10,468 Works

Shielding effectiveness of original and modified building materials

T. Frenzel, J. Stumpf & M. Koch
This contribution deals with the determination of the shielding effectiveness of building materials used for office, factory and government buildings. Besides the examination of standard materials, measurements were also performed on modified materials, e.g. ferro concrete with enhanced shielding effectiveness due to a changed mixture or structure of the reinforcement. The measurements of original and modified materials were carried out in a fully anechoic room (FAR) according to IEEE 299-1997 from 80 MHz up to...

The Complexity of Satisfiability for Fragments of CTL and CTL⋆

Arne Meier, Martin Mundhenk, Michael Thomas & Heribert Vollmer
The satisfiability problems for CTL and CTL⋆ are known to be EXPTIME-complete, resp. 2EXPTIME-complete (Fischer and Ladner (1979), Vardi and Stockmeyer (1985)). For fragments that use less temporal or propositional operators, the complexity may decrease. This paper undertakes a systematic study of satisfiability for CTL- and CTL⋆-formulae over restricted sets of propositional and temporal operators. We show that restricting the temporal operators yields satisfiability problems complete for 2EXPTIME, EXPTIME, PSPACE, and NP. Restricting the propositional...

Theoretical study of the electronic states of hollandite vanadate K 2V8O16

S. Horiuchi, T. Shirakawa & Y. Ohta
Electronic states of hollandite vanadate K2V8O 16, a one-dimensional zigzag-chain system of t2g orbitals in a mixed valent state, are considered. We calculate the Madelung energies to determine the most stable charge-ordering pattern that is consistent with the observed superlattice structure. We then develop the strong-coupling perturbation theory to derive the effective spin-orbit Hamiltonian, starting from the triply-degenerate t2g orbitals in the VO6 octahedral structure. An exact-diagonalization technique is used on small clusters of this...

Intake of Minerals from Food Supplements in a German Population - A Nationwide Survey

Janina Willers, Michaela Heinemann, Norman Bitterlich & Andreas Hahn
Introduction: Studies indicate that 17.9% - 60% of adults in Germany and Europe regularly use food supplements. Some reports suggest that their use might be responsible for excessive nutrient intake. The purpose of this survey was to examine the quantitative mineral intakes from food supplements: whether the tolerable upper intake levels (ULs) with supplements alone, or in combination with food was exceeded was checked. Methods: The survey was carried out by the Association for Consumer...

Investigation of the Transition Reaction of Tobermorite to Xonotlite under Influence of Additives

Andrea Hartmann, David Schulenberg & Josef-Christian Buhl
The objective of the present work was to investigate the transition reaction of the calcium silicate hydrate tobermorite into xonotlite under influence of additives. Tobermorite is the main binding agent in steam hardened building materials and the appearance of xonotlite indicates the progress of hardening and an overcuring of the material. Hydrothermal experiments under addition of sucrose, calcium formate and calcium chloride dihydrate to the main components quartz and lime were done using temperatures of...

Molecular Markers for Genetic Diversity Studies in African Leafy Vegetables

Emmanuel O. Omondi, Thomas Debener, Marcus Linde, Mary Abukutsa-Onyango, Fekadu F. Dinssa & Traud Winkelmann
African leafy vegetables are becoming important crops in tackling nutrition and food security in many parts of sub-Saharan Africa, since they provide important micronutrients and vitamins, and help resource-poor farm families bridge lean periods of food shortage. Genetic diversity studies are essential for crop improvement programmes as well as germplasm conservation efforts, and research on genetic diversity of these vegetables using molecular markers has been increasing over time. Diversity studies have evolved from the use...

Zeolite Synthesis under Insertion of Silica Rich Filtration Residues from Industrial Wastewater Reconditioning

Andrea Hartmann, V. Petrov, Josef-Christian Buhl, K. Rübner, M. Lindemann, C. Prinz & A. Zimathies
Zeolite synthesis was studied using two silica rich filtration residues (FR 1 and FR 2) as Si-source and sodium aluminate in a direct synthesis at 60°C at strong alkaline conditions (8 M - 16 M NaOH). In addition to these one-pot syntheses, a two-step process was investigated. Here, an alkaline digestion of FR at 60°C was followed by gel precipitation with sodium aluminate and gel crystallization under usual conditions of 80°C - 90°C. The results...

A three-enzyme-system to degrade curcumin to natural vanillin

Vida Esparan, Ulrich Krings, Marlene Struch & Ralf Günter Berger
The symmetrical structure of curcumin includes two 4-hydroxy-3-methoxyphenyl substructures. Laccase catalyzed formation of a phenol radical, radical migration and oxygen insertion at the benzylic positions can result in the formation of vanillin. As vanillin itself is a preferred phenolic substrate of laccases, the formation of vanillin oligomers and polymers is inevitable, once vanillin becomes liberated. To decelerate the oligomerization, one of the phenolic hydroxyl groups was protected via acetylation. Monoacetyl curcumin with an approximate molar...

Analysis and Design of Stimulus Response Curves of E. coli

Andreas Kremling, Anna Goehler, Knut Jahreis, Markus Nees, Benedikt Auerbach, Wolfgang Schmidt-Heck, Oznur Kokpinar, Robert Geffers, Ursula Rinas & Katja Bettenbrock
Metabolism and signalling are tightly coupled in bacteria. Combining several theoretical approaches, a core model is presented that describes transcriptional and allosteric control of glycolysis in Escherichia coli. Experimental data based on microarrays, signalling components and extracellular metabolites are used to estimate kinetic parameters. A newly designed strain was used that adjusts the incoming glucose flux into the system and allows a kinetic analysis. Based on the results, prediction for intracelluar metabolite concentrations over a...

Analysis and simulation of reduced FIR filters

Lj. Radic & Wolfgang Mathis
High order FIR filters employ model reduction techniques, in order to decrease power consumption and time delay. During reduction high order FIR filters are converted into low order IIR filters preserving stability and phase linearity as main features. Matlab simulations of an audio system with these reduced filters are presented. Furthermore, the influence of order on power consumption is discussed. © 2005 Copernicus GmbH.

Cohalogenation of Allyl and Vinylsilanes using Polymer-bound Haloate(I)-Reagents

Silvie Domann, Georgia Sourkouni-Argirusi, Nuria Merayo, Andreas Schönberger & Andreas Kirschning
Polymer-supported electrophilic halogenate(I) complexes 2 and 3 promote smooth addition to vinyl and allylsilanes without loss of the silyl group. In conjunction with Amberlyst A26 (OH− -form) vinyl silanes are converted into epoxysilanes.

Design and analysis of fully integrated differential VCOs

M. Prochaska, A. Belski & Wolfgang Mathis
Oscillators play a decisive role for electronic equipment in many fields-like communication, navigation or data processing. Especially oscillators are key building blocks in integrated transceivers for wired and wireless communication systems. In this context the study of fully integrated differential VCOs has received attention. In this paper we present an analytic analysis of the steady state oscillation of integrated differential VCOs which is based on a nonlinear model of the oscillator. The outcomes of this...

Dispersion scenarios for pollution release in an occupied underground station - a numerical study with a micro-scale and a multi-Agent model

Günter Gross
The release of hazardous material in a subway station is a dangerous situation for passengers and staff. To achieve an acceptable level of risk, a correct marking of emergency exits and escape routes is essential., For this purpose, underground air dispersion, which depends on source characteristics, the construction layout of the station, and meteorological conditions, must be known. In this paper a micro-scale wind model is combined with a dispersion model to calculate the spread...

Transmission characteristics of a TEM waveguide for transient signals by the use of a damped sinusoidal

Niklas Briest, Heyno Garbe & Stefan Potthast
This article broaches the issue of the propagation of transient signals in gigahertz transverse electromagnetic (GTEM) cells. As a representative for transient signals a damped sinusoidal (DS) is used with three different mid-band frequencies. The signal transmission of the DS in the GTEM1250 is qualified and discussed on the basis of the Pearson correlation coefficient (Pcc). The Pcc gives an overview of the signal transmission quality for all measuring points within the testvolume and signal...

Impedance spectra classification for determining the state of charge on a lithium iron phosphate cell using a support vector machine

P. Jansen, D. Vergossen, D. Renner, Werner John & J. Götze
An alternative method for determining the state of charge (SOC) on lithium iron phosphate cells by impedance spectra classification is given. Methods based on the electric equivalent circuit diagram (ECD), such as the Kalman Filter, the extended Kalman Filter and the state space observer, for instance, have reached their limits for this cell chemistry. The new method resigns on the open circuit voltage curve and the parameters for the electric ECD. Impedance spectra classification is...

Influence of turbulence on the drop growth in warm clouds, Part II: Sensitivity studies with a spectral bin microphysics and a Lagrangian cloud model

Theres Riechelmann, Ulrike Wacker, Klaus D. Beheng, Dieter Etling & Siegfried Raasch
Raindrops in warm clouds grow faster than predicted by classical cloud models. One of the possible reasons for this discrepancy is the influence of cloud turbulence on the coagulation process. In Part I (Siewert et al., 2014) of this paper series, a turbulent collision kernel has been derived from wind tunnel experiments and direct numerical simulations (DNS). Here we use this new collision kernel to investigate the influence of turbulence on coagulation and rain formation...

Numerical modelling of nonlinear electromechanical coupling of an atomic force microscope with finite element method

J. Freitag & Wolfgang Mathis
In this contribution, an atomic force microscope is modelled and in this context, a non-linear coupled 3-D-boundary value problem is solved numerically using the finite element method. The coupling of this system is done by using the Maxwell stress tensor. In general, an iterative weak coupling is used, where the two physical problems are solved separately. However, this method does not necessarily guarantee convergence of the nonlinear computation. Hence, this contribution shows the possibility of...

Recent Developments of Magnetoresistive Sensors for Industrial Applications

Lisa Jogschies, Daniel Klaas, Rahel Kruppe, Johannes Rittinger, Piriya Taptimthong, Anja Wienecke, Lutz Rissing & Marc Christopher Wurz
The research and development in the field of magnetoresistive sensors has played an important role in the last few decades. Here, the authors give an introduction to the fundamentals of the anisotropic magnetoresistive (AMR) and the giant magnetoresistive (GMR) effect as well as an overview of various types of sensors in industrial applications. In addition, the authors present their recent work in this field, ranging from sensor systems fabricated on traditional substrate materials like silicon...

The Impact of Photobleaching on Microarray Analysis

Marcel Von Der Haar, John-Alexander Preuss, Kathrin Von Der Haar, Patrick Lindner, Thomas Scheper & Frank Stahl
DNA-Microarrays have become a potent technology for high-throughput analysis of genetic regulation. However, the wide dynamic range of signal intensities of fluorophore-based microarrays exceeds the dynamic range of a single array scan by far, thus limiting the key benefit of microarray technology: parallelization. The implementation of multi-scan techniques represents a promising approach to overcome these limitations. These techniques are, in turn, limited by the fluorophores' susceptibility to photobleaching when exposed to the scanner's laser light....

Auxiliary superfields in N=1 supersymmetric self-dual electrodynamics

Evgeny Ivanov, Olaf Lechtenfeld & Boris Zupnik
We construct the general formulation of N = 1 supersymmetric self-dual abelian gauge theory involving auxiliary chiral spinor superfields. Self-duality in this context is just U(N) invariance of the nonlinear interaction of the auxiliary superfields. Focusing on the U(1) case, we present the most general form of the U(1) invariant auxiliary interaction, consider a few instructive examples and show how to generate self-dual N = 1 models with higher derivatives in this approach.

Benefit Transfer for Water Management along the Han River in South Korea Using Meta-Regression Analysis

Hio-Jung Shin, Hyun No Kim, Chul-Hyun Jeon, Min-Woo Jo, Trung Thanh Nguyen & John Tenhunen
This study estimates the magnitude of economic benefits that are justified in transfer from downstream users to upstream users for the use of the Han River in South Korea in terms of foregone economic benefits by regulations. Based on the existing non-market valuation studies associated with water management issues in South Korea from 1997 to 2014, a meta-regression analysis was performed to provide alternatives for regional benefit sharing of water resource use. The benefits from...

Comparison of Selective Laser Melted Titanium and Magnesium Implants Coated with PCL

Julia Matena, Svea Petersen, Matthias Gieseke, Michael Teske, Martin Beyerbach, Andreas Kampmann, Hugo Murua Escobar, Nils-Claudius Gellrich, Heinz Haferkamp & Ingo Nolte
Degradable implant material for bone remodeling that corresponds to the physiological stability of bone has still not been developed. Promising degradable materials with good mechanical properties are magnesium and magnesium alloys. However, excessive gas production due to corrosion can lower the biocompatibility. In the present study we used the polymer coating polycaprolactone (PCL), intended to lower the corrosion rate of magnesium. Additionally, improvement of implant geometry can increase bone remodeling. Porous structures are known to...

Conductance through single biphenyl molecules: symmetric and asymmetric coupling to electrodes

Karthiga Kanthasamy & Herbert Pfnür
The contacts and the chemical bonds formed between metallic electrodes and molecules determine to a large extent the conductive properties of single molecular junctions, which represent the smallest possible active elements in an electronic circuit. We therefore investigated in a comparative study, using the break junction technique (MCBJ), the conductive properties of [1,1'-biphenyl]-4,4'-dithiol (M1) and of 4'-mercapto-[1,1'-biphenyl]-4-carbonitrile (M2) between gold electrodes. As a function of electrode separation, characterized by the conductance close to 0 V,...

Herbaceous Legume Encroachment Reduces Grass Productivity and Density in Arid Rangelands

Thomas C. Wagner, Susanne Hane, Dave F. Joubert & Christina Fischer
Worldwide savannas and arid grasslands are mainly used for livestock grazing, providing livelihood to over a billion people. While normally dominated by perennial C-4 grasses, these rangelands are increasingly affected by the massive spread of native, mainly woody legumes. The consequences are often a repression of grass cover and productivity, leading to a reduced carrying capacity. While such encroachment by woody plants has been extensively researched, studies on similar processes involving herbaceous species are rare....

Local determination of the amount of integration of an atom into a crystal surface

K. Volgmann, H. Gawronski, C. Zaum, G.G. Rusina, S.D. Borisova, E.V. Chulkov & K. Morgenstern
Collective vibrational modes of crystal lattices, called phonons, determine fundamental material properties, such as their thermal and electrical conductivities. Bulk phonon spectra are influenced by point defects. More recently, the importance of phonons on nanostructures has come into the focus of attention. Here we show a spatially resolved phonon spectra of point defects that reveal distinctly different signatures for a cavity alone and an impurity atom fully integrated into the surface as opposed to one...

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