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71.
The occurrence of a negative birefringence in water-in-oil (W/O) microemulsions has been substantiated and analyzed. The analysis is based on the well-established aqueous nanodroplet model of W/O microemulsions. In the particularly investigated water/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/aliphatic oil systems, the AOT monolayer exhibits a negative induced intrinsic birefringence, which is brought about by the pronounced polarizability of the alkyl moiety of the AOT molecule approximately perpendicular to the direction of its permanent dipolement. 相似文献
72.
Bertolt Eicke 《Numerical Functional Analysis & Optimization》2013,34(5-6):413-429
Minimization problems in Hilbert space with quadratic objective function and closed convex constraint set C are considered. In case the minimum is not unique we are looking for the solution of minimal norm. If a problem is ill-posed, i.e. if the solution does not depend continuously on the data, and if the data are subject to errors then it has to be solved by means of regularization methods. The regularizing properties of some gradient projection methods—i.e. convergence for exact data, order of convergence under additional assumptions on the solution and stability for perturbed data—are the main issues of this paper. 相似文献
73.
Beck R Frey M Camadanli S Klein HF 《Dalton transactions (Cambridge, England : 2003)》2008,(37):4981-4983
C-H activation through the coordination of a benzyl sulfide anchoring group with a C-S bond cleavage at a Co(v) center constitutes a regiospecific access to four- and five-membered metallacycles under mild conditions. 相似文献
74.
<正>The structural changes around a crack tip in a high density polyethylene were investigated by means of scanning synchrotron microfocus small-angle X-ray scattering technique.The scattering data confirm the process of craze structure development near a crack tip based on the evolution of voids.In addition,it was found that the main stress in the plastic zone near a crack tip exhibited a gradient distribution with respect to its strength and direction.The whole damaged area showed a strain distribution indicating a flow behavior toward the crack tip. 相似文献
75.
Kirchhoff D Grützmacher HF Grützmacher H 《European journal of mass spectrometry (Chichester, England)》2006,12(3):171-180
The unimolecular reactions of the radical cation of dimethyl phenylarsane, C6H5As(CH3)2, 1*+ and of the methyl phenylarsenium cation, C6H5As+CH3, 2+, in the gas phase were investigated using deuterium labeling and methods of tandem mass spectrometry. Additionally, the rearrangement and fragmentation processes were analyzed by density functional theory (DFT) calculations at the level UBHLYP/6- 311+G(2d,p)//UBHLYP/5-31+G(d). The molecular ion 1*+ decomposes by loss of a .CH3 radical from the As atom without any rearrangement, in contrast to the behavior of the phenylarsane radical cation. In particular, no positional exchange of the H atoms of the CH3 group and at the phenyl ring is observed. The results of DFT calculations show that a rearrangement of 1*+ by reductive elimination of As and shift of the CH3 group is indeed obstructed by a large activation barrier. The MIKE spectrum of 2+ shows that this arsenium cation fragments by losses of H2 and AsH. The fragmentation of the trideuteromethyl derivative 2-d3+ proves that all H atoms of the neutral fragments originate specifically from the methyl ligand. Identical fragmentation behavior is observed for metastable m-tolyl arsenium cation, m-CH3C6H4As+H, 2tol+. The loss of AsH generates ions C7H7+ which requires rearrangement in 2+ and bond formation between the phenyl and methyl ligands prior to fragmentation. The DFT calculations confirm that the precursor of this fragmentation is the benzyl methylarsenium cation 2bzl+, and that 2bzl+ is also the precursor ion fo the elimination of H2. The analysis of the pathways for rearrangements of 2+ to the key intermediate 2bzl+ by DFT calculations show that the preferred route corresponds to a 1,2-H shift of a H atom from the CH3 ligand to the As atom and a shift of the phenyl group in the reverse direction. The expected rearrangement by a reductive elimination of the As atom, which is observed for the phenylarsenium cation and for halogeno phenyl arsenium cations, requires much more activation enthalpy. 相似文献
76.
Robert Beck Tingting Zheng Xiaoyan Li Hans-Friedrich Klein 《Journal of organometallic chemistry》2008,693(23):3471-3478
Fe(CH3)2(PMe3)4 reacts with 1-(diphenylphosphino)naphthalene or benzyldiphenylphosphine within 4 h at 20 °C to give the novel metallated methyl iron complexes Fe(CH3){P(C6H5)2(C10H6)}(PMe3)3 (1) and Fe(CH3){(C6H4)CH2P(C6H5)2}(PMe3)3 (3), respectively, via selective activation of the C-H bond of the pre-chelating ligands. The complexes are thermally unstable releasing metal through a reductive elimination of the aromatic backbone and leading to a C,C-coupling product that is regiospecifically methylated, namely 8-methyl(diphenylphosphino)naphthalene (2). Carbonylation (1 bar, 20 °C, 1 h) of complex 1 effects monosubstitution of a trimethylphosphine ligand trans to the metallated 8-C atom to afford Fe(CH3){P(C6H5)2(C10H6)}(CO)(PMe3)2 (4). The remaining methyl group in the parent complex 1 reacts with trimethylsilylethyne and tert-butylethyne affording the new complexes 5 and 6 bearing an alkynyl substituent trans to the diphenylphosphino anchoring group. The complexes 1 and 3-6 are diamagnetic and possess octahedral coordination geometry. All novel complexes were fully characterized by spectroscopic methods and by X-ray diffraction. 相似文献
77.
78.
A constant stress rheometer in the creep mode was used to perform free oscillatory shear measurements on soft solids. The results obtained are in good to excellent agreement compared to forced oscillatory shear measurement data. Depending on the rheologic properties of the sample and the moment of inertia of the rotating device of the measurement system, free oscillations are suited to confirm or supplemented forced oscillatory measurement results.Dedicated to Professor W. Nitsch on the occasion of his 60th birthday. 相似文献
79.
Peter B. Kraikivskii Hans-Friedrich Klein Nils E. Schlörer 《Journal of organometallic chemistry》2011,696(21):3376-3383
The interactions of the nickel imine-amide allyl complex 1 with carbon monoxide and unsaturated hydrocarbons have been studied. It is shown that this complex reacts readily with carbon monoxide to form the nickel(0) diimine carbonyl complex [(2-(1-propenyl)-[1,10]phenanthroline)Ni(CO)2] 2. During the process the ligand undergoes a deep transformation within the nickel coordination sphere. Specifically, the nickel-nitrogen σ-bond turns to an N-donor bond with aromatization of a ring in the nitrogen-containing ligand. This novel heteroaromatic ligand 2-(1-propenyl)-[1,10]phenanthroline has been isolated; the nickel(0) diimine carbonyl complex 2 has been studied with X-ray diffraction method. The comparative spectral studies of complexes 1, 2, and 2-(1-propenyl)-[1,10]phenanthroline have been carried out with UV/vis, IR-FT, and 2D NMR spectroscopy. It has been shown that the planar 16-electron nickel(II) imine-amide allyl complex 1 is indifferent to olefins and acetylenes. Based on the NMR data, this fact can be explained by the inability of the π-δ rearrangement into 1. 相似文献
80.
Peter B. Kraikivskii Markus Frey Armin Gembus Ingrid Svoboda Vitaly V. Saraev Hans-Friedrich Klein 《Journal of organometallic chemistry》2009,694(12):1869-3490
(2-Diphenylphosphanyl)thiophenol (P^pSH) or (3-diphenylphosphanyl)-2-thionaphthol (P^nSH) react with Ni(PMe3)4 to form NiH(P^pS)(PMe3)2 (1) or NiH(P^nS)(PMe3)2 (2). 1,3-Bis(diphenylphosphanyl)propane (P^P) replaces the monodentate phosphane ligands to give NiH(P^pS)(P^P) (3). NiMe(OMe)(PMe3) or NiMe2(PMe3)3 react with P^pSH to form NiMe(P^pS)(PMe3) (4) and NiMe(P^pS)(PMe3)2 (5), respectively, and P^nSH affords NiMe(P^nS)(PMe3)2 (6), NiMe(P^nS)(PMe3) (7). Dissociation of PMe3 ligands induces transformation of 1 to Ni(P^pS)(PMe3)2 (8) and Ni(P^pS)2. Crystal and molecular structures are given for 1, 5-8, and dynamic solution spectra (NMR, EPR) are discussed. 相似文献