bluuebunny/crossref_metadata_2025 huggingface dataset:
Re-tuning the past, selling the future: Tata-AIG and theTree of Love
Authors: Beaster-Jones Jayson
Published: September 2011

This article explores the mobilisation of Indian popular music in the Tata-AIG life insurance company television advertisement ‘Tree of Love’ (2004). I address ways in which music representing different periods of Hindi film, along with visual representations of Indian material culture, have been integrated into an advertising narrative that alludes to India's technological and economic development. I suggest that a range of aural and visual signs subtly complement each other in creating a narrative that not only marks the passage of time, but reframes past social and economic debates into contemporary terms. I contextualise this advertisement – and the signs that it uses – within the field of the Indian insurance industry, as well as within the social-historical context of modern India. Then, utilising elements of Peircean semiotic theory, I closely analyse the aural representations of the passage of time and different eras of Indian musical culture. The analysis ties together the interactions of musical and non-musical signs with the cultural memories that the commercial is designed to evoke. Ultimately, I argue that musical meaning in this advertising context emerges from the complex interaction of these aural and visual signs, and produces memory as much as it reflects it.
On the interaction of alliteration with rhythm and metre in popular music
Authors: Salley Keith
Published: September 2011

A number of scholars have written on characteristics of vocal melody in popular music, but little attention has been paid at the level of phonetic detail. This study argues that the phonetic structure of a melody can contribute in important ways to a song's reception and success, given the ways that listeners react and respond to vocalised melody. This article discusses different ways in which stressed syllables in familiar pop songs alliterate, and it investigates the way these patterns interact rhythmically with metre.
The constraints of colour: popular music listening and the interrogation of ‘race’ in post-apartheid South Africa
Authors: Robertson Mary
Published: September 2011

In post-apartheid popular culture, there is a tension between the persistence of ‘race’ as a structural category of difference, and its transformation in the lives of young South Africans. In this paper, through the examination of case-studies, I explore how popular music may allow for the mediation of this tension. Drawing on Heidegger's notion of an ‘equipmental whole’ to conceptualise ‘race’, I discuss the specific ways in which individuals may come to an awareness of the potential fluidity of racial identities, and the role of music-listening practices in this process. I argue that reflecting on articulations between music and racial categories allowed listeners to critique understandings of ‘race’ underpinning post-apartheid political discourse. Such a critique enabled listeners either instrumentally to affirm a reconfigured understanding of a racial identity, or to reject ‘race’ as a meaningful category of difference altogether.
Racial Orders, Congress, and the Agricultural Welfare State, 1865–1940
Authors: Johnson Kimberley S.
Published: September 2011

One of the key questions posed by analysts of modern, twentieth-century agricultural politics is, “How and when did agrarian democracy end and the dominance of agribusiness interests begin?” In this article I argue that the roots of this transformation lie in the origins of the agricultural welfare state and the overlapping of its birth with distinct eras in America's racial orders—those moments in time when political players mobilized coalitions and institutions around racial issues such as slavery, Reconstruction, or the segregated state of the Jim Crow order. As a result of these historical overlaps, the agricultural welfare state was shaped in surprising and not-well-understood ways by America's racial orders. In order to trace these two intertwining aspects of racial governance and agricultural welfare state development, I provide a reinterpretation of the development of the agricultural welfare state from its Civil War origins to its New Deal transformation. I show that, from 1865 to 1964, the confluence of racial orders, partisan alignments, and congressional orders created an agricultural welfare state in which African Americans were variously included and excluded in a pattern of “two-tier” citizenship. The broader racial governance aims of the Jim Crow order also had a significant role in shaping the development of the organizational ethos and administrative structures and practices within the United States Department of Agriculture (USDA). The practice of “two-tier” agricultural citizenship, which initially affected only African American and other minority farmers, was gradually extended to reflect the divide between large commercial farmers and the rural poor (including small farmers). The results from this analysis strengthen our understanding of how the American welfare state has been shaped—in particular, the ways in which racial governance and racial orders are deeply embedded in the American state building process.
Rogers' Chocolates Ltd. and the Corporation of the City of Victoria: A Case Comment on Involuntary Designation and the Conservation of Heritage Buildings
Authors: Piggott Gillian S. J.
Published: September 2011

The process adopted by the local government to protect the interior of an old building in Victoria, British Columbia, culminated in a significant compensation award in favor of the building's owner and highlights the shortcomings of a coercive regulatory approach to heritage conservation. This study focuses on the relationship between cooperative resolution of conflicts between the rights of the public to protect heritage buildings and the rights of private property owners to the use of their property without interference, on the one hand, and the long-term utility and conservation of historic buildings and the sustainability of local government heritage programs, on the other. Analysis includes discussion on (a) key issues arising out of an involuntary heritage designation, (b) flexible alternative conservation mechanisms and incentives available to local governments, (c) approaches to conservation of heritage buildings in other jurisdictions, and (d) opportunities for improvement in the local government heritage conservation program.
Heart rate variability in children with acute rheumatic fever
Authors: Karacan Mehmet , Ceviz Naci , Olgun Haşim
Published: September 2011

Objective

Acute rheumatic fever is a systemic inflammatory disease occurring after acute streptococcal tonsillopharyngitis. The PR prolongation in these patients is thought to be due to increased vagal activity. There has been no previous study investigating the autonomic balance in patients with acute rheumatic fever. In this study, we aimed to investigate the balance of the autonomic nervous system in children with acute rheumatic fever by analysis of heart rate variability.

Methods

We evaluated the heart rate variability parameters in 50 patients with acute rheumatic fever and 37 comparable control subjects. Both groups underwent 24-hour electrocardiography monitoring, and time- and frequency-domain heart rate variability parameters were calculated. A total of 39 patients (78%), with (n = 28) or without (n = 11) other major findings, had carditis, and the remaining 11 (22%) did not. The PR interval was found to be prolonged in 10 (20%) of the patients at the beginning.

Results

In the study group, the time- and frequency-domain heart rate variability parameters showed a sympathetic dominance compared with the control group, with a p-value less than 0.05. When compared with the control group, the time- and frequency-domain heart rate variability parameters showed a significant sympathetic dominance in patients with both prolonged PR and normal PR intervals in the acute period, with a p-value less than 0.05. When compared with patients with normal PR interval, mean normalised low frequency and normalised high frequency parameters suggested a relatively lower sympathetic dominance in patients with prolonged PR interval, with a p-value less than 0.05.

Conclusion

Our results indicated that in the acute period of rheumatic fever, sympathetic dominance is apparent; in patients with prolonged PR interval, sympathetic dominance is relatively lower when compared with the patients with normal PR interval.
H-CONTACT UNIT TANGENT SPHERE BUNDLES OF FOUR-DIMENSIONAL RIEMANNIAN MANIFOLDS
Authors: CHUN SUN HYANG , PARK JEONGHYEONG , SEKIGAWA KOUEI
Published: September 2011

We study the geometric properties of a base manifold whose unit tangent sphere bundle, equipped with the standard contact metric structure, is H-contact. We prove that a necessary and sufficient condition for the unit tangent sphere bundle of a four-dimensional Riemannian manifold to be H-contact is that the base manifold is 2-stein.
Examining Collaborative Dialogue Among Couples
Authors: Margrett Jennifer A. , Reese-Melancon Celinda , Rendell Peter G.
Published: September 2011

Prospective memory is a key ability required for independent living and consistent with Einstein and McDaniel (1990) , we hypothesized that social partners can serve as useful external memory aids, particularly in middle and late life when these abilities may wane. We employed the Virtual Week (Rendell & Craik, 2000) task in a novel way to investigate the contribution of social partners to the prospective memory process. We examined the collaborative interactions of 11 middle-aged (M = 52.15 years; n = 5) and older (M = 75.24 years; n = 6) married dyads. The dialogue of collaborating partners reflected important PM processes (e.g., encoding, monitoring, tutoring). Age group differences favored middle-aged adults, and preliminary evidence suggested a link between collaborative dialogue and PM performance. Further investigation can determine how social partners can be used strategically to improve prospective memory outcomes.
Prospective Memory, Personality, and Working Memory
Authors: Smith Rebekah E. , Persyn Deborah , Butler Patrick
Published: September 2011

Prospective memory (PM) involves remembering to perform an action in the future. The current study applies a multinomial model to investigate the contribution of individual differences in personality, as well as individual differences in working memory (WM) span, to performance in an event-based PM task. The model includes a parameter P that measures the prospective component, or remembering that something is to be done. The model also includes a parameter M that measures the ability to discriminate between target and non-target events, part of the retrospective component of PM tasks. The model has been applied to investigate the effects of WM variability in just one prior study, but has not been used in previous investigations of personality and PM. WM span and the personality dimension of conscientiousness showed differences between the higher and lower groups in PM performance. Modeling results showed that individuals higher in conscientiousness had higher estimate of M relative to individuals lower on the conscientiousness dimension. Conscientiousness did not affect the P parameter. In contrast, individuals with higher WM span scores had higher estimates of P relative to individuals with lower span scores, but the two WM groups did not differ in terms of parameter M.
Demonstration of a room temperature 2.48–2.75 THz coherent spectroscopy source
Authors: Pearson John C. , Drouin Brian J. , Maestrini Alain , Mehdi Imran , Ward John , Lin Robert H. , Yu Shanshan , Gill John J. , Thomas Bertrand , Lee Choonsup , Chattopadhyay Goutam , Schlecht Erich , Maiwald Frank W. , Goldsmith Paul F. , Siegel Peter
Published: September 2011

We report the first demonstration of a continuous wave coherent source covering 2.48–2.75 THz, with greater than 10% instantaneous tuning bandwidth and having 1–14 μW of output power at room temperature. This source is based on a 91.8–101.8 GHz synthesizer followed by a power amplifier and three cascaded frequency triplers. It demonstrates for the first time that purely electronic solid-state sources can generate a useful amount of power in a region of the electromagnetic spectrum where lasers (solid state or gas) were previously the only available coherent sources. The bandwidth, agility, and operability of this THz source have enabled wideband, high resolution spectroscopic measurements of water, methanol, and carbon monoxide with a resolution and signal-to-noise ratio unmatched by any other existing system, providing new insight in the physics of these molecules. Furthermore, the power and optical beam quality are high enough to observe the Lamb-dip effect in water. The source frequency has an absolute accuracy better than 1 part in 1012 and the spectrometer achieves sub-Doppler frequency resolution better than 1 part in 108. The harmonic purity is better than 25 dB. This source can serve as a coherent signal for absorption spectroscopy, a local oscillator for a variety of heterodyne systems and can be used as a method for precision control of more powerful but much less frequency agile quantum mechanical terahertz sources.
Efficient quantum dot single photon extraction into an optical fiber using a nanophotonic directional coupler
Authors: Davanço M. , Rakher M. T. , Wegscheider W. , Schuh D. , Badolato A. , Srinivasan K.
Published: September 2011

We demonstrate a spectrally broadband and efficient technique for collecting emission from a single InAs quantum dot directly into a standard single mode optical fiber. In this approach, an optical fiber taper waveguide is placed in contact with a suspended GaAs nanophotonic waveguide with embedded quantum dots, forming a broadband directional coupler with standard optical fiber input and output. Efficient photoluminescence collection over a wavelength range of tens of nanometers is demonstrated, and a maximum collection efficiency of 6% (corresponding single photon rate of 3.0 MHz) into a single mode optical fiber is estimated for a single quantum dot exciton.
Influence of temperature on thymine-to-solvent vibrational energy transfer
Authors: West Brantley A. , Womick Jordan M. , Moran Andrew M.
Published: September 2011

At the instant following the non-radiative deactivation of its ππ* electronic state, the vibrational modes of thymine possess a highly non-equilibrium distribution of excitation quanta (i.e., >4 eV in excess energy). Equilibrium is re-established through rapid (5 ps) vibrational energy transfer to the surrounding solvent. The mechanisms behind such vibrational cooling (VC) processes are examined here using femtosecond transient grating and two-dimensional photon echo spectroscopies conducted at 100 K and 300 K in a mixture of methanol and water. Remarkably, we find that this variation in temperature has essentially no impact on the VC kinetics. Together the experiments and a theoretical model suggest three possible mechanisms consistent with this behavior: (i) vibrational energy transfer from the solute to solvent initiates (directly) in intramolecular modes of the solute with frequencies >300 cm−1; (ii) the relaxation induced increase in the temperature of the environment reduces the sensitivity of VC to the temperature of the equilibrium system; (iii) the time scale of solvent motion approaches 0.1 ps even at 100 K. Mechanism (i) deserves strong consideration because it is consistent with the conclusions drawn in earlier studies of isotope effects on VC in hydrogen bonding solvents. Our model calculations suggest that mechanism (ii) also plays a significant role under the present experimental conditions. Mechanism (iii) is ruled out on the basis of long-lived correlations evident in the photon echo line shapes at 100 K. These insights into photoinduced relaxation processes in thymine are made possible by our recent extension of interferometric transient grating and photon echo spectroscopies to the mid UV spectral region.
Magnetotunneling in resonant tunneling structures with spin − orbit interaction
Authors: Isić Goran , Indjin Dragan , Milanović Vitomir , Radovanović Jelena , Ikonić Zoran , Harrison Paul
Published: September 2011

Magnetotunneling spectroscopy of resonant tunneling structures provides information on the nature of the two-dimensional electron gas in the well. We describe a model based on nonequilibrium Green’s functions that allows for a comprehensive study of the density of states, tunneling currents and current spin polarization. The investigated effects include the electron − phonon interaction, interface roughness scattering, Zeeman effect and the Rashba spin − orbit interaction. A qualitative agreement with experimental data is found regarding the satellite peaks. The spin polarization is predicted to be >10% for magnetic fields above 2 T and having a structure even at the satellite peaks. The Rashba effect is confirmed to be observable as a beating pattern in the density of states but found to be too small to affect the tunneling current.
Self-assembly and electron-beam-induced direct etching of suspended graphene nanostructures
Authors: Goler Sarah , Piazza Vincenzo , Roddaro Stefano , Pellegrini Vittorio , Beltram Fabio , Pingue Pasqualantonio
Published: September 2011

We report on suspended single-layer graphene deposition by a transfer-printing approach based on polydimethylsiloxane stamps. The transfer printing method allows the exfoliation of graphite flakes from a bulk graphite sample and their residue-free deposition on a silicon dioxide substrate. This deposition system creates a “blistered” graphene surface due to strain induced by the transfer process itself. Single-layer-graphene deposition and its blistering on the substrate are demonstrated by a combination of Raman spectroscopy, scanning electron microscopy, and atomic-force microscopy measurements. Finally, we demonstrate that blister-like suspended graphene are self-supporting single-layer structures and can be flattened by employing a spatially resolved direct-lithography technique based on electron-beam induced etching.
Fingering instability down the outside of a vertical cylinder
Authors: Smolka Linda B. , SeGall Marc
Published: September 2011

We present an experimental and numerical study examining the dynamics of a gravity-driven contact line of a thin viscous film traveling down the outside of a vertical cylinder of radius R. Experiments on cylinders with radii ranging between 0.159 and 3.81 cm show that the contact line is unstable to a fingering pattern for two fluids with differing viscosities, surface tensions, and wetting properties. The dynamics of the contact line is studied and results are compared to previous studies of inclined plane experiments in order to understand the influence substrate curvature plays on the fingering pattern. A lubrication model is derived for the film height in the limit that ε=H/R≪1, where H is the upstream film thickness, and in terms of a Bond number ρgR3/(γH), and the linear stability of the contact line is analyzed using traveling wave solutions. Curvature controls the capillary ridge height of the traveling wave and the range of unstable wavelength when ε=O(10-1), whereas the shape and stability of the contact line converge to the behavior one observes on a vertical plane when ε≤O(10-2). The most unstable wave mode, cutoff wave mode for neutral stability, and maximum growth rate scale as Bô0.45 where Bô=ρgR2/γ≥1.3, and the contact line is unstable to fingering when Bô≥0.56. Using the experimental data to extrapolate outside the range of validity of the thin film model, we estimate the contact line is stable when Bô<0.56. Agreement is excellent between the model and the experimental data for the wave number (i.e., number of fingers) and wavelength of the fingering pattern that forms along the contact line.
Side wall effects on the instability of thin gravity-driven films—From long-wave to short-wave instability
Authors: Pollak Thilo , Haas André , Aksel Nuri
Published: September 2011

We study the effects of side walls on the primary instability of a gravity-driven thin liquid film flowing down a flat channel. The influences of different capillary boundary layer effects at the side walls on the instability of the free surface are resolved experimentally, by varying the crosswise side wall distance of the measurement positions between 5 mm and the channel center-line. The height of the capillary elevation and, thus, the resulting pretensioning of the free surface and the magnitude of a possible velocity overshoot have been adjusted by changing the contact angle between the liquid and the side wall. The influence of the contact angle on the stability of the flow, and especially its range, is remarkable. The difference of the neutral stability curves for the two investigated contact angles is up to 25% and remains significant even up to a side wall distance of 17 times the capillary length. Irrespective of the contact angle, the type of the free surface instability undergoes a transition from long-wave in the center of the channel to short-wave, as is well known for boundary layer flows, when the side wall distance is reduced. Furthermore, we have found that the presence of a velocity overshoot tends to destabilize the free surface.
2 W high efficiency PbS mid-infrared surface emitting laser
Authors: Ishida A. , Sugiyama Y. , Isaji Y. , Kodama K. , Takano Y. , Sakata H. , Rahim M. , Khiar A. , Fill M. , Felder F. , Zogg H.
Published: September 2011

High efficiency laser operation with output power exceeding 2 W was obtained for vertical external-cavity PbS based IV-VI compound surface emitting quantum-well structures. The laser showed external quantum efficiency as high as 16%. Generally, mid-infrared III-V or II-VI semiconductor laser operation utilizing interband electron transitions are restricted by Auger recombination and free carrier absorption. Auger recombination is much lower in the IV-VI semiconductors, and the free-carrier absorption is significantly reduced by an optically pumped laser structure including multi-step optical excitation layers.
Non-Fourier heat conductions in nanomaterials
Authors: Wang Moran , Yang Nuo , Guo Zeng-Yuan
Published: September 2011

We study the non-Fourier heat conductions in nanomaterials based on the thermomass theory. For the transient heat conduction in a one-dimensional nanomaterial with a low-temperature step at both ends, the temperature response predicted by the present model is consistent with those by the existing theoretical models for small temperature steps. However, if the step is large, the unphysical temperature distribution under zero predicted by the other models, when two low-temperature cooling waves meet, does not appear in the predictions by the present model. The steady-state non-Fourier heat conduction equation derived by the present model has been applied to predict the effective thermal conductivities of nanomaterials. The temperature and size dependences of effective thermal conductivities of nanofilms, nanotubes, and nanowires from the present predictions agree well with the available data from experiments in the literature and our molecular dynamics simulation results, which again proves the validity of the proposed heat conduction equations. The present analysis suggests that the inertial effect of high-rate heat and the interactions between heat and surface in confined nanostructures dominate the non-Fourier heat conduction in nanomaterials.
Regularized shock solutions in coating flows with small surface tension
Authors: Badali D. , Chugunova M. , Pelinovsky D. E. , Pollack S.
Published: September 2011

We study the dynamics of thin liquid films on the surface of a rotating horizontal cylinder in the presence of gravity in the small surface tension limit. Using dynamical system methods, we show that the continuum of shock solutions increasing across the jump point persists in the small surface tension limit, whereas the continuum of shock solutions decreasing across the jump point terminates in the limit. Using delicate numerical computations, we show that the number of steady states with equal mass increases as the surface tension parameter goes to zero. This corresponds to an increase in the number of loops on the mass-flux bifurcation diagram. If n is the number of loops in the mass-flux diagram with 2n + 1 solution branches, we show that n + 1 solution branches are stable with respect to small perturbations in the time evolution of the liquid film.
Enhanced light diffraction from self-assembled double-layer colloidal crystals
Authors: Matsushita Sachiko , Takagi Toshihide , Kamimura Keita , Kasaya Takeshi , Miyazaki Hideki T.
Published: September 2011

We demonstrate that double-layer colloidal photonic crystals function as wavelength- and polarization-insensitive blazed transmission gratings with efficiencies as high as 63% in the high-energy spectral region. This phenomenon, which is known as specular-resonance-enhanced diffraction, has been reported for a small-scale cluster of microspheres with a limited size parameter. By performing accurate characterization employing large-area colloidal crystal films self-assembled by an inclined dip-coating method with a controlled number of layers, this peculiar and efficient diffraction was demonstrated to be a universal property of double-layer colloidal crystal films.
Comparing different protocols of temperature selection in the parallel tempering method
Authors: Fiore Carlos E.
Published: September 2011

Parallel tempering Monte Carlo simulations have been applied to a variety of systems presenting rugged free-energy landscapes. Despite this, its efficiency depends strongly on the temperature set. With this query in mind, we present a comparative study among different temperature selection schemes in three lattice-gas models. We focus our attention in the constant entropy method (CEM), proposed by Sabo et al. In the CEM, the temperature is chosen by the fixed difference of entropy between adjacent replicas. We consider a method to determine the entropy which avoids numerical integrations of the specific heat and other thermodynamic quantities. Different analyses for first- and second-order phase transitions have been undertaken, revealing that the CEM may be an useful criterion for selecting the temperatures in the parallel tempering.
Isotopic effect on the vibrational lifetime of the carbon-deuterium stretch excitation on graphene
Authors: Sakong Sung , Kratzer Peter
Published: September 2011

The relaxation of vibrational energy in the H and D stretch modes has been studied on the graphene surface using ab initio calculations. The dissipation of the vibrational energy stored in the stretching modes proceeds through vibration-phonon coupling, while the dissipation through electronic excitations makes only minor contributions. Recently, we reported the fast relaxation of the H stretch energy on graphene [S. Sakong and P. Kratzer, J. Chem. Phys. 133, 054505 (2010)]10.1063/1.3474806. Interestingly, we predict the lifetime of the D stretch to be markedly longer compared to the relaxation of the H stretch. This is unexpected since the vibrational amplitudes at carbon atoms in the joint C–D vibrational modes are larger than in the joint C–H modes, due to the mass ratio mD/mC > mH/mC. However, the vibrational relaxation rate for the D stretch is smaller than for the H stretch, because the energy is dissipated to an acoustic phonon of graphene in the case of C–D rather than an optical phonon as is the case in C–H, and hence, the corresponding phonon density of states is lower in the C–D case. To rationalize our findings, we propose a general scheme for estimating vibrational lifetimes of adsorbates based on four factors: the density of states of the phonons that mediates the transitions, the vibration-phonon coupling strength, the anharmonic coupling between local modes, and the number of quanta involved in the transitions. Mainly the first two of these factors are responsible for the differences in the lifetimes of the C–H and C–D stretches. The possible role of the other factors is illustrated in the context of vibrational lifetimes in other recently studied systems.
A 2 MV Van de Graaff accelerator as a tool for planetary and impact physics research
Authors: Mocker Anna , Bugiel Sebastian , Auer Siegfried , Baust Günter , Colette Andrew , Drake Keith , Fiege Katherina , Grün Eberhard , Heckmann Frieder , Helfert Stefan , Hillier Jonathan , Kempf Sascha , Matt Günter , Mellert Tobias , Munsat Tobin , Otto Katharina , Postberg Frank , Röser Hans-Peter , Shu Anthony , Sternovsky Zoltán , Srama Ralf
Published: September 2011

Investigating the dynamical and physical properties of cosmic dust can reveal a great deal of information about both the dust and its many sources. Over recent years, several spacecraft (e.g., Cassini, Stardust, Galileo, and Ulysses) have successfully characterised interstellar, interplanetary, and circumplanetary dust using a variety of techniques, including in situ analyses and sample return. Charge, mass, and velocity measurements of the dust are performed either directly (induced charge signals) or indirectly (mass and velocity from impact ionisation signals or crater morphology) and constrain the dynamical parameters of the dust grains. Dust compositional information may be obtained via either time-of-flight mass spectrometry of the impact plasma or direct sample return. The accurate and reliable interpretation of collected spacecraft data requires a comprehensive programme of terrestrial instrument calibration. This process involves accelerating suitable solar system analogue dust particles to hypervelocity speeds in the laboratory, an activity performed at the Max Planck Institut für Kernphysik in Heidelberg, Germany. Here, a 2 MV Van de Graaff accelerator electrostatically accelerates charged micron and submicron-sized dust particles to speeds up to 80  km s−1. Recent advances in dust production and processing have allowed solar system analogue dust particles (silicates and other minerals) to be coated with a thin conductive shell, enabling them to be charged and accelerated. Refinements and upgrades to the beam line instrumentation and electronics now allow for the reliable selection of particles at velocities of 1–80  km s−1 and with diameters of between 0.05  μm and 5  μm. This ability to select particles for subsequent impact studies based on their charges, masses, or velocities is provided by a particle selection unit (PSU). The PSU contains a field programmable gate array, capable of monitoring in real time the particles’ speeds and charges, and is controlled remotely by a custom, platform independent, software package. The new control instrumentation and electronics, together with the wide range of accelerable particle types, allow the controlled investigation of hypervelocity impact phenomena across a hitherto unobtainable range of impact parameters.
Plasma-assisted catalytic ionization using porous nickel plate
Authors: Oohara W. , Maeda T. , Higuchi T.
Published: September 2011

Hydrogen atomic pair ions, i.e., H+ and H− ions, are produced by plasma-assisted catalytic ionization using a porous nickel plate. Positive ions in a hydrogen plasma generated by dc arc discharge are irradiated to the porous plate, and pair ions are produced from the back of the irradiation plane. It becomes clear that the production quantity of pair ions mainly depends on the irradiation current of positive ions and the irradiation energy affects the production efficiency of H− ions.
An experimental setup for high resolution 10.5 eV laser-based angle-resolved photoelectron spectroscopy using a time-of-flight electron analyzer
Authors: Berntsen M. H. , Götberg O. , Tjernberg O.
Published: September 2011

We present an experimental setup for laser-based angle-resolved time-of-flight photoemission. Using a picosecond pulsed laser, photons of energy 10.5 eV are generated through higher harmonic generation in xenon. The high repetition rate of the light source, variable between 0.2 and 8 MHz, enables high photoelectron count rates and short acquisition times. By using a time-of-flight analyzer with angle-resolving capabilities, electrons emitted from the sample within a circular cone of up to ±15° can be collected. Hence, simultaneous acquisition of photoemission data for a complete area of the Brillouin zone is possible. The current photon energy enables bulk sensitive measurements, high angular resolution, and the resulting covered momentum space is large enough to enclose the entire Brillouin zone in cuprate high-Tc superconductors. Fermi edge measurements on polycrystalline Au shows an energy resolution better than 5 meV. Data from a test measurement of the Au(111) surface state are presented along with measurements of the Fermi surface of the high-Tc superconductor Bi2Sr2CaCu2O8 + δ (Bi2212).
Independently driven four-probe method for local electrical characteristics in organic thin-film transistors under controlled channel potential
Authors: Yoshimoto S. , Tsutsui T. , Mukai K. , Yoshinobu J.
Published: September 2011

We describe an independently driven four-probe method to investigate local channel mobility in organic field-effect transistors (OFETs). In OFET devices, probe-organic contact resistance affects device characteristics even in four-probe measurement because a change in contact resistance at the source probe induces a change in channel potential, resulting in different local carrier density. To overcome this problem, we introduced a feedback circuit between the source probe and a channel voltage probe to keep the channel potential constant. We demonstrate four-probe \documentclass[12pt]{minimal}\begin{document}$I\text{–}V$\end{document}I–V measurement on a pentacene thin film (50 nm thick) under controlled channel potential. The feedback successfully enables us to separate contact resistance and channel resistance even under different contact conditions. We also measured four-probe resistance as a function of gate bias and channel probe position. The present results were in good agreement with two-dimensional model calculation by arranging four probes in a defect-free area; the mobility of the pentacene single grain was evaluated to be 0.25 cm2/(V s).
Demixing in cobalt clusters embedded in a carbon matrix evidenced by magnetic measurements
Authors: Tamion Alexandre , Hillenkamp Matthias , Hillion Arnaud , Tournus Florent , Tuaillon-Combes Juliette , Boisron Olivier , Zafeiratos Spiros , Dupuis Véronique
Published: September 2011

We report on the magnetic properties of cobalt clusters embedded in amorphous carbon using magnetic and structural investigations. From the analysis of the mFC, mZFC, and m(H) curves, we determine the Co magnetic diameter probability density function. An initially magnetically dead interface layer is attributed to a metastable carbide. We found that annealing at 750 K favors the graphitization of the matrix and removes the dead layer without deteriorating the nanoparticle size distribution or changing the magnetic anisotropy constant.
Structural analysis and electrical properties of pure Ge3N4 dielectric layers formed by an atmospheric-pressure nitrogen plasma
Authors: Hayakawa Ryoma , Yoshida Masashi , Ide Kouta , Yamashita Yoshiyuki , Yoshikawa Hideki , Kobayashi Keisuke , Kunugi Shunsuke , Uehara Tsuyoshi , Fujimura Norifumi
Published: September 2011

Pure germanium nitride (Ge3N4) thin films were successfully formed on n-type Ge (111) substrate using an atmospheric-pressure (AP) nitrogen plasma. Their film structures and electrical properties were then examined in detail. Synchrotron radiation photoelectron spectroscopy clearly revealed that the Ge3N4 thin films formed by AP plasma had superior oxidative resistance compared to those made using conventional plasma techniques. Films fabricated at 500 °C showed only minor post-oxidation, even after exposure to air, which is a potentially very useful feature for passivation layers at high-permittivity (high-k) dielectric film–Ge interfaces. The films also showed excellent electrical properties. Capacitance-voltage measurements revealed no hysteresis or kinks, indicating that the trap-state density was low at the Ge3N4–Ge interface. The leakage current density is also lower than in films fabricated using other plasma systems. Direct-tunneling current simulations revealed that the effective tunneling mass increased due to the formation of high-quality Ge3N4 thin films, resulting in superior leakage current. These results suggest that our nitridation technique would show major benefits in Ge field-effect transistors.
A new nonlinear reconstruction method based on total variation regularization of neutron penumbral imaging
Authors: Qian Weixin , Qi Shuangxi , Wang Wanli , Cheng Jinming , Liu Dongbing
Published: September 2011

Neutron penumbral imaging is a significant diagnostic technique in laser-driven inertial confinement fusion experiment. It is very important to develop a new reconstruction method to improve the resolution of neutron penumbral imaging. A new nonlinear reconstruction method based on total variation (TV) regularization is proposed in this paper. A TV-norm is used as regularized term to construct a smoothing functional for penumbral image reconstruction in the new method, in this way, the problem of penumbral image reconstruction is transformed to the problem of a functional minimization. In addition, a fixed point iteration scheme is introduced to solve the problem of functional minimization. The numerical experimental results show that, compared to linear reconstruction method based on Wiener filter, the TV regularized nonlinear reconstruction method is beneficial to improve the quality of reconstructed image with better performance of noise smoothing and edge preserving. Meanwhile, it can also obtain the spatial resolution with 5 μm which is higher than the Wiener method.
Thermal stability of epitaxial Mn5Ge3 and carbon-doped Mn5Ge3 films
Authors: Spiesser Aurélie , Le Thanh Vinh , Bertaina Sylvain , Michez Lisa A.
Published: September 2011

The thermal stability of epitaxial Mn5Ge3 and carbon-doped Mn5Ge3 films was investigated by combining structural and magnetic characterizations. It is shown that ferromagnetic Mn5Ge3 films transform into antiferromagnetic Mn11Ge8 upon post-annealing at 650 °C whereas carbon-doped Mn5Ge3 conserves its ferromagnetism up to 850 °C. The magnetic properties of Mn5Ge3 (Curie temperature, magnetization at saturation, and magnetic moment per Mn atom) are found to undergo a reversible transition upon carbon doping and its extraction during thermal annealing. The stability of carbon-doped Mn5Ge3 films will be discussed in terms of carbon filling of interstitial sites of Mn5Ge3, which prevents Ge diffusion from the substrate.
Effects of annealing on structural and optical properties of InGaN/GaN multiple quantum wells at emission wavelength of 490 nm
Authors: Liu H. F. , Liu W. , Yong A. M. , Zhang X. H. , Chua S. J. , Chi D. Z.
Published: September 2011

We report on structural and optical properties of Si-doped InGaN/GaN multiple quantum wells (MQWs) investigated by employing high-resolution x-ray diffraction (HRXRD), reciprocal space mapping (RSM), continuous-wave photoluminescence (PL) spectroscopy, and time-resolved photoluminescence (TRPL) spectroscopy. The MQWs were grown on c-plane sapphire substrate by metal-organic chemical vapor deposition (MOCVD). HRXRD and RSM revealed that the MQWs are coherently strained on the GaN base layer and the coherence remains intact after annealing at temperatures up to 1100 °C. They also revealed an occurrence of In/Ga atoms interdiffusion across the QW interfaces at elevated temperatures. The shift in PL emissions towards their lower-energy sides with increasing annealing temperatures provides evidence for the enhanced formation of In-rich regions (quantum dots, QDs) within the QWs. An anomalous photon-energy dependence of PL lifetimes is observed at 5 K; however, the dependence reverts to normal when the temperature is increased to 200 K. This optical transition behavior is discussed based on the self-forming of QDs due to the enhanced In-clustering at elevated temperatures and the anneal-induced generation/activation of defects/impurities-related recombination centers.
Modified long-range surface plasmon polariton modes for laser nanoresonators
Authors: Ikeda Kazuhiro , Fainman Yeshaiahu , Alan Shore K. , Kawaguchi Hitoshi
Published: September 2011

We investigate a modification of long-range surface plasmon polariton modes supported by thin metal-coated dielectric cylinders for laser nanoresonators. A drawback of the low loss surface modes is the small mode overlap with the core dielectric cylinder that will be intended for the gain region in typical nanolasers. We show that increasing the refractive index of the outermost dielectric cladding improves the poor mode overlap, but still keeps the mode low loss and well confined in a small radius of the cylinder. The high refractive index of the dielectric cladding offers another possibility of a nanolaser structure whose gain region resides in the cladding.
Shattering dissociation in high-energy molecular collisions between nitrate esters
Authors: Schweigert Igor V. , Dunlap Brett I.
Published: September 2011

We present ab initio molecular dynamics simulations of head-on collisions between ethyl nitrate molecules at collisional energies from 200 to 1200 kJ/mol. Above a threshold energy, an increasing fraction of the collisions led to rapid dissociation on impact—“shattering.” The probability of the shattering dissociation was derived from the quasiclassical trajectories sampling the initial vibrational motion at Tvib = 300 K. Even for the zero impact parameter and a fixed orientation considered, the observed dissociation probability exhibited a wide spread (much larger than kTvib) as a function of the collision energy. This is attributed to variations in the initial vibrational phase. We propose a closed-form expression for the energy-dependent dissociation probability that captures the dependence on the phase and use it to analyze the probability of the shattering dissociation of a larger nitrate ester, pentaerythritol tetranitrate.
Curvature singularity and film-skating during drop impact
Authors: Duchemin Laurent , Josserand Christophe
Published: September 2011

We study the influence of the surrounding gas in the dynamics of drop impact on a smooth surface. We use an axisymmetric model for which both the gas and the liquid are incompressible; lubrication regime applies for the gas film dynamics and the liquid viscosity is neglected. In the absence of surface tension a finite time singularity whose properties are analysed is formed and the liquid touches the solid on a circle. When surface tension is taken into account, a thin jet emerges from the zone of impact, skating above a thin gas layer. The thickness of the air film underneath this jet is always smaller than the mean free path in the gas suggesting that the liquid film eventually wets the surface. We finally suggest an aerodynamical instability mechanism for the splash.
Exciplex current mechanism for ambipolar bilayer organic light emitting diodes
Authors: Liu Feilong , Paul Ruden P. , Campbell Ian H. , Smith Darryl L.
Published: September 2011

The effect of exciplex dynamics on the current in a bilayer organic light emitting diode with ambipolar injection is explored. Exciplex formation facilitates intermolecular electron-hole recombination across the interface. We discuss the characteristics of the exciplex recombination current with respect to different energy level alignments, interface recombination rates, and exciplex relaxation lifetimes, using a model device consisting of a C60/tetracene bilayer.
Phosphorescent organic light emitting diode efficiency enhancement using functionalized silver nanoparticles
Authors: Liu Feng , Nunzi Jean-Michel
Published: September 2011

Silica coated silver nanoparticles (NPs) were incorporated into the emissive layer of a phosphorescent organic light emitting diode (PHOLED). As a result, the luminescence efficiency of the PHOLED was significantly improved under low charge carrier injection level. The silver NPs facilitate the exciton formation event and are responsible for the PHOLED performance improvement. In contrast, the incorporation of uncoated bare silver NPs greatly suppresses luminescence of the PHOLED due to metal NPs induced luminescence and exciton quenching. The silica shell coated on Ag NPs surface plays a dual role in enhancing the PHOLED luminescence efficiency: as an optical spacer, it avoids luminescence quenching of the dye caused by Ag NPs; as an insulator, it prevents exciton recombination at the Ag NPs surface. Therefore, a silica shell with thickness 13 nm or above is essential to enhance the PHOLED performance.
Precise, real-time, single-shot carrier-envelope phase measurement in the multi-cycle regime
Authors: Möller M. , Sayler A. M. , Rathje T. , Chini M. , Chang Zenghu , Paulus G. G.
Published: September 2011

Polarization gating is used to extend a real-time, single-shot, carrier-envelope phase (CEP) measurement, based on high-energy above-threshold ionization in xenon, to the multi-cycle regime. The single-shot CEP precisions achieved are better than 175 and 350 mrad for pulse durations up to 10 fs and 12.5 fs, respectively, while only 130 μJ of pulse energy are required. This opens the door to study and control of CEP-dependent phenomena in ultra-intense laser-matter interaction using optical parametric chirped pulse amplifier based tera- and petawatt class lasers.
Demonstration of enhanced optical polarization for improved deep ultraviolet light extraction in coherently grown semipolar Al0.83Ga0.17N/AlN on ZnO substrates
Authors: Ueno Kohei , Kobayashi Atsushi , Ohta Jitsuo , Oshima Masaharu , Fujioka Hiroshi
Published: September 2011

We have grown a semipolar Al0.83Ga0.17N/AlN heterostructure on ZnO (11¯02) substrates and investigated the optical polarization characteristics of the near-band-edge (NBE) emission of Al0.83Ga0.17N experimentally and theoretically. Reciprocal space mapping measurements revealed that AlN is fully relaxed with respect to ZnO, and Al0.83Ga0.17N grows coherently in both of the in-plane orthogonal directions on AlN. The NBE emissions of coherently grown Al0.83Ga0.17N (11¯02) at 5.4 eV were clearly polarized with E||X2. The polarization ratio of the surface emission was as high as −0.66 at room temperature. This phenomenon is consistent with a large crystal splitting energy, which was clarified by theoretical investigations based on the k · p method.
Second harmonic generation in quantum cascade lasers pumped by femtosecond mid-infrared pulses
Authors: Liu Sheng , Cai Hong , Lalanne Elaine , Liu Peter Q. , Wang Xiaojun , Gmachl Claire , Johnson Anthony M.
Published: September 2011

Second harmonic generation (SHG) pulses at λ ∼ 2.25 µm have been obtained from a 4.5 µm quantum cascade laser (QCL) when it is resonantly pumped by transverse magnetic polarized 120 fs, λ = 4.5 µm pulses through the QCL’s front facet at room temperature. The measured SHG spectrum narrows when the bias across the QCL increases due to the electron population re-distribution and subband realignment. The expected quadratic dependence of the SHG with pump power is observed but saturates at higher pump powers. The linear to nonlinear power conversion efficiency is calculated (∼2 µW/W2) and compared with theoretical calculation. This experiment provides an alternative way of investigating the carrier dynamics in QCLs.