517 research outputs found
Effects of different levels of dietary nucleotide on growth performance, survival and liver enzyme activity of Caspian salmon (Salmo trutta caspius Kessler, 1877) juveniles
Caspian salmon (Salmo trutta caspius) juveniles were fed with dietary nucleotide levels of 0, 0.15, 0.25, 0.35 and 0.5% to investigate their effects on growth performance, survival rate and liver enzymes. Juveniles with an initial average weight of 12.26±0.001g were fed with the experimental diets for 60 days. The trial was carried out in 300 liter tanks each containing 35 fish which were fed with five meals a day at the rate of 34•5% of body weight. Statistical analysis was performed using One-way ANOVA. Results of the study showed that the addition of dietary nucleotide led to significant increase of body weight gain (BW), weight increase percentage (BWI), specific growth rate (SGR), protein efficiency ratio (PER), protein productive value (PPV) and feed intake but significant decrease of food conversion ratio (FCR) as compared to the control treatment (P0.05). The best value of growth improvement indices was observed at the dietary level of 0.25% nucleotide. Liver enzymes including AST, ALT and LDH at the level of 0.35% and ALP at the level of 0.25% were significantly lower than control treatment (P<0.05). Our results also indicated that dietary nucleotide can have positive effects on growth performance and would decrease liver demolition
Plasma biomarkers of brain injury in COVID-19 patients with neurological symptoms
Objective: Neurological symptoms (NS) were often reported in COVID-19 infection. We examined the plasma levels of glial fibrillary acidic protein (GFAP) and S100B together, as brain injury biomarkers, in relation to persistent NS in a cohort of patients with COVID-19 during the acute phase of the disease.Methods: A total of 20 healthy controls and 58 patients with confirmed COVID-19 were enrolled in this prospective study. Serum GFAP and S100B levels were measured by using enzymle linked immunoassay method from blood samples.Results: Serum GFAP levels were found to be significantly higher in the severe group than in the controls (p = 0.007). However, serum S100B levels were similar between control and disease groups (p > 0.05). No significant results for GFAP and S100B were obtained between the disease groups depending on whether the sampling time was below or above 5 days (p > 0.05). We did not find a correlation between serum GFAP and S100B levels and the presence of NS (p > 0.05). However, serum S100B levels were slightly higher in patients with multiple NS than in those with a single symptom (p = 0.044).Conclusions: Elevated GFAP was associated with disease severity but not with NS in COVID-19 patients. Whereas, high serum S100B was associated with the multipl NS in these patients. Our data suggest that GFAP and S100B may be of limited value currently in order to represent the neuronal damage, though serving a basis for the future work
Irrigation by Crop in the Continental United States From 2008 to 2020
Agriculture is the largest user of water in the United States. Yet, we do not understand the spatially resolved sources of irrigation water use (IWU) by crop. The goal of this study is to estimate crop-specific IWU from surface water withdrawals (SWW), total groundwater withdrawals (GWW), and nonrenewable groundwater depletion (GWD). To do this, we employ the PCR-GLOBWB 2 global hydrology model to partition irrigation information from the U.S. Geological Survey Water Use Database to specific crops across the Continental United States (CONUS). We incorporate high-resolution input data on agricultural production and climate within the CONUS to obtain crop-specific irrigation estimates for SWW, GWW, and GWD for 20 crops and crop groups from 2008 to 2020 at county spatial resolution. Over the study period, SWW decreased by 20%, while both GWW and GWD increased by 3%. On average, animal feed (alfalfa/hay) uses the most irrigation water across all water sources: 33 from SWW, 13 from GWW, and 10Â km3/yr from GWD. Produce used less SWW (43%), but more GWW (57%), and GWD (27%) over the study time-period. The largest changes in IWU for each water source between the years 2008 and 2020 are: rice (SWW decreased by 71%), sugar beets (GWW increased by 232%), and rapeseed (GWD increased by 405%). These results present the first national-scale assessment of irrigation by crop, water source, and year. In total, we contribute nearly 2.5 million data points to the literature (3,142 counties; 13Â years; 3 water sources; and 20 crops)
Radio Spectra of Giant Radio Galaxies from RATAN-600 Data
Measurements of the flux densities of the extended components of seven giant
radio galaxies obtained using the RATAN-600 radio telescope at wavelengths of
6.25 and 13 cm ar e presented. The spectra of components of these radio
galaxies are constructed using these new RA TAN-600 data together with data
from the WENSS, NVSS, and GB6 surveys. The spectral indices in the stu died
frequency range are calculated, and the need for detailed estimates of the
integrated contributi on of such objects to the background emission is
demonstrated.Comment: 7 pages, 2 figures, 5 table
The Evolution of Relativistic Binary Progenitor Systems
Relativistic binary pulsars, such as B1534+12 and B1913+16 are characterized
by having close orbits with a binary separation of ~ 3 R_\sun. The progenitor
of such a system is a neutron star, helium star binary. The helium star, with a
strong stellar wind, is able to spin up its compact companion via accretion.
The neutron star's magnetic field is then lowered to observed values of about
10^{10} Gauss. As the pulsar lifetime is inversely proportional to its magnetic
field, the possibility of observing such a system is, thus, enhanced by this
type of evolution. We will show that a nascent (Crab-like) pulsar in such a
system can, through accretion-braking torques (i.e. the "propeller effect") and
wind-induced spin-up rates, reach equilibrium periods that are close to
observed values. Such processes occur within the relatively short helium star
lifetimes. Additionally, we find that the final outcome of such evolutionary
scenarios depends strongly on initial parameters, particularly the initial
binary separation and helium star mass. It is, indeed, determined that the
majority of such systems end up in the pulsar "graveyard", and only a small
fraction are strongly recycled. This fact might help to reconcile theoretically
expected birth rates with limited observations of relativistic binary pulsars.Comment: 24 pages, 10 Postscript figures, Submitted to The Astrophysical
Journa
A multifrequency study of giant radio sources-II. Spectral ageing analysis of the lobes of selected sources
Multifrequency observations with the GMRT and the VLA are used to determine
the spectral breaks in consecutive strips along the lobes of a sample of
selected giant radio sources (GRSs) in order to estimate their spectral ages.
The maximum spectral ages estimated for the detected radio emission in the
lobes of our sources range from 6 to 36 Myr with a median value of
20 Myr using the classical equipartition fields. Using the magnetic field
estimates from the Beck & Krause formalism the spectral ages range from 5
to 38 Myr with a median value of 22 Myr. These ages are significantly
older than smaller sources. In all but one source (J1313+6937) the spectral age
gradually increases with distance from the hotspot regions, confirming that
acceleration of the particles mainly occurs in the hotspots. Most of the GRSs
do not exhibit zero spectral ages in the hotspots, as is the case in earlier
studies of smaller sources. This is likely to be largely due to contamination
by more extended emission due to relatively modest resolutions. The injection
spectral indices range from 0.55 to 0.88 with a median value of
0.6. We discuss these values in the light of theoretical expectations,
and show that the injection spectral index appears to be correlated with
luminosity and/or redshift as well as with linear size.Comment: 12 Pages, 13 Figures, 9 Tables, Accepted for publication in MNRA
The r-modes in accreting neutron stars with magneto-viscous boundary layers
We explore the dynamics of the r-modes in accreting neutron stars in two
ways. First, we explore how dissipation in the magneto-viscous boundary layer
(MVBL) at the crust-core interface governs the damping of r-mode perturbations
in the fluid interior. Two models are considered: one assuming an
ordinary-fluid interior, the other taking the core to consist of superfluid
neutrons, type II superconducting protons, and normal electrons. We show,
within our approximations, that no solution to the magnetohydrodynamic
equations exists in the superfluid model when both the neutron and proton
vortices are pinned. However, if just one species of vortex is pinned, we can
find solutions. When the neutron vortices are pinned and the proton vortices
are unpinned there is much more dissipation than in the ordinary-fluid model,
unless the pinning is weak. When the proton vortices are pinned and the neutron
vortices are unpinned the dissipation is comparable or slightly less than that
for the ordinary-fluid model, even when the pinning is strong. We also find in
the superfluid model that relatively weak radial magnetic fields ~ 10^9 G (10^8
K / T)^2 greatly affect the MVBL, though the effects of mutual friction tend to
counteract the magnetic effects. Second, we evolve our two models in time,
accounting for accretion, and explore how the magnetic field strength, the
r-mode saturation amplitude, and the accretion rate affect the cyclic evolution
of these stars. If the r-modes control the spin cycles of accreting neutron
stars we find that magnetic fields can affect the clustering of the spin
frequencies of low mass x-ray binaries (LMXBs) and the fraction of these that
are currently emitting gravitational waves.Comment: 19 pages, 8 eps figures, RevTeX; corrected minor typos and added a
referenc
Absorption of Electro-magnetic Waves in a Magnetized Medium
In continuation to our earlier work, in which the structure of the vacuum
polarisation tensor in a medium was analysed in presence of a background
electro-magnetic field, we discuss the absorptive part of the vacuum
polarization tensor. Using the real time formalism of finite temperature field
theory we calculate the absorptive part of 1-loop vacuum polarisation tensor in
the weak field limit (). Estimates of the absorption probability are
also made for different physical conditions of the background medium.Comment: 9 Pages. One figure. LaTe
Detection of non-thermal X-ray emission in the lobes and jets of Cygnus A
This article has been published in Monthly Notices of the Royal Astronomical Society © 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. 21 pages, 8 figuresWe present a spectral analysis of the lobes and X-ray jets of Cygnus A, using more than 2 Ms of observations. The X-ray jets are misaligned with the radio jets and significantly wider. We detect non-thermal emission components in both lobes and jets. For the eastern lobe and jet, we find 1 keV flux densities of nJy and nJy, and photon indices of and respectively. For the western lobe and jet, we find flux densities of nJy and nJy, and photon indices of and respectively. Using these results, we modeled the electron energy distributions of the lobes as broken power laws with age breaks. We find that a significant population of non-radiating particles is required to account for the total pressure of the eastern lobe. In the western lobe, no such population is required and the low energy cutoff to the electron distribution there needs to be raised to obtain pressures consistent with observations. This discrepancy is a consequence of the differing X-ray photon indices, which may indicate that the turnover in the inverse-Compton spectrum of the western lobe is at lower energies than in the eastern lobe. We modeled the emission from both jets as inverse-Compton emission. There is a narrow region of parameter space for which the X-ray jet can be a relic of an earlier active phase, although lack of knowledge about the jet's electron distribution and particle content makes the modelling uncertain.Peer reviewedFinal Published versio
- …