990 resultados para Tracks
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Tracks have been made across peatlands for as long as human society has existed. Un - made tracks (i.e. those created simply by regular use, with no construction involved) were probably first created by grazing animals and then presumably also used by early human communities. F ind ing these increasingly impassable with regular use , human societies began to construct ' corduroy roads ' during Neolithic, Bronze and Iron Age times. These first constructed tracks were made from cut timbers ( below ) . Across Europe, ma ny examples of these corduroy roads have been found preserved in lowland bogs, perhaps most famously in the Somerset Levels and more recently at Hatfield Moors on the Humberhead Levels.
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Covers Manhattan south of 62nd Street.
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The effects of individual teacher expectations have been the subject of intensive research. Results indicate that teachers use their expectations to adapt their interactions with their students to some degree (as summarized in a review by Jussim & Harber, 2005). This can in turn lead to expectancy-confirming student developments. While there are studies on the Pygmalion effect on individual students, there is only little research on teacher judgements of whole classes and schools. Our study aims to extend the perspective of teacher judgements at the collective level to stereotypes within the context of school tracking. The content and structure of teachers school track stereotypes are investigated as well as the question of whether these stereotypical judgements are related to teachers perception of obstacles to their teaching and their teaching self-efficacy beliefs. Cross-sectional data on 341 teachers at two different school types from the Panel Study at the Research School Education and Capabilities in North Rhine-Westphalia (PARS) (see Bos et al., 2016) were used for two purposes: First, the structure of teachers stereotypes was identified via an exploratory factor analysis. Second, in follow-up regression analyses, the stereotype dimensions extracted were used to predict teachers perceptions of obstacles to their classroom work and their individual and collective teacher self-efficacy beliefs. Results showed that after controlling for the average cognitive abilities and the average cultural capital of the students teacher stereotypes were indeed related to perceived obstacles concerning their classroom work and their self-efficacy beliefs. After a discussion of the strengths and limitations of the present research, the article closes with a short proposal of a future research framework for collective Pygmalion effects. (DIPF/Orig.)
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Mixed media. 23" x 19", Complexity Series.
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Rsum : Les ions hydronium (H3O + ) sont forms, temps courts, dans les grappes ou le long des trajectoires de la radiolyse de l'eau par des rayonnements ionisants faible transfert dnergie linaire (TEL) ou TEL lev. Cette formation in situ de H3O + rend la rgion des grappes/trajectoires du rayonnement temporairement plus acide que le milieu environnant. Bien que des preuves exprimentales de lacidit dune grappe aient dj t signales, il n'y a que des informations fragmentaires quant son ampleur et sa dpendance en temps. Dans ce travail, nous dterminons les concentrations en H3O + et les valeurs de pH correspondantes en fonction du temps partir des rendements de H3O + calculs laide de simulations Monte Carlo de la chimie intervenant dans les trajectoires. Quatre ions incidents de diffrents TEL ont t slectionns et deux modles de grappe/trajectoire ont t utiliss : 1) un modle de grappe isole "sphrique" (faible TEL) et 2) un modle de trajectoire "cylindrique" (TEL lev). Dans tous les cas tudis, un effet de pH acide brusque transitoire, que nous appelons un effet de "pic acide", est observ immdiatement aprs lirradiation. Cet effet ne semble pas avoir t explor dans l'eau ou un milieu cellulaire soumis un rayonnement ionisant, en particulier haut TEL. cet gard, ce travail soulve des questions sur les implications possibles de cet effet en radiobiologie, dont certaines sont voques brivement. Nos calculs ont ensuite t tendus ltude de l'influence de la temprature, de 25 350 C, sur la formation in situ dions H3O + et leffet de pic acide qui intervient temps courts lors de la radiolyse de leau faible TEL. Les rsultats montrent une augmentation marque de la rponse de pic acide hautes tempratures. Comme de nombreux processus intervenant dans le cur dun racteur nuclaire refroidi l'eau dpendent de faon critique du pH, la question ici est de savoir si ces fortes variations dacidit, mme si elles sont hautement localises et transitoires, contribuent la corrosion et lendommagement des matriaux.
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Monte Carlo track structures (MCTS) simulations have been recognized as useful tools for radiobiological modeling. However, the authors noticed several issues regarding the consistency of reported data. Therefore, in this work, they analyze the impact of various user defined parameters on simulated direct DNA damage yields. In addition, they draw attention to discrepancies in published literature in DNA strand break (SB) yields and selected methodologies. The MCTS code Geant4-DNA was used to compare radial dose profiles in a nanometer-scale region of interest (ROI) for photon sources of varying sizes and energies. Then, electron tracks of 0.28 keV-220 keV were superimposed on a geometric DNA model composed of 2.7 10(6) nucleosomes, and SBs were simulated according to four definitions based on energy deposits or energy transfers in DNA strand targets compared to a threshold energy ETH. The SB frequencies and complexities in nucleosomes as a function of incident electron energies were obtained. SBs were classified into higher order clusters such as single and double strand breaks (SSBs and DSBs) based on inter-SB distances and on the number of affected strands. Comparisons of different nonuniform dose distributions lacking charged particle equilibrium may lead to erroneous conclusions regarding the effect of energy on relative biological effectiveness. The energy transfer-based SB definitions give similar SB yields as the one based on energy deposit when ETH 10.79 eV, but deviate significantly for higher ETH values. Between 30 and 40 nucleosomes/Gy show at least one SB in the ROI. The number of nucleosomes that present a complex damage pattern of more than 2 SBs and the degree of complexity of the damage in these nucleosomes diminish as the incident electron energy increases. DNA damage classification into SSB and DSB is highly dependent on the definitions of these higher order structures and their implementations. The authors' show that, for the four studied models, different yields are expected by up to 54% for SSBs and by up to 32% for DSBs, as a function of the incident electrons energy and of the models being compared. MCTS simulations allow to compare direct DNA damage types and complexities induced by ionizing radiation. However, simulation results depend to a large degree on user-defined parameters, definitions, and algorithms such as: DNA model, dose distribution, SB definition, and the DNA damage clustering algorithm. These interdependencies should be well controlled during the simulations and explicitly reported when comparing results to experiments or calculations.
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Universidade Estadual de Campinas . Faculdade de Educao Fsica
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A comunidade de mamferos terrestres foi amostrada em trs localidades (1-Mateiros, TO; 2- Rio da Conceio, TO e 3- Formosa do Rio Preto, BA) no interior da Estao Ecolgica Serra Geral do Tocantins. Para o registro dos marsupiais e pequenos roedores foram utilizadas armadilhas convencionais (5.396 armadilhas.noite) e armadilhas de queda (5.300 pitfalls.noite) nas diferentes fitofisionomias encontradas, entre elas: campo mido, campo limpo, campo sujo, campo cerrado, cerrado sensu stricto, cerrado com afloramentos rochosos, mata de galeria e mata de galeria mida. No caso dos mamferos de mdio e grande porte, foram obtidos registros casuais atravs de observao direta e evidncias indiretas (rastros, fezes, crnios e carcaas de animais encontrados mortos). Foram amostradas 24 espcies de pequenos mamferos e 17 espcies de mamferos de mdio e grande porte, totalizando 41 espcies para a regio. Considerando-se os pequenos mamferos, a comunidade foi representada por vrias espcies raras e de abundncia intermediria, e poucas espcies muito abundantes. Os roedores cricetdeos dominaram tanto em nmero de espcies (14) quanto em abundncia (50% da comunidade). As espcies se distriburam, basicamente, em dois tipos de fisionomias: um grupo esteve restrito aos ambientes florestais, e outro s formaes abertas, demonstrando a grande seletividade de hbitats e a importncia de se amostrar o mosaico de hbitats presente na regio para uma melhor caracterizao da diversidade deste grupo de mamferos. Em termos biogeogrficos, a fauna de pequenos mamferos amostrada apresentou certa sobreposio com a fauna da Caatinga e da Amaznia, evidenciando a importncia destes domnios para a composio de espcies das comunidades que habitam a poro norte do Cerrado, alm da presena de espcies endmicas e de distribuio geogrfica restrita ao norte do domnio, caracterizando uma comunidade distinta de outras regies do Cerrado. Em relao aos mamferos de mdio e grande porte, a presena de um elevado nmero de espcies ameaadas de extino (10) tambm ressalta a importncia da preservao desta regio.
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Aims. The CMa R1 star-forming region contains several compact clusters as well as many young early-B stars. It is associated with a well-known bright rimmed nebula, the nature of which is unclear (fossil HII region or supernova remnant). To help elucidate the nature of the nebula, our goal was to reconstruct the star-formation history of the CMa R1 region, including the previously unknown older, fainter low-mass stellar population, using X-rays. Methods. We analyzed images obtained with the ROSAT satellite, covering similar to 5 sq. deg. Complementary VRI photometry was performed with the Gemini South telescope. Colour-magnitude and colour-colour diagrams were used in conjunction with pre-main sequence evolutionary tracks to derive the masses and ages of the X-ray sources. Results. The ROSAT images show two distinct clusters. One is associated with the known optical clusters near Z CMa, to which similar to 40 members are added. The other, which we name the ""GU CMa"" cluster, is new, and contains similar to 60 members. The ROSAT sources are young stars with masses down to M(star) similar to 0.5 M(circle dot), and ages up to 10 Myr. The mass functions of the two clusters are similar, but the GU CMa cluster is older than the cluster around Z CMa by at least a few Myr. Also, the GU CMa cluster is away from any molecular cloud, implying that star formation must have ceased; on the contrary (as already known), star formation is very active in the Z CMa region.
