950 resultados para Standards of length.


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We report on the realization of a capacitive dilatometer, designed for high-resolution measurements of length changes of a material for temperatures 1.4K ≤ T ≤ 300K and hydrostatic pressure P ≤ 250MPa. Helium ( 4He) is used as a pressure-transmitting medium, ensuring hydrostatic-pressure conditions. Special emphasis has been given to guarantee, to a good approximation, constant-pressure conditions during temperature sweeps. The performance of the dilatometer is demonstrated by measurements of the coefficient of thermal expansion at pressures P ≃ 0.1MPa (ambient pressure) and 104MPa on a single crystal of azurite, Cu 3(CO 3) 2(OH) 2, a quasi-one-dimensional spin S = 1/2 Heisenberg antiferromagnet. The results indicate a strong effect of pressure on the magnetic interactions in this system. © 2012 American Institute of Physics.

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The aim of this study was to evaluate the in vitro growth of Cattleya loddigesii in alternative agents to agar with starch and physical matrix with acclimatization of regenerated plants. Protocorms with 90 days after sowing (0.5 cm of length) were subcultured in 1/2 MS culture medium among the treatments consisting of: agar 7 g L-1 (T1, which corresponds the control), agar 3,5 g L-1 with cassava starch 30 g L-1 (T2), cassava starch 60 g L-1 (T3), cotton fiber (T4) and chopped polyurethane foam (T5). Plantlets were retained in these treatments for over 150 days, and at the end of in vitro culture, were analyzed by their biometric data and acclimatized in a greenhouse during 120 days and evaluated the survival and relative growth rate (RGR). The substrate comprising of chopped polyurethane foam (T5) showed greater efficiency for growth in vitro and also increased survival rate, while substrate cassava starch (T3) provided delay for plantlet growth. Therefore, chopped polyurethane foam is recommended because of low cost and suitable characteristics for the propagation of Cattleya loddigesii.

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Recent searches suggest that social skills and time management as control variables of stress. In order to analyze possible relations between these variables and stress, it was done a descriptive study with a sample of convenience. Eighty three freshmen students, both of gender, of Biology, Civil Engineering and Psychology answered the Stress Inventory (ISSL), Social Skills Inventory (IHS) and a Time Management Inventory adaptation (ADT). It is emphasized that methodology of adaptation, the pro rata system, was not based on high standards of psychometry, which can lead to change of configuration of the instrument and the data it provides. The most of participants were unde rthe media in Social Skills and 72,29% manage badly the time. The stress rate was 48,19%. It was found connection between bad time management and stress and the lack of social skills was associated to bad time management. There wasn't statistic connection between stress and social skills lack. Students in Civil Engineering had the smaller stress rate, as well as the bigger lack of a Social Skills category.

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