Level of deprivation does not affect degree of discounting in pigeons     

Luís Oliveira  Amanda L. Calvert  Leonard Green  Joel Myerson 《Learning & behavior》2013,41(2):148-158

Two experiments tested the effects of food deprivation on discounting in pigeons. An adjusting-amount procedure was used to estimate the subjective value of food at delays ranging from 1 to 24 s. Experiment 1 compared pigeons’ discounting of delayed food reinforcers at 75 %–80 % and 90 %–95 % of free-feeding weight. Experiment 2 compared discounting under 1- and 23-h food deprivation. In both experiments at both deprivation levels, discounting was well described by the hyperboloid discounting function. No systematic effect of level of deprivation on degree of discounting was observed in either experiment. This finding is consistent with the view that pigeons’ choices are controlled by the relative, rather than the absolute, value of reinforcers.  相似文献   

Implicit indexing of natural language text by reorganizing bytecodes     

Nieves R. Brisaboa  Antonio Fari?a  Susana Ladra  Gonzalo Navarro 《Information Retrieval》2012,15(6):527-557

Word-based byte-oriented compression has succeeded on large natural language text databases, by providing competitive compression ratios, fast random access, and direct sequential searching. We show that by just rearranging the target symbols of the compressed text into a tree-shaped structure, and using negligible additional space, we obtain a new implicitly indexed representation of the compressed text, where search times are drastically improved. The occurrences of a word can be listed directly, without any text scanning, and in general any inverted-index-like capability, such as efficient phrase searches, can be emulated without storing any inverted list information. We experimentally show that our proposal performs not only much more efficiently than sequential searches over compressed text, but also than explicit inverted indexes and other types of indexes, when using little extra space. Our representation is especially successful when searching for single words and short phrases.  相似文献   

International trends in health science librarianship: Part 4 – Four Southern European countries     

Evagelia Lappa  Artemis Chaleplioglou  Gaetana Cognetti  Maurella Della Seta  Federica Napolitani Cheyne  Veronica Juan‐Quilis  Laura Muñoz‐Gonzalez  Sílvia Lopes 《Health information and libraries journal》2012,29(4):338-343

This is the fourth in a series of articles exploring international trends in health science librarianship in four Southern European countries in the first decade of the 21st century. The invited authors are from Greece, Italy, Spain and Portugal. Future issues will track trends in Latin America and Central Europe. JM  相似文献   

Modeling the probabilistic distribution of the impact factor     

José María Sarabia  Faustino PrietoCarmen Trueba 《Journal of Informetrics》2012,6(1):66-79

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Validating chemical and structural changes in painting materials by principal component analysis of spectroscopic data using internal mineral standards     

Julia Romero-Pastor  Carolina Cardell  África Yebra-Rodríguez  Alejandro B. Rodríguez-Navarro 《Journal of Cultural Heritage》2013,14(6):509-514

This work shows the capability of principal component analysis (PCA) to detect molecular, chemical and mineralogical changes in historic painting materials subjected to a thermal ageing test (< 250 °C). To simulate the heat-induced alterations an ageing accelerated process was performed on two sets of samples containing two mineral phases (hydroxyapatite and quartz) and two organic compounds (collagen and albumin). The chosen minerals behaved as internal standards during the tests since they are stable and chemically inert at the tested temperatures. Raman microscopy (RM) was applied to characterise one set of samples made of bone, containing ca. 70% hydroxyapatite and 30% collagen. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was used to study the other set of samples made of four different quartz/albumin mixtures with quartz contents of 30%, 50%, 70% and 90% (w/w). The aim was to identify the ideal proportion of internal standard to be validated by ATR-FTIR and PCA, determined to be 70%. PCA analyses detected changes in the molecular structures of the organic components while the internal mineral standard remained stable. Moreover, the internal standard IR/Raman bands were constant during the tests and confirmed that the results of PCA analyses were independent of instrumental and technical factors, as well as sample collecting and handling. This demonstrates the potential benefits of our approach to study historical painting materials, which have suffered any type of heat-induced alteration.  相似文献   

Erratum to “Transylvanian glass icons: A GC/MS study on the binding media” [J. Culher. (2012) doi:10.1016/j.culher.2012.10.009]     

Márta Júlia Guttmann  Anna Lluveras-Tenorio  Alessia Andreotti  Maria Perla Colombini  Luminiţa Silaghi-Dumitrescu  Olimpia Coman-Sipeanu 《Journal of Cultural Heritage》2013,14(5):448

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Toward a Longitudinal Model of e-Commerce: Environmental,Technological, and Organizational Drivers of B2C Adoption     

Inma Rodríguez-Ardura  Antoni Meseguer-Artola 《The Information Society》2013,29(3):209-227

Despite the important benefits for firms of commercial initiatives on the Internet, e-commerce is still an emerging distribution channel, even in developed countries. Thus, more needs to be known about the mechanisms affecting its development. A large number of works have studied firms' e-commerce adoption from technological, intraorganizational, institutional, or other specific perspectives, but there is a need for adequately tested integrative frameworks. Hence, this work proposes and tests a model of firms' business-to-consumer (called B2C) e-commerce adoption that is founded on a holistic vision of the phenomenon. With this integrative approach, the authors analyze the joint influence of environmental, technological, and organizational factors; moreover, they evaluate this effect over time. Using various representative Spanish data sets covering the period 1996–2005, the findings demonstrate the suitability of the holistic framework. Likewise, some lessons are learned from the analysis of the key building blocks. In particular, the current study provides evidence for the debate about the effect of competitive pressure, since the findings show that competitive pressure disincentivizes e-commerce adoption in the long term. The results also show that the development or enrichment of the consumers' consumption patterns, the technological readiness of the market forces, the firm's global scope, and its competences in innovation continuously favor e-commerce adoption.  相似文献   

Los mitos esenciales del deporte español     

Raúl Sánchez García 《国际体育史杂志》2013,30(10):1501-1503

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Friday Night Fighter: Gaspar ‘Indio' Ortega and the Golden Age of Television Boxing     

Ignacio M. García 《国际体育史杂志》2013,30(18):2239-2240

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不同生态效度的呈现方式对专业乒乓球运动员知觉预测的影响     

章建成  李安民  施之皓  张大为  赵思 《西安体育学院学报》2013,(3):257-262

生态学效度是运动领域研究需要考虑的重要因素,实验旨在探讨虚拟全景呈现方式和单一屏幕呈现方式下乒乓球运动员对发球旋转的判断是否存在差异。研究选取9名上海体育学院乒乓球专项二级运动员为被试,在运动员判断发球旋转时记录下他们的反应时、正确率和事件相关联电位数据。结果表明,运动员的决策过程在不同呈现条件下存在差异,更具生态效度的呈现方式下反应时更长,且完成认知加工过程所需的潜伏期及振幅也存在差异。  相似文献