New physical principles of contact thermoelectric cooling

We suggest a new approach to the theory of the contact thermoelectric cooling (Peltier effect). The metal-metal, metal-n-type semiconductor, metal-p-type semiconductor, p-n junction contacts are analyzed. Both degenerate and non-degenerate electron and hole gases are considered. The role of recombination in the contact cooling effect is discussed by the first time.Comment: 8 pages, 8 figures, revtex

Modelling languages quality evaluation by taxonomic analysis: a preliminary proposal

El paradigma de la ingeniería dirigida por modelos (MDE por sus siglas en inglés) promueve el uso de modelos conceptuales en procesos de ingeniería e investigación sobre sistemas de información. Como productos de ingeniería los modelos conceptuales deben tener calidad, la cual aplica tanto a los modelos conceptuales como los lenguajes de modelado empleados para construir dichos modelos. Debido a los múltiples retos, divergencias y tendencias para evaluación y aseguramiento de la calidad en contextos MDE, una forma para ejecutar un proceso de evaluación de la calidad es usar una técnica donde la aplicabilidad y metas de los artefactos de modelado puedan ser contrastadas con los principios esenciales del desarrollo de sistemas de información. Este trabajo formula un conjunto de requisitos conceptuales y metodológicos para un marco de evaluación de la calidad de lenguajes de modelado con el potencial de abordar algunos de los retos abiertos de calidad en MDE. Para este propósito, se propone usar principios del popular marco de trabajo Zachman para sistemas de información, como una herramienta taxonómica aplicada sobre artefactos de modelado usados en un desarrollo de un sistema de información, en aras de ejecutar procedimientos analíticos sobre modelos alineados con una arquitectura de referencia para sistemas de información, y con razonamientos ontológicos. En este trabajo se expone cómo el marco Zachman soporta análisis sobre modelos para propósitos de calidad por su administración nativa de la semántica.The Model-Driven Engineering (mde) paradigm promotes the usage of conceptual models in information systems (is) engineering and research. As engineering products, conceptual models must have quality, which applies on both conceptual models and modeling language employed to build them. This paper presents a modeling language quality evaluation framework. This framework uses the principles from the popular Zachman framework for information systems as a taxonomic tool applied over modeling rtifacts used in an information system development. The purpose of this taxonomic tool is to perform analytic procedures that are aligned with an is reference architecture and ontological reasoning. Throughout this work, we describe how the Zachman framework supports analytics over modeling languages for quality purposes by its native management of semantics

Individual, Family, and Institutional Factors That Propel Latino/A Students Beyond High School

The study was designed to determine the extent to which individual and institutional support variables can predict Latino/a students\u27 successful completion of high school and enrollment in post-secondary institutions in the U.S. Current research suggests that the Hispanic population will constitute approximately 25 of the national workforce in the USA by the year 2050. However, according to the NCES (2002) data, the high level of dropout rates from high school among Latino/a (11.5 for males and 10.3 for females) is alarming. The study examined individual student factors as well as institutional and family variables that may enhance the likelihood of Latino/a students\u27 completion of secondary education and enrollment in post-secondary institutions. Using the 2002-2006 Education Longitudinal Study data, consisting of a sample of 2,217 Latino/a students, the binary logistic regression model identified students\u27 socioeconomic status, their educational aspirations as well as the aspirations of their parents, and school support programs to be significant predictors of high school completion as well as enrollment in post-secondary education. The findings indicate significant differences between the predictive power of the individual and institutional variables on the completion of high school and enrollment in post-secondary institutions of first, second and third generations of Latino/a students in the U.S. In this study, females of first and second generation Latino/a students were found to be two times more likely than males in the same group to complete high school on time. This trend did not apply to third generation female students who were found to be less likely than males of the same group to complete high school on time, with males holding 20 more chances of completion of high school. The presence of institutional based Dropout Prevention Programs was significantly associated with less likelihood of Completion of High School and Enrollment in Post-Secondary Institution across all generation of La

Análisis de la señal ECG en pacientes con enfermedad de Párkinson

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Quantum point contact conductance in NINS junctions

The effect of an insulating barrier located at a distance $a$ from a NS quantum point contact is analyzed in this work. The Bogoliubov de Gennes equations are solved for NINS junctions (S: anysotropic superconductor, I: insulator and N: normal metal), where the NIN region is a quantum wire. For $a\neq0$, bound states and resonances in the differential conductance are predicted. These resonances depend on the symmetry of the pair potential, the strength of the insulating barrier and $a$. Our results show that in a NINS quantum point contact the number of resonances vary with the symmetry of the order parameter. This is to be contrasted with the results for the NINS junction, in which only the position of the resonances changes with the symmetry.Comment: 5 pages, 5 Figures, RevTex

A moving target defense to detect stealthy attacks in cyber-physical systems

Cyber-Physical Systems (CPS) have traditionally been considered more static, with regular communication patterns when compared to classical information technology networks. Because the structure of most CPS remains unchanged during long periods of time, they become vulnerable to adversaries who can tailor their attacks based on their precise knowledge of the system dynamics, communications, and control. Moving Target Defense (MTD) has emerged as a strategy to add uncertainty about the state and execution of a system in order to prevent adversaries from having predictable effects with their attacks. In this work we propose a novel type of MTD strategy that randomly changes the availability of the sensor data, so that it is harder for adversaries to tailor stealthy attacks and at the same time it can minimize the impact of false-data injection attacks. Using tools from switched control systems we formulate an optimization problem to find the probability of the switching signals that increase the visibility of stealthy attacks while decreasing the deviation caused by false data injection attacks

Brachial plexus injury mimicking a spinal-cord injury.

Objective High-energy impact to the head, neck, and shoulder can result in cervical spine as well as brachial plexus injuries. Because cervical spine injuries are more common, this tends to be the initial focus for management. We present a case in which the initial magnetic resonance imaging (MRI) was somewhat misleading and a detailed neurological exam lead to the correct diagnosis.Clinical presentation A 19-year-old man presented to the hospital following a shoulder injury during football practice. The patient immediately complained of significant pain in his neck, shoulder, and right arm and the inability to move his right arm. He was stabilized in the field for a presumed cervical-spine injury and transported to the emergency department.Intervention Initial radiographic assessment (C-spine CT, right shoulder x-ray) showed no bony abnormality. MRI of the cervical-spine showed T2 signal change and cord swelling thought to be consistent with a cord contusion. With adequate pain control, a detailed neurological examination was possible and was consistent with an upper brachial plexus avulsion injury that was confirmed by CT myelogram. The patient failed to make significant neurological recovery and he underwent spinal accessory nerve grafting to the suprascapular nerve to restore shoulder abduction and external rotation, while the phrenic nerve was grafted to the musculocutaneous nerve to restore elbow flexion.Conclusion Cervical spinal-cord injuries and brachial plexus injuries can occur by the same high energy mechanisms and can occur simultaneously. As in this case, MRI findings can be misleading and a detailed physical examination is the key to diagnosis. However, this can be difficult in polytrauma patients with upper extremity injuries, head injuries or concomitant spinal-cord injury. Finally, prompt diagnosis and early surgical renerveration have been associated with better long-term recovery with certain types of injury