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891.
A convenient and regioselective synthesis of 6-O-sugar esters, which are useful additives as emulsifiers in food technology and cosmetics, without the use of protecting groups or catalysts is described 相似文献
892.
Marcos A. P. Martins Paulo Muraro Paulo Beck Pablo Machado Clarissa P. Frizzo Nilo Zanatta 《合成通讯》2013,43(20):3465-3476
Twelve novel 3-alkyl[aryl]-1-carboxamides-5-trichloromethyl-5-hydroxy-4,5-dihydro-lH-pyrazole have been synthesized in good yields (72–90%) using environmentally benign microwave-induced techniques. The compounds were synthesized from the cyclocondensation of 4-alkoxy-1,1,1-trichloro-3-alkyl[aryl]-2-ones [Cl3CC(O)C(R2) = C(R1)OR, where R = Me, Et; R1 = H, Me, Et, Pr, i-Pr, i-Bu, t-Bu, Ph, Ph-4-NO2, Ph-4-F, Ph-4-Cl, Ph-4-Br; and R2 = H, Me] with semicarbazide hydrochloride in the presence of pyridine and using methanol/water (3:1 v/v) as the solvent. The advantages of using microwave irradiation, rather than a conventional method, were demonstrated. 相似文献
893.
Recently, biomaterials research has focused on developing functional implant surfaces with well-defined topographic nanostructures in order to influence protein adsorption and cellular behavior. To enhance our understanding of how proteins interact with such surfaces, we analyze the adsorption of lysozyme on an oppositely charged nanostructure using a computer simulation. We present an algorithm that combines simulated Brownian dynamics with numerical field calculation methods to predict the preferred adsorption sites for arbitrarily shaped substrates. Either proteins can be immobilized at their initial adsorption sites or surface diffusion can be considered. Interactions are analyzed on the basis of Derjaguin-Landau-Verway-Overbeek (DLVO) theory, including electrostatic and London dispersion forces, and numerical solutions are derived using the Poisson-Boltzmann and Hamaker equations. Our calculations show that for a grooved nanostructure (i.e., groove and plateau width 8 nm, height 4 nm), proteins first contact the substrate primarily near convex edges because of better geometric accessibility and increased electric field strengths. Subsequently, molecules migrate by surface diffusion into grooves and concave corners, where short-range dispersion interactions are maximized. In equilibrium, this mechanism leads to an increased surface protein concentration in the grooves, demonstrating that the total amount of protein per surface area can be increased if substrates have concave nanostructures. 相似文献
894.
Wei S Messerer R Tsogoeva SB 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(51):14380-14384
Two birds one stone: A new atom-economical one-pot approach to enantioselective chiral drug synthesis, involving in situ multistep organocatalyst formation and the application of the reaction for multistep sequential synthesis of β-adrenergic blockers is disclosed (see scheme). 相似文献
895.
896.
Joanna Prażmowska Adam Szyszka Regina Paszkiewicz Marek Tłaczała 《Central European Journal of Physics》2011,9(2):398-403
In this paper, a study of the influence of hydrogen (concentrations 6 ppm − 1%) on the work function of thin metallic films
at moderately elevated temperatures is presented. The work function was measured indirectly by the observation of the surface
potential of dedicated test structures using scanning surface potential microscope. Metallic layers with thicknesses of 10,
20, 30, and 50 nm were deposited on semiconductor substrates as well as on a thick gold layer. The investigations were focused
on palladium thin films although a comparison to results obtained for platinum layers was also discussed. 相似文献
897.
Regina S. Burachik Alfredo N. Iusem Jefferson G. Melo 《Journal of Global Optimization》2010,46(3):347-361
We apply a modified subgradient algorithm (MSG) for solving the dual of a nonlinear and nonconvex optimization problem. The
dual scheme we consider uses the sharp augmented Lagrangian. A desirable feature of this method is primal convergence, which means that every accumulation point of a primal sequence (which is automatically generated during the process), is
a primal solution. This feature is not true in general for available variants of MSG. We propose here two new variants of
MSG which enjoy both primal and dual convergence, as long as the dual optimal set is nonempty. These variants have a very
simple choice for the stepsizes. Moreover, we also establish primal convergence when the dual optimal set is empty. Finally,
our second variant of MSG converges in a finite number of steps. 相似文献
898.
899.
900.
Heinz Böhland Helmut Härtung Ute Baumeister Gerhard König Regina Matthäus 《Mikrochimica acta》1997,125(1-4):149-152
Na4[Mn(NCS)6] · 13H2O was prepared and characterized by chemical analysis, magnetic susceptibility, thermal dehydration reactions, and single crystal X-ray structure analysis. The crystals are triclinic with a=9.310(1)Å, b=9.367(1)Å, c=9.730(2)Å, = 89.89(1)°,=75.33(1)°, =70.72(1)°, space group P¯I.Z=1. The structure is built up from Na(H2O)5 S, Na(H2O)6, and Mn(NCS)6, octahedra. All water molecules are coordinated to Na+ -ions in terminal as well as bridging fashion. They form O-H···O as well as O-H···S hydrogen bonds.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday 相似文献