12,265 research outputs found
Research Study for Determination of Liquid Surface Profile in a Cryogenic Tank During Gas Injection Annual Report, 18 Jun. 1967 - 17 Jun. 1968
Determining entrainment of entrapped liquid as function of air flow, and viscosit
Research Study for Determination of Liquid Surface Profile in a Cryogenic Tank During Gas Injection Quarterly Report, 18 Dec. 1967 - 17 Mar. 1968
Correlation equation on entrainment-viscosity behavior in cryogenic tank during gas injectio
Spin-ladders with spin gaps: A description of a class of cuprates
We investigate the magnetic properties of the Cu-O planes in stoichiometric
SrCuO (n=3,5,7,...) which consist of CuO double chains
periodically intergrown within the CuO planes. The double chains break up
the two-dimensional antiferromagnetic planes into Heisenberg spin ladders with
rungs and legs and described by
the usual antiferromagnetic coupling J inside each ladder and a weak and
frustrated interladder coupling J. The resulting lattice is a new
two-dimensional trellis lattice. We first examine the spin excitation spectra
of isolated quasi one dimensional Heisenberg ladders which exhibit a gapless
spectra when is even and is odd ( corresponding to n=5,9,...) and a
gapped spectra when is odd and is even (corresponding to
n=3,7,...). We use the bond operator representation of quantum
spins in a mean field treatment with self-energy corrections and obtain a spin
gap of for the simplest single rung ladder (n=3), in
agreement with numerical estimates.Comment: 21 pages, 5 figures upon request, REVTEX, ETH-TH/93-3
Current-eddy interaction in the Agulhas Return Current region from the seismic oceanography perspective
Interleaving in the Agulhas Return Current (ARC) frontal region is commonly manifested in the form of thermohaline intrusions, as sub-tropical and sub-polar water masses of similar density meet. In Jan/Feb 2012, the Naval Research Laboratory and collaborators carried out a field experiment in which seismic and traditional hydrographic observations were acquired to examine frontal zone mixing processes. The high lateral resolution (10 m) of the seismic observations allowed fine-scale lateral tracking of thermal intrusions, which were corroborated with simultaneous XBT casts. Between seismic deployments both salinity and temperature data were acquired via CTD, Underway-CTD and microstructure profiles. This study focuses on analyzing seismic reflection data in a particular E-W transect where the northward flowing ARC interacted with the southward flowing portion of a large anticyclonic eddy. Strong reflectors were most prominent at the edge of a hyperbolic zone formed between the eddy and ARC, where sub-polar waters interacted with waters of sub-tropical origin on either side. Reflectors were shallow within the hyperbolic zone and extended to 1200 m below the ARC. The nature of the observed reflectors will be determined from comparison of seismic reflection and derived ∂T/∂z fields, and XBT and TS profiles from the available hydrographic data
Current-driven vortex dynamics in untwinned superconducting single crystals
Current-driven vortex dynamics of type-II superconductors in the weak-pinning limit is investigated by quantitatively studying the current-dependent vortex dissipation of an untwinned YBa2Cu3O7 single crystal. For applied current densities (J) substantially larger than the critical current density (Jc), non-linear resistive peaks appear below the thermodynamic first-order vortex-lattice melting transition temperature (Tm), in contrast to the resistive hysteresis in the low-current limit (J < Jc). These resistive peaks are quantitatively analysed in terms of the current-driven coherent and plastic motion of vortex bundles in the vortex-solid phase, and the non-linear current - voltage characteristics are found to be consistent with the collective flux-creep model. The effects of high-density random point defects on the vortex dynamics are also investigated via proton irradiation of the same single crystal. Neither resistive hysteresis at low currents nor peak effects at high currents are found after the irradiation. Furthermore, the current-voltage characteristics within the instrumental resolution become completely ohmic over a wide range of currents and temperatures, despite theoretical predictions of much larger Jc-values for the given experimental variables. This finding suggests that the vortex-glass phase, a theoretically proposed low-temperature vortex state which is stabilized by point disorder and has a vanishing resistivity, may become unstable under applied currents significantly smaller than the theoretically predicted Jc. More investigation appears necessary in order to resolve this puzzling issue
Heterogeneous responses of dorsal root ganglion neurons in neuropathies induced by peripheral nerve trauma and the antiretroviral drug stavudine
© 2014 The Authors. European Journal of Pain published by John Wiley & Sons Ltd on behalf of European Pain Federation - EFIC®. Funding sources E.K.B. was funded by a BBSRC PhD studentship. A.N., A.S.C.R. and T.P. were funded by a Wellcome Trust Strategic Award (London Pain Consortium; ref. 083259). A.S.C.R. and W.H. were funded by the Innovative Medicines Initiative Joint Undertaking (Europain; grant agreement no. 115007). We thank Pfizer for providing stavudine. Conflicts of interest None declared. Funded by BBSRC PhD studentship Wellcome Trust Strategic Award. Grant Number: 083259 Innovative Medicines Initiative Joint Undertaking. Grant Number: 115007Peer reviewedPublisher PD
Testing of the LSST's photometric calibration strategy at the CTIO 0.9 meter telescope
The calibration hardware system of the Large Synoptic Survey Telescope (LSST)
is designed to measure two quantities: a telescope's instrumental response and
atmospheric transmission, both as a function of wavelength. First of all, a
"collimated beam projector" is designed to measure the instrumental response
function by projecting monochromatic light through a mask and a collimating
optic onto the telescope. During the measurement, the light level is monitored
with a NIST-traceable photodiode. This method does not suffer from stray light
effects or the reflections (known as ghosting) present when using a flat-field
screen illumination, which has a systematic source of uncertainty from
uncontrolled reflections. It allows for an independent measurement of the
throughput of the telescope's optical train as well as each filter's
transmission as a function of position on the primary mirror. Second, CALSPEC
stars can be used as calibrated light sources to illuminate the atmosphere and
measure its transmission. To measure the atmosphere's transfer function, we use
the telescope's imager with a Ronchi grating in place of a filter to configure
it as a low resolution slitless spectrograph. In this paper, we describe this
calibration strategy, focusing on results from a prototype system at the Cerro
Tololo Inter-American Observatory (CTIO) 0.9 meter telescope. We compare the
instrumental throughput measurements to nominal values measured using a
laboratory spectrophotometer, and we describe measurements of the atmosphere
made via CALSPEC standard stars during the same run
Seismic oceanography imaging of thermal intrusions in strong frontal regions
The Naval Research Laboratory and collaborating partners carried out two dedicated seismic oceanography field experiments in two very different strong frontal regions. ADRIASEISMIC took seismic oceanography measurements at the confluence of North Adriatic Dense Water advected along the Western Adriatic Current and Modified Levantine Intermediate Water advected around the topographic rim of the Southern Adriatic basin. ARC12 took seismic oceanography measurements in and around the Agulhas Return Current as it curved northwards past the Agulhas Plateau and interacted with a large anticyclone that had collided with the current. Despite one study focused on coastal boundary currents and the other focused on a major Western Boundary Current extension, the complex horizontal structures seen through seismic imaging are tied to the processes of thermal intrusions and interleaving in both systems. Seismic Oceanography provides a unique capability of tracking the fine-scale horizontal extent of these intrusions
Quasiparticles in the Pseudogap Phase of Underdoped Cuprate
Recent angle resolved photoemission \cite{yang-nature-08} and scanning
tunneling microscopy \cite{kohsaka-nature-08} measurements on underdoped
cuprates have yielded new spectroscopic information on quasiparticles in the
pseudogap phase. New features of the normal state such as particle-hole
asymmetry, maxima in the energy dispersion and accompanying drops in the
spectral weight of quasiparticles agree with the ansatz of Yang \textit{et al.}
for the single particle propagator in the pseudogap phase. The coherent
quasiparticle dispersion and reduced asymmetry in the tunneling density of
states in the superconducting state can also be described by this propagator.Comment: updated version, 6 pages, 7 figures, 1 table, EPL 86 (2009) 37002
(https://www.epletters.net
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