bluuebunny/crossref_metadata_2025 huggingface dataset:
Why Do Colours Look the Way They Do?
Authors: Unwin Nicholas
Published: June 2011

A major part of the mind–body problem is to explain why a given set of physical processes should give rise to perceptual qualities of one sort rather than another. Colour hues are the usual example considered here, and there is a lively debate as to whether the results of colour vision science can provide convincing explanations of why colours actually look the way they do. The internal phenomenological structure of colours is considered here in some detail, and a comparison is drawn with sounds and their synthesis. This paper examines the type of explanation that is needed, and it is concluded that it does not have to be reductive to be effective. What needs to be explained more than anything is why invertedhuescenarios are more intuitive than other sensory inversions: and the issue of physicalism versus dualism is argued to be of only marginal relevance.
The relationship between maghāzī and ḥadīth in early Islamic scholarship
Authors: Görke Andreas
Published: June 2011

The relationship between the traditional biographical material on Muḥammad (maghāzī- or sīra-material) and the narrations of his words and deeds (ḥadīth-material) has long been debated in Islamic studies. While some scholars have argued that the biographical material is fundamentally ḥadīth material arranged chronologically, others have argued the opposite: that ḥadīth material originally consists of narrative reports about the life of Muḥammad which were later deprived of their historical context to produce normative texts. This article argues that both views are untenable and that maghāzī and ḥadīth emerged as separate fields; each influenced the other but they preserved their distinctive features. While traditions that originated and were shaped in one field were sometimes transferred to the other, the transfer of traditions from one field to the other apparently did not as a rule involve any deliberate changes to the text.
The public role ofDhimmīsduring ʿAbbāsid times
Authors: Sirry Mun'im
Published: June 2011

This article examines how and why non-Muslimdhimmīswere employed in a variety of important posts during the ʿAbbāsid period, notably as viziers (wuzarā') and secretaries (kuttāb). One of the aims is to show that Jews and Christians were employed in the state administration to the extent that some of them were able to achieve the second highest office after the caliph: the vizier. It is argued that, despite certain legal restrictions outlined by Muslim jurists,dhimmīemployment in the government had long been an established policy. The first section discusses the juristic debate on whether non-Muslims could be appointed to public office. The second examines examples of non-Muslim viziers and the nature of their political power. The final section offers possible explanations as to why non-Muslims were needed to help the caliphs administer this governmental office. The article concludes with a brief reflection on the significance of this study for the discussion of the nature of state–religion relations in early Islam.
Hearts, desires and behavioural patterns: Debating human nature in ancient China
Authors: Gassmann Robert H.
Published: June 2011

Thinkers in the Zhànguó period of Chinese history debated intensely whether men were by nature “good” or “bad”. This debate has for many years been an important focus of sinological interest, but usually these properties were not attributed to men, but rather to so-called “human nature” (xìng 性) – thus, in effect, mirroring well-known (and problematic) “European” positions and discussions. The aim of this paper is, on the one hand, to redirect attention to the original Zhànguó positions and to explore the reasons for their variance by offering novel and close historical readings of relevant passages, and on the other, to propose a viable historical reconstruction of the common anthropological assumptions underlying these positions by blending it with the traces of a dominant cognitive image present in the texts. This calls for a systematic rethinking of the role of hearts (in the plural), desires, and behavioural patterns in their interplay and as elements of a concept of the psychological build of human beings current in early China.
Introduction to Ideas of Asian Regionalism
Authors: HE BAOGANG , INOGUCHI TAKASHI
Published: June 2011

Most of the current scholarship focuses on the functional aspects of regionalism such as economic and security issues, and the literature tends to be too focused on American or European concerns (Katzenstein, 2005; Higgott, 2007; Ravenhill, 2008). Despite the early examination of varied ideas of Asian regionalism (Milner and Johnson 1997, He, 2004, Acharya 2009), there remains a substantive lack of critical scholarship that focuses on the study of Asian ideas, proposals, and visions of regionalism.
Balancing Act: Competition and Cooperation in US Asia-Pacific Regionalism
Authors: BOUTIN J. D. KENNETH
Published: June 2011

While the United States is an important Asia-Pacific actor, its engagement with the region is complex and often difficult. Not only must US regionalism balance the diverse requirements of an ambitious policy agenda, but also US policy norms and priorities often clash with those of other regional actors. This has important implications for the capacity of the United States to provide regional leadership. Recent years have seen growing policy convergence between the United States and other Asia-Pacific actors, particularly in economic terms, but US regionalism continues to feature competition alongside collaboration.
Consequences of Test Anxiety on Adaptive Versus Fixed Item Testing
Authors: Ortner Tuulia M. , Caspers Juliane
Published: June 2011

We investigated the effects of test anxiety on test performance using computerized adaptive testing (CAT) versus conventional fixed item testing (FIT). We hypothesized that tests containing mainly items with medium probabilities of being solved would have negative effects on test performance for testtakers high in test anxiety. A total of 110 students (aged 16 to 20) from a German secondary modern school filled out a short form of the Test Anxiety Inventory (TAI-G; Wacker, Jaunzeme, & Jaksztat, 2008 ) and then were presented with items from the Adaptive Matrices Test (AMT; Hornke, Etzel, & Rettig, 1999 ) on the computer, either in CAT form or in a fixed item test form with a selection of items arranged in order of increasing item difficulty. Additionally, half of the students were given a short summary of information about the mode of item selection in adaptive testing before working on the CAT. In a moderated regression approach, a significant interaction of test anxiety and test mode was revealed. The effect of test mode on the AMT score was stronger for students with higher scores on test anxiety than for students with lower test anxiety. Furthermore, getting information about CAT led to significantly better results than receiving standard test instructions. Results are discussed with reference to test fairness.
Validation of the Basque Revised NEO Personality Inventory (NEO PI-R)
Authors: Gorostiaga Arantxa , Balluerka Nekane , Alonso-Arbiol Itziar , Haranburu Mikel
Published: June 2011

Although personnel selection processes for Basque civil servants often involve the assessment of personality, there are currently no Basque self-report instruments that provide valid and reliable measures of the Big-Five factors of personality. The aim of this study was to validate the Basque version of the Revised NEO Personality Inventory (NEO PI-R; Costa & McCrae, 1992 ), by examining its psychometric properties. We assessed the dimensionality of the instrument, the convergent and discriminant validity, the temporal stability, and the internal consistency of each dimension. Relationships between NEO PI-R domains and other variables (i.e., gender and age) were also examined. The sample was composed of 1,790 participants (1,031 women and 759 men), whose ages ranged between 16 and 65. Results suggest that the Basque version of NEO PI-R allows assessing personality from the Big-Five framework in a valid and accurate way. The age and gender pattern of personality domains are in consonance with previous findings in other cultures, notably with those observed in Spanish samples.
The Coparenting Inventory for Parents and Adolescents (CI-PA)
Authors: Teubert Daniela , Pinquart Martin
Published: June 2011

This study introduces an inventory that assesses coparenting from the perspective of parents and their adolescent offspring. Within two independent samples of families, we examined reliability and validity of the Coparenting Inventory for Parents and Adolescents (CI-PA). We postulated a model that consists of cooperation, conflict, and triangulation as dimensions of coparenting. Our results showed that this three-factor solution, compared to two- or one-factor solutions, fit the data best. Convergence between mothers and fathers was satisfactory, whereas convergence between parents and their adolescent offspring was weaker, but mostly significant. Moreover, the concurrent validity of the CI-PA was supported by high correlations with a conceptually related questionnaire, and discriminant validity by small to moderate correlations with scales assessing parents’ marital quality as well as their individual parenting. Concerning criterion validity, the subscales of the CI-PA accounted for 20% of variance of adolescent psychosocial adjustment. Finally, we discuss implications and limitations of our results.
Early arrival of Southern Source Water in the deep North Atlantic prior to Heinrich event 2
Authors: Gutjahr Marcus , Lippold Jörg
Published: June 2011

The Atlantic Meridional Overturning Circulation (AMOC) plays an important role in the Northern Hemisphere climate system. Significant interest went into the question of how excessive freshwater input through melting of continental ice can affect its overturning vigor and, hence, heat supply, to higher northern latitudes. Such forcing can be tested by investigating its behavior during extreme iceberg discharge events into the open North Atlantic during the last glacial period, the so‐called Heinrich events (HE). Here we present neodymium (Nd) isotope compositions of past seawater, a sensitive chemical water mass tag, extracted from sediments of Ocean Drilling Program Site 1063 in the western North Atlantic (Bermuda Rise), covering the period surrounding HE 2, the Last Glacial Maximum, and the early deglaciation. These data are compared with a record of the kinematic circulation tracer (231Pa/230Th)xs extracted from the same sediment core. Both tracers indicate significant circulation changes preceding intense ice rafting during HE 2 by almost 2 kyr. Moreover, the Nd isotope record suggests the presence of deeply ventilating North Atlantic Deep Water early during Marine Isotope Stage 2 until it was replaced by Southern Source Water at ∼27 ka. The early switch to high (Pa/Th)xs and radiogenic ɛNd in relation to intensified ice rafting during HE 2 suggests that ice rafting into the open North Atlantic during major HE 2 was preceded by an early change of the AMOC. This opens the possibility that variations in AMOC contributed to or even triggered the ice sheet instability rather than merely responding to it.
Phase space coherent structure of charged particles system
Authors: Lin H. , Shen B. F. , Xu Z. Z.
Published: June 2011

A class of 3-D numerical solutions of Vlasov-Maxwell equation set is obtained from standard power series solution. Such a class of 3-D numerical solutions corresponds to some phase space coherent structures in electron distribution function, which are more complicated than the well-known hole structure. Based on these solutions, various profiles of related physical quantities are also calculated.
Using hole screening effect on hole–phonon interaction to estimate hole density in Mg-doped InN
Authors: Su Yi-En , Wen Yu-Chieh , Hong Yu-Liang , Lee Hong-Mao , Gwo Shangjr , Lin Yuan-Ting , Tu Li-Wei , Liu Hsiang-Lin , Sun Chi-Kuang
Published: June 2011

The screening effect of heavy-hole LO–phonon interaction is observed and studied through the pump-probe transmission measurement in Mg-doped InN. Combining the measured transient hole dynamics with the absorption spectra, the optical based observation is able to prevent the influence of the surface n-type layer and the depression layer in Mg-doped InN. With the observed heavy-hole heating time at different photoexcited carrier densities and the measured absorption edge, we show that it is now possible to estimate the background hole density and band gap energy in Mg-doped InN.
Dynamical reweighting: Improved estimates of dynamical properties from simulations at multiple temperatures
Authors: Chodera John D. , Swope William C. , Noé Frank , Prinz Jan-Hendrik , Shirts Michael R. , Pande Vijay S.
Published: June 2011

Dynamical averages based on functionals of dynamical trajectories, such as time-correlation functions, play an important role in determining kinetic or transport properties of matter. At temperatures of interest, the expectations of these quantities are often dominated by contributions from rare events, making the precise calculation of these quantities by molecular dynamics simulation difficult. Here, we present a reweighting method for combining simulations from multiple temperatures (or from simulated or parallel tempering simulations) to compute an optimal estimate of the dynamical properties at the temperature of interest without the need to invoke an approximate kinetic model (such as the Arrhenius law). Continuous and differentiable estimates of these expectations at any temperature in the sampled range can also be computed, along with an assessment of the associated statistical uncertainty. For rare events, aggregating data from multiple temperatures can produce an estimate with the desired precision at greatly reduced computational cost compared with simulations conducted at a single temperature. Here, we describe use of the method for the canonical (NVT) ensemble using four common models of dynamics (canonical distribution of Hamiltonian trajectories, Andersen thermostatting, Langevin, and overdamped Langevin or Brownian dynamics), but it can be applied to any thermodynamic ensemble provided the ratio of path probabilities at different temperatures can be computed. To illustrate the method, we compute a time-correlation function for solvated terminally-blocked alanine peptide across a range of temperatures using trajectories harvested using a modified parallel tempering protocol.
Resolving statistical uncertainty in correlation dimension estimation
Authors: Borovkova Svetlana , Rosa Rodolfo , Sardonini Laura
Published: June 2011

In this paper we propose a novel method for obtaining standard errors and confidence intervals for the correlation dimension estimated on an observed chaotic time series. This method is based on the U-Statistics theory and an ingenious combination of the moving block and parametric bootstrap procedures. We test the method on the basis of computer simulations for both clean and noisy series. We show that the distribution of the correlation dimension estimate obtained by our method agrees very well with the “true” distribution obtained by the Monte Carlo simulation. One of the main advantage of our method is the ability to estimate the distribution (and hence, the standard error) of the correlation dimension estimate using only one observed time series.
Intermediate frequency band digitized high dynamic range radiometer system for plasma diagnostics and real-time Tokamak control
Authors: Bongers W. A. , van Beveren V. , Thoen D. J. , Nuij P. J. W. M. , de Baar M. R. , Donné A. J. H. , Westerhof E. , Goede A. P. H. , Krijger B. , van den Berg M. A. , Kantor M. , Graswinckel M. F. , Hennen B. A. , Schüller F. C.
Published: June 2011

An intermediate frequency (IF) band digitizing radiometer system in the 100–200 GHz frequency range has been developed for Tokamak diagnostics and control, and other fields of research which require a high flexibility in frequency resolution combined with a large bandwidth and the retrieval of the full wave information of the mm-wave signals under investigation. The system is based on directly digitizing the IF band after down conversion. The enabling technology consists of a fast multi-giga sample analog to digital converter that has recently become available. Field programmable gate arrays (FPGA) are implemented to accomplish versatile real-time data analysis. A prototype system has been developed and tested and its performance has been compared with conventional electron cyclotron emission (ECE) spectrometer systems. On the TEXTOR Tokamak a proof of principle shows that ECE, together with high power injected and scattered radiation, becomes amenable to measurement by this device. In particular, its capability to measure the phase of coherent signals in the spectrum offers important advantages in diagnostics and control. One case developed in detail employs the FPGA in real-time fast Fourier transform (FFT) and additional signal processing. The major benefit of such a FFT-based system is the real-time trade-off that can be made between frequency and time resolution. For ECE diagnostics this corresponds to a flexible spatial resolution in the plasma, with potential application in smart sensing of plasma instabilities such as the neoclassical tearing mode (NTM) and sawtooth instabilities. The flexible resolution would allow for the measurement of the full mode content of plasma instabilities contained within the system bandwidth.
Direct band Ge and Ge/InGaAs quantum wells in GaAs
Authors: Aleshkin V. Ya. , Dubinov A. A.
Published: June 2011

The possibility of the creation of direct band Ge and Ge/InGaAs quantum wells in GaAs is shown for small Ge quantum well thickness. Such quantum wells can emit efficiently the radiation in the 1.3–1.5 μm wavelength range and can be used in laser diodes.
Microwave-excited microplasma thruster with helium and hydrogen propellants
Authors: Takahashi Takeshi , Takao Yoshinori , Ichida Yugo , Eriguchi Koji , Ono Kouichi
Published: June 2011

Microplasma thruster of electrothermal type has been investigated with feed or propellant gases of He and H2. The thruster consisted of an azimuthally symmetric microwave-excited microplasma source 1.5 mm in diameter and 10 mm long with a rod antenna on axis, and a converging-diverging micronozzle 1 mm long with a throat 0.2 mm in diameter. Surface wave-excited plasmas were established by 4.0-GHz microwaves at powers of ≤ 6 W, with the source pressure in the range 0.5–12 kPa at flow rates of 2–70 sccm. The microplasma generation, micronozzle flow, and thrust performance with He were numerically analyzed by using a two-dimensional fluid model, coupled with an electromagnetic model for microwaves interacting with plasmas in the source region. In experiments, the plasma electron density and gas temperature in the microplasma source were measured at around the top of the microwave antenna, or just upstream of the micronozzle inlet, by optical emission spectroscopy with a small amount of additive gases of H2 and N2. In the case of He propellant, the Stark broadening of H Balmer-β line and the vibronic spectrum of N2 2nd positive (0, 2) band indicated that the electron density was in the range (2-5)×1019m-3 and the gas or rotational temperature was in the range 600–700 K. The thrust performance was also measured by using a target-type microthrust stand, giving a thrust in the range 0.04–0.51 mN, a specific impulse in the range 150–270 s, and a thrust efficiency in the range 2%–12%. These experimental results were consistent with those of numerical analysis, depending on microwave power and gas flow rate. Similar plasma characteristics and thrust performance were obtained with H2 propellant, where the specific impulse of ≤ 450 s was more than 1.5 times higher than that with He, owing to a difference in mass between He and H2. A comparison with previous studies with Ar propellant [T. Takahashi et al., Phys. Plasmas 16, 083505 (2009)] indicated that in the presence as well as absence of plasma discharge, the specific impulse was enhanced by more than 3–5 times with light-mass propellants He and H2 as has been known for large-scale propulsion systems. Thus, it follows that in the microplasma thruster of electrothermal type, the high diffusivity and thermal conductivity of He and H2 in the microplasma source of high surface-to-volume ratios do not lead to a deterioration of the thrust performance, primarily owing to a more significant thermal energy gain due to elastic collisions between electrons and heavy particles in He and H2.
A study on the application of two different acoustic analogies to experimental PIV data
Authors: Koschatzky V. , Westerweel J. , Boersma B. J.
Published: June 2011

The aim of the present study is to compare two different acoustic analogies applied to time-resolved particle image velocimetry (PIV) data for the prediction of the acoustic far-field generated by the flow over a rectangular cavity. We consider the model problem of sound radiating from an open, two-dimensional, shallow cavity with an aspect ratio of 2 at a Reynolds number of 3.0 × 104 (based on the cavity length). The study is carried out by simultaneous high-speed two-dimensional PIV and sound measurements. The instantaneous flow field is obtained from the PIV measurements. The emitted sound is then calculated using Curle’s analogy and Vortex Sound Theory. To our knowledge, Vortex Sound Theory is used here for the first time in combination with time-resolved PIV data. The acoustic analogies are derived through rather different pathways, and the mathematical schemes used to solve the equations are sensitive in a different way to factors such as data resolution, noise level, and complexity of the geometry. Both methods indicate that the trailing edge of the cavity is the main sound source. The predictions of the acoustic field obtained by applying the two methods are analyzed and compared with the measured sound. For the presented case, the results show that both analogies estimate the overall sound pressure level quite well and that they give very similar results, both in total intensity and in the spectral distribution of the emitted sound.
Accuracy of existing atomic potentials for the CdTe semiconductor compound
Authors: Ward D. K. , Zhou X. W. , Wong B. M. , Doty F. P. , Zimmerman J. A.
Published: June 2011

CdTe and CdTe-based Cd1–xZnxTe (CZT) alloys are important semiconductor compounds that are used in a variety of technologies including solar cells, radiation detectors, and medical imaging devices. Performance of such systems, however, is limited due to the propensity of nano- and micro-scale defects that form during crystal growth and manufacturing processes. Molecular dynamics simulations offer an effective approach to study the formation and interaction of atomic scale defects in these crystals, and provide insight on how to minimize their concentrations. The success of such a modeling effort relies on the accuracy and transferability of the underlying interatomic potential used in simulations. Such a potential must not only predict a correct trend of structures and energies of a variety of elemental and compound lattices, defects, and surfaces but also capture correct melting behavior and should be capable of simulating crystalline growth during vapor deposition as these processes sample a variety of local configurations. In this paper, we perform a detailed evaluation of the performance of two literature potentials for CdTe, one having the Stillinger-Weber form and the other possessing the Tersoff form. We examine simulations of structures and the corresponding energies of a variety of elemental and compound lattices, defects, and surfaces compared to those obtained from ab initio calculations and experiments. We also perform melting temperature calculations and vapor deposition simulations. Our calculations show that the Stillinger-Weber parameterization produces the correct lowest energy structure. This potential, however, is not sufficiently transferrable for defect studies. Origins of the problems of these potentials are discussed and insights leading to the development of a more transferrable potential suitable for molecular dynamics simulations of defects in CdTe crystals are provided.
Origin of resistivity change in NiO thin films studied by hard x-ray photoelectron spectroscopy
Authors: Calka P. , Martinez E. , Lafond D. , Minoret S. , Tirano S. , Detlefs B. , Roy J. , Zegenhagen J. , Guedj C.
Published: June 2011

We investigated origins of the resistivity change during the forming of NiO based resistive random access memories in a nondestructive way using hard x-ray photoelectron spectroscopy. Energy shifts and bandgap states observed after switching suggest that oxygen vacancies are created in the low resistive state. As a result conduction may occur via defects such as electrons traps and metallic nickel impurities. Migration of oxygen atoms seems to be the driving mechanism. This provides concrete evidence of the major role played by oxygen defects in decreasing resistivity. This is a key point since oxygen vacancies are particularly unstable and thus difficult to identify by physico-chemical analyses.
Increasing the efficiency of charge extraction limited poly-(3-hexylthiophene):[6,6] phenyl C61 butyric acid methyl ester solar cells using single walled carbon nanotubes with metallic characteristics
Authors: Mallajosyula Arun Tej , Sundar Kumar Iyer S. , Mazhari Baquer
Published: June 2011

The charge transport properties of bulk heterojunction solar cells formed by blending poly-(3-hexylthiophene) (P3HT) and [6,6] phenyl C61 butyric acid methyl ester (PCBM) were improved by doping with single walled carbon nanotubes (SWNTs). The SWNTs used were not functionalized, and contained both metallic and semiconducting tubes. Their work function was found to be 4.89 eV. Unlike P3HT:PCBM interface, the P3HT:SWNT interface has been inefficient for charge generation. Using SWNTs at concentrations below 1 wt. %, the solar cell efficiency increased from 2.86% to 3.52% for 80 nm devices and from 2% to 3% in 125 nm devices at low light intensities. In both cases, the increment is because of higher fill factor with no change in short circuit current density and open circuit voltage. At higher light intensities, a 43% increase in fill factor and a 37% increase in short circuit current density were obtained, which doubled the efficiency. These improvements were primarily because of reduced recombination through improved charge extraction by SWNTs.
Fluid velocity fluctuations in a collision of a sphere with a wall
Authors: Pacheco J. Rafael , Ruiz-Angulo Angel , Zenit Roberto , Verzicco Roberto
Published: June 2011

We report on the results of a combined experimental and numerical study on the fluid motion generated by the controlled approach and arrest of a solid sphere moving towards a solid wall at moderate Reynolds number. The experiments are performed in a small tank filled with water for a range of Reynolds numbers for which the flow remains axisymmetric. The fluid agitation of the fluid related to the kinetic energy is obtained as function of time in the experiment in a volume located around the impact point. The same quantities are obtained from the numerical simulations for the same volume of integration as in the experiments and also for the entire volume of the container. As shown in previous studies, this flow is characterized by a vortex ring, initially in the wake of the sphere, that spreads radially along the wall, generating secondary vorticity of opposite sign at the sphere surface and wall. It is also observed that before the impact, the kinetic energy increases sharply for a small period of time and then decreases gradually as the fluid motion dies out. The measure of the relative agitation of the collision is found to increase weakly with the Reynolds number Re. The close agreement between the numerics and experiments is indicative of the robustness of the results. These results may be useful in light of a potential modelling of particle-laden flows. Movies illustrating the spatio-temporal dynamics are provided with the online version of this paper.
Laser dispersion and ignition of metal fuel particles
Authors: Abdel-Hafez Ahmed A. , Brodt Matthew W. , Carney Joel R. , Lightstone James M.
Published: June 2011

The development of a laser-shock technique for dispersing Al metal fuel particles at velocities approaching those expected in a detonating explosive is discussed. The technique is described in detail by quantifying how air drag affects the temporal variation of the velocity of the dispersed particle plume. The effect of particle size is incorporated by examining various poly-dispersed commercial Al powders at different dispersion velocities (390–630 m/s). The technique is finally tested within a preliminary study of particle ignition delay and burn time, where the effect of velocity is highlighted for different particle sizes. It was found that plume velocity exhibits a modified exponential temporal profile, where smaller particles are more susceptible to air drag than larger ones. Moreover, larger particles exhibit longer ignition delays and burn times than smaller ones. The velocity of a particle was found to significantly affect its ignition delay, burn time, and combustion temperature, especially for particles in the diffusion-controlled regime. Shorter ignition delays and burn times and lower temperatures were observed at higher particle velocities. The utility of this technique as a combustion screening test for future, novel fuels is discussed.
High-sensitivity strain mapping around epitaxial oxide nanostructures using scanning x-ray nanodiffraction
Authors: Sun Tao , Pan Zixiao , Xie Sujing , Cai Zhonghou , Wang Jin , Dravid Vinayak P.
Published: June 2011

The generation and presence of strain around nanostructures of oxides is a key to their growth, properties, and functions, but it has been a challenge to experimentally measure its sign, magnitude, and spatial distribution. Combining diffuse scattering with scanning x-ray nanodiffraction, we have mapped the strain distribution in an oxide-on-oxide nanopatterned structure with a high sensitivity (10−4) and a submicrometer spatial resolution. An edge-induced strain distribution is observed from a sample of CoFe2O4 nanolines epitaxially grown on MgO substrate, which agrees quantitatively with the numerical simulations.
Gain induced optical transparency in metamaterials
Authors: Strangi G. , De Luca A. , Ravaine S. , Ferrie M. , Bartolino R.
Published: June 2011

We demonstrate that fluorophores coupled to plasmonic nanoparticles promote resonant excitation energy transfer processes leading to low-loss building block metamaterials. Experimental observations of Rayleigh scattering enhancement, accompanied by an increase in transmission as function of the gain, clearly reveal optical loss compensation effects. Fluorescence quenching is also observed in gain assisted nanoparticles owing to the increase in nonradiative decay rate triggered by plasmonic resonances. The gain induced transparency at optical frequencies is an unambiguous consequence of loss reduction in metamaterial subunits, representing a promising step to enable a wide range of electromagnetic properties of optical metamaterials.
Synthesis of higher diamondoids by pulsed laser ablation plasmas in supercritical CO2
Authors: Nakahara Sho , Stauss Sven , Kato Toru , Sasaki Takehiko , Terashima Kazuo
Published: June 2011

Pulsed laser ablation (wavelength 532 nm; fluence 18 J/cm2; pulse width 7 ns; repetition rate 10 Hz) of highly oriented pyrolytic graphite was conducted in adamantane-dissolved supercritical CO2 with and without cyclohexane as a cosolvent. Micro-Raman spectroscopy of the products revealed the presence of hydrocarbons possessing sp3-hybridized carbons similar to diamond structures. The synthesis of diamantane and other possible diamondoids consisting of up to 12 cages was confirmed by gas chromatography–mass spectrometry. Furthermore, gas chromatography–mass spectrometry measurements of samples before and after pyrolysis treatment indicate the synthesis of the most compact decamantane, namely, superadamantane. It is thought that oxidant species originating from CO2 during pulsed laser ablation might lead to the selective dissociation of C-H bonds, enabling the synthesis of low H/C ratio molecules. Therefore, laser ablation in supercritical CO2 is proposed as a practical method for synthesizing diamondoids.
A KDP equation of state for laser-induced damage applications
Authors: Hébert D. , Hallo L. , Voisin L. , Desanlis T. , Galtié A. , Bicrel B. , Maunier C. , Mercier P. , Duchateau G.
Published: June 2011

High power lasers such as NIF in the USA or LMJ in France are being developed for inertial confinement fusion applications. However, the performance of the optics is limited by laser-induced damage (LID), which occurs, for instance, in the potassium dihydrogen phosphate (KH2PO4 or KDP) crystals utilized for frequency conversion. An accurate equation of state (EOS) is required to explain the LID process and to predict damage size. For the design of such EOS, a pulsed electron beam was used to generate a quasi-plane stress wave of 0.7 GPa in KDP. The sample response was deduced from photonic Doppler velocimetry. Equations of state and deviatoric stress components are designed and compared to experimental data. They are used in laser-induced bulk damage simulations, showing that strength may play a significant role.
Break-up of suspension drops settling under gravity in a viscous fluid close to a vertical wall
Authors: Myłyk Anna , Meile Walter , Brenn Günter , Ekiel-Jeżewska Maria L.
Published: June 2011

The evolution of suspension drops sedimenting under gravity in a viscous fluid close to a vertical wall was studied experimentally and numerically with the use of the point-force model, in the Stokes flow regime. The fluid inside and outside the drop was identical. The initial distribution of the suspended solid heavy particles was uniform inside a spherical volume. In the experiments and in the simulations, the suspension drops evolved qualitatively in the same way as in an unbounded fluid. However, it was observed, both experimentally and numerically, that, on the average, the destabilization time T and the distance L traveled by the drop until break-up were smaller for a closer distance h of the drop center from the wall, with approximately linear dependence of T and L on D/h, for h larger or comparable to the drop diameter D. Destabilization times and lengths of individual drops with different random configurations of the particles were shown to differ significantly from each other, owing to the chaotic nature of the particle dynamics.
Rotational microfluidic motor for on-chip microcentrifugation
Authors: Shilton Richie J. , Glass Nick R. , Chan Peggy , Yeo Leslie Y. , Friend James R.
Published: June 2011

We report on the design of a surface acoustic wave (SAW) driven fluid-coupled micromotor which runs at high rotational velocities. A pair of opposing SAWs generated on a lithium niobate substrate are each obliquely passed into either side of a fluid drop to drive rotation of the fluid, and the thin circular disk set on the drop. Using water for the drop, a 5 mm diameter disk was driven with rotation speeds and start-up torques up to 2250 rpm and 60 nN m, respectively. Most importantly for lab-on-a-chip applications, radial accelerations of 172 m/s2 was obtained, presenting possibilities for microcentrifugation, flow sequencing, assays, and cell culturing in truly microscale lab-on-a-chip devices.
The shape of an elastic filament in a two-dimensional corner flow
Authors: Autrusson Nicolas , Guglielmini Laura , Lecuyer Sigolene , Rusconi Roberto , Stone Howard A.
Published: June 2011

The deformation of a flexible filament held fixed at one end in a nonuniform viscous flow with curved streamlines is considered, with a focus on the filament dynamics and steady-state shape. Our motivation arises from recent microfluidic experiments on biofilm formation in a channel with bends, where thread-like structures, or streamers, were observed, attached to the side walls downstream of each corner and connecting consecutive corners while floating in the middle plane of the channel [Rusconi et al., J. R. Soc. Interface 7, 1293 (2010)]. We discuss the time evolution and final shape of the filament in different corner geometries as a function of a non-dimensional elasticity parameter that compares viscous and elastic effects. Since the filament develops tension, when the flow has curved streamlines the filament does not align with the flow, as occurs in a rectilinear flow, but rather it crosses the streamlines.
Graphene network on indium tin oxide nanodot nodes for transparent and current spreading electrode in InGaN/GaN light emitting diode
Authors: Seo Tae Hoon , Lee Kang Jea , Oh Tae Su , Lee Yong Seok , Jeong Hyun , Park Ah Hyun , Kim Hun , Choi Young Ran , Suh Eun-Kyung , Cuong Tran Viet , Pham Viet Hung , Chung Jin Suk , Kim Eui Jung
Published: June 2011

We report a device that combines indium tin oxide (ITO) nanodot nodes with two-dimensional chemically converted graphene (CCG) films to yield a GaN-based light emitting diode (LED) with interesting characteristics for transparent and current spreading electrodes for the potential use in the ultraviolet region. The current-voltage characteristics and electroluminescence output power performance showed that CCG network on ITO nanodot nodes operated as a transparent and current spreading electrode in LED devices.
High-k (k=30) amorphous hafnium oxide films from high rate room temperature deposition
Authors: Li Flora M. , Bayer Bernhard C. , Hofmann Stephan , Dutson James D. , Wakeham Steve J. , Thwaites Mike J. , Milne William I. , Flewitt Andrew J.
Published: June 2011

Amorphous hafnium oxide (HfOx) is deposited by sputtering while achieving a very high k∼30. Structural characterization suggests that the high k is a consequence of a previously unreported cubiclike short range order in the amorphous HfOx (cubic k∼30). The films also possess a high electrical resistivity of 1014 Ω cm, a breakdown strength of 3 MV cm−1, and an optical gap of 6.0 eV. Deposition at room temperature and a high deposition rate (∼25 nm min−1) makes these high-k amorphous HfOx films highly advantageous for plastic electronics and high throughput manufacturing.
Temperature driven in-situ phase transformation of PbWO4 nanobelts
Authors: Wang Xue , Ding Yong , Wang Zhong Lin , Hu Chenguo
Published: June 2011

Monoclinic raspite PbWO4 nanobelts were synthesized by a facile composite-salt-mediated method. By in situ heating to above 538 °C inside the chamber of a transmission electron microscope, the raspite nanobelts transformed irreversibly to tetragonal scheelite phase. By analyzing the experimental data, three possible topotactic transformation relationships between raspite and scheelite phases have been proposed. With further increasing the temperature up to 618 °C, part of the PbWO4 nanobelts reduced to tetragonal WO3 nanorods owing to the evaporation of Pb.
Influence of an Au capping layer on the magnetic properties of CoPt nanowires
Authors: Byrne Fiona N. , Monzon Lorena M. A. , Stamenov P. , Venkatesan M. , Coey J. M. D.
Published: June 2011

Equiatomic CoPt nanowires with a gold cap layer have been fabricated by electrochemical template synthesis. Au improves the structural and magnetic properties of the L10 ordered CoPt, leading to coercivities of up to 1.43 T. The anisotropy constant K1 was estimated as 3.9(9) MJ m−3 from the approach to saturation, and four effective anisotropy constants were determined from analysis of torque curves in a 14 T field. Multisegmented magnetic nanowires are produced using gold interlayers.
Three dimensional cross-correlation dynamic light scattering by non-ergodic turbid media
Authors: Haro-Pérez C. , Ojeda-Mendoza G. J. , Rojas-Ochoa L. F.
Published: June 2011

We investigate dynamic light scattering by non-ergodic turbid media with an adapted version of the method proposed by Pusey and van Megen [Physica A 157, 705 (1989)]10.1016/0378-4371(89)90063-0. Our formulation follows the derivation of the original method by extending it to the three dimensional cross-correlation scheme (3DDLS). The main finding is an expression to obtain the dynamic structure factor from light scattering that takes into account the system turbidity and the peculiarities of the 3D geometry. From 3DDLS measurements in well-controlled solid-like systems of different turbidity, we confirm that our results can be interpreted reasonably well by the theoretical approach described here. Good agreement is found with earlier reported results on similar systems.
High shunt resistance in polymer solar cells comprising a MoO3 hole extraction layer processed from nanoparticle suspension
Authors: Stubhan Tobias , Ameri Tayebeh , Salinas Michael , Krantz Johannes , Machui Florian , Halik Marcus , Brabec Christoph J.
Published: June 2011

In this report, we present solution processed molybdenum trioxide (MoO3) layers incorporated as hole extraction layer (HEL) in polymer solar cells (PSCs) and demonstrate the replacement of the commonly employed poly(3,4-ethylene dioxythiophene):(polystyrene sulfonic acid) (PEDOT:PSS). MoO3 is known to have excellent electronic properties and to yield more stable devices compared to PEDOT:PSS. We demonstrate fully functional solar cells with up to 65 nm thick MoO3 HEL deposited from a nanoparticle suspension at low temperatures. The PSCs with an active layer comprising a blend of poly(3-hexylthiophene) and [6,6]-phenyl-C61 butyric acid methyl ester and a MoO3 HEL show comparable performance to reference devices with a PEDOT:PSS HEL. The best cells with MoO3 reach a fill factor of 66.7% and power conversion efficiency of 2.92%. Moreover, MoO3 containing solar cells exhibit an excellent shunt behavior with a parallel resistance of above 100 kΩ cm2.
Insensitive dependence of delay-induced oscillation death on complex networks
Authors: Zou Wei , Zheng Xing , Zhan Meng
Published: June 2011

Oscillation death (also called amplitude death), a phenomenon of coupling induced stabilization of an unstable equilibrium, is studied for an arbitrary symmetric complex network with delay-coupled oscillators, and the critical conditions for its linear stability are explicitly obtained. All cases including one oscillator, a pair of oscillators, regular oscillator networks, and complex oscillator networks with delay feedback coupling, can be treated in a unified form. For an arbitrary symmetric network, we find that the corresponding smallest eigenvalue of the Laplacian λN (0 >λN ≥ –1) completely determines the death island, and as λN is located within the insensitive parameter region for nearly all complex networks, the death island keeps nearly the largest and does not sensitively depend on the complex network structures. This insensitivity effect has been tested for many typical complex networks including Watts-Strogatz (WS) and Newman-Watts (NW) small world networks, general scale-free (SF) networks, Erdos-Renyi (ER) random networks, geographical networks, and networks with community structures and is expected to be helpful for our understanding of dynamics on complex networks.
Structural origins of relaxor behavior in a 0.96(Bi1/2Na1/2)TiO3–0.04BaTiO3 single crystal under electric field
Authors: Daniels John E. , Jo Wook , Rödel Jürgen , Rytz Daniel , Donner Wolfgang
Published: June 2011

Diffuse x-ray scattering intensities from a single crystal of 0.96(Bi1/2Na1/2TiO3)–0.04(BaTiO3) have been collected at room temperature with and without application of an electric field along the [100] direction. Distinct features in the diffuse scattering intensities indicate correlations on a nanometer length scale. It is shown that locally correlated planar-like structures and octahedral tilt-domains within the room temperature rhombohedral R3c phase are both electrically active and are irreversibly affected by application of an electric field of 4.3 kV/mm. The field dependence of these nanoscale structures is correlated with the relaxor behavior of the material by macroscopic permittivity measurements.
360° domain wall mediated reversal in rhombic Co/Cu/NiFe magnetic rings
Authors: Mascaro Mark D. , Körner Helmut S. , Nam Chunghee , Ng Bryan G. , Ross C. A.
Published: June 2011

The reversal process of thin film micron-scale Co/Cu/NiFe rhombic rings in an in-plane magnetic field is investigated by micromagnetic simulation and magnetoresistance measurements. Simulations show that the impingement of reverse domains leads to the formation of multiple 360° domain walls in the ring during low-field cycling. Two types of reversal process can be identified experimentally which are attributed to the presence or absence of residual 360° domain walls in the ring. The reversal path depends on the field history, which affects the population of walls in the ring.
Index k saddles and dividing surfaces in phase space with applications to isomerization dynamics
Authors: Collins Peter , Ezra Gregory S. , Wiggins Stephen
Published: June 2011

In this paper, we continue our studies of the phase space geometry and dynamics associated with index k saddles (k > 1) of the potential energy surface. Using Poincaré-Birkhoff normal form (NF) theory, we give an explicit formula for a “dividing surface” in phase space, i.e., a codimension one surface (within the energy shell) through which all trajectories that “cross” the region of the index k saddle must pass. With a generic non-resonance assumption, the normal form provides k (approximate) integrals that describe the saddle dynamics in a neighborhood of the index k saddle. These integrals provide a symbolic description of all trajectories that pass through a neighborhood of the saddle. We give a parametrization of the dividing surface which is used as the basis for a numerical method to sample the dividing surface. Our techniques are applied to isomerization dynamics on a potential energy surface having four minima; two symmetry related pairs of minima are connected by low energy index 1 saddles, with the pairs themselves connected via higher energy index 1 saddles and an index 2 saddle at the origin. We compute and sample the dividing surface and show that our approach enables us to distinguish between concerted crossing (“hilltop crossing”) isomerizing trajectories and those trajectories that are not concerted crossing (potentially sequentially isomerizing trajectories). We then consider the effect of additional “bath modes” on the dynamics, by a study of a four degree-of-freedom system. For this system we show that the normal form and dividing surface can be realized and sampled and that, using the approximate integrals of motion and our symbolic description of trajectories, we are able to choose initial conditions corresponding to concerted crossing isomerizing trajectories and (potentially) sequentially isomerizing trajectories.
Capillary flow in sacrificially etched nanochannels
Authors: Hamblin Mark N. , Hawkins Aaron R. , Murray Dallin , Maynes Daniel , Lee Milton L. , Woolley Adam T. , Tolley H. Dennis
Published: June 2011

Planar nanochannels are fabricated using sacrificial etching technology with sacrificial cores consisting of aluminum, chromium, and germanium, with heights ranging from 18 to 98 nm. Transient filling via capillary action is compared against the Washburn equation [E. W. Washburn, Phys. Rev. 17, 273 (1921)], showing experimental filling speeds significantly lower than classical continuum theory predicts. Departure from theory is expressed in terms of a varying dynamic contact angle, reaching values as high as 83° in channels with heights of 18 nm. The dynamic contact angle varies significantly from the macroscopic contact angle and increases with decreasing channel dimensions.