Sequence distribution of cis-1,4- and trans-1,4-units in polyisoprenes

The ¹³C n.m.r. spectra of chicle polyisoprene and cis-trans isomerized 1, 4-polyisoprenes were studied. The splittings of signals were observed in the C₁, C₂, and C₄ carbon signals of the isomerized polyisoprenes. The newly appearing signals were assigned to the carbon atoms in cis-trans linkages. The fractions of the diad sequences (trans-trans, trans-cis, cis-trans, and cis-cis) were determined by using the four signals of C₁ carbon. It was found that the cis-1, 4- and trans-1, 4-units were randomly distributed in the isomerized polyisoprenes and it was confirmed that the chicle polyisoprene was a mixture of cis-1, 4- and trans-1, 4-polyisoprenes.     

Polymerization of macromers

Summary The possibility of group transfer polymerization of methyl methacrylate-terminated polystyrene macromer (MA-PSt) was explored by using 1-methoxy-1-(trimethylsiloxy)-2-methyl-1-propene and tris(dimethylamino)sulfonium difluorotrimethylsilicate as initiator and catalyst, respectively. The results obtained at the polymerization temperature of 0°C were undesirable. However, the oligomerization at -78°C gave almost quantitatively oligo(MA-PSt) of which the degree of polymerization was in good agreement with the mole ratio of macromer to initiator. The GPC curve of oligo(MA-PSt) was sharp and symmetrical. In addition, it was shown by the copolymerization with methyl methacrylate that the polymerizability of the macromer was markedly enhanced in the presence of methyl methacrylate comonomer.     

Morphology and breaking of latex particle deposits at a cylindrical collector in a microfluidic chamber

We report an analysis for the morphology and breaking behavior of deposits of spherical latex particles (1 and 3.6 μm in diameter) at a cylindrical collector in a microfluidic channel fabricated by soft-lithography. In-situ observation of particle deposition over a large range of flow rate conditions evidence the relationship between deposit morphology and mode of particle transport toward the collector. For low Pe?clet number (Pe), particle deposits are nearly uniform all over the collector surface except at the rear where particles do not attach. Upon increase of Pe, deposits gradually adopt a columnar morphology at the collector stagnation point. These results are qualitatively consistent with previously reported Monte Carlo simulations of deposits formation in stagnation point flow systems. However, these simulations fail to quantitatively predict the observed deposition at the rear of the collector for sufficiently high flow rate. Additional deposit breaking experiments together with numerical evaluations of particle flux around the collector suggest that such "anomalous" deposition at large Pe is significantly governed by concomitant detachment of deposited particles at the stagnation point and the presence of recirculation flow at the collector rear. Finally, kinetics of deposition are discussed in connection with particle size-dependence of deposit breaking features.     

Metal-Induced Structural Switching of a Folded Quinone-Sandwiched Porphyrin

We report the synthesis of a novel quinone-sandwiched porphyrin in which two benzoquinones are connected oppositely at the meso positions of a porphyrin through rigid 3-amido 2,2′-bipyridine linkers. ¹H-NMR and single crystal X-ray analyses revealed that the quinone-sandwiched porphyrin has a folded structure in which the porphyrin unit was inserted into the two quinone moieties via π-stacking. Insertion of a Zn(II) ion into the porphyrin center induced a drastic conformational change which is resulted in coordination of the oxygen atoms of both benzoquinone moieties to the Zn-porphyrin to afford a 6-coordinated structure.     

Novel Structures for Porous Silicon Light-Emitting Diodes

In this paper, two novel structures of porous silicon (PS) light-emitting diodes (LEDs) are proposed aiming at the reduction of series resistance, R_s. The basic idea of the novel structures is to suppress the excessive growth of nanoporous silicon (nano-PS) layer that is electroluminescence- (EL-) active but highly resistive. The initial wafer of the first structure consists of a lightly-doped layer stacked on a highly-doped substrate. As a consequence of anodization, nano-PS layer is formed only in the lightly-doped layer, while meso-PS layer with moderate resistivity is formed in the highly-doped substrate. The second structure consists of alternately stacked nano- and meso-PS layers, since it is expected that multiple thin nano-PS layers connected in series are less resistive than a single thick nano-PS layer. Preliminary experimental results proved the effectiveness of these novel structures on the reduction of R_s.     

Highly elongated,low‐aspect‐ratio tokamak produced by negative‐biased theta pinch

Ultra Low Aspect Ratio Tokamaks (ULART) are produced by using a negative‐biased theta‐pinch device. A slender conducting rod which serves as a toroidal field coil is newly installed along a geometrical center axis of the theta‐pinch coil. The ULART is quickly formed for about 10 μs by applying programmed current flows from three sets of fast banks and a slow bank to these coils and is sustained for about 100 μs. The plasma diagnosed from a magnetic probe array has a low aspect ratio A = 1.1 and a poloidal surface with a high elongation ratio κ = 10. The safety factor reaches about 30 near the separatrix edge when I_p = 280 kA flows in the plasma and I_tfc = 30 kA in the conducting rod. A preliminary result on global MHD characteristics of the ULART is also given. The plasma is unstable with respect to a vertical displacement and a toroidal n = 1 mode. The amplitudes of these modes depend on the values of I_tfc and κ. © 2001 Scripta Technica, Electr Eng Jpn, 134(4): 19–27, 2001     

Developed Modeling and Numerical Simulation for Mismatching Photovoltaic Performance Evaluation

A simplified simulation method was described for charactering mismatching photovoltaic performance integrated with bypass and string diodes, which are configured additionally compared with the tradition design for avoiding deterioration to modules in series or in parallel connection. The Newton-Raphson method was adopted for numerical simulations, with some computation problem discussed for fast convergence. It was proven to be suitable and effective when model validation coinciding with manufacturer specification. Furthermore, maximal power point (MPP) peak positions were reviewed roundly via simulations of the total characteristic curves. Multi-power peaks with multi-diodes installed were also investigated. The proposed method can be benefit for better comprehension on the physical circuit and provides greater program expansibility, and such simulation researches should be applicable for manufacturer to evaluate the configuration of photovoltaic module. © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Construction of simulation model for spray flash desalination system

This paper describes a simulation model for a spray flash desalination system which makes fresh water from sea water by using the temperature difference between warm surface sea water and cool deep sea water. The spray flash desalination system can be modeled by using the energy conservation law and the mass conservation law. Simulation results of the model are compared with the experimental results and show the accuracy of the proposed simulation model. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(4): 9–17, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20975