bluuebunny/crossref_metadata_2025 huggingface dataset:
Photoluminescence studies in CuInS2 thin films grown by sulfurization using ditertiarybutylsulfide
Authors: Liu X. H. , Dou X. M. , Sugiyama M.
Published: December 2012

The defect-related levels of CuInS2 thin films prepared by sulfurization using ditertiarybutylsulfide [(t-C4H9)2S:DTBS] have been investigated by photoluminescence (PL) spectroscopy. The PL spectra exhibit four peaks at 1.43, 1.27, 1.21, and 1.17 eV. On the basis of the PL spectra observed at various excitation intensities and temperatures, the peak emissions are attributed to donor–acceptor pair transitions. The ionization energies of donors in CuInS2 thin films are determined to be 66, 330, 300, and 150 meV, and the ionization energies of acceptors are estimated to be 100, 170, and 390 meV, respectively. As a result of the different sulfurization conditions and times, the donors corresponding to these ionization energies are due to indium interstitial (Ini), indium atoms-occupied sulfur vacancies (InS), sulfur atoms-occupied copper vacancies (SCu), and sulfur vacancies (VS), and the acceptors are determined to be due to copper vacancies (VCu), sulfur interstitial (Si), and sulfur atoms-occupied indium vacancies (SIn), respectively. Using these data, a band diagram for the defect levels of CuInS2 thin films has been proposed.
Rebound and jet formation of a fluid-filled sphere
Authors: Killian Taylor W. , Klaus Robert A. , Truscott Tadd T.
Published: December 2012

This study investigates the impact dynamics of hollow elastic spheres partially filled with fluid. Unlike an empty sphere, the internal fluid mitigates some of the rebound through an impulse driven exchange of energy wherein the fluid forms a jet inside the sphere. Surprisingly, this occurs on the second rebound or when the free surface is initially perturbed. Images gathered through experimentation show that the fluid reacts more quickly to the impact than the sphere, which decouples the two masses (fluid and sphere), imparts energy to the fluid, and removes rebound energy from the sphere. The experimental results are analyzed in terms of acceleration, momentum and an energy method suggesting an optimal fill volume in the neighborhood of 30%. While the characteristics of the fluid (i.e., density, viscosity, etc.) affect the fluid motion (i.e., type and size of jet formation), the rebound characteristics remain similar for a given fluid volume independent of fluid type. Implications of this work are a potential use of similar passive damping systems in sports technology and marine engineering.
Melting behavior of Ag14 cluster: An order parameter by instantaneous normal modes
Authors: Tang Ping-Han , Wu Ten-Ming , Hsu P. J. , Lai S. K.
Published: December 2012

This paper studies the melting behavior of Ag14 cluster employing the instantaneous normal mode (INM) analysis that was previously developed for bimetallic cluster Ag17Cu2. The isothermal Brownian-type molecular dynamics simulation is used to generate atom configurations of Ag14 at different temperatures up to 1500 K. At each temperature, these atomic configurations are then analyzed by the INM technique. To delve into the melting behavior of Ag14 cluster which differs from Ag17Cu2 by the occurrence of an anomalous prepeak in the specific heat curve in addition to the typical principal peak, we appeal to examining the order parameter τ(T) defined in the context of the INM method. Two general approaches are proposed to calculate τ(T). In one, τ(T) is defined in terms of the INM vibrational density of states; in another, τ(T) is defined considering the cluster as a rigid body with its rotational motions described by three orthogonal eigenvectors. Our results for Ag14 by these two methods indicate the mutual agreement of τ(T) calculated and also the consistent interpretation of the melting behavior with the specific heat data. The order parameter τ(T) provides in addition an insightful interpretation between the melting of clusters and the concept of broken symmetry which has been found successful in studies of the melting transition of bulk systems.
Biased swimming cells do not disperse in pipes as tracers: A population model based on microscale behaviour
Authors: Bearon R. N. , Bees M. A. , Croze O. A.
Published: December 2012

There is much current interest in modelling suspensions of algae and other micro-organisms for biotechnological exploitation, and many bioreactors are of tubular design. Using generalized Taylor dispersion theory, we develop a population-level swimming-advection-diffusion model for suspensions of micro-organisms in a vertical pipe flow. In particular, a combination of gravitational and viscous torques acting on individual cells can affect their swimming behaviour, which is termed gyrotaxis. This typically leads to local cell drift and diffusion in a suspension of cells. In a flow in a pipe, small amounts of radial drift across streamlines can have a major impact on the effective axial drift and diffusion of the cells. We present a Galerkin method to calculate the local mean swimming velocity and diffusion tensor based on local shear for arbitrary flow rates. This method is validated with asymptotic results obtained in the limits of weak and strong shear. We solve the resultant swimming-advection-diffusion equation using numerical methods for the case of imposed Poiseuille flow and investigate how the flow modifies the dispersion of active swimmers from that of passive scalars. We establish that generalized Taylor dispersion theory predicts an enhancement of gyrotactic focussing in pipe flow with increasing shear strength, in contrast to earlier models. We also show that biased swimming cells may behave very differently to passive tracers, drifting axially at up to twice the rate and diffusing much less.
Investigation of flow features around shallow round cavities subject to subsonic grazing flow
Authors: Marsden Olivier , Bogey Christophe , Bailly Christophe
Published: December 2012

The focus of this work is the study of the asymmetric mean flow which can appear inside shallow cavities of circular planform, and for which limited experimental data is available. To this end, the behaviour of cylindrical cavities in grazing flow is investigated numerically, for varying ratios of diameter to depth. Large-eddy simulations (LESs) of cylindrical cavities of diameter D = 10 cm and depths H ranging from 1 to 10 cm, grazed by a flow at a Mach number 0.25, are reported. The diameter-based Reynolds number of these cavity flows is 600 000. The incoming boundary layer, of thickness δ/D = 0.17, is numerically tripped, in order to reach a highly disturbed state upstream of the cavity. Numerical flow results are compared to experimental findings obtained for similar configurations, and mean flow dependence on the ratio H/D is shown to be correctly reproduced. For cavities of depth greater than 0.7 times their diameter, a symmetric mean flow is obtained, as expected. For shallower cavities, of depth between 0.4 and 0.7 times the diameter, an asymmetric mean flow regime is observed, as previously described in a few experimental papers. Over a small range of depths, from 0.2 to 0.4 times the diameter, very low frequency flow unsteadiness or switching is found. Based on the LES results, a detailed description of these different flow patterns, in terms of both steady and unsteady aspects, is proposed. This description both confirms and adds to the relatively small amount of experimental data available for shallow cylindrical cavity flows.
Local variation of fragility and glass transition temperature of ultra-thin supported polymer films
Authors: Hanakata Paul Z. , Douglas Jack F. , Starr Francis W.
Published: December 2012

Despite extensive efforts, a definitive picture of the glass transition of ultra-thin polymer films has yet to emerge. The effect of film thickness h on the glass transition temperature Tg has been widely examined, but this characterization does not account for the fragility of glass-formation, which quantifies how rapidly relaxation times vary with temperature T. Accordingly, we simulate supported polymer films of a bead-spring model and determine both Tg and fragility, both as a function of h and film depth. We contrast changes in the relaxation dynamics with density ρ and demonstrate the limitations of the commonly invoked free-volume layer model. As opposed to bulk polymer materials, we find that the fragility and Tg do not generally vary proportionately. Consequently, the determination of the fragility profile—both locally and for the film as a whole—is essential for the characterization of changes in film dynamics with confinement.
Electronic structure and characteristics of Fe 3d valence states of Fe1.01Se superconductors under pressure probed by x-ray absorption spectroscopy and resonant x-ray emission spectroscopy
Authors: Chen J. M. , Haw S. C. , Lee J. M. , Chen S. A. , Lu K. T. , Deng M. J. , Chen S. W. , Ishii H. , Hiraoka N. , Tsuei K. D.
Published: December 2012

The electronic structure and characteristics of Fe 3d valence states of iron-chalcogenide Fe1.01Se superconductors under pressure were probed with x-ray absorption spectroscopy and resonant x-ray emission spectroscopy (RXES). The intensity of the pre-edge peak at ∼7112.7 eV of the Fe K-edge x-ray absorption spectrum of Fe1.01Se decreases for pressure from 0.5 GPa increased to 6.9 GPa. The satellite line Kβ′ was reduced in intensity upon applying pressure and became absent for pressure 52 GPa. Fe1.01Se shows a small net magnetic moment of Fe2+, likely arising from strong Fe-Fe spin fluctuations. The 1s3p-RXES spectra of Fe1.01Se at pressures 0.5, 6.9, and 52 GPa recorded at the Fe K-edge reveal that unoccupied Fe 3d states exhibit a delocalized character, stemming from hybridization of Fe 3d and 4p orbitals arising from a local distortion around the Fe atom in a tetrahedral site. Application of pressure causes suppression of this on-site Fe 3d-Fe 4p hybridization, and thereby decreases the intensity of the pre-edge feature in the Fe K-edge absorption spectrum of Fe1.01Se. Compression enhances spin fluctuations at Fe sites in Fe1.01Se and increases the corresponding Tc, through a competition between nearest-neighbor ferromagnetic and next-nearest-neighbor antiferromagnetic superexchange interactions. This result aids our understanding of the physics underlying iron-based superconductors.
First results on disruption mitigation by massive gas injection in Korea Superconducting Tokamak Advanced Research
Authors: Yu Yaowei , Kim Young-Ok , Kim Hak-Kun , Kim Hong-Tack , Kim Woong-Chae , Kim Kwang-Pyo , Son Soo-Hyun , Bang Eun-Nam , Zhuang Huidong , Chen Zhongyong , Hong Suk-Ho , Yoon Si-Woo
Published: December 2012

Massive gas injection (MGI) system was developed on Korea Superconducting Tokamak Advanced Research (KSTAR) in 2011 campaign for disruption studies. The MGI valve has a volume of 80 ml and maximum injection pressure of 50 bar, the diameter of valve orifice to vacuum vessel is 18.4 mm, the distance between MGI valve and plasma edge is ∼3.4 m. The MGI power supply employs a large capacitor of 1 mF with the maximum voltage of 3 kV, the valve can be opened in less than 0.1 ms, and the amount of MGI can be controlled by the imposed voltage. During KSTAR 2011 campaign, MGI disruptions are carried out by triggering MGI during the flat top of circular and limiter discharges with plasma current 400 kA and magnetic field 2–3.5 T, deuterium injection pressure 39.7 bar, and imposed voltage 1.1–1.4 kV. The results show that MGI could mitigate the heat load and prevent runaway electrons with proper MGI amount, and MGI penetration is deeper under higher amount of MGI or lower magnetic field. However, plasma start-up is difficult after some of D2 MGI disruptions due to the high deuterium retention and consequently strong outgassing of deuterium in next shot, special effort should be made to get successful plasma start-up after deuterium MGI under the graphite first wall.
Translocation of stiff polymers through a nanopore driven by binding particles
Authors: Yu Wancheng , Ma Yiding , Luo Kaifu
Published: December 2012

We investigate the translocation of stiff polymers in the presence of binding particles through a nanopore by two-dimensional Langevin dynamics simulations. We find that the mean translocation time shows a minimum as a function of the binding energy ɛ and the particle concentration ϕ, due to the interplay of the force from binding and the frictional force. Particularly, for the strong binding the translocation proceeds with a decreasing translocation velocity induced by a significant increase of the frictional force. In addition, both ɛ and ϕ have a notable impact on the distribution of the translocation time. With increasing ɛ and ϕ, it undergoes a transition from an asymmetric and broad distribution under the weak binding to a nearly Gaussian one under the strong binding, and its width becomes gradually narrower.
A setup for resonant inelastic soft x-ray scattering on liquids at free electron laser light sources
Authors: Kunnus Kristjan , Rajkovic Ivan , Schreck Simon , Quevedo Wilson , Eckert Sebastian , Beye Martin , Suljoti Edlira , Weniger Christian , Kalus Christian , Grübel Sebastian , Scholz Mirko , Nordlund Dennis , Zhang Wenkai , Hartsock Robert W. , Gaffney Kelly J. , Schlotter William F. , Turner Joshua J. , Kennedy Brian , Hennies Franz , Techert Simone , Wernet Philippe , Föhlisch Alexander
Published: December 2012

We present a flexible and compact experimental setup that combines an in vacuum liquid jet with an x-ray emission spectrometer to enable static and femtosecond time-resolved resonant inelastic soft x-ray scattering (RIXS) measurements from liquids at free electron laser (FEL) light sources. We demonstrate the feasibility of this type of experiments with the measurements performed at the Linac Coherent Light Source FEL facility. At the FEL we observed changes in the RIXS spectra at high peak fluences which currently sets a limit to maximum attainable count rate at FELs. The setup presented here opens up new possibilities to study the structure and dynamics in liquids.
Sensitivity of transport and stability to the current profile in steady-state scenario plasmas in DIII-D
Authors: Turco F. , Holcomb C. T. , Ferron J. R. , Luce T. C. , Politzer P. A. , Park J. M. , White A. E. , Brennan D. P. , Turnbull A. D. , Hanson J. M. , Okabayashi M. , In Y.
Published: December 2012

Recent experiments on DIII-D have provided the first systematic data on the impact of the current profile on the transport and stability properties of high-performance, steady-state scenario plasmas. In a future tokamak, to achieve 100% noninductive conditions and produce net power, the current profile J must be sustained by a large fraction of bootstrap current JBS, which is nonlinearly coupled with the kinetic profiles. Systematic scans of qmin and q95 were performed to determine empirically the best alignment of the noninductive currents with J and the variation of the transport properties with q. Transport analysis indicates that χe and χi are sensitive to the details of J in a way that makes the pressure profile peaking and JBS scale nonlinearly with both q and β in the experiment. Drift wave stability analysis yields linear growth rates that do not reproduce experimental trends in χ with qmin and q95. At high beta, necessary to maximize fBS, the plasma duration is often limited by n=1 tearing modes, whose stability also depends on the J profile. Broadly deposited electron cyclotron (EC) current at mid-radius was found to supply part of the required noninductive current and to positively affect the tearing stability. The modes appear when JEC is turned off for stable cases and always appear when the EC deposition is shifted outwards. The variation in the EC scan results is consistent with PEST3 calculations, showing that the tearing stability becomes extremely sensitive to small perturbations of the equilibrium in wall-stabilized plasmas run close to the ideal MHD limit. These modeling results are being used to design new experiments with higher ideal and tearing limits. A new capability for off-axis neutral beam injection system will be used to explore higher qmin scenarios and different current alignments.
Generation of shock/discontinuity compound structures through magnetic reconnection in the geomagnetic tail
Authors: Weng C. J. , Lin C. C. , Lee L. C. , Chao J. K.
Published: December 2012

We use 1-D hybrid code to simulate the generation and evolution of MHD discontinuities associated with magnetic reconnection in a current sheet. It is found that the leakage of slow shock (SS) downstream particles to upstream region tends to increase the ion parallel temperature and temperature anisotropy with βi||/βi⊥≫1, where βi||(βi⊥) is the ion parallel (perpendicular) beta. As a result, the propagation speed of rotational discontinuity (RD) is highly reduced and RD becomes attached to SS, leading to formation of various compound structures in the reconnection outflow region. Four types of compound structure are found in our simulations: (a) RD-SS compound structure: the RD is attached to the leading part of SS, (b) SS-RD (DD) compound structure: RD is attached to the rear part of SS, (c) SS-RD-SS compound structure: RD is trapped inside SS, and (d) switch-off slow shock (SSS) with a rotational wave train. The type of compound structure generated depends on initial ion beta βi0 and magnetic shear angle ϕ. RD tends to move in front of SS to form an RD-SS compound structure for cases with low βi0. RD stays behind SS and form an SS-RD (DD) compound structure for large βi0. The SS-RD-SS compound structure is formed for intermediate values of βi0. When the shear angle is 180°, SSS with a wave train is formed.
Group velocity of extraordinary waves in superdense magnetized quantum plasma with spin-1/2 effects
Authors: Li Chunhua , Wu Zhengwei , Ren Haijun , Yang Weihong , Chu Paul K.
Published: December 2012

Based on the one component plasma model, a new dispersion relation and group velocity of elliptically polarized extraordinary electromagnetic waves in a superdense quantum magnetoplasma are derived. The group velocity of the extraordinary wave is modified due to the quantum forces and magnetization effects within a certain range of wave numbers. It means that the quantum spin-1/2 effects can reduce the transport of energy in such quantum plasma systems. Our work should be of relevance for the dense astrophysical environments and the condensed matter physics.
Current ramp-up with lower hybrid current drive in EAST
Authors: Ding B. J. , Li M. H. , Fisch N. J. , Qin H. , Li J. G. , Wilson J. R. , Kong E. H. , Zhang L. , Wei W. , Li Y. C. , Wang M. , Xu H. D. , Gong X. Z. , Shen B. , Liu F. K. , Shan J. F. ,   EAST Team
Published: December 2012

More economical fusion reactors might be enabled through the cyclic operation of lower hybrid current drive. The first stage of cyclic operation would be to ramp up the plasma current with lower hybrid waves alone in low-density plasma. Such a current ramp-up was carried out successfully on the EAST tokamak. The plasma current was ramped up with a time-averaged rate of 18 kA/s with lower hybrid (LH) power. The average conversion efficiency Pel/PLH was about 3%. Over a transient phase, faster ramp-up was obtained. These experiments feature a separate measurement of the L/R time at the time of current ramp up.
The modulational instability in the extended Hasegawa-Mima equation with a finite Larmor radius
Authors: Gallagher S. , Hnat B. , Connaughton C. , Nazarenko S. , Rowlands G.
Published: December 2012

The effects of the finite Larmor radius on the generation of zonal flows by the four-wave modulational instability are investigated using an extended form of the Hasegawa-Mima equation. Growth rates of the zonal mode are quantified using analytical predictions from a four-mode truncated model, as well as from direct numerical simulation of the nonlinear extended Hasegawa-Mima equation. We not only consider purely zonal flows but also examine the generic oblique case and show that, for small Larmor radii, off-axis modes may become dominant. We find a key parameter Mρ which characterises the behaviour of the system due to changes in the Larmor radius. We find that, similarly to previous results obtained by changing the driving wave amplitude, two separate dynamical regimes can be accessed. These correspond to oscillatory energy transfer between zonal flows and a driving wave and the fully saturated zonal flow.
Direct observation of substitutional Ga after ion implantation in Ge by means of extended x-ray absorption fine structure
Authors: Decoster S. , Johannessen B. , Glover C. J. , Cottenier S. , Bierschenk T. , Salama H. , Kremer F. , Temst K. , Vantomme A. , Ridgway M. C.
Published: December 2012

We present an experimental lattice location study of Ga atoms in Ge after ion implantation at elevated temperature (250°C). Using extended x-ray absorption fine structure (EXAFS) experiments and a dedicated sample preparation method, we have studied the lattice location of Ga atoms in Ge with a concentration ranging from 0.5 at. % down to 0.005 at. %. At Ga concentrations ≤0.05 at.%, all Ga dopants are substitutional directly after ion implantation, without the need for post-implantation thermal annealing. At higher Ga concentrations, a reduction in the EXAFS amplitude is observed, indicating that a fraction of the Ga atoms is located in a defective environment. The local strain induced by the Ga atoms in the Ge matrix is independent of the Ga concentration and extends only to the first nearest neighbor Ge shell, where a 1% contraction in bond length has been measured, in agreement with density functional theory calculations.
Effects of Be doping on InP nanowire growth mechanisms
Authors: Yee R. J. , Gibson S. J. , Dubrovskii V. G. , LaPierre R. R.
Published: December 2012

Be-doped InP nanowires were grown by the gold-assisted vapour-liquid-solid mechanism in a gas source molecular beam epitaxy system. The InP nanowire length versus diameter [L(D)] dependence revealed an unexpected transition with increasing Be dopant concentration. At Be dopant concentration below ∼1018 cm−3, nanowires exhibited the usual inverse L(D) relationship, indicating a diffusion-limited growth regime. However, as dopant concentration increased, the nanowire growth rate was suppressed for small diameters, resulting in an unusual L(D) dependence that increased before saturating in height at about 400 nm. The cause of this may be a change in the droplet chemical potential, introducing a barrier to island nucleation. We propose a model accounting for the limitations of diffusion length and monolayer nucleation to explain this behaviour.
Sensitivity study of ignition capsule implosion performance on the hard x-ray spectral distribution of hohlraum
Authors: Gu Jianfa , Zou Shiyang , Li Yongsheng , Dai Zhensheng , Ye Wenhua
Published: December 2012

The paper investigates theoretically the sensitivities of ignition capsule implosion performance on the hard x-ray spectral distribution of hohlraum. In the simulation, the hohlraum radiation is represented by a Planckian spectrum for the main drive plus a gaussian bump centered at energy Ec for preheating x-rays. Simulation results show that with the increasing of center energy Ec, the Atwood number at the fuel-ablator interface increases rapidly due to the preheating and expanding of the inner undoped CH layer. The growing of Atwood number indicates the hydrodynamic instability (HI) growth and mixing at this interface. On the other hand, the increasing of Ec results in a large density gradient scale length of ablation front and stabilizes the HI growth at ablation front. The changes of the hard x-ray spectrum have significant influences on other important implosion parameters including the ablator mass remaining, shock timing, implosion velocity, and yield as well. High-precision results on the hard x-ray spectral distribution of hohlraum are thus critical for optimizing the ignition capsule design to limit the HI growth.
Fluid equations in the presence of electron cyclotron current drive
Authors: Jenkins Thomas G. , Kruger Scott E.
Published: December 2012

Two-fluid equations, which include the physics imparted by an externally applied radiofrequency source near electron cyclotron resonance, are derived in their extended magnetohydrodynamic forms using the formalism of Hegna and Callen [Phys. Plasmas 16, 112501 (2009)]. The equations are compatible with the closed fluid/drift-kinetic model developed by Ramos [Phys. Plasmas 17, 082502 (2010); 18, 102506 (2011)] for fusion-relevant regimes with low collisionality and slow dynamics, and they facilitate the development of advanced computational models for electron cyclotron current drive-induced suppression of neoclassical tearing modes.
Dust-acoustic shock waves in a charge varying electronegative magnetized dusty plasma with suprathermal electrons
Authors: Tribeche Mouloud , Bacha Mustapha
Published: December 2012

The combined effects of an oblique magnetic field and electron suprathermality on weak dust-acoustic (DA) waves in a charge varying electronegative dusty plasmas with application to the Halley Comet are investigated. The correct suprathermal electron charging current is derived based on the orbit-motion limited approach. A weakly nonlinear analysis is carried out to derive a Korteweg-de Vries-Burger equation. The electron suprathermality, the obliqueness, and magnitude of the magnetic field are found to modify the dispersive properties of the DA shock structure. Our results may aid to explain and interpret the nonlinear oscillations that may occur in the Halley Comet plasma.
Coherent microwave radiation from a laser induced plasma
Authors: Shneider M. N. , Miles R. B.
Published: December 2012

We propose a method for generation of coherent monochromatic microwave/terahertz radiation from a laser-induced plasma. It is shown that small-scale plasma, located in the interaction region of two co-propagating plane-polarized laser beams, can be a source of the dipole radiation at a frequency equal to the difference between the frequencies of the lasers. This radiation is coherent and appears as a result of the so-called optical mixing in plasma.
Development of high-power gyrotrons with gradually tapered cavity
Authors: Chaojun Lei , Sheng Yu , Xinjian Niu , Yinghui Liu , Hongfu Li , Xiang Li
Published: December 2012

In high power gyrotrons, the parasitic modes coupled with the operating mode cannot be avoided in the beam-wave interaction. These parasitic modes will decrease the efficiency of the gyrotrons. The purity of the operating mode affected by different tapers should be carefully studied. The steady-state self-consistent nonlinear theory for gyrotron with gradually tapered cavity is developed in this paper. A steady-state calculation code including “cold cavity” and “hot cavity” is designed. By comparison, a time-domain model analysis of gyrotron operation is also studied by particle-in-cell (PIC). It is found that the tapers of gyrotron have different influences on the modes coupling between the operating mode and the parasitic modes. During the study, an example of 94 GHz gyrotron with pure operating mode TE03 has been designed. The purity of the operating mode in the optimized cavity is up to −77 dB, and in output waveguide of the cavity is up to −76 dB. At the same time, the beam-wave interaction in the designed cavity has been simulated, too. An output power of 120 kW, corresponding to 41.6% efficiency and an oscillation frequency of 94.099 GHz have been achieved with a 50 kV, 6 A helical electron beam at a guiding magnetic field of 3.5485 T. The results show that the power in spurious modes of the optimized cavity may be kept far below than that of the traditional tapered cavity.
Electrically modulated photoluminescence in ferroelectric liquid crystal
Authors: Ganguly Prasun , Joshi T. , Singh S. , Haranath D. , Biradar A. M.
Published: December 2012

Electrical modulation and switching of photoluminescence (PL) have been demonstrated in pure deformed helix ferroelectric liquid crystal (DHFLC) material. The PL intensity increases and peak position shifts towards lower wavelength above a threshold voltage which continues up to a saturation voltage. This is attributed to the helix unwinding phenomenon in the DHFLC on the application of an electric field. Moreover, the PL intensity could be switched between high intensity (field-on) and low intensity (field-off) positions. These studies would add a new dimension to ferroelectric liquid crystal's application in the area of optical devices.
Efficient focalization of antisymmetric Lamb waves in gradient-index phononic crystal plates
Authors: Zhao Jinfeng , Marchal Rémi , Bonello Bernard , Boyko Olga
Published: December 2012

The focalization of elastic waves within a two dimensional gradient-index phononic crystal (GRIN PC) is numerically and experimentally investigated. The structure is formed by a square lattice of air holes in a silicon plate with transverse variation of holes’ diameters. The geometry and efficiency of focalization are computed with a finite element method. A non-contact laser-ultrasonic technique is used both to excite flexural Lamb waves and to monitor in situ the displacements field within the GRIN PC. The efficient subwavelength focusing is achieved and analyzed; furthermore, we describe the oscillatory behavior of focusing and show the relationship between the responses of waves in GRIN PC and the source intensity.
Stochastic switching asymmetry in magnetoresistive stacks due to adjacent nanowire stray field
Authors: Bryan M. T. , Porter N. A. , Claydon J. S. , Bashir M. A. , Burnell G. , Marrows C. H. , Schrefl T. , Allwood D. A.
Published: December 2012

Giant-magnetoresistance was used to measure the switching of patterned multilayer stacks either close to or removed from a ferromagnetic nanowire. Stray fields from the nanowire greatly changed the stack's free layer hysteresis characteristics. Four distinct switching modes were observed when the applied field opposed the pinned layer magnetization, but reproducible switching occurred otherwise. Micromagnetic modeling suggested that the asymmetry was due to interlayer stray field interactions and the Oersted field from the measuring current, while the switching modes were due to transverse components from the nanowire stray field. The results demonstrate the feasibility of remote electrical detection of nanowire magnetization.
Epitaxial growth of (111)-oriented LaAlO3/LaNiO3 ultra-thin superlattices
Authors: Middey S. , Meyers D. , Kareev M. , Moon E. J. , Gray B. A. , Liu X. , Freeland J. W. , Chakhalian J.
Published: December 2012

The epitaxial stabilization of a single layer or superlattice structures composed of complex oxide materials on polar (111) surfaces is severely burdened by the reconstructions at the interface that commonly arise to neutralize the polarity. We report on the synthesis of high quality LaNiO3/mLaAlO3 pseudo cubic (111) superlattices on polar (111)-oriented LaAlO3, the proposed complex oxide candidate for a topological insulating behavior. Comprehensive X-Ray diffraction measurements, reflection high energy electron diffraction, and element specific resonant X-ray absorption spectroscopy affirm their high structural and chemical quality. The study offers an opportunity to fabricate interesting interface and topology controlled (111)-oriented superlattices based on ortho-nickelates.
Efficiency enhancement in mesogenic-phthalocyanine-based solar cells with processing additives
Authors: Duy Dao Quang , Hori Tetsuro , Fukumura Kaoru , Masuda Tetsuya , Kamikado Toshiya , Fujii Akihiko , Shimizu Yo , Ozaki Masanori
Published: December 2012

Bulk heterojunction (BHJ) solar cells, fabricated by spin casting processes, with phase-separated small molecules including a phthalocyanine derivative, 1,4,8,11,15,18,22,25-octahexylphthalocyanine (C6PcH2), and a fullerene derivative, 1-(3-methoxy-carbonyl)-propyl-1-1-phenyl-(6,6)C61 (PCBM), have been demonstrated to have a power conversion efficiency exceeding 4.1%. The C6PcH2:PCBM BHJ surface morphology and the phase separation have been controlled by utilizing processing additives in various solvents. The effects of the processing additives on the crystallization of the discotic C6PcH2 columns in hexagonal structures have been discussed.
Reconfigurable assemblies of active, autochemotactic gels
Authors: Dayal Pratyush , Kuksenok Olga , Balazs Anna C.
Published: December 2012

Using computational modeling, we show that self-oscillating Belousov–Zhabotinsky (BZ) gels can both emit and sense a chemical signal and thus drive neighboring gel pieces to spontaneously self-aggregate, so that the system exhibits autochemotaxis. To the best of our knowledge, this is the closest system to the ultimate self-recombining material, which can be divided into separated parts and the parts move autonomously to assemble into a structure resembling the original, uncut sample. We also show that the gels’ coordinated motion can be controlled by light, allowing us to achieve selective self-aggregation and control over the shape of the gel aggregates. By exposing the BZ gels to specific patterns of light and dark, we design a BZ gel “train” that leads the movement of its “cargo.” Our findings pave the way for creating reconfigurable materials from self-propelled elements, which autonomously communicate with neighboring units and thereby actively participate in constructing the final structure.
Synapse-specific and size-dependent mechanisms of spine structural plasticity accompanying synaptic weakening
Authors: Oh Won Chan , Hill Travis C. , Zito Karen
Published: December 2012

Refinement of neural circuits in the mammalian cerebral cortex shapes brain function during development and in the adult. However, the signaling mechanisms underlying the synapse-specific shrinkage and loss of spiny synapses when neural circuits are remodeled remain poorly defined. Here, we show that low-frequency glutamatergic activity at individual dendritic spines leads to synapse-specific synaptic weakening and spine shrinkage on CA1 neurons in the hippocampus. We found that shrinkage of individual spines in response to low-frequency glutamate uncaging is saturable, reversible, and requires NMDA receptor activation. Notably, shrinkage of large spines additionally requires signaling through metabotropic glutamate receptors (mGluRs) and inositol 1,4,5-trisphosphate receptors (IP
3
Rs), supported by higher levels of mGluR signaling activity in large spines. Our results support a model in which signaling through both NMDA receptors and mGluRs is required to drive activity-dependent synaptic weakening and spine shrinkage at large, mature dendritic spines when neural circuits undergo experience-dependent modification.
Liquid transport facilitated by channels in
Bacillus subtilis
biofilms
Authors: Wilking James N. , Zaburdaev Vasily , De Volder Michael , Losick Richard , Brenner Michael P. , Weitz David A.
Published: December 2012

Many bacteria on earth exist in surface-attached communities known as biofilms. These films are responsible for manifold problems, including hospital-acquired infections and biofouling, but they can also be beneficial. Biofilm growth depends on the transport of nutrients and waste, for which diffusion is thought to be the main source of transport. However, diffusion is ineffective for transport over large distances and thus should limit growth. Nevertheless, biofilms can grow to be very large. Here we report the presence of a remarkable network of well-defined channels that form in wild-type
Bacillus subtilis
biofilms and provide a system for enhanced transport. We observe that these channels have high permeability to liquid flow and facilitate the transport of liquid through the biofilm. In addition, we find that spatial variations in evaporative flux from the surface of these biofilms provide a driving force for the flow of liquid in the channels. These channels offer a remarkably simple system for liquid transport, and their discovery provides insight into the physiology and growth of biofilms.
Mfge8 suppresses airway hyperresponsiveness in asthma by regulating smooth muscle contraction
Authors: Kudo Makoto , Khalifeh Soltani S. M. Amin , Sakuma Stephen A. , McKleroy William , Lee Ting-Hein , Woodruff Prescott G. , Lee Jae Woo , Huang Katherine , Chen Chun , Arjomandi Mehrdad , Huang Xiaozhu , Atabai Kamran
Published: December 2012

Airway obstruction is a hallmark of allergic asthma and is caused primarily by airway smooth muscle (ASM) hypercontractility. Airway inflammation leads to the release of cytokines that enhance ASM contraction by increasing ras homolog gene family, member A (RhoA) activity. The protective mechanisms that prevent or attenuate the increase in RhoA activity have not been well studied. Here, we report that mice lacking the gene that encodes the protein Milk Fat Globule-EGF factor 8 (
Mfge8
−/−
) develop exaggerated airway hyperresponsiveness in experimental models of asthma.
Mfge8
−/−
ASM had enhanced contraction after treatment with IL-13, IL-17A, or TNF-α. Recombinant Mfge8 reduced contraction in murine and human ASM treated with IL-13. Mfge8 inhibited IL-13–induced NF-κB activation and induction of RhoA. Mfge8 also inhibited rapid activation of RhoA, an effect that was eliminated by an inactivating point mutation in the RGD integrin-binding site in recombinant Mfge8. Human subjects with asthma had decreased Mfge8 expression in airway biopsies compared with healthy controls. These data indicate that Mfge8 binding to integrin receptors on ASM opposes the effect of allergic inflammation on RhoA activity and identify a pathway for specific inhibition of ASM hypercontractility in asthma.
Humean Rationality
Authors: Smith Michael
Published: December 2012

This article focuses on the relationship between reasons and rationality. It begins by explaining how Hume is led to his (grotesque) conclusion. The explanation lies in his view that the concepts of reason and rationality are best explained by reference to their relations in the theoretical domain, specifically in the domain of deductive reasoning. It then considers how Hume's conclusion might be avoided. The issue, to anticipate, is whether, once the understandings of the terms “reason” and “rationality” are liberalized in the way required to take a more sensible view about the nature of reason and rationality in the theoretical domain, there is a stable position left to take in the practical domain that retains anything of the spirit of Hume's remarks.
Bayesianism
Authors: Joyce James M.
Published: December 2012

This article is concerned with Bayesian epistemology. Bayesianism claims to provide a unified theory of epistemic and practical rationality based on the principle of mathematical expectation. In its epistemic guise, it requires believers to obey the laws of probability. In its practical guise, it asks agents to maximize their subjective expected utility. This article explains the five pillars of Bayesian epistemology, each of which claims and evaluates some of the justifications that have been offered for them. It also addresses some common objections to Bayesianism, in particular the “problem of old evidence” and the complaint that the view degenerates into an untenable subjectivism. It closes by painting a picture of Bayesianism as an “internalist” theory of reasons for action and belief that can be fruitfully augmented with “externalist” principles of practical and epistemic rationality.
Rationality and Game Theory
Authors: Bicchieri Cristina
Published: December 2012

This article on rationality and game theory deals with the modeling of interaction between decision makers. Game theory aims to understand situations in which decision makers interact. Chess is an example of such interaction, as are firms competing for business, politicians competing for votes, jury members deciding on a verdict, animals fighting over prey, bidders competing in auctions, threats and punishments in long-term relationships, and so on. What all these situations have in common is that the outcome of the interaction depends on what the parties jointly do. Rationality assumptions and equilibrium play are the basic ingredients of game theory. The main focus of this article is on the relationship between rationality assumptions and equilibrium play.
Motivated Irrationality
Authors: Mele Alfred R.
Published: December 2012

The literature on motivated irrationality has two primary foci: action and belief. This article explores two of the central topics falling under this rubric: akratic action (action exhibiting so-called weakness of will or deficient self-control) and motivationally biased belief (including self-deception). Among other matters, this article offers a resolution of Donald Davidson's worry about the explanation of irrationality. When agents act akratically, they act for reasons, and in central cases, they make rational judgments about what it is best to do. The rationality required for that is in place. However, to the extent to which their actions are at odds with these judgments, they act irrationally. Motivationally biased believers test hypotheses and believe on the basis of evidence. Again there is a background of rationality. But owing to the influence of motivation, they violate general standards of epistemic rationality.
Rationality and Psychology
Authors: Samuels Richard , Stich Stephen P.
Published: December 2012

This article explores the debate over the extent to which ordinary human reasoning and decision making is rational. It starts by detailing some key experimental findings from the heuristics and biases tradition and describes a range of pessimistic claims about the rationality of ordinary people that these and related findings are sometimes taken to support. Such pessimistic interpretations of the experimental findings have not gone unchallenged, however, and one of the most sustained and influential critiques come from evolutionary psychology. This article outlines some of the research on reasoning that has been done by evolutionary psychologists and describes a cluster of more optimistic theses about ordinary reasoning that such psychologists defend. Although this article states that the most dire pronouncements made by writers in the heuristics and biases tradition are unwarranted, it also maintains that the situation is rather more pessimistic than sometimes suggested by evolutionary psychologists.
Legal Theory and the Rational Actor
Authors: Finkelstein Claire
Published: December 2012

The application of rational actor theory to the law has been dominated by the law and economics movement. Law and economics began as a methodology for approaching legal questions; this combiation suggested using the tools provided by economic theory to solve problems in manifestly economic fields like antitrust and taxation. But it quickly moved beyond methodology to acquire both a normative and a descriptive thesis of its own. Law and economics thus regards law as a vehicle for maximizing utility, and it maintains that much of law can be explained as serving that function already. This article suggests reasons why laws that maximize social utility are not necessarily the best legal rules for individuals that seek to maximize their personal utility. In particular, it suggests that ideally rational individuals would be unlikely to select the principle of utility maximization as the basis for choosing ideal legal rules.
The Study of New York Government
Authors: Benjamin Gerald
Published: December 2012

Six of New York's nine constitutional conventions occurred before the turn of the twentieth century. The New York constitution mandated in 1848 that a referendum be held every twenty years on whether a state convention should be held. One result of the governing processes defined in the state constitution is the public record that offers the basis for professional analysis and commentary on New York State government. Columbia University—and therefore New York State—was the American birthplace of the academic study of state government. The development of university-based public opinion polling organizations has a major impact on the study of state government and politics. This book assumes that governmental structure and institutions are the shaping factors in governance. It therefore tries to demonstrate how and why New York is governed.
Lobbying and the Interest Group System
Authors: Adler Norman , Gyory Bruce N.
Published: December 2012

This article explores the lobbying industry and how it has changed within the interest group system in New York. New York is known for its activist government. It has also a bipartisan tradition of commitment to social justice and willingness to undertake programmatic experimentation. New York State's two major parties appear never to engage in the type of lobbying activity that would require them to register. It is noted that interest groups and their lobbyists spend a great deal of time both fashioning coalitions and trying to ensure that notice is taken of these coalitions. Proposed reforms could influence lobbying and perhaps even aim at shifting that lightening rod of public opinion away from the legislature to the lobbying community. Lobbying in New York has become an integrated component of the transmission system within the engine of state government.
The Judiciary and Judicial Reform
Authors: Salkin Patricia E. , Lavine Amy
Published: December 2012

This article describes the judiciary and judicial reform in New York. Reform has been ongoing, and in recent years the courts in New York have evolved into a unified system to manage better, among other things, the volume of cases, physical infrastructure, and human resources. The administrative board plays a mostly advisory role; many of the chief judge's responsibilities have in practice been delegated to the chief administrator. The court of appeals is responsible for appointing the state board of law examiners and establishing regulations for the admission of attorneys to practice law in the State of New York. The court of appeals has also become embroiled in nonfiscal issues that have major political dimensions and are arguably better resolved through the legislative process.
New York State and the National Government
Authors: Lefkowitz Joel
Published: December 2012

This article addresses the national government of New York State. New York State policy and institutional innovations, and the state's role in sectional alliances and conflict, influenced other states and national politics from the beginning, as did New Yorkers in the three branches of the national government. New Yorkers and New York initiated political institutions and articulated related political ideas that sometimes spread to other states and to national politics. New Yorkers had the most effect in the executive branch from the late nineteenth century through the New Deal. Supreme Court consideration of New York State laws set the stage for major constitutional changes. The purposes, methods, and magnitude of New York's power have varied over time and across different institutions. In recent years, New York gives more than it gets, and has a diminished role in the federal system.
New York in Fiscal Federalism
Authors: Ward Robert B.
Published: December 2012

This article explores New York State's dollars-and-cents relationship with Washington and the nation in the context of broad changes over time in the respective fiscal roles of Washington and the states. The 1970s brought what many participants and observers called the “New Federalism,” in which Washington provided “more fiscal aid on a more flexible basis to state and local governments in the form of revenue sharing and block grants.” Furthermore, it turns to a description of broad fiscal policies and trends in the Empire State itself. Seeking new federal funding is a basic part of annual budget strategy. Federal funding was a significant source of assistance for cities in the 1970s, but has not kept pace with growth in overall budgets since then. Issues of federalism will continue to produce important impacts on the scope, nature, cost, and quality of public services in New York and the nation.