Statistico-Thermodynamical Studies on the Fundamental Reactions concerning Steel-Making. IV : The Oxidation and Reduction Equilibrium of Magnetite with Gas Phases

It is known that magnetite crystals can contain excess oxygen over the stoichiometric composition of Fe_3O_4 by high temperature oxidation, and the oxygen content depends on the oxygen pressure in atmosphere and on the temperature. The Fe_3O_4 crystal has a crystal structure of the inversed-spinel type, in which O^ ions occupy the closed packed cubic lattice points, and the tetrahedral lattice sites (8 f) of its unit cell are occupied by 8 Fe^ ions, and octahedral lattice sites (16 c) by 8 Fe^ and 8 Fe^ ions statistically. When the magnetite crystal contains excess oxygen under an oxidizing atmosphere, it can be assumed that a vacant site accompanying two electron defects which result in two Fe^ ions is found on the octahedral lattice points occupied by Fe^ ions. Under these circumstances we can calculate the partition function of magnetite phase, from which the equilibrium relation between the oxygen content in magnetite, the partial pressure of oxygen in atmosphere and the temperature is deduced theoretically. These results are in good agreement with observations by Greig et al. and Darken and Gurry

Theory of Plasticity I : Correlation between Lattice Transformation and Plastic Gliding in Metals

Two fundamental relations, which are essential to express the resistance against the plastic gliding in terms of the thermodynamic function were derived, by considering the structure of dislocation. One is a relation which connects the free energy difference ΔG dissipated during the lattice transformation with the mechanical energy f・ΔL required for the plastic gliding and it has been assumed in the previous report. Here f is the resistance against the plastic gliding and ΔL the amount of deformation in the process of lattice transformation, its numerical value being 0.306. Another relation gives a method to obtain the free energy difference ΔG for a crystal in which the lattice transformation cannot take place under the usual condition

Effect of Shot-Peening on fatigue Strength of Metals. II : Effects on Decarburized Steels

The effect of shot-peening on the fatigue strength of decarburized Si-Mn spring steels was examined by the rotary-bending and the reversed torsional method. The effect was very striking and it was observed that the endurance limit at 10^7 cycles of decarburized steels, which was reduced by about 50 per cent of limit of the polished specimen on account of the soft layer only about 0.05mm in thickness, increased by 40～50 per cent as the result of shot-peening of the decarburized layer. It might be possible to recover the strength in the non-decarburized state by increasing the peening intensity

Induction of mammotroph development by a combination of epidermal growth factor, insulin, and estradiol-17β in rat pituitary tumor GH3 cells

Several reports have indicated that prolactin-secreting cells (PRL cells) are generated from growth hormone-secreting cells (GH cells). We have shown that treatment with a combination of epidermal growth factor (EGF), insulin, and estradiol-17beta (E-2) induces the appearance of PRL cells in pituitary tumor GH3 cells. The aim of the present study was to clarify the involvement of mitosis in the cytogenesis of PRL cells in rat pituitary and GH3 cells. The effects of the treatment with EGF, insulin and E-2 on DNA-replication were studied by detecting the uptake of bromodeoxyuridine (BrdU) into the nucleus. In cultured rat pituitary cells, BrdU-labeled PRL cells were observed irrespective of the hormone treatment. In GH3 cells, BrdU-Iabeled GH cells and mammosomatotrophs (MS cells) were detected; BrdU-labeled PRL cells were not detected, however, when GH3 cells were treated with BrdU for 3 hr and then immediately examined for BrdU-labeling. BrdU-Iabeled PRL cells were found only when GH3 cells treated with BrdU were allowed to grow for another 3 days. This finding suggests that during the additional 3-day culture, BrdU-labeled PRL cells were generated from BrdU-Iabeled cells other than PRL cells. These results indicate that PRL cells are transdifferentiated from GH cells or VIS cells in GH3 cells by a combined treatment with EGF, insulin and E-2, while PRL cells in rat pituitaries are able to proliferate in response to the hormone treatment. Thus, there may be two pathways for cytogenesis of PRL cells the transdifferentiation of GH cells or VIS cells, and a self-duplication of PRL cells

Statistico-Thermodynamical Studies on the Fundamental Reactions concerning Steel-Making. II : The Equilibrium Relationship between Oxygen and Carbon in Liquid Iron under Various Pressures of CO Gas

It has been considered that the concentration of oxygen dissolved in a molten iron is decreased by the addition of carbon under the following relation : [O] ・[C] = Constant . This formula has been deduced by regarding the liquid state of iron dissolving oxygen and carbon as an ideal solution. But from the many experimental evidences such a liquid state of iron cannot be considered as an ideal solution. This deviation from the ideal behaviour shows that the mutual interactions between these solute atoms cannot be neglected in discussions of the equilibrium relation between the liquid iron and the gas mixture CO-CO_2. If we compute the equilibrium relation between [O] and [C] in connection with the partial pressure of gas phaes in contact with the liquid iron under the above circumstances, it can be written in the following formula : xy= P_/K_1・K_2{1-2(x+y)}^2exp[-2/1-(x+y){x ψOC/kT+y(ψOC/kT+ψCC/kT)}], where x and y are atomic fractions of [O] and [C], respectively, and K_1 and K_2 are the so-called equilibrium constants for [O] and [C], respectively. If ψ/kT= O, the above equation is reduced to the formula [O] ・[C] = const. But it was determined experimentally that the probable values of ψCC/kT and ψOC/kT are 2.68 and -10.7, respectively, at 1540℃. Consequently, the product [O] ・ [C] increases with the increase of [C] concentration and the inclination of curve [O] ・ [C] vs. [C] becomes larger as the pressure P_ becomes higher. These results are in good agreement with Chipman\u27s observations. And it is also shown that [O] decreases rapidly with the increase of [C] in a region of low carbon content and attains a minimum value at a certain concentration of [C], but on the contrary, it rather increases with the addition of carbon in the range of higher carbon content. Thus the deoxidation by carbon in the molten state of iron is available only in the region of small concentration of carbon