344 research outputs found
Quantum discord in spin-cluster materials
The total quantum correlation (discord) in Heisenberg dimers is expressed via
the spin-spin correlation function, internal energy, specific heat or magnetic
susceptibility. This allows one to indirectly measure the discord through
neutron scattering, as well as calorimetric or magnetometric experiments. Using
the available experimental data, we found the discord for a number of binuclear
Heisenberg substances with both antiferro- and ferromagnetic interactions. For
the dimerized antiferromagnet copper nitrate Cu(NO_3)_2*2.5H_2O, the three
independent experimental methods named above lead to a discord of approximately
0.2-0.3 bit/dimer at a temperature of 4 K. We also determined the temperature
behavior of discord for hydrated and anhydrous copper acetates, as well as for
the ferromagnetic binuclear copper acetate complex [Cu_2L(OAc)]*6H_2O, where L
is a ligand.Comment: 7 pages, 6 figure
A Lithium Experiment in the Program of Solar Neutrino Research
The experiments sensitive to pp-neutrinos from the Sun are very perspective
for the precise measurement of a mixing angle . A e
scattering experiment (Xmass) and/or a charged-current experiment (the indium
detector) can measure the flux of electron pp-neutrinos. One can find the total
flux of pp-neutrinos from a luminosity constraint after the contribution of
Be and CNO neutrinos to the total luminosity of the Sun are measured. The
radiochemical experiment utilizing a lithium target has the high sensitivity to
the CNO neutrinos, thus, it has a good promise for the precise measurement of a
mixing angle and for the test of a current theory of the evolution of the
stars.Comment: 6 pages, 2 figures, 1 table, A report made by A.Kopylov at
International Conference NANP-2005, June 2005, Dubna, Russi
Hanbury Brown-Twiss interferometry and second-order correlations of inflaton quanta
The quantum theory of optical coherence is applied to the scrutiny of the
statistical properties of the relic inflaton quanta. After adapting the
description of the quantized scalar and tensor modes of the geometry to the
analysis of intensity correlations, the normalized degrees of first-order and
second-order coherence are computed in the concordance paradigm and are shown
to encode faithfully the statistical properties of the initial quantum state.
The strongly bunched curvature phonons are not only super-Poissonian but also
super-chaotic. Testable inequalities are derived in the limit of large angular
scales and can be physically interpreted in the light of the tenets of Hanbury
Brown-Twiss interferometry. The quantum mechanical results are compared and
contrasted with different situations including the one where intensity
correlations are the result of a classical stochastic process. The survival of
second-order correlations (not necessarily related to the purity of the initial
quantum state) is addressed by defining a generalized ensemble where
super-Poissonian statistics is an intrinsic property of the density matrix and
turns out to be associated with finite volume effects which are expected to
vanish in the thermodynamic limit.Comment: 42 pages, 3 included figures; corrected typos; to appear in Physical
Review
Anomalously strong pinning of the filling factor nu=2 in epitaxial graphene
We explore the robust quantization of the Hall resistance in epitaxial
graphene grown on Si-terminated SiC. Uniquely to this system, the dominance of
quantum over classical capacitance in the charge transfer between the substrate
and graphene is such that Landau levels (in particular, the one at exactly zero
energy) remain completely filled over an extraordinarily broad range of
magnetic fields. One important implication of this pinning of the filling
factor is that the system can sustain a very high nondissipative current. This
makes epitaxial graphene ideally suited for quantum resistance metrology, and
we have achieved a precision of 3 parts in 10^10 in the Hall resistance
quantization measurements
Fabrication of YAG:RE (RE = Yb, Nd, Cr) Ceramics Using Divalent Sintering Aids
High-quality YAG:RE (Yb, Nd, Cr) ceramics with CaO and MgO as sintering aids were manufactured by solid state reactive sintering method in vacuum. Influence of annealing temperature on optical properties was studied. This combination of sintering aids requires annealing temperatures at least 1300∘C to fully eliminate oxygen vacancies and at least 1400∘C to convert Cr3+ to Cr4+. It was found that annealing in oxidizing atmosphere creates strong changes in short wavelength transmittance.
Keywords: laser ceramics, Yttrium aluminium garnet, sintering aid
Problems of High-quality Doped Y2O3-ceramics Fabrication
Tm:Y2O3 , Ho:Y2O3 and Yb:Y2O3 ceramic samples were fabricated using different heat treatments modes. La2O3 (0.5 mol.%) and ZrO2 (1.5 mol.%) were used as sintering additives. Based on the investigation of structural properties of obtained samples, annealing mode was adjusted, and another set of samples with better optical quality was fabricated. In-line transmittance of the latter samples is 70% at 400nm and 75.6% at 600nm.
Keywords: Y2O3 , laser ceramic
RC J1148+0455 identification: gravitational lens or group of galaxies ?
The structure of the radio source RC B1146+052 of the ``Cold'' catalogue is
investigated by data of the MIT-GB-VLA survey at 4850 MHz. This source belongs
to the steep spectrum radio sources subsample of the RC catalogue. Its spectral
index is = -1.04. The optical image of this source obtained with 6m
telescope is analysed. The radio source center is situated in a group of 8
galaxies of about 24 in the R-filter. The possible explanations of the
complex structure of radio components are considered.Comment: 6 pages, 5 figures, uses psfig.sty. This was the poster as presented
on Gamow Memorial Internat. Conference GMIC'99 "Early Universe: Cosmological
Problems and Instrumental Technologies" in St.Petersburg, 23-27 Aug., 1999.
Submitted to Proceedings to be published in A&A Transaction
Theory of plastic vortex creep
We develop a theory for plastic flux creep in a topologically disordered
vortex solid phase in type-II superconductors. We propose a detailed
description of the plastic vortex creep of the dislocated, amorphous vortex
glass in terms of motion of dislocations driven by a transport current . The
{\em plastic barriers} show power-law divergence at
small drives with exponents for single dislocation creep and for creep of dislocation bundles. The suppression of the creep rate is a
hallmark of the transition from the topologically ordered vortex lattice to an
amorphous vortex glass, reflecting a jump in from ,
characterizing creep in the topologically ordered vortex lattice near the
transition, to its plastic values. The lower creep rates explain the observed
increase in apparent critical currents in the dislocated vortex glass.Comment: 4 pages, 1 figur
Some aspects of examination of children with combined spine and pelvis pathology living in an industrial city
The aim of the study was to analyze the peculiarities of combined spinal and pelvic pathology in children living on the industrial area of the Irkutsk Region. To perform the analysis we carried out the clinical-roentgenological research, and when making orthopedic examination we took into consideration ecological factors and used the chart of multivariative analysis. It was found that in the structure of combined pathology, pelvis asymmetry ranks first, scoliosis ranks second, Legg - Calve - Perthes disease ranks third. According to the assessment of age structure of combined pathology we can conclude that at the equal manifestations of scoliosis, Spina bifida, retrospondylolisthesis, pelvis asymmetry, children of 11-15 y.o. more often have Legg - Calve - Perthes disease, children of 16-21 y.o. - coxarthrosis. In its turn relative share of Legg - Calve - Perthes disease cases in children living within a radius of 5 km from the industrial center is the largest (21 из 28 cases). It's important to mention that Legg - Calve - Perthes disease was registered in all examined boys and only in 35.5 % of girls. I and II degrees of manifestation of clinicoroentgenologic disorders of combined spine and pelvis pathology prevail (77 and 43 cases correspondingly) over the disorders of the III degree (15 cases)
CONCOMITANT DEFORMITIES AND DISORDERS OF THE SPINE AND PELVIS IN TERMS OF AGE ASPECT (LITERATURE REVIEW)
The article presents review of literature data concerning modern vision of concomitant deformities and disorders of the spine and pelvis in terms of age aspect, covering the causes of development of locomotor system functional disorders in children and teenagers and considering information on concomitant orthopedic pathology. The authors analyse new approaches to health evaluation in various age groups of population. The conclusion has been made, that despite certain success obtained in studying separate degenerative-dystrophic disorders of locomotor system, there is no unique solution to the problem of concomitant deformities and disorders of the spine and pelvis and their mutual interaction
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