The stopping of swift protons in matter and its implication for astrophysical fusion reactions

The velocity dependence of the stopping power of swift protons and deuterons in low energy collisions is investigated. At low projectile energies the stopping is mainly due to nuclear stopping and charge exchange of the electron. The second mechanism dominates after Ep >=200 eV. A dynamical treatment of the charge exchange mechanism based on two-center electronic wavefunctions yields very transparent results for the exchange probability. We predict that the stopping cross sections vary approximately as v to the 1.35 power for projectile protons on hydrogen targets in the 1 keV energy region.Comment: 4 figure

The Role of Functional, Social, and Mobility Dynamics in Facilitating Older African Americans Participation in Clinical Research

Purpose: Older African Americans experience disproportionately higher incidence of morbidity and mortality related to chronic and infectious diseases, yet are significantly underrepresented in clinical research compared to other racial and ethnic groups. This study aimed to understand the extent to which social support, transportation access, and physical impediments function as barriers or facilitators to clinical trial recruitment of older African Americans. Methods: Participants (N=221) were recruited from six African American churches in Atlanta and surveyed on various influences on clinical trial participation

Depression-Related Differences in Learning and Forgetting Responses to Unrelated Cues

Using the think/no-think paradigm, we examined the effect of a meaningful connection between emotionally neutral cues and targets on initial learning and later recall by students in dysphoric or nondysphoric mood states. Compared to meaningfully connected cue-target pairs, unrelated pairs were less easily learned and more easily forgotten, even when initial learning was controlled. Depressive deficits were obtained in initial learning (only marginally) and final recall. When examined separately within each cuing condition, the recall deficit associated with depressed mood was restricted to the unrelated condition, but when initial learning differences were controlled this deficit was only marginally significant. Results are discussed in relation to other recent findings concerning depression-related performance in this paradigm and to findings of depression and memory more generally

Cognitive Bias Modification: Past Perspectives, Current Findings, and Future Applications

Research conducted within the general paradigm of Cognitive Bias Modification (CBM) reveals that emotional biases in attention, interpretation, and memory are not merely associated with emotional disorders but contribute to them. After briefly describing research on both emotional biases and their modification, we examine similarities between CBM paradigms and older experimental paradigms used in research on learning and memory. We also compare the techniques and goals of CBM research to other approaches to understanding cognition/emotion interactions. From a functional perspective, the CBM tradition reminds us to use experimental tools to evaluate assumptions about clinical phenomena and more generally, about causal relationships between cognitive processing and emotion

Dark/Visible Parallel Universes and Big Bang Nucleosynthesis

We develop a model for visible matter-dark matter interaction based on the exchange of a massive gray boson called herein the Mulato. Our model hinges on the assumption that all known particles in the visible matter have their counterparts in the dark matter. We postulate six families of particles five of which are dark. This leads to the unavoidable postulation of six parallel worlds, the visible one and five invisible worlds. A close study of big bang nucleosynthesis (BBN), baryon asymmetries, cosmic microwave background (CMB) bounds, galaxy dynamics, together with the Standard Model assumptions, help us to set a limit on the mass and width of the new gauge boson. Modification of the statistics underlying the kinetic energy distribution of particles during the BBN is also discussed. The changes in reaction rates during the BBN due to a departure from the Debye-Hueckel electron screening model is also investigated.Comment: Invited talk at the Workshops "CompStar: the physics and astrophysics of compact stars", Tahiti, June 4-8, 2012, "New Directions in Nuclear Astrophysics", Castiglion Fiorentino, Italy, June 18-22, 2012, and "Carpathian Summer School of Physics", Sinaia, Romania, June 24 - July 7, 2012. To be published in AIP Proceeding