27,040 research outputs found
Electronic Structure of ZnCNi3
According to a recent report by Park et al, ZnCNi3 is isostructural and
isovalent to the superconducting (Tc = 8 K) anti-perovskite, MgCNi3, but shows
no indication of a superconducting transition down to 2K. A comparison of
calculated electronic structures shows that the main features of MgCNi3,
particularly the van Hove singularity near the Fermi energy, are preserved in
ZnCNi3. Thus the reported lack of superconductivity in ZnCNi3 is not
explainable in terms of Tc being driven to a very low value by a small Fermi
level density of states. We propose that the lack of superconductivity, the
small value of the linear specific heat coefficient, gamma, and the discrepancy
between theoretical and experimental lattice constants can all be explained if
the material is assumed to be a C-deficient alpha-ZnCNi3 similar to the
analogous non-superconducting phase of MgCNi3
Oxidation Behavior of a Pd_(43)Cu_(27)Ni_(10)P_(20) Bulk Metallic Glass and Foam in Dry Air
The oxidation behavior of both Pd_(43)Cu_(27)Ni_(10)P_(20) bulk metallic glass (Pd4-BMG) and its amorphous foam containing 45 pct porosity (Pd4-AF) was investigated over the temperature range of 343 K (70 °C) to 623 K (350 °C) in dry air. The results showed that virtually no oxidation occurred in the Pd4-BMG at T < 523 K (250 °C), revealing the alloyâs favorable oxidation resistance in this temperature range. In addition, the oxidation kinetics at T â„ 523 K (250 °C) followed a parabolic-rate law, and the parabolic-rate constants (k_p values) generally increased with temperature. It was found that the oxidation k_p values of the Pd4-AF are slightly lower than those of the Pd4-BMG, indicating that the porous structure contributes to improving the overall oxidation resistance. The scale formed on the alloys was composed exclusively of CuO at T â„ 548 K (275 °C), whose thickness gradually increased with increasing temperature. In addition, the amorphous structure remained unchanged at T †548 K (275 °C), while a triplex-phase structure developed after the oxidation at higher temperatures, consisting of Pd_2Ni_2P, Cu_3P, and Pd_3P
Magnetic coupling of a rotating black hole with its surrounding accretion disk
Effects of magnetic coupling (MC) of a rotating black hole (BH) with its
surrounding accretion disk are discussed in detail in the following aspects:
(i) The mapping relation between the angular coordinate on the BH horizon and
the radial coordinate on the disk is modified based on a more reasonable
configuration of magnetic field, and a condition for coexistence of the
Blandford-Znajek (BZ) and the MC process is derived. (ii) The transfer
direction of energy and angular momentum in MC process is described
equivalently by the co-rotation radius and by the flow of electromagnetic
angular momentum and redshifted energy, where the latter is based on an
assumption that the theory of BH magnetosphere is applicable to both the BZ and
MC processes. (iii) The profile of the current on the BH horizon and that of
the current density flowing from the magnetosphere onto the horizon are given
in terms of the angular coordinate of the horizon. It is shown that the current
on the BH horizon varies with the latitude of the horizon and is not continuous
at the angular boundary between the open and closed magnetic field lines. (iv)
The MC effects on disk radiation are discussed, and a very steep emissivity is
produced by MC process, which is consistent with the recent XMM-Newton
observation of the nearby bright Seyfert 1 galaxy MCG-6-30-15 by a variety of
parameters of the BH-disk system.Comment: 24 pages, 19 figures. Accepted by Ap
Distributed Adaptive Attitude Synchronization of Multiple Spacecraft
This paper addresses the distributed attitude synchronization problem of
multiple spacecraft with unknown inertia matrices. Two distributed adaptive
controllers are proposed for the cases with and without a virtual leader to
which a time-varying reference attitude is assigned. The first controller
achieves attitude synchronization for a group of spacecraft with a leaderless
communication topology having a directed spanning tree. The second controller
guarantees that all spacecraft track the reference attitude if the virtual
leader has a directed path to all other spacecraft. Simulation examples are
presented to illustrate the effectiveness of the results.Comment: 13 pages, 11 figures. To appear in SCIENCE CHINA Technological
Science
Composition, vigor, and proteome of mature soybean seeds developed under high temperature
The effects of high temperature treatment on soybean [Glycine max (L.) Merr.] seed composition, vigor, and proteome were investigated using mature dry seeds harvested from plants grown in environment-controlled chambers. High day/night temperatures (37/30[degrees]C) from stages R5 through R8 altered ratios of individual fatty acids to total fatty acid compared to the control (27/18[degrees]C). Concentration of sugars decreased, but total protein and phytic acid concentration were unchanged. High temperature resulted in a greater proportion of abnormal seeds, but normal-appearing seed exhibited reduced germination and vigor. Proteomic analysis detected 20 protein identities whose accumulations were changed by the high temperature. Fourteen spots were identified as seven subunits of seed storage proteins. The remaining six proteins were identified as those responding to abiotic stresses or having a function in respiration: (i) sucrose binding protein, (ii) Class III acidic endochitinase, (iii) heat shock protein (HSP22), (iv) late embryo abundant protein, (v) Bowman-Birk proteinase inhibitor, and (vi) formate dehydrogenase. High temperature during seed development changed soybean seed composition and decreased seed vigor, but also changed seed protein expression profiles
Plasmon assisted transmission of high dimensional orbital angular momentum entangled state
We present an experimental evidence that high dimensional orbital angular
momentum entanglement of a pair of photons can be survived after a
photon-plasmon-photon conversion. The information of spatial modes can be
coherently transmitted by surface plasmons. This experiment primarily studies
the high dimensional entangled systems based on surface plasmon with
subwavelength structures. It maybe useful in the investigation of spatial mode
properties of surface plasmon assisted transmission through subwavelength hole
arrays.Comment: 7 pages,6 figure
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