Anomalous properties of poly(γ-benzyl L-glutamate) film composed of unusual 7/2 helices

Poly(γ-benzyl L-glutamate) film composed of unusual 7-residue 2-turn (7/2) helices was prepared by slow casting from chloroform solution. The 7/2 helical conformation was irreversibly transformed at 84°C to the normal 18/5 conformation. In d.s.c. thermograms the transformation appeared as an endothermic first order transition with an enthalpy change of 3.4 cal g⁻¹. The viscoelastic and dielectric measurements indicated that the loss peak due to the side chain motion in this film was reduced to a great extent compared to the film of 18/5 helices. The dielectric relaxation strength dictated that there was a motional restriction in three quarters of the side chains. By comparison to a racemic mixture of poly(γ-benzyl glutamate), these anomalous properties were attributed to the stack of terminal benzyl groups of side chains (ormed in an alternating manner between neighbouring chains). The first order transition arises from the cooperative fusion of the stack and the side chains with their benzyl groups which are restricted in thermal motion. Such stacks may be facilitated by the precise ‘knob (side chain) and hole (space between side chains)’ packing which can be attained between neighbouring 7/2 helices.     

Architecture of a packet switch based on banyan switching networkwith feedback loops

The authors propose and describe an original feedback banyan switching network topology and control algorithm. This feedback banyan network prevents congestion even at high throughput. It does so by establishing a feedback route for the output packets from the output port to the input port of the banyan switching network. Input accommodated logical channels that do not encounter congestion within the switching network are output directly from the intended output port. Other packets are returned to the input port via the feedback route, then rerouted     

Development of Concrete Bridge Rating Prototype Expert System with Machine Learning

Efforts to develop practical expert systems have mostly concentrated on how to implement experience-based machine learning successfully. Recently several active research projects on machine learning have been undertaken from the viewpoint of knowledge-based management. The aim of this study is to develop the Concrete Bridge Rating (Diagnosis) Prototype Expert System with machine learning, employing the combination of a neural network and bidirectional associative memories (BAM). The introduction of machine learning into this system facilitates knowledge-based refinement. By applying the system to an actual in-service bridge, it has been verified that the machine learning method employed that uses the results of questionnaire surveys involving bridge experts is effective for the system.     

Formation of acrylamide in a processed food model system, and examination of inhibitory conditions

Acrylamide (AAm) is formed from asparagine (Asn) and reducing sugar during cooking of foods at high temperature. We examined the formation of AAm in a model system using a glass fiber filter paper, and looked for suitable conditions for inhibiting AAm formation. In frying, the formation rate was about 10 times that in a moistureless oven. Increase of frying temperature and frying time increased AAm formation when the residual moisture was 5% or less. AAm increased with increasing amount of glucose (Glc) addition up to 1:1 with respect to Asn, but then decreased. On the other hand, in the case of fructose, as the amount added was increased, AAm increased accordingly. The AAm formation rate with respect to Asn increased when valine (Val) was co-present in a Glc and Asn reaction system. Cysteine and lysine inhibited the AAm formation rate. Pathways for the formation of AAm are proposed.     

Improvement in physical properties of poly(vinyl chloride) by radiation-induced graft copolymerization with mixed monomers

Gamma-ray-induced graft copolymerization of butadiene with vinyl monomers onto PVC was attempted to improve the physical properties of PVC. The Izod impact strength was increased from 2 kg·cm/cm² to more than 100 kg·cm/cm² by grafting ca. 10% butadiene. But the tensile strength and melt flow were decreased by the grafting. The electron micrograph showed that the mass of polybutadiene in the graft copolymer had a convenient diameter (0.1–1 μ) for absorbing the impact energy. The weatherability of PVC grafted with butadiene was improved by cografting of butadiene with acrylates and methacrylates which had long side chains.     

Low Temperature Phase Transition in C70 and Solvation Effects

The heat capacity of C₇₀ has been measured by adiabatic calorimetry between 14 and 320 K. The orientational phase transition is observed as a broad hump in the heat capacity curve, which is strongly influenced by small amount of solvent remaining in the sample.     

Cellulose/syndiotactic polypropylene composites: Effects of maleated polypropylene as a compatibilizer and silanized cellulose on the morphology and tensile properties

To improve the interaction between syndiotactic polypropylene (SPP) and fibrous cellulose (FC), the effects of the addition of maleated polypropylene (MAPP) and FC surface modification with 3‐aminopropyltriethoxysilane (APTES) on SPP/FC composites were studied with respect to the morphology and the tensile properties. The addition of MAPP brought about an improvement in the interfacial adhesion between SPP and FC according to scanning electron microscopy observations and tensile testing. This improvement was, however, less effective than the improvement in the interfacial adhesion between isotactic polypropylene (IPP) and FC. SPP and MAPP partially or microscopically phase‐separated because of the IPP‐like polymer chain structure of MAPP. With respect to the compatibility between SPP and FC, FC surface modification with APTES was more suitable. The increase in Young's modulus was remarkable in the SPP/silanized FC composite with APTES. The tensile strength of the SPP/silanized FC composite with APTES was, however, considerably lower than that of the SPP/FC/MAPP composite. These results suggest that interfacial improvement between SPP and FC requires a compatibilizer or a surface modifier with a suitable primary structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mechanical properties of silane‐treated,silica‐particle‐filled polyisoprene rubber composites: Effects of the loading amount and alkoxy group numbers of a silane coupling agent containing mercapto groups

The surface treatment of spherical silica particles with a silane coupling agent with mercapto groups was carried out. The treated silica particles were incorporated within polyisoprene and then vulcanized. The effects of the loading amount and alkoxy group number of silane on the stress–strain curve of the filled composite were investigated. For this purpose, silanes with dialkoxy and trialkoxy structures were used. The loading amount of silane on the silica surface was varied from 1 to 8 times the amount required for monolayer coverage. The stress at the same strain increased with the silane treatment, and it was higher in the dialkoxy structure than in the trialkoxy structure above 300% strain. There was no significant influence of the loading amount on the stress for the trialkoxy silane structure. However, the stress was influenced by the loading amount, and the maximum stress was observed at 4 times the silane amount required for monolayer coverage for the dialkoxy structure. The stress had a good relationship with the crosslinking density of silica‐filled polyisoprene rubber (measured with a swelling test). The reinforcement effect by the silane treatment of silica was found to be affected strongly both by the entanglement of the silane chain and polyisoprene rubber matrix and by the crosslinking reaction between the mercapto group of silane and polyisoprene rubber in the interfacial region. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009