1,437 research outputs found
An optical parsec-scale jet from a massive young star in the Large Magellanic Cloud
Highly collimated parsec-scale jets, generally linked to the presence of an
accretion disk, are a commonly observed phenomenon from revealed low-mass young
stellar objects. In the past two decades, only a very few of these objects have
been directly (or indirectly) observed towards high-mass (M > 8 M)
young stellar objects, adding to the growing evidence that disk-mediated
accretion is a phenomenon also occurring in high-mass stars, the formation
mechanism of which is still poorly understood. Of the observed jets from
massive young stars, none is in the optical regime (due to these being
typically highly obscured by their native material), and none are found outside
of the Milky Way. Here, we report the detection of HH 1177, the first
extragalactic optical ionized jet originating from a massive young stellar
object located in the Large Magellanic Cloud. The jet is highly collimated over
the entire measured extent of at least 10 pc, and has a bipolar geometry. The
presence of a jet indicates ongoing, disk-mediated accretion, and together with
the high degree of collimation, this system is therefore likely to be an
up-scaled version of low-mass star formation. We conclude that the physics
governing jet launching and collimation is independent of stellar mass.Comment: 9 pages, 5 figures, 2 table
Geolocator studies on Ruddy Turnstones Arenaria interpres and Greater Sandplovers Charadrius leschenaultii in the East Asian-Australasia Flyway reveal widely different migration strategies
In 2010, following successful trials with geolocators on Ruddy Turnstones in 2009, a total of 105 units, of four different models, were deployed at five locations on Ruddy Turnstones and Greater Sandplovers. Geolocator retrieval rates were 44% on Ruddy Turnstone and 27% on Greater Sandplover. Complete (59%) and partial (15%) technical failure rates on geolocators were high and were mostly the result of wear and saltwater corrosion. All 30 units from the Swiss Ornithological Institute failed. Only half of the Mk10 and Mk12 units from the British Antarctic Survey produced full migration histories. The northward migration of Ruddy Turnstones was on a narrow path with many birds completing an initial non-stop flight of 7,600 km to Taiwan. Later, most made a stopover in the Yellow Sea. Median migration duration was 39.5 days and average migration speed of the first major leg of the journey (assuming the birds followed the great circle route between stopovers) was 63.4 kph. Southward migration paths showed a much wider spread, ranging from Mongolia to the central Pacific. The latter involved the same bird that had been tracked along this route the previous year. It has now been logged on similar 27,000 km round trips in two successive years. The median duration of southward migration (78 days) was nearly twice that of northward migration and data on average migration speed for just two migration legs indicated that it might be lower, 30 and 40 kph being the values recorded. Greater Sandplovers were only tracked on northward migration but seemed to follow a similar migration strategy with a large initial non-stop flight followed by shorter flights and more regular stopovers. Plans are outlined for further analyses and future deployments of geolocators
Carina's Pillars of Destruction: the view from ALMA
Forming high-mass stars have a significant effect on their natal environment.
Their feedback pathways, including winds, outflows, and ionising radiation,
shape the evolution of their surroundings which impacts the formation of the
next generation of stars. They create or reveal dense pillars of gas and dust
towards the edges of the cavities they clear. They are modelled in feedback
simulations, and the sizes and shapes of the pillars produced are consistent
with those observed. However, these models predict measurably different
kinematics which provides testable discriminants. Here we present the first
ALMA Compact Array (ACA) survey of 13 pillars in Carina, observed in CO,
CO and CO J=2-1, and the 230 GHz continuum. The pillars in this
survey were chosen to cover a wide range in properties relating to the amount
and direction of incident radiation, proximity to nearby irradiating clusters
and cloud rims, and whether they are detached from the cloud. With these data,
we are able to discriminate between models. We generally find pillar velocity
dispersions of 1 km s and that the outer few layers of molecular
emission in these pillars show no significant offsets from each other,
suggesting little bulk internal motions within the pillars. There are instances
where the pillars are offset in velocity from their parental cloud rim, and
some with no offset, hinting at a stochastic development of these motions.Comment: 24 Pages, 19 figures. Accepted to MNRA
The ionised, radical and molecular Milky Way: spectroscopic surveys with the SKA
Mark Thompson, et al, ‘The ionised,radical and molecular Milky Way: spectroscopic surveys with the SKA’, Proceedings, Advancing Astrophysics with the Square Kilometre Array (AASKA14): Giardini Naxos, Italy, June 9-13, 2014. © 2015 The Authors, under the Creative Commons Attribution-NonCommercial-ShareAlike CC BY-NC-SA license https://creativecommons.org/licenses/by-nc-sa/4.0/.The bandwith, sensitivity and sheer survey speed of the SKA offers unique potential for deep spectroscopic surveys of the Milky Way. Within the frequency bands available to the SKA lie many transitions that trace the ionised, radical and molecular components of the interstellar medium and which will revolutionise our understanding of many physical processes. In this chapter we describe the impact on our understanding of the Milky Way that can be achieved by spectroscopic SKA surveys, including "out of the box" early science with radio recombination lines, Phase 1 surveys of the molecular ISM using anomalous formaldehyde absorption, and full SKA surveys of ammonia inversion lines
Strong Pinning in High Temperature Superconductors
Detailed measurements of the critical current density jc of YBa2Cu3O7 films
grown by pulsed laser deposition reveal the increase of jc as function of the
filmthickness. Both this thickness dependence and the field dependence of the
critical current are consistently described using a generalization of the
theory of strong pinning of Ovchinnikov and Ivlev [Phys. Rev. B 43, 8024
(1991)]. From the model, we deduce values of the defect density (10^21 m^-3)
and the elementary pinning force, which are in good agreement with the
generally accepted values for Y2O3-inclusions. In the absence of clear evidence
that the critical current is determined by linear defects or modulations of the
film thickness, our model provides an alternative explanation for the rather
universal field dependence of the critical current density found in YBa2Cu3O7
films deposited by different methods.Comment: 11 pages; 8 Figures; Published Phys. Rev. B 66, 024523 (2002
Personalized surveillance and aftercare for non-metastasized breast cancer:the NABOR study protocol of a multiple interrupted time series design
Background: Follow-up of curatively treated primary breast cancer patients consists of surveillance and aftercare and is currently mostly the same for all patients. A more personalized approach, based on patients’ individual risk of recurrence and personal needs and preferences, may reduce patient burden and reduce (healthcare) costs. The NABOR study will examine the (cost-)effectiveness of personalized surveillance (PSP) and personalized aftercare plans (PAP) on patient-reported cancer worry, self-rated and overall quality of life and (cost-)effectiveness.Methods: A prospective multicenter multiple interrupted time series (MITs) design is being used. In this design, 10 participating hospitals will be observed for a period of eighteen months, while they -stepwise- will transit from care as usual to PSPs and PAPs. The PSP contains decisions on the surveillance trajectory based on individual risks and needs, assessed with the ‘Breast Cancer Surveillance Decision Aid’ including the INFLUENCE prediction tool. The PAP contains decisions on the aftercare trajectory based on individual needs and preferences and available care resources, which decision-making is supported by a patient decision aid. Patients are non-metastasized female primary breast cancer patients (N = 1040) who are curatively treated and start follow-up care. Patient reported outcomes will be measured at five points in time during two years of follow-up care (starting about one year after treatment and every six months thereafter). In addition, data on diagnostics and hospital visits from patients’ Electronical Health Records (EHR) will be gathered. Primary outcomes are patient-reported cancer worry (Cancer Worry Scale) and overall quality of life (as assessed with EQ-VAS score). Secondary outcomes include health care costs and resource use, health-related quality of life (as measured with EQ5D-5L/SF-12/EORTC-QLQ-C30), risk perception, shared decision-making, patient satisfaction, societal participation, and cost-effectiveness. Next, the uptake and appreciation of personalized plans and patients’ experiences of their decision-making process will be evaluated. Discussion: This study will contribute to insight in the (cost-)effectiveness of personalized follow-up care and contributes to development of uniform evidence-based guidelines, stimulating sustainable implementation of personalized surveillance and aftercare plans. Trial registration: Study sponsor: ZonMw. Retrospectively registered at ClinicalTrials.gov (2023), ID: NCT05975437.</p
Record RF performance of standard 90 nm CMOS technology
We have optimized 3 key RF devices realized in standard logic 90 nm CMOS technology and report a record performance in terms of n-MOS maximum oscillation frequency f/sub max/ (280 GHz), varactor tuning range and varactor and inductor quality factor
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