72 research outputs found
Different strategies for latent TB assessment in patients undergoing anti-TNF treatment: an economic model
No full textOBJECTIVES: Since treatment with biologics may reactivate latent TB, testing and prophylaxes before initiating therapy are mandatory. However, there is not a unique solution for the number and type of tests to be used for detecting the presence of TB, and for the definition of when prophylaxis should be prescribed. Which alternative should be preferred depends on the effectiveness of treatment and also on the cost associated. This methodological study aims to define a general economic model to assess different protocols for latent TB detection in patients undergoing anti-TNF treatment.
METHODS: A decision tree approach has been designed for comparing alternative protocols in terms of (a) expected costs of different strategies for latent TB assessment in patients undergoing anti-TNF treatment; b) the economic convenience of the prophylaxis therapy in presence of a negative chest X-ray. Uncertainty is expressed by the probability of being positive and negative to the tests. In the NHS perspective the model considers: costs of tests; costs of TB onsets for rheumatologic patients who undergo biologics; costs of extending anti TB prophylaxis also to false negative patients; costs related to 1-month biologic therapy delay because of prophylaxis; costs for adverse events therapy and/or test related. Indirect costs are also considered in the broader societal perspective.
RESULTS: Costs assessed are useful to choose the less costly alternatives. The comparison also considers the reduction of false negatives to the tests which do not follow prophylaxis while being affected by latent TB.
CONCLUSIONS: The model, that can represent a useful tool both for clinical and health policy decision making, is a general one; it can be applied to any country by inserting the country specific epidemiological, clinical, and economical data, and to any anti-TNF drug, by using the specific biologic drug-related risk factor
Human Impacts on Seals, Sea Lions, and Sea Otters: Integrating Archaeology and Ecology of the Northeast Pacific
No full textReview of Human Impacts on Seals, Sea Lions, and Sea Otters: Integrating Archaeology and Ecology of the Northeast Pacific. Todd J. Braje and Torben C. Rick, editors. 2011. University of California Press, Berkeley. Pp. 328. $65.00 (hardcover). ISBN 9780520267268.</span
Radiopacity and fatigue characterization of a novel acrylic bone cement with sodium fluoride
No full textAcrylic bone cement must provide good radiographic visibility and good long-term mechanical resistance in joint replacements. A new formulation of cement with 6% barium sulfate and 6% sodium fluoride was developed (Fluoride Bone Cement). Barium sulfate is a necessary addition to allow radiographic visibility although it reduces the mechanical strength of the material. Sodium fluoride promotes bone formation. However, its effect on the mechanical behavior is currently unknown while its influence on radiopacity can only be roughly estimated. The aim of this investigation was to establish if the new formulation would be suitable for clinical trials. In this respect, a mechanical (fatigue test) and radiographic (optical density measurements on x-ray films) characterization was performed on a typical commercially available cement with barium sulfate added and on the Fluoride Bone Cement. It was demonstrated that the fluoride cement has a (marginally) superior fatigue strength and comparable radiopacity to commercial radiopaque cements
Hot pressing of nanocrystalline TiO2 (anatase) ceramics with controlled microstructure
No full textThe preparation conditions of nanocrystalline phase-pure TiO2 anatase ceramics by hot pressing are described. Density, surface area, pore size distribution and grain size are determined by various techniques, including gas adsorption, mercury porosimetry, transmission electron microscopy (TEM) and X-ray diffraction (XRD). The evolution of the structural parameters is followed as function of temperature and pressure programme. It is shown that the porosity, grain and pore size of the ceramics can be controlled by a suitable choice of experimental conditions. Ceramics with densities higher than 90% of the theoretical limit with a mean grain size of 30 nm can be obtained at temperatures as low as 490 ◦C under 0.45 GPa for 2 h. The experimental results are discussed in view of the sintering theory
Application of QC_DR software for acceptance testing and routine quality control of direct digital radiography systems: initial experiences using the Italian Association of Physicist in Medicine quality control protocol
No full textIdeally, medical x-ray imaging systems should be designed to deliver maximum image quality at an acceptable radiation risk to the patient. Quality assurance procedures are employed to ensure that these standards are maintained. A quality control protocol for direct digital radiography (DDR) systems is described and discussed. Software to automatically process and analyze the required images was developed. In this paper, the initial results obtained on equipment of different DDR manufacturers were reported. The protocol was developed to highlight even small discrepancies in standard operating performance
SOVEREIGNTY THROUGH ASSIMILATION: THE FEDERAL CONSTITUTION OF THE CHEROKEE NATION
No full textThis dissertation examines federal Indian law of the late nineteenth and twentieth centuries as constitutive rhetoric. Focusing specifically on the Cherokee Nation, I argue that the word "tribe," as used in three federal acts, ascribed three different meanings to the people described by the term. With the passage of each act, Cherokee identity was federally manipulated, as the United States government integrated members of the Cherokee Nation into the American economy. First, the Curtis Act, imposed with little input from tribes themselves, dissolved Indigenous national governments in Indian Territory - now the state of Oklahoma - and defined the citizens of those nations as individual landowners, identities significantly different from the collective tribalism that had previously dominated in Indian Territory. Almost four decades later, the Oklahoma Indian Welfare Act imposed yet another identity on Indigenous Oklahomans, as they were allowed to reorganize, but only under entrepreneurial identities. Finally, in 1970, the Principal Chiefs Act allowed Oklahoma's tribal collectives to engage in tribal elections, allowing a democratic citizen identity, but only under the auspices of the federal government. I conclude with implications for the modern Cherokee Nation's tribal sovereignty, and for the continued use of imposed constitutive rhetoric by the United States government in its relations with tribal peoples worldwide
Models and heuristics for hard routing and knapsack problems
No full textOne of the world’s biggest challenges is that living beings have to share a limited amount of resources. As people of science, we strive to find innovative ways to better use these resources, to reach and positively affect more and more people. In the field of optimization, we aim at finding an optimal allocation of limited sets of resources to maximize a certain objective. Some of these problems can be solved in polynomial time; others are more difficult to be solved. Current state-of-the-art methods can solve NP-hard problems (a class of optimization problems) in exponential time, in the worst case. To give an idea, for input size n Æ 100 and parameter k Æ 2: polynomial time nk Æ 1002 Æ 10,000; exponential time kn Æ 2100 Æ 1,267,650,600,228,229,401,496,703,205,376. Yet, many relevant and practical problems are NP-hard and have to be solved in a short amount of time. Our research focuses on formulating and solving four of these problems. Among those, three are vehicle routing problems (VRP, Chapters 2, 3 and 4). VRPs are problems where vehicles have to perform routes in order to minimize an objective function (for example, minimize routing costs) while being subjected to constraints (for example, each location has to be visited). Routing costs have a significant impact on society and on the cost of products (the transportation sector makes up 13.2% of the EU’s GDP (Joint Research Centre, 2021)). Although VRPs have been thoroughly studied for over half a century, new technologies (autonomous driving, real-time information, etc.) and new customers’ demands (increase in online shopping, a more competitive delivery market, etc.) create variants of the standard VRP that are more and more complex to formulate and solve. VRPs are well-known for being NP-hard and difficult to approximate, and hence solve. We formulated three novel VRPs and solve those both exactly via branch-and-bound (Chapters 3 and 4, the latter also uses valid inequalities) and metaheuristicly (Chapters 2 and 4). To increase generalizability, we introduced an almost non-parametric algorithm that encompasses all the most famous heuristic operators for VRP (Chapter 4). To increase performance, we proposed an adaptive, i.e., selftuning, algorithm (Chapter 2) that can detect problem’s features and steer its decisions to achieve better solutions. Lastly, Chapter 5 focuses on what we believe will be the most radical transformation in the metaheuristic field in coming years: machine learning for combinatorial optimization. Machine learning established its fundamental importance in many fields and it is currently paving its way into combinatorial optimization. We developed a selfattention based deep reinforcement learning algorithm without any problem-specific knowledge to solve one of the most studied combinatorial optimization problems. Our results suggest that machine learning can (and we conjecture that it will) tackle combinatorial optimization on its own, without problem-specific knowledge and will be a fundamental element in future state-of-the-art heuristics for combinatorial optimization.Discrete Mathematics and Optimizatio
Liquid dynamic medicine and N-of-1 clinical trials: A change of perspective in oncology research
No full textThe increasing use of genomics to define the pattern of actionable mutations and to test and validate new therapies for individual cancer patients, and the growing application of liquid biopsy to dynamically track tumor evolution and to adapt molecularly targeted therapy according to the emergence of tumor clonal variants is shaping modern medical oncology., In order to better describe this new therapeutic paradigm we propose the term "Liquid dynamic medicine" in the place of "Personalized or Precision medicine". Clinical validation of the "Liquid dynamic medicine" approach is best captured by N-of-1 trials where each patient acts as tester and control of truly personalized therapies. © 2017 The Author(s)
Adaptive Iterated Local Search with Random Restarts for the Balanced Travelling Salesman Problem
No full textMetaheuristics have been widely used to solve NP-hard problems, with excellent results. Among all NP-hard problems, the Travelling Salesman Problem (TSP) is potentially the most studied one. In this work, a variation of the TSP is considered; the main differences being, edges may have positive or negative costs and the objective is to return a Hamiltonian cycle with cost as close as possible to zero. This variation is called the balanced TSP (BTSP). To tackle this new problem, we present an adaptive variant of the iterated local search metaheuristic featuring also random restart. This algorithm was tested on the MESS2018 metaheuristic competition and achieved notable results, scoring the 5th position overall. In this paper, we detail all the components of the algorithm itself and present the best solutions identified. Even though this metaheuristic was tailored for the BTSP, with small modifications its structure can be applied to virtually any NP-hard problem. In particular, we introduce the uneven reward-and-punishment rule which is a powerful tool, applicable in many contexts where fast responses to dynamic changes are crucial.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Discrete Mathematics and Optimizatio
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