Ciudad Universitaria

Buenos Aires, Argentina

Ciudad Universitaria

Buenos Aires, Argentina
Time filter
Source Type

Matsudo C.M.,Ciudad Universitaria | Salio P.V.,Ciudad Universitaria
Atmospheric Research | Year: 2011

Conventional surface data and quantitative estimations of precipitation are used to document the occurrence and spatial distribution of severe weather phenomena associated with deep moist convection over southeastern South America.Data used in this paper are 24-hour rainfall, maximum hourly gusts and present weather reports from the surface station network for Argentina to the north of 40°S and cover the period 2000-2005. Hourly rainfall estimated with the CMORPH technique (CPC MORPHing technique, R. J. Joyce et al., 2004) is included in the analysis in order to increase the density of the precipitation database from January 2003 to December 2005. Extreme events are detected by means of a 95th-percentile analysis of the 24-hour rainfall and wind; values greater than 30mm and 25ms-1 respectively are considered extreme in the study area. These results are related to the presence of deep convection by considering the 235K and 218K cloud shield evolution in Geostationary Operational Environmental Satellite-12 Infrared (GOES-IR) imagery evaluated by the Forecasting and Tracking of Cloud Cluster (FORTRACC) technique. Rainfall above 30mmday-1 and present convection-related weather events tend to occur in the northeast of the country.Finally, an analysis is made of the relationship between severe phenomena and the location and lifecycle of Mesoscale Convective Systems (MCSs) defined by the 218K or 235K levels. According to the reports, favorable locations for severe weather concentrate to the northeast of the cloud shield anvil centroid although most of the cases are found in the northwest. This feature can be seen in systems with anvil areas larger than 250,000km2 in association to the predominant mid-level wind shear direction from the northwest over the area. Moreover, systems with centers located north of 30°S present a more circular shape while those to the south are more elongated with a NW-SE main axis clearly related to the presence and interaction with frontal zones over the area. Most of the events occur previous to the moment when the systems reach their maximum extension, between 2 and 10h after the initiation of the system depending on the size of the MCSs. © 2010 Elsevier B.V.

Crespo F.,Centro Militar Of Criacaballar | Gosalvez J.,Autonomous University of Madrid | Gutierrez-Cepeda L.,Ciudad Universitaria | Serres C.,Complutense University of Madrid | Johnston S.D.,University of Queensland
Reproduction in Domestic Animals | Year: 2013

Stallion spermatozoa recovered and examined immediately after colloidal centrifugation resulted in a higher straight-line velocity (VSL) than sperm processed using direct conventional centrifugation (p=0.000), but there was no differences in the progressive motility or sperm DNA fragmentation (SDF) as determined by the sperm chromatin dispersion assay. However, when centrifuged spermatozoa were incubated at 37°C for 24h to determine the rate of SDF (r-SDF), a lower r-SDF (p=0.0011) was observed in those sperm recovered after colloidal separation (0.5±0.1%/h) compared to direct (1.2±0.4%/h) or no centrifugation (r-SDF = 1.2 ±0.3%/h). These results confirm that colloidal separation of stallion spermatozoa results in prolonged sperm DNA longevity, but these differences were only apparent following a period of incubation and dynamic assessment. Consequently, we strongly recommend the use of the dynamic form of the SDF assay for evaluating centrifugation and/or other ex vivo procedures, as a single basal assessment of SDF may inadvertently result in a false-positive evaluation of DNA quality. © 2012 Blackwell Verlag GmbH.

Auguste A.J.,University of Texas Medical Branch | Lemey P.,Rega Institute for Medical Research | Bergren N.A.,University of Texas Medical Branch | Giambalvo D.,Ciudad Universitaria | And 5 more authors.
Emerging Infectious Diseases | Year: 2015

Phylogenetic analysis of yellow fever virus (YFV) strains isolated from Venezuela strongly supports YFV maintenance in situ in Venezuela, with evidence of regionally independent evolution within the country. However, there is considerable YFV movement from Brazil to Venezuela and between Trinidad and Venezuela. © 2015, Centers for Disease Control and Prevention (CDC). All rights reserved.

Colin P.,National Autonomous University of Mexico | Avila-Reese V.,National Autonomous University of Mexico | Roca-Fabrega S.,Ciudad Universitaria | Valenzuela O.,National Autonomous University of Mexico
Astrophysical Journal | Year: 2016

We introduce a new set of eight Milky Way-sized cosmological simulations performed using the AMR code Adaptive Refinement Tree + Hydrodynamics in a λCDM cosmology. The set of zoom-in simulations covers present-day virial masses that range from 8.3x1011M⊙ to 1.56 x1012 M⊙and is carried out with our simple but effective prescriptions for deterministic star formation (SF) and "explosive" stellar feedback. The work focuses on showing the goodness of the simulated set of field" Milky Way-sized galaxies. To this end, we compare some of the predicted physical quantities with the corresponding observed ones. Our results are as follows. (a) In agreement with some previous works, we found curves of circular velocity that are flat or slightly peaked. (b) All simulated galaxies with a significant disk component are consistent with the observed Tully-Fisher, radius-mass, and cold gas-stellar mass correlations of late-type galaxies. (c) The disk-dominated galaxies have stellar specific angular momenta in agreement with those of late-type galaxies, with values around 103 km s-1 kpc-1. (d) The SF rates at z=0 of all runs but one are comparable to those estimated for the star-forming galaxies. (e) The two most spheroid-dominated galaxies formed in halos with late active merger histories and late bursts of SF, but the other run that ends also dominated by a spheroid never had major mergers. (f) The simulated galaxies lie in the semiempirical correlation of stellar to halo mass of local central galaxies, and those that end up as disk-dominated evolve mostly along the low-mass branch of this correlation. Moreover, the growth histories of baryonic and stellar mass of these galaxies are proportional to their growth histories of halo mass over the last 6.5-10 Gyr. (g) Within the virial radii of the simulations, ≈25%-50% of the baryons are missed; the amount of gas in the halo is similar to the amount in stars in the galaxy, and most of this gas is in the warm-hot phase. (h) The profiles of z∼0 vertical gas velocity dispersion, σz(r), are nearly flat and can be mostly explained by the kinetic energy injected by stars. The average values of σz increase at higher redshifts, following roughly the shape of the SF history.

Mosquera J.C.,Technical University of Madrid | Gargoum L.A.,Ciudad Universitaria
International Journal of Steel Structures | Year: 2014

A practical method to achieve the minimum weight design of 2D steel frames, built with European standard I-shaped crosssections, is hereby presented. The optimization methodology consists of an incremental iterative technique. It is based on the addition of lacking material by successive increasing of the size of the most stressed member. Second-order effects are considered in this approach. Eurocode 3 restrictions for both the Ultimate Limit States (ULS) and Serviceability Limit States (SLS) are also taken into account. The numerical procedure has been coded in MatLab. The proposed method gives, with reasonably small computing effort, a sound approach to the exact optimum solution. An illustrative example of applying this methodology for designing a steel portal frame is presented; besides, its results are validated for a classical benchmark problem. © 2014 Korean Society of Steel Construction and Springer-Verlag Berlin Heidelberg.

Cisneros B.E.J.,Ciudad Universitaria
CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources | Year: 2011

This paper is a review of the international literature concerning both the positive and negative effects on the environment and public health of the use of treated or non-treated wastewater for agricultural irrigation. It includes not only physical but also social and economic aspects. The extent of the use of treated and non-treated wastewater for agriculture is discussed along with its drivers. The data clearly show that non-treated wastewater is used more commonly than treated wastewater. This occurs mainly in around urban and peri-urban areas where municipal wastewater is produced that is better suited to this practice. The impacts observed on agricultural production, human health, the quality of the irrigation water, groundwater and surface water sources, food security, animal health, the local economy, reduction of poverty and food exports are presented, considering especially developing countries. These factors are further discussed to gain an understanding of how the practice, if well managed, contributes to sustainable development. Barriers to increasing the reuse of wastewater to irrigate are explained, considering the social perception in both developed and developing countries. The importance of reusing wastewater to reclaim water and nutrients are summarized. The positive and negative impacts resulting from the expected increase in the practice are discussed, together with control measures to obtain maximum benefits. © CAB International 2011.

Leff E.,Ciudad Universitaria
Environmental Ethics | Year: 2012

From the beginning of the environmental crisis, a constellation of ecosophies, theories, ideologies, discourses, and narratives have irrupted in the emergent complex ground of environmental philosophy and political ecology. In this non-unifyable field of forces, sociological analysis has been intended to sketch maps and derive typologies to order the different views and standpoints in science, ecological thinking, and environmental ethics so as to guide academic research or political action. From this will to set and settle differences in thought and strategy, a diversity of environmentalisms has emerged; the lines are drawn from North to South, rich to poor, masculine to feminine, naturalism to culturalism. Environmentalisms differentiate their sources, attachments, and derivations from mother theories and their approaches from different disciplines. Thus, the prefix eco- or the adjective environmental are attached to traditional disciplines. Latin American environmental thinking draws its sources from critical philosophical thought; it differs from other systems of thought by a radical epistemological concept of environment; and it acquires its identity from the cultural heritage of its peoples and the ecological potentials of its territories.

Aldana-Bobadilla E.,Ciudad Universitaria | Alfaro-Perez C.,Ciudad Universitaria
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2015

A common task in data analysis is to find the appropriate data sample whose properties allow us to infer the parameters of the data population. The most frequently dilemma related to sampling is how to determine the optimal size of the sample. To solve it, there are typical methods based on asymptotical results from the Central Limit Theorem. However, the effectiveness of such methods is bounded by several considerations as the sampling strategy (simple, stratified, cluster-based, etc.), the size of the population or even the dimensionality of the space of the data. In order to avoid such constraints, we propose a method based on a measure of information of the data in terms of Shannon’s Entropy. Our idea is to find the optimal sample of size N whose information is as similar as possible to the information of the population, subject to several constraints. Finding such sample represents a hard optimization problem whose feasible space disallows the use of traditional optimization techniques. To solve it, we resort to Genetic Algorithms. We test our method with synthetic datasets; the results show that our method is suitable. For completeness, we used a dataset from a real problem; the results confirm the effectiveness of our proposal and allow us to visualize different applications. © Springer International Publishing Switzerland 2015.

Raimondo F.,Ciudad Universitaria | Kamienkowski J.E.,University of Buenos Aires | Sigman M.,University of Buenos Aires | Fernandez Slezak D.,Ciudad Universitaria
Computational Intelligence and Neuroscience | Year: 2012

In recent years, Independent Component Analysis (ICA) has become a standard to identify relevant dimensions of the data in neuroscience. ICA is a very reliable method to analyze data but it is, computationally, very costly. The use of ICA for online analysis of the data, used in brain computing interfaces, results are almost completely prohibitive. We show an increase with almost no cost (a rapid video card) of speed of ICA by about 25 fold. The EEG data, which is a repetition of many independent signals in multiple channels, is very suitable for processing using the vector processors included in the graphical units. We profiled the implementation of this algorithm and detected two main types of operations responsible of the processing bottleneck and taking almost 80 of computing time: vector-matrix and matrix-matrix multiplications. By replacing function calls to basic linear algebra functions to the standard CUBLAS routines provided by GPU manufacturers, it does not increase performance due to CUDA kernel launch overhead. Instead, we developed a GPU-based solution that, comparing with the original BLAS and CUBLAS versions, obtains a 25x increase of performance for the ICA calculation. © Copyright 2012 Federico Raimondo et al.

Lopez L.,Ciudad Universitaria | Piegari E.,Ciudad Universitaria | Sigaut L.,Ciudad Universitaria | Dawson S.P.,Ciudad Universitaria
Frontiers in Physiology | Year: 2012

Many natural phenomena display "self-organized criticality" (SOC), (Bak et al., 1987). This refers to spatially extended systems for which patterns of activity characterized by different lengthscales can occur with a probability density that follows a power law with pattern size. Differently from power laws at phase transitions, systems displaying SOC do not need the tuning of an external parameter. Here we analyze intracellular calcium (Ca 2+) signals, a key component of the signaling toolkit of almost any cell type. Ca2+ 2+ signals can either be spatially restricted (local) or propagate throughout the cell (global). Different models have suggested that the transition from local to global signals is similar to that of directed percolation. Directed percolation has been associated, in turn, to the appearance of SOC. In this paper we discuss these issues within the framework of simple models of Ca 2+ signal propagation. We also analyze the size distribution of local signals ("puffs") observed in immature Xenopus Laevis oocytes. The puff amplitude distribution obtained from observed local signals is not Gaussian with a noticeable fraction of large size events. The experimental distribution of puff areas in the spatio-temporal record of the image has a long tail that is approximately log-normal. The distribution can also be fitted with a power law relationship albeit with a smaller goodness of fit. The power law behavior is encountered within a simple model that includes some coupling among individual signals for a wide range of parameter values. An analysis of the model shows that a global elevation of the Ca 2+ concentration plays a major role in determining whether the puff size distribution is long-tailed or not. This suggests that Ca 2+-clearing from the cytosol is key to determine whether IP3-mediated Ca 2+ signals can display a SOC-like behavior or not. © 2012 Lopez, Piegari, Sigaut and Ponce Dawson.

Loading Ciudad Universitaria collaborators
Loading Ciudad Universitaria collaborators