On modelling of kinematic hardening for ratcheting behaviour

A kinematic hardening rule is formulated on the assumption that each component α_i of back stress has a critical state for its dynamic recovery to be fully activated. The rule has a feature that only the projection of plastic strain rate to the direction of α_i contributes to the dynamic recovery. This is in contrast with previous rules in which the accumulated plastic strain rate enters into the dynamic recovery term. Applying the present and previous rules to experiments of modified 9Cr-1Mo steel at 550°C, we discuss effects of the feature mentioned above on simulating the multiaxial as well as uniaxial ratcheting behaviour.     

Direct activation of human CD8+ cytotoxic T lymphocytes by interleukin-18

Direct activation of human cytotoxic T lymphocytes (CTL) by interleukin (IL)-18 was observed in a system in which CTL effective against autologous tumor cells were generated. Peripheral blood mononuclear cells (PBMC) from tumor-bearing patients, after removal of natural killer (NK) cells, were cultured in a medium containing IL-1, -2, -4, and -6, with or without IL-18, and stimulated with autologous tumor cells. IL-18 increased the activity of the CTL and the proportion of autologous CD8+ T cells present after 28 days in the induction culture. When purified CD8+ T cells were cultured in the presence of IL-18 and IL-2 for 7 days, the CTL showed enhanced cytotoxic activity against autologous tumor cells. Moreover, a purified CD8+ T cell population, which did not exhibit any apparent cytotoxic activity against autologous tumor cells, displayed cytotoxic activity after 7-day incubation with IL-18. These results suggest that IL-18 may be useful to generate autologous CTL in humans and may thereby contribute to adoptive immunotherapy for tumors.     

Application of GaN-based heterojunction FETs for advanced wirelesscommunication

We review the features of GaN-based FETs and describe their expected development direction, GaN has a high breakdown field, but this does not necessarily mean it is suitable for high-voltage and high-power applications. The main advantage is that it enables scaling down beyond the silicon MOSFET miniaturization limitation from the Maxwell-Boltzmann distribution. Thus, fine gate patterns together with a high carrier velocity make GaN-based FETs be suited for millimeter and near millimeter wavelength high-power applications. In addition, by using large-area sapphire substrates, high-performance and low-cost MMICs can be produced on GaN. We expect that such devices will be the key to future advanced wireless communication systems     

HLA antigens and toxoplasmic retinochoroiditis

HLA (Human Leukocyte-A) antigens of 20 patients with toxoplasmic retinochoroiditis were determined by the standard microlymphocyte cytotoxicity test to see if these patients have different immunogenetic backgrounds from the normal controls. The results showed that there were no significant differences between the patients and the normal controls.     

Theory and practice of optimal control in continuous fermentation process

In this paper a mathematical model of aminoacid fermentation using bacteria is built based on the kinetic study of experimental data of the pilot plant. This model makes it possible to formulate mathematically two optimal control problems in the actual process: (1) the problem of optimal start-up to a desired steady state, involving the optimization of the steady state, and (2) the problem of dynamical operation aiming at the maximum production of the amino-acid within a specified operation period. Both problems are solved by the maximum principle and Green's theorem. The numerical results suggest one of the most practical patterns of operation.     

Androgen and estrogen receptors in the developing mouse brain

Specific binding of the androgens, 5alpha-dihydrotestosterone (DHT) and testosterone, and of 17beta-estradiol by brain cytosol from mice at 3-5,9-11, and 18-23 days of age was measured by charcoal assay and glycerol gradient centrifugation and analyzed by Scatchard plots. The immature mouse brain contains putative receptors for these steroids which migrate at 8 S in gradients at low ionic strength and at 5 S in 0.5 M KCl. Investigation of estradiol binding was complicated by the presence in cytosol from 3-5 day-old mice, and to a lesser extent from 9-11 day-old mice, of the high capacity, fetoneonatal estradiol binding protein (FEBP) which is no longer detectable at 3 weeks. The rapid dissociation of the FEBP-estradiol complex under non-equilibrium conditions probably led to over-estimation of free steroid concentration and thus to an apparent increase in the affinity of 8 S receptor for estradiol with age (for female brain cytosol KD=9.5 X 10(-10)M at 3-5 days and 2.7 X 10(-10)M at 18-23 days). The number of estradiol binding sites remains relatively constant during the first 3 weeks at 7-9 fmol/mg protein, while the number of DHT binding sites in female brain increases from 3.2+/-0.3 to 6.6+/-0.9 to 9.6+/-0.3 (mean+/-SE) fmol/mg protein in the 3 age groups. Dissociation constants and numbers of sites for both DHT and estradiol binding are similar in brain cytosol from male and female mice. Testosterone and DHT compete for the same binding site, but its affinity for DHT is about twice that for testosterone. The high affinity of the brain receptor for DHT (KD=4-5 X 10(-10)M) may reflect the slow metabolism of DHT to 5alpha-androstanediols, amounting to less than 10% after 2 h at 0 C. Binding of DHT and estradiol to cytosol from brain regions was also investigated. DHT receptors increase in parallel in various regions with age; the concentration of sites in the hypothalamus-preoptic area (HPOA) is 1.2-3.4 times that in the cerebral cortex (C). The concentration of estradiol binding sites in HPOA to that in C increases about 12-fold from neonatal to adult stages, reflecting both an increase in HPOA sites and a decrease in C sites, while the concentration in the remainder of the brain shows little change. Androgen and estrogen receptors in brain cytosol from immature mice can be distinguished by their different specificities and developmental patterns in whole brain and brain regions. The presence and properties of these receptors in the brain of neonatal mice are discussed with respect to their possible role in sexual differentiation of the brain.     

Non-steady-state rates of dissolution of iron and cobalt in liquid copper under static conditions

The horizontal bottom face of cylindrical iron or cobalt is exposed to liquid copper, and their dissolution rates are determined at 1473 to 1476 (±10) K and 1573 to 1576 (±10) K for the Cu-Fe system and at 1473 to 1475 (±10) K for the Cu-Co system. The decrease in height of the cylinder, z (m), is proportional to the square root of time, √t(s^1/2), as is expected in mass transfer controlled by non-steady-state diffusion. The observed value of α (m · s^?1/2) in the equationz = α√t is 1.95 × 10^?6 (m · s^?1/2) in the lower temperature range and 3.53 × 10^?6 (m · s^?1/2) in the higher temperature range for the Cu-Fe system, and 2.66 × 10^?6 (m · s^?1/2) for the Cu-Co system. Under fixed experimental conditions, the value of α calculated on the basis of the expression that the rate of diffusion in liquid is proportional to the activity gradient of a diffusing substance is in agreement with the observed value, but that calculated on the basis of Fick’s first law is 1.9 to 2.7 times as great as the observed value. For this expression to be valid it is necessary that the ratio of the phenomenological coefficient defined by irreversible thermodynamics to the activity is independent of the concentration. An estimate of the density gradients caused by dissolution suggests that no natural convection occurs in the vicinity of the solid-liquid interface.