370 research outputs found
Autofluorescence in parathyroidectomy: signal intensity correlates with serum calcium and parathyroid hormone but routine clinical use is not justified
BACKGROUND: The inability to identify the pathological gland at surgery results in failure to cure hyperparathyroidism in 2-5%. The poorly understood characteristic of parathyroid tissue to manifest autofluorescence (AF) under near-infrared (NIR) light has been promoted as an intraoperative adjunct in parathyroid surgery. This study sought to explore potential clinical correlates for AF and assess the clinical utility of AF in parathyroid surgery. METHODS: Consecutive patients undergoing parathyroid surgery for primary and renal disease were included. NIR imaging was used intraoperatively and the degree of AF of parathyroid glands graded by the operating surgeon. Variables assessed for correlation with AF were: pre-operative serum calcium and PTH, SestaMIBI positivity, gland weight and histological composition. RESULTS: Ninety-six patients underwent parathyroidectomy over an 8-month period: 49 bilateral explorations, 41 unilateral and 6 focussed lateral approaches: 284 potentially 'visualisable' glands in total. Two hundred and fifty-seven glands (90.5%) were visualised with NIR. Correlation was found between the degree of fluorescence and pre-operative serum calcium and PTH, but not between gland weight and SestaMIBI positivity. In those with renal hyperparathyroidism, a predominance of oxyphil cells correlated with increased AF. CONCLUSION: Autofluorescence intensity correlates with serum calcium, PTH and gland composition. Further refinements would be required for this information to be of value in a clinical setting. Improvements allowing NIR to visualise the additional 9.5% of parathyroids and overcome the variation in signal intensity due to depth of access are required for the routine adoption of this technology. At present, its routine use in a clinical setting cannot be justified
Struggling and juggling: a comparison of assessment loads in research and teaching-intensive universities
In spite of the rising tide of metrics in UK higher education, there has been scant attention paid to assessment loads, when evidence demonstrates that heavy demands lead to surface learning. Our study seeks to redress the situation by defining assessment loads and comparing them across research-and teaching intensive universities. We clarify the concept of ‘assessment load’ in response to findings about high volumes of summative assessment on modular degrees. We define assessment load across whole undergraduate degrees, according to four measures: the volume of summative assessment; volume of formative assessment; proportion of examinations to coursework; number of different varieties of assessment. All four factors contribute to the weight of an assessment load, and influence students’ approaches to learning. Our research compares programme assessment data from 73 programmes in 14 UK universities, across two institutional categories. Research-intensives have higher summative assessment loads and a greater proportion of examinations; teaching-intensives have higher varieties of assessment. Formative assessment does not differ significantly across both university groups. These findings pose particular challenges for students in different parts of the sector. Our study questions the wisdom that ‘more’ is always better, proposing that lighter assessment loads may make room for ‘slow’ and deep learning
The Planetary Nebulae Spectrograph: the green light for Galaxy Kinematics
Planetary nebulae are now well established as probes of galaxy dynamics and
as standard candles in distance determinations. Motivated by the need to
improve the efficiency of planetary nebulae searches and the speed with which
their radial velocities are determined, a dedicated instrument - the Planetary
Nebulae Spectrograph or PN.S - has been designed and commissioned at the 4.2m
William Herschel Telescope. The high optical efficiency of the spectrograph
results in the detection of typically ~ 150 PN in galaxies at the distance of
the Virgo cluster in one night of observations. In the same observation the
radial velocities are obtained with an accuracy of ~ 20 km/sComment: Accepted by PASP, to appear November 2002; the figures have been
degraded for archival purpose
SkyMapper Filter Set: Design and Fabrication of Large Scale Optical Filters
The SkyMapper Southern Sky Survey will be conducted from Siding Spring
Observatory with u, v, g, r, i and z filters that comprise glued glass
combination filters of dimension 309x309x15 mm. In this paper we discuss the
rationale for our bandpasses and physical characteristics of the filter set.
The u, v, g and z filters are entirely glass filters which provide highly
uniform band passes across the complete filter aperture. The i filter uses
glass with a short-wave pass coating, and the r filter is a complete dielectric
filter. We describe the process by which the filters were constructed,
including the processes used to obtain uniform dielectric coatings and
optimized narrow band anti-reflection coatings, as well as the technique of
gluing the large glass pieces together after coating using UV transparent epoxy
cement. The measured passbands including extinction and CCD QE are presented.Comment: 9 pages, 2 tables, 7 figure
Structure of Be probed via secondary beam reactions
The low-lying level structure of the unbound neutron-rich nucleus Be
has been investigated via breakup on a carbon target of secondary beams of
B at 35 MeV/nucleon. The coincident detection of the beam velocity
Be fragments and neutrons permitted the invariant mass of the
Be+ and Be++ systems to be reconstructed. In the case of
the breakup of B, a very narrow structure at threshold was observed in
the Be+ channel. Contrary to earlier stable beam fragmentation
studies which identified this as a strongly interacting -wave virtual state
in Be, analysis here of the Be++ events demonstrated that
this was an artifact resulting from the sequential-decay of the
Be(2) state. Single-proton removal from B was found to
populate a broad low-lying structure some 0.70 MeV above the neutron-decay
threshold in addition to a less prominent feature at around 2.4 MeV. Based on
the selectivity of the reaction and a comparison with (0-3)
shell-model calculations, the low-lying structure is concluded to most probably
arise from closely spaced J=1/2 and 5/2 resonances
(E=0.400.03 and 0.85 MeV), whilst the broad
higher-lying feature is a second 5/2 level (E=2.350.14 MeV). Taken
in conjunction with earlier studies, it would appear that the lowest 1/2
and 1/2 levels lie relatively close together below 1 MeV.Comment: 14 pages, 13 figures, 2 tables. Accepted for publication in Physical
Review
Trace Metal and Chlorinated Hydrocarbon Concentrations in Shellfish from Irish Waters, 1997-1999
In accordance with the monitoring requirements of Council Directive 79/923/EEC, on the quality required of shellfish waters, and Council Directive 91/492/EEC, laying down the health conditions for the production and placing on the market of live bivalve molluscs, the Marine Institute collected water and shellfish samples from major shellfish growing areas and analysed for physicochemical parameters, trace metal levels and chlorinated hydrocarbon concentrations. Since, with the exception of mercury, there are no currently applicable European standards for the concentration of these contaminants in shellfish, the levels were compared with the available standards and guidance values for human consumption, as compiled by the Oslo and Paris Commission (OSPAR) countries.
As in previous years, the water quality from shellfish growing areas was good and conformed to the guidelines and requirements of the Directive. Petroleum hydrocarbons were not observed in any of the shellfish waters or as deposits on the shellfish. Chlorinated hydrocarbon levels were very low, evidence of the clean, unpolluted nature of Irish shellfish and shellfish producing waters. Trace metal levels were consistently low with the exception of cadmium in oyster tissue, which was slightly elevated in the 1999 samples from Clew Bay, Inner Tralee Bay, Aughinish Limerick and Kilkieran. However these levels did not exceed the Dutch human consumption standard value or the EU maximum limit of 1.0 mg/kg wet weight due to apply from 2002.
This survey confirms previous studies which show Irish shellfish products are effectively free from trace metal and chlorinated hydrocarbon contamination.Funder: Marine Institut
Neutron-hole strength in the N = 81 isotones
The distribution of neutron-hole strength has been studied in the N 81 isotones 137Ba, 139Ce, 141Nd and 143Sm through the single-neutron removing reactions (p,d) and ( 3He,α), at energies of 23 and 34 MeV, respectively. Systematic cross section measurements were made at angles sensitive to the transferred angular momentum, and spectroscopic factors extracted through a distorted-wave Born approximation analysis. Application of the MacFarlane-French sum rules indicate an anomalously low summed g7/2 spectroscopic factor, most likely due to extensive fragmentation of the single-particle strength. Single-particle energies, based upon the centroids of observed strength, are presented. © Published under licence by IOP Publishing Ltd
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