406 research outputs found
IACT observations of gamma-ray bursts: prospects for the Cherenkov Telescope Array
Gamma rays at rest frame energies as high as 90 GeV have been reported from
gamma-ray bursts (GRBs) by the Fermi Large Area Telescope (LAT). There is
considerable hope that a confirmed GRB detection will be possible with the
upcoming Cherenkov Telescope Array (CTA), which will have a larger effective
area and better low-energy sensitivity than current-generation imaging
atmospheric Cherenkov telescopes (IACTs). To estimate the likelihood of such a
detection, we have developed a phenomenological model for GRB emission between
1 GeV and 1 TeV that is motivated by the high-energy GRB detections of
Fermi-LAT, and allows us to extrapolate the statistics of GRBs seen by lower
energy instruments such as the Swift-BAT and BATSE on the Compton Gamma-ray
Observatory. We show a number of statistics for detected GRBs, and describe how
the detectability of GRBs with CTA could vary based on a number of parameters,
such as the typical observation delay between the burst onset and the start of
ground observations. We also consider the possibility of using GBM on Fermi as
a finder of GRBs for rapid ground follow-up. While the uncertainty of GBM
localization is problematic, the small field-of-view for IACTs can potentially
be overcome by scanning over the GBM error region. Overall, our results
indicate that CTA should be able to detect one GRB every 20 to 30 months with
our baseline instrument model, assuming consistently rapid pursuit of GRB
alerts, and provided that spectral breaks below 100 GeV are not a common
feature of the bright GRB population. With a more optimistic instrument model,
the detection rate can be as high as 1 to 2 GRBs per year.Comment: 28 pages, 24 figures, 4 tables, submitted to Experimental Astronom
Interaction and filling induced quantum phases of dual Mott insulators of bosons and fermions
Many-body effects are at the very heart of diverse phenomena found in
condensed-matter physics. One striking example is the Mott insulator phase
where conductivity is suppressed as a result of a strong repulsive interaction.
Advances in cold atom physics have led to the realization of the Mott
insulating phases of atoms in an optical lattice, mimicking the corresponding
condensed matter systems. Here, we explore an exotic strongly-correlated system
of Interacting Dual Mott Insulators of bosons and fermions. We reveal that an
inter-species interaction between bosons and fermions drastically modifies each
Mott insulator, causing effects that include melting, generation of composite
particles, an anti-correlated phase, and complete phase-separation. Comparisons
between the experimental results and numerical simulations indicate intrinsic
adiabatic heating and cooling for the attractively and repulsively interacting
dual Mott Insulators, respectively
Colorectal cancer screening, perceived discrimination, and low-income and trust in doctors: a survey of minority patients
<p>Abstract</p> <p>Background</p> <p>Completion of colorectal cancer (CRC) screening testing is lower among low-income and minority groups than the population as a whole. Given the multiple cancer screening health disparities known to exist within the U.S., this study investigated the relationship between perceived discrimination, trust in most doctors, and completion of Fecal Occult Blood Testing (FOBT) among a low-income, minority primary care population in an urban setting.</p> <p>Methods</p> <p>We recruited a convenience sample of adults over age 40 (n = 282) from a federally qualified community health center (70% African American). Participants completed a survey which included measures of trust in most doctors, perceived discrimination, demographics and report of cancer screening.</p> <p>Results</p> <p>Participants reported high levels of trust in most doctors, regardless of sex, race, education or income. High trust was associated with low perceived discrimination (p < 0.01). The trend was for older participants to express more trust (p = 0.09) and less perceived discrimination (p < 0.01). Neither trust nor discrimination was associated with race or education. Trust was higher among participants over 50 who were up-to-date on FOBT screening vs. those who were not (31 vs. 29 (median), p < 0.05 by T-test). Among those over 50, up-to-date FOBT screening was nearly associated with high trust (p < 0.06; 95% CI 0.99, 1.28) and low perceived discrimination (p < 0.01; 95% CI 0.76, 0.96). Nevertheless, in multivariate-modeling, age and income explained FOBT completion better than race, trust and discrimination.</p> <p>Conclusion</p> <p>Perceived discrimination was related to income, but not race, suggesting that discrimination is not unique to minorities, but common to those in poverty. Since trust in most doctors trended toward being related to age, FOBT screening could be negatively influenced by low trust and perceived discrimination in health care settings. A failure to address these issues in middle-aged, low income individuals could exacerbate future disparities in CRC screening.</p
Phycodnavirus Potassium Ion Channel Proteins Question the Virus Molecular Piracy Hypothesis
Phycodnaviruses are large dsDNA, algal-infecting viruses that encode many genes with homologs in prokaryotes and eukaryotes. Among the viral gene products are the smallest proteins known to form functional K+ channels. To determine if these viral K+ channels are the product of molecular piracy from their hosts, we compared the sequences of the K+ channel pore modules from seven phycodnaviruses to the K+ channels from Chlorella variabilis and Ectocarpus siliculosus, whose genomes have recently been sequenced. C. variabilis is the host for two of the viruses PBCV-1 and NY-2A and E. siliculosus is the host for the virus EsV-1. Systematic phylogenetic analyses consistently indicate that the viral K+ channels are not related to any lineage of the host channel homologs and that they are more closely related to each other than to their host homologs. A consensus sequence of the viral channels resembles a protein of unknown function from a proteobacterium. However, the bacterial protein lacks the consensus motif of all K+ channels and it does not form a functional channel in yeast, suggesting that the viral channels did not come from a proteobacterium. Collectively, our results indicate that the viruses did not acquire their K+ channel-encoding genes from their current algal hosts by gene transfer; thus alternative explanations are required. One possibility is that the viral genes arose from ancient organisms, which served as their hosts before the viruses developed their current host specificity. Alternatively the viral proteins could be the origin of K+ channels in algae and perhaps even all cellular organisms
QGP Theory: Status and Perspectives
The current status of Quark-Gluon-Plasma Theory is reviewed. Special emphasis
is placed on QGP signatures, the interpretation of current data and what to
expect from RHIC in the near future.Comment: 20 pages, invited overview talk at the 4th International Conference
on the Physcis and Astrophysics of the Quark-Gluon-Plasma, November 2001,
Jaipur, India, to appear in Praman
Patient perspective on the management of atrial fibrillation in five European countries
Bakhai A, Sandberg A, Mittendorf T, et al. Patient perspective on the management of atrial fibrillation in five European countries. In: BMC Cardiovascular Disorders. Vol 13. BMC; 2013
Extending basic principles of measurement models to the design and validation of Patient Reported Outcomes
A recently published article by the Scientific Advisory Committee of the Medical Outcomes Trust presents guidelines for selecting and evaluating health status and health-related quality of life measures used in health outcomes research. In their article, they propose a number of validation and performance criteria with which to evaluate such self-report measures. We provide an alternate, yet complementary, perspective by extending the types of measurement models which are available to the instrument designer. During psychometric development or selection of a Patient Reported Outcome measure it is necessary to determine which, of the five types of measurement models, the measure is based on; 1) a Multiple Effect Indicator model, 2) a Multiple Cause Indicator model, 3) a Single Item Effect Indicator model, 4) a Single Item Cause Indicator model, or 5) a Mixed Multiple Indicator model. Specification of the measurement model has a major influence on decisions about item and scale design, the appropriate application of statistical validation methods, and the suitability of the resulting measure for a particular use in clinical and population-based outcomes research activities
Quality of life in patients with advanced renal cell carcinoma treated with temsirolimus or interferon-α
Synthesis and White-Light Emission of ZnO/HfO2: Eu Nanocables
ZnO/HfO2:Eu nanocables were prepared by radio frequency sputtering with electrospun ZnO nanofibers as cores. The well-crystallized ZnO/HfO2:Eu nanocables showed a uniform intact core–shell structure, which consisted of a hexagonal ZnO core and a monoclinic HfO2 shell. The photoluminescence properties of the samples were characterized. A white-light band emission consisted of blue, green, and red emissions was observed in the nanocables. The blue and green emissions can be attributed to the zinc vacancy and oxygen vacancy defects in ZnO/HfO2:Eu nanocables, and the yellow–red emissions are derived from the inner 4f-shell transitions of corresponding Eu3+ ions in HfO2:Eu shells. Enhanced white-light emission was observed in the nanocables. The enhancement of the emission is ascribed to the structural changes after coaxial synthesis
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