bluuebunny/crossref_metadata_2025 huggingface dataset:
Using Aided AAC Models, Recasts, and Contrastive Targets to Teach Grammatical Morphemes to Children Who Use AAC
Authors: Binger Cathy , Maguire-Marshall Molly , Kent-Walsh Jennifer
Published: August 2010

Purpose

The purpose of the investigation was to evaluate the effects of using aided augmentative and alternative communication (AAC) modeling and recasting on the expression of grammatical morphemes with children who used AAC.

Method

A single-subject, multiple-probe, across-targets design was used for the study. Three participants were each taught to use 3 grammatical structures. Intervention consisted of aided AAC models and recasts during storybook reading tasks.

Results

All three children readily began using the targeted grammatical morphemes. However, none of the participants maintained use of the first morpheme. Error analyses revealed that the children either omitted the targeted morpheme or replaced it with another morpheme. To address this issue, a second intervention phase was implemented for the targets that were not maintained. During this phase, various grammatical morphemes were contrasted with each other (e.g., past tense
–ed
vs. possessive
's
). Following the second intervention phase, participants maintained all targets.

Conclusions

Aided AAC models and recasts may be used as part of intervention packages designed to help children acquire production of grammatical morphemes; however, it is important to provide contrasts of grammatical forms to ensure acquisition. Theoretical and clinical implications are discussed.
The Main Concept Analysis in Cantonese Aphasic Oral Discourse: External Validation and Monitoring Chronic Aphasia
Authors: Pak-Hin Kong Anthony
Published: August 2010

Purpose

The 1st aim of this study was to further establish the external validity of the main concept (MC) analysis by examining its relationship with the Cantonese Linguistic Communication Measure (CLCM; Kong, 2006; Kong & Law, 2004)—an established quantitative system for narrative production—and the Cantonese version of the Western Aphasia Battery (CAB; Yiu, 1992). The 2nd purpose of the study was to evaluate how well the MC analysis reflects the stability of discourse production among chronic Cantonese speakers with aphasia.

Method

Sixteen participants with aphasia were evaluated on the MC analysis, CAB, and CLCM in the summer of 2008 and were subsequently reassessed in the summer of 2009. They encompassed a range of aphasia severity (with an Aphasia Quotient ranging between 30.2/100 and 94.8/100 at the time of the 1st evaluation).

Results

Significant associations were found between the MC measures and the corresponding CLCM indices and CAB performance scores that were relevant to the presence, accuracy, and completeness of content in oral narratives. Moreover, the MC analysis was found to yield comparable scores for chronic speakers on 2 occasions 1 year apart.

Conclusion

The present study has further established the external validity of MC analysis in Cantonese. Future investigations involving more speakers with aphasia will allow adequate description of its psychometric properties.
Acoustic Evidence for Positional and Complexity Effects on Children’s Production of Plural
–s
Authors: Theodore Rachel M. , Demuth Katherine , Shattuck-Hufnagel Stefanie
Published: August 2010

Purpose

Some variability in children’s early productions of grammatical morphemes reflects phonological factors. For example, production of 3rd person singular
–s
is increased in utterance-final versus utterance-medial position and in simple versus cluster codas (e.g.,

see
s

vs.

hi
ts

). Understanding the factors that govern such variability is an important step toward modeling developmental processes. In this study, the authors examined the generality of these effects by determining whether position and coda complexity influence production of plural
–s
, which phonologically manifests the same as 3rd person singular
–s
.

Method

The authors used an elicited imitation task to examine the speech of 16 two-year-olds. Eight plural nouns (half contained simple codas, half contained cluster codas) were elicited utterance-medially and utterance-finally. Acoustic analysis of each noun was used to identify acoustic cues associated with coda production.

Results

Results showed that plural production was more robust in utterance-final versus utterance-medial position but equally robust in simple versus cluster codas.

Conclusions

These findings extend positional effects on morpheme production to plural
–s
. An effect of coda complexity was not observed for plural but was observed for 3rd person singular, which raises the possibility that the morphological representation proper influences the degree to which phonological factors affect morpheme production.
The Role of Pragmatic Language Use in Mediating the Relation Between Hyperactivity and Inattention and Social Skills Problems
Authors: Leonard Melinda A. , Milich Richard , Lorch Elizabeth P.
Published: August 2010

Purpose

In the present study, the authors explored whether pragmatic language use was associated with, and perhaps accounted for, the social skills problems that children with varying levels of hyperactivity and inattention experience.

Method

A community sample of 54 children aged 9–11 years participated. Pragmatic language use, hyperactivity and inattention, and social skills were examined utilizing data collected from standardized parent-report rating scales.

Results

Pragmatic language use fully mediated the relation between hyperactivity and social skills problems and partially mediated the relation between inattention and social skills problems. Further, pragmatic language use provided a unique contribution in the estimate of children’s social skills of 21.6% above and beyond the contribution of hyperactivity and 17.2% above and beyond the contribution of inattention.

Conclusions

Possible explanations for these mediation results are discussed in terms of children with attention-deficit/hyperactivity disorder and the problems that they experience with social relations.
Green backlighting for TV liquid crystal display using carbon nanotubes
Authors: Delepierre Gabriel , Mahfouz Rami , Cadete Santos Aires Francisco J. , Dijon Jean
Published: August 2010

A methodology to evaluate the emission characteristics of carbon nanotube layers in the context of liquid crystal display backlighting has been elaborated. Carbon nanotube layers with emission characteristics compatible with backlighting have been demonstrated for growth temperature as low as 400 °C, thanks to the use of plasma pretreatment before growth. This very low growth temperature allows to use soda lime glass for the backlight unit and thus to expect very low cost and very low power consumption devices with this technology.
Many-particle transport in the channel of quantum wire double-gate field-effect transistors with charged atomistic impurities
Authors: Albareda G. , Saura X. , Oriols X. , Suñé J.
Published: August 2010

One of the most reported causes of variations in electron devices characteristics (coming from the atomistic nature of matter) are discrete doping induced fluctuations. In this work we highlight the importance of accurately accounting for (time-dependent) coulomb correlations among (transport) electrons in the analysis of such fluctuations. In particular, we study the effect of single ionized dopants on the performance of a quantum wire double-gate metal-oxide-semiconductor field-effect transistor, mainly when its lateral dimensions approach the effective cross section of the charged impurities. In this regard, we use a recently developed many-particle semiclassical simulation approach by Albareda et al. [Phys. Rev. B 79, 075315 (2009)] which provides an accurate treatment of electron–electron and electron–impurity interactions (avoiding the mean-field approximation). We reveal the significant impact of the sign and position of the impurity along the transistor channel on the on-current, the threshold voltage, the distribution of the current in the channel cross-section, the transmission probabilities, and the distribution of transit times. We find that neglecting the (time-dependent) coulomb correlations among (transport) electrons can lead to misleading predictions of the previous results.
Thermal conductivity modeling of circular-wire nanocomposites
Authors: Hsieh Tse-Yang , Yang Jaw-Yen
Published: August 2010

A phonon Boltzmann equation solver using multiblock-structured grid system is developed and applied to study transverse thermal transport in silicon–germanium circular-wire nanocomposite (silicon nanowires embedded in germanium host matrix). Past studies usually assume geometric simplification for the circular-wire nanocomposite, so the heat transfer is actually modeled in a square-wire nanocomposite. To demonstrate geometry effect, phonon transport in both the circular-wire and square-wire nanocomposites are investigated with various wire spacings, volume fractions, and dimensions. In ballistic phonon transport, due to the smoothness of circular shape, the circular wire imposes less thermal resistance than the square wire. Nevertheless, in the geometric simplification, the wire spacing of the square-wire nanocomposite is larger than that of the circular-wire nanocomposite. The usual geometric simplification can overestimate the thermal conductivity of the circular-wire nanocomposite. The obtained results can provide essential information for the development of bulk-nanostructured thermoelectric devices.
A discrete interaction model/quantum mechanical method for describing response properties of molecules adsorbed on metal nanoparticles
Authors: Morton Seth Michael , Jensen Lasse
Published: August 2010

A new polarizable quantum mechanics/molecular mechanics method for the calculation of response properties of molecules adsorbed on metal nanoparticles is presented. This method, which we denote the discrete interaction model/quantum mechanics (DIM/QM) method, represents the nanoparticle atomistically which enables the modeling of the influence of the local environment of a nanoparticle surface on the optical properties of a molecule. Using DIM/QM, we investigate the excitation energies of rhodamine-6G (R6G) and crystal violet (CV) adsorbed on silver and gold nanoparticles of different quasispherical shapes and sizes. The metal nanoparticle is characterized by its static total polarizability, a reasonable approximation for frequencies far from the plasmon resonance. We observe that for both R6G and CV, the presence of the nanoparticle shifts the strongest excitation to the red ∼40 nm and also increases the oscillator strength of that excitation. The shifts in excitation energies due to the nanoparticle surface are found to be comparable to those due to solvation. We find that these shifts decay quickly as the molecule is moved away from the surface. We also find that the wavelength shift is largest when the transition dipole moment is aligned with the edges of the nanoparticle surface where the electric field is expected to be the largest. These results show that the molecular excitations are sensitive to the local environment on the nanoparticle as well as the specific orientation of the molecule relative to the surface.
Contact voltage-induced softening of RF microelectromechanical system gold-on-gold contacts at cryogenic temperatures
Authors: Berman D. , Walker M. J. , Krim J.
Published: August 2010

A series of experiments were performed in vacuum environments to investigate the impact of rf micromechanical system switch contact voltage versus resistance for gold-on-gold contacts at cryogenic temperatures. The purpose of this work was twofold as follows: (1) to examine whether asperity heating models already validated for high temperature contacts were also applicable at cryogenic temperatures and (2) to explore the implications and validity of prior suggestions that contact temperatures between 338 and 373 K are high enough to dissociate adsorbed film and/or push them aside but low enough to prevent asperities from becoming soft and adherent. Measurements on two distinct switch types, fabricated at independent laboratories, were performed in the temperature range 79–293 K and for contact voltages ranging from 0.01 to 0.13 V. Contact resistance values at all temperatures were observed to be lower for higher contact voltages, consistent with the aforementioned asperity heating models, whereby increased contact currents are associated with increased heating and softening effects. In situ removal of adsorbed species by oxygen plasma cleaning resulted in switch adhesive failure. Switches that had not been cleaned meanwhile exhibited distinct reductions in resistance at contact temperatures close to 338 K, consistent with suggestions that films begin to desorb, disassociate, and/or be pushed aside at that temperature.
New portable sensor system for rotational seismic motion measurements
Authors: Brokešová Johana , Málek Jiří
Published: August 2010

A new mechanical sensor system for recording the rotation of ground velocity has been constructed. It is based on measurements of differential motions between paired sensors mounted along the perimeter of a rigid (undeformable) disk. The elementary sensors creating the pairs are sensitive low-frequency geophones currently used in seismic exploration to record translational motions. The main features of the new rotational seismic sensor system are flat characteristics in the wide frequency range from 1 to 200 Hz and sensitivity limit of the order of 10−8 rad/s. Notable advantages are small dimensions, portability, easy installation and operation in the field, and the possibility of calibrating the geophones in situ simultaneously with the measurement. An important feature of the instrument is that it provides records of translational seismic motions together with rotations, which allows many important seismological applications. We have used the new sensor system to record the vertical rotation velocity due to a small earthquake of ML=2.2, which occurred within the earthquake swarm in Western Bohemia in autumn 2008. We found good agreement of the rotation record with the transverse acceleration as predicted by theory. This measurement demonstrates that this device has a much wider application than just to prospecting measurements, for which it was originally designed.
Optical properties of deformed few-layer graphenes with AB stacking
Authors: Lee S. H. , Ho Y. H. , Chiu C. W. , Lin M. F.
Published: August 2010

Optical excitations of deformed AB-stacked graphenes are studied through the gradient approximation. The interlayer atomic interactions induce prominent peaks, shoulder structures, and transition gaps in the low-energy absorption spectra. The uniaxial stress changes the energy spacing at the band-edge states and the Fermi momenta, which reflects on the spectrum peak frequencies and the transition gaps, respectively. These optical characteristics are also influenced by the layer number. Besides, deformation shows some similar and different effects in comparison with electric and magnetic fields. These predicted optical properties can be verified by optical measurements.
III-nitride nanopyramid light emitting diodes grown by organometallic vapor phase epitaxy
Authors: Wildeson Isaac H. , Colby Robert , Ewoldt David A. , Liang Zhiwen , Zakharov Dmitri N. , Zaluzec Nestor J. , García R. Edwin , Stach Eric A. , Sands Timothy D.
Published: August 2010

Nanopyramid light emitting diodes (LEDs) have been synthesized by selective area organometallic vapor phase epitaxy. Self-organized porous anodic alumina is used to pattern the dielectric growth templates via reactive ion etching, eliminating the need for lithographic processes. (In,Ga)N quantum well growth occurs primarily on the six {11¯01} semipolar facets of each of the nanopyramids, while coherent (In,Ga)N quantum dots with heights of up to ∼20 nm are incorporated at the apex by controlling growth conditions. Transmission electron microscopy (TEM) indicates that the (In,Ga)N active regions of the nanopyramid heterostructures are completely dislocation-free. Temperature-dependent continuous-wave photoluminescence of nanopyramid heterostructures yields a peak emission wavelength of 617 nm and 605 nm at 300 K and 4 K, respectively. The peak emission energy varies with increasing temperature with a double S-shaped profile, which is attributed to either the presence of two types of InN-rich features within the nanopyramids or a contribution from the commonly observed yellow defect luminescence close to 300 K. TEM cross-sections reveal continuous planar defects in the (In,Ga)N quantum wells and GaN cladding layers grown at 650–780 °C, present in 38% of the nanopyramid heterostructures. Plan-view TEM of the planar defects confirms that these defects do not terminate within the nanopyramids. During the growth of p-GaN, the structure of the nanopyramid LEDs changed from pyramidal to a partially coalesced film as the thickness requirements for an undepleted p-GaN layer result in nanopyramid impingement. Continuous-wave electroluminescence of nanopyramid LEDs reveals a 45 nm redshift in comparison to a thin-film LED, suggesting higher InN incorporation in the nanopyramid LEDs. These results strongly encourage future investigations of III-nitride nanoheteroepitaxy as an approach for creating efficient long wavelength LEDs.
Optimization of irradiation configuration in laser fusion utilizing self-organizing electrodynamic system
Authors: Murakami M. , Sarukura N. , Azechi H. , Temporal M. , Schmitt A. J.
Published: August 2010

A simple numerical method to determine an optimum beam configuration for highly uniform irradiation is proposed for direct-drive laser fusion systems and is applied to an arbitrary number of laser beams, NB. Driven by the Coulomb repulsion force, NB randomly distributed like charges move on a spherical surface to settle with a stable configuration having the minimum Coulomb energy for the system. Such resultant charge configurations practically do not depend on the initial conditions, and thus the solutions are very robust and unique. The irradiation uniformity is numerically assessed by overlapping NB beam patterns and calculating the laser absorption based on various spatial absorption patterns for the individual beams. The present method provides some improved illumination configurations for laser fusion compared with previously proposed designs. In particular, new coordinates for NB=48 and 72 are found to give an extraordinarily higher uniformity than for other numbers of NB. The influence of system imperfection on the irradiation uniformity is also discussed.
Optimization of La0.7Ba0.3MnO3−δ complex oxide laser ablation conditions by plume imaging and optical emission spectroscopy
Authors: Amoruso S. , Aruta C. , Bruzzese R. , Maccariello D. , Maritato L. , Granozio F. Miletto , Orgiani P. , Scotti di Uccio U. , Wang X.
Published: August 2010

The properties of thin films of complex oxides, such as La1−xDxMnO3−δ (D=Ba, Ca, Sr, etc.), produced by pulsed laser deposition depend critically on the experimental parameters in which laser ablation is carried out. Here, we report a comparative analysis of the pulsed laser ablation process of La0.7Ba0.3MnO3−δ, in oxygen background, in the ambient pressure range from 10−2 to 1 mbar, typically employed in pulsed laser deposition of manganites. The laser ablation plume was studied by using time-gated imaging and optical emission spectroscopy techniques. It was found that at a pressure of ≈10−2 mbar, the plume species arriving at the substrate are characterized by hyperthermal kinetic energy (≈10 eV), and high degree of excitation. On the contrary, at larger oxygen pressure (0.1–1 mbar), the velocity of plume species reaching the substrate, and their degree of excitation are much reduced by the confining effects of the background gas. These features explain why an appropriate choice of the experimental conditions in which the deposition process is carried out leads to better quality films, providing helpful indications to improve control over the growth process of both La1−xDxMnO3−δ and other perovskitic oxides.
Electric-field control of ferromagnetic resonance in monolithic BaFe12O19–Ba0.5Sr0.5TiO3 heterostructures
Authors: Das Jaydip , Song Young-Yeal , Wu Mingzhong
Published: August 2010

This paper demonstrates an electric-field tuning of the ferromagnetic resonance (FMR) responses at millimeter wave frequencies for a monolithic magneto-electric heterostructure. The layered stack is comprised of c-axis oriented and low loss barium hexaferrite (BaM) and (111) oriented ferroelectric barium strontium titanate (BSTO) layers along with embedded platinum electrode layers, all fabricated by pulsed laser deposition technique. A tunability of the FMR frequency as large as 3.5 MHz/V has been observed at 60 GHz due to application of bias voltages in the range of several volts. The realization of such a large tunability relies on the quasi-lattice-to-lattice contact between the BaM and BSTO layers as well as the high quality of those layers.
Composite metal/quantum-dot nanoparticle-array waveguides with compensated loss
Authors: Holmström Petter , Thylén Lars , Bratkovsky Alexander
Published: August 2010

We calculate the dispersion properties of waveguides composed of near-field-coupled arrays of metal-clad quantum dots (QDs). The high optical loss incurred by operating the metal shells close to resonance is mitigated by using optical gain in the QDs. A condition for achieving loss compensated operation is given based on realistic material parameters and neglecting inhomogeneous broadening.
Surface tension of short flexible Lennard-Jones chains: Corresponding states behavior
Authors: Galliero Guillaume
Published: August 2010

Molecular dynamics simulations of surface tensions of short flexible Lennard-Jones chains, composed of 2, 3, 4, and 5 segments, have been performed in this work. Using the simulation results, it is shown that the reduced surface tension depends only on the chain length and the reduced temperature. As a consequence, simple three parameters corresponding states using the acentric factor is shown to yield an excellent estimation of the reduced surface tension of the flexible Lennard-Jones chain fluid model. In addition, it has been noticed that the reduced surface tension of this fluid model is a unique function of the coexisting liquid and vapor reduced densities (i.e., there exist a universal Parachor behavior) for all chain lengths tested. When applied to real fluids, this universal behavior holds rather well for a large class of real species which can be nonspherical, nonlinear, and even polar. Only the surface tension of hydrogen-bonding compounds seems to largely deviate from this universal Parachor behavior. These interesting features of the surface tension, written in appropriate scaled forms, can probably be used to improve molecular models, in particular, those on which modern molecular based equations of state rely on.
Hydrogen bond symmetrization and superconducting phase of HBr and HCl under high pressure: An ab initio study
Authors: Duan Defang , Tian Fubo , He Zhi , Meng Xing , Wang Liancheng , Chen Changbo , Zhao Xiusong , Liu Bingbing , Cui Tian
Published: August 2010

Ab initio calculations are performed to probe the hydrogen bonding, structural, and superconducting behaviors of HBr and HCl under high pressure. The calculated results show that the hydrogen bond symmetrization (Cmc21→Cmcm transition) of HBr and HCl occurs at 25 and 40 GPa, respectively, which can be attributed to the symmetry stretching A1 mode softening. After hydrogen bond symmetrization, a pressure-induced soft transverse acoustic phonon mode of Cmcm phase is identified and a unique metallic phase with monoclinic structure of P21/m (4 molecules/cell) for both compounds is revealed by ab initio phonon calculations. This phase preserves the symmetric hydrogen bond and is stable in the pressure range from 134 to 196 GPa for HBr and above 233 GPa for HCl, while HBr is predicted to decompose into Br2+H2 above 196 GPa. Perturbative linear-response calculations predict that the phase P21/m is a superconductor with Tc of 27–34 K for HBr at 160 GPa and 9–14 K for HCl at 280 GPa.
Analysis of the orientational order effect on n-alkanes: Evidences on experimental response functions and description using Monte Carlo molecular simulation
Authors: Bessières D. , Piñeiro M. M. , De Ferron G. , Plantier F.
Published: August 2010

Short-range correlations of the molecular orientations in liquid n-alkanes have been extensively studied from depolarized Rayleigh scattering and thermodynamic measurements. These correlations between segments induce structural anisotropy in the fluid bulk. This phenomenon, which is characteristic of linear chain molecules when the constituting segments are nor freely jointed, but interact through a given angular potential, is then present in the linear n-Cn series, increasing its magnitude with chain length, and it is therefore less relevant or even completely absent in branched alkanes. This intermolecular effect is clearly revealed in second-order excess magnitudes such as heat capacities when the linear molecule is mixed with one whose structure approaches sphericity. The mixing process of different aspect ratio chain molecules is thought to modify the original pure fluid structure, by producing a diminution of the orientational order previously existing between pure n-alkane chains. However, second-order thermodynamics quantities of pure liquids CP, (∂v/∂T)P, and (∂v/∂P)P are known to be very sensitive to the specific interactions occurring at the microscopic level. In other words, the behavior of these derived properties versus temperature and pressure can be regarded as response functions of the complexity of the microscopic interactions. Thus, the purpose of the present work is to rationalize the orientational order evolution with both temperature and molecular chain length from the analysis of pure fluid properties. To this aim, we focused on two linear alkanes, n-octane (n-C8) and n-hexadecane (n-C16), and two of their branched isomers, i.e., 2,2,4-trimethylpentane (br-C8) and 2,2,4,4,6,8,8-heptamethylnonane (br-C16). For each compound, we propose a combined study from direct experimental determination of second-order derivative properties and Monte Carlo simulations. We performed density ρ, speed of sound c, and isobaric heat capacity CP measurements in broad ranges of pressure and temperature allowing a complete thermodynamic characterization of these compounds. Monte Carlo simulations provide a link between the molecular scale model and the experimental thermodynamic properties. Additional information about the microscopic structure of the simulated fluid model was derived, through the calculation of the radius of gyration and average end-to-end distances. Orientational order is clearly revealed by the experimental residual heat capacity trend of pure linear alkanes. The close agreement observed between this experimental macroscopic property and the calculated theoretical structural parameters support the conclusion that the orientational order between segments of linear molecules should be regarded as a conformational effect due to the flexibility of the chain.
Determination of diffusion lengths in nanowires using cathodoluminescence
Authors: Gustafsson Anders , Bolinsson Jessica , Sköld Niklas , Samuelson Lars
Published: August 2010

We used cathodoluminescence imaging to determine diffusion lengths in III-V semiconductor nanowires, grown by metal-organic chemical vapor deposition seeded by gold nanoparticles. Intensity profiles were recorded either from the interface between the substrate and homogeneous nanowires, or from segments in nanowires containing axial heterostructures to determine the diffusion length. We determined diffusion lengths of 0.10 to 0.90 μm, the shortest for uncapped wires. The reduction is attributed largely to surface recombination.
Communication: Two stages of ultrafast hydrogen migration in methanol driven by intense laser fields
Authors: Xu Huailiang , Marceau Claude , Nakai Katsunori , Okino Tomoya , Chin See-Leang , Yamanouchi Kaoru
Published: August 2010

Hydrogen migration in methanol induced by an intense laser field (0.2 PW/cm2) is investigated in real time by a pump-probe coincidence momentum imaging method. The observed temporal evolution of the kinetic energy spectra reveals that there are two distinctively different stages in the hydrogen migration processes in the singly charged methanol: ultrafast hydrogen migration occurring within the intense laser field (∼38 fs) and slower postlaser pulse hydrogen migration (∼150 fs).
Loss of momentum in a viscous compressible fluid due to no-slip boundary condition at one or two planar walls
Authors: Felderhof B. U.
Published: August 2010

The loss of fluid momentum due to friction at one or two planar walls bounding a viscous compressible fluid is studied as a function of time for the situation where the flow is due to a sudden impulse applied at a selected point in initially quiescent fluid. The no-slip condition is assumed to hold at the walls, and the initial impulse is assumed to be sufficiently small, so that the linearized Navier–Stokes equations may be used. When the initial impulse is directed parallel to the walls the time-dependent total fluid momentum is independent of compressibility and volume viscosity. For initial impulse directed perpendicular to the walls an echoing effect, corresponding to sound bouncing between the two walls, is observed.
Near-field optical data storage using C-apertures
Authors: Leen J. Brian , Hansen Paul , Cheng Yao-Te , Gibby Aaron , Hesselink Lambertus
Published: August 2010

We demonstrate the all-optical recording of deeply subwavelength data bits in Ge2Sb2Te5 using a near-field scanning optical microscope (NSOM) probe that utilizes a C-aperture fabricated using through membrane focused ion beam milling. Data bits recorded with various optical powers were read out optically by C-aperture NSOM and the physical bit size was measured by atomic force microscopy (AFM). Both optical and AFM measurements were found to be in excellent agreement with simulation. We achieved a minimum physical bit size of 53.5×50.2 nm2 at a wavelength of 980 nm (λ/20) indicating a data density of 223 Gbit/in.2.
Photodissociation dynamics of tryptophan and the implication of asymmetric photolysis
Authors: Tseng Chien-Ming , Dyakov Yuri A. , Huang Huai Ching , Huang Kuan Yu , Lee Yuan T. , Ni Chi-Kung , Chiang Su-Yu
Published: August 2010

Photodissociation of amino acid tryptophan in a molecular beam at wavelengths of 212.8 and 193 nm, corresponding to excitation to the second and third absorption bands, was investigated using multimass ion imaging techniques. The respective wavelengths also represent excitation to the edge of a positive circular dichroism band and the center of a negative circular dichroism band of L-tryptophan. Only one dissociation channel was observed at both photolysis wavelengths: C8NH6CH2CHNH2COOH→C8NH6CH2+CHNH2COOH. Dissociation rates were found to be 1.3×106 and 5×106 s−1 at the respective wavelengths. Comparison to theoretical calculation indicates that dissociation occurs on the ground state after internal conversion. Implication of asymmetric photolysis is discussed.
Synthesis and formation mechanism of hydrogenated boron clusters B12Hn with controlled hydrogen content
Authors: Ohishi Yuji , Kimura Kaoru , Yamaguchi Masaaki , Uchida Noriyuki , Kanayama Toshihiko
Published: August 2010

We present the formation of hydrogen-content-controlled B12Hn+ clusters through the decomposition and ion-molecule reactions of the decaborane (B10H14) and diborane (B2H6) molecules in an external quadrupole static attraction ion trap. The hydrogen- and boron-contents of the B10−yHx+ cluster are controlled by charge transfer from ambient gas ions. In the process of ionization, a certain number of hydrogen and boron atoms are detached from decaborane ions by the energy caused by charge transfer. The energy caused by the ion-molecule reactions also induces H atom detachment. Ambient gas of Ar leads to the selective generation of B10H6+. The B10H6+ clusters react with B2H6 molecules, resulting in the selective formation of B12H8+ clusters. Ambient gas of Ne (He) leads to the generation of B10−yHx+ clusters with x=4–10 and y=0–1 (with x=2–10 and y=0–2), resulting in the formation of B12Hn+ clusters with n=4–8 (n=2,4–8). The introduction of ambient gas also increases the production of clusters. PBE0/6-311+G(d)//B3LYP/6-31G(d)-level density functional theory calculations are conducted to investigate the structure and the mechanism of formation of B10−yHx+ and B12Hn+ clusters.
Ultrafast all-optical modulator for 1.5 μm controlled by Ti:Al2O3 laser
Authors: Ermolenko M. V. , Buganov O. V. , Tikhomirov S. A. , Stankevich V. V. , Gaponenko S. V. , Shulenkov A. S.
Published: August 2010

The concept of ultrafast light modulator for wavelength ∼1.5 μm controlled by fundamental harmonic of a Ti:Al2O3 laser has been demonstrated. The possibility of realization of this concept was experimentally confirmed. We have demonstrated strong spectrally wide nonlinear response in multilayer heterostructures based on GaAs/(AlGa)xOy with the relaxation time of 1–3 ps in the spectral range where both materials have negligible absorption.
Spherical and cylindrical imploding and exploding shock waves in plasma system dominated by pair production
Authors: ul Haq Muhammad Noaman , Saeed R. , Shah Asif
Published: August 2010

The propagation of ion acoustic shock waves in cylindrical and spherical geometries has been investigated. The plasma system consists of cold ions, Boltzmannian electrons and positrons. Spherical, cylindrical Korteweg–de Vries–Burger equations have been derived by reductive perturbation technique and their shock behavior is studied by employing finite difference method. Our main emphasis is on the behavior of shock as it moves toward and away from center of spherical and cylindrical geometries. It is noticed, that the shock wave strength and steepness accrues with time as it moves toward the center and shock enervates as it moves away from center. The strength of shock in spherical geometry is found to dominate over shock strength in cylindrical geometry. Positron concentration, kinematic viscosity are also found to have significant effect on the shock structure and propagation. The results may have relevance in the inertial confinement fusion plasmas.
Nature of counterflow and circulation in vortex separators
Authors: Shtern Vladimir N. , Borissov Anatoli A.
Published: August 2010

This paper focuses on the physical mechanism of elongated counterflows occurring in vortex tubes and hydrocyclones. To this end, a new solution to the Navier–Stokes equations is obtained which describes a flow pattern consisting of two through-flows and the global meridional circulation. One of the through-flows has U-shape geometry. It is shown that swirl decay due to fluid-wall friction induces both the U-shape through-flow and the circulation. The circulation does not deteriorate particle separation. The solution illustrates how the swirl-induced pressure distribution drives the counterflow and results in the paradoxical centrifugal stratification where the high-density fluid located at the periphery is hot while the low-density fluid located near the axis is cold.
Preparation, characterization, emission (Eu3+), and electron spin resonance (Gd3+) studies of Y2−xLnxTi2O7 (Ln=Eu and Gd, x=0.0,0.05)
Authors: Kumar B. Vijaya , Velchuri Radha , Devi V. Rama , Prasad G. , Sreedhar B. , Bansal C. , Vithal M.
Published: August 2010

Bulk and nanopyrochlore materials of composition Y2−xLnxTi2O7 (Ln=Eu and Gd, x=0.0,0.05) have been prepared by sol-gel method via peroxo titanium complex precursor. All the samples were characterized by powder x-ray diffraction (XRD), Raman spectra, and transmission electron microscopy (TEM). The unit cell parameters were obtained from Rietveld analysis of XRD patterns. The influence of particle size on the emission of Eu3+ (in Y2−xEuxTi2O7), the electron spin resonance (ESR) of Gd3+ (in Y2−xGdxTi2O7) and optical absorption spectra have been studied. The band gap energy of Y1.95Ln0.05Ti2O7 (Ln=Eu and Gd) was determined and compared with parent Y2Ti2O7. The variation in the emission intensity of Eu3+ is accounted with the particle size and short range order. The spin-Hamiltonian parameters of Gd3+ were obtained from the powder ESR spectra. The single-ion anisotropy was taken in to account in the analysis of powder ESR spectra. The crystallite size was obtained from powder XRD and TEM images.
Terahertz sensing with carbon nanotube layers coated on silica fibers: Carrier transport versus nanoantenna effects
Authors: Seliuta Dalius , Kašalynas Irmantas , Macutkevic Jan , Valušis Gintaras , Shuba Mikhail V. , Kuzhir Polina P. , Slepyan Gregory Ya. , Maksimenko Sergey A. , Ksenevich Vitaly K. , Samuilov Vladimir , Lu Qi
Published: August 2010

Carbon nanotube layers prepared as coatings on silica fibers are found to be suitable for terahertz detection in 0.5–7.3 THz range within temperatures of 4.2–70 K. In time-domain of terahertz excitation, two following constituents in the photoresponse are discriminated: the first one is attributed to the bolometric effect while the other one is related to the photoconductivity caused by the terahertz-induced hopping effect. In frequency domain, nonmonotonic behavior of the photoconductivity is associated with prevailing carbon nanotube-induced antenna effects in the electronic transport. The experimental observations are supported by theoretical estimates.
Axial and lateral particle ordering in finite Reynolds number channel flows
Authors: Humphry Katherine J. , Kulkarni Pandurang M. , Weitz David A. , Morris Jeffrey F. , Stone Howard A.
Published: August 2010

Inertial focusing in a pressure-driven flow refers to the positioning of particles transverse to the mean flow direction that occurs as a consequence of a finite particle Reynolds number. In channels with rectangular cross-sections, and for a range of channel aspect ratios and particle confinement, experimental results are presented to show that both the location and the number of focusing positions depend on the number of particles per unit length along the channel. This axial number density is a function of both the channel cross-section and the particle volume fraction. These results are rationalized using simulations of the particle-laden flow to show the manner in which hydrodynamic interactions set the preferred locations in these confined flows. A criterion is presented for the occurrence of a stepwise transition from one to two or more trains of particles.
Effect of significant data loss on identifying electric signals that precede rupture estimated by detrended fluctuation analysis in natural time
Authors: Skordas E. S. , Sarlis N. V. , Varotsos P. A.
Published: August 2010

Electric field variations that appear before rupture have been recently studied by employing the detrended fluctuation analysis (DFA) to quantify their long-range temporal correlations. These studies revealed that seismic electric signal (SES) activities exhibit a scale invariant feature with an exponent αDFA≈1 over all scales investigated (around five orders of magnitude). Here, we study what happens upon significant data loss, which is a question of primary practical importance, and show that the DFA applied to the natural time representation of the remaining data still reveals for SES activities an exponent close to 1.0, which markedly exceeds the exponent found in artificial (man-made) noises. This enables the identification of a SES activity with probability of 75% even after a significant (70%) data loss. The probability increases to 90% or larger for 50% data loss.
Reverse-emission-state-transition mode locking of a two-section InAs/InGaAs quantum dot laser
Authors: Breuer Stefan , Rossetti Mattia , Elsässer Wolfgang , Drzewietzki Lukas , Bardella Paolo , Montrosset Ivo , Krakowski Michel , Hopkinson Mark
Published: August 2010

Reverse-emission-state-transition mode locking in a two-section InAs/InGaAs quantum dot laser is experimentally investigated and confirmed by simulations. Stable mode locking starts on the first excited state (λ=1207 nm) and then, with increasing gain current, a transition to stable simultaneous two-state mode locking on excited state and ground state (λ=1270 nm) takes place. This particular state-transition occurs already at 0 V reverse-bias and at moderate gain-section currents. It is attributed to the strong active region chirping of the gain medium and in particular to a photon pumping process in the saturable absorber section.
Electron microscopy of GaAs/MnAs core/shell nanowires
Authors: Dellas N. S. , Liang J. , Cooley B. J. , Samarth N. , Mohney S. E.
Published: August 2010

GaAs/MnAs core/shell nanowire heterostructures were synthesized by catalyst-free molecular beam epitaxy. Transmission electron microscopy (TEM) reveals that the GaAs core predominantly grows with the zinc-blende crystal structure with a [111] growth direction. In a small population of wires, the crystal structure transitions from zinc blende to wurtzite with a [001] growth direction. Cross-sectional TEM shows that the MnAs grows epitaxially on the GaAs core in the NiAs prototype structure with an epitaxial relation of [202¯1] MnAs∥[111]GaAs and (011¯0) MnAs∥GaAs (1¯10). When the GaAs core is in the wurtzite structure, the epitaxial relation between the GaAs and MnAs changes to [0001] MnAs∥[0001]GaAs and (1¯21¯0) MnAs∥(1¯21¯0)GaAs.
Tuning of current-induced domain wall resonance frequency using Gd doping
Authors: Lepadatu S. , Claydon J. S. , Ciudad D. , Kinane C. J. , Langridge S. , Dhesi S. S. , Marrows C. H.
Published: August 2010

The current-induced resonance frequencies of domain walls in parabolic pinning potentials are measured in Gd doped NiFe as a function of doping level. The modification of magnetic properties due to Gd doping results in an order of magnitude increase in resonance frequencies for 10% Gd doping, due to the induced out-of-plane anisotropy, and the resonance frequencies are excited at lower current densities compared to undoped NiFe. These results are reproduced using a one-dimensional model of domain wall resonance, and found to be in good agreement in the small oscillation amplitude limit.
Bipolar resistance switching driven by tunnel barrier modulation in TiOx/AlOx bilayered structure
Authors: Baik Seung Jae , Lim Koeng Su
Published: August 2010

A TiOx/AlOx resistance switching device was investigated as a prototype of a bilayered structure composed of a “transport layer” and a “tunnel layer.” Study of its carrier transport led to the conclusion that resistance switching is driven by the modulation of the AlOx tunnel barrier. Redox in the AlOx layer causes the decrease in tunneling resistance that scales with the inverse of the area. The appropriate switching characteristics in a bilayered structure can be obtained by adopting a tunnel layer that has a higher lattice binding energy than the transport layer.
Defect activation in willemite-type Zn2GeO4 by nanocrystallization
Authors: Takahashi Yoshihiro , Ando Masataka , Iwasaki Kenichiro , Masai Hirokazu , Fujiwara Takumi
Published: August 2010

We demonstrated the selective introduction of interstitial Zn defects (Zni•) into willemite-type semiconductive Zn2GeO4 by nanocrystallization of 15Li2O–15ZnO–70GeO2 glass. The resulting nanocrystallized glass consisting of Zn2GeO4 exhibited a long-lasting photoluminescence (LLP). It is suggested that the Zni• is produced by capturing a zinc ion through six-membered rings of the Zn2GeO4 phase during nanocrystallization and the excess Zni• acts as an electron trap for the LLP. This defect activation through nanocrystallization is a promising new approach to functionalization.
Demonstration of mode splitting in an optical microcavity in aqueous environment
Authors: Kim Woosung , Özdemir Şahin Kaya , Zhu Jiangang , He Lina , Yang Lan
Published: August 2010

Scatterer induced modal coupling and the consequent mode splitting in a whispering gallery mode resonator is demonstrated in aqueous environment. The rate of change in splitting as particles enter the resonator mode volume strongly depends on the concentration of particle solution. The higher is the concentration, the higher is the rate of change. Polystyrene nanoparticles of radius 50 nm with concentration as low as 5×10−6 wt % have been detected using the mode splitting spectra. Observation of mode splitting in water paves the way for constructing advanced resonator based sensors for measuring nanoparticles and biomolecules in various environments.
Influence of doping at the nanoscale at LaAlO3/SrTiO3 interfaces
Authors: Fix T. , Schoofs F. , MacManus-Driscoll J. L. , Blamire M. G.
Published: August 2010

The origin of the free charge layer which forms at the LaAlO3/SrTiO3 interface is still uncertain. By varying the doping concentration and the nature of the dopant in SrTiO3 at the LaAlO3/SrTiO3 interface, we show the extreme sensitivity of the system and confirm that the underlying phenomenon accounting for the conduction is most likely an electronic reconstruction. We explain that although doping these interfaces might be useful to induce additional properties such as ferromagnetism or useful to probe the electronic reconstruction, undoped interfaces provide the highest carrier density.
Formation of antiphase domains in NiFe2O4 thin films deposited on different substrates
Authors: Datta R. , Kanuri S. , Karthik S. V. , Mazumdar D. , Ma J. X. , Gupta A.
Published: August 2010

Thin films of NiFe2O4 have been deposited on various substrates using pulsed laser deposition and the defect structures investigated by transmission electron microscopy. Owing to the simultaneous nucleation of cation-disordered sites during the nonequilibrium growth, the NiFe2O4 films exhibit antiphase domains of ∼20 nm, irrespective of the substrate symmetry. For growth on isostructural spinel substrates, the density of antiphase appears to decrease with decreasing lattice mismatch. Aberration corrected high resolution transmission electron microscopy reveals that the interchange of equivalent tetrahedral cation positions in the host oxygen sublattice as one of the possible mechanisms leading to the formation of antiphase domains.
Highly conductive ZnO grown by pulsed laser deposition in pure Ar
Authors: Scott Robin C. , Leedy Kevin D. , Bayraktaroglu Burhan , Look David C. , Zhang Yong-Hang
Published: August 2010

Ga-doped ZnO was deposited by pulsed laser deposition at 200 °C on SiO2/Si, Al2O3, or quartz in 10 mTorr of pure Ar. The as-grown, bulk resistivity at 300 K is 1.8×10−4 Ω cm, three-times lower than that of films deposited at 200 °C in 10 mTorr of O2 followed by an anneal at 400 °C in forming gas. Furthermore, depth uniformity of the electrical properties is much improved. Mobility analysis shows that this excellent resistivity is mostly due to an increase in donor concentration, rather than a decrease in acceptor concentration. Optical transmittance is approximately 90% in the visible and near-IR spectral regions.
Large thermoelectric figure of merit for three-dimensional topological Anderson insulators via line dislocation engineering
Authors: Tretiakov O. A. , Abanov Ar. , Murakami Shuichi , Sinova Jairo
Published: August 2010

We study the thermoelectric properties of three-dimensional topological Anderson insulators with line dislocations. We show that at high densities of dislocations the thermoelectric figure of merit ZT can be dominated by one-dimensional topologically protected conducting states channeled through the lattice screw dislocations in the topological insulator materials with a nonzero time-reversal-invariant momentum such as Bi0.9Sb0.1. When the chemical potential does not exceed much the mobility edge the ZT at room temperatures can reach large values, much higher than unity for reasonable parameters, hence making this system a strong candidate for applications in heat management of nanodevices.