The influence of a transverse magnetic field on a subnormal glow discharge in air

In subnormal glow discharge under d.c. excitation at different pressure in a varying transverse magnetic field (0 to 30 G) some measurements have been carried out for various initial average tube currents. The voltage across the discharge increases and average tube current and residual current decreases in the magnetic field. With the help of Beckman’s expression [4] for the axial field and the electron density distribution in a transverse magnetic field the observed variation of current and voltage can be satisfactorily explained. The variation of axial electric field with transverse magnetic field can be represented to a fair degree of accuracy by the derived equation. The behaviour of residual current with magnetic field has been observed in these oscillations.     

Modification of magnetic anisotropy in metallic glasses using high-energy ion beam irradiation

Heavy ion irradiation in the electronic stopping power region induces macroscopic dimensional change in metallic glasses and introduces magnetic anisotropy in some magnetic materials. The present work is on the irradiation study of ferromagnetic metallic glasses, where both dimensional change and modification of magnetic anisotropy are expected. Magnetic anisotropy was measured using Mössbauer spectroscopy of virgin and irradiated Fe₄₀Ni₄₀B₂₀ and Fe₄₀Ni₃₈Mo₄B₁₈ metallic glass ribbons. 90 MeV ¹²⁷I beam was used for the irradiations. Irradiation doses were 5×10¹³ and 7.5×10¹³ ions/cm². The relative intensity ratios D ₂₃ of the second and third lines of the Mössbauer spectra were measured to determine the magnetic anisotropy. The virgin samples of both the materials display in-plane magnetic anisotropy, i.e., the spins are oriented parallel to the ribbon plane. Irradiation is found to cause reduction in magnetic anisotropy. Near-complete randomization of magnetic moments is observed at high irradiation doses. Correlation is found between the residual stresses introduced by ion irradiation and the change in magnetic anisotropy.     

Precise mass measurement of a double-stranded 500 base-pair (309 kDa) polymerase chain reaction product by negative ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) has been used to determine the mass of a double-stranded 500 base-pair (bp) polymerase chain reaction (PCR) product with an average theoretical mass of the blunt-ended (i.e. unadenylated) species of 308 859.35 Da. The PCR product was generated from the linearized bacteriophage Lambda genome which is a double-stranded template. Utilization of ethanol precipitation in tandem with a rapid microdialysis step to purify and desalt the PCR product was crucial to obtain a precise mass measurement. The PCR product (0.8 pmol/μL) was electrosprayed from a solution containing 75% acetonitrile, 25 mM piperidine, and 25 mM imidazole and was infused at a rate of 200 nL/min. The average molecular mass and the corresponding precision were determined using the charge-states ranging from 172 to 235 net negative charges. The experimental mass and corresponding precision (reported as the 95% confidence interval of the mean) was 309 406 +/- 27 Da (87 ppm). The mass accuracy was compromised due to the fact that the PCR generates multiple products when using Taq polymerase due to the non-template directed 3'-adenylation. This results in a mixture of three PCR products with nearly identical mass (i.e. blunt-ended, mono-adenylated and di-adenylated) with unknown relative abundances that were not resolved in the spectrum. Thus, the experimental mass will be a weighted average of the three species which, under our experimental conditions, reflects a nearly equal concentration of the mono- and di-adenylated species. This report demonstrates that precise mass measurements of PCR products up to 309 kDa (500 bp) can be routinely obtained by ESI-FTICR requiring low femtomole amounts. Copyright 1999 John Wiley & Sons, Ltd.     

Radiochemical neutron activation analysis of chromium in biological materials using ion chromatography with “on-line” yield determination

The use of ion chromatography with continuous UV detection for radiochemical separation of Cr with simultaneous yield determination is presented. The RNAA method consists of sample destruction in HNO₃+HClO₄, extraction of Cr(VI) with tribenzylamine in CHCl₃, backextraction in NaOH and chromatography of chromate. From radiotracer experiments, the ratio of signals for⁵¹Cr and Cr spike was found to be constant for a chromium mass range of 15 to 100 g. Application of the RNAA method to Cr determination in biological reference materials showed a reasonable agreement with the reference values. A relative standard deviation of 3% on the 100 g/kg level for homogeneous material was achieved.IAEA-fellow, on leave from the Philippine Nuclear Research Institute Philippine     

Ray propagation and compression in a strictly adiabatic taper

In this paper we construct the exact ray paths for a strictly adiabatic taper. Ray invariants are given and explicit formulae for the components of the ray path are found. We investigate the characteristics of the bound and leaky rays and compare them with the behaviour of the exact bound and radiating modal fields. The compression of rays within the taper is discussed from the viewpoint of concentrator theory.     

Stochastic simulation of infrared non-Gaussian natural terrain imagery

We describe a new technique for the fast simulation of natural IR imagery with non-Gaussian statistics. We pass samples of the imagery through an invertible pointwise nonlinear transform, to give samples of a new random field with Gaussian marginal probability density. We compute the correlation function for the transformed samples, and simulate Gaussian random fields (GRFs) with these correlations. Passing the simulated GRFs through the inverse transform gives our simulations of the original imagery. We discuss the effectiveness of this approach for simulating natural terrain backgrounds.     

Temperaturabhängigkeit der Gleichgewichtsspreitungsdrucke homologer Lezithine an der Grenzfläche n-Heptan/0,1 M NaCl

Ohne ZusammenfassungMit 1 Abbildung und 1 Tabelle     

Splicing of optical waveguides with lossless graded-index tapers

Marcatili has proposed a class of graded-index (GRIN) tapers which do not radiate along their length. We investigated the splicing of such tapers to dissimilar waveguides, and derive a simple formula for the coupling efficiency, which clearly reveals the loss due to mismatch of spot-size and the curvature of the wavefronts.