Continuity properties of a factor of Markov chains

Starting from a Markov chain with a finite alphabet, we consider the chain obtained when all but one symbol are undistinguishable for the practitioner. We study necessary and sufficient conditions for this chain to have continuous transition probabilities with respect to the past

Evangelización e inculturación en Guatemala

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Broad-band X-ray spectral evolution of GX 339-4 during a state transition

We report on X-ray and soft gamma-ray observations of the black-hole candidate GX 339-4 during its 2007 outburst, performed with the RXTE and INTEGRAL satellites. The hardness-intensity diagram of all RXTE/PCA data combined shows a q-shaped track similar to that observed in previous outbursts.The evolution in the diagram suggested that a transition from hard-intermediate state to soft-intermediate state occurred, simultaneously with INTEGRAL observations performed in March. The transition is confirmed by the timing analysis presented in this work, which reveals that a weak type-A quasi-periodic oscillation (QPO) replaces a strong type-C QPO. At the same time, spectral analysis shows that the flux of the high-energy component shows a significant decrease in its flux. However, we observe a delay (roughly one day) between variations of the spectral parameters of the high-energy component and changes in the flux and timing properties. The changes in the high-energy component can be explained either in terms the high-energy cut-off or in terms of a variations in the reflection component. We compare our results with those from a similar transition during the 2004 outburst of GX 339-4.Comment: 8 pages, 6 figures, accepted for publication in MNRAS Main Journa

Correlated X-ray and Optical Variability in V404 Cyg in Quiescence

We report simultaneous X-ray and optical observations of V404 Cyg in quiescence. The X-ray flux varied dramatically by a factor of >20 during a 60ks observation. X-ray variations were well correlated with those in Halpha, although the latter include an approximately constant component as well. Correlations can also be seen with the optical continuum, although these are less clear. We see no large lag between X-ray and optical line variations; this implies they are causally connected on short timescales. As in previous observations, Halpha flares exhibit a double-peaked profile suggesting emission distributed across the accretion disk. The peak separation is consistent with material extending outwards to at least the circularization radius. The prompt response in the entire Halpha line confirms that the variability is powered by X-ray (and/or EUV) irradiation.Comment: 5 pages; Accepted for publication in the Astrophysical Journal Letter

The first accurate parallax distance to a black hole

Using astrometric VLBI observations, we have determined the parallax of the black hole X-ray binary V404 Cyg to be 0.418 +/- 0.024 milliarcseconds, corresponding to a distance of 2.39 +/- 0.14 kpc, significantly lower than the previously accepted value. This model-independent estimate is the most accurate distance to a Galactic stellar-mass black hole measured to date. With this new distance, we confirm that the source was not super-Eddington during its 1989 outburst. The fitted distance and proper motion imply that the black hole in this system likely formed in a supernova, with the peculiar velocity being consistent with a recoil (Blaauw) kick. The size of the quiescent jets inferred to exist in this system is less than 1.4 AU at 22 GHz. Astrometric observations of a larger sample of such systems would provide useful insights into the formation and properties of accreting stellar-mass black holes.Comment: Accepted for publication in ApJ Letters. 6 pages, 2 figure

A Low-Flux State in IRAS 00521-7054 seen with NuSTAR and XMM-Newton: Relativistic Reflection and an Ultrafast Outflow

We present results from a deep, coordinated $XMM$-$Newton$+$NuSTAR$ observation of the Seyfert 2 galaxy IRAS 00521-7054. The $NuSTAR$ data provide the first detection of this source in high-energy X-rays ($E > 10$ keV), and the broadband data show this to be a highly complex source which exhibits relativistic reflection from the inner accretion disc, further reprocessing by more distant material, neutral absorption, and evidence for ionised absorption in an extreme, ultrafast outflow ($v_{\rm{out}} \sim 0.4c$). Based on lamppost disc reflection models, we find evidence that the central supermassive black hole is rapidly rotating ($a > 0.77$), consistent with previous estimates from the profile of the relativistic iron line, and that the accretion disc is viewed at a fairly high inclination ($i \sim 59^{\circ}$). Based on extensive simulations, we find the ultrafast outflow is detected at $\sim$4$\sigma$ significance (or greater). We also estimate that the extreme outflow should be sufficient to power galaxy-scale feedback, and may even dominate the energetics of the total output from the system.Comment: 12 pages, 8 figures; accepted for publication in MNRA

Clinical characteristics, risk factors and outcomes in patients with severe COVID-19 registered in the International Severe Acute Respiratory and Emerging Infection Consortium WHO clinical characterisation protocol: a prospective, multinational, multicentre, observational study

Respiratory infections and tuberculosisInfecciones respiratorias y tuberculosisInfeccions respiratòries i tuberculosiDue to the large number of patients with severe coronavirus disease 2019 (COVID-19), many were treated outside the traditional walls of the intensive care unit (ICU), and in many cases, by personnel who were not trained in critical care. The clinical characteristics and the relative impact of caring for severe COVID-19 patients outside the ICU is unknown. This was a multinational, multicentre, prospective cohort study embedded in the International Severe Acute Respiratory and Emerging Infection Consortium World Health Organization COVID-19 platform. Severe COVID-19 patients were identified as those admitted to an ICU and/or those treated with one of the following treatments: invasive or noninvasive mechanical ventilation, high-flow nasal cannula, inotropes or vasopressors. A logistic generalised additive model was used to compare clinical outcomes among patients admitted or not to the ICU. A total of 40 440 patients from 43 countries and six continents were included in this analysis. Severe COVID-19 patients were frequently male (62.9%), older adults (median (interquartile range (IQR), 67 (55–78) years), and with at least one comorbidity (63.2%). The overall median (IQR) length of hospital stay was 10 (5–19) days and was longer in patients admitted to an ICU than in those who were cared for outside the ICU (12 (6–23) days versus 8 (4–15) days, p<0.0001). The 28-day fatality ratio was lower in ICU-admitted patients (30.7% (5797 out of 18 831) versus 39.0% (7532 out of 19 295), p<0.0001). Patients admitted to an ICU had a significantly lower probability of death than those who were not (adjusted OR 0.70, 95% CI 0.65–0.75; p<0.0001). Patients with severe COVID-19 admitted to an ICU had significantly lower 28-day fatality ratio than those cared for outside an ICU.This work was supported by the UK Foreign, Commonwealth and Development Office and Wellcome (215091/Z/18/Z), the Bill and Melinda Gates Foundation (OPP1209135), Canadian Institutes of Health Research Coronavirus Rapid Research Funding Opportunity OV2170359, grants from Rapid European COVID-19 Emergency Response Research (Horizon 2020 project 101003589), the European Clinical Research Alliance on Infectious Diseases (965313), The Imperial National Institute for Health Research (NIHR) Biomedical Research Centre, and The Cambridge NIHR Biomedical Research Centre; and endorsed by the Irish Critical Care Clinical Trials Group, co-ordinated in Ireland by the Irish Critical Care Clinical Trials Network at University College Dublin and funded by the Health Research Board of Ireland (CTN-2014-12). Data and Material provision was supported by grants from: the NIHR (award CO-CIN-01), the Medical Research Council (grant MC_PC_19059), the NIHR Health Protection Research Unit (HPRU) in Emerging and Zoonotic Infections at University of Liverpool in partnership with Public Health England (PHE) (award 200907), Wellcome Trust (Turtle, Lance-fellowship 205228/Z/16/Z), NIHR HPRU in Respiratory Infections at Imperial College London with PHE (award 200927), Liverpool Experimental Cancer Medicine Centre (grant C18616/A25153), NIHR Biomedical Research Centre at Imperial College London (award IS-BRC-1215-20013), and NIHR Clinical Research Network providing infrastructure support. This work was by Research Council of Norway grant number 312780, and a philanthropic donation from Vivaldi Invest A/S owned by Jon Stephenson von Tetzchner

Correction of tau mis-splicing caused by FTDP-17 MAPT mutations by spliceosome-mediated RNA trans-splicing

Frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17) is caused by mutations in the MAPT gene, encoding the tau protein that accumulates in intraneuronal lesions in a number of neurodegenerative diseases. Several FTDP-17 mutations affect alternative splicing and result in excess exon 10 (E10) inclusion in tau mRNA. RNA reprogramming using spliceosome-mediated RNA trans-splicing (SMaRT) could be a method of choice to correct aberrant E10 splicing resulting from FTDP-17 mutations. SMaRT creates a hybrid mRNA through a trans-splicing reaction between an endogenous target pre-mRNA and a pre-trans-splicing RNA molecule (PTM). However, FTDP-17 mutations affect the strength of cis-splicing elements and could favor cis-splicing over trans-splicing. Excess E10 inclusion in FTDP-17 can be caused by intronic mutations destabilizing a stem-loop protecting the 5′ splice site at the E10/intron 10 junction. COS cells transfected with a minigene containing the intronic +14 mutation produce exclusively E10+ RNA. Generation of E10− RNA was restored after co-transfection with a PTM designed to exclude E10. Similar results were obtained with a target containing the exonic N279K mutation which strengthens a splicing enhancer within E10. Conversely, increase or decrease in E10 content was achieved by trans-splicing from a target carrying the Δ280K mutation, which weakens the same splicing enhancer. Thus E10 inclusion can be modulated by trans-splicing irrespective of the strength of the cis-splicing elements affected by FTDP-17 mutations. In conclusion, RNA trans-splicing could provide the basis of therapeutic strategies for impaired alternative splicing caused by pathogenic mutations in cis-acting splicing elements

Disentangling the NIR/optical emission of the black hole XTE J1650-500 during outburst

Context: While the sources of X-ray and radio emission in the different states of low-mass X-ray binaries are relatively well understood, the origin of the near-infrared (NIR) and optical emission is more often debated. It is likely that the NIR/optical flux originates from an amalgam of different emission regions, because it occurs at the intersecting wavelengths of multiple processes. Aims: We aim to identify the NIR/optical emission region(s) of one such low-mass X-ray binary and black hole candidate, XTE J1650−500, via photometric, timing, and spectral analyses.Methods: We present unique NIR/optical images and spectra, obtained with the ESO-New Technology Telescope, during the peak of the 2001 outburst of XTE J1650−500. Results: The data suggest that the NIR/optical flux is due to a combination of emission mechanisms including a significant contribution from X-ray reprocessing and, at early times in the hard state, a relativistic jet that is NIR/radio dim compared to similar sources. Conclusions: The jet of XTE J1650−500 is relatively weak compared to that of other black hole low-mass X-ray binaries, possibly because we observe as it is being “turned off” or quenched at the state transition. While there are several outliers to the radio-X-ray correlation of the hard state of low-mass X-ray binaries, XTE J1650−500 is the first example of an outlier to the NIR/optical-X-ray correlation

A Full Characterisation of the Supermassive Black Hole in IRAS 09149-6206

We present new broadband X-ray observations of the type-I Seyfert galaxy IRAS 09149-6206, taken in 2018 with $XMM$-$Newton$, $NuSTAR$ and $Swift$. The source is highly complex, showing a classic 'warm' X-ray absorber, additional absorption from highly ionised iron, strong relativistic reflection from the innermost accretion disc and further reprocessing by more distant material. By combining X-ray timing and spectroscopy, we have been able to fully characterise the supermassive black hole in this system, constraining both its mass and - for the first time - its spin. The mass is primarily determined by X-ray timing constraints on the break frequency seen in the power spectrum, and is found to be $\log[M_{\rm{BH}}/M_{\odot}] = 8.0 \pm 0.6$ (1$\sigma$ uncertainties). This is in good agreement with previous estimates based on the H$\alpha$ and H$\beta$ line widths, and implies that IRAS 09149-6206 is radiating at close to (but still below) its Eddington luminosity. The spin is constrained via detailed modelling of the relativistic reflection, and is found to be $a^* = 0.94^{+0.02}_{-0.07}$ (90% confidence), adding IRAS 09149-6206 to the growing list of radio-quiet AGN that host rapidly rotating black holes. The outflow velocities of the various absorption components are all relatively modest ($v_{\rm{out}} \lesssim 0.03c$), implying these are unlikely to drive significant galaxy-scale AGN feedback.Comment: 19 pages, 15 figures, accepted for publication in MNRA