Fak. 2 Mathematik und Naturwissenschaften

1957 Items

Recent Submissions
IR-spektroskopische Charakterisierung von organisch-funktionalisierten Monolagen und Immobilisierung von Peptiden auf Silizium Oberflächen

Borowski, Anne (2018)

Das Interesse an der Entwicklung und Forschung von Biosensoren hat sich in den letzten Jahren stetig gesteigert. Die Verwendung von optischen, auf SOI (silicon-on-isulator) basierenden Sensoren, bietet die Möglichkeit Protein-Ligand-Wechselwirkungen auf ihre thermodynamischen und kinetischen Eigenschaften zu untersuchen. Das Konzept von selbstassemblierten Monoschichten (SAMs) mit definierten o...

Well-ordered iron oxide and sulfide thin films

Davis, Earl Matthew (2018)

In this thesis, the growth of iron oxide and iron sulfide thin films has been investigated. These are materials that are abundantly found in the earth's crust and have long been studied by humanity, having a wide range of properties that have seen their use in many applications. Among these applications, iron oxides have played an important role in catalytic processes such as the Haber-Bosch p...

Finite-Size Effects on Traveling Wave Solutions to Neural Field Equations

Lang, Eva ; Stannat, Wilhelm (2017-07-06)

Neural field equations are used to describe the spatio-temporal evolution of the activity in a network of synaptically coupled populations of neurons in the continuum limit. Their heuristic derivation involves two approximation steps. Under the assumption that each population in the network is large, the activity is described in terms of a population average. The discrete network is then approx...

The inverse perovskite BaLiF3: single-crystal neutron diffraction and analyses of potential ion pathways

Wiedemann, Dennis ; Meutzner, Falk ; Fabelo, Oscar ; Ganschow, Steffen (2018)

Doped barium lithium trifluoride has attracted attention as component for scintillators, luminescent materials and electrodes. With lithium and fluoride, it contains two possibly mobile species, which may account for its ionic conductivity. In this study, neutron diffraction on oxide-containing BaLiF3 single-crystals is performed at up to 636.2°C. Unfortunately, ion-migration pathways could not...

Electronic and vibrational properties of diamondoid derivatives, graphite, and carbon nanotubes

Tyborski, Christoph (2018)

In this work, we present an analysis of vibrational and electronic properties of diamondoids, graphene, multilayer graphene, graphite, and carbon nanotubes. The realized studies are based on optical spectroscopy, such as Raman spectroscopy, photo luminescence, photo luminescence excitation, and absorption spectroscopy, but also on in-depth model calculations. Although the analyzed material syst...

Quantification of silver nanoparticle uptake and distribution within individual human macrophages by FIB/SEM slice and view

Gührs, Erik ; Schneider, Michael ; Günther, Christian M. ; Hessing, Piet ; Heitz, Karen ; Wittke, Doreen ; Oliver, Ana López-Serrano ; Jakubowski, Norbert ; Plendl, Johanna ; Eisebitt, Stefan ; Haase, Andrea (2017-03-21)

Background Quantification of nanoparticle (NP) uptake in cells or tissues is very important for safety assessment. Often, electron microscopy based approaches are used for this purpose, which allow imaging at very high resolution. However, precise quantification of NP numbers in cells and tissues remains challenging. The aim of this study was to present a novel approach, that combines precise ...

Exact and soft recovery of structured signals from atomic and total variation norm regularization

Flinth, Axel (2018)

This thesis treats regularization techniques of inverse problems using TV- and atomic norms. In the first part of the thesis, the two concepts are connected, making a unified treatment in the rest of the thesis possible. Concretely, it is proven that for reasonable dictionaries, atomic norms can be calculated with the help of TV -minimization, and that the TV -norm can be considered as an atomi...

Dissipative systems with nonlocal delayed feedback control

Grawitter, Josua ; van Buel, Reinier ; Schaaf, Christian ; Stark, Holger (2018-11-07)

We present a linear model, which mimics the response of a spatially extended dissipative medium to a distant perturbation, and investigate its dynamics under delayed feedback control. The time a perturbation needs to propagate to a measurement point is captured by an inherent delay time (or latency). A detailed linear stability analysis demonstrates that a nonzero system delay acts to destabili...

At the Gates: The Tantalum-Rich Phase Hf3Ta2O11 and its Commensurately Modulated Structure

Wiedemann, Dennis ; Lüdtke, Tobias ; Palatinus, Lukáš ; Willinger, Elena ; Willinger, Marc G. ; Mühlbauer, Martin J. ; Lerch, Martin (2018)

Generic mixtures in the system (Zr,Hf)O2–(Nb,Ta)2O5 are employed as tunable gate materials for field-effect transistors. Whereas production processes and target compositions are well-defined, resulting crystal structures are vastly unexplored. In this study, we summarize the sparse reported findings and present the new phase Hf3Ta2O11 as synthesized via a sol–gel route. Its commensurately modul...

The Viscosity Coefficients of Biaxial-Nematic Liquid Crystals. Phenomenology and Affine Transformation Model

Baalss, Dieter (1990)

The viscosity tensor of biaxial-nematic liquid crystals contains 16 independent elements. A complete set of these viscosity coefficients is introduced and related to experimentally accessible quantities. Furthermore, the flow alignment and its stability against an arbitrary infinitesimal disturbance are discussed. By the affine transformation model, formerly established for the uniaxial symmetr...

Studies on Herbicide Binding in Photosystem II Membrane Fragments from Spinach

Fromme, R. ; Renger, G. (1990)

The mechanism of atrazine binding and its modification by Chelex-100-induced Ca2+ depletion and proteolytic degradation by trypsin, was analyzed in PS II membrane fragments from spinach. It was found: 1) Chelex-100 treatment leads in a comparatively slow process (t1/2 = 5 - 10 min) to Ca2+ re moval from a site that is characterized by a high affinity as reflected by KD values of the order of 10...

The Flash Pattern of Photosynthetic Oxygen Evolution after Treatment with Low Concentrations of Hydroxylamine as a Function of the Previous S1/S0-Ratio Further Evidence that NH2OH Reduces the Water Oxidizing Complex in the Dark

Messinger, J. ; Pauly, S. ; Witt, H. T. (1991)

Flash induced oxygen evolution patterns of isolated PS II complexes from the cyanobacterium Synechococcus were measured with a Joliot-type electrode. By suitable preflash and dark adaptation procedures, samples were prepared in the state S1 (100%), as well as enriched in S0 (60% S0, 40% S,). After treatment with low concentrations of NH2OH (≤ 100 μм), the two flash patterns were identical. This...

Static and Dynamic Properties of Ferroelectric Liquid Crystals in the Vicinity of a First-Order SmA-SmC* Phase Transition

Netz, Roland R. ; Hess, Siegfried (1992)

A unified theoretical description of static and dynamic properties of ferroelectric liquid crystals in terms of a Landau free energy is presented. The shear deformation tensor is used as principal order parameter. Results for the stationary case for tilt angle variation and dielectric properties are compared with experiments on a compound with a pronounced first-order SmA-SmC* phase transition ...

Effect of Tentoxin on the Activation and on the Catalytic Reaction of Reconstituted H+-ATPase from Chloroplasts

Fromme, Petra ; Dahse, Ingo ; Gräber, Peter (1992)

The proton-translocating ATPase from chloroplasts, CF0F1, was isolated, purified and reconstituted into asolectin liposomes. The effect of the energy transfer inhibitor, tentoxin, on different functions of the enzyme was investigated. Tentoxin does not inhibit the nucleotide release during energization by a pH /ΔΨ jump, i.e. the activation of the enzyme is not influenced. ATP synthesis driven b...

1-[4-{1,1′,1″,1‴,1′′′′-(1,3-Cyclopentadien-1,2,3,4,5-pentayl)pentakis}]-(4,1-phenylen)-alkanone und -benzoesäure pentaalkylester und deren Natrium- und Thallium(I)-Komplexe

Schumann, Herbert ; Kucht, Homa ; Kucht, Andreas (1992)

Pentaphenylcyclopentadiene (1) reacts with acyl chlorides RC(O)Cl (R = CH3, C3H7, C5H11, C7H15) with formation of the corresponding [(cyclopentadiene pentayl)pentakis] (1,4-phenylene) alkanones C5H(C6H4C(O)R-4)5 (2a, 2c, 2d and 2e). 2 a reacts with KOCl in water/dioxane to yield C5Cl(C6H4C(O)OH-4)5 (3), which after reaction with C2H5OH and C5H11OH gives the pentaesters C5Cl(C6H4C(O)OR-4)5 (4b a...

Photosystem II: Thermodynamics and Kinetics of Electron Transport from QA- to QB(QB- ) and Deleterious Effects of Copper(II)

Renger, G. ; Gleiter, H. M. ; Haag, E. ; Reifarth, F. (1993)

Studies on thermodynamics and kinetics of electron transfer from QA- to QB(QB-) were performed by monitoring laser flash induced changes of the relative fluorescence emission as a function of temperature (220 K < T < 310 K) in isolated thylakoids and PS II membrane fragments. In addition, effects of bivalent metal ions on PS II were investigated by measuring conventional fluorescence induction ...

X-Ray Structural Analysis and Vibrational Spectra of Sodium Cysteine-S-sulfonate, +H3NCH(COO-)CH2S2O3Na • 3/2H2O [1]

Steudel, Ralf ; Albertsen, Angela ; Kustos, Monika ; Pickardt, Joachim (1993)

The title compound crystallizes orthorhombically (space group C 2221) with a = 797.0, b = 870.3 and c = 2739.0 pm. The anions are zwitterions which are heavily involved in intra- and intermolecular NH •••O and OH•••O hydrogen bonding. The two types of sodium cations are coordinated by six oxygen atoms each of which belongs to either SO3 groups (Na 2) or water molecules and SO3 groups (Na1). A s...

The Bishydridobis(tetrazol-1-yl)borate Anion, [H2B(CHN4)2]-: Synthesis and Structure of the First Tetrazolylborate

Janiak, Christoph ; Esser, Lothar (1993)

Potassium bishydridobis(tetrazol-1-yl)borate (1) has been synthesized from KBH4 and tetrazole and characterized spectroscopically. Its crystal structure has been determined. 1 crystallizes in the monoclinic space group P21/n with a = 537.8(2), b = 1703.5(9), c = 919.6(3) pm, β = 106.12(3)° and V = 809.4(6)· 106 pm3.

Metallkomplexe mit 1,4,7-Trithiacyclononan: Kristallstrukturen von [CdI2 · C6H12S3]2 und [Hg(C6H12S3)2](HgI3)2

Pickardt, Joachim ; Shen, Jing (1993)

Crystals of the complexes [CdI2 · C6H12S3]2 (1) and [Hg(C6H12S3)2](HgI3)2 (2) were obtained by diffusion of 1,4,7-trithiacyclononane (9 S 3) in ethanol into aqueous solutions of cadmium iodide and mercuric iodide/potassium iodide, resp. Both compounds crystallize monoclinically,1: space group P21/n, Z = 4, a = 1207.1(5), b = 909.9(2), c = 1240.3(7) pm, β = 92.59(9)°; 2: P21/c, Z = 2, a = 804.7(...

Kristallstruktur des „supramolekularen“ Silber(I)thiocyanat-Cyclam-Komplexes [Ag(SCN)·(C10H24N4)1/2]

Pickardt, Joachim ; Shen, Jing (1994)

Colourless crystals of the 1,4,8,11-tetraazacyclotetradecane (cyclam) silver(I) thiocyanate complex [Ag(SCN) · (C10H24N4)1/2] were obtained by diffusion of a solution of cyclam in ethanol into an aqueous solution of K[Ag(SCN)2], The crystals are tetragonal, space group P42/n, Z = 8, a = b - 1256.0(4), c = 1185.5(9) pm. The SCN groups act as μ3 ligands, the S atoms of two SCN groups bridge two n...