Accreting Black Holes

This chapter provides a general overview of the theory and observations of black holes in the Universe and on their interpretation. We briefly review the black hole classes, accretion disk models, spectral state classification, the AGN classification, and the leading techniques for measuring black hole spins. We also introduce quasi-periodic oscillations, the shadow of black holes, and the observations and the theoretical models of jets.Comment: 41 pages, 18 figures. To appear in "Tutorial Guide to X-ray and Gamma-ray Astronomy: Data Reduction and Analysis" (Ed. C. Bambi, Springer Singapore, 2020). v3: fixed some typos and updated some parts. arXiv admin note: substantial text overlap with arXiv:1711.1025

Apolipoprotein epsilon 3 alleles are associated with indicators of neuronal resilience

<p>Abstract</p> <p>Background</p> <p>Epilepsy is associated with precocious development of Alzheimer-type neuropathological changes, including appearance of senile plaques, neuronal loss and glial activation. As inheritance of <it>APOE ε4 </it>allele(s) is reported to favor this outcome, we sought to investigate neuronal and glial responses that differ according to <it>APOE </it>genotype. With an eye toward defining ways in which <it>APOE ε3 </it>alleles may foster neuronal well-being in epilepsy and/or <it>APOE ε4 </it>alleles exacerbate neuronal decline, neuronal and glial characteristics were studied in temporal lobectomy specimens from epilepsy patients of either <it>APOE ε4,4 </it>or <it>APOE ε3,3 </it>genotype.</p> <p>Methods</p> <p>Tissue and/or cellular expressions of interleukin-1 alpha (IL-1α), apolipoprotein E (ApoE), amyloid β (Aβ) precursor protein (βAPP), synaptophysin, phosphorylated tau, and Aβ were determined in frozen and paraffin-embedded tissues from 52 <it>APOE ε3,3 </it>and 7 <it>APOE ε4,4 </it>(0.25 to 71 years) epilepsy patients, and 5 neurologically normal patients using Western blot, RT-PCR, and fluorescence immunohistochemistry.</p> <p>Results</p> <p>Tissue levels of IL-1α were elevated in patients of both <it>APOE ε3,3 </it>and <it>APOE ε4,4 </it>genotypes, and this elevation was apparent as an increase in the number of activated microglia per neuron (<it>APOE </it>ε<it>3,3 </it>vs <it>APOE ε4,4 </it>= 3.7 ± 1.2 vs 1.5 ± 0.4; <it>P </it>< 0.05). This, together with increases in βAPP and ApoE, was associated with apparent neuronal sparing in that <it>APOE ε4,4 </it>genotype was associated with smaller neuron size (<it>APOE ε4,4 </it>vs <it>APOE ε3,3 </it>= 173 ± 27 vs 356 ± 45; <it>P </it>≤ 0.01) and greater DNA damage (<it>APOE ε4,4 </it>vs <it>APOE ε3,3 </it>= 67 ± 10 vs 39 ± 2; <it>P </it>= 0.01). 3) Aβ plaques were noted at early ages in our epilepsy patients, regardless of <it>APOE </it>genotype (<it>APOE ε4,4 </it>age 10; <it>APOE ε3,3 </it>age 17).</p> <p>Conclusions</p> <p>Our findings of neuronal and glial events, which correlate with lesser neuronal DNA damage and larger, more robust neurons in epilepsy patients of <it>APOE ε3,3 </it>genotype compared to <it>APOE ε4,4 </it>genotype carriers, are consistent with the idea that the <it>APOE </it>ε<it>3,3 </it>genotype better protects neurons subjected to the hyperexcitability of epilepsy and thus confers less risk of AD (Alzheimer's disease).</p> <p>Please see related article: <url>http://www.biomedcentral.com/1741-7015/10/36</url></p

Is health-related quality of life associated with the risk of low-energy wrist fracture: a case-control study

<p>Abstract</p> <p>Background</p> <p>Some risk factors for low-energy wrist fracture have been identified. However, self-reported measures such as health-related quality of life (HRQOL) have not been examined as potential risk factors for wrist fracture. The aims of this study were to compare HRQOL prior to a low-energy wrist fracture in elderly patients (≥ 50 years) with HRQOL in age- and sex-matched controls, and to explore the association between HRQOL and wrist fracture after adjusting for known risk factors for fracture such as age, weight, osteoporosis and falls.</p> <p>Methods</p> <p>Patients with a low-energy wrist fracture (n = 181) and age- and sex-matched controls (n = 181) were studied. Shortly after fracture (median 10 days), patients assessed their HRQOL before fracture using the Short Form 36 (SF-36). Statistical tests included <it>t </it>tests and multivariate logistic regression analysis.</p> <p>Results</p> <p>Several dimensions of HRQOL were significantly associated with wrist fracture. The direction of the associations with wrist fracture varied between the different sub-dimensions of the SF-36. After controlling for demographic and clinical variables, higher scores on <it>general health </it>(odds ratio (OR) = 1.31, 95% confidence interval (CI) = 1.10–1.56), <it>bodily pain </it>(OR = 1.18, 95% CI = 1.03–1.34) and <it>mental health </it>(OR = 1.39, 95% CI = 1.09–1.79) were related to an increased chance of being a wrist fracture patient rather than a control. In contrast, higher scores on <it>physical role limitation </it>(OR = 0.87, 95% CI = 0.79–0.95) and <it>social function </it>(OR = 0.65, 95% CI 0.53–0.80) decreased this chance. Significant associations with wrist fracture were also found for living alone (OR = 1.91, 95% CI 1.07–3.4), low body mass index (BMI) (OR = 0.92, 95% CI 0.86–0.98), osteoporosis (OR = 3.30, 95% CI 1.67–6.50) and previous falls (OR = 2.01, 95% CI 1.16–3.49).</p> <p>Conclusion</p> <p>Wrist fracture patients perceive themselves to be as healthy as the controls before fracture. Our data indicate that patients with favourable and unfavourable HRQOL measures may be at increased risk of wrist fracture.</p

X-ray Absorption and Reflection in Active Galactic Nuclei

X-ray spectroscopy offers an opportunity to study the complex mixture of emitting and absorbing components in the circumnuclear regions of active galactic nuclei, and to learn about the accretion process that fuels AGN and the feedback of material to their host galaxies. We describe the spectral signatures that may be studied and review the X-ray spectra and spectral variability of active galaxies, concentrating on progress from recent Chandra, XMM-Newton and Suzaku data for local type 1 AGN. We describe the evidence for absorption covering a wide range of column densities, ionization and dynamics, and discuss the growing evidence for partial-covering absorption from data at energies > 10 keV. Such absorption can also explain the observed X-ray spectral curvature and variability in AGN at lower energies and is likely an important factor in shaping the observed properties of this class of source. Consideration of self-consistent models for local AGN indicates that X-ray spectra likely comprise a combination of absorption and reflection effects from material originating within a few light days of the black hole as well as on larger scales. It is likely that AGN X-ray spectra may be strongly affected by the presence of disk-wind outflows that are expected in systems with high accretion rates, and we describe models that attempt to predict the effects of radiative transfer through such winds, and discuss the prospects for new data to test and address these ideas.Comment: Accepted for publication in the Astronomy and Astrophysics Review. 58 pages, 9 figures. V2 has fixed an error in footnote

Two-year changes in quality of life in elderly patients with low-energy hip fractures. A case-control study

<p>Abstract</p> <p>Background</p> <p>The long-term effect of hip fracture on health-related quality of life (HRQOL) and global quality of life (GQOL) has not been thoroughly studied in prospective case-control studies.</p> <p>Aims</p> <p>a) to explore whether patients with low-energy hip fracture regain their pre-fracture levels in HRQOL and GQOL compared with changes in age- and sex-matched controls over a two year period; b) to identify predictors of changes in HRQOL and GQOL after two years.</p> <p>Methods</p> <p>We examined 61 patients (mean age = 74 years, <it>SD </it>= 10) and 61 matched controls (mean age = 73 years, <it>SD </it>= 8). The Short Form 36 assessed HRQOL and the Quality of Life Scale assessed GQOL. Paired samples <it>t </it>tests and multiple linear regression analyses were applied.</p> <p>Results</p> <p>HRQOL decreased significantly between baseline and one-year follow-up in patients with hip fractures, within all the SF-36 domains (<it>p </it>< 0.04), except for social functioning (<it>p </it>= 0.091). There were no significant decreases within the SF-36 domains in the controls. Significantly decreased GQOL scores (<it>p </it>< 0.001) were observed both within patients and within controls between baseline and one-year follow-up. The same pattern persisted between baseline and two-year follow-up, except for the HRQOL domain mental health (<it>p </it>= 0.193). The patients with hip fractures did not regain their HRQOL and GQOL. Worsened physical health after two years was predicted by being a patient with hip fracture (B = -5.8, <it>p </it>< 0.001) and old age (B = -1.0, <it>p </it>= 0.015), while worsened mental health was predicted by co-morbidity (B = -2.2, <it>p </it>= 0.029). No significant predictors of differential changes in GQOL were identified.</p> <p>Conclusion</p> <p>A hip fracture has a long-term impact on HRQOL and is a strong predictor of worsened physical health. Our data emphasize the importance of preventing hip fracture in the elderly to maintain physical health. This knowledge should be included in decision-making and health care plans.</p

Depression after low-energy fracture in older women predicts future falls: a prospective observational study

<p>Abstract</p> <p>Background</p> <p>Falls are one of the main causes of fractures in elderly people and after a recent fracture, the risk of another fall is increased, resulting in subsequent fracture. Therefore, risk factors for future falls should be determined. We prospectively investigated the relationship between depression and the incidence of falls in post-menopausal women after a low-energy fracture.</p> <p>Methods</p> <p>At baseline, 181 women aged 60 years and older who presented with a recent low-energy fracture were evaluated at the fracture and osteoporosis outpatient clinics of two hospitals. As well as clinical evaluation and bone mineral density tests, the presence of depression (measured using the Edinburgh Depression Scale, EDS, depression cut-off > 11) and risk factors for falling were assessed. During two years of follow-up, the incidence of falls was registered annually by means of detailed questionnaires and interviews.</p> <p>Results</p> <p>Seventy-nine (44%) of the women sustained at least one fall during follow-up. Of these, 28% (<it>n </it>= 22) suffered from depression at baseline compared to 10% (<it>n </it>= 10) of the 102 women who did not sustain a fall during follow-up (<it>Χ</it>²= 8.76, df = 1, <it>p </it>= .003). Multiple logistic regression showed that the presence of depression and co-morbidity at baseline were independently related to falls (OR = 4.13, 95% CI = 1.58-10.80; OR = 2.25, 95% CI = 1.11-4.56, respectively) during follow-up.</p> <p>Conclusions</p> <p>The presence of depression in women aged 60 years and older with recent low-energy fractures is an important risk factor for future falls. We propose that clinicians treating patients with recent low-energy fractures should anticipate not only on skeletal-related risk factors for fractures, but also on fall-related risk factors including depression.</p

No long-term impact of low-energy distal radius fracture on health-related quality of life and global quality of life: a case-control study

<p>Abstract</p> <p>Background</p> <p>Changes in patient-reported outcomes like health related quality of life (HRQOL) and global quality of life (GQOL) in patients with low-energy distal radius fracture might be related to fracture, or be within the normal range of variation in an elderly population. Hence, the present study aims to examine: Whether patients with low-energy distal radius fracture attain their pre-fracture levels in HRQOL and GQOL one year after the fracture and compare these levels with age- and sex-matched controls; and whether objective factors predict changes in HRQOL and GQOL during the same one year period.</p> <p>Methods</p> <p>We examined 160 patients and 169 age- and sex matched controls, respectively (mean ± SD) 67 ± 9 and 66 ± 9 years of age. HRQOL was assessed by the Modified Health Assessment Questionnaire (MHAQ) and the Short–Form 36 (SF-36). The Quality of Life Scale (QOLS) assessed GQOL. Paired sample t-tests and multiple linear regression analyses were applied.</p> <p>Results</p> <p>After one year no differences were found in HRQOL (assessed as arm functions, physical health and mental health) compared to pre-fracture level in the patient group. Both patients with distal radius fracture and controls reported a reduced GQOL after one year (p < 0.001). Low-energy distal radius fracture did not predict worsened HRQOL or GQOL one year after inclusion, and few predictors of changes were identified. Worsened arm function was predicted by low BMI (B = -0.20, p = 0.019) at baseline, worsened physical health was predicted by low education (B = 1.37, p = 0.017) at baseline, and living with someone predicted worsened mental health (B = 2.85, p = 0.009)</p> <p>Conclusion</p> <p>Patients with a distal radius fracture seem to manage well despite the fracture, and distal radius fracture is not an independent predictor of worsened HRQOL and GQOL.</p

Protein profiling of the dimorphic, pathogenic fungus, Penicillium marneffei

<p>Abstract</p> <p>Background</p> <p><it>Penicillium marneffei </it>is a pathogenic fungus that afflicts immunocompromised individuals having lived or traveled in Southeast Asia. This species is unique in that it is the only dimorphic member of the genus. Dimorphism results from a process, termed phase transition, which is regulated by temperature of incubation. At room temperature, the fungus grows filamentously (mould phase), but at body temperature (37°C), a uninucleate yeast form develops that reproduces by fission. Formation of the yeast phase appears to be a requisite for pathogenicity. To date, no genes have been identified in <it>P. marneffei </it>that strictly induce mould-to-yeast phase conversion. In an effort to help identify potential gene products associated with morphogenesis, protein profiles were generated from the yeast and mould phases of <it>P. marneffei</it>.</p> <p>Results</p> <p>Whole cell proteins from the early stages of mould and yeast development in <it>P. marneffei </it>were resolved by two-dimensional gel electrophoresis. Selected proteins were recovered and sequenced by capillary-liquid chromatography-nanospray tandem mass spectrometry. Putative identifications were derived by searching available databases for homologous fungal sequences. Proteins found common to both mould and yeast phases included the signal transduction proteins cyclophilin and a RACK1-like ortholog, as well as those related to general metabolism, energy production, and protection from oxygen radicals. Many of the mould-specific proteins identified possessed similar functions. By comparison, proteins exhibiting increased expression during development of the parasitic yeast phase comprised those involved in heat-shock responses, general metabolism, and cell-wall biosynthesis, as well as a small GTPase that regulates nuclear membrane transport and mitotic processes in fungi. The cognate gene encoding the latter protein, designated <it>RanA</it>, was subsequently cloned and characterized. The <it>P. marneffei </it>RanA protein sequence, which contained the signature motif of Ran-GTPases, exhibited 90% homology to homologous <it>Aspergillus </it>proteins.</p> <p>Conclusion</p> <p>This study clearly demonstrates the utility of proteomic approaches to studying dimorphism in <it>P. marneffei</it>. Moreover, this strategy complements and extends current genetic methodologies directed towards understanding the molecular mechanisms of phase transition. Finally, the documented increased levels of RanA expression suggest that cellular development in this fungus involves additional signaling mechanisms than have been previously described in <it>P. marneffei</it>.</p

Black hole spin: theory and observation

In the standard paradigm, astrophysical black holes can be described solely by their mass and angular momentum - commonly referred to as `spin' - resulting from the process of their birth and subsequent growth via accretion. Whilst the mass has a standard Newtonian interpretation, the spin does not, with the effect of non-zero spin leaving an indelible imprint on the space-time closest to the black hole. As a consequence of relativistic frame-dragging, particle orbits are affected both in terms of stability and precession, which impacts on the emission characteristics of accreting black holes both stellar mass in black hole binaries (BHBs) and supermassive in active galactic nuclei (AGN). Over the last 30 years, techniques have been developed that take into account these changes to estimate the spin which can then be used to understand the birth and growth of black holes and potentially the powering of powerful jets. In this chapter we provide a broad overview of both the theoretical effects of spin, the means by which it can be estimated and the results of ongoing campaigns.Comment: 55 pages, 5 figures. Published in: "Astrophysics of Black Holes - From fundamental aspects to latest developments", Ed. Cosimo Bambi, Springer: Astrophysics and Space Science Library. Additional corrections mad