scholarly journals Numerical simulation of orthosilicic acid polycondensation and silica particles formation inhydrothermal solutions

2019 ◽  
pp. 18-28 ◽  
Author(s):  
V. V. Potapov ◽  
A. A. Cerdan ◽  
I. A. Kashutina
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Silica Particles ◽  
Orthosilicic Acid ◽  
Mineral Formation ◽  
Mineral Synthesis ◽  
Chemical Conditions ◽  
Physical And Chemical ◽  
Hydrothermal Mineral

Numerical simulation of the process of polycondensation of orthosilicic acid and colloid silica particles growth under different physical and chemical conditions was done: temperature, pH, ionic strength and other. Calculated dependences of orthosilicic acid concentration and mean radius of silica particles versus time, graphs of particles dimensions distributions were received. Results of calculations were compared with experimental data. Research is important for to make clear role of colloid silica on hydrothermal mineral formation and for industrial extraction and utilization of silica, and also for mineral synthesis.

Mossbauer Investigation of the Chelyabinsk Meteorite Fragment

2016 ◽  
Vol 845 ◽  
pp. 269-272
Author(s):  
Magomed Guseynov ◽  
Sergey Taskaev ◽  
Ibragimkhan Kamilov
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Effective Magnetic Field ◽  
Iron Ions ◽  
Qualitative Explanation ◽  
Chelyabinsk Meteorite ◽  
Chemical Conditions ◽  
The Individual ◽  
Physical And Chemical ◽  
Quadruple Splitting

The article devoted to study of the fragments of Chelyabinsk meteorite with the help of Mossbauer spectroscopy. It is shown that the iron in various fragments of the meteorite exist in different crystallographic, physical and chemical conditions. A new phenomenon of sharp increasing effective magnetic field in the region of the iron nuclei in the temperature range of 553-573 К and jumps of the main parameters of Mossbauer spectra at other temperatures are observed. According to the data of the isomer shifts and quadruple splitting of the individual spectra, iron ions have a valence of Fe2+ − 3d6, Fe3+ − 3d5, Fe4+ − 3d4, Fe6+ − 3d2 and also intermediate between them. A qualitative explanation of the experimental data is proposed.

scholarly journals Spatiotemporal Distribution of Marine Magnetotactic Bacteria in a Seasonally Stratified Coastal Salt Pond

2004 ◽  
Vol 70 (10) ◽  
pp. 6230-6239 ◽  
Author(s):  
S. L. Simmons ◽  
S. M. Sievert ◽  
R. B. Frankel ◽  
D. A. Bazylinski ◽  
K. J. Edwards
Keyword(s):  
Alternative Model ◽  
Physiological Role ◽  
Magnetotactic Bacteria ◽  
Respiratory Metabolism ◽  
Population Abundance ◽  
Seasonal Fluctuations ◽  
Salt Pond ◽  
Chemical Conditions ◽  
Physical And Chemical

ABSTRACT The occurrence and distribution of magnetotactic bacteria (MB) were studied as a function of the physical and chemical conditions in meromictic Salt Pond, Falmouth, Mass., throughout summer 2002. Three dominant MB morphotypes were observed to occur within the chemocline. Small microaerophilic magnetite-producing cocci were present at the top of the chemocline, while a greigite-producing packet-forming bacterium occurred at the base of the chemocline. The distributions of these groups displayed sharp changes in abundance over small length scales within the water column as well as strong seasonal fluctuations in population abundance. We identified a novel, greigite-producing rod in the sulfidic hypolimnion that was present in relatively constant abundance over the course of the season. This rod is the first MB that appears to belong to the γ-Proteobacteria, which may suggest an iron- rather than sulfur-based respiratory metabolism. Its distribution and phylogenetic identity suggest that an alternative model for the ecological and physiological role of magnetotaxis is needed for greigite-producing MB.

scholarly journals Biofilms Confer Resistance to Simulated Extra-terrestrial Geochemical Extremes

2017 ◽  
Author(s):  
Adam H. Stevens ◽  
Delma Childers ◽  
Mark Fox-Powell ◽  
Charles S. Cockell
Keyword(s):  
Planktonic Cells ◽  
Planetary Protection ◽  
Aqueous Environments ◽  
Groundwater Systems ◽  
Acidic Conditions ◽  
High Sulfate ◽  
Chemical Conditions ◽  
Physical And Chemical ◽  
Over Time

1AbstractBiofilms improve microbes’ resistance to a variety of extreme physical and chemical conditions on Earth. The discovery of putative aqueous environments on other planetary bodies such as Mars motivates an interest in understanding the viability of life, and the potential role of biofilms, in previously unexplored geochemical extremes. We investigated the loss of viability of planktonic cells and biofilms ofSphingomonas desiccabilis(a Gram-negative, desiccation resistant, soil crust-forming organism) to simulated Martian brines. These brines were produced from geochemical modelling of past aqueous environments on Mars, and their high sulfate concentrations make them different to most terrestrial brines, although similar briny environments have been found in locations such as the Basque Lakes in Canada or in deep subsurface groundwater systems. Biofilms grown on basaltic scoria were subjected to the simulated martian brines and the viability of cells was measured over time and compared to equivalent planktonic cultures. Crystal violet assay was used to measure how the biomass of the biofilms changed over time in response to the brines. While certain brines were highly hostile to microbial viability, we found that biofilms that were desiccated prior to being treated with brines maintained viability over a longer treatment period when compared to planktonic cells. Our results show that biofilms confer short-term protection to the harsh osmotic, ionic, and acidic conditions of Mars-relevant brines. However, in the most extreme simulated brines, even biofilms eventually lost viability. By demonstrating that biofilms confer protection to conditions that are potentially analogous to current day recurrent slope lineae (thought to be produced by the flow of briny fluids) on Mars, our results show that contaminant biofilm-forming microorganisms may have a greater chance of surviving in so-called ‘Special Regions’ on Mars, with implications for planetary protection in missions that aim to explore these regions.

scholarly journals The Role of Biotic and Abiotic Factors in Prevalence of Cyprinidae Fishes and Trout Parasites in the Fish Farms of Azerbaijan

2021 ◽  
Vol 7 (4) ◽  
Author(s):  
A. Suleymanova
Keyword(s):  
Abiotic Factors ◽  
Fish Parasites ◽  
Pathogenic Species ◽  
Fish Farms ◽  
Factors Affecting ◽  
Causative Agents ◽  
Hot Season ◽  
Chemical Conditions ◽  
Physical And Chemical

During 2013–2017 years biotic and abiotic of environmental conditions affecting to the extensiveness of invasion by causative agents of carp and trout parasitosis in fish farms in the territory of Azerbaijan Republic were studied. In addition, we studied the seasonal and age dynamics of diseases of the farm fishes. The prevalence of fish parasites infection in hot season (May-July) in comparison with cold month (October) was recorded. Twenty species of parasites from various systematical groups were found: protozoans (4 species); monogenean worms (3 species); cestodes (4 species); trematodes (3 species); nematodes (2 species); acanthocephalans (2 species); crustaceans (2 species). All investigations were conducted by considering of various factors affecting on production of fish. 386 specimens of carp and 415 specimens of trout were examined by the method of full parasitological dissection. We analyzed the physical and chemical conditions of water from the fish pools and other artificial basins in fish farms. In conclusion of our investigation the list of most pathogenic species of cultivated parasites were composed: Metechinorhyncnus truttae, Acanthocephalus clavulae, Paradilepis scolecina, Proteocephalus torulosus, Rhabdochon agnedini.

scholarly journals Primorskoye epithermal Ag-Au deposit (Northeast of Russia): geologic aspects, mineralogic and geochemical features, and ore formation conditions

2019 ◽  
Vol 61 (1) ◽  
pp. 52-74
Author(s):  
N. E. Savva ◽  
A. V. Volkov ◽  
A. A. Sidorov ◽  
E. E. Kolova ◽  
K. Yu. Murashov
Keyword(s):  
High Temperature ◽  
Elevated Concentration ◽  
Epithermal Deposit ◽  
Ore Formation ◽  
Low Concentrations ◽  
Formation Conditions ◽  
High Concentrations ◽  
Chemical Conditions ◽  
Physical And Chemical

As a potentially large Ag-Au epithermal deposit, Primorskoye comprises the following three areas: Kholodny, Spiridonych, and Teply. This deposit is located in the Omsukchan district of the Magadan Region, where similar deposits, including Dukat, Lunnoye, Goltsovoye, Arylakh, Tidit, and Perevalnoye, have developed. The deposit can be attributed to the Kalalagian volcano-tectonic depression and is localized in a flat-lying rock mass in the Late Cretaceous ignimbrites and rhyolites having thicknesses of greater than 700 m, which is cut through by numerous dykes of medium and major composition. According to the drilling data, the solid mass of leucocratic granites is located in deposits at a depth of 400–500 m with outcrops in the northeastern part of the ore field. The presence of Bi-containing galena and matildite, the availability of mid and high temperature facies of metasomatites (epidote and actinolite), and the specific physical and chemical conditions during the formation of the epithermal Ag-Au ores indicate the intrusive position above and the role of granitoids as generators of high temperature magmatic fluids, which introduced Bi and heated the rocks enclosing the mineralization. The geochemical features of the ores are well correlated with their mineral compositions. The high concentrations of Mn and Ag, elevated concentration of Au, low concentrations of Cu, Pb, Zn, Sb, As, Bi, and Te, low sum of REE, and negative Eu- and positive Се-anomalies were observed. The high values of the Te/Se, Sr/Ba, Y/Ho, and U/Th indicators in the ores are associated with the deposit location in the zone of granitoid massif effect. Further, the physical and chemical parameters of ore formation in the Teply area are unusual and are characterized by high temperatures, low concentrations of salts, and fluid density, which are indicative of the typical “dry steam” conditions. The obtained results allow the Primorskoye epithermal deposit to be attributed to the intermediate class. The information present in the article is practically valuable for the regional forecast and metallogenic developments as well as for searching and assessing the epithermal Ag-Au deposits.

Nitrification potential in waste stabilisation ponds: comparison of a secondary and tertiary pond system

2010 ◽  
Vol 61 (3) ◽  
pp. 781-788 ◽  
Author(s):  
A. Yamamoto ◽  
M. D. Short ◽  
B. van den Akker ◽  
N. J. Cromar ◽  
H. J. Fallowfield
Keyword(s):  
Nitrogen Cycling ◽  
Field Experiments ◽  
Waste Stabilisation Ponds ◽  
Nitrification Potential ◽  
Laboratory Microcosm ◽  
Natural Pond ◽  
Chemical Conditions ◽  
Physical And Chemical

This study compared the nitrification potential of two separate Waste Stabilisation Ponds (WSPs) operating under differing physical and chemical conditions. In order to probe the nitrification potential of each system, the oxidation of ammonium and also the intermediate product nitrite was assessed using both in situ and laboratory micro-scale incubations. The role of sediment in determining the nitrification potential of the two WSPs was also investigated. Results from laboratory microcosm incubations revealed a competent and strikingly similar nitrification potential for both WSPs in spite of their differing nitrogen and organic loadings, and also suggested a significant role for sediment in WSP nitrogen cycling. Results from in situ field experiments identified biomass uptake to be the dominant nitrogen removal mechanism in natural pond environments. Other aspects of WSP nitrogen cycling are also discussed.

Quantitative Environmental Assessment for Deep-Sea Mining: Status and Approaches

2009 ◽  
Author(s):  
Tetsuo Yamazaki
Keyword(s):  
Environmental Assessment ◽  
Deep Sea ◽  
Industrial Development ◽  
Mining Operation ◽  
Benthic Habitat ◽  
The World ◽  
Chemical Conditions ◽  
Physical And Chemical ◽  
Alternative Resource

Deep-sea mining has been a subject of interest for several groups and countries for over four decades, due to its potential for the economic recovery of large reserves of minerals that would provide an alternative resource of strategic metals for industrial development. A deep-sea mining operation will offer a variety of challenges, owing to deep-sea mineral occurrences, extreme physical and chemical conditions and unknown environmental settings. Owing to growing concern for the environmental impact of deep-sea mining, multi-disciplinary environmental studies have been progressive in many countries. The historic approaches in the world are summarized. The important role of quantified environmental assessment for deep-sea mining is introduced. Some efforts necessary for keeping benthic habitat safe and sustainable in the coming commercial mining phases are discussed.

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