967 resultados para Personal values
New uniform algorithm to predict reversed phase retention values under different gradient conditions
Resumo:
A new numerical emulation algorithm was established to calculate retention parameters in RP-HPLC with several retention times under different linear or nonlinear binary gradient elution conditions and further predict the retention time under any other binary gradient conditions. A program was written according to this algorithm and nine solutes were used to test the program. The prediction results were excellent. The maximum relative error of predicted retention time was less than 0.45%. (C) 2002 Elsevier Science B.V. All rights reserved.
Resumo:
beta-NaYF4 microcrystals with a variety of morphologies, such as microrod, hexagonal microprism, and octadecahedron, have been synthesized via a facile hydrothermal route. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra were used to characterize the samples. The intrinsic structural feature of beta-NaYF4 seeds and two important external factors, namely, the pH values in the initial reaction solution and fluoride sources, are responsible for shape determination of beta-NaYF4 microcrystals. It is found that the organic additive trisodium citrate (Cit(3-)) as a shape modifier has the dynamic effect by adjusting the growth rate of different facets under different experimental conditions, resulting in the formation of the anisotropic geometries of various beta-NaYF4 microcrystals. The possible formation mechanisms for products with various architectures have been presented. A systematic study on the photoluminescence of Tb3+-doped beta-NaYF4 samples with rod, prism, and octadecahedral shapes has shown that the optical properties of these phosphors are strongly dependent on their morphologies and sizes.
Resumo:
We demonstrate the pH-induced assembly of 2-mercaptosuccinic acid-functionalized silver nanoparticles (MSA-Ag NPs) in the absence of hard or soft template. Two-dimensional (2D) and three-dimensional (3D) networks of silver NPs were achieved by tuning pH of the medium. The assembly process was monitored using atomic forces microscopy. The key factor affects the formation of network of silver NPs may be intermolecular hydrogen bonding between two carboxylic acid groups of MSA on two adjacent silver NPs.
Resumo:
The quantum-chemical descriptors were used for QSPR study of the structures of carboxylic acids and their pK(a) values. The algorithm of "Leaps and Bounds" regression was performed for selection of the variables. The CoMFA method was carried out for 3D-QSPR. As the introduction of the charge of oxygen atom(Q(2)), the results obtained by CoMFA were improved greatly.
Resumo:
Open-top chambers were used to estimate the possible effects of global warming on delta C-13 of seven plant species grown in alpine meadow ecosystem. The delta C-13 values of plant species were lower after long-term growth in open-top chambers. In the course of experiment, temperature significantly increased inside the chambers by 4 degrees C. Plant species grown at a lower elevation above sea level had higher delta C-13 values as compared to those grown at a higher elevation. This was in accordance with the effect of open-top chamber on delta C-13 values in plants. Greater availability of CO2 and lower water vapor as indicated by an increase in discrimination against (CO2)-C-13, probably result in more negative delta C-13 values of plants because higher stomatal conductance increases availability of CO2 and causes greater discrimination against (CO2)-C-13. The plant species studied could be the indicator species for testing global warming by the change in carbon isotope ratios at the two growth temperatures.
Resumo:
A study was conducted on grass mixtures that included smooth bromegrass (SB) + drooping wild ryegrass (DW), smooth bromegrass + Siberian wild ryegrass (SW) + crested wheatgrass (CW) and smooth bromegrass + Siberian wild ryegrass + drooping wild ryegrass + crested wheatgrass in the alpine region of Qinghai-Tibetan Plateau. The study was conducted from 1998 to 2000 to investigate the effects of N application rates and growing year on herbage dry matter (DM) yield and nutritive values. Herbage DM production increased linearly with N application rates. The effect of N application on DM yields was greater (P < 0.05) in the 2nd and 3rd production years than in the establishment year. Dry matter yields of SB + SW + CW and SB + SW + DW + CW can reach as high as 15 000 kg ha(-1) at 345 kg ha(-1) N rate in the 3rd growing year. With increased N application rates, crude protein (CP) contents and 48 h in sacco DM degradability of grasses increased (P < 0.05). No effect (P > 0.05) of N application was detected on organic matter (OM) and acid detergent fibre (ADF) concentration. It can be concluded that for increased biomass production in the alpine region of the Qinghai-Tibetan Plateau, a minimum of 345 kg N ha(-1) should be applied to grass stands in three split application of 115 kg N ha(-1), in early June, early July and late July
Resumo:
The aim of this study was to investigate consuming values and behaviors in Chinese college students, to detect the factorial structure in consuming values, and to explore possible determinants of those values and their effects on consuming behaviors. A total of 778 students from various universities in Beijing were investigated with questionnaire survey. The main results and conclusions are as follows: (1) College students were basically satisfied with their current life and study conditions in university, and their main pressures or stresses were from their studies. They were highly motivated in the development of their academic and life careers, and also valued the importance of family and having children in the future. About 11% of the students had pressures due to less favorable financial conditions of their families. (2) Five basic consuming values were found among college students, namely, “industrious and thrifty-aimed value”, “status and brand-aimed value”, “personal and unique-oriented value”, “relation-aimed value”, and “autonomous-aimed value”. The “industrious and thrifty-aimed value” stands for the traditional consuming values in the culture, and the “status and brand-aimed value” shows an explicit tendency of consumerism. The other three consuming values had moderate relations with both of the two values. (3) There was a high negative correlation between the first two values, which showed both a general acceptance and the main trend of “industrious and thrifty-aimed value” among the students. The basic “status and brand-aimed value” was shown among 3.3% of the students. (4) The consuming values were significantly correlated with life values, indicating that consuming values could be in consistence with or be determined by basic life values. The “industrious and thrifty-aimed value” and the “autonomous-aimed value” were shown as collectivistic values, while the “status and brand-aimed value” and “relation-aimed value” were shown as individualistic values. (5) Consuming values had significant influences on consuming behaviors. (6) The demographic factors such as financial conditions of parents, children of number in family, urban-rural location of family, gender, age, and campus culture could affect consuming values and consuming behaviors of college students in both direct and indirect ways.
Resumo:
A numerical approach has been developed for the correlation of retention limes (total retention lime) with temperature in gas chromatography, which allows the calculation of retention parameters including retention index from data acquired under two or more different temperature program conditions. By using this procedure the optimization of temperature condition can be further achieved, especially when a temperature-programmed run is the most suitable mode in the preliminary development of an analytical method for the analysis of an unknown sample.