Structure and properties of the mesophase of syndiotactic polystyrene. II. Effect of stepwise extraction on the preparation of the mesophase

In this study, a novel stepwise extraction method has been examined. The guest molecules housed between the helices of the clathrate δ form of syndiotactic polystyrene can be removed completely with this method. A systematic study of the preparation of a solvent‐free mesophase (emptied clathrate) membrane, its helical and residual solvent contents, and its structural transformations has been performed. In this first attempt, an enhancement in the TTGG helical content has been observed in the extracted membrane, and a conceptual mechanism is proposed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 269–273, 2003     

Structure and properties of the mesophase of syndiotactic polystyrene—III. Selective sorption of the mesophase of syndiotactic polystyrene

Syndiotactic polystyrene (sPS) has various crystalline forms such as α, β, γ, and δ forms, and a mesophase depending on the preparation method. In this study, we focused on the mesophase with the molecular cavity of sPS, which is obtained by step‐wise extraction of the guest molecules from the sPS δ form. To prepare the mesophase containing different shapes and sizes of the cavity, two kinds of the sPS δ form membrane cast from either toluene or chloroform solution were first prepared and then the guest molecules were removed by a step‐wise extraction method using acetone and methanol. We could succeed in the preparation of two kinds of mesophase with different shapes and sizes of the molecular cavity. Either toluene or chloroform vapor sorption to the sPS mesophase membranes was examined at 25 °C. Sorption analysis indicates that the mesophase with large molecular cavities can mainly sorb large molecules; on the other hand, the mesophase with small cavities can sorb only the small molecules, and is unable to sorb a large amount of large molecule because the cavity was too small to sorb the large molecules. Therefore, the sPS mesophase membrane has sorption selectivity based on the size of the molecular cavity. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 238–245, 2004     

Factors affecting physicochemical properties of liposomes prepared with hydrogenated purified egg yolk lecithins by the microencapsulation vesicle method

We examined hydrogenated purified egg yolk lecithins, having practical advantages over non-hydrogenated ones, as liposomal membrane materials. Liposomes were prepared by the microencapsulation vesicle (MCV) method in which liposomes are formed through two-step emulsification and dispersion. Three types of purified egg yolk lecithins with different iodine values were examined after being dissolved in one of three lipid solvents. The liposome size increased as the temperature during the second emulsification increased, being closer to the boiling temperature of the solvent. The preparation temperature in relation to the transition temperature of each lecithin was also a factor affecting liposome sizes. As for the encapsulation efficiencies of the model compound calcein in liposomes, they differed mainly depending on the solubility of each lecithin in a lipid solvent and it was more obvious in hydrogenated lecithins. A high preparation temperature resulted in lower encapsulation efficiencies, suggesting that leakage of encapsulated calcein was facilitated at high temperature in the MCV methods. There was a significant correlation between liposome sizes and encapsulation efficiencies in non-hydrogenated purified egg yolk lecithin but not in hydrogenated ones. When using hydrogenated purified egg yolk lecithins as liposomal membrane materials, it was suggested that a lipid solvent should be chosen so that a lecithin completely dissolves under the preparation condition in order to achieve a higher encapsulation efficiency. Smaller liposome particles were obtained when the second emulsification was performed at a lower temperature compared with the boiling point of the lipid solvent. These findings can be applied to control encapsulation efficiencies and particle sizes in each particular liposome preparation enclosing therapeutic agents.     

Dioxopyrrolines. LXII. Diels-Alder reaction of 1-Aryl-4- and 5-methoxycarbonyl-1H-pyrrole-2,3-diones with various 1,3-dienes

Two new dioxopyrrolines (1-aryl-4-methoxycarbonyl-1H-pyrrole-2,3-dione 6 and the 5-methoxycarbonyl isomer 8) behaved as good dienophiles to some kind of 1,3-dienes examined. In most cases, the products were explained by the reaction where the largest lobe of HOMO of dienes reacted to the larger LUMO of dienophiles in an expected cis-endo manner. However, in the reactions of 8 with alkylbutadienes, piperylene and isoprene, abnormality in the reaction was observed, which was well explained by taking account of steric factors.     

Spinel, YbFe2O4, and Yb2Fe3O7 types of structures for compounds in the In2O3 and Sc2O3---A2O3---BO systems [A: Fe, Ga, or Al; B: Mg, Mn, Fe, Ni, Cu, or Zn] at temperatures over 1000°C

In the Sc₂O₃---Ga₂O₃---CuO, Sc₂O₃---Ga₂O₃---ZnO, and Sc₂O₃---Al₂O₃---CuO systems, ScGaCuO₄, ScGaZnO₄, and ScAlCuO₄ with the YbFe₂O₄-type structure and Sc₂Ga₂CuO₇ with the Yb₂Fe₃O₇-type structure were obtained. In the In₂O₃---A₂O₃---BO systems (A: Fe, Ga, or Al; B: Mg, Mn, Fe, Ni, or Zn), InGaFeO₄, InGaNiO₄, and InFe³⁺MgO₄ with the spinel structure, InGaZnO₄, InGaMgO₄, and InAlCuO₄ with the YbFe₂O₄-type structure, and In₂Ga₂MnO₇ and In₂Ga₂ZnO₇ with the Yb₂Fe₃O₇-type structure were obtained. InGaMnO₄ and InFe₂O₄ had both the YbFe₂O₄-type and spinel-type structures. The revised classification for the crystal structures of AB₂O₄ compounds is presented, based upon the coordination numbers of constituent A and B cations.     

The ASACUSA CUSP: an antihydrogen experiment

In order to test CPT symmetry between antihydrogen and its counterpart hydrogen, the ASACUSA collaboration plans to perform high precision microwave spectroscopy of ground-state hyperfine splitting of antihydrogen atom in-flight. We have developed an apparatus (“cusp trap”) which consists of a superconducting anti-Helmholtz coil and multiple ring electrodes. For the preparation of slow antiprotons and positrons, Penning-Malmberg type traps were utilized. The spectrometer line was positioned downstream of the cusp trap. At the end of the beamline, an antihydrogen beam detector was located, which comprises an inorganic Bismuth Germanium Oxide (BGO) single-crystal scintillator housed in a vacuum duct and surrounding plastic scintillators. A significant fraction of antihydrogen atoms flowing out the cusp trap were detected.     

Formation of a Ligand‐Assisted Complex of Two RNA Hairpin Loops

The hairpin structure is one of the most common secondary structures in RNA and holds a central position in the stream of RNA folding from a non‐structured RNA to structurally complex and functional ribonucleoproteins. Since the RNA secondary structure is strongly correlated to the function and can be modulated by the binding of small molecules, we have investigated the modulation of RNA folding by a ligand‐assisted formation of loop–loop complexes of two RNA hairpin loops. With a ligand (NCT6), designed based on the ligand binding to the G–G mismatches in double‐stranded DNA, we successfully demonstrated the formation of both inter‐ and intra‐molecular NCT6‐assisted complex of two RNA hairpin loops. NCT6 selectively bound to the two hairpin loops containing (CGG)₃ in the loop region. Native polyacrylamide gel electrophoresis analysis of two doubly‐labeled RNA hairpin loops clearly showed the formation of intermolecular NCT6‐assisted loop–loop complex. Förster resonance energy‐transfer studies of RNA constructs containing two hairpin loops, in which each hairpin was labeled with Alexa488 and Cy3 fluorophores, showed the conformational change of the RNA constructs upon binding of NCT6. These experimental data showed that NCT6 simultaneously bound to two hairpin RNAs at the loop region, and can induce the conformational change of the RNA molecule. These data strongly support that NCT6 functions as molecular glue for two hairpin RNAs.     

Evaluating a time-delay of hydrogen production quantitatively in photosynthetic bacteria for stabilizing intermittency

Renewable energy is regarded as a clean energy source but has some problems, one of which is intermittency. To reduce this, the time-delay of hydrogen production by photosynthetic bacteria can be effective. In this study, we qualitatively evaluated the time-delay of hydrogen production by photosynthetic bacteria under various irradiation conditions, and we also quantitatively evaluated it by fitting the experimental data and the hydrogen production model with a genetic algorithm. As a result of model fitting, we found that the relationship between the lengths of the optimized time-delay of hydrogen production by photosynthetic bacteria and the amount of light irradiation is linear. And we also found that the time-delay of hydrogen production by photosynthetic bacteria had an upper limit under low light intensity. We have suggested the existence of an energy store mechanism in photosynthetic bacteria.     

Plasma heating by a modulated relativistic electron beam-plasma interaction

We study experimentally the interaction of a current-modulated relativistic electron beam with a mirror-confined plasma. A high-power transmitter (500 MHz, 1 GW) is developed. Rapid heating takes place up to ≈ 900 eV, which is interpreted as a lower-hybrid parametric instability.