X-ray and neutron diffraction studies of coupled structural phase transitions in DyBaCo2_{2}O5.5_{5.5}

A structural transition at $T\approx 322$ K from the $Pmmm$ to $Pmma$ phase is found to coincide with an anomaly of resistivity. Another structural phase transition doubling the lattice parameter $c$, which has been postulated earlier to accompany a low-temperature magnetic transition in TbBaCo$_{2}$O$_{5.5}$, is observed in a single crystal DbBaCo$_{2}$O$_{5.5}$ by means of the X-ray and neutron diffraction. The low temperature phase does not belong to the space group $Pcca$ that has been chosen earlier as the highest subgroup of the $Pmma$. The transition is of the first order with the temperature hysteresis, between $T\approx 100$ and $T\approx 200$ K, which probably explains anomalous magnetic properties in this temperature range.Comment: 6 pages, 4 figure

Phonon Raman scattering in LaMn₁₋xCoxO₃ (x = 0, 0.2, 0.3, 0.4, and 1.0)

The Raman-active phonons in perovskite-like LaMn₁–xCoxO₃ (x = 0, 0.2, 0.3, 0.4, and 1.0) were studied by measuring Raman spectra at temperatures of 295 and 5 K. The changes in the spectra with Co doping are correlated with the decrease of orthorhombic distortions. Surprisingly more phonon lines than allowed for the rhombohedral LaCoO₃ structure were observed

Nab: Measurement Principles, Apparatus and Uncertainties

The Nab collaboration will perform a precise measurement of 'a', the electron-neutrino correlation parameter, and 'b', the Fierz interference term in neutron beta decay, in the Fundamental Neutron Physics Beamline at the SNS, using a novel electric/magnetic field spectrometer and detector design. The experiment is aiming at the 10^{-3} accuracy level in (Delta a)/a, and will provide an independent measurement of lambda = G_A/G_V, the ratio of axial-vector to vector coupling constants of the nucleon. Nab also plans to perform the first ever measurement of 'b' in neutron decay, which will provide an independent limit on the tensor weak coupling.Comment: 12 pages, 6 figures, 1 table, talk presented at the International Workshop on Particle Physics with Slow Neutrons, Grenoble, 29-31 May 2008; to appear in Nucl. Instrum. Meth. in Physics Research

Spin oscillations in transient diffusion of a spin pulse in n-type semiconductor quantum wells

By studying the time and spatial evolution of a pulse of the spin polarization in $n$-type semiconductor quantum wells, we highlight the importance of the off-diagonal spin coherence in spin diffusion and transport. Spin oscillations and spin polarization reverse along the the direction of spin diffusion in the absence of the applied magnetic field are predicted from our investigation.Comment: 5 pages, 4 figures, accepted for publication in PR

ACUTE EPIGLOTTITIS IN CHILDREN (ETIOPATHOGENESIS, DIAGNOSIS, TREATMENT)

Acute epiglottitis (AE) must be considered as not a separate entdisease but as compound pathology with wide polymorphism, which can often need an intervention of different medical specialists: experts in resuscitation, infectiologists, immunologists, pulmonologists, and cardiologists. The increase of rate of AE and its septic complications and severe outcomes in last years forced us to consider this problem in detail on the basis of longstanding experience of Morozov children's city clinical hospital.Key words: children, acute epiglottitis, etiology, diagnosis, treatment

Magnetic properties lithium-doped manganite single crystals

Magnetic and resistivity properties of La₁₋xLixMnO₃ single crystals with the perovskite structure at lithium concentrations x=0.06 and 0.2 are investigated over a broad temperature range at fields of up to 50 kOe. The Curie temperature is TC=90 K (x=0.06) and 300 K (x=0.2), respectively. The electrical resistance of the single crystal with x=0.06 increases steadily with temperature decrease, while the crystal with x=0.2 exhibits a magnetoresistance effect of ~ 8% at an external field of 9 kOe. The different dependence of the magnetizations MFC and MZFC of the sample with lower lithium content in the temperature range below TC is associated with the formation of a cluster glass and is caused by high coercivity and magnetic anisotropy of the crystal