Determination of amino acids in biological fluids by capillary gas chromatography with nitrogen-phosphorus selective detection

A selective and sensitive method for the determination of protein and non-protein amino acids in biological fluids by capillary gas chromatography (GC) has been developed. The amino acids in the samples were directly converted into their N(O,S)-isobutoxycarbonyl methyl ester derivatives and measured by GC with nitrogen-phosphorus selective detection (NPD) using a DB-17ht capillary column. Using this method, the derivatives of the 21 protein amino acids and the 25 non-protein amino acids provided excellent NPD responses and were quantitatively and reproducibly resolved within 28 min. The lower detection limits of these amino acids, at a signal-to-noise ratio of 3, were ca. 6-150 pg injected. The calibration curves for each amino acid in the range of 0.02-2 micrograms were linear and sufficiently reproducible for quantitative analysis. This method was successfully applied to small urine and serum samples without prior clean-up; there was no evidence of interference from coexisting substances. Overall recoveries of amino acids added to urine and serum samples were 83-112%. The intra-assay and inter-assay R.S.D. of amino acids in these samples were 0.3-8.9% (n = 3) and 1.9-15.8% (n = 3), respectively.     

InSb MOS structures fabricated by a novel thermal oxidation method

Interfaces between InSb and its native oxide grown by a novel thermal oxidation method have been clarified to have good electrical characteristics. The interface state density was of a V-shaped form with the minimum value of less than 1012/cm2 eV, and the field-effect mobility of the holes at 77 K was about 300 cm2/Vs.     

Morphology and ultrastructure of the antennal chemoreceptors and mechanoreceptors of worker Coptotermes formosanus Shiraki

Data on respiratory symptoms and smoking for 2749 white American high school students from two linked surveys, separated by a one year lapse, are presented. There was a significantly higher likelihood of smoking at second survey among those who had initial symptoms. (There had been no educational efforts linking smoking and respiratory symptoms in the interim.) This difference was almost entirely contributed by those who had been ex-smokers and light (less than or equal to four cigarettes/day) smokers at first survey. Initial ex-smokers and light smokers also had, overall, least fixed smoking habits. Whatever the initial smoking or symptom status, symptoms at second survey were far more likely with current smoking. Controlling for initial symptom and smoking status, the gradient of symptoms between current smokers and non-smokers was over two and a half fold, except among those who had had symptoms and had not been smoking, and whose initial symptoms presumably arose from causes other than current cigarette smoking. Even among that group, symptoms at second survey were half as likely again among those who reported having become smokers (p less than-001). There were also strong linear trends of increased likelihood of symptoms with increased numbers of cigarettes smoked. Symptom rates at second survey of those who had symptoms a year earlier, and who stopped smoking during the year, were not as low as for those who also stopped smoking, but who had not had initial symptoms, suggesting that symptoms associated with smoking were not completely reversible in the time interval of this study. The difference, however, was not significant.     

Dark-field transmission electron microscopy for a tilt series of ordering alloys: toward electron tomography

Here we show a technique to obtain a tilt series of dark-field (DF) transmission electron microscopy (TEM) images in ordering alloys for tomographic three-dimensional (3D) observations. A tilt series of DF TEM images of D1a-ordered Ni4Mo precipitates in a Ni-Mo alloy was successfully obtained by adjusting a diffraction condition for a superlattice reflection from the Ni4Mo precipitates. Since the superlattice reflection usually has a long extinction distance, dynamic diffraction effects such as thickness fringes can be suppressed to some extent with precise realignment of the diffraction condition. By using the tilt series of the DF TEM images, we attempted a computed TEM tomography to visualize 3D shapes and positions of the precipitates.     

Zerstörungskinetik des technisch reinen Eisens bei Kavitationsbeanspruchung

Beschreibung einer Versuchseinrichtung zur Simulierung erosionsintensiver Kavitationsbeanspruchung. Veränderung des technisch reinen Eisens durch implodierende Kavitationsblasen während der Inkubationsperiode und im Spätstadium der Schädigung, Hinweise für Erhöhung des Kavitationswiderstandes.     

Cut-off frequency in radially inhomogeneous single-mode fibre

The limit for single-mode operation in a graded-index fibre has been obtained by calculating the normalised cut-off frequency of the TE01 mode, The affect of diffusion at the core-cladding boundary has been estimated.     

Pulse response of a graded-index optical fibre

An analysis has been made of pulse dispersion in an optical fibre having a continuous radial variation of refractive index. Solutions are presented for Selfoc fibre showing the effects of mode and material dispersion and of group delay. The predicted dispersions range from very low values up to about 1 ns/km, depending on the launching conditions.     

Mode excitation in a multimode optical-fibre waveguide

For normal incidence of a Gaussian beam on a multimode optical fibre, theory predicts that only HE1m, modes are excited, and this is confirmed experimentally for a liquid-core fibre of normalised frequency v = 125. Discrete-mode propagation is observed, indicating that the amount of mode conversion due to fibre imperfections is thus very small.     

Effect of dip in the referctive index on the cut-off frequency of a single-mode fibre

The normalised frequency for single-mode cut-off in an optical fibre has been calculated as a function of the dip in the refractive index at the centre of the core. For a particular class of profiles, dip width up to 40% have a negligible effect on the propagation characteristics.