The value of myocardial perfusion scintigraphy in the diagnosis and management of angina and myocardial infarction : a probabilistic analysis

Background and Aim. Coronary heart disease (CHD) is the most common cause of death in the United Kingdom, accounting for more than 120,000 deaths in 2001, among the highest rates in the world. This study reports an economic evaluation of single photon emission computed tomography myocardial perfusion scintigraphy (SPECT) for the diagnosis and management of coronary artery disease (CAD). Methods. Strategies involving SPECT with and without stress electrocardiography (ECG) and coronary angiography (CA) were compared to diagnostic strategies not involving SPECT. The diagnosis decision was modelled with a decision tree model and long-term costs and consequences using a Markov model. Data to populate the models were obtained from a series of systematic reviews. Unlike earlier evaluations, a probabilistic analysis was included to assess the statistical imprecision of the results. The results are presented in terms of incremental cost per quality-adjusted life year (QALY). Results. At prevalence levels of CAD of 10.5%, SPECT-based strategies are costeffective; ECG-CA is highly unlikely to be optimal. At a ceiling ratio of _20,000 per QALY, SPECT-CA has a 90% likelihood of being optimal. Beyond this threshold, this strategy becomes less likely to be cost-effective. At more than _75,000 per QALY, coronary angiography is most likely to be optimal. For higher levels of prevalence (around 50%) and more than a _10,000 per QALY threshold, coronary angiography is the optimal decision. Conclusions. SPECTbased strategies are likely to be cost-effective when risk of CAD is modest (10.5%). Sensitivity analyses show these strategies dominated non-SPECT-based strategies for risk of CAD up to 4%. At higher levels of prevalence, invasive strategies may become worthwhile. Finally, sensitivity analyses show stress echocardiography as a potentially costeffective option, and further research to assess the relative cost-effectiveness of echocardiography should also be performed.This article was developed from a Technology Assessment Review conducted on behalf of the National Institute for Clinical Excellence (NICE) and was funded by the Department of Health on a grant administered by the National Coordinating Centre for Health Technology Assessment. The Health Economics Research Unit and the Health Services Research Unit are core funded by the Chief Scientist Office of the Scottish Executive Health Department.Peer reviewedAuthor versio

COUNTS WITH AN ENDOGENOUS BINARY REGRESSOR: A SERIES EXPANSION APPROACH

We propose an estimator for count data regression models where a binary regressor is endogenously determined. This estimator departs from previous approaches by using a flexible form for the conditional probability function of the counts. Using a Monte Carlo experiment we show that our estimator improves the fit and provides a more reliable estimate of the impact of regressors on the count when compared to alternatives which do restrict the mean to be linear-exponential. In an application to the number of trips by households in the US, we find that the estimate of the treatment effect obtained is considerably different from the one obtained under a linear-exponential mean specification.Count data, Polynominal Poisson Expansions, Flexible Functional Form.

Estrategias de solución de problemas matemáticos en estudiantes preuniversitarios

El objetivo de esta investigación es analizar las estrategias de solución de problemas matemáticos de los estudiantes del Ciclo de Iniciación Universitaria (CIU) de la Universidad Simón Bolívar sede del Litoral y cómo el docente apoya este proceso. Se pretende realizar una investigación descriptiva. Para ello, se propone que los estudiantes actúen como resolvedores de problemas esto es, que desarrollen o consoliden sus habilidades y destrezas en la comprensión y solución de los problemas. Y que el docente desarrolle estrategias didácticas para apoyar este proceso

Use of airborne vehicles as research platforms

This is the accepted version of the following chapter: Gratton, G. 2012. Use of Airborne Vehicles as Research Platforms. Encyclopedia of Aerospace Engineering, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/9780470686652.eae604/full. Copyright @ John Wiley & Sons 2012.The use of aircraft is often valuable to position airborne sensors or to conduct experiments in ways not possible purely on the ground. An airframe, typically an older one, must be selected then adapted to the role – likely to include inlets, windows, structural changes, power supply, computing and data recording capacity, and likely the provision of external hardpoints. Once the research vehicle is created, the instruments on board will require calibration, either in isolation or by intercomparison against already calibrated instruments on board another aircraft. This calibration process will continue throughout the life of the airplane. Additionally, an operating organization must be created and obtain any necessary organizational approvals. For some specialist applications, unmanned aerial vehicles (UAVs) may also be used, which carry some special considerations of autonomy and interoperability, but similar concerns of instrument, vehicle, and operational integrity

"Narco" Emotions: Affect and Desensitization in Social Media during the Mexican Drug War

Social media platforms have emerged as prominent information sharing ecosystems in the context of a variety of recent crises, ranging from mass emergencies, to wars and political conflicts. We study affective responses in social media and how they might indicate desensitization to violence experienced in communities embroiled in an armed conflict. Specifically, we examine three established affect measures: negative affect, activation, and dominance as observed on Twitter in relation to a number of statistics on protracted violence in four major cities afflicted by the Mexican Drug War. During a two year period (Aug 2010-Dec 2012), while violence was on the rise in these regions, our findings show a decline in negative emotional expression as well as a rise in emotional arousal and dominance in Twitter posts: aspects known to be psychological markers of desensitization. We discuss the implications of our work for behavioral health, facilitating rehabilitation efforts in communities enmeshed in an acute and persistent urban warfare, and the impact on civic engagement.Comment: Best paper award at the 32nd annual ACM conference on Human factors in computing systems (CHI '14). ACM, New York, NY, USA, pages 3563-357

Networks of Gratitude: Structures of Thanks and User Expectations in Workplace Appreciation Systems

Appreciation systems--platforms for users to exchange thanks and praise--are becoming common in the workplace, where employees share appreciation, managers are notified, and aggregate scores are sometimes made visible. Who do people thank on these systems, and what do they expect from each other and their managers? After introducing the design affordances of 13 appreciation systems, we discuss a system we call Gratia, in use at a large multinational company for over four years. Using logs of 422,000 appreciation messages and user surveys, we explore the social dynamics of use and ask if use of the system addresses the recognition problem. We find that while thanks is mostly exchanged among employees at the same level and different parts of the company, addressing the recognition problem, managers do not always act on that recognition in ways that employees expect.Comment: in Tenth International AAAI Conference on Web and Social Media, 201