3,050 Works

Plutonium release from Fukushima Daiichi fosters the need for more detailed investigations

Stephanie Schneider, Clemens Walther, Stefan Bister, Viktoria Schauer, Marcus Christl, Hans-Arno Synal, Katsumi Shozugawa & Georg Steinhauser
The contamination of Japan after the Fukushima accident has been investigated mainly for volatile fission products, but only sparsely for actinides such as plutonium. Only small releases of actinides were estimated in Fukushima. Plutonium is still omnipresent in the environment from previous atmospheric nuclear weapons tests. We investigated soil and plants sampled at different hot spots in Japan, searching for reactor-borne plutonium using its isotopic ratio Pu-240/Pu-239. By using accelerator mass spectrometry, we clearly demonstrated...

Numerical simulation of strain-adaptive bone remodelling in the ankle joint

Anas Bouguecha, Nelly Weigel, Bernd-Arno Behrens, Christina Stukenborg-Colsman & Hazibullah Waizy
Background: The use of artificial endoprostheses has become a routine procedure for knee and hip joints while ankle arthritis has traditionally been treated by means of arthrodesis. Due to its advantages, the implantation of endoprostheses is constantly increasing. While finite element analyses (FEA) of strain-adaptive bone remodelling have been carried out for the hip joint in previous studies, to our knowledge there are no investigations that have considered remodelling processes of the ankle joint. In...

Quantification of microbial communities in subsurface marine sediments of the Black Sea and off Namibia

Axel Schippers, Dagmar Kock, Carmen Hoeft, Gerrit Koeweker & Michael Siegert
Organic-rich subsurface marine sediments were taken by gravity coring up to a depth of 10 m below seafloor at six stations from the anoxic Black Sea and the Benguela upwelling system off Namibia during the research cruises Meteor 72-5 and 76-1, respectively. The quantitative microbial community composition at various sediment depths was analyzed using total cell counting, catalyzed reporter deposition fluorescence in situ hybridization (CARD FISH) and quantitative real-time PCR (Q-PCR). Total cell counts decreased...

Measurement of finite-frequency current statistics in a single-electron transistor

Niels Ubbelohde, Christian Fricke, Christian Flindt, Frank Hohls & Rolf J. Haug
Electron transport in nanoscale structures is strongly influenced by the Coulomb interaction that gives rise to correlations in the stream of charges and leaves clear fingerprints in the fluctuations of the electrical current. A complete understanding of the underlying physical processes requires measurements of the electrical fluctuations on all time and frequency scales, but experiments have so far been restricted to fixed frequency ranges, as broadband detection of current fluctuations is an inherently difficult experimental...

Do Children's Health Resources Differ According to Preschool Physical Activity Programmes and Parental Behaviour? A Mixed Methods Study

Elena Sterdt, Natalie Pape, Silke Kramer, Sebastian Liersch, Michael Urban, Rolf Werning & Ulla Walter
Preschool can have positive effects on the development of a healthy lifestyle. The present study analysed to what extent different conditions, structures and behavioural models in preschool and family-children's central social microsystems-can lead to differences in children's health resources. Using a cross-sectional mixed methods approach, contrast analyses of "preschools with systematic physical activity programmes" versus "preschools without physical activity programmes" were conducted to assess the extent to which children's physical activity, quality of life and...

Physiological and molecular analysis of the interaction between aluminium toxicity and drought stress in common bean (Phaseolus vulgaris)

Zhong-Bao Yang, Dejene Eticha, Alfonso Albacete, Idupulapati Madhusudana Rao, Thomas Roitsch & Walter Johannes Horst
Aluminium (Al) toxicity and drought are two major factors limiting common bean (Phaseolus vulgaris) production in the tropics. Short-term effects of Al toxicity and drought stress on root growth in acid, Al-toxic soil were studied, with special emphasis on Al-drought interaction in the root apex. Root elongation was inhibited by both Al and drought. Combined stresses resulted in a more severe inhibition of root elongation than either stress alone. This result was different from the...

Absorption Measurements of Periodically Poled Potassium Titanyl Phosphate (PPKTP) at 775 nm and 1550 nm

Jessica Steinlechner, Stefan Ast, Christoph Krueger, Amrit Pal Singh, Tobias Eberle, Vitus Haendchen & Roman Schnabel
The efficient generation of second-harmonic light and squeezed light requires non-linear crystals that have low absorption at the fundamental and harmonic wavelengths. In this work the photo-thermal self-phase modulation technique is exploited to measure the absorption coefficient of periodically poled potassium titanyl phosphate (PPKTP) at 1,550 nm and 775 nm. The measurement results are (84 +/- 40) ppm/cm and (127 +/- 24) ppm/cm, respectively. We conclude that the performance of state-of-the-art frequency doubling and squeezed...

Characterization of nanoparticle mediated laser transfection by femtosecond laser pulses for applications in molecular medicine

Markus Schomaker, Dag Heinemann, Stefan Kalies, Saskia Willenbrock, Siegfried Wagner, Ingo Nolte, Tammo Ripken, Hugo Murua Escobar, Heiko Meyer & Alexander Heisterkamp
Background: In molecular medicine, the manipulation of cells is prerequisite to evaluate genes as therapeutic targets or to transfect cells to develop cell therapeutic strategies. To achieve these purposes it is essential that given transfection techniques are capable of handling high cell numbers in reasonable time spans. To fulfill this demand, an alternative nanoparticle mediated laser transfection method is presented herein. The fs-laser excitation of cell-adhered gold nanoparticles evokes localized membrane permeabilization and enables an...

Influence of Cobalt on the Properties of Load-Sensitive Magnesium Alloys

Christian Klose, Christian Demminger, Gregor Mroz, Wilfried Reimche, Friedrich-Wilhelm Bach, Hans Jürgen Maier & Kai Kerber
In this study, magnesium is alloyed with varying amounts of the ferromagnetic alloying element cobalt in order to obtain lightweight load-sensitive materials with sensory properties which allow an online-monitoring of mechanical forces applied to components made from Mg-Co alloys. An optimized casting process with the use of extruded Mg-Co powder rods is utilized which enables the production of magnetic magnesium alloys with a reproducible Co concentration. The efficiency of the casting process is confirmed by...

AUXIN-BINDING-PROTEIN1 (ABP1) in phytochrome-B-controlled responses

Yunus Effendi, Alan M. Jones & Günther F.E. Scherer
The auxin receptor ABP1 directly regulates plasma membrane activities including the number of PIN-formed (PIN) proteins and auxin efflux transport. Red light (R) mediated by phytochromes regulates the steady-state level of ABP1 and auxin-inducible growth capacity in etiolated tissues but, until now, there has been no genetic proof that ABP1 and phytochrome regulation of elongation share a common mechanism for organ elongation. In far red (FR)-enriched light, hypocotyl lengths were larger in the abp1-5 and...

Entgrenzung und Zusammenarbeit – die Notwendigkeit von Kooperationen im Lernraum

Anne May & Susanne Kannenberg
Die Hochschule ist ein Lernraum – dieser Satz ist für die meisten ein Allgemeinplatz. Dahinter verbirgt sich aber weit mehr – eine entwicklungsfähige Zukunftsaufgabe, bei der es um mehr als ein räumlich- infrastrukturelles Angebot für Studierende geht. Für einen vielseitigen, zukunftsfähigen Lernraum ist die Entgrenzung institutioneller Zuständigkeiten notwendige Voraussetzung. Diese Notwendigkeit ergibt sich sowohl für die Entwicklung und den Betrieb von räumlich-technischen Infrastrukturen als auch für die Weiterentwicklung von Beratungs- und Schulungsangeboten. Dienstleistungskooperation ist nötig...

Non-Abelian quasi-particles in electronic systems

Daniel Borcherding
Ever since the proposal of Kitaev for decoherence-free quantum computing based on non-Abelian anyons physical realizations of these exotic particles have been investigated extensively. Starting from one-dimensional models of interacting fermions with different symmetries the emergence and condensation of $\mathfrak{su}(2)_{N_f}$, $\mathfrak{su}(3)_{N_f}$ and $\mathfrak{so}(5)_{N_f}$ anyons is studied in the framework of integrable perturbed WZNW models. For sufficiently small temperatures and fields non-Abelian anyons residing on massive solitonic excitations are identified by their quantum dimension. By tuning...

Traceability of the Hannover FG5X-220 to the SI units

Manuel Schilling & Ludger Timmen
The absolute measurement of g is currently realized through the laser interferometric measurement of a free falling retro-reflector. The Micro-g LaCoste FG5X is a free-fall gravimeter with a laser interferometer in Mach-Zehnder configuration which uses simultaneous time and distance measurements to calculate the absolute value of g. Because the instrument itself contains the necessary working standards for precise time and length measurements, it is considered independent of external references. The timing is kept with a...

Konzepte zur Beleuchtung von Lichtmodulatoren

Peer-Phillip Ley, Marcel Philipp Held, Alexander Wolf & Roland Lachmayer
Hochauflösende Pixellichtsysteme werden mithilfe verschiedener Modulatortechnologien in unterschiedlichen Anwendungsbereichen eingesetzt. Zur Umsetzung wirkungsgradstarker Systeme sind geeignete Beleuchtungskonzepte der Modulatorfläche erforderlich. Dieses Paper stellt anwendungsbezogene Vor- und Nachteile abbildender und nichtabbildender Beleuchtungskonzepte gegenüber.

Anforderungen an die Ausleuchtung von Lichtmodulatoren

Marcel Philipp Held, Peer-Phillip Ley, Alexander Wolf & Roland Lachmayer
Hochaufgelöste Beleuchtungssysteme erfordern für einen effizienten und lichtstarken Betrieb eine möglichst exakte Ausleuchtung der lichtmodulierenden Fläche. In diesem Paper werden relevante Technologien gegenübergestellt und hinsichtlich eines Einsatzes in der Fahrzeuglichttechnik evaluiert.

Herstellung, Charakterisierung und mikromechanische Modellierung von magneto-sensitiven Elastomeren

Sahbi Aloui
Magneto-sensitive elastomers (MSE) belong to the class of smart materials. They show a self-adjusting and adaptive behaviour in random occurrences and are also denoted as intelligent materials. They are characterised by the ability to react in a target-oriented acting to changes in operating or environmental conditions without external regulation. MSE are prepared by mixing magnetic fillers within the rubber matrix. Mechanical and magnetorheological measurements show that particle size, filler loading and coupling agent considerably influence...

Targetomics, application of in vitro screening methods for the identification of new drugs

Sona Mohammadi Ostad Kalayeh
The effect of various natural products and chemical compounds to their corresponding molecular target is often unidentified. Drugs are effective by binding to a molecule (the target) and inhibiting its function. In order to perform an efficient target-oriented drug discovery, target and related tests are needed. These tests are mostly based on a binding or catalytic function, which are usually visualized by optical methods. Subsequently, the cell- or enzyme-based drug tests can be done. In...

Optimizing Selective Laser Melting for Reflective Optics

Georg Leuteritz, René Bastian Lippert & Roland Lachmayer
This work examines an approach for the optimization of the optical quality of additively manufactured reflectors. Therefore the parameters of a Selective Laser Melting process, which manipulate surface properties are distinguished and varied in order to achieve optimized reflectance and roughness values. Influences are evaluated with specific samples and optical measurement equipment.

Functional integration for additively manufactured reflectors

Georg Leuteritz, Markus Rohling & Roland Lachmayer
This work investigates the possibilities of functional integration for reflective optics that are manufactured via Selective Laser Melting. A method for identifying a broad range of technical functions and concepts that are suitable for functional integration is presented. Using a flashlight and a bicycle headlamp, selected concepts are realized.

Comparison of Additive Manufacturing techniques regarding mechanical and optical properties

Georg Leuteritz, René Bastian Lippert, Katharina Rettschlag & Roland Lachmayer
This article examines whether optical and mechanical components can be additively manufactured with net shape properties. Furthermore various Additive Manufacturing techniques are investigated regarding the suitability for an integrated process. Hence, the possibility of producing multimaterial components and optomechanical systems without the necessity for assembly and adjustment is evaluated.

Predictability and anomalies in equity and commodity markets

Björn Tharann
This thesis studies the predictability of stock and commodity returns. It also examines the sources of return anomalies in financial markets. Chapter 1 introduces the main concepts and delivers an overview of the subsequent chapters. Chapter 2 begins with the analysis of stock return predictability around the globe. By studying more than 80 countries for a sample period of up to 144 years, we conduct the most comprehensive analysis of equity premium predictability that thus...

Bestimmung von Codephasen-Variationen bei GNSS-Empfangsantennen und deren Einfluss auf die Positionierung, Navigation und Zeitübertragung

Tobias Kersten
Die globale Positionierung, Navigation sowie Zeit- und Frequenzübertragung [positioning, navigation and timing] (PNT) ist in der heutigen Gesellschaft zu einem integralen Bestandteil des täglichen Lebens geworden, so dass die präzise und autonome Georeferenzierung in der letzten Dekade in weiten Teilen unseres Lebensbereiches rasant Einzug gehalten hat. Positionierungs- und Navigationsverfahren werden u.a. in der öffentlichen Infrastruktur, dem See-, Land- und Luftverkehr intensiv verwendet. Sicherheitskritische Anwendungen verlangen ein Integritätsmonitoring der empfangenen Signale, die robuste und zertifizierte Signale...

Anforderungsgenaues EMV-Design von Gehäusen aus Werkstoffverbunden für Automotive-Anwendungen

Hermann L. Aichele & Sven Robert Raisch
In der vorgelegten Arbeit wurde ein zweistufiges Verfahren zur Auswahl von geeigneten Gehäusewerkstoffen aus Werkstoffverbunden und Verbundwerkstoffen vorgestellt. Es wurden zwei Messverfahren aufgebaut und Messungen an schirmend modifizierten Kunststoffgehäusen mit realen Produkten durchgeführt. Dabei zeigte sich, dass eine Vielzahl der untersuchten kunststofftechnischen Lösungsansätze eine akzeptable Schirmdämpfung hinsichtlich ihrer Materialeigenschaften haben und sich diese positiv in den Komponentenmessungen wiederspiegeln. Durch die Ergebnisse kann die Wirksamkeit vorgeschlagener Kunststoff-Verbundwerkstoffe und Werkstoffverbunde im EMV-Bereich besser eingeschätzt werden.

Breitbandiger aktiver Hybrid-Filter für Kfz-Anwendungen

Bastian Arndt, Peter Olbrich, Hartwig Reindl & Christian Waldera
In der bisherigen gängigen Praxis werden insbesondere im automobilen Bereich meist passive Bauteile zur Filterung von leitungsgebundenen Störungen verwendet. Bei aktuellen Kfz-Hochvoltsystemen stoßen diese Filterstrategien an ihre Grenzen. Mittels passiver Filterkomponenten könnten Filtertopologien mit Y-Kondensatoren aufgrund von Sicherheitsvorschriften nicht in dem hier gezeigten Umfang angewendet werden, da die maximal zulässigen Kapazitätswerte in HV-Systemen limitiert sind und damit für den Bereich kleiner 1 MHz kaum anwendbar sind. Die Kombination aus aktiven und passiven Filterstrukturen und deren...

Stromkompensierte Drosseln mit hochpermeablen nanokristallinen Kernen für den 1000 A - Bereich

Stefan Becker & Dietrich Sekels
Der Vortrag stellt volumenoptimierte stromkompensierte Drosseln mit hochpermeablen nanokristallinen Kernen vor, deren spezieller Wicklungsaufbau Induktivitätseinbrüche durch partielle seffekte bei sehr hohen Strömen vermeidet. Die Nachteile der geringen Streuinduktivität können durch zusätzliche lineare Einleiterdrosseln oder eine Streusteg kompensiert werden.

Registration Year

  • 2015
  • 2016
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  • 2018
  • 2019

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  • Leibniz Universität Hannover