Peel Test Using Nonstationary Peel Method

The cohesive peel spectra of pressure-sensitive adhesive (PSA) tapes have been measured using a non-stationary peel tester. The experimental evidence and a viscoelastic analysis based on a peel model indicate that there are no significant effects of acceleration in the normal rate region. The nonstationary peel tester can be regarded as a useful tool for testing and evaluating PSA tapes.     

Drilling of Multi-Layer Printed-Circuit Boards

With the recent improvement in the performance and miniaturization of computers, communication equipment, and various other pieces of electronic apparatus, multi-layer printed-circuit boards have attained wide usage. The need for drilling such boards has been increasing. A multi-layer printed-circuit board used in the computer is usually provided with 2,000 to 3,000 holes 0.5-0.9 mm in diameter, each made by a NC high-speed automatic drilling machine. It is estimated that the number of holes made for the drilling of printed-circuit boards might well have reached 200 billion in 1971. Drilling printed-circuit boards is accomplished by using a drill, a punch, a laser beam, an electron beam and liquid jet, or by other methods. It is considered that the use of a drill is most suitable from the point of view of surface quality of drilled holes, reliability of their plating through holes, workability, and so forth.     

Simple,Mild, and Practical Esterification,Thioesterification, and Amide Formation Utilizing p‐Toluenesulfonyl Chloride and N‐Methylimidazole

We have developed an efficient method for the esterification or thioesterification of equimolar amounts of carboxylic acids and alcohols or thiols using a novel reagent, p‐toluenesulfonyl chloride (TsCl) together with N‐methylimidazole. The present method is simple, mild, and reactive, uses readily available and economical reagents. The choice of amine is critical for the present method. The amine, N‐methylimidazole, has two roles: (i) as an HCl scavenger for the initial smooth generation of mixed anhydrides between carboxylic acids and TsCl and (ii) successive formation of highly reactive ammonium intermediates from mixed anhydrides. This method could be applied to various types of carboxylic acids, alcohols, and thiols: a) several functionalities were tolerated; b) two N‐Cbz amino acids were smoothly esterified without racemization; and c) the labile 1β‐methylcarbapenem key intermediate and a pyrethroid insecticide, prallethrin, were successfully prepared. The related amide formation between carboxylic acids and primary or secondary amines was also performed. The proposed reaction mechanism involves a novel method for producing the reactive acylammonium intermediates. The production of these intermediates was rationally supported by a careful ¹H NMR monitoring study.     

Optical assessment of silicon nanowire arrays fabricated by metal-assisted chemical etching

Silicon nanowire (SiNW) arrays were prepared on silicon substrates by metal-assisted chemical etching and peeled from the substrates, and their optical properties were measured. The absorption coefficient of the SiNW arrays was higher than that for the bulk silicon over the entire region. The absorption coefficient of a SiNW array composed of 10-μm-long nanowires was much higher than the theoretical absorptance of a 10-μm-thick flat Si wafer, suggesting that SiNW arrays exhibit strong optical confinement. To reveal the reason for this strong optical confinement demonstrated by SiNW arrays, angular distribution functions of their transmittance were experimentally determined. The results suggest that Mie-related scattering plays a significant role in the strong optical confinement of SiNW arrays.     

Improvement of carrier diffusion length in silicon nanowire arrays using atomic layer deposition

To achieve a high-efficiency silicon nanowire (SiNW) solar cell, surface passivation technique is very important because a SiNW array has a large surface area. We successfully prepared by atomic layer deposition (ALD) high-quality aluminum oxide (Al₂O₃) film for passivation on the whole surface of the SiNW arrays. The minority carrier lifetime of the Al₂O₃-depositedSiNW arrays with bulk silicon substrate was improved to 27 μs at the optimum annealing condition. To remove the effect of bulk silicon, the effective diffusion length of minority carriers in the SiNW array was estimated by simple equations and a device simulator. As a result, it was revealed that the effective diffusion length in the SiNW arrays increased from 3.25 to 13.5 μm by depositing Al₂O₃ and post-annealing at 400°C. This improvement of the diffusion length is very important for application to solar cells, and Al₂O₃ deposited by ALD is a promising passivation material for a structure with high aspect ratio such as SiNW arrays.     

The physical character of coal char formed during rapid pyrolysis at high pressure

Rapid pyrolysis was conducted in a drop tube reactor using seven coals under various operating conditions. In addition to dense char, porous chars (network char and cenospheric char) were formed by the rapid pyrolysis under certain conditions. Porous char was mainly composed of film-like carbon and skeleton carbon. The pyrolyzed coal char particles were characterized in detail. Morphology and bulk density of porous char were quite different from the dense char formed under the same conditions, but elemental composition and BET surface area were similar to each other. CO₂ gasification reactivity of porous char was lower than dense char in the later gasification stage, and this was ascribed to the low reactivity of skeleton carbon.     

Hydrophobic Tagged Dihydrofolate Reductase for Creating Misfolded Glycoprotein Mimetics

In the endoplasmic reticulum (ER), nascent glycoproteins that have not acquired the native conformation are either repaired or sorted for degradation by specific quality‐control systems composed by various proteins. Among them, UDP‐glucose:glycoprotein glucosyltransferase (UGGT) serves as a folding sensor in the ER. However, the molecular mechanism of its recognition remains obscure. This study used pseudo‐misfolded glycoproteins, comprising a modified dihydrofolate reductase with artificial pyrene–cysteine moiety on the protein surface (pDHFR) and Man₉GlcNAc₂‐methotrexate (M9‐MTX). All five M9‐MTX/pDHFR complexes, with a pyrene group at different positions, were found to be good substrates of UGGT, irrespective of the site of pyrene modification. These results suggest UGGT's mode of substrate recognition is fuzzy, thus allowing various glycoproteins to be accommodated in the folding cycle.     

Pervaporation separation of water/ethanol mixtures through polysaccharide membranes. II. The permselectivity of chitosan membrane

The separation of water/alcohol mixtures through chitosan membrane was investigated. The degree of the deacetylation of chitosan did not affect the selectivity of the membrane in the separation of the water/ethanol mixture. The selectivity of the chitosan membrane was affected by the specific salts such as CoSO₄, ZnSO₄, and MnSO₄ and it increased when the salts were present in the feed mixture or the membrane was pretreated with the salt solution. This behavior would be explained by the contraction of the “holes” produced by the thermal motion of polymer chains and this contraction would be correlated with the conformation change of chitosan molecule due to the formation of complexes with metal ions.     

The metabolism and distribution of docosapentaenoic acid (n−6) in rats and rat hepatocytes

In this study, a new marine oil that contains 45% docosahexaenoic acid (DHA, 22∶6n−3) and 13% docosapentaenoic acid (DPA, 22∶5n−6) was administered to rats. The metabolism and distribution of DPA in rats was investigated. In experiment 1, the effects of DHA and n−6 fatty acids (linoleic acid, I A; arachidonic acid, AA; and DPA) on AA contents were investigated in vivo. LA group: LA 25%, DHA 30%; LA-DPA group: LA 15%, DPA 10%, DHA 35%; LA-AA-DPA group: LA 10%, AA 5%, DPA 10%, DHA 35% were administered to rats for 4 wk. In the liver, the AA content in the LA-DPA and LA-AA-DPA groups was significantly higher than in the LA group. The decreased AA contents in the LA group might be caused by DHA administration. Although DHA also was administered in the LA-DPA and LA-AA-DPA groups, the AA contents in these two groups did not decrease. These results suggested that DPA retroconverted to AA, blunting the decrease in AA content caused by DHA administration. To conduct a detailed investigation on DPA metabolism and its relation with AA and DHA, rat hepatocytes were cultured with pruified DPA and DHA for 24 h. We discovered the retroconversion of DPA to AA occurred only when AA content was decreased by a high DHA administration; it did not occur when AA content was maintained at a normal level.