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Search Results: 1 - 10 of 298756 matches for " J Wood "
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Loss to follow up within an HIV cohort
H Wood,J Dhar
Journal of the International AIDS Society , 2012, DOI: 10.7448/ias.15.6.18389
Abstract: BHIVA guidelines recommend that all ARV-na ve and stable on-treatment patients are monitored at least 6 monthly [1]. Studies have shown that loss to follow up (LFU) not only worsens outcomes [2] but has increased potential for onward transmission. Case notes of 1275 HIV patients registered under our care up to January 2011 were examined for attendance within the previous 6 months. 788 (61%) patients had not been seen within the previous 6 months. Reasons for non attendance were identified. These are outlined below: 76% of the 130 LFU whose demographics were further examined were of Black African ethnicity, 54% female, 51% of single marital status and 48% of patients had been taking ARVs at the time of LFU. Interestingly, 53% of patients were lost to follow up within 1 year of diagnosis. The LFU patients (88) that had a local GP and a registered current address were sent recall letters. A small number of patients reengaged with care as a result of this action, some having not attended for over 5 years. Partner notification led to a number of new diagnoses in these cases. Failure to respond led to subsequent letters inviting them to clinic and finally a letter to their GP informing them of non attendance. In September 2011, a new recall system using Lillie Electronic Patient Records (EPR) was introduced to promptly recognise if a patient had not attended for care as planned. Prior to this, recall was a manual process carried out by the Health Advising Team. We conclude that within our cohort we had a particularly mobile group of patients; 455 (36%) transferring care to another clinic within the UK, 54 (4%) moving out of UK. 76% of the LFU group being of Black African ethnicity highlights the ongoing problem of retention of care in this group. Further exploration is needed to identify additional issues besides housing and immigration that lead to LFU. Furthermore, the disportionate number of patients (53%) disengaging with services within 1 year of diagnosis should encourage HIV services to provide additional support within this time period to reduce LFU. This study highlights the need for robust recall systems within clinics to identify those individuals not engaging with services or not attending for routine monitoring. These may be easier to implement with the increasing use of EPR. An audit of the recall system is planned in September 2012 to re-examine loss to follow up rates after its implementation.
Non-completely positive maps: properties and applications
Christopher J. Wood
Physics , 2009,
Abstract: We investigate the evolution of open quantum systems in the presence of initial correlations with an environment. Here the standard formalism of describing evolution by completely positive trace preserving (CPTP) quantum operations can fail and non-completely positive (non-CP) maps may be observed. A new classification of correlations between a system and environment using quantum discord is explored. However, we find quantum discord is not a symmetric quantity between exchange of systems and this leads to ambiguity in classifications - states which are both quantum and classically correlated depending on the order of the two systems. State preparation in quantum process tomography is investigated with regard to non-CP maps. In SQPT the preparation procedure can influence the complete-positivity of the reconstructed quantum operation if our system is initially correlated with an environment. We examine a recently proposed preparation procedures using projective measurements, and propose our own protocol that uses a single measurement followed by unitary rotations. The former can give rise to non-CP evolution while the later will always give rise to a CP map. State preparation in AAPT was found always to give rise to CP evolution. We examine the effect of statistical noise in process tomography and find it can result in the identification of a non-CP when the evolution should be CP. The variance of the distribution for reconstructed processes is found to be inversely proportional to the number of copies of a state used to perform tomography. Finally, we detail an experiment using currently available linear optics QC devices to demonstrate non-CP maps arising in SQPT.
Partition Learning for Multiagent Planning
Jared Wood,J. Karl Hedrick
Journal of Robotics , 2012, DOI: 10.1155/2012/590479
Abstract: Automated surveillance of large geographic areas and target tracking by a team of autonomous agents is a topic that has received significant research and development effort. The standard approach is to decompose this problem into two steps. The first step is target track estimation and the second step is path planning by optimizing directly over target track estimation. This standard approach works well in many scenarios. However, an improved approach is needed for the scenario when general, nonparametric estimation is required, and the number of targets is unknown. The focus of this paper is to present a new approach that inherently handles the task to search for and track an unknown number of targets within a large geographic area. This approach is designed for the case when the search is performed by a team of autonomous agents and target estimation requires general, nonparametric methods. There are consequently very few assumptions made. The only assumption made is that a time-changing target track estimation is available and shared between the agents. This estimation is allowed to be general and nonparametric. Results are provided that compare the performance of this new approach with the standard approach. From these results it is concluded that this new approach improves search and tracking when the number of targets is unknown and target track estimation is general and nonparametric. 1. Introduction The advancement of computing technology has enabled the practical development of intelligent autonomous systems. Intelligent autonomous systems can be used to perform difficult sensing tasks. One such sensing task is to search for and track targets over large geographic areas. Much research has gone into this task resulting in a standard approach. This standard approach decomposes the problem into two steps. (1)Target track estimation. (2)Agent path optimization based on target track estimation. Significant research has been accomplished for each of these steps. Target track estimation has largely been solved [1–5] and this paper proposes no new methods for target track estimation. Agent path optimization based on target track estimation has been solved for many scenarios. However, the general scenario of when the number of targets is unknown still requires more development. The standard approach in general works particularly well when it can be assumed that there is a single target [6–14]. And in many scenarios the standard approach works well even when there are multiple targets [15, 16]. However, when there are multiple targets, methods following
Coronal diagnostics
J. C. Raymond,K. Wood
Revista mexicana de astronomía y astrofísica , 2000,
Abstract: Los cocientes de l neas de emisi on en el UV han permitido diagnosticar la densidad, temperatura, abundancias de elementos y el estado de ionizaci on de los plasmas astrof sicos. Con la nueva generaci on de sat elites de rayos-X, estas t ecnicas podr an usarse en los espectros de rayos-X. Es importante recordar que los cocientes proveen valores promediados a lo largo de la l nea de visi on y diferentes diagn osticos dar an valores pesados de forma diferente. Existen varias suposiciones impl citas en los an alisis de estos cocientes. En particular, se suele suponer que la profundi- dad optica es despreciable. Damos algunos ejemplos de las bondades de usar la dispersi on de fotones como una nueva herramienta de diagn ostico, ilustrando los peligros de usar los m etodos usuales cuando la opacidad es alta.
Multimodality Fusion with MRI, CT, and Ultrasound Contrast for Ablation of Renal Cell Carcinoma
Hayet Amalou,Bradford J. Wood
Case Reports in Urology , 2012, DOI: 10.1155/2012/390912
Abstract:
Multimodality Fusion with MRI, CT, and Ultrasound Contrast for Ablation of Renal Cell Carcinoma
Hayet Amalou,Bradford J. Wood
Case Reports in Urology , 2012, DOI: 10.1155/2012/390912
Abstract: Fusion technology with electromagnetic (EM) tracking enables navigation with multimodality feedback that lets the operator use different modalities during different parts of the image-guided procedure. This may be particularly helpful in patients with renal insufficiency undergoing kidney tumor ablation, in whom there is a desire to minimize or avoid nephrotoxic iodinated contrast exposure. EM tracking software merges and fuses different imaging modalities such as MRI, CT, and ultrasound and can also display the position of needles in real time in relation to preprocedure imaging, which may better define tumor targets than available intraoperative imaging. EM tracking was successfully used to ablate a poorly visualized renal tumor, through the combined use of CT, gadolinium-enhanced MR, and contrast-enhanced US imaging to localize the tumor. 1. Introduction Although surgical resection remains the gold standard for treating renal cell carcinoma, radiofrequency ablation (RFA) or cryoablation of renal lesions is widely becoming accepted as an effective treatment modality for patients that are poor surgical candidates, or in whom poor renal function necessitates a nephron-sparing approach [1]. The most technically challenging portion of an ablation procedure may be the localization of the tumor margins, which may be best defined on a modality (or enhancement phase) not immediately available during the procedure. Renal tumors may be poorly visualized with unenhanced CT or US and may be only visible on contrast-enhanced ultrasound (US), CT, and MRI [1]. However, MR-guided interventions are limited by cost, availability, and special equipment needs. EM tracking allows real-time visualization of needle-tip position and angle of trajectory superimposed upon a pre-procedural image. Such systems require an electromagnetic field generator and a special introducer needle or stylet with a sensor coil embedded within an introducer needle or clipped to the needle hub. A small current is induced by the coil, as it moves within the changing electromagnetic field. This changing current reports three dimensional position coordinates and trajectory. Coregistration or matching of modalities is accomplished by placing fiducials or a fiducial patch on the skin near the field of interest. The coordinates are semiautomatically matched between the image and the fiducial, then a virtual image of the needle position is superimposed upon prior CT, MRI, and/or PET [2]. A composite fusion image can be displayed blending (or displaying side by side) two or more modalities along with
MicroRNAs in opioid addiction: elucidating evolution
Emily J. Wood,Leonard Lipovich
Frontiers in Genetics , 2012, DOI: 10.3389/fgene.2012.00241
Abstract: Three reviews in the Frontiers Research Topic “Non-Coding RNA and Addiction” (He and Wang, 2012; Rodriguez, 2012; Zheng et al., 2012), grouped under the chapter “MicroRNAs and Morphine,” focus on the contribution of microRNAs to opioid abuse. Although animal models have been fundamental to our understanding of addiction pathways, the assumption that microRNAs implicated in opioid tolerance – and their binding sites in mRNAs – are conserved in mammalian evolution was not examined by the authors. Inspired by recent reports which highlight a surprising lack of evolutionary conservation in non-coding RNA genes, in this perspective we use public genome, annotation, and transcriptome datasets to verify microRNA host gene, mature microRNA, and microRNA binding site conservation at key loci functional in opioid addiction. We reveal a complex evolutionary landscape in which certain directional regulatory edges of the microRNA–mRNA hub-and-spoke network lack pan-mammalian conservation.
Radiative Equilibrium and Temperature Correction in Monte Carlo Radiation Transfer
J. E. Bjorkman,Kenneth Wood
Physics , 2001, DOI: 10.1086/321336
Abstract: We describe a general radiative equilibrium and temperature correction procedure for use in Monte Carlo radiation transfer codes with sources of temperature-independent opacity, such as astrophysical dust. The technique utilizes the fact that Monte Carlo simulations track individual photon packets, so we may easily determine where their energy is absorbed. When a packet is absorbed, it heats a particular cell within the envelope, raising its temperature. To enforce radiative equilibrium, the absorbed packet is immediately re-emitted. To correct the cell temperature, the frequency of the re-emitted packet is chosen so that it corrects the temperature of the spectrum previously emitted by the cell. The re-emitted packet then continues being scattered, absorbed, and re-emitted until it finally escapes from the envelope. As the simulation runs, the envelope heats up, and the emergent spectral energy distribution (SED) relaxes to its equilibrium value, without iteration. This implies that the equilibrium temperature calculation requires no more computation time than the SED calculation of an equivalent pure scattering model with fixed temperature. In addition to avoiding iteration, our method conserves energy exactly, because all injected photon packets eventually escape. Furthermore, individual packets transport energy across the entire system because they are never destroyed. This long-range communication, coupled with the lack of iteration, implies that our method does not suffer the convergence problems commonly associated with lambda-iteration. To verify our temperature correction procedure, we compare our results to standard benchmark tests, and finally we present the results of simulations for two-dimensional axisymmetric density structures.
Harmonic morphisms, conformal foliations and shear-free ray congruences
P. Baird,J. C. Wood
Mathematics , 1996,
Abstract: Equivalences between conformal foliations on Euclidean $3$-space, Hermitian structures on Euclidean $4$-space, shear-free ray congruences on Minkowski $4$-space, and holomorphic foliations on complex $4$-space are explained geometrically and twistorially; these are used to show that 1) any real-analytic complex-valued harmonic morphism without critical points defined on an open subset of Minkowski space is conformally equivalent to the direction vector field of a shear-free ray congruence, 2) the boundary values at infinity of a complex-valued harmonic morphism on hyperbolic $4$-space define a real-analytic conformal foliation by curves of an open subset of Euclidean $3$-space and all such foliations arise this way. This gives an explicit method of finding such foliations; some examples are given.
Twistorial harmonic morphisms with one-dimensional fibres on self-dual four-manifolds
R. Pantilie,J. C. Wood
Mathematics , 2003,
Abstract: We introduce a general notion of twistorial map and classify twistorial harmonic morphisms with one-dimensional fibres from self-dual four-manifolds. Such maps can be characterised as those which pull back Abelian monopoles to self-dual connections. In fact, the constructions involve solving a generalised monopole equation, and also the Beltrami fields equation of hydrodynamics, and lead to constructions of self-dual metrics.
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