1,256 research outputs found
Does tiny-scale atomic structure exist in the interstellar medium ?
We report on preliminary results from the recent multi-epoch neutral hydrogen
absorption measurements toward three pulsars, B0823+26, B1133+16 and B2016+28,
using the Arecibo telescope. We do not find significant variations in optical
depth profiles over periods of 0.3 and 9--10 yr, or on spatial scales of 10--20
and 70--85 AU. The large number of non detections of the tiny scale atomic
structure suggests that the AU-sized structure is not ubiquitous in the
interstellar medium and could be quite a rare phenomenon.Comment: Accepted by ApJ Letters, 5 pages, 2 figure
Recipes for stellar jets: results of combined optical/infrared diagnostics
We examine the conditions of the plasma along a sample of 'classical'
Herbig-Haro jets located in the Orion and Vela star forming regions, through
combined optical-infrared spectral diagnostics. Our sample includes HH 111, HH
34, HH 83, HH 73, HH 24 C/E, HH 24 J, observed at moderate spatial/spectral
resolution. The obtained spectra cover a wide wavelength range from 0.6-2.5 um,
including many transitions from regions of different excitation conditions.
This allows us to probe the density and temperature stratification which
characterises the cooling zones behind the shock fronts along the jet. The
derived physical parameters (such as the extinction, the electron density and
temperature, the ionisation fraction, and the total density) are used to
estimate the depletion onto dust grains of Calcium and Iron with respect to
solar abundances. This turns out to be between 70% and 0% for Ca and ~90% for
Fe, suggesting that the weak shocks present in the beams are not capable of
completely destroying the dust grains. We then derive the mass flux rates
(Mdot_jet is on average 5 10^-8 M_solar yr^-1) and the associated linear
momentum fluxes. The latter are higher than, or of the same order as, those
measured in the coaxial molecular flows, suggesting that the flows are jet
driven. Finally, we discuss differences between jets in our sample.Comment: 19 pages, 15 figures, accepted by A&
Multi-wavelength observations of the young binary system Haro 6-10: The case of misaligned discs
Context. We present a multi-wavelength, high-resolution observational survey
of the young binary system Haro 6-10 (GV Tau, IRAS 04263+2426), which is
harbouring one of the few known infrared companions. Aims. The primary goal of
this project is to determine the physical and geometrical properties of the
circumstellar and circumbinary material in the Haro 6-10 system. Methods.
High-resolution optical (HST/WFPC2) and near-infrared (VLT/NACO) images in
different bands were analysed to investigate the large-scale structures of the
material around the binary.Mid-infrared interferometry (VLTI/MIDI) and
spectroscopy (TIMMI2 at the 3.6m ESO telescope) were carried out to determine
the structure and optical depth of the circumstellar material around the
individual components. Results. The multi-wavelength observations suggest that
both components of the binary system Haro 6-10 are embedded in a common
envelope. The measured extinction indicates a dust composition of the envelope
similar to that of the interstellar medium. Each component of the system has a
circumstellar disc-like structure typical of young stars. The discs are highly
misaligned: the northern component is seen almost edge-on and the southern
component is an almost face-on disc. Conclusions. The two main formation
scenarios of binary systems with misaligned discs are the gravitational capture
of a passing object in a dense environment, and the fragmentation of the
collapsing molecular cloud. Given the low-density environment of the
Taurus-Aurigae star-forming region, the first scenario is unlikely for Haro
6-10. The binary system most probably formed via fragmentation of two different
parts of the collapsing molecular cloud combined with other dynamical processes
related to the cloud and/or the protostars. This can be the explanation also
for other binary systems with an infrared companion.Comment: accepted for publication in A&A on July 15, 201
CSO Bolocam 1.1 mm continuum mapping of the Braid Nebula star formation region in Cygnus OB7
We present a 1.1 mm map of the Braid Nebula star formation region in Cygnus OB7 taken using Bolocam on the Caltech Submillimeter Observatory. Within the 1 deg2 covered by the map, we have detected 55 cold dust clumps all of which are new detections. A number of these clumps are coincident with IRAS point sources although the majority are not. Some of the previously studied optical/near-IR sources are detected at 1.1 mm. We estimate total dust/gas masses for the 55 clumps together with peak visual extinctions. We conclude that over the whole region, approximately 20% of the clumps are associated with IRAS sources suggesting that these are protostellar objects. The remaining 80% are classed as starless clumps. In addition, both FU Orionis (FUor) like objects in the field, the Braid Star and HH 381 IRS, are associated with strong millimeter emission. This implies that FUor eruptions can occur at very early stages of pre-main-sequence life. Finally, we determine that the cumulative clump mass function for the region is very similar to that found in both the Perseus and Ï? Ophiuchus star-forming regions. © 2011. The American Astronomical Society. All rights reserved
V2494 cyg: A unique FU ori type object in the cygnus OB7 complex
A photometric and spectral study of the variable star V2494 Cyg in the L 1003 dark cloud is presented. The brightness of the star, formerly known as HH 381 IRS, increased by 2.5 mag in R (probably in the 1980s) and since then has remained nearly constant. Since the brightness increase, V2494 Cyg has illuminated a bipolar cometary nebula. The stellar spectrum has several features typical of the FU Ori (FUor) type, plus it exhibits very strong Ha and forbidden emissionlines with high-velocity components. These emission lines originate in the Herbig-Haro (HH) jet near the star. The kinematic age of the jet is consistent with it forming at the time of the outburst leading to the luminosity increase. V2494 Cyg also produces a rather extended outflow; it is the first known FUor with both an observed outburst and a parsec-sized HH flow. The nebula, illuminated by V2494 Cyg, possesses similar morphological and spectral characteristics to Hubble's variable nebula (R Monocerotis/NGC 2261). © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
Acidification increases abundances of Vibrionales and Planctomycetia associated to a seaweed-grazer system: potential consequences for disease and prey digestion efficiency
Ocean acidification significantly affects marine organisms in several ways, with complex interactions. Seaweeds might benefit from rising CO2 through increased photosynthesis and carbon acquisition, with subsequent higher growth rates. However, changes in seaweed chemistry due to increased CO2 may change the nutritional quality of tissue for grazers. In addition, organisms live in close association with a diverse microbiota, which can also be influenced by environmental changes, with feedback effects. As gut microbiomes are often linked to diet, changes in seaweed characteristics and associated microbiome can affect the gut microbiome of the grazer, with possible fitness consequences. In this study, we experimentally investigated the effects of acidification on the microbiome of the invasive brown seaweed Sargassum muticum and a native isopod consumer Synisoma nadejda. Both were exposed to ambient CO2 conditions (380 ppm, pH 8.16) and an acidification treatment (1,000 ppm, pH 7.86) for three weeks. Microbiome diversity and composition were determined using high-throughput sequencing of the variable regions V5-7 of 16S rRNA. We anticipated that as a result of acidification, the seaweed-associated bacterial community would change, leading to further changes in the gut microbiome of grazers. However, no significant effects of elevated CO2 on the overall bacterial community structure and composition were revealed in the seaweed. In contrast, significant changes were observed in the bacterial community of the grazer gut. Although the bacterial community of S. muticum as whole did not change, Oceanospirillales and Vibrionales (mainly Pseudoalteromonas) significantly increased their abundance in acidified conditions. The former, which uses organic matter compounds as its main source, may have opportunistically taken advantage of the possible increase of the C/N ratio in the seaweed under acidified conditions. Pseudoalteromonas, commonly associated to diseased seaweeds, suggesting that acidification may facilitate opportunistic/pathogenic bacteria. In the gut of S. nadejda, the bacterial genus Planctomycetia increased abundance under elevated CO2. This shift might be associated to changes in food (S. muticum) quality under acidification. Planctomycetia are slow-acting decomposers of algal polymers that could be providing the isopod with an elevated algal digestion and availability of inorganic compounds to compensate the shifted C/N ratio under acidification in their food. In conclusion, our results indicate that even after only three weeks of acidified conditions, bacterial communities associated to ungrazed seaweed and to an isopod grazer show specific, differential shifts in associated bacterial community. These have potential consequences for seaweed health (as shown in corals) and isopod food digestion. The observed changes in the gut microbiome of the grazer seem to reflect changes in the seaweed chemistry rather than its microbial composition.Erasmus Mundus Doctoral Programme MARES on Marine Ecosystem Health Conservation [MARES_13_08]; FCT (Foundation for Science and Technology, Portugal) [SFRH/BPD/63703/2009, SFRH/BPD/107878/2015, SFRH/BPD/116774/2016]; EU SEAS-ERA project INVASIVES [SEAS-ERA/0001/2012]; [CCMAR/Multi/04326/2013
Conductive Composite Microneedle Sensors Based on Cellulose Acetate Phthalate: Investigating Performance and Biodegradability
СОЦІО-ЕКОНОМІЧНІ АСПЕКТИ ОРГАНІЗАЦІЇ«РОЗУМНОГО МІСТА»
<p>Breteau Index represents number of positive containers per 100 houses inspected. Stars indicate surveys with nil detection.</p
Metagenomic next-generation sequencing aids the diagnosis of viral infections in febrile returning travellers
Objectives
Travel-associated infections are challenging to diagnose because of the broad spectrum of potential aetiologies. As a proof-of-principle study, we used MNGS to identify viral pathogens in clinical samples from returning travellers in a single center to explore its suitability as a diagnostic tool.
Methods
Plasma samples from 40 returning travellers presenting with a fever of ≥38°C were sequenced using MNGS on the Illumina MiSeq platform and compared with standard-of-care diagnostic assays.
Results
In total, 11/40 patients were diagnosed with a viral infection. Standard of care diagnostics revealed 5 viral infections using plasma samples; dengue virus 1 (n = 2), hepatitis E (n = 1), Ebola virus (n = 1) and hepatitis A (n = 1), all of which were detected by MNGS. Three additional patients with Chikungunya virus (n = 2) and mumps virus were diagnosed by MNGS only. Respiratory infections detected by nasal/throat swabs only were not detected by MNGS of plasma. One patient had infection with malaria and mumps virus during the same admission.
Conclusions
MNGS analysis of plasma samples improves the sensitivity of diagnosis of viral infections and has potential as an all-in-one diagnostic test. It can be used to identify infections that have not been considered by the treating physician, co-infections and new or emerging pathogens.
Summary
Next generation sequencing (NGS) has potential as an all-in-one diagnostic test. In this study we used NGS to diagnose returning travellers with acute febrile illness in the UK, highlighting cases where the diagnosis was missed using standard methods
Evaluation of the impact of a school gardening intervention on children's fruit and vegetable intake: a randomised controlled trial.
Background: Current academic literature suggests that school gardening programmes can provide an interactive environment with the potential to change children’s fruit and vegetable intake. This is the first cluster randomised controlled trial (RCT) designed to evaluate whether a school gardening programme can have an effect on children’s fruit and vegetable intake.
Methods: The trial included children from 23 schools; these schools were randomised into two groups, one to receive the Royal Horticultural Society (RHS)-led intervention and the other to receive the less involved Teacher-led intervention. A 24-hour food diary (CADET) was used to collect baseline and follow-up dietary intake 18 months apart. Questionnaires were also administered to evaluate the intervention implementation.
Results: A total of 641 children completed the trial with a mean age of 8.1 years (95% CI: 8.0, 8.4). The unadjusted results from multilevel regression analysis revealed that for combined daily fruit and vegetable intake the Teacher-led group had a higher daily mean change of 8 g (95% CI: −19, 36) compared to the RHS-led group -32 g (95% CI: −60, −3). However, after adjusting for possible confounders this difference was not significant (intervention effect: −40 g, 95% CI: −88, 1; p = 0.06). The adjusted analysis of process measures identified that if schools improved their gardening score by 3 levels (a measure of school gardening involvement - the scale has 6 levels from 0 ‘no garden’ to 5 ‘community involvement’), irrespective of group allocation, children had, on average, a daily increase of 81 g of fruit and vegetable intake (95% CI: 0, 163; p = 0.05) compared to schools that had no change in gardening score.
Conclusions: This study is the first cluster randomised controlled trial designed to evaluate a school gardening intervention. The results have found very little evidence to support the claims that school gardening alone can improve children’s daily fruit and vegetable intake. However, when a gardening intervention is implemented at a high level within the school it may improve children’s daily fruit and vegetable intake by a portion. Improving children’s fruit and vegetable intake remains a challenging task
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