Biomedical subjects

K N Yu

Publications and source records attributed to K N Yu.

66 records · Page 4Linked to original sources

PubMed1997

A survey of radon properties in underground shopping centers in Hong Kong.

A number of radon-related properties have been surveyed in underground shopping centers in Hong Kong. These parameters include the radon concentration, the total potential alpha energy concentration of radon progeny, the equilibrium factor and the unattached fraction of radon progeny. The mean values recorded for these were 29.2 +/- 7.8 Bq/m3, 3.60 +/- 1.53 mWL, 0.46 +/- 0.16 and 0.05 +/- 0.03, respectively. Based on these figures, we have calculated the average radon dose received by employees in an underground shopping center in Hong Kong to be 0.22 mSv/yr, which represents an approximate increase of 8% over the total dose of about 2.7 mSv/yr received by the average person in Hong Kong.

Air Pollutants, Radioactive↗

PubMed1997

A study of radioactivities in six types of fish consumed in Hong Kong.

The contents of natural and artificial radionuclides in two types of fresh water fish and four types of marine fish commonly consumed by the Hong Kong population have been measured using HPGe gamma-ray spectrometry. The two types of fresh water fish are grey mullet (mugil cephalus) and grass carp (ctenopharyngodon idellus). The four types of marine fish are white pomfret (pampus argenteus), red bullseye (priacanthus macracanthus), golden thread (nemipterus) and ginkgo (gymnocranius griseus). All measurements of U and Th chain radionuclides in the samples have yielded values below MDA except for positive detection of 228Ra (assuming 228Ra to be in equilibrium with 228Ac) in grey mullet and bullseye perch. The 40K and 137Cs radionuclides were detectable in all samples, with values of 0.01-0.2 and 41.23-111.47 Bq/kg fresh respectively. The different levels of radioactivity in different species of fish is suggested to be due to differences in metabolism and feeding patterns. The radionuclide 60Co, the only other artificial radionuclide to be investigated herein, recorded values below MDA for most of the samples; observable values ranged from 0.01 to 0.04 Bq/kg fresh. Committed effective doses due to ingestion of radionuclides from fish have been estimated to be 1.2 (male) and 6.4 (female) microSv/yr for natural radionuclides; 0.027 (male) and 0.026 (female) microSv/yr for artificial radionuclides.

Animals↗

PubMed1997

A survey of radon and thoron progeny for dwellings in Hong Kong.

The potential alpha energy concentrations of radon and thoron progeny have been surveyed for dwellings in Hong Kong and the mean values are obtained as 3.58 and 2.29 mWL, respectively. The relative importance of the value for thoron is unexpectedly high, which is attributed to the high 232Th content of the building materials used in Hong Kong. It has also been found that the potential alpha energy concentration values for radon progeny changed dramatically with the season due to the different aerosol contents in the air in different seasons. The factors affecting the potential alpha energy concentration values have also been studied. These factors fall into three categories, namely (1) the building characteristics including age of the buildings, wall coverings and floor coverings; (2) the location of sites including nearby environments and the elevation of the sites; and (3) the meteorological parameters including wind speed, atmospheric pressure, air temperature and relative humidity. For categories (1) and (2), all factors seem to affect the potential alpha energy concentration values, although the effects may be different for radon and thoron progeny, which may be due to the very much different half lives of radon and thoron gas and to the different behavior of radon and thoron progeny in the attachment to aerosols. For category (3), only wind speed has been found to have effects.

Construction Materials↗

PubMed1996

A study of factors affecting indoor radon properties.

The factors affecting indoor radon properties in Hong Kong have been studied, including the radon concentration, the total potential alpha energy concentration of radon progeny, the equilibrium factor, and the fraction of unattached radon progeny. These factors fall into three categories, namely, (1) the building characteristics, including cooling method, age of the buildings, wall coverings and floor coverings; (2) the location of sites, including nearby environments, geological materials of the area, and the elevation of the sites; and (3) the meteorological parameters, including rainfall, relative humidity, pressure, temperature, and wind speeds. For category (1), only the ventilation is found to affect the indoor radon properties. For category (2), only the nearby environments have effects. For category (3), the rainfall and temperature are found to have significant effects.

Air Pollutants, Radioactive↗

PubMed1996

The bioconcentration of 131I in fresh water fish.

The dynamic characteristics of the radionuclide concentration process in fresh water fish have been studied. The experimental data for the tilapias were fitted using a simple compartment model to get characteristic parameters such as concentration factors, elimination rate constants, and initial concentration rates, which are 3.08 Bq kg-1/Bq L-1, 0.00573 h-1, and 12.42 Bq kg-1 h-1, respectively. The relative concentrations of 131I in different parts, i.e., head, gills, flesh, bone and internal organs, of the tilapias are also determined, which are found to be 10.8, 15.4, 26.1, 11.0, and 37.0%, respectively. The effects of different factors on the transfer of radionuclides in fresh water fishes are also discussed. Experiments on the tilapias and the common carp show that the variation of concentration factors for different species may be significant even for the same radionuclide and the same ecological system. On the other hand, the variation in the concentration factors for the flesh of the tilapias is not significant for a certain range of 131I concentrations in the water.

Animals↗

PubMed1995

The variation of radon exhalation rates from building surfaces of different ages.

Standardized activated charcoal canisters (according to the U.S. EPA) have been used to collect radon exhaled from concrete surfaces covered with thin plaster (categorically different from thick plaster) of 32 buildings of different ages (0.5-31 y) in Hong Kong. Concrete surfaces covered with thin plaster is the commonest wall configuration in Hong Kong. The canisters are analyzed using gamma spectroscopy to obtain the radon exhalation rates. The results show that the radon exhalation rate decreases with the building age.

Air Pollution, Indoor↗

PubMed1995

Assessment of radon levels in soil and water.

Radon gas and its progeny are radioactive and may induce lung cancer. A main source of indoor radon concentration is the radon gas which comes from the soil under a house or building. Therefore, accurate measurement of the radon concentrations in the soil are very helpful in identifying doubtful areas and in minimizing some radon hazards. A method of assessing the radon concentration in soil is described. The results were compared with the radon concentrations in associated water samples. It was found that the concentrations in soil and water were correlated, except for some anomalies and that the measurement of concentrations in soil were more direct and sensitive.

Geological Phenomena↗

PubMed1994

A preliminary study on the radon concentrations in water in Hong Kong and the associated health effects.

Tap water, flushing water and drinking water including natural mineral water, artificial mineral water and distilled water have been investigated for their radon concentrations. It has been found that the radon concentration in natural mineral water samples is the highest and that in tap water is the second highest, while other categories have values very near to the detection limit. From these the corresponding annual effective doses for the stomach and the lung are determined. It is found that annual effective dose due to direct consumption of water (mineral and tap water) is far greater than that due to inhalation of radon emanated from tap water and flushing water. Moreover, it is also shown that the annual effective doses due to inhalation of radon emanated from tap water and flushing water is negligible when compared to the total annual effective dose for indoor radon in Hong Kong.

Hong Kong↗

PubMed1994

Inactivation cross section of ions for dry enzymes and viruses.

In this note, a semi-empirical analytical formula for the inactivation cross section of ions for dry enzymes and viruses is developed based on the delta-ray theory of track structure. Using the experimental characteristic dose of gamma rays, the cross sections are calculated and compared with experimental results. The average ratio of the experimental to the calculated cross section is 0.96 +/- 0.17.

Algorithms↗

PubMed1993

Monitoring 90Sr contamination in terms of 131I contamination in imported food.

This paper describes a method for monitoring 90Sr contamination in terms of 131I contamination in food imported from a country with a recent nuclear power plant accident. For imported food, the guideline levels set by the Codex Alimentarius Commission will be applied, which requires that the contamination in food by beta emitters (typically strontium) be monitored. However, the measurement of strontium contamination cannot be made within a reasonably short time as it requires rather time-consuming chemical extraction and sample preparation procedures in advance. We propose here to use the contamination level of 131I in these foodstuffs as indicators of 90Sr contamination levels. Possible accident scenarios are employed to estimate the abundance ratio of 131I and 90Sr deposited on soil and intercepted by plants. Using a dynamic food chain model, we can calculate their relative activities in the food products which, when combined with the 131I levels present, give the theoretical 90Sr levels present.

Accidents↗

PubMed1992

Building materials and environmental health: radon in Hong Kong.

The origin and health effect of radon are first identified. In Hong Kong, the main contribution to the indoor radon concentration comes from building materials. The relatively high radium content in building materials used in Hong Kong explains the high indoor radon concentrations measured. Using risk analysis and established data, radon induced lung cancer deaths have been estimated and remedial measures have been recommended. The variations with age of building and type of ventilation are stated to be additional controlling factors. The possible effects of radon solubility in water are also explored.

Construction Materials↗

PubMed1990

[Citation analysis of Acta Pharmacologica Sinica 1984-1989].

Citation analysis was made bibliometrically on the collection and dispersion of the references in Acta Pharmacologica Sinica 1984-1989. Core periodicals were sorted out: 31 in foreign languages and 6 in Chinese. Suggestions are proposed to the information services.

Bibliometrics↗