6,088 research outputs found
The Specific Heat of a Ferromagnetic Film.
We analyze the specific heat for the vector model on a -dimensional
film geometry of thickness using ``environmentally friendly''
renormalization. We consider periodic, Dirichlet and antiperiodic boundary
conditions, deriving expressions for the specific heat and an effective
specific heat exponent, \alpha\ef. In the case of , for , by
matching to the exact exponent of the two dimensional Ising model we capture
the crossover for \xi_L\ra\infty between power law behaviour in the limit
{L\over\xi_L}\ra\infty and logarithmic behaviour in the limit
{L\over\xi_L}\ra0 for fixed , where is the correlation length in
the transverse dimensions.Comment: 21 pages of Plain TeX. Postscript figures available upon request from
[email protected]
Dimensional Crossover in the Large N Limit
We consider dimensional crossover for an Landau-Ginzburg-Wilson model
on a -dimensional film geometry of thickness in the large -limit. We
calculate the full universal crossover scaling forms for the free energy and
the equation of state. We compare the results obtained using ``environmentally
friendly'' renormalization with those found using a direct, non-renormalization
group approach. A set of effective critical exponents are calculated and
scaling laws for these exponents are shown to hold exactly, thereby yielding
non-trivial relations between the various thermodynamic scaling functions.Comment: 25 pages of PlainTe
Field Theory Entropy, the -theorem and the Renormalization Group
We consider entropy and relative entropy in Field theory and establish
relevant monotonicity properties with respect to the couplings. The relative
entropy in a field theory with a hierarchy of renormalization group fixed
points ranks the fixed points, the lowest relative entropy being assigned to
the highest multicritical point. We argue that as a consequence of a
generalized theorem Wilsonian RG flows induce an increase in entropy and
propose the relative entropy as the natural quantity which increases from one
fixed point to another in more than two dimensions.Comment: 25 pages, plain TeX (macros included), 6 ps figures. Addition in
title. Entropy of cutoff Gaussian model modified in section 4 to avoid a
divergence. Therefore, last figure modified. Other minor changes to improve
readability. Version to appear in Phys. Rev.
A New Method of Measuring 81Kr and 85Kr Abundances in Environmental Samples
We demonstrate a new method for determining the 81Kr/Kr ratio in
environmental samples based upon two measurements: the 85Kr/81Kr ratio measured
by Atom Trap Trace Analysis (ATTA) and the 85Kr/Kr ratio measured by Low-Level
Counting (LLC). This method can be used to determine the mean residence time of
groundwater in the range of 10^5 - 10^6 a. It requires a sample of 100 micro-l
STP of Kr extracted from approximately two tons of water. With modern
atmospheric Kr samples, we demonstrate that the ratios measured by ATTA and LLC
are directly proportional to each other within the measurement error of +/-
10%; we calibrate the 81Kr/Kr ratio of modern air measured using this method;
and we show that the 81Kr/Kr ratios of samples extracted from air before and
after the development of the nuclear industry are identical within the
measurement error
The Change in Prevalence of Campylobacter on Chicken Carcasses During Processing: A Systematic Review
A systematic review was conducted to evaluate the change in prevalence of Campylobacter on chicken carcasses during processing. A structured literature search of 8 electronic databases using the key words for Campylobacter, chicken, and processing identified 1,734 unique citations. Abstracts were screened for relevance by 2 independent reviewers. Thirty-two studies described prevalence at more than one stage during processing and were included in this review. Of the studies that described the prevalence of Campylobacter on carcasses before and after specific stages of processing, the chilling stage had the greatest number of studies (9), followed by washing (6), defeathering (4), scalding (2), and evisceration (1). Studies that sampled before and after scalding or chilling, or both, showed that the prevalence of Campylobacter generally decreased immediately after the stage (scalding: 20.0 to 40.0% decrease; chilling: 100.0% decrease to 26.6% increase). The prevalence of Campylobacter increased after defeathering (10.0 to 72.0%) and evisceration (15.0%). The prevalence after washing was inconsistent among studies (23.0% decrease to 13.3% increase). Eleven studies reported the concentration of Campylobacter, as well as, or instead of, the prevalence. Studies that sampled before and after specific stages of processing showed that the concentration of Campylobacter decreased after scalding (minimum decrease of 1.3 cfu/g, maximum decrease of 2.9 cfu/mL), evisceration (0.3 cfu/g), washing (minimum 0.3 cfu/mL, maximum 1.1 cfu/mL), and chilling (minimum 0.2 cfu/g, maximum 1.7 cfu/carcass) and increased after defeathering (minimum 0.4 cfu/g, maximum 2.9 cfu/mL). Available evidence is sparse and suggests more data are needed to understand the magnitude and mechanism by which the prevalence and concentration of Campylobacter changes during processing. This understanding should help researchers and program developers identify the most likely points in processing to implement effective control efforts. For example, if contamination will occur during defeathering and likely during evisceration, critical control points postevisceration are likely to have a greater effect on the end product going to the consumer
Control of Cheese Microflora using Bacteriocins.
End of Project ReportBacteriocins are proteins, produced by some bacteria which are capable of
inhibiting other bacteria. The overall aim of this project was the
development and exploitation of bacteriocins such as Lacticin 3147
(produced by a food-grade microorganism), as biological tools to control the
microflora of foods.
Lacticin 3147-producing strains were evaluated for their ability to improve
the microbial quality of a variety of dairy products and in particular,
Cheddar cheese. The manipulation of cheese flora using bacteriocins should
offer manufacturers greater control in the consistency and quality of the final
product, in addition to improving its safety.
In concert with these studies, Lacticin 3147 was studied in detail at the
molecular level resulting in its biochemical and genetic analysis. These
studies have demonstrated the complexity and uniqueness of this potent
antimicrobial.Department of Agriculture, Food and the Marin
Spontaneous symmetry breakdown in fuzzy spheres
We study and analyse the questions regarding breakdown of global symmetry on
noncommutative sphere. We demonstrate this by considering a complex scalar
field on a fuzzy sphere and isolating Goldstone modes. We discuss the role of
nonlocal interactions present in these through geometrical considerations.Comment: 8 pages, 7 figure
Simulational Study on Dimensionality-Dependence of Heat Conduction
Heat conduction phenomena are studied theoretically using computer
simulation. The systems are crystal with nonlinear interaction, and fluid of
hard-core particles. Quasi-one-dimensional system of the size of is simulated. Heat baths are put in both end:
one has higher temperature than the other. In the crystal case, the interaction
potential has fourth-order non-linear term in addition to the harmonic
term, and Nose-Hoover method is used for the heat baths. In the fluid case,
stochastic boundary condition is charged, which works as the heat baths.
Fourier-type heat conduction is reproduced both in crystal and fluid models in
three-dimensional system, but it is not observed in lower dimensional system.
Autocorrelation function of heat flux is also observed and long-time tails of
the form of , where denotes the dimensionality of the
system, are confirmed.Comment: 4 pages including 3 figure
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