Synthesis of nickel base alloys for use as magnetic standards

The goal of this research is to prepare a series of alloys having sharp, reproducible magnetic transitions for calibrating temperature in thermogravimetry from the magnetic transition temperature of pure cobalt (1121°C) to below room temperature.Alloys in the Ni-Co and Ni-Cu systems were prepared by the thermal decomposition of coprecipitated oxalates in argon. The alloys were subsequently annealed under 5% hydrogen.Magnetic transition temperatures were measured using simultaneous thermomagnetometry/differential thermal analysis. Transition temperatures were corrected using well known meltingpoint standards. Magnetic transition temperatures along with precision are reported as a function of composition.     

An FDTD method for the simulation of dispersive metallic structures

In this paper, we present a formulation of the finite-difference time-domain method for the simulation of metallic structures. The frequency dependent dielectric function of metals is approximated by a combined Drude–Lorentzian multi-pole expansion and fitting errors of only a few percent are obtained. An auxiliary differential equation technique is used to extend the standard FDTD algorithm with the dispersive material equations. The algorithm is validated by calculating reflection and transmission coefficients for thin metal layers, elliptical nano-particles and by simulating a surface plasmon resonance device. Excellent agreement between the FDTD simulations and exact theoretical results are obtained.     

Applications of Schochet''s methods to parabolic equations

Methods used by S. Schochet in [32] enable one to find a lower bound for the life span of solutions of hyperbolic PDEs with a small parameter. We prove a similar theorem for such equations where a diffusion term has been added, with the minimal assumption on the Sobolev regularity of the initial data ( in the d-dimensional torus). When the data is smooth and under a “small divisor” assumption on the perturbation, the first term of an asymptotic expansion of the solution is computed. Those results are then applied to prove global existence theorems, for arbitrary initial data, in the case of the primitive system of the quasigeostrophic equations, followed by the rotating fluid equations. We finally prove a more precise existence theorem for the latter, using anisotropic Sobolev and Besov spaces.     

Multiphoton double ionization of barium

The multiphoton double ionization of Ba from ~280 to 700 nm was investigated using laser pulses 5 ns long of peak intensity ~10¹⁰ W/cm². The spectrum consists of a number of strong resonances, which can be assigned to Ba⁺ transitions. Most of the assignments have been verified by pump-probe techniques. Thus, the Ba⁺⁺ observed is due to sequential ionization. The multiphoton ionization probability is highest for λ~500 nm, which matches a series of strong Ba and Ba⁺ transitions leading to double ionization     

Purine photoproducts

Abstract— DNA purine modifications by ultraviolet irradiation have not been as extensively studied as those of pyrimidines. However, a number of such reactions have been identified. These include photochemical addition of amino acids, photoalkylation by alcohols, amines and other compounds, photochemical activation of procarcinogens to mutagenic electrophiles, and formation of covalent linkages between DNA purines and adjacent bases. The recent characterization of two adenine-adenine di-adducts and the finding of endonucleases from two sources that incise ultraviolet-irradiated DNA at purine photoproducts indicate the possible biological importance of these moieties.     

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