Bioproduction strategies for rare hexose sugars

A new strategy for the bioproduction of all ketohexoses was developed using hexitols as intermediates. Biocatalysts used to employ the strategy were D-tagatose 3-epimerase, which epimerizes ketohexoses at the C-3 position, and oxidoreductases, which catalyze oxidation-reduction reactions between ketohexoses and the corresponding hexitols. Arranging all the ketohexoses and hexitols in a symmetric ring and connecting them with 20 biochemical reactions, I was able to construct a design for the bioproduction of all the rare ketohexoses. Various aldose isomerases transform ketohexoses into the corresponding aldohexoses, so the strategy is useful for the bioproduction of all the rare hexose sugars. Furthermore, the design revealed that there are four routes to the L-hexose world from the D-hexose one.     

Evaluating Sediment Stability at Sites with Historic Contamination

The stability of cohesive sediment deposits during a rare storm is a critical component in the evaluation of remedial options at a contaminated sediment site. Estimating scour depths during a rare storm, and the resulting contaminant concentrations in the surficial layer of the bed, is necessary for comparing the efficacy of various remedial alternatives. Evaluation of sediment stability is accomplished using sediment transport analyses that employ quantitative procedures. Qualitative analyses or conceptual models can be useful for developing and validating quantitative analysis tools; however, qualitative techniques alone generally are insufficient for conducting defensible remedial alternative evaluations. The level of analysis used for a specific site depends on data availability, required level of accuracy, and time and budget constraints. A tier 1 analysis involves the use of approximate equations to produce order-of-magnitude estimates of scour depths during a rare storm. The second tier of this analysis scheme employs the development and application of a sediment transport model to evaluate bed stability. State-of-the-science sediment transport models have been effectively used as management tools for evaluating remedial options at several contaminated sediment sites. It should not be presumed that rare storm events cause catastrophic impacts at the site under review. Two case studies demonstrate that a rare storm is not necessarily catastrophic; significant increases in surficial bed concentrations caused by reexposure of elevated concentrations buried at depth in the bed will not necessarily occur during a rare storm. However, it is important to note that sediment stability is site-specific.     

Patterns of Streamwater Acidity in Lye Brook Wilderness,Vermont, USA

Under the United States Clean Air Act Amendments of 1977, a class I designation safeguards wilderness areas from the negative effects of new sources of air pollution. We monitored streamwater chemistry in the class I Lye Brook Wilderness in southwestern Vermont from May 1994 through August 1995. Stream samples were collected biweekly at nine sampling locations throughout the wilderness and were analyzed for major cations and anions, dissolved organic carbon, pH, and acid-neutralizing capacity. Eight of nine sites sampled had mean annual acid neutralizing capacity values below zero. During the study period, decreases in streamwater acid neutralizing capacity values were caused primarily by SO₄ ²⁻. At some sites, however, NO₃ ⁻ and naturally occurring, weak organic acids were seasonally important. During high discharge, the low pH and high concentrations of inorganic monomeric Al were at levels that are toxic to acid-sensitive aquatic species. Watershed mass balances were calculated to determine annual gains or losses for measured ions. These budgets indicate that S inputs and outputs were nearly equal, there was a net loss of base cations, and a net gain in N. How long these watersheds can continue to assimilate additional N inputs is unknown.     

利用造纸黑液制备水煤浆添加剂

利用造纸黑液中有效成分，经过适当处理制备水煤浆添加剂，并且对添加剂的性能进行了测试。结果表明，依照该工艺生产的添加剂，性能优良，能够满足工业生产需要。     

Waste reduction through variable charging programs: its sustainability and contributing factors

 In this study, we analyzed the sustainability and determinant factors of waste reduction through variable charging schemes. We drew three main conclusions from the study. (1) Waste reduction was achieved by variable charging and was sustained over an average of at least 10 years. The results regarding the sustainability of the price effect were inconclusive. (2) The main factors contributing to the combustible waste reduction achieved through variable charging were two-tier pricing and the price of waste bags. The effect of two-tier pricing programs was positive. (3) Waste paper recycling and variable charging reinforce each other to promote waste reduction. Received: September 3, 2001 / Accepted: January 13, 2002     

A Baumol–Oates approach to solid waste taxation

A national Baumol–Oates tax on waste in Denmark helped achieve a reduction of 26% in net solid waste from 1987 to 1998. The tax, which is levied per ton of waste, was particularly effective as regards the heavier waste streams such as construction waste and garden waste. When it comes to industrial and commercial waste, there are indications that the waste tax is not sufficiently significant to induce changes in behavior, and that except for very waste-intensive enterprises, companies do not seem to be very price sensitive. For household waste, the impact of the tax can be improved where tariffs for garbage collection are weight based, rather than per unit. However, the waste sector is an area in which the price signals are modified and filtered by institutionalized practices in municipal administration, and in which true-cost pricing is not easy to achieve. Hence, the rational choice assumption of environmental economics needs to be supplemented by an institutional dimension to interpret responses to environmental taxes correctly. Received: July 13, 2001 / Accepted: October 2, 2001