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221.
Clausen C 《Waste management (New York, N.Y.)》2004,24(4):401-405
In this study, three possible improvements to a remediation process for chromated-copper-arsenate- (CCA) treated wood were evaluated. The process involves two steps: oxalic acid extraction of wood fiber followed by bacterial culture with Bacillus licheniformis CC01. The three potential improvements to the oxalic acid extraction step were (1) reusing oxalic acid for multiple extractions, (2) varying the ratio of oxalic acid to wood, and (3) using a noncommercial source of oxalic acid such as Aspergillus niger, which produces oxalic acid as a metabolic byproduct. Reusing oxalic acid for multiple extractions removed significant amounts of copper, chromium, and arsenic. Increasing the ratio of wood to acid caused a steady decline in metal removal. Aspergillus niger removed moderate amounts of copper, chromium, and arsenic from CCA-treated wood. Although A. niger was effective, culture medium costs are likely to offset any benefits. Repeated extraction with commercial oxalic acid appears to be the most cost-effective method tested for the two-step process. 相似文献
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This paper reviews selected research on classroom and school environments, using a framework that views schools from three perspectives—as places for learning, as places for socialization and as places for psychological development. Studies are included that deal with the impact of noise and classroom design on learning; the relationship between seating position, achievement and status; spatial cognition; the classroom environment and sex role stereotyping; privacy; and density. The need for classrooms to enhance children's feelings of competence, security and self-esteem is also stressed. The goal of the paper is to point out ways in which environmental psychologists can contribute to the improvement of the educational system and to the quality of life in schools. 相似文献
225.
All known cosmic and geological conditions and laws of chemistry and thermodynamics allow that complex organic matter could
have formed spontaneously on pristine planet Earth about 4,000 mya. Simple gasses and minerals on the surface and in oceans
of the early Earth reacted and were eventually organized in supramolecular aggregates and enveloped cells that evolved into
primitive forms of life. Chemical evolution, which preceded all species of extant organisms, is a fact. In this review, we
have concentrated on experimental and theoretical research published over the last two decades, which has added a wealth of
new details and helped to close gaps in our previous understanding of this multifaceted field. Recent exciting progress in
the molecular and genetic analyses of existing life, in particular microorganisms of ancient origin, even supports the possibility
that a cellular, self-reproducing common ancestor might be assembled and resurrected in anaerobic cultures at some time in
the future. Charles Darwin did not, and indeed, could not, address and specify the earliest phases of life which preceded
the Origin of Species. However, in a famous letter, he sketched “a warm little pond with all sorts of… (chemicals, in which) …a protein was chemically
formed.” We try to trace the impact of his charming clear-sighted metaphor up to the present time. 相似文献