68 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
Supplemental Material, Appendix_1_revised_June_7 - Management of Cancer-Associated Intestinal Obstruction in the Final Year of Life
No full textSupplemental Material, Appendix_1_revised_June_7 for Management of Cancer-Associated Intestinal Obstruction in the Final Year of Life by Shaila J. Merchant, Susan B. Brogly, Christopher M. Booth, Craig Goldie, Yingwei Peng, Sulaiman Nanji, Sunil V. Patel, Katherine Lajkosz and Nancy N. Baxter in Journal of Palliative Care</p
Influence of tacticity on the conformation and development of acid-base adducts of PMMA homopolymers adsorbed on aluminium mirrors
No full textEuradh 96, CAMBRIDGE, ENGLAND, 1996International audienceThe influence of tacticity on (1) the conformation of adsorption at a polymer/substrate interface and (2) the magnitude and density of acid-base interactions developed at the interface, has been studied. Films of poly(methyl methacrylate) (PMMA) homopolymers of various tacticities were spin-coated on aluminium mirror substrates. Ellipsometric measurements show that the PMMA film thickness increases linearly with the syndiotactic sequence length (as determined by C-13 nuclear magnetic resonance spectroscopy.) These results tend to prove that the backbone conformation, the spatial extension and the segmental rigidity are affected when the density of racemic diads increases. Fourier transform infra-red reflection-absorption spectroscopy (IRAS) reveals orbital overlapping between the sp bonding orbital of the PMMA carbonyl oxygen atom and the sigma* antibonding hydroxyl orbital and allows us to calculate an enthalpy of interaction of -10.5 kJ mol(-1) Moreover, it is shown that for low amount of adsorbed polymer (10(-2)M), the density of acid-base interfacial adducts decreases as the average syndiotactic sequence length of the PMMA increases. This tends to confirm that the conformations of adsorbed isotactic PMMA chains are more extended than those for syndiotactic chains. IRAS analysis shows that the development of interfacial acid-base adducts induces backbone trans-gauche conformations changes in trans-trans conformations, leading then to an increase in the conformational energy of the main chain. This effect is magnified as the isotacticity of the adsorbed PMMA homopolymer increases. (C) 1997 Elsevier Science Ltd
Extension du modèle de Hertz pour la prise en compte de la tension de surface dans les essais de nano-indentation des matériaux souples
No full textInternational audienceThe contact between a spherical indenter and a solid is considered. A numerical finite element model (F. E. M) to taking into account the surface tension of the solid is presented and assessed. It is shown that for nano-indentation of soft materials, the surface tension of the solid influences significantly the reaction force due to indentation. The validity of the classical Hertz model is defined. In very good approximation, the force vs. indentation depth curve can be fitted by a power law function F = a d where F denotes the force acting on the indentor, d the indentation depth, a and b in ]1, 1.5] are constants depending on the materials and the size of the indentor.Le contact entre un indenteur sphérique et un solide élastique est considéré. Un modèle par éléments finis permettant de prendre en compte la tension de surface du solide est présenté et validé. Il est montré que pour la nano-indentation de matières souples, la tension de surface du solide peut influencer considérablement la courbe force vs. profondeur d’indentation. Il est ainsi définit quand le modèle de Hertz classique ne convient plus. En très bonne approximation, la courbe force vs. profondeur d’indentation peux être décrite par une croissance allométrique F = a d où F désigne la force agissant sur l'indenteur, d la profondeur d’indentation, a et b dans ]1, 1.5] sont des constantes qui dépendent du matériau et du rayon de pointe
Effects of the composition of hot-melt adhesives on their bulk and interfacial properties
No full textSpecific interactions in binary blends, models of hot-melt adhesives, of ethylene-vinylacetate copolymer (EVA) with different terpene-phenol low molecular weight tackifying resins (TPR) are first investigated by means of Fourier transform infrared spectroscopy (FTIR) as a function of the composition of the blend. Molecular electron donor-acceptor (or "acid-base" according to Lewis' concept) complexes are clearly evidenced between TPR hydroxyl and EVA carbonyl groups. Quantitative data on the fraction of acid-base bonded carbonyl groups and the enthalpy of pair formation are then obtained. Secondly, the analysis of the interface between the blends and basic (aluminium) or acidic (glass) substrates by FTIR allows us to show the establishment and to quantify the strength of acid-base interfacial interactions in both cases. Finally, the comparison between the interfacial and bulk properties data and adhesive strength measurements (peel energy) leads to the estimation of fundamental parameters of adhesion science, in particular the acid-base component of the energy of adhesion and the number of acid-base interactions per unit interfacial area
Evidence of electron acceptor - electron donor interactions in thermoplastic polymer blends by using FTIR - ATR spectroscopy
No full textChain flattening of spin-cast PMMMA on aluminum mirrors: Influence of polymer tacticity
No full textInternational audiencePolymer tacticity has already been shown to be an influential parameter governing the behavior of polymer solutions and polymer blends, but not for polymer adsorption. However, using PMMA having a racemic fraction (f(r)) ranging from 0.1 to 0.9, spin-cast on aluminum mirror surfaces, makes it possible to work out configuration differences in the adsorbed layer. Reflectance infra-red spectroscopy has been used to evaluate the fraction of surface bonded carbonyl groups (f(C=0)(ab)) and local conformations of both main and side chain. The f(C=0)(ab) value is 0.1 for highly syndiotactic PMMA and reaches 0.7 for mainly isotactic PMMA. This latter very high value of f(C=0)(ab) can only be explained by chain flattening resulting from a distortion from its isotropic state. This distortion may be due to both strong interactions that may exist between PMMA and the aluminium substrate, and also to the spin-cast process that may lead to chain straightening and flattening. The assumption of conformational energy changes of both backbone and side chain is confirmed by changes in the FT-IR A upsilon(2)(1245 cm(-1))/A upsilon(1)(1265-1275 cm(-1)) ratio. Ellipsometric spectroscopy has provided information on the global conformation of adsorbed chains by precise thickness measurements. Thus, thickness (h) increases for diluted solutions linearly from 10 to 70 Angstrom as the average syndiotactic sequence length (n(s)) increases. However, IR and ellipsometric results tend to prove that isotactic PMMA may adsorb on the aluminum surface in a more flattened way with longer chains than atactic and syndiotactic chains. This can be explained by the ability of chain segmental rearrangements (meso tg state) that may allow isotactic PMMA to favor the establishment of interfacial acid-base bonds while the syndiotactic PMMA local stiffness of the tt state does not. The influence of the chain entropy in solution is also discussed as an important parameter. (C) 1997 Elsevier Science Ltd. All rights reserved
Fourier transform IR study of acid—base interactions: Blends of ethylene—vinylacetate copolymer and terpene-phenol resins
No full textExtension of the Hertz Model for Accounting to Surface Tension in Nano-indentation Tests of Soft Materials
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