Estudio de las especies del país del genero "Azotobacter"

El género Azotobacter agrupa varias especies da microorganismos aerobios capaces de fijar al nitrógeno molecular atmosférico. Beijerinck, en 1901, descubrió la existencia da éstos gérmenes, aislándolos de suelos y aguas del canal de Delft. En el presente trabajo se citan, en breve reseña histórica, los investigadores que han profundizado en este tema describiendo nuevas especies aisladas de distintos suelos, como asimismo, las diversas opiniones vertidas respecto a las especies que merecen ser consideradas. En el siguiente capítulo se describen distintas espacies de Azotobacter, su metabolismo carbonado y nitrogenado y las influencias que sobre ellos ejercen los factores físicos y químicos. A continuación, ilustrando con algunas fotografías, se detallan los métodos y técnicas ensayados para el aislamiento da gérmenes del grupo Azotobacter, utilizando medios líquidos y solidificados y también medios naturales y placas de gel silíceo. En capítulo aparte, se puntualizan, en un cuadro, las especies de Azotobacter identificadas en 55 de las 45 muestras da tierra del país examinadas, detallando los medios nutritivos utilizados y el estudio de los caracteres morfológicos, tintoriales y fisiológicos efectuado, citando los métodos de coloración empleados.Tesis digitalizada en SEDICI gracias a la Biblioteca Central de la Facultad de Ciencias Exactas (UNLP).Los datos en la portada de la tesis son los siguientes: Universidad Nacional de Eva Perón, Facultad de Química y Farmacia, ciudad Eva Perón.Facultad de Ciencias Exacta

Estudio de las especies del país del genero "Azotobacter"

El género Azotobacter agrupa varias especies da microorganismos aerobios capaces de fijar al nitrógeno molecular atmosférico. Beijerinck, en 1901, descubrió la existencia da éstos gérmenes, aislándolos de suelos y aguas del canal de Delft. En el presente trabajo se citan, en breve reseña histórica, los investigadores que han profundizado en este tema describiendo nuevas especies aisladas de distintos suelos, como asimismo, las diversas opiniones vertidas respecto a las especies que merecen ser consideradas. En el siguiente capítulo se describen distintas espacies de Azotobacter, su metabolismo carbonado y nitrogenado y las influencias que sobre ellos ejercen los factores físicos y químicos. A continuación, ilustrando con algunas fotografías, se detallan los métodos y técnicas ensayados para el aislamiento da gérmenes del grupo Azotobacter, utilizando medios líquidos y solidificados y también medios naturales y placas de gel silíceo. En capítulo aparte, se puntualizan, en un cuadro, las especies de Azotobacter identificadas en 55 de las 45 muestras da tierra del país examinadas, detallando los medios nutritivos utilizados y el estudio de los caracteres morfológicos, tintoriales y fisiológicos efectuado, citando los métodos de coloración empleados.Tesis digitalizada en SEDICI gracias a la Biblioteca Central de la Facultad de Ciencias Exactas (UNLP).Los datos en la portada de la tesis son los siguientes: Universidad Nacional de Eva Perón, Facultad de Química y Farmacia, ciudad Eva Perón.Facultad de Ciencias Exacta

Single machine scheduling with controllable processing times by submodular optimization

In scheduling with controllable processing times the actual processing time of each job is to be chosen from the interval between the smallest (compressed or fully crashed) value and the largest (decompressed or uncrashed) value. In the problems under consideration, the jobs are processed on a single machine and the quality of a schedule is measured by two functions: the maximum cost (that depends on job completion times) and the total compression cost. Our main model is bicriteria and is related to determining an optimal trade-off between these two objectives. Additionally, we consider a pair of associated single criterion problems, in which one of the objective functions is bounded while the other one is to be minimized. We reduce the bicriteria problem to a series of parametric linear programs defined over the intersection of a submodular polyhedron with a box. We demonstrate that the feasible region is represented by a so-called base polyhedron and the corresponding problem can be solved by the greedy algorithm that runs two orders of magnitude faster than known previously. For each of the associated single criterion problems, we develop algorithms that deliver the optimum faster than it can be deduced from a solution to the bicriteria problem

Application of submodular optimization to single machine scheduling with controllable processing times subject to release dates and deadlines

In this paper, we study a scheduling problem on a single machine, provided that the jobs have individual release dates and deadlines, and the processing times are controllable. The objective is to find a feasible schedule that minimizes the total cost of reducing the processing times. We reformulate the problem in terms of maximizing a linear function over a submodular polyhedron intersected with a box. For the latter problem of submodular optimization, we develop a recursive decomposition algorithm and apply it to solving the single machine scheduling problem to achieve the best possible running time

Wigner Functions on a Lattice

The Wigner functions on the one dimensional lattice are studied. Contrary to the previous claim in literature, Wigner functions exist on the lattice with any number of sites, whether it is even or odd. There are infinitely many solutions satisfying the conditions which reasonable Wigner functions should respect. After presenting a heuristic method to obtain Wigner functions, we give the general form of the solutions. Quantum mechanical expectation values in terms of Wigner functions are also discussed.Comment: 11 pages, no figures, REVTE

Functional characterization of two melanocortin (MC) receptors in lamprey showing orthology to the MC1 and MC4 receptor subtypes

<p>Abstract</p> <p>Background</p> <p>The melanocortin (MC) receptors have a key role in regulating body weight and pigmentation. They belong to the rhodopsin family of G protein-coupled receptors (GPCRs). The purpose of this study was to identify ancestral MC receptors in agnathan, river lamprey.</p> <p>Results</p> <p>We report cloning of two MC receptors from river lamprey. The lamprey receptors, designated MCa and MCb, showed orthology to the MC1 and MC4 receptor subtypes, respectively. The molecular clock analysis suggested that lamprey MC receptor genes were not duplicated recently and diverged from each other more than 400 MYR ago. Expression and pharmacological characterization showed that the lamprey MCa receptor was able to bind and be activated by both lamprey and human MSH peptides. The lamprey MCa receptor had relatively high affinity for ACTH derived peptides similarly to the fish MC receptors. We found that both of the lamprey MC receptors were expressed in skin, while the MCb receptor was also found in liver, heart and skeletal muscle.</p> <p>Conclusion</p> <p>This study shows presence of MC receptors in agnathans indicating early signs of specific functions of melanocortin receptor subtypes.</p

Eccrine porocarcinoma of the head: An important differential diagnosis in the elderly patient

Background: Eccrine porocarcinoma is a rare malignant tumor of the sweat gland, characterized by a broad spectrum of clinicopathologic presentations. Surprisingly, unlike its benign counterpart eccrine poroma, eccrine porocarcinoma is seldom found in areas with a high density of eccrine sweat glands, like the palms or soles. Instead, eccrine porocarcinoma frequently occurs on the lower extremities, trunk and abdomen, but also on the head, resembling various other skin tumors, as illustrated in the patients described herein. Observations: We report 5 cases of eccrine porocarcinoma of the head. All patients were initially diagnosed as having epidermal or melanocytic skin tumors. Only after histopathologic examination were they classified as eccrine porocarcinoma, showing features of epithelial tumors with abortive ductal differentiation. Characteristic clinical, histopathologic and immunohistochemical findings of eccrine porocarcinomas are illustrated. Conclusion: Eccrine porocarcinomas are potentially fatal adnexal malignancies, in which extensive metastatic dissemination may occur. Porocarcinomas are commonly overlooked, or misinterpreted as squamous or basal cell carcinomas as well as other common malignant and even benign skin tumors. Knowledge of the clinical pattern and histologic findings, therefore, is crucial for an early therapeutic intervention, which can reduce the risk of tumor recurrence and serious complications. Copyright (c) 2008 S. Karger AG, Basel

Projecting ozone hole recovery using an ensemble of chemistry-climate models weighted by model performance and independence

Calculating a multi-model mean, a commonly used method for ensemble averaging, assumes model independence and equal model skill. Sharing of model components amongst families of models and research centres, conflated by growing ensemble size, means model independence cannot be assumed and is hard to quantify. We present a methodology to produce a weighted-model ensemble projection, accounting for model performance and model independence. Model weights are calculated by comparing model hindcasts to a selection of metrics chosen for their physical relevance to the process or phenomena of interest. This weighting methodology is applied to the Chemistry-Climate Model Initiative (CCMI) ensemble to investigate Antarctic ozone depletion and subsequent recovery. The weighted mean projects an ozone recovery to 1980 levels, by 2056 with a 95 % confidence interval (2052-2060), 4 years earlier than the most recent study. Perfect-model testing and out-of-sample testing validate the results and show a greater projective skill than a standard multi-model mean. Interestingly, the construction of a weighted mean also provides insight into model performance and dependence between the models. This weighting methodology is robust to both model and metric choices and therefore has potential applications throughout the climate and chemistry-climate modelling communities