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Search Results: 1 - 10 of 526403 matches for " M. G. Davies "
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Effects of copper and zinc on proteoglycan metabolism in articular cartilage
M. Pasqualicchio,R. Gasperini,G. P. Velo,M. E. Davies
Mediators of Inflammation , 1996, DOI: 10.1155/s0962935196000154
Abstract:
Issues of diffuse pollution model complexity arising from performance benchmarking
M. G. Hutchins, C. Dilks, H. N. Davies,A. Deflandre
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2007,
Abstract: Flow and nitrate dynamics were simulated in two catchments, the River Aire in northern England and the River Ythan in north-east Scotland. In the case of the Aire, a diffuse pollution model was coupled with a river quality model (CASCADE-QUESTOR); in the study of the Ythan, an integrated model (SWAT) was used. In each study, model performance was evaluated for differing levels of spatial representation in input data sets (rainfall, soils and land use). In respect of nitrate concentrations, the performance of the models was compared with that of a regression model based on proportions of land cover. The overall objective was to assess the merits of spatially distributed input data sets. In both catchments, specific measures of quantitative performance showed that models using the most detailed available input data contributed, at best, only a marginal improvement over simpler implementations. Hence, the level of complexity used in input data sets has to be determined, not only on multiple criteria of quantitative performance but also on qualitative assessments, reflecting the specific context of the model application and the current and likely future needs of end-users.
A Comparison of Mortality following Distal Femoral Fractures and Hip Fractures in an Elderly Population
R. W. Jordan,G. S. Chahal,M. Davies,K. Srinivas
Advances in Orthopedic Surgery , 2014, DOI: 10.1155/2014/873785
Abstract: Introduction. Patients suffering a distal femoral fracture are at a high risk of morbidity and mortality. Currently this cohort is not afforded the same resources as those with hip fractures. This study aims to compare their mortality rates and assess whether surgical intervention improves either outcome or mortality following distal femoral fractures. Methods. Patients over sixty-five admitted with a distal femoral fracture between June 2007 and 2012 were retrospectively identified. Patients mobility was categorised as unaided, walking aid, zimmer frame, or immobile. The 30-day, six-month, and one-year mortality rates were recorded for this group as well as for hip fractures during the same period. Results. 68 patients were included in the study. The mortality rate for all patients with distal femoral fractures was 7% at 30 days, 26% at six months, and 38% at one year, higher than hip fractures during the same period by 8%, 13%, and 18%, respectively. Patients managed surgically had lower mortality rates and higher mobility levels. Conclusion. Patients suffering a distal femoral fracture have a high mortality rate and surgical intervention seems to improve both mobility and mortality. 1. Introduction Distal femoral fractures can result from either high energy injuries in young adults or low energy injuries in elderly patients with osteoporotic bone [1–3]. This injury accounts for around 6% of all fragility fractures [3] and its frequency is likely to rise with the increasing geriatric population. The prevalence of periprosthetic fractures following knee arthroplasty is 0.5%–2.2% [4, 5] which is also likely to increase with the rise in arthroplasties being performed [6]. Patients suffering a distal femoral fracture are at a high risk of complication given the prevalence of medical comorbidities in this cohort [7–9]. The mortality rates have been reported to be around 18% at six months and 18–30% at one year [1, 2, 10, 11]. The presence of either a knee arthroplasty or a significant comorbidity is associated with an increased mortality [2]. The injury has a significant effect on patients’ mobility with one series reporting only 18% were able to walk unaided with 23% housebound and 26% not able to perform social activities [12]. Traditionally traction followed by cast bracing was the common treatment technique [13]; however this option results in prolonged bed rest [14], loss of motion [15, 16], and either nonunion or malunion [17]. Butt et al. performed a randomised controlled trial comparing six weeks of traction followed by bracing with plate fixation.
Handling uncertainties in background shapes: the discrete profiling method
P. D. Dauncey,M. Kenzie,N. Wardle,G. J. Davies
Physics , 2014, DOI: 10.1088/1748-0221/10/04/P04015
Abstract: A common problem in data analysis is that the functional form, as well as the parameter values, of the underlying model which should describe a dataset is not known a priori. In these cases some extra uncertainty must be assigned to the extracted parameters of interest due to lack of exact knowledge of the functional form of the model. A method for assigning an appropriate error is presented. The method is based on considering the choice of functional form as a discrete nuisance parameter which is profiled in an analogous way to continuous nuisance parameters. The bias and coverage of this method are shown to be good when applied to a realistic example.
Entanglement quantification by local unitaries
A. Monras,G. Adesso,S. M. Giampaolo,G. Gualdi,G. B. Davies,F. Illuminati
Physics , 2011, DOI: 10.1103/PhysRevA.84.012301
Abstract: Invariance under local unitary operations is a fundamental property that must be obeyed by every proper measure of quantum entanglement. However, this is not the only aspect of entanglement theory where local unitaries play a relevant role. In the present work we show that the application of suitable local unitary operations defines a family of bipartite entanglement monotones, collectively referred to as "mirror entanglement". They are constructed by first considering the (squared) Hilbert-Schmidt distance of the state from the set of states obtained by applying to it a given local unitary. To the action of each different local unitary there corresponds a different distance. We then minimize these distances over the sets of local unitaries with different spectra, obtaining an entire family of different entanglement monotones. We show that these mirror entanglement monotones are organized in a hierarchical structure, and we establish the conditions that need to be imposed on the spectrum of a local unitary for the associated mirror entanglement to be faithful, i.e. to vanish on and only on separable pure states. We analyze in detail the properties of one particularly relevant member of the family, the "stellar mirror entanglement" associated to traceless local unitaries with nondegenerate spectrum and equispaced eigenvalues in the complex plane. This particular measure generalizes the original analysis of [Giampaolo and Illuminati, Phys. Rev. A 76, 042301 (2007)], valid for qubits and qutrits. We prove that the stellar entanglement is a faithful bipartite entanglement monotone in any dimension, and that it is bounded from below by a function proportional to the linear entropy and from above by the linear entropy itself, coinciding with it in two- and three-dimensional spaces.
Weathering of coil-coatings: UV radiation and thermal effects
Castela, A. S.,Sim?es, A. M.,Davies, G.,Ferreira, M. G. S.
Revista de Metalurgia , 2003,
Abstract: The effect of heat and of QUV ageing on coil coatings was tested by electrochemical impedance, and the results compared with surface analysis of the polymers by FTIR and XPS. It was shown that UV radiation is more relevant than heat to chemical degradation. A different correlation between water permeation and chemical degradation was observed depending on the coating thickness: for the thinner coatings, the higher UV degradation has corresponded to increased water absorption, whereas in the thicker coating, the bulk effect of heat was more relevant to water permeation. El efecto del calor y del envejecimiento, QUV, sobre recubrimiemtos de bobinas se probó mediante la impedancia electroquímica, y los resultados se compararon con análisis superficiales de los polímeros usando FTIR y XPS. Se encontró que la radiación UV es más importante que el calor en la degradación química. Una correlación diferente, entre agua infiltrada y degradación química, se observó, dependiendo del espesor del recubrimiento: para los recubrimientos más delgados, mayor degradación UV correspondió a un incremento de absorción de agua; en cambio, para los recubrimientos más gruesos, el efecto del calor fue más importante para la infiltración del agua.
9C continued: a radio-source survey at 15 GHz
E. M. Waldram,G. G. Pooley,M. L. Davies,K. J. B. Grainge,P. F. Scott
Physics , 2009, DOI: 10.1111/j.1365-2966.2010.16333.x
Abstract: In our first paper we described three regions of the 9C survey of radio sources with the Ryle telescope at 15.2 GHz, constituting a total area of 520 deg^2 to a completeness limit of approximately 25 mJy. Here we report on a series of deeper regions, amounting to an area of 115 deg^2 complete to approximately 10 mJy and of 29 deg^2 complete to approximately 5.5 mJy. We have investigated the source counts and the distributions of the 1.4 to 15.2 GHz spectral index (alpha) for these deeper samples. The whole catalogue of 643 sources is available online. Down to our lower limit of 5.5 mJy we detect no evidence for any change in the differential source count from the earlier fitted count above 25 mJy. We have matched both our new and earlier catalogues with the NRAO VLA Sky Survey (NVSS) catalogue at 1.4 GHz. For samples of sources selected at 15.2 GHz, in three flux density ranges, we detect a significant shift in the median value of alpha; samples with higher flux densities have higher proportions of sources with flat and rising spectra. We suggest that this observed shift is consistent with a model containing two distinct source populations having differently sloped source counts. Samples selected at 1.4 GHz contain significantly smaller proportions of sources with flat and rising spectra. Also, in our area complete to approximately 10 mJy, we find 5 sources between 10 to 15 mJy, amounting to 4.3 per cent of sources in this range, with no counterpart in the NVSS catalogue. These results illustrate the problems inherent in using a low frequency catalogue to characterise the source population at a much higher frequency and emphasise the value of our blind 15.2 GHz survey.
Ultraluminous X-Ray Sources in External Galaxies
A. R. King,M. B. Davies,M. J. Ward,G. Fabbiano,M. Elvis
Physics , 2001, DOI: 10.1086/320343
Abstract: We investigate models for the class of ultraluminous non-nuclear X-ray sources (ULXs) seen in a number of galaxies and probably associated with star-forming regions. Models where the X-ray emission is assumed to be isotropic run into several difficulties. In particular formation of sufficient numbers of the required ultramassive black-hole X-ray binaries is problematic, and the likely transient behaviour of the resulting systems is not in good accord with observation. The assumption of mild X-ray beaming suggests instead that ULXs may represent a shortlived but extremely common stage in the evolution of a wide class of X-ray binaries. The best candidate for this is the phase of thermal-timescale mass transfer inevitable in many intermediate and high-mass X-ray binaries. This in turn suggests a link with the Galactic microquasars. The short lifetimes of high-mass X-ray binaries would explain the association of ULXs with episodes of star formation. These considerations still allow the possibility that individual ULXs may contain extremely massive black holes.
GALEX selected Lyman Break Galaxies at z~2: Comparison with other Populations
L. Haberzettl,G. M. Williger,M. D. Lehnert,N. P. H. Nesvadba,L. J. M. Davies
Physics , 2011, DOI: 10.1088/0004-637X/745/1/96
Abstract: We present results of a search for bright Lyman break galaxies at 1.5<=z<=2.5 in the GOODS-S field using a NUV-dropout technique in combination with color-selection. We derived a sample of 73 LBG candidates. We compare our selection efficiencies to BM/BX- and BzK methods (techniques solely based on ground-based data sets), and find the NUV data to provide greater efficiency for selecting star-forming galaxies. We estimate LBG candidate ages, masses, star formation rates, and extinction from fitting PEGASE synthesis evolution models. We find about 20% of our LBG candidates are comparable to infrared luminous LBGs or sub-millimeter galaxies which are thought to be precursors of massive elliptical galaxies today. Overall, we can show that although BM/BX and BzK methods do identify star-forming galaxies at z~2, the sample they provide biases against those star-forming galaxies which are more massive and contain sizeable red stellar populations. A true Lyman break criterion at z~2 is therefore more directly comparable to the populations found at z~3, which does contain a red fraction.
Refractory oxides containing aluminium and barium
Davies T. J.,Biedermann M.,Chen Q-G.,Emblem H. G.
Ceramica , 1998,
Abstract: Oxides containing aluminium and barium, optionally with chromium, are refractory with several possible industrial uses. A gel precursor of an oxide having the formula BaO.n(Al2xCr2yO3), where 1
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