Effect of polarization on a solid immersion lens of arbitrary thickness

A solid immersion lens can be applied for high-resolution subsurface analysis of integrated circuits and other physical systems. We present a thorough analysis of the focal field distribution of a solid immersion lens system of arbitrary thickness. Cases of linearly and radially polarized illumination are examined and accurate expressions derived for the electric field in the image space. The effect of the spherical interface on both transverse and axial intensity profiles is analyzed. The performance and practicality of configurations deviating from the hemispherical and aplanatic cases are studied. The results show that optimal resolution is obtained at focal positions between the hemispherical and aplanatic points when radially polarized illumination is applied.     

Growth mechanism of CdS nanofilms prepared by chemical bath deposition

Deposition of CdS nanofilms was performed using the chemical bath deposition method, as a function of the concentration ratio of [S] to [Cd] (S/Cd) and of deposition temperature. As the S/Cd ratio and deposition temperature increased, the deposition rate of the films increased, and the transmittance was improved. With increasing S/Cd ratio, the crystallinity of the CdS nanofilms decreased due to the formation of small grains therein. Atomic force microscopy revealed that the surface morphology of the films became smooth with increasing S/Cd ratio and deposition temperature. The evolution of the grain formation showed that the slow deposition rate of the films leads to a small number of grains at the initial stage of the deposition, followed by fast grain growth, resulting in a rough surface. On the other hand, a fast deposition rate initially causes the formation of many grains on the entire surface as well as slow grain growth, making the films smooth. It is evident that the deposition rate affects the physical and optical properties of the films due to their different growth mechanisms.     

Tensile,dielectric, and thermal properties of epoxy composites filled with silica,mica, and calcium carbonate

The minerals silica, mica, and calcium carbonate (CaCO₃) were used as fillers to produce epoxy thin film composites for capacitor application. The effects of filler loading and type on the morphology, tensile, dielectric, and thermal properties of the epoxy thin film composites were determined. Results showed that epoxy thin films with 20 vol% filler loading showed good dielectric properties, thermal conductivity, and thermal stability. However, the tensile properties of the thin films were reduced as the filler loading was increased due to brittleness. Dielectric constant and dielectric loss of epoxy/inorganic composite films generally increased with increasing mineral filler loading. Meanwhile, the presence of mineral filler improved the thermal stability of the thin film composites. The highest dielectric constant of 5.75 with 20 vol% filler loading at a frequency of 1 MHz was exhibited by the epoxy/CaCO₃ composite, followed by epoxy/mica and epoxy/silica. Therefore, the epoxy/CaCO₃ composite is the most potential candidate for capacitor application. Moreover, precipitated CaCO₃ provided better tensile properties and slightly improved the dielectric properties compared with mineral CaCO₃.     

Directed Divergent Evolution of a Thermostable D‐Tagatose Epimerase towards Improved Activity for Two Hexose Substrates

Functional promiscuity of enzymes can often be harnessed as the starting point for the directed evolution of novel biocatalysts. Here we describe the divergent morphing of an engineered thermostable variant (Var8) of a promiscuous D ‐tagatose epimerase (DTE) into two efficient catalysts for the C3 epimerization of D ‐fructose to D ‐psicose and of L ‐sorbose to L ‐tagatose. Iterative single‐site randomization and screening of 48 residues in the first and second shells around the substrate‐binding site of Var8 yielded the eight‐site mutant IDF8 (ninefold improved k_cat for the epimerization of D ‐fructose) and the six‐site mutant ILS6 (14‐fold improved epimerization of L ‐sorbose), compared to Var8. Structure analysis of IDF8 revealed a charged patch at the entrance of its active site; this presumably facilitates entry of the polar substrate. The improvement in catalytic activity of variant ILS6 is thought to relate to subtle changes in the hydration of the bound substrate. The structures can now be used to select additional sites for further directed evolution of the ketohexose epimerase.     

Stress redistribution and ground arch development during tunneling

Three-dimensional stress adjustment caused by tunneling is related with ground arching development. Investigating the development of ground arching by stress redistribution during tunneling is presented. A three-dimensional numerical simulation model was developed to gain understanding of adjustment of tunneling stress. Vertical stress adjustments σ_ZZ above the tunnel roof during tunneling are analyzed, using four different cover depths H and four lateral pressure coefficients K. Shift of the inflection points of σ_ZZ-depth curves above the tunnel roof during tunneling can be a reliable index to show the development of ground arching.     

Compatibility of phospholipid liposomal spray with silicone hydrogel contact lens wear

Purpose

To assess the effects of two weeks of regular phospholipid liposomal spray application on lipid layer grade, tear film stability, subjective comfort, visual acuity, and lipid deposition in silicone hydrogel contact lens wearers.

Rheological study of crosslinking and gelation in bismaleimide/cyanate ester interpenetrating polymer network

In searching for high performance polymer resins that have a combination of low dielectric constant and loss, high temperature resistance, ease of being processed, and other desirable properties, an interpenetrating polymer network (IPN) based on cyanate ester (CE) and 2,2′‐diallylbisphenol A (DBA) modified bismaleimide resin (BMI) was prepared via prepolymerization followed by thermal curing. This work discusses the use of multiple waveform rheological technique to investigate the crosslinking and gelation behavior of this resin system at various temperatures. The gel point can be accurately determined from a single experiment using this technique. At the point of gelation, both the storage modulus (G′) and loss modulus (G″) of the IPN follow a similar power law equation with oscillation frequency used in the rheological measurement. Both the relaxation exponent n, a viscoelastic parameter related to the cluster size of the gel, and gel strength S, related to the mobility of the crosslinked chain segments, were determined via a curve fitting method. Both n and S were found to be temperature dependent in this BMI/DBA–CE IPN system. The apparent activation energy of gelation or curing reaction was found to be approximately 47.6 kJ/mol. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2437–2445, 2001     

Pre‐Vulcanization of Large and Small Natural Rubber Latex Particles: Film‐Forming Behavior and Mechanical Properties

The pre‐vulcanized large rubber particle (LRP) and small rubber particle (SRP) latices are independently prepared to investigate their film‐forming process and mechanical properties after being cast into films. The surface morphologies and roughness of both LRP and SRP films are found to be dependent on crosslink densities. The networks inside each rubber particle (RP) restrict particle deformation resulting in residual contour of RP within the film surface. For highly crosslinked RP, the collapse of the top surface of the RPs in the LRP films appears to create many “crater‐like” structures within the film surfaces, while they present only protruding particles within the SRP and blend films. This seems to indicate that LRPs are easier to coalesce and form film than SRPs. Additionally, dynamic and mechanical properties and strain‐induced crystallization (SIC) behaviors of the latex films, are effectively enhanced after pre‐vulcanization. The pre‐vulcanized LRP films perform better tensile properties and SIC than the SRP can.     

Effects of NanoTag Markers in Palm Methyl Esters and Their Blends with Petroleum Diesel

Given the critical need to address smuggling and unauthorised usage of subsidised diesel, the Malaysia Government introduced fuel marking for subsidised diesel under the NanoTag Program in April 2006. NanoTag markers mixture consists of VisioTag (dye) and NanoTag (immunoassay marker) were spiked into palm methyl esters (PME) and its diesel blends. The blending ratio tested was 5, 10 and 20% (by volume) of fatty acid methyl esters (FAME) in diesel fuel. Both NanoTag and VisioTag markers were found to be stable in PME and blended fuel after 9 months of storage. The concentration of the NanoTag marker (MTK-021) remains consistent as determined by HPLC–UV detector. No colour change or discolouration was observed for the VisioTag marker. Other important fuel quality parameters such as acid value, oxidative stability, and moisture content of the samples were studied. The results showed that NanoTag markers pose no significant measurable effects on blended PME and diesel fuel quality upon storage up to B20.