188 research outputs found
The model constraints from the observed trends for the quasi-periodic oscillation in RE J1034+396
We analyze the time variability of the X-ray emission of RE J1034+396 -- an
active galactic nucleus with the first firm detection of a quasi-periodic
oscillations (QPO). Based on the results of a wavelet analysis, we find a drift
in the QPO central frequency. The change in the QPO frequency correlates with
the change in the X-ray flux with a short time delay. The data specifically
suggest a linear dependence between the QPO period and the flux, and this gives
important constraints on the QPO models. In particular, it excludes explanation
in terms of the orbiting hot spot model close to a black hole. Linear
structures such as shocks, spiral waves, or very distant flares are favored.Comment: Astronomy & Astrophysics, in pres
QPO in RE J1034+396: model constraints from observed trends
We analyze the time variability of the X-ray emission of RE J1034+396, an
active galactic nucleus with the first firm detection of a quasi-periodic
oscillations (QPO). Based on the results of a wavelet analysis, we find a drift
in the QPO central frequency. The change inthe QPO frequency correlates with
the change in the X-ray flux with a short time delay. Linear structures such as
shocks, spiral waves, orvery distant flares seem to be a favored explanation
for this particular QPO event.Comment: to appear in the proceedings to "The Central Kiloparsec in Galactic
Nuclei (AHAR2011)", Journal of Physics: Conference Series (JPCS), IOP
Publishin
Effects of natural plant tenderizers on proteolysis and texture of dry sausages produced with wild boar meat addition
This study was conducted to develop a method for improving tenderness and overall qualities of tough wild boar meat used to dry sausage production with direct addition of raw pineapple (Ananas comosus), mango (Mangifera indica), kiwifruit - fuzzy kiwi (Actinidia deliciosa), or ginger (Zingiber officinale roscoe - ginger rhizome) juices contained a plant proteolytic enzyme. Dry-sausages were subjected to various chemical, mechanical and sensory evaluations. An increase in proteolysis was observed in all enzyme-treated samples compared to the control and as a consequence an improvement in juiciness, tenderness and overall acceptability scores were observed. Ginger or kiwifruit juice-treated sausages received better scores for texture, flavor, and overall acceptability. From these results, it is shown that those enzymes as a raw plant juices could be used as tenderizers in dry sausage production.Keywords: Dry sausages, wild boar meat, plant enzymes, proteolysis, texture, sensory properties.African Journal of Biotechnology Vol. 12(38), pp. 5670-567
The doubling of the superorbital period of Cyg X-1
We study properties of the superorbital modulation of the X-ray emission of
Cyg X-1. We find that it has had a stable period of about 300 d in soft and
hard X-rays and in radio since 2005 until at least 2010, which is about double
the previously seen period. This new period, seen in the hard spectral state
only, is detected not only in the light curves but also in soft X-ray hardness
ratios and in the amplitude of the orbital modulation. On the other hand, the
spectral slope in hard X-rays, >20 keV, averaged over superorbital bins is
constant, and the soft and hard X-rays and the radio emission change in phase.
This shows that the superorbital variability consists of changing the
normalization of an intrinsic spectrum of a constant shape and of changes of
the absorbing column density with the phase. The maximum column density is
achieved at the superorbital minimum. The amplitude changes are likely to be
caused by a changing viewing angle of an anisotropic emitter, most likely a
precessing accretion disc. The constant shape of the intrinsic spectrum shows
that this modulation is not caused by a changing accretion rate. The modulated
absorbing column density shows the presence of a bulge around the disc centre,
as proposed previously. We also find the change of the superorbital period from
about 150 d to about 300 d to be associated with almost unchanged average X-ray
fluxes, making the period change difficult to explain in the framework of
disc-irradiation models. Finally, we find no correlation of the X-ray and radio
properties with the reported detections in the GeV and TeV gamma-ray range.Comment: MNRAS, in press, 8 page
Modeling the time-resolved quasi-periodic oscillations in AGNs
Observation of the bright Seyfert 1 galaxy RE J1034+396 is believed to
demonstrate a drift of the central period of the Quasi Periodic Oscillation
(QPO) linearly correlated with the temporary X-ray luminosity. We show, using a
specific scenario of the oscillation mechanism in black hole accretion disc,
that modeling such correlated trends puts very strong constraints on the nature
of this oscillation and the characteristic features of the hot flow in Active
Galactic Nuclei (AGN). In our model, QPO oscillations are due to the
oscillations of the shock formed in the low angular momentum hot accretion
flow, and the variation of the shock location corresponds to the observed
changes in the QPO period and the X-ray flux. In this scenario, change in the
shock location caused by perturbation of the flow angular momentum is
compatible with the trends observed in RE J1034+396, whereas the perturbation
of the specific flow energy results in too strong flux response to the change
of the oscillation period. Using a complete general relativistic framework to
study the accretion flow in the Kerr metric, we discuss the role of the black
hole spin in the period drift. Future missions are expected to bring more
active galaxies with time-resolved quasi-periodic oscillations so similar
quantitative study for other QPO scenarios will be necessary.Comment: Final version accepted for publication in MNRAS. Several
modifications made. Eight pages. Six colour figure
Therapeutic Properties of Vanadium Complexes
Vanadium is a hard, silver-grey transition metal found in at least 60 minerals and fossil fuel deposits. Its oxide and other vanadium salts are toxic to humans, but the toxic effects depend on the vanadium form, dose, exposure duration, and route of intoxication. Vanadium is used by some life forms as an active center in enzymes, such as the vanadium bromoperoxidase of ocean algae and nitrogenases of bacteria. The structure and biochemistry of vanadate resemble those of phosphate, hence vanadate can be regarded as a phosphate competitor in a variety of biochemical enzymes such as kinases and phosphatases. In this review, we describe the biochemical pathways regulated by vanadium compounds and their potential therapeutic benefits for a range of disorders including type 2 diabetes, cancer, cardiovascular disease, and microbial pathology
Quasiperiodic oscillations in a strong gravitational field around neutron stars testing braneworld models
The strong gravitational field of neutron stars in the brany universe could
be described by spherically symmetric solutions with a metric in the exterior
to the brany stars being of the Reissner-Nordstrom type containing a brany
tidal charge representing the tidal effect of the bulk spacetime onto the star
structure. We investigate the role of the tidal charge in orbital models of
high-frequency quasiperiodic oscillations (QPOs) observed in neutron star
binary systems. We focus on the relativistic precession model. We give the
radial profiles of frequencies of the Keplerian (vertical) and radial epicyclic
oscillations. We show how the standard relativistic precession model modified
by the tidal charge fits the observational data, giving estimates of the
allowed values of the tidal charge and the brane tension based on the processes
going in the vicinity of neutron stars. We compare the strong field regime
restrictions with those given in the weak-field limit of solar system
experiments.Comment: 26 pages, 6 figure
Voice-based assessments of trustworthiness, competence, and warmth in blind and sighted adults
The study of voice perception in congenitally blind individuals allows researchers rare insight into how a lifetime of visual deprivation affects the development of voice perception. Previous studies have suggested that blind adults outperform their sighted counterparts in low-level auditory tasks testing spatial localization and pitch discrimination, as well as in verbal speech processing; however, blind persons generally show no advantage in nonverbal voice recognition or discrimination tasks. The present study is the first to examine whether visual experience influences the development of social stereotypes that are formed on the basis of nonverbal vocal characteristics (i.e., voice pitch). Groups of 27 congenitally or early-blind adults and 23 sighted controls assessed the trustworthiness, competence, and warmth of men and women speaking a series of vowels, whose voice pitches had been experimentally raised or lowered. Blind and sighted listeners judged both men’s and women’s voices with lowered pitch as being more competent and trustworthy than voices with raised pitch. In contrast, raised-pitch voices were judged as being warmer than were lowered-pitch voices, but only for women’s voices. Crucially, blind and sighted persons did not differ in their voice-based assessments of competence or warmth, or in their certainty of these assessments, whereas the association between low pitch and trustworthiness in women’s voices was weaker among blind than sighted participants. This latter result suggests that blind persons may rely less heavily on nonverbal cues to trustworthiness compared to sighted persons. Ultimately, our findings suggest that robust perceptual associations that systematically link voice pitch to the social and personal dimensions of a speaker can develop without visual input
Involvement of Dopamine Receptors in Binge Methamphetamine-Induced Activation of Endoplasmic Reticulum and Mitochondrial Stress Pathways
Single large doses of methamphetamine (METH) cause endoplasmic reticulum (ER) stress and mitochondrial dysfunctions in rodent striata. The dopamine D1 receptor appears to be involved in these METH-mediated stresses. The purpose of this study was to investigate if dopamine D1 and D2 receptors are involved in ER and mitochondrial stresses caused by single-day METH binges in the rat striatum. Male Sprague-Dawley rats received 4 injections of 10 mg/kg of METH alone or in combination with a putative D1 or D2 receptor antagonist, SCH23390 or raclopride, respectively, given 30 min prior to each METH injection. Rats were euthanized at various timepoints afterwards. Striatal tissues were used in quantitative RT-PCR and western blot analyses. We found that binge METH injections caused increased expression of the pro-survival genes, BiP/GRP-78 and P58IPK, in a SCH23390-sensitive manner. METH also caused up-regulation of ER-stress genes, Atf2, Atf3, Atf4, CHOP/Gadd153 and Gadd34. The expression of heat shock proteins (HSPs) was increased after METH injections. SCH23390 completely blocked induction in all analyzed ER stress-related proteins that included ATF3, ATF4, CHOP/Gadd153, HSPs and caspase-12. The dopamine D2-like antagonist, raclopride, exerted small to moderate inhibitory influence on some METH-induced changes in ER stress proteins. Importantly, METH caused decreases in the mitochondrial anti-apoptotic protein, Bcl-2, but increases in the pro-apoptotic proteins, Bax, Bad and cytochrome c, in a SCH23390-sensitive fashion. In contrast, raclopride provided only small inhibition of METH-induced changes in mitochondrial proteins. These findings indicate that METH-induced activation of striatal ER and mitochondrial stress pathways might be more related to activation of SCH23390-sensitive receptors
Temperature, stress, and structural-relaxation dependence of the magnetostriction in ( Co
- …