9,062 research outputs found
Proposed experiments to probe the non-abelian \nu=5/2 quantum Hall state
We propose several experiments to test the non-abelian nature of
quasi-particles in the fractional quantum Hall state of \nu=5/2. One set of
experiments studies interference contribution to back-scattering of current,
and is a simplified version of an experiment suggested recently. Another set
looks at thermodynamic properties of a closed system. Both experiments are only
weakly sensitive to disorder-induced distribution of localized quasi-particles.Comment: Additional references and an improved figure, 5 page
Thermopower as a Possible Probe of Non-Abelian Quasiparticle Statistics in Fractional Quantum Hall Liquids
We show in this paper that thermopower is enhanced in non-Abelian quantum
Hall liquids under appropriate conditions. This is because thermopower measures
entropy per electron in the clean limit, while the degeneracy and entropy
associated with non-Abelian quasiparticles enhance entropy when they are
present. Thus thermopower can potentially probe non-Abelian nature of the
quasiparticles, and measure their quantum dimension.Comment: 5 pages. Minor revisions in response to referee comments. Published
versio
On the transcendence degree of the differential field generated by Siegel modular forms
It is a classical fact that the elliptic modular functions satisfies an
algebraic differential equation of order 3, and none of lower order. We show
how this generalizes to Siegel modular functions of arbitrary degree. The key
idea is that the partial differential equations they satisfy are governed by
Gauss--Manin connections, whose monodromy groups are well-known. Modular theta
functions provide a concrete interpretation of our result, and we study their
differential properties in detail in the case of degree 2.Comment: 21 pages, AmSTeX, uses picture.sty for 1 LaTeX picture; submitted for
publicatio
Theory of Spin Hall conductivity in n-doped GaAs
We develop a theory of extrinsic spin currents in semiconductors, resulting
from spin-orbit coupling at charged scatterers, which leads to skew scattering
and side jump contributions to the spin Hall conductance. Applying the theory
to bulk n-GaAs, without any free parameters, we find spin currents that are in
reasonable agreement with recent experiments by Kato et al. [Science 306, 1910
(2004)].Comment: 5 pages, 1 figur
Hybridization gap and anisotropic far-infrared optical conductivity of URu2Si2
We performed far-infrared optical spectroscopy measurements on the heavy
fermion compound URu 2 Si 2 as a function of temperature. The light's
electric-field was applied along the a-axis or the c-axis of the tetragonal
structure. We show that in addition to a pronounced anisotropy, the optical
conductivity exhibits for both axis a partial suppression of spectral weight
around 12 meV and below 30 K. We attribute these observations to a change in
the bandstructure below 30 K. However, since these changes have no noticeable
impact on the entropy nor on the DC transport properties, we suggest that this
is a crossover phenomenon rather than a thermodynamic phase transition.Comment: To be published in Physical Review
Digital, memory and mixed-signal test engineering education: five centres of competence in Europe
The launching of the EuNICE-Test project was announced two years ago at the first DELTA Conference. This project is now completed and the present paper describes the project actions and outcomes. The original idea was to build a long-lasting European Network for test engineering education using both test resource mutualisation and remote experiments. This objective is fully fulfilled and we have now, in Europe, five centres of competence able to deliver high-level and high-specialized training courses in the field of test engineering using a high-performing industrial ATE. All the centres propose training courses on digital testing, three of them propose mixed-signal trainings and three of them propose memory trainings. Taking into account the demand in test engineering, the network is planned to continue in a stand alone mode after project end. Nevertheless a new European proposal with several new partners and new test lessons is under construction
bif1, a new BMP signaling inhibitor, regulates embryonic hematopoiesis in the zebrafish.
Hematopoiesis maintains the entire blood system, and dysregulation of this process can lead to malignancies (leukemia), immunodeficiencies or red blood cell diseases (anemia, polycythemia vera). We took advantage of the zebrafish model that shares most of the genetic program involved in hematopoiesis with mammals to characterize a new gene of unknown function, si:ch73-299h12.2, which is expressed in the erythroid lineage during primitive, definitive and adult hematopoiesis. This gene, required during primitive and definitive erythropoiesis, encodes a C2H2 zinc-finger protein that inhibits BMP signaling. We therefore named this gene blood-inducing factor 1 and BMP inhibitory factor 1 (bif1). We identified a bif1 ortholog in Sinocyclocheilus rhinocerous, another fish, and in the mouse genome. Both genes also inhibit BMP signaling when overexpressed in zebrafish. In conclusion, we have deorphanized a new zebrafish gene of unknown function: bif1 codes for a zinc-finger protein that inhibits BMP signaling and also regulates primitive erythropoiesis and definitive hematopoiesis
Cellulose Gum: a new additive for wine tartaric stability. Tentative of structures determination involved in the haze formation after CMC addition in wine
International audienceCellulose gum (or sodium carboxymethylcellulose / CMC) is a new additive permitted by the European Community for tartaric stabilization (maximum dosage: 10g/HL). CMC is known to have a high eciency for potassium bitartrate and calcium tartrate crystallization inhibition in white and sparkling wines. Hypotheses suggest an inhibition of the nuclei growth at the beginning of their formation. However some problems remain, such as the formation of a low increase of the turbidity in white wine (from 0,1 to 0,4 NTU at room temperature) requiring a ltration step and the formation of a high lumps volume when CMC is used in some red wines. The goal of the following experiments was to determine which molecules are involved in the haze formed in white or red wines. 1. On white wines: A unique Sauvignon wine is treated from 0 up to 600mg/L of activated bentonite. After ltration, each batch was added (or not) with 100mg/L of CMC previously dissolved in tap water (conc.:50g/L). After 1 week of storage at 13°C, samples were heated at 80°C during ½ h and then stored at RT during 24h before running turbidity. 2. On red wines: 1L of red wine (blend of Cinsault, Merlot and Cab. Sauvignon) was added with 100mg/L of CMC (see above) and stored at-4°C for 4 days. After this time, the wine showed a high level of red clouds. At negative temperature, the deposit was ltered on 0.2 µm nitrocellulose lter membrane and extensively washed with a hydro-alcoholic solution (12% ethanol v/v-pH: 3,5/HCl) kept at-4°C. The membrane was then dried under vacuum and the deposit was collected and exchanged 3 times with D2O for H1-NMR study (HRMAS)
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