1,264 research outputs found
Direct solar energy conversion for large scale terrestrial use
Various techniques to increase the open circuit voltage are being explored. It had been previously observed that cells made on CdS deposited from a single source gave a consistently higher V sub oc. Further tests have now shown that this effect may in fact relate to differences in source and substrate temperatures. The resulting differences in CdS structure and crystallinity are being documented. Deposits of mixed CdS and ZnS are being produced and will be initially made into cells using the conventional barriering technique. Analysis of I-V characteristics at temperatures between 25 and 110 C is being perfected to provide nondestructive analysis of the Cu2S. Changes due to vacuum heat treatments and exposure to oxygen are also being monitored by the same technique. Detailed spectral response measurements are being made
Views and attitudes towards blood donation: a qualitative investigation of Indian non-donors living in England
OBJECTIVE:
To explore the views and attitudes of Indians living in England on blood donation.
BACKGROUND:
In light of the predicted shortages in blood supply, it is vital to consider ways in which to maximise donation rates. These include addressing the issue of lower donation rates among ethnic minorities, including Indians. However research specifically among minority ethnicities in UK is sparse.
SETTING:
General practice in North London.
PARTICIPANTS: A convenience sample of 12 non-donor Indians living in England.
METHODS: This is a qualitative investigation involving semistructured interviews. Themes derived were analysed using thematic framework analysis.
RESULTS:
Five key themes emerged from the data, and these concerned participants’ perspectives regarding attitudes towards blood, blood donation as a ‘good thing’, donation disincentives, the recipient matters and the donor matters.
CONCLUSION:
A variety of attitudes were presented, but were generally positive, and blood was conceptualised in a manner previously found to be consistent with donation. However, lack of awareness and accessibility were prominent barriers, indicating the need for improvement in these capacities. In contrast to this, blood was also greatly associated with family and acted as a symbol of kinship: this ‘emotional charge’ often acted to dissuade participants from separating with their blood through donation. Possibly due to this, there was also a strong preference for donated blood to be distributed within the family, as opposed to strangers. This presents a potential barrier to blood donation for some Indians within the current system in which donations are given to unknown recipients
Active Carbon and Oxygen Shell Burning Hydrodynamics
We have simulated 2.5 s of the late evolution of a star with full hydrodynamic behavior. We present the first simulations
of a multiple-shell burning epoch, including the concurrent evolution and
interaction of an oxygen and carbon burning shell. In addition, we have evolved
a 3D model of the oxygen burning shell to sufficiently long times (300 s) to
begin to assess the adequacy of the 2D approximation. We summarize striking new
results: (1) strong interactions occur between active carbon and oxygen burning
shells, (2) hydrodynamic wave motions in nonconvective regions, generated at
the convective-radiative boundaries, are energetically important in both 2D and
3D with important consequences for compositional mixing, and (3) a spectrum of
mixed p- and g-modes are unambiguously identified with corresponding adiabatic
waves in these computational domains. We find that 2D convective motions are
exaggerated relative to 3D because of vortex instability in 3D. We discuss the
implications for supernova progenitor evolution and symmetry breaking in core
collapse.Comment: 5 pages, 4 figures in emulateapj format. Accepted for publication in
ApJ Letters. High resolution figure version available at
http://spinach.as.arizona.ed
The Impact of Hydrodynamic Mixing on Supernova Progenitors
Recent multidimensional hydrodynamic simulations have demonstrated the
importance of hydrodynamic motions in the convective boundary and radiative
regions of stars to transport of energy, momentum, and composition. The impact
of these processes increases with stellar mass. Stellar models which
approximate this physics have been tested on several classes of observational
problems. In this paper we examine the implications of the improved treatment
on supernova progenitors. The improved models predict substantially different
interior structures. We present pre-supernova conditions and simple explosion
calculations from stellar models with and without the improved mixing treatment
at 23 solar masses. The results differ substantially.Comment: 12 pages, 2 figures, accepted for publication in the Astrophysical
Journal Letter
Anisotropic anomalous diffusion modulated by log-periodic oscillations
We introduce finite ramified self-affine substrates in two dimensions with a
set of appropriate hopping rates between nearest-neighbor sites, where the
diffusion of a single random walk presents an anomalous {\it anisotropic}
behavior modulated by log-periodic oscillations. The anisotropy is revealed by
two different random walk exponents, and , in the {\it x} and
{\it y} direction, respectively. The values of these exponents, as well as the
period of the oscillation, are analytically obtained and confirmed by Monte
Carlo simulations.Comment: 7 pages, 7 figure
On the multifractal statistics of the local order parameter at random critical points : application to wetting transitions with disorder
Disordered systems present multifractal properties at criticality. In
particular, as discovered by Ludwig (A.W.W. Ludwig, Nucl. Phys. B 330, 639
(1990)) on the case of diluted two-dimensional Potts model, the moments
of the local order parameter scale with a set
of non-trivial exponents . In this paper, we revisit
these ideas to incorporate more recent findings: (i) whenever a multifractal
measure normalized over space occurs in a random
system, it is crucial to distinguish between the typical values and the
disorder averaged values of the generalized moments , since
they may scale with different generalized dimensions and
(ii) as discovered by Wiseman and Domany (S. Wiseman and E. Domany, Phys Rev E
{\bf 52}, 3469 (1995)), the presence of an infinite correlation length induces
a lack of self-averaging at critical points for thermodynamic observables, in
particular for the order parameter. After this general discussion valid for any
random critical point, we apply these ideas to random polymer models that can
be studied numerically for large sizes and good statistics over the samples. We
study the bidimensional wetting or the Poland-Scheraga DNA model with loop
exponent (marginal disorder) and (relevant disorder). Finally,
we argue that the presence of finite Griffiths ordered clusters at criticality
determines the asymptotic value and the minimal value of the typical multifractal spectrum
.Comment: 17 pages, 20 figure
Demonstrating the importance of sulfur in fertilizer plans for corn and barley using polyhalite
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