561 research outputs found
Temperature phase transition and an effective expansion parameter in the O(N)-model
The temperature phase transition in the N-component scalar field theory with
spontaneous symmetry breaking is investigated in the perturbative approach. The
second Legendre transform is used together with the consideration of the gap
equations in the extrema of the free energy. Resummations are performed on the
super daisy level and beyond. The phase transition turns out to be weakly of
first order. The diagrams beyond the super daisy ones which are calculated
correspond to next-to-next-to-leading order in 1/N. It is shown that these
diagrams do not alter the phase transition qualitatively. In the limit N goes
to infinity the phase transition becomes second order. A comparison with other
approaches is done.Comment: 28 pages, 5 figures, corrected for some misprints, unnecessary
section remove
Alloy surface segregation in reactive environments: A first-principles atomistic thermodynamics study of Ag3Pd(111) in oxygen atmospheres
We present a first-principles atomistic thermodynamics framework to describe
the structure, composition and segregation profile of an alloy surface in
contact with a (reactive) environment. The method is illustrated with the
application to a Ag3Pd(111) surface in an oxygen atmosphere, and we analyze
trends in segregation, adsorption and surface free energies. We observe a wide
range of oxygen adsorption energies on the various alloy surface
configurations, including binding that is stronger than on a Pd(111) surface
and weaker than that on a Ag(111) surface. This and the consideration of even
small amounts of non-stoichiometries in the ordered bulk alloy are found to be
crucial to accurately model the Pd surface segregation occurring in
increasingly O-rich gas phases.Comment: 13 pages including 6 figures; related publications can be found at
http://www.fhi-berlin.mpg.de/th/th.htm
The Role of the Magnetic Field in the Interstellar Medium of the Post-Starburst Dwarf Irregular Galaxy NGC 1569
(abridged) NGC 1569 is a nearby dwarf irregular galaxy which underwent an
intense burst of star formation 10 to 40 Myr ago. We present observations that
reach surface brightnesses two to eighty times fainter than previous radio
continuum observations and the first radio continuum polarization observations.
These observations allow us to probe the relationship of the magnetic field of
NGC 1569 to the rest of its interstellar medium. We confirm the presence of an
extended radio continuum halo at 20 cm and see for the first time the radio
continuum feature associated with the western Halpha arm at wavelengths shorter
than 20cm. The spectral index trends in this galaxy support the theory that
there is a convective wind at work in this galaxy. We derive a total magnetic
field strength of 38 microG in the central regions and 10-15 microG in the
halo. The magnetic field is largely random in the center of the galaxy; the
uniform field is ~3-9 microG and is strongest in the halo. We find that the
magnetic pressure is the same order of magnitude but, in general, a factor of a
few less than the other components of the interstellar medium in this galaxy.
The uniform magnetic field in NGC 1569 is closely associated with the Halpha
bubbles and filaments. We suggest that a supernova-driven dynamo may be
operating in this galaxy. The outflow of hot gas from NGC 1569 is clearly
shaping the magnetic field, but the magnetic field in turn may be aiding the
outflow by channeling gas out of the disk of the galaxy. Dwarf galaxies with
extended radio continuum halos like that of NGC 1569 may play an important role
in magnetizing the intergalactic medium.Comment: ApJ accepted. 56 pages, 14 figures (low resolution), 8 tables.
Version with high resolution figures at
http://www.astro.virginia.edu/~aak8t/data/n1569/ms.pd
Estimating the cost-effectiveness of detecting cases of chronic hepatitis C infection on reception into prison
Background
In England and Wales where less than 1% of the population are Injecting drug users (IDUs), 97% of HCV reports are attributed to injecting drug use. As over 60% of the IDU population will have been imprisoned by the age of 30 years, prison may provide a good location in which to offer HCV screening and treatment. The aim of this work is to examine the cost effectiveness of a number of alternative HCV case-finding strategies on prison reception
Methods
A decision analysis model embedded in a model of the flow of IDUs through prison was used to estimate the cost effectiveness of a number of alternative case-finding strategies. The model estimates the average cost of identifying a new case of HCV from the perspective of the health care provider and how these estimates may evolve over time.
Results
The results suggest that administering verbal screening for a past positive HCV test and for ever having engaged in illicit drug use prior to the administering of ELISA and PCR tests can have a significant impact on the cost effectiveness of HCV case-finding strategies on prison reception; the discounted cost in 2017 being ÂŁ2,102 per new HCV case detected compared to ÂŁ3,107 when no verbal screening is employed.
Conclusion
The work here demonstrates the importance of targeting those individuals that have ever engaged in illicit drug use for HCV testing in prisons, these individuals can then be targeted for future intervention measures such as treatment or monitored to prevent future transmission
Another exact inflationary solution
A new closed-form inflationary solution is given for a hyperbolic interaction
potential. The method used to arrive at this solution is outlined as it appears
possible to generate additional sets of equations which satisfy the model. In
addition a new form of decaying cosmological constant is presented.Comment: 10 pages, 0 figure
Developing Crisis Training Software for Local Governments – From User Needs to Generic Requirements
In this paper we analyze and present the generic requirements identified for a software aiming at supporting crisis management training in local governments. The generic requirements are divided into overall requirements, requirements connected to the trainer’s role and requirements connected to the trainee’s role. Moreover, the requirements are mapped to problems as well as opportunities. Finally, we present examples of elaborations of the addressed requirements based on software design considerations. In our work we applied a design science approach and the artifact presented in this paper is a list of generic requirement. The presented requirements and the systems development process used, provide guidelines for systems analysts and developers in future systems development projects aiming at constructing new software for crisis management training
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The ribosomal protein genes and Minute loci of Drosophila melanogaster.
BACKGROUND: Mutations in genes encoding ribosomal proteins (RPs) have been shown to cause an array of cellular and developmental defects in a variety of organisms. In Drosophila melanogaster, disruption of RP genes can result in the 'Minute' syndrome of dominant, haploinsufficient phenotypes, which include prolonged development, short and thin bristles, and poor fertility and viability. While more than 50 Minute loci have been defined genetically, only 15 have so far been characterized molecularly and shown to correspond to RP genes. RESULTS: We combined bioinformatic and genetic approaches to conduct a systematic analysis of the relationship between RP genes and Minute loci. First, we identified 88 genes encoding 79 different cytoplasmic RPs (CRPs) and 75 genes encoding distinct mitochondrial RPs (MRPs). Interestingly, nine CRP genes are present as duplicates and, while all appear to be functional, one member of each gene pair has relatively limited expression. Next, we defined 65 discrete Minute loci by genetic criteria. Of these, 64 correspond to, or very likely correspond to, CRP genes; the single non-CRP-encoding Minute gene encodes a translation initiation factor subunit. Significantly, MRP genes and more than 20 CRP genes do not correspond to Minute loci. CONCLUSION: This work answers a longstanding question about the molecular nature of Minute loci and suggests that Minute phenotypes arise from suboptimal protein synthesis resulting from reduced levels of cytoribosomes. Furthermore, by identifying the majority of haplolethal and haplosterile loci at the molecular level, our data will directly benefit efforts to attain complete deletion coverage of the D. melanogaster genome.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are
A unique therapeutic approach to emesis and itch with a proanthocyanidin-rich genonutrient
<p>Abstract</p> <p>Background</p> <p>We examined the therapeutic potential of a proprietary <it>Croton palanostigma </it>extract (Zangrado<sup>®</sup>) in the management of emesis and itch.</p> <p>Methods</p> <p>Emesis was induced in ferrets with morphine-6-glucuronide (0.05 mg/kg sc) in the presence of Zangrado (3 mg/kg, ip) and the cannabinoid receptor 1 antagonist, AM 251 (5 mg/kg, ip). Topical Zangrado (1%) was assessed for anti-pruretic actions in the 5-HT-induced scratching model in rats and evaluated in capsaicin-induced gastric hyperemia as measured by laser doppler flow. In the <it>Apc</it><sup><it>Min</it></sup>mouse model of precancerous adenomatosis polyposis, mice received Zangrado (100 μg/ml in drinking water) from the age of 6 – 16 weeks for effects on polyp number. In RAW 264.7 cells Zangrado was examined for effects on lipopolysaccharide-induced nitrite production.</p> <p>Results</p> <p>Zangrado was a highly effective anti-emetic, reducing morphine-induced vomiting and retching by 77%. These benefits were not associated with sedation or hypothermia and were not reversed by cannabinoid receptor antagonism. Itch responses were blocked in both the morphine and 5-HT models. Zangrado did not exacerbate the <it>Apc</it><sup><it>Min</it></sup>condition rather health was improved. Capsaicin-induced hyperemia was blocked by Zangrado, which also attenuated the production of nitric oxide by activated macrophages.</p> <p>Conclusion</p> <p>Zangrado is an effective anti-emetic and anti-itch therapy that is devoid of common side-effects, cannabinoid-independent and broadly suppresses sensory afferent nerve activation. This complementary medicine represents a promising new approach to the management of nausea, itch and irritable bowel syndrome.</p
Evolution of the Scale Factor with a Variable Cosmological Term
Evolution of the scale factor a(t) in Friedmann models (those with zero
pressure and a constant cosmological term Lambda) is well understood, and
elegantly summarized in the review of Felten and Isaacman [Rev. Mod. Phys. 58,
689 (1986)]. Developments in particle physics and inflationary theory, however,
increasingly indicate that Lambda ought to be treated as a dynamical quantity.
We revisit the evolution of the scale factor with a variable Lambda-term, and
also generalize the treatment to include nonzero pressure. New solutions are
obtained and evaluated using a variety of observational criteria. Existing
arguments for the inevitability of a big bang (ie., an initial state with a=0)
are substantially weakened, and can be evaded in some cases with Lambda_0 (the
present value of Lambda) well below current experimental limits.Comment: 29 pages, 12 figures (not included), LaTeX, uses Phys Rev D style
files (revtex.cls, revtex.sty, aps.sty, aps10.sty, prabib.sty). To appear in
Phys Rev
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