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81.
Surface films on metals and alloys often protect them from reaction with the environment, and hence a knowledge of their protective
properties and composition could be invaluable for predicting their corrosion behaviour. XPS (x-ray photoelectron spectroscopy)
could provide a quantitative analysis of the chemical composition, the nature of valence states and elemental distribution
within the surface films.
The present paper reviews the potential of this technique in corrosion studies. A brief review of the work done on the passivation
of iron and iron-chromium alloys and on the inhibition studies on copper base alloys has been given. A few examples of investigations
carried out at authors’ laboratory are also included. An attempt has been made to establish a correlation between the compositions
of the films formed and corrosion behaviour of carbon steel in 10.5 pH lithium hydroxide solution and of Cu-Ni alloys and
sacrificial Al-Zn-Sn alloys in synthetic sea-water. 相似文献
82.
X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements have been done
at the K-edge of Cu in Cu-Ti glasses and on the K-edges of Ni and Zr in Ni-Zr glasses using a synchrotron radiation source.
The results are discussed in terms of the shape shift and intensity of the absorption edge as well as the principal absorption
maximum. The values of bondlength calculated by the one-electron multiple scattering XANES theory as well as the graphical
analysis EXAFS technique show good agreement. 相似文献
83.
A. V. Eremeev A. A. Romanova V. V. Servakh S. S. Chauhan 《Journal of Applied and Industrial Mathematics》2007,1(4):433-441
The problem is considered of optimizing the product delivery from suppliers to consumers. The size of each open supply is bounded both below and above, the size of consumption for each consumer is bounded below, the supply cost functions are linear for nonzero volumes of supply. A fully polynomial time approximation scheme is proposed for this problem in the case of one consumer, and the complexity of the problem is studied in the general case. 相似文献
84.
Ramesh B. Reddy Premansh Dudhe Priyanka Chauhan Sagnik Sengupta Venkatesh Chelvam 《Tetrahedron》2018,74(48):6946-6953
An efficient synthesis of N-Boc-tubuphenylalanine benzyl ester (N-Boc-Tup-OBn, 1a) and N-Boc-epi-tubuphenylalanine benzyl ester (N-Boc-epi-Tup-OBn, 1b) is reported herein. Regioselective aziridine 4 ring opening with carbon nucleophiles followed by hydroboration of 1,1-substituted aminoalkene 3 using 9-BBN and subsequent oxidation in an alkaline medium are used as the key steps to provide N-tosyl 1,4-aminoalcohols. The 1,4-aminoalcohols are successfully transformed into the desired products with an overall yield of 23% for 1a and 11% for 1b over 8 consecutive steps separately. 相似文献
85.
Allium schoenoprasum L. (family Amaryllidaceae), commonly known as chives has great culinary value besides being used as ethnomedicine. This review emphasises on phytochemistry and pharmacological activities of A. schoenoprasum, and discusses the future opportunities for systematic investigations. Scientific evaluation of chives validates its traditional claims and demonstrates diverse pharmacological potential including an anti-inflammatory, anticancer, antioxidant, anthelmintic and antihypertensive. Though phytochemical studies revealed the presence of sulphur and phenolic compounds, flavonoids, saponin and steroidal glycosides yet methodical research to identify bioactive compounds is required. This review confirms the medicinal importance of A. schoenoprasum and could stimulate future research on its unexplored aspects, especially identification of bioactive compounds and related mechanisms and safety, which might develop it as a drug. 相似文献
86.
An efficient procedure for catalyst solubility, recycling and easy product isolation in oxidation of thiols to disulfides with molecular oxygen catalyzed by cobalt(II) phthalocyanines dissolved in ionic liquid at room temperature is reported. 相似文献
87.
Moderate yields of benzaldehyde, benzyl alcohol and benzylamine are obtained by the biomimetic oxidation of N-nitrosodibenzylamine
with molecular oxygen catalysed by water soluble anionic manganese(III) 5,10,15,20-tetraphenylporphyrin acetate/sodium dithionite/methylene
blue in aerosol-OT (AOT) reverse micelles, under phase transfer conditions with AOT concentration higher than 10−3M. The formation of α-hydroxy-N-nitrosodibenzylamine and its decomposition products, benzaldehyde and benzyl alcohol in reverse
micellar systems are governed by the ratio of water and AOT, pH and other changes in the microenvirpnment. 相似文献
88.
This paper theoretically explores the application of electric field flow fractionation (EFFF) for the size-based separation of DNA strands in a microchannel. An axial electric field cannot separate DNA strands in solution because the electrical mobility of the strands is independent of the length. However, lateral electric fields coupled with an axial Poiseuille flow can separate the DNA strands of different sizes. By using regular perturbation analysis, we obtain the effective diffusivity and the mean velocity of the DNA molecules that are undergoing a pressure driven Poiseuille flow in a 2D channel in presence of a lateral electric field. The mean velocities and the dispersion coefficients are then utilized to determine the scaling for length of the channel and the time required for separation of DNA molecules in different parameter regimes. The results show that EFFF can separate DNA strands in the range of 10 kbp that differ in size by about 2.5 kbp in about half an hour in a 1 cm long channel. While DNA strands can be separated by EFFF, the performance of devices based on EFFF seems to be at best comparable to other techniques such as entropic trapping. 相似文献
89.
Chauhan SM Sahoo B Mohapatra PP Kalra B Gulati A 《Chemical & pharmaceutical bulletin》2001,49(9):1232-1233
The oxidation of 8-methoxypsoralen (2) with hydrogen peroxide and potassium superoxide catalyzed by 5,10,15,20-(2,4,6-trimethylphenyl)porphyrinatoiron(III) chlorides [Me12TPPFe(III)Cl] (1a) and 5,10,15,20-(2,6-dichlorophenyl)porphyrinatoiron(III) chlorides [Cl8TPPFe(III)Cl] (1b) in dichloromethane gives 6-formyl-7-hydroxy-8-methoxycoumarin (3) in moderate yields, whereas the oxidation of (2) with H2O2 catalyzed by 5,10,15,20-(2,6-dichlorophenyl)-beta-octahaloporphyrinatoiron(III) chlorides [Cl8betaX8TPPFe(III)Cl] (X=Cl, Br) (1c, 1d) gives specifically 5,8-dioxopsoralen (4) in moderate yields. 相似文献
90.