18,199 research outputs found
Polarization Measurements and the Pairing Gap in the Universal Regime
We analyze recent cold-atom experiments on imbalanced Fermi systems using a
minimal model with a BCS-like superfluid phase coexisting with a normal phase.
This model is used to extract the T=0 pairing gap in the fully paired
superfluid state. The recently measured particle density profiles are in good
agreement with the theoretical predictions obtained from the universal
parameters from previous Quantum Monte Carlo calculations. We find that the T=0
pairing gap is greater than 0.4 times the Fermi energy , with a preferred
value of . The ratio of the pairing gap to the
Fermi Energy is larger here than in any other system of strongly-paired
fermions in which individual pairs are unbound.Comment: 4 pages, 3 figures. Revised verison includes cosmetic changes to the
text and figures. One reference adde
Detection of the primary scintillation light from dense Ar, Kr and Xe with novel photosensitive gaseous detectors
The detection of primary scintillation light in combination with the charge
or secondary scintillation signals is an efficient technique to determine the
events t=0 as well as particle / photon separation in large mass TPC detectors
filled with noble gases and/or condensed noble gases. The aim of this work is
to demonstrate that costly photo-multipliers could be replaced by cheap novel
photosensitive gaseous detectors: wire counters, GEMs or glass capillary tubes
coupled with CsI photocathodes. We have performed systematic measurements with
Ar, Kr and Xe gas at pressures in the range of 1-50 atm as well as some
preliminary measurements with liquid Xe and liquid Ar. With the gaseous
detectors we succeeded in detecting scintillation light produced by 22 keV
X-rays with an efficiency of close to 100%. We also detected the scintillation
light produced by bs (5 keV deposit energy) with an efficiency close to 25%.
Successful detection of scintillation from 22 keV gammas open new experimental
possibilities not only for nTOF and ICARUS experiments, but also in others,
like WIMPs search through nuclear recoil emission
MHD oxidant intermediate temperature ceramic heater study
The use of three types of directly fired ceramic heaters for preheating oxygen enriched air to an intermediate temperature of 1144K was investigated. The three types of ceramic heaters are: (1) a fixed bed, periodic flow ceramic brick regenerative heater; (2) a ceramic pebble regenerative heater. The heater design, performance and operating characteristics under conditions in which the particulate matter is not solidified are evaluated. A comparison and overall evaluation of the three types of ceramic heaters and temperature range determination at which the particulate matter in the MHD exhaust gas is estimated to be a dry powder are presented
Primer for the Transportable Applications Executive
The Transportable Applications Executive (TAE), an interactive multipurpose executive that provides commonly required functions for scientific analysis systems, is discussed. The concept of an executive is discussed and the various components of TAE are presented. These include on-line help information, the use of menus or commands to access analysis programs, and TAE command procedures
Effective Widths and Effective Number of Phonons of Multiphonon Giant Resonances
We discuss the origin of the difference between the harmonic value of the
width of the multiphonon giant resonances and the smaller observed value.
Analytical expressions are derived for both the effective width and the average
cross-section. The contribution of the Brink-Axel mechanism in resolving the
discrepancy is pointed out.Comment: 9 pages, 4 figure
Tracer Dispersion in a Self-Organized Critical System
We have studied experimentally transport properties in a slowly driven
granular system which recently was shown to display self-organized criticality
[Frette {\em et al., Nature} {\bf 379}, 49 (1996)]. Tracer particles were added
to a pile and their transit times measured. The distribution of transit times
is a constant with a crossover to a decaying power law. The average transport
velocity decreases with system size. This is due to an increase in the active
zone depth with system size. The relaxation processes generate coherently
moving regions of grains mixed with convection. This picture is supported by
considering transport in a cellular automaton modeling the experiment.Comment: 4 pages, RevTex, 1 Encapsulated PostScript and 4 PostScript available
upon request, Submitted to Phys. Rev. Let
Evaluating matrix elements relevant to some Lorenz violating operators
Carlson, Carone and Lebed have derived the Feynman rules for a consistent
formulation of noncommutative QCD. The results they obtained were used to
constrain the noncommutativity parameter in Lorentz violating noncommutative
field theories. However, their constraint depended upon an estimate of the
matrix element of the quark level operator (gamma.p - m) in a nucleon. In this
paper we calculate the matrix element of (gamma.p - m), using a variety of
confinement potential models. Our results are within an order of magnitude
agreement with the estimate made by Carlson et al. The constraints placed on
the noncommutativity parameter were very strong, and are still quite severe
even if weakened by an order of magnitude.Comment: 4 pages, 3 figures, RevTex, minor change
Dynamic stall modeling and correlation with experimental data on airfoils and rotors
Two methods for modeling dynamic stall have been developed. The alpha, A, B method generates lift and pitching moments as functions of angle of attack and its first two time derivatives. The coefficients are derived from experimental data for oscillating airfoils. The Time Delay Method generates the coefficients from steady state airfoil characteristics and an associated time delay in stall beyond the steady state stall angle. Correlation with three types of test data shows that the alpha, A, B method is somewhat better for use in predicting helicopter rotor response in forward flight. Correlation with lift and moment hysteresis loops generated for oscillating airfoils was good for both models
Production of human recombinant proapolipoprotein A-I in Escherichia coli: purification and biochemical characterization
A human liver cDNA library was used to isolate a clone coding for apolipoprotein A-I (Apo A-I). The clone
carries the sequence for the prepeptide (18 amino acids), the propeptide (6 amino acids), and the mature protein
(243 amino acids). A coding cassette for the proapo A-I molecule was reconstructed by fusing synthetic
sequences, chosen to optimize expression and specifying the amino-terminal methionine and amino acids -6
to +14, to a large fragment of the cDNA coding for amino acids 15-243. The module was expressed in
pOTS-Nco, an Escherichia coli expression vector carrying the regulatable X P^ promoter, leading to the production
of proapolipoprotein A-I at up to 10% of total soluble proteins. The recombinant polypeptide was
purified and characterized in terms of apparent molecular mass, isoelectric point, and by both chemical and
enzymatic peptide mapping. In addition, it was assayed in vitro for the stimulation of the enzyme lecithin:
cholesterol acyltransferase. The data show for the first time that proapo A-I can be produced efficiently in
E. coli as a stable and undegraded protein having physical and functional properties indistinguishable from
those of the natural product
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