Recentní vznik limonitové bahenní železné rudy v Hulíně (niva řeky Moravy)

2020 ◽  
Vol 28 (2) ◽  
pp. 412-416
Author(s):  
Zdeněk Dolníček
Keyword(s):  
Iron Ore ◽  
Iron Hydroxide ◽  
Flood Plain ◽  
Well Water ◽  
Mechanism Of Formation ◽  
Transitional Metals ◽  
Solid Iron ◽  
Morava River ◽  
Subterranean Waters

There is described a new occurrence of mud limonite iron ore in this paper. Limonite originates recently in streams situated in flood plain of the Morava River near Hulín (central Moravia, Czech Republic). The chemical composition of precipitated limonite indicates that a contamination of subterranean waters by phosphorus, arsenic and some transitional metals (Cr, Zn) occurs here, very probably due to long-lasting intense agricultural usage of the surrounding fields. Based on experimental precipitation of limonite from local well water, a probable mechanism of formation of limonite was outlined. The Fe2+ ions, dissolved in the subterranean waters, are after their seepage into the stream oxidized by aerial oxygen to Fe3+, which is subsequently hydrolysed and precipitated in form of solid iron hydroxide. An important role of microorganisms and/or organic matter during precipitation of limonite is not suggested by collected data.

Silicon Substitution for Calcium in the Shell of the Fingernail Clam, Musculium Transversum Studied By X-Ray Analysis

1980 ◽  
Vol 38 ◽  
pp. 560-561
Author(s):  
Judith A. Murphy ◽  
Anthony Paparo ◽  
Richard Sparks
Keyword(s):  
Carbonic Anhydrase ◽  
River Water ◽  
Food Chains ◽  
Well Water ◽  
Shell Formation ◽  
X Ray ◽  
Molluscan Shell ◽  
Fingernail Clams

Fingernail clams (Muscu1ium transversum) are dominant bottom-dwelling animals in some waters of the midwest U.S. These organisms are key links in food chains leading from nutrients in water and mud to fish and ducks which are utilized by man. In the mid-1950’s, fingernail clams disappeared from a 100-mile section of the Illinois R., a tributary of the Mississippi R. Some factor(s) in the river and/or sediment currently prevent clams from recolonizing areas where they were formerly abundant. Recently, clams developed shell deformities and died without reproducing. The greatest mortality and highest incidence of shell deformities appeared in test chambers containing the highest proportion of river water to well water. The molluscan shell consists of CaCO3, and the tissue concerned in its secretion is the mantle. The source of the carbonate is probably from metabolic CO2 and the maintenance of ionized Ca concentration in the mantle is controlled by carbonic anhydrase. The Ca is stored in extracellular concentric spherical granules(0.6-5.5μm) which represent a large amount of inertCa in the mantle. The purpose of this investigation was to examine the role of raw river water and well water on shell formation in the fingernail clam.

scholarly journals Utilisation of satellite data in identification of geomorphic landform and its role in arsenic release in groundwater

2014 ◽  
Vol II-8 ◽  
pp. 29-35 ◽  
Author(s):  
R. P. Singh ◽  
N. Singh ◽  
S. Shashtri ◽  
S. Mukherjee
Keyword(s):  
Organic Matter ◽  
Iron Hydroxide ◽  
Satellite Image ◽  
Flood Plain ◽  
Spectral Signature ◽  
Brahmaputra River ◽  
Arsenic In Groundwater ◽  
Groundwater Samples ◽  
Geomorphic Features ◽  
Geomorphic Units

The present study was conducted to explore the influence of geomorphic features of the area on the mobilization of arsenic in groundwater. In this study, remote sensing and GIS techniques were used to prepare the geomorphic and slope map of the area. Different geomorphic features were identified on the basis of spectral signature on the LISS III and Landsat satellite image and field survey. Groundwater samples were collected from each representative geomorphic feature to inspect the arsenic contamination in the area. The study area is drained by the Brahmaputra river and its tributaries and contain mainly fluvial geomorphic units especially older flood plain, palaeochannels, oxbow lakes, channel islands; and hilly areas at some of the places. In this study it was observed that enrichment of arsenic in groundwater varies along the geomorphic units in following trends Paleochannel> Younger alluvial plain> Active flood plain> channel island > dissected hills. The above trend shows that a higher concentration of arsenic is found in the groundwater samples collected from the fluvial landforms as compared to those collected from structural landforms. Brahmaputra River and its tributaries carry the sediment load from the Himalayan foothills, which get deposited in these features during the lateral shift of the river’s courses. Arsenic bearing minerals may get transported through river and deposit in the geomorphological features along with organic matter. The flat terrain of the area as seen from the slope map provides more residence time to water to infiltrate into the aquifer. The microbial degradation of organic matter generates the reducing environment and facilitates the dissolution of iron hydroxide thus releasing the adsorbed arsenic into the groundwater.

The role of normal and activated bentonite on the pelletization of barite iron ore concentrate and the quality of pellets

2003 ◽  
Vol 130 (1-3) ◽  
pp. 277-282 ◽  
Author(s):  
O.A Mohamed ◽  
M.E.H Shalabi ◽  
N.A El-Hussiny ◽  
M.H Khedr ◽  
F Mostafa
Keyword(s):  
Iron Ore ◽  
Activated Bentonite ◽  
Iron Ore Concentrate

Theoretical study of first row transitional metals effects on stabilization of verdoheme analogues

2019 ◽  
Vol 23 (10) ◽  
pp. 1100-1109
Author(s):  
Afsaneh Taghizadeh ◽  
Maryam Daghighi Asli ◽  
Parisa Rajabali Jamaat
Keyword(s):  
Chemical Potential ◽  
Dft Method ◽  
Basis Set ◽  
Orbital Energy ◽  
Central Metal ◽  
Transitional Metals ◽  
Solvent Phase ◽  
Energy Formula ◽  
Homo And Lumo

Heme catabolism is an important physiological process that converts heme to biliverdin in the presence of heme oxygenase which has an essential role in destroying unwanted heme. Verdohemes, the green iron (II) complexes of the 5-oxaporphyrin macrocycle are produced by oxidative destruction of heme. The main goal of this study is clarification of the central metal effect on stabilization of metal 5-oxaporphyrin molecules. To investigate the role of central metal on geometric and electronic properties of five coordinated verdoheme analogues, the first row transitional metals, including Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn, as the central metal of five-coordinated metal 5-oxaporphyrins were systematically calculated without any symmetry constraint by using the B3LYP as DFT method and the 6-31G basis set in gas and solvent phases. According to the results, the stabilization energy of metal 5-oxaporphyrins increases with atomic mass in the solvent phase more than in the gas phase. By reviewing the properties such as the computed frontier orbital energy, HOMO and LUMO gap energy [Formula: see text], hardness [Formula: see text], chemical potential [Formula: see text], softness (s) and electrophilicity [Formula: see text], the pharmaceutical use of this compound can be discussed.

Role of MgO and Its Different Minerals on Properties of Iron Ore Pellet

2015 ◽  
Vol 69 (6) ◽  
pp. 1141-1153 ◽  
Author(s):  
Md. Meraj ◽  
Susanta Pramanik ◽  
Jagannath Pal
Keyword(s):  
Iron Ore ◽  
Iron Ore Pellet

The role of bending stress on the initiation of reverse transverse defects

2020 ◽  
Vol 235 (1) ◽  
pp. 61-72
Author(s):  
Soumyajit Mojumder ◽  
Hang Su ◽  
Cong Qiu ◽  
Peter Mutton ◽  
Aparna Singh ◽  
...  
Keyword(s):  
Finite Element ◽  
Iron Ore ◽  
Maximum Stress ◽  
Load Ratio ◽  
Element Model ◽  
Bending Stress ◽  
Vertical Load ◽  
Lower Head ◽  
Longitudinal Bending

This paper investigated the role of longitudinal reverse bending stress on the initiation of reverse transverse defects. The longitudinal reverse bending stress occurs due to the reverse bending of the rail between two-wheel passage leading to the generation of tensile bending stress at the railhead and the lower head areas. The longitudinal bending stress was investigated as part of a parametric study on the rail cant angle, rail stiffness, lateral-to-vertical load ratio, and rail profile. A finite element model was created by using ABAQUS to analyze the extent of reverse bending in rails with respect to the chosen set of parameters. Under different lateral-to-vertical load ratios of 0, 0.3, 0.5, and 0.7, the maximum stress at the rail lower gauge corner was found to vary between 14.57MPa and 15.47MPa under the reverse bending condition. Similarly, low values of tensile stress under the reverse bending scenario were observed with changes in the rail cant angle and axle spacing with respect to different coal and iron ore wagons. The results revealed that the magnitude of the bending stress under different conditions of reverse bending was not significant enough to initiate a crack at the lower gauge corner.

scholarly journals Encountering automation: Redefining bodies through stories of technological change

2020 ◽  
pp. 026377582096312
Author(s):  
David Bissell
Keyword(s):  
Technological Change ◽  
Knowledge Production ◽  
Iron Ore ◽  
Mining Sector ◽  
Generative Process ◽  
Industry Sector ◽  
Making Sense ◽  
Complex Picture

This article enhances our understanding of the thoroughly embodied nature of knowledge production in relation to automation by demonstrating how making sense of automation is a generative process, rather than the demystification of an already existing object of analysis. It argues that the process of knowing automation involves situated encounters that transform bodies at the level of their indeterminate capacities to affect and be affected which, in turn, contributes to the production of what automation is. Contrasting with more generalised diagnoses about how automation is deskilling or reskilling bodies, it evaluates the constitutive role of situated encounters that register in sensing bodies for reshaping capacities. Focusing on iron ore mining in Australia, an industry sector that is currently increasing its automated operations, the paper draws on a series of fieldwork encounters with people differently positioned in the mining sector. Through the presentation of five stories that incorporate combinations of these fieldwork encounters, the paper constructs a more complex picture of how automation is redefining different bodies. Rather than taken to be mere representations of automation, it argues that the listening to and telling of stories about automation is a form of encounter that redefines bodies in the process.

scholarly journals Understanding Factors that Control the Structural (Dis)Assembly of Sulphur-Bridged Bimetallic Sites

Inorganics ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 42 ◽  
Author(s):  
Riyadh Alrefai ◽  
Henri Eggenweiler ◽  
Hartmut Schubert ◽  
Andreas Berkefeld
Keyword(s):  
Cyclic Voltammetry ◽  
Structure Function ◽  
General Type ◽  
Biological Function ◽  
Mechanism Of Formation ◽  
Model Compounds ◽  
Nickel Ions ◽  
Stereoelectronic Properties ◽  
Bimetallic Structures

Bimetallic structures of the general type [M2(µ-S)2] are omnipresent in nature, for biological function [M2(µ-S)2] sites interconvert between electronically distinct, but isostructural, forms. Different from structure-function relationships, the current understanding of the mechanism of formation and persistence of [M2(µ-S)2] sites is poorly developed. This work reports on bimetallic model compounds of nickel that interconvert between functional structures [Ni2(µ-S)2]+/2+ and isomeric congeners [2{κ-S–Ni}]2+/+, S = Aryl-S−, in which the nickel ions are geometrically independent. Interconversion of the two sets of structures was studied quantitatively by UV–VIS absorption spectroscopy and cyclic voltammetry. Assembly of the [Ni2(µ-S)2]+ core from [2{κ-S–Ni}]+ is thermodynamically and kinetically highly preferred over the disassembly of [Ni2(µ-S)2]2+ into [2{κ-S–Ni}]2+. Labile Ni-η2/3-bonding to aromatic π-systems of the primary thiophenol ligand is critical for modeling (dis)assembly processes. A phosphine coligand mimics the role of anionic donors present in natural sites that saturate metal coordination. Three parameters have been identified as critical for structure formation and persistence. These are, first, the stereoelectronic properties of the metals ions, second, the steric demand of the coligand, and, third, the properties of the dative bond between nickel and coligand. The energies of transition states connecting functional and precursor forms have been found to depend on these parameters.

“They Wandered in the Deserts and Mountains, and Caves and Holes in the Ground”

2019 ◽  
Vol 3 (3) ◽  
pp. 436-471
Author(s):  
Elisabeth R. O'Connell
Keyword(s):  
Flood Plain ◽  
Nile Valley ◽  
The West ◽  
Archaeological Evidence ◽  
Literary Representation

This contribution examines how models of exile were adopted and adapted in non-Chalcedonian communities following the establishment of a parallel Severan episcopal hierarchy under Archbishop Peter IV of Alexandria (576–577) and the consolidation of the Severan non-Chalcedonian church under his successor Damian (578–c. 607). Peter's predecessor Theodosius spent most of his long episcopacy (536–566) exiled in Constantinople, where he died, and Peter himself contended with three rivals to the patriarchate of Alexandria. Drawing on literary, documentary, and archaeological sources, I explore how the memory of non-Chalcedonian heroes was mobilized partly in order to validate the uncomfortable truth that members of the new network of bishops did not always live in their capitals, but in local monasteries, just as Peter and Damian did not live in Alexandria, but in the Enaton, nine miles to the west. After a brief survey of the role of exile in the Alexandrian Church, I concentrate on the literary representation of the appropriate places for exile in monastic literature, in particular the identification of the “deserts” and “mountains,” “caves” and “holes” of the wandering Hebrews (Heb 11.38) with the monastic landscape of Egypt in the late sixth and early seventh centuries. At this time, monastic habitation of natural caves, gallery quarries, and rock-cut tombs on the desert escarpment above the Nile Valley flood plain flourished. Finally, I survey the archaeological evidence of one region where bishops appointed by Damian settled, and how they put their models of exile into practice.

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