bluuebunny/crossref_metadata_2025 huggingface dataset:
Thinking Outside of the Assessment Box: Assessing Social Communicative Functioning in Students With ASD
Authors: Dodd Janet L.
Published: October 2010

The assessment of a student suspected of an autism spectrum disorder (ASD) diagnosis requires the integration of information collected by a variety of professionals across various domains of functioning. One of the core deficits of students with ASD is a deficit related to social communicative competence (SCC). SCC requires the integration of language, social cognition, and higher order executive functions (Coggins, Olswang, Carmichael Olsson, & Timler, 2003) This article will propose an assessment model of social communicative functioning that was developed based on the SCC framework of Coggins and colleagues as a component of the Comprehensive Multidisciplinary Assessment Protocols for Autism Spectrum Disorders (CMAPS; Dodd & Franke, 2010).
The Role of Dynamic Assessment Within the Response to Intervention Model in School-Age English Language Learners
Authors: Rosa-Lugo Linda I. , Rivera Elizabeth , Rierson Terrie Kate
Published: October 2010

Response to Intervention (RtI) has been recommended in IDEA (2004) as an alternative approach for addressing the needs of all learners. This article discusses the role of dynamic assessment (DA) within the RtI Model for school-age English Language Learners (ELLs). This article provides an overview of DA and RtI, notes their similarities and differences, and discusses the usefulness of DA and RtI in helping speech-language pathologists (SLPs) discriminate language differences from language disorders and monitor progress in ELLs. A case study is presented to demonstrate how SLPs can use DA and RtI in the assessment of ELLs.
Development of CO2 laser dispersion interferometer with photoelastic modulator
Authors: Akiyama T. , Kawahata K. , Okajima S. , Nakayama K.
Published: October 2010

A dispersion interferometer is one of the promising methods of the electron density measurement on large and high density fusion devices. This paper describes development of a CO2 laser dispersion interferometer with a photoelastic modulator for phase modulation. In order to make the dispersion interferometer free from variations of the detected intensity, a new phase extraction method is introduced: The phase shift is evaluated from a ratio of amplitudes of the fundamental and the second harmonics of the phase modulation frequency in the detected interference signal. The proof-of-principle experiments demonstrate the feasibility of this method.
Simultaneous two-dimensional laser-induced-fluorescence measurements of argon ions
Authors: Hansen A. K. , Galante Matthew , McCarren Dustin , Sears Stephanie , Scime E. E.
Published: October 2010

Recent laser upgrades on the Hot Helicon Experiment at West Virginia University have enabled multiplexed simultaneous measurements of the ion velocity distribution function at a single location, expanding our capabilities in laser-induced fluorescence diagnostics. The laser output is split into two beams, each modulated with an optical chopper and injected perpendicular and parallel to the magnetic field. Light from the crossing point of the beams is transported to a narrow-band photomultiplier tube filtered at the fluorescence wavelength and monitored by two lock-in amplifiers, each referenced to one of the two chopper frequencies.
Hard x-ray transmission crystal spectrometer at the OMEGA-EP laser facility
Authors: Seely J. F. , Szabo C. I. , Feldman U. , Hudson L. T. , Henins A. , Audebert P. , Brambrink E.
Published: October 2010

The transmission crystal spectrometer (TCS) is approved for taking data at the OMEGA-EP laser facility since 2009 and will be available for the OMEGA target chamber in 2010. TCS utilizes a Cauchois type cylindrically bent transmission crystal geometry with a source to crystal distance of 600 mm. Spectral images are recorded by image plates in four positions, one IP on the Rowland circle and three others at 200, 400, and 600 mm beyond the Rowland circle. An earlier version of TCS was used at LULI on experiments that determined the x-ray source size from spectral line broadening on one IP positioned behind the Rowland circle. TCS has recorded numerous backlighter spectra at EP for point projection radiography and for source size measurements. Hard x-ray source size can be determined from the source broadening of both K shell emission lines and from K absorption edges in the bremsstrahlung continuum, the latter being a new way to measure the spatial extent of the hard x-ray bremsstrahlung continuum.
Quasimonochromatic x-ray backlighting on the COrnell Beam Research Accelerator (COBRA) pulsed power generator
Authors: Knapp P. F. , Greenly J. B. , Gourdain P. A. , Hoyt C. L. , Pikuz S. A. , Shelkovenko T. A. , Hammer D. A.
Published: October 2010

Monochromatic x-ray backlighting has been employed with great success for imaging of plasmas with strong self-emission such as x-pinches and wire array z-pinches. However, implementation of a monochromatic backlighting system typically requires extremely high quality spherically bent crystals which are difficult to manufacture and can be prohibitively expensive. Furthermore, the crystal must have a direct line of sight to the object, which typically emits copious amounts of radiation and debris. We present a quasimonochromatic x-ray backlighting system which employs an elliptically bent mica crystal as the dispersive element. In this scheme a narrow band of continuum radiation is selected for imaging, instead of line radiation in the case of monochromatic imaging. The flat piece of mica is bent using a simple four-point bending apparatus that allows the curvature of the crystal to be adjusted in situ for imaging in the desired wavelength band. This system has the advantage that it is very cost effective, has a large aperture, and is extremely flexible. The principles of operation of the system are discussed and its performance is analyzed.
A novel, multichannel, comb-frequency Doppler backscatter system
Authors: Peebles W. A. , Rhodes T. L. , Hillesheim J. C. , Zeng L. , Wannberg C.
Published: October 2010

Doppler backscattering has emerged in recent years as a powerful diagnostic tool in high temperature fusion plasmas. The technique is sensitive to plasma turbulence flow and has been utilized to determine radial electric field and to study geodesic acoustic modes, zonal flows, and intermediate scale density turbulence. The current manuscript describes a novel technique for creating a stable, multichannel system covering the V-band frequency range (50–75 GHz) which enables simultaneous monitoring of turbulent flows and fluctuation levels at eight distinct spatial locations. The system is based on a high-frequency, low phase noise comb-frequency generator combined with a filter bank and quadrature detection system. The system is now in operation on DIII-D and has allowed monitoring of the flow and turbulence levels across the plasma radius during events such as the L-H transition.
First real-time detection of surface dust in a tokamak
Authors: Skinner C. H. , Rais B. , Roquemore A. L. , Kugel H. W. , Marsala R. , Provost T.
Published: October 2010

The first real-time detection of surface dust inside a tokamak was made using an electrostatic dust detector. A fine grid of interlocking circuit traces was installed in the NSTX vessel and biased to 50 V. Impinging dust particles created a temporary short circuit and the resulting current pulse was recorded by counting electronics. The techniques used to increase the detector sensitivity by a factor of ×10 000 to match NSTX dust levels while suppressing electrical pickup are presented. The results were validated by comparison to laboratory measurements, by the null signal from a covered detector that was only sensitive to pickup, and by the dramatic increase in signal when Li particles were introduced for wall conditioning purposes.
Far-forward collective scattering measurements of density fluctuations in the helically symmetric experiment stellarator
Authors: Deng C. B. , Brower D. L.
Published: October 2010

The multichannel interferometer system on the helically symmetric experiment (HSX) stellarator is reconfigured to perform far-forward collective scattering measurements of electron density fluctuations. The collective scattering system has nine viewing chords with 1.5 cm spacing. Scattered power is measured using a homodyne detection scheme. Far-forward collective scattering provides a line-integrated measurement of fluctuations within the divergence of the probe beam covering wavenumber range: k⊥<2 cm−1. The perpendicular wavenumber consists of poloidal and radial contributions that vary with chord position. Both coherent modes and broadband fluctuation are measured. When HSX is operated without quasihelical symmetry at BT=1 T and ne∼4×1012 cm−3, a coherent electrostatic fluctuation is observed.
On the role of spectral resolution in velocity shear layer measurements by Doppler reflectometry
Authors: Happel T. , Blanco E. , Estrada T.
Published: October 2010

The signal quality of a Doppler reflectometer depends strongly on its spectral resolution, which is influenced by the microwave beam properties and the radius of curvature of the cutoff layer in the plasma. If measured close to a strong perpendicular velocity shear layer, the spectrum of the backscattered signal is influenced by different velocities. This can give rise to two Doppler shifted peaks in the spectrum as observed in TJ-II H-mode plasmas. It is shown by two-dimensional full wave simulations that the two peaks are separable provided the spectral resolution of the system is sufficient. However, if the spectral resolution is poor, the two peaks blend into one and yield an intermediate and incorrect velocity.
Target diagnostic control system implementation for the National Ignition Facility (invited)
Authors: Shelton R. T. , Kamperschroer J. H. , Lagin L. J. , Nelson J. R. , O’Brien D. W.
Published: October 2010

The extreme physics of targets shocked by NIF’s 192-beam laser is observed by a diverse suite of diagnostics. Many diagnostics are being developed by collaborators at other sites, but ad hoc controls could lead to unreliable and costly operations. A diagnostic control system (DCS) framework for both hardware and software facilitates development and eases integration. Each complex diagnostic typically uses an ensemble of electronic instruments attached to sensors, digitizers, cameras, and other devices. In the DCS architecture each instrument is interfaced to a low-cost WINDOWS XP processor and JAVA application. Each instrument is aggregated with others as needed in the supervisory system to form an integrated diagnostic. The JAVA framework provides data management, control services, and operator graphical user interface generation. DCS instruments are reusable by replication with reconfiguration for specific diagnostics in extensible markup language. Advantages include minimal application code, easy testing, and high reliability. Collaborators save costs by assembling diagnostics with existing DCS instruments. This talk discusses target diagnostic instrumentation used on NIF and presents the DCS architecture and framework.
Measurements of neutral helium density in helicon plasmas
Authors: Houshmandyar Saeid , Sears Stephanie H. , Thakur Saikat Chakraborty , Carr Jerry , Galante Matthew E. , Scime Earl E.
Published: October 2010

Laser-induced-fluorescence (LIF) is used to measure the density of helium atoms in a helicon plasma source. For a pump wavelength of 587.725 nm (vacuum) and laser injection along the magnetic field, the LIF signal exhibits a signal decrease at the Doppler shifted central wavelength. The drop in signal results from the finite optical depth of the plasma and the magnitude of the decrease is proportional to the density of excited state neutral atoms. Using Langmuir probe measurements of plasma density and electron temperature and a collisional-radiative model, the absolute ground state neutral density is calculated from the optical depth measurements. Optimal plasma performance, i.e., the largest neutral depletion on the axis of the system, is observed for antenna frequencies of 13.0 and 13.5 MHz and magnetic field strengths of 550–600 G.
Preliminary results from the Alcator C-Mod polarimeter
Authors: Xu P. , Irby J. H. , Bergerson W. F. , Bosco J. , Brower D. L. , Ding W. X. , Kanojia A. , Leccacorvi R. , Mansfield D. K. , Marmar E. S. , Michael P. , Murray R. , Rokhman Y. , Vieira R.
Published: October 2010

A poloidally viewing far infrared polarimeter diagnostic is being developed for the Alcator C-Mod tokamak, and will be used to determine the q-profile and to study density and magnetic field fluctuations. A three-chord version of what will eventually be up to a ten-chord system has been designed and fabricated and will be installed on C-Mod before the end of the current run period. Bench tests of a single chord mock-up of this system show acceptable noise levels for the planned measurements. We will discuss the analysis and experimental techniques used to diagnose and reduce noise sources.
Inverse Hall–Petch relationship in the nanostructured TiO2: Skin-depth energy pinning versus surface preferential melting
Authors: Liu X. J. , Yang L. W. , Zhou Z. F. , Chu Paul K. , Sun Chang Q.
Published: October 2010

The functional dependence of stress, elastic modulus, melting point, and their interdependence on the identities (bond order, nature, length, and strength) of a representative bond of the specimen has been established for deeper insight into the transition from the conventional Hall–Petch relationship (HPR) to the inverse HPR (IHPR) for nanostructured TiO2. Theoretical reproduction of the observed inverse HPR suggests that the intrinsic competition between the energy-density gain (elastic modulus enhancement) and the cohesive-energy remnant (melting point depression) in the grain boundaries originates and the extrinsic competition between the activation and the inhibition of atomic dislocations activates the IHPR.
Pulse-burst laser systems for fast Thomson scattering (invited)
Authors: Den Hartog D. J. , Ambuel J. R. , Borchardt M. T. , Falkowski A. F. , Harris W. S. , Holly D. J. , Parke E. , Reusch J. A. , Robl P. E. , Stephens H. D. , Yang Y. M.
Published: October 2010

Two standard commercial flashlamp-pumped Nd:YAG (YAG denotes yttrium aluminum garnet) lasers have been upgraded to “pulse-burst” capability. Each laser produces a burst of up to 15 2 J Q-switched pulses (1064 nm) at repetition rates of 1–12.5 kHz. Variable pulse-width drive (0.15–0.39 ms) of the flashlamps is accomplished by insulated gate bipolar transistor (IGBT) switching of electrolytic capacitor banks. Direct control of the laser Pockels cell drive enables optimal pulse energy extraction, and up to four 2 J laser pulses during one flashlamp pulse. These lasers are used in the Thomson scattering plasma diagnostic system on the MST reversed-field pinch to record the dynamic evolution of the electron temperature profile and temperature fluctuations. To further these investigations, a custom pulse-burst laser system with a maximum pulse repetition rate of 250 kHz is now being commissioned.
Streaked radiography measurements of convergent ablator performance (invited)
Authors: Hicks D. G. , Spears B. K. , Braun D. G. , Olson R. E. , Sorce C. M. , Celliers P. M. , Collins G. W. , Landen O. L.
Published: October 2010

The velocity and remaining ablator mass of an imploding capsule are critical metrics for assessing the progress toward ignition of an inertially confined fusion experiment. These and other ablator rocket parameters have been measured using a single streaked x-ray radiograph. A regularization technique has been used to determine the ablator density profile ρ(r) at each time step; moments of ρ(r) then provide the areal density, average radius, and mass of the unablated, or remaining, ablator material, with the velocity determined from the time derivative of the average radius. The technique has been implemented on experiments at the OMEGA laser facility.
Measurement of the ratio of hydrogen to deuterium at the KSTAR 2009 experimental campaign
Authors: Kwak Jong-Gu , Wang Son Jong , Kim Sun Ho , Park Jae Min , Na Hoon Kyun
Published: October 2010

The control of the ratio of hydrogen to the deuterium is one of the very important issues for ion cyclotron range of frequency (ICRF) minority heating as well as the plasma wall interaction in the tokamak. The ratio of hydrogen to deuterium during the tokamak shot was deduced from the emission spectroscopy measurements during the KSTAR 2009 experimental campaign. Graphite tiles were used for the plasma facing components (PFCs) at KSTAR and its surface area exposed to the plasma was about 11 m2. The data showed that it remained as high as around 50% during the campaign period because graphite tiles were exposed to the air for about two months and the hydrogen contents at the tiles are not fully pumped out due to the lack of baking on the PFC in the 2009 campaign. The validation of the spectroscopy method was checked by using the Zeeman effects and the ratio of hydrogen to the deuterium is compared with results from the residual gas analysis. During the tokamak shot, the ratio is low below 10% initially and saturated after around 1 s. When there is a hydrogen injection to the vessel via ion cyclotron wall conditioning and the boronization process where the carbone is used, the ratio of the hydrogen to the deuterium is increased by up to 100% and it recovers to around 50% after one day of operation. However it does not decrease below 50% at the end of the experimental campaign. It was found that the full baking on the PFC (with a high temperature and sufficient vacuum pumping) is required for the ratio control which guarantees the efficient ICRF heating at the KSTAR 2010 experimental campaign.
Engineering and manufacturing of ITER first mirror mock-ups
Authors: Joanny M. , Travère J. M. , Salasca S. , Corre Y. , Marot L. , Thellier C. , Gallay G. , Cammarata C. , Passier B. , Fermé J. J.
Published: October 2010

Most of the ITER optical diagnostics aiming at viewing and monitoring plasma facing components will use in-vessel metallic mirrors. These mirrors will be exposed to a severe plasma environment and lead to an important tradeoff on their design and manufacturing. As a consequence, investigations are carried out on diagnostic mirrors toward the development of optimal and reliable solutions. The goals are to assess the manufacturing feasibility of the mirror coatings, evaluate the manufacturing capability and associated performances for the mirrors cooling and polishing, and finally determine the costs and delivery time of the first prototypes with a diameter of 200 and 500 mm. Three kinds of ITER candidate mock-ups are being designed and manufactured: rhodium films on stainless steel substrate, molybdenum on TZM substrate, and silver films on stainless steel substrate. The status of the project is presented in this paper.
Fluid-structure interaction of two bodies in an inviscid fluid
Authors: Tchieu A. A. , Crowdy D. , Leonard A.
Published: October 2010

The interaction of two arbitrary bodies immersed in a two-dimensional inviscid fluid is investigated. Given the linear and angular velocities of the bodies, the solution of the potential flow problem with zero circulation around both bodies is reduced to the determination of a suitable Laurent series in a conformally mapped domain that satisfies the boundary conditions. The potential flow solution is then used to determine the force and moment acting on each body by using generalized Blasius formulas. The current formulation is applied to two examples. First, the case of two rigid circular cylinders interacting in an unbounded domain is investigated. The forces on two cylinders with prescribed motion (forced-forced) is determined and compared to previous results for validation purposes. We then study the response of a single “free” cylinder due to the prescribed motion of the other cylinder (forced-free). This forced-free situation is used to justify the hydrodynamic benefits of drafting in aquatic locomotion. In the case of two neutrally buoyant circular cylinders, the aft cylinder is capable of attaining a substantial propulsive force that is the same order of magnitude of its inertial forces. Additionally, the coupled interaction of two cylinders given an arbitrary initial condition (free-free) is studied to show the differences of perfect collisions with and without the presence of an inviscid fluid. For a certain range of collision parameters, the fluid acts to deflect the cylinder paths just enough before the collision to drastically affect the long time trajectories of the bodies. In the second example, the flapping of two plates is explored. It is seen that the interactions between each plate can cause a net force and torque at certain instants in time, but for idealized sinusoidal motions in irrotational potential flow, there is no net force and torque acting at the system center.
A general model for chemical erosion of carbon materials due to low-energy H+ impact
Authors: Liu Shengguang , Sun Jizhong , Dai Shuyu , Stirner Thomas , Wang Dezhen
Published: October 2010

Modeling the chemical erosion of carbon materials due to low-energy H+ impact is of paramount importance for the prediction of the behavior of carbon-based plasma-facing components in nuclear fusion devices. In this paper a simple general model describing both energy and temperature dependence of carbon-based chemical erosion is presented. Enlightened by Hopf’s model {Hopf et al., [J. Appl. Phys. 94, 2373 (2003)}, the chemical erosion is separated into the contributions from three mechanisms: thermal chemical erosion, energetic chemical sputtering, and ion-enhanced chemical erosion. Using input from the Monte Carlo code TRIDYN, this model is able to reproduce experimental data well.
Localization of multidimensional Wigner distributions
Authors: Lieb Elliott H. , Ostrover Yaron
Published: October 2010

A well known result of P. Flandrin states that a Gaussian uniquely maximizes the integral of the Wigner distribution over every centered disk in the phase plane. While there is no difficulty in generalizing this result to higher-dimensional polydisks, the generalization to balls is less obvious. In this note we provide such a generalization.
The applicability of three-dimensional aromaticity in BiSnn− Zintl analogues
Authors: Clayborne Peneé A. , Gupta Ujjwal , Reber Arthur C. , Melko Joshua J. , Khanna Shiv N. , Castleman A. W.
Published: October 2010

Three-dimensional aromaticity is shown to play a role in the stability of deltahedral Zintl clusters and here we examine the connection between aromaticity and stability. In order to gain further insight, we have studied Zintl analogs comprised of bismuth doped tin clusters with photoelectron spectroscopy and theoretical methods. To assign aromaticity, we examine the ring currents induced around the cage by using the nucleus independent chemical shift. In the current study, BiSn4− is a stable cluster and fits aromatic criteria, while BiSn5− is found to fit antiaromatic criteria and has reduced stability. The more stable clusters exhibit an aromatic character which originates from weakly interacting s-states and bonding orbitals parallel to the surface of the cluster, while nonbonding lone pairs perpendicular to the surface of the cluster account for antiaromaticity and reduced stability. The effect of three-dimensional aromaticity on the electronic structure does not result in degeneracies, so the resulting variations in stability are smaller than those seen in conventional aromaticity.
Electronic structures of AlB2-type superconducting YbGa1+xSi1−x alloys probed by NMR and Seebeck coefficient
Authors: Fang C. P. , Lue C. S. , Hsu Y. D. , Kuo Y. K.
Published: October 2010

We report the electronic properties of the AlB2-type compounds YbGa1+xSi1−x (x=0, 0.15, and 0.3) studied by means of the nuclear magnetic resonance (NMR) and the Seebeck coefficient measurements. These materials are of current interest due to the presence of superconductivity with Yb element. From the analysis of G69a NMR spin-lattice relaxation rates, we deduce the Ga 4s partial Fermi level density of states Ns(EF) for these compounds. The result indicates a gradual increase in Ns(EF) with increasing x in YbGa1+xSi1−x. In addition, the evolution of the Seebeck coefficient feature can be understood well within the band-filling scenario. From the Seebeck coefficient analysis, we find that the variation in the total Fermi level density of states N(EF) is not consistent with the trend of superconducting temperature Tc which shows a gradual decrease with Ga content. These observations support the hypothesis that the electronic Fermi level density of states is not the key factor in determining the superconducting transition temperature of YbGa1+xSi1−x.
Biased diffusion in tubes formed by spherical compartments
Authors: Berezhkovskii Alexander M. , Dagdug Leonardo
Published: October 2010

We study the effect of the driving force on Brownian motion of a point particle in a tube formed by identical spherical compartments, which create periodic entropy potential for the motion along the tube axis. The focus is on (i) the effective mobility and diffusion coefficient of the particle as functions of the driving force, (ii) localization of the particle in the central part of the tube induced by the driving force, and (iii) transit time of the particle between the openings connecting neighboring compartments. Some of the results at very small and large driving force are obtained analytically, while the majority of the results are obtained from Brownian dynamics simulations.
Magnetohydrodynamic effects on a charged colloidal sphere with arbitrary double-layer thickness
Authors: Hsieh Tzu H. , Keh Huan J.
Published: October 2010

An analytical study is presented for the magnetohydrodynamic (MHD) effects on a translating and rotating colloidal sphere in an arbitrary electrolyte solution prescribed with a general flow field and a uniform magnetic field at a steady state. The electric double layer surrounding the charged particle may have an arbitrary thickness relative to the particle radius. Through the use of a simple perturbation method, the Stokes equations modified with an electric force term, including the Lorentz force contribution, are dealt by using a generalized reciprocal theorem. Using the equilibrium double-layer potential distribution from solving the linearized Poisson–Boltzmann equation, we obtain closed-form formulas for the translational and angular velocities of the spherical particle induced by the MHD effects to the leading order. It is found that the MHD effects on the particle movement associated with the translation and rotation of the particle and the ambient fluid are monotonically increasing functions of κa, where κ is the Debye screening parameter and a is the particle radius. Any pure rotational Stokes flow of the electrolyte solution in the presence of the magnetic field exerts no MHD effect on the particle directly in the case of a very thick double layer (κa→0). The MHD effect caused by the pure straining flow of the electrolyte solution can drive the particle to rotate, but it makes no contribution to the translation of the particle.
Coexistence of unipolar and bipolar resistive switching characteristics in ZnO thin films
Authors: Lee Seunghyup , Kim Heejin , Park Jinjoo , Yong Kijung
Published: October 2010

This paper reports the coexistence of unipolar and bipolar resistive switching (BRS) in an Ag/ZnO/Pt structure fabricated by sputtering deposition at room temperature. The structure shows reproducible and stable unipolar resistive switching after electroforming with high compliance current (Ic)=40 mA, regardless of the applied voltage polarity. With low Ic=5 mA at electroforming, BRS was also observed; this phenomenon depended on the voltage polarity. Both states were stable and reproducible over 100 cycles. The switching mode was changed with adjusting Ic but the transition was irreversible. Based on the results, switching mechanism based on filament theory is proposed to explain both resistive switching.
Synthesis, magnetic, optical, and electrical transport properties of the nanocomposites of polyaniline with some rare earth chlorides
Authors: Gupta K. , Chakraborty G. , Ghatak S. , Jana P. C. , Meikap A. K. , Babu R
Published: October 2010

Nanocomposites of polyaniline with some rare earth chlorides like neodymium chloride, europium chloride, and dysprosium chloride were synthesized by chemical oxidative polymerization of aniline. Morphological, structural, thermal, optical, magnetic, and electrical properties of the samples were characterized by scanning electron microscope, x-ray diffractometer, Fourier transform infrared spectrometer, thermogravimetric analyzer, differentiating scanning calorimeter, optical absorption spectroscopy, room temperature magnetic susceptibility measurement, and low temperature electrical transport measurement. Nanocomposites were thermally more stable than pure polyaniline and they were more crystalline than pure polyaniline. Magnetic susceptibilities of the samples were field dependent. Three-dimensional variable range hopping charge transport mechanism was followed by the samples. The dc magnetoconductivity of the composites can be explained in terms of forward interference effect and wave function shrinkage effect. dc conductivity of Europium chloride-polyaniline composite shows a transition from forward interference model to wave function shrinkage model. Ac conductivity of the investigated samples can be explained in terms of correlated barrier hopping model. Permittivity of the sample is dominated by the grain boundary behavior in low frequency and by the grain phase in the high frequency and frequency dependence of real part of impedance is explained by Maxwell–Wagner capacitor model.
Spintronic properties of zigzag-edged triangular graphene flakes
Authors: Şahin H. , Senger R. T. , Ciraci S.
Published: October 2010

We investigate quantum transport properties of triangular graphene flakes with zigzag edges by using first principles calculations. Triangular graphene flakes have large magnetic moments which vary with the number of hydrogen atoms terminating its edge atoms and scale with its size. Electronic transmission and current-voltage characteristics of these flakes, when contacted with metallic electrodes, reveal spin valve and remarkable rectification features. The transition from ferromagnetic to antiferromagnetic state under bias voltage can, however, terminate the spin polarizing effects for specific flakes. Geometry and size dependent transport properties of graphene flakes may be crucial for spintronic nanodevice applications.
Influence of the magnetic field annealing on the extrinsic damping of FeCoB soft magnetic films
Authors: Yang Yi , Liu Bailin , Tang Dongming , Zhang Baoshan , Lu Mu , Lu Huaixian
Published: October 2010

In order to investigate the high-frequency damping properties of the ferromagnetic film for the electromagnetic shielding applications, FeCoB films with the thickness of 200 nm were fabricated by the rf magnetron sputtering and subsequently annealed with a static in-plane magnetic field of 2000 Oe under a series of temperatures. The annealed films exhibit excellent soft magnetic and microwave loss properties. The local resonance from the multiphase microstructure and two-magnon scattering at anisotropy inhomogeneities make an additional contribution to the extrinsic damping of the films. As a result, the film annealed at 450 °C achieves a high full width at half maximum Δf up to 6 GHz for the imaginary part of the frequency-dependent permeability. These films could be novel candidates for the electromagnetic shielding applications.
The incorporation of the Cauchy stress matrix tensor in micromagnetic simulations
Authors: Dean J. , Bryan M. T. , Hrkac G. , Goncharov A. , Freeman C. L. , Bashir M. A. , Schrefl T. , Allwood D. A.
Published: October 2010

A method of simulating complex deformational changes of magnetoelastic systems has been developed. This involves incorporation of the complete Cauchy stress matrix tensor into a finite element micromagnetic code. Finite element modeling was used to precompute the stress on each mesh-element in the studied model. This stress-map is then imported into a finite element micromagnetic code to solve the resultant changes in magnetization. The veracity of this method is demonstrated by comparing simulations of the Villari effect and a hybrid piezoelectric-piezomagnetic system to experimental observations.
Preventing optical deactivation of nanocluster Si sensitized Er using nanometer-thin SiNx/SiO2:Er heterolayer thin film
Authors: Kim In Yong , Kim Kyung Joong , Shin Jung H.
Published: October 2010

Multilayer thin films consisting of nanometer-thin, Er-doped luminescent layers (either SiO2:Er or Si3N4:Er) interlaced with nanometer-thin, Si-rich sensitizing layers (either Si-rich oxide or Si-rich nitride) are proposed as a solution to loss of Er3+ optical activity during nanocluster Si (nc-Si) sensitization of Er3+. Comparison of Er3+ photoluminescence (PL) intensities and luminescence lifetimes under both direct, resonant pumping and under nc-Si sensitized pumping shows that by using a heterolayer structure that consists of Si-rich silicon nitride sensitization layers with SiO2:Er luminescing layers, anneal-induced optical deactivation and desensitization of Er3+ that often accompany nc-Si sensitization can be prevented such that the most effective nc-Si sensitization and strongest Er3+ activity can be obtained simultaneously without a compromise between the two. Based on high-resolution transmission electron microscopy and PL spectroscopy, we identify the maintenance of compositional and structural integrity of the heterolayer thin film through the use of nitride layers, and the subsequent maintenance of subnanometer scale spatial separation between nc-Si and Er3+ even after high temperature annealing at 1050 °C as being the critical factors for the observed advantage of the heterostructure.
Spin-dependent transport in a Rashba ring connected to noncollinear ferromagnetic leads
Authors: Chi Feng , Bai Xufang , Huang Ling , Zhao Jia
Published: October 2010

We analyze spin-dependent transport through a quantum ring coupled to two ferromagnetic leads, whose magnetic moments lie in a common plane and form an arbitrary angle with respect to each other. The Rashba spin-orbit (RSO) interaction existed in the ring arms is taken into consideration. We calculate the linear conductance in terms of the Green’s functions method based on the equation of motion technique. It is found that due to the quantum interference effect arising from the RSO-induced spin precession phase factor, the conductance is greatly suppressed when the Fermi energy is aligned to the on-site energies of the ring, where the spin polarization and the tunnel magnetoresistance (TMR) have their maximums. The conductance, spin polarization, and the TMR are monotonously tuned by the relative angle of the leads’ magnetization directions, which shows the typical spin-valve effect. We pay special attention on the situation when one magnetic lead is polarized along z axis while the other one is pointing at x direction. The peak value of the TMR is suppressed now and can become either positive or negative when the on-site energies of the two ring arms are different from each other. This device is realizable with current technology and may practical applications in spintronics.
Four-fold magnetic anisotropy induced by the antiferromagnetic order in FeMn/Co/Cu(001) system
Authors: Chen G. , Li J. , Liu F. Z. , Zhu J. , He Y. , Wu J. , Qiu Z. Q. , Wu Y. Z.
Published: October 2010

Single crystalline FeMn/Co bilayers were grown epitaxially on Cu(001) and investigated by magneto-optic Kerr effect (MOKE). By doing the MOKE measurement within a rotating magnetic field, we were able to retrieve quantitatively the anisotropy constant of the ferromagnetic Co layer. We show unambiguously that as the FeMn layer changes from paramagnetic (PM) to antiferromagnetic (AFM) states, it enhances the interfacial magnetic anisotropy at the FeMn/Co interface by an order of magnitude. A thickness dependent study of the magnetic anisotropy constant revealed that this induced magnetic anisotropy may originate from the FeMn/Co interfacial spin frustration.
Communication: Experimental and theoretical investigations of the effects of the reactant bending excitations in the F+CHD3 reaction
Authors: Czakó Gábor , Shuai Quan , Liu Kopin , Bowman Joel M.
Published: October 2010

The effects of the reactant bending excitations in the F+CHD3 reaction are investigated by crossed molecular beam experiments and quasiclassical trajectory (QCT) calculations using a high-quality ab initio potential energy surface. The collision energy (Ec) dependence of the cross sections of the F+CHD3(vb=0,1) reactions for the correlated product pairs HF(v′)+CD3(v2=0,1) and DF(v′)+CHD2(v4=0,1) is obtained. Both experiment and theory show that the bending excitation activates the reaction at low Ec and begins to inactivate at higher Ec. The experimental F+CHD3(vb=1) excitation functions display surprising peak features, especially for the HF(v′=3)+CD3(v2=0,1) channels, indicating reactive resonances (quantum effects), which cannot be captured by quasiclassical calculations. The reactant state-specific QCT calculations predict that the v5(e) bending mode excitation is the most efficient to drive the reaction and the v6(e) and v5(e) modes enhance the DF and HF channels, respectively.
Analysis of InGaN-delta-InN quantum wells for light-emitting diodes
Authors: Zhao Hongping , Liu Guangyu , Tansu Nelson
Published: October 2010

The design of InGaN-delta-InN quantum wells (QWs) leads to significant redshift for nitride active region with large electron-hole wave function overlap (Γe_hh) and spontaneous emission rate. The analysis was carried out by using self-consistent six-band k⋅p band formalism. The design of active region consisting of 30 Å In0.25Ga0.75N QW with InN delta-layer leads to large Γe_hh of >50% with emission wavelength in the yellow and red spectral regimes, which is applicable for nitride-based light-emitting diodes.
Characterization of a soluble anthradithiophene derivative
Authors: Conrad B. R. , Chan C. K. , Loth M. A. , Parkin S. R. , Zhang X. , DeLongchamp D. M. , Anthony J. E. , Gundlach D. J.
Published: October 2010

The structural and electrical properties of a solution processable material, 2,8-difluoro-5,11-tert-butyldimethylsilylethynyl anthradithiophene (TBDMS), were measured for single crystal transistors. TBDMS is observed to readily form single crystals from physical vapor zone sublimation. A columnar packing crystal structure, with an approximate π/4 radian rotational offset between neighboring molecules, is observed. Single crystal TBDMS transistors display a maximum observed saturation mobility μS of 0.07 cm2/V s, current on-off ratio >107, and subthreshold swing S≈1 dec/V. The spectral current noises of single crystal devices display a 1/f flicker noise, while the metal-semiconductor charge injection barrier is estimated by ultraviolet photoemission spectroscopy.
Integrated silicon optofluidic ring resonator
Authors: Testa Genni , Huang Yujian , Sarro Pasqualina M. , Zeni Luigi , Bernini Romeo
Published: October 2010

The feasibility of an integrated silicon optofluidic ring resonator is demonstrated. Liquid core antiresonant reflecting optical waveguides are used to realize a rectangular ring resonator with a multimode interference liquid core coupler between the ring and the bus waveguide. In this configuration the same waveguide used to confine the light is able to deliver the liquid sample without the need for any additional microfluidics, resulting in a very compact device with a required liquid volume of about 0.11 nl. Optical characterization shows that ring with a good quality factor (Q∼800) can be achieved in good agreement with the numerical results.
GaAs
/
Al
0.15
Ga
0.85
As
terahertz quantum cascade lasers with double-phonon resonant depopulation operating up to 172 K
Authors: Adams Robert W. , Vijayraghavan Karun , Wang Qi Jie , Fan Jonathan , Capasso Federico , Khanna Suraj P. , Davies A. Giles , Linfield Edmund H. , Belkin Mikhail A.
Published: October 2010

We report the design and performance of GaAs/Al0.15Ga0.85As terahertz quantum cascade lasers with double-phonon resonant depopulation and a vertical lasing transition. Devices were processed into gold-clad double-metal waveguides. Lasing at 3 THz was observed up to a heat-sink temperature of 172 K, which compares favorably with the performance of single-phonon resonant depopulation devices based on vertical lasing transitions. These results demonstrate that terahertz quantum cascade lasers based on double-phonon depopulation designs may be a viable alternative to single-phonon depopulation designs for achieving high-temperature operation.
Broad area photonic crystal distributed feedback quantum cascade lasers emitting 34 W at λ∼4.36 μm
Authors: Gökden B. , Bai Y. , Bandyopadhyay N. , Slivken S. , Razeghi M.
Published: October 2010

We demonstrate room temperature, high power, single mode, and diffraction limited operation of a two dimensional photonic crystal distributed feedback quantum cascade laser emitting at 4.36 μm. Total peak power up to 34 W is observed from a 3 mm long laser with 400 μm cavity width at room temperature. Far-field profiles have M2 figure of merit as low as 2.5. This device represents a significant step toward realization of spatially and spectrally pure broad area high power quantum cascade lasers.
Integrated electrical concentration and lysis of cells in a microfluidic chip
Authors: Church Christopher , Zhu Junjie , Huang Guohui , Tzeng Tzuen-Rong , Xuan Xiangchun
Published: October 2010

Lysing cells is an important step in the analysis of intracellular contents. Concentrating cells is often required in order to acquire adequate cells for lysis. This work presents an integrated concentration and lysis of mammalian cells in a constriction microchannel using dc-biased ac electric fields. By adjusting the dc component, the electrokinetic cell motion can be precisely controlled, leading to an easy switch between concentration and lysis of red blood cells in the channel constriction. These two operations are also used in conjunction to demonstrate a continuous concentration and separation of leukemia cells from red blood cells in the same microchannel. The observed cell behaviors agree reasonably with the simulation results.
Thermal mixing of two miscible fluids in a T-shaped microchannel
Authors: Xu Bin , Wong Teck Neng , Nguyen Nam-Trung , Che Zhizhao , Chai John Chee Kiong
Published: October 2010

In this paper, thermal mixing characteristics of two miscible fluids in a T-shaped microchannel are investigated theoretically, experimentally, and numerically. Thermal mixing processes in a T-shaped microchannel are divided into two zones, consisting of a T-junction and a mixing channel. An analytical two-dimensional model was first built to describe the heat transfer processes in the mixing channel. In the experiments, de-ionized water was employed as the working fluid. Laser induced fluorescence method was used to measure the fluid temperature field in the microchannel. Different combinations of flow rate ratios were studied to investigate the thermal mixing characteristics in the microchannel. At the T-junction, thermal diffusion is found to be dominant in this area due to the striation in the temperature contours. In the mixing channel, heat transfer processes are found to be controlled by thermal diffusion and convection. Measured temperature profiles at the T-junction and mixing channel are compared with analytical model and numerical simulation, respectively.
Third generation biosensing matrix based on Fe-implanted ZnO thin film
Authors: Saha Shibu , Gupta Vinay , Sreenivas K. , Tan H. H. , Jagadish C.
Published: October 2010

Third generation biosensor based on Fe-implanted ZnO (Fe-ZnO) thin film has been demonstrated. Implantation of Fe in rf-sputtered ZnO thin film introduces redox center along with shallow donor level and thereby enhance its electron transfer property. Glucose oxidase (GOx), chosen as model enzyme, has been immobilized on the surface of the matrix. Cyclic voltammetry and photometric assay show that the prepared bioelectrode, GOx/Fe-ZnO/ITO/Glass is sensitive to the glucose concentration with enhanced response of 0.326 μA mM−1 cm−2 and low Km of 2.76 mM. The results show promising application of Fe-implanted ZnO thin film as an attractive matrix for third generation biosensing.
C-band electromodulation in silicon–germanium ring and linear devices
Authors: Lim Peng Huei , Cai Jingnan , Ishikawa Yasuhiko , Wada Kazumi
Published: October 2010

We report C-band electromodulation in waveguide-integrated silicon–germanium (SiGe) ring and linear devices. With a 7 V peak-to-peak, 5 MHz sinusoidal input, a waveguide absorption change of 14.9 cm−1 for the linear modulator, and 3.26 cm−1 for the ring were calculated, corresponding to respective modulation depths of 30% and 0.7%. A 2.6×10−5 ring index change was also noted using a technique capable of resolving minute electrorefraction, even with simultaneous electroabsorption and background attenuation. Our results deliver a proof-of-concept for SiGe field-effect devices using optical interference, which may be suitable for high speed and low power optical switches.
Stress-induced Sn Nanowires from Si–Sn Nanocomposite Coatings
Authors: Xiao X. , Sachdev A. K. , Haddad D. , Li Y. , Sheldon B. W. , Soni S. K.
Published: October 2010

The growth of stress-induced tin (Sn) whiskers has been considered responsible for the failure of many electronic devices and many approaches have been developed to mitigate their growth. In this report, however, we describe a simple approach based on the same mechanism to promote the growth of Sn nanowires. The thermal expansion induced stress was utilized as the driving force to initiate the growth of Sn nanowires from Si–Sn phase-separated nanocomposite coatings. The nanostructure of the Si–Sn matrix was the key to controlling the shape and diameter of Sn nanowires. This approach provides additional flexibility for making desirable metallic nanowires with controlled dimensions.
Metastability across the antiferromagnetic–ferromagnetic intermediate phase transition and enhanced giant magnetoresistance in Zn-doped antiperovskite compounds Ga1−xZnxCMn3
Authors: Wang B. S. , Li C. C. , Lin J. C. , Lin S. , Tong P. , Zhu X. B. , Zhao B. C. , Lu W. J. , Yang Z. R. , Song W. H. , Dai J. M. , Sun Y. P.
Published: October 2010

We report the detailed investigations of the magnetic properties, electronic transport, and specific heat in Zn-doped antiperovskite compounds Ga1−xZnxCMn3. Magnetic measurements indicate the metastability of the antiferromagnetic (AFM)–ferromagnetic intermediate (FI) phase transition and the coexistence of different magnetic phases at lower temperature. The enhanced giant magnetoresistance (GMR) is observed with a maximum value of 70% spanning a temperature range of 100 K at 50 kOe. The analysis of heat capacity reveals that the metastability of the AFM–FI transition and the enhanced GMR observed in Ga1−xZnxCMn3 may originate from the reconstruction of Fermi surface accompanying AFM–FI transition.