653 results on '"A. Waag"'
Search Results
2. Back-compatible Color QR Codes for colorimetric applications
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Benito-Altamirano, Ismael, primary, Martínez-Carpena, David, additional, Casals, Olga, additional, Fábrega, Cristian, additional, Waag, Andreas, additional, and Prades, Joan Daniel, additional
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- 2023
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3. P12-27 THP-1 cells as a suitable screening tool for NLRP3 inflammasome activation applied to micro- and nanoplastics
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Busch, M., primary, Bredeck, G., additional, Waag, F., additional, Rahimi, K., additional, Ramachandran, H., additional, Bessel, T., additional, Barcikowski, S., additional, Herrmann, A., additional, Rossi, A., additional, and Schins, R., additional
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- 2022
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4. P12-27 THP-1 cells as a suitable screening tool for NLRP3 inflammasome activation applied to micro- and nanoplastics
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M. Busch, G. Bredeck, F. Waag, K. Rahimi, H. Ramachandran, T. Bessel, S. Barcikowski, A. Herrmann, A. Rossi, and R. Schins
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General Medicine ,Toxicology - Published
- 2022
5. Chronic adolescent stress increases exploratory behavior but does not appear to change the acute stress response in adult male C57BL/6 mice
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Sturman, Oliver, primary, von Ziegler, Lukas, additional, Privitera, Mattia, additional, Waag, Rebecca, additional, Duss, Sian, additional, Vermeiren, Yannick, additional, Giovagnoli, Letizia, additional, de Deyn, Peter, additional, and Bohacek, Johannes, additional
- Published
- 2021
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6. Electron beam lithography for contacting single nanowires on non-flat suspended substrates
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Albert Romano-Rodriguez, Isabel Gràcia, Juan Daniel Prades, Xavier Borrisé, Andreas Waag, Carles Cané, Guillem Domènech-Gil, Jordi Samà, Frederik Steib, Sven Barth, and Universitat de Barcelona
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Materials science ,Fabrication ,Nanowire ,02 engineering and technology ,Substrate (electronics) ,010402 general chemistry ,01 natural sciences ,Focused ion beam ,Nanomaterials ,Nanosensor ,Materials Chemistry ,Electrical and Electronic Engineering ,Instrumentation ,Resistive touchscreen ,Feixos electrònics ,Nanoestructures ,business.industry ,Metals and Alloys ,Electron beams ,Gas detectors ,Detectors de gasos ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Nanostructures ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Optoelectronics ,0210 nano-technology ,business ,Electron-beam lithography - Abstract
A methodology based on the use of Electron Beam Lithography for contacting individual nanowires on top of non-flat micromembranes and microhotplates has been implemented, and the practical details have been exhaustively described. The different fabrication steps have been adapted to the substrate’s topology, requiring specific holders and conditions. The methodology is demonstrated on individual SnO2 nanowires, which, after fabrication, have been characterized as functional resistive gas nanosensors towards NH3 and benchmarked against similar devices fabricated using more conventional Dual Beam Focused Ion Beam techniques, demonstrating the superior properties of the here presented methodology, which can be further extended to other non-conventional suspended substrates and nanomaterials.
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- 2019
7. Ablation target cooling by maximizing the nanoparticle productivity in laser synthesis of colloids
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Friedrich Waag, Bilal Gökce, and Stephan Barcikowski
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Materials science ,Water flow ,medicine.medical_treatment ,Chemie ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Fluence ,law.invention ,law ,medicine ,Laser ablation ,business.industry ,Surfaces and Interfaces ,General Chemistry ,Dissipation ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Laser ,Ablation ,0104 chemical sciences ,Surfaces, Coatings and Films ,Heat generation ,Optoelectronics ,0210 nano-technology ,business ,Thermal energy - Abstract
Even if ultrashort laser pulses are used during the laser synthesis of colloids, a significant amount of laser energy is converted into thermal energy, which results in heating the ablation target and the colloid. To date, little attention has been paid to these heating effects in the literature. This study was focused on measurements of the process temperature during the high-power, ultrashort-pulsed laser ablation of a nickel target in a continuous water flow setup. Time-resolved monitoring of the temperature of the ablation target and of the colloid indicated that there was an initial rapid uptake of thermal energy followed by a thermally-stable state in which there was very little additional heating. Shifting the focal plane from behind the target onto its surface and further into the fluid provided insight concerning the different mechanisms of heat generation, dissipation, and transfer in the laser synthesis of colloids. It even was possible to distinguish the fluence effects and the colloid re-irradiation effects. New possibilities of process control were identified by correlating the productivity of laser ablation at different focal plane shifts with the measured thermal data. Counterintuitively, the temperature of the target was minimized via ablation cooling when the productivity of the process was maximized.
- Published
- 2019
8. Thermal performance analysis of GaN nanowire and fin-shaped power transistors based on self-consistent electrothermal simulations
- Author
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Kristian Frank, Muhammad Fahlesa Fatahilah, Friedhard Römer, Hutomo Suryo Wasisto, Feng Yu, Klaas Strempel, Bernd Witzigmann, Andreas Waag, and Hamed Kamrani
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Materials science ,Nanowire ,02 engineering and technology ,Substrate (electronics) ,01 natural sciences ,law.invention ,Fin (extended surface) ,law ,0103 physical sciences ,Thermal ,Power semiconductor device ,Electrical and Electronic Engineering ,Safety, Risk, Reliability and Quality ,Sheet resistance ,010302 applied physics ,business.industry ,Transistor ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Heat flux ,Optoelectronics ,0210 nano-technology ,business - Abstract
We present self-consistent electrothermal simulations of the GaN nanowire-based field-effect transistor (NWFET) and vertical fin field-effect transistor (FinFET) by taking into account all major heat flux paths. Simulation results of a NWFET validated by experimental data are compared to the results of a vertical FinFET designed with same sizes that ensures a fair comparison of their thermal performance. It is found that the peak temperature in the NWFET is close to the uppermost contact, which facilitates heat removal from top. As a result, NWFETs have the potential to achieve a higher power density at a temperature limit compared with the FinFETs, especially when the heat removal from the top contact is eased. The impact of the thermal surface resistance of the top contact and substrate thinning on the thermal performance of these two vertical structures is also investigated.
- Published
- 2018
9. Comparison of three non-human primate aerosol models for glanders, caused by Burkholderia mallei
- Author
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Waag, David M., primary, Chance, Taylor B., additional, Trevino, Sylvia R., additional, Rossi, Franco D., additional, Fetterer, David P., additional, Amemiya, Kei, additional, Dankmeyer, Jennifer L., additional, Ingavale, Susham S., additional, Tobery, Steven A., additional, Zeng, Xiankun, additional, Kern, Steven J., additional, Worsham, Patricia L., additional, Cote, Christopher K., additional, and Welkos, Susan L., additional
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- 2021
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10. The Acute Stress Response in the Multiomic Era
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Floriou-Servou, Amalia, primary, von Ziegler, Lukas, additional, Waag, Rebecca, additional, Schläppi, Christa, additional, Germain, Pierre-Luc, additional, and Bohacek, Johannes, additional
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- 2021
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11. Attack rates amongst household members of outpatients with confirmed COVID-19 in Bergen, Norway: A case-ascertained study
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Kuwelker, Kanika, primary, Zhou, Fan, additional, Blomberg, Bjørn, additional, Lartey, Sarah, additional, Brokstad, Karl Albert, additional, Trieu, Mai Chi, additional, Bansal, Amit, additional, Madsen, Anders, additional, Krammer, Florian, additional, Mohn, Kristin GI, additional, Tøndel, Camilla, additional, Linchausen, Dagrunn Waag, additional, Cox, Rebecca J., additional, Langeland, Nina, additional, Corydon, Annette, additional, Real, Francisco, additional, Bredholt, Geir, additional, Bartsch, Hauke, additional, Sandnes, Helene Heitmann, additional, Vahokoski, Juha, additional, Jacobsen, Kjerstin, additional, Eidsheim, Marianne, additional, Sævik, Marianne, additional, Ertesvåg, Nina Urke, additional, Hauge, Synnøve Ygre, additional, and Onyango, Therese Bredholt, additional
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- 2021
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12. Seroconversion in household members of COVID-19 outpatients
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Cox, Rebecca J, primary, Brokstad, Karl A, additional, Krammer, Florian, additional, Langeland, Nina, additional, Blomberg, Bjørn, additional, Kuwelker, Kanika, additional, Lartey, Sarah, additional, Linchausen, Dagrun Waag, additional, Mohn, Kristin GI, additional, Real, Francisco Gomez, additional, Bansal, Amit, additional, Bredholt, Geir, additional, Madsen, Anders, additional, Onanygo, Therese Bredholt, additional, Trieu, Mai Chi, additional, Vahokoski, Juha, additional, and Zhou, Fan, additional
- Published
- 2021
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13. Performance analysis and simulation of vertical gallium nitride nanowire transistors
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Andreas Waag, Kristian Frank, Feng Yu, Bernd Witzigmann, Klaas Strempel, Hans Werner Schumacher, Friedhard Römer, Hutomo Suryo Wasisto, and Muhammad Fahlesa Fatahilah
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Materials science ,Transconductance ,Nanowire ,Gallium nitride ,02 engineering and technology ,01 natural sciences ,law.invention ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,law ,Saturation current ,0103 physical sciences ,Materials Chemistry ,Electrical and Electronic Engineering ,Saturation (magnetic) ,010302 applied physics ,business.industry ,Transistor ,Doping ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Threshold voltage ,chemistry ,Optoelectronics ,0210 nano-technology ,business - Abstract
Gallium nitride (GaN) nanowire transistors are analyzed using hydrodynamic simulation. Both p-body and n-body devices are compared in terms of threshold voltage, saturation behavior and transconductance. The calculations are calibrated using experimental data. The threshold voltage can be tuned from enhancement to depletion mode with wire doping. Surface states cause a shift of threshold voltage and saturation current. The saturation current depends on the gate design, with a composite gate acting as field plate in the p-body device.
- Published
- 2018
14. Fabrication and characterization of single-pair thermoelectric generators of bismuth telluride using silver-sintering technology
- Author
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Wenze Wu, Andreas Waag, Erwin Peiner, and Abdelhamid Bentaleb
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Interconnection ,Fabrication ,Materials science ,020209 energy ,Pellets ,chemistry.chemical_element ,Sintering ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Copper ,Nickel ,chemistry.chemical_compound ,Thermoelectric generator ,chemistry ,0202 electrical engineering, electronic engineering, information engineering ,Bismuth telluride ,Composite material ,0210 nano-technology - Abstract
Silver sintering technology was investigated as a method for interconnect formation of thermoelectric generators (TEGs). Using silver sintering we were able to assemble commercial bismuth telluride pellets and copper legs to fabricate TEGs, which are designed to work at elevated temperatures. Nickel was deposited electroless for 30, 60, and 90 minutes on the bismuth telluride pellets to serve as an anti-diffusion barrier between Ag and Bi2Te3. The impact of different fabrication conditions (i.e. sintering temperatures from 210 to 265°C and pressures from 5 to 7 MPa, respectively) on the properties of single-pair TEGs was investigated. Lowest specific contact resistances of (5.07 ± 3.00) × 10-5 Ω·cm2 were obtained which agree well with state of the art for soldered contacts of bismuth telluride. With TEGs sintered at 6 MPa and 265°C long-term operation tests were performed at temperature gradients across the TEG of 190°C for 360 hours. The Seebeck power remained unchanged showing values around 0.3 mV/K, which slightly depended on the anti-diffusion-layer thickness.
- Published
- 2018
15. Use of recycled materials as mid layer in three layered structures-new possibility in design for recycling
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Radusin, Tanja, primary, Nilsen, Jorunn, additional, Larsen, Sondre, additional, Annfinsen, Steffen, additional, Waag, Charlotte, additional, Eikeland, Marianne Sørflaten, additional, Pettersen, Marit Kvalvåg, additional, and Fredriksen, Siw Bodil, additional
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- 2020
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16. Femtosecond-laser induced two-photon absorption of GaN and AlxGa1-xN thin films: Tuning the nonlinear optical response by alloying and doping
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Vivas, M.G., primary, Manoel, D.S., additional, Dipold, J., additional, Martins, R.J., additional, Fonseca, R.D., additional, Manglano-Clavero, I., additional, Margenfeld, C., additional, Waag, A., additional, Voss, T., additional, and Mendonca, C.R., additional
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- 2020
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17. The effect of downstream laser fragmentation on the specific surface area and photoelectrochemical performance of barium tantalum oxynitride
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Haydous, Fatima, primary, Waag, Friedrich, additional, Si, Wenping, additional, Li, Fei, additional, Barcikowski, Stephan, additional, Gökce, Bilal, additional, and Lippert, Thomas, additional
- Published
- 2020
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18. The influence of drying and calcination on surface chemistry, pore structure and mechanical properties of hierarchically organized porous silica monoliths
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Putz, Florian, primary, Waag, Anna, additional, Balzer, Christian, additional, Braxmeier, Stephan, additional, Elsaesser, Michael S., additional, Ludescher, Lukas, additional, Paris, Oskar, additional, Malfait, Wim J., additional, Reichenauer, Gudrun, additional, and Hüsing, Nicola, additional
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- 2019
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19. Study of 3D-growth conditions for selective area MOVPE of high aspect ratio GaN fins with non-polar vertical sidewalls
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Tansen Varghese, Johannes Ledig, Frederik Steib, Martin Dr. Straßburg, Adrian Stefan Avramescu, Lars Nicolai, Achim Trampert, Andreas Waag, Hergo-Heinrich Wehmann, Tilman Schimpke, Hans-Jürgen Lugauer, Hao Zhou, Jana Hartmann, and Sönke Fündling
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010302 applied physics ,Materials science ,Fin ,business.industry ,One-Step ,Heterojunction ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Laser ,01 natural sciences ,Crystallographic defect ,law.invention ,Inorganic Chemistry ,law ,0103 physical sciences ,Homogeneity (physics) ,Materials Chemistry ,Optoelectronics ,Metalorganic vapour phase epitaxy ,0210 nano-technology ,business ,Light-emitting diode - Abstract
GaN fins are 3D architectures elongated in one direction parallel to the substrate surface. They have the geometry of walls with a large height to width ratio as well as small footprints. When appropriate symmetry directions of the GaN buffer are used, the sidewalls are formed by non-polar {1 1 −2 0} planes, making the fins particularly suitable for many device applications like LEDs, FETs, lasers, sensors or waveguides. The influence of growth parameters like temperature, pressure, V/III ratio and total precursor flow on the fin structures is analyzed. Based on these results, a 2-temperature-step-growth was developed, leading to fins with smooth side and top facets, fast vertical growth rates and good homogeneity along their length as well as over different mask patterns. For the core–shell growth of fin LED heterostructures, the 2-temperature-step-growth shows much smoother sidewalls and less crystal defects in the InGaN QW and p-GaN shell compared to structures with cores grown in just one step. Electroluminescence spectra of the 2-temperature-step-grown fin LED are demonstrated.
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- 2017
20. The influence of MOVPE growth conditions on the shell of core-shell GaN microrod structures
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Andreas Koller, Jana Hartmann, Hans-Jürgen Lugauer, Adrian Stefan Avramescu, Andreas Waag, Tilman Schimpke, Amalia Fernando-Saavedra, Johannes Ledig, and Martin Strassburg
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010302 applied physics ,Telecomunicaciones ,Materials science ,Dopant ,Scanning electron microscope ,chemistry.chemical_element ,Gallium nitride ,Nanotechnology ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Epitaxy ,01 natural sciences ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,0103 physical sciences ,Materials Chemistry ,Wafer ,Metalorganic vapour phase epitaxy ,Gallium ,Composite material ,0210 nano-technology ,Vicinal - Abstract
A core-shell geometry is employed for most next-generation, three-dimensional opto-electric devices based on III–V semiconductors and grown by metal organic vapor phase epitaxy (MOVPE). Controlling the shape of the shell layers is fundamental for device optimization, however no detailed analysis of the influence of growth conditions has been published to date. We study homogeneous arrays of gallium nitride core-shell microrods with height and diameter in the micrometer range and grown in a two-step selective area MOVPE process. Changes in shell shape and homogeneity effected by deliberately altered shell growth conditions were accurately assessed by digital analysis of high-resolution scanning electron microscope images. Most notably, two temperature regimes could be established, which show a significantly different behavior with regard to material distribution. Above 900 °C of wafer carrier temperature, the shell thickness along the growth axis of the rods was very homogeneous, however variations between vicinal rods increase. In contrast, below 830 °C the shell thickness is higher close to the microrod tip than at the base of the rods, while the lateral homogeneity between neighboring microrods is very uniform. This temperature effect could be either amplified or attenuated by changing the remaining growth parameters such as reactor pressure, structure distance, gallium precursor, carrier gas composition and dopant materials. Possible reasons for these findings are discussed with respect to GaN decomposition as well as the surface and gas phase diffusion of growth species, leading to an improved control of the functional layers in next-generation 3D V–III devices.
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- 2017
21. Eddy current thermography imaging for condition-based maintenance of overlay welded components under multi-degradation
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Tor Inge Waag, Boyan Yuan, and Christian Spiessberger
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0209 industrial biotechnology ,Materials science ,Mathematical model ,business.industry ,020209 energy ,Mechanical Engineering ,Acoustics ,Condition-based maintenance ,Ocean Engineering ,02 engineering and technology ,Welding ,Overlay ,Structural engineering ,Discrete Fourier transform ,law.invention ,020901 industrial engineering & automation ,Mechanics of Materials ,law ,Thermography ,0202 electrical engineering, electronic engineering, information engineering ,Eddy current ,General Materials Science ,Structural health monitoring ,business - Abstract
This paper presents a new multi-wave imaging method for the condition-based maintenance of offshore hydraulic systems containing overlay welded components under multi-degradation. These components suffer from combined tribocorrosion interacting with static and cyclic loading, for which effective mathematical models have not yet been established. In this paper, we propose eddy current thermography imaging for real-time structural health monitoring to enable condition-based maintenance of these critical components. The main challenge for the structural health monitoring of these components is that defects are often embedded at the substrate-coating interfacial regions that have irregular shapes in anisotropic and heterogeneous material as a result of the welding process. The eddy current thermography imaging method utilizes coupled electromagnetic–thermal fields and diffusion waves for robust detection of these hidden defects. A mathematical algorithm and software based on the discrete Fourier transform of thermal videos registered by an infrared detector was developed to characterize and visualize defects. The detectability of this method was investigated using a real cobalt superalloy overlay welded onto a carbon steel piston rod, in which an artificial volumetric defect was made at the interfacial region. The probability of detection and condition-based maintenance using the detected defect data is discussed based on the P-F curve and the probability of failure graphs.
- Published
- 2017
22. Application-specific electrical characterization of high power batteries with lithium titanate anodes for electric vehicles
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Wladislaw Waag, Alexander Farmann, and Dirk Uwe Sauer
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Battery (electricity) ,Materials science ,020209 energy ,Analytical chemistry ,chemistry.chemical_element ,02 engineering and technology ,Impedance parameters ,Industrial and Manufacturing Engineering ,chemistry.chemical_compound ,0202 electrical engineering, electronic engineering, information engineering ,Electrical and Electronic Engineering ,Lithium titanate ,Civil and Structural Engineering ,business.industry ,Mechanical Engineering ,Direct current ,Building and Construction ,021001 nanoscience & nanotechnology ,Pollution ,Dielectric spectroscopy ,Anode ,General Energy ,chemistry ,Equivalent circuit ,Optoelectronics ,Lithium ,0210 nano-technology ,business - Abstract
This study shows results of extensive experimental measurements performed on high power lithium titanate based batteries. Characterization tests are performed over a wide temperature range (−20 °C – +40 °C) by employing electrochemical impedance spectroscopy and modified hybrid pulse power characterization tests. Furthermore, the behavior of battery impedance parameters over the battery lifetime with regard to temperature, State-of-Charge and their influence on available battery power in an example of electric vehicles is discussed. Based on extracted parameters, a reduced order equivalent circuit model considering the nonlinearity of the charge transfer resistance is parametrized. The obtained results indicate that ohmic resistance increases with decreasing State-of-Charge while the shape of the curve remains almost constant over the battery lifetime. The total impedance determined at 1 mHz shows almost no dependence on State-of-Charge and remains constant over the whole State-of-Charge range. The necessity of considering the impact of the current dependence of the direct current resistance at least at low temperatures (i.e., below 0 °C) is confirmed. Moreover, by investigating the Butler-Volmer equation the behavior of exchange current density and symmetry factor is analyzed for various temperatures and State-of-Charges over the battery lifetime.
- Published
- 2016
23. Nanodiamond modified copolymer scaffolds affects tumour progression of early neoplastic oral keratinocytes
- Author
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Thilo Waag, Doris Steinmüller-Nethl, Anne Christine Johannessen, Anke Krueger, Emmet McCormack, Salwa Suliman, Amani O. Hamza, Kamal Mustafa, Tereza Osdal, Daniela Elena Costea, Anna Finne-Wistrand, Himalaya Parajuli, Joachim Nickel, Yang Sun, and Publica
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Keratinocytes ,Scaffold ,Cellular differentiation ,Bone Morphogenetic Protein 2 ,02 engineering and technology ,medicine.disease_cause ,Bone tissue engineering ,Mice ,0302 clinical medicine ,BMP-2 ,Mouth neoplasm ,Tissue Scaffolds ,Optical Imaging ,Cell Differentiation ,021001 nanoscience & nanotechnology ,Cell Transformation, Neoplastic ,Oral squamous cell carcinoma ,Mechanics of Materials ,030220 oncology & carcinogenesis ,Female ,Mouth Neoplasms ,Biocompatibility ,0210 nano-technology ,ddc:547 ,Microenvironment ,Materials science ,Polyesters ,Biophysics ,Bioengineering ,Bone morphogenetic protein 2 ,Bone and Bones ,Nanodiamonds ,Biomaterials ,03 medical and health sciences ,Cell Line, Tumor ,medicine ,Animals ,Humans ,ddc:610 ,Cell Proliferation ,Tumorigenicity ,Cell growth ,Mouth Mucosa ,Cancer ,Fibroblasts ,medicine.disease ,Ceramics and Composites ,Cancer research ,Carcinogenesis ,Biomedical engineering - Abstract
This study aimed to evaluate the tumorigenic potential of functionalising poly(LLA-co-CL) scaffolds. The copolymer scaffolds were functionalised with nanodiamonds (nDP) or with nDP and physisorbed BMP-2 (nDP-PHY) to enhance osteoinductivity. Culturing early neoplastic dysplastic keratinocytes (DOK\(^{Luc}\)) on nDP modified scaffolds reduced significantly their subsequent sphere formation ability and decreased significantly the cells' proliferation in the supra-basal layers of in vitro 3D oral neoplastic mucosa (3D-OT) when compared to DOK\(^{Luc}\) previously cultured on nDP-PHY scaffolds. Using an in vivo non-invasive environmentally-induced oral carcinogenesis model, nDP scaffolds were observed to reduce bioluminescence intensity of tumours formed by DOK\(^{Luc}\) + carcinoma associated fibroblasts (CAF). nDP modification was also found to promote differentiation of DOK\(^{Luc}\) both in vitro in 3D-OT and in vivo in xenografts formed by DOKLuc alone. The nDP-PHY scaffold had the highest number of invasive tumours formed by DOK\(^{Luc}\) + CAF outside the scaffold area compared to the nDP and control scaffolds. In conclusion, in vitro and in vivo results presented here demonstrate that nDP modified copolymer scaffolds are able to decrease the tumorigenic potential of DOK\(^{Luc}\), while confirming concerns for the therapeutic use of BMP-2 for reconstruction of bone defects in oral cancer patients due to its tumour promoting capabilities.
- Published
- 2016
24. Biofunctionalization of scaffold material with nano-scaled diamond particles physisorbed with angiogenic factors enhances vessel growth after implantation
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Johann Kern, Thilo Waag, Günter Lepperdinger, Anke Krueger, Peter Buschmann, Magdalena M. Schimke, Michael Rasse, Robert Stigler, Doris Steinmüller-Nethl, Gerold Untergasser, and Xujun Wu
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Vascular Endothelial Growth Factor A ,Scaffold ,Materials science ,Biocompatibility ,Angiogenesis ,Biomedical Engineering ,Neovascularization, Physiologic ,Pharmaceutical Science ,Medicine (miscellaneous) ,Bioengineering ,Nanotechnology ,Chick Embryo ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Regenerative medicine ,Nanomaterials ,Coated Materials, Biocompatible ,Tissue engineering ,Angiopoietin-1 ,Animals ,Humans ,General Materials Science ,Nanodiamond ,Sheep ,Tissue Engineering ,Tissue Scaffolds ,Mesenchymal Stem Cells ,021001 nanoscience & nanotechnology ,Nanostructures ,0104 chemical sciences ,Bone Substitutes ,Molecular Medicine ,Surface modification ,Angiogenesis Inducing Agents ,Adsorption ,Diamond ,0210 nano-technology - Abstract
Biofunctionalized scaffold facilitates complete healing of large defects. Biological constraints are induction and ingrowth of vessels. Angiogenic growth factors such as vascular endothelial growth factor or angiopoietin-1 can be bound to nano-scaled diamond particles. Corresponding bioactivities need to be examined after biofunctionalization. We therefore determined the physisorptive capacity of distinctly manufactured, differently sized nDP and the corresponding activities of bound factors. The properties of biofunctionalized nDPs were investigated on cultivated human mesenchymal stem cells and on the developing chicken embryo chorio-allantoic membrane. Eventually porous bone substitution material was coated with nDP to generate an interface that allows biofactor physisorption. Angiopoietin-1 was applied shortly before scaffold implantation into an osseous defect in sheep calvaria. Biofunctionalized scaffolds exhibited significantly increased rates of angiogenesis already one month after implantation. Conclusively, nDP can be used to ease functionalization of synthetic biomaterials. From the Clinical Editor With the advances in nanotechnology, many nano-sized materials have been used in the biomedical field. This is also true for nano-diamond particles (nDP). In this article, the authors investigated the physical properties of functionalized nano-diamond particles in both in-vitro and in-vivo settings. The positive findings would help improve understanding of these nanomaterials in regenerative medicine.
- Published
- 2016
25. Fabrication and characterization of low cost Cu 2 O/ZnO:Al solar cells for sustainable photovoltaics with earth abundant materials
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Andreas Waag, Andrey Bakin, Johannes Ledig, Azat Sharafeev, V. Marín-Borrás, Mohsen Mohamed Mosaad, Abdelhamid El-Shaer, Alexander Wagner, Mahmoud Abdelfatah, and Peter Lemmens
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010302 applied physics ,Materials science ,Renewable Energy, Sustainability and the Environment ,business.industry ,Open-circuit voltage ,Heterojunction ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,Optics ,Depletion region ,law ,Photovoltaics ,0103 physical sciences ,Solar cell ,Optoelectronics ,Quantum efficiency ,Thin film ,0210 nano-technology ,business ,Short circuit - Abstract
The low cost electrodeposition method was used to grow Cu2O thin films and experimentally determine the optimal absorber layer thickness. Raman scattering studies indicate the presence of solely crystalline Cu2O and SEM images show that the thin films consist of grains with a pyramidal shape. The influence of the thickness of the light absorbing Cu2O layer on the basic characteristic of the heterojunction and their properties have been investigated using reflectivity, current–voltage (J–V), capacitance–voltage (C–V) and the external quantum efficiency (EQE) measurements. The depletion layer, the charge collection length of the minority carrier, and reflectivity are the main factors describing the device properties. The efficiency of 1.09% with an open circuit voltage of Voc=0.35 V, a short circuit current density Jsc=6.21 mA cm−2 and a filling factor of FF=50% was obtained as the highest value for our solar cells. A Gaussian fit shows that the film thickness of around 3 µm is an optimum with respect to a high efficiency of the solar cells. C–V measurements shows that the estimated value of the built-in potential is Vb=0.35 V and the acceptor concentration at the junction is NA=4.375×1016 cm−3 for solar cell with the highest efficiency.
- Published
- 2016
26. Fabrication and characterization of flexible solar cell from electrodeposited Cu2O thin film on plastic substrate
- Author
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Mahmoud Abdelfatah, Andreas Waag, Andrey Bakin, Alexander Wagner, Johannes Ledig, Peter Lemmens, Azat Sharafeev, Abdelhamid El-Shaer, and Mohsen Mohamed Mosaad
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Materials science ,Renewable Energy, Sustainability and the Environment ,business.industry ,Open-circuit voltage ,Heterojunction ,Polymer solar cell ,law.invention ,Atomic layer deposition ,law ,Solar cell ,Optoelectronics ,General Materials Science ,Quantum efficiency ,Thin film ,business ,Layer (electronics) - Abstract
We present here for the first time the fabracition of a p-Cu 2 O/ZnO/AZO flexible heterojunction solar cell by electrodeposition of Cu 2 O thin film on a plastic substrate and sputtering of ZnO:Al layer. The Atomic Layer Deposition (ALD) has been employed to insert 5 nm ZnO as buffer layer. The heterojunction solar cell was characterized by Raman spectroscopy and scanning electron microscopy that show pyramidal shape and phonon modes for Cu 2 O thin film. Current–voltage ( J – V ), capacitance–voltage ( C – V ) and the external quantum efficiency (EQE) measurements were performed to understand the heterojunction properties. The solar cell device exhibits a power conversion efficiency of 0.897 ± 0.005% with an open circuit voltage of V oc = 300 mV, a short circuit current density of J sc = 6.819 ± 0.048 mA cm −2 and a fill factor of FF = 0.439 ± 0.006. The values of the built-in potential and the acceptor concentration at the junction were estimated from the reverse bias C – V measurement to be 0.37 V and 6.67 × 10 16 cm −3 , respectively.
- Published
- 2015
27. Adaptive approach for on-board impedance parameters and voltage estimation of lithium-ion batteries in electric vehicles
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Wladislaw Waag, Alexander Farmann, and Dirk Uwe Sauer
- Subjects
Battery (electricity) ,Engineering ,Renewable Energy, Sustainability and the Environment ,business.industry ,Constant phase element ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Impedance parameters ,Ion ,chemistry ,Electronic engineering ,Equivalent circuit ,Lithium ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,business ,Electrical impedance ,Voltage - Abstract
Robust algorithms using reduced order equivalent circuit model (ECM) for an accurate and reliable estimation of battery states in various applications become more popular. In this study, a novel adaptive, self-learning heuristic algorithm for on-board impedance parameters and voltage estimation of lithium-ion batteries (LIBs) in electric vehicles is introduced. The presented approach is verified using LIBs with different composition of chemistries (NMC/C, NMC/LTO, LFP/C) at different aging states. An impedance-based reduced order ECM incorporating ohmic resistance and a combination of a constant phase element and a resistance (so-called ZARC-element) is employed. Existing algorithms in vehicles are much more limited in the complexity of the ECMs. The algorithm is validated using seven day real vehicle data with high temperature variation including very low temperatures (from −20 °C to +30 °C) at different Depth-of-Discharges (DoDs). Two possibilities to approximate both ZARC-elements with finite number of RC-elements on-board are shown and the results of the voltage estimation are compared. Moreover, the current dependence of the charge-transfer resistance is considered by employing Butler–Volmer equation. Achieved results indicate that both models yield almost the same grade of accuracy.
- Published
- 2015
28. The influence of drying and calcination on surface chemistry, pore structure and mechanical properties of hierarchically organized porous silica monoliths
- Author
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Christian Balzer, Michael S. Elsaesser, Oskar Paris, Florian Putz, Gudrun Reichenauer, Anna M Waag, Wim J. Malfait, Stephan Braxmeier, Lukas Ludescher, and Nicola Hüsing
- Subjects
Chemistry ,Scanning electron microscope ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,law.invention ,Adsorption ,Chemical engineering ,Mechanics of Materials ,law ,Desorption ,Surface modification ,General Materials Science ,Calcination ,0210 nano-technology ,Porosity ,Thermal analysis ,Porous medium - Abstract
Hierarchically organized, porous materials exhibit unique combinations of physical and chemical properties depending on their pore sizes, pore structure and surface chemistry. Extraction and drying methods as well as post synthetic thermal treatments influence the characteristics of the resulting porous network and thus the achievable properties. Here we present a comprehensive investigation of the effects of drying conditions and post synthesis treatments on surface chemistry, pore structure and resulting mechanical properties of hierarchically structured silica monoliths comprising pores on three hierarchy levels (micro-, meso- and macropores). Samples were either dried supercritically (SCD) with carbon dioxide or at ambient pressure (APD) after surface silylation. In addition, the impact of a post synthetic heat treatment at two different temperatures (300 °C and 500 °C) is investigated. The focus of the study is on chemical and structural changes in/at the (meso-)pore walls, including the presence of micropores and the influence of organic components on the macroscopic properties. We discuss the implications of these modifications on mechanical properties, such as their deformation behavior during fluid adsorption related to their respective bulk and skeletal Young's moduli. Scanning electron microscopy, nitrogen adsorption/desorption measurements, simultaneous thermal analysis, solid-state NMR spectroscopy, small-angle X-ray scattering, sound velocity measurements and nitrogen adsorption/desorption with in-situ dilatometry were performed on each sample. This set of data illustrates the significant impact of different fabrication steps such as drying or calcination on material properties.
- Published
- 2019
29. 3D GaN nanoarchitecture for field-effect transistors
- Author
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Fatahilah, Muhammad Fahlesa, primary, Strempel, Klaas, additional, Yu, Feng, additional, Vodapally, Sindhuri, additional, Waag, Andreas, additional, and Wasisto, Hutomo Suryo, additional
- Published
- 2019
- Full Text
- View/download PDF
30. Electron beam lithography for contacting single nanowires on non-flat suspended substrates
- Author
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Samà, Jordi, primary, Domènech-Gil, Guillem, additional, Gràcia, Isabel, additional, Borrisé, Xavier, additional, Cané, Carles, additional, Barth, Sven, additional, Steib, Frederik, additional, Waag, Andreas, additional, Prades, Juan Daniel, additional, and Romano-Rodríguez, Albert, additional
- Published
- 2019
- Full Text
- View/download PDF
31. Ablation target cooling by maximizing the nanoparticle productivity in laser synthesis of colloids
- Author
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Waag, Friedrich, primary, Gökce, Bilal, additional, and Barcikowski, Stephan, additional
- Published
- 2019
- Full Text
- View/download PDF
32. Thermal performance analysis of GaN nanowire and fin-shaped power transistors based on self-consistent electrothermal simulations
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Kamrani, Hamed, primary, Yu, Feng, additional, Frank, Kristian, additional, Strempel, Klaas, additional, Fatahilah, Muhammad Fahlesa, additional, Wasisto, Hutomo Suryo, additional, Römer, Friedhard, additional, Waag, Andreas, additional, and Witzigmann, Bernd, additional
- Published
- 2018
- Full Text
- View/download PDF
33. Handheld personal airborne nanoparticle detector based on microelectromechanical silicon resonant cantilever
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Erik Uhde, Stephan Merzsch, Hutomo Suryo Wasisto, Erwin Peiner, Andreas Waag, and Publica
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Materials science ,Cantilever ,integrated system ,business.industry ,airborne nanoparticles ,Detector ,Analytical chemistry ,Condensed Matter Physics ,Piezoresistive effect ,Atomic and Molecular Physics, and Optics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Phase-locked loop ,cantilever resonator ,Calibration ,Optoelectronics ,Mass concentration (chemistry) ,Particle ,Electronics ,electrophoretic sampler ,Electrical and Electronic Engineering ,business - Abstract
Display Omitted We develop a handheld cantilever-based airborne nanoparticle detector (CANTOR-2).Main components of CANTOR-2 are described in details.CANTOR-2 is evaluated using carbon aerosols in typical workplace conditions.CANTOR-2 is calibrated with a fast mobility particle sizer (FMPS, TSI 3091).Comparison with other particle monitoring instruments is demonstrated. The development and real-time performance test of a fully integrated low-cost handheld cantilever-based airborne nanoparticle (NP) detector (CANTOR-2) are described in this paper. The device is the enhancement of the previously developed cylindrical electrophoretic NP sampler (CANTOR-1), which is used for direct-reading of exposure to airborne carbon engineered nanoparticles (ENPs) in indoor workplaces. All components of the proposed detector can be divided into two main units depending on their packaging placements (i.e., the NP sampler head and the electronics mounted in a handy-format housing). For the NP sampler, a miniaturized electrophoretic aerosol sampler created in a cubical shape and an electrothermal piezoresistive resonant silicon cantilever mass sensor are employed for collecting the ENPs from the air stream to the cantilever surfaces and measuring their mass concentration, respectively. To realize a real-time measurement, a frequency tracking system based on phase-locked loop (PLL) is built and integrated to the device. From the device calibration, a good correlation of the CANTOR-2 data is found with the fast mobility particle sizer (FMPS, TSI 3091) reference at a precision of 8-14%. By having a total device volume of 540cm3, weight of 375g, and power consumption of 1.25W in the current version, this developed CANTOR-2 provides a very good portability for being used as a personal airborne NP monitoring device, which can be easily held or worn by workers during their activities.
- Published
- 2015
34. Critical review of on-board capacity estimation techniques for lithium-ion batteries in electric and hybrid electric vehicles
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Andrea Marongiu, Dirk Uwe Sauer, Wladislaw Waag, and Alexander Farmann
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Estimation ,Battery (electricity) ,Engineering ,Renewable Energy, Sustainability and the Environment ,business.industry ,Electrical engineering ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Battery pack ,Automotive engineering ,Energy storage ,Lithium-ion battery ,Battery management systems ,chemistry ,Lithium ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,business ,Driving range - Abstract
This work provides an overview of available methods and algorithms for on-board capacity estimation of lithium-ion batteries. An accurate state estimation for battery management systems in electric vehicles and hybrid electric vehicles is becoming more essential due to the increasing attention paid to safety and lifetime issues. Different approaches for the estimation of State-of-Charge, State-of-Health and State-of-Function are discussed and analyzed by many authors and researchers in the past. On-board estimation of capacity in large lithium-ion battery packs is definitely one of the most crucial challenges of battery monitoring in the aforementioned vehicles. This is mostly due to high dynamic operation and conditions far from those used in laboratory environments as well as the large variation in aging behavior of each cell in the battery pack. Accurate capacity estimation allows an accurate driving range prediction and accurate calculation of a battery's maximum energy storage capability in a vehicle. At the same time it acts as an indicator for battery State-of-Health and Remaining Useful Lifetime estimation.
- Published
- 2015
35. Air-coupled ultrasonic through-transmission thickness measurements of steel plates
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Lars Hoff, Grunde Waag, and Petter Norli
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Angular spectrum method ,Shear waves ,Optics ,Materials science ,Acoustics and Ultrasonics ,business.industry ,Nondestructive testing ,Ultrasonic testing ,Plane wave ,Resonance ,Ultrasonic sensor ,business ,Piezoelectricity - Abstract
Non-destructive ultrasonic testing of steel structures provide valuable information in e.g. inspection of pipes, ships and offshore structures. In many practical applications, contact measurements are cumbersome or not possible, and air-coupled ultrasound can provide a solution. This paper presents air-coupled ultrasonic through-transmission measurements on a steel plate with thicknesses 10.15 mm; 10.0 mm; 9.8 mm. Ultrasound pulses were transmitted from a piezoelectric transducer at normal incidence, through the steel plate, and were received at the opposite side. The S1, A2 and A3 modes of the plate are excited, with resonance frequencies that depend on the material properties and the thickness of the plate. The results show that the resonances could be clearly identified after transmission through the steel plate, and that the frequencies of the resonances could be used to distinguish between the three plate thicknesses. The S1-mode resonance was observed to be shifted 10% down compared to a simple plane wave half-wave resonance model, while the A2 and S2 modes were found approximately at the corresponding plane-wave resonance frequencies. A model based on the angular spectrum method was used to predict the response of the through-transmission setup. This model included the finite aperture of the transmitter and receiver, and compressional and shear waves in the solid. The model predicts the frequencies of the observed modes of the plate to within 1%, including the down-shift of the S1-mode.
- Published
- 2015
36. Characterization of cellular immune response and innate immune signaling in human and nonhuman primate primary mononuclear cells exposed to Burkholderia mallei
- Author
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David M. Waag, Kamal U. Saikh, Kei Amemiya, Robert C. Bernhards, Robert G. Ulrich, and Shahabuddin Alam
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medicine.medical_treatment ,Inflammation ,Burkholderia mallei ,Microbiology ,Immune system ,Chlorocebus aethiops ,medicine ,Animals ,Humans ,Immunity, Cellular ,Innate immune system ,biology ,Burkholderia pseudomallei ,Glanders ,medicine.disease ,biology.organism_classification ,Macaca mulatta ,Immunity, Innate ,Disease Models, Animal ,Macaca fascicularis ,Rhesus macaque ,Infectious Diseases ,Cytokine ,Immunology ,Leukocytes, Mononuclear ,Cytokines ,medicine.symptom - Abstract
Burkholderia pseudomallei infection causes melioidosis and is often characterized by severe sepsis. Although rare in humans, Burkholderia mallei has caused infections in laboratory workers, and the early innate cellular response to B. mallei in human and nonhuman primates has not been characterized. In this study, we examined the primary cellular immune response to B. mallei in PBMC cultures of non-human primates (NHPs), Chlorocebus aethiops (African Green Monkeys), Macaca fascicularis (Cynomolgus macaque), and Macaca mulatta (Rhesus macaque) and humans. Our results demonstrated that B. mallei elicited strong primary pro-inflammatory cytokines (IFN-γ, TNF-α, IL-1β, and IL-6) equivalent to the levels of B. pseudomallei in primary PBMC cultures of NHPs and humans. When we examined IL-1β and other cytokine responses by comparison to Escherichia coli LPS, African Green Monkeys appears to be most responsive to B. mallei than Cynomolgus or Rhesus. Characterization of the immune signaling mechanism for cellular response was conducted by using a ligand induced cell-based reporter assay, and our results demonstrated that MyD88 mediated signaling contributed to the B. mallei and B. pseudomallei induced pro-inflammatory responses. Notably, the induced reporter activity with B. mallei, B. pseudomallei, or purified LPS from these pathogens was inhibited and cytokine production was attenuated by a MyD88 inhibitor. Together, these results show that in the scenario of severe hyper-inflammatory responses to B. mallei infection, MyD88 targeted therapeutic intervention may be a successful strategy for therapy.
- Published
- 2015
37. Study of 3D-growth conditions for selective area MOVPE of high aspect ratio GaN fins with non-polar vertical sidewalls
- Author
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Hartmann, Jana, Steib, Frederik, Zhou, Hao, Ledig, Johannes, Nicolai, Lars, Fündling, Sönke, Schimpke, Tilman, Avramescu, Adrian, Varghese, Tansen, Trampert, Achim, Straßburg, Martin, Lugauer, Hans-Jürgen, Wehmann, Hergo-Heinrich, and Waag, Andreas
- Subjects
A1. Crystal morphology, A3. Metalorganic vapor phase epitaxy, B.1 Gallium compounds, B.1 Nitrides, B.3 Light emitting diodes ,ddc:6 ,Veröffentlichung der TU Braunschweig ,ddc:621 ,ddc:62 ,Article - Abstract
GaN fins are 3D architectures elongated in one direction parallel to the substrate surface. They have the geometry of walls with a large height to width ratio as well as small footprints. When appropriate symmetry directions of the GaN buffer are used, the sidewalls are formed by non-polar {11-20} planes, making the fins particularly suitable for many device applications like LEDs, FETs, lasers, sensors or waveguides. The influence of growth parameters like temperature, pressure, V/III ratio and total precursor flow on the fin structures is analyzed. Based on these results, a 2-temperature-step-growth was developed, leading to fins with smooth side and top facets, fast vertical growth rates and good homogeneity along their length as well as over different mask patterns. For the core-shell growth of fin LED heterostructures, the 2-temperature-step-growth shows much smoother sidewalls and less crystal defects in the InGaN QW and p-GaN shell compared to structures with cores grown in just one step. Electroluminescence spectra of the 2-temperature-step-grown fin LED are demonstrated.
- Published
- 2017
- Full Text
- View/download PDF
38. On-line adaptive battery impedance parameter and state estimation considering physical principles in reduced order equivalent circuit battery models part 2. Parameter and state estimation
- Author
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Dirk Uwe Sauer, Christian Fleischer, Hans-Martin Heyn, and Wladislaw Waag
- Subjects
Battery (electricity) ,Engineering ,Renewable Energy, Sustainability and the Environment ,business.industry ,State of health ,Energy Engineering and Power Technology ,Response time ,Estimator ,Control engineering ,Power (physics) ,Nonlinear system ,Control theory ,Equivalent circuit ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,business ,Voltage - Abstract
Lithium-ion battery systems employed in high power demanding systems such as electric vehicles require a sophisticated monitoring system to ensure safe and reliable operation. Three major states of the battery are of special interest and need to be constantly monitored. These include: battery state of charge (SoC), battery state of health (capacity fade determination, SoH), and state of function (power fade determination, SoF). The second paper concludes the series by presenting a multi-stage online parameter identification technique based on a weighted recursive least quadratic squares parameter estimator to determine the parameters of the proposed battery model from the first paper during operation. A novel mutation based algorithm is developed to determine the nonlinear current dependency of the charge-transfer resistance. The influence of diffusion is determined by an on-line identification technique and verified on several batteries at different operation conditions. This method guarantees a short response time and, together with its fully recursive structure, assures a long-term stable monitoring of the battery parameters. The relative dynamic voltage prediction error of the algorithm is reduced to 2%. The changes of parameters are used to determine the states of the battery. The algorithm is real-time capable and can be implemented on embedded systems.
- Published
- 2014
39. On-line adaptive battery impedance parameter and state estimation considering physical principles in reduced order equivalent circuit battery models
- Author
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Christian Fleischer, Hans-Martin Heyn, Dirk Uwe Sauer, and Wladislaw Waag
- Subjects
Battery (electricity) ,Engineering ,Renewable Energy, Sustainability and the Environment ,State of health ,business.industry ,Process (computing) ,Automotive industry ,Energy Engineering and Power Technology ,Control engineering ,Power (physics) ,Microcontroller ,Equivalent circuit ,State (computer science) ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,business - Abstract
Lithium-ion battery systems employed in high power demanding systems such as electric vehicles require a sophisticated monitoring system to ensure safe and reliable operation. Three major states of the battery are of special interest and need to be constantly monitored, these include: battery state of charge (SoC), battery state of health (capcity fade determination, SoH), and state of function (power fade determination, SoF). In a series of two papers, we propose a system of algorithms based on a weighted recursive least quadratic squares parameter estimator, that is able to determine the battery impedance and diffusion parameters for accurate state estimation. The functionality was proven on different battery chemistries with different aging conditions. The first paper investigates the general requirements on BMS for HEV/EV applications. In parallel, the commonly used methods for battery monitoring are reviewed to elaborate their strength and weaknesses in terms of the identified requirements for on-line applications. Special emphasis will be placed on real-time capability and memory optimized code for cost-sensitive industrial or automotive applications in which low-cost microcontrollers must be used. Therefore, a battery model is presented which includes the influence of the Butler–Volmer kinetics on the charge-transfer process. Lastly, the mass transport process inside the battery is modeled in a novel state-space representation.
- Published
- 2014
40. Critical review of the methods for monitoring of lithium-ion batteries in electric and hybrid vehicles
- Author
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Christian Fleischer, Wladislaw Waag, and Dirk Uwe Sauer
- Subjects
Battery (electricity) ,Engineering ,Renewable Energy, Sustainability and the Environment ,business.industry ,State of health ,Electrical engineering ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Technical literature ,Automotive engineering ,Power (physics) ,Software ,State of charge ,chemistry ,Hardware_GENERAL ,Battery state of charge ,Lithium ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,business - Abstract
Lithium-ion battery packs in hybrid and pure electric vehicles are always equipped with a battery management system (BMS). The BMS consists of hardware and software for battery management including, among others, algorithms determining battery states. The continuous determination of battery states during operation is called battery monitoring. In this paper, the methods for monitoring of the battery state of charge, capacity, impedance parameters, available power, state of health, and remaining useful life are reviewed with the focus on elaboration of their strengths and weaknesses for the use in on-line BMS applications. To this end, more than 350 sources including scientific and technical literature are studied and the respective approaches are classified in various groups.
- Published
- 2014
41. The MOVPE growth mechanism of catalyst-free self-organized GaN columns in H2 and N2 carrier gases
- Author
-
Andreas Waag, Johannes Ledig, Martin Dr. Straßburg, Xue Wang, Hergo-H. Wehmann, Uwe Jahn, and Martin Mandl
- Subjects
Materials science ,Hydrogen ,business.industry ,Doping ,chemistry.chemical_element ,Nanotechnology ,Condensed Matter Physics ,Epitaxy ,Silane ,Catalysis ,Inorganic Chemistry ,chemistry.chemical_compound ,Semiconductor ,Chemical engineering ,chemistry ,Phase (matter) ,Materials Chemistry ,Metalorganic vapour phase epitaxy ,business - Abstract
Columnar structures of III–V semiconductors recently attract considerable attention because of their potential applications in novel optoelectronic and electronic devices. In the present study, the mechanisms for the growth of catalyst-free self-organized GaN columns on sapphire substrate by metal organic vapor phase epitaxy have been thoroughly investigated. The growth behaviours are strongly affected by the choice of carrier gas. If pure nitrogen is used, Ga droplets are able to accumulate on the top of columns during growth, and they are converted into a high quality GaN layer during the cool down phase due to nitridation. Hydrogen as the carrier gas can improve the optical quality of the overall GaN columns substantially, and in addition increase the vertical growth rate. In this case, no indication of Ga droplets could be detected. Furthermore, silane doping during the growth promotes the vertical growth in both cases either pure nitrogen or pure hydrogen as the carrier gas.
- Published
- 2013
42. Application-specific parameterization of reduced order equivalent circuit battery models for improved accuracy at dynamic load
- Author
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Dirk Uwe Sauer, Stefan Käbitz, and Wladislaw Waag
- Subjects
Battery (electricity) ,Engineering ,business.industry ,Applied Mathematics ,Condensed Matter Physics ,Dynamic load testing ,Weighting ,Control theory ,Frequency domain ,Non-linear least squares ,Electronic engineering ,Equivalent circuit ,Time domain ,Electrical and Electronic Engineering ,business ,Instrumentation ,Electrical impedance - Abstract
Reduced order equivalent circuit battery models are widely used for modeling batteries as a part of complex system or as a basis for battery monitoring algorithms. These models are often parameterized in frequency domain using impedance spectroscopy or in time domain by applying current profile and measuring respective voltage response. This paper shows how the frequency characteristic of a typical battery load in a given application can be considered during parameterization to improve the accuracy of the model when it is used in this application with dynamic load. The method uses impedance-based parameterization technique by adopting additional weighting coefficients to the complex nonlinear least squares (CNLS) fitting procedure without introducing any restrictions on its applicability. As an example, modeling of lithium-ion battery in electric vehicles is considered. The proposed techniques reduce the inaccuracy of modeled dynamic battery voltage response by 40% in the considered example.
- Published
- 2013
43. Silicon resonant nanopillar sensors for airborne titanium dioxide engineered nanoparticle mass detection
- Author
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Hutomo Suryo Wasisto, Stephan Merzsch, Erik Uhde, Erwin Peiner, Andreas Waag, Tunga Salthammer, Andrej Stranz, and Publica
- Subjects
Thermal oxidation ,Materials science ,Polydimethylsiloxane ,Silicon ,Metals and Alloys ,chemistry.chemical_element ,Nanotechnology ,silicon nanopillars ,ICP cryogenic dry etching ,airborne engineered nanoparticles ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,chemistry ,mass sensitivity ,Materials Chemistry ,Engineered Nanoparticle ,Ultrasonic sensor ,Dry etching ,Electrical and Electronic Engineering ,Inductively coupled plasma ,Instrumentation ,Nanopillar - Abstract
This work demonstrates mass measurement of airborne titanium dioxide (TiO2) engineered nanoparticles (ENPs) using silicon resonant nanopillar sensors by monitoring resonant frequency shifts induced by the mass of trapped ENPs. Inductively coupled plasma (ICP) cryogenic dry etching and thermal oxidation have been used in the sensor fabrication. A piezo shear actuator and an electrostatic precipitator are utilized to excite the nanopillars in resonant mode and collect the flowing TiO2 ENPs, respectively. By using the fundamental bending frequency, the sensor can achieve a mass sensitivity of 7.22 Hz/fg, which enables its application to a nanobalance to detect airborne ENPs in the femtogram mass range. Two methods of ENP removals (i.e., polydimethylsiloxane (PDMS) and ultrasonic cleanings) have also been performed to remove the adhered ENPs, thus efficiently extending the operating life of the sensor. This developed sensor is targeted to be implemented as a handheld ENP monitoring device at workplaces.
- Published
- 2013
44. Adaptive on-line prediction of the available power of lithium-ion batteries
- Author
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Christian Fleischer, Wladislaw Waag, and Dirk Uwe Sauer
- Subjects
Battery (electricity) ,Test bench ,Engineering ,Renewable Energy, Sustainability and the Environment ,State of health ,business.industry ,Energy Engineering and Power Technology ,Battery pack ,Automotive engineering ,Power (physics) ,Microcontroller ,Nonlinear system ,State of charge ,Electronic engineering ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,business - Abstract
In this paper a new approach for prediction of the available power of a lithium-ion battery pack is presented. It is based on a nonlinear battery model that includes current dependency of the battery resistance. It results in an accurate power prediction not only at room temperature, but also at lower temperatures at which the current dependency is substantial. The used model parameters are fully adaptable on-line to the given state of the battery (state of charge, state of health, temperature). This on-line adaption in combination with an explicit consideration of differences between characteristics of individual cells in a battery pack ensures an accurate power prediction under all possible conditions. The proposed trade-off between the number of used cell parameters and the total accuracy as well as the optimized algorithm results in a real-time capability of the method, which is demonstrated on a low-cost 16 bit microcontroller. The verification tests performed on a software-in-the-loop test bench system with four 40 Ah lithium-ion cells show promising results.
- Published
- 2013
45. Evaluation of photoresist-based nanoparticle removal method for recycling silicon cantilever mass sensors
- Author
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Tunga Salthammer, Hutomo Suryo Wasisto, Stephan Merzsch, Andreas Waag, Erwin Peiner, Erik Uhde, and Publica
- Subjects
Materials science ,Cantilever ,Silicon ,airborne nanoparticles ,Nanoparticle ,chemistry.chemical_element ,quality factor ,Nanotechnology ,Photoresist ,engineering.material ,Coating ,photorestist ,Relative humidity ,Electrical and Electronic Engineering ,Instrumentation ,business.industry ,Metals and Alloys ,Wet cleaning ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry ,cantilever resonators ,engineering ,Optoelectronics ,business ,Layer (electronics) - Abstract
Photoresist-based nanoparticle (NP) removal is evaluated as an approach to extend the life time of silicon resonant cantilever-based mass sensors for airborne NP monitoring. Integrated with a miniaturized electrostatic NP sampler, the cantilever can collect and detect airborne NP mass. Prior to airborne NP sampling, the cantilever surface is covered by a sacrificial layer of photoresist. Within a lift-off process of wet cleaning, the photoresist layer is removed together with the trapped NPs with cleaning efficiencies of ∼95–99%. The resonant frequencies and the quality factors ( Q -factors) of the cantilevers are characterized for different thicknesses of the photoresist layers given by their viscosities. The proposed recycling technique is found to be most effective when a thin photoresist film is used. By using higher order resonant modes, Q -factors of more than 1000 in air are maintained even after the photoresist coating. As necessary for an application under workplace conditions, the limitations of the sensor sensitivity influenced by the environment, i.e., ambient temperature and relative humidity ( rH ), are also measured.
- Published
- 2013
46. Adaptive estimation of the electromotive force of the lithium-ion battery after current interruption for an accurate state-of-charge and capacity determination
- Author
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Wladislaw Waag and Dirk Uwe Sauer
- Subjects
Battery (electricity) ,Engineering ,Electromotive force ,business.industry ,Mechanical Engineering ,Electrical engineering ,Building and Construction ,Management, Monitoring, Policy and Law ,Lithium-ion battery ,Microcontroller ,General Energy ,State of charge ,Hardware_GENERAL ,Equivalent circuit ,Voltage source ,Relaxation (approximation) ,business - Abstract
The online estimation of battery states and parameters is one of the challenging tasks when battery is used as a part of the pure electric or hybrid energy system. For the determination of the available energy stored in the battery, the knowledge of the present state-of-charge (SOC) and capacity of the battery is required. For SOC and capacity determination often the estimation of the battery electromotive force (EMF) is employed. The electromotive force can be measured as an open circuit voltage (OCV) of the battery when a significant time has elapsed since the current interruption. This time may take up to some hours for lithium-ion batteries and is needed to eliminate the influence of the diffusion overvoltages. This paper proposes a new approach to estimate the EMF by considering the OCV relaxation process within only some first minutes after the current interruption. The approach is based on an online fitting of an OCV relaxation model to the measured OCV relaxation curve. This model is based on an equivalent circuit consisting of a voltage source (represents the EMF) in series with the parallel connection of the resistance and a constant phase element (CPE). Based on this fitting the model parameters are determined and the EMF is estimated. The application of this method is exemplarily demonstrated for the state-of-charge and capacity estimation of the lithium-ion battery in an electrical vehicle. In the presented example the battery capacity is determined with the maximal inaccuracy of 2% using the EMF estimated at two different levels of state-of-charge. The real-time capability of the proposed algorithm is proven by its implementation on a low-cost 16-bit microcontroller (Infineon XC2287).
- Published
- 2013
47. Performance analysis and simulation of vertical gallium nitride nanowire transistors
- Author
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Witzigmann, Bernd, primary, Yu, Feng, additional, Frank, Kristian, additional, Strempel, Klaas, additional, Fatahilah, Muhammad Fahlesa, additional, Schumacher, Hans Werner, additional, Wasisto, Hutomo Suryo, additional, Römer, Friedhard, additional, and Waag, Andreas, additional
- Published
- 2018
- Full Text
- View/download PDF
48. Fabrication and characterization of single-pair thermoelectric generators of bismuth telluride using silver-sintering technology
- Author
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Wu, Wenze, primary, Bentaleb, Abdelhamid, additional, Waag, Andreas, additional, and Peiner, Erwin, additional
- Published
- 2018
- Full Text
- View/download PDF
49. Portable cantilever-based airborne nanoparticle detector
- Author
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Erwin Peiner, Andreas Waag, Tunga Salthammer, Stephan Merzsch, Hutomo Suryo Wasisto, Erik Uhde, and Publica
- Subjects
Materials science ,Cantilever ,Silicon ,Cleaning methods ,chemistry.chemical_element ,Nanoparticle ,Nanotechnology ,Operating life ,airborne engineered nanoparticles ,Resonator ,mass sensitivity ,Materials Chemistry ,Electrical and Electronic Engineering ,Instrumentation ,business.industry ,Detector ,Metals and Alloys ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry ,electrostatic sampler ,cantilever resonators ,Optoelectronics ,business ,Sensitivity (electronics) - Abstract
A portable cantilever-based airborne nanoparticle detector (CANTOR) was designed and manufactured for detecting engineered nanoparticles (ENPs) in workplace air by monitoring the resonant frequency shift induced by the mass of the particles trapped on the cantilever resonator. The CANTOR consists of two main modules, i.e., a silicon resonant cantilever sensor and a miniaturized electrostatic ENP sampler. Tested in 15-min aerosol sampling with ∼100 nm carbon-based ENPs having a concentration of ∼6000 NPs/cm3, the sensor exhibited a mass sensitivity of 36.51 Hz/ng when the second resonant mode was used. Two simple cleaning methods, i.e., dry and wet cleanings, to remove the attached ENPs were successfully demonstrated in order to extend the operating life of the sensor.
- Published
- 2013
50. Dependence of N-polar GaN rod morphology on growth parameters during selective area growth by MOVPE
- Author
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Andreas Waag, Sönke Fündling, Hergo-Heinrich Wehmann, Xue Wang, Shunfeng Li, Martin Strassburg, Werner Bergbauer, Milena Erenburg, Jiandong Wei, Martin Mandl, and Matin Sadat Mohajerani
- Subjects
010302 applied physics ,Photoluminescence ,Materials science ,Analytical chemistry ,chemistry.chemical_element ,Nanotechnology ,02 engineering and technology ,Partial pressure ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Epitaxy ,01 natural sciences ,Nitrogen ,Rod ,Inorganic Chemistry ,Hydrogen carrier ,chemistry ,0103 physical sciences ,Materials Chemistry ,sense organs ,Metalorganic vapour phase epitaxy ,Growth rate ,0210 nano-technology - Abstract
Selective area growth of GaN rods by metalorganic vapor phase epitaxy has attracted great interest due to its novel applications in optoelectronic and photonics. In this work, we will present the dependence of GaN rod morphology on various growth parameters i.e. growth temperature, H 2 /N 2 carrier gas concentration, V/III ratio, total carrier gas flow and reactor pressure. It is found that higher growth temperature helps to increase the aspect ratio of the rods, but reduces the height homogeneity. Furthermore, H 2 /N 2 carrier gas concentration is found to be a critical factor to obtain vertical rod growth. Pure nitrogen carrier gas leads to irregular growth of GaN structure, while an increase of hydrogen carrier gas results in vertical GaN rod growth. Higher hydrogen carrier gas concentration also reduces the diameter and enhances the aspect of the GaN rods. Besides, increase of V/III ratio causes reduction of the aspect ratio of N-polar GaN rods, which could be explained by the relatively lower growth rate on (000-1) N-polar top surface when supplying more ammonia. In addition, an increase of the total carrier gas flow leads to a decrease in the diameter and the average volume of GaN rods. These phenomena are tentatively explained by the change of partial pressure of the source materials and boundary layer thickness in the reactor. Finally, it is shown that the average volume of the N-polar GaN rods keeps a similar value for a reactor pressure P R of 66 and 125 mbar , while an incomplete filling of the pattern opening is observed with P R of 250 mbar. Room temperature photoluminescence spectrum of the rods is also briefly discussed.
- Published
- 2013
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