Thermodynamic information about the vapor—liquid equilibria of systems containing water and ethanolamines is needed in the design and optimization of important industrial processes. This knowledge is also useful in the investigation of some phenomena such as the thermal conversion of ethanolamines or their complexation reactions with metals.Physico-chemical investigations involving aqueous solutions of ethanolamines are scarce, and sometimes contradictory, in the literature. It has been stated [1] that the system diethanolamine—water obeys Raoult's law. However, there have been studies [2] indicating departure from ideal behavior for this system.The purpose of this work was to determine the molar excess Gibbs free energies of the systems formed by water and the ethanolamines. 相似文献
PMR studies of a series of 2,4- and 2,6- dinitrophenyl- and 2,4-dinitronaphthyl- aryl ethers strongly indicate the existence of preferred conformations. Extensive conjugation of the ether linkage with the dinitro ring, resulting in their coplanarity, is an important stereochemical influence. In the ensuing skew conformation the dinitro ring is positioned in such a way that the 6-substituent is proximal to the other ring. In the case of the 2,4-dinitrophenyl ethers ( 1 ) this is the 6-proton, which shows the expected shielding due to the ring current in the other ring. In the 2,6-dinitrophenyl-( 2 ) and 2,4-dinitronaphthyl-( 3 ) ethers, this is a nitro group, twisted out of coplanarity to fit over the other ring, whose magnetic anisotropy is reflected in the shielding experienced by the 6′-protons. When there is a 2′-substituent present the ring which bears it twists in such a way as to bring the 6′-proton closer to the proximal nitro-group, explaining the greater shielding observed in these cases. Variable temperature studies provided further evidence in favor of these conformations since no significant changes were observed from ?55° to + 155°, even for compounds with four substituents flanking the ether linkage. Nevertheless, the compounds studied here are not frozen in these conformations, but probably inter-convert via concerted rotation with others. 相似文献
The translational and rotational motions of optically anisotropic spherical particles embedded in cross-linked polyacrylamide gels is studied by dynamic light scattering. The particles are liquid crystal droplets solidified in the nematic phase. The amount of cross linkers is varied to cross the sol-gel transition where the system becomes nonergodic for both translational and rotational diffusion modes of the probes. The translational and rotational dynamic correlation functions are obtained by measuring the intensity correlation function between crossed polarizers in the parallel and perpendicular geometries. Data from nonergodic systems is analyzed using an extension, to include rotations, of the method of Pusey and van Megen [Physica A 157, 705 (1989)]. Both diffusion modes are observed to be arrested as the rigidity of the gel increases. 相似文献
An automatic system for high-throughput (HT) characterisation of large libraries of solid materials by photoluminescence spectroscopy is described. The system provides time-resolved transient emission spectra in the microsecond scale and can be employed for characterisation of materials of interest in the fields of catalysis and electroluminescence, amongst others. Here, we present its application to the optimisation of the ship-in-a-bottle synthesis of a novel electroluminescent polymer (PPV) and a photocatalyst (TP+), both encapsulated in large-pore zeolites. 相似文献
We prove that any variety
in which every factor congruence is compact has
Boolean factor congruences, i.e., for all A in
the set of factor congruences of A is a distributive sublattice of the congruence lattice
of A. 相似文献
The purpose of this paper is to obtain new criteria for existence and asymptotic stability of periodic solutions of a Duffing equation x + cx + g(t, x) = 0, taking advantage of a new maximum principle with Lp-conditions combined with known relations between upper and lower solutions, topological degree and stability.Partially supported by D.G.I. BFM2002-01308, Ministerio Ciencia y Tecnología, Spain. 相似文献
We have proposed theoretically and confirmed numerically the possibility of controlling chaotic solitons in damped, driven Frenkel-Kontorova chains subjected to additive bounded noise by weak periodic excitations. Theoretically, we obtained an effective equation of motion governing the dynamics of the soliton center of mass for which we deduced Melnikov's method-based predictions concerning the regions in the control parameter space where homoclinic bifurcations are frustrated. Numerically, we found that such theoretical predictions can be reliably applied to the original Frenkel-Kontorova chains, even for the case of localized application of the soliton-taming excitations, and there is strikingly good agreement between analytical estimates and numerical results. 相似文献
We use a result of E. Lehmer in cubic residuacity to find an algorithm to determine primality of numbers of the form , odd, . The algorithm represents an improvement over the more general algorithm that determines primality of numbers of the form , , presented by Berrizbeitia and Berry (1999).