Diameter control of poly(p-oxycinnamoyl) microspheres prepared by self-organizing polycondensation

The diameter control of poly(p-oxycinnamoyl) (POC) microspheres was examined. POC microspheres were prepared by the polycondensation of (E)-4-acetoxycinnamic acid in liquid paraffin at 320 °C. The microspheres were formed through the formation of microdroplets by the reaction-induced liquid-liquid phase separation and the subsequent polymerization of oligomers in the microdroplets leading to the solidification. The size of the microspheres was actually governed by the coalescence of the microdroplets in the growth process. In order to control the coalescence of the microdroplets, 4-octadecyloxybiphenyl (ODB) was added to the polymerization solution as a coalescence inhibitor, which exhibited amphiphilicity to liquid paraffin and POC. ODB inhibited the coalescence of the microdroplets. The average diameter decreased with the increase of the ODB concentration, and it was tunable from 0.97 to 4.61 μm.     

Anionic ring-opening polymerization of 2-phenyl-1,3,4-oxadiazolin-5-one and conversion of the resulting polymer,N-benzamido-1-nylon,to N-amino-1-nylon

Summary The ring-opening polymerization of 2-phenyl-1,3,4-oxadiazolin-5-one (1) was carried out anionically both in bulk and in DMF solution at 140°C for 15 h in the presence of various initiators, such as alkaline metal salts of 1, alkaline metal fluorides and tertiary amines, leading to N-benzamido-l-nylon (2) having Mns up to 2,000. Hydrolysis of the pendant benzamido groups of the resulting polymer was successfully achieved in aqueous ethanol containing concentrated hydrochloric acid at 100°C to give N-amino-l-nylon (3). The original polymer dissolves easily in aliphatic and aromatic alcohols and polar aprotic solvents, whereas the hydrolyzed polymer is not soluble in these solvents but highly soluble in water. In dilute aqueous solutions, the latter polymer behaves as common polyelectrolytes with flexible backbone. Polymers 2 and 3 began to lose weight in air at around 200 and 170°C, respectively.     

Electrochemical methane conversion over SrFeO3−δ perovskite on an yttrium stabilized zirconia membrane

Oxidative methane coupling and the related chemical reactions have been studied in an electrochemical membrane cell of the type: CH₄, (O₂), SrFeO_3– , Au¦8%Y₂O₃:ZrO₂¦Ag, air. The results are compared to a fixed bed study of SrFeO_3– . The C₂₊ selectivity and the alkene/alkane ratio may be higher in the cell reactor than in the fixed bed reactor, but the C₂₊ yield never exceeded fixed bed data. The maximum C₂₊ yield observed in the cell reactor was 3.1%. The electric fields in the cell when electrodes were connected influenced the selectivity to CO₂ in a manner which may be related to the NEMCA effect.     

Computational study of flow in a curved pipe with circular cross section

Laminar imcompressible flows in a circular sectioned pipe were investigated by seeking numerical solutions to the Navier-Stokes equations. Three semi-circular pipes of radius ratios 0.05, 0.143 and 0.148 were studied. These calculations covered the Dean number ranging from 183 to 3847. In the range of low and medium Dean numbers, a steady-state solution was obtained; when the Dean number was high, a three-dimensional separation and the associated secondary flow were clearly observed far downstream near the outlet. Extensive flow visualizations were made to depict the computed results.     

立足于"结构设计"的建筑

序言 “结构设计”是通过运用各种技术工程学使非凡超越的建筑设计成为可能。 如果不以结构为立足点只是一味的追求刺激、感动.忽略满足居住性、经济性、耐久性、生产性等的建筑创造.要实现它是不可能的。 对于开辟今后的新时代以及社会的建筑空间创造来说,我确信“结构设计”的研究是不可或缺的。     

A Nifedipine Coground Mixture with Sodium Deoxycholate. I. Colloidal Particle Formation and Solid-State Analysis

Sodium deoxycholate (DCNa) is a bile salt that forms multimolecular inclusion compounds with a variety of organic substances. In this study, complex formulation of DCNa with nifedipine, a poorly water soluble drug, by grinding was investigated. The coground mixture was prepared with a vibration rod mill, and its solid state was characterized using powder X-ray diffraction, differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy. A laser diffraction particle size analyzer was also used to determine the particle size distribution curve in solution. When a nifedipine-DCNa (1:2 w/w) mixture coground for 30 min was dispersed into water and a pH 6.8 buffer solution, a semitransparent colloidal solution occurred immediately; 90% of the total particles formed in solution had a diameter less than 600 nm. Both powder X-ray diffraction peaks and DSC endothermic peak of nifedipine crystals were not found for the coground mixture, whereas a new exothermic peak was observed on DSC thermograms. The magnitude of this exothermic peak depended on the weight fraction of DCNa and the grinding time, indicating that nifedipine crystals changed into an amorphous state by complex formation with DCNa during the grinding process. In the FTIR spectrum of the coground mixture, the peaks of aromatic CH out-of-plane bend and dihydropyridine NH stretch of nifedipine were considerably weakened, suggesting that van der Waals interaction may be present between the drug and DCNa molecules. From these results, it is clear that the cogrinding method with DCNa is very useful for the formation of amorphous nifedipine in the solid state and the production of colloidal particles of the drug in solution.     

Removal of histone tails from nucleosome dissects the physical mechanisms of salt-induced aggregation,linker histone H1-induced compaction,and 30-nm fiber formation of the nucleosome array

In order to reveal the roles of histone tails in the formation of higher-order chromatin structures, we employed atomic force microscopy (AFM), and an in vitro reconstitution system to examine the properties of reconstituted chromatin composed of tail-less histones and a long DNA (106-kb plasmid) template. The tail-less nucleosomes did not aggregate at high salt concentrations or with an excess amount of core histones, in contrast with the behavior of nucleosomal arrays composed of nucleosomes containing normal, N-terminal tails. Analysis of our nucleosome distributions reveals that the attractive interaction between tail-less nucleosomes is weakened. Addition of linker histone H1 into the tail-less nucleosomal array failed to promote the formation of 30 nm chromatin fibers that are usually formed in the normal nucleosomal array. These results demonstrate that the attractive interaction between nucleosomes via histone tails plays a critical role in the formation of the uniform 30-nm chromatin fiber.     

Fracture behavior of carbon steel pipe with local wall thinning subjected to bending load

To evaluate the structural integrity of power plant piping, monotonic bending tests are conducted on 4- and 3.5-in. diameter full-scale carbon steel pipe specimens with local wall thinning. The local wall thinning is simulated as erosion/corrosion metal loss. The eroded area of the wall thinning is subjected to tensile or compressive stress by applied bending moment. The deformations or fracture behaviors at maximum moments are found to be classified into three types. When the eroded area is subjected to tensile stress, ovalization or crack initiation/growth occurs at the maximum moment. When an eroded area is subjected to compressive stress, ovalization or local buckling occurs. The occurrence of ovalization, crack initiation/growth, or local buckling depends on the initial size of local wall thinning. From the relationships among ovalization, crack growth and local buckling, allowable sizes for local wall thinning are proposed.     

Frequency domain discussions on PD signal propagation characteristics in GIS

The frequency dependency of PD signal propagation in GIS was investigated at an underground substation. Injecting dummy pulses into a GIS through its internal electrode, frequency spectra were measured by a spectrum analyzer at various points of the GIS. It is shown that this measurement is very reproducible and the signal propagation phenomena are independent of its direction. It is also clarified that the PD signal reduction phenomena are closely related with mode transfer from TEM to TE or TM. The major higher mode seems to be TE₁₁. Pulse waveforms were also measured with 65‐MHz bandpass filter. Their magnitudes are compared with the gain of the 65‐MHz component of the frequency spectra and good agreement is obtained. This implies the possibility of PD location by observing a frequency pattern with several bandpass filters. © 2000 Scripta Technica, Electr Eng Jpn 133(3): 9–17, 2000