共查询到20条相似文献,搜索用时 15 毫秒
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Julia Lindberg Peter Saetre Seiji Nishino Emmanuel Mignot Elena Jazin 《BMC neuroscience》2007,8(1):34
Background
Narcolepsy causes dramatic behavioral alterations in both humans and dogs, with excessive sleepiness and cataplexy triggered by emotional stimuli. Deficiencies in the hypocretin system are well established as the origin of the condition; both from studies in humans who lack the hypocretin ligand (HCRT) and in dogs with a mutation in hypocretin receptor 2 (HCRTR2). However, little is known about molecular alterations downstream of the hypocretin signals. 相似文献3.
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M. Davier S. Descotes-Genon A. Höcker B. Malaescu Z. Zhang 《The European Physical Journal C - Particles and Fields》2008,56(3):305-322
We revisit the determination of α
S
(m
τ
2) using a fit to inclusive τ hadronic spectral moments in light of (1) the recent calculation of the fourth-order perturbative coefficient K
4 in the expansion of the Adler function, (2) new precision measurements from BABAR of e+e− annihilation cross sections, which decrease the uncertainty in the separation of vector and axial-vector spectral functions,
and (3) improved results from BABAR and Belle on τ branching fractions involving kaons. We estimate that the fourth-order perturbative prediction reduces the theoretical uncertainty,
introduced by the truncation of the series, by 20% with respect to earlier determinations. We discuss to some detail the perturbative
prediction of two different methods: fixed-order perturbation theory (FOPT) and contour-improved perturbative theory (CIPT).
The corresponding theoretical uncertainties are studied at the τ and Z mass scales. The CIPT method is found to be more stable with respect to the missing higher order contributions and to renormalization
scale variations. It is also shown that FOPT suffers from convergence problems along the complex integration contour. Nonperturbative
contributions extracted from the most inclusive fit are small, in agreement with earlier determinations. Systematic effects
from quark-hadron duality violation are estimated with simple models and found to be within the quoted systematic errors.
The fit based on CIPT gives α
S
(m
τ
2)=0.344±0.005±0.007, where the first error is experimental and the second theoretical. After evolution to M
Z
we obtain α
S
(M
Z
2)=0.1212±0.0005±0.0008±0.0005, where the errors are respectively experimental, theoretical and due to the evolution. The result
is in agreement with the corresponding N3LO value derived from essentially the Z width in the global electroweak fit. The α
S
(M
Z
2) determination from τ decays is the most precise one to date. 相似文献
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V. A. Demin E. A. Konstantinova M. B. Gongal’skii 《Russian Journal of Physical Chemistry B, Focus on Physics》2008,2(5):753-756
The special features of the interaction of silicon dangling bonds on the surface of porous silicon with oxygen molecules were studied by EPR spectroscopy. The effectiveness of magnetic dipole-dipole interaction between these defects and oxygen molecules decreased as the size of sample granules diminished, because the concentration of defects then increased and, as a consequence, the contribution of their mutual dipole-dipole relaxation grew. 相似文献
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Decay properties of <Emphasis Type="Italic">N</Emphasis>∼<Emphasis Type="Italic">Z</Emphasis> nuclei
E. Roeckl 《Physics of Atomic Nuclei》2002,65(4):689-696
By using heavy-ion induced fusion-evaporation reactions at the on-line mass separator of GSI, the decay properties of neutron-deficient isotopes between 56Ni and 100Sn were investigated. The experimental results will be presented and discussed in comparison with model predictions. 相似文献
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Through phase transformation kinetic analysis and experimental observation, the δ/γ transformation occurring in the non-equilibrium peritectic Fe-4.33at.%Ni alloys was systematically investigated. According to JMA solid-state transformation kinetic theory, the Time-Temperature-Transformation (TTT) curves of the δ/γ transformation in peritectic Fe-Ni alloy were calculated. On this basis, the physical correlation between the δ/γ transformation and the initial undercooling of melt (△T) was elucidated. The results indicate that the change of △T can alter not only the overall δ/γ transformation pathways but also the transformation fraction with respect to each transformation mechanism. 相似文献
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Employing the transfer matrix method, we study the electromagnetic field of one-dimensional photonic crystals with a defect
inserted by pairs of μ-negative (MNG) and ε-negative (ENG) material layers. The fields within the pairs of layers and the matrix defect are independent of each other,
and the whole field is their superposition. The whole defect field can be significantly enhanced by pairs of ε-negative and μ-negative layers. In contrast to the conventional defect modes, the intensity and volume of the defect field with pairs of
ε-negative and μ-negative layers can be precisely adjusted. 相似文献
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Cestmir Burdik Sergey Krivonos Andrey Shcherbakov 《Czechoslovak Journal of Physics》2005,55(11):1357-1364
We show that it is possible to construct a supersymmetric mechanics with four supercharges possessing not conformally flat
target space. A general idea of constructing such models is presented. A particular case with Eguchi-Hanson target space is
investigated in detail: we present the standard and quotient approaches to get the Eguchi-Hanson model, demonstrate their
equivalence, give a full set of nonlinear constraints, study their properties and give an explicit expression for the target
space metric.
Presented at the International Colloquium “Integrable Systems and Quantum Symmetries”, Prague, 16–18 June 2005. 相似文献
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The properties of polycrystalline CdTe with a grain size of 5–30 μm have been investigated using the microphotoluminescence
methods of spectral analysis and topography. This material has been prepared by direct synthesis in a vapor flow of components
at a low temperature. The dominance of the Y and Z bands in the spectra reflects a nonequilibrium character of the crystallization processes. The superlinear dependences of
the luminescence intensity on the level of the band-to-band excitation indicate the exciton nature of the corresponding transitions.
The activation energies for temperature quenching of luminescence in the temperature range T = 100–150 K are found to be 120 meV for the Y luminescence and 180 meV for the Z luminescence, which correspond to the dissociation of excitons bound to defects with the transition of charge carriers to
the conduction and valence bands. The monochromatic topography data indicate that Y and Z defects have different material bases. 相似文献
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Ctirad Klimčík 《International Journal of Theoretical Physics》2007,46(10):2443-2463
We show that D-branes in the Euclidean AdS
3 can be naturally associated to the maximally isotropic subgroups of the Lu–Weinstein double of SU(2). This picture makes very transparent the residual loop group symmetry of the D-brane configurations and gives also immediately the D-branes shapes and the σ-model boundary conditions in the de Sitter T-dual of the SL(2,C)/SU(2) WZW model. 相似文献