We applied high-resolution laser-scanning microscopy, electron microscopy, and non-radioactive in situ hybridization histochemistry to determine the cellular and intracellular localization of lipocalin-type prostaglandin D synthase, the major brain-derived protein component of cerebrospinal fluid, and its mRNA in leptomeninges, choroid plexus, and parenchyma of the adult rat brain. Both immunoreactivity and mRNA for prostaglandin D synthase were located in arachnoid barrier cells, arachnoid trabecular cells, and arachnoid pia mater cells. Furthermore, meningeal macrophages and perivascular microglial cells, identified by use of ED2 antibody, were immunopositive for prostaglandin D synthase. In the arachnoid trabecular cells, the immunoreactivity for prostaglandin D synthase was located in the nuclear envelope, Golgi apparatus, and secretory vesicles, indicating the active production and secretion of prostaglandin D synthase. In the meningeal macrophages, prostaglandin D synthase was not found around the nucleus but in lysosomes in the cytoplasm, pointing to an uptake of the protein from the cerebrospinal fluid. Furthermore, the existence of meningeal cyclooxygenase (COX) -1 and COX-2 was investigated by Western blot, Northern blot, and reverse transcriptase-polymerase chain reaction (RT-PCR), and the colocalization of COX-2 and prostaglandin D synthase was demonstrated in virtually all cells of the leptomeninges, choroid plexus epithelial cells, and perivascular microglial cells, suggesting that these cells synthesize prostaglandin D(2) actively. Alternatively, oligodendrocytes showed prostaglandin D synthase immunoreactivity without detectable COX-2. The localization of lipocalin-type prostaglandin D synthase in meningeal cells and its colocalization with COX-2 provide evidence for its function as a prostaglandin D(2)-producing enzyme.

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This study evaluated the mechanical properties and piezoresistivity of core–shell silicon carbide nanowires (C/S-SiCNWs) synthesized by a vapor–liquid–solid technique, which are a promising material for harsh environmental micro electromechanical systems (MEMS) applications. The C/S-SiCNWs were composed of a crystalline cubic (3C) SiC core wrapped by an amorphous silicon dioxide (SiOx) shell; however, TEM observations of the NWs showed that hexagonal polytypes (2H, 4H , and 6H) were partially induced in the core by a stacking fault owing to a Shockley partial dislocation. The stress–strain relationship of the C/S-SiCNWs and SiC cores without an SiOx shell was examined using MEMS-based nanotensile tests. The tensile strengths of the C/S-SiCNWs and SiC cores were 7.0 GPa and 22.4 GPa on average, respectively. The lower strength of the C/S-SiCNWs could be attributed to the SiOx shell with the surface roughness as the breaking point. The Young’s modulus of the C/S-SiCNWs was 247.2 GPa on average, whereas that of the SiC cores had a large value with scatter data ranging from 450 to 580 GPa. The geometrical model of the SiC core based on the transmission electron microscopy observations rationalized this scatter data by the volume content of the stacking fault in the core. The piezoresistive effects of the C/S-SiCNW and SiC core were also evaluated from the I–V characteristics under uniaxial tensile strain. The gauge factor of –30.7 at 0.008 ε for the C/S-SiCNW was approximately two-times larger than that of –15.8 at 0.01 ε for the SiC core. This could be caused by an increase of the surface state density at the SiOx/SiC interface owing to the positive fixed oxide charge of the SiOx shell.

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We report the effects of surface damage and crystal orientation on fracture strength of single crystal silicon (SCS) by means of tensile test using electrostatic-force grip. The specimens of three major crystal orientations fabricated from (110) SOI wafer were characterized with different surface morphologies prepared by the specimen patterning process.Our specimen patterning process was composed of Bosch process and wet etching process for surface residue removal.We changed processing time and sequence of the two processes to get different surface morphologies. As result of uni-axial tensile test of 9 types of specimens (length: 120 μm, width: 5 μm, thickness: 5 μm), i.e. specimens of 3 crystal orientations with 3 different surface morphologies, improvement of surface morphology doubled average tensile strength: e.g. <110> strength varied from 1.8 GPa to 3.6 GPa, while average tensile strength difference among crystal orientations was less than 20 % on each fabrication conditions. The fracture surfaces mainly consisted of (111) plane.We found tensile fracture characteristics of 3 crystal orientations: in <100> specimens the fracture origin location changed by the fabrication conditions, while <110> and <111> specimens respectively showed quantitative relationships between surface morphology and tensile strength common to different fabrication conditions. These results are beneficial for tensile strength prediction from surface morphology.

This paper reports development of a high-temperature tensile testing machine and testing of single crystal silicon (SCS) for investigation of the size effect on brittle–ductile transition temperature (BDTT). Two different-width 〈110〉 SCS specimens (120 µm long, 5 µm thick and 4 or 9 µm wide) were tested in a vacuum at the temperature range from room temperature to 600 °C. The specimens tested at 500 °C and above exhibit slip, which indicated that the micrometer-sized silicon structures have lower BDTT compared to millimeter-sized ones. By investigating the temperature ranges of the slip occurrences among the differently-sized specimens including other researchers’ reports, we found that the length along slip direction, i.e., thickness, might dominate the BDTT.

This paper investigates the effect of crystallographic orientation on tensile fractures of silicon microstructures. Specimens 5 μm wide and 5 μm thick were fabricated on (100) and (110) wafers with <100>, <110>, and <111> tensile axes. To explore the effects of different surface orientations and morphologies, these specimens were patterned from (100) and (110) silicon-on-insulator (SOI) wafers using the Bosch process under identical fabrication conditions, while other specimens were fabricated from (110) wafers under different conditions. Tensile tests of specimens prepared under the identical fabrication conditions showed that (100) specimens had lower strength than (110) specimens along <100> and <110> axes; the average strength decreased from 3.62 GPa to 3.14 GPa for <110>. This decrease in strength is related to differences in damage that ultimately causes fractures. While (110) specimens fractured due to fabrication damage at top corners, fractures of (100) specimens were due to pit-like defects on bottom surfaces. Since these defects were introduced during SOI bonding processes, the fractures of (100) specimens were dominated by intrinsic SOI defects rather than damage introduced during specimen fabrication processes. To realize higher-strength structures on SOI wafers, both the damage caused during fabrication and the intrinsic defects need to be controlled.

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