433 research outputs found
The nature of very faint X-ray binaries; hints from light curves
Very faint X-ray binaries (VFXBs), defined as having peak luminosities Lx of
10^34-10^36 erg/s, have been uncovered in significant numbers, but remain
poorly understood. We analyse three published outburst light curves of two
transient VFXBs using the exponential and linear decay formalism of King and
Ritter (1998). The decay timescales and brink luminosities suggest orbital
periods of order 1 hour. We review various estimates of VFXB properties, and
compare these with suggested explanations of the nature of VFXBs. We suggest
that: 1) VFXB outbursts showing linear decays might be explained as partial
drainings of the disc of "normal" X-ray transients, and many VFXB outbursts may
belong to this category; 2) VFXB outbursts showing exponential decays are best
explained by old, short-period systems involving mass transfer from a low-mass
white dwarf or brown dwarf; 3) persistent (or quasi-persistent) VFXBs, which
maintain an Lx of 10^34-10^35 erg/s for years, may be explained by
magnetospheric choking of the accretion flow in a propeller effect, permitting
a small portion of the flow to accrete onto the neutron star's surface. We thus
predict that (quasi-)persistent VFXBs may also be transitional millisecond
pulsars, turning on as millisecond radio pulsars when their Lx drops below
10^32 erg/s.Comment: 12 pages, 4 figures. MNRAS, in pres
A survey of growth performance, intestinal micro-flora and meat shelf-life in rainbow trout fed with Pistacia atlantica kurdica essential oil
In this study, the essential oil (EO) of Pistacia atlantica subsp. kurdica was added at the rate of 10 g/kg of daily diet of rainbow trout and its effect on gut microbiota (Enterobacteriaceae, Lactobacillus spp., total count), growth performance and antioxidant status of rainbow trout fillet was investigated. Sixty apparently healthy rainbow trout with an approximate weight of 150 g ±3.5 were randomly divided into treatment and control groups. Physical and chemical conditions of water were adjusted to optimal for fish farming and sampling was done after 3 months. The results showed that feed conversion ratio in the control group was significantly (p0.05) after 1 and 7 days cold storage (3°C). According to the obtained results, the EO of Pistacia atlantica kurdica at this dose is not advised for increasing the shelf life of meat and growth performance of fish
Short communication: A survey on growth performance, intestinal micro-flora and meat shelf-life in rainbow trout fed with Pistacia atlantica kurdica essential oil
Qualitative characteristics and nutritional value of fish can reduce by microbial growth and oxidative changes during storage (Rezaei et al., 2008). To prevent or delay such deteriorative changes and extend fish meat shelf life, several ways were recommended. The use of natural preservatives such as essential oils is one of the suggested solutions (Çoban, 2013). Essential oils (EOs) which are aromatic oily liquids of plant material consider in many aspects such as antioxidant, antibacterial, antiviral, antimycotic, antitoxigenic and antiparasitic properties (Burt, 2004; Miguel, 2010). EOs can also replace antibiotic growth promoters in aquatic and terrestrial animal feeds. Supplementation of animal’s diet with EOs can effect on growth performance, intestinal microbiota,non-specific immune response and antioxidant status of their products (Giannenas et al., 2012)
Two heterostigmatic mite species (Acari: Dolichocybidae, Podapolipidae) associated with Scarabaeus pius (Coleoptera: Scarabaeidae) from Iran
During a study on insect-associated heterostigmatic mites (Acari: Prostigmata) in southern Isfahan Province, Central Iran, two colonies of mites were found on Scarabaeus pius (Illiger, 1803) (Coleoptera: Scarabaeidae): Pavania lanceolata sp. n. Bahramian et Hajiqanbar (Dolichocybidae) that is easily discernible by some modified foliate setae on tarsi I–III; and
Tarsopolipus massai Husband, 1989 (Podapolipidae) for which Scarabaeus pius is a new host recor
Evolution of the disc atmosphere in the X-ray binary MXB 1659-298, during its 2015-2017 outburst
We report on the evolution of the X-ray emission of the accreting neutron
star (NS) low mass X-ray binary (LMXB), MXB 1659-298, during its most recent
outburst in 2015-2017. We detected 60 absorption lines during the soft state
(of which 21 at more than 3 ), that disappeared in the hard state
(e.g., the Fe xxv and Fe xxvi lines). The absorbing plasma is at rest, likely
part of the accretion disc atmosphere. The bulk of the absorption features can
be reproduced by a high column density () of highly
ionised () plasma. Its disappearance during the
hard state is likely the consequence of a thermal photo-ionisation instability.
MXB 1659-298's continuum emission can be described by the sum of an absorbed
disk black body and its Comptonised emission, plus a black body component. The
observed spectral evolution with state is in line with that typically observed
in atoll and stellar mass black hole LMXB. The presence of a relativistic Fe
K disk-line is required during the soft state. We also tentatively
detect the Fe xxii doublet, whose ratio suggests an electron density of the
absorber of , hence, the absorber is likely located at
from the illuminating source, well inside the Compton and
outer disc radii. MXB 1659-298 is the third well monitored atoll LMXB
showcasing intense Fe xxv and Fe xxvi absorption during the soft state that
disappears during the hard state.Comment: MNRAS in pres
Short communication: Effect of oral consumption of Aloe vera gel on intestinal microflora and liver tissue of rainbow trout
Rainbow trout as an important breeding fish has a special place in the food basket of human societies. Statistical survey shows that in the period between the years of 1995 to 2011, the number of trout breeding farms and the amount of salmon production in Iran have increased respectively by more than 23 and 70 times. ... In recent years, several studies have been conducted on adding the medicinal plants to the feed and using their beneficial effects in aquaculture, while the diversity of medicinal plants and their treatment effects require extensive research. A. vera plant belongs to Liliaceae family which in traditional medicine, various effects such as rejuvenating, antiinflammatory, antifungal and germicidal have been listed for it. Sixty percent of the dry matter of A. vera gel is polysaccharides and if they have prebiotic material specifications, they can affect intestinal bacteria populations. … The aim of this study is addition of A. vera gel in rainbow trout feed and investigate its effect on intestinal microbial flora population and liver tissues of fish
Cu/Ni/Au multilayers by electrochemistry: A crucial system in electronics - A critical review
International audienc
Limits on thermal variations in a dozen quiescent neutron stars over a decade
In quiescent low-mass X-ray binaries (qLMXBs) containing neutron stars, the
origin of the thermal X-ray component may be either release of heat from the
core of the neutron star, or continuing low-level accretion. In general, heat
from the core should be stable on timescales years, while continuing
accretion may produce variations on a range of timescales. While some quiescent
neutron stars (e.g. Cen X-4, Aql X-1) have shown variations in their thermal
components on a range of timescales, several others, particularly those in
globular clusters with no detectable nonthermal hard X-rays (fit with a
powerlaw), have shown no measurable variations. Here, we constrain the spectral
variations of 12 low mass X-ray binaries in 3 globular clusters over
years. We find no evidence of variations in 10 cases, with limits on
temperature variations below 11% for the 7 qLMXBs without powerlaw components,
and limits on variations below 20% for 3 other qLMXBs that do show non-thermal
emission. However, in 2 qLMXBs showing powerlaw components in their spectra
(NGC 6440 CX 1 & Terzan 5 CX 12) we find marginal evidence for a 10% decline in
temperature, suggesting the presence of continuing low-level accretion. This
work adds to the evidence that the thermal X-ray component in quiescent neutron
stars without powerlaw components can be explained by heat deposited in the
core during outbursts. Finally, we also investigate the correlation between
hydrogen column density (N) and optical extinction (A) using our sample
and current models of interstellar X-ray absorption, finding .Comment: 16 pages, 5 figures, MNRAS, in pres
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