Search PubMed⌕ Search

Biomedical subjects

H Yonehara

Publications and source records attributed to H Yonehara.

At least 19 recordsLinked to original sources
PubMed2003

Instrument performance of a radon measuring system with the alpha-track detection technique.

An instrument performance test has been carried out for a radon measuring system made in Hungary. The system measures radon using the alpha-track detection technique. It consists of three parts: the passive detector, the etching unit and the evaluation unit. A CR-39 detector is used as the radiation detector. Alpha-track reading and data analysis are carried out after chemical etching. The following subjects were examined in the present study: (1) radon sensitivity, (2) performance of etching and evaluation processes and (3) thoron sensitivity. The radon sensitivity of 6.9 x 10(-4) mm(-2) (Bq m(-3) d)(-1) was acceptable for practical application. The thoron sensitivity was estimated to be as low as 3.3 x 10(-5) mm(-2) (Bq m(-3) d)(-1) from the experimental study.

Air Pollutants, Radioactive↗
PubMed2002

Intercomparison of whole-body counters by using a subject who had incorporated 137Cs into the body.

During the years 1996-2000, eight whole-body counting facilities (WBC) from Finland, Germany, Japan and Russia took part in an intercomparison using a resident of the Russian town of Novozybkov who had been seriously contaminated as a result of the Chernobyl accident. The subject R (adult male, height 172 cm average body mass 64 kg; and 137Cs body burden within the range of 1-15 kBq) was investigated in the participating institutions during his business trips. The experimentally obtained data for his 137Cs body burden were compared with the predicted values, which had been deduced from the measurements of subject R using the reference WBC (St Petersburg Institute of Radiation Hygiene) and from his effective half-time of 137Cs in the body (68 days). The obtained results did not deviate more than 20% from reference activities. Four facilities were able to quantity the 40K in the subject's body. The differences between reported values of potassium did not exceed 10%. For subject R, the average annual effective dose from radiocaesium was 0.25 mSv and it was 0.18 mSv from 40K in the years 1996/97. The reliability of using a subject with naturally incorporated artificial radionuclides ('walking standard') instead of an anthropomorphous phantom for calibration and intercomparison of whole-body counters in a large-scale nuclear accident is discussed.

Accidents↗
PubMed2001

Determination of radionuclides produced by neutrons in heavily exposed workers of the JCO criticality accident in Tokai-mura for estimating an individual's neutron fluence.

In the Tokai-mura criticality accident, three workers were heavily exposed. Biological materials, such as blood, urine, vomit and hair, were collected from the workers and analyzed for radioactivities, produced by the neutron irradiation. Activation products. such as 24Na, -K and 82Br, were found in these materials by gamma-ray spectrometry. The radionuclide of the highest activity observed in biological materials was 24Na, e.g. the concentrations of this nuclide in the blood samples from the three patients at the accident time were 169, 92 and 23 Bq/ml, respectively. The concentrations of stable sodium in the same samples were determined by ICP-AES to obtain specific activities of 24Na (concentration ratio between the produced 24Na and stable 23Na), which are essential for estimating the neutron fluences and radiation doses. The specific activities of 24Na obtained for the three patients through the blood analysis were 8.2 x 10(4),4.3 x 10(4) and 1.2 x 10(4) Bq24Na/g23Na. Based on these values, individual's neutron fluences were estimated to be 5.7 x 10(11), 3.0 x 10(-1) and 0.85 x 10(11) cm(-2), respectively.

Adult↗
PubMed2001

Dose estimation based on a behavior survey of residents around the JCO facility.

The NIRS staff interviewed the residents in the evacuated zone around the JCO facility in Tokai-mura on 19 and 20 November, 1999, to obtain the following parameters every 30 minutes starting from 10:35 A.M. on 30 September to 6:15 A.M. on 1 October: the distance from the precipitation tank, the type of the house, positions in the house, wall materials and their thickness in order to estimate individual doses due to the accident. The ambient dose equivalents were obtained based on monitoring data during the accident. In addition, computer calculations were conducted to evaluate the conversion factor from ambient dose equivalent to effective dose equivalent as well as the shielding effect of the house or factory to estimate the effective dose equivalent to the residents. The estimated individual doses based on the behavior survey were in the range from zero to 21 mSv. The individual doses were reported to the residents during the second visit to each house and factory at the end of January, 2000.

Behavior↗
PubMed1998

Beam commissioning of the SPring-8 synchrotron.

The beam commissioning of the SPring-8 synchrotron was started in December 1996. In the first ten days, the coarse tuning of the pulse magnets for beam injection from the linac, and the excitation pattern of the dipole and the quadrupole magnets, were accomplished during energy ramping of the beam. The acceleration of the beam up to 8 GeV proceeded smoothly. From January to February 1997, the fine-tuning of the synchrotron was continued and the operating parameters of all of the synchrotron equipment were decided.

Journal Article↗
PubMed1997

Influence of air flow on the behavior of thoron and its progeny in a traditional Japanese house.

Air flow influence on the spatial distribution of thoron (220Rn) concentration in a typical Japanese traditional house was investigated at various indoor air flow levels. The effect of air flow on the behavior of both thoron and radon progeny were examined simultaneously. Measurements were carried out by using two types of passive monitors, the radon-thoron discriminative monitor and the Radtrak monitor. Thoron and radon progeny were measured by filter grab sampling with ZnS scintillation counting. Under static condition, a horizontal distribution with greatly varied thoron concentrations was found as reported by previous studies. Under turbulent conditions, thoron concentrations in the middle of the room increased and the concentration gradient of thoron gas became lower. An obvious vertical distribution of thoron was also observed. Prominent diurnal variation of radon progeny concentrations was observed whereas that of thoron progeny concentrations was not. Concentration of thoron progeny changed little at different air flow levels, although the thoron gas level at the middle of the room varied significantly. The influence of air flows on detection efficiencies of the two types of thoron monitors were also checked. The mechanism of behavioral change of thoron and its progeny in turbulent atmosphere is discussed.

Air Movements↗
PubMed1996

Effect of radon exposure on superoxide dismutase (SOD) activity in rats.

Effect of radon exposure on the activities of superoxide dismutase (SOD) in blood, kidney, liver and spleen of male Wistar rats were investigated. Radon exposure was carried out in a newly developed chamber with 226Ra as the radon source. SOD activity, measured by the spin trap method using an electron spin resonance spectrometer, increased greatly in liver and kidney after 4 hour exposure whereas it decreased significantly after 16 hour exposure. Despite approximately same total doses by the radon exposure, the stimulated SOD activity after 4 hour exposure was not observed after 16 hour exposure in kidney, liver and spleen except blood, suggesting that the stimulating effect could last for a short period.

Animals↗
PubMed1995

Radon concentrations in residential housing in Hiroshima and Nagasaki.

A measurement of indoor radon (222Rn) concentrations in Hiroshima and Nagasaki was carried out to assess the variability of exposure expected among atomic bomb survivors. Two hundred dwellings, mostly belonging to members of the fixed cohort of atomic bomb survivors under study by the Radiation Effects Research Foundations, were selected for this measurement. The geometric mean values of the radon concentrations for 100 dwellings in Hiroshima and 99 dwellings in Nagasaki measured by Track-Etch Type SF detectors were 56.8 Bq m-3 and 28.5 Bq m-3, respectively. No statistically significant difference was observed between lung cancer mortalities in the low-dose range in the two cities. However, apparent values of the mortality rate for low dose range in Hiroshima are consistently greater than those in Nagasaki. The exposure to radon and its progeny and the atomic bomb radiation effect might have some cooperative effects on the lung cancer incidence.

Air Pollutants, Radioactive↗
PubMed1994

Spatial distribution of thoron and radon concentrations in the indoor air of a traditional Japanese wooden house.

A radon-thoron discriminative passive dosimeter has been developed that can estimate both radon (222Rn) and thoron (220Rn) concentrations at the same time. Two polycarbonate films are installed as solid-state nuclear track detectors in the dosimeter housing. One film registers alpha tracks originating from predominantly thoron and its progeny together with a small contribution from radon, and the other film registers alpha tracks originating from radon and its progeny together with a negligible contribution from thoron. The lower detection limit is estimated to be 2.9 Bq m-3 for the radon concentration and 9.0 Bq m-3 for the thoron concentration for 2 mo exposure. Preliminary measurements from 1991-1992, in a traditional Japanese wooden house located in Kyoto, indicated that the indoor thoron concentration increases exponentially as the interior mud (or plaster-coated) wall is approached. A soil-based plaster commonly used in Japanese wooden houses to fill walls (or as a surface coating on the walls) is the probable source of the indoor thoron. Since thoron is not measured by the usual radon measurements, and the majority of Japanese houses are made of wood, attention should be paid to indoor thoron and its decay products, which may give a significant fraction of the total natural radiation exposure to the general public.

Air Pollutants, Radioactive↗
PubMed1993

Prefabricated venous flaps: an experimental study in rabbits.

Prefabrication is a method for creating donor flaps by implantation of a nourishing pedicle prior to harvesting the flap. Based on the concept that implantation of a "flow-through" vein results in sufficient vascularisation to support a skin flap, we used a rabbit model to investigate the viability of prefabricated total venous perfusion (TVP) flaps. Prefabrication of an abdominal wall donor site was performed using the left epigastric vein in 25 male New Zealand white rabbits. An 8 x 10 cm skin flap was elevated 1, 2, 3, 4, and 6 weeks after prefabrication (n = 5 per group). A silicone sheet was implanted under the skin flap. The mean survival rate of skin flaps was 24%, 52%, 87%, 83%, 84%, respectively. Results of this study show that reproducible survival of a prefabricated TVP flap can be obtained when the flap is elevated more than 3 weeks after prefabrication.

Abdominal Muscles↗