhibitors

Hernansanz, A., Zerbato, D., Gasperotti, L., Scandola, M., Casals, A., Fiorini, P., (2012). Assessment of virtual fixtures for the development of basic skills in robotic surgery International Journal of Computer Assisted Radiology and Surgery CARS 2012 Computer Assisted Radiology and Surgery , Springer (Pisa, Italy) 7 (Supplement 1) - Surgical Modelling, Simulation and Education, S186-S188

Teleoperation, by adequately adapting computer interfaces, can benefit from the knowledge on human factors and psychomotor models in order to improve the effectiveness and efficiency in the execution of a task. While scaling is one of the performances frequently used in teleoperation tasks that require high precision, such as surgery, this article presents a scaling method that considers the system dynamics as well. The proposed dynamic scaling factor depends on the apparent position and velocity of the robot and targets. Such scaling improves the performance of teleoperation interfaces, thereby reducing user's workload.

Keywords: Human-robot interaction, Throughput, Scaling functions, Motor control performance

Muñoz, L. M., Casals, A., (2012). Dynamic scaling interface for assisted teleoperation IEEE International Conference on Robotics and Automation (ICRA) , IEEE (Minnesota, USA) , 4288-4293

Teleoperation, by adequately adapting computer interfaces, can benefit from the knowledge on human factors and psychomotor models in order to improve the effectiveness and efficiency in the execution of a task. While scaling is one of the performances frequently used in teleoperation tasks that require high precision, such as surgery, this article presents a scaling method that considers the system dynamics as well. The proposed dynamic scaling factor depends on the apparent position and velocity of the robot and targets. Such scaling improves the performance of teleoperation interfaces, thereby reducing user's workload.

Keywords: Human-robot interaction, Motor control performance, Scaling functions, Throughput

Chaparro, J.A., Giraldo, B.F., Caminal, P., Benito, S., (2012). Performance of respiratory pattern parameters in classifiers for predict weaning process Engineering in Medicine and Biology Society (EMBC) 34th Annual International Conference of the IEEE , IEEE (San Diego, USA) , 4349-4352

Weaning trials process of patients in intensive care units is a complex clinical procedure. 153 patients under extubation process (T-tube test) were studied: 94 patients with successful trials (group S), 38 patients who failed to maintain spontaneous breathing and were reconnected (group F), and 21 patients with successful test but that had to be reintubated before 48 hours (group R). The respiratory pattern of each patient was characterized through the following time series: inspiratory time (TI), expiratory time (TE), breathing cycle duration (TTot), tidal volume (VT), inspiratory fraction (TI/TTot), half inspired flow (VT/TI), and rapid shallow index (f/VT), where f is respiratory rate. Using techniques as autoregressive models (AR), autoregressive moving average models (ARMA) and autoregressive models with exogenous input (ARX), the most relevant parameters of the respiratory pattern were obtained. We proposed the evaluation of these parameters using classifiers as logistic regression (LR), linear discriminant analysis (LDA), support vector machines (SVM) and classification and regression tree (CART) to discriminate between patients from groups S, F and R. An accuracy of 93% (98% sensitivity and 82% specificity) has been obtained using CART classification.

Keywords: Accuracy, Indexes, Logistics, Regression tree analysis, Support vector machines, Time series analysis, Autoregressive moving average processes, Medical signal processing, Pattern classification, Pneumodynamics, Regression analysis, Sensitivity, Signal classification, Support vector machines, Time series, SVM, T-tube testing, Autoregressive models-with-exogenous input, Autoregressive moving average models, Breathing cycle duration, Classification-and-regression tree, Expiratory time, Extubation process, Half inspired flow, Inspiratory fraction, Inspiratory time, Intensive care units, Linear discriminant analysis, Logistic regression, Rapid shallow index, Respiratory pattern parameter performance, Sensitivity, Spontaneous breathing, Support vector machines, Tidal volume, Time 48 hr, Time series, Weaning process classifiers

Amigo, L. E., Fernandez, Q., Giralt, X., Casals, A., Amat, J., (2012). Study of patient-orthosis interaction forces in rehabilitation therapies IEEE Conference Publications 4th IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics (BioRob) , IEEE (Roma, Italy) , 1098-1103

The design of mechanical joints that kinematically behave as their biological counterparts is a challenge that if not addressed properly can cause inadequate forces transmission between robot and patient. This paper studies the interaction forces in rehabilitation therapies of the elbow joint. To measure the effect of orthosis-patient misalignments, a force sensor with a novel distributed architecture has been designed and used for this study. A test-bed based on an industrial robot acting as a virtual exoskeleton that emulates the action of a therapist has been developed and the interaction forces analyzed.

Keywords: Force, Force measurement, Force sensors, Joints, Medical treatment, Robot sensing systems, Force sensors, Medical robotics, Patient rehabilitation, Biological counterparts, Distributed architecture, Elbow joint, Force sensor, Inadequate forces transmission, Industrial robot, Mechanical joints design, Orthosis-patient misalignments, Patient-orthosis interaction forces, Rehabilitation therapies, Robot, Test-bed, Virtual exoskeleton

Auffarth, Benjamin, Gutierrez-Galvez, Agustín, Marco, Santiago, (2011). Continuous spatial representations in the olfactory bulb may reflect perceptual categories Frontiers in Systems Neuroscience , 5, (82), 1-8

In sensory processing of odors, the olfactory bulb is an important relay station, where odor representations are noise-filtered, sharpened, and possibly re-organized. An organization by perceptual qualities has been found previously in the piriform cortex, however several recent studies indicate that the olfactory bulb code reflects behaviorally relevant dimensions spatially as well as at the population level. We apply a statistical analysis on 2-deoxyglucose images, taken over the entire bulb of glomerular layer of the rat, in order to see how the recognition of odors in the nose is translated into a map of odor quality in the brain. We first confirm previous studies that the first principal component could be related to pleasantness, however the next higher principal components are not directly clear. We then find mostly continuous spatial representations for perceptual categories. We compare the space spanned by spatial and population codes to human reports of perceptual similarity between odors and our results suggest that perceptual categories could be already embedded in glomerular activations and that spatial representations give a better match than population codes. This suggests that human and rat perceptual dimensions of odorant coding are related and indicates that perceptual qualities could be represented as continuous spatial codes of the olfactory bulb glomerulus population.

Keywords: Glomeruli, Memory organization, Odor quality, Olfaction, Olfactory bulb, Perceptual categories, Population coding, Spatial coding

Ivon Rodriguez-Villarreal, Angeles, Tarn, Mark D., Madden, Leigh A., Lutz, Julia B., Greenman, John, Samitier, Josep, Pamme, Nicole, (2011). Flow focussing of particles and cells based on their intrinsic properties using a simple diamagnetic repulsion setup Lab on a Chip , 11, (7), 1240-1248

The continuous flow focussing and manipulation of particles and cells are important factors in microfluidic applications for performing accurate and reproducible procedures downstream. Many particle focussing methods require complex setups or channel designs that can limit the process and its applications. Here, we present diamagnetic repulsion as a simple means of focussing objects in continuous flow, based only on their intrinsic properties without the requirement of any label. Diamagnetic polystyrene particles were suspended in a paramagnetic medium and pumped through a capillary between a pair of permanent magnets, whereupon the particles were repelled by each magnet into the central axis of the capillary, thus achieving focussing. By investigating this effect, we found that the focussing was greatly enhanced with (i) increased magnetic susceptibility of the medium, (ii) reduced flow rate of the suspension, (iii) increased particle size, and (iv) increased residence time in the magnetic field. Furthermore, we applied diamagnetic repulsion to the flow focussing of living, label-free HaCaT cells.

Keywords: Feeble magnetic substances, On-chip, Blood-cells, Microfluidic device, Separation, Field, Levitation, Magnetophoresis, Fractionation, Nanoparticles

Krishnan, Ramaswamy, Klumpers, Darinka D., Park, Chan Y., Rajendran, Kavitha, Trepat, Xavier, van Bezu, Jan, van Hinsbergh, Victor W. M., Carman, Christopher V., Brain, Joseph D., Fredberg, Jeffrey J., Butler, James P., van Nieuw Amerongen, Geerten P., (2011). Substrate stiffening promotes endothelial monolayer disruption through enhanced physical forces American Journal of Physiology - Cell Physiology , 300, (1), C146-C154

A hallmark of many, sometimes life-threatening, inflammatory diseases and disorders is vascular leakage. The extent and severity of vascular leakage is broadly mediated by the integrity of the endothelial cell (EC) monolayer, which is in turn governed by three major interactions: cell-cell and cell-substrate contacts, soluble mediators, and biomechanical forces. A potentially critical but essentially uninvestigated component mediating these interactions is the stiffness of the substrate to which the endothelial monolayer is adherent. Accordingly, we investigated the extent to which substrate stiffening influences endothelial monolayer disruption and the role of cell-cell and cell-substrate contacts, soluble mediators, and physical forces in that process. Traction force microscopy showed that forces between cell and cell and between cell and substrate were greater on stiffer substrates. On stiffer substrates, these forces were substantially enhanced by a hyperpermeability stimulus (thrombin, 1 U/ml), and gaps formed between cells. On softer substrates, by contrast, these forces were increased far less by thrombin, and gaps did not form between cells. This stiffness-dependent force enhancement was associated with increased Rho kinase activity, whereas inhibition of Rho kinase attenuated baseline forces and lessened thrombin-induced inter-EC gap formation. Our findings demonstrate a central role of physical forces in EC gap formation and highlight a novel physiological mechanism. Integrity of the endothelial monolayer is governed by its physical microenvironment, which in normal circumstances is compliant but during pathology becomes stiffer.

Keywords: Contraction, Human umbilical vein endothelial cells, Permeability, Traction force, Cell-cell contact, Cell-substrate contact, Substrate stiffness, Rho kinase, Vascular endothelial cadherin, Thrombin

Gugutkov, Dencho, Gonzalez-Garcia, Cristina, Altankov, George, Salmeron-Sanchez, Manuel, (2011). Fibrinogen organization at the cell-material interface directs endothelial cell behavior Journal of Bioactive and Compatible Polymers , 26, (4), 375-387

Fibrinogen (FG) adsorption on surfaces with controlled fraction of -OH groups was investigated with AFM and correlated to the initial interaction of primary endothelial cells (HUVEC). The -OH content was tailored making use of a family of copolymers consisting of ethyl acrylate (EA) and hydroxyl ethyl acrylate (HEA) in different ratios. The supramolecular distribution of FG changed from an organized network-like structure on the most hydrophobic surface (-OH(0)) to dispersed molecular aggregate one as the fraction of -OH groups increases, indicating a different conformation by the adsorbed protein. The best cellular interaction was observed on the most hydrophobic (-OH(0)) surface where FG assembled in a fibrin-like appearance in the absence of any thrombin. Likewise, focal adhesion formation and actin cytoskeleton development was poorer as the fraction of hydroxy groups on the surface was increased. The biological activity of the surface-induced FG network to provide 3D cues in a potential tissue engineered scaffold, making use of electrospun PEA fibers (-OH(0)), seeded with human umbilical vein endothelial cells was investigated. The FG assembled on the polymer fibers gave rise to a biologically active network able to direct cell orientation along the fibers (random or aligned), promote cytoskeleton organization and focal adhesion formation.

Keywords: Fibrinogen, Cell-material interactions, HUVEC, Electrospun fibers, Fibrinogen organization, Cell-material interface, Endothelial cell behavior, Ethyl acrylate, Hydroxyl ethyl acrylate

Tahirbegi, I. B., Mir, M., (2011). Slit-wave model for band structures in solid state physics Modern Physics Letters B , 25, (3), 151-161

The reason behind the entire development in silicon technology was band models in solid state physics. However, the theories postulated in order to give response to this phenomenon do not explain all kinds of materials. In a bid to overcome this limitation, we approach the problem from another point of view. In this work, the wave properties of the electrons from the external orbitals of the atoms and its diffraction patterns through the lattice structure of the material have been used to explain the band structure of metals, semiconductor and insulators. In order to probe this hypothesis, a simulation has been used and according to the relation between the lattice constant and the atomic diameter, the splitting of the bands have been observed for different kind of materials, showing a strong correlation between the simulation and the experimental results.

Keywords: Electrical band structure, Band gap, Fraunhofer diffraction, Semiconductor, Insulator

Moore, S. W., Roca-Cusachs, P., Sheetz, M. P., (2010). Stretchy proteins on stretchy substrates: The important elements of integrin-mediated rigidity sensing Developmental Cell , 19, (2), 194-206

Matrix and tissue rigidity guides many cellular processes, including the differentiation of stem cells and the migration of cells in health and disease. Cells actively and transiently test rigidity using mechanisms limited by inherent physical parameters that include the strength of extracellular attachments, the pulling capacity on these attachments, and the sensitivity of the mechanotransduction system. Here, we focus on rigidity sensing mediated through the integrin family of extracellular matrix receptors and linked proteins and discuss the evidence supporting these proteins as mechanosensors.

Keywords: Focal adhesion kinase, Atomic Force Microscopy, Smooth-muscle cells, Traction forces, Living cells, Mechanical force, Locomoting cells

Morgenstern, C., Schwaibold, M., Randerath, W., Bolz, A., Jané, R., (2010). Automatic non-invasive differentiation of obstructive and central hypopneas with nasal airflow compared to esophageal pressure Engineering in Medicine and Biology Society (EMBC) 32nd Annual International Conference of the IEEE , IEEE (Buenos Aires, Argentina) , 6142-6145

The differentiation of obstructive and central respiratory events is a major challenge in the diagnosis of sleep disordered breathing. Esophageal pressure (Pes) measurement is the gold-standard method to identify these events but its invasiveness deters its usage in clinical routine. Flattening patterns appear in the airflow signal during episodes of inspiratory flow limitation (IFL) and have been shown with invasive techniques to be useful to differentiate between central and obstructive hypopneas. In this study we present a new method for the automatic non-invasive differentiation of obstructive and central hypopneas solely with nasal airflow. An overall of 36 patients underwent full night polysomnography with systematic Pes recording and a total of 1069 hypopneas were manually scored by human experts to create a gold-standard annotation set. Features were automatically extracted from the nasal airflow signal to train and test our automatic classifier (Discriminant Analysis). Flattening patterns were non-invasively assessed in the airflow signal using spectral and time analysis. The automatic non-invasive classifier obtained a sensitivity of 0.71 and an accuracy of 0.69, similar to the results obtained with a manual non-invasive classification algorithm. Hence, flattening airflow patterns seem promising for the non-invasive differentiation of obstructive and central hypopneas.

Keywords: Practical, Experimental/ biomedical measurement, Feature extraction, Flow measurement, Medical disorders, Medical signal processing, Patient diagnosis, Pneumodynamics, Pressure measurement, Signal classification, Sleep, Spectral analysis/ automatic noninvasive differentiation, Obstructive hypopnea, Central hypopnea, Inspiratory flow limitation, Nasal airflow, Esophageal pressure, Polysomnography, Feature extraction, Discriminant analysis, Spectral analysis

Aranda, J., Vinagre, M., Marti n, E. X., Casamitjana, M., Casals, A., (2010). Friendly human-machine interaction in an adapted robotized kitchen Computers Helping People with Special Needs 12th International Conference, ICCHP 2010 (ed. Miesenberger, K., Klaus, J., Zagler, W., Karshmer, A.), Springer (Vienna, Austria) 1, 312-319

The concept and design of a friendly human-machine interaction system for an adapted robotized kitchen is presented. The kitchen is conceived in a modular way in order to be adaptable to a great diversity in level and type of assistance needs. An interaction manager has been developed which assist the user to control the system actions dynamically according to the given orders and the present state of the environment. Real time enhanced perception of the scenario is achieved by means of a 3D computer vision system. The main goal of the present project is to provide this kitchen with the necessary intelligent behavior to be able to actuate efficiently by interpreting the users' will.

Keywords: Human computer interaction, Intelligent robots, Robot vision

Casals, A., (2010). Human – Robot cooperation techniques in surgery ICINCO 2010 7th International conference on Informatics in Control, Automation and Robotics , Springer (Madeira, Portugal) , 1-4

The growth of robotics in the surgical field is consequence of the progress in all its related areas, as: perception, instrumentation, actuators, materials, computers, and so. However, the lack of intelligence of current robots makes teleoperation an essential means for robotizing the Operating Room (OR), helping in the improvement of surgical procedures and making the best of the human-robot couple, as it already happens in other robotic application fields. The assistance a teleoperated system can provide is the result of the control strategies that can combine the high performance of computers with the surgeon knowledge, expertise and will. In this lecture, an overview of teleoperation techniques and operating modes suitable in the OR is presented, considering different cooperation levels. A special emphasis will be put on the selection of the most adequate interfaces currently available, able to operate in such quite special environments.

Keywords: Medical Robotics, Human Robot Interaction, Human Machine Interfaces, Surgical Robots

Mesquita, J., Fiz, J. A., Solà, J., Morera, J., Jané, R., (2010). Regular and non regular snore features as markers of SAHS Engineering in Medicine and Biology Society (EMBC) 32nd Annual International Conference of the IEEE , IEEE (Buenos Aires, Argentina) , 6138-6141

Sleep Apnea-Hypopnea Syndrome (SAHS) diagnosis is still done with an overnight multi-channel polysomnography. Several efforts are being made to study profoundly the snore mechanism and discover how it can provide an opportunity to diagnose the disease. This work introduces the concept of regular snores, defined as the ones produced in consecutive respiratory cycles, since they are produced in a regular way, without interruptions. We applied 2 thresholds (TH/sub adaptive/ and TH/sub median/) to the time interval between successive snores of 34 subjects in order to select regular snores from the whole all-night snore sequence. Afterwards, we studied the effectiveness that parameters, such as time interval between successive snores and the mean intensity of snores, have on distinguishing between different levels of SAHS severity (AHI (Apnea-Hypopnea Index)<5h/sup -1/, AHI<10 h/sup -1/, AHI<15h/sup -1/, AHI<30h/sup -1/). Results showed that TH/sub adaptive/ outperformed TH/sub median/ on selecting regular snores. Moreover, the outcome achieved with non-regular snores intensity features suggests that these carry key information on SAHS severity.

Keywords: Practical, Experimental/ acoustic signal processing, Bioacoustics, Biomedical measurement, Diseases, Feature extraction, Medical signal processing, Patient diagnosis, Pneumodynamics, Sleep/ nonregular snore features, SAHS markers, Sleep apnea hypopnea syndrome, Overnight multichannel polysomnography, Snore mechanism

Andonovski, B., Ponsa, P., Casals, A., (2010). Towards the development of a haptics guideline in human-robot systems 3rd International Conference on Human System Interactions (HSI) 3rd International Conference on Human System Interactions (HSI) (ed. Pardela, T.), IEEE (Rzeszow, Poland) , 380-387

The main goal of this work is to propose a haptics guideline in human-robot systems focused on the relationship between the human and robot task, the use of a physical interface and the object to manipulate. With this aim, this guideline presents two main parts: a set of heuristic indicators and a qualitative evaluation. In order to assess its ergonomic validation, an application over a well known haptics interface is presented. The final goal of this work is the study of possible applications in regular laboratory conditions in order to improve the design and use of human-robot haptic interfaces in telerobotics applications.

Keywords: Haptic interface design, Human-robot interaction, Surgical applications, Teleoperation

Salmeron-Sanchez, M., Altankov, G., (2010). Cell-Protein-Material interaction in tissue engineering Tissue Engineering (ed. Eberli, D.), Intech (Vukovar, Croatia) , 77-102

The initial cellular events that take place at the biomaterials interface mimic to a certain extent the natural adhesive interaction of cells with the extracellular matrix (ECM) (Spie, 2002; Griffin & Naughton, 2002; Grinnell, 1986). In fact, the living cells cannot interact directly with foreign materials, but they readily attach to the adsorbed layer of proteins (upon contact with physiological fluids in vivo or culture medium in vitro) such as fibronectin (FN), vitronectin (VN), fibrinogen (FG), representing the so-called soluble matrix proteins in the biological fluids (Grinnell 1986).

Keywords: Tissue Engineering, Protein-material interaction, ECM, Biomaterials

Sunyer, R., Trepat, X., Fredberg, J. J., Farre, R., Navajas, D., (2009). The temperature dependence of cell mechanics measured by atomic force microscopy Physical Biology , 6, (2), 25009

The cytoskeleton is a complex polymer network that regulates the structural stability of living cells. Although the cytoskeleton plays a key role in many important cell functions, the mechanisms that regulate its mechanical behaviour are poorly understood. Potential mechanisms include the entropic elasticity of cytoskeletal filaments, glassy-like inelastic rearrangements of cross-linking proteins and the activity of contractile molecular motors that sets the tensional stress (prestress) borne by the cytoskeleton filaments. The contribution of these mechanisms can be assessed by studying how cell mechanics depends on temperature. The aim of this work was to elucidate the effect of temperature on cell mechanics using atomic force microscopy. We measured the complex shear modulus (G*) of human alveolar epithelial cells over a wide frequency range (0.1-25.6 Hz) at different temperatures (13-37 degrees C). In addition, we probed cell prestress by mapping the contractile forces that cells exert on the substrate by means of traction microscopy. To assess the role of actomyosin contraction in the temperature-induced changes in G* and cell prestress, we inhibited the Rho kinase pathway of the myosin light chain phosphorylation with Y-27632. Our results show that with increasing temperature, cells become stiffer and more solid-like. Cell prestress also increases with temperature. Inhibiting actomyosin contraction attenuated the temperature dependence of G* and prestress. We conclude that the dependence of cell mechanics with temperature is dominated by the contractile activity of molecular motors.

Keywords: Membrane Stress Failure, Frog Skeletal-Muscle, Extracellular-Matrix, Glass-Transition, Energy Landscape, Actin-Filaments, Living Cell, Single, Traction, Cytoskeleton

Malandrino, A., Planell, J. A., Lacroix, D., (2009). Statistical factorial analysis on the poroelastic material properties sensitivity of the lumbar intervertebral disc under compression, flexion and axial rotation Journal of Biomechanics 42, (16), 2780-2788

A statistical factorial analysis approach was conducted on a poroelastic finite element model of a lumbar intervertebral disc to analyse the influence of six material parameters (permeabilities of annulus, nucleus, trabecular vertebral bone, cartilage endplate and Young's moduli of annulus and nucleus) on the displacement, fluid pore pressure and velocity fields. Three different loading modes were investigated: compression, flexion and axial rotation. Parameters were varied considering low and high levels in agreement with values found in the literature for both healthy and degenerated lumbar discs. Results indicated that annulus stiffness and cartilage endplate permeability have a strong effect on the overall fluid- and solid-phase responses in all loading conditions studied. Nucleus stiffness showed its main relevance in compression while annulus permeability influenced mainly the annular pressure field. This study confirms the permeability's central role in biphasic modelling and highlights for the lumbar disc which experiments of material property characterization should be performed. Moreover, such sensitivity study gives important guidelines in poroelastic material modelling and finite element disc validation.

Keywords: Intervertebral disc, Permeability, Fractional factorial design, Design of experiments, Finite element analysis

Gimenez-Oya, V., Villacanas, O., Fernàndez-Busquets, X., Rubio-Martinez, J., Imperial, S., (2009). Mimicking direct protein-protein and solvent-mediated interactions in the CDP-methylerythritol kinase homodimer: a pharmacophore-directed virtual screening approach Journal of Molecular Modeling , 15, (8), 997-1007

The 2C-methylerythritol 4-phosphate (MEP) pathway for the biosynthesis of isopentenyl pyrophosphate and its isomer dimethylallyl pyrophosphate, which are the precursors of isoprenoids, is present in plants, in the malaria parasite Plasmodium falciparum and in most eubacteria, including pathogenic agents. However, the MEP pathway is absent from fungi and animals, which have exclusively the mevalonic acid pathway. Given the characteristics of the MEP pathway, its enzymes represent potential targets for the generation of selective antibacterial, antimalarial and herbicidal molecules. We have focussed on the enzyme 4-(cytidine 5'-diphospho)-2-C-methyl-D: -erythritol kinase (CMK), which catalyses the fourth reaction step of the MEP pathway. A molecular dynamics simulation was carried out on the CMK dimer complex, and protein-protein interactions analysed, considering also water-mediated interactions between monomers. In order to find small molecules that bind to CMK and disrupt dimer formation, interactions observed in the dynamics trajectory were used to model a pharmacophore used in database searches. Using an intensity-fading matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry approach, one compound was found to interact with CMK. The data presented here indicate that a virtual screening approach can be used to identify candidate molecules that disrupt the CMK-CMK complex. This strategy can contribute to speeding up the discovery of new antimalarial, antibacterial, and herbicidal compounds.

Keywords: Solvent-mediated interactions, Protein-protein interactions, Molecular dynamics, Drug design, Intensisty-fading MALDI-TOF mass spectrometry

Munoz, L. M., Casals, A., (2009). Improving the human-robot interface through adaptive multispace transformation IEEE Transactions on Robotics , 25, (5), 1208-1213

Teleoperation is essential for applications in which, despite the availability of a precise geometrical definition of the working area, a task cannot be explicitly programmed. This paper describes a method of assisted teleoperation that improves the execution of such tasks in terms of ergonomics, precision, and reduction of execution time. The relationships between the operating spaces corresponding to the human-robot interface triangle are analyzed. The proposed teleoperation aid is based on applying adaptive transformations between these spaces.

Keywords: Human factors, Human-robot interaction, Teleoperation

Puig, F., Gavara, N., Sunyer, R., Carreras, A., Farre, R., Navajas, D., (2009). Stiffening and contraction induced by dexamethasone in alveolar epithelial cells Experimental Mechanics , 49, (1), 47-55

The structural integrity of the alveolar monolayer, which is compromised during lung inflammation, is determined by the balance between cell-cell and cell-matrix tethering forces and the centripetal forces owing to cell viscoelasticity and contraction. Dexamethasone is an anti-inflammatory glucocorticoid with protective effects in lung injury. To determine the effects of Dexamethasone on the stiffness and contractility of alveolar epithelial cells. Cell stiffness (G') and average traction exerted by the cell (T) were measured by magnetic twisting cytometry and by traction microscopy, respectively. A549 cells were treated 24 h with Dexamethasone (1 mu M) or vehicle (control). G' and T were measured before and 5 min after challenge with the inflammatory mediator Thrombin (0.5 U/ml). Changes induced by Dexamethasone in actin cytoskeleton polymerization were assessed by the fluorescent ratio between F-actin and G-actin obtained by staining cells with phalloidin and DNase I. Dexamethasone significantly increased G' and T by 56% (n = 11; p < 0.01) and by 80% (n = 17; p < 0.05), respectively. Dexamethasone also increased F/G-actin ratio from 2.68 +/- 0.07 to 2.96 +/- 0.09 (n = 10; p < 0.05). The relative increase in stiffness and contraction induced by Thrombin in control cells was significantly (p < 0.05) reduced by Dexamethasone treatment: from 190 to 98% in G' and from 318 to 105% in T. The cytoskeleton remodelling and the increase in cell stiffness and contraction induced by Dexamethasone could account for its protective effect in the alveolar epithelium when subjected to inflammatory challenge.

Keywords: Cell mechanics, Cytoskeleton, Magnetic twisting cytometry, Traction microscopy, Respiratory diseases

Casals, A., Frigola, M., Amat, J., (2009). Robotics, a valuable tool in surgery Revista Iberoamericana de Automatica e Informatica Industrial , 6, (1), 5-19

Continuous advances on diagnostic techniques based on medical images, as well as the incorporation of new techniques in surgical instruments are progressively changing the new surgical procedures. Also, new minimally invasive techniques, which are currently highly consolidated, have produced significant advances, both from the technological and from the surgical treatment perspectives. The limitations that the manual realization of surgical interventions implies, in what refers to precision and accessibility, can be tackled with the help of robotics. In the same way, sensor based robot control techniques are opening new possibilities for the introduction of more improvements in these procedures, either relying on teleoperation, in which the surgeon and the robot establish their best synergy to get the optimal results, or by means of the automation of some specific actions or tasks. In this article the effect of robotics in the evolution of surgical techniques is described. Starting with a review of the robotics application fields, the article continues analyzing the methods and technologies involved in the process of robotizing surgical procedures, as well as the surgeon-robot interaction systems.

Keywords: Robotics, Medical Applications, Teleoperation, Biomedical Systems, Computer Aided Surgery, Human-Machine Interaction

Rodriguez-Segui, S. A., Bucior, I., Burger, M. M., Errachid, A., Fernàndez-Busquets, X., (2009). Application of the quartz crystal microbalance to the study of multivalent carbohydrate-carbohydrate adhesion Sensor Letters 6th Maghreb-Europe Meeting on Materials and Their Applications for Devices and Physical, Chemical and Biological Sensors , AMER SCIENTIFIC PUBLISHERS (Rabat, Morocco) 7, (5), 782-787

Carbohydrate-carbohydrate interactions in cell adhesion are being increasingly explored as important players in cell-cell and cell-extracellular matrix interactions that are characterized by finelytuned on-off rates. The emerging field of glycomics requires the application of new methodologies to the study of the generally weak and multivalent carbohydrate binding sites. Here we use the quartz crystal microbalance (QCM) for the analysis of the self-binding activity of the g200 glycan, a molecule of marine sponge origin that is responsible for Ca2+-dependent species-specific cell adhesion. The QCM has the advantages over other highly sensitive techniques of having only one of the interacting partners bound to a surface, and of lacking microfluidics circuits prone to be clogged by self-aggregating glycans. Our results show that g200 self-interaction is negligible in the absence of Ca2+. Different association kinetics at low and high Ca2+ concentrations suggest the existence of two different Ca2+ binding sites in g200. Finally, the observation of a non-saturable binding indicates that g200 has more than one self-adhesion site per molecule. This work represents the first report to date using the QCM to study carbohydrate-carbohydrate interactions involved in cell adhesion.

Keywords: Ca2+-dependent binding, Carbohydrate-carbohydrate interaction, Cell adhesion, Proteoglycan, Quartz crystal microbalance, Sponges

Banos, R. C., Pons, J. I., Madrid, C., Juarez, A., (2008). A global modulatory role for the Yersinia enterocolitica H-NS protein Microbiology , 154, (5), 1281-1289

The H-NS protein plays a significant role in the modulation of gene expression in Gram-negative bacteria. Whereas isolation and characterization of hns mutants in Escherichia coli, Salmonella and Shigella represented critical steps to gain insight into the modulatory role of H-NS, it has hitherto not been possible to isolate hns mutants in Yersinia. The hns mutation is considered to be deleterious in this genus. To study the modulatory role of H-NS in Yersinia we circumvented hns lethality by expressing in Y. enterocolitica a truncated H-NS protein known to exhibit anti-H-NS activity in E. coli (H-NST(EPEC)). Y. enterocolitica cells expressing H-NST(EPEC) showed an altered growth rate and several differences in the protein expression pattern, including the ProV protein, which is modulated by H-NS in other enteric bacteria. To further confirm that H-NST(EPEC) expression in Yersinia can be used to demonstrate H-NS-dependent regulation in this genus, we used this approach to show that H-NS modulates expression of the YmoA protein.

Keywords: Bacterial Proteins/biosynthesis/genetics/ physiology, DNA-Binding Proteins/biosynthesis/genetics/ physiology, Electrophoresis, Gel, Two-Dimensional, Gene Expression Profiling, Gene Expression Regulation, Bacterial, Genes, Essential, Proteome/analysis, RNA, Bacterial/biosynthesis, RNA, Messenger/biosynthesis, Reverse Transcriptase Polymerase Chain Reaction, Sequence Deletion, Yersinia enterocolitica/chemistry/genetics/growth & development/ physiology

Rodriguez, Segui, Bucior, I., Burger, M. M., Samitier, J., Errachid, A., Fernàndez-Busquets, X., (2007). Application of a bio-QCM to study carbohydrates self-interaction in presence of calcium Transducers '07 & Eurosensors Xxi, Digest of Technical Papers 14th International Conference on Solid-State Sensors, Actuators and Microsystems , IEEE (Lyon, France) 1-2, 1995-1998

In the past years, the quartz crystal microbalance (QCM) has been successfully applied to follow interfacial physical chemistry phenomena in a label free and real time manner. However, carbohydrate self adhesion has only been addressed partially using this technique. Carbohydrates play an important role in cell adhesion, providing a highly versatile form of attachment, suitable for biologically relevant recognition events in the initial steps of adhesion. Here, we provide a QCM study of carbohydrates' self-recognition in the presence of calcium, based on a species-specific cell recognition model provided by marine sponges. Our results show a difference in adhesion kinetics when varying either the calcium concentration (with a constant carbohydrate concentration) or the carbohydrate concentration (with constant calcium concentration).

Keywords: Biomedical materials, Calcium, Cellular biophysics, Microbalances, Porous materials, Quartz, Surface chemistry/ bio-QCM, Carbohydrates self-interaction, Quartz crystal microbalance, Interfacial physical chemistry phenomena, Carbohydrate self adhesion, Biologically relevant recognition events, Marine sponges, Adhesion kinetics, Calcium concentration, Carbohydrate concentration, Biosensors, Biomedical materials, Surface chemistry, Cellular biophysics