The geometry of the accretion flow around stellar-mass black holes can change on timescales of days to months1–3. When a black hole emerges from quiescence (that is, it ‘turns on’ after accreting ...material from its companion) it has a very hard (high-energy) X-ray spectrum produced by a hot corona4,5 positioned above its accretion disk, and then transitions to a soft (lower-energy) spectrum dominated by emission from the geometrically thin accretion disk, which extends to the innermost stable circular orbit6,7. Much debate persists over how this transition occurs and whether it is driven largely by a reduction in the truncation radius of the disk8,9 or by a reduction in the spatial extent of the corona10,11. Observations of X-ray reverberation lags in supermassive black-hole systems12,13 suggest that the corona is compact and that the disk extends nearly to the central black hole14,15. Observations of stellar-mass black holes, however, reveal equivalent (mass-scaled) reverberation lags that are much larger16, leading to the suggestion that the accretion disk in the hard-X-ray state of stellar-mass black holes is truncated at a few hundreds of gravitational radii from the black hole17,18. Here we report X-ray observations of the black-hole transient MAXI J1820+07019,20. We find that the reverberation time lags between the continuum-emitting corona and the irradiated accretion disk are 6 to 20 times shorter than previously seen. The timescale of the reverberation lags shortens by an order of magnitude over a period of weeks, whereas the shape of the broadened iron K emission line remains remarkably constant. This suggests a reduction in the spatial extent of the corona, rather than a change in the inner edge of the accretion disk.
Insufficient hemodynamics during agonal phase—ie, the period between withdrawal of life‐sustaining treatment and circulatory arrest—in Maastricht category III circulatory‐death donors (DCD) ...potentially exacerbate ischemia/reperfusion injury. We included 409 Dutch adult recipients of DCD donor kidneys transplanted between 2006 and 2014. Peripheral oxygen saturation (SpO2‐with pulse oximetry at the fingertip) and systolic blood pressure (SBP‐with arterial catheter) were measured during agonal phase, and were dichotomized into minutes of SpO2 > 60% or SpO2 < 60%, and minutes of SBP > 80 mmHg or SBP < 80 mmHg. Outcome measures were and primary non‐function (PNF), delayed graft function (DGF), and three‐year graft survival. Primary non‐function (PNF) rate was 6.6%, delayed graft function (DGF) rate was 67%, and graft survival at three years was 76%. Longer periods of agonal phase (median 16 min IQR 11‐23) contributed significantly to an increased risk of DGF (P = .012), but not to PNF (P = .071) and graft failure (P = .528). Multiple logistic regression analysis showed that an increase from 7 to 20 minutes in period of SBP < 80 mmHg was associated with 2.19 times the odds (95% CI 1.08‐4.46, P = .030) for DGF. In conclusion, duration of agonal phase is associated with early transplant outcome. SBP < 80 mmHg during agonal phase shows a better discrimination for transplant outcome than SpO2 < 60% does.
This investigation of the predictive ability of hemodynamics during the agonal phase of circulatory death donors shows that systolic blood pressure discriminates short‐term transplant outcomes better than peripheral oxygenation does.
Abstract
During the course of its 2005 outburst, the black hole X-ray binary GRO J1655–40 launched an accretion disk wind associated with deep X-ray absorption lines and strong Compton scattering. ...Little is known about this apparently super-Eddington wind, but previous works have discovered optical/infrared (OIR) emission from the wind that varies on the orbital period—a possible clue to its origin and geometry. However, there is significant uncertainty in the orbital phases, and a more precise value of the orbital period is needed to accurately phase fold the wind emission. We present our analysis of the
I
-band photometry from observations taken with the Small and Medium Aperture Research Telescope System 1.3 m telescope between 2006 and 2016. We have implemented two methods—data-driven and model-based—to determine the orbital period, which we report as 2.62193 ± 0.00002 days from the data-driven method and 2.621928 ± 0.000004 days from the model-based method, a significant (25×) increase in precision over prior measurements. We discuss the possible existence of a period derivative, implications of a peculiar deep minimum in the outburst lightcurve of the system, and connections between OIR variability and the geometry of the super-Eddington wind.
After 26 yr in outburst, the black hole X-ray binary GRS 1915+105 dimmed considerably in early 2018; its flux dropped sharply in mid-2019, and it has remained faint ever since. This faint period, the ..."obscured state," is punctuated by occasional X-ray flares, many of which have been observed by NICER as part of our regular monitoring program. Here we present detailed time-resolved spectroscopy of one bright flare, whose spectrum shows evidence of high column density partial covering absorption and extremely deep absorption lines (equivalent widths over 100 eV in some cases). We study the time-dependent ionization of the obscuring gas with xstar, ultimately attributing the absorption to a radially stratified absorber of density ∼10^(12)–10^(13) per cu.cm at ∼few ×10^(11) cm from the black hole. We argue that a vertically extended outer disk could explain this obscuration. We discuss several scenarios to explain the obscured state, including massive outflows, an increase in the mass accretion rate, and changes in the outer disk that herald the approach of quiescence, but none are entirely satisfactory. Alternative explanations, such as obscuration by the accretion stream impact point, may be testable with current or future data.
Children with very low weight for age or height and those who do not maintain an appropriate growth pattern may have failure to thrive (FTT), also known as weight faltering. If confirmed by repeated ...valid measurements, FTT should prompt a search for causes of undernutrition, including neglect, family food insecurity, and underlying medical conditions. Inadequate caloric intake is the most common cause of FTT, but inadequate nutrient absorption or increased metabolism is also possible. Difficulty attaining or maintaining appropriate weight is the first indication of FTT, and sustained undernutrition can impede appropriate height, head circumference, and the development of cognitive skills or immune function in extreme cases. Early identification and management of the issues causing undernutrition are critical. In most cases, an appropriate growth velocity can be established with outpatient management based on proper nutrition and family support. Primary care physicians can effectively treat most children with FTT, and subspecialist consultation or hospitalization is rarely indicated.
In this paper we study the relation of radio emission to X–ray spectral and variability properties for a large sample of black hole X–ray binary systems. This is done to test, refine and extend – ...notably into the timing properties – the previously published ‘unified model’ for the coupling of accretion and ejection in such sources. In 14 outbursts from 11 different sources we find that in every case the peak radio flux, on occasion directly resolved into discrete relativistic ejections, is associated with the bright hard to soft state transition near the peak of the outburst. We also note the association of the radio flaring with periods of X–ray flaring during this transition in most, but not all, of the systems. In the soft state, radio emission is in nearly all cases either undetectable or optically thin, consistent with the suppression of the core jet in these states and ‘relic’ radio emission from interactions of previously ejected material and the ambient medium. However, these data cannot rule out an intermittent, optically thin, jet in the soft state. In attempting to associate X–ray timing properties with the ejection events we find a close, but not exact, correspondence between phases of very low integrated X–ray variability and such ejections. In fact the data suggest that there is not a perfect one–to–one correspondence between the radio, X–ray spectral or X–ray timing properties, suggesting that they may be linked simply as symptoms of the underlying state change and not causally to one another. We further study the sparse data on the reactivation of the jet during the transition back to the hard state in decay phase of outbursts, and find marginal evidence for this in one case only. In summary we find no strong evidence against the originally proposed model, confirming and extending some aspects of it with a much larger sample, but note that several aspects remain poorly tested.
ABSTRACT During its 2005 outburst, GRO J1655-40 was observed at high spectral resolution with the Chandra High-Energy Transmission Grating Spectrometer, revealing a spectrum rich with blueshifted ...absorption lines indicative of an accretion disk wind-apparently too hot, too dense, and too close to the black hole to be driven by radiation pressure or thermal pressure (Miller et al.). However, this exotic wind represents just one piece of the puzzle in this outburst, as its presence coincides with an extremely soft and curved X-ray continuum spectrum, remarkable X-ray variability (Uttley & Klein-Wolt), and a bright, unexpected optical/infrared blackbody component that varies on the orbital period. Focusing on the X-ray continuum and the optical/infrared/UV spectral energy distribution, we argue that the unusual features of this "hypersoft state" are natural consequences of a super-Eddington Compton-thick wind from the disk: the optical/infrared blackbody represents the cool photosphere of a dense, extended outflow, while the X-ray emission is explained as Compton scattering by the relatively cool, optically thick wind. This wind obscures the intrinsic luminosity of the inner disk, which we suggest may have been at or above the Eddington limit.
We report on deep, coordinated radio and X-ray observations of the black hole X-ray binary XTE J1118+480 in quiescence. The source was observed with the Karl G. Jansky Very Large Array for a total of ...17.5 h at 5.3 GHz, yielding a 4.8 ± 1.4 μJy radio source at a position consistent with the binary system. At a distance of 1.7 kpc, this corresponds to an integrated radio luminosity between 4 and 8 × 1025 erg s−1, depending on the spectral index. This is the lowest radio luminosity measured for any accreting black hole to date. Simultaneous observations with the Chandra X-ray Telescope detected XTE J1118+480 at 1.2 × 10−14 erg s−1 cm−2 (1–10 keV), corresponding to an Eddington ratio of ∼4 × 10−9 for a 7.5 M⊙ black hole. Combining these new measurements with data from the 2005 and 2000 outbursts available in the literature, we find evidence for a relationship of the form ℓr = α+βℓX (where ℓ denotes logarithmic luminosities), with β = 0.72 ± 0.09. XTE J1118+480 is thus the third system – together with GX339-4 and V404 Cyg – for which a tight, non-linear radio/X-ray correlation has been reported over more than 5 dex in ℓX. Confirming previous results, we find no evidence for a dependence of the correlation normalization of an individual system on orbital parameters, relativistic boosting, reported black hole spin and/or black hole mass. We then perform a clustering and linear regression analysis on what is arguably the most up-to-date collection of coordinated radio and X-ray luminosity measurements from quiescent and hard-state black hole X-ray binaries, including 24 systems. At variance with previous results, a two-cluster description is statistically preferred only for random errors ≲0.3 dex in both ℓr and ℓX, a level which we argue can be easily reached when the known spectral shape/distance uncertainties and intrinsic variability are accounted for. A linear regression analysis performed on the whole data set returns a best-fitting slope β = 0.61 ± 0.03 and intrinsic scatter σ0 = 0.31 ± 0.03 dex.
It is assumed that fatigue crack initiation in Fibre Metal Laminates is determined by the stress cycles in the metal layers only. It is further assumed that if the stress cycles in the metal layers ...are known, the fatigue initiation life can be established using
S–
N data available for the given metal alloy.
The internal stresses in the aluminium layers of a Fibre Metal Laminate are different from the applied stresses on the laminate because of differences in stiffness and coefficient of thermal expansion between the metal and fibre layers. The difference in thermal expansion will cause residual stresses during cooling down after the curing process of the laminate. Classical laminate theory can be applied to calculate the internal stresses. Additional elastic considerations have led to accounting for the effect of anisotropy on the stress concentration factor.
Validation fatigue tests on Glare 3-3/2-0.3, Glare 4B-3/2-0.3 and monolithic aluminium 2024-T3 showed that the above assumptions proved to be correct. The tests showed also that the effect of off-axis loading could be predicted with the classical laminate theory.
Further, is has been shown that exposure to high temperature (70
°C) and humidity (85%) for 3000
h prior to testing has no effect on the fatigue initiation properties of Glare 3-3/2-0.3.
•We explored the role of exercise motives in the context of the acceptance model of intuitive eating.•Body acceptance by others was linked with higher functional exercise motives.•Functional exercise ...motives positively, and appearance motives inversely, contributed to body appreciation.•Results suggest the importance of encouraging functional reasons for exercise.
The acceptance model of intuitive eating posits that body acceptance by others facilitates body appreciation and internal body orientation, which contribute to intuitive eating. Two domains of exercise motives (functional and appearance) may also be linked to these variables, and thus were integrated into the model. The model fit the data well for 406 physically active U.S. college students, although some pathways were stronger for women. Body acceptance by others directly contributed to higher functional exercise motives and indirectly contributed to lower appearance exercise motives through higher internal body orientation. Functional exercise motives positively, and appearance exercise motives inversely, contributed to body appreciation. Whereas body appreciation positively, and appearance exercise motives inversely, contributed to intuitive eating for women, only the latter association was evident for men. To benefit positive body image and intuitive eating, efforts should encourage body acceptance by others and emphasize functional and de-emphasize appearance exercise motives.
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