1,446 research outputs found

    Quantum phase transition in HTSC thick films: YBa2Cu 3O x, YBa2Cu3O x (5 % Ag-Doped) in a Strong Pulsed Magnetic Field up to 32 T at low temperatures (58-100 K), current densities and stress-effect

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    We have researched the influence of pulsed magnetic fields up to 32 T on the magneto-resistance of thick films (50 Mk) of YBa2Cu3O x and YBa2Cu3O x (5 % Ag-doped) that were produced from synthesized powders. (Figs. 1-9): concentrate with 6.85-6.9 % O2 and a tail fraction 6.5-6.6 % O2. We observed a linear plot at currents of more than 1 mA at 77 K in YBa2Cu 3O x (5 % Ag-doped) at B>5 T and in the concentrate YBa2Cu3O x samples with I=1 mA, T=68.2 K. Pulsed magnetic fields up to 32 T, at I=1 mA had practically no influence on the value of the magneto-resistance in the concentrate YBa2Cu 3O x specimens at T=57.9 K and up to 17 T for YBa 2Cu3O x (5 % Ag) at 77 K (Meissner effect). However, for B>17 T, YBa2Cu3O x (5 % Ag) at 77 K demonstrates a tendency toward lower resistance. In the presence to 10 pulses in a cyclic pulsed magnetic field of 32 T, there is a sharp change of magnetic properties of an HTSC that can lead to nontrivial changes in the transition temperature, due to the strong mechanic stresses, sharp change value structure, and because one of the phases becomes superconducting (Figs. 3A, 3B). The behavior of the magnetoresistance of S-N-S contacts in pulsed magnetic fields is described via the system's parallel resistance, R n, and the inductance, L S-N-S. Analysis of microscopic models of quantum phase transitions was made in a granular superconductor in an attempt to explain the results on the studied HTSC-films and to give a physical interpretation to the deduced parameters of some experiments on the basis of "spin (vortex) glass" (vortex ice). © 2012 Springer Science+Business Media New York

    Leer entre… La formación de jóvenes mediadores culturales como política de lectura

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    A partir del análisis de dos experiencias de formación de jóvenes mediadores culturales comunitarios realizadas en Pacheco, Buenos Aires, y Las Heras, Santa Cruz, se desarrollan tres conceptos en torno a las políticas de lectura: el gesto, la trama y la representación

    Heterogeneous nucleation near a metastable vapour-liquid transition: the effect of wetting transitions

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    Phase transformations such as freezing typically start with heterogeneous nucleation. Heterogeneous nucleation near a wetting transition, of a crystalline phase is studied. The wetting transition occurs at or near a vapour-liquid transition which occurs in a metastable fluid. The fluid is metastable with respect to crystallisation, and it is the crystallisation of this fluid phase that we are interested in. At a wetting transition a thick layer of a liquid phase forms at a surface in contact with the vapour phase. The crystalline nucleus is then immersed in this liquid layer, which reduces the free energy barrier to nucleation and so dramatically increases the nucleation rate. The variation in the rate of heterogeneous nucleation close to wetting transitions is calculated for systems in which the longest-range forces are dispersion forces.Comment: 11 pages including 3 figure

    Cholinergic cells in the nucleus basalis of mice express the N-methyl-D-aspartate-receptor subunit NR2C and its replacement by the NR2B subunit enhances frontal and amygdaloid acetylcholine levels

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    It is known that glutamatergic and cholinergic systems interact functionally at the level of the cholinergic basal forebrain. The N-methyl-D-aspartate receptor (NMDA-R) is a multiprotein complex composed of NR1, NR2 and/or NR3 subunits. The subunit composition of NMDA-R of cholinergic cells in the nucleus basalis has not yet been investigated. Here, by means of choline acetyl transferase and NR2B or NR2C double staining, we demonstrate that mice express both the NR2C and NR2B subunits in nucleus basalis cholinergic cells.We generated NR2C-2B mutant mice in which an insertion of NR2B cDNA into the gene locus of the NR2C gene replaced NR2C by NR2B expression throughout the brain. This NR2C-2B mutant was used to examine whether a subunit exchange in cholinergic neurons would affect acetylcholine (ACh) content in several brain structures. We found increased ACh levels in the frontal cortex and amygdala in the brains of NR2C-2B mutant mice. Brain ACh has been implicated in neuroplasticity, novelty-induced arousal and encoding of novel stimuli. We therefore assessed behavioral habituation to novel environments and objects as well as object recognition in NR2C-2B subunit exchange mice. The behavioral analysis did not indicate any gross behavioral alteration in the mutant mice compared with the wildtype mice. Our results show that the NR2C by NR2B subunit exchange in mice affects ACh content in two target areas of the nucleus basalis.

    A Subgroup of First-Degree Relatives of Crohn's Disease Patients Shows a Profile of Inflammatory Markers in the Blood Which Is More Typical of Crohn's Disease Patients Than of Normal Individuals

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    Introduction. Family member with IBD is the greatest risk factor for developing the disease. The hematological profile of first-degree relatives (FDRs) of Crohn's disease (CD) patients was studied in order to identify healthy FDRs at risk to develop disease. Materials and methods. Thirty CD patients, 90 FDRs, and 28 non-related individuals (controls) were enrolled. Hematological profile and C-reactive protein were determined. Results. All hematological parameters were significantly different in CD patients compared to controls, with significantly higher levels of CRP, WBC, PMN, MONO, and PLT and lower Hb and lymphocyte count. The hematological profile of FDRs showed values between the controls and CD patients with ten FDRs that their parameters matched those of CD patients and significantly different from other FDRs. This group was defined as high-risk relatives (HRRs). Conclusions. Analysis of the hematological profile and CRP level might be proven as a fast, reliable, and less money-consuming tool to identify FDRs with a probable increased risk to develop the disease

    Dysphagia lusoria in children

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