3,121 research outputs found
Modelling Electron Spin Accumulation in a Metallic Nanoparticle
A model describing spin-polarized current via discrete energy levels of a
metallic nanoparticle, which has strongly asymmetric tunnel contacts to two
ferromagnetic leads, is presented.
In absence of spin-relaxation, the model leads to a spin-accumulation in the
nanoparticle, a difference () between the chemical potentials of
spin-up and spin-down electrons, proportional to the current and the Julliere's
tunnel magnetoresistance. Taking into account an energy dependent
spin-relaxation rate , as a function of bias
voltage () exhibits a crossover from linear to a much weaker dependence,
when equals the spin-polarized current through the
nanoparticle. Assuming that the spin-relaxation takes place via electron-phonon
emission and Elliot-Yafet mechanism, the model leads to a crossover from linear
to dependence. The crossover explains recent measurements of the
saturation of the spin-polarized current with in Aluminum nanoparticles,
and leads to the spin-relaxation rate of in an Aluminum
nanoparticle of diameter , for a transition with an energy difference of
one level spacing.Comment: 37 pages, 7 figure
Water vapor radiometry research and development phase
This report describes the research and development phase for eight dual-channel water vapor radiometers constructed for the Crustal Dynamics Project at the Goddard Space Flight Center, Greenbelt, Maryland, and for the NASA Deep Space Network. These instruments were developed to demonstrate that the variable path delay imposed on microwave radio transmissions by atmospheric water vapor can be calibrated, particularly as this phenomenon affects very long baseline interferometry measurement systems. Water vapor radiometry technology can also be used in systems that involve moist air meteorology and propagation studies
Anyonic Realization of the Quantum Affine Lie Superalgebra U_q(A(M,N)^{(1)})
We give a realization of the quantum affine Lie superalgebras U_q(A(M,N))^(1)
in terms of anyons defined on a one or two-dimensional lattice, the deformation
parameter q being related to the statistical parameter of the anyons by q
= exp(i\pi\nu). The construction uses anyons contructed from usual fermionic
oscillators and deformed bosonic oscillators. As a byproduct, realization
deformed in any sector of the quantum superalgebras U_q(A(M,N)) is obtained.Comment: 14p LaTeX Document (should be run twice
In-vitro activity of OPC-17116 against more than 6000 consecutive clinical isolates: a multicentre international study
Spectrum in multi-species asymmetric simple exclusion process on a ring
The spectrum of Hamiltonian (Markov matrix) of a multi-species asymmetric
simple exclusion process on a ring is studied. The dynamical exponent
concerning the relaxation time is found to coincide with the one-species case.
It implies that the system belongs to the Kardar-Parisi-Zhang or
Edwards-Wilkinson universality classes depending on whether the hopping rate is
asymmetric or symmetric, respectively. Our derivation exploits a poset
structure of the particle sectors, leading to a new spectral duality and
inclusion relations. The Bethe ansatz integrability is also demonstrated.Comment: 46 pages, 9 figure
High Surface Area, Thermally Stable, Hydrophobic, Microporous, Rigid Gels Generated at Ambient from MeSi(OEt)3/(EtO)3SiCH2CH2Si(OEt)3 Mixtures by FââCatalyzed Hydrolysis
High surface area materials are of considerable interest for gas storage/capture, molecular sieving, catalyst supports, as well as for slowârelease drugâdelivery systems. We report here a very simple and fast route to very high surface area, mechanically robust, hydrophobic polymer gels prepared by fluorideâcatalyzed hydrolysis of mixtures of MeSi(OEt)3 and bisâtriethoxysilylethane (BTSE) at room temperature. These materials offer specific surface areas up to 1300â
m2âgâ1, peak pore sizes of 0.8â
nm and thermal stabilities above 200â°C. The gelation times and surface areas can be controlled by adjusting the solvent volume (dichloromethane), percent fluoride (as nBu4NF or TBAF) and the BTSE contents. Polymers with other corners and linkers were also explored. These materials will further expand the materials databank for use in vacuum insulation panels and as thermally stable release and capture media.Simple fluorideâcatalyzed polymerization of methyltriethoxysilane and bistriethyoxysilylethane leads to the formation of amorphous materials with little postâsynthesis processing. These materials have surface areas up to 1300â
m2âgâ1, densities as low as 0.06â
gâmLâ1 and nonâpolar solvent uptake of about 500â% by mass.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141416/1/chem201704941.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141416/2/chem201704941_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141416/3/chem201704941-sup-0001-misc_information.pd
Crystal energy functions via the charge in types A and C
The Ram-Yip formula for Macdonald polynomials (at t=0) provides a statistic
which we call charge. In types A and C it can be defined on tensor products of
Kashiwara-Nakashima single column crystals. In this paper we prove that the
charge is equal to the (negative of the) energy function on affine crystals.
The algorithm for computing charge is much simpler and can be more efficiently
computed than the recursive definition of energy in terms of the combinatorial
R-matrix.Comment: 25 pages; 1 figur
Transfer matrix eigenvalues of the anisotropic multiparametric U model
A multiparametric extension of the anisotropic U model is discussed which
maintains integrability. The R-matrix solving the Yang-Baxter equation is
obtained through a twisting construction applied to the underlying Uq(sl(2|1))
superalgebraic structure which introduces the additional free parameters that
arise in the model. Three forms of Bethe ansatz solution for the transfer
matrix eigenvalues are given which we show to be equivalent.Comment: 26 pages, no figures, LaTe
Integrable multiparametric quantum spin chains
Using Reshetikhin's construction for multiparametric quantum algebras we
obtain the associated multiparametric quantum spin chains. We show that under
certain restrictions these models can be mapped to quantum spin chains with
twisted boundary conditions. We illustrate how this general formalism applies
to construct multiparametric versions of the supersymmetric t-J and U models.Comment: 17 pages, RevTe
- âŠ