H-T Phase Diagram of Rare-Earth -- Transition Metal Alloy in the Vicinity of the Compensation Point

Anomalous hysteresis loops of ferrimagnetic amorphous alloys in high magnetic field and in the vicinity of the compensation temperature have so far been explained by sample inhomogeneities. We obtain H-T magnetic phase diagram for ferrimagnetic GdFeCo alloy using a two-sublattice model in the paramagnetic rare-earth ion approximation and taking into account rare-earth (Gd) magnetic anisotropy. It is shown that if the magnetic anisotropy of the $f$-sublattice is larger than that of the $d$-sublattice, the tricritical point can be at higher temperature than the compensation point. The obtained phase diagram explains the observed anomalous hysteresis loops as a result of high-field magnetic phase transition, the order of which changes with temperature. It also implies that in the vicinity of the magnetic compensation point the shape of magnetic hysteresis loop is strongly temperature dependent.Comment: 8 pages, 3 figure

Selection Rules for All-Optical Magnetic Recording in Iron Garnet

Finding an electronic transition a subtle excitation of which can launch dramatic changes of electric, optical or magnetic properties of media is one of the long-standing dreams in the field of photo-induced phase transitions [1-5]. Therefore the discovery of the magnetization switching only by a femtosecond laser pulse [6-10] triggered intense discussions about mechanisms responsible for these laser-induced changes. Here we report the experimentally revealed selection rules on polarization and wavelengths of ultrafast photo-magnetic recording in Co-doped garnet film and identify the workspace of the parameters (magnetic damping, wavelength and polarization of light) allowing this effect. The all-optical magnetic switching under both single pulse and multiple-pulse sequences can be achieved at room temperature, in narrow spectral ranges with light polarized either along or crystallographic axes of the garnet. The revealed selection rules indicate that the excitations responsible for the coupling of light to spins are d-electron transitions in octahedral and tetrahedral Co-sublattices, respectively

Ceria Entrapped Palladium Novel Composites for Hydrogen Oxidation Reaction in Alkaline Medium

A new heterogeneous catalyst for hydrogen oxidation reaction (HOR), metallic palladium within which nanoparticles of ceria are entrapped, CeO2@Pd, is described. Its preparation is based on a new materials methodology of molecular doping of metals. The metallic matrix, which encages the nanoparticles, is prepared in foam architecture, to ensure easy molecular diffusion. Characterization of the structural properties of the CeO2@Pd composite using SEM, STEM, TEM, XRD, EXAFS and nitrogen adsorption reveals its morphological architecture, which leads to improved catalytic activity. In-situ electrochemical and H2 temperature-programmed reduction (H2-TPR) spectra provide direct experimental evidence of the weakening of Pd‒H bond in the CeO2@Pd composites, relative to pure (undoped) Pd catalysts. Gas diffusion electrodes based on the entrapped CeO2@Pd catalysts demonstrated one order of magnitude higher activity than pure Pd analog in the HOR reaction in an alkaline medium

Effects of antibodies to glutamate on cerebral expression of the Tnfrsf1A gene under conditions of spatial amnesia induced by proinflammatory protein S100A9 fibrils in aging mice

Proinflammatory S100A9 protein is a promoter of inflammation-linked neurodegeneration and the Tnfrsf1A gene encodes the TNF receptor 1A that binds TNFα to function as a regulator of inflammation. We studied the effects of chronic intranasal administration of in vitro prepared S100A9 fibrils alone or in combination with anti-glutamate antibodies on the expression of the Tnfrsf1A gene in the hippocampus, prefrontal cortex, and cerebellum of aging C57BL/6 mice under conditions of impaired spatial memory. A differential cerebral pattern of Tnfrsf1A gene activity and its modification by S100A9 fibrillar structures were observed: inhibition of Tnfrsf1A gene expression in the hippocampus and cerebellum and its activation in the prefrontal cortex. Anti-glutamate antibodies normalized the expression of the Tnfrsf1A gene in the prefrontal cortex by affecting the TNF signaling pathway and preventing the development of inflammation

CELLULAR IMMUNITY PARAMETERS IN PATIENTS WITH REMITTING MULTIPLE SCLEROSIS

The aim of this work was to study some parameters of cellular immunity in patients with multiple sclerosis (MS). The study included 10 patients with relapsing-remitting MS aged 32 to 50 years. Diagnosis was clinically established and confirmed by magnetic resonance imaging. Patients did not receive immunosuppressive therapy for at least 6 months prior to study entry. The neurological status of all examined patients was assessed using the Kurtzke functional scale using the Extended Disability Scale (EDSS) and averaged 4.0±0.67 points, the mean number of exacerbations per year was 1.25±0.25. While studying such parameters of the immune status such as the number of T, B, NK-cells, the content of immunoglobulins, the phagocytic activity of monocytes and granulocytes, their production of reactive oxygen species, no significant differences were observed in patients with MS in comparison with the normal donor level. At the same time, we have noted an increase in the proliferative response of mononuclear blood cells to myelin antigen by 2.35 times. The content of CD4+CD45RO+CD62L+ and CD8+CD45RO+CD62L+ central memory T-cells, as well as CD8+CD45RO+CD62L- effector memory T-cells in the blood of MS patients significantly exceeded the control values (p < 0.05). Also, in MS patients, compared with healthy individuals, there was an increased level of naive IFNγ-positive CD4+CD45RO- and CD8+CD45ROT-cells (p < 0.01), and an increase in CD4+CD45RO+ and CD8+CD45RO+ memory T-cells producing IFNγg or IFNγg together with IL-4 in response to the activation (p < 0.01). Consistent with these data, there were significantly increased serum IFNγ and IL-17 levels and no changes in IL-4 levels. The relative level of naive CD4+CD25+FoxP3+, as well as induced CD4+CD25- FoxP3+ regulatory T-cells in MS patients did not significantly change compared to donor values. The results of assessing some parameters of the immune status in MS patients indicate a functional reshaping of the immune system towards the Th1 type of immune response. It is obvious that immunotropic treatment of MS should be aimed at inactivating auto-immune Tand B-lymphocytes, suppressing the production of proinflammatory mediators, and enhancing the activity of natural and induced regulatory T-cells

Effects of internal molecular degrees of freedom on the thermal conductivity of some glasses and disordered crystals

The thermal conductivity κ(T) of the fully ordered stable phase II, the metastable phase III, the orientationally disordered (plastic) phase I, as well as the nonergodic orientational glass (OG) phase, of the glass former cyclohexanol (C 6H 11OH) has been measured under equilibrium vapor pressure within the 2-200 K temperature range. The main emphasis is here focused on the influence of the conformational disorder upon the thermal properties of this material. Comparison of results with those regarding cyanoclyclohexane (C 6H 11CN), a chemically related compound, serves to quantify the role played by the terminal groups -OH and -CN on the phonon scattering processes. The picture that emerges shows that motions of such groups do play a minor role as scattering centers, both within the low-temperature orientationally ordered phases as well as in the OG states. The results are analyzed within the Debye-Peierls relaxation time model for isotropic solids comprising mechanisms for long-wave phonon scattering within the OG and orientational ordered low-temperature phases, as well as others arising from localized short-wavelength vibrational modes as pictured by the Cahill-Pohl model. By means of complementary neutron and Raman scattering we show that in the OG state the energy landscapes for both compounds are very similar. © 2012 American Physical Society.This work was financially supported in part by the Spanish Ministry of Science and Innovation (Grant No. FIS2008-00837) and the Catalan Government (Grant No. 2009SGR-1251)Peer Reviewe

Tracking azimuthons in nonlocal nonlinear media

We study the formation of azimuthons, i.e., rotating spatial solitons, in media with nonlocal focusing nonlinearity. We show that whole families of these solutions can be found by considering internal modes of classical non-rotating stationary solutions, namely vortex solitons. This offers an exhaustive method to identify azimuthons in a given nonlocal medium. We demonstrate formation of azimuthons of different vorticities and explain their properties by considering the strongly nonlocal limit of accessible solitons.Comment: 11 pages, 7 figure