450 research outputs found
Classifying the embedded young stellar population in Perseus and Taurus & the LOMASS database
Context. The classification of young stellar objects (YSOs) is typically done
using the infrared spectral slope or bolometric temperature, but either can
result in contamination of samples. More accurate methods to determine the
evolutionary stage of YSOs will improve the reliability of statistics for the
embedded YSO population and provide more robust stage lifetimes. Aims. We aim
to separate the truly embedded YSOs from more evolved sources. Methods. Maps of
HCO+ J=4-3 and C18O J=3-2 were observed with HARP on the James Clerk Maxwell
Telescope (JCMT) for a sample of 56 candidate YSOs in Perseus and Taurus in
order to characterize emission from high (column) density gas. These are
supplemented with archival dust continuum maps observed with SCUBA on the JCMT
and Herschel PACS to compare the morphology of the gas and dust in the
protostellar envelopes. The spatial concentration of HCO+ J=4-3 and 850 micron
dust emission are used to classify the embedded nature of YSOs. Results.
Approximately 30% of Class 0+I sources in Perseus and Taurus are not Stage I,
but are likely to be more evolved Stage II pre-main sequence (PMS) stars with
disks. An additional 16% are confused sources with an uncertain evolutionary
stage. Conclusions. Separating classifications by cloud reveals that a high
percentage of the Class 0+I sources in the Perseus star forming region are
truly embedded Stage I sources (71%), while the Taurus cloud hosts a majority
of evolved PMS stars with disks (68%). The concentration factor method is
useful to correct misidentified embedded YSOs, yielding higher accuracy for YSO
population statistics and Stage timescales. Current estimates (0.54 Myr) may
overpredict the Stage I lifetime on the order of 30%, resulting in timescales
of 0.38 Myr for the embedded phase.Comment: 33 pages, 21 figures, 6 tables, Accepted to be published in A&
Effects of prenatal depressive symptoms on maternal and infant cortisol reactivity.
Prenatal depression is associated with adverse offspring outcomes, and the prevailing mechanistic theory to account for mood-associated effects implicates alterations of the maternal and foetal hypothalamic-pituitary adrenal (HPA) axes. Recent research suggests that depression may be associated with a failure to attenuate cortisol reactivity during early pregnancy. The aim of the current study is to investigate whether this effect continues into mid and late gestation. A further aim is to test whether maternal prenatal cortisol reactivity directly predicts infant cortisol reactivity. One hundred three pregnant women were recruited during either the second or third trimester. Depressive symptoms were assessed by self-report, and maternal salivary cortisol responses to a stressor (infant distress film) were measured. Approximately 2Â months after birth, mothers (nâ=â88) reported postnatal depression and infant salivary cortisol responses to inoculation were measured. Prenatal depression was not associated with cortisol reactivity to acute stress in mid and late pregnancy. Similarly, neither prenatal depression nor maternal prenatal cortisol reactivity predicted infant cortisol reactivity to inoculation at 2Â months. If the effects of prenatal depression on foetal and infant development are mediated by alterations of the maternal and foetal HPA axes, then early pregnancy may be a particularly vulnerable period. Alternatively, changes to HPA reactivity may not be as central to this association as previously thought
Invariantâbased performance analysis of timed Petri net models
In timed Petri nets, temporal properties are associated with transitions as transition firing times (or occurrence times). For net models which can be decomposed into a family of place invariants, performance analysis can be conveniently performed on the basis of its components. The paper presents an approach to finding place invariants of net models and proposes an incremental method which, for large models, can significantly reduce the required amount of computations
Towards a Notion of Distributed Time for Petri Nets
We set the ground for research on a timed extension of Petri nets where time parameters are associated with tokens and arcs carry constraints that qualify the age of tokens required for enabling. The novelty is that, rather than a single global clock, we use a set of unrelated clocks --- possibly one per place --- allowing a local timing as well as distributed time synchronisation. We give a formal definition of the model and investigate properties of local versus global timing, including decidability issues and notions of processes of the respective models
The derivation of performance expressions for communication protocols from timed Petri net models
Petri Net models have been extended in a variety of ways and have been used to prove the correctness and evaluate the performance of communication protocols. Several extensions have been proposed to model time. This work uses a form of Timed Petri Nets and presents a technique for symbolically deriving expressions which describe system performance. Unlike past work on performance evaluation of Petri Nets which assumes a priori knowledge of specific time delays, the technique presented here applies to a wide range of time delays so long as the delays satisfy a set of timing constraints. The technique is demonstrated using a simple communication protocol
Priprava i vrednovanje biorazgradljivih implantata s kontroliranim oslobaÄanjem za postoperativnu primjenu
Biodegradable implants of ciprofloxacin hydrochloride for post operative site delivery were prepared using glyceryl monostearate and different concentrations of polyethylene glycol (PEG 6000) glycerol and Tween 80 as erosion enhancers by compression and molding technique. Formulations were subjected to in vitro drug release by the USP dissolution method, while promising formulations were subjected to in vitro drug release by the agar gel method and also to stability studies. It was observed that glyceryl monostearate formed hydrophobic matrix and delayed the drug delivery. Antibiotic release profile was controlled by using different combinations of erosion enhancers. The formulation prepared by compression method showed more delayed release as compared to formulations prepared by molding method.Biorazgradljivi implantati ciprofloksacin hidroklorida za postoperativnu primjenu pripravljeni su pomoÄu gliceril monostearata (GMS) i razliÄitih koncentracija polietilen glikola (PEG 6000), glicerola i Tween 80 kao promotora erozije metodom kompresije i lijevanja. OslobaÄanje ljekovite tvari iz pripravaka praÄeno je in vitro prema USP metodi. Pripravci koji su dali dobre rezultate ispitani su i in vitro metodom s agarom te su podvrgnuti testovima stabilnosti. PrimijeÄeno je da gliceril monostearat tvori hidrofobni matriks i usporava oslobaÄanje lijeka. KoristeÄi razliÄite kombinacije promotora erozije postignuto je kontrolirano oslobaÄanje antibiotika. OslobaÄanje iz implantata dobivenih metodom kompresije sporije je od implantata dobivenih metodom lijevanja
Feasibility trial of a psychoeducational intervention for parents with personality difficulties: the Helping Families Programme
The Helping Families Programme is a psychoeducational parenting intervention that aims to improve outcomes and engagement for parents affected by clinically significant personality difficulties. This is achieved by working collaboratively with parents to explore ways in which their emotional and relational difficulties impact on parenting and child functioning, and to identify meaningful and realistic goals for change. The intervention is delivered via one-to-one sessions at weekly intervals over a period of 16 weeks. This protocol describes a two arm parallel RCT in which consenting parents are randomly allocated in a 1:1 ratio to either the Helping Families Programme plus the usual services that the parent may be receiving from their mental health and/or social care providers, or to standard care (usual services plus a brief parenting advice session). The primary clinical outcome will be child behaviour. Secondary clinical outcomes will be child and parental mental health, parenting satisfaction, parenting behaviour and therapeutic alliance. Health economic measures will be collected on quality of life and service use. Outcome measures will be collected at the initial assessment stage, after the intervention is completed and at 6-month follow-up by research staff blind to group allocation. Trial feasibility will be assessed using rates of trial participation at the three time points and intervention uptake, attendance and retention.
A parallel process evaluation will use qualitative interviews to ascertain key-workersâ and parent participants' experiences of intervention delivery and trial participation. The results of this feasibility study will determine the appropriateness of proceeding to a full-scale trial
Salivary cortisol response to infant distress in pregnant women with depressive symptoms.
The Hypothalamic-Pituitary-Adrenal (HPA) axis has been proposed as a potential underlying biological mechanism linking prenatal depression with adverse offspring outcomes. However, it is unknown whether the reactivity of this system to stress is altered in pregnant women experiencing depression. The objective of this study was to investigate whether salivary cortisol response to a distressed infant film is enhanced in pregnant women with symptoms of depression compared with non-depressed controls. Salivary cortisol and subjective mood responses to the film were measured in 53 primiparous women, between 11 and 18 weeks gestation. Both groups showed similar increases in state anxiety in response to the film, but there was a significantly increased cortisol response in women experiencing symptoms of depression. Depression during pregnancy is associated with increased reactivity of the HPA axis. This is consistent with altered HPA axis functioning being a key mechanism by which prenatal mood disturbance can impact upon fetal development
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