bluuebunny/crossref_metadata_2025 huggingface dataset:
The vortex shedding around four circular cylinders in an in-line square configuration
Authors: Tong Feifei , Cheng Liang , Zhao Ming , Zhou Tongming , Chen Xiao-bo
Published: March 2014

This paper presents a numerical study of three-dimensional (3D) vortex shedding flow in the wake of four circular cylinders in a square configuration with a constant space-to-diameter ratio of 2. Numerical tests are carried out for Reynolds number (Re) in the range from 100 to 500. Four wake flow regimes are identified at this spacing ratio. Regime 1 ($100 \le {\mathop{\rm Re}\nolimits} \le 220$100≤ Re ≤220) is characterized by the inclination of weak spanwise vortices and weak streamwise vortices, where the wake behind four cylinder array shares similar features to that behind a single cylinder with a large equivalent diameter. It is observed that the onset of three-dimensionality in the wake behind four cylinder array occurs at lower Re than that behind a single cylinder. Regime 2 ($240 \le {\mathop{\rm Re}\nolimits} \le 300$240≤ Re ≤300) is characterized by the appearance of the regular wavy spanwise vortices and rib-shaped streamwise vortices. The wavelength of the spanwise vortices is about 1.2 and the wake flow is similar to the transition mode B of a single cylinder. Regime 3 ($320 \le {\mathop{\rm Re}\nolimits} \le 380$320≤ Re ≤380) is characterized by severe vortex dislocations in the wake of the cylinders and regime 4 ($400 \le {\mathop{\rm Re}\nolimits} \le 500$400≤ Re ≤500) is characterized by the absence of vortex dislocations and the strong streamwise vortices. The flow between the upstream and the downstream cylinders is predominantly two-dimensional in regimes 1, 2, and 3 and becomes 3D in regime 4. Physical mechanisms responsible for different flow regimes are proposed and discussed in details. Significant changes in the root-mean-square force coefficients, wake formation length, and phase angle of the lift coefficients on the downstream cylinders are observed when the flow transits from one regime to another.
Indentation of a flat circular punch with uniform heat flux at its base into transversely isotropic magneto-electro-thermo-elastic half space
Authors: Yang Jing , Jin Xianyu
Published: March 2014

The indentation problem of a flat circular punch with uniform heat flux distributed at its base, pressed into a semi-infinite transversely isotropic magneto-electro-thermo-elastic space is investigated. The closed-form solution in the full space is obtained by potential theory method. In addition, the factors of indentation stiffness that relates mechanical force, electric charge, magnetic induction with the heat flux are presented. The obtained solution can be degenerated for the corresponding problems of thermopiezoelectric, thermomagnetoelastic, and thermoelastic materials and can also be superposed to construct the solution to the corresponding indentation problems with coupled thermal, electric, magnetic, mechanical effects. In addition, the solution presented in this article can not only help to investigate mechanisms of the image formation in the area of nanoscience and nanotechnology, but also can serve as benchmarks for future numerical studies of multiphase composites.
Accurate determination of the binding energy of the formic acid dimer: The importance of geometry relaxation
Authors: Kalescky Robert , Kraka Elfi , Cremer Dieter
Published: March 2014

The formic acid dimer in its C2h-symmetrical cyclic form is stabilized by two equivalent H-bonds. The currently accepted interaction energy is 18.75 kcal/mol whereas the experimental binding energy D0 value is only 14.22 ±0.12 kcal/mol [F. Kollipost, R. W. Larsen, A. V. Domanskaya, M. Nörenberg, and M. A. Suhm, J. Chem. Phys. 136, 151101 (2012)]. Calculation of the binding energies De and D0 at the CCSD(T) (Coupled Cluster with Single and Double excitations and perturbative Triple excitations)/CBS (Complete Basis Set) level of theory, utilizing CCSD(T)/CBS geometries and the frequencies of the dimer and monomer, reveals that there is a 3.2 kcal/mol difference between interaction energy and binding energy De, which results from (i) not relaxing the geometry of the monomers upon dissociation of the dimer and (ii) approximating CCSD(T) correlation effects with MP2. The most accurate CCSD(T)/CBS values obtained in this work are De = 15.55 and D0 = 14.32 kcal/mol where the latter binding energy differs from the experimental value by 0.1 kcal/mol. The necessity of employing augmented VQZ and VPZ calculations and relaxing monomer geometries of H-bonded complexes upon dissociation to obtain reliable binding energies is emphasized.
On phase change in Marangoni-driven flows and its effects on the hydrothermal-wave instabilities
Authors: Sáenz P. J. , Valluri P. , Sefiane K. , Karapetsas G. , Matar O. K.
Published: March 2014

This paper investigates the effects of phase change on the stability of a laterally heated liquid layer for the first time. The interface is open to the atmosphere and vapor diffusion is the rate-limiting mechanism for evaporation. In this configuration, the planar layer is naturally vulnerable to the formation of travelling thermal instabilities, i.e., hydrothermal waves (HTWs), due to the presence of temperature gradients along the gas-liquid interface. Recent work carried out for deformable interfaces and negligible evaporation indicates that the HTWs additionally give rise to interface deformations of similar features, i.e., physical waves. The study presented here reveals that phase change plays a dual role through its effect on these instabilities: the latent energy required during the evaporation process tends to inhibit the HTWs while the accompanying level reduction enhances the physical waves by minimizing the role of gravity. The dynamics of the gas phase are also discussed. The HTW-induced convective patterns in the gas along with the travelling nature of the instabilities have a significant impact on the local evaporation flux and the vapor distribution above the interface. Interestingly, high (low) concentrations of vapor are found above cold (hot) spots. The phase-change mechanism for stable layers is also investigated. The Marangoni effect plays a major role in the vapor distribution generating a vacuum effect in the warm region and vapor accumulations at the cold boundary capable of inverting the phase change, i.e., the capillary flow can lead to local condensation. This work also demonstrates the inefficiencies of the traditional phase change models based on pure vapor diffusion to capture the dynamics of thermocapillary flows.
Communication: Multireference equation of motion coupled cluster: A transform and diagonalize approach to electronic structure
Authors: Nooijen Marcel , Demel Ondřej , Datta Dipayan , Kong Liguo , Shamasundar K. R. , Lotrich V. , Huntington Lee M. , Neese Frank
Published: March 2014

The novel multireference equation-of-motion coupled-cluster (MREOM-CC) approaches provide versatile and accurate access to a large number of electronic states. The methods proceed by a sequence of many-body similarity transformations and a subsequent diagonalization of the transformed Hamiltonian over a compact subspace. The transformed Hamiltonian is a connected entity and preserves spin- and spatial symmetry properties of the original Hamiltonian, but is no longer Hermitean. The final diagonalization spaces are defined in terms of a complete active space (CAS) and limited excitations (1h, 1p, 2h, …) out of the CAS. The methods are invariant to rotations of orbitals within their respective subspaces (inactive, active, external). Applications to first row transition metal atoms (Cr, Mn, and Fe) are presented yielding results for up to 524 electronic states (for Cr) with an rms error compared to experiment of about 0.05 eV. The accuracy of the MREOM family of methods is closely related to its favorable extensivity properties as illustrated by calculations on the O2–O2 dimer. The computational costs of the transformation steps in MREOM are comparable to those of closed-shell Coupled Cluster Singles and Doubles (CCSD) approach.
Gradient of molecular Hartree–Fock–Bogoliubov energy with a linear combination of atomic orbital quasiparticle wave functions
Authors: Kobayashi Masato
Published: March 2014

The analytical gradient for the atomic-orbital-based Hartree–Fock–Bogoliubov (HFB) energy functional, the modified form of which was proposed by Staroverov and Scuseria to account for the static electron correlation [J. Chem. Phys. 117, 11107 (2002)], is derived. Interestingly, the Pulay force for the HFB energy is expressed with the same formula as that for the Hartree–Fock method. The efficiency of the present HFB energy gradient is demonstrated in the geometry optimizations of conjugated and biradical systems. The geometries optimized by using the HFB method with the appropriate factor ζ, which controls the degree of static correlation included, are found to show good agreement with those obtained by using a complete active-space self-consistent field method, although they are significantly dependent on ζ.
Spatial anisotropy and heterogeneity in contractility and adhesion distribution may contribute to cell steering during migration
Authors: S Soumya S , Kolwankar Subodh , George Edna , Basu Santanu K. , Sen Shamik , Inamdar Mandar M.
Published: March 2014

Transition from random to persistent cell motility requires spatiotemporal organization of the cytoskeleton and focal adhesions. The influence of these two structures on cell steering can also be gleaned from trypsin de-adhesion experiments, wherein cells exposed to trypsin round up, exhibiting a combination of rotation and translation. Here, we present a model to evaluate the contributions of contractility and bond distribution to experimentally observed de-adhesion. We show that while asymmetry in bond distribution causes only cell translation, a combination of asymmetric bond distribution and non-uniform contractility is required for translation and rotation and may guide cell migration.
Rovibrational energy transfer in the He-C3 collision: Potential energy surface and bound states
Authors: Denis-Alpizar Otoniel , Stoecklin Thierry , Halvick Philippe
Published: March 2014

We present a four-dimensional potential energy surface (PES) for the collision of C3 with He. Ab initio calculations were carried out at the coupled-cluster level with single and double excitations and a perturbative treatment of triple excitations, using a quadruple-zeta basis set and mid-bond functions. The global minimum of the potential energy is found to be −26.9 cm−1 and corresponds to an almost T-shaped structure of the van der Waals complex along with a slightly bent configuration of C3. This PES is used to determine the rovibrational energy levels of the He-C3 complex using the rigid monomer approximation (RMA) and the recently developed atom-rigid bender approach at the Close Coupling level (RB-CC). The calculated dissociation energies are −9.56 cm−1 and −9.73 cm−1, respectively at the RMA and RB-CC levels. This is the first theoretical prediction of the bound levels of the He-C3 complex with the bending motion.
Low TC Fe-Cr-Nb-B glassy submicron powders for hyperthermia applications
Authors: Chiriac H. , Lupu N. , Lostun M. , Ababei G. , Grigoraş M. , Dănceanu C.
Published: March 2014

Fe79.7−xNb0.3CrxB20 (x = 11.5–13.5 at. %) submicron powders with glassy structure and sizes between a few tens of nm and 1 μm have been prepared by high-energy ball milling from glassy melt-spun ribbons (MSRs) precursors. The glassy structure existing in the MSRs, and consisting of Fe-Cr clusters embedded within the (Fe,Nb)3B residual amorphous matrix, is preserved by milling the annealed MSRs in oleic acid and n-heptane. The glassy structure of the submicron powders confers the specific magnetic properties and allows tuning the Curie temperatures in the range of 15–50 °C. The precipitation of α-Fe in excess shifts the Curie temperature to 780 °C. The use of surfactants (oleic acid or heptane) avoids partially the agglomeration of powders, and their individual size goes down to 25–40 nm. The heating efficiency of the submicron powders in a.c. fields (H = 350 mT and f = 153 kHz) evidences a working regime in the range of 33–45 °C, depending on Cr content, indicating the suitability of using the Fe-Cr-Nb-B powders for hyperthermia applications.
Magnetic field control of the intraband optical absorption in two-dimensional quantum rings
Authors: Olendski O. , Barakat T.
Published: March 2014

Linear and nonlinear optical absorption coefficients of the two-dimensional semiconductor ring in the perpendicular magnetic field B are calculated within independent electron approximation. Characteristic feature of the energy spectrum are crossings of the levels with adjacent nonpositive magnetic quantum numbers as the intensity B changes. It is shown that the absorption coefficient of the associated optical transition is drastically decreased at the fields corresponding to the crossing. Proposed model of the Volcano disc allows to get simple mathematical analytical results, which provide clear physical interpretation. An interplay between positive linear and intensity-dependent negative cubic absorption coefficients is discussed; in particular, critical light intensity at which additional resonances appear in the total absorption dependence on the light frequency is calculated as a function of the magnetic field and levels' broadening.
Spinning disk test study on erase band and write width for shingled magnetic recording
Authors: Chandrasekaran S. , Supnithi P. , Warisarn C. , Bai D.
Published: March 2014

Shingled magnetic recording (SMR) has been predicted as one of the novel technologies to extend the areal density beyond 1 Tb/in2. It was widely thought by many researchers that very wide writers could be used for SMR, as it involves corner writing and thus writability would no longer be an issue in SMR. However, in our experimental study, we reveal that there exists an optimal write width for a given writer design due to the erase band limitations. Also we propose the optimal write width for a given shingle track pitch condition.
Twofold reentrant melting in a double-Gaussian fluid
Authors: Prestipino Santi , Speranza Cristina , Malescio Gianpietro , Giaquinta Paolo V.
Published: March 2014

Isotropic pair potentials that are bounded at the origin have been proposed from time to time as models of the effective interaction between macromolecules of interest in the chemical physics of soft matter. We present a thorough study of the phase behavior of point particles interacting through a potential which combines a bounded short-range repulsion with a much weaker attraction at moderate distances, both of Gaussian shape. Notwithstanding the fact that the attraction acts as a small perturbation of the Gaussian-core model potential, the phase diagram of the double-Gaussian model (DGM) is far richer, showing two fluid phases and four distinct solid phases in the case that we have studied. Using free-energy calculations, the various regions of confluence of three distinct phases in the DGM system have all been characterized in detail. Moreover, two distinct lines of reentrant melting are found, and for each of them a rationale is provided in terms of the elastic properties of the solid phases.
Computed tomography image using sub-terahertz waves generated from a high-Tc superconducting intrinsic Josephson junction oscillator
Authors: Kashiwagi T. , Nakade K. , Saiwai Y. , Minami H. , Kitamura T. , Watanabe C. , Ishida K. , Sekimoto S. , Asanuma K. , Yasui T. , Shibano Y. , Tsujimoto M. , Yamamoto T. , Marković B. , Mirković J. , Klemm R. A. , Kadowaki K.
Published: March 2014

A computed tomography (CT) imaging system using monochromatic sub-terahertz coherent electromagnetic waves generated from a device constructed from the intrinsic Josephson junctions in a single crystalline mesa structure of the high-Tc superconductor Bi2Sr2CaCu2O8+δ was developed and tested on three samples: Standing metallic rods supported by styrofoam, a dried plant (heart pea) containing seeds, and a plastic doll inside an egg shell. The images obtained strongly suggest that this CT imaging system may be useful for a variety of practical applications.
Ab-initio study of hydrogen doping and oxygen vacancy at anatase TiO2 surface
Authors: Sotoudeh M. , Hashemifar S. J. , Abbasnejad M. , Mohammadizadeh M. R.
Published: March 2014

Density functional–pseudopotential calculations were performed to study the effects of hydrogen doping and oxygen vacancy, both individually and together, on the electronic structure and stability of (001) surface of TiO2 in the anatase phase. Based on our calculations, O/Ti termination is the most stable one, and it appears that p-states of deep and surface O atoms and d-orbitals of surface Ti atoms have roles in the valence band and, the conduction band comes from the d-orbitals of deep Ti atoms. Although, no considerable change was seen during H doping, a mid-gap state appeared below the conduction band in the O vacancy configuration. In the framework of ab-initio atomistic thermodynamics, we argue that the anatase TiO2 prefers a defected O layer termination in the [001] direction. The obtained electronic structures indicate that H doping in the bulk creates the empty mid-gap state below the conduction band and hence decreases the band gap of the system. This phenomenon may explain the enhanced photocatalytic activity of the anatase TiO2 (001) surface after hydrogenation.
Initial stages of ITO/Si interface formation: In situ x-ray photoelectron spectroscopy measurements upon magnetron sputtering and atomistic modelling using density functional theory
Authors: Løvvik O. M. , Diplas S. , Romanyuk A. , Ulyashin A.
Published: March 2014

Initial stages of indium tin oxide (ITO) growth on a polished Si substrate upon magnetron sputtering were studied experimentally using in-situ x-ray photoelectron spectroscopy measurements. The presence of pure indium and tin, as well as Si bonded to oxygen at the ITO/Si interface were observed. The experimental observations were compared with several atomistic models of ITO/Si interfaces. A periodic model of the ITO/Si interface was constructed, giving detailed information about the local environment at the interface. Molecular dynamics based on density functional theory was performed, showing how metal-oxygen bonds are broken on behalf of silicon-oxygen bonds. These theoretical results support and provide an explanation for the present as well as previous ex-situ and in-situ experimental observations pointing to the creation of metallic In and Sn along with the growth of SiOx at the ITO/Si interface.
Indirect measurement of thermal conductivity in silicon nanowires
Authors: Pennelli Giovanni , Nannini Andrea , Macucci Massimo
Published: March 2014

We report indirect measurements of thermal conductivity in silicon nanostructures. We have exploited a measurement technique based on the Joule self-heating of silicon nanowires. A standard model for the electron mobility has been used to determine the temperature through the accurate measurement of the nanowire resistance. We have applied this technique to devices fabricated with a top-down process that yields nanowires together with large silicon areas used both as electrical and as thermal contacts. As there is crystalline continuity between the nanowires and the large contact areas, our thermal conductivity measurements are not affected by any temperature drop due to the contact thermal resistance. Our results confirm the observed reduction of thermal conductivity in nanostructures and are comparable with those previously reported in the literature, achieved with more complex measurement techniques.
Effect of oxygen plasma on field emission characteristics of single-wall carbon nanotubes grown by plasma enhanced chemical vapour deposition system
Authors: Kumar Avshish , Parveen Shama , Husain Samina , Ali Javid , Zulfequar Mohammad , Harsh  , Husain Mushahid
Published: March 2014

Field emission properties of single wall carbon nanotubes (SWCNTs) grown on iron catalyst film by plasma enhanced chemical vapour deposition system were studied in diode configuration. The results were analysed in the framework of Fowler-Nordheim theory. The grown SWCNTs were found to be excellent field emitters, having emission current density higher than 20 mA/cm2 at a turn-on field of 1.3 V/μm. The as grown SWCNTs were further treated with Oxygen (O2) plasma for 5 min and again field emission characteristics were measured. The O2 plasma treated SWCNTs have shown dramatic improvement in their field emission properties with emission current density of 111 mA/cm2 at a much lower turn on field of 0.8 V/μm. The as grown as well as plasma treated SWCNTs were also characterized by various techniques, such as scanning electron microscopy, high resolution transmission electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy before and after O2 plasma treatment and the findings are being reported in this paper.
Magnetization reversal of in-plane uniaxial Co films and its dependence on epitaxial alignment
Authors: Idigoras O. , Suszka A. K. , Vavassori P. , Obry B. , Hillebrands B. , Landeros P. , Berger A.
Published: March 2014

This work studies the influence of crystallographic alignment onto magnetization reversal in partially epitaxial Co films. A reproducible growth sequence was devised that allows for the continuous tuning of grain orientation disorder in Co films with uniaxial in-plane anisotropy by the controlled partial suppression of epitaxy. While all stable or meta-stable magnetization states occurring during a magnetic field cycle exhibit a uniform magnetization for fully epitaxial samples, non-uniform states appear for samples with sufficiently high grain orientation disorder. Simultaneously with the occurrence of stable domain states during the magnetization reversal, we observe a qualitative change of the applied field angle dependence of the coercive field. Upon increasing the grain orientation disorder, we observe a disappearance of transient domain wall propagation as the dominating reversal process, which is characterized by an increase of the coercive field for applied field angles away from the easy axis for well-ordered epitaxial samples. Upon reaching a certain disorder threshold level, we also find an anomalous magnetization reversal, which is characterized by a non-monotonic behavior of the remanent magnetization and coercive field as a function of the applied field angle in the vicinity of the nominal hard axis. This anomaly is a collective reversal mode that is caused by disorder-induced frustration and it can be qualitatively and even quantitatively explained by means of a two Stoner-Wohlfarth particle model. Its predictions are furthermore corroborated by Kerr microscopy and by Brillouin light scattering measurements.
High resolution fabrication of nanostructures using controlled proximity nanostencil lithography
Authors: Jain T. , Aernecke M. , Liberman V. , Karnik R.
Published: March 2014

Nanostencil lithography has a number of distinct benefits that make it an attractive nanofabrication processes, but the inability to fabricate features with nanometer precision has significantly limited its utility. In this paper, we describe a nanostencil lithography process that provides sub-15 nm resolution even for 40-nm thick structures by using a sacrificial layer to control the proximity between the stencil and substrate, thereby enhancing the correspondence between nanostencil patterns and fabricated nanostructures. We anticipate that controlled proximity nanostencil lithography will provide an environmentally stable, clean, and positive-tone candidate for fabrication of nanostructures with high resolution.
Limit of detection of field effect transistor biosensors: Effects of surface modification and size dependence
Authors: Rajan Nitin K. , Brower Kara , Duan Xuexin , Reed Mark A.
Published: March 2014

Field-effect transistor biosensors have shown great promise in the detection of biomolecules. However, a quantitative understanding of what limits the smallest measurable concentration of analyte (limit of detection or LOD) is still missing. By considering the signal-to-noise ratio (SNR), extracted from a combination of noise and I-V characterization, we are able to accurately predict and experimentally confirm a LOD of 0.01 pH. Our results also show that devices with larger area and with amine functionalized surfaces have larger SNR. We are able to extract the associated oxide trap densities and, thus, quantify the improvements in LOD.
Anomalous refraction of heat flux in thermal metamaterials
Authors: Vemuri Krishna P. , Bandaru Prabhakar R.
Published: March 2014

We discuss the possibility of bending of heat flux in a multilayered composite typical to abnormal negative refraction, according to which the horizontal and the vertical components of the incident and refracted heat flux vectors point in the opposite direction. The engineered anisotropy of the thermal conductivity tensor is integral to such effects. We propose practical designs where such anomalous refraction phenomena may be observed and be used for heat flux redirection.
Quantum transport through the system of parallel quantum dots with Majorana bound states
Authors: Wang Ning , Lv Shuhui , Li Yuxian
Published: March 2014

We study the tunneling transport properties through a system of parallel quantum dots which are coupled to Majorana bound states (MBSs). The conductance and spectral function are computed using the retarded Green's function method based on the equation of motion. The conductance of the system is 2e2/h at zero Fermi energy and is robust against the coupling between the MBSs and the quantum dots. The dependence of the Fermi energy on the spectral function is different for the first dot (dot1) than for the second dot (dot2) with fixed dot2-MBSs coupling. The influence of the Majorana bound states on the spectral function was studied for the series and parallel configurations of the system. It was found that when the configuration is in series, the Majorana bound states play an important role, resulting in a spectral function with three peaks. However, the spectral function shows two peaks when the system is in a parallel configuration. The zero Fermi energy spectral function is always 1/2 not only in series but also in the parallel configuration and robust against the coupling between the MBSs and the quantum dots. The phase diagram of the Fermi energy versus the quantum dot energy levels was also investigated.
Experimental and simulation analysis of concave-down resistance curve during electromigration in solder joints
Authors: Lin C. K. , Chang Yuan Wei , Chen Chih
Published: March 2014

Resistance curves play a crucial role in detecting damage of solder joints during electromigration. In general, resistance increases slowly in the beginning, and then rises abruptly in the very late stage; i.e., the resistance curve behaves concave-up. However, several recent studies have reported concave-down resistance curves in solder joints with no satisfactory explanation for the discrepancy. In this study, electromigration failure mode in Sn2.5Ag solder joints was experimentally investigated. The bump resistance curve exhibited concave-down behavior due to formation of intermetallic compounds (IMCs). In contrast, the curve was concave-up when void formation dominated the failure mechanism. Finite element simulation was carried out to simulate resistance curves due to formation of IMCs and voids, respectively. The simulation results indicate that the main reason causing the concave-down curve is rapid formation of resistive Cu6Sn5 IMCs in the current-crowding region, which are 9 times larger than Cu IMCs. Therefore, when Cu reacted with Sn to form Cu6Sn5 IMCs, resistance increased abruptly, resulting in the concave-down resistance curve.
Observation of large magnetocaloric effect in HoRu2Si2
Authors: Paramanik Tapas , Das Kalipada , Samanta Tapas , Das I.
Published: March 2014

Detailed magnetic, magnetotransport, and magnetocaloric measurements on HoRu2Si2 have been performed. In this Letter, we report presence of spin reorientation transition below paramagnetic to antiferromagnetic transition temperature (TN = 19 K). Large magnetic entropy change 9.1 J/kg K and large negative magnetoresistance ∼21% in a magnetic field of 5 T has been observed around TN, which is associated with field induced spin-flip metamagnetic transition.
Origin of stress gradients induced in capped, copper metallization
Authors: Murray Conal E.
Published: March 2014

Stress gradients generated near the top surface of Cu thin films by capping layers, as measured using a combination of conventional and glancing incidence x-ray diffraction, exhibit heterogeneous behavior that is directly related to plastic anisotropy within the Cu grains. A comparison of stress gradients measured from several x-ray reflections to their corresponding Schmid factors yields a consistent, critical resolved shear stress. The results experimentally verify that dislocation-mediated plasticity is responsible for the creation of stress gradients at the Cu film/cap interface. Depth-dependent measurements reveal that the observed gradients are localized to within 200 nm of this interface.
Absence of exchange interaction between localized magnetic moments and conduction-electrons in diluted Er3+ gold-nanoparticles
Authors: Lesseux G. G. , Iwamoto W. , García-Flores A. F. , Urbano R. R. , Rettori C.
Published: March 2014

The Electron Spin Resonance (ESR) of diluted Er3+ magnetic ions in Au nanoparticles (NPs) is reported. The NPs were synthesized by reducing chloro triphenyl-phosphine gold(I) and erbium(III) trifluoroacetate. The Er3+ g-value along with the observed hyperfine splitting indicate that the Er3+ impurities are in a local cubic symmetry. Furthermore, the Er3+ ESR spectra show that the exchange interaction between the 4f and the conduction electrons (ce) is absent or negligible in Au1–xErx NPs, in contrast to the ESR results in bulk Au1–xErx. Therefore, the nature of this interaction needs to be reexamined at the nano scale range.
Trend of tunnel magnetoresistance and variation in threshold voltage for keeping data load robustness of metal–oxide–semiconductor/magnetic tunnel junction hybrid latches
Authors: Ohsawa T. , Ikeda S. , Hanyu T. , Ohno H. , Endoh T.
Published: March 2014

The robustness of data load of metal–oxide–semiconductor/magnetic tunnel junction (MOS/MTJ) hybrid latches at power-on is examined by using Monte Carlo simulation with the variations in magnetoresistances for MTJs and in threshold voltages for MOSFETs involved in 90 nm technology node. Three differential pair type spin-transfer-torque-magnetic random access memory cells (4T2MTJ, 6T2MTJ, and 8T2MTJ) are compared for their successful data load at power-on. It is found that the 4T2MTJ cell has the largest pass area in the shmoo plot in TMR ratio (tunnel magnetoresistance ratio) and Vdd in which a whole 256 kb cell array can be powered-on successfully. The minimum TMR ratio for the 4T2MTJ in 0.9 V < Vdd < 1.9 V is 140%, while the 6T2MTJ and the 8T2MTJ cells require TMR ratio larger than 170%.
Structural feature controlling superconductivity in compressed BaFe2As2
Authors: Yang Wenge , Jia Feng-Jiang , Tang Ling-Yun , Tao Qian , Xu Zhu-An , Chen Xiao-Jia
Published: March 2014

Superconductivity can be induced with the application of pressure but it disappears eventually upon heavy compression in the iron-based parent compound BaFe2As2. Structural evolution with pressure is used to understand this behavior. By performing synchrotron X-ray powder diffraction measurements with diamond anvil cells up to 26.1 GPa, we find an anomalous behavior of the lattice parameter with a S shape along the a axis but a monotonic decrease in the c-axis lattice parameter with increasing pressure. The close relationship between the axial ratio c/a and the superconducting transition temperature Tc is established for this parent compound. The c/a ratio is suggested to be a measure of the spin fluctuation strength. The reduction of Tc with the further increase of pressure is a result of the pressure-driven weakness of the spin-fluctuation strength in this material.
Two-photon polarization data storage in bacteriorhodopsin films and its potential use in security applications
Authors: Imhof Martin , Rhinow Daniel , Hampp Norbert
Published: March 2014

Bacteriorhodopsin (BR) films allow write-once-read-many recording of polarization data by a two-photon-absorption (TPA) process. The optical changes in BR films induced by the TPA recording were measured and the Müller matrix of a BR film was determined. A potential application of BR films in security technology is shown. Polarization data can be angle-selective retrieved with high signal-to-noise ratio. The BR film does not only carry optical information but serves also as a linear polarizer. This enables that polarization features recorded in BR films may be retrieved by merely using polarized light from a mobile phone display.
Study of negative thermal expansion in the frustrated spinel ZnCr2Se4
Authors: Chen X. L. , Yang Z. R. , Tong W. , Huang Z. H. , Zhang L. , Zhang S. L. , Song W. H. , Pi L. , Sun Y. P. , Tian M. L. , Zhang Y. H.
Published: March 2014

The origin of negative thermal expansion (NTE) in the bond frustrated ZnCr2Se4 has been explored. ESR and FTIR document an ideal paramagnetic state above 100 K, below which ferromagnetic clusters coexist with the paramagnetic state down to TN. By fitting the inverse susceptibility above 100 K using a modified paramagnetic Curie-Weiss law, an exponentially changeable exchange integral J is deduced. In the case of the variable J, magnetic exchange and lattice elastic energy couple with each other effectively via magnetoelastic interaction in the ferromagnetic clusters, where NTE occurs at a loss of exchange energy while a gain of lattice elastic one.
Ab initio calculations on magnetism induced by composite defects in magnesium oxide
Authors: Zhang Yao-Fang , Feng Min , Shao Bin , Lu Yuan , Liu Hong , Zuo Xu
Published: March 2014

The local magnetic state induced by the composite defects, composed of an oxygen vacancy and a nitrogen substituting oxygen, in magnesium oxide has been studied by using ab initio calculation based on density functional theory. The calculated results show that local magnetic moment can be induced by the composite defects around the oxygen vacancy, when the exchange split of the oxygen vacancy is enhanced either by the hybridization between the N-p and nearest neighbor O-p orbitals or by applying on-site Coulomb repulsion (U) and exchange interaction (J). We show that the magnetic state induced by the composite defect is energetically more stable than the non-magnetic state. In addition, we show that the U and J applied on the p-orbitals of N and O atoms may significantly impact the calculated magnetic state of the composite defect, resulting in magnetic state for a configuration that is non-magnetic by generalized gradient approximation.
Magneto-optical properties of nanometer crystal giant magneto-optical BiAlDyIG thin film materials post-treated by rapid recurrent thermal annealing method
Authors: Qing-hui Yang , Huai-wu Zhang , Ying-li Liu , Qiye Wen
Published: March 2014

In this paper, high quality BiAlDyIG thin films with different bismuth contents have been prepared by using a sol-gel method and post-treated by a rapid recurrent thermal annealing (RRTA) method. Results indicate that the RRTA method improves the Faraday Effect of the films notably, a maximum Faraday angle of −4.9° in the 450 nm thickness film (Bi1.96Dy1.04Fe4AlO12) was obtained at the wavelength of 520 nm, which is about two times larger than that of the common thermal annealed sample, and furthermore the reason of giant Faraday angle was also analyzed in detail. These results are potentially helpful to improve the recording density and signal-to-noise ratio of magneto-optical disk.
Persistent photoconductivity in high resistive Zn3P2
Authors: Sierański K. , Szatkowski J. , Pawlikowski J. M.
Published: March 2014

Resistivity and photoconductivity of p-type Zn3P2 polycrystals grown by closed tube vapour transport method have been investigated. Persistent photoconductivity (PPC) has been observed at temperatures T < 200 K. At 77 K, the photoconduction persists for over 103 s after termination of the light. The PPC buildup and decay kinetics have been measured at 77 K and analyzed in the frame of large lattice-relaxed deep levels. We have determined the spectral dependence for the optical cross section and obtain an optical ionization energy of 0.83 eV.
Li1.1(Zn1−xCrx)As: Cr doped I–II–V diluted magnetic semiconductors in bulk form
Authors: Wang Quan , Man Huiyuan , Ding Cui , Gong Xin , Guo Shengli , Jin Huike , Wang Hangdong , Chen Bin , Ning F. L.
Published: March 2014

We report the synthesis and characterization of bulk form diluted magnetic semiconductors I–II–V Li1.1(Zn1−xCrx)As (x = 0.03, 0.05, 0.10, 0.15) with a cubic crystal structure identical to that of III–V GaAs and II–VI zinc-blende ZnSe. With p-type carriers created by excess Li, 10% Cr substitution for Zn results in a ferromagnetic ordering below TC ∼ 218 K. Li(Zn,Cr)As represents another magnetic semiconducting system with the advantage of decoupling carriers and spins, where carriers are created by adding extra Li and spins are introduced by Cr substitution for Zn.
Phosphorescence of Ce-doped Gd3Al2Ga3O12 crystals studied using luminescence spectroscopy
Authors: Kitaura M. , Sato A. , Kamada K. , Ohnishi A. , Sasaki M.
Published: March 2014

Photoluminescence (PL) and thermally stimulated luminescence (TSL) properties of Ce-doped Gd3Al2Ga3O12 (Ce:GAGG) crystals have been studied in the temperature range of 10–300 K under electron excitation from the 4f level to the 5d levels of Ce3+ ions. PL and TSL spectra commonly exhibit a prominent band around 2.31 eV, due to electron transitions from the lowest 5d (5d1) level to the 4f levels. The intensity of the Ce3+ PL band is significantly changed with temperature under excitation from the lowest 4f level to a higher-lying 5d (5d2) level, whereas it is scarcely changed under excitation from the 4f level to the 5d1 level. Such change correlates well with the appearance of TSL glow peaks at 84 and 175 K. The luminescence properties are apparently influenced by the thermal behavior of electrons trapped at some lattice site, but not by nonradiative processes of electrons starting from the 5d1 level. The phosphorescence process will be discussed using a phenomenological model based on the results obtained.
Few-body models for nuclear astrophysics
Authors: Descouvemont P. , Baye D. , Suzuki Y. , Aoyama S. , Arai K.
Published: March 2014

We present applications of microscopic models to nuclear reactions of astrophysical interest, and we essentially focus on few-body systems. The calculation of radiative-capture and transfer cross sections is outlined, and we discuss the corresponding reaction rates. Microscopic theories are briefly presented, and we emphasize on the matrix elements of four-body systems. The microscopic extension of the R-matrix theory to nuclear reactions is described. Applications to the 2H(d, γ)4He, 2H(d, p)3H and 2H(d, n)3He reactions are presented. We show the importance of the tensor force to reproduce the low-energy behaviour of the cross sections.
Vibration characteristic analysis method for the quartz microgyroscope based on the admittance circle
Authors: Wang Haoxu , Dong Peitao , Xie Liqiang , Wu Xuezhong
Published: March 2014

The vibration characteristic analysis method for a quartz microgyroscope based on the admittance circle is reported in this paper. Admittance theory is introduced and the admittance circle principle is analysed to study the vibration characteristics of the quartz microgyroscope. The prototype gyroscope was fabricated by micro-electromechanical systems (MEMS) technology. The admittance and phase diagram of the work mode were obtained by vibration mode test systems. Then the admittance circle of the work mode was drawn, and the parameter identification of the transfer function between the voltage and current was completed to analyse the vibration characteristics. Therefore, the vibration characteristic analysis method based on the admittance circle can be used to build the transfer function of the quartz microgyroscope, which is helpful for the design of a high performance quartz microgyroscope.
Regular arrays of Al nanoparticles for plasmonic applications
Authors: Schade Martin , Fuhrmann Bodo , Bohley Christian , Schlenker Sven , Sardana Neha , Schilling Jörg , Leipner Hartmut S.
Published: March 2014

Optical properties of aluminium nanoparticles deposited on glass substrates are investigated. Laser interference lithography allows a quick deposition of regular, highly periodic arrays of nanostructures with different sizes and distances in order to investigate the shift of the surface plasmon resonance for, e.g., photovoltaic, plasmonic or photonic applications. The variation of the diameter of cylindrical Al nanoparticles exhibits a nearly linear shift of the surface plasmon resonance between 400 nm and 950 nm that is independent from the polarization vector of the incident light. Furthermore, particles with quadratic or elliptic base areas are presented exhibiting more complex and polarization vector dependent transmission spectra.
Structure optimization and simulation analysis of the quartz micromachined gyroscope
Authors: Wu Xuezhong , Wang Haoxu , Xie Liqiang , Dong Peitao
Published: March 2014

Structure optimization and simulation analysis of the quartz micromachined gyroscope are reported in this paper. The relationships between the structure parameters and the frequencies of work mode were analysed by finite element analysis. The structure parameters of the quartz micromachined gyroscope were optimized to reduce the difference between the frequencies of the drive mode and the sense mode. The simulation results were proved by testing the prototype gyroscope, which was fabricated by micro-electromechanical systems (MEMS) technology. Therefore, the frequencies of the drive mode and the sense mode can match each other by the structure optimization and simulation analysis of the quartz micromachined gyroscope, which is helpful in the design of the high sensitivity quartz micromachined gyroscope.
Chemical order in GexAsySe1-x-y glasses probed by high resolution X-ray photoelectron spectroscopy
Authors: Xu S. W. , Wang R. P. , Luther-Davies B. , Kovalskiy A. , Miller A. C. , Jain H.
Published: March 2014

We have measured high-resolution x-ray photoelectron spectra of GexAsySe1-x-y glasses with a mean coordination number (MCN) from 2.2 to 2.78. The valence band spectra showed that a number of Se–Se–Se trimers can be found in Se-rich samples, whilst multiband features induced by phase separation can be observed in extremely Se-poor samples. When the Ge, As, and Se 3d spectra were decomposed into several doublets, which correspond, respectively, to different chemical environments, the perfect AsSe3/2 pyramidal and GeSe4/2 tetrahedral structures in Se-rich samples gradually evolved into defect structures, including As–As and Ge–Ge homopolar bonds, with increasing Ge and As concentrations. Two transition-like features were found at MCN = 2.5 and 2.64–2.72 that correspond first to the disappearance of Se-chains in the glass network and, subsequently, destruction of the perfect GeSe4/2 tetrahedral structures, respectively.
High-throughput sequencing reveals inbreeding depression in a natural population
Authors: Hoffman Joseph I. , Simpson Fraser , David Patrice , Rijks Jolianne M. , Kuiken Thijs , Thorne Michael A. S. , Lacy Robert C. , Dasmahapatra Kanchon K.
Published: March 2014

Significance

Many studies of wild populations reveal links between heterozygosity and fitness, with relatively heterozygous individuals carrying fewer parasites, living longer and being more attractive to mates. These patterns appear ubiquitous and are often highly significant, but heterozygosity usually accounts for very little of the total variation in fitness. However, most studies analyze only around 10 loci, representing a tiny fraction of the genome. We therefore used high-throughput DNA sequencing to estimate genome-wide heterozygosity based on over 10,000 loci and found it to accurately reflect inbreeding. Applied to wild harbor seals, genome-wide heterozygosity explained almost half of the variation in parasite infection. By implication, a greater proportion of fitness variation could be linked to genotype than previously thought.
TGF-β–inducible microRNA-183 silences tumor-associated natural killer cells
Authors: Donatelli Sarah S. , Zhou Jun-Min , Gilvary Danielle L. , Eksioglu Erika A. , Chen Xianghong , Cress W. Douglas , Haura Eric B. , Schabath Matthew B. , Coppola Domenico , Wei Sheng , Djeu Julie Y.
Published: March 2014

Significance

Natural killer (NK) cells are potent tumor-cell killers, but exposure to transforming growth factor beta-1 (TGF-β) abrogates their effectiveness. Here, we show that this suppression is a result of TGF-β induction of microRNA (miR)-183, which binds and represses DNAX activating protein 12 kDa (DAP12), a signal adaptor for lytic function in NK cells. Because introduction of miR-183 alone or its functional blockade in the presence of TGF-β reduced or restored DAP12 levels in NK cells, we define miR-183 as a key factor in TGF-β–mediated immunosuppression. Since DAP12 is required for signaling through multiple NK cytotoxicity receptors and TGF-β is overexpressed by diverse solid malignancies, our data may have significant importance in the development of NK-based cancer immunotherapies.
Multiple cells-of-origin of mutant K-Ras–induced mouse lung adenocarcinoma
Authors: Sutherland Kate D. , Song Ji-Ying , Kwon Min Chul , Proost Natalie , Zevenhoven John , Berns Anton
Published: March 2014

Significance

By using a series of cell-type–restricted Adeno-Cre vectors, we show that expression of mutant K-Ras in different cell types in mouse lungs can give rise to adenocarcinomas. Moreover, the cell-of-origin appears to be a determining factor in the histopathological characteristics of the resulting tumor. This is most apparent in the early stages of tumor development, whereby different routes of tumor development are taken when either Clara cells or alveolar type 2 cells serve as the initiating cell type. Both the physical site of onset and the marker expression of the early lesions are distinct. Future studies should reveal whether this affects other tumor characteristics, such as the mutation spectrum and response to treatment.
NRAS isoforms differentially affect downstream pathways, cell growth, and cell transformation
Authors: Eisfeld Ann-Kathrin , Schwind Sebastian , Hoag Kevin W. , Walker Christopher J. , Liyanarachchi Sandya , Patel Ravi , Huang Xiaomeng , Markowitz Joseph , Duan Wenrui , Otterson Gregory A. , Carson William E. , Marcucci Guido , Bloomfield Clara D. , de la Chapelle Albert
Published: March 2014

Significance

The members of the rat sarcoma (RAS) gene family Kirsten rat sarcoma viral oncogene homolog, Harvey rat sarcoma viral oncogene homolog, and neuroblastoma RAS viral oncogene homolog (NRAS) belong to the most extensively studied oncogenes and are central players in carcinogenesis. Since their discovery approximately 30 y ago, efforts to target their aberrant activation have not led to major breakthroughs. We herein report the discovery of four so far undescribed variants of NRAS that differ in their expression patterns and, strikingly, in their downstream effects. Our results suggest that NRAS should be studied in the context of its variants. In addition, this discovery may open opportunities to develop more efficient anticancer therapies.