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101.
102.
Directional Newton methods for functions of variables are shown to converge, under standard assumptions, to a solution of . The rate of convergence is quadratic, for near-gradient directions, and directions along components of the gradient of with maximal modulus. These methods are applied to solving systems of equations without inversion of the Jacobian matrix.
103.
A novel system consisting of Rh-DuPHOS and ionic liquid for asymmetric hydrogenations 总被引:1,自引:0,他引:1
Guernik S Wolfson A Herskowitz M Greenspoon N Geresh S 《Chemical communications (Cambridge, England)》2001,(22):2314-2315
The ionic liquid [bmim][PF6] was found to provide extra stability to the air-sensitive chiral catalyst Rh-MeDuPHOS in asymmetric hydrogenation of enamides. 相似文献
104.
The envelope theorem is a statement about derivatives along an optimal trajectory. In dynamic programming the envelope theorem can be used to characterize and compute the optimal value function from its derivatives. We illustrate this here for the linear-quadratic control problem, the resource allocation problem, and the inverse problem of dynamic programming. 相似文献
105.
A sustainable one-pot synthesis of cinnamyl acetate from cinnamaldehyde is demonstrated for the first time using immobilized Baker’s yeast and free or immobilized acid as catalysts and triacetin as solvent. Employing the immobilized yeast and Amberlyst-36 allowed full conversion and 91% selectivity for cinnamyl acetate after 96 h at room temperature, and both the catalysts and triacetin were successfully recycled. 相似文献
106.
107.
A new sensitive surface-enhanced Raman scattering (SERS) assay for detection of cholinesterase inhibitors such as organophosphorous pesticides using silver colloidal nanoparticles was developed and optimized. Acetylcholinesterase (AChE) mediated the hydrolysis of acetylthiocholine to produce thiocholine, which interacted with the silver nanoparticles to give a specific SERS spectrum. Variation in enzyme activity due to inhibition was measured from changes in intensity of a characteristic peak (772 cm−1) of the SERS spectrum that was directly correlated with the concentration of produced thiocholine. The method was demonstrated for the detection of paraoxon as reference AChE inhibitor. Limit of detection of paraoxon for 5 min incubation at 25 °C was 1.8 × 10−8 M. This assay can be utilized for the detection of trace amounts of any AChE inhibitor. 相似文献
108.
109.
The presence of ionic interactions can be used to control the degree of miscibility of otherwise immiscible polymer systems. This control, in turn, allows one to prepare blends with a very wide range of “tailor-made” properties. Several examples are cited. In some of these, the interactions are based on proton transfer from a donor site on one polymer to an aceptor site on another leading to ion-ion interactions. In others, the transfer of a metal cation from an ionomer to a polar polymer, as a result of ion-dipole interactions, is involved. Systems studied to date include, among others, mixtures of polystyrene with poly(ethyl acrylate), polyisoprene, segmented poly urethanes, poly(ethyleneimine), and poly(ethylene oxide). The polyurethane blends with polystyrene are discussed in some detail, focussing especially on the mechanism of miscibility enhancement as determined by NMR. This technique has also been utilised to study the dynamics of the coil overlap process in solution as well as the proximity of the polymer coils to each other. Two particularly noteworthy applications involve mixtures of poly (tetrafluoroethylene) (PTFE) or of phenylated poly(phenylene oxide) with poly (ethyl acrylate), which are also discussed in some detail. Blends of this type may be of special interest in membrane applications. 相似文献
110.
It has been found that asymmetric, amphiphilic diblock copolymers can form a wide range of vesicle architectures in solution. These include small uniform vesicles, large polydisperse vesicles, entrapped vesicles, hollow concentric vesicles, onions, and vesicles with hollow tubes in the walls. The experimental conditions required for preparation and the proposed mechanisms for the formation of each type of structure are discussed. 相似文献