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1.
Rosa RicciardiChristine Gaillet Guylaine DucouretFrançoise Lafuma Françoise Lauprêtre 《Polymer》2003,44(11):3375-3380
The structure and rheological behavior of atactic poly(vinyl alcohol) (a-PVA) hydrogels prepared by freeze/thaw cycles were investigated as a function of polymer concentration and number of freeze/thaw cycles. The presence of phases with different mobilities was observed using 13C CP/MAS and DP/MAS NMR experiments. The degree of crystallinity of the a-PVA-rich phase was determined by 1H NMR free decay experiments. Measurements of the shear storage and loss modulus were performed at a fixed frequency of 1 Hz and a strain value of 0.1%, i.e. under conditions where the deformation imposed on the gel structure is entirely reversible. Results thus obtained showed that an increase in the number of freeze/thaw cycles induces an increase in the degree of crystallinity in the polymer-rich phase together with an increase in the storage modulus. The a-PVA hydrogels became more fragile as the number of freeze/thaw cycles was increased. Moreover, both the percentage of protons in a rigid environment measured by 1H NMR and the storage modulus values tended to a limiting value after six freeze/thaw cycles. These results show that the first five or six freeze/thaw cycles play a very important role in determining the hydrogel structure and rheological properties. A more detailed comparison of NMR and rheological data led to the conclusion that the storage modulus is mainly controlled by the a-PVA crystallinity while the hydrogen bond interactions have a much smaller contribution. 相似文献
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Sandra Pagan Michael J. Kozluk Guylaine Goszczynski 《Nuclear Engineering and Design》2009,239(3):477-483
The Canadian Nuclear Standard CSA N285.4 requires the periodic metallurgical examination of removed ex-service steam generator tubes. This paper describes the practices used for the characterization and structural integrity tests of ex-service steam generator tubes at Ontario Power Generation (OPG). It shows that there is no degradation of mechanical properties of Monel 400 tubes after 7-18 effective full power years (EFPY) of operation and Incoloy 800 tubes after more than 10 EFPY of operation. 相似文献
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Electric arc furnace dust (EAFD) is a toxic waste product made in the remelting of scrap steel. The results of a Toxicity Characteristic Leaching Procedure (TCLP) conducted on a sample of EAFD originating from the remelting of stainless steel scrap showed that the total Cr and Cr (VI) liquor concentrations (9.7 and 6.1 mg/L, respectively) exceeded the Toxicity Characteristic Regulatory Level (TCRL). The EAFD showed a complex heterogeneous mineralogy with spinel minerals group predominance. A sequential extractions method has permitted the determination of the amount of available metals (potentially mobile component) from the EAFD as follows: Cr (3%), Ni (6%), Pb (49%) and Zn (40%). Solubility controls on Cr, Pb, Zn and Ni were identified in the EAFD. This means that the Cr, Pb, Zn and Ni concentrations in solution were controlled by the solubility of some phases from EAFD. The concentrations of Ni and Zn, which are metals not regulated by TCRL were below 0.41 and 1.3 mg/L, respectively. The solubility control on Pb was sufficient to decrease its concentration (<0.24 mg/L) to a level below the TCRL. However, the control on Cr was not sufficient to decrease its concentration (between 117 and 331 mg/L) to below the TCRL. 相似文献
4.
Muriel J. Wagner Michel Loubat Alain Sommier Dominique Le Ray Guylaine Collewet Bertrand Broyart Honoré Quintard Armel Davenel Gilles Trystram & Tiphaine Lucas 《International Journal of Food Science & Technology》2008,43(6):1129-1139
An oven dedicated to a magnetic resonance imager (MRI) was designed and constructed for continuous monitoring of the entire baking process. The general aim was to test whether response variables conventionally measured on bread loaves, such as temperature, density, and water loss, were consistent with those reported for similar products baked in classical convection ovens. MRI images acquired during baking are presented and discussed, emphasising the need to develop quantitative MRI methods allowing conversion of the MRI signal into one variable of interest, such as local density or local water content. 相似文献
5.
C?té Guylaine; Gauthier Janel G.; Laberge Benoit; Cormier Hugues J.; Plamondon Jacques 《Canadian Metallurgical Quarterly》1993,25(1):45
Reviews the mainly English-language clinical research and some studies by the present authors on the use of cognitive and behavioral procedures to treat panic disorder. Controlled studies and noncontrolled studies are considered. Use of relaxation, respiratory control, and exposure is discussed. (English abstract) (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
6.
Disposal of industrial solid wastes can cause environmental risks due to the mobility of toxic elements. Stabilization/solidification (s/s) is an effective tool in the treatment of various wastes; however, there is a lack of chemical fixation on the concentrations of Cr. Thus, Cr, in particular Cr6+, remains free in the leachate. Some phases of the blast furnace slag seem to be able to exert a solubility control on chromium. This study evaluates the effect of various binders on the fixation of Cr ions. Static leaching tests were conducted at two different water-solid ratios as a means to distinguish elements that have solubility controls. The results show that Cr content decreases very quickly to obtain values near 0.03 ppm soon after the contact between the contaminated solution and the different binders. The sample containing only the slag was the most effective. Cr was evenly distributed in the C-S-H as detected by scanning electron microscope (SEM). 相似文献
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Both tumor necrosis factor-α (TNF-α) and EFA deficiency (EFAD) have been established as causes of marked perturbations in
lipid and lipoprotein metabolism. Excessive levels of circulating TNF-α can coexist with EFAD in various clinical disorders
such as cystic fibrosis and type I diabetes. The present study therefore aimed to investigate their combined effects on lipid
profile and lipoprotein composition by administering TNF-α to EFAD rats. Lipoprotein lipase (LPL), the ratelimiting enzyme
in TG catabolism, was also measured in epididymal adipose tissue. EFAD, after a 4-wk period, induced significant increases
in plasma TG (80%, P<0.001), total cholesterol (TC, 27%, P<0.025), and HDL-cholesterol (HDL-C, 62%). Two hours after the administration of TNF-α, a further rise in TG (43%, P<0.05) was noted in controls, but not EFAD animals. TC and HDL-C were unaffected by TNF-α treatment. In addition, TNF-α modified
lipoprotein-lipid composition. VLDL and HDL2 derived from EFAD rats were depleted in apolipoprotein (apo) E and apo A-II, and enriched in apo A-12 h after TNF-α administration.
Finally, TNF-α decreased adipose tissue LPL activity in both control and EFAD animals. The TNF-α-induced inhibition was more
marked in EFAD rats. The present results demonstrated that TNF-α can amplify or antagonize the effects of EFAD on lipid profile,
lipoprotein composition, and LPL activity. These data also suggest that the host's nutritional status is a determining factor
for the modulating effect of TNF-α on lipid metabolism. 相似文献
10.
The interaction mechanisms of the Cr(VI) ion in presence of GGBFS and OPC were evaluated by chromium binding isotherms and by pore solution analysis. The chromium in the final leaching solution was measured and the solid samples were investigated by SEM and by XRD. GGBFS was more efficient than OPC in fixing Cr ions at lower initial concentrations. However, from an initial Cr(VI) concentration of 2000 and 5000 mg/L, OPC was more efficient.
For an initial Cr(VI) concentration of 50 000 mg/L, around 145 mg Cr/g was fixed by OPC and only 8 and 55 mg Cr/g were fixed by GGBFS in alkaline and water-based immersion solutions, respectively. The Cr-bearing phases identified by XRD and SEM are: CaCrO4 and CaCrO4·2H2O, C–S–H and calcium aluminate phases. The pore solution chemistry indicates that a value around 92% of chromium was retained by GGBFS and 87% by OPC. 相似文献