Likelihood prediction for generalized linear mixed models under covariate uncertainty

This paper presents the techniques of likelihood prediction for the generalized linear mixed models. Methods of likelihood prediction is explained through a series of examples; from a classical one to more complicated ones. The examples show, in simple cases, that the likelihood prediction (LP) coincides with already known best frequentist practice such as the best linear unbiased predictor. The paper outlines a way to deal with the covariate uncertainty while producing predictive inference. Using a Poisson error-in-variable generalized linear model, it has been shown that in complicated cases LP produces better results than already know methods.

Parameter estimation of Poisson generalized linear mixed models based on three different statistical principles : a simulation study

Generalized linear mixed models are flexible tools for modeling non-normal data and are useful for accommodating overdispersion in Poisson regression models with random effects. Their main difficulty resides in the parameter estimation because there is no analytic solution for the maximization of the marginal likelihood. Many methods have been proposed for this purpose and many of them are implemented in software packages. The purpose of this study is to compare the performance of three different statistical principles - marginal likelihood, extended likelihood, Bayesian analysis-via simulation studies. Real data on contact wrestling are used for illustration.

The fall descriptions and health characteristics of older adults with hip fracture : a mixed methods study

Background: In light of the multifactorial etiology of fall-related hip fracture, knowledge of fall circumstances may be especially valuable when placed in the context of the health of the person who falls. We aimed to investigate the circumstances surrounding fall-related hip fractures and to describe fall circumstances in relation to participants' health and functional characteristics. Methods: The fall circumstances of 125 individuals (age >= 50 years) with hip fracture were investigated using semi-structured interviews. Data concerning participants' health (comorbidities and medications) and function (self-reported performance of mobility, balance, personal activities of daily living and physical activity, previous falls and hand grip strength) were collected via medical records, questionnaires and dynamometry. Using a mixed methods design, both data sets were analysed separately and then merged in order to provide a comprehensive description of fall events and identify eventual patterns in the data. Results: Fall circumstances were described as i) Activity at the time of the fall: Positional change (n = 24, 19%); Standing (n = 16, 13%); Walking (n = 71, 57%); Balance challenging (n = 14, 11%) and ii) Nature of the fall: Environmental (n = 32, 26%); Physiological (n = 35, 28%); Activity-related indoor (n = 8, 6%) and outdoor (n = 8, 6%); Trips and slips on snow (n = 20, 16%) and in snow-free conditions (n = 12, 10%) and Unknown (n = 10, 8%). We observed the following patterns regarding fall circumstances and participants' health: those who fell i) during positional change had the poorest functional status; ii) due to environmental reasons (indoors) had moderate physical function, but high levels of comorbidity and fall risk increasing medications; iii) in snow-free environments (outdoors) appeared to have a poorer health and functional status than other outdoor groups. Conclusions: Our findings indicate that patterns exist in relation to the falls circumstances and health characteristics of people with hip fracture which build upon that previously reported. These patterns, when verified, can provide useful information as to the ways in which fall prevention strategies can be tailored to individuals of varying levels of health and function who are at risk for falls and hip fracture.

A biogeographically mixed, Middle Permian brachiopod fauna from the Baoshan Block, Western Yunnan, China

A small brachiopod fauna is described from the carbonate rocks of the basal Shazipo Formation of the Baoshan Block, western Yunnan, south-west China, including significant new ventral and dorsal internal morphological features of Cryptospirifer omeishanensis Huang. This fauna is regarded as Wordian (Middle Guadalupian, Middle Permian) because of the presence of Cryptospirifer omeishanensis Huang and associated fusulinids (Neoschwagerina craticulifera Zone). Palaeobiogeographically, the brachiopod fauna is of considerable interest because of its admixed nature characterized by typical warm-water Cathaysian elements intermingled with temperate Peri-Gondwanan taxa. This in turn is interpreted to indicate that the Baoshan Block may have been situated in an intermediate palaeogeographical position between Gondwanaland to the south and Cathaysia to the north during the Mid Permian and, as such, it probably furnished an important 'stepping stone' for the dispersal of Mid Permian eastern Tethyan marine invertebrate taxa (e.g. Cryptospirifer) to the western Tethys.

Mixed-initiative decision support for care planning based on clinical practice guidelines

Care Plan On-Line (CPOL) is an intranet based system that supports a “Coordinated Care” model for chronic/complex disease management. CPOL combines provision of solicited and unsolicited advice features based on integration of the electronic medical record (EMR) with its decision support logic. The objective is to support General Practitioners (GPs) in formulating a 12-month care plan of services such that: (a) the plan is proactive and patient-centered; (b) the GP is kept in awareness of project- and diseasespecific clinical practice guidelines; and (c) the support integrates with GP workflow in a natural fashion. A key feature of our approach is to blur the distinction of EMR and decision support by presenting guidelines in layers with the top-most being a problem-oriented presentation of patient status, progressing on through to patient-independent supporting evidence. In conjunction with a degree of automated inclusion of care planning services, the system demonstrates mixed user and software initiative. We describe the CPOL deployment setting, the challenges of guideline-based clinical decision support, our approach to guideline delivery, and the CPOL architecture.

Modeling dialogue with mixed initiative in design space exploration

Exploration with a generative formalism must necessarily account for the nature of interaction between humans and the design space explorer. Established accounts of design interaction are made complicated by two propositions in Woodbury and Burrow's Keynote on design space exploration. First, the emphasis on the primacy of the design space as an ordered collection of partial designs (version, alternatives, extensions). Few studies exist in the design interaction literature on working with multiple threads simultaneously. Second, the need to situate, aid, and amplify human design intentions using computational tools. Although specific research and practice tools on amplification (sketching, generation, variation) have had success, there is a lack of generic, flexible, interoperable, and extensible representation to support amplification. This paper addresses the above, working with design threads and computer-assisted design amplification through a theoretical model of dialogue based on Grice's model of rational conversation. Using the concept of mixed initiative, the paper presents a visual notation for representing dialogue between designer and design space formalism through abstract examples of exploration tasks and dialogue integration.

The determination of all syzygies for the dependent polynomial invariants of the Riemann Tensor. II. mixed invariants of Eeven degree in the Ricci Spinor

We continue our analysis of the polynomial invariants of the Riemann tensor in a four-dimensional Lorentzian space. We concentrate on the mixed invariants of even degree in the Ricci spinor Φ_ABȦḂ and show how, using constructive graph-theoretic methods, arbitrary scalar contractions between copies of the Weyl spinor ψ_ABCD, its conjugate ψ_ȦḂĊḊ and an even number of Ricci spinors can be expressed in terms of paired contractions between these spinors. This leads to an algorithm for the explicit expression of dependent invariants as polynomials of members of the complete set. Finally, we rigorously prove that the complete set as given by Sneddon [J. Math. Phys. 39, 1659-1679 (1998)] for this case is both complete and minimal.

Knowledge extraction from a mixed transfer function artificial neural network

One of the main problems with Artificial Neural Networks (ANNs) is that their results are not intuitively clear. For example, commonly used hidden neurons with sigmoid activation function can approximate any continuous function, including linear functions, but the coefficients (weights) of this approximation are rather meaningless. To address this problem, current paper presents a novel kind of a neural network that uses transfer functions of various complexities in contrast to mono-transfer functions used in sigmoid and hyperbolic tangent networks. The presence of transfer functions of various complexities in a Mixed Transfer Functions Artificial Neural Network (MTFANN) allow easy conversion of the full model into user-friendly equation format (similar to that of linear regression) without any pruning or simplification of the model. At the same time, MTFANN maintains similar generalization ability to mono-transfer function networks in a global optimization context. The performance and knowledge extraction of MTFANN were evaluated on a realistic simulation of the Puma 560 robot arm and compared to sigmoid, hyperbolic tangent, linear and sinusoidal networks.

Benchmark generation algorithm for stochastic mixed model assembly shop simulation and optimization

The Operations Research (OR) community have defined many deterministic manufacturing control problems mainly focused on scheduling. Well-defined benchmark problems provide a mechanism for communication of the effectiveness of different optimization algorithms. Manufacturing problems within industry are stochastic and complex. Common features of these problems include: variable demand, machine part specific breakdown patterns, part machine specific process durations, continuous production, Finished Goods Inventory (FGI) buffers, bottleneck machines and limited production capacity. Discrete Event Simulation (DES) is a commonly used tool for studying manufacturing systems of realistic complexity. There are few reports of detail-rich benchmark problems for use within the simulation optimization community that are as complex as those faced by production managers. This work details an algorithm that can be used to create single and multistage production control problems. The reported software implementation of the algorithm generates text files in eXtensible Markup Language (XML) format that are easily edited and understood as well as being cross-platform compatible. The distribution and acceptance of benchmark problems generated with the algorithm would enable researchers working on simulation and optimization of manufacturing problems to effectively communicate results to benefit the field in general.