Optimization of Operating Parameters for the Selective Flotation of Heavy Metals from Contaminated Fine Sediment Using Response Surface Model

In this study, the effect of different flotation operating variables, such as pH, pulp density, collector concentration, impeller speed, frother concentration, and air flow rate, on selective flotation of heavy metals, especially Cu, from fine dredged sediment has been evaluated. Parameter optimization was done using the single parameter at a time method and response surface method (RSM) using Box-Behnken design and was assessed in terms of metal removal, metal recovery, metal concentration factor, and mass recovery. Among the operating variables studied, pulp pH, collector concentration, pulp density, and impeller speed were found to have significant effect on metal flotation selectivity. A validation study of the response surface model showed its aptness to predict the optimum values of operating parameters and their interactions on flotation responses which evaluate flotation performance. Flotation experiments under optimum operating parameters showed good flotation selectivity for Cu (3.3 ± 0.2) with a mass recovery of (mass of sediment in the froth) 14.1 ± 1 and Cu removal of 37.4 ± 3.6%.     

A Thirteen-Gene Expression Signature Predicts Survival of Patients with Pancreatic Cancer and Identifies New Genes of Interest

Background

Currently, prognostication for pancreatic ductal adenocarcinoma (PDAC) is based upon a coarse clinical staging system. Thus, more accurate prognostic tests are needed for PDAC patients to aid treatment decisions.

Methods and Findings

Affymetrix gene expression profiling was carried out on 15 human PDAC tumors and from the data we identified a 13-gene expression signature (risk score) that correlated with patient survival. The gene expression risk score was then independently validated using published gene expression data and survival data for an additional 101 patients with pancreatic cancer. Patients with high-risk scores had significantly higher risk of death compared to patients with low-risk scores (HR 2.27, p = 0.002). When the 13-gene score was combined with lymph node status the risk-score further discriminated the length of patient survival time (p<0.001). Patients with a high-risk score had poor survival independent of nodal status; however, nodal status increased predictability for survival in patients with a low-risk gene signature score (low-risk N1 vs. low-risk N0: HR = 2.0, p = 0.002). While AJCC stage correlated with patient survival (p = 0.03), the 13-gene score was superior at predicting survival. Of the 13 genes comprising the predictive model, four have been shown to be important in PDAC, six are unreported in PDAC but important in other cancers, and three are unreported in any cancer.

Conclusions

We identified a 13-gene expression signature that predicts survival of PDAC patients and could prove useful for making treatment decisions. This risk score should be evaluated prospectively in clinical trials for prognostication and for predicting response to chemotherapy. Investigation of new genes identified in our model may lead to novel therapeutic targets.     

Fate and Persistence of Particulate and Dissolved Microcystin-LA from Microcystis Blooms

Few studies have estimated fate and persistence of the hepatotoxic microcystins (MCs) in situ, making ecological and human health risk assessments challenging. We determined fate and persistence of MC congeners during 2 years of Microcystis blooms in a small, shallow, closed-basin lake in Ontario, Canada. In situ half-lives were compared to estimates obtained in vitro under controlled temperature and light. The blooms produced elevated microcystin-LA (MC-LA) (maximum ～4.2 mg L^?1) with minor concentrations of MC-LR, -RR, and -YR. Dissolved MC-LA declined more slowly and persisted longer than particulate MC-LA with in situ half-lives (total 1.5–8.5 days) shorter than in vitro (total 6.8–60.0 days). Half-lives in 2010 were two to eight times shorter compared to 2009, likely due to differences in bloom phenology and species/strain composition. In vitro, higher temperature (4°C → 25°C in dark), and irradiance (dark → 45 → 260 μE m^?2s^?1 at 25°C) accelerated particulate and dissolved MC-LA decline, respectively. MC-RR accumulated in surface sediments while MC-LA was near detection despite elevated surface water concentrations. MC-LA appears to persist longer in surface waters than the equally toxic MC-LR, requiring almost the entire recreational season (9.5 weeks) to reach guideline concentrations (20 μg L^?1).     

Gene copy number variations in adaptive evolution: The genomic distribution of gene copy number variations revealed by genetic mapping and their adaptive role in an undomesticated species,white spruce (Picea glauca)

Gene copy number variation (CNV) has been associated with phenotypic variability in animals and plants, but a genomewide understanding of their impacts on phenotypes is largely restricted to human and agricultural systems. As such, CNVs have rarely been considered in investigations of the genomic architecture of adaptation in wild species. Here, we report on the genetic mapping of gene CNVs in white spruce, which lacks a contiguous assembly of its large genome (~20 Gb), and their relationships with adaptive phenotypic variation. We detected 3,911 gene CNVs including de novo structural variations using comparative genome hybridization on arrays (aCGH) in a large progeny set. We inferred the heterozygosity at CNV loci within parents by comparing haploid and diploid tissues and genetically mapped 82 gene CNVs. Our analysis showed that CNVs were distributed over 10 linkage groups and identified four CNV hotspots that we predict to occur in other species of the Pinaceae. Significant relationships were found between 29 of the gene CNVs and adaptive traits based on regression analyses with timings of bud set and bud flush, and height growth, suggesting a role for CNVs in climate adaptation. The importance of CNVs in adaptive evolution of white spruce was also indicated by functional gene annotations and the clustering of 31% of the mapped adaptive gene CNVs in CNV hotspots. Taken together, these results illustrate the feasibility of studying CNVs in undomesticated species and represent a major step towards a better understanding of the roles of CNVs in adaptive evolution.     

Ecdysone 20-hydroxylation in imaginal wing discs of Pieris brassicae (lepidoptera): Correlations with ecdysone and 20-hydroxyecdysone titers in pupae

Ecdysone 20-hydroxylase activity has been detected in pupal wing discs of Pieris brassicae. This activity is due to an enzyme system located in microsomal fractions. Its apparent Km is 58 nM for ecdysone. The enzyme is inhibited by the reaction product 20-hydroxyecdysone with an apparent Ki of 2.6 μM. Its activity varied during pupal-adult development with a maximum on day 4, when ecdysone levels are the highest in the animal. Although low, the peak activity is sufficient to assure 25% of the conversion of endogenous ecdysone into 20-hydroxyecdysone in pupae. Ecdysone and 20-hydroxyecdysone levels were measured in hemolymph and whole animals; ecdysone appears to be mainly located in hemolymph, whereas 20-hydroxyecdysone seems to be equally distributed between hemolymph and tissues. All these findings are discussed in relation to the roles of ecdysone and 20-hydroxyecdysone during pupal-adult development.     

Microbial DNA records historical delivery of anthropogenic mercury

Mercury (Hg) is an anthropogenic pollutant that is toxic to wildlife and humans, but the response of remote ecosystems to globally distributed Hg is elusive. Here, we use DNA extracted from a dated sediment core to infer the response of microbes to historical Hg delivery. We observe a significant association between the mercuric reductase gene (merA) phylogeny and the timing of Hg deposition. Using relaxed molecular clock models, we show a significant increase in the scaled effective population size of the merA gene beginning ~200 years ago, coinciding with the Industrial Revolution and a coincident strong signal for positive selection acting on residues in the terminal region of the mercuric reductase. This rapid evolutionary response of microbes to changes in the delivery of anthropogenic Hg indicates that microbial genomes record ecosystem response to pollutant deposition in remote regions.     

Atmospheric loading of Zn,Cu, Ni,Cr, and Pb to lake sediments: The role of catchment,lake morphometry,and physico-chemical properties of the elements

Although catchments have been implicated as an important source of metals to lakes, the catchment contribution of different metals is poorly known, and the anthropogenic contribution is not known at all. We determine the anthropogenic lake sediment burdens of Zn, Cu, Ni, Cr, and Pb for several Quebec and Ontario lakes, not subject to point source loading, to obtain estimates of atmospheric loading and inputs from terrestrial sources. To do this, we first collected multiple cores across 11 lake basins to estimate the whole-lake Pb burdens. As the whole-lake Pb burdens did not differ among lakes that spanned over two orders of magnitude in drainage ratios (drainage basin area/lake area), we conclude that catchment retention of anthropogenic Pb is complete. The anthropogenic Pb burdens were then used as a correction for focusing for the other metals. Among the metals, Cr and Ni were the most readily exported from drainage basins, followed by Cu. Zn showed no increase with drainage ratio, indicating Zn to be effectively retained by catchments. The export coefficients of the Pb corrected metals correlate well with ocean residence time, revealing a similar metal sorption/precipitation sequence in both soils and oceans. Sediment metal burdens provide a relatively easy way to obtain not only metal export coefficients from drainage basins, but also the atmospheric deposition of anthropogenic metals (e.g. Pb: S.E. Quebec, 950 mg^*m^–2: Laurentians, north of Montreal, 420 mg^*m^–2). The export coefficients are not only simpler to obtain than by mass balance measurements, but, in addition, identify the anthropogenic component.     

Secondary metabolites ofPenicillium bilaii strain PB-50

A phosphate-solubilizing strain ofPenicillium bilaii was tested for the production of gliotoxin and other toxic compounds. The strain was fermented under five different conditions to allow the expression of various metabolites, including gliotoxin. These included Czapek-yeast extract medium under both shaken and still conditions as well as Czapek-yeast extract/malt extract/peptone medium and sucrose/glycerol medium in shake flasks. In addition, culture filtrate from an industrial fermentation of the fungus was examined. No gliotoxin was produced in any of the media. No other expectedP. bilaii metabolites were found. Three compounds were identified in all samples: dibutyl phthalate, 1-(4-hydroxy-phenyl)ethanone and 4-hydroxy-3,6-dimethyl-2H-pyran-2-one. The production of other metabolites was dependent on the culture conditions. Two hyalodendrin derivatives were found in some fermentations and two related compounds were tentatively identified. None of the compounds found have been reported as toxic. The identity of the culture was confirmed by comparison with the ex-type culture ofP. bilaii.     

Use of a hydrophobic cloth for enzyme immunoassay

Summary As an adsorbent for enzyme immunoassay, a macroporous polyester cloth was superior to the conventional non-porous microtiter plate in that it provides a much larger surface area for immunoreactions (thus, faster reactions), can accommodate a larger volume of sample, and permits easier washing. These attributes should enable polyester cloth to provide rapid and simple field assays.     

La vie sexuelle des grecs anciens

In this paper, the authors present their point of view concerning the sexuality of the Ancient Greeks and try to improve the reputation of their sexual practices.