Modelling spectral and timing properties of accreting black holes: the hybrid hot flow paradigm

The general picture that emerged by the end of 1990s from a large set of optical and X-ray, spectral and timing data was that the X-rays are produced in the innermost hot part of the accretion flow, while the optical/infrared (OIR) emission is mainly produced by the irradiated outer thin accretion disc. Recent multiwavelength observations of Galactic black hole transients show that the situation is not so simple. Fast variability in the OIR band, OIR excesses above the thermal emission and a complicated interplay between the X-ray and the OIR light curves imply that the OIR emitting region is much more compact. One of the popular hypotheses is that the jet contributes to the OIR emission and even is responsible for the bulk of the X-rays. However, this scenario is largely ad hoc and is in contradiction with many previously established facts. Alternatively, the hot accretion flow, known to be consistent with the X-ray spectral and timing data, is also a viable candidate to produce the OIR radiation. The hot-flow scenario naturally explains the power-law like OIR spectra, fast OIR variability and its complex relation to the X-rays if the hot flow contains non-thermal electrons (even in energetically negligible quantities), which are required by the presence of the MeV tail in Cyg X-1. The presence of non-thermal electrons also lowers the equilibrium electron temperature in the hot flow model to <100 keV, making it more consistent with observations. Here we argue that any viable model should simultaneously explain a large set of spectral and timing data and show that the hybrid (thermal/non-thermal) hot flow model satisfies most of the constraints.Comment: 26 pages, 13 figures. To be published in the Space Science Reviews and as hard cover in the Space Sciences Series of ISSI - The Physics of Accretion on to Black Holes (Springer Publisher

Application of low tube potentials in CCTA results from the PROTECTION VI study

OBJECTIVES The aim of this study was to assess the use of low tube potentials for coronary computed tomography angiography (CCTA) in worldwide clinical practice and its influence on radiation exposure, contrast agent volume, and image quality.BACKGROUND CCTA is frequently used in clinical practice. Lowering of tube potential is a potent method to reduce radiation exposure and to economize contrast agent volume.METHODS CCTAs of 4,006 patients from 61 international study sites were analyzed regarding very-tow (= 130 kVp) tube potentials. The impact on dose-length product (DLP) and contrast agent volume was analyzed. Image quality was determined by evaluation of the diagnostic applicability and assessment of the objective image parameters signal-to-noise-ratio (SNR) and contrast-to-noise-ratio (CNR).RESULTS When compared with conventional tube potentials, low tube potentials were used in 56% of CCTAs (<= 80 kVp 9%; 90 to 100 kVp: 47%), which varied among sites from 0% to 100%. Tube potential reduction was associated with low-cardiovascular risk profile, low body mass index (BMI), and new-generation scanners. Median radiation exposure was lowered by 68% or 50% and median contrast agent volume by 25% or 13% for tube potential protocols of <= 80 kVp or 90 to 100 kVp when compared with conventional tube potentials, respectively (all p < 0.001). With the use of lower tube potentials, the frequency of diagnostic scans was maintained (p = 0.41), whereas SNR and CNR significantly improved (both p < 0.001). Considering BMI eligibility criteria, 58% (n = 946) of conventionally scanned patients would have been suitable for low tube potential protocols, and 44% (n = 831) of patients scanned with 90 to 100 kVp would have been eligible for very-low tube potential CCTA imaging of <= 80 kVp.CONCLUSIONS This large international registry confirms the feasibility of tube potential reduction in clinical practice leading to rower radiation exposure and lower contrast volumes. The current registry also demonstrates that this strategy is stilt underused in daily practice. (C) 2020 by the American College of Cardiology Foundation.Cardiolog

Brainless but not clueless: earthworms boost their ejaculates when they detect fecund non-virgin partners

In many animals in which females store sperm, males may detect female mating status and, in order to outcompete rival sperm, increase ejaculate size when copulating with non-virgin females. Although most studies have been restricted to organisms with separate sexes, theoretical models suggest that sperm competition should also be an important selective agent shaping life-history traits in simultaneous hermaphrodites. Nevertheless, the empirical support for ejaculate adjustment in a mating opportunity is scarce in hermaphrodites. In the present study, we performed a double-mating experiment to determine whether earthworms (Eisenia andrei) detect the mating status of their partners and whether they respond by adjusting their ejaculate. We found that earthworms triplicated the donated sperm when mating with a non-virgin mate. Moreover, such increases were greater when the worms were mated with larger (more fecund) partners, indicating that earthworms perform a fine-tune control of ejaculate volume. The results of the present study suggest that, under high intensity of sperm competition, partner evaluation is subject to intense selection in hermaphrodite animals, and donors are selective about to whom they donate how much sperm

Governmental structure of the Russian Federation with respect to environmental and energy programs

An investigation was conducted by the Environmental Planning Group, Inc., to provide an overview of the structure of government environmental and energy programs in the Russian Federation. The investigation was undertaken to provide a baseline of information to the US Department of Energy (DOE), so that technologies applicable to DOE environmental restoration and monitoring programs can be identified, tested, and transferred. Data for the report were collected through a network of Russian and American sources knowledgeable about environmental and energy programs in the Russian Federation. Sources of information included both US and Russian government personnel, nongovernmental organizations, private consultants, and experts from the academic and scientific communities. The peculiarities of the Union of Soviet Socialist Republics (USSR) remain prevalent in the structure of the Newly Independent States, especially in Russia. The legacy of communism is visible in all aspects of society, most particularly in the extreme environmental degradation that has resulted from careless central planning and policies of forced industrialization. Reforms initiated under Mikhail Gorbachev during the period of Perestroika were aimed at shifting power from the party to the respective government organs. In 1992 the Commonwealth of Independent States was created, joining 11 of the 15 republics into a loose federation. The investigation undertaken by the Environmental Planning Group, Inc., focused on the executive organs of the present Russian government in an effort to define key ministries with environmental and energy responsibilities. The structure of the Ministry of Ecology and Natural Resources (Minpriroda) and the Ministry of Atomic Power (Minatom) are presented. The Academy of Sciences and other ministries that have relevance to the transfer of technologies are discussed, as well as research institutions in which technologies appropriate to DOE programs are likely to reside