993 research outputs found
Theory of the critical state of low-dimensional spin glass
We analyse the critical region of finite-()-dimensional Ising spin glass,
in particular the limit of closely above the lower critical dimension
. At criticality the thermally active degrees of freedom are surfaces
(of width zero) enclosing clusters of spins that may reverse with respect to
their environment. The surfaces are organised in finite interacting structures.
These may be called {\em protodroplets}\/, since in the off-critical limit they
reduce to the Fisher and Huse droplets. This picture provides an explanation
for the phenomenon of critical chaos discovered earlier. It also implies that
the spin-spin and energy-energy correlation functions are multifractal and we
present scaling laws that describe them. Several of our results should be
verifiable in Monte Carlo studies at finite temperature in .Comment: RevTeX, 33 pages + 1 PostScript figure (uuencoded). Uses german.sty
and an input file def.tex, joined. Three additional figures may be requested
from the author
Generation of interface for an Allen-Cahn equation with nonlinear diffusion
In this note, we consider a nonlinear diffusion equation with a bistable
reaction term arising in population dynamics. Given a rather general initial
data, we investigate its behavior for small times as the reaction coefficient
tends to infinity: we prove a generation of interface property
Asymptotic statistics of the n-sided planar Poisson-Voronoi cell. I. Exact results
We achieve a detailed understanding of the -sided planar Poisson-Voronoi
cell in the limit of large . Let be the probability for a cell to
have sides. We construct the asymptotic expansion of up to
terms that vanish as . We obtain the statistics of the lengths of
the perimeter segments and of the angles between adjoining segments: to leading
order as , and after appropriate scaling, these become independent
random variables whose laws we determine; and to next order in they have
nontrivial long range correlations whose expressions we provide. The -sided
cell tends towards a circle of radius (n/4\pi\lambda)^{\half}, where
is the cell density; hence Lewis' law for the average area of
the -sided cell behaves as with . For
the cell perimeter, expressed as a function of the polar
angle , satisfies , where is known Gaussian
noise; we deduce from it the probability law for the perimeter's long
wavelength deviations from circularity. Many other quantities related to the
asymptotic cell shape become accessible to calculation.Comment: 54 pages, 3 figure
Development of Fungal Applications on Netting Substrates for Malaria Vector Control
Mosquito resistance to chemical insecticides is considered a serious threat for the sustainable use of contemporary malaria vector control methods. Fungal entomopathogens show potential as alternative biological control agents against (insecticide-resistant) anophelines. This study was designed to test whether the fungus, Beauveria bassiana, could be delivered to mosquitoes on netting materials that might be used in house screens, such as eave curtains. Tests were conducted to determine effects of formulation, application method, netting material, and nature of mosquito contact. Beauveria had a twice as high impact on Anopheles gambiae s.s. longevity when suspended in Shellsol solvent compared with Ondina oil (HR = 2.12, 95% confidence interval = 1.83–2.60, P 90% of mosquitoes within 10 d. Results indicate that the use of fungal spores dissolved in Shellsol and sprayed on small-meshed cotton eave curtain nets would be the most promising option for field implementation. Biological control with fungus-impregnated eave curtains could provide a means to target host-seeking mosquitoes upon house entry, and has potential for use in integrated vector management strategies, in combination with chemical vector control measures, to supplement malaria control in areas with high levels of insecticide resistance
Aardgas is prima trekkerbrandstof
Op proefbedrijf De Marke is een trekker (Fendt 306) omgebouwd naar een dual-fuel diesel-aardgas-trekker. De trekker heeft gedurende de onderzoeksperiode technisch goed gefunctioneerd. De lange vultijd van de gastanks op de trekker wordt wel als een praktisch probleem ervaren. Er kan niet snel even getankt worde
Note on a q-modified central limit theorem
A q-modified version of the central limit theorem due to Umarov et al.
affirms that q-Gaussians are attractors under addition and rescaling of certain
classes of strongly correlated random variables. The proof of this theorem
rests on a nonlinear q-modified Fourier transform. By exhibiting an invariance
property we show that this Fourier transform does not have an inverse. As a
consequence, the theorem falls short of achieving its stated goal.Comment: 10 pages, no figure
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