Magnetic reversal of the ferroelectric polarization in a multiferroic spinel oxide

Ferroelectric transition has been detected in a ferrimagnetic spinel oxide of CoCr2O4 upon the transition to the conical spin order below 25 K. The direction [110] of the spontaneous polarization is normal to both the magnetization easy axis [001] and to the propagation axis [110] of the transverse spiral component, in accord with the prediction based on the spin-current model. The reversal of the spontaneous magnetization by a small magnetic field (approximately 0.1 T) induces the reversal of the spontaneous polarization, indicating the clamping of the ferromagnetic and ferroelectric domain walls.     

Phenylpropanoid and phenylethanoid derivatives from Kigelia pinnata DC. fruits

Further phytochemical investigation of the fruits of Kigelia pinnata DC. has yielded a new phenylpropanoid derivative identified as 6-p-coumaroyl-sucrose (1) together with ten known phenylpropanoid and phenylethanoid derivatives (2-11) and a flavonoid glycoside (12). The structures of the isolated compounds were elucidated using various techniques of NMR and MS spectral analysis.     

Semipermeable polymer vesicle (PICsome) self-assembled in aqueous medium from a pair of oppositely charged block copolymers: physiologically stable micro-/nanocontainers of water-soluble macromolecules

A new entity of polymer vesicle with a polyion complex (PIC) membrane, a PICsome, was prepared by simple mixing of a pair of oppositely charged block copolymers, composed of biocompatible PEG and poly(amino acid)s, in an aqueous medium. Flow particle image analysis revealed the formation of spherical particles with a size range up to 10 mum. Observation by dark-field and confocal laser scanning microscopes clearly confirmed that the PICsome has a hollow structure with an inner-water phase, in which FITC-dextran emitting green fluorescence was successfully encapsulated simply by the simultaneous mixing with the block copolymers. Confocal laser scanning microscopic observation and spectral analysis revealed the smooth penetration of a low molecular weight fluorescent dye (TRITC; MW = 443.5) emitting red fluorescence into the FITC-dextran encapsulated PICsome to give the PICsome image with a merged color of yellows, indicating the semipermeable nature of the PICsome membrane. The PICsomes showed appreciable physiological stability even in the presence of serum proteins, suggesting their feasibility in biomedical fields such as carriers of therapeutic compounds and compartments for diagnostic enzymes.     

Spontaneous Formation of Giant Unilamellar Vesicles from Microdroplets of a Polyion Complex by Thermally Induced Phase Separation

Water pump : Polyion complex (PIC) vesicles are spontaneously formed from PIC microdroplets, which are formed by mixing cationic and anionic polymers (see picture). The formation process can be reversibly controlled by local heating with a focused infrared laser that triggers microphase separation and subsequent water influx. The size of the resulting giant unilamellar vesicles is determined by the initial size of the PIC droplets.

     

Synthesis of [3]Rotaxanes that Utilize the Catalytic Activity of a Macrocyclic Phenanthroline–Cu Complex: Remarkable Effect of the Length of the Axle Precursor

[3]Rotaxanes, which consist of one macrocyclic phenanthroline compound and two axle components, were prepared by the oxidative dimerization of an alkyne compound with bulky tris[4′‐cyclohexyl‐(1,1′‐biphenyl)‐4‐yl]methyl blocking group. The catalytic activity of a macrocyclic phenanthroline–Cu complex was utilized to thread the two axle components inside the ring. The alkyne compound with chain of 15 or 20 methylene groups gave [3]rotaxanes in high yields, whereas the axle with a chain of six methylene groups afforded a [3]rotaxane in very poor yield. We also examined the effect of the ring size on the synthesis of [3]rotaxanes. [3]Rotaxanes were not isolated when a macrocyclic phenanthroline compound with a smaller ring size was used.     

Extended vacancy-type defects in silicon induced at low temperatures by electron irradiation

We have observed the formation of extended defects in silicon at low temperatures (below 25 K) by means of in-situ high-resolution transmission electron microscopy (HRTEM). The defects are distorted spheres, occasionally truncated by facets, less than 5 nm in diameter. These defects are stable up to 773 K, and they gradually shrink during annealing in the temperature range from 773 to 973 K. From the analysis of HRTEM images of the defects, we have suggested that the defects are voids formed via athermal migration of vacancies under electron irradiation.     

Evaluation of Ph and granite/hot water interaction under geothermal conditions

Abstract

The in-situ laboratory measurement of pH in a granite-hot water reaction system has been undertaken under flowing conditions. The calculation of fluid pH and multi-component chemical equilibria in the granite-hot water reaction system was made, using the calculation program SOLVEQ92. In this study, the chemical equilibrium relationship of granite and hot water interaction was also deduced using the some program. The measurement of in-situ pH in the granite-hot water reaction system was undertaken in the temperature and pressure range of 100–250°C and 20MPa respectively. The in-situ pH value shows good agreement with the pH calculation value with regard to multi-component chemical equilibria. As a result of this work, it is reasonable to suggest that the pH of reservoir fluids in geothermal system can be readily estimated by use of the SOLVEQ92 calculation program, which provides a ‘calculated’ pH value.     

A Chemical Synthesis of 3-Deoxy-D-manno-2-octulosonic Acid from D-mannose

A chemical synthesis of Kdo was achieved via the condensation of a protected D-mannofuranose-5,6-cyclic sulfate with ethyl 1,3-dithiane-2-carboxylate, which is an efficient equivalent for installing an α-ketoester unit as a key step.     

Characterization of hydrophilic networks synthesized by group transfer polymerization

Group transfer polymerization was used to synthesize several series of hydrophilic random and model networks. Cationic random networks were prepared both in bulk and in tetrahydrofuran (THF) using a monofunctional initiator and simultaneous polymerization of monomer and branch units, while a bifanctional initiator was employed in THF for the synthesis of model networks comprising basic or acidic chains. Upon polymerization of the monomer, the latter initiator gives linear polymer chains with two “living” ends, which are subsequently interconnected to a polymer network by the addition of a branch unit. Homopolymer network star polymers were also synthesized in THF by a one‐pot procedure. The synthesis involved the use of a monofunctional initiator and the four‐step addition of the following reagents: (i) monomer, to give linear homopolymers; (ii) branch unit, to form “arm‐first” star polymers; (iii) monomer, to form secondary arms and give “in‐out” star polymers; and, finally (iv) branch unit again, to interconnect the “in‐out” stars to networks. Different networks were prepared for which the degree of polymerization (DP) of the linear chains between junction points was varied systematically. For all networks synthesized, the linear segments, the “arm‐first” and the “in‐out” stars were characterized in terms of their molecular weight (MW) and molecular weight distribution (MWD) using gel permeation chromatography (GPC). The degrees of swelling of both the random and model networks in water were measured and the effects of DP, pH, and monomer type were investigated.