1,061 research outputs found
Instability of Myelin Tubes under Dehydration: deswelling of layered cylindrical structures
We report experimental observations of an undulational instability of myelin
figures. Motivated by this, we examine theoretically the deformation and
possible instability of concentric, cylindrical, multi-lamellar membrane
structures. Under conditions of osmotic stress (swelling or dehydration), we
find a stable, deformed state in which the layer deformation is given by \delta
R ~ r^{\sqrt{B_A/(hB)}}, where B_A is the area compression modulus, B is the
inter-layer compression modulus, and h is the repeat distance of layers. Also,
above a finite threshold of dehydration (or osmotic stress), we find that the
system becomes unstable to undulations, first with a characteristic wavelength
of order \sqrt{xi d_0}, where xi is the standard smectic penetration depth and
d_0 is the thickness of dehydrated region.Comment: 5 pages + 3 figures [revtex 4
Quantum Structure in Cognition: Why and How Concepts are Entangled
One of us has recently elaborated a theory for modelling concepts that uses
the state context property (SCoP) formalism, i.e. a generalization of the
quantum formalism. This formalism incorporates context into the mathematical
structure used to represent a concept, and thereby models how context
influences the typicality of a single exemplar and the applicability of a
single property of a concept, which provides a solution of the 'Pet-Fish
problem' and other difficulties occurring in concept theory. Then, a quantum
model has been worked out which reproduces the membership weights of several
exemplars of concepts and their combinations. We show in this paper that a
further relevant effect appears in a natural way whenever two or more concepts
combine, namely, 'entanglement'. The presence of entanglement is explicitly
revealed by considering a specific example with two concepts, constructing some
Bell's inequalities for this example, testing them in a real experiment with
test subjects, and finally proving that Bell's inequalities are violated in
this case. We show that the intrinsic and unavoidable character of entanglement
can be explained in terms of the weights of the exemplars of the combined
concept with respect to the weights of the exemplars of the component concepts.Comment: 10 page
Topological Defects in Gravitational Lensing Shear Fields
Shear fields due to weak gravitational lensing have characteristic coherent
patterns. We describe the topological defects in shear fields in terms of the
curvature of the surface described by the lensing potential. A simple
interpretation of the characteristic defects is given in terms of the the
umbilical points of the potential surface produced by ellipsoidal halos. We
show simulated lensing shear maps and point out the typical defect
configurations. Finally, we show how statistical properties such as the
abundance of defects can be expressed in terms of the correlation function of
the lensing potential.Comment: 17 pages, 4 figure
Global persistence exponent of the two-dimensional Blume-Capel model
The global persistence exponent is calculated for the
two-dimensional Blume-Capel model following a quench to the critical point from
both disordered states and such with small initial magnetizations.
Estimates are obtained for the nonequilibrium critical dynamics on the
critical line and at the tricritical point.
Ising-like universality is observed along the critical line and a different
value is found at the tricritical point.Comment: 7 pages with 3 figure
The serum proteome of Atlantic salmon, Salmo salar, during pancreas disease (PD) following infection with salmonid alphavirus subtype 3 (SAV3)
Salmonid alphavirus is the aetological agent of pancreas disease (PD) in marine Atlantic salmon, Salmo salar, and rainbow trout, Oncorhynchus mykiss, with most outbreaks in Norway caused by SAV subtype 3 (SAV3). This atypical alphavirus is transmitted horizontally causing a significant economic impact on the aquaculture industry. This histopathological and proteomic study, using an established cohabitational experimental model, investigated the correlation between tissue damage during PD and a number of serum proteins associated with these pathologies in Atlantic salmon. The proteins were identified by two-dimensional electrophoresis, trypsin digest and peptide MS/MS fingerprinting. A number of humoral components of immunity which may act as biomarkers of the disease were also identified. For example, creatine kinase, enolase and malate dehydrogenase serum concentrations were shown to correlate with pathology during PD. In contrast, hemopexin, transferrin, and apolipoprotein, amongst others, altered during later stages of the disease and did not correlate with tissue pathologies. This approach has given new insight into not only PD but also fish disease as a whole, by characterisation of the protein response to infection, through pathological processes to tissue recovery.
Biological significance:
Salmonid alphavirus causes pancreas disease (PD) in Atlantic salmon, Salmo salar, and has a major economic impact on the aquaculture industry. A proteomic investigation of the change to the serum proteome during PD has been made with an established experimental model of the disease. Serum proteins were identified by two-dimensional electrophoresis, trypsin digest and peptide MS/MS fingerprinting with 72 protein spots being shown to alter significantly over the 12 week period of the infection. The concentrations of certain proteins in serum such as creatine kinase, enolase and malate dehydrogenase were shown to correlate with tissue pathology while other proteins such as hemopexin, transferrin, and apolipoprotein, altered in concentration during later stages of the disease and did not correlate with tissue pathologies. The protein response to infection may be used to monitor disease progression and enhance understanding of the pathology of PD
Infrared problem for the Nelson model on static space-times
We consider the Nelson model with variable coefficients and investigate the
problem of existence of a ground state and the removal of the ultraviolet
cutoff. Nelson models with variable coefficients arise when one replaces in the
usual Nelson model the flat Minkowski metric by a static metric, allowing also
the boson mass to depend on position. A physical example is obtained by
quantizing the Klein-Gordon equation on a static space-time coupled with a
non-relativistic particle. We investigate the existence of a ground state of
the Hamiltonian in the presence of the infrared problem, i.e. assuming that the
boson mass tends to 0 at infinity
Universality and scaling study of the critical behavior of the two-dimensional Blume-Capel model in short-time dynamics
In this paper we study the short-time behavior of the Blume-Capel model at
the tricritical point as well as along the second order critical line. Dynamic
and static exponents are estimated by exploring scaling relations for the
magnetization and its moments at early stage of the dynamic evolution. Our
estimates for the dynamic exponents, at the tricritical point, are and .Comment: 12 pages, 9 figure
Thermoluminescence, photoluminescence and optically stimulated luminescence characteristics of CaSO4:Eu phosphor: experimental and density functional theory (DFT) investigations
The CaSO4:Eu phosphor in nanocrystalline form was obtained by chemical method. The sample was annealed at various temperatures and quenched. The structural, electronic and optical properties are studied using various experimental techniques. As synthesized CaSO4:Eu particles have nanorod shapes with diameter of ~15 nm and length of ~250 nm. After annealing (at around 900 °C) a significant increase in their size (~2–4 μm) with phase transformation from hexagonal to orthorhombic was observed. Thermoluminescence (TL) and optically stimulated luminescence (OSL) intensities were found to increase with temperature up to 900 °C and decrease thereafter for 1 Gy of test dose of β-rays from 90Sr-90Yr source. However, the maximum OSL sensitivity was found to be more than that of CaSO4:Eu microcrystalline phosphor (prepared by acid recrystallization method) contrary to the usually found in the literature but much less than that of commercially available α-Al2O3:C phosphor. The activation energy for thermally assisted OSL process was found to be 0.0572 ± 0.0028 eV. The dose ranges of TL and OSL response was found from 0.04 Gy to 100 Gy and 0.02 Gy–100 Gy, respectively. The experimental results are also correlated with computational calculations based on density functional theory (DFT). The crystal structures and electronic structures of both hexagonal and orthorhombic CaSO4 and CaSO4:Eu materials show that they are direct band gap (5.67–5.86 eV) insulators, with Ca2+ substitution by Eu2+ found to introduce donor states in the band gap near Fermi level and the valence band edge of CaSO4 on doping with Eu2+ impurity ions
Equidistribution of zeros of holomorphic sections in the non compact setting
We consider N-tensor powers of a positive Hermitian line bundle L over a
non-compact complex manifold X. In the compact case, B. Shiffman and S.
Zelditch proved that the zeros of random sections become asymptotically
uniformly distributed with respect to the natural measure coming from the
curvature of L, as N tends to infinity. Under certain boundedness assumptions
on the curvature of the canonical line bundle of X and on the Chern form of L
we prove a non-compact version of this result. We give various applications,
including the limiting distribution of zeros of cusp forms with respect to the
principal congruence subgroups of SL2(Z) and to the hyperbolic measure, the
higher dimensional case of arithmetic quotients and the case of orthogonal
polynomials with weights at infinity. We also give estimates for the speed of
convergence of the currents of integration on the zero-divisors.Comment: 25 pages; v.2 is a final update to agree with the published pape
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