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161.
A pure cubic oscillator with a constant and a harmonic force acting on it, which represents a nonlinear asymmetric system, is considered. Building on previous studies on the matter, analytical and numerical approaches are used to examine and illustrate its dynamics related to the phenomenon of period-doubling bifurcations and their development into chaos for different values of the constant force. The region of control parameters in which this scenario is possible is determined and discussed with a view to revisiting literature results and to giving novel and deeper insights into the phenomenon related to the influence of the magnitude of the constant force and certain resonances. 相似文献
162.
Ivana Chamradová Lucy Vojtová Lenka Michlovská Petr Polá?ek Josef Jan?á? 《Chemical Papers》2012,66(10):977-980
Functionalised triblock copolymers based on poly((lactic acid)-co-(glycolic acid)) and poly(ethylene glycol) (PLGA-PEG-PLGA) further modified with 3-methylenetetrahydrofuran-2,5-dione (itaconic anhydride; ITA) exhibited sol-gel transition induced by increasing temperature. Rheological properties of a series of ITA/PLGA-PEG-PLGA/ITA copolymer concentrations (6?C24 mass %) in deionised Milli-Q water were studied by both the test tube inverting method (TTIM) and rheometer. The gel stiffness increased with the polymer concentration shifting the gel point of the copolymer to the lower temperature. The present study demonstrates that each method describes a sol-gel transition, but the combined method gives comprehensive information about changes in colour, viscosity, elastic and loss moduli. Characterisation of such a gel is necessary for its further use, in order to determine whether the material is appropriate as an injectable biomedical hydrogel. 相似文献
163.
1-(N,N-Dimethylaminomethyl)-1′-(diphenylphosphanyl)ferrocene (1) was synthesized in good yield by lithiation of 1-bromo-1′-(diphenylphosphanyl)ferrocene and subsequent reaction with Eschenmoser''s salt (dimethylmethylideneammonium iodide). Making use of an easily accessible, nontoxic starting material, this procedure represents a convenient alternative to the original synthetic protocol based on stepwise lithiation/functionalization of 1,1′-bis(tributylstannyl)ferrocene and reductive amination [M. E. Wright, Organometallics
1990, 9, 853–856]. Compound 1 has typical hybrid-donor properties. When reacted with [AuCl(tht)] (tht=tetrahydrothiophene), it afforded the expected AuI phosphane complex [AuCl(1-κP)] (2). An attempted removal of the chloride ligand from 2 with AgClO4 produced an ill-defined material formulated as Au(1)ClO4. The uncoordinated amine substituent reacted with traces of hydrogen chloride formed by slow decomposition typically occurring in solution. In this manner, complexes [AuCl(Ph2PfcCH2NHMe2)]Cl (3, fc=ferrocene-1,1′-diyl) and [AuCl(Ph2PfcCH2NHMe2)]ClO4 (4) were isolated from crystallizations experiments with 2 and Au(1)ClO4, respectively. On a larger scale, complex 3 was prepared easily from 2 and hydrogen chloride. The course of reactions between [PdCl2(cod)] (cod=cycloocta-1,5-diene) and 1 were found to depend on the ligand-to-metal ratio. Whereas the reaction with two equivalents of 1 afforded bis(phosphane) complex trans-[PdCl2(1-κP)2] (5), that of a Pd:P ratio 1:1 produced ligand-bridged dimer [(μ-1)PdCl2]2 (6). With hydrogen chloride, complex 6 reacted to afford zwitterionic complex [PdCl3(1H-κP)] (7), which was also formed when ligand 1 and [PdCl2(cod)] were allowed to react slowly by liquid-phase diffusion of their chloroform solutions. The compounds were characterized by spectroscopic methods (multinuclear NMR and ESI–MS), and the molecular structures of complex 2–4, 6⋅2CHCl3 and 7⋅1.5CHCl3 were determined by single-crystal X-ray diffraction analysis. 相似文献
164.
Jerković I Gašo-Sokač D Pavlović H Marijanović Z Gugić M Petrović I Kovač S 《Molecules (Basel, Switzerland)》2012,17(2):2058-2072
GC and MS were used for the analysis of Croatian Centaurium erythraea Rafn essential oil (obtained by hydrodistillation) and headspace (applying headspace solid-phase microextraction). The headspace contained numerous monoterpene hydrocarbons (the major ones were terpinene-4-ol, methone, p-cymene, γ-terpinene and limonene). Oxygenated monoterpenes were present in the headspace and oil, while 1,8-cineole, bornyl acetate and verbenone were present only in the headspace. High headspace percentages of toluene and naphthalene were found, followed by hemimellitene. Lot of similarities were observed with Serbian C. erythraea oil [neophytadiene (1.4%), thymol (2.6%), carvacrol (6.1%) and hexadecanoic acid (5.7%)], but different features were also noted such as the presence of menthol, menthone and phytone. The oil fractionation enabled identification of other minor compounds not found in total oil such as norisoprenoides, alk-1-enes or chromolaenin. The essential oil showed antimicrobial potential on Escherichia coli, Salmonella enteritidis, Staphylococcus aureus and Bacillus cereus. On the other hand, no antibacterial activity of the oil was observed on Pseudomonas fluorescens and Lysteria monocytogenes. 相似文献
165.
Aleš Korotvička Dr. Ivana Císařová Prof. Jana Roithová Prof. Martin Kotora 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(14):4200-4207
Substituted phenanthrenes and picenes were easily prepared by reaction of biphenylene or angular [3]phenylene with various alkynes in the presence of a catalytic amount of [IrCl(cod)]2/dppe (cod=1,5‐cyclooctadiene, dppe=1,2‐bis(diphenylphosphino)ethane). The reaction is based on C? C bond activation of the cyclobutane ring. The reaction tolerates the presence of bulky groups on the alkyne, such as the ferrocene moiety. In addition, a catalytic system based on [RhCl(cod)]2/dppe enabled the, hitherto unreported, reaction of biphenylene with nitriles to provide phenanthridines. 相似文献
166.
Ivana Bochicchio Ettore Laserra Agata Longobardi Enrico Mazziotti 《Ricerche di matematica》2012,61(2):219-230
This work is focused on the geometrical and physical characteristics of the class of reference frames associated to harmonic coordinates. Precisely, we express in relative form the harmonicity conditions and consider the so called ??spatially harmonicity?? of a reference frame in spherical symmetry. The initial data problem is then analyzed in polar coordinates and the obtained results are applied to special cases of exact solutions. 相似文献
167.
A simple synthesis of a hexadehydrotribenzo[a,e,i][12]annulene by insertion of acetylene into an open-chain diiodo precursor under Sonogashira coupling conditions has been developed and used to prepare a rigid three-armed star connector for testing as a building block for a two-dimensional hexagonal hydrogen-bonding array. 相似文献
168.
169.
Dr. Tana Koudelakova Dr. Radka Chaloupkova Dr. Jan Brezovsky Dr. Zbynek Prokop Dr. Eva Sebestova Dr. Martin Hesseler Dr. Morteza Khabiri Maryia Plevaka Daryna Kulik Dr. Ivana Kuta Smatanova Dr. Pavlina Rezacova Dr. Rudiger Ettrich Prof. Uwe T. Bornscheuer Prof. Jiri Damborsky 《Angewandte Chemie (International ed. in English)》2013,52(7):1959-1963
170.
Dr. Alexander Hoffmann Cooper Citek Dr. Stephan Binder Arne Goos Prof. Dr. Michael Rübhausen Oliver Troeppner Prof. Dr. Ivana Ivanović‐Burmazović Prof. Dr. Erik C. Wasinger Prof. Dr. T. Daniel P. Stack Prof. Dr. Sonja Herres‐Pawlis 《Angewandte Chemie (International ed. in English)》2013,52(20):5398-5401