1,684 research outputs found
Superconducting/magnetic three state nanodevice for memory and reading applications
We present a simple nanodevice that can operate in two modes: i) three-state
memory and ii) reading device. The nanodevice is fabricated with an array of
ordered triangular-shaped nanomagnets embedded in a superconducting thin film.
The input signal is ac current and the output signal is dc voltage. Vortex
ratchet effect in combination with out of plane magnetic anisotropy of the
nanomagnets is the background physics which governs the nanodevice performance.Comment: 10 pages, 4 figure
Caracterización de trenes de descargas preliminares en rayos nube a tierra negativos registrados durante una temporada de lluvias en la Sabana de Bogotá, Colombia
Lightning-generated electric field measurement is used to characterize cloud-to-ground (CG) flashes. Prior to the first return stroke (FRS), these signals sometimes exhibit a pulse train, known as preliminary breakdown pulses (PBP), whose study provides information about the first event that originate the breakdown process inside the cloud. Considering that characteristics of PBPs may change according to geographical conditions, in this work, six parameters (temporal and magnitude) associated with 69 trains identified in negative CG flashes that occurred in the Bogota savannah, Colombia were analyzed. The signatures were recorded in 2017 using a fast response antenna (10 MHz bandwidth), a 100 ns sampling time and a window of 500 ms. Among the most relevant results, it was found that the train duration ( ) varied from 0.5 ms up to 5.2 ms with arithmetic mean (AM) of 1.74 ms, while the time interval between the peak of the train and the FRS (PBP-FRS) had an AM and a geometric mean (GM) of 35.7 ms and 10.2 ms, respectively. On the other hand, the ratio between the peak value of the PBP and its FRS ( ) exhibited an AM of 0.7 and a GM of 0.56. It was concluded that PBP train starts with low amplitude pulses, later increases its magnitude in the central region and decreases at the end. Furthermore, bipolar pulses with similar polarity to that of the FRS were identified at the beginning and in the middle of the train, while unipolar pulses were observed at the end of the signatures.La medición del campo eléctrico generado por rayos es comúnmente usada para caracterizar rayos nube-tierra (CG). Previo a la primera descarga de retorno (FRS), estas señales exhiben algunas veces un tren de pulsos conocido como pulsos de descargas preliminares (PBP), cuyo estudio proporciona información sobre el primer evento que origina el proceso de descarga dentro de la nube. Considerando que las características de los PBP pueden cambiar de acuerdo con las condiciones geográficas, en este trabajo se analizaron seis parámetros (temporales y de magnitud) asociados a 69 trenes identificados en rayos CG negativos ocurridos en la Sabana de Bogotá, Colombia. Las señales se registraron en 2017 usando una antena de respuesta rápida (ancho de banda de 10 MHz), un tiempo de muestreo de 100 ns y una ventana de 500 ms. Dentro de los resultados más relevantes se encontró que la duración del tren ( ) varió entre 0.5 ms y 5.2 ms con una media aritmética (AM) de 1.74 ms, mientras el tiempo entre el pico del tren y el FRS (PBP-FRS) tuvo una AM y una media geométrica (GM) de 35.7 ms y 10.2 ms, respectivamente. Por su parte, la relación entre el pico del PBP y su FRS ( ) exhibió una AM de 0.7 y una GM de 0.56. Se concluye que el tren comienza con pulsos de baja amplitud, aumenta su magnitud en la región central y disminuye al final. Adicionalmente, se identificaron pulsos bipolares con polaridad similar a la FRS al principio y en la mitad del tren, mientras pulsos unipolares fueron observados al final de las señales
PGI28 Cost-Effectiveness of Hepatitis C Virus (HCV) Treatment with Telaprevir/Pegylated Interferon Alpha/Ribavirin Triple Therapy Versus Waiting for New Regimens in France
Chemical disinfection as a simple and reliable method to control the amphibian chytrid fungus at breeding points of endangered amphibians.
Chytridiomycosis caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd) is pushing amphibians towards extinction. Whilst mitigation methods were suggested a decade ago, we lack field trials testing their efficacy. We used the agrochemical fungicide, tebuconazole, to treat Bd infected breeding waterbodies of an endangered species that is highly susceptible to the fungus. Just two applications of tebuconazole led to a significant reduction in infection loads in the vast majority of sites, and at six sites the disinfection remained one/two-years post-application. Tebuconazole values drastically decreased in the waterbodies within a week after application, with no significant effects on their hydrochemical and hydrobiological characteristics. Although the use of chemicals in natural populations is undesirable, the growing existential threat to amphibians all over the world indicates that effective interventions in selected populations of endangered species are urgently needed
The su(1,1) dynamical algebra from the Schr\"odinger ladder operators for N-dimensional systems: hydrogen atom, Mie-type potential, harmonic oscillator and pseudo-harmonic oscillator
We apply the Schr\"odinger factorization to construct the ladder operators
for hydrogen atom, Mie-type potential, harmonic oscillator and pseudo-harmonic
oscillator in arbitrary dimensions. By generalizing these operators we show
that the dynamical algebra for these problems is the Lie algebra.Comment: 10 page
Crossover in the nature of the metallic phases in the perovskite-type RNiO_3
We have measured the photoemission spectra of NdSmNiO,
where the metal-insulator transition and the N\'{e}el ordering occur at the
same temperature for and the metal-insulator transition
temperature () is higher than the N\'{e}el temperature for . For , the spectral intensity at the Fermi level is high in the
metallic phase above and gradually decreases with cooling in the
insulating phase below while for it shows a pseudogap-like
behavior above and further diminishes below . The results
clearly establish that there is a sharp change in the nature of the electronic
correlations in the middle () of the metallic phase of the
NiO system.Comment: 4 pages, 4 figure, submitted to Phys. Rev.
Short-range charge-order in NiO perovskites (=Pr,Nd,Eu) probed by X-ray absorption spectroscopy
The short-range organization around Ni atoms in orthorhombic NiO
(=Pr,Nd,Eu) perovskites has been studied over a wide temperature range by Ni
K-edge x-ray absorption spectroscopy. Our results demonstrate that two
different Ni sites, with different average Ni-O bond lengths, coexist in those
orthorhombic compounds and that important modifications in the Ni nearest
neighbors environment take place across the metal-insulator transition. We
report evidences for the existence of short-range charge-order in the
insulating state, as found in the monoclinic compounds. Moreover, our results
suggest that the two different Ni sites coexists even in the metallic state.
The coexistence of two different Ni sites, independently on the ion,
provides a common ground to describe these compounds and shed new light in the
understanding of the phonon-assisted conduction mechanism and unusual
antiferromagnetism present in all NiO compounds.Comment: 4 pages, 3 figures, accepted PRB - Brief Report Dec.200
Experimental realization of smectic phase in vortex matter induced by symmetric potentials arranged in two-fold symmetry arrays
Smectic order has been generated in superconducting Nb films with two-fold
symmetry arrays of symmetric pinning centers. Magnetic fields applied
perpendicularly to the films develop a vortex matter smectic phase that is
easily detected when the vortices commensurate with the pinning center array.
The smectic phase can be turned on and off with external parameters.Comment: 15 pages, 5 figure
The effect of data analysis strategies in density estimation of mountain ungulates using distance sampling
Distance sampling is being extensively used to estimate the abundance of animal populations. Nevertheless, the great variety of ways in which data can be analyzed may limit comparisons due to the lack of standardization of such protocols. In this study, the influence of analytical procedures for distance sampling data on density estimates and their precision was assessed. We have used data from 21 surveys of mountain ungulates in the Iberian Peninsula, France and the Italian Alps. Data from such surveys were analyzed with the program Distance 6.0. Our analyses show that estimated density can be higher for higher levels of data truncation. We also confirm that the estimates tend to be more precise when data are analyzed without binning and without truncating. We found no evidence of size biased sampling as group size and distances were uncorrelated in most of our surveys. Despite distance sampling being a fairly robust methodology, it can be sensitive to some data analysis strategies
Quantifying Li-content for compositional tailoring of lithium ferrite ceramics
Owing to their multiple applications, lithium ferrites are relevant materials
for several emerging technologies. For instance, LiFeO2 has been spotted as an
alternative cathode material in Li-ion batteries, while LiFe5O8 is the lowest
damping ferrite, holding promise in the field of spintronics. The Li-content in
lithium ferrites has been shown to greatly affect the physical properties, and
in turn, the performance of functional devices based on these materials.
Despite this, lithium content is rarely accurately quantified, as a result of
the low number of electrons in Li hindering its identification by means of
routine materials characterization methods. In the present work, magnetic
lithium ferrite powders with Li:Fe ratios of 1:1, 1:3 and 1:5 have been
synthesized, successfully obtaining phase-pure materials (LiFeO2 and LiFe5O8),
as well as a controlled mixture of both phases. The powders have been compacted
and subsequently sintered by thermal treatment (Tmax = 1100 {\deg}C) to
fabricate dense pellets which preserve the original Li:Fe ratios. Li-content on
both powders and pellets has been determined by two independent methods: (i)
Rutherford backscattering spectroscopy combined with nuclear reaction analysis
and (ii) Rietveld analysis of powder X-ray diffraction data. With good
agreement between both techniques, it has been confirmed that the Li:Fe ratios
employed in the synthesis are maintained in the sintered ceramics. The same
conclusion is drawn from spatially-resolved confocal Raman microscopy
experiments on regions of a few microns. Field emission scanning electron
microscopy has evidenced the substantial grain growth taking place during the
sintering process - mean particle sizes rise from about 600 nm in the powders
up to 3.8(6) um for dense LiFeO2 and 10(2) um for LiFe5O8 ceramics
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