Results 1 - 10 of 570
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[en] The methods of synthesis and reactions of organosilicon and organogermanium peroxides are surveyed. The emphasis is placed on the studies reported in the last two decades, because in this period, the use of singlet oxygen and the Isayama–Mukaiyama reaction for the synthesis of organosilicon peroxides started. The use of these compounds in the development of antiparasitic agents is considered. The bibliography includes 220 references.
[en] The history and state of the art of research on silylium ions are summarised. Achievements of the last two decades in the preparation of silylium ions as individual species in solutions and crystals and as intermediates in reactions of organosilicon compounds are considered. Attention is focused on ion-molecular reactions of silylium ions with nucleophilic reagents in the gas and condensed phases.
[en] The published data on the synthesis, properties and transformations of alkoxy(alkyl)silylalkyl derivatives of nitrogen-containing heterocycles of the general formula Het(CH2)nSiX3 are surveyed and systematised. Data on the biological activities and applications of these compounds are presented. The bibliography includes 255 references.
[en] Cationic waterborne polyurethane (WPU) is limited in wider applications due to its poor water resistance and worse flexibility. However, polysiloxane is widely used because of the advantages in these two aspects. To improve the water resistance and the flexibility of cationic WPU, combining with the characteristics of organosilicon compound, the hydroxyalkyl-containing bifunctional group polysiloxane (PPC) and self-made trifunctional group modifier PPS were used to modify the cationic WPU. The particle size and size distribution of the modified cationic WPU emulsion, the water resistance and the surface moisture resistance of the corresponding membrane were investigated. The results indicated that the cationic WPU modified by PPC will show the moderate hydrophilicity, which had positive effect on the water resistance. Although PPS had a negative effect on the dispersion and the emulsification of the polymer, a small amount of introduction can greatly improve the water resistance and the water repellency of its membrane. (paper)
[en] For the first time, 1,4-diisocyanatobutane (DICB) was used as the covalent molecular linker in this study to prepare the uniformly oriented zeolite L monolayer with relatively high coverage degree and close packing degree. This could be ascribed to substantial amounts of DICB self-assemble and standing on the substrate surface instead of folding up into a U-shape. This point has been further verified by the quality of oriented zoelite L monolayers obtained from the procedure involving DICB, 1, 4-bis (triethoxysilyl) benzene (BTSEB) and 1,2-bis(trimethoxysilyl)ethane (BTMSE) as covalent molecular linkers. - Graphical abstract: 1, 4-diisocyanatobutane (DICB) was used as the covalent molecular linker in this study to prepare the uniformly oriented zeolite L monolayer with a relatively high coverage degree and close packing degree. This could be ascribed to substantial amounts of DICB self-assemble and standing on the substrate surface instead of folding up into a U-shape. This point has been further verified by the quality of oriented zoelite L monolayers obtained from the procedure involving DICB, 1, 4-bis (triethoxysilyl) benzene (BTSEB) and 1,2-bis(trimethoxysilyl)ethane (BTMSE) as covalent molecular linkers
[en] Dependence of decamethylcyclopentasiloxane (DMCPS) organosilicon dissociation on ionized energy in the energy range of 25 eV to 70 eV is investigated by using a quadrupole mass spectrometry At the ionized energy below 55 eV, the dissociation of DMCPS is dominant. As the ionized energy is above 55 eV, the DMCPS dissociation achieves the maximum cross section, while the fragments from the DMCPS dissociation can further dissociate, which leads to a different ingredient of fragments. At the lower ionized energy of 25 eV, the main fragments are SiOC2H5+, SiCH+, Si+, O2+ and CH3+ ions, which shows an important effect on the SiCOH low-k film deposition.
[en] Published results concerning the synthesis and study of the transport characteristics of polynorbornenes are considered and analyzed. Conclusions are drawn regarding the effect of the backbone rigidity and the nature of side groups on the gas permeability level. The prospects of using addition organosilicon polynorbornenes as gas separating membrane materials are discussed.
[en] To compare the mean changes in central corneal thickness (CCT) and corneal endothelial-cell density (CED) after removal of silicon oil (ROSO) using anterior (limbal) versus posterior (pars plana) approach in aphakic patients following successful retinal re attachment surgery. Study Design: Randomized controlled trial. Place and Duration of Study: Armed Forces Institute of Ophthalmology (AFIO) Rawalpindi, from Dec 2014 to Aug 2015. Material and Methods: Sixty eyes of 60 aphakic patients who underwent removal of silicon oil from December 2014 to August 2015 in AFIO after successful retinal re-attachment surgery were analysed. Thirty eyes underwent removal of silicon oil through anterior (limbal) approach (group1) and 30 eyes through posterior (pars plana) approach (group-2). Pre-operative central corneal thickness and corneal endothelial-cell density was measured and compared with central corneal thickness and corneal endothelial-cell density measurements 3 months after removal of silicon oil. Results: Mean age of study population was 49.93 +- 5.18 years. Both groups were age and sex matched (p=0.694 and p=0.80 respectively). In group 1, mean change in CCT was 1.80 +- 6.58 micro meters (micro m) and mean change in CED was 196.30 +- 33.78 cells per millimetres square (mm/sup 2/), while in group 2, mean change in CCT was 1.63 +- 8.96 micro m and mean change in CED was 60.20 +- 39.75 cells/mm/sup 2/ after 3 months of ROSO. Mean change in CCT between two groups was not statistically significant (p=0.935), however, mean change in CED between two groups was statistically significant (p<0.001). Conclusion: Removal of silicon oil through anterior (limbal) approach causes significant reduction in CED, as compared to posterior (pars plana) approach in aphakic patients following successful retinal reattachment surgery. (author)