Mechanisms of Action and Targets of Nitric Oxide in the Oculomotor System

Nitric oxide (NO) production by neurons in the prepositus hypoglossi (PH) nucleus is necessary for the normal performance of eye movements in alert animals. In this study, the mechanism(s) of action of NO in the oculomotor system has been investigated. Spontaneous and vestibularly induced eye movements were recorded in alert cats before and after microinjections in the PH nucleus of drugs affecting the NO–cGMP pathway. The cellular sources and targets of NO were also studied by immunohistochemical detection of neuronal NO synthase (NOS) and NO-sensitive guanylyl cyclase, respectively. Injections of NOS inhibitors produced alterations of eye velocity, but not of eye position, for both spontaneous and vestibularly induced eye movements, suggesting that NO produced by PH neurons is involved in the processing of velocity signals but not in the eye position generation. The effect of neuronal NO is probably exerted on a rich cGMP-producing neuropil dorsal to the nitrergic somas in the PH nucleus. On the other hand, local injections of NO donors or 8-Br-cGMP produced alterations of eye velocity during both spontaneous eye movements and vestibulo-ocular reflex (VOR), as well as changes in eye position generation exclusively during spontaneous eye movements. The target of this additional effect of exogenous NO is probably a well defined group of NO-sensitive cGMP-producing neurons located between the PH and the medial vestibular nuclei. These cells could be involved in the generation of eye position signals during spontaneous eye movements but not during the VOR.Fondo de Investigación Sanitaria Grants 94/0388 and 97/2054Comunidad Autónoma de Madrid Grant 08.5/0019/1997Dirección General de Investigación Científica y Technológica Grant PB 93–117

Study of Finite Elements-based reliability and maintenance algorithmic methodologies analysis applied to aircraft structures and design optimization

This thesis presents the development of a research methodology oriented to the analysis of an aircraft structure in terms of operational reliability and maintainability requirements regarding its airworthiness. The study has been focused on modern commercial aircraft models, carrying out a market research and model selection according to different criteria. The study then develops a practical implementation consisting of the design approach of the aircraft airframe and main structural components for its subsequent numerical analysis and simulation. The numerical simulations will be computed by application of the Finite Elements Method on the main structural systems of the aircraft and establishment of boundary conditions. These simulations will allow the development of a computational study on linear, non-linear, and transient simulations of static loads, buckling, modal analysis, temperature, fatigue and thermal stress of individual structures and full assembly in different conditions. Finally, these results will be assessed and exported to a Matlab code which will compute an algorithmic methodology in order to approach the operational reliability and safety of the aircraft in the studied conditions. The thesis will conclude with a review of airworthiness regulations a proposal of research paths and further development of the methodology implemented

On the influence of metastable states and the behavior of the EEDF in the characterization of the negative glow of a N2-Ar discharge by OES

Optical emission spectroscopy (OES) is an essential diagnostic technique in many plasma systems, such as those used for surface treatments or fabrication of thin films. Despite the simplicity of application of OES, its interpretation is not straightforward. In particular, it requires the use of models, which due to the complexity and variety of discharge conditions, have not yet been fully understood [1]–[3]. In addition, Langmuir probes have been widely used to characterize plasmas. They allow the measurement of several parameters of interest, such as the electron density and temperature, as well as the determination of the electron energy distribution function (EEDF) by numerical derivation of the characteristic V − I [4] or by probe-current modulation [5]. In this work, some second positive system bands in the negative glow of an Ar-N2 plasma at a pressure of 2.5 Torr were investigated both by OES and Langmuir probes, for different mixture concentrations. The main purpose of this study was to verify how metastable states and the behavior of the EEDF may influence the interpretation of OES dataFil: Isola, Lucio Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: López, Maia Melina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Gomez, Bernardo Jose Armando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Guerra, Vasco. Instituto Superior Tecnico; Portuga

Nitric oxide controls excitatory/inhibitory balance in the hypoglossal nucleus during early postnatal development

Synaptic remodeling during early postnatal development lies behind neuronal networks refinement and nervous system maturation. In particular, the respiratory system is immature at birth and is subjected to significant postnatal development. In this context, the excitatory/inhibitory balance dramatically changes in the respiratory-related hypoglossal nucleus (HN) during the 3 perinatal weeks. Since, development abnormalities of hypoglossal motor neurons (HMNs) are associated with sudden infant death syndrome and obstructive sleep apnea, deciphering molecular partners behind synaptic remodeling in the HN is of basic and clinical relevance. Interestingly, a transient expression of the neuronal isoform of nitric oxide (NO) synthase (NOS) occurs in HMNs at neonatal stage that disappears before postnatal day 21 (P21). NO, in turn, is a determining factor for synaptic refinement in several physiopathological conditions. Here, intracerebroventricular chronic administration (P7-P21) of the broad spectrum NOS inhibitor l-NAME (N(omega)-nitro-l-arginine methyl ester) differentially affected excitatory and inhibitory rearrangement during this neonatal interval in the rat. Whilst l-NAME led to a reduction in the number of excitatory structures, inhibitory synaptic puncta were increased at P21 in comparison to administration of the inactive stereoisomer d-NAME. Finally, l-NAME decreased levels of the phosphorylated form of myosin light chain in the nucleus, which is known to regulate the actomyosin contraction apparatus. These outcomes indicate that physiologically synthesized NO modulates excitatory/inhibitory balance during early postnatal development by acting as an anti-synaptotrophic and/or synaptotoxic factor for inhibitory synapses, and as a synaptotrophin for excitatory ones. The mechanism of action could rely on the modulation of the actomyosin contraction apparatus

Stress analysis of finite anisotropic plates with cutouts under displacement boundary conditions

XI CONGRESO NACIONAL DE MATERIALES COMPUESTOS. Celebrado en Móstoles los días 6, 7 y 8 de julio de 2015The aim of this article is to provide an analytical tool to estímate the stress concentration in anisotropic plates weakened by a circular or elliptical hole; it is achieved by developing Lekhnitskii formalism in order to allow fínite boundary effects to be added (original formulation considers infinite plates). Only membrane problem is herein considered, particularly when prescribed displacements are applied at externa! boundaries, which could simulate boundary conditions of a manhole structure between wing spars. A boundary collocation method in conjunction with a least squares approach is used to solve the problem.Ministerio de Economía y Competitividad de España DPT2012-3718

Contabilidad de Costos : Diseño de un Sistema de Contabilidad de Costos para Procesos a la empresa Jugos Nica,S.A.

El proyecto se desarrolla en JUGO NICA S.A., una pequeña empresa localizada en el departamento de Managua, Nicaragua. JUGO NICA S.A, produce y comercializa jugos de naranja en tres presentaciones para el mercado nacional; los principales objetivos que los autores plantean son identificar, medir, controlar y gestionar los costos de producción. Este trabajo fue realizado con el fin de diseñar un sistema de costos para la empresa JUGO NICA S.A., este trabajo investigativo se desarrolló en varias partes; En la primera, se destacan las definiciones esenciales para el desarrollo de un sistema de contabilidad de costos por proceso, se describen aspectos generales de la contabilidad de costos, en la siguiente parte se explican los diferentes elementos de los cuales está compuesta la contabilidad de costos y los sistemas de costos que existen para determinar cuál es el adecuado de acuerdo al giro de la empresa. De igual forma, se elaboró un caso práctico de manera que se aprecie en la práctica la forma del registro en un sistema de costo por proceso

Weak convergence of varying measures and Hermite-Padé orthogonal polynomials

23 pages, no figures.-- MSC1991 codes: 42C05, 30E10.MR#: MR1702795 (2000j:42036)Zbl#: Zbl 1058.42503It is known that the common denominator of the Hermite-Padé approximants of a mixed Angelesco-Nikishin system shares orthogonality relations with respect to each function in the system. It is less well known that they also satisfy full orthogonality with respect to a varying measure. This problem motivates our interest in extending the class of varying measures with respect to which weak asymptotics of orthogonal polynomials takes place. In particular, for the case of a Nikishin system, we prove weak asymptotics of the corresponding varying measures.Research by second author (G.L.L.) was supported by Dirección General de Enseñanza Superior under grant PB 96-0120-C03-01 and by INTAS under grant 93-0219 EXT.Publicad

Strong asymptotics for orthogoal polynomials with varying measures and Hermite-Padé approximants

13 pages, no figures.-- MSC1991 codes: 42C05; 30E10.-- Issue title: "Proceedings of the VIIIth Symposium on Orthogonal Polynomials and Their Application" (Seville, Spain, Sep. 1997), edited by Antonio J. Durán.MR#: MR1662686 (99i:42035)Zbl#: Zbl 0933.42017The strong asymptotic behaviour of orthogonal polynomials with respect to a general class of varying measures is given for the case of the unit circle and the real line. These results are used to obtain certain asymptotic relations for the polynomials involved in the construction of Hermite-Padé approximants of a Nikishin system of functions.The research of the second author (G.L.L.) was partially supported by Dirección General de Enseñanza Superior under grant PB 96-0120-C03-01 and by INTAS under grant 93-0219 EXT.Publicad