Preferred-handed helical conformation in organic–inorganic hybrid block copolymers with well-controlled stereoregularity

A novel block copolymer containing polyhedral oligomeric silsesquioxanes (POSS) features a well-controlled stereoregularity, that is, isotactic polymethacrylate-functionalized POSS-b-polymethyl methacrylate (it-PMAPOSS-b-PMMA), was prepared via controlled-anionic polymerization. The stereoregularity of each segment in the it-PMAPOSS-b-PMMA is evaluated using nuclear magnetic resonance (NMR) spectroscopy, which reveals an isotactic configuration in both the PMAPOSS and PMMA segments. The secondary structure of it-PMAPOSS-b-PMMA in a mixture with a small chiral dopant is clarified with electronic circular dichroism and vibrational circular dichroism measurements. By adding a chiral dopant, a controlled preferential helical conformation of the unilateral segment in achiral it-PMAPOSS-b-PMMA is achieved.     

Binaural active noise control using parametric array loudspeakers

This paper reports the binaural active noise control (ANC) system developed to deal with factory noise. The control points are located in the vicinity of the left and right ears of a worker sitting along the production line. Due to the complicated safety requirements in the factory, secondary sources and error microphones are not allowed to be placed near the worker. Therefore, the proposed ANC system employs the feedforward structure and adopts the parametric array loudspeakers (PALs) as the secondary sources. The PAL is a type of directional loudspeaker that generates a much narrower sound field as compared to the conventional loudspeaker. Once the proposed ANC system has been trained offline, the error microphones can be removed. The performance of the binaural ANC system is successfully demonstrated based on a digital signal processor (DSP) implementation.     

Observation of hydrogen in deuterated methane hydrate by maximum entropy method with neutron powder diffraction

The crystal structure of deuterated methane hydrate (structure I, space group: Pm(-)3n) was investigated by neutron powder diffraction at temperatures of 7.7-185 K. The scattering amplitude density distribution was examined by a combination of Rietveld method and maximum entropy method (MEM). The distribution of the D atoms in both D(2)O and CD(4) molecules was clarified from three-dimensional graphic images of the scattering amplitude density. The MEM results showed that there were low-density sites for the D atom of D(2)O in a particular location within the D(2)O cage at low temperatures. The MEM provided more reasonable results because of the decrease in the R factor that is attainable by this method. Accordingly, the low-density sites for the D atom of D(2)O probably exist within the D(2)O cage. This suggests that a spatial disorder of the D atom of D(2)O occurs at these sites and that hydrogen bonds between D(2)O molecules become partially weakened. With regard to the CD(4) molecules, there were high-density sites for the D atom of CD(4), and the density distribution of the C and D atoms was observed separately in the scattering amplitude density image. Consequently, the C-D bonds of CD(4) were not observed clearly because the CD(4) molecules had an orientational disorder. The D atoms of CD(4) were displaced from the line between the C and O atoms, and were located near the face center of the polygon in the cage. Accordingly, the D atoms of CD(4) were not bonded to specific O atoms. This result is consistent with the hydrophobicity of the CD(4) molecule. We also report the difference between the small and the large cages in the density distribution map and the temperature dependence of the scattering amplitude density.     

Investigation of interaction of Leu-enkephalin with lipid membranes

Enkephalins are peptides with morphine-like activity. To achieve their biological function, they must be transported from an aqueous phase to the lipid-rich environment of their membrane bound receptor proteins. In our study, zeta potential (ZP) method was used to detect the association of Leu-enkephalin and Leu-enkephalinamide with phospholipid liposomes constituted from egg-phosphatidylcholine (EPC), dioleoyl-phosphatidylethanolamine (DOPE), cholesterol (Chol), sphingomyelin (SM) as well as soybean phospholipid (SBPL). Transfer of the peptides over lipid membranes was examined by electrophysiology technique (ET) and fluorescence spectroscopy (FS), and further confirmed using 4-fluoro-7-nitrobenzofurazan (NBD-F) labeled Leu-enkephalin (NBD-F-enkephalin) with confocal laser scanning microscopy method (CLSM). Results of zeta potential showed that enkephalinamide associated with lipid membranes and gradually saturated on the membranes either hydrophobically or electrostatically or both. Data from electrophysiology technique indicated that Leu-enkephalin could cause transmembrane currents, suggesting the transfer of peptides across lipid membranes. Transfer examined by fluorescence spectroscopy implied that it could be separated into three steps, adsorption, transportation and desorption, which was afterward reaffirmed by confocal laser scanning microscopy. Transfer efficiencies of enkephalin across SBPL, EPC/DOPE, EPC/DOPE/SM, EPC/SM and EPC/Chol lipid bilayer membranes were evaluated with ET and CLSM experiments. Results showed that the addition of either sphingomyelin or cholesterol, or negatively charged lipid in lipid membrane composition could lower the transfer efficiency.     

Magnetic properties of the compounds ThCO2Ge2 and ThCo2Si2

Rather old preparation of the compounds ThCo₂Ge₂ and ThCo₂Si₂ and their magnetic study in the temperature range 100–570 K, published by Omejec and Ban [Z. Anorg. Allg. Chem. 380 (1971) 111], indicated that both compounds ordered ferrromagnetically below 100 K. In order to verify the old data, polycrystalline samples of ThCo₂Ge₂ and ThCo₂Si₂ have been prepared by arc melting and subsequent annealing, and studied by X-ray diffraction at room temperature (RT), by superconducting quantum interference device (SQUID)-magnetization and AC-susceptibility measurements at 2–320 K, and by dc-magnetization measurements in variable magnetic fields up to 120 kOe at 5, 80, and 283 K. The magnetic measurements confirm the ferromagnetic ordering in both compounds, but with totally different Curie temperatures: ≈120(20) K for ThCo₂Ge₂ and above 320 K for ThCo₂Si₂. The paramagnetic values of ThCo₂Ge₂ and the ordering of both compounds are discussed and compared with the old results of Omejec and Ban.     

Pipe flow with solid particles fixed in space

A group of solid particles were hung by slender rods in a pipe to make a model of two-phase flow of coarse particles. Pressure gradient and velocities were measured for different types of the models. The drag on the particles (spheres) were obtained from measurements of pressure gradient with some assumptions. The results are summarized as follows. (1) Mean velocities of fluid are lower in the central part of the pipe than in the circumferential part. Turbulence is remarkably increased by particles. The spectrum distribution of turbulent velocity becomes flatter. These results are similar to the gas-solid flow of coarse particles in a vertical pipe. (2) At a large Reynolds number, the drag coefficient per one sphere in the group is larger than that of a single isolated sphere in a uniform flow. When the spheres are arranged along the same line in the longitudinal direction, the drag coefficient becomes smaller as the longitudinal distance between the spheres is shortened.     

Investigation of the possibility of geometrical electrophoresis

We investigate the possibility of geometrical electrophoresis, which is based on nanofabrication techniques. (GEE) utilizes geometrical effects during electrophoresis, which are generated by physical interactions between walls and a macromolecule confined in spaces smaller than the Flory radius. When a polymer is injected into a small space, confinement energy is usually required. However, the confinement energy form depends on the geometry of the space. In the case of electrophoresis, the electric field itself changes depending on the geometry. Using a nanofabricated quartz chip with a curved channel, we investigated electrophoretic behavior of high molecular weight DNA based on the curvature effect.