On the initiation of wedge-type cracks at grain-boundary triple junctions during high-temperature creep

The typical grain boundary cracks are often formed at the grain-boundary triple junction as a result of blocking of grain-boundary sliding. However, a theoretical discussion has not fully been made on the nucleation of grain corner cracks at high temperatures where diffusional recovery occurs. In this study, a continuum mechanics model which incorporated the recovery effect by diffusion of atoms has been developed to explain the initiation of wedge-type cracking during high-temperature creep. A good agreement was found between the result of calculation based on this model and experimental results in austenite steels. It was considered that there is a critical creep rate for wedge-type cracking. The model was also applied to the prediction of the rupture life in creep.     

Comprehensive treatment of advanced neuroblastoma involving autologous bone marrow transplant

Encouraging results are reported with high-dose chemotherapy and total body irradiation followed by autologous bone marrow transplantation in the treatment of advanced neuroblastoma. However, relapse remains a significant problem. We used high-dose chemotherapy, surgery, intraoperative radiation and an autologous bone marrow transplant treated in vitro to remove tumor cells followed by 13-cis-retinoic acid to treat 36 children with advanced neuroblastoma. This comprehensive treatment appears to improve the survival rate of patients with advanced neuroblastoma, including those with N-myc amplification and bony involvement. The disease-free survival rate was 66% (95% confidence interval, 49-84%) at 3 years. All patients who received 13-cis-retinoic acid developed cheilitis, but no bone marrow depression occurred in these patients. Five patients developed hemolytic uremic syndrome (HUS) post-transplant. This may have been related to the procedure used for total body irradiation. Patients who had their kidneys shielded during this procedure did not develop this syndrome. Patients who received local irradiation at the primary site showed no evidence of relapse in this region, indicating that such therapy may help to prevent a relapse. These data suggest a high rate of 3 year disease-free survival with this treatment strategy. The nonrandomized nature of the study and use of multiple modalities precludes analysis of the specific contribution of each.     

Characterization of Ni---W/A12O3-SiO2 aromatics saturation catalysts used in a one-year commercial HDS run

A series of Ni---W/A1₂O₃-SiO₂ catalysts with different A1₂O₃/SiO₂ ratios were prepared and loaded in a commercial HDS unit for a year. The catalytic properties of the freshly sulfided and spent catalysts were investigated by performing structural analyses and model test reactions. The aggregation of the WS₂ slabs in the lateral direction, which was observed by EXAFS and TEM, was a major cause of the catalyst deactivation. The addition of SiO₂ into the catalyst support was found to suppress the structural changes of the catalyst.     

Cytokines and gut

Cytokines are soluble proteins or glycoproteins produced by a wide variety of cell types. Cytokines are local regulatory factors which are involved in cell growth, cell differentiation, inflammation, and immune responses. In the gastrointestinal mucosa, not only inflammatory cells but also epithelial and mesenchymal cells secrete cytokines in response to various stimuli. Inflammatory cytokines are playing critical roles in the inflammation associated with gastrointestinal infections, including Helicobacter pylori infection in the gastric mucosa. Animal studies have shown that abnormal cytokine response may be risk for developing inflammatory bowel diseases, such as ulcerative colitis and Crohn's disease. Cytokines will be important therapeutic targets in these diseases.     

Joining of silicon nitride to silicon nitride and to Invar alloy using an aluminium interlayer

Si₃N₄ has been bonded to Si₃N₄ and to the Invar alloy using an aluminium interlayer at temperatures above the melting point of aluminium. Reaction was hardly observed at the interface between Si₃N₄ and aluminium up to 1223 K. The highest strength of the Si₃N₄-Al-Si₃N₄ joints was beyond 500 M Pa. In the Si₃N₄-Al-Invar joint, two main intermetallic compound layers were formed at the AI-Invar interface. The strength of the joints was between 150 and 200 MPa. It is expected that the aluminium layer and the reaction layer with the fine cracks growing perpendicular to the interface play an important role to compensate for the thermal expansion mismatch.     

Expression and purification of the extracellular ligand binding region of metabotropic glutamate receptor subtype 1

Each metabotropic glutamate receptor possesses a large extracellular domain that consists of a sequence homologous to the bacterial periplasmic binding proteins and a cysteine-rich region. Previous experiments have proposed that the extracellular domain is responsible for ligand binding. However, it is currently unknown whether the extracellular ligand binding site can bind ligands without other domains of the receptor. We began by obtaining a sufficient amount of receptor protein on a baculovirus expression system. In addition to the transfer vector that encodes the entire coding region, transfer vectors that encode portions of the extracellular domain were designed. Here, we report a soluble metabotropic glutamate receptor that encodes only the extracellular domain and retains a ligand binding characteristic similar to that of the full-length receptor. The soluble receptor secreted into culture medium showed a dimerized form. Furthermore, we have succeeded in purifying it to homogeneity. Dose-response curves of agonists for the purified soluble receptor were examined. The effective concentration for half-maximal inhibition (IC50) of quisqualate for the soluble receptor was 3.8 x 10(-8) M, which was comparable to that for the full-length receptor. The rank order of inhibition of the agonists was quisqualate > ibotenate >/= L-glutamate approximately (1S,3R)-1-aminocyclopentane-1, 3-dicarboxylic acid. These data demonstrate that a ligand binding event in metabotropic glutamate receptors can be dissociated from the membrane domain.     

Phase relations and crystallization of glass in the system PbO-GeO2

Thermal properties and chemical compositions of glasses suitable for crystallization of ferro-electric Pb₅Ge₃O₁₁ are described. The crystallization of lead germanate glass was investigated by DTA and X-ray diffraction. In the range from 62 to 62.5 of PbO in mole per cent, Pb₅Ge₃O₁₁ was obtained as a single phase after a heat treatment. In the chemical composition around 5PbO·3GeO₂ in the binary system of PbO-GeO₂, Pb₅Ge₃O₁₁ and two new phases of Pb₃Ge₂O₇ and Pb₃GeO₅ were found to exist. The crystal structure of Pb₃Ge₂O₇ had a hexagonal symmetry witha=10.16 Å andc=19.37 Å, and Pb₃GeO₅ was classified into orthorhombic system witha=4.85 Å,b=15.52 Å and c=11.77 Å.     

Distribution of catecholamine containing nerve endings in the hypothalamus of the rhesus monkey

Using the Falck-Hillarp method, the distribution of catecholamine nerve terminals in the rhesus monkey hypothalamus was studied. The distribution pattern was fundamentally similar to that in the rat, cat and human fetus; abundunt catecholamine varicosities (presumed noradrenaline nerve terminals) were observed in the dorsomedial nucleus, supraoptic nucleus, paraventricular nucleus, medial forebrain bundle, periventricular layer and internal layer of the infundibulum, while little were in the mamillary nucleus, ventromedial nucleus and anterior hypothalamic area. A band of diffuse green fluorescence (dopamine nerve terminals) was observed around the capillary loops in the external layer of the infundibulum. the discrepancy with the rat was noted in the abundunt noradrenaline nerve terminals in the suprachiasmatic nucleus and denser innervation of them in the arcuate nucleus and internal layer of the infundibulum. In addition to the noradrenaline nerve fibers from the peripheral sympathetic NA nerve, the noradrenaline nerve terminals of central origin closely approximated to the small intracerebral vessels.