Antimatter production in supernova remnants

We calculate the energy spectra of cosmic rays (CR) and their secondaries produced in a supernova remnant (SNR), taking into account the time-dependence of the SNR shock. We model the trajectories of charged particles as a random walk with a prescribed diffusion coefficient, accelerating the particles at each shock crossing. Secondary production by CRs colliding with gas is included as a Monte Carlo process. We find that SNRs produce less antimatter than suggested previously: The positron/electron ratio and the antiproton/proton ratio are a few percent and few $\times 10^{-5}$, respectively. Moreover, the obtained positron/electron ratio decreases with energy, while the antiproton/proton ratio rises at most by a factor of two above 10 GeV.Comment: 8 pages, 8 eps figures; extended version of arXiv:1004.1118; v2: minor corrections, matches published versio

Gravitational Collapse and Fragmentation in Molecular Clouds with Adaptive Mesh Refinement

We describe a powerful methodology for numerical solution of 3-D self-gravitational hydrodynamics problems with extremely high resolution. Our method utilizes the technique of local adaptive mesh refinement (AMR), employing multiple grids at multiple levels of resolution. These grids are automatically and dynamically added and removed as necessary to maintain adequate resolution. This technology allows for the solution of problems in a manner that is both more efficient and more versatile than other fixed and variable resolution methods. The application of AMR to simulate the collapse and fragmentation of a molecular cloud, a key step in star formation, is discussed. Such simulations involve many orders of magnitude of variation in length scale as fragments form. In this paper we briefly describe the methodology and present an illustrative application for nonisothermal cloud collapse. We describe the numerical Jeans condition, a criterion for stability of self-gravitational hydrodynamics problems. We show the first well-resolved nonisothermal evolutionary sequence beginning with a perturbed dense molecular cloud core that leads to the formation of a binary system consisting of protostellar cores surrounded by distinct protostellar disks. The scale of the disks, of order 100 AU, is consistent with observations of gaseous disks surrounding single T-Tauri stars and debris disks surrounding systems such as $\beta$ Pictoris.Comment: 10 pages, 6 figures (color postscript). To appear in the proceedings of Numerical Astrophysics 1998, Tokyo, March 10-13, 199

A Multi-dimensional Code for Isothermal Magnetohydrodynamic Flows in Astrophysics

We present a multi-dimensional numerical code to solve isothermal magnetohydrodynamic (IMHD) equations for use in modeling astrophysical flows. First, we have built a one-dimensional code which is based on an explicit finite-difference method on an Eulerian grid, called the total variation diminishing (TVD) scheme. Recipes for building the one-dimensional IMHD code, including the normalized right and left eigenvectors of the IMHD Jacobian matrix, are presented. Then, we have extended the one-dimensional code to a multi-dimensional IMHD code through a Strang-type dimensional splitting. In the multi-dimensional code, an explicit cleaning step has been included to eliminate non-zero $\nabla\cdot B$ at every time step. To estimate the proformance of the code, one- and two-dimensional IMHD shock tube tests, and the decay test of a two-dimensional Alfv\'{e}n wave have been done. As an example of astrophysical applications, we have simulated the nonlinear evolution of the two-dimensional Parker instability under a uniform gravity.Comment: Accepted for publication in ApJ, using aaspp4.sty, 22 text pages with 10 figure

Antimatter spectra from a time-dependent modeling of supernova remnants

We calculate the energy spectra of cosmic rays (CR) and their secondaries produced in a supernova remnant (SNR), taking into account the time-dependence of the SNR shock. We model the trajectories of charged particles as a random walk with a prescribed diffusioncoefficient, accelerating the particles at each shock crossing. Secondary production by CRs colliding with gas is included as a Monte Carlo process. We find that SNRs produce less antimatter than suggested previously: The positron/electron ratio and the antiproton/proton ratio are a few percent and few $\times 10^{-5}$, respectively. Both ratios do not rise with energy.Comment: 4 pages, 4 eps figures; v2: results for time-dependent magnetic field adde

Developing trauma-informed teacher education in England

Trauma-informed practice in education is an area of growing interest in England and internationally. Embracing trauma-informed practice in schools requires trauma and related content to be included in teacher education. Over a period of eight years, a short course was developed and incorporated into the teacher preparation programmes at a large university in England. Through methods of teacher educator self-study and autoethnography, we examine the process of the course’s development and identify mechanisms, enablers and barriers to change in the current policy context of teacher education in England. Important factors that supported change were the gradual development, external collaboration, positive outcomes as a warrant and source of motivation, the development of champions and enthusiasts for trauma-informed practice, and departmental leadership support. Barriers to the development were the constraints of prescribed content on initial teacher education courses, prevailing practices in some schools and settings, challenges in adapting material suitably for all education phases, and some beginning teachers’ responses to personally relevant course content. The successful introduction of the short course demonstrates that inclusion of trauma-informed content in initial teacher education is possible even in an unfavourable policy environment

Analysis of Vaccine Effectiveness against COVID-19 and the Emergence of Delta and Other Variants of Concern in Utah

Since the emergence of SARS-CoV-2, vaccines have been heralded as the best way to curtail the COVID-19 pandemic. Clinical trials have shown SARS-CoV-2 vaccines to be highly efficacious against both disease and infection. However, those vaccines currently in use were primarily tested against early lineages. Data on vaccine effectiveness against variants of concern (VOCs) remains limited, including the Delta variant (B.1.617.2)

Co-Occurrence Patterns of Common and Rare Leaf-Litter Frogs, Epiphytic Ferns and Dung Beetles across a Gradient of Human Disturbance

Indicator taxa are commonly used to identify priority areas for conservation or to measure biological responses to environmental change. Despite their widespread use, there is no general consensus about the ability of indicator taxa to predict wider trends in biodiversity. Many studies have focused on large-scale patterns of species co-occurrence to identify areas of high biodiversity, threat or endemism, but there is much less information about patterns of species co-occurrence at local scales. In this study, we assess fine-scale co-occurrence patterns of three indicator taxa (epiphytic ferns, leaf litter frogs and dung beetles) across a remotely sensed gradient of human disturbance in the Ecuadorian Amazon. We measure the relative contribution of rare and common species to patterns of total richness in each taxon and determine the ability of common and rare species to act as surrogate measures of human disturbance and each other. We find that the species richness of indicator taxa changed across the human disturbance gradient but that the response differed among taxa, and between rare and common species. Although we find several patterns of co-occurrence, these patterns differed between common and rare species. Despite showing complex patterns of species co-occurrence, our results suggest that species or taxa can act as reliable indicators of each other but that this relationship must be established and not assumed

The mass and energy budget of Cassiopeia A

Further analysis of X-ray spectroscopy results recently obtained from the MOS CCD cameras on-board XMM-Newton provides a detailed description of the hot and cool X-ray emitting plasma in Cas A. Measurement of the Doppler broadening of the X-ray lines is consistent with the expected ion velocities, ~1500 km/s along the line of sight, in the post shock plasma. Assuming a constant total pressure throughout the remnant we estimate the total remnant mass as 10 Msun and the total thermal energy as 7E43 J. We derive the differential mass distribution as a function of ionisation age for both X-ray emitting components. This distribution is consistent with a hot component dominated by swept up mass heated by the primary shock and a cool component which are ablated clumpy ejecta material which were and are still being heated by interaction with the preheated swept up material. We calculate a balanced mass and energy budget for the supernova explosion giving 1E44 J in ejected mass; approximately 0.4 Msun of the ejecta were diffuse with an initial rms velocity of 15000 km/s while the remaining ~1.8 Msun were clumpy with an initial rms velocity of ~2400 km/s. Using the Doppler velocity measurements of the X-ray spectral lines we can project the mass into spherical coordinates about the remnant. This provides quantitative evidence for mass and energy beaming in the supernova explosion. The mass and energy occupy less than 4.5 sr (<40 % of the available solid angle) around the remnant and 64 % of the mass occurs in two jets within 45 degrees of a jet axis. We calculate a swept up mass of 7.9 Msun in the emitting plasma and estimate that the total mass lost from the progenitor prior to the explosion could be as high as ~20 Msun.Comment: 8 pages, 7 figures, submitted to Astronomy & Astrophysic