Specific-heat study for ferromagnetic and antiferromagnetic phases in SrRu_{1-x}Mn_xO3

Low-temperature electronic states in SrRu_{1-x}Mn_xO_3 for x <= 0.6 have been investigated by means of specific-heat C_p measurements. We have found that a jump anomaly observed in C_p at the ferromagnetic (FM) transition temperature for SrRuO_3 changes into a broad peak by only 5% substitution of Mn for Ru. With further doping Mn, the low-temperature electronic specific-heat coefficient gamma is markedly reduced from the value at x=0 (33 mJ/K^2 mol), in connection with the suppression of the FM phase as well as the enhancement of the resistivity. For x >= 0.4, gamma approaches to ~ 5 mJ/K^2 mol or less, where the antiferromagnetic order with an insulating feature in resistivity is generated. We suggest from these results that both disorder and reconstruction of the electronic states induced by doping Mn are coupled with the magnetic ground states and transport properties.Comment: 4 pages, 2 figures, submitted to the proceedings of ICM2009 (Karlsruhe

Spin density distribution in a partially magnetized organic quantum magnet

Polarized neutron diffraction experiments on an organic magnetic material reveal a highly skewed distribution of spin density within the magnetic molecular unit. The very large magnitude of the observed effect is due to quantum spin fluctuations. The data are in quantitative agreement with direct diagonalization results for a model spin Hamiltonian, and provide insight on the actual microscopic origin of the relevant exchange interactions.Comment: 5 pages 4 figure

Perfil ambiental de la industria azucarera de la provincia de Tucumán obtenido a partir de la técnica del Análisis del Ciclo de Vida

La industria del azúcar es una importante actividad a nivel mundial. Durante la campaña 2009/2010, se produjeron 1.683 millones de toneladas de caña de azúcar en el mundo. De los 115 países productores de azúcar, 67 de ellos la producen a partir de caña de azúcar, 39 a partir de remolacha y 9 de caña y remolacha (4). El azúcar de caña se produce principalmente en América y Asia, mientras que el de remolacha se produce principalmente en Europa y, en menor cuantía, en Norteamérica. Hacia 1980, la materia prima para la producción de azúcar era la caña y la remolacha en partes iguales, mientras que en la actualidad, el 80% de la producción mundial de azúcar y gran parte del etanol combustible provienen del cultivo de caña, siendo éste el único que se desarrolla en nuestro país.Fil: Nishihara Hun, Andrea L.. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnologia; ArgentinaFil: Mele, Fernando Daniel. Universidad Nacional de Tucumán. Facultad de Ciencias Exactas y Tecnologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pérez, Gonzalo A.. Instituto Nacional de Tecnología Agropecuaria; Argentin

The alternatively spliced fibronectin CS1 isoform regulates IL-17A levels and mechanical allodynia after peripheral nerve injury.

BackgroundMechanical pain hypersensitivity associated with physical trauma to peripheral nerve depends on T-helper (Th) cells expressing the algesic cytokine, interleukin (IL)-17A. Fibronectin (FN) isoform alternatively spliced within the IIICS region encoding the 25-residue-long connecting segment 1 (CS1) regulates T cell recruitment to the sites of inflammation. Herein, we analyzed the role of CS1-containing FN (FN-CS1) in IL-17A expression and pain after peripheral nerve damage.MethodsMass spectrometry, immunoblotting, and FN-CS1-specific immunofluorescence analyses were employed to examine FN expression after chronic constriction injury (CCI) in rat sciatic nerves. The acute intra-sciatic nerve injection of the synthetic CS1 peptide (a competitive inhibitor of the FN-CS1/α4 integrin binding) was used to elucidate the functional significance of FN-CS1 in mechanical and thermal pain hypersensitivity and IL-17A expression (by quantitative Taqman RT-PCR) after CCI. The CS1 peptide effects were analyzed in cultured primary Schwann cells, the major source of FN-CS1 in CCI nerves.ResultsFollowing CCI, FN expression in sciatic nerve increased with the dominant FN-CS1 deposition in endothelial cells, Schwann cells, and macrophages. Acute CS1 therapy attenuated mechanical allodynia (pain from innocuous stimulation) but not thermal hyperalgesia and reduced the levels of IL-17A expression in the injured nerve. CS1 peptide inhibited the LPS- or starvation-stimulated activation of the stress ERK/MAPK pathway in cultured Schwann cells.ConclusionsAfter physical trauma to the peripheral nerve, FN-CS1 contributes to mechanical pain hypersensitivity by increasing the number of IL-17A-expressing (presumably, Th17) cells. CS1 peptide therapy can be developed for pharmacological control of neuropathic pain

Electronic structure of the strongly hybridized ferromagnet CeFe2

We report on results from high-energy spectroscopic measurements on CeFe2, a system of particular interest due to its anomalous ferromagnetism with an unusually low Curie temperature and small magnetization compared to the other rare earth-iron Laves phase compounds. Our experimental results indicate very strong hybridization of the Ce 4f states with the delocalized band states, mainly the Fe 3d states. In the interpretation and analysis of our measured spectra, we have made use of two different theoretical approaches: The first one is based on the Anderson impurity model, with surface contributions explicitly taken into account. The second method consists of band-structure calculations for bulk CeFe2. The analysis based on the Anderson impurity model gives calculated spectra in good agreement with the whole range of measured spectra, and reveals that the Ce 4f -- Fe 3d hybridization is considerably reduced at the surface, resulting in even stronger hybridization in the bulk than previously thought. The band-structure calculations are ab initio full-potential linear muffin-tin orbital calculations within the local-spin-density approximation of the density functional. The Ce 4f electrons were treated as itinerant band electrons. Interestingly, the Ce 4f partial density of states obtained from the band-structure calculations also agree well with the experimental spectra concerning both the 4f peak position and the 4f bandwidth, if the surface effects are properly taken into account. In addition, results, notably the partial spin magnetic moments, from the band-structure calculations are discussed in some detail and compared to experimental findings and earlier calculations.Comment: 10 pages, 8 figures, to appear in Phys. Rev. B in December 200

Interlayer magnetoresistance due to chiral soliton lattice formation in hexagonal chiral magnet CrNb3S6

We investigate the interlayer magnetoresistance (MR) along the chiral crystallographic axis in the hexagonal chiral magnet CrNb3S 6. In a region below the incommensurate-commensurate phase transition between the chiral soliton lattice and the forced ferromagnetic state, a negative MR is obtained in a wide range of temperature, while a small positive MR is found very close to the Curie temperature. Normalized data of the negative MR almost falls into a single curve and is well fitted by a theoretical equation of the soliton density, meaning that the origin of the MR is ascribed to the magnetic scattering of conduction electrons by a nonlinear, periodic, and countable array of magnetic soliton kinks. © 2013 American Physical Society

Temperature behavior of sound velocity of fluorine-doped vitreous silica thin films studied by picosecond ultrasonics

Vitreous silica (v-SiO2) shows anomalous temperature dependence of velocity, including positive temperature coefficient of velocity (TCV) and velocity minimum around 70 K. The former characteristic allows its application in acoustic-resonator devices as a temperature compensating material. In this paper, we study the temperature dependence of velocity of fluorine-doped v-SiO2 (v-SiO2-xFx) thin films using picosecond ultrasonic spectroscopy. To correct the temperature increase caused by irradiation with light pulses, we calculated the steady temperature increase in the measuring volume with a finite volume method, considering the temperature dependence of thermal conductivity, and find that temperature in the measurement region remains high even when the back surface is cryogenically cooled. Using the corrected temperature, we determine TCV of v-SiO2-xFx thin films for 0 < x < 0.264, which increases as x increases and is smaller than reported bulk values by a factor of 0.5 - 0.7. The velocity minimum is absent for the film with x = 0, but it is clearly observed at 70 K for the film with the highest fluorine concentration of x = 0.264. These temperature behaviors are attributed to the change in the Si-O-Si bond angle caused by the fluorine doping.Nagakubo A., Ogi H., Ishida H., et al. Temperature behavior of sound velocity of fluorine-doped vitreous silica thin films studied by picosecond ultrasonics. Journal of Applied Physics, 118(1), 014307 (2015) https://doi.org/10.1063/1.4923353.https://doi.org/10.1063/1.492335

Nuclear Spin-Lattice Relaxation in One-Dimensional Heisenberg Ferrimagnets: Three-Magnon versus Raman Processes

Nuclear spin-lattice relaxation in one-dimensional Heisenberg ferrimagnets is studied by means of a modified spin-wave theory. We consider the second-order process, where a nuclear spin flip induces virtual spin waves which are then scattered thermally via the four-magnon exchange interaction, as well as the first-order process, where a nuclear spin directly interacts with spin waves via the hyperfine interaction. We point out a possibility of the three-magnon relaxation process predominating over the Raman one and suggest model experiments.Comment: to be published in J. Phys. Soc. Jpn. 73, No. 6 (2004

Experimental Evidence for a Glass forming "Stripe Liquid" in the Magnetic Ground State of La1.65Eu0.2Sr0.15CuO4

We report measurements of the longitudinal ($^{139}T_1^{-1}$) and transverse ($^{139}T_2^{-1}$) decay rates of the magnetization of $^{139}$La nuclei performed in a high quality single crystal of La$_{1.65}$Eu$_{0.2}$Sr$_{0.15}$CuO$_{4}$. We observe a dramatic slowing of the Cu 3d spins manifested as a sharp increase of both $^{139}T_1^{-1}$ and $^{139}T_2^{-1}$ below 30 K. We find that in this temperature range the fluctuations involve a unique time scale $\tau$ which diverges as $(T-T_{\rm A})^{-1.9}$ with $T_{\rm A}\thickapprox 5$ K. This behavior is distinct from the continuous freezing observed in underdoped La$_{1-x}$Sr$_x$CuO$_4$ which involves a distribution of energy barriers. By contrast, in La$_{1.65}$Eu$_{0.2}$Sr$_{0.15}$CuO$_{4}$, the freezing below 30K is intrinsic to its magnetic ground state and the observed power law supports the existence of a glass forming "charge stripe liquid".Comment: 5 pages, 3 Figures. Revised version, resubmitte

Three Dimensional Relativistic Electromagnetic Sub-cycle Solitons

Three dimensional (3D) relativistic electromagnetic sub-cycle solitons were observed in 3D Particle-in-Cell simulations of an intense short laser pulse propagation in an underdense plasma. Their structure resembles that of an oscillating electric dipole with a poloidal electric field and a toroidal magnetic field that oscillate in-phase with the electron density with frequency below the Langmuir frequency. On the ion time scale the soliton undergoes a Coulomb explosion of its core, resulting in ion acceleration, and then evolves into a slowly expanding quasi-neutral cavity.Comment: 5 pages, 6 figures; http://www.ile.osaka-u.ac.jp/research/TSI/Timur/soliton/index.htm