1,441 research outputs found
First Principles LCGO Calculation of the Magneto-optical Properties of Nickel and Iron
We report a first principles, self-consistent, all electron, linear
combination of Gaussian orbitals (LCGO) calculation of a comprehensive
collection of magneto-optical properties of nickel and iron based on density
functional theory. Among the many magneto-optical effects, we have studied the
equatorial Kerr effect for absorption in the optical as well as soft X-ray
region, where it is called X-ray magnetic linear dichroism (X-MLD). In the
optical region the effect is of the order of 2\% while in the X-ray region it
is of the order of 1\% for the incident angles considered. In addition, the
polar Kerr effect, X-ray magnetic circular dichroism (X-MCD) and total X-ray
absorption at the L edges, soft X-ray Faraday effect at the L
edges have also been calculated. Our results are in good agreement with
experiments and other first principles methods that have been used to calculate
some of these properties.Comment: 22 pages RevTex. 8 figures submitted separately as a uuencoded,
compressed tar fil
HI gas in rejuvenated radio galaxies: GMRT observations of the DDRG J1247+6723
We report the detection of HI absorption towards the inner double of the
double-double radio galaxy (DDRG) J1247+6723 with the Giant Metrewave Radio
Telescope (GMRT). The inner double is a Giga-hertz peaked spectrum (GPS) source
with a linear size of 14 pc while the overall size defined by the outer double
is 1195 kpc, making it a giant radio source. The absorption profile is well
resolved and consists of a number of components on either side of the optical
systemic velocity. The neutral hydrogen column density is estimated to be
N(HI)=6.73*10^{20}(T_s/100)(f_c/1.0) cm^{-2}, where T_s and f_c are the spin
temperature and covering factor of the background source respectively. We
explore any correlation between the occurrence of HI absorption and
rejuvenation of radio activity and suggest that there could be a strong
relationship between them.Comment: 5 pages, 2 figures, accepted for publication in MNRAS Letter
Detecting cold gas at intermediate redshifts: GMRT survey using Mg II systems
Intervening HI 21-cm absorption systems at z > 1.0 are very rare and only 4
confirmed detections have been reported in the literature. Despite their
scarcity, they provide interesting and unique insights into the physical
conditions in the interstellar medium of high-z galaxies. Moreover, they can
provide independent constraints on the variation of fundamental constants. We
report 3 new detections based on our ongoing Giant Metrewave Radio Telescope
(GMRT) survey for 21-cm absorbers at 1.10< z_abs< 1.45 from candidate damped
Lyman_alpha systems. The 21-cm lines are narrow for the z_abs = 1.3710 system
towards SDSS J0108-0037 and z_abs = 1.1726 system toward SDSS J2358-1020. Based
on line full-width at half maximum, the kinetic temperatures are <= 5200 K and
<=800 K, respectively. The 21-cm absorption profile of the third system, z_abs
=1.1908 system towards SDSS J0804+3012, is shallow, broad and complex,
extending up to 100 km/s. The centroids of the 21-cm lines are found to be
shifted with respect to the corresponding centroids of the metal lines derived
from SDSS spectra. This may mean that the 21-cm absorption is not associated
with the strongest metal line component.Comment: 13 pages with 5 figures. Accepted for publication in ApJ
A study to evaluate the immediate effect of proprioceptive neuromuscular facilitation versus active dynamic stretching during warm-up on 20-meter sprint in amateur soccer players
Background: Soccer is a highly popular sport and is played worldwide. It is an explosive sport and has a high incidence of injuries. In soccer, sprinting dominates the majority of the game, and it imposes a demand on players to have strong, flexible, and dynamic lower limbs. Amateur soccer players donât usually practice warm-ups before their matches; hence, an appropriate warm-up protocol is required that can be incorporated into the training routine of players to avoid injuries and improve performance. The current study aims to evaluate and compare the immediate effect of PNF stretching versus active dynamic stretching during warm-up on 20-meter sprint performance in amateur soccer players.
Methods: According to the inclusion criteria, 80 amateur soccer players participated in this cross-sectional study design. They were randomly distributed into 2 groups: A) PNF stretching (N = 40) and B) active dynamic stretching (N = 40). Participants in both groups performed the 20-meter sprint test initially, followed by their respective warm-up intervention, after which the 20-meter sprint test was repeated and new readings were recorded.
Results: Both Group A and Group B showed improved performance; however, Group B was significantly better. (p value<0.05).
Conclusions: This study therefore concludes that both PNF and active dynamic stretching can be used as a warm-up protocol. However, according to the inter-group comparison, active dynamic stretching shows a noteworthy improvement in 20-m sprint performance in amateur soccer players
Unification scheme and the distribution of neutral gas in compact radio sources
We examine the consistency of HI properties with the unification scheme for
radio galaxies and quasars, and any correlation with the symmetry parameters
for a sample of CSS and GPS sources. In our sample, 15 out of 23 galaxies
exhibit 21-cm absorption as against 1 out of 9 quasars, which is broadly
consistent with the unification scheme. Also there is a tendency for the
detection rate as well as the column density for galaxies to increase with core
prominence, f_c, a statistical indicator of the orientation of the jet axis to
the line of sight. This can be understood in a scenario where radio sources are
larger than the scale of the circumnuclear HI disk so that the lines of sight
to the lobes at very large inclinations do not intersect the disk. The sources
in our sample also exhibit the known anti-correlation between HI column density
and source size. This suggests that small linear size, along with intermediate
values of core prominence, is a good recipe for detecting 21-cm absorption in
CSS and GPS objects. Some of the absorption could also be arising from clouds
which may have interacted with the radio jet. The HI column density and
velocity shift of the primary absorption component, however, show no dependence
on the degree of misalignment and the separation ratio of the radio sources.Comment: 6 pages, 4 figures, accepted for publication in MNRA
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