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Fraiman D.,University of San Andrés | Fraiman D.,CONICET | Dawson S.P.,FCEN UBA | Dawson S.P.,CONICET
Physical Biology | Year: 2014

Puffs are localized Ca2 + signals that arise in oocytes in response to inositol 1,4,5-trisphosphate (IP3). They are the result of the liberation of Ca2 + from the endoplasmic reticulum through the coordinated opening of IP3 receptor/channels clustered at a functional release site. The presence of buffers that trap Ca2 + provides a mechanism that enriches the spatio-temporal dynamics of cytosolic calcium. The expression of different types of buffers along the cell's life provides a tool with which Ca2 + signals and their responses can be modulated. In this paper we extend the stochastic model of a cluster of IP3R-Ca2 + channels introduced previously to elucidate the effect of buffers on sequences of puffs at the same release site. We obtain analytically the probability laws of the interpuff time and of the number of channels that participate of the puffs. Furthermore, we show that under typical experimental conditions the effect of buffers can be accounted for in terms of a simple inhibiting function. Hence, by exploring different inhibiting functions we are able to study the effect of a variety of buffers on the puff size and interpuff time distributions. We find the somewhat counter-intuitive result that the addition of a fast Ca 2 + buffer can increase the average number of channels that participate of a puff. © 2014 IOP Publishing Ltd.

Petroni A.,FCEN UBA | Carbajal M.J.,FCEN UBA | Sigman M.,Torcuato Di Tella University
PLoS ONE | Year: 2015

The neurobiology of reaching has been extensively studied in human and non-human primates. However, the mechanisms that allow a subject to decide-without engaging in explicit action-whether an object is reachable are not fully understood. Some studies conclude that decisions near the reach limit depend on motor simulations of the reaching movement. Others have shown that the body schema plays a role in explicit and implicit distance estimation, especially after motor practice with a tool. In this study we evaluate the causal role of multisensory body representations in the perception of reachable space. We reasoned that if body schema is used to estimate reach, an illusion of the finger size induced by proprioceptive stimulation should propagate to the perception of reaching distances. To test this hypothesis we induced a proprioceptive illusion of extension or shrinkage of the right index finger while participants judged a series of LEDs as reachable or non-reachable without actual movement. Our results show that reach distance estimation depends on the illusory perceived size of the finger: illusory elongation produced a shift of reaching distance away from the body whereas illusory shrinkage produced the opposite effect. Combining these results with previous findings, we suggest that deciding if a target is reachable requires an integration of body inputs in high order multisensory parietal areas that engage in movement simulations through connections with frontal premotor areas. Copyright: © 2015 Petroni et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Pedre S.,FCEN UBA | Krajnik T.,Czech Technical University | Todorovich E.,FCE UNICEN | Borensztejn P.,FCEN UBA
Journal of Real-Time Image Processing | Year: 2016

Many image processing applications need real-time performance, while having restrictions of size, weight and power consumption. Common solutions, including hardware/software co-designs, are based on Field Programmable Gate Arrays (FPGAs). Their main drawback is long development time. In this work, a co-design methodology for processor-centric embedded systems with hardware acceleration using FPGAs is proposed. The goal of this methodology is to achieve real-time embedded solutions, using hardware acceleration, but achieving development time similar to that of software projects. Well established methodologies, techniques and languages from the software domain—such as Object-Oriented Paradigm design, Unified Modelling Language, and multithreading programming—are applied; and semiautomatic C-to-HDL translation tools and methods are used and compared. The methodology is applied to achieve an embedded implementation of a global vision algorithm for the localization of multiple robots in an e-learning robotic laboratory. The algorithm is specifically developed to work reliably 24/7 and to detect the robot’s positions and headings even in the presence of partial occlusions and varying lighting conditions expectable in a normal classroom. The co-designed implementation of this algorithm processes 1,600 × 1,200 pixel images at a rate of 32 fps with an estimated energy consumption of 17 mJ per frame. It achieves a 16× acceleration and 92 % energy saving, which compares favorably with the most optimized embedded software solutions. This case study shows the usefulness of the proposed methodology for embedded real-time image processing applications. © 2013, Springer-Verlag Berlin Heidelberg.

Pedre S.,FCEN UBA | Krajnik T.,Czech Technical University | Todorovich E.,FCE UNICEN | Borensztejn P.,FCEN UBA
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012

Many image processing applications need real time performance, while having restrictions of size, weight and power consumption. These include a wide range of embedded systems from remote sensing applications to mobile phones. FPGA-based solutions are common for these applications, their main drawback being long development time. In this work a co-design methodology for processor-centric embedded systems with hardware acceleration using FPGAs is applied to an image processing method for localization of multiple robots. The goal of the methodology is to achieve a real-time embedded solution using hardware acceleration, but with development time similar to software projects. The final embedded co-designed solution processes 1600×1200 pixel images at a rate of 25 fps, achieving a 12.6× acceleration from the original software solution. This solution runs with a comparable speed as up-to-date PC-based systems, and it is smaller, cheaper and demands less power. © 2012 Springer-Verlag.

Sigaut L.,FCEN UBA | Ponce M.L.,FCEN UBA | Colman-Lerner A.,Institute Fisiologia | Dawson S.P.,FCEN UBA
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2010

In many cell-signaling pathways information is transmitted via the diffusion of messenger molecules. In most cases, messengers react with other substances and diffuse at the same time. Effective diffusion coefficients may be introduced to characterize the net transport rate that results from the combined effect of these two processes. It was shown in that even in the simplest scenario in which one bimolecular reaction is involved, two different effective coefficients are relevant. One gives the rate at which small perturbations spread out with time while the other relates the mean square displacement of a single particle to the time elapsed. They coincide in the absence of reactions but may be very different in other cases. Optical techniques provide a relatively noninvasive means by which transport rates can be estimated. In the above mentioned paper it was discussed why, under certain conditions, fluorescence recovery after photobleaching (FRAP), a technique commonly used to estimate diffusion rates in cells, provides information on one of the two effective coefficients. In the present paper we show that, under the same conditions, another commonly used optical technique, fluorescence correlation spectroscopy (FCS), gives information on the other one. This opens up the possibility of combining experiments to obtain information that goes beyond effective transport rates. In the present paper we discuss different ways to do so. © 2010 The American Physical Society.

Reis S.D.S.,City College of New York | Reis S.D.S.,Federal University of Ceará | Hu Y.,City College of New York | Babino A.,FCEN UBA | And 6 more authors.
Nature Physics | Year: 2014

Networks in nature do not act in isolation, but instead exchange information and depend on one another to function properly. Theory has shown that connecting random networks may very easily result in abrupt failures. This finding reveals an intriguing paradox: if natural systems organize in interconnected networks, how can they be so stable? Here we provide a solution to this conundrum, showing that the stability of a system of networks relies on the relation between the internal structure of a network and its pattern of connections to other networks. Specifically, we demonstrate that if interconnections are provided by network hubs, and the connections between networks are moderately convergent, the system of networks is stable and robust to failure. We test this theoretical prediction on two independent experiments of functional brain networks (in task and resting states), which show that brain networks are connected with a topology that maximizes stability according to the theory.

Olle Resa C.P.,Fellow of National Agency ANPCyT | Olle Resa C.P.,University of Buenos Aires | Jagus R.J.,University of Buenos Aires | Gerschenson L.N.,FCEN UBA
Materials Science and Engineering C | Year: 2014

In this paper, films based on tapioca starch and containing nisin, natamycin and glycerol were characterized in relation to their physicochemical properties, roughness and hydrophobicity. The content of glycerol affected the mechanical properties of the films studied and the roughness and it was observed an increase in WVP with the increase in glycerol content. The addition of antimicrobials affected the mechanical properties, being nisin the one that produced the greater decrease in the Young modulus. The color was highly affected by the joint presence of natamycin and nisin, which increased the yellow index. The contact angle increased with antimicrobial addition indicating a decrease in hydrophilicity. Nisin also affected the roughness of the films. Water vapor permeability was slightly reduced by the presence of natamycin. It was observed that water vapor permeability and contact angle were correlated with the roughness of the films. © 2014 Elsevier B.V.

Robledo F.A.,CONICET | Vera C.,CONICET | Penalba O.C.,FCEN UBA
International Journal of Climatology | Year: 2016

A singular value decomposition (SVD) analysis was performed jointly on the daily intensity of extreme rainfall (DIER) over Argentina and sea surface temperature (SST) anomalies from 17.5°N-90°S to describe and understand the influence of the large-scale variability of the SSTs on the regional extreme rainfall events for spring summer, autumn and winter. Three main leading modes were identified in agreement with previous works. Mode 1 activity is strongly related to El Niño-Southern Oscillation (ENSO). Warm anomalies in the central-eastern tropical Pacific and western Indian Ocean induce circulation anomalies extended along the South Pacific and the development of a continental-scale circulation gyre in South America promoting moisture convergence, and in turn favouring DIER positive anomalies, in eastern Argentina. The combined influence of SST anomalies in the tropical Atlantic and western tropical Pacific characterizes Mode 2 activity, which induces an anticyclonic (cyclonic) circulation gyre in southeastern South America promoting anomalous moisture convergence (divergence) and thus positive (negative) DIER anomalies in eastern Argentina in spring and fall (summer and winter). Finally, Mode 3 activity is also influenced by SST anomalies in tropical central-eastern Pacific from winter to summer. The associated teleconnections contribute to the development of a cyclonic circulation mainly influencing southeastern South America (SESA) circulation to the north of 30°S from summer to winter, and further south in spring. © 2016 Royal Meteorological Society.

Ipina E.P.,FCEN UBA | Dawson S.P.,FCEN UBA
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2013

Diffusion is one of the main transport processes that occur inside cells determining the spatial and time distribution of relevant action molecules. In most cases these molecules not only diffuse but also interact with others as they get transported. When these interactions occur faster than diffusion the resulting transport can be characterized by "effective diffusion coefficients" that depend on both the reaction rates and the "free" diffusion coefficients. Fluorescence correlation spectroscopy (FCS) gives information on effective rather than free diffusion coefficients under this condition. In the present paper we investigate what coefficients can be drawn from FCS experiments for a wide range of values of the ratio of reaction to diffusion time scales, using different fitting functions. We find that the effective coefficients can be inferred with relatively small errors even when the condition of fast reactions does not exactly hold. Since the diffusion time scale depends on the size of the observation volume and the reaction time scale depends on concentrations, we also discuss how by changing either one or the other property one can switch between the two limits and extract more information on the system under study. © 2013 American Physical Society.

Robledo F.A.,CONICET | Penalba O.C.,FCEN UBA | Bettolli M.L.,CONICET
International Journal of Climatology | Year: 2013

A Singular value decomposition (SVD) analysis was performed jointly on the daily intensity of extreme rainfall (DIER) over Argentina and the sea surface temperature (SST) of all the oceans from 17.5°N to 90°S in order to identify the large-scale variability of the SSTs related to extreme rainfall, in the period 1962-2005. The main objective of the article is to objectively recognize regions of the tropical and subtropical oceans that could be related with the extreme rainfall over Argentina. Spring is the season that is best represented by the first mode, accounting for up to 45% of the covariance between the DIER and SST. The first SVD mode of spring, summer and autumn presents a pattern of SST relating to the El Niño-Southern Oscillations (ENSO) phenomena with an enhanced DIER in different zones of centre and east of Argentina. In the second SVD mode of spring and summer, the SST patterns show cold conditions in the tropical and subtropical Atlantic and near Indonesia with an enhancement of the DIER in the centre and east of Argentina. These modes show a significant decadal variability. In the third SVD mode of spring and summer, the SST patterns present warm and cold conditions in the Indian Ocean and the centre and western Pacific Ocean (PO) with decreased rainfall in the northern and eastern portion of Argentina, respectively. This mode shows a significant period of temporal variability of around 14 years. The third mode of autumn presents warm conditions in the tropical Atlantic and the southwest PO with a low DIER in the centre and east of Argentina. This mode also presents temporal variability of around 14 years. The correlation between each mode derived from analysis of SVD and climate indices related with SST were computed. © 2012 Royal Meteorological Society.

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