GRAPE - A Balloon-Borne Gamma-Ray Polarimeter Experiment

This paper reviews the development status of GRAPE (the Gamma-Ray Polarimeter Experiment), a hard X-ray Compton Polarimeter. The purpose of GRAPE is to measure the polarization of hard X-rays in the 50-300 keV energy range. We are particularly interested in X-rays that are emitted from solar flares and gamma-ray bursts (GRBs), although GRAPE could also be employed in the study of other astrophysical sources. Accurately measuring the polarization of the emitted radiation will lead to a better understating of both emission mechanisms and source geometries. The GRAPE design consists of an array of plastic scintillators surrounding a central high-Z crystal scintillator. The azimuthal distribution of photon scatters from the plastic array into the central calorimeter provides a measure of the polarization fraction and polarization angle of the incident radiation. The design of the detector provides sensitivity over a large field-of-view (>pi steradian). The design facilitates the fabrication of large area arrays with minimal deadspace. This paper presents the latest design concept and the most recent results from laboratory tests of a GRAPE science model.Comment: 6 pages; paper presented at the FRASCATI Workshop 2005 on Multifrequency Behaviour of High Energy Cosmic Sources; submitted to Chinese Journal of Astronomy and Astrophysic

Influence of prior activity (warm-up) and inspiratory muscle training upon between- and within-day reliability of maximal inspiratory pressure measurement

This is the post-print version of the article. The official published version can be obtained from the link below.BACKGROUND: A specific inspiratory muscle ‘warm-up’ (IWU) prior to assessment of maximal inspiratory mouth pressure (PImax) may reduce the number of measurements required to obtain reproducible, representative estimates of PImax. The influence of inspiratory muscle training (IMT) upon this phenomenon is unknown. OBJECTIVE: Compare the impact of an IWU on the between- and within-day reliability of PImax before and after IMT. METHOD: Eight participants were assessed on 4 separate occasions: 2 trials preceded IMT and 2 followed it. At each assessment, the highest of 3 initial efforts was recorded as the pre-IWU value (PI). The highest of 9 subsequent efforts that followed 2 sets of 30 breaths at 40% PI was recorded as PImax. Following 4 weeks of IMT, the trials were repeated. RESULTS: IWU increased PI by 11–17% (p ≤ 0.01), irrespective of IMT status. After IWU, 5–6 efforts were required to determine PImax, irrespective of IMT status. PImax was similar between the 2 trials before IMT and the 2 trials after IMT (p ≥ 0.05), and was 21% higher after IMT (p ≤ 0.01). The coefficient of variation was excellent before and after IWU, both before (1.9 and 0.6%, respectively) and after IMT (1.1 and 0.3%, respectively). Limits of agreement and sample sizes for effect sizes ≤10% were substantially smaller after IWU in all trials. CONCLUSIONS: (1) IWU enhances the between-day reliability of PImax measurement, and this is unaffected by IMT, and (2) judgements regarding acceptability in relation to PImax reliability should be made in relation to analytical goals and we present data to facilitate this

Rethinking the value of initial claims as a forecasting tool

The weekly numbers on initial claims for unemployment insurance convey key information about the labor market. But how reliable are claims in predicting changes in the much anticipated monthly employment report? According to a simple forecasting model, claims consistently send an accurate signal about employment during recessions but not during expansions.Unemployment insurance ; Forecasting ; Employment (Economic theory)

Linear-Time Algorithms for Finding Tucker Submatrices and Lekkerkerker-Boland Subgraphs

Lekkerkerker and Boland characterized the minimal forbidden induced subgraphs for the class of interval graphs. We give a linear-time algorithm to find one in any graph that is not an interval graph. Tucker characterized the minimal forbidden submatrices of binary matrices that do not have the consecutive-ones property. We give a linear-time algorithm to find one in any binary matrix that does not have the consecutive-ones property.Comment: A preliminary version of this work appeared in WG13: 39th International Workshop on Graph-Theoretic Concepts in Computer Scienc

Time-scales of Radio Emission in PSR J0437-4715 at 327 MHz

Time-scales of radio emission are studied in PSR J0437-4715 at 327 MHz using almost half a million periods of high quality data from Ooty Radio Telescope. The radio emission in this milli second pulsar occurs on a short (s) time-scale of approximately 0.026 +- 0.001 periods, and on a (l) time-scale that is much longer than the widths of the components of the integrated profile (approximately 0.05 periods). The width of the s emission increases with its increasing relative contribution to the total radio emission. This may provide constraints for the details of discharge of vacuum gaps above pulsar polar caps. The s emission occasionally takes place in the form of intense spikes, which are confined to the main component of the integrated profile for 90 per cent of the time. The positions of spikes within a component of the integrated profile have no simple relation to the shape of that component. This may have impact on the interpretation of the integrated profile components in terms of independent regions of emission on the polar cap.Comment: Accepted for publication in Vol 543 (1 Nov 2000) of The Astrophysical Journa

COMPTEL solar flare measurements

We review some of the highlights of the COMPTEL measurements of solar flares. These include images of the Sun in γ rays and neutrons. One of the important features of the COMPTEL instrument is its capability to measure weak fluxes of γ rays and neutrons in the extended phase of flares. These data complement the spectra taken with the COMPTEL burst spectrometer and the telescope during the impulsive phase of flares. We focus our attention on some of these general capabilities of the instrument and the latest results of two long‐duration γ‐ray flares, i.e., 11 and 15 June 199

The Formation and Evolution of Massive Black Holes

The past 10 years have witnessed a change of perspective in the way astrophysicists think about massive black holes (MBHs), which are now considered to have a major role in the evolution of galaxies. This appreciation was driven by the realization that black holes of millions solar masses and above reside in the center of most galaxies, including the Milky Way. MBHs also powered active galactic nuclei known to exist just a few hundred million years after the Big Bang. Here, I summarize the current ideas on the evolution of MBHs through cosmic history, from their formation about 13 billion years ago to their growth within their host galaxies.Comment: Review for Science Special Issue on black hole

Relations between extensional tectonics and magmatism within the Southern Oklahoma aulacogen

Variations in the geometry, distribution and thickness of Cambrian igneous and sedimentary units within southwest Oklahoma are related to a late Proterozoic - early Paleozoic rifting event which formed the Southern Oklahoma aulacogen. These rock units are exposed in the Wichita Mountains, southwest Olkahoma, located on the northern margin of a Proterozoic basin, identified in the subsurface by COCORP reflection data. Overprinting of the Cambrian extensional event by Pennyslvanian tectonism obsured the influence of pre-existing basement structures and contrasting basement lithologies upon the initial development of the aulacogen