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排序方式: 共有226条查询结果,搜索用时 984 毫秒
21.
Haviland Amelia; Nagin Daniel S.; Rosenbaum Paul R.; Tremblay Richard E. 《Canadian Metallurgical Quarterly》2008,44(2):422
A central theme of research on human development and psychopathology is whether a therapeutic intervention or a turning-point event, such as a family break-up, alters the trajectory of the behavior under study. This article describes and applies a method for using observational longitudinal data to make more transparent causal inferences about the impact of such events on developmental trajectories. The method combines 2 distinct lines of research: work on the use of finite mixture modeling to analyze developmental trajectories and work on propensity score matching. The propensity scores are used to balance observed covariates and the trajectory groups are used to control pretreatment measures of response. The trajectory groups also aid in characterizing classes of subjects for which no good matches are available. The approach is demonstrated with an analysis of the impact of gang membership on violent delinquency based on data from a large longitudinal study conducted in Montréal, Canada. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
22.
Pedro Henrique Hatumura Guilherme Santana de Oliveira Gustavo Galo Marcheafave Miroslava Rakocevic Roy Edward Bruns Ieda Spacino Scarminio Amelia Elena Terrile 《Food Analytical Methods》2018,11(7):1906-1914
High planting density has been used to increase coffee production but there are few studies related to the variations it provokes in metabolite compositions. The use of 1H NMR data associated with chemometric techniques allows the determination of metabolic fingerprints and verification of metabolic changes when coffee is subjected to high planting densities. The aim of this work is to investigate 1H NMR spectral data of green bean extracts of Coffea arabica cv. IAPAR 59 grown in a square pattern at two planting densities, 6000 and 10,000 plants ha?1. Thirty extracts were obtained using a simplex centroid design with four solvents (ethanol, acetone, dichloromethane, and hexane). The lyophilized extracts were dissolved in DMSO-d6 to obtain the 1H NMR spectra. The spectral data were analyzed with principal component (PCA) and cluster analyses (CA). Significant differences between ethanolic and non-ethanolic extracts were found by PCA. Only the ethanolic mean spectrum showed characteristic chemical shifts of sugars and trigonelline. Acetone extracts were separated by cluster analysis. 相似文献
23.
Inhibition of return (IOR) describes a performance decrement for stimuli appearing at recently cued locations. Both attentional and motor processes have been implicated in the IOR effect. The present data reveal a double dissociation between the attentional and motor components of IOR whereby the motor-based component of IOR is present when the response is oculomotor, and the attention-based component of IOR is present when the response is manual. These 2 distinct components should be considered and studied separately, as well as in relation to each other, if a comprehensive theory of IOR is to be achieved. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
24.
Anthony Mshandete Lovisa Bjrnsson Amelia K. Kivaisi M.S.T. Rubindamayugi Bo Mattiasson 《Renewable Energy》2006,31(14):2385-2392
The degradation and biogas production potential of sisal fibre waste could be significantly increased by pre-treatment for reduction of particle size. Batch-wise anaerobic digestion of sisal fibre waste was carried out in 1-l digesters with fibre sizes ranging from 2 to 100 mm, at an ambient temperature of 33 °C. Sediment from a stabilisation pond at a sisal production plant was used as starter seed. Total fibre degradation increased from 31% to 70% for the 2 mm fibres, compared to untreated sisal fibres. Furthermore, the results confirmed that methane yield was inversely proportional to particle size. Methane yield increased by 23% when the fibres were cut to 2 mm size and was 0.22 m3 CH4/kg volatile solids, compared to 0.18 m3 CH4/kg volatile solids for untreated fibres. By anaerobic digestion and biogas production, the 148,000 tonne of waste sisal fibres generated annually in Tanzania could yield 22 million m3 of methane, and an additional 5 million m3 of methane if pre-treatment by size reduction to 2 mm was applied. 相似文献
25.
Two new polymeric matrices functionalized with 3-hydroxy-4-pyridinone chelating units (HP-NH-SEPH and HP-C=NH-SEPH) have been prepared and studied for their chelating ability towards a set of metal ions (e.g. Fe(III), Al(III), and Th(IV)). Both matrices demonstrated excellent ability to complex these metal ions, but HP-NH-SEPH evidenced higher chelating capacity than HP-C=NH-SEPH. The corresponding metal-complex gels presented high stability in the pH range 3-7, and their chelating capacity followed the order, Fe(III)≈Th(IV)>Al(III), in agreement with previously reported thermodynamics of the corresponding monomeric ligand-metal complexes in aqueous solution. These functionalized supports also showed capacity to be regenerated and reused. Thus, there are good perspectives for potential environmental and medical applications of these new metal sorbents. 相似文献
26.
The group velocity dispersion (GVD) coefficient of four different dyes in solution is measured as a function of wavelength and concentration using a white-light Michelson interferometer. We find that the wavelength dependence of the GVD can be considerably different at wavelengths above and below the absorption resonance in a dye. Above the absorption resonance, the dye molecules can make a strong, wavelength-dependent contribution to the GVD of the solution. Below the absorption resonance, the dye molecules tend to contribute negligibly to the GVD of the solution. We find that the contribution of the dye molecules to the GVD can be modeled quite accurately using a simple Lorentz model with parameters set using the measured linear absorption properties of the dye. 相似文献
27.
On-Line Algorithms for the Dynamic Traveling Repair Problem 总被引:1,自引:0,他引:1
We consider the dynamic traveling repair problem in which requests with deadlines arrive through time on points in a metric
space. Servers move from point to point at constant speed. The goal is to plan the motion of servers so that the maximum number
of requests are met by their deadline. We consider a restricted version of the problem in which there is a single server and
the length of time between the arrival of a request and its deadline is constant. We give upper bounds for the competitive
ratio of two very natural algorithms as well as several lower bounds for any deterministic algorithm. Most of the results
in this paper are expressed as a function of β, the diameter of the metric space. In particular, we prove that the upper bound
given for one of the two algorithms is within a constant factor of the best possible competitive ratio. 相似文献
28.
In the present work, the changed properties of isotactic polypropylene caused by adding untreated sepiolite and n-decylaldehyde treated sepiolite were analyzed by studying the isothermal crystallization processes and the dynamic properties of the resulting composites. Variations in the surface activity of the n-decylaldehyde treated sepiolite leads to significant changes in the measured properties compared to those observed in the composites containing untreated sepiolite. This allows the assumption that the structure of the interface filler/polymer is modified as a function of filler activity. 相似文献
29.
30.
Erchul William P.; Scott Susan S.; Dombalis Amelia O.; Schulte Ann C. 《Canadian Metallurgical Quarterly》1989,4(2):103
A national sample of 251 1st- and 2nd-yr doctoral students in school psychology responded to a questionnaire measuring demographic characteristics, preferences among applied specialties in professional psychology, graduate program applications, anticipated internship setting, preferred client population, personal interests, professional goals, and satisfaction with current training. Survey responses showed a clear preference for working directly with children and adolescents following graduation, a high degree of correspondence between training program emphases and student interests and goals, and a moderate degree of student satisfaction with training experiences. Results are interpreted with respect to training trends and standards in school psychology, the relationship between school and clinical psychology, satisfaction of students in clinical and counseling psychology programs, and methodology limitations. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献