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  • 1
    Call number: AWI G6-18-91326
    Type of Medium: Monograph available for loan
    Pages: 279 Seiten , Diagramme, Karten
    ISBN: 9783110402421
    Language: English
    Note: Contents: Preface. - Acknowledgements. - 1 Introduction. - 1.1 Origin and characters of silicon and its isotopes. - 1.2 A brief description of silicon geochemistry. - 1.3 The history of silicon isotope studies. - 2 Analytical methods of silicon isotope composition. - 2.1 Gas source isotope ratio mass spectrometric analysis of silicon isotopes. - 2.2 Multi-collector inductively coupled plasma mass spectrometric (MC-ICPMS) analysis of silicon isotopes. - 2.3 Secondary ion mass spectrometry analyses. - 2.4 Standards and reference materials for silicon isotope measurement. - 2.5 Comparison of different methods on silicon isotope analyses. - 3 Mechanisms of silicon isotope fractionation. - 3.1 The thermodynamic silicon isotope exchange fractionation. - 3.2 Kinetic fractionation of silicon isotopes. - 4 Distribution of silicon isotopes in nature. - 4.1 Silicon isotope compositions of extraterrestrial materials. - 4.2 Silicon isotope distribution in lithosphere. - 4.3 Silicon isotope compositions of soils. - 4.4 Hydrosphere. - 4.5 Biosphere. - 5 Several aspects of silicon isotope applications. - 5.1 Studies on global silicon cycle. - 5.2 Silicon isotope studies on environmental variation of ocean. - 5.3 Studies on mechanisms of absorption, transportation and precipitation of silicon in plant growth processes. - 5.4 Studies on silicon source and genesis of ore deposits. - References. - Index.
    Location: AWI Reading room
    Branch Library: AWI Library
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  • 2
    Publication Date: 2012-07-01
    Description: Large-scale nitrate deposits are rare on Earth’s surface due to the high solubility of nitrate minerals. Exceptions are found in extremely old (to 14 m.y.) and hyperarid deserts such as the Atacama Desert in northern Chile, or the McMurdo Dry Valleys in Antarctica. The nitrate in both of these regions has been determined to originate from atmospheric oxidation of NOx. Here we report a new type of massive atmospheric nitrate deposit, with resources equivalent to the Atacama deposits, in the Turpan-Hami area, northwestern China. This deposit is characterized by (1) a location in the center of a large continent; (2) young age (Pleistocene); (3) general enrichment near the surface rather than at depth; and (4) high spatial variability in the nitrogen and triple oxygen isotope composition within this arid region, the δ15N ranging from 0.7‰ to 27.6‰, δ18O from 30.2‰ to 46.7‰, and Δ17O from 5.9‰ to 20.7‰. The Turpan-Hami nitrate deposit nitrogen and triple oxygen isotope composition is closely between those of the Mojave Desert (southwestern United States) and the Atacama Desert, suggesting that (1) Earth’s low-middle latitudes (i.e., non-polar sites) have been receiving atmospheric nitrate deposition of similar nitrogen and triple oxygen isotope composition; and (2) local or regional isotope differences in nitrate deposits can be attributed to postdepositional processes, namely the difference in aridity and associated microbial activities.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
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  • 3
    Publication Date: 2019
    Description: The origin of the Zhaoanzhuang serpentine-magnetite deposit in the southern North China Craton (NCC) is highly disputed, with some investigators having proposed an ultramafic origin, whereas others favor a chemical sedimentary origin. These discrepancies are largely due to the difficulty in determining the protolithic characteristics of the highly metamorphosed rocks. Sulfur, magnesium, and boron isotope geochemistry combined with detailed petrography was carried out in this study to constrain the original composition of the Zhaoanzhuang iron orebodies. Anhydrite is present as coarse crystals intergrown with magnetite, indicating that the anhydrite formed simultaneously with the magnetite during metamorphism rather than as a product of later hydrothermal alteration. The anhydrite has a narrow range of positive δ34S values from +19.8 to +22.5‰ with a mean value of +21.1‰. These values are significantly higher than that of typical magmatic sulfur (δ34S = 0 ± 5‰) and deviate away from primary igneous anhydrite towards mantle-sulfur isotopic values, but they are similar to those of marine evaporitic anhydrite and gypsum (~+21‰). The sulfur isotopic compositions of several samples show obvious signs of mass-independent sulfur fractionation (Δ33S = −0.47‰ to +0.90‰), suggesting that they were influenced by an external sulfur source through a photochemical reaction at low oxygen concentrations, which is consistent with the Neoarchean-Paleoproterozoic atmosphere. Coarse-grained tourmaline from the tourmaline-rich interlayers of the orebodies occurs closely with Mg-rich minerals such as phlogopite, talc, and diopside, indicating that it has a metamorphic origin. The δ11B values of the tourmaline range from −0.2‰ to +3.6‰ with a mean value of +2.0‰, which is much positive relative to that of magmatic tourmaline but is consistent with that of carbonate-derived tourmaline. The magnesium isotopic analyses of the serpentine–magnetite ores and the magnesium-rich wall rocks revealed a wide range of very negative δ26Mg values from −1.20‰ to −0.34‰ with an average value of −0.80‰. The value is higher than that of ultramafic rocks (δ26Mg = −0.25‰) and exhibits minor Mg isotopic fractionation. However, these values are consistent with those of marine carbonate rocks, which have lower δ26Mg values and larger Mg isotopic variations (δ26Mg = −0.45‰ to −4.5‰). Collectively, the S–Mg–B isotopic characteristics of the Zhaoanzhuang iron orebodies clearly indicate a chemical sedimentary origin. The protoliths of these orebodies most likely reflect a series of Fe–Si–Mg-rich marine carbonate rocks with a considerable evaporite component, indicating a carbonate-rich superior-type banded iron formation precipitated in an evaporitic shallow marine sedimentary environment.
    Electronic ISSN: 2075-163X
    Topics: Geosciences
    Published by MDPI
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  • 4
    Publication Date: 2010-10-01
    Print ISSN: 1001-6538
    Electronic ISSN: 1861-9541
    Topics: Natural Sciences in General
    Published by Springer
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  • 5
    Publication Date: 2014-03-29
    Description: Cyanobacteria are oxygenic photosynthetic prokaryotes that play important roles in the global carbon cycle. Recently, engineered cyanobacteria capable of producing various small molecules from CO2 have been developed. However, cyanobacteria are seldom considered as factories for producing proteins, mainly because of the lack of efficient strong promoters. Here, we report the discovery and verification of a super-strong promoter Pcpc560, which contains two predicted promoters and 14 predicted transcription factor binding sites (TFBSs). Using Pcpc560, functional proteins were produced at a level of up to 15% of total soluble protein in the cyanobacterium Synechocystis sp. 6803, a level comparable to that produced in Escherichia coli. We demonstrated that the presence of multiple TFBSs in Pcpc560 is crucial for its promoter strength. Genetically transformable cyanobacteria neither have endotoxins nor form inclusion bodies; therefore, Pcpc560 opens the possibility to use cyanobacteria as alternative hosts for producing heterogeneous proteins from CO2 and inorganic nutrients. Scientific Reports 4 doi: 10.1038/srep04500
    Electronic ISSN: 2045-2322
    Topics: Natural Sciences in General
    Published by Springer Nature
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  • 6
    Publication Date: 2017-11-20
    Description: Energies, Vol. 10, Pages 1901: An Intelligent Optimization Method for Vortex-Induced Vibration Reducing and Performance Improving in a Large Francis Turbine Energies doi: 10.3390/en10111901 Authors: Xuanlin Peng Jianzhong Zhou Chu Zhang Ruhai Li Yanhe Xu Diyi Chen In this paper, a new methodology is proposed to reduce the vortex-induced vibration (VIV) and improve the performance of the stay vane in a 200-MW Francis turbine. The process can be divided into two parts. Firstly, a diagnosis method for stay vane vibration based on field experiments and a finite element method (FEM) is presented. It is found that the resonance between the Kármán vortex and the stay vane is the main cause for the undesired vibration. Then, we focus on establishing an intelligent optimization model of the stay vane’s trailing edge profile. To this end, an approach combining factorial experiments, extreme learning machine (ELM) and particle swarm optimization (PSO) is implemented. Three kinds of improved profiles of the stay vane are proposed and compared. Finally, the profile with a Donaldson trailing edge is adopted as the best solution for the stay vane, and verifications such as computational fluid dynamics (CFD) simulations, structural analysis and fatigue analysis are performed to validate the optimized geometry.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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  • 7
    Publication Date: 2017-12-20
    Description: Energies, Vol. 10, Pages 2175: Experimental and Finite Element Analysis to Investigate the Vibration of Oblique-Stud Stator Frame in a Large Hydropower Generator Unit Energies doi: 10.3390/en10122175 Authors: Jianzhong Zhou Xuanlin Peng Ruhai Li Yanhe Xu Han Liu Diyi Chen This paper presents an investigation on the undesirable vibration of an oblique-stud stator frame in a large hydropower generator by means of experimental and finite element (FE) analysis. First, field experimental tests were performed, and the results indicate that the main vibration component comes from electromagnetic factors. Then, a 2D-magnetic and 3D-mechanical FE model was developed to investigate the vibration of the stator frame under the action of electromagnetic forces. A set of contrast models was established to study the effects of different kinds of eccentricity and different structures. Based on the comparative analysis between the results of simulations and experimental tests, it can be inferred that the abnormal vibration is generated because of the lack of stiffness in the upper part of structure and the existence of dynamic eccentricity in the rotor–stator system. In addition, the structural simulation analysis shows that the flexible designed oblique-stud stator frame is relatively vulnerable against the electromagnetic forces.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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  • 8
    Publication Date: 2017-12-25
    Description: Energies, Vol. 11, Pages 35: A Real-Time Accurate Model and Its Predictive Fuzzy PID Controller for Pumped Storage Unit via Error Compensation Energies doi: 10.3390/en11010035 Authors: Jianzhong Zhou Zhigao Zhao Chu Zhang Chaoshun Li Yanhe Xu Model simulation and control of pumped storage unit (PSU) are essential to improve the dynamic quality of power station. Only under the premise of the PSU models reflecting the actual transient process, the novel control method can be properly applied in the engineering. The contributions of this paper are that (1) a real-time accurate equivalent circuit model (RAECM) of PSU via error compensation is proposed to reconcile the conflict between real-time online simulation and accuracy under various operating conditions, and (2) an adaptive predicted fuzzy PID controller (APFPID) based on RAECM is put forward to overcome the instability of conventional control under no-load conditions with low water head. Respectively, all hydraulic factors in pipeline system are fully considered based on equivalent lumped-circuits theorem. The pretreatment, which consists of improved Suter-transformation and BP neural network, and online simulation method featured by two iterative loops are synthetically proposed to improve the solving accuracy of the pump-turbine. Moreover, the modified formulas for compensating error are derived with variable-spatial discretization to improve the accuracy of the real-time simulation further. The implicit RadauIIA method is verified to be more suitable for PSUGS owing to wider stable domain. Then, APFPID controller is constructed based on the integration of fuzzy PID and the model predictive control. Rolling prediction by RAECM is proposed to replace rolling optimization with its computational speed guaranteed. Finally, the simulation and on-site measurements are compared to prove trustworthy of RAECM under various running conditions. Comparative experiments also indicate that APFPID controller outperforms other controllers in most cases, especially low water head conditions. Satisfying results of RAECM have been achieved in engineering and it provides a novel model reference for PSUGS.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI Publishing
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  • 9
    Publication Date: 1997-07-01
    Print ISSN: 1000-9426
    Electronic ISSN: 1993-0364
    Topics: Chemistry and Pharmacology , Geosciences
    Published by Springer
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  • 10
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