Progress Report: Land Use and Wetland Drainage Effects on Prairie Water Quality Study

© Centre for Hydrology, University of Saskatchewan, Saskatoon, Saskatchewan, January 2009This report is an update on progress made to the end of December 2008. According to our study plan, we should have completed one summer worth of data collection and made progress in laboratory analytical work. Outlined in the report are data collection methods and progress to date made on our research objective of “determining changes in water quality of streams and impacts to ecosystem function associated with wetland drainage”. Considerable progress toward the research objective was achieved during the reporting period, and overall, the project is on schedule. Smith Creek was broken down into its tributaries (North Fork, South Fork and Thingvalla). Water samples at the outlet and tributaries of Smith Creek were taken on 35 occasions during the spring, summer and fall. Chemical analysis of these samples is 70% complete. The wetland for the drainage experiment was selected and instrumented with an electronic water level recorder and precipitation gauge. A bathymetry survey of the wetland was carried out and used to compute the volume of water stored in the wetland at different water levels. Water chemistry for the wetland was analyzed 29 times during the spring, summer and fall. Preliminary results show concentrations of DOC increased over the spring and early part of the summer as the wetland evaporated. Concentrations then fell to post-snowmelt values during the unusually wet late summer period. The wetland was drained this fall ahead of schedule due to the needs of the landowner. Once drained, the wetland lost 42% of its volume within 22 hours. Preliminary findings were that the drain was a source of TP during the first 2.5 hours and then transitioned to a sink. The Benthic Entomology (BENT Lab) of the Saskatchewan Watershed Authority (SWA) provided a preliminary assessment of the biotic health in the Smith Creek watershed. Sampling was conducted in spring 2008, and the progress of this assessment is as follows: a) Four sites were sampled in the watershed; b) 83% of all samples have been processed and identified; c) to date, a total of 9,669 individuals have been identified, representing 80 taxa; and d) of the samples processed, they are characterized primarily by pollution-tolerant fly larvae, and fast growing non-insect taxa typical of seasonal prairie streams. SWA is now preparing plans for additional assessment in 2009, and further evaluation of 2008 results using a reference condition approach and test site analysis in order to obtain robust measures of ecosystem health in the Smith Creek watershed

Wetland Drainage Effects on Prairie Water Quality : Final Report

Agriculture Development FundNon-Peer ReviewedThis report describes factors influencing the spatial variation in wetland water quality and how drainage of wetlands affects downstream receiving waters in terms of their water quality and biotic health. The specific objectives of this work were to: 1) characterize the spatial and temporal variation in water quality of prairie potholes after snowmelt; 2) quantify solute export along a newly constructed wetland drainage ditch; 3) characterize solute export from drained pothole wetlands; 4) determine the extent to which stream water quality is influenced by wetland drainage; 5) contribute to the understanding of how wetland drainage affects ecosystem health. The research was conducted at the Smith Creek watershed, southeastern Saskatchewan, where there has been controversy over recent renewed efforts to drain wetlands to increase agricultural production

Using atomic interference to probe atom-surface interaction

We show that atomic interference in the reflection from two suitably polarized evanescent waves is sensitive to retardation effects in the atom-surface interaction for specific experimental parameters. We study the limit of short and long atomic de Broglie wavelength. The former case is analyzed in the semiclassical approximation (Landau-Zener model). The latter represents a quantum regime and is analyzed by solving numerically the associated coupled Schroedinger equations. We consider a specific experimental scheme and show the results for rubidium (short wavelength) and the much lighter meta-stable helium atom (long wavelength). The merits of each case are then discussed.Comment: 11 pages, including 6 figures, submitted to Phys. Rev. A, RevTeX sourc

La pince optique : Un outil interdisciplinaire

L’invention de la pince optique, c’est l’histoire d’un chercheur qui s’amuse mais qui avance méthodiquement et patiemment pour améliorer un concept simple jusqu’à en faire un outil indispensable dans deux domaines de recherche très différents. En biologie et en physique atomique, la pince optique est devenue un instrument de laboratoire courant

Les miroirs à atomes

The manuscript summarizes work done on atom mirrors in the Atom Optics group between 1991 and 2000. Most of the work concerns mirrors for Rb atoms using evanescent waves. An important goal has been the realization of high quality optical elements for atom optics, particularly coherent atom mirrors. It is necessary to reduce spontaneous emission by enhancing the intensity of the evanescent wave as well as to understand the influence surface roughness. It is also possible to introduce a controlled periodic corrugation producing diffraction at both normal and grazing incidence. We have used the apparatus to make a surface nanoprobe sensitive to van der Waals interactions between an atom and the surface. The manuscript describes interference measurements on bouncing atoms which use velocity selective Raman Transitions.Ce manuscrit présente une synthèse des travaux réalisés sur les miroirs à atomes dans le groupe d'Optique Atomique de 1991 à 2000. Il s'agit principalement d'expériences utilisant un miroir à onde évanescente pour réfléchir des atomes de rubidium. Notre objectif étant la réalisation d'éléments optiques de qualité pour l'optique atomique, nous nous sommes attachés à l'étude du maintien de la cohérence à la réflexion : réduction de l'émission spontanée grâce à l'exaltation de l'onde évanescente, influence de la rugosité de surface voire d'une « rugosité contrôlée », en incidence normale et en incidence rasante. Nous avons également mis à profit la grande sensibilité de notre dispositif pour utiliser les atomes comme nanosonde d'effets de surface : mesure de l'interaction de van der Waals, y compris grâce à une méthode interférométrique prometteuse pour la mesure des effets de retard, et caractérisation de la rugosité de surface grâce à une nouvelle méthode, basée sur des transitions Raman sélectives en vitesse

Etude de cinétique de la traduction eucaryote à l'échelle de la molécule unique

La synthèse des protéines est un mécanisme central de la vie cellulaire dont la compréhension est un enjeu du domaine biomédical. Les études en molécule unique permettent d observer chaque système réactionnel individuellement et donnent accès à des évènements asynchrones difficilement observables en mesure d ensemble, tels la traduction de protéines.Cette thèse présente les premiers résultats en molécule unique sur la traduction par un ribosome eucaryote (mammifère). Nous observons les systèmes traductionnels grâce à des marqueurs fluorescents liés à des oligonucléotides pouvant s hybrider sur les séquences d ARN traduites. L observation de ces marqueurs est faite par microscopie de fluorescence en onde évanescente (TIRF), les ARN étant fixés sur une lamelle de microscope. En lisant l ARN, le ribosome détache les marqueurs, et leurs instants de départs donnent des informations sur le passage du ribosome à différentes positions sur l ARN. Cette méthode permet d obtenir des données cinétiques sur un grand nombre de systèmes traductionnels en parallèle pouvant alors être interpolées par des lois de probabilité. Nous obtenons par cette méthode des mesures de la cinétique in vitro de l élongation eucaryote et nous observons un délai dû à une initiation non-canonique. En effet, nous complexons le ribosome sur l ARN grâce à une structure de type IRES. Dans nos conditions d expérience, l incorporation d un acide aminé prend environ une seconde tandis que cette structure induit un retard à la traduction de plusieurs dizaines de secondes. Ces résultats ouvrent des perspectives d étude cinétique dans des cas plus complexes tels le franchissement de structures secondaires de l ARN.Protein synthesis is a central mechanism of cellular life and understanding it is a challenge in biomedical research. Single molecule studies permit each reactive system to be observed individually and provide access to asynchronous events difficult to observe in ensemble experiments, such as protein translation.This thesis presents the first results on single molecule eukaryotic (mammalian) translation. We observe the translational systems using fluorophores linked to oligonucleotides annealed to the RNA translated sequences. The observation of these fluorophores is done by total internal reflection fluorescence microscopy, the RNA being attached to a microscope slide. When reading the RNA, the ribosome unzips the fluorescent oligonucleotides and their departure times provide information about the position of the ribosome at different locations on the RNA strand. This method provides kinetic data on a large number of parallel translational systems that can be fitted using probability laws.With this method, we measure the in vitro kinetics of eukaryotic elongation and we reveal a delay due to a non-canonical initiation of the ribosome. Indeed, in our experiments, the ribosome is initially complexed on an RNA structure called Internal Ribosome Entry Site. In our experimental conditions, each incorporation of an amino acid in the nascent protein takes about one second while the IRES structure induces a delay of several tens of seconds on the first incorporation. These results open new perspectives for kinetic studies in more complex configurations such as the passage of the ribosome through RNA secondary structures.PARIS11-Inst. Optique (914712302) / SudocSudocFranceF

Former les futur.e.s ingénieur.e.s en termes d'égalité femmes-hommes par le théâtre

International audienc

Former les futur.e.s ingénieur.e.s aux questions d'égalité femmes-hommes avec des ateliers d'écriture créative

International audienc

Conférence internationale sur les femmes en physique

La sixième Conférence internationale sur les femmes en physique (ICWIP 2017) a eu lieu à Birmingham, du 16 au 20 juillet 2017. Cette conférence a réuni 210 personnes de 47 pays et a proposé six conférences plénières représentant des disciplines et des pays variés, deux séances posters (posters nationaux sur les femmes en physique dans les différents pays et posters scientifiques), cinq ateliers ainsi que deux évènements exceptionnels