Representation and learning about evaporation

While there has been considerable research on children's understanding of evaporation, the representational issues entailed in this understanding have not been investigated in depth. This study explored students' engagement with evaporation phenomena through various representational modes. Primary school classroom sequences and structured interviews shortly after, and a year later, indicated significant advances in learning flowing from negotiation of meaning around particle representations. A case study of one child's learning is used to demonstrate how a molecular distribution representation can offer the possibility of significant advances in children's thinking about evaporation. The findings suggest that teacher-mediated negotiation of representational issues can support enriched student learning

Representational issues in students learning about evaporation

This study draws on recent research on the central role of representation in learning. While there has been considerable research on students’ understanding of evaporation, the representational issues entailed in this understanding have not been investigated in depth. The study explored students’ engagement with evaporation phenomena through various representational modes. The study indicates how a focus on representation can provide fresh insights into the conceptual task involved in learning science through an investigation of students’ responses to a structured classroom sequence and subsequent interviews over a year. A case study of one child’s learning demonstrates the way conceptual advances are integrally connected with the development of representational modes. The findings suggest that teacher-mediated negotiation of representational issues as students construct different modal accounts can support enriched learning by enabling both (a) richer conceptual understanding by students, and (b) enhanced teacher insights into students’ thinking.

Multiple representation in learning about evaporation

This study draws on recent research on the central role of representation in learning. While there has been considerable research on Children’s understanding of evaporation, the representational issues entailed in this understanding have not been investigated in depth. The study explored students’ engagement with science concepts relating to evaporation through various representational modes such as diagrams, verbal accounts, gestures, and captioned drawings. This engagement entails students a) clarifying their thinking through exploring representational resources, b) developing understanding of what these representations signify and c) learning how to construct and interpret the representational aspects of scientific explanation. The study indicates how a focus on representation can provide fresh insights into the conceptual task involved in learning science. Primary school classroom sequences and structured interviews with 12 children indicated a range of learning potentialities flowing from this focus. The findings suggest that teacher-mediated negotiation of representational issues as students construct different modal accounts can support enriched learning by enabling both a) richer conceptual understanding by students and b) enhanced teacher insights into students’ thinking.

Multiple representation in learning about evaporation

There has been extensive research on children's understanding of evaporation, but representational issues entailed in this understanding have not been investigated in depth. This study explored three students' engagement with science concepts relating to evaporation through various representational modes, such as diagrams, verbal accounts, gestures, and captioned drawings. This engagement entailed students (a) clarifying their thinking through exploring representational resources; (b) developing understanding of what these representations signify; and (c) learning how to construct representational aspects of scientific explanation. The study involved a sequence of classroom lessons on evaporation and structured interviews with nine children, and found that a focus on representational challenges provided fresh insights into the conceptual task involved in learning science. The findings suggest that teacher-mediated negotiation of representational issues as students construct different modal accounts can support enriched learning by enabling both (a) richer conceptual understanding by students; and (b) enhanced teacher insights into students' thinking.

Anomalous evaporation behavior of ZnO powder milled mechanically under high-energy conditions

ZnO powder showed anomalous evaporation behavior after its mechanical milling treatment under high-energy conditions. The amount of generated vapor is about 10 times higher in the first 15 min of annealing at 1300 °C than that of unmilled ZnO powders. The strong ball impacts are responsible for the greatly enhanced evaporation ability. Low-energy ball milling involving shearing actions and rare weak impacts leads only to a small evaporation rate enhancement. The possible explanation of the high evaporation rate of the heavily milled material is the existence of large fraction of weakly bonded atoms in grain boundaries, surface defects and strained areas.

There's a black boy dead and a migloo holding a gun : death, Aboriginality and history in Australian adolescent literature

This essay is concerned with the extent to which the attitudes and ideologies of colonial discourse continue to influence contemporary signifying practices in Australian adolescent historical fiction. Under scrutiny are three novels which take issue with the violent aspects of colonisation when so many members of the Indigenous population either died or were forcibly displaced: Melissa Lucashenko’s Killing Darcy, Gary Crew’s No Such Country and Mark Svendsen’s Poison Under Their Lips. Although these texts share a desire to interrogate monolithic versions of Australia’s history, it is argued that such motivations offer no guarantee that the implied audience is positioned to come to an understanding of perspectives belonging to ex-centric Others.

In-situ confocal Raman monitoring of evaporation process during protein crystallization

We have introduced an in-situ Raman monitoring technique to investigate the crystallization process inside protein drops. In addition to a conventional vapour-diffusion process, a novel procedure which actively stimulates the evaporation from a protein drop during crystallization was also evaluated, with lysozyme as a model protein. In contrast to the conventional vapour-diffusion condition, the evaporation-stimulated growth of crystals was initiated in a simple dehydration scheme and completed within a significantly shorter time. To gain an understanding of crystallization behaviours under the conditions with and without such evaporation stimulation, confocal Raman spectroscopy combined with linear regression analysis was used to monitor both lysozyme and HEPES buffer concentrations in real time. The confocal measurements having a high spatial resolution and good linear response revealed areas of local inhomogeneity in protein concentration when the crystallization started. The acquired concentration profiles indicated that (1)ÿthe evaporation-stimulated crystallization proceeded with protein concentrations lower than those under conventional vapour diffusion, and (2)ÿcrystals under the evaporation-stimulated condition were noticeable within an early stage of crystallization before the protein concentration approached its maximum value. The HEPES concentration profiles, on the other hand, increased steadily towards the end of the process regardless of the conditions used for crystallization. In particular, the observed local inhomogeneities specific to protein distribution suggested an accumulation mechanism of protein molecules that initiates the nucleation of crystals.

Stability of aqueous films between bubbles. Part 2. Effects of trace impurities and evaporation

The stability of water films has been investigated with a Mysels-Scheludko type film balance. Minor trace impurities in water do not affect the lifetime of water films under vapor saturation, but significantly influence the stability in free evaporation. Trace amounts of positively adsorbed contaminants induce Marangoni-driven flow that destabilizes films under evaporation conditions whereas negatively adsorbed electrolytes actually prolong stability by reversing interfacial tension gradients and driving a steady circulation within the film. At high thinning rates, pure-water films develop exotic-appearing flow patterns and break due to a strong coupling between hydrodynamic and interfacial tensiongradient adsorption stresses. The most dominant factor of transient film stabilization in dynamic conditions under evaporation is a surface tension gradient created in the film. We discuss surface tension gradients in transient films created by temperature differences, impurity concentration, and expansion of the films.

O novo sistema de análise prévia dos atos de concentração e a questão do Gun-Jumping: traçando parâmetros para as empresas

Em 29 de maio de 2012 entrou em vigor a Lei nº 12.529/2011, que introduziu no Brasil o sistema de análise prévia dos atos de concentração. Nesse novo regime, as empresas deverão preservar as condições de concorrência entre si e não mais poderão consumar a operação antes de sua aprovação pelo Conselho Administrativo de Defesa Econômica (CADE), sob pena de violarem as regras do sistema de análise prévia das operações, i.e., praticarem gun-jumping ilegal. Contudo, nem a Nova Lei, nem o Novo Regimento Interno do CADE especificaram quais práticas implicariam a consumação da operação. Dessa forma, o presente trabalho buscou identificar parâmetros, através da experiência americana e europeia e da análise de acordos de preservação da reversibilidade da operação, que pudessem auxiliar as empresas a conduzirem suas atividades no momento que antecede a aprovação da operação.

An economic model of gun control

Guns stolen from law-abiding households provide the principal source of guns for criminals. The lethality of crime instruments increases with the availability of guns, so the gun market is subject to externalities that generate excessive ownership and inadequate spending on protective measures to deter gun theft. One motive for gun ownership is self defense, and the gun market is subject to coordination failure: the more guns purchased lawfully, the more will be stolen by criminals, so the greater the incentive for lawful . consumers to purchase guns for self defense. As a result, there may be multiple equilibria in the gun market and more than one equilibrium crime rate. We show that a simple refundable deposit for guns will internalize the externalities in the gun market and may cause large downward jumps in gun ownership, the lethality of crime instruments, and the social costs of crime.