Mercury concentrations in hair are typically used as a biomarker to assess exposure to mercury. A total of 108 hair samples were collected from residents (age range 5-73 years) of Wujiazhan town, northeast China, to determine total mercury concentrations. Hair mercury concentrations ranged from 0.16 to 199 mg kg(-1) with an average value of 3.41 mg kg(-1). The relationships between mercury concentration and gender and between hair mercury concentration and age were not significant. Overall, 16.7% of all samples were above the RfD value published by the United States Environmental Protection agency. The results indicate that there may be some been health risk from mercury exposure to the residents in the study area.
"Generally speaking, under the situation of non-mercury pollution, Hg concentration in hair is quite low (no more than 1 mg/kg) . In order to obtain the accurate testing result of hair Hg contents, it is necessary for the experimental system of CAAS to possess the lower blank value and limit of detection, and the higher accuracy. "
[Show abstract][Hide abstract] ABSTRACT: It is shown that for directed graphs, reachability can not be expressed by an existential monadic second-order sentence. The proof makes use of Ehrenfeucht-Fraisse games, along with probabilistic. However, it is shown that for directed graphs with degree at most k, reachability is expressible by an existential monadic second-order sentence. One reason for the interest in the main result is that while there is considerable empirical evidence (in terms of the efficiency of algorithms that have been discovered) that reachability in directed graphs is 'harder' than reachability in undirected graphs, this is the first proof in a precise technical sense that this is so.
[Show abstract][Hide abstract] ABSTRACT: FIRST LEGO League (FLL) is an international initiative to encourage students aged 9-14 to pursue careers in technological fields. In its four years of existence, the competition has grown dramatically. During the Fall 2001 semester, several Michigan Technological University students served as mentors for local FLL teams. This paper presents details about the national FIRST LEGO League program, and statistics from a survey of FLL coaches in Minnesota are summarized to shed light on the current state of the program. Michigan Tech's FLL mentorship program is described along with the desired outcomes and summarized assessment results. The paper then presents several issues Universities must consider if they would like to begin an FLL mentorship program. Finally, preliminary conclusions are drawn based on the first year of the Michigan Tech program.
Frontiers in Education, 2002. FIE 2002. 32nd Annual; 12/2002
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