University of Calgary

About: University of Calgary is a education organization based out in Calgary, Alberta, Canada. It is known for research contribution in the topics: Population & Health care. The organization has 44284 authors who have published 104970 publications receiving 3669161 citations. The organization is also known as: U of C & UCalgary.

A population‐based study of multiple sclerosis in twins: Update

Abstract: This study is a 7.5-year follow-up of a population-based series of twins with multiple sclerosis (MS) whose mean age now exceeds 50 years. The twin pairs were identified through the Canadian nationwide system of MS clinics and were drawn from a population of 5,463 patients. After 7.5 years, the monozygotic concordance rate increased from 25.9 to 30.8% and the dizygotic-like sex concordance rate from 2.4 to 4.7%. These results are very similar to those of other population-based studies and to our own modified replication twin data reported here. We interpret the data to mean that MS susceptibility is genetically influenced, and a single dominant or even a single recessive gene is unlikely to account for this effect. The difference in concordance rates suggests that at least two or more genes are operative. These data also have important implications for the nature of the environmental effect(s) in MS susceptibility. Most monozygotic twins are discordant even after a correction for age and magnetic resonance imaging findings. This unambiguously demonstrates the powerful effect of nonheritable factors.

Dispositions and Conditionals

Abstract: A l'aide de deux exemples, l'A. essaie de prouver que l'equivalence proclamee entre les enonces attribuant des dispositions ou pouvoirs causaux et les enonces conditionnels n'est pas defendable si l'enonce conditionnel est formule d'une certaine facon. Cela peut etre evite par une reformulation triviale du conditionnel

Neuropsychological outcomes after epilepsy surgery: systematic review and pooled estimates.

Abstract: Summary Purpose: Epilepsy surgery is a safe surgical procedure, but it may be associated with cognitive changes. Estimates of the risk of decline in specific neuropsychological domains after epilepsy surgery would assist surgical decision making in clinical practice. The goal of this study was to conduct a systematic review to derive pooled estimates of the rate of losses and gains in neuropsychological functions after epilepsy surgery, using empirically based methods for quantifying cognitive change. Methods: An extensive literature search using PubMed, EmBase, and the Cochrane database was conducted, yielding 5,061 articles on epilepsy surgery, with 193 on neuropsychological outcomes (IQ, memory, language, executive functioning, attention, and subjective cognitive changes). Key Findings: Of these, 23 met final eligibility criteria, with 22 studies involving temporal surgery only. Key aspects of inclusion criteria were N ≥ 20 and use of reliable change index or standardized regression-based change estimates. In addition to the proportion of patients experiencing losses and gains in each individual test, a single pooled estimate of gains and losses for each cognitive domain was derived using a random effects model. Weighted estimates indicated a risk to verbal memory with left-sided temporal surgery of 44%, twice as high as the rate for right-sided surgery (20%). Naming was reduced in 34% of left-sided temporal patients, with almost no patients with gains (4%). Pooled data on IQ, executive functioning, and attention indicated few patients show declines post surgery, but a substantial rate of improvement in verbal fluency with left-sided temporal surgery (27%) was found. Self-reported cognitive declines after epilepsy surgery were uncommon, and gains were reported in some domains where losses were found on objective tests (i.e., verbal memory and language). Variations in surgical techniques did not appear to have a large effect on cognitive outcomes, except for naming outcomes, which appeared better with more conservative resections. Sensitivity to postoperative changes differed across visual memory tests, but not verbal memory tests. Few conclusions could be made regarding cognitive risks and benefits of extratemporal epilepsy surgery, or of epilepsy surgery in children. Significance: In sum, epilepsy surgery is associated with specific cognitive changes, but may also improve cognition in some patients. The results provide base rate estimates of expected cognitive gains and losses associated with epilepsy surgery that may prove useful in clinical settings.

Reassessment of net surface mass balance in Antarctica

Abstract: Recent in situ measurements of surface mass balance and improved calculation techniques are used to produce an updated assessment of net surface mass balance over Antarctica. A new elevation model of Antarctica derived from ERS-1 satellite altimetry supplemented with conventional data was used to delineate the ice flow drainage basins across Antarctica. The areas of these basins were calculated using the recent digital descriptions of coastlines and grounding lines. The delineation of drainage basins was achieved using an automatic procedure, which gave similar results to earlier hand-drawn catchment basins. More than 1800 published and unpublished in situ measurements of net surface mass balance from Antarctica were collated and then interpolated. A net surface mass balance map was derived from passive microwave satellite data, being employed as a forcing field to control the interpolation of the sparse in situ observations. Basinwide integrals of net surface mass balance were calculated using t...

Sources of nitrate in rivers draining sixteen watersheds in the northeastern U.S.: Isotopic constraints

Abstract: The feasibility of using nitrogen and oxygen isotope ratios of nitrate (NO 3 − ) for elucidating sources and transformations of riverine nitrate was evaluated in a comparative study of 16 watersheds in the northeastern U.S.A. Stream water was sampled repeatedly at the outlets of the watersheds between January and December 1999 for determining concentrations, δ 15N values, and δ 180 values of riverine nitrate.