40,565 research outputs found
Developing a Compton Polarimeter to Measure Polarization of Hard X-Rays in the 50-300 keV Energy Range
This paper discusses the latest progress in the development of GRAPE
(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). Accurately measuring the
polarization of the emitted radiation from these sources will lead, to a better
understating of both the emission mechanisms and source geometries. The GRAPE
design consists of an array of plastic scintillators surrounding a central
high-Z crystal scintillator. We can monitor individual Compton scatters that
occur in the plastics and determine whether the photon is photo absorbed by the
high-Z crystal or not. A Compton scattered photon that is immediately photo
absorbed by the high-Z crystal constitutes a valid event. These valid events
provide us with the interaction locations of each incident photon and
ultimately produces a modulation pattern for the Compton scattering of the
polarized radiation. Comparing with Monte Carlo simulations of a 100% polarized
beam, the level of polarization of the measured beam can then be determined.
The complete array is mounted on a flat-panel multi-anode photomultiplier tube
(MAPMT) that can measure the deposited energies resulting from the photon
interactions. The design of the detector allows for a large field-of-view (>pi
steradian), at the same time offering the ability to be close-packed with
multiple modules in order to reduce deadspace. We plan to present in this paper
the latest laboratory results obtained from GRAPE using partially polarized
radiation sources.Comment: 10 pages; conference paper presented at the SPIE conference "UV,
X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XIV." To be
published in SPIE Conference Proceedings, vol. 589
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The family drug & alcohol court (FDAC) evaluation project
This report presents the findings from the evaluation of the first pilot Family Drug and Alcohol Court (FDAC) in Britain. FDAC is a new approach to care proceedings, in cases where parental substance misuse is a key element in the local authority decision to bring proceedings. It is being piloted at the Inner London Family Proceedings Court in Wells Street. Initially the pilot was to run for three years, to the end of December 2010, but is now to continue until March 2012. The work is co-funded by the Department for Education (formerly the Department for Children, Schools and Families), the Ministry of Justice, the Home Office, the Department of Health and the three pilot authorities (Camden, Islington and Westminster). The evaluation was conducted by a research team at Brunel University, with funding from the Nuffield Foundation and the Home Office. FDAC is a specialist court for a problem that is anything but special. Its potential to help break the inter-generational cycle of harm associated with parental substance misuse goes straight to the heart of public policy and professional practice. Parental substance misuse is a formidable social problem and a key factor in around a third of long-term cases in children’s services in some areas. It is a major risk factor for child maltreatment, family separation and offending in adults, and for poor educational performance and substance misuse by children and young people. The parents’ many difficulties create serious problems for their children and place major demands on health, welfare and criminal justice services. For these reasons, parental substance misuse is a cross-cutting government agenda. FDAC is distinctive because it is a court-based family intervention which aims to improve children’s outcomes by addressing the entrenched difficulties of their parents. It has been adapted to English law and practice from a model of family treatment drug courts that is used widely in the USA and is showing promising results with a higher number of cases where parents and children were able to remain together safely, and with swifter alternative placement decisions for children if parents were unable to address their substance misuse successfully. The catalysts for the FDAC pilot were the encouraging evidence from the USA and concerns about the response to parental substance misuse through ordinary care proceedings in England: poor coordination of adult and children’s services; late interventions to protect children; delays in reaching decisions in court; and soaring costs of proceedings, linked to the cost of expert evidence.The work is co-funded by the Department for Education (formerly the Department for Children, Schools and Families), the Ministry of Justice, the Home Office, the Department of Health and the three pilot authorities (Camden, Islington and Westminster).1 The evaluation was conducted by a research team at Brunel University, with funding from the Nuffield Foundation and the Home Office
The spectrum of radial, orbital and gluonic excitations of charmonium
We present results for the charmonium spectrum from dynamical QCD
simulations on anisotropic lattices. Using all-to-all
propagators we determine the ground and excited states of S, P and D waves and
hybrids. We also evaluate the disconnected (OZI suppressed) contribution to the
and Comment: 6 pages, 3 figures, Presented at 24th International Symposium on
Lattice Field Theory (Lattice 2006), Tucson, Arizona, 23-28 Jul 200
Quantum bounds for gravitational de Sitter entropy and the Cardy-Verlinde formula
We analyze different types of quantum corrections to the Cardy-Verlinde
entropy formula in a Friedmann-Robertson-Walker universe and in an (anti)-de
Sitter space. In all cases we show that quantum corrections can be represented
by an effective cosmological constant which is then used to redefine the
parameters entering the Cardy-Verlinde formula so that it becomes valid also
with quantum corrections, a fact that we interpret as a further indication of
its universality. A proposed relation between Cardy-Verlinde formula and the
ADM Hamiltonian constraint is given.Comment: LaTeX file, 15 pages, reference is adde
Effect of polar discontinuity on the growth of LaNiO3/LaAlO3 superlattices
We have conducted a detailed microscopic investigation of [LaNiO3(1
u.c.)/LaAlO3(1 u.c.)]N superlattices grown on (001) SrTiO3 and LaAlO3 to
explore the influence of polar mismatch on the resulting electronic and
structural properties. Our data demonstrate that the initial growth on the
non-polar SrTiO3 surface leads to a rough morphology and unusual 2+ valence of
Ni in the first LaNiO3 layer, which is not observed after growth on the polar
surface of LaAlO3. A newly devised model suggests that the polar mismatch can
be resolved if the perovskite layers grow with an excess of LaO, which also
accounts for the observed electronic, chemical, and structural effects.Comment: 3 pages, 3 figure
Lattice QCD at the end of 2003
I review recent developments in lattice QCD. I first give an overview of its
formalism, and then discuss lattice discretizations of fermions. We then turn
to a description of the quenched approximation and why it is disappearing as a
vehicle for QCD phenomenology. I describe recent claims for progress in
simulations which include dynamical fermions and the interesting theoretical
problems they raise. I conclude with brief descriptions of the calculations of
matrix elements in heavy flavor systems and for kaons.Comment: Review for Int J Mod Phys A. 58 pages, latex, WSPC macros,, 22
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