55 research outputs found
Preventing strokes associated with carotid endarterectomy: Detection of embolisation by transcranial doppler monitoring
Planar lattice gases with nearest-neighbour exclusion
We discuss the hard-hexagon and hard-square problems, as well as the
corresponding problem on the honeycomb lattice. The case when the activity is
unity is of interest to combinatorialists, being the problem of counting binary
matrices with no two adjacent 1's. For this case we use the powerful corner
transfer matrix method to numerically evaluate the partition function per site,
density and some near-neighbour correlations to high accuracy. In particular
for the square lattice we obtain the partition function per site to 43 decimal
places.Comment: 16 pages, 2 built-in Latex figures, 4 table
A cost analysis of surgery for ruptured abdominal aortic aneurysm
AbstractObjective: this study compares our costs of salvaging patients with ruptured abdominal aortic aneurysms (AAA) with the costs for unruptured AAAs. Methods: details of all AAAs presenting over 18 months were obtained. Costs of repair were carefully calculated for each case and were based upon ITU and ward stay and the use of theatre, radiology and pathology services. We compared the costs in unruptured AAAs with both uncomplicated ruptures and ruptures with one or more system failure. Results: the mortality rate for ruptures undergoing repair was 18% and for elective repairs was 1.6%. The median cost for uncomplicated ruptures was £6427 (range £2012-13 756). For 12 complicated ruptures, it was £20 075 (range £13 864-166 446), and for 63 unruptured AAAs, was £4762 (range £2925-47 499). Conclusion: relatively low operative mortality rates for ruptured AAA repair can be achieved but this comes at substantial cost. On average, a ruptured AAA requiring system support costs four times as much as an elective repair.Eur J Vasc Endovasc Surg 26, 299-302 (2003
A Policy of Quality Control Assessment Helps to Reduce the Risk of Intraoperative Stroke During Carotid Endarterectomy
AbstractObjectivesa pilot study in our unit suggested that a combination of transcranial Doppler (TCD) plus completion angioscopy reduced incidence of intra-operative stroke (i.e. patients recovering from anaesthesia with a new deficit) during carotid endarterectomy (CEA). The aim of the current study was to see whether routine implementation of this policy was both feasible and associated with a continued reduction in the rate of intraoperative stroke (IOS).Materials and methodsprospective study in 252 consecutive patients undergoing carotid endarterectomy between March 1995 and December 1996.Resultscontinuous TCD monitoring was possible in 229 patients (91%), while 238 patients (94%) underwent angioscopic examination. Overall, angioscopy identified an intimal flap requiring correction in six patients (2.5%), whilst intraluminal thrombus was removed in a further six patients (2.5%). No patient in this series recovered from anaesthesia with an IOS, but the rate of postoperative stroke was 2.8%.Conclusionsour policy of TCD plus angioscopy has continued to contribute towards a sustained reduction in the risk of IOS following CEA, but requires access to reliable equipment and technical support. However, a policy of intra-operative quality control assessment may not necessarily alter the rate of postoperative stroke
Pocket Monte Carlo algorithm for classical doped dimer models
We study the correlations of classical hardcore dimer models doped with
monomers by Monte Carlo simulation. We introduce an efficient cluster
algorithm, which is applicable in any dimension, for different lattices and
arbitrary doping. We use this algorithm for the dimer model on the square
lattice, where a finite density of monomers destroys the critical confinement
of the two-monomer problem. The monomers form a two-component plasma located in
its high-temperature phase, with the Coulomb interaction screened at finite
densities. On the triangular lattice, a single pair of monomers is not
confined. The monomer correlations are extremely short-ranged and hardly change
with doping.Comment: 6 pages, REVTeX
First- and second-order phase transitions in a driven lattice gas with nearest-neighbor exclusion
A lattice gas with infinite repulsion between particles separated by
lattice spacing, and nearest-neighbor hopping dynamics, is subject to a drive
favoring movement along one axis of the square lattice. The equilibrium (zero
drive) transition to a phase with sublattice ordering, known to be continuous,
shifts to lower density, and becomes discontinuous for large bias. In the
ordered nonequilibrium steady state, both the particle and order-parameter
densities are nonuniform, with a large fraction of the particles occupying a
jammed strip oriented along the drive. The relaxation exhibits features
reminiscent of models of granular and glassy materials.Comment: 8 pages, 5 figures; results due to bad random number generator
corrected; significantly revised conclusion
On Ising and dimer models in two and three dimensions
Motivated by recent interest in 2+1 dimensional quantum dimer models, we
revisit Fisher's mapping of two dimensional Ising models to hardcore dimer
models. First, we note that the symmetry breaking transition of the
ferromagetic Ising model maps onto a non-symmetry breaking transition in dimer
language -- instead it becomes a deconfinement transition for test monomers.
Next, we introduce a modification of Fisher's mapping in which a second dimer
model, also equivalent to the Ising model, is defined on a generically
different lattice derived from the dual. In contrast to Fisher's original
mapping, this enables us to reformulate frustrated Ising models as dimer models
with positive weights and we illustrate this by providing a new solution of the
fully frustrated Ising model on the square lattice. Finally, by means of the
modified mapping we show that a large class of three-dimensional Ising models
are precisely equivalent, in the time continuum limit, to particular quantum
dimer models. As Ising models in three dimensions are dual to Ising gauge
theories, this further yields an exact map between the latter and the quantum
dimer models. The paramagnetic phase in Ising language maps onto a deconfined,
topologically ordered phase in the dimer models. Using this set of ideas, we
also construct an exactly soluble quantum eight vertex model.Comment: 10 pages, 9 figures autmatically include
The Ising Susceptibility Scaling Function
We have dramatically extended the zero field susceptibility series at both
high and low temperature of the Ising model on the triangular and honeycomb
lattices, and used these data and newly available further terms for the square
lattice to calculate a number of terms in the scaling function expansion around
both the ferromagnetic and, for the square and honeycomb lattices, the
antiferromagnetic critical point.Comment: PDFLaTeX, 50 pages, 5 figures, zip file with series coefficients and
background data in Maple format provided with the source files. Vs2: Added
dedication and made several minor additions and corrections. Vs3: Minor
corrections. Vs4: No change to eprint. Added essential square-lattice series
input data (used in the calculation) that were removed from University of
Melbourne's websit
Rare SLC13A1 variants associate with intervertebral disc disorder highlighting role of sulfate in disc pathology
Publisher Copyright: © 2022, The Author(s).Back pain is a common and debilitating disorder with largely unknown underlying biology. Here we report a genome-wide association study of back pain using diagnoses assigned in clinical practice; dorsalgia (119,100 cases, 909,847 controls) and intervertebral disc disorder (IDD) (58,854 cases, 922,958 controls). We identify 41 variants at 33 loci. The most significant association (ORIDD = 0.92, P = 1.6 × 10−39; ORdorsalgia = 0.92, P = 7.2 × 10−15) is with a 3’UTR variant (rs1871452-T) in CHST3, encoding a sulfotransferase enzyme expressed in intervertebral discs. The largest effects on IDD are conferred by rare (MAF = 0.07 − 0.32%) loss-of-function (LoF) variants in SLC13A1, encoding a sodium-sulfate co-transporter (LoF burden OR = 1.44, P = 3.1 × 10−11); variants that also associate with reduced serum sulfate. Genes implicated by this study are involved in cartilage and bone biology, as well as neurological and inflammatory processes.Peer reviewe
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