1,996 research outputs found
A new approach to crystal growth of Hg1−xCdxTe by the travelling heater method (THM)
Crystal growth by the travelling heater method (THM) is reported using a source material preparation process that is different from all methods used before. Non-stoichiometric (Hg, Cd)Te melts were homogenized and quenched to prevent macroscopic segregation effects. Inclusions of excess Te were removed during a first THM pass, resulting in stoichiometric solid alloys with a shift of the mole fraction towards higher CdTe contents. The amount of the shift, dependent on the Te excess and on the equilibrium temperature of the first THM run, was calculated and taken into account in the preparation of x=0.22 and x=0.30 Hg1-xCdxTe single crystals. Source material ingots, as well as THM single crystals, were characterized with special emphasis of the compositional homogeneity. Radial as well as axial homogeneity are comparable with the best results on THM crystals reported so far. The described method can be used in growing all materials for which THM is possible. However, quantitative calculation requires the exact knowledge of the particular ternary phase diagram
Superconductivity in metal rich Li-Pd-B ternary Boride
8K superconductivity was observed in the metal rich Li-Pd-B ternary system.
Structural, microstructural, electrical and magnetic investigations for various
compositions proved that Li2Pd3B compound, which has a cubic structure composed
of distorted Pd6B octahedrons, is responsible for the superconductivity. This
is the first observation of superconductivity in metal rich ternary borides
containing alkaline metal and Pd as a late transition metal. The compound
prepared by arc melting has high density, is stable in the air and has an upper
critical field, Hc2(0), of 6T.Comment: 4 pages, 5 figur
Damping by slow relaxing rare earth impurities in Ni80Fe20
Doping NiFe by heavy rare earth atoms alters the magnetic relaxation
properties of this material drastically. We show that this effect can be well
explained by the slow relaxing impurity mechanism. This process is a
consequence of the anisotropy of the on site exchange interaction between the
4f magnetic moments and the conduction band. As expected from this model the
magnitude of the damping effect scales with the anisotropy of the exchange
interaction and increases by an order of magnitude at low temperatures. In
addition our measurements allow us to determine the relaxation time of the 4f
electrons as a function of temperature
Unique Transcriptional Profile of Sustained Ligand-Activated Preconditioning in Pre- and Post-Ischemic Myocardium
BACKGROUND: Opioidergic SLP (sustained ligand-activated preconditioning) induced by 3–5 days of opioid receptor (OR) agonism induces persistent protection against ischemia-reperfusion (I-R) injury in young and aged hearts, and is mechanistically distinct from conventional preconditioning responses. We thus applied unbiased gene-array interrogation to identify molecular effects of SLP in pre- and post-ischemic myocardium. METHODOLOGY/PRINCIPAL FINDINGS: Male C57Bl/6 mice were implanted with 75 mg morphine or placebo pellets for 5 days. Resultant SLP did not modify cardiac function, and markedly reduced dysfunction and injury in perfused hearts subjected to 25 min ischemia/45 min reperfusion. Microarray analysis identified 14 up- and 86 down-regulated genes in normoxic hearts from SLP mice (≥1.3-fold change, FDR≤5%). Induced genes encoded sarcomeric/contractile proteins (Myh7, Mybpc3,Myom2,Des), natriuretic peptides (Nppa,Nppb) and stress-signaling elements (Csda,Ptgds). Highly repressed genes primarily encoded chemokines (Ccl2,Ccl4,Ccl7,Ccl9,Ccl13,Ccl3l3,Cxcl3), cytokines (Il1b,Il6,Tnf) and other proteins involved in inflammation/immunity (C3,Cd74,Cd83, Cd86,Hla-dbq1,Hla-drb1,Saa1,Selp,Serpina3), together with endoplasmic stress proteins (known: Dnajb1,Herpud1,Socs3; putative: Il6, Gadd45g,Rcan1) and transcriptional controllers (Egr2,Egr3, Fos,Hmox1,Nfkbid). Biological themes modified thus related to inflammation/immunity, together with cellular/cardiovascular movement and development. SLP also modified the transcriptional response to I-R (46 genes uniquely altered post-ischemia), which may influence later infarction/remodeling. This included up-regulated determinants of cellular resistance to oxidant (Mgst3,Gstm1,Gstm2) and other forms of stress (Xirp1,Ankrd1,Clu), and repression of stress-response genes (Hspa1a,Hspd1,Hsp90aa,Hsph1,Serpinh1) and Txnip. CONCLUSIONS: Protection via SLP is associated with transcriptional repression of inflammation/immunity, up-regulation of sarcomeric elements and natriuretic peptides, and modulation of cell stress, growth and development, while conventional protective molecules are unaltered
Virial theorem for rotating self-gravitating Brownian particles and two-dimensional point vortices
We derive the proper form of Virial theorem for a system of rotating
self-gravitating Brownian particles. We show that, in the two-dimensional case,
it takes a very simple form that can be used to obtain general results about
the dynamics of the system without being required to solve the
Smoluchowski-Poisson system explicitly. We also develop the analogy between
self-gravitating systems and two-dimensional point vortices and derive a
Virial-like relation for the vortex system
The Vlasov continuum limit for the classical microcanonical ensemble
For classical Hamiltonian N-body systems with mildly regular pair interaction
potential it is shown that when N tends to infinity in a fixed bounded domain,
with energy E scaling quadratically in N proportional to e, then Boltzmann's
ergodic ensemble entropy S(N,E) has the asymptotic expansion S(N,E) = - N log N
+ s(e) N + o(N); here, the N log N term is combinatorial in origin and
independent of the rescaled Hamiltonian while s(e) is the system-specific
Boltzmann entropy per particle, i.e. -s(e) is the minimum of Boltzmann's
H-function for a perfect gas of "energy" e subjected to a combination of
externally and self-generated fields. It is also shown that any limit point of
the n-point marginal ensemble measures is a linear convex superposition of
n-fold products of the H-function-minimizing one-point functions. The proofs
are direct, in the sense that (a) the map E to S(E) is studied rather than its
inverse S to E(S); (b) no regularization of the microcanonical measure
Dirac(E-H) is invoked, and (c) no detour via the canonical ensemble. The proofs
hold irrespective of whether microcanonical and canonical ensembles are
equivalent or not.Comment: Final version; a few typos corrected; minor changes in the
presentatio
High power and spectral purity continuous-wave photonic THz source tunable from 1 to 4.5 THz for nonlinear molecular spectroscopy
We report a diffraction-limited photonic terahertz (THz) source with linewidth \u3c 10 MHz that can be used for nonlinear THz studies in the continuous wave (CW) regime with uninterrupted tunability in a broad range of THz frequencies. THz output is produced in orientation-patterned (OP) gallium arsenide (GaAs) via intracavity frequency mixing between the two closely spaced resonating signal and idler waves of an optical parametric oscillator (OPO) operating near lambda = 2 mu m. The doubly resonant type II OPO is based on a periodically poled lithium niobate (PPLN) pumped by a single-frequency Yb:YAG disc laser at 1030 nm. We take advantage of the enhancement of both optical fields inside a high-finesse OPO cavity: with 10 W of 1030 nm pump, 100 W of intracavity power near 2 mu m was attained with GaAs inside cavity. This allows dramatic improvement in terms of generated THz power, as compared to the state-of-the art CW methods. We achieved \u3e 25 mu W of single-frequency tunable CW THz output power scalable to \u3e 1 mW with proper choice of pump laser wavelength
Nonperturbative calculation of Born-Infeld effects on the Schroedinger spectrum of the hydrogen atom
We present the first nonperturbative numerical calculations of the
nonrelativistic hydrogen spectrum as predicted by first-quantized
electrodynamics with nonlinear Maxwell-Born-Infeld field equations. We also
show rigorous upper and lower bounds on the ground state.
When judged against empirical data our results significantly restrict the
range of viable values of the new electromagnetic constant which is introduced
by the Born-Infeld theory.
We assess Born's own proposal for the value of his constant.Comment: 4p., 2 figs, 1 table; submitted for publicatio
Monotonicity of quantum ground state energies: Bosonic atoms and stars
The N-dependence of the non-relativistic bosonic ground state energy is
studied for quantum N-body systems with either Coulomb or Newton interactions.
The Coulomb systems are "bosonic atoms," with their nucleus fixed, and the
Newton systems are "bosonic stars". In either case there exists some third
order polynomial in N such that the ratio of the ground state energy to the
respective polynomial grows monotonically in N. Some applications of these new
monotonicity results are discussed
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