89 research outputs found
Mutagenicity of Baltic seawater and the relation to certain chemical and microbiological parameters
No full textThe presented work investigates the mutagenicity of seawater with regard to its distribution along the German Baltic Sea coastline. Further on in this paper the relationship between mutagenic activity and certain chemical, microbiological and physical parameters is analysed. Water samples were drawn from eight places between Eckernforde and Ribnitz-Damgarten. Seawater was concentrated using XAD-2/7 resin. Extracts of up to 3-1 per plate were tested with the Salmonella mutagenesis assay employing the strains TA 98 and TA 100 with and without addition of S9-mixture for metabolic activation. Samples from Weilssenhaus, Travemunde and Wismar demonstrated a mutagenic activity with the strain TA 98. Tested filter sediment was not mutagenic. The sum of six polycyclic aromatic hydrocarbons (PAH) concentrated by XAD resin and obtained by high performance liquid chromatography (HPLC) were between 0.03 and 34.11 ng/l seawater. No correlation of measured mutagenicity and chemical or physical parameters could be established. The sampling place Wismar with one mutagenic sample had the highest number of colony forming units of Eseherichia coli. (C) 2001 Elsevier Science Ltd. All rights reserved
Near-field ptychography: phase retrieval for inline holography using a structured illumination
No full textInline holography is a common phase-contrast imaging method which uses free-space propagation to encode the phase signal into measured intensities. However, quantitative retrieval of the sample's image remains challenging, imposing constraints on the nature of the sample or on the propagation distance. Here, we present a way of simultaneously retrieving the sample's complex-valued transmission function and the incident illumination function from near-field diffraction patterns. The procedure relies on the measurement diversity created by lateral translations of the sample with respect to a structured illumination. The reconstruction approach, in essence identical to that employed in ptychography, is applied to hard X-ray synchrotron measurements and to simulations. Compared to other inline holography techniques, we expect near-field ptychography to reduce reconstruction artefacts by factoring out wavefront imperfections and relaxing constraints on the sample's scattering properties, thus ultimately improving the robustness of propagation-based X-ray phase tomography
Characterization of Nanoporous Materials with Atom Probe Tomography
No full textA method to characterize open-cell nanoporous materials with atom probe tomography (APT) has been developed. For this, open-cell nanoporous gold with pore diameters of around 50 nm was used as a model system, and filled by electron beam-induced deposition (EBID) to obtain a compact material. Two different EBID precursors were successfully tested-dicobalt octacarbonyl [Co-2(CO)(8)] and diiron nonacarbonyl [Fe-2(CO)(9)]. Penetration and filling depth are sufficient for focused ion beam-based APT sample preparation. With this approach, stable APT analysis of the nanoporous material can be performed. Reconstruction reveals the composition of the deposited precursor and the nanoporous material, as well as chemical information of the interfaces between them. Thus, it is shown that, using an appropriate EBID process, local chemical information in three dimensions with sub-nanometer resolution can be obtained from nanoporous materials using APT
X-ray near-field ptychography for optically thick specimens
No full textInline holography, like other lensless imaging methods, circumvents limitations of x-ray optics through an a posteriori phase-retrieval step. However, phase retrieval for optically thick, i.e., strongly absorbing and phase shifting, specimens remains challenging. In this paper, we demonstrate that near-field ptychography can be used to efficiently perform phase retrieval on a uranium sphere with a diameter of about 46 μm, which acts as an optically thick sample. This particular sample was not accessible by inline holography previously. The reconstruction is based on a statistical model and incorporates partial coherence by decomposing the illumination into coherent modes. Furthermore, we observe that phase vortices, which can occur as artifacts during the reconstruction, pose a greater challenge than in far-field methods. We expect that the methods described in this paper will allow production of reliable phase maps of samples which cannot be accessed by inline holography
Comparison of Aviation and Automotive Standards and Methods in Terms of Safety and Cybersecurity
No full textSafety and security methods from the aviation and automotive are compared. Current safety and security standards and regulations for both product development aspects like systems engineering, hardware/software development and their management are considered. Methods and processes are investigated. The main purpose is to figure out and understand the backgrounds and to characterize the similarities and differences. Moreover, potential opportunities for transferring methods from one industry to another are identified. Aviation has more systematic development and involves authorities throughout the complete development lifecycle. Huge volumes in automotive leads to quality-driven development. Assessment structure and process activities provide potential transfer. For security both areas face same challenges and standardization activities and development run parallel. Methods are being mainly taken over from safety and assessment is incorporated into the safety assessment lifecycle today. For certification process, authorities must take action in both areas since the security ecosystem includes a bigger scope like infrastructure, communication devices, traffic control
Fortgeschrittene Gitter- und Propagations-basierte Röntgen-Phasenkontrast Bildsgebung mit Synchrotron Strahlung
No full textThis thesis presents the results of X-ray multi-modal images acquired using grating interferometry and propagation-based imaging techniques at a synchrotron source.
Since the absorption contrast is not very suited to visualize small density differences in the sample, it is necessary to explore novel contrast mechanisms that can overcome this difficulty. Phase-contrast is more sensitive to small density differences and dark-field contrast gives information on the local scattering power of the sample. These novel contrast mechanisms have the power to give complementary information that can help to better understand the composition of a sample.
X-ray grating interferometry, provides high sensitive images using the above mentioned three image contrasts. Up to now, this technique was mainly used for the characterization of soft tissues at photon energies up to 50 keV. The use of such a sensitive technique at energies over 100 keV, can be very interesting for the imaging of hard and dense specimens and it remains unexplored. However, the fabrication requirements of the gratings composing the interferometer make its implementation at high photon energies rather challenging. Furthermore, it is not clear that the different image signals will give complementary information, since at these high energies the attenuation and the phase contrast tend to depend on the material in a similar way. One part of the present thesis is focused on the investigation of grating interferometry at photon energies over 100 keV. The results show the characterization of grating interferometry at such high photon energies. The possibility to characterize samples at these high energies opens a path in many different fields, such as biomedical sciences, fundamental physics, and material sciences.
Propagation-based imaging is another X-ray imaging technique that in combination with a suited algorithm access the phase-contrast information. This technique uses the coherent properties of the source and lets the X-rays propagate in order to access the phase information. Its implementation remains therefore simple, since it doesn't need additional optics in the beam. One part of the present thesis is focused on the experimental evaluation of the grating interferometry and propagation-based imaging capabilities to access the phase-contrast information. The analysis is performed in a phantom sample which contains different density gradients. Additionally, the evaluation is completed by applying both techniques to the visualization and characterization of pancreatic cancerous tissue. The results presented show the complementarity of the techniques to assess the material composition of different samples.Die vorliegende Arbeit präsentiert Ergebnisse von multimodalen Röntgenbildgebungstechniken, die an einer Synchrotronquelle mit gitterinterferometrischen und propagationsbasierten Bildgebungsmethoden erzielt wurden.
Geringe Elektronendichteunterschiede können mittels konventioneller Röntgenabsorption nur schlecht dargestellt werden. Daher bieten sich neue Kontrastmechanismen an, die diese Schwierigkeit überwinden. Das Phasenkontrastsignal ist deutlich sensitiver in Bezug auf geringe Elektronendichteunterschiede und das Dunkelfeldkontrastsignal erlaubt zusätzlich die Darstellung des lokalen Streuungverhaltens der Probe. Diese neuartigen Kontrastmechanismen ermöglichen komplementäre Bildsignale für ein besseres Verständnis der Probenkomposition.
Röntgengitterinterferometrie ist das sensitivste Bildsignal der drei hier behandelten Bildkontrastmodalitäten. Bis jetzt wurde dieses Verfahren hauptsächlich für Weichgewebscharakterisierung bei Photonenenergien bis zu 50 keV angewandt. Die Applikation einer so hochsensitiven Methode bei Energien über 100 keV ist von großem Interesse für die Bildgebung harter und dichter Objekte und ist bisher unerforscht. Jedoch sind die Herstellungsanforderungen der Gitter des Interferometers für solch hohe Energien eine technische Herausforderung. Desweiteren stellt sich die Frage nach dem Verhalten der Komplementarität der unterschiedlichen Bildsignale bei höheren Energien, da sich die Energie- und Materialabhängigkeit von Absorptions- und Phasenkontrast bei hohen Energien annähert.
Ein Teil dieser Arbeit widmet sich der Untersuchung der Anwendbarkeit von Gitterinterferometrie bei Photonenergien oberhalb von 100 keV. Als Resultat wird die Charakterisierung von Gitterinterferometrie bei solch hohen Energien präsentiert. Die Möglichkeit, Proben bei so hohen Energien zu charakterisieren erlaubt eine Anwendung in vielen unterschiedlichen Bereichen wie der biomedizinischen Forschung, der physikalischen Grundlagenforschung und der Materialwissenschaft.
Propagationsbasierte Bildgebung ist eine weitere Röntgenbildgebungstechnik, die in Kombination mit passenden Algorithmen ebenfalls die Darstellung der Phasenkontrastinformation erlaubt. Diese Technik basiert auf der Kohärenz der Synchrotronquelle und ermöglicht dadurch eine Propagation der Röntgenstahlen, um das Phasensignal zu erhalten. Die Implementation dieser Technik ist experimentell einfach, da keinerlei zusätzliche optische Strahlkomponenten benutzt werden müssen.
Ein weiterer Teil der vorliegenden Arbeit handelt von der experimentellen Evaluation der Bildgebungsmöglichkeiten von Gitterinterferometrie und propagationsbasierter Röntgenbildgebung. Diese Evaluation wird anhand einer Phantomprobe mit unterschiedlichen Dichtegradienten durchgeführt. Komplettiert wird diese Evaluation anhand der Anwendung beider Methoden zur Visualisierung und Charakterisierung von pankreatischem Krebsgewebe.
Die präsentierten Resultate verdeutlichen die Komplementarität der beiden Techniken, um die Materialkomposition unterschiedlicher Proben zu bestimmen
Structural Optimization Of A Vertical Axis Wind Turbine With Aeroelastic Analysis
No full textCurrently, the price per kW of offshore wind energy is 55% larger than onshore [38, 52]. Of this price, the rotor corresponds to 22%. To reduce the price of wind energy, it is necessary to investigate wind turbine concepts with scales above 10 MW. The commonly known Horizontal Axis Wind Turbine (HAWT) requires offshore a large support structure. If the turbine is designed to be floating, a deep floater is needed to limit the tilt angle. A possible concept to meet this challenges is the lift-driven Vertical Axis Wind Turbine (VAWT). This thesis aims to optimize the structural design of a VAWT rotor blade and to decrease the mass to area ratio by varying blade shape and structural layout. The choice of mass to rotor area ratio as an optimization function follows from the fact that this area is directly proportional to the energy output while mass drives production and installation costs. The VAWT is defined by an axis perpendicular to the unperturbed flow direction. The rotor geometry is described through a Troposkein shape. It is assumed that the blades carry their own weight leading to a reinforced root region. During operation the blades experience aerodynamic and inertia forces, which are deflecting the blades outwards, leading to an alternation of the aerodynamic loads.The interplay of load alternation and blade deflection could lead to a diverging flutter motion. After a fitting design is obtained, the blade motion has to be inspected for a safe use during operation. The rotor is designed with an adjusted optimizer, originally written by M. Schelbergen [62]. The optimizer uses the Matlab optimization toolbox in combination with Nastran. The modification allows a smooth transition of the thickness of skin, shear web and girder. The airfoil section is varied along the blade. The optimization is based on load cases such as a parked rotor and the maximum up- and downwind forces. These loads are simplified and assumed to vary neither by the motion nor the deflections of the blade. In addition, an aeroelastic model is required to observe the blades’ motion. Through out thisthesis two aeroelastic codes were used. The VAWT AeroElastic Multibody Panel Solver (VÆMPS) was created by coupling Sandia National Laboratories OWENS and the near wake panel solver UMPM. However, its computational performance was not satisfying and it was decided to use HAWC2 coupled with an actuator cylinder model to determine the induction.European Wind Energy Masters (EWEM
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Designing Video-Based Interactive Instructions
No full textWhen attempting to accomplish unfamiliar tasks, people often look for tutorials to follow instructions. While it is easy to access online instructions shared by domain experts, navigating step-by-step guidance using existing tools remains inefficient. In addition, producing high-quality instructions that are easy to follow requires authoring expertise and a significant time investment in editing. This dissertation introduces video-based recording, editing, and playback tools optimized for creating and consuming tutorials from author demonstrations. Our interactive systems capture videos and high-level events that are important to a learner. Using video and audio analysis techniques, we develop algorithms that automatically produce high-quality instructions, which dramatically reduce the effort required for amateur creators. By introducing novel tutorial formats combined with video content, these designs in turn improve viewers’ learning experience.We present a series of authoring tools that enable amateur authors to create effective tutorials: 1) MixT is a system that automatically generates step-by-step mixed media tutorials from software demonstrations. 2) DemoWiz is a tool that provides an increased awareness of upcoming events in a software demonstration video. 3) DemoCut is a semi-automatic video editing tool for physical tasks. 4) Kinectograph is a recording device that automatically follows an instructor for filming a physical demonstration. 5) DemoDraw is a multi-modal system to generate step-by-step motion illustrations from author’s body movements. Current authoring practices from professionals are encoded into automatic algorithms and interactive techniques. These systems are evaluated through a series of studies, which demonstrate that users can efficiently create and follow concise instructions using our tools
Contracting Out Temporary Help Services in Germany
No full textSince 2003 the German Public Employment Service (PES) has been experimenting with the contracting out of various services. One of the new labour market programmes is the Personnel Service Agencies, which provide client firms with jobseekers on a temporary assignment basis and are responsible for integrating jobseekers into non-subsidised employment. By contracting out employment services, the PES seeks to exploit efficiency gains characteristic of enterprises that compete in quasi-markets. In order to integrate jobseekers as rapidly as possible, a result-oriented system of incentives has been developed. This paper describes the institutional setting and examines its appropriateness for efficient job placement services.contracting out, quasi-markets, temporary agency work, Personnel Service Agency
Endolymphatic Hydrops Magnet Resonance Imaging in Ménière’s Disease Patients after Cochlea Implantation
No full textPfeiffer C, Gehl H-B, Scholtz L-U, Goon P, Sudhoff H, Todt I. Endolymphatic Hydrops Magnet Resonance Imaging in Ménière’s Disease Patients after Cochlea Implantation. Brain Sciences. 2023;13(6): 853.Introduction: Cochlear implantation in patients with Ménière’s disease (MD) is the treatment of choice in cases of functional deafness. Additional vertigo control is of central importance in this group of patients. Endolymphatic hydrops (ELH) is the pathophysiological correlate of MD and can be evaluated by magnet resonance imaging (MRI). Bilateral MD occurs in 10–33% and can be the reason for a postoperative persisting or newly occurring vertigo in this group. Recent developments in the field of implant magnets and experience in MRI sequences allow the diagnostic performance of MRI in cochlear implantees to be evaluated. The aim of the present study was to evaluate the possibility of MRI as a visual diagnostic tool for endolymphatic hydrops in cochlear implantees. Material and Methods: This was a retrospective study including three cochlear implantees (age: 61–76 years, one female, two male) suffering from MD who, postoperatively, had a recurrence of vertigo with Ménière’s-like symptoms. An MRI was performed for the evaluation of ELH (ELH-MRI). MRI observation was performed by a 4 h iv. delayed Gad 3 D Flair sequence. Results: In all cases, the ipsilateral implant magnet artifact covered the vestibulum, the semicircular canals and the cochlea. The contralateral vestibulum, the semicircular canal and the cochlea were fully observable, and a classification of the ELH-MRI could be performed. Conclusion: ELH-MRI scanning allows for the detection of contralateral labyrinthine endolymphatic hydrops and is a tool for the postoperative evaluation of vertigo in cochlear implantees
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