4,634 research outputs found
Large collection of astrophysical S-factors and its compact representation
Numerous nuclear reactions in the crust of accreting neutron stars are
strongly affected by dense plasma environment. Simulations of superbursts, deep
crustal heating and other nuclear burning phenomena in neutron stars require
astrophysical S-factors for these reactions (as a function of center-of-mass
energy E of colliding nuclei). A large database of S-factors is created for
about 5000 non-resonant fusion reactions involving stable and unstable isotopes
of Be, B, C, N, O, F, Ne, Na, Mg, and Si. It extends the previous database of
about 1000 reactions involving isotopes of C, O, Ne, and Mg. The calculations
are performed using the Sao Paulo potential and the barrier penetration
formalism. All calculated S-data are parameterized by an analytic model for
S(E) proposed before [Phys. Rev. C 82, 044609 (2010)] and further elaborated
here. For a given reaction, the present S(E)-model contains three parameters.
These parameters are easily interpolated along reactions involving isotopes of
the same elements with only seven input parameters, giving an ultracompact,
accurate, simple, and uniform database. The S(E) approximation can also be used
to estimate theoretical uncertainties of S(E) and nuclear reaction rates in
dense matter, as illustrated for the case of the 34Ne+34Ne reaction in the
inner crust of an accreting neutron star.Comment: 13 pages, 2 figures, Phys. Rev. C, accepte
Muon spin rotation studies of niobium for superconducting RF applications
In this work we investigate superconducting properties of niobium samples via
application of the muon spin rotation/relaxation (muSR) technique. We employ
for the first time the muSR technique to study samples that are cutout from
large and small grain 1.5 GHz radio frequency (RF) single cell niobium
cavities. The RF test of these cavities was accompanied by full temperature
mapping to characterize the RF losses in each of the samples. Results of the
muSR measurements show that standard cavity surface treatments like mild baking
and buffered chemical polishing (BCP) performed on the studied samples affect
their surface pinning strength. We find an interesting correlation between high
field RF losses and field dependence of the sample magnetic volume fraction
measured via muSR. The muSR line width observed in ZF-muSR measurements matches
the behavior of Nb samples doped with minute amounts of Ta or N impurities. An
upper bound for the upper critical field Hc2 of these cutouts is found.Comment: 20 pages, 14 figure
Rain: Relaxations in the sky
We demonstrate how, from the point of view of energy flow through an open
system, rain is analogous to many other relaxational processes in Nature such
as earthquakes. By identifying rain events as the basic entities of the
phenomenon, we show that the number density of rain events per year is
inversely proportional to the released water column raised to the power 1.4.
This is the rain-equivalent of the Gutenberg-Richter law for earthquakes. The
event durations and the waiting times between events are also characterised by
scaling regions, where no typical time scale exists. The Hurst exponent of the
rain intensity signal . It is valid in the temporal range from
minutes up to the full duration of the signal of half a year. All of our
findings are consistent with the concept of self-organised criticality, which
refers to the tendency of slowly driven non-equilibrium systems towards a state
of scale free behaviour.Comment: 9 pages, 8 figures, submitted to PR
Using Incongruent Equilibrium Hydration Reactions to Model Latter-Stage Crystallization in Plutons: Examples from the Bell Island Tonalite, Alaska
Models using hydration crystallization reactions (the reverse of dehydration melting reactions such as amph + qtz = px + melt) for the Bell Island pluton define incongruent equilibrium crystallization paths from hydrous + melt + pyroxene + Fe-Ti oxides + calcic andesine (30%-50% solid) to a solid tonalite consisting mostly of hornblende, lower temperature end of Bowen\u27s discontinuous reaction series and apply it to natural samples. Hydration crystallization provides an alternative to crystal fractionation for explaining variations in pluton chemistry, especially the compositions of late plutonic melts. Another characteristic of hydration crystallization is that the reactions have the potential to buffer the water content of the melt during crystallization. Two closed-system models, representing different sets of starting conditions and phases, are considered, based on least squares, mass-balance calculations of reactions and constrained by the petrography of the rocks. Model 1 starts with an average modified Bell Island leucotonalite melt coexisting with two pyroxenes, two Fe-Ti oxides, and plagioclase at the beginning of hydration crystallization. The starting assemblage of model 2 omits orthopyroxene and magnetite, includes amphibole, and uses a calculated melt composition. Both models generally predict, via different series of hydration crystallization reactions, the observed subsolidus mode. Model 2, however, is preferred based on petrographic observations of the Bell Island rocks, specifically the lack of magnetite and orthopyroxene, as well as certain textural features
QCD as a Quantum Link Model
QCD is constructed as a lattice gauge theory in which the elements of the
link matrices are represented by non-commuting operators acting in a Hilbert
space. The resulting quantum link model for QCD is formulated with a fifth
Euclidean dimension, whose extent resembles the inverse gauge coupling of the
resulting four-dimensional theory after dimensional reduction. The inclusion of
quarks is natural in Shamir's variant of Kaplan's fermion method, which does
not require fine-tuning to approach the chiral limit. A rishon representation
in terms of fermionic constituents of the gluons is derived and the quantum
link Hamiltonian for QCD with a U(N) gauge symmetry is expressed in terms of
glueball, meson and constituent quark operators. The new formulation of QCD is
promising both from an analytic and from a computational point of view.Comment: 27 pages, including three figures. ordinary LaTeX; Submitted to Nucl.
Phys.
The cost-effectiveness of high dose chemotherapy in the treatment of relapsed Hodgkin's disease and non-Hodgkin's lymphoma
As part of an NHS Executive Trent regional initiative we considered the role and cost-effectiveness of high dose chemotherapy in the treatment of relapsed Hodgkin's disease and non-Hodgkin's lymphoma. The key trials and case series show an additional patient benefit of 0.8–1.1 life years over standard chemotherapy. We estimate incremental cost per life year gained of £12 800–£17 600, which reduces further if long-term benefits are considered. High dose chemotherapy in these conditions is both life-saving and cost-effective. © 2000 Cancer Research Campaig
Short-term effects of announcing revised lower risk national drinking guidelines on related awareness and knowledge: A trend analysis of monthly survey data in England.
Objectives: To evaluate short-term effects of publishing revised lower-risk national drinking
guidelines on related awareness and knowledge. To examine where drinkers heard about guidelines
over the same period.
Design: Trend analysis of the Alcohol Toolkit Study, a monthly repeat cross-sectional national survey.
Setting: England, November 2015 to May 2016.
Participants: A total of 11,845 adults (18+) living in private households in England
Intervention: Publication of revised national drinking guidelines in January 2016 which reduced the
male guideline by approximately one-third to 14 units per week.
Measurements: Whether drinkers (i) had heard of drinking guidelines (awareness), (ii) stated the
guideline was above, exactly or below 14 units (knowledge), and (iii) reported seeing the stated
guideline number of units in the last month in each of 11 locations (exposure). Sociodemographics:
sex, age (18-34, 35-64, 65+), social grade (AB, C1C2, DE). Alcohol consumption derived from
graduated frequency questions: low risk (<14 units/week), increasing/high risk (14+ units/week).
Results: Following publication of the guidelines, the proportion of drinkers aware of guidelines did
not increase from its baseline level of 85.1% (CI:82.7-87.1). However, the proportion of male
drinkers saying the guideline was 14 units or less increased from 22.6% (CI:18.9-26.7) in December
to 43.3% (CI:38.9-47.8) in January and was at 35.6% (CI:31.6-39.9) in May. Last month exposure to
the guidelines was below 25% in all locations except television/radio where exposure increased from
33% (CI:28.8-36.2) in December to 65% (CI:61.2-68.3) in January. Awareness and knowledge of
guidelines was lowest in social grade DE and this gap remained after publication.
Conclusions: Publication of new or revised lower risk drinking guidelines can improve drinkers’
knowledge of these guidelines within all sociodemographic groups; however, in the absence of
sustained promotional activity, positive effects may not be maintained and social inequalities in
awareness and knowledge of guidelines are likely to persist
The Square-Lattice Heisenberg Antiferromagnet at Very Large Correlation Lengths
The correlation length of the square-lattice spin-1/2 Heisenberg
antiferromagnet is studied in the low-temperature (asymptotic-scaling) regime.
Our novel approach combines a very efficient loop cluster algorithm --
operating directly in the Euclidean time continuum -- with finite-size scaling.
This enables us to probe correlation lengths up to
lattice spacings -- more than three orders of magnitude larger than any
previous study. We resolve a conundrum concerning the applicability of
asymptotic-scaling formulae to experimentally- and numerically-determined
correlation lengths, and arrive at a very precise determination of the
low-energy observables. Our results have direct implications for the
zero-temperature behavior of spin-1/2 ladders.Comment: 12 pages, RevTeX, plus two Postscript figures. Some minor
modifications for final submission to Physical Review Letters. (accepted by
PRL
Preclinical correction of human Fanconi anemia complementation group A bone marrow cells using a safety-modified lentiviral vector.
One of the major hurdles for the development of gene therapy for Fanconi anemia (FA) is the increased sensitivity of FA stem cells to free radical-induced DNA damage during ex vivo culture and manipulation. To minimize this damage, we have developed a brief transduction procedure for lentivirus vector-mediated transduction of hematopoietic progenitor cells from patients with Fanconi anemia complementation group A (FANCA). The lentiviral vector FancA-sW contains the phosphoglycerate kinase promoter, the FANCA cDNA, and a synthetic, safety-modified woodchuck post transcriptional regulatory element (sW). Bone marrow mononuclear cells or purified CD34(+) cells from patients with FANCA were transduced in an overnight culture on recombinant fibronectin peptide CH-296, in low (5%) oxygen, with the reducing agent, N-acetyl-L-cysteine (NAC), and a combination of growth factors, granulocyte colony-stimulating factor (G-CSF), Flt3 ligand, stem cell factor, and thrombopoietin. Transduced cells plated in methylcellulose in hypoxia with NAC showed increased colony formation compared with 21% oxygen without NAC (P<0.03), showed increased resistance to mitomycin C compared with green fluorescent protein (GFP) vector-transduced controls (P<0.007), and increased survival. Thus, combining short transduction and reducing oxidative stress may enhance the viability and engraftment of gene-corrected cells in patients with FANCA
Use of aids for smoking cessation and alcohol reduction: A population survey of adults in England.
BACKGROUND: It is important for policy planning to chart the methods smokers and high-risk drinkers use to help them change their behaviour. This study assessed prevalence of use, and characteristics of users, of support for smoking cessation and alcohol reduction in England. METHODS: Data were used from the Smoking and Alcohol Toolkit Studies, which involve monthly face-to-face computer-assisted interviews of adults aged 16+ in England. We included data collected between June 2014 and July 2015 on 1600 smokers who had made at least one quit attempt and 911 high-risk drinkers (defined as scores >8+ on the full AUDIT or 5+ on questions 1-3 of the AUDIT-C) who had made an attempt to cut down in the past 12 months. Participants provided information on their socio-demographic characteristics and use of aids during their most recent quit attempt including pharmacotherapy, face-to-face counselling, telephone support, self-help materials (digital and printed), and complementary medicine. RESULTS: A total of 60.3% of smokers used aids in the past year, compared with just 14.9% of high-risk drinkers. Use of pharmacotherapy was high among smokers and very low among drinkers (56.0%versus1.2%). Use of other aids was low for both behaviours: face-to-face counselling (2.6%versus4.8%), self-help materials (1.4%versus4.1%) and complementary medicine (1.0%versus0.5%). Use of aids was more common among smokers aged 25-54 compared with 16-24 year olds (25-34,ORadj1.49,p = 0.012; 35-44,ORadj1.93,p 10 relative to 20,ORadj4.23,p = 0.001), and less common among ethnic minorities (ORadj0.69,p = 0.026). For alcohol reduction, use of aids was higher among ethnic minority groups (ORadj2.41;p = 0.015), and those of social-grade D/E relative to AB (ORadj2.29,p = 0.012&ORadj3.13,p < 0.001). CONCLUSION: In England, the use of pharmacotherapy is prevalent for smoking cessation but not alcohol reduction. Other aids are used at a low rate, with face-to-face counselling being more common for alcohol reduction than smoking cessation
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