333 research outputs found
Comparative study of complex N- and O-bearing molecules in hot molecular cores
We have observed several emission lines of two Nitrogen-bearing (C2H5CN and
C2H3CN) and two Oxygen-bearing (CH3OCH3 and HCOOCH3) molecules towards a sample
of well-known hot molecular cores (HMCs) in order to check whether the chemical
differentiation seen in the Orion-HMC and W3(H_2O) between O- and N-bearing
molecules is a general property of HMCs. With the IRAM-30m telescope we have
observed 12 HMCs in 21 bands, centered at frequencies from 86250 to 258280 MHz.
The rotational temperatures obtained range from ~100 to ~150 K in these HMCs.
Single Gaussian fits performed to unblended lines show a marginal difference in
the line peak velocities of the C2H5CN and CH3OCH3 lines, indicating a possible
spatial separation between the region traced by the two molecules. On the other
hand, neither the linewidths nor the rotational temperatures and column
densities confirm such a result. By comparing the abundance ratio of the pair
C2H5CN/C2H3CN with the predictions of theoretical models, we derive that the
age of our cores ranges between 3.7 and 5.9x10^{4} yrs. The abundances of
C2H5CN and C2H3CN are strongly correlated, as expected from theory which
predicts that C2H3CN is formed through gas phase reactions involving C2H5CN. A
correlation is also found between the abundances of C2H3CN and CH3OCH3, and
C2H5CN and CH3OCH3. In all tracers the fractional abundances increase with the
H_2 column density while they are not correlated with the gas temperature.Comment: Accepted for publication in A&A, 56 page
Multiwavelength observations of the supernova remnant G349.7+02 interacting with a molecular cloud
We present molecular-line observations at millimetre, centimetre and infrared
wavelengths of the region containing OH(1720 MHz) masers in the supernova
remnant (SNR) G349.7+0.2, using the Australia Telescope (AT) Mopra antenna, the
Swedish-ESO Submillimeter Telescope, the AT Compact Array and the UNSW Infrared
Fabry-Perot narrow-band filter installed on the Anglo-Australian Telescope.
Several molecular transitions were observed between 1.6 and 3 mm to constrain
the physical parameters of the molecular cloud interacting with the SNR and to
investigate the effects of the SNR shock on the gas chemistry. We detected
shock-excited near-infrared H2 emission towards the centre of the SNR,
revealing highly clumped molecular gas and a good correlation with published
mid-infrared images from the Spitzer Space Telescope. An excellent correlation
between the H2 clumps and OH(1720 MHz) maser positions supports the shock
excitation of the OH(1720 MHz) maser emission. Furthermore, we detected OH
absorption at 1665 and 1667 MHz which shows a good correlation with the shocked
H2 emission and the masers. We found maser emission at 1665 MHz near the
OH(1720 MHz) masers in this SNR, which is found to be associated with a GLIMPSE
source SSTGLMC G349.7294+00.1747. We also detected 1665 and 1667 MHz OH masers,
and weak 4.8 GHz H2CO absorption towards the ultracompact HII region IRAS
17147-3725 located to the southeast of the SNR. We found no 4.7- or 6-GHz
excited-state OH masers or 6-GHz CH3OH maser towards either the SNR or the HII
region.Comment: 25 pages, 13 figures, published in MNRA
Comparative study of CH+ and SH+ absorption lines observed towards distant star-forming regions
Aims. The HIFI instrument onboard Herschel has allowed high spectral
resolution and sensitive observations of ground-state transi- tions of three
molecular ions: the methylidyne cation CH+, its isotopologue 13CH+, and
sulfanylium SH+. Because of their unique chemical properties, a comparative
analysis of these cations provides essential clues to the link between the
chemistry and dynamics of the diffuse interstellar medium. Methods. The CH+,
13CH+, and SH+ lines are observed in absorption towards the distant high-mass
star-forming regions (SFRs) DR21(OH), G34.3+0.1, W31C, W33A, W49N, and W51, and
towards two sources close to the Galactic centre, SgrB2(N) and SgrA*+50. All
sight lines sample the diffuse interstellar matter along pathlengths of several
kiloparsecs across the Galactic Plane. In order to compare the velocity
structure of each species, the observed line profiles were deconvolved from the
hyperfine structure of the SH+ transition and the CH+, 13CH+, and SH+ spectra
were independently decomposed into Gaussian velocity components. To analyse the
chemical composition of the foreground gas, all spectra were divided, in a
second step, into velocity intervals over which the CH+, 13CH+, and SH+ column
densities and abundances were derived. Results. SH+ is detected along all
observed lines of sight, with a velocity structure close to that of CH+ and
13CH+. The linewidth distributions of the CH+, SH+, and 13CH+ Gaussian
components are found to be similar. These distributions have the same mean
( ~ 4.2 km s-1) and standard deviation
(\sigma(\delta\u{psion}) ~ 1.5 km s-1). This mean value is also close to that
of the linewidth distribution of the CH+ visible transitions detected in the
solar neighbourhood. We show that the lack of absorption components narrower
than 2 km s-1 is not an artefact caused by noise: the CH+, 13CH+, and SH+ line
profiles are therefore statistically broader than those of most species
detected in absorption in diffuse interstellar gas (e. g. HCO+, CH, or CN). The
SH+/CH+ column density ratio observed in the components located away from the
Galactic centre spans two orders of magnitude and correlates with the CH+
abundance. Conversely, the ratio observed in the components close to the
Galactic centre varies over less than one order of magnitude with no apparent
correlation with the CH+ abundance. The observed dynamical and chemical
properties of SH+ and CH+ are proposed to trace the ubiquitous process of
turbulent dissipation, in shocks or shears, in the diffuse ISM and the specific
environment of the Galactic centre regions
A fresh look at the evolution and diversification of photochemical reaction centers
In this review, I reexamine the origin and diversification of photochemical reaction centers based on the known phylogenetic relations of the core subunits, and with the aid of sequence and structural alignments. I show, for example, that the protein folds at the C-terminus of the D1 and D2 subunits of Photosystem II, which are essential for the coordination of the water-oxidizing complex, were already in place in the most ancestral Type II reaction center subunit. I then evaluate the evolution of reaction centers in the context of the rise and expansion of the different groups of bacteria based on recent large-scale phylogenetic analyses. I find that the Heliobacteriaceae family of Firmicutes appears to be the earliest branching of the known groups of phototrophic bacteria; however, the origin of photochemical reaction centers and chlorophyll synthesis cannot be placed in this group. Moreover, it becomes evident that the Acidobacteria and the Proteobacteria shared a more recent common phototrophic ancestor, and this is also likely for the Chloroflexi and the Cyanobacteria. Finally, I argue that the discrepancies among the phylogenies of the reaction center proteins, chlorophyll synthesis enzymes, and the species tree of bacteria are best explained if both types of photochemical reaction centers evolved before the diversification of the known phyla of phototrophic bacteria. The primordial phototrophic ancestor must have had both Type I and Type II reaction centers
Design, Development, Implementation, and On-orbit Performance of the Dynamic Ionosphere CubeSat Experiment Mission
Funded by the NSF CubeSat and NASA ELaNa programs, the Dynamic Ionosphere CubeSat Experiment (DICE) mission consists of two 1.5U CubeSats which were launched into an eccentric low Earth orbit on October 28, 2011. Each identical spacecraft carries two Langmuir probes to measure ionospheric in-situ plasma densities, electric field probes to measure in-situ DC and AC electric fields, and a science grade magnetometer to measure in-situ DC and AC magnetic fields. Given the tight integration of these multiple sensors with the CubeSat platforms, each of the DICE spacecraft is effectively a “sensorsat” capable of comprehensive ionospheric diagnostics. The use of two identical sensor-sats at slightly different orbiting velocities in nearly identical orbits permits the de-convolution of spatial and temporal ambiguities in the observations of the ionosphere from a moving platform. In addition to demonstrating nanosat-based constellation science, the DICE mission is advancing a number of groundbreaking CubeSat technologies including miniaturized mechanisms and high-speed downlink communications
How service‐users with intellectual disabilities understand challenging behaviour and approaches to managing it
Background This study explored understandings that service‐users with intellectual disabilities and challenging behaviour held around their behaviour, what shaped these understandings, and the relationship between how behaviours are managed and well‐being. Methods Eight participants (three female, five male) partook in individual semi‐structured qualitative interviews. Interviews were transcribed and analysed using interpretative phenomenological analysis. Results Three master themes emerged from this analysis: (a) challenging behaviour can be explained via an internal or external frame of reference, with each framework having different implications for how participants attempted to manage behaviour. (b) Positive relationships provide a long‐term buffer to challenging behaviour, with positive relationships with family, staff and peers operating through different mechanisms to achieve this. (c) A greater ability to exert power and control in day‐to‐day life was perceived to reduce challenging behaviour in the long term. Conclusions Implications for practice are discussed
The effectiveness of US mitigation and monitoring practices for the threatened Valley elderberry longhorn beetle
Systemic inflammatory response and neuromuscular involvement in amyotrophic lateral sclerosis
OBJECTIVE: To evaluate the combined blood expression of neuromuscular and inflammatory biomarkers as predictors of disease progression and prognosis in amyotrophic lateral sclerosis (ALS). METHODS: Logistic regression adjusted for markers of the systemic inflammatory state and principal component analysis were carried out on plasma levels of creatine kinase (CK), ferritin, and 11 cytokines measured in 95 patients with ALS and 88 healthy controls. Levels of circulating biomarkers were used to study survival by Cox regression analysis and correlated with disease progression and neurofilament light chain (NfL) levels available from a previous study. Cytokines expression was also tested in blood samples longitudinally collected for up to 4 years from 59 patients with ALS. RESULTS: Significantly higher levels of CK, ferritin, tumor necrosis factor (TNF)-α, and interleukin (IL)-1β, IL-2, IL-8, IL-12p70, IL-4, IL-5, IL-10, and IL-13 and lower levels of interferon (IFN)-γ were found in plasma samples from patients with ALS compared to controls. IL-6, TNF-α, and IFN-γ were the most highly regulated markers when all explanatory variables were jointly analyzed. High ferritin and IL-2 levels were predictors of poor survival. IL-5 levels were positively correlated with CK, as was TNF-α with NfL. IL-6 was strongly associated with CRP levels and was the only marker showing increasing expression towards end-stage disease in the longitudinal analysis. CONCLUSIONS: Neuromuscular pathology in ALS involves the systemic regulation of inflammatory markers mostly active on T-cell immune responses. Disease stratification based on the prognostic value of circulating inflammatory markers could improve clinical trials design in ALS
Demographics of Piscivorous Colonial Waterbirds and Management Implications for ESA-listed Salmonids on the Columbia Plateau
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