Abschätzung der Pyritoxidation in einem Braunkohletagebau mithilfe numerischer Modellrechnungen

Kurzfassung Beim Abbau von Braunkohle kann die Oxidation von im Sediment vorhandenen Pyriten zu einer Versauerung des Sickerwassers führen und damit zu einer Mobilisierung von Schwermetallen. Um den Oxidationsgrad der Pyrite in der unbehandelten Abraumkippe eines Braunkohletagebaus abzuschätzen, wurden am Lehrstuhl für Angewandte Geologie der Ruhr-Universität Bochum neben umfangreichen Felduntersuchungen und Laborversuchen auch numerische Simulationsrechnungen durchgeführt. Um die in einem Tagebau oxidierten Pyritmengen zu berechnen, wurde mithilfe des numerischen Modells gw-chem.f sowohl die Oxidation auf der Abbauseite als auch die Oxidation auf der Kippenseite berechnet. Die genaue Kenntnis der umgesetzten Pyritmenge ist notwendig, um die Kalkmenge zu ermitteln, die benötigt wird, um die bei der Pyritoxidation entstehende Schwefelsäure zu neutralisieren. Dadurch soll das Grundwasser geschützt werden, wenn der Tagebau wieder geflutet wird.

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Numerical simulation of pyrite oxidation in a lignite open cast mine

Abstract Lignite mining leads to the oxidation of pyrite minerals in the sediments of the overburden dumps. The resulting acid mine drainage problem can lead to high concentration of heavy metals in percolating soil water and in groundwater. To estimate the degree of pyrite oxidation in the untreated overburden dump many field observations, laboratory experiments and numerical simulations were conducted at the Chair of Applied Geology (Ruhr University of Bochum). To calculate the amount of oxidised pyrite at the winning and dumping side of an open cast mine, the numerical model gw-chem.f was used. The amount of oxidised pyrite is to be known to estimate the amount of alkaline substances like crushed limestone, which is necessary to neutralise the sulphuric acid produced by the pyrite oxidation. The aim is to improve groundwater quality after mine closure and filling of the overburden dump with groundwater.

     

Absch?tzung der Pyritoxidation in einem Braunkohletagebau mithilfe numerischer Modellrechnungen

Beim Abbau von Braunkohle kann die Oxidation von im Sediment vorhandenen Pyriten zu einer Versauerung des Sickerwassers führen und damit zu einer Mobilisierung von Schwermetallen. Um den Oxidationsgrad der Pyrite in der unbehandelten Abraumkippe eines Braunkohletagebaus abzuschätzen, wurden am Lehrstuhl für Angewandte Geologie der Ruhr-Universität Bochum neben umfangreichen Felduntersuchungen und Laborversuchen auch numerische Simulationsrechnungen durchgeführt. Um die in einem Tagebau oxidierten Pyritmengen zu berechnen, wurde mithilfe des numerischen Modells gw-chem.f sowohl die Oxidation auf der Abbauseite als auch die Oxidation auf der Kippenseite berechnet. Die genaue Kenntnis der umgesetzten Pyritmenge ist notwendig, um die Kalkmenge zu ermitteln, die benötigt wird, um die bei der Pyritoxidation entstehende Schwefelsäure zu neutralisieren. Dadurch soll das Grundwasser geschützt werden, wenn der Tagebau wieder geflutet wird.     

Degenerative changes at the knee and ankle related to malunion of tibial fractures. 15-year follow-up of 88 patients

We re-examined clinically and radiologically 88 patients with a fracture of the lower leg at a mean follow-up of 15 years. Forty-three fractures (49%) had healed with malalignment of at least 5 degrees. More arthritis was found in the knee and ankle adjacent to the fracture than in the comparable joints of the uninjured leg. Malaligned fractures showed significantly more degenerative changes. Eighteen patients (20%) had symptoms in the fractured leg. There was a significant correlation between symptoms in the knee and arthritis but not between symptoms and ankle arthritis or malalignment. We conclude that fractures of the lower leg should be managed so that the possibility of angular deformity and thereby late arthritis is minimised.     

Turn-on jitter of zero-biased nearly single-mode VCSEL's

The turn-on jitter of zero-biased nearly single-mode vertical-cavity surface-emitting lasers (VCSEL's) is experimentally investigated. Since during the turn-on event both the dominant and the suppressed polarization are exited, an analytical expression describing the probability density function of the turn-on delay for a single-mode VCSEL is derived, which accounts for both polarizations. The measurement results and the theory are in good agreement as long as the VCSEL is transversal single-mode     

Noise analysis of frequency converters utilizingsemiconductor-laser amplifiers

This paper deals with a general problem concerning semiconductor-laser amplifiers used for frequency conversion. The amplified spontaneous emission (ASE) of a saturated amplifier is investigated experimentally and theoretically. An analytical solution accounting for the spatial dependence of the inversion parameter as well as the spectral dependence of the ASE is derived. Hence, the results can be applied to arbitrary saturation conditions and frequency shifts. Our theory is applied to frequency converters based on four-wave mixing and is found to be in good agreement with both the numerical results and the experimental data. In order to quantify the performance of a frequency converter, a noise figure is defined and shown to be strongly dependent on the frequency detuning and the power of the input waves     

连铸自动化技术的近期发展与前景

连铸自动化系统已高度发展，并逐渐走向集成化。产品质量是开发先进的质量控制系统的重要方面，今天的质量控制技术能让钢铁企业充分挖掘设备的潜能。自20世纪80年代初以来，奥钢联就致力于连铸自动化技术的研究开发，工艺控制系统开发所取得的突皮性进展，工艺模型的应用以及处理工艺和产品质量信息的先进方法的采用，极大地提高了连铸产品的质量。这是秘更高效，更具竞争力的生产迈出的重大一步。     

Specific binding of tetratricopeptide repeat proteins to the C-terminal 12-kDa domain of hsp90

The molecular chaperone hsp90 in the eukaryotic cytosol interacts with a variety of protein cofactors. Several of these cofactors have protein domains containing tetratricopeptide repeat (TPR) motifs, which mediate binding to hsp90. Using a yeast two-hybrid screen, the 12-kDa C-terminal domain of human hsp90alpha (C90) was found to mediate the interaction of hsp90 with TPR-containing sequences from the hsp90 cofactors FKBP51/54 and FKBP52. In addition, the mitochondrial outer membrane protein hTOM34p was identified as a TPR-containing putative partner protein of hsp90. In experiments with purified proteins, the TPR-containing cofactor p60 (Hop) was shown to form stable complexes with hsp90. A deletion mutant of hsp90 lacking the C90 domain was unable to bind p60, whereas deletion of the approximately 25-kDa N-terminal domain of hsp90 did not affect complex formation. Both p60 and FKBP52 bound specifically to the C90 domain fused to glutathione S-transferase and competed with each other for binding. In reticulocyte lysate, the C90 fusion protein recognized the TPR proteins p60, FKBP52, and Cyp40. Thus, our results identify the C90 domain as the specific binding site for a set of hsp90 cofactors having TPR domains.     

An advanced modelling tool for simulating complex river systems

The present paper describes MOHID River Network (MRN), a 1D hydrodynamic model for river networks as part of MOHID Water Modelling System, which is a modular system for the simulation of water bodies (hydrodynamics and water constituents). MRN is capable of simulating water quality in the aquatic and benthic phase and its development was especially focused on the reproduction of processes occurring in temporary river networks (flush events, pools formation, and transmission losses). Further, unlike many other models, it allows the quantification of settled materials at the channel bed also over periods when the river falls dry. These features are very important to secure mass conservation in highly varying flows of temporary rivers. The water quality models existing in MOHID are base on well-known ecological models, such as WASP and ERSEM, the latter allowing explicit parameterization of C, N, P, Si, and O cycles. MRN can be coupled to the basin model, MOHID Land, with computes runoff and porous media transport, allowing for the dynamic exchange of water and materials between the river and surroundings, or it can be used as a standalone model, receiving discharges at any specified nodes (ASCII files of time series with arbitrary time step). These features account for spatial gradients in precipitation which can be significant in Mediterranean-like basins. An interface has been already developed for SWAT basin model.     

Turn-on jitter in zero-biased single-mode semiconductor lasers

An analytical expression for the turn-on delay probability density function (pdf) of single-mode lasers biased below threshold is derived, which is in good agreement with results based on computer simulations and measurements. It is shown, that the pdf obtained only depends on the on-state yielding simple requirements for the transmitter in order to achieve a given BER. The results are of particular interest for designing optical interconnects, where zero-biased lasers are used.