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31.
Xiaohong Gu Tinh Nguyen Mounira Oudina David Martin Bouchra Kidah Joan Jasmin Aziz Rezig Lipiin Sung Eric Byrd Jonathan W. Martin Derek L. Ho Y. C. Jean 《Journal of Coatings Technology and Research》2005,2(7):547-556
Atomic force microscopy (AFM) has been used to study the morphology and microstructure of an amine-cured epoxy before and
after outdoor exposure. Measurements were made from samples prepared in an essentially CO2-free, H2O-free glove box and from samples prepared in ambient conditions. For those prepared in a CO2-free glove box, AFM imaging was conducted on (1) an unexposed air/coating surface, (2) an unexposed coating bulk, (3) an
unexposed coating/substrate interface, and (4) a field exposed air/coating surface. For samples prepared in ambient conditions,
only the unexposed air/coating surface was investigated. The same regions of the exposed samples were scanned periodically
by the AFM to monitor changes in the surface morphology of the coating as UV exposure progressed. Small angle neutron scattering
and Fourier transform infrared spectroscopy (FTIR) studies were performed to verify the microstructure and to follow chemical
changes during outdoor exposure, respectively. The results have shown that amine blushing, which occurs only under ambient
conditions, had a significant effect on the surface morphology and microstructure of the epoxy. The surface morphology of
the samples prepared under CO2-free, dry conditions was generally smooth and homogeneous. However, the interface and the bulk samples clearly revealed a
two-phase structure consisting of bright nodular domains and dark interstitial regions, indicating an inhomogeneous microstructure.
Such heterogeneous structure of the bulk was in good agreement with results obtained by small angle neutron scattering of
unexposed samples and by AFM phase imaging of the degraded sample surface. The relationship between submicrometer physical
changes and molecular chemical degradation is discussed.
Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004, in Chicago,
IL. 相似文献
32.
S. M. Khan A. Aziz Khan M. A. Beg 《European Journal of Lipid Science and Technology》1969,71(6):451-454
The kinetics of oxidation of isobutyric and isovaleric acids by chromic acid in sulphuric acid medium have been studied. The end product acetic acid is supposed to be derived from the ketones which are the initial oxidation products of the corresponding branched chain fatty acids. The influence of acetic acid on the oxidation velocity has been examined and a marked effect on the rate constants with increasing acetic acid concentration has been observed. A mechanism involving the electrophilic attack of the oxidant on the tertiary carbon atom of the fatty acid to yield a carbonium ion has been postulated. 相似文献
33.
Aziz Rezig Tinh Nguyen David Martin Lipiin Sung Xiaohong Gu Joan Jasmin Jonathan W. Martin 《Journal of Coatings Technology and Research》2006,3(3):173-184
The relationship between chemical degradation and thickness loss of an unpigmented, non UV-stabilized, crosslinked amine-cured
epoxy coating exposed to three UV conditions was investigated. Spin-coated samples having a thickness of approximately 7 μm
on an Si substrate were prepared from a stochiometric mixture of a bisphenol A epoxy resin and a tetra-functional amine curing
agent. Samples were exposed outdoors and to two accelerated laboratory UV environments. Chemical degradation and thickness
loss were measured by transmission Fourier transform infrared spectroscopy (FTIRS) and laser scanning confocal microscopy
(LSCM), respectively. In addition, surface roughness and morphological changes were measured by atomic forcemicrosocopy (AFM)
and LSCM. Substantial chemical degradation, thickness loss, and morpholocal changes occurred in the exposed films, and the
rate of chemical degradation was greater than that due to the thickness loss. This additional chemical loss was attributed
to an inhomogeneous degradation process in which nanoscale localized depressions initiate at certain sites on the surface,
which then enlarge and deepen with exposure time. The results of this study provide a better understanding of the degradation
mechanism and should lead to the development of scientific-based models for predicting the service life of crosslinked amine-cured
epoxy coatings.
Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004, in Chicago,
IL 相似文献
34.
Aziz Tekin Melih Cizmeci Hulya Karabacak Muammer Kayahan 《Journal of the American Oil Chemists' Society》2002,79(5):443-445
Trans FA (TFA), solid fat contents (SFC), and slip melting points of 12 different tub and stick margarines marketed in Turkey were
examined in this study. No trans isomers were found in four margarines, which suggests they were formulated from interesterified or blended fats and oils.
The products with no TFA generally had more short-chain saturated FA, which suggests coconut oil-based oil components. TFA
content of the other 10 products varied from 7.7 to 37.8%. Compared to the products formulated in North America, Turkish margarines
contain more TFA and have higher SFC. 相似文献
35.
Epidemiological studies suggest the existence of a strong relationship between the incidence of prostatic cancer and the intake
of dietary lipids in humans. However, very little information is available on intracellular fatty acid metabolism in human
prostatic tissue. The objective of this study was to identify and subsequently characterize a fatty acid binding protein of
human prostatic tissue. A fatty acid binding protein (FABP) was purified and characterized from human prostatic tissue. The
purified FABP had an apparent molecular mass of 15.0±1.0 kDa as averaged from three different methods, sodium dodecylsulfate-polyacrylamide
gel electrophoresis (SDS-PAGE), gel filtration and amino acid analysis. The pI value of the protein was determined to be 6.8.
Scatchard analysis of fatty acid binding to the purified FABP from malignant prostatic tissue showed a Kd value of 0.53±0.02
μM for arachidonic acid (n=5). The Kd values of FABP purified from benign prostatic tissue were 0.57±0.02 μM for oleic acid
and 0.51±0.04 μM for arachidonic acid (n=5). Fatty acid analysis revealed that the level of endogenously bound arachidonic
acid was about 2.5-fold higher in FABP from malignant than from benign tissue. In addition, both malignant and benign tissues
contained the same concentration of FABP. The concentrations of FABP in malignant and benign tissues were 19.2±1.8 and 21.4±2.1
μg per mg of total cytosolic protein, respectively. Characterization based on amino acid composition, isoelectric point and
fluorescence with dansyl undecanoic acid suggests that the FABP may not be of the heart type, but is rather more closely related
to the liver type. As malignant prostatic tissue produces more PGE2 compared to benign tissue, our data suggest that FABP may help enhancing the synthesis of the prostaglandin in malignant
tissue by facilitating arachidonic acid transport.
A preliminary account of this work was presented at the Biochemical Society Meeting, London, December 16–18, 1991, and published
as an abstract (Ref. 1). 相似文献
36.
Xiaojing Zhang Yuquan Cai Xianwei Zhang Tariq Aziz Hong Fan Carla Bittencourt 《应用聚合物科学杂志》2021,138(22):50515
A eugenol-based silicone-containing monomer 4,4′-(1,1,3,3-tetramethyldisiloxane-1,3-dipropyl)bis-2-methoxyphenol(EUSi) was synthesized from eugenol and 1,1,3,3-tetramethyldisiloxane via the hydrosilylation reaction. And waterborne polyurethane (WPU) with excellent properties was obtained by using EUSi as a type of diol chain extender. The unique combination of rigidity and flexibility in the chemical structure of EUSi greatly facilitated the mechanical properties, thermal properties, and water resistance of WPU. With only a 3% dosage of EUSi, the maximum tensile strength was increased from 6.2 to 22.4 MPa, while the water absorption was decreased from 31.3% to a surprisingly 7.6%. Our work provides a new convenient strategy for the preparation of organosilicon-modified WPU with improved performance. 相似文献
37.
Poly(N-methylaniline) (PNMA) coatings have been electropolymerized on 304 stainless steel alloy by potentiodynamic, galvanostatic and potentiostatic synthesis techniques from aqueous solutions of 0.1 M N-methylaniline (NMA) and 0.3 M oxalic acid. Characterization of PNMA coatings was carried out by cyclic voltammetry, UV-Vis and FTIR spectroscopy techniques. Corrosion behavior of PNMA coated stainless steel electrodes was investigated using linear anodic potentiodynamic polarization, Tafel test, chronoamperometry and electrochemical impedance spectroscopy (EIS) techniques in 0.5 M aqueous HCl solutions. Corrosion test results showed that PNMA coatings possessed protection to uncoated stainless steel against corrosion. 相似文献
38.
Benjamin Aziz 《Journal of Grid Computing》2016,14(3):477-493
This paper presents an abstract specification of an enforcement mechanism of usage control for Grids, and verifies formally that such mechanism enforces UCON policies. Our technique is based on KAOS, a goal-oriented requirements engineering methodology with a formal LTL-based language and semantics. KAOS is used in a bottom-up form. We abstract the specification of the enforcement mechanism from current implementations of usage control for Grids. The result of this process is agent and operation models that describe the main components and operations of the enforcement mechanism. KAOS is used in top-down form by applying goal-refinement in order to refine UCON policies. The result of this process is a goal-refinement tree, which shows how a goal (policy) can be decomposed into sub-goals. Verification that a policy can be enforced is then equivalent to prove that a goal can be implemented by the enforcement mechanism represented by the agent and operation models. 相似文献
39.
Joongheon?Kim Aziz?Mohaisen Song-Nam?HongEmail author 《Multimedia Tools and Applications》2015,74(19):8613-8629
In this paper we provide a method for computing and estimating the impact of interference on real-time online 1080p@30Hz and 1080p@60Hz high-definition video streaming in 60 GHz wireless smart TV platforms. The analysis involves two different interference scenarios: 1) downlink interference from deployed 60 GHz access points to the associated mobile ad-hoc devices, and 2) uplink interference from randomly deployed 60 GHz ad-hoc mobile devices to their associated access points. With these interference scenarios, the interference impact on the quality of main 1080p@30Hz and 1080p@60Hz wireless high-definition video streaming with various simulation settings are measured and estimated in terms of signal-to-interference-plus-noise ratio. 相似文献
40.
Hatami Aziz Navt Ketvan Dargahi Akbar 《通讯和计算机》2009,6(8):23-30
With the fast developments and growth of electronic applications and a great demand for increasing the speed of processors, VLSI circuits and on-chip interconnections the "Networks-On-Chip" (NOC) is the best solution for "System-On-Chip" (SOC). The most fundamental part of networks On-Chip is the On-Chip interconnection. The model presented in this article describes the method of sending data on On-Chip interconnection by using a current-mode multi-valued logic instead of voltage-mode in order to increase speed and reduce the number of interconnection wires. 相似文献