bluuebunny/crossref_metadata_2025 huggingface dataset:
Toward the observation of quartet states of the ozone radical cation: Insights from coupled cluster theory
Authors: Speakman Lucas D. , Turney Justin M. , Schaefer Henry F.
Published: June 2008

Since the discovery of ozone depletion, the doublet electronic states of the ozone radical cation have received much attention in experimental and theoretical investigations, while the low-lying quartet states have not. In the present research, viable pathways to the quartet states from the lowest three triplet states of ozone, A23, B23, and B13, and excitations from the A12 and B22 states of the ozone radical cation have been studied in detail. The potential energy surfaces, structural optimizations, and vibrational frequencies for several states of ozone and its radical cation have been thoroughly investigated using the complete active space self-consistent field, unrestricted coupled cluster theory from a restricted open-shell Hartree-Fock reference including all single and double excitations (UCCSD), UCCSD method with the effects of connected triple excitations included perturbatively, and unrestricted coupled cluster including all single, double, and triple excitations with the effects of connected quadruple excitations included perturbatively. These methods used Dunning’s correlation-consistent polarized core-valence basis sets, cc-pCVXZ (X=D, T, Q, and 5). The most feasible pathways (symmetry and spin allowed transitions) to the quartet states are A14←A23, A24←A23, A14←B23, A24←B13, B24←B13, A24←A11, B24←A11, and A14←A11 with vertical ionization potentials of 12.46, 12.85, 12.82, 12.46, 12.65, 13.43, 13.93, and 14.90eV, respectively.
Color-stable, efficient fluorescent pure-white organic light-emitting diodes with device architecture preventing excessive exciton formation on guest
Authors: Jou Jwo-Huei , Wang Chun-Jan , Lin Yu-Pu , Chung Yu-Chiao , Chiang Po-Hsuan , Wu Ming-Hsuan , Wang Chung-Pei , Lai Chun-Liang , Chang Champion
Published: June 2008

Color-stable, high-efficiency fluorescent pure-white organic light-emitting diodes were fabricated using an electroluminescence-efficient blue host 2-(N,N-diphenylamino)-6-[4-(N,N-diphenylamino)styryl]naphthalene and yellow 5,6,11,12–tetra-phenylnaphthacene in a single emissive layer. The resultant power efficiency, at 100cd∕m2, for example, was 9.5lm∕W, and its emission changed from (0.321, 0.357) to (0.315, 0.344) for brightness increasing from 100to10000cd∕m2. The high color stability may be attributed to the device structure enabling the generation of excitons on host so that lesser excitons would form on guest, preventing exciton-quenching-caused blueshift.
Relativistic electron beam driven instabilities in the presence of an arbitrarily oriented magnetic field
Authors: Bret A. , Dieckmann M. E.
Published: June 2008

The electromagnetic instabilities driven by a relativistic electron beam, which moves through a magnetized plasma, are analyzed with a cold two-fluid model. It allows for any angle θB between the beam velocity vector and the magnetic field vector and considers any orientation of the wavevector in the two-dimensional plane spanned by these two vectors. If the magnetic field is strong, the two-stream instability dominates if θB=0 and the oblique modes grow faster at larger θB. A weaker magnetic field replaces the two-stream modes with oblique modes as the fastest-growing waves. The threshold value separating both magnetic regimes is estimated. A further dimensionless parameter is identified, which determines whether or not the wavevector of the most unstable wave is changed continuously, as θB is varied from 0 to π∕2. The fastest growing modes are always found for a transverse propagation of the beam with θB=π∕2, irrespective of the magnetic field strength.
Critical behavior of long straight rigid rods on two-dimensional lattices: Theory and Monte Carlo simulations
Authors: Matoz-Fernandez D. A. , Linares D. H. , Ramirez-Pastor A. J.
Published: June 2008

The critical behavior of long straight rigid rods of length k (k-mers) on square and triangular lattices at intermediate density has been studied. A nematic phase, characterized by a big domain of parallel k-mers, was found. This ordered phase is separated from the isotropic state by a continuous transition occurring at an intermediate density θc. Two analytical techniques were combined with Monte Carlo simulations to predict the dependence of θc on k, being θc(k)∝k−1. The first involves simple geometrical arguments, while the second is based on entropy considerations. Our analysis allowed us also to determine the minimum value of k (kmin=7), which allows the formation of a nematic phase on a triangular lattice.
Nanopore processing in dielectric materials and dielectric template-assisted nanoarray synthesis: Using pulsed bias to enhance process throughput and precision
Authors: Wu Xiaochen , Zhong Xiaoxia , Ostrikov Kostya (Ken)
Published: June 2008

An effective technique to improve the precision and throughput of energetic ion condensation through dielectric nanoporous templates and reduce nanopore clogging by using finely tuned pulsed bias is proposed. Multiscale numerical simulations of ion deposition show the possibility of controlling the dynamic charge balance on the upper template’s surface to minimize ion deposition on nanopore sidewalls and to deposit ions selectively on the substrate surface in contact with the pore opening. In this way, the shapes of nanodots in template-assisted nanoarray fabrication can be effectively controlled. The results are applicable to various processes involving porous dielectric nanomaterials and dense nanoarrays.
Theoretical study of the C6H3 potential energy surface and rate constants and product branching ratios of the C2H(Σ+2)+C4H2(Σg+1) and C4H(Σ+2)+C2H2(Σg+1) reactions
Authors: Landera Alexander , Krishtal Sergey P. , Kislov Vadim V. , Mebel Alexander M. , Kaiser Ralf I.
Published: June 2008

Ab initio CCSD(T)∕cc-pVTZ//B3LYP∕6-311G** and CCSD(T)/complete basis set (CBS) calculations of stationary points on the C6H3 potential energy surface have been performed to investigate the reaction mechanism of C2H with diacetylene and C4H with acetylene. Totally, 25 different C6H3 isomers and 40 transition states are located and all possible bimolecular decomposition products are also characterized. 1,2,3- and 1,2,4-tridehydrobenzene and H2CCCCCCH isomers are found to be the most stable thermodynamically residing 77.2, 75.1, and 75.7kcal∕mol lower in energy than C2H+C4H2, respectively, at the CCSD(T)/CBS level of theory. The results show that the most favorable C2H+C4H2 entrance channel is C2H addition to a terminal carbon of C4H2 producing HCCCHCCCH, 70.2kcal∕mol below the reactants. This adduct loses a hydrogen atom from the nonterminal position to give the HCCCCCCH (triacetylene) product exothermic by 29.7kcal∕mol via an exit barrier of 5.3kcal∕mol. Based on Rice–Ramsperger–Kassel–Marcus calculations under single-collision conditions, triacetylene+H are concluded to be the only reaction products, with more than 98% of them formed directly from HCCCHCCCH. The C2H+C4H2 reaction rate constants calculated by employing canonical variational transition state theory are found to be similar to those for the related C2H+C2H2 reaction in the order of magnitude of 10−10cm3molecule−1s−1 for T=298–63K, and to show a negative temperature dependence at low T. A general mechanism for the growth of polyyne chains involving C2H+H(CC)nH→H(CC)n+1H+H reactions has been suggested based on a comparison of the reactions of ethynyl radical with acetylene and diacetylene. The C4H+C2H2 reaction is also predicted to readily produce triacetylene+H via barrierless C4H addition to acetylene, followed by H elimination.
Accurate ab initio intermolecular potential energy surface for the quintet state of the O2(Σg−3)–O2(Σg−3) dimer
Authors: Bartolomei Massimiliano , Carmona-Novillo Estela , Hernández Marta I. , Campos-Martínez José , Hernandez-Lamoneda Ramón
Published: June 2008

A new potential energy surface (PES) for the quintet state of rigid O2(Σg−3)+O2(Σg−3) has been obtained using restricted coupled-cluster theory with singles, doubles, and perturbative triple excitations [RCCSD(T)]. A large number of relative orientations of the monomers (65) and intermolecular distances (17) have been considered. A spherical harmonic expansion of the interaction potential has been built from the ab initio data. It involves 29 terms, as a consequence of the large anisotropy of the interaction. The spherically averaged term agrees quite well with the one obtained from analysis of total integral cross sections. The absolute minimum of the PES corresponds to the crossed (D2d) structure (X shape) with an intermolecular distance of 6.224bohrs and a well depth of 16.27meV. Interestingly, the PES presents another (local) minimum close in energy (15.66meV) at 6.50bohrs and within a planar skewed geometry (S shape). We find that the origin of this second structure is due to the orientational dependence of the spin-exchange interactions which break the spin degeneracy and leads to three distinct intermolecular PESs with singlet, triplet, and quintet multiplicities. The lowest vibrational bound states of the O2–O2 dimer have been obtained and it is found that they reflect the above mentioned topological features of the PES: The first allowed bound state for the O16 isotope has an X structure but the next state is just 0.12meV higher in energy and exhibits an S shape.
Polarization-tunable electroluminescence using phase retardation based on photonic bandgap liquid crystal
Authors: Jeong Soon Moon , Ha Na Young , Takezoe Hideo , Nishimura Suzushi , Suzaki Goro
Published: June 2008

We have demonstrated polarization-tunable electroluminescence (EL) from organic light-emitting diodes (OLEDs) using a combination of polymeric cholesteric liquid crystal (PCLC) and nematic liquid crystal (NLC). By electrically controlling NLC alignment, the proposed EL device shows a continuous polarization tunability including two circular (right and left) and two linear polarizations without loss of light. This simple polarization-tunable EL device is based on photonic-device concept using spin-coatable PCLC. Hence, there is no limitation for choosing emissive materials with high internal efficiency. Also, its polarization tunability will be available in various optical devices and can extend OLED application to photonic technologies.
Stress and magnetoelastic properties control of amorphous Fe80B20 thin films during sputtering deposition
Authors: Fernández-Martínez I. , Costa-Krämer J. L. , Briones F.
Published: June 2008

In situ stress measurements during sputtering deposition of amorphous Fe80B20 films are used to control their stress and magnetoelastic properties. The substrate curvature induced by the deposited film is measured optically during growth and quantitatively related to the deposition induced accumulated stress. The resulting magnetic properties are later correlated with the measured stress for a wide range of sputtering pressures [(2−25)×10−3 mbar]. A significant tensile stress develops at the film-substrate interface during the early growth stages (initial 2–3 nm). At a critical thickness, a transition is observed from tensile to compressive stress, which is associated with amorphous island coalescence. By further increasing the thickness, a compressive stress follows, which is related to the local distortion induced by the ion peening effect. The Monte Carlo simulations of the sputtering process describe quantitatively the experimental results as a function of the Ar pressure and target bias voltage.
Direct observation of conducting filaments on resistive switching of NiO thin films
Authors: Son J. Y. , Shin Y.-H.
Published: June 2008

The Hg∕NiO∕Pt capacitor with a Hg top electrode diameter of about 35μm showed the typical bistable resistive switching characteristic. After the removal of the Hg top electrode, we directly observed the formation and removal of filaments for a high resistive state (Roff) and a low resistive state (Ron) by conducting atomic force microscope (CAFM). CAFM images for Roff and Ron states directly exhibit evidence of the formation and removal of filaments on the surface, which supports well the filament model as a switching mechanism of resistive random access memory.
Motional narrowing in the time-averaging approximation for simulating two-dimensional nonlinear infrared spectra
Authors: la Cour Jansen Thomas , Ruszel Wioletta M.
Published: June 2008

The diagonal linewidth in two-dimensional infrared spectra is often narrower than the distribution of transition frequencies. The width along the antidiagonal is broader than predicted by the lifetime broadening. These effects arise from time-dependent fluctuations of the transition frequencies. They can be accounted for with a semiclassical approach. For systems with many coupled vibrational modes, this approach, however, becomes computationally too demanding to be practically applicable. A time-averaging approximation was suggested for linear infrared absorption spectra. In this paper, we demonstrate that the averaging can be optimized to fit a broader scale of frequency fluctuations by using a Gaussian weight function instead of the originally proposed box function. We further generalize the time-averaging method to allow the simulation of two-dimensional infrared spectra and demonstrate the method on a simple system. The approximation delivers a large speed-up of the calculation without losing significant accuracy.
Ab initio intermolecular potential energy surface and second pressure virial coefficients of methane
Authors: Hellmann Robert , Bich Eckard , Vogel Eckhard
Published: June 2008

A six-dimensional potential energy hypersurface (PES) for two interacting rigid methane molecules was determined from high-level quantum-mechanical ab initio computations. A total of 272 points for 17 different angular orientations on the PES were calculated utilizing the counterpoise-corrected supermolecular approach at the CCSD(T) level of theory with basis sets of aug-cc-pVTZ and aug-cc-pVQZ qualities. The calculated interaction energies were extrapolated to the complete basis set limit. An analytical site-site potential function with nine sites per methane molecule was fitted to the interaction energies. In addition, a semiempirical correction to the analytical potential function was introduced to take into account the effects of zero-point vibrations. This correction includes adjustments of the dispersion coefficients and of a single-parameter within the fit to the measured values of the second virial coefficient B(T) at room temperature. Quantitative agreement was then obtained with the measured B values over the whole temperature range of the measurements. The calculated B values should definitely be more reliable at very low temperatures (T<150K) than values extrapolated using the currently recommended equation of state.
Far-infrared absorption of water clusters by first-principles molecular dynamics
Authors: Lee Mal-Soon , Baletto F. , Kanhere D. G. , Scandolo S.
Published: June 2008

Based on first-principle molecular dynamic simulations, we calculate the far-infrared spectra of small water clusters (H2O)n (n=2,4,6) at frequencies below 1000cm−1 and at 80K and at atmospheric temperature (T>200K). We find that cluster size and temperature affect the spectra significantly. The effect of the cluster size is similar to the one reported for confined water. Temperature changes not only the shape of the spectra but also the total strength of the absorption, a consequence of the complete anharmonic nature of the classical dynamics at high temperature. In particular, we find that in the frequency region up to 320cm−1, the absorption strength per molecule of the water dimer at 220K is significantly larger than that of bulk liquid water, while tetramer and hexamer show bulklike strengths. However, the absorption strength of the dimer throughout the far-infrared region is too small to explain the measured vapor absorption continuum, which must therefore be dominated by other mechanisms.
Anharmonic vibrational frequencies and vibrationally averaged structures and nuclear magnetic resonance parameters of FHF−
Authors: Hirata So , Yagi Kiyoshi , Ajith Perera S. , Yamazaki Shiori , Hirao Kimihiko
Published: June 2008

The anharmonic vibrational frequencies of FHF− were computed by the vibrational self-consistent-field, configuration-interaction, and second-order perturbation methods with a multiresolution composite potential energy surface generated by the electronic coupled-cluster method with various basis sets. Anharmonic vibrational averaging was performed for the bond length and nuclear magnetic resonance indirect spin-spin coupling constants, where the latter computed by the equation-of-motion coupled-cluster method. The calculations placed the vibrational frequencies at 580 (ν1), 1292 (ν2), 1313 (ν3), 1837 (ν1+ν3), and 1864cm−1 (ν1+ν2), the zero-point H–F bond length (r0) at 1.1539Å, the zero-point one-bond spin-spin coupling constant [J01(HF)] at 124Hz, and the bond dissociation energy (D0) at 43.3kcal∕mol. They agreed excellently with the corresponding experimental values: ν1=583cm−1, ν2=1286cm−1, ν3=1331cm−1, ν1+ν3=1849cm−1, ν1+ν2=1858cm−1, r0=1.1522Å, J01(HF)=124±3Hz, and D0=44.4±1.6kcal∕mol. The vibrationally averaged bond lengths matched closely the experimental values of five excited vibrational states, furnishing a highly dependable basis for correct band assignments. An adiabatic separation of high- (ν3) and low-frequency (ν1) stretching modes was examined and found to explain semiquantitatively the appearance of a ν1 progression on ν3. Our calculations predicted a value of 186Hz for experimentally inaccessible J02(FF).
Direct measurement of beam size in a spectroscopic ellipsometry setup
Authors: Tay Arthur , Ng Tuck Wah , Wang Yuheng , Zhao Shao
Published: June 2008

Spectroscopic ellipsometry signals used in thin film analysis are dependent on the beam probe size. In this work, we report a technique to determine the beam size that uses the existing detection facilities in a spectroscopic ellipsometry setup without the need to rearrange the optical components. The intensity signal recorded with the technique comprises a coupled boundary diffraction and knife edge wave that can be isolated using nonlinear fitting. This then permitted an accurate measurement of the beam size with the stronger knife edge component. The technique has the added advantage of picking up chromatic aberration in the probing lens which may be a factor in ellipsometry measurement.
Evolution of strain and composition of Ge islands on Si (001) grown by molecular beam epitaxy during postgrowth annealing
Authors: Singha R. K. , Das S. , Majumdar S. , Das K. , Dhar A. , Ray S. K.
Published: June 2008

Self-assembled Ge islands have been grown using a Stranski–Krastanov growth mechanism on Si (001) substrates by solid source molecular beam epitaxy. We performed time varying annealing experiments at a representative temperature of 650°C to study the shape and size evolution of islands for a relatively high Ge coverage. Islands are found to coarsen due to heat treatment via structural and compositional changes through continuous strain relaxation. Different island morphologies, namely, “pyramids,” “transitional domes,” and “domes” are found during the annealing sequence. The dominant coarsening mechanisms for the temporal evolution of islands of as-grown and annealed samples are explained by the comprehensive analysis of Rutherford back scattering, Raman spectroscopy, high-resolution x-ray diffraction, and atomic force microscopy. A correlation of the morphological evolution with the composition and strain relaxation of grown islands is presented.
Negative transconductance in apertured electron guns
Authors: Harris John R. , O’Shea Patrick G.
Published: June 2008

Passing an electron beam through an aperture can serve to reduce the beam current or change the transverse beam profile. For a sufficiently intense beam, space charge will drive a radial expansion of the beam, which may cause the current passing through the aperture to decrease even though the current arriving at the aperture is increasing. When a gridded electron gun is used, this may be expressed by stating that the transconductance of the apertured gun is negative. Here, we explain this effect and explore some of the key factors governing when it can occur and influencing its strength.
Plasma deposition of elastic wear resistant Si–C coatings on nickel-titanium for biomedical applications
Authors: Schauer Janine-Christina , Winter Jörg
Published: June 2008

A bilayer system consisting of carbon and silicon has been developed to coat metals such as copper, stainless steel, nickel, and especially NiTi with an elastic, wear, and corrosion resistant film. The plasma deposited film system exhibits excellent adhesion on all metals under investigation. This adhesion is promoted by silicide formation. Additionally, the film system shows good performance under extremely high load induced via cavitation admission. Tensile tests reveal high elasticity of the film system, in that it can be elongated up to 5% before occurrence of damage of the film. The intrinsic stress inside this film system is reduced compared to pure diamondlike carbon films. Both good chemical bonding and reduced stress lead to good adhesion of the film systems on metals.
Dependence of charge storage and programming characteristics on dot number of floating dot memory
Authors: Nakajima Anri , Fujiaki Tomo , Fukuda Yuusuke
Published: June 2008

We fabricated a nonvolatile memory with a narrow channel and self-aligned Si nanoscale floating dots and studied the dependence of charge storage and programming characteristics on the dot number along the channel. Almost the same threshold voltage shift in the memory window was observed for devices with one or two floating dots. This indicates that the threshold voltage shift is determined only by the charge in one floating dot even when two floating dots are positioned in series along the narrow channel. Better retention characteristics were obtained for devices with two floating dots than those for devices with one floating dot, while almost the same programming characteristics were obtained. Therefore, the metal-oxide-semiconductor field-effect transistor with multiple self-aligned Si floating dots positioned along the narrow channel in series is a promising candidate for future extremely low power memory having a long retention time without sacrificing programming characteristics.
Quantum dot-embedded microspheres for remote refractive index sensing
Authors: Pang Shuo , Beckham Richard E. , Meissner Kenith E.
Published: June 2008

We present a refractometric sensor based on quantum dot-embedded polystyrene microspheres. Optical resonances within a microsphere, known as whispering-gallery modes (WGMs), produce narrow spectral peaks. For sensing applications, spectral shifts of these peaks are sensitive to changes in the local refractive index. In this work, two-photon excited luminescence from the quantum dots couples into several WGMs within the microresonator. By optimizing the detection area, the spectral visibility of the WGMs is improved. The spectral shifts are measured as the surrounding index of the refraction changes. The experimental sensitivity is about five times greater than that predicted by the Mie theory.
Method for full Bloch sphere control of a localized spin via a single electrical gate
Authors: Pingenot Joseph , Pryor Craig E. , Flatté Michael E.
Published: June 2008

We calculate the dependence on an applied electric field of the g tensor of a single electron in a self-assembled InAs∕GaAs quantum dot. We identify dot sizes and shapes for which one in-plane component of the g tensor changes sign for realistic electric fields, and show that this should permit full Bloch sphere control of the electron spin in the quantum dot using only a static magnetic field and a single vertical electric gate.
High capacity and excellent cycling stability of single-walled carbon nanotube/SnO2 core-shell structures as Li-insertion materials
Authors: Chen Yu-Jin , Zhu Chun-Ling , Xue Xin-Yu , Shi Xiao-Ling , Cao Mao-Sheng
Published: June 2008

The single-walled carbon nanotube (SWNT)/SnO2 core-shell structures with small diameters as Li-insertion materials are investigated. The initial discharge capacity is up to 1339mAh∕g, and the reversible capacity retention is 89.8% after 100cycles, which is comparable to the performance of commercial graphite anodes. Such good electrochemical properties are attributed to large surface-to-volume ratio of SnO2 and good electrical conductivity of SWNT. Our results demonstrate that the SWNT/core-shell structures are very promising for active Li-insertion materials for Li-ion batteries.
Highly flexible and transparent InZnSnOx∕Ag∕InZnSnOx multilayer electrode for flexible organic light emitting diodes
Authors: Choi Kwang-Hyuk , Nam Ho-Jun , Jeong Jin-A , Cho Sung-Woo , Kim Han-Ki , Kang Jae-Wook , Kim Do-Geun , Cho Woon-Jo
Published: June 2008

By inserting a very thin layer of Ag between two layers of amorphous indium zinc tin oxide (IZTO), we fabricated a highly flexible, low resistance, and highly transparent IZTO-Ag-IZTO multilayer electrode on a polyethylene terephthalate (PET) substrate. Due to surface plasmon resonance (SPR) effects and the ductility of the Ag layer, the IZTO-Ag-IZTO electrode exhibited a low sheet resistance of 4.99Ω∕sq. and a high transparency of 86% as well as superior flexibility despite the very thin thickness of the IZTO layer (30nm). It was found that the transition of the Ag layer from distinct islands to a continuous film occurred at a critical thickness (∼14nm). Continuity of the Ag film is very important for SPR in IZTO-Ag-IZTO electrode. The current density-voltage-luminance characteristics of flexible organic light emitting diodes (OLEDs) fabricated on IZTO-Ag-IZTO/PET were better than those of flexible OLEDs fabricated on an ITO/PET substrate due to the low sheet resistance and high work function of the IZTO.
Gasless sputtering: Opportunities for ultraclean metallization, coatings in space, and propulsion
Authors: Andersson Joakim , Anders André
Published: June 2008

Pulsed magnetron sputtering was demonstrated in high vacuum: no sputter gas was used at any time. Sustained self-sputtering was initiated by multiply charged ions from a short vacuum arc. Copper ion currents to an ion collector in excess of 30A were measured, implying a plasma density of about 6×1018m−3. This technology may prove useful for metal coatings free of noble gas inclusions and suggests that magnetrons could operate in the vacuum of space. In addition to coating objects in space, the momentum of the sputtered atoms and ions may be utilized in space thrusters.
Organic photovoltaic cells based on an acceptor of soluble graphene
Authors: Liu Qian , Liu Zunfeng , Zhang Xiaoyan , Zhang Nan , Yang Liying , Yin Shougen , Chen Yongsheng
Published: June 2008

In this paper, an organic photovoltaic device based on an acceptor of solution-processable functionalized graphene was designed. A short circuit current density (Jsc) of 4.0mAcm−2, open circuit voltage (Voc) of 0.72V, and a solar power conversion efficiency of 1.1% were obtained for the device of indium tin oxide/poly(ethylene dioxythiophene) doped with polystyrene sulfonic acid (40nm)/poly(3-hexylthiophene-1, 3-diyl):graphene (graphene 10wt%, 100nm)/LiF (1nm)/Al (70nm) after an annealing treatment under simulated AM1.5G 100mW illumination in air. Because of the low price, ease of preparation, and inertness against ambient conditions, soluble graphene will be a promising candidate used for acceptor materials in the photovoltaic applications.
ac field enhanced protein crystallization
Authors: Hou Diana , Chang Hsueh-Chia
Published: June 2008

Uniform and nonuniform ac electric fields sustained by internal microfabricated electrodes are shown to sensitively affect protein crystallization by reducing the number of nucleation sites and enhancing the quality of the crystals formed. Under conditions when massive spontaneous nucleation occurs, a properly tuned ac field can desolvate the protein molecules to form a gel matrix with only a few nucleation sites. A dielectrophoretic force generated by the nonuniform ac field further consolidates these crystallites. Upon field removal, the gel transforms into crystals around these nucleation sites to form high-quality large crystals.
Effect of hydrogen incorporation temperature in
in plane
-engineered GaAsN∕GaAsN:H heterostructures
Authors: Trotta R. , Polimeni A. , Capizzi M. , Giubertoni D. , Bersani M. , Bisognin G. , Berti M. , Rubini S. , Martelli F. , Mariucci L. , Francardi M. , Gerardino A.
Published: June 2008

The influence of temperature on deuterium (or hydrogen) diffusion in GaAsN is investigated by secondary ion mass spectrometry and photoluminescence (PL). Deuterium incorporation at 200°C leads to an extremely sharp D concentration profile, which decreases by a factor of 10 within 5nm. This has great relevance to the attainment of an in-plane band gap engineering of dilute nitrides as demonstrated by PL in ensembles of artificial GaAsN wires.
Spin-polarized current in permalloy clusters electrodeposited on silicon: Two-dimensional giant magnetoresistance
Authors: de Araujo C. I. L. , Munford M. L. , Delatorre R. G. , da Silva R. C. , Zoldan V. C. , Pasa André A. , Garcia N.
Published: June 2008

We design a semigranular system consisting of permalloy clusters electrodeposited on silicon substrates that permits us to transfer and polarize spin of practically unpolarized currents injected between Ohmic contacts on silicon. The experiments are done for different times of electrodeposition and the magnetoresistance signal is measured. We realize a method to coherently couple, through currents, properties of individual clusters.
Enhanced electrical properties of SrTiO3 thin films grown by atomic layer deposition at high temperature for dynamic random access memory applications
Authors: Lee Sang Woon , Kwon Oh Seong , Han Jeong Hwan , Hwang Cheol Seong
Published: June 2008

Sr Ti O 3 (STO) thin films were deposited at 370°C by atomic layer deposition using H2O as the oxidant, and Ti(O–iPr)2(thd)2 and Sr(thd)2 as Ti, and Sr precursors, respectively. Denser STO films were produced at this deposition temperature. The saturated growth rate was 0.15Å∕cycle. The adoption of a thin crystallized seed layer resulted in crystallized perovskite STO films at the as-deposited state without higher temperature post-annealing. A tox of 0.72nm (dielectric constant of 108) and a low leakage current density (∼10−7A∕cm2 at 0.8V) were obtained from a planar capacitor structure consisting of Pt∕20-nm-thick STO/Ru (bottom).
Is there a critical level of shoot phosphorus concentration for cluster-root formation in Lupinus albus?
Authors: Li Haigang , Shen Jianbo , Zhang Fusuo , Tang Caixian , Lambers Hans
Published: June 2008

This study examined the effects of localised phosphorus (P) supply on cluster-root formation and citrate exudation in white lupin (Lupinus albus L. cv. Kiev Mutant). White lupin plants were grown in nutrient solutions with a range of P supplies in a split-root system with one root half deprived of P and the other root supplied with 0, 2, 5, 8, 10 or 75 μm P. Plants were also grown in soil with or without organic matter added to the top layer. The proportion of cluster roots as a percentage of the total root biomass decreased similarly on both root halves with increasing P supply in the hydroponic experiments. More than 18% of the P taken up by the P-supplied root halves was incorporated into the P-deprived halves. Irrespective of the P supply or organic matter addition in the experiments, the proportion of cluster roots and the rate of citrate exudation decreased sharply with increasing P concentration in the shoots up to a critical level of 2–3 mg P g–1 dry weight. In contrast, the rate of proton release was higher in P-deprived root halves than in P-supplied ones. The formation of cluster roots is regulated by shoot P concentration with a critical level of 2–3 mg g–1. Citrate exudation is predominantly governed by shoot P status, whereas proton release strongly responds to local P supply.
Regulation of sulfate uptake, expression of the sulfate transporters Sultr1;1 and Sultr1;2, and APS reductase in Chinese cabbage (Brassica pekinensis) as affected by atmospheric H2S nutrition and sulfate deprivation
Authors: Koralewska Aleksandra , Stuiver C. Elisabeth E. , Posthumus Freek S. , Kopriva Stanislav , Hawkesford Malcolm J. , De Kok Luit J.
Published: June 2008

The activity and expression of sulfate transporters and adenosine 5′-phosphosulfate (APS) reductase (APR) in plants are modulated by the plant sulfur status and the demand for growth. To elucidate regulatory mechanisms in Chinese cabbage [Brassica pekinensis (Lour.) Rupr.], the interactions between atmospheric H2S and sulfate nutrition and the impact on the activity and expression of the Group 1 sulfate transporters and APR were studied. At an ample sulfate supply, H2S exposure of Chinese cabbage resulted in a partial decrease of the sulfate uptake capacity, and at concentrations ≥0.25 μL L−1 a decreased expression of Sultr1;2 in the root and APR in the root and shoot. Upon sulfate deprivation there was a more than 3-fold increase in the sulfate uptake capacity of the root, accompanied by an induced expression of Sultr1;1 and an enhanced expression of Sultr1;2 in the root, along with an induction of Sultr1;2 in the shoot. The enhanced sulfate uptake capacity, the expression of the sulfate transporters in the root and the altered shoot-to-root partitioning appearing during sulfate deprivation were not alleviated upon H2S exposure and not rapidly affected by sulfate re-supply. Expression of APR was strongly enhanced in the root and shoot of sulfate-deprived plants and decreased again upon H2S exposure and sulfate re-supply. The significance of shoot-to-root interaction and sulfate and thiols as regulating signals in the activity and expression of Sultr1;1 and 1;2 is evaluated.
Carbon partitioning in N2 fixing Medicago sativa plants exposed to different CO2 and temperature conditions
Authors: Aranjuelo Iker , Irigoyen Juan J. , Sánchez-Díaz Manuel , Nogués Salvador
Published: June 2008

Many of the studies analysing the CO2 effect on plant development have been conducted in optimal growth conditions. Furthermore, although some of those studies suggest that legumes might show a steady productivity increase with rising CO2, the role of nodule activity on the plant responsiveness to predicted atmospheric CO2 enhancement is not well understood. In this study, C (metabolism and allocation) and N (nodule activity) interaction between the plant and the bacterial symbiont during the photosynthetic acclimation of N2-fixing alfalfa (Medicago sativa L. cv. Aragón) plants exposed to elevated CO2 and temperature conditions was analysed. The plants were grown in temperature gradient greenhouses (TGG) where, in the case of elevated CO2 treatments, the isotopic 13C/12C composition (δ13C) inside the TGG was modified. Compared with the corresponding temperature treatment, exposure to 700 μmol mol–1 CO2 enhanced dry mass (DM) of plants in elevated temperature treatments (26%), whereas no significant effect was detected in ambient temperature treatments. The δ13C data revealed that although all the carbon corresponding to leaf total organic matter (TOM) came from newly assimilated C, plants exposed to elevated CO2 did not develop strong sink activity (especially in ambient temperature conditions). Leaf carbohydrate build-up induced reduction in the Rubisco (E.C. 4.1.1.39) carboxylation capacity of plants. Despite this reduction in Rubisco content, plants exposed to elevated CO2 conditions maintained (at ambient temperature) or increased (at elevated temperature) photosynthetic rates (measured at growth conditions) by increasing N use efficiency. The larger C sink strength of nodules in plants grown at elevated CO2 and temperature conditions did not contribute towards overcoming photosynthetic acclimation. Further, the inhibitory effect of CO2 on nodule total activity was caused by a large depletion in total soluble protein (TSP) of nodules. Depletion of leaf N demand, together with the reduction in nodule carbohydrate availability (as reflected by the nodule starch concentration), negatively affected the nodule TSP content and enzymatic activity.
The role of phytochrome C in gravitropism and phototropism in Arabidopsis thaliana
Authors: Kumar Prem , Montgomery Crystal E. , Kiss John Z.
Published: June 2008

The phytochrome (phy) photoreceptors, which consist of a small gene family PHYA-E in dicot plants, play important roles in regulating many light-induced responses in plants. Although the best characterised phytochromes are phytochrome A (phyA) and phytochrome (phyB), the functions of phyD and phyE have been increasingly studied. Phytochrome C (phy C) has been the most poorly understood member of the photoreceptor family, since isolation of phyC mutants only has been accomplished within the last few years. Recent reports show that phyC functions in hypocotyl elongation, rosette leaf morphology, and timing of flowering. In the present study, we show that phyC plays a role in tropisms in seedlings and inflorescence stems of light-grown Arabidopsis thaliana (L.) Heynh. (Wassilewskija ecotype). Phytochrome C has a positive effect on gravitropism in hypocotyls and stems, but it has a limited role in root gravitropism. In contrast, phyC attenuates the positive phototropic response to blue light in hypocotyls and the red-light-based positive phototropism in roots. Phytochrome D (phy D) also mediates gravitropism in hypocotyls and inflorescence stems and attenuates positive phototropism in response to blue in hypocotyls and stems. Thus, phyC can be added to the list of the other four phytochromes, which play various roles in both gravitropism and phototropism in plant organs. This report also supports the growing body of evidence demonstrating cross talk between phytochromes and blue-light photoreceptors.
Integrated crop-livestock production systems in China
Authors: Hou F. J. , Nan Z. B. , Xie Y. Z. , Li X. L. , Lin H. L. , Ren J. Z.
Published: June 2008

The integrated crop-livestock production system provides most of the food needed by the people of China. Five types of integrated production systems are recognised; rangeland, grain crops, crop/pasture, agro-silvopastoral and ponds. Development of more sustainable and integrated crop-pasture-rangeland-livestock production systems has been recently achieved. Demonstrations of the integrated systems at household, village and regional levels are occurring for rain-fed agriculture on the Loess Plateau, the Hexi Corridor, north-western China and the Karst region of Guizhou Province, south-western China. These indicate that integration of crop, livestock and forage are effective means of improving agricultural productivity, environmental sustainability and farmers’ incomes. Widespread adoption of integrated farming systems should also reduce rangeland degradation.
Grassland development in tropical and subtropical southern China
Authors: Liu G. D. , Michalk D. L. , Bai C. J. , Yu D. G. , Chen Z. Q.
Published: June 2008

China’s 79 million ha of tropical and subtropical grasslands represent a significant national forage resource with a potential for further development for sustainable livestock production. The species rich original forest vegetation has been converted through natural and human activities to secondary forest, grassland and agricultural land. The grasslands which include savannah, shrubland, coppice forest and arable land sown with exotic legumes and grasses are expected to become China’s third largest livestock production zone. Despite degradation the grasslands retain a high level of biodiversity which has been preserved in germplasm depositories with on-going collection expeditions throughout south China. Productivity of natural grasses is moderate (<5 t DM/ha) but can be increased significantly by augmenting with Stylosanthes and other introduced legumes adapted to the infertile or acidic soils and seasonal rainfall.

Stylosanthes species which is used for grazing, green chop or leaf-meal production, as well as a cover crop in orchards, plantations and forest are successful because they are simple to establish and deliver immediate profits to farmers through improved livestock production or sale of forage for leaf meal manufacture. On-going plant breeding programs are delivering new higher yielding legume and grass cultivars with disease resistance and acid soil tolerance. They are expanding selection priorities to address environmental concerns (e.g. soil acidifying legumes) and to meet the needs of new integrated production systems. Introduced legumes and grasses have provided benefits to the environment through improved soil fertility, reduced soil erosion, increased infiltration rates and reduced weed invasion.
Experts believe that the southern tropical and subtropical grasslands still have the capacity to safely increase production and contribute significantly to the improvement of the regional ecosystem. However, this can only be achieved if current programs on germplasm preservation, breeding new cultivars and developing management systems for integrated production systems need to be balanced with work precision livestock management and promotion of monitoring individual animal performance to achieve improved livestock production efficiency.
Type noun uses in the English NP
Authors: Davidse Kristin , Brems Lieselotte , De Smedt Liesbeth
Published: June 2008

This article addresses the relatively neglected question of identifying and characterizing the various uses of sort, kind and type in the English NP. It does so on the basis of close analysis of a set of data extracted from the Times subcorpus of the COBUILD corpus. The proposed description refers to the general functions fulfilled by elements of the NP, which, from right to left, form an objective — subjective continuum. At the same time, we characterize the specific grammatical, collocational and discoursal patterns that can be observed to shape each use in the empirical data. In this way, we distinguish, besides the generally recognized head and qualifier uses, also modifier, postdeterminer and quantifier uses. We then consider these intra-NP type noun uses as a possible case of Adamson’s (2000) hypothesis, which correlates subjectification with leftward movement in the NP.
Prosodic and syntactic-pragmatic mechanisms of grammatical variation
Authors: De Sutter Gert , Speelman Dirk , Geeraerts Dirk
Published: June 2008

This paper reports on a quantitative corpus-based study of the impact of a postverbal constituent (PVC) on the choice of word order in Dutch written clause final verb clusters consisting of a participle and an auxiliary verb. The study verifies the results of previous research by analyzing the effect of the presence vs. the absence of a PVC, while at the same time extending previous research by scrutinizing this effect more in depth. More specifically, it is investigated whether there is an effect of the grammatical relationship between the PVC and its head, the syntactic weight of the PVC and the accent distribution within the PVC. Based on several statistical measures for bivariate and stratified analysis, we are able to show that these factors simultaneously affect the choice of word order in written clause final verb clusters. These results lead us to explore the relationship between the prosodic and syntactic-pragmatic determinants of word order variation.
The influence of robot personality on perceived and preferred level of user control
Authors: Meerbeek Bernt , Hoonhout Jettie , Bingley Peter , Terken Jacques M.B.
Published: June 2008

This paper describes the design and evaluation of a personality for the robotic user interface “iCat”. An application was developed that helps users find a TV-programme that fits their interests. Two experiments were conducted to investigate what personality users prefer for the robotic TV-assistant, what level of control they prefer (i.e. how autonomous the robot should behave), and how personality and the level of control relate to each other. The first experiment demonstrated that it is possible to create convincing personalities of the TV-assistant by applying various social cues. The results of the second experiment showed that an extravert and agreeable TV-assistant was preferred over a more introvert and formal one. Overall, the most preferred combination was an extravert and friendly personality with low user control. Additionally, it was found that perceived level of control was influenced by the robot’s personality. This suggests that the robot’s personality can be used as a means to increase the amount of control that users perceive.
Content-based control of goal-directed attention during human action perception
Authors: Demiris Yiannis , Khadhouri Bassam
Published: June 2008

During the perception of human actions by robotic assistants, the robotic assistant needs to direct its computational and sensor resources to relevant parts of the human action. In previous work we have introduced HAMMER (Hierarchical Attentive Multiple Models for Execution and Recognition) (Demiris and Khadhouri, 2006), a computational architecture that forms multiple hypotheses with respect to what the demonstrated task is, and multiple predictions with respect to the forthcoming states of the human action. To confirm their predictions, the hypotheses request information from an attentional mechanism, which allocates the robot’s resources as a function of the saliency of the hypotheses. In this paper we augment the attention mechanism with a component that considers the content of the hypotheses’ requests, with respect to the content’s reliability, utility and cost. This content-based attention component further optimises the utilisation of the resources while remaining robust to noise. Such computational mechanisms are important for the development of robotic devices that will rapidly respond to human actions, either for imitation or collaboration purposes.
Language as social practice
Authors: Amouzadeh Mohammad
Published: June 2008

This paper aims to investigate the language used by newspapers in post-revolutionary Iran. More precisely, the paper sets out to analyze how such a language is deployed to represent relevant hegemonic ideologies. The approach adopted for this purpose draws inspiration mainly from critical linguistics, where it is hypothesized that, as far as the pertinent metadiscourse goes, media genres serve to activate and perpetuate social power relations. In keeping with this theoretical stance, the paper argues that socially constructed texts can be said to perform two complementary functions; on the one hand, they shed light on the realities experienced in social life; on the other, they reveal such aspects of those realities as are constructed through the use of language. It is thus in this context that the media language used in the post-revolutionary Iran lends itself to analytical investigation, where the available data reveal the co-existence of three competing discourse processes of ‘Islamization’, ‘Iranian Nationalism’ and ‘Western liberalism’, relating to the third stage development of post-revolutionary Iran.