Relación de la escala de intensidad de Mercalli y la información instrumental como una tarea de clasificación de patrones

A pesar de los progresos ocurridos en la instrumentación sísmica, la valoración de vulnerabilidad sísmica y el daño con índices cualitativos, tal como los proporcionados por Intensidad de Mercalli Modificada (IMM), siguen siendo altamente favorables y útiles para los propósitos prácticos. Para vincular las medidas cualitativas de acción del terremoto y sus efectos, es habitualmente aplicada la regresión estadística. En este artículo, se adopta un planteamiento diferente, el cual consiste en expresar la Intensidad de Mercalli, como una clase en vez de un valor numérico. Una herramienta de clasificación estadística moderna, conocida como máquina de vectores de soporte, se usa para clasificar la información instrumental con el fin de evaluar la intensidad de Mercalli correspondiente. Se muestra que el método da resultados satisfactorios con respecto a las altas incertidumbres y a la medida del daño sísmico cualitativo

How reliable are Hanle measurements in metals in a three-terminal geometry?

We test the validity of Hanle measurements in three-terminal devices by using aluminum (Al) and gold (Au). The obtained Hanle and inverted Hanle-like curves show an anomalous behavior. First, we measure Hanle signals 8 orders of magnitude larger than those predicted by standard theory. Second, the temperature and voltage dependences of the signal do not match with the tunneling spin polarization of the ferromagnetic contact. Finally, the spin relaxation times obtained with this method are independent of the choice of the metallic channel. These results are not compatible with spin accumulation in the metal. Furthermore, a scaling of the Hanle signal with the interface resistance of the devices suggests that the measured signal is originated in the tunnel junction.Comment: 9 pages, 5 figure

Spin Hall magnetoresistance at Pt/CoFe2O4 interfaces and texture effects

We report magnetoresistance measurements on thin Pt bars grown on epitaxial (001) and (111) CoFe2O4 (CFO) ferrimagnetic insulating films. The results can be described in terms of the recently discovered spin Hall magnetoresistance (SMR). The magnitude of the SMR depends on the interface preparation conditions, being optimal when Pt/CFO samples are prepared in situ, in a single process. The spin-mixing interface conductance, the key parameter governing SMR and other relevant spin-dependent phenomena such as spin pumping or spin Seebeck effect, is found to be different depending on the crystallographic orientation of CFO, highlighting the role of the composition and density of magnetic ions at the interface on spin mixing.Comment: 13 pages, 5 figure

Modulation of pure spin currents with a ferromagnetic insulator

We propose and demonstrate spin manipulation by magnetically controlled modulation of pure spin currents in cobalt/copper lateral spin valves, fabricated on top of the magnetic insulator Y$_3$Fe$_5$O$_{12}$ (YIG). The direction of the YIG magnetization can be controlled by a small magnetic field. We observe a clear modulation of the non-local resistance as a function of the orientation of the YIG magnetization with respect to the polarization of the spin current. Such a modulation can only be explained by assuming a finite spin-mixing conductance at the Cu/YIG interface, as it follows from the solution of the spin-diffusion equation. These results open a new path towards the development of spin logics.Comment: 5 pages and 4 figures + supplemental material (10 pages, 7 figures

Room-temperature air-stable spin transport in bathocuproine-based spin valves

Organic semiconductors, characterized by weak spin-scattering mechanisms, are attractive materials for those spintronic applications in which the spin information needs to be retained for long times. Prototypical spin-valve devices employing organic interlayers sandwiched between ferromagnetic materials possess a figure of merit (magnetoresistance (MR)) comparable to their fully inorganic counterparts. However, these results are a matter of debate as the conductivity of the devices does not show the expected temperature dependence. Here we show spin valves with an interlayer of bathocuproine in which the transport takes place unambiguously through the organic layer and where the electron spin coherence is maintained over large distances (>60 nm) at room temperature. Additionally, the devices show excellent air stability, with MR values almost unaltered after 70 days of storage under ambient conditions, making bathocuproine an interesting material for future spintronic applications.Fil: Sun, Xiangnan. CIC nanoGUNE; EspañaFil: Gobbi, Marco. Université de Strasbourg; Francia. CIC nanoGUNE; EspañaFil: Bedoya Pinto, Amilcar. CIC nanoGUNE; EspañaFil: Txoperena, Oihana. CIC nanoGUNE; EspañaFil: Golmar, Federico. CIC nanoGUNE; España. Instituto Nacional de Tecnología Industrial; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Llopis, Roger. CIC nanoGUNE; EspañaFil: Chuvilin, Andrey. CIC nanoGUNE; España. Fundación Vasca para la Ciencia; EspañaFil: Casanova, Félix. CIC nanoGUNE; España. Fundación Vasca para la Ciencia; EspañaFil: Hueso, Luis E.. CIC nanoGUNE; España. Fundación Vasca para la Ciencia; Españ

Cornering the unphysical vertex

In the classical pure spinor worldsheet theory of AdS5xS5 there are some vertex operators which do not correspond to any physical excitations. We study their flat space limit. We find that the BRST operator of the worldsheet theory in flat space-time can be nontrivially deformed without deforming the worldsheet action. Some of these deformations describe the linear dilaton background. But the deformation corresponding to the nonphysical vertex differs from the linear dilaton in not being worldsheet parity even. The nonphysically deformed worldsheet theory has nonzero beta-function at one loop. This means that the classical Type IIB SUGRA backgrounds are not completely characterized by requiring the BRST symmetry of the classical worldsheet theory; it is also necessary to require the vanishing of the one-loop beta-function.Comment: LaTeX 40pp; v2: explained the relation to the linear dilaton background (Section 6), changes in Introduction and Abstrac

Phase diagram of silicon from atomistic simulations

In this letter we present a calculation of the temperature-pressure phase diagram of Si in a range of pressures covering from -5 to 20 GPa and temperatures up to the melting point. The phase boundaries and triple points between the diamond, liquid, $\beta$-Sn and ${Si}_{34}$ clathrate phases are reported. We have employed efficient simulation techniques to calculate free energies and to numerically integrate the Clausius-Clapeyron equation, combined with a tight binding model capable of an accuracy comparable to that of first-principles methods. The resulting phase diagram agrees well with the available experimental data.Comment: 5 pages, 1 figure, accepted in PR

In-situ monitoring by thermal lens microscopy of a photocatalytic reduction process of hexavalent chromium

In this work, we describe the application of a micro-spatial thermal lens spectroscopy setup (thermal lens microscope, TLM) with coaxial counter-propagating pump, and probe laser beams, and an integrated passive optical Fabry-Perot, to quantify the Cr-VI concentration in water during a photocatalytic reaction in-situ. A series of test samples was analyzed using the 1.5 diphenil carbazide colorimetric method. A calibration curve was obtained by plotting of the TLM signal as a function of the concentration of Cr(VI) in a range between 0 and 10 mu g/L (1 mu g/L = 1 ppb, part per billion), with a detection limit of 53 ng/L (1 ng/L = 1 ppt, part per trillion). A solution of 10 mu g/L Cr(VI) in distillated water was placed into a cell in contact with an iron-incorporated titanium dioxide film, which was previously grown onto a 1 mm thick glass microscope slide by the sol-gel dip-coating technique. The TLM signal was registered as a function of the photocatalysis time measured from the beginning of the process, radiating the film with UV-violet light. The Cr(VI) concentration was determined with the calibration curve and after the first 50 minutes a reduction of 95 % of Cr(VI) was observed, being the chemical reaction kinetic described by a potential time decreasing function.645507511Agências de fomento estrangeiras apoiaram essa pesquisa, mais informações acesse artig