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  • Author or Editor: K. Saito x
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Summary Thermogravimetry (TG) and Me2CO adsorption measurements for flexible porous crystalline coordination polymers with 2-dimensional (2-D) frameworks, {[Co(NCS)2(3-pia)2]·4Me2CO}n (1⊃4Me2CO, 3-pia=N-(3-pyridyl)isonicotinamide), were carried out. Taking advantages of capability of hydrogen bonding of amide groups for a dynamic properties, 1⊃4Me2CO show crystal (non-porous)-to-crystal (porous) structural rearrangement in Me2CO adsorption/desorption processes. The activation energy for the Me2CO desorption process of 1⊃4Me2CO was obtained using Flynn-Wall-Ozawa’s (FWO) method. The Me2CO adsorption isotherms on 1 have a threshold pressure (P th) for abrupt accommodation of Me2CO molecules, which is regarded as the equilibrium pressure for the inclusion reaction of Me2CO

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Liquid scintillation counting of40K in ordinary potassium propionate is a highly suitable experimental task in the general education on radioactivity. The counting efficiency is about 90%, depending little on the measurement conditions. Potassium propionate is of suitable properties and can be easily obtained commercially or by conversion from other compounds. The result of counting, about 1,700 cpm/g, is highly impressive to many students, indicating the existence of40K radioactivity unexpectedly high in the normal nature, and can be used for the exercise of calculating our internal radiation exposure.

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Abstract  

A simple separation method was applied to determine rhenium in river water using Q-ICP-MS and HR-ICP-MS. Re was concentrated from 420-925 ml river water using a TEVA resin minicolumn. Such extraction using a resin could separate Re from most sample matrices and trace elements. Almost 100% recovery was found throughout the method as determined with radioactive multitracers. The HR-ICP-MS was also used for the direct determination because of its low detection limit for Re (0.007 pg/ml). The Re concentration in the river water samples ranged from 0.9 to 6.5 pg/ml and the three analysis results showed good agreement with each other.

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Summary We have performed low-temperature heat capacity measurements on pellet samples of (DMe-DCNQI)2M (M=Li, Ag) which is known to show spin-Peierls transitions at 51 and 86 K, respectively. A linearly temperature-dependent term in the low-temperature heat capacity has been observed for both the samples: It is attributable to the spin-wave excitations induced by the inhomogeneous pressure effects produced in the pellet forming process. Although the temperature dependences of the magnetic susceptibility in both materials are almost the same, the coefficient of T-linear term of the Ag salt becomes three times larger that that of the Li salt. The peculiar electronic state originating from the competition of the spin-Peierls mechanism and the Coulomb repulsion is suggested.

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The heat capacities and magnetic susceptibilities of powdered samples of FexNbS2 (x=0.14, 0.21 and 0.30) were measured at temperatures from 8 to 303 K and from 5 to 300 K, respectively. For Fe0.14NbS2, the magnetic susceptibility exhibited an anomaly as a shoulder at about 57 K, but no heat capacity anomaly was observed at this temperature, indicating the appearance of a spin-glass state. Anomalies in the heat capacity for FexNbS2 (x=0.21 and 0.30) occurred at 100.5 and 45.0 K, respectively, where the magnetic susceptibility displayed a maximum, corresponding to an antiferro-paramagnetic phase transition. The electronic state of the iron atom is discussed on the basis of entropy analysis.

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A convenient non-destructive method for the determination of low level210Pb and226Ra with an ordinary high-purity Ge-detector is presented. The ordinary Ge-detectors used in this work were available to measure 46.5 keV -rays of210Pb. These detectors were also useful for the non-destructive analysis of low-level226Ra in lime-stone and calcium chemicals when a stream of nitrogen gas was maintained around the detectors. By this method, measurements could be carried out not only for210Pb and226Ra but also for other -emitting radionuclides simultaneously, using the same detector. The detection limits of about 1 Bq per sample for210Pb and about 0.05 Bq per sample for226Ra, respectively, were estimated, when the samples were counted for 1–2 days.

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Vanadium in marine organisms from Onagawa Bay in Miyagi, Japan, was determined by an instrumental neutron activation analysis (INAA) method using anti-coincidence gamma-ray spectrometry at the Dalhousie University SLOWPOKE-2 Reactor (DUSR) facility in Canada. Seaweeds, cultivated oysters, plankton, and four different species of sea squirt were collected from Onagawa Bay during 2005–2008. Vanadium levels around 20 μg g−1 (dry weight) were found in Japanese tangle and hijiki seaweeds. One species of sea squirt (Ciona savignyi) contained 160–500 ppm of V and it was highest among the four species of sea squirts studied. Protein-bound V species were separated by gel permeation chromatography (GPC) and the element determined by inductively coupled plasma atomic emission spectrometry (ICP-AES).

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Journal of Radioanalytical and Nuclear Chemistry
Authors: K. Takamiya, T. Inoue, K. Nakanishi, A. Yokoyama, N. Takahashi, T. Saito, H. Baba, and Y. Nakagome

Abstract  

In order to estimate the deformation rate of fission fragment at the scission point for thermal neutron-induced fission of233,235U and239Pu, double-velocity and double-energy measurements were carried out. As the result of the estimation of the deformation rate, two types of scission point configurations were found. One type is composed of deformed light and heavy fragments, and the other type is a combination of deformed light and spherical heavy fragments. Mass and total kinetic energy distributions were sorted in two distributions by means of the type of configuration.

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Summary Using a thermal relaxation calorimetry technique, we have measured heat capacities of κ-(BEDT-TTF)4Hg2.89Br8 system under magnetic fields between 0 and 6 T. With the increase of cooling rate from room temperature to liquid helium temperature, we have observed a remarkable but systematic tendency that the thermal anomaly associated with the superconductive transition shifts to the lower temperatures. The course of this phenomenon is attributable to the degree of disorder in the mercury chains which give an incommensurate potential to the superconducting planes.

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The size distribution of free-volume (<~0.1 nm3) of ethylene-vinyl alcohol copolymer with various crystalline degrees was estimated by positronium lifetime measurement. With increasing degree of crystallinity, the size distribution significantly narrowed and the intensity of positronium decreased. This indicates that the inhomogeneity reduces with the increase of the degree of crystallinity. It is found that the free-volume fraction estimated is reflected by the fraction of the amorphous region.

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