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排序方式: 共有1291条查询结果,搜索用时 15 毫秒
161.
Clara Guglieri Eva Céspedes Ana Espinosa María Ángeles Laguna‐Marco Noemi Carmona Yukiharu Takeda Tetsuo Okane Tetsuya Nakamura Mar García‐Hernández Miguel Ángel García Jesús Chaboy 《Advanced functional materials》2014,24(14):2094-2100
Discoveries of room‐temperature ferromagnetism (RTFM) in semiconductors hold great promise in future spintronics technologies. Unfortunately, this ferromagnetism remains poorly understood and the debate concerning the nature, carrier‐mediated versus defect‐mediated, of this ferromagnetism in semiconducting oxides is still open. Here, by using X‐ray absorption (XAS) and X‐ray magnetic circular dichroism (XMCD), it is demonstrated that the oxygen ions have a ferromagnetic response in different ZnO‐based compounds showing RTFM behavior: ZnO nanoparticles capped with organic molecules and ZnO/ZnS heterostructures. These results demonstrate the intrinsic occurrence of RTFM in these systems, and point out that it is not related to the metallic cation but it relays on the conduction band of the semiconductor. 相似文献
162.
Dutková Erika Sayagués María Jesús Fabián Martin Kováč Jaroslav Kováč Jaroslav Baláž Matej Stahorský Martin 《Journal of Materials Science: Materials in Electronics》2021,32(18):22898-22909
Journal of Materials Science: Materials in Electronics - In this work, the very rapid one-step mechanochemical synthesis of nanocrystalline ternary chalcogenide chalcostibite CuSbS2 prepared from... 相似文献
163.
F. Pedro-García L.G. Betancourt-Cantera A.M. Bolarín-Miró C.A. Cortés-Escobedo A. Barba-Pingarrón F. Sánchez-De Jesús 《Ceramics International》2019,45(8):10114-10119
We report the effects of the Sr2+ and Ni2+ co-doping of BiFeO3 on the crystal structure and multiferroic properties of Bi1?xSrxFe1-yNiyO3 (x?=?0.05, 0.0?≤?y?≤?0.10, and Δy?=?0.05) that is synthesized using assisted high-energy ball milling. The mixtures of Bi2O3, Fe2O3, SrO and NiO were milled for 5?h, pressed at 900?MPa, and sintered at 800?°C in order to obtain cylindrical test pieces. X-ray diffraction and Rietveld refinement elucidated the effects of Sr2+ and Ni2+ on the crystal structure. Co-doping with SrNi in suitable proportions stabilizes rhombohedral BiFeO3. High contents of Ni2+ promote the precipitation of secondary phases in the forms of NiFe2O4 and Bi25FeO40. The magnetic behavior was examined by means of vibrating sample magnetometry. The results showed a change in the magnetic order from antiferromagnetic for the undoped sample to the ferromagnetic order for the co-doped samples. This change is attributed to the modulations in the magnetic moment due to crystal structure distortions. All samples show high relative permittivity values, which were enhanced by doping with Sr2+. Ni2+ cations increase the dielectric dissipation factor; this enhancement is related to their interactions with cations of a different oxidation state, such as Fe3+, Fe2+, Ni2+, Bi3+ and Sr2+ in the crystal structure of BiFeO3. The magnetoelectric coupling that was evaluated using magnetodielectric measurements was above 4% at 1?kHz for the higher applied magnetic field of 18?kOe. 相似文献
164.
Míguez-Framil M Moreda-Piñeiro A Bermejo-Barrera P López P Tabernero MJ Bermejo AM 《Analytical chemistry》2007,79(22):8564-8570
The use of ultrasound energy for accelerating the pronase E enzymatic hydrolysis of human hair for extracting illicit drugs has been novelty tested. The enzymatic extracts obtained after 30 min of sonication in an ultrasonic water bath were subjected to an optimized solid-phase extraction process, which involved a solution of 2.0% (v/v) acetic acid in methanol as eluting solution and concentration by N2 stream evaporation. A gas chromatography/mass spectrometry method was used to separate and determine cocaine, benzoylecgonine, codeine, morphine, and 6-monoacethylmorphine in 20 min. Variables affecting ultrasound-assisted pronase E hydrolysis such as hydrolysis temperature, hydrolysis time, enzyme concentration, catalyzer (1,4-dithiothreitol) concentration, ionic strength, pH, and ultrasound frequency were simultaneously evaluated by a Plackett-Burman design 2(8) PBD of resolution III. The most statistically significant variables were ionic strength and pH, which means that analyte extraction is mainly attributed to pronase E activity. The optimization or evaluation of all the factors has led to an accelerated pronase E hydrolysis of human hair, which can be completed in 30 min. Results have been found to be statistically similar to those obtained with conventional pronase E hydrolysis. The accelerated method was finally applied to several human hair samples from multidrug abusers. 相似文献
165.
We present a complete mechanized proof of the result in homological algebra known as basic perturbation lemma. The proof has
been carried out in the proof assistant Isabelle, more concretely, in the implementation of higher-order logic (HOL) available
in the system. We report on the difficulties found when dealing with abstract algebra in HOL, and also on the ongoing stages
of our project to give a certified version of some of the algorithms present in the Kenzo symbolic computation system.
J. Aransay was partially supported by Ministerio de Educación y Ciencia, MTM2006/06513, and by Gobierno de La Rioja ANGI2005/19
and J. Rubio was partially supported by Ministerio de Educación y Ciencia, MTM2006/06513, and by Gobierno de La Rioja ANGI2005/19. 相似文献
166.
Batch sorption experiments of the insecticide imidacloprid by ten widely different Spanish soils were carried out. The sorption was studied for the active ingredient and its registered formulation Confidor. The temperature effect was studied at 15 degrees C and 25 degrees C. The addition of a vermicompost from spent grape marc (natural and ground), containing 344 g kg(-1) organic carbon, on the sorption of imidacloprid by two selected soils, a sandy loam and a silty clay loam, having organic carbon content of 3.6 g kg(-1) and 9.3 g kg(-1), respectively, was evaluated. Prior to the addition of this vermicompost, desorption isotherms with both selected soils, were also performed. The apparent hysteresis index (AHI) parameter was used to quantify sorption-desorption hysteresis. Sorption coefficients, K(d) and K(f), for the active ingredient and Confidor(R) in the different soils were similar. Sorption decreased with increasing temperature, this fact has special interest in greenhouse systems. A significant correlation (R(2)=0.965; P<0.01) between K(f) values and the organic carbon (OC) content was found, but some soils showed higher sorption coefficients than that expected from their OC values. The normalized sorption coefficients with the soil organic carbon content (K(oc)) were dispersed and low, implying that other characteristics of soils could contribute to the retention capacity as well. The spent grape marc vermicompost was an effective sorbent of this insecticide (K(f)=149). The sorption of imidacloprid increased significantly in soils amended with this vermicompost. The most pronounced effect was found in the sandy loam soil with low OC content, where the addition of 5% and 10% of vermicompost increased K(f) values by 8- and 15-fold, respectively. Soil desorption of imidacloprid was slower for the soil with the higher OC and clay content. 相似文献
167.
In 3 prior meta-analyses, the relationship between the Big Five factors of personality and job criteria was investigated. However, these meta-analyses showed different findings. Furthermore, these reviews included studies carried out only in the United States and Canada. This study reports meta-analytic research on the same topic but with studies conducted in the European Community, which were not included in the prior reviews. The results indicate that Conscientiousness and Emotional Stability are valid predictors across job criteria and occupational groups. The remaining factors are valid only for some criteria and for some occupational groups. Extraversion was a predictor for 2 occupations, and Openness and Agreeableness were valid predictors of training proficiency. These findings are consistent with M. R. Barrick and M. K. Mount (see record 1991-22928-001) and L. M. Hough et al (see record 1991-06268-001). Implications of the results for future research and the practice of personnel selection are suggested. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
168.
Probability matching is a nonoptimal strategy consisting of selecting each alternative in proportion to its reinforcement contingency. However, matching is related to hypothesis testing in an incidental, marginal, and methodologically disperse manner. Although some authors take it for granted, the relationship has not been demonstrated. Fifty-eight healthy participants performed a modified, bias-free probabilistic two-choice task, the Simple Prediction Task (SPT). Self-reported spurious rules were recorded and then graded by two independent judges. Participants who produced the most complex rules selected the probability matching strategy and were therefore less successful than those who did not produce rules. The close relationship between probability matching and rule generating makes SPT a complementary instrument for studying decision making, which might throw some light on the debate about irrationality. The importance of the reaction times, both before and after responding, is also discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
169.
Victoria Fernández Azahara Díaz Álvaro Blanco Jesús Val 《Journal of the science of food and agriculture》2009,89(13):2323-2330
BACKGROUND: A strategy to supply Ca directly to fruits as a tool for improving peach quality has been devised and tested under field conditions. Since peaches in the area of study (Calanda, Spain) are routinely bagged shortly after thinning, a method based on the application of Ca gels to the fruit surface was introduced. The effect of surface treatments was assessed in terms of quality, nutrient balance and surface deposition. RESULTS: Application of Ca‐containing formulations increased mesocarp and exocarp Ca concentrations, providing evidence for the penetration of Ca through the peach skin. Surface Ca treatments had a particular mode of deposition and in some instances improved the shelf life of fruits without affecting their quality. CONCLUSION: Surface treatment with Ca‐containing gels appears to be a viable approach to increase fruit Ca, quality and storability of bagged peach cultivars and should be optimised in future studies. Copyright © 2009 Society of Chemical Industry 相似文献
170.
A System Dynamics Model to Evaluate Temporary Water Transfers in the Mexican Conchos Basin 总被引:1,自引:1,他引:0
The flows of the Rio Conchos are of vital economic importance not only to the agricultural sector in the Mexican side of the
Rio Grande basin but also for meeting Mexico’s obligation to deliver water to the United States. During the previous decade,
a severe drought dramatically decreased the basin’s runoff, generating serious economic, social, and political problems in
both countries. A System Dynamics (SD) model designed to serve as a decision-support system (DSS) for water managers has been
created. This DSS is a lumped semi-distributed model operating on a monthly basis. This DSS incorporates the most important
elements of the Conchos basin’s water resources system: main rivers, irrigation distribution canals, reservoirs, aquifer,
and the three Irrigation Districts. The DSS simulates different short and long term scenarios combining inside and outside
Irrigation Districts (IDs). Also, different short scenarios are implemented to investigate the benefits of water transfer
from México to the United States. This study has prompted awareness with regards to the degree of complexity and uncertainty
of the water right allocation process to different economic variables such as crop yield, production costs, crop prices, subsidies,
and water distribution efficiencies. 相似文献