The thermal unfolding of insulin was studied at various pHs by an adiabatic DSC. The involvement of self-association of insulin in both folded and unfolded sates caused complex profiles in DSC curves. The exothermic heat effect due to the aggregation of the unfolded molecule was found to be associated with the endothermic heat effect due to the unfolding of native insulin at neutral pH and at pHs below 2. At a pH range from 2 to 4.5, the unfolding was quantitatively reversible. DSC curves observed in acetic acid solution where the molecular association is negligible showed a broad peak indicating that the monomeric insulin has a relatively loose structure in the aspect of thermodynamic cooperativity.

View full abstract

The present study is concerned with the fabrication of humidity sensor of Tantalum oxide film for the Effluent gas analysis. Water vapor is rapidly adsorbed on and desorbed from Tantalum oxide layer formed on the surface of Tantalum wire by high temperature oxidation.
The sensor detected the relative humidity change quickly. In the low humidity region (0 to 30% RH), the output of sensor increased linearly with increase in the amount of humidity in atmosphere. Sensor is stable over a long period of time.

View full abstract

Highly pure silicon and silicon compounds are required in the fields of high technology products such as semiconductor and optical fiber. Rice hulls contists of 71-87wt% of organic components such as cellulose and 13-29% of inorganic components. 87-97wt% of the inorganic components is silica (SiO₂). The reactivity of rice hull SiO₂ is assumed to be higher than that of mineral SiO₂ because rice plant accumulates it in a living body. The rice hull SiO₂ has high possibility to use as industrial raw materials though rice hulls are now utilizing only as agricultural materials or waste materials for now. To utilize the rice hull SiO₂ in the field of high technology industries, the production process of pure silicon compound from rice hull ashes is proposed in this paper. The process is that SiO₂ in rice hull ashes is reacted with Cl₂ under coexistence of C to be converted to SiCl₄,
SiO₂+2Cl₂+2C→SiCl₄+2CO
SiCl₄ is distilled to be purified. The effeciency of the process of SiCl₄ production from rice hull ashes was much higher than that from mineral SiO₂, and it is found that coexistance of potassium salts and sulfur accelerated the chlorination of SiO₂.

View full abstract

Various elementary models proposed to understand the order-disorder transition behavior of binary substitutional alloys are reviewed. These models are evaluated for binary body- and face-centered cubic lattices by comparing the calculated entropies with the experimental ones. Among these models, the cluster variation method proposed by Kikuchi is a good model to explain the order-disorder transition of binary alloys.

View full abstract