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71.
Improvements in the Multiplex Sample NMR method are investigated to explore its capabilities of analyzing multiple samples simultaneously. Issues of quantitation and resolution in the multiple-coil probe are examined in one- and two-dimensional experiments. Improvements in quantitation are shown to result from the use of reference deconvolution for one-dimensional experiments, while the use of two-dimensional methods has much improved resolution and shows the potential for significantly increased parallelism. A multiplicative scheme is shown to be an easily implemented, effective method for generating individual sub-spectra from individual samples. 相似文献
72.
In this work we consider a general class of Schr?dinger type operators, associated with multi-quasi-elliptic symbols. We give
a precise estimate of the remainder of the so-called Weyl asymptotic formula for the eigenvalues of these operators. In order
to reach our aim, we use the Weyl–H?rmander calculus, with locally temperate metrics and weights, and interpolation techniques.
Received: February 14, 2000; in final form: October 29, 2000?Published online: July 13, 2001 相似文献
73.
Lingshuine ( 1 ), a novel sesquiterpene amide, along with three known N‐containing compounds, 2 – 4 , have been isolated from the Hainan sponge Axinyssa variabilis. The structure of 1 was elucidated by detailed analysis of the spectroscopic data and by chemical methods. Lingshuine represents the first example of a Passerini product formed during the isolation process. 相似文献
74.
Márcio Lazzarotto Francine Furtado Nachtigall Eduardo Ernesto Castellano 《Thermochimica Acta》2005,429(1):111-117
Thermo gravimetric analysis of ammonium-p-tert-butylcalix[6]arene salts were carried out to determine the stoichiometry of the inclusion compounds and the temperature of leaving of the ammonium cation, as amine, from the solid phase by a reverse proton transfer reaction to calixarene. The chain length of the amine molecules and their relative basicity order are the main factors which determine the decomplexation temperatures for the ammonium salts of piperidinium, diethylammonium, ethylenediammonium, morpholinium, s-butylammonium, butylammonium, hexylammonium and triethylammonium salts of p-tert-butylcalix[6]arene anion. The solid state structure of bis-diethylammonium-p-tert-butylcalix[6]arene dianion is reported. The calix moiety adopts a 1,2,3 alternate conformation, with one ammonium as exo-calix and other as endo-calix, with an intricate array of hydrogen bonds between phenol, phenolate and ammonium cations. 相似文献
75.
Denis A. Knyazkov Artëm M. Dmitriev Oleg P. Korobeinichev Ksenia N. Osipova Gianmaria Pio Andrey G. Shmakov Ernesto Salzano 《Proceedings of the Combustion Institute》2021,38(2):2467-2475
The knowledge of the combustion chemistry of oxygenated fuels is essential for the development of detailed kinetic mechanisms suitable for the combustion processes involving biofuels. Moreover, epoxidized olefins, are increasingly used as chemical intermediates or as bulk chemicals. Nevertheless, a dearth of data for their reactivity in the oxidative environment can be observed in the current literature. This study reports the experimental and the model characterization of the flame structure of propylene oxide at stoichiometric and fuel-rich conditions at atmospheric pressure. To this aim, the species mole fractions in three premixed flames stabilized on a flat-flame burner have been quantitatively measured by using the flame sampling molecular beam mass spectrometry. Three chemical kinetic mechanisms retrieved from the current literature involving propylene oxide chemistry have been validated against the novel experimental data. In general, the predictions appeared to be in satisfactory agreement with measurements except for acetaldehyde and ketene. The rate of production analysis in the flame has shown that the discrepancies observed for these species are related basically to the incorrect ratio between the rates of primary reaction pathways of propylene oxide destruction. 相似文献
76.
Ernesto Estrada 《Journal of mathematical chemistry》2017,55(4):1021-1033
The atom-bond connectivity index—abbreviated ABC—has proven to describe the heat of formation of alkanes with an accuracy comparable to that of high-level ab initio and DFT methods. Its physical interpretation in terms of quantum-theory, its generalization, and many of its mathematical properties have been reported. Here, a probabilistic interpretation of the generalized ABC index is provided. It indicates that the terms defining this index represent the probability of visiting a nearest neighbor edge from one side or the other of a given edge in a graph. This interpretation is general enough as to cover the case of polarizing bonds in a molecular context. We then introduce a matrix representation of these probabilities in the form of generalized ABC matrices. Using this representation we study some indices related to the eigenvalues of the ABC matrices, such as the ABC energy and the ABC Estrada index. We provide some bounds for these parameters in general graphs. 相似文献
77.
Aránzazu Martínez-Gómez Ernesto Pérez Antonio Bello 《Colloid and polymer science》2010,288(8):859-867
The phase transitions and the orientational behavior of liquid crystalline poly(triethylene glycol p,p′-bibenzoate) have been studied. The real-time synchrotron diffraction results indicate that, on cooling from the isotropic
melt, an orthogonal SmA mesophase is formed first, and later it is transformed into a tilted SmC mesophase. However, the SmA
mesophase is stable in a rather wide temperature interval, and the transformation into the SmC phase occurs at temperatures
close to the glass transition, so that not very high tilting angles are attained. The uniaxial deformation of the SmC mesophase
indicates that usual parallel orientation of the molecular axes in relation to the stretching direction is obtained at high
strain rates, while anomalous perpendicular orientation occurs at low deformation rates, with the smectic layers aligned with
the stretching direction and the molecular axes almost perpendicular. A mixture of the two types of orientation is observed
at intermediate rates, with rather interesting features. 相似文献
78.
Cd(SePh)2, CdBr2·4H2O/CdI2 and PCh3 (Ph = phenyl; PCh3 = tricyclohexylphosphine) react to give [(SePh)2Cd2Br2(PCh3)2] (1), [(SePh)2Cd2I2(PCh3)2] (2) and [(SePh)7Cd4Br(PCh3)]n (3). 相似文献
79.
Tagliazucchi M Williams FJ Calvo EJ 《Chemical communications (Cambridge, England)》2010,46(47):9004-9006
We present polyelectrolyte multilayer modified electrodes exhibiting novel chemically responsive redox behaviour due to the combination of both redox and metal-ion-ligand functionalities on the same sites. 相似文献
80.