TY  - GEN
A1  - Höhle, Barbara
A1  - Weissenborn, Jürgen
A1  - Kiefer, Dorothea
A1  - Schulz, Antje
A1  - Schmitz, Michaela
T1  - Functional elements in infants’ speech processing : the role of determiners in the syntactic categorization of lexical elements
N2  - How do children determine the syntactic category of novel words? In this article we present the results of 2 experiments that investigated whether German children between 12 and 16 months of age can use distributional knowledge that determiners precede nouns and subject pronouns precede verbs to syntactically categorize adjacent novel words. Evidence from the head-turn preference paradigm shows that, although 12- to 13-month-olds cannot do this, 14- to 16-month-olds are able to use a determiner to categorize a following novel word as a noun. In contrast, no categorization effect was found for a novel word following a subject pronoun. To understand this difference we analyzed adult child-directed speech. This analysis showed that there are in fact stronger co-occurrence relations between determiners and nouns than between subject pronouns and verbs. Thus, in German determiners may be more reliable cues to the syntactic category of an adjacent novel word than are subject pronouns. We propose that the capacity to syntactically categorize novel words, demonstrated here for the first time in children this young, mediates between the recognition of the specific morphosyntactic frame in which a novel word appears and the word-to-world mapping that is needed to build up a semantic representation for the novel word.
T3  - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe - paper 023 
Y1  - 2004
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-16285
ER  - 
TY  - GEN
A1  - Ascher, Uri M.
A1  - Chin, Hongsheng
A1  - Petzold, Linda R.
A1  - Reich, Sebastian
T1  - Stabilization of constrained mechanical systems with DAEs and invariant manifolds
N2  - Many methods have been proposed for the simulation of constrained mechanical systems. The most obvious of these have mild instabilities and drift problems. Consequently, stabilization techniques have been proposed A popular stabilization method is Baumgarte's technique, but the choice of parameters to make it robust has been unclear in practice. Some of the simulation methods that have been proposed and used in computations are reviewed here, from a stability point of view. This involves concepts of differential-algebraic equation (DAE) and ordinary differential equation (ODE) invariants. An explanation of the difficulties that may be encountered using Baumgarte's method is given, and a discussion of why a further quest for better parameter values for this method will always remain frustrating is presented. It is then shown how Baumgarte's method can be improved. An efficient stabilization technique is proposed, which may employ explicit ODE solvers in case of nonstiff or highly oscillatory problems and which relates to coordinate projection methods. Examples of a two-link planar robotic arm and a squeezing mechanism illustrate the effectiveness of this new stabilization method.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 033 
Y1  - 1994
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-15698
ER  - 
TY  - GEN
A1  - Leimkuhler, Benedict
A1  - Reich, Sebastian
T1  - Symplectic integration of constrained Hamiltonian systems
N2  - A Hamiltonian system in potential form (formula in the original abstract) subject to smooth constraints on q can be viewed as a Hamiltonian system on a manifold, but numerical computations must be performed in Rn. In this paper methods which reduce "Hamiltonian differential algebraic equations" to ODEs in Euclidean space are examined. The authors study the construction of canonical parameterizations or local charts as well as methods based on the construction of ODE systems in the space in which the constraint manifold is embedded which preserve the constraint manifold as an invariant manifold. In each case, a Hamiltonian system of ordinary differential equations is produced. The stability of the constraint invariants and the behavior of the original Hamiltonian along solutions are investigated both numerically and analytically.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 032 
KW  - differential-algebraic equations
KW  - constrained Hamiltonian systems
KW  - canonical discretization schemes
KW  - symplectic methods
Y1  - 1994
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-15653
ER  - 
TY  - GEN
A1  - Reich, Sebastian
T1  - Smoothed dynamics of highly oscillatory Hamiltonian systems
N2  - We consider the numerical treatment of Hamiltonian systems that contain a potential which grows large when the system deviates from the equilibrium value of the potential. Such systems arise, e.g., in molecular dynamics simulations and the spatial discretization of Hamiltonian partial differential equations. Since the presence of highly oscillatory terms in the solutions forces any explicit integrator to use very small step size, the numerical integration of such systems provides a challenging task. It has been suggested before to replace the strong potential by a holonomic constraint that forces the solutions to stay at the equilibrium value of the potential. This approach has, e.g., been successfully applied to the bond stretching in molecular dynamics simulations. In other cases, such as the bond-angle bending, this methods fails due to the introduced rigidity. Here we give a careful analysis of the analytical problem by means of a smoothing operator. This will lead us to the notion of the smoothed dynamics of a highly oscillatory Hamiltonian system. Based on our analysis, we suggest a new constrained formulation that maintains the flexibility of the system while at the same time suppressing the high-frequency components in the solutions and thus allowing for larger time steps. The new constrained formulation is Hamiltonian and can be discretized by the well-known SHAKE method.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 031 
Y1  - 1995
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-15639
ER  - 
TY  - GEN
A1  - Ascher, Uri M.
A1  - Chin, Hongsheng
A1  - Reich, Sebastian
T1  - Stabilization of DAEs and invariant manifolds
N2  - Many methods have been proposed for the stabilization of higher index differential-algebraic equations (DAEs). Such methods often involve constraint differentiation and problem stabilization, thus obtaining a stabilized index reduction. A popular method is Baumgarte stabilization, but the choice of parameters to make it robust is unclear in practice. Here we explain why the Baumgarte method may run into trouble. We then show how to improve it. We further develop a unifying theory for stabilization methods which includes many of the various techniques proposed in the literature. Our approach is to (i) consider stabilization of ODEs with invariants, (ii) discretize the stabilizing term in a simple way, generally different from the ODE discretization, and (iii) use orthogonal projections whenever possible. The best methods thus obtained are related to methods of coordinate projection. We discuss them and make concrete algorithmic suggestions.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 030 
Y1  - 1994
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-15625
ER  - 
TY  - GEN
A1  - Riemer, Nathanael
T1  - Stories of the Ma’aseh Book (Maysebook) in the Scriptures of Christian Hebraists
N2  - This document contains a list of the Stories of the Ma’aseh Book (Maysebook) in the Scriptures of Christian Hebraists and exhibits an overview about the reception of the Yiddish literature in the world of letters.
N2  - Das Dokument enthält eine tabellarische Auflistung der Erzählungen des Maassebuches, welche sich in den Werken der christlichen Hebraisten befinden und bietet damit einen Überblick über die Rezeption der jiddischen Literatur in der christlichen Gelehrtenwelt.
KW  - Maysebuch
KW  - Maassebuch
KW  - Maaseh Book
KW  - christliche Hebraisten
KW  - Erzählungen
KW  - Judentum
KW  - Maysebuch
KW  - Maassebuch
KW  - Maaseh Book
KW  - Christian Hebraists
KW  - stories
KW  - Judaism
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-15498
ER  - 
TY  - THES
A1  - Frankovitch, Christine Marie
T1  - Optical methods for monitoring biological parameters of phototropic microorganisms during cultivation
T1  - Optische Verfahren zur Beobachtung biologischer Parameter während der Kultivierung phototropischer Mikroorganismen
N2  - Phototropic microalgae have a large potential for producing valuable substances for the feed, food, cosmetics, pigment, bioremediation, and pharmacy industries as well as for biotechnological processes. Today it is estimated that the microalgal aquaculture worldwide production is 5000 tons of dry matter per year (not taking into account processed products) making it an approximately $1.25 billion U.S. per year industry. In this work, several spectroscopic techniques were utilized for the investigation of microalgae cells. Specifically, photondensity wave spectroscopy was applied as a technique for the on-line observation of the culture. For effective evaluation of the photosynthetic growth processes, fast and non-invasive sensor systems that analyze the relevant biological and technical process parameters are preferred. Traditionally, the biomass in a photobioreactor is quantified with the help of turbidimetry measurements, which require extensive calibration. Another problem frequently encountered when using spectral analysis for investigating solutions is that samples of interest are often undiluted and highly scattering and do not adhere to Beer-Lambert's law. Due to the fluorescence properties of chlorophyll, fluorescence spectroscopy techniques including fluorescence lifetime imaging and single photon counting could be applied to provide images of the cells as well as determine the effects of excitation intensity on the fluorescence lifetime, which is an indicator of the condition of the cell. A photon density wave is a sinusoidally intensity-modulated optical wave stemming from a point-source of light, which propagates through diffuse medium and exhibits amplitude and phase variations. Light propagation though strongly scattering media can be described by the P1 approximation to the Boltzmann transport equation. Photon density wave spectroscopy enables the ability to differentiate between scattered and absorbed light, which is desired so that an independent determination of the reduced scattering and absorption coefficients can be made. The absorption coefficient is related to the pigment content in the cells, and the reduced scattering coefficient can be used to characterize physical and morphological properties of the medium and was here applied for the determination of the average cell size.
N2  - Phototropische Mikroalgen besitzen ein großes Potential für die Herstellung von wertvollen Substanzen sowohl für die Futtermittel-, Lebensmittel-, kosmetische und pharmazeutische Industrie, als auch für die Farbstoffsynthese. Heutzutage werden schätzungsweise 5000 Tonnen Mikroalgen Trockensubstanz pro Jahr mit einem Jahresumsatz von 1,25 Mrd. US-Dollar produziert. In dieser Arbeit wurden diverse spektroskopische Untersuchungsmethoden für die Betrachtung der Zellen verwendet. Die Photonendichtewellenspektroskopie (PDW) fand dabei insbesondere bei der on-line Beobachtung der Zellen Anwendung. Voraussetzungen für die effektive Beobachtung von photosynthetischen Wachstumsprozessen sind schnell und nicht-invasiv arbeitende Sensoren. Normalerweise wird die dabei zu untersuchende Biomasse in einem Photobioreaktor mittels Trübungsmessungen quantifiziert. Dies setzt jedoch eine sehr aufwendige Kalibration voraus. Da diese Proben zusätzlich meist in unverdünnter Form vorliegen, streuen sie stark und folgen daher nicht dem Lambert-Beer'schen Gesetz. Aufgrund der Fluoreszenzeigenschaften des Chlorophylls können fluoreszenzspektroskopische Methoden wie fluorescence lifetime imaging microscopy (FLIM) und time correlated single photon counting (TCSPC) angwendet werden. Diese Methoden werden dabei für die visuelle Darstellung der Zellen und für die Messung der Fluoreszenzlebenszeit genutzt. Eine Photondichtewelle ist eine sinusförmig intensitätsmodulierte optische Welle, die sich, ausgehend von einer punktförmigen Lichtquelle, durch das untersuchte Medium ausbreitet, wobei sich Phase und Amplitude der Welle verändern. Die Ausbreitung der Welle wird von der P1-Näherung der Boltzmann-Transport-Gleichung beschrieben. Mittels PDW kann zwischen streuenden und absorbierenden Eigenschaften von trüben Probe unterschieden werden. Dies erlaubt die Absolutbestimmung des Absorptions- und reduzierten Streukoeffizienten, die für die Qualifizierung der Probe, insbesondere der Teilchengrößenbestimmung, herangezogen werden.
KW  - Photonendichtewellen
KW  - Mikroalgen
KW  - Photon density waves
KW  - Microalgae
KW  - On.Line Monitoring
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-15403
ER  - 
TY  - JOUR
A1  - Arnold, Holger
T1  - A linearized DPLL calculus with learning
N2  - This paper describes the proof calculus LD for clausal propositional logic, which is a linearized form of the well-known DPLL calculus extended by clause learning. It is motivated by the demand to model how current SAT solvers built on clause learning are working, while abstracting from decision heuristics and implementation details. The calculus is proved sound and terminating. Further, it is shown that both the original DPLL calculus and the conflict-directed backtracking calculus with clause learning, as it is implemented in many current SAT solvers, are complete and proof-confluent instances of the LD calculus.
N2  - Dieser Artikel beschreibt den Beweiskalkül LD für aussagenlogische Formeln in Klauselform. Dieser Kalkül ist eine um Klausellernen erweiterte linearisierte Variante des bekannten DPLL-Kalküls. Er soll dazu dienen, das Verhalten von auf Klausellernen basierenden SAT-Beweisern zu modellieren, wobei von Entscheidungsheuristiken und Implementierungsdetails abstrahiert werden soll. Es werden Korrektheit und Terminierung des Kalküls bewiesen. Weiterhin wird gezeigt, dass sowohl der ursprüngliche DPLL-Kalkül als auch der konfliktgesteuerte Rücksetzalgorithmus mit Klausellernen, wie er in vielen aktuellen SAT-Beweisern implementiert ist, vollständige und beweiskonfluente Spezialisierungen des LD-Kalküls sind.
KW  - SAT
KW  - DPLL
KW  - Klausellernen
KW  - Automatisches Beweisen
KW  - SAT
KW  - DPLL
KW  - Clause Learning
KW  - Automated Theorem Proving
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-15421
ER  - 
TY  - CHAP
ED  - Kurths, Jürgen
ED  - Fradkov, Alexander
ED  - Chen, Guanrong
T1  - The 3rd international IEEE scientific conference on physics and control (PhysCon 2007) : September 3rd-7th 2007 at the University of Potsdam
N2  - During the last few years there was a tremendous growth of scientific activities in the fields related to both Physics and Control theory: nonlinear dynamics, micro- and nanotechnologies, self-organization and complexity, etc. New horizons were opened and new exciting applications emerged. Experts with different backgrounds starting to work together need more opportunities for information exchange to improve mutual understanding and cooperation. The Conference "Physics and Control 2007" is the third international conference focusing on the borderland between Physics and Control with emphasis on both theory and applications. With its 2007 address at Potsdam, Germany, the conference is located for the first time outside of Russia. The major goal of the Conference is to bring together researchers from different scientific communities and to gain some general and unified perspectives in the studies of controlled systems in physics, engineering, chemistry, biology and other natural sciences. We hope that the Conference helps experts in control theory to get acquainted with new interesting problems, and helps experts in physics and related fields to know more about ideas and tools from the modern control theory.
KW  - nonlinear dynamics
KW  - micro- and nanotechnologies
KW  - self-organization
KW  - complexity
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-15228
PB  - Universitätsverlag Potsdam
CY  - Potsdam
ER  - 
TY  - INPR
A1  - Volosevich, Alexandra V.
A1  - Meister, Claudia-Veronika
T1  - Nonlinear interaction of Farley-Buneman waves
N2  - The nonlinear interaction of waves excited by the modified two-stream instability (Farley-Buneman instability) is considered. It is found that, during the linear stage of wave growth, the enhanced pressure of the high-frequency part of the waves locally generates a ponderomotive force. This force acts on the plasma particles and redistributes them. Thus an additional electrostatic polarization field occurs, which influences the low-frequency part of the waves. Then, the low-frequency waves also cause a redistribution of the high-frequency waves. In the paper, a self-consistent system of equations is obtained, which describes the nonlinear interaction of the waves. It is shown that the considered mechanism of wave interaction causes a nonlinear stabilization of the high-frequency waves’ growth and a formation of local density structures of the charged particles. The density modifications of the charged particles during the non-linear stage of wave growth and the possible interval of aspect angles of the high-frequency waves are estimated.
T3  - NLD Preprints - 52 
Y1  - 1998
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14851
ER  - 
TY  - INPR
A1  - Böckmann, Christine
A1  - Sarközi, Janos
T1  - The ill-posed inversion of multiwavelength lidar data by a hybrid method of variable projection
N2  - The ill-posed problem of aerosol distribution determination from a small number of backscatter and extinction lidar measurements was solved successfully via a hybrid method by a variable dimension of projection with B-Splines. Numerical simulation results with noisy data at different measurement situations show that it is possible to derive a reconstruction of the aerosol distribution only with 4 measurements.
T3  - NLD Preprints - 53 
KW  - Ill-posed problem
KW  - inversion
KW  - variable projection method
KW  - multiwavelength Lidar
KW  - aerosol distribution
Y1  - 1999
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14847
ER  - 
TY  - INPR
A1  - Liperovsky, V.A.
A1  - Pochotelov, O.A.
A1  - Liperovskaya, E.V.
A1  - Parrot, M.
A1  - Meister, C.-V.
A1  - Alimov, O. A.
T1  - Modifications of sporadic E-layers caused by seismic activity
N2  - Contents: 1 Introduction 2 Formation and destruction of sporadic E-layers 3 Temporal variations of parameters of sporadic E-layers during earthquake preparation 3.1 Temporal variations of fbEs with time-scales of a few hours 3.2 Study of fbEs variations with characteristic time-scales of 0.5-3 hours 3.3 Variations of the parameters of sporadic E-layers with characteristic time-scales of 15-45 minutes 3.4 Sporadic E-layer variations with characteristic time-scales of 2-15 minutes 4 On the spatial scales of sporadic E-layer disturbances related to seismic activity 5 Complex experimental researches of the ionosphere, electromagnetic noise and the geomagnetic field 5.1 Ionospheric and electromagnetic phenomena of the Kayraccum earthquake in 1985 5.2 Comparison of anomalies with characteristic time-scales of 2-3 hours for ionospheric E- and F-layers, and temporal behaviour of electromagnetic noise emission intensity 5.3 Night airglow emissions in the E-region before earthquakes and sporadic E-layer variations 6 Physical models of lithosphere-ionosphere links 6.1 Lithosphere-ionosphere links due to AGW 6.2 Electromagnetic models for the lithosphere-ionosphere coupling 6.3 Sporadic E-layers as current generators 7 Discussion and conclusion
T3  - NLD Preprints - 49 
Y1  - 1998
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14799
ER  - 
TY  - INPR
A1  - Dicken, Volker
T1  - Simultaneous activity and attenuation reconstruction in emission tomography
N2  - In single photon emission computed tomography (SPECT) one is interested in reconstructing the activity distribution f of some radiopharmaceutical. The data gathered suffer from attenuation due to the tissue density µ. Each imaged slice incorporates noisy sample values of the nonlinear attenuated Radon transform (formular at this place in the original abstract) Traditional theory for SPECT reconstruction treats µ as a known parameter. In practical applications, however, µ is not known, but either crudely estimated, determined in costly additional measurements or plainly neglected. We demonstrate that an approximation of both f and µ from SPECT data alone is feasible, leading to quantitatively more accurate SPECT images. The result is based on nonlinear Tikhonov regularization techniques for parameter estimation problems in differential equations combined with Gauss-Newton-CG minimization.
T3  - NLD Preprints - 50 
KW  - SPECT
KW  - tomogrphy
KW  - attenuated Radon transform
KW  - nonlinear invers problem
KW  - Tikhonov regularization
KW  - nonlinear optimization
Y1  - 1998
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14747
ER  - 
TY  - INPR
A1  - Maaß, Peter
A1  - Pereverzev, Sergei V.
A1  - Ramlau, Ronny
A1  - Solodky, Sergei G.
T1  - An adaptive discretization for Tikhonov-Phillips regularization with a posteriori parameter selection
N2  - The aim of this paper is to describe an efficient strategy for descritizing ill-posed linear operator equations of the first kind: we consider Tikhonov-Phillips-regularization χ^δ α = (a * a + α I)^-1 A * y ^δ with a finite dimensional approximation A n instead of A. We propose a sparse matrix structure which still leads to optimal convergences rates but requires substantially less scalar products for computing A n compared with standard methods.
T3  - NLD Preprints - 48 
Y1  - 1998
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14739
ER  - 
TY  - INPR
A1  - Böckmann, Christine
A1  - Niebsch, Jenny
T1  - Examination of the nonlinear LIDAR-operator : the influence of inhomogeneous absorbing spheres on the operator
N2  - The determination of the atmospheric aerosol size distribution is an inverse illposed problem. The shape and the material composition of the air-carried particles are two substantial model parameters. Present evaluation algorithms only used an approximation with spherical homogeneous particles. In this paper we propose a new numerically efficient recursive algorithm for inhomogeneous multilayered coated and absorbing particles. Numerical results of real existing particles show that the influence of the two parameters on the model is very important and therefore cannot be ignored.
T3  - NLD Preprints - 47 
KW  - multiwavelength lidar
KW  - aerosol size distribution
KW  - inverse ill-posed problem
KW  - multilayered coated and absorbing aerosol
KW  - new recursive algorithm
Y1  - 1998
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14725
ER  - 
TY  - INPR
A1  - Braun, Robert
A1  - Feudel, Fred
A1  - Guzdar, Parvez
T1  - The route to chaos for a two-dimensional externally driven flow
N2  - We have numerically studied the bifurcations and transition to chaos in a two-dimensional fluid for varying values of the Reynolds number. These investigations have been motivated by experiments in fluids, where an array of vortices was driven by an electromotive force. In these experiments, successive changes leading to a complex motion of the vortices, due to increased forcing, have been explored [Tabeling, Perrin, and Fauve, J. Fluid Mech. 213, 511 (1990)]. We model this experiment by means of two-dimensional Navier-Stokes equations with a special external forcing, driving a linear chain of eight counter-rotating vortices, imposing stress-free boundary conditions in the vertical direction and periodic boundary conditions in the horizontal direction. As the strength of the forcing or the Reynolds number is raised, the original stationary vortex array becomes unstable and a complex sequence of bifurcations is observed. Several steady states and periodic branches and a period doubling cascade appear on the route to chaos. For increasing values of the Reynolds number, shear flow develops, for which the spatial scale is large compared to the scale of the forcing. Furthermore, we have investigated the influence of the aspect ratio of the container as well as the effect of no-slip boundary conditions at the top and bottom, on the bifurcation scenario.
T3  - NLD Preprints - 46 
Y1  - 1998
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14717
ER  - 
TY  - INPR
A1  - Lukaschewitsch, Michael
T1  - Geoelectrical conductivity problems on unbounded domains
N2  - This paper deals with the electrical conductivity problem in geophysics. It is formulated as an elliptic boundary value problem of second order for a large class of bounded and unbounded domains. A special boundary condition, the so called "Complete Electrode Model", is used. Poincaré inequalities are formulated and proved in the context of weighted Sobolev spaces, leading to existence and uniqueness statements for the boundary value problem. In addition, a parameter-to-solution operator arising from the inverse conductivity problem in medicine (EIT) and geophysics is investigated mathematically and is shown to be smooth and analytic.
T3  - NLD Preprints - 45 
Y1  - 1998
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14704
ER  - 
TY  - GEN
A1  - Köchy, Martin
T1  - Opposite trends in life stages of annual plants caused by daily rainfall variability
BT  - interaction with climate change
N2  - Global Circulation Models of climate predict not only a change of annual precipitation amounts but also a shift in the daily distribution. To improve the understanding of the importance of daily rain pattern for annual plant communities, which represent a large portion of semi-natural vegetation in the Middle East, I used a detailed, spatially explicit model. The model explicitly considers water storage in the soil and has been parameterized and validated with data collected in field experiments in Israel and data from the literature. I manipulated daily rainfall variability by increasing the mean daily rain intensity on rainy days (MDI, rain volume/day) and decreasing intervals between rainy days while keeping the mean annual amount constant. In factorial combination, I also increased mean annual precipitation (MAP). I considered five climatic regions characterized by 100, 300, 450, 600, and 800 mm MAP. Increasing MDI decreased establishment when MAP was >250 mm but increased establishment at more arid sites. The negative effect of increasing MDI was compensated by increasing mortality with increasing MDI in dry and typical Mediterranean regions (c. 360–720 mm MAP). These effects were strongly tied to water availability in upper and lower soil layers and modified by competition among seedlings and adults. Increasing MAP generally increased water availability, establishment, and density. The order of magnitudes of MDI and MAP effects overlapped partially so that their combined effect is important for projections of climate change effects on annual vegetation. The effect size of MAP and MDI followed a sigmoid curve along the MAP gradient indicating that the semi-arid region (≈300 mm MAP) is the most sensitive to precipitation change with regard to annual communitie
KW  - Klimaänderung
KW  - Klimawandel
KW  - Einjahrespflanzen
KW  - Schwankung
KW  - tägliche Regenmenge
KW  - Israel
KW  - climate change
KW  - daily rainfall variability
KW  - annual plant
KW  - Israel
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14699
SP  - 347
EP  - 357
ER  - 
TY  - INPR
A1  - Seehafer, Norbert
A1  - Schumacher, Jörg
T1  - Resistivity profile and instability of the plane sheet pinch
N2  - The stability of the quiescent ground state of an incompressible, viscous and electrically conducting fluid sheet, bounded by stress-free parallel planes and driven by an external electric field tangential to the boundaries, is studied numerically. The electrical conductivity varies as cosh–2(x1/a), where x1 is the cross-sheet coordinate and a is the half width of a current layer centered about the midplane of the sheet. For a <~ 0.4L, where L is the distance between the boundary planes, the ground state is unstable to disturbances whose wavelengths parallel to the sheet lie between lower and upper bounds depending on the value of a and on the Hartmann number. Asymmetry of the configuration with respect to the midplane of the sheet, modelled by the addition of an externally imposed constant magnetic field to a symmetric equilibrium field, acts as a stabilizing factor.
T3  - NLD Preprints - 44 
Y1  - 1998
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14686
ER  - 
TY  - INPR
A1  - Rüdiger, Sten
A1  - Feudel, Fred
A1  - Seehafer, Norbert
T1  - Dynamo bifurcations in an array of driven convection-like rolls
N2  - The bifurcations in a three-dimensional incompressible, electrically conducting fluid with an external forcing of the Roberts type have been studied numerically. The corresponding flow can serve as a model for the convection in the outer core of the Earth and is realized in an ongoing laboratory experiment aimed at demonstrating a dynamo effect. The symmetry group of the problem has been determined and special attention has been paid to symmetry breaking by the bifurcations. The nonmagnetic, steady Roberts flow loses stability to a steady magnetic state, which in turn is subject to secondary bifurcations. The secondary solution branches have been traced until they end up in chaotic states.
T3  - NLD Preprints - 43 
Y1  - 1998
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14678
ER  - 
TY  - INPR
A1  - Zienicke, Egbert
A1  - Seehafer, Norbert
A1  - Feudel, Fred
T1  - Bifurcations in two-dimensional Rayleigh-Bénard convection
N2  - Two-dimensional bouyancy-driven convection in a horizontal fluid layer with stress-free boundary conditions at top and bottom and periodic boundary conditions in the horizontal direction is investigated by means of numerical simulation and bifurcation-analysis techniques. As the bouyancy forces increase, the primary stationary and symmetric convection rolls undergo successive Hopf bifurcations, bifurcations to traveling waves, and phase lockings. We pay attention to symmetry breaking and its connection with the generation of large-scale horizontal flows. Calculations of Lyapunov exponents indicate that at a Rayleigh number of 2.3×105 no temporal chaos is reached yet, but the system moves nonchaotically on a 4-torus in phase space.
T3  - NLD Preprints - 42 
Y1  - 1997
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14534
ER  - 
TY  - INPR
A1  - Engbert, Ralf
A1  - Scheffczyk, Christian
A1  - Krampe, Ralf-Thomas
A1  - Rosenblum, Mikhael
A1  - Kurths, Jürgen
A1  - Kliegl, Reinhold
T1  - Tempo-induced transitions in polyrhythmic hand movements
N2  - We investigate the cognitive control in polyrhythmic hand movements as a model paradigm for bimanual coordination. Using a symbolic coding of the recorded time series, we demonstrate the existence of qualitative transitions induced by experimental manipulation of the tempo. A nonlinear model with delayed feedback control is proposed, which accounts for these dynamical transitions in terms of bifurcations resulting from variation of the external control parameter. Furthermore, it is shown that transitions can also be observed due to fluctuations in the timing control level. We conclude that the complexity of coordinated bimanual movements results from interactions between nonlinear control mechanisms with delayed feedback and stochastic timing components.
T3  - NLD Preprints - 41 
Y1  - 1997
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14380
ER  - 
TY  - INPR
A1  - Seehafer, Norbert
A1  - Schumacher, Jörg
T1  - Squire‘s theorem for the magnetohydrodynamic sheet pinch
N2  - The stability of the quiescent ground state of an incompressible viscous fluid sheet bounded by two parallel planes, with an electrical conductivity varying across the sheet, and driven by an external electric field tangential to the boundaries is considered. It is demonstrated that irrespective of the conductivity profile, as magnetic and kinetic Reynolds numbers (based on the Alfvén velocity) are raised from small values, two-dimensional perturbations become unstable first.
T3  - NLD Preprints - 40 
Y1  - 1997
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14628
ER  - 
TY  - INPR
A1  - Scheel, Stefan
A1  - Seehafer, Norbert
T1  - Bifurcation to oscillations in three-dimensional Rayleigh-Bénard convection
N2  - Three-dimensional bouyancy-driven convection in a horizontal fluid layer with stress-free boundary conditions at the top and bottom and periodic boundary conditions in the horizontal directions is investigated by means of numerical simulation and bifurcation-analysis techniques. The aspect ratio is fixed to a value of 2√2 and the Prandtl number to a value of 6.8. Two-dimensional convection rolls are found to be stable up to a Rayleigh number of 17 950, where a Hopf bifurcation leads to traveling waves. These are stable up to a Rayleigh number of 30 000, where a secondary Hopf bifurcation generates modulated traveling waves. We pay particular attention to the symmetries of the solutions and symmetry breaking by the bifurcations.
T3  - NLD Preprints - 39 
Y1  - 1997
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14370
ER  - 
TY  - INPR
A1  - Böckmann, Christine
A1  - Biele, Jens
A1  - Neuber, Roland
A1  - Niebsch, Jenny
T1  - Retrieval of multimodal aerosol size distribution by inversion of multiwavelength data
N2  - The ill-posed problem of aerosol size distribution determination from a small number of backscatter and extinction measurements was solved successfully with a mollifier method which is advantageous since the ill-posed part is performed on exactly given quantities, the points r where n(r) is evaluated may be freely selected. A new twodimensional model for the troposphere is proposed.
T3  - NLD Preprints - 38 
KW  - Multiwavelength LIDAR
KW  - aerosol size distribution
KW  - ill-posed problem
KW  - inversion
KW  - mollifier method
KW  - coated and absorbing aerosols
Y1  - 1997
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14360
ER  - 
TY  - BOOK
ED  - Ishihara, Shinichiro
ED  - Jannedy, Stefanie
ED  - Schwarz, Anne
T1  - Interdisciplinary studies on information structure : ISIS ; Working papers of the SFB 632. - Vol. 8
N2  - The 8th volume of the working paper series Interdisciplinary Studies on Information Structure (ISIS) of the SFB 632 contains a collection of eight papers contributed by guest authors and SFB-members. The first paper on “Biased Questions” is an invited contribution by Nicholas Asher (CNRS, Laboratoire IRIT) & Brian Reese (University of Texas at Austin). Surveying English tag questions, negative polar questions, and what they term “focus” questions, they investigate the effects of prosody on discourse function and discourse structure and analyze the interaction between prosody and discourse in SDRT (Segmented Discourse Representation Theory). Stefan Hinterwimmer (A2) explores the interpretation of singular definites and universally quantified DPs in adverbially quantified English sentences. He suggests that the availability of a co-varying interpretation is more constrained in the case of universally quantified DPs than in the case of singular definites, because different from universally quantified DPs, co-varying definites are inherently focus-marked. The existence of striking similarities between topic/comment structure and bimanual coordination is pointed out and investigated by Manfred Krifka (A2). Showing how principles of bimanual coordination influence the expression of topic/comment structure beyond spoken language, he suggests that bimanual coordination might have been a preadaptation of the development of Information Structure in human communication. Among the different ways of expressing focus in Foodo, an underdescribed African Guang language of the Kwa family, the marked focus constructions are the central topic of the paper by Ines Fiedler (B1 & D2). Exploring the morphosyntactic facilities that Foodo has for focalization, she suggests that the two focus markers N and n have developed out of a homophone conjunction. Focus marking in another scarcely documented African tone language, the Gur language Konkomba, is treated by Anne Schwarz (B1 & D2). Comparing the two alleged focus markers lé and lá of the language, she argues that lé is better interpreted as a syntactic device rather than as a focus marker and shows that this analysis is corroborated by parallels in related languages. The reflexes of Information Structure in four different European languages (French, German, Greek and Hungarian) are compared and validated by Sam Hellmuth & Stavros Skopeteas (D2). The production data was collected with selected materials of the Questionnaire on Information Structure (QUIS) developed at the SFB. The results not only allow for an evaluation of the current elicitation paradigms, but also help to identify potentially fruitful venues of future research. Frank Kügler, Stavros Skopeteas (D2) & Elisabeth Verhoeven (University of Bremen) give an account of the encoding of Information Structure in Yucatec Maya, a Mayan tone language spoken on the Yucatecan peninsula in Mexico. The results of a production experiment lead them to the conclusion that focus is mainly expressed by syntax in this language. Stefanie Jannedy (D3) undertakes an instrumental investigation on the expressions and interpretation of focus in Vietnamese, a language of the Mon-Khmer family contrasting six lexical tones. The data strongly suggests that focus in Vietnamese is exclusively marked by prosody (intonational emphasis expressed via duration, f0 and amplitude) and that different focus conditions can reliably be recovered. This volume offers insights into current work conducted at the SFB 632, comprising empirical and theoretical aspects of Information Structure in a multitude of languages. Several of the papers mine field work data collected during the first phase of the SFB and explore the expression of Information Structure in tone and non-tone languages from various regions of the world.
T3  - Interdisciplinary studies on information structure : ISIS ; working papers of the SFB 632 - 8 
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14359
SN  - 978-3-939469-72-8
SN  - 1866-4725
SN  - 1614-4708
PB  - Universitätsverlag Potsdam
CY  - Potsdam
ER  - 
TY  - INPR
A1  - Braun, Robert
A1  - Feudel, Fred
A1  - Seehafer, Norbert
T1  - Bifurcations and chaos in an array of forced vortices
N2  - We have studied the bifurcation structure of the incompressible two-dimensional Navier-Stokes equations with a special external forcing driving an array of 8×8 counterrotating vortices. The study has been motivated by recent experiments with thin layers of electrolytes showing, among other things, the formation of large-scale spatial patterns. As the strength of the forcing or the Reynolds number is raised the original stationary vortex array becomes unstable and a complex sequence of bifurcations is observed. The bifurcations lead to several periodic branches, torus and chaotic solutions, and other stationary solutions. Most remarkable is the appearance of solutions characterized by structures on spatial scales large compared to the scale of the forcing. We also characterize the different dynamic regimes by means of tracers injected into the fluid. Stretching rates and Hausdorff dimensions of convected line elements are calculated to quantify the mixing process. It turns out that for time-periodic velocity fields the mixing can be very effective.
T3  - NLD Preprints - 37 
Y1  - 1997
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14564
ER  - 
TY  - INPR
A1  - Witt, Annette
A1  - Neiman, Alexander
A1  - Kurths, Jürgen
T1  - Characterizing the dynamics of stochastic bistable systems by measures of complexity
N2  - The dynamics of noisy bistable systems is analyzed by means of Lyapunov exponents and measures of complexity. We consider both the classical Kramers problem with additive white noise and the case when the barrier fluctuates due to additional external colored noise. In case of additive noise we calculate the Lyapunov exponents and all measures of complexity analytically as functions of the noise intensity resp. the mean escape time. For the problem of fluctuating barrier the usual description of the dynamics with the mean escape time is not sufficient. The application of the concept of measures of complexity allows to describe the structures of motion in more detail. Most complexity measures sign the value of correlation time at which the phenomenon of resonant activation occurs with an extremum.
T3  - NLD Preprints - 36 
Y1  - 1997
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14556
ER  - 
TY  - INPR
A1  - Schmidtmann, Olaf
A1  - Feudel, Fred
A1  - Seehafer, Norbert
T1  - Nonlinear Galerkin methods for the 3D magnetohydrodynamic equations
N2  - The usage of nonlinear Galerkin methods for the numerical solution of partial differential equations is demonstrated by treating an example. We desribe the implementation of a nonlinear Galerkin method based on an approximate inertial manifold for the 3D magnetohydrodynamic equations and compare its efficiency with the linear Galerkin approximation. Special bifurcation points, time-averaged values of energy and enstrophy as well as Kaplan-Yorke dimensions are calculated for both schemes in order to estimate the number of modes necessary to correctly describe the behavior of the exact solutions.
T3  - NLD Preprints - 35 
Y1  - 1997
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14431
ER  - 
TY  - INPR
A1  - Jansen, Wolfgang
T1  - A note on the determination of the type of communication areas
N2  - The paper presents a method that determines, by standard numerical means, the type of mutual relations of fold and flip bifurcations (configured as a so-called communication area) of a map. Equation systems are developed for the computation of points where a transition between areas of different types occurs. Furthermore, it is shown that saddle area<->spring area transitions can exist which have not yet been considered in the literature. Analytical conditions of that transition are derived.
T3  - NLD Preprints - 33 
Y1  - 1996
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14339
ER  - 
TY  - INPR
A1  - Seehafer, Norbert
A1  - Zienicke, Egbert
A1  - Feudel, Fred
T1  - Absence of magnetohydrodynamic activity in the voltage-driven sheet pinch
N2  - We have numerically studied the bifurcation properties of a sheet pinch with impenetrable stress-free boundaries. An incompressible, electrically conducting fluid with spatially and temporally uniform kinematic viscosity and magnetic diffusivity is confined between planes at x1=0 and 1. Periodic boundary conditions are assumed in the x2 and x3 directions and the magnetofluid is driven by an electric field in the x3 direction, prescribed on the boundary planes. There is a stationary basic state with the fluid at rest and a uniform current J=(0,0,J3). Surprisingly, this basic state proves to be stable and apparently to be the only time-asymptotic state, no matter how strong the applied electric field and irrespective of the other control parameters of the system, namely, the magnetic Prandtl number, the spatial periods L2 and L3 in the x2 and x3 directions, and the mean values B¯2 and B¯3 of the magnetic-field components in these directions.
T3  - NLD Preprints - 32 
Y1  - 1996
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14328
ER  - 
TY  - INPR
A1  - Feudel, Fred
A1  - Seehafer, Norbert
A1  - Galanti, Barak
A1  - Rüdiger, Sten
T1  - Symmetry breaking bifurcations for the magnetohydrodynamic equations with helical forcing
N2  - We have studied the bifurcations in a three-dimensional incompressible magnetofluid with periodic boundary conditions and an external forcing of the Arnold-Beltrami-Childress (ABC) type. Bifurcation-analysis techniques have been applied to explore the qualitative behavior of solution branches. Due to the symmetry of the forcing, the equations are equivariant with respect to a group of transformations isomorphic to the octahedral group, and we have paid special attention to symmetry-breaking effects. As the Reynolds number is increased, the primary nonmagnetic steady state, the ABC flow, loses its stability to a periodic magnetic state, showing the appearance of a generic dynamo effect; the critical value of the Reynolds number for the instability of the ABC flow is decreased compared to the purely hydrodynamic case. The bifurcating magnetic branch in turn is subject to secondary, symmetry-breaking bifurcations. We have traced periodic and quasi- periodic branches until they end up in chaotic states. In particular detail we have analyzed the subgroup symmetries of the bifurcating periodic branches, which are closely related to the spatial structure of the magnetic field.
T3  - NLD Preprints - 31 
Y1  - 1996
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14317
ER  - 
TY  - JOUR
A1  - Lipke, Katrin
A1  - Zitzmann, Max
A1  - Amberger, Manuel
A1  - Ehlert, Carsten
A1  - Rößler, Dirk
A1  - Krüger, Frank
A1  - Ohrnberger, Matthias
T1  - Traveltime residuals at regional and teleseismic distances for SE-Asia
N2  - Traveltime residuals for worldwide seismic stations are calculated. We use P and S waves from earthquakes in SE-Asia at teleseismic and regional distances. The obtained station residuals help to enhance earthquake localisation. Furthermore we calculated regional source dependent station residuals. They show a systematic dependence of the locality of the source. These source dependent residuals reflect heterogenities along the path and can be used for a refinement of earthquake localisation.
N2  - Laufzeitresiduen für weltweite seismische Stationen werden berechnet. Wir nutzen P - und S-Wellen von Erdbeben in Südostasien in teleseismischen und regionalen Distanzen. Die so erhaltenen Stationsresiduen helfen, die Lokaliesierung von Erdbeben zu verbessern. Außerdem berechnen wir regional quellabhängige Stationsresiduen. Diese zeigen eine systematische Abhänbgigkeit vom Ort der Quelle. Sie spiegeln Heterogenitäten entlang des Strahlweges wieder und können für eine Verfeinerung der Ersbebenlokaliesierung genutzt werden.
KW  - Seismologie
KW  - Südostasien
KW  - Laufzeitresiduen
KW  - GITEWS
KW  - Wellengeschwindigkeiten
KW  - seismology
KW  - Southeast Asia
KW  - traveltime
KW  - residuals
KW  - GITEWS
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14117
ER  - 
TY  - INPR
A1  - Maaß, Peter
A1  - Rieder, Andreas
T1  - Wavelet-accelerated Tikhonov-Phillips regularization with applications
N2  - Contents: 1 Introduction 1.1 Tikhanov-Phillips Regularization of Ill-Posed Problems 1.2 A Compact Course to Wavelets 2 A Multilevel Iteration for Tikhonov-Phillips Regularization 2.1 Multilevel Splitting 2.2 The Multilevel Iteration 2.3 Multilevel Approach to Cone Beam Reconstuction 3 The use of approximating operators 3.1 Computing approximating families {Ah}
T3  - NLD Preprints - 30 
Y1  - 1996
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14104
ER  - 
TY  - INPR
A1  - Braun, Robert
A1  - Feudel, Fred
T1  - Supertransient chaos in the two-dimensional complex Ginzburg-Landau equation
N2  - We have shown that the two-dimensional complex Ginzburg-Landau equation exhibits supertransient chaos in a certain parameter range. Using numerical methods this behavior is found near the transition line separating frozen spiral solutions from turbulence. Supertransient chaos seems to be a common phenomenon in extended spatiotemporal systems. These supertransients are characterized by an average transient lifetime which depends exponentially on the size of the system and are due to an underlying nonattracting chaotic set.
T3  - NLD Preprints - 29 
Y1  - 1996
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14099
ER  - 
TY  - INPR
A1  - Voss, Henning
A1  - Kurths, Jürgen
A1  - Schwarz, Udo
T1  - Reconstruction of grand minima of solar activity from Delta 14 C data : linear and nonlinear signal analysis
N2  - Using a special technique of data analysis, we have found out 34 grand minima of solar activity obtained from a 7,700 years long Δ14C record. The method used rests on a proper filtering of the Δ14C record and the extrapolation of verifiable results for the later history back in time. Additionally, we use a method of nonlinear dynamics, the recurrence rate, to back up the results. Our findings are not contradictory to the record of solar maxima resp. minima by Eddy [5], but constitute a considerable extension. Hence, it has become possible to look closer at the validity of models. This way, we have tested several models for solar activity, esp. the model of Barnes et al. [1]. There are hints for that the grand minima might solely be driven by the 209 year period found in the Δ14C record.
T3  - NLD Preprints - 28 
Y1  - 1996
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-14083
ER  - 
TY  - INPR
A1  - Jansen, Wolfgang
T1  - CANDYS/QA : algorithms, programs, and user‘s manual
N2  - Contents: I. Algorithms 1. Theoretical Backround 2. Numerical Procedures 3. Graph Representation of the Solutions 4. Applications and Example II. Users' Manual 5. About the Program 6. The Course of a Qualitative Analysis 7. The Model Module 8. Input description 9. Output Description 10. Example 11. Graphics
T3  - NLD Preprints - 27 
Y1  - 1995
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-13920
ER  - 
TY  - GEN
A1  - Zyla, Benjamin
T1  - Multilateralism à la Carte? : The Bush II administration and US foreign policy
N2  - The use of unilateral force under George W. Bush is not a new phenomenon in US foreign policy. As the author argues, it is merely a continuation of Bill Clinton’s foreign policy and is deeply rooted in both the foreign policy traditions of Jacksonianism and Wilsonianism. The analysis concludes that Clinton used unilateralist foreign policy with a 'smile' whereas the Bush administration uses it with an attitude.
N2  - Die unilaterale Außenpolitik unter George W. Bush ist kein neues Phänomen der US-Diplomatie. Dem Autor zufolge ist sie vielmehr eine Fortführung der Politik der Clinton-Regierung und hat ihre Wurzeln in den Traditionen eines Andrew Jackson und Woodrow Wilson. Clinton vermochte jedoch seine unilaterale Politik mit einem "Lächeln" zu verkaufen, wohingegen die Art und Weise der Bush-Administration stets Irritationen hervorrief.
KW  - US-Außenpolitik
KW  - George W. Bush
KW  - Unilateralismus
KW  - US foreign policy
KW  - George W. Bush
KW  - unilateralism
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-13439
ER  - 
TY  - GEN
A1  - Köchy, Martin
T1  - Stochastic time series of daily precipitation for the interior of Israel
N2  - This contribution describes a generator of stochastic time series of daily precipitation for the interior of Israel from c. 90 to 900 mm mean annual precipitation (MAP) as a tool for studies of daily rain variability. The probability of rainfall on a given day of the year is described by a regular Gaussian peak curve function. The amount of rain is drawn randomly from an exponential distribution whose mean is the daily mean rain amount (averaged across years for each day of the year) described by a flattened Gaussian peak curve. Parameters for the curves have been calculated from monthly aggregated, long-term rain records from seven meteorological stations. Parameters for arbitrary points on the MAP gradient are calculated from a regression equation with MAP as the only independent variable. The simple structure of the generator allows it to produce time series with daily rain patterns that are projected under climate change scenarios and simultaneously control MAP. Increasing within-year variability of daily precipitation amounts also increases among-year variability of MAP as predicted by global circulation models. Thus, the time series incorporate important characteristics for climate change research and represent a flexible tool for simulations of daily vegetation or surface hydrology dynamics.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 029 
KW  - stochastische Zeitreihen
KW  - täglicher Niederschlag
KW  - Israel
KW  - Klimawandel
KW  - stochastic time series
KW  - daily precipitation
KW  - Israel
KW  - climate change
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-13155
ER  - 
TY  - GEN
A1  - Kaafarani, Bilal R.
A1  - Wex, Brigitte
A1  - Strehmel, Bernd
A1  - Neckers, Douglas C.
T1  - Structural concept for fluorinated Y-enynes with solvatochromic properties
N2  - An approach to the development of fluorescent probes to follow polymerizations in situ using fluorinated cross-conjugated enediynes (Y-enynes) is reported. Different substitution patterns in the Y-enynes result in distinct solvatochromic behavior. β,β-Bis(phenylethynyl)pentafluorostyrene 7, which bears no donor substituents and only fluorine at the styrene moiety, shows no solvatochromism. Donor substituted β,β-bis(3,4,5-trimethoxyphenylethynyl) pentafluorostyrene 8 and β,β-bis(4-butyl-2,3,5,6-tetrafluorophenylethynyl)-3,4,5-trimethoxystyrene 9 exhibit solvatochromism upon change of solvent polarity. Y-enyne 8 showed the largest solvatochromic shift (94 nm bathochromic shift) upon changing solvent from cyclohexane to acetonitrile. A smaller solvatochromic response (44 nm bathochromic shift) was observed for 9. Lippert–Mataga treatment of 8 and 9 yields slopes of -10,800 and -6,400 cm -1, respectively. This corresponds to a change in dipole moment of 9.6 and 6.9 D, respectively. The solvatochromic behavior in 8 and 9 supports the formation of an intramolecular charge transfer (ICT) state. The low fluorescence quantum yields are caused by competitive double bond rotation. The fluorescence decay time of 9 decreases in methyltetrahydrofuran from 2.1 ns at 77 K to 0.11 ns at 200 K. Efficient single bond rotation in 9 was frozen at -50 °C in a configuration in which the trimethoxyphenyl ring is perpendicular to the fluorinated rings. 7–9 are photostable compounds. The X-ray structure of 7 shows it is not planar and that its conjugation is distorted. Y-enyne 7 stacks in the solid state showing coulombic, actetylene–arene, and fluorine–π interactions.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 027 
Y1  - 2002
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-13168
ER  - 
TY  - GEN
A1  - Reich, Oliver
A1  - Löhmannsröben, Hans-Gerd
A1  - Schael, Frank
T1  - Optical sensing with photon density waves: investigation of model media
N2  - Investigations with frequency domain photon density waves allow elucidation of absorption and scattering properties of turbid media. The temporal and spatial propagation of intensity modulated light with frequencies up to more than 1 GHz can be described by the P1 approximation to the Boltzmann transport equation. In this study, we establish requirements for the appropriate choice of turbid model media and characterize mixtures of isosulfan blue as absorber and polystyrene beads as scatterer. For these model media, the independent determination of absorption and reduced scattering coefficients over large absorber and scatterer concentration ranges is demonstrated with a frequency domain photon density wave spectrometer employing intensity and phase measurements at various modulation frequencies.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 026 
Y1  - 2003
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-13147
ER  - 
TY  - GEN
A1  - Rößler, Dirk
A1  - Krüger, Frank
A1  - Ohrnberger, Matthias
T1  - Rupture propagation of recent large TsE off-coast Sumatra and Java
N2  - The spatio-temporal evolution of the three recent tsunamogenic earthquakes (TsE) off-coast N-Sumatra (Mw9.3), 28/03/2005 (Mw8.5) off-coast Nias, on 17/07/2006 (Mw7.7) off-coast Java. Start time, duration, and propagation of the rupture are retrieved. All parameters can be obtained rapidly after recording of the first-arrival phases in near-real time processing. We exploit semblance analysis, backpropagation and broad-band seismograms within 30°-95° distance. Image enhancement is reached by stacking the semblance of arrays within different directions. For the three events, the rupture extends over about 1150, 150, and 200km, respectively. The events in 2004, 2005, and 2006 had source durations of at least 480s, 120s, and 180s, respectively. We observe unilateral rupture propagation for all events except for the rupture onset and the Nias event, where there is evidence for a bilateral start of the rupture. Whereas average rupture speed of the events in 2004 and 2005 is in the order of the S-wave speed (≈2.5-3km/s), unusually slow rupturing (≈1.5 km/s) is indicated for the July 2006 event. For the July 2006 event we find rupturing of a 200 x 100 km wide area in at least 2 phases with propagation from NW to SE. The event has some characteristics of a circular rupture followed by unilateral faulting with change in slip rate. Fault area and aftershock distribution coincide. Spatial and temporal resolution are frequency dependent. Studies of a Mw6.0 earthquake on 2006/09/21 and one synthetic source show a ≈1° limit in resolution. Retrieved source area, source duration as well as peak values for semblance and beam power generally increase with the size of the earthquake making possible an automatic detection and classification of large and small earthquakes.
KW  - Tsunami
KW  - Erdbeben
KW  - Indischer Ozean
KW  - Bruchausbreitung
KW  - Seismologie
KW  - Tsunami
KW  - Earthquake
KW  - Indonesia
KW  - Indian Ocean
KW  - Rupture Propagation
KW  - Seismology
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-13039
ER  - 
TY  - BOOK
ED  - Ishihara, Shinichiro
ED  - Schmitz, Michaela
ED  - Schwarz, Anne
T1  - Interdisciplinary studies on information structure : ISIS ; Working papers of the SFB 632 - Vol. 5
N2  - In this paper we compare the behaviour of adverbs of frequency (de Swart 1993) like usually with the behaviour of adverbs of quantity like for the most part in sentences that contain plural definites. We show that sentences containing the former type of Q-adverb evidence that Quantificational Variability Effects (Berman 1991) come about as an indirect effect of quantification over situations: in order for quantificational variability readings to arise, these sentences have to obey two newly observed constraints that clearly set them apart from sentences containing corresponding quantificational DPs, and that can plausibly be explained under the assumption that quantification over (the atomic parts of) complex situations is involved. Concerning sentences with the latter type of Q-adverb, on the other hand, such evidence is lacking: with respect to the constraints just mentioned, they behave like sentences that contain corresponding quantificational DPs. We take this as evidence that Q-adverbs like for the most part do not quantify over the atomic parts of sum eventualities in the cases under discussion (as claimed by Nakanishi and Romero (2004)), but rather over the atomic parts of the respective sum individuals.
T3  - Interdisciplinary studies on information structure : ISIS ; working papers of the SFB 632 - 5 
KW  - Adverbial Quantification
KW  - Situations
KW  - Tense Semantics
KW  - Adverbs of Frequency
KW  - Adverbs of Quantity
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-13047
SN  - 1866-4725
PB  - Universitätsverlag Potsdam
CY  - Potsdam
ER  - 
TY  - THES
A1  - Ott, Christian David
T1  - Stellar iron core collapse in {3+1} general relativity and the gravitational wave signature of core-collapse supernovae
T1  - Stellarer Eisenkernkollaps in Allgemeiner Relativitätstheorie und die Gravitationswellensignatur von Kern-Kollaps-Supernovae
N2  - I perform and analyse the first ever calculations of rotating stellar iron core collapse in {3+1} general relativity that start out with presupernova models from stellar evolutionary calculations and include a microphysical finite-temperature nuclear equation of state, an approximate scheme for electron capture during collapse and neutrino pressure effects. Based on the results of these calculations, I obtain the to-date most realistic estimates for the gravitational wave signal from collapse, bounce and the early postbounce phase of core collapse supernovae. I supplement my {3+1} GR hydrodynamic simulations with 2D Newtonian neutrino radiation-hydrodynamic supernova calculations focussing on (1) the late postbounce gravitational wave emission owing to convective overturn, anisotropic neutrino emission and protoneutron star pulsations, and (2) on the gravitational wave signature of accretion-induced collapse of white dwarfs to neutron stars.
N2  - Ich präsentiere die ersten Computer-Simulationen des rotierenden Kollapses stellarer Eisenkerne, die in der {3+1}-Zerlegung der Allgemeinen Relativitätstheorie durchgeführt werden und Vorsupernova-Sternmodelle aus Sternentwicklungsrechnungen, eine heiße nukleare Zustandsgleichung und ein näherungsweises Verfahren zur Beschreibung des Elektroneneinfangs enthalten und Neutrinodruck-Effekte berücksichtigen. Basierend auf den Ergebnissen dieser Rechnungen erhalte ich die zur Zeit realistischsten Vorhersagen für das Gravitationswellensignal der Kollaps, Abprall, Abkling und frühen Nach-Abprallphase einer Kern-Kollaps-Supernova. Neben den {3+1} Simulationen diskutiere ich newtonsche axisymmetrische Kern-Kollaps-Supernova-Simulationen mit Schwerpunkten auf: (1) der Gravitationswellenabstrahlung in der späten Nach-Abprallphase durch Konvektionsströmungen, anisotropische Neutrinoemission und Proto-Neutronenstern Pulsationen und (2) der Gravitationswellensignatur des Kollapses weißer Zwergsterne zu Neutronensternen, der durch Akkretion eingeleitet wird.
KW  - Gravitationswellen
KW  - Kern-Kollaps-Supernovae
KW  - Allgemeine Relativitätstheorie
KW  - Gravitational Waves
KW  - Core-Collapse Supernovae
KW  - General Relativity
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12986
ER  - 
TY  - JOUR
A1  - Rößler, Dirk
A1  - Krüger, Frank
A1  - Rümpker, Georg
A1  - Psencik, Ivan
T1  - Tensile source components of swarm events in West Bohemia in 2000 by considering seismic anisotropy
N2  - Earthquake swarms occur frequently in West Bohemia, Central Europe. Their occurrence is correlated with and propably triggered by fluids that escape on the earth's surface near the epicentres. These fluids raise up periodically from a seemingbly deep-seated source in the upper mantle. Moment tensors for swarm events in 1997 indicate tensile faulting. However, they were determined under assumption of seismic isotropy although anisotropy can be observed. Anisotropy may obscure moment tensors and their interpretation. In 2000, more than 10,000 swarm earthquakes occurred near Novy Kostel, West Bohemia. Event triggering by fluid injection is likely. Activity lasted from 28/08 until 31/12/00 (9 phases) with maximum ML=3.2. High quality P-wave seismograms were used to retrieve the source mechanisms for 112 events between 28/08/00 and 30/10/00 using > 20 stations. We determine the source geometry using a new algorithm and different velocity models including anisotropy. From inversions of P waves we observe ML<3.2, strike-slip events on steep N-S oriented faults with additional normal or reverse components. Tensile components seem to be evident for more than 60% of the processed swarm events in West Bohemia during the phases 1-7. Being most significant at great depths and at phases 1-4 during the swarm they are time and location dependent. Although tensile components are reduced when anisotropy is assumed they persist and seem to be important. They can be explained by pore-pressure changes due to the injection of fluids that raise up. Our findings agree with other observations e.g. correlation of fluid transport and seismicity, variations in b-value, forcing rate, and in pore pressure diffusion. Tests of our results show their significance.
KW  - Seismologie
KW  - Erbeben
KW  - Momententensor
KW  - Anisotropie
KW  - Vogtland
KW  - Seismology
KW  - tensile earthquake
KW  - moment tensor
KW  - anisotropy
KW  - West Bohemia
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12975
ER  - 
TY  - JOUR
A1  - Rößler, Dirk
A1  - Krüger, Frank
A1  - Ohrnberger, Matthias
T1  - Rupture propagation of the TsE (Mw7.7) on 17 July 2006 off-coast Java
N2  - The Mw=7.7 tsunamogenic earthquake (TsE) on 17 July 2006, 08:19:28 shock the Indian Ocean at about 15 km depth off-coast Java, Indonesia. It caused a local tsunami with wave heights exceeding 2 m. The death toll reached several hundred. Thousands of people were displaced. By means of standard array methods, we have investigated the propagation and the extent of the rupture front of the causative earthquake. Waveform similarity is expressed by means of the semblance. We back-propagate the semblance for first-arrival phases recorded at broad-band stations within teleseismic distances (30°-95°). Image enhancement is realised by stacking the semblance of 8 arrays within different epicentral and azimuthal directions. From teleseismic observations we find rupturing of a 200 x 100 km wide area in at least 2 phases with propagation from NW to SE and source duration >125 s. The event has some characteristics of a circular rupture followed by unilateral faulting with change in slip rate. Unusually slow rupturing (≈1.5 km/s) is indicated. Fault area and aftershock distribution coincide. Spatial and temporal resolution are frequency dependent. Studies of a Mw6.0 earthquake on 2006/09/21 and one synthetic source show a ≈1° limit in resolution. Retrieved source area, source duration as well as peak values for semblance and beam power increase with the size of the earthquake making possible an automatic detection and classification of large and small earthquakes.
KW  - Seismologie
KW  - Erdbeben
KW  - Tsunami
KW  - Indischer Ozean
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12964
ER  - 
TY  - THES
A1  - Lunemann, Carolin
T1  - Quantum cryptography : security analysis of multiuser quantum communication with embedded authentication
N2  - Three quantum cryptographic protocols of multiuser quantum networks with embedded authentication, allowing quantum key distribution or quantum direct communication, are discussed in this work. The security of the protocols against different types of attacks is analysed with a focus on various impersonation attacks and the man-in-the-middle attack. On the basis of the security analyses several improvements are suggested and implemented in order to adjust the investigated vulnerabilities. Furthermore, the impact of the eavesdropping test procedure on impersonation attacks is outlined. The framework of a general eavesdropping test is proposed to provide additional protection against security risks in impersonation attacks.
N2  - In der Diplomarbeit werden drei verschiedene quantenkryptographische Protokolle mit dem Schwerpunkt auf authentifizierten Quantennetzwerken analysiert. Die Sicherheit der Protokolle gegenüber verschiedenen Angriffen wird untersucht, wobei der Fokus auf kompletten Personifikationsattacken („impersonation attacks“) liegt. Auf Basis der Sicherheitsanalyse und den Netzwerkanforderungen werden entsprechende Verbesserungen vorgeschlagen. Um die Gefahr von Personifikationen realistisch abschätzen zu können, wird außerdem der Einfluss des Testablaufs analysiert. Um zusätzlichen Schutz gegen Personifikationsattacken zu gewährleisten, werden die Rahmenbedingungen für eine allgemeine Testspezifikation festgelegt.
KW  - Kryptographie
KW  - Quantenkryptographie
KW  - Authentifizierung
KW  - Netzwerk
KW  - cryptography
KW  - quantum cryptography
KW  - authentication
KW  - multiuser
KW  - network
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12756
ER  - 
TY  - GEN
A1  - Köchy, Martin
A1  - Tielbörger, Katja
T1  - Hydrothermal time model of germination : parameters for 36 Mediterranean annual species based on a simplified approach
N2  - Germination rates and germination fractions of seeds can be predicted well by the hydrothermal time (HTT) model. Its four parameters hydrothermal time, minimum soil temperature, minimum soil moisture, and variation of minimum soil moisture, however, must be determined by lengthy germination experiments at combinations of several levels of soil temperature and moisture. For some applications of the HTT model it is more important to have approximate estimates for many species rather than exact values for only a few species. We suggest that minimum temperature and variation of minimum moisture can be estimated from literature data and expert knowledge. This allows to derive hydrothermal time and minimum moisture from existing data from germination experiments with one level of temperature and moisture. We applied our approach to a germination experiment comparing germination fractions of wild annual species along an aridity gradient in Israel. Using this simplified approach we estimated hydrothermal time and minimum moisture of 36 species. Comparison with exact data for three species shows that our method is a simple but effective method for obtaining parameters for the HTT model. Hydrothermal time and minimum moisture supposedly indicate climate related germination strategies. We tested whether these two parameters varied with the climate at the site where the seeds had been collected. We found no consistent variation with climate across species, suggesting that variation is more strongly controlled by site-specific factors.
N2  - Keimungsgeschwindigkeit und Anteil gekeimter Samen lassen sich gut mit dem Hydrothermalzeit-Modell bestimmen. Dessen vier Parameter Hydrothermalzeit, Mindesttemperatur, Mindestbodenfeuchte und Streuung der Mindestbodenfeuchte müssen jedoch durch aufwendige Keimungsversuche bei Kombinationen von mehreren Temperatur- und Feuchtigkeitsstufen bestimmt werden. Für manche Anwendungen des Hydrothermalzeit-Modells sind aber ungefähre Werte für viele Arten wichtiger als genaue Werte für wenige Arten. Wenn die Mindesttemperatur und die Streuung der Mindestfeuchte aus Veröffentlichungen und Expertenwissen geschätzt würde, können die Hydrothermalzeit und Mindestbodenfeuchte aus vorhandenen Daten von Keimungsversuchen mit nur einer Temperatur- und Feuchtigkeitsstufe berechnet werden. Wir haben unseren Ansatz auf einen Keimungsversuch zum Vergleich der Keimungsquote wilder einjähriger Arten entlang eines Trockenheitsgradienten in Israel angewendet. Mit diesem Ansatz bestimmten wir die Hydrothermalzeit und Mindestfeuchtigkeit von 36 Arten. Der Vergleich mit genauen Werten für drei Arten zeigt, dass mit unserem Ansatz Hydrothermalzeit-Parameter einfach und effektiv bestimmt werden können. Hydrothermalzeit und Mindestfeuchtigkeit sollten auch bestimmte klimabedingte Keimungsstrategien anzeigen. Deshalb testeten wir, ob diese zwei Parameter mit dem Klima am Ursprungsort der Samen zusammenhängen. Wir fanden jedoch keinen für alle Arten übereinstimmenden Zusammenhang, so dass die Unterschiede vermutlich stärker durch standörtliche als durch klimatische Ursachen hervorgerufen werden.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 022 
KW  - Keimungsrate
KW  - Dormanz
KW  - Hydrothermalzeit-Modell
KW  - einjährige Pflanzen
KW  - Mittelmeerraum
KW  - germination rate
KW  - dormancy
KW  - hydrothermal time model
KW  - annual plant species
KW  - Mediterranean
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12406
ER  - 
TY  - GEN
A1  - Engelhard, Sonja
A1  - Kumke, Michael Uwe
A1  - Löhmannsröben, Hans-Gerd
T1  - OPQS – optical process and quality sensing : exemplary applications in the beerbrewing and polyurethane foaming processes
N2  - Optical methods play an important role in process analytical technologies (PAT). Four examples of optical process and quality sensing (OPQS) are presented, which are based on three important experimental techniques: near-infrared absorption, luminescence quenching, and a novel method, photon density wave (PDW) spectroscopy. These are used to evaluate four process and quality parameters related to beer brewing and polyurethane (PU) foaming processes: the ethanol content and the oxygen (O2) content in beer, the biomass in a bioreactor, and the cellular structures of PU foam produced in a pilot production plant.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 004 
KW  - process analytical technology
KW  - beer
KW  - biomass
KW  - foam analysis
KW  - NIR spectroscopy
KW  - fluorescence quenching
KW  - photon density wave spectroscopy
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12191
ER  - 
TY  - GEN
A1  - Schmälzlin, Elmar
A1  - Walz, Bernd
A1  - Klimant, Ingo
A1  - Schewe, Bettina
A1  - Löhmannsröben, Hans-Gerd
T1  - Monitoring hormone-induced oxygen consumption in the salivary glands of the blowfly, Calliphora vicina, by use of luminescent microbeads
N2  - The salivary glands of the blowfly were injected with luminescent oxygen-sensitive microbeads. The changes in oxygen content within individual gland tubules during hormone-induced secretory activity were quantified. The measurements are based on an upgraded phase-modulation technique, where the phase shift of the sensor phosphorescence is determined independently from concentration and background signals. We show that the combination of a lock-in amplifier with a fluorescence microscope results in a convenient setup to measure oxygen concentrations within living animal tissues at the cellular level.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 006 
Y1  - 2006
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12206
ER  -