An Infinite Family of Generalized Kalnajs Disks

An infinite family of axially symmetric thin disks of finite radius is presented. The family of disks is obtained by means of a method developed by Hunter and contains, as its first member, the Kalnajs disk. The surface densities of the disks present a maximum at the center of the disk and then decrease smoothly to zero at the edge, in such a way that the mass distribution of the higher members of the family is more concentrated at the center. The first member of the family have a circular velocity proportional to the radius, representing thus a uniformly rotating disk. On the other hand, the circular velocities of the other members of the family increases from a value of zero at the center of the disks until a maximum and then decreases smoothly until a finite value at the edge of the disks, in such a way that for the higher members of the family the maximum value of the circular velocity is attained nearest the center of the disks

Efficient dynamic simulation of pH in processes associated to biofiltration of volatile inorganic pollutants

This work proposes a generic methodology to include the pH as a state variable in mathematical models of bioreactors. An ordinary differential equation for pH is stated and introduced into the general model structure of a biotrickling filter. All chemical equilibriums were considered and included into the model framework. A preliminary evaluation was performed by comparing results predicted by the model with experimental data obtained from the oxidation of thiosulfate by sulfide-oxidizing bacteria under alkaline conditions. The model was able to describe adequately the evolution of the main state variables including the pH for the initial complete oxidation of thiosulfate. The methodology presented here can be easily adapted to other mathematical models dealing with biological waste treatment processes in which pH appears as a key factor.Postprint (published version

Cuantización topológica y cohomología de Cech

En este trabajo se revisa el procedimiento de cuantización topológica basado en la cohomología de Cech, de acuerdo con los trabajos de O. Álvarez [4] y [5]. Se muestra cómo el método de  cuantización se funda­menta en la libertad de escogencia del lagrangiano apropiado para una teoría de campos, a partir de una familia de lagrangianos que difieren entre sí por un término igual a una derivada total

Cuantización topológica y cohomología de Cech

En este trabajo se revisa el procedimiento de cuantización topológica basado en la cohomología de Cech, de acuerdo con los trabajos de O. Álvarez [4] y [5]. Se muestra cómo el método de  cuantización se funda­menta en la libertad de escogencia del lagrangiano apropiado para una teoría de campos, a partir de una familia de lagrangianos que difieren entre sí por un término igual a una derivada total

Clinical Evolution of New Delhi Metallo-β-Lactamase (NDM) optimizes resistance under Zn(II) Deprivation

Carbapenem-resistant Enterobacteriaceae (CRE) are rapidly spreading and taking a staggering toll on all health care systems, largely due to the dissemination of genes coding for potent carbapenemases. An important family of carbapenemases are the Zn(II)-dependent β-lactamases, known as metallo-β-lactamases (MBLs). Among them, the New Delhi metallo-β-lactamase (NDM) has experienced the fastest and widest geographical spread. While other clinically important MBLs are soluble periplasmic enzymes, NDMs are lipoproteins anchored to the outer membrane in Gram-negative bacteria. This unique cellular localization endows NDMs with enhanced stability upon the Zn(II) starvation elicited by the immune system response at the sites of infection. Since the first report of NDM-1, new allelic variants (16 in total) have been identified in clinical isolates differing by a limited number of substitutions. Here, we show that these variants have evolved by accumulating mutations that enhance their stability or the Zn(II) binding affinity in vivo, overriding the most common evolutionary pressure acting on catalytic efficiency. We identified the ubiquitous substitution M154L as responsible for improving the Zn(II) binding capabilities of the NDM variants. These results also reveal that Zn(II) deprivation imposes a strict constraint on the evolution of this MBL, overriding the most common pressures acting on catalytic performance, and shed light on possible inhibitory strategies.Fil: Bahr, Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Vitor Horen, Luisina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Bethel, Christopher R.. Louis Stokes Cleveland VA Medical Center; Estados UnidosFil: Bonomo, Robert A.. Louis Stokes Cleveland VA Medical Center; Estados UnidosFil: Gonzalez, Lisandro Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Vila, Alejandro Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; Argentin

GABA Neuron Alterations, Cortical Circuit Dysfunction and Cognitive Deficits in Schizophrenia

Schizophrenia is a brain disorder associated with cognitive deficits that severely affect the patients' capacity for daily functioning. Whereas our understanding of its pathophysiology is limited, postmortem studies suggest that schizophrenia is associated with deficits of GABA-mediated synaptic transmission. A major role of GABA-mediated transmission may be producing synchronized network oscillations which are currently hypothesized to be essential for normal cognitive function. Therefore, cognitive deficits in schizophrenia may result from a GABA synapse dysfunction that disturbs neural synchrony. Here, we highlight recent studies further suggesting alterations of GABA transmission and network oscillations in schizophrenia. We also review current models for the mechanisms of GABA-mediated synchronization of neural activity, focusing on parvalbumin-positive GABA neurons, which are altered in schizophrenia and whose function has been strongly linked to the production of neural synchrony. Alterations of GABA signaling that impair gamma oscillations and, as a result, cognitive function suggest paths for novel therapeutic interventions