Nitto Chemical Industry (Japan)

ABSTRACT: Angiotensin I‐converting enzyme (ACE)‐inhibitory peptides from the thermolysin digest of chicken muscle and the peptic digest of ovalbumin were isolated. However, some of them failed to show antihypertensive activity in spontaneously hypertensive rats (SHR). To clarify this discrepancy, ACE‐inhibitory peptides from various sources were preincubated with ACE before measurement of ACE‐inhibitory activity and classified into 3 groups: (1) inhibitor type, IC 50 values of peptides that are not affected after preincubation with ACE; (2) substrate type, peptides that are hydrolyzed by ACE to give peptides with weaker activity; and (3) prodrug‐type inhibitor, these peptides are converted to true inhibitors by ACE or gastrointestinal proteases. Peptides belonging to the 1st and the 3rd groups exert antihypertensive activities even after oral administration in SHR.

Measurements of the gas-phase E.P.R. spectra of OH in the J = 9/2 and 11/2 levels of the X2II state at 26 GHz and 35 GHz respectively are reported. Confocal and semi-confocal optical resonators have been used in place of the more conventional microwave cavities for these experiments. The data are analysed, together with previous measurements by Radford on other rotational levels in the determination of six independent g factors: These parameters are interpreted in terms of the electronic structure of the OH radical. In agreement with previous workers, it is found that the major contaminant of the X2II state is the A2Σ+ state and that this pair of states is a good example of Van Vleck's pure precession hypothesis.

X-ray photoelectron spectroscopy has been used to determine the oxidation state of copper in various kinds of copper minerals. Cuprite Cu2O is found to be stable to air oxidation. Photoelectron spectra of carrollite Co2CuS4, germanite Cu3(Ge, Fe) (S, As)4 and covelline CuS reveal that these minerals contain univalent copper.

A positron pulsing system has been constructed for variable energy positron lifetime spectroscopy. The system consists of a reflection type chopper, a sub-harmonic prebuncher, and a double harmonic buncher. By operating the system with an intense slow positron beam generated by an electron linac, positron lifetime spectra have been successfully measured in an extended time range of more than 45 ns with a good time resolution (250 ps). Furthermore, Doppler broadening profiles of annihilation radiations can be obtained simultaneously with the lifetime measurements.

The x-ray photoelectron spectra of tetraphenylporphin, phthalocyanine and their copper complexes were measured. The copper complexes show a single nitrogen 1s photoline, whereas the metal free bases give rise to a doublet nitrogen 1s photoline. The central pyrrole and aza nitrogens in the metal free bases could be identified, whereas the central and meso-bridging aza nitrogens in phthalocyanine could not be discriminated. Each of the central two protons in the metal free bases is localized on one of the central four porphinato nitrogens. The shifts in N 1s binding energy observed in the present work could be reproduced by the shifts in the charge density on nitrogen obtained for the bonded structure by an extended Hückel molecular orbital calculation.

Abstract Soft fiber‐reinforced polymers (FRPs), consisting of rubbery matrices and rigid fabrics, are widely utilized in industry because they possess high specific strength in tension while allowing flexural deformation under bending or twisting. Nevertheless, existing soft FRPs are relatively weak against crack propagation due to interfacial delamination, which substantially increases their risk of failure during use. In this work, a class of soft FRPs that possess high specific strength while simultaneously showing extraordinary crack resistance are developed. The strategy is to synthesize tough viscoelastic matrices from acrylate monomers in the presence of woven fabrics, which generates soft composites with a strong interface and interlocking structure. Such composites exhibit fracture energy, Γ , of up to 2500 kJ m −2 , exceeding the toughest existing materials. Experimental elucidation shows that the fracture energy obeys a simple relation, Γ = W · l T , where W is the volume‐weighted average of work of extension at fracture of the two components and l T is the force transfer length that scales with the square root of fiber/matrix modulus ratio. Superior Γ is achieved through a combination of extraordinarily large l T (10–100 mm), resulting from the extremely high fiber/matrix modulus ratios (10 4 –10 5 ), and the maximized energy dissipation density, W . The elucidated quantitative relationship provides guidance toward the design of extremely tough soft composites.

The thermodynamic properties of and related compounds have been estimated and utilized to correlate sinterability with phase relations in the La‐M‐Cr‐O systems. Chemical equilibria calculations reveal that calculated vapor pressures of gaseous chromium oxides (especially ) can be well correlated with our previous experimental results on sinterability. The poor sinterability can be ascribed to the formation of a thin layer of which is formed from incongruently vaporized at the interparticle neck during the initial stage of sintering in air. Improvement of sinterability of oxides can be achieved by removing this layer or by decreasing vapor pressure to prevent the formation of layer. These suggest that perovskites are the most suitable materials for high sinterability, since these materials have the low vapor pressure without precipitation of .

Chemical reactions of and have been analyzed using chemical potential diagrams for the La‐Zr‐M‐O systems under a condition of . A vs. plot is appropriate for representing diffusion paths, because the layered arrangement of the reaction zone corresponds well to the geometrical configuration of stability polygons of reactants ( and ) and products (, MO, , etc.). A complicated arrangement including a ternary perovskite phase, , observed in the couple can be represented by a simple diffusion path having the same slope in the chemcial potential diagram as in the couple. The effect of lanthanum nonstoichiometry for has been discussed in relation to formation and manganese dissolution into YSZ cubic phases.

The infrared band intensities of formaldehyde and formaldehyde-d2 have been measured in the gas phase using an FT–IR spectrometer. The effect of the polymerization of the sample molecule was minimized to measure the correct intensities. When the bands overlapped each other, their individual intensities have been determined by a band simulation calculation taking account of the Coriolis interactions. The signs of the dipole moment derivatives (∂p/∂Qi) have completely been determined by the least-squares method, and the results were compared with those obtained by the molecular orbital calculation (CNDO/2) and by the analyses of the Coriolis interactions. The local intensity parameters of the CH2 group of this molecule were calculated and compared with the corresponding ones of ethylene.

Abstract Calculation methods for the single-stage permeation of a multicomponent gas mixture are presented for five flow patterns: cocurrent flow, countercurrent flow, cross flow, perfect mixing, and one-side mixing. The derivations are cast in a form suitable for computer calculation. The calculation methods presented are appropriate for systems with any number of components. Calculation results are shown for the separations of a NH3, H2, and N2 gaseous mixture by means of a polyethylene membrane, and for a H2, CH4, CO, N2, and CO2 mixture through a microporous glass membrane.

Abstract The pH value of an adsorption edge (i.e., the pH value where a change occurs in the amount of aqueous ions adsorbed by a solid phase) is dependent on the surface‐metal bonding strength and, consequently, on the type of adsorption site involved. The metal‐adsorption sites of natural (untreated) kaolinite, montmorillonite, and synthetic mordenite were elucidated by comparing the pH values of their adsorption edges with those of Si and Al oxides. Cation adsorption by these clays is strongly influenced by the Si/Al surfacesite ratio, steric effects of interlayers or channels, Lewis acid strength of the metal, and pH of the medium. Using Ni, kaolinite showed additive adsorption behavior by the Si and Al oxide surfaces with well‐defined boundaries. The adsorption edge of Ni by mordenite occurred at low pH values and was attributed to the increased Ni‐binding stability inside the channels of the zeolite structure. Several heavy metals (Ni, Zn, Cd, and Pb) were used to properly identify the various adsorption edges on montmorillonite. The adsorption of Ni by montmorillonite was similar to the Si and Al oxide surfaces but with an additional adsorption edge observed at low pH values, which was attributed to the interlayer structure of the clay. The presumed pH‐independent cation‐adsorption behavior below pH 6 by 2:1 clay minerals is probably due to pH‐dependent adsorption on amorphous Si oxide sites that can induce ion‐exchange reactions at much lower pH values than previously assumed.

The vapor-deposited low-density amorphous phase of H(2)O was directly compressed at 77 kelvin with a diamond-anvil cell, and the boundary between the low-density amorphous phase and the high-density amorphous phase was observed while the sample was warmed under compression. The transition from the low-density amorphous phase to the high-density amorphous phase was distinct and reversible in an apparently narrow pressure range at approximately 130 to approximately 150 kelvin, which provided experimental evidence for polymorphism in amorphous H(2)O.

The thermodynamically and kinetically stable peralkyloctasilacubane 1 is formed in the reaction of SiCl3 (R = CMe2CHMe2) with Na. The orange-red compound is soluble in hydrocarbons and was characterized by spectroscopy and X-ray crystallography. Both its long-wavelength electronic transition in the UV/VIS spectrum at λ ≈ 500 nm and its low oxidation potential found by cyclic voltammetry at 0.43 V—unusual values for cy-clopolysilanes—are traced back to the highly strained Si8 framework.

Abstract Natural (untreated) clays are most probably amorphous on their outermost surface layers due to the continuous and natural process of partial dissolution and reprecipitation of the clay components at the solid‐aqueous interface. The pH‐dependent adsorption on Al and Si oxides, mordenite, kaolinite, and montmorillonite of a humic acid (HA) and a fulvic acid (FA) was described as occurring on Al and Si sites. The surfaces of the clay minerals were modeled as mixtures of amorphous Al and Si oxides. The results showed a strong adsorption of the organics by the Al sites on the Al oxide and kaolinite, and a weak adsorption of organics by the Si sites on the Si oxide, mordenite, and montmorillonite. At low pH values, the Si sites on the Si oxide, mordenite, and montmorillonite adsorbed FA; these latter observations strongly suggest that the adsorption of FA by the interplanar spaces of expanding clays is driven by forces that can be studied using amorphous Si oxide as the adsorbent. Multivalent cations will form organo‐metallic complexes that significantly increase adsorption, particularly on Si sites; exceptions were found with some FA‐metal complexes, which were attributed to the degree of complexation. The implication of these observations is that, in natural systems, the adsorption of aqueous compounds is highly dependent on the type of (amorphous) surface present at the outermost layer of the solid phase in contact with the liquid phase.

Abstract Molecular aggregation in a commercial polyimide film, Du Pont Kapton, was investigated by small‐angle x‐ray scattering (SAXS). From the analysis of the desmeared SAXS curve, it is concluded that aggregation in the Kapton film can be elucidated in terms of a two‐phase structure having electron density fluctuations within the phases. For comparison with the molecular aggregation in Kapton, molecular aggregation in polyimides synthesized in our laboratory was also investigated. It was found in this case that molecular aggregation is controlled by the initial imidization temperature. Molecular aggregation of polyamic acid and polyimide cyclized at a low temperature gives amorphous structures. On the other hand, molecular aggregation of polyimide cyclized at high temperatures gives two‐phase structures like that of Kapton film. The SAXS curve for a polyimide having the two‐phase structure shows a peak due to interference between ordered regions. The two‐phase structure of the polyimide can be explained in terms of a one‐dimensional model. The more ordered phase is produced at the higher initial imidization temperature. The relative density difference between two phases is only a few percent for polyimide films cyclized at high temperatures. This result shows that the two‐phase structure of aromatic polyimide differs essentially from that of ordinary crystalline polymers.

Abstract In practical applications of liquid membranes containing a mobile camer, three main types of membranes have been studied: liquid surfactant, supported liquid, and solvent polymeric membranes (2-6). In these membranes the solvent polymeric membrane which consists of a polymer film containing a plasticizer generally exhibits a low ionic permeability compared with the other types of membranes, although it has a high stability and durability. This is because the transference of the carrier in the membrane is depressed by its high viscosity and high electrical resistance. Accordingly, the ionic permeability may be improved by selecting an appropriate plasticizer.

The mechanism and kinetics of the pressure-induced polymerization of acetylene were studied by Raman spectroscopy. The polymerization reaction occurred in the orthorhombic phase at room temperature and pressures above 3.5 GPa. Dominant formation of trans-polyacetylene suggested that the monomer underwent trans opening of the triple bond and polymerized along the diagonal of the bc plane of the unit cell. The reaction was described as an idealized one-step and one-dimensional growth process by an Avrami equation with an exponent 1.34.

Reinforcing hydrogels with a rigid scaffold is a promising method to greatly expand the mechanical and physical properties of hydrogels. One of the challenges of creating hydrogel composites is the significant stress that occurs due to swelling mismatch between the water-swollen hydrogel matrix and the rigid skeleton in aqueous media. This stress can cause physical deformation (wrinkling, buckling, or fracture), preventing the fabrication of robust composites. Here, a simple yet versatile method is introduced to create "macroscale" hydrogel composites, by utilizing a rigid reinforcing phase that can relieve stress-induced deformation. A low-melting-point alloy that can transform from a load-bearing solid state to a free-deformable liquid state at relatively low temperature is used as a reinforcing skeleton, which enables the release of any swelling mismatch, regardless of the matrix swelling degree in liquid media. This design can generally provide hydrogels with hybridized functions, including excellent mechanical properties, shape memory, and thermal healing, which are often difficult or impossible to achieve with single-component hydrogel systems. Furthermore, this technique enables controlled electrochemical reactions and channel-structure templating in hydrogel matrices. This work may play an important role in the future design of soft robots, wearable electronics, and biocompatible functional materials.

To obtain fundamental data for the extraction and concentration of furfural produced in a reactor by using supercritical CO2, the isothermal high pressure vapor–liquid equilibria for two binary systems (CO2–water and CO2–furfural) and a ternary system (CO2–water–furfural) were measured in the temperature range from 343 to 421 K. Additionally, the experimental data were compared with results calculated by various equations of state. As a result, it was found that (1) the Peng–Robinson and Soave–Redlich–Kwong equations of state combined with the mixing rules proposed by Panagiotopoulos correlated the two binary systems satisfactorily and predicted the ternary system well, and (2) the furfural produced could be selectively extracted from the reactor and concentrated to 95 wt% by a new process proposed on the basis of a knowledge of the vapor–liquid equilibria.

Abstract In order to reduce the internal stress in a cured epoxy resin, the submicron polymer particles were dispersed therein prior to curing. For this purpose, four kinds of poly(butyl acrylate), poly(methyl methacrylate) core‐shell particles were prepared by seeded emulsion polymerization for methyl methacrylate with poly(butyl acrylate) seed particles having different particle diameter, and subsequently were powdered by drying at room temperature. It was observed by SEM that poly(butyl acrylate) particles as core were dispersed in the cured epoxy matrix. Poly(methyl methacrylate) as shell seems to dissolve in the matrix. The internal stress of cured epoxy resin decreased with the modification of the particles and the tendency was enhanced with a decreasing in the particle diameter.