Simulation or cohort models? Continuous time simulation and discretized Markov models to estimate cost-effectiveness

The choice of model design for decision analytic models in cost-effectiveness analysis has been the subject of discussion. The current work addresses this issue by noting that, when time is to be explicitly modelled, we need to represent phenomena occurring in continuous time. Multistate models evaluated in continuous time might be used but closed form solutions of expected time in each state may not exist or may be difficult to obtain. Two approximations can then be used for costeffectiveness estimation: (1) simulation models, where continuous time estimates are obtained through Monte Carlo simulation, and (2) discretized models. This work draws recommendations on their use by showing that, when these alternative models can be applied, it is preferable to implement a cohort discretized model than a simulation model. Whilst the bias from the first can be minimized by reducing the cycle length, the second is inherently stochastic. Even though specialized literature advocates this framework, the current practice in economic evaluation is to define clinically meaningful cycle lengths for discretized models, disregarding potential biases.

Piezoelectric actuators for bone mechanical stimulation: exploring the concept.

Arthroplasty is liable to cause intense changes on strain levels and distribution in the boné surrounding the implant, namely stress shielding. Several solutions have been proposed for this, namely design variations and development of controlled-stiffness implants. A new approach to this problem, with potential application to other orthopaedic problems and other medical fields, would be the development of smart implants integrating systems for bone mechanical stimulation. Ideally, the implant should presente sensing capability and the ability to maintain physiological levels of strain at the implant interface. Piezoelectric materials’ huge potential as a mean to produce direct mechanical stimulation lies on the possibility of producing stimuli at a high range of frequencies and in multiple combinations. The present in vitro and preliminary in vivo studies were a first step towards the validation of the concept

Jet Deflection via Cross winds: Laboratory Astrophysical Studies

We present new data from High Energy Density (HED) laboratory experiments designed to explore the interaction of a heavy hypersonic radiative jet with a cross wind. The jets are generated with the MAGPIE pulsed power machine where converging conical plasma flows are produced from a cylindrically symmetric array of inclined wires. Radiative hypersonic jets emerge from the convergence point. The cross wind is generated by ablation of a plastic foil via soft-X-rays from the plasma convergence region. Our experiments show that the jets are deflected by the action of the cross wind with the angle of deflection dependent on the proximity of the foil. Shocks within the jet beam are apparent in the data. Analysis of the data shows that the interaction of the jet and cross wind is collisional and therefore in the hydro-dynamic regime. MHD plasma code simulations of the experiments are able to recover the deflection behaviour seen in the experiments. We consider the astrophysical relevance of these experiments applying published models of jet deflection developed for AGN and YSOs. Fitting the observed jet deflections to quadratic trajectories predicted by these models allows us to recover a set of plasma parameters consistent with the data. We also present results of 3-D numerical simulations of jet deflection using a new astrophysical Adaptive Mesh Refinement code. These simulations show highly structured shocks occurring within the beam similar to what was observed in the experimentsComment: Submitted to ApJ. For a version with figures go to http://web.pas.rochester.edu/~afrank/labastro/CW/Jet-Wind-Frank.pd

Click-through rate prediction : a comparative study of ensemble techniques in real-time bidding

Dissertation presented as a partial requirement for obtaining the Master’s degree in Information Management, with a specialization in Business Intelligence and Knowledge ManagementReal-Time Bidding is an automated mechanism to buy and sell ads in real time that uses data collected from internet users, to accurately deliver the right audience to the best-matched advertisers. It goes beyond contextual advertising by motivating the bidding focused on user data and also, it is different from the sponsored search auction where the bid price is associated with keywords. There is extensive literature regarding the classification and prediction of performance metrics such as click-through-rate, impression rate and bidding price. However, there is limited research on the application of advanced machine learning techniques, such as ensemble methods, on predicting click-through rate of real-time bidding campaigns. This paper presents an in-depth analysis of predicting click-through rate in real-time bidding campaigns by comparing the classification results from six traditional classification models (Linear Discriminant Analysis, Logistic Regression, Regularised Regression, Decision trees, k-nearest neighbors and Support Vector Machines) with two popular ensemble learning techniques (Voting and BootStrap Aggregation). The goal of our research is to determine whether ensemble methods can accurately predict click-through rate and compared to standard classifiers. Results showed that ensemble techniques outperformed simple classifiers performance. Moreover, also, highlights the excellent performance of linear algorithms (Linear Discriminant Analysis and Regularized Regression)

Neural networks for variational problems in engineering

In this work a conceptual theory of neural networks (NNs) from the perspective of functional analysis and variational calculus is presented. Within this formulation, the learning problem for the multilayer perceptron lies in terms of finding a function, which is an extremal for some functional. Therefore, a variational formulation for NNs provides a direct method for the solution of variational problems. This proposed method is then applied to distinct types of engineering problems. In particular a shape design, an optimal control and an inverse problem are considered. The selected examples can be solved analytically, which enables a fair comparison with the NN results. Copyright © 2008 John Wiley & Sons, Ltd

Hydrodynamical Models of Outflow Collimation in YSOs

We explore the physics of time-dependent hydrodynamic collimation of jets from Young Stellar Objects (YSOs). Using parameters appropriate to YSOs we have carried out high resolution hydrodynamic simulations modeling the interaction of a central wind with an environment characterized by a moderate opening angle toroidal density distribution. The results show that the the wind/environment interaction produces strongly collimated supersonic jets. The jet is composed of shocked wind gas. Using analytical models of wind blown bubble evolution we show that the scenario studied here should be applicable to YSOs and can, in principle, initiate collimation on the correct scales (R ~ 100 AU). The simulations reveal a number of time-dependent non-linear features not anticipated in previous analytical studies including: a prolate wind shock; a chimney of cold swept-up ambient material dragged into the bubble cavity; a plug of dense material between the jet and bow shocks. We find that the collimation of the jet occurs through both de Laval nozzles and focusing of the wind via the prolate wind shock. Using an analytical model for shock focusing we demonstrate that a prolate wind shock can, by itself, produce highly collimated supersonic jets.Comment: Accepted by ApJ, 31 pages with 12 figures (3 JPEG's) now included, using aasms.sty, Also available in postscript via a gzipped tar file at ftp://s1.msi.umn.edu/pub/afrank/SFIC1/SFIC.tar.g

The effectiveness of knowledge sharing: the case of ProMusa

This brief is based on a report by Genowefa Blundo-Canto and Elisabetta Gotor ‘Evaluation of Bioversity International’s ProMusa networkIn 2013, a study was undertaken to assess the nature and effectiveness of ProMusa from the point of view of its members and subscribers, what outputs are produced and how these are translated into outcomes and disseminated outside the network. The network provides the type and quality of services that its members expect: InfoMus@ and the mailing lists are the most successful service. An efficient and timely service on disease outbreaks and other breaking news is also a fundamental tool for ProMusa’s members and subscribers, and it should be a priority

On a Second Order Condition for Max-Semistable Laws

2000 Mathematics Subject Classification: 62G32, 62G20.In statistics of extremes the great importance of the Normal approximation of intermediate order statistics is well known when the parent distribution function is in a max-stable domain of attraction and verifies the first and the second order extreme value conditions. The generalization of these conditions to max-semistable contexts is the object of this paper, aiming to be a basis of future developments in statistical inference under max-semistability.Research partially supported by FCT/POCTI, POCI and PPCDT/FEDER

Football manager-s turnover: a deep analysis based on empirical findings

A football manager's job is always under great scrutiny, as the pressure of good results from the fans, the management and the media create a high turnover ratio in this position. This paper tries to measure, from a sample of 208 experiences of coaches in 54 different European clubs if certain variables such as the presence in the European Competitions ,the Tier of the team or the timing (Midseason or not) of the sacking influence the job tenure of the manager and the short-term performance effect of the team after the sacking of a manager

Evolución de la ley (AG/CU) en monedas árabes durante los siglos VIII al X D.C mediante SEM-EDX y TXRF

En este trabajo se presenta el estudio analítico, mediante fluorescencia de ra yos X por reflexión total (TXRF) y microscopía electrónica de barrido con aná lisis de energía dispersiva de rayos X (SEM-EDX). de un amplio grupo de mo nedas islámicas (532 piezas), con el fin de establecer una correlación entre la ley de la moneda islámica en España y los acontecimientos históricos más relevan tes tícurridos durante los siglos VIII al X d.C. Los resultados analíticos obteni dos han permitido establecer el proceso de devaluación en la riqueza de la alea- ción Ag/Cu. en este período. Las tendencias observadas se correlacionan con el déficit de plata sufrido por el estado Omeya de Córdoba. Por otro lado, la com binación de las técnicas de TXRF y SEM-EDX ha permitido caracterizar de forma concluyente la tecnología de la producción, así como la evolución histórica su frida por este tipo de materiales