54,251 research outputs found
Crystal nuclei templated nanostructured membranes prepared by solvent crystallization and polymer migration
Currently, production of porous polymeric membranes for filtration is predominated by the phase-separation process. However, this method has reached its technological limit, and there have been no significant breakthrough over the last decade. Here we show, using polyvinylidene fluoride as a sample polymer, a new concept of membrane manufacturing by combining oriented green solvent crystallization and polymer migration is able to obtain high performance membranes with pure water permeation flux substantially higher than those with similar pore size prepared by conventional phase-separation processes. The new manufacturing procedure is governed by fewer operating parameters and is, thus, easier to control with reproducible results. Apart from the high water permeation flux, the prepared membranes also show excellent stable flux after fouling and superior mechanical properties of high pressure load and better abrasion resistance. These findings demonstrate the promise of a new concept for green manufacturing nanostructured polymeric membranes with high performances
Relatively hyperbolic groups, rapid decay algebras, and a generalization of the Bass conjecture
By deploying dense subalgebras of we generalize the Bass
conjecture in terms of Connes' cyclic homology theory. In particular, we
propose a stronger version of the -Bass Conjecture. We prove that
hyperbolic groups relative to finitely many subgroups, each of which posses the
polynomial conjugacy-bound property and nilpotent periodicity property, satisfy
the -Stronger-Bass Conjecture. Moreover, we determine the
conjugacy-bound for relatively hyperbolic groups and compute the cyclic
cohomology of the -algebra of any discrete group.Comment: 32 pages, 2 figures; added an appendix also by C. Ogl
Counting Form Factors of Twist-Two Operators
We present a simple method to count the number of hadronic form factors based
on the partial wave formalism and crossing symmetry. In particular, we show
that the number of independent nucleon form factors of spin-n, twist-2
operators (the vector current and energy-momentum tensor being special
examples) is n+1. These generalized form factors define the generalized
(off-forward) parton distributions that have been studied extensively in the
recent literature. In proving this result, we also show how the J^{PC} rules
for onium states arise in the helicity formalism.Comment: 7 pages, LaTeX (revtex
Dynamic simulations of water at constant chemical potential
The grand molecular dynamics (GMD) method has been extended and applied to examine the density dependence of the chemical potential of a three-site water model. The method couples a classical system to a chemical potential reservoir of particles via an ansatz Lagrangian. Equilibrium properties such as structure and thermodynamics, as well as dynamic properties such as time correlations and diffusion constants, in open systems at a constant chemical potential, are preserved with this method. The average number of molecules converges in a reasonable amount of computational effort and provides a way to estimate the chemical potential of a given model force field
Disentangling Intertwined Embedded States and Spin Effects in Light-Front Quantization
Naive light-front quantization, carried out by a light-front energy
integration of covariant amplitudes, is not guaranteed to generate the
corresponding Feynman amplitudes. In an explicit example we show that the
nonvalence contribution to the minus-component of the EM current of a meson
with fermion constituents has a persistent end-point singularity. Only after
this term is subtracted, the result is covariant and satisfies current
conservation. If the spin-1/2 constituents are replaced by spin zero ones, the
singularity does not occur and the result is, without any adjustment, identical
to the Feynman amplitude. Numerical estimates of valence and nonvalence
contributions are presented for the cases of fermion and boson constituents.Comment: 17 pages and 9 figure
INCREASING THE ACCURACY OF OPTION PRICING BY USING IMPLIED PARAMETERS RELATED TO HIGHER MOMENTS
The inaccuracy of the Black-Scholes formula arises from two aspects: the formula is for European options while most real option contracts are American; the formula is based on the assumption that underlying asset prices follow a lognormal distribution while in the real world asset prices cannot be described well by a lognormal distribution. We develop an American option pricing model that allows non-normality. The theoretical basis of the model is Gaussian quadrature and dynamic programming. The usual binomial and trinomial models are special cases. We use the Jarrow-Rudd formula and the relaxed binomial and trinomial tree models to imply the parameters related to the higher moments. The results demonstrate that using implied parameters related to the higher moments is more accurate than the restricted binomial and trinomial models that are commonly used.option pricing, volatility smile, Edgeworth series, Gaussian Quadrature, relaxed binomial and trinomial tree models, Marketing, Risk and Uncertainty,
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