231 research outputs found
VLBI study of water maser emission in the Seyfert 2 galaxy NGC5793. I: Imaging blueshifted emission and the parsec-scale jet
We present the first result of VLBI observations of the blueshifted water
maser emission from the type 2 Seyfert galaxy NGC5793, which we combine with
new and previous VLBI observations of continuum emission at 1.7, 5.0, 8.4, 15,
and 22 GHz. Maser emission was detected earlier in single-dish observations and
found to have both red- and blueshifted features relative to the systemic
velocity. We could image only the blueshifted emission, which is located 3.6 pc
southwest of the 22 GHz continuum peak. The blueshifted emission was found to
originate in two clusters that are separated by 0.7 milliarcsecond (0.16 pc).
No compact continuum emission was found within 3.6 pc of the maser spot. A
compact continuum source showing a marginally inverted spectrum between 1.7 and
5.0 GHz was found 4.2 pc southwest of the maser position. The spectral turnover
might be due to synchrotron self-absorption caused by a shock in the jet owing
to collision with dense gas, or it might be due to free-free absorption in an
ionized screen possibly the inner part of a disk, foreground to the jet.
The water maser may be part of a maser disk. If so, it would be rotating in
the opposite sense to the highly inclined galactic disk observed in CO
emission. We estimate a binding mass within 1 pc of the presumed nucleus to be
on the order of 10^7 Msun. Alternatively, the maser emission could result from
the amplification of a radio jet by foreground circumnuclear molecular gas. In
this case, the high blueshift of the maser emission might mean that the masing
region is moving outward away from the molecular gas surrounding an active
nucleus.Comment: 20 pages, 6 figures, to appear in ApJ, Oct. 200
Late Time Observations of the Afterglow and Environment of GRB 030329
We present Very Long Baseline Interferometry (VLBI) observations 217 days
after the gamma-ray burst of 2003 March 29. These observations provide further
measurements of the size and position of GRB 030329 that are used to constrain
the expansion rate and proper motion of this nearby GRB. The expansion rate
appears to be slowing down with time, favoring expansion into a constant
density interstellar medium, rather than a circumstellar wind with an r^-2
density profile. We also present late time Arecibo observations of the
redshifted HI and OH absorption spectra towards GRB 030329. No absorption (or
emission) is seen allowing us to place limits on the atomic neutral hydrogen of
N_H < 8.5 x 10^20 cm^-2, and molecular hydrogen of N_H_2 < 1.4 x 10^22 cm^-2.
Finally, we present VLA limits on the radio polarization from the afterglow of
<2% at late times.Comment: 6 pages, 5 figures, Accepted to ApJ on Dec. 17, 200
Organometallic vapor-phase homoepitaxy of gallium arsenide assisted by a downstream hydrogen afterglow plasma in the growth region
Includes bibliographical references (page 3146).In situ generated arsenic hydrides are reacted downstream with trimethylgallium (TMGa), both in the presence of and in the absence of a downstream hydrogen afterglow plasma. The homoepitaxial activation energy dramatically changes from 62 kcal/mol for the pure thermal to 21 kcal/mol for the plasma-assisted growth. The carbon incorporation mechanism for the plasma-assisted growth at temperatures less than 400 °C has a distinct activation energy for carbon incorporation of 23 kcal/mol, independent of V-III ratios. At temperatures above 400 °C, the level of carbon incorporated in the films reaches a level that appears to be dependent on the gas-phase precursor V-III ratio. The activation energy of the low-temperature region is consistent with the surface decomposition of arsenic hydrides
Characterizing evolved Galactic stellar population: a challenge for astrometric measurements
Stars and planetary system
Very Large Array Observations of Galactic Center OH 1720 MHz Masers in Sagittarius A East and in the Circumnuclear Disk
We present Very Large Array (VLA) radio interferometry observations of the
1720 MHz OH masers in the Galactic Center (GC). Most 1720 MHz OH masers arise
in regions where the supernova remnant Sgr A East is interacting with the
interstellar medium. The majority of the newly found 1720 MHz OH masers are
located to the northeast, independently indicating and confirming an area of
shock interaction with the +50 km/s molecular cloud (M-0.02-0.07) on the far
side of Sgr A East. The previously known bright masers in the southeast are
suggested to be the result of the interaction between two supernova remnants,
instead of between Sgr A East and the surrounding molecular clouds as generally
found elsewhere in the Galaxy. Together with masers north of the circumnuclear
disk (CND) they outline an interaction on the near side of Sgr A East. In
contrast to the interaction between the +50 km/s cloud and Sgr A East, OH
absorption data do not support a direct interaction between the CND material
and Sgr A East. We also present three new high-negative velocity masers,
supporting a previous single detection. The location and velocities of the
high-negative and high-positive velocity masers are consistent with being near
the tangent points of, and physically located in the CND. We argue that the
high velocity masers in the CND are pumped by dissipation between density
clumps in the CND instead of a shock generated by the supernova remnant. That
is, the CND masers are not coupled to the supernova remnant and are sustained
independently.Comment: accepted to ApJ, 9 pages 3 figure
HI Absorption in the Gigamaser Galaxy TXS 2226-184 and the Relation between HI Absorption and Water Emission
We report on the discovery of HI in absorption toward the gigamaser galaxy
TXS2226-184 using the VLA. The absorption appears to consist of two components
-- one with a width of 125 km/s, and one broader (420 km/s), both toward the
compact radio source in the nucleus of the galaxy. Based on these large
velocity widths we suggest that the HI absorption is produced in the central
parsecs of the galaxy, on a similar scale to that which gives rise to the water
maser emission. This brings to eight the number of galaxies known to exhibit
both water masers and HI absorption. We explore the relationship between these
two phenomena, and present a physically motivated (but unfruitful) search for
water maser emission in five radio galaxies known to exhibit strong HI
absorption.Comment: 19 pages including 5 figures, LaTeX, Accepted to Ap
Oral Health Status of Patients with Mental Disorders in Southwest Ethiopia
BACKGROUND: Psychiatric disorders are known to be a risk factor for the development of different oral health problems especially for dental caries and periodontal diseases. In spite of this fact, no study has been conducted to reveal its magnitude in Ethiopia. Hence, this study was conducted to determine the oral health status of psychiatric patients at Jimma University Specialized Hospital (JUSH), Psychiatric Clinic. METHODS: A hospital based cross- sectional study was used from January to May 2011. A total of 240 participants were included in the study. Dental examination was done to measure indices of oral health: decayed, missing, and filled teeth (DMFT) index and community periodontal index (CPI). Oral examination was performed using mirror, probe and explorer by experienced dental doctors. A simple random sampling technique was implemented to collect data. ANOVA test, binary logistic and multinomial logistic regression analyses were done using SPSS 16.0 statistical software. RESULTS: The mean DMFT score among the psychiatric patients was 1.94 ± 2.12 (mean ± SD) with 1.28 ± 1.69, 0.51 ± 1.19 and 0.14 ± 0.48 (mean ± SD) for decayed, missed and filled teeth respectively. Only about 24% of the psychiatric patients had a healthy CPI score. Incorrect tooth brushing technique was significantly associated with a DMFT score greater than 2 (AOR = 3.58; 95% CI: 1.65, 7.79). The habit of sweet intake was also associated with dental caries (AOR = 2.91; 95% CI: 1.43, 5.95). Similarly, patients with a smoking habit also demonstrated statistically significant association with dental caries (AOR = 18.98; 95% CI: 5.06, 71.24). CONCLUSION: The oral health status of the psychiatric patients was poor. Thus, health education about oral hygiene should be given for psychiatric patients so they can avoid the frequent intake of sweets, smoking and learn correct tooth brushing technique
Relationship between soy and isoflavone intake and periodontal disease: The Freshmen in Dietetic Courses Study II
<p>Abstract</p> <p>Background</p> <p>Much research has shown that soy products inhibited various diseases. However, no published studies have examined the effects of consumption of soy and isoflavones on periodontal disease. The aim of this study was to investigate whether soy and isoflavone intake is associated with the prevalence of periodontal disease.</p> <p>Methods</p> <p>The subjects were 3956 Japanese female students, aged 18 to 22 years, who were taking a dietetic course. Periodontal disease was defined as present when a subject reported diagnosis of the disorder by a dentist. Information on dietary factors was collected using a validated diet history questionnaire. Logistic regression analysis was used to estimate the odds ratios and their confidence intervals of periodontal disease. Adjustment was made for cigarette smoking, toothbrushing frequency, region of residence, and body mass index.</p> <p>Results</p> <p>The prevalence of periodontal disease was 8.0%. Intake of total soy product and tofu was independently associated with a decreased prevalence of periodontal disease; multivariate odds ratios in comparison of the highest with the lowest quintile were 0.68 and 0.68, respectively (95% confidence intervals = 0.47–0.97 and 0.47–0.98, <it>P </it>for trend = 0.01 and 0.004, respectively). A significant inverse dose-response relationship between the intake of isoflavones and the prevalence of periodontal disease was observed, although the difference in the adjusted odds ratio between the extreme quintiles was of borderline significance (<it>P </it>for trend = 0.04). There were no measurable dose-response relationships between consumption of tofu products, fermented soybeans, boiled soybeans, miso, or miso soup and the prevalence of periodontal disease.</p> <p>Conclusion</p> <p>Our findings suggest that soy and isoflavone intake may decrease the likelihood of periodontal disease. Further investigations with objective measures for periodontal disease are needed to confirm our findings.</p
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