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  • Author: Y. Ishii x
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Abstract

This paper aims to computationally investigate flow patterns of gas-liquid two-phase with an abrupt expansion. To do so, the present computation is nicely verified against the previous experimental results for a good wettability surface. These rectangular channels have a thickness narrower than the Laplace constant of the present situation. Under a poor wettability condition, this narrow thickness affects the flow pattern; e.g., the air phase forms channeling behind the expansion in a low airflow rate whereas the air phase becomes fragments of bubbles due to the expansion under a good wettability condition.

Abstract

This paper computationally visualizes two-phase flow patterns through a horizontally placed hydrophilic or hydrophobic rectangular channel with an abrupt contraction. The rectangular duct used in this study has a thickness narrower than the Laplace constant so that the surface tension governs the fluid system rather than the inertia force. In particular, the computed bubble behavior at the abrupt contraction seemed to be a similar nature against the preliminary experimental result.

Abstract

Oxidative stress evokes various cellular events, including activation of transcription factors, apoptosis, and cell cycle arrest. Accumulating evidence shows that reduction/oxidation (redox) plays an important role in the regulation of apoptosis and cell cycle arrest elicited by oxidative stress. Cellular redox is controlled by the thioredoxin (TRX) and glutathione (GSH) systems. TRX and GSH systems regulate cell growth and cell death by the activation of transcription factors, the sensitivity of cells to cytokines and growth factors, and the components of the apoptosis pathways. This brief review describes the current knowledge on the redox regulation of cell growth and apoptosis.

Summary

Chemical studies on element 104, rutherfordium (Rf), at JAERI (Japan Atomic Energy Research Institute) are reviewed. The transactinide nuclide 261Rf has been produced in the reaction 248Cm(18O, 5n) at the JAERI tandem accelerator with the production cross section of about 13 nb. On-line anion-exchange experiments on Rf together with the lighter homologues, group-4 elements Zr and Hf, in acidic solutions have been conducted with a rapid ion-exchange separation apparatus. From the systematic study of the anion-exchange behavior of Rf, it has been found that the properties of Rf in HCl and HNO3 solutions are quite similar to those of Zr and Hf, definitely confirming that Rf is a member of the group-4 elements. However, we have observed an unexpected chemical behavior of Rf in HF solutions; the fluoride complex formation of Rf is significantly different from those of the homologues. Prospects of extending chemical studies on transactinide elements in the near future at JAERI are briefly considered.

Conversations on Race and Racializations

Summary

Formation of anionic fluoride-complexes of element 104, rutherfordium, produced in the 248Cm(18O,5n) 261Rf reaction was studied by anion-exchange on an atom-at-a-time scale. It was found that the hexafluoro complex of Rf, [RfF6]2−, was formed in the studied fluoride ion concentrations of 0.0005–0.013 M. Formation of [RfF6]2− was significantly different from that of the homologues Zr and Hf, [ZrF6]2− and [HfF6]2−; the evaluated formation constant of [RfF6]2− is at least one-order of magnitude smaller than those of [ZrF6]2− and [HfF6]2−.

The extraction behavior of rutherfordium (Rf) into tributylphosphate (TBP) from hydrochloric acid (HCl) has been studied together with those of the lighter group-4 elements Zr and Hf. The extractability of 261Rf, 169Hf, and 85Zr into TBP was investigated under identical conditions in 7.2–8.0 M HCl by on-line reversed-phase extraction chromatography. The percent extractions of Rf, Hf, and Zr into the TBP resin increase steeply with increasing HCl concentration, and the order of extraction is Zr > Hf ≈ Rf. By considering the order of chloride complexation among these elements, it is suggested that the stability of the TBP complex of Rf tetrachloride is lower than those of Zr and Hf.