5,117 research outputs found
Irreducible completely pointed modules of quantum groups of type
We give a classification of all irreducible completely pointed
modules over a characteristic zero field in which
is not a root of unity. This generalizes the classification result of
Benkart, Britten and Lemire in the non quantum case. We also show that any
infinite-dimensional irreducible completely pointed
can be obtained from some irreducible completely pointed module over the
quantized Weyl algebra .Comment: 25 page
Low temperature electron transfer in strongly condensed phase
Electron transfer coupled to a collective vibronic degree of freedom is
studied in strongly condensed phase and at lower temperatures where quantum
fluctuations are essential. Based on an exact representation of the reduced
density matrix of the electronic+reaction coordinate compound in terms of path
integrals, recent findings on the overdamped limit in quantum dissipative
systems are employed. This allows to give for the first time a consistent
generalization of the well-known Zusman equations to the quantum domain.
Detailed conditions for the range of validity are specified. Using the Wigner
transform these results are also extended to the quantum dynamics in full phase
space. As an important application electronic transfer rates are derived that
comprise adiabatic and nonadiabatic processes in the low temperature regime
including nuclear tunneling. Accurate agreement with precise quantum Monte
Carlo data is observed.Comment: 16 pages, 6 figures, revised version with minor change
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Structure of the novel membrane-coating material in proton-secreting epithelial cells and identification as an H+ATPase.
Specialized proton-secreting cells known collectively as mitochondria-rich cells are found in a variety of transporting epithelia, including the kidney collecting duct (intercalated cells) and toad and turtle urinary bladders. These cells contain a population of characteristic tubulovesicles that are believed to be involved in the shuttling of proton pumps (H+ATPase) to and from the plasma membrane. These transporting vesicles have a dense, studlike material coating the cytoplasmic face of their limiting membranes and similar studs are also found beneath parts of the plasma membrane. We have recently shown that this membrane coat does not contain clathrin. The present study was performed to determine the structure of this coat in rapidly frozen and freeze-dried tissue, and to determine whether the coat contains a major membrane protein transported by these vesicles, a proton pumping H+ATPase. The structure of the coat was examined in proton-secreting, mitochondria-rich cells from toad urinary bladder epithelium by rapidly freezing portions of apical membrane and associated cytoplasm that were sheared away from the remainder of the cell using polylysine-coated coverslips. Regions of the underside of these apical membranes as large as 0.2 micron2 were decorated by studlike projections that were arranged into regular hexagonal arrays. Individual studs had a diameter of 9.5 nm and appeared to be composed of multiple subunits arranged around a central depression, possibly representing a channel. The studs had a density of approximately 16,800 per micron2 of membrane. Similar arrays of studs were also found on vesicles trapped in the residual band of cytoplasm that remained attached to the underside of the plasma membrane, but none were seen in adjacent granular cells. To determine whether these arrays of studs contained H+ATPase molecules, we examined a preparation of affinity-purified bovine medullary H+ATPase, using the same technique, after incorporation of the protein eluted from a monoclonal antibody affinity column into phospholipid liposomes. The affinity-purified protein was shown to be capable of ATP-dependent acidification. In such preparations, large paracrystalline arrays of studs identical in appearance to those seen in situ were found. The dimensions of the studs as well as the number per square micrometer of membrane were identical to those of toad bladder mitochondria-rich cells: 9.5 nm in diameter, 16,770 per micron2 of membrane.(ABSTRACT TRUNCATED AT 400 WORDS
Analysis of low temperature trapping and recombination in II-VI compounds using photodielectric techniques
Using photodielectric effect to detect densities of free and trapped carriers in II-VI compounds at cryogenic temperature
Research on digital transducer principles. Volume 6 - The photodielectric effect in cadmium sulfide, 1 July 1967 - 30 June 1968
Cadmium sulfide photodielectric effect at cryogenic temperatures with bibliograph
Experimental Effervescence and Freezing Point Depression Measurements of Nitrogen in Liquid Methane-Ethane Mixtures
NASA is designing an unmanned submarine to explore the depths of the hydrocarbon-rich seas on Saturn's moon Titan. Data from Cassini indicates that the Titan north polar environment sustains stable seas of variable concentrations of ethane, methane, and nitrogen, with a surface temperature near 93 K. The submarine must operate autonomously, study atmosphere/sea exchange, interact with the seabed, hover at the surface or any depth within the sea, and be capable of tolerating variable hydrocarbon compositions. Currently, the main thermal design concern is the effect of effervescence on submarine operation, which affects the ballast system, science instruments, and propellers. Twelve effervescence measurements on various liquid methane-ethane compositions with dissolved gaseous nitrogen are thus presented from 1.5 bar to 4.5 bar at temperatures from 92 K to 96 K to simulate the conditions of the seas. After conducting effervescence measurements, two freezing point depression measurements were conducted. The freezing liquid line was depressed more than 15 K below the triple point temperatures of pure ethane (90.4 K) and pure methane (90.7 K). Experimental effervescence measurements will be used to compare directly with effervescence modeling to determine if changes are required in the design of the thermal management system as well as the propellers
Simplicity and maximal commutative subalgebras of twisted generalized Weyl algebras
In this paper we show that each non-zero ideal of a twisted generalized Weyl
algebra (TGWA) intersects the centralizer of the distinguished subalgebra
in non-trivially. We also provide a necessary and sufficient condition
for the centralizer of in to be commutative, and give examples of TGWAs
associated to symmetric Cartan matrices satisfying this condition. By imposing
a certain finiteness condition on (weaker than Noetherianity) we are able
to make an Ore localization which turns out to be useful when investigating
simplicity of the TGWA. Under this mild assumption we obtain necessary and
sufficient conditions for the simplicity of TGWAs. We describe how this is
related to maximal commutativity of in and the (non-) existence of
non-trivial -invariant ideals of . Our result is a generalization of
the rank one case, obtained by D. A. Jordan in 1993. We illustrate our theorems
by considering some special classes of TGWAs and providing concrete examples.Comment: 32 pages, no figures, minor improvements of the presentation of the
materia
Solvent-mediated interactions between nanoparticles at fluid interfaces
We investigate the solvent mediated interactions between nanoparticles
adsorbed at a liquid-vapor interface in comparison to the solvent mediated
interactions in the bulk liquid and vapor phases of a Lennard-Jones solvent.
Molecular dynamics simulation data for the latter are in good agreement with
results from integral equations in the reference functional approximation and a
simple geometric approximation. Simulation results for the solvent mediated
interactions at the interface differ markedly from the interactions of the
particles in the corresponding bulk phases. We find that at short interparticle
distances the interactions are considerably more repulsive than those in either
bulk phase. At long interparticle distances we find evidence for a long-ranged
attraction. We discuss these observations in terms of interfacial interactions,
namely, the three-phase line tension that would operate at short distances, and
capillary wave interactions for longer interparticle distances.Comment: 22 pages, 6 figure
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