6,000 research outputs found
B stars as a diagnostic of star-formation at low and high redshift
We have extended the evolutionary synthesis models by Leitherer et al.
(1999b) by including a new library of B stars generated from the IUE
high-dispersion spectra archive. We present the library and show how the
stellar spectral properties vary according to luminosity classes and spectral
types. We have generated synthetic UV spectra for prototypical young stellar
populations varying the IMF and the star formation law. Clear signs of age
effects are seen in all models. The contribution of B stars in the UV line
spectrum is clearly detected, in particular for greater ages when O stars have
evolved. With the addition of the new library we are able to investigate the
fraction of stellar and interstellar contributions and the variation in the
spectral shapes of intense lines. We have used our models to date the spectrum
of the local super star cluster NGC1705-1. Photospheric lines of CIII1247,
SiIII1417, and SV1502 were used as diagnostics to date the burst of NGC 1705-1
at 10 Myr. We have selected the star-forming galaxy 1512-cB58 as a first
application of the new models to high-z galaxies. This galaxy is at z=2.723, it
is gravitationally lensed, and its high signal-to-noise Keck spectrum show
features typical of local starburst galaxies, such as NGC 1705-1. Models with
continuous star formation were found to be more adequate for 1512-cB58 since
there are spectral features typical of a composite stellar population of O and
B stars. A model with Z =0.4Z_solar and an IMF with alpha=2.8 reproduces the
stellar features of the 1512-cB58 spectrum.Comment: 23 pages with figures, see
http://sol.stsci.edu/~demello/welcomeb.htm
The ‘co’ in co-production of climate action: challenging boundaries within and between science, policy and practice
Effective action taken against climate change must find ways to unite scientific and practice-based knowledges associated with the various stakeholders who see themselves as invested in the global delivery of climate governance. Political decision-makers, climate scientists and practitioners approach this challenge from what are often radically different perspectives and experiences. While considerable work has been done to develop the idea of ‘co-production’ in the development of climate action outputs, questions remain over how to best unite the contrasting epistemological traditions and norms associated with different stakeholders. Drawing on the existing literatures on climate action co-production and from translational perspectives on the science-policy interface, in this paper we develop the concept of ‘boundary agency’. Defining this as the agency ‘possessed’ when willing and able to translate between different epistemological communities invested in a similar policy and governance challenge such as climate change, we offer it as a useful means to reflect on participants’ understanding of the ‘co’ in co-production. This is in contrast to the more established (often academic-led) focus on what it is that is being produced by co-production processes. We draw from two complementary empirical studies, which explicitly encouraged i) engagement and ii) reflection on cross-boundary co-production between climate action stakeholders from different backgrounds. Reflecting on the two studies, we discuss the benefits of (and barriers to) encouraging more active and sustained engagement between climate action stakeholders so as to try to actively blur the boundaries between science and policy and, in doing so, invent new epistemological communities of practice
Everyday cosmopolitanism in representations of Europe among young Romanians in Britain
The paper presents an analysis of everyday cosmopolitanism in constructions of Europe among young Romanian nationals living in Britain. Adopting a social representations approach, cosmopolitanism is understood as a cultural symbolic resource that is part of everyday knowledge. Through a discursively-oriented analysis of focus group data, we explore the ways in which notions of cosmopolitanism intersect with images of Europeanness in the accounts of participants. We show that, for our participants, representations of Europe are anchored in an Orientalist schema of West-vs.-East, whereby the West is seen as epitomising European values of modernity and progress, while the East is seen as backward and traditional. Our findings further show that representations of cosmopolitanism reinforce this East/West dichotomy, within a discourse of ‘Occidental cosmopolitanism’. The paper concludes with a critical discussion of the diverse and complex ideological foundations of these constructions of European cosmopolitanism and their implications
FUSE Observations of a Full Orbit of Hercules X-1: Signatures of Disk, Star, and Wind
We observed an entire 1.7 day orbit of the X-ray binary Hercules X-1 with the
Far Ultraviolet Spectroscopic Explorer (FUSE). Changes in the O VI 1032,1037
line profiles through eclipse ingress and egress indicate a Keplerian accretion
disk spinning prograde with the orbit. These observations may show the first
double-peaked accretion disk line profile to be seen in the Hercules X-1
system. Doppler tomograms of the emission lines show a bright spot offset from
the Roche lobe of the companion star HZ Her, but no obvious signs of the
accretion disk. Simulations show that the bright spot is too far offset from
the Roche lobe to result from uneven X-ray heating of its surface. The absence
of disk signatures in the tomogram can be reproduced in simulations which
include absorption from a stellar wind. We attempt to diagnose the state of the
emitting gas from the C III 977, C III 1175, and N III 991 emission lines. The
latter may be enhanced through Bowen fluorescence.Comment: Accepted for publication in The Astrophysical Journa
The temporal relationship between the neural and vascular actions of kallidin within the nose
The time course of effect of the B2-receptor agonist kallidin (K) on induced changes of nasal airflow, rhinorrhoea, nasal pain, sneezing and nasal microvascular leakage has been examined and compared with its B2 metabolite agonist bradykinin (B) and the B1-agonist [des-arg9]-bradykinin (D). When administered as a single dose K and B induced an immediate sensation of pain, rhinorrhoea, elevations in lavage albumin and protein levels and a sustained increase in nasal airways resistance (NAR) for 5–40 min post-challenge. [des-arg9]-Bradykinin and vehicle placebo (V) were without effect on any of these indices. These studies identify the action of K and B within the nose and differentiate the neural and vascular effects of these kinins in addition to suggesting the potential that nasal blockage and nasal microvascular leakage represent alterations in differing vascular compartments. These findings have implications for the understanding and therapeutic manipulation of rhinitis
Aquaculture and eelgrass Zostera marina interactions in temperate ecosystems
This paper reviews the impacts of shellfish and finfish aquaculture on eelgrassZostera marina, the most widely distributed seagrass species in the northern hemisphere. Shellfish aquaculture can have positive, neutral, and negative effects on eelgrass. Positive interactions can be generated by the filtering activity of cultured bivalves, which may improve water quality and reduce epiphyte loads, and shellfish biodeposits may provide more nutrients to eelgrass and other vegetation. However, negative responses are more commonly reported and can be causedby shading and sedimentation. These negative effects tend to occur directly under and immediately surrounding shellfish farms and rapidly diminish with increasing distance. In contrast to shellfish aquaculture, only one field study has investigated the effects of finfish aquaculture on eelgrass in a temperate setting, and the results were inconclusive. However, many studies have investigated the effects of Mediterranean finfish farms on 2 other species of seagrass (Posidoniaoceanica and Cymodocea nodosa). These studies reported clear negative interactions, which have been linked to increased nutrient concentrations, sulphides, sedimentation, epiphyte loads, and grazing pressure. It is unknown if these studies are relevant for finfish aquaculture in temperate regions due to differences in environmental conditions, and because the studies focused on differ-ent species of seagrass. Thus, further study in a temperate setting is warranted. We conclude by highlighting key research gaps that could help regulators establish unambiguous operational and siting guidelines that minimize the potential for negative interactions between aquaculture and eelgrass
Advancing methodology for scoping reviews: recommendations arising from a scoping literature review (SLR) to inform transformation of Children and Adolescent Mental Health Services
Background
There is consensus that health services commissioning and clinical practice should be driven by scientific evidence. However, workload pressures, accessibility of peer reviewed publications and skills to find, appraise, and synthesise relevant evidence are often cited as barriers to uptake of research evidence by practitioners and commissioners alike. In recent years a growing requirement for rapid evidence synthesis to inform commissioning decisions about healthcare service delivery and provision of care contributed to an increasing popularity of scoping literature reviews (SLRs). Yet, comprehensive guidelines for conducting and reporting SLRs are still relatively scarce.
Methods
The exemplar review used as a worked example aimed to provide a readily available, comprehensive, and user-friendly repository of research evidence for local commissioners to help them make evidence-informed decisions about redesigning East of England Children and Adolescent Mental Health Services. In conducting the review, we were broadly guided by Arksey and O’Malley’s framework, however some modifications were made at different stages to better reflect the largely pragmatic objective of this review. This paper compares the methodology used with existing methodological frameworks for scoping studies, to add to the existing knowledge base.
Results
We proposed the following advancements to the existing SLR frameworks: (i) Assemble a research team with complementary skills and expertise; (ii); Draw on expertise of external partners, particularly practitioners, decision-makers and commissioners who will be translating findings into practice; (iii) Pre-register the review protocol. Keep a detailed record of all steps and decisions and consider how they would impact on generalisability and utility of review findings; (iv) Use systematic procedures for literature searchers, selection of studies, data extraction and analysis; (v) If feasible, appraise the quality of included evidence; (vi) Be transparent about limitations of findings.
Conclusions
Despite some methodological limitations, scoping literature reviews are a useful method of rapidly synthesising a large body of evidence to inform commissioning and transformation of CAMHS. SLRs allow researchers to start with a broader questions, to explore the issue from different perspectives and perhaps find more comprehensive solutions that are not only effective, but also accounted for their feasibility and acceptability to key stakeholders
Enhancement of electron magnetic susceptibility due to many-body interactions in monolayer MoSe
Employing the original, all-optical method, we quantify the magnetic
susceptibility of a two-dimensional electron gas (2DEG) confined in the
MoSe monolayer in the range of low and moderate carrier densities. The
impact of electron-electron interactions on the 2DEG magnetic susceptibility is
found to be particularly strong in the limit of, studied in detail, low carrier
densities. Following the existing models, we derive for the
bare (single particle) g-factor of the ground state electronic band in the
MoSe monolayer. The derived value of this parameter is discussed in the
context of estimations from other experimental approaches. Surprisingly, the
conclusions drawn differ from theoretical ab-initio studies
TERC polymorphisms are associated both with susceptibility to colorectal cancer and with longer telomeres.
Shorter telomeres have been associated with increased risk of malignancy, including colorectal cancer (CRC). Telomere length is heritable and may be an intermediate phenotype linked to genetic susceptibility to CRC
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