@phdthesis{Stock2010, author = {Stock, Maria}, title = {Charakterisierung der troposph{\"a}rischen Aerosolvariabilit{\"a}t in der europ{\"a}ischen Arktis}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-49203}, school = {Universit{\"a}t Potsdam}, year = {2010}, abstract = {Auf der Grundlage von Sonnenphotometermessungen an drei Messstationen (AWIPEV/ Koldewey in Ny-{\AA}lesund (78.923 °N, 11.923 °O) 1995-2008, 35. Nordpol Driftstation - NP-35 (84.3-85.5 °N, 41.7-56.6 °O) M{\"a}rz/April 2008, Sodankyl{\"a} (67.37 °N, 26.65 °O) 2004-2007) wird die Aerosolvariabilit{\"a}t in der europ{\"a}ischen Arktis und deren Ursachen untersucht. Der Schwerpunkt liegt dabei auf der Frage des Zusammenhanges zwischen den an den Stationen gemessenen Aerosolparametern (Aerosol optische Dicke, Angstr{\"o}m Koeffizient, usw.) und dem Transport des Aerosols sowohl auf kurzen Zeitskalen (Tagen) als auch auf langen Zeitskalen (Monate, Jahre). Um diesen Zusammenhang herzustellen, werden f{\"u}r die kurzen Zeitskalen mit dem Trajektorienmodell PEP-Tracer 5-Tage R{\"u}ckw{\"a}rtstrajektorien in drei Starth{\"o}hen (850 hPa, 700 hPa, 500 hPa) f{\"u}r die Uhrzeiten 00, 06, 12 und 18 Uhr berechnet. Mit Hilfe der nicht-hierarchischen Clustermethode k-means werden die berechneten R{\"u}ckw{\"a}rtstrajektorien dann zu Gruppen zusammengefasst und bestimmten Quellgebieten und den gemessenen Aerosol optischen Dicken zugeordnet. Die Zuordnung von Aerosol optischer Dicke und Quellregion ergibt keinen eindeutigen Zusammenhang zwischen dem Transport verschmutzter Luftmassen aus Europa oder Russland bzw. Asien und erh{\"o}hter Aerosol optischer Dicke. Dennoch ist f{\"u}r einen konkreten Einzelfall (M{\"a}rz 2008) ein direkter Zusammenhang von Aerosoltransport und hohen Aerosol optischen Dicken nachweisbar. In diesem Fall gelangte Waldbrandaerosol aus S{\"u}dwestrussland in die Arktis und konnte sowohl auf der NP-35 als auch in Ny-{\AA}lesund beobachtet werden. In einem weiteren Schritt wird mit Hilfe der EOF-Analyse untersucht, inwieweit großskalige atmosph{\"a}rische Zirkulationsmuster f{\"u}r die Aerosolvariabilit{\"a}t in der europ{\"a}ischen Arktis verantwortlich sind. {\"A}hnlich wie bei der Trajektorienanalyse ist auch die Verbindung der atmosph{\"a}rischen Zirkulation zu den Photometermessungen an den Stationen in der Regel nur schwach ausgepr{\"a}gt. Eine Ausnahme findet sich bei der Betrachtung des Jahresganges des Bodendruckes und der Aerosol optischen Dicke. Hohe Aerosol optische Dicken treten im Fr{\"u}hjahr zum einen dann auf, wenn durch das Islandtief und das sibirische Hochdruckgebiet Luftmassen aus Europa oder Russland/Asien in die Arktis gelangen, und zum anderen, wenn sich ein kr{\"a}ftiges Hochdruckgebiet {\"u}ber Gr{\"o}nland und weiten Teilen der Arktis befindet. Ebenso zeigt sich, dass der {\"U}bergang zwischen Fr{\"u}hjahr und Sommer zumindest teilweise bedingt ist durch denWechsel vom stabilen Polarhoch im Winter und Fr{\"u}hjahr zu einer st{\"a}rker von Tiefdruckgebieten bestimmten arktischen Atmosph{\"a}re im Sommer. Die geringere Aerosolkonzentration im Sommer kann zum Teil mit einer Zunahme der nassen Deposition als Aerosolsenke begr{\"u}ndet werden. F{\"u}r Ny-{\AA}lesund wird neben den Transportmustern auch die chemische Zusammensetzung des Aerosols mit Hilfe von Impaktormessungen an der Zeppelinstation auf dem Zeppelinberg (474m {\"u}.NN) nahe Ny-{\AA}lesund abgeleitet. Dabei ist die positive Korrelation der Aerosoloptischen Dicke mit der Konzentration von Sulfationen und Ruß sehr deutlich. Beide Stoffe gelangen zu einem Großteil durch anthropogene Emissionen in die Atmosph{\"a}re. Die damit nachweisbar anthropogen gepr{\"a}gte Zusammensetzung des arktischen Aerosols steht im Widerspruch zum nicht eindeutig herstellbaren Zusammenhang mit dem Transport des Aerosols aus Industrieregionen. Dies kann nur durch einen oder mehrere gleichzeitig stattfindende Transformationsprozesse (z. B. Nukleation von Schwefels{\"a}urepartikeln) w{\"a}hrend des Transportes aus den Quellregionen (Europa, Russland) erkl{\"a}rt werden.}, language = {de} } @phdthesis{Yin2010, author = {Yin, Fan}, title = {Mathematic approaches for the calibration of the CHAMP satellite magnetic field measurements}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-41201}, school = {Universit{\"a}t Potsdam}, year = {2010}, abstract = {CHAMP (CHAllenging Minisatellite Payload) is a German small satellite mission to study the earth's gravity field, magnetic field and upper atmosphere. Thanks to the good condition of the satellite so far, the planned 5 years mission is extended to year 2009. The satellite provides continuously a large quantity of measurement data for the purpose of Earth study. The measurements of the magnetic field are undertaken by two Fluxgate Magnetometers (vector magnetometer) and one Overhauser Magnetometer (scalar magnetometer) flown on CHAMP. In order to ensure the quality of the data during the whole mission, the calibration of the magnetometers has to be performed routinely in orbit. The scalar magnetometer serves as the magnetic reference and its readings are compared with the readings of the vector magnetometer. The readings of the vector magnetometer are corrected by the parameters that are derived from this comparison, which is called the scalar calibration. In the routine processing, these calibration parameters are updated every 15 days by means of scalar calibration. There are also magnetic effects coming from the satellite which disturb the measurements. Most of them have been characterized during tests before launch. Among them are the remanent magnetization of the spacecraft and fields generated by currents. They are all considered to be constant over the mission life. The 8 years of operation experience allow us to investigate the long-term behaviors of the magnetometers and the satellite systems. According to the investigation, it was found that for example the scale factors of the FGM show obvious long-term changes which can be described by logarithmic functions. The other parameters (offsets and angles between the three components) can be considered constant. If these continuous parameters are applied for the FGM data processing, the disagreement between the OVM and the FGM readings is limited to \pm1nT over the whole mission. This demonstrates, the magnetometers on CHAMP exhibit a very good stability. However, the daily correction of the parameter Z component offset of the FGM improves the agreement between the magnetometers markedly. The Z component offset plays a very important role for the data quality. It exhibits a linear relationship with the standard deviation of the disagreement between the OVM and the FGM readings. After Z offset correction, the errors are limited to \pm0.5nT (equivalent to a standard deviation of 0.2nT). We improved the corrections of the spacecraft field which are not taken into account in the routine processing. Such disturbance field, e.g. from the power supply system of the satellite, show some systematic errors in the FGM data and are misinterpreted in 9-parameter calibration, which brings false local time related variation of the calibration parameters. These corrections are made by applying a mathematical model to the measured currents. This non-linear model is derived from an inversion technique. If the disturbance field of the satellite body are fully corrected, the standard deviation of scalar error \triangle B remains about 0.1nT. Additionally, in order to keep the OVM readings a reliable standard, the imperfect coefficients of the torquer current correction for the OVM are redetermined by solving a minimization problem. The temporal variation of the spacecraft remanent field is investigated. It was found that the average magnetic moment of the magneto-torquers reflects well the moment of the satellite. This allows for a continuous correction of the spacecraft field. The reasons for the possible unknown systemic error are discussed in this thesis. Particularly, both temperature uncertainties and time errors have influence on the FGM data. Based on the results of this thesis the data processing of future magnetic missions can be designed in an improved way. In particular, the upcoming ESA mission Swarm can take advantage of our findings and provide all the auxiliary measurements needed for a proper recovery of the ambient magnetic field.}, language = {en} } @phdthesis{Wu2010, author = {Wu, Ye}, title = {Nonlinear dynamics in complex networks and modeling human dynamics}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-47358}, school = {Universit{\"a}t Potsdam}, year = {2010}, abstract = {Durch große Datenmengen k{\"o}nnen die Forscher die Eigenschaften komplexer Systeme untersuchen, z.B. komplexe Netzwerk und die Dynamik des menschlichen Verhaltens. Eine große Anzahl an Systemen werden als große und komplexe Netzwerke dargestellt, z.B. das Internet, Stromnetze, Wirtschaftssysteme. Immer mehr Forscher haben großes Interesse an der Dynamik des komplexen Netzwerks. Diese Arbeit besteht aus den folgenden drei Teilen. Der erste Teil ist ein einfacher dynamischer Optimierungs-Kopplungs-Mechanismus, aber sehr wirksam. Durch den Mechanismus kann synchronisation in komplexen Netzwerken mit und ohne Zeitverz{\"o}gerung realisiert, und die F{\"a}higkeit der Synchronisation von small-world und scale-free Netze verbessert werden. Im zweiten Teil geht um die Verst{\"a}rkung der Robustheit der scale-free Netze im Zusammenhang mit der Gemeinden-Struktur. Einige Reaktionsmuster und topologische Gemeinden sind einheitlich. Die Ergebnisse zeigen einen neuen Aspekt der Beziehung zwischen den Funktionen und der Netzwerk-Topologie von komplexen Netzwerken. Im dritten Teil welche eine wichtige Rolle in komplexen Netzwerken spielt, wird die Verhaltens-Dynamik der menschliche Mitteilung durch Daten- und Modellanalysierung erforscht, dann entsteht ein neues Mitteilungsmodell. Mit Hilfe von einem Interaktion priority-Queue Model kann das neue Modell erkl{\"a}rt werden. Mit Hilfe des Models k{\"o}nnen viele praktische Interaktions-Systeme erkl{\"a}rt werden, z.B. E-Mail und Briefe (oder Post). Mit Hilfe meiner Untersuchung kann man menschliches Verhalten auf der Individuums- und Netzwerkebene neu kennenlernen. Im vierter Teil kann ich nachweisen, dass menschliches Kommentar-Verhalten in on-line Sozialsystemen, eine andere Art der Interaktionsdynamik von Mensch non-Poisson ist und dieses am Modell erkl{\"a}ren. Mit Hilfe der non-Poisson Prozesse kann man das pers{\"o}nliche Anziehungskraft-Modell besser verstehen. Die Ergebnisse sind hilfreich zum Kennenlernen des Musters des menschlichen Verhaltens in on-line Gesellschaften und der Entwicklung von {\"o}ffentlicher Meinung nicht nur in der virtuellen Gesellschaftn sondern auch in der Realgesellschaft. Am Ende geht es um eine Prognose von menschlicher Dynamik und komplexen Netzwerken.}, language = {en} } @article{KliemRustSeehafer2010, author = {Kliem, Bernhard and Rust, S. and Seehafer, Norbert}, title = {Helicity transport in a simulated coronal mass ejection}, series = {Proceedings of the International Astronomical Union}, journal = {Proceedings of the International Astronomical Union}, publisher = {International Astronomical Union}, address = {Cambridge}, issn = {1743-9213}, doi = {10.1017/S1743921311006715}, pages = {125 -- 128}, year = {2010}, language = {en} } @article{VotrubaFeldmeierKrtickaetal.2010, author = {Votruba, Viktor and Feldmeier, Achim and Krticka, Jiri and Kub{\´a}t, Jiř{\´i}}, title = {Multicomponent stellar wind from hot subdwarfs stars}, issn = {0004-640X}, doi = {10.1007/s10509-010-0402-2}, year = {2010}, abstract = {Stellar wind from hot subdwarf stars is mainly accelerated by the interaction of ultraviolet photospheric radiation with metals, mainly oxygen. Absorbing ions share momentum through Coulombic collisions with the remaining passive part of the plasma (namely protons). We found that in the case of the winds from hot subdwarfs, interactions could be so small that they stop the momentum transfer between the passive bulk of plasma and absorbing ions. As a result wind decouples at a certain point.}, language = {en} } @article{BimonteHaakhHenkeletal.2010, author = {Bimonte, Giuseppe and Haakh, Harald Richard and Henkel, Carsten and Intravaia, Francesco}, title = {Optical BCS conductivity at imaginary frequencies and dispersion energies of superconductors}, issn = {1751-8113}, doi = {10.1088/1751-8113/43/14/145304}, year = {2010}, abstract = {We present an efficient expression for the analytic continuation to arbitrary complex frequencies of the complex optical and ac conductivity of a homogeneous superconductor with an arbitrary mean free path. Knowledge of this quantity is fundamental in the calculation of thermodynamic potentials and dispersion energies involving type-I superconducting bodies. When considered for imaginary frequencies, our formula evaluates faster than previous schemes involving Kramers-Kronig transforms. A number of applications illustrate its efficiency: a simplified low-frequency expansion of the conductivity, the electromagnetic bulk self-energy due to longitudinal plasma oscillations, and the Casimir free energy of a superconducting cavity.}, language = {en} } @article{HaakhIntravaiaHenkel2010, author = {Haakh, Harald Richard and Intravaia, Francesco and Henkel, Carsten}, title = {Temperature dependence of the plasmonic Casimir interaction}, issn = {1050-2947}, doi = {10.1103/Physreva.82.012507}, year = {2010}, abstract = {We investigate the role of surface plasmons in the electromagnetic Casimir effect at finite temperature, including situations out of global thermal equilibrium. The free energy is calculated analytically and expanded for different regimes of distances and temperatures. Similar to the zero-temperature case, the interaction changes from attraction to repulsion with distance. Thermal effects are shown to be negligible for small plate separations and at room temperature but become dominant and repulsive at large values of these parameters. In configurations out of global thermal equilibrium, we show that the selective excitation of surface plasmons can create a repulsive Casimir force between metal plates.}, language = {en} } @article{HenkelIntravaia2010, author = {Henkel, Carsten and Intravaia, Francesco}, title = {On the Casimir entropy between "perfect crystals"}, issn = {0217-751X}, doi = {10.1142/S0217751x10049608}, year = {2010}, abstract = {We give a re-interpretation of an 'entropy defect' in the electromagnetic Casimir effect. The electron gas in a perfect crystal is an electromagnetically disordered system whose entropy contains a finite Casimir- like contribution. The Nernst theorem (third law of thermodynamics) is not applicable.}, language = {en} } @article{WangFruebingWirgesetal.2010, author = {Wang, Feipeng and Fr{\"u}bing, Peter and Wirges, Werner and Gerhard, Reimund and Wegener, Michael}, title = {Enhanced Polarization in Melt-quenched and Stretched Poly(vinylidene Fluoride-Hexafluoropropylene) Films}, issn = {1070-9878}, doi = {10.1109/TDEI.2010.5539679}, year = {2010}, abstract = {beta-phase poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) copolymer films were prepared by uniaxially stretching solution-cast or melt-quenched samples. Different preparation routes lead to different amounts of the crystalline alpha and beta phases in the films, as detected by means of Fourier-transform infrared spectroscopy and X-ray diffractometry. The beta phase is significantly enhanced in melt-quenched and stretched films in comparison to solution-cast and stretched films. This is particularly true for copolymer samples with higher HFP content. The beta- phase enhancement is also observed in ferroelectric-hysteresis experiments where a rather high polarization of 58 mC/ m(2) was found on melt-quenched and stretched samples after poling at electric fields of 140 MV/m. After poling at 160 MV/m, one of these samples exhibited a piezoelectric d(33) coefficient as high as 21 pC/N. An electric-field-induced partial transition from the alpha to the beta phase was also observed on the melt-quenched and stretched samples. This effect leads to a further increase in the applications-relevant dipole polarization. Uniaxially stretched ferroelectric- polymer films are highly anisotropic. Dielectric resonance spectroscopy reveals a strong increase of the transverse piezoelectric d(32) coefficient and a strong decrease of the transverse elastic modulus c(32) upon heating from 20 to 50 degrees C.}, language = {en} } @article{TobieGieseHurfordetal.2010, author = {Tobie, Gabriel and Giese, Bernd and Hurford, Terry Anthony and Lopes, Rosaly M. and Nimmo, Francis and Postberg, Frank and Retherford, Kurt D. and Schmidt, J{\"u}rgen and Spencer, John R. and Tokano, Tetsuya and Turtle, Elizabeth P.}, title = {Surface, subsurface and atmosphere exchanges on the satellites of the outer solar system}, issn = {0038-6308}, doi = {10.1007/s11214-010-9641-3}, year = {2010}, abstract = {The surface morphology of icy moons is affected by several processes implicating exchanges between their subsurfaces and atmospheres (if any). The possible exchange of material between the subsurface and the surface is mainly determined by the mechanical properties of the lithosphere, which isolates the deep, warm and ductile ice material from the cold surface conditions. Exchanges through this layer occur only if it is sufficiently thin and/or if it is fractured owing to tectonic stresses, melt intrusion or impact cratering. If such conditions are met, cryomagma can be released, erupting fresh volatile-rich materials onto the surface. For a very few icy moons (Titan, Triton, Enceladus), the emission of gas associated with cryovolcanic activity is sufficiently large to generate an atmosphere, either long- lived or transient. For those moons, atmosphere-driven processes such as cryovolcanic plume deposition, phase transitions of condensable materials and wind interactions continuously re-shape their surfaces, and are able to transport cryovolcanically generated materials on a global scale. In this chapter, we discuss the physics of these different exchange processes and how they affect the evolution of the satellites' surfaces.}, language = {en} } @article{SureshSenthilkumarLakshmananetal.2010, author = {Suresh, R. and Senthilkumar, Dharmapuri Vijayan and Lakshmanan, Muthusamy and Kurths, J{\"u}rgen}, title = {Global phase synchronization in an array of time-delay systems}, issn = {1539-3755}, doi = {10.1103/Physreve.82.016215}, year = {2010}, abstract = {We report the identification of global phase synchronization (GPS) in a linear array of unidirectionally coupled Mackey-Glass time-delay systems exhibiting highly non-phase-coherent chaotic attractors with complex topological structure. In particular, we show that the dynamical organization of all the coupled time-delay systems in the array to form GPS is achieved by sequential synchronization as a function of the coupling strength. Further, the asynchronous ones in the array with respect to the main sequentially synchronized cluster organize themselves to form clusters before they achieve synchronization with the main cluster. We have confirmed these results by estimating instantaneous phases including phase difference, average phase, average frequency, frequency ratio, and their differences from suitably transformed phase coherent attractors after using a nonlinear transformation of the original non-phase-coherent attractors. The results are further corroborated using two other independent approaches based on recurrence analysis and the concept of localized sets from the original non-phase-coherent attractors directly without explicitly introducing the measure of phase.}, language = {en} } @article{ShklyaevStraube2010, author = {Shklyaev, Sergey and Straube, Arthur V.}, title = {Formation and evolution of bubbly screens in confined oscillating bubbly liquids}, issn = {1539-3755}, doi = {10.1103/Physreve.81.016321}, year = {2010}, abstract = {We consider the dynamics of dilute monodisperse bubbly liquid confined by two plane solid walls and subject to small-amplitude high-frequency oscillations normal to the walls. The initial state corresponds to the uniform distribution of bubbles and motionless liquid. The period of external driving is assumed much smaller than typical relaxation times for a single bubble but larger than the period of volume eigenoscillations. The time-averaged description accounting for the two-way coupling between the liquid and the bubbles is applied. We show that the model predicts accumulation of bubbles in thin sheets parallel to the walls. These singular structures, which are formally characterized by infinitely thin width and infinitely high concentration, are referred to as bubbly screens. The formation of a bubbly screen is described analytically in terms of a self-similar solution, which is in agreement with numerical simulations. We study the evolution of bubbly screens and detect a one-dimensional stationary state, which is shown to be unconditionally unstable.}, language = {en} } @article{SkoczowskyJechowStuermeretal.2010, author = {Skoczowsky, Danilo and Jechow, Andreas and St{\"u}rmer, Herbert and Poßner, Torsten and Sacher, Joachim and Menzel, Ralf}, title = {Quasi-monolithic ring resonator for efficient frequency doubling of an external cavity diode laser}, issn = {0946-2171}, doi = {10.1007/s00340-009-3802-7}, year = {2010}, abstract = {A quasi-monolithic second-harmonic-generation ring resonator assembled with miniaturized components is presented. The ring contains a 10-mm-long bulk periodically poled lithium niobate crystal for second-harmonic generation, four plane mirrors and two gradient-index lenses. All parts are mounted on a glass substrate with an overall size of 19.5 mmx8.5 mmx4 mm. As pump source a broad-area laser diode operated in an external resonator with Littrow arrangement is utilized. This external cavity diode laser provides near diffraction limited, narrow-bandwidth emission with an optical output power of 450 mW at a wavelength of 976 nm. Locking of the diode laser emission to the resonance frequency of the ring cavity was achieved by an optical self-injection locking technique. With this setup more than 126 mW of diffraction-limited blue light at 488 nm could be generated. The opto-optical conversion efficiency was 28\% and a wall plug efficiency better than 5.5\% could be achieved.}, language = {en} } @article{VitaglianoRieraLatorre2010, author = {Vitagliano, Giuseppe and Riera, Arnau and Latorre, Jos{\´e} Ignacio}, title = {Volume-law scaling for the entanglement entropy in spin-1/2 chains}, issn = {1367-2630}, doi = {10.1088/1367-2630/12/11/113049}, year = {2010}, abstract = {Entanglement entropy obeys area law scaling for typical physical quantum systems. This may naively be argued to follow from the locality of interactions. We show that this is not the case by constructing an explicit simple spin chain Hamiltonian with nearest-neighbor interactions that presents an entanglement volume scaling law. This non- translational model is contrived to have couplings that force the accumulation of singlet bonds across the half-chain. This configuration of the couplings is suggested by real-space renormalization group arguments. Computation of the entanglement entropy is performed by mapping the system to free fermions and diagonalizing numerically its correlation matrix. An analytical relationship between the entanglement entropy and the Frobenius norm of the correlation matrix is also established. Our result is complementary to the known relationship between non-translational invariant, nearest- neighbor interacting Hamiltonians and quantum Merlin-Arthur (QMA)complete problems.}, language = {en} } @article{VladkovaKoynovaTeuchneretal.2010, author = {Vladkova, Radka and Koynova, Rumiana and Teuchner, Klaus and Tenchov, Boris}, title = {Bilayer structural destabilization by low amounts of chlorophyll a}, issn = {0005-2736}, doi = {10.1016/j.bbamem.2010.05.008}, year = {2010}, abstract = {The present study shows that small admixtures of one chlorophyll a (Chla) molecule per several hundred lipid molecules have strong destabilizing effect on lipid bilayers. This effect is clearly displayed in the properties of the L-alpha-H-II transformations and results from a Chla preference for the H-II relative to the L-alpha phase. Chla disfavors the lamellar liquid crystalline phase L-alpha and induces its replacement with inverted hexagonal phase H-II, as is consistently demonstrated by DSC and X-ray diffraction measurements on phosphatidylethanolamine (PE) dispersions. Chla lowers the L-alpha-H-II transition temperature (42 degrees C) of the fully hydrated dipalmitoleoyl PE (DPoPE) by similar to 8 degrees C and similar to 17 degrees C at Chla/DPoPE molar ratios of 1:500 and 1:100, respectively. Similar Chla effect was recorded also for dielaidoyl PE dispersions. The lowering of the transition temperature and the accompanying significant loss of transition cooperativity reflect the Chla repartitioning and preference for the H-II phase. The reduction of the H-II phase lattice constant in the presence of Chla is an indication that Chla favors v phase formation by decreasing the radius of spontaneous monolayer curvature, and not by filling up the interstitial spaces between the H-II phase cylinders. The observed Chla preference for H-II phase and the substantial bilayer destabilization in the vicinity of a bilayer-to-nonbilayer phase transformation caused by low Chla concentrations can be of interest as a potential regulatory or membrane-damaging factor.}, language = {en} } @article{StoyanovKolloscheMcCarthyetal.2010, author = {Stoyanov, Hristiyan and Kollosche, Matthias and McCarthy, Denis N. and Kofod, Guggi}, title = {Molecular composites with enhanced energy density for electroactive polymers}, issn = {0959-9428}, doi = {10.1039/C0jm00519c}, year = {2010}, abstract = {Actuators based on soft dielectric elastomers deform due to electric field induced Maxwell's stress, interacting with the mechanical properties of the material. The relatively high operating voltages of such actuators can be reduced by increasing the permittivity of the active material, while maintaining the mechanical properties and high electrical breakdown strength. Approaches relying on the use of highly polarizable molecules or conjugated polymers have so far provided the best results, however it has been difficult to maintain high breakdown strengths. In this work, a new approach for increasing the electrostatic energy density of a soft polymer based on molecular composites is presented, relying on chemically grafting soft gel-state pi-conjugated conducting macromolecules (polyaniline (PANI)) to a flexible elastomer backbone SEBS-g-MA (poly-styrene-co-ethylene-co-butylene-co-styrene-g-maleic anhydride). The approach was found to result in composites of increased permittivity (470\% over the elastomer matrix) with hardly any reduction in breakdown strength (from 140 to 120 V mu m(-1)), resulting in a large increase in stored electrostatic energy. This led to an improvement in the measured electromechanical response as well as in the maximum actuation strain. A transition was observed when amounts of PANI exceeded 2 vol\%, which was ascribed to the exhaustion of the MA- functionality of the SEBS-g-MA. The transition led to drastic increases in permittivity and conductivity, and a sharp drop in electrical breakdown strength. Although the transition caused further improvement of the electromechanical response, the reduction in electrical breakdown strength caused a limitation of the maximum achievable actuation strain.}, language = {en} } @article{SunYang2010, author = {Sun, Zong Kui and Yang, Xiao Li}, title = {Parameters identification and synchronization of chaotic delayed systems containing uncertainties and time- varying delay}, issn = {1024-123X}, doi = {10.1155/2010/105309}, year = {2010}, abstract = {Time delays are ubiquitous in real world and are often sources of complex behaviors of dynamical systems. This paper addresses the problem of parameters identification and synchronization of uncertain chaotic delayed systems subject to time-varying delay. Firstly, a novel and systematic adaptive scheme of synchronization is proposed for delayed dynamical systems containing uncertainties based on Razumikhin condition and extended invariance principle for functional differential equations. Then, the proposed adaptive scheme is used to estimate the unknown parameters of nonlinear delayed systems from time series, and a sufficient condition is given by virtue of this scheme. The delayed system under consideration is a very generic one that includes almost all well-known delayed systems (neural network, complex networks, etc.). Two classical examples are used to demonstrate the effectiveness of the proposed adaptive scheme.}, language = {en} } @book{Wisotki2010, author = {Wisotki, Lutz}, title = {Galaxien, Schwarze L{\"o}cher, Quasare : Antrittsvorlesung 2010-12-08}, publisher = {Univ.-Bibl.}, address = {Potsdam}, year = {2010}, language = {de} } @article{EisertCramerPlenio2010, author = {Eisert, Jens and Cramer, Marcus and Plenio, Martin B.}, title = {Colloquium : area laws for the entanglement entropy}, issn = {0034-6861}, doi = {10.1103/RevModPhys.82.277}, year = {2010}, abstract = {Physical interactions in quantum many-body systems are typically local: Individual constituents interact mainly with their few nearest neighbors. This locality of interactions is inherited by a decay of correlation functions, but also reflected by scaling laws of a quite profound quantity: the entanglement entropy of ground states. This entropy of the reduced state of a subregion often merely grows like the boundary area of the subregion, and not like its volume, in sharp contrast with an expected extensive behavior. Such "area laws" for the entanglement entropy and related quantities have received considerable attention in recent years. They emerge in several seemingly unrelated fields, in the context of black hole physics, quantum information science, and quantum many-body physics where they have important implications on the numerical simulation of lattice models. In this Colloquium the current status of area laws in these fields is reviewed. Center stage is taken by rigorous results on lattice models in one and higher spatial dimensions. The differences and similarities between bosonic and fermionic models are stressed, area laws are related to the velocity of information propagation in quantum lattice models, and disordered systems, nonequilibrium situations, and topological entanglement entropies are discussed. These questions are considered in classical and quantum systems, in their ground and thermal states, for a variety of correlation measures. A significant proportion is devoted to the clear and quantitative connection between the entanglement content of states and the possibility of their efficient numerical simulation. Matrix-product states, higher-dimensional analogs, and variational sets from entanglement renormalization are also discussed and the paper is concluded by highlighting the implications of area laws on quantifying the effective degrees of freedom that need to be considered in simulations of quantum states.}, language = {en} } @article{ChenShiauTsengetal.2010, author = {Chen, Jin-Long and Shiau, Yuo-Hsien and Tseng, Yin-Jiun and Chiu, Hung-Wen and Hsiao, Tzu-Chien and Wessel, Niels and Kurths, J{\"u}rgen and Chu, Woei-Chyn}, title = {Concurrent sympathetic activation and vagal withdrawal in hyperthyroidism : evidence from detrended fluctuation analysis of heart rate variability}, issn = {0378-4371}, doi = {10.1016/j.physa.2009.12.062}, year = {2010}, abstract = {Despite many previous Studies on the association between hyperthyroidism and the hyperadrenergic state, controversies still exist. Detrended fluctuation analysis (DFA) is a well recognized method in the nonlinear analysis of heart rate variability (HRV), and it has physiological significance related to the autonomic nervous system. In particular, an increased short-term scaling exponent alpha 1 calculated from DFA is associated with both increased sympathetic activity and decreased vagal activity. No study has investigated the DFA of HRV in hyperthyroidism. This study was designed to assess the sympathovagal balance in hyperthyroidism. We performed the DFA along with the linear analysis of HRV in 36 hyperthyroid Graves' disease patients (32 females and 4 males; age 30 +/- 1 years, means +/- SE) and 36 normal controls matched by sex, age and body mass index. Compared with the normal controls, the hyperthyroid patients revealed a significant increase (P < 0.001) in alpha 1 (hyperthyroid 1.28 +/- 0.04 versus control 0.91 +/- 0.02), long-term scaling exponent alpha 2 (1.05 +/- 0.02 versus 0.90 +/- 0.01), overall scaling exponent alpha (1.11 +/- 0.02 versus 0.89 +/- 0.01), low frequency power in normalized units (LF\%) and the ratio of low frequency power to high frequency power (LF/HF); and a significant decrease (P < 0.001) in the standard deviation of the R-R intervals (SDNN) and high frequency power (HF). In conclusion, hyperthyroidism is characterized by concurrent sympathetic activation and vagal withdrawal. This sympathovagal imbalance state in hyperthyroidism helps to explain the higher prevalence of atrial fibrillation and exercise intolerance among hyperthyroid patients.}, language = {en} }