Diffusion Time-Scale Invariance, Markovization Processes and Memory Effects in Lennard-Jones Liquids

We report the results of calculation of diffusion coefficients for Lennard-Jones liquids, based on the idea of time-scale invariance of relaxation processes in liquids. The results were compared with the molecular dynamics data for Lennard-Jones system and a good agreement of our theory with these data over a wide range of densities and temperatures was obtained. By calculations of the non-Markovity parameter we have estimated numerically statistical memory effects of diffusion in detail.Comment: 10 pages, 3 figure

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

Jet disc coupling in black hole binaries

In the last decade multi-wavelength observations have demonstrated the importance of jets in the energy output of accreting black hole binaries. The observed correlations between the presence of a jet and the state of the accretion flow provide important information on the coupling between accretion and ejection processes. After a brief review of the properties of black hole binaries, I illustrate the connection between accretion and ejection through two particularly interesting examples. First, an INTEGRAL observation of Cygnus X-1 during a 'mini-' state transition reveals disc jet coupling on time scales of orders of hours. Second, the black hole XTEJ1118+480 shows complex correlations between the X-ray and optical emission. Those correlations are interpreted in terms of coupling between disc and jet on time scales of seconds or less. Those observations are discussed in the framework of current models.Comment: Invited talk at the Fifth Stromlo Symposium: Disks, Winds & Jets - from Planets to Quasars. Accepted for publication in Astrophysics & Space Scienc

Atomic X-ray Spectroscopy of Accreting Black Holes

Current astrophysical research suggests that the most persistently luminous objects in the Universe are powered by the flow of matter through accretion disks onto black holes. Accretion disk systems are observed to emit copious radiation across the electromagnetic spectrum, each energy band providing access to rather distinct regimes of physical conditions and geometric scale. X-ray emission probes the innermost regions of the accretion disk, where relativistic effects prevail. While this has been known for decades, it also has been acknowledged that inferring physical conditions in the relativistic regime from the behavior of the X-ray continuum is problematic and not satisfactorily constraining. With the discovery in the 1990s of iron X-ray lines bearing signatures of relativistic distortion came the hope that such emission would more firmly constrain models of disk accretion near black holes, as well as provide observational criteria by which to test general relativity in the strong field limit. Here we provide an introduction to this phenomenon. While the presentation is intended to be primarily tutorial in nature, we aim also to acquaint the reader with trends in current research. To achieve these ends, we present the basic applications of general relativity that pertain to X-ray spectroscopic observations of black hole accretion disk systems, focusing on the Schwarzschild and Kerr solutions to the Einstein field equations. To this we add treatments of the fundamental concepts associated with the theoretical and modeling aspects of accretion disks, as well as relevant topics from observational and theoretical X-ray spectroscopy.Comment: 63 pages, 21 figures, Einstein Centennial Review Article, Canadian Journal of Physics, in pres

Induced thermal shocking by BiMTheCh technology as a new approach for enhanced oil recovery from tight reservoirs with heavy oil

This work is devoted to investigate the ability of thermal shocking to create fractures in rock samples and thermal cracking of heavy crude oil structure. In order to study the thermobaric characterizations of catalytic and thermal decomposition reaction of binary mixture (BM), a series of experiments was designed in high-temperature and high-pressure reactor (HTHP) and the time to reach the maximum temperature and pressure were monitored. Before and after the experiments, core samples were scanned by 4D tomography. In addition, SARA analysis was done to study the effect of thermal shocking on heavy oil composition. The results showed that using BiMTheCh, the temperature in the reaction zone was increased up to 273 °C during very short time (2 seconds) after activation of the reaction. Either, the pressure was increased up to 129 atm. As results showed, the simultaneous sudden increase in temperature and pressure creates a thermal shock which reduces breakdown pressure from 235 to 12 atm. Computed scanning tomography results confirmed formation of new fractures on the surface of core samples. Results of the SARA analysis also confirmed that the molecular structure of heavy oil due to the binary mixture's reaction was changed. Sharp increase in pressure and temperature induced transformation of heavy components of crude oil such as asphaltenes into lighter components such as saturates. Generally, the binary mixture technology can be used as a new high-efficient and eco-friendly technology for enhanced heavy oil recovery from tight heavy oil reservoirs

Low-field NMR-relaxometry as fast and simple technique for in-situ determination of SARA-composition of crude oils

In this study a new, fast and simple method based on low field NMR-relaxometry for in-situ determination of SARA (saturates, aromatics, resins and asphaltenes) composition of crude oils was proposed. This method was tested on 22 samples of crude oils with a wide range of SARA-composition and API gravity values (4.6–42.0°), including extra-heavy, heavy, medium and light crude oils. Results obtained by low-field nuclear magnetic resonance (LF-NMR) were compared with conventional SARA analysis method (ASTM D 4124). Comparison shows good coincidence between SARA values determined by LF-NMR and conventional method data for heavy fractions of asphaltenes and resins (R2 is equal to 0.98 and 0.91, respectively) and for the sum of light fractions including saturates and aromatics (R2 = 0.96). However, comparison for saturated and aromatic compounds separately gave low correlation coefficients (R2 ≤ 0.61 and 0.27, respectively) and relatively soaring standard deviation for individual correlations for saturates and aromatics (8.18 and 9.20). Consequently, LF- NMR relaxation as an alternative method for studying the composition of crude oil allows the determination of asphaltenes, resins and the sum of light fractions (saturates and aromatics) without their extraction (in-situ), which greatly simplifies and accelerates conventional chromatographic analysis. This method can be successfully applied for different types of crude oils with a wide range of API gravity and viscosity values

New and simple methods of determination partition coefficient and degree hydrolysis of tracer for estimating residual oil saturation by SWCTT technologies

SWCTT (Single-Well Chemical Tracer Test) actively used to determine the reservoir oil saturation as cost effective and quick method. To use this technology, the partition coefficients K and hydrolysis degree H of the tracer which determined experimentally in laboratories are essential for calculation of residual oil and estimation shut-off period of the well. In this paper, FTIR-spectroscopy and pH-metry were proposed for determination of partition coefficient of chemical tracer (ethyl acetate) and hydrolysis degree. Results obtained by these methods showed good correspondence with the data obtained by standard gas chromatographic analysis that confirms its applicability. All of these methods were used for the study of SWCTT parameters for four oilfields with different formation temperatures in the range 27–70 °C and formation water salinities up to 215,015 ppm. It was shown that oil-water partition coefficient of partitioning tracer increases with the rise of salinity. The apparent activation parameters of the hydrolysis reaction were determined by data on the degree of hydrolysis (pH-metry) and the concentration changes of tracer (head space gas chromatography analysis)