Experimental evidence and theoretical analysis for the chiral symmetry breaking in the growth front of conglomerate crystal phase of 1,1'-binaphthyl

Chirally asymmetric states, chemical oscillations, propagating chemical waves, and spatial patterns, are examples of far-from-equilibrium self-organization. We have found that the crystal growth front of 1,1(')-binaphthyl shows many of the characteristics of an open system in which chiral symmetry breaking has occurred. From its supercooled molten phase, 1,1(')-binaphthyl crystallizes as a conglomerate of R and S crystals when the temperature is above 145 degrees C. In addition, 1,1(')-binaphthyl in its molten phase is always racemic due to its high racemization rate. Under appropriate conditions, bimodal probability distribution of enantiomeric excess (ee) with maxima around 60% was observed. The ee was mass independent, indicating that the growth front maintains a constant ee. A kinetic model that theoretically analyzes the chiral symmetry breaking transition in the growth front of a conglomerate crystal phase was formulated. Computer simulation of the model reproduced not only the average but also the large variation of the ee observed in crystallization experiments.     

The effect of the polarization electric field on helix-unwinding in a planar chiral smectic C liquid-crystal cell

The effect of the polarization electric field on helix-unwinding in a thin planar chiral smectic C liquid-crystal cell is studied by using the nematic-like expression for the elastic deformation free-energy density. It is found that the elongation of the helical pitch when the cell thickness decreases is greater when the spontaneous polarization is larger. This is due to the Coulomb repulsion between polarization charges concentrated at ± 2π disclinations.     

Electrical Properties of Silver Photodoped Amorphous Red Phosphorus

Abstract

Effects of photodoping and thermal doping of silver into sputtered amorphous red phosphorus films (a-P_red) on the electrical properties are studied. The d. c. efectrical conductivity of the photodoped a-p_red at room temperature is about 1×10^?5 Scm^?1 which is a very high value comparing with that of the undoped a-p_red (1×10^?14 Scm^?1). The activation energy for the conduction of the photodoped a-P_red is lower than that of the a-p^red. In contrast, the activation energy of the thermally doped a-p_red is essentially the same as that of the undoped a-p_red. SEM-EDX analyses show that colloidal silver was deposited in the thermally doped a-p_red but not in the photodoped a-p_red. It seems that the photo-doping involves the ionization process of silver by illumination, i.e., Ag^o → Ag⁺ + e^?.     

Intelligent feedback release systems and the application to neuron network model research

Intelligent feedback release systems, consisting of radiation-prepared porous polycarbonate film or silicone chip and radiation crosslinked stimuli-sensitive hydrogels with immobilized enzymes as a sensor–actuator gate were constructed. Those systems showed various signal responsive substance release functions, and selective signal transfer functions. The application of those integrated intelligent systems as neural network model was investigated.     

Stretching of slow positron pulses generated with an electron linac

A facility for generating a high intensity slow positron beam using an electron linear accelerator has been constructed. A conversion efficiency of 6×10^–7 slow positrons per incident electron has been obtained for 75 MeV electrons. Storage and stretching of pulsed slow positrons have been successfully carried out with a Penning trap.     

Colorimetric detection of fluoride ion in an aqueous solution using a thioglucose-capped gold nanoparticle

The thioglucose-capped gold nanoparticles have been prepared by the chemical reduction of HAuCl₄ using thioglucose as the reducing and capping agent, which displays selective colorimetric detection of fluoride ion in 10 mM HEPES buffer at physiological pH.     

Determination of the As(III)/As(V) ratio in soil by X-ray absorption near-edge structure (XANES) and its application to the arsenic distribution between soil and water.

The details of a method used to determine the As(III)/As(V) ratio in soil by arsenic K-edge XANES spectroscopy are described. The spectra of mixtures of NaAs(III)O2 and NaH2As(V)O4, conducted for an As(III)/As(V) calibration, were well-fitted by combining normalized spectra of NaAsO2 and Na2HAsO4, where the coefficients multiplied by the normalized spectra were identical to the molar ratio of As(III) and As(V) in the mixtures. XANES spectra of arsenic in soil samples could also be fitted by a linear combination of the spectra of NaAsO2 and Na2HAsO4, which enabled us to estimate the As(III)/As(V) in a soil containing 10.2 mg/kg arsenic. The As(III)/As(V) ratio in the soil was compared with that of a soil solution contacted with the soil determined by HPLC-ICP-MS, showing that As(III) is distributed to water more readily than As(V). The application of the XANES method is important for a better understanding of the behavior of As(III) and As(V) independently in a natural aquifer.     

Catalytic cyclopropanation of alkenes via (2-furyl)carbene complexes from 1-benzoyl-cis-1-buten-3-yne with transition metal compounds

The reaction of alkenes with conjugated ene-yne-ketones, such as 1-benzoyl-2-ethynylcycloalkenes, with a catalytic amount of Cr(CO)(5)(THF) gave 5-phenyl-2-furylcyclopropane derivatives in good yields. The key intermediate of this cyclopropanation is a (2-furyl)carbene complex generated by a nucleophilic attack of carbonyl oxygen to an internal alkyne carbon in pi-alkyne complex or sigma-vinyl cationic complex. A wide range of late transition metal compounds, such as [RuCl(2)(CO)(3)](2), [RhCl(cod)](2), [Rh(OAc)(2)](2), PdCl(2), and PtCl(2), also catalyzes the cyclopropanation of alkenes with ene-yne-ketones effectively. When the reactions were carried out with dienes as a carbene acceptor, the more substituted or more electron-rich alkene moiety was selectively cyclopropanated with the (2-furyl)carbenoid intermediate.     

Synthesis of tetra-aza macrocycles with remarkably high efficiency

Tetra-aza macrocycles with 28- to 44-membered rings can be readily synthesized by reaction of dibromide and ditosyldiamide without use of a high dilution method. The reaction proceeded very smoothly with a 10 mM concentration in DMF, and gave the macrocycles in excellent yields (60–80%). Favorable effects of cesium ion on the cyclization have been observed.