1000 resultados para Multiple diffraction
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Régner, Escribe, and Dupeyrat (2007) recently demonstrated that not only performance-approach and performance-avoidance goals (respectively, the desire to outperform others and not to be outperformed by others) but also mastery goals (the desire to acquire knowledge) were related to social comparison orientation (SCO, the tendency to search for social comparison information). In the present article, the possibility of a link between mastery goals and social comparison that depends on the level of performance-approach goals-a possibility supported by a multiple-goal perspective-was tested by examining the interaction effect between mastery and performance-approach goals. This is an important endeavor, as educational settings are rarely free from performance-approach goals, even when mastery goals are promoted. In Study 1, we tested self-set achievement goals (mastery, performance-approach, and performance-avoidance goals) as predictors of SCO; the interaction between mastery goals and performance-approach goals indicated that the higher the performance-approach goal endorsement, the stronger the link between mastery goals and SCO. In Study 2, we manipulated goal conditions; mastery goals predicted interest in social comparison in the performance-approach goal condition only. Results are discussed in terms of the importance of multiple-goal pursuit in academic settings. (PsycINFO Database Record (c) 2009 APA, all rights reserved)
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Regulator of G-protein signalling (RGS) proteins negatively regulate heterotrimeric G-protein signalling through their conserved RGS domains. RGS domains act as GTPase-activating proteins, accelerating the GTP hydrolysis rate of the activated form of Gα-subunits. Although omnipresent in eukaryotes, RGS proteins have not been adequately analysed in non-mammalian organisms. The Drosophila melanogaster Gαo-subunit and the RGS domain of its interacting partner CG5036 have been overproduced and purified; the crystallization of the complex of the two proteins using PEG 4000 as a crystallizing agent and preliminary X-ray crystallographic analysis are reported. Diffraction data were collected to 2.0 Å resolution using a synchrotron-radiation source.
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The two goals of this project stated in the Proposal were: (1) study lime diffusion in clayey soils, and (2) find the role of MgO in soil-dolomitic lime stabilization. Because of the practice significance of these goals we temporarily overstaffed this project, giving somewhat a "crash" program. As a result, proposed work was finished up early (as were the funds), and more important, some of the findings were early enough and of sufficient merit to put into field trials in the Fall of 1964. The work now being completed and the funds all being expended, this Final Report is therefore submitted before the anticipated project termination date.
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Genetic diversity benefits for social insect colonies headed by polyandrous queens have received intense attention, whereas sexual selection remains little explored. Yet mates of the same queen may engage in sperm competition over the siring of offspring, and this could confer benefits on queens if the most successful sire in each colony (the majority sire) produces gynes (daughter queens) of higher quality. These benefits could be increased if high-quality sires make queens increase the percentage of eggs that they fertilize (unfertilized eggs develop into sons in social hymenopterans), or if daughters of better genetic quality are over-represented in the gyne versus worker class. Such effects would lead to female-biased sex ratios in colonies with high-quality majority gynes. I tested these ideas in field colonies of Lasius niger black garden ants, using body mass of gynes as a fitness trait as it is known to correlate with future fecundity. Also, I established the paternity of gynes through microsatellite DNA offspring analyses. Majority sires did not always produce heavier gynes in L. niger, but whenever they did do so colonies produced more females, numerically and in terms of the energetic investment in female versus male production. Better quality sires may be able to induce queens to fertilize more eggs or so-called caste shunting may occur wherever the daughters of better males are preferentially shunted to into the gyne caste. My study supports that integrating sexual selection and social evolutionary studies may bring a deeper understanding of mating system evolution in social insects.
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The nose-horned viper (Vipera ammodytes) occurs in a large part of the south-eastern Europe and Asia Minor. Phylogenetic relationships were reconstructed for a total of 59 specimens using sequences from three mitochondrial regions (16S and cytochrome b genes, and control region, totalling 2308 bp). A considerable number of clades were observed within this species, showing a large genetic diversity within the Balkan peninsula. Splitting of the basal clades was evaluated to about 4 million years ago. Genetic results are in contradiction with presently accepted taxonomy based on morphological characters: V. a. gregorwallneri and V. a. ruffoi do not display any genetic difference compared with the nominotypic subspecies (V. a. ammodytes), involving that these subspecies can be regarded as synonyms. High genetic divergence in the central part of the Balkan peninsula is not concordant with low morphological differentiation. Finally, the extensive genetic diversity within the Balkan peninsula and the colonisation routes are discussed
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The most abundant clay mineral group in Iowa soils is montmorillonite, most commonly calcium-saturated (Hanway et al, 1960). The calcium montmorillonite-water system was therefore selected for detailed X-ray study. Montmorillonite is unusual among minerals in that it has an expanding lattice in the c direction. That is, upon wetting with water, the individual silicate layers separate to allow entry of water, and the mineral expands. Characteristics of this expansion are readily studied by means of X-ray diffraction: the X-ray diffraction angle gives the average layer-to-layer "d001" spacing for any given moisture condition; the sharpness of the diffraction peak is a measure of uniformity of the d001 spacing; and the intensity of the peak relates to uniformity of the d001 spacing and in addition to the electron density distribution within the repeating elements. The latter is embodied in the "structure factor".
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Two goals were pursued in this research: first, to evaluate statistically some effects of sample preparation and instrument geometry on reproducibility of X-ray diffraction intensity data; and second, to develop a procedure for finding minimum peak and background counting times for a desired level of accuracy. The ratio of calcite to dolomite in limestones was determined in trials. Ultra-fine wet grinding of the limestone in porcelain impact type ball mill gave most consistent X-ray results, but caused considerable line broadening, and peaks were best measured on an area count basis. Sample spinning reduced variance about one third, and a coarse beam-medium detector slit arrangement was found to be best. An equation is developed relating coefficient of variation of a count ratio to peak and background counts. By use of the equation or graphs the minimum coefficient of variation is predicted from one fast scan, and the number and optimum arrangement of additional counting periods to reduce variation to a desired limit may be obtained. The calculated coefficient is the maximum which may be attributed to the counting statistic but does not include experimental deviations.
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OBJECTIVE: To determine risk of Down syndrome (DS) in multiple relative to singleton pregnancies, and compare prenatal diagnosis rates and pregnancy outcome. DESIGN: Population-based prevalence study based on EUROCAT congenital anomaly registries. SETTING: Eight European countries. POPULATION: 14.8 million births 1990-2009; 2.89% multiple births. METHODS: DS cases included livebirths, fetal deaths from 20 weeks, and terminations of pregnancy for fetal anomaly (TOPFA). Zygosity is inferred from like/unlike sex for birth denominators, and from concordance for DS cases. MAIN OUTCOME MEASURES: Relative risk (RR) of DS per fetus/baby from multiple versus singleton pregnancies and per pregnancy in monozygotic/dizygotic versus singleton pregnancies. Proportion of prenatally diagnosed and pregnancy outcome. STATISTICAL ANALYSIS: Poisson and logistic regression stratified for maternal age, country and time. RESULTS: Overall, the adjusted (adj) RR of DS for fetus/babies from multiple versus singleton pregnancies was 0.58 (95% CI 0.53-0.62), similar for all maternal ages except for mothers over 44, for whom it was considerably lower. In 8.7% of twin pairs affected by DS, both co-twins were diagnosed with the condition. The adjRR of DS for monozygotic versus singleton pregnancies was 0.34 (95% CI 0.25-0.44) and for dizygotic versus singleton pregnancies 1.34 (95% CI 1.23-1.46). DS fetuses from multiple births were less likely to be prenatally diagnosed than singletons (adjOR 0.62 [95% CI 0.50-0.78]) and following diagnosis less likely to be TOPFA (adjOR 0.40 [95% CI 0.27-0.59]). CONCLUSIONS: The risk of DS per fetus/baby is lower in multiple than singleton pregnancies. These estimates can be used for genetic counselling and prenatal screening.
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trans-Resveratrol (trans-3,5,4'-trihydroxystilbene) is a natural polyphenol that occurs in grapes, berries, peanuts, and several traditional medicines. A number of studies have demonstrated that this polyphenol holds promise against numerous age-associated diseases including cancer, diabetes, Alzheimer, cardiovascular and pulmonary diseases. In view of these studies, resveratrol's prospects for use in the clinics are rapidly accelerating. This review summarizes our work on the mechanisms involved in the intestinal absorption and its population pharmacokinetics. Finally, various targets of resveratrol and its therapeutic potential are described.
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INTRODUCTION: In patients with multiple sclerosis (MS), conventional magnetic resonance imaging (MRI) provides only limited insights into the nature of brain damage with modest clinic-radiological correlation. In this study, we applied recent advances in MRI techniques to study brain microstructural alterations in early relapsing-remitting MS (RRMS) patients with minor deficits. Further, we investigated the potential use of advanced MRI to predict functional performances in these patients. METHODS: Brain relaxometry (T1, T2, T2*) and magnetization transfer MRI were performed at 3T in 36 RRMS patients and 18 healthy controls (HC). Multicontrast analysis was used to assess for microstructural alterations in normal-appearing (NA) tissue and lesions. A generalized linear model was computed to predict clinical performance in patients using multicontrast MRI data, conventional MRI measures as well as demographic and behavioral data as covariates. RESULTS: Quantitative T2 and T2* relaxometry were significantly increased in temporal normal-appearing white matter (NAWM) of patients compared to HC, indicating subtle microedema (P = 0.03 and 0.004). Furthermore, significant T1 and magnetization transfer ratio (MTR) variations in lesions (mean T1 z-score: 4.42 and mean MTR z-score: -4.09) suggested substantial tissue loss. Combinations of multicontrast and conventional MRI data significantly predicted cognitive fatigue (P = 0.01, Adj-R (2) = 0.4), attention (P = 0.0005, Adj-R (2) = 0.6), and disability (P = 0.03, Adj-R (2) = 0.4). CONCLUSION: Advanced MRI techniques at 3T, unraveled the nature of brain tissue damage in early MS and substantially improved clinical-radiological correlations in patients with minor deficits, as compared to conventional measures of disease.
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First trimester biochemical trisomy screening is based on serum concentrations of pregnancy-associated plasma protein A (PAPP-A) and human chorionic gonadotrophin (hCG). Our aim was to confirm previously suggested modifications in serum marker concentrations after in vitro fertilisation (IVF) and embryo transfer (ET), and to assess the need of establishing normal medians for trisomy screening in these. We compared 56 singleton pregnancies obtained after ET (of which 40 in gonadotrophin stimulation cycles) with 120 gestation-matched spontaneous controls. For multiple pregnancies, 17 treated cycles were compared with 25 controls. The levels of PAPP-A, hCG, and pregnancy-specific β1-glycoprotein were determined and compared between treated and spontaneous pregnancies. Serum PAPP-A levels were reduced in pregnancies achieved after gonadotrophin-stimulated IVF and ET, and this was more pronounced in earlier gestational stages. SP1 followed the same trend, while hCG tended to be increased, and this not only in pregnancies obtained from gonadotrophin-stimulated but also from oestrogen supported cycles, and with a more pronounced effect in the later gestational ages examined here. Decreased PAPP-A together with increased hCG concentrations produce falsely elevated results in first trimester Down syndrome screening, but we do not recommend the establishment of normal medians for IVF pregnancies due to the variations in stimulation protocols.
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Precession electron diffraction (PED) is a hollow cone non-stationary illumination technique for electron diffraction pattern collection under quasikinematicalconditions (as in X-ray Diffraction), which enables “ab-initio” solving of crystalline structures of nanocrystals. The PED technique is recently used in TEMinstruments of voltages 100 to 300 kV to turn them into true electron iffractometers, thus enabling electron crystallography. The PED technique, when combined with fast electron diffraction acquisition and pattern matching software techniques, may also be used for the high magnification ultra-fast mapping of variable crystal orientations and phases, similarly to what is achieved with the Electron Backscatter Diffraction (EBSD) technique in Scanning ElectronMicroscopes (SEM) at lower magnifications and longer acquisition times.
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In this article the main possibilities of single crystal and powder diffraction analysis using conventional laboratory x-ray sources are introduced. Several examples of applications with different solid samples and in different fields of applications are shown illustrating the multidisciplinary capabilities of both techniques.