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81.
The author designed 3 experiments to study pigeons' adjustment to unexpected shifts in reinforcer magnitude with a single trial per day. Extinction was faster or poorer after training with a small magnitude (1 food pellet) than after training with a large magnitude (10 or 15 pellets). A shift from 15 to 1 pellet was accompanied by a gradual adjustment, with no indication of a successive negative contrast effect. Pigeons discriminated the reinforcer magnitudes but yielded no evidence of spaced-trial simultaneous negative contrast. Moreover, extinction was faster for a stimulus paired with 1 pellet than for a stimulus paired with 15 pellets. The results can be interpreted in terms of simple strengthening-weakening learning rules and without reference to anticipatory frustration. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
82.
Andrés R. Botello-Méndez Florentino López-Urías Mauricio Terrones Humberto Terrones 《Nano Research》2008,1(5):420-426
Inspired by recent experimental results, the electronic and magnetic properties of sulfur-passivated ZnO clusters and zigzag
nanoribbons have been studied using first principles calculations in the framework of the local spin density approximation.
In the case of the ZnO nanoribbons, the sulfur atoms or thiol groups were attached in different ways to the zinc or oxygen
atoms located at the edges, whereas in clusters, the sulfur atoms were set on the surface, mainly interacting with atoms with
low-coordinate number. After an exhaustive atomic relaxation, we found that a magnetic moment emerges in zigzag nanoribbons
both with and without sulfur-passivation on the edges. However, the magnitude of the magnetic moment is very sensitive to
sulfur passivation. In particular, we found that when sulfur is attached to the zinc atoms in an alternating fashion along
the ribbon edges, the magnetic moment is a maximum (1.4 μB/unit cell). In the case of clusters, we found that the Zn15O15 cluster exhibits a high spin moment of 5.5 μB when capped with sulfur atoms. Our calculations indicate that sulfur-passivating of ZnO nanosystems could be responsible
for recently observed ferromagnetic responses.
This article is published with open access at Springerlink.com 相似文献
83.
Camilo García Diego Villagra Francesco Caruso Miriam Rossi Betty Matsuhiro Leonora Mendoza María J. Aguirre Mauricio Isaacs 《Inorganic chemistry communications》2009,12(5):392-395
The complex [FeII(Imz-phen)3](PF6)2, (Imz-phen = imidazolidine-[4,5-f]-1,10-phenanthroline) has been prepared and characterized using X-ray diffraction, UV–vis and IR spectroscopy, elemental analysis, fast atomic bombardment (FAB) mass spectrometry, and cyclic voltammetry. Its crystal lattice includes acetonitrile (π–π bound to phenanthroline), methanol, and water molecules. Scanning continuously between 1000 mV and 1650 mV in CH3CN, a modified electrode that includes the iron (II) complex is obtained; after the 25th continuous cycle a stable film is formed that is electrocatalytically active in the reduction of sulfur oxoanions. When the electrocatalytic properties are evaluated in ethanol/water solution, the current achieved from the electroreduction of these sulfur species is linearly dependent on the respective concentrations, suggesting potential application in sulfite determination. 相似文献
84.
Raimund Bürger Ricardo Ruiz Kai Schneider Mauricio A. Sepúlveda 《Journal of Engineering Mathematics》2008,60(3-4):365-385
A fully adaptive finite volume multiresolution scheme for one-dimensional strongly degenerate parabolic equations with discontinuous
flux is presented. The numerical scheme is based on a finite volume discretization using the Engquist–Osher approximation
for the flux and explicit time-stepping. An adaptive multiresolution scheme with cell averages is then used to speed up CPU
time and meet memory requirements. A particular feature of our scheme is the storage of the multiresolution representation
of the solution in a dynamic graded tree, for the sake of data compression and to facilitate navigation. Applications to traffic
flow with driver reaction and a clarifier–thickener model illustrate the efficiency of this method. 相似文献
85.
A Fernández Fernández R Franco Manzano M Fernández Ruíz G Otero Mauricio 《Canadian Metallurgical Quarterly》1997,21(1):72-74
Severe protein deprivation at weaning provokes an arrest of cellular proliferation and maturation, and an increase of ADA and PNP activities in the thymus of growing rats. A 20% casein diet fed during 9 days was enough to reverse the effect on ADA and PNP. The supplementation with 24 mg/d of n-3 PUFA, was able to recover thymus' cellular proliferation and maturation. 相似文献
86.
Pelham Brett W.; Carvallo Mauricio; DeHart Tracy; Jones John T. 《Canadian Metallurgical Quarterly》2003,85(5):800
B. W. Pelham, M. C. Mirenberg, and J. T. Jones (see record 2002-12744-001) argued that most people prefer stimuli that are associated with the self, a preference they called implicit egotism. In support of implicit egotism, Pelham et al presented evidence from 10 archival studies showing that people gravitate toward careers and places of residence that resemble their names or birthday numbers. M. Gallucci (see record 2003-09138-001) argued that alternate analyses of the same data provide strong evidence against implicit egotism. Whereas Gallucci was correct that Pelham et al's original analyses were flawed, their results remain significant even when more conservative tests are used. The authors also present new data in support of implicit egotism, including exhaustive studies of (a) common surnames and US city names and (b) common surnames and street names. The new studies also revealed that as sample sizes grow larger, studies are more likely to produce evidence of implicit egotism. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
87.
Bentosela Mariana; Ruetti Eliana; Muzio Rubén N.; Mustaca Alba E.; Papini Mauricio R. 《Canadian Metallurgical Quarterly》2006,120(2):371
Rats given access to a 32% sucrose solution and then downshifted to a 4% solution exhibit less contact with the sipper tube than unshifted controls always given access to 4% solution. This phenomenon, called consummatory successive negative contrast, was facilitated in Experiment 1 by a posttrial injection of corticosterone (3 mg/kg) administered immediately after the first downshift trial. Experiment 2 demonstrated that this facilitatory effect of posttrial corticosterone does not occur when administered 3 hr after the first downshift trial. These results support the hypothesis that corticosterone strengthens an aversive emotional component elicited by the surprising downshift in reward magnitude during the initial downshift trial. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
88.
Graphene: Large‐Area Si‐Doped Graphene: Controllable Synthesis and Enhanced Molecular Sensing (Adv. Mater. 45/2014) 下载免费PDF全文
89.
Mauricio CL Martins MM Ramos EV Souza-Santos D 《Radiation protection dosimetry》2011,144(1-4):130-136
Instituto de Radioprote??o e Dosimetria, a Brazilian government research institute, provides individual monitoring services since 1972. Its dosemeters are: film-based thorax for whole body photons, thermoluminescence dosimetry (TLD) albedo for whole body neutrons and TLD ring for extremity photons. About 6000 radiation workers are currently being monitored with film dosemeters in 256 different facilities in Brazil, most of them working in health-related activities. Around 400 Brazilian radiation workers are monitored with TLD albedo neutron monitor and about 500 workers use TLD rings. This paper describes the monitoring systems used, presents the results obtained in internal quality programs and in intercomparison exercises and analyses the measured dose values from 1985 to 2009. 相似文献
90.
Armita Abolghasemi Maria Paulina Carullo Ester Cisneros Aguilera Asma Laroui Rosalie Plantefeve Daniela Rojas Serine Benachenhou María Victoria Ramírez Mlodie Proteau-Lemieux Jean-Franois Lepage Franois Corbin Mlanie Plourde Mauricio Farez Patricia Cogram Artuela aku 《International journal of molecular sciences》2022,23(18)
Fragile X Syndrome (FXS) is the most prevalent monogenic cause of Autism Spectrum Disorders (ASDs). Despite a common genetic etiology, the affected individuals display heterogenous metabolic abnormalities including hypocholesterolemia. Although changes in the metabolism of fatty acids (FAs) have been reported in various neuropsychiatric disorders, it has not been explored in humans with FXS. In this study, we investigated the FA profiles of two different groups: (1) an Argentinian group, including FXS individuals and age- and sex-matched controls, and (2) a French-Canadian group, including FXS individuals and their age- and sex-matched controls. Since phospholipid FAs are an indicator of medium-term diet and endogenous metabolism, we quantified the FA profile in plasma phospholipids using gas chromatography. Our results showed significantly lower levels in various plasma FAs including saturated, monosaturated, ω-6 polyunsaturated, and ω-3 polyunsaturated FAs in FXS individuals compared to the controls. A decrease in the EPA/ALA (eicosapentaenoic acid/alpha linoleic acid) ratio and an increase in the DPA/EPA (docosapentaenoic acid/eicosapentaenoic acid) ratio suggest an alteration associated with desaturase and elongase activity, respectively. We conclude that FXS individuals present an abnormal profile of FAs, specifically FAs belonging to the ω-3 family, that might open new avenues of treatment to improve core symptoms of the disorder. 相似文献