Massive Star Evolution: Nucleosynthesis and Nuclear Reaction Rate Uncertainties

We present a nucleosynthesis calculation of a 25 solar mass star of solar composition that includes all relevant isotopes up to polonium. In particular, all stable isotopes and necessary nuclear reaction rates are covered. We follow the stellar evolution from hydrogen burning till iron core collapse and simulate the explosion using a ``piston'' approach. We discuss the influence of two key nuclear reaction rates, C12(a,g) and Ne22(a,n), on stellar evolution and nucleosynthesis. The former significantly influences the resulting core sizes (iron, silicon, oxygen) and the overall presupernova structure of the star. It thus has significant consequences for the supernova explosion itself and the compact remnant formed. The later rate considerably affects the s-process in massive stars and we demonstrate the changes that different currently suggested values for this rate cause.Comment: 6 pages, including 4 PostScript figures, to appear in Proc. "Astronomy with Radioactivities III", New Astronomy Review

Meditation experts try Virtual Reality Mindfulness: a pilot study evaluation of the feasibility and acceptability of Virtual Reality to facilitate mindfulness practice in people attending a Mindfulness conference

Regular mindfulness practice benefits people both mentally and physically, but many populations who could benefit do not practice mindfulness. Virtual Reality (VR) is a new technology that helps capture participants’ attention and gives users the illusion of “being there” in the 3D computer generated environment, facilitating sense of presence. By limiting distractions from the real world, increasing sense of presence and giving people an interesting place to go to practice mindfulness, Virtual Reality may facilitate mindfulness practice. Traditional Dialectical Behavioral Therapy (DBT®) mindfulness skills training was specifically designed for clinical treatment of people who have trouble focusing attention, however severe patients often show difficulties or lack of motivation to practice mindfulness during the training. The present pilot study explored whether a sample of mindfulness experts would find useful and recommend a new VR Dialectical Behavioral Therapy (DBT®) mindfulness skills training technique and whether they would show any benefit. Forty four participants attending a mindfulness conference put on an Oculus Rift DK2 Virtual Reality helmet and floated down a calm 3D computer generated virtual river while listening to digitized DBT® mindfulness skills training instructions. On subjective questionnaires completed by the participants before and after the VR DBT® mindfulness skills training session, participants reported increases/improvements in state of mindfulness, and reductions in negative emotional states. After VR, participants reported significantly less sadness, anger, and anxiety, and reported being significantly more relaxed. Participants reported a moderate to strong illusion of going inside the 3D computer generated world (i.e., moderate to high “presence” in VR) and showed high acceptance of VR as a technique to practice mindfulness. These results show encouraging preliminary evidence of the feasibility and acceptability of using VR to practice mindfulness based on clinical expert feedback. VR is a technology with potential to increase computerized dissemination of DBT® skills training modules. Future research is warranted

Milagrito: a TeV air-shower array

Milagrito, a large, covered water-Cherenkov detector, was the world's first air-shower-particle detector sensitive to cosmic gamma rays below 1 TeV. It served as a prototype for the Milagro detector and operated from February 1997 to May 1998. This paper gives a description of Milagrito, a summary of the operating experience, and early results that demonstrate the capabilities of this technique.Comment: 38 pages including 24 figure

Kontsevich product and gauge invariance

We analyze the question of $U_{\star} (1)$ gauge invariance in a flat non-commutative space where the parameter of non-commutativity, $\theta^{\mu\nu} (x)$, is a local function satisfying Jacobi identity (and thereby leading to an associative Kontsevich product). We show that in this case, both gauge transformations as well as the definitions of covariant derivatives have to modify so as to have a gauge invariant action. We work out the gauge invariant actions for the matter fields in the fundamental and the adjoint representations up to order $\theta^{2}$ while we discuss the gauge invariant Maxwell theory up to order $\theta$. We show that despite the modifications in the gauge transformations, the covariant derivative and the field strength, Seiberg-Witten map continues to hold for this theory. In this theory, translations do not form a subgroup of the gauge transformations (unlike in the case when $\theta^{\mu\nu}$ is a constant) which is reflected in the stress tensor not being conserved.Comment: 7 page

Axion-like particles as ultra high energy cosmic rays?

If Ultra High Energy Cosmic Rays (UHECRs) with E>4 10^{19} eV originate from BL Lacertae at cosmological distances as suggested by recent studies, the absence of the GZK cutoff can not be reconciled with Standard-Model particle properties. Axions would escape the GZK cutoff, but even the coherent conversion and back-conversion between photons and axions in large-scale magnetic fields is not enough to produce the required flux. However, one may construct models of other novel (pseudo)scalar neutral particles with properties that would allow for sufficient rates of particle production in the source and shower production in the atmosphere to explain the observations. As an explicit example for such particles we consider SUSY models with light sgoldstinos.Comment: 5 pages, 2 postscript figures, ref. adde

"Dark energy" in the Local Void

The unexpected discovery of the accelerated cosmic expansion in 1998 has filled the Universe with the embarrassing presence of an unidentified "dark energy", or cosmological constant, devoid of any physical meaning. While this standard cosmology seems to work well at the global level, improved knowledge of the kinematics and other properties of our extragalactic neighborhood indicates the need for a better theory. We investigate whether the recently suggested repulsive-gravity scenario can account for some of the features that are unexplained by the standard model. Through simple dynamical considerations, we find that the Local Void could host an amount of antimatter ($\sim5\times10^{15}\,M_\odot$) roughly equivalent to the mass of a typical supercluster, thus restoring the matter-antimatter symmetry. The antigravity field produced by this "dark repulsor" can explain the anomalous motion of the Local Sheet away from the Local Void, as well as several other properties of nearby galaxies that seem to require void evacuation and structure formation much faster than expected from the standard model. At the global cosmological level, gravitational repulsion from antimatter hidden in voids can provide more than enough potential energy to drive both the cosmic expansion and its acceleration, with no need for an initial "explosion" and dark energy. Moreover, the discrete distribution of these dark repulsors, in contrast to the uniformly permeating dark energy, can also explain dark flows and other recently observed excessive inhomogeneities and anisotropies of the Universe.Comment: 6 pages, accepted as a Letter to the Editor by Astrophysics and Space Scienc

Upper critical field for underdoped high-T_c superconductors. Pseudogap and stripe--phase

We investigate the upper critical field in a stripe--phase and in the presence of a phenomenological pseudogap. Our results indicate that the formation of stripes affects the Landau orbits and results in an enhancement of $H_{c2}$. On the other hand, phenomenologically introduced pseudogap leads to a reduction of the upper critical field. This effect is of particular importance when the magnitude of the gap is of the order of the superconducting transition temperature. We have found that a suppression of the upper critical field takes place also for the gap that originates from the charge--density waves.Comment: 7 pages, 5 figure

Observation of the Ankle and Evidence for a High-Energy Break in the Cosmic Ray Spectrum

We have measured the cosmic ray spectrum at energies above $10^{17}$ eV using the two air fluorescence detectors of the High Resolution Fly's Eye experiment operating in monocular mode. We describe the detector, PMT and atmospheric calibrations, and the analysis techniques for the two detectors. We fit the spectrum to models describing galactic and extragalactic sources. Our measured spectrum gives an observation of a feature known as the ``ankle'' near $3\times 10^{18}$ eV, and strong evidence for a suppression near $6\times 10^{19}$ eV.Comment: 14 pages, 9 figures. To appear in Physics Letters B. Accepted versio

A New Framework for Music Education Knowledge and Skill

This study investigates perceptions of secondary school band and orchestra teachers regarding the relative importance of knowledge and skill categories to professional success, using a framework modeled after Schulman (1986, 1987). Band and orchestra teachers in secondary schools (N = 214) complete an anonymous, online survey ranking the relative importance of various knowledge and skill categories. Participants rank pedagogical content knowledge, content knowledge, and general pedagogical knowledge highest. There are no significant differences in the rankings of the categories among various subgroups at the p < .05 level. Results confirm the applicability of Schulman's model to music education. This framework has implications for undergraduate, graduate, and continuing professional education. Analysis of categories' interaction provides insight into effective classroom instruction.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline

Longitudinal double-spin asymmetry and cross section for inclusive neutral pion production at midrapidity in polarized proton collisions at sqrt(s) = 200 GeV

We report a measurement of the longitudinal double-spin asymmetry A_LL and the differential cross section for inclusive Pi0 production at midrapidity in polarized proton collisions at sqrt(s) = 200 GeV. The cross section was measured over a transverse momentum range of 1 < p_T < 17 GeV/c and found to be in good agreement with a next-to-leading order perturbative QCD calculation. The longitudinal double-spin asymmetry was measured in the range of 3.7 < p_T < 11 GeV/c and excludes a maximal positive gluon polarization in the proton. The mean transverse momentum fraction of Pi0's in their parent jets was found to be around 0.7 for electromagnetically triggered events.Comment: 6 pages, 3 figures, submitted to Phys. Rev. D (RC