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921.
J. Pollanen K.R. Shirer S. Blinstein J.P. Davis H. Choi T.M. Lippman W.P. Halperin L.B. Lurio 《Journal of Non》2008,354(40-41):4668-4674
We discuss two methods by which high porosity silica aerogels can be engineered to exhibit global anisotropy. First, anisotropy can be introduced with axial strain (i.e. axial compression). In addition, intrinsic anisotropy can result during growth and drying stages and, suitably controlled, it can be correlated with preferential radial shrinkage in cylindrical samples. We have performed small angle X-ray scattering (SAXS) to characterize these two types of anisotropy. We show that global anisotropy originating from either strain or shrinkage leads to optical birefringence and that optical cross-polarization studies are a useful characterization of the uniformity of the imposed global anisotropy. 相似文献
922.
L. A. Oparina O. V. Vysotskaya A. V. Stepanov I. V. Rodionova G. F. Myachina N. K. Gusarova B. A. Trofimov 《Russian Journal of Organic Chemistry》2008,44(1):120-123
2-Hydroxymethylfuran reacted with acetylene in superbasic catalytic systems MOH-DMSO (M = Na, K) under mild temperature conditions (75–85°C, 1–2 h), yielding 80% of 2-vinyloxymethylfuran. The product, as well as acetaldehyde acetals derived therefrom, turned out to be promising as modifiers for electrolyte in lithium-sulfur rechargeable batteries. 相似文献
923.
924.
Y. S. Hong K. C. Kim V. I. Volkov V. D. Skirda C. -H. Lee 《Applied magnetic resonance》2005,29(2):351-361
The diffusion phenomenon of a nonionic surfactant, polyoxyethylene sorbitan monooleate (POE-SMO), micelle in aqueous solution
was investigated by pulsed field gradient nuclear magnetic resonance (PFG NMR) with a high gradient strength of 17.4 T/m at
the diffusion timet
d varied from 3 to 300 ms. This high gradient strength allowed us to measure the slow self-diffusion coefficient of POE-SMO
micelle, and the short diffusion time below 10 ms showed the restricted diffusion of the micelle. At the shortt
d the self-diffusion of the micelle was restricted and the restricted sizes were 1.8, 1.5, and 0.8 μm for the POE-SMO concentration
of 100, 200 and 300 mM, respectively, and 0.6 μm for the POE-SMO only. The possible reason of this restriction was assumed
to be the formation of a spatial network or a micellar clustering. Furthermore, a proton exchange between water molecule and
surfactant OH group on the micelle surface was proposed. With respect to this proposal, the residence time of the proton at
the micelle surface and the thickness of the surface were investigated from proton self-diffusion coefficients by PFG NMR. 相似文献
925.
S. Tripathi S. K. Sengupta O. P. Pandey 《Russian Journal of Coordination Chemistry》2007,33(9):704-709
Lanthanum(III) and praseodymium(III) complexes of the type [Ln(L)Cl(H2O)]2 (Ln = La(III) or Pr(III); LH2 = dithiosemicarbazone ligands derived from piperazine dithiosemicarbazide and benzaldehyde, 4-nitrobenzaldehyde, and 2-methoxybenzaldehyde)
have been synthesized in methanol in the presence of sodium hydroxide. The complexes have been characterized by elemental
analyses, molecular weight, molar conductance, electronic absorption, IR, and 1H and 13C NMR spectral studies. Nephelauxetic ratio, covalency parameter, and bonding parameter for these complexes have also been
calculated. Thermal studies of the complexes have been carried out using TG, DTG, and DSC techniques. Kinetic parameters, such as apparent activation energy and order of reaction, were determined by the Coats-Redfern
graphical method. The heats of reaction for different reaction steps were calculated from DSC curves.
The article was submitted by the authors in English. 相似文献
926.
K. V. Usenko 《Optics and Spectroscopy》2007,103(2):196-201
The contradiction between the fidelity necessary to determine the entanglement of states and the noise accompanying high-precision measurements is discussed. The unitary nonequivalence of quantum field representations in different regions of space leads to an additional noise, analogously to the Unruh effect. The cause of this noise is eliminated by rejecting the assumption of statistical independence of single-particle states of the quantum field. The smearing of one-particle states eliminates the reasons for the appearance of the Unruh noise and, simultaneously, leads to imaginary entanglement due to overlapping of these states. 相似文献
927.
928.
Based on an analysis of the processes of intramolecular signal transfer (the ordered motion of a quasiparticle, vibron) and structural isomerization, it was pointed out that, in principle, reagents of a new type can be developed with analytical effects fundamentally different from usual ones. The type of analytical response can vary depending on the molecular structure and intramolecular processes induced. General principles of the molecular design of systems of this kind are discussed. 相似文献
929.
930.
A ring is said to be a left essential extension of a reduced ring (domain) if it contains a left ideal which is a reduced ring (domain) and intersects nontrivially every nonzero twosided ideal of the ring. We prove that every ring which is a left essential extension of a reduced ring is a subdirect sum of rings which are essential extensions of domains, but the converse implication does not hold. We give some applications of this result and discuss several related questions.Received: 6 January 2003 相似文献