Hiroshi Hidaka

Chemical properties of Central African carbonado and its genetic implications

Abstract Carbonado diamonds from Central African Republic exhibit very intense laser-induced photoluminescence due to the presence of the radiation damages. From the spectral profiles of photoluminescence obtained for these samples, the carbonado stones were grouped into three groups depending on a variation in the structure of radiation-damage products; Group-A carbonado with 504 nm band (3H band), Group-B carbonado with 575 nm band in addition to weak background peaks centered at 512 and 580 nm, and the Group-AB carbonado with features intermediate between Group-A and Group-B. When heating Group-A carbonado, Group-A was found to transform to Group-B at temperatures higher than 400°C. Thermogravimetry and Differential Thermal Analysis (TG-DTA) clarified the difference in thermal properties between Group-A and Group-B. While Group-A carbonado yields one intense and narrow exothermic peak at 800°C, Group-B carbonado exhibits a broad exothermic peak at 785°C. The distinct difference in the oxidation rate could be attributed to the difference in the density of micropores in carbonado. Chondrite-normalized rare earth element (REE) patterns for the bulk carbonado samples show negative Eu anomalies, and the inclinations of the patterns are similar to those of kimberlites and much steeper than that of continental crust as represented by continental shales. In the chondrite-normalized value, La/Lu ratios were of the order of 10 2 and the light REE abundances were as high as 10 3 relative to chondrite. Further, 1384 cm −1 absorption band was observed in IR (infrared) spectra of both Group-A and Group-B, which suggests the presence of nitrogen platelet in carbonado. These REE and IR results imply that the seed crystal of carbonado was formed at high pressure and high temperature and was subjected to the annealing process to generate nitrogen platelets. The genesis of Central African carbonado is discussed as a reconciliation of these experimental results.

Nuclide analyses of rare earth elements of the Oklo uranium ore samples: a new method to estimate the neutron fluence

Abstract Isotopic ratios and abundances of all REE in two Oklo ore samples have been measured. We have succeeded in developing a new method to estimate the neutron fluence, the conversion factor of uranium and the average neutron energy (or temperature) based on Gd and U isotopic ratios. This new calculation is found to be useful in evaluating those parameters for the natural nuclear reactors at Oklo. Comparison is made between the neutron fluence values evaluated by our new method employing Gd isotopes and a previous one [11] employing Sm and Nd isotopes. The relative agreement becomes better with the increase of fluence. A relationship between the abundances of fissiongenic nuclides of La, Ce, Nd, Sm, and Gd and their mass numbers is also presented.

Induction by fibroblast growth factor of angiotensin converting enzyme in vascular endothelial cells invitro

Induction of vascular endothelial cells with pituitary fibroblast growth factor (FGF) provoked an increase in angiotensin converting enzyme activity. The stimulatory effect of FGF on ACE activity was dose-dependent (ED50 = 1.0 ng/ml). Our results suggest a possible role for pituitary FGF in regulation of ACE production in vascular endothelial cells.

Relationship Between Alcohol Consumption, Body Weight, Family History of Hypertension and Blood Pressure in Young Adults

It is not clear why blood pressure rises with age in civilized countries. We examined the relationship between alcohol consumption, obesity, family history of hypertension and blood pressures at medical checkups in 534 male office workers, aged 20 to 40. The results in two age groups, 20-30 and 31-40, are as follows. Those who drank heavily (greater than 60 ml of ethanol) the previous night and/or habitual heavy drinkers (greater than 60 ml/day) had the highest blood pressure. Obese workers had higher blood pressure. Subjects with a family history of hypertension had higher blood pressure. The frequencies of heavy drinkers and obesity were higher in the group aged 31 to 40 than in the other group. These factors might contribute to the blood pressure elevation with age. 5) A histogram of the first readings of systolic blood pressure showed a bimodal distribution only in persons with a family history of hypertension.