SPH simulations of clumps formation by dissipative collision of molecular clouds - I. Non magnetic case

Computer experiments of interstellar cloud collisions were performed with a new smoothed-particle-hydrodynamics (SPH) code. The SPH quantities were calculated by using spatially adaptive smoothing lengths and the SPH fluid equations of motion were solved by means of a hierarchical multiple time-scale leapfrog. Such a combination of methods allows the code to deal with a large range of hydrodynamic quantities. A careful treatment of gas cooling by H, H(2), CO and H II, as well as a heating mechanism by cosmic rays and by H(2) production on grains surface, were also included in the code. The gas model reproduces approximately the typical environment of dark molecular clouds. The experiments were performed by impinging two dynamically identical spherical clouds onto each other with a relative velocity of 10 km s(-1) but with a different impact parameter for each case. Each object has an initial density profile obeying an r(-1)-law with a cutoff radius of 10 pc and with an initial temperature of 20 K. As a main result, cloud-cloud collision triggers fragmentation but in expense of a large amount of energy dissipated, which occurred in the head-on case only. Off-center collision did not allow remnants to fragment along the considered time (similar to 6 Myr). However, it dissipated a considerable amount of orbital energy. Structures as small as 0.1 pc, with densities of similar to 10(4) cm(-3), were observed in the more energetic collision.

Power-law distributions for the citation index of scientific publications and scientists

The number of citations of a scientific publication or of an individual scientist has become an important factor of quality assessment in science. We report a study of the statistical distribution of the citation index of both scientific publications and scientists. We give numerical evidence that Tsallis (power law) statistics explains the entire distribution over eight orders of magnitude (10-4 to 10(4)). Also, we draw Zipf plots in order to analyze the statistical distribution of the citation index of Brazilian and international physicists and chemists. The relatively small group of Brazilian scientists seems more adequate to explain the dynamics of the citation index. In this case, we find that the distribution of the citation index can also be explained by a gradually truncated power law with similar parameters. We finally discuss possible mechanisms behind the citation index of scientists and scientific publications.

Power law distribution in education: University entrance examination

We studied the statistical distribution of candidate's performance which is measured through their marks in university entrance examination (Vestibular) of UNESP (Universidade Estadual Paulista) for years 1998, 1999, and 2000. All students are divided in three groups: Physical, Biological and Humanities. We paid special attention to the examination of Portuguese language which is common for all and examinations for the particular area. We observed long ubiquitous power law tails in Physical and Biological sciences. This indicate the presence of strong positive feedback in sciences. We are able to explain completely these statistical distributions through Gradually Truncated Power law distributions which we developed recently to explain statistical behavior of financial market. The statistical distribution in case of Portuguese language and humanities is close to normal distribution. We discuss the possible reason for this peculiar behavior.

Adolescentes em conflito com a lei e sua noção de regras no jogo de futebol

Adolescents with a course of life based on the lack of ethical and moral values are more vulnerable to the practice of infractions, and in this case the statute of the child and adolescent assumes their insertion on socio educative measures. The objective of this research is to identify the moral development phase in adolescents who are in confl ict with the law. Thirty male adolescents between fi fteen and eighteen years old, who are inserted on the socio educative care Center, were studied. Data were collected through futsal game observation, without the presence of a referee and structured interview, according to the general lines of the Clinical Method of PIAGET (1994). The arrangement of the collected data confi rmed our hypothesis – these adolescents are still with the characteristics of a heteronomical moral, confi rmed by the differences between conscience and the practice of rules in a game situation. Although they know the rules, these are only respected in order to get some benefi ts, like not charging foul, deceive the opponent or simply win the match. It is presumed that the rules would only be respected in the presence of an authority (referee), because he would impose punishments and privations. However, it is believed that the results of this study may become a parameter to educators in order to create favorable situations which can be preventive and interventive to the socio moral development, minimizing suffering and seizing opportunities to the formation of citizens with higher ethical and moral standards, who are able to choose the way to the solidarity, cooperation and justice.