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Search Results: 1 - 10 of 2799 matches for " Dominik Schulz "
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Using Quaternion-Valued Linear Algebra
Dominik Schulz,Reiner S. Thom?
Mathematics , 2013,
Abstract: Linear algebra is usually defined over a field such as the reals or complex numbers. It is possible to extend this to skew fields such as the quaternions. However, to the authors' knowledge there is no commonly accepted notation of linear algebra over skew fields. To this end, we discuss ways of notation that account for the non-commutativity of the quaternion multiplication.
Spin dynamics in high-mobility two-dimensional electron systems
Tobias Korn,Dominik Stich,Robert Schulz,Dieter Schuh,Werner Wegscheider,Christian Schüller
Physics , 2008, DOI: 10.1007/978-3-540-85859-1_12
Abstract: Understanding the spin dynamics in semiconductor heterostructures is highly important for future semiconductor spintronic devices. In high-mobility two-dimensional electron systems (2DES), the spin lifetime strongly depends on the initial degree of spin polarization due to the electron-electron interaction. The Hartree-Fock (HF) term of the Coulomb interaction acts like an effective out-of-plane magnetic field and thus reduces the spin-flip rate. By time-resolved Faraday rotation (TRFR) techniques, we demonstrate that the spin lifetime is increased by an order of magnitude as the initial spin polarization degree is raised from the low-polarization limit to several percent. We perform control experiments to decouple the excitation density in the sample from the spin polarization degree and investigate the interplay of the internal HF field and an external perpendicular magnetic field. The lifetime of spins oriented in the plane of a [001]-grown 2DES is strongly anisotropic if the Rashba and Dresselhaus spin-orbit fields are of the same order of magnitude. This anisotropy, which stems from the interference of the Rashba and the Dresselhaus spin-orbit fields, is highly density-dependent: as the electron density is increased, the kubic Dresselhaus term becomes dominant and reduces the anisotropy.
Analysis and Characterization of Flow-Generated Sound  [PDF]
Dominik Surek
American Journal of Computational Mathematics (AJCM) , 2013, DOI: 10.4236/ajcm.2013.34046
Abstract:

Flow-generated sound and velocity distributions of free flows are characterized by frequency spectra (FFT and several spectra from the octave spectrum over the one-third octave spectrum till the narrow band spectrum), by the PSD (power spectrum density) and wavelets. Whereas previously, flow processes are characterized by the average velocity, by the local velocity, if needed also by the three-dimensional velocity distribution and the degree of turbulence, also the flows and particular velocity distributions could be described by the acoustic pressure and level, by the power spectrum density and by wavelets, especially by the Gabor-Wavelet, as shown below.

SIRT and Its Unresolved Problems—Is Imaging the Solution? A Review  [PDF]
Franziska Schulz, Michael Friebe
Journal of Cancer Therapy (JCT) , 2016, DOI: 10.4236/jct.2016.77054
Abstract: Selective Internal Radiation Therapy (SIRT) is used as a treatment option for unresectable liver tumors. In SIRT, microspheres, which have a radioactive substance as an integral component, are placed via image guided catheters into the hepatic artery. The ionizing radiation is directly delivered to the tumor. Currently used commercially available microspheres are based on Yttrium 90, a β-emitter, which has been shown to be safe and to produce good clinical results. The technical features of Y90, their applications and their limitations are presented. Image guidance and intraoperative depiction of Yttrium 90 microspheres are restricted, which is currently one of the main limitations in SIRT. Therapy planning and control is currently based on pre- and post-operative images to evaluate the placement of the microspheres respectively. Holmium 166, another possible nuclide integrated into the microspheres emits a higher amount of secondary γ-radiation (Bremsstrahlung) than Yttrium 90. This enables an improved depiction of the microspheres inside the patient during and immediately after application, but comes with other shortfalls. Imaging of delivery and verification of the microsphere placement could solve many of the identified problems with SIRT. The different technologies are reviewed and an outlook in future developments is given particularly on image guidance and therapy control.
Radiation–Induced Signaling Results in Mitochondrial Impairment in Mouse Heart at 4 Weeks after Exposure to X-Rays
Zarko Barjaktarovic, Dominik Schmaltz, Alena Shyla, Omid Azimzadeh, Sabine Schulz, Julia Haagen, Wolfgang D?rr, Hakan Sarioglu, Alexander Sch?fer, Michael J. Atkinson, Hans Zischka, Soile Tapio
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0027811
Abstract: Backround Radiation therapy treatment of breast cancer, Hodgkin's disease or childhood cancers expose the heart to high local radiation doses, causing an increased risk of cardiovascular disease in the survivors decades after the treatment. The mechanisms that underlie the radiation damage remain poorly understood so far. Previous data show that impairment of mitochondrial oxidative metabolism is directly linked to the development of cardiovascular disease. Methodology/Principal findings In this study, the radiation-induced in vivo effects on cardiac mitochondrial proteome and function were investigated. C57BL/6N mice were exposed to local irradiation of the heart with doses of 0.2 Gy or 2 Gy (X-ray, 200 kV) at the age of eight weeks, the control mice were sham-irradiated. After four weeks the cardiac mitochondria were isolated and tested for proteomic and functional alterations. Two complementary proteomics approaches using both peptide and protein quantification strategies showed radiation-induced deregulation of 25 proteins in total. Three main biological categories were affected: the oxidative phophorylation, the pyruvate metabolism, and the cytoskeletal structure. The mitochondria exposed to high-dose irradiation showed functional impairment reflected as partial deactivation of Complex I (32%) and Complex III (11%), decreased succinate-driven respiratory capacity (13%), increased level of reactive oxygen species and enhanced oxidation of mitochondrial proteins. The changes in the pyruvate metabolism and structural proteins were seen with both low and high radiation doses. Conclusion/Significance This is the first study showing the biological alterations in the murine heart mitochondria several weeks after the exposure to low- and high-dose of ionizing radiation. Our results show that doses, equivalent to a single dose in radiotherapy, cause long-lasting changes in mitochondrial oxidative metabolism and mitochondria-associated cytoskeleton. This prompts us to propose that these first pathological changes lead to an increased risk of cardiovascular disease after radiation exposure.
X-ray monitoring of the radio and gamma-ray loud Narrow-Line Seyfert 1 Galaxy PKS 2004-447
Annika Kreikenbohm,Matthias Kadler,J?rn Wilms,Robert Schulz,Cornelia Müller,Roopesh Ojha,Eduardo Ros,Karl Mannheim,Dominik Els?sser
Physics , 2013, DOI: 10.1051/epjconf/20136104017
Abstract: We present preliminary results of the X-ray analysis of XMM-Newton and Swift observations as part of a multi-wavelength monitoring campaign in 2012 of the radio-loud narrow line Seyfert 1 galaxy PKS 2004-447. The source was recently detected in gamma-rays by Fermi/LAT among only four other galaxies of that type. The 0.5-10 keV X-ray spectrum is well-described by a simple absorbed powerlaw (photon index ~ 1.6). The source brightness exhibits variability on timescales of months to years with indications for spectral variability, which follows a 'bluer-when-brighter' behaviour, similar to blazars.
The 2013 multiwavelength campaign on the Narrow-Line Seyfert 1 galaxy 1H 0323+342: a rosetta stone for the jet/disk paradigm
Omar Tibolla,Sarah Kaufmann,Luigi Foschini,Karl Mannheim,Shu Zhang,Jian Li,Emmanouil Angelakis,Lars Fuhrmann,Paul Haeusner,Jannik Kania,Dominik Elsaesser,Annika Kreikenbohm,Robert Schulz,Matthias Kadler
Physics , 2013,
Abstract: Narrow-Line Seyfert 1 galaxies have been established as a new class of gamma-ray emitting AGN with relatively low black hole masses, but near-Eddington accretion rates. Other extragalactic gamma-ray sources observed so far such as Flat Spectrum Radio Quasars, Radio Galaxies, and BL Lacertae Objects generally exhibit much higher black hole masses and, in the case of BL Lac objects and FRI Radio Galaxies, much lower accretions rates. The multifrequency campaign of 2013 centered on the bright source 1H 0323+342 will provide further insights into the nature of the jets and their gamma ray production mechanisms in a largely unexplored corner of AGN parameter space. Here, we show preliminary results of this campaign and discuss them.
Novel model for wine fermentation including the yeast dying phase
Alfio Borzì,Juri Merger,Jonas Müller,Achim Rosch,Christina Schenk,Dominik Schmidt,Stephan Schmidt,Volker Schulz,Kai Velten,Christian von Wallbrunn,Michael Z?nglein
Quantitative Biology , 2014,
Abstract: This paper presents a novel model for wine fermentation including a death phase for yeast and the influence of oxygen on the process. A model for the inclusion of the yeast dying phase is derived and compared to a model taken from the literature. The modeling ability of the several models is analyzed by comparing their simulation results.
Microscopic Study of Defect Luminescence between 0.72 - 0.85 eV by Optical Microscopy  [PDF]
Dominik Lausch, Christian Hagendorf
Microscopy Research (MR) , 2014, DOI: 10.4236/mr.2014.21002
Abstract:

In this contribution, an experimental setup to investigate the defect luminescence between 0.72 - 0.85 eV of single defects in Silicon by optical microscopy is introduced. For this purpose, an optical microscope is equipped with an InGaAs CCD detector and a longpass filter with a cut-off wavelength at 1450 nm in order to filter out the band-to-band luminescence at around 1.1 eV. Grain boundaries showing homogeneous distributed defect luminescence can be localized at a μm-scale.

The Game of Life, Decision and Communication  [PDF]
Roland Mühlenbernd, Simon Schulz
Natural Science (NS) , 2014, DOI: 10.4236/ns.2014.613097
Abstract:

The game of life represents a spatial environment of cells that live and die according to fixed rules of nature. In the basic variant of the game a cell’s behavior can be described as reactive and deterministic since each cell’s transition from an actual state to a subsequent state is straight-forwardly defined by the rules. Furthermore, it can be shown that the alive cells’ spatial occupation share of the environment decreases quickly and levels out at a really small value (around 3%), virtually independent of the initial number of alive cells. In this study we will show that this occupation share can be strongly increased if alive cells become more active by making non-deterministic sacrificial decisions according to their individual positions. Furthermore, we applied signaling games in combination with reinforcement learning to show that results can be even more improved if cells learn to signal for navigating the behavior of neighbor cells. This result stresses the assumption that individual behavior and local communication supports the optimization of resourcing and constitute important steps in the evolution of creature and man.

 

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