Statistics in disease ecology: introduction to a special issue

The three papers included in this special issue represent a set of presentations in an invited session on disease ecology at the 2005 Spring Meeting of the Eastern North American Region of the International Biometric Society. The papers each address statistical estimation and inference for particular components of different disease processes and, taken together, illustrate the breadth of statistical issues arising in the study of the ecology and public health impact of disease. As an introduction, we provide a very brief overview of the area of “disease ecology”, a variety of synonyms addressing different aspects of disease ecology, and present a schematic structure illustrating general components of the underlying disease process, data collection issues, and different disciplinary perspectives ranging from microbiology to public health surveillance.

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An examination of the factorial,construct, and predictive validity and utility of the regulatory focus at work scale

Although interest in regulatory focus research continues to grow, there has been very little work to date on the assessment and usefulness of regulatory focus in the workplace. The present research effort reports the results of a series of studies designed to assess the validity and utility of the Regulatory Focus at Work Scale (RWS). The results indicate that the RWS is reliable, valid, and showed incremental validity beyond general and trait‐like measures of regulatory focus in predicting relevant work outcomes of task performance, citizenship performance, safety performance, and productivity performance. The overall results of these studies support our claims that the RWS shows utility in predicting workplace outcomes and should prove useful for future research on regulatory focus in the workplace. Copyright © 2008 John Wiley & Sons, Ltd.     

Modification of a full-scale sequencing batch reactor operational mode for biological nutrient removal.

Two biological nutrient removal modes, consisting of anaerobic, anoxic, and oxic sequences, were tested in a full-scale sequencing batch reactor. The modes, identified as BNR-S1 and BNR-S2, had average total nitrogen removals of 84 and 89%, respectively, for the months of August to October. Over the same period, total phosphorus removals for BNR-S1 and BNR-S2 were 88 and 87%, respectively. In contrast, total nitrogen and total phosphorus removals for the regular aerobic mode were 54.7 and 44.7%, respectively. When the wastewater temperature changed from approximately 20 to 15 degrees C in the winter months, total nitrogen and total phosphorus removals for BNR-S2 were reduced to 81 and 70%, respectively. Total nitrogen effluent concentrations were between 2.5 and 4 mg-N/L (at approximately 20 degrees C), while the effluent total phosphorus concentrations were between 1 and 2 mg/L. The BNR-S2 mode was found to require less energy per kilogram of soluble chemical oxygen demand removed than the regular and BNR-S1 modes.     

Detection of free and covalently bound microcystins in animal tissues by liquid chromatography-tandem mass spectrometry

Microcystins are cyanobacterial hepatotoxins capable of accumulation into animal tissues. The toxins act by inhibiting specific protein phosphatases and both non-covalent and covalent interactions occur. The 2-methyl-3-methoxy-4-phenylbutyric acid (MMPB) method determines the total, i.e. the sum of free and protein-bound microcystin in tissues. The aim of the method development in this paper was to tackle the problems with the MMPB methodology: the rather laborious workflow and the loss of material during different steps of the method. In the optimised workflow the oxidation recovery was of acceptable level (29-40%), the extraction efficiency good (62-97%), but the signal suppression effect from the matrix remained severe in our system (16-37% signal left). The extraction efficiency for the determination of the free, extractable microcystins, was found to be good, 52-100%, depending on the sample and the toxin variant and concentration.     

Congener-specific egg contribution of polychlorinated biphenyls to nestlings in two passerine species

Quantifying polychlorinated biphenyl (PCB) residues in nestlings of avian species is a common method for assessing trophic transfer and risk at PCB-contaminated sites. The proportion of nestling PCB mass due to maternal transfer is often accounted for by subtracting total PCB mass in eggs from nestlings. However, variation in physicochemical properties and metabolism among congeners may lead to differences between egg contribution based on total PCBs and dioxin-like congeners. We examined congener-specific variation in contribution of PCBs from eggs to nestlings in tree swallows and European starlings. Egg contribution of total PCB mass was 14.3 and 16.2%, respectively, whereas contribution based on dioxin-like congeners was 14.8 and 13.6%, respectively. These data suggest that using total PCB mass in eggs to adjust estimates of PCB accumulation in nestlings may not reflect patterns for dioxin-like congeners, potentially over or under-estimating the risk of toxicity of PCBs.     

自养型生物过滤器硝化氧化一氧化氮

采用一种新的工程材料多孔碳作为填料,在3个φ50.8mm填充着不同孔径多孔碳和驯化培养好的自养型亚硝酸盐硝化菌的生物过滤器中,进行了净化气体中NO的探索性研究.实验采用亚硝酸盐为唯一氮源,在多孔碳的表面培养生物膜,采用超声波气溶胶发生器来维持过滤器内的湿度并保持多孔碳表面液膜的厚度较小.液相硝化试验用来比较3种不同孔径的多孔碳之间硝化性能的潜力和差异结果表明,在亚氮(NO₂^--N)进口负荷约200～800g/(L·min)的范围内.24孔/cm(Pores Per Centimeter,PPC)多孔碳过滤器的硝化速率最大,达到94%～98%;8PPC和18PPC多孔碳过滤器的硝化速率分别达到15%～21%和30%～40%.气相试验表明,在NO空床停留时间3.5min、进口浓度66.97～267.86mg/m³的范围内,24PPC多孔碳过滤器对NO的去除效率为41%～52%左右,表明了该自养硝化系统在NO废气治理中的应用潜力.     

Extended bioremediation of PAH/PCP contaminated soils from the POPILE wood treatment facility

A study was conducted using two pilot-scale land-treatment units (LTUs) to evaluate the efficacy of different cultivation and maintenance schedules during bioremediation of contaminated soil from a wood treatment facility using landfarming technology. The soil contained high concentrations of polycyclic aromatic hydrocarbons (PAHs, approximately 13000 ppm) as well as of pentachlorophenol (PCP, approximately 1500 ppm). An initial 6-month intensive-treatment phase was followed by 24 months of less-intensive treatment. During the first phase, traditional landfarming practice of regular cultivation was compared with a gas-phase composition based cultivation strategy, and both the landfarming units were intensively monitored and maintained with respect to moisture control and delivery of nutrients. The two strategies resulted in similar contaminant concentration profiles with time during this phase, although different microbial populations developed in the two-landfarming units. The second (less-intensive) treatment phase involved no moisture control and nutrient delivery beyond the initial adjustments, and compared natural attenuation (no cultivation) with quarterly cultivation of soil. Both the strategies showed similar behavior again. GC/MS analysis of the soil samples showed PAH removal including four-ring homologues. Leachability tests at zero time and after 6 and 22 months of operation showed significant reductions in leaching of PCP and low molecular weight PAHs. Extended treatment resulted in some leaching of high molecular weight PAHs. Significant biological activity was demonstrated, even at the high contaminant concentrations. Phospholipid ester-linked fatty acid (PLFA) analysis showed an increase in biomass and a divergence in community composition in soils depending on the treatment conducted.