3,694 research outputs found
The Ionization Fraction in Dense Molecular Gas II: Massive Cores
We present an observational and theoretical study of the ionization fraction
in several massive cores located in regions that are currently forming stellar
clusters. Maps of the emission from the J = 1-> O transitions of C18O, DCO+,
N2H+, and H13CO+, as well as the J = 2 -> 1 and J = 3 -> 2 transitions of CS,
were obtained for each core. Core densities are determined via a large velocity
gradient analysis with values typically 10^5 cm^-3. With the use of
observations to constrain variables in the chemical calculations we derive
electron fractions for our overall sample of 5 cores directly associated with
star formation and 2 apparently starless cores. The electron abundances are
found to lie within a small range, -6.9 < log10(x_e) < -7.3, and are consistent
with previous work. We find no difference in the amount of ionization fraction
between cores with and without associated star formation activity, nor is any
difference found in electron abundances between the edge and center of the
emission region. Thus our models are in agreement with the standard picture of
cosmic rays as the primary source of ionization for molecular ions. With the
addition of previously determined electron abundances for low mass cores, and
even more massive cores associated with O and B clusters, we systematically
examine the ionization fraction as a function of star formation activity. This
analysis demonstrates that the most massive sources stand out as having the
lowest electron abundances (x_e < 10^-8).Comment: 35 pages (8 figures), using aaspp4.sty, to be published in
Astrophysical Journa
Column Supported Embankments with Geosynthetic Encased Columns: Validity of the Unit Cell Concept
Abstract: Column supported embankments (CSEs) are used to overcome common problems associated with the construction of embankments over soft compressible soils. The use of granular columns as deep foundation elements for CSEs can be problematic in soft soils due to the lack of adequate lateral confining pressure, particularly in the upper portion of the column. Using a high-strength geosynthetic for granular column confinement forms geosynthetic encased columns (GECs); the confinement imposed by the geosynthetic increases the strength of the column, and also prevents its lateral displacement into the soft surrounding soil. This paper presents the results of finite element analyses of a hypothetical geosynthetic reinforced column supported embankment (GRCSE) (i.e., a CSE underlain by geosynthetic reinforcement) that is constructed with GECs as the deep foundation elements. Full three-dimensional (3-d), 3-d unit cell, and axisymmetric unit cell analyses of the GRCSE were carried out to investigate the validity of the unit cell concept. The effect of the degree of nodal constraint along the bottom boundary when numerically modeling GRCSEs was also studied in this paper. Numerical results show that a full 3-d idealization is required to more precisely determine the tension forces that are produced in the geosynthetic reinforcement that underlies the GRCSE. A number of design parameters such as the average vertical stresses carried by the GECs, lateral displacement of the GECs, and the maximum settlement of the soft foundation soil, however, can be successfully calculated using unit cell analyses
First results from a VLBA proper motion survey of H2O masers in low-mass YSOs: the Serpens core and RNO15-FIR
This article reports first results of a long-term observational program aimed
to study the earliest evolution of jet/disk systems in low-mass YSOs by means
of VLBI observations of the 22.2 GHz water masers. We report here data for the
cluster of low-mass YSOs in the Serpens molecular core and for the single
object RNO~15-FIR. Towards Serpens SMM1, the most luminous sub-mm source of the
Serpens cluster, the water maser emission comes from two small (< 5 AU in size)
clusters of features separated by ~25 AU, having line of sight velocities
strongly red-shifted (by more than 10 km/s) with respect to the LSR velocity of
the molecular cloud. The two maser clusters are oriented on the sky along a
direction that is approximately perpendicular to the axis of the radio
continuum jet observed with the VLA towards SMM1. The spatial and velocity
distribution of the maser features lead us to favor the interpretation that the
maser emission is excited by interaction of the receding lobe of the jet with
dense gas in the accretion disk surrounding the YSO in SMM1. Towards
RNO~15-FIR, the few detected maser features have both positions and (absolute)
velocities aligned along a direction that is parallel to the axis of the
molecular outflow observed on much larger angular scales. In this case the
maser emission likely emerges from dense, shocked molecular clumps displaced
along the axis of the jet emerging from the YSO. The protostar in Serpens SMM1
is more massive than the one in RNO~15-FIR. We discuss the case where a high
mass ejection rate can generate jets sufficiently powerful to sweep away from
their course the densest portions of circumstellar gas. In this case, the
excitation conditions for water masers might preferably occur at the interface
between the jet and the accretion disk, rather than along the jet axis.Comment: 18 pages (postscript format); 9 figures; to be published into
Astronomy & Astrophysics, Main Journa
Hearing the voices of older adult patients: processes and findings to inform health services research
Background
Clinical academic research and service improvement is planned using Patient and Public Involvement and Engagement (PPIE) but older PPIE participants are consulted less often due to the perception that they are vulnerable or hard to engage.
Objectives
To consult frail older adults about a recently adopted service, discharge to assess (D2A), and to prioritise services improvements and research topics associated with the design and delivery of discharge from hospital. To use successive PPIE processes to enable a permanent PPIE panel to be established.
Participants
Following guidance from an established hospital PPI panel 27 older adult participants were recruited. Participants from Black, Asian and Minority Ethnic (BAME) communities, affluent and non-affluent areas and varied social circumstances were included.
Methods
Focus groups and individual interviews were conducted in participants own homes or nearby social venues.
Results
Priorities for discharge included remaining independent despite often feeling lonely at home; to remain in hospital if needed; and for services to ensure effective communication with families. The main research priority identified was facilitating independence, whilst establishing a permanent PPIE panel involving older adults was viewed favourably.
Conclusions
Taking a structured approach to PPIE enabled varied older peoplesâ voices to express their priorities and concerns into early discharge from hospital, as well as enabling the development of health services research into hospital discharge planning and management. Older people as participants identified research priorities after reflecting on their experiences. Listening and reflection enabled researchers to develop a new âCommunity PPIE Elders Panelâ to create an enduring PPIE infrastructure for frail older housebound people to engage in research design, development and dissemination
Every child mattered in England: but what matters to children?
âEvery Child Mattersâ under New Labour provided a framework for services for young childrenâs care and education. It was pushed aside by the Conservative led coalition and replaced by âMore Great Childcareâ. The UK as a signatory to the United Nations Convention on the Rights of the Child, and therefore has obligations for legislation, policy and curriculum, specifically with regard to childrenâs rights and participation. On the 25th anniversary of the UNCRC, in practice there may be different levels of participation employed to engage childrenâs views in the development of policy about them. This project set out to ask children about what âmattersâ to them. Ninety finalist Early Childhood Studies students worked as co-researchers in this project. Five themes are discussed highlighting the powerful thoughts and ideas of children. A range of âchild-friendlyâ methods were used to collect data from children including role-play, interviews, drawings and artefacts, and story-telling
Sustainable Polymers: New 4-H STEM Curricula
There are many environmental issues surrounding the global production and use of plastics. Three science curricula (Grades K-2, 3-5, and 6-8) were developed to introduce youth to the past, present, and future of plastics. Designed using research-based methods and grounded in effective science pedagogy, the curricula provide young people opportunities to explore viable alternatives to plastics and develop knowledge and skills necessary to help mitigate environmental impacts associated with the production, use and disposal of plastics. Evaluation results demonstrated that youth improved their understanding of polymers and intention to help reduce impacts of plastics on the environment
The interlayer cohesive energy of graphite from thermal desorption of polyaromatic hydrocarbons
We have studied the interaction of polyaromatic hydrocarbons (PAHs) with the
basal plane of graphite using thermal desorption spectroscopy. Desorption
kinetics of benzene, naphthalene, coronene and ovalene at sub-monolayer
coverages yield activation energies of 0.50 eV, 0.85 eV, 1.40 eV and 2.1 eV,
respectively. Benzene and naphthalene follow simple first order desorption
kinetics while coronene and ovalene exhibit fractional order kinetics owing to
the stability of 2-D adsorbate islands up to the desorption temperature.
Pre-exponential frequency factors are found to be in the range
- as obtained from both Falconer--Madix (isothermal
desorption) analysis and Antoine's fit to vapour pressure data. The resulting
binding energy per carbon atom of the PAH is 5 meV and can be identified
with the interlayer cohesive energy of graphite. The resulting cleavage energy
of graphite is ~meV/atom which is considerably larger than previously
reported experimental values.Comment: 8 pages, 4 figures, 2 table
Hypofractionated Stereotactic Ablative Radiotherapy for Recurrent or Oligometastatic Tumours in Children and Young Adults
AIMS
Cancer remains a leading cause of death in children and adolescents in the developed world. Despite advances in oncological management, rates of primary treatment failure remain significant. Radiation of recurrent or metastatic disease improves survival in adults but there is little data to support clinical decision making in the paediatric/teenage and young adult population.
Materials And Methods
We present a retrospective case series of 14 patients treated with stereotactic ablative body radiotherapy or stereotactic radiosurgery at The Royal Marsden Hospital from September 2011 to December 2015. Eligible patients were aged <25 years, with Lansky/Karnofsky performance status â„60 with confirmed relapsed or metastatic tumour in fewer than three sites. Follow-up was in accordance with standard clinical care and included regular outpatient review and radiological surveillance. Local control, progression-free survival and overall survival are presented.
RESULTS
Data for 14 patients with 18 treated lesions were included. The median patient age was 15 years (range 5â20 years). Nine patients were treated for local recurrence and five for metastatic lesions. All patients had already undergone multiple previous treatments. Eleven patients had undergone previous radiotherapy. The median interval between the completion of initial radiotherapy and reirradiation was 29.0 months (range 0.2â49.5 months). The median follow-up was 3.4 years (range 0.28â6.4 years). The 1-year local control rate was 78.6% and the 2-year local control rate was 57.1%. Overall median survival was 58.4 months (95% confidence interval 33.8â82.9 months). Cumulative biologically effective doses (BED) over 200 Gy were associated with late toxicity (P = 0.04).
CONCLUSION
Radical doses of short-course hypofractionated radiotherapy can achieve excellent local control and may contribute to the prolongation of overall survival. There is a need for prospective trials exploring the use of ablative radiotherapy in metastatic disease in paediatric/teenage and young adult patients in order to establish safe and effective treatment schedules
Poor oral health including active caries in 187 UK professional male football players: clinical dental examination performed by dentists
The few studies that have assessed oral health in professional/elite football suggest poor oral health with minimal data on impact on performance. The aim of this research was to determine oral health in a representative sample of professional footballers in the UK and investigate possible determinants of oral health and self-reported impact on well-being, training and performance
Impact of Spiritual Well-Being, Spiritual Perspective, and Religiosity on the Self-Rated Health of Jordanian Arab Christians
The purpose of this study was to explore associations of spiritual well-being, spiritual perspective, and religiosity with self-rated health in a convenience sample of 340 adult Jordanian Arab Christians. Data were collected through church and community groups. Results indicated that spiritual well-being and religiosity were positively associated with self-rated health, but in the final regression model only spiritual well-being retained a significant association after controlling for the other spiritual and religious measures. In conclusion, spirituality and religiosity are important to Jordanian Arab Christiansâ health and well-being, and the implications for nursing practice are explored
- âŠ