Monotone interpolation of order 3 by C2 cubic splines

We propose a local solution for the problem of interpolatingmonotone data by monotone C² cubic splines with two additionalknots per interval, on an arbitrary partition, and with an approximationof order 3. Our paper extends recent works by Archer & LeGruyer and Pruess.     

TOPICAL UROCANIC ACID ENHANCES UV-INDUCED TUMOUR YIELD AND MALIGNANCY IN THE HAIRLESS MOUSE

Epidermal urocanic acid has been postulated to be the mediator of the specific state of immunosuppression induced by UV irradiation, by which UV-initiated tumour cells are able to evade normal recognition and can survive to grow progressively into malignant tumours. These experiments demonstrate that topical application of UV-irradiated urocanic acid systemically suppresses the contact type hypersensitivity response to oxazolone in hairless mice. In addition, topically applied urocanic acid markedly increases the overt tumour yield and the degree of malignancy in hairless mice exposed chronically to daily minimally erythemal doses of simulated solar UV light. Topical urocanic acid also increases the number of latent UV-initiated tumours, detectable by croton oil promotion. Therefore UV photoproducts of urocanic acid can both systemically suppress contact hypersensitivity in the epidermis, and also enhance early survival of UV-initiated tumour cells resulting in augmentation of UV photocarcinogenesis.     

Computing stability regions--Runge-Kutta methods for delay differential equations

We discuss the practical determination of stability regionswhen various fixed-stepsize Runge-Kutta (RK) methods, combinedwith continuous extensions, are applied to the linear delaydifferential equation (DDE) y'(t)= y(t)+µ(t–) (t) with fixed delay . It is significant that the delay is not limitedto an integer multiple of the stepsize, and that we considervarious continuous extensions. The stability loci obtained in practice indicate that the standardboundary-locus technique (BLT) can fail to map the RK DDE stabilityregion correctly. The aim of this paper is to present an alternativestability boundary algorithm that overcomes the difficultiesencountered using the BLT. This new algorithm can be used forboth explicit and implicit RK methods.     

RADIATIVE AND NON-RADIATIVE LOSSES IN THE RETINOL POLYENES

Abstract— The radiative fluorescence lifetimes of the all-trans, 9 cis and 13 cis retinol, have been measured at various temperatures, and in various solvents. The comparison of these results and of the data calculated from the absorption spectra using the Strickler and Berg equation shows that the transition probabilities are at least one hundred times lower for the radiative emission than for the absorption. Such a discrepancy, which is a general property of the polyenic structure, is closely related to the magnitude of the shift between absorption and fluorescence spectra. We interpret the observed elongation of the radiative fluorescence lifetimes and the temperature dependence of the radiative transitions in the case of all trans retinol as being due to the fact that only the lowest vibrorotational sublevels of ¹S₁, have a reasonable radiative transition probability: the temperature dependence of the radiationless transitions is considered to be due to the existence of a non radiative decay pathway at 550cal/mole above the '0' level.     

THE ORIENTATION OF THE REACTION CENTER CAROTENOID TRIPLET STATE MAGNETIC AXES IN CHROMATOPHORES OF Rhodopseudomonas sphaeroides WILD TYPE

Abstract— The orientation of the principal magnetic axes of the reaction center carotenoid from Rps. sphaeroides wild type is presented. The parameters needed to simulate the observed carotenoid triplet state spectra indicate that the carotenoid adopts a planar structure within the reaction center. A high degree of geometrical and structural specificity is shown to exist for this carotenoid molecule.     

Synthesis of phenanthro[a] phenazine derivatives: a novel ring structure forming discotic liquid crystals

Phenanthro[a] phenazine, a new heterocyclic ring structure of both biological and physical interest, has been prepared by coupling 1,2-phenylenediamine with triphenylene-1,2-diquinone derivatives in high yields. 2,3,6,7,10-Penta-alkoxyphenanthro[a] phenazines are mesogenic over a broad temperature range. These novel unsymmetrical, coloured, polar, heteroaromatic discotic mesogens are potential candidates for the study of conducting, photoconducting, electroluminescence, photorefrective, etc. properties.     

Precision two-photon spectroscopy of alkali elements

In this paper, we have briefly reviewed the work on two-photon spectroscopy of alkali elements and its applications. The technique of Doppler-free two-photon spectroscopy is briefly summarized. A review of various techniques adopted for measuring absolute frequencies of the atomic transitions and precision measurements of isotope shifts and hyperfine structures (HFS) is presented. Some of the recent works on precision measurements of HFS constants of 6s ² S _1/2 level of ³⁹K and ⁴¹K, 9s ² S _1/2level and 7d ² D _3/2 level of ¹³³Cs are also discussed.     

Generation of tunable 16 μm radiation from CO2 by cascade lasing

In this paper we propose a scheme to generate tunable 16 μm radiation from CO₂ molecules by cascade lasing. The stimulating 9.5 μm radiation is generated internally by the fast rotating mirror Q-switching technique. The optical scheme proposed by us uses an intracavity prism to separate the 9.5 μm and the 16 μm beams. This facilitates independent tuning of the two beams if required. In the present configuration, only the 16 μm cavity is dispersive. The 9.5 μm beam grows spontaneously in a stable semiconfocal resonator. We have developed a theoretical model to simulate the proposed scheme. The model predicts the energy and power of 16 μm radiation. The calculated values are much higher than the previously obtained experimental values. The results point out the feasibility of developing a laser system based on the theoretical design parameters presented in this paper. Such laser systems can find application in uranium isotope separation studies.