20,259 research outputs found
Investigation of potential anti-radiation and anti-neoplastic compounds related to plant growth regulators second quarterly progress report, 1 oct. 1964 - 1 jan. 1965
Antiradiation and antineoplastic compounds related to plant growth regulators - cytotoxic effects and radiation protectio
Cryogenic Hydrogen/helium Storage and Supply System, Phase 1
An existing cryogenic tank was refurbished, microspheres were installed in the tank annulus, and the thermal performance of the unit was tested. The performance data was compared with NRC-2 multilayer insulation and low emittance aluminized surfaces installed in tanks of the same basic design. The cryogenic tank modified during the program was originally designed for the Manned Orbiting Laboratory (MOL) Program, and subsequently modified by vacuum-depositing aluminum on all annulus surfaces and leaving out the NRC-2 multilayer insulation. It is concluded that the application of aluminized-microsphere insulation is not yet very predictable for tank design purposes, especially at LH2 temperature and in the presence of a vapor-cooled shield
Quasiparticle mirages in the tunneling spectra of d-wave superconductors
We illustrate the importance of many-body effects in the Fourier transformed
local density of states (FT-LDOS) of d-wave superconductors from a model of
electrons coupled to an Einstein mode with energy Omega_0. For bias energies
significantly larger than Omega_0 the quasiparticles have short lifetimes due
to this coupling, and the FT-LDOS is featureless if the electron-impurity
scattering is treated within the Born approximation. In this regime it is
important to include boson exchange for the electron-impurity scattering which
provides a `step down' in energy for the electrons and allows for long
lifetimes. This many-body effect produces qualitatively different results,
namely the presence of peaks in the FT-LDOS which are mirrors of the
quasiparticle interference peaks which occur at bias energies smaller than ~
Omega_0. The experimental observation of these quasiparticle mirages would be
an important step forward in elucidating the role of many-body effects in
FT-LDOS measurements.Comment: revised text with new figures, to be published, Phys Rev
Magnetoelliptic Instabilities
We consider the stability of a configuration consisting of a vertical
magnetic field in a planar flow on elliptical streamlines in ideal
hydromagnetics. In the absence of a magnetic field the elliptical flow is
universally unstable (the ``elliptical instability''). We find this universal
instability persists in the presence of magnetic fields of arbitrary strength,
although the growthrate decreases somewhat. We also find further instabilities
due to the presence of the magnetic field. One of these, a destabilization of
Alfven waves, requires the magnetic parameter to exceed a certain critical
value. A second, involving a mixing of hydrodynamic and magnetic modes, occurs
for all magnetic-field strengths. These instabilities may be important in
tidally distorted or otherwise elliptical disks. A disk of finite thickness is
stable if the magnetic fieldstrength exceeds a critical value, similar to the
fieldstrength which suppresses the magnetorotational instability.Comment: Accepted for publication in Astrophysical Journa
The Temperature Evolution of the Spectral Peak in High Temperature Superconductors
Recent photoemission data in the high temperature cuprate superconductor
Bi2212 have been interpreted in terms of a sharp spectral peak with a
temperature independent lifetime, whose weight strongly decreases upon heating.
By a detailed analysis of the data, we are able to extract the temperature
dependence of the electron self-energy, and demonstrate that this intepretation
is misleading. Rather, the spectral peak loses its integrity above Tc due to a
large reduction in the electron lifetime.Comment: 5 pages, revtex, 4 encapsulated postscript figure
Long-range quantum gates using dipolar crystals
We propose the use of dipolar spin chains to enable long-range quantum logic
between distant qubits. In our approach, an effective interaction between
remote qubits is achieved by adiabatically following the ground state of the
dipolar chain across the paramagnet to crystal phase transition. We demonstrate
that the proposed quantum gate is particularly robust against disorder and
derive scaling relations, showing that high-fidelity qubit coupling is possible
in the presence of realistic imperfections. Possible experimental
implementations in systems ranging from ultracold Rydberg atoms to arrays of
Nitrogen-Vacancy defect centers in diamond are discussed.Comment: 5 pages, 3 figure
Extraction of the Electron Self-Energy from Angle Resolved Photoemission Data: Application to Bi2212
The self-energy , the fundamental function which
describes the effects of many-body interactions on an electron in a solid, is
usually difficult to obtain directly from experimental data. In this paper, we
show that by making certain reasonable assumptions, the self-energy can be
directly determined from angle resolved photoemission data. We demonstrate this
method on data for the high temperature superconductor
(Bi2212) in the normal, superconducting, and pseudogap phases.Comment: expanded version (6 pages), to be published, Phys Rev B (1 Sept 99
Cargo/Logistics Airlift System Study (CLASS), Volume 2
Air containerization is discussed in terms of lower freight rates, size and pallet limitations, refrigeration, backhaul of empties, and ownership. It is concluded that there is a need for an advance air cargo system as indicated by the industry/transportation case studies, and a stimulation of the air cargo would result in freight rate reductions
Cargo/Logistics Airlift System Study (CLASS), Volume 1
Current and advanced air cargo systems are evaluated using industrial and consumer statistics. Market and commodity characteristics that influence the use of the air mode are discussed along with a comparison of air and surface mode on typical routes. Results of on-site surveys of cargo processing facilities at airports are presented, and institutional controls and influences on air cargo operations are considered
Cargo/Logistics Airlift System Study (CLASS), Executive Summary
The current air cargo system is analyzed along with advanced air cargo systems studies. A forecast of advanced air cargo system demand is presented with cost estimates. It is concluded that there is a need for a dedicated advance air cargo system, and with application of advanced technology, reductions of 45% in air freight rates may be achieved
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