Neutron skin of 208Pb, nuclear symmetry energy, and the parity radius experiment

A precise determination of the neutron skin thickness of a heavy nucleus sets a basic constraint on the nuclear symmetry energy (the neutron skin thickness is the difference of the neutron and proton rms radii of the nucleus). The parity radius experiment (PREX) may achieve it by electroweak parity-violating electron scattering (PVES) on 208Pb. We investigate PVES in nuclear mean field approach to allow the accurate extraction of the neutron skin thickness of 208Pb from the parity-violating asymmetry probed in the experiment. We demonstrate a high linear correlation between the parity-violating asymmetry and the neutron skin thickness in successful mean field forces as the best means to constrain the neutron skin of 208Pb from PREX, without assumptions on the neutron density shape. Continuation of the experiment with higher precision in the parity-violating asymmetry is motivated since the present method can support it to constrain the density slope of the nuclear symmetry energy to new accuracy.

Do Schools Discriminate Against Homosexual Parents? Evidence from an Internet Field Experiment

The recognition of homosexual rights is a controversial issue in many countries. Spain was the third country in the world (after Netherlands and Belgium) to introduce a law recognizing homosexual marriage and adoption of children. In this paper, we examine for the first time whether schools are more hesitant to give feedback to homosexual parents during children's pre-registration period in Spain. In order to do that, we designed an internet field experiment to be conducted in schools. We created three types of fictitious couples; one heterosexual, one male homosexual and one female homosexual, and send emails to schools making sexual orientation explicit. Our results show that men homosexual couples had a significant lower probability to receive and answer than heterosexual couples (22.5 percentage points less). No statistically significant differences in the response rate were found between female homosexual and heterosexual couples. This result suggests that male homosexual couples might be penalized because of the lack of a maternal figure. Keywords: Discrimination, field experiment, schools, homosexual rights. JEL codes: H41, I20, K36

Social Presence Approach Within the Question and Answering eLearning Model: An Experiment with a Multi-Agent System

The model of Questions Answering (Q&A) for eLearning is based on collaborative learning through questions that are posed by students and their answers to that questions which are given by peers, in contrast with the classical model in which students ask questions to the teacher only. In this proposal we extend the Q&A model including the social presence concept and a quantitative measure of it is proposed; besides it is considered the evolution of the resulting Q&A social network after the inclusion of the social presence and taking into account the feedback on questions posed by students and answered by peers. The social network behaviorwas simulated using a Multi-Agent System to compare the proposed social presence model with the classical and the Q&A models

La escala de análisis: un tema central en didáctica de la geografía = The scale of analysis a central didactic theme in Geography

Geographical scale is not merely a technical question. The learning of geographical scale goes beyond geometricunderstanding; it implies the etymological comprehension of the concept, the recognition of the importance of scale in theelaboration of the geographical discourse. It implies placing oneself in the centre of the teaching and learning of Geographyand asking oneself, what scale? Why this scale? What progression of scales? The answer to these questions puts in doubtthe scientific discourse that is presently taught in schools especially on the scale of analysis, the sequencing of studiedspaces and the false dichotomy local and global

'Situaciones problema' y desarrollo de la competencia motriz en educación física escolar: cuestiones didácticas = Problem situations and developing motor competence in Physical Education at school: didactic questions

From the areas of motor learning and the teaching of Physical Education we promote coherent methodological orientationswith the present curricular guide that are focused in such a way so that the student is able to act independently. In thissense we may consider the problem situations as a good example for methodological proposals. So as to determine its useand adequateness for Physical Education it is conveniente to analyse the characteristics of the motor tasks that areproposed as well as the features of the teaching intervention in such a way as to ease the adquisition and development ofthe motor competence of the students