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Fraiman D.,University of San Andres | 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. Source

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. Source

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. Source

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. Source

Reis S.D.S.,City College of New York | Reis S.D.S.,Federal University of Ceara | 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. Source

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