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971.
The synthetic utility and shortcomings of resins which activate carboxyl groups to form anhydrides, esters, or amides such as polycarbodiimide resins and poly-EEDQ resins are examined. The use of a polymer-bound yneamine function for such purposes is proposed, and synthetic approaches to this goal are described. Tentative evidence for the existence of a stable intermediate in the reaction of an insoluble yneamine with benzoic acid is also presented. 相似文献
972.
Emergent Swarming States in Active Particles System with Opposite Anisotropic Interactions 下载免费PDF全文
From the organization of animal flocks to the emergence of swarming behaviors in bacterial suspension, populations of motile organisms at all scales display coherent collective motion. Recent studies showed that the anisotropic interaction between active particles plays a key role in the phase behaviors. Here we investigate the collective behaviors of based-active Janus particles that experience an anisotropic interaction of which the orientation is opposite to the direction of active force by using Langevin dynamics simulations in two dimensional space. Interestingly, the system shows emergence of collective swarming states upon increasing the total area fraction of particles, which is not observed in systems without anisotropic interaction or activity. The threshold for emergence of swarming states decreases as particle activity or interaction strength increases. We have also performed basic kinetic analysis to reproduce the essential features of the simulation results. Our results demonstrate that anisotropic interactions at the individual level are sufficient to set homogeneous active particles into stable directed motion. 相似文献
973.
1,4‐Diazabicyclo[2.2.2]octane was used as an efficient catalyst in the Knoevenagel condensation reaction of various kinds of aromatic/aliphatic/heterocyclic/αβ‐unsaturated aldehydes and ketones with active methylene compounds. This is a convenient and rapid method for Knoevenagel condensation, which affords the corresponding substituted electrophilic alkenes in excellent yields. The reaction condition is mild and the method is operationally simple. The products, only E‐isomers were detected, did not need to be purified. The use of water as the reaction medium makes the process environmentally benign. The catalysts can be recycled six times without activity loss. 相似文献
974.
A mixture of triphosgene/triphenylphosphine in methylene chloride converts primary and secondary alcohols to chlorides at room temperature. 相似文献
975.
Tetra‐n‐butylammonium hydroxide (TBAH) has been utilized as a novel and efficient catalyst for the Knoevenagel condensation of aldehydes with acidic methylene compounds such as methyl‐ and ethylcyanoacetate, malononitrile, and cyanoacetamide to afford substituted olefins. 相似文献
976.
977.
978.
Stoyanka Christoskova Maria Stoyanova Dragomir Vasilev 《Monatshefte für Chemie / Chemical Monthly》2006,137(8):1043-1051
Summary. The effect of the synthesis conditions of individual and modified with Mn Ni- and Co-oxide systems on the content and the
mobility of their active oxygen has been studied by means of chemical and IR spectral analyses. The results obtained show
that the main part of the active oxygen in Ni-oxide system is located on the catalyst’s surface (Os
* is approximately 73% of the total active oxygen), while Co-oxide system is characterized by much lower surface active oxygen
content. Ni- and Co-oxide systems modified with Mn have comparatively higher active oxygen content as compared to the individual
ones. Data of the IR spectral analysis reveal that Mn, as a modifying component, affects the mobility of the active oxygen,
the latter contributing to the activity of oxide systems in oxidation processes. The high content of loosely bonded active
oxygen formed during the synthesis determines a high catalytic activity of the studied samples in reactions of complete oxidation
in the low temperature region. 相似文献
979.
U. H. Hegazy 《Archive of Applied Mechanics (Ingenieur Archiv)》2009,79(4):335-345
The problem of suppressing the vibrations of a hinged–hinged flexible beam that is subjected to primary and principal parametric
excitations is tackled. Different control laws are proposed, and saturation phenomenon is investigated to suppress the vibrations
of the system. The dynamics of the beam are modeled with a second-order nonlinear ordinary-differential equation. The method
of multiple scales is used to derive two-first ordinary differential equations that govern the time variation of the amplitude
and phase of the response. These equations are used to determine the steady-state responses and their stability. The results
of perturbation solution have been verified through numerical simulations, where different effects of the system parameters
on the steady-state amplitude and on saturation phenomena at resonance have been reported. 相似文献
980.
Qunjiao Zhang 《Physics letters. A》2008,372(9):1416-1421
This Letter introduces another novel type of chaos synchronization—full state hybrid lag projective synchronization (FSHLPS), which includes complete synchronization, anti-synchronization, lag synchronization, general projective synchronization and FSHPS in [M. Hu, Z. Xu, R. Zhang, Commun. Nonlinear Sci. Numer. Simul. 13 (2008) 456; M. Hu, Z. Xu, R. Zhang, A. Hu, Phys. Lett. A 361 (2007) 231]. Furthermore, systematic FSHLPS schemes are respectively proposed for the continuous and discrete systems. Finally, some numerical simulations are given to verify the effectiveness of the developed schemes. 相似文献