284 research outputs found

    Gold Difluorocarbenoid Complexes: Spectroscopic and Chemical Profiling

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    Gold carbenes of the general type [LAu=CR2]+ are sufficiently long‐lived for spectroscopic inspection only if the substituents compensate for the largely missing stabilization of the carbene center by the [LAu]+ fragment. π‐Donation by two fluorine substituents (R=F) is insufficient; rather, difluorocarbene complexes are so deprived in electron density that they sequester even “weakly coordinating” anions such as triflate or triflimide. This particular bonding situation translates into unmistakable carbenium ion chemistry upon reaction with stilbene as a model substrate

    A computer-supported learning platform for pupils with cognitive disabilities

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    Although there is no doubt that computers are highly capable to provide pupils with cognitive disabilities in learning we observe an immense lack of professional learning software for this target group. On the one hand, there are products designed by special education teachers with a high level of instructional design. But these products are usually at a low technical level, unflexible and adapted for the special situation they are designed for. On the other hand there are loads of colourful animated commercial products, but with absence of any instructional quality. In our project we want to overcome these problems by developing a learning platform for this special target group in an interdisciplinary group based on participatory design principles

    (Un-) Coupling gaze and attention outside central vision

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    In normal vision, shifts of attention and gaze are tightly coupled. Here we ask if this coupling affects performance also when central vision is not available. To this aim, we trained normal-sighted participants to perform a visual search task while vision was restricted to a gaze-contingent viewing window ("forced field location") either in the left, right, upper, or lower visual field. Gaze direction was manipulated within a continuous visual search task that required leftward, rightward, upward, or downward eye movements. We found no general performance advantage for a particular part of the visual field or for a specific gaze direction. Rather, performance depended on the coordination of visual attention and eye movements, with impaired performance when sustainedattention and gaze have to be moved in oppositedirections. Our results suggest that during early stages of central visual field loss, the optimal location for the substitution of foveal vision does not depend on the particular retinal location alone, as has previously been thought, but also on the gaze direction required by the task the patient wishes to perform

    Simulação do impacto das atividades florestais na fragilidade potencial em plantios de pinus.

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    Este trabalho, realizado em uma área com povoamento de Pinus taeda, teve por objetivo simular e mapear a influência do valor de impacto das atividades florestais na fragilidade potencial. Variáveis do solo, de declividade do terreno, valor de impacto e de cobertura vegetal foram utilizadas para gerar os mapas. Os resultados expressos pelo modelo adotado mostraram que as áreas mais frágeis apresentam em sua maioria declividades superiores a 75 % e textura que variam de arenosa a média, e as áreas menos frágeis apresentam predominantemente relevo plano (até 3 %) e textura argilosa. Quando simulado o impacto das atividades florestais sobre esse ambiente, verificou-se que na maior parte da área (78 %) todas as atividades florestais podem ser realizadas sem influência na degradação do meio ambiente e para algumas áreas (11 %) o ambiente foi considerado menos frágil, em razão da presença de cobertura vegetal

    Polyunsaturated C-Glycosidic 4-Hydroxy-2-pyrone Derivatives: Total Synthesis Shows that Putative Orevactaene Is Likely Identical with Epipyrone A

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    Orevactaene and epipyrone A were previously thought to comprise the same polyunsaturated tail but notably different C-glycosylated 4-hydroxy-2-pyrone head groups. Total synthesis now shows that the signature bicyclic framework assigned to orevactaene is a chimera; the compound is almost certainly identical with epipyrone A, whose previously unknown stereochemistry has also been established during this study. Key to success was the ready formation of the bicyclic core of putative orevactaene by a sequence of two alkyne cycloisomerization reactions using tungsten and gold catalysis. Equally important was the flexibility in the assembly process gained by the use of heterobimetallic polyunsaturated modules whose termini could be selectively and consecutively addressed in a practical one-pot cross-coupling sequence

    Modelagem uni e bivariada da variabilidade espacial de rendimento de Pinus taeda L.

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    O objetivo deste estudo foi avaliar a variabilidade espacial de rendimento de Pinus taeda L. em função de teores de argila do solo obtidos de um mapeamento detalhado de solos, na escala 1:10.000, em uma área localizada no município de Rio Negrinho, estado de Santa Catarina. Os dados dendrométricos para a realização deste estudo, coletados em parcelas de inventário florestal contínuo, foram obtidos de um povoamento com área de 2.252,11 ha. Propriedades do solo e rendimentos de Pinus taeda foram analisados através de métodos geoestatísticos, usando-se semivariogramas, modelos espaciais uni e bivariados e interpolação espacial por krigagem e cokrigagem para construção de mapas que descrevam o rendimento na região. Pelos semivariogramas, avaliou-se a estrutura de continuidade espacial do incremento médio anual volumétrico (IMA), pelo interesse prático nessa variável e também por ter sido a que melhor se correlacionou com os dados de solos. A comparação dos dois mapas obtidos de IMA obtidos pela modelagem uni e bivariada sugere que a última proporciona uma descrição mais detalhada do atributo de interesse na área, sendo o detalhamento da variabilidade espacial dependente do maior ou menor número de dados obtidos geograficamente para o estudo

    Carcass Quality of Slaughtered Cika and Brown Cattle in Slovenia

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    The aim of the study was to compare carcass traits between Cika and Brown cattle of all slaughter categories. The data used were collected in Slovenian slaughterhouses from 2007 to 2010. After the slaughter carcass weight was recorded and carcass conformation and fatness were scored according to the EUROP system. Net daily gain was calculated. Data were analysed by GLM procedure of statistical package SAS/ STAT considering breed, month of the slaughter and year of the slaughter nested within the breed as fixed effects. Cika bulls (under 24 months old) were two months younger at slaughter (20.2 months) and achieved lower carcass weight (266.7 kg) compared to Brown bulls (22.4 months, 330.0 kg). Also in all other categories except in calves under eight months old, Brown cattle had higher carcass weight. Bulls under 24 months old, steers, cows and calves over eight to 12 months old of Brown cattle were older at slaughter compared to Cika breed. Net daily gain was also higher in all slaughtered categories of Brown cattle. Even if the slaughtered Brown cattle had heavier carcass weight compared to Cika cattle there was almost no significant difference in carcass conformation. Carcasses of Cika bulls under 24 months old had conformation 6.4 while Brown bulls 6.3. Likewise carcasses of Cika calves over eight to 12 months had higher conformation score (5.7) than Brown (4.8) calves. Fatness was higher in Brown bulls, steers and heifers compared to Cika cattle, while Cika cows had higher fatness than Brown cows
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