A abordagem de alguns números irracionais notáveis nos livros didáticos do ensino fundamental e médio

Este texto descreve os resultados de uma pesquisa orientada pela questão ‘Como são abordados os números irracionais no ensino básico, considerando-se como fonte o livro didático?’. Em uma amostra de livros didáticos, observamos se e como são apresentados ‘o número PI’, ‘o número de Euler’ e ‘o número de Ouro’. A investigação utilizou os núcleos de significação para analisar os sentidos do discurso presente nos textos dos livros didáticos. Constatamos que os temas apontados são introduzidos por um viés empírico ou pela definição formal, porém não ocorre intercâmbio destes pólos. Observamos que o número PI é empiricamente abordado, o número de Euler é apenas citado como uma possível base dos logaritmos e fica destaca a interface artística do número de Ouro articulada a representação algébrica. Em síntese, esta opção dos livros didáticos reforça uma concepção tecnicista, limitando a compreensão da complexidade dos números irracionais no Ensino Fundamental e Médio.Palavras-chave: Livro Didático. Núcleos de Significação. Número PI. Número de Euler. Número de Ouro

Low Energy Singlets in the Excitation Spectrum of the Spin Tetrahedra System Cu_2Te_2O_5Br_2

Low energy Raman scattering of the s=1/2 spin tetrahedra system Cu_2Te_2O_5Br_2 is dominated by an excitation at 18 cm^{-1} corresponding to an energy E_S=0.6\Delta, with \Delta the spin gap of the compound. For elevated temperatures this mode shows a soft mode-like decrease in energy pointing to an instability of the system. The isostructural reference system Cu_2Te_2O_5Cl_2 with a presumably larger inter-tetrahedra coupling does not show such a low energy mode. Instead its excitation spectrum and thermodynamic properties are compatible with long range Neel-ordering. We discuss the observed effects in the context of quantum fluctuations and competing ground states.Comment: 5 pages, 2 figures, ISSP-Kashiwa 2001, Conference on Correlated Electron

Jeder für sich oder alle zusammen? : Das Stuttgarter Startup Ökosystem

Im bekanntesten Startup Ökosystem der Welt, dem Silicon Valley, steht die Stanford University im Zentrum. Wie sieht es demgegenüber im Stuttgarter Startup Ökosystem aus? Mittels einer Netzwerkanalyse kartieren wir die zentralen Akteure dieses Ökosystems und ihre Beziehungen zueinander. Dabei zeigt sich: Das Stuttgarter Ökosystem zerfällt in drei separate Communities. Dies sind eine Unterstützungscommunity, in der sich hauptsächlich Unternehmertum fördernde Akteure bewegen, eine Potenzialcommunity rundherum um Fachhochschulen und Universitäten, welche die innovative Basis für viele Gründungsideen schafft, und eine Unternehmercommunity. Diese gewachsene Struktur erfüllt ihren Zweck, birgt jedoch Optimierungspotenzial

Contribuição da abordagem geocientífica no ensino fundamental : tempo geológico, origem do petróleo e mudanças ambientais

O presente artigo descreve uma experiência em sala de aula com alunos da 4ª série do ensino fundamental em escola pública em São Paulo, Brasil. Em 2007 foram desenvolvidas atividades do conteúdo programático de Ciências, segundo uma abordagem geológica. O objetivo inicial da professora era dar aos alunos referenciais importantes para explorarem e compreenderem os recursos naturais renováveis e não renováveis, usando como tema gerador o petróleo e as conseqüências ecológicas dos grandes derramamentos ou vazamentos do produto no mar. Baseando-se na metodologia dialética, a partir de argumentações e perguntas elaboradas, procurou-se estabelecer contextos, diferentes significados e representações do assunto, sendo a parceria entre professora e pesquisadora essencial para a superação da fragmentação do saber sobre a questão do conteúdo e sua relação com a didática

Common genetic and environmental contributions to post-traumatic stress disorder and alcohol dependence in young women

BACKGROUND: The few genetically informative studies to examine post-traumatic stress disorder (PTSD) and alcohol dependence (AD), all of which are based on a male veteran sample, suggest that the co-morbidity between PTSD and AD may be attributable in part to overlapping genetic influences, but this issue has yet to be addressed in females. METHOD: Data were derived from an all-female twin sample (n=3768) ranging in age from 18 to 29 years. A trivariate genetic model that included trauma exposure as a separate phenotype was fitted to estimate genetic and environmental contributions to PTSD and the degree to which they overlap with those that contribute to AD, after accounting for potential confounding effects of heritable influences on trauma exposure. RESULTS: Additive genetic influences (A) accounted for 72 % of the variance in PTSD ; individual-specific environmental (E) factors accounted for the remainder. An AE model also provided the best fit for AD, for which heritability was estimated to be 71 %. The genetic correlation between PTSD and AD was 0.54. CONCLUSIONS: The heritability estimate for PTSD in our sample is higher than estimates reported in earlier studies based almost exclusively on an all-male sample in which combat exposure was the precipitating traumatic event. However, our findings are consistent with the absence of evidence for shared environmental influences on PTSD and, most importantly, the substantial overlap in genetic influences on PTSD and AD reported in these investigations. Additional research addressing potential distinctions by gender in the relative contributions of genetic and environmental influences on PTSD is merited

Dzyaloshinsky-Moriya Spin Canting in the LTT Phase of La2-x-yEuySrxCuO4

The Cu spin magnetism in La2-x-yEuySrxCuO4 (x<=0.17; y<=0.2) has been studied by means of magnetization measurements up to 14 T. Our results clearly show that in the antiferromagnetic phase Dzyaloshinsky-Moriya (DM)superexchange causes Cu spin canting not only in the LTO phase but also in the LTLO and LTT phases. In La1.8Eu0.2CuO4 the canted DM-moment is about 50% larger than in pure La2CuO4 which we attribute to the larger octahedral tilt angle. We also find clear evidence that the size of the DM-moment does not change significantly at the structural transition at T_LT from LTO to LTLO and LTT. The most important change induced by the transition is a significant reduction of the magnetic coupling between the CuO2 planes. As a consequence, the spin-flip transition of the canted Cu spins which is observed in the LTO phase for magnetic field perpendicular to the CuO2 planes disappears in the LTT phase. The shape of the magnetization curves changes from the well known spin-flip type to a weak-ferromagnet type. However, no spontaneous weak ferromagnetism is observed even at very low temperatures, which seems to indicate that the interlayer decoupling in our samples is not perfect. Nonetheless, a small fraction (<15%) of the DM-moments can be remanently magnetized throughout the entire antiferromagnetically ordered LTT/LTLO phase, i.e. for T<T_LT and x<0.02. It appears that the remanent DM-moment is perpendicular to the CuO2 planes. For magnetic field parallel to the CuO2 planes we find that the critical field of the spin-flop transition decreases in the LTLO phase, which might indicate a competition between different in-plane anisotropies. To study the Cu spin magnetism in La2-x-yEuySrxCuO4, a careful analysis of the Van Vleck paramagnetism of the Eu3+ ions was performed.Comment: 22 pages, 27 figure

Green Production of Anionic Surfactant Obtained from Pea Protein

A pea protein isolate was hydrolyzed by a double enzyme treatment method in order to obtain short peptide sequences used as raw materials to produce lipopeptides-based surfactants. Pea protein hydrolysates were prepared using the combination of Alcalase and Flavourzyme. The influence of the process variables was studied to optimize the proteolytic degradation to high degrees of hydrolysis. The average peptide chain lengths were obtained at 3–5 amino acid units after a hydrolysis of 30 min with the mixture of enzymes. Then, N-acylation in water, in presence of acid chloride (C12 and C16), carried out with a conversion rate of amine functions of 90%, allowed to obtain anionic surfactant mixtures (lipopeptides and sodium fatty acids). These two steps were performed in water, in continuous and did not generate any waste. This process was therefore in line with green chemistry principles. The surface activities (CMC, foaming and emulsifying properties) of these mixtures were also studied. These formulations obtained from natural renewable resources and the reactions done under environmental respect, could replace petrochemical based surfactants for some applications

Development of the Tilburg Pregnancy Distress Scale: the TPDS

Contains fulltext : 96807.pdf (publisher's version ) (Open Access)ABSTRACT: BACKGROUND: Pregnant women with high levels of stress, depression and/or anxiety are at increased risk for adverse perinatal outcomes and impaired neurologic and emotional development of the offspring. Pregnancy specific instruments to measure psychological functioning during gestation are scarce and do not define items based on in-depth interviews of pregnant and recently delivered women. The current study developed a pregnancy specific scale that measures psychological functioning using in-depth interviews. METHODS: Three focus groups were formed to discuss issues most relevant to pregnancy distress; 22 candidate items were derived for pilot testing (study I, n = 419) its psychometric properties by means of explorative factor analyses (EFA). This resulted in a 17-item TPDS which was further explored by confirmatory factor analyses (CFA) and concurrent and construct validity assessment (study II, n = 454). RESULTS: EFA in study I suggested a two component solution (negative affect (NA) and partner involvement (PI)). CFA in study II resulted in a higher order model of the NA subscale into three more subscales: NA regarding confinement, delivery and general health. TPDS, EPDS and GAD-7 were all significantly correlated. CONCLUSIONS: The TPDS constitutes a valid and user friendly instrument to assess pregnancy distress. In addition to its proven ability to pick up pregnancy specific negative affect it also includes an important sub-scale measuring perceived partner involvement