Gasogênio: energia alternativa na agricultura.

O que e gasogenio; Historico; Situacao atual do uso do gasogenio no Brasil; Aplicacoes na agricultura; Componentes e funcionamento de um gasogenio; Tipos de gasogenio; A escolha do gasogenio; O bom combustivel; Construcao e montagem; Manutencao e problemas com o gasogenio; Economia comparativa; Anexo A - dados gerais (regiao cerrado); Anexo B - Glossario.bitstream/item/37498/1/Circ-11-1.pd

Combined cerebellar and bilateral cervical posterior spinal artery stroke demonstrated on MRI

Combined cerebellar and spinal ischemic stroke is a rare, critical condition. We report a patient with combined cerebellar and bilateral posterolateral cervical spinal cord infarction due to bilateral stenosis of the vertebral arteries. MRI is the method of choice for imaging this condition; diffusion-weighted imaging of the spinal cord gives reliable results

Participation costs for responders can reduce rejection rates in ultimatum bargaining

This paper reports data from an ultimatum mini-game in which responders first had to choose whether or not to participate. Participation was costly, but the participation cost was smaller than the minimum payoff that a responder could guarantee himself in the ultimatum game. Compared to a standard treatment, we find that the rejection rate of unfavorable offers is significantly reduced when participation is costly. A possible explanation based on cognitive dissonance is offered

Concepções e práticas de professores de ciências em relação ao trabalho prático, experimental, laboratorial e de campo

Este trabalho avaliou a situação da formação docente de um grupo de professores de Ciências no que concerne às quatro modalidades didáticas no ensino de Ciências: trabalho prático, experimental, laboratorial e de campo. Foram entrevistados, utilizando-se de um questionário, oito professores de Ciências de uma escola estadual e de uma particular do município de Maringá (Paraná-Brasil), com diferentes perfis e tempo de trabalho na área educacional. Trata-se de uma pesquisa qualitativa, com o intuito de verificar se as concepções e práticas destes professores em relação às modalidades didáticas apresentam lacunas que podem comprometer a construção do conhecimento científico pelos alunos. A análise dos dados foi realizada por meio do método de análise de conteúdo, que norteou a elaboração das discussões e conclusões apresentadas no trabalho

Mechanisms underlying the prereversal enhancement of the vertical plasma drift in the low-latitude ionosphere

The evening prereversal enhancement (PRE) of the vertical plasma drift has important consequences for the Appleton density anomaly and the stability of the nighttime ionosphere. Simplified simulations were used to review the three competing theories of the PRE origin, to explore their relative importance, and to indentify their interdependence. The mechanisms involved in the generation and climatology of the PRE are, first, a curl-free electric field response to rapid changes in the vertical electric field associated with the nighttime F region dynamo; second, a divergence of Hall currents in the E region away from the magnetic equator; and, third, the moderating effect of the large Cowling conductivities in the equatorial E region. The simulations indicate that the equatorial Cowling conductivity creates an important current path that limits the other two mechanisms prior to equatorial sunset and releases them after equatorial sunset. The curl-free mechanism is the dominant mechanism when the terminator and magnetic meridian are aligned in part due to the accelerating F region zonal wind. When the solar terminator is not aligned with the magnetic meridian, there is an interaction involving all three mechanisms contributing to the magnitude and timing of the PRE. Finally, the altitude profile of the PRE decays more quickly with altitude when the curl-free mechanism dominates as compared to when the Hall current mechanism dominates. ©2015. American Geophysical Union. All Rights Reserved

The flow of plasma in the solar terrestrial environment

The overall goal of our NASA Theory Program was to study the coupling, time delays, and feedback mechanisms between the various regions of the solar-terrestrial system in a self-consistent, quantitative manner. To accomplish this goal, it will eventually be necessary to have time-dependent macroscopic models of the different regions of the solar-terrestrial system and we are continually working toward this goal. However, with the funding from this NASA program, we concentrated on the near-earth plasma environment, including the ionosphere, the plasmasphere, and the polar wind. In this area, we developed unique global models that allowed us to study the coupling between the different regions. These results are highlighted in the next section. Another important aspect of our NASA Theory Program concerned the effect that localized 'structure' had on the macroscopic flow in the ionosphere, plasmasphere, thermosphere, and polar wind. The localized structure can be created by structured magnetospheric inputs (i.e., structured plasma convection, particle precipitation or Birkland current patterns) or time variations in these input due to storms and substorms. Also, some of the plasma flows that we predicted with our macroscopic models could be unstable, and another one of our goals was to examine the stability of our predicted flows. Because time-dependent, three-dimensional numerical models of the solar-terrestrial environment generally require extensive computer resources, they are usually based on relatively simple mathematical formulations (i.e., simple MHD or hydrodynamic formulations). Therefore, another goal of our NASA Theory Program was to study the conditions under which various mathematical formulations can be applied to specific solar-terrestrial regions. This could involve a detailed comparison of kinetic, semi-kinetic, and hydrodynamic predictions for a given polar wind scenario or it could involve the comparison of a small-scale particle-in-cell (PIC) simulation of a plasma expansion event with a similar macroscopic expansion event. The different mathematical formulations have different strengths and weaknesses and a careful comparison of model predictions for similar geophysical situations provides insight into when the various models can be used with confidence

Academic achievement : the role of praise in motivating students

The motivation of students is an important issue in higher education, particularly in the context of the increasing diversity of student populations. A social-cognitive perspective assumes motivation to be dynamic, context-sensitive and changeable, thereby rendering it to be a much more differentiated construct than previously understood. This complexity may be perplexing to tutors who are keen to develop applications to improve academic achievement. One application that is within the control of the tutor, at least to some extent, is the use of praise. Using psychological literature the article argues that in motivating students, the tutor is not well served by relying on simplistic and common sense understandings of the construct of praise and that effective applications of praise are mediated by students' goal orientations, which of themselves may be either additive or interactive composites of different objectives and different contexts

Auroral ion velocity distributions for a polarization collision model

We have calculated the effect that convection electric fields have on the velocity distribution of auroral ions at the altitudes where the plasma is weakly-ionized and where the various ion-neutral collision frequencies are much smaller than the ion cyclotron frequencies, i.e. between about 130 and 300 km. The appropriate Boltzmann equation has been solved by expanding the ion velocity distribution function in a generalized orthogonal polynomial series about a bi-Maxwellian weight factor. We have retained enough terms in the series expansion to enable us to obtain reliable quantitative results for electric field strengths as large as 90 mV m-1. Although we have considered a range of ion-neutral scattering mechanisms, our main emphasis has been devoted to the long-range polarization interaction. In general, we have found that to lowest order the ion velocity distribution is better represented by a two-temperature or bi-Maxwellian distribution than by a one-temperature Maxwellian, with there being different ion temperatures parallel and perpendicular to the geomagnetic field. However, the departures from this zeroth-order bi-Maxwellian distribution become significant when the ion drift velocity approaches (or exceeds) the neutral thermal speed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22969/1/0000536.pd