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Discrete event simulation

T Mee, N F Kirkby, K J Kirkby
Proton beam therapy (PBT) is still relatively new in cancer treatment and the clinical evidence base is relatively sparse. Mathematical modelling offers assistance when selecting patients for PBT and predicting the demand for service. Discrete event simulation, normal tissue complication probability, quality-adjusted life-years and Markov Chain models are all mathematical and statistical modelling techniques currently used but none is dominant. As new evidence and outcome data become available from PBT, comprehensive models will emerge that are less dependent on the specific technologies of radiotherapy planning and delivery...
February 13, 2018: Clinical Oncology: a Journal of the Royal College of Radiologists
David Axelrod, Mark A Schnitzler, Huiling Xiao, William Irish, Elizabeth Tuttle-Newhall, Su-Hsin Chang, Bertram L Kasiske, Tarek Alhamad, Krista L Lentine
Kidney transplant is the optimal therapy for end stage renal disease, prolonging survival and reducing healthcare spending. Prior economic analyses of kidney transplant using Markov models, have generally assumed compatible, low risk, donors. The economic implications of using deceased donor kidneys with high kidney donor profile index (KPDI) scores, ABO incompatible or HLA incompatible living donors has not been assessed. The costs of transplant and dialysis were compared using discrete event simulation over a 10-year period, using data from the United States Renal Data System, Vizient ™ (Irving, Texas), and literature review...
February 16, 2018: American Journal of Transplantation
Spyros Kolovos, Judith E Bosmans, Heleen Riper, Karine Chevreul, Veerle M H Coupé, Maurits W van Tulder
BACKGROUND: An increasing number of model-based studies that evaluate the cost effectiveness of treatments for depression are being published. These studies have different characteristics and use different simulation methods. OBJECTIVE: We aimed to systematically review model-based studies evaluating the cost effectiveness of treatments for depression and examine which modelling technique is most appropriate for simulating the natural course of depression. METHODS: The literature search was conducted in the databases PubMed, EMBASE and PsycInfo between 1 January 2002 and 1 October 2016...
September 2017: PharmacoEconomics Open
Riccardo Dal Bello, Joao Seco, Paulo Magalhaes Martins
PURPOSE: Range uncertainties limit the potential of charged particle therapy. In vivo and online range verification techniques could increase the confidence in the dose delivery distribution and lead to more conformal treatments. Prompt gamma imaging and prompt gamma spectroscopy (PGS) have been demonstrated for such purpose. The successful application of these techniques requires the development of a dedicated detector system optimized to the radiation energy ranges and the intensity...
February 7, 2018: Medical Physics
Satish Kumar Panda, Martin Lindsay Buist
Soft tissues exhibit highly nonlinear rate and time-dependent stress-strain behaviour. Strain and strain rate dependencies are often modelled using a hyperelastic model and a discrete (standard linear solid) or continuous spectrum (quasi-linear) viscoelastic model, respectively. However, these models are unable to properly capture the materials characteristics because hyperelastic models are unsuited for time-dependent events, whereas the common viscoelastic models are insufficient for the nonlinear and finite strain viscoelastic tissue responses...
January 31, 2018: Journal of Biomechanics
Claudia Nau, Shiriki Kumanyika, Joel Gittelsohn, Atif Adam, Michelle S Wong, Yeeli Mui, Bruce Y Lee
INTRODUCTION: Residents of low-income communities often purchase sugar-sweetened beverages (SSBs) at small, neighborhood "corner" stores. Lowering water prices and increasing SSB prices are potentially complementary public health strategies to promote more healthful beverage purchasing patterns in these stores. Sustainability, however, depends on financial feasibility. Because in-store pricing experiments are complex and require retailers to take business risks, we used a simulation approach to identify profitable pricing combinations for corner stores...
January 25, 2018: Preventing Chronic Disease
Xiaohui Zhu, Yong Yue, Prudence W H Wong, Yixin Zhang, Jianhong Tan
Affected by regular tides, bidirectional water flows play a crucial role in surface river systems. Using optimization theory to design a water quality monitoring network can reduce the redundant monitoring nodes as well as save the costs for building and running a monitoring network. A novel algorithm is proposed to design an optimum water quality monitoring network for tidal rivers with bidirectional water flows. Two optimization objectives of minimum pollution detection time and maximum pollution detection probability are used in our optimization algorithm...
January 24, 2018: International Journal of Environmental Research and Public Health
Zlatan Coralic, Hendry R Sawe, Juma A Mfinanga, Alfredo Cortez, Jennifer Koehl, Hannah Siroker, Teri A Reynolds
STUDY OBJECTIVE: We describe ketamine procedural sedations and associated adverse events in low-acuity and high-acuity patients in a resource-limited ED. METHODS: This was a prospective observational study of ketamine procedural sedations at the Emergency Medical Department at the Muhimbili National Hospital in Dar es Salaam, Tanzania. We observed consecutive procedural sedations and recorded patient demographics, medications, vital signs, pulse oximetry, capnography and a priori defined adverse events (using standard definitions in emergency medicine sedation guidelines)...
January 22, 2018: Emergency Medicine Journal: EMJ
Zhi-Yong Wang, Pengli Zhang, Zengwei Ma
The conventional paradigm for characterizing surface overcharging and charge reversal is based on the so-called Stern layer, in which surface dissociation reaction and specific chemical adsorption are assumed to take place. In this article, a series of Monte Carlo simulations have been applied to obtain useful insights into the underlying physics responsible for these two kinds of anomalous phenomena at the interface of two dielectrics, with special emphasis on the case of divalent counterions that are more relevant in natural and biological environments...
January 22, 2018: Physical Chemistry Chemical Physics: PCCP
John D Rice, Brent A Johnson, Robert L Strawderman
Many longitudinal studies with a binary outcome measure involve a fraction of subjects with a homogeneous response profile. In our motivating data set, a study on the rate of human immunodeficiency virus (HIV) self-testing in a population of men who have sex with men (MSM), a substantial proportion of the subjects did not self-test during the follow-up study. The observed data in this context consist of a binary sequence for each subject indicating whether or not that subject experienced any events between consecutive observation time points, so subjects who never self-tested were observed to have a response vector consisting entirely of zeros...
January 4, 2018: Biostatistics
Guanglei Yu, Liang Zhu, Jianguo Sun, Leslie L Robison
This paper discusses regression analysis of a type of incomplete mixed data arising from event history studies with the proportional rates model. By mixed data, we mean that each study subject may be observed continuously during the whole study period, continuously over some study periods and at some time points, or only at some discrete time points. Therefore, we have combined recurrent event and panel count data. For the problem, we present a multiple imputation-based estimation procedure and one advantage of the proposed marginal model approach is that it can be easily implemented...
2018: Statistics and its Interface
Koen Degeling, Stefano Schivo, Niven Mehra, Hendrik Koffijberg, Rom Langerak, Johann S de Bono, Maarten J IJzerman
BACKGROUND: With the advent of personalized medicine, the field of health economic modeling is being challenged and the use of patient-level dynamic modeling techniques might be required. OBJECTIVES: To illustrate the usability of two such techniques, timed automata (TA) and discrete event simulation (DES), for modeling personalized treatment decisions. METHODS: An early health technology assessment on the use of circulating tumor cells, compared with prostate-specific antigen and bone scintigraphy, to inform treatment decisions in metastatic castration-resistant prostate cancer was performed...
December 2017: Value in Health: the Journal of the International Society for Pharmacoeconomics and Outcomes Research
Amy Trentham-Dietz, Mehmet Ali Ergun, Oguzhan Alagoz, Natasha K Stout, Ronald E Gangnon, John M Hampton, Kim Dittus, Ted A James, Pamela M Vacek, Sally D Herschorn, Elizabeth S Burnside, Anna N A Tosteson, Donald L Weaver, Brian L Sprague
PURPOSE: Due to limitations in the ability to identify non-progressive disease, ductal carcinoma in situ (DCIS) is usually managed similarly to localized invasive breast cancer. We used simulation modeling to evaluate the potential impact of a hypothetical test that identifies non-progressive DCIS. METHODS: A discrete-event model simulated a cohort of U.S. women undergoing digital screening mammography. All women diagnosed with DCIS underwent the hypothetical DCIS prognostic test...
November 28, 2017: Breast Cancer Research and Treatment
Anna Irene Vedel Sørensen, Nils Toft, Anette Boklund, Carmen Espinosa-Gongora, Kaare Græsbøll, Jesper Larsen, Tariq Halasa
Before an efficient control strategy for livestock-associated methicillin resistant Staphylococcus aureus (LA-MRSA) in pigs can be decided upon, it is necessary to obtain a better understanding of how LA-MRSA spreads and persists within a pig herd, once it is introduced. We here present a mechanistic stochastic discrete-event simulation model for spread of LA-MRSA within a farrow-to-finish sow herd to aid in this. The model was individual-based and included three different disease compartments: susceptible, intermittent or persistent shedder of MRSA...
2017: PloS One
Abidemi K Adeniji, Jesse Y Hsu, Abdus S Wahed
The product limit or Kaplan-Meier (KM) estimator is commonly used to estimate the survival function in the presence of incomplete time to event. Application of this method assumes inherently that the occurrence of an event is known with certainty. However, the clinical diagnosis of an event is often subject to misclassification due to assay error or adjudication error, by which the event is assessed with some uncertainty. In the presence of such errors, the true distribution of the time to first event would not be estimated accurately using the KM method...
November 26, 2017: Pharmaceutical Statistics
Pelham Barton, James P Sheppard, Cristina M Penaloza-Ramos, Sue Jowett, Gary A Ford, Daniel Lasserson, Jonathan Mant, Ruth M Mellor, Tom Quinn, Peter M Rothwell, David Sandler, Don Sims, Richard J McManus
OBJECTIVES: The aim of this study was to examine the impact of transient ischaemic attack (TIA) service modification in two hospitals on costs and clinical outcomes. DESIGN: Discrete event simulation model using data from routine electronic health records from 2011. PARTICIPANTS: Patients with suspected TIA were followed from symptom onset to presentation, referral to specialist clinics, treatment and subsequent stroke. INTERVENTIONS: Included existing versus previous (less same day clinics) and hypothetical service reconfiguration (7-day service with less availability of clinics per day)...
November 25, 2017: BMJ Open
Mehdi Najafzadeh, Jorge A Garces, Alejandra Maciel
BACKGROUND: The response to therapeutics varies widely in patients with depression and anxiety, making selection of an optimal treatment choice challenging. IDgenetix(®), a novel pharmacogenomic test, has been shown to improve outcomes by predicting the likelihood of response to different psychotherapeutic medications. OBJECTIVE: The objective of this study was to estimate the cost effectiveness of implementing a novel pharmacogenomic test (IDgenetix(®)) to guide treatment choices in patients with depression and/or anxiety compared with treatment as usual from the US societal perspective...
November 6, 2017: PharmacoEconomics
Magali Alexander López Chavira, Ricardo Marcelín-Jiménez
The study of complex networks has become an important subject over the last decades. It has been shown that these structures have special features, such as their diameter, or their average path length, which in turn are the explanation of some functional properties in a system such as its fault tolerance, its fragility before attacks, or the ability to support routing procedures. In the present work, we study some of the forces that help a network to evolve to the point where structural properties are settled...
2017: PloS One
Vladimir Klinshov, Vladimir Nekorkin
Pulse-mediated interactions are common in networks of different nature. Here we develop a general framework for simulation of networks with pulse delayed coupling. We introduce the discrete map governing the dynamics of such networks and describe the computation algorithm for its numerical simulation.
October 2017: Chaos
Jonathon R Campbell, James C Johnston, Mohsen Sadatsafavi, Victoria J Cook, R Kevin Elwood, Fawziah Marra
BACKGROUND: The majority of tuberculosis in migrants to Canada occurs due to reactivation of latent TB infection. Risk of tuberculosis in those with latent tuberculosis infection can be significantly reduced with treatment. Presently, only 2.4% of new migrants are flagged for post-landing surveillance, which may include latent tuberculosis infection screening; no other migrants receive routine latent tuberculosis infection screening. To aid in reducing the tuberculosis burden in new migrants to Canada, we determined the cost-effectiveness of using different latent tuberculosis infection interventions in migrants under post-arrival surveillance and in all new migrants...
2017: PloS One
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