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21.
Marina Serantoni Elisa Mercadelli Anna Luisa Costa Magda Blosi Laura Esposito Alessandra Sanson 《Ceramics International》2010,36(1):103-106
Sub-micrometer powder (100–150 nm diameter) of Yb-doped yttrium oxide was obtained, for the first time, by microwave-assisted polyol (diethylene glycol, DEG) method. This method is based on fast and homogeneous increase of temperature, due to the microwave heating, and on addition of the hydrolysing agent (water) at high temperature. This promotes a fast nucleation followed by a controlled growth of nuclei. Different procedures were used to process the as-synthesized powders. In some cases washing by ultrapure water was used to dissolve nitrate and DEG by-products, this treatment allowed the use of a lower calcination temperature (150–200 °C less) to obtain the crystalline phase. Analysis of the calcined powder showed different levels of structures: from nanocrystal (10–15 nm), to primary particles (100–150 nm), to micrometer soft aggregates (2–4 μm). The microwave-assisted polyol method resulted an easy way to dope yttria with the desired amount of Yb3+. This work was carried out in order to prepare particles to be used as rare-earth doped Y2O3 and YAG polycrystalline transparent ceramic for laser source applications. 相似文献
22.
Aflatoxin M1 in pasteurized and ultrapasteurized milk with different fat content in Mexico 总被引:1,自引:0,他引:1
High per capita milk consumption in Mexico indicated a strong need for documentation of aflatoxin M1 (AFM1) levels in milk. A survey of 580, 2-liter samples (n = 290), was conducted to quantify AFM1 using high-performance liquid chromatography, considering two maximum tolerance levels (0.05 and 0.5 microg/liter). We relate aflatoxin levels in the seven most consumed brands from different regions, with two processes (pasteurized and ultrapasteurized), different expiration dates, and different fat content: whole fat (28, 30, and 33 g), half-skimmed (10, 16, and 20 g), light (1, 2, and 4 g), and with vegetable oil. Pasteurization and ultrapasteurization did not diminish AFM1 contamination present at levels of 0 to 8.35 microg/liter in 40% of the milk samples at concentrations > or = 0.05 microg/liter and in 10% of the samples at > or = 0.5 microg/liter. Statistically significant relationships were AFM1 contamination with brand (P = 0.002 at the > or = 0.05 microg/liter level and P = 0.034 at the > or = 0.5 microg/ liter level) and higher AFM1 levels with mild or warm seasons of the year (P = 0.0003). Samples with greater fat content had slightly more probability (P = 0.067) of being contaminated by AFM1 at the > or = 0.5 microg/liter level. The milk with the lowest contamination of AFM1 was a brand imported as powder and rehydrated in Mexico. 相似文献
23.
A problem of a modelling of vibrations of thin plates with a functionally graded macrostructure and a tolerance-periodic microstructure in planes parallel to the plate midplane is analysed. The proposed model, based on the Kirchhoff plate theory assumptions and additional hypothesis of the tolerance averaging technique [Wo?niak et al., editors. Thermomechanics of heterogeneous solids and structures. Tolerance averaging approach. ?ód?, University Press, Technical University of ?ód?; 2008], describes the effect of the microstructure size on dynamic behaviour of the plate. In this paper, as an example there are analysed free vibration frequencies of a functionally graded plate band. These frequencies are obtained in the framework of two proposed models—the tolerance model and the asymptotic model, using the known Ritz method. 相似文献
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25.
G. E. Mitchell W. I. Furman E. V. Lychagin A. Yu. Muzichka G. V. Nekhaev A. V. Strelkov E. I. Sharapov V. N. Shvetsov Yu. I. Chernuhin B. G. Levakov V. I. Litvin A. E. Lyzhin E. P. Magda B. E. Crawford S. L. Stephenson C. R. Howell W Tornow 《Journal of research of the National Institute of Standards and Technology》2005,110(3):225-230
Although crucial for resolving the issue of charge symmetry in the nuclear force, direct measurement of nn-scattering by colliding free neutrons has never been performed. At present the Russian pulsed reactor YAGUAR is the best neutron source for performing such a measurement. It has a through channel where the neutron moderator is installed. The neutrons are counted by a neutron detector located 12 m from the reactor. In preliminary experiments an instantaneous value of 1.1 × 1018/cm2s was obtained for the thermal neutron flux density. The experiment will be performed by the DIANNA Collaboration as International Science & Technology Center (ISTC) project No. 2286. 相似文献
26.
Burke Jeffrey D.; Loeber Rolf; White Helene Raskin; Stouthamer-Loeber Magda; Pardini Dustin A. 《Canadian Metallurgical Quarterly》2007,116(2):249
The authors examined the prediction from inattention to tobacco use among 2 cohorts (ages 7 and 13) of a community sample followed to young adulthood. Changes in self-reported tobacco use were tested with marginal transitional regression models, using parent and teacher ratings of inattention, hyperactivity-impulsivity, and other psychopathology, along with other factors, as predictors. Inattention, but not hyperactivity-impulsivity, significantly predicted adolescent tobacco use and young adult daily tobacco use. Peer substance use, parental substance use, and conduct disorder also predicted increases in tobacco use. African American ethnicity was strongly protective against later tobacco use. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
27.
An easy procedure for the preparation of solutions containing certain types of reactive dye and their subsequent application on cotton is described. This procedure takes advantage of the expected high reactivity of these dyes, which have adjacent hydroxy and amino groups in the molecule, and strives to evade the problems usually associated with the preparation and application of such dyes in the solid form. Several factors that affect the colour strength of reactive dyeings thus obtained are investigated. Possible disadvantages when applying this procedure are discussed. 相似文献
28.
Keltner Dacher; Moffitt Terrie E.; Stouthamer-Loeber Magda 《Canadian Metallurgical Quarterly》1995,104(4):644
On the basis of the widespread belief that emotions underpin psychological adjustment, the authors tested 3 predicted relations between externalizing problems and anger, internalizing problems and fear and sadness, and the absence of externalizing problems and social–moral emotion (embarrassment). Seventy adolescent boys were classified into 1 of 4 comparison groups on the basis of teacher reports using a behavior problem checklist: internalizers, externalizers, mixed (both internalizers and externalizers), and nondisordered boys. The authors coded the facial expressions of emotion shown by the boys during a structured social interaction. Results supported the 3 hypotheses: (a) Externalizing adolescents showed increased facial expressions of anger, (b) on 1 measure internalizing adolescents showed increased facial expressions of fear, and (c) the absence of externalizing problems (or nondisordered classification) was related to increased displays of embarrassment. Discussion focused on the relations of these findings to hypotheses concerning the role of impulse control in antisocial behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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30.
A. V. Bochkov A. V. Zagidulin É. P. Magda V. V. Mironenko G. S. Sofienko A. S. Podymako 《Technical Physics Letters》2006,32(10):843-844
The possibility of lasing in a YAP:Tm3+ crystal with 3F4 level of the Tm3+ ion directly pumped by narrowband radiation of a gas laser operating in the middle IR range has been studied. The efficiency of the pumped energy conversion into spontaneous emission on the 3F4-3H6 transition in the Tm3+ ion was within 65–75%. The efficiency of generation with respect to the absorbed pumping energy was ~4%. 相似文献