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Recent Submissions

Active video games and health indicators in children and youth: A systematic review
(Public Library of Science, 2013-06-14) LeBlanc, Allana G.; Chaput, Jean-Philippe; McFarlane, Allison; Colley, Rachel C.; Thivel, David; Biddle, Stuart J. H.; Maddison, Ralph; Leatherdale, Scott T.; Tremblay, Mark S.
Background Active video games (AVGs) have gained interest as a way to increase physical activity in children and youth. The effect of AVGs on acute energy expenditure (EE) has previously been reported; however, the influence of AVGs on other health-related lifestyle indicators remains unclear. Objective This systematic review aimed to explain the relationship between AVGs and nine health and behavioural indicators in the pediatric population (aged 0-17 years). Data sources Online databases (MEDLINE, EMBASE, psycINFO, SPORTDiscus and Cochrane Central Database) and personal libraries were searched and content experts were consulted for additional material. Data selection Included articles were required to have a measure of AVG and at least one relevant health or behaviour indicator: EE (both habitual and acute), adherence and appeal (i.e., participation and enjoyment), opportunity cost (both time and financial considerations, and adverse events), adiposity, cardiometabolic health, energy intake, adaptation (effects of continued play), learning and rehabilitation, and video game evolution (i.e., sustainability of AVG technology). Results 51 unique studies, represented in 52 articles were included in the review. Data were available from 1992 participants, aged 3–17 years, from 8 countries, and published from 2006–2012. Overall, AVGs are associated with acute increases in EE, but effects on habitual physical activity are not clear. Further, AVGs show promise when used for learning and rehabilitation within special populations. Evidence related to other indicators was limited and inconclusive. Conclusions Controlled studies show that AVGs acutely increase light- to moderate-intensity physical activity; however, the findings about if or how AVG lead to increases in habitual physical activity or decreases in sedentary behaviour are less clear. Although AVGs may elicit some health benefits in special populations, there is not sufficient evidence to recommend AVGs as a means of increasing daily physical activity.
Investigating the link between molecular subtypes of glioblastoma, epithelial-mesenchymal transition, and CD133 cell surface protein
(Public Library of Science, 2013-05-29) Zarkoob, Hadi; Taube, Joseph H.; Singh, Sheila K.; Mani, Sendurai A.; Kohandel, Mohammad
In this manuscript, we use genetic data to provide a three-faceted analysis on the links between molecular subclasses of glioblastoma, epithelial-to-mesenchymal transition (EMT) and CD133 cell surface protein. The contribution of this paper is three-fold: First, we use a newly identified signature for epithelial-to-mesenchymal transition in human mammary epithelial cells, and demonstrate that genes in this signature have significant overlap with genes differentially expressed in all known GBM subtypes. However, the overlap between genes up regulated in the mesenchymal subtype of GBM and in the EMT signature was more significant than other GBM subtypes. Second, we provide evidence that there is a negative correlation between the genetic signature of EMT and that of CD133 cell surface protein, a putative marker for neural stem cells. Third, we study the correlation between GBM molecular subtypes and the genetic signature of CD133 cell surface protein. We demonstrate that the mesenchymal and neural subtypes of GBM have the strongest correlations with the CD133 genetic signature. While the mesenchymal subtype of GBM displays similarity with the signatures of both EMT and CD133, it also exhibits some differences with each of these signatures that are partly due to the fact that the signatures of EMT and CD133 are inversely related to each other. Taken together these data shed light on the role of the mesenchymal transition and neural stem cells, and their mutual interaction, in molecular subtypes of glioblastoma multiforme.
Developing a vulnerability mapping methodology: Applying the water-associated disease index to dengue in Malaysia
(Public Library of Science, 2013-05-08) Dickin, Sarah K.; Schuster-Wallace, Corinne J.; Elliott, Susan J.
The Water-associated Disease Index (WADI) was developed to identify and visualize vulnerability to different water-associated diseases by integrating a range of social and biophysical determinants in map format. In this study vulnerability is used to encompass conditions of exposure, susceptibility, and differential coping capacity to a water-associated health hazard. By assessing these conditions, the tool is designed to provide stakeholders with an integrated and long-term understanding of subnational vulnerabilities to water-associated disease and contribute to intervention strategies to reduce the burden of illness. The objective of this paper is to describe and validate the WADI tool by applying it to dengue. A systemic ecohealth framework that considers links between people, the environment and health was applied to identify secondary datasets, populating the index with components including climate conditions, land cover, education status and water use practices. Data were aggregated to create composite indicators of exposure and of susceptibility in a Geographic Information System (GIS). These indicators were weighted by their contribution to dengue vulnerability, and the output consisted of an overall index visualized in map format. The WADI was validated in this Malaysia case study, demonstrating a significant association with dengue rates at a sub-national level, and illustrating a range of factors that drive vulnerability to the disease within the country. The index output indicated high vulnerability to dengue in urban areas, especially in the capital Kuala Lumpur and surrounding region. However, in other regions, vulnerability to dengue varied throughout the year due to the influence of seasonal climate conditions, such as monsoon patterns. The WADI tool complements early warning models for water-associated disease by providing upstream information for planning prevention and control approaches, which increasingly require a comprehensive and geographically broad understanding of vulnerability for implementation.
Could sensory mechanisms be a core factor that underlies freezing of gait in Parkinson's disease?
(Public Library of Science, 2013-05-08) Martens, Kaylena A. Ehgoetz; Pieruccini-Faria, Frederico; Almeida, Quincy J.
The main objective of this study was to determine how manipulating the amount of sensory information available about the body and surrounding environment influenced freezing of gait (FOG), while walking through a doorway. It was hypothesized that the more limited the sensory information, the greater the occurrence of freezing of gait. Nineteen patients with Parkinsoǹs disease who experience freezing of gait (PD-FOG) walked through a doorway or into open space in complete darkness. The three doorway conditions included: (i) FRAME (DARK) – walking through the remembered door frame; (ii) FRAME - walking through the door with the door frame illuminated; (iii) FRAME+BODY - walking through the door (both the door and the limbs illuminated). Additionally, two conditions of walking away from the doorway included: (iv) NO FRAME (DARK) - walking into open space; (v) NO FRAME+BODY - walking into open space with the limbs illuminated, to evaluate whether perception (or fear) of the doorway might account for FOG behaviour. Key outcome measures included: the number of freezing of gait episodes recorded, total duration of freezing of gait, and the percentage of time spent frozen. Significantly more freezing of gait episodes occurred when participants walked toward the doorway in complete darkness compared to walking into open space (p<0.05). Similar to previous studies, velocity (p<0.001) and step length (p<0.0001) significantly decreased when walking through the door in complete darkness, compared to all other conditions. Significant increases in step width variability were also identified but only when walking into open space (p<0.005). These results support the notion that sensory deficits may have a profound impact on freezing of gait that need to be carefully considered.
Categorical 't Hooft Expansion and Twisted Holography
(University of Waterloo, 2026-06-15) Lopez Raven, Adrian Khalil
This thesis studies ideas of Holography and 't Hooft expansions in the context of Twisted Holography. The 1st part introduces a novel entry in the Twisted Holography dictionary, associating to certain boundary operators, bulk instantonic deformations of D1-D5 brane systems in SL(2,C). From the boundary operators, we are able to extract the data of both the shape and Chan-Paton bundle of the dual brane, encoding it in a derived coherent sheaf. We then apply this construction to chiral algebras with SO and Sp gauge groups, obtaining branes with Z2 identifications consistent with conjectures relating these chiral algebras to orientifolds of the bulk B-model theory. The second part, extends the conjecture of Twisted Holography to a wide family of chiral algebras. In particular, we study boundary theories containing several βγ-systems with several U(N) gauge groups. Amongst these one has known chiral algebras arising from the twist of quiver-gauge theories, but also new chiral algebras whose dual B-model lives in non-commutative backgrounds. Using techniques from String Field Theory and Homological Algebra, we extract from these chiral algebras, algebraic properties of the conjectural dual worldsheet theories, and track how they deform under backreaction.