Effects of chromate treatments on environmental stability of lead/tin alloy joints bonded with an ethylene–acrylic acid copolymer. II. Failure mechanism in distilled water

The environmental stability in distilled water and the failure mechanism of cathodically chromated tin, lead, and lead/tin alloy joints bonded with an ethylene–acrylic acid copolymer have been investigated by T-peel tests and ESCA and SEM analyses of the fractured surfaces. The peel strength of chromated lead/tin alloy joints and of both untreated and chromated tin joints is kept unchanged with water immersion, whereas that of untreated lead/tin alloy joints and of both untreated and chromated lead joints decreases rapidly with water immersion. ESCA and SEM observations show that lead/tin alloy surfaces consist of both lead and tin phases and that the tin phase interface deteriorates gradually with water immersion after premature deterioration of the lead phase interface. The stabilization effect of chromate treatments for lead/tin alloy joints is due to retardation of the underfilm corrosion of the tin phase.     

Polarising fibre coupler with high extinction ratio

Fused polarising fibre couplers have been fabricated using single-polarisation single-mode fibres. When circularly polarised light is fed into the coupler, one of the two orthogonal polarisation modes suffers strong attenuation, and only one polarisation mode couples in the fused biconical taper region. The extinction ratio of the coupler is 41 dB at a wavelength ? = 1.3 ?m with a coupling ratio of 48:52.     

Lower levels of physical functioning are associated with higher body weight among middle-aged and older women

OBJECTIVE: To compare levels of physical function, across levels of body mass index (BMI), among middle- to older-aged women. DESIGN: Cross-sectional study. Physical function, body weight and other covariates were measured in 1992. SUBJECTS: 56510 women aged 45-71 y, free of cardiovascular disease and cancer, participating in the Nurses' Health Study. MAIN OUTCOME MEASURES: The four physical function scores on the Medical Outcomes Study (MOS) Short Form-36 (SF36) Health Survey: physical functioning, vitality, bodily pain and role limitations. RESULTS: After adjusting for age, race, smoking status, menopausal status, physical activity and alcohol consumption, there was a significant dose-response gradient between increasing levels of BMI in 1992 and reduced function. For example, women with a BMI between 30-34.9 kg/m2 averaged: 9.0 point lower physical functioning score (95% Confidence interval (CI) -9.5, -8.5), 5.6 point lower vitality score (95% CI: -6.1, -5.1), and 7.0 point lower freedom from pain score (95% CI: -7.6, -6.4). These declines represent an approximate 10% loss of function compared to the reference category of women with BMIs ranging from 22.0-23.9 kg/m2. For the same BMI comparison, heavier women were at 66% increased risk of limitations in ability to work or perform other roles (RR = 1.66; 95% odds ratio (OR) CI: 1.56, 1.76). These findings were replicated when the sample was restricted to women who had maintained their BMI over a ten year period. CONCLUSIONS: In addition to increasing risk of chronic health conditions, greater adiposity is associated with lower every day physical functioning, such as climbing stairs or other moderate activities, as well as lower feelings of well-being and greater burden of pain.     

Microlens formation on VAD single-mode fibre ends

The letter describes microlens formation process on VAD single-mode fibre ends by a chemical-etching/fire-polishing technique. No central dip in the VAD fibres leads to high-quality lens formation.     

Synthesis of coherent two-port lattice-form optical delay-linecircuit

A method is presented for synthesizing a coherent two-port lattice-form optical delay-line circuit that is composed of optical delay lines, directional couplers, and phase shifters. The two bases of the method are the use of a unimodulus para-unitary matrix as a transfer matrix and the division of the transfer matrix into basic component transfer matrices. We succeeded in obtaining a set of recurrent equations with which to calculate circuit parameters to use for designing an optical delay-line circuit with a desired cross-port (through-port) transfer function. In the developed method, it is shown that two-port optical delay-line circuits can have the same transmission characteristics as finite impulse response digital filters with complex expansion coefficients. Three synthesis examples for optical frequency filters are described: a linear-phase Chebyshev filter, a multi-channel selector, and a group-delay dispersion equalizer. It is confirmed that transmission characteristics with a maximum transmittance of 100% can be always synthesized. The allowable parameter error for the synthesized linear-phase Chebyshev filter is also discussed     

Pulsed laser annealing of GaAs in a high-pressure argon gas ambience

Pulsed laser annealing was carried out for n-type semiconducting GaAs in air, 1 bar nitrogen, 1 bar argon, and 100 bar argon gas ambiences. Depth profiles of the atomic ratio measured by SIMS indicate that pulse annealing in air results in As loss and penetration of oxygen into the crystal, both of which affect dopant redistribution and deteriorate electrical properties of the annealed layer. High electrical activity (100%) and electron mobilities were achieved for high-dose implants of Si⁺ (1 × 10¹⁵ cm⁻²) by pulsed laser annealing in the high-pressure ambience.     

Nondestructive evaluation of coupling constants in single-modeoptical channel waveguides

A nondestructive method is proposed for evaluating power coupling coefficients of directional couplers contained in an optical integrated circuit. This technique, which is based on optical heterodyne interferometry, makes it possible to obtain individual coupler element information without removing the element from the optical circuit. General N-channel waveguide coupling characteristics are analyzed, and they are experimentally evaluated for two- and four-channel waveguides that have been practically designed as frequency multi/demultiplexers operating in the 1.55-μm-wavelength region