4,622 research outputs found
Sulphur-bearing molecules in AGB stars I: The occurrence of hydrogen sulfide
Through a survey of (sub-)millimetre emission lines of various
sulphur-bearing molecules, we aim to determine which molecules are the primary
carriers of sulphur in different types of AGB stars. In this paper, the first
in a series, we investigate the occurrence of HS in AGB circumstellar
envelopes and determine its abundance, where possible. We have surveyed 20 AGB
stars with a range of mass-loss rates and of different chemical types using the
APEX telescope to search for rotational transition lines of five key
sulphur-bearing molecules: CS, SiS, SO, SO and HS. Here we present our
results for HS, including detections, non-detections and detailed radiative
transfer modelling of the detected lines. We compare results based on different
descriptions of the molecular excitation of HS and different abundance
distributions, including those derived from chemical modelling results. We
detected HS towards five AGB stars, all of which have high mass-loss rates
of yr and are oxygen-rich. HS
was not detected towards the carbon or S-type stars that fall in a similar
mass-loss range. For the stars in our sample with detections, we find peak
o-HS abundances relative to H between and . Overall, we conclude that HS can play a significant role in
oxygen-rich AGB stars with higher mass-loss rates, but is unlikely to play a
key role in stars of other chemical types or the lower mass-loss rate
oxygen-rich stars. For two sources, V1300 Aql and GX Mon, HS is most likely
the dominant sulphur-bearing molecule in the circumstellar envelope.Comment: 14 pages, 7 figures, accepted in A&
Effect of high-dose melphalan on marrow and intestinal epithelium in mice pretreated with cyclophosphamide.
The lethal effect of high-dose melphalan in mice could be offset by pretreatment with cyclophosphamide, cytosine arabinoside or low-dose melphalan. The reason for improved survival is unclear. Althoug animals given high-dose melphalan died with symptoms of gut death, in only one instance, that with low-dose melphalan itself, did pretreatment protect the intestinal epithelium as measured by the microcolony assay. A small enhancement in the recovery of the haemopoietic tissue in pretreated animals was noted, although this on its own is unlikely to explain the phenomenon. Experiments in tumour-bearing mice showed that pretreatment with cyclophosphamide did not reduce the toxicity of melphalan to the Lewis lung carcinoma
Universal Scaling of Optimal Current Distribution in Transportation Networks
Transportation networks are inevitably selected with reference to their
global cost which depends on the strengths and the distribution of the embedded
currents. We prove that optimal current distributions for a uniformly injected
d-dimensional network exhibit robust scale-invariance properties, independently
of the particular cost function considered, as long as it is convex. We find
that, in the limit of large currents, the distribution decays as a power law
with an exponent equal to (2d-1)/(d-1). The current distribution can be exactly
calculated in d=2 for all values of the current. Numerical simulations further
suggest that the scaling properties remain unchanged for both random injections
and by randomizing the convex cost functions.Comment: 5 pages, 5 figure
Enhanced anti-tumour activity of carmustine (BCNU) with tumour necrosis factor in vitro and in vivo.
The effects on experimental melanoma of a combination of recombinant human tumour necrosis factor alpha (rhTNF alpha) and carmustine (BCNU) were studied in vitro and in vivo. In vitro, BCNU alone was cytotoxic to murine B16 melanoma cells, and at all concentrations of BCNU this toxicity was increased by the addition of TNF. In vivo, BCNU and TNF, when given separately, caused tumour growth delay of B16 melanoma and of human melanoma xenografts in immune-deprived mice. The combination of TNF at low dose 2.5 x 10(5) U kg-1 = 122 ng kg-1) with BCNU (35 mg kg-1) resulted in significant growth delay (compared with either drug alone) in B16 melanoma (P = 0.005). There was no significant increase in toxicity as assessed by weight loss and peripheral blood counts. Experiments with human melanoma xenografts yielded similar results (P = 0.001) but only at higher doses of TNF (1 x 10(6) U kg-1 = 489 ng kg-1). The enhancement of BCNU cytotoxicity by TNF may be important if it can be translated into patients with melanoma. A randomised study is now underway to investigate the clinical potential of this observation
Large scale grain mantle disruption in the Galactic Center
We present observations of C2H5OH toward molecular clouds in Sgr A, Sgr B2
and associated with thermal and non-thermal features in the Galactic center.
C2H5OH emission in Sgr A and Sgr B2 is widespread, but not uniform. C2H5OH
emission is much weaker or it is not detected in some molecular clouds in both
complexes, in particular those with radial velocities between 70 and 120 km/s.
While most of the clouds associated with the thermal features do not show
C2H5OH emission, that associated with the Non-Thermal Radio Arc shows emission.
The fractional abundance of C2H5OH in most of the clouds with radial velocities
between 0 and 70 km/s in Sgr A and Sgr B2 is relatively high, of few 1e-8. The
C2H5OH abundance decreases by more than one order of magnitude (aprox. 1e-9) in
the clouds associated with the thermal features. The large abundance of C2H5OH
in the gas-phase indicates that C2H5OH has formed in grains and released to
gas-phase by shocks in the last aprox. 1e5 years.Comment: In press in Astrophysical Journal Letters 7 pages, 1 table, 1 figur
Mycobacterium tuberculosis subverts negative regulatory pathways in human macrophages to drive immunopathology.
Tuberculosis remains a global pandemic and drives lung matrix destruction to transmit. Whilst pathways driving inflammatory responses in macrophages have been relatively well described, negative regulatory pathways are less well defined. We hypothesised that Mycobacterium tuberculosis (Mtb) specifically targets negative regulatory pathways to augment immunopathology. Inhibition of signalling through the PI3K/AKT/mTORC1 pathway increased matrix metalloproteinase-1 (MMP-1) gene expression and secretion, a collagenase central to TB pathogenesis, and multiple pro-inflammatory cytokines. In patients with confirmed pulmonary TB, PI3Kδ expression was absent within granulomas. Furthermore, Mtb infection suppressed PI3Kδ gene expression in macrophages. Interestingly, inhibition of the MNK pathway, downstream of pro-inflammatory p38 and ERK MAPKs, also increased MMP-1 secretion, whilst suppressing secretion of TH1 cytokines. Cross-talk between the PI3K and MNK pathways was demonstrated at the level of eIF4E phosphorylation. Mtb globally suppressed the MMP-inhibitory pathways in macrophages, reducing levels of mRNAs encoding PI3Kδ, mTORC-1 and MNK-1 via upregulation of miRNAs. Therefore, Mtb disrupts negative regulatory pathways at multiple levels in macrophages to drive a tissue-destructive phenotype that facilitates transmission
The distribution of H13CN in the circumstellar envelope around IRC+10216
H13CN J=8-7 sub-millimetre line emission produced in the circumstellar
envelope around the extreme carbon star IRC+10216 has been imaged at
sub-arcsecond angular resolution using the SMA. Supplemented by a detailed
excitation analysis the average fractional abundance of H13CN in the inner wind
(< 5E15 cm) is estimated to be about 4E-7, translating into a total HCN
fractional abundance of 2E-5 using the isotopic ratio 12C/13C=50.
Multi-transitional single-dish observations further requires the H13CN
fractional abundance to remain more or less constant in the envelope out to a
radius of about 4E16 cm, where the HCN molecules are effectively destroyed,
most probably, by photodissociation. The large amount of HCN present in the
inner wind provides effective line cooling that can dominate over that
generated from CO line emission. It is also shown that great care needs to be
taken in the radiative transfer modelling where non-local, and non-LTE, effects
are important and where the radiation field from thermal dust grains plays a
major role in exciting the HCN molecules. The amount of HCN present in the
circumstellar envelope around IRC+10216 is consistent with predicted
photospheric values based on equilibrium chemical models and indicates that any
non-equilibrium chemistry occurring in the extended pulsating atmosphere has no
drastic net effect on the fractional abundance of HCN molecules that enters the
outer envelope. It further suggests that few HCN molecules are incorporated
into dust grains.Comment: Accepted for publication in ApJ. 20 pages, 7 figure
Pressure injury prevalence in a private health service : risks and recommendations
A pressure injury point prevalence was conducted by a private healthcare service (PHS) to determine the prevalence of pressure injuries in inpatients and to provide statistics for use in future comparison studies. The survey was conducted as part of the quality improvement programme of the PHS and the survey instrument was a modified version of a widely used existing tool. On the day of the survey, data collectors, working in pairs, performed skin inspections and completed the survey. Data were then collated and analysed. The overall pressure injury prevalence was 28.2% but with the exclusion of stage one injuries, decreased to 9.9%. Multivariate analysis revealed that the main risk factors for pressure injury development were the inability to reposition independently, older age and having a diagnosis of cancer. The major recommendations for practice change included the provision of pressure relieving devices to all patients unable to reposition independently, alteration of the Braden Scale risk score used on admission to identify older patients at risk from 16 to 18 in accordance with published literature and provision of further education to nurses about use of the Braden Scale and of pressure relieving devices. This study has also highlighted the need for further investigation into the reasons for patient non-participation in research and the direct and indirect relationships between surgery and acquisition of pressure injuries.\u
Atomic Diagnostics of X-ray Irradiated Protoplanetary Disks
We study atomic line diagnostics of the inner regions of protoplanetary disks
with our model of X-ray irradiated disk atmospheres which was previously used
to predict observable levels of the NeII and NeIII fine-structure transitions
at 12.81 and 15.55mum. We extend the X-ray ionization theory to sulfur and
calculate the fraction of sulfur in S, S+, S2+ and sulfur molecules. For the
D'Alessio generic T Tauri star disk, we find that the SI fine-structure line at
25.55mum is below the detection level of the Spitzer Infrared Spectrometer
(IRS), in large part due to X-ray ionization of atomic S at the top of the
atmosphere and to its incorporation into molecules close to the mid-plane. We
predict that observable fluxes of the SII 6718/6732AA forbidden transitions are
produced in the upper atmosphere at somewhat shallower depths and smaller radii
than the neon fine-structure lines. This and other forbidden line transitions,
such as the OI 6300/6363AA and the CI 9826/9852AA lines, serve as complementary
diagnostics of X-ray irradiated disk atmospheres. We have also analyzed the
potential role of the low-excitation fine-structure lines of CI, CII, and OI,
which should be observable by SOFIA and Herschel.Comment: Accepted by Ap
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