Helium burning and neutron sources in the stars

Helium burning represents an important stage of stellar evolution as it contributes to the synthesis of key elements such as carbon, through the triple-alfa process, and oxygen, through the 12C(alfa, gamma)16O reaction. It is the ratio of carbon to oxygen at the end of the helium burning stage that governs the following phases of stellar evolution leading to different scenarios depending on the initial stellar mass. In addition, helium burning in Asymptotic Giant Branch stars, provides the two main sources of neutrons, namely the 13C(alfa, n)16O and the 22Ne(alfa, n)25Mg, for the synthesis of about half of all elements heavier than iron through the s-process. Given the importance of these reactions, much experimental work has been devoted to the study of their reaction rates over the last few decades. However, large uncertainties still remain at the energies of astrophysical interest which greatly limit the accuracy of stellar models predictions. Here, we review the current status on the latest experimental efforts and show how measurements of these important reaction cross sections can be significantly improved at next-generation deep underground laboratories

Electron screening in 7Li(p,α)α and 6Li(p,α)3He for different environments

The electronscreening in the 7Li(p,α)α reaction has been studied at Ep=30 to 100 keV for differentenvironments: Li2WO4 insulator, Li metal, and PdLi alloys. For the insulator a screening potential energy of Ue=185±150 eV was observed, consistent with previous work and the atomic adiabatic limit. However, for the Li metal and the PdLi alloys we find large values of Ue=1280±60 and 3790±330 eV, respectively: the values can be explained by the plasma model of Debye applied to the quasi-free metallic electrons in these samples. Similar results have been found for the 6Li3(p,α)He reaction supporting the hypothesis of the isotopic independence of the electronscreening effect. The data together with previous studies of d(d,p)t and 9Be6(p,α)Li in metals verify the Debye model scaling Ue∝Zt (charge number of target)

Caminhos do cuidado: itinerários de pessoas que convivem com HIV Routes to care: the itineraries of people living with HIV

O adoecimento pelo HIV na atualidade apresenta-se como crônico e controlável. Assim, torna-se pertinente considerar as implicações das trajetórias individuais da busca de cuidado na vida cotidiana de seus portadores. Essas trajetórias são configuradas pelos caminhos que os usuários fazem em busca de respostas a seu adoecimento. Este estudo, de caráter qualitativo, objetivou analisar o itinerário terapêutico das pessoas convivendo com HIV/Aids. Os sujeitos da pesquisa foram homens e mulheres com o vírus HIV, assistidos em um Serviço de Assistência Especializada e no Hospital Universitário, ambos públicos localizados em um município de Minas Gerais. A abordagem dos participantes deu-se por meio de entrevista e para análise dos dados elegeu-se a técnica de análise temática. Dos caminhos singulares que desenharam essas narrativas, emergiram os itinerários dessas pessoas que convivem com o HIV. Estes abrangeram temas como as peregrinações e a forma de entrada no sistema de atendimento, as implicações do custo e acesso, a gestão do tratamento e a importância das relações de vínculo. Essas questões que nortearam a organização do trabalho permitiram inferir sobre as fragilidades e as fortalezas presentes no sistema de atendimento ao portador do HIV, ao ser considerada a vivência pessoal desses indivíduos em primeiro plano.<br>Living with HIV infection is currently chronic but manageable. Therefore, it is important to consider the implications of individual trajectories of seeking care for the disease in the daily life of its carriers. These trajectories are in the routes followed by users seeking answers to their illness. This qualitative study sought to analyze the therapeutic itinerary of people living with HIV/AIDS. The subjects studied were men and women with HIV attended in a Specialized Healthcare unit and the University Hospital, both public services located in a municipality of Minas Gerais state, Brazil. The participants were approached through interviews and data were analyzed using the thematic analysis technique. From the individual routes that permeated these narratives, the itineraries of individuals living with HIV emerged. These covered topics such as being sent from place to place and finally discovering how to enter the care system, the implications of cost and access, management of treatment and the importance of affiliation bonds. These questions that oriented the work made it possible to infer the strengths and weaknesses in the healthcare service to the HIV carrier, by considering the personal experience of these individuals