摘要:

The results of optical absorption measurements on potassium colloids in KCl crystals have been presented in this paper. The samples were annealed at various temperatures with different time. It is found that the colloids band is dependent on the annealing temperature and annealing time. The transformation process between F-centers and colloidal centers were observed. The colloids band shows complex structures for the samples which did not attained equilibrium, indicating that there are different kinds of colloidal centers in such samples. Also we found that in these samples(which is in the nonequilibrium state), the transformation process from F-centers to colloidal centers does not stop even at room temperature.

ISSN:0038-7010    

DOI:10.1080/00387019808006766

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In this MRI work the Fast Gradient-Echo technique has been applied to the detection of the geometrical and elastic properties of the chest aorthic descending artery to check probable troubles in the blood flux which subtend several heart pathologies. The average diameter and the time variations of the aorthic vessel have been measured in the axial scanning plane to minimize the experimental errors. From the analysis of the vessel average diameter and the related root mean square deviation, a parameter named Contractility has been defined, in close relation with the elastic properties of the aorthic vessel. This parameter measured in patients affected from heavy cardiac pathologies such as aorthic arc aneurysm and right atrial mixoma shows remarkable variations when compared to the values obtained in healthy subjects. The use of the Contractility is suggested for a quick MRI determination of these cardiocircolatory pathologies.

ISSN:0038-7010    

DOI:10.1080/00387019808006767

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

It is argued that the double-beam method for the automatic correction of fluorescence excitation spectra, which proved to be a great boon in the days of analog instrumentation, has become, after the advent of digital techniques for acquiring and manipulating spectral data, more of a hindrance than a help; the benefits of reverting to a single beam device and makingin situmeasurement of the excitation intensity are pointed out.

ISSN:0038-7010    

DOI:10.1080/00387019808006768

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Infrared transmission, Reflectance-Absorption (RA) and Ultra-Violet (UV) spectra were measured for mono-and multi-layers Langmuir-Blodgett (LB) films of 4-[4′-(4″-decyIoxy phenylazo)naphthloxy] butyl trimethylammonium bromide formed with SDS to study the molecular orientation and aggregation. The results indicate that the compound do not aggregate in the LB films, and the alkyl tail is nearly perpendicular to the substrate surface and the chromorphore part adopts trans-zigzag conformation. These results also suggest that the molecular orientation and aggregation are not depend upon the number of monolayers The comparison of infrared transmission and RA spectra indicates that the hydrocarbon chain is nearly perpendicular to the substrate surface, but the two rings in the chromophore part are tilted considerably from the surface normal.

ISSN:0038-7010    

DOI:10.1080/00387019808006769

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The direct chemical deposition of silver on HCl-etched iron surface was first found to be able to present a SERS-active iron substrate. This method was used to study the adsorption of 2-mercaptoethanol on iron surface. For the propose of comparison, the adsorption of this substance on silver mirror was investigated. The results compounds could be chemisorbed HCl-etched iron plate and silver mirror surface in similar state and form a self-assembled monolayer of their thiolates.

ISSN:0038-7010    

DOI:10.1080/00387019808006770

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Two sensitive and accurate colorimetric and spectrofluonmetric methods, are presented for the determination of melatonin in tablets and serum. The first method utilizes the reactions of p-dimethylaminobenzaldehyde in hydrochloric acid (van Urk reagent)-ferric chloride in sulphuric acid (Salkowski reagent) mixture. The blue color of the resulting reaction product is measured at 630 nm. The second method is based on the reaction of melatonin with o-phthalaldehyde in acid medium which yields highly fluorescent condensation product that is measured at 465 nm as emission wavelength, using excitation wavelength at 355 nm. No interference was observed from tableting additives, and the applicability of the methods was examined by analysing tablets containing melatonin (single and combined with pyridoxine). Mean percentage recoveries from tablets were found to be 99.9+0.31 for single and 100.5+0.15 for combined tablets using colorimetric method, while by applying spectrofluorimetric method the recoveries were found to be 100.610.41 for single and 100.2+0.39 for combined tablets. Furthermore, the proposed methods were extended to the in-vitro determination of melatonin in serum. The detection limits are 0.27 ug ml−1for colorimetric method and 0.00035 ug ml−1for spectrofluorimetric method.

ISSN:0038-7010    

DOI:10.1080/00387019808006771

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The hydrolysis and polymerization of a non-catalyzed silica sol was investigated by Fourier Transform Infrared Spectroscopy (FT-IR) and deconvolution of the infrared spectra. The hydrolysis was followed by the 1168 and 812 cm−1bands which have been observed that decrease continously with the reaction time, and they dissapear showing the complete hydrolysis. The bands located at 1200 and 1147 cm−1are assigned to polymerization of Si-OH groups forming Si-O-Si bonds in cyclic or linear structures respectively. Both bands increase with time and are present simultaneously in the spectra showing that both kind of cross-linking of Si-OH groups are taking place in the sol to form the gel. In the gel the presence of Si-OH groups and Si-O−free broken bonds have been detected by means of the bonds located at 960 and 920 cm−1respectively.

ISSN:0038-7010    

DOI:10.1080/00387019808006772

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The enol-keto tautomerism of N-(2-hydroxy-1-naphthylidene)anilines was studied. In response to the action of salts (e.g. CaCl2), in ethanolic solution the equilibrium is shifted extensively in the direction of the keto form; this allows determination of the concentration of the keto form and of the equilibrium constant of the process. In accordance with the Hammett equation, the equilibrium constant varies as a function of the constants a of the substituents on the aniline ring.

ISSN:0038-7010    

DOI:10.1080/00387019808006773

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The photoacoustic spectra(PAS) of the coprecipitates Tb3+-Gd3+-Sal complexes are reported. With the increase of the concentration of Gd3+ion, the PA intensity of complexes decrease firstly, then increase. It is indicated that the addition of the second rare earth ion Gd3+changes the relaxation processes of the complexes. The changes of the fluorescence spectra turn out complementary to the PAS. The intramolecular energy transfer and the intermolecular energy transfer processes in coprecipitates are discussed.

ISSN:0038-7010    

DOI:10.1080/00387019808006774

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A method for transmitting radiation of the arc plasma with multimode fused quartz fiber onto the spectrograph has been studied. The plot of the Boltzmann function in emission spectral analysis is used for measuring temperature of the arc plasma. The measured temperature of the arc plasma is 5946.6K from least square linear regression ofln[λI/(gA)]andEifor a number of the emission line intensities of the excited copper atom. Its regression coefficient and measured precision are −0.97% and 1.7%, respectively. The advantages of the method of the diagnostic temperature for the arc plasma are absolute measurements of the temperature, remote sensing, precision and suitable for mal-environment, such as high temperature, toxic, explosion, strong magnetic or/and electrical fields.

ISSN:0038-7010    

DOI:10.1080/00387019808006775

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor