266 research outputs found
Narrowband Biphoton Generation due to Long-Lived Coherent Population Oscillations
We study the generation of paired photons due to the effect of four-wave
mixing in an ensemble of pumped two-level systems that decay via an
intermediate metastable state. The slow population relaxation of the metastable
state to the ground state is utilized to create long-lived coherent population
oscillation, leading to narrowband nonlinear response of the medium. The
biphotons have a narrow bandwidth, long coherence time and length, which can be
controlled by the pump field. In addition, the biphotons are antibunched, with
antibunching period determined by the dephasing time. During this period,
damped oscillations of the biphoton wavefunction occurs if the pump detuning is
non-zero.Comment: 7 pages, 2 figure
Comparative analysis of results of treatment patients with severe spinal deformities using screw and a hybrid hardware
Purpose: evaluation of efficacy of operative treatment with the use of screw and hybrid metal constructions in idiopathic scoliosis associated with severe spine deformities. Material and methods: The outcomes of treatment of 34 patients aged 15 to 27 years old with severe scoliosisoperated on using screw metal constructions, were reviewed. 22 patients operated on with the use of hybrid metal constructions, made a control group. The groups were compared by the following parameters: pre- and postoperative Cobb angle, deformity mobility according to traction test, total sagittal/frontal balance, CT apical vertebra rotation, operation time, intraoperative blood loss, the number of instrumented vertebrae, and correction failure at 24-hr spondylograms. Results: Group A (screw spine fixation) demonstrated better outcomes compared to group B (combined spine fixation) in the following parameters. Postoperative correction was 48% and 41%;apical vertebra rotation decreased from 78° to 55° (30%) and from 74° to 59°(21%);total sagittal/frontal balance decreased from 39/25 mmto 14/12 mm (64/52%) and from 35/26 mm to 16/15 mm (55/43%), correspondingly. These results suggest better trunk compensation and postoperative correction in a group of patients with screw fixation. Smaller values of correction failure of the main arc as well as insignificant increase of thoracic kyphosis in the postoperative period (24 months) 3.8%/4.3% in group A compared to 6.2%/7.5% in group B testify to greater reliability and stability of ‘all screw’ metal constructions. The number of fixed elements was on average one more in a group with combined fixation (13 and 14, correspondingly)
OPERATIVE TREATMENT OF SPINAL DEFORMITIES IN PATIENTS WITH CEREBRAL PALSY
Surgical treatment of scoliosis on the background of cerebral palsy is carried out by the correction and polysegmental fixation of the spine and helps to improve balance the body, activate patient in a wheelchair, to prevent the subsequent progression of spinal deformity and rib cage, and improve self-care patients
Mutation yellow in agouti loci prevents age-related increase of skeletal muscle genes regulating free fatty acids oxidation
The lethal yellow mutation in agouti loci (Ay mutation) reduces the activity of melanocortin (MC) receptors and causes hyperphagia, obesity and type two diabetes mellitus in aging mice (Ay mice). It is unknown if changes in distinct elements of the metabolic system such as white adipose tissue (WAT) and brown adipose tissue (BAT), and skeletal muscle will manifest before the development of obesity. The aim of this work was to measure the relative gene expression of key proteins that regulate carbohydrate-lipid metabolism in WAT, BAT and skeletal muscle in Ay mice before the development of obesity. C57Bl/6J mice bearing a dominant autosomal mutation Ay (Ay /a mice) and mice of the standard genotype (a/a mice, control) have been studied in three age groups: 10, 15 and 30 weeks. The relative mRNA level of genes was measured by real-time PCR in skeletal muscles (uncoupling protein 3 (Ucp3) and carnitine palmitoyl transferase 1b (Cpt1b) (free fatty acids oxidation), solute carrier family 2 (facilitated glucose transporter), member 4 (Slc2a4) (glucose uptake)), in WAT lipoprotein lipase (Lpl) (triglyceride deposition), hormone-sensitive lipase (Lipe) (lipid mobilization), and Slc2a4 (glucose uptake)), and in BAT: uncoupling protein 1 (Ucp1) (energy expenditure). The expression of Cpt1b was reduced in young Ay mice (10 weeks), there was no transient peak of transcription of Cpt1b, Ucp3 in skeletal muscle tissue and Lipe, Slc2a4 in WAT in early adult Ay mice (15 weeks), which was noted in а/а mice. Reduction of the transcriptional activity of the studied genes in skeletal muscle and white adipose tissue can initiate the development of melanocortin obesity in Ay mice
Superconductivity on the localization threshold and magnetic-field-tuned superconductor-insulator transition in TiN films
Temperature- and magnetic-field dependent measurements of the resistance of
ultrathin superconducting TiN films are presented. The analysis of the
temperature dependence of the zero field resistance indicates an underlying
insulating behavior, when the contribution of Aslamasov-Larkin fluctuations is
taken into account. This demonstrates the possibility of coexistence of the
superconducting and insulating phases and of a direct transition from the one
to the other. The scaling behavior of magnetic field data is in accordance with
a superconductor-insulator transition (SIT) driven by quantum phase
fluctuations in two-dimensional superconductor. The temperature dependence of
the isomagnetic resistance data on the high-field side of the SIT has been
analyzed and the presence of an insulating phase was confirmed. A transition
from the insulating to a metallic phase is found at high magnetic fields, where
the zero-temperature asymptotic value of the resistance being equal to h/e^2.Comment: 5 pages, 4 eps figures, RevTeX4, Published versio
Towards the electron EDM search. Theoretical study of PbF
We report ab initio relativistic correlation calculations of potential curves
and spectroscopic constants for four lowest-lying electronic states of the lead
monofluoride. We also calculated parameters of the spin-rotational Hamiltonian
for the ground and the first excited states including P,T-odd and P-odd terms.
In particular, we have obtained hyperfine constants of the Pb nucleus.
For the state MHz, MHz and for
the A MHz, MHz. Our values of
the ground state hyperfine constants are in good agreement with the previous
theoretical studies. We discuss and explain seeming disagreement in the sign of
the constant with the recent experimental data. The effective
electric field on the electron , which is important for the planned
experiment to search for the electric dipole moment of the electron, is found
to be 3.3 * 10^{10} V/cm
Strong-Pinning Effects in Low-Temperature Creep: Charge-Density Waves in TaS_3
Nonlinear conduction in the quasi-one dimensional conductor o-TaS_3 has been
studied in the low-temperature region down to 30 mK. It was found that at
temperatures below a few Kelvins the current-voltage (I-V) characteristics
consist of several branches. The temperature evolution of the I-V curve
proceeds through sequential freezing-out of the branches. The origin of each
branch is attributed to a particular strong pinning impurity type.
Similar behavior is expected for other physical systems with collective
transport (spin-density waves, Wigner crystals, vortex lattices in type-II
superconductors etc.) in the presence of strong pinning centers.Comment: 11 pages, 3 ps figures, Revtex, To be published in Phys. Rev. Letters
(1997
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