The spectral properties of non-condensate particles in Bose-condensed atomic hydrogen

The strong spin-dipole relaxation, accompanying BEC in a gas of atomic hydrogen, determines the formation of a quasistationary state with a flux of particles in energy space to the condensate. This state is characterized by a significant enhancement of the low-energy distribution of non-condensate particles resulting in a growth of their spatial density in the trap. This growth leads to the anomalous reconstruction of the optical spectral properties of non-condensate particles.Comment: revised, 4 pages, RevTeX, 2 figure

Evidence for LineLike Vortex Liquid Phase in Tl2_2Ba2_2CaCu2_2O8_8 Probed by the Josephson Plasma Resonance

We measured the Josephson plasma resonance (JPR) in optimally doped Tl$_2$Ba$_2$CaCu$_2$O$_{8+\delta}$ thin films using terahertz time-domain spectroscopy in transmission. The temperature and magnetic field dependence of the JPR frequency shows that the c-axis correlations of pancake vortices remain intact at the transition from the vortex solid to the liquid phase. In this respect Tl$_2$Ba$_2$CaCu$_2$O$_{8+\delta}$ films, withanisotropy parameter $\gamma\approx 150$, are similar to the less anisotropic YBa$_2$Cu$_3$O$_{7-\delta}$ $(\gamma\approx 8)$ rather than to the most anisotropic Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ single crystals $\gamma\geq 500$).Comment: Submitted to Physical Review Letter

Josephson vortices and solitons inside pancake vortex lattice in layered superconductors

In very anisotropic layered superconductors a tilted magnetic field generates crossing vortex lattices of pancake and Josephson vortices (JVs). We study the properties of an isolated JV in the lattice of pancake vortices. JV induces deformations in the pancake vortex crystal, which, in turn, substantially modify the JV structure. The phase field of the JV is composed of two types of phase deformations: the regular phase and vortex phase. The phase deformations with smaller stiffness dominate. The contribution from the vortex phase smoothly takes over with increasing magnetic field. We find that the structure of the cores experiences a smooth yet qualitative evolution with decrease of the anisotropy. At large anisotropies pancakes have only small deformations with respect to position of the ideal crystal while at smaller anisotropies the pancake stacks in the central row smoothly transfer between the neighboring lattice positions forming a solitonlike structure. We also find that even at high anisotropies pancake vortices strongly pin JVs and strongly increase their viscous friction.Comment: 22 pages, 11 figures, to appear in Phys. Rev.

Effective nonlinear optical properties of composite media of graded spherical particles

We have developed a nonlinear differential effective dipole approximation (NDEDA), in an attempt to investigate the effective linear and third-order nonlinear susceptibility of composite media in which graded spherical inclusions with weak nonlinearity are randomly embedded in a linear host medium. Alternatively, based on a first-principles approach, we derived exactly the linear local field inside the graded particles having power-law dielectric gradation profiles. As a result, we obtain also the effective linear dielectric constant and third-order nonlinear susceptibility. Excellent agreement between the two methods is numerically demonstrated. As an application, we apply the NDEDA to investigate the surface plasma resonant effect on the optical absorption, optical nonlinearity enhancement, and figure of merit of metal-dielectric composites. It is found that the presence of gradation in metal particles yields a broad resonant band in the optical region, and further enhances the figure of merit.Comment: 20 pages, 5 figure

El desarrollo del habla coherente de niños en edad preescolar con trastornos del habla en el proceso de actividades de desarrollo cognitivo

At the present stage of development of defectological science and practice, the problem of speech correction of children with disabilities, in particular, preschool children with General underdevelopment of speech (GUS) has a great scientific and practical importance. The overcoming of speech disorders and the ability to choose an educational route determine the need of the organization and determination of the content of targeted comprehensive speech therapy assistance. The article scientifically justifies the possibility of using cognitive research activities to improve the performance of the speech development of children with disabilities. The efficiency of the program of development of coherent speech of preschool children with General underdevelopment of speech in cognitive research activity is experimentally proved. It is clearly shown that the inclusion of preschool children with General underdevelopment in the educational and research activities promotes the formation and development of skills of making coherent statements: phrases and sentences of the story on the demonstrated actions, story description, story based on personal experience.En la etapa actual de desarrollo de la ciencia y práctica defectológica, el problema de la corrección del habla de los niños con discapacidades, en particular, los niños en edad preescolar con subdesarrollo general del habla (GUS) tiene una gran importancia científica y práctica. La superación de los trastornos del habla y la capacidad de elegir una ruta educativa determinan la necesidad de la organización y la determinación del contenido de la asistencia integral de terapia del habla. El artículo justifica científicamente la posibilidad de utilizar actividades de investigación cognitiva para mejorar el rendimiento del desarrollo del habla de niños con discapacidades. La eficacia del programa de desarrollo del habla coherente de niños en edad preescolar con subdesarrollo general del habla en la actividad de investigación cognitiva se demuestra experimentalmente. Se muestra claramente que la inclusión de niños en edad preescolar con subdesarrollo general en las actividades educativas y de investigación promueve la formación y el desarrollo de habilidades para hacer declaraciones coherentes: frases y oraciones de la historia sobre las acciones demostradas, descripción de la historia, historia basada en la experiencia personal

Association of Insulin Resistance with Serum Interleukin-6 and TNF-α Levels During Normal Pregnancy

Overview The purpose of this study was to evaluate the role of Tumor Necrosis Factor-α (TNF-α) in insulin resistance (IR) during normal pregnancy. Approach This cross sectional study was carried out on 86 healthy pregnant women including 26, 23 and 37 individuals in the 1st, 2nd and 3rd trimesters, respectively, and in 21 healthy non pregnant women. Serum TNF-α concentration was measured by Enzyme Linked Immunosorbent Assay (ELISA) method. Results There were significant differences between serum TNF-α and IL-6 levels in pregnant women as compared with maternal healthy controls. There was significant correlation between gestational age and Body Mass Index (BMI) (r = 0.28, P = 0.01). There was no significant correlation between gestational age and insulin resistance (IR). We also did not find correlations between IR and TNF-α and IR and IL-6 in pregnant women. Conclusion In conclusion, our findings suggest that TNF-α and IL-6 are not greatly contributed to pregnancy induced insulin resistance in normal pregnancy

Quantum correlations and fluctuations in the pulsed light produced by a synchronously pumped optical parametric oscillator below its oscillation threshold

We present a simple quantum theory for the pulsed light generated by a synchronously pumped optical parametric oscillator (SPOPO) in the degenerate case where the signal and idler trains of pulses coincide, below threshold and neglecting all dispersion effects. Our main goal is to precise in the obtained quantum effects, which ones are identical to the c.w. case and which ones are specific to the SPOPO. We demonstrate in particular that the temporal correlations have interesting peculiarities: the quantum fluctuations at different times within the same pulse turn out to be totally not correlated, whereas they are correlated between nearby pulses at times that are placed in the same position relative to the centre of the pulses. The number of significantly correlated pulses is of the order of cavity finesse. We show also that there is perfect squeezing at noise frequencies multiple of the pulse repetition frequency when one approaches the threshold from below on the signal field quadrature measured by a balanced homodyne detection with a local oscillator of very short duration compared to the SPOPO pulse length.Comment: 12 pages, 3 figure

Photon-Photon Scattering, Pion Polarizability and Chiral Symmetry

Recent attempts to detect the pion polarizability via analysis of $\gamma\gamma\rightarrow\pi\pi$ measurements are examined. The connection between calculations based on dispersion relations and on chiral perturbation theory is established by matching the low energy chiral amplitude with that given by a full dispersive treatment. Using the values for the polarizability required by chiral symmetry, predicted and experimental cross sections are shown to be in agreement.Comment: 21 pages(+10 figures available on request), LATEX, UMHEP-38

Quasiparticle and Cooper Pair Tunneling in the Vortex State of Bi-2212

From measurements of the c-axis I-V characteristics of intrinsic Josephson junctions in Bi_2Sr_2CaCu_2O_{8+delta} (Bi-2212) mesas we obtain the field dependence (H || c) of the quasiparticle (QP) conductivity, sigma_q(H,T), and of the Josephson critical current density, J_c(H,T). The quasiparticle conductivity sigma_q(H) increases sharply with H and reaches a plateau at 0.05 T <H< 0.3 T. We explain such behavior by the dual effect of supercurrents around vortices. First, they enhance the QP DOS, leading to an increase of sigma_q with H at low H and, second, they enhance the scattering rate for specular tunneling as pancakes become disordered along the c-axis at higher H, leading to a plateau at moderate H.Comment: 4 pages, 4 figure

Effects of spin-elastic interactions in frustrated Heisenberg antiferromagnets

The Heisenberg antiferromagnet on a compressible triangular lattice in the spin- wave approximation is considered. It is shown that the interaction between quantum fluctuations and elastic degrees of freedom stabilizes the low symmetric L-phase with a collinear Neel magnetic ordering. Multi-stability in the dependence of the on-site magnetization on an unaxial pressure is found.Comment: Revtex, 4 pages, 2 eps figure