Direct growth of CdTe on (100), (211), and (111) Si by metalorganic chemical vapor deposition

CdTe epilayers were grown directly on (100), (211), and (111) silicon substrates by metalorganic chemical vapor deposition (MOCVD). The crystallinity and the growth orientation of the CdTe film were dependent on the surface treatment of the Si substrate. The surface treatment consisted of exposure of the Si surface to diethyltelluride (DETe) at temperatures over 600°C prior to CdTe growth. Direct growth of CdTe on (100) Si produced polycrystalline films whereas (lll)B single crystals grew when Si was exposed to DETe prior to CdTe growth. On (211) Si, single crystal films with (133)A orientation was obtained when grown directly; but produced films with (211)A orientation when the Si surface was exposed to DETe. On the other hand, only (lll)A CdTe films were possible on (111) Si, both with and without Te source exposure, although twinning was increased after exposure. The results indicate that the exposure to a Te-source changes the initial growth stage significantly, except for the growth on (111) Si. We propose a model in which a Te atom replaces a Si atom that is bound to two Si atoms.     

Biodegradation of glutaraldehyde-tanned human umbilical vein grafts

A retrospective analysis of the long-term behavior of 111 glutaraldehyde-tanned human umbilical vein (HUV) grafts implanted between September 1977 and December 1993 was conducted. A total of 81 patients, with a mean age of 68.7 years, received the grafts and were followed up for between 1 and 131 months. The 5-year primary cumulative patency rate for above-knee femoropopliteal bypass was 83.1%, whereas that of other bypasses was 60.9%. An aneurysm of the graft was defined as a physically apparent localized dilatation, with diffuse ectasia being excluded. There were 11 aneurysms found in 9 grafts, 2 of which arose at the factory-made suture lines. The accumulated incidence of aneurysms had reached 21.9% by the 6th year. One aneurysm compressed the graft and resulted in limb-threatening ischemia and another resulted in frank rupture. Moreover, reinforcement of the mesh could not prevent aneurysm development, the repair of which is mandatory due to the risk of rupture and acute thrombosis. The HUV grafts showed an acceptable patency rate in the above-knee location, but the incidence of aneurysm formation after 5 years was abnormally high. Thus, both the risks and benefits of HUV grafts must be taken into account when considering their clinical application.     

Eight-channel flat spectral response arrayed-waveguide multiplexer with asymmetrical Mach-Zehnder filters

An eight-channel flat spectral response arrayed-waveguide grating (AWG) multiplexer with asymmetrical Mach-Zehnder filters has been fabricated on the planar lightwave circuit (PLC). The monotonic spectral loss characteristics of AWG have been canceled by the opposite spectral response in the asymmetric MZ filter. The 1.5 dB bandwidth of 141 GHz and 3 dB bandwidth of 159 GHz are obtained for the 200 GHz channel spacing. The 1.5 dB bandwidth becomes 1.8 times wider than that of the conventional AWG. Crosstalks to neighboring and all other channels are less than -24 dB and the on-chip insertion losses range from 7.0 to 7.4 dB, respectively.     

Clinicopathological study of incidental renal cell carcinoma

BACKGROUND: The objective of this study is to evaluate the clinicopathological features of incidental renal cell carcinoma, compared with non-incidental carcinoma. METHODS: Between July 1st, 1984 and June 30, 1994, 87 renal cell carcinoma patients were treated at our hospital; 56 had non-incidental renal cell carcinoma and 31 had incidental carcinoma. The clinicopathological features were examined. RESULTS: The incidence of incidental cancer ranges from 0 to 66%, and the incidence has increased in recent years. The median value of maximal tumor size was 4.0cm (1.5 approximately 8.0cm) for incidental cancer, and 8.0cm (3.0 approximately 16cm) for incidental cancer, and 8.0cm (3.0 approximately 16cm) for non-incidental cancer, i.e., the incidental cancer was significantly smaller than the non-incidental one (p < 0.001). The pathological stage of the resected non-incidental renal cell carcinoma (n = 47) was pT1, pT2, pT3 and pT4 in 0, 23, 21 and 3 patients, respectively. For the resected incidental renal cell carcinoma (n = 31) 3, 26, 2 and 0 patients showed pathological stages pT1, pT2, pT3 and pT4, respectively; the pathological stage of incidental renal cell carcinoma was significantly lower than that of non-incidental carcinoma (p < 0.001). Eighteen and 29 resected non-incidental renal cell carcinoma were grades 1 and 2, respectively, whereas 17 and 14 resected incidental renal cell carcinomas were in grades 1 and 2, respectively. Vascular invasion by tumor cells was shown in 31 (66.0%) and 8 (25.8%) patients with non-incidental and incidental renal cell carcinomas, respectively; the incidence of vascular invasion in incidental cancer being significantly lower than in non-incidental cancer (p < 0.001). The performance status and general condition in patients with incidental renal cell carcinoma were superior to those in patients with the non-incidental cancer. The 1, 3 and 5-year survival rate of all 87 renal cell carcinoma patients was 81, 62 and 57%, respectively. These rates for patients with non-incidental renal cell carcinoma were 72, 48 and 41%, respectively, and those for incidental cancer patients were 100%. The survival of patients with incidental renal cell carcinoma was significantly better than that of non-incidental carcinoma patients (p < 0.005). CONCLUSION: Our results suggest that the detection of incidental renal cell carcinoma will increase, and that the prognosis for renal cell carcinoma will improve. However, even in incidental renal cell carcinoma, careful long-term follow up may be necessary, since some tumors are comparatively large and exhibit vascular invasion.     

Dispersion of ZrO2 particles in aqueous suspensions by ammonium polyacrylate

The effects of poly anionic-electrolyte (ammonium polyacrylate, PAA) as a dispersant on two kinds of ZrO₂ (monoclinic and yttria-doped tetragonal zirconia) aqueous suspensions were examined by the measurements of-potential and viscosity, the sedimentation test and the determination of the wet point and flow point of the powders. Additions above 2.5 wt% PAA to zirconia gave a negative high-potential above –30 mV, and then –45 and –30 mV were obtained for monoclinic and tetragonal zirconia above 5 wt% PAA, respectively. A high negative-potential above –30 mV was retained with 5 wt% PAA for a change in pH over a wider range (pH 6 to 10 for monoclinic ZrO₂, 7 to 9 for tetragonal ZrO₂) in comparison to that of ZrO₂ without dispersant. The increase of the-potential resulted in a decrease in the viscosity. The evaluation of dispersion by the sedimentation test was correlated well with the value of-potential and the viscosity of the suspensions. The presence of native positive charge of monoclinic and tetragonal zirconia powders required an excess amount of PAA to attain dispersion of the suspension. There was a small difference in the least amount of PAA required to attain good dispersion between monoclinic and tetragonal ZrO₂. The difference was also indicated by changes of the flow point on PAA addition. Addition of 0.1% PAA to monoclinic ZrO₂ and 0.25 wt% to tetragonal ZrO₂ gave a maximum value of the flow point, whereas the positive-potential fell to zero. Measurement of the flow point was a simple and useful technique for rapid evaluation of a required amount of dispersant for ZrO₂ suspensions.     

Laser spectroscopic measurement of quenching and doublet mixing rates of the Na(3P(3/2, 1/2)) doublet in a propane-air flame

We have measured the quenching rate of the Na 3P level and the doublet mixing rates of the Na 3P(3/2) and 3P(1/2) levels in a propane-air flame at atmospheric pressure. To obtain these rates, subnanosecond time-resolved fluorescence measurements were made using a mode-locked dye laser and the time-correlated single-photon counting method. Our results are 1.4 x 10(9) s(-1) for the quenching rate and 3.0 x 10(9) s(-1) for the 3P(3/2) --> 3P(1/2) mixing rate.