An adjustment algorithm for the construction of optimal run orders.

Using a systematic run order can be the proper way to conduct an experiment when a temporal trend is present. The construction of run orders that are optimally balanced for time trend effects is based on the maximization of the information on the important parameters whereas the parameters of the postulated time trend are treated as nuisance parameters. In this paper, an adjustment algorithm is presented to improve the efficiency of the run orders obtained from a search over a predefined set of candidate points. This is done by repeatedly moving the design points or the time points of the candidate list a small amount along their axes as long as an improvement in the efficiency is obtained. It is illustrated that the adjustment algorithm involves substantial increases in the efficiency of the run orders. The use of the adjustment algorithm in addition to a search over a coarse grid of candidate points is especially recommended in situations where the computation time has to be kept within reasonable limits.Optimal;

(Dt,C) Optimal run orders.

Cost considerations have rarely been taken into account in optimum design theory. A few authors consider measurement costs, i.e. the costs associated with a particular factor level combination. A second cost approach results from the fact that it is often expensive to change factor levels from one observation to another. We refer to these costs as transition costs. In view of cost minimization, one should minimize the number of factor level changes. However, there is a substantial likelihood that there is some time order dependence in the results. Consequently, when considering both time order dependence and transition costs, an optimal ordering is not easy to find. There is precious little in the literature on how to select good time order sequences for arbitrary design problems and up to now, no thorough analysis of both costs is found in the literature. For arbitrary design problems, our proposed design algorithm incorporates cost considerations in optimum design construction and enables one to compute cost-efficient run orders that are optimally balanced for time trends. The results show that cost considerations in the construction of trend-resistant run orders entail considerable reductions in the total cost of an experiment and imply a large increase in the amount of information per unit cost.Optimal; Run orders;

Trend-resistant design of experiments under budget constraints.

When experiments are to be performed in a time sequence, the observed responses are affected by a time trend. The construction of trend-resistant run orders is extensively described in the literature. However, run orders that are optimally balanced for time trends usually involve huge costs and they are often of low practical value in view of economical considerations. This paper presents a design algorithm for the construction of trend-resistant run orders under budget constraints. The algorithm offers the experimenter a general method for solving a wide range of practical design problems.

Nonparametric time trends in optimal design of experiments.

When performing an experiment, the observed responses are often influenced by a temporal trend due to aging of material, learning effects, equipment wear-out, warm-up effects, etc. The construction of run orders that are optimally balanced for time trend effects relies on the incorporation of a parametric representation of the time dependence in the response model. The parameters of the time trend are then treated as nuisance parameters. However, the price one has to pay for by purely parametric modeling is the biased results when the time trend is misspecified. This paper presents a design algorithm for the construction of optimal run orders when kernel smoothing is used to model the temporal trend nonparametrically. The benefits of modeling the time trend nonparametrically are outlined. Besides, the influence of the bandwidth and the kernel function on the performance of the optimal run orders is investigated. The presented design algorithm shows to be very useful when it is hard to model the time dependence parametrically or when the functional form of the time trend is unknown. An industrial example illustrates the practical utility of the proposed design algorithm.Optimal; Trends;

Efficient D-optimal designs under multiplicative heteroscedasticity.

In optimum design theory designs are constructed that maximize the information on the unknown parameters of the response function. The major part deals with designs optimal for response function estimation under the assumption of homoscedasticity. In this paper, optimal designs are derived in case of multiplicative heteroscedasticity for either response function estimation or response and variance function estimation by using a Bayesian approach. The efficiencies of Bayesian designs derived with various priors are compared to those of the classic designs with respect to various variance functions. The results show that any prior knowledge about the sign of the variance function parameters leads to designs that are considerably more efficient than the classic ones based on homoscedastic assumptions.Optimal;

3D-printing techniques in a medical setting : a systematic literature review

Background: Three-dimensional (3D) printing has numerous applications and has gained much interest in the medical world. The constantly improving quality of 3D-printing applications has contributed to their increased use on patients. This paper summarizes the literature on surgical 3D-printing applications used on patients, with a focus on reported clinical and economic outcomes. Methods: Three major literature databases were screened for case series (more than three cases described in the same study) and trials of surgical applications of 3D printing in humans. Results: 227 surgical papers were analyzed and summarized using an evidence table. The papers described the use of 3D printing for surgical guides, anatomical models, and custom implants. 3D printing is used in multiple surgical domains, such as orthopedics, maxillofacial surgery, cranial surgery, and spinal surgery. In general, the advantages of 3D-printed parts are said to include reduced surgical time, improved medical outcome, and decreased radiation exposure. The costs of printing and additional scans generally increase the overall cost of the procedure. Conclusion: 3D printing is well integrated in surgical practice and research. Applications vary from anatomical models mainly intended for surgical planning to surgical guides and implants. Our research suggests that there are several advantages to 3D- printed applications, but that further research is needed to determine whether the increased intervention costs can be balanced with the observable advantages of this new technology. There is a need for a formal cost-effectiveness analysis

Tensions, parallèles et interférences entre texte et musique. Le cas de Pierrot lunaire d’Arnold Schoenberg.

Cet article vise un double objectif. Il propose d’abord un examen détaillé des interférences entre le texte (forme et sémantique) et les structures musicales dans Pierrot lunaire d’Arnold Schoenberg. Les résultats de cette analyse suggèrent que le rapport texte-musique de cette oeuvre ne se conçoit que sur un mode hétérogène et extrêmement ambigu. Le deuxième objectif est de montrer que l’examen des exemples doit être étayé par une réflexion théorique sur les conditions de possibilité des interférences musico-textuelles, et sur les outils de description dont l’analyste dispose pour les mettre à jour.This article has two goals. First, it proposes a detailed analysis of the interference between the text (in its formal and semantic aspects) and the musical structures in Arnold Schoenberg’s Pierrot lunaire. The results suggest that the text-music relation in this work must be conceived of as heterogeneous and extremely ambivalent. The second goal is to show that such an analysis needs to be elaborated within a more general theoretical reflection about, on the one hand, the very conditions of possibility of the musical-textual interference and, on the other hand, the descriptive tools the researcher has at his disposition to reveal them

An early health technology assessment of 3D anatomic models in pediatric congenital heart surgery : potential cost-effectiveness and decision uncertainty

Background: Three-dimensional anatomic models have been used for surgical planning and simulation in pediatric congenital heart surgery. This research is the first to evaluate the potential cost-effectiveness of 3D anatomic models with the intent to guide surgeons and decision makers on its use. Method: A decision tree and subsequent Markov model with a 15-year time horizon was constructed and analyzed for nine cardiovascular surgeries. Epidemiological, clinical, and economic data were derived from databases. Literature and experts were consulted to close data gaps. Scenario, one-way, threshold, and probabilistic sensitivity analysis captured methodological and parameter uncertainty. Results: Incremental costs of using anatomical models ranged from -366euro (95% credibility interval: -2595euro; 1049euro) in the Norwood operation to 1485euro (95% CI: 1206euro; 1792euro) in atrial septal defect repair. Incremental health-benefits ranged from negligible in atrial septal defect repair to 0.54 Quality Adjusted Life Years (95% CI: 0.06; 1.43) in truncus arteriosus repair. Variability in the results was mainly caused by a temporary postoperative quality-adjusted life years gain. Conclusion: For complex operations, the implementation of anatomic models is likely to be cost-effective on a 15 year time horizon. For the right indication, these models thus provide a clinical advantage at an acceptable cost