bluuebunny/crossref_metadata_2025 huggingface dataset:
Design, synthesis and biological activity of 4′-[(benzimidazol-1-yl)methyl]biphenyl-2-sulphonamides as dual angiotensin II and endothelin A receptor antagonists
Authors: Hao Li-Ping , Xue Wei-Zhe , Han Xiao-Feng , He Xing , Zhang Jun , Zhou Zhi-Ming
Published: January 2015

A series of novel 4′-[(benzimidazol-1-yl)methyl]biphenyl-2-sulphonamides was designed, and their molecular model simulation fitting to a new HipHop 3D pharmacophore model was examined.
Overcoming the concentration-dependence of responsive probes for magnetic resonance imaging
Authors: Ekanger Levi A. , Allen Matthew J.
Published: January 2015

Responsive probes for magnetic resonance imaging are often limited by concentration-dependence; in this review, we describe strategies to overcome this limitation.
Non-destructive functionalisation for atomic layer deposition of metal oxides on carbon nanotubes: effect of linking agents and defects
Authors: Kemnade N. , Shearer C. J. , Dieterle D. J. , Cherevan A. S. , Gebhardt P. , Wilde G. , Eder D.
Published: January 2015

The hybridisation of metal oxides and nanocarbons has created a promising new class of functional materials for environmental and sustainable energy applications.
A high-density graphene–sulfur assembly: a promising cathode for compact Li–S batteries
Authors: Zhang Chen , Liu Dong-Hai , Lv Wei , Wang Da-Wei , Wei Wei , Zhou Guang-Min , Wang Shaogang , Li Feng , Li Bao-Hua , Kang Feiyu , Yang Quan-Hong
Published: January 2015

A high-density graphene–sulfur cathode is fabricated for high volumetric capacity Li–S batteries, and the potential of the cathode for compact energy storage is demonstrated.
Microsphere assembly of TiO2 mesoporous nanosheets with highly exposed (101) facets and application in a light-trapping quasi-solid-state dye-sensitized solar cell
Authors: Tao Xiyun , Ruan Peng , Zhang Xiang , Sun Hongxia , Zhou Xingfu
Published: January 2015

Microsphere of TiO2 mesoporous nanosheets with exposed (101) facets were fabricated. Quasi-solid-state DSSC using these special microspheres showed a 45.8% increase in the conversion efficiency.
Spherical core–shell magnetic particles constructed by main-chain palladium N-heterocyclic carbenes
Authors: Zhao Huaixia , Li Liuyi , Wang Jinyun , Wang Ruihu
Published: January 2015

The spherical core–shell magnetic particles were presented by the encapsulation of Fe3O4nanoparticles inside the main-chain palladium N-heterocyclic carbene matrices.
Synthesis of directly fused porphyrin dimers through Fe(OTf)3-mediated oxidative coupling
Authors: Feng Chuan-Mi , Zhu Yi-Zhou , Zhang Shao-Chun , Zang Yun , Zheng Jian-Yu
Published: January 2015

A practical and general Fe(OTf)3-mediated oxidative coupling method was developed for the synthesis of doubly or triply linked porphyrin dimers.
Insight into molecular interactions of Aβ peptide and gelatinase from Enterococcus faecalis: a molecular modeling approach
Authors: Jalkute Chidambar B. , Barage Sagar H. , Sonawane Kailas D.
Published: January 2015

Alzheimer's disease is characterized by the presence of extracellular deposition of amyloid beta (Aβ) peptides.
Adsorption of carbon monoxide, methane and nitrogen on alkaline earth metal ion exchanged zeolite-X: structure, cation position and adsorption relationship
Authors: Sethia Govind , Somani Rajesh S. , Chand Bajaj Hari
Published: January 2015

The present study reports adsorption of carbon monoxide, methane and nitrogen on alkaline earth metal ion exchanged zeolite-X and relationship between zeolite structure, cation position and adsorption properties.
Targeting cancer cells using aptamers: cell-SELEX approach and recent advancements
Authors: Barman Jharna
Published: January 2015

Aptamers are short single stranded nucleic acid based therapeutic and diagnostic molecules which can be isolated from a random pool of oligonucleotides by Systematic Evolution of Ligands by EXponential Enrichment (SELEX).
Polyhedral oligomeric silsesquioxane/polyamide bio-nanocomposite membranes: structure-gas transport properties
Authors: Gnanasekaran Dhorali , Shanavas A. , Focke Walter W. , Sadiku Rotimi
Published: January 2015

Prepared cost-effective and environmentally-friendly POSS/PA by facile synthesis via solvent casting method. Conspectus study and morphology correlation with gas-transport properties. Effective H-bonds of POSS and PA facilitate separation properties.
Mechanical properties and stabilities of g-ZnS monolayers
Authors: Peng Qing , Han Liang , Wen Xiaodong , Liu Sheng , Chen Zhongfang , Lian Jie , De Suvranu
Published: January 2015

Planar graphene-like ZnS monolayers are mechanically stable under various large strains.
Novel photovoltaic donor 1–acceptor–donor 2–acceptor terpolymers with tunable energy levels based on a difluorinated benzothiadiazole acceptor
Authors: Deng Zhiqiang , Wu Feiyan , Chen Lie , Chen Yiwang
Published: January 2015

Novel donor 1–acceptor–donor 2–acceptor (PBDT-DTffBT-F-DTffBT) type terpolymers offer an opportunity to further tune the energy levels compared with the corresponding D–A type bipolymers.
Fluorescent/phosphorescent dual-emissive conjugated polymer dots for hypoxia bioimaging
Authors: Zhao Qiang , Zhou Xiaobo , Cao Tianye , Zhang Kenneth Yin , Yang Lijuan , Liu Shujuan , Liang Hua , Yang Huiran , Li Fuyou , Huang Wei
Published: January 2015

Fluorescent/phosphorescent dual-emissive conjugated polymer dots were designed and synthesized, ere used for tumor hypoxia sensing via ratiometric imaging and photoluminescence lifetime imaging.
Superior sodium–lithium intercalation and depressed moisture sensitivity of a hierarchical sandwich-type nanostructure for a graphene–sulfate composite: a case study on Na2Fe(SO4)2·2H2O
Authors: Meng Yu , Zhang Sen , Deng Chao
Published: January 2015

A three-dimensional hierarchical sandwich-type graphene–Na2Fe(SO4)2·2H2O composite exhibits improved sodium–lithium intercalation chemistry and depressed moisture sensitivity.
Highly cross-linked fluorescent poly(cyclotriphosphazene-co-curcumin) microspheres for the selective detection of picric acid in solution phase
Authors: Wei Wei , Lu Rongjie , Tang Shuyuan , Liu Xiaoya
Published: January 2015

Poly(cyclotriphosphazene-co-curcumin) microspheres were facilely prepared by a one-step precipitation copolymerization and exhibited a highly selective fluorescence quenching response toward picric acid due to the unique acid–base interaction.
Cation ordering in A-site-deficient Li-ion conducting perovskites La(1−x)/3LixNbO3
Authors: Gao Xiang , Fisher Craig A. J. , Ikuhara Yumi H. , Fujiwara Yasuyuki , Kobayashi Shunsuke , Moriwake Hiroki , Kuwabara Akihide , Hoshikawa Keigo , Kohama Keiichi , Iba Hideki , Ikuhara Yuichi
Published: January 2015

Atomic-resolution STEM reveals complex ordering of A-site cations and vacancies, as well as NbO6octahedral tilting and distortion, in Li-conducting perovskites La(1−x)/3LixNbO3.
Superior electric double layer capacitors using micro- and mesoporous silicon carbide sphere
Authors: Kim Myeongjin , Oh Ilgeun , Kim Jooheon
Published: January 2015

Three-dimensional silicon carbide-based frameworks with hierarchical micro and mesoporous structures (MMPSiC) are prepared by employing the template method and carbonization reaction via the aerosol-spray drying method.
A columnar liquid crystal with permanent polar order
Authors: Guilleme J. , Aragó J. , Ortí E. , Cavero E. , Sierra T. , Ortega J. , Folcia C. L. , Etxebarria J. , González-Rodríguez D. , Torres T.
Published: January 2015

The self-assembly of axial dipolar subphthalocyanine molecules in the presence of electric fields leads to uniaxially oriented columnar liquid crystalline materials that exhibit permanent polarization.
Low‐complexity user scheduling for MMSE relaying with large‐scale arrays
Authors: Liu Haijing , Gao Hui , Lv Tiejun
Published: January 2015

An enhanced round‐robin scheduling (RRS) scheme for multi‐pair multi‐input–multi‐output relay systems is proposed, where the relay is equipped with a large‐scale antenna array and performs minimum mean‐square error (MMSE) data processing. Compared with the traditional RRS, significant sum rate performance improvement by setting the number of active user pairs to an appropriate value is achieved.
Adaptively determining regularisation parameters in non‐local total variation regularisation for image denoising
Authors: Zheng Yuhui , Jeon Byeungwoo , Zhang Jianwei , Chen Yunjie
Published: January 2015

A non‐local selection scheme of regularisation parameters is exploited for non‐local total variation (NLTV) regularisation, based on a content‐aware function that can determine regularisation parameters through discriminating image contents, with the aid of a non‐local structure tensor calculated using the weights from the original NLTV. Experimental results on simulated and real noisy images show the relatively good performance of the proposed scheme based on NLTV, in terms of visual improvement and peak signal‐to‐noise ratio value.
Error probability analysis of a novel adaptive beamforming receiver for large‐scale multiple‐input–multiple‐output communication system
Authors: Tran Tuong Xuan , Teh Kah Chan
Published: January 2015

A novel adaptive beamforming (BF) receiver is proposed for a multiple‐input–multiple‐output communication system over multipath fading channels. By dividing a large number of receive antennas into many adaptive beamformers (ABFs), the proposed system reduces the array dimension in order to simplify the signal detection process and enjoys the benefit of BF techniques to improve the symbol‐error‐rate (SER) performance. The effectiveness of the proposed system depends on the number of ABFs and the number of antennas per ABF. The statistical properties of complex Wishart matrices are applied to analyse the SER performance of the proposed system with both maximum‐likelihood (ML) detection and zero‐forcing detection. Furthermore, the authors have derived an upper bound for SER of the ML detection based on the smallest eigenvalue distribution. Through the authors analysis, it has been shown that the proposed system using ML detection provides comparable SER performance, but with a lower complexity as compared with that of a conventional ML receiver because of reduced array dimensions.
A comparative analysis of clustering algorithms: O2 migration in truncated hemoglobin I from transition networks
Authors: Cazade Pierre-André , Zheng Wenwei , Prada-Gracia Diego , Berezovska Ganna , Rao Francesco , Clementi Cecilia , Meuwly Markus
Published: January 2015

The ligand migration network for O2–diffusion in truncated Hemoglobin N is analyzed based on three different clustering schemes. For coordinate-based clustering, the conventional k–means and the kinetics-based Markov Clustering (MCL) methods are employed, whereas the locally scaled diffusion map (LSDMap) method is a collective-variable-based approach. It is found that all three methods agree well in their geometrical definition of the most important docking site, and all experimentally known docking sites are recovered by all three methods. Also, for most of the states, their population coincides quite favourably, whereas the kinetics of and between the states differs. One of the major differences between k–means and MCL clustering on the one hand and LSDMap on the other is that the latter finds one large primary cluster containing the Xe1a, IS1, and ENT states. This is related to the fact that the motion within the state occurs on similar time scales, whereas structurally the state is found to be quite diverse. In agreement with previous explicit atomistic simulations, the Xe3 pocket is found to be a highly dynamical site which points to its potential role as a hub in the network. This is also highlighted in the fact that LSDMap cannot identify this state. First passage time distributions from MCL clusterings using a one- (ligand-position) and two-dimensional (ligand-position and protein-structure) descriptor suggest that ligand- and protein-motions are coupled. The benefits and drawbacks of the three methods are discussed in a comparative fashion and highlight that depending on the questions at hand the best-performing method for a particular data set may differ.
A simple compact UHV and high magnetic field compatible inertial nanopositioner
Authors: Pang Zongqiang , Li Xiang , Xu Lei , Rong Zhou , Liu Ruilan
Published: January 2015

We present a novel simple piezoelectric nanopositioner which just has one piezoelectric scanner tube (PST) and one driving signal, using two short quartz rods and one BeCu spring which form a triangle to press the central shaft and can promise the nanopositioner’s rigidity. Applying two pulse inverted voltage signals on the PST’s outer and inner electrodes, respectively, according to the principle of piezoelectricity, the PST will elongate or contract suddenly while the central shaft will keep stationary for its inertance, so the central shaft will be sliding a distance relative to quartz rods and spring, and then withdraw the pulse voltages slowly, the central shaft will move upward or downward one step. The heavier of the central shaft, the better moving stability, so the nanopositioner has high output force. Due to its compactness and mechanical stability, it can be easily implanted into some extreme conditions, such as ultrahigh vacuum, ultralow temperature, and high magnetic field.
Fibre optics wavemeters calibration using a self-referenced optical frequency comb
Authors: Galindo-Santos J. , Velasco A. V. , Corredera P.
Published: January 2015

Self-referenced optical frequency combs enable the measurement of optical frequencies with a very high accuracy, achieving uncertainties close to the atomic clock used as reference (<10−13 s). In this paper, we present the technique for the measurement of laser frequencies for optical communications followed at IO-CSIC and its application to the calibration of two wavemeters in the 1.5 μm optical communication window. Calibration uncertainties down to 12 MHz and 59 MHz were obtained, respectively, for each of the devices. Furthermore, the long-term behaviour of the higher resolution wavemeter was studied during a 750 h period of sustained operation, exhibiting a dispersion in the measurements of 7.72 MHz. Temperature dependence of the device was analysed, enabling to further reduce dispersion down to a 2.15 MHz range, with no significant temporal deviations.
Brownian dynamics simulations of coagulation of dilute uniform and anisotropic particles under shear flow spanning low to high Peclet numbers
Authors: Mohammadi Maziar , Larson Eric D. , Liu Jun , Larson Ronald G.
Published: January 2015

Brownian dynamics simulations are performed to study the binding kinetics in the dilute-sphere limit by considering interactions of two spheres under shear flow across the entire range of Peclet numbers, spanning both perikinetic (diffusion-controlled) and orthokinetic (flow-controlled) coagulation regimes. The dilute regime is attained by carrying out two-sphere simulations in periodic boxes of different sizes and aspect ratios and extrapolating toward the infinite box limit. Effects of particle type (Janus and isotropic particles), shear rate, hydrodynamic interactions, and inter-particle potential are explored. We find that rectangular boxes with appropriate aspect ratios overcome a particle “shadow effect” that cannot be overcome with cubic boxes unless huge boxes are used. With rectangular boxes, we obtain converged binding kinetics for the whole Peclet number range, while cubic boxes of increasing size allow converged results only in the absence of flow. We consider the effect of binding both in a secondary minimum controlled by a combination of electrostatic repulsion and depletion attraction, as well as in a primary minimum governed by induced-dipole attraction. Results are computed using both realistic interaction potentials and by replacing the potential with a simple cutoff gap distance at which binding is deemed to occur. Results agree with several existing reports including Smoluchowski predictions in the zero- and infinite-shear-rate limits, and high-Pe perturbation results of Feke and Schowalter [J. Fluid Mech. 133, 17-35 (1983)] at Peclet numbers (Pe) above 100. Finally, we compute binding times for anisotropic Janus particles which have both repulsive and attractive faces, for a wide range of Pe number.
The nature of interfaces and charge trapping sites in photocatalytic mixed-phase TiO2 from first principles modeling
Authors: Garcia Juan C. , Nolan Michael , Deskins N. Aaron
Published: January 2015

Mixed phase rutile/anatase catalysts show increased reactivity compared with the pure phases alone. However, the mechanism causing this effect is not fully understood. The electronic properties of the interface and the relative energy of the electron in each phase play a key role in lowering the rate of recombination of electron hole pairs. Using density functional theory and the +U correction, we calculated the bands offsets between the phases taking into account the effect of the interface. Our model included several thousands atoms, and thus is a good representation of an interface between actual nanoparticles. We found rutile to have both higher conduction and valence band offsets than rutile, leading to an accumulation of electrons in the anatase phase accompanied by hole accumulation in the rutile phase. We also probed the electronic structure of our heterostructure and found a gap state caused by electrons localized in undercoordinated Ti atoms which were present within the interfacial region. Interfaces between bulk materials and between exposed surfaces both showed electron trapping at undercoordinated sites. These undercoordinated (typically four) atoms present localized electrons that could enable reduction reactions in the interfacial region, and could explain the increased reactivity of mixed-phase TiO2 photocatalyst materials.
Critical island-size, stability, and morphology of 2D colloidal Au nanoparticle islands
Authors: Hubartt Bradley C. , Amar Jacques G.
Published: January 2015

The critical island-size, stability, and morphology of 2D colloidal Au nanoparticle islands formed during drop-drying are studied using an empirical potential which takes into account core-core, ligand-ligand, and ligand-solvent interactions. Good agreement with experiment is obtained for the dependence of the critical island-size on nanoparticle diameter. Our results for the critical length-scale for smoothing via edge-diffusion are also consistent with the limited facet size and island-relaxation observed in experiments. In addition, the relatively high rate of monomer diffusion on an island as well as the low barrier for interlayer diffusion are consistent with experimental observations that second-layer growth does not occur until after the first layer is complete.
Thermal equilibrium properties of surface hopping with an implicit Langevin bath
Authors: Sherman M. C. , Corcelli S. A.
Published: January 2015

The ability of fewest switches surface hopping (FSSH) approach, where the classical degrees of freedom are coupled to an implicit Langevin bath, to establish and maintain an appropriate thermal equilibrium was evaluated in the context of a three site model for electron transfer. The electron transfer model consisted of three coupled diabatic states that each depends harmonically on the collective bath coordinate. This results in three states with increasing energy in the adiabatic representation. The adiabatic populations and distributions of the collective solvent coordinate were monitored during the course of 250 ns FSSH-Langevin (FSSH-L) simulations performed at a broad range of temperatures and for three different nonadiabatic coupling strengths. The agreement between the FSSH-L simulations and numerically exact results for the adiabatic population ratios and solvent coordinate distributions was generally favorable. The FSSH-L method produces a correct Boltzmann distribution of the solvent coordinate on each of the adiabats, but the integrated populations are slightly incorrect because FSSH does not rigorously obey detailed balance. The overall agreement is better at high temperatures and for high nonadiabatic coupling, which agrees with a previously reported analytical and simulation analysis [J. R. Schmidt, P. V. Parandekar, and J. C. Tully, J. Chem. Phys. 129, 044104 (2008)] on a two-level system coupled to a classical bath.
The statistical behaviour of attached eddies
Authors: Woodcock J. D. , Marusic I.
Published: January 2015

Townsend’s attached eddy hypothesis forms the basis of an established model of the logarithmic layer in wall-bounded turbulent flows in which this inertially dominated region is characterised by a hierarchy of geometrically self-similar eddying motions that scale with their distance to the wall. The hypothesis has gained considerable support from high Reynolds number measurements of the second-order moments of the fluctuating velocities. Recently, Meneveau and Marusic [“Generalized logarithmic law for high-order moments in turbulent boundary layers,” J. Fluid Mech. 719, R1 (2013)] presented experimental evidence that all even-ordered moments of the streamwise velocity will exhibit a logarithmic dependence on the distance from the wall. They demonstrated that this was consistent with the attached eddy hypothesis, so long as the velocity distribution is assumed to be Gaussian (which allows the use of the central limit theorem). In this paper, we derive this result from the attached eddy model without assuming a Gaussian velocity distribution, and find that such logarithmic behaviours are valid in the large Reynolds number limit. We also revisit the physical and mathematical basis of the attached eddy hypothesis, in order to increase rigour and minimise the assumptions required to apply the hypothesis. To this end, we have extended the proof of Campbell’s theorem to apply to the velocity field corresponding to a forest of variously sized eddies that are randomly placed on the wall. This enables us to derive all moments of the velocity in the logarithmic region, including cross-correlations between different components of the velocity. By contrast, previous studies of the attached eddy hypothesis have considered only the mean velocity and its second order moments. From this, we obtain qualitatively correct skewnesses and flatnesses for the spanwise and wall-normal fluctuations. The issue of the Reynolds number dependence of von Kármán’s constant is also addressed.
Fluorescence imaging of lattice re-distribution on step-index direct laser written Nd:YAG waveguide lasers
Authors: Martínez de Mendívil Jon , Ródenas Airán , Benayas Antonio , Aguiló Magdalena , Diaz Francesc , Pérez Delgado Alberto , Lifante Ginés , Jaque Daniel , Kar Ajoy K.
Published: January 2015

The laser performance and crystalline micro-structural properties of near-infrared step-index channel waveguides fabricated inside Neodymium doped YAG laser ceramics by means of three-dimensional sub-picosecond pulse laser direct writing are reported. Fluorescence micro-mapping of the waveguide cross-sections reveals that an essential crystal lattice re-distribution has been induced after short pulse irradiation. Such lattice re-distribution is evidenced at the waveguide core corresponding to the laser written refractive index increased volume. The waveguides core surroundings also present diverse changes including slight lattice disorder and bi-axial strain fields. The step-index waveguide laser performance is compared with previous laser fabricated waveguides with a stress-optic guiding mechanism in absence of laser induced lattice re-distribution.
The influence of current collectors on Tayler instability and electro-vortex flows in liquid metal batteries
Authors: Weber N. , Galindo V. , Priede J. , Stefani F. , Weier T.
Published: January 2015

The Tayler instability (TI) is a kink-type flow instability which occurs when the electrical current through a conducting fluid exceeds a certain critical value. Originally studied in the astrophysical context, the instability was recently discussed as a possible limiting factor for the upward scalability of liquid metal batteries. In this paper, we continue our efforts to simulate this instability for liquid metals within the framework of an integro-differential equation approach. The original solver is enhanced by multi-domain support with Dirichlet-Neumann partitioning for the static boundaries. Particular focus is laid on the detailed influence of the axial electrical boundary conditions on the characteristic features of the Tayler instability and, second, on the occurrence of electro-vortex flows and their relevance for liquid metal batteries. Electro-vortex flows might pose a larger risk to the integrity of the battery than the TI.
Large reversible magnetocaloric effect in Ni-Mn-In-Co
Authors: Gottschall Tino , Skokov Konstantin P. , Frincu Bianca , Gutfleisch Oliver
Published: January 2015

We report on the high irreversible adiabatic temperature change of −8 K in a magnetic field change of 1.95 T in the Heusler compound Ni45.7Mn36.6In13.5Co4.2 showing a first-order magnetostructural transition. Due to the large thermal hysteresis of 10 K, this high ΔTad cannot be obtained in a cyclic way but still the reversible magnetocaloric effect amounts to −3 K—an unexpectedly high value which compares to the ΔTad of La(Fe,Si,Co)13. In order to reveal the nature of this high reversible magnetocaloric effect, in-situ temperature dependent optical microscopy of minor loops of thermal hysteresis has been done.
Dissipation enhanced vibrational sensing in an olfactory molecular switch
Authors: Chęcińska Agata , Pollock Felix A. , Heaney Libby , Nazir Ahsan
Published: January 2015

Motivated by a proposed olfactory mechanism based on a vibrationally activated molecular switch, we study electron transport within a donor-acceptor pair that is coupled to a vibrational mode and embedded in a surrounding environment. We derive a polaron master equation with which we study the dynamics of both the electronic and vibrational degrees of freedom beyond previously employed semiclassical (Marcus-Jortner) rate analyses. We show (i) that in the absence of explicit dissipation of the vibrational mode, the semiclassical approach is generally unable to capture the dynamics predicted by our master equation due to both its assumption of one-way (exponential) electron transfer from donor to acceptor and its neglect of the spectral details of the environment; (ii) that by additionally allowing strong dissipation to act on the odorant vibrational mode, we can recover exponential electron transfer, though typically at a rate that differs from that given by the Marcus-Jortner expression; (iii) that the ability of the molecular switch to discriminate between the presence and absence of the odorant, and its sensitivity to the odorant vibrational frequency, is enhanced significantly in this strong dissipation regime, when compared to the case without mode dissipation; and (iv) that details of the environment absent from previous Marcus-Jortner analyses can also dramatically alter the sensitivity of the molecular switch, in particular, allowing its frequency resolution to be improved. Our results thus demonstrate the constructive role dissipation can play in facilitating sensitive and selective operation in molecular switch devices, as well as the inadequacy of semiclassical rate equations in analysing such behaviour over a wide range of parameters.
Automatic droplet transportation on a plastic microfluidic device having wettability gradient surface
Authors: Nakashima Y. , Nakanishi Y. , Yasuda T.
Published: January 2015

This paper presents a microfluidic device that can automatically transport a droplet on a plastic plate. This device consists of a Cyclo Olefin Polymer (COP) plate and a SiO2 membrane and has wettability gradient surface. Lithographic patterns of hydrophilic SiO2 permitted wettability modification of a hydrophobic COP surface. A series of alternate hydrophobic and hydrophilic wedge-shaped patterns generated a required gradient in wettability. When we dropped a droplet on the wettability gradient surface, it moved along the wettability gradient due to an imbalance between surface tension forces acting on the opposite sides of the droplet edge. The droplet transportation test was carried out using water of 5 μl. As a result, we succeeded in automatically transporting the droplet on the SiO2/COP wettability gradient pattern. We also carried out droplet transportation in an enclosed microchannel for preventing droplet evaporation using DI (Deionized) water of 5 μl. In this case, the droplet was automatically transported by forming the wettability gradient pattern at the top and bottom in an enclosed microchannel without evaporation.
Experimental study of the growth of mixing zone in miscible viscous fingering
Authors: Malhotra Sahil , Sharma Mukul M. , Lehman Eric R.
Published: January 2015

An experimental study is performed to quantify the growth of the mixing zone in miscible viscous fingering. Rectilinear flow displacement experiments are performed in a Hele-Shaw cell over a wide range of viscosity ratios (1–1225) by injecting water into glycerol solutions at different flow rates. All the experiments are performed at high Peclet numbers and linear growth in mixing zone is observed. The mixing zone velocity increases with the viscosity ratio up to viscosity ratios of 340 and the trend is consistent with Koval’s model. However, at higher viscosity ratios, the mixing velocity plateaus signifying no further effect of viscosity contrast on the growth of mixing zone. The front (fingertip) velocities also increase up to viscosity ratios of 340 above which the velocities plateau.
Ultraviolet surface plasmon-mediated low temperature hydrazine decomposition
Authors: Peng Siying , Sheldon Matthew T. , Liu Wei-Guang , Jaramillo-Botero Andres , Goddard William Andrew , Atwater Harry A.
Published: January 2015

Conventional methods require elevated temperatures in order to dissociate high-energy nitrogen bonds in precursor molecules such as ammonia or hydrazine used for nitride film growth. We report enhanced photodissociation of surface-absorbed hydrazine (N2H4) molecules at low temperature by using ultraviolet surface plasmons to concentrate the exciting radiation. Plasmonic nanostructured aluminum substrates were designed to provide resonant near field concentration at λ = 248 nm (5 eV), corresponding to the maximum optical cross section for hydrogen abstraction from N2H4. We employed nanoimprint lithography to fabricate 1 mm × 1 mm arrays of the resonant plasmonic structures, and ultraviolet reflectance spectroscopy confirmed resonant extinction at 248 nm. Hydrazine was cryogenically adsorbed to the plasmonic substrate in a low-pressure ambient, and 5 eV surface plasmons were resonantly excited using a pulsed KrF laser. Mass spectrometry was used to characterize the photodissociation products and indicated a 6.2× overall enhancement in photodissociation yield for hydrazine adsorbed on plasmonic substrates compared with control substrates. The ultraviolet surface plasmon enhanced photodissociation demonstrated here may provide a valuable method to generate reactive precursors for deposition of nitride thin film materials at low temperatures.
Impedance spectroscopy and scaling behaviors of Sr3Co2Fe24O41 hexaferrite
Authors: Tang Rujun , Jiang Chen , Jian Jie , Liang Yan , Zhang Xin , Wang Haiyan , Yang Hao
Published: January 2015

The impedance spectroscopy of Z-type hexaferrite Sr3Co2Fe24O41 (SCFO) has been investigated as a function of temperature from 303 to 503 K. The frequency dependent impedance (Z″) and modulus (M″) spectra show that for the air annealed SCFO, the electrical responses of SCFO are thermal activated and there is a distribution of relaxation times. The scaling behaviors of Z″ and M″ spectra further suggest that the distribution of relaxation times is temperature independent. The Cole-Cole plots in impedance formalism show that the electrical response of SCFO originates from both the grain and the grain-boundaries. The activation energies for grain and grain boundary are 0.66 eV and 0.67 eV, respectively. The frequency dependent conductivity (σ′) spectra follow the universal power law. The fitting results of σ′ spectra show that the small polaron hopping is the most probable conduction mechanism for SCFO. Moreover, the scaling behavior of σ′ spectra further confirms that the distribution of local electrical response times is temperature independent. The air plus O2 annealed SCFO shows thermally activated electrical responses and scaling behaviors as well. The above results show that although the electrical responses of SCFO are temperature dependent, the relaxation mechanism in SCFO is temperature independent.
Highly resistive epitaxial Mg-doped GdN thin films
Authors: Lee C.-M. , Warring H. , Vézian S. , Damilano B. , Granville S. , Al Khalfioui M. , Cordier Y. , Trodahl H. J. , Ruck B. J. , Natali F.
Published: January 2015

We report the growth by molecular beam epitaxy of highly resistive GdN, using intentional doping with magnesium. Mg-doped GdN layers with resistivities of 103 Ω cm and carrier concentrations of 1016 cm−3 are obtained for films with Mg concentrations up to 5 × 1019 atoms/cm3. X-ray diffraction rocking curves indicate that Mg-doped GdN films have crystalline quality very similar to undoped GdN films, showing that the Mg doping did not affect the structural properties of the films. A decrease of the Curie temperature with decreasing the electron density is observed, supporting a recently suggested magnetic polaron scenario [F. Natali, B. J. Ruck, H. J. Trodahl, D. L. Binh, S. Vézian, B. Damilano, Y. Cordier, F. Semond, and C. Meyer, Phys. Rev. B 87, 035202 (2013)].
Efficient three-color white organic light-emitting diodes with a spaced multilayer emitting structure
Authors: Yan Fei , Xing Guichuan , Chen Rui , Demir Hilmi Volkan , Sun Handong , Sum Tze Chien , Sun Xiao Wei
Published: January 2015

By employing a spaced multilayer structure in a uniformly mixed P and N co-host, we developed a three-color white organic light emitting device with a stable Commission Internationale de L'Eclairage coordinates insensitive to the applied bias voltage. This insensitivity was achieved by suppressing the exciton quenching and shifting recombination zone effectively. Besides the achieved stable color coordinates of (0.411 ± 0.007, 0.382 ± 0.003), a high power efficiency of 30.7 lm/W and high color rendering index >80 were realized simultaneously.
Near-field radiative heat transfer between two parallel SiO2 plates with and without microcavities
Authors: Ijiro T. , Yamada N.
Published: January 2015

Near-to-far-field radiative heat transfer between two macroscopic SiO2 plates—with and without microcavities—was observed using a highly precise and accurate optical gap-measurement method. The experiments, conducted near 300 K, measured heat transfer as a function of gap separation from 1.0 μm to 50 μm and also as a function of temperature differences between 4.1 and 19.5 K. The gap-dependent heat flux was in excellent agreement with theoretical predictions. Furthermore, the effects of microcavities on the plate surfaces were clearly observed and significant enhancement of near-field radiative heat transfer was confirmed between gold-coated microcavities with narrow vacuum separation.
Electromagnetic effects on dynamics of high-beta filamentary structures
Authors: Lee Wonjae , Umansky Maxim V. , Angus J. R. , Krasheninnikov Sergei I.
Published: January 2015

The impacts of the electromagnetic effects on blob dynamics are considered. Electromagnetic BOUT++ simulations on seeded high-beta blobs demonstrate that inhomogeneity of magnetic curvature or plasma pressure along the filament leads to bending of the blob filaments and the magnetic field lines due to increased propagation time of plasma current (Alfvén time). The bending motion can enhance heat exchange between the plasma facing materials and the inner scrape-off layer (SOL) region. The effects of sheath boundary conditions on the part of the blob away from the boundary are also diminished by the increased Alfvén time. Using linear analysis and BOUT++ simulations, it is found that electromagnetic effects in high temperature and high density plasmas reduce the growth rate of resistive drift wave instability when resistivity drops below a certain value. The blobs temperature decreases in the course of its motion through the SOL and so the blob can switch from the electromagnetic to the electrostatic regime where resistive drift waves become important again.
Repetitive formation and decay of current sheets in magnetic loops: An origin of diverse magnetic structures
Authors: Kumar Dinesh , Bhattacharyya R. , Smolarkiewicz P. K.
Published: January 2015

In this work, evolution of an incompressible, thermally homogeneous, infinitely conducting, viscous magnetofluid is numerically explored as the fluid undergoes repeated events of magnetic reconnection. The initial magnetic field is constructed by a superposition of two linear force-free fields and has similar morphology as the magnetic loops observed in the solar corona. The results are presented for computations with three distinct sets of footpoint geometries. To onset reconnection, we rely on numerical model magnetic diffusivity, in the spirit of implicit large eddy simulation. It is generally expected that in a high Lundquist number fluid, repeated magnetic reconnections are ubiquitous and hence can lead to a host of magnetic structures with considerable observational importance. In particular, the simulations presented here illustrate formations of magnetic islands, rotating magnetic helices and rising flux ropes—depending on the initial footpoint geometry but through the common process of repeated magnetic reconnections. Further, we observe the development of extended current sheets in two case studies, where the footpoint reconnections generate favorable dynamics.
Measurement of the shock front velocity produced in a T-tube
Authors: Djurović S. , Mijatović Z. , Vujičić B. , Kobilarov R. , Savić I. , Gavanski L.
Published: January 2015

A set of shock front velocity measurements is described in this paper. The shock waves were produced in a small electromagnetically driven shock T-tube. Most of the measurements were performed in hydrogen. The shock front velocity measurements in other gases and the velocity of the gas behind the shock front were also analyzed, as well as the velocity dependence on applied input energy. Some measurements with an applied external magnetic field were also performed. The used method of shock front velocity is simple and was shown to be very reliable. Measured values were compared with the calculated ones for the incident and reflected shock waves.
Non-destructive assessment of the polarity of GaN nanowire ensembles using low-energy electron diffraction and x-ray photoelectron diffraction
Authors: Romanyuk O. , Fernández-Garrido S. , Jiříček P. , Bartoš I. , Geelhaar L. , Brandt O. , Paskova T.
Published: January 2015

We investigate GaN nanowire ensembles spontaneously formed in plasma-assisted molecular beam epitaxy by non-destructive low-energy electron diffraction (LEED) and x-ray photoelectron diffraction (XPD). We show that GaN nanowire ensembles prepared on AlN-buffered 6H-SiC(0001¯) substrates with well-defined N polarity exhibit similar LEED intensity-voltage curves and angular distribution of photo-emitted electrons as N-polar free-standing GaN layers. Therefore, as in the case of GaN layers, LEED and XPD are found to be suitable techniques to assess the polarity of GaN nanowire ensembles on a macroscopic scale. The analysis of GaN nanowire ensembles prepared on bare Si(111) allows us to conclude that, on this non-polar substrate, the majority of nanowires is also N-polar.
Lateral current generation in n-AlGaAs/GaAs heterojunction channels by Schottky-barrier gate illumination
Authors: Kawazu Takuya , Noda Takeshi , Sakuma Yoshiki , Sakaki Hiroyuki
Published: January 2015

We observe lateral currents induced in an n-AlGaAs/GaAs heterojunction channel of Hall bar geometry, when an asymmetric position of the Schottky metal gate is locally irradiated by a near-infrared laser beam. When the left side of the Schottky gate is illuminated with the laser, the lateral current flows from left to right in the two dimensional electron gas (2DEG) channel. In contrast, the right side illumination leads to the current from right to left. The magnitude of the lateral current is almost linearly dependent on the beam position, the current reaching its maximum for the beam at the edge of the Schottky gate. The experimental findings are well explained by a theory based on the current-continuity equation, where the lateral current in the 2DEG channel is driven by the photocurrent which vertically flows from the 2DEG to the Schottky gate.
Trapping of surface plasmon wave through gradient corrugated strip with underlayer ground and manipulating its propagation
Authors: Zhang Wenjuan , Zhu Guiqiang , Sun Liguo , Lin Fujiang
Published: January 2015

Corrugated metal surface with underlayer metal as ground is designed as spoof surface plasmons polaritons (SSPPs) structure in microwave frequencies. Efficient conversion from guided wave to SSPP is required for energy feeding into and signal extracting from such plasmonic structure. In this paper, first a high efficient transition design is presented by using gradient corrugated strip with underlayer metal as ground and by using the impedance matching theory. The SSPP wave is highly confined within the teeth part of the corrugated surface. By using this characteristic, then the simple wire-based metamaterial is added below the strip to manipulate the SSPP wave within the propagating band. Two aforementioned devices are designed and fabricated. The simulated and measured results on the scattering coefficients demonstrate the excellent conversion and excellent manipulating of SSPP transmitting. Such results have very important value to develop advanced plasmonic integrated circuits in the microwave frequencies.
Thermal quenching of photoluminescence in Ga(AsBi)
Authors: Shakfa M. K. , Wiemer M. , Ludewig P. , Jandieri K. , Volz K. , Stolz W. , Baranovskii S. D. , Koch M.
Published: January 2015

We report on a comparative experimental and theoretical study of the thermal quenching of the photoluminescence (PL) intensity in Ga(AsBi)/GaAs heterostructures. An anomalous plateau in the PL thermal quenching is observed at intermediate temperatures under relatively low excitation intensities. Theoretical analysis based on a well-approved approach shows that this peculiar behavior points at a non-monotonous density of states (DOS) in the disorder-induced band tails with at least two-energy-scales. While in previous studies carried out at relatively high excitation intensities a single-energy-scale was sufficient to fit the thermal quenching of the PL in Ga(AsBi), our study at lower excitation intensities proves that two-energy-scales of disorder contribute to the thermal quenching of the PL. Possible energy shapes of the DOS, which can fit experimental data, are revealed.
Interfacial nucleation behavior of inkjet-printed 6,13 bis(tri-isopropylsilylethynyl) pentacene on dielectric surfaces
Authors: Wang Xianghua , Yuan Miao , Lv Shenchen , Qin Mengzhi , Chen Mengjie , Qiu Longzhen , Zhang Guobing , Lu Hongbo
Published: January 2015

The performance of organic thin film transistors (OTFTs) is heavily dependent on the interface property between the organic semiconductor and the dielectric substrate. Device fabrication with bottom-gate architecture by depositing the semiconductors with a solution method is highly recommended for cost-effectiveness. Surface modification of the dielectric layer is employed as an effective approach to control film growth. Here, we perform surface modification via a self-assembled monolayer of silanes, a spin-coated polymer layer or UV-ozone cleaning, to prepare surfaces with different surface polarities and morphologies. The semiconductor is inkjet-printed on the surface-treated substrates as single-line films with overlapping drop assignment. Surface morphologies of the dielectric before film deposition and film morphologies of the inkjet-printed semiconductor are characterized with polarized microscopy and AFM. Electrical properties of the films are studied through organic thin-film transistors with bottom-gate/bottom-contact structure. With reduced surface polarity and nanoscale aggregation of silane molecules on the substrates, semiconductor nucleates from the interior interface between the ink solution and the substrate, which contributes to film growth with higher crystal coverage and better film quality at the interface. Surface treatment with hydrophobic silanes is a promising approach to fabrication of high performance OTFTs with nonpolar conjugated molecules via solution methods.
Tungsten dust impact on ITER-like plasma edge
Authors: Smirnov R. D. , Krasheninnikov S. I. , Pigarov A. Yu. , Rognlien T. D.
Published: January 2015

The impact of tungsten dust originating from divertor plates on the performance of edge plasma in ITER-like discharge is evaluated using computer modeling with the coupled dust-plasma transport code DUSTT-UEDGE. Different dust injection parameters, including dust size and mass injection rates, are surveyed. It is found that tungsten dust injection with rates as low as a few mg/s can lead to dangerously high tungsten impurity concentrations in the plasma core. Dust injections with rates of a few tens of mg/s are shown to have a significant effect on edge plasma parameters and dynamics in ITER scale tokamaks. The large impact of certain phenomena, such as dust shielding by an ablation cloud and the thermal force on tungsten ions, on dust/impurity transport in edge plasma and consequently on core tungsten contamination level is demonstrated. It is also found that high-Z impurities provided by dust can induce macroscopic self-sustained plasma oscillations in plasma edge leading to large temporal variations of edge plasma parameters and heat load to divertor target plates.
Energy levels distribution in supersaturated silicon with titanium for photovoltaic applications
Authors: Pérez E. , Castán H. , García H. , Dueñas S. , Bailón L. , Montero D. , García-Hernansanz R. , García-Hemme E. , Olea J. , González-Díaz G.
Published: January 2015

In the attempt to form an intermediate band in the bandgap of silicon substrates to give it the capability to absorb infrared radiation, we studied the deep levels in supersaturated silicon with titanium. The technique used to characterize the energy levels was the thermal admittance spectroscopy. Our experimental results showed that in samples with titanium concentration just under Mott limit there was a relationship among the activation energy value and the capture cross section value. This relationship obeys to the well known Meyer-Neldel rule, which typically appears in processes involving multiple excitations, like carrier capture/emission in deep levels, and it is generally observed in disordered systems. The obtained characteristic Meyer-Neldel parameters were Tmn = 176 K and kTmn = 15 meV. The energy value could be associated to the typical energy of the phonons in the substrate. The almost perfect adjust of all experimental data to the same straight line provides further evidence of the validity of the Meyer Neldel rule, and may contribute to obtain a deeper insight on the ultimate meaning of this phenomenon.