Measurements of L-shell X-ray emission lines of neonlike europium on an electron beam ion trap

We report a measurement of the two X-ray transitions that proceed from the and (1s²2s_1/22p⁶3p_1/2)_{J = 1} upper levels to the (1s²2s²2p⁶)_{J = 0} ground level in neonlike Eu⁵³⁺ (Z = 63), that is,  near the previously documented avoided crossing of the two upper levels at Z = 68. The measurement was carried out using the calorimeter spectrometer on the Livermore EBIT-I electron beam ion trap. It affirms the trends set by the neighboring neonlike ions both in terms of the relative intensity of the two lines and in terms of the magnitude of disagreement with theoretical energy level predictions.     

Algorithms for fast multidimensional signal extraction

In recent studies operator factorization techniques have been developed for problems associated with multidimensional control and image processing. In particular the “special factorization” of Gohberg and Krein and the Schur-Coleski factorization have both been extended to the multivariate setting. The present study focuses on computational aspects of the earlier results. Also of interest are implications for designing computer architectures which facilitate high-speed, online computation of the operator factors.     

Wave scattering by an array of periodic barriers

The 2D scattering of a plane harmonic wave obliquely incidenton an array of perforated barriers is investigated. The geometrygeneralises that previously considered and is subject only tothe requirement of periodicity along the barriers. By partitioninga matrix-valued integral operator into a combination of anothersuch operator and a matrix system, the interactions betweenthe barriers are decoupled. This approach, which extends theusual wide-spacing approximation so as to include a finite numberof evanescent modes, leads to structural simplicity and computationalsaving without compromising accuracy. The couplings betweenthe individual barriers arise naturally through a sequence oftransfer matrices without the need to postulate a matching procedure.Numerical results obtained by using a variational approach aregiven to confirm the efficiency of the method and to give examplesof the scattering process. In particular, the phenomenon ofBragg resonance that occurs in the case of equally spaced, identicalbarriers is examined.     

Extended control of marine fouling

A process for microencapsulation by complex coacervation, introduced by Green and Schleider in 1957, produced a dry powder form of the liquid biocide tributyltin chloride (TBTCL). Static immersion testing of fiberglass panels painted with the shipbottom paint formulated with 14% w/w TBTCL microcapsules (10–30 μm diam.) gave excellent test results (0% fouling for up to 49 mo) when three coats of this paint were applied to panels. Rationale for the extension of protection against attachment and growth of common marine forms in this formulation are given.     

Cold crystallization and thermal shrinkage of uniaxially drawn poly(ethylene 2,6-naphthalate) by solid-state coextrusion

Solid-state coextrusion has been used to prepare uniaxially drawn films from isotropic poly(ethylene 2,6-naphthalate) (PEN) of a minimum degree of crystallinity (ca. 5%) both below and above its glass transition temperature T_g. The onset of cold crystallization (T_c) of the drawn films has been studied as a function of the extrusion temperature (ET) and the draw ratio (EDR). It has been shown that T_c decreases markedly on draw, as much as 95°C, and, at constant draw ratio T_c goes through a minimum in the T_g region. For undrawn PEN, annealing below 153°C has no significant effect on T_c. To evaluate the crystallization rate constant (k) and the activation energy (E_a) of the drawn specimens, a nonisothermal DSC procedure has been used. With increasing EDR, k increases markedly and E_a goes down over threefold compared with the undrawn polymer. At high ET, strain-induced crystallization has also been shown to play an important role in lowering E_a for cold crystallization. Thermal shrinkage above T_m indicates a high elastic recovery, underlining the efficiency of deformation, ca. 93%, achieved by solid-state coextrusion.     

Spider silk as a model biomaterial

Spider silk combines strength and extensibility, and a wide range of mechanical properties can be achieved with only minute (if any) changes in chemical structure. It appears that the full range of thermo-mechanical properties of such silk fibres can be predicted by examining the energy imparted during stretching with the theoretical framework provided by Mean Field Theory for Polymers. This approach attempts to integrate strain and tensile stress with a range of relevant energetic and mechanical parameters such as the loss tangent and potential energy of atomic inter-chain bonding as well as the tensile and bulk elastic moduli. The model reveals that the underlying design principle of silks seems to share an inherent and surprising simplicity at the macromolecular level. We conclude that our modelling approach allows in-depth analysis of natural silks as well as a comparison with synthetic fibres.     

The Schwarzschild H space

The usual construction of anH space from asymptotic data onI ⁺ uses only the radiative component of the asymptotic gravitational field and ignores the longitudinal part of the field [2]. While Penrose and Sparling [1] have given the construction of a deformed twistor space encoding the Schwarzschild structure by exponentiating the linearized spin 2 monopole field, one would like to have a directH space construction as a step toward constructingH spaces containing all the asymptotic degrees of freedom. The first step of giving a directH space construction for the Schwarzschild asymptotic data is contained in the following. Several interesting new structures arise in this process.