1,882 research outputs found
First detection of a low-mass stellar halo around the young open cluster Eta Chamaeleontis
We have identified several lithium-rich low-mass (0.08<M<0.3 Msun) stars
within 5.5 deg of the young open cluster Eta Chamaeleontis, nearly four times
the radius of previous search efforts. Of these stars we propose 4 new probable
cluster members, and 3 possible members requiring further investigation. These
findings are consistent with a dynamical origin for the current configuration
of the cluster, without the need to invoke an abnormal Initial Mass Function
deficient in low-mass objects. Candidates were selected on the basis of DENIS
and 2MASS photometry, NOMAD astrometry and extensive follow-up spectroscopy.Comment: 5 Pages. 5 Figures and 1 Table. Accepted for publication in MNRAS
Letters. Higher resolution figures available at
http://www.mso.anu.edu.au/~murphysj/
Venturing into schools : locating mental health initiatives in complex environments
Schools provide viable settings for mental health promotion initiatives, such as programs to develop students’ social and emotional capabilities (SEC). Complexity in the school
environments into which initiatives are introduced, such as diverse student capabilities,
school structures, and teachers’ knowledge and confidence, will play an integral role in the success of those initiatives. This paper investigates the environments of schools about to receive the KidsMatter mental heath promotion, prevention and early intervention initiative in Australia, using information sourced from questionnaires about 2598 students and their teachers in 50 Australian primary schools. The focus of the report is on the status of the schools’ work in one of the key focus areas for the intervention, namely students’ SEC. Analysis showed relatively high levels of students’ SEC across the whole sample, but with sub-group differences. Teachers’ attitudes towards SEC learning were highly positive. Teachers’ self-rated knowledge and approaches in dealing with SEC were moderate, and point to requirements for additional pre-service and professional development. The extent of regular and sustained delivery of SEC programs and mental health initiatives in general showed variability, suggesting the need to attend to school systems and structural supports. Implications of these areas of diversity in school environments on the selection and methods of delivery of mental health promotion programs in schools are discussed.peer-reviewe
Tracing organic matter composition and distribution and its role on arsenic release in shallow Cambodian groundwaters
Biogeochemical processes that utilize dissolved organic carbon are widely thought to be responsible for the liberation of arsenic from sediments to shallow groundwater in south and southeast Asia. The accumulation of this known carcinogen to hazardously high concentrations has occurred in the primary source of drinking water in large parts of densely populated countries in this region. Both surface and sedimentary sources of organic matter have been suggested to contribute dissolved organic carbon in these aquifers. However, identification of the source of organic carbon responsible for driving arsenic release remains enigmatic and even controversial. Here, we provide the most extensive interrogation to date of the isotopic signature of ground and surface waters at a known arsenic hotspot in Cambodia. We present tritium and radiocarbon data that demonstrates that recharge through ponds and/or clay windows can transport young, surface derived organic matter in to groundwater to depths of 44 m under natural flow conditions. Young organic matter dominates the dissolved organic carbon pool in groundwater that is in close proximity to these surface water sources and we suggest this is likely a regional relationship. In locations distal to surface water contact, dissolved organic carbon represents a mixture of both young surface and older sedimentary derived organic matter. Ground-surface water interaction therefore strongly influences the average dissolved organic carbon age and how this is distributed spatially across the field site. Arsenic mobilization rates appear to be controlled by the age of dissolved organic matter present in these groundwaters. Arsenic concentrations in shallow groundwaters (< 20 m) increase by 1 ÎĽg/l for every year increase in dissolved organic carbon age compared to only 0.25 ÎĽg/l for every year increase in dissolved organic carbon age in deeper (> 20 m) groundwaters. We suggest that, while the rate of arsenic release is greatest in shallow aquifer sediments, arsenic release also occurs in deeper aquifer sediments and as such remains an important process in controlling the spatial distribution of arsenic in the groundwaters of SE Asia. Our findings suggest that any anthropogenic activities that alter the source of groundwater recharge or the timescales over which recharge takes place may also drive changes in the natural composition of dissolved organic carbon in these groundwaters. Such changes have the potential to influence both the spatial and temporal evolution of the current groundwater arsenic hazard in this region
Episodic disk accretion in the halo of the 'old' Pre-Main Sequence cluster Eta Chamaeleontis
We present multi-epoch medium-resolution observations of two M4.5 candidate
members in the halo of the ~8 Myr Eta Chamaeleontis open cluster. Over six
months of observations both stars exhibited variations in their H-alpha line
profiles on timescales of days to months, with at least one episode of
substantial activity attributable to accretion from a circumstellar disk. We
derive an accretion rate ~10^-8.7 Msun/yr for this event, with a rate of
~10^-10.6 Msun/yr in quiescence. Episodic accretion like that observed here
means existing surveys of accreting Weak-lined T-Tauri Stars in young clusters
are likely incomplete and that gas dissipation timescales calculated from the
fraction of accreting objects are underestimates.Comment: 5 pages, 5 figures, 1 table. Accepted for publication in MNRAS
Letter
Students\u27 Use of Good Quality Learning Strategies: A multi-level model of change over five years of secondary school
Concurrent Session Block
Recommended from our members
Individual 17-Hydroxyprogesterone Responses to hCG Are Not Correlated With Follicle Size in Polycystic Ovary Syndrome.
Context:In women with polycystic ovary syndrome (PCOS), 17-hydroxyprogesterone (17-OHP) responses to gonadotropin stimulation vary from increased to indistinguishable compared with normal controls. Objective:To determine whether 17-OHP responses to recombinant-human chorionic gonadotropin (r-hCG) are individually correlated to the size of antral follicles among women with PCOS. Design Setting and Participants:A prospective study conducted in 19 women with PCOS and 20 normal controls at an academic medical center. Interventions:Blood samples were obtained before and 24 hours after administration of 25 μg of r-hCG. Ovarian imaging was conducted with three-dimensional pelvic ultrasonography. Each subject underwent a 2-hour oral glucose tolerance test. Main Outcome Measures:Basal and stimulated levels of 17-OHP, androgens, estradiol, progesterone, anti-Mullerian hormone (AMH), insulin, glucose, follicle number, and size. Results:In women with PCOS, mean antral follicle count (AFC) was greater than that of controls, although the size of cohort follicles within individual subjects was not correlated to 17-OHP responses. The numbers of 2- to 3-mm and 3- to 4-mm follicles in PCOS were significantly greater than in controls, whereas differences between larger follicles were not observed. Increased AMH in PCOS was correlated to AFC, but not 17-OHP responses. Insulin sensitivity did not correlate to r-hCG‒stimulated 17-OHP after adjustment for body mass index. Conclusions:17-OHP responses to hCG in individuals with PCOS were not correlated to the distribution of antral follicles. Greater numbers of small antral follicles in women with PCOS than in controls suggest an extension of accelerated growth from the preantral stage
Mrgprd Enhances Excitability in Specific Populations of Cutaneous Murine Polymodal Nociceptors
The Mas-related G protein-coupled receptor D (Mrgprd) is selectively expressed in nonpeptidergic nociceptors that innervate the outer layers of mammalian skin. The function of Mrgprd in nociceptive neurons and the physiologically relevant somatosensory stimuli that activate Mrgprd^-expressing (Mrgprd^+) neurons are currently unknown. To address these issues, we studied three Mrgprd knock-in mouse lines using an ex vivo somatosensory preparation to examine the role of the Mrgprd receptor and Mrgprd+ afferents in cutaneous somatosensation. In mouse hairy skin, Mrgprd, as marked by expression of green fluorescent protein reporters, was expressed predominantly in the population of nonpeptidergic, TRPV1-negative, C-polymodal nociceptors. In mice lacking Mrgprd, this population of nociceptors exhibited decreased sensitivity to cold, heat, and mechanical stimuli. Additionally, in vitro patch-clamp studies were performed on cultured dorsal root ganglion neurons from Mrgprd^(–/–) and Mrgprd^(+/–) mice. These studies revealed a higher rheobase in neurons from Mrgprd^(–/–) mice than from Mrgprd^(+/–) mice. Furthermore, the application of the Mrgprd ligand β-alanine significantly reduced the rheobase and increased the firing rate in neurons from Mrgprd^(+/–) mice but was without effect in neurons from Mrgprd^(–/–) mice. Our results demonstrate that Mrgprd influences the excitability of polymodal nonpeptidergic nociceptors to mechanical and thermal stimuli
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