Images in Christmas Balls

We describe light-reflection properties of spherically curved mirrors, like balls in the Christmas tree. In particular, we study the position of the image which is formed somewhere beyond the surface of a spherical mirror, when an eye observes the image of a pointlike light source. The considered problem, originally posed by Abu Ali Hasan Ibn al-Haitham -- alias Alhazen -- more than a millennium ago, turned out to have the now well known analytic solution of a biquadratic equation, being still of great relevance, e.g. for the aberration-free construction of telescopes. We do not attempt to perform an exhaustive survey of the rich historical and engineering literature on the subject, but develop a simple pedagogical approach to the issue, which we believe to be of continuing interest in view of its maltreating in many high-school textbooks.Comment: 13 pages, 7 figures plain LaTeX; Also see http://cft.fis.uc.pt/eef/mirrors.htm, revised version has simplified formulas, more transparent for a wider audience, one reference adde

Regulation of Brown and White Adipocyte Transcriptome by the Transcriptional Coactivator NT-PGC-1α

The β3-adrenergic receptor (AR) signaling pathway is a major component of adaptive thermogenesis in brown and white adipose tissue during cold acclimation. The β3-AR signaling highly induces the expression of transcriptional coactivator PGC-1α and its splice variant N-terminal (NT)-PGC-1α, which in turn activate the transcription program of adaptive thermogenesis by co-activating a number of transcription factors. We previously reported that NT-PGC-1α is able to increase mitochondrial number and activity in cultured brown adipocytes by promoting the expression of mitochondrial and thermogenic genes. In the present study, we performed genome-wide profiling of NT-PGC-1α-responsive genes in brown adipocytes to identify genes potentially regulated by NT-PGC-1α. Canonical pathway analysis revealed that a number of genes upregulated by NT-PGC-1α are highly enriched in mitochondrial pathways including fatty acid transport and β-oxidation, TCA cycle and electron transport system, thus reinforcing the crucial role of NT-PGC-1α in the enhancement of mitochondrial function. Moreover, canonical pathway analysis of NT-PGC-1α-responsive genes identified several metabolic pathways including glycolysis and fatty acid synthesis. In order to validate the identified genes in vivo, we utilized the FL-PGC-1α-/- mouse that is deficient in full-length PGC-1α (FL-PGC-1α) but expresses a slightly shorter and functionally equivalent form of NT-PGC-1α (NT-PGC-1α254). The β3-AR-induced increase of NT-PGC-1α254 in FL-PGC-1α-/-brown and white adipose tissue was closely associated with elevated expression of genes involved in thermogenesis, mitochondrial oxidative metabolism, glycolysis and fatty acid synthesis. Increased adipose tissue thermogenesis by β3-AR activation resulted in attenuation of adipose tissue expansion in FL-PGC-1α-/- adipose tissue under the high-fat diet condition. Together, the data strengthen our previous findings that NT-PGC-1α regulates mitochondrial genes involved in thermogenesis and oxidative metabolism in brown and white adipocytes and further suggest that NT-PGC-1α regulates a broad spectrum of genes to meet cellular needs for adaptive thermogenesis

Novel tools and best practices for education about invasive alien species

Increasing public awareness is a prerequisite for successful management of invasive alien species (IAS). Environmental education can play an important role in this process by providing relevant learning outcomes and experiences for youth and students, as well as professionals in different sectors associated with introduction pathways or who are involved in mitigation and eradication of IAS. This paper responds to the urgent call for the inclusion of the IAS topic in education through the development, implementation and evaluation of novel and user-friendly educational materials. The aim of this paper is to describe best practices in IAS education and to share the lessons learned from eight educational projects from seven different countries. We discuss four challenges for IAS education, related to (1) inconsistent and ambiguous terminology, (2) communicating risk, (3) implementation of education materials, and (4) evaluation of learning effects. Examples of best practices are the use of smartphone applications and gaming elements, place-based education and exhibitions. We also note the importance of open access publishing of education materials to make them easily available. We intend this discussion to serve as a source of inspiration to researchers, science communicators and teachers and to spur the development of new teaching materials worldwide.Peer reviewe

The quality of options in strategic decision making: a study about creativity and completeness in business decision making

A qualidade das decisões estratégicas dos empresários está diretamente relacionada à capacidade que eles demonstram para encontrar alternativas criativas quando enfrentam os problemas de suas empresas. Essas alternativas podem ser geradas intuitivamente, utilizando heurísticas. As pesquisas sobre geração de alternativas têm indicado consistentemente que as pessoas não são eficientes nessa atividade. As explicações para esse fato, contidas na literatura sobre decisão, não são conclusivas e permitem especulações a respeito. Para explorar essa questão e relacioná-la ao administrador brasileiro, foi idealizado um experimento com 174 alunos de quatro cursos de MBA para avaliar a originalidade e a completude das alternativas. O experimento e a respectiva análise basearam-se na confluência da pesquisa experimental, oriunda da psicologia cognitiva da decisão, com as visões da ciência da decisão organizacional tradicional e o novo campo de estudo das decisões intuitivas ou naturalísticas. Para mensurar a criatividade das alternativas apresentadas durante o experimento, empregou-se o conceito de árvore hierárquica, que demonstrou ser uma poderosa ferramenta para a tipologia de alternativas. O resultado desse experimento confirmou o baixo desempenho em geração de alternativas dos gerentes e, ao mesmo tempo, indicou que, provavelmente, a etapa de geração de alternativas isolada da etapa de escolha pode melhorar a qualidade das alternativas. A heurística, por sua vez, não demonstrou influenciar o conjunto de alternativas geradas. _________________________________________________________________________________________ ABSTRACT: The quality of strategic decisions of executives is directly related to the ability they have to find creative alternatives when facing business problems. These alternatives could be generated intuitively, using heuristics. On the other hand, the researches on alternatives generation have consistently indicated that people are not efficient on this duty. The argument for that, contained in the decision’s literature, is not conclusive and it allows speculation about it. To explore this issue and relate it to the Brazilian Administration, an experiment was designed for 174 students of four courses of MBA. The experiment and the analysis were resulted from the confluence between the experimental research from decision cognitive psychology with science’s vision of the traditional organizational decision and the new field of study on naturalistic or intuitive decisions. To measure the creativity of the alternatives presented during the experiment, the concept of hierarchical tree was utilized and it has proved a powerful tool to the typology of alternatives. The result of this experiment confirmed the poor performance in alternatives generation by managers and at the same time, indicated that probably, the generation of options isolated of analysis can produce better quality of alternatives. The heuristic, do not demonstrated any influence on options generated