A Self-Consistent Model for Positronium Formation from Helium Atoms

The differential and total cross sections for electron capture by positrons from helium atoms are calculated using a first-order distorted wave theory satisfying the Coulomb boundary conditions. In this formalism a parametric potential is used to describe the electron screening in a consistent and realistic manner. The present procedure is self consistent because (i) it satisfies the correct boundary conditions and post-prior symmetry, and (ii) the potential and the electron binding energies appearing in the transition amplitude are consistent with the wave functions describing the collision system. The results are compared with the other theories and with the available experimental measurements. At the considered range of collision energies, the results agree reasonably well with recent experiments and theories. [Note: This paper will be published on volume 42 of the Brazilian Journal of Physics

The Great American Biotic Interchange: Dispersals, Tectonics, Climate, Sea Level and Holding Pens

The biotic and geologic dynamics of the Great American Biotic Interchange are reviewed and revised. Information on the Marine Isotope Stage chronology, sea level changes as well as Pliocene and Pleistocene vegetation changes in Central and northern South America add to a discussion of the role of climate in facilitating trans-isthmian exchanges. Trans-isthmian land mammal exchanges during the Pleistocene glacial intervals appear to have been promoted by the development of diverse non-tropical ecologies

Activity pacing: moving beyond taking breaks and slowing down

This brief communication responds to the paper by Jeong and Cho (Qual Life Res 26(4):903–911, 2017) that has described activity pacing in limited terms of adjusting activities through going at a slower rate and taking breaks. Activity pacing was reported as not involving goal setting, in comparison to other strategies for long-term conditions such as Acceptance and Commitment Therapy. This brief communication aims to challenge this limited perception of activity pacing in light of numerous studies that recognise pacing to be a more complex strategy. Pacing is considered to be a multifaceted coping strategy, including broad themes of not only adjusting activities, but also planning activities, having consistent activity levels, acceptance of current abilities and gradually increasing activities, and one that includes goal setting as a key facet. It is essential that pacing is both defined and measured as a multifaceted strategy in order to assess the outcomes of pacing, and for meaningful comparisons with other strategies regarding efficacy for the management of long-term conditions

Patient characteristics associated with differences in patients' evaluation of their general practitioner

<p>Abstract</p> <p>Background</p> <p>Knowledge of the extent to which patient characteristics are systematically associated with variation in patient evaluations will enable us to adjust for differences between practice populations and thereby compare GPs. Whether this is appropriate depends on the purpose for which the patient evaluation was conducted. Associations between evaluations and patient characteristics may reflect gaps in the quality of care or may be due to inherent characteristics of the patients. This study aimed to determine such associations in a setting with a comprehensive list system and gate-keeping.</p> <p>Methods</p> <p>A nationwide Danish patient evaluation survey among voluntarily participating GPs using the EUROPEP questionnaire, which produced 28,260 patient evaluations (response rate 77.3%) of 365 GPs. In our analyses we compared the prevalence of positive evaluations in groups of patients.</p> <p>Results</p> <p>We found a positive GP assessment to be strongly associated with increasing patient age and increasing frequency of attendance. Patients reporting a chronic condition were more positive, whereas a low self-rated health was strongly associated with less positive scores also after adjustment. The association between patient gender and assessment was weak and inconsistent and depended on the focus. We found no association either with the patients' educational level or with the duration of listing with the GP even after adjusting for patient characteristics.</p> <p>Conclusion</p> <p>Adjustment for patient differences may produce a more fair comparison between GPs, but may also blur the assessment of GPs' ability to meet the needs of the populations actually served. On the other hand, adjusted results will enable us to describe the significance of specific patient characteristics to patients' experience of care.</p

Allometry of the Duration of Flight Feather Molt in Birds

Replacement of flight feathers takes disproportionately more time for large birds than it does for small birds, because feather length increases with body size almost twice as fast as feather growth rate increases

Pain coping skills training for African Americans with osteoarthritis (STAART): study protocol of a randomized controlled trial

Background: African Americans bear a disproportionate burden of osteoarthritis (OA), with higher prevalence rates, more severe pain, and more functional limitations. One key barrier to addressing these disparities has been limited engagement of African Americans in the development and evaluation of behavioral interventions for management of OA. Pain Coping Skills Training (CST) is a cognitive-behavioral intervention with shown efficacy to improve OA-related pain and other outcomes. Emerging data indicate pain CST may be a promising intervention for reducing racial disparities in OA symptom severity. However, there are important gaps in this research, including incorporation of stakeholder perspectives (e.g. cultural appropriateness, strategies for implementation into clinical practice) and testing pain CST specifically among African Americans with OA. This study will evaluate the effectiveness of a culturally enhanced pain CST program among African Americans with OA. Methods/Design: This is a randomized controlled trial among 248 participants with symptomatic hip or knee OA, with equal allocation to a pain CST group and a wait list (WL) control group. The pain CST program incorporated feedback from patients and other stakeholders and involves 11 weekly telephone-based sessions. Outcomes are assessed at baseline, 12 weeks (primary time point), and 36 weeks (to assess maintenance of treatment effects). The primary outcome is the Western Ontario and McMaster Universities Osteoarthritis Index, and secondary outcomes include self-efficacy, pain coping, pain interference, quality of life, depressive symptoms, and global assessment of change. Linear mixed models will be used to compare the pain CST group to the WL control group and explore whether participant characteristics are associated with differential improvement in the pain CST program. This research is in compliance with the Helsinki Declaration and was approved by the Institutional Review Boards of the University of North Carolina at Chapel Hill, Durham Veterans Affairs Medical Center, East Carolina University, and Duke University Health System. Discussion: This culturally enhanced pain CST program could have a substantial impact on outcomes for African Americans with OA and may be a key strategy in the reduction of racial health disparities.Funded by Patient-Centered Outcomes Research Institute (PCORI) Award (AD-1408-19519)

A Surprising Prevention Success: Why Did the HIV Epidemic Decline in Zimbabwe?

Daniel Halperin and colleagues examine reasons for the remarkable decline in HIV in Zimbabwe, in the context of severe social, political, and economic disruption

Severe traumatic injury during long duration spaceflight: Light years beyond ATLS

Traumatic injury strikes unexpectedly among the healthiest members of the human population, and has been an inevitable companion of exploration throughout history. In space flight beyond the Earth's orbit, NASA considers trauma to be the highest level of concern regarding the probable incidence versus impact on mission and health. Because of limited resources, medical care will have to focus on the conditions most likely to occur, as well as those with the most significant impact on the crew and mission. Although the relative risk of disabling injuries is significantly higher than traumatic deaths on earth, either issue would have catastrophic implications during space flight. As a result this review focuses on serious life-threatening injuries during space flight as determined by a NASA consensus conference attended by experts in all aspects of injury and space flight

Culture dependent and independent analyses of 16S rRNA and ATP citrate lyase genes : a comparison of microbial communities from different black smoker chimneys on the Mid-Atlantic Ridge

Author Posting. © Springer, 2008. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Extremophiles 12 (2008): 627-640, doi:10.1007/s00792-008-0167-5.The bacterial and archaeal communities of three deep-sea hydrothermal vent systems located on the Mid-Atlantic Ridge (MAR; Rainbow, Logatchev and Broken Spur) were investigated using an integrated culture-dependent and independent approach. Comparative molecular phylogenetic analyses, using the 16S rRNA gene and the deduced amino acid sequences of the alpha and beta subunits of the ATP citrate lyase encoding genes were carried out on natural microbial communities, on an enrichment culture obtained from the Broken Spur chimney, and on novel chemolithoautotrophic bacteria and reference strains originally isolated from several different deep-sea vents. Our data showed that the three MAR hydrothermal vent chimneys investigated in this study host very different microbial assemblages. The microbial community of the Rainbow chimney was dominated by thermophilic, autotrophic, hydrogen-oxidizing, sulfur- and nitrate reducing Epsilonproteobacteria related to the genus Caminibacter. The detection of sequences related to sulfur-reducing bacteria and archaea (Archaeoglobus) indicated that thermophilic sulfate reduction might also be occurring at this site. The Logatchev bacterial community included several sequences related to mesophilic sulfur-oxidizing bacteria, while the archaeal component of this chimney was dominated by sequences related to the ANME-2 lineage, suggesting that anaerobic oxidation of methane may be occurring at this site. Comparative analyses of the ATP citrate lyase encoding genes from natural microbial communities suggested that Epsilonproteobacteria were the dominant primary producers using the reverse TCA cycle (rTCA) at Rainbow, while Aquificales of the genera Desulfurobacterium and Persephonella were prevalent in the Broken Spur chimney.This research was supported by NSF grants MCB 04-56676 (C.V.), OCE 03-27353 (C.V.), MCB 04-56689 (S.M.S.), a grant from the New Jersey Agricultural Experiment Station to C.V., and a NIH Ph.D. Training Program in Biotechnology Fellowship (NIH NIGMS 5 T32 GM08339) to J.V. M.H. was supported through a postdoctoral scholarship from the Woods Hole Oceanographic Institution