University of Saskatchewan

About: University of Saskatchewan is a education organization based out in Saskatoon, Saskatchewan, Canada. It is known for research contribution in the topics: Population & Health care. The organization has 25021 authors who have published 52579 publications receiving 1483049 citations. The organization is also known as: USask.

What do we mean by sensitivity analysis? The need for comprehensive characterization of “global” sensitivity in Earth and Environmental systems models

Abstract: Sensitivity analysis is an essential paradigm in Earth and Environmental Systems modeling. However, the term “sensitivity” has a clear definition, based in partial derivatives, only when specified locally around a particular point (e.g., optimal solution) in the problem space. Accordingly, no unique definition exists for “global sensitivity” across the problem space, when considering one or more model responses to different factors such as model parameters or forcings. A variety of approaches have been proposed for global sensitivity analysis, based on different philosophies and theories, and each of these formally characterizes a different “intuitive” understanding of sensitivity. These approaches focus on different properties of the model response at a fundamental level and may therefore lead to different (even conflicting) conclusions about the underlying sensitivities. Here we revisit the theoretical basis for sensitivity analysis, summarize and critically evaluate existing approaches in the literature, and demonstrate their flaws and shortcomings through conceptual examples. We also demonstrate the difficulty involved in interpreting “global” interaction effects, which may undermine the value of existing interpretive approaches. With this background, we identify several important properties of response surfaces that are associated with the understanding and interpretation of sensitivities in the context of Earth and Environmental System models. Finally, we highlight the need for a new, comprehensive framework for sensitivity analysis that effectively characterizes all of the important sensitivity-related properties of model response surfaces.

Biofeedback game design: using direct and indirect physiological control to enhance game interaction

Abstract: Prior work on physiological game interaction has focused on dynamically adapting games using physiological sensors. In this paper, we propose a classification of direct and indirect physiological sensor input to augment traditional game control. To find out which sensors work best for which game mechanics, we conducted a mixed-methods study using different sensor mappings. Our results show participants have a preference for direct physiological control in games. This has two major design implications for physiologically controlled games: (1) Direct physiological sensors should be mapped intuitively to reflect an action in the virtual world; (2) Indirect physiological input is best used as a dramatic device in games to influence features altering the game world.

The influence of osteoporotic fractures on health-related quality of life in community-dwelling men and women across Canada.

Abstract: Health-related quality of life (HRQL) was examined in relation to prevalent fractures in 4816 community-dwelling Canadian men and women 50 years and older participating in the Canadian Multicentre Osteoporosis Study (CaMos). Fractures were of three categories: clinically recognized main fractures, subclinical vertebral fractures and fractures at other sites. Main fractures were divided and analyzed at the hip, spine, wrist/forearm, pelvis and rib sites. Baseline assessments of anthropometric data, medical history, therapeutic drug use, spinal radiographs and prevalent fractures were obtained from all participants. The SF-36 instrument was used as a tool to measure HRQL. A total of 652 (13.5%) main fractures were reported. Results indicated that hip, spine, wrist/forearm, pelvis and rib fractures had occurred in 78 (1.6%), 40 (0.8%), 390 (8.1%), 19 (0.4%) and 125 (2.6%) individuals, respectively (subjects may have had more than one main fracture). Subjects who had experienced a main prevalent fracture had lower HRQL scores compared with non-fractured participants. The largest differences were observed in the physical functioning (−4.0; 95% confidence intervals (CI): −6.0, −2.0) and role-physical functioning domains (−5.8; 95% CI: −9.5, −2.2). In women, the physical functioning domain was most influenced by hip (−14.9%; 95% CI: −20.9, −9.0) and pelvis (−18.1; 95% CI: −27.6, −8.6) fractures. In men, the role-physical domain was most affected by hip fractures (−35.7; 95% CI: −60.4, −11.1). Subjects who experienced subclinical vertebral fractures had lower HRQL scores than those without prevalent fractures. In conclusion, HRQL was lower in the physical functioning domain in women and the role-physical domain in men who sustained main fractures at the hip. Subclinical vertebral fractures exerted a moderate effect on HRQL.

Elemental and Chemically Specific X-ray Fluorescence Imaging of Biological Systems

Abstract: From the perspective of a chemist, biology confers a rich variety of roles on a number of metal ions. It is widely agreed that a large fraction of the genomic output of living things contains metal or metalloid ions, although estimates of this fraction vary widely and depend upon which metal ions are considered.1−3 Moreover, recent reports suggest that, at least in some cases, there are many uncharacterized metalloproteins.4 With inclusion of the s-block metals such as Na, K, Mg, and Ca, the proportion likely approaches 100%; recent estimates from the protein data bank indicate that the prevalence of heavier metal ions of atomic number above 20 within proteins is around 22%,5 with Zn2+ proteins alone constituting about 11%. Living organisms have an inherent and very rich physical structure, with relevant length scales ranging from the nanometer scale for subcellular structure to hundreds of micrometers and above for tissue, organ, or organism-level organization. The ability to derive the spatial distribution of elements on this diversity of length scales is a key to understanding their function. Metals play essential and central roles in the most important and chemically challenging processes required for life, with active site structures and mechanisms that, at the time of their discovery, have usually not yet been duplicated in the chemical laboratory. Furthermore, diseases of metal dysregulation can cause disruption in the distribution of metals.6 For example, Menke’s disease and Occipital Horn Syndrome,7 and Wilson’s disease,8 involve disruption in copper uptake and excretion, respectively, through mutation in the ATP7A and ATP7B Cu transporters.9 The mechanisms of action of toxic elements such as mercury and arsenic are also of interest, as are essential nonmetal trace elements, such as selenium. Likewise, an increasing number of pharmaceuticals include metals or heavier elements; such chemotherapeutic drugs include the platinum derivatives cisplatin and carboplatin,10 some promising new ruthenium drugs,11 and arsenic trioxide, which has been used to treat promyelocytic leukemia.12 Understanding the localization, speciation, and distribution of these at various length scales is of significant interest. A wide variety of heavier elements can be probed by X-ray spectroscopic methods; these are shown graphically in Figure ​Figure1.1. X-ray fluorescence imaging is a powerful technique that can be used to determine elemental and chemical species distributions at a range of spatial resolutions within samples of biological tissues. Most modern applications require the use of synchrotron radiation as a tunable and high spectral brightness source of X-rays. The method uses a microfocused X-ray beam to excite X-ray fluorescence from specific elements within a sample. Because the method depends upon atomic physics, it is highly specific and enables a wide range of chemical elements to be investigated. A significant advantage over more conventional methods is the ability to measure intact biological samples without significant treatment with exogenous reagents. The technique is capable of determining metal and nonmetal distributions on a variety of length scales, with information on chemical speciation also potentially available. Figure ​Figure22 shows examples of rapid-scan X-ray fluorescence imaging at two contrasting length scales: rapid-scan imaging13 of a section of a human brain taken from an individual suffering from multiple sclerosis and showing elemental profiles for Fe, Cu, and Zn;14 and a high-resolution image showing mercury and other elements in a section of retina from a zebrafish larva treated with methylmercury chloride.15 We will discuss both the state of the art in terms of experimental methods and some recent applications of the methods. This Review considers X-ray fluorescence imaging with incident X-ray energies in the hard X-ray regime, which we define as 2 keV and above. We review technologies for producing microfocused X-ray beams and for detecting X-ray fluorescence, as well as methods that confer chemical selectivity or three-dimensional visualization. We discuss applications in key areas with a view to providing examples of how the technique can provide information on biological systems. We also discuss synergy with other methods, which have overlapping or complementary capabilities. Our goal is to provide useful and pertinent information to encourage and enable further use of this powerful method in chemical and biochemical studies of living organisms. Figure 1 Periodic table of the elements showing elements of biological interest that can be probed using X-ray fluorescence imaging. Elements are divided into three categories, those that are physiologically important, those that are pharmacologically active, ...