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Item Open Access Self-consistent modelling of pulsar magnetospheres(1989) Herold, Heinz; Ertl, Thomas; Finkbeiner, Bernd; Ruder, HannsThe magnetosphere of a rapidly rotating, strongly magnetized neutron star with aligned magnetic and rotational axes (parallel rotator) is modelled numerically. Including the radiation of the particles accelerated to relativistic energies as an efficient damping mechanism, we obtain a quasi-stationary selfconsistent solution to this classical problem. The numerical simulation, which was started from the well-known vacuum solution, yields a global magnetospheric structure that can be characterized by two regions of oppositely charged particles, which eventually produce a relativistic pulsar wind, separated by a vacuum gap of considerable extent.Item Open Access Wärmeübertragung in einem axial rotierenden, durchströmten Rohr im Bereich des thermischen Einlaufs. T. 2, Einfluß der Rotation auf eine laminare Strömung(1989) Weigand, Bernhard; Beer, HansDer Einfluß der Rotation auf das Temperaturprofil und die Wärmeübergangszahl einer laminaren Rohrströmung im Bereich des thermischen Einlaufs wird theoretisch untersucht. Es wird angenommen, daß das Geschwindigkeitsprofil voll ausgebildet ist. Die Rotation hat einen destabilisierenden Einfluß auf die Laminarströmung, die umschlägt und turbulent wird. Aufgrund der Anfachung der Turbulenz durch die Rotation verbessert sich die Wärmeübertragung mit steigender Rotations-Reynoldszahl und die thermische Einlauflänge nimmt beträchtlich ab.Item Open Access Effects of radiation damping on particle motion in pulsar vacuum fields(1989) Finkbeiner, Bernd; Herold, Heinz; Ertl, Thomas; Ruder, HannsThe effects of radiation reaction on the motion of charged particles are studied in strong electric and magnetic fields with special attention to the vacuum near-field region of an oblique rotator. For strong radiation damping a local velocity field is derived from the Lorentz-Dirac equation, which efficiently describes the motion of electrons and positrons in the whole range of typical pulsar parameters. The velocity field makes it possible to define regions in the inner magnetosphere, where particle trapping occurs due to the radiation losses. By numerical integration of particle trajectories from the pulsar surface, regions around the magnetic poles are found which are defined by particle emission into the wave zone. The shapes of the escape regions on the pulsar surface are determined to a considerable extent by the presence of the accumulation regions.Item Open Access Temperature dependence of the elastic constants for biaxial nematic liquid crystals(1989) Monselesan, Didier; Trebin, Hans-RainerThe elastic constants K ij of the Frank-Oseen energy density for uniaxial nematic liquid crystals depend on the Maier-Saupe order parameter S and hence on temperature. Longa et al. recently used an extended Landau-Ginzburg-de Gennes theory to expand the functions K ij(S) up to fourth order in S. Here, a similar procedure is applied for the elastic energy density of biaxial nematic liquid crystals. The three chiral and 15 achiral constants are expressed as fourth-order polynomials in the order parameter S and the degree of biaxiality T. Via the temperature dependence of the quantities S and T also the temperature dependence of the elastic constants is fixed.Item Open Access Mikro-Profilometrie zur Bestimmung der Topographie und Rauheit technischer Oberflächen mittels Heterodyn-Laserinterferometrie(1989) Leonhardt, Klaus; Rippert, Karl-Heinz; Tiziani, Hans J.Ein Heterodyn-Profilometer zur Messung der Rauheit polierter und feingeschliffener Oberflächen und zur Formmessung wird beschrieben. Die Vertikal- oder Höhenauflösung liegt bei 0,5 nm, der Meßbereich für Formmessungen an glatten Oberflächen bei 40 pm bei einer maximalen Abtastlänge von 300 mm. Die Lateralauflösung kann je nach Aperturausleuchtung bis zu 0,5 pm eingestellt werden. Anwendungen und Grenzen werden gezeigt, Formeln zur Lateralauflösung und zur Erfassung von Phasensprüngen sowie Profilhöhen-Übertragungsfunktionen werden diskutiert.Item Open Access Stability of organic thin films on inorganic substrates : prototype studies using metal phthalocyanines(1989) Rager, Albrecht; Gompf, Bruno; Dürselen, Lucas; Mockert, Helga; Schmeisser, Dieter; Göpel, WolfgangThin films of metal phthalocyanines (PbPc and RuPc) on inorganic substrates (Ag, Pt, Cu, Au, Al203 and Agl) In the submonolayer and monolayer range were investigated. Their chemical compositions and electronic and dynamic structures were characterized by means of photoemission and vibrational spectroscopy, with particular emphasis on the influence of the film/substrate and film/gas phase interfaces. The results indicate that RuPc surfaces are always unstable in air because of an energetically favourable oxide formation involving the central (Ru) atom. Lead phthalocyanina is more stable. Lead oxides are formed only after exposing thin films prepared under ultra-hlgh vacuum to pure oxygen. Even for PbPc, decomposition was observed at certain substrate/film interfaces: organic fragments were found in the submonolayer range on platinum substrates, an exchange of the central atom on copper substrates and catalytic decomposition of organic films on gold substrates after storage in air. Chemically perfect films without decomposition were found on Al203, Agl and Ag substrates. The results are discussed by taking into account the energetic structure of interfacial electronic states.Item Open Access Integrity basis approach to the elastic free energy functional of liquid crystals. 1, Classification of basic elastic modes(1989) Longa, Lech; Trebin, Hans-RainerUsing the method integrity basis, the most general SO(3)-invariant free energy density up to all powers in xβ and up to second order in Q xβ,y is established. The method provides all analytically independent elastic modes for nematics and cholesterics in the form of 33 so-called, irreducible invariants. Interestingly, among the irreducible invariants there are only three chiral terms (i.e. linear in Q δ,β,y ). They give rise locally to three independent helix modes in chiral, biaxial liquid crystals. This conclusion generalizes results of Trebin and Govers and Vertogen and contradicts a statement of Pleiner and Brandt, according to which only one twist term is supposed to exist. The most general free energy expansion can be written as sum of 39 additive invariants, which are multiplied by arbitrary polynomials in TrQ 2 and TrQ 3.Item Open Access Biological effects and physical characterization of shock waves by an XL-1 experimental lithotripter(1989) Brümmer, Franz; Staudenraus, Joachim; Nesper, Martina; Suhr, Dierk; Eisenmenger, Wolfgang; Hülser, Dieter F.Extracorporeal shock wave lithotripsy (ESWL) has become the clinical standard method for non-invasive disintegration not only of concrements in kidney and urinary tract but also of gallstones. Despite the widespread clinical use of ESWL, the mechanism of stone destruction is not yet really understood, but several possibilities (cavitation, shock wave reflection) are discussed. The final cause of various side effects is still under discussion. Nevertheless, during the last few years much effort was put into possible extensions of ESWL applications On the other hand , physical characterizations of shock waves are rarely reported and combined measurements of biological effects in vitro and physical characterization of the applied shock waves are not available. We, therefore, examined the influence of water temperature and gas content on the shock wave efficency in biological systems and determined several physical characteristics (pressure amplitudes, rise time etc.) of the shock waves under the same experimental conditions.Item Open Access Polarization distributions in isotropic, stretched or annealed PVDF films(1989) Bihler, Eckardt; Holdik, Karl; Eisenmenger, WolfgangThe time development of the polarization distribution across the film thickness in polyvinylidene fluoride (PVDF) was observed using the pressure step response technique. The crystallite phase composition of the samples was changed by annealing and stretching at elevated temperatures. It is shown that the crystallite phase composition, e.g., the β crystallite content, determines the spatial distribution of the permanent polarization in PVDF.Item Open Access Optical methods of measuring rough surfaces(1989) Leonhardt, Klaus; Rippert, Karl-Heinz; Tiziani, Hans J.The statistical parameters of surfaces to be measured for industrial applications vary over several orders of magnitude. Surfaces with large slopes or edges are particularly difficult to be recorded. Some measuring methods developed in our laboratory are compared and the range of applications are discussed. For polished and fine ground glass and metal surfaces a heterodyne profilometer with a vertical resolution of 0.5 nm, lateral resolution of 0.6 μm, and large scanning length is discussed. The interferometer can be changed from single- to double-pass operation by rotation of a quarter-wave-plate. For rougher surfaces a profilometer of the photometric-balance type with resolution Rq < 4 nm and dynamic range of 20 μm and an interference microscope with automated fringe evaluation is described. An integral white light roughness sensor covers the roughness range 0.04μm to 10μm and measures independently mean roughness and autocorrelation width.