Near-Earth Supernova Explosions: Evidence, Implications, and Opportunities

There is now solid experimental evidence of at least one supernova explosion within 100 pc of Earth within the last few million years, from measurements of the short-lived isotope ⁶⁰Fe in widespread deep-ocean samples, as well as in the lunar regolith and cosmic rays. This is the first established example of a specific dated astrophysical event outside the Solar System having a measurable impact on the Earth, offering new probes of stellar evolution, nuclear astrophysics, the astrophysics of the solar neighborhood, cosmic-ray sources and acceleration, multi-messenger astronomy, and astrobiology. Interdisciplinary connections reach broadly to include heliophysics, geology, and evolutionary biology. Objectives for the future include pinning down the nature and location of the established near-Earth supernova explosions, seeking evidence for others, and searching for other short-lived isotopes such as ²⁶Al and ²⁴⁴Pu. The unique information provided by geological and lunar detections of radioactive ⁶⁰Fe to assess nearby supernova explosions make now a compelling time for the astronomy community to advocate for supporting multi-disciplinary, cross-cutting research programs

A Legal Fig Leaf?

A summary of the debate between Judge Posner and Professor Stone over the merits and legal and policy implications of the National Security Administration’s domestic surveillance program. The arguments focused on whether the program violates either (or both) the Fourth Amendment’s prohibition of unreasonable searches and seizures or the Foreign Intelligence Surveillance Act

WELL-FUNDED: A REORIENTATION OF PUBLIC SAFETY GRANTS FOR A SAFER HOMELAND

Extraneous and even misused equipment amassed by local first response agencies has been made possible through federal grants and resources with little oversight and insufficient governing mechanisms. Acquisitions, particularly of tactical gear, have far outpaced the development of best practices and guidance for proper use of such government resources. The relative ease in purchasing these items has led to far-reaching implications for public safety leadership and the public, particularly police militarization. This thesis examines how gaps in oversight, transparency, and performance measurement in the delivery of federal grants and resources to public safety organizations have contributed to unintended uses. It analyzes original grant language, available case studies of grant misuse, and academic research, as well as peer-reviewed documents and scholarly commentary to understand the multi-level political strategies that grants-in-aid facilitate. This thesis ultimately recommends that communities should determine how public safety is serving them in ways that matter to them. This measure is vital if the grant system is to see any real regulation, structure, and oversight. This thesis finds that greater public engagement throughout the grant and acquisition process adds the missing layer of accountability at the local level—weighing in on, authorizing, and defining the parameters of use and informing future grant awards and allocations.Civilian, Los Angeles Fire DepartmentApproved for public release. Distribution is unlimited

An experimental investigation of flow-induced oscillations of the Bruel and Kjaer in-flow microphone

One source contributing to wind tunnel background noise is microphone self-noise. An experiment was conducted to investigate the flow-induced acoustic oscillations of Bruel & Kjaer (B&K) in-flow microphones. The results strongly suggest the B&K microphone cavity behaves more like an open cavity. Their cavity acoustic oscillations are likely caused by strong interactions between the cavity shear layer and the cavity trailing edge. But the results also suggest that cavity shear layer oscillations could be coupled with cavity acoustic resonance to generate tones. Detailed flow velocity measurements over the cavity screen have shown inflection points in the mean velocity profiles and high disturbance and spectral intensities in the vicinity of the cavity trailing edge. These results are the evidence for strong interactions between cavity shear layer oscillations and the cavity trailing edge. They also suggest that beside acoustic signals, the microphone inside the cavity has likely recorded hydrodynamic pressure oscillations, too. The results also suggest that the forebody shape does not have a direct effect on cavity oscillations. For the FITE (Flow Induced Tone Eliminator) microphone, it is probably the forebody length and the resulting boundary layer turbulence that have made it work. Turbulence might have thickened the boundary layer at the separation point, weakened the shear layer vortices, or lifted them to miss impinging on the cavity trailing edge. In addition, the study shows that the cavity screen can modulate the oscillation frequency but not the cavity acoustic oscillation mechanisms

Results of an Interlaboratory Study of the ASTM Standard Test Method for Tensile Properties of Polymer Matrix Composites D 3039

An investigation was conducted on the ASTM Standard Test Method for Tensile Properties of Polymer Matrix Composites (D 3039). This investigation consisted of both preliminary testing and an interlaboratory test program. Information generated from preliminary testing was used to determine the effects of various parameters and to optimize the interlaboratory test plan and test protocol. The interlaboratory study portion of this investigation was conducted on six composite material systems in a variety of lay-up configurations. The number of participating labs ranged from five to nine depending on the material type. Precision statistics were determined for the ASTM D 3039 standard from the data generated by the interlaboratory testing in accordance with the ASTM Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method (E 691)

Near-Earth Supernova Explosions: Evidence, Implications, and Opportunities

There is now solid experimental evidence of at least one supernova explosion within 100 pc of Earth within the last few million years, from measurements of the short-lived isotope ⁶⁰Fe in widespread deep-ocean samples, as well as in the lunar regolith and cosmic rays. This is the first established example of a specific dated astrophysical event outside the Solar System having a measurable impact on the Earth, offering new probes of stellar evolution, nuclear astrophysics, the astrophysics of the solar neighborhood, cosmic-ray sources and acceleration, multi-messenger astronomy, and astrobiology. Interdisciplinary connections reach broadly to include heliophysics, geology, and evolutionary biology. Objectives for the future include pinning down the nature and location of the established near-Earth supernova explosions, seeking evidence for others, and searching for other short-lived isotopes such as ²⁶Al and ²⁴⁴Pu. The unique information provided by geological and lunar detections of radioactive ⁶⁰Fe to assess nearby supernova explosions make now a compelling time for the astronomy community to advocate for supporting multi-disciplinary, cross-cutting research programs

Metastable Charged Sparticles and the Cosmological Li7 Problem

We consider the effects of metastable charged sparticles on Big-Bang Nucleosynthesis (BBN), including bound-state reaction rates and chemical effects. We make a new analysis of the bound states of negatively-charged massive particles with the light nuclei most prominent in BBN, and present a new code to track their abundances, paying particular attention to that of Li7. Assuming, as an example, that the gravitino is the lightest supersymmetric particle (LSP), and that the lighter stau slepton, stau_1, is the metastable next-to-lightest sparticle within the constrained minimal supersymmetric extension of the Standard Model (CMSSM), we analyze the possible effects on the standard BBN abundances of stau_1 bound states and decays for representative values of the gravitino mass. Taking into account the constraint on the CMSSM parameter space imposed by the discovery of the Higgs boson at the LHC, we delineate regions in which the fit to the measured light-element abundances is as good as in standard BBN. We also identify regions of the CMSSM parameter space in which the bound state properties, chemistry and decays of metastable charged sparticles can solve the cosmological Li7 problem.Comment: 49 pages, 29 eps figure