The Leaching of Hematite in Acid Solutions

The reactions of hematite in aqueous hydrochloric acid, perchloric acid, and sulfuric acid solutions with or without the addition of common or uncommon salts were studied using monosized particulates in a well-stirred reactor and dilute solid concentration to obtain fundamental details of the reaction kinetics. The experimental rate data suggest that the entire leaching reaction is controlled by a chemical process. The leaching rate of hematite was seen to be first order with respect to hydrogen ion activity, a(H⁺), in hydrochloric acid or perchloric acid solutions, with or without the addition of common salts, while the rate was of a half order in sulfuric acid solutions with or without the addition of sodium sulfate. A theoretical analysis showed that the anions next to the surface in the double layer were chloride ion and perchlorate ion in hydrochloric acid and perchloric acid solutions, respectively, and sulfate ion in sulfuric acid solutions, with or without the addition of sodium sulfate. The fact that the leaching rates of hematite were quite different in various acids having identical α(H⁺ values indicates the importance of anion adsorption. The dependency of the leaching rate upon α(H⁺) appeared to be controlled by adsorbed anions next to the surface in the double layer. TAKUMI MISHIMA, formerly Graduate Student, Kyoto University     

Mouse dendritic epidermal T cells exhibit chemotactic migration toward PAM 212 keratinocyte culture supernatants

Dendritic epidermal T cells (DETCs) are Thy-1+, CD45+, CD3+, CD4-, CD8-, and T-cell receptor-V gamma 3/V delta 1+ leukocytes that reside normally in adult mouse skin. We have demonstrated previously that keratinocytes serve as adhesion substrates for DETCs, and that interleukin 7 (IL-7), which is produced by keratinocytes, serves as a growth factor for DETCs. The present study was conducted to address the mechanisms by which DETCs migrate into the epidermis, reasoning that keratinocytes may also be a source of chemotactic activity. Short-term DETC lines were 35S-labeled and tested for migration toward Pam 212 keratinocyte culture supernatants using a modified Boyden chamber method; cell movement from upper chambers toward test samples in lower chambers was traced by counting radioactivity. DETC displayed rapid (within 60 min) and marked (> 50%) migration toward keratinocyte supernatants. The majority of cells that had migrated into keratinocyte supernatants expressed the V gamma 3 T-cell receptor, thus verifying that the migrating cells were DETCs. Addition of keratinocyte supernatants to the upper chambers completely blocked migration, suggesting its chemotactic nature. By contrast, no DETC migration was observed toward 3T3 fibroblast supernatants. Chemotactic activities were 1) produced by Pam 212 cells even in the absence of serum; 2) greater than 12 kD in size; 3) heat and pH labile; 4) trypsin sensitive; and 5) precipitated by 60-100% ammonium sulfate. Several cytokines (e.g., IL-1 alpha and IL-8) failed to mediate DETC migration when added to the lower chambers. Likewise, the same cytokines, when added to the upper chambers, failed to inhibit DETC migration toward Pam 212 supernatants. These results support our hypothesis that keratinocytes facilitate the residence of DETC in epidermis by secreting unique chemotactic factors, by providing adhesion substrates, and by elaborating specific growth factors.     

Open/folded bit-line arrangement for ultra-high-density DRAM's

An open/folded bit-line (BL) arrangement for scaled DRAM's is proposed. This BL arrangement offers small die size and good array noise immunity. In this arrangement, one BL of an open BL pair is placed in between a folded BL pair, and the sense amplifiers (SA's) for open BL's and those for folded BL's are placed alternately between the memory arrays. This arrangement features a small 6F² memory cell, where F is the device feature size, and a relaxed SA pitch of 6F. The die size of a 64-Mb DRAM can be reduced to 81.6% compared with the one using the conventional folded BL arrangement. The BL-BL coupling noise is reduced to one-half of that of the conventional folded BL arrangement, thanks to the shield effect. Two new circuit techniques, 1) a multiplexer for connecting BL's to SA's, and 2) a binary-to-ternary code converter for the multiplexer have been developed to realize the new BL arrangement     

The Creep and Thermal Stability Characteristics of a Unidirectionally Solidified Al2O3/YAG Eutectic Composite

Compressive creep characteristics at 1773, 1873, and 1973 K, oxidation resistance over 1000 h at a temperature of 1973 K in ambient air, and the thermal stability characteristics at 1973 K in ambient air of a unidirectionally solidified Al2O3/YAG eutectic composite were evaluated. At a test temperature of 1873 K and a strain rate of 10–4/s, the compressive creep strength of a eutectic composite manufactured by the unidirectional solidification method is approximately 13 times higher than that of a sintered composite with the same chemical composition. The insite eutectic composite also showed greater thermal stability, with no change in mass after an exposure of 1000 hours at 1973 K in ambient air. The superior high-temperature characteristics are closely related to such factors as (1) the in-situ eutectic composite having a microstructure, in which single crystal Al2O3 and single crystal YAG are three-dimensionally and continuously connected and finely entangled without grain boundaries and (2) no amorphous phase is formed at the interface between the Al2O3 and the YAG phases.     

Antiatherogenic effects of the antioxidant BO-653 in three different animal models

Antioxidants have been proposed to have antiatherogenic potential by their inhibition of low density lipoprotein (LDL) oxidation. Here, we report an antioxidant, BO-653 (2,3-dihydro-5-hydroxy-2, 2-dipentyl-4,6-di-tert-butylbenzofuran), designed to exhibit antioxidative potency comparable to that of alpha-tocopherol, but yet possess a high degree of lipophilicity comparable to that of probucol. BO-653 exhibits a high affinity for LDL and is well distributed in aortic vessels in vivo. In atherosclerosis models of rabbits and mice, BO-653 has been shown to be able to suppress the formation of atherosclerotic lesions without untoward side effects. Specifically, there was no reduction of high density lipoprotein levels. This antioxidant provides additional evidence in support of the oxidized-LDL hypothesis, and itself is a promising candidate antioxidant for clinical use.     

Gastric cancer occurring in a patient with Plummer-Vinson syndrome: report of a case

We report herein the unusual case of a 59-year-old woman with Plummer-Vinson syndrome who developed gastric cancer. The patient had a longstanding history of dysphagia and iron deficiency anemia, for which she had sporadically taken iron supplements that improved the dysphagia to some extent, but not completely. Owing to her tolerance of the dysphagia, she had not been taking iron supplements for the past 17 years. On admission, she was in fair nutritional condition and not anemic. Blood chemistry results were all normal, including the serum iron level. Gastrointestinal radiographic series demonstrated cervical esophageal webs and advanced gastric cancer. Her dysphagia was successfully treated by endoscopic bougienage through the webs, and a distal partial gastrectomy with nodal dissection was performed. Histology of the resected stomach revealed atrophic mucosal change and, by chance, an adenomatous lesion in addition to adenocarcinoma. Her postoperative course was uneventful and she is now well, without any signs of recurrence. Although Plummer-Vinson syndrome is known to be associated with upper alimentary tract cancers, gastric cancer is extremely rare. A discussion on the etiology of Plummer-Vinson syndrome and its link with potential carcinogenesis follows this case report.     

Index for predicting post-operative residual liver function by pre-operative dynamic liver SPET

To predict residual liver function before hepatic resection, we devised a predictive index by combining clearance values with functional liver volume measured by liver dynamic single photon emission tomography (SPET). Forty-seven patients with liver disease underwent liver dynamic SPET with 99Tcm-Sn colloid before hepatic resection. There were no operation-related deaths. Three patients died from hepatic failure more than 1 month following the operation. Their predictive indices were 0.24, 0.33 and 0.34. When the predictive index was above 0.35, no patient had symptoms of hepatic failure or died. Our data suggest that when the predictive index is above 0.35, there is a low probability of hepatic failure after hepatectomy.     

Effect of silicon content and carbon addition on primary recrystallization of Fe-3 pct si

A study was made on the effect of the increase of silicon content and the addition of carbon on the primary recrystallization of silicon steel sheet containing MnS and AlN as inhibitors. The increase of silicon content led to the reduction of the size of primary grains and the intensity of {110} that is considered to represent the amount of {110}〈001〉-oriented nuclei, to the gain of the size of precipitates, and to the coarse dispersion of the precipitates. The carbon addition promoted primary recrystallization and decreased the size of primary grains. From the points mentioned earlier, the increase of silicon content is considered disadvantageous, and the carbon addition is advantageous to the secondary recrystallization of the {110}〈001〉 texture.     

Gait analysis of people walking on tactile ground surface indicators.

Tactile ground surface indicators installed on sidewalks help visually impaired people walk safely. The visually impaired distinguish the indicators by stepping into its convexities and following them. However, these indicators sometimes cause the nonvisually impaired to stumble. This study examines the effects of these indicators by comparing the kinematic and kinetic variables of walking on paths with and without indicators. The results suggest that walking on the indicators causes extra movements of the lower extremities such as increased minimum toe heights during the midswing phase, increased peak hip flex moments, and increased peak hip heights. This study also suggests that a functional leg length discrepancy while walking on the indicators is one of the reasons for the extra movements of the lower extremities. Therefore, we designed a new recessed tactile surface to offset the differences of surface depth while walking on the path containing indicators, and found that the newly designed recessed tactile surface was effective in reducing the extra movements while walking on the path in which indicators were installed. These indicators may help both the visually impaired and elderly people with normal vision to walk safely.     

Loss of tuberin from cerebral tissues with tuberous sclerosis and astrocytoma

We studied the expression of tuberin, the TSC2 gene product, in cerebra with or without tuberous sclerosis. Tuberin was abundant in the gray matter of normal cerebra, but was undetectable in the subependymal astrocytomas from 3 patients with tuberous sclerosis. In 1 patient, cortical tubers and normally appearing cortical tissue also showed a marked loss of tuberin. These results indicate the critical role of tuberin in the neuropathology of tuberous sclerosis.