51,271 research outputs found
Screening in Ionic Systems: Simulations for the Lebowitz Length
Simulations of the Lebowitz length, , are reported
for t he restricted primitive model hard-core (diameter ) 1:1 electrolyte
for densi ties and .
Finite-size eff ects are elucidated for the charge fluctuations in various
subdomains that serve to evaluate . On extrapolation to the
bulk limit for the low-density expansions (Bekiranov and
Fisher, 1998) are seen to fail badly when (with ). At highe r densities rises above the Debye
length, \xi_{\text{D}} \prop to \sqrt{T/\rho}, by 10-30% (upto ); the variation is portrayed fairly well by generalized
Debye-H\"{u}ckel theory (Lee and Fisher, 19 96). On approaching criticality at
fixed or fixed , remains finite with
but displays a
weak entropy-like singularity.Comment: 4 pages 5 figure
Fractal Droplets in Two Dimensional Spin Glasses
The two-dimensional Edwards-Anderson model with Gaussian bond distribution is
investigated at T=0 with a numerical method. Droplet excitations are directly
observed. It turns out that the averaged volume of droplets is proportional to
l^D with D = 1.80(2) where l is the spanning length of droplets, revealing
their fractal nature. The exponent characterizing the l dependence of the
droplet excitation energy is estimated to be -0.42(4), clearly different from
the stiffness exponent for domain wall excitations.Comment: 4 pages 4 figure
Current-voltage scaling of chiral and gauge-glass models of two-dimensional superconductors
The scaling behavior of the current-voltage characteristics of chiral and
gauge glass models of disordered superconductors, are studied numerically, in
two dimensions. For both models, the linear resistance is nonzero at finite
temperatures and the scaling analysis of the nonlinear resistivity is
consistent with a phase transition at T=0 temperature characterized by a
diverging correlation length and thermal critical
exponent . The values of , however, are found to be different
for the chiral and gauge glass models, suggesting different universality
classes, in contrast to the result obtained recently in three dimensions.Comment: 4 pages, 4 figures (included), to appear in Phys. Rev.
When is diabetes distress clinically meaningful?: establishing cut points for the Diabetes Distress Scale.
ObjectiveTo identify the pattern of relationships between the 17-item Diabetes Distress Scale (DDS17) and diabetes variables to establish scale cut points for high distress among patients with type 2 diabetes.Research design and methodsRecruited were 506 study 1 and 392 study 2 adults with type 2 diabetes from community medical groups. Multiple regression equations associated the DDS17, a 17-item scale that yields a mean-item score, with HbA(1c), diabetes self-efficacy, diet, and physical activity. Associations also were undertaken for the two-item DDS (DDS2) screener. Analyses included control variables, linear, and quadratic (curvilinear) DDS terms.ResultsSignificant quadratic effects occurred between the DDS17 and each diabetes variable, with increases in distress associated with poorer outcomes: study 1 HbA(1c) (P < 0.02), self-efficacy (P < 0.001), diet (P < 0.001), physical activity (P < 0.04); study 2 HbA(1c) (P < 0.03), self-efficacy (P < 0.004), diet (P < 0.04), physical activity (P = NS). Substantive curvilinear associations with all four variables in both studies began at unexpectedly low levels of DDS17: the slope increased linearly between scores 1 and 2, was more muted between 2 and 3, and reached a maximum between 3 and 4. This suggested three patient subgroups: little or no distress, <2.0; moderate distress, 2.0-2.9; high distress, ≥3.0. Parallel findings occurred for the DDS2.ConclusionsIn two samples of type 2 diabetic patients we found a consistent pattern of curvilinear relationships between the DDS and HbA(1c), diabetes self-efficacy, diet, and physical activity. The shape of these relationships suggests cut points for three patient groups: little or no, moderate, and high distress
Thermodynamic Casimir effects involving interacting field theories with zero modes
Systems with an O(n) symmetrical Hamiltonian are considered in a
-dimensional slab geometry of macroscopic lateral extension and finite
thickness that undergo a continuous bulk phase transition in the limit
. The effective forces induced by thermal fluctuations at and above
the bulk critical temperature (thermodynamic Casimir effect) are
investigated below the upper critical dimension by means of
field-theoretic renormalization group methods for the case of periodic and
special-special boundary conditions, where the latter correspond to the
critical enhancement of the surface interactions on both boundary planes. As
shown previously [\textit{Europhys. Lett.} \textbf{75}, 241 (2006)], the zero
modes that are present in Landau theory at make conventional
RG-improved perturbation theory in dimensions ill-defined. The
revised expansion introduced there is utilized to compute the scaling functions
of the excess free energy and the Casimir force for temperatures
T\geqT_{c,\infty} as functions of , where
is the bulk correlation length. Scaling functions of the
-dependent residual free energy per area are obtained whose
limits are in conformity with previous results for the Casimir amplitudes
to and display a more reasonable
small- behavior inasmuch as they approach the critical value
monotonically as .Comment: 23 pages, 10 figure
Fluctuating loops and glassy dynamics of a pinned line in two dimensions
We represent the slow, glassy equilibrium dynamics of a line in a
two-dimensional random potential landscape as driven by an array of
asymptotically independent two-state systems, or loops, fluctuating on all
length scales. The assumption of independence enables a fairly complete
analytic description. We obtain good agreement with Monte Carlo simulations
when the free energy barriers separating the two sides of a loop of size L are
drawn from a distribution whose width and mean scale as L^(1/3), in agreement
with recent results for scaling of such barriers.Comment: 11 pages, 4 Postscript figure
New varieties top 1967 yield tests
LARGE gains can result from using improved cereal varieties and in recent years activity in breeding varieties adapted to local conditions has increased.
The varieties available and their suitability for different areas and conditions need constant review
Varieties and time of sowing
THE extent to which seasonal conditions favour the various stages of plant development has a marked effect on cereal yields. Because varieties differ in their development they react in different ways to a particular seasonal pattern
Probability distribution of the order parameter in the directed percolation universality class
The probability distributions of the order parameter for two models in the
directed percolation universality class were evaluated. Monte Carlo simulations
have been performed for the one-dimensional generalized contact process and the
Domany-Kinzel cellular automaton. In both cases, the density of active sites
was chosen as the order parameter. The criticality of those models was obtained
by solely using the corresponding probability distribution function. It has
been shown that the present method, which has been successfully employed in
treating equilibrium systems, is indeed also useful in the study of
nonequilibrium phase transitions.Comment: 6 pages, 4 figure
Cereal yield tests in 1966
FARMER\u27S main guide in his choice of a cereal variety is its capacity to produce high overall yields of saleable grain over many years in a particular district
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