Laser induced copper electroless plating on polyimide with Q-switch Nd:YAG laser

The results of laser induced deposition of copper on polyimide substrate from copper electrolyte solution are reported. Unlike most work reported in the literatures where CW Ar⁺ lasers were used, a second harmonic (532 nm wavelength) Q-switch Nd:YAG laser was used for our experiments. The deposition process was conducted by laser-catalyzing of the polyimide surface and subsequent photothermal-accelerated reduction of copper-complex ions in an alkaline reducing environment. The characteristics of the deposited copper line were investigated in terms of laser beam scanning speed, and the number of scans. The surface morphology and chemical composition of the deposited copper were analyzed using field emission scanning electron microscope (FESEM) and energy dispersive spectrometer (EDX). The optimum processing conditions have been identified. The copper deposit was found to adhere well to the substrate.     

Dynamical Characteristics of Traveling Wave Packets of Total Electron Content Disturbances

Using the COPHASE method and the GPS interferometry method for travelling ionospheric disturbances, we analyze in detail the spatio-temporal properties of travelling wave packets (TWP) of total electron content (TEC) disturbances. The analysis is performed on the example of a clearest TWP manifestation observed in California, USA, in October 18, 2001, using the GLOBDET technique, developed at the Institute of Solar-Terrestrial Physics of the Siberian Branch of RAS for global detection and monitoring of natural and technogenic ionospheric disturbances on the basis of TEC variations retrieved from the global network of GPS receivers. In the time domain, TWPs are quasi-periodic TEC oscillations of duration about 1 h, period of 10–20 min, and amplitude exceeding that of the background TEC fluctuations by at least one order of magnitude. The velocity and direction of TWP motion are similar to those of mid-latitude mesoscale travelling ionospheric disturbances, as obtained earlier from the analysis of phase parameters of HF radio signals and the signals of geostationary satellites and discrete space radio sources.     

TOPOLOGY DESIGN OF STRUCTURES SUBJECTED TO PERIODIC LOADING

Although a lot of attention in the topology optimization literature has focused on the optimization of eigenfrequencies in free vibration problems, relatively little work has been done on the optimization of structures subjected to periodic loading. In this paper, we propose two measures, one global and the other local, for the minimization of vibrations of structures subjected to periodic loading. The global measure which we term as the “dynamic compliance” reduces the vibrations in an overall sense, and thus has important implications from the viewpoint of reducing the noise radiated from a structure, while the local measure reduces the vibrations at a user-defined point. Both measures bring about a reduction in the vibration level by moving the natural frequencies which contribute most significantly to the measures, away from the driving frequencies, although, as expected, in different ways. Quite surprisingly, the structure of the dynamic compliance optimization problem turns out to be very similar to the structure of the static compliance optimization problem. The availability of analytical sensitivities results in an efficient algorithm for both measures. We show the effectiveness of the measures by presenting some numerical examples.     

Semi‐analytical integration of the 8‐node plane element stiffness matrix using symbolic computation

The semi‐analytical integration of an 8‐node plane strain finite element stiffness matrix is presented in this work. The element is assumed to be super‐parametric, having straight sides. Before carrying out the integration, the integral expressions are classified into several groups, thus avoiding duplication of calculations. Symbolic manipulation and integration is used to obtain the basic formulae to evaluate the stiffness matrix. Then, the resulting expressions are postprocessed, optimized, and simplified in order to reduce the computation time. Maple symbolic‐manipulation software was used to generate the closed expressions and to develop the corresponding Fortran code. Comparisons between semi‐analytical integration and numerical integration were made. It was demonstrated that semi‐analytical integration required less CPU time than conventional numerical integration (using Gaussian‐Legendre quadrature) to obtain the stiffness matrix. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2006     

Three-dimensional mapping of cholinergic molecules by confocal laser scanning microscopy in sea urchin larvae.

Confocal laser scanning microscopy (CLSM) was used to examine molecules related to the cholinergic neurotransmission system and detected at all the larval stages of Paracentrotus lividus, by histochemical and immunohistochemical methods. CLSM, providing spatial resolution of the cells located both at the larval surface and at depth, allows a complete mapping in a three-dimensional volumetric frame. At early larval stages acetylcholinesterase- as well as choline acetyltransferase-like molecules were found mainly in the gut wall cells, and along the ciliary bands of the arms, together with muscarinic acetylcholine receptors. At perimetamorphic stages, cholinergic molecules were present in the ciliate strands along the arms, in the larval body and in the rudiment. At metamorphosis, positivity to cholinergic molecules translocated to the juvenile, where a high frequency of mAChR- and ChAT-like positive cells was found.     

Expansion of monomer units in poly(ethylene terephthalate) molecules under conditions of thermal and zero-point atomic vibrations

The temperature dependence of the expansion ?_C of trans conformers of the carbon skeleton of macromolecules in crystallized and amorphous poly(ethylene terephthalate) (PET) due to zero-point and thermal atomic vibrations is investigated by IR spectroscopy. It is found that the thermal expansion coefficient β_C jumpwise increases at the characteristic temperatures T _t and T _b. This increase is associated with the crossover from the quantum to classical statistics of torsional and bending vibration modes. The quantum and classical contributions to the expansion ?_C are determined for each mode. The quantum and classical contributions of the torsional vibrational mode in the amorphous polymer are approximately 1.5 times larger than those in the crystallized polymer. This effect is caused by an increase in the anharmonicity of torsional vibrations in the amorphous polymer.     

Stoner-Wohlfarth-type behavior of a close-packed array of high-anisotropy hexaferrite nanoparticles

Magnetization and remagnetization processes in a close-packed nanodispersed barium hexaferrite powder sample in the magnetically stable state were analyzed. Reversibility effects were discussed in terms of interparticle interaction. Judging from the magnetization curve and the parameters characterizing remagnetization irreversibility, the sample under study is a model system of small Stoner-Wohlfarth particles.     

A negatively charged silicon vacancy in SiC: Spin polarization effects

The equilibrium geometry and hyperfine interaction constants of the nearest and next-to-nearest neighbor atoms are calculated for a negatively charged silicon vacancy in the high-spin state in cubic SiC. The calculations are performed within the cluster approach in terms of the density-functional theory (DFT). It is shown that the results of calculations with the use of a 70-atom cluster are in good agreement with experimental data. A detailed consideration is given to spin polarization in the electron subsystem and the applicability of a simple LCAO model that is commonly used in the interpretation of the electron paramagnetic resonance data for semiconductors. The spin density distribution for the defect under investigation is analyzed in terms of localized orbitals.