1,137 research outputs found
Effective potential and geodesic motion in Kerr-de Sitter space-time
In the present work, geodesic trajectories in Kerr-de Sitter geometry is
analyzed. From the mathematical solution of Lagrangian formalism appropriate to
motions in the equatorial plane (for which 'theta' = 0 and 'theta' =
(constant)= pi/2) can give potential energy of massive and massless particles
for rotating axisymetric black hole. From this, for a particular value of
cosmological constant, Kerr parameter, mass, angular momentum and impact
parameter; variation of potential with distance can be found. Similarly, for a
particular value of cosmological constant, mass and Kerr parameter; variation
of velocity with distance can be found
Electric and Magnetic fields due to Dirac particles in FRW spacetime
Some solutions of the Maxwell equations with Dirac particles for the source
in FRW spacetime are discussed. The Green's function of the equation for the
radial component of the Maxwell fields, F_{r\eta} and F_{\theta\phi} is solved.
Green's function is found to reduce to that of Minkowskian spacetime in the
appropriate limit. Also, the Lienard-Wiechert type solution is derived. Also,
the solutions with the Dirac particle current is also presented. It is found
that the F_{r\eta} is composed of even angular momentum states while the odd
states constitue F_{\theta\phi} .Comment: 8 pages including 2 figure
Involving Nepali academics in health research
JMBTO SEE JHIn a world dominated by globalization and knowledge exchange conducting research and academic publishing has become increasingly important. In this light it is important to report the findings of research conducted in Nepal as it may be relevant and useful in North Korea as in Namibia. The editorial outlines some of the barriers and opportunities that exist for academics in Nepal
The effect of mother’s educational status on early initiation of breastfeeding: further analysis of three consecutive Nepal Demographic and Health Surveys
Background: The World Health Organization recommends initiating breastfeeding within the first hour of birth. This study is aimed at assessing the effect of the mother’s education on early initiation of breastfeeding. Methods: Data from the Nepal Demographic and Health Surveys (NDHS) 2001, 2006 and 2011 were used which included 12,845 last born children born within 5 years before the surveys. Early initiation of breastfeeding was defined as the initiation of breastfeeding within the first hour after birth. Hierarchical modelling was used to ascertain the association of maternal education and early initiation of breastfeeding, after controlling for other covariates in a multiple logistic regression. Results: Maternal education was associated with a higher likelihood of early initiation of breastfeeding in each survey. Pooled data analysis revealed higher odds of early initiation of breastfeeding among the mothers with primary education (adjusted odds ratio (OR) 1.24, 95 % confidence interval (CI): 1.09, 1.42) and secondary or higher education (OR: 1.63 95 % CI: 1.42, 1.88). In the most recent NDHS 2011 survey, odds of early initiation of breastfeeding was higher among mothers with primary education (OR: 1.52; 95 % CI: 1.21, 1.91) and mothers with secondary or higher education (OR: 2.20; 95 % CI: 1.76, 2.76) compared to mothers with no education. Similarly, the odds of early initiation of breastfeeding was higher among mothers with secondary and higher education in the 2006 data (OR: 1.66; 95 % CI: 1.30, 2.12) and in 2001 (OR = 1.30; 95 % CI: 1.00, 1.67).Conclusions: As the association between a mother ’ s educational status and her likelihood of early initiation of breastfeeding increases, long-term approaches to prioritising education for women and girls should be explored. In the short term, uneducated mothers should be targeted with breastfeeding promotion strategies such as counselling and peer education
Evaluation of flux expulsion and flux trapping sensitivity of srf cavities fabricated from cold work Nb sheet with successive heat treatment
The main source of RF losses leading to lower quality factor of
superconducting radio-frequency cavities is due to the residual magnetic flux
trapped during cool-down. The loss due to flux trapping is more pronounced for
cavities subjected to impurities doping. The flux trapping and its sensitivity
to rf losses are related to several intrinsic and extrinsic phenomena. To
elucidate the effect of re-crystallization by high temperature heat treatment
on the flux trapping sensitivity, we have fabricated two 1.3 GHz single cell
cavities from cold-worked Nb sheets and compared with cavities made from
standard fine-grain Nb. Flux expulsion ratio and flux trapping sensitivity were
measured after successive high temperature heat treatments. The cavity made
from cold worked Nb showed better flux expulsion after 800 C/3h heat treatments
and similar behavior when heat treated with additional 900 C/3h and 1000 C/3h.
In this contribution, we present the summary of flux expulsion, trapping
sensitivity, and RF results.Comment: 21st International Conference on Radio-Frequency Superconductivity
(SRF 2023
Quench Detection in a Superconducting Radio Frequency Cavity with Combine Temperature and Magnetic Field Mapping
Local dissipation of RF power in superconducting radio frequency cavities
create so called hot spots, primary precursors of cavity quench driven by
either thermal or magnetic instability. These hot spots are detected by a
temperature mapping system, and a large increase in temperature on the outer
surface is detected during cavity quench events. Here, we have used combined
magnetic and temperature mapping systems using anisotropic magnetoresistance
(AMR) sensors and carbon resisters to locate the hot spots and areas with high
trapped flux on a 3.0 GHz single-cell Nb cavity during the RF tests at 2.0 K.
The quench location and hot spots were detected near the equator when the
residual magnetic field in the Dewar is kept < 1 mG. The hot spots and quench
locations moved when the magnetic field is trapped locally, as detected by
T-mapping system. No significant dynamics of trapped flux is detected by AMR
sensors, however, change in magnetic flux during cavity quench is detected by a
flux gate magnetometer, close to the quench location. The result provides the
direct evidence of hot spots and quench events due to localized trapped
vortices.Comment: 21st International Conference on Radio-Frequency Superconductivity
(SRF 2023
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