Caries prevalence in preschool children in industrial cities

Caries incidence was analyzed in preschool children attending kindergartens living in two industrial towns differing by the level and specific features of air pollution and by fluorine levels in potable water. Caries incidence was found to be higher in a ferrous metallurgy center with very low (0.1 to 0.3 ml/l) fluorine levels in potable water. Passive smoking factor was found to contribute to development of caries in children, particularly so in girls. Motor car transport effects on caries development in children were not confirmed. Recommendations on reduction of caries development intensity are suggested.     

Heavy metals in human hair and teeth: the correlation with metal concentration in the environment

We introduce a new method, activity diaries, in order to evaluate human water contact among fishing communities in an area moderately endemic for Schistosoma japonicum in the Dongting Lake region of Southern China. Two hundred and forty-nine subjects (76% male) were followed prospectively over a 9-month-period in order to verify exposure and reinfection. Exposure was determined crudely with questionnaires, direct 12-h water observations, and more precisely with activity diaries and an adjusted exposure model which took into account the time of day, the duration of contact and the percent body surface area in contact with water. Cohort subjects filled in activity diaries for an average of 85 days as compared with 2 days for the direct water observations. The typical unadjusted mean daily water contact (duration) based on the activity diaries was 53 min with 62% of this time spent in fishing. In contrast, the direct water observations revealed an average daily duration of 149 min with 53% of the time spent in fishing. Human water contact patterns (min/day) by site, activity and body part exposed were examined with the activity diaries. Individuals in the 36-49-year-old age range had the highest degree of water contact. Most of this daily contact occurred by males on the hands (mean+/-S.D.; 83.53+/-67.80 min/day) while fishing (mean+/-S.D.; 87.84+/-8.88 min/day) on the lake (mean+/-S.D.; 85.98+/-69.90 min/day). There was a strong positive log correlation (r=0.95) between the crude and adjusted (based on our derived exposure model) diary outcomes for the entire study sample, however, at higher exposure levels this relationship was differentially weaker (r=0.70). Results from this study suggest that current methods used in evaluating schistosomiasis exposure in China may overestimate and bias measures of the risk of infection. Activity diaries adjusted for the time of day, duration and the percent body surface area exposed are cost-effective and practical instruments to accurately quantify human exposure in the vast lake regions of Southern China where most of the endemic schistosomiasis japonica occurs.     

Heavy metal content in sediment samples taken from drinking-water reservoir (author's transl)

Sediment samples were taken from the small preliminary catchment basin of the Wahnbachtal reservoir at Siegburg, extracted under mild conditions with nitric acid and hydrogen peroxide and analysed for their content of heavy metals. The sediment sample of the most recent date showed the highest concentrations of metal, that of older date revealed lower values, but by far the lowest metal content was found in the clay of the former valley. The high metal contents in the sediment are not only to be attributed to human influence but are primarily caused by the lead and zinc ores in the catchment area. The hygienic significance of these results is to be seen in the remobilization processes which could lead to an undesirable increase of metal concentrations in the raw water fed to the drinking water treatment plant.     

Metal content in children from Katowice and Rabka. I. Magnesium in blood and hair

The authors determined the magnesium content in the blood and hair by atomic mass absorption. The studied material included preschool children from a kindergarten situated in the center of Katowice (n = 60) and their older teenage brothers and sisters (n = 10). The control group was made up to 24 preschool children from Rabka (a health resort in the mountains). It was found that the majority (over 60%) of preschool children in Katowice had a magnesium deficit. The magnesium content in teenagers was significantly higher than in their preschool siblings. Children from Rabka had much more favorable results.     

工业废水中金属元素的测定

工业废水中金属离子对水环境造成污染,并危及人体健康,应准确进行测定.论述了原子吸收分光光度法测定工业废水中金属元素的原理,重点论述了测定Zn的条件、范围、干扰等因素,总结了测定锌的条件及测定结果;实验证明,用原子吸收分光光度法测定工业废水中的Zn元素,可取得较好的结果.     

Relationship between the elemental content and pH of human hair

In this study, significant correlations were discovered between the following three parameters: (i) pH values of human hair, (ii) K, Ca, Mg, Zn contents of human hair and (iii) sex. We also discovered that most trace elements are not significantly correlated with hair pH.     

Heavy metals in the hair of opossum from Palo Verde, Costa Rica

Levels of lead, cadmium, mercury, chromium, and manganese were measured in the hair of opossum (Didelphis virginiana) from Palo Verde, Guanacaste, Costa Rica. This area has some agriculture, but is slated for extensive water development that will increase ecosystem exposure to a variety of agricultural chemicals. Metal levels were generally not intercorrelated except for chromium and lead, chromium and cadmium, and cadmium and lead. There were significant gender differences only for lead and chromium, with the significantly smaller females having higher levels. It is suggested that hair from mammals, particularly abundant ominivores may be useful, bioindicators of environmental quality over a long time period.     

Heavy metal concentrations in two populations of crayfish

To monitor the environmental contamination of heavy metals in Tuskegee Lake (TL) and National Forest Creek (NFC), Tuskegee, Alabama, adult crayfish muscle and exoskeleton and sediment samples were collected and analyzed for Hg, Pb, Cd, Cu, Co, Ni and Zn. In both TL and NFC crayfish Cu and Zn were not different in muscle and exoskeleton; however, Pb and Cd were significantly different. The Pb in exoskeleton and the Cu and Zn in muscle and exoskeleton of TL crayfish were significantly higher than that of NFC crayfish; however, Cd and Ni were not different between tissues or crayfish sources. Levels of Hg and Co were not detectable.     

Cadmium content in human kidney and hair in the Gdańsk region

BACKGROUND: Previous research has found a significant positive relationship between dependency and level of depression. The aim of the present study, using factor analysis method, is to test the hypothesis that dependency and depression constitute distinct dimensions. METHODS: In a sample of 202 university students, a correlation matrix comprising items from both the Interpersonal Dependency Inventory and the abridged form of the Beck Depression Inventory was analysed using a principal components analysis followed by an orthogonal varimax rotation. RESULTS: Evidence for a four-factor solution was found with almost no overlap of the significant factor loadings for the items from each scale, and with the factors corresponding closely with their respective construct. CONCLUSION: The findings support the view that depression and dependency constitute different constructs. LIMITATION: The results must be confirmed on clinical and heterogeneous nonclinical samples. CLINICAL RELEVANCE: The independency between depression and dependency could lead to different therapeutic strategies notably in 'socially dependent' type of depression.     

Selenium content in cattle hair in areas with incidence of nutrition-induced muscular dystrophy

In the South Bohemian Region which is an area of enzootic incidence of nutritional muscle dystrophy selenium content in the fur of dairy cows and young cattle was determined. In the breeds in which the "white muscle disease" appeared in the past years in young cattle, lambs and calves the lowest mean selenium values in the fur dry matter found were: 0.18 +/- 0.07, 0.19 +/- 0.06, and 0.21 +/- 0.08 ppm, with repeated findings of mere 0.09 ppm Se. 60 to 100 per cent samples from these farms showed selenium values below the 0.25 ppm level. The fur of heifers which recovered from nutritional muscle dystrophy and were treated 10 days prior to sampling with a selenium preparation in injection form (Selevit inf. SPOFA) contained 0.29 ppm selenium (+/- 0.11). In other breeds 0.30 +/- 0.07 to 3.33 +/- 0.16 ppm selenium was found in the fur of cows and young cattle. The initial field essay of selenium content in cattle fur indicated a relation of low selenium values to the frequency of clinical forms of nutritional muscle dystrophy in domestic ruminants.     

铁水预处理脱硫过程氮含量预测

根据铁水预处理的实际生产工艺,利用BP神经网络建立了铁水预处理脱硫时铁水中氮含量的预报模型.利用生产数据对网络进行训练后,可以用于预测铁水预处理脱硫后铁水中氮含量,预报相对误差可以控制在22%以下,w[N]的绝对误差值控制在8×10-4%以内.给各输入参量增加扰动后,模型计算表明,初始温度和初始[N],[C],[P]含量,四因素影响最大,且温度和[C]含量为负扰动,[N]为正扰动,说明增加温度和碳含量有利于脱氮.     

Research on determination of the rare-earth content in metal phases of steel

The behavior of the rare-earth dissolved in a-Fe, of the iron-cerium intermetallic compounds and of the rare-earth inclusions in electrolytic separation process has been studied by means of counting measurements of radioactivity, the electron probe, and X-ray analysis. The experimental results show that the rare-earth sulfide and the rare-earth oxide are stable completely in the electrolytic separation process, when the composition of the electrolytic solution is 1 pct 4-methyl ammonium chloride, 5 pct triethanolamine, 5 pct glycerin, and 89 pct methyl alcohol, and the controlling anode current density is ≤100 mA/cm². But Fe-Ce intermetallic compounds and the rare-earth dissolved in a-Fe enter into electrolytic solution as ions. When the cerium ion concentration in electrolytic solution is >7.87 X 10^-5 mol/liter electrolyte, precipitates of cerium hydroxide will be formed. When the inclusions are separated quantitatively, the electrolytic solution must be filtered by using a funnel with filter paper pulp thick up to 6 mm, and not be filtered directly with single filter paper. Samples without rare-earth were remelted and a radioactive isotope¹⁴¹Ce was added to the steel. Inclusions were separated by the electrolytic method in the nonaqueous solution. The counting of 14lCe in the electrolytic solution was measured. Thus the rare-earth content in the metal phases can be calculated. Experimental results show that the rare-earth content in the metal phases increases with the total rare-earth content in steel. The rare-earth content in the metal phases of the steel was also found to increase as the aluminum content in steel was increased. This method for determining the rare-earth content in the metal phases of steel is very sensitive. The sensitivity is 10^-6 pct.     

高炉铁水降硅的实验研究

从理论上分析了降低铁水中硅含量的三个途径:控制硅源;降低滴落带的高度;增加炉缸渣中的氧化性.在实验室进行了降低铁水中硅含量的实验,得到了铁水中硅含量的影响因素:提高二元碱度有利于降硅;增加渣中氧化物可降低SiO₂的活度有利于降硅;Al₂O₃和SiO₂不利于降硅;冶炼时焦炭中SiO₂的挥发量随温度的升高而增多,使铁水中硅含量增加;随着滴落带高度的增加,铁水中硅含量不断增加.根据实验室研究针对唐山建龙公司高炉特点提出降低铁水中硅含量的措施,降硅效果明显,铁水中硅的质量分数由原来的0.55%左右降到了0.40%左右.     

Carburization of hot metal by industrial and special cokes

In the present paper, a study has been made of carbon dissolution from industrial cokes and specially treated cokes in hot metal. With these results obtained together with earlier investigations, a model is now presented, which attempts to explain carbon pick-up from coke by hot metal. Factors relating to hot metal, coke and experimental conditions are included in the model. An attempt is also made to quantify carbon dissolution behaviour from coke in hot metal in comparison with that of pure graphite. It was determined, that the carburizing ability of cokes can be modified by controlling the ash compositon. The results of the special cokes indicate clearly that the presence of iron oxide is favourable for carburization. Some additives, i.e. CaO, MgO, SiO₂ and Al₂O₃ reduce significantly the dissolution of carbon.