2,742 research outputs found
Bauxite formation on Tertiary sediments and Proterozoic bedrock in Suriname
No full textThe lateritic bauxite deposits in Suriname are traditionally distinguished into Coastal plain bauxites and Plateau bauxites, a subdivision that is primarily based on their topographic and geographic position. The first group is located in the lowlands of the coastal plain, while the second group is located on relatively high plateaus in the country’s interior. The Coastal plain deposits are mostly buried under younger sediments. Bauxite formation in Suriname peaked in Late Cretaceous – Early Tertiary times, when favourable conditions for bauxitisation prevailed worldwide. The parent rock composition is the most influential difference between these two deposit groups as the Coastal plain bauxites originated on Cenozoic sediments, and the Plateau bauxites on a diverse collection of Proterozoic rocks, which range from (ultra)high-temperature metamorphic gneissic and amphibolitic rocks in the Bakhuis Mountains (Granulite Belt in west Suriname) to greenschist-facies metabasalts and other meta-igneous rocks in the Greenstone Belt in east Suriname (Nassau Mountains, Lely Mountains and Brownsberg). The more ferruginous character of the Plateau bauxites is directly correlated to the higher iron contents of their crystalline parent rocks. The major element concentrations are linked to the principal minerals in specific zones of the lateritic profile as gibbsite is the prominent aluminum-bearing phase in the bauxite zone, while kaolinite prevails in the saprolite, and hematite and goethite are dominant in the duricrust that is covering the lateritic profiles. Bauxites are products of several weathering processes such as leaching of soluble elements ( e.g. Si, K, Na, Mg and Ca) from unstable minerals in the precursor rock, relative accumulation of poorly soluble or immobile components ( e.g. Al, Ti, Zr, Nb), and iron enrichment controlled by fluctuating groundwater levels and redox conditions. The enrichment of high field-strength elements (HFSE) and heavy rare earth elements (HREE) can be directly correlated to the resistance of zircon and other mineral hosts against weathering, especially in the Coastal plain bauxites where placer-like accumulations of these particular minerals are present in the terrigenous precursor sediments. Trace element signatures and petrologic observations of the Coastal plain deposits revealed that there is no direct genetic relationship between bauxite and the underlying saprolitic clay. The geochemical signatures, grade and volumes of the Surinamese bauxites are influenced by certain weathering processes (leaching, enrichment, fractionation), the primary compositional differences of parent rocks, nature and content of the accessory minerals, landscape morphology, local hydrological conditions, drainage efficiency, and unequal responses to multiple bauxitization cycles
Bauxite formation on Tertiary sediments and Proterozoic bedrock in Suriname
No full textThe lateritic bauxite deposits in Suriname are traditionally distinguished into Coastal plain bauxites and Plateau bauxites, a subdivision that is primarily based on their topographic and geographic position. The first group is located in the lowlands of the coastal plain, while the second group is located on relatively high plateaus in the country’s interior. The Coastal plain deposits are mostly buried under younger sediments. Bauxite formation in Suriname peaked in Late Cretaceous – Early Tertiary times, when favourable conditions for bauxitisation prevailed worldwide. The parent rock composition is the most influential difference between these two deposit groups as the Coastal plain bauxites originated on Cenozoic sediments, and the Plateau bauxites on a diverse collection of Proterozoic rocks, which range from (ultra)high-temperature metamorphic gneissic and amphibolitic rocks in the Bakhuis Mountains (Granulite Belt in west Suriname) to greenschist-facies metabasalts and other meta-igneous rocks in the Greenstone Belt in east Suriname (Nassau Mountains, Lely Mountains and Brownsberg). The more ferruginous character of the Plateau bauxites is directly correlated to the higher iron contents of their crystalline parent rocks. The major element concentrations are linked to the principal minerals in specific zones of the lateritic profile as gibbsite is the prominent aluminum-bearing phase in the bauxite zone, while kaolinite prevails in the saprolite, and hematite and goethite are dominant in the duricrust that is covering the lateritic profiles. Bauxites are products of several weathering processes such as leaching of soluble elements ( e.g. Si, K, Na, Mg and Ca) from unstable minerals in the precursor rock, relative accumulation of poorly soluble or immobile components ( e.g. Al, Ti, Zr, Nb), and iron enrichment controlled by fluctuating groundwater levels and redox conditions. The enrichment of high field-strength elements (HFSE) and heavy rare earth elements (HREE) can be directly correlated to the resistance of zircon and other mineral hosts against weathering, especially in the Coastal plain bauxites where placer-like accumulations of these particular minerals are present in the terrigenous precursor sediments. Trace element signatures and petrologic observations of the Coastal plain deposits revealed that there is no direct genetic relationship between bauxite and the underlying saprolitic clay. The geochemical signatures, grade and volumes of the Surinamese bauxites are influenced by certain weathering processes (leaching, enrichment, fractionation), the primary compositional differences of parent rocks, nature and content of the accessory minerals, landscape morphology, local hydrological conditions, drainage efficiency, and unequal responses to multiple bauxitization cycles
Design metrics for evaluating the propulsive efficiency of future ships
No full textThere is an increasing need for the ship design process to take account of environmental issues such as the emission of greenhouse gases and the likely extension of a carbon dioxide charging mechanism to international shipping. These issues, together with the need for economic viability, provide further incentives to improve the efficiency of propulsion of ships. The main components of powering are firstly reviewed. Individual components and other power saving devices are identified which should contribute to improvements in the overall efficiency of propulsion. Suitable design metrics and procedures, taking into account economic and environmental factors, are recommended for the design of future ships
Brief note: some observations on oscillating tangential forces and wear in general plane contacts
No full textFor general plane contact of elastically similar materials, including cases where there are multiple regions of contact, general properties of the partial slip solution for conditions of constant normal force and monotonically increasing shearing force have been found recently by the first author. An extension is given here to cover the unloading and cyclic loading cases. Further, it is shown that, if the tangential load varies between two fixed limits, the region of stick does not change, even if relative microslip causes wear, changing continuously the profile of the indenter. The contact area will change, but wear will not enter the original region of adhesion. The theoretical limit to which wear will eventually, asymptotically proceed is established, viz. almost complete contact over what is the initial stick zone, although it may, in practice, take a long time to reach this state
The description of Kabarda by D.A. Milutin in the context of the cauсasus version of russian orien-talism foundation
No full textThe paper pertains to the analysis of a manuscript authored by D.A. Milutin in the first half of the 19th century, regarding the region of Kabarda. This manuscript, hitherto unpublished in academic circles, has been the subject of our examination. Our endeavor was to uncover the utilization of orientalist clichés by the manuscript's author, in order to depict both the geographical delineations of this ethno-political entity and the ethnography, livelihood, societal structure, and customary legal norms of its inhabitants. A remarkable parallel can be observed between certain aspects of the manuscript and the ideas propounded by E. Said in his discourse on European Orientalism. The researcher drew a comparison between the political framework and traditions of the Kabardian people and those prevalent in Europe. Moreover, the researcher romanticized the region's historical past, employing the conceptof "reverse human progress," along with other typical methodologies embraced by Orientalist thinkers of that era. Concomitantly, D.A. Milutin provided detailed descriptions of the political, social, and everyday existence in Kabarda, thereby endowing the manuscript with an intrinsic value as an original historical and cultural resource for contemporary scholars. It is concluded that, similar to numerous analogous texts produced by Orientalist scholars, the significance of D.A. Milutin's man-uscript lies not in its political arguments concerning the military and economic dominion of the Russian Empire over the Caucasian peoples, or the imperative to extend colonial governance to these ethnic territorie
Elements of Ethnotaxonomy in Dhule and Nandurbar Districts (Maharashtra)
No full textDhule and Nandurbar districts of Maharashtra are mainly inhabited by tribals and rural folks. The author’s ethnobotanical and floristic forays in these districts brought out certain elements of ethnotaxonomy like ethnotaxonomic markers, classifications, principles of nomenclature and exomorphic features. The facts gathered indicated that the people in the area are fairly flooded with reckonable elements of ethnotaxonomy. And 22 ethnotaxonomic markers are identified. These are evaluated and discussed pertinently in this paper.-----------------------------------------------------------------------------------------------------Post Graduate Department of Botany, S.S.V.P.S’s L.K. P.R.Ghogrey Science College, Dhule-424005 (Maharashtra), India*Corresponding author, Email: [email protected] Cite This Article As: D.A. Patil. 2010. Elements of Ethnotaxonomy in Dhule and Nandurbar Districts (Maharashtra). J. Ecobiotechnol. 2(3): 18-25
Aanteekeningen omtrent de gevolgen van zware stormvloeden, tusschen 1500 en 1825 voorgekomen, voor de dijken en polders langs het Zuidwestelijk deel der Zuiderzee: samengesteld door den ingenieur van den Rijkswaterstaat D.A. van Heyst
No full textOverzicht van stormvloeden (1500 - 1825) die tot overstromingen langs de Zuiderzee geleid hebben. Aanleiding was de overstroming van 1916, en men wilde weten of deze stormvloed inderdaad uniek was
The dynamical influences of a hard transition zone on post-glacial uplifts and rotational signatures
No full textRecent investigations from laboratory and Monte-Carlo inversion of geophysical signatures have suggested that the transition zone of the mantle between 400 and 670 km depth may be stiffer than the lower and the upper mantle. By means of a five-layer viscoelastic spherical Earth model, we have calculated the displacement fields associated with post-glacial rebound, the induced polar motions, the temporal variations of the coefficients of the geopotential up to degree eight and the stress fields induced by deglaciation in the lithosphere and the upper mantle. Temporal variations of stress fields in the lithosphere reveal a non-monotonic behaviour due to the viscosity stratification. The results demonstrate the importance of the coming LAGEOS II geodetic satellite mission on constraining the rheological nature of the transition zone in the mantle. -from Author
Author Correction: Coupling electrochemical CO<sub>2</sub> conversion with CO<sub>2</sub> capture (Nature Catalysis, (2021), 4, 11, (952-958), 10.1038/s41929-021-00699-7)
No full textIn the version of this article, there were errors in Fig. 2a and d. In Fig. 2a, we have changed Cu2+ to Cu(0) in the revised version. While the two references cited in our paper used Cu2+ in their schematics,1,2 we believe that Cu(0) is the correct representation for the electrochemically mediated amine regeneration (EMAR)3. To be clear, the Cu metal anode is oxidized into cupric ions. The cupric ions then bind to the carbamate and displace the CO2 and form a copper–amine complex. The copper–amine complex is then reduced at the cathode where Cu metal is plated out. In Fig. 2d, we have changed the polarity of the cathode and anode in the revised version. A proton is released at the anode, while a hydroxide is released at the cathode. We have also simplified the quinone/hydroquinone chemistry in the revised version to be consistent with proton and hydroxide stoichiometry. The original and revised Fig. 2 images are shown below. The changes have been made to the html and PDF versions of the article.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public. Author correction to DOI 10.1038/s41929-021-00699-7ChemE/Transport Phenomen
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