6,501 research outputs found
Magnetic field splitting of the spin-resonance in CeCoIn5
Neutron scattering in strong magnetic fields is used to show the
spin-resonance in superconducting CeCoIn5 (Tc=2.3 K) is a doublet. The
underdamped resonance (\hbar \Gamma=0.069 \pm 0.019 meV) Zeeman splits into two
modes at E_{\pm}=\hbar \Omega_{0}\pm g\mu_{B} \mu_{0}H with g=0.96 \pm 0.05. A
linear extrapolation of the lower peak reaches zero energy at 11.2 \pm 0.5 T,
near the critical field for the incommensurate "Q-phase" indicating that the
Q-phase is a bose condensate of spin excitons.Comment: 5 pages, 4 figure
Generalized Pseudopotentials for Higher Partial Wave Scattering
We derive a generalized zero-range pseudopotential applicable to all partial
wave solutions to the Schroedinger equation based on a delta-shell potential in
the limit that the shell radius approaches zero. This properly models all
higher order multipole moments not accounted for with a monopolar delta
function at the origin, as used in the familiar Fermi pseudopotential for
s-wave scattering. By making the strength of the potential energy dependent, we
derive self-consistent solutions for the entire energy spectrum of the
realistic potential. We apply this to study two particles in an isotropic
harmonic trap, interacting through a central potential, and derive analytic
expressions for the energy eigenstates and eigenvalues.Comment: RevTeX 4 pages, 1 figure, final published versio
Mapuera virus, a rubulavirus that inhibits interferon signalling in a wide variety of mammalian cells without degrading STATs
Mapuera virus (MPRV) is a paramyxovirus that was originally isolated from bats, but its host range remains unknown. It was classified as a member of the genus Rubulavirus on the basis of structural and genetic features. Like other rubulaviruses it encodes a V protein (MPRV/V) that functions as an interferon (IFN) antagonist. Here we show that MPRV/V differs from the IFN antagonists of other rubulaviruses in that it does not induce the proteasomal degradation of STAT proteins, key factors in the IFN signalling cascade. Rather, MPRV/V prevents the nuclear translocation of STATs in response to IFN stimulation and inhibits the formation of the transcription factor complex ISGF3. We also show that MPRV/V blocks IFN signalling in cells from diverse mammalian species and discuss the IFN response as a barrier to cross-species infections
Farmlan valuation for federal estate tax purposes : new provisions in the tax law
"Inflated land values have increased the impact of the federal estate tax on heirs of family farm operations. In an effort to alleviate the added tax burden, Congress included a special provision for farmlan valuation for federal estate tax purposes in the Tax Reform Act of 1976. This guide sheet explains the 'current use' provision and discusses its pros and cons."--First page.Stephen F. Matthews and Randall K. Stock (Department of Agricultural Economics, College of Agriculture)11/77/10
Dynamic concentration of motors in microtubule arrays
We present experimental and theoretical studies of the dynamics of molecular
motors in microtubule arrays and asters. By solving a convection-diffusion
equation we find that the density profile of motors in a two-dimensional aster
is characterized by continuously varying exponents. Simulations are used to
verify the assumptions of the continuum model. We observe the concentration
profiles of kinesin moving in quasi two-dimensional artificial asters by
fluorescent microscopy and compare with our theoretical results.Comment: 4pages, 4 figures revte
What is the meaning of the statistical hadronization model?
The statistical model of hadronization succeeds in reproducing particle
abundances and transverse momentum spectra in high energy collisions of
elementary particles as well as of heavy ions. Despite its apparent success,
the interpretation of these results is controversial and the validity of the
approach very often questioned. In this paper, we would like to summarize the
whole issue by first outlining a basic formulation of the model and then
comment on the main criticisms and different kinds of interpretations, with
special emphasis on the so-called "phase space dominance". While the ultimate
answer to the question why the statistical model works should certainly be
pursued, we stress that it is a priority to confirm or disprove the fundamental
scheme of the statistical model by performing some detailed tests on the rates
of exclusive channels at lower energy.Comment: 14 pages, to be published in the Proceedings of the International
workshop "Focus on multiplicity", Bari (Italy) June 17-19 200
Magnetism and superconductivity driven by identical 4 states in a heavy-fermion metal
The apparently inimical relationship between magnetism and superconductivity
has come under increasing scrutiny in a wide range of material classes, where
the free energy landscape conspires to bring them in close proximity to each
other. This is particularly the case when these phases microscopically
interpenetrate, though the manner in which this can be accomplished remains to
be fully comprehended. Here, we present combined measurements of elastic
neutron scattering, magnetotransport, and heat capacity on a prototypical heavy
fermion system, in which antiferromagnetism and superconductivity are observed.
Monitoring the response of these states to the presence of the other, as well
as to external thermal and magnetic perturbations, points to the possibility
that they emerge from different parts of the Fermi surface. This enables a
single 4 state to be both localized and itinerant, thus accounting for the
coexistence of magnetism and superconductivity.Comment: 4 pages, 4 figure
Exact quantum statistics for electronically nonadiabatic systems using continuous path variables
We derive an exact, continuous-variable path integral (PI) representation of
the canonical partition function for electronically nonadiabatic systems.
Utilizing the Stock-Thoss (ST) mapping for an N-level system, matrix elements
of the Boltzmann operator are expressed in Cartesian coordinates for both the
nuclear and electronic degrees of freedom. The PI discretization presented here
properly constrains the electronic Cartesian coordinates to the physical
subspace of the mapping. We numerically demonstrate that the resulting PI-ST
representation is exact for the calculation of equilibrium properties of
systems with coupled electronic and nuclear degrees of freedom. We further show
that the PI-ST formulation provides a natural means to initialize semiclassical
trajectories for the calculation of real-time thermal correlation functions,
which is numerically demonstrated in applications to a series of nonadiabatic
model systems.Comment: 10 pages, 6 figure
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