bluuebunny/crossref_metadata_2025 huggingface dataset:
Relativistic equations of motion of massive bodies
Authors: Blanchet Luc
Published: January 2010

Highly relativistic equations of motions will play a crucial role for the detection and analysis of gravitational waves emitted by inspiralling compact binaries in detectors LIGO/VIRGO on ground and LISA in space. Indeed these very relativistic systems (with orbital velocities of the order of half the speed of light in the last orbital rotations) require the application of a high-order post-Newtonian formalism in general relativity for accurate description of their motion and gravitational radiation [1]. In this contribution the current state of the art which has reached the third post-Newtonian approximation for the equations of motion [2–6] and gravitational waveform [7–9] has been described (see [10] for an exhaustive review). We have also emphasized the successful matching of the post-Newtonian templates to numerically generated predictions for the merger and ring-down in the case of black-hole binaries [11].
Proper stellar directions and astronomical aberration
Authors: Crosta Mariateresa , Vecchiato Alberto
Published: January 2010

The general relativistic definition of astrometric measurement needs an appropriate use of the concept of reference frame, which should then be linked to the conventions of the IAU Resolutions (Soffel et al., 2003), which fix the celestial coordinate system. A consistent definition of the astrometric observables in the context of General Relativity is also essential to find uniquely the stellar coordinates and proper motion, this being the main physical task of the inverse ray tracing problem. Aim of this work is to set the level of reciprocal consistency of two relativistic models, GREM and RAMOD (Gaia, ESA mission), in order to guarantee a physically correct definition of light direction to a star, an essential item for deducing the star coordinates and proper motion within the same level of measurement accuracy.
Spectroscopic binary mass determination using relativity
Authors: Zucker Shay , Alexander Tal
Published: January 2010

High-precision radial-velocity techniques, which enabled the detection of extra-solar planets, are now sensitive to the lowest-order relativistic effects in the data of spectroscopic binary stars (SBs). We show how these effects can be used to derive the absolute masses of the components of eclipsing single-lined SBs and double-lined SBs from Doppler measurements alone. High-precision stellar spectroscopy can thus substantially increase the number of measured stellar masses, thereby improving the mass-radius and mass-luminosity calibrations.
The art of precision pulsar timing
Authors: Bailes Matthew
Published: January 2010

Pulsar timing has proven to be a wonderful tool with which to study neutron stars, providing insights into their ages, distances, proper motions, magnetic field strengths, internal structure, binary histories and evolution, and for tests of General Relativity. Here I describe how to optimise strategies for millisecond pulsar timing to enable the highest timing precision.
Binary pulsars and tests of general relativity
Authors: Stairs I. H.
Published: January 2010

Binary pulsars are a valuable laboratory for gravitational experiments. Double-neutron-star systems such as the double pulsar provide the most stringent tests of strong-field gravity available to date, while pulsars with white-dwarf companions constrain departures from general relativity based on the difference in gravitational binding energies in the two stars. Future observations may open up entirely new tests of the predictions of general relativity.
Astrometric and timing effects of gravitational waves
Authors: Schutz Bernard F.
Published: January 2010

Gravitational wave detection can be done by precision timing of millisecond pulsars, and (with less likelihood) by precision astrometry on distant objects whose light or radio waves pass through gravitational waves on their way to our observatories. Underlying both of these is the relatively simple theory of light propagation in spacetimes with gravitational waves, which is also the basis of interferometric gravitational wave detectors. I review this theory and apply it to the timing and astrometric methods of detection. While pulsar timing might even be the first way that we directly detect gravitational waves, light deflection by gravitational waves seems out of reach.
Gravitational wave astronomy, relativity tests, and massive black holes
Authors: Bender Peter L.
Published: January 2010

The gravitational wave detectors that are operating now are looking for several kinds of gravitational wave signals at frequencies of tens of Hertz to kilohertz. One of these is mergers of roughly 10M⊙BH binaries. Sometime between now and about 8 years from now, it is likely that signals of this kind will be observed. The result will be strong tests of the dynamical predictions of general relativity in the high field regime. However, observations at frequencies below 1 Hz will have to wait until the launch of the Laser Interferometer Space Antenna (LISA), hopefully only a few years later. LISA will have 3 main objectives, all involving massive BHs. The first is observations of mergers of pairs of intermediate mass (100 to 105M⊙) and higher mass BHs at redshifts out to roughly z=10. This will provide new information on the initial formation and growth of BHs such as those found in most galaxies, and the relation between BH growth and the evolution of galactic structure. The second objective is observations of roughly 10M⊙BHs, neutron stars, and white dwarfs spiraling into much more massive BHs in galactic nuclei. Such events will provide detailed information on the populations of such compact objects in the regions around galactic centers. And the third objective is the use of the first two types of observations for testing general relativity even more strongly than ground based detectors will. As an example, an extreme mass ratio event such as a 10M⊙BH spiraling into a galactic center BH can give roughly 105observable cycles during about the last year before merger, with a mean relative velocity of 1/3 to 1/2 the speed of light, and the frequencies of periapsis precession and Lense-Thirring precession will be high. The LISA Pathfinder mission to prepare for LISA is scheduled for launch in 2011.
The galactic center: The ideal laboratory for studying supermassive black holes
Authors: Eisenhauer Frank
Published: January 2010

The Galactic Center constitutes the best astrophysical evidence for the existence of black holes, and it is the ideal laboratory for studying physics in the vicinity of such objects. The combination of infrared observations of three dimensional orbits of stars within the central light days and the extreme compactness and motionlessness of the radio-counterpart of the gravitational center have shown beyond any reasonable doubt that the Galactic Center harbors a supermassive black hole. The flaring activity from the black hole gives first insights to the physical processes close to the last stable orbit. Here I review the current state of observations and theory of the Galactic Center black hole and give an update on the latest results. I also outline the next steps towards even higher angular resolution observations, which give promise to directly probe the physics and space-time curvature just outside the event horizon.
Optical interferometry from the Earth
Authors: Quirrenbach Andreas
Published: January 2010

Ground-based optical interferometers can perform astrometric measurements with a precision approaching 10μas between pairs of stars separated by ~10″ on the sky. These narrow-angle measurements can be used to search for extrasolar planets and to determine their orbital parameters, to characterize microlensing events, and to measure the orbits of stars around the black hole at the center of our Galaxy.
Gaia: Astrometric performance and current status of the project
Authors: Lindegren Lennart
Published: January 2010

The scientific objectives of the Gaia mission cover areas of galactic structure and evolution, stellar astrophysics, exoplanets, solar system physics, and fundamental physics. Astrometrically, its main contribution will be the determination of millions of absolute stellar parallaxes and the establishment of a very accurate, dense and faint non-rotating optical reference frame. With a planned launch in spring 2012, the project is in its advanced implementation phase. In parallel, preparations for the scientific data processing are well under way within the Gaia Data Processing and Analysis Consortium. Final mission results are expected around 2021, but early releases of preliminary data are expected. This review summarizes the main science goals and overall organisation of the project, the measurement principle and core astrometric solution, and provide an updated overview of the expected astrometric performance.
Optimising the Gaia scanning law for relativity experiments
Authors: de Bruijne Jos , Siddiqui Hassan , Lammers Uwe , Hoar John , O'Mullane William , Prusti Timo
Published: January 2010

Gaia is ESA's upcoming astrometry mission, building on the heritage of its predecessor, Hipparcos. The Gaia nominal scanning law (NSL) prescribes the ideal attitude of the spacecraft over the operational phase of the mission. As such, it precisely determines when certain areas of the sky are observed. From theoretical considerations on sky-sampling uniformity, it is easy to show that the optimum scanning law for a space astrometry experiment like Gaia is a revolving scan with uniform rotation around the instrument symmetry axis. Since thermal stability requirements for Gaia's payload require the solar aspect angle to be fixed, the optimum parallax resolving power is obtained by letting the spin axis precess around the solar direction. The precession speed has been selected as compromise, limiting the across-scan smearing of images when they transit the focal plane, providing sufficient overlap between successive “great-circle” scans of the fields of view, and guaranteeing overlap of successive precession loops. With this scanning law, with fixed solar-aspect angle, spin rate, and precession speed, only two free parameters remain: the initial spin phase and the initial precession angle, at the start of science operations. Both angles, and in particular the initial precession angle, can be initialized following various (programmatic) criteria. Examples are optimization/fine-tuning of the Earth-pointing angle, of the number and total duration of Galactic-plane scans, or of the ground-station scheduling. This paper explores various criteria, with particular emphasis on the opportunity to optimise the scanning-law initial conditions to “observe” the most favorable passages of bright stars very close to Jupiter's limb. This would allow a unique determination of the light deflection due to the quadrupole component of the gravitational field of this planet.
Practical relativistic clock synchronization for high-accuracy space astrometry
Authors: Le Poncin-Lafitte Christophe
Published: January 2010

Future high-accuracy space astrometry missions, such as Gaia and SIM, will need a time-tagging of observations consistent with General Relativity nowadays used as standard background for global data processing scheme. In this work, we are focusing on the realization of the onboard time scale. The onboard clock, being not ideal and consequently tainted with systematic biases, has to be carefully calibrated to the ideal relativistic proper time of the satellite. We present here a modeling of this essential step to provide a reliable relation between the onboard time and TCB, a time scale suitable for global data processing.
Lorentz violation and gravity
Authors: Bailey Quentin G.
Published: January 2010

In the last decade, a variety of high-precision experiments have searched for miniscule violations of Lorentz symmetry. These searches are largely motivated by the possibility of uncovering experimental signatures from a fundamental unified theory. Experimental results are reported in the framework called the Standard-Model Extension (SME), which describes general Lorentz violation for each particle species in terms of its coefficients for Lorentz violation. Recently, the role of gravitational experiments in probing the SME has been explored in the literature. In this talk, I will summarize theoretical and experimental aspects of these works. I will also discuss recent lunar laser ranging and atom interferometer experiments, which place stringent constraints on gravity coefficients for Lorentz violation.
Measurement of gravitational time delay using drag-free spacecraft and an optical clock
Authors: Ashby Neil , Bender Peter L. , Hall John L. , Ye Jun , Diddams Scott A. , Jefferts Steven R. , Newbury Nathan , Oates Chris , Dolesi Rita , Vitale Stefano , Weber William J.
Published: January 2010

Improved accuracy in measurement of the gravitational time delay of electromagnetic waves passing by the sun may be achieved with two drag-free spacecraft, one with a stable clock and laser transmitter and one with a high-stability transponder. We consider one spacecraft near the Earth-Sun L1 point with an advanced optical clock, and the transponder on a second satellite, which has a 2 year period orbit and eccentricity e = 0.37. Superior conjunctions will occur at aphelion 1, 3, and 5 years after launch of the second spacecraft. The measurements can be made using carrier phase comparisons on the laser beam that would be sent to the distant spacecraft and then transponded back. Recent development of clocks based on optical transitions in cooled and trapped ions or atoms indicate that a noise spectral amplitude of about 5 × 10−15/ at frequencies down to at least 1 microhertz can be achieved in space-borne clocks. An attractive candidate is a clock based on a single laser-cooled Yb+ trapped ion. Both spacecraft can be drag-free at a level of 1×10−13m/s2/ at frequencies down to at least 1 microhertz. The corresponding requirement for the LISA gravitational wave mission is 3 × 10−15m/s2/ at frequencies down to 10−4 Hz, and Gravitational Reference Sensors have been developed to meet this goal. They will be tested in the LISA Pathfinder mission, planned by ESA for flight in 2011. The requirements to extend the performance to longer times are mainly thermal. The achievable accuracy for determining the PPN parameter γ is about 1 × 10−8.
Wie lassen sich Beckenbodenprobleme sinnvoll in die Hausarzttätigkeit integrieren?
Authors: Schuessler Bernhard
Published: January 2010

Harninkontinenz, Stuhlinkontinenz und Prolaps genitalis sowie genitale Schmerzen sind ein weit verbreitetes Problem bei der Frau. Trotz vielfältiger Aufklärungskampagnen sind diese Beschwerden für die Betroffenen häufig noch im Tabubereich angesiedelt. Der Hausarzt hat deshalb eine wichtige Aufgabe, diese Probleme aufzuspüren und entsprechend den Guidelines der International Consultation of Incontinence zu behandeln. Eine seriöse Vernetzung mit dem urogynäkologischen Spezialisten ist dafür die beste Voraussetzung.
Beckenboden in der Schwangerschaft und unter der Geburt
Authors: Hösli Irene
Published: January 2010

Drei bis sechs Monate nach der Geburt leiden etwa ein Drittel der Frauen unter einer Urininkontinenz, ein Zehntel unter einer Stuhlinkontinenz und 1 Prozent unter einem Prolaps. Das Prolapsrisiko nimmt nach vaginaler Geburt mit jeder weiteren Geburt zu, eine primäre Indikation für eine Sectio muss auf Grund der multifaktoriellen Genese und der geringen Prävalenz gegenüber den Risiken einer Sectio, insbesondere der Plazentainsertionstörungen, sehr gut abgewogen werden. In Bezug auf die Urininkontinenz nimmt die Assoziation mit dem Geburtsmodus mit zunehmender Parität und bei Untersuchungen nach 65 Jahren ab. Eine Stuhlinkontinenz hängt vorwiegend vom Geburtsmodus ab und tritt meist in Verbindung mit einer okkulten oder auch erkannten höhergradigen Dammverletzung oder durch neuronale Schädigung des N. pudendus auf. Auf Grund unterschiedlicher Definitionen, Populationen und fehlender randomisierter Studien sind die Prävalenzraten und Risikoberechnungen sehr divergierend. Eine allgemeine Empfehlung bezüglich elektiver Sectio kann auf Grund mangelnder Evidenz und bekannter plazentarer Risiken bei Folgeschwangerschaften nicht gegeben werden. Entscheidungen über den Geburtsmodus können sehr komplex sein, deshalb sind bekannte Risikofaktoren, beeinflussbare Lifestylefaktoren und Maßnahmen zur evidenzbasierten Prävention wichtige Informationen für das Gespräch in der antenatalen Beratung. Frauen mit einem hohen Risiko für Beckenbodenverletzungen zu identifizieren, bleibt Gegenstand weiterer Studien.
Urininkontinenz
Authors: Kuhn Annette
Published: January 2010

Inkontinenz ist ein zunehmendes, altersabhängiges Problem das sich bei Frauen hauptsächlich als Belastungsinkontinenz, hyperaktive Blase, gemischte Inkontinenz und seltenere Formen präsentiert. Die Anamnese, gynäkologische und neurologische Untersuchung gehört zum ersten Abklärungsschritt dazu sowie eine Untersuchung des Mittelstrahlurins; sollte dieser technisch schwierig zu gewinnen sein, hilft ein Katheterurin weiter. Gelgentlich können weiterführende Untersuchungen wie Zystoskopie, Urodynamik und Ultraschall notwendig sein. Die Belastungsinkontinenz sollte initial mit konservativen Maßnahmen wie Beckenbodentherapie und Gewichtsreduktion therapiert werden, sollte dies nicht ausreichend sein, kann eine operative Intervention empfohlen werden, dies zumeist in Form von suburethralen Schlingen, die minimalinvasiv eingelegt werden und eine gute Erfolgsrate von ca. 85 % haben. Die hyperaktive Blase wird mit Blasentraining und Anticholinergika therapiert; bei letzteren muss man bei älteren Patientinnen und Polymedikaktion auf eine mögliche Summation anticholinerger Effekte achten, die z. B. zu Verwirrung und Desorientiertheit führen kann.
Beckenbodeninsuffizienz – konservative Therapie
Authors: Geissbühler Verena
Published: January 2010

Konservative Therapien der Beckenbodeninsuffizienz sind einfach in der Handhabung, haben keinen negativen Einfluss auf ergänzende Therapien oder spätere Operationen, keine Nebenwirkungen und verursachen geringe Kosten. Damit konservative Therapien Erfolg zeigen, braucht es Geduld und Motivation von Seiten der Patientin sowie eine liebevolle Begleitung und Betreuung durch ein engagiertes Team. Die Erfolgsraten schwanken zwischen 40–70 %. Zu den konservativen Therapien zählen: Lifestyleberatung, Trink- und Miktionstraining, Physiotherapie des Beckenbodens, Pessare / Vaginaltampons, lokale Östrogene, Inkontinenzhilfen und komplementärmedizinische Maßnahmen. Konservative Therapien sollen miteinander kombiniert werden. Pessare und Vaginaltampons zeigen bei Belastungsinkontinenz und Deszensusbeschwerden rasche Therapieerfolge.
Operative Therapie der Beckenbodeninsuffizienz
Authors: Schär Gabriel
Published: January 2010

Operationen bei Beckenbodeninsuffizienz sollten konzeptionell angegangen werden. Die Grundlage dazu bilden die Beschwerden der betroffenen Frau und die Ansprüche an Funktionalität von Vagina, Blase und Darm. Es gilt zudem die anatomischen Defekte richtig zu beurteilen, da darauf die Entscheidung zugunsten einer Operationstechnik oder von Kombinationstechniken gefällt wird. Ein apikaler Deszensus sollte entweder mittels sakrospinaler Fixation oder mittels Sakrokolpopexie korrigiert werden. Bei der Zystozele ist entscheidend, ob es sich um einen zentralen oder lateralen Defekt handelt, da nur beim zentralen Defekt eine Diaphragmaplastik zum Ziel führt, während beim lateralen Defekt eine laterale Fixation notwendig ist, welche heute zunehmend mittels Netzeinlage durchgeführt wird. Die Rektozele wird mittels Kolpoperineoplastik korrigiert. Kenntnis von Erfolgsraten und möglichen Komplikationen sind für die Operationsentscheide und die Information der Patientin von großer Bedeutung.
Stuhlinkontinenz
Authors: Hamel Christian T. , Marti Walter R.
Published: January 2010

Die fäkale Inkontinenz wird in ihrer Häufigkeit deutlich unterschätzt. In den meisten Fällen von leichter Inkontinenz ist die konservative Therapie erfolgreich. Schwere Formen der Inkontinenz sollen in einem Interdisziplinären Ansatz formal abgeklärt werden, damit die Patienten den geeigneten Therapieoptionen zugeführt werden können. Ob allenfalls eine chirurgische Intervention indiziert ist, kann erst nach einem entsprechenden Abklärungsprozerdere bestimmt werden. Das Ziel der chirurgischen Intervention zur Verbesserung der Kontinenzleistung kann erstens die Reparatur eines Defektes, die Augmentation des Beckenbodens oder sogar die Formation eines Neosphinkters sein. Bei verletztem Musculus sphincter ani externus kann die Sphinkerplastik zum Erfolg führen. Während bei der dynamisierten Grazilisplastik ein eigener Muskel als Sphinkterersatz verwendet wird, wird das gleiche Ziel bei dem Artificial bowel sphincter durch einen auffüllbaren Cuff erreicht. Bei intakter Muskulatur und neuraler Störung kommt heute die sakrale Nervenstimmulation zum Einsatz. Es ist entscheidend, die richtige Therapiemethode basierend auf der zu Grunde liegenden Pathologie zu wählen.
Characterization of cyanobacterial communities from high‐elevation lakes in the Bolivian Andes
Authors: Fleming Erich D. , Prufert‐Bebout Leslie
Published: January 2010

The Bolivian Altiplano is a harsh environment for life with high solar irradiation (visible and UVR), below freezing temperatures, and some of the lowest precipitation rates on the planet. However, microbial life is visibly abundant in small isolated refugia of spring or snowmelt‐fed lakes. In this study, we characterized the cyanobacterial composition of a variety of microbial mats present in three lake systems: Laguna Blanca, Laguna Verde (elevation 4300 m), and a summit lake in the Licancabur Volcano cone (elevation 5970 m). These lakes and their adjacent geothermal springs present an interesting diversity of environments within a geographically small region (5 km2). From these sites, 78 cyanobacterial cultures were isolated in addition to ∼400 cyanobacterial 16S rRNA gene sequences from environmental genomic DNA. Based on microscopy, cultivation, and molecular analyses, these communities contained many heterocytous, nitrogen‐fixing cyanobacteria (e.g., Calothrix, Nostoc, Nodularia) as well as a large number of cyanobacteria belonging to the form‐genus Leptolyngbya. More than a third (37%) of all taxa in this study were new species (≤96% 16S rRNA gene sequence identity), and 11% represented new and novel taxa distantly related (≤93% identity) to any known cyanobacteria. This is one of the few studies to characterize cyanobacterial communities based on both cultivation‐dependent and cultivation‐independent analyses.
Simulation of multisite precipitation using an extended chain‐dependent process
Authors: Zheng Xiaogu , Renwick James , Clark Anthony
Published: January 2010

The chain‐dependent process is a popular stochastic model for precipitation sequence data. In this paper, the effect of daily regional precipitation occurrence is incorporated into the stochastic model. This model is applied to analyze the daily precipitation at a small number of sites in the upper Waitaki catchment, New Zealand. In this case study, the probability distributions of daily precipitation occurrence and intensity, spatial dependences, and the relation between precipitation and atmospheric forcings are simulated quite well. Specifically, some behaviors which are not well modeled by existing models, such as the extremal behavior of daily precipitation intensity, the lag 1 cross correlation of daily precipitation occurrence, spatial intermittency, and spatial correlation of seasonal precipitation totals, are significantly improved. Moreover, a new and simpler approach is proposed which successfully eliminates overdispersion, i.e., underestimation of the variance of seasonal precipitation totals.
Optical, radiative, and source characteristics of aerosols at Minicoy, a remote island in the southern Arabian Sea
Authors: Vinoj V. , Satheesh S. K. , Moorthy K. Krishna
Published: January 2010

Extensive measurements of aerosol radiative and microphysical properties were made at an island location, Minicoy (8.3°N, 73.04°E) in the southern Arabian Sea. A large variability in aerosol characteristics associated with changes in air mass and precipitation characteristics was observed. Six distinct transport pathways were identified on the basis of cluster analysis. The Indo‐Gangetic Plain, along with the northern Arabian Sea and west Asia (NWA), was identified to be the region having the highest potential for aerosol mass loading at the island. This estimate is based on the concentration weighted trajectory as well as cluster analysis. Dust transport from the NWA region was found to make a substantial contribution to the supermicron mass fraction. The black carbon mass mixing ratios observed were the lowest compared to previous measurements over this region. Consequently, the atmospheric radiative forcing efficiency was low and was in the range 10–28 W m−2.
A geometric framework for channel network extraction from lidar: Nonlinear diffusion and geodesic paths
Authors: Passalacqua Paola , Do Trung Tien , Foufoula‐Georgiou Efi , Sapiro Guillermo , Dietrich William E.
Published: January 2010

A geometric framework for the automatic extraction of channels and channel networks from high‐resolution digital elevation data is introduced in this paper. The proposed approach incorporates nonlinear diffusion for the preprocessing of the data, both to remove noise and to enhance features that are critical to the network extraction. Following this preprocessing, channels are defined as curves of minimal effort, or geodesics, where the effort is measured on the basis of fundamental geomorphological characteristics such as flow accumulation area and isoheight contours curvature. The merits of the proposed methodology, and especially the computational efficiency and accurate localization of the extracted channels, are demonstrated using light detection and ranging (lidar) data of the Skunk Creek, a tributary of the South Fork Eel River basin in northern California.
Crystalline silicon surface passivation by high-frequency plasma-enhanced chemical-vapor-deposited nanocomposite silicon suboxides for solar cell applications
Authors: Mueller Thomas , Schwertheim Stefan , Fahrner Wolfgang R.
Published: January 2010

A passivation scheme, featuring nanocomposite amorphous silicon suboxides (a-SiOx:H) is investigated and analyzed in this work. The a-SiOx:H films are deposited by high-frequency plasma-enhanced chemical-vapor deposition via decomposition of silane (SiH4), carbon dioxide (CO2), and hydrogen (H2) as source gases. The plasma deposition parameters of a-SiOx:H films are optimized in terms of effective lifetime, while the oxygen content and the resulting optical band gap EG of the a-SiOx:H films are controlled by varying the CO2 partial pressure χO=[CO2]/([CO2]+[SiH4]). Postannealing at low temperatures of those films shows a beneficial effect in form of a drastic increase of the effective lifetime. This improvement of the passivation quality by low temperature annealing for the a-SiOx:H likely originates from defect reduction of the film close to the interface. Raman spectra reveal the existence of Si–(OH)x and Si–O–Si bonds after thermal annealing of the layers, leading to a higher effective lifetime, as it reduces the defect absorption of the suboxides. The surface passivation quality of a-SiOx:H within both n-type and p-type silicon has been studied as a function of injection level. Record high effective lifetime values of 4.7 ms on 1 Ω cm n-type float zone (FZ) wafers and 14.2 ms on 130 Ω cm p-type FZ wafers prove the applicability for a surface passivation of silicon wafers applicable to any kind of silicon-based solar cells. The effective lifetime values achieved on a highly doped crystalline wafer (1 Ω cm resistivity) appears to be the highest value ever reported. Samples prepared in this way feature a high quality passivation yielding effective lifetime values exceeding those of record SiO2 and SiNx passivation schemes.
Detecting dynamical boundaries from kinematic data in biomechanics
Authors: Ross Shane D. , Tanaka Martin L. , Senatore Carmine
Published: January 2010

Ridges in the state space distribution of finite-time Lyapunov exponents can be used to locate dynamical boundaries. We describe a method for obtaining dynamical boundaries using only trajectories reconstructed from time series, expanding on the current approach which requires a vector field in the phase space. We analyze problems in musculoskeletal biomechanics, considered as exemplars of a class of experimental systems that contain separatrix features. Particular focus is given to postural control and balance, considering both models and experimental data. Our success in determining the boundary between recovery and failure in human balance activities suggests this approach will provide new robust stability measures, as well as measures of fall risk, that currently are not available and may have benefits for the analysis and prevention of low back pain and falls leading to injury, both of which affect a significant portion of the population.
Precise probing spin wave mode frequencies in the vortex state of circular magnetic dots
Authors: Awad A. A. , Guslienko K. Y. , Sierra J. F. , Kakazei G. N. , Metlushko V. , Aliev F. G.
Published: January 2010

We report on detailed broadband ferromagnetic resonance measurements of azimuthal and radial spin wave excitations in circular Permalloy dots in the vortex ground state. Dots with aspect ratio (β=height over radius) varied from 0.03 to 0.1 were explored. The frequency splitting of two lowest azimuthal modes was observed. The experimentally observed dependence of the frequency splitting on β was reasonably well described by dynamic splitting model accounting the spin waves and vortex gyrotropic mode interaction.
Using hyperbolic Lagrangian coherent structures to investigate vortices in bioinspired fluid flows
Authors: Green Melissa A. , Rowley Clarence W. , Smits Alexander J.
Published: January 2010

We use direct Lyapunov exponents to identify Lagrangian coherent structures (LCSs) in a bioinspired fluid flow: the wakes of rigid pitching panels with a trapezoidal planform geometry chosen to model idealized fish caudal fins. When compared with commonly used Eulerian criteria, the Lagrangian method has previously exhibited the ability to define structure boundaries without relying on a preselected threshold. In addition, qualitative changes in the LCS have previously been shown to correspond to physical changes in the vortex structure. For this paper, digital particle image velocimetry experiments were performed to obtain the time-resolved velocity fields for Strouhal numbers of 0.17 and 0.27. A classic reverse von Kármán vortex street pattern was observed along the midspan of the near wake at low Strouhal number, but at higher Strouhal number the complexity of the wake increased downstream of the trailing edge. The spanwise vortices spread transversely across the wake and lose coherence, and this event was shown to correspond to a qualitative change in the LCS at the same time and location.
Scanning tunneling microscopy studies of the formation and coarsening of manganese silicides on Si(111)
Authors: Zou Zhi-Qiang , Wang Dan , Sun Jing-Jing , Liang Jia-Miao
Published: January 2010

Solid-phase epitaxial growth of manganese silicides on a Si(111)-7×7 surface at temperatures between room temperature and ∼750 °C has been studied using scanning tunneling microscopy. The as-deposited Mn film of ∼0.6–1 ML shows an ordered honeycomb structure with each Mn cluster occupying a half of the 7×7 unit cell. The Mn clusters begin to react with the Si substrate to form silicides at ∼250 °C. Two types of silicides, the three-dimensional (3D) and tabular islands, which correspond to Mn-rich silicides and monosilicide MnSi, respectively, coexist on the Si(111) surface at annealing temperatures between 250 and 500 °C. At 500 °C annealing, all 3D islands convert into tabular islands and MnSi is the only Mn silicide phase. Above 600 °C, the tabular islands convert into large 3D islands that are likely to be Si-rich manganese silicides. With increasing annealing temperature and time, the number density of silicide islands decreases, while the average size (area) of the remaining islands increases. The growth of large islands is a result of the dissolution of small ones, which can be understood in the context of Ostwald ripening mechanism.
Invariant-tori-like Lagrangian coherent structures in geophysical flows
Authors: Beron-Vera Francisco J. , Olascoaga María J. , Brown Michael G. , Koçak Huseyin , Rypina Irina I.
Published: January 2010

The term “Lagrangian coherent structure” (LCS) is normally used to describe numerically detected structures whose properties are similar to those of stable and unstable manifolds of hyperbolic trajectories. The latter structures are invariant curves, i.e., material curves of fluid that serve as transport barriers. In this paper we use the term LCS to describe a different type of structure whose properties are similar to those of invariant tori in certain classes of two-dimensional incompressible flows. Like stable and unstable manifolds, invariant tori are invariant curves that serve as transport barriers. There are many differences, however, between traditional LCSs and invariant-tori-like LCSs. These differences are discussed with an emphasis on numerical techniques that can be used to identify invariant-tori-like LCSs. Structures of this type are often present in geophysical flows where zonal jets are present. A prime example of an invariant-torus-like LCS is the transport barrier near the core of the polar night jet in the Earth’s lower and middle stratospheres in the austral winter and early spring; this is the barrier that traps ozone-depleted air inside the ozone hole. This example is investigated using both a simple analytically prescribed flow and a velocity field produced by a general circulation model of the Earth’s atmosphere.
Quality control of polymer solar modules by lock-in thermography
Authors: Hoppe Harald , Bachmann Jonas , Muhsin Burhan , Drüe Karl-Heinz , Riedel Ingo , Gobsch Gerhard , Buerhop-Lutz Claudia , Brabec Christoph J. , Dyakonov Vladimir
Published: January 2010

We have characterized lateral imperfections of photovoltaic modules based on solution processed polymer-fullerene semiconductor blends by means of lock-in thermography (LIT). The active layer of the solar cell modules is based on the heterogeneous organic semiconductor system poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester and the power conversion efficiency of the modules reached nearly 2% under irradiation of an AM 1.5 solar simulator. Applying highly sensitive LIT allowed us to detect several kinds of laterally distributed defects originating from imperfections in the respective functional layers as well as in the quality of encapsulation. We show that LIT is a powerful method for the quality control of large area polymer solar cells and modules, enabling fast feedback for optimization of production parameters.
Clustering criterion for inertial particles in two-dimensional time-periodic and three-dimensional steady flows
Authors: Sapsis Themistoklis , Haller George
Published: January 2010

We derive an analytic condition that predicts the exact location of inertial particle clustering in three-dimensional steady or two-dimensional time-periodic flows. The particles turn out to cluster on attracting inertial Lagrangian coherent structures that are smooth deformations of invariant tori. We illustrate our results on three-dimensional steady flows, including the Hill’s spherical vortex and the Arnold–Beltrami–Childress flow, as well as on a two-dimensional time and space periodic flow that models a meandering jet in a channel.
Computational analysis of an aortic valve jet with Lagrangian coherent structures
Authors: Shadden Shawn C. , Astorino Matteo , Gerbeau Jean-Frédéric
Published: January 2010

Important progress has been achieved in recent years in simulating the fluid-structure interaction around cardiac valves. An important step in making these computational tools useful to clinical practice is the development of postprocessing techniques to extract clinically relevant information from these simulations. This work focuses on flow through the aortic valve and illustrates how the computation of Lagrangian coherent structures can be used to improve insight into the transport mechanics of the flow downstream of the valve, toward the goal of aiding clinical decision making and the understanding of pathophysiology.
Phase behavior of repulsive polymer-tethered colloids
Authors: Bozorgui Behnaz , Sen Maya , Miller William L. , Pàmies Josep C. , Cacciuto Angelo
Published: January 2010

We report molecular dynamics simulations of a system of repulsive, polymer-tethered colloidal particles. We use an explicit polymer model to explore how the length and the behavior of the polymer (ideal or self-avoiding) affect the ability of the particles to organize into ordered structures when the system is compressed to moderate volume fractions. We find a variety of different phases whose origin can be explained in terms of the configurational entropy of polymers and colloids. Finally, we discuss and compare our results to those obtained for similar systems using simplified coarse-grained polymer models, and set the limits of their applicability.
Room-temperature ferromagnetism properties of Cu-doped SnO2 nanowires
Authors: Li Lijun , Yu Ke , Tang Zheng , Zhu Ziqiang , Wan Qing
Published: January 2010

The Cu-doped SnO2 nanowires (NWs) with average diameter of 40–100 nm were synthesized by thermal chemical vapor transport method. High-resolution transmission electron microscopy and energy dispersive spectroscopy studies of Cu-doped SnO2 NWs demonstrate that the NWs are single-crystal structures and Cu is homogeneously doped into the SnO2 lattice. X-ray photoelectron spectroscopy measurements evidence the existence of divalent Cu ions (Cu2+). Although the NWs consist of only nonmagnetic elements, room-temperature ferromagnetism is observed and its origin is attributed to both the structure defects and strong p-d ferromagnetic coupling between the local magnetic moment of Cu2+ and the polarized valence electrons of the surrounding oxygen based on first-principles calculations.
Interaction of acoustic levitation field with liquid reflecting surface
Authors: Hong Z. Y. , Xie W. J. , Wei B.
Published: January 2010

Single-axis acoustic levitation of substances, such as foam, water, polymer, and aluminum, is achieved by employing various liquids as the sound reflectors. The interaction of acoustic levitation field with liquid reflecting surface is investigated theoretically by considering the deformation of the liquid surface under acoustic radiation pressure. Numerical calculations indicate that the deformation degree of the reflecting surface shows a direct proportion to the acoustic radiation power. Appropriate deformation is beneficial whereas excessive deformation is unfavorable to enhance the levitation capability. Typically, the levitation capability with water reflector is smaller than that with the concave rigid reflector but slightly larger than that with the planar rigid reflector at low emitter vibration intensity. Liquid reflectors with larger surface tension and higher density behave more closely to the planar rigid reflector.
Magnetic instability of MgB2 thin film triggered by the various sweeping rates of an applied magnetic field
Authors: Lee Jae-Yeap , Lee Hu-Jong , Jung Myung-Hwa , Lee Sung-Ik , Choi Eun-Mi , Kang W. N.
Published: January 2010

Up to now, the vortex avalanche is known to depend critically on the changing of some external parameters, such as the applied magnetic field, the temperature, and the demagnetization factor. In this study, we found the sweeping rate (SR) of the applied magnetic field to be another parameter that contributed to the appearance of the vortex avalanche. For example, a fast SR 500 Oe/s enhanced the vortex avalanche quietly compared to the case of a slow SR of 3 Oe/s. The dependence of the appearance of the vortex avalanche on the SR was quite strong, especially at low temperatures. A H-T phase diagram that distinguishes the regions of magnetic stability and instability is drawn for each SR.
Twinning rotation and ferroelectric behavior of epitaxial BiFeO3 (001) thin film
Authors: Liu Huajun , Yang Ping , Yao Kui , Wang John
Published: January 2010

A twinning rotation structure is revealed by reciprocal space mappings obtained from synchrotron X-ray diffraction for the epitaxial BiFeO3 thin film that was grown on (001) SrTiO3 substrate. The lattice strain is not fully relaxed at a film thickness of 720 nm. The structure is indexed as a monoclinic with lattice parameters a=5.610(1) Å, b=5.529(1) Å, c=4.031(1) Å, and β=89.34(1)°. The twinning rotation leads to an enhanced remanent polarization (2Pr=164 μC/cm2, 2Ec=510 kV/cm) and greatly reduced leakage current density of 1.2×10−6 A/cm2 at 100 kV/cm.
Structure and electrical properties of Bi3.15Nd0.85Ti3O12 nanofibers synthesized by electrospinning and sol-gel method
Authors: Liao M. , Zhong X. L. , Wang J. B. , Xie S. H. , Zhou Y. C.
Published: January 2010

Bi 3.15 Nd 0.85 Ti 3 O 12 (BNT) nanofibers with radii in the range of 30–200 nm have been prepared by the electrospinning and sol-gel method, and the structure and morphology of the nanofibers were characterize by x-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The phase transition and piezoelectric characteristics of the BNT nanofibers were performed by thermal analysis and scanning probe microscopy, respectively. The BNT nanofiber exhibits an effective piezoelectric coefficient of 89 pm/V and a Curie temperature of 500 °C, which are higher than that of the BNT bulk.
High-sensitive scanning laser magneto-optical imaging system
Authors: Murakami Hironaru , Tonouchi Masayoshi
Published: January 2010

A high-sensitive scanning laser magneto-optical (MO) imaging system has been developed. The system is mainly composed of a laser source, galvano meters, and a high-sensitive differential optical-detector. Preliminary evaluation of system performance by using a Faraday indicator with a Faraday rotation coefficient of 3.47×10−5 rad/μm Oe shows a magnetic sensitivity of about 5 μT, without any need for accumulation or averaging processing. Using the developed MO system we have succeeded in the fast and quantitative imaging of a rotationally symmetric magnetic field distribution around an YBa2Cu3O7−δ (YBCO) strip line applied with dc-biased current, and also succeeded in the detection of quantized fine signals corresponding to magnetic flux quantum generation in a superconducting loop of an YBCO Josephson vortex flow transistor. Thus, the developed system enables us not only to do fast imaging and local signal detection but also to directly evaluate both the strength and direction of a magnetic signal.
Surface plasmon-enhanced emission from Ag-coated Ce doped Y3Al5O12 thin films phosphor capped with a dielectric layer of SiO2
Authors: Chao Wen-Hsuan , Wu Ren-Jye , Tsai Chih-Song , Wu Tai-Bor
Published: January 2010

The effect of a surface plasmon (SP) on the yellow emission of Ce doped Y3Al5O12 (YAG:Ce) phosphor thin films was studied. The coating of YAG:Ce thin films with silver nanoislands on a 3-nm-thick SiO2 spacer significantly enhanced their photoluminescence (PL). The PL enhancement is caused by the resonant coupling of photoemission in YAG:Ce into SP and the electric field of incident light at the metal interfaces. Varying the mass thickness and the annealing condition of the Ag layer indicated that the PL intensity was highest at an Ag mass thickness of 20 nm. Therefore, yellow emission was enhanced by tuning the matching conditions of thin film phosphor-SP coupling by controlling the structure of silver nanoislands. The PL intensity can be further and remarkably enhanced by capping Ag islands with a 10-nm-thick SiO2 layer as a dielectric medium.
The surface tension of TIP4P/2005 water model using the Ewald sums for the dispersion interactions
Authors: Alejandre José , Chapela Gustavo A.
Published: January 2010

The liquid-vapor phase equilibria and surface tension of the TIP4P/2005 water model is obtained by using the Ewald summation method to determine the long range Lennard-Jones and electrostatic interactions. The method is implemented in a straightforward manner into standard simulation programs. The computational cost of using Ewald sums in dispersion interactions of water is estimated in direct simulation of interfaces. The results of this work at 300 K show a dramatic change in surface tension with an oscillatory behavior for surface areas smaller than 5×5σ2, where σ is the Lennard-Jones oxygen diameter. The amplitude of such oscillations substantially decreases with temperature. Finite size effects are less important on coexisting densities. Phase equilibria and interfacial properties can be determined using a small number of water molecules; their fluctuations are around the same size of simulation error at all temperatures, even in systems where the interfaces are separated a few molecular diameters only. The difference in surface tension of this work compared to the results of other authors is not significant (on the contrary, there is a good agreement). What should be stressed is the different and more consistent approach to obtain the surface tension using the Ewald sums for dispersion interactions. There are two relevant aspects at the interface: An adsorption of water molecules is observed at small surface areas and its thickness systematically increases with system size.
Detection of an endocrine disrupter biomarker, vitellogenin, in largemouth bass serum using AlGaN/GaN high electron mobility transistors
Authors: Chu Byung Hwan , Chang C. Y. , Kroll Kevin , Denslow Nancy , Wang Yu-Lin , Pearton S. J. , Dabiran A. M. , Wowchak A. M. , Cui B. , Chow P. P. , Ren Fan
Published: January 2010

Endocrine disrupters are known to have negative effects on the environment and human health. Real time detection of vitellogenin, an endocrine disrupter biomarker, was demonstrated using AlGaN/GaN high electron mobility transistors (HEMTs). Anti-vitellogenin antibodies were chemically anchored to the gold-coated gate area of the HEMT and immobilized with thioglycolic acid. The potential difference that occurs from the vitellogenin antigen-antibody interaction-induced caused a drain current change in the HEMT. The HEMT sensor was tested for vitellogenin detection both in phosphate buffer saline and largemouth bass serum.
A polarity-controllable graphene inverter
Authors: Harada Naoki , Yagi Katsunori , Sato Shintaro , Yokoyama Naoki
Published: January 2010

We propose and experimentally demonstrate a functional electron device, which is a polarity-controllable inverter constructed using a four-terminal ambipolar graphene field effect transistor (FET). The FET has two input terminals, both a top gate and a back gate, and the polarity of the FET can be switched by switching the input to the back gate. The slope of the inverter transfer curves can be changed by changing the back-gate voltage. By adding binary digital data and sinusoidal carrier waves into the back gate and the top gate of the inverter, respectively, the one-transistor binary digital phase modulator can be constructed and operated.
High-Q conical polymeric microcavities
Authors: Grossmann Tobias , Hauser Mario , Beck Torsten , Gohn-Kreuz Cristian , Karl Matthias , Kalt Heinz , Vannahme Christoph , Mappes Timo
Published: January 2010

We report on the fabrication of high-Q microresonators made of low-loss, thermoplastic polymer poly(methyl methacrylate) (PMMA) directly processed on a silicon substrate. Using this polymer-on-silicon material in combination with a thermal reflow step enables cavities of conical geometry with an ultrasmooth surface. The cavity Q factor of these PMMA resonators is above 2×106 in the 1300 nm wavelength range. Finite element simulations show the existence of a variety of “whispering gallery” modes in these resonators explaining the complexity of the measured transmission spectra.