9,468 research outputs found
Statistical Uncertainties in Temperature Diagnostics for Hot Coronal Plasma Using the ASCA SIS
Statistical uncertainties in determining the temperatures of hot (0.5 keV to
10 keV) coronal plasmas are investigated. The statistical precision of various
spectral temperature diagnostics is established by analyzing synthetic ASCA
Solid-state Imaging Spectrometer (SIS) CCD spectra. The diagnostics considered
are the ratio of hydrogen-like to helium-like line complexes of
elements, line-free portions of the continuum, and the entire spectrum. While
fits to the entire spectrum yield the highest statistical precision, it is
argued that fits to the line-free continuum are less susceptible to atomic data
uncertainties but lead to a modest increase in statistical uncertainty over
full spectral fits. Temperatures deduced from line ratios can have similar
accuracy but only over a narrow range of temperatures. Convenient estimates of
statistical accuracies for the various temperature diagnostics are provided
which may be used in planning ASCA SIS observations.Comment: postscript file of 8 pages+3 figures; 4 files tarred, compressed and
uuencoded. To appear in the Astrophysical Journal Letters; contents copyright
1994 American Astronomical Societ
âCascading participationâ and the role of teachers in a collaborative HIV and Aids curriculum development project
This paper presents findings of four Grade 6 teachersâ involvement as facilitators of a participatory action research (PAR) project conducted in three South African primary schools. Based on the results of Phase One research which indicated that Grade 6s learn about sexuality, Human Immunodeficiency Virus (HIV) and Acquired Immunodeficiency Syndrome (AIDS) from multiple sources, the Phase Two project designers developed a toolkit to help Life Orientation (LO) teachers consult learners on what they know and how they want to be taught. In each school, a curriculum development group comprising the participating teacher, learners, parents and an HIV and Aids specialist worked to enhance the official HIV and Aids curriculum using the information gathered each week by the teacher. This dialogue between the study participants represents the culmination of what we describe as the projectâs âcascading participationâ research model, a term denoting the multiple levels of participant involvement in the study. Although theories of participation often depict a binary relationship between those with power and those without it, the implementation of this project shows how the official curriculum, cultural norms and low parent involvement can exert pressure at different levels to diminish teachersâ ability to facilitate social and educational change.Keywords: curriculum development; HIV and Aids; HIV and Aids knowledge; participatory action research; teacher
Investigating 16O with the 15N(p,{\alpha})12C reaction
The 16O nucleus was investigated through the 15N(p,{\alpha})12C reaction at
excitation energies from Ex = 12 231 to 15 700 keV using proton beams from a 5
MeV Van de Graaff accelerator at beam energies of Ep = 331 to 3800 keV. Alpha
decay from resonant states in 16O was strongly observed for ten known excited
states in this region. The candidate 4-alpha cluster state at Ex = 15.1 MeV was
investigated particularly intensely in order to understand its particle decay
channels.Comment: Submitted for Proceedings of Fourth International Workshop on State
of the Art in Nuclear Cluster Physics (SOTANCP4), held from May 13 - 18, 2018
in Galveston, TX, US
Measurements with the Chandra X-Ray Observatory's flight contamination monitor
NASA's Chandra X-ray Observatory includes a Flight Contamination Monitor
(FCM), a system of 16 radioactive calibration sources mounted to the inside of
the Observatory's forward contamination cover. The purpose of the FCM is to
verify the ground-to-orbit transfer of the Chandra flux scale, through
comparison of data acquired during the ground calibration with those obtained
in orbit, immediately prior to opening the Observatory's sun-shade door. Here
we report results of these measurements, which place limits on the change in
mirror--detector system response and, hence, on any accumulation of molecular
contamination on the mirrors' iridium-coated surfaces.Comment: 7pages,8figures,for SPIE 4012, paper 7
A double junction model of irradiated silicon pixel sensors for LHC
In this paper we discuss the measurement of charge collection in irradiated
silicon pixel sensors and the comparison with a detailed simulation. The
simulation implements a model of radiation damage by including two defect
levels with opposite charge states and trapping of charge carriers. The
modeling proves that a doubly peaked electric field generated by the two defect
levels is necessary to describe the data and excludes a description based on
acceptor defects uniformly distributed across the sensor bulk. In addition, the
dependence of trap concentrations upon fluence is established by comparing the
measured and simulated profiles at several fluences and bias voltages.Comment: Talk presented at the 10th European Symposium on Semiconductor
Detectors, June 12-16 2005, Wildbad Kreuth, Germany. 9 pages, 4 figure
Experimental study of the reaction at MeV
Our understanding of the low-lying resonance structure in C remains
incomplete. We have used the reaction at
proton energies of MeV as a selective probe of the excitation
region above the threshold in C. Transitions to individual
levels in C were identified by measuring the 3 final state with
a compact array of charged-particle detectors. Previously identified
transitions to narrow levels were confirmed and new transitions to broader
levels were observed for the first time. Here, we report cross sections, deduce
partial -decay widths and discuss the relative importance of direct and
resonant capture mechanisms.Comment: 9 pages, 7 figures, 5 tables; added details on data analysi
How Insurers Competed in the Affordable Care Act's First Year
Prior to the Affordable Care Act (ACA), most states' individual health insurance markets were dominated by one or two insurance carriers that had little incentive to compete by providing efficient services. Instead, they competed mainly by screening and selecting people based on their risk of incurring high medical costs. One of the ACA's goals is to encourage carriers to participate in the health insurance marketplaces and to shift the focus from competing based on risk selection to processes that increase consumer value, like improving efficiency of services and quality of care. Focusing on six statesâArkansas, California, Connecticut, Maryland, Montana, and Texasâthis brief looks at how carriers are competing in the new marketplaces, namely through cost-sharing and composition of provider networks
Lattice-dynamics of a Disordered solid-solid Interface
Generic properties of elastic phonon transport at a disordered interface are
studied. The results show that phonon transmittance is a strong function of
frequency and the disorder correlation length. At frequencies lower than the
van Hove singularity the transmittance at a given frequency increases as the
correlation length decreases. At low frequencies, this is reflected by
different power-laws for phonon conductance across correlated and uncorrelated
disordered interfaces which are in approximate agreement with perturbation
theory of an elastic continuum. These results can be understood in terms of
simple mosaic and two-colour models of the interface.Comment: 17 pages, 5 figures, submitted to PR
Position Dependence of Charge Collection in Prototype Sensors for the CMS Pixel Detector
This paper reports on the sensor R&D activity for the CMS pixel detector.
Devices featuring several design and technology options have been irradiated up
to a proton fluencec of 1E15 n_eq/cm**2 at the CERN PS. Afterward they were
bump bonded to unirradiated readout chips and tested using high energy pions in
the H2 beam line of the CERN SPS. The readout chip allows a non zero suppressed
full analogue readout and therefore a good characterization of the sensors in
terms of noise and charge collection properties. The position dependence of
signal is presented and the differences between the two sensor options are
discussed.Comment: Contribution to the IEEE-NSS Oct. 2003, Portland, OR, USA, submitted
to IEEE-TNS 7 pages, 8 figures, 1 table. Revised, title change
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