Effect of high-temperature neutron irradiation on the crystallites of graphite materials

Changes in crystal lattice parameter, c-axis lattice strain and apparent crystallite height induced by neutron irradiation at 720–1350°C were investigated by means of X-ray diffraction for fourteen specimens which included five bands of nuclear graphite and two kinds of pyrolytic graphite. All irradiated materials show a marked increase in c-axis lattice strain, while changes in the lattice parameters are very small. The relation between lattice strain and layer spacing was analyzed for pre- and post-irradiated graphites, and it is inferred that, whereas the predominant constituent of strain in the unirradiated graphite is the statistical fluctuation in distribution of layer spacings, for the irradiated material it is the distortion of layer planes. On the basis of the relation between c-axis lattice strain and apparent crystallite height, the stacking height of graphite layer planes is estimated to be about 70 Å for pre-irradiated graphite.     

Microstructure Characterization of Gas-Pressure-Sintered β-Silicon Nitride Containing Large β-Silicon Nitride Seeds

Fine β-Si₃N₄ powders with or without the addition of 5 wt% of large β-Si₃N₄ particles (seeds) were gas-pressure sintered at 1900°C for 4 h using Y₂O₃ and Al₂O₃ as sintering aids. The microstructures were examined on polished and plasmaetched surfaces. These materials had a microstructure of in situ composites with similar small matrix grains and different elongated grains. The elongated grains in the materials with seeds had a larger diameter and a smaller aspect ratio than those in the materials without seeds. A core/rim structure was observed in the elongated grains; the core was pure β-Si₃N₄ and the rim was β-SiAION. These results show that the large β-Si₃N₄ particles acted as seeds for abnormal grain growth and the rim was formed by precipitation from the liquid containing aluminum.     

High-Temperature Phase Transition of Y4Al2O9

Reversible thermal phase transition was observed for Y₄Al₂O₉ at 1377°C with a hysteresis width of 78°C using differential scanning calorimetry. The enthalpy of the transition (Δ H ) was about 300 cal/mol. Powder X-ray diffraction peaks of the high-temperature phase, as well as the peaks of the low-temperature phase, were characterized with a monoclinic unit cell. Thermal hysteresis was also confirmed by the temperature dependence of the lattice parameter. The unit cell volume of the high-temperature phase was 0.5% smaller than that of the low-temperature phase at 1400°C.     

Predictors for the massive thrombi occurring in the right coronary artery related to acute myocardial infarction

Acute myocardial infarction (AMI) related to the right coronary artery (RCA) is associated with a lower reperfusion rate and higher reocclusion rate in the acute phase than AMI related to the left coronary artery. The greater susceptibility of the RCA to development of large thrombi makes successful reperfusion more difficult to achieve. This study investigated predictive factors for massive thrombus in the RCA before the selection of the treatment to achieve better rates of reperfusion. We classified 51 patients with AMI related to RCA into the massive (linear intraluminal radiolucency > 3 cm) thrombus group (9 patients) and the non-massive thrombus group (42 patients). 1) History: Patients in the massive thrombus group had a greater incidence of hypertension than the non-massive thrombus group, with more left ventricular hypertrophy (p < 0.05). There were no significant differences in other coronary risk factors. 2) RCA morphology: The maximum RCA diameter was significantly greater in the massive thrombus group than that in the non-massive thrombus group [proximal to the right ventricular branch, 4.2 vs 3.2 mm (median); distal to the right ventricular branch, 4.2 vs 3.4 mm, p < 0.05]. 3) Conditions of onset: The elapsed time was significantly longer in the massive thrombus group (15 hours) than that in the non-massive thrombus group (2.5 hours, p < 0.05). More massive thrombus cases were observed in summer (p < 0.05), but there was no evident correlation between massive thrombus formation and the onset time of day, weather, Hct and coagulation factor at the onset, left ventricular ejection fraction or left ventricular end-diastolic pressure.(ABSTRACT TRUNCATED AT 250 WORDS)     

Rapid isolation of cell-type-specific protein tyrosine kinases by degenerate polymerase chain reaction combined with differential hybridization technique

To identify protein tyrosine kinase (PTK) genes preferentially expressed in renal cell carcinoma cell line, we screened a PTK-cDNA-enriched library constructed from RNA of an renal cell carcinoma cell line with a PTK probe, each produced from renal cell carcinoma, gastric cancer or esophageal cancer cell lines by degenerate polymerase chain reaction. Two cDNA fragments of PTK genes, FRK and FLT-3, were isolated from the PTK-cDNA-enriched library of the renal cell carcinoma cell line by differential hybridization technique. The FRK cDNA clone represented 15.8% of the PTK-cDNA-enriched library from the renal cell carcinoma cell line, while the FLT-3 cDNA clone was 2.8% of the same library. Both of the two PTK genes were expressed preferentially in renal cell carcinoma cell lines. This method, described here, is useful for the rapid isolation of PTK cDNA fragments, including a low abundant cDNA, preferentially expressed in a specific cell line.     

Process integration of single-wafer technology in a 300-mm fab, realizing drastic cycle time reduction with high yield and excellent reliability

In this paper, we discuss a new technology implemented with single-wafer processing for a 300-mm fab. Newly developed equipment and chemicals reduce the process time and provide cost savings. The combination of fully automated systems and single-wafer processing significantly reduces queuing time. The process has been re-integrated to eliminate long time processes and make it suitable for single-wafer technologies. As a result, a very aggressive cycle time (0.25 days/layer) with high yield, in double-polysilicon, sextuple-metal, 0.18-/spl mu/m logic process has been demonstrated. High-performance devices with excellent reliability are also obtained. A new methodology for detecting parametric errors effectively in the early stages of production is implemented for quick yield ramp up.     

Fine yellow α-SiAlON:Eu phosphors for white LEDs prepared by the gas-reduction–nitridation method

Yellow-emitting α-SiAlON:Eu²⁺ phosphors were synthesized by the gas reduction and nitridation of a homogeneous oxide precursor in a CaO–Al₂O₃–SiO₂–Eu₂O₃ system at 1400–1450 °C using an NH₃–CH₄ mixture gas as a reduction–nitridation agent. The precursor was prepared by a sol–gel process using a low-cost nitrate, tetraethyl orthosilicate and citric acid as the starting materials. The effects of reaction parameters such as heating rate, temperature, holding time and CH₄ content on the composition, microstructure and photoluminescence of the prepared powders were investigated. Nearly single-phase α-SiAlON was successfully synthesized by the one-step gas reduction and nitridation without the need for post-annealing at a higher temperature. The prepared powders consisted of relatively well-dispersed and uniform crystals with a hexagonal shape. The photoluminescence spectra of Eu-doped Ca-α-SiAlON phosphors excited by near-ultraviolet or blue light showed a broad, yellow emission band at 500–700 nm, which agrees well with that obtained from phosphors prepared by the conventional solid-state reaction.     

Involvement of p53 gene mutations in human endometrial carcinomas

Mutations in the p53 gene are associated with a wide variety of human malignancies. Point mutation in one allele and loss of the remaining one generally lead to inactivation of p53 protein. A high frequency of allelic losses corresponding to the 17p13.3 region that contained the p53 gene sequence was also noted in human endometrial carcinoma. Thus, in order to confirm involvement of the p53 gene in endometrial carcinogenesis, we searched for nucleotide sequence change in this gene in 42 endometrial carcinomas that had been subjected to previous LOH analyses. Using the polymerase-chain-reaction-single-strand conformation polymorphism (PCR-SSCP) method, we detected p53 gene mutations in 4 specimens. Two adenocarcinomas with allelic loss on 17p contained a mutant p53 gene in the allele that was retained. One specimen with a p53 gene mutation contained a 17q deletion but was uninformative for LOH on 17p. p53 gene mutation was also noted in the remaining stage-I carcinoma, though the 17p deletion was not detected in the previous LOH examination. However, 5 specimens with the LOH on 17p retained the wild-type p53 gene. In the remaining 33 specimens, both alleles of p53 gene seemed to be normal. The mutations observed in 2 specimens (cases 10 and 24), involving C-to-T and T-to-G substitutions, were located in a highly conserved region. However, the mutations identified in the remaining 2 cases (29 and 35) were at regions positioned outside conserved stretches.     

A synchronous digital hierarchy network management system

The critical issues in multivendor environments and operation systems of telecommunication networks essential to speeding up the handling of service orders and service restoration after failures are discussed. To overcome these problems as the software backlog grows, the authors propose the application of a telecommunications management network (TMN) architecture together with an object-oriented network resource (ONR) model. The second phase of the synchronous digital hierarchy (SDH) network management system, which is based on the TMN architecture and ONR model, is examined