458 research outputs found
Polycyclic Aromatic Hydrocarbons with armchair edges and the 12.7 {\mu}m band
In this Letter we report the results of density functional theory
calculations on medium-sized neutral Polycyclic Aromatic Hydrocarbon (PAH)
molecules with armchair edges. These PAH molecules possess strong C-H
stretching and bending modes around 3 {\mu}m and in the fingerprint region
(10-15 {\mu}m), and also strong ring deformation modes around 12.7 {\mu}m.
Perusal of the entries in the NASA Ames PAHs Database shows that ring
deformation modes of PAHs are common - although generally weak. We then propose
that armchair PAHs with NC >65 are responsible for the 12.7 {\mu}m Aromatic
Infrared Band in HII regions and discuss astrophysical implications in the
context of the PAH life-cycle.Comment: Minor editin
Optical spectrum of proflavine and its ions
Motivated by possible astrophysical and biological applications we calculate
visible and near UV spectral lines of proflavine (C13H11N3,
3,6-diaminoacridine) in vacuum, as well as its anion, cation, and dication. The
pseudopotential density functional and time-dependent density functional
methods are used. We find a good agreement in spectral line positions
calculated by two real-time propagation methods and the Lanczos chain method.
Spectra of proflavine and its ions show characteristic UV lines which are good
candidates for a detection of these molecules in interstellar space and various
biological processes
Sequence structure emission in The Red Rectangle Bands
We report high resolution (R~37,000) integral field spectroscopy of the
central region (r<14arcsec) of the Red Rectangle nebula surrounding HD44179.
The observations focus on the 5800A emission feature, the bluest of the
yellow/red emission bands in the Red Rectangle. We propose that the emission
feature, widely believed to be a molecular emission band, is not a molecular
rotation contour, but a vibrational contour caused by overlapping sequence
bands from a molecule with an extended chromophore. We model the feature as
arising in a Polycyclic Aromatic Hydrocarbon (PAH) with 45-100 carbon atoms.Comment: 13 pages, 9 figures, accepted for publication in ApJ. A version of
the paper with full resolution figures is available at:
http://www.aao.gov.au/local/www/rgs/Sequence-Structure
Centrosymmetric molecules as possible carriers of diffuse interstellar bands
In this paper, we present new data with interstellar C2 (Phillips bands A-X),
from observations made with the Ultraviolet-Visual Echelle Spectrograph of the
European Southern Observatory. We have determined the interstellar column
densities and excitation temperatures of C2 for nine Galactic lines. For seven
of these, C2 has never been observed before, so in this case the still small
sample of interstellar clouds (26 lines of sight), where a detailed analysis of
C2 excitation has been made, has increased significantly. This paper is a
continuation of previous works where interstellar molecules (C2 and diffuse
interstellar bands) have been analysed. Because the sample of interstellar
clouds with C2 has increased, we can show that the width and shape of the
profiles of some diffuse interstellar bands (6196 and 5797 A) apparently depend
on the gas kinetic and rotational temperatures of C2; the profiles are broader
because of the higher values of the gas kinetic and rotational temperatures of
C2. There are also diffuse interstellar bands (4964 and 5850 A) for which this
effect does not exist.Comment: 8 pages, 4 figures, accepted to MNRAS 201
Unusually Weak Diffuse Interstellar Bands toward HD 62542
As part of an extensive survey of diffuse interstellar bands (DIBs), we have
obtained optical spectra of the moderately reddened B5V star HD 62542, which is
known to have an unusual UV extinction curve of the type usually identified
with dark clouds. The typically strongest of the commonly catalogued DIBs
covered by the spectra -- those at 5780, 5797, 6270, 6284, and 6614 A -- are
essentially absent in this line of sight, in marked contrast with other lines
of sight of similar reddening. We compare the HD 62542 line of sight with
others exhibiting a range of extinction properties and molecular abundances and
interpret the weakness of the DIBs as an extreme case of deficient DIB
formation in a dense cloud whose more diffuse outer layers have been stripped
away. We comment on the challenges these observations pose for identifying the
carriers of the diffuse bands.Comment: 20 pages, 4 figures; aastex; accepted by Ap
Comparative transcriptome profiling of the injured zebrafish and mouse hearts identifies miRNA-dependent repair pathways.
The adult mammalian heart has poor regenerative capacity. In contrast, the zebrafish heart retains a robust capacity for regeneration into adulthood. These distinct responses are consequences of a differential utilization of evolutionary-conserved gene regulatory networks in the damaged heart. To systematically identify miRNA-dependent networks controlling cardiac repair following injury, we performed comparative gene and miRNA profiling of the cardiac transcriptome in adult mice and zebrafish.
Using an integrated approach, we show that 45 miRNA-dependent networks, involved in critical biological pathways, are differentially modulated in the injured zebrafish vs. mouse hearts. We study, more particularly, the miR-26a-dependent response. Therefore, miR-26a is down-regulated in the fish heart after injury, whereas its expression remains constant in the mouse heart. Targets of miR-26a involve activators of the cell cycle and Ezh2, a component of the polycomb repressive complex 2 (PRC2). Importantly, PRC2 exerts repressive functions on negative regulators of the cell cycle. In cultured neonatal cardiomyocytes, inhibition of miR-26a stimulates, therefore, cardiomyocyte proliferation. Accordingly, miR-26a knockdown prolongs the proliferative window of cardiomyocytes in the post-natal mouse heart.
This novel strategy identifies a series of miRNAs and associated pathways, in particular miR-26a, which represent attractive therapeutic targets for inducing repair in the injured heart
Studies of Diffuse Interstellar Bands. V. Pairwise Correlations of Eight Strong DIBs and Neutral Hydrogen, Molecular Hydrogen, and Color Excess
We establish correlations between equivalent widths of eight diffuse
interstellar bands (DIBs), and examine their correlations with atomic hydrogen,
molecular hydrogen, and EB-V . The DIBs are centered at \lambda\lambda 5780.5,
6204.5, 6283.8, 6196.0, 6613.6, 5705.1, 5797.1, and 5487.7, in decreasing order
of Pearson\^as correlation coefficient with N(H) (here defined as the column
density of neutral hydrogen), ranging from 0.96 to 0.82. We find the equivalent
width of \lambda 5780.5 is better correlated with column densities of H than
with E(B-V) or H2, confirming earlier results based on smaller datasets. We
show the same is true for six of the seven other DIBs presented here. Despite
this similarity, the eight strong DIBs chosen are not well enough correlated
with each other to suggest they come from the same carrier. We further conclude
that these eight DIBs are more likely to be associated with H than with H2, and
hence are not preferentially located in the densest, most UV shielded parts of
interstellar clouds. We suggest they arise from different molecules found in
diffuse H regions with very little H (molecular fraction f<0.01). Of the 133
stars with available data in our study, there are three with significantly
weaker \lambda 5780.5 than our mean H-5780.5 relationship, all of which are in
regions of high radiation fields, as previously noted by Herbig. The
correlations will be useful in deriving interstellar parameters when direct
methods are not available. For instance, with care, the value of N(H) can be
derived from W{\lambda}(5780.5).Comment: Accepted for publication in The Astrophysical Journal; 37 pages, 11
figures, 6 table
Recommendations for exercise adherence measures in musculoskeletal settings : a systematic review and consensus meeting (protocol)
Background: Exercise programmes are frequently advocated for the management of musculoskeletal disorders; however, adherence is an important pre-requisite for their success. The assessment of exercise adherence requires the use of relevant and appropriate measures, but guidance for appropriate assessment does not exist. This research will identify and evaluate the quality and acceptability of all measures used to assess exercise adherence within a musculoskeletal setting, seeking to reach consensus for the most relevant and appropriate measures for application in research and/or clinical practice settings.
Methods/design: There are two key stages to the proposed research. First, a systematic review of the quality and acceptability of measures used to assess exercise adherence in musculoskeletal disorders; second, a consensus meeting. The systematic review will be conducted in two phases and reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to ensure a robust methodology. Phase one will identify all measures that have been used to assess exercise adherence in a musculoskeletal setting. Phase two will seek to identify published and unpublished evidence of the measurement and practical properties of identified measures. Study quality will be assessed against the COnsensus-based Standards for the selection of health Measurement Instruments (COSMIN) guidelines. A shortlist of best quality measures will be produced for consideration during stage two: a meeting of relevant stakeholders in the United Kingdom during which consensus on the most relevant and appropriate measures of exercise adherence for application in research and/or clinical practice settings will be sought.
Discussion: This study will benefit clinicians who seek to evaluate patientsâ levels of exercise adherence and those intending to undertake research, service evaluation, or audit relating to exercise adherence in the musculoskeletal field. The findings will impact upon new research studies which aim to understand the factors that predict adherence with exercise and which test different adherence-enhancing interventions. PROSPERO reference: CRD4201300621
The Rotational Excitation Temperature of the 6614 Diffuse Interstellar Band Carrier
Analysis of high spectral resolution observations of the 6614
diffuse interstellar band (DIB) line profile show systematic variations in the
positions of the peaks in the substructure of the profile. These variations --
shown here for the first time -- can be understood most naturally in the
framework of rotational contours of large molecules, where the variations are
caused by changes in the rotational excitation temperature. We show that the
rotational excitation temperature for the DIB carrier is likely significantly
lower than the gas kinetic temperature -- indicating that for this particular
DIB carrier angular momentum buildup is not very efficient.Comment: Accepted by ApJ Letters; 16 pages, 2 figure
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