7,149 research outputs found
Rescue in Space - TDRS Flight 1
On 4 April 1983, the shuttle or biter Challenger released the Flight 1 spacecraft of trie Tracking and Data Relay Satellite System ITDRSS) and Its Inertial Upper Stage (IUS) booster In low altitude orbit. Altho perogee burn of the IDS was accomplished without incident, approximately threequarters of the way through the orbital injection burn, the IDS lost control. At the completion of the IUS burn, the spacecraft- IUS stack was tumbling violently in an anomalous eliptic orbit. During the succeeding hours spacecraft separation was accomplished and the spacecraft was stabilized and placed under positive attitude control. After assuring spacecraft safety and analyzing the state of health of onboard equipment, firings of the spacecraft onboard attitude and velocity control engines were used to raise the spacecraft from its eliptic orbit into the desired circular synchronous orbit. Final orbit correction was accomplished on 29 June 1983, almost 3 months after initial launch. This paper describes the spacecraft and its mission, the sequence of events leading to and following its injection into anomalous orbit, a description of onboard propulsion and attitude control equipment, and how this equipment was used to correct the orbit
Geometric phase for a dimerized disordered continuum: Topological shot noise
Geometric phase shift associated with an electron propagating through a
dimerized-disordered continuum is shown to be 0, or (modulo 2),
according as the associated circuit traversed in the two-dimensional parameter
space excludes, or encircles a certain singularity. This phase-shift is a
topological invariant. Its discontinuous dependence on the electron energy and
disorder implies a statistical spectral and conductance fluctuation in a
corresponding mesoscopic system. Inasmuch as the fluctuation derives from the
discreteness of the phase shift, it may aptly be called a topological
shot-noise.Comment: 10 pages(LATEX) + 1 figure, (revised version). Will appear in
Europhys. Let
Superconducting Fluctuations in a Multi-Band 1D Hubbard Model
A renormalization-group and bosonization approach for a multi-band Hubbard
Hamiltonian in one dimension is described. Based on the limit of many bands, it
is argued that this Hamiltonian with bare repulsive electron-electron
interactions is scaled under specific conditions to a model in which
superconducting fluctuations dominate.Comment: 12 pages + 1 fig, Revtex, Preprint - Los Alamo
Finite-Size Bosonization of 2-Channel Kondo Model: a Bridge between Numerical Renormalization Group and Conformal Field Theory
We generalize Emery and Kivelson's (EK) bosonization-refermionization
treatment of the 2-channel Kondo model to finite system size and on the EK-line
analytically construct its exact eigenstates and finite-size spectrum. The
latter crosses over to conformal field theory's (CFT) universal
non-Fermi-liquid spectrum (and yields the most-relevant operators' dimensions),
and further to a Fermi-liquid spectrum in a finite magnetic field. Our approach
elucidates the relation between bosonization, scaling techniques, the numerical
renormalization group (NRG) and CFT. All CFT's Green's functions are recovered
with remarkable ease from the model's scattering states.Comment: 4 pages, 1 figure, Revte
Variable temperature study of the crystal and magnetic structures of the giant magnetoresistant materials LMnAsO (L=La, Nd)
Peer reviewedPublisher PD
Impact of older adults’ experience with psychotherapy on treatment engagement
The goal of the study was to characterize older adults\u27 experience with psychotherapy and examine its impact on engagement in psychotherapy. The study included 50 adults over age 60 who screened positive for depression and participated in the BRIGHTEN Program, an interdisciplinary geriatric mental health program. Qualitative analyses revealed five themes leading to treatment initiation: health concerns, family issues, the experience of depressive symptoms, beliefs about what participants could get from psychotherapy, and positive outcomes seen in others. Those without a history of mental health treatment were more likely to endorse health concerns as a treatment motivator and were more likely to terminate treatment early. Future research is warranted to determine how to effectively engage older adults seeking mental health treatment for the first time
Theory of Magnetic Field Induced Spin Density Wave in High Temperature Superconductors
The induction of spin density wave (SDW) and charge density wave (CDW)
orderings in the mixed state of high superconductors (HTS) is
investigated by using the self-consistent Bogoliubov-de Gennes equations based
upon an effective model Hamiltonian with competing SDW and d-wave
superconductivity interactions. For optimized doping sample, the modulation of
the induced SDW and its associated CDW is determined by the vortex lattice and
their patterns obey the four-fold symmetry. By deceasing doping level, both SDW
and CDW show quasi-one dimensional like behavior, and the CDW has a period just
half that of the SDW along one direction. From the calculation of the local
density of states (LDOS), we found that the majority of the quasi-particles
inside the vortex core are localized. All these results are consistent with
several recent experiments on HTS
Evidence of Strong-Coupled Superconductivity in CaC6 from Tunneling Spectroscopy
Point-contact tunneling on CaC crystals reproducibly reveals
superconducting gaps, , of 2.30.2 meV which are ~40% larger
than earlier reports. That puts CaC into the class of very strong-coupled
superconductors since 2/kT~4.6. Thus soft Ca phonons will be
primarily involved in the superconductivity, a conclusion that explains the
large Ca isotope effect found recently for CaC. Consistency among
superconductor-insulator-normal metal (SIN), SIS and Andreev reflection (SN)
junctions reinforces the intrinsic nature of this result.Comment: 2nd version, 4 pages, 4 figures, re-submitted to Physical Review
Letter
On Emery-Kivelson line and universality of Wilson ratio of spin anisotropic Kondo model
Yuval-Anderson's scaling analysis and Affleck-Ludwig's Conformal Field Theory
approach are applied to the channel {\em spin anisotropic} Kondo model.
Detailed comparisons with the available Emery-Kivelson's Abelian Bosonization
approaches are made. It is shown that the EK line exists for any , although
it can be mapped to free fermions only when or . The Wilson ratio is
universal if or , but {\em not} universal if . The leading low
temperature correction to the electron resistivity is {\em not} affected by the
spin anisotropy for {\em any} . A new universal ratio for is proposed
to compare with experiments.Comment: 12 pages, REVTEX, no figures, to appear in Phys. Rev. Lett
Incommensurate Magnetism around Vortices and Impurities in High- Superconductors
By solving self-consistently an effective Hamiltonian including interactions
for both antiferromagnetic spin-density wave (SDW) and d-wave superconducting
(DSC) orderings, a comparison study is made for the local magnetic structure
around superconducting vortices and unitary impurities. To represent the
optimally doped regime of cuprates, the parameter values are chosen such that
the DSC is dominant while the SDW is vanishingly small. We show that when
vortices are introduced into the superconductor, an oscillating SDW is induced
around them. The oscillation period of the SDW is microscopically found,
consistent with experiments, to be eight lattice constants (). The
associated charge-density wave (CDW) oscillates with a period of one half
() of the SDW. In the case of unitary impurities, we find a SDW
modulation with identical periodicity, however without an associated CDW. We
propose neutron scattering experiments to test this prediction.Comment: 5 pages, 4 eps figures (color) included in the tex
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