Chlorine isotope fractionation associated with volcanic activity at the Kusatsu-Bandaiko hot spring in Japan

Stable chlorine isotope compositions (δ³⁷Cl, per-mil: ‰, vs. a standard sample of sea water) of Kusatsu-bandaiko hot water samples, taken regularly in the years between 1974 and 1995 in the Kusatsu-Shirane volcanic region, Japan, were measured mass-spectrometrically. The results show that the δ³⁷Cl values of the waters taken before 1984 were at around?0.12‰, whereas those after 1984 were at around+0.18‰. The δ³⁷Cl values are thus distinct across 1984, which is consistent with the classification by the Cl to S molar ratio (Cl/S): the higher the Cl/S ratio, the larger the δ³⁷Cl value. The δ³⁷Cl value increased as much as 0.30‰ during 5 years between 1980 and 1984. This isotopic enrichment is likely correlated with increasing Cl/S ratios, suggesting that the heavier isotope (³⁷Cl) may have preferentially increased in the original Cl source of the hot spring across 1984 when volcanic activity likely increased at Mt Kusatsu-Shirane.     

Understanding Covalent Mechanochemistry

The time is ripe : A general theoretical framework based on force‐transformed potential energy surfaces rationalizes the intriguing results of recent experiments in the emerging field of covalent mechanochemistry.

     

Mössbauer spectroscopic characterization of iron compounds in paddy soil

Chemical states of iron and their vertical distribution in paddy soil, which was derived from weathered volcanic ashes, have been investigated by⁵⁷Fe Mössbauer spectroscopy. The relative amount of paramagnetic Fe³⁺ has no dependence on depth, whereas that of magnetic Fe³⁺ decreases with an increase in depth. The paramagnetic Fe²⁺ can be divided into two fractions which show an opposite dependence on depth from each other. The depth profile of the iron components clearly reflects the chemical conditions characteristic of the paddy environment, and the origin of the iron components is also discussed.     

Carbon Whisker Membrane

We report a recent developed membrane called carbon whisker membrane (CWM). The CWMs consist of a tubular ceramic membrane covered by a layer of carbon film and carbon whiskers formed on the surface of the carbon film. Hydrocarbons such as methane and a modified chemical vapor deposition apparatus were employed for fabricating uniformed CWMs. Because of the unique feature of the CWMs, the filtration performance of the CWMs was investigated and it was found that the CWMs possess a function of anti-attachment of particles and/or biomaterials on the membranes so that the permeate flux and the cleaning process of the membrane can be improved.     

Development of vapor phase decomposition-total-reflection X-ray fluorescence spectrometer

A total reflection X-ray fluorescence spectrometer integrated with vapor phase decomposition, VPD-TXRF, was newly developed. This instrument was designed to achieve a minimum footprint, to avoid cross contamination during operation, and to protect people and instruments from HF gas. Comparisons between analysis by VPD-TXRF and by atomic absorption spectrometry (AAS) indicated very good agreement in a wide range, from 10⁸ to 10¹² atoms/cm². The lower limits of detection (LLDs) were improved by two orders of magnitude compared with straight TXRF. For 300-mm Si wafers, the LLDs were 5×10⁸ atoms/cm² and 1×10⁷ atoms/cm² for Al and Ni, respectively. VPD-TXRF was able to perform ultra-trace analysis at the level of 10⁸ atoms/cm².     

Theoretical study on isotope and temperature effect in hydronium ion using ab initio path integral simulation

We have applied the ab initio path integral molecular dynamics simulation to study hydronium ion and its isotopes, which are the simplest systems for hydrated proton and deuteron. In this simulation, all the rotational and vibrational degrees of freedom are treated fully quantum mechanically, while the potential energies of the respective atomic configurations are calculated "on the fly" using ab initio quantum chemical approach. With the careful treatment of the ab initio electronic structure calculation by relevant choices in electron correlation level and basis set, this scheme is theoretically quite rigorous except for Born-Oppenheimer approximation. This accurate calculation allows a close insight into the structural shifts for the isotopes of hydronium ion by taking account of both quantum mechanical and thermal effects. In fact, the calculation is shown to be successful to quantitatively extract the geometrical isotope effect with respect to the Walden inversion. It is also shown that this leads to the isotope effect on the electronic structure as well as the thermochemical properties.     

Oxygen Selectivity on Partially K Exchanged Na-A Type Zeolite at Low Temperature

In previous work by the authors on Na-A zeolite (Izumi et al., Japan Patent Toku-Kou-Shou 63-058614, 1988), it was shown that the combination of high-temperature calcination and operation of the adsorption step at low temperatures improved the selectivity for oxygen over nitrogen from air (Izumi et al., CATS J Meeting Abstracts, 31(2A), 10, 1989; Izumi and Suzuki, Adsorption, 6, 2000). Berlin discloses in his U.S. Patent 3282028 (1966) that the partial exchange of potassium ions for sodium ions in the Na-A type zeolite also improved selectivity for oxygen by reducing the uptake rate of nitrogen. It was therefore expected that the oxygen selectivity of Na-K-A with high-temperature calcination and low-temperature adsorption might be enhanced. For the confirmation of optimum conditions for the appearance of oxygen selectivity on Na-K-A, samples were prepared with a K exchange ratio varied from 0–20 mol% (0–2.4 K ions/unit cell), and a calcination temperature varied from 923 to 1073 K, and an experiment concerning oxygen and nitrogen adsorption on Na-K-A was undertaken with a small adsorbent column under pressure swing adsorption (PSA) conditions at adsorption temperatures from room temperature to 213 K. It was found that (a) the K exchange ratio of 7 mol% (0.84 K ions/unit cell), and (b) the calcination temperature of 993 K, resulted in a remarkable increase in oxygen selectivity. Under optimum conditions for Na-K-A, the oxygen separation factor was about 8. Na-K-A has the potential to effectively separate oxygen and nitrogen from air by means of PSA.