Part-whole relations between food webs and the validity of local food-web descriptions

This work analyzes the relationship between large food webs describing potential feeding relations between species and smaller sub-webs thereof describing relations actually realized in local communities of various sizes. Special attention is given to the relationships between patterns of phylogenetic correlations encountered in large webs and sub-webs. Based on the current theory of food-web topology as implemented in the matching model, it is shown that food webs are scale invariant in the following sense: given a large web described by the model, a smaller, randomly sampled sub-web thereof is described by the model as well. A stochastic analysis of model steady states reveals that such a change in scale goes along with a re-normalization of model parameters. Explicit formulae for the renormalized parameters are derived. Thus, the topology of food webs at all scales follows the same patterns, and these can be revealed by data and models referring to the local scale alone. As a by-product of the theory, a fast algorithm is derived which yields sample food webs from the exact steady state of the matching model for a high-dimensional trophic niche space in finite time. (C) 2008 Elsevier B.V. All rights reserved.

Representing part-whole relationships in conceptual modeling: An empirical evaluation

The part-of or part-whole construct is a fundamental element of many conceptual modeling grammars that is used to associate one thing (a component) with another thing (a composite). Substantive theoretical issues surrounding the part-whole construct remain to be resolved, however. For instance, contrary to widespread claims, the relationship between components and composites is not always transitive. Moreover, how the partwhole construct should be represented in a conceptual schema diagram remains a contentious issue. Some analysts argue composites should be represented as a relationship or association. Others argue they should be represented as an entity. In this paper we use an ontological theory to support our arguments that composites should be represented as entities and not relationships or associations. We also describe an experiment that we undertook to test whether representing composites as relationships or entities enables users to understand a domain better. Our results support our arguments that using entities to represent composites enables users to better understand a domain.

Event-related potential effects of object repetition depend on attention and part-whole configuration

The effects of spatial attention and part-whole configuration on recognition of repeated objects were investigated with behavioral and event-related potential (ERP) measures. Short-term repetition effects were measured for probe objects as a function of whether a preceding prime object was shown as an intact image or coarsely scrambled (split into two halves) and whether or not it had been attended during the prime display. In line with previous behavioral experiments, priming effects were observed from both intact and split primes for attended objects, but only from intact (repeated same-view) objects when they were unattended. These behavioral results were reflected in ERP waveforms at occipital-temporal locations as more negative-going deflections for repeated items in the time window between 220 and 300 ms after probe onset (N250r). Attended intact images showed generally more enhanced repetition effects than split ones. Unattended images showed repetition effects only when presented in an intact configuration, and this finding was limited to the right-hemisphere electrodes. Repetition effects in earlier (before 200 ms) time-windows were limited to attended conditions at occipito-temporal sites (N1), a component linked to the encoding of object structure, while repetition effects at central locations during the same time window (P150) were found only from objects repeated in the same intact configuration—both previously attended and unattended probe objects. The data indicate that view-generalization is mediated by a combination of analytic (part-based) representations and automatic view-dependent representations.

Tals del-helhetsrelationer : Elevers sätt att urskilja del-helhetsrelationer i öppna utsagor.

På vilket sätt kan vi hjälpa alla elever att bli förtrogna med matematikens uttrycksformer? Ett sätt är att bygga en stadig aritmetisk grund för eleverna där de befäster talens innehåll. Det är vad den här uppsatsen handlar om. Uppsatsen beskriver vad som skiljer användandet av del-helhetsrelationer från andra sätt att lösa öppna utsagor på. Uppsatsen beskriver även vilka kritiska aspekter om öppna utsagor som kan förekomma hos elever i årskurs 1 och 2. Uppsat-sen är skriven ur en fenomenografisk ansats med variationsteoretiska inslag eftersom de två teorierna är nära besläktade. Studien genomfördes genom filmade intervjuer med 11 elever som valdes ut genom en munt-lig och en skriftlig diagnos samt ett skriftligt arbetsblad. Resultatet visar att elever som använ-der automatiserade del-helhetsrelationer har en fördel när de löser öppna utsagor jämfört med elever som använder andra lösningsmetoder. Skillnaderna syns tydligt när det gäller lösandet av öppna subtraktionsutsagor där helheten saknas. En väg till den abstrakta förståelsen för tals del-helhetsrelationer går via fingertalen. Min slutsats är att eleverna redan tidigt i skolan måste få undervisning om fingertalen samt talens del-helhetsrelationer för att undvika att de utvecklar matematiksvårigheter.

The roles of shared vs. Distinctive conceptual features in lexical access

Contemporary models of spoken word production assume conceptual feature sharing determines the speed with which objects are named in categorically-related contexts. However, statistical models of concept representation have also identified a role for feature distinctiveness, i.e., features that identify a single concept and serve to distinguish it quickly from other similar concepts. In three experiments we investigated whether distinctive features might explain reports of counter-intuitive semantic facilitation effects in the picture word interference (PWI) paradigm. In Experiment 1, categorically-related distractors matched in terms of semantic similarity ratings (e.g., zebra and pony) and manipulated with respect to feature distinctiveness (e.g., a zebra has stripes unlike other equine species) elicited interference effects of comparable magnitude. Experiments 2 and 3 investigated the role of feature distinctiveness with respect to reports of facilitated naming with part-whole distractor-target relations (e.g., a hump is a distinguishing part of a CAMEL, whereas knee is not, vs. an unrelated part such as plug). Related part distractors did not influence target picture naming latencies significantly when the part denoted by the related distractor was not visible in the target picture (whether distinctive or not; Experiment 2). When the part denoted by the related distractor was visible in the target picture, non-distinctive part distractors slowed target naming significantly at SOA of -150 ms (Experiment 3). Thus, our results show that semantic interference does occur for part-whole distractor-target relations in PWI, but only when distractors denote features shared with the target and other category exemplars. We discuss the implications of these results for some recently developed, novel accounts of lexical access in spoken word production.

Reunitising hundredths: prototypic and nonprototypic representations

This paper reports on a study in which 29 Year 6 students (selected from the top 30% of 176 Year 6 students) were individually interviewed to explore their ability to reunitise hundredths as tenths (Behr, Harel, Post & Lesh, 1992) when represented by prototypic (PRO) and nonprototypic (NPRO) models. The results showed that 55.2% of the students were able to unitise both models and that reunitising was more successful with the PRO model. The interviews revealed that many of these students had incomplete, fragmented or non-existent structural knowledge of the reunitising process and often relied on syntactic clues to complete the tasks. The implication for teaching is that instruction should not be limited to PRO representations of the part/whole notion of fraction and that the basic structures (equal parts, link between name and number of equal parts) of the part/whole notion needs to be revisited often.

The power of percent

Which statistic would you use if you were writing the newspaper headline for the following media release: "Tassie’s death rate of deaths arising from transport-related injuries was 13 per 100,000 people, or 50% higher than the national average”? (Martain, 2007). The rate “13 per 100,000” sounds very small whereas “50% higher” sounds quite large. Most people are aware of the tendency to choose between reporting data as actual numbers or using percents in order to gain attention. Looking at examples like this one can help students develop a critical quantitative literacy viewpoint when dealing with “authentic contexts” (Australian Curriculum, Assessment and Reporting Authority [ACARA], 2013a, p. 37, 67). The importance of the distinction between reporting information in raw numbers or percents is not explicitly mentioned in the Australian Curriculum: Mathematics (ACARA, 2013b, p. 42). Although the document specifically mentions making “connections between equivalent fractions, decimals and percentages” [ACMNA131] in Year 6, there is no mention of the fundamental relationship between percent and the raw numbers represented in a part-whole fashion. Such understanding, however, is fundamental to the problem solving that is the focus of the curriculum in Years 6 to 9. The purpose of this article is to raise awareness of the opportunities to distinguish between the use of raw numbers and percents when comparisons are being made in contexts other than the media. It begins with the authors’ experiences in the classroom, which motivated a search in the literature, followed by a suggestion for a follow-up activity.

A aprendizagem dos números racionais através das conexões entre as suas representações:uma experiência de ensino no 2º ciclo do ensino básico

Tese de doutoramento, Educação (Didática da Matemática), Universidade de Lisboa, Instituto de Educação, 2014

Other-race faces : limitations of expert face recognition /

Adults' expert face recognition is limited to the kinds of faces they encounter on a daily basis (typically upright human faces of the same race). Adults process own-race faces holistically (Le., as a gestalt) and are exquisitely sensitive to small differences among faces in the spacing of features, the shape of individual features and the outline or contour of the face (Maurer, Le Grand, & Mondloch, 2002), however this expertise does not seem to extend to faces from other races. The goal of the current study was to investigate the extent to which the mechanisms that underlie expert face processing of own-race faces extend to other-race faces. Participants from rural Pennsylvania that had minimal exposure to other-race faces were tested on a battery of tasks. They were tested on a memory task, two measures of holistic processing (the composite task and the part/whole task), two measures of spatial and featural processing (the JanelLing task and the scrambledlblurred faces task) and a test of contour processing (JanelLing task) for both own-and other-race faces. No study to date has tested the same participants on all of these tasks. Participants had minimal experience with other-race faces; they had no Chinese family members, friends or had ever traveled to an Asian country. Results from the memory task did not reveal an other-race effect. In the present study, participants also demonstrated holistic processing of both own- and other-race faces on both the composite task and the part/whole task. These findings contradict previous findings that Caucasian adults process own-race faces more holistically than other-race faces. However participants did demonstrate an own-race advantage for processing the spacing among features, consistent with two recent studies that used different manipulations of spacing cues (Hayward et al. 2007; Rhodes et al. 2006). They also demonstrated an other-race effect for the processing of individual features for the Jane/Ling task (a direct measure of featural processing) consistent with previous findings (Rhodes, Hayward, & Winkler, 2006), but not for the scrambled faces task (an indirect measure offeatural processing). There was no own-race advantage for contour processing. Thus, these results lead to the conclusion that individuals may show less sensitivity to the appearance of individual features and the spacing among them in other-race faces, despite processing other-race faces holistically.

Approche probabiliste pour l’analyse de l’impact des changements dans les programmes orientés objet

Nous proposons une approche probabiliste afin de déterminer l’impact des changements dans les programmes à objets. Cette approche sert à prédire, pour un changement donné dans une classe du système, l’ensemble des autres classes potentiellement affectées par ce changement. Cette prédiction est donnée sous la forme d’une probabilité qui dépend d’une part, des interactions entre les classes exprimées en termes de nombre d’invocations et d’autre part, des relations extraites à partir du code source. Ces relations sont extraites automatiquement par rétro-ingénierie. Pour la mise en oeuvre de notre approche, nous proposons une approche basée sur les réseaux bayésiens. Après une phase d’apprentissage, ces réseaux prédisent l’ensemble des classes affectées par un changement. L’approche probabiliste proposée est évaluée avec deux scénarios distincts mettant en oeuvre plusieurs types de changements effectués sur différents systèmes. Pour les systèmes qui possèdent des données historiques, l’apprentissage a été réalisé à partir des anciennes versions. Pour les systèmes dont on ne possède pas assez de données relatives aux changements de ses versions antécédentes, l’apprentissage a été réalisé à l’aide des données extraites d’autres systèmes.

L’évolution de la course à pied en endurance et ses impacts sur le corps humain

Travail d'intégration réalisé dans le cadre du cours PHT-6113.

Síndrome de Burnout en médicos generales de consulta externa

Objetivos : Establecer la prevalencia de Síndrome de Burnout en 17 médicos de consulta externa de una IPS de Bogotá, antes de la jornada laboral y después de la misma. Determinar las dimensiones del Síndrome de Burnout y relacionarlas con las variables sociodemográficas escogidas para este caso. Metodología: Se realizó un estudio longitudinal con una población de 17 médicos generales de consulta externa de una IPS de la cuidad de Bogotá Colombia, en el año 2009. Se les aplicó el Test de Maslach, para determinar las tres dimensiones del Síndrome de Burnout las cuales son: agotamiento emocional, despersonalización y realización personal para establecer la relación con las variables escogidas previamente. Para el análisis estadístico se usó el Software Epi Info Versión 3.51. Las variables cuantitativas fueron resumidas teniendo en cuenta medidas de tendencia central y las variables cuantitativas se expresaron en forma de proporciones. Para realizar las comparaciones se utilizó la prueba Ji cuadrado con ajuste por Test de Fischer. Se consideró significancia estadística con p ‹ 0.05. Resultado : La población estudiada fue en su mayoría de género femenino, con una mediana de edad de 30 años. El 41.2% de los médicos trabajan 8 horas diarias y el 35.3% trabajan más de 8 horas al día. Se calificaron las tres dimensiones que propone el test de Maslach, las cuales son agotamiento emocional, despersonalización y realización personal dando un puntaje de alto medio y bajo según las respuestas de los médicos evaluados. . Dentro de las dimensiones analizadas del test de Maslach antes de la jornada laboral el 35.3 % presentan agotamiento emocional dentro de la puntuación alta y después de la jornada se aumenta a 47.1%. En cuanto al puntaje para medio en esta misma dimensión fue de 23.5 % y bajo 41.2% previo a la jornada , con un porcentaje al finalizar de la jornada de 17.6% y 35.3% respectivamente. La dimensión de despersonalización antes de la jornada fue de 29,4% para alto, 23.5% para medio y 47.1% para bajo. Al finalizar la jornada no se observan cambios significativos en los porcentajes de esta dimensión. No se obtuvo prevalencia significativa entre las variables estudiadas y cada una de las dimensiones del Test de Maslach. Discusión : Los resultados muestran que existe un cambio en la dimensión de agotamiento emocional al inicio de la jornada laboral comparado con el final de la misma. Las calificaciones obtenidas tuvieron valores altos, mientras que en los de valores medio y bajo disminuyó este agotamiento al finalizar la jornada. Para la despersonalización los valores no se vieron modificados tras la jornada de trabajo. En cuanto a la realización personal hubo una variación ya que los sujetos que fueron calificados al iniciar la jornada con valores altos disminuyeron al finalizar y los de valores medio y bajo aumentaron su realización personal al finalizar la jornada. De otra parte no se establecieron relaciones significativas con los factores extralaborales e individuales evaluados, teniendo en cuenta probablemente el tamaño de la población de estudio y el tiempo de evaluación.