Fernandez A.,University of Montevideo
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016
Pattern recognition and localization along with feature extraction are image processing applications of great interest in defect inspection and robot vision among others. In comparison to purely digital methods, the attractiveness of optical processors for pattern recognition lies in their highly parallel operation and real-time processing capability. This work presents an optical implementation of the generalized Hough transform (GHT), a well-established technique for the recognition of geometrical features in binary images. Detection of a geometric feature under the GHT is accomplished by mapping the original image to an accumulator space; the large computational requirements for this mapping make the optical implementation an attractive alternative to digital- only methods. Starting from the integral representation of the GHT, it is possible to device an optical setup where the transformation is obtained, and the size and orientation parameters can be controlled, allowing for dynamic scale and orientation-variant pattern recognition. A compact system for the above purposes results from the use of an electrically tunable lens for scale control and a rotating pupil mask for orientation variation, implemented on a high-contrast spatial light modulator (SLM). Real-time (as limited by the frame rate of the device used to capture the GHT) can also be achieved, allowing for the processing of video sequences. Besides, by thresholding of the GHT (with the aid of another SLM) and inverse transforming (which is optically achieved in the incoherent system under appropriate focusing setting), the previously detected features of interest can be extracted. © 2016 SPIE.
Solari S.,University of Granada |
Losada M.A.,University of Montevideo
Journal of Geophysical Research: Oceans | Year: 2011
The most popular methods of simulating time series for wave heights and other meteorological and oceanic variables are based on the use of autoregressive models and the transformation of variables to make them normal and stationary. Generally, when these models are used, attention is centered on their capacity to represent the autocorrelation of the series. In this article, a simulation model is proposed that is based on the following: (i) a non-stationary parametric mixture model for the marginal distribution of the variable, that combines a log-normal distribution for main-mass regime and generalized Pareto distributions for upper and lower tail regimes, and (ii) the use of copulas to model the time dependency of the variable. The model has been evaluated by comparing the original series and the simulated series in terms of the autocorrelation function, the mean, the annual maxima and peaks-over-threshold regimes, and the persistences regime. It has also been compared to an ARMA model and found to yield more satisfactory results. © 2011 by the American Geophysical Union.
Manzanares W.,University of Montevideo |
Hardy G.,Massey University
Current Opinion in Clinical Nutrition and Metabolic Care | Year: 2010
Purpose of review: To analyse the anti-inflammatory and antioxidant properties of vitamin B12 and evaluate current evidence on vitamin B12 status in the critically ill with systemic inflammation. Recent findings: Data on vitamin B12 status of intensive care unit patients are scarce. Cobalamins could potentially be useful agents for inhibiting nitric oxide synthase and nitric oxide production, controlling nuclear factor-kappa B activation, and restoring optimal bacteriostasis and phagocytosis in which transcobalamins play a proven role. The antioxidant properties of vitamin B12, with a glutathione-sparing effect, are secondary to stimulation of methionine synthase activity and reaction with free oxygen or nitrogen radicals. Large parenteral doses are routinely administered for cyanide poisoning, with only mild, reversible side-effects. Current evidence suggests that high-dose parenteral vitamin B12 may prove an innovative approach to treat critically ill systemic inflammatory response syndrome patients, especially those with severe sepsis/septic shock. In this setting, vitamin B12 and transcobalamins could modulate systemic inflammation contributing to the anti-inflammatory cascade and potentially improve outcome. Summary: Despite evidence from animal studies, so far there are no clinical intervention trials that have studied vitamin B12 as a pharmaconutrient strategy for critical care. Well designed animal and clinical studies are required to clarify several outstanding questions on the optimal posology, safety, and efficacy of high-dose vitamin B12 in the critically ill. © 2010 Wolters Kluwer Health. Lippincott Williams & Wilkins.
Manzanares W.,University of Montevideo |
Hardy G.,Massey University
Current Opinion in Clinical Nutrition and Metabolic Care | Year: 2011
Purpose of Review: To summarize the properties of thiamine and evaluate current evidence on thiamine status and supplementation, for different populations of critically ill patients. Recent Findings: Thiamine, in the form of thiamine pyrophosphate, is a critical co-factor in the glyocolysis and oxidative decarboxylation of carbohydrates for energy production. Different studies have shown that critical illness in adults and children is characterized by absolute or relative thiamine depletion, which is associated with an almost 50% increase in mortality. Thiamine deficiency should be suspected in different clinical scenarios such as severe sepsis, burns, unexplained heart failure or lactic acidosis, neurological disorder in patients with previous history of alcoholism, starvation, chronic malnutrition, long-term parenteral feeding, hyperemesis gravidarum, or bariatric surgery. Nonetheless, thiamine supplements are not routinely given to critically ill patients. Clinicians should be able to suspect and recognize risk factors for the occurrence of severe neurological disorders secondary to thiamine deficiency, as early treatment can prevent the appearance of permanent neurological damage. Summary: Symptoms and signs associated with thiamine deficiency lack sensitivity and specificity in critically ill patients. Consequently, depletion is frequently unrecognized and underdiagnosed by clinicians. Potentially deleterious consequences of thiamine depletion should be avoided by early and appropriate supplementation. © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins.
Lessa E.P.,University of Montevideo |
D'ElIa G.,University of Concepción |
PardiNas U.F.J.,Centro Nacional Patagonico
Molecular Ecology | Year: 2010
Species are impacted by climate change at both ecological and evolutionary time scales. Studies in northern continents have provided abundant evidence of dramatic shifts in distributions of species subsequent to the last glacial maximum (LGM), particularly at high latitudes. However, little is known about the history of southern continents, especially at high latitudes. South America is the only continent, other than Antarctica, that extends beyond 40 °S. Genetic studies of a few Patagonian species have provided seemingly conflicting results, indicating either postglacial colonization from restricted glacial refugia or persistence through glacial cycles and in situ differentiation. Using mitochondrial DNA sequences of 14 species of sigmodontine rodents, a major faunal ensemble of Patagonia and Tierra del Fuego, we show that at least nine of these species bear genetic footprints of demographic expansion from single restricted sources. However, timing of demographic expansion precedes the LGM in most of these species. Four species are fragmented phylogeographically within the region. Our results indicate that (i) demographic instability in response to historical climate change has been widespread in the Patagonian-Fueguian region, and is generally more pronounced at high latitudes in both southern and northern continents; (ii) colonization from lower latitudes is an important component of current Patagonian-Fueguian diversity; but (iii) in situ differentiation has also contributed to species diversity. © 2010 Blackwell Publishing Ltd.
Denis P.A.,University of Montevideo
Journal of Physical Chemistry C | Year: 2014
By means of first principle calculations, we have performed a theoretical characterization of the stability and electronic properties of sheets and nanoribbons that were recently synthesized employing octafunctionalized biphenylenes as building blocks. We found that the biphenylene sheet has a strong metallic character that is difficult to inhibit employing low levels of functionalization. Hydrogenation at full coverage induces a metal to insulator transition, but the band gap opened is very large, i.e., 6.6 eV. When other functional groups such as fluorine or chlorine are attached, the band gap can be regulated. The most effective chemical modification, in terms of gap opening, is the combination of hydrogen/chlorine or fluorine/chlorine. For the latter functional groups, band gaps similar to those of rutile were calculated at the HSEH1PBE/6-31G∗ level of theory. The biphenylene sheet functionalized on one side with fluorine and with chlorine on the other presented a CC bond length equal to 1.76 Å, one of the longest reported up to date. In contrast with recent claims, we found that, for armchair biphenylene nanoribbons, the twist induced by the functionalization of the edges does not increase the band gaps of the nanoribbons. Moreover, in some cases the gaps were reduced as we observed when the edges where saturated with hydrogen atoms. Finally, the high reactivity of the sheet indicated that it is may have promising applications in catalysis. © 2014 American Chemical Society.
Cid A.,University of Montevideo
Prevention Science | Year: 2016
In this paper, I review an issue that is an urgent challenge in the development field—the effectiveness of after-school programs for preventing school-age youth violence in vulnerable settings in Latin American and the Caribbean. These programs have proliferated in the region and include sports, recreation, music, tutoring, and other focused activities. Given their popularity and because they target known risk factors for violence (such as drop-out from school, poor academic performance, lack of motivation, too much idle time, low quality and quantity of adult supervision, and social isolation), it is critical to examine empirically whether they can be effective prevention strategies. Unfortunately, most rigorous trials of after-school interventions to prevent youth violence have been conducted in developed countries, with far fewer in Latin America. In this review, a broad range of databases was searched systematically. Only six studies in five Latin American and Caribbean countries were identified. Reported results indicate at least some benefits for youth behavior, although not across all youth. Additional concerns regarding how these programs are implemented and whether specific components can be tied to violence prevention are noted. The need for more rigorous evaluation of these programs is noted. © 2016 Society for Prevention Research
Salinas G.,University of Montevideo
Antioxidants and Redox Signaling | Year: 2013
Parasite redox biology is vital for understanding parasite-host interactions and adaptations. Studies in this area are leading to discoveries regarding drug targets and drug leads to treat infections caused by protozoan and worm parasites for which there are few effective drugs. Parasite unique and nonredundant core redox enzymes are choke points of metabolism and pharmacological targets. This Forum revises this concept and proposes new drug targets. It also highlights recent studies using genetically manipulated and natural strains that reveal emerging regulatory functions of antioxidant enzymes in parasite differentiation, apoptosis, virulence, acute infection, and disease progression and outcome. The challenge ahead is to understand the redox changes linked to differentiation and drastic transitions between environments that take place during parasitic complex life cycles. The combined use of new tools and techniques, such as genetically-manipulated parasites, live imaging, redox sensors, and proteomics, allow the challenge to be undertaken. Some of these methodologies, for example, transgenic parasites encoding redox biosensors, can also be applied to drug high throughput screening and to assess the effect of currently known drugs that affect redox homeostasis. Antioxid. Redox Signal. 19, 661-664. © Copyright 2013, Mary Ann Liebert, Inc. 2013.
Caffera M.,University of Montevideo
Environment and Development Economics | Year: 2011
I review the few programs implemented in Latin America to control pollution with direct economic instruments and draw general lessons for the future implementation of these instruments in the region. The available evidence suggests that a combination of low capacities and political economy issues negatively affected the implementation of these programs. As a result, the capacity of the economic instruments to induce emission reductions cost effectively and their future political viability in these countries in the short- or medium-run may have been compromised. This present state of affairs provides more evidence in favor of the policy recommendation that Latin American countries should build local capacities before implementing direct economic instruments, than in favor of the alternative that these countries should adapt direct economic instruments to their institutional and political characteristics. © Copyright Cambridge University Press 2010.
Romanelli A.,University of Montevideo |
Hernndez G.,University of Montevideo
Physica A: Statistical Mechanics and its Applications | Year: 2011
We investigate the global chirality distribution of the quantum walk on the line when decoherence is introduced either through simultaneous measurements of the chirality and particle position, or as a result of broken links. The first mechanism drives the system towards a classical diffusive behavior. This is used to build new quantum games, similar to the spin-flip game. The second mechanism involves two different possibilities: (a) All the quantum walk links have the same probability of being broken. (b) Only the quantum walk links on a half-line are affected by random breakage. In case (a) the decoherence drives the system to a classical Markov process, whose master equation is equivalent to the dynamical equation of the quantum density matrix. This is not the case in (b) where the asymptotic global chirality distribution unexpectedly maintains some dependence with the initial condition. Explicit analytical equations are obtained for all cases. © 2010 Elsevier B.V. All rights reserved.