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To this date, it is difficult to find high-level statistics on YouTube that paint a fair picture of the platform in its entirety. This study attempts to provide an overall characterization of YouTube, based on a random sample of channel and video data, by showing how video provision and consumption evolved over the course of the past 10 years. It demonstrates stark contrasts between video genres in terms of channels, uploads and views, and that a vast majority of on average 85% of all views goes to a small minority of 3% of all channels. The analytical results give evidence that older channels have a significantly higher probability to garner a large viewership, but also show that there has always been a small chance for young channels to become successful quickly, depending on whether they choose their genre wisely.
In this paper, the temperature dependent cyclic mechanical properties of the martensitic hot work tool steel 1.2367 after tempering are investigated. To this end, hardness measurements as well as monotonic and cyclic tests at temperatures in the range from room temperature to 650 °C are performed on material tempered for different tempering times and temperatures. To describe the observed time and temperature dependent softening during tempering a kinetic model for the evolution of the mean size of secondary carbides based on Ostwald ripening is developed. Furthermore, mechanism-based as well as phenomenological relations for the cyclic mechanical properties of the Ramberg-Osgood model depending on carbide size and temperature are introduced. A good overall agreement of the measured and the calculated stress-strain hysteresis loops for different temperatures and heat treatments is obtained using the determined material properties of the kinetic and mechanical model.
Techno-economic comparison of membrane distillation and MVC in a zero liquid discharge application
(2018)
Membrane distillation (MD) is a thermally driven membrane process for the separation of vapour from a liquid stream through a hydrophobic, microporous membrane. However, a commercial breakthrough on a large scale has not been achieved so far. Specific developments on MD technology are required to adapt the technology for applications in which its properties can potentially outshine state of the art technologies such as standard evaporation. In order to drive these developments in a focused manner, firstly it must be shown that MD can be economically attractive in comparison to state of the art systems. Thus, this work presents a technological design and economic analysis for AGMD and v-AGMD for application in a zero liquid discharge (ZLD) process chain and compares it to the costs of mechanical vapour compression (MVC) for the same application. The results show that MD can potentially be ~40% more cost effective than MVC for a system capacity of 100 m3/day feed water, and up to ~75% more cost effective if the MD is driven with free waste heat.
Quantification of astaxanthin in salmons by chemiluminescence and absorption after TLC separation
(2018)
Astaxanthin is a keto-carotenoid, belongs to the chemical class of terpenes and is a yellow lipid soluble compound. The compound is present in marine animals like salmons and crustacean. Its colour is due to conjugated double bonds and these double bonds are responsible for its antioxidant effect. Its antioxidant activity is ten times stronger than other carotenoids and nearly 500 fold stronger than vitamin-E. We present a new thin layer chromatography (TLC) method to measure astaxanthin on TLC-plates (Merck, 1.05554) in the visible absorption range as well as by using chemiluminescence. For separation a solvent mixture of cyclohexane and acetone (10 + 2.4, v/v) was used. The RF-value of astaxanthin is 0.14.The limit of detection in vis-absorption is 64 ng / band and the limit of quantification is 92 ng/band. In chemiluminescence the values are 90 ng / band and 115 ng/band. The method offers two independently working measurement modes on a single plate which increase the accuracy of the quantification.
Cardiac contractility modulation (CCM) is a device-based therapy for the treatment of systolic left ventricular chronic heart failure. Unlike other device-based therapies for heart failure, CCM delivers non-excitatory pacing signals to the myocardium. This leads to an extension of the action potential and to an improved contractility of the heart. The modeling and simulation was done with the electromagnetic simulation software CST. Three CCM electrodes were inserted into the Offenburg heart rhythm model and subsequently simulated the electric field propagation in CCM therapy.
In addition, simulations of CCM have been performed with electrodes from other device-based therapies, such as cardiac resynchronization therapy (CRT) and implantable cardioverter / defibrillator (ICD) therapy. At the same distance to the simulation electrode, the electric field is slightly stronger in CCM therapy than in CCM therapy with additionally implanted CRT or ICD electrodes. In addition, there is a change in the electric field propagation at the electrodes of the CRT and the shock electrode of the ICD.
By simulating several different therapy procedures on the heart, it is possible to check how they affect their behavior during normal operation. CCM heart rhythm model simulation allows the evaluation the individual electrical pacing and sensing field during CCM.
On the Fundamental and Practical Aspects of Modeling Complex Electrochemical Kinetics and Transport
(2018)
Numerous technologies, such as batteries and fuel cells, depend on electrochemical kinetics. In some cases, the responsible electrochemistry and charged-species transport is complex. However, to date, there are essentially no general-purpose modeling capabilities that facilitate the incorporation of thermodynamic, kinetic, and transport complexities into the simulation of electrochemical processes. A vast majority of the modeling literature uses only a few (often only one) global charge-transfer reactions, with the rates expressed using Butler–Volmer approximations. The objective of the present paper is to identify common aspects of electrochemistry, seeking a foundational basis for designing and implementing software with general applicability across a wide range of materials sets and applications. The development of new technologies should be accelerated and improved by enabling the incorporation of electrochemical complexity (e.g., multi-step, elementary charge-transfer reactions and as well as supporting ionic and electronic transport) into the analysis and interpretation of scientific results. The spirit of the approach is analogous to the role that Chemkin has played in homogeneous chemistry modeling, especially combustion. The Cantera software, which already has some electrochemistry capabilities, forms the foundation for future capabilities expansion.
For an elastic medium containing a homogeneous distribution of micro-cracks, an effective one-dimensional stress-strain relation has been determined with finite element simulations. In addition to flat micro-cracks, voids were considered that contain a Hertzian contact, which represents an example for micro-cracks with internal structure. The orientation of both types of micro-cracks was fully aligned or, for flat micro-cracks, totally random. For micro-cracks with Hertzian contacts, the case of random orientation was treated in an approximate way. The two types of defects were found to give rise to different degrees of non-analytic behavior of the effective stress-strain relation, which governs the nonlinear propagation of symmetric (S0) Lamb waves in the long-wavelength limit. The presence of flat micro-cracks causes even harmonics to grow linearly with propagation distance with amplitudes proportional to the amplitude of the fundamental wave, and gives rise to a static strain. The presence of the second type of defects leads to a linear growth of all harmonics with amplitudes proportional to the power 3/2 of the fundamental amplitude, and to a strain-dependent velocity shift. Simple expressions are given for the growth rates of higher harmonics of S0 Lamb waves in terms of the parameters occurring in the effective stress-strain relation. They have partly been determined quantitatively with the help of the FEM results for different micro-crack concentrations.
The authors claim that location information of stationary ICT components can never be unclassified. They describe how swarm-mapping crowd sourcing is used by Apple and Google to worldwide harvest geo-location information on wireless access points and mobile telecommunication systems' base stations to build up gigantic databases with very exclusive access rights. After having highlighted the known technical facts, in the speculative part of this article, the authors argue how this may impact cyber deterrence strategies of states and alliances understanding the cyberspace as another domain of geostrategic relevance. The states and alliances spectrum of activities due to the potential existence of such databases may range from geopolitical negotiations by institutions understanding international affairs as their core business, mitigation approaches at a technical level, over means of cyber deterrence-by-retaliation.
One of the bottlenecks hindering the usage of polymer electrolyte membrane fuel cell technology in automotive applications is the highly load-sensitive degradation of the cell components. The cell failure cases reported in the literature show localized cell component degradation, mainly caused by flow-field dependent non-uniform distribution of reactants. The existing methodologies for diagnostics of localized cell failure are either invasive or require sophisticated and expensive apparatus. In this study, with the help of a multiscale simulation framework, a single polymer electrolyte membrane fuel cell (PEMFC) model is exposed to a standardized drive cycle provided by a system model of a fuel cell car. A 2D multiphysics model of the PEMFC is used to investigate catalyst degradation due to spatio-temporal variations in the fuel cell state variables under the highly transient load cycles. A three-step (extraction, oxidation, and dissolution) model of platinum loss in the cathode catalyst layer is used to investigate the cell performance degradation due to the consequent reduction in the electro-chemical active surface area (ECSA). By using a time-upscaling methodology, we present a comparative prediction of cell end-of-life (EOL) under different driving behavior of New European Driving Cycle (NEDC) and Worldwide Harmonized Light Vehicles Test Cycle (WLTC).
We present a planar chromatographic separation method for the phytoestrogenic active compound equol, separated on RP-18 W (Merck, 1.14296) phase. It could be shown that an ethanolic cattle manure extract contains this phytoestrogenic active compound to a larger amount. As solvents for the mobile phase, hexane, ethyl acetate, and acetone (45:15:10, v/v); acetone and water (15:10, v/v); and n-hexane, CH2Cl2, ethyl acetate, methanol, and formic acid (40:40:20:5:1, v/v) have been used. After separation, a modified yeast estrogen screen (YES) test was applied, using the yeast strain Saccharomyces cerevisiae BJ3505 containing an estrogen receptor. Its activation by equol induces the reporter gene lacZ which encodes the enzyme β-galactosidase. The enzyme activity is measured directly on the TLC plate by using the substrate MUG (4-methylumbelliferyl-β-d-galactopyranoside) or the substrate X-β-Gal (5-bromo-4-chloro-3-indoxyl-β-d-galactopyranoside). β-Galactosidase cleaves MUG into a fluorescing compound. X-β- Gal is also hydrolyzed and then oxidized by oxygen forming the deep-blue dye 5,5′-dibromo-4,4′-dichloro-indigo. Both reactions in combination with a thin-layer chromatography (TLC) separation allow very specific detecting of equol in cattle manure, although that is a very challenging matrix. Preliminary results show that the average content of equol in liquid manure is roughly 60 μg g−1. The value for urine is 50 μg mL−1.
Nonlinearity can give rise to intermodulation distortions in surface acoustic wave (SAW) devices operating at high input power levels. To understand such undesired effects, a finite element method (FEM) simulation model in combination with a perturbation theory is applied to find out the role of different materials and higher order nonlinear tensor data for the nonlinearities in such acoustic devices. At high power, the SAW devices containing metal, piezoelectric substrate, and temperature compensating (TC) layers are subject to complicated geometrical, material, and other nonlinearities. In this paper, third-order nonlinearities in TC-SAW devices are investigated. The materials used are LiNbO 3 -rot128YX as the substrate and copper electrodes covered with a SiO 2 film as the TC layer. An effective nonlinearity constant for a given system is determined by comparison of nonlinear P-matrix simulations to third-order intermodulation measurements of test filters in a first step. By employing these constants from different systems, i.e., different metallization ratios, in nonlinear periodic P-matrix simulations, a direct comparison to nonlinear periodic FEM-simulations yields scaling factors for the materials used. Thus, the contribution of the different materials to the nonlinear behavior of TC-SAW devices is obtained and the role of metal electrodes, substrate, and TC film are discussed in detail.
Numerous 2,5-dimethoxy-N-benzylphenethylamines (NBOMe), carrying a variety of lipophilic substituents at the 4-position, are potent agonists at 5-hydroxytryptamine (5HT2A ) receptors and show hallucinogenic effects. The present study investigated the metabolism of 25D-NBOMe, 25E-NBOMe, and 25N-NBOMe using the microsomal model of pooled human liver microsomes (pHLM) and the microbial model of the fungi Cunninghamella elegans (C. elegans). Identification of metabolites was performed using liquid chromatography-high resolution-tandem mass spectrometry (LC-HR-MS/MS) with a quadrupole time-of-flight (QqToF) instrument. In total, 36 25D-NBOMe phase I metabolites, 26 25E-NBOMe phase I metabolites and 24 25N-NBOMe phase I metabolites were detected and identified in pHLM. Furthermore, 14 metabolites of 25D-NBOMe, 11 25E-NBOMe metabolites, and nine 25N-NBOMe metabolites could be found in C. elegans. The main biotransformation steps observed were oxidative deamination, oxidative N-dealkylation also in combination with hydroxylation, oxidative O-demethylation possibly combined with hydroxylation, oxidation of secondary alcohols, mono- and dihydroxylation, oxidation of primary alcohols, and carboxylation of primary alcohols. Additionally, oxidative di-O-demethylation for 25E-NBOMe and reduction of the aromatic nitro group and N-acetylation of the primary aromatic amine for 25N-NBOMe took place. The resulting 25N-NBOMe metabolites were unique for NBOMe compounds. For all NBOMes investigated, the corresponding 2,5-dimethoxyphenethylamine (2C-X) metabolite was detected. This study reports for the first time 25X-NBOMe N-oxide metabolites and hydroxylamine metabolites, which were identified for 25D-NBOMe and 25N-NBOMe and all three investigated NBOMes, respectively. C. elegans was capable of generating all main biotransformation steps observed in pHLM and might therefore be an interesting model for further studies of new psychoactive substances (NPS) metabolism.
Various methods of Digital Manufacturing (DM) have been available for the manufacturing of physical architectural models for several years. This paper highlights the advantages of 3D printing for digital manufacturing of detailed architectural models. In particular, the representation of architectural details and textures is treated. Furthermore, two new methods are being developed in order to improve the conditions for the application of digital manufacturing of architectural models.
In the 19th century Alexander von Humboldt explored the nature and was conceived a new vision of nature that still influences the way we understand the new world. Humboldt believed in the importance of accurate measurements and precise description of observations. His vision of nature included not only facts but also emotions.
Nowadays smart solutions will be developed by using computer technology, which will influence our relationship to nature, our handling of the complexity and diversity of nature itself and the technological influences on the society. Could we avoid a new form of “Colonialism”, when a network of super computers will create a smarter world?