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1
Balicka, Adrianna, and Jan Szadkowski. "Analysis of adsorption of heavy metals from water solutions by wood of selected domestic species using X-Ray Fluorescence (XRF)." Annals of WULS, Forestry and Wood Technology 111 (September 30, 2020): 73–82. http://dx.doi.org/10.5604/01.3001.0014.6773.
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Analysis of adsorption of heavy metals from water solutions by wood of selected domestic species using X-Ray Fluorescence (XRF).The aim of this study was to analyze the absorption of three specific heavy metals from model water solution by wood species from domestic Polish forests. This paper focuses on XRF method to determine metal content in samples. European aspen (Populus tremula L.) and Black locust (Robinia pseudoacacia L.) have been chosen. Firstly, shavings were prepared and soaked with standard solutions of lead (II) nitrate, cadmium nitrate and mercury (II) chloride for 7 days. Then, the material was dried and reduced to ashes using muffle furnace. Finally, content of absorbed metal was marked (XRF) and analyzed with a view to initial contents of metal ions in standard solutions. It was established, that the higher the concentration of mercury in standard solution is, the higher impulse counts is obtained for European aspen. This reversal of the dependence is noticeable for second analyzed species.
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Bahadori, Elnaz, Francesco Conte, Antonio Tripodi, Gianguido Ramis, and Ilenia Rossetti. "Photocatalytic Selective Oxidation of Ammonia in a Semi-Batch Reactor: Unravelling the Effect of Reaction Conditions and Metal Co-Catalysts." Catalysts 11, no. 2 (February 5, 2021): 209. http://dx.doi.org/10.3390/catal11020209.
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Photocatalysis has been used for the oxidation of ammonia/ammonium in water. A semibatch photoreactor was developed for this purpose, and nanostructured TiO2-based materials, either commercial P25 or prepared by flame spray pyrolysis (FSP), were used as catalysts. In the present work, we investigated the effect of (i) metal co-catalysts, (ii) pH, and (iii) ammonia concentration on the efficiency of oxidation and on the selectivity to the undesired overoxidation byproduct, i.e., nitrites and nitrates. Several metals were added to both titania samples, and the physicochemical properties of every sample were studied by XRD, BET, and UV-Vis spectroscopy. The pH, which was investigated in the range of 2.5–11.5, was the most important parameter. The optimum pH values, resulted as 11.5 and 4.8 for P25 and FSP respectively, matching the best compromise between an acceptable conversion and a limited selectivity toward nitrite and nitrate formation. For both titania samples (P25 and FSP), ammonia conversion vs. nitrite and nitrate formation were highly dependent on the pH. At pH ≥ 9, the initial rate of photooxidation was high, with selective formation of overoxidized byproducts, whereas, at a more acidic pH, the conversion was lower, but the selectivity toward nitrogen formation was higher. P25 samples added with noble metal co-catalysts (0.1 mol% Ag, Au, Pd, Pt) at pH = 11.5 remarkably increased the selectivity to nitrite and nitrate, while, in the case of FSP samples (pH = 4.8), the co-catalysts increased the selectivity toward N2 with respect to the unpromoted catalyst and also the conversion in the case of Au and Pt. Reactivity was discussed, leading to the proposing of a mechanism that correlates the activity with either surface adsorption (depending of the surface charge of the catalyst and on pH) or the homogeneous reactivity of oxidizing species.
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Papuc, Camelia, Corina Predescu, Valentin Nicorescu, Georgeta Stefan, and Isabela Nicorescu. "Antioxidant Properties of a Parsley (Petroselinum crispum) Juice Rich in Polyphenols and Nitrites." Current Research in Nutrition and Food Science Journal 4, Special-Issue-October (October 4, 2016): 114–18. http://dx.doi.org/10.12944/crnfsj.4.special-issue-october.15.
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Parsley (Petroselinum crispum) is an herbaceous vegetable used as foodstuff, spice and medicinal plant because it provides antioxidants especially flavonoids (apigenin), vitamins (K, C and A), and volatile oils, among other compounds. Because parsley has important concentrations of nitrates and flavonoids, very little vegetal pigment and a mild flavour profile, it was chosen for this study. The aim of this study was to obtain parsley juice rich in nitrite and polyphenols and to assess its antioxidant activity. To obtain nitrite from nitrate by enzymatic reaction, Staphylococcus xylosus ATCC 29971 was used as nitrate reductase source. To obtain the vegetable juice, fresh roots were minced and homogenized in aqueous solution. The sterile juice was filtered and then inoculated with S. xylosus and incubated at 37°C. The nitrate and nitrite concentrations (mg/L) were determined using a colorimetric method using salicylic acid and Griess reagent, respectively. The total polyphenols content (TPC) was measured with Folin-Ciocalteu reagent and expressed as mg gallic acid equivalent / 100 mL (mg GAE / 100 mL). The total flavonoids content (TFC) was measured with aluminium chloride reagent, and expressed as mg catechin equivalent / 100 mL (mg CE / 100 mL). To determine the antioxidant activity of parsley juice, the ability to reduce DPPH synthetic radical, reducing power of Fe3+ ion and the capacity of chelating transition metal ions were assessed. Maximum concentration of nitrites was achieved for parsley juice in the presence of S. xylosus after 24 hours; TPC was 14.87 mg GAE / 100 mL and TFC was 11.21 mg CE / 100 mL. The ability of parsley fermented juice to reduce DPPH synthetic radical was 79.45%, while the capacity to reduce Fe3+ was 0.758 ± 0.14 (absorbance at 700 nm) and to chelate Fe2+ ion was 23.64%. Parsley juice represents an important source of natural nitrate and flavonoids, with important antioxidant capacity.
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Kodentsov, Alexander. "Diffusion-Limited Reactions of Non-Oxide Ceramics with Transition Metals." Diffusion Foundations 21 (March 2019): 85–126. http://dx.doi.org/10.4028/www.scientific.net/df.21.85.
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Thermodynamic and diffusion models are given to describe morphological evolution of the reaction zone during diffusion-limited interaction between non-oxide Si-containing ceramics (SiC and Si3N4) and transition metals (Cr, Mo, Ti, Ni, Co, Pt). In the case of diffusion-controlled process in the ternary metal-ceramic systems, reaction phenomena can be rationalized using chemical potential diagrams. However, in some cases, a periodic layered morphology is found in the transition zone, which is not fully understood, and it is difficult to predict a priori. Silicide formation in systems based on dense Silicon Nitride and non-nitride forming metals can be explained by assuming a nitrogen pressure build-up at the contact surface. This pressure determines the chemical potential of Silicon at the interface, and hence, the product phases in the diffusion zone. Traces of Oxygen in the ambient atmosphere might affect the interaction in non-oxide ceramic/transition metal systems. The thermodynamic stability of the condensed phases in the systems where volatile species may form can be interpreted using predominant area-type diagrams.
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Jasman, Siti Maryam, Hendrik Oktendy Lintang, Siew Ling Lee, and Leny Yuliati. "Photocatalytic oxidation of nitrite ion over carbon nitride." Malaysian Journal of Fundamental and Applied Sciences 14, no. 1-2 (April 30, 2018): 174–78. http://dx.doi.org/10.11113/mjfas.v14n1-2.987.
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Nitrite ion (NO2-) is a toxic inorganic contaminant, which is widely used in industry and agriculture as a food preservative and a fertilizing agent. One of the methods to reduce the toxicity of the NO2- is by oxidizing it into less hazardous compounds, such as nitrate ion (NO3-). In this study, we demonstrated that a simple and green photocatalytic process can be employed to oxidize the NO2- to NO3- over a metal free-carbon nitride photocatalyst under ultraviolet (UV) light irradiation. The carbon nitride was synthesized via pyrolysis of urea precursor by a thermal polymerization process at 823 K for 4 hours. The prepared carbon nitride was then characterized by using X-ray diffractometer (XRD), field emission scanning electron microscope (FESEM), diffuse reflectance UV-visible (DR UV-vis), fluorescence, and Fourier transform infrared (FTIR) spectrophotometers, as well as nitrogen adsorption-desorption isotherm analyzer. All the characterization results supported the successful synthesis of the carbon nitride. The carbon nitride was then used as the photocatalyst for oxidation of NO2- to NO3- under UV light irradiation for 3 h. The decrease of the NO2- and the formation of the NO3- were analyzed by using a high performance liquid chromatography (HPLC) equipped with Hypersil GoldTM PFP column. The mobile phase used was a mixture of methanol (MeOH) and water (H2O) with the ratio of MeOH:H2O was 30:70. The addition of orthophosphoric acid was required to set the pH at 2.5. The flow rate was fixed at 0.8 ml min-1 and the monitored wavelength was 220 nm. It was revealed that carbon nitride could oxidize NO2- to NO3- with a moderate conversion of 15%. Fluorescence quenching showed that there were good interactions between the emission sites of carbon nitride and the NO2- molecules. The good interactions would be one driving force for the carbon nitride to act as a good photocatalyst to oxidize the NO2- to NO3-. The oxidation pathway by the photogenerated species was also proposed.
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Percival, H. J., T. W. Speir, and A. Parshotam. "Soil solution chemistry of contrasting soils amended with heavy metals." Soil Research 37, no. 5 (1999): 993. http://dx.doi.org/10.1071/sr98055.
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The soil solution chemistry of heavy metal amended soils is of great importance in assessing the bioavailability of heavy metals and their toxicity to the soil biota. Three contrasting soils were amended with Cd(II), Cu(II), Ni(II), Pb(II), Zn(II), and Cr(III) nitrate salts at rates of 10–100 mmol/kg. This concentration range was chosen to encompass a wide range of effects on sensitive soil biochemical properties as part of a larger project. Soil solutions were extracted and analysed for pH, and for concentrations of heavy metals, and major cations and anions. Heavy metal speciation was calculated with the GEOCHEM-PC model. Heavy metal concentrations in the soil solutions increased both in absolute terms and as a percentage of added heavy metal as amendment rates increased. This observation is due to decreasing specific adsorption (caused by decreasing pH induced by the amendments), and to increasing saturation of cation exchange sites. For all 3 soils, the percentage increase commonly follows the order Cr(III) < Pb < Cu < Ni < Cd < Zn. The percentage of each metal held in the soil solution increased from soil to soil as cation exchange capacity, and therefore sorptivity, decreased. Both the concentration and activity of free heavy metal ions were substantially lower than the corresponding total metal concentration. This was ascribed to ion-pairing of metal ions with anions, particularly nitrate introduced in the amending solutions, as well as to increases in ionic strength as a result of amendment. Metal-anion species were mainly inorganic but where Cu and Pb were relatively low in concentration because of strong adsorption by the soils, organic complexation was likely to be significant. Speciation trends were similar for the 3 soils but different in magnitude.
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Lebel, Hélène, and Henri Piras. "Stereoselective Synthesis of Chiral Sulfilimines from N-Mesyloxycarbamates: Metal-Nitrenes versus Metal-Nitrenoids Species." Journal of Organic Chemistry 80, no. 7 (March 18, 2015): 3572–85. http://dx.doi.org/10.1021/acs.joc.5b00256.
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Starkenburg, Shawn R., Frank W. Larimer, Lisa Y. Stein, Martin G. Klotz, Patrick S. G. Chain, Luis A. Sayavedra-Soto, Amisha T. Poret-Peterson, et al. "Complete Genome Sequence of Nitrobacter hamburgensis X14 and Comparative Genomic Analysis of Species within the Genus Nitrobacter." Applied and Environmental Microbiology 74, no. 9 (March 7, 2008): 2852–63. http://dx.doi.org/10.1128/aem.02311-07.
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ABSTRACT The alphaproteobacterium Nitrobacter hamburgensis X14 is a gram-negative facultative chemolithoautotroph that conserves energy from the oxidation of nitrite to nitrate. Sequencing and analysis of the Nitrobacter hamburgensis X14 genome revealed four replicons comprised of one chromosome (4.4 Mbp) and three plasmids (294, 188, and 121 kbp). Over 20% of the genome is composed of pseudogenes and paralogs. Whole-genome comparisons were conducted between N. hamburgensis and the finished and draft genome sequences of Nitrobacter winogradskyi and Nitrobacter sp. strain Nb-311A, respectively. Most of the plasmid-borne genes were unique to N. hamburgensis and encode a variety of functions (central metabolism, energy conservation, conjugation, and heavy metal resistance), yet ∼21 kb of a ∼28-kb “autotrophic” island on the largest plasmid was conserved in the chromosomes of Nitrobacter winogradskyi Nb-255 and Nitrobacter sp. strain Nb-311A. The N. hamburgensis chromosome also harbors many unique genes, including those for heme-copper oxidases, cytochrome b 561, and putative pathways for the catabolism of aromatic, organic, and one-carbon compounds, which help verify and extend its mixotrophic potential. A Nitrobacter “subcore” genome was also constructed by removing homologs found in strains of the closest evolutionary relatives, Bradyrhizobium japonicum and Rhodopseudomonas palustris. Among the Nitrobacter subcore inventory (116 genes), copies of genes or gene clusters for nitrite oxidoreductase (NXR), cytochromes associated with a dissimilatory nitrite reductase (NirK), PII-like regulators, and polysaccharide formation were identified. Many of the subcore genes have diverged significantly from, or have origins outside, the alphaproteobacterial lineage and may indicate some of the unique genetic requirements for nitrite oxidation in Nitrobacter.
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Yu, Guo Xian, Ji Bing Li, Xiao Long Zhou, Cheng Lie Li, Li Fang Chen, and Jin An Wang. "Adsorption of Dibenzothiophene on Transition Metals Loaded Activated Carbon." Advanced Materials Research 132 (August 2010): 141–48. http://dx.doi.org/10.4028/www.scientific.net/amr.132.141.
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Transition metal-modified carbon-based adsorbents were prepared by impregnating activated carbon with solutions of copper, cobalt or nickel chloride or nitrate. The mixtures were dried and then calcined under nitrogen stream. The surface metal species were analyzed by XRD technique and the surface oxygen-containing groups were characterized by FTIR. Their adsorption capacities for dibenzothiophene (DBT) were measured by using DBT-containing n-octane solution as model oil. Experimental results show that the metal species on the carbon surface could be controlled by the calcination process under nitrogen atmosphere. Both the transition metal precursors and kinds of metal species on the carbon surface have significant effects on DBT adsorption capacity.
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Yoshie, S., N. Noda, T. Miyano, S. Tsuneda, A. Hirata, and Y. Inamori. "Characterization of microbial community in nitrogen removal process of metallurgic wastewater by PCR-DGGE." Water Science and Technology 46, no. 11-12 (December 1, 2002): 93–98. http://dx.doi.org/10.2166/wst.2002.0722.
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The metallurgic wastewater generated from the processes of recovering precious metals from industrial wastes contains high concentrations of nitrogen compounds such as ammonia and nitric acid and of salts such as sodium chloride and sodium sulfate. Biological nitrogen removal from this wastewater was attempted by a circulating bioreactor system equipped with an anoxic packed bed and an aerobic fluidized bed. The anoxic packed bed of this system was found to effectively remove nitrite and nitrate from the wastewater by denitrification at a removal ratio of 97%. As a result of denitrification activity tests at various NaCl concentrations, the sludge obtained from the anoxic packed bed exhibited accumulation of nitrite at 5.0 and 8.4% NaCl concentrations, suggesting that the reduction of nitrite is the key step in the denitrification pathway under hypersaline conditions. The microbial community analysis by denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S ribosomal DNA (rDNA) fragments revealed that the community diversity varied in accordance with water temperature, nitrate-loading rate and ionic strength. When particular major DGGE bands were excised, reamplified and directly sequenced, the dominant species in the anoxic packed bed were affiliated with the beta and gamma subclasses of the class Proteobacteria such as Alcaligenes defragrans and Pseudomonas spp., respectively.
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Green, Stefan J., Om Prakash, Thomas M. Gihring, Denise M. Akob, Puja Jasrotia, Philip M. Jardine, David B. Watson, Steven D. Brown, Anthony V. Palumbo, and Joel E. Kostka. "Denitrifying Bacteria Isolated from Terrestrial Subsurface Sediments Exposed to Mixed-Waste Contamination." Applied and Environmental Microbiology 76, no. 10 (March 19, 2010): 3244–54. http://dx.doi.org/10.1128/aem.03069-09.
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ABSTRACTIn terrestrial subsurface environments where nitrate is a critical groundwater contaminant, few cultivated representatives are available to verify the metabolism of organisms that catalyze denitrification. In this study, five species of denitrifying bacteria from three phyla were isolated from subsurface sediments exposed to metal radionuclide and nitrate contamination as part of the U.S. Department of Energy's Oak Ridge Integrated Field Research Challenge (OR-IFRC). Isolates belonged to the generaAfipiaandHyphomicrobium(Alphaproteobacteria),Rhodanobacter(Gammaproteobacteria),Intrasporangium(Actinobacteria), andBacillus(Firmicutes). Isolates from the phylumProteobacteriawere complete denitrifiers, whereas the Gram-positive isolates reduced nitrate to nitrous oxide. rRNA gene analyses coupled with physiological and genomic analyses suggest that bacteria from the genusRhodanobacterare a diverse population of denitrifiers that are circumneutral to moderately acidophilic, with a high relative abundance in areas of the acidic source zone at the OR-IFRC site. Based on genome analysis,Rhodanobacterspecies contain two nitrite reductase genes and have not been detected in functional-gene surveys of denitrifying bacteria at the OR-IFRC site. Nitrite and nitrous oxide reductase gene sequences were recovered from the isolates and from the terrestrial subsurface by designing primer sets mined from genomic and metagenomic data and from draft genomes of two of the isolates. We demonstrate that a combination of cultivation and genomic and metagenomic data is essential to thein situcharacterization of denitrifiers and that current PCR-based approaches are not suitable for deep coverage of denitrifiers. Our results indicate that the diversity of denitrifiers is significantly underestimated in the terrestrial subsurface.
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Li, Yan, Tianyu Tang, Haejune Lee, and Kiwon Song. "Cold Atmospheric Pressure Plasma-Activated Medium Induces Selective Cell Death in Human Hepatocellular Carcinoma Cells Independently of Singlet Oxygen, Hydrogen Peroxide, Nitric Oxide and Nitrite/Nitrate." International Journal of Molecular Sciences 22, no. 11 (May 24, 2021): 5548. http://dx.doi.org/10.3390/ijms22115548.
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Cold atmospheric pressure plasma (CAP) and plasma-activated medium (PAM) induce cell death in diverse cancer cells and may function as powerful anti-cancer agents. The main components responsible for the selective anti-cancer effects of CAP and PAM remain elusive. CAP or PAM induces selective cell death in hepatocellular carcinoma cell lines Hep3B and Huh7 containing populations with cancer stem cell markers. Here, we investigated the major component(s) of CAP and PAM for mediating the selective anti-proliferative effect on Hep3B and Huh7 cells. The anti-proliferative effect of CAP was mediated through the medium; however, the reactive oxygen species scavenger N-acetyl cysteine did not suppress PAM-induced cell death. Neither high concentrations of nitrite or nitrite/nitrate nor a low concentration of H2O2 present in the PAM containing sodium pyruvate affected the viability of Hep3B and Huh7 cells. Inhibitors of singlet oxygen, superoxide anions, and nitric oxide retained the capacity of PAM to induce anti-cancer effects. The anti-cancer effect was largely blocked in the PAM prepared by placing an aluminum metal mesh, but not a dielectric PVC mesh, between the plasma source and the medium. Hence, singlet oxygen, hydrogen peroxide, nitric oxide, and nitrite/nitrate are not the main factors responsible for PAM-mediated selective death in Hep3B and Huh7 cells. Other factors, such as charged particles including various ions in CAP and PAM, may induce selective anti-cancer effects in certain cancer cells.
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Lebel, Helene, and Henri Piras. "ChemInform Abstract: Stereoselective Synthesis of Chiral Sulfilimines from N-Mesyloxycarbamates: Metal-Nitrenes versus Metal-Nitrenoids Species." ChemInform 46, no. 33 (July 28, 2015): no. http://dx.doi.org/10.1002/chin.201533118.
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Livingstone, Keith, Sophie Bertrand, Jenna Mowat, and Craig Jamieson. "Metal-free C–C bond formation via coupling of nitrile imines and boronic acids." Chemical Science 10, no. 44 (2019): 10412–16. http://dx.doi.org/10.1039/c9sc03032h.
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Janke, H., TM Yamada, DAS Beraldo, CMR Botta, MRL Nascimento, and AA Mozeto. "Assessment of the acute toxicity of eutrophic sediments after the addition of calcium nitrate (Ibirité reservoir, Minas Gerais-SE Brazil): initial laboratory experiments." Brazilian Journal of Biology 71, no. 4 (November 2011): 903–14. http://dx.doi.org/10.1590/s1519-69842011000500011.
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This study evaluated the acute toxicity of sediment in a eutrophic reservoir after remediation with a calcium nitrate solution to retain phosphorus. The study involved microcosms of surface sediments and water from the sediment-water interface in the Ibirité reservoir. This reservoir, located in the vicinity of metropolitan Belo Horizonte (Minas Gerais, SE Brazil), is a water body that receives treated effluents from an oil refinery (REGAP-Petrobras), as well as high loads of untreated urban effluents from the city of Ibirité and surrounding areas and industrial effluents from a major industrial park. Incubation times of the treatment experiments were: t = 0, t = 5, t = 10, t = 25, t = 50, t = 85 and t = 135 days. One control microcosm and three treated microcosms were analysed in each time interval. Acute toxicity of water samples was assessed with Ceriodaphnia silvestrii Daday, 1902 and that of bulk sediment samples with Chironomus xanthus Rempel, 1939. Toxicity tests were carried out concomitantly with chemical analyses of dissolved inorganic nitrogen species (ammonia, nitrate and nitrite), sulfate and metals in the water samples of the microcosms. Acid volatile sulfides (AVS), simultaneously extracted metal (SEM) and potentially bioavailable metal were analyzed in bulk sediment samples. Neither of the tested organisms showed toxicity in the control microcosm samples. The water column of the treated microcosm showed toxicity to C. silvestrii, starting at t = 10 days, while the sediment pore water toxicity started at t = 0 day. However, toxicity was found to decline from t = 85 days to t = 135 days. Sediments showed toxicity to C. xanthus during the entire experiment, except at the longest incubation time (t = 135 days). The overall results indicate that nitrate, which reached concentrations exceeding 1,200 mg N-NO3- L-1 in the sediment pore water of the treated microcosms, was most probably responsible for the toxicity of the samples. Although the calcium nitrate technology proved effective in retaining phosphorus, promoting sediment oxidation via denitrification, from the ecotoxicological standpoint and under the experimental conditions of this study, the application of nitrate for remediation of the sediments in the Ibirité reservoir did not prove effective up to a period of 135 days of incubation. However, we presume that after longer periods of incubation, treated sediments may recover their ability to sustain a benthic community. More advanced experiments are planned involving longer incubation times, thus extending the denitrification process, which may lead to a higher phosphorus retention capacity and to more complete abatement of sediment toxicity.
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Ding, Dewu, Meineng Wang, Meili Wu, Chengzhi Gan, and Pu Wu. "Condition-Specific Molecular Network Analysis Revealed That Flagellar Proteins Are Involved in Electron Transfer Processes of Shewanella piezotolerans WP3." Genetics Research 2021 (July 29, 2021): 1–9. http://dx.doi.org/10.1155/2021/9953783.
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Because of the ability to metabolize a large number of electron acceptors such as nitrate, nitrite, fumarate, and metal oxides, Shewanella species have attracted much attention in recent years. Generally, the use of these electron acceptors is mainly achieved through electron transfer proteins and their interactions which will dynamically change across different environmental conditions in cells. Therefore, functional analysis of condition-specific molecular networks can reveal biological information on electron transfer processes. By integrating expression data and molecular networks, we constructed condition-specific molecular networks for Shewanella piezotolerans WP3. We then identified condition-specific key genes and studied their potential functions with an emphasis on their roles in electron transfer processes. Functional module analysis showed that different flagellar assembly modules appeared under these conditions and suggested that flagellar proteins are important for these conditions. We also identified the electron transfer modules underlying these various environmental conditions. The present results could help with screening electron transfer genes and understanding electron transfer processes under various environmental conditions for the Shewanella species.
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Rader, W. Scott, Ljiljana Solujic, E. B. Milosavljevic, J. L. Hendrix, and J. H. Nelson. "Photochemistry of Aqueous Solutions of Dicyanomercury(II) and Potassium Tetracyanomercurate(II)." Journal of Solar Energy Engineering 116, no. 3 (August 1, 1994): 125–29. http://dx.doi.org/10.1115/1.2930070.
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Photochemically induced reactions of dicyanomercury(II) and potassium tetracyanomercurate(II) in alkaline aqueous solutions were investigated in detail. The studies were conducted in the presence or absence of a titanium(IV) oxide semiconductor photocatalyst utilizing sunlight as the irradiation source. It was established that the cyanide ion liberated from the thermodynamically stable mercury-cyano species can be photocatalytically oxidized via cyanate and nitrite to nitrate. In addition, the process removes over 99 mol% of mercury from the solution. In the absence of the photocatalyst, no photoproducts were detected and mercury remained in solution. The results obtained may have ramifications for the use of solar power for the efficient treatment of large quantities of precious metals mill tailings wastes containing various cyanide species. In addition, in order to follow the fate of cyanide in these experiments, a novel gas-diffusion flow injection analysis system for the determination of cyanide from the thermodynamically stable mercury-cyano complexes was utilized.
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Chen, Zupeng, Evgeniya Vorobyeva, Sharon Mitchell, Edvin Fako, Núria López, Sean M. Collins, Rowan K. Leary, Paul A. Midgley, Roland Hauert, and Javier Pérez-Ramírez. "Single-atom heterogeneous catalysts based on distinct carbon nitride scaffolds." National Science Review 5, no. 5 (April 17, 2018): 642–52. http://dx.doi.org/10.1093/nsr/nwy048.
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Abstract Carbon nitrides integrating macroheterocycles offer unique potential as hosts for stabilizing metal atoms due to their rich electronic structure. To date, only graphitic heptazine-based polymers have been studied. Here, we demonstrate that palladium atoms can be effectively isolated on other carbon nitride scaffolds including linear melem oligomers and poly(triazine/heptazine imides). Increased metal uptake was linked to the larger cavity size and the presence of chloride ions in the polyimide structures. Changing the host structure leads to significant variation in the average oxidation state of the metal, which can be tuned by exchange of the ionic species as evidenced by X-ray photoelectron spectroscopy and supported by density functional theory. Evaluation in the semi-hydrogenation of 2-methyl-3-butyn-2-ol reveals an inverse correlation between the activity and the degree of oxidation of palladium, with oligomers exhibiting the highest activity. These findings provide new mechanistic insights into the influence of the carbon nitride structure on metal stabilization.
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Pawlowska, Teresa E., Rufus L. Chaney, Mel Chin, and Iris Charvat. "Effects of Metal Phytoextraction Practices on the Indigenous Community of Arbuscular Mycorrhizal Fungi at a Metal-Contaminated Landfill." Applied and Environmental Microbiology 66, no. 6 (June 1, 2000): 2526–30. http://dx.doi.org/10.1128/aem.66.6.2526-2530.2000.
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ABSTRACT Phytoextraction involves use of plants to remove toxic metals from soil. We examined the effects of phytoextraction practices with three plant species (Silene vulgaris, Thlaspi caerulescens, and Zea mays) and a factorial variation of soil amendments (either an ammonium or nitrate source of nitrogen and the presence or absence of an elemental sulfur supplement) on arbuscular mycorrhizal (AM) fungi (Glomales, Zygomycetes) at a moderately metal-contaminated landfill located in St. Paul, Minn. Specifically, we tested whether the applied treatments affected the density of glomalean spores and AM root colonization in maize. Glomalean fungi from the landfill were grouped into two morphotypes characterized by either light-colored spores (LCS) or dark-colored spores (DCS). Dominant species of the LCS morphotype were Glomus mosseae and an unidentified Glomus sp., whereas the DCS morphotype was dominated by Glomus constrictum. The density of spores of the LCS morphotype from the phytoremediated area was lower than the density of these spores in the untreated landfill soil. Within the experimental area, spore density of the LCS morphotype in the rhizosphere of mycorrhizal maize was significantly higher than in rhizospheres of nonmycorrhizal S. vulgaris or T. caerulescens. Sulfur supplement increased vesicular root colonization in maize and exerted a negative effect on spore density in maize rhizosphere. We conclude that phytoextraction practices, e.g., the choice of plant species and soil amendments, may have a great impact on the quantity and species composition of glomalean propagules as well as on mycorrhiza functioning during long-term metal-remediation treatments.
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Kim, Kwang-Soo, Ji-Seon Yoo, Sungyoun Kim, Hee Ja Lee, Kwang-Ho Ahn, and In S. Kim. "Relationship between the electric conductivity and phosphorus concentration variations in an enhanced biological nutrient removal process." Water Science and Technology 55, no. 1-2 (January 1, 2007): 203–8. http://dx.doi.org/10.2166/wst.2007.053.
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Phosphorus release and uptake in a sequencing batch reactor were monitored by the simple on-line measurements of electric conductivity (EC) and oxidation-reduction potential (ORP), and the result was verified by the measurement of phosphate concentration changes. The influence of nitrate ion presence on the phosphorus removal was evaluated by a jar test operated in the cyclic anaerobic (anoxic)–aerobic condition. The relationships of EC, ORP and metal species with phosphorus concentrations were investigated. Under strict anaerobic conditions, EC showed positive correlation with phosphorus concentrations, but it became negligible under anoxic conditions with nitrate present. Strong inverse correlation was found between ORP values and phosphorus concentration. The increase and decrease of magnesium and potassium ions took place in accordance with phosphorus release and uptake, and the relationship between the metal species and phosphorus changes was clearer in the anaerobic condition than anoxic condition.
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Prakash, Om, Stefan J. Green, Puja Jasrotia, Will A. Overholt, Andy Canion, David B. Watson, Scott C. Brooks, and Joel E. Kostka. "Rhodanobacter denitrificans sp. nov., isolated from nitrate-rich zones of a contaminated aquifer." International Journal of Systematic and Evolutionary Microbiology 62, Pt_10 (October 1, 2012): 2457–62. http://dx.doi.org/10.1099/ijs.0.035840-0.
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Bacterial strains 2APBS1T and 116-2 were isolated from the subsurface of a nuclear legacy waste site where the sediments are co-contaminated with large amounts of acids, nitrate, metal radionuclides and other heavy metals. A combination of physiological and genetic assays indicated that these strains represent the first member of the genus Rhodanobacter shown to be capable of complete denitrification. Cells of strain 2APBS1T and 116-2 were Gram-negative, non-spore-forming rods, 3–5 µm long and 0.25–0.5 µm in diameter. The isolates were facultative anaerobes, and had temperature and pH optima for growth of 30 °C and pH 6.5; they were able to tolerate up to 2.0 % NaCl, although growth improved in its absence. Strains 2APBS1T and 116-2 contained fatty acid and quinone (ubiquinone-8; 100 %) profiles that are characteristic features of the genus Rhodanobacter . Although strains 2APBS1T and 116-2 shared high 16S rRNA gene sequence similarity with Rhodanobacter thiooxydans LCS2T (>99 %), levels of DNA–DNA relatedness between these strains were substantially below the 70 % threshold used to designate novel species. Thus, based on genotypic, phylogenetic, chemotaxonomic and physiological differences, strains 2APBS1T and 116-2 are considered to represent a single novel species of the genus Rhodanobacter , for which the name Rhodanobacter denitrificans sp. nov. is proposed. The type strain is 2APBS1T ( = DSM 23569T = JCM 17641T).
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Chohan, Zahid H., and S. K. A. Sherazi. "Synthesis, Characterization and Role of Anions (Nitrate, Sulphate, Oxalate and Acetate) \in the Biological Activity of Hydrazine Derived Compounds and Their Metal Chelates." Metal-Based Drugs 4, no. 6 (January 1, 1997): 327–32. http://dx.doi.org/10.1155/mbd.1997.327.
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Hydrazine derived compounds and its Co(II), Cu(II) and Ni(II) chelates having the same metal ion but different anions (e.g., nitrate, sulphate, oxalate and acetate) have been synthesised and characterised by their physical, spectral and analytical data. In order to evaluate the participating role of anions in the antibacterial activity, these synthesised ligands and its metal chelates have been screened against bacterial species such as Staphylococcus aureous, pseudomonas aeruginosa, Klebsiella pneumonae and Proteus vulgarus, and the results are reported.
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Yang, Xiaoyun, Sina He, Yijin Shu, Zhangping Shi, Yulin Guo, Qingsheng Gao, and Yi Tang. "Controlled nitridation of tantalum (oxy)nitride nanoparticles towards optimized metal-support interactions with gold nanocatalysts." RSC Advances 5, no. 108 (2015): 89282–89. http://dx.doi.org/10.1039/c5ra19644b.
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Optimized metal-support interactions were achieved on ionothermally prepared tantalum (oxy)nitrides with controlled nitridation, and the as-formed Auδ− species on TaON is efficient for nitrobenzene hydrogenation.
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Macdonald, Katrina M., Sangeeta Sharma, Desiree Toom, Alina Chivulescu, Andrew Platt, Mike Elsasser, Lin Huang, et al. "Temporally delineated sources of major chemical species in high Arctic snow." Atmospheric Chemistry and Physics 18, no. 5 (March 9, 2018): 3485–503. http://dx.doi.org/10.5194/acp-18-3485-2018.
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Abstract. Long-range transport of aerosol from lower latitudes to the high Arctic may be a significant contributor to climate forcing in the Arctic. To identify the sources of key contaminants entering the Canadian High Arctic an intensive campaign of snow sampling was completed at Alert, Nunavut, from September 2014 to June 2015. Fresh snow samples collected every few days were analyzed for black carbon, major ions, and metals, and this rich data set provided an opportunity for a temporally refined source apportionment of snow composition via positive matrix factorization (PMF) in conjunction with FLEXPART (FLEXible PARTicle dispersion model) potential emission sensitivity analysis. Seven source factors were identified: sea salt, crustal metals, black carbon, carboxylic acids, nitrate, non-crustal metals, and sulfate. The sea salt and crustal factors showed good agreement with expected composition and primarily northern sources. High loadings of V and Se onto Factor 2, crustal metals, was consistent with expected elemental ratios, implying these metals were not primarily anthropogenic in origin. Factor 3, black carbon, was an acidic factor dominated by black carbon but with some sulfate contribution over the winter-haze season. The lack of K+ associated with this factor, a Eurasian source, and limited known forest fire events coincident with this factor's peak suggested a predominantly anthropogenic combustion source. Factor 4, carboxylic acids, was dominated by formate and acetate with a moderate correlation to available sunlight and an oceanic and North American source. A robust identification of this factor was not possible; however, atmospheric photochemical reactions, ocean microlayer reaction, and biomass burning were explored as potential contributors. Factor 5, nitrate, was an acidic factor dominated by NO3−, with a likely Eurasian source and mid-winter peak. The isolation of NO3− on a separate factor may reflect its complex atmospheric processing, though the associated source region suggests possibly anthropogenic precursors. Factor 6, non-crustal metals, showed heightened loadings of Sb, Pb, and As, and correlation with other metals traditionally associated with industrial activities. Similar to Factor 3 and 5, this factor appeared to be largely Eurasian in origin. Factor 7, sulfate, was dominated by SO42− and MS with a fall peak and high acidity. Coincident volcanic activity and northern source regions may suggest a processed SO2 source of this factor.
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Chohan, Zahid H. "Biologically Active Transition Metal Chelates of Ni(II), Cu(II) and Zn(II) With 2-Aminothiazole-Derived Schiff-bases: Their Synthesis, Characterization and the Role of Anions (NO3 , SO42− , C2O42- and CH3CO2− ) on Their Antibacterial Properties." Metal-Based Drugs 6, no. 3 (January 1, 1999): 187–92. http://dx.doi.org/10.1155/mbd.1999.187.
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Biologically active nickel(ll), copper(ll) and zinc(ll) chelates with thiazole-derived nitro- and chlorosalicylaldehyde Schiff-bases having the same metal ion but different anions, e.g. nitrate, sulfate, oxalate and acetate have been synthesized and characterized on the basis of their physical, spectral and analytical data. In order to evaluate the possible participating role of anions on the antibacterial properties, these ligands and their synthesized metal chelates with various anions have been screened against bacterial species Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus.
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THAMAE, MAMOTHIBE A., and TEBELLO NYOKONG. "Spectroscopic studies of the interaction of cobalt(II) N,N',N″,N‴-tetramethyltetra-3,4-pyridinoporphyrazine with amino acids and nitrogen oxides." Journal of Porphyrins and Phthalocyanines 05, no. 12 (December 2001): 839–45. http://dx.doi.org/10.1002/jpp.551.
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The interaction of histidine, cysteine, NO and nitrite with cobalt(II) N,N',N″,N‴-tetramethyltetra-3,4-tetrapyridinoporphyrazine ([ Co II tmtppa ]4+) is reported. Metal-based autoreduction of [ Co II tmtppa ]4+ occurs with the formation of the [ Co I tmtppa (-2)]3+ species in the presence of histidine and cysteine. Kinetic data for the auto reduction of [ Co II tmtppa ]4+ in the presence of these amino acids gave the rate constants k f = 2.1 × 101 and 2.8 dm3 mol-1 s-1, for cysteine and histidine, respectively. One molecule of NO or nitrite was found to coordinate to the [ Co II tmtppa ]4+ species. The equilibrium and rate constants for the coordination of the nitric oxide were K = 2.3 × 104 dm 3 mol -1 and k f = 7.5 dm 3 mol -1 s -1, respectively. The coordination of nitrite to [ Co II tmtppa ]4+ occurred with an equilibrium constant of K = 2.0 × 102 dm 3 mol -1 and a rate constant of k f = 4.0 × 10-3 dm 3 mol -1 s -1. There was no evidence for the coordination of two molecules of nitrite to the [ Co II tmtppa ]4+ species.
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Sinha, S. K., H. S. Srivastava, and S. N. Mishra. "Effect of lead on nitrate reductase activity and nitrate assimilation in pea leaves." Acta Societatis Botanicorum Poloniae 57, no. 4 (2014): 457–63. http://dx.doi.org/10.5586/asbp.1988.043.
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The effect of Pb on nitrate reductase activity, protein, total organic nitrogen and on the chlorophyll content in excised and intact leaf tissues of <em>Pisum sativum</em> was examine. Enzyme activity assayed in vitro or in vivo in the excised leaves showed marked increase at lower concentrations of Pb while being inhibited at higher concentrations. In intact leaf tissues, the enzyme activity (in vivo or in vitro) was unaffected at lower concentrations but was inhibited at higher concentrations of Pb. Chlorophyll, carotenoids (non-nitrogenous pigments), soluble protein and organic nitrogen contents remained almost unaffected at all concentrations of Pb tested. It seems that nitrate reductase has a different response towards Pb pollution in this species, which is more tolerant to heavy metal pollution, especially Pb.
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Kalčíková, Gabriela, Jana Zagorc-Končan, and Andreja Žgajnar Gotvajn. "Artemia salina acute immobilization test: a possible tool for aquatic ecotoxicity assessment." Water Science and Technology 66, no. 4 (August 1, 2012): 903–8. http://dx.doi.org/10.2166/wst.2012.271.
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Despite the fact that the marine crustacean Artemia salina is extensively used in ecotoxicology, there is still a lack of information about its sensitivity to commonly used chemicals. In the presented study, acute toxicity of 18 commonly used chemicals – including organic solvents, industrial chemicals, metals and inorganic compounds – to A. salina was evaluated. A. salina showed a range of sensitivities to tested chemicals. Regarding all of the investigated organics, phenolic compounds expressed the highest toxicity to A. salina. Nitrite and mercury were the most toxic inorganic substances applied in the study. On the other hand, dimethyl sulfoxide, nitrate and ammonium were the least toxic. The possibility to use A. salina for interspecies correlation was assessed by comparison of sensitivities of different organisms (bacteria, fish, crustacean) to organic compounds. Correlation between various species was observed, especially between A. salina and fish. Due to the strong relation between toxicity and the logarithm of the octanol/water partition coefficient logPOW, lipophilicity was found to be the main factor influencing toxicity of the chosen organic compounds. No significant correlation between toxicity to A. salina and physico-chemical parameters of metals was observed.
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Wattanathana, Worawat, Suttipong Wannapaiboon, Chatchai Veranitisagul, Navadol Laosiripojana, Nattamon Koonsaeng, and Apirat Laobuthee. "Preparation of Palladium-Impregnated Ceria by Metal Complex Decomposition for Methane Steam Reforming Catalysis." Advances in Materials Science and Engineering 2017 (2017): 1–10. http://dx.doi.org/10.1155/2017/5828067.
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Palladium-impregnated ceria materials were successfully prepared via an integrated procedure between a metal complex decomposition method and a microwave-assisted wetness impregnation. Firstly, ceria (CeO2) powders were synthesized by thermal decomposition of cerium(III) complexes prepared by using cerium(III) nitrate or cerium(III) chloride as a metal source to form a metal complex precursor with triethanolamine or benzoxazine dimer as an organic ligand. Palladium(II) nitrate was consequently introduced to the preformed ceria materials using wetness impregnation while applying microwave irradiation to assist dispersion of the dopant. The palladium-impregnated ceria materials were obtained by calcination under reduced atmosphere of 10% H2 in He stream at 700°C for 2 h. Characterization of the palladium-impregnated ceria materials reveals the influences of the metal complex precursors on the properties of the obtained materials. Interestingly, the palladium-impregnated ceria prepared from the cerium(III)-benzoxazine dimer complex revealed significantly higher BET specific surface area and higher content of the more active Pdδ+ (δ > 2) species than the materials prepared from cerium(III)-triethanolamine complexes. Consequently, it exhibited the most efficient catalytic activity in the methane steam reforming reaction. By optimization of the metal complex precursors, characteristics of the obtained palladium-impregnated ceria catalysts can be modified and hence influence the catalytic activity.
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North, Nadia N., Sherry L. Dollhopf, Lainie Petrie, Jonathan D. Istok, David L. Balkwill, and Joel E. Kostka. "Change in Bacterial Community Structure during In Situ Biostimulation of Subsurface Sediment Cocontaminated with Uranium and Nitrate." Applied and Environmental Microbiology 70, no. 8 (August 2004): 4911–20. http://dx.doi.org/10.1128/aem.70.8.4911-4920.2004.
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ABSTRACT Previous studies have demonstrated that metal-reducing microorganisms can effectively promote the precipitation and removal of uranium from contaminated groundwater. Microbial communities were stimulated in the acidic subsurface by pH neutralization and addition of an electron donor to wells. In single-well push-pull tests at a number of treated sites, nitrate, Fe(III), and uranium were extensively reduced and electron donors (glucose, ethanol) were consumed. Examination of sediment chemistry in cores sampled immediately adjacent to treated wells 3.5 months after treatment revealed that sediment pH increased substantially (by 1 to 2 pH units) while nitrate was largely depleted. A large diversity of 16S rRNA gene sequences were retrieved from subsurface sediments, including species from the α, β, δ, and γ subdivisions of the class Proteobacteria, as well as low- and high-G+C gram-positive species. Following in situ biostimulation of microbial communities within contaminated sediments, sequences related to previously cultured metal-reducing δ-Proteobacteria increased from 5% to nearly 40% of the clone libraries. Quantitative PCR revealed that Geobacter-type 16S rRNA gene sequences increased in biostimulated sediments by 1 to 2 orders of magnitude at two of the four sites tested. Evidence from the quantitative PCR analysis corroborated information obtained from 16S rRNA gene clone libraries, indicating that members of the δ-Proteobacteria subdivision, including Anaeromyxobacter dehalogenans-related and Geobacter-related sequences, are important metal-reducing organisms in acidic subsurface sediments. This study provides the first cultivation-independent analysis of the change in metal-reducing microbial communities in subsurface sediments during an in situ bioremediation experiment.
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Chohan, Zahid H., and M. Praveen. "Biological Role of Anions (Sulfate, Nitrate , Oxalate and Acetate) on the Antibacterial Properties of Cobalt (II) and Nickel(II) Complexes With Pyrazinedicarboxaimide Derived, Furanyl and Thienyl Compounds." Metal-Based Drugs 6, no. 2 (January 1, 1999): 95–99. http://dx.doi.org/10.1155/mbd.1999.95.
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A number of biologically active complexes of cobalt(II) and nickel(II) with pyrazinedicarboxaimido derived thienyl and furanyl compounds having the same metal ion but different anions such as sulphate, nitrate, oxalate and acetate have been synthesized and characterized on the basis of their physical, spectral and analytical data. In order to evaluate the role of anions on their antibacterial properties, these ligands and their synthesized metal complexes with various anions have been screened against bacterial species Escherichia coil,Pseudomonas aeruginosa and Staphylococcus aureus. The title studies have proved a definitive role of anions in increasing the antibacterial properties.
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Kroll, Kristin, Vera Pähtz, Falk Hillmann, Yakir Vaknin, Wolfgang Schmidt-Heck, Martin Roth, Ilse D. Jacobsen, Nir Osherov, Axel A. Brakhage, and Olaf Kniemeyer. "Identification of Hypoxia-Inducible Target Genes of Aspergillus fumigatus by Transcriptome Analysis Reveals Cellular Respiration as an Important Contributor to Hypoxic Survival." Eukaryotic Cell 13, no. 9 (August 1, 2014): 1241–53. http://dx.doi.org/10.1128/ec.00084-14.
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ABSTRACT Aspergillus fumigatus is an opportunistic, airborne pathogen that causes invasive aspergillosis in immunocompromised patients. During the infection process, A. fumigatus is challenged by hypoxic microenvironments occurring in inflammatory, necrotic tissue. To gain further insights into the adaptation mechanism, A. fumigatus was cultivated in an oxygen-controlled chemostat under hypoxic and normoxic conditions. Transcriptome analysis revealed a significant increase in transcripts associated with cell wall polysaccharide metabolism, amino acid and metal ion transport, nitrogen metabolism, and glycolysis. A concomitant reduction in transcript levels was observed with cellular trafficking and G-protein-coupled signaling. To learn more about the functional roles of hypoxia-induced transcripts, we deleted A. fumigatus genes putatively involved in reactive nitrogen species detoxification ( fhpA ), NAD + regeneration ( frdA and osmA ), nitrogen metabolism ( niaD and niiA ), and respiration ( rcfB ). We show that the nitric oxygen (NO)-detoxifying flavohemoprotein gene fhpA is strongly induced by hypoxia independent of the nitrogen source but is dispensable for hypoxic survival. By deleting the nitrate reductase gene niaD , the nitrite reductase gene niiA , and the two fumarate reductase genes frdA and osmA , we found that alternative electron acceptors, such as nitrate and fumarate, do not have a significant impact on growth of A. fumigatus during hypoxia, but functional mitochondrial respiratory chain complexes are essential under these conditions. Inhibition studies indicated that primarily complexes III and IV play a crucial role in the hypoxic growth of A. fumigatus .
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Lyhatskyi, P. H., L. S. Fira, D. B. Fira, and I. P. Kuzmak. "Molecular mechanisms of metabolic disorders in the organs of rats of different ages affected by sodium nitrite in the context of tobacco intoxication." Regulatory Mechanisms in Biosystems 8, no. 2 (April 25, 2017): 259–64. http://dx.doi.org/10.15421/021740.
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Among pollutants a significant threat is posed by heavy metals, nitrate fertilizers and industrial waste. However, people also contribute to this threat through bad habits such as smoking and alcohol. All these factors affect health and can cause death. The aim of this study was to investigate the content of reactive oxygen species, markers of cytolysis of hepatocytes, cardoza and the degree of endogenous intoxication in the organism of rats affected by nitrite of sodium on the background of tobacco intoxication. The experiments were carried out on white rats, which were divided into three age categories: immature, mature and old, who for 30 days were exposed to tobacco smoke. The research animals were divided into three groups. One of them for 24 hours before the end of the experiment was given sodium nitrite, the second group was given sodium nitrite 72 hours before the end of the experiment. 30 days after poisoning we tested the contents of reactive oxygen species in neutrophils, cytolysis of erythrocyte membrane was investigated by erythrocytic index of intoxication, hepatocytes and cardiocytes – aminotransferase activity. The degree of endogenous intoxication was evaluated by the content of average weight molecules in blood serum. Poisoning of rats with sodium nitrite on the background of the 30 day intoxication by tobacco smoke led to a significant formation of ROS in neutrophils of rats of different age groups. We investigated the activity of aminotransferases in the blood serum and the above organs of rats after exposing them to sodium nitrite and 30 day tobacco smoke. In the blood serum of adult and aged rats, the activity of alanine aminotransferase increased in these conditions by 2.1 and 1.6 times, respectively. Sodium nitrite, which was an additional factor in the intoxication of the rats of all age groups by smoke, caused more pronounced changes in the activity of the studied enzyme in the blood serum. In the liver and myocardium of rats of different ages a reliable decrease of this index was observed in all experimental groups. There was a significant increase in the serum of rats at different ages of aspartate aminotransferase activity. Aspartate aminotransferase activity in the myocardium of all experimental animals showed a reduction by 1.2–1.3 times after smoke inhalation and 1.5–1.6 times with simultaneous intoxication of the rats by sodium nitrite and tobacco smoke. Sodium nitrite, as an additional toxin raised the penetration capacity of erythrocytes among rats poisoned with smoke.By the end of the experiment, the erythrocyte index of intoxication increased in all age groups: immature rats by 31.7%, mature – by 36.0%, in old rats – by 23.6%. The next step of our research was to investigate the markers of endogenous intoxication – average molecular weight. After the simultaneous intoxication of rats by sodium nitrate and tobacco smoke, at the end of the experiment the content of average weight molecules was λ = 254 and of average mass λ=280 inthe blood serum of rats of all age groups increased by 3.1–3.3 times compared with the intact control group. Immature rats proved most sensitive to the action of sodium nitrite and tobacco.
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Chohan, Zahid Hussain, and Abdur Rauf. "Pharmacological Role of Anions (Sulphate, Nitrate, Oxalate and Acetate) on the Antibacterial Activity of Cobalt(II), Copper(II) and Nickel(II) Complexes With Nicotinoylhydrazine-Derived ONO, NNO and SNO Ligands." Metal-Based Drugs 3, no. 5 (January 1, 1996): 211–17. http://dx.doi.org/10.1155/mbd.1996.211.
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Mixed ligands biologically active complexes of cobalt(II), copper(II) and nickel(II) with nicotinoylhydrazine-derived ONO, NNO and SNO donor schiff-base ligands having the same metal ion but different anions such as sulphate, nitrate, oxalate and acetate have been synthesised and characterised on the basis of their physical, analytical and spectral data. In order to evaluate the role of anions on their bioability, these ligands and their synthesised metal complexes with various anions have been screened against bacterial species such as Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus and the title studies have proved a definative role of anions in increasing the biological activity
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Deyab, Mohamed, Magda El-Adl, Fatma Ward, and Eman Omar. "Trophic status, phytoplankton diversity, and water quality at Kafr El-Shinawy drinking-water treatment plant, Damietta." Journal of Water Supply: Research and Technology-Aqua 70, no. 3 (February 9, 2021): 342–60. http://dx.doi.org/10.2166/aqua.2021.122.
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Abstract This work aims to study the seasonal fluctuation in physicochemical characteristics, trophic status, and some pollutants influencing phytoplankton diversity, and water quality at a compact Kafr El-Shinawy drinking-water treatment plant, Damietta – Egypt seasonally during 2018. Phytoplankton distribution was affected by the trophic status of water, level of pollutants, and physicochemical treatment processes of water. The predominance of phytoplankton species, especially Aphanizomenon flos aquae (Cyanophyta), Gomphosphaeria lacustris (Cyanophyta), Microcystis aeruginosa (Cyanophyta), Nostoc punctiforme (Cyanophyta), Oscillatoria limnetica (Cyanophyta), Pediastrum simplex (Chlorophyta), and Melosira granulata (Bacillariophyta) in treated water was much less than that in raw water. Trihalomethanes (THMs) levels in treated waters were higher than in raw water, while lower concentrations of heavy metals were recorded in treated water. Intracellular levels of microcystins were lower, whereas the extracellular levels were higher in treated water than raw water, and the former recorded the highest level in raw water during summer. Hence, the levels of dissolved microcystins and THMs in treated water were higher especially during summer, the season of luxurious growth of Microcystis species. Trophic state index (TSI) was relatively high in raw water compared with treated water due to high concentrations of nutrients (total-P, total-N, nitrite, nitrate, and ammonia) in raw water.
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Shi, Zheng-Jun, Ming-Guo Ma, and Jie-Fang Zhu. "Recent Development of Photocatalysts Containing Carbon Species: A Review." Catalysts 9, no. 1 (December 28, 2018): 20. http://dx.doi.org/10.3390/catal9010020.
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Undoubtedly, carbon-based (nano)composites can be promising photocatalysts with improved photocatalytic activity due to the coupling effect from the incorporation of carbon species. In this mini-review, we focus on the recent development of photocatalysts based on carbon-based (nano)composites. TiO2 is well-known as a typical photocatalyst. Special attention is paid to the various types of carbon–TiO2 composites such as C-doped TiO2, N–C-doped TiO2, metal–C-doped TiO2, and other co-doped C/TiO2 composites. Various synthetic strategies including the solvothermal/hydrothermal method, sol–gel method, and template-directed method are reviewed for the preparation of carbon-based TiO2 composites. C/graphitic carbon nitride (g-C3N4) composites and ternary C-doped composites are also summarized and ascribed to the unique electronic structure of g-C3N4 and the synergistic effect of the ternary interfaces, respectively. In the end, we put forward the future perspective of the photocatalysts containing carbon species based on our knowledge.
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Khuna, Surapong, Nakarin Suwannarach, Jaturong Kumla, Jomkhwan Meerak, Wipornpan Nuangmek, Tanongkiat Kiatsiriroat, and Saisamorn Lumyong. "Apophysomyces thailandensis (Mucorales, Mucoromycota), a new species isolated from soil in northern Thailand and its solubilization of non-soluble minerals." MycoKeys 45 (January 29, 2019): 75–92. http://dx.doi.org/10.3897/mycokeys.45.30813.
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A new species of soil fungi, described herein asApophysomycesthailandensis, was isolated from soil in Chiang Mai Province, Thailand. Morphologically, this species was distinguished from previously describedApophysomycesspecies by its narrower trapezoidal sporangiospores. A physiological determination showed thatA.thailandensisdiffers from otherApophysomycesspecies by its assimilation of D-turanose, D-tagatose, D-fucose, L-fucose, and nitrite. A phylogenetic analysis, performed using combined internal transcribed spacers (ITS), the large subunit (LSU) of ribosomal DNA (rDNA) regions, and a part of the histone 3 (H3) gene, lends support to our the finding thatA.thailandensisis distinct from otherApophysomycesspecies. The genetic distance analysis of the ITS sequence supportsA.thailandensisas a new fungal species. A full description, illustrations, phylogenetic tree, and taxonomic key to the new species are provided. Its metal minerals solubilization ability is reported.
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Hatcher, Lauren E., and Paul R. Raithby. "Solid-state photochemistry of molecular photo-switchable species: the role of photocrystallographic techniques." Acta Crystallographica Section C Crystal Structure Communications 69, no. 12 (November 30, 2013): 1448–56. http://dx.doi.org/10.1107/s010827011303223x.
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Over the last 30 years, the single-crystal photocrystallographic technique has been developed to determine the three-dimensional crystal and molecular structures of metastable species which have been generated in the crystal photochemically. Transition-metal complexes that have been investigated using this methodology include complexes that contain nitrosyl, dinitrogen, sulfur dioxide and nitrite ligands, all of which form new linkage isomers in the solid state when photoactivated by light of the appropriate wavelength. Both steric and electronic factors determine the level of the conversion from the ground-state structure to the metastable isomeric structure, and both the `reaction cavity' size and the nature of the intermolecular interactions are shown to be among the key factors that influence the percentage conversion.
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Baudys, Michal, Šárka Paušová, Petr Praus, Vlasta Brezová, Dana Dvoranová, Zuzana Barbieriková, and Josef Krýsa. "Graphitic Carbon Nitride for Photocatalytic Air Treatment." Materials 13, no. 13 (July 7, 2020): 3038. http://dx.doi.org/10.3390/ma13133038.
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Graphitic carbon nitride (g-C3N4) is a conjugated polymer, which recently drew a lot of attention as a metal-free and UV and visible light responsive photocatalyst in the field of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability and earth-abundant nature. In the present work, bulk g-C3N4 was synthesized by thermal decomposition of melamine. This material was further exfoliated by thermal treatment. S-doped samples were prepared from thiourea or further treatment of exfoliated g-C3N4 by mesylchloride. Synthesized materials were applied for photocatalytic removal of air pollutants (acetaldehyde and NOx) according to the ISO 22197 and ISO 22197-1 methodology. The efficiency of acetaldehyde removal under UV irradiation was negligible for all g-C3N4 samples. This can be explained by the fact that g-C3N4 under irradiation does not directly form hydroxyl radicals, which are the primary oxidation species in acetaldehyde oxidation. It was proved by electron paramagnetic resonance (EPR) spectroscopy that the dominant species formed on the irradiated surface of g-C3N4 was the superoxide radical. Its production was responsible for a very high NOx removal efficiency not only under UV irradiation (which was comparable with that of TiO2), but also under visible irradiation.
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Lenzi, Anna, Alessandro Orlandini, Roberta Bulgari, Antonio Ferrante, and Piero Bruschi. "Antioxidant and Mineral Composition of Three Wild Leafy Species: A Comparison Between Microgreens and Baby Greens." Foods 8, no. 10 (October 12, 2019): 487. http://dx.doi.org/10.3390/foods8100487.
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Wild plants may play an important role in human nutrition and health and, among them, many are the leafy species. We hypothesized that the wild greens could be profitably grown as microgreens and baby greens, specialty products whose market is increasing. We compared three wild leafy species (Sanguisorba minor Scop., Sinapis arvensis L., and Taraxacum officinale Weber ex F. H. Wigg.) harvested at the microgreen and baby green stages. Seedlings were grown hydroponically in a half-strength Hoagland nutrient solution under controlled climatic conditions. At harvest, the yield was assessed, and chlorophylls, carotenoids, anthocyanins, phenolic index, nitrate, and mineral elements were measured in the two types of product. The potential contribution to human mineral intake was calculated, and the possible risk due to the presence of metals potentially detrimental for health was estimated. Results showed that micro/baby greens of the studied wild plants achieved competitive yields and could contribute to the dietary intake of macroelements, microelements, and non-nutrient bioactive compounds. On the other hand, the wild greens showed high amounts of nitrate and traces of some metals potentially detrimental for health, suggesting the need for caution in the use of wild species for producing microgreens and baby leaves.
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Turner, N., A. L. Ballard, R. C. Bray, and S. Ferguson. "Investigation by electron paramagnetic resonance spectroscopy of the molybdenum centre of respiratory nitrate reductase from Paracoccus denitrificans." Biochemical Journal 252, no. 3 (June 15, 1988): 925–26. http://dx.doi.org/10.1042/bj2520925.
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The molybdenum centre of respiratory nitrate reductase from Paracoccus denitrificans has been investigated by e.p.r. spectroscopy of Mo(V). In common with the centres of the analogous enzymes from Escherichia coli and Pseudomonas aeruginosa, it undergoes a pH- and anion-dependent transition between two different e.p.r. signal-giving species. Comparison of the relevant e.p.r. parameters extracted with the help of computer simulations reveals ligation of the metal in the active centres of the three enzymes to be identical.
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Kwan, Billy K. Y., Virginia K. Y. Un, S. G. Cheung, and Paul K. S. Shin. "Horseshoe crabs as potential sentinel species for coastal health: juvenile haemolymph quality and relationship to habitat conditions." Marine and Freshwater Research 69, no. 6 (2018): 894. http://dx.doi.org/10.1071/mf17210.
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As an interface between terrestrial and marine environments, coastal and estuarine areas are particularly prone to various pollution stresses. Identification of sentinel species is, therefore, essential to provide precautionary information on coastal health conditions. Given their significant ecological roles in estuarine ecosystems, horseshoe crabs are a potential species to indicate the general health status of coastal habitats. The present study demonstrated that the changes in haemolymph composition pattern of two Asian juvenile horseshoe crab species (Tachypleus tridentatus and Carcinoscorpius rotundicauda) are sensitive to reflect heavy metal (lead, nickel and iron) and nutrient (nitrate and ammonia) concentrations of intertidal sediments. In particular, a significant negative correlation was found for the amebocyte viability and ratio of granular–spherical to granular–flattened and degranulated dendritic-like morphological states of amebocytes in juvenile haemolymph with nitrate and lead concentrations respectively. There were also significantly higher concentrations of haemolymph haemocyanin and plasma protein in juvenile C. rotundicauda than in T. tridentatus on the same shore, possibly being related to the difference in foraging habitats of these two horseshoe crab species. Such non-lethal sampling of haemolymph from juvenile horseshoe crabs can be useful for a further development of the monitoring program in assessing potential environmental impacts by anthropogenic activities.
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Tang, Rong, Renli Ding, and Xianchuan Xie. "Preparation of oxygen-doped graphitic carbon nitride and its visible-light photocatalytic performance on bisphenol A degradation." Water Science and Technology 78, no. 5 (August 20, 2018): 1023–33. http://dx.doi.org/10.2166/wst.2018.361.
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Abstract A novel metal-free oxygen-doped graphitic carbon nitride (O-g-C3N4) was synthesized by the pre-treatment of bulk graphitic carbon nitride (g-C3N4) with hydrogen peroxide (H2O2), and combined with high-temperature calcination treatment. The obtained 2-O-g-C3N4 catalyst exhibits high activity in visible light photocatalytic degradation of bisphenol A (BPA) with a mineralization rate as high as 62.3%. According to the characterization results of X-ray diffraction, transmission electron microscopy, UV-visible spectroscopy, Brunauer-Emmett-Teller and photoluminescence spectroscopy analyses, the markedly higher visible-light-driven oxidation activity of 2-O-g-C3N4 is attributed to the larger specific surface area, wider range of light responses and low charge recombination rate. Moreover, the trapping experiment shows that superoxide radicals (•O2−) are the dominant active species in the BPA decomposition process over 2-O-g-C3N4. This study presents a simple and environment-friendly method to synthesise oxygen-doped graphitic carbon nitride.
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Large, Alexander I., Sebastian Wahl, Salvatore Abate, Ivan da Silva, Juan Jose Delgado Jaen, Nicola Pinna, Georg Held, and Rosa Arrigo. "Investigations of Carbon Nitride-Supported Mn3O4 Oxide Nanoparticles for ORR." Catalysts 10, no. 11 (November 6, 2020): 1289. http://dx.doi.org/10.3390/catal10111289.
Full textAbstract:
Earth-abundant Mn-based oxide nanoparticles are supported on carbon nitride using two different immobilization methods and tested for the oxygen reduction reaction. Compared to the metal free CN, the immobilization of Mn oxide enhances not only the electrocatalytic activity but also the selectivity towards the 4e- reduction reaction of O2 to H2O. The XPS analysis reveals the interaction of the pyridine N species with Mn3O4 nanoparticles being particularly beneficial. This interaction is realized—although to a limited extent—when preparing the catalysts via impregnation; via the oleic acid route it is not observed. Whilst this work shows the potential of these systems to catalyze the ORR, the main limiting factor is still the poor conductivity of the support which leads to overpotential.
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Chang, Cecily C. Y., James S. Kuwabara, and Sofie P. Pasilis. "Phosphate and Iron Limitation of Phytoplankton Biomass in Lake Tahoe." Canadian Journal of Fisheries and Aquatic Sciences 49, no. 6 (June 1, 1992): 1206–15. http://dx.doi.org/10.1139/f92-136.
Full textAbstract:
Field measurements and bioassay experiments were coupled to investigate the interdependent processes affecting phytoplankton biomass at Lake Tahoe using a trace metal protocol. Water samples were analyzed for suspended particulate matter, dissolved organic carbon, major ions and macronutrients, adenosine triphosphate, and phytoplankton abundance. Concentrations of total Cd [Formula: see text], Cu (2.25–8.85 nM), and Fe (22–49 nM) were similar to or lower than those reported for other oligotrophic lakes. Bioassays were carried out to assess the response of inoculated, single-species diatom populations (Cyclotella meneghiniana and Aulocosiera italica) to additions of synthetic chelators (EDTA, EDDHA) and phosphate. A chemical speciation model along with the field data was also used to predict how trace metal speciation, and hence bioavailability, was affected by the chelator additions. Results suggest that phosphate was limiting to phytoplankton biomass. Other solutes, Fe in particular, may also exert controls on biomass. Nitrate limitation seems less likely, although Fe-limiting conditions, as suggested by the bioassays, may have led to an effective N limitation because algae require Fe to carry out nitrate reduction. Small perturbations in water chemistry may have pronounced effects on phytoplankton biomass in oligotrophic systems where essential nutrients are at low concentrations.
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Krupa, Elena, Sophia Barinova, Sophia Romanova, Moldir Aubakirova, and Nazia Ainabaeva. "Planktonic Invertebrates in the Assessment of Long-Term Change in Water Quality of the Sorbulak Wastewater Disposal System (Kazakhstan)." Water 12, no. 12 (December 4, 2020): 3409. http://dx.doi.org/10.3390/w12123409.
Full textAbstract:
The multicomponent composition of wastewater makes it challenging to assess its quality objectively, but the last one is a prerequisite for the safe re-use of wastewater. The solution to this problem should be aimed at finding criteria that make it possible to increase the objectivity of assessing the water quality of reservoirs with multicomponent pollution. This work analyzes the water quality of the Sorbulak wastewater disposal system in the summer of 2017, based on chemical variables and zooplankton structure and assess the long-term changes in the water quality of Sorbulak. According to the Kruskal–Wallis test, in 2017, the differences between the studied water bodies in the content of nutrients and heavy metals were mostly insignificant. From 2000–2002 to 2017, nitrate, nitrite nitrogen, and heavy metals in Sorbulak significantly decreased. Zooplankton communities consisted of a relatively small number of eurybiontic species resistant to environmental factors. The variability of the quantitative variables of zooplankton was associated with the nutrients. Males dominated the population of the cyclopoid copepods Acanthocyclops trajani. In 2000–2002 individuals with morphological anomalies were found in cyclopoid copepods populations, but were absent in 2017. The appearance of individuals with morphological anomalies was associated with copper or lead. The chemical data and structure of zooplankton communities indicated that the toxic pollution of Sorbulak decreased by 2017 compared to 2000–2002. Our results demonstrate that the structural variables of zooplankton communities could be successfully used to assess the water quality of water bodies with mixed pollution. We recommend using not only the traditional set of biological variables (abundance, biomass, diversity indices, and the average mass of an individual), but also data on the structure of species dominance, the sex structure of copepod populations, and the presence of individuals with morphological anomalies for monitoring of water bodies with mixed pollution.
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Nielsen, Marie Bank, Kasper Urup Kjeldsen, and Kjeld Ingvorsen. "Desulfitibacter alkalitolerans gen. nov., sp. nov., an anaerobic, alkalitolerant, sulfite-reducing bacterium isolated from a district heating plant." International Journal of Systematic and Evolutionary Microbiology 56, no. 12 (December 1, 2006): 2831–36. http://dx.doi.org/10.1099/ijs.0.64356-0.
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A novel alkalitolerant, anaerobic bacterium, designated strain sk.kt5T, was isolated from a metal coupon retrieved from a corrosion-monitoring reactor of a Danish district heating plant (Skanderborg, Jutland). The cells of strain sk.kt5T were motile, rod-shaped (0.4–0.6×2.5–9.6 μm), stained Gram-positive and formed endospores. Strain sk.kt5T grew at pH 7.6–10.5 (with optimum growth at pH 8.0–9.5), at temperatures in the range 23–44 °C (with optimum growth at 35–37 °C), at NaCl concentrations in the range 0–5 % (w/v) (with optimum growth at 0–0.5 %) and required yeast extract for growth. Only a limited number of substrates were utilized as electron donors, including betaine, formate, lactate, methanol, choline and pyruvate. Elemental sulfur, sulfite, thiosulfate, nitrate and nitrite, but not sulfate or Fe(III) citrate, were used as electron acceptors. The G+C content of the DNA was 41.6 mol%. Phylogenetic analyses of the sequence data for the dsrAB genes [encoding the major subunits of dissimilatory (bi)sulfite reductase] and the 16S rRNA gene placed strain sk.kt5T within a novel lineage in the class Clostridia of the phylum Firmicutes. Taken together, the physiological and genotypic data suggest that strain sk.kt5T represents a novel species within a novel genus, for which the name Desulfitibacter alkalitolerans gen. nov., sp. nov. is proposed. The type strain of Desulfitibacter alkalitolerans is sk.kt5T (=JCM 12761T=DSM 16504T).
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Kaksonen, Anna H., Stefan Spring, Peter Schumann, Reiner M. Kroppenstedt, and Jaakko A. Puhakka. "Desulfurispora thermophila gen. nov., sp. nov., a thermophilic, spore-forming sulfate-reducer isolated from a sulfidogenic fluidized-bed reactor." International Journal of Systematic and Evolutionary Microbiology 57, no. 5 (May 1, 2007): 1089–94. http://dx.doi.org/10.1099/ijs.0.64593-0.
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A thermophilic, Gram-positive, endospore-forming, sulfate-reducing bacterium was isolated from a sulfidogenic fluidized-bed reactor treating acidic metal- and sulfate-containing water. The strain, designated RA50E1T, was rod-shaped and motile. The strain grew at 40–67 °C (optimum growth at 59–61 °C) and pH 6.4–7.9 (optimum growth at pH 7.0–7.3). The strain tolerated up to 1 % NaCl. Sulfate, sulfite, thiosulfate and elemental sulfur were used as electron acceptors, but not nitrate, nitrite or iron(III). Electron donors utilized were H2/CO2 (80 : 20, v/v), alcohols, various carboxylic acids and some sugars. Fermentative growth occurred on lactate and pyruvate. The cell wall contained meso-diaminopimelic acid and the major respiratory isoprenoid quinone was menaquinone MK-7. Major whole-cell fatty acids were iso-C15 : 0 and iso-C17 : 0. Strain RA50E1T was distantly related to representatives of the genera Desulfotomaculum, Pelotomaculum, Sporotomaculum and Cryptanaerobacter. On the basis of 16S rRNA gene sequence data, the strain cannot be assigned to any known genus. Based on the phenotypic and phylogenetic features of strain RA50E1T, it is proposed that the strain represents a novel species in a new genus, for which the name Desulfurispora thermophila gen. nov., sp. nov. is proposed. The type strain of Desulfurispora thermophila is RA50E1T (=DSM 16022T=JCM 14018T).
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Liu, Hongjin, Haining Wu, Jun Lv, Guangqing Xu, Xing Chen, Xinyi Zhang, and Yucheng Wu. "SBA-15 Templated Mesoporous Graphitic C3N4 for Remarkably Enhanced Photocatalytic Degradation of Organic Pollutants under Visible Light." Nano 14, no. 11 (November 2019): 1950136. http://dx.doi.org/10.1142/s1793292019501364.
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Organic pollutants in water have been threatening public and environmental health. Developing efficient and sustainable photocatalysts working for degradation of organic pollutants under visible light becomes a big challenge. In this paper, high-efficiency visible light driven catalyst ordered mesoporous graphite nitride carbon (mpg-C3N4) was prepared by using SBA-15 as template and dicyandiamide (C2H4N4) as precursor. The specific surface area of mpg-C3N4 can be increased remarkably as compared to that of the bulk graphite nitrite carbon (g-C3N4) by adjusting the ratio of SBA-15 to dicyandiamide. Photocatalytic performance of mpg-C3N4 were evaluated systematically by degradation of Rhodamine B (RhB), malachite green (MG) and tetracycline hydrochloride (TC) under visible light irradiation. The results showed that the mpg-C3N4 (1:0.5) has the highest photocatalytic activity and stability and the degradation rate is for RhB, MG and TC are all more than seven times that of bulk g-C3N4. After five recycling runs, the mpg-C3N4 (1:0.5) remains high photocatalytic activities for the degradation of MG (94%) and TC (81%), respectively. Additionally, radical trapping experiments certified that the main active species are [Formula: see text] and h[Formula: see text], while the role of [Formula: see text]OH is irrelevant in the reaction processes. This work provides a promising pathway to prepare metal-free photocatalyst for degradation of organic pollutants under visible light irradiation.
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Moreau, John W., Robert A. Zierenberg, and Jillian F. Banfield. "Diversity of Dissimilatory Sulfite Reductase Genes (dsrAB) in a Salt Marsh Impacted by Long-Term Acid Mine Drainage." Applied and Environmental Microbiology 76, no. 14 (May 14, 2010): 4819–28. http://dx.doi.org/10.1128/aem.03006-09.
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ABSTRACT Sulfate-reducing bacteria (SRB) play a major role in the coupled biogeochemical cycling of sulfur and chalcophilic metal(loid)s. By implication, they can exert a strong influence on the speciation and mobility of multiple metal(loid) contaminants. In this study, we combined DsrAB gene sequencing and sulfur isotopic profiling to identify the phylogeny and distribution of SRB and to assess their metabolic activity in salt marsh sediments exposed to acid mine drainage (AMD) for over 100 years. Recovered dsrAB sequences from three sites sampled along an AMD flow path indicated the dominance of a single Desulfovibrio species. Other major sequence clades were related most closely to Desulfosarcina, Desulfococcus, Desulfobulbus, and Desulfosporosinus species. The presence of metal sulfides with low δ34S values relative to δ34S values of pore water sulfate showed that sediment SRB populations were actively reducing sulfate under ambient conditions (pH of ∼2), although possibly within less acidic microenvironments. Interestingly, δ34S values for pore water sulfate were lower than those for sulfate delivered during tidal inundation of marsh sediments. 16S rRNA gene sequence data from sediments and sulfur isotope data confirmed that sulfur-oxidizing bacteria drove the reoxidation of biogenic sulfide coupled to oxygen or nitrate reduction over a timescale of hours. Collectively, these findings imply a highly dynamic microbially mediated cycling of sulfate and sulfide, and thus the speciation and mobility of chalcophilic contaminant metal(loid)s, in AMD-impacted marsh sediments.