bluuebunny/crossref_metadata_2025 huggingface dataset:
Low temperature synthesis of nanocrystalline Dy3+ doped cobalt ferrite: Structural and magnetic properties
Authors: Kambale R. C. , Song K. M. , Koo Y. S. , Hur N.
Published: September 2011

In the present work, the effect of Dy3+ substitution on the structural and magnetic properties of CoFe2-xDyxO4 (x = 0.00 to 0.1 in step of 0.025) system synthesized by solution combustion method were investigated. The thermal decomposition process was investigated by means of differential and thermal gravimetric analysis that showed that the precursor could yield the final product after calcination above 600 °C. The phase purity and crystal lattice symmetry were estimated from X-ray diffraction studies. The microstructural features were observed by scanning electron microscopy that demonstrates the fine clustered particles with an increase of average grain size with Dy3+ content. The existence of constituent’s, i.e., Co, Fe, and Dy were authenticated by energy dispersive X-ray analysis. An infrared spectroscopy study shows the presence of two absorption bands in the frequency range around 590 cm−1 (ν1) and around 480 cm−1 (ν2); which indicate the presence of tetrahedral and octahedral group complexes, respectively, within the spinel lattice. Room temperature magnetization measurements showed that the saturation magnetization and hysteresis losses (coercivity) decreases with Dy3+ addition, which implies that these materials may be applicable for magnetic data storage and recording media.
Early-stage plasma dynamics with air ionization during ultrashort laser ablation of metal
Authors: Hu Wenqian , Shin Yung C. , King Galen
Published: September 2011

In this study, the early-stage plasma evolution generated by an ultrashort laser pulse is investigated through pump-probe shadowgraph measurements and simulations. The measurements are performed to show the evolution of the plasma front, while the simulation model is used to further investigate the evolution process and mechanism. Specifically, the laser pulse propagation in air is simulated using the beam propagation method with the slowly varying envelope approximation. The lattice dynamics, the electron dynamics and the multi-scattering event, and the evolution of charged particles (free electrons and ions), are simulated using a molecular dynamics method, a Monte Carlo method, and a particle-in-cell method, respectively. With this simulation model, the refractive index and plasma evolutions are calculated and compared with measured results to validate the simulation model. Different plasma expansion processes, caused by the air ionization, are found with the focal point slightly above and below the target. Air ionization occurs in both cases, but their primary mechanisms are shown to be different.
Accurate time dependent wave packet calculations for the N + OH reaction
Authors: Bulut Niyazi , Roncero Octavio , Jorfi Mohamed , Honvault Pascal
Published: September 2011

We present accurate quantum calculations of state-to-state cross sections for the N + OH → NO + H reaction performed on the ground 3A′′ global adiabatic potential energy surface of Guadagnini et al. [J. Chem. Phys. 102, 774 (1995)]10.1063/1.469191. The OH reagent is initially considered in the rovibrational state v = 0, j = 0 and wave packet calculations have been performed for selected total angular momentum, J = 0, 10, 20, 30, 40,…,120. Converged integral state-to-state cross sections are obtained up to a collision energy of 0.5 eV, considering a maximum number of eight helicity components, Ω = 0,…,7. Reaction probabilities for J = 0 obtained as a function of collision energy, using the wave packet method, are compared with the recently published time-independent quantum mechanical one. Total reaction cross sections, state-specific rate constants, opacity functions, and product state-resolved integral cross-sections have been obtained by means of the wave packet method for several collision energies and compared with recent quasi-classical trajectory results obtained with the same potential energy surface. The rate constant for OH(v = 0, j = 0) is in good agreement with the previous theoretical values, but in disagreement with the experimental data, except at 300 K.
Ion-orbital coupling in Car-Parrinello calculations of hydrogen-bond vibrational dynamics: Case study with the NH3–HCl dimer
Authors: Ong S. W. , Lee B. X. B. , Kang H. C.
Published: September 2011

We have performed Car-Parrinello molecular dynamics (CPMD) calculations of the hydrogen-bonded NH3–HCl dimer. Our main aim is to establish how ionic-orbital coupling in CPMD affects the vibrational dynamics in hydrogen-bonded systems by characterizing the dependence of the calculated vibrational frequencies upon the orbital mass in the adiabatic limit of Car-Parrinello calculations. We use the example of the NH3–HCl dimer because of interest in its vibrational spectrum, in particular the magnitude of the frequency shift of the H–Cl stretch due to the anharmonic interactions when the hydrogen bond is formed. We find that an orbital mass of about 100 a.u. or smaller is required in order for the ion-orbital coupling to be linear in orbital mass, and the results for which can be accurately extrapolated to the adiabatic limit of zero orbital mass. We argue that this is general for hydrogen-bonded systems, suggesting that typical orbital mass values used in CPMD are too high to accurately describe vibrational dynamics in hydrogen-bonded systems. Our results also show that the usual application of a scaling factor to the CPMD frequencies to correct for the effects of orbital mass is not valid. For the dynamics of the dimer, we find that the H–Cl stretch and the N–H–Cl bend are significantly coupled, suggesting that it is important to include the latter degree of freedom in quantum dynamical calculations. Results from our calculations with deuterium-substitution show that both these degrees of freedom have significant anharmonic interactions. Our calculated frequency for the H–Cl stretch using the Becke-exchange Lee-Yang-Parr correlation functional compares reasonably well with a previous second-order Møller-Plesset calculation with anharmonic corrections, although it is low compared to the experimental value for the dimer trapped in a neon-matrix.
Electronic spectroscopy of CoNe+ via mass-selected photodissociation
Authors: Mosley J. D. , Cheng T. C. , Hasbrouck S. D. , Ricks A. M. , Duncan M. A.
Published: September 2011

The CoNe+ diatomic cation is produced by laser vaporization in a pulsed-nozzle source and studied with photodissociation spectroscopy at visible wavelengths. Vibronic structure is assigned to the 3Π2 ← 3Δ3 band system correlating to the Co+(3P2 ← 3F4) + Ne asymptote. The origin band (13 529 cm−1) and a progression of 14 other vibrational bands are detected ending in the dissociation limit at 14 191 cm−1. The excited state dissociation energy is therefore D0′ = 662 cm−1, and an energetic cycle using this, the origin band energy, and the atomic transition produces a ground state dissociation energy of D0″ = 930 cm−1. The excited state vibrational frequency is 116.1 cm−1. A rotationally resolved study of the origin band confirms the electronic transition assignment and provides the bond distance of r0″ = 2.36 Å. The properties of CoNe+ are compared to those of other CoRG+ and MNe+ complexes studied previously.
Cluster cross sections from pickup measurements: Are the established methods consistent?
Authors: Fedor J. , Poterya V. , Pysanenko A. , Fárník M.
Published: September 2011

Pickup of several molecules, H2O, HBr, and CH3OH, and Ar atoms on free ArN clusters has been investigated in a molecular beam experiment. The pickup cross sections of the clusters with known mean sizes, \documentclass[12pt]{minimal}\begin{document}$\bar{N}\approx$\end{document}N¯≈ 150 and 260 were measured by two independent methods: (i) the cluster beam velocity decrease due to the momentum transfer of the picked up molecules to the clusters, and (ii) Poisson distribution of a selected cluster fragment ion as a function of the pickup pressure. In addition, the pickup cross sections were calculated using molecular dynamics and Monte Carlo simulations. The simulations support the results of the velocity measurements. On the other hand, the Poisson distributions yield significantly smaller cross sections, inconsistent with the known ArN cluster sizes. These results are discussed in terms of: (i) an incomplete coagulation of guest molecules on the argon clusters when two or more molecules are picked up; and (ii) the fragmentation pattern of the embedded molecules and their clusters upon ionization on the Ar cluster. We conclude that the Poisson distribution method has to be cautiously examined, if conclusions should be drawn about the cluster cross section, or the mean cluster size \documentclass[12pt]{minimal}\begin{document}$\bar{N}$\end{document}N¯, and the number of picked up molecules.
Non-Gaussian statistics of electrostatic fluctuations of hydration shells
Authors: Friesen Allan D. , Matyushov Dmitry V.
Published: September 2011

This paper aims to understand the statistics of the electric field produced by water interfacing a non-polar solute of nanometer dimension. We study, by numerical simulations, the interface between SPC/E water and a Kihara solute, which is a hard-sphere core with a Lennard-Jones layer at its surface. The distribution of the interfacial electric field is monitored as a function of the magnitude of a point dipole placed close to the solute-water interface. The free energy surface as a function of the electric field projected on the dipole direction shows a cross-over with increasing dipole magnitude. While it is a single-well harmonic function at low dipole values, it becomes a double-well surface at intermediate dipole moment magnitudes, transforming into a single-well surface again, with a non-zero minimum position, at still higher dipoles. This transformation, reminiscent of a discontinuous phase transition in bulk materials, has a broad intermediate region where the interfacial waters fluctuate between the two minima. This region is characterized by intense field fluctuations, with non-Gaussian statistics and variance far exceeding expectations from the linear-response approximation. The excited state of the surface water is found to be lifted above the ground state by the energy required to break approximately two hydrogen bonds. This state is pulled down in energy by the external electric field of the solute dipole, making it readily accessible to thermal excitations. The excited state is a surface defect in the hydrogen-bond network, creating a stress in the nearby network, but otherwise relatively localized in the region closest to the solute dipole.
Dynamic stabilization of classical Rayleigh-Taylor instability
Authors: Piriz A. R. , Piriz S. A. , Tahir N. A.
Published: September 2011

Dynamic stabilization of classical Rayleigh-Taylor instability is studied by modeling the interface vibration with the simplest possible wave form, namely, a sequence of Dirac deltas. As expected, stabilization results to be impossible. However, in contradiction to previously reported results obtained with a sinusoidal driving, it is found that in general the perturbation amplitude is larger than in the classical case. Therefore, no beneficial effect can be obtained from the vertical vibration of a Rayleigh-Taylor unstable interface between two ideal fluids.
Single mode phonon energy transmission in functionalized carbon nanotubes
Authors: Lee Jonghoon , Varshney Vikas , Roy Ajit K. , Farmer Barry L.
Published: September 2011

Although the carbon nanotube (CNT) features superior thermal properties in its pristine form, the chemical functionalization often required for many applications of CNT inevitably degrades the structural integrity and affects the transport of energy carriers. In this article, the effect of the side wall functionalization on the phonon energy transmission along the symmetry axis of CNT is studied using the phonon wave packet method. Three different functional groups are studied: methyl (–CH3), vinyl (–C2H3), and carboxyl (–COOH). We find that, near Γ point of the Brillouin zone, acoustic phonons show ideal transmission, while the transmission of the optical phonons is strongly suppressed. A positive correlation between the energy transmission coefficient and the phonon group velocity is observed for both acoustic and optical phonon modes. On comparing the transmission due to functional groups with equivalent point mass defects on CNT, we find that the chemistry of the functional group, rather than its molecular mass, has a dominant role in determining phonon scattering, hence the transmission, at the defect sites.
First-principles simulation of molecular dissociation–recombination equilibrium
Authors: Kylänpää Ilkka , Rantala Tapio T.
Published: September 2011

For the first time, the equilibrium composition of chemical dissociation–recombination reaction is simulated from first-principles, only. Furthermore, beyond the conventional ab initio Born–Oppenheimer quantum chemistry the effects from the thermal and quantum equilibrium dynamics of nuclei are consistently included, as well as, the nonadiabatic coupling between the electrons and the nuclei. This has been accomplished by the path integral Monte Carlo simulations for full NVT quantum statistics of the \documentclass[12pt]{minimal}\begin{document}${\rm H}_3^+$\end{document}H3+ ion. The molecular total energy, partition function, free energy, entropy, and heat capacity are evaluated in a large temperature range: from below room temperature to temperatures relevant for planetary atmospheric physics. Temperature and density dependent reaction balance of the molecular ion and its fragments above 4000 K is presented, and also the density dependence of thermal ionization above 10 000 K is demonstrated.
High-resolution spectroscopy of the C–N stretching band of methylamine
Authors: Lees Ronald M. , Sun Zhen-Dong , Billinghurst B. E.
Published: September 2011

The C–N stretching infrared fundamental of CH3NH2 has been investigated by high-resolution laser sideband and Fourier transform synchrotron spectroscopy to explore the energy level structure and to look for possible interactions with high-lying torsional levels of the ground state and other vibrational modes. The spectrum is complicated by two coupled large-amplitude motions in the molecule, the CH3 torsion and the NH2 inversion, which lead to rich spectral structure with a wide range of energy level splittings and relative line intensities. Numerous sub-bands have been assigned for K values ranging up to 12 for the stronger a inversion species for the vt = 0 torsional state, along with many of the weaker sub-bands of the s species. The C–N stretching sub-state origins have been determined by fitting the upper-state term values to J(J + 1) power-series expansions. For comparison with the ground-state behaviour, both ground and C–N stretch origins have been fitted to a phenomenological Fourier series model that produces an interesting pattern with the differing periodicities of the torsional and inversion energies. The amplitude of the torsional energy oscillation increases substantially for the C–N stretch, while the amplitude of the inversion energy oscillation is relatively unchanged. Independent inertial scale factors ρ were fitted for the torsion and the inversion and differ significantly in the upper state. The C–N stretching vibrational energy is determined to be 1044.817 cm−1, while the effective upper state B-value is 0.7318 cm−1. Several anharmonic resonances with vt = 4 ground-state levels have been observed and partially characterized. A variety of J-localized level-crossing resonances have also been seen, five of which display forbidden transitions arising from intensity borrowing that allow determination of the interaction coupling constants.
Epitaxial BaTiO3(100) films on Pt(100): A low-energy electron diffraction, scanning tunneling microscopy, and x-ray photoelectron spectroscopy study
Authors: Förster Stefan , Huth Michael , Schindler Karl-Michael , Widdra Wolf
Published: September 2011

The growth of epitaxial ultrathin BaTiO3 films on a Pt(100) substrate has been studied by scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and x-ray photoelectron spectroscopy (XPS). The films have been prepared by radio-frequency-assisted magnetron sputter deposition at room temperature and develop a long-range order upon annealing at 900 K in O2. By adjusting the Ar and O2 partial pressures of the sputter gas, the stoichiometry was tuned to match that of a BaTiO3(100) single crystal as determined by XPS. STM reveals the growth of continuous BaTiO3 films with unit cell high islands on top. With LEED already for monolayer thicknesses, the formation of a BaTiO3(100)-(1 × 1) structure has been observed. Films of 2-3 unit cell thickness show a brilliant (1 × 1) LEED pattern for which an extended set of LEED I-V data has been acquired. At temperatures above 1050 K the BaTiO3 thin film starts to decay by formation of vacancy islands. In addition (4 × 4) and (3 × 3) surface reconstructions develop upon prolonged heating.
Variable coefficient nonlinear Schrödinger equations with four-dimensional symmetry groups and analysis of their solutions
Authors: Özemir C. , Güngör F.
Published: September 2011

Analytical solutions of variable coefficient nonlinear Schrödinger equations having four-dimensional symmetry groups, which are in fact the next closest to the integrable ones occurring only when the Lie symmetry group is five-dimensional, are obtained using two different tools. The first tool is to use one-dimensional subgroups of the full symmetry group to generate solutions from those of the reduced ordinary differential equations, namely, group invariant solutions. The other is by truncation in their Painlevé expansions.
Determination of binding kinetics using whispering gallery mode microcavities
Authors: Soteropulos Carol E. , Hunt Heather K. , Armani Andrea M.
Published: September 2011

Silica optical microcavity sensors show great promise in the kinetic evaluation of binding pairs, fundamental in understanding biomolecular interactions. Here, we develop and demonstrate a novel platform, based on bioconjugated silica microsphere resonators, to study the binding kinetics of the biotin-streptavidin system. We characterize the optical performance, verify the covalent attachment of biotin to the surface, and perform streptavidin detection experiments. We perform preliminary kinetic analysis of the detection data which shows the potential of whispering gallery mode resonators in the determination of the dissociation constant of the binding pair, which is in good agreement with previously published values.
Properties of the SiO2- and SiNx-capped GaAs(100) surfaces of GaInAsN/GaAs quantum-well heterostructures studied by photoelectron spectroscopy and photoluminescence
Authors: Dahl J. , Polojärvi V. , Salmi J. , Laukkanen P. , Guina M.
Published: September 2011

SiO2 and SiNx layers are routinely deposited onto III-V(100) surfaces at different device processing steps. We elucidate these insulator-interface properties with photoemission and photoluminescence (PL) of SiO2- and SiNx-capped GaAs(100) surfaces of GaInAsN/GaAs quantum wells (QWs). Post-growth annealing led to an increase of the QW-PL intensity, of which origin can be clearly linked to the SiO2 and SiNx interfaces. Concomitantly, Ga2O–related photoemission increased, indicating useful formation of Ga2O at both insulator interfaces. Furthermore, higher Ga-oxidation-state emission, identified with Ga diffused into SiO2 and SiNx, correlates with the blue-shift of the QW-PL wavelength. Also, interfacial As-As related photoemission was identified.
PN junction rectification in electrolyte gated Mg-doped InN
Authors: Alarcón-Lladó E. , Mayer M. A. , Boudouris B. W. , Segalman R. A. , Miller N. , Yamaguchi T. , Wang K. , Nanishi Y. , Haller E. E. , Ager J. W.
Published: September 2011

PN junction rectification is demonstrated in indium nitride. The junction is formed between the n-type surface accumulation layer and the Mg-doped, p-type bulk in a top-contacted thin film structure. The parasitic shorting path between the top contacts is controlled by gating with an electrolyte. For positive gate voltages, electrons accumulate at the surface and the current flows preferentially through n type regions, and linear current-voltage (I-V) behavior is observed. However, for negative gate voltages, surface electrons are depleted and current flows through the p-type bulk. This creates an n-p-n structure and a characteristic non-linear I-V curve is observed.
Probing liquid distribution in partially saturated porous materials with hydraulic admittance
Authors: Cheung P. , Fairweather J. F. , Schwartz D. T.
Published: September 2011

The distribution of two immiscible fluids in a complex porous material during displacement is often central to understanding its function. Characterization of this distribution is traditionally determined via optically transparent flow cells. However, for opaque or thin porous materials of the order of hundreds of microns, optical visualization proves to be difficult and requires sophisticated imaging techniques that are expensive and difficult to come by. We describe here a bench-top tool that dynamically probes the hydraulic pathways leading to each free-interface within a single capillary and a bundle of seven capillaries at various saturations (i.e., hydraulic path lengths). A small volumetric displacement was applied to each interface such that the interfaces remained pinned at the capillary walls and the resultant oscillatory pressure drop was measured to determine the hydraulic admittance at each applied oscillation frequency. When the magnitude of the hydraulic admittance was plotted vs. applied oscillation frequency, a resonance peak was found for each degenerately filled capillary. The corresponding peaks were represented by a half-loop (100% filled) and full loops (partially filled) in a Nyquist plot. We compared the theoretical and measured admittance curves and found good agreement for both capillary systems at high filled states. The theoretical predictions became worse when the hydraulic path length was comparable to the capillary radius. The analysis for the hydraulic admittance of a bundle of capillaries is developed here and experimentally validated for the first time.
Refraction-contrast tomosynthesis imaging using dark-field imaging optics
Authors: Sunaguchi Naoki , Yuasa Tetsuya , Huo Qingkai , Ichihara Shu , Ando Masami
Published: September 2011

A soft tissue tomosynthesis imaging system using Laue-case analyzer for dark-field imaging (DFI) optics is described. Two images from which refraction component is deduced are obtained in a single exposure of DFI, while two exposures are required in diffraction enhanced imaging (DEI). The measurement time and radiation dose are thus reduced to half those from DEI. Additionally, the proposed reconstruction algorithm, using only one tenth the number of projections required in computed tomography (CT) imaging, produced images in no way inferior to refraction-contrast CT images. We ex vivo imaged an excised human lung tissue using the system constructed at the KEK vertical wiggler beamline PF-BL14C to demonstrate the proposed imaging protocol efficacy.
Benchmarking the performance of ultrathin body InAs-on-insulator transistors as a function of body thickness
Authors: Takei Kuniharu , Chuang Steven , Fang Hui , Kapadia Rehan , Liu Chin-Hung , Nah Junghyo , Sul Kim Ha , Plis E. , Krishna Sanjay , Chueh Yu-Lun , Javey Ali
Published: September 2011

The effect of body thickness (5-13 nm) on the leakage currents of top-gated, InAs-on-insulator field-effect-transistors with a channel length of ∼200 nm is explored. From a combination of experiments and simulation, it is found that the OFF-state currents are primarily dominated by Shockley Read Hall recombination/generation and trap-assisted tunneling. The OFF currents are shown to decrease with thickness reduction, highlighting the importance of the ultrathin body device configuration. The devices exhibit promising performances, with a peak extrinsic and intrinsic transconductances of ∼1.7 and 2.3 mS/μm, respectively, at a low source/drain voltage of 0.5 V and a body thickness of ∼13 nm.
Ho substitution suppresses collinear Dy spin order and enhances polarization in DyMnO3
Authors: Zhang N. , Guo Y. Y. , Lin L. , Dong S. , Yan Z. B. , Li X. G. , Liu J.-M.
Published: September 2011

The multiferroic behaviors of Dy1−xHoxMnO3 are investigated in order to reveal the effects of Ho-substitution on the independent collinear Dy spin order and ferroelectric polarization at low temperature. It is demonstrated that a partial Ho-substitution of Dy ions significantly suppresses the independent Dy spin order at low temperature on one hand, and maintains the R-Mn spin coupling on the other hand, thus leading to a remarkable enhancement of the polarization at low temperature.
Highly selective standoff detection and imaging of trace chemicals in a complex background using single-beam coherent anti-Stokes Raman scattering
Authors: Bremer Marshall T. , Wrzesinski Paul J. , Butcher Nathan , Lozovoy Vadim V. , Dantus Marcos
Published: September 2011

A non-destructive and highly selective method of standoff detection is presented and quantitatively evaluated. The method is found to be orders of magnitude more sensitive than previous coherent spectroscopy methods, identifying concentrations as low as 2 μg/cm2 of an explosive simulant mixed in a polymer matrix. The approach uses a single amplified femtosecond laser to generate high-resolution multiplex coherent anti-Stokes Raman scattering (CARS) spectra encompassing the fingerprint region (400−2500 cm−1) at standoff distance. Additionally, a standoff imaging modality is introduced, visually demonstrating similar sensitivity and high selectivity, providing promising results toward highly selective trace detection of explosives or warfare agents.
Effect of cationic substitution on the thermoelectric properties of In4−xMxSe2.95 compounds (M = Na, Ca, Zn, Ga, Sn, Pb; x = 0.1)
Authors: Ahn Kyunghan , Cho Eunseog , Rhyee Jong-Soo , Il Kim Sang , Mock Lee Sang , Hyoung Lee Kyu
Published: September 2011

We report an electrical and thermal transport study for polycrystalline samples of In4Se3−x substituted with various metals. Our experimental and theoretical investigation revealed that the Na, Ca, and Pb substitutions at the In4 site in the 4:3 indium selenide lattice are more effective for increase in electron concentration than the Zn, Ga, and Sn substitutions at other sites, and the Peierls distortion in cationic substituted compounds may not be as strong as In4Se3−x based on higher lattice thermal conductivities of the former than the latter. It is found that the cationic substitutions may weaken the effect of Peierls distortion on thermal properties for In4Se3−x while they maintain the same trend for electrical properties of In4Se3−x with different electron concentrations.
Communication: Are metallic glasses different from other glasses? A closer look at their high frequency dynamics
Authors: Bruna P. , Baldi G. , Pineda E. , Serrano J. , Suck J. B. , Crespo D. , Monaco G.
Published: September 2011

Using high resolution inelastic x-ray scattering we studied the collective dynamics of the Pd77Si16.5Cu6.5 metallic glass, focusing on the energy-momentum region where the boson peak appears. The dispersion relation and the width of the acoustic excitations are determined showing how the longitudinal acoustic modes maintain their dispersive character for frequencies well above the boson peak frequencies. Moreover, we prove that close to these frequencies there is a softening of the apparent sound speed indicating a failure of the Debye continuum approximation at the boson peak frequencies and challenging previous results on other metallic glasses.
Communication: Rationale for a new class of double-hybrid approximations in density-functional theory
Authors: Toulouse Julien , Sharkas Kamal , Brémond Eric , Adamo Carlo
Published: September 2011

We provide a rationale for a new class of double-hybrid approximations introduced by Brémond and Adamo [J. Chem. Phys. 135, 024106 (2011)]10.1063/1.3604569 which combine an exchange-correlation density functional with Hartree-Fock exchange weighted by λ and second-order Møller-Plesset (MP2) correlation weighted by λ3. We show that this double-hybrid model can be understood in the context of the density-scaled double-hybrid model proposed by Sharkas et al. [J. Chem. Phys. 134, 064113 (2011)]10.1063/1.3544215, as approximating the density-scaled correlation functional Ec[n1/λ] by a linear function of λ, interpolating between MP2 at λ = 0 and a density-functional approximation at λ = 1. Numerical results obtained with the Perdew-Burke-Ernzerhof density functional confirms the relevance of this double-hybrid model.
Measurement of the elastic tensor of SmScO3 and NdScO3 using resonant ultrasound spectroscopy with ab initio calculations
Authors: Pestka K. A. , Scott E. S. , Le Page Y.
Published: September 2011

The complete elastic tensors of SmScO3 and NdScO3 were measured using resonant ultrasound spectroscopy (RUS) in combination with ab-initio calculations. Measurement of the elastic tensor of these recently synthesized single crystal RE scandates is essential for understanding dynamic lattice applications including phonon confinement, strain induced thin film growth and superlattice construction. On average, the experimental elastic constants differed by less than 5% of the theoretical values, further validating the accuracy of modern ab-initio calculations as a means of estimating the initial elastic constants used in RUS measurements.
Synergic reprogramming of mammalian cells by combined exposure to mitotic
Xenopus
egg extracts and transcription factors
Authors: Ganier Olivier , Bocquet Stéphane , Peiffer Isabelle , Brochard Vincent , Arnaud Philippe , Puy Aurore , Jouneau Alice , Feil Robert , Renard Jean-Paul , Méchali Marcel
Published: September 2011

Transfer of somatic cell nuclei to enucleated eggs and ectopic expression of specific transcription factors are two different reprogramming strategies used to generate pluripotent cells from differentiated cells. However, these methods are poorly efficient, and other unknown factors might be required to increase their success rate. Here we show that
Xenopus
egg extracts at the metaphase stage (M phase) have a strong reprogramming activity on mouse embryonic fibroblasts (MEFs). First, they reset replication properties of MEF nuclei toward a replication profile characteristic of early development, and they erase several epigenetic marks, such as trimethylation of H3K9, H3K4, and H4K20. Second, when MEFs are reversibly permeabilized in the presence of M-phase
Xenopus
egg extracts, they show a transient increase in cell proliferation, form colonies, and start to express specific pluripotency markers. Finally, transient exposure of MEF nuclei to M-phase
Xenopus
egg extracts increases the success of nuclear transfer to enucleated mouse oocytes and strongly synergizes with the production of pluripotent stem cells by ectopic expression of transcription factors. The mitotic stage of the egg extract is crucial, because none of these effects is detected when using interphasic
Xenopus
egg extracts. Our data demonstrate that mitosis is essential to make mammalian somatic nuclei prone to reprogramming and that, surprisingly, the heterologous
Xenopus
system has features that are conserved enough to remodel mammalian nuclei.
Integrated molecular profiles of invasive breast tumors and ductal carcinoma in situ (DCIS) reveal differential vascular and interleukin signaling
Authors: Kristensen Vessela N. , Vaske Charles J. , Ursini-Siegel Josie , Van Loo Peter , Nordgard Silje H. , Sachidanandam Ravi , Sørlie Therese , Wärnberg Fredrik , Haakensen Vilde D. , Helland Åslaug , Naume Bjørn , Perou Charles M. , Haussler David , Troyanskaya Olga G. , Børresen-Dale Anne-Lise
Published: September 2011

We use an integrated approach to understand breast cancer heterogeneity by modeling mRNA, copy number alterations, microRNAs, and methylation in a pathway context utilizing the pathway recognition algorithm using data integration on genomic models (PARADIGM). We demonstrate that combining mRNA expression and DNA copy number classified the patients in groups that provide the best predictive value with respect to prognosis and identified key molecular and stromal signatures. A chronic inflammatory signature, which promotes the development and/or progression of various epithelial tumors, is uniformly present in all breast cancers. We further demonstrate that within the adaptive immune lineage, the strongest predictor of good outcome is the acquisition of a gene signature that favors a high T-helper 1 (Th1)/cytotoxic T-lymphocyte response at the expense of Th2-driven humoral immunity. Patients who have breast cancer with a basal HER2-negative molecular profile (PDGM2) are characterized by high expression of protumorigenic Th2/humoral-related genes (24–38%) and a low Th1/Th2 ratio. The luminal molecular subtypes are again differentiated by low or high FOXM1 and ERBB4 signaling. We show that the interleukin signaling profiles observed in invasive cancers are absent or weakly expressed in healthy tissue but already prominent in ductal carcinoma in situ, together with ECM and cell-cell adhesion regulating pathways. The most prominent difference between low and high mammographic density in healthy breast tissue by PARADIGM was that of STAT4 signaling. In conclusion, by means of a pathway-based modeling methodology (PARADIGM) integrating different layers of molecular data from whole-tumor samples, we demonstrate that we can stratify immune signatures that predict patient survival.
Cobalt-based magnetic nanocomposites: fabrication, fundamentals and applications
Authors: Wen Tianlong , Krishnan Kannan M
Published: September 2011

Recently, magnetic nanocomposites (MNC) have aroused significant scientific and technological interests because their properties strongly rely on the interplay between those of the constituent components. Here, using three types of cobalt-based MNCs, we demonstrate how their physical behaviour, including thermal, electrical and magnetic, can be strongly affected by such interplays. First, using Aucore–Coshell nanoparticles (NPs), we demonstrate that their thermal stabilities are critically dependent on various boundaries and they structurally transform from the core–shells to the peanut structures via several intermediate states by a series of energy minimizations including the grain boundaries, Co/Au interface and strain. Second, the microstructures of the MNC are co-determined by the properties of the individual components, which in turn will strongly affect their overall properties. We illustrate this by a careful study of the electron transport in cobalt/poly (3-hexylthiophene, 2, 5-diyl) (P3HT) hybrid thin films, and show that they satisfy a fluctuation-induced tunnelling model that is strongly depended on their microstructures; moreover, a magnetoresistance in these thin films was also observed. Finally, the magnetic properties and phase stability of MNCs can also be strongly altered as a result of this interplay. Three phase transformations are observed in cobalt ferrofluids for T ∼ 10–300 K, namely second order magnetic phase transformations (blocked–unblocked transition) at the blocking temperature of the magnetic NP, first order magnetic and structural phase transformations at the solvent melting temperature, T
M, and second order premelting transformation at T
PM < T < T
M. These transformations show specific magnetic signatures in field-cool and zero-field-cool magnetization measurements and are qualitatively in agreement with predictions using M-spectrum theory.
Effect of doped atom magnetism on electronic transport through C59X and C69X(X = B and N) molecular junctions
Authors: Yaghobi Mojtaba
Published: September 2011

In this paper, a theoretical study of spin-polarized quantum transport through a C
n

X molecular junction is presented applying the Keldysh non-equilibrium Green's function formalism. The effects of contacts, doped atom and cage type and the gate and bias voltages on spin-polarized quantum transport through the C
n

X molecular junction are considered in calculations. The calculations indicate that the spin-dependent local density of states of the C
n

X molecules is the cause of magnetic moment on every carbon atom in the vicinity of the doped atom. Also, the spin polarization can reach as high as about 100% with proper selection of bias and gate voltages.
Influence of strain relaxation on the optical properties of InGaN/GaN multiple quantum well nanorods
Authors: Wang Q , Bai J , Gong Y P , Wang T
Published: September 2011

Optical investigation has been carried out on InGaN/GaN nanorod structures with different indium compositions, fabricated from InGaN/GaN multiple quantum well (MQW) epitaxial wafers using a self-organized nickel nano-mask and subsequent dry etching techniques. In comparison with the as-grown InGaN/GaN MQWs, the internal quantum efficiencies of the nanorods are significantly improved, in particular, for the green InGaN/GaN nanorods with a high indium composition, the internal quantum efficiency is enhanced by a factor of 8, much larger than the enhancement factor of 3.4 for the blue InGaN/GaN nanorods. X-ray reciprocal space mapping (RSM) measurements have been performed in order to quantitatively evaluate the stain relaxation in the nanorods, demonstrating that the majority of strain in InGaN/GaN MQWs can be relaxed as a result of fabrication into nanorods. The excitation-power-dependent photoluminescence measurements have also clearly shown that a significant reduction in the strain-induced quantum confined stark effect has occurred to the nanorod structures.
Modelling of the thermal conductivity in polymer nanocomposites and the impact of the interface between filler and matrix
Authors: Kochetov R , Korobko A V , Andritsch T , Morshuis P H F , Picken S J , Smit J J
Published: September 2011

In this paper the thermal conductivity of epoxy-based composite materials is analysed. Two- and three-phase Lewis–Nielsen models are proposed for fitting the experimental values of the thermal conductivity of epoxy-based polymer composites. Various inorganic nano- and micro- particles were used, namely aluminium oxide, aluminium nitride, magnesium oxide and silicon dioxide with average particle size between 20 nm and 20 µm. It is shown that the filler–matrix interface plays a dominant role in the thermal conduction process of the nanocomposites. The two-phase model was proposed as an initial step for describing systems containing 2 constituents, i.e. an epoxy matrix and an inorganic filler. The three-phase model was introduced to specifically address the properties of the interfacial zone between the host polymer and the surface modified nanoparticles.
Thermal and gamma-ray induced relaxation in As–S glasses: modelling and experiment
Authors: Lucas Pierre , King Ellyn A , Erdmann Robert G , Riley Brian J , Sundaram S K , McCloy John S
Published: September 2011

Enthalpy relaxation was measured in a series of As–S glasses irradiated with gamma rays and these samples are compared with a set of identical control samples kept in the dark. It is shown that gamma irradiation lifts the kinetic barrier for relaxation at room temperature and speeds up the enthalpy release. The measured values of thermal relaxation in the dark agree closely with modelling results obtained by fitting differential scanning calorimetry curves with the Tool–Narayanaswamy–Moynihan (TNM) equations. The measured values of activation energy for enthalpy relaxation are also in close agreement with that predicted by the TNM model, therefore lending credence to the fitting results. These measurements permit extraction of the effect of gamma irradiation on the glass structure for a series of As–S glasses with increasing structural coordination, and gamma irradiation is shown to reduce the structural relaxation time. It is also shown that lower coordination glasses exhibit greater radiation sensitivity but also greater thermal relaxation due to their lower T
g. On the other end, over-coordinated glasses show lower relaxation and almost no radiation sensitivity. This behaviour is similar to the glass response under sub-bandgap light irradiation.
Barium zirconate-titanate/barium calcium-titanate ceramics via sol–gel process: novel high-energy-density capacitors
Authors: Puli Venkata Sreenivas , Kumar Ashok , Chrisey Douglas B , Tomozawa M , Scott J F , Katiyar Ram S
Published: September 2011

Lead-free barium zirconate-titanate/barium calcium-titanate, [(BaZr0.2Ti0.80)O3]1−x
–[(Ba0.70Ca0.30)TiO3]
x
(x = 0.10, 0.15, 0.20) (BZT–BCT) ceramics with high dielectric constant, low dielectric loss and moderate electric breakdown field were prepared by the sol–gel synthesis technique. X-ray diffraction patterns revealed tetragonal crystal structure and this was further confirmed by Raman spectra. Well-behaved ferroelectric hysteresis loops and moderate polarizations (spontaneous polarization, P
s ∼ 3–6 µC cm−2) were obtained in these BZT–BCT ceramics. Frequency-dependent dielectric spectra confirmed that ferroelectric diffuse phase transition (DPT) exists near room temperature. Scanning electron microscope images revealed monolithic grain growth in samples sintered at 1280 °C. 1000/ε versus (T) plots revealed ferroelectric DPT behaviour with estimated γ values of ∼1.52, 1.51 and 1.88, respectively, for the studied BZT–BCT compositions. All three compositions showed packing-limited breakdown fields of ∼47–73 kV cm−1 with an energy density of 0.05–0.6 J cm−3 for thick ceramics (>1 mm). Therefore these compositions might be useful in Y5V-type capacitor applications.
Suitability of an MRMCE (multi-resolution minimum cross entropy) algorithm for online monitoring of a two-phase flow
Authors: Wang Qi , Wang Huaxiang , Xin Shan
Published: September 2011

The flow regimes are important characteristics to describe two-phase flows, and measurement of two-phase flow parameters is becoming increasingly important in many industrial processes. Computerized tomography (CT) has been applied to two-phase/multi-phase flow measurement in recent years. Image reconstruction of CT often involves repeatedly solving large-dimensional matrix equations, which are computationally expensive, especially for the case of online flow regime identification. In this paper, minimum cross entropy reconstruction based on multi-resolution processing (MRMCE) is presented for oil–gas two-phase flow regime identification. A regularized MCE solution is obtained using the simultaneous multiplicative algebraic reconstruction technique (SMART) at a coarse resolution level, where important information on the reconstructed image is contained. Then, the solution in the finest resolution is obtained by inverse fast wavelet transformation. Both computer simulation and static/dynamic experiments were carried out for typical flow regimes. Results obtained indicate that the proposed method can dramatically reduce the computational time and improve the quality of the reconstructed image with suitable decomposition levels compared with the single-resolution maximum likelihood expectation maximization (MLEM), alternating minimization (AM), Landweber, iterative least square technique (ILST) and minimum cross entropy (MCE) methods. Therefore, the MRMCE method is suitable for identification of dynamic two-phase flow regimes.
Quasi-classical Trajectory Study of C+CD→C2+D at Different Collision Energy
Authors: Shi Ying , Xie Ting-xian , Jin Ming-xing
Published: September 2011

Quasi-classical trajectory calculations have been employed to investigate the influence of collision energy on the stereodynamics of the title reaction C+CD→C2+D on the potential energy surface of the 12A′ state developed by Boggio-Pasqua et al. [Mol. Phys. 98, 1925 (2000)]. The product angular distributions which reflect the vector correlation have been calculated. In addition, two polarization-dependent different cross-sections are also presented in the center-of-mass frame respectively. The results indicate that the product C2 is sensitively affected by collision energy.
Hamiltonian Reduction of Quantum Systems Controlled by Pulses
Authors: Xu Qiang , Wang Yao-xiong , Shuang Feng , Rabitz Herschel
Published: September 2011

We explores Hamiltonian reduction in pulse-controlled finite-dimensional quantum systems with near-degenerate eigenstates. A quantum system with a non-degenerate ground state and several near-degenerate excited states is controlled by a short pulse, and the objective is to maximize the collective population on all excited states when we treat all of them as one level. Two cases of the systems are shown to be equivalent to effective two-level systems. When the pulse is weak, simple relations between the original systems and the reduced systems are obtained. When the pulse is strong, these relations are still available for pulses with only one frequency under the first-order approximation.
Hydrolysis Mechanism of the NAMI-A-type Antitumor Complex (HL)[trans-RuCl4L(dmso-S)] (L=1-methyl-1,2,4-triazole)
Authors: Chen Lan-mei , Chen Jin-can , Liao Si-yan , Liu Jiang-qin , Luo Hui , Zheng Kang-cheng
Published: September 2011

The hydrolysis process of Ru(III) complex (HL)[trans-RuCl4L(dmso-S)] (L=1-methyl-1,2,4-triazole and dmso-S=S-dimethyl sulfoxide) (1), a potential antitumor complex similar to the well-known antitumor agent (Him)[trans-RuCl4(dmso-S)(im)] (NAMI-A, im=imidazole), was investigated using density functional theory combined with the conductor-like polarizable continuum model approach. The structural characteristics and the detailed energy profiles for the hydrolysis processes of this complex were obtained. For the first hydrolysis step, complex 1 has slightly higher barrier energies than the reported anticancer drug NAMI-A, and the result is in accordance with the experimental evidence indicating larger half-life for complex 1. For the second hydrolysis step, the formation of cis-diaqua species is thermodynamic preferred to that of trans isomers. In addition, on the basis of the analysis of electronic characteristics of species in the hydrolysis process, the trend in nucleophilic attack abilities of hydrolysis products by pertinent biomolecules is revealed and predicted.
Atomistic Model of Uranium
Authors: Li Ru-song , He Bing , Zhang Quan-hu
Published: September 2011

The electronic state and potential data of U2 molecules are performed by first principle calculations with B3LYP hybrid exchange-correlation functional, the valence electrons of U atom are treated with the (5s4p3d4f)/[3s3p2d2f] contraction basis sets, and the cores are approximated with the relativistic effective core potential. The results show that the ground electronic state is X9Σ+g. The pair potential data are fitted with a Murrell-Sorbie analytical potential function. The U-U embedded atom method (EAM) interatomic potential is determined based on the generalized gradient approximation calculation within the framework of the density functional theory using Perdew-Burke-Ernzerhof exchange-correlation functional at the spin-polarized level. The physical properties, such as the cohesive energy, the lattice constant, the bulk modulus, the shear modulus, the sc/fcc relative energy, the hcp/fcc relative energy, the shear modulus and the monovacancy formation energy are used to evaluate the EAM potential parameters. The U-U pair potential determined by the first principle calculations is in agreement with that defined by the EAM potential parameters. The EAM calculated formation energy of the monovacancy in the fcc structure is also found to be in close agreement with DFT calculation.