Effects of additives on sintering of CVD-MgO powders

The effects of a large number of sintering aids for the densification of magnesia were examined. Al₂O₃, BaO, Fe₂O₃, P₂O₅, SiO₂, TiO₂, Y₂O₃ and ZrO₂ are effective for the sintering of CVD-MgO powders at low doping levels. The effects of TiO₂ and ZrO₂ are significant. Heavy doping is harmful for densification. The eight oxides above are also effective for the sintering of seawater MgO, but the degree of effectiveness is smaller than for CVD-MgO. In the doping of BaO, P₂O₅, SiO₂ and TiO₂, which form eutectic liquids with MgO below 1600°C, there is an optimum firing temperature for densification.

Vickers hardness of doped MgO is proportional to the relative density and is unaffected by doping. Corrosion resistance of MgO ceramics for liquid PbO is also unaffected by dopants, except for P₂O₅.     

自组织InAs/GaAs量子点的表面氮化研究

用低温光荧光(PL)和透射电子显微镜(TEM)研究了表面氮化自组织InAs/GaAs量子点的光学性能和微观结构。结果表明氮化后形成薄层的InAsN薄膜作为应变缓和层覆盖在量子点的表面,使得随着氮化时间的增加,InAs量子点的位错密度提高、尺寸变大、纵横比提高、发光波长变长、强度变低。     

Expression of apolipoprotein E in normal and diverse neurodegenerative disease brain

Brains from 21 patients with Alzheimer's disease (AD), nine with diffuse Lewy body disease (DLBD), six with progressive supranuclear palsy (PSP) and five with Parkinson's disease (PD) as well as 20 normal subjects were examined to detect apolipoprotein E (ApoE) by immunohistochemistry and immunoblotting. ApoE antigenicity was optimally preserved in Bouin-fixed tissues compared with those fixed in neutral-buffered formalin, 70% ethanol or denatured by microwave energy. ApoE immunoreactivity was prominent in senile plaques and in intra- and extra-neuronal tangles, as well as in a diverse neurones and their processes and astroglial cells. Notably, tangles in PSP and Lewy bodies in PD and DLBD were both devoid of ApoE immunoreactivity. Western blots of cerebral cortex revealed an immunoreactive ApoE band with mol. wt of 34 kDa. Our results suggest that ApoE is not a crucial factor in the development of neuronal inclusions in DLBD, PSP and PD.     

Effects of oxygen content of porous titanium metal on its apatite-forming ability and compressive strength

Porous titanium metal subjected to NaOH and heat treatments is useful as a bone substitute as it shows high mechanical strength as well as osteoconductivity and osteoinductivity. However, the porous metal is liable to be contaminated with oxygen gas during the fabrication process and this incorporated oxygen could lead to adverse effects on the bioactivity and mechanical properties of the prepared porous body. In this study, oxygen contamination during fabrication of bioactive porous bodies was measured. It was found that the oxygen content of the titanium metal was increased from 0.08 to 0.23 mass% when the porous body was prepared from bar stock, and it further increased up to 0.51 mass% when it was subjected to NaOH and heat treatments. Despite this, the porous bodies subjected to NaOH and heat treatments formed apatite on their pore walls within 1 day in a simulated body fluid. This result was consistent with the apatite-forming ability of NaOH- and heat-treated titanium plates with different oxygen contents in the range of 0.05 to 0.30 mass%. The compressive strength of the porous body was increased about 10% by the NaOH and heat treatments.     

Physical-chemical composition of in natura goat milk from cross Saanen throughout lactation period

The analyzed milk samples were collected from cross Saanen goats of different ages and different cross breeding types, throughout the lactation period, from September 1996 to December 1997. For the physical-chemical characteristics measured in this experiment, the following average values were obtained, followed by their respective standard deviations: pH (6.69 +/- 0.20); acidity (12.96 +/- 3.64 degrees D); density (1.030 +/- 0.009 mg.cm-3); fat (3.83 +/- 1.04%); crude protein (3.34 +/- 0.73%) and total solids (12.25 +/- 1.94 g.100 g-1). The lactation period influenced the values of acidity, fat, crude protein and total solids; these values decreased during the initial months and increased at the end of the lactation. The correlations were analyzed among the studied characteristics during the lactation, resulting in positive (p < 0.05) acidity/density correlation (r = 0.2115), stand out also the positive correlations (p < 0.01) among fat/total solids (r = 0.7715) and crude protein/total solids (r = 0.6228).     

Full-photonic-bandgap structures for prospective dye-sensitized solar cells

The photonic bands of various TiO₂ photonic crystals filled with acetonitrile were investigated with the perspective for application to dye-sensitized solar cells. Finite-difference time-domain methods revealed that three-dimensional (3D) photonic crystals with diamond-log and inverse-diamond-log structures composed of TiO₂ and an electrolyte had full photonic band gaps under certain conditions. The quality factor of the band gap and the electrolyte filling factor of the structures were optimized. Moreover, with the consideration for easy fabrication of such photonic crystals, two-dimensional (2D) photonic crystals, i.e., TiO₂ slabs with square holes filled with electrolytes, were also investigated. Two-dimensional structures that have a full photonic band gap were also discovered. These discoveries may lead to early electrochemical applications of dye-sensitized photonic-crystal electrodes.     

A facile approach to the fabrication of ultrathin polymer films and application to optical lenses

A facile approach to the fabrication of ultrathin polymer films on a flat or curved substrate is presented. Polymers with unsaturated pendant groups were spin-coated on a photoinitiator tethered surface, which was then photoirradiated and washed with a solvent. The obtained films were uniform, smooth (R_a < 0.2 nm) and exhibited robustness toward solvents. The thickness of the films was determined by the molecular weight of the coated polymer and was not dependent on the initial spin-coated thickness. A mechanism for the formation of the ultrathin film and application to optical lenses is presented.     

Fluorous Surface‐Active Distannoxane Catalysts

Fluorous distannoxanes (XR^f₂SnOSnR^f₂X)₂⋅n H₂O (R_f=C₆F₁₃C₂H₄) ( 1 : X=C₈F₁₇SO₃, n=10; 4 : X=Cl, n=0) ( 1 ) catalyze the Mukaiyama aldol reaction and the allylation of aldehydes with tetraallyltin at room temperature in fluorous/organic biphasic solvent systems, in which the reactions proceed more rapidly than in a single organic or fluorous solvent. Due to the unique surface activity of 1 , the catalyst, organic substrate(s), and reagent(s) are distributed in both organic and fluorous phases to facilitate smooth reactions. Upon dilution with toluene after the reaction, the catalyst concentrates to the fluorous phase, while the organic substances migrate to the organic phase to effect facile catalyst recovery and recycling. By virtue of such a unique solvophilicity, a new version of fluorous biphase technology has been developed.