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排序方式: 共有145条查询结果,搜索用时 15 毫秒
41.
42.
This work examines the influence of the amount of silver nanoparticles added to polyacrylonitrile spinning solutions on their rheological properties as well as the structure and properties of the fibers produced. The influence of the amount of silver nanoparticles on the supramolecular structure of nanocomposite polyacrylonitrile precursor fibers, their porosity, as well as thermal and tensile strength properties was determined. The distribution of the nano‐ additive in fiber cross‐sections and on the surface was estimated. It was found that the addition of silver nanoparticles to polyacrylonitrile precursor fibers in an amount of up to 1.5% does not cause a decrease in the susceptibility of the fiber matter to deformation at the drawing stage. The produced fibers were characterized by an increased total volume of pores of 0.35 cm3/g and tenacity of more than 34 cN/tex. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
43.
Mikołajczyk M Krysiak JA Midura WH Wieczorek MW Rózycka-Sokołowska E 《The Journal of organic chemistry》2006,71(23):8818-8823
A new one-pot synthesis of heterocyclic and carbocyclic vinyl sulfoxides has been developed which involves reaction of alpha-phosphorylvinyl sulfoxides with carbonyl compounds bearing oxygen, nitrogen, and carbon nucleophilic centers. Use of optically active alpha-phosphorylvinyl p-tolyl sulfoxides in this tandem Michael addition/Horner olefination reaction leads to the corresponding optically active cyclic sulfoxides. In this way, a variety of optically active chromene, pyrrolizine, chinoline, and cyclopentene sulfoxides have been efficiently prepared. 相似文献
44.
We present theoretical analysis of bromine adsorption on the Ge(001)-p(1×2) surface. Bromine adsorbs dissociatively at the
Ge(001) surface and the adlayer of bromine develops ordered structures of adatoms bound to substrate dimers. We analyse atomic
configurations of the Ge(001) surface covered by 0.25, 0.5, 0.75 and 1 monolayer of bromine. Various stable surface structures,
found in calculations, are presented and their energies are compared. Simulated STM images are also discussed for the considered
configurations.
相似文献
45.
T. Stacewicz J. Wojtas Z. Bielecki M. Nowakowski J. Mikołajczyk R. Mędrzycki B. Rutecka 《Opto-Electronics Review》2012,20(1):53-60
We describe several applications of cavity ring-down spectroscopy (CRDS) for trace matter detection. NO2 sensor was constructed in our team using this technique and blue-violet lasers (395–440 nm). Its sensitivity is better than
single ppb. CRDS at 627 nm was used for detection of NO3. Successful monitoring of N2O in air requires high precision mid-infrared spectroscopy. These sensors might be used for atmospheric purity monitoring
as well as for explosives detection. Here, the spectroscopy on sharp vibronic molecular resonances is performed. Therefore
the single mode lasers which can be tuned to selected molecular lines are used. Similarly, the spectroscopy at 936 nm was
used for sensitive water vapour detection. The opportunity of construction of H2O sensor reaching the sensitivity about 10 ppb is also discussed. 相似文献
46.
J. Omelańczuk P. Kielbasiński J. Michalski J. Mikołajczak M. Mikołajczyk A. Skowrońska 《Tetrahedron》1975,31(22):2809-2814
The reaction of acyclic oxophosphoranesulphenyl chlorides, with phosphorus trichloride has been found to give thiophosphoryl chlorides, and phosphoryl oxychloride—the products of the exclusive deoxygenation of sulphenyl chloride. Optically active phosphonochloridothionates and phosphorochloridothionates in a high state of optical purity have been obtained with inversion of configuration from optically active sulphenyl chlorides and phosphorus trichloride. It has been shown, however, that cyclic oxophosphoranesulphenyl chlorides undergo simultaneous desulphurisation and deoxygenation when treated with phosphorus trichloride. Using cis- and trans-isomers of 2-chlorothio-4-methyl-1,3,2-dioxaphosphorinan-2-one it has been demonstrated that deoxygenation is accompanied by inversion, whereas desulphurisation occurs with retention at phosphorus. The mechanism of the title reaction is discussed. 相似文献
47.
The tittle reagent, (+)-(S)-1, was prepared from (+)-(S)s-α-diethoxy-phosphorylethyl p-tolyl sulfoxide 2 by phenylselenylation-deselenylation procedure. Its reactivity was demonstrated by diastereoselective Michael addition of ethanethiol giving rise to 3, tandem Michael addition/intramolecular Horner--Wittig reaction with 2-formyl pyrrole leading to the corresponding pyrrolizine sulfoxide 5 and cycloaddition with cyclopentadiene affording the diastereomeric adducts 6. The steric course of the Diels-Alder reaction is briefly discussed. 相似文献
48.
Lefèvre R Goffman MF Derycke V Miko C Forró L Bourgoin JP Hesto P 《Physical review letters》2005,95(18):185504
We report a method for probing electromechanical properties of multiwalled carbon nanotubes (CNTs). This method is based on atomic force microscopy measurements on a doubly clamped suspended CNT electrostatically deflected by a gate electrode. We measure the maximum deflection as a function of the applied gate voltage. Data from different CNTs scale into an universal curve within the experimental accuracy, in agreement with a continuum model prediction. This method and the general validity of the scaling law constitute a very useful tool for designing actuators and in general conducting nanowire-based nanoelectromechanical systems. 相似文献
49.
Jan Michalski Jerzy Mikołajczak Marek Pakulski Aleksandra Skowronska 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):233-234
Abstract The oxidative addition of molecules X–Y to three-coordinated phosphorus compounds is of considerable general interest. If one of the groups attached to the phosphorus atom is an alkoxy, OR, the final product is almost always > P(O)Y with the formation of an alkyl halide RX. The above process is known as Arbuzov reaction, the mechanism of which can be represented, in the light of our present knowledge, as follows: mental mechanistic problem for the Arbuzov reaction. The R(?)phosphite (4) was prepared from R(+)2-octanol of 95% opt. purity, [α]20 D + 9.4° (neat) and the chlorophosphite (3) by standard condensation in the presence of tertiary amine and purified by distilla tion in vacuo, δ31P ?127.5 ppm, [α]D 20 ?25.6° (neat). Equimolar amounts of the phosphite (4) and the corresponding halogen in CH2 C12 solution were allowed 相似文献
50.
M. Mikołajczyk Piotr Bałczewski P. Graczyk 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):225-228
Abstract Synthesis, reactivity and conformation of cyclic S,S-thioacetals of formylphosphonates are described. The chemistry of α-trimethylsilyl-α-methylthiometanephosphonate is briefly discussed. 相似文献