Takashi Hamasaki

Flame Speeds in Combustible Vortex Rings

Flame speeds in vortex rings of a stoichiometric methane/air mixture have been investigated. The flame speeds have been measured by a high-speed video camera, and the maximum tangential velocities in the vortex have been measured by a hot-wire anemometer. Results show that the flame velocity is approximately proportional to the maximum tangential velocity and its proportionality factor is about unity. By considering conservation of mass, linear momentum, and angular momentum across the flame, a simple theory has been proposed. A good agreement has been obtained between the theory and the experiment. The vortex bursting mechanism and the baroclinic torque mechanism have been discussed.

Mizoribine in steroid-dependent nephrotic syndrome of childhood.

Abstract. We evaluated a 1-year course of a newly developed immunosuppressant, mizoribine (at a dosage of 3 mg/kg body weight per day), in nine children with steroid-dependent nephrotic syndrome. Steroid treatment could be discontinued in two patients and the maintenance dosage of steroid could be reduced to less than half of that given before mizoribine therapy in a third. There were no beneficial effects in the remaining six patients. No adverse effects of mizoribine were observed during the course of therapy.

Measurements of flame speeds in combustible vortex rings: Validity of the back-pressure drive flame propagation mechanism

Using a vortex ring with a large diameter core, the flame speed V f along the vortex axis has been measured for lean, stoichiometric, and rich methane/air mixtures. The maximum tangential velocity V θmax has been measured by hot-wire anemometry and the flame/core diameter ratio d f / d has been roughly measured by schlieren photography. The results show that the flame speed V f increases almost linearly with the maximum tangential velocity V θmax , and its slope is about unity for all three mixtures. With an increase in V θmax , the d f / d ratio is decreased, and it becomes less than 0.5 in the lean mixture, takes a value between 0.5 and 1.0 in the stoichiometric mixture, but remains around unity in the rich mixture. Accordingly, the flame speed is lowered down in the lean mixture for V θmax ≥5 m/s, saturated in the stoichiometric mixture for V θmax ≥10 m/s, but still increased in the rich mixture up to V θmax =14 m/s. Except when the flame speed is lowered down in the lean mixture or saturated in the stoichiometric mixture, the measured flame speeds are in good quantitative agreement with the values predicted by the back-pressure drive flame propagation mechanism, if the mixture is assumed to expand radially. This elucidates the validity of this new mechanism and also indicates the lateral expansion nature of the flame propagation in the vortex ring in contrast to the axial expansion nature of flame propagation in the vortex flows in a tube. A baroclinic torque mechanism has been briefly discussed on the basis of the vorticity equation.

Intracellular Ca2+ mobilization in immature and more mature U937 induced to differentiate by dimethyl sulfoxide or phorbol myristate acetate

Intracellular Ca2+ mobilization in U937 cells was studied. Stimulation of immature U937 cells with leukotriene B4 (LTB4) increased intracellular Ca2+ levels, whereas stimulation with N-formyl-methionyl-leucyl-phenylalanine (fMLP) failed to increase intracellular Ca2+ levels. U937 cells cultured with 1.5% dimethyl sulfoxide (DMSO) for 4 days (DMSO-U937 cells) responded to LTB4 and possessed the ability to respond to fMLP. U937 cells cultured with 1 ng/ml phorbol myristate acetate (PMA) for 4 days (PMA-U937 cells) lost the ability to respond to LTB4, although they responded to fMLP. Treatment of DMSO-U937 cells with 100 ng/ml PMA for 3 min suppressed intracellular Ca2+ increase induced by LTB4 and fMLP. The fMLP-induced Ca2+ rise in PMA-U937 cells was not suppressed by a further treatment with 100 ng/ml PMA. DMSO-U937 cells responded to inositol 1,4,5-trisphosphate (IP3), indicating that IP3 functions as a messenger of intracellular Ca2+ mobilization from endoplasmic reticulum in U937. The magnitude and duration of the rise in Ca2+ induced by IP3 in DMSO-U937 cells treated with 100 ng/ml PMA for 3 min were similar to those of the controls. When DMSO-U937 cells were Ca2+-depleted, addition of Ca2+ resulted in a transient overshoot of Ca2+ influx. However, the transient overshoot was not observed, when PMA-U937 cells were tested. These results indicate that Ca2+ efflux in PMA-U937 cells is increased by an activated exit pump, which may be directly or indirectly related to the functional state of PMA-U937 cells.

Leukotriene B4 metabolism in neutrophils of patients with chronic granulomatous disease: phorbol myristate acetate decreases endogenous leukotriene B4via NADPH oxidase-dependent mechanism

Abstract. We studied the effect of phorbol myristate acetate (PMA) on endogenous leukotriene B4 (LTB4) metabolism of calcium ionophore A23187‐stimulated human neutrophils. Preincubation of normal neutrophils with PMA significantly suppressed the recovery of endogenous LTB4 induced by A23187. PMA did not suppress the recovery of LTB4 produced by neutrophils from patients with chronic granulomatous disease (CGD), which is known to be defective in NADPH oxidase activation to produce reactive oxygen species (ROS). PMA inhibited the formation of ω‐oxidation products of LTB4, but enhanced arachidonic acid release in normal and CGD neutrophils. Furthermore, 5‐lipoxygenase activity of 10000 times g supernatants from normal neutrophils pretreated with PMA was equivalent to that of the controls. Decrease in LTB4 recovery was not attributed to the suppression of the intracellular Ca2+ increase. Thus, it is suggested that reactive oxygen species (ROS) produced by PMA may directly affect endogenous LTB4 and convert it into metabolite(s) distinct from ω‐oxidation products.

C7 deficiency and persistent haematuria

A 14-year-old boy had persistent haematuria along with complete C7 deficiency. No significant changes in glomeruli and tubules were found in a renal biopsy specimen by light microscopy and immunofluorescence gave negative results for immune deposits. Electron microscopic examination demonstrated an attenuation of the glomerular capillary basement membrane without lamination and a diagnosis of thin basement membrane disease was made. It would be difficult to conclude that patients with C7 deficiency were predisposed to develop glomerulonephritis caused by immunologic aberrations. A family study failed to provide evidence of an association of C7 deficiency and thin basement membrane disease.

Haemophilus influenzae type D infection and JgG2 deficiency in a patient with chronic mucocutaneous candidiasis

A 14 year old boy with chronic mucocutaneous candidiasis and persistent pulmonary infection caused by Haemophylus influenzae and Streptococcus pneumoniae is reported. Initial bacterial culture studies showed H. influenzae type B and S. pneumoniae as causative agents. H. influenzae type D was constantly isolated from the patients sputum. Abnormally low levels of serum immunoglobulin G2 (IgG2) found in the patient may have contributed to the pulmonary infection and H. influenzae type D may be an important causative agent in immunodeficient patients.

Idiopathic thrombocytopenic purpura treated with high doses of intravenous gammaglobulin and prednisolone; a case report.

This work was supported in part by a grant-in-aid from the Japan Medical Research Foundation and by Scientific Research Grants (project No. 57770632) from the Ministry of Education, Science and Culture of Japan.