bluuebunny/crossref_metadata_2025 huggingface dataset:
The use of fractional derivation in modeling ferroelectric dynamic hysteresis behavior over large frequency bandwidth
Authors: Guyomar D. , Ducharne B. , Sebald G.
Published: June 2010

The present article proposes a dynamical model to obtain ferroelectric hysteresis dynamics based on fractional derivatives. The consideration of a fractional derivative term widely increases the frequency bandwidth of the accuracy of the traditional hysteresis models. As a consequence, the model is suited for successfully taking into account the well-known scaling relations of the ferroelectric hysteresis area, ⟨A⟩, versus the frequency, f, and field amplitude, E0. Under low frequency excitation, simulation tests provided good results regarding the comparison of the fractional model, experimental results and the well-known nonentire power law ⟨A⟩∞f1/3E02/3 (where ⟨A⟩ represents the hysteresis loop area). These results were followed by comparing the hysteresis area obtained from the fractional model with that from the well known scaling relations as f→∞, and the results were proposed as validation of the high frequency behavior. Next, the model was tested on large frequency bandwidths (>6 decades) and validated with success using the comparison between simulation tests and the only experimental results available in literature obtained in such conditions by Liu et al. [J. Phys.: Condens. Matter 16, 1189 (2004)] for BNT thin film samples.
The pressure-volume-temperature equation of state of MgO derived from shock Hugoniot data and its application as a pressure scale
Authors: Jin Ke , Li Xinzhu , Wu Qiang , Geng Huayun , Cai Lingcang , Zhou Xianming , Jing Fuqian
Published: June 2010

The pressure-volume-temperature (P-V-T) equation of state (EOS) of MgO is widely used as a pressure scale in static compression experiments. However, there are remarkable inconsistencies among different previously proposed MgO pressure scales. We calculated the P-V-T EOS of MgO up to 300 GPa and 3000 K based on experimental shock Hugoniot data and a simple thermal pressure model within the Mie-Grüneisen-type analysis framework. All of the parameters used can be measured experimentally with high accuracies. We found that, in overall, the calculated P-V-T EOS of MgO has excellent agreement with the available volume compression data over a wide range of pressure and temperature. A comparison of our results with the previous theoretical investigations has also been performed and confirms that our calculated P-V-T EOS of MgO can be used as a reliable pressure scale for static experiments at high pressures and high temperatures.
Enabling enelike reactions on Si(111)-7×7 through tuning organic molecular structures
Authors: Cai Ying Hui , Shao Yan Xia , Ning Yue Sheng , Tang Hai Hua , Wang Shuai , Xu Guo Qin
Published: June 2010

We previously demonstrated that acetonitrile (NCCH3) binds to the adjacent adatom-rest atom pair of Si(111)-7×7 through a [2+2]-like cycloaddition reaction, forming a (Si)NC(Si)CH3-like surface species [Tao et al., J. Phys. Chem. B 106, 3890 (2002)]. Current investigation clearly showed that chloroacetonitrile (NCCH2Cl), propargyl chloride (HCCCH2Cl), and 3-chloropropionitrile (NCCH2CH2Cl) react with the surface via enelike reactions, concurrently involving NC/CC as well as the breakage of the CCl/CH bond. Further separation of the unsaturated bond (CC) from the CCl bond using CH2 spacers in 5-chloro-1-pentyne (CHCCH2CH2CH2Cl) would direct the reaction to a [2+2]-like cycloaddition. These experimental results clearly suggest the possibility of controlling the surface reaction pathways by tuning the organic molecular structures. This strategy can be useful in designing and fabricating functional molecular templates on Si(111)-7×7.
Counterflow driven by swirl decay
Authors: Shtern Vladimir N. , Borissov Anatoli A.
Published: June 2010

The global meridional circulation of a viscous fluid, caused by swirl decay in a cylindrical container, is studied. To this end, a new solution to the Navier–Stokes equations is obtained, and simple experiments are performed to verify the predictions of the theory. The swirl decay mechanism explains elongated counterflows in hydrocyclones and vortex tubes sometimes extending over a hundred diameters.
Acoustic streaming in simplified liquid rocket engines with transverse mode oscillations
Authors: Fischbach Sean R. , Flandro Gary A. , Majdalani Joseph
Published: June 2010

This study considers a simplified model of a liquid rocket engine in which uniform injection is imposed at the faceplate. The corresponding cylindrical chamber has a small length-to-diameter ratio with respect to solid and hybrid rockets. Given their low chamber aspect ratios, liquid thrust engines are known to experience severe tangential and radial oscillation modes more often than longitudinal ones. In order to model this behavior, tangential and radial waves are superimposed onto a basic mean-flow model that consists of a steady, uniform axial velocity throughout the chamber. Using perturbation tools, both potential and viscous flow equations are then linearized in the pressure wave amplitude and solved to the second order. The effects of the headwall Mach number are leveraged as well. While the potential flow analysis does not predict any acoustic streaming effects, the viscous solution carried out to the second order gives rise to steady secondary flow patterns near the headwall. These axisymmetric, steady contributions to the tangential and radial traveling waves are induced by the convective flow motion through interactions with inertial and viscous forces. We find that suppressing either the convective terms or viscosity at the headwall leads to spurious solutions that are free from streaming. In our problem, streaming is initiated at the headwall, within the boundary layer, and then extends throughout the chamber. We find that nonlinear streaming effects of tangential and radial waves act to alter the outer solution inside a cylinder with headwall injection. As a result of streaming, the radial wave velocities are intensified in one-half of the domain and reduced in the opposite half at any instant of time. Similarly, the tangential waves are either enhanced or weakened in two opposing sectors that are at 90° angle to the radial velocity counterparts. The second-order viscous solution that we obtain clearly displays both an oscillating and a steady flow component. The steady part can be an important contributor to wave steepening, a mechanism that is often observed during the onset of acoustic instability.
Microstructure, electrical, magnetic, and extraordinary Hall effect studies in Ni:SiO2 nanogranular films synthesized by atom beam sputtering
Authors: Kumar Hardeep , Ghosh Santanu , Bürger Danilo , Zhou Shengqiang , Kabiraj Debdulal , Avasthi Devesh Kumar , Grötzschel Rainer , Schmidt Heidemarie
Published: June 2010

In this work we report on the synthesis of Ni:SiO2 nanogranular films with different metal fraction (0.10≤x≤0.68) and a homogeneous distribution of Ni particles by atom beam sputtering technique and on the study of their microstructure, electrical transport, magnetic properties, and on the observation of extraordinary Hall effect (EHE). Films with the Ni fraction x above percolation threshold (x≥0.58>xp) as revealed by resistivity versus temperature measurements have a large Ni particle size, pronounced ferromagnetic characteristics, and appreciable extraordinary Hall resistivity at 300 K. Furthermore, films above percolation have a relatively low, nearly temperature independent Ohmic resistivity smaller than 10−3 Ω cm and may be useful for Hall sensor applications. On the other hand, films below percolation threshold (x≤0.54<xp) have a small Ni particle size, superparamagnetic behavior, and do not show EHE at 300 K. However, at 5 K all films (xxp) show ferromagnetic characteristics with an enhanced EHE.
Ferroelectric AgNa(NO2)2 crystals as novel highly efficient nonlinear optical material: Phase matched second harmonic generation driven by a spontaneous and electric field induced polarizations
Authors: Sahraoui B. , Czaplicki R. , Klöpperpieper A. , Andrushchak A. S. , Kityk A. V.
Published: June 2010

Paper reports the second harmonic generation (SHG) in ferroelectric AgNa(NO2)2 crystals being driven by the spontaneous and electric field induced polarizations. Obtained results are interpreted within the phenomenological theory which considers the free energy describing the interaction between the spontaneous or electric field induced polarizations and spatially inhomogeneous electric polarizations resulted from propagating optical waves. Relatively high magnitudes of the effective second order nonlinear optical (NLO) susceptibilities in these crystals are combined with several phase matching geometries which allows to consider them as high-performance materials for potential NLO applications, such as parametric generation and amplification, frequency doubling, or other applications that require high-efficient frequency conversion. In addition, an anomalously large response of NLO susceptibilities with respect to an applied electric field has been found in the vicinity of the Curie point. This may also have a number of applications, especially in those devices where an efficient tunable control of SHG intensity is demanded.
Rotating cylindrical magnetron sputtering: Simulation of the reactive process
Authors: Depla D. , Li X. Y. , Mahieu S. , Van Aeken K. , Leroy W. P. , Haemers J. , De Gryse R. , Bogaerts A.
Published: June 2010

A rotating cylindrical magnetron consists of a cylindrical tube, functioning as the cathode, which rotates around a stationary magnet assembly. In stationary mode, the cylindrical magnetron behaves similar to a planar magnetron with respect to the influence of reactive gas addition to the plasma. However, the transition from metallic mode to poisoned mode and vice versa depends on the rotation speed. An existing model has been modified to simulate the influence of target rotation on the well known hysteresis behavior during reactive magnetron sputtering. The model shows that the existing poisoning mechanisms, i.e., chemisorption, direct reactive ion implantation and knock on implantation, are insufficient to describe the poisoning behavior of the rotating target. A better description of the process is only possible by including the deposition of sputtered material on the target.
Photoinduced absorption study of carrier dynamics in Ru-doped Bi12SiO20 crystals after nanosecond laser pulse excitation
Authors: Marinova V. , Ahmad I. , Goovaerts E.
Published: June 2010

The charge carrier dynamics in the sillenite type crystal Bi12SiO20 (BSO) doped with ruthenium is studied by monitoring the optical density changes after nanosecond laser pulse excitation using a frequency-doubled Nd:yttrium aluminum garnet laser. Ruthenium doping leads to a relatively high density of trap levels that significantly increase the relaxation time of excited charge carriers in comparison with a nondoped BSO. Relaxation dynamics with two different decay time constants is observed in BSO:Ru in the studied submicron to 100 s time range and their dependences on pump intensity and on temperature are investigated. From the observed temperature dependence of the slower and faster of the two decay components, thermal activation energies of Ea,s=0.80±0.03 eV and Ea,f=0.68±0.03 eV were determined, respectively. The results indicate that in BSO:Ru at least two different traps centers are involved in the long-lived photoinduced carrier dynamics.
Analytic Morse/long-range potential energy surfaces and predicted infrared spectra for CO2–H2
Authors: Li Hui , Roy Pierre-Nicholas , Le Roy Robert J.
Published: June 2010

Five-dimensional ab initio potential energy surfaces (PESs) for CO2–H2 that explicitly incorporate dependence on the Q3 asymmetric-stretch normal-mode coordinate of the CO2 monomer and are parametrically dependent on its Q1 symmetric-stretch coordinate have been calculated. Analytic four-dimensional PESs are obtained by least-squares fitting vibrationally averaged interaction energies for v3(CO2)=0, and 1 to the Morse/long-range potential function form. These fits to 23 113 points have root-mean-square (rms) deviations of 0.143 and 0.136 cm−1, and require only 167 parameters. The resulting vibrationally averaged PESs provide good representations of the experimental infrared data: for infrared transitions of para- and ortho-H2–CO2, the rms discrepancies are only 0.004 and 0.005 cm−1, respectively. The calculated infrared band origin shifts associated with the ν3 fundamental of CO2 are −0.179 and −0.092 cm−1 for para-H2–CO2 and ortho-H2–CO2, in good agreement with the (extrapolated) experimental values of −0.198 and −0.096 cm−1.
Tomography of an ultrafast laser driven proton source
Authors: Ter-Avetisyan S. , Schnürer M. , Nickles P. V. , Sandner W. , Borghesi M. , Nakamura T. , Mima K.
Published: June 2010

Using a multichannel Thomson spectrometer we have implemented a tomographic approach allowing the reconstruction of the emission characteristic of a laser driven proton source with high energy and spatial resolution. The results demonstrate the complexity of the temporal and spatial characteristics of such a source. The emitted proton beam, which is laminar and divergent at high energies, becomes convergent at low energies. This implies that a fraction of the proton beam having this kinetic energy is emitted in a collimated way from the target at the “turning point” between these two behaviors. Only a finite fraction of the target surface is contributing to the ion spectrum, which is measured at a specific angle within the beam cone. Therefore the momentum distribution of the protons in the emitted beam at any point in space can be controlled by determining the proton source area.
An alignment-free fiber-coupled microsphere resonator for gas sensing applications
Authors: Gregor Markus , Pyrlik Christoph , Henze Rico , Wicht Andreas , Peters Achim , Benson Oliver
Published: June 2010

In this paper we report on the assembly of a robust sensor system consisting of a polystyrene microsphere resonator attached to an optical fiber taper. Since the sphere is only supported by the micrometer-sized fiber no further alignment is necessary. This results in a thermally and mechanically well isolated optical resonator system with quality factors as high as 6×105. The narrow resonances of whispering gallery modes supported by the polystyrene resonators shift with temperature at a rate of 3.8 GHz/K. Thus, a sensitive thermometer is established which allows to detect the surrounding gas via its characteristic thermal conductivity.
A study on axial and torsional resonant mode matching for a mechanical system with complex nonlinear geometries
Authors: Watson Brett , Yeo Leslie , Friend James
Published: June 2010

Making use of mechanical resonance has many benefits for the design of microscale devices. A key to successfully incorporating this phenomenon in the design of a device is to understand how the resonant frequencies of interest are affected by changes to the geometric parameters of the design. For simple geometric shapes, this is quite easy, but for complex nonlinear designs, it becomes significantly more complex. In this paper, two novel modeling techniques are demonstrated to extract the axial and torsional resonant frequencies of a complex nonlinear geometry. The first decomposes the complex geometry into easy to model components, while the second uses scaling techniques combined with the finite element method. Both models overcome problems associated with using current analytical methods as design tools, and enable a full investigation of how changes in the geometric parameters affect the resonant frequencies of interest. The benefit of such models is then demonstrated through their use in the design of a prototype piezoelectric ultrasonic resonant micromotor which has improved performance characteristics over previous prototypes.
Measurement of electron temperature and ion density using the self-bias effect in plasmas
Authors: Hwang Kwang-Tae , Oh Se-Jin , Choi Ik-Jin , Chung Chin-Wook
Published: June 2010

For novel plasma diagnostics, the rf floating probe was revisited. For inducing the self-bias effect, ac bias voltage (∼kilohertz) was applied through a dc blocking capacitor between a probe and a signal generator. The dc self-bias potential was changed not only with ac bias voltages but also with electron temperatures, and therefore, the electron temperature was derived from the variations in the self-bias potential with and without ac bias voltage. The harmonic component of the probe contains information about the ion flux, and using a fast Fourier transform analysis of the probe current, the ion density was derived from the first harmonic current of the probe. The experimental results were compared with a single Langmuir probe. The electron temperature and the ion density were in good agreement with those from the Langmuir probe. Because the amplitude of the ac bias voltage is very low (<3 V), local ionizations affected by a high bias-voltage can be neglected.
Collisionless magnetic reconnection in the presence of a sheared velocity field
Authors: Faganello M. , Pegoraro F. , Califano F. , Marradi L.
Published: June 2010

The linear theory of magnetic field lines reconnection in a two-dimensional configuration in the presence of a (Kelvin–Helmholtz stable) sheared velocity field is investigated within a single fluid model, where the onset of magnetic field line reconnection is made possible by the effect of electron inertia in the so called large Δ′ regime.
Communications: Intramolecular basis set superposition error as a measure of basis set incompleteness: Can one reach the basis set limit without extrapolation?
Authors: Balabin Roman M.
Published: June 2010

One of only two error sources in the solution of the electronic Schrödinger equation is addressed: The basis set convergence (incompleteness) error (BSIE). The results of ab initio (first principles) correlated methods, for which the Møller–Plesset second order perturbation theory (MP2) was chosen as an example, were extrapolated to the complete basis set (CBS) limit using a Dunning-type basis set series. Basis sets as large as cc-pV5Z and cc-pV6Z were used. A representative molecular set that included nitrogen (N2), acetylene (C2H2), ethylene (C2H4), carbon dioxide (CO2), water (H2O), ammonia (NH3), hydrogen cyanide (HCN), and ethanol (C2H5OH) molecules was used for the calculations. The intramolecular basis set superposition error (BSSE) was found to be correlated with BSIE, meaning that intramolecular BSSE can be used as a measure of basis set incompleteness. The BSIE dependence on BSSE could be qualitatively approximated (±25%) by a power-law dependence: BSIE=A×BSSEp, where log10(A)=1.45±0.21 and p=1.27±0.09. This leads to the fact that CBS values at the MP2 theory level can be obtained using only one energy value and the corresponding intermolecular BSSE. The same power-law dependence was confirmed for all of the molecular systems studied. The universality of the BSIE versus BSSE dependence presented was checked using Pople-type basis sets. Even the results obtained with 6-311G, 6-311G∗∗, and 6-311G(2df,2pd) basis sets were found to be nicely described by the same (universal) power law. Benchmark studies of nitrogen and acetylene contraction (compaction) showed that BSIE can be decreased by up to 83% (at the cc-pVTZ level) using the CBS-BSSE strategy described. The presented BSIE versus BSSE dependence can greatly aid in obtaining CBS results for large molecular systems of chemical or biological interest.
Frequency dependent rotation and translation of nanowires in liquid environment
Authors: Marczak Marcin , Hourlier Djamila , Mélin Thierry , Adamowicz Leszek , Diesinger Heinrich
Published: June 2010

In this paper, an approach of aligning and handling silicon nanowires in liquid environment on the large scale is presented. Traveling dielectrophoresis was used to simultaneously pump a weakly ionic nanowire suspension and to rotate nanowires in a plane perpendicular to the electrodes. The pumping force on the solution was maximized by monitoring the cell impedance using impedance spectroscopy and by matching the frequency of the supply voltage to the impedance crossover. At frequencies above or below impedance crossover, trapping or rotation of nanowires was observed which is explained by means of a competition between stationary and drag forces.
Abelian link invariants and homology
Authors: Guadagnini Enore , Mancarella Francesco
Published: June 2010

We consider the link invariants defined by the quantum Chern–Simons field theory with compact gauge group U(1) in a closed oriented 3-manifold M. The relation of the Abelian link invariants with the homology group of the complement of the links is discussed. We prove that, when M is a homology sphere or when a link—in a generic manifold M—is homologically trivial, the associated observables coincide with the observables of the sphere S3. Finally, we show that the U(1) Reshetikhin–Turaev surgery invariant of the manifold M is not a function of the homology group only, nor a function of the homotopy type of M alone.
Three-dimensional evolution of the fast reconnection mechanism in a force-free current sheet
Authors: Ugai M.
Published: June 2010

As a sequence of the recent paper on the fast reconnection evolution in a sheared current sheet [M. Ugai, Phys. Plasmas 17, 032313 (2010)], the present paper further studies the three-dimensional fast reconnection evolution in a force-free current sheet system. In general, for the larger sheared field magnitude, the fast reconnection evolution requires the larger spatial scales of the current sheet. For the force-free current sheet system, the critical condition for the fast reconnection evolution is that the current sheet width (extent) in the sheet current direction is about six times larger than its thickness. Once the fast reconnection evolves, the low-β plasma pressure is drastically enhanced in the reconnection outflow region to become comparable with the ambient magnetic pressure. Ahead of the Alfvénic fast reconnection jet, a large-scale plasmoid is formed, where the enhanced plasma pressure is stored. Inside the plasmoid, the sheared field lines are piled up in the form of a core and are significantly wound (or bent) in the sheared field (sheet current) direction because of the oblique plasmoid propagation along the sheared field. The resulting spatial changes in magnetic fields in the plasmoid are found to be in good agreement with the magnetic field signatures usually obtained by satellite observations inside the plasmoid propagating down in the geomagnetic tail.
Modeling of a negative ion source. III. Two-dimensional structure of the extraction region
Authors: Taccogna F. , Minelli P. , Longo S. , Capitelli M. , Schneider R.
Published: June 2010

The self-consistent production and transport of H− in the extraction region of a hybrid negative ion source is modeled by means of a two-dimensional particle-in-cell/Monte Carlo simulation. The normal coordinate and one parallel coordinate with respect to the plasma grid are considered to analyze the transport of negative ions. Results show that, in order to establish space charge compensation, the extraction of surface-produced negative ions is limited by the flux of positive ions directed toward the plasma grid surface. An electrostatic barrier appears just in front of the wall, reflecting the majority of surface-produced H− and reducing by this their extraction probability to only 8.5%. Results reproduce the experimentally observed influence of the plasma grid bias voltage on the extraction identifying as a key element the presence of a saddle point in the electric potential distribution.
Anomalous molecular orbital variation upon adsorption on a wide band gap insulator
Authors: Chen Wei , Tegenkamp Christoph , Pfnür Herbert , Bredow Thomas
Published: June 2010

It is commonly believed that organic molecules are physisorbed on the ideal nonpolar surfaces of wide band gap insulators with limited variation in the electronic properties of the adsorbate molecule. On the basis of first principles calculations within density functional theory (DFT) and GW approximation, we show that this is not generally true. We find that the molecular frontier orbitals undergo significant changes when a hydroxy acid (here we chose gluconic acid) is adsorbed on MgSO4⋅H2O(100) surface due to the complex interaction between the molecule and the insulating surface. The predicted trend of the adsorption effect on the energy gap obtained by DFT is reversed when the surface polarization effect is taken into account via the many-body corrections.
Effect of ion beam on the propagation of rarefactive solitons in multicomponent plasma with negative ions
Authors: Bailung H. , Sharma S. K. , Nakamura Y.
Published: June 2010

Propagation characteristics of rarefactive solitons excited in a multicomponent plasma with negative ions have been studied in the presence of a positive ion beam in a double plasma device. The Korteweg–de Vries equation for ion beam-multicomponent plasma system admits rarefactive (compressive) soliton solutions when the beam velocity is below (above) a critical value. An ion beam is found to enhance the amplitude of the rarefactive solitary waves. The Mach velocities and widths of the rarefactive solitons are measured for different beam velocities and compared with the theoretical results.
Low-energy electron-stimulated desorption of cations and neutrals from Si(111)-(7×7):C2D2
Authors: Shepperd Kristin R. , Lane Christopher D. , Orlando Thomas M.
Published: June 2010

The interactions of low-energy (5–50 eV) electrons with acetylene-d2 (C2D2) adsorbed on the Si(111)-(7×7) surface have been examined by monitoring the stimulated desorption products. These include primary cation desorbates, D+ and C2D2+ (C2HD+), the fragment ion C2D+, smaller amounts of C2+, CDH+ (CH3+), and neutral D(S2). The ∼23–25 eV threshold energies for D+ and hydrocarbon fragment ion detection indicate involvement of two-hole or two-hole one electron final states that Coulomb explode. These multihole states can be created via Auger decay of single holes in shallow core levels localized on C or Si surface atoms. The ∼12 eV appearance threshold for the C2D2+ molecular ion can be correlated with direct excitation of an adsorbate-induced surface state, which may initially possess character of the A3 surface state of Si. The 18 eV threshold for C2D+ correlates with decomposition of C2D2+ with excess vibronic energy. C2D+ desorption via direct excitation of the dissociative ∑u+2-type state of the C2D2+ ion is also possible. The ∼8 eV threshold energy for production and desorption of neutral D(S2) may correlate with excitation of the perturbed/mixed F ∑u+1←X ∑g+1 and E ∑u+1←X∑g+1 dissociative transitions of adsorbed acetylene molecules. Time-of-flight distributions of D(S2) indicate both nonthermal (557 and 116 meV; 4300 and 900 K) and thermal (17 meV; 130 K) components. The two fast components can be related to the geometry of di-σ bonded acetylene on the Si(111)-(7×7) surface.
Instabilities of relativistic counterstreaming proton beams in the presence of a thermal electron background
Authors: Yalinewich A. , Gedalin M.
Published: June 2010

A linear stability analysis is performed for two counterstreaming proton beams in the presence of a thermal electron background. Growth rates and polarization properties of unstable modes are calculated for various density ratios of the proton beams. It is found that in most cases, two unstable modes grow simultaneously: an electromagnetic filamentary mode that propagates perpendicular to the beam and an electrostatic mode that propagates parallel to the beam. The growth rates of the two modes are comparable, so that one expects that the instability would result in the development of a filamentary structure with a superimposed electrostatic pattern.
Study of physical properties of integrated ferroelectric/ferromagnetic heterostructures
Authors: Martínez R. , Kumar A. , Palai R. , Katiyar R. S. , Scott J. F.
Published: June 2010

Superlattices (SLs) with different periodicity of ferromagnetic La0.7Sr0.3MnO3 (LSMO) and ferroelectric Ba0.7Sr0.3TiO3 as constitutive layers were fabricated on conducting LaNiO3 coated (001) oriented MgO substrates using pulsed laser deposition. The crystallinity, ferroelectric, and magnetic properties of the SLs were studied over a wide range of temperatures and frequencies. The structure exhibited ferromagnetic behavior at 300 K and ferroelectric behavior over a range of temperatures between 100 and 300 K. A frequency-dependent change in dielectric constant and tangent loss were observed above the ferromagnetic-paramagnetic temperature. The frequency-dependent dielectric anomalies are attributed to the change in metallic and magnetic nature of LSMO and also the interfacial effect of two different phases that are connected alternatively in series. The effect of ferromagnetic LSMO layers on ferroelectric properties of the SLs indicated strong influence of the interfaces. The asymmetric behavior of ferroelectric loop and the capacitance-voltage relationship suggest development of a built field in the SLs due to high strain across the interfaces.
First-principles study of the IVA group atoms adsorption on graphene
Authors: Gao Haigen , Zhou Jian , Lu Minghui , Fa Wei , Chen Yanfeng
Published: June 2010

The adsorption of five different IVA group atoms on graphene is studied by using the density functional theory. The adsorption energy, geometric, and electronic structure are calculated. We find that the adsorption energy decreases when the atomic number of adsorbate increases. The interaction between the adsorbate and graphene also changes from the strong covalent bond to the weak van der Waals interaction from C to Pb. For C and Si atoms, the stablest adsorption site is the bridge site, while for Ge, Sn, and Pb atoms, both the top and bridge sites are same stable. The spin-polarized calculations show that graphene could be magnetic when the IVA group atom adsorbed on it. Detailed analysis shows that the magnetic moment comes from the localized p orbital of IVA group atom.
Ab initio simulations of molten Ni alloys
Authors: Woodward Christopher , Asta Mark , Trinkle Dallas R. , Lill James , Angioletti-Uberti Stefano
Published: June 2010

Convective instabilities responsible for misoriented grains in directionally solidified turbine airfoils are produced by variations in liquid–metal density with composition and temperature across the solidification zone. Here, fundamental properties of molten Ni-based alloys, required for modeling these instabilities, are calculated using ab initio molecular dynamics simulations. Equations of state are derived from constant number-volume-temperature ensembles at 1830 and 1750 K for elemental, binary (Ni–X, X=Al, W, Re, and Ta) and ternary (Ni–Al–X, X=W, Re, and Ta) Ni alloys. Calculated molar volumes agree to within 0.6%–1.8% of available measurements. Predictions are used to investigate the range of accuracy of a parameterization of molar volumes with composition and temperature based on measurements of binary alloys. Structural analysis reveals a pronounced tendency for icosahedral short-range order for Ni–W and Ni–Re alloys and the calculations provide estimates of diffusion rates and their dependence on compositions and temperature.
Comparison of the room temperature 1.53 μm Er photoluminescence from flash lamp and furnace annealed Er-doped Ge-rich SiO2 layers
Authors: Kanjilal A. , Prucnal S. , Rebohle L. , Voelskow M. , Helm M. , Skorupa W.
Published: June 2010

The furnace and flash-lamp annealing (FLA) temperature dependent variation in the room temperature 1.53 μm Er photoluminescence (PL) from Er-doped Ge-rich SiO2 layers is investigated. The appearance of the 1.53 μm Er PL is discussed in the framework of the phonon-assisted fluorescent resonant energy transfer from Ge-related luminescence-centers (LCs) to the Er3+. Detailed analyses suggest that in case of FLA the decrease in the 1.53 μm Er PL intensity is governed by the temperature dependent recrystallization of Ge nanoclusters, while for furnace-annealing it is associated with the reduction in the LC-Er3+ coupling due to Ge out-diffusion and the formation of Er-rich clusters with increasing temperature.
Fluorescence spectroscopy of jet-cooled o-fluoroanisole: Mixing through Duschinsky effect and Fermi resonance
Authors: Isozaki Tasuku , Sakeda Kosaku , Suzuki Tadashi , Ichimura Teijiro
Published: June 2010

Laser-induced fluorescence (LIF) excitation, UV-UV hole burning, and single vibronic level fluorescence (SVLF) spectra of jet-cooled o-fluoroanisole (o-FA) were measured. The most intense lowest-frequency band at 36 612 cm−1 was assigned to the origin band of the most stable trans conformer. The UV-UV hole-burning spectrum demonstrated that the prominent bands in the LIF excitation spectrum were responsible for the trans conformer. The metastable non-planar conformer was not observed in the spectra. The vibrational band assignments were performed with the aid of quantum chemical calculations at the B3LYP/cc-pVTZ and CIS/6-311G(d,p) levels. The precise analysis of the SVLF spectra indicated that strong vibrational mixing through the Duschinsky effect and the Fermi resonance occurs in the S1 state.
A modified Landau–Devonshire thermodynamic potential for strontium titanate
Authors: Sheng G. , Li Y. L. , Zhang J. X. , Choudhury S. , Jia Q. X. , Gopalan V. , Schlom D. G. , Liu Z. K. , Chen L. Q.
Published: June 2010

The range of reported values of the Landau energy coefficients of bulk SrTiO3 leads to uncertainty in not only the magnitude but also the direction of the calculated spontaneous polarization in SrTiO3 thin films in a state of biaxial tension. In this study, we use experimental results from strained SrTiO3 films together with phase-field simulations to refine the values of the Landau energy coefficients and report a modified thermodynamic potential for bulk strontium titanate. The transition temperatures and ferroelectric/antiferrodistortive domain stabilities predicted from this modified potential agree well with measurements on biaxially strained SrTiO3 thin films.
The impact of nonlinearity on degenerate parametric amplifiers
Authors: Rhoads Jeffrey F. , Shaw Steven W.
Published: June 2010

This work investigates the effects of system nonlinearities on degenerate parametric amplifiers. A simple, Duffing-type nonlinearity is appended to a representative equation of motion for a mechanical or electromechanical parametric amplifier, and classical perturbation methods are used to characterize the resulting effects on the amplifier’s frequency response and performance. Ultimately, the work demonstrates that parametric amplification can be realized in nonlinear, dynamic-range limited systems, such as resonant micro- or nanosystems, but at the expense of performance degradation. Additionally, it is shown that nonlinear amplifiers can be operated above their linear instability threshold but that doing so results in bistable amplified responses.
Negative magnetoresistance in a V3+/V4+ mixed valent vanadate
Authors: Maignan A. , Lebedev O. I. , Van Tendeloo G. , Martin C. , Hébert S.
Published: June 2010

The magnetotransport and magnetic properties of the PbV6O11 vanadate, crystallizing in the P63mc space group, reveal the existence of a negative magnetoresistance related to its ferromagnetic state (TC∼90 K). The maximum effect is observed at 20 K reaching −30% in 9 T. The structural study of this ceramic reveals a V/Pb ratio smaller than expected from the formula. This is explained by the presence of numerous stacking faults observed by high resolution transmission electron microscopy. The existence of these planar defects acting as resistive barriers along the c axis could be responsible for tunneling magnetoresistance.
The effect of yttrium dopant on the proton conduction pathways of BaZrO3, a cubic perovskite
Authors: Gomez Maria A. , Chunduru Mythili , Chigweshe Lorencia , Foster Leigh , Fensin S. J. , Fletcher Katharyn M. , Fernandez Laura E.
Published: June 2010

When BaZrO3 is doped with Y in 12.5% of Zr sites, density functional theory with the PBE functional predicts octahedral distortions within a cubic phase yielding a greater variety of proton binding sites than undoped BaZrO3. Proton binding sites, transition states, and normal modes are found and used to calculate transition state theory rate constants. The binding sites are used to represent vertices in a graph. The rate constants connecting binding sites are used to provide weights for graph edges. Vertex and color coding are used to find proton conduction pathways in BaZr0.875Y0.125O3. Many similarly probable proton conduction pathways which can be periodically replicated to yield long range proton conduction are found. The average limiting barriers at 600 K for seven step and eight step periodic pathways are 0.29 and 0.30 eV, respectively. Inclusion of a lattice reorganization barrier raises these to 0.42 and 0.33 eV, respectively. The majority of the seven step pathways have an interoctahedral rate limiting step while the majority of the eight step pathways have an intraoctahedral rate limiting step. While the average limiting barrier of the seven step periodic pathway including a lattice reorganization barrier is closer to experiment, how to appropriately weight different length periodic pathways is not clear. Likely, conduction is influenced by combinations of different length pathways. Vertex and color coding provide useful ways of finding the wide variety of long range proton conduction pathways that contribute to long range proton conduction. They complement more traditional serial methods such as molecular dynamics and kinetic Monte Carlo.
An infrared invisibility cloak composed of glass
Authors: Semouchkina Elena , Werner Douglas H. , Semouchkin George B. , Pantano Carlo
Published: June 2010

We propose to implement a nonmetallic low-loss cloak for the infrared range from identical chalcogenide glass resonators. Based on transformation optics for cylindrical objects, our approach does not require metamaterial response to be homogeneous and accounts for the discrete nature of elementary responses governed by resonator shape, illumination angle, and inter-resonator coupling. Air fractions are employed to obtain the desired distribution of the cloak effective parameters. The effect of cloaking is verified by full-wave simulations of the true multiresonator structure. The feasibility of cloak fabrication is demonstrated by prototyping glass grating structures with the dimensions characteristic for the cloak resonators.
Nucleation of amyloid fibrils
Authors: Kashchiev Dimo , Auer Stefan
Published: June 2010

We consider nucleation of amyloid fibrils in the case when the process occurs by the mechanism of direct polymerization of practically fully extended protein segments, i.e., β-strands, into β-sheets. Applying the classical nucleation theory, we derive a general expression for the work to form a nanosized amyloid fibril (protofilament) constituted of successively layered β-sheets. Analysis of this expression reveals that with increasing its size, the fibril transforms from one-dimensional to two-dimensional aggregate in order to preserve the equilibrium shape corresponding to minimal formation work. We determine the size of the fibril nucleus, the fibril nucleation work, and the fibril nucleation rate as explicit functions of the concentration and temperature of the protein solution. The results obtained are applicable to homogeneous nucleation, which occurs when the solution is sufficiently pure and/or strongly supersaturated.
Theory of binary mixtures of a rodlike polymer and a liquid crystal
Authors: Matsuyama Akihiko
Published: June 2010

We present a mean field theory to describe phase separations in mixtures of a low molecular-weight-liquid crystalline (LC) molecule and a rigid-rodlike polymer (rod) such as carbon nanotubes (CNTs) and LC polymers. By taking into account two orientational order parameters of the rod and the LC, we find three nematic phases (N0,N1,N2) on the temperature-concentration plane, depending on the attractive or repulsive interactions between the rod and the LC. We discuss the phase behavior of the systems where the rod and the LC are oriented to be parallel or perpendicular with each other and find that the phase diagrams of the parallel alignment are different from that of the perpendicular one. We predict the appearances of a lower critical solution temperature (LCST) and an upper one, a tricritical point, a critical point, and the first- and the second-order nematic-isotropic phase transitions. The theory can qualitatively describe the phase diagram with a LCST observed in a rod/LC mixture. We also predict a variety of phase separations in CNT/LC mixtures.
Formation mechanism of polycyclic aromatic hydrocarbons in benzene combustion: Quantum chemical molecular dynamics simulations
Authors: Saha Biswajit , Irle Stephan , Morokuma Keiji
Published: June 2010

High temperature quantum chemical molecular dynamics simulations on the polycyclic aromatic hydrocarbon (PAH) formation during combustion of benzene were performed using the density-functional tight-binding (DFTB) method. Systems with varying H/C of 0.8, 0.6, 0.4, and 0.2 and temperatures of Tn=2500 K and Tn=3000 K were employed for the study of the PAH formation and growth mechanism, and trajectories were analyzed by recording average C:H compositions, common elementary reactions and molecular species, ring count, and other characteristic quantities as functions of time. We found that at H/C=0.8 mostly short polyacetylenic hydrocarbons were formed, and no significant PAH growth was found. At lower H/C ratio, longer polyacetylenic chains started to form and new five- and six-membered rings were created due to chain entanglement. Significant PAH growth forming only pericondensed PAHs was observed at lower H/C ratios of 0.4 and 0.2. In addition, smaller hydrocarbon species, such as C2H2, C2H, and C2, are constantly produced by fragmentation of hydrocarbons (unimolecular reactions) and remain common species, although they are simultaneously consumed by the H-abstraction-C2H2-addition growth mechanism. Hydrogen is found to have a clear inhibitive effect on PAH and carbon cluster growth in general, in agreement with recent experimental observations.
Collimation of horizontally polarized shear waves by means of ridge grating supported Love modes
Authors: Christensen J. , Martín-Moreno L. , García-Vidal F. J.
Published: June 2010

In this paper a theoretical study on transmission phenomena of horizontally polarized shear waves propagating through a subwavelength solid probe surrounded by ridges is presented. In this context, the resonant components responsible for enhanced transmission and elastic beaming are identified as Fabry–Perot resonances inside the probe, and ridge induced Love waves. Apart from the fundamental interest, it is envisaged that the ability to enhance elastic vibrations through subwavelength channels and to focus the emerged field, will give rise to improved ultrasonic devices for sensing and testing applications.
Metal-oxide-semiconductor tunneling photodiodes with enhanced deep depletion at edge by high-k material
Authors: Cheng Jen-Yuan , Lu Hui-Ting , Hwu Jenn-Gwo
Published: June 2010

Metal-oxide-semiconductor (MOS) photodetector with the high-k material enhanced deep depletion at edge was demonstrated. The mechanism of saturated substrate injection current in MOS capacitor was adopted. By building HfO2 based devices that with the direct observation of the enhanced edge charge collection efficiency due to fringing field effect in inversion, we are able to show a photodetector with 3000 times (ratio of photocurrent to dark current) improvement in sensitivity than the conventional SiO2 based tunneling photodiodes (approximate 100 times) in the visible.
UV-Raman imaging of the in-plane strain in single ultrathin strained silicon-on-insulator patterned structure
Authors: Moutanabbir O. , Reiche M. , Hähnel A. , Erfurth W. , Motohashi M. , Tarun A. , Hayazawa N. , Kawata S.
Published: June 2010

Confocal UV-Raman with glycerin-immersed high numerical aperture objective lens was used to probe the local strain in individual strained Si structures. The investigated structures were fabricated from 15 nm thick strained silicon-on-insulator substrates with a tensile strain of 0.8%. Two-dimensional maps of the postpatterning strain were obtained for single structures with lateral dimension of 500 nm. We found that the strain measured at the center partially relaxes and drops to 0.67% as a result of patterning-induced free surfaces. This relaxation increases toward the edges following nearly a parabolic behavior. A different strain behavior was observed for larger structures.
Atomic Weights of the Elements 1991
Authors:   IUPAC Commission on Atomic Weights and Isotopic Abundances
Published: June 2010

The biennial review of atomic weight Ar(E), determinations, and other cognate data has resulted in changes for the standard atomic weight of indium from 114.82±0.01 to 114.818±0.003, for tungsten from 183.85±0.03 to 183.84±0.01, and for osmium from 190.2±0.1 to 190.23±0.03 due to new high precision measurements. Recent investigations on silicon and antimony confirmed the presently accepted Ar values. The footnote ‘‘g’’ was added for carbon and potassium because it has come to the notice of the Commission that isotope abundance variations have been found in geological specimens in which these elements have an isotopic composition outside the limits for normal material. The value of 272 is recommended for the 14N/15N ratio of N2 in air for the calculation of atom percent 15N from measured δ 15N values. Because many elements have a different isotopic composition in nonterrestrial materials, recent data on nonterrestrial material are included in this report for the information of the interested scientific community.
Evaluated Bimolecular Ion-Molecule Gas Phase Kinetics of Positive Ions for Use in Modeling Planetary Atmospheres, Cometary Comae, and Interstellar Clouds
Authors: Anicich Vincent G.
Published: June 2010

Recommendations of reaction rate coefficients and product distributions for bimolecular positive ion-molecule reactions of importance in planetary atmospheres, cometary comae, and interstellar clouds are presented. Two publications Anicich and Huntress, 1986, Ap. J. Supplement Series 62, 553 and Anicich, 1993, Ap. J. Supplement Series 84, 215 served as the basis for this evaluation, which covers the literature from 1965 through 1991 with some additional citations missed in the original surveys.