Spectral states in Be/X-ray pulsars

In the last quarter of a century, a unified characterization of the spectral evolution of low-mass X-ray binaries, both containing a neutron star and a black hole, was possible. In this context, the notion of source states characterizing the X-ray emission from black-hole binaries and neutron-star low-mass X-ray binaries revealed to be a very useful tool to disentangle the complex spectral and aperiodic phenomenology displayed by those classes of accreting objects. Be/X-ray binaries constitute another major class of transient accreting binaries, for which very little work has been done on the correlated timing and spectral variability. Especially, no definition of source states exists for this class, in spite of their highly variable X-ray emission. When active, Be/X-ray binaries are among the brightest objects in the X-ray sky and are characterized by dramatic variability in brightness on timescales ranging from seconds to years. It is then worth it to ask whether a definition of spectral states is possible for these systems. In this work, we try to address such a question, investigating whether accreting X-ray pulsars display source states and characterizing those states through their spectral properties. Our results show that Be/X-ray pulsars trace two different branches in their hardness-intensity diagram: the horizontal branch, a low-intensity state, and the diagonal branch, a high-intensity state that only appears when the X-ray luminosity exceeds a critical limit. We propose that the two branches are the phenomenological signature of two different accretion modes -- in agreement with recently proposed models -- depending on whether the luminosity of the source is above or below a critical value.Comment: Proceedings of "An INTEGRAL view of the high-energy sky (the first 10 years)" the 9th INTEGRAL Workshop, October 15-19, 2012, Paris, France, in Proceedings of Science (INTEGRAL 2012), Eds. A. Goldwurm, F. Lebrun and C. Winkler, (http://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=176), id 02

Patterns of variability in Be/X-ray pulsars during giant outbursts

The discovery of source states in the X-ray emission of black-hole binaries and neutron-star low-mass X-ray binaries constituted a major step forward in the understanding of the physics of accretion onto compact objects. While there are numerous studies on the correlated timing and spectral variability of these systems, very little work has been done on high-mass X-ray binaries, the third major type of X-ray binaries. The main goal of this work is to investigate whether Be accreting X-ray pulsars display source states and characterise those states through their spectral and timing properties. We have made a systematic study of the power spectra, energy spectra and X-ray hardness-intensity diagrams of nine Be/X-ray pulsars. The evolution of the timing and spectral parameters were monitored through changes over two orders of magnitude in luminosity. We find that Be/X-ray pulsars trace two different branches in the hardness-intensity diagram: the horizontal branch corresponds to a low-intensity state of the source and it is characterised by fast colour and spectral changes and high X-ray variability. The diagonal branch is a high-intensity state that emerges when the X-ray luminosity exceeds a critical limit. The photon index anticorrelates with X-ray flux in the horizontal branch but correlates with it in the diagonal branch. The correlation between QPO frequency and X-ray flux reported in some pulsars is also observed if the peak frequency of the broad-band noise that accounts for the aperiodic variability is used. The two branches may reflect two different accretion modes, depending on whether the luminosity of the source is above or below a critical value. This critical luminosity is mainly determined by the magnetic field strength, hence it differs for different sources.Comment: Complete missing words in title. Proof corrections adde

Compact and explicit physical model for lateral metal-oxide-semiconductor field-effect transistor with nanoelectromechanical system based resonant gate

We propose a simple analytical model of a metal-oxide-semiconductor field-effect transistor with a lateral resonant gate based on the coupled electromechanical equations, which are self-consistently solved in time. All charge densities according to the mechanical oscillations are evaluated. The only input parameters are the physical characteristics of the device. No extra mathematical parameters are used to fit the experimental results. Theoretical results are in good agreement with the experimental data in static and dynamic operation. Our model is comprehensive and may be suitable for any electromechanical device based on the field-effect transduction

Directive Microstrip Antennas for Specific Below −2.45 GHz Applications

Microstrip printed antennas are the preferred choice in high data ratio modern communications, mainly at 2.45 GHz and above. In this paper, we propose two different approaches of microstrip printed antennas for lower frequency usage. In this sense, we present a printed microstrip Yagi-like antenna at 868 MHz and a printed dipole log-periodic antenna for wider band applications. We focus on the use of low-cost substrates, with a good performance at these frequencies, and giving antennas with useful sizes for such applications. For the analysis, we make use of standard experimental characterization combined with full-wave 3D-FDTD specifically developed simulations. In this way, the S11, radiation patterns, and gain/efficiency figures are given

A jet model for black-hole X-ray sources

A jet model for Galactic black-hole X-ray binaries will be presented that appears to explain several observational characteristics. In particular, it explains the energy spectrum from radio to hard X-rays, the time-lags as a function of Fourier frequency, the increase of the variability amplitude (QPO and high frequency) with increasing photon energy, and the narrowing of the autocorrelation function with increasing photon energy. On the other hand, there are additional observational constraints that no model has tried to explain yet. It is important that we all try to address these constraints if we are to make any progress in understanding black-hole X-ray source

Monolithic integration of Giant Magnetoresistance (GMR) devices onto standard processed CMOS dies

Giant Magnetoresistance (GMR) based technology is nowadays the preferred option for low magnetic fields sensing in disciplines such as biotechnology or microelectronics. Their compatibility with standard CMOS processes is currently investigated as a key point for the development of novel applications, requiring compact electronic readout. In this paper, such compatibility has been experimentally studied with two particular non-dedicated CMOS standards: 0.35 μm from AMS (Austria MicroSystems) and 2.5 μm from CNM (Centre Nacional de Microelectrònica, Barcelona) as representative examples. GMR test devices have been designed and fabricated onto processed chips from both technologies. In order to evaluate so obtained devices, an extended characterization has been carried out including DC magnetic measurements and noise analysis. Moreover, a 2D-FEM (Finite Element Method) model, including the dependence of the GMR device resistance with the magnetic field, has been also developed and simulated. Its potential use as electric current sensors at the integrated circuit level has also been demonstrated

Valor de la resonancia magnética en el diagnóstico de las lesiones de rodilla

Para determinar la eficacia diagnóstica de la resonancia magnética en las lesiones de la rodilla se han estudiado 60 pacientes tomando como referencia los hallazgos obtenidos en la artroscopia. Se han estudiado la sensibilidad, especificidad, valor predictivo positivo, valor predictivo negativo y valor predictivo global respecto a ambos meniscos, ligamentos cruzados y lesiones cartilaginosas. Para los meniscos la sensibilidad ha sido del 95%, la especificidad del 85% y el valor predictivo global del 89%; para el LCA la sensibilidad ha sido del 75%, la especificidad del 94% y el valor predictivo del 90%, y para las lesiones del cartílago la sensibilidad ha sido del 54%, la especificidad del 100% y el valor predictivo del 82%.In order to evaluate the efficacy of magnetic resonance imaging (MRI) in the diagnosis of knee patology, the MRI charts of 60 patients were reviewed, considering as a reference the findings of the arthroscopy. Sensitivity, specificity, predictive positive value, predictive negative value and predictive global value of the technique were determined. The results showed a sensitivity of 95%, a specificity of 85% and a predictive global value of 89% for the meniscus. A sensitivity of 75%, a specificity of 94% and a predictive global value of 90% for the anterior cruciate ligament. The articular cartilage abnormalities had a sensitivity of 54% a specificity of 100% and a predictive global value of 82%