72 research outputs found
Psychophysiological responses to visceral and somatic pain in functional chest pain identify clinically relevant pain clusters
Background: Despite chronic pain being a feature of functional chest pain (FCP) its experience is variable. The factors responsible for this variability remain unresolved. We aimed to address these knowledge gaps, hypothesizing that the psychophysiological profiles of FCP patients will be distinct from healthy subjects. Methods: 20 Rome III defined FCP patients (nine males, mean age 38.7 years, range 28-59 years) and 20 healthy age-, sex-, and ethnicity-matched controls (nine males, mean 38.2 years, range 24-49) had anxiety, depression, and personality traits measured. Subjects had sympathetic and parasympathetic nervous system parameters measured at baseline and continuously thereafter. Subjects received standardized somatic (nail bed pressure) and visceral (esophageal balloon distension) stimuli to pain tolerance. Venous blood was sampled for cortisol at baseline, post somatic pain and post visceral pain. Key Results: Patients had higher neuroticism, state and trait anxiety, and depression scores but lower extroversion scores vs controls (all p < 0.005). Patients tolerated less somatic (p < 0.0001) and visceral stimulus (p = 0.009) and had a higher cortisol at baseline, and following pain (all p < 0.001). At baseline, patients had a higher sympathetic tone (p = 0.04), whereas in response to pain they increased their parasympathetic tone (p ≤ 0.008). The amalgamating the data, we identified two psychophysiologically distinct 'pain clusters'. Patients were overrepresented in the cluster characterized by high neuroticism, trait anxiety, baseline cortisol, pain hypersensitivity, and parasympathetic response to pain (all p < 0.03). Conclusions & Inferences: In future, such delineations in FCP populations may facilitate individualization of treatment based on psychophysiological profiling
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
The long-term survival chances of young massive star clusters
We review the long-term survival chances of young massive star clusters
(YMCs), hallmarks of intense starburst episodes often associated with violent
galaxy interactions. We address the key question as to whether at least some of
these YMCs can be considered proto-globular clusters (GCs), in which case these
would be expected to evolve into counterparts of the ubiquitous old GCs
believed to be among the oldest galactic building blocks. In the absence of
significant external perturbations, the key factor determining a cluster's
long-term survival chances is the shape of its stellar initial mass function
(IMF). It is, however, not straightforward to assess the IMF shape in
unresolved extragalactic YMCs. We discuss in detail the promise of using
high-resolution spectroscopy to make progress towards this goal, as well as the
numerous pitfalls associated with this approach. We also discuss the latest
progress in worldwide efforts to better understand the evolution of entire
cluster systems, the disruption processes they are affected by, and whether we
can use recently gained insights to determine the nature of at least some of
the YMCs observed in extragalactic starbursts as proto-GCs. We conclude that
there is an increasing body of evidence that GC formation appears to be
continuing until today; their long-term evolution crucially depends on their
environmental conditions, however.Comment: invited refereed review article; ChJA&A, in press; 33 pages LaTeX (2
postscript figures); requires chjaa.cls style fil
General Overview of Black Hole Accretion Theory
I provide a broad overview of the basic theoretical paradigms of black hole
accretion flows. Models that make contact with observations continue to be
mostly based on the four decade old alpha stress prescription of Shakura &
Sunyaev (1973), and I discuss the properties of both radiatively efficient and
inefficient models, including their local properties, their expected stability
to secular perturbations, and how they might be tied together in global flow
geometries. The alpha stress is a prescription for turbulence, for which the
only existing plausible candidate is that which develops from the
magnetorotational instability (MRI). I therefore also review what is currently
known about the local properties of such turbulence, and the physical issues
that have been elucidated and that remain uncertain that are relevant for the
various alpha-based black hole accretion flow models.Comment: To be published in Space Science Reviews and as hard cover in the
Space Sciences Series of ISSI: The Physics of Accretion on to Black Holes
(Springer Publisher
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