Thermally-induced Transition in Aqueous Solution of Cationic Surfactant Containing Aromatic Ring

Heat capacities of aqueous solutions of cetyltrimethylammonium (CTA) salicylate, of CTA m-hydroxybenzoate and of CTA p-hydroxybenzoate were measured using a scanning microcalorimeter. Only the salicylate solution exhibited heat-capacity anomaly around 330 K, depending on the heating rate. The transition enthalpy was 3.5±0.2 kJ mol^–1, which was similar to that observed in solution of 1:1 intermolecular compound between CTA bromide (CTAB) and o-iodophenol (OIPh). The enthalpy of formation H_f of the 1:1 intermolecular compound from CTAB and OIPh was determined by measuring the enthalpies of solution of the relevant crystals into ethanol. Positive value _fH=3.0±0.3 kJ mol^–1 was explained from a large difference between the heat capacities of the 1:1 compound and 1:1 mixture of the component crystals.This revised version was published online in November 2005 with corrections to the Cover Date.     

Modes selection in polymer mixtures undergoing phase separation by photochemical reactions

Phase separation kinetics and morphology of binary polymer mixtures (A/B) in the presence of photochemical reactions were investigated by using phase-contrast optical microscopy combined with digital image analysis. The polymers were chemically designed in such a way that two types of chemical reactions, intermolecular photodimerization and intramolecular photoisomerization, of polymer segments can be induced and controled by irradiation with ultraviolet light. Unlike the conventional case, the phase separation in the presence of these reactions is spontaneously frozen due to the suppression of the long-wavelength instabilities, resulting in stationary spatial structures with intrinsic periodicities. These characteristic length scales are determined by the competition between the two antagonistic interactions: phase separation as a relatively short-range activation and the photochemical reaction as a long-range inhibition. Furthermore, it was found that the spatial symmetry breaking of concentration fluctuations can emerge from the elastic stress associated with the nonhomogeneous kinetics of the reactions. Experimental data obtained with three types of reactions: A-A only cross-link, A-A and B-B simultaneous cross-links and the reversible A<-->B photoisomerization are described. These results do not only indicate that combination of chemical reactions and phase separation could provide a novel method to control the morphology of multiphase polymer materials, but also suggest that photoreactive polymers can be used as a chemical system to study the mode-selection process in polymers far from thermodynamic equilibrium. (c) 1999 American Institute of Physics.     

Direct detection of RNAs in living cells using peptide-inserted Renilla luciferase

In this study, non-engineered RNAs were detected in living cells using bioluminescence. Two types of probe were utilized: a peptide inserted RLuc (PI-RLuc) probe and a split-RNA probe. Incorporation of the PI-RLuc and split-RNA probes enabled the direct detection of RNA introduced into living cells.     

The magnetic phase transition of an amorphous FePC and its alloys containing Ni and Cr

The magnetic phase transition of the amorphous ferromagnetic alloys Fe₈₀P₁₃C₇, Fe₇₀Cr₁₀P₁₃C₇ and Fe₇₀Ni₁₀P₁₃C₇ has been investigated by magnetization and specific heat measurements. From the field dependence of the isothermal magnetization, the critical exponents and the Curie temperature (T_C) of Fe₈₀P₁₃C₇ were obtained to be β = 0.38 ± 0.02, γ = 1.30 ± 0.05, θ = 4.47 ± 0.05 and T_c = 586.55 ± 0.1°K. These exponents sufficiently satisfy the static scaling law. The specific heat of Fe₈₀P₁₃C₇ showed an approximate logarithmic singularity at T_c. The specific heat from Fe₇₀Ni₁₀P₁₃C₇ shows fairly broad peak and the peak almost smears out for Fe₇₀Cr₁₀P₁₃C₇.