1,084 research outputs found
NMR evidence for very slow carrier density fluctuations in the organic metal (TMTSF)ClO
We have investigated the origin of the large increase in spin-echo decay
rates for the Se nuclear spins at temperatures near to in the
organic superconductor (TMTSF)ClO. The measured angular dependence of
demonstrates that the source of the spin-echo decays lies with
carrier density fluctuations rather than fluctuations in TMTSF molecular
orientation. The very long time scales are directly associated with the
dynamics of the anion ordering occurring at , and the inhomogeneously
broadened spectra at lower temperatures result from finite domain sizes. Our
results are similar to observations of line-broadening effects associated with
charge-ordering transitions in quasi-two dimensional organic conductors.Comment: 5 pages, 4 figure
EVIDENCE for the PARTICIPATION of the SSP-3 ANTIGEN in the INVASION of NONPHAGOCYTIC MAMMALIAN-CELLS BY TRYPANOSOMA-CRUZI
Trypomastigotes of Trypanosoma cruzi have to invade mammalian cells in order to multiply. They bear on their plasma membrane a sialic acid-containing epitope (Ssp-3) defined by a series of monoclonal antibodies (mAbs). Previous investigations have shown that Fab fragments of these mAbs inhibit the attachment of trypomastigotes to 3T3 fibroblasts. To further define the role of Ssp-3 in invasion, here we use, as targets for infection, L cells and CHO cells stably transfected with cDNA coding for the mouse Fc receptors genes. When the trypomastigotes are incubated with small, nonagglutinating amounts of antibodies to Ssp-3, their attachment to the transfected cells is greatly enhanced, without a parallel increase in invasion. the enhancement in attachment is Fc mediated, since it is abolished by treatment of the transfected cells with mAbs to Fc receptors. in contrast, both attachment to, and invasion of, the transfected cells are increased if the parasites are incubated with polyclonal or monoclonal antibodies against T. cruzi surface membrane antigens other than Ssp-3. If, however, antibodies to Ssp-3 are added to the incubation mixtures containing any of the other anti-T. cruzi antibodies, the enhancement of invasion (but not of attachment) is reversed. These results suggest that Ssp-3-bearing molecules participate in the process of parasite internalization.NYU MED CTR,DEPT PATHOL,550 1ST AVE,NEW YORK,NY 10016NYU MED CTR,KAPLAN CANC CTR,NEW YORK,NY 10016SLOAN KETTERING MEM CANC CTR,DEWITT WALLACE LAB,NEW YORK,NY 10021ESCOLA PAULISTA MED SCH,DISCIPLINA BIOL CELULAR,BR-04023 São Paulo,BRAZILESCOLA PAULISTA MED SCH,DISCIPLINA BIOL CELULAR,BR-04023 São Paulo,BRAZILWeb of Scienc
Effect of grain size on thermoelectric properties of n-type nanocrystalline bismuth-telluride based thin films
The effect of grain size on the thermoelectric properties of n-type nanocrystalline bismuth-telluridebased thin films is investigated. We prepare the nanocrystalline thin films with average grain sizesof 10, 27, and 60 nm by a flash-evaporation method followed by a hydrogen annealing process. Thethermoelectric properties, in terms of the thermal conductivity by a differential 3 method, theelectrical conductivity, and the Seebeck coefficient are measured at room temperature and used toevaluate the figure of merit. The minimum thermal conductivity is 0.61 W m−1 K−1 at the averagegrain size of 10 nm. We also estimate the lattice thermal conductivity of the nanocrystalline thinfilms and compare it with a simplified theory of phonon scattering on grain boundaries. Fornanosized grains, the lattice thermal conductivity of nanocrystalline thin films decreases rapidly forsmaller grains, corresponding to the theoretical calculation. The figure of merit is also decreased asthe grain size decreases, which is attributed to the increased number of defects at the grainboundaries
Ikaros has a crucial role in regulation of B cell receptor signaling
transcription factor Ikaros, a key regulator of hematopoiesis, has an essential role in lymphocyte development. In mice, fetal lymphoid differentiation is blocked in the absence of Ikaros, and whereas T cells develop postnatally, B cells are totally absent. The significance of Ikaros in the B cell development is evident, but how Ikaros regulates B cell function has neither been established nor previously been studied with B cells that lack Ikaros expression. Here we show that disruption of Ikaros in the chicken B cell line DT40 induces a B cell receptor (BCR) signaling defect with reduced phospholipase C gamma 2 phosphorylation and impaired intracellular calcium mobilization, which is restored by Ikaros reintroduction. Furthermore, we show that lack of Ikaros induces hyperphosphorylation of Casitas B lymphoma protein subsequent to BCR activation. These results indicate that the absolute need of Ikaros for development, cell fate decisions and maintenance of B cells is due to the enhancement of BCR signaling
Spin-Wave Theory of the Multiple-Spin Exchange Model on a Triangular Lattice in a Magnetic Field : 3-Sublattice Structures
We study the spin wave in the S=1/2 multiple-spin exchange model on a
triangular lattice in a magnetic field within the linear spin-wave theory. We
take only two-, three- and four-spin exchange interactions into account and
restrict ourselves to the region where a coplanar three-sublattice state is the
mean-field ground state. We found that the Y-shape ground state survives
quantum fluctuations and the phase transition to a phase with a 6-sublattice
structure occurs with softening of the spin wave. We estimated the quantum
corrections to the ground state sublattice magnetizations due to zero-point
spin-wave fluctuations.Comment: 8 pages, 20 figure
A new common functional coding variant at the DDC gene change renal enzyme activity and modify renal dopamine function.
The intra-renal dopamine (DA) system is highly expressed in the proximal tubule and contributes to Na+ and blood pressure homeostasis, as well as to the development of nephropathy. In the kidney, the enzyme DOPA Decarboxylase (DDC) originating from the circulation. We used a twin/family study design, followed by polymorphism association analysis at DDC locus to elucidate heritable influences on renal DA production. Dense single nucleotide polymorphism (SNP) genotyping across the DDC locus on chromosome 7p12 was analyzed by re-sequencing guided by trait-associated genetic markers to discover the responsible genetic variation. We also characterized kinetics of the expressed DDC mutant enzyme. Systematic polymorphism screening across the 15-Exon DDC locus revealed a single coding variant in Exon-14 that was associated with DA excretion and multiple other renal traits indicating pleiotropy. When expressed and characterized in eukaryotic cells, the 462Gln variant displayed lower Vmax (maximal rate of product formation by an enzyme) (21.3 versus 44.9 nmol/min/mg) and lower Km (substrate concentration at which half-maximal product formation is achieved by an enzyme.)(36.2 versus 46.8 μM) than the wild-type (Arg462) allele. The highly heritable DA excretion trait is substantially influenced by a previously uncharacterized common coding variant (Arg462Gln) at the DDC gene that affects multiple renal tubular and glomerular traits, and predicts accelerated functional decline in chronic kidney disease
Non-Abelian hydrodynamics and the flow of spin in spin-orbit coupled substances
Motivated by heavy ion collision experiments, we study the hydrodynamic
properties of non-Abelian systems. These issues arise in condensed matter
physics in the context of transport of spins in the presence of spin orbit
coupling: the Pauli Hamiltonian governing the leading relativistic corrections
in condensed matter systems can be rewritten in a language of SU(2) covariant
derivatives, where the role of the non-Abelian gauge fields is taken by the
physical electromagnetic fields. Taking a similar perspective as Jackiw and
coworkers, we show that non-abelian hydrodynamical currents can be factored in
a non-coherent 'classical' part, and a coherent part requiring macroscopic
non-abelian quantum entanglement. Non-abelian flow being thus a much richer
affair than familiar hydrodynamics, permits us to classify the various spin
transport phenomena in in condensed matter physics in a unifying framework.In
semiconductor spintronics, the absence of hydrodynamics is well known, but in
our formulation it is directly associated with the fact that non-abelian
currents are only covariantly conserved.We analyze the quantum mechanical
single particle currents of relevance to mesoscopic transport with as highlight
the Aharonov-Casher effect, where we demonstrate that the non-abelian transport
structure renders it much more fragile than its abelian counterpart, the
Aharonov-Bohm effect. We subsequently focus on spin flows protected by order
parameters, of which the spin-spiral magnets and the spin superfluids are
important examples. The surprising bonus is that the presence of an order
parameter, being single-valued, restores hydrodynamics. We demonstrate a new
effect: the trapping of electrical line charge, being the 'fixed frame'
non-Abelian analogue of the familiar magnetic flux trapping by superconductors.Comment: 23 pages, 7 figure
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