7,601 research outputs found
Critical organizational challenges in delivering business value from IT:the Perspective of Lebanese CIOs
Recent trends in the incidence of anxiety diagnoses and symptoms in primary care.
Anxiety is common, with significant morbidity, but little is known about presentations and recording of anxiety diagnoses and symptoms in primary care. This study aimed to determine trends in incidence and socio-demographic variation in General Practitioner (GP) recorded diagnoses of anxiety, mixed anxiety/depression, panic and anxiety symptoms
Variants on Dantzig-Wolfe Decomposition with Applications to Multistage Problems
The initial representation of an LP problem to which the Dantzig-Wolfe decomposition procedure is applied, is of the essence. We study this here, and, in particular, we consider two transformations of the problem, by introducing suitable linking rows and variables. We study the application of the Dantzig-Wolfe procedure to these new representations of the original problem and the relationship to previously proposed algorithms. Advantages and disadvantages from a computational viewpoint are discussed. Finally we develop a decomposition algorithm based upon these ideas for solving multistage staircase-structured LP problems
Algorithms Based upon Generalized Linear Programming for Stochastic Programs with Recourse
In this paper, the author discusses solution algorithms for a particular form of two-stage stochastic linear programs with recourse. The algorithms considered are based upon the generalized linear programming method of Wolfe.
The author first gives an alternative formulation of the original problem and uses this to examine the relation between tenders and certainty equivalents. He then considers problems with simple recourse, discussing algorithms for two cases: (a) when the distribution is discrete and probabilities are known explicitly; (b) when the probability distribution is other than discrete or when it is only known implicitly through some simulation model. The latter case is especially useful because it makes possible the transition to general recourse. Some possible solution strategies based upon generalized programming for general recourse problems are then discussed.
This paper is a product of the Adaptation and Optimization Project within the System and Decision Sciences Program
Analogues of Dixon's and Powell's Theorems for Unconstrained Minimization with Inexact Line Searches
By modifying the way in which search directions are defined, we show how to relax the restrictive assumption that line searches must be exact in the theorems of Dixon and Powell. We show also that the BFGS algorithm modified in this way is equivalent to the three-term-recurrence (TTR) method for quadratic functions
An Adaptive Method for Minimizing a Sum of Squares of Nonlinear Functions
The Gauss-Newton and the Levenberg-Marquardt algorithms for solving nonlinear least squares problems, minimize F(x) = sum_i=1^m (f_i(x))^2 for x in R^n, are both based upon the premise that one term in the Hessian of F(x) dominates its other terms, and that the Hessian may be approximated by this dominant term J^T J, where J_ij = ( delta f_i / delta x_j ). We are motivated here by the need for an algorithm which works well when applied to problems for which this premise is substantially violated, and is yet able to take advantage of situations where the premise holds. We describe and justify a method for approximating the Hessian of F ( x ) which uses a convex combination of J^T J and a matrix obtained by making quasi-Newton updates. In order to evaluate the usefulness of this idea, we construct a nonlinear least squares algorithm which uses this Hessian approximation, and report test results obtained by applying it to a set of test problems. A merit of our approach is that it demonstrates how a single adaptive algorithm can be used to efficiently solve unconstrained nonlinear optimization problems (whose Hessians have no particular structure), small residual and large residual, nonlinear least squares problems. Our paper can also be looked upon as an investigation for one problem area, of the following more general question: how can one combine two different Hessian approximations (or model functions) which are simultaneously available? The technique suggested here may thus be more widely applicable and may be of use, for example, when minimizing functions which are only partly composed of sums of squares arising in penalty function methods
Histórias De Vida - notas e reflexões de pesquisa
Este texto aborda o tema das histórias de vida e narrativas autobiográficas, em seus aspectos teóricos e no relato de experiências de pesquisa. Apresenta alguns conceitos sobre o método História de Vida e apresenta possibilidades de uso do mesmo no campo da saúde coletiva. Agrega comentários e reflexões pautando-se nas experiências da autora em pesquisas com histórias de vida de mulheres, famílias e sujeitos em situação de vulnerabilidade. A autora entende que o método de Histórias de Vida, assim como as narrativas, possibilita tanto ao narrador quanto ao pesquisador a reconstrução de suas experiências e a ressignificação do vivido.This article considers life stories and autobiographical narratives as research instruments. It explains the life story method and its possible uses in the field of public health. It includes comments and reflections based on the author's experiences as she did research on the life stories of women, families and individuals in vulnerable situations. The author argues that the life story method, as well as the narratives, enables both the narrator and the researcher to reconstruct their experiences and to the reinterpret the meaning of what happened
Initiation rates of statin therapy for the primary prevention of cardiovascular disease: An assessment of differences between countries of the United Kingdom and between regions within England
Objectives To investigate the extent to which variation exists in the initiation rate of statin therapy for the primary prevention of cardiovascular disease between countries of the UK and between different regions within England.
Design Cohort study using data from a large UK primary care database.
Setting UK.
Participants 4 820 885 individuals from 554 general practices during the period 2004–2012.
Main outcome measures Rate of statin therapy initiation per 1000 person-years.
Results Relative to a fixed English rate of 1 initiation per 1000 person-years and accounting for gender, age and social deprivation level, the rate was similar for Scotland at 0.92 (95% CI 0.84 to 1.00) and rates for Northern Ireland and Wales were higher at 1.40 (95% CI 1.20 to 1.62) and 1.18 (95% CI 1.05 to 1.32), respectively. Within England, the regions could be classified into three groups with respect to statin therapy initiation rates (relative to a rate of 1 initiation per 1000 person-years for London): the South Central 0.73 (95% CI 0.64 to 0.83), South West 0.80 (95% CI 0.71 to 0.91), East of England 0.81 (95% CI 0.71 to 0.94) and South East Coast 0.83 (95% CI 0.73 to 0.95); strategic health authorities had similar low rates followed by the East Midlands 0.88 (95% CI 0.73 to 1.05), West Midlands 0.96 (95% CI 0.84 to 1.09), North East 0.96 (95% CI 0.79 to 1.16), Yorkshire and Humber 0.97 (95% CI 0.81 to 1.17) and London strategic health authorities. North West England exhibited the highest rate of statin therapy initiation of 1.16 (95% CI 1.02 to 1.31).
Conclusions Considerable variation in the rate of statin therapy initiation was observed between the four countries of the UK and between different geographical regions within England
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Remembering the forgotten child: the role of immune checkpoint inhibition in patients with human immunod eficiency virus and cancer.
Patients with human immunodeficiency virus (HIV) infection have a high risk of developing virally-mediated cancers. These tumors have several features that could make them vulnerable to immune checkpoint inhibitors (ICIs) including, but not limited to, increased expression of the CTLA-4 and PD-1 checkpoints on their CD4+ T cells. Even so, HIV-positive patients are generally excluded from immunotherapy cancer clinical trials due to safety concerns. Hence, only case series have been published regarding HIV-positive patients with cancer who received ICIs, but these reports of individuals with a variety of malignancies demonstrate that ICIs have significant activity, exceeding a 65% objective response rate in Kaposi sarcoma. Furthermore, high-grade immune toxicities occurred in fewer than 10% of treated patients. The existing data suggest that the underlying biologic mechanisms that mediate development of cancer in HIV-infected patients should render them susceptible to ICI treatment. Preliminary, albeit limited, clinical experience indicates that checkpoint blockade is both safe and efficacious in this setting. Additional clinical trials that include HIV-positive patients with cancer are urgently needed
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