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Corresponding Pairs (corresponding + pair)

Distribution by Scientific Domains
Chemistry75%

Selected Abstracts

A three-dimensional hydrogen-bonded framework in (2S*,4R*)-7-fluoro-2- exo -[(E)-styryl]-2,3,4,5-tetrahydro-1H -1,4-epoxy-1-benzazepine

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2010
Lina M. Acosta
Molecules of the title compound, C18H16FNO, are linked into a three-dimensional framework structure by a combination of two C,H...O hydrogen bonds and three C,H...,(arene) hydrogen bonds. Comparisons are made with the (2R,4R) diastereoisomer and with the corresponding pair of diastereoisomeric 7-chloro analogues. [source]

Semi-empirical model for site effects on acceleration time histories at soft-soil sites.

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 11 2004
Part 1: formulation, development
Abstract A criterion is developed for the simulation of realistic artificial ground motion histories at soft-soil sites, corresponding to a detailed ground motion record at a reference firm-ground site. A complex transfer function is defined as the Fourier transform of the ground acceleration time history at the soft-soil site divided by the Fourier transform of the acceleration record at the firm-ground site. Working with both the real and the imaginary components of the transfer function, and not only with its modulus, serves to keep the statistical information about the wave phases (and, therefore, about the time variation of amplitudes and frequencies) in the algorithm used to generate the artificial records. Samples of these transfer functions, associated with a given pair of soft-soil and firm-ground sites, are empirically determined from the corresponding pairs of simultaneous records. Each function included in a sample is represented as the superposition of the transfer functions of the responses of a number of oscillators. This formulation is intended to account for the contributions of trains of waves following different patterns in the vicinity of both sites. The properties of the oscillators play the role of parameters of the transfer functions. They vary from one seismic event to another. Part of the variation is systematic, and can be explained in terms of the influence of ground motion intensity on the effective values of stiffness and damping of the artificial oscillators. Another part has random nature; it reflects the random characteristics of the wave propagation patterns associated with the different events. The semi-empirical model proposed recognizes both types of variation. The influence of intensity is estimated by means of a conventional one-dimensional shear wave propagation model. This model is used to derive an intensity-dependent modification of the values of the empirically determined model parameters in those cases when the firm-ground earthquake intensity used to determine these parameters differs from that corresponding to the seismic event for which the simulated records are to be obtained. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Straw bed priming enhances the methane yield and speeds up the start-up of single-stage, high-solids anaerobic reactors treating plant biomass

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2006
L Mattias Svensson
Abstract A simple and potentially inexpensive implementation of a high-solids reactor is a single-stage, stratified bed reactor, in which the bed is made up of the plant biomass fed into the system. In the present study, the stratified bed was started up for a period of four weeks by either direct feeding of sugar beet leaves at four different feeding rates, or by introducing a straw bed primer which was batch digested without feeding. During weeks five to six both systems were fed with sugar beet leaves at such a rate that the total amount of beet leaves added at the end of week six was the same in each of the four corresponding pairs of straw and ,no-straw' reactors. Straw bed priming enhanced the methane yield of the sugar beet leaves, with 0.33,0.37 m3 kg,1 VSadded (volatile solids) accumulated at average solid retention times as short as 11,25 days, while the ,no-straw' reactors had lower yields at longer average solid retention times. The levels and speciation of the organic acids suggested that both the rate and extent of the anaerobic digestion of the sugar beet leaves added in the straw reactors were improved. At the highest loading rate, the straw reactor failed, while the ,no-straw' reactor did not. It is hypothesised that the microbial biomass was better established in the straw reactors than in the ,no-straw' reactors. Copyright © 2006 Society of Chemical Industry [source]

7-Amino-5-methyl-2-phenyl-6-(phenyldiazenyl)pyrazolo[1,5- a]pyrimidine crystallizes with Z, = 2: pseudosymmetry and the formation of complex sheets built from N,H...N and C,H...,(arene) hydrogen bonds

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2010
Jaime Portilla
The title compound, C19H16N6, crystallizes with Z, = 2 in the space group P21/n. The two molecules in the selected asymmetric unit are approximate mirror images of one another; most corresponding pairs of atoms are related by an approximate half-cell translation along [100]. Each molecule contains an intramolecular N,H...N hydrogen bond and the molecules are linked into complex sheets by a combination of two intermolecular N,H...N and four C,H...,(arene) hydrogen bonds. Comparisons are made with some other 7-aminopyrazolo[1,5- a]pyrimidines. [source]