716 research outputs found
Exact spin dynamics of the 1/r^2 supersymmetric t-J model in a magnetic field
The dynamical spin structure factor S^{zz}(Q,omega) in the small momentum
region is derived analytically for the one-dimensional supersymmetric t-J model
with 1/r^2 interaction. Strong spin-charge separation is found in the spin
dynamics. The structure factor S^{zz}(Q,omega) with a given spin polarization
does not depend on the electron density in the small momentum region. In the
thermodynamic limit, only two spinons and one antispinon (magnon) contribute to
S^{zz}(Q,omega). These results are derived via solution of the SU(2,1)
Sutherland model in the strong coupling limit.Comment: 20 pages, 8 figures. Accepted for publication in J.Phys.
Basic properties of three-leg Heisenberg tube
We study three-leg antiferromagnetic Heisenberg model with the periodic
boundary conditions in the rung direction. Since the rungs form regular
triangles, spin frustration is induced. We use the density-matrix
renormalization group method to investigate the ground state. We find that the
spin excitations are always gapped to remove the spin frustration as long as
the rung coupling is nonzero. We also visibly confirm spin-Peierls dimerization
order in the leg direction. Both the spin gap and the dimerization order are
basically enhanced as the rung coupling increases.Comment: 4 pages, 2 figure
"Hot Electron Spectra in Plain, Cone and Integrated Targets for FIREX-I Using Electron Spectrometer"
Interaction and thermodynamics of spinons in the XX chain
The mapping between the fermion and spinon compositions of eigenstates in the
one-dimensional spin-1/2 XX model on a lattice with N sites is used to describe
the spinon interaction from two different perspectives: (i) For finite N the
energy of all eigenstates is expressed as a function of spinon momenta and
spinon spins, which, in turn, are solutions of a set of Bethe ansatz equations.
The latter are the basis of an exact thermodynamic analysis in the spinon
representation of the XX model. (ii) For N -> infinity the energy per site of
spinon configurations involving any number of spinon orbitals is expressed as a
function of reduced variables representing momentum, filling, and magnetization
of each orbital. The spins of spinons in a single orbital are found to be
coupled in a manner well described by an Ising-like equivalent-neighbor
interaction, switching from ferromagnetic to antiferromagnetic as the filling
exceeds a critical level. Comparisons are made with results for the
Haldane-Shastry model.Comment: 16 pages, 3 figure
An Electron/Ion Spectrometer with the Ability of Low Energy Electron Measurement for Fast Ignition Experiment
An electron energy spectrometer (ESM) is one of the most fundamental diagnostics in the fast ignition experiment. It is necessary to observe the spectra down to a low energy range in order to obtain the accurate deposition efficiency toward the core. Here, we realize the suitable ESM by using a ferrite magnet with a moderate magnetic field of 0.3 T and a rectangular magnetic circuit covered with a steel plate in the inlet side
No effect of exercise on insulin-like growth factor (IGF)-1, insulin and glucose in young women participating in a 16-week randomized controlled trial
Introduction: Insulin-like growth factor 1 (IGF-1) and IGF binding protein 3 (IGFBP-3) have been associated with increased risk of breast cancer.
Methods: We report our findings on the effects of 16 weeks of aerobic exercise on IGF axis proteins, insulin, glucose and insulin resistance of 319 young sedentary women.
Demographics, health surveys, body composition, dietary intake and blood samples were collected at baseline and 16 weeks. IGF-1 and IGF binding proteins 1, 2, and 3 were measured by ELISA’s.
Results: Exercise adherence was 88% and the dropout rates for the exercise and control groups were 21.7% and 14.5%, respectively. There was a small significant change from baseline in IGFBP-3 concentrations. IGFBP-3 levels decreased in controls and increased in exercisers. The between group difference was significant. No other changes were noted.
Conclusion: Sixteen weeks of exercise had minimum or no effect on IGF proteins of young women.
Impact: Our study supports findings from previous studies conducted in older populations and raises the question of what type of intervention is needed to change circulating levels of IGF proteins in humans
Collective Antenna Effects in the Terahertz and Infrared Response of Highly Aligned Carbon Nanotube Arrays
We study macroscopically-aligned single-wall carbon nanotube arrays with
uniform lengths via polarization-dependent terahertz and infrared transmission
spectroscopy. Polarization anisotropy is extreme at frequencies less than
3 THz with no sign of attenuation when the polarization is perpendicular
to the alignment direction. The attenuation for both parallel and perpendicular
polarizations increases with increasing frequency, exhibiting a pronounced and
broad peak around 10 THz in the parallel case. We model the electromagnetic
response of the sample by taking into account both radiative scattering and
absorption losses. We show that our sample acts as an effective antenna due to
the high degree of alignment, exhibiting much larger radiative scattering than
absorption in the mid/far-infrared range. Our calculated attenuation spectrum
clearly shows a non-Drude peak at 10 THz in agreement with the
experiment.Comment: 5 pages, 5 figure
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