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Experimental and FEM based investigation of the influence of the deposition temperature on the mechanical properties of SiC coatings

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Journal of Advanced Ceramics 2021年第1期10卷 139-151页

作者： Thomas SCHLECH siegfried HORN Charles WIJAYAWARDHANA Arash RASHIDI SGL Carbon GmbH Werner-von-Siemens-Strasse 1886405 MeitingenGermany Experimental PhysicsⅡ Institute of PhysicsUniversity of Augsburg86135 AugsburgGermany SGL Carbon GmbH Drachenburgstrasse 153170 BonnGermany

Scanning electron microscopy shows that the microstructure,in particular the overall grain size,of chemical vapor deposited silicon carbide coatings depends on the deposition ***,the influence of the microstructure on the mechanical properties of such coatings is not well described in *** investigate the influence of the deposition temperature on the mechanical properties of the coating,nanoindentation is used in this *** the measurement results of nanoindentation can be affected by the substrate material,the contribution of the substrate material is taken into account utilizing a finite element *** model is then employed to generate information about elastic and plastic properties of the coating by inverse *** evaluate the fracture toughness of the coating,the generated material model is used in a cohesive-zone based formulation of the fracture process during indentation at higher *** results of this model allow determining the fracture toughness of silicon carbide coatings deposited at different temperatures.

关键词： nanoindentation finite element analysis coatings ceramics fracture mechanics

Syntheses of Macrocyclic Amides from L-Amino Acid Esters by RCM

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Chemical Research in Chinese Universities 2007年第1期23卷 22-30页

作者： ZHAO Bao-xiang SCHAUDT Marco BLECHERT siegfried Institute of Organic Chemistry School of Chemistry and Chemical Engineering Shandong University Jinan 250100 P.R. China Institut fuer Chemie Technische Universittit Berlin Strasse des 17. Juni 135 D-10623 Berlin Germany

A series of succinate-derived macrocyclic amides（1） was synthesized via ring-closing metathesis（RCM） as the key step. The substrate included 12 to 15 members. The metathesis precursors were obtained from the amide coupling of ten-butyl 3-carboxyhex-5-enoate（2） with numerous side-chain aikenylated amino acid esters of general type（3） derived from L-lysine and L-ornithine.

关键词： Ring-closing metathesis L-Lysine L-Ornithine Allyl succinate Macrocycle

Design and Synthesis of Potential Macrocyclic Zinc Metalloprotease Inhibitors

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Chinese Journal of Chemistry 2006年第8期24卷 1080-1085页

作者：赵宝祥 SCHAUDT,Marco BLECHERT,siegfried Institute of Organic Chemistry School of Chemistry and Chemical Engineering Shandong University Jinan Shandong 250100 China Institutfiir Chemie Technische Universitat Berlin Strasse des 17. Juni 135 D-10623 Berlin Germany

A series of succinate-derived macrocyclic amides 1 were synthezized using ring-closing metathesis in the key step. The substrate scope includes rings of 11 to 14 members. The cyclic dicarboxylic acids 1 represent a family of new model compounds for potential zinc metalloprotease inhibitors. The metathesis precursors were provided by amide coupling of tert-butyl 3-carboxyhex-5-enoate 2 with numerous side chain alkenylated amino acid esters of general type 3 derived from L-tyrosine and L-cysteine.

关键词： metathesis macrocycle aminoacid derivative

Epiphytic orchids and their ecological niche under anthropogenic influence in central Himalayas,Nepal

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Journal of Mountain Science 2016年第5期13卷 774-784页

作者： ADHIKARI Yagya Prasad FISCHER Anton FISCHER Hagen siegfried Geobotany Department of Ecology and Ecosystem ManagementTechnische Universit?t München

The survival chance of epiphytie orchids today not only depends on the natural site conditions required by the orchids but also on anthropogenic changes in site conditions. This study answers two questions：（1） What is the ecological niche of the different epiphytic orchid species？（2） What are the ecological factors that threaten epiphytic orchid＇s population under anthropogenic disturbances？ Our study area was the Kathmandu valley, Nepal, with its subtropical forest. We established 156 systematically selected sampling points in the Kathmandu area covering different types of ecosystems under human impacts such as densely populated area, agricultural land, mixed agricultural and settled area, old tree patches, and a natural forest in a national park. The ecological niche of the orchid species was analyzed with a principal component analysis （PCA）. The correlations between the different site factors were statistically significant. Spearman＇s rank correlation matrices showed that the variables land-use intensities with altitude, and height with diameter in breast height （dbh） of host had the highest significant positive correlation coefficient （0.67 and 0.64 respectively）. On the other hand, host bark pH and altitude as well as land use had a significantly strong negative correlation coefficient （-0.80 and -0.61, respectively）. Different epiphytic orchid species interact differently with the given set of environmental factors： for occurrence of Vanda cristata there is no single environmental factor of special influence, while for Rhynehostylis retusa high bark pH and high light availability are important. First two axis of the PCA explained more than 50% of the total variance. Most orchid species occupy a specific, narrow niche in this ecological space. The main causes of anthropogenie influence of orchid population in the Kathmandu Valley are loss of adequate host trees （species and size） and increasing air pollution, resulting in increasing host bark pH.

关键词： Host characteristics Epiphytic orchids Anthropogenic disturbances Canopy ecosystem Ecological niche Himalayas

A Wavelet-Free Approach for Multiresolution-Based Grid Adaptation for Conservation Laws

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Communications on Applied Mathematics and Computation 2022年第1期4卷 108-142页

作者： Nils Gerhard siegfried Müller Aleksey Sikstel Institut für Geometrie und Praktische Mathematik RWTH AachenTemplergraben 55Aachen 52056Germany

In recent years the concept of multiresolution-based adaptive discontinuous Galerkin(DG)schemes for hyperbolic conservation laws has been *** key idea is to perform a multiresolution analysis of the DG solution using multiwavelets defined on a hierarchy of nested *** this concept is applied to dyadic grid hierarchies where the explicit construction of the multiwavelets has to be performed only for one reference *** non-uniform grid hierarchies multiwavelets have to be constructed for each element and,thus,becomes extremely *** overcome this problem a multiresolution analysis is developed that avoids the explicit construction of multiwavelets.

关键词： Discontinuous Galerkin Grid adaptivity Multiwavelets Multiresolution analysis Conservation laws

Micro-site Conditions of Epiphytic Orchids in a Human Impact Gradient in Kathmandu Valley, Nepal

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Journal of Mountain Science 2012年第3期9卷 331-342页

作者： Yagya Prasad ADHIKARI Anton FISCHER Hagen siegfried FISCHER Geobotany Department of Ecology and Ecosystem Management Technische Universitt München Hans-Carl-von-Carlowitz-Platz 2 D-85354 Freising Germany

We studied distribution and site conditions of epiphytic orchids in a gradient of human interference in Kathmandu valley, central Nepal. The aim was to understand the recent distribution pattern of epiphytic orchids, with respect to (i) the micro-site conditions and (ii) the type and intensity of land use. The occurrence of epiphytic orchids was recorded for a grid with 1.5 km cell size. The cells represent different types and intensities of human impact. Site factors such as bark rugosity, bark pH, diameter at breast height (dbh; 1.3 m) of host trees, exposure to wind and sunlight intensity were recorded. With regard to the species richness and abundance of epiphytic orchids, we compared different human impact categories from very strong human impact (settlement area) to very low human impact (national park). Remote sensing was used for a supervised classification of land cover. Ficus religiosa turned out to be the most important host species for orchids in urban areas, while Schima wallichii and Alnus nepalensis significantly host orchids in the other categories. Both species richness and abundance of epiphytic orchids were significantly higher under very low human impact (forest in national park) and also some remaining patches of primary forest than the other regions. Micro-climate is crucial for orchid populations. Host bark pH, bark rugosity, sunlight intensity and host exposure were significantly different for all human impact categories in order to harbour epiphytic orchid species. Habitats with a mixture of mature trees are suitable and essential for the conservation of viable populations of epiphytic orchids in settled areas. The study reveals that to improve the population size of orchids it is essential for future urban forestry to: (i) Protect old trees as carriers of existing epiphytic orchid diversity, (ii) protect medium old trees to ensure that they may become old trees, (iii) plant new host trees for the future, (iv) plant in groups instead of sing

关键词： Human impact Host tree Micro-climate Epiphytic orchids Remote sensing Conservation Nepal

Immunohistochemical study in dural arteriovenous fistula and possible role of ephrin-B2 for development of dural arteriovenous fistula

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Chinese Medical Journal 2004年第12期17卷 1815-1820页

作者：王宝隆卞留贯 Helmut Bertalanffy siegfried Bien Ulrich Sure Department of Neurosurgery Philipps University Marburg 35033 Germany Department of Neuroradiology Philipps University Marburg 35033 Germany

Background Although there were several clinical and experimental studies discussing the pathogenesis of dural arteriovenous fistula (DAVF), the pathological process leading to intracranial DAVF so far remains unknown In this study, we investigated the expression of vascular growth factors in order to elucidate the possible role of these factors for the development of DAVF and to study the biological activity of this uncommon lesion Methods We examined the histological features, proliferative and angiogenic capacities of the tissue specimens obtained from 6 patients who underwent surgery at our institution Immunohistochemical staining for vascular endothelial growth factor (VEGF), its receptors Flk 1 and Flt 1, ephrin B2, MIB 1 and proliferating cell nuclear antigen (PCNA) was performed using standard immunohistochemical techniques Results A positive immunostaining was found for all antibodies studied except MIB 1, whereas nuclear endothelial expression of PCNA was observed in only 3/6 cases VEGF stained positive in all of the available specimens (6/6) Flk 1 showed a positive immunoreaction in only 2/6 cases and Flt 1 in 4/6 cases Ephrin B2 was expressed in the majority (5/6) of the cases Conclusions These results support the hypothesis that DAVFs might be acquired dynamic vascular malformations with low biological activity Vascular growth factors like VEGF and ephrin B2 might play a pivotal role in the formation of DAVF

关键词： central nervous system vascular malformations · neovascularization pathologic · ephrin B2

Contemporaneous assembly of Western Gondwana and final Rodinia break-up:Implications for the supercontinent cycle

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Geoscience Frontiers 2017年第6期8卷 1431-1445页

作者： Sebastián Oriolo Pedro Oyhantcabal Klaus Wemmer siegfried Siegesmund Geoscience Center Georg-August-Universitat GottingenGoldschmidtstrae 337077 GottingenGermany Departamento de Geología Facultad de CienciasUniversidad de la RepúblicaMontevideoUruguay

Geological,geochronological and isotopic data are integrated in order to present a revised model for the Neoproterozoic evolution of Western *** the classical geodynamic scenario assumed for the period 800-700 Ma is related to Rodinia break-up and the consequent opening of major oceanic basins,a significantly different tectonic evolution can be inferred for most Western Gondwana *** cratons occupied a marginal position in the southern hemisphere with respect to Rodinia and recorded subduction with back-arc extension,island arc development and limited formation of oceanic crust in internal *** period was thus characterized by increased crustal growth in Western Gondwana,resulting from addition of juvenile continental crust along convergent *** contrast,crustal reworking and metacratonization were dominant during the subsequent assembly of *** Rio de la Plata,Congo-Sao Francisco,West African and Amazonian cratons collided at ca.630-600 Ma along the West Gondwana *** events overlap in time with the onset of the opening of the Iapetus Ocean at ca.610-600 Ma,which gave rise to the separation of Baltica,Laurentia and Amazonia and resulted from the final Rodinia *** East African/Antarctic Orogen recorded the subsequent amalgamation of Western and Eastern Gondwana after ca.580 Ma,contemporaneously with the beginning of subduction in the Terra Australis Orogen along the southern Gondwana ***,the Kalahari Craton was lately incorporated during the Late Ediacaran-Early *** proposed Gondwana evolution rules out the existence of Pannotia,as the final Gondwana amalgamation postdates latest connections between Laurentia and ***,a combination of introversion and extroversion is proposed for the assembly of *** contemporaneous record of final Rodinia break-up and Gondwana assembly has major implications for the supercontinent cycle,as supercontinent amalgamation and break-

关键词： Brasiliano-Pan-African Orogeny Neoproterozoic Collisional tectonics Pannotia Metacratonization Introversion-extroversion

NITROGEN FIXATION OF Azorhizobium IN ARTIFICIALLY INDUCED ROOT PARA-NODULES IN WHEAT

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Science China Chemistry 1992年第12期35卷 1463-1470页

作者：陈廷伟 siegfried SCHERER PETER BGER Soils and Fertilizer Institute Chinese Academy of Agriculiural SciencesBeijing 100081PRC Bacteriological Institute Faculty of Agriculture Technical University Munchen D-8050 Freising Germany Lehrstuhl für Physiologie und Biochemie der Pflanzen Universitat Konstanz D-7750 Konstanz Germany

Nodule-like structures (para-nodules) can be induced in wheat roots by low concentrationsof 2,4-dichlorophenoxyacetic acid (2,4-D), a synthetic analogue of the plant growth hor-mone indole-acetic acid. Growth of nodulated wheat plants was not affected by 2,4-D treat-ment. Infection of these?para-nodules by adding oxygen-tolerant Azorhizobium caulinodans isolat-ed from stem nodules of the tropical legume Sesbania rostrata resulted in massive prolifera-tion of bacterial cells in the intercellular spaces as well as inside the para-nodular ***-nodules colonized by Azorhizobium coulinodans not only reduced acetylene, but alsotransferred fixed nitrogen to the plant, contributing up to 16--23% of the nitrogen budgetof infected wheat.

关键词： Azorhizobium nitrogen fixation nodules wheat