Small angle scattering by dust grains causes a significant contribution to the total interstellar extinction for any X-ray instrument with sub-arcminute resolution (Chandra, Swift, XMM–Newton). ...However, the dust-scattering component is not included in the current absorption models: phabs, TBabs, and TBnew. We simulate a large number of Chandra spectra to explore the bias in the spectral fit and N
H measurements obtained without including extinction from dust scattering. We find that without incorporating dust scattering, the measured N
H will be too large by a baseline level of 25 per cent. This effect is modulated by the imaging resolution of the telescope, because some amount of unresolved scattered light will be captured within the aperture used to extract point source information. In high-resolution spectroscopy, dust scattering significantly enhances the total extinction optical depth and the shape of the photoelectric absorption edges. We focus in particular on the Fe–L edge at 0.7 keV, showing that the total extinction template fits well to the high-resolution spectrum of three X-ray binaries from the Chandra archive: GX 9+9, XTE J1817-330, and Cyg X-1. In cases where dust is intrinsic to the source, a covering factor based on the angular extent of the dusty material must be applied to the extinction curve, regardless of angular imaging resolution. This approach will be particularly relevant for dust in quasar absorption line systems and might constrain clump sizes in active galactic nuclei.
The dust scattering halo of Cygnus X-3 Corrales, L. R; Paerels, F
Monthly Notices of the Royal Astronomical Society,
10/2015, Letnik:
453, Številka:
1
Journal Article
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Odprti dostop
Dust grains scatter X-ray light through small angles, producing a diffuse halo image around bright X-ray point sources situated behind a large amount of interstellar material. We present analytic ...solutions to the integral for the dust scattering intensity, which allow for a Bayesian analysis of the scattering halo around Cygnus X-3. Fitting the optically thin 4–6 keV halo surface brightness profile yields the dust grain size and spatial distribution. We assume a power-law distribution of grain sizes (n ∝ a
−p
) and fit for p, the grain radius cut-off a
max, and dust mass column. We find that a p ≈ 3.5 dust grain size distribution with a
max ≈ 0.2 μm fits the halo profile relatively well, whether the dust is distributed uniformly along the line of sight or in clumps. We find that a model consisting of two dust screens, representative of foreground spiral arms, requires the foreground Perseus arm to contain 80 per cent of the total dust mass. The remaining 20 per cent of the dust, which may be associated with the outer spiral arm of the Milky Way, is located within 1 kpc of Cyg X-3. Regardless of which model was used, we found
$\tau _{\rm sca} \sim 2 \ E_{\rm keV}^{-2}$
. We examine the energy resolved haloes of Cyg X-3 from 1 to 6 keV and find that there is a sharp drop in scattering halo intensity when E < 2–3 keV, which cannot be explained with multiple scattering effects. We hypothesize that this may be caused by large dust grains or material with unique dielectric properties, causing the scattering cross-section to depart from the Rayleigh–Gans approximation that is used most often in X-ray scattering studies. The foreground Cyg OB2 association, which contains several evolved stars with large extinction values, is a likely culprit for grains of unique size or composition.
The aim of this study was to evaluate the superovulation response of Beef and Dairy donor cows to two differentfollicular emergence synchronization protocols. Twenty-two beef and dairy cows were ...divided into two groups viz.Conventional group (n=8) having four Holsteins and four Charolais cows between days 10 and 11 of their estrouscycle and IVD+EB group (n=14) with six Holsteins and eight Charolais cows treated with an intravaginal device (IVD) containing 1.9 g of P4 + 2 mg of estradiol benzoate (EB) between days 10 and 11 of their estrous cycle. The superovulation protocol consisted of intramuscular application of FSHp twice a day for four days, in decreasing doses (850 IU for Dairy cows and 500 IU for Beef cows). The number of follicles (13±1.1 vs. 7.5±0.9) and embryoscollected (11.7±2.1 vs 6.1±1.0) were significantly affected by the treatment in the Beef cows but, the protocols didnot significantly affect these variables in Dairy cows (12.2±0.9 vs 10.4±0.7, respectively). Regarding the productionof non-viable embryos, a significant difference was only found in the group of Beef cows for both treatments (8.2±2.3 vs. 1.3±0.3, respectively). Results showed that IVD+EB is not necessary for the superstimulation of the emergence of a new follicular wave before superovulation when it starts in the mid-luteal phase of the estrous cycle in Holstein cows and beef cows, since they had similar results without significant differences between both treatments.
We report the detection of a dust-scattering halo around a recently discovered X-ray transient, Swift J174540.7-290015, which in early 2016 February underwent one of the brightest outbursts (FX 5 × ...10−10 erg cm−2 s−1) observed from a compact object in the Galactic Center field. We analyze four Chandra images that were taken as follow-up observations to Swift discoveries of new Galactic Center transients. After adjusting our spectral extraction for the effects of detector pile-up, we construct a point-spread function for each observation and compare it to the GC field before the outburst. We find residual surface brightness around Swift J174540.7-290015, which has a shape and temporal evolution consistent with the behavior expected from X-rays scattered by foreground dust. We examine the spectral properties of the source, which shows evidence that the object transitioned from a soft to hard spectral state as it faded below LX ∼ 1036 erg s−1. This behavior is consistent with the hypothesis that the object is a low-mass X-ray binary in the Galactic Center.
Abstract Objective: Our goal was to conduct the generation and piloting of a discriminative and evaluative tool for pediatric post-thrombotic syndrome. Methods: We followed a formative model for the ...development of the tool, focusing on the signs/symptoms (items) that define post-thrombotic syndrome. For item generation, pediatric thrombosis experts and subjects diagnosed with extremity post-thrombotic syndrome during childhood nominated items. In the piloting phase, items were cross-sectionally measured in children with limb deep vein thrombosis to examine the performance of the items. Result: Twenty-three experts and 16 subjects listed 34 items, which were then measured in 140 subjects with previous diagnosis of limb deep vein thrombosis (70 upper extremity and 70 lower extremity). The items with strongest correlation with post-thrombotic syndrome severity and largest area under the curve were pain (in older children), paresthesia, and swollen limb for the upper extremity group, and pain (in older children), tired limb, heaviness, tightness and paresthesia for the lower extremity group. Conclusion: Diagnostic properties and correlation with post-thrombotic syndrome severity of the different signs and symptoms varied according to the assessed venous territory. The information gathered in this study will help experts decide which item should be considered for inclusion in the new tool.
We investigate the energy states of confined electrons in doped quantum structures with Razavy-like confining potentials. The theoretical investigation is performed within the effective mass and ...parabolic band approximations, including the influence of externally applied electric and magnetic fields. First, we analyze the case of a Razavy quantum well and determine its conduction subband spectrum, focusing on the lowest energy levels and their probability densities. These properties have been numerically determined by self-consistently solving the coupled system of Schrödinger, Poisson, and charge neutrality equations. Doping is introduced via an on-center
δ
-like layer. In order to evaluate the associated total (linear plus nonlinear) optical absorption coefficient (TOAC), we have calculated the corresponding diagonal and off-diagonal electric dipole matrix elements, the main energy separation, and the occupancy ratio which are the main factors governing the variation in this optical response. A detailed discussion is given about the influence of doping concentration as well as electric and magnetic fields, which can produce shifts in the light absorption signal, toward either lower or higher frequencies. As an extension of the self-consistent method to a two-dimensional problem, the energy states of quantum wire system of circular cross section, with internal doping and Razavy potential, have been calculated. The response of eigenvalues, self-consistent potentials and electron densities is studied with the variation in
δ
-doping layer width and of the donor density. Finally, the origin of Friedel-like oscillations, that arise in the density profile, generated by the occupation of internal and surface electronic states has been explained.
The incidence of systemic lupus in children with discoid lupus is unknown.
This study assessed the baseline characteristics of patients with pediatric discoid lupus erythematosus (pDLE).
Medical ...records at 17 sites were reviewed for pediatric dermatology and rheumatology patients with discoid lupus erythematosus. The inclusion criteria were clinical and/or histopathologic diagnosis of discoid lupus erythematosus with an age at onset of <18 years. Baseline data were collected at the first documented visit. Outcomes included diagnosis of systemic lupus erythematosus (SLE) at the baseline visit using the 1997 American College of Rheumatology (primary) and the 2012 Systemic Lupus International Collaborating Clinics (secondary) criteria.
Of the >1500 charts reviewed, 438 patients met the inclusion criteria. The cohort was predominantly female (72%) and racially/ethnically diverse. A diagnosis of SLE at the baseline visit (pDLE + SLE) was rendered in 162 (37%) patients using the American College of Rheumatology and in 181 (41%) patients using the Systemic Lupus International Collaborating Clinics criteria. Patients with pDLE + SLE were older at the time of rash onset (median, 12.9 vs 8.9 years; P < .001), with shorter time from discoid lupus erythematosus onset to diagnosis, compared with patients with pDLE-only (median, 2 vs 7 months; P < .001). Patients with pDLE + SLE were more likely to be female (P = .004), with generalized discoid lupus erythematosus and clinically aggressive disease, including end-organ involvement, positive serologies, and higher- titer levels of antinuclear antibodies (P < .001).
Retrospective study.
A diagnosis of discoid lupus erythematosus in adolescence should prompt thorough screening for SLE.
The donor-impurity-related optical absorption, relative refractive index changes, and Raman scattering in GaAs cone-like quantum dots are theoretically investigated. Calculations are performed within ...the effective mass and parabolic band approximations, using the variational procedure to include the electron-impurity correlation effects. The study involves 1s-like, 2px-like, and 2pz-like states. The conical structure is chosen in such a way that the cone height is large enough in comparison with the base radius thus allowing the use a quasi-analytic solution of the uncorrelated Schrödinger-like electron states.
Signal variance in gamma-ray detectors—A review Devanathan, R.; Corrales, L.R.; Gao, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2006, Letnik:
565, Številka:
2
Journal Article
Recenzirano
Signal variance in gamma-ray detector materials is reviewed with an emphasis on intrinsic variance. Phenomenological models of electron cascades are examined and the Fano factor (
F) is discussed in ...detail. In semiconductors,
F is much smaller than unity and charge carrier production is nearly proportional to energy. Based on a fit to a number of semiconductors and insulators, a new relationship between the average energy for electron–hole pair production and band gap energy is proposed. In scintillators, the resolution is governed mainly by photoelectron statistics and proportionality of light yield with respect to energy.
•The role of visible collateral circulation in pediatric PTS was explored•A simplified scale for assessment of visible collaterals was developed•Visible collaterals showed no or only weak correlation ...with other PTS findings•Inter-rater reliability of the simplified scale was almost perfect
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