bluuebunny/crossref_metadata_2025 huggingface dataset:
Modelling epigenetic regulation of gene expression in 12 human cell types reveals combinatorial patterns of cell‐type‐specific genes
Authors: Lu Yiming , Qu Wubin , Min Bo , Liu Zheyan , Chen Changsheng , Zhang Chenggang
Published: February 2014

The maintenance of the diverse cell types in a multicellular organism is one of the fundamental mysteries of biology. Modelling the dynamic regulatory relationships between the histone modifications and the gene expression across the diverse cell types is essential for the authors to understand the mechanisms of the epigenetic regulation. Here, the authors thoroughly assessed the histone modification enrichment profiles at the promoters and constructed quantitative models between the histone modification abundances and the gene expression in 12 human cell types. The author's results showed that the histone modifications at the promoters exhibited remarkably cell‐type‐dependent variability in the cell‐type‐specific (CTS) genes. They demonstrated that the variable profiles of the modifications are highly predictive for the dynamic changes of the gene expression across all the cell types. Their findings revealed the close relationship between the combinatorial patterns of the histone modifications and the CTS gene expression. They anticipate that the findings and the methods they used in this study could provide useful information for the future studies of the regulatory roles of the histone modifications in the CTS genes.
A multi-point constraints based layout design of multi-component systems
Authors: Gao Huan-Huan , Zhu Ji-Hong , Zhang Wei-Hong
Published: February 2014

The primary purpose of this paper was to present an efficient method to implement the layout design of multi-component systems. In this study, two kinds of design variables: topology variables and geometry variables are simultaneously optimized to maximize the structure stiffness. The multi-point constraints (MPC) are used to simulate the connection behavior between these movable components and supporting structure. So during the optimization iterations, mesh regeneration caused by moving components is avoided compared to the linkage of nodal coincidence. At the same time, the precise geometry shapes and properties of components are maintained to reduce the model building error. At the last of the paper, the numerical example is presented to show the validity of this method.
Recent Guidelines and Recommendations for Laboratory Detection of Lupus Anticoagulants
Authors: Moore Gary
Published: February 2014

The International Society on Haemostasis and Thrombosis (ISTH) and the British Committee for Standards in Haematology (BCSH) have recently updated their lupus anticoagulant (LA) detection guidelines. The Clinical and Laboratory Standards Institute (CLSI) subsequently will publish its first LA guideline. General agreement exists on issues such as sample preparation, the use of dilute Russell viper venom time (dRVVT) in diagnostic repertoires, the use of normalized ratios, calculations to demonstrate phospholipid dependence, calculations to demonstrate inhibition, and interpretive reporting. The ISTH recommendation to employ only dRVVT and activated partial thromboplastin time is not mirrored in the BCSH and CLSI documents. The potential for false negatives in mixing tests is acknowledged by all panels, yet they remain mandated by ISTH as there are occasions when they are crucial to diagnostic accuracy. BCSH indicates that a negative mixing test need not exclude the presence of a LA, and CLSI reprioritizes test order to screen-confirm-mix, the latter being considered unnecessary in specific circumstances. Opinions in the guidelines differ on setting cutoff levels (i.e., 97.5th vs. 99th percentile for normally distributed data). All guidelines cover testing of anticoagulated patients, more detail being given by BCSH and CLSI, who suggest that Taipan snake venom time is a useful adjunct test in patients receiving vitamin K antagonists. Although complete agreement is not apparent, the guidelines represent significant moves toward engendering common practices.
In situ flame chemistry tracing by imaging photoelectron photoion coincidence spectroscopy
Authors: Oßwald P. , Hemberger P. , Bierkandt T. , Akyildiz E. , Köhler M. , Bodi A. , Gerber T. , Kasper T.
Published: February 2014

Adaptation of a low-pressure flat flame burner with a flame-sampling interface to the imaging photoelectron photoion coincidence spectrometer (iPEPICO) of the VUV beamline at the Swiss Light Source is presented. The combination of molecular-beam mass spectrometry and iPEPICO provides a new powerful analytical tool for the detailed investigation of reaction networks in flames. First results demonstrate the applicability of the new instrument to comprehensive flame diagnostics and the potentially high impact for reaction mechanism development for conventional and alternative fuels. Isomer specific identification of stable and radical flame species is demonstrated with unrivaled precision. Radical detection and identification is achieved for the initial H-abstraction products of fuel molecules as well as for the reaction controlling H, O, and OH radicals. Furthermore, quantitative evaluation of changing species concentrations during the combustion process and the applicability of respective results for kinetic model validation are demonstrated. Utilization of mass-selected threshold photoelectron spectra is shown to ensure precise signal assignment and highly reliable spatial profiles.
Modulation of cosmic microwave background polarization with a warm rapidly rotating half-wave plate on the Atacama B-Mode Search instrument
Authors: Kusaka A. , Essinger-Hileman T. , Appel J. W. , Gallardo P. , Irwin K. D. , Jarosik N. , Nolta M. R. , Page L. A. , Parker L. P. , Raghunathan S. , Sievers J. L. , Simon S. M. , Staggs S. T. , Visnjic K.
Published: February 2014

We evaluate the modulation of cosmic microwave background polarization using a rapidly rotating, half-wave plate (HWP) on the Atacama B-Mode Search. After demodulating the time-ordered-data (TOD), we find a significant reduction of atmospheric fluctuations. The demodulated TOD is stable on time scales of 500–1000 s, corresponding to frequencies of 1–2 mHz. This facilitates recovery of cosmological information at large angular scales, which are typically available only from balloon-borne or satellite experiments. This technique also achieves a sensitive measurement of celestial polarization without differencing the TOD of paired detectors sensitive to two orthogonal linear polarizations. This is the first demonstration of the ability to remove atmospheric contamination at these levels from a ground-based platform using a rapidly rotating HWP.
Quantitative characterization for dielectrophoretic behavior of biological cells using optical tweezers
Authors: Park In Soo , Hee Park Se , Woo Lee Sang , Sung Yoon Dae , Kim Beop-Min
Published: February 2014

We report a method to precisely quantify dielectrophoretic (DEP) forces and cutoff frequencies (fc) of viable and nonviable yeast cells. The method consists of a two-step process in which generated DEP forces act upon a cell through a micro-electrode device, followed by direct measurement of DEP forces using optical tweezers. DEP behaviors of viable and nonviable yeast cells are monitored as a function of AC frequency. We believe that the proposed method can be used as a powerful platform for cell-based assays to characterize the DEP behavior of various cell types including cancer and normal cells.
Note: High-efficiency energy harvester using double-clamped piezoelectric beams
Authors: Zheng Yingmei , Wu Xuan , Parmar Mitesh , Lee Dong-weon
Published: February 2014

In this study, an improvement in energy conversion efficiency has been reported, which is realized by using a double-clamped piezoelectric beam, based on uniaxial stretching strain. The buckling mechanism is applied to maximize axial stress in the double-clamped beam. The voltage generated by using the double-clamped piezoelectric beam is higher than that generated by using other conventional structures, such as bending cantilevers coated/sandwiched with piezoelectric film, which is proven both theoretically and experimentally. The power generation efficiency is enhanced by further optimizing the double-clamped structure. The optimized high-efficiency energy harvester utilizing double-clamped piezoelectric beams generates a peak output power of 80 μW, under an acceleration of 0.1g.
The method of planes pressure tensor for a spherical subvolume
Authors: Heyes D. M. , Smith E. R. , Dini D. , Zaki T. A.
Published: February 2014

Various formulas for the local pressure tensor based on a spherical subvolume of radius, R, are considered. An extension of the Method of Planes (MOP) formula of Todd et al. [Phys. Rev. E 52, 1627 (1995)] for a spherical geometry is derived using the recently proposed Control Volume formulation [E. R. Smith, D. M. Heyes, D. Dini, and T. A. Zaki, Phys. Rev. E 85, 056705 (2012)]. The MOP formula for the purely radial component of the pressure tensor is shown to be mathematically identical to the Radial Irving-Kirkwood formula. Novel offdiagonal elements which are important for momentum conservation emerge naturally from this treatment. The local pressure tensor formulas for a plane are shown to be the large radius limits of those for spherical surfaces. The radial-dependence of the pressure tensor computed by Molecular Dynamics simulation is reported for virtual spheres in a model bulk liquid where the sphere is positioned randomly or whose center is also that of a molecule in the liquid. The probability distributions of angles relating to pairs of atoms which cross the surface of the sphere, and the center of the sphere, are presented as a function of R. The variance in the shear stress calculated from the spherical Volume Averaging method is shown to converge slowly to the limiting values with increasing radius, and to be a strong function of the number of molecules in the simulation cell.
The role of inhomogeneity of perpendicular anisotropy in magnetic properties of ultra thin CoFeB film
Authors: Wang Yi , Wei Dan , Gao Kai-Zhong , Cao Jiangwei , Wei Fulin
Published: February 2014

In this work, the hysteresis loops of ultra thin CoFeB films with perpendicular anisotropy are simulated using a micromagnetic model with microstructure included. An inhomogeneous region of the perpendicular uniaxial anisotropy constant K is introduced in the model, and this is the key factor to explain why the in-plane saturation field is several thousand Oersted, while the perpendicular coercivity can be on the order of 100 Oersted. Tendency of the simulated loops with increasing total simulation size reveals that this model is reliable, and the calculated loops basically agree with experiments. The effects of different K distribution, defect sizes, defect patterns, and higher order magnetic anisotropy on simulated M-H loops are also discussed in the paper.
Unraveling multi-spin effects in rotational resonance nuclear magnetic resonance using effective reduced density matrix theory
Authors: SivaRanjan Uppala , Ramachandran Ramesh
Published: February 2014

A quantum-mechanical model integrating the concepts of reduced density matrix and effective Hamiltonians is proposed to explain the multi-spin effects observed in rotational resonance (R2) nuclear magnetic resonance (NMR) experiments. Employing this approach, the spin system of interest is described in a reduced subspace inclusive of its coupling to the surroundings. Through suitable model systems, the utility of our theory is demonstrated and verified with simulations emerging from both analytic and numerical methods. The analytic results presented in this article provide an accurate description/interpretation of R2 experimental results and could serve as a test-bed for distinguishing coherent/incoherent effects in solid-state NMR.
Determination of acoustic speed for improving leak detection and location in gas pipelines
Authors: Li Shuaiyong , Wen Yumei , Li Ping , Yang Jin , Yang Lili
Published: February 2014

The commonly used cross-correlation technique for leak location requires that the acoustic speed is known and invariable. In practice, the gas leakage-induced acoustic waves propagate along multiple paths including in-pipe gas and pipe wall, and the acoustic waves in different transmission paths exhibit different acoustic speeds and different dispersive behaviors, which bring a great challenge for leak detection and location in the gas pipelines. In this study, based on the vibration theory of cylindrical elastic thin shell, the wavenumber formulae in different transmission paths are derived to predict the acoustic speeds and the acoustical coupling between the in-pipe gas and the pipe wall is analyzed to determine the dominant transmission path. In addition, the velocity dispersions in the dominant transmission path are suppressed by selection of a characteristic frequency band of the gas leakage-induced acoustic waves. The theoretical predictions are verified in the experiment and the results show that the theoretical acoustic speed is slightly larger than the measured acoustic speed. Thus, the theoretical acoustic speed formula is modified considering the effect of the structural loss factor and consequently the location error using the modified acoustic speed is reduced by two times compared to that using the theoretical acoustic speed.
Hydrogen-bonded aggregates in precise acid copolymers
Authors: Lueth Christopher A. , Bolintineanu Dan S. , Stevens Mark J. , Frischknecht Amalie L.
Published: February 2014

We perform atomistic molecular dynamics simulations of melts of four precise acid copolymers, two poly(ethylene-co-acrylic acid) (PEAA) copolymers, and two poly(ethylene-co-sulfonic acid) (PESA) copolymers. The acid groups are spaced by either 9 or 21 carbons along the polymer backbones. Hydrogen bonding causes the acid groups to form aggregates. These aggregates give rise to a low wavevector peak in the structure factors, in agreement with X-ray scattering data for the PEAA materials. The structure factors for the PESA copolymers are very similar to those for the PEAA copolymers, indicating a similar distance between aggregates which depends on the spacer length but not on the nature of the acid group. The PEAA copolymers are found to form more dimers and other small aggregates than do the PESA copolymers, while the PESA copolymers have both more free acid groups and more large aggregates.
Mean-field dynamics of fermions with relativistic dispersion
Authors: Benedikter Niels , Porta Marcello , Schlein Benjamin
Published: February 2014

We extend the derivation of the time-dependent Hartree-Fock equation recently obtained by Benedikter et al. [“Mean-field evolution of fermionic systems,” Commun. Math. Phys. (to be published)] to fermions with a relativistic dispersion law. The main new ingredient is the propagation of semiclassical commutator bounds along the pseudo-relativistic Hartree-Fock evolution.
The structure of PX3 (X = Cl, Br, I) molecular liquids from X-ray diffraction, molecular dynamics simulations, and reverse Monte Carlo modeling
Authors: Pothoczki Szilvia , Temleitner László , Pusztai László
Published: February 2014

Synchrotron X-ray diffraction measurements have been conducted on liquid phosphorus trichloride, tribromide, and triiodide. Molecular Dynamics simulations for these molecular liquids were performed with a dual purpose: (1) to establish whether existing intermolecular potential functions can provide a picture that is consistent with diffraction data and (2) to generate reliable starting configurations for subsequent Reverse Monte Carlo modelling. Structural models (i.e., sets of coordinates of thousands of atoms) that were fully consistent with experimental diffraction information, within errors, have been prepared by means of the Reverse Monte Carlo method. Comparison with reference systems, generated by hard sphere-like Monte Carlo simulations, was also carried out to demonstrate the extent to which simple space filling effects determine the structure of the liquids (and thus, also estimating the information content of measured data). Total scattering structure factors, partial radial distribution functions and orientational correlations as a function of distances between the molecular centres have been calculated from the models. In general, more or less antiparallel arrangements of the primary molecular axes that are found to be the most favourable orientation of two neighbouring molecules. In liquid PBr3 electrostatic interactions seem to play a more important role in determining intermolecular correlations than in the other two liquids; molecular arrangements in both PCl3 and PI3 are largely driven by steric effects.
Photodissociation of (SO2⋯XH) Van der Waals complexes and clusters (XH = C2H2, C2H4, C2H6) excited at 32 040–32 090 cm−1 with formation of HSO2 and X
Authors: Makarov Vladimir I. , Kochubei Sergei A. , Khmelinskii Igor
Published: February 2014

We studied photodecomposition dynamics of (SO2⋯XH) Van der Waals’ (VdW) complexes and clusters in gas phase, with X = C2H, C2H3, and C2H5. SO2 was excited by frequency-doubled radiation of a tunable dye laser and resonance-enhanced multiphoton ionization was used to detect the C2H (m/z 25), C2H3 (m/z 27), and C2H5 (m/z 29) ions by time-of-flight mass spectroscopy. Spectra obtained at higher nozzle pressures (P0 > 2.5 atm) indicate formation of clusters. Detailed studies of the VdW complex structure were carried out by analyzing the rotational structure of the respective action spectra. We also performed ab initio theoretical analysis of structures of the VdW complexes and transitional states leading to photodecomposition. We find that the structure of the transition state is significantly different as compared to the equilibrium ground-state structure of the respective complex. The photodecomposition mechanism depends on the hydrocarbon molecule bound to SO2.
The collisional depolarization of OH(A 2Σ+) and NO(A 2Σ+) with Kr
Authors: Chadwick H. , Brouard M. , Chang Y.-P. , Eyles C. J. , McCrudden G. , Perkins T. , Seamons S. A. , Kłos J. , Alexander M. H. , Dagdigian P. J. , Herráez-Aguilar D. , Aoiz F. J.
Published: February 2014

Quantum beat spectroscopy has been used to measure rate coefficients at 300 K for collisional depolarization for NO(A 2Σ+) and OH(A 2Σ+) with krypton. Elastic depolarization rate coefficients have also been determined for OH(A) + Kr, and shown to make a much more significant contribution to the total depolarization rate than for NO(A) + Kr. While the experimental data for NO(A) + Kr are in excellent agreement with single surface quasiclassical trajectory (QCT) calculations carried out on the upper 2A′ potential energy surface, the equivalent QCT and quantum mechanical calculations cannot account for the experimental results for OH(A) + Kr collisions, particularly at low N. This disagreement is due to the presence of competing electronic quenching at low N, which requires a multi-surface, non-adiabatic treatment. Somewhat improved agreement with experiment is obtained by means of trajectory surface hopping calculations that include non-adiabatic coupling between the ground 1A′ and excited 2A′ states of OH(X/A) + Kr, although the theoretical depolarization cross sections still significantly overestimate those obtained experimentally.
Contact line pinning and the relationship between nanobubbles and substrates
Authors: Liu Yawei , Wang Jianjun , Zhang Xianren , Wang Wenchuan
Published: February 2014

We report a theoretical study of nanobubble stabilization on a substrate by contact line pinning. In particular, we predict the magnitude of the pinning force required to stabilize a nanobubble and the threshold values of the pinning force that the substrate can provide. We show that the substrate chemistry and the local structures of substrate heterogeneity together determine whether or not surface nanobubbles are stable. We find that for stable nanobubbles, the contact angles are independent of substrate chemistry as its effects are cancelled out by the pinning effect. This prediction is in agreement with available experimental data.
Investigation of particle diffusion and suprathermal electrons in a magnetized helium plasma column
Authors: Lefevre T. , Escarguel A. , Stamm R. , Godbert-Mouret L. , Rosmej F. B.
Published: February 2014

Studying radiative properties of magnetized helium plasma via high-resolution spectroscopy identified close correlations between the particle diffusion and suprathermal electrons for different modes of operation of the MISTRAL installation. The standard diagnostic emission lines in neutral helium (1s3d 3D-1s2p 3P, 1s3s 3S-1s2p 3P, 1s3d 1D-1s2p 1P, and 1s3s 1S-1s2p 1P) show anomalous ratios that are related to enhanced particle diffusion and suprathermal electron generation. The supplementary investigation of singlet/triplet Rydberg series (transitions 1snd 3D-1s2p 3P and 1s5p 1P-1s2s 1S) as well as ionic lines (HeII, transitions n = 3–4 at 469 nm and n = 4–6 at 656 nm) allowed quantitative characterization. Simulations carried out with the atomic physics code SOPHIA demonstrate that simultaneous implementation of diffusion processes and suprathermal electrons matches all experimental findings. Single consideration, however, of either diffusion or hot electrons is in contradiction to the proposed extended set of HeI and HeII emission lines. The high precision achieved with the LSJ-split level structure of SOPHIA coupled to Langmuir probe measurements allowed to conclude to a Bohm type diffusion in MISTRAL.
Zethrene biradicals: How pro-aromaticity is expressed in the ground electronic state and in the lowest energy singlet, triplet, and ionic states
Authors: Zafra José Luis , González Cano Rafael C. , Ruiz Delgado M. Carmen , Sun Zhe , Li Yuan , López Navarrete Juan T. , Wu Jishan , Casado Juan
Published: February 2014

A analysis of the electronic and molecular structures of new molecular materials based on zethrene is presented with particular attention to those systems having a central benzo-quinoidal core able to generate Kekulé biradicals whose stability is provided by the aromaticity recovery in this central unit. These Kekulé biradicals display singlet ground electronic states thanks to double spin polarization and have low-energy lying triplet excited states also featured by the aromaticity gain. Pro-aromatization is also the driving force for the stabilization of the ionized species. Moreover, the low energy lying singlet excited states also display a profound biradical fingerprint allowing to singlet exciton fission. These properties are discussed in the context of the size of the zethrene core and of its substitution. The work encompasses all known long zethrenes and makes use of a variety of experimental techniques, such as Raman, UV-Vis-NIR absorption, transient absorption, in situ spectroelectrochemistry and quantum chemical calculations. This study reveals how the insertion of suitable molecular modules (i.e., quinoidal) opens the door to new intriguing molecular properties exploitable in organic electronics.
Complex structural rearrangements in As-Se glasses
Authors: Golovchak R. , Oelgoetz J. , Vlcek M. , Esposito A. , Saiter A. , Saiter J.-M. , Jain H.
Published: February 2014

Structural relaxation of As-Se glasses through the glass-to-supercooled liquid transition interval is studied with temperature-modulated differential scanning calorimetry. It is shown that connectivity of glass network and long-term physical ageing change not only the full width at half maximum of the out-of-phase component of complex heat capacity, which is conventionally used for analysis, but also its asymmetry value. The latter is shown to carry very important information on the dynamic heterogeneity in glasses. Raman spectroscopy is used as complementary technique to reveal possible structural rearrangements in the investigated glass network.
Patterned electrochemical deposition of copper using an electron beam
Authors: den Heijer Mark , Shao Ingrid , Radisic Alex , Reuter Mark C. , Ross Frances M.
Published: February 2014

We describe a technique for patterning clusters of metal using electrochemical deposition. By operating an electrochemical cell in the transmission electron microscope, we deposit Cu on Au under potentiostatic conditions. For acidified copper sulphate electrolytes, nucleation occurs uniformly over the electrode. However, when chloride ions are added there is a range of applied potentials over which nucleation occurs only in areas irradiated by the electron beam. By scanning the beam we control nucleation to form patterns of deposited copper. We discuss the mechanism for this effect in terms of electron beam-induced reactions with copper chloride, and consider possible applications.
Ab initio calculations for the far infrared collision induced absorption by N2 gas
Authors: Bussery-Honvault Béatrice , Hartmann Jean-Michel
Published: February 2014

We present (far-infrared) Collision Induced Absorption (CIA) spectra calculations for pure gaseous N2 made for the first time, from first-principles. They were carried out using classical molecular dynamics simulations based on ab initio predictions of both the intermolecular potential and the induced-dipole moment. These calculations reproduce satisfactory well the experimental values (intensity and band profile) with agreement within 3% at 149 K. With respect to results obtained with only the long range (asymptotic) dipole moment (DM), including the short range overlap contribution improves the band intensity and profile at 149 K, but it deteriorates them at 296 K. The results show that the relative contribution of the short range DM to the band intensity is typically around 10%. We have also examined the sensitivity of the calculated CIA to the intermolecular potential anisotropy, providing a test of the so-called isotropic approximation used up to now in all N2 CIA calculations. As all these effects interfere simultaneously with quantitatively similar influences (around 10%), it is rather difficult to assert which one could explain remaining deviations with the experimental results. Furthermore, the rather large uncertainties and sometimes inconsistencies of the available measurements forbid any definitive conclusion, stressing the need for new experiments.
Semiconductor to metal transition by tuning the location of N2AA in armchair graphene nanoribbons
Authors: Chen Tong , Li Xiao-Fei , Wang Ling-Ling , Li Quan , Luo Kai-Wu , Zhang Xiang-Hua , Xu Liang
Published: February 2014

The electronic band structures and transport properties of N2AA-doped armchair graphene nanoribbons (aGNRs) with two quasi-adjacent substitutional nitrogen atoms incorporated in pairs of neighboring carbon atoms in the same sublattice A are investigated by using non-equilibrium Green function formalism in combination with density functional theory. The results show that the coupling effect between the Pz orbitals of carbon and nitrogen atoms plays an important role in the transition between semiconductor and metal by different locations of N2AA-doped aGNRs. And the striking negative differential resistance behaviors can be found in such devices. These tremendous properties suggest potential application of N2AA-doped aGNRs in graphene-based nanoelectronic devices.
Continuous flow ultrasonic particle trapping in a glass capillary
Authors: Gralinski Ian , Raymond Samuel , Alan Tuncay , Neild Adrian
Published: February 2014

Ultrasonic manipulation devices frequently exploit ultrasonic standing waves to trap particles in locations across the width of a fluidic channel or chamber. In contrast, this work describes a device, which traps particles along the length of the channel and hence at different locations along the direction of fluid flow. Actuation is achieved using a single piezoelectric transducer bonded to a borosilicate glass capillary, which defines the fluidic channel. Modes of operation have been found experimentally and through use of finite element simulation methods in which the particles can be trapped at locations away from the piezoelectric transducer allowing optimal visual access to the clumps of particles. These locations are separated by distances significantly greater than half the acoustic wavelength. When flow is introduced, a single clump is formed and optical access is unhindered by the opaque transducer allowing a method of capturing particles for multi-axial optical analysis. Applications could include determination of sample concentration or creation of concentrated samples for subsequent batch operations.
Controlled self-assembly of multiferroic core-shell nanoparticles exhibiting strong magneto-electric effects
Authors: Sreenivasulu Gollapudi , Popov Maksym , Chavez Ferman A. , Hamilton Sean L. , Lehto Piper R. , Srinivasan Gopalan
Published: February 2014

Ferromagnetic-ferroelectric composites show strain mediated coupling between the magnetic and electric sub-systems due to magnetostriction and piezoelectric effects associated with the ferroic phases. We have synthesized core-shell multiferroic nano-composites by functionalizing 10–100 nm barium titanate and nickel ferrite nanoparticles with complementary coupling groups and allowing them to self-assemble in the presence of a catalyst. The core-shell structure was confirmed by electron microscopy and magnetic force microscopy. Evidence for strong strain mediated magneto-electric coupling was obtained by static magnetic field induced variations in the permittivity over 16–18 GHz and polarization and by electric field induced by low-frequency ac magnetic fields.
Influence of carbon content on the copper-telluride phase formation and on the resistive switching behavior of carbon alloyed Cu-Te conductive bridge random access memory cells
Authors: Devulder Wouter , Opsomer Karl , Franquet Alexis , Meersschaut Johan , Belmonte Attilio , Muller Robert , De Schutter Bob , Van Elshocht Sven , Jurczak Malgorzata , Goux Ludovic , Detavernier Christophe
Published: February 2014

In this paper, we investigate the influence of the carbon content on the Cu-Te phase formation and on the resistive switching behavior in carbon alloyed Cu0.6Te0.4 based conductive bridge random access memory (CBRAM) cells. Carbon alloying of copper-tellurium inhibits the crystallization, while attractive switching behavior is preserved when using the material as Cu-supply layer in CBRAM cells. The phase formation is first investigated in a combinatorial way. With increasing carbon content, an enlargement of the temperature window in which the material stays amorphous was observed. Moreover, if crystalline phases are formed, subsequent phase transformations are inhibited. The electrical switching behavior of memory cells with different carbon contents is then investigated by implementing them in 580 μm diameter dot TiN/Cu0.6Te0.4-C/Al2O3/Si memory cells. Reliable switching behavior is observed for carbon contents up to 40 at. %, with a resistive window of more than 2 orders of magnitude, whereas for 50 at. % carbon, a higher current in the off state and only a small resistive window are present after repeated cycling. This degradation can be ascribed to the higher thermal and lower drift contribution to the reset operation due to a lower Cu affinity towards the supply layer, leading cycle-after-cycle to an increasing amount of Cu in the switching layer, which contributes to the current. The thermal diffusion of Cu into Al2O3 under annealing also gives an indication of the Cu affinity of the source layer. Time of flight secondary ion mass spectroscopy was used to investigate this migration depth in Al2O3 before and after annealing, showing a higher Cu, Te, and C migration for high carbon contents.
Space charge limited conduction in ultrathin PbS quantum dot solid diodes
Authors: Kwan Kim Jun , Hoon Song Jung , Choi Hyekyoung , Jae Baik Seung , Jeong Sohee
Published: February 2014

As a simple and direct characterization of carrier transport in nanocrystal quantum dot (NQD) solids, current-voltage characterization of ultrathin diodes is proposed. We found the space charge limited conduction (SCLC) behavior in ultrathin PbS NQD diodes with active layer thickness half of the full depletion width; and extracted hole concentrations in the order of 1015 cm−3, hole mobilities from 10−4 to 10−5 cm2/Vs, trap energy depths varying from 140 meV to 200 meV, and volume trap density around 1017 cm−3 for thin films with NQDs of diameters 3.3 and 3.6 nm, respectively. We further discuss the validity of applying SCLC to the NQD solids based diodes and the implications of the extracted parameters extensively. Proposed characterization method here is a direct measure of carrier transport in solar cell structures which could provide exact directions in NQD solids based solar cell fabrication and modeling.
Manifesting pseudo-spin polarization of graphene with field emission image
Authors: Chen Jingkun , Li Zhibing , Wang Weiliang
Published: February 2014

Coherent emission of electron from graphene in both electric and magnetic fields is studied. We obtain the emission wave function analytically. The emission current density is calculated. The structure of Landau levels is recognizable in the emission image. The emission pattern depends on the phase difference of two sub-lattices. We find that the pattern changes obviously with the gate voltage on the edge. It provides a way to manipulate the emission pattern.
Inverse magnetocaloric effect in Mn2NiGa and Mn1.75Ni1.25Ga magnetic shape memory alloys
Authors: Singh Sanjay , Esakki Muthu S. , Senyshyn A. , Rajput P. , Suard E. , Arumugam S. , Barman S. R.
Published: February 2014

Inverse magnetocaloric effect is demonstrated in Mn2NiGa and Mn1.75Ni1.25Ga magnetic shape memory alloys. The entropy change at the martensite transition is larger in Mn1.75Ni1.25Ga, and it increases linearly with magnetic field in both the specimens. Existence of inverse magnetocaloric effect is consistent with the observation that magnetization in the martensite phase is smaller than the austenite phase. Although the Mn content is smaller in Mn1.75Ni1.25Ga, from neutron diffraction, we show that the origin of inverse magnetocaloric effect is the antiferromagnetic interaction between the Mn atoms occupying inequivalent sites.
Fabrication and characterization of aluminum airbridges for superconducting microwave circuits
Authors: Chen Zijun , Megrant A. , Kelly J. , Barends R. , Bochmann J. , Chen Yu , Chiaro B. , Dunsworth A. , Jeffrey E. , Mutus J. Y. , O'Malley P. J. J. , Neill C. , Roushan P. , Sank D. , Vainsencher A. , Wenner J. , White T. C. , Cleland A. N. , Martinis John M.
Published: February 2014

Superconducting microwave circuits based on coplanar waveguides (CPW) are susceptible to parasitic slotline modes which can lead to loss and decoherence. We motivate the use of superconducting airbridges as a reliable method for preventing the propagation of these modes. We describe the fabrication of these airbridges on superconducting resonators, which we use to measure the loss due to placing airbridges over CPW lines. We find that the additional loss at single photon levels is small, and decreases at higher drive powers.
Inverse spin Hall effect induced by spin pumping into semiconducting ZnO
Authors: Lee Jung-Chuan , Huang Leng-Wei , Hung Dung-Shing , Chiang Tung-Han , Huang J. C. A. , Liang Jun-Zhi , Lee Shang-Fan
Published: February 2014

The inverse spin Hall effect (ISHE) of n-type semiconductor ZnO thin films with weak spin-orbit coupling has been observed by utilizing the spin pumping method. In the ferromagnetic resonance condition, the spin pumping driven by the dynamical exchange interaction of a permalloy film injects a pure spin current into the adjacent ZnO layer. This spin current gives rise to a DC voltage through the ISHE in the ZnO layer, and the DC voltage is proportional to the microwave excitation power. The effect is sizeable even when the spin backflow is considered.
Quantum oscillations and subband properties of the two-dimensional electron gas at the LaAlO3/SrTiO3 interface
Authors: McCollam A. , Wenderich S. , Kruize M. K. , Guduru V. K. , Molegraaf H. J. A. , Huijben M. , Koster G. , Blank D. H. A. , Rijnders G. , Brinkman A. , Hilgenkamp H. , Zeitler U. , Maan J. C.
Published: February 2014

We have performed high field magnetotransport measurements to investigate the interface electron gas in a high mobility SrTiO3/SrCuO2/LaAlO3/SrTiO3 heterostructure. Shubnikov-de Haas oscillations reveal several 2D conduction subbands with carrier effective masses of 0.9me and 2me, quantum mobilities of order 2000 cm2/V s, and band edges only a few millielectronvolts below the Fermi energy. Measurements in tilted magnetic fields confirm the 2D character of the electron gas, and show evidence of inter-subband scattering.
Dominant role of oxygen vacancies in electrical properties of unannealed LaAlO3/SrTiO3 interfaces
Authors: Liu Z. Q. , Sun L. , Huang Z. , Li C. J. , Zeng S. W. , Han K. , Lü W. M. , Venkatesan T. , Ariando
Published: February 2014

We report that in unannealed LaAlO3/SrTiO3 (LAO/STO) heterostructures the critical thickness for the appearance of the two-dimensional electron gas can be less than 4 unit cell, the interface is conducting even for STO substrates with mixed terminations and the low-temperature resistance upturn in LAO/STO heterostructures with thick LAO layers strongly depends on laser fluence. Our experimental results provide fundamental insights into the different roles played by oxygen vacancies and polarization catastrophe in the two-dimensional electron gas in crystalline LAO/STO heterostructures.
Modeling of capacitance transients of thin-film solar cells: A valuable tool to gain information on perturbing layers or interfaces
Authors: Lauwaert Johan , Lauwaert Jeroen , Van Puyvelde Lisanne , Thybaut Joris W. , Vrielinck Henk
Published: February 2014

Thin-film electronic and photovoltaic devices often comprise, in addition to the anticipated p-n junctions, additional non-ideal ohmic contacts between layers. This may give rise to additional signals in capacitance spectroscopy techniques that are not directly related to defects in the structure. In this paper, we present a fitting algorithm for transient signals arising from such an additional junction. The fitting results are in excellent agreement with the diode characteristics extracted from static measurements on individual components. Finally, the algorithm is applied for determining the barriers associated with anomalous signals reported for selected CuIn1–xGaxSe2 and CdTe solar cells.
Graphene as broadband terahertz antireflection coating
Authors: Zhou Yixuan , Xu Xinlong , Hu Fangrong , Zheng Xinliang , Li Weilong , Zhao Penghui , Bai Jintao , Ren Zhaoyu
Published: February 2014

We examined the potential of stacked multilayer graphene as broadband terahertz (THz) antireflection coating based on the impedance matching effect in experiment and theory. The reflected pulses from the quartz and silicon substrates were observed to change with the layer number and doping concentration of the graphene coating. Remarkable broadband impedance matching was achieved due to optimized THz conductivity. Theoretical analysis based on Drude model and thin film Fresnel coefficients have been used to explain the experimental phenomena, which indicated the shift of Fermi level caused by chemical doping. This work paves the way for graphene-based broadband THz antireflection coating.
High performance vertical tunneling diodes using graphene/hexagonal boron nitride/graphene hetero-structure
Authors: Hwan Lee Seung , Sup Choi Min , Lee Jia , Ho Ra Chang , Liu Xiaochi , Hwang Euyheon , Hee Choi Jun , Zhong Jianqiang , Chen Wei , Jong Yoo Won
Published: February 2014

A tunneling rectifier prepared from vertically stacked two-dimensional (2D) materials composed of chemically doped graphene electrodes and hexagonal boron nitride (h-BN) tunneling barrier was demonstrated. The asymmetric chemical doping to graphene with linear dispersion property induces rectifying behavior effectively, by facilitating Fowler-Nordheim tunneling at high forward biases. It results in excellent diode performances of a hetero-structured graphene/h-BN/graphene tunneling diode, with an asymmetric factor exceeding 1000, a nonlinearity of ∼40, and a peak sensitivity of ∼12 V−1, which are superior to contending metal-insulator-metal diodes, showing great potential for future flexible and transparent electronic devices.
On the stabilizing effect of a liquid film on a cylindrical core by oscillatory motions
Authors: Rohlfs Wilko , Binz Matthias , Kneer Reinhold
Published: February 2014

Liquid films on cylindrical bodies like wires or fibres disintegrate if their length exceeds a critical size (Plateau-Rayleigh instability). Stabilization can be achieved by an axial oscillation of the solid core provided that a suitable combination of forcing amplitude and frequency is given. To investigate the stabilizing effect, direct numerical simulations (DNS) of the axisymmetric problem are conducted with a height function based solver. It is found that the mechanism of film stabilization is caused by the interaction between an inertia dominated region (high film thickness) and a viscosity dominated region (low film thickness). Replenishing of the thin film region is thereby supported while depleting is suppressed, finally leading to a stable film flow on an oscillating cylinder. To the end, a systematic variation of the main system parameters, e.g., the Weber number, the ratio between the radius of the inner core and the average film coating thickness, and the oscillation frequency is presented and the influence of the parameters discussed.
Temperature- and size-dependent characteristics in ultrathin inorganic light-emitting diodes assembled by transfer printing
Authors: Kim Tae-il , Hyun Lee Soo , Li Yuhang , Shi Yan , Shin Gunchul , Dan Lee Sung , Huang Yonggang , Rogers John A. , Su Yu Jae
Published: February 2014

Favorable temperature- and size-dependent device characteristics in mechanically flexible, thin (∼6.45 μm thick), microscale inorganic InGaN/GaN-based light-emitting diodes enable their use as highly efficient, robust devices that are capable of integration on diverse classes of unconventional substrates, including sheets of plastic. Finite element analysis and systematic studies of the operational properties establish important thermal, electrical, and optical considerations for this type of device.
Synchronization of coupled large-scale Boolean networks
Authors: Li Fangfei
Published: February 2014

This paper investigates the complete synchronization and partial synchronization of two large-scale Boolean networks. First, the aggregation algorithm towards large-scale Boolean network is reviewed. Second, the aggregation algorithm is applied to study the complete synchronization and partial synchronization of large-scale Boolean networks. Finally, an illustrative example is presented to show the efficiency of the proposed results.
Analysis of micro-lens integrated flip-chip InGaN light-emitting diodes by confocal microscopy
Authors: Li K. H. , Feng C. , Choi H. W.
Published: February 2014

A hexagonally close-packed microlens array has been integrated onto the sapphire face of a flip-chip bonded InGaN light-emitting diode (LED). The micro-optics is formed by etching a self-assembled monolayer of 1-μm silica microspheres coated on the sapphire substrate, producing hemispherical sapphire lenses. Without degrading electrical characteristic, the light output power of the lensed LED is increased by more than a quarter compared with the unlensed LED. Enhanced light extraction via micro-optics is verified by rigorous coupled wave analysis. The focusing behavior of the micro-lenses, as well as the emission characteristics of the lensed LED, is studied by confocal microscopy.
Electrochemical corrosion behavior, microstructure and magnetic properties of sintered Nd-Fe-B permanent magnet doped by CuZn5 powders
Authors: Liu W. Q. , Wang Z. , Sun C. , Yue M. , Liu Y. Q. , Zhang D. T. , Zhang J. X.
Published: February 2014

Nd-Fe-B permanent magnets with a small amount of CuZn5 powders doping were prepared by conventional sintered method. The effects of CuZn5 contents on magnetic properties and microstructure, electrochemical corrosion resistance of sintered Nd-Fe-B magnets were systematically studied. The results show that the magnetic properties of magnets do not have a significant variation by CuZn5 powders doping; the coercivity of magnets rises gradually, while the remanence of the magnets decreases a little with increasing of the CuZn5 amount. The CuZn5 doped magnets have more positive corrosion potential, Ecorr, and much lower corrosion current density, icorr, than the magnets without CuZn5 doping, indicating CuZn5 doping could improve the corrosion resistance. Both Zn and Cu enrich mainly into the Nd-rich phase, fully improve the wettability between the Nd-rich phase and the Nd2Fe14B phase, and repair the defects of the main phase, so the coercivity of magnets doped with CuZn5 powders rises. Such microstructure modification effectively restrains the aggressive inter-granular corrosion. As a result, the CuZn5 doped magnet possesses excellent corrosion resistance in NaCl electrolyte.
Experimentally driven atomistic model of 1,2 polybutadiene
Authors: Gkourmpis Thomas , Mitchell Geoffrey R.
Published: February 2014

We present an efficient method of combining wide angle neutron scattering data with detailed atomistic models, allowing us to perform a quantitative and qualitative mapping of the organisation of the chain conformation in both glass and liquid phases. The structural refinement method presented in this work is based on the exploitation of the intrachain features of the diffraction pattern and its intimate linkage with atomistic models by the use of internal coordinates for bond lengths, valence angles, and torsion rotations. Atomic connectivity is defined through these coordinates that are in turn assigned by pre-defined probability distributions, thus allowing for the models in question to be built stochastically. Incremental variation of these coordinates allows for the construction of models that minimise the differences between the observed and calculated structure factors. We present a series of neutron scattering data of 1,2 polybutadiene at the region 120–400 K. Analysis of the experimental data yields bond lengths for CC and C  C of 1.54 Å and 1.35 Å, respectively. Valence angles of the backbone were found to be at 112° and the torsion distributions are characterised by five rotational states, a three-fold trans-skew± for the backbone and gauche± for the vinyl group. Rotational states of the vinyl group were found to be equally populated, indicating a largely atactic chan. The two backbone torsion angles exhibit different behaviour with respect to temperature of their trans population, with one of them adopting an almost all trans sequence. Consequently, the resulting configuration leads to a rather persistent chain, something indicated by the value of the characteristic ratio extrapolated from the model. We compare our results with theoretical predictions, computer simulations, RIS models and previously reported experimental results.
Hydrophobic catalytic Janus motors: Slip boundary condition and enhanced catalytic reaction rate
Authors: Manjare Manoj , Ting Wu Yuan , Yang Bo , Zhao Y.-P.
Published: February 2014

A hydrophobic front surface in Janus catalytic motors could introduce two effects to the motion kinetics: a partially slippery surface and a change in catalytic reaction rate. Experimentally, the hydrophobic Janus motors have been observed to move appreciably faster than the hydrophilic ones for large size motors with high fuel concentrations. Numerical investigation and experimental data reveal that the slippery surface has an insignificant effect on motor kinetics compared to an enhanced catalytic reaction rate, which could result from the water depletion layer around the hydrophobic surface and the strong hydrophobic interaction between the generated O2 and the hydrophobic surface.