Phase coexistence in a monolayer of active particles induced by Marangoni flows

Thermally or chemically active colloids generate thermodynamic gradients in the solution in which they are immersed and thereby induce hydrodynamic flows that affect their dynamical evolution. Here we study a mean-field model for the many-body dynamics of a monolayer of active particles located at a fluid-fluid interface. In this case, the activity of the particles creates long-ranged Marangoni flows due to the response of the interface, which compete with the direct interaction between the particles. For the most interesting case of a $r^{-3}$ soft repulsion that models the electrostatic or magnetic interparticle forces, we show that an "onion-like" density distribution will develop within the monolayer. For a sufficiently large average density, two-dimensional phase transitions (freezing from liquid to hexatic, and melting from solid to hexatic) should be observable in a radially stratified structure. Furthermore, the analysis allows us to conclude that, while the activity may be too weak to allow direct detection of such induced Marangoni flows, it is relevant as a collective effect in the emergence of the experimentally observable spatial structure of phase coexistences noted above. Finally, the relevance of these results for potential experimental realizations is critically discussed.Comment: 11 page

Effective interaction between active colloids and fluid interfaces induced by Marangoni flows

We show theoretically that near a fluid-fluid interface a single active colloidal particle generating, e.g., chemicals or a temperature gradient experiences an effective force of hydrodynamic origin. This force is due to the fluid flow driven by Marangoni stresses induced by the activity of the particle; it decays very slowly with the distance from the interface, and can be attractive or repulsive depending on how the activity modifies the surface tension. We show that, for typical systems, this interaction can dominate the dynamics of the particle as compared to Brownian motion, dispersion forces, or self-phoretic effects. In the attractive case, the interaction promotes the self-assembly of particles into a crystal-like monolayer at the interface.Comment: The manuscript proper and the supplementary information have been merged consecutively into a single PDF fil

Fuzzy measures on the Gene Ontology for gene product similarity

pre-printOne of the most important objects in bioinformatics is a gene product (protein or RNA). For many gene products, functional information is summarized in a set of Gene Ontology (GO) annotations. For these genes, it is reasonable to include similarity measures based on the terms found in the GO or other taxonomy. In this paper, we introduce several novel measures for computing the similarity of two gene products annotated with GO terms. The fuzzy measure similarity (FMS) has the advantage that it takes into consideration the context of both complete sets of annotation terms when computing the similarity between two gene products. When the two gene products are not annotated by common taxonomy terms, we propose a method that avoids a zero similarity result. To account for the variations in the annotation reliability, we propose a similarity measure based on the Choquet integral. These similarity measures provide extra tools for the biologist in search of functional information for gene products. The initial testing on a group of 194 sequences representing three proteins families shows a higher correlation of the FMS and Choquet similarities to the BLAST sequence similarities than the traditional similarity measures such as pairwise average or pairwise maximum

Smart Processing for Systems under Uncertainty or Perturbation

-----Eneko Osaba would like to thank the Basque Government for its funding through the EMAITEK program

Lifestyle Changes and Weight Loss: Effects in PCOS

Even though controversies surrounding the polycystic ovary syndrome are not yet close to be solved, its clinical manifestations are well known—insulin resistance and obesity, hirsutism, irregular and anovulatory menstrual cycles. The treatment of polycystic ovarian syndrome (PCOS) is mainly symptomatic as its etiology is not yet clear. Lifestyle changes are the primary therapy in overweight and obese women with PCOS. According to majority of the studies, lifestyle changes are the most effective form of treatment not only for weight loss but also for the improvement of insulin sensitivity, decreasing incidence of metabolic syndrome and type 2 diabetes. Studies also show that weight loss has fertility benefits by restoring ovulatory cycles. Although initial studies researching pharmacologic treatment were showing excellent results concerning the weight loss, maintenance of weight loss and reduction of cardiovascular risks, some of these drugs were in the end, has proven to actually increase the risk for cardiovascular events and were removed from the market. Bariatric surgery has been demonstrated to improve or even cure type 2 diabetes, hypertension, hyperlipidemia, and obstructive sleep apnea. More so, there are studies that reported complete resolution of all features of PCOS, even hirsutism, hyperandrogenism, anovulation, and menstrual irregularity

Effective Interaction between Active Colloids and Fluid Interfaces Induced by Marangoni Flows

We show theoretically that near a fluid-fluid interface a single active colloidal particle generating, e.g., chemicals or a temperature gradient experiences an effective force of hydrodynamic origin. This force is due to the fluid flow driven by Marangoni stresses induced by the activity of the particle; it decays very slowly with the distance from the interface, and can be attractive or repulsive depending on how the activity modifies the surface tension. We show that, for typical systems, this interaction can dominate the dynamics of the particle as compared to Brownian motion, dispersion forces, or self-phoretic effects. In the attractive case, the interaction promotes the self-assembly of particles into a crystal-like monolayer at the interface.COST Action MP1106European Cooperation in Science and Technology MP110

A Novel Web-Based Depth Video Rewind Approach toward Fall Preventive Interventions in Hospitals

Falls in the hospital rooms are considered a huge burden on healthcare costs. They can lead to injuries, extended length of stay, and increase in cost for both the patients and the hospital. It can also lead to emotional trauma for the patients and their families [1]. Having Microsoft Kinects installed in the hospital rooms to capture and process every movement in the room, we deployed our previously developed fall-detection system to detect naturally occurring falls, generate a real-time fall alarm and broadcast it to hospital nurses for immediate intervention. These systems also store a processed and reduced version of the 3D depth videos on a central file storage to provide information to the dedicated nursing team for post-fall quality improvement process. The compression technique that helps reducing video size by omitting non-movement frames from it also makes it almost impossible for the hospital staff to find the event that led to a fall alarm. There was a need to visualize fall events and the video contents accordingly. In this paper, we describe a web-application with a handy user interface to easily search among terabytes of depth videos to facilitate the finding and reviewing of the chain of events that lead to a patient fall. We will also discuss the improvements in the new version of the application which reduced the size of transferred videos by converting them to MP4 videos and makes the application platform free. This improvements in speed and compatibility on different browsers, caused more user satisfaction and more frequent use of the web-application

Self-Motility of an Active Particle Induced by Correlations in the Surrounding Solution

Current models of phoretic transport rely on molecular forces creating a “diffuse” particle-fluid interface. We investigate theoretically an alternative mechanism, in which a diffuse interface emerges solely due to a nonvanishing correlation length of the surrounding solution. This mechanism can drive self-motility of a chemically active particle. Numerical estimates indicate that the velocity can reach micrometers per second. The predicted phenomenology includes a bilinear dependence of the velocity on the activity and a possible double velocity reversal upon varying the correlation length.Spanish Government through Grant No. FIS2017-87117-P (partially financed by FEDER funds

Cardiovascular function and ballistocardiogram: a relationship interpreted via mathematical modeling

Objective: to develop quantitative methods for the clinical interpretation of the ballistocardiogram (BCG). Methods: a closed-loop mathematical model of the cardiovascular system is proposed to theoretically simulate the mechanisms generating the BCG signal, which is then compared with the signal acquired via accelerometry on a suspended bed. Results: simulated arterial pressure waveforms and ventricular functions are in good qualitative and quantitative agreement with those reported in the clinical literature. Simulated BCG signals exhibit the typical I, J, K, L, M and N peaks and show good qualitative and quantitative agreement with experimental measurements. Simulated BCG signals associated with reduced contractility and increased stiffness of the left ventricle exhibit different changes that are characteristic of the specific pathological condition. Conclusion: the proposed closed-loop model captures the predominant features of BCG signals and can predict pathological changes on the basis of fundamental mechanisms in cardiovascular physiology. Significance: this work provides a quantitative framework for the clinical interpretation of BCG signals and the optimization of BCG sensing devices. The present study considers an average human body and can potentially be extended to include variability among individuals