Broadband Analysis of Holographic Power Combining Circuits

Holography is a promising technique for power combining applications in the frequency range of short millimeter and submillimeter waves. In this paper, quasi-optical holographic power combining circuits are investigated. An equivalent network is utilized which rigorously models horn arrays and biperiodic dielectric structures in order to design computer-generated holograms. We apply the network model to a 5-element quasi-optical power combiner and demonstrate its capability. The hologram is designed for 150 GHz and has an efficiency of 92.5 % with a 90 % bandwidth of 5.3 %. With the aid of a broadband waveguide power divider and a vector field measurement system, the circuit is analyzed.     

Identification and characterization of individual airborne volcanic ash particles by Raman microspectroscopy

We present for the first time the Raman microspectroscopic identification and characterization of individual airborne volcanic ash (VA) particles. The particles were collected in April/May 2010 during research aircraft flights, which were performed by Deutsches Zentrum für Luft- und Raumfahrt in the airspace near the Eyjafjallajökull volcano eruption and over Europe (between Iceland and Southern Germany). In addition, aerosol particles were sampled by an Electrical Low Pressure Impactor in Munich, Germany. As references for the Raman analysis, we used the spectra of VA collected at the ground near the place of eruption, of mineral basaltic rock, and of different minerals from a database. We found significant differences in the spectra of VA and other aerosol particles (e.g., soot, nitrates, sulfates, and clay minerals), which allowed us to identify VA among other atmospheric particulate matter. Furthermore, while the airborne VA shows a characteristic Raman pattern (with broad band from ca. 200 to ca. 700 cm^?1 typical for SiO₂ glasses and additional bands of ferric minerals), the differences between the spectra of aged and fresh particles were observed, suggesting differences in their chemical composition and/or structure. We also analyzed similarities between Eyjafjallajökull VA particles collected at different sampling sites and compared the particles with a large variety of glassy and crystalline minerals. This was done by applying cluster analysis, in order to get information on the composition and structure of volcanic ash.

LC-UV Assay of Tolperisone HCl from Sustained Release Matrix Tablets

Tolperisone HCl is a central muscle relaxant, which was incorporated in a matrix system formulated with poly(ethylene oxide)–PEO, in order to achieve adequate gastric residence time. This tablet presents considerable analytical difficulties in the quantitative determination of the drug, because the PEO matrix causes significant increase of viscosity in the samples. Our purpose was to develop a reproducible sample preparation method, which is adapted from parameters of the in vitro dissolution test and validate an LC-UV analytical method, which allows good recovery of the drug (99.97%). The developed analytical method was suitable for quantitative analysis of tolperisone HCl in matrix tablets.     

Automated computation of spin- and colour-correlatedBorn matrix elements

I report on an implementation of an algorithm for the automated numerical calculation of spin- and colour-correlated Born matrix elements in QCD. These spin- and colour-correlated matrix elements are needed for NLO calculations in combination with the subtraction method. Both massless and massive quarks are considered. There are no restrictions on the number of external particles. As a trivial sub-case, the algorithm also applies to Born matrix elements without any correlations. These are sufficient for leading order calculations.     

Thermokapillare Grenzflächenkonvektion an Gasblasen in einem Temperaturgradientenfeld

Kurzfassung Bei freien Grenzflächen spielt die thermokapillare Konvektion eine nicht zu vernachlässigende Rolle auf den Wärmetransport. In zwei Experimenten wird deren Einfluß aufgezeigt. In Silikonölen verschiedener Viskosität mit thermisch stabiler Schichtung werden Luftblasen eingebracht und das durch die thermokapillaren Kräfte gegen den Auftrieb erzeugte Geschwindigkeitsfeld vermessen. In einem zweiten Experiment wird die Erhöhung des Wärmeübergangs durch eine Luftblase an einem beheizten Draht gemessen. Trotz kleiner Berührungsfläche kann der Wärmeübergang gegenüber dem Draht ohne Blase verdoppelt werden, was der zusätzlichen Marangoni-Konvektion zuzuschreiben ist. In Wasser wurde dieser Effekt nicht beobachtet, hier wurde durch die Luftblase der Wärmeübergang um 30% reduziert.

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Thermocapillary convection on gasbubbles caused by temperature gradients

The thermocapillary convection on free surfaces is an important mechanism for heat transfer, it is demonstrated in two experiments. Silicon-oil of various viscosity is used as experimental liquid. In the thermal stable stratified liquid air bubbles were injected. Around the bubbles velocity profiles, induced by the thermocapillary force against the buoyancy force were measured. In the second experiment the enhancement of heat transfer induced by air bubbles touching a heated wire is investigated in various liquids. In spite of the small contact area between the bubble and the wire the increase of heat transfer was more than twice of the wire without bubble which is attributed to the Marangoni convection. Using water this enhancement could not be observed. At the bubble the free convection from the wire was hindered and the heat reduced by 30%.

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Herrn Prof. Dr.-Ing. K. Stephan zum 60. Geburtstag gewidmet     

Glucocorticoids Directly Affect Hyaluronan Production of Orbital Fibroblasts; A Potential Pleiotropic Effect in Graves’ Orbitopathy

Orbital connective tissue expansion is a hallmark of Graves’ orbitopathy (GO). In moderate-to-severe active GO, glucocorticoids (GC) are the first line of treatment. Here we show that hydrocortisone (HC), prednisolone (P), methylprednisolone (MP), and dexamethasone (DEX) inhibit the hyaluronan (HA) production of orbital (OF) and dermal (DF) fibroblasts. HA production of GO OFs (n = 4), NON-GO OFs (n = 4) and DFs (n = 4) was measured by ELISA. mRNA expression of enzymes of HA metabolism and fibroblast proliferation was examined by RT-PCR and BrdU incorporation, respectively. After 24 h of GC treatment (1µM) HA production decreased by an average of 67.9 ± 3.11% (p < 0.0001) in all cell cultures. HAS2, HAS3 and HYAL1 expression in OFs also decreased (p = 0.009, p = 0.0005 and p = 0.015, respectively). Ten ng/mL PDGF-BB increased HA production and fibroblast proliferation in all cell lines (p < 0.0001); GC treatment remained effective and reduced HA production under PDGF-BB-stimulated conditions (p < 0.0001). MP and DEX reduced (p < 0.001, p = 0.002, respectively) PDGF-BB-induced HAS2 expression in OFs. MP and DEX treatment decreased PDGF-BB stimulated HAS3 expression (p = 0.035 and p = 0.029, respectively). None of the GCs tested reduced the PDGF-BB stimulated proliferation rate. Our results confirm that GCs directly reduce the HA production of OFs, which may contribute to the beneficial effect of GCs in GO.     

Comparison of phase space slicing and dipole subtraction methods for \gamma^* \rightarrow Q\bar{Q}

We compare the phase space slicing and dipole subtraction methods in the computation of the inclusive and differential next-to-leading order cross sections for heavy quark production in the simple process . For the phase space slicing method we study the effects of improvement terms that remove restrictions on the slicing parameter . For the dipole method our comparison is a first check on some of its counterterms involving massive quarks, derived recently. In our comparison we address issues such as numerical accuracy and efficiency. Received: 15 October 2001 / Published online: 25 January 2002     

Mean field calculations and defect gases in lattice gauge theory

We investigate the relationship between local defects and the mean field method in lattice gauge theory. In particular we clarify the role of defects in establishing the equivalence between mean field calculations with and without gauge fixing. In two dimensions we derive the area law for the Wilson loop by a mean field calculation incorporating defects. We also establish a general rule about mean field variables which are appropriate to handle defects induced by an action that almost possesses a local symmetry group, and we apply it to theZ(2) Higgs model and to the mixedSU(2)-SO(3) model.