Structure and viscoelastic properties of epoxy resins prepared from four-nuclei novolacs

The relation between the structure and the viscoelastic properties of seven kinds of epoxy resins was studied. Seven tetraglycidylethers were synthesized from four-nuclei novolacs in which the positions of methylene linkage or number of kind of substituents were different. These epoxy compounds were cured with diaminodiphenylmethane as a hardener. From the viscoelastic properties of the fully cured resins with the hardener, characteristic properties such as glass transition temperature (T_g), average molecular weight between crosslinking points (M̄_c), and front factor (ϕ) were obtained. It was concluded that higher linearity in the main chain of epoxy resins gave a cured resin with a higher T_g, a smaller M̄_c, and a larger ϕ.     

ARCOR,a new photolithography technique with antireflective coating on resist

The multiple interference effect is one of the major causes of the fluctuation in critical dimension control (CD) and in mark detection for alignment. Suppressing this effect is critical for future photolithography. We propose a new photolithography technique called anti reflective coating on resist (ARCOR), which improves linewidth accuracy and overlay accuracy by suppressing multiple interference. ARCOR consists of relatively simple processes: A clear antireflective film is spun onto the resist prior to the mark detecting for alignment and exposure. The film is subsequently removed and the resist developed in the conventional way. ARCOR differs from ARC, which suppresses the reflection at the resist/substrate interface. ARCOR suppresses the reflection at the air/resist interface. ARCOR allows mark detection and exposure without light intensity-loss and multiple interference. The experiments mainly examine polysiloxane and perfluoroalkylpolyether as ARCOR materials. It is shown that linewidth accuracy can be improved from 0.3 to 0.03 μm. The signal-to-noise ratio of the alignment signal is drastically improved, and the overlay error is about half that of the conventional method. ARCOR is also effective for directly measuring the reflectivity at the resist/substrate interface, which is a key parameter of the multiple interference effect and the halation. Using ARCOR and a thin resist film, the measured ratio of reflected light to incident light indicates the reflectivity at the resist/substrate interface. Because, the probe light does not reflect off the resist surface and the intensity-loss at the resist surface is suppressed. With perfluoroalkylpolyether film, the measurement error is ～ 1.5%.     

Ceramic fibres from polymer precursor containing Si-O-Ti bonds

Polycarbosilanes containing titanium alkoxide as pendant groups (atom ratio Ti/Si = 0.07 and 0.15) were synthesized. These polymers were melt-spun and then heat-treated in a vacuum, in oxygen or ammonia gas flow, resulting in Si-Ti-C-O, Si-Ti-0 and Si-Ti-O-N fibres, respectively. The pyrolysis process of the polymer is discussed in connection with the mechanical properties and the structure of the fibre. At high heat-treatment temperatures, -SiC and TiC (in Si-Ti-C-O fibre), anatase (in Si-Ti-O fibre) and TiN (in Si-Ti-O-N fibre) crystallized, which may be closely related to the decomposition of the Si-O-Ti bond in the fibre.     

Mechanical strengthening of Si cantilever by chemical KOH etching and its surface analysis by TEM and AFM

Mechanical strengthening of a Si cantilever by applying KOH wet etching was investigated. Two kinds of Si cantilever specimens having the different crystallographic orientations of the sidewall surfaces, i.e., Si{100} and Si{110}, were fabricated from the same SOI wafer by a Bosch process. The typical height and pitch of the scalloping formed on the sidewall were 248 and 917 nm, respectively. A 50 % KOH (40 °C) chemical wet etching was applied to increase the fracture stress of the Si cantilever. The fracture stress in the both of Si{100} and Si{110} cantilevers increased with the advance of the etching. The obtained maximum fracture stress in Si{100} and Si{110} were 4.2 and 3.7 GPa, respectively. Sidewall surface of the cantilever was analyzed to investigate the mechanical strengthening of Si cantilever by wet etching. The etched surface crystalline was analyzed by the transmission electron microscope (TEM), and confirmed that the thickness of the affected flow layer was less than 10 nm from the obtained TEM image. Then the change of the surface roughness by the KOH etching was analyzed by the atomic force microscope. The surface was smoothened with the advance of the KOH etching. The roughness value of Ra in Si{100} and Si{110} decreased to 12.1 and 37.7 nm, respectively.     

Analysis of electro‐optical properties of polymer‐stabilized OCB and the application to TFT‐LCDs

Abstract— A 9‐in. full‐color polymer‐stabilized OCB TFT‐LCD with stable bend alignment in the absence of an electric field was developed. The condition of the polymer stabilization, the characteristics of UV‐curable monomers, and their influence on the configurations of the polymer network in the cell were studied. Possible models of the configuration were proposed and their relationship to the electro‐optical properties was analyzed using a novel simulation method considering the distribution of anchoring effects from both alignment surfaces and the polymer network. It was suggested that a good performance such as high contrast ratio and fast response could be expected in the polymer network originating from newly developed monomers composed of multifunctional LC acrylates due to a relatively weak‐anchoring effect and presumably its localization near the alignment surfaces. By using the newly developed monomers under the optimized polymer‐stabilizing process, a high contrast ratio of 250:1 and fast response nearly equal to that of a conventional OCB cell were achieved.     

Methanation of carbon deposited directly from CO2 on rhodium-bearing activated magnetite

Methanation reactivity was studied for the surface carbon deposited from CO₂ on the surface of Rh-bearing activated magnetite. The most active material (Rh=0.83 wt %) for methanation was prepared by the impregnation method at 60°C and showed 98% conversion at 300°C. The surface carbon was composed of elemental carbon (-carbon) and polymerized carbon (-carbon), the proportion being dependent on the density of carbon deposited. In temperature-programmed surface reaction, the extent of conversion of the - and -carbon to CH₄ was 0.34 (-carbon) and 0.53 (-carbon), respectively, and the total conversion was 0.87. This result indicates that not only elemental carbon but polymerized carbon (-carbon) could be converted to CH₄ on the Rh-bearing activated (-carbon) magnetite, whereas -carbon is not hydrogenated on activated magnetite.     

Characterization of the Advanced Satellite for Cosmology and Astrophysics x-ray telescope: preflight calibration and ray tracing

The x-ray properties of multinested thin-foil mirror x-ray telescopes (XRT's) on board ASCA, the Advanced Satellite for Cosmology and Astrophysics, were fully evaluated with an x-ray pencil beam.Scanning over the telescope aperture of 35 cm in diameter with an x-ray pencil beam, we found the effective area of a set of XRT's to be 325, 200, and 113 cm(2) at energies of 1.5, 4.5, and 8.0 keV, respectively. We derive the point-spread functions (PSF's) of the XRT's by measuring the image profile at the focal plane with an x-ray CCD. The PSF is found to exhibit a sharp core concentrated within 30 arcsec and a broad wing extended to 3 arcmin in half-power diameter. We also evaluate the contribution of stray light, which is caused by the single reflection of x rays by primary or secondary mirrors and by the backside reflection of the mirrors. To obtain the characteristics of the XRT in the energy region of 0.5-10.0 keV, incorporated with the measurements at discrete energies, we develop a ray-tracing method with the telescope design parameter, the PSF, and optical constants. In particular, we obtain the optical constants around the gold-atom M shell (Au-M) absorption-edge energies by measuring the reflectivity of our mirror sample, with monochromatized x-rays in the energy range of 2.0-3.5 keV from synchrotron radiation. Taking into account the PSF's and optical constants, we find that our ray-tracing program can reproduce all these XRT performances.     

The cluster of arachnoid diverticula in the occipital bone: report of two cases with literature review

The authors report two cases of multicentric osteolytic lesions in the occipital bone without any history of head trauma. The excisional biopsy of the first case revealed that the lesion was multicentric but a continuous cavity with the subarachnoid space through various sizes of dural defect, and the cavities were covered by arachnoid lining. Together with the previously reported similar 5 cases, the characteristic common feature is multicentric osteolytic lesions in the occipital bone at advanced age without marginal sclerosis. "The cluster of arachnoid diverticula in the occipital bone (CADOB)" is probably the most appropriate term for these non-traumatic lesions with the following characteristics: elderly patients, occipital bone, midline, multiple, intact outer table, nonsclerotic margin and without history of trauma. Operation may not be indicated because of its non-progressive and benign nature.     

Effect of poly(acrylic acid) on the preparation of thick silica films by electrophoretic sol–gel deposition of re-dispersed silica particles

Thick silica films were prepared by the electrophoretic sol–gel deposition technique in the presence of poly(acrylic acid) (PAA) using monodispersed silica particles; the particles were prepared by the sol–gel method, pre-heat treated and then re-dispersed in the mixture of H2O and ethanol. The weight of deposited silica films was maximized when 0.2 mass % of PAA against the whole amount of sol was added. The particles constructing the thick silica films were packed densely when the amount of added PAA was less than 0.2 mass%. The weight of the film increased with decrease in the content of H2O in the sol when a fixed amount of PAA was added. After the heat treatment of deposited films at 800 °C, crack-free silica films of about 30 m thickness were prepared. © 1998 Chapman & Hall     

Reduction of false positives in lung nodule detection using a two-level neural classification

The authors have developed a neural-digital computer-aided diagnosis system, based on a parameterized two-level convolution neural network (CNN) architecture and on a special multilabel output encoding procedure. The developed architecture was trained, tested, and evaluated specifically on the problem of diagnosis of lung cancer nodules found on digitized chest radiographs. The system performs automatic "suspect" localization, feature extraction, and diagnosis of a particular pattern-class aimed at a high degree of "true-positive fraction" detection and low "false-positive fraction" detection. In this paper, the authors aim at the presentation of the two-level neural classification method in reducing false-positives in their system. They employed receiver operating characteristics (ROC) method with the area under the ROC curve (A(z)) as the performance index to evaluate all the simulation results. The two-level CNN showed superior performance (A(z)=0.93) to the single-level CNN (A(z)=0.85). The proposed two-level CNN architecture is proven to be promising and to be extensible, problem-independent, and therefore, applicable to other medical or difficult diagnostic tasks in two-dimensional (2-D) image environments.