Orbiton-mediated multi-phonon scattering in La1−x_{1-x}Srx_xMnO3_3

We report on Raman scattering measurements of single crystalline La$_{1-x}$Sr$_x$MnO$_3$ ($x$=0, 0.06, 0.09 and 0.125), focusing on the high frequency regime. We observe multi-phonon scattering processes up to fourth-order which show distinct features: (i) anomalies in peak energy and its relative intensity and (ii) a pronounced temperature-, polarization-, and doping-dependence. These features suggest a mixed orbiton-phonon nature of the observed multi-phonon Raman spectra.Comment: 6pages, 6figures, submitted to PR

Pressure-induced melting of the orbital polaron lattice in La1-xSrxMnO3

We report on the pressure effects on the orbital polaron lattice in the lightly doped manganites $\mathrm{La_{1-x}Sr_xMnO_{3}}$, with $x\sim 1/8$. The dependence of the orbital polaron lattice on $negative$ chemical pressure is studied by substituting Pr for La in $\mathrm{(La_{1-y}Pr_y)_{7/8}Sr_{1/8}MnO_{3}}$. In addition, we have studied its hydrostatic pressure dependence in $\mathrm{(La_{0.9}Pr_{0.1})_{7/8}Sr_{1/8}MnO_{3}}$. Our results strongly indicate that the hopping $t$ significantly contributes to the stabilization of the orbital polaron lattice and that the orbital polarons are ferromagnetic objects which get stabilized by local double exchange processes. The analysis of short range orbital correlations and the verification of the Grueneisen scaling by hard x-ray, specific heat and thermal expansion data reinforces our conclusions.Comment: 7 figure

Vaccination par le BCG : enquête auprès d'enfants de moins de 5 ans consultant dans un service d'urgences hospitalières

International audienceFrance is a country with a low incidence of tuberculosis. However, there are important local variations: some parts of the city of Marseilles (southern France) presented a yearly incidence greater than 30/100,000 in 2010. The main goal of this study was to evaluate the BCG vaccine coverage among at-risk children younger than 5 years consulting in one of the city's pediatric emergency departments. Material and methods. This descriptive study took place in February 2013 and used a semi-directive questionnaire distributed to parents. Results. One hundred and thirty-five children were included, 98 (72.6 %) were considered as being at risk of tuberculosis and among them 75 (76.5 %, 95 % CI [68.0–85.1]) were vaccinated with BCG. Parents' knowledge of tuberculosis was relevant in 48 % of the respondents. Only 19 % of the parents reported that BCG protects against tuberculosis, but 73 % were in favor of this vaccination. Two criteria significantly increased vaccine coverage among at-risk children: birth in Marseilles and age more than 6 months on the consultation day. The child living in a poor family and type of medical follow-up did not significantly influence BCG vaccine coverage. Conclusion. BCG coverage was high in at-risk children younger than 5 years born in Marseilles. Cooperation between private physicians , maternity hospitals and mothers, and children's public health services probably facilitates this high level of protection.Malgré une faible incidence de la tuberculose en France, il existe de grandes variations à l'échelle communale : certains quartiers de Marseille présentent ainsi une incidence annuelle supérieure à 30/ 100 000. Le but de notre étude etait d'évaluer la couverture vaccinale par le vaccin de Calmette et Guérin (BCG) des enfants à risque aâgés de moins de 5 ans consultant dans un service d'urgences pédiatriques. Matériel et méthodes : Cette étude descriptive a eété réalisée en février 2013 à l'aide d'un questionnaire semi-directif proposé aux parents. Résultats : Cent-trente-cinq enfants ont été inclus, 98 (72,6 %) étaient considérés àrisque de tuberculose et parmi ces derniers 75 (76,5 %, IC 95 % [68,0–85,1]) eétaient vaccinés par le BCG. Seuls 48 % des parents connaissaient la tuberculose et 19 % savaient que le BCG protégeait contre cette maladie, mais 73 % étaient favorables à ce vaccin. Deux paramètres étaient liés à la vaccination des enfants à risque : une naissance à Marseille et un âge supérieur à 6 mois le jour de la consultation. La précarité des conditions de vie et le type de suivi médical n' influençaient pas significativement la couverture vaccinale des enfants à risque. Conclusion : En 2013, la couverture vaccinale par le BCG des enfants de moins de 5 ans nés à Marseille et à risque de tuberculose était correcte mais perfectible. Une coopération entre médecins de ville, maternités et services de protection maternelle et infantile (PMI) permet probablement d'obtenir cette bonne couverture vaccinale

Existence of orbital polarons in ferromagnetic insulating La1−x_{1-x}Srx_xMnO3_{3} (0.11<x<<x<0.14) evidenced by giant phonon softening

We present an inelastic light scattering study of single crystalline (La$_{1-y}$Pr$_y$)$_{1-x}$Sr$_{x}$MnO$_3$ ($0\leq x\leq0.14$,$y=0$ and $x=1/8$,$0\leq y\leq0.5$). A giant softening up to 20 - 30 cm$^{-1}$ of the Mn-O breathing mode has been observed only for the ferromagnetic insulating (FMI) samples ($0.11\leq x \leq 0.14$) upon cooling below the Curie temperature. With increasing Pr-doping the giant softening is gradually suppressed. This is attributed to a coupling of the breathing mode to orbital polarons which are present in the FMI phase.Comment: 4 pages, 5 figure

Noble Gas (Argon and Xenon)-Saturated Cold Storage Solutions Reduce Ischemia-Reperfusion Injury in a Rat Model of Renal Transplantation

Background: Following kidney transplantation, ischemia-reperfusion injury contributes to adverse outcomes. The purpose of this study was to determine whether a cold-storage solution saturated with noble gas (xenon or argon) could limit ischemia-reperfusion injury following cold ischemia. Methods: Sixty Wistar rats were randomly allocated to 4 experimental groups. Kidneys were harvested and then stored for 6 h before transplantation in cold-storage solution (Celsior®) saturated with either air, nitrogen, xenon or argon. A syngenic orthotopic transplantation was performed. Renal function was determined on days 7 and 14 after transplantation. Transplanted kidneys were removed on day 14 for histological and immunohistochemical analyses. Results: Creatinine clearance was significantly higher and urinary albumin significantly lower in the argon and xenon groups than in the other groups at days 7 and 14. These effects were considerably more pronounced for argon than for xenon. In addition, kidneys stored with argon, and to a lesser extent those stored with xenon, displayed preserved renal architecture as well as higher CD-10 and little active caspase-3 expression compared to other groups. Conclusion: Argon- or xenon-satured cold-storage solution preserved renal architecture and function following transplantation by reducing ischemia-reperfusion injury

Epitaxy and magnetotransport of Sr_2FeMoO_6 thin films

By pulsed-laser deposition epitaxial thin films of Sr_2FeMoO_6 have been pre- pared on (100) SrTiO_3 substrates. Already for a deposition temperature of 320 C epitaxial growth is achieved. Depending on deposition parameters the films show metallic or semiconducting behavior. At high (low) deposition temperature the Fe,Mo sublattice has a rock-salt (random) structure. The metallic samples have a large negative magnetoresistance which peaks at the Curie temperature. The magnetic moment was determined to 4 mu_B per formula unit (f.u.), in agreement with the expected value for an ideal ferrimagnetic arrangement. We found an ordinary Hall coefficient of -6.01x10^{-10} m^3/As at 300 K, corresponding to an electronlike charge-carrier density of 1.3 per Fe,Mo-pair. In the semiconducting films the magnetic moment is reduced to 1 mu_B/f.u. due to disorder in the Fe,Mo sublattice. In low fields an anomalous holelike contribution dominates the Hall voltage, which vanishes at low temperatures for the metallic films only.Comment: Institute of Physics, University of Mainz, Germany, 4 pages, including 5 pictures and 1 Table, submitted to Phys. Rev.

Согласование показателей свойств руды и режимов измельчения

В случае соответствия максимумов измельчительной характеристики мельницы и моды распределения вкрапленности железной руды наблюдается повышенное раскрытие рудного минерала по сравнению, если такого соответствия нет.В случае соответствия максимумов измельчительной характеристики мельницы и моды распределения вкрапленности железной руды наблюдается повышенное раскрытие рудного минерала по сравнению, если такого соответствия нет

23Na NMR study of sodium order in Na xCoO 2 with 22 K Néel temperature

We report a systematic study of the c-lattice parameter in the Na xCoO 2 phases versus Na content x>0.5, in which sodium always displays ordered arrangements. This allows us to single out the first phase which exhibits an antiferromagnetic order at a Néel temperature T N=22 K, which is found to occur for x0.77(1). Pure samples of this phase have been studied both as aligned powders and single crystals. They exhibit identical 23Na NMR spectra in which three sets of Na sites could be fully resolved, and are found to display T dependencies of their NMR shifts, which scale with each other. This allows us to establish that the T variation of the shifts is due to the paramagnetism of the Co sites with formal charge state larger than 3 +. The existence of a sodium site with axial charge symmetry and the intensity ratio between the sets of 23Na lines permits us to reveal that the two-dimensional structure of the Na order corresponds to ten Na sites on top of a thirteen-Co-sites unit cell, that is with x=10/130.77. This structure fits with that determined from local density calculations and involves triangles of three Na sites located on top of Co sites [so-called Na1 sites]. The associated ordering of the Na vacancies is quite distinct from that found for x<0.75. © 2012 American Physical Society

Melting of the orbital order in LaMnO3 probed by NMR

The Mn spin correlations were studied near the O′-O phase transition at TJT=750 K up to 950 K with 17O and 139La NMR in a stoichiometric LaMnO3 crystalline sample. The measured local hyperfine fields originate from the electron density transferred from the eg and t2g orbitals to the 2s(O) and 6s(La) orbits, respectively. By probing the oxygen nuclei, we show that the correlations of the Mn spins are ferromagnetic in the ab plane and robust up to TJT, whereas along the c axis they are antiferromagnetic and start to melt below TJT, at about 550 K. Above TJT, the ferromagnetic Mn-Mn exchange interaction is found isotropic. The room-temperature orbital mixing angle, φNMR= 109±1.5â̂̃, of the eg ground state is close to the reported value which was deduced from structural data on Jahn-Teller distorted MnO6 octahedra. For T>TJT, LaMnO3 can be described in terms of nonpolarized eg orbitals since both eg orbitals are equally occupied. © 2013 American Physical Society