bluuebunny/crossref_metadata_2025 huggingface dataset:
Traces of a Lost Autobiographical Work by a Courtier of Selim II
Authors: Meredith-Owens G. M.
Published: January 2010

Autobiography is a genre not frequently encountered in Ottoman literature. In recent years two works have been published which fall into this category—the autobiography of ‘Omān Āghā who was a prisoner of war in Austria towards the close of the seventeenth century, and the memoirs of Ma'jūnjuzāde Muṣṭafa Efendi describing his experiences after his capture by the Knights of Malta in 1597.
Notes on theYüan-Ch'ao Pi-Shih
Authors: Waley Arthur
Published: January 2010

I have in the following notes expressed occasional disagreement with Pelliot, Haenisch, Mostaert, and Cleaves. This does not mean that in general I underrate their immense services to Mongol studies.
Some Recent Work in Mongolian Studies
Authors: Bawden C. R.
Published: January 2010

The study of the language and civilization of the Mongols was for long a preserve of Russian scholars and of foreigners working in Russia. The publications of Schmidt, Kowalewski, Pozdneev and others, who built in the nineteenth century to some extent on the pioneer work of P. S. Pallas and his interpreter Jaehrig in the eighteenth, remain in full use even to-day. Only at the turn of the present century, with Ramstedt's studies of the Khalkha dialect, did isolated schools of Mongol scholarship begin to grow up elsewhere in Europe, notably in Helsinki and in Warsaw. In Germany and France, under such scholars as Professor Haenisch and the late Professor Pelliot, the study of Mongol remained a subordinate field of another discipline, sinology, while in England, apart from some interest at the School of Oriental and African Studies, Mongol remained an almost unknown subject until the arrival in Cambridge in 1948 of Mr. Denis Sinor. Nowadays studies continue in the U.S.S.R.—notably in Leningrad under Pučkovskii, and in Moscow under Sanjeev and Dylykov. But the post-war years have seen a general growth of interest in Mongol studies elsewhere as an independent discipline. Thus in Budapest, a group of young scholars, pupils of Professor Ligeti, have recently been publishing the results of field-work carried out in Mongolia itself. In Western Europe the material foundation for the extension of Mongol studies was undoubtedly laid by the late Professor Kaare Granbech, who assembled in Copenhagen a large and comprehensive collection of Mongol manuscripts. His work has been enthusiastically continued by Professor Heissig of Bonn, whose researches, based on the Copenhagen material and the collections in German libraries and in his own possession, have shown the great possibilities for literary and historical research in this field. Not the least of Heissig's services has been the founding and almost single-handed nursing of the series ‘Göttinger Asiatische Forschungen’ (now ‘Asiatische Forschungen’) which, though not restricted to Mongol studies, contains several text editions and studies in this field. In the United States of America, apart from the philological work being directed by Professor Poppe in Seattle, the enterprise of the Reverend Antoine Mostaert and Professor F. W. Cleaves, combined with the generosity of the Harvard-Yenching Institute, has resulted in the publication of three beautiful sets of volumes of texts in facsimile reproduction in the series ‘Scripta Mongolica’. The present article will deal with the latest volumes of the Bonn and Harvard series.
Kitāb Al-Farq: A Work on the Habe Kingdoms Attributed to ‘U

th

mān Dan Fodio
Authors: Hiskett M.
Published: January 2010

The K. al-farq bayn wilāyāt ahi al-islām wa bayn wilāyāt ahi al-kufr is one of the minor works attributed to the Shehu ‘Umān dan Fodio. The work is not among those mentioned by Sultan Bello in the Infāq al-maysūr, nor is it listed by Whitting or Vajda. It is listed by Kensdale, and Smith notes a MS among the De Gironcourt papers which bears an almost identical title. The writer has been assured by Malam Junaidu, Wazirin Sokoto that the work is well known to be by the Shehu ‘Umān. Malam Abubakar Gumi of the School for Arabic Studies, Kano, and a Sokoto scholar deeply versed in the Fulani Arabic literature, also confirms that the work has been known to him from his youth as that of the Shehu. Finally the author identifies himself in the preamble as ‘Umān b. Fūdī.
Meccan trade and Qur'ānic exegesis (Qur'ān 2: 198)
Authors: Rubin Uri
Published: January 2010

Qur'ān 2: 198 states that it is no fault in the Muslims that they should seek the faḍl of their lord: laysa ‘alaykum junāḥun an tabtaghū faḍlan min rabbikum. This verse occurs within a series of godly ordinances pertaining to the Muslim ḥajj, and it is therefore quite obvious why Muslim exegetes thought that the faḍl of Allāh in our verse ought to be sought by the believers during the ḥajj. In order to convey this view, the exegetes used a simple device, they added the following clause at the end of the verse: fī mawāsim al-ḥajj—during the rites of, or, in the stations of the ḥajj. Several traditions in al-Ṭabarī contain this addition. Most of the isnāds of these traditions are Meccan, which implies that the scholars of this place were particularly interested in encouraging the believers to come to the holy places of the Meccan ḥajj. Thus, tradition no. 18 in al-Ṭabarī which contains the addition fī mawāsim al-ḥajj is transmitted from the Meccan ‘Ubaydallāh b. Abī Yazīd (d. 126 A.H.), who quotes Ibn al-Zubayr. In fact, the clause fī mawāsim al-ḥajj gained the rank of a qirā'a. In some traditions it is transmitted as such from the Meccan ‘Aṭā’ b. Abī Rabāh (d. 114 A.H.) on the authority of Ibn ‘Abbās. ‘Aṭā’ is quoted through the Meccan Talḥa b. ‘Amr (d. 152 A.H.), as well as through Ḥajjāj b. Arṭāt (d. 145 A.H.). The Medinese ‘Ikrima (d. 105 A.H.) also spread the same qirā'a. In al-Ṭabarī he is quoted by the Basrian Ayyūb al-Sakhtiyānī (d. 131 A.H.).
‘Class I present’, subjunctive and middle voice in Indo-European
Authors: Hart Gillian R.
Published: January 2010

Section 1.Introduction1.01. All the above-mentioned categories have been the subject of considerable interest in the last few years. T. Gotō (1987) has devoted a book to Class I presents (thematic presents with normal grade of the root and stable root accent) in Sanskrit, and H. Rix has published a monograph on Indo-European moods (1986) and an article on the middle voice (1988). B. Barschel (1986) has addressed the question of the antiquity of the subjunctive and optative, and their absence from the Anatolian branch of IE. The question of the special primary endings of the singular active in the thematic conjugation was reopened by W. Cowgill (1985). Yet despite all this attention some questions still remain puzzling.
Beyond the standard IAU framework
Authors: Kopeikin Sergei
Published: January 2010

We discuss three conceivable scenarios of extension and/or modification of the IAU relativistic resolutions on time scales and spatial coordinates beyond the Standard IAU Framework. These scenarios include: (1) the formalism of the monopole and dipole moment transformations of the metric tensor replacing the scale transformations of time and space coordinates; (2) implementing the parameterized post-Newtonian formalism with two PPN parameters – β and γ; (3) embedding the post-Newtonian barycentric reference system to the Friedman-Robertson-Walker cosmological model.
Units of measurement in relativistic context
Authors: Guinot Bernard
Published: January 2010

In the Newtonian approximation of General Relativity, employed for the dynamical modelling in the solar system, the coordinates have the dimension of time and length. As these coordinates are close to their Newtonian counterpart, the adherence to the rules of the Quantity Calculus does not raise practical difficulties: the second and the metre should be used as their units, in an abstract conception of these units. However, the scaling of coordinate times, applied for practical reasons, generates controversies, because there is a lack of information about the metrics to which they pertain. Nevertheless, it is not satisfactory to introduce specific units for these scaled coordinate times.
Models and nomenclature in Earth rotation
Authors: Capitaine Nicole
Published: January 2010

The celestial Earth's orientation is required for many applications in fundamental astronomy and geodesy; it is currently determined with sub-milliarcsecond accuracy by astro-geodetic observations. Models for that orientation rely on solutions for the rotation of a rigid Earth model and on the geophysical representation of non-rigid Earth effects. Important IAU 2000/2006 resolutions on reference systems have been passed (and endorsed by the IUGG) that recommend a new paradigm and high accuracy models to be used in the transformation from terrestrial to celestial systems. This paper reviews the consequences of these resolutions on the adopted Earth orientation parameters, IAU precession-nutation models and associated nomenclature. It summarizes the fundamental aspects of the current IAU precession-nutation models and reports on the consideration of General Relativity (GR) in the solutions. This shows that the current definitions and nomenclature for Earth's rotation are compliant with GR and that the IAU precession-nutation is compliant with the IAU 2000 definition of the geocentric celestial reference system in the GR framework; however, the underlying Earth's rotation models basically are Newtonian.
Gravitational light deflection, time delay and frequency shift in Einstein-Aether theory
Authors: Tang Kai , Huang Tian-Yi , Tang Zheng-Hong
Published: January 2010

Einstein-Aether gravity theory has been proven successful in passing experiments of different scales. Especially its Eddington parameters β and γ have the same numerical values as those in general relativity. Recently Xie and Huang (2008) have advanced this theory to a second post-Newtonian approximation for an N-body model and obtained an explicit metric when the bodies are point-like masses. This research considers light propagation in the above gravitational field, and explores the light deflection, time delay, frequency shift etc. The results will provide for future experiments in testing gravity theories.
A relativistic motion integrator: numerical accuracy and illustration with BepiColombo and Mars-NEXT
Authors: Hees A. , Pireaux S.
Published: January 2010

Today, the motion of spacecraft is still described by the classical Newtonian equations of motion plus some relativistic corrections. This approach might become cumbersome due to the increasing precision required. We use the Relativistic Motion Integrator (RMI) approach to numerically integrate the native relativistic equations of motion for a spacecraft. The principle of RMI is presented. We compare the results obtained with the RMI method with those from the usual Newton plus correction approach for the orbit of the BepiColombo (around Mercury) and Mars-NEXT (around Mars) orbiters. Finally, we present a numerical study of RMI and we show that the RMI approach is relevant to study the orbit of spacecraft.
Relativistic aspects of the JPL planetary ephemeris
Authors: Folkner W. M.
Published: January 2010

The orbits of the planets as represented by the JPL planetary ephemerides are now primarily determined by radio tracking of spacecraft. Analysis of the data and propagation of the orbits relies on an internally consistent set of equations of motion and propagation of radio signals including relativistic effects at the centimeter level. The planetary ephemeris data set can be used to test some aspects of the underlying theory such as estimates of PPN parameters γ and β, time variation in the gravitational constant G, rotation of the solar system relative to distant objects (Mach's principle), and place stringent limits on the possible violation of the inverse-square law.
Gravity tests with INPOP planetary ephemerides
Authors: Fienga A. , Laskar J. , Kuchynka P. , Leponcin-Lafitte C. , Manche H. , Gastineau M.
Published: January 2010

We present here several gravity tests made with the latest INPOP08 planetary ephemerides. We first propose two methods to estimate the PPN parameter β and its correlated value, the Sun J2, and we discuss the correlation between the Sun J2 and the mass of the asteroid ring. We estimate a possible advance in the planet perihelia. We also show that no constant acceleration larger than 1/4 of the Pioneer anomaly is compatible with the observed motion of the planets in our Solar System.
Probing general relativity with radar astrometry in the inner solar system
Authors: Margot Jean-Luc , Giorgini Jon D.
Published: January 2010

We describe a long-term program designed to obtain and interpret high-precision radar range measurements of a number of near-Earth objects (NEOs) that have trajectories reaching deep inside the gravitational well of the Sun. Objects in our sample have perihelion shift rates 1.5 to 2.5 times that of (1566) Icarus (10″/cy) and span a wide range of inclinations and semi-major axes, allowing for an unambiguous separation of general relativistic and solar oblateness effects. Four objects have been observed at Arecibo on at least two apparitions since 2000, with typical uncertainties of a few hundred meters. Within the next three years, we anticipate securing a total of 15 observations of 5 different NEOs. This program is expected to provide a purely dynamical measurement of the oblateness of the Sun (J2 at the 10−8 level) and to constrain the Eddington parameter β at the 10−4 level. Although our objects are selected to minimize Yarkovsky orbital drift, we also anticipate measuring Yarkovsky drift rates, which are orthogonal to the GR and J2 signatures.
Open loop doppler tracking in Chinese forthcoming Mars mission
Authors: Shang Kun , Ping Jinsong , Dai Chunli , Jian Nianchuan
Published: January 2010

Using the radio telescopes in Chinese VLBI Network and the K5/VSSP32 VLBI system of NICT in Japan, we have developed algorithms that can extract open loop Doppler information from the Chang'E-1 and Mars Express radio tracking data. Our latest results indicate the Doppler accuracy of open loop three-way Doppler is about 1mm/s in 1 second integration time, relative to a 8.4GHz carrier. In the forthcoming joint Russian-Chinese Martian mission in 2009, the current software algorithms and hardware performance will be improved, and we will attempt to use the high precision Doppler shift and phase information to test gravitation theories.
Pulsar timing array projects
Authors: Hobbs G.
Published: January 2010

Pulsars are amongst the most stable rotators known in the Universe. Over many years some millisecond pulsars rival the stability of atomic clocks. Comparing observations of many such stable pulsars may allow the first direct detection of gravitational waves, improve the Solar System planetary ephemeris and provide a means to study irregularities in terrestrial time scales. Here we review the goals and status of current and future pulsar timing array projects.
Observing a black hole event horizon: (sub)millimeter VLBI of Sgr A*
Authors: Fish Vincent L. , Doeleman Sheperd S.
Published: January 2010

Very strong evidence suggests that Sagittarius A*, a compact radio source at the center of the Milky Way, marks the position of a super massive black hole. The proximity of Sgr A* in combination with its mass makes its apparent event horizon the largest of any black hole candidate in the universe and presents us with a unique opportunity to observe strong-field GR effects. Recent millimeter very long baseline interferometric observations of Sgr A* have demonstrated the existence of structures on scales comparable to the Schwarzschild radius. These observations already provide strong evidence in support of the existence of an event horizon. (Sub)Millimeter VLBI observations in the near future will combine the angular resolution necessary to identify the overall morphology of quiescent emission, such as an accretion disk or outflow, with a fine enough time resolution to detect possible periodicity in the variable component of emission. In the next few years, it may be possible to identify the spin of the black hole in Sgr A*, either by detecting the periodic signature of hot spots at the innermost stable circular orbit or parameter estimation in models of the quiescent emission. Longer term, a (sub)millimeter VLBI “Event Horizon Telescope” will be able to produce images of the Galactic center emission to the see the silhouette predicted by general relativistic lensing. These techniques are also applicable to the black hole in M87, where black hole spin may be key to understanding the jet-launching region.
Global astrometric sphere reconstruction in Gaia: challenges and first results of the Verification Unit
Authors: Vecchiato Alberto , Abbas Ummi , Bucciarelli Beatrice , Lattanzi Mario G. , Morbidelli Roberto
Published: January 2010

Gaia will estimate the astrometric and physical data of approximately one billion objects. The core of this process, the global sphere reconstruction, is represented by the reduction of a subset of these objects, which will constitute the largest and most precise catalog of absolute astrometry in the history of Astronomy, and will put General Relativity to test by estimating the PPN parameter γ with unprecedented accuracy. As the Hipparcos mission showed, and as it is natural for all kind of absolute measurements, possible errors in the data reduction can hardly be identified at the end of the processing, and can lead to systematic errors in all the works which will use these results. In order to avoid such kind of problems, a Verification Unit was established by the Gaia Data Processing and Analysis Consortium (DPAC). One of its jobs is to implement and perform an independent global sphere reconstruction, parallel to the baseline one, to compare the two results, and to report any significant difference.
Perspective acceleration and gravitational redshift. Measuring masses of individual white dwarfs using Gaia + SIM astrometry
Authors: Anglada-Escudé Guillem , Debes John
Published: January 2010

According to current plans, the SIM/NASA mission will be launched just after the end of operations for the Gaia/ESA mission. This is a new situation which enables long term astrometric projects that could not be achieved by either mission alone. Using the well-known perspective acceleration effect on astrometric measurements, the true heliocentric radial velocity of a nearby star can be measured with great precision if the time baseline of the astrometric measurements is long enough. Since white dwarfs are compact objects, the gravitational redshift can be quite large (40–80 km/s), and is the predominant source of any shift in wavelength. The mismatch of the true radial velocity with the spectroscopic shift thus leads to a direct measure of the Mass–Radius relation for such objects. Using available catalog information about the known nearby white dwarfs, we estimate how many masses/gravitational redshift measurements can be obtained with an accuracy better than 2%. Nearby white dwarfs are relatively faint objects (10 < V < 15), which can be easily observed by both missions. We also briefly discuss how the presence of a long period planet can mask the astrometric signal of perspective acceleration.
Space astrometry with the Joint Milliarcsecond Astrometry Pathfinder
Authors: Hennessy Gregory S. , Gaume Ralph
Published: January 2010

The Joint Milliarcsecond Astrometry Pathfinder Survey (JMAPS) is a small, space-based, all sky, visible wavelength, astrometric and photometric survey mission for 0ththrough 14thI-band magnitude stars with a planned 2013 launch. The primary objective of the JMAPS mission is the generation of an astrometric star catalog with 1 milliarcsecond (mas) positional accuracy or better and photometry to the 1% accuracy level or better at 1stto 12thmag. A 1-mas all–sky survey will have a significant impact on our current understanding of galactic and stellar astrophysics. JMAPS will improve our understanding of the origins of nearby young stars, provide insight into the dynamics of star formation regions and associations, investigate the dynamics and membership of nearby open clusters.
Two cylindrical masses in orbit for the test of the equivalence principle
Authors: Chhun Ratana , Touboul Pierre , Lebat Vincent
Published: January 2010

Two pairs of solid test-masses have been considered to perform in space the test of the universality of free fall with an accuracy of at least 10−15. These cylindrical masses are precisely at the heart of the MICROSCOPE mission instrument comprising two differential electrostatic accelerometers. These masses shall exhibit material quality, shapes, positions and alignments in regard to stringent experimental requirements. Indeed the space experiment is based on the control of the two masses submitted to the same gravity acceleration along the same orbit at 810 km altitude with an accuracy of 10−11 m. Thus effects of Earth and satellite gravity gradients shall be contained as well as any other disturbances of the mass motions induced by their magnetic susceptibility or electrical dissymmetries, by outgassing of the materials or radiation emissivity. Furthermore, the electrostatic levitation of the two masses depends dramatically on the mass shapes and electrical properties in particular for the definition of the sensitive axes orientation. All these aspects will be presented from the mass characteristics to the space MICROSCOPE experiment performance.
Modelling and simulation of the space mission MICROSCOPE
Authors: Bremer Stefanie , List Meike , Selig Hanns , Lämmerzahl Claus
Published: January 2010

The French space mission MICROSCOPE aims at testing the weak Equivalence Principle (EP) with an accuracy of 10−15. The payload, which is developed and built by the French institute ONERA consists of two high-precision capacitive differential accelerometers. The detection of the test mass movement and their control is done via a complex electrode system. The German department ZARM is member of the MICROSCOPE performance team. In addition to drop tower tests, mission simulations and the preparation of the mission data evaluation are realized in close cooperation with the French partners CNES, ONERA and OCA. Therefore a comprehensive simulation of the real system including the science signal and all error sources is built for the development and testing of data reduction and data analysis algorithms to extract the EP violation signal. In this context the focus lays on the correct modeling of the environmental disturbances. Currently new effort to study the influence of the solar radiation and the Earth albedo to the MICROSCOPE mission scenario is underway.
Microscope – A space mission to test the equivalence principle
Authors: List Meike , Selig Hanns , Bremer Stefanie , Lämmerzahl Claus
Published: January 2010

MICROSCOPE is a ESA/CNES space mission for testing the validity of the weak equivalence principle. The mission's goal is to determine the Eötvös parameter η with an accuracy of 10−15. The French space agency CNES is responsible for designing the satellite which is developed and produced within the Myriade series. The satellite's payload T–SAGE (Twin Space Accelerometer for Gravitation Experimentation) consists of two high–precision capacitive differential accelerometers and is developed and built by the French institute ONERA.

As a member of the MICROSCOPE performance team, the German department ZARM performs free fall tests of the MICROSCOPE differential accelerometers at the Bremen drop tower. The project's concepts and current results of the free fall tests are shortly presented.
New precise method for accurate modeling of thermal recoil forces
Authors: Rievers Benny , Lämmerzahl Claus
Published: January 2010

The exact modeling of external and internal perturbations acting on spacecraft becomes increasingly important as the scientific requirements become more demanding. Disturbance models included in orbit determination and propagation tools need to be improved to account for the needed accuracy. At ZARM (Center of Applied Space Technology and Microgravity) algorithms for the simulation and analysis of thermal perturbations have been developed. The applied methods are based on the inclusion of the actual spacecraft geometry by means of Finite Element (FE) models in the calculation of the disturbance forces. Thus the modeling accuracy is increased considerably and also housekeeping and sensor data can be included in the calculations. Preliminary results for a test case geometry of the Pioneer 10/11 mission are presented and discussed with respect to the Pioneer anomaly. It is shown that thermal effects cannot be neglected for the magnitude scale of the observed anomalous effect.
Braids of entangled particle trajectories
Authors: Thiffeault Jean-Luc
Published: January 2010

In many applications, the two-dimensional trajectories of fluid particles are available, but little is known about the underlying flow. Oceanic floats are a clear example. To extract quantitative information from such data, one can measure single-particle dispersion coefficients, but this only uses one trajectory at a time, so much of the information on relative motion is lost. In some circumstances the trajectories happen to remain close long enough to measure finite-time Lyapunov exponents, but this is rare. We propose to use tools from braid theory and the topology of surface mappings to approximate the topological entropy of the underlying flow. The procedure uses all the trajectory data and is inherently global. The topological entropy is a measure of the entanglement of the trajectories, and converges to zero if they are not entangled in a complex manner (for instance, if the trajectories are all in a large vortex). We illustrate the techniques on some simple dynamical systems and on float data from the Labrador Sea. The method could eventually be used to identify Lagrangian coherent structures present in the flow.
Efficient and accurate simulations of two-dimensional electronic photon-echo signals: Illustration for a simple model of the Fenna–Matthews–Olson complex
Authors: Sharp Leah Z. , Egorova Dassia , Domcke Wolfgang
Published: January 2010

Two-dimensional (2D) photon-echo spectra of a single subunit of the Fenna–Matthews–Olson (FMO) bacteriochlorophyll trimer of Chlorobium tepidum are simulated, employing the equation-of-motion phase-matching approach (EOM-PMA). We consider a slightly extended version of the previously proposed Frenkel exciton model, which explicitly accounts for exciton coherences in the secular approximation. The study is motivated by a recent experiment reporting long-lived coherent oscillations in 2D transients [Engel et al., Nature 446, 782 (2007)] and aims primarily at accurate simulations of the spectroscopic signals, with the focus on oscillations of 2D peak intensities with population time. The EOM-PMA accurately accounts for finite pulse durations as well as pulse-overlap effects and does not invoke approximations apart from the weak-field limit for a given material system. The population relaxation parameters of the exciton model are taken from the literature. The effects of various dephasing mechanisms on coherence lifetimes are thoroughly studied. It is found that the experimentally detected multiple frequencies in peak oscillations cannot be reproduced by the employed FMO model, which calls for the development of a more sophisticated exciton model of the FMO complex.
Fluid transport and coherent structures of translating and flapping wings
Authors: Eldredge Jeff D. , Chong Kwitae
Published: January 2010

The Lagrangian coherent structures (LCSs) of simple wing cross sections in various low Reynolds number motions are extracted from high-fidelity numerical simulation data and examined in detail. The entrainment process in the wake of a translating ellipse is revealed by studying the relationship between attracting structures in the wake and upstream repelling structures, with the help of blocks of tracer particles. It is shown that a series of slender lobes in the repelling LCS project upstream from the front of the ellipse and “pull” fluid into the wake. Each lobe is paired with a corresponding wake vortex, into which the constituent fluid particles are folded. Flexible and rigid foils in flapping motion are studied, and the resulting differences in coherent structures are used to elucidate their differences in force generation. The clarity with which these flow structures are revealed, compared to the vorticity or velocity fields, provides new insight into the vortex shedding mechanisms that play an important role in unsteady aerodynamics.
A novel method to form conducting channels in SiOx(Si) films for field emission application
Authors: Semenenko M. , Evtukh A. , Yilmazoglu O. , Hartnagel H. L. , Pavlidis D.
Published: January 2010

The electrical and field emission properties of SiOx(Si) films are studied. SiOx(Si) films of 40–100nm thick are obtained by plasma-enhanced chemical vapor deposition and thermal evaporation of Si powder onto Si substrates. Nanosized electrical conducting channels are formed in SiOx(Si) films by electrical conditioning at high current densities. The structures with conducting channels demonstrate increased field emission current and decreased threshold voltage compared to as-deposited SiOx(Si) films. The decrease in threshold voltage for electron field emission is explained by local enhancement of electric field. The diameters of conducting channels are estimated from the effective emission area to be in the range of 1–2nm.
Correlating the structural, chemical, and optical properties at nanometer resolution
Authors: Gu L. , Özdöl V. B. , Sigle W. , Koch C. T. , Srot V. , van Aken P. A.
Published: January 2010

Valence electron spectroscopic imaging (VESI) techniques, taking advantages of the energy-losses suffered by inelastic scattering of the fast electrons in the transmission electron microscope, offer an inherently high spatial resolution to characterize the electronic structure of materials close to the Fermi level. Here we demonstrate that the combination of an electron monochromator and a highly dispersive imaging energy filter, which has become available only recently, allows reliable measurements of local bandgaps on the nanometer scale. In addition, the correlations of structural, chemical, and optical properties can be revealed via VESI using monochromated electrons with a high spatial resolution.
Comparison of the magnetic properties of GaInAs/MnAs and GaAs/MnAs hybrids with random and ordered arrangements of MnAs nanoclusters
Authors: Elm M. T. , Michel C. , Stehr J. , Hofmann D. M. , Klar P. J. , Ito S. , Hara S. , Krug von Nidda H.-A.
Published: January 2010

Random arrangements of ferromagnetic MnAs nanoclusters were deposited on (111)B-GaInAs surfaces by standard metal-organic vapor-phase epitaxy (MOVPE). Ordered arrangements of MnAs nanoclusters and cluster chains were obtained by selective-area MOVPE on prepatterned (111)B-GaAs substrates. This new method enables one to control the arrangement of nanoclusters in the growth process offering interesting opportunities to tune the properties of individual MnAs clusters as well as the interaction between the carriers in the surrounding semiconductor matrix and the clusters. The magnetic anisotropy of the MnAs clusters was investigated by magnetic force microscopy and ferromagnetic resonance measurements. The in-plane magnetic anisotropy is mainly determined by the interplay of cluster shape and magnetocrystalline anisotropy while the hard magnetic axis of the clusters is perpendicular to the sample plane independent of cluster shape. The magnetotransport measurements demonstrate that the cluster arrangements strongly influence the transport properties.
Comprehensive understanding of field-dependent conduction mechanisms of sub-4-nm-thick post-soft-breakdown SiO2 films
Authors: Omura Yasuhisa
Published: January 2010

The experimentally determined conduction mechanisms of gate leakage current are examined for two different soft-breakdown events: analog-soft breakdown and digital-soft breakdown. It is strongly suggested that space-charge-limited conduction does not, by itself, represent the main conduction mechanism after analog-soft-breakdown events. In contrast, the analog-soft-breakdown current behaviors suggest that various variable-range-hopping conduction mechanisms play important roles in the transport process. On the other hand, it is found that the incremental gate current after digital-soft-breakdown events can be experimentally expressed in a simple closed form as functions of temperature and gate voltage; the empirical expression given herein indicates that the post-digital-soft-breakdown current is not ruled by a simple or single conduction mechanism. Features of the post-digital-soft-breakdown current are examined by the field-dependent lifetime model formulated by Schenk [Solid-State Electron. 35, 1585 (1992)] it is strongly suggested that Schenk’s theory primarily supports the experimental results. It is also suggested that the space-charge-limited current plays an important role, a background leakage current, in the post-digital-soft breakdown current.
Controlled synthesis of carbon nanotubes and linear C chains by arc discharge in liquid nitrogen
Authors: Scalese S. , Scuderi V. , Bagiante S. , Simone F. , Russo P. , D’Urso L. , Compagnini G. , Privitera V.
Published: January 2010

Arc discharge between two graphite rods in liquid nitrogen has been investigated in order to identify the main factors ruling the formation of carbon nanotubes (CNTs) and linear C chains. The influence of the experimental parameters on the structural properties of the produced materials was evaluated and interpreted, taking into account the existing models. We found that the electrode size and discharge current values greatly influence the structural quality of the nanotubes (e.g., presence of carbonaceous impurities, innermost tube diameter) and a proper combination of these parameters allows one to control the synthesis of CNTs and/or CNT-linear C chain hybrid systems.
Electrical and magnetic properties of GaN codoped with Eu and Si
Authors: Wang R. , Steckl A. J. , Nepal N. , Zavada J. M.
Published: January 2010

GaN thin films codoped with Eu and Si were grown on sapphire by solid source molecular beam epitaxy technique. Si incorporation changed GaN:Eu thin films from highly resistive to n-type conductive but not to levels normally achieved in conventional Si-doped GaN films. The magnetic properties of the codoped GaN films were measured by an alternating gradient magnetometer. While all samples exhibited hysteresis behavior at room temperature, there was a marked dependence on the Si codoping. At low-to-moderate Si doping levels, an increase up to approximately nine times in saturation magnetization was observed for films having higher conductivity, which also displayed an anomalous Hall effect. Under illumination at 371 nm, an increase in saturation magnetization was observed for all samples.
Trapping effects in Al2O3/AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistor investigated by temperature dependent conductance measurements
Authors: Kordoš P. , Stoklas R. , Gregušová D. , Gaži Š. , Novák J.
Published: January 2010

Frequency dependent conductance measurements at varied temperature between 25 and 260 °C were performed to analyze trapping effects in the Al2O3/AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors. The trap states with a time constant τT,f≅(0.1–1) μs (fast) and τT,s=10 ms (slow) were identified. The conductance measurements at increased temperatures made it possible to evaluate the fast trap states in about a four times broader energy range than that from room temperature measurement. The density of the fast traps decreased from 1.4×1012 cm−2 eV−1 at an energy of 0.27 eV to about 3×1011 cm−2 eV−1 at ET=0.6 eV. The density of the slow traps was significantly higher than that of the fast traps, and it increased with increased temperature from about 3×1012 cm−2 eV−1 at 25–35 °C to 8×1013 cm−2 eV−1 at 260 °C.
Sensitivity of Lagrangian coherent structure identification to flow field resolution and random errors
Authors: Olcay Ali B. , Pottebaum Tait S. , Krueger Paul S.
Published: January 2010

The effect of spatial and temporal resolutions and random errors on identification of Lagrangian coherent structures (LCSs) from Eulerian velocity fields is evaluated using two canonical flows: a two-dimensional vortex pair and a vortex ring formed by transient ejection of a jet from a tube. The flow field for the vortex pair case was steady and obtained analytically while the transient vortex ring flow was simulated using computational fluid dynamics. To evaluate resolution and random error effects, the flow fields were degraded by locally smoothing the flow and sampling it on a sparser grid to reduce spatial resolution, adding Gaussian distributed random noise to provide random errors, and/or subsampling the time series of vector fields to reduce the temporal resolution (the latter applying only for the vortex ring case). The degradation methods were meant to emulate distortions and errors introduced in common flow measurement methods such as digital particle image velocimetry. Comparing the LCS corresponding to the vortex boundary (separatrix) obtained from the degraded velocity fields with the true separatrix (obtained analytically for the vortex pair case or from high resolution, noise-free velocity fields for the vortex ring case) showed that noise levels as low as 5%–10% of the vortex velocity can cause the separatrix to significantly deviate from its true location in a random fashion, but the “mean” location still remained close to the true location. Temporal and spatial resolution degradations were found to primarily affect transient portions of the flow with strong spatial gradients. Significant deviations in the location of the separatrix were observed even for spatial resolutions as high as 2% of the jet diameter for the vortex ring case.
Mechanisms of lighting enhancement of Al nanoclusters-embedded Al-doped ZnO film in GaN-based light-emitting diodes
Authors: Lee Hsin-Ying , Chou Ying-Hung , Lee Ching-Ting , Yeh Wen-Yung , Chu Mu-Tao
Published: January 2010

Aluminum (Al)-doped ZnO (AZO) films with embedded Al nanoclusters were proposed and utilized to enhance the light output power and maximum operation current of GaN-based light-emitting diodes (LEDs). The AZO films were sputtered using ZnO and Al targets in a magnetron cosputtering system. With Al dc power of 7 W and ZnO 100 W ac power, the electron concentration of 4.1×1020 cm−3, electron mobility of 16.2 cm2/V s, and resistivity of 7.2×10−4 Ω cm were obtained for the deposited AZO film annealed at 600 °C for 1 min in a N2 ambient. As verified by a high resolution transmission electron microscopy, the deposited AZO films with embedded Al nanoclusters were clearly observed. A 35% increase in light output power of the GaN-based LEDs with Al nanoclusters-embedded AZO films was realized compared with the conventional LEDs operated at 500 mA. It was verified experimentally that the various characteristics of GaN-based LEDs including the antireflection, light scattering, current spreading, and the light extraction efficiency in light emission could be significantly enhanced with the use of Al nanoclusters-embedded AZO films.
Limitations and recommendations for the calculation of shear viscosity using reverse nonequilibrium molecular dynamics
Authors: Tenney Craig M. , Maginn Edward J.
Published: January 2010

The reverse nonequilibrium molecular dynamics (RNEMD) method calculates the shear viscosity of a fluid by imposing a nonphysical exchange of momentum and measuring the resulting shear velocity gradient. In this study we investigate the range of momentum flux values over which RNEMD yields usable (linear) velocity gradients. We find that nonlinear velocity profiles result primarily from gradients in fluid temperature and density. The temperature gradient results from conversion of heat into bulk kinetic energy, which is transformed back into heat elsewhere via viscous heating. An expression is derived to predict the temperature profile resulting from a specified momentum flux for a given fluid and simulation cell. Although primarily bounded above, we also describe milder low-flux limitations. RNEMD results for a Lennard-Jones fluid agree with equilibrium molecular dynamics and conventional nonequilibrium molecular dynamics calculations at low shear, but RNEMD underpredicts viscosity relative to conventional NEMD at high shear.
Dual band terahertz waveguiding on a planar metal surface patterned with annular holes
Authors: Williams C. R. , Misra M. , Andrews S. R. , Maier S. A. , Carretero-Palacios S. , Rodrigo S. G. , Garcia-Vidal F. J. , Martin-Moreno L.
Published: January 2010

We report studies of the guiding of terahertz radiation on a copper surface textured with an array of blind annular holes. The structure supports two tightly bound surface plasmon-polaritonlike electromagnetic waves associated with TE11 and TEM coaxial waveguide modes. The TE11-like surface mode has a cutoff determined by the array period while the TEM mode can be arranged to have a lower frequency cut-off by adjusting the hole depth. The ability to guide two modes in independently variable bands could be useful in quantitative chemical sensing.
The effects of non-normality and nonlinearity of the Navier–Stokes operator on the dynamics of a large laminar separation bubble
Authors: Cherubini S. , Robinet J.-Ch. , De Palma P.
Published: January 2010

The effects of non-normality and nonlinearity of the two-dimensional Navier–Stokes differential operator on the dynamics of a large laminar separation bubble over a flat plate have been studied in both subcritical and slightly supercritical conditions. The global eigenvalue analysis and direct numerical simulations have been employed in order to investigate the linear and nonlinear stability of the flow. The steady-state solutions of the Navier–Stokes equations at supercritical and slightly subcritical Reynolds numbers have been computed by means of a continuation procedure. Topological flow changes on the base flow have been found to occur close to transition, supporting the hypothesis of some authors that unsteadiness of separated flows could be due to structural changes within the bubble. The global eigenvalue analysis and numerical simulations initialized with small amplitude perturbations have shown that the non-normality of convective modes allows the bubble to act as a strong amplifier of small disturbances. For subcritical conditions, nonlinear effects have been found to induce saturation of such an amplification, originating a wave-packet cycle similar to the one established in supercritical conditions, but which is eventually damped. A transient amplification of finite amplitude perturbations has been observed even in the attached region due to the high sensitivity of the flow to external forcing, as assessed by a linear sensitivity analysis. For supercritical conditions, the non-normality of the modes has been found to generate low-frequency oscillations (flapping) at large times. The dependence of such frequencies on the Reynolds number has been investigated and a scaling law based on a physical interpretation of the phenomenon has been provided, which is able to explain the onset of a secondary flapping frequency close to transition.
Exact quantum scattering study of the Ne+H2+ reaction on a new ab initio potential energy surface
Authors: Lv Shuang-Jiang , Zhang Pei-Yu , Han Ke-Li , He Guo-Zhong
Published: January 2010

We present a new potential energy surface (PES) for the ground state (12A′) of the chemical reaction Ne+H2+ from a set of accurate ab initio data, which were computed using highly correlated complete active space self-consistent field and multireference configuration interaction wave functions with a basis set of aug-cc-pV5Z. The quantum reactive scattering dynamics calculation was carried out over the collision energy (Ecol) range of 0.5–1.5 eV based on the new PES. In this work we have taken the Coriolis coupling (CC) effect into account. The importance of including the CC quantum scattering calculation has been revealed by the comparison between the CC and the centrifugal sudden approximation calculation. The magnitude and profile of the CC total cross sections for v=0 and j=1 over the collision energy range of 0.5–1.5 eV are found to be in good agreement with the available experimental measurements obtained recently by Zhang et al. [J. Chem. Phys. 119, 10175 (2003)] after taking into account the experimental uncertainties.
Introduction to Focus Issue: Lagrangian Coherent Structures
Authors: Peacock Thomas , Dabiri John
Published: January 2010

The topic of Lagrangian coherent structures (LCS) has been a rapidly growing area of research in nonlinear dynamics for almost a decade. It provides a means to rigorously define and detect transport barriers in dynamical systems with arbitrary time dependence and has a wealth of applications, particularly to fluid flow problems. Here, we give a short introduction to the topic of LCS and review the new work presented in this Focus Issue.
Generation of solitons and breathers in the extended Korteweg–de Vries equation with positive cubic nonlinearity
Authors: Grimshaw R. , Slunyaev A. , Pelinovsky E.
Published: January 2010

The initial-value problem for box-like initial disturbances is studied within the framework of an extended Korteweg–de Vries equation with both quadratic and cubic nonlinear terms, also known as the Gardner equation, for the case when the cubic nonlinear coefficient has the same sign as the linear dispersion coefficient. The discrete spectrum of the associated scattering problem is found, which is used to describe the asymptotic solution of the initial-value problem. It is found that while initial disturbances of the same sign as the quadratic nonlinear coefficient result in generation of only solitons, the case of the opposite polarity of the initial disturbance has a variety of possible outcomes. In this case solitons of different polarities as well as breathers may occur. The bifurcation point when two eigenvalues corresponding to solitons merge to the eigenvalues associated with breathers is considered in more detail. Direct numerical simulations show that breathers and soliton pairs of different polarities can appear from a simple box-like initial disturbance.
Induced magnetism of carbon atoms at the graphene/Ni(111) interface
Authors: Weser M. , Rehder Y. , Horn K. , Sicot M. , Fonin M. , Preobrajenski A. B. , Voloshina E. N. , Goering E. , Dedkov Yu. S.
Published: January 2010

We report an element-specific investigation of electronic and magnetic properties of the graphene/Ni(111) system. Using x-ray magnetic circular dichroism, the occurrence of an induced magnetism of the carbon atoms in the graphene layer is observed. We attribute this magnetic moment to the strong hybridization between C π and Ni 3d valence band states. The net magnetic moment of carbon in the graphene layer is estimated to be in the range of 0.05–0.1 μB per atom.