Precipitates in Biomedical Co-Cr-Mo-C-N-Si-Mn Alloys

The microstructures of biomedical ASTM F 75/F 799 Co-28Cr-6Mo-0.25C-0.175N-(0 to 1)Si-(0 to 1)Mo alloys (mass pct) were investigated before and after heat treatment, with special attention paid to the effect of nitrogen on the phases and the dissolution of precipitates. The heat treatment temperatures and holding periods employed ranged from 1448 to 1548 K (1175 to 1275 °C) and 0 to 43.2 ks, respectively. A blocky-dense π-phase precipitate and a lamellar cellular colony, which consisted of an M₂X type precipitate and a γ phase, were mainly detected in the as-cast alloys with and without added Si, respectively. The addition of nitrogen caused cellular precipitation, while the addition of Si suppressed it and enhanced the formation of the π phase. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) analyses suggested that a discontinuous reaction, i.e., γ ₁ → γ ₂ + M₂X, might be a possible formation mechanism for the lamellar cellular colony. Nitrogen was enriched in the M₂X type, η-phase, and π-phase precipitates, but was excluded from the M₂₃X₆ type precipitate. Complete precipitate dissolution was observed in all of the alloys under varied heat treatment conditions depending on the alloy composition. The addition of nitrogen decreased the time required for complete precipitate dissolution at low heat-treatment temperatures. At high temperatures, i.e., 1548 K (1275 °C), complete precipitate dissolution was delayed by the partial melting that accompanied the formation of the precipitates such as the π phase resulting in the boundary between the complete and incomplete precipitate dissolution regions in having a C-curved shape.     

Computer-aided diagnosis scheme using a filter bank for detection of microcalcification clusters in mammograms

Mammography is considered the most effective method for early detection of breast cancers. However, it is difficult for radiologists to detect microcalcification clusters. Therefore, we have developed a computerized scheme for detecting early-stage microcalcification clusters in mammograms. We first developed a novel filter bank based on the concept of the Hessian matrix for classifying nodular structures and linear structures. The mammogram images were decomposed into several subimages for second difference at scales from 1 to 4 by this filter bank. The subimages for the nodular component (NC) and the subimages for the nodular and linear component (NLC) were then obtained from analysis of the Hessian matrix. Many regions of interest (ROIs) were selected from the mammogram image. In each ROI, eight features were determined from the subimages for NC at scales from 1 to 4 and the subimages for NLC at scales from 1 to 4. The Bayes discriminant function was employed for distinguishing among abnormal ROIs with a microcalcification cluster and two different types of normal ROIs without a microcalcification cluster. We evaluated the detection performance by using 600 mammograms. Our computerized scheme was shown to have the potential to detect microcalcification clusters with a clinically acceptable sensitivity and low false positives.     

Bending properties of friction stir welded joints – Studies on characteristics of friction stir welded joints in structural aluminum alloys (report 4)

The objective of this work is to determine the best parameters for brazing ceramic joints of pre-metallized Al₂O₃ with Ti by a plasma process using amorphous ribbons of Cu₄₉Ag₄₅Ce_x alloy as the addition metal. The alloys were prepared in an arc oven, and later processed by melt spinning, varying Cerium content by 4–6%. Brazing took place in a vacuum oven and the following variables were analysed: deposition time of the Ti film and temperature and brazing time, which were related to the flex resistance in three points of the brazed joint. A linear regression equation was obtained, and the interaction between these factors was verified. The metallized ceramic surfaces showed excellent uniformity and the brazed joints demonstrated very good adhesion, achieving flex resistance values of up to176.8 MPa.     

Circuit and Latch Capable of Masking Soft Errors with Schmitt Trigger

In VLSIs, soft errors resulting from radiation-induced transient pulses frequently occur. In recent high-density and low-power VLSIs, the operation of systems is seriously affected by not only soft errors occurring on memory systems and the latches of logic circuits but also those occurring on the combinational parts of logic circuits. The existing tolerant methods for soft errors on the combinational parts do not provide enough high tolerant capability with small performance penalty. This paper proposes a class of soft error masking circuits by using a Schmitt trigger circuit and a pass transistor. The paper also presents a construction of soft error masking latches (SEM-latches) capable of masking transient pulses occurring on combinational circuits. Moreover, simulation results show that the proposed method has higher soft error tolerant capability than the existing methods. For supply voltage V _DD ?=?3.3 V, the proposed method is capable of masking transient pulses of magnitude 4.0 V or less.     

Neuroblastoma of parotid gland: report of a case and immunohistochemical characteristics

A case of a parotid mass in a 2-year-old boy, postoperatively diagnosed as neuroblastoma, a rare tumour not previously reported in the parotid gland is presented. The neoplasm developed within the parotid gland as a painless mass without regional lymphadenopathy. Histopathologically, the tumour showed primitive nerve cells-neuroblasts-with round or oval dark basophilic nuclei and scanty cytoplasm. The cells were arranged in circular rosettes around an eosinophilic mass consisting of very fine filaments originating in the tumour cells or papillary configuration and sometimes scattered in the poorly developed stroma. Immunohistochemical evaluation of the tumour showed a positive immunoreactivity for vimentin, alpha and beta subunits of S-100 protein, neurone-specific enolase (NSE), substance P, met-enkephalin and chromogranin but cytokeratins, desmin, actin, myosin, glial fibrillary acidic protein (GFAP) and calcitonin gene related peptide (CGRP) were negative. The histopathological and immunohistochemical findings conclude a diagnosis of neuroblastoma of the parotid gland.     

Studies on injection locking of a TEA-CO2laser for stable high-power operation

Optimum Conditions for stable operation of an injected TEA-CO2laser with high-power output have been pursued both theoretically and experimentally. The stability of injection locking as well as the obtainable peak power was analyzed based on a transient mathematical model which deals with buildup of the electric fields. Predicted dependence of injection locking on the injection intensity, the output coupling, and the resonator length was tested and verified in the experiments.     

Interferon-gamma inhibition of human thyrotropin receptor gene expression

To evaluate the role of interferon-gamma (IFN gamma) on human thyroid-specific gene expression, the effect of IFN gamma on TSH- and cAMP-induced TSH receptor gene expression was studied using cultured thyroid cells obtained from normal thyroid glands and those from patients with Graves' disease. Incubation of Graves' thyroid cells with 1.0 U/L bovine TSH or 1.0 mM 8-bromo-cAMP resulted in a 2-fold increase in TSH receptor mRNA expression, which was markedly inhibited in the presence of IFN gamma in a dose- and time-dependent manner. This inhibitory effect was completely neutralized by monoclonal antibody against IFN gamma. IFN alpha and -beta had no influence on TSH- and cAMP-stimulated TSH receptor mRNA expression. Paranodular normal thyroid cells showed the same results as those obtained using Graves' thyroid cells. Scatchard analysis of the [125I]TSH binding study showed that IFN gamma inhibited the number of TSH receptors up-regulated by TSH on the cell surface at the low affinity binding site (4.1 vs. 8.2 x 10(5)/cell). These results indicate that IFN gamma suppresses TSH- and cAMP stimulated human TSH receptor gene expression, resulting in a decrease in the number of TSH receptors. In conclusion, IFN gamma interacts via an intermediate pathway of TSH signal transduction and attenuates TSH receptor synthesis in normal and Graves' thyroid cells.     

Announcement of coming events

Basic characteristics of ion beam lithography and its potential as a high resolution, high-speed lithography technique are described. The technique is thought to be one which allows delineation of fine patterns with a feature size less than 0.1 μm, rendering it increasingly important in micro- or nanometer devices.     

Supermirror hard-x-ray telescope

The practical use of a grazing x-ray telescope is demonstrated for hard-x-ray imaging as hard as 40 keV by means of a depth-graded d-spacing multilayer, a so-called supermirror. Platinum-carbon multilayers of 26 layer pairs in three blocks with a different periodic length d of 3-5 nm were designed to enhance the reflectivity in the energy range from 24 to 36 keV at a grazing angle of 0.3 deg. The multilayers were deposited on thin-replica-foil mirrors by a magnetron dc sputtering system. The reflectivity was measured to be 25%-30% in this energy range; 20 mirror shells thus deposited were assembled into the tightly nested grazing-incidence telescope. The focused hard-x-ray image was observed with a newly developed position-sensitive CdZnTe solid-state detector. The angular resolution of this telescope was found to be 2.4 arc min in the half-power diameter.