1,935 research outputs found
A multipole-Taylor expansion for the potential of gravitational lens MG J0414+0534
We employ a multipole-Taylor expansion to investigate how tightly the
gravitational potential of the quadruple-image lens MG J0414+0534 is
constrained by recent VLBI observations. These observations revealed that each
of the four images of the background radio source contains four distinct
components, thereby providing more numerous and more precise constraints on the
lens potential than were previously available. We expand the two-dimensional
lens potential using multipoles for the angular coordinate and a modified
Taylor series for the radial coordinate. After discussing the physical
significance of each term, we compute models of MG J0414+0534 using only VLBI
positions as constraints. The best-fit model has both interior and exterior
quadrupole moments as well as exterior m=3 and m=4 multipole moments. The
deflector centroid in the models matches the optical galaxy position, and the
quadrupoles are aligned with the optical isophotes. The radial distribution of
mass could not be well constrained. We discuss the implications of these models
for the deflector mass distribution and for the predicted time delays between
lensed components.Comment: 44 pages, 5 figures, 11 tables, accepted for publication in Ap
Chaos, containment and change: responding to persistent offending by young people
This article reviews policy developments in Scotland concerning 'persistent young offenders' and then describes the design of a study intended to assist a local planning group in developing its response. The key findings of a review of casefiles of young people involved in persistent offending are reported. It emerges that youth crime and young people involved in offending are more complex and heterogeneous than is sometimes assumed. This, along with a review of some literature about desistance from offending, reaffirms the need for properly individualised interventions. Studies of 'desisters' suggest the centrality of effective and engaging working relationships in this process. However, these studies also re-assert the significance of the social contexts of workers’ efforts to bring 'change' out of 'chaos'. We conclude therefore that the 'new correctionalism' must be tempered with appreciation of the social exclusion of young people who offend
A 23 GHz Survey of GRB Error Boxes
The Haystack 37-meter telescope was used in a pilot project in May 1995 to
observe GRB error boxes at 23~GHz. Seven BATSE error boxes and two IPN arcs
were scanned by driving the beam of the telescope rapidly across their area.
For the BATSE error boxes, the radio observations took place two to eighteen
days after the BATSE detection, and several boxes were observed more than once.
Total power data were recorded continuously as the telescope was driven at a
rate of 0.2~degrees/second, yielding Nyquist sampling of the beam with an
integration time of 50~milliseconds, corresponding to a theoretical rms
sensitivity of 0.5~Jy. Under conditions of good weather, this sensitivity was
achieved. In a preliminary analysis of the data we detect only two sources,
3C273 and 0552+398, both catalogued sources that are known to be variable at
23~GHz. Neither had a flux density that was unusally high or low at the time of
our observations.Comment: 5 pages, 1 postscript figure. To appear in Proceedings of the Third
Huntsville Symposium on Gamma-Ray Bursts (eds. C. Kouveliotou, M. S. Briggs,
and G. J. Fishman
Robust Chauvenet Outlier Rejection
Sigma clipping is commonly used in astronomy for outlier rejection, but the
number of standard deviations beyond which one should clip data from a sample
ultimately depends on the size of the sample. Chauvenet rejection is one of the
oldest, and simplest, ways to account for this, but, like sigma clipping,
depends on the sample's mean and standard deviation, neither of which are
robust quantities: Both are easily contaminated by the very outliers they are
being used to reject. Many, more robust measures of central tendency, and of
sample deviation, exist, but each has a tradeoff with precision. Here, we
demonstrate that outlier rejection can be both very robust and very precise if
decreasingly robust but increasingly precise techniques are applied in
sequence. To this end, we present a variation on Chauvenet rejection that we
call "robust" Chauvenet rejection (RCR), which uses three decreasingly
robust/increasingly precise measures of central tendency, and four decreasingly
robust/increasingly precise measures of sample deviation. We show this
sequential approach to be very effective for a wide variety of contaminant
types, even when a significant -- even dominant -- fraction of the sample is
contaminated, and especially when the contaminants are strong. Furthermore, we
have developed a bulk-rejection variant, to significantly decrease computing
times, and RCR can be applied both to weighted data, and when fitting
parameterized models to data. We present aperture photometry in a contaminated,
crowded field as an example. RCR may be used by anyone at
https://skynet.unc.edu/rcr, and source code is available there as well.Comment: 62 pages, 48 figures, 7 tables, accepted for publication in ApJ
Listening and learning : the reciprocal relationship between worker and client
The relationship between worker and client has for the best part of 100 years been the mainstay of probation, and yet has recently been eroded by an increased emphasis on punishment, blame and managerialism. The views of offenders are in direct contradiction to these developments within the criminal justice system and this article argues that only by taking account of the views of those at the 'coal face' will criminologists, policy makers and practitioners be able to effect real change in crime rates. The article thus focuses on the views of a sample of previously persistent offenders in Scotland about offending, desistance and how the system can help them. It explores not only their need for friendship and support in youth but also the close association between relationships and the likelihood of offending. It also demonstrates the views of offenders themselves about the importance of the working relationship with supervising officers in helping them desist from crime. The article concludes that the most effective way of reducing offending is to re-engage with the message of the Probation Act of 100 years ago, namely, to 'advise, assist and befriend' offenders rather than to 'confront, challenge and change' offending behaviour
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Cost-effectiveness analysis of maternal immunisation against group B Streptococcus (GBS) disease: A modelling study
Background
There is a considerable global burden of invasive group B streptococcal (GBS) disease. Vaccines are being developed for use in pregnant women to offer protection to neonates.
Objective
To estimate the potential impact and cost-effectiveness of maternal immunisation against neonatal and maternal invasive GBS disease in the UK.
Methods
We developed a decision-tree model encompassing GBS-related events in infants and mothers, following a birth cohort with a time horizon equivalent to average life expectancy (81 years). We parameterised the model using contemporary data from disease surveillance and outcomes in GBS survivors. Costs were taken from NHS sources and research studies. Maternal immunisation in combination with risk-based intrapartum antibiotic prophylaxis (IAP) was compared to the current standard practice of risk-based IAP alone from an NHS and Personal Social Services (health-provider) perspective. We estimated the cases averted and cost per QALY gained through vaccination. One-way sensitivity analysis, scenario analysis and probabilistic sensitivity analysis were performed.
Results
An effective maternal immunisation programme could substantially reduce the burden of GBS disease. The deterministic analysis estimated the threshold cost-effective price for a GBS vaccine to be £54 per dose at £20,000/QALY (£71 per dose at £30,000/QALY). Results were most sensitive to assumptions on disease incidence, sequelae rate and vaccine efficacy. Probabilistic analysis showed 90.66% of iterations fell under the £30,000 threshold at a vaccine price of £55. Inclusion of modest prevention of stillbirths and/or, preterm births, carer health impacts, maternal GBS deaths and 1.5% discounting improved cost-effectiveness compared to the base case. Lowering vaccine strain coverage made the vaccine less cost-effective. A key limitation is that the properties of the final GBS vaccine are unknown.
Conclusions
Maternal GBS immunisation is expected to be cost-effective, even at a relatively high vaccine price
VLBA Imaging of the OH Maser in IIIZw35
We present a parsec-scale image of the OH maser in the nucleus of the active
galaxy IIIZw35, made using the Very Long Baseline Array at a wavelength of 18
cm. We detected two distinct components, with a projected separation of 50 pc
(for D=110 Mpc) and a separation in Doppler velocity of 70 km/s, which contain
50% of the total maser flux. Velocity gradients within these components could
indicate rotation of clouds with binding mass densities of ~7000 solar masses
per cubic parsec, or total masses of more than 500,000 solar masses. Emission
in the 1665-MHz OH line is roughly coincident in position with that in the
1667-MHz line, although the lines peak at different Doppler velocities. We
detected no 18 cm continuum emission; our upper limit implies a peak apparent
optical depth greater than 3.4, assuming the maser is an unsaturated amplifier
of continuum radiation.Comment: 10 pages, 3 figure
The Seroepidemiology of Haemophilus influenzae Type B Prior to Introduction of an Immunization Programme in Kathmandu, Nepal.
Haemophilus influenzae type b (Hib) is now recognized as an important pathogen in Asia. To evaluate disease susceptibility, and as a marker of Hib transmission before routine immunization was introduced in Kathmandu, 71 participants aged 7 months-77 years were recruited and 15 cord blood samples were collected for analysis of anti-polyribosylribitol phosphate antibody levels by enzyme-linked immunosorbent assay. Only 20% of children under 5 years old had levels considered protective (>0.15 µg/ml), rising to 83% of 15-54 year-olds. Prior to introduction of Hib vaccine in Kathmandu, the majority of young children were susceptible to disease
Case management and Think First completion
“The final, definitive version of this article has been published in the Journal, Probation Journal, Vol 53 Issue 3, 2006, Copyright The Trade Union and Professional Association for Family Court and Probation Staff, by SAGE Publications Ltd at: http://prb.sagepub.com/ " DOI: 10.1177/0264550506066771This article considers the findings of a small-scale study of the practice of case managers supervising offenders required to attend the Think First Group. It explores the interface between one-to-one and group-based work within multi-modal programmes of supervision and seeks to identify those practices that support individuals in completing a group.Peer reviewe
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