a-Si:H/SiO2 multilayer films fabricated by radio-frequency magnetron sputtering for optical filters

We examined the optical properties of a-Si:H/SiO2 multilayer films fabricated by radio-frequency magnetron sputtering for optical bandpass filters (BPFs). Because of the high refractive-index contrast between a-Si:H and SiO2, the total number of layers of an a-Si:H/SiO2 multilayer can be relatively small. We obtained an a-Si:H refractive index of 3.6 at lambda = 1550 nm and its extinction coefficient k < 1 x 10(-4) and confirmed by Fourier-transform infrared spectroscopy that such small k is influenced by the Si-H bonding in the film. We fabricated a-Si:H/SiO2 BPFs by using in situ optical monitoring. Thermal tuning of a-Si:H/SiO2 BPF upon a silica substrate was also performed, and a thermal tunability coefficient of 0.07 nm/degree C was obtained.     

Explicit formulas for transmission characteristics of graded-index oval core fibers

Transmission characteristics of graded-index oval (GIO) core fibers are theoretically analyzed, and basic equations representing the specific properties of the fiber are obtained. Formulas for the propagation constant, the field-profile function, the cutoff condition, and the total number of guided modes are derived in explicit forms. The formula for the change of the Gaussian beam radius as a function of the propagation distance is also given, and the numerical example agrees well with experimental data and agrees completely with that obtained by the beam-propagation method. These explicit expressions are useful for finding optimum structural parameters of GIO fibers to be used in practical fields.     

Thermophysical Property Measurements of Liquid and Supercooled Iridium by Containerless Methods

Thermophysical properties of equilibrium and supercooled liquid iridium were measured using noncontact diagnostic techniques in an electrostatic levitator. Over the 2300–3000 K temperature range, the density can be expressed as ρ (T)=19.5×10³ − 0.85(T− T_m) (kg·m⁻³) with T_m=2719 K. The volume expansion coefficient is given by 4.4 × 10⁻⁵ K⁻¹. In addition, the surface tension can be expressed as γ (T)=2.23 × 10³ − 0.17(T−T_m)(10⁻³N·m⁻¹) over the 2373–2833 K span and the viscosity as η(T)=1.85 exp [3.0× 10⁴/(RT)](10⁻³Pa·s) over the same temperature range.     

Subcritical Crack Growth in Soda-Lime Glass under Combined Modes I and III Loading

Fracture and subcritical crack-growth characteristics under combined Modes I and III loading were studied using the modified compact tension (CT) specimens of soda-lime glass. The combined mode load was applied to the specimen in the direction β with respect to the initial crack. By superposition of Mode III, the advancing crack begins to rotate at an angle Ψ to the initial crack plane, which nearly maximizes the Mode I stress intensity factor K _I(Ψ), and the crack continues to propagate in the same direction. In this case, unlike combined Modes I and II, the crack breaks into multiple partial fronts, and ligamentary bridging forms fracture lances when these segmented cracks are held together. The crack velocity d a /d t was plotted versus the maximum Mode I stress intensity factor K _I(Ψ) for combined Modes I and III loading. The d a /d t values are initially high, and the crack growth tends to be discontinuous compared with the result for pure Mode I. The subcritical crack growth seems to occur when the K _I value for the initial crack reaches a certain value. The d a /d t - K _I(Ψ) curves for combined Modes I and III lie roughly on the same curve as that for pure Mode I as the crack growth increases.     

Direct synthesis of poly(l-lactic acid) in supercritical carbon dioxide with dicyclohexyldimethylcarbodiimide and 4-dimethylaminopyridine

The direct synthesis of poly(l-lactic acid) (PLLA) from an l-lactic acid oligomer has been performed in supercritical carbon dioxide (scCO₂) using an esterification promoting agent, dicyclohexyldimethylcarbodiimide (DCC), and 4-dimethylaminopyridine (DMAP) as a catalyst. PLLA within M_n of 13,500 g/mol was synthesised in 90% yield at 3500 psi and 80 °C after 24 h. The molecular weight distribution of the products was narrower than PLLA prepared with melt-solid phase polymerisation under conventional conditions. Both DCC and DMAP showed high solubility in scCO₂ (DCC: 7.6 wt% (1.63×10⁻² mol/mol CO₂) at 80 °C, 3385 psi, DMAP: 4.5 wt% (1.62×10⁻²mol/mol CO₂) at 80 °C, 3386 psi) and supercritical fluid extraction was found to be effective at removing excess DMAP and DCC after the polymerisation was complete. We show that DCC and DMAP are effective esterification promoting reagents with further applications for condensation polymerisations in scCO₂.     

The Use of Ozone in Advanced Chip Manufacturing.

Ozonized Water Generator has been developed for use in semiconductor manufacturing processes. The use of ozonized water produced with this system permits effective wafer cleaning at room temperature. It is this possible to dispense with RCA cleaning that requires high temperatures and highly concentrated chemicals. Ozonized water has a promising application potential not only in the semiconductor industry but also in the liquid crystal display industry.     

Thermo-induced Vesicular Dynamics of Membranes Containing Cholesterol Derivatives

Membrane structural organization is an intrinsic property of a cell membrane. Any changes in lipid composition, and/or any stimuli that affect molecular packing induce structural re-organization. It membrane dynamics provide a means by which changes in structure organization can be determined, upon a change in the membrane internal or external environment. Here, we report on the effect of thermo-stress on membranes containing cholesterol liquid crystal (LC) compounds cholesterol benzoate (BENZO) and oxidized cholesterols. We have (1) revealed that lipid vesicles containing this artificial cholesterol derivative (BENZO) is thermo-responsive, and that this thermo-sensitivity is significantly similar to naturally oxy-cholesterols (2) elucidated the mechanism behind the membrane perturbation. Using Langmuir monolayer experiments, we have demonstrated that membrane perturbation was due to an increase in the molecular surface area, (3) discussed the similarities between cholesterol benzoate in the cholesterol LC state and in lipid bilayer membranes. Last, (4) drawing from previously reported findings, our new data on membrane dynamics, and the discussion above, we propose that artificial cholesterol derivatives such as BENZO, open new possibilities for controlled and tailored design using model membrane systems. Examples could include the development of membrane technology and provide a trigger for progress in thermo-tropical liquid crystal engineering.     

Silver Nanoparticle Impregnated Polycarbonate Substrates for Surface Enhanced Raman Spectroscopy

The embedding of nanoscopic metal structures into polymeric matrices represents a convenient way to stabilise a controlled dispersion of protected nanoparticles whilst taking advantage of their physical characteristics. Supercritical carbon dioxide (scCO₂) has been used to produce silver nanoparticles in optically transparent polycarbonate (PC) matrices allowing fine scale dispersions of particles to be produced within a prefabricated polymer component. Characterization of these nanocomposites has been performed using transmission electron microscopy (TEM) and UV‐vis spectroscopy. The substrates give excellent responses in surface‐enhanced Raman spectroscopy (SERS) for both 4‐aminothiophenol and rhodamine 6G target molecules. They offer significant benefits over more conventional SERS substrates in that they are cheap, flexible, mechanically robust and temporally stable. Post‐processing the films via simple etching techniques, provides an additional degree of design control and the potential to fabricate devices with unique excitation and detection geometries for a wide range of applications.     

Thermophysical properties of molten tungsten measured with an electrostatic levitator

Thermophysical properties of liquid and supercooled tungsten were measured using non‐contact techniques in combination with an electrostatic levitator. Over the 3125–3707 K temperature range, the density measurements can be expressed as ρ (T) = 16.7(± 0.33)× 10³ ? 1.08(± 0.08) (kg? m^?3) with T_m = 3695 K, leading to a volume expansion coefficient of 6.6×10^?5 K^?1. In addition, over the 3398–3695 K temperature range, the surface tension (γ) and viscosity (η) data can be expressed respectively as γ (T) = 2.48× 10³(± 75) ? 0.31(± 0.08) (T ? T_m) (10^?3 N? m^?1) and η (T) = 0.11(± 0.02) exp[12.8(± 4.1) × 10⁴/(RT)] (10^?3 Pa? s). © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(2): 152–164, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20101     

Recent US activities on advanced He-cooled W-alloy divertor concepts for fusion power plants

Several advanced He-cooled W-alloy divertor concepts have been considered recently for power plant applications. They range in scale from a plate configuration with characteristic dimension of the order of 1 m, to the ARIES-CS T-tube configuration with characteristic dimension of the order of 10 cm, to the EU FZK finger concept with characteristic dimension of the order of 1.5 cm. The trend in moving to smaller-scale units is aimed at minimizing the thermal stress under a given heat load; however, this is done at the expense of increasing the number of units, with a corresponding impact on the reliability of the system. The possibility of optimizing the design by combining different configurations in an integrated design, based on the anticipated divertor heat flux profile, also has been proposed. Several heat transfer enhancement schemes have been considered in these designs, including slot jet, multi-hole jet, porous media and pin arrays. This paper summarizes recent US efforts in this area, including optimization and assessment of the different concepts under power plant conditions. Analytical and experimental studies of the concepts and cooling schemes are presented. Key issues are identified and discussed to help guide future R&D, including fabrication, joining, material behavior under the fusion environment and impact of design choice on reliability.