National University of Central Buenos Aires

www.unicen.edu.ar
Olavarria, Argentina

The National University of Central Buenos Aires is a public institution of higher learning located in Tandil, a city in the central region of Buenos Aires Province, Argentina. It was founded in 1974 as part of University of Buenos Aires Professor Alberto Taquini's plan to geographically diversify Argentina's National University system.Established with the unification of a private school and a campus of the National University of the South, the university includes 10 schools offering 21 undergraduate, 58 graduate, and 19 post-graduate degrees. It maintains secondary campuses in Azul, Olavarría and Quequén. Wikipedia.


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Yannibelli V.,National University of Central Buenos Aires | Amandi A.,CONICET
Engineering Optimization | Year: 2013

In this article, the project scheduling problem is addressed in order to assist project managers at the early stage of scheduling. Thus, as part of the problem, two priority optimization objectives for managers at that stage are considered. One of these objectives is to assign the most effective set of human resources to each project activity. The effectiveness of a human resource is considered to depend on its work context. The other objective is to minimize the project makespan. To solve the problem, a multi-objective evolutionary algorithm is proposed. This algorithm designs feasible schedules for a given project and evaluates the designed schedules in relation to each objective. The algorithm generates an approximation to the Pareto set as a solution to the problem. The computational experiments carried out on nine different instance sets are reported. © 2013 Copyright Taylor and Francis Group, LLC.


Tironi A.,National University of Central Buenos Aires | Trezza M.A.,National University of Central Buenos Aires | Scian A.N.,CONICET | Irassar E.F.,National University of Central Buenos Aires
Cement and Concrete Composites | Year: 2013

The pozzolanic activity of calcined clays depends on the type and amount of clayed minerals, the nature and amount of impurities, the thermal treatment used for its activation and the specific surface obtained after calcination. In this paper, four test methods for assessment the pozzolanic activity on seven calcined clays (five kaolinites and two bentonites) were analyzed. Natural clays were calcined and investigated by two direct tests (Frattini and saturated lime) and two indirect tests (strength activity index and electrical conductivity). Frattini test and the strength activity index (SAI) were found to be the most accurate and reliable methods to assess pozzolanic activity over time. Frattini test evaluates accurately the calcium hydroxide (CH) consumption by pozzolanic reaction, and SAI test discriminates the real contribution of pozzolanic reaction to densification of microstructure. The electrical conductivity (EC) and the lime consumption (LC) tests evaluate the ability of pozzolanic material to fix CH during the first time of contact and their results are correlated with the specific surface of calcined clay.© 2012 Elsevier Ltd. All rights reserved.


Benvenuto O.G.,National University of La Plata | Benvenuto O.G.,National University of Central Buenos Aires | Bersten M.C.,University of Tokyo | Nomoto K.,University of Tokyo
Astrophysical Journal | Year: 2013

We perform binary stellar evolutionary calculations following the simultaneous evolution of both stars in the system to study a potential progenitor system for the Type IIb supernova 2011dh. Pre-explosion photometry as well as light-curve modeling has provided constraints on the physical properties of the progenitor system. Here, we present a close binary system (CBS) that is compatible with such constraints. The system is formed by stars of solar composition with 16 M⊙ + 10 M⊙ on a circular orbit with an initial period of 125 days. The primary star ends its evolution as a yellow supergiant with a mass of ≈4 M⊙, a final hydrogen content of ≈(3-5) × 10-3 M⊙, and with an effective temperature and luminosity in agreement with the Hubble Space Telescope (HST) pre-explosion observations of SN 2011dh. These results are nearly insensitive to the adopted accretion efficiency factor β. At the time of explosion, the companion star has an effective temperature of 22,000-40,000 K, depending on the value of β, and lies near the zero-age main sequence. Considering the uncertainties in the HST pre-SN photometry, the secondary star is only marginally detectable in the bluest observed band. CBSs, as opposed to single stars, provide a natural frame to explain the properties of SN 2011dh. © 2013. The American Astronomical Society. All rights reserved..


Ekeroth R.M.A.,National University of Central Buenos Aires | Lester M.,National University of Central Buenos Aires
Plasmonics | Year: 2013

The optical extinction spectra of micro- and nanoparticles made up of high-contrast dielectrics exhibit a set of very intense peaks due to the excitations of morphology-dependent resonances (MDRs). These kind of resonances are well known at the microscopic scale as whispering gallery modes. In this work, we study numerically the optical spectra corresponding to a core-shell structure composed by an infinite silicon nanowire coated with a silver shell. This structure shows a combination of both excitations: MDRs and the well-known surface plasmon resonances in dielectric metallic core-shell nanoparticles (Ekeroth Abraham and Lester, Plasmon 2012). We compute in an exact form the complete electromagnetic response for both bare and coated silicon nanowires in the range of 24-200 nm of cross-sectional sizes. We take into account an experimental bulk dielectric function of crystalline silicon and silver by using a correction by size of the metal dielectric function. In this paper, we consider small silver shells in the range of 1-10 nm of thickness as coatings. We analyze the optical response in both the far and near fields, involving wavelengths in the extended range of 300-2,400 nm. We show that the MDRs excited at the core are selectively perturbated by the metallic shell through the bonding and antibonding surface plasmons (SPs). This perturbation depends on both the size of the core and the thickness of the shell, and, as a consequence, we get an efficient tuneable and detectable simple system. Our calculations apply perfectly to long nanotubes compared to the wavelength for the two fundamental polarizations (s, p). © 2013 Springer Science+Business Media New York.


Buscaglia C.,National University of Central Buenos Aires
Avian Diseases | Year: 2013

The presence of reticuloendotheliosis virus (REV) was examined in flocks affected with Marek's disease (MD). Sera were positive to REV antibodies by agar gel precipitation. However, these findings were not conclusive since fowlpox vaccines can have REV fragments or the whole genome inserted. Frozen sections from tumors were positive for MD virus (MDV) but negative for REV. Chicken embryo fibroblast (CEF) and chicken kidney cell (CKC) culture inoculated with buffy coat cells or blood from the affected birds were examined. Positive cells were shown for REV and MDV by fluorescent antibodies tests in CEF and CKC, respectively, indicating the presence of REV in Argentinean layer flocks. This is the first report of REV in Argentina and also in South America. © American Association of Avian Pathologists.


Flensborg G.,National University of Central Buenos Aires
HOMO- Journal of Comparative Human Biology | Year: 2011

Several archaeological researches in northeastern Patagonia and southeastern Pampas have evaluated various indicators of the diets of hunter-gatherers who inhabited these regions during the Late Holocene, including the role of plant foods. Dental analysis is an important way to introduce new information about subsistence. In this sense, the objective of this work is to document and interpret dento-alveolar lesions in an osteological sample recovered from the Paso Alsina 1 archaeological site (eastern Pampean-Patagonian transition, Argentina). This paper will explore the oral health status of individuals and discuss palaeodietary information of hunter-gatherers that inhabited the lower valley of the Colorado River during the final Late Holocene (ca. 500 years BP). The site is defined as a formal area bundle composed of 10 secondary multiple burials containing 56 individuals of both sexes and various ages (e.g., perinatal, infant, and adult). In this study, 781 teeth and 1036 alveoli from 47 maxillae and 38 mandibles were analysed from 51 adult individuals. The results indicate a moderate rate of dental wear, and dental calculus, and low percentages of caries, abscesses, and antemortem tooth loss. The information obtained suggests a diet based on a combination of proteins, fat and carbohydrates. Results are then compared with those from other lines of analysis for the study area and for the neighboring regions (northeastern Patagonia and southeastern Pampas). © 2011 Elsevier GmbH.


Purslow P.,National University of Central Buenos Aires
Meat Science | Year: 2016

A recent article in this journal documents enhanced sensory qualities of pork cooked to low temperatures. The aim of this letter is to point out that the incidence of Trichinella spiralis in many countries and the more widespread incidence of Toxoplasma gondii present a concern for the adoption of low temperature cooking of pork unless extended cooking times are used. © 2016.


Marino B.M.,National University of Central Buenos Aires | Thomas L.P.,National University of Central Buenos Aires
Journal of Physics: Conference Series | Year: 2011

The evolution of gravity currents generated in open channels which represent those present in estuaries and many hydraulics structures are studied analytically and experimentally. We are particularly interested in the effects of the cross-section shape on the dam-break flows that satisfy the shallow-water equations by considering an equivalent channel cross-section represented by a power law. A stratified two-layer system is assumed and an analytical model based on the balances of mass and momentum in the frontal region, whose results are successfully compared with those obtained by means of experiments, is proposed. The solutions describe the dynamics of the gravity currents with sharp fronts and can be applied to a wide range of natural situations where the turbulence is not dominant.


Pereira J.A.,National University of Central Buenos Aires
Journal of Arid Environments | Year: 2010

The activity pattern of mammalian carnivores is influenced by several factors, including environmental conditions, interference from competitors, and behavioral thermoregulation. Facing extreme environmental conditions the activity rhythm of animals may change. The activity patterns of Geoffroy's cats (Leopardus geoffroyi) were studied during a period of prey scarcity in a scrubland area of central Argentina, based on five individuals radio-collared and monitored by radio-telemetry. Activity readings were recorded every 15 min during 6- to 24-h observation periods, and a total of 3121 fixes totaling 780.3 h of monitoring were gathered for these cats. Geoffroy's cats were significantly more active during daytime (58.1 ± 9.4% of active fixes) than during the night (33.6 ± 2.9%). Although they were active at any time of the day, an activity peak was recorded from 12.00 to 17.00 h. This pattern is opposite to those observed in other areas or even to that recorded for this species in the same area during a period of higher prey abundance. This apparent shift toward diurnal activity could be a response to a combination of ecological (prey availability, predators or competition avoidance) and physiological (energy saving) factors. Geoffroy's cats are behaviorally flexible, but this ability may not be enough to maintain survival (and population size) under harsh environmental conditions. © 2010 Elsevier Ltd.


Simoy M.V.,National University of Central Buenos Aires
Ecological Modelling | Year: 2011

It is often necessary to estimate the weight that an individual may be capable of gaining depending on its degree of activity. A simple individual-based model was developed for studying the dynamics of weight in terms of daily behavior and ingestion rate. It was based on the balance between the individual's energy intake and the cost of its daily activities. Costs depend on the weight of the individual and the photoperiod, as well as on the time spent on each activity. Different combinations of ingestion rate, individual's weight, photoperiod length, and time assigned to different activities were used for simulating the weight dynamics, taking the species Rhea americana as a study case. Estimations of energetic costs of the activities were obtained from specialized literature. Using different photoperiods and individual behaviors, the model yields field metabolic rate (FMR) values in agreement with those obtained from direct measurements for other omnivorous bird species. © 2010 Elsevier B.V.

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