bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of substrate type and quality on carrier mobility in graphene nanoribbons
Authors: Poljak M. , Suligoj T. , Wang K. L.
Published: August 2013

We report the results of a thorough numerical study on carrier mobility in graphene nanoribbons (GNRs) with the widths from ∼250 nm down to ∼1 nm, with a focus on the influence of substrate type (SiO2, Al2O3, HfO2, and h-BN) and substrate quality (different interface impurity densities) on GNR mobility. We identify the interplay between the contributions of Coulomb and surface optical phonon scattering as the crucial factor that determines the optimum substrate in terms of carrier mobility. In the case of high impurity density (∼1013 cm−2), we find that HfO2 is the optimum substrate irrespective of GNR width. In contrast, for low impurity density (1010 cm−2), h-BN offers the greatest enhancement, except for nanoribbons wider than ∼200 nm for which the mobility is highest on HfO2.
Parametric design criteria of an irreversible vacuum thermionic generator
Authors: Wang Yuan , Su Shanhe , Lin Bihong , Chen Jincan
Published: August 2013

A new model of the vacuum thermionic generator (TIG) including internal and external irreversible heat losses is proposed. The energy balance equations of the cathode and anode of the TIG are used to determine the operating temperatures of two electrode plates. Analytic expressions for the power output and efficiency of the system are derived. The power output and efficiency under different conditions are optimized. The effects of the work functions of electrode materials and the output voltage on the performance of the system are discussed. The optimal regions of several important parameters are determined. The optimum design criteria, which may provide some guidance for the choice of electrode materials and the operation of the TIG, are obtained.
Terahertz surface plasmons excitation by nonlinear mixing of lasers in over ultrathin metal film coated dielectric
Authors: Kumar Pawan , Tripathi V. K.
Published: August 2013

An ultrathin metal film deposited on dielectric plate supports low loss THz surface plasma wave (SPW). The SPW field falls off away from the metal film both inside the dielectric as well as in free space. Two lasers normally incident, from free space on the planar structure, exert a difference frequency ponderomotive force on the free electrons of the film and resonantly excite THz SPW. The ratio of SPW amplitude to lasers is 10−3 at laser intensity of 3 × 1012 W/cm2 at 1 μ m wavelength. The growth rate falls monotonically because at higher frequency the coupling of SPW is weak.
Grain boundary and triple junction constraints during martensitic transformation in shape memory alloys
Authors: Ueland Stian M. , Schuh Christopher A.
Published: August 2013

We investigate the role of grain constraint upon martensitic transformation through in situ scanning electron microscope tensile experiments on shape memory microwires with a small number of grains and grain junctions. The martensite transformation morphology becomes more complex with increasing grain constraint: In unconstrained monocrystalline regions, the transformation is simple, single variant, and complete; near grain boundaries, the transformation is only partial, containing regions of untransformed austenite; near a triple junction, the morphology is complex, the transformation is partial and also multi-variant. These observations speak of transformation-induced stress concentrations that are more severe around triple junctions than around grain boundaries. Finite element modeling also provides an estimate for constraint effects on martensitic transformation yielding higher stresses near triple junctions than near grain boundaries. Towards the goal of developing polycrystalline Cu-based shape memory alloys that avoid intergranular fracture, our results support three design objectives: (1) Removal of triple junctions, (2) reduction of the total grain boundary area, and (3) geometry design containing unconstrained regions where the transformation can be most easily accommodated.
Measurement of the effect of plasmon gas oscillation on the dielectric properties of p- and n-doped AlxGa1−xN films using infrared spectroscopy
Authors: Rahbany N. , Kazan M. , Tabbal M. , Tauk R. , Jabbour J. , Brault J. , Damilano B. , Massies J.
Published: August 2013

We report on the application of infrared (IR) spectroscopy as an approach to nondestructive optical method for quantitative measurement of relevant optoelectronic properties in complex multilayer systems. We developed a numerical technique to analyze quantitatively the dielectric properties and plasmon gas characteristics from infrared reflectivity measurements. The developed technique is based on the combination of Kramers-Kronig theorem with the classical theory of electromagnetic wave propagation in a system of thin films. We applied the approach to deduce the dielectric properties and plasmon gas characteristics in p- and n-doped AlGaN alloys of various compositions, deposited on AlN(100 nm)/GaN(30 nm)/Al2O3. The results agreed with the electrical measurements, and the back calculation reproduced satisfactory the reflectivity measurements, demonstrating the accuracy of the developed technique.
Aspect ratio and radius ratio dependence of flow pattern driven by differential rotation of a cylindrical pool and a disk on the free surface
Authors: Wu Chun-Mei , Li You-Rong , Ruan Deng-Fang
Published: August 2013

The aspect ratio and radius ratio dependence of the flow pattern driven by the differential rotation of a cylindrical pool and a disk on the free surface is investigated through a series of unsteady three-dimensional numerical simulations. The aspect ratio, which is defined as the height to the radius ratio of the pool, varies from 0.06 to 2.0 and the radius ratio of the disk to the cylindrical pool varies from 0.15 to 0.9. The rotation Reynolds numbers of the pool and disk range from 0 to 4730 and 0 to −5677, respectively, where the minus sign means the rotation direction of the disk is contrary to that of the cylindrical pool. The results show that the basic flow state is axisymmetric and steady but has rich structures at the meridian plane depending on the aspect and radius ratios. With the increase of the rotation Reynolds number, the flow transits to three-dimensional oscillatory flow, characterized by the velocity fluctuation waves traveling in the counter-clockwise or clockwise direction at different aspect ratios. The corresponding wave number and angular velocity of the fluctuation wave dependent on the aspect ratio are discussed. In addition, the flow characteristics also show an important dependence on the radius ratio. Various polygonal flow patterns are presented varying with the radius ratio and rotation Reynolds numbers. The fluctuation wave number decreases with the increase of the disk rotation Reynolds number, and the shear layer induced by the counter-rotation of the disk and pool is responsible for producing this flow instability.
Development of high-speed and wide-angle visible observation diagnostics on Experimental Advanced Superconducting Tokamak using catadioptric optics
Authors: Yang J. H. , Yang X. F. , Hu L. Q. , Zang Q. , Han X. F. , Shao C. Q. , Sun T. F. , Chen H. , Wang T. F. , Li F. J. , Hu A. L.
Published: August 2013

A new wide-angle endoscope for visible light observation on the Experimental Advanced Superconducting Tokamak (EAST) has been recently developed. The head section of the optical system is based on a mirror reflection design that is similar to the International Thermonuclear Experimental Reactor-like wide-angle observation diagnostic on the Joint European Torus. However, the optical system design has been simplified and improved. As a result, the global transmittance of the system is as high as 79.6% in the wavelength range from 380 to 780 nm, and the spatial resolution is <5 mm for the full depth of field (4000 mm). The optical system also has a large relative aperture (1:2.4) and can be applied in high-speed camera diagnostics. As an important diagnostic tool, the optical system has been installed on the HT-7 (Hefei Tokamak-7) for its final experimental campaign, and the experiments confirmed that it can be applied to the investigation of transient processes in plasma, such as ELMy eruptions in H-mode, on EAST.
Enhanced electrostricitive properties and thermal endurance of textured (Bi0.5Na0.5)TiO3–BaTiO3–(K0.5Na0.5)NbO3 ceramics
Authors: Hao Jigong , Ye Chenggen , Shen Bo , Zhai Jiwei
Published: August 2013

Textured 0.92(Bi0.5Na0.5)TiO3–0.06BaTiO3–0.02(K0.5Na0.5)NbO3 (BNT–BT–KNN) ceramics have been produced by tape casting with pure-phase (Bi0.5Na0.5)TiO3 templates. Through the approach of texture construction, enhanced electrostrictive response was obtained with an electrostrictive coefficient Q33 (∼0.024 m4/C2 at 60 kV/cm) and good thermostability comparable with that of traditional Pb-based electrostrictors. Even at an electric-field as low as 35 kV/cm or at a temperature as high as 180 °C, samples still possess a large electrostrictive response with Q33 > 0.022 m4/C2, suggesting it is very promising for practical applications as a lead-free electrostrictive material owning to its wide usage range. Moreover, reducing the applied electric-filed or increasing temperature can both induce the predominant to pure electrostriction transition due to the little contributions of electrostriction strain from ferroelectric domain switching. Our work may provide a new recipe for designing high-performance BNT-based lead-free electrostrictive materials by means of texture construction.
Observation of orientation-dependent photovoltaic behaviors in aligned organic nanowires
Authors: Oh Joon Hak , Helena Wong Lydia , Yu Hojeong , Park Young Jun , Min Kim Jong , Bao Zhenan
Published: August 2013

We fabricated organic nanowire (NW) solar cells based on aligned NWs of n-channel organic semiconductor, N,N′-bis(2-phenylethyl)-perylene-3,4:9,10-tetracarboxylic diimide via a filtration-and-transfer alignment method. It is well known that most efficient charge transport typically takes place along the long axis of organic NWs. However, there is no systematic study on the correlation between the orientation of NWs in the active layer and the power conversion efficiency (PCE) of solar cells. Our results demonstrate the effects of alignment direction of NWs on the PCE of organic solar cells with single-crystalline NWs.
Phase locking of a 3.4 THz third-order distributed feedback quantum cascade laser using a room-temperature superlattice harmonic mixer
Authors: Hayton D. J. , Khudchenko A. , Pavelyev D. G. , Hovenier J. N. , Baryshev A. , Gao J. R. , Kao T. Y. , Hu Q. , Reno J. L. , Vaks V.
Published: August 2013

We report on the phase locking of a 3.4 THz third-order distributed feedback quantum cascade laser (QCL) using a room temperature GaAs/AlAs superlattice diode as both a frequency multiplier and an internal harmonic mixer. A signal-to-noise level of 60 dB is observed in the intermediate frequency signal between the 18th harmonic of a 190.7 GHz reference source and the 3433 GHz QCL. A phase-lock loop with 7 MHz bandwidth results in QCL emission that is 96% locked to the reference source. We characterize the QCL temperature and electrical tuning mechanisms and show that frequency dependence of these mechanisms can prevent phase-locking under certain QCL bias conditions.
Monolithically grown multi-color InAs quantum dots as a spectral-shape-controllable near-infrared broadband light source
Authors: Ozaki Nobuhiko , Takeuchi Koichi , Ohkouchi Shunsuke , Ikeda Naoki , Sugimoto Yoshimasa , Oda Hisaya , Asakawa Kiyoshi , Hogg Richard A.
Published: August 2013

We have grown monolithic multi-color InAs quantum dots (QDs) for use as a near-infrared (NIR) broadband light source. Our previously developed rotational metal mask enables selective-area growth of QD ensembles with emission peak wavelengths controlled by strain-reducing layers thicknesses, varying the emission approximately 1.2–1.3 μm. The peak shift value was up to 120 nm, and a combined 160-nm-bandwidth emission spectrum was achieved. Further, the emission spectra shapes were controlled using specific optical excitation powers for each QD ensemble. These results demonstrate the effectiveness of multi-color QDs as a spectrum-shape-controllable NIR broadband light source, particularly suited for optical coherence tomography.
The effect of stair case electron injector design on electron overflow in InGaN light emitting diodes
Authors: Zhang F. , Li X. , Hafiz S. , Okur S. , Avrutin V. , Özgür Ü. , Morkoç H. , Matulionis A.
Published: August 2013

Effect of two-layer (In0.04Ga0.96N and In0.08Ga0.92N) staircase electron injector (SEI) on quantum efficiency of light-emitting-diodes (LEDs) in the context of active regions composed of single and quad 3 nm double heterostructures (DHs) is reported. The experiments were augmented with the first order model calculations of electron overflow percentile. Increasing the two-layer SEI thickness from 4 + 4 nm up to 20 + 20 nm substantially reduced, if not totally eliminated, the electron overflow in single DH LEDs at low injections without degrading the material quality evidenced by the high optical efficiency observed at 15 K and room temperature. The improvement in quad 3 nm DH LEDs with increasing SEI thickness is not so pronounced as the influence of SEI is less for thicker active regions, which in and of themselves necessarily thermalize the carriers.
Understanding the origin of the S-curve in conjugated polymer/fullerene photovoltaics from drift-diffusion simulations
Authors: Finck B. Y. , Schwartz B. J.
Published: August 2013

We utilize drift-diffusion modeling to investigate the cause of S-shaped current-voltage curves in organic solar cells. We find that even a many order-of-magnitude mismatch of the carrier mobilities is insufficient to generate S-shaped J-V curves. Instead, S-shaped J-V curves result when a sigmoid-shaped electron mobility profile is entered into the calculation. This suggests that S-curves in bulk heterojunction photovoltaics are caused by factors that affect the extraction of electrons near the device cathode. Such factors could include surface recombination, partially blocking contacts caused by interfacial layers, or vertical phase separation of the fullerenes away from the cathode interface.
Tuning multiple Fano and plasmon resonances in rectangle grid quasi-3D plasmonic-photonic nanostructures
Authors: Wang Daqian , Yu Xinglong , Yu Qiuming
Published: August 2013

Plasmonic and photonic nanostructures can manipulate light-matter interaction, leading to a wide range of tunable properties. Here, we show that multiple Fano and plasmon resonances can be generated in quasi-3D plasmonic nanostructure arrays on rectangle grid photonic nanostructure substrates. The Fano resonances are the quasiguided modes coupled with the plasmon resonance while the distinct plasmon resonances are the localized surface plasmon resonances of the top gold thin film with sub-wavelength nanohole array and the bottom gold nanodisk array. The Fano and plasmon resonances can be tuned separately and selectively by changing the dimension of photonic and plasmonic nanostructures.
Large exciton g-factors in anisotropically strained A-plane GaN film measured using magneto-optical Kerr effect spectroscopy
Authors: Arora Ashish , Hatui Nirupam , Bhattacharya Arnab , Ghosh Sandip
Published: August 2013

Exciton Landé g-factors in wurtzite GaN epitaxial films with (0001) C-plane and (112¯0) A-plane orientations have been measured in magnetic fields B up to 1.8 T, using polar magneto-optical Kerr effect (MOKE) spectroscopy. A procedure is developed for extracting the Zeeman splitting and thereby the g-factor, from Kerr ellipticity and rotation spectra of A-plane films, which have in-plane polarization anisotropy. In the C-plane film the measured g-factors for the A, B, and C exciton transitions were gA=0.09±0.02, gB=0.74±0.05, and gC=3.9±0.2, respectively, with B∥c-axis and comparable to earlier reports. The MOKE spectra of the A-plane film have one dominant exciton feature each for analyzer axis ⊥ and ∥ to the c-axis of GaN, and they arise at different energies. The measured g-factors for these were much larger, with values g⊥c=4.7±1 and g||c=7.1±1.2 with B⊥c-axis. Comparison with a k·p perturbation theory based calculation, which included the influence of strain, indicates that the features in the A-plane film are associated with exciton transitions involving bands that are strongly mixed by the anisotropic in-plane strain.
The formation mechanisms and optical characteristics of GaSb quantum rings
Authors: Lin Wei-Hsun , Wang Kai-Wei , Liao Yu-An , Pao Chun-Wei , Lin Shih-Yen
Published: August 2013

The growth mechanisms and optical characteristics of GaSb quantum rings (QRs) are investigated. Although As-for-Sb exchange is the mechanism responsible for the dot-to-ring transition, significant height difference between GaSb quantum dots (QDs) and QRs in a dot/ring mixture sample suggests that the dot-to-ring transition is not a spontaneous procedure. Instead, it is a rapid transition procedure as long as it initiates. A model is established to explain this phenomenon. Larger ring inner diameters and heights of the sample with longer post Sb soaking time suggest that As-for-Sb exchange takes places in both vertical and lateral directions. The decreasing ring densities, enlarged ring inner/outer diameters and eventually flat GaSb surfaces observed with increasing growth temperatures are resulted from enhanced adatom migration and As-for-Sb exchange with increasing growth temperatures.
Weak morphology dependent valence band structure of boron nitride
Authors: Zhi Chunyi , Ueda Shigenori , Zeng Haibo , Wang Xuebin , Tian Wei , Wang Xi , Bando Yoshio , Golberg Dmitri
Published: August 2013

We report a hard X-ray photoelectron spectroscopy (HX-PES) investigation on valence band structure of Boron Nitrides (BN) having different morphologies, including nanosheets, nanotubes, and micro-sized particles. Very weak morphology/valence band structure dependence was observed. For each case, the B-N π-band overlapping with σ-band between 0 to −12.5 eV and the s-band below −15 eV were identified. No obvious morphology-induced band shifts and intensity variations were observed. First-principles calculations based on density functional theory were performed and the results were compared with the experimental data. This theoretical analysis well explains the weak morphology dependent valence band spectra of BN nanomaterials obtained during HX-PES measurements.
On the spatial inhomogeneity of charge generation and collection in inverted all polymer solar cells
Authors: Perulli A. , Lattante S. , Persano A. , Cola A. , Di Giulio M. , Anni M.
Published: August 2013

Simultaneous photoluminescence (PL) and external quantum efficiency (EQE) confocal mapping is used to investigate the correlation between the local PL and the EQE in a regioregular poly(3-exylthiophene):poly(9,9-dioctylfluorene-co-benzothiadiazole) inverted bulk heterojunction solar cell. We show that the charge generation and charge collection are strongly non-uniform on a length scale up to 100 μm. Our results evidence that organic solar cells optimization requires not only the control of the submicrometric active materials arrangement but also the control of the large scale device uniformity.
Pi-gate tunneling field-effect transistor charge trapping nonvolatile memory based on all tunneling transportation
Authors: Jhan Yi-Ruei , Wu Yung-Chun , Lin Hsin-Yi , Hung Min-Feng
Published: August 2013

This work demonstrates the feasibility of a charge-trapping nonvolatile memory based on Pi-gate polycrystalline silicon tunneling field-effect transistor, which has a silicon-oxide-nitride-oxide-silicon structure. Both the conducting current and the program/erase operations are based on quantum tunneling. In addition to a large threshold voltage shift of 4.7 V when Vg of 17 V is applied for only 1 ms, the proposed nonvolatile memory exhibits superior endurance of 88% after 104 P/E cycles. Moreover, only 35% of its initial charges are lost after ten years at a high temperature of 85 °C.
Alloy enhanced anisotropy in the thermal conductivity of SixGe1−x nanowires
Authors: Li Wu , Mingo Natalio
Published: August 2013

A strong dependence on crystalline orientation with a most conductive ⟨001⟩ growth direction is theoretically predicted for the thermal conductivity (κ) of SixGe1−x nanowires, even above room temperature and above 1 μm thickness. For instance, the room temperature κ of a 100 nm thick Si0.6Ge0.4 nanowire in the ⟨001⟩ direction is 16% higher than in the ⟨111⟩ direction. In contrast, the dependence for Si or Ge nanowires of the same diameter is much weaker at the same temperature, and ⟨111⟩ direction can be the most conductive one at relatively thin nanowires. In the low temperature limit, the anisotropy of κ can reach 87% at any alloy concentration. The anisotropy arises from the phonon focusing effect on the long mean free path phonons. The low frequency phonons focus in the ⟨001⟩ direction, while the intermediate frequency phonons focus in the ⟨111⟩ direction. The relative contribution to κ from the low frequency phonons is largely enhanced by alloying. Moreover, alloying eliminates the anisotropy caused by the intermediate frequency phonons. Our results imply that orientation has to be taken into account when engineering alloyed nanowire devices, such as thermoelectric modules, even if the corresponding bulk material is completely isotropic.
Direct observation of carrier delocalization in highly conducting polyaniline
Authors: Unuma Takeya , Yamada Naruki , Nakamura Arao , Kishida Hideo , Lee Seung-Chul , Hong Eun-Young , Lee Suck-Hyun , Kwon O-Pil
Published: August 2013

We investigate the complex conductivity spectra σ̃(ω) of doped polyaniline, prepared as a typical conjugated polymer with various dc electrical conductivities up to 1000 S/cm, by using terahertz transmission spectroscopy. With the increase in dc conductivity, the imaginary part of σ̃(ω) is found to definitely change its sign from negative to positive throughout the measured frequency range. This shows that the optoelectronic nature of carriers in conducting polyaniline shifts from the localized regime to the delocalized regime. The real and imaginary parts of σ̃(ω) can be simultaneously reproduced by an extended Drude model, giving the degrees of carrier (de)localization.
Ultrafast and low temperature laser annealing for crystalline TiO2 nanostructures patterned by electro-hydrodynamic lithography
Authors: Cha SeungNam , Lee Suok , Eun Jang Jae , Jang Arang , Pyo Hong Jin , Lee Jaejong , Inn Sohn Jung , Joon Kang Dae , Min Kim Jong
Published: August 2013

Direct patterning of inorganic materials based on electro-hydrodynamic lithography (EHL) has attracted tremendous attentions as next generation soft-lithography technologies owing to its simple and cost-effective process. We show that the EHL technique based nanoscale inorganic pattern transfer coupled with ultrafast laser annealing is suitable for obtaining nanostructured TiO2 over a large area with great fidelity. The laser annealing technique enables us to overcome a technical issue of EHL associated with long processing time and high annealing temperature. We further demonstrated the enhanced switching performance by using the laser annealed TiO2 layer as an electron transport layer in the electro-chromic device.
Electrostatic formation of liquid marbles and agglomerates
Authors: Liyanaarachchi K. R. , Ireland P. M. , Webber G. B. , Galvin K. P.
Published: August 2013

We report observations of a sudden, explosive release of electrostatically charged 100 μm glass beads from a particle bed. These cross an air gap of several millimeters, are engulfed by an approaching pendant water drop, and form a metastable spherical agglomerate on the bed surface. The stability transition of the particle bed is explained by promotion of internal friction by in-plane electrostatic stresses. The novel agglomerates formed this way resemble the “liquid marbles” formed by coating a drop with hydrophobic particles. Complex multi-layered agglomerates may also be produced by this method, with potential industrial, pharmaceutical, environmental, and biological applications.
Buckling characterizations of an individual multi-walled carbon nanotube: Insights from quantitative in situ transmission electron microscope nanoindentation and molecular dynamics
Authors: Tsai Ping-Chi , Jeng Yeau-Ren , Huang Yu-Xian , Wu Kuan-Te
Published: August 2013

Nanomechanics and real-time buckling deformation of an individual multi-walled carbon nanotube (MWCNT) were investigated through in situ nanoindentation within a transmission electron microscope (TEM). These in situ observations reveal a significant shell-to-Euler phase transformation in the buckling response of the nanotube. Objective evidences that the MWCNT possesses time-dependent characteristic were first suggested by combining in situ TEM nanoindentation performed strain rate influences on an individual MWCNT with classical molecular dynamics simulations. Structural evolutions and buckling instabilities for thin-wall and thick-wall CNTs are theoretically studied, indicating the role of the tube thickness and interwall van der Waals interactions in governing buckling behavior.
Atom insertion into grain boundaries and stress generation in physically vapor deposited films
Authors: Magnfält D. , Abadias G. , Sarakinos K.
Published: August 2013

We present evidence for compressive stress generation via atom insertion into grain boundaries in polycrystalline Mo thin films deposited using energetic vapor fluxes (<∼120 eV). Intrinsic stress magnitudes between −3 and +0.2 GPa are obtained with a nearly constant stress-free lattice parameter marginally larger (0.12%) than that of bulk Mo. This, together with a correlation between large compressive film stresses and high film densities, implies that the compressive stress is not caused by defect creation in the grains but by grain boundary densification. Two mechanisms for diffusion of atoms into grain boundaries and grain boundary densification are suggested.
Near field imaging of a semiconductor laser by scanning probe microscopy without a photodetector
Authors: Dunaevskiy M. S. , Alekseev P. A. , Baranov A. N. , Monakhov A. M. , Teissier R. , Arinero R. , Girard P. , Titkov A. N.
Published: August 2013

We propose an experimental method of near field optical imaging by scanning probe microscopy in which the probe itself serves as an infrared photodetector. The method providing a submicron spatial resolution is based on detection of a shift of the probe resonance related to its heating by absorbed IR radiation. The method does not require an apertured probe and can be realized with a conventional silicon probe used in atomic force microscopy. The method has been employed for visualization of infrared emission from a half-disk semiconductor whispering gallery mode laser.
>750 mV open circuit voltage measured on 50 μm thick silicon heterojunction solar cell
Authors: Herasimenka Stanislau Y. , Dauksher William J. , Bowden Stuart G.
Published: August 2013

This paper presents experimental evidence that silicon solar cells can achieve >750 mV open circuit voltage at 1 Sun illumination providing very good surface passivation is present. 753 mV local open circuit voltage was measured on a 50 μm thick non-metalized silicon heterojunction solar cell. The paper also considers a recombination model at open circuit based on the recent Auger and radiative recombination parameterization and the measured surface saturation current density. The loss mechanisms at open circuit and several practical pathways to achieve >760 mV open circuit voltage in silicon heterojunction solar cells are discussed.
Blue-phase-polymer-templated nematic with sub-millisecond broad-temperature range electro-optic switching
Authors: Xiang Jie , Lavrentovich Oleg D.
Published: August 2013

We report on fast electro-optic switching (response time 0.1 ms) of a blue-phase-polymer templated nematic with a broad-temperature range of thermodynamic stability and hysteresis-free performance. The nematic fills a polymer template that imposes a periodic structure with cubic symmetry and submicron period. In the field-free state, the nematic in polymer template is optically isotropic. An applied electric field causes non-zero optical retardance. The approach thus combines beneficial structural and optical features of the blue phase (cubic structure with submicron periodicity) and superior thermodynamic stability and electro-optic switching ability of the nematic filler.
Colossal magnetocapacitance near room temperature in ferromagnetic Cr2O3 film
Authors: Ghosh A. , Dey K. , Sabyasachi Sk. , Karmakar A. , Majumdar S. , Giri S.
Published: August 2013

We report significantly large magnetocapacitance (∼32%) close to room temperature in Cr2O3 film fabricated using pulsed laser deposition technique. Magnetic hysteresis loop exhibits typical signature of a soft ferromagnetic character at room temperature in contrast to that observed in antiferromagnetic bulk counterpart. The value of saturation magnetization (MS) is significantly large with MS≈1.0μB at room temperature. A significant strain ascribed to the lattice mismatch is suggested for the occurrence of ferromagnetism and is correlated to the significant magnetocapacitance close to room temperature.
A bi-stable nanoelectromechanical non-volatile memory based on van der Waals force
Authors: Soon Bo Woon , Jiaqiang Ng Eldwin , Qian You , Singh Navab , Julius Tsai Minglin , Lee Chengkuo
Published: August 2013

By using complementary-metal-oxide-semiconductor processes, a silicon based bi-stable nanoelectromechanical non-volatile memory is fabricated and characterized. The main feature of this device is an 80 nm wide and 3 μm high silicon nanofin (SiNF) of a high aspect ratio (1:35). The switching mechanism is realized by electrostatic actuation between two lateral electrodes, i.e., terminals. Bi-stable hysteresis behavior is demonstrated when the SiNF maintains its contact to one of the two terminals by leveraging on van der Waals force even after voltage bias is turned off. The compelling results indicate that this design is promising for realization of high density non-volatile memory application due to its nano-scale footprint and zero on-hold power consumption.
Giant secondary grain growth in Cu films on sapphire
Authors: Miller David L. , Keller Mark W. , Shaw Justin M. , Rice Katherine P. , Keller Robert R. , Diederichsen Kyle M.
Published: August 2013

Single crystal metal films on insulating substrates are attractive for microelectronics and other applications, but they are difficult to achieve on macroscopic length scales. The conventional approach to obtaining such films is epitaxial growth at high temperature using slow deposition in ultrahigh vacuum conditions. Here we describe a different approach that is both simpler to implement and produces superior results: sputter deposition at modest temperatures followed by annealing to induce secondary grain growth. We show that polycrystalline as-deposited Cu on α-Al2O3(0001) can be transformed into Cu(111) with centimeter-sized grains. Employing optical microscopy, x-ray diffraction, and electron backscatter diffraction to characterize the films before and after annealing, we find a particular as-deposited grain structure that promotes the growth of giant grains upon annealing. To demonstrate one potential application of such films, we grow graphene by chemical vapor deposition on wafers of annealed Cu and obtain epitaxial graphene grains of 0.2 mm diameter.
Cool-season grain legume improvement in Australia—Use of genetic resources
Authors: Siddique K. H. M. , Erskine W. , Hobson K. , Knights E. J. , Leonforte A. , Khan T. N. , Paull J. G. , Redden R. , Materne M.
Published: August 2013

The cool-season grain legume industry in Australia, comprising field pea (Pisum sativum L.), chickpea (Cicer arietinum L.), faba bean (Vicia faba L.), lentil (Lens culinaris ssp. culinaris Medik.), and narrow-leaf lupin (Lupinus angustifolius L.), has emerged in the last 40 years to occupy a significant place in cropping systems. The development of all major grain legume crops—including field pea, which has been grown for over 100 years—has been possible through large amounts of genetic resources acquired and utilised in breeding. Initially, several varieties were released directly from these imports, but the past 25 years of grain legume breeding has recombined traits for adaptation and yield for various growing regions. Many fungal disease threats have been addressed through resistant germplasm, with varying successes. Some threats, e.g. black spot in field pea caused by Mycosphaerella pinodes (Berk. and Blox.) Vestergr., require continued exploration of germplasm and new technology. The arrival of ascochyta blight in chickpea in Australia threatened to destroy the chickpea industry of southern Australia, but thanks to resistant germplasm, it is now on its way to recovery. Many abiotic stresses including drought, heat, salinity, and soil nutritional toxicities continue to challenge the expansion of the grain legume area, but recent research shows that genetic variation in the germplasm may offer new solutions. Just as the availability of genetic resources has been key to successfully addressing many challenges in the past two decades, so it will assist in the future, including adapting to climate change. The acquisition of grain legume germplasm from overseas is a direct result of several Australians who fostered collaborations leading to new collection missions enriching the germplasm base for posterity.
Variability of in vitro ruminal fermentation and methanogenic potential in the pasture legume biserrula (Biserrula pelecinus L.)
Authors: Banik Bidhyut Kumar , Durmic Zoey , Erskine William , Nichols Phillip , Ghamkhar Kioumars , Vercoe Philip
Published: August 2013

Biserrula (Biserrula pelecinus L.) is an important annual pasture legume for the wheatbelt of southern Australia and has been found to have lower levels of methane output than other pasture legumes when fermented by rumen microbes. Thirty accessions of the biserrula core germplasm collection were grown in the glasshouse to examine intra-specific variability in in vitro rumen fermentation, including methane output. One biserrula cultivar (Casbah) was also grown at two field locations to confirm that low methanogenic potential was present in field-grown samples. All of the biserrula accessions had significantly reduced methane [range 0.5–8.4 mL/g dry matter (DM)] output compared with subterranean clover (28.4 mL/g DM) and red clover (36.1 mL/g DM). There was also significant variation in fermentability profiles (except for volatile fatty acids) among accessions of the core collection. Methanogenic potential exhibited 86% broad-sense heritability within the biserrula core collection. The anti-methanogenic and gas-suppressing effect of biserrula was also confirmed in samples grown in the field. In conclusion, biserrula showed variability in in vitro fermentation traits including reduced methane production compared with controls. This bioactivity of biserrula also persists in the field, indicating scope for further selection of biserrula as an elite methane-mitigating pasture.
Agglomeration and dissolution of zinc oxide nanoparticles: role of pH, ionic strength and fulvic acid
Authors: Domingos Rute F. , Rafiei Zohreh , Monteiro Carlos E. , Khan Mohammad A.K. , Wilkinson Kevin J.
Published: August 2013

Environmental context
The number of nano-enabled products reaching consumers is growing exponentially, inevitably resulting in their release to the environment. The environmental fate and mobility of nanomaterials will depend on their physicochemical form(s) under natural conditions. For ZnO nanoparticles, determinations of agglomeration and dissolution under environmentally relevant conditions of pH, ionic strength and natural organic matter content will provide insight into the potential environmental risk of these novel products.

Abstract
The increasing use of engineered nanoparticles (ENPs) in industrial and household applications has led to their release into the environment and increasing concern about their effects. Proper assessment of the ecological risks of ENPs will require data on their bioavailability, persistence and mobility over a broad range of physicochemical conditions, including environmentally relevant pH, ionic strength and concentrations of natural organic matter (NOM). In this study, fluorescence correlation spectroscopy was used to determine the agglomeration of a ZnO ENP (nZnO) with a nominal size of 20nm. Particle dissolution was followed using scanned stripping chronopotentiometry. The effects of Suwannee River fulvic acid (SRFA, 0–60mgL–1) and the roles of pH (4–10) and ionic strength (0.005–0.1M) were carefully evaluated. Agglomeration of the bare nZnO increased for pH values near the zero point of charge, whereas the dissolution of the particles decreased. At any given pH, an increase in ionic strength generally resulted in a less stable colloidal system. The role of SRFA was highly dependent upon its concentration with increased agglomeration observed at low SRFA : nZnO mass ratios and decreased agglomeration observed at higher SRFA : nZnO mass ratios. The results indicated that in natural systems, both nZnO dispersion and dissolution will be important and highly dependent upon the precise conditions of pH and ionic strength.
Homological and homotopical Dehn functions are different
Authors: Abrams Aaron , Brady Noel , Dani Pallavi , Young Robert
Published: August 2013

The homological and homotopical Dehn functions are different ways of measuring the difficulty of filling a closed curve inside a group or a space. The homological Dehn function measures fillings of cycles by chains, whereas the homotopical Dehn function measures fillings of curves by disks. Because the two definitions involve different sorts of boundaries and fillings, there is no a priori relationship between the two functions; however, before this work, there were no known examples of finitely presented groups for which the two functions differ. This paper gives such examples, constructed by amalgamating a free-by-cyclic group with several Bestvina–Brady groups.
Heterogeneity in protein expression induces metabolic variability in a modeled
Escherichia coli
population
Authors: Labhsetwar Piyush , Cole John Andrew , Roberts Elijah , Price Nathan D. , Luthey-Schulten Zaida A.
Published: August 2013

Stochastic gene expression can lead to phenotypic differences among cells even in isogenic populations growing under macroscopically identical conditions. Here, we apply flux balance analysis in investigating the effects of single-cell proteomics data on the metabolic behavior of an
in silico Escherichia coli
population. We use the latest metabolic reconstruction integrated with transcriptional regulatory data to model realistic cells growing in a glucose minimal medium under aerobic conditions. The modeled population exhibits a broad distribution of growth rates, and principal component analysis was used to identify well-defined subpopulations that differ in terms of their pathway use. The cells differentiate into slow-growing acetate-secreting cells and fast-growing CO
2
-secreting cells, and a large population growing at intermediate rates shift from glycolysis to Entner–Doudoroff pathway use. Constraints imposed by integrating regulatory data have a large impact on NADH oxidizing pathway use within the cell. Finally, we find that stochasticity in the expression of only a few genes may be sufficient to capture most of the metabolic variability of the entire population.
Topic management in French L2
Authors: König Clelia
Published: August 2013

Drawing on Conversation Analysis, this paper investigates free occurring conversational data in French as a second language. Its focus of attention is a debated concept within the conversation analytic approach, i.e., topic management. After an overview of the existing literature on topic management and the conceptualisation of learning and L2 interactional competence, the main part of the article will be concerned with data analysis. The data show an au-pair girl speaking French with her host-family at different points in time. The longitudinal design allows for describing in detail and conceptualising L2 interactional competence and its development. In fact, taking into consideration interactional aspects, such as sequential and action organisation, it contributes to a better understanding of L2 learning. The results show how topic management is not only the object of, but also the means for, learning an L2, whilst being socialised into the very same L2. This article contributes to an ongoing debate in the field of CA and, especially, CA-SLA about conceptualising L2 learning and tracking the development of L2 interactional competence.
Posthandling Survival and PIT Tag Retention by Alewives—A Comparison of Gastric and Surgical Implants
Authors: Castro-Santos Theodore , Vono Volney
Published: August 2013

We compared survival and tag retention of Alewives Alosa pseudoharengus tagged with PIT tags, using intraperitoneal (IP) surgical implants, gastric implants (GI), and untagged controls held for 38 d. Retention was 100% for IP-tagged Alewives and 98% for GI-tagged implants. No significant difference in survival was observed among any of these groups. These results lend support to the use of PIT telemetry for studying fish passage and migration of anadromous herring. Both methods hold promise for improving estimates of freshwater survival of adult anadromous clupeids; further research should make it also possible to refine estimates of adult marine survival.

Received February 4, 2013; accepted May 29, 2013
Results of a Pilot Test of a Self-Administered Smartphone-Based Treatment System for Alcohol Use Disorders: Usability and Early Outcomes
Authors: Dulin Patrick L. , Gonzalez Vivian M. , Campbell Kendra
Published: August 2013

Background

This paper provides results from a pilot study focused on assessing early-stage effectiveness and usability of a smartphone-based intervention system that provides a stand-alone, self-administered intervention option, the Location-Based Monitoring and Intervention for Alcohol Use Disorders (LBMI-A). The LBMI-A provided numerous features for intervening with ongoing drinking, craving, connection with supportive others, managing life problems, high-risk location alerting, and activity scheduling.

Methods

Twenty-eight participants, ranging in age from 22 to 45, who met criteria for an alcohol use disorder used an LBMI-A–enabled smartphone for 6 weeks.

Results

Participants indicated the LBMI-A intervention modules were helpful in highlighting alcohol use patterns. Tools related to managing alcohol craving, monitoring consumption, and identifying triggers to drink were rated by participants as particularly helpful. Participants also demonstrated significant reductions in hazardous alcohol use while using the system (56% of days spent hazardously drinking at baseline vs. 25% while using the LBMI-A) and drinks per day diminished by 52%.

Conclusions

Implications for system improvement as well as suggestions for designing ecological momentary assessment and intervention systems for substance use disorders are discussed.
The relative Hochschild-Serre spectral sequence and the Belkale-Kumar product
Authors: Evens Sam , Graham William
Published: August 2013

We consider the Belkale-Kumar cup product

⊙
t

\odot _t

on

H
∗

(
G

/

P
)

H^*(G/P)

for a generalized flag variety

G

/

P

G/P

with parameter

t
∈

C

m

t \in \mathbb {C}^m

, where

m
=
dim
⁡
(

H
2

(
G

/

P
)
)

m=\dim (H^2(G/P))

. For each

t
∈

C

m

t\in \mathbb {C}^m

, we define an associated parabolic subgroup

P
K

⊃
P

P_K \supset P

. We show that the ring

(

H
∗

(
G

/

P
)
,

⊙
t

)

(H^*(G/P), \odot _t)

contains a graded subalgebra

A
A

isomorphic to

H
∗

(

P
K

/

P
)

H^*(P_K/P)

with the usual cup product, where

P
K

P_K

is a parabolic subgroup associated to the parameter

t
t

. Further, we prove that

(

H
∗

(
G

/

P
K

)
,

⊙
0

)

(H^*(G/P_K), \odot _0)

is the quotient of the ring

(

H
∗

(
G

/

P
)
,

⊙
t

)

(H^*(G/P), \odot _t)

with respect to the ideal generated by elements of positive degree of

A
A

. We prove the above results by using basic facts about the Hochschild-Serre spectral sequence for relative Lie algebra cohomology, and most of the paper consists of proving these facts using the original approach of Hochschild and Serre.
A Regional Bio‐economic Model of Nitrogen Use in Cropping
Authors: Mérel Pierre , Yi Fujin , Lee Juhwan , Six Johan
Published: August 2013

We develop a programming model of crop production to predict the effects of environmental policies on agriculture and the environment. The model is calibrated against acreages, yields, and exogenous supply elasticities following positive mathematical programming. In addition, crop production functions are calibrated to yield elasticities with respect to nitrogen and irrigation obtained from a biogeochemical model. We study the effects of a nitrogen tax in Yolo County, California, intended to mitigate nitrogen pollution from field crops. The behavioral and environmental responses to the tax are largely due to intensive margin adjustments. Sizable reductions in nitrate leaching are achieved at a low social cost.
Gamma-rays from millisecond pulsar population within the central stellar cluster in the Galactic Centre
Authors: Bednarek W. , Sobczak T.
Published: August 2013

It was proposed that the central dense stellar cluster in the Galactic Centre, containing the mass of ∼4 times larger than that of the central black hole, had been formed as a result of a merging of several massive globular clusters. These globular clusters are expected to provide a large number of millisecond pulsars (MSPs) within the central parsec of the Galactic Centre. We propose that the GeV γ-ray emission observed from the Galactic Centre is in fact a cumulative effect of the emission from several globular clusters captured by the Galactic Centre black hole. Moreover, the MSPs in globular clusters accelerate leptons in their wind zones to energies of the order of a few tens of TeV injecting them into the dense infrared and optical radiation region present within the central parsec. We calculate the expected TeV γ-ray emission produced by these leptons by the inverse Compton scattering process in the soft radiation field. It is shown that this emission can be responsible for the multi-TeV γ-rays observed by the Cherenkov telescopes from the Galactic Centre for reasonable densities of the soft radiation, diffusion models for the propagation of leptons, their injection parameters (fluxes and spectral proprieties). If the energy conversion efficiency from the pulsars to the relativistic leptons is of the order of 10 per cent, then about a thousand of MSPs have to be present in the central cluster in the Galactic Centre.