5,556 research outputs found
A High Efficiency Lateral Light Emitting Device on SOI
The infrared light emission of lateral p/sup +/-p-n/sup +/ diodes realized on SIMOX-SOI (separation by implantation of oxygen - silicon on insulator) substrates has been studied. The confinement of the free carriers in one dimension due to the buried oxide was suggested to be a key point to increase the band-to-band recombination probability in silicon light emitters. We found in our devices an external quantum efficiency comparable to previous results presented in the literature. The wavelength range of the emission was found to be 900-1300 nm which is common for indirect band to band recombination in Si. The SOI technology incorporates an insulating layer between the thin single crystal silicon layer and the much thicker substrate. This electrically insulating layer is also a thermal isolator and so self-heating effects are common in devices fabricated on SOI wafers. Investigation of its influence on the light emission and the light distribution in the device has been carried out in our research. In this paper, the characteristics of the device with different active region lengths were investigated and explained quantitatively based on the recombination rate of carriers inside the active area by using the simulation model in Silvaco
Probing the internal magnetic field of slowly pulsating B-stars through g modes
We suggest that high-order g modes can be used as a probe of the internal
magnetic field of SPB (slowly pulsating B) stars. The idea is based on earlier
work by the authors which analytically investigated the effect of a vertical
magnetic field on p and g modes in a plane-parallel isothermal stratified
atmosphere. It was found that even a weak field can significantly shift the
g-mode frequencies -- the effect increases with mode order. In the present
study we adopt the classical perturbative approach to estimate the internal
field of a 4 solar mass SPB star by looking at its effect on a low-degree
() and high-order () g mode with a period of about 1.5 d. We find
that a polar field strength of about 110 kG on the edge of the convective core
is required to produce a frequency shift of 1%. Frequency splittings of that
order have been observed in several SPB variables, in some cases clearly too
small to be ascribed to rotation. We suggest that they may be due to a poloidal
field with a strength of order 100 kG, buried in the deep interior of the star.Comment: 4 pages, 2 figures (to appear in Astronomy & Astrophysics
XMM-Newton and INTEGRAL analysis of the Supergiant Fast X-ray Transient IGR J17354-3255
We present the results of combined INTEGRAL and XMM-Newton observations of
the supergiant fast X-ray transient (SFXT) IGR J173543255. Three XMM-Newton
observations of lengths 33.4 ks, 32.5 ks and 21.9 ks were undertaken, the first
an initial pointing to identify the correct source in the field of view and the
latter two performed around periastron. Simultaneous INTEGRAL observations
across of the orbital cycle were analysed but the source was neither
detected by IBIS/ISGRI nor by JEM-X. The XMM-Newton light curves display a
range of moderately bright X-ray activity but there are no particularly strong
flares or outbursts in any of the three observations. We show that the spectral
shape measured by XMM-Newton can be fitted by a consistent model throughout the
observation, suggesting that the observed flux variations are driven by
obscuration from a wind of varying density rather than changes in accretion
mode. The simultaneous INTEGRAL data rule out simple extrapolation of the
simple powerlaw model beyond the XMM-Newton energy range.Comment: 13 pages, 9 figures, This article has been accepted for publication
in Monthly Notices of the Royal Astronomical Society Published by Oxford
University Pres
New insights on accretion in Supergiant Fast X-ray Transients from XMM-Newton and INTEGRAL observations of IGR J175442619
XMM-Newton observations of the supergiant fast X-ray transient
IGRJ175442619 are reported and placed in the context of an analysis of
archival INTEGRAL/IBIS data that provides a refined estimate of the orbital
period at 4.92720.0004 days. A complete outburst history across the
INTEGRAL mission is reported. Although the new XMM-Newton observations (each
lasting 15 ks) targeted the peak flux in the phase-folded hard X-ray
light curve of IGRJ175442619, no bright outbursts were observed, the
source spending the majority of the exposure at intermediate luminosities of
the order of several 10ergs (0.510keV) and
displaying only low level flickering activity. For the final portion of the
exposure, the luminosity of IGRJ175442619 dropped to
410ergs (0.5 - 10 keV), comparable with the
lowest luminosities ever detected from this source, despite the observations
being taken near to periastron. We consider the possible orbital geometry of
IGRJ175442619 and the implications for the nature of the mass transfer
and accretion mechanisms for both IGRJ175442619 and the SFXT population.
We conclude that accretion under the `quasi-spherical accretion' model provides
a good description of the behaviour of IGRJ175442619, and suggest an
additional mechanism for generating outbursts based upon the mass accumulation
rate in the hot shell (atmosphere) that forms around the NS under the
quasi-spherical formulation. Hence we hope to aid in explaining the varied
outburst behaviours observed across the SFXT population with a consistent
underlying physical model.Comment: 12 pages, 5 figures, accepted for publication in MNRA
Fine and ultrafine particle number and size measurements from industrial combustion processes : primary emissions field data
This study is to our knowledge the first to present the results of on-line measurements of residual nanoparticle numbers downstream of the flue gas treatment systems of a wide variety of medium- and large-scale industrial installations. Where available, a semi-quantitative elemental composition of the sampled particles is carried out using a Scanning Electron Microscope coupled with an Energy Dispersive Spectrometer (SEM-EDS). The semi-quantitative elemental composition as a function of the particle size is presented. EU's Best Available Technology documents (BAT) show removal efficiencies of Electrostatic Precipitator (ESP) and bag filter dedusting systems exceeding 99% when expressed in terms of weight. Their efficiency decreases slightly for particles smaller than 1 mu m but when expressed in terms of weight, still exceeds 99% for bag filters and 96% for ESP. This study reveals that in terms of particle numbers, residual nanoparticles (NP) leaving the dedusting systems dominate by several orders of magnitude. In terms of weight, all installations respect their emission limit values and the contribution of NP to weight concentrations is negligible, despite their dominance in terms of numbers. Current World Health Organisation regulations are expressed in terms of PM2.5 wt concentrations and therefore do not reflect the presence or absence of a high number of NP. This study suggests that research is needed on possible additional guidelines related to NP given their possible toxicity and high potential to easily enter the blood stream when inhaled by humans
Analysis of MERCATOR data Part I: variable B stars
We re-classified 31 variable B stars which were observed more than 50 times
in the Geneva photometric system with the P7 photometer attached to the
MERCATOR telescope (La Palma) during its first 3 years of scientific
observations. HD89688 is a possible beta Cephei/slowly pulsating B star hybrid
and the main mode of the COROT target HD180642 shows non-linear effects. The
Maia candidates are re-classified as either ellipsoidal variables or spotted
stars. Although the mode identification is still ongoing, all the
well-identified modes so far have a degree l = 0, 1 or 2.Comment: 4 pages, 3 figures. To appear in: Proceedings of JENAM 2005 'Distant
worlds', Communications in Asteroseismolog
Investigating the reliability and validity of the Dutch versions of the illness management and recovery scales among clients with mental disorders
Background: The Illness Management and Recovery scales (IMRS) can measure the progress of clients’ illness self-management and recovery. Previous studies have examined the psychometric properties of the IMRS.
Aims: This study examined the reliability and validity of the Dutch version of the IMRS.
Method: Clients (n = 111) and clinicians (n = 40) completed the client and clinician versions of the IMRS, respectively. The scales were administered again 2 weeks later to assess stability over time. Validity was assessed with the Utrecht Coping List (UCL), Dutch Empowerment Scale (DES), and Brief Symptom Inventory (BSI).
Results: The client and clinician versions of the IMRS had moderate internal reliability, with α = 0.69 and 0.71, respectively. The scales showed strong test–retest reliability, r = 0.79, for the client version and r = 0.86 for the clinician version. Correlations between client and clinician versions ranged from r = 0.37 to 0.69 for the total and subscales. We also found relationships in expected directions between the client IMRS and UCL, DES and BSI, which supports validity of the Dutch version of the IMRS.
Conclusions: The Dutch version of the IMRS demonstrated good reliability and validity. The IMRS could be useful for Dutch-speaking programs interested in evaluating client progress on illness self-management and recovery
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