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Search Results: 1 - 10 of 229644 matches for " John P. Fletcher "
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Venous Thromboembolism Following Colorectal Surgery for Suspected or Confirmed Malignancy
Brenton Sanderson,Kerry Hitos,John P. Fletcher
Thrombosis , 2011, DOI: 10.1155/2011/828030
Abstract: Surgery for colorectal cancer conveys a high risk of venous thromboembolism (VTE). The effect of thromboprophylactic regimens of varying duration on the incidence of VTE was assessed in 417 patients undergoing surgery between 2005 and 2009 for colorectal cancer. Low-dose unfractionated heparin (LDUH) was used in 52.7% of patients, low-molecular-weight heparin (LMWH) in 35.3%, and 10.7% received LDUH followed by LMWH. Pharmacological prophylaxis was continued after hospitalisation in 31.6%. Major bleeding occurred in 4% of patients. The 30-day mortality rate was 1.9%. The incidence of symptomatic VTE from hospital admission for surgery to 12 months after was 2.4%. There were no in-hospital VTE events. The majority of events occurred in the three-month period after discharge, but there were VTE events up to 12 months, especially in patients with more advanced cancer and multiple comorbidities.
Venous Thromboembolism Following Colorectal Surgery for Suspected or Confirmed Malignancy
Brenton Sanderson,Kerry Hitos,John P. Fletcher
Thrombosis , 2011, DOI: 10.1155/2011/828030
Abstract: Surgery for colorectal cancer conveys a high risk of venous thromboembolism (VTE). The effect of thromboprophylactic regimens of varying duration on the incidence of VTE was assessed in 417 patients undergoing surgery between 2005 and 2009 for colorectal cancer. Low-dose unfractionated heparin (LDUH) was used in 52.7% of patients, low-molecular-weight heparin (LMWH) in 35.3%, and 10.7% received LDUH followed by LMWH. Pharmacological prophylaxis was continued after hospitalisation in 31.6%. Major bleeding occurred in 4% of patients. The 30-day mortality rate was 1.9%. The incidence of symptomatic VTE from hospital admission for surgery to 12 months after was 2.4%. There were no in-hospital VTE events. The majority of events occurred in the three-month period after discharge, but there were VTE events up to 12 months, especially in patients with more advanced cancer and multiple comorbidities. 1. Introduction Major surgery conveys a significant risk of venous thromboembolism (VTE), a condition that encompasses both deep vein thrombosis (DVT) and pulmonary embolism (PE). The first-time incidence of VTE in the general population is approximately 100 persons per 100,000 per year [1]. VTE is a common cause of morbidity and mortality in surgical patients which is preventable in the majority of cases with appropriate prophylaxis [1, 2]. There are numerous risk factors for developing VTE and, importantly, for colorectal cancer surgery patients, include increasing age, history of VTE, malignancy and its treatment, and surgery duration [3–5]. The presence of these risk factors places colorectal cancer surgery patients at an increased risk of VTE compared to general surgical patients [5, 6]. A retrospective analysis examined VTE in colorectal cancer patients, 70% of whom underwent surgery, and found a VTE incidence of 3.1% (2,100 patients) at two years [6]. The incidence rate was found to decrease over the two-year period, demonstrating the importance of VTE prophylaxis in the period after diagnosis and perioperatively [6]. The strongest predictors for VTE occurrence in this patient group were found to be the presence of metastatic disease and multiple co-morbidities [6]. In the American College of Chest Physicians (ACCP) evidence-based clinical practice guidelines, colorectal cancer surgery patients are judged as having a high risk of VTE and are recommended to receive both anticoagulant and mechanical VTE prophylaxis unless contraindicated [7]. For anticoagulant prophylaxis, colorectal cancer surgery patients are recommended to receive low-molecular-weight
Platelets and Smooth Muscle Cells Affecting the Differentiation of Monocytes
Michelle W. Y. Williams, Ann K. Guiffre, John P. Fletcher
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0088172
Abstract: Background Atherosclerosis is characterised by the formation of plaques. Monocytes play a pivotal role in plaque development as they differentiate into foam cells, a component of the lipid core whilst smooth muscle cells (SMC) are the principal cell identified in the cap. Recently, the ability of monocytes to differentiate into a myriad of other cell types has been reported. In lieu of these findings the ability of monocytes to differentiate into SMCs/smooth muscle (SM)-like cells was investigated. Method and Results Human monocytes were co-cultured with platelets or human coronary aortic SMCs and then analysed to assess their differentiation into SMCs/SM-like cells. The differentiated cells expressed a number of SMC markers and genes as determined by immunofluorescence staining and quantitative polymerase chain reaction (qPCR). CD array analysis identified marker expression profiles that discriminated them from monocytes, macrophages and foam cells as well as the expression of markers which overlapped with fibroblast and mesenchymal cells. Electron microscopy studies identified microfilaments and increased amounts of rough endoplasmic reticulum indicative of the SM- like cells, fibroblasts. Conclusions In the appropriate environmental conditions, monocytes can differentiate into SM-like cells potentially contributing to cap formation and plaque stability. Thus, monocytes may play a dual role in the development of plaque formation and ultimately atherosclerosis.
Computing Hulls And Centerpoints In Positive Definite Space
P. Thomas Fletcher,John Moeller,Jeff M. Phillips,Suresh Venkatasubramanian
Mathematics , 2009,
Abstract: In this paper, we present algorithms for computing approximate hulls and centerpoints for collections of matrices in positive definite space. There are many applications where the data under consideration, rather than being points in a Euclidean space, are positive definite (p.d.) matrices. These applications include diffusion tensor imaging in the brain, elasticity analysis in mechanical engineering, and the theory of kernel maps in machine learning. Our work centers around the notion of a horoball: the limit of a ball fixed at one point whose radius goes to infinity. Horoballs possess many (though not all) of the properties of halfspaces; in particular, they lack a strong separation theorem where two horoballs can completely partition the space. In spite of this, we show that we can compute an approximate "horoball hull" that strictly contains the actual convex hull. This approximate hull also preserves geodesic extents, which is a result of independent value: an immediate corollary is that we can approximately solve problems like the diameter and width in positive definite space. We also use horoballs to show existence of and compute approximate robust centerpoints in positive definite space, via the horoball-equivalent of the notion of depth.
A poética das ausências: a arte contemporanea em Belém como experiência de sentidos urbanos e memoriais
John Fletcher,Afonso Medeiros
Revista Digital do LAV , 2013, DOI: 10.5902/19837348
Abstract: Compreender uma produ o visual nos dias atuais é buscar uma forma de situar tal poética como um registro dos processos culturais contemporaneos, uma vez que sua lógica de cria o se insere em um contexto de culturalidades híbridas e de encurtamento de fronteiras. Sob essa ótica, a presente pesquisa trata de um recorte de processos artísticos visuais em Belém, PA, os quais têm se utilizado de premissas sobre o sentido de ausência para espelhar e discutir interpretativamente problemáticas urbanas relacionadas ao patrim nio arquitet nico e à memória; reconhecimento da experiência de um mundo interconectado e atravessado por assimetrias e transforma es.
Sensing and Multiscale Structure
John F. A. Fletcher
Physics , 2012,
Abstract: We introduce a method of estimating parameters associated with a fractal random scattering medium, which utilizes the multiscale properties of the scattered field. The example of ray-density fluctuations beyond a phase screen with fractal slope is considered. An exact solution to the forward problem, in the case of the Brownian fractal, leads to an expression for the volatility of the slope. This expression is invariant under a change of probability measure, a fact which gives rise to the corresponding result for a (stationary) Ornstein-Uhlenbeck slope. We demonstrate that our analytical results are consistent with numerical simulations. Finally, an application to the determination of sea ice thickness via sonar is discussed.
A limit theorem for the sum of squared differences of an integrated Ito process with application to inverse scattering
John F. A. Fletcher
Physics , 2012,
Abstract: We investigate a functional obtained by summing the squared differences of the integral of an Ito process over disjoint intervals. The limit of this sum is shown to converge in probability to two thirds the quadratic variation of the underlying process. An application to inverse scattering from a random fractal surface is presented.
The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances
John L. Tonry,Alan Dressler,John P. Blakeslee,Edward A. Ajhar,Andre B. Fletcher,Gerard A. Luppino,Mark R. Metzger,Christopher B. Moore
Physics , 2000, DOI: 10.1086/318301
Abstract: We report data for $I$ band Surface Brightness Fluctuation (SBF) magnitudes, V-I colors, and distance moduli for 300 galaxies. The Survey contains E, S0 and early-type spiral galaxies in the proportions of 49:42:9, and is essentially complete for E galaxies to Hubble velocities of 2000 km/s, with a substantial sampling of E galaxies out to 4000 km/s. The median error in distance modulus is 0.22 mag. We also present two new results from the Survey. (1) We compare the mean peculiar flow velocity (bulk flow) implied by our distances with predictions of typical cold dark matter transfer functions as a function of scale, and find very good agreement with cold, dark matter cosmologies if the transfer function scale parameter $\Gamma$, and the power spectrum normalization $\sigma_8$ are related by $\sigma_8 \Gamma^{-0.5} \approx 2\pm0.5$. Derived directly from velocities, this result is independent of the distribution of galaxies or models for biasing. The modest bulk flow contradicts reports of large-scale, large-amplitude flows in the $\sim200$ Mpc diameter volume surrounding our Survey volume. (2) We present a distance-independent measure of absolute galaxy luminosity, \Nbar, and show how it correlates with galaxy properties such as color and velocity dispersion, demonstrating its utility for measuring galaxy distances through large and unknown extinction.
STUDIES ON VACUUM-DRYING FOR THE PRESERVATION OF PLANT PATHOGENIC BACTERIA
Maureen J. Fletcher and John M. Young
Journal of Culture Collections , 1998,
Abstract: A comparison of freeze-drying and vacuum-drying of plant pathogenic bacteria showed no short-term differences in survival. Storage long term with vacuum-drying suggests that this simpler method offers similar survival rates to freeze-drying. A modification of the procedure in which the condenser is by-passed in the latter stages of drying offers the prospect of achieving lower pressures which are not limited by the vapour pressure of ice.
Prevalence of gastrointestinal pathogens in Sub-Saharan Africa: systematic review and meta-analysis
Stephanie M. Fletcher,Damien Stark,John Ellis
Journal of Public Health in Africa , 2011, DOI: 10.4081/jphia.2011.e30
Abstract: A significant proportion of vulnerable people in sub-Saharan Africa (SSA) remain at risk for contracting diarrhoeal diseases due to the presence of many risk factors facilitating their transmission. A systematic review of published articles from the SSA region was done to determine the prevalence and types of diarrhoeal pathogens in circulation, based on a search of databases, including EBSCO host, PubMed, Scopus, Science Direct, Google scholar and Web of Science was done between September 2009 and December 2010. Data were summarized from 27 studies, with pooled data analysed and reported. Pathogens were isolated from between 26.8-65.6% of cases, with an overall isolation rate of 55.7% (95% CI, 48.2-62.9%). Isolation rates were highest amongst adult cases followed by children, and the odds of isolating a pathogen was greater in diarrhoeal cases (Odds Ratio 4.93 (95% CI, 1.99 to 12.23), than in asymptomatic controls. Overall isolation ranged from 8% to 99%; and heterogeneity testing suggests differences between age groups (Q=5.806; df=2, P=0. 055). Mixed E. coli spp., (29.95%), Cryptosporidium (21.52%), Cyclospora (18%), Entamoeba, (13.8%), Shigella spp. (10.49%), Salmonella spp. (8.36%), and Campylobacter spp. (8.33%), were most commonly reported, and rotavirus was the most common virus isolated. This is the first review to look at the range of enteric pathogens circulating in SSA, and has confirmed high rates of isolation of pathogens from diarrhoeal cases. Public health practitioners can use this information to understanding the challenges related to diarrhoeal illness and set priorities for their prevention and control.
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