23,479 research outputs found
Quantum Resonances of Weakly Linked, Mesoscopic, Superconducting Dots
We examine quantum properties of mesoscopic, Josephson coupled
superconducting dots, in the limit that charging effects and quantization of
energy levels within the dots are negligible, but quasi-particle transmission
into the weak link is not. We demonstrate that quasi-particle resonances lead
to current-phase relations, which deviate markedly from those of weak links
connecting macroscopic superconductors. Results for the steady state dc
Josephson current of two coupled dots are presented.Comment: Tex, 3 figures available on request to [email protected] (Andy
Martin
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Galactic R Coronae Borealis Stars: The C-2 Swan Bands, The Carbon Problem, And The C-12/C-13 Ratio
Observed spectra of R Coronae Borealis (RCB) and hydrogen-deficient carbon (HdC) stars are analyzed by synthesizing the C-2 Swan bands (1, 0), (0, 0), and (0, 1) using our detailed line list and the Uppsala model atmospheres. The (0, 1) and (0, 0) C-2 bands are used to derive the C-12 abundance, and the (1, 0) (CC)-C-12-C-13 band to determine the C-12/C-13 ratios. The carbon abundance derived from the C-2 Swan bands is about the same for the adopted models constructed with different carbon abundances over the range 8.5 (C/He = 0.1%) to 10.5 (C/He = 10%). Carbon abundances derived from C I lines are about a factor of four lower than the carbon abundance of the adopted model atmosphere over the same C/He interval, as reported by Asplund et al., who dubbed the mismatch between adopted and derived C abundance as the "carbon problem." In principle, the carbon abundances obtained from C-2 Swan bands and that assumed for the model atmosphere can be equated for a particular choice of C/He that varies from star to star. Then, the carbon problem for C-2 bands is eliminated. However, such C/He ratios are in general less than those of the extreme helium stars, the seemingly natural relatives to the RCB and HdC stars. A more likely solution to the C-2 carbon problem may lie in a modification of the model atmosphere's temperature structure. The derived carbon abundances and the C-12/C-13 ratios are discussed in light of the double degenerate and the final flash scenarios.Robert A. Welch Foundation of Houston, TX F-634McDonald Observator
Measuring the pro-poorness of income growth within an elasticity framework
Poverty reduction has become a fundamental objective of development, and therefore a metric for assessing the effectiveness of various interventions. Economic growth can be a powerful instrument of income poverty reduction. This creates a need for meaningful ways of assessing the poverty impact of growth. This paper follows the elasticity approach to propose a measure of pro-poorness defined as a weighted average of the deviation of a growth pattern from the benchmark case. The measure can help assess pro-poorness both in terms of aggregate poverty measures, which are members of the additively separable class, and at percentiles. It also lends itself to a decomposition procedure, whereby the overall pattern of income growth can be unbundled, and the contributions of income components to overall pro-poorness identified. An application to data for Indonesia in the 1990s reveals that the amount of poverty reduction achieved over that period remains far below what would have been achieved under distributional neutrality. This conclusion is robust to the choice of a poverty measure among members of the additively separable class, and can be tracked back to changes in expenditure components.Achieving Shared Growth,Population Policies,Services&Transfers to Poor,Inequality,Rural Poverty Reduction
Cure by age and stage at diagnosis for colorectal cancer patients in North West England, 1997-2004: a population-based study.
BACKGROUND: Stage and age at diagnosis are important prognostic factors for patients with colorectal cancer. However, the proportion cured by stage and age is unknown in England. MATERIALS AND METHODS: This population-based study includes 29,563 adult patients who were diagnosed and registered with colorectal cancer during 1997-2004 and followed till 2007 in North West England. Multiple imputation was used to provide more reliable estimates of stage at diagnosis, when these data were missing. Cure mixture models were used to estimate the proportion 'cured' and the median survival of the uncured by age and stage. RESULTS: For both colon and rectal cancer the proportion of patients cured and median survival time of the uncured decreased with advancing stage and increasing age. Patients aged under 65 years had the highest proportion cured and longest median survival of the uncured. CONCLUSION: Cure of colorectal cancer patients is dependent on stage and age at diagnosis with younger patients or those with less advanced disease having a better prognosis. Further efforts are required, in order to reduce the proportion of patients presenting with stage III and IV disease and ultimately increase the chance of cure
Freund-Rubin Revisited
We utilise the duality between M theory and Type IIA string theory to show
the existence of Freund-Rubin compactifications of M theory on 7-manifolds with
singularities supporting chiral fermions. This leads to a concrete way to study
phenomenologically interesting quantum gravity vacua using a holographically
dual three dimensional field theory.Comment: reference adde
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