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91.
NA Tamarina WD McMillan VP Shively WH Pearce 《Canadian Metallurgical Quarterly》1997,122(2):264-71; discussion 271-2
BACKGROUND: Abdominal aortic aneurysms (AAAs) are characterized by degradation of collagen and elastin resulting from increases in matrix metalloproteinase (MMP) activity. Previous authors have identified isolated increases in expression of specific MMPs in AAAs, but none have compared relative levels of expression of particular MMPs to one another or to those of their inhibitors, the tissue inhibitors of metalloproteinases (TIMPs). This study proposes to quantify relative mRNA levels for interstitial collagenase (MMP-1), 72 kd type IV collagenase (MMP-2), 92 kd type IV collagenase (MMP-9), TIMP-1, and TIMP-2 in normal aorta (NA) and AAA to provide insight as to the relative importance of each in aneurysm formation. METHODS: Competitive polymerase chain reactions (PCRs) with gene-specific external standards and cDNA derived from AAAs (n = 8; mean age, 67.4 years) and NA (n = 5; mean age, 40.6 years) were used to quantify mRNA levels. Results were normalized to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA levels, determined by means of competitive PCR, and compared by means of Mann-Whitney statistics. RESULTS: Significant increases in MMP mRNA expression in AAA over NA were observed for MMP-1 (3.64 versus 0.3, p = 0.007), MMP-9 (78.03 versus 3.35, p = 0.003), TIMP-1 (835.32 versus 477.2, p = 0.027), and TIMP-2 (18.09 versus 4.14, p = 0.003). The ratio of MMP to TIMP mRNA levels was higher in AAA than NA (0.135 versus 0.045, p = 0.018). CONCLUSIONS: Increases in expression of MMP-1, MMP-9, and MMP/TIMP ratios may result in increased proteolysis and matrix degradation, which characterize AAAs. MMP-9 appears to be the predominant metalloproteinase expressed in AAA, because its mRNA levels were more than 20 times and 2 times higher than those of MMP-1 and MMP-2, respectively. TIMP-1 mRNA levels were in molar excess to those of any of the metalloproteinases studied. 相似文献
92.
DK Bhuyan X Huang G Kuriakose WH Garner KC Bhuyan 《Canadian Metallurgical Quarterly》1997,16(6):519-526
This article takes issue with procedural reductionism, which is the inclination to reduce all matters of judgement and responsibility to the following of some procedure or rule. Two scenarios provide content for a discussion of professional discretion in the context of accountability. The author shows that in professional life there will always be situations that stand beyond the rules of procedures and require the unique judgement of the professional at the time. While this judgement may be determined by the facts available in a situation of uncertainty, it cannot be reduced to the facts (including facts about rules and procedures). The moral judgement will still have an essential indeterminancy about it. 相似文献
93.
J Poon M Bailey DJ Winzor BE Davidson WH Sawyer 《Canadian Metallurgical Quarterly》1997,73(6):3257-3264
Fluorescence quenching has been used to measure quantitatively the effects of sucrose and triethylene glycol on the interaction between the Escherichia coli regulatory protein TyrR and a 30-basepair oligonucleotide containing the strong TyrR box of the TyrR operon. It was observed that the apparent binding constant increased in the presence of co-solutes, the dependence of the logarithm of the apparent binding constant on molar concentration being indistinguishable and essentially linear for both co-solutes. This activation of the TyrR-oligonucleotide interaction is attributed to thermodynamic nonideality arising from molecular crowding, an interpretation which is supported by the reasonable agreement observed between the experimental extent of reaction enhancement and that predicted on the statistical-mechanical basis of excluded volume. 相似文献
94.
95.
The effect of water salinity on the reactions occurring during pressure acid leaching of an arid-region laterite ore, using hypersaline water, seawater, sub-potable water and tap water, is examined. Particular emphasis is placed on the mineralogy of the residue and its implications with regard to residue volume/mass, overall acid consumption and nickel extraction. Analysis of a pressure acid leach residue by electron microprobe indicates that the residual nickel is present in phases that contain silicon and varying concentrations of aluminium, but are deficient in sulphur. Incomplete extraction of nickel from the ore may not be attributed to any one mineral phase. 相似文献
96.
Walsh Benjamin M.; Matthews Russell A.; Tuller Michael D.; Parks Kizzy M.; McDonald Daniel P. 《Canadian Metallurgical Quarterly》2010,15(2):191
To date, minimal work has explored associations between equal opportunity (EO) climate and employee work attitudes, and no known research has investigated the effects of EO climate beyond the individual level. We address these gaps in the literature by testing a multilevel structural equation model in which effects of EO climate are considered at both the individual and unit levels. At the individual level, we predicted that psychological EO climate would be directly associated with job stress and job satisfaction, as well as indirectly related to job satisfaction via stress. In addition, cross-level associations between unit EO climate and job stress and job satisfaction were hypothesized to be mediated by cohesion. Findings supported the proposed model; hypothesized relations were supported at both levels of analysis. We conclude with a discussion of the findings, study limitations, and directions for future EO climate research. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
97.
The metabolism of α-linolenic acid from canola oil was studied in eight normolipidemic men. The 42-day study was divided into
three periods: a 6-day pre-experimental and two 18-day experimental. Approximately 75% of the dietary fat (28% of total energy)
was provided by a mixture of fats during the pre-experimental period and either canola oil (CO) or sunflower oil (SO) during
the experimental periods. The CO and SO diets were fed in a cross-over design. The ratios of linoleic to linolenic acid were
2.6∶1 and 73.9∶1 in the CO and SO diets, respectively. Dietary fat source had an effect on plasma phospholipid fatty acids:
18∶1n−9, 18∶3n−3 and 20∶5n−3 were higher (p<0.05), and 18∶2n−6 was lower in the phosphatidylcholine fraction; 18∶1n−9 was
higher and 20∶4n−6 lower in the phosphatidyl-ethanolamine fraction; and 18∶1n−9 and 20∶5n−3 were higher and 20∶4n−6 and 22∶6n−3
were lower in the alkenylacyl-ethanolamine phospholipid fraction on the CO diet as compared to the SO diet. Consumption of
the canola oil diet resulted in higher n−3 fatty acid levels and lower n−6 fatty acid levels in plasma phospholipids than
consumption of the sunflower oil diet. 相似文献
98.
Lignin valorization by forming toughened thermally stimulated shape memory copolymeric elastomers: Evaluation of different fractionated industrial lignins 下载免费PDF全文
Lignin‐based thermal responsive dual shape memory copolymeric elastomers were prepared with a highly branched prepolymer (HBP, A2B3 type) via a simple one‐pot bulk polycondensation reaction. The effect of fractionated lignin type (with good miscibility in the HBP) on copolymer properties was investigated. The thermal and mechanical properties of the copolymers were characterized by DMA, DSC, and TGA. Tensile properties were dominated by HBP <45% lignin content while lignin dominated >45% content. The copolymers glass transition temperature (Tg) increased with lignin content and lignin type did not play a significant role. Thermally stimulated dual shape memory effects (SME) of the copolymers were quantified by cyclic thermomechanical tests. All copolymers had shape fixity rate >95% and >90% shape recovery for all compositions. The copolymer shape memory transition temperature (Ttrans) increased with lignin content and Ttrans was 20°C higher than Tg. Lignin, a renewable resource, can be used as a netpoint segment in polymer systems with SME behavior. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41389. 相似文献
99.
Courtney L. Herring Paola Massoli Donna Sueper Matthew H. Erickson Jacob D. McDonald 《Aerosol science and technology》2013,47(11):1131-1148
This article presents a new methodology to potentially quantify polycyclic aromatic hydrocarbon (PAH) isomers using high-resolution time of flight aerosol mass spectrometer (HR-AMS). The fragmentation of PAHs within the HR-AMS is such that significant signal remains at the molecular ion. After quantifying the molecular ion signal and taking into account potential interferences, the amount of the parent PAH in the aerosol may be inferred once its fragmentation pattern is also known. The potential of this approach was evaluated using mixed gasoline and diesel engine exhaust sampled under varying conditions. This dataset led to the identification and quantification within the aerosol mass spectra of the molecular ions associated with 53 PAH isomers, including both unsubstituted and functionalized species. An evaluation of anticipated interferences shows that interferences from larger molecular weight PAHs (i.e., PAH/PAH interferences) could be constrained based on the fragmentation behavior of PAHs from existing HR-AMS laboratory spectra. Other signal interferences for this data set are typically less than 5% of the total signal or, for 13C isotopic interferents, are well constrained by measurements of the dominant isotope. The experimental data reveal that the fractional PAH molecular ion signal remained stable despite dramatic temporal variability of the total particulate organic signal. The fractional contributions of the molecular ions for grouped PAH species and even individual compounds were remarkably consistent across experiments. The distribution of PAHs showed no apparent dependence on engine load or exhaust type. Full application of this approach will require a greater number of standard HR-AMS spectra for PAHs, so that the relationship between compounds and their molecular ions may be understood more precisely.Copyright 2015 American Association for Aerosol Research 相似文献
100.
Magnetic resonance studies of cement based materials in inhomogeneous magnetic fields 总被引:1,自引:0,他引:1
Joanna Boguszynska Peter J. McDonald Jonathan Mitchell Jadwiga Tritt-Goc 《Cement and Concrete Research》2005,35(10):2033-2040
Single-sided magnets give hope that Nuclear Magnetic Resonance (NMR) might in future be used for in situ characterisation of hydration and water transport in the surface layers of concrete slabs. Towards that end, a portable NMR-MOUSE (MObile Universal Surface Explorer) has been used to follow the hydration of gypsum based plaster, a Portland cement paste and concrete mortar. The results compare favourably to those obtained using a standard laboratory bench-top spectrometer. Further, stray field imaging (STRAFI) based methods have been used with embedded NMR detector coils to study water transport across a mortar/topping interface. The measured signal amplitudes are found to correlate with varying sample conditions. 相似文献