3,513 research outputs found
Progression of lumbar disc degeneration over a decade: a heritability study
Lumbar disc degeneration (LDD) is prevalent, age-related and contributes to low back pain. Cross-sectional LDD as determined by MRI scan is known to be highly heritable. The authors postulated that the rate of progression might also be controlled by genetic factors
Excitations in the Halo Nucleus He-6 Following The Li-7(gamma,p)He-6 Reaction
A broad excited state was observed in 6-He with energy E_x = 5 +/- 1 MeV and
width Gamma = 3 +/- 1 MeV, following the reaction Li-7(gamma,p)He-6. The state
is consistent with a number of broad resonances predicted by recent cluster
model calculations. The well-established reaction mechanism, combined with a
simple and transparent analysis procedure confers considerable validity to this
observation.Comment: 3 pages of LaTeX, 3 figures in PostScript, approved for publication
in Phys. Rev. C, August, 200
Upgrade of the Glasgow photon tagging spectrometer for Mainz MAMI-C
The Glasgow photon tagging spectrometer at Mainz has been upgraded so that it
can be used with the 1500 MeV electron beam now available from the Mainz
microtron MAMI-C. The changes made and the resulting properties of the
spectrometer are discussed.Comment: 20 pages, 12 figure
Mobile Elements in a Single-Filament Orange Guaymas Basin Beggiatoa (âCandidatus Maribeggiatoaâ) sp. Draft Genome: Evidence for Genetic Exchange with Cyanobacteria
ABSTRACT The draft genome sequence of a single orange Beggiatoa (â Candidatus Maribeggiatoaâ) filament collected from a microbial mat at a hydrothermal site in Guaymas Basin (Gulf of California, Mexico) shows evidence of extensive genetic exchange with cyanobacteria, in particular for sensory and signal transduction genes. A putative homing endonuclease gene and group I intron within the 23S rRNA gene; several group II catalytic introns; GyrB and DnaE inteins, also encoding homing endonucleases; multiple copies of sequences similar to the fdxN excision elements XisH and XisI (required for heterocyst differentiation in some cyanobacteria); and multiple sequences related to an open reading frame (ORF) (00024_0693) of unknown function all have close non- Beggiatoaceae matches with cyanobacterial sequences. Sequences similar to the uncharacterized ORF and Xis elements are found in other Beggiatoaceae genomes, a variety of cyanobacteria, and a few phylogenetically dispersed pleiomorphic or filamentous bacteria. We speculate that elements shared among filamentous bacterial species may have been exchanged in microbial mats and that some of them may be involved in cell differentiation
Statistics of Magnetic Fields for OB Stars
Based on an analysis of the catalog of magnetic fields, we have investigated
the statistical properties of the mean magnetic fields for OB stars. We show
that the mean effective magnetic field of a star can be used as a
statistically significant characteristic of its magnetic field. No correlation
has been found between the mean magnetic field strength and
projected rotational velocity of OB stars, which is consistent with the
hypothesis about a fossil origin of the magnetic field. We have constructed the
magnetic field distribution function for B stars, , that has a
power-law dependence on with an exponent of . We have
found a sharp decrease in the function F for {\cal B}\lem 400 G
that may be related to rapid dissipation of weak stellar surface magnetic
fields.Comment: 22 pages, 7 figures, accepted Astronomy Letters, 2010, vol.36, No.5,
pp.370-379, contact E-mail: [email protected]
In-medium modifications of the interaction in photon-induced reactions
Differential cross sections of the reactions
and have been measured for several
nuclei (H,C, and Pb) at an incident-photon energy of
=400-460 MeV at the tagged-photon facility at MAMI-B using the TAPS
spectrometer. A significant nuclear-mass dependence of the
invariant-mass distribution is found in the channel. This
dependence is not observed in the channel and is
consistent with an in-medium modification of the interaction in the
==0 channel. The data are compared to -induced measurements and to
calculations within a chiral-unitary approach
ALMA 1.3 Millimeter Map of the HD 95086 System
Planets and minor bodies such as asteroids, Kuiper-belt objects and comets
are integral components of a planetary system. Interactions among them leave
clues about the formation process of a planetary system. The signature of such
interactions is most prominent through observations of its debris disk at
millimeter wavelengths where emission is dominated by the population of large
grains that stay close to their parent bodies. Here we present ALMA 1.3 mm
observations of HD 95086, a young early-type star that hosts a directly imaged
giant planet b and a massive debris disk with both asteroid- and Kuiper-belt
analogs. The location of the Kuiper-belt analog is resolved for the first time.
The system can be depicted as a broad (0.84), inclined
(30\arcdeg3\arcdeg) ring with millimeter emission peaked at 2006 au
from the star. The 1.3 mm disk emission is consistent with a broad disk with
sharp boundaries from 1066 to 32020 au with a surface density
distribution described by a power law with an index of --0.50.2. Our deep
ALMA map also reveals a bright source located near the edge of the ring, whose
brightness at 1.3 mm and potential spectral energy distribution are consistent
with it being a luminous star-forming galaxy at high redshift. We set
constraints on the orbital properties of planet b assuming co-planarity with
the observed disk.Comment: accepted for publication in A
Experimental and Computational Studies of Ruthenium Complexes Bearing Z-Acceptor Aluminum-Based Phosphine Pincer Ligands
Reaction of [Ru(C 6H 4PPh 2) 2(Ph 2PC 6H 4AlMe(THF))H] with CO results in clean conversion to the Ru-Al heterobimetallic complex [Ru(AlMePhos)(CO) 3] (1), where AlMePhos is the novel P-Al(Me)-P pincer ligand (o-Ph 2PC 6H 4) 2AlMe. Under photolytic conditions, 1 reacts with H 2to give [Ru(AlMePhos)(CO) 2(Îź-H)H] (2) that is characterized by multinuclear NMR and IR spectroscopies. DFT calculations indicate that 2 features one terminal and one bridging hydride that are respectively anti and syn to the AlMe group. Calculations also define a mechanism for H 2addition to 1 and predict facile hydride exchange in 2 that is also observed experimentally. Reaction of 1 with B(C 6F 5) 3results in Me abstraction to form the ion pair [Ru(AlPhos)(CO) 3][MeB(C 6F 5) 3] (4) featuring a cationic [(o-Ph 2PC 6H 4) 2Al] +ligand, [AlPhos] +. The Ru-Al distance in 4 (2.5334(16) Ă
) is significantly shorter than that in 1 (2.6578(6) Ă
), consistent with an enhanced Lewis acidity of the [AlPhos] +ligand. This is corroborated by a blue shift in both the observed and computed ν COstretching frequencies upon Me abstraction. Electronic structure analyses (QTAIM and EDA-ETS) comparing 1, 4, and the previously reported [Ru(ZnPhos)(CO) 3] analogue (ZnPhos = (o-Ph 2PC 6H 4) 2Zn) indicate that the Lewis acidity of these pincer ligands increases along the series ZnPhos < AlMePhos < [AlPhos] +. copy; 2022 American Chemical Society.</p
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