The former site of a major petroleum storage facility adjacent to a major urban watercourse was found to have potentially significant concentrations of hydrocarbons in soil and groundwater that needed to be addressed prior to redevelopment. A series of intrusive investigations were undertaken to collect physical and chemical data for a Quantitative Risk Assessment (QRA) of potential impacts on human health and the wider environment, in order to derive a remedial strategy for redevelopment of the site for light industrial use. A site-specific QRA methodology was devel oped using both U.K. and U.S. guidance to produce Risk-Based Clean-up Levels (RBCLs) for benzene, and other petroleum hydrocarbons. The U.K. has no nationally based guidance on risk assessment and studies are designed by the consultant for submission to the U.K. Environment Agency (EA) for their approval. It is the EA's role to determine whether the work has been undertaken satisfactorily. To achieve these RBCLs, ex situ bioremediation was identified as the best practicable remedial option. This was carried out in windrows using mechanical aeration (to achieve oxygenation with ammonia nitrate granule and woodchip addition) for a total of approximately 5291?m3 of soil. The bioremediation process was successful in achieving the site specific RBCLs for benzene and for other hydrocarbons within an average of 5 to 6 weeks. This article describes the successful implementation of Risk-Based Corrective Action (RBCA) at this petroleum release site as a demonstration of how risk-based remedial standards for contaminated sites can be achieved with regulatory approval. 相似文献
Diet composition in pinnipeds is widely estimated using hard prey remains recovered from feces. To estimate the size and number of prey represented in fecal samples accurately, digestion correction factors (DCFs) must be applied to measurements and counts of fish otoliths and cephalopod beaks. In this study, 101 whole prey feeding trials were conducted with six harbor seals (Phoca vitulina) and 18 prey species. We derived species‐ and grade‐specific estimates of digestion coefficients (DCs) and species‐specific recovery rates (RRs) to account for partial and complete digestion, respectively. Greater than 98% of otoliths were passed within three days of consumption. RRs were smallest for Atlantic salmon smolts (RR = 0.306, SE = 0.031) and increasingly larger for sandeels (RR = 0.494, SE = 0.017), flatfish (RR = 0.789, SE = 0.033), and large gadoids (RR = 0.944, SE = 0.034). Species‐specific otolith width DCs were smallest for Trisopterus species (DC = 1.14, SE = 0.015) and increasingly larger for flatfish (DC = 1.27, SE = 0.045), large gadoids (DC = 1.32, SE = 0.067) and sandeels (DC = 1.57, SE = 0.035). RRs were similar to those from gray seals (Halichoerus grypus), but harbor seal species‐ and grade‐specific DCs were generally smaller. Differences in partial and complete digestion rates among prey species and between seal species highlight the importance of applying DCFs when reconstructing diet. 相似文献
The transitions between phases of the cell cycle have evolved to be robust and switch-like, which ensures temporal separation of DNA replication, sister chromatid separation, and cell division. Mathematical models describing the biochemical interaction networks of cell cycle regulators attribute these properties to underlying bistable switches, which inherently generate robust, switch-like, and irreversible transitions between states. We have recently presented new mathematical models for two control systems that regulate crucial transitions in the cell cycle: mitotic entry and exit,1Mochida S, Rata S, Hino H, Nagai T, Novák B. Two Bistable Switches Govern M Phase Entry. Curr Biol. 2016;26:3361-3367. doi:10.1016/j.cub.2016.10.022. PMID:27889260[Crossref], [PubMed], [Web of Science ®][Google Scholar] and the mitotic checkpoint.2Mirkovic M, Hutter LH, Novák B, Oliveira RA. Premature sister chromatid separation is poorly detected by the spindle assembly checkpoint as a result of system-level feedback. Cell Rep. 2015;13:469-478. doi:10.1016/j.celrep.2015.09.020[Crossref], [PubMed], [Web of Science ®][Google Scholar] Each of the two control systems is characterized by two interlinked bistable switches. In the case of mitotic checkpoint control, these switches are mutually activating, whereas in the case of the mitotic entry/exit network, the switches are mutually inhibiting. In this Perspective we describe the qualitative features of these regulatory motifs and show that having two interlinked bistable mechanisms further enhances robustness and irreversibility. We speculate that these network motifs also underlie other cell cycle transitions and cellular transitions between distinct biochemical states. 相似文献
Fluorescence Lifetime Imaging (FLIM) is an attractive microscopy method in the life sciences, yielding information on the sample otherwise unavailable through intensity‐based techniques. A novel Noise‐Corrected Principal Component Analysis (NC‐PCA) method for time‐domain FLIM data is presented here. The presence and distribution of distinct microenvironments are identified at lower photon counts than previously reported, without requiring prior knowledge of their number or of the dye's decay kinetics. A noise correction based on the Poisson statistics inherent to Time‐Correlated Single Photon Counting is incorporated. The approach is validated using simulated data, and further applied to experimental FLIM data of HeLa cells stained with membrane dye di‐4‐ANEPPDHQ. Two distinct lipid phases were resolved in the cell membranes, and the modification of the order parameters of the plasma membrane during cholesterol depletion was also detected.
Noise‐corrected Principal Component Analysis of FLIM data resolves distinct microenvironments in cell membranes of live HeLa cells. 相似文献
Over the last half century, the most frequently used assay for chlorophylls in higher plants and green algae, the Arnon assay
[Arnon DI (1949) Plant Physiol 24: 1–15], employed simultaneous equations for determining the concentrations of chlorophylls
a and b in aqueous 80% acetone extracts of chlorophyllous plant and algal materials. These equations, however, were developed using
extinction coefficients for chlorophylls a and b derived from early inaccurate spectrophotometric data. Thus, Arnon's equations give inaccurate chlorophyll a and b determinations and, therefore, inaccurate chlorophyll a/b ratios, which are always low. This paper describes how the ratios are increasingly and alarmingly low as the proportion of
chlorophyll a increases. Accurate extinction coefficients for chlorophylls a and b, and the more reliable simultaneous equations derived from them, have been published subsequently by many research groups;
these new post-Arnon equations, however, have been ignored by many researchers. This Minireview records the history of the
development of accurate simultaneous equations and some difficulties and anomalies arising from the retention of Arnon's seriously
flawed equations.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
The formation of a novel complex between magnesium and p-nitro-o-carboxylazochromotropic acid (NCBAC) has been observed which is sensitive and selective at pH 10.4 in the presence of ethylenediamine and fluoride. The constants of formation of this complex have been determined by a spectral correction technique, and the complexation reaction has been applied to the spectrophotometric determination of trace magnesium in plants and in water with satisfactory results. 相似文献