Fragmentation Phase Transition in Atomic Clusters II - Coulomb Explosion of Metal Clusters -

We discuss the role and the treatment of polarization effects in many-body systems of charged conducting clusters and apply this to the statistical fragmentation of Na-clusters. We see a first order microcanonical phase transition in the fragmentation of $Na^{Z+}_{70}$ for Z=0 to 8. We can distinguish two fragmentation phases, namely evaporation of large particles from a large residue and a complete decay into small fragments only. Charging the cluster shifts the transition to lower excitation energies and forces the transition to disappear for charges higher than Z=8. At very high charges the fragmentation phase transition no longer occurs because the cluster Coulomb-explodes into small fragments even at excitation energy $\epsilon^* = 0$.Comment: 19 text pages +18 *.eps figures, my e-mail adress: [email protected] submitted to Z. Phys.

Chimpanzees’ Socially Maintained Food Preferences Indicate both Conservatism and Conformity

Chimpanzees remain fixed on a single strategy, even if a novel, more efficient, strategy is introduced. Previous studies reporting such findings have incorporated paradigms in which chimpanzees learn one behavioural method and then are shown a new one that the chimpanzees invariably do not adopt. This study provides the first evidence that chimpanzees show such conservatism even when the new method employs the identical required behaviour as the first, but for a different reward. Groups of chimpanzees could choose to exchange one of two inedible tokens; one was rewarded with a highly preferred food (grape) and the other with a less preferred food (carrot). Individuals first observed a model chimpanzee from their social group trained to choose one of the two types of tokens. In one group, this token earned a carrot, while in the other, control, group the token earned a grape. In both groups, chimpanzees conformed to the trained model’s choice. This was especially striking for those gaining the pieces of carrot; the less favoured reward. This resulted in a population-level trend of food choices, even when counter to their original, individual, preferences. Moreover, the chimpanzees’ food preferences did not change over time, demonstrating that these results were not due to a simple shift in preferences. We discuss social factors apparent in the interactions and suggest that, despite seeming to be inefficient, in chimpanzees, conformity may benefit them, possibly by assisting with the maintenance of group relations

Impact of Gender on Separation-Reunification Experiences of Latino Adolescent Immigrants

Many Latino immigrants who enter the US in late childhood or adolescence are reunifying with parents after lengthy separations, and yet there is limited research on this process from their point of view. This article discusses the impact of gender relations on family re-engagement and immigrant adaptation of young men and young women. Young people were interviewed as part of a grounded theory study exploring the process of family separation and reunification for Latino immigrant adolescents who have been separated from their parents for at least four years during immigration. Focus groups, individual interviews and participant observation were used to gather data from 20 Mexican and Central American immigrant adolescents, 12 young men and 8 young women. Participants reported a range of personal and family beliefs about gender roles and their impact on separation and reunification, Young men reported greater exposure to violence, generally had less access to health care, and reported more emotional isolation from families and peers than young women. Fathers and adult male role models were missing from most of their lives, and this absence was particularly difficult for young men. Young women reported greater skills and persistence in emotional re-engagement with their families in the United States.Beaucoup d'immigrés latinos entrés aux Etats-Unis à la fin de l'enfance ou au début de l'adolescence retrouvent leurs parents après une longue période de séparation, et pourtant il n'existe que très peu d'études sur ce sujet relatant leur point de vue. Cet article traite de l'impact des rapports de genre sur le regroupement familial et l'adaptation des jeunes hommes et femmes immigrés. Des jeunes ont été interrogés dans le cadre d'une étude basée sur la théorie ancrée qui analysait le processus de séparation et de regroupement familial chez les adolescents immigrés latinos qui avaient été séparés de leurs parents pendant au moins quatre ans durant la période d'immigration. Des groupes cibles, des entretiens individuels et l'observation des participants ont permis de recueillir des données auprès de 20 adolescents immigrés originaires du Mexique et d'Amérique Centrale, dont 12 jeunes hommes et 8 jeunes femmes. Les participants ont décrit un ensemble de croyances personnelles et familiales sur les rôles sexuels, et leur impact sur la séparation et le regroupement familial. Les jeunes hommes ont ainsi déclaré être plus exposés à la violence, avoir généralement un accès aux soins plus limité, et souffrir d'une plus grande isolation émotionnelle vis-à-vis de leurs familles et de leurs pairs que les jeunes femmes. Les pères et les modèles adultes masculins étaient pour la plupart absents de leur vie, et cette absence était particulièrement difficile à vivre pour les jeunes hommes. Les jeunes femmes ont quant à elles montré plus de capacités et de persévérance dans le réengagement émotionnel avec leurs familles aux Etats-Unis.Muchos inmigrantes latinos que entran en Estados Unidos al final de su infancia o en su adolescencia  se reunifican con sus padres después de largos periodos de separación. Sin embargo, existen muy pocos estudios sobre este proceso desde su punto de vista. Este artículo analiza el impacto de las relaciones de género en la reunificación familiar y la adaptación como inmigrantes de hombres y mujeres jóvenes. Se entrevistó a chicos y chicas en el marco de un estudio de teoría fundamentada que explora el proceso de la separación familiar y su posterior reunificación en el caso de inmigrantes latinos adolescentes que han sido separados de sus padres durante al menos cuatro años en el transcurso de la inmigración. Se utilizaron reuniones de grupo, entrevistas individuales y observaciones para recabar datos de 20 inmigrantes adolescentes mexicanos y centroamericanos, 12 chicos y 8 chicas. Los participantes reflejaban diversas creencias personales y familiares sobre los roles de género y su impacto en la separación y reunificación. Los chicos reflejaron una mayor exposición a la violencia, un acceso más limitado en general a la asistencia sanitaria y un mayor aislamiento emocional de sus familias y compañeros que las chicas. En sus familias no había referencias paternas o de adultos masculinos y esta ausencia resultaba especialmente difícil para los chicos. Las chicas, en cambio, mostraron mayores habilidades y persistencia en la reunificación emocional con sus familias en suelo estadounidense

Impact of Gender on Separation-Reunification Experiences of Latino Adolescent Immigrants

Many Latino immigrants who enter the US in late childhood or adolescence are reunifying with parents after lengthy separations, and yet there is limited research on this process from their point of view. This article discusses the impact of gender relations on family re-engagement and immigrant adaptation of young men and young women. Young people were interviewed as part of a grounded theory study exploring the process of family separation and reunification for Latino immigrant adolescents who have been separated from their parents for at least four years during immigration. Focus groups, individual interviews and participant observation were used to gather data from 20 Mexican and Central American immigrant adolescents, 12 young men and 8 young women. Participants reported a range of personal and family beliefs about gender roles and their impact on separation and reunification, Young men reported greater exposure to violence, generally had less access to health care, and reported more emotional isolation from families and peers than young women. Fathers and adult male role models were missing from most of their lives, and this absence was particularly difficult for young men. Young women reported greater skills and persistence in emotional re-engagement with their families in the United States.Beaucoup d'immigrés latinos entrés aux Etats-Unis à la fin de l'enfance ou au début de l'adolescence retrouvent leurs parents après une longue période de séparation, et pourtant il n'existe que très peu d'études sur ce sujet relatant leur point de vue. Cet article traite de l'impact des rapports de genre sur le regroupement familial et l'adaptation des jeunes hommes et femmes immigrés. Des jeunes ont été interrogés dans le cadre d'une étude basée sur la théorie ancrée qui analysait le processus de séparation et de regroupement familial chez les adolescents immigrés latinos qui avaient été séparés de leurs parents pendant au moins quatre ans durant la période d'immigration. Des groupes cibles, des entretiens individuels et l'observation des participants ont permis de recueillir des données auprès de 20 adolescents immigrés originaires du Mexique et d'Amérique Centrale, dont 12 jeunes hommes et 8 jeunes femmes. Les participants ont décrit un ensemble de croyances personnelles et familiales sur les rôles sexuels, et leur impact sur la séparation et le regroupement familial. Les jeunes hommes ont ainsi déclaré être plus exposés à la violence, avoir généralement un accès aux soins plus limité, et souffrir d'une plus grande isolation émotionnelle vis-à-vis de leurs familles et de leurs pairs que les jeunes femmes. Les pères et les modèles adultes masculins étaient pour la plupart absents de leur vie, et cette absence était particulièrement difficile à vivre pour les jeunes hommes. Les jeunes femmes ont quant à elles montré plus de capacités et de persévérance dans le réengagement émotionnel avec leurs familles aux Etats-Unis.Muchos inmigrantes latinos que entran en Estados Unidos al final de su infancia o en su adolescencia  se reunifican con sus padres después de largos periodos de separación. Sin embargo, existen muy pocos estudios sobre este proceso desde su punto de vista. Este artículo analiza el impacto de las relaciones de género en la reunificación familiar y la adaptación como inmigrantes de hombres y mujeres jóvenes. Se entrevistó a chicos y chicas en el marco de un estudio de teoría fundamentada que explora el proceso de la separación familiar y su posterior reunificación en el caso de inmigrantes latinos adolescentes que han sido separados de sus padres durante al menos cuatro años en el transcurso de la inmigración. Se utilizaron reuniones de grupo, entrevistas individuales y observaciones para recabar datos de 20 inmigrantes adolescentes mexicanos y centroamericanos, 12 chicos y 8 chicas. Los participantes reflejaban diversas creencias personales y familiares sobre los roles de género y su impacto en la separación y reunificación. Los chicos reflejaron una mayor exposición a la violencia, un acceso más limitado en general a la asistencia sanitaria y un mayor aislamiento emocional de sus familias y compañeros que las chicas. En sus familias no había referencias paternas o de adultos masculinos y esta ausencia resultaba especialmente difícil para los chicos. Las chicas, en cambio, mostraron mayores habilidades y persistencia en la reunificación emocional con sus familias en suelo estadounidense

When Given the Opportunity, Chimpanzees Maximize Personal Gain Rather than “Level the Playing Field”

We provided chimpanzees (Pan troglodytes) with the ability to improve the quality of food rewards they received in a dyadic test of inequity.We were interested to see if this provision influenced their responses and, if so, whether it was mediated by a social partner’s outcomes. We tested eight dyads using an exchange paradigm in which, depending on the condition, the chimpanzees were rewarded with either high-value (a grape) or low-value (a piece of celery) food rewards for each completed exchange. We included four conditions. In the first, “Different” condition, the subject received different, less-preferred, rewards than their partner for each exchange made (a test of inequity). In the “Unavailable” condition, high-value rewards were shown, but not given, to both chimpanzees prior to each exchange and the chimpanzees were rewarded equally with low-value rewards (a test of individual contrast). The final two conditions created equity. In these High-value and Low-value “Same” conditions both chimpanzees received the same food rewards for each exchange.Within each condition, the chimpanzees first completed ten trials in the Baseline Phase, in which the experimenter determined the rewards they received, and then ten trials in the Test Phase. In the Test Phase, the chimpanzees could exchange tokens through the aperture of a small wooden picture frame hung on their cage mesh in order to receive the high-value reward. Thus, in the Test Phase, the chimpanzees were provided with an opportunity to improve the quality of the rewards they received, either absolutely or relative to what their partner received. The chimpanzees responded in a targeted manner; in the Test Phase they attempted to maximize their returns in all conditions in which they had received low-value rewards during the Baseline Phase. Thus, the chimpanzees were apparently motivated to increase their reward regardless of their partners’, but they only used the mechanism provided when it afforded the opportunity for them to increase their rewards.We also found evidence that the chimpanzees’ responses were enhanced by social facilitation. Specifically, the chimpanzees were more likely to exchange their tokens through the frame when their test partner also did so, even in circumstances in which their reward value could not be improved. Our paradigm provided the chimpanzees with the possibility to improve the quality of rewards they received in the Test Phase. We found that refusals – to exchange tokens or to eat rewards – decreased significantly in the Test Phase compared to the Baseline Phase, where no such opportunity for improvement of outcomes existed. Thus, the chimpanzees participated more when they could improve the rewards they received

Chimpanzees demonstrate individual differences in social information use

Studies of transmission biases in social learning have greatly informed our understanding of how behaviour patterns may diffuse through animal populations, yet within-species inter-individual variation in social information use has received little attention and remains poorly understood. We have addressed this question by examining individual performances across multiple experiments with the same population of primates. We compiled a dataset spanning 16 social learning studies (26 experimental conditions) carried out at the same study site over a 12-year period, incorporating a total of 167 chimpanzees. We applied a binary scoring system to code each participant’s performance in each study according to whether they demonstrated evidence of using social information from conspecifics to solve the experimental task or not (Social Information Score—‘SIS’). Bayesian binomial mixed effects models were then used to estimate the extent to which individual differences influenced SIS, together with any effects of sex, rearing history, age, prior involvement in research and task type on SIS. An estimate of repeatability found that approximately half of the variance in SIS was accounted for by individual identity, indicating that individual differences play a critical role in the social learning behaviour of chimpanzees. According to the model that best fit the data, females were, depending on their rearing history, 15–24% more likely to use social information to solve experimental tasks than males. However, there was no strong evidence of an effect of age or research experience, and pedigree records indicated that SIS was not a strongly heritable trait. Our study offers a novel, transferable method for the study of individual differences in social learning

Sex Differences in the Relationship Between Planum Temporale Asymmetry and Corpus Callosum Morphology in Chimpanzees (\u3cem\u3ePan troglodytes\u3c/em\u3e): A Combined MRI and DTI Analysis

Increases brain size has been hypothesized to be inversely associated with the expression of behavioral and brain asymmetries within and between species. We tested this hypothesis by analyzing the relation between asymmetries in the planum temporale (PT) and different measures of the corpus callosum (CC) including surface area, streamline count as measured from diffusion tensor imaging, fractional anisotropy values and the ratio in the number of fibers to surface area in a sample of chimpanzees. We found that chimpanzees with larger PT asymmetries in absolute terms had smaller CC surface areas, fewer streamlines and a smaller ratio of fibers to surface area. These results were largely specific to male but not female chimpanzees. Our results partially support the hypothesis that brain asymmetries are linked to variation in corpus callosum morphology, although these associations may be sex-dependent

An Evaluation of the Efficacy of Video Displays for Use With Chimpanzees (Pan troglodytes)

Video displays for behavioral research lend themselves particularly well to studies with chimpanzees (Pan troglodytes), as their vision is comparable to humans', yet there has been no formal test of the efficacy of video displays as a form of social information for chimpanzees. To address this, we compared the learning success of chimpanzees shown video footage of a conspecific compared to chimpanzees shown a live conspecific performing the same novel task. Footage of an unfamiliar chimpanzee operating a bidirectional apparatus was presented to 24 chimpanzees (12 males, 12 females), and their responses were compared to those of a further 12 chimpanzees given the same task but with no form of information. Secondly, we also compared the responses of the chimpanzees in the video display condition to responses of eight chimpanzees from a previously published study of ours, in which chimpanzees observed live models. Chimpanzees shown a video display were more successful than those in the control condition and showed comparable success to those that saw a live model. Regarding finegrained copying (i.e. the direction that the door was pushed), only chimpanzees that observed a live model showed significant matching to the model's methods with their first response. Yet, when all the responses made by the chimpanzees were considered, comparable levels of matching were shown by chimpanzees in both the live and video conditions. Am. J. Primatol. 00:1-8, 2012. C 2012 Wiley Periodicals, Inc

Nonadjacent dependency processing in monkeys, apes and humans

The ability to track syntactic relationships between words, particularly over distances (“nonadjacent dependencies”), is a critical faculty underpinning human language, although its evolutionary origins remain poorly understood. While some monkey species are reported to process auditory nonadjacent dependencies, comparative data from apes are missing, complicating inferences regarding shared ancestry. Here, we examined nonadjacent dependency processing in common marmosets, chimpanzees, and humans using “artificial grammars”: strings of arbitrary acoustic stimuli composed of adjacent (nonhumans) or nonadjacent (all species) dependencies. Individuals from each species (i) generalized the grammars to novel stimuli and (ii) detected grammatical violations, indicating that they processed the dependencies between constituent elements. Furthermore, there was no difference between marmosets and chimpanzees in their sensitivity to nonadjacent dependencies. These notable similarities between monkeys, apes, and humans indicate that nonadjacent dependency processing, a crucial cognitive facilitator of language, is an ancestral trait that evolved at least ~40 million years before language itself