39 research outputs found
The Depositional Environment of the Queenston Formation in Southern Ontario
No full textTitle: The Depositional Environment of the Queenston Formation in Southern Ontario, Author: Paul J. Brogly, Location: ThodeThe Queenston Formation has been interpreted as a
non-marine deltaic deposit since the turn of the century
because of its apparent lack of fossils, and evidence for
subaerial exposure. The source of the sediment was interpreted
to be an orogenic zone in New York or Pennsylvannia. Features such as gypsum nodules and limy siltstones
were interpreted as being secondary. However, petrographic
studies have found that the siltstones contain marine fossils
and some gypsum nodules have inclusions of halite. Moreover,
the fine sand grains in the mudrock are not aeolian. Paleocurrents
indicate that the source of the sediment transport
was generally north-south not east-west. The siltstone and
limestone interbeds are flat based, graded, and show no
evidence for channeling. Some beds also contain large escape
burrows. It is proposed that the Queenston Formation was
deposited as a supratidal; mudflat that was regularly flooded
by the sea. The mud could have been transported by longshore
drift from a river somewhere towards the north, as the
paleocurrents in the Queenston mimic major tradewind patterns
for the Late Ordovician.ThesisBachelor of Science (BSc
Glass transition of stereoregular poly(methyl methacrylate) at interfaces
No full textInternational audienceThe glass transition temperature (T-g) of layers of stereoregular poly(methyl methacrylate) (PMMA) spin-cast on silicon and aluminum surfaces has been investigated by ellipsometry. The interfacial specific interactions were highlighted and quantified by infrared reflection absorption spectroscopy. It was found that depending on PMMA tacticity, a strong correlation exists between the density of the polymer/surface interactions and the T-g of that polymer at the interface. Indeed, i-PMMA with a large density of interfacial interactions increases its T-g at the interface whereas s-PMMA with a lower value of bonded segments exhibits a T-g depression. It is suggested that a certain level of interfacial interactions associated with an increase of density of the layer will compensate for the increase of mobility resulting from a reduction of the entanglement density or a segregation of chain ends at an interface
Organization of PCL-b-PMMA Diblock Thin Films: Relationship to the Adsorption Substrate Chemistry
No full textInfluence Of Specific Thermal Treatment On Young'S Modulus Changes In A Natural Rubber–Based Compound: Study By Afm Nanoindentation
No full textInternational audienceThe determination and study of Young's modulus at the nanometric scale in an efficient and fast way is carried out using atomic force microscopy (AFM) in contact mode. The aim of this study is to evaluate the impact of a specific thermal treatment on Young's modulus changes from the surface toward the bulk of a cured natural rubber (NR)–based compound. The AFM nanoindentation experiments were conducted on a cross-linked NR sample. Following a depth profiling analysis method, AFM deflection distance curves were measured every 40 μm from the oxygen-exposed surface toward the bulk, and then the Hertz's model was applied to force-indentation curves for the calculation of the Young's modulus. Investigations on the thermal-treated samples revealed an overall increase of the Young's modulus along the samples after heating. Moreover, a decrease of Young's modulus values from the surface exposed to oxygen during heating toward the bulk was observed, indicating a stiffening of the sample at the surface
Exploring associations between perceived HCV status and injecting risk behaviors among recent initiates to injecting drug use in Glasgow
No full textThe aim of this study was to explore the influence of testing for hepatitis C virus (HCV) and perceived HCV status on injecting risk behavior. A cross-sectional, community-wide survey was undertaken at multiple sites throughout Greater Glasgow during 2001-2002. Four hundred ninety-seven injecting drug users (IDUs) consented to participate and were interviewed using a structured questionnaire to ascertain HCV test history and injecting risk behavior. The average age of participants was 27 years and the majority of the sample were male (70.4%). Participants had been injecting for an average duration of 2.5 years. Logistic regression analysis revealed no significant associations between having been tested and injecting risk behavior. After adjustment for potential confounding variables, HCV-negatives were significantly less likely to borrow needles/syringes and spoons or filters as compared with unawares and were significantly less likely to borrow spoons or filters as compared with HCV-positives. Due to the cross-sectional design of the study, it is uncertain whether this reduction in risk behavior could be attributed to perception of HCV status. Further research is recommended to consolidate the evidence for this relationship
Starch in rubbery and glassy states by FTIR spectroscopy
No full textInternational audienceThe organization of various starch samples varying in molecular structure, organization and moisture content was studied by ATR-FTIR spectroscopy. The comparison of the infrared spectra showed that band intensities in the 1065-870 cm(-1) region can be explained by their mobility related to the glass transition, T-g, which occurs at room temperature in the 15-21% water content range. Spectra analyzed using principal component analysis showed main structure/moisture changes for the 1000/1022 cm(-1) intensity ratio. The helix organization at a short order range was weakly moisture dependant below T-g, whereas the signal became increasingly water dependant with the crystalline/amorphous ratio above T-g. This result is in agreement with the model of liquid crystal structure and mesophase variation: water allows the self-assembly of amylopectin helices leading to layered organized structure
Défaillance cardiaque aiguë associée à une cardiomyopathie dilatée en post-partum précoce : traitement par ballon de contrepulsion aortique et lévosimendan
No full textPregnancy is associated with elevation of liver enzymes in HIV-positive women on antiretroviral therapy.
No full textThe objective of this study is to assess whether pregnancy is associated with an increased risk of liver enzyme elevation (LEE) and severe LEE in HIV-positive women on antiretroviral therapy (ART)
Ultrasound differences of six needles of regional anaesthesia in animal tissue and phantom models
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