Foreign Object Damage Resistance of Silicon Nitride and Silicon Carbide

To clarify the foreign object damage (FOD) resistance of ceramics, chipping fracture mode and flexural fracture mode were investigated using several types of Si₃N₄ and Sic. The critical velocity which is the threshold impact velocity of the projectile for chipping fracture and flexural fracture was determined. The critical velocity of the chipping fracture mode is explained as a function of K ^5/2_IC a ^–5/4, and depends on the hardness and the shape of the projectile. The critical velocity of the flexural fracture mode is explained as a function of σ^5/6_C t ^5/3. The mechanisms of impact damage are discussed.     

Effects of dimethylpyrazine isomers on reproductive and accessory reproductive organs in male rats

Glycosyl-phosphatidylinositol-specific phospholipase D (GPI-PLD) is an amphiphilic protein which, in serum, is associated with high-density lipoproteins (HDL). It is shown that the major component of the HDL fraction, apolipoprotein A-I (apo A-I), is responsible for this association. In the absence of apo A-I, purified GPI-PLD occurred as virtually inactive aggregates which became disaggregated by apo A-I. The enzyme/apo A-I complex efficiently hydrolyzed the solubilized GPI-anchored substrate, acetylcholinesterase. Triton X-100 was also able to dissociate aggregated GPI-PLD, however, it strongly inhibited enzyme activity at detergent concentrations above the critical micellar concentration.     

Carrier transport and structural properties of polysilicon films prepared by layer-by-layer technique

Polycrystalline silicon (poly-Si) films have been deposited on glass substrates by a layer-by-layer technique at very low temperature, 300°C, using fluorinated precursors. The electronic transport was characterized by Hall effect and conductivity measurements over a wide temperature range, 100 K to 400 K. The structure of the materials is a function of the film thickness. The measured Hall mobility increases as the thickness increases. The Hall mobility Arrhenius plot shows linear dependence with a negative slope over the temperature range examined, suggesting that carrier conduction is limited by grain boundary barriers.     

Immunohistochemical localization of nitric oxide synthase in normal human skin: expression of endothelial-type and inducible-type nitric oxide synthase in keratinocytes

Nitric oxide (NO) is a critical mediator of various biological functions. NO is generated from L-arginine by nitric oxide synthase (NOS), which has three isoforms; endothelial-type NOS (eNOS) and brain-type NOS (bNOS) are constitutive enzymes, and inducible-type NOS (iNOS) is expressed after stimulation. We investigated the expression of NOS in normal human skin by an immunohistochemical technique and western blotting analysis. In human skin, epidermal keratinocytes and the outer root sheath were labeled with not only eNOS antibody but also with iNOS antibody. Both eNOS and iNOS protein in epidermal keratinocytes were confirmed by western blotting. eNOS immunoreactivity was observed in endothelial cells, fibroblasts, the arrector pili muscle, apocrine secretory gland, eccrine coiled duct, and eccrine secretory gland. bNOS immunoreactivity was observed in mast cells. No staining with anti-bNOS antibody was observed in any other cell type. Our present findings suggest that epidermal keratinocytes in normal human skin contain both eNOS and iNOS.     

Dissociable contributions of the prefrontal and neocerebellar cortex to time perception

We report a series a three psychophysical experiments designed to differentiate the contributions of the neocerebellar and prefrontal cortex to time perception. Comparison of patients with focal, unilateral neocerebellar or prefrontal lesions on temporal discrimination of 400-ms and 4-s intervals (Expt. 1) indicated that neocerebellar damage impaired timing in both millisecond and seconds ranges, whereas prefrontal damage resulted in deficits that were robust only at the longer duration. Patients with prefrontal lesions, however, also exhibited working memory deficits on a non-temporal task (Expt. 2), biases in point of subjective equality indicative of attentional deficits, and were disproportionately sensitive to strategic manipulations in a long-duration discrimination task (Expt. 3). In contrast, the pervasive timing deficits of cerebellar patients were relatively insensitive to strategic support and could not be readily explained by general deficits in working memory or attention. These findings support the hypothesis that neocerebellar regions subserve a central timing mechanism, whereas the prefrontal cortex subserves supportive functions associated with the acquisition, maintenance, monitoring and organization of temporal representations in working memory. Such functions serve to bridge the output of the central timing mechanism with behavior. Together, these regions appear to participate in a working memory system involved in discrimination of durations extending from a few milliseconds to many seconds.     

A low-noise and broad-band erbium-doped tellurite fiber amplifier with a seamless amplification band in the C- and L-bands

A low-noise broad-band EDFA with a seamless amplification band in both the C- and L-bands is successfully developed by using erbium-doped tellurite fibers. This EDFA exhibits a broad amplification bandwidth of 70.8 nm (from 1532.7 to 1603.5 nm) with a gain excursion of less than 1.5 dB, an average gain of 24.3 dB, and a noise figure of less than 6 dB (less than 5.3 dB for extracting the insertion loss of the input end).     

A three-dimensional MEMS optical switching module having 100 input and 100 output ports

This paper describes an optical switching module based on microelectromechanical systems (MEMS) two-axis tilt mirror arrays and low-cost highly accurate free-space optics. The MEMS mirror arrays are integrated on single-crystal silicon wafers and provide reliable switching operation at a low driving voltage. The free-space optics consists of two-dimensional optical fiber and microlens arrays based on low-cost and highly accurate polymer-based components. They provide a compact switching module (approximately 80/spl times/60/spl times/35 mm [170 cc]) and are assembled passively by using dowel pins. A prototype switch module with 100-ch optical fiber I/O has a low coupling loss of 4.0 dB, a low crosstalk within -60 dB, and switching time of 3 ms.     

High-frequency power transmission and selective distribution among loads by using distributed constant lines

A widely used high-frequency induction heating system usually consists of a high-frequency power source and a load circuit to be heated. Since such a system can heat only one load circuit, heating two or more loads requires that other sytems be devised. Several problems result, including the need for many power sources, switches, and high-frequency power transmission lines. To solve these problems, the authors propose a new system that can selectively supply two induction heating circuits with high-frequency power. This system is composed of a high-frequency voltage-type inverter, a parallel resonant load circuit, and a series resonant load circuit, which are connected in series by distributed constant lines of specific length. Analysis of the operating characteristics of the system confirms that the system can supply the loads with high-frequency power selectively and efficiently, with minimum interference between loads. The authors have compared theoretical simulation waveforms with actual waveforms observed on experimental equipment with output ratings of 1 to 2 MHz and 1 kW. As a result, experimental data agree well with theoretical data. This paper describes an operating principle and operating conditions of the system, and verifies that the theory we discuss is reasonable.     

New insights into the immunoultrastructural organization of cutaneous basement membrane zone molecules

The epidermal basement membrane zone (BMZ) is composed of various molecules, each of which plays an important role in dermo-epidermal adhesion. Genetic abnormality of certain BMZ molecules leads to an inherited group of skin diseases collectively referred to as epidermolysis bullosa, whose hallmark is skin fragility of varying degrees. Furthermore, development of autoantibodies to certain BMZ molecules leads to the onset of a number of acquired autoimmune blistering diseases in which dermo epidermal separation occurs, including bullous pemphigoid and epidermolysis bullosa acquisita. The ultrastructural location of each BMZ molecule has been studied using a range of immunoelectron microscopy (immuno-EM) techniques. Recent technical advances in immuno-EM and in molecular engineering for production of epitope-specific antibodies have enabled a more correct and precise elucidation of the native ultrastructural molecular organization of the respective molecules and their relationship to each other. These recent studies have also revealed several misinterpretations in the previously established model of the immunoultrastructural organization of BMZ molecules. In response to these findings, this review focuses on three major BMZ-related molecules, type VII collagen, BPAG2 and laminin 5, for which recent immuno-EM studies have produced a revision in the accepted dogma on their ultrastructural distribution at the BMZ.     

A new concept of p-(n-)/p-(n ) thin-film epitaxial silicon wafers for MOS ULSI's that ensuresexcellent gate oxide integrity

A new concept of epitaxial silicon (Si) wafers (NC epi) in which p ^-(n^-) thin-film layers are grown on p^-(n^-) Czochralski (CZ)-Si substrates (substrate resistivity: approximately 10 Ω cm) is proposed for metal oxide semiconductor (MOS) ultra large-scale integrated circuits (ULSI's) as a starting material. A thickness of 0.3-1 μm for the epitaxial layer (p ^-/p^- structure) is shown to be sufficient for improving the gate oxide integrity for MOS-ULSI's. The epitaxial layer grown on Si substrate greatly reduces weak spots in the gate oxide layer by covering microdefects in the CZ-Si represented by the crystal originated particle (COP). The p^-/p^$thin-film epitaxial structure results in very controlled resistivity for the electrically active region in the device, which in turn results in a lower growth cost and higher feasibility for use in current ULSI's. The features of NC epi in combination with proximity gettering is presented. An application of NC epi in shallow-trench isolation processes is discussed, considering the retrograde-type well-tub. The amenability of epitaxial wafers to wafer enlargement (over 300 mm) is discussed to eliminate the bad effects of COP