2,243 research outputs found
Highly enriched Betaproteobacteria growing anaerobically with p-xylene and nitrate
The identity of the microorganisms capable of anaerobic p-xylene degradation under denitrifying conditions is hitherto unknown. Here, we report highly enriched cultures of freshwater denitrifying bacteria that grow anaerobically with p-xylene as the sole organic carbon source and electron donor. Long curved rods, with 95% 16S rRNA gene sequence identity to Denitratisoma oestradiolicum, dominated the enrichment cultures (>91% of all cells), as detected by phylotype-specific probes. These Rhodocyclaceae microorganisms were distantly related to other denitrifying hydrocarbon-degrading Betaproteobacteria from the Azoarcus-Thauera clade. Complete oxidation p-xylene to CO(2) coupled to denitrification was suggested by quantitative measurements of substrate consumption. Metabolite analysis identified (4-methylbenzyl)succinate and (4-methylphenyl)itaconate, suggesting addition to fumarate as an initial activation reaction
The Case for Optically-Thick High Velocity Broad Line Region Gas in Active Galactic Nuclei
A combined analysis of the profiles of the main broad quasar emission lines
in both Hubble Space Telescope and optical spectra shows that while the
profiles of the strong UV lines are quite similar, there is frequently a strong
increase in the Ly-alpha/H-alpha ratio in the high-velocity gas. We show that
the suggestion that the high velocity gas is optically-thin presents many
problems. We show that the relative strengths of the high velocity wings arise
naturally in an optically-thick BLR component. An optically-thick model
successfully explains the equivalent widths of the lines, the Ly-alpha/H-alpha
ratios and flatter Balmer decrements in the line wings, the strengths of CIII]
and the lambda 1400 blend, and the strong variability of high-velocity,
high-ionization lines (especially HeII and HeI).Comment: 34 pages in AASTeX, including 10 pages of figures. Submitted to
Astrophysical Journa
The reddest ISO-2MASS quasar
In the course of the NIR/MIR AGN search combining the 6.7 mu ISOCAM Parallel
Survey and 2MASS we have discovered 24 type-1 quasars about a third of which
are too red to be discriminated by optical/UV search techniques. Here we report
on a detailed case study of the reddest type-1 quasar of our sample (J2341) at
redshift z=0.236 with M_K=-25.8 and J-K=1.95. We performed spectroscopy in the
optical with VLT/FORS1 and in the MIR with Spitzer as well as NIR imaging with
ISPI at CTIO. The optical and NIR observations reveal a star forming
emission-line galaxy at the same redshift as the quasar with a projected linear
separation of 1.8 arcsec (6.7 kpc). The quasar and its companion are embedded
in diffuse extended continuum emission. Compared with its companion the quasar
exhibits redder optical-NIR colours, which we attribute to hot nuclear dust.
The MIR spectrum shows only few emission lines superimposed on a power-law
spectral energy distribution. However, the lack of strong FIR emission suggests
that our potentially interacting object contains much less gas and dust and is
in a stage different from dust reddened ULIRG-AGN like Mrk 231. The optical
spectrum shows signatures for reddening in the emission-lines and no
post-starburst stellar population is detected in the host galaxy of the quasar.
The optical continuum emission of the active nucleus appears absorbed and
diluted. Even the combination of absorption and host dilution is not able to
match J2341 with standard quasar templates. While the BLR shows only a rather
moderate absorption of E_(B-V)=0.3, the continuum shorter than 4500 AA requires
strong obscuration with E_(B-V)=0.7, exceeding the constraints from the low
upper limit on the 9.7 mu silicate absorption. This leads us to conclude that
the continuum of J2341 is intrinsically redder than that of typical quasars.Comment: 8 pages, 9 figure
Опыт участия в международном летнем кампусе РАНХиГС 2017
Extraordinarily well-preserved chitinozoans from an Upper Silurian sedimentary sequence in south-east Turkey were recovered from different depth levels, hand-picked from the palynological residue, cleaned and analysed by micro-FTIR and Curie point pyrolysis-gas chromatography-mass spectrometry. Hand-picked chitinozoans were predominantly represented by the genera Bursachitina, Calpichitina, Cingulochitina, Ancyrochitina, Angochitina and Pterochitina. Both spectroscopic and pyrolytic investigations suggest that biogeomacromolecules of these Chitinozoa consist of both aliphatic and aromatic moieties. The micro-FTIR spectra of Chitinozoa are characterized by aliphatic CH, (3000-2800 and 1460-1450 cm(-1)) and CH3 (1375 cm(-1)) absorptions and aromatic C = C (1560-1610 cm(-1)) and CH (3050 cm(-1) and 700-900 cm(-1)) absorptions. Major pyrolysis products from the Chitinozoa include both aromatic compounds such as alkylbenzenes, alkylnaphthalenes, alkylphenols and alkylphenanthrenes and aliphatic hydrocarbons including a homologous series of n-alkene/n-alkane doublets. Aromatic compounds predominate over aliphatic compounds. 1,2,3,4-Tetramethylbenzene is the most abundant pyrolysis product of the studied Chitinozoa. No pyrolysis products diagnostic of chitin were detected in the present study and it is unlikely that the original biomacromolecules of Chitinozoa prior to fossilization were made of chitin. (c) 200
The Molonglo Reference Catalog 1-Jy radio source survey IV. Optical spectroscopy of a complete quasar sample
Optical spectroscopic data are presented here for quasars from the Molonglo
Quasar Sample (MQS), which forms part of a complete survey of 1-Jy radio
sources from the Molonglo Reference Catalogue. The combination of low-frequency
selection and complete identifications means that the MQS is relatively free
from the orientation biases which affect most other quasar samples. To date,
the sample includes 105 quasars and 6 BL Lac objects, 106 of which have now
been confirmed spectroscopically. This paper presents a homogenous set of
low-resolution optical spectra for 79 MQS quasars, the majority of which have
been obtained at the Anglo-Australian Telescope. Full observational details are
given and redshifts, continuum and emission-line data tabulated for all
confirmed quasars.Comment: 40 pages, ApJS in pres
Development of Low Density Titanium Alloys for Structural Applications
In this report the results of a program designed to reduce the density of titanium by adding magnesium are presented. Because these two elements are immiscible under conventional ingot metallurgy techniques, two specialized powder metallurgy methods namely, mechanical alloying (MA) and physical vapor deposition (PVD) were implemented. The mechanical alloying experiments were done both at the University of Idaho and at the Defense Research Agency in UK. Since titanium is reactive with interstitial elements, a secondary goal of this research was to correlate solubility extensions with interstitial contamination content, especially oxygen and nitrogen. MA was carried out in SPEX 8000 shaker mils and different milling containers were utilized to control the level of contamination. Results showed that solubilities of Mg in Ti were obtained up to 28 at.% (16.4 wt. %) Mg in Ti for Ti-39.6 at. % (25 wt. %) Mg alloys, which greatly exceed those obtained under equilibrium conditions. This reflects a density reduction of approximately 26 %. Contamination of oxygen and nitrogen seemed to increase the solubility of magnesium in titanium in some cases; however, we were not able to make a clear correlation between contamination levels with solubilities. Work at the DRA has emphasized optimization of present PVD equipment, specifically composition and temperature control. Preliminary PVD data has shown Ti-Mg deposits have successfully been made up to 2 mm thick and that solubility extensions were achieved. The potential for density reduction of titanium by alloying with magnesium has been demonstrated; however, this work has only scratched the surface of the development of such low density alloys. Much research is needed before such alloys could be implemented into industry. Further funding is required in order to optimize the MA/PVD processes including contamination control, determination of optimal alloy compositions, microstructure development, and mechanical property determination
Neutrino Spin Transitions and the Violation of the Equivalence Principle
The violation of the equivalence principle (VEP) causing neutrino
oscillations is of current interest. We study here the possibility of not only
flavor oscillation but spin flavor oscillation of ultra high energy ( 1
PeV) neutrinos emanating from AGN due to VEP and due to the presence of a large
magnetic field ( 1 Tesla) in AGN. In particular we look at the resonance
spin flavor conversion driven by the AGN potential. Interesting bounds on the
transition magnetic moment of neutrinos may therefore be obtained.Comment: Latex, 12 pages, no figures. To appear in Journal of Physics G:
Nuclear and Particle Physics. Two references adde
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