Spin effects in ppˉp\bar p interaction and their possible use to polarize antiproton beams

Low energy $p\bar p$ interaction is considered taking into account the polarization of both particles. The corresponding cross sections are calculated using the Paris nucleon-antinucleon optical potential. Then they are applied to the analysis of the polarization buildup which is due to the interaction of stored antiprotons with polarized protons of a hydrogen target. It is shown that, at realistic parameters of a storage ring and a target, the filtering mechanism provides a noticeable polarization in a time comparable with the beam lifetime.Comment: 10 pages, 4 figure

'A boy would be friends with boys... and a girl... with girls' : gender norms in early adolescent friendships in Egypt and Belgium

Purpose: A gender analysis was conducted to illuminate the key elements of friendships highlighted by early adolescent girls and boys in two sites for the purpose of better understanding the impact of gender norms on adolescent friendships in different contexts. Methods: Narrative interviews with early adolescents were conducted in two sites: Assiut, Egypt (n = 37) and Ghent, Belgium (n = 30). The interviews were recorded, transcribed, translated into English, and coded using Atlas.ti for analysis. Results: In both Assiut and Ghent, early adolescents reported some similarities in defining key characteristics of their same-sex friends as well as in the activities they share. However, differences were noticed among boys and girls within each site. In addition, the scope of shared activity was broader in Ghent than in Assiut. In both sites, few opposite-sex friendships were reported. Gender norms influenced choice of friends as well as the type and place of shared activities. Conclusions: Building on knowledge that adolescent friendships guide and reinforce attitudes, beliefs, and behaviors that impact immediate and long-term health, our findings indicate that gender norms inform early adolescent friendships, which may impact healthy development

Carbon dioxide emissions from diesel and compressed natural gas buses during acceleration

Motor vehicle emission factors are generally derived from driving tests mimicking steady state conditions or transient drive cycles. However, neither of these test conditions completely represents real world driving conditions. In particular, they fail to determine emissions generated during the accelerating phase – a condition in which urban buses spend much of their time. In this study we analyse and compare the results of time-dependant emission measurements conducted on diesel and compressed natural gas (CNG) buses during an urban driving cycle on a chassis dynamometer and we derive power-law expressions relating carbon dioxide (CO2) emission factors to the instantaneous speed while accelerating from rest. Emissions during acceleration are compared with that during steady speed operation. These results have important implications for emission modelling particularly under congested traffic conditions

Applicability of viscous hydrodynamics at RHIC

In an earlier work (arXiv:0808.0953) we established that causal Israel-Stewart viscous hydrodynamics is only accurate in RHIC applications at very low shear viscosities 4 pi eta_s / s < ~ 1.5-2. We show here that the region of applicability is significantly reduced if bulk viscosity plays a role in the dynamics.Comment: Presentation at Quark Matter 2009 - contribution to the proceedings. v2: very minor changes in text and labels in Fig.

Desenvolvimento de novo ligante e complexo binuclear de cobre (ii) de relevância bioinorgânica: modelo para catecol oxidase

TCC (graduação) - Universidade Federal de Santa Catarina. Centro de Ciências Físicas e Matemáticas. Curso de Química.A catecol oxidase é uma metaloenzima de cobre do tipo III, que catalisa a oxidação de o-catecóis às correspondentes o-quinonas. Recentemente, sua estrutura cristalina foi determinada por cristalografia de raios X, a partir da batata doce, a qual consiste de dois centros de Cu(II) com geometria pirâmide trigonal, estando cada cobre coordenado por três átomos de nitrogênio de resíduos de histidinas e um grupo hidróxido fazendo ponte entre os dois centros metálicos. A distância Cu...Cu foi determinada como sendo 2,9 A. O espectro eletrônico da catecol oxidase apresenta máximos na faixa de 700-800 nm atribuídos a transições d-d e uma transição na faixa de 310 e 330 nm atribuída a uma banda de transferência de carga do tipo ligante metal. Neste trabalho, apresentamos a síntese e caracterização de um novo complexo binuclear de CuII com o novo ligante N,N’,N’- [tris-(2-piridilmetil)]- N- (2-hidroxi-3,5-diterc- butilbenzil)- 1,3- diaminopropano-2-ol = H2L, com o objetivo de se correlacionar com o sítio ativo da catecol oxidase. Tanto o ligante quanto os precursores foram convenientemente caracterizados por espectroscopia no infravermelho e RMN 1H apresentando bons resultados. Do complexo sintetizado resultaram monocristais adequados á resolução da estrutura cristalina por difração de raios X. O grupo espacial do mesmo é P-1 (triclínico), sendo que a estrutura revela que os átomos de cobre estão ligados por um derivado do ligante alcóxido e um íon acetato exógeno. Ambos estão pentacoordenados, sendo a geometria do Cu1 pirâmide de base quadrada e do Cu2 bipirâmide trigonal. A distância Cu1-Cu2 é de 3.3975 Å. Os espectros eletrônicos do complexo 1, em estado sólido apresenta duas bandas d-d, e em solução apresenta além das bandas d-d, uma banda de TCLM, que pode ser relacionada a um processo do tipo Ofenolato ® Cu(II). O complexo simula a distância metal-metal de aproximadamente 3,0 A para a metaloenzima de cobre do tipo III, servindo assim como modelo estrutural para a mesma. Além disso, foi eficiente na oxidação do 3,5-di-tercbutilcatecol a correspondente o-quinona, podendo então ser considerado como modelo funcional para catecol oxidase

O que está em jogo no confronto entre criacionismo e evolução

Lidar com o embate entre perspectivas criacionistas e evolucionis-tas é parte da realidade de muitos professores de biologia. Neste ensaio buscamos caracterizar esse confronto, sugerindo que ele não pode ser carac-terizado como um “debate”. A seguir argumentamos que a perspectiva cria-cionista, quando apresentada como alternativa excludente à evolução, acaba por trazer prejuízos para o ensino de ciências que vão muito além do ensino da biologia. No final oferecemos algumas sugestões para ajudar professores a se posicionarem diante de perspectivas criacionistas

s-Process Nucleosynthesis in Advanced Burning Phases of Massive Stars

We present a detailed study of s-process nucleosynthesis in massive stars of solar-like initial composition and masses 15, 20,25, and 30 Msun. We update our previous results of s-process nucleosynthesis during the core He-burning of these stars and then focus on an analysis of the s-process under the physical conditions encountered during the shell-carbon burning. We show that the recent compilation of the Ne22(alpha,n)Mg25 rate leads to a remarkable reduction of the efficiency of the s-process during core He-burning. In particular, this rate leads to the lowest overproduction factor of Kr80 found to date during core He-burning in massive stars. The s-process yields resulting from shell carbon burning turn out to be very sensitive to the structural evolution of the carbon shell. This structure is influenced by the mass fraction of C12 attained at the end of core helium burning, which in turn is mainly determined by the C12(alpha,gamma)O16 reaction. The still present uncertainty in the rate for this reaction implies that the s-process in massive stars is also subject to this uncertainty. We identify some isotopes like Zn70 and Rb87 as the signatures of the s-process during shell carbon burning in massive stars. In determining the relative contribution of our s-only stellar yields to the solar abundances, we find it is important to take into account the neutron exposure of shell carbon burning. When we analyze our yields with a Salpeter Initial Mass Function, we find that massive stars contribute at least 40% to s-only nuclei with mass A 90, massive stars contribute on average ~7%, except for Gd152, Os187, and Hg198 which are ~14%, \~13%, and ~11%, respectively.Comment: 52 pages, 16 figures, accepted for publication in Ap

Hydrogen-Poor Disks in Compact X-Ray Binaries

We show that accretion disks in several compact X-ray binaries with hydrogen-depleted donors are likely subject to a thermal ionization instability, unless they are strongly irradiated. These disks are particularly interesting in that their MHD-turbulent properties in the neutral phase may be quite different from those of standard, hydrogen-rich disks.Comment: 10 pages, accepted for publication in ApJ

Exploration of gender norms and socialization among early adolescents : the use of qualitative methods for the global early adolescent study

Purpose: The Global Early Adolescent Study (GEAS) was launched in 2014 with the primary goal of understanding the factors in early adolescence that predispose young people to subsequent sexual risks, and conversely, those that promote healthy sexuality across different cultural contexts. The present article describes the methodology that was used for the first phase of GEAS, which consisted of conducting qualitative research to understand the gendered transitions into adolescence and the role that gender norms play within the key relationships of adolescents. Researchers from each of the sites that had completed data collection were also elicited for their feedback on the key strengths, challenges, and lessons learned from conducting research among 11- to 14-year-old adolescents. The purpose of this article is to present the description of each of the methods that were used in GEAS, as well as the researchers' perspectives of using the methods among early adolescents in their sites. Methods: The GEAS is being implemented through a collaboration of university and nongovernmental institutions from 15 cities: Assiut (Egypt) Baltimore (U.S.), Blantyre (Malawi), Cape Town (South Africa), Cochabomba (Bolivia), Cuenca (Ecuador), Edinburgh (Scotland), Ghent (Belgium), Hanoi (Vietnam), Ile-Ife (Nigeria), Kinshasa (DRC), Nairobi (Kenya), New Delhi (India), Ouaga-dougou (Burkina Faso), and Shanghai (China). Approximately 30 in-depth interviews among adolescents and 30 in-depth interviews with their parent/guardian were conducted at each site, with adults and adolescents interviewed separately. To build trust and increase engagement among the adolescent participants, we used two different visual research methods: (1) timeline exercise which was small group based and (2) the Venn diagram exercise which was conducted individually and used at the start of the in-depth interview. Results: The visual aspects of both the timeline and the Venn diagrams not only helped to produce data for the purposes of the study, but also were a successful way of engaging the adolescent participants across sites. While the narrative interviews produced extremely rich data, researchers did notice that there were a few challenges among the younger adolescents. Challenges were related to the length of the interview, comprehension of questions, as some of the questions were either too abstract or asked adolescents about an experience they had not yet had and therefore could not address or articulate. Conclusions: Conducting the first phase of GEAS revealed important insights for research with participants who are in this developmental phase of early adolescence. Methods that involve greater engagement and those that are visual were shown to work well irrespective of the cultural setting