Absolute metrology by phase and frequency modulation for multiwavelength interferometry

A fiber interferometer for absolute distance measurements is presented whereby wavelength variation is achieved via a sinusoidal strain modulation of a fiber Bragg grating to generate a series of beat wavelengths. The interferometer employs fiber laser sources where the design is based on the use of narrow-bandwidth fiber Bragg gratings. The accuracy of the beat wavelengths is improved compared to the use of multiple wavelengths measured with conventional optical spectrum analyzers or available wavemeters. Initial measurements are presented for beat wavelengths of 254.74 mm and 27.4 m over an optical path difference of 200 mm and 3.8 m, respectively. Combined with a two (or three) wavelength interferometer, this technique has the potential for ultrahigh dynamic range metrology ranging over several meters while preserving subfringe resolution and a low system complexity.     

Lie Algebras with Nilpotent Length Greater than that of each of their Subalgebras

The main purpose of this paper is to study the finite-dimensional solvable Lie algebras described in its title, which we call minimal non- \({\mathcal N}\). To facilitate this we investigate solvable Lie algebras of nilpotent length k, and of nilpotent length ≤k, and extreme Lie algebras, which have the property that their nilpotent length is equal to the number of conjugacy classes of maximal subalgebras. We characterise the minimal non-\({\mathcal N}\) Lie algebras in which every nilpotent subalgebra is abelian, and those of solvability index ≤3.     

New approaches to the full-field analysis of photoelastic stress patterns

This paper presents two new methods that provide a complete solution for the automatic fringe analysis of photoelastic data. Previous solutions have not yet provided a complete full-field analysis of both fringe sets (isochromatic and isoclinic) over a multiple number of fringes with an automatic measurement of absolute magnitude. This paper reviews previous approaches and discusses the options along which this work has been directed. Specifically, two new algorithms are presented. Firstly, the combination of phase maps at three wavelengths in order to remove the isochromatic ambiguity at every π turning point, that would occur in a single phase map. Additionally, this algorithm allows the automatic measurement of absolute magnitude, providing the neutral axis is within the field of view. Secondly, a new method is proposed that removes the areas of 2π ambiguity in an isoclinic phase map by cross-correlating regions of low modulation at two different wavelengths. The algorithms are demonstrated by applying them to the analysis of an engine connecting rod. The rod was manufactured as a full-scale three-dimensional model in araldite (Ciba-Geigy CT200), from which a central slice was taken after having been stress frozen.     

Alpha-particle decay widths and narrow cluster states in15N

The total widths of¹⁵N* excited cluster states with E_x, J^π=12.55 MeV, 9/2⁺ and 13.00 MeV, 11/2^? are estimated by measuring the total alpha-particle decay probability and assuming that the reduced width does not exceed the Wigner limit for alpha-particle decay.     

FURTHER STUDIES ON THE ANTIVIRAL ACTIVITY OF HARMINE, A PHOTOACTIVE β-CARBOLINE ALKALOID

The UV-A mediated antiviral effect of harmine was investigated using murine cytomegalovirus (MCMV) as the target. Virus, which had been inactivated by harmine + UVA, was used to infect cultured mouse cells, and various stages in the viral replication cycle were examined. No viral protein synthesis or RNA synthesis (as measured by polyacrylamide gel electrophoresis or DNA-RNA hybridization) could be detected, and the viral DNA did not replicate (measured by DNA-DNA hybridization). In contrast virus which had been treated with harmine in the dark promoted a complete growth cycle in mouse cells.
An attempt was made to identify the primary target of harmine + UVA activity by examining the bacteriophages T4 and M13, which unlike MCMV do not possess membranes. Both bacteriophages were sensitive, but the single-stranded DNA phage M13 was considerably more so. These results, together with others discussed in the text, suggest that DNA and possibly other macromolecules can serve as targets for harmine photoactivity.     

MONOADDITION OF DICTAMNINE TO SYNTHETIC DOUBLE-STRANDED POLYDEOXYRIBONUCLEOTIDES IN UVA AND THE EFFECT OF PHOTOMODIFIED DNA ON TEMPLATE ACTIVITY

Abstract— The photoreactivity of dictamnine, a furoquinoline alkaloid, towards different synthetic DNAs has been studied. The ratio of the photobinding of [₃H]-dictamnine to poly(dA-dT) poly(dA-dT): poly(dG-dC) poly(dG-dC): poly(dA-dU) poly(dA-dU): poly(dA) poly(dT), in relation to that of calf thymus DNA, is 18:1:0.5:0.3. Prior treatment of calf thymus DNA with dictamnine in light inhibits the subsequent incorporation of 8-methoxypsoralen (8-MOP). These results suggest that the sites in DNA for the photobinding of dictamnine are probably identical with those for monoad-ducts of 8-MOP. Furthermore, the template activity of photomodified DNA in the RNA polymerase reaction is considerably inhibited for poly(dA-dT)poly(dA-dT), to a lesser extent for calf thymus DNA, but almost not affected for the linear copolymer, poly(dA)-poly(dT).     

GENOTOXICITY OF THE NATURAL FUROCHROMONES, KHELLIN AND VISNAGIN AND THE IDENTIFICATION OF A KHELLIN-THYMINE PHOTOADDUCT

Abstract— Longwave UV irradiation of a frozen aqueous solution of khellin and thymine resulted in the formation of a 2+2 photoadduct between the 2,3 double bond of khellin and the 5', 6' double bond of thymine. This behaviour is analogous to that of the furocoumarins and serves as a mechanism to describe the genotoxicity of the furochromones khellin and visnagin. These two compounds are phototoxic towards bacteria and fungi and inhibit mitosis and cause gross chromosomal changes in Chinese hamster ovary (CHO) cells in near UV light. For comparative purposes, 8-methoxypsoralen was also tested and was found to be more active than visnagin which, in turn, was more active than khellin.