799 research outputs found
A novel pathway producing dimethylsulphide in bacteria is widespread in soil environments
The volatile compound dimethylsulphide (DMS) is important in climate regulation, the sulphur cycle and signalling to higher organisms. Microbial catabolism of the marine osmolyte dimethylsulphoniopropionate (DMSP) is thought to be the major biological process generating DMS. Here we report the discovery and characterisation of the first gene for DMSP-independent DMS production in any bacterium. This gene, mddA, encodes a methyltransferase that methylates methanethiol (MeSH) and generates DMS. MddA functions in many taxonomically diverse bacteria including sediment-dwelling pseudomonads, nitrogen-fixing bradyrhizobia and cyanobacteria, and mycobacteria, including the pathogen Mycobacterium tuberculosis. The mddA gene is present in metagenomes from varied environments, being particularly abundant in soil environments, where it is predicted to occur in up to 76% of bacteria. This novel pathway may significantly contribute to global DMS emissions, especially in terrestrial environments, and could represent a shift from the notion that DMSP is the only significant precursor of DMS
Bats Use Magnetite to Detect the Earth's Magnetic Field
While the role of magnetic cues for compass orientation has been confirmed in numerous animals, the mechanism of detection is still debated. Two hypotheses have been proposed, one based on a light dependent mechanism, apparently used by birds and another based on a “compass organelle” containing the iron oxide particles magnetite (Fe3O4). Bats have recently been shown to use magnetic cues for compass orientation but the method by which they detect the Earth's magnetic field remains unknown. Here we use the classic “Kalmijn-Blakemore” pulse re-magnetization experiment, whereby the polarity of cellular magnetite is reversed. The results demonstrate that the big brown bat Eptesicus fuscus uses single domain magnetite to detect the Earths magnetic field and the response indicates a polarity based receptor. Polarity detection is a prerequisite for the use of magnetite as a compass and suggests that big brown bats use magnetite to detect the magnetic field as a compass. Our results indicate the possibility that sensory cells in bats contain freely rotating magnetite particles, which appears not to be the case in birds. It is crucial that the ultrastructure of the magnetite containing magnetoreceptors is described for our understanding of magnetoreception in animals
Do self-reported intentions predict clinicians behaviour: a systematic review.
Background: Implementation research is the scientific study of methods to promote the systematic uptake of
clinical research findings into routine clinical practice. Several interventions have been shown to be effective in
changing health care professionals' behaviour, but heterogeneity within interventions, targeted behaviours, and
study settings make generalisation difficult. Therefore, it is necessary to identify the 'active ingredients' in
professional behaviour change strategies. Theories of human behaviour that feature an individual's "intention" to
do something as the most immediate predictor of their behaviour have proved to be useful in non-clinical
populations. As clinical practice is a form of human behaviour such theories may offer a basis for developing a
scientific rationale for the choice of intervention to use in the implementation of new practice. The aim of this
review was to explore the relationship between intention and behaviour in clinicians and how this compares to
the intention-behaviour relationship in studies of non-clinicians.
Methods: We searched: PsycINFO, MEDLINE, EMBASE, CINAHL, Cochrane Central Register of Controlled
Trials, Science/Social science citation index, Current contents (social & behavioural med/clinical med), ISI
conference proceedings, and Index to Theses. The reference lists of all included papers were checked manually.
Studies were eligible for inclusion if they had: examined a clinical behaviour within a clinical context, included
measures of both intention and behaviour, measured behaviour after intention, and explored this relationship
quantitatively. All titles and abstracts retrieved by electronic searching were screened independently by two
reviewers, with disagreements resolved by discussion.
Discussion: Ten studies were found that examined the relationship between intention and clinical behaviours in
1623 health professionals. The proportion of variance in behaviour explained by intention was of a similar
magnitude to that found in the literature relating to non-health professionals. This was more consistently the case
for studies in which intention-behaviour correspondence was good and behaviour was self-reported. Though firm
conclusions are limited by a smaller literature, our findings are consistent with that of the non-health professional
literature. This review, viewed in the context of the larger populations of studies, provides encouragement for
the contention that there is a predictable relationship between the intentions of a health professional and their
subsequent behaviour. However, there remain significant methodological challenges
Methanethiol-dependent dimethylsulfide production in soil environments
Dimethylsulfide (DMS) is an environmentally important trace gas with roles in sulfur cycling, signalling to higher organisms and in atmospheric chemistry. DMS is believed to be predominantly produced in marine environments via microbial degradation of the osmolyte dimethylsulfoniopropionate (DMSP). However, significant amounts of DMS are also generated from terrestrial environments, for example, peat bogs can emit ~6 μmol DMS m−2 per day, likely via the methylation of methanethiol (MeSH). A methyltransferase enzyme termed ‘MddA’, which catalyses the methylation of MeSH, generating DMS, in a wide range of bacteria and some cyanobacteria, may mediate this process, as the mddA gene is abundant in terrestrial metagenomes. This is the first study investigating the functionality of MeSH-dependent DMS production (Mdd) in a wide range of aerobic environments. All soils and marine sediment samples tested produced DMS when incubated with MeSH. Cultivation-dependent and cultivation-independent methods were used to assess microbial community changes in response to MeSH addition in a grassland soil where 35.9% of the bacteria were predicted to contain mddA. Bacteria of the genus Methylotenera were enriched in the presence of MeSH. Furthermore, many novel Mdd+ bacterial strains were isolated. Despite the abundance of mddA in the grassland soil, the Mdd pathway may not be a significant source of DMS in this environment as MeSH addition was required to detect DMS at only very low conversion rates
GLAST: Understanding the High Energy Gamma-Ray Sky
We discuss the ability of the GLAST Large Area Telescope (LAT) to identify,
resolve, and study the high energy gamma-ray sky. Compared to previous
instruments the telescope will have greatly improved sensitivity and ability to
localize gamma-ray point sources. The ability to resolve the location and
identity of EGRET unidentified sources is described. We summarize the current
knowledge of the high energy gamma-ray sky and discuss the astrophysics of
known and some prospective classes of gamma-ray emitters. In addition, we also
describe the potential of GLAST to resolve old puzzles and to discover new
classes of sources.Comment: To appear in Cosmic Gamma Ray Sources, Kluwer ASSL Series, Edited by
K.S. Cheng and G.E. Romer
The stellar halo of the Galaxy
Stellar halos may hold some of the best preserved fossils of the formation
history of galaxies. They are a natural product of the merging processes that
probably take place during the assembly of a galaxy, and hence may well be the
most ubiquitous component of galaxies, independently of their Hubble type. This
review focuses on our current understanding of the spatial structure, the
kinematics and chemistry of halo stars in the Milky Way. In recent years, we
have experienced a change in paradigm thanks to the discovery of large amounts
of substructure, especially in the outer halo. I discuss the implications of
the currently available observational constraints and fold them into several
possible formation scenarios. Unraveling the formation of the Galactic halo
will be possible in the near future through a combination of large wide field
photometric and spectroscopic surveys, and especially in the era of Gaia.Comment: 46 pages, 16 figures. References updated and some minor changes.
Full-resolution version available at
http://www.astro.rug.nl/~ahelmi/stellar-halo-review.pd
Cues for Early Social Skills: Direct Gaze Modulates Newborns' Recognition of Talking Faces
Previous studies showed that, from birth, speech and eye gaze are two important
cues in guiding early face processing and social cognition. These studies tested
the role of each cue independently; however, infants normally perceive speech
and eye gaze together. Using a familiarization-test procedure, we first
familiarized newborn infants (n = 24) with videos of
unfamiliar talking faces with either direct gaze or averted gaze. Newborns were
then tested with photographs of the previously seen face and of a new one. The
newborns looked longer at the face that previously talked to them, but only in
the direct gaze condition. These results highlight the importance of both speech
and eye gaze as socio-communicative cues by which infants identify others. They
suggest that gaze and infant-directed speech, experienced together, are powerful
cues for the development of early social skills
The influence of institutional factors on corporate narratives: a thematic content analysis of Guinness
This paper provides a thematic content analysis of the Chairman’s Statement of Arthur Guinness & Son Ltd over time. The analysis traces the evolution of the content over four distinct periods using a coding scheme developed from extant research. The objective is to study whether the corporate narratives change in line with the institutional factors over time. To interpret the results, we draw on an institutional theory-based lens to offer potential explanations of some of the change and stability noted. Institutions can constrain behaviour, but they can also support and empower agents to bring about change. The results of the longitudinal content analysis reveals some variations over time, but in general the content is relatively stable. This may be explained by the organisation itself being an institution that is sufficiently institutionalised so that corporate reporting remained relatively stable. This suggests Guinness may be an example of a strong institution over time. "The final, definitive version of this paper has been published in Accounting History, 2020, 25(3), 425-447, published by SAGE Publishing. Available online: https://doi.org/10.1177/1032373219881811. DOI: 10.1177/1032373219881811. Please
cite the published version.
TESS hunt for young and maturing exoplanets (THYME). VI. an 11 Myr giant planet transiting a very-low-mass star in lower centaurus crux
Mature super-Earths and sub-Neptunes are predicted to be ≃ Jovian radius when younger than 10 Myr. Thus, we expect to find 5–15 R⊕ planets around young stars even if their older counterparts harbor none. We report the discovery and validation of TOI 1227b, a 0.85 ± 0.05 RJ (9.5 R⊕) planet transiting a very-low-mass star (0.170 ± 0.015 M⊙) every 27.4 days. TOI 1227's kinematics and strong lithium absorption confirm that it is a member of a previously discovered subgroup in the Lower Centaurus Crux OB association, which we designate the Musca group. We derive an age of 11 ± 2 Myr for Musca, based on lithium, rotation, and the color–magnitude diagram of Musca members. The TESS data and ground-based follow-up show a deep (2.5%) transit. We use multiwavelength transit observations and radial velocities from the IGRINS spectrograph to validate the signal as planetary in nature, and we obtain an upper limit on the planet mass of ≃0.5 MJ. Because such large planets are exceptionally rare around mature low-mass stars, we suggest that TOI 1227b is still contracting and will eventually turn into one of the more common <5 R⊕ planets
Expanding ART for Treatment and Prevention of HIV in South Africa: Estimated Cost and Cost-Effectiveness 2011-2050
Background: Antiretroviral Treatment (ART) significantly reduces HIV transmission. We conducted a cost-effectiveness analysis of the impact of expanded ART in South Africa. Methods: We model a best case scenario of 90% annual HIV testing coverage in adults 15-49 years old and four ART eligibility scenarios: CD4 count <200 cells/mm3(current practice), CD4 count <350, CD4 count <500, all CD4 levels. 2011-2050 outcomes include deaths, disability adjusted life years (DALYs), HIV infections, cost, and cost per DALY averted. Service and ART costs reflect South African data and international generic prices. ART reduces transmission by 92%. We conducted sensitivity analyses. Results: Expanding ART to CD4 count <350 cells/mm3prevents an estimated 265,000 (17%) and 1.3 million (15%) new HIV infections over 5 and 40 years, respectively. Cumulative deaths decline 15%, from 12.5 to 10.6 million; DALYs by 14% from 109 to 93 million over 40 years. Costs drop 3.9 billion over 40 years with breakeven by 2013. Compared with the current scenario, expanding to <500 prevents an additional 585,000 and 3 million new HIV infections over 5 and 40 years, respectively. Expanding to all CD4 levels decreases HIV infections by 3.3 million (45%) and costs by 0.6 billion versus current; other ART scenarios cost 17.5 billion. Sensitivity analyses suggest that poor retention and predominant acute phase transmission reduce DALYs averted by 26% and savings by 7%. Conclusion: Increasing the provision of ART to <350 cells/mm3 may significantly reduce costs while reducing the HIV burden. Feasibility including HIV testing and ART uptake, retention, and adherence should be evaluated
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