Probing Fine-Scale Ionospheric Structure with the Very Large Array Radio Telescope

High resolution (~1 arcminute) astronomical imaging at low frequency (below 150 MHz) has only recently become practical with the development of new calibration algorithms for removing ionospheric distortions. In addition to opening a new window in observational astronomy, the process of calibrating the ionospheric distortions also probes ionospheric structure in an unprecedented way. Here we explore one aspect of this new type of ionospheric measurement, the differential refraction of celestial source pairs as a function of their angular separation. This measurement probes variations in the spatial gradient of the line-of-sight total electron content (TEC) to 0.001 TECU/km accuracy over spatial scales of under 10 km to over 100 km. We use data from the VLA Low-frequency Sky Survey (VLSS; Cohen et al. 2007, AJ 134, 1245), a nearly complete 74 MHz survey of the entire sky visible to the Very Large Array (VLA) telescope in Socorro, New Mexico. These data comprise over 500 hours of observations, all calibrated in a standard way. While ionospheric spatial structure varies greatly from one observation to the next, when analyzed over hundreds of hours, statistical patterns become apparent. We present a detailed characterization of how the median differential refraction depends on source pair separation, elevation and time of day. We find that elevation effects are large, but geometrically predictable and can be "removed" analytically using a "thin-shell" model of the ionosphere. We find significantly greater ionospheric spatial variations during the day than at night. These diurnal variations appear to affect the larger angular scales to a greater degree indicating that they come from disturbances on relatively larger spatial scales (100s of km, rather than 10s of km).Comment: Accepted for publication by The Astronomical Journa

A View of Professional Learning Communities Through Three Frames: Leadership, organization, and culture

In this discussion of professional learning communities (PLCs) in North American public schools, we examine three theoretical frames – leadership, organization, and culture. Issues related to learning are infused throughout our presentation of the frames. Based on our analysis of the current literature on this topic, PLCs offer a promising tool for system-wide change and collaborative mentorship in public schools. Implications for collaborative mentorship within PLCs are uncovered in relation to the professional learning of teachers and leaders and their community development. We dovetail the literature on learning, learning communities, and mentoring in order to identify such expanded possibilities for school teams that are supported by practical examples of change.Au sein de cette discussion sur les communautés d’apprentissages professionnelles (CAPs) dans les écoles publiques nord-américaines, nous faisons l’examen du phénomène via trois cadres théoriques – le leadership, l’organisation et la culture. Les problématiques reliées à l’apprentissage sont également introduites à travers les mêmes cadres. Suite à notre analyse de la littérature courante sur le sujet, les CAPs semblent un outil prometteur pour faciliter des changements systémiques étendus et des initiatives de mentorats collaboratifs dans les écoles publiques. Les tenants et aboutissants du mentorat collaboratifs sont dévoilés en mettant en évidence leurs liens avec les apprentissages professionnels des enseignants et des leaders en regard du développement de leur communauté. Ce faisant, nous combinons la littérature sur l’apprentissage, les communautés d’apprentissages et le mentorat afin d’identifier de nouvelles possibilités pour les équipes-écoles qui sont appuyées par des expériences pratiques de changement

Saving incentives, old-age provision and displacement effects: evidence from the recent German pension reform

In response to population aging, pay-as-you-go pensions are being reduced in almost all developed countries. In many countries, governments aim to fill the resulting gap with subsidized private pensions. This paper exploits the recent German pension reform to shed new light on the uptake of voluntary, but heavily subsidized private pension schemes. Specifically, we investigate how the uptake of the recently introduced "Riester pensions” depends on state-provided saving incentives, and how well the targeting to families and low-income households works in practice. We show that, after a slow start, private pension plans took off very quickly. While saving incentives were effective in reaching parents, they were less successful in attracting low-income earners, although Riester pensions exhibit a more equal pattern by income than occupational pensions and unsubsidized private pension plans. We also provide circumstantial evidence on displacement effects between saving for old-age provision and other purposes. Households who plan to purchase housing are less likely to have a Riester pension. The same holds for households who attach high importance to a bequest motive. Occupational pensions and other forms of private pensions, however, act as complements rather than as substitute

A quenching apparatus for the gaseous products of the solar thermal dissociation of ZnO

Rapid cooling for avoiding the recombination of Zn vapor and O2 derived from the solar thermal dissociation of ZnO is investigated using a thermogravimeter coupled to a quenching apparatus. The ZnO sample, which is placed in a cavity receiver and directly exposed to concentrated solar irradiation, underwent dissociation in the temperature range 1,820-2,050K at a rate monitored by on-line thermogravimetry. The product gases were quenched by water-cooled surfaces and by injection of cold Ar at cooling rates from 20,000 to 120,000K/s, suppressing the formation of ZnO in the gas phase and at the walls. Zinc content of the collected particles downstream varied in the range 40-94% for Ar/Zn(g) dilutions of 170 to 1,50

Dayside midlatitude ionospheric response to storm time electric fields: A case study for 7 September 2002

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95503/1/jgra21582.pd

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

Cultivating competence, self-efficacy, and intrinsic interest through proximal self-motivation.

Abstract: The present experiment tested the hypothesis that self-motivation through proximal goal setting serves as an effective mechanism for cultivating competencies, self-percepts of efficacy, and intrinsic interest. Children who exhibited gross deficits and disinterest in mathematical tasks pursued a program of self-directed learning under conditions involving either proximal subgoals, distal goals, or no goals. Results of the multifaceted assessment provide support for the superiority of proximal self-influence. Under proximal subgoals, children progressed rapidly in self-directed learning, achieved substantial mastery of mathematical operations, and developed a sense of personal efficacy and intrinsic interest in arithmetic activities that initially held little attraction for them. Distal goals had no demonstrable effects. In addition to its other benefits, goal proximity fostered veridical self-knowledge of capabilities as reflected in high congruence between judgments of mathematical self-efficacy and subsequent mathematical performance. Perceived self-efficacy was positively related to accuracy of mathematical performance and to intrinsic interest in arithmetic activities. Article: Much human behavior is directed and sustained over long periods, even though the external inducements for it may be few and far between. Under conditions in which external imperatives are minimal and discontinuous, people must partly serve as agents of their own motivation and action. In social learning theory (Bandura, 1977b, in press), self-directedness operates through a self system that comprises cognitive structures and subfunctions for perceiving, evaluating, motivating, and regulating behavior. An important, cognitively based source of self-motivation relies on the intervening processes of goal setting and self-evaluative re-actions to one's own behavior. This form of self-motivation, which operates largely through internal comparison processes, re-quires personal standards against which to evaluate ongoing performance. By making self-satisfaction conditional on a certain level of performance, individuals create self-inducements to persist in their efforts until their performances match internal standards. Both the anticipated satisfactions for matching attainments and the dissatisfactions with insufficient ones provide incentives for self-directed actions. Personal goals or standards do not automatically activate the evaluative processes that affect the level and course of one's behavior. Certain properties of goals, such as their specificity and level, help to provide clear standards of adequacy In the social learning view, adopting proximal subgoals for one's own behavior can have at least three major psychological effects. As already alluded to, such goals have motivational effects. One of the propositions tested in the present experiment is that self-motivation can be best created and sustained by attainable subgoals that lead to larger future ones. Proximal subgoals provide immediate incentives and guides for performance

How Research Data Management Plans Can Help in Harmonizing Open Science and Approaches in the Digital Economy

Within this perspective article, we intend to summarise definitions and terms that are often used in the context of open science and data-driven R&D and we discuss upcoming European regulations concerning data, data sharing and handling. With this background in hand, we take a closer look at the potential connections and permeable interfaces of open science and digital economy, in which data and resulting immaterial goods can become vital pieces as tradeable items. We believe that both science and the digital economy can profit from a seamless transition and foresee that the scientific outcomes of publicly funded research can be better exploited. To close the gap between open science and the digital economy, and to serve for a balancing of the interests of data producers, data consumers, and an economy around services and the public, we introduce the concept of generic research data management plans (RDMs), which have in part been developed through a community effort and which have been evaluated by academic and industry members of the NFDI4Cat consortium. We are of the opinion that in data-driven research, RDMs do need to become a vital element in publicly funded projects

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