Gelation in dilute aqueous L-cysteine solutions containing various electrolytes is studied by rotational viscometry in different
dynamic regimes. It is revealed that gels are formed at rather low concentrations of cysteine of no higher than 0.1 vol %.
In the linear range of mechanical actions, gels of all examined compositions behave as elastic solid-like media; their elastic
moduli, which lie in a range of 10–100 Pa, are independent of frequency and their mechanical losses are low. However, these
gels exhibit dualistic properties and can flow at low shear stresses with a Newtonian viscosity on the order of 103–105 Pa s. On reaching a critical stress (yield point), gels are destroyed, their viscosity decreases by six to seven decimal
orders of magnitude, and they are transformed into low-viscosity liquids. At rest, the initial structure and properties are
recovered. Mechanisms of percolation network formation are proposed. 相似文献
A Fitting class $ \mathfrak{F} A Fitting class is said to be π-maximal if is an inclusion maximal subclass of the Fitting class of all finite soluble π-groups. We prove that is a π-maximal Fitting class exactly when there is a prime p ∊ π such that the index of the -radical in G is equal to 1 or p for every π-subgroup of G. Hence, there exist maximal subclasses in a local Fitting class. This gives a negative answer to Skiba’s conjecture that
there are no maximal Fitting subclasses in a local Fitting class (see [1, Question 13.50]).
Original Russian Text Copyright ? 2008 Savelyeva N. V. and Vorob’ev N. T.
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Vitebsk. Translated from Sibirskiĭ Matematicheskiĭ Zhurnal, Vol. 49, No. 6, pp. 1411–1419, November–December, 2008. 相似文献
Russian Chemical Bulletin - Using the CuI-catalyzed 1,3-dipolar cycloaddition of terminal alkynes to azides, neuraminic acid di-, tri-, and tetrapseudosaccharides were synthesized, in which... 相似文献
Synthesis and structure of a novel thermochromic complex (CH8N4)2[CuCl6] are reported. X-ray analysis of the compound was carried out for a single crystal 0.4×0.2×0.05 mm in size (a bright-yellow plate). The monoclinic unit cell parameters are a=7.167(1), b=15.561(3), c=7.328(1) Å, β=118.73(3)°, V=716.7(2) Å3, space group P21, Z=2 (CH8N4)2[CuCl6] dcalc=1.99 g/cm3, μ(MoKα)=2.65 mm?1, R=0.0264, and Rw=0.0290 for 1411 Ihkl>2σI. 相似文献
Call a Fitting class $\mathfrak{F}$π-maximal if $\mathfrak{F}$ is (inclusion-)maximal in the class $\mathfrak{C}_\pi$ of all finite π-groups, where π stands for a nonempty set of primes. We establish a π-maximality criterion for a Fitting class $\mathfrak{F}$ of finite π-groups: we prove that a nontrivial Fitting class $\mathfrak{F}$ is π-maximal if and only if there is a prime p ∈ π such that, for every π-group G, the index of the $\mathfrak{F}$-radical $G_\mathfrak{F}$ in G is equal to 1 or p. This implies Laue’s familiar result on a necessary and sufficient condition of the maximality of an arbitrary Fitting class of finite groups in the class $\mathfrak{C}$ of all finite groups. The π-maximality criterion obtained also gives a confirmation of the negative solution of Skiba’s Problem asking whether a local Fitting class has no inclusion-maximal Fitting subclasses (see Problem 13.50, The Kourovka Notebook: Unsolved Problems in Group Theory, 14th ed., Sobolev Institute of Mathematics, Novosibirsk, 1999). 相似文献
A means of nonlinear interferential comb spectroscopy with increased sensitivity is propsed. Radiation from the comb-generator of a femtosecond laser is focused at the center of a cell with vapors of rubidium atoms, mounted in an arm of a Michelson interferometer. This technique is an improvement of Rozhdestvenski hooks method, with digital registration by the detectors on a CCD array being substituted for the photographic registration of interferograms, resulting in increased interferometric sensitivity (holographic interferometry). A primary spectrogram is processed in digital form on a dual-beam interferometer equipped with a phase modulator to improve sensitivity with the possibility of an a posteriori increase in interferometric sensitivity. Dispersive signals appear in the interferogram spectrogram on two-photon absorption lines when the pumping radiation is focused at the center of a cell with Rb vapors. Nonlinear processes of coherent radiation due to nonlinear interference effects are studied. Numerical simulations are performed that confirm the proposed theoretical model. 相似文献
A series of inclusion compounds prepared by saturation of the solid adamantyl[4]calixarene (host 1) with vaporous organic guests at 298 K was studied by thermal gravimetry and static headspace GC analyses. The sorption isotherms of guests by host 1, the stoichiometry of the guest—host inclusion compounds, and the Gibbs energies of their formation were determined. The data obtained give evidence of the molecular recognition of the guest shape by host 1. Hence, compound 1 can be used in sensors for recognizing volatile organic compounds with no strong hydrogen or donor-acceptor bonds involved. 相似文献
A series of random copolymers and block copolymers containing water‐soluble 4AM and fluorescent VAK are synthesized by NMP. The homopolymerizations of 4AM and VAK and 4AM/VAK random copolymerization are performed in 50 wt% DMF using 10 mol% SG1, resulting in a linear increase in versus conversion, and final polymers with narrow molecular weight distributions ( < 1.4). Reactivity ratios rVAK = 0.64 ± 0.52 and r4AM = 0.86 ± 0.66 are obtained for the 4AM/VAK random copolymerization. In addition, a poly(4AM) macroinitiator is used to initiate a surfactant‐free suspension polymerization of VAK. After 2.5 h, the resulting amphiphilic block copolymer has = 12.6 kg · mol?1, = 1.48, molar composition FVAK = 0.38 with latex particle sizes between 270 and 475 nm.