Breakdown of the Korringa Law of Nuclear Spin Relaxation in Metallic GaAs

We present nuclear spin relaxation measurements in GaAs epilayers using a new pump-probe technique in all-electrical, lateral spin-valve devices. The measured T1 times agree very well with NMR data available for T > 1 K. However, the nuclear spin relaxation rate clearly deviates from the well-established Korringa law expected in metallic samples and follows a sub-linear temperature dependence 1/T1 ~ T^0.6 for 0.1 K < T < 10 K. Further, we investigate nuclear spin inhomogeneities.Comment: 5 pages, 4 (color) figures. arXiv admin note: text overlap with arXiv:1109.633

End-to-End Learning in Optical Fiber Communications: Experimental Demonstration and Future Trends

Fiber-optic auto-encoders are demonstrated on an intensity modulation/direct detection testbed, outperforming state-of-the-art signal processing. Algorithms for end-to-end optimization using experimentally collected data are discussed. The end-to-end learning framework is extended for performing optimization of the symbol distribution in probabilistically-shaped coherent systems

Biochemical and aggregation analysis of Bence Jones proteins from different light chain diseases

Deposition of immunoglobulin light chains is a result of clonal proliferation of monoclonal plasma cells that secrete free immunoglobulin light chains, also called Bence Jones proteins (Bence Jones proteins). These Bence Jones proteins are present in circulation in large amounts and excreted in urine in various light chain diseases such as light chain amyloidosis (AL), light chain deposition disease (LCDD) and multiple myeloma (MM). BJP from patients with AL, LCDD and MM were purified from their urine and studies were performed to determine their secondary structure, thermodynamic stability and aggregate formation kinetics. Our results show that LCDD and MM proteins have the lowest free energy of folding while all proteins show similar melting temperatures. Incubation of the BJP at their melting temperature produced morphologically different aggregates: amyloid fibrils from the AL proteins, amorphous aggregates from the LCDD proteins and large spherical species from the MM proteins. The aggregates formed under in vitro conditions suggested that the various proteins derived from patients with different light chain diseases might follow different aggregation pathways

Ion induced fragmentation of biomolecular systems at low collision energies

In this paper, we present results of different collision experiments between multiply charged ions at low collision energies (in the keV-region) and biomolecular systems. This kind of interaction allows to remove electrons form the biomolecule without transferring a large amount of vibrational excitation energy. Nevertheless, following the ionization of the target, fragmentation of biomolecular species may occur. It is the main objective of this work to study the physical processes involved in the dissociation of highly electronically excited systems. In order to elucidate the intrinsic properties of certain biomolecules (porphyrins and amino acids) we have performed experiments in the gas phase with isolated systems. The obtained results demonstrate the high stability of porphyrins after electron removal. Furthermore, a dependence of the fragmentation pattern produced by multiply charged ions on the isomeric structure of the alanine molecule has been shown. By considering the presence of other surrounding biomolecules (clusters of nucleobases), a strong influence of the environment of the biomolecule on the fragmentation channels and their modification, has been clearly proven. This result is explained, in the thymine and uracil case, by the formation of hydrogen bonds between O and H atoms, which is known to favor planar cluster geometries.</p

Spinor Field in Bianchi type-I Universe: regular solutions

Self-consistent solutions to the nonlinear spinor field equations in General Relativity has been studied for the case of Bianchi type-I (B-I) space-time. It has been shown that, for some special type of nonliearity the model provides regular solution, but this singularity-free solutions are attained at the cost of broken dominant energy condition in Hawking-Penrose theorem. It has also been shown that the introduction of $\Lambda$-term in the Lagrangian generates oscillations of the B-I model, which is not the case in absence of $\Lambda$ term. Moreover, for the linear spinor field, the $\Lambda$ term provides oscillatory solutions, those are regular everywhere, without violating dominant energy condition. Key words: Nonlinear spinor field (NLSF), Bianch type -I model (B-I), $\Lambda$ term PACS 98.80.C CosmologyComment: RevTex, 21 page

Helmholtz theorem and the v-gauge in the problem of superluminal and instantaneous signals in classical electrodynamics

In this work we substantiate the applying of the Helmholtz vector decomposition theorem (H-theorem) to vector fields in classical electrodynamics. Using the H-theorem, within the framework of the two-parameter Lorentz-like gauge (so called v-gauge), we show that two kinds of magnetic vector potentials exist: one of them (solenoidal) can act exclusively with the velocity of light c and the other one (irrotational) with an arbitrary finite velocity $v$ (including a velocity more than c . We show also that the irrotational component of the electric field has a physical meaning and can propagate exclusively instantaneously.Comment: This variant has been accepted for publication in Found. Phys. Letter

Waste valorization in winery and distillery industry by producing biofertilizers and organic amendments

Resumen La industria vitivinícola y de destilación de bebidas espirituosas generan una notable cantidad de subproductos y residuos, cuya gestión inadecuada puede generar problemas socioeconómicos y riesgos ambientales debido a algunas características de disponibilidad estacional y elementos contaminantes. Tradicionalmente, las estrategias de valorización se han enfocado en el compostaje, para uso directo como mejorador de suelos en el viñedo. Sin embargo, este proceso requiere un tiempo prolongado y gran disposición de espacio libre (aeróbico), pudiendo causar fitotoxicidad y un efecto antimicrobiano. Una estrategia alternativa de tratamiento de estos residuos orgánicos es la digestión anaeróbica, después de la cual, en un periodo menor a 25 días y en una reducida área de trabajo, se obtienen dos digestatos: un líquido y un sólido, aptos para el uso agrícola en el viñedo. El objetivo del presente estudio fue evaluar la factibilidad de aprovechar las lías de vinificación y las vinazas de destilación para la elaboración de biofertilizantes y enmiendas orgánicas mediante digestión anaeróbica usando consorcios microbianos y estimar su valorización económica a mediana escala para una bodega vitivinícola del valle de Cañete (Perú). Se monitoreó la evolución del proceso de digestión (pH, Conductividad Eléctrica y Temperatura) para finalmente realizar una caracterización fisicoquímica y microbiológica de los digestatos obtenidos. Los resultados muestran que los productos elaborados presentan una significativa concentración de materia orgánica y fitonutrientes (Nitrógeno, Fosforo, Potasio, etc.) en un medio ligeramente ácido (pH entre 3.8 y 5.8), debido a la presencia de algunas especies de bacterias acido-lácticas y Bacillus, lo que podría conferirles propiedades como bioestimulantes y agentes de biocontrol. La estabilidad de los productos (pH, color y olor) fue evaluada durante 30 días más, mostrando excelentes condiciones higiénicas, debido a la ausencia de microorganismos patógenos, posibilitando su incorporación junto a otras enmiendas durante la mitad de la temporada vitícola. Por lo tanto, la valorización de estos subproductos y residuos vitivinícolas en la producción de biofertilizantes y enmiendas orgánicas para uso agrícola, podría suplir en gran parte el uso de fertilización sintética y recuperar la fertilidad del suelo. Los beneficios socio-económicos y ambientales serían múltiples, dentro de un enfoque de transición agroecológica y de economía circular

Spatial optical solitons in nonlinear photonic crystals

We study spatial optical solitons in a one-dimensional nonlinear photonic crystal created by an array of thin-film nonlinear waveguides, the so-called Dirac-comb nonlinear lattice. We analyze modulational instability of the extended Bloch-wave modes and also investigate the existence and stability of bright, dark, and ``twisted'' spatially localized modes in such periodic structures. Additionally, we discuss both similarities and differences of our general results with the simplified models of nonlinear periodic media described by the discrete nonlinear Schrodinger equation, derived in the tight-binding approximation, and the coupled-mode theory, valid for shallow periodic modulations of the optical refractive index.Comment: 15 pages, 21 figure

Fragmentation of α- and β-alanine molecules by ions at Bragg-peak energies

The interaction of keV He(+), He(2+), and O(5+) ions with isolated alpha and beta isomers of the amino acid alanine was studied by means of high resolution coincidence time-of-flight mass spectrometry. We observed a strong isomer dependence of characteristic fragmentation channels which manifests in strongly altered branching ratios. Despite the ultrashort initial perturbation by the incoming ion, evidence for molecular rearrangement leading to the formation of H(3)(+) was found. The measured kinetic energies of ionic alanine fragments can be sufficient to induce secondary damage to DNA in a biological environment. (C) 2008 American Institute of Physics