543 research outputs found
Holographic Screening Length in a Hot Plasma of Two Sphere
We study the screening length of a quark-antiquark pair moving in a hot
plasma living in two sphere manifold using AdS/CFT correspondence where
the background metric is four dimensional Schwarzschild-AdS black hole. The
geodesic solution of the string ends at the boundary is given by a stationary
motion in the equatorial plane as such the separation length of
quark-antiquark pair is parallel to the angular velocity . The
screening length and the bound energy are computed numerically using
Mathematica. We find that the plots are bounded from below by some functions
related to the momentum transfer of the drag force configuration. We
compare the result by computing the screening length in the quark-antiquark
reference frame where the gravity dual are "Boost-AdS" and Kerr-AdS black
holes. Finding relations of the parameters of both black holes, we argue that
the relation between mass parameters of the Schwarzschild-AdS black
hole and of the Kerr-AdS black hole in high temperature is given by
, where is the angular momentum
parameter.Comment: Major revision: title changed, adding authors, 13 pages, 8 figures,
etc. Accepted for publication in European Physical Journal
Discovery of 35 New Supernova Remnants in the Inner Galaxy
We report the discovery of up to 35 new supernova remnants (SNRs) from a 42
arcsec resolution 90cm multi-configuration Very Large Array survey of the
Galactic plane covering 4.5 deg< l <22.0 deg and |b| < 1.25 deg. Archival 20cm,
11cm, and 8 micron data have also been used to identify the SNRs and constrain
their properties. The 90cm image is sensitive to SNRs with diameters 2.5 arcmin
to 50 arcmin and down to a surface brightness limit of about 10^{-21} W m^{-2}
Hz^{-1} sr^{-1}. This survey has nearly tripled the number of SNRs known in
this part of the Galaxy, and represents an overall 15% increase in the total
number of Galactic SNRs. These results suggest that further deep low frequency
surveys of the inner Galaxy will solve the discrepancy between the expected
number of Galactic SNRs and the significantly smaller number of currently known
SNRs.Comment: 5 pages; Accepted to ApJL, high resolution figures available from
http://www.ifa.hawaii.edu/~cbrogan/high_res
The kinks in charge radii across = 82 and 126 revisited
We revisit the studies of the isotopic shift in the charge radii of {\it
even-even} isotopes of Sn and Pb nuclei at = 82, and 126, respectively,
within the relativistic mean-field and Relativistic-Hartree-Bogoliubov
approach. The shell model is also used to estimate isotopic shift in these
nuclei, for the first time, to the best of our knowledge. The ground state
single-particle energies () are calculated for non-linear NL3 \& NL3
and density-dependent DD-ME2 parameter sets compared with the experimental
data, wherever available. We establish a correlation between the filling of
single-particle levels and the isotopic shift in occupation probabilities. The
obtained from the relativistic mean-field and
Relativistic-Hartree-Bogoliubov approaches are in line with those used in the
shell model and experimental data for both the Sn and Pb isotopic chains. The
shell model calculated isotopic shift agrees with relativistic mean-field and
Relativistic-Hartree-Bogoliubov approaches that explain the experimental data
quite well.Comment: Published in Journal of Physics G: Nuclear and Particle Physic
An Assessment of Risk of Iodine Deficiency Among Pregnant Women in Sarawak, Malaysia
Previous findings from a state-wide Iodine Deficiency Disorders (IDD) study among pregnant women (PW) in Sarawak indicated that PW are at risk of IDD and further assessment is needed. This paper describes the methodology used in conducting this study for an assessment of risk of iodine deficiency among pregnant women in Sarawak, Malaysia. A total of 30 maternal child health care clinics (MCHCs) were selected using probability proportional to population size (PPS) sampling technique. The PW sample size was calculated based on 95% confidence interval (CI), relative precision of 5%, design effect of 2, anticipated IDD prevalence of 65.0% and non-response rate of 20%. Thus, the total sample size required was 750 (25 respondents per selected MCHC). The WHO Expanded Programme on Immunization (EPI) surveys approach was used to randomly select the first respondent and subsequent respondents were chosen until the required number of PW was met. The required data were obtained through: face-to-face interviews (socio-demographic and food frequency questionnaire), clinical assessments (thyroid size, and hyper/hypothyroidism) and biochemical analysis (urine and blood serum). A total of 677 PW responded in the study with a response rate of 90.2%. Majority of the PW were at second gravida, aged 25-29 years old and of Malay ethnicity. The methodology used in this study was based on International guidelines which may provide state's estimates. All the necessary steps were taken into consideration to ensure valid and reliable findings on current iodine status among PW
The VLA Low-frequency Sky Survey
The Very Large Array (VLA) Low-frequency Sky Survey (VLSS) has imaged 95% of
the 3*pi sr of sky north of declination = -30 degrees at a frequency of 74 MHz
(4 meter wavelength). The resolution is 80" (FWHM) throughout, and the typical
RMS noise level is ~0.1 Jy/beam. The typical point-source detection limit is
0.7 Jy/beam and so far nearly 70,000 sources have been catalogued. This survey
used the 74 MHz system added to the VLA in 1998. It required new imaging
algorithms to remove the large ionospheric distortions at this very low
frequency throughout the entire ~11.9 degree field of view. This paper
describes the observation and data reduction methods used for the VLSS and
presents the survey images and source catalog. All of the calibrated images and
the source catalog are available online (http://lwa.nrl.navy.mil/VLSS) for use
by the astronomical community.Comment: 53 pages, including 3 tables and 15 figures. Has been accepted for
publication in the Astronomical Journa
2x2 waveguide based thermooptic photonic switch
We demonstrate a waveguide based thermooptic photonic switch with low electric power consumption using polymer material. The buried square core waveguides structure has been adopted for single mode operation at third telecommunication window. The index contrast of the upper cladding and the waveguiding layers is 0.2%, the lateral section of the waveguiding and lower cladding layer is 0.35%. The asymmetrical fabricated switch exhibits very low switching power of 12.26 mW. The crosstalk level of -30 dB for the initial and switching states have been achieved, respectively
The 74MHz System on the Very Large Array
The Naval Research Laboratory and the National Radio Astronomy Observatory
completed implementation of a low frequency capability on the VLA at 73.8 MHz
in 1998. This frequency band offers unprecedented sensitivity (~25 mJy/beam)
and resolution (~25 arcsec) for low-frequency observations. We review the
hardware, the calibration and imaging strategies, comparing them to those at
higher frequencies, including aspects of interference excision and wide-field
imaging. Ionospheric phase fluctuations pose the major difficulty in
calibrating the array. Over restricted fields of view or at times of extremely
quiescent ionospheric ``weather'', an angle-invariant calibration strategy can
be used. In this approach a single phase correction is devised for each
antenna, typically via self-calibration. Over larger fields of view or at times
of more normal ionospheric ``weather'' when the ionospheric isoplanatic patch
size is smaller than the field of view, we adopt a field-based strategy in
which the phase correction depends upon location within the field of view. This
second calibration strategy was implemented by modeling the ionosphere above
the array using Zernike polynomials. Images of 3C sources of moderate strength
are provided as examples of routine, angle-invariant calibration and imaging.
Flux density measurements indicate that the 74 MHz flux scale at the VLA is
stable to a few percent, and tied to the Baars et al. value of Cygnus A at the
5 percent level. We also present an example of a wide-field image, devoid of
bright objects and containing hundreds of weaker sources, constructed from the
field-based calibration. We close with a summary of lessons the 74 MHz system
offers as a model for new and developing low-frequency telescopes. (Abridged)Comment: 73 pages, 46 jpeg figures, to appear in ApJ
Quality of life satisfaction among converted Kelantan Chinese Muslims
This article investigates the quality of life of the Kelantan Chinese Muslim community before and after conversion to Islam, focusing on their level of satisfaction in term of economic aspect. This research was carried out using the sequential explanatory mixed method design involving 75 respondents selected for quantitative and five respondents for qualitative. The sampling method adopted was convenience and snowball samplings. The research data was collected using questionnaires and semi-structured interviews. The results revealed that respondents were moderately satisfied before conversion and satisfied after conversion. Besides that, there is no significant difference of quality of life before and after conversion to Islam (F = 0.868, p = 0.355) and it was not influenced by the period of conversion to Islam (F = 0.832, p = 0.589). This analysis indicates numerous respondents are still moderately satisfied in their quality of life even though the average data shows they are satisfied after conversion
Radio Astronomy in LSST Era
A community meeting on the topic of "Radio Astronomy in the LSST Era" was
hosted by the National Radio Astronomy Observatory in Charlottesville, VA (2013
May 6--8). The focus of the workshop was on time domain radio astronomy and sky
surveys. For the time domain, the extent to which radio and visible wavelength
observations are required to understand several classes of transients was
stressed, but there are also classes of radio transients for which no visible
wavelength counterpart is yet known, providing an opportunity for discovery.
From the LSST perspective, the LSST is expected to generate as many as 1
million alerts nightly, which will require even more selective specification
and identification of the classes and characteristics of transients that can
warrant follow up, at radio or any wavelength. The LSST will also conduct a
deep survey of the sky, producing a catalog expected to contain over 38 billion
objects in it. Deep radio wavelength sky surveys will also be conducted on a
comparable time scale, and radio and visible wavelength observations are part
of the multi-wavelength approach needed to classify and understand these
objects. Radio wavelengths are valuable because they are unaffected by dust
obscuration and, for galaxies, contain contributions both from star formation
and from active galactic nuclei. The workshop touched on several other topics,
on which there was consensus including the placement of other LSST "Deep
Drilling Fields," inter-operability of software tools, and the challenge of
filtering and exploiting the LSST data stream. There were also topics for which
there was insufficient time for full discussion or for which no consensus was
reached, which included the procedures for following up on LSST observations
and the nature for future support of researchers desiring to use LSST data
products.Comment: Conference summary, 29 pages, 1 figure; to be published in the Publ.
Astron. Soc. Pacific; full science program and presentations available at
http://science.nrao.edu/science/event/RALSST201
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