19 research outputs found
The Radial Extent and Warp of the Ionized Galactic Disk. II. A Likelihood Analysis of Radio-Wave Scattering Toward the Anticenter
We use radio-wave scattering data to constrain the distribution of ionized
gas in the outer Galaxy. Like previous models, our model for the H II disk
includes parameters for the radial scale length and scale height of the H II,
but we allow the H II disk to warp and flare. Our model also includes the
Perseus arm. We use a likelihood analysis on 11 extragalactic sources and 7
pulsars. Scattering in the Perseus arm is no more than 60% of the level
contributed by spiral arms in the inner Galaxy, equivalent to a 1 GHz
scattering diameter of 1.5 mas. Our analysis favors an unwarped, nonflaring
disk with a 1 kpc scale height, though this may reflect the non-uniform and
coarse coverage provided by the available data. The lack of a warp indicates
that VLBI observations near 1 GHz with an orbiting station having baseline
lengths of a few Earth diameters will not be affected by interstellar
scattering at Galactic latitudes |b| ~ 15 degrees. The radial scale length is
15--20 kpc, but the data cannot distinguish between a gradual decrease in the
electron density and a truncated distribution. We favor a truncated one,
because we associate the scattering with massive star formation, which is also
truncated near 20 kpc. The distribution of electron density turbulence
decreases more rapidly with Galactocentric distance than does the hydrogen
distribution. Alternate ionizing and turbulent agents---the intergalactic
ionizing flux and satellite galaxies passing through the disk---do not
contribute significantly to scattering. We cannot exclude the possibility that
a largely ionized, but quiescent disk extends to >~ 100 kpc, similar to that
for some Ly-alpha absorbers.Comment: 34 pages, LaTeX2e with AASTeX aaspp4 macro, 9 figures in 9 PostScript
files, accepted for publication in Ap
GMRT detection of HI 21 cm associated absorption towards the z=1.2 red quasar 3C 190
We report the GMRT detection of associated HI 21 cm-line absorption in the
z=1.1946 red quasar 3C 190. Most of the absorption is blue-shifted with respect
to the systemic redshift. The absorption, at 647.7 MHz, is broad and
complex, spanning a velocity width of 600 \kms. Since the core is
self-absorbed at this frequency, the absorption is most likely towards the
hotspots. Comparison of the radio and deep optical images reveal linear
filaments in the optical which overlap with the brighter radio jet towards the
south-west. We therefore suggest that most of the HI 21 cm-line absorption
could be occurring in the atomic gas shocked by the south-west jet.Comment: 8 pages, 1 fugure. To appear in Journal of Astrophysics and Astronom
A Study of 3CR Radio Galaxies from z = 0.15 to 0.65. II. Evidence for an Evolving Radio Structure
Radio structure parameters were measured from the highest quality radio maps
available for a sample of 3CR radio galaxies in the redshift range 0.15 < z <
0.65. Combined with similar data for quasars in the same redshift range, these
morphology data are used in conjunction with a quantification of the richness
of the cluster environment around these objects (the amplitude of the
galaxy-galaxy spatial covariance function, Bgg) to search for indirect evidence
of a dense intracluster medium (ICM). This is done by searching for confinement
and distortions of the radio structure that are correlated with Bgg.
Correlations between physical size and hot spot placement with Bgg show
evidence for an ICM only at z 0.4,
suggesting an epoch of z ~ 0.4 for the formation of an ICM in these Abell
richness class 0-1, FR2-selected clusters. X-ray selected clusters at
comparable redshifts, which contain FR1 type sources exclusively, are
demonstrably richer than the FR2-selected clusters found in this study. The
majority of the radio sources with high Bgg values at z < 0.4 can be described
as ``fat doubles'' or intermediate FR2/FR1s. The lack of correlation between
Bgg and bending angle or Bgg and lobe length asymmetry suggests that these
types of radio source distortion are caused by something other than interaction
with a dense ICM. Thus, a large bending angle cannot be used as an unambiguous
indicator of a rich cluster around powerful radio sources. These results
support the hypothesis made in Paper 1 that cluster quasars fade to become
FR2s, then FR1s, on a timescale of 0.9 Gyrs (for H0 = 50 km s^-1 Mpc^-1).Comment: 44 pages, 8 figures, 2 tables; to be published in the September 2002
issue of The Astronomical Journa
GJB2 mutation spectrum in 2063 Chinese patients with nonsyndromic hearing impairment
Background: Mutations in GJB2 are the most common molecular defects responsible for autosomal recessive nonsyndromic hearing impairment (NSHI). The mutation spectra of this gene vary among different ethnic groups. Methods: In order to understand the spectrum and frequency of GJB2 mutations in the Chinese population, the coding region of the GJB2 gene from 2063 unrelated patients with NSHI was PCR amplified and sequenced. Results: A total of 23 pathogenic mutations were identified. Among them, five (p.W3X, c.99delT, c.155_c.158delTCTG, c.512_c.513insAACG, and p.Y152X) are novel. Three hundred and seven patients carry two confirmed pathogenic mutations, including 178 homozygotes and 129 compound heterozygotes. One hundred twenty five patients carry only one mutant allele. Thus, GJB2 mutations account for 17.9% of the mutant alleles in 2063 NSHI patients. Overall, 92.6% (684/739) of the pathogenic mutations are frame-shift truncation or nonsense mutations. The four prevalent mutations; c.235delC, c.299_c.300delAT, c.176_c.191del16, and c.35delG, account for 88.0% of all mutantalleles identified. The frequency of GJB2 mutations (alleles) varies from 4% to 30.4% among different regions of China. It also varies among different sub-ethnic groups. Conclusion: In some regions of China, testing of the three most common mutations can identify at least one GJB2 mutant allele in all patients. In other regions such as Tibet, the three most common mutations account for only 16% the GJB2 mutant alleles. Thus, in this region, sequencing of GJB2 would be recommended. In addition, the etiology of more than 80% of the mutant alleles for NSHI in China remains to be identified. Analysis of other NSHI related genes will be necessary
Detection of Dihydrocoumarin in Coconut Juice via Photoelectric Detection System Based on Ultraviolet Absorption Spectrometry
Based on ultraviolet absorption spectroscopy technology combined with stoichiometry, a portable photoelectric detection system with wireless transmission was designed with the advantages of simple operation, low cost, and quick response to realize the non-destructive detection of dihydrocoumarin content in coconut juice. Through the detection of a sample solution, the light intensity through the solution is measured and converted into absorbance. Particle swarm optimization (PSO) is applied to optimize support vector regression (SVR) to establish a corresponding concentration prediction model. At the same time, in order to solve the shortcomings of the conventional portable photoelectric detection equipment in data storage, data transmission, and other aspects, based on the optimal PSO-SVR model, we used Python language to develop a friendly graphical user interface (GUI), integrating data collection, storage, analysis, and prediction modeling in one, greatly simplifying the operation process. The experimental results show that, compared with the traditional methods, the system achieves the purpose of rapid and non-destructive detection and has a small gap compared with the detection results of the ultraviolet spectrophotometer. It provides a good method for the determination of dihydrocoumarin in coconut juice
Metaheuristic searching genetic algorithm based reliability assessment of hybrid power generation system
Generating systems are known as adequately reliable when satisfying the load demand. Meanwhile, the efficiency of electrical systems is currently being more influenced by the growing adoption of the Wind/Solar energy in power systems compared to other conventional power sources. This paper proposed a new optimization approach called Metaheuristic Scanning Genetic Algorithm (MSGA) for the evaluation of the efficiency of power generating systems. The MSGA is based on a combination of metaheuristic scanning and Genetic Algorithm. The MSGA technique is used for evaluating the reliability and adequacy of generation systems integrated with wind/Solar energy is developed. The usefulness of the proposed algorithm was tested using Reliability Test System ‘IEEE-RTS-79’ which include both of wind power and solar power generation. The result approve the effectiveness of the proposed algorithm in improving the computation time by 85% and 2% in comparison with the particle swarm optimization (PSO) and differential evolution optimization algorithm (DEOA) respectively. In addition, the proposed model can be used to test the power capacity forecasting scheme of the hybrid power generation system with the wind, solar and storage