The effect of Cu-rich sub-layer on the increased corrosion resistance of Cu-xZn alloys in chloride containing borate buffer

The electrochemical behaviour of Cu-xZn alloys, as well as their constituent metals, in a borate buffer containing chloride ions in the molar range from 0.01 to 1 M are studied. Characteristics of these materials under anodic polarization are compared and the composition and morphology of the corrosion products formed in the course of polarization experiment are analysed by SEM and EDS. X-ray photoelectron spectroscopy and electrochemical impedance measurements are used for characterization of the surface layers formed on Cu, Zn and Cu-40Zn alloy during 2-h immersion at E_oc in a borate buffer containing two different concentrations of chloride ions. New aspects of the behaviour of brass under E_oc condition are revealed. The improved corrosion resistance of brass in chloride media, if compared to zinc metal, is attributed to a Cu-rich layer formed by the selective dissolution of zinc. Based on the results, a structural model describing the improved corrosion resistance of Cu-40Zn alloy with respect to Zn metal is proposed.     

A 10 bit 20 MS/s 3 V supply CMOS A/D converter

A 10 bit CMOS A/D converter with 3 V power supply has been developed for being integrated into system VLSI's. In this A/D converter, redundant binary encoders named “twin encoders” enhance tolerance to substrate noise, together with employing differential amplifiers in comparators. The bias circuit using a replica of the amplifier is developed for biasing differential comparators with 3 V power supply. Subranging architecture along with a multilevel tree decoding structure improves dynamic performance of the ADC at 3 V power supply. The A/D converter is fabricated in double-polysilicon, double-metal, 0.8 μm CMOS technology. The experimental results show that the ADC operates at 20 MS/s and the twin encoders suppress the influence of substrate noise effectively. This ADC has a single power supply of 3 V, and dissipates 135 mW at 20 MS/s operation     

Oxidation of methane to formaldehyde over Fe/SiO2 and Sn---W mixed oxides

In an attempt to develop new catalysts for the formation of formaldehyde from methane, the promotion effect of Fe on SiO₂ and that of Sn on WO₃ have been studied. The formation of formaldehyde on silica can be appreciably enhanced by the impregnation of Fe, as far as iron loadings are kept below 0.1 atom.% (Fe/Si × 100). In the case of Sn---W---Ox catalysts, both the addition of Sn to WO₃, and that of W on SnO₂ were effective to the selective formaldehyde formation. Absorption spectra (UV-Vis) and ESR measurements revealed that tetrahedrally coordinated Fe³⁺ in the silica network plays an important role in the formation of formaldehyde. A thin surface layer consisting of W and Sn oxides can account for the selective formaldehyde formation on the Sn---W---Ox catalysts.     

A new non-random chromosomal translocation t(3;6)(q27;p21.3) associated with BCL6 rearrangement in two patients with non-Hodgkin's lymphoma

We describe two cases of non-Hodgkin's lymphoma associated with t(3;6)(q27;p21.3) and BCL6 rearrangement. The first case was in a 78-year old woman, whose performance status (PS) was 1, the serum lactate dehydrogenase (LDH) level was elevated, and the Ann Arbor stage was IIIA with no extra nodal lymphomatous site. The pathological diagnosis from a biopsy of the inguinal lymph node was 'malignant lymphoma (ML), follicular, small cleaved' according to the Working Formulation. Complete remission was achieved. Although she had relapse in 1992, remission was obtained again. The second case was in a 62-year old man, whose PS was 1, the serum LDH was normal, and Ann Arbor stage was IVA with the involvement of the small intestine. Histological diagnosis of the cervical lymph node was 'ML, diffuse, large cell'. Complete remission was obtained without relapse. The 3q27 translocations, found in 20-30% of non-Hodgkin's lymphoma, are unique in having multiple chromosomal translocation partners. Chromosome band 6p21.3 is one of these partner sites that may be the site of a novel gene. The two cases presented here show that this translocation is a non-random chromosomal change involving 3q27 and BCL6. Since t(3;6) was the sole karyotypic abnormality in one case, this translocation may play a role in lymphomagenesis.     

Stromal CCL5 Promotes Breast Cancer Progression by Interacting with CCR3 in Tumor Cells

Chemokines secreted from stromal cells have important roles for interactions with carcinoma cells and regulating tumor progression. C-C motif chemokine ligand (CCL) 5 is expressed in various types of stromal cells and associated with tumor progression, interacting with C-C chemokine receptor (CCR) 1, 3 and 5 expressed in tumor cells. However, the expression on CCL5 and its receptors have so far not been well-examined in human breast carcinoma tissues. We therefore immunolocalized CCL5, as well as CCR1, 3 and 5, in 111 human breast carcinoma tissues and correlated them with clinicopathological characteristics. Stromal CCL5 immunoreactivity was significantly correlated with the aggressive phenotype of breast carcinomas. Importantly, this tendency was observed especially in the CCR3-positive group. Furthermore, the risk of recurrence was significantly higher in the patients with breast carcinomas positive for CCL5 and CCR3 but negative for CCR1 and CCR5, as compared with other patients. In summary, the CCL5-CCR3 axis might contribute to a worse prognosis in breast cancer patients, and these findings will contribute to a better understanding of the significance of the CCL5/CCRs axis in breast carcinoma microenvironment.     

Age-related accumulation of phosphatidylcholine hydroperoxide in cultured human diploid cells and its prevention by α-tocopherol

The levels of phosphatidylcholine hydroperoxide in serially cultured human fetal diploid fibroblasts at various population doubling levels were determined by high-performance liquid chromatography combined with chemiluminescence detections. This methodology utilizes a mixture of cytochromec and luminol as post-column hydroperoxide group specific luminescent reagents. The cellular hydroperoxide content increased with age from 0.34 to 27.72 pmol/10⁶ cells. At the end of the cells'in vitro lifespan (51st population doubling level), the hydroperoxide content per 10⁶ cells reached about 80 times the level found in cells of the 20th population doubling level. Supplementation of exogenous α-tocopherol to the culture medium prevented hydroperoxide accumulation, but did not extent the lifespanin vitro. The results indicate that substantial intracellular phospholipid hydroperoxide accumulation occurred in the course of aging of human fetal liploid fibroblasts.     

Catalytic activity and solid acidity of vanadium oxide thin layer loaded on TiO2, ZrO2, and SnO2

Vanadium oxide spread highly on TiO₂ (anatase, A) and SnO₂, and rather densely on TiO₂ (rutile, R) and ZrO₂ to make the monolayer in less than 4–5 V nm⁻². Profile of acid site of the monolayer was measured by temperature programmed desorption of ammonia, and its relation with the surface oxidation state was studied. The acid site density was high on the V₂O₅/TiO₂ (A) independent of the degree of oxidation. On the other hand, that of V₂O₅/TiO₂ (R) and V₂O₅/ZrO₂ depended on the oxidation state, and the high value of the concentration was observed on the oxidized one. The strength of acid site generated on the V₂O₅ monolayer on TiO₂ was as high as on the HZSM-5 zeolite. Turnover frequency (TOF) of propane conversion, and product selectivity were measured in propane oxidation. Among tested oxides, the V₂O₅/TiO₂ (A) showed the high TOF and selectivity to form propylene, while those loaded on TiO₂ (R) and ZrO₂ the small TOF and poor selectivity. Therefore, the reaction profile of activity and selectivity could be related with the extent of spreading and solid acidity. An idea of limit of the acid site density ca. 1.5 nm⁻² on the monolayer was elucidated.     

Decomposition of chlorofluorocarbons on TiO2ZrO2

The decomposition of chlorofluorocarbons (CFCs) in the presence of water was examined over a variety of solid acid catalysts. The TiO₂ZrO₂ catalyst was found to have the highest activity and longest life among the catalysts examined. The activity of the TiO₂ZrO₂ catalysts depended upon the content of TiO₂. At the contents of TiO₂ from 58 to 90 mole%, the TiO₂ZrO₂ catalysts exhibited high activity, and these catalysts were proven to contain TiZrO₄ crystal. From the study of the XRD peak intensity of the TiZrO₄ crystal, it was highest on the TZ-58 which contained 58 mole% of TiO₂, and decreased with increasing the content of TiO₂. Furthermore, the conversion of CFC113 measured at 673 K was highest at TZ-58, and decreased gradually with increasing TiO₂ content. Therefore, the TiZrO₄ crystal influences the activity of decomposition of CFC113. However, the TiO₂ZrO₂ catalyst was gradually deactivated during the reaction due to the elimination of titanium atoms. A good relationship was found between the activity on TiO₂ZrO₂ catalyst and bond energy of CCl in the compounds of chlorofluorocarbons and hydrochlorocarbons, suggesting that the rate controlling step was the cleavage of CCl bond.     

Carbon molecular sieve membranes derived from trimethylsilyl substituted poly(phenylene oxide) for gas separation

Carbon molecular sieve membranes for gas separation prepared using poly(phenylene oxide) (PPO) as precursor have been examined. The PPO precursor was modified by introducing a trimethylsilyl (TMS) substituent and its effect on the gas transport property of the resulting carbon membrane was examined. TMS-substituted PPO (TMSPPO) was prepared in a high yield by a simple one-step reaction, and its carbon membrane was successfully fabricated. The modification improved the gas permeability of the resulting membrane which also exhibited excellent O₂/N₂ and CO₂/CH₄ separation performance comparable to those of polyimide-derived carbon membranes. From the analysis of the microstructure of the TMSPPO carbon membranes, it is believed that the TMS groups improve gas diffusivity by increasing the micropore volume.