Activated sludge inhibition by chemical stressors--a comprehensive study.

The effects of shock loads of 1-chloro-2,4-dinitrobenzene (CDNB); cadmium; 1-octanol; 2,4-dinitrophenol (DNP); weakly complexed cyanide; pH 5, 9, and 11; and high ammonia levels on activated sludge biomass growth, respiration rate, flocculation, chemical oxygen demand removal, dewaterability, and settleability were studied. For all chemical shocks, except ammonia and pH, concentrations that caused 15, 25, and 50% respiration inhibition were used to provide a single pulse shock to sequencing batch reactor systems containing a nitrifying or non-nitrifying biomass. Cadmium and pH 11 shocks were most detrimental to all processes, followed by CDNB. The DNP and cyanide primarily affected respiration, while pH 5, pH 9, octanol, and ammonia did not affect the treatment process to a significant extent. A chemical source-process effect matrix is provided, which we believe will aid in the development of methods that prevent and/or attenuate the effects of toxic shock loads on activated sludge systems.     

Simulation of the evolution of particle size distributions in a vehicle exhaust plume with unconfined dilution by ambient air

Over the past several years, numerous studies have linked ambient concentrations of particulate matter (PM) to adverse health effects, and more recent studies have identified PM size and surface area as important factors in determining the health effects of PM. This study contributes to a better understanding of the evolution of particle size distributions in exhaust plumes with unconfined dilution by ambient air. It combines computational fluid dynamics (CFD) with an aerosol dynamics model to examine the effects of different streamlines in an exhaust plume, ambient particle size distributions, and vehicle and wind speed on the particle size distribution in an exhaust plume. CFD was used to calculate the flow field and gas mixing for unconfined dilution of a vehicle exhaust plume, and the calculated dilution ratios were then used as input to the aerosol dynamics simulation. The results of the study show that vehicle speed affected the particle size distribution of an exhaust plume because increasing vehicle speed caused more rapid dilution and inhibited coagulation. Ambient particle size distributions had an effect on the smaller sized particles (approximately 10 nm range under some conditions) and larger sized particles (>2 microm) of the particle size distribution. The ambient air particle size distribution affects the larger sizes of the exhaust plume because vehicle exhaust typically contains few particles larger than 2 microm. Finally, the location of a streamline in the exhaust plume had little effect on the particle size distribution; the particle size distribution along any streamline at a distance x differed by less than 5% from the particle size distributions along any other streamline at distance x.     

Migration,remittances, livelihood trajectories,and social resilience

We argue that all aspects of demographic change, including migration, impact on the social resilience of individuals and communities, as well as on the sustainability of the underlying resource base. Social resilience is the ability to cope with and adapt to environmental and social change mediated through appropriate institutions. We investigate one aspect of the relationship between demographic change, social resilience, and sustainable development in contemporary coastal Vietnam: the effects of migration and remittances on resource-dependent communities in population source areas. We find, using longitudinal data on livelihood sources, that emigration and remittances have offsetting effects on resilience within an evolving social and political context. Emigration is occurring concurrently with, not driving, the expansion of unsustainable coastal aquaculture. Increasing economic inequality also undermines social resilience. At the same time diversification and increasing income levels are beneficial for resilience.     

Survey of the occurrence and morphology of sub-cuticular bacteria in shelf echinoderms from the north-east Atlantic Ocean

Echinoderms from the shelf seas around the British Isles were examined by epifluorescence and transmission electron microscopy for the presence of sub-cuticular bacteria (SCB). Information was obtained on SCB distribution in 63 of the 88 species known from this area, and 40 of these contained SCB. The SCB were present in all five classes. Only 39% of the holothurian species had SCB. In each of the other four classes, 60% of the species were associated with SCB. No correlation was noted between host ecology and SCB distribution or morphology. SCB distribution appeared to be related to host phylogeny. Congeneric echinoderms almost always had or lacked SCB, and this was usually also true for co-familial species. SCB showed limited morphological diversity, with all of them fitting into a classification of three general types. There was no morphological evidence suggesting that they are chemoautotrophs or methylotrophs. Some species had two morphological types of symbiont. SCB load was quantified for four species, three of which had symbiont densities >10⁹ SCB g^-1 ash-free dry wt. SCB are probably heterotrophic and may be co-evolving with their hosts.     

Interspecific interference competition and mate choice in the soldier beetle,Chauliognathus pennsylvanicus

Summary Interference competition directed at soldier beetles, Chauliognathus pennsylvanicus, by four aggressive wasp species changed the mate choice of females. In the absence of wasps, females mated more frequently with males of greater weight and greater antennal scape diameter. Only in the presence of wasps did females frequently mate when they did not contain mature ova. When wasps were abundant, the proportion of beetles mating was higher. Wasps reacted aggressively toward mating beetles less frequently than toward single beetles. Therefore, females may have fed more efficiently in the presence of wasps when coupled.     

Cumulative ecological and socioeconomic effects of forest policies in coastal Oregon.

Forest biodiversity policies in multi-ownership landscapes are typically developed in an uncoordinated fashion with little consideration of their interactions or possible unintended cumulative effects. We conducted an assessment of some of the ecological and socioeconomic effects of recently enacted forest management policies in the 2.3-million-ha Coast Range Physiographic Province of Oregon. This mountainous area of conifer and hardwood forests includes a mosaic of landowners with a wide range of goals, from wilderness protection to high-yield timber production. We projected forest changes over 100 years in response to logging and development using models that integrate land use change and forest stand and landscape processes. We then assessed responses to those management activities using GIS models of stand structure and composition, landscape structure, habitat models for focal terrestrial and aquatic species, timber production, employment, and willingness to pay for biodiversity protection. Many of the potential outcomes of recently enacted policies are consistent with intended goals. For example, we project the area of structurally diverse older conifer forest and habitat for late successional wildlife species to strongly increase. 'Other outcomes might not be consistent with current policies: for example, hardwoods and vegetation diversity strongly decline within and across owners. Some elements of biodiversity, including streams with high potential habitat for coho salmon (Oncorhynchus kisutch) and sites of potential oak woodland, occur predominately outside federal lands and thus were not affected by the strongest biodiversity policies. Except for federal lands, biodiversity policies were not generally characterized in sufficient detail to provide clear benchmarks against which to measure the progress or success. We conclude that land management institutions and policies are not well configured to deal effectively with ecological issues that span broad spatial and temporal scales and that alternative policies could be constructed that more effectively provide for a mix of forest values from this region.     

Adjustment costs from environmental change

The paper is concerned with the case whereby the distribution of a firm's productivity shocks changes without the knowledge of the firm. Over time the firm learns about the nature and extent of the change in the distribution of the shock and adjusts, incurring adjustment costs in the process. The long-run loss in profits (±) due to the shift in the distribution we term the equilibrium response. The transitory loss in profits, incurred while the firm is learning about the distribution shift, is termed the adjustment cost. The theory is then applied to the problem of measuring adjustment costs in the face of imperfectly observed climate change in agriculture. The empirical part of the paper involves estimating a restricted profit function for agricultural land in a five-state region of the Midwest US as a function of prices, land characteristics, actual weather realizations and expected weather. We then simulate the effect of an unobserved climate shock, where learning about the climate shock is by observing the weather and updating prior knowledge using Bayes Rule. We find adjustment costs to climate change are 1.4% of annual land rents.     

煤尘润湿接触角的BP神经网络估算方法研究

通过采集和测定35个矿区煤样品的化学组成、结构参数和润湿接触角,构建了以13个影响因子为输入参数和以接触角为输出目标的3层BP人工神经网络,并利用该模型估算煤尘润湿接触角。结果表明,隐含层节点数为19时,接触角估算值与实测值的决定系数R2=0.957,平均相对误差为4.59%,表明基于BP神经网络建立的煤尘润湿接触角估算模型具有很高的精度。