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Comparison of depth-averaged concentration and bed load flux sediment transport models of dam-break flow

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Water Science and Engineering 2017年第4期10卷 287-294页

作者： Jia-heng Zhao Ilhan Ozgen Dong-fang Liang Reinhard Hinkelmann Department of Civil Engineering Technische Universitat BerlinBerlin 13355Germany Department of Engineering University of CambridgeCambridge CB2 1PZUK

This paper presents numerical simulations of dam-break flow over a movable bed. Two different mathematical models were compared: a fully coupled formulation of shallow water equations with erosion and deposition terms(a depth-averaged concentration flux model), and shallow water equations with a fully coupled Exner equation(a bed load flux model). Both models were discretized using the cell-centered finite volume method, and a second-order Godunov-type scheme was used to solve the equations. The numerical flux was calculated using a Harten, Lax, and van Leer approximate Riemann solver with the contact wave restored(HLLC). A novel slope source term treatment that considers the density change was introduced to the depth-averaged concentration flux model to obtain higher-order accuracy. A source term that accounts for the sediment flux was added to the bed load flux model to reflect the influence of sediment movement on the momentum of the water. In a onedimensional test case, a sensitivity study on different model parameters was carried out. For the depth-averaged concentration flux model,Manning's coefficient and sediment porosity values showed an almost linear relationship with the bottom change, and for the bed load flux model, the sediment porosity was identified as the most sensitive parameter. The capabilities and limitations of both model concepts are demonstrated in a benchmark experimental test case dealing with dam-break flow over variable bed topography.

关键词： Shallow water Sediment transport Bed load flux model Depth-averaged concentration flux model Dam break

Boosting T cell immunity against cytomegalovirus:a potential strategy combating human aging and age-related diseases

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Signal Transduction and Targeted Therapy 2023年第10期8卷 4417-4418页

作者： Matthias Wirth Walburgis Brenner Oliver H.Kramer Department of Hematology Oncology and Cancer ImmunologyCampus Benjamin FranklinCharite-Universitatsmedizin Berlincorporate member of Freie Universitat Berlin and Humboldt-Universitat zu BerlinBerlinGermany University Medical Center Gottingen Department of GeneralVisceral and Pediatric SurgeryGottingenGermany German Cancer Consortium(DKTK) German Cancer Research Center(DKFZ)HeidelbergGermany Clinic for Obstetrics and Women's Health University Medical CenterJohannes Gutenberg University MainzLangenbeckstr.155131 MainzGermany Department of Toxicology University Medical CenterMainzGermany

In a recent publication in Cell,Hasegawa and colleagues reveal that cytotoxic CD4-positive cytotoxic T lymphocytes(CD4+CTLs)eliminate senescent fibroblasts with a surface expression of the immunologically important human leukocyte antigen class Il(HLA-)and the human cytomegalovirus glycoprotein B(HCMV-gB).1 This implies that a virome-immune cell interaction controls the fate of human skin cells that are linked to the aging process and associated diseases.

关键词： immunity cytomegalovirus cytotoxic

Towards efficient data exchange and sharing for big-data driven materials science:metadata and data formats

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npj Computational Materials 2017年第1期3卷 70-78页

作者： Luca M.Ghiringhelli Christian Carbogno Sergey Levchenko Fawzi Mohamed Georg Huhs Martin Luders Micael Oliveira Matthias Scheffler Fritz Haber Institute of the Max Planck Society BerlinGermany Barcelona Supercomputing Center BarcelonaSpain humboldt-universitat zu berlin BerlinGermany Daresbury Laboratory WarringtonUK University of Liege LiegeBelgium Max Planck Institute for the Structure and Dynamics of Matter HamburgGermany Department of Chemistry and Biochemistry and Materials Department University of California-Santa BarbaraSanta BarbaraCA 93106-5050USA

With big-data driven materials research,the new paradigm of materials science,sharing and wide accessibility of data are becoming crucial ***,a prerequisite for data exchange and big-data analytics is standardization,which means using consistent and unique conventions for,e.g.,units,zero base lines,and file *** are two main strategies to achieve this *** accepts the heterogeneous nature of the community,which comprises scientists from physics,chemistry,bio-physics,and materials science,by complying with the diverse ecosystem of computer codes and thus develops“converters”for the input and output files of all important *** converters then translate the data of each code into a standardized,codeindependent *** other strategy is to provide standardized open libraries that code developers can adopt for shaping their inputs,outputs,and restart files,directly into the same code-independent *** this perspective paper,we present both strategies and argue that they can and should be regarded as complementary,if not even *** represented appropriate format and conventions were agreed upon by two teams,the Electronic Structure Library(ESL)of the European Center for Atomic and Molecular Computations(CECAM)and the NOvel MAterials Discovery(NOMAD)Laboratory,a European Centre of Excellence(CoE).A key element of this work is the definition of hierarchical metadata describing state-of-the-art electronic-structure calculations.

关键词： metadata exchange translate

Spent coffee ground as source for hydrocarbon fuels

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Journal of Energy Chemistry 2016年第1期25卷 146-152页

作者： Peter Döhlert Maik Weidauer Stephan Enthalera Technische universitat berlin Department of ChemistryCluster of Excellence"Unifying Concepts in Catalysis"Straβe des 17.Juni 135/C2D-10623 BerlinGermany universitat Hamburg Department of ChemistryMartin-Luther-King-Platz 6D-20146 HamburgGermany

The conversion of triglycerides（coffee oil） obtained from spent coffee ground to produce hydrocarbon fuel（diesel） was studied. In more detail, a catalytic hydrodeoxygenation of the coffee oil was performed applying polymethylhydrosiloxane（PMHS） as cheap reductant under mild reaction conditions. However, along with the hydrocarbons significant amounts of PMHS-waste are generated, since only～1.7% of the PMHS is required for the reduction process. Based on that, in a subsequent depolymerization step the PMHS-waste was converted to methyltrifluorosilane and difluoromethylsilane, which can be applied as building blocks for the production of new silicones, with boron trifluoride diethyl etherate（BF3OEt2） as depolymerization reagent.

关键词： Catalysis Triglyceride Hydrocarbons Hydrodeoxygenation Depolymerization

Detrimental role of hydrogen evolution and its temperature-dependent impact on the performance of vanadium redox flow batteries

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Journal of Energy Chemistry 2019年第5期28卷 57-62页

作者： Abdulmonem Fetyan Gumaa A. El-Nagar Iver Lauermann Maike Schnucklake Jonathan Schneider Christina Roth Institute for Chemistry and Biochemistry Freie Universitat BerlinTakustr.3D-14195 BerlinGermany Chemistry Department Faculty of ScienceCairo UniversityCairo 12613Egypt Helmholtz-Zentrum berlin fur Materialien und Energie Hahn-Meitner-Platz 114109 BerlinGermany

This paper addresses the damaging role of the parasitic hydrogen evolution reaction (HER) in the negative half-cell of a vanadium redox flow battery (VRFB) on state-of-the-art carbon felt electrodes at different temperatures. It was found that increasing the temperature resulted in a better catalytic performance for both the positive and negative half-cell reactions. In addition, increasing the temperature significantly enhanced the undesired HER at the negative side. Operating the VRFB cell at higher temperature led to a decrease in the coulombic efficiency attributed to the higher hydrogen production. More pronounced hydrogen production caused an oxidation on the surface of the carb on fibers and a degradation of the electrode as indicated from scanning electron microscopy and X-ray photoelectron spectroscopy measurements. This observed degradation results in fading of the overall performance of the vanadium redox flow battery over time.

关键词： Hydrogen evolution Carbon felt Degradation Electrode Redox flow batteries

Error Estimates of Some Numerical Atomic Orbitals in Molecular Simulations

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Communications in Computational Physics 2015年第6期18卷 125-146页

作者： Huajie Chen Reinhold Schneider Zentrum Mathematik Technische Universitat MunchenBoltzmannstraße 385747 GarchingGermany Institut fur Mathematik Technische Universitat BerlinStraße des 17.Juni 136D-10623 BerlinGermany

Numerical atomic orbitals have been successfully used in molecular simulations as a basis set,which provides a nature,physical description of the electronic states and is suitable for ■(N)calculations based on the strictly localized *** paper presents a numerical analysis for some simplified atomic orbitals,with polynomial-type and confined Hydrogen-like radial basis functions *** give some a priori error estimates to understand why numerical atomic orbitals are computationally efficient in electronic structure calculations.

关键词： Kohn-Sham density functional theory numerical atomic orbitals Slater-type orbitals a priori error estimate

Evaluating metallic artefact of biodegradable magnesium-based implants in magnetic resonance imaging

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Bioactive Materials 2022年第9期7卷 382-391页

作者： Jonathan Espiritu Mostafa Berangi Christina Yiannakou Eduarda Silva Roberto Francischello Andre Kuehne Thoralf Niendorf Soren Konneker Regine Willumeit-Romer Jan-Marten Seitz Syntellix AG HannoverGermany MRI.TOOLS GmbH BerlinGermany Charit´e-universitatsmedizin berlin Corporate Member of Freie Universitat Berlin and Humboldt Universitat zu BerlinBerlinGermany berlin Ultrahigh Field Facility(B.U.F.F.) Max-Delbrueck Center for Molecular Medicine in the Helmholtz AssociationBerlinGermany Hannover Medical School HannoverGermany Institute of Clinical Physiology National Research CouncilPisaItaly Chemistry and Industrial Chemistry Department Universita di PisaVia Moruzzi 13PisaItaly Fondazione Toscana Gabriele Monasterio Via Moruzzi 1PisaItaly Institute for Materials Research Helmholtz Zentrum HereonGeesthachtGermany

Magnesium(Mg)implants have shown to cause image artefacts or distortions in magnetic resonance imaging(MRI).Yet,there is a lack of information on how the degradation of Mg-based implants influences the image quality of MRI *** this study,Mg-based implants are analysed in vitro,ex vivo,and in the clinical setting for various magnetic field strengths with the aim to quantify metallic artefact *** vitro corroded Mg-based screws and a titanium(Ti)equivalent were imaged according to the ASTM ***-based and Ti pins were also implanted into rat femurs for different time points and scanned to provide insights on the influence of soft and hard tissue on metallic ***,MRI data of patients with scaphoid fractures treated with CE-approved Mg-based compression screws(MAGNEZIX®)were analysed at various time points *** artefact production of the Mg-based material decreased as implant material degraded in all *** worst-case imaging scenario was determined to be when the imaging plane was selected to be perpendicular to the implant ***,the Mg-based implant outperformed the Ti equivalent in all experiments by producing lower metallic artefact(p<0.05).This investigation demonstrates that Mg-based implants generate significantly lower metallic distortion in MRI when compared to *** positive findings suggest and support further research into the application of Mg-based implants including post-operative care facilitated by MRI monitoring of degradation kinetics and bone/tissue healing processes.

关键词： Magnetic resonance imaging Magnesium Biodegradable implants Medical imaging Translational medicine

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非相干变频转换实现室温下红外单光子源

红外与激光工程 2014年第11期43卷 3709-3712页

作者：江萍郭蒙蒙 Tim Schroeder Oliver Benson 中国石油大学(华东)理学院山东青岛266580 Institute for Physics Humboldt-Universitat Zu BerlinBerlin Germany 10245

纳米金刚石中的NV-center(Nitrogen-Vacancy center)是目前室温下具有高发射率和稳定性的可见光波段单光子源,而如何实现及优化红外单光子源则是未来实现量子信息和量子通信应用的一大挑战。介绍了一种近期提出的实现红外单光子源的新... 详细信息

纳米金刚石中的NV-center(Nitrogen-Vacancy center)是目前室温下具有高发射率和稳定性的可见光波段单光子源,而如何实现及优化红外单光子源则是未来实现量子信息和量子通信应用的一大挑战。介绍了一种近期提出的实现红外单光子源的新型机制。该方法以金刚石中的NV-center作为可见光波段的单光子源,利用非相干变频转换实现室温下近红外波段稳定、无闪烁的单光子源。具体的实施方案为在中空芯光子晶体光纤中选择性地填充含有量子点的溶液,以可见光波段的单光子源作为激励源,选择合适的量子点即可得到红外波段的单光子源。中空芯光子晶体光纤保证了较高的单光子吸收效率以及荧光收集效率。该方案的实施在理论上可以达到26%的转换效率,而初步的实验得到了0.1%的转换效率。进一步分析了一些影响转换效率的因素,并提出了一些解决方案。

关键词：单光子源红外中空芯光子晶体光纤

Chapter model systems in heterogeneous catalysis at the atomic level: a personal view

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Science China Chemistry 2020年第4期63卷 426-447页

作者： Hans-Joachim Freund Markus Heyde Helmut Kuhlenbeck Niklas Nilius Thomas Risse Thomas Schmidt Shamil Shaikhutdinov Martin Sterrer Fritz Haber Institute of the Max Planck Society Faradayweg 4-6Berlin D-14195Germany Fakultat V-Mathematik und Naturwissenschaften Carl von Ossietzky Universitat OldenburgGermany Institut fur Chemie und Biochemie Freie UniversitatBerlinGermany Institute of Physics University of GrazGrazAustria

The review presents an overview of studies in the surface science of oxide and related surfaces with an emphasis of the studies performed in the authors’ group. Novel instruments and technique developments, as well as their applications are reported, in an attempt to cover studies on model systems of increasing complexity, including some of the key ingredients of an industrially applied heterogeneous catalyst and its fabrication. The review is intended to demonstrate the power of model studies in understanding heterogeneous catalysis at the atomic level. The studies include those on supported nano-particles, both, prepared in vacuum and from solution, interaction of surfaces and the underlying bulk with molecules from the gas phase, strong metal support interaction, as well as the first attempt to include studies on reactions in confined spaces.

关键词： model catalysts oxide surfaces structure and spectroscopy supported nanoparticles reactions in the confined space