摘要:

The results of the investigations of oil quality level and wear ageing obtained by measuring the slope of the1H NMR absorption line splitting depth as a function of temperature for groups CH2 and CH3 have been reported.

ISSN:0038-7010    

DOI:10.1080/00387018908053950

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The ESR spectroscopic investigations on the formation of neutral and anionic radical species from 1,1′-Bi-2-naphthol and 1,1′-Bi-2-phenol at room temperature are reported. The photogeneration of the neutral radicals is accompanied by an unusual kinetic decay in the presence of light. The nature and the structure of the radicals are discussed.

ISSN:0038-7010    

DOI:10.1080/00387018908053951

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The carbon chemical shifts of pyridine associated to various aliphatic and aromatic alcohols are measured. Actual effects of hydrogen bonding formation on 13c shifts, have been characterized by evaluating in first, anisotropy and non specific medium effects. Linear relationships are obtained between 13C shifts and the IR frequency shifts. Positive slopes are observed for C-β and C-γ in agreement with the electron population change, but a reverse slope results for C-α carbon.

ISSN:0038-7010    

DOI:10.1080/00387018908053952

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

In reversed-phase liquid chromatography the separation mechanism depends on the solute-stationary phase and solute-solvent interactions. These interactions can be studied under near-normal chromatographic conditions by total internal reflection fluorescence (TIRF) spectroscopy. Quartz crystals chemically modified with n-octadecyl-substituted-silanes, which are common derivatizing reagents used to modify chromatographic surfaces, can be used as a model stationary phase in TIRF studies. To facilitate study of the separation mechanisms using TIRF, surfaces of quartz crystals were chemically modified with silylating reagents and characterized by Fourier Transform Infrared Spectroscopy (FT-IR). Susceptibility tests of the modified surfaces were performed using protic and aprotic solvents. Siloxane bonds were formed, between the reagent and the quartz surface, at high reaction temperature in the absence of any solvent. Siloxane bond formation in the presence of organic solvent at room temperature was observed only when the crystal was previously dehydrated at high temperature.

ISSN:0038-7010    

DOI:10.1080/00387018908053953

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Franck-Condon factors and R-centroids for the B-X transition of I2have been calculated from recent molecular parameters. From our radiative lifetimes and others reported in the literature, the validity of several proposed electronic transition moment functions has been checked. Acombination of the Bhale and Koffend functions seems to give the best fitting with the experimental radiative lifetimes.

ISSN:0038-7010    

DOI:10.1080/00387018908053954

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A comprehensive study of Xe II line shifts (after considering more than 900 transitions) provides the basis for establishing a simple empirical linear relation between the shifts and the inverse of the ionization potential for the er level.

ISSN:0038-7010    

DOI:10.1080/00387018908053955

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Two photometric methods have been described for the assay of three phenothiazine drugs, isothipendyl hydrochloride, dimethothiazine mesylate & trimeprazine tartarate in their tablets. The first is the differential tartarate in their tablets. The first is the differential spectro-photometric method & based on the measurement of the absorbance (Δ A-), first derivative (Δ D1−) or second derivative (Δ D2−) values of the sulphoxide product of phenothiazine versus the intact. The second is based on the absorbance measurement of the pink coloured complex formed in a ratio of two drug moles t o one palladium ion. All these values are following Beer's law, which pernits the phenothiazines determination in their tablets with high accuracy. Using t-test & F-test the results of different methods are of equal accuracy and reproducibility. Both methods complement each ot her during the routine analysis and quality control of the investigated phenothiazine drugs.

ISSN:0038-7010    

DOI:10.1080/00387018908053956

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Dynamic and structural features of N-Isopropyl-N- {3-[4(4-Methoxybenzoylamino)Phenoxy]-2-Hydroxypropyl} Ammonium Chloride in [2H6]DMSO were investigated by measuring13C and1H spin-lattice relaxation rates and13C- {1H} and1H- {1H} n.O.e. Correlation times for main and internal reorientational motions were interpreted in terms of internal rotation around the two planal axes. Selective and double-selective1H spin-lattice relaxation rates were measured, wherefrom relevant proton-proton intramolecular distances were calculated. It was shown that the β1− blocking agent assumes a preferred conformation where extensive intramolecular H-bonding prevents segmental motion along the quaternary ammonium sidechain.

ISSN:0038-7010    

DOI:10.1080/00387018908053957

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The InF bands excited in a hollow cathode discharge have been used for fluorine determination in solid samples (containing from 10−6to 10−1% F) and solutions (at the F−concentrations from 1 μg/ml to 1 mg/ml). The discharge operated at direct current (dc) or high frequency current (hf). A dependence of the InF band intensities on the fluorine concentration has been investigated. Matrix effects caused by some metals and halides have been studied and discussed.

ISSN:0038-7010    

DOI:10.1080/00387018908053958

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The rigid polycyclic nitrogen compound was considered as a test for the reliability of internuclear distances calculated by1H-NMR spin-lattice relaxation rates. The ‘isotropic’ motional correlation time was calculated from13C relaxation rates (τC= 0.11 ns at 298 K). Dipolar cross-relaxation rates were calculated by measuring non-, mono- and double-selective proton spin-lattice relaxation rates. All the experimental relaxation rates were thoroughly accounted for by dipolar pairwise interactions. Only at high temperatures a certain contribution from the spin rotational mechanism was apparent.

ISSN:0038-7010    

DOI:10.1080/00387018908053959

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor