摘要:

Emission spectra from plasma arc welds were observed under a variety of current, voltage, polarity, and standoffs. If reverse polarity (welding torch positive) welds are struck below 50 amperes most of the power is deposited at the electrode rather than the workpiece because of low carrier density within the arc. Straight polarity, on the other hand, suffers no such limitation because of electrons created in the pilot arc used to start the weld process.

ISSN:0038-7010    

DOI:10.1080/00387019108018132

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Hydrotalcite-like compounds containing Ni(II) and Al(III) cations and with different Ni/Al ratios in the brucite layers have been prepared and studied using FT-IR and V-UV/DR spectroscopies. It has been found that the local environment of the Ni(II) cations is the same in all cases, occupying octahedral holes, but the orientation of the interlayer carbonate anions changes with the Ni/Al ratio.

ISSN:0038-7010    

DOI:10.1080/00387019108018133

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Gossypol and its two 2:1 and 4:1 tetrabutylammonium salts were investigated by1H and13C NMR spectroscopy in CDCl3solution. In this solution gossypol exists as a symmetrical aldehyde-aldehyde tautomer. In the case of the two 2:1 and 4:1 tetrabutylammonium salts of gossypol in chloroform the anhydrogossypol form was observed, instead of the ketol form which was determined in CD3CN solution.

ISSN:0038-7010    

DOI:10.1080/00387019108018134

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The Franck-Condon factors, qv′,v″and r-centroids, rv′,v″, for the bands of the B1Σ+− X1Σ+transition of Be18O molecule (420–520 nm) are determined. A comparison of calculated qv′,v″values with the experimental estimated intensities of the bands shows reasonable agreement.

ISSN:0038-7010    

DOI:10.1080/00387019108018135

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Various fundamental and applied aspects of pressurized atomization are discussed. The graphite furnaces are shown to be non-isobar in space and time. This is determined by the non-isothermality in space and time. Volatile and non-volatile forms of the same element are shown to be influenced differently by pressure. The ashing temperature used also influences the behaviour of analytes vis à vis atomization pressure. It is suggested that furnace designs that avoid high pressures within the furnace during atomization may lead to an enhancement of sensitivity, at least in the case of volatile elements. The use of matrix modifiers may change the spectral conditions by altering the shape and profile of spectral lines. Our discussion refers only to the case when line sources of radiation are used.

ISSN:0038-7010    

DOI:10.1080/00387019108018136

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0038-7010    

DOI:10.1080/00387019108018137

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Chromaticity colorimetry has been used to the study of Co (II) salts solvatochromism. It has been shown that the change of the color of CoCl2solutions as determined by chromaticity coordinates is due to the change in symmetry of cobalt ions in agreement with spectroscopic and other physicochemical data. Determination of the dominant wavelength or hue-angle makes possible the ranking of solvents according to their ability to form complex ions of particular symmetry.

ISSN:0038-7010    

DOI:10.1080/00387019108018138

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Instrumental neutron activation analysis was used for the determination of Na, Al, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Rb, Sb, Cs, La, Ce, Sm, Eu, Dy, Yb, Lu, Hf, Ta, Pa, and U in bitter cola (Garcinia cola), Tatassai (Capsicum spp), sweet pepper (Capsicum annum), chillies (Capsicum spp.), alligator pepper (Aframomum melagueta) and onions (Allium caps) which are the major Nigerian stimulants.

ISSN:0038-7010    

DOI:10.1080/00387019108018139

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Infrared data for N-benzylideneanilines mono- and disubstituted predict, in agreement with CNDO molecular orbital calculations, that the internal energy transfer is induced mainly by a donor group in para position of the benzylidene ring; this effect confers to this molecular portion a prevalent planar structure. However, the charge transfer is restricted by a steric interaction between one of the ortho hydrogen atoms of the aniline ring and the azomethine hydrogen; this situation constraints this molecular portion to adopt a major non planar conformation.

ISSN:0038-7010    

DOI:10.1080/00387019108018140

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

C-13 NMR spectra of fifteen N-aminopyridinium perchlorates show the effect of amination of the ring nitrogen atom to be similar to that observed in the pyridine N-oxide spectra, particularly for the 2(6) and 3(5) positions. Benzene and pyridine increments predict well the carbon chemical shifts for the title compounds unless both positions 2 and 6 are occupied. The chemical shifts of some carbon atoms in the compounds studied are linearly dependent on those in the respective benzene derivatives as well as on the Hammett σ constants.

ISSN:0038-7010    

DOI:10.1080/00387019108018141

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor