Distribution of aquatic plants and absorption of radionuclides by plants through the leaf surface in brackish Lake Obuchi, Japan, bordered by nuclear fuel cycle facilities

We investigated the distribution of aquatic plants and the absorption of radionuclides by them in the brackish Lake Obuchi, Japan, which is bordered by nuclear fuel cycle facilities. We studied 5 species of submerged plants: Zannichellia palustris, Ruppia maritima, Potamogeton pectinatus, Zostera japonica, and Z. marina. The plants contained many elements, including radionuclides. The concentrations of ²³⁸U, ¹³⁷Cs, and ⁹⁰Sr in Z. marina were 11.3-12.4, 0.000-0.144, and 0.151-0.202 Bq^.kg^-1 dw, respectively. Those in Z. japonica were 5.2-8.8, 0.000-0.267, and 0.081-0.175 Bq^.kg^-1 dw, respectively. The concentrations of these radionuclides in the plants tended to be higher in higher-salinity regions than in lower-salinity regions of the lake. We found a close relationship between photosynthetic activity and the absorption of stable Sr by plants in the laboratory. Salinity, illumination, and water temperature influenced the photosynthetic activity of the plants and the consequent absorption of elements.     

Minimaxity of a preliminary test estimator for the mean of normal distribution

Summary The problem is to estimate the mean of the normal distribution under the situation where there is vague information that the mean might be equal to zero. A minimax property of the preliminary test estimator obtained by the use of AIC (Akaike information Criterion) procedure is proved under a loss function based on the Kullback-Leibler information measure.     

Optical-fibre remote sensing system of low-level propane gas using a 1·68 μm InGaAs light emitting diode

A fully optical remote detection system for propane gas was realized in real time by a near-infrared absorption method employing a 2-km long low-loss silica optical-fibre link in conjunction with an InGaAs light emitting diode at 1.68 μm. The detection sensitivity for propane gas in air, which was achieved to lower than 2 torr, i.e. nearly 12% of the lower explosion limit for propane, demonstrates the practical feasibility and reliability of this kind of fibre-optic remote gas sensor system with electrical and thermal safety.     

Doubly coprime representation of linear systems and its application to simultaneous stabilization

This paper develops a new representation theory of multivariabletime-invariant linear systems based on the well-known coprimefactorizations of their transfer matrices. This representationfully uses the algebraic structure of coprime factorizations,and hence has a number of advantages for describing variousproperties of linear systems in simpler and/or more compactforms than the usual transfer matrix representation. In theframework of this new representation theory, various stabilityand stabilizability properties of linear systems are characterizedand finally a simultaneous stabilization problem for a givenset of linear systems is examined.     

Semi-local units modulo Gauss sums

For the p-th cyclotomic field k, Iwasawa proved that p does not divide the class number of its maximal real subfield if and only if the odd part of the group of local units coincides with its subgroup generated by Jacobi sums related to k. We refine and give a quantitative version of this result for more general imaginary abelian fields. Our result is an analogy of the famous result on “semi-local units modulo cyclotomic units”. Received: 2 May 1997 / Revised version: 11 November 1997     

Reformatsky type additions of haloacetonitriles to aldehydes mediated by metallic nickel

Nickel in the metallic state was found to carry out the Reformatsky type addition of haloacetonitriles to aldehydes via cyanomethylnickel halides to give β-hydroxynitriles in good yields.     

Colloids for Catalysts: A Concept for the Preparation of Superior Catalysts of Industrial Relevance

Compared to conventional preparation methods for supported heterogeneous catalysts, the use of colloidal nanoparticles (NPs) allows for a precise control over size, size distribution, and distribution/location of the NPs on the support. However, common colloidal syntheses have restrictions that limit their applicability for industrial catalyst preparation. We present a simple, surfactant‐free, and scalable preparation method for colloidal NPs to overcome these restrictions. We demonstrate how precious‐metal NPs are prepared in alkaline methanol, how the particle size can be tuned, and how supported catalysts are obtained. The potential of these colloids in the preparation of improved catalysts is demonstrated by two examples from heterogeneous catalysis and electrocatalysis.     

A facile cleavage of oxirane with hydrazoic acid in dmf A new route to chiral β-hydroxy-α-amino acids

Chiral β-hydroxy-α-amino acids such as erythro-β-hydroxy-L-aspartic acid and erythro-β-hydroxymethyl-L-serine derivatives have been synthesized in optically pure form from L- and D-tartaric acids through a novel oxirane ring-opening reaction and a selective reduction of α-hydroxy ester as key steps.     

Heat capacity of iron-chromium spinels,Fe3−xCrxO4

The heat capacity of Fe_3?xCr_xO₄ with the composition x = 0.6, 0.8, and 1.0 was measured from 200 to 850 K. A γ-type heat capacity anomaly due to the ferri-paramagnetic transition was observed for all compositions. The transition temperatures were 652, 563, and 451 K for the compositions x = 0.6, 0.8, and 1.0, respectively. The variation of transition temperature with composition is discussed in terms of cation distribution. The magnetic contribution to the observed heat capacity was obtained by assuming that the heat capacity is expressed by the sum of the lattice heat capacity C_v(1), the dilation contribution d(d), and the magnetic contribution C(m). Entropy changes due to the transition were calculated from C(m) as 52.6, 49.7, and 46.3 J K^?1 mole^?1 for the compositions x = 0.6, 0.8, and 1.0, respectively, which are from 7 to 12 J K^?1 mole^?1 higher than the calculated values based on the assumption of randomization of unpaired spins on each ion. The difference between the observed and the calculated values is roughly explained by taking into account the orbital contribution of Fe²⁺ ions on octahedral and tetrahedral sites.