Un estudio evolutivo a cerca de la distinción entre objetos animados e inanimados: implicaciones para la atribución causal.

Comprobar en qué medida afecta la edad y el conocimiento de la naturaleza de los objetos, evaluado mediante la capacidad de empleo de una operación lógico-matemática (la clasificación) a los razonamientos causales. 72 sujetos: 39 niños y 33 niñas de edad comprendida entre 7-9 años elegidos al azar de 8 centros de EGB de la provicincia de Murcia, elegidos también al azar mediante muestreo aleatorio estratificado con distintos niveles socioeconómicos y un nivel medio de rendimiento académico. Fueron distribuídos en cuatro grupos: A/ 9 sujetos (4 niños y 5 niñas) de primero de Preescolar; B/ 13 sujetos (7 niños y 6 niñas) de segundo de Preescolar; C/ 26 sujetos (15 niños y 11 niñas) de primero de EGB; D/ 24 sujetos (13 niños y 11 niñas) de segundo de EGB. Para evitar el efecto rebote, es decir, que los resultados de una prueba afecten a la otra se realizó un estudio piloto en el que se contrabalanceó el orden de aplicación, de donde se dedujo que la aplicación de las pruebas debía seguir el orden siguiente: A/ Prueba de clasificación. B/ Prueba de causalidad. Posteriormente se realizó un estudio correlacional teniendo en cuenta las variables independientes de edad y clasificación, y como dependiente la causalidad. Prueba de clasificación y prueba de causalidad. Análisis de regresión univariado para ver la relación entre variables independientes con dependiente. Análisis de regresión multivariado con las pruebas de: LAMBDA de Wilks, prueba de Pillat, prueba de Hotelling-Lawley y la Theta, para comprobar si los contenidos de la situación causal afectan a juicios causales. Parece ser que la variable edad no es una variable predictiva de la ejecución causal, mientras que la capacidad de explicar lo real (variable clasificación), sí puede serlo, aunque no es la única, de ahí la necesidad de introducir otras variables de naturaleza cognitiva. Otro aspecto a resaltar es que los contenidos de la situación causal parecen no tener incidencia sobre la elaboración de las inferencias correspondientes para emitir sus juicios causales. Se pueden conciliar las investigaciones sobre causalidad, con el modelo del equilibrio sobre causalidad propuesto por Piaget si se elabora un modelo específico y explicativo de la causalidad en donde tendrían cabida los dos tipos de causalidad (física y psicológica). Este es el curso que deben seguir las futuras investigaciones.

Autoevaluaci??n de competencias informacionales en Educaci??n Secundaria : propuesta de modelo causal desde una perspectiva de g??nero

La inclusi??n en los curr??culos de educaci??n b??sica de competencias clave relacionadas con el manejo de la informaci??n, responde a la transformaci??n social relacionada con el impacto de las tecnolog??as de la informaci??n y la comunicaci??n. Por otra parte, proliferan estudios de g??nero que evidencias diferencias por sexo en la adquisici??n de habilidades inform??ticas. Dada la estrecha relaci??n entre las competencias informacionales y estas tecnolog??as, el objetivo es analizar las diferencias de g??nero en el desarrollo de las citadas competencias a partir del dise??o de un modelo causal.

Hacia un modelo causal de las dimensiones del estrés académico en estudiantes de Enfermería

Resumen basado en el de la publicación.

Classical and causal inference approaches to statistical mediation analysis

Resumen tomado de la publicaci??n

Dynamic causal modeling applied to fMRI data shows high reliability

Sensitivity, specificity, and reproducibility are vital to interpret neuroscientific results from functional magnetic resonance imaging (fMRI) experiments. Here we examine the scan–rescan reliability of the percent signal change (PSC) and parameters estimated using Dynamic Causal Modeling (DCM) in scans taken in the same scan session, less than 5 min apart. We find fair to good reliability of PSC in regions that are involved with the task, and fair to excellent reliability with DCM. Also, the DCM analysis uncovers group differences that were not present in the analysis of PSC, which implies that DCM may be more sensitive to the nuances of signal changes in fMRI data.

Antifungal activity of Bacillus subtilis filtrate to control Fusarium oxysporum f.sp. lentis, the causal organism of lentil vascular wilt

In dual cultures, the supernatant filtrate of the biological control agent Bacillus subtilis was evaluated against (Fusarium oxysporum f.sp. lentis) the causal organism of lentil vascular wilt. The antagonistic activity was evaluated as percent reduction of fungal growth (certainly due, in part, to the antifungal metabolites produced by the antagonistic bacterium). The in-vitro experiments showed that B. subtilis filtrate, whether solid or liquid media, had a strong inhibiting activity on the spore germination and mycelial growth of F. oxysporum f. sp. lentis. In a glasshouse experiment, soil was drenched with B. subtilis filtrate at 30 ml/kg (vol/wt) around seedlings of a susceptible lentil line (ILL 4605). In this treatment there was only 31% mortality compared with 100% kill of plants in the control treatment (P≤0.05).

DNA variation in a 13-Mb region including the F9 gene: inferring the genealogical history and causal role of a hemophilia B mutation (IVS 5+13 A -> G)

About 5.5% of all UK hemophilia B patients have the base substitution IVS 5+13 A-->G as the only change in their factor (F)IX gene (F9). This generates a novel donor splice site which fits the consensus better than the normal intron 5 donor splice. Use of the novel splice site should result in a missense mutation followed by the abnormal addition of four amino acids to the patients' FIX. In order to explain the prevalence of this mutation, its genealogical history is examined. Analysis of restriction fragment length polymorphism in the 21 reference UK individuals (from different families) with the above mutation showed identical haplotypes in 19 while two differed from the rest and from each other. In order to investigate the history of the mutation and to verify that it had occurred independently more than once, the sequence variation in 1.5-kb segments scattered over a 13-Mb region including F9 was examined in 18 patients and 15 controls. This variation was then analyzed with a recently developed Bayesian approach that reconstructs the genealogy of the gene investigated while providing evidence of independent mutations that contribute disconnected branches to the genealogical tree. The method also provides minimum estimates of the age of the mutation inherited by the members of coherent trees. This revealed that 17 or 18 mutant genes descend from a founder who probably lived 450 years ago, while one patient carries an independent mutation. The independent recurrence of the IVS5+13 A-->G mutation strongly supports the conclusion that it is the cause of these patients' mild hemophilia.

Modèle d'état à coefficient aléatoire: filtrage par densités approchées

Le filtrage de Bucy-Kalman s'applique au modèle d'état comprenant des équations linéaires bruitées, décrivant l'évolution de l'état et des équations linéaires bruitées d'observation . Ce filtrage consiste dans le cas gaussien, à calculer de façon récursive, la loi de probabilité, a posteriori, de l'état, au vu de l' observation actuelle et des observations passées . Le filtrage par densités approchées permet de traiter des équations d'état, non linéaires ou à bruits non Gaussiens. Pour un coefficient de rappel aléatoire, cas typique d'une situation de changements de modèles, l'article introduit une famille de lois de probabilité, paramétrées, bimodales servant, par ajustement des paramètres, à approcher les lois a posteriori de l'état aux divers instants . Les paramètres sont recalculés récursivement, lors des mises à jour et des prédictions.

Pseudomonas syringae pv. coryli, the causal agent of bacterial twig dieback of Corylus avellana

Thirty-eight bacterial strains isolated from hazelnut (Corylus avellana) cv. Tonda Gentile delle Langhe showing a twig dieback in Piedmont and Sardinia, Italy, were studied by a polyphasic approach. All strains were assessed by fatty acids analysis and repetitive sequence-based polymerase chain reaction (PCR) fingerprinting using BOX and ERIC primer sets. Representative strains also were assessed by sequencing the 16S rDNA and hrpL genes, determining the presence of the syrB gene, testing their biochemical and nutritional characteristics, and determining their pathogenicity to hazelnut and other plants species or plant organs. Moreover, they were compared with reference strains of other phytopathogenic pseudomonads. The strains from hazelnut belong to Pseudomonas syringae (sensu latu), LOPAT group Ia. Both fatty acids and repetitive-sequence-based PCR clearly discriminate such strains from other Pseudomonas spp., including P. avellanae and other P. syringae pathovars as well as P. syringae pv. syringae strains from hazelnut. Also, the sequencing of 16S rDNA and hrpL genes differentiated them from P. avellanae and from P. syringae pv. syringae. They did not possess the syrB gene. Some nutritional tests also differentiated them from related P. syringae pathovars. Upon artificial inoculation, these strains incited severe twig diebacks only on hazelnut. Our results justify the creation of a new pathovar because the strains from hazelnut constitute a homogeneous group and a discrete phenon. The name of P. syringae pv. coryli is proposed and criteria for routine identification are presented.

The causal surface and its effect on distribution transparency in a distributed virtual environment

One goal in the development of distributed virtual environments (DVEs) is to create a system such that users are unaware of the distribution-the distribution should be transparent. The paper begins by discussing the general issues in DVEs that might make this possible, and a system that allows some level of distribution transparency is described. The system described suffers from effects of inconsistency, which in turn cause undesirable visual effects. The causal surface is introduced as a solution that removes these visual effects. The paper then introduces two determining factors of distribution transparency relating to user perception and performance. With regard to these factors, two hypotheses are stated relating to the causal surface. A user-trial on forty-five subjects is used to validate the hypotheses. A discussion of the results of the trial concludes that the causal surface solution does significantly improve the distribution transparency in a DVE.

Causal volumes in distributed virtual reality

Research to date has tended to concentrate on bandwidth considerations to increase scalability in distributed interactive simulation and virtual reality systems. This paper proposes that the major concern for latency in user interaction is that of the fundamental limit of communication rate due to the speed of light. Causal volumes and surfaces are introduced as a model of the limitations of causality caused by this fundamental delay. The concept of virtual world critical speed is introduced, which can be determined from the causal surface. The implications of the critical speed are discussed, and relativistic dynamics are used to constrain the object speed, in the same way speeds are bounded in the real world.

Maximising concurrency and scalability in a consistent, causal, distributed virtual reality system, whilst minimising the effect of network delays

The development of large scale virtual reality and simulation systems have been mostly driven by the DIS and HLA standards community. A number of issues are coming to light about the applicability of these standards, in their present state, to the support of general multi-user VR systems. This paper pinpoints four issues that must be readdressed before large scale virtual reality systems become accessible to a larger commercial and public domain: a reduction in the effects of network delays; scalable causal event delivery; update control; and scalable reliable communication. Each of these issues is tackled through a common theme of combining wall clock and causal time-related entity behaviour, knowledge of network delays and prediction of entity behaviour, that together overcome many of the effects of network delay.