On-line TDPAC studies with the 19O beam

A new ¹⁹F probe disintegrated from short-lived ¹⁹O has been developed for the first time for time-differential perturbed angular correlation method. The angular correlation coefficient for the relevant cascade has been experimentally estimated to be A₂₂ = -0.17±0.01. As the first application of this technique to condensed matter physics, the probe was implanted in polycrystalline fullerene C₆₀. We have observed two contrastive perturbations acting on the probe nuclei, which reflect electrostatic and dynamic interactions with the extranuclear field.     

Hyperfine interactions of interstitial12B in Fe,V and Ta studied by use of the asymmetric β decay

Magnetic hyperfine fields and spin-lattice relaxation times of interstitial and substitutional¹²B nuclei in Fe are studied in a temperature range, 100 K<T<1200 K, by use of the asymmetric decay from the spin polarized nuclei and NMR detection. In order to infer information regarding the location of¹²B nuclei and expansion in the nearest Fe surrounding following recoil implantation, hyperfine interactions of¹²B in non-magnetic bcc V and Ta crystals are studied.     

Automated odor-sensing system based on plural semiconductor gas sensors and computerized pattern recognition techniques

Although odor is an inherent characteristic of chemical substances, no methods to measure or identify odor objectively have been available. A computerized method for classification and identification of odor is reported. Odors are detected by using eight semiconductor gas-sensor elements which have different sensing properties for gases; the output from the odor-detecting apparatus for a gas sample is represented by an 8-dimensional vector. The vectors for 30 substances were examined by clustering analysis and four obvious clusters were observed. These clusters corresponded to ethereal, etherealminty, ethereal-pungent and pungent substances.     

Optical activity induced by helical arrangements of tryptamine and 4-chlorobenzoic acid in their cocrystal

Optical rotatory powers of chiral cocrystals formed from the achiral molecules tryptamine and 4-chlorobenzoic acid were determined by the HAUP (high accuracy universal polarimeter) method. These cocrystals belonged to space group P2(1)2(1)2(1), and their absolute configuration was confirmed by the Flack parameter. In the M-crystal, 2-fold helical arrangements are formed in a counterclockwise direction between the two components through the quaternary ammonium salt bridge, hydrogen bond, and the aromatic pi-piinteraction along the c axis, while clockwise helices alone exist in the P-crystal. Large rotatory powers rho(3)(M) = -355 and rho(3)(P) = +352 deg mm(-)(1) were obtained along the c axis in the M- and P-crystal, respectively, at 632.8 nm and 303 K. The magnitude was 10 to 100 times larger than those for ordinary organic crystals. Further, it was confirmed that the negative sign was induced by the counterclockwise helical structures and the positive sign by the clockwise helices. In contrast, the rotations along the a and b axis which are in perpendicular directions to the screw axis were rho(1)(M) = +138, rho(1)(P) = -140 deg mm(-)(1), and rho(2)(M) = -56, rho(2)(P) = +58 deg mm(-)(1), much smaller than rho(3)(M) and rho(3)(P) . The results revealed that the helically arranged aromatic pi electrons as well as the helical ionic and hydrogen bond networks in the crystal contributed to the enhancement of the magnitude of these rotations.     

Freezing-out of nuclear polarization in radioactive core ions of microclusters, “snowballs” in superfluid helium

A novel method was tried successfully to trap ions and to freeze out their nuclear polarization inside aggregates of helium atoms, snowballs, in superfluid helium. Spin polarized¹²B (T _1/2=20.4 ms) ions were introduced into superfluid helium and snowballs were created around the impinged impurity ions. Beta-ray asymmetry was measured to obtain the nuclear polarization of decaying¹²B. The comparison with the initial value of¹²B polarization produces that no relaxation in polarization was observed throughout lifetime of¹²B.     

A vertex ordering characterization of simple-triangle graphs

Consider two horizontal lines in the plane. A point on the top line and an interval on the bottom line define a triangle between two lines. The intersection graph of such triangles is called a simple-triangle graph. This paper shows a vertex ordering characterization of simple-triangle graphs as follows: a graph is a simple-triangle graph if and only if there is a linear ordering of the vertices that contains both an alternating orientation of the graph and a transitive orientation of the complement of the graph.     

Electrochemical carboxylation with carbon dioxide

Studies carried out in the past two years on electrochemical fixation of carbon dioxide with carbon-carbon bond formation, so-called electrochemical carboxylation or electrocarboxylation, are reviewed. Among about twenty papers on electrochemical carboxylation published from 2014 to the present, recent advances in electrochemical carboxylation regarding asymmetric carboxylation, sacrificial anode-free carboxylation, and carboxylation following aryl radical cyclization are focused on and discussed.     

NMR chemical shift study of the methanol—benzene-d6 system

The OH proton chemical shifts of methanol referred to the CH₃ proton in the methanol — benzene-d₆ system have been measured from room temperature up to the supercritical region. MD simulations have also been performed at the same composition as experiment at 575 K. The chemical shift results in the supercritical region are in good agreement with those of pure methanol at the same density within experimental errors. The results of NMR and MD simulation suggest that the hydrogen-bonded structure of methanol is practically not affected by addition of benzene molecules.