1,011 research outputs found
Individual surgeon mortality rates: can outliers be detected? A national utility analysis
Objectives: There is controversy on the proposed
benefits of publishing mortality rates for individual
surgeons. In some procedures, analysis at the level of
an individual surgeon may lack statistical power. The
aim was to determine the likelihood that variation in
surgeon performance will be detected using published
outcome data.
Design: A national analysis surgeon-level mortality
rates to calculate the level of power for the reported
mortality rate across multiple surgical procedures.
Setting: The UK from 2010 to 2014.
Participants: Surgeons who performed colon cancer
resection, oesophagectomy or gastrectomy, elective
aortic aneurysm repair, hip replacement, bariatric
surgery or thyroidectomy.
Outcomes: The likelihood of detecting an individual
with a 30-day, 90-day or in-patient mortality rate of up
to 5 times the national mean or median (as available).
This was represented using a novel heat-map
approach.
Results: Overall mortality rates for the procedures
ranged from 0.07% to 4.5% and mean/median
surgeon volume was between 23 and 75 cases. The
national median case volume for colorectal (n=55) and
upper gastrointestinal (n=23) cancer resections
provides around 20% power to detect a mortality rate
of 3 times the national median, while, for hip
replacement, this is a rate 5 times the national average.
At the mortality rates reported for thyroid (0.08%) and
bariatric (0.07%) procedures, it is unlikely a surgeon
would perform a sufficient number of procedures in
his/her entire career to stand a good chance of
detecting a mortality rate 5 times the national average.
Conclusions: At present, surgeons with increased
mortality rates are unlikely to be detected. Performance
within an expected mortality rate range cannot be
considered reliable evidence of acceptable
performance. Alternative approaches should focus on
commonly occurring meaningful outcome measures,
with infrequent events analysed predominately at the
hospital level
Using thermoluminescence signals from feldspars for low-temperature thermochronology
Natural thermoluminescence (TL) signals from feldspar crystals extracted from thermally stable drill cores (View the MathML sourceC) exhibit a strong dependence on geologic and laboratory thermal conditions. As burial temperature increases, the position of the TL glow curve at half-maximum intensity (i.e., the T1/2 parameter) shifts to higher measurement temperatures. This shift is also observed following isothermal treatments in the laboratory. This relationship can be explained using a kinetic model originally developed for the optical luminescence dating of feldspar grains. The thermal history of a sample is preserved in the degree of electron trap saturation as a function of thermal detrapping probability, which varies with recombination distance. A natural feldspar sample contains a range of thermal stabilities: the least stable traps will remain empty, the most stable will be full, and those traps which are partially filled will, in the case of thermal equilibrium, be diagnostic of the storage temperature. The T1/2 parameter of a TL glow curve reflects which sites remain occupied. This interpretation is further borne out by additive dose measurements which illustrate that samples buried at lower temperatures are fully saturated at lower TL measurement temperatures (View the MathML sourceC) relative to warmer samples. This signal is estimated to be useful in rapidly-cooling bedrock and should grow measurably for ∼102−106 years
Interlayer Exchange Coupling Mediated by Valence Band Electrons
The interlayer exchange coupling mediated by valence band electrons in
all-semiconductor IV-VI magnetic/nonmagnetic superlattices is studied
theoretically. A 3D tight-binding model, accounting for the band and magnetic
structure of the constituent superlattice components is used to calculate the
spin-dependent part of the total electronic energy. The antiferromagnetic
coupling between ferromagnetic layers in EuS/PbS superlattices is obtained, in
agreement with the experimental evidences. The results obtained for the
coupling between antiferromagnetic layers in EuTe/PbTe superlattices are also
presented.Comment: 8 pages, 6 figures, to be submitted to Phys.Rev.
A solenoidal electron spectrometer for a precision measurement of the neutron -asymmetry with ultracold neutrons
We describe an electron spectrometer designed for a precision measurement of
the neutron -asymmetry with spin-polarized ultracold neutrons. The
spectrometer consists of a 1.0-Tesla solenoidal field with two identical
multiwire proportional chamber and plastic scintillator electron detector
packages situated within 0.6-Tesla field-expansion regions. Select results from
performance studies of the spectrometer with calibration sources are reported.Comment: 30 pages, 19 figures, 1 table, submitted to NIM
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Late miocene/pliocene origin of the inverted metamorphism of the Central Himalaya
The spatial association of intracontinental thrusting and inverted metamorphism, recognized in the Himalaya more than a century ago, has inspired continuing efforts to identify their causal relationship. Perhaps the best known sequence of inverted metamorphism is that found immediately beneath the Himalayan Main Central Thrust (MCT), generally thought to have been active during the Early Miocene. It has been widely assumed that the pattern of inverted metamorphism also developed at that time. Using a new approach, in situ Th-Pb dating of monazite included in garnet, we have discovered that the peak metamorphic recrystallization recorded in the footwall of the MCT fault occurred at ca. 5 Ma. The apparent inverted metamorphism resulted from activation of a broad shear zone beneath the MCT zone which juxtaposed two right-way-up metamorphic sequences. Recognition of this remarkably youthful phase of metamorphism resolves outstanding problems in Himalayan tectonics, such as why the MCT (and not the more recently initiated thrusts) marks the break in slope of the present day mountain range, and transcends others, such as the need for exceptional conditions to explain Himalayan anatexis
Amine Templated Zinc Phosphates Phases for Membrane Separations
This research is focused on developing inorganic molecular sieve membranes for light gas separations such as hydrogen recovery and natural gas purification, and organic molecular separations, such as chiral enantiomers. The authors focus on zinc phosphates because of the ease in crystallization of new phases and the wide range of pore sizes and shapes obtained. With hybrid systems of zinc phosphate crystalline phases templated by amine molecules, the authors are interested in better understanding the association of the template molecules to the inorganic phase, and how the organic transfers its size, shape, and (in some cases) chirality to the bulk. Furthermore, the new porous phases can also be synthesized as thin films on metal oxide substrates. These films allow one to make membranes from organic/inorganic hybrid systems, suitable for diffusion experiments. Characterization techniques for both the bulk phases and the thin films include powder X-ray diffraction, TGA, Scanning Electron Micrograph (SEM) and Electron Dispersive Spectrometry (EDS)
The utility of exhaled nitric oxide in patients with suspected asthma
The value of FENO measurements in patients with symptoms suggestive of asthma is unclear. We performed an observational study to assess the ability of FENO to diagnose asthma and to predict response to inhaled corticosteroids (ICS). Our findings suggest FENO is not useful for asthma diagnosis but is accurate at predicting ICS response
Why equality? On justifying liberal egalitarianism
The debate over the nature of egalitarianism has come to dominate political philosophy. As ever more sophisticated attempts are made to describe the principles of an egalitarian distribution or to specify the good or goods that should be distributed equally, little is said about the fundamental basis of equality. In virtue of what should people be regarded as equal? Egalitarians have tended to dismiss this question of fundamental equality. In the first part of the paper I will examine some of these strategies of marginalisation and assess whether the issue of fundamental equality matters. Jeremy Waldron has criticised this strategy of avoidance in his recent book God, Locke and equality. He argues that Locke's turn to a theistic grounding for fundamental equality provides a better approach to the problem than the approach taken by contemporary liberals such as John Rawls. I will examine Waldron's critique of Rawls and show that it is wanting. I will conclude by suggesting that Rawls's approach to the issue has a bearing on the way in which equality should be understood as a political value. This argument for the primacy of a political conception of egalitarianism has a bearing on the interconnection between core liberal values and the idea of the state that has been emphasised by Rawls, Dworkin and Nagel
Structure, Photophysics and the Order-Disorder Transition to the Beta Phase in Poly(9,9-(di -n,n-octyl)fluorene)
X-ray diffraction, UV-vis absorption and photoluminescence (PL) spectroscopy
have been used to study the well-known order-disorder transition (ODT) to the
beta phase in poly(9,9-(di n,n-octyl)fluorene)) (PF8) thin film samples through
combination of time-dependent and temperature-dependent measurements. The ODT
is well described by a simple Avrami picture of one-dimensional nucleation and
growth but crystallization, on cooling, proceeds only after molecular-level
conformational relaxation to the so called beta phase. Rapid thermal quenching
is employed for PF8 studies of pure alpha phase samples while extended
low-temperature annealing is used for improved beta phase formation. Low
temperature PL studies reveal sharp Franck-Condon type emission bands and, in
the beta phase, two distinguishable vibronic sub-bands with energies of
approximately 199 and 158 meV at 25 K. This improved molecular level structural
order leads to a more complete analysis of the higher-order vibronic bands. A
net Huang-Rhys coupling parameter of just under 0.7 is typically observed but
the relative contributions by the two distinguishable vibronic sub-bands
exhibit an anomalous temperature dependence. The PL studies also identify
strongly correlated behavior between the relative beta phase 0-0 PL peak
position and peak width. This relationship is modeled under the assumption that
emission represents excitons in thermodynamic equilibrium from states at the
bottom of a quasi-one-dimensional exciton band. The crystalline phase, as
observed in annealed thin-film samples, has scattering peaks which are
incompatible with a simple hexagonal packing of the PF8 chains.Comment: Submitted to PRB, 12 files; 1 tex, 1 bbl, 10 eps figure
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