11,801 research outputs found
Fluorine in the solar neighborhood - is it all produced in AGB-stars?
The origin of 'cosmic' fluorine is uncertain, but there are three proposed
production sites/mechanisms: AGB stars, nucleosynthesis in Type II
supernovae, and/or the winds of Wolf-Rayet stars. The relative importance of
these production sites has not been established even for the solar
neighborhood, leading to uncertainties in stellar evolution models of these
stars as well as uncertainties in the chemical evolution models of stellar
populations.
We determine the fluorine and oxygen abundances in seven bright, nearby
giants with well-determined stellar parameters. We use the 2.3 m
vibrational-rotational HF line and explore a pure rotational HF line at 12.2
m. The latter has never been used before for an abundance analysis. To be
able to do this we have calculated a line list for pure rotational HF lines. We
find that the abundances derived from the two diagnostics agree.
Our derived abundances are well reproduced by chemical evolution models only
including fluorine production in AGB-stars and therefore we draw the conclusion
that this might be the main production site of fluorine in the solar
neighborhood. Furthermore, we highlight the advantages of using the 12 m
HF lines to determine the possible contribution of the -process to the
fluorine budget at low metallicities where the difference between models
including and excluding this process is dramatic
TEXES Observations of M Supergiants: Dynamics and Thermodynamics of Wind Acceleration
We have detected [Fe II] 17.94 um and 24.52 um emission from a sample of M
supergiants using TEXES on the IRTF. These low opacity emission lines are
resolved at R = 50, 000 and provide new diagnostics of the dynamics and
thermodynamics of the stellar wind acceleration zone. The [Fe II] lines, from
the first excited term, are sensitive to the warm plasma where energy is
deposited into the extended atmosphere to form the chromosphere and wind
outflow. These diagnostics complement previous KAO and ISO observations which
were sensitive to the cooler and more extended circumstellar envelopes. The
turbulent velocities, Vturb is about 12 to 13 km/s, observed in the [Fe II]
forbidden lines are found to be a common property of our sample, and are less
than that derived from the hotter chromospheric C II] 2325 Angstrom lines
observed in alpha Ori, where Vturb is about 17 to 19 km/s. For the first time,
we have dynamically resolved the motions of the dominant cool atmospheric
component discovered in alpha Ori from multi-wavelength radio interferometry by
Lim et al. (1998). Surprisingly, the emission centroids are quite Gaussian and
at rest with respect to the M supergiants. These constraints combined with
model calculations of the infrared emission line fluxes for alpha Ori imply
that the warm material has a low outflow velocity and is located close to the
star. We have also detected narrow [Fe I] 24.04 um emission that confirms that
Fe II is the dominant ionization state in alpha Ori's extended atmosphere.Comment: 79 pages including 10 figures and 2 appendices. Accepted by Ap
Adult attachment style as a risk factor for maternal postnatal depression: a systematic review.
BACKGROUND: Postnatal depression (PND) is an important health problem of global relevance for maternal health and impacts on the health and wellbeing of the child over the life-course. Multinational data is hard to locate, the economic burden of PND on health care systems have been calculated in several countries, including Canada and in the UK. In Canada, health and social care costs for a mother with PND were found to be just over twice that of mothers with no mental illness. The extra community care cost for women with PND living in the UK was found to be £35.7 million per year. METHOD: We carried out a systematic search to the literature to investigate the associations between attachment style and PND, using meta-narrative analysis methods, reporting statistical data and life narratives. The following databases were searched: PsycInfo, PsycExtra Web of Science, The Cochrane Library and Pubmed. We focused on research papers that examined adult attachment styles and PND, and published between 1991 and 2013. We included any papers showing relationship between maternal adult attachment and PND. Out of 353 papers, 20 met the study inclusion criteria, representing a total of 2306 participants. Data from these 20 studies was extracted by means of a data extraction table. RESULTS: We found that attachment and PND share a common aetiology and that 'insecure adult attachment style' is an additional risk factor for PND. Of the insecure adult attachment styles, anxious styles were found to be associated with PND symptoms more frequently than avoidant or dismissing styles of attachment. CONCLUSION: More comprehensive longitudinal research would be crucial to examine possible cause-effect associations between adult attachment style (as an intergenerational construct and risk factor) and PND (as an important maternal mental health), with new screening and interventions being essential for alleviating the suffering and consequences of PND. If more is understood about the risk profile of a new or prospective mother, more can be done to prevent the illness trajectory (PND); as well as making existing screening measures and treatment options more widely available
Spatiotemporal changes to low flow and catchment storage following a step change rainfall decline in Southwest Western Australia
Understanding how summer low flows in a Mediterranean climate are influenced by climate and land use is critical for managing both water resources and in-stream ecohydrological health. The Eucalyptus forest ecosystems of southwestern Australia are experiencing a drying and warming climate, with a regional step decline in rainfall in the mid-1970s. Reductions in catchment water storage may be exacerbated by the deep rooting habit of key overstorey species (>30 m has been reported), which can buffer against drought during dry years. Root exploitation of deep soil moisture reserves and/or groundwater can accelerate the long term decline in summer low flows, with a trend towards more ephemeral flow regimes. In contrast, conversion of forests to agricultural land in some catchments can lead to counter-trends of increased low flows due to a rise in groundwater pressure. These are invariably associated with an increase in stream salinity as regolith stores of salt are mobilized. There has also been extennsive reforestation of farmland in some catchments.
In this study we perform a detailed analysis of changes to annual summer seven day low flow trends in perennial catchments and flow duration curves in ephemeral catchments across 39 catchments in south-western Australia that have long term records of runoff, rainfall and land cover. Results showed that 15% of catchments exhibited increased low flows and 85% decreased flows or decreased flow days since the 1970s. Significant downward step changes in low flows were observed in 17 catchments (44%). The earliest downward step changes occurred in three catchments between 1981-82 (a lag of one decade after the rainfall decline), with the most recent step changes for five catchments occurring in 2001-2004 (three decades after rainfall decline). Eleven catchments were already ephemeral in the 1970s, but exhibited continued declines in the number of annual flow days over subsequent decades. Step changes occur when groundwater becomes disconnected or reconnected to the stream invert, with disconnection associated with rainfall decline and vegetative water use.
The statistical methods we used in this study can be applied to any catchment in order to aid land and water managers assess the impact of climate change and land cover manipulation on low flow response
Are children living with obesity more likely to experience musculoskeletal symptoms during childhood? A linked longitudinal cohort study using primary care records.
OBJECTIVE: To assess whether there is a higher incidence of musculoskeletal consultations in general practice among children with obesity. DESIGN: Longitudinal SETTING: 285 north-east London general practitioners (GPs). PARTICIPANTS: 63 418 (50.9% boys) Reception and 55 364 (50.8% boys) Year 6 National Child Measurement Programme (NCMP) participants, linked to GP electronic health records (EHRs). MAIN OUTCOME MEASURE: A GP consultation with a recorded musculoskeletal symptom or diagnosis. METHODS: We calculated proportions with a musculoskeletal consultation by ethnic-adjusted weight status (underweight <2nd; overweight ≥91st; obese ≥98th centile), sex, ethnicity, and area-level deprivation. We estimated mutually-adjusted hazard ratios (HR) and 95% confidence intervals (95% CI) using Cox's proportional regression models stratified by school year and sex. RESULTS: We identified 1868 (3.0%) Reception and 4477 (8.1%) Year 6 NCMP participants with at least one musculoskeletal consultation. In adjusted analyses, Reception year girls with a body mass index (BMI) classified as overweight (HR 1.24, 95% CI 1.02 to 1.52) or obese (HR 1.67, 95% CI 1.35 to 2.06) were more likely to have at least one musculoskeletal consultation. Year 6 girls with obesity were more likely (HR 1.20, 95% CI 1.07 to 1.35), and boys with a BMI in the underweight range were less likely (HR 0.39, 95% CI 0.21 to 0.73), to have a musculoskeletal consultation. CONCLUSIONS: Girls living with obesity at the start or end of primary school are more likely to attend their GP for a musculoskeletal consultation. Routine linkage of NCMP data to EHRs provides useful insights into childhood health conditions related to excess weight in early childhood. Recognition of obesity as a contributing factor for musculoskeletal symptoms may inform clinical management, particularly in girls
Quantifying model uncertainty to improve watershed-level ecosystem service quantification: a global sensitivity analysis of the RUSLE
Ecosystem service-support tools are commonly used to guide natural resource management. Often, empirically based models are preferred due to low data requirements, simplicity and clarity. Yet, uncertainty produced by local context or parameter estimation remains poorly quantified and documented. We assessed model uncertainty of the Revised Universal Soil Loss Equation – RUSLE developed mainly from US data. RUSLE is the most commonly applied model to assess watershed-level soil loss. We performed a global sensitivity analysis (GSA) on RUSLE with four dissimilar datasets to understand uncertainty and to provide recommendations for data collection and model parameterization. The datasets cover varying spatial levels (plot, watershed and continental) and environmental conditions (temperate and tropical). We found cover management and topography create the most uncertainty regardless of environmental conditions or data parameterization techniques. The importance of other RUSLE factors varies across contexts. We argue that model uncertainty could be reduced through better parameterization of cover management and topography factors while avoiding severe soil losses by targeting soil conservation practices in areas where both factors interact and enhance soil loss. We recommend incorporating GSA to assess empirical models’ uncertainty, to guide model parameterization and to target soil conservation efforts
Water vapor on supergiants. The 12 micron TEXES spectra of mu Cephei
Several recent papers have argued for warm, semi-detached, molecular layers
surrounding red giant and supergiant stars, a concept known as a MOLsphere.
Spectroscopic and interferometric analyses have often corroborated this general
picture. Here, we present high-resolution spectroscopic data of pure rotational
lines of water vapor at 12 microns for the supergiant mu Cephei. This star has
often been used to test the concept of molecular layers around supergiants.
Given the prediction of an isothermal, optically thick water-vapor layer in
Local Thermodynamic Equilibrium around the star (MOLsphere), we expected the 12
micron lines to be in emission or at least in absorption but filled in by
emission from the molecular layer around the star. Our data, however, show the
contrary; we find definite absorption. Thus, our data do not easily fit into
the suggested isothermal MOLsphere scenario. The 12 micron lines, therefore,
put new, strong constraints on the MOLsphere concept and on the nature of water
seen in signatures across the spectra of early M supergiants. We also find that
the absorption is even stronger than that calculated from a standard,
spherically symmetric model photosphere without any surrounding layers. A cool
model photosphere, representing cool outer layers is, however, able to
reproduce the lines, but this model does not account for water vapor emission
at 6 microns. Thus, a unified model for water vapor on mu Cephei appears to be
lacking. It does seem necessary to model the underlying photospheres of these
supergiants in their whole complexity. The strong water vapor lines clearly
reveal inadequacies of classical model atmospheres.Comment: Accepted for publication in the Astrophysical Journa
Dealing with mobility: Understanding access anytime, anywhere
The rapid and accelerating move towards the adoption and use of mobile technologies has increasingly provided people and organisations with the ability to work away from the office and on the move. The new ways of working afforded by these technologies are often characterised in terms of access to information and people ‘anytime, anywhere’. This paper presents a study of mobile workers that highlights different facets of access to remote people and information, and different facets of anytime, anywhere. Four key factors in mobile work are identified from the study: the role of planning, working in ‘dead time’, accessing remote technological and informational resources, and monitoring the activities of remote colleagues. By reflecting on these issues, we can better understand the role of technology and artefact use in mobile work and identify the opportunities for the development of appropriate technological solutions to support mobile workers
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