1,458 research outputs found
Carbamazepine on a carbamazepine monolayer forms unique 1D supramolecular assemblies
High-resolution STM imaging of the structures formed by carbamazepine molecules adsorbed onto a pseudo-ordered carbamazepine monolayer on Au(111) shows the formation of previously unreported 1-dimensional supramolecular assemblies
Probing discs around massive young stellar objects with CO first overtone emission
We present high resolution (R~50,000) spectroastrometry over the CO 1st
overtone bandhead of a sample of seven intermediate/massive young stellar
objects. These are primarily drawn from the red MSX source (RMS) survey, a
systematic search for young massive stars which has returned a large, well
selected sample of such objects. The mean luminosity of the sample is
approximately 5 times 10^4 L_\odot, indicating the objects typically have a
mass of ~15 solar masses. We fit the observed bandhead profiles with a model of
a circumstellar disc, and find good agreement between the models and
observations for all but one object. We compare the high angular precision
(0.2-0.8 mas) spectroastrometric data to the spatial distribution of the
emitting material in the best-fitting models. No spatial signatures of discs
are detected, which is entirely consistent with the properties of the
best-fitting models. Therefore, the observations suggest that the CO bandhead
emission of massive young stellar objects originates in small-scale disks, in
agreement with previous work. This provides further evidence that massive stars
form via disc accretion, as suggested by recent simulations.Comment: Accepted for publication in MNRA
Introduction to a Biological Systems Science
Biological systems analysis and biodynamic modelling of physiological and biological interrelationships in human body and mammal
Molecular Line Emission Towards High-Mass Clumps: The MALT90 Catalogue
The Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey aims to characterise the physical and chemical evolution of high-mass clumps. Recently completed, it mapped 90 GHz line emission toward 3246 high-mass clumps identified from the ATLASGAL 870 �m Galactic plane survey. By utilising the broad frequency coverage of the Mopra telescope's spectrometer, maps in 16 different emission lines were simultaneously obtained. Here we describe the �first line catalog of the detected emission, generated by Gaussian profile �fitting to spectra extracted toward each clumps' dust peak. Synthetic spectra show that the catalog has a completeness of >95%, a probability of a false-positive detection of <0.3%, and a relative uncertainty in the measured quantities of <20% over the range of detection criteria. We find that the detection rates are highest for the (1{0) molecular transitions of HCO+, HNC, N2H+, and HCN (72{88%). The majority of clumps (~� 95%) are detected in at least one of the molecular transitions, just under half of the clumps (�~48%) are detected in 4 or more of the transitions, while only 2 clumps are detected in 13 or more transitions. We find several striking trends in the ensemble of properties for the different molecular transitions when plotted as a function of the clumps' evolutionary state. In particular, the optically thickest HCO+ emission shows a `blue-red asymmetry' that indicates overall collapse that monotonically decreases as the clumps evolve. This catalog represents the largest compiled database of molecular line emission toward high-mass clumps and is a valuable data set for detailed studies of these objects
CO bandhead emission of massive young stellar objects: determining disc properties
Massive stars play an important role in many areas of astrophysics, but numerous details regarding their formation remain unclear. In this paper we present and analyse high-resolution (R~30 000) near-infrared 2.3 μm spectra of 20 massive young stellar objects (MYSOs) from the Red MSX Source (RMS) data base, in the largest such study of CO first overtone bandhead emission to date. We fit the emission under the assumption it originates from a circumstellar disc in Keplerian rotation. We explore three approaches to modelling the physical conditions within the disc-a disc heated mainly via irradiation from the central star, a disc heated mainly via viscosity, and a disc in which the temperature and density are described analytically. We find that the models described by heating mechanisms are inappropriate because they do not provide good fits to the CO emission spectra. We therefore restrict our analysis to the analytic model, and obtain good fits to all objects that possess sufficiently strong CO emission, suggesting circumstellar discs are the source of this emission. On average, the temperature and density structure of the discs correspond to geometrically thin discs, spread across a wide range of inclinations. Essentially all the discs are located within the dust sublimation radius, providing strong evidence that the CO emission originates close to the central protostar, on astronomical unit scales. In addition, we show that the objects in our sample appear no different to the general population of MYSOs in the RMS data base, based on their near- and mid-infrared colours. The combination of observations of a large sample of MYSOs with CO bandhead emission and our detailed modelling provide compelling evidence of the presence of small-scale gaseous discs around such objects, supporting the scenario in which massive stars form via disc accretion. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society
Impact of bovine oocyte maturation media on oocyte transcript levels, blastocyst development, cell number, and apoptosis.
The objectives were 1) to investigate the effects of oocyte maturation in serum-free and amino acid-supplemented defined media on oocyte transcript levels, blastocyst cell number, and apoptosis; 2) to investigate the influence of oocyte maturation culture atmosphere on blastocyst development, total cell number, and apoptosis; and 3) to examine the influence of epidermal growth factor (EGF) during oocyte maturation on blastocyst cell number and apoptosis. The results demonstrate that blastocysts derived from in vitro maturation, fertilization, and embryo culture protocols undergo apoptosis but that apoptotic levels are not greatly influenced by the oocyte maturation environment. Amino acid supplementation of oocyte maturation media was associated with enhanced developmental frequencies, increased blastocyst cell number, and elevated oocyte maternal mRNA levels. Oocyte maturation with supplemented synthetic oviduct fluid medium (cSOFMaa) resulted in blastocyst cell numbers comparable to those observed with Tissue Culture Medium 199 + newborn calf serum. Blastocyst development was reduced following oocyte maturation under a 5% CO(2), 7% O(2), 88% N(2) culture atmosphere. EGF supplementation of oocyte maturation medium resulted in a concentration-dependent increase in blastocyst development but did not influence blastocyst total cell number or apoptosis. Our findings indicate that cSOFMaa medium is an effective base medium for bovine oocyte maturation
Factors that may mediate the relationship between physical activity and the risk for developing knee osteoarthritis
Studies investigating the effect of physical activity on risk for developing osteoarthritis at weight-bearing joints have reported conflicting results. We examine evidence to suggest that this may be due to the existence of subgroups of individuals who differ in their response to physical activity, as well as methodological issues associated with the assessment of knee joint structure and physical activity. Recommendations for future studies of physical activity and the development of knee osteoarthritis are discussed
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Evaluation of outreach services for primary care and mental health; assessing the impact
Objectives: This paper reports an evaluation, carried out for London Health Libraries, of the impact of outreach services to primary care and mental health workers in thirteen different settings. The main aims of the project were to identify the impact being made by the service, and to produce best practice guidelines for outreach services in this kind of ‘difficult’ community setting.
Methods: Methods used were: analysis of documents (all 13 services); analysis of any evaluation already performed by or for the service (all 13 services); interviews with outreach librarians (11 services); questionnaire survey of a representative sample of users (8 services, with 66 returned questionnaires, 35% response rate). The services evaluated were very diverse, in terms of setting, structure, functions and activities, and extent and nature of self-evaluation and reporting. The evaluation was therefore largely qualitative, in order to deal with the lack of a consistent ‘template’ for analysis. Emphasis was placed on trying to identify critical incidents , where it could be shown unambiguously that the outreach services made a difference to practice.
Study limitations included the difficulty of summarising and comparing very different situations and diverse services, difficulty in identifying critical incidents, and an inability to study ‘non-users’.
Findings: Service recipients felt better informed, more up-
to-date, more aware of resources, more confident and supported in their work, and saved time. Services contributed to a richer information environment. Direct impacts, demonstrably improved patient care, cost savings etc., were more difficult to establish
X-ray and radio observations of central black holes in nearby low-mass early-type galaxies: Preliminary evidence for low Eddington fractions
We present new radio and X-ray observations of two nearby ( Mpc)
low-mass early-type galaxies with dynamically-confirmed central black holes:
NGC 5102 and NGC 205. NGC 5102 shows a weak nuclear X-ray source and has no
core radio emission. However, for the first time we demonstrate that it shows
luminous extended radio continuum emission in low-resolution, low-frequency ( GHz) data, consistent with jet lobes on scales pc formed from
past accretion and jet activity. By contrast, in new, extremely deep,
strictly-simultaneous Very Large Array and Chandra observations, no radio or
X-ray emission is detected from the black hole in NGC 205. We consider these
measurements and upper limits in the context of the few other low-mass
early-type galaxies with dynamically-confirmed black holes, and show that the
mean ratio of bolometric to Eddington luminosity in this sample is only
. These Eddington
ratios are lower than typical in a comparison sample of more massive early-type
galaxies, though this conclusion is quite tentative due to our small sample of
low-mass galaxies and potential biases in the comparison sample. This
preliminary result is in mild tension with previous work using less sensitive
observations of more distant galaxies, which predict higher X-ray luminosities
than we observe for low-mass galaxies. If it is confirmed that central black
holes in low-mass galaxies typically have low Eddington ratios, this presents a
challenge to measuring the occupation fraction of central black holes with
standard optical emission line, X-ray, or radio surveys.Comment: 13 pages, 4 figures, 3 tables. Accepted for publication in Ap
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