bluuebunny/crossref_metadata_2025 huggingface dataset:
Interplay of the photovoltaic and photoconductive operation modes in visible-blind photodetectors based on axial p-i-n junction GaN nanowires
Authors: Jacopin G. , De Luna Bugallo A. , Rigutti L. , Lavenus P. , Julien F. H. , Lin Yuan-Ting , Tu Li-Wei , Tchernycheva M.
Published: January 2014

We report on the mixed photovoltaic/photoconductive operation mode of a visible blind photodetector based on GaN nanowires containing a p-i-n junction. The photodetector operates as a photovoltaic device close to zero bias and exhibits a photoconductive gain (>100) for biases above |V| > 2 V. We show that this unusual behavior of a p-i-n photodiode is specific to the case of nanowires. The gain is attributed to the illumination-induced modulation of the width of the depleted region at the nanowire lateral surface allowed because of the specific nanowire geometry with the p-i-n junction orthogonal to the lateral nanowire surface.
Vortex flows induced by drop-like aggregate drift in magnetic fluids
Authors: Ivanov A. S. , Pshenichnikov A. F.
Published: January 2014

The paper reports a new phenomenon—vortex flows in isothermal magnetic fluids in the vicinity of the localized source of magnetic field (magnetized iron sphere) induced by the drift of drop-like aggregates. Although the observed magnetic precipitation of drop-like aggregates resembles an ordinary rainfall in the Earth atmosphere, its origin and nature are quite different. In magnetic fluids this “rain” is induced by the non-uniform magnetic field and occurs at the scale of 1 mm, not at the scale of several kilometers as in the Earth atmosphere. The reason of this phenomenon is that the applied magnetic field initiates phase transition of “gas-liquid” type which is accompanied by formation of condensed phase represented by drop-like aggregates with the characteristic dimension of about tens of micrometers elongated along the field lines. Inhomogeneous spatial distribution of drop-like aggregates leads to deviation of the ponderomotive force, which is responsible for the formation of vortex flows in the fluid. The “rain” is the primary reason for the vortex flows and it lasts until all magnetic particles capable of condensing into drop-like aggregates precipitate at the surface of the condensation core (iron sphere). Thus, vortex flows induced by drop-like aggregate magnetophoresis represent one variant of “gas-liquid” phase transition. Hydrodynamic flows intensify mass transfer in vicinity of magnetic condensation core and considerably speed it up.
Fast contactless vibrating structure characterization using real time field programmable gate array-based digital signal processing: Demonstrations with a passive wireless acoustic delay line probe and vision
Authors: Goavec-Mérou G. , Chrétien N. , Friedt J.-M , Sandoz P. , Martin G. , Lenczner M. , Ballandras S.
Published: January 2014

Vibrating mechanical structure characterization is demonstrated using contactless techniques best suited for mobile and rotating equipments. Fast measurement rates are achieved using Field Programmable Gate Array (FPGA) devices as real-time digital signal processors. Two kinds of algorithms are implemented on FPGA and experimentally validated in the case of the vibrating tuning fork. A first application concerns in-plane displacement detection by vision with sampling rates above 10 kHz, thus reaching frequency ranges above the audio range. A second demonstration concerns pulsed-RADAR cooperative target phase detection and is applied to radiofrequency acoustic transducers used as passive wireless strain gauges. In this case, the 250 ksamples/s refresh rate achieved is only limited by the acoustic sensor design but not by the detection bandwidth. These realizations illustrate the efficiency, interest, and potentialities of FPGA-based real-time digital signal processing for the contactless interrogation of passive embedded probes with high refresh rates.
Equiatomic CoPt thin films with extremely high coercivity
Authors: Varghese Binni , Piramanayagam S. N. , Yang Yi , Kai Wong Seng , Khume Tan Hang , Kiat Lee Wee , Okamoto Iwao
Published: January 2014

In this paper, magnetic and structural properties of near-equiatomic CoPt thin films, which exhibited a high coercivity in the film-normal direction—suitable for perpendicular magnetic recording media applications—are reported. The films exhibited a larger coercivity of about 6.5 kOe at 8 nm. The coercivity showed a monotonous decrease as the film thickness was increased. The transmission electron microscopy images indicated that the as fabricated CoPt film generally consists of a stack of magnetically hard hexagonal-close-packed phase, followed by stacking faults and face-centred-cubic phase. The thickness dependent magnetic properties are explained on the basis of exchange-coupled composite media. Epitaxial growth on Ru layers is a possible factor leading to the unusual observation of magnetically hard hcp-phase at high concentrations of Pt.
Effect of interlayer exchange coupling parameter on switching time and critical current density in composite free layer
Authors: Singh Amritpal , Gupta Subhadra , Kuteifan Majd , Lubarda Marko , Lomakin Vitaliy , Mryasov Oleg
Published: January 2014

We investigated the effect of interlayer exchange coupling parameter on switching current density and switching time in the [CoPt-ML]/Ta/CoFeB composite free layer. The fundamental parameters for the micromagnetic model were extracted from experimental results and ab-initio calculations of the Fe/MgO and Fe/Ta interfaces. We found that the critical current density and switching current decrease with decreasing interlayer exchange coupling. It was observed experimentally that perpendicular magnetic anisotropy (PMA) increases with increasing thickness of Ta insertion due to enhancement of CoFeB/MgO interfacial anisotropy, whereas the interlayer exchange coupling strength decreases. Therefore, our modeling and experimental results indicate that the optimized Ta insertion in the composite layer leads to improved thermal stability via combined interface and bulk anisotropies, lower critical current density, and reduced switching time as compared to the composite layer without Ta insertion.
Fabry-Pérot-multichannel spectrometer tandem for ultra-high resolution Raman spectroscopy
Authors: Rozas Guillermo , Jusserand Bernard , Fainstein Alejandro
Published: January 2014

We present a novel ultra-high resolution Raman spectroscopy technique based in a Fabry-Pérot/triple spectrometer tandem with multichannel acquisition. We describe the system, detail the calibration process, and experimentally test the technique, showing that effective finesses in excess of 1000 are possible. The technique is specifically tailored for low intensity, complex and spectrally extended Raman spectra, providing shorter acquisition times with respect to similar tandem systems with monochannel detectors.
A density functional tight binding/force field approach to the interaction of molecules with rare gas clusters: Application to (C6H6)+/0Arn clusters
Authors: Iftner Christophe , Simon Aude , Korchagina Kseniia , Rapacioli Mathias , Spiegelman Fernand
Published: January 2014

We propose in the present paper a SCC-DFTB/FF (Self-Consistent-Charge Density Functional based Tight Binding/Force-Field) scheme adapted to the investigation of molecules trapped in rare gas environments. With respect to usual FF descriptions, the model involves the interaction of quantum electrons in a molecule with rare gas atoms in an anisotropic scheme. It includes polarization and dispersion contributions and can be used for both neutral and charged species. Parameters for this model are determined for hydrocarbon-argon complexes and the model is validated for small hydrocarbons. With the future aim of studying polycyclic aromatic hydrocarbons in Ar matrices, extensive benchmark calculations are performed on (C6H6)+/0Arn clusters against DFT and CCSD(T) calculations for the smaller sizes, and more generally against other experimental and theoretical data. Results on the structures and energetics (isomer ordering and energy separation, cohesion energy per Ar atom) are presented in detail for n = 1–8, 13, 20, 27, and 30, for both neutrals and cations. We confirm that the clustering of Ar atoms leads to a monotonous decrease of the ionization potential of benzene for n ⩽ 20, in line with previous experimental and FF data.
Atomic state and characterization of nitrogen at the SiC/SiO2 interface
Authors: Xu Y. , Zhu X. , Lee H. D. , Xu C. , Shubeita S. M. , Ahyi A. C. , Sharma Y. , Williams J. R. , Lu W. , Ceesay S. , Tuttle B. R. , Wan A. , Pantelides S. T. , Gustafsson T. , Garfunkel E. L. , Feldman L. C.
Published: January 2014

We report on the concentration, chemical bonding, and etching behavior of N at the SiC(0001)/SiO2 interface using photoemission, ion scattering, and computational modeling. For standard NO processing of a SiC MOSFET, a sub-monolayer of nitrogen is found in a thin inter-layer between the substrate and the gate oxide (SiO2). Photoemission shows one main nitrogen related core-level peak with two broad, higher energy satellites. Comparison to theory indicates that the main peak is assigned to nitrogen bound with three silicon neighbors, with second nearest neighbors including carbon, nitrogen, and oxygen atoms. Surprisingly, N remains at the surface after the oxide was completely etched by a buffered HF solution. This is in striking contrast to the behavior of Si(100) undergoing the same etching process. We conclude that N is bound directly to the substrate SiC, or incorporated within the first layers of SiC, as opposed to bonding within the oxide network. These observations provide insights into the chemistry and function of N as an interface passivating additive in SiC MOSFETs.
Active remote detection of radioactivity based on electromagnetic signatures
Authors: Sprangle P. , Hafizi B. , Milchberg H. , Nusinovich G. , Zigler A.
Published: January 2014

This paper presents a new concept for the remote detection of radioactive materials. The concept is based on the detection of electromagnetic signatures in the vicinity of radioactive material and can enable stand-off detection at distances greater than 100 m. Radioactive materials emit gamma rays, which ionize the surrounding air. The ionized electrons rapidly attach to oxygen molecules forming O2− ions. The density of O2− around radioactive material can be several orders of magnitude greater than background levels. The elevated population of O2− extends several meters around the radioactive material. Electrons are easily photo-detached from O2− ions by laser radiation. The photo-detached electrons, in the presence of laser radiation, initiate avalanche ionization which results in a rapid increase in electron density. The rise in electron density induces a frequency modulation on a probe beam, which becomes a direct spectral signature for the presence of radioactive material.
Novel K rattling: A new route to thermoelectric materials?
Authors: Shoko Elvis , Okamoto Y. , Kearley Gordon J. , Peterson Vanessa K. , Thorogood Gordon J.
Published: January 2014

We have performed ab initio molecular dynamics simulations to study the alkali-metal dynamics in the Al-doped (KAl0.33W1.67O6 and RbAl0.33W1.67O6) and undoped (KW2O6 and RbW2O6) defect pyrochlore tungstates. The K atoms exhibit novel rattling dynamics in both the doped and undoped tungstates while the Rb atoms do not. The KAl0.33W1.67O6 experimental thermal conductivity curve shows an unusual depression between ∼50 K and ∼250 K, coinciding with two crossovers in the K dynamics: the first at ∼50 K, from oscillatory to diffusive, and the second at ∼250 K, from diffusive back to oscillatory. We found that the low-temperature crossover is a result of the system transitioning below the activation energy of the diffusive dynamics, whereas the high-temperature crossover is driven by a complex reconstruction of the local potential around the K atoms due to the cage dynamics. This leads to a hardening of the K potential with increasing temperature. This unusual reconstruction of the potential may have important implications for the interpretation of finite-temperature dynamics based on zero-temperature potentials in similar materials. The key result is that the novel K rattling, involving local diffusion, leads to a significant reduction in the thermal conductivity. We suggest that this may open a new route in the phonon engineering of cage compounds for thermoelectric materials, where the rattlers are specifically selected to reduce the lattice thermal conductivity by the mechanism of local diffusion.
Generation and control of spin-polarized photocurrents in GaMnAs heterostructures
Authors: Bezerra Anibal T. , Castelano Leonardo K. , Degani Marcos H. , Maialle Marcelo Z. , Farinas Paulo F. , Studart Nelson
Published: January 2014

Photocurrents are calculated for a specially designed GaMnAs semiconductor heterostructure. The results reveal regions in the infrared range of the energy spectrum, in which the proposed structure is remarkably spin-selective. For such photon energies, the generated photocurrents are strongly spin-polarized. Application of a relatively small static bias in the growth direction of the structure is predicted to efficiently reverse the spin-polarization for some photon energies. This behavior suggests the possibility of conveniently simple switching mechanisms. The physics underlying the results is studied and understood in terms of the spin-dependent properties emerging from the particular potential profile of the structure.
An analytical model for analyzing the current-voltage characteristics of bulk heterojunction organic solar cells
Authors: Arnab Salman M. , Kabir M. Z.
Published: January 2014

An analytical model for analyzing the current-voltage (J-V) characteristics of bulk heterojunction (BHJ) organic solar cells is developed by incorporating exponential photon absorption, dissociation efficiency of bound electron-hole pairs (EHPs), carrier trapping, and carrier drift and diffusion in the photon absorption layer. Modified Braun's model is used to compute the electric field-dependent dissociation efficiency of the bound EHPs. The charge carrier concentrations and hence the photocurrent are calculated by solving the carrier continuity equation for both holes and electrons in the organic layer. The overall load current is calculated considering the actual solar spectrum and voltage dependent forward dark current. The model is verified by published experimental results. The efficiency of the P3HT:PCBM based solar cells critically depends on the dissociation of bound EHPs. On the other hand, cells made of a blend of the conjugated polymer (PCDTBT) with the soluble fullerene derivative (PCBM) show nearly unity dissociation efficiency, and their cell efficiency strongly depends on the charge collection efficiency. The effects of carrier lifetimes on the performance of PCDTBT solar cells have also been studied. The model is also used to investigate the effect of titanium oxide (TiOx) layer (at the back contact) on the J-V characteristics of PCDTBT solar cells. The results of this paper indicate that improvement of charge carrier transport in PCDTBT:PCBM blend and dissociation of bound EHPs in P3HT:PCBM blend are extremely important to increase the power conversion efficiency of the respective BHJ solar cells.
Computational study on electrical properties of transition metal dichalcogenide field-effect transistors with strained channel
Authors: Harada Naoki , Sato Shintaro , Yokoyama Naoki
Published: January 2014

The performance limits of monolayer transition metal dichalcogenide (TMDC) field-effect transistors (FETs) with isotropic biaxial strain were examined with the “top-of-the-barrier” ballistic MOSFET model. Using a first-principle theory, we calculated the band structures and density of states of strained monolayer MoS2 and WS2, and used the results in model calculations. Introducing strain moves the positions of the conduction band minimum and valence band maximum in k-space with resultant variation in the effective mass and population of carriers. Introducing 2% tensile strain into n-type MoS2 FETs decreases the electron effective mass and, at the same time, increases energy separation between the lower and the higher valleys in the conduction band, resulting in 26% improvement of the ON current up to 1260 A/m. Whereas compressive strain results in complicated effects, −2% strain also improves the ON current by 15%. These results suggest that introducing artificial strain is promising to improve TMDC FET performance.
Engineering of gadofluoroprobes: Broad-spectrum applications from cancer diagnosis to therapy
Authors: Dutta Ranu A. , Sharma Prashant K. , Tiwari Vandana , Tiwari Vivek , Patel Anant B. , Pandey Ravindra , Pandey Avinash C.
Published: January 2014

The engineering of the Gadolinium based nanostructures have been demonstrated in this paper. Nanostructures of α-Gd2S3 exhibit a unique transition between ferromagnetic state and paramagnetic state of the system. It was demonstrated that their properties could be tuned for a wide range of applications ranging from hyperthermia to Magnetic Resonance Imaging, owing to their magnetic moments and large relaxivities. Metallic Gd nanoparticles obtained by reduction method were employed for cancer imaging in mice. The Gd nanoparticles were coated with Curcumin and their biomedical implications in the field of simultaneous diagnosis and therapy of cancer and related diseases has been discussed.
A kinetic model for heterogeneous condensation of vapor on an insoluble spherical particle
Authors: Luo Xisheng , Fan Yu , Qin Fenghua , Gui Huaqiao , Liu Jianguo
Published: January 2014

A kinetic model is developed to describe the heterogeneous condensation of vapor on an insoluble spherical particle. This new model considers two mechanisms of cluster growth: direct addition of water molecules from the vapor and surface diffusion of adsorbed water molecules on the particle. The effect of line tension is also included in the model. For the first time, the exact expression of evaporation coefficient is derived for heterogeneous condensation of vapor on an insoluble spherical particle by using the detailed balance. The obtained expression of evaporation coefficient is proved to be also correct in the homogeneous condensation and the heterogeneous condensation on a planar solid surface. The contributions of the two mechanisms to heterogeneous condensation including the effect of line tension are evaluated and analysed. It is found that the cluster growth via surface diffusion of adsorbed water molecules on the particle is more important than the direct addition from the vapor. As an example of our model applications, the growth rate of the cap shaped droplet on the insoluble spherical particle is derived. Our evaluation shows that the growth rate of droplet in heterogeneous condensation is larger than that in homogeneous condensation. These results indicate that an explicit kinetic model is benefit to the study of heterogeneous condensation on an insoluble spherical particle.
Creating large second-order optical nonlinearity in optical waveguides written by femtosecond laser pulses in boro-aluminosilicate glass
Authors: An Hong-Lin , Arriola Alexander , Gross Simon , Fuerbach Alexander , Withford Michael J. , Fleming Simon
Published: January 2014

The thermal poling technique was applied to optical waveguides embedded in a commercial boro-aluminosilicate glass, resulting in high levels of induced second-order optical nonlinearity. The waveguides were fabricated using the femtosecond laser direct-write technique, and thermally poled samples were characterized with second harmonic optical microscopy to reveal the distribution profile of the induced nonlinearity. It was found that, in contrast to fused silica, the presence of waveguides in boro-aluminosilicate glass led to an enhancement of the creation of the second-order nonlinearity, which is larger in the laser written waveguiding regions when compared to the un-modified substrate. The magnitude of the nonlinear coefficient d33 achieved in the core of the laser-written waveguides, up to 0.2 pm/V, was comparable to that in thermally poled fused silica, enabling the realization of compact integrated electro-optic devices in boro-aluminosilicate glasses.
Two-dimensional imaging of gas-to-particle transition in flames by laser-induced nanoplasmas
Authors: Zhang Yiyang , Li Shuiqing , Ren Yihua , Yao Qiang , Law Chung K.
Published: January 2014

Two-dimensional imaging of gas/particle phase transition of metal oxides in their native high-temperature flow conditions, using laser-driven localized nanoplasmas, was obtained by utilizing the gap between the excitation energies of the gas and particle phases such that only the Ti atoms in the particle phase were selectively excited without detectable Bremsstrahlung background. These in situ images of the particle phase Ti distribution allow the quantitative visualization of the transition of the gas precursors to the nanoparticle phase across the flame sheet as well as diffusion of the particle concentration in the post-flame zone.
Note: Design and construction of a multi-scale, high-resolution, tube-generated X-Ray computed-tomography system for three-dimensional (3D) imaging
Authors: Mertens J. C. E. , Williams J. J. , Chawla Nikhilesh
Published: January 2014

The design and construction of a high resolution modular x-ray computed tomography (XCT) system is described. The approach for meeting a specified set of performance goals tailored toward experimental versatility is highlighted. The instrument is unique in its detector and x-ray source configuration, both of which enable elevated optimization of spatial and temporal resolution. The process for component selection is provided. The selected components are specified, the custom component design discussed, and the integration of both into a fully functional XCT instrument is outlined. The novelty of this design is a new lab-scale detector and imaging optimization through x-ray source and detector modularity.
Multilevel charging and discharging mechanisms of nonvolatile memory devices based on nanocomposites consisting of monolayered Au nanoparticles embedded in a polystyrene layer
Authors: Yeol Yun Dong , Hyun Lee Nam , Seong Kim Hak , Wook Lee Sang , Whan Kim Tae
Published: January 2014

Capacitance-voltage (C-V) curves for Al/Au nanoparticles embedded in a polystyrene (PS) layer/p-Si devices at 300 K showed a metal-insulator-semiconductor behavior with flat-band voltage shifts of the C-V curves due to the existence of charge trapping. Memory windows between 2.6 and 9.9 V were observed at different sweep voltages, indicative of multilevel behavior. Capacitance-time measurements demonstrated that the charge-trapping capability of Au nanoparticles embedded in a PS layer was maintained for retention times larger than 1 × 104 s without significant degradation. The multilevel charging and discharging mechanisms of the memory devices are described on the basis of the experimental results.
Ultrafast laser control of backward superfluorescence towards standoff sensing
Authors: Ariunbold Gombojav O. , Sautenkov Vladimir A. , Rostovtsev Yuri V. , Scully Marlan O.
Published: January 2014

We study infrared backward cooperative emission in a rubidium vapor induced by ultrafast two-photon optical excitations. The laser coherent control of the backward emission is demonstrated by using a pair of 100 fs pulses with a variable time delay. The temporal variation (quantum beat) of the backward beam intensity due to interference of atomic transitions in the rubidium atomic level system 5S-5P-5D is produced and controlled. Based on the obtained experimental results, we discuss possible applications of the developed approach for creation of an effective “guide star” in the sodium atomic layer in the upper atmosphere (mesosphere).
A phononic bandgap shield for high-Q membrane microresonators
Authors: Yu P.-L. , Cicak K. , Kampel N. S. , Tsaturyan Y. , Purdy T. P. , Simmonds R. W. , Regal C. A.
Published: January 2014

A phononic crystal can control the acoustic coupling between a resonator and its support structure. We micromachine a phononic bandgap shield for high Q silicon nitride membranes and study the driven displacement spectra of the membranes and their support structures. We find that inside the observed bandgaps, the density and amplitude of non-membrane modes are greatly suppressed, and membrane modes are shielded from an external mechanical drive by up to 30 dB.
Rapid magnetic wiper featuring biogenic guanine particles: Magnetic non-contact switching of opto-fluidic mirrors featuring biogenic guanine crystals
Authors: Iwasaka M. , Mizukawa Y. , Miyashita Y.
Published: January 2014

In the present study, we prepared a diamagnetic fluid with magnetically controlled visual transparency. Light scattering control by the magnetic orientation of organic and diamagnetic microcrystals was applied for developing a functional diamagnetic fluid, by controlling its turbidity and transparency. The light scattering fluid was prepared by guanine crystal particles suspension (GPS), which were collected from the scales of goldfish, in an aqueous solution. It is revealed that GPS can control light scattering with magnetic fields. The method we developed can be utilized for controlling the visibility of light-reflective objects by using magnetic fields on a millitesla scale.
Molecular dynamics simulation of graphene growth on Ni(100) facet by chemical vapor deposition
Authors: Rasuli R. , Mostafavi Kh. , Davoodi J.
Published: January 2014

We present a molecular dynamics simulation of chemical vapor deposition of graphene. Single layer graphene growth on a Ni (100) facet was studied at different substrate temperatures, C flow rates, and C flow energies. Results show that a single layer graphene film grows through a combined deposition mechanism on a Ni substrate, rather than by surface segregation. These simulations suggest that high quality graphene deposition is theoretically possible on Ni (100) facet under high flux energy.
Hybrid radiosity-SP3 equation based bioluminescence tomography reconstruction for turbid medium with low- and non-scattering regions
Authors: Chen Xueli , Zhang Qitan , Yang Defu , Liang Jimin
Published: January 2014

To provide an ideal solution for a specific problem of gastric cancer detection in which low-scattering regions simultaneously existed with both the non- and high-scattering regions, a novel hybrid radiosity-SP3 equation based reconstruction algorithm for bioluminescence tomography was proposed in this paper. In the algorithm, the third-order simplified spherical harmonics approximation (SP3) was combined with the radiosity equation to describe the bioluminescent light propagation in tissues, which provided acceptable accuracy for the turbid medium with both low- and non-scattering regions. The performance of the algorithm was evaluated with digital mouse based simulations and a gastric cancer-bearing mouse based in situ experiment. Primary results demonstrated the feasibility and superiority of the proposed algorithm for the turbid medium with low- and non-scattering regions.
Two dimensional metallic photonic crystals for light trapping and anti-reflective coatings in thermophotovoltaic applications
Authors: Shemelya Corey , DeMeo Dante F. , Vandervelde Thomas E.
Published: January 2014

We report the development of a front-side contact design for thermophotovoltaics that utilizes metallic photonic crystals (PhCs). While this front-side grid replacement covers more surface area of the semiconductor, a higher percentage of photons is shown to be converted to usable power in the photodiode. This leads to a 30% increase in the short-circuit current of the gallium antimonide thermophotovoltaic cell.
Structural phase transition and erasable optically memorized effect in layered γ-In2Se3 crystals
Authors: Ho Ching-Hwa , Chen Ying-Cen , Pan Chia-Chi
Published: January 2014

We have grown In2Se3 layered-type crystals using chemical vapor transport method with ICl3 as the transport agent. The as-grown crystals show two different color groups of black shiny for α-phase In2Se3 and red to yellow for γ-phase In2Se3. High-resolution transmission electron micro scopy verifies crystalline state and structural polytype of the as-grown In2Se3. The results indicate that the α-In2Se3 crystals present more crystalline states than those of the other amorphous γ-In2Se3. The amorphous effect on the advancing of optoelectronic property of γ-In2Se3 shows erasable optical-memorized effect in the disordered and polycrystalline γ-In2Se3 layers. Laser-induced photodarkening and annealed-recovery test verified that a reversible structural-phase transition of γ↔α can occur inside the γ-In2Se3. Thermoreflectance and Raman scattering measurements are carried out to identify the inter-phase transformation of the γ-In2Se3 polycrystals using different heat treatments. Direct band gaps and Raman vibration modes for the γ- and α-In2Se3 crystalline phases are, respectively, characterized and identified. The character of γ↔α inter-phase transition promotes feasible optical and optoelectronic applications of the γ-In2Se3 material in optical memory, optics, and solar-energy devices.
Polarization converting textures of nematic liquid crystal in glass cavities
Authors: Wang Xiahui , Xu Miao , Ren Hongwen
Published: January 2014

When a nematic liquid crystal (LC) is filled in a glass cavity, the LC molecules present azimuthal orientations in the cavity. If the surface of the cavity is coated with a homeotropic polyimide, then the LC molecules exhibit radial orientations. By treating the LC on one side of the cavity with homogeneous alignment, the former orientations change to a twisted-azimuthal texture, while the latter orientations change to a twisted-radial texture. Both textures are verified experimentally, and they can convert a linearly polarization light to an azimuthal and/or radial polarization light, depending on the polarization direction of the incident light. In contrast to previous approaches, various LC textures can be easily formed in a cavity, and the fabrication procedure is simple. Since the LC texture is confined in a cavity, an array pattern of the texture can be obtained, if the employed substrate has multiple cavities. A LC with twisted-azimuthal and/or twisted-radial textures in a cavity array has potential applications in phase modulation, polarization compensating, sharp focus, and material processing.
The best recovery of Nannochloropsis oculata from the culture broth and effect on content of lipids
Authors: Martínez M. R. , Ulloa G. , Saldívar J. , Beristain R. , Meza-Escalante E. R.
Published: January 2014

Nannochloropsis oculata is an interesting microorganism in the field of marine biotechnology because of its high lipid content. Biodiesel from this microorganism has been demonstrated to be a feasible replacement of petroleum-derived fuels. The effect of pH, flocculant dosage (FeCl3), and cell density has been studied in order to maximize biomass recovery and lipids. A partial factorial design was used to screen the main factors involved in the maximal biomass recovery from the culture broth, indicating that the best harvesting efficiency of 94.2% was obtained at pH 7, 47.6 × 106 of cell density and flocculant dosage of 13 mg FeCl3/l. Oleic acid, palmitic acid, and palmitoleic acid (omega-7) were identified inside the microalgae harvested. Omega-7 fatty acid is five times more potent than omega-3 at lowering triglycerides. The lipids identified had lower degree of unsaturation; this makes microalgal lipids a potential replacement for fossil fuel. 0.76% of reduction in eicosapentaenoic unsaturated fatty acid (EPA) was observed probably due to flocculant addition and that is beneficial for providing an increased lipid stability. In summary, this work is devoted to demonstrate that the optimization of the separation of microalgae from culture broth is mostly dependent on the pH, cell density, and flocculants dosage.
Perfect and robust phase-locking of a spin transfer vortex nano-oscillator to an external microwave source
Authors: Hamadeh A. , Locatelli N. , Naletov V. V. , Lebrun R. , de Loubens G. , Grollier J. , Klein O. , Cros V.
Published: January 2014

We study the synchronization of the auto-oscillation signal generated by the spin transfer driven dynamics of two coupled vortices in a spin-valve nanopillar to an external source. Phase-locking to the microwave field hrf occurs in a range larger than 10% of the oscillator frequency for drive amplitudes of only a few Oersteds. Using synchronization at the double frequency, the generation linewidth is found to decrease by more than five orders of magnitude in the phase-locked regime (down to 1 Hz, limited by the resolution bandwidth of the spectrum analyzer) in comparison to the free running regime (140 kHz). This perfect phase-locking holds for frequency detuning as large as 2 MHz, which proves its robustness. We also analyze how the free running spectral linewidth impacts the main characteristics of the synchronization regime.
Resonant cavity modes of circular plasmonic patch nanoantennas
Authors: Minkowski Fred , Wang Feng , Chakrabarty Ayan , Wei Qi-Huo
Published: January 2014

We present theoretical analysis and numerical studies of cavity modes in circular plasmonic patch nanoantennas. There exist both even and odd cavity modes, while the even cavity modes were often missed in the literature because they can only be excited by oblique illumination. The cavity resonance frequencies are affected by near-field coupling at small periods and by coupling with surface plasmon outside the cavity at large periods. For intermediate periods with non-coupling effects, a simple resonant condition is obtained and validated by numerical simulations to relate the gap plasmon wave number and the effective patch size.
Polycrystalline CVD diamond detector: Fast response and high sensitivity with large area
Authors: Liu Linyue , Ouyang Xiaoping , Zhang Jianfu , Zhang Xianpeng , Zhong Yunhong
Published: January 2014

Polycrystalline diamond was successfully used to fabricate a large area (diameter up to 46 mm) radiation detector. It was proven that the developed detector shows a fast pulsed response time and a high sensitivity, therefore its rise time is lower than 5 ns, which is two times faster than that of a Si-PIN detector of the same size. And because of the large sensitive area, this detector shows good dominance in fast pulsed and low density radiation detection.
Spin transport in benzofurane bithiophene based organic spin valves
Authors: Palosse Mathieu , Séguy Isabelle , Bedel-Pereira Élena , Villeneuve-Faure Christina , Mallet Charlotte , Frère Pierre , Warot-Fonrose Bénédicte , Biziere Nicolas , Bobo Jean-François
Published: January 2014

In this paper we present spin transport in organic spin-valves using benzofurane bithiophene (BF3) as spacer layer between NiFe and Co ferromagnetic electrodes. The use of an AlOx buffer layer between the top electrode and the organic layer is discussed in terms of improvements of stacking topology, electrical transport and oxygen contamination of the BF3 layer. A study of magnetic hysteresis cycles evidences spin-valve behaviour. Transport properties are indicative of unshorted devices with non-linear I-V characteristics. Finally we report a magnetoresistance of 3% at 40 K and 10 mV in a sample with a 50 nm thick spacer layer, using an AlOx buffer layer.
Dynamic Adaptive Policies: A Way to Improve the Cost—Benefit Performance of Megaprojects?
Authors: Yzer Jerrel R , Walker Warren E , Marchau Vincent A W J , Kwakkel Jan H
Published: January 2014

Megaprojects are large, costly, complex infrastructure projects. To assess the financial viability of a megaproject, a cost—benefit analysis (CBA) is usually performed; the results depend upon the accuracy of the cost estimations and the predictive models used to forecast future demand for the use of the infrastructure. The outcomes of the models are very vulnerable to unexpected events. As a result, the CBA may become unreliable and give an unrealistic picture of the financial viability of a project. An alternative way of policy making that tries to take uncertainty into account is the dynamic adaptive policy (DAP) approach. This approach involves a systematic method for designing and implementing a policy over time that is based on a clear set of constraints and objectives and that involves monitoring the environment, gathering information, and adjusting and readjusting to new circumstances. The efficacy of this type of policy making has already been shown, but whether DAP leads to a better cost—benefit performance of megaprojects is unknown. In this paper we focus on answering two research questions: How can CBA be applied to DAP? How good is the cost—benefit performance of megaprojects when using DAP compared with the cost—benefit performance when using the static policy-making approach? In this paper a framework based on real options theory is specified, enabling a CBA to be performed on a dynamic adaptive policy. This framework is then applied to a case involving Schiphol Airport, Amsterdam, to compare the cost—benefit performance of the static policy with the cost—benefit performance using the DAP approach. For this case, the cost—benefit performance of the megaproject under the DAP approach turns out to be better compared with its performance under the static policy. This result provides a first indication that adaptive policies might be able to improve the cost—benefit performance of megaprojects.
Towards a Macroregional Climate Change Adaptation Strategy in the Baltic Sea Region
Authors: Van Well Lisa , Scherbenske Stefanie Lange
Published: January 2014

In this paper we ponder this question: what types of institutional principles would help to establish a macroregional climate change adaptation strategy in the Baltic Sea Region? Inspired by a new institutionalism approach, we trace some of the important elements of regulatory and normative institutional functions. We then discuss how top-down and bottom-up government and governance can contribute to a macroregional climate change adaptation strategy, and profile the local, national, and transnational development efforts that are already underway to facilitate coordination and learning about climate change adaptation in the Baltic Sea Region. Finally, we look at the specific role that a macroregional climate change adaptation strategy has in helping to manage institutional complexity inherent in a multilevel governance context.
Programming Environments: Environmentality and Citizen Sensing in the Smart City
Authors: Gabrys Jennifer
Published: January 2014

A new wave of smart-city projects is underway that proposes to deploy sensorbased ubiquitous computing across urban infrastructures and mobile devices to achieve greater sustainability. But in what ways do these smart and sustainable cities give rise to distinct material—political arrangements and practices that potentially delimit urban ‘citizenship’ to a series of actions focused on monitoring and managing data? And what are the implications of computationally organized distributions of environmental governance that are programmed for distinct functionalities and are managed by corporate and state actors that engage with cities as datasets to be manipulated? In this paper I discuss the ways in which smart-city proposals might be understood through processes of environmentality or the distribution of governance within and through environments and environmental technologies. I do this by working through an early and formative smart-city design proposal, the Connected Sustainable Cities (CSC) project, developed by MIT and Cisco within the Connected Urban Development initiative between 2007 and 2008. Revisiting and reworking Foucault's notion of environmentality in the context of the CSC smart-city design proposal, I advance an approach to environmentality that deals not with the production of environmental subjects, but rather with the specific spatial—material distribution and relationality of power through environments, technologies, and ways of life. By updating and advancing environmentality through a discussion of computational urbanisms, I consider how practices and operations of citizenship emerge that are a critical part of the imaginings of smart and sustainable cities. This reversioning of environmentality through the smart city recasts who or what counts as a ‘citizen’ and attends to the ways in which citizenship is articulated environmentally through the distribution and feedback of monitoring and urban data practices, rather than through governable subjects or populations.
The social reality of blogging and empowerment among Malaysian bloggers
Authors: Ahmad Abdul Latiff , Bromley Michael , Cokley John
Published: January 2014

The study focuses on the issue of empowerment among Malaysian bloggers. In Malaysia, there are issues considered as taboo and are not discussed openly in the mainstream media. The rise of blogs in the earlier part of the 21st century has led to the discovery of a new platform of interaction. Malaysia is unique in the sense that it has its own interpretation of press freedom, a multicultural society and Islam as the official religion. Though there is a general awareness on ‘what is illegal offline, should be illegal online’, there are those who found new freedom in this new realm. The new world of blogosphere is considered as a haven for self-experimentation, discourses and sharing of opinions where it allows individuals to express themselves openly with or without considering the legal, religious or even cultural restrictions. Some people have used the new avenue positively and found empowerment which they would never have found if the blog had never existed while others may take advantage of this new platform for malicious activities. Forty Malaysian bloggers were interviewed during the course of this study where they share their personal blogging experiences and how blogging has brought about changes to their lives.
Fluence et prononciation de phonèmes en L1 et L2
Authors: Vialettes-Basmoreau Lucie , Spanghero-Gaillard Nathalie
Published: January 2014

Learning how to read is an important step in a child’s education. Our longitudinal study focuses on four native English-speaking children going to a French immersion school in the United States, as well as their families. These children learn to read in French, which is a foreign language to them. We aimed at finding out whether their home environment could explain good results in reading in the two languages: English, their mother tongue, and French, the foreign language, as Cummins (1981) suggests. To this end, we measured their performance in reading through their pronunciation and their reading fluency, and we had their family complete a questionnaire about their reading habits at home. The results show that the home environment does seem to play a role in the children’s performance but more generalizations must await further research.
India and its Diaspora: making sense of Hindu identity in South Africa
Authors: Gopal Nirmala Devi , Khan Sultan , Singh Shanta Balgobind
Published: January 2014

Indian immigrants to South Africa in the late nineteenth century differed in terms of their origins, motivations, belief systems, customs, and practices from the indigenous African population as well as from the ruling white settler elite. It is within this context that this paper interrogates some of the ways in which several generations of (Indian) Hindus constructed and continue to (re)construct their religious identities in South Africa. Data for this study were achieved by administering face-to-face questionnaires to 66 individuals in the Metropolitan Area of Durban in KwaZulu-Natal, South Africa. The sample (selected through snowball sampling) comprised third to fifth generation Indians belonging to the four major language groups (Tamil, Telegu, Gujarati, and Hindi) residing in South Africa. Following the questionnaire responses, interviews were conducted with a selected number of respondents from the same sample. Quantitative data were analysed using SPSS while analysis of qualitative data followed a thematic model.
Calpain-mediated proteolysis of tropomodulin isoforms leads to thin filament elongation in dystrophic skeletal muscle
Authors: Gokhin David S. , Tierney Matthew T. , Sui Zhenhua , Sacco Alessandra , Fowler Velia M.
Published: January 2014

Duchenne muscular dystrophy (DMD) induces sarcolemmal mechanical instability and rupture, hyperactivity of intracellular calpains, and proteolytic breakdown of muscle structural proteins. Here we identify the two sarcomeric tropomodulin (Tmod) isoforms, Tmod1 and Tmod4, as novel proteolytic targets of m-calpain, with Tmod1 exhibiting ∼10-fold greater sensitivity to calpain-mediated cleavage than Tmod4 in situ. In mdx mice, increased m-calpain levels in dystrophic soleus muscle are associated with loss of Tmod1 from the thin filament pointed ends, resulting in ∼11% increase in thin filament lengths. In mdx/mTR mice, a more severe model of DMD, Tmod1 disappears from the thin filament pointed ends in both tibialis anterior (TA) and soleus muscles, whereas Tmod4 additionally disappears from soleus muscle, resulting in thin filament length increases of ∼10 and ∼12% in TA and soleus muscles, respectively. In both mdx and mdx/mTR mice, both TA and soleus muscles exhibit normal localization of α-actinin, the nebulin M1M2M3 domain, Tmod3, and cytoplasmic γ-actin, indicating that m-calpain does not cause wholesale proteolysis of other sarcomeric and actin cytoskeletal proteins in dystrophic skeletal muscle. These results implicate Tmod proteolysis and resultant thin filament length misspecification as novel mechanisms that may contribute to DMD pathology, affecting muscles in a use- and disease severity–dependent manner.
The light-induced transcriptome of the zebrafish pineal gland reveals complex regulation of the circadian clockwork by light
Authors: Ben-Moshe Zohar , Alon Shahar , Mracek Philipp , Faigenbloom Lior , Tovin Adi , Vatine Gad D. , Eisenberg Eli , Foulkes Nicholas S. , Gothilf Yoav
Published: January 2014

Light constitutes a primary signal whereby endogenous circadian clocks are synchronized (‘entrained’) with the day/night cycle. The molecular mechanisms underlying this vital process are known to require gene activation, yet are incompletely understood. Here, the light-induced transcriptome in the zebrafish central clock organ, the pineal gland, was characterized by messenger RNA (mRNA) sequencing (mRNA-seq) and microarray analyses, resulting in the identification of multiple light-induced mRNAs. Interestingly, a considerable portion of the molecular clock (14 genes) is light-induced in the pineal gland. Four of these genes, encoding the transcription factors dec1, reverbb1, e4bp4-5 and e4bp4-6, differentially affected clock- and light-regulated promoter activation, suggesting that light-input is conveyed to the core clock machinery via diverse mechanisms. Moreover, we show that dec1, as well as the core clock gene per2, is essential for light-entrainment of rhythmic locomotor activity in zebrafish larvae. Additionally, we used microRNA (miRNA) sequencing (miR-seq) and identified pineal-enhanced and light-induced miRNAs. One such miRNA, miR-183, is shown to downregulate e4bp4-6 mRNA through a 3′UTR target site, and importantly, to regulate the rhythmic mRNA levels of aanat2, the key enzyme in melatonin synthesis. Together, this genome-wide approach and functional characterization of light-induced factors indicate a multi-level regulation of the circadian clockwork by light.