bluuebunny/crossref_metadata_2025 huggingface dataset:
A sequential transformation approach to the internally contracted multireference coupled cluster method
Authors: Evangelista Francesco A. , Hanauer Matthias , Köhn Andreas , Gauss Jürgen
Published: May 2012

The internally contracted multireference coupled cluster (ic-MRCC) approach is formulated using a new wave function ansatz based on a sequential transformation of the reference function (sqic-MRCC). This alternative wave function simplifies the formulation of computationally viable methods while preserving the accuracy of the ic-MRCC approach. The structure of the sqic-MRCC wave function allows folding the effect of the single excitations into a similarity-transformed Hamiltonian whose particle rank is equal to the one of the Hamiltonian. Consequently, we formulate an approximation to the sqic-MRCC method with singles and doubles (included respectively up to fourfold and twofold commutators, sqic-MRCCSD[2]) that contains all terms present in the corresponding single-reference coupled cluster scheme. Computations of the potential energy curves for the dissociation of BeH2 show that the untruncated sqic-MRCCSD scheme yields results that are almost indistinguishable from the ordinary ic-MRCCSD method. The energy obtained from the computationally less expensive sqic-MRCCSD[2] approximation is found to deviate from the full ic-MRCCSD method by less than 0.2 mEh for BeH2, while, in the case of water, the harmonic vibrational frequencies of ozone, the singlet-triplet splitting of p-benzyne, and the dissociation curve of N2, sqic-MRCCSD[2] faithfully reproduces the results obtained via the ic-MRCCSD scheme truncated to two commutators. A formal proof is given of the equivalence of the ic-MRCC and sqic-MRCC methods with the internally contracted and full configuration interaction approaches.
Explicitly correlated second-order Møller-Plesset perturbation theory employing pseudospectral numerical quadratures
Authors: Bokhan Denis , Trubnikov Dmitrii N.
Published: May 2012

We implemented explicitly correlated second-order Møller-Plesset perturbation theory with numerical quadratures using pseudospectral construction of grids. Introduction of pseudospectral approach for the calculation of many-electron integrals gives a possibility to use coarse grids without significant loss of precision in correlation energies, while the number of points in the grid is reduced about nine times. The use of complementary auxiliary basis sets as the sets of dealiasing functions is justified at both theoretical and computational levels. Benchmark calculations for a set of 16 molecules have shown the possibility to keep an error of second-order correlation energies within 1 milihartree (mH) with respect to MP2-F12 method with dense grids. Numerical tests for a set of 13 isogyric reactions are also performed.
Plasmonic versus dielectric enhancement in thin-film solar cells
Authors: Dühring Maria B. , Asger Mortensen N. , Sigmund Ole
Published: May 2012

Several studies have indicated that broadband absorption of thin-film solar cells can be enhanced by use of surface-plasmon induced resonances of metallic parts like strips or particles. The metallic parts may create localized modes or scatter incoming light to increase absorption in thin-film semiconducting material. For a particular case, we show that coupling to the same type of localized slab-waveguide modes can be obtained by a surface modulation consisting of purely dielectric strips. The purely dielectric device turns out to have a significantly higher broadband enhancement factor compared to its metallic counterpart. We show that the enhanced normalized short-circuit current for a cell with silicon strips can be increased 4 times compared to the best performance for strips of silver, gold, or aluminium. For this particular case, the simple dielectric grating may outperform its plasmonic counterpart due to the larger Ohmic losses associated with the latter.
Functional K-doping of eumelanin thin films: Density functional theory and soft x-ray spectroscopy experiments in the frame of the macrocyclic protomolecule model
Authors: Borghetti P. , Ghosh P. , Castellarin-Cudia C. , Goldoni A. , Floreano L. , Cossaro A. , Verdini A. , Gebauer R. , Drera G. , Sangaletti L.
Published: May 2012

We demonstrate the possibility to achieve the doping of eumelanin thin films through K+ incorporation during the electrodeposition of the film. K-doping changes the optical properties of the eumelanin thin films, reducing the energy gap from 1.0 to 0.6 eV, with possible implications for the photophysical properties. We have identified the doping-related occupied and unoccupied electronic states and their spectral weight using resonant photoemission spectroscopy (ResPES) and x-ray absorption at the C and N K-edges (near edge x-ray absorption fine spectroscopy, NEXAFS). All data are consistently interpreted by ab initio calculations of the electronic structure within the frame of the macrocycle model developed for the eumelanin protomolecule. Our analysis puts in evidence the intercalation of K with one specific oligomer (a tetramer composed of one indolequinone and 3 hydroquinone monomers) in correspondence of the nitrogen macrocycle. The predicted variation of the tetramer spacing is also in agreement with the recent x-ray diffraction experiments. The charge donation from K to N and C atoms gives rise to new electronic states at the top of the valence band and in NEXAFS resonances of the unoccupied orbitals. The saturation of the tetramer macrocycles leaves an excess of K that bind to N and C atoms in alternative configurations, as witnessed by the occurrence of additional spectral features in the carbon-related ResPES measurements.
High-force NdFeB-based magnetic tweezers device optimized for microrheology experiments
Authors: Lin Jun , Valentine Megan T.
Published: May 2012

We present the design, calibration, and testing of a magnetic tweezers device that employs two pairs of permanent neodymium iron boron magnets surrounded by low-carbon steel focusing tips to apply large forces to soft materials for microrheology experiments. Our design enables the application of forces in the range of 1–1800 pN to ∼4.5 μm paramagnetic beads using magnet-bead separations in the range of 0.3–20 mm. This allows the use of standard coverslips and sample geometries. A high speed camera, custom LED-based illumination scheme, and mechanically stabilized measurement platform are employed to enable the measurement of materials with viscoelastic moduli as high as ∼1 kPa.
Sensitivity of the properties of ruthenium “blue dimer” to method, basis set, and continuum model
Authors: Ozkanlar Abdullah , Clark Aurora E.
Published: May 2012

The ruthenium “blue dimer” [(bpy)2RuIIIOH2]2O4+ is best known as the first well-defined molecular catalyst for water oxidation. It has been subject to numerous computational studies primarily employing density functional theory. However, those studies have been limited in the functionals, basis sets, and continuum models employed. The controversy in the calculated electronic structure and the reaction energetics of this catalyst highlights the necessity of benchmark calculations that explore the role of density functionals, basis sets, and continuum models upon the essential features of blue-dimer reactivity. In this paper, we report Kohn-Sham complete basis set (KS-CBS) limit extrapolations of the electronic structure of “blue dimer” using GGA (BPW91 and BP86), hybrid-GGA (B3LYP), and meta-GGA (M06-L) density functionals. The dependence of solvation free energy corrections on the different cavity types (UFF, UA0, UAHF, UAKS, Bondi, and Pauling) within polarizable and conductor-like polarizable continuum model has also been investigated. The most common basis sets of double-zeta quality are shown to yield results close to the KS-CBS limit; however, large variations are observed in the reaction energetics as a function of density functional and continuum cavity model employed.
A numerical study of carrier impact ionization in AlxGa1−xN
Authors: Bellotti Enrico , Bertazzi Francesco
Published: May 2012

Using a full-band Monte Carlo model we have computed the carrier impact ionization coefficients in AlxGa1−xN for seven alloy compositions between x = 0 (GaN) and x = 1.0 (AlN). We have found that holes dominate the impact ionization process for compositions below 50%, while electrons dominate for larger aluminum contents. The model also predicts that, due to the particular features of the AlxGa1−xN valence band structure, holes impact ionization processes are effectively negligible for aluminum composition above 60%. Furthermore, we find that the electron-alloy scattering significantly reduces the electron ionization coefficients leading to the dominant behavior of holes in for an aluminum composition below 50%.
Sol-gel NiFe2O4 nanoparticles: Effect of the silica coating
Authors: Larumbe S. , Pérez-Landazábal J. I. , Pastor J. M. , Gómez-Polo C.
Published: May 2012

NiFe2O4 and NiFe2O4-SiO2 nanoparticles were synthesized by a sol-gel method using citric acid as fuel, giving rise its combustion to the crystallization of the spinel phase. Different synthesis conditions were analyzed with the aim of obtaining stoichiometric NiFe2O4 nanoparticles. The spinel structure in the calcined nanoparticles (400 °C, 2 h) was evaluated by x-ray diffraction. Their nanometer size (mean diameters around 10–15 nm) was confirmed through electron microscopy (field emission scanning electron microscopy and transmission electron microscopy). Rietveld refinement indicates the existence of a small percentage of NiO and Fe3O4 phases and a certain degree of structural disorder. The main effect of the silica coating is to enhance the disorder effects and prevent the crystalline growth after post-annealing treatments. Due to the small particle size, the nanoparticles display characteristic superparamagnetic behaviour and surface effects associated to a spin-glass like state: i.e., reduction in the saturation magnetization values and splitting of the zero field cooled (ZFC)-field cooled (FC) high field magnetization curves. The fitting of the field dependence of the ZFC-FC irreversibility temperatures to the Almeida—Thouless equation confirms the spin-glass nature of the detected magnetic phenomena. Exchange bias effects (shifts in the FC hysteresis loops) detected below the estimated freezing temperature support the spin-glass nature of the spin disorder effects.
Phase diagram and universality of the Lennard-Jones gas-liquid system
Authors: Watanabe Hiroshi , Ito Nobuyasu , Hu Chin-Kun
Published: May 2012

The gas-liquid phase transition of the three-dimensional Lennard-Jones particles system is studied by molecular dynamics simulations. The gas and liquid densities in the coexisting state are determined with high accuracy. The critical point is determined by the block density analysis of the Binder parameter with the aid of the law of rectilinear diameter. From the critical behavior of the gas-liquid coexisting density, the critical exponent of the order parameter is estimated to be β = 0.3285(7). Surface tension is estimated from interface broadening behavior due to capillary waves. From the critical behavior of the surface tension, the critical exponent of the correlation length is estimated to be ν = 0.63(4). The obtained values of β and ν are consistent with those of the Ising universality class.
ONIOM approach for non-adiabatic on-the-fly molecular dynamics demonstrated for the backbone controlled Dewar valence isomerization
Authors: Fingerhut Benjamin P. , Oesterling Sven , Haiser Karin , Heil Korbinian , Glas Andreas , Schreier Wolfgang J. , Zinth Wolfgang , Carell Thomas , de Vivie-Riedle Regina
Published: May 2012

Non-adiabatic on-the-fly molecular dynamics (NA-O-MD) simulations require the electronic wavefunction, energy gradients, and derivative coupling vectors in every timestep. Thus, they are commonly restricted to the excited state dynamics of molecules with up to ≈20 atoms. We discuss an approximation that combines the ONIOM(QM:QM) method with NA-O-MD simulations to allow calculations for larger molecules. As a proof of principle we present the excited state dynamics of a (6-4)-lesion containing dinucleotide (63 atoms), and especially the importance to include the confinement effects of the DNA backbone. The method is able to include electron correlation on a high level of theory and offers an attractive alternative to QM:MM approaches for moderate sized systems with unknown force fields.
Controlled volume transfer and lens shape formation by liquid bridge disconnection
Authors: Jang Yun-Ho , Lee Kyounggun , Kim Yong-Kweon
Published: May 2012

A liquid bridge was created and disconnected to transfer a controlled volume of mixture to a cylindrical post for the formation of parabolic lens shapes. We investigated a transferred volume and the focal length of the lens shape in terms of four parameters: post radius, withdrawal speed, dipping depth, and mixture thickness. The presented method is simple and flexible to transfer a pre-analyzed volume and subsequently to fabricate a lens shape on post structures, which can be beneficial to implementing self-aligned and smooth lenses integrated in micro structures.
Band-gap tuning at the strong quantum confinement regime in magnetic semiconductor EuS thin films
Authors: Poulopoulos Panagiotis , Lewitz Björn , Straub Andreas , Pappas Spiridon D. , Droulias Sotirios A. , Baskoutas Sotirios , Fumagalli Paul
Published: May 2012

Ultraviolet-visible absorption spectra of nanoscaled EuS thin films reveal a blue shift of the energy between the top-valence and bottom-conduction bands. This band-gap tuning changes smoothly with decreasing film thickness and becomes significant below the exciton Bohr diameter ∼3.5 nm indicating strong quantum confinement effects. The results are reproduced in the framework of the potential morphing method in Hartree Fock approximation. The large values of the effective mass of the holes, due to localization of the EuS f-states, limit the blue shift to about 0.35 eV. This controllable band-gap tuning of magnetic semiconductor EuS renders it useful for merging spintronics and optoelectronics.
Optically pumped lasing from organic two-dimensional planar photonic crystal microcavity
Authors: Gourdon F. , Chakaroun M. , Fabre N. , Solard J. , Cambril E. , Yacomotti A.-M. , Bouchoule S. , Fischer A. , Boudrioua A.
Published: May 2012

In this letter, we report the realization and characterization of a planar two-dimensional organic photonic crystal microcavity laser. The gain medium consists of a tris(8-hydroxyquinolinato) aluminum doped with 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran and is deposited on a lithographically patterned silicon nitride two dimensional photonic crystal H2 microcavity. The experimental results show a laser emission at 662 nm with a threshold of 9.7 μJ/cm2.
L1 structure formation in slow-cooled Fe-Au nanoclusters
Authors: Mukherjee P. , Zhang Y. , Kramer M. J. , Lewis L. H. , Shield J. E.
Published: May 2012

An ordered L10 structure has been formed in near-stoichiometric Fe-Au alloy nanoparticles. The L10 structure with a = 0.367 nm and c = 0.360 nm was observed in nanoclusters with diameters below 10 nm after slow cooling from 600 °C. The stable L10 structure formed from a parent fcc solid solution phase observed in the as-formed clusters. The fcc phase has a lattice parameter of 0.417 nm, significantly expanded compared to both Au and γ-Fe. The saturation magnetization and coercivity of both fcc and L10 structures were much lower than expected considering Fe dilution effects suggesting competing ferromagnetic and anti-ferromagnetic ordering.
Disorder enhancement due to structural relaxation in amorphous Ge2Sb2Te5
Authors: Fantini P. , Ferro M. , Calderoni A. , Brazzelli S.
Published: May 2012

This work investigates the atomic structural relaxation accounting for the resistance drift of the amorphous phase of the Ge2Sb2Te5 (α-GST) chalcogenide alloy. A joint electrical and optical characterization over time on both the phase change memory cell in the reset state and the as-deposited amorphous GST film has been performed to elucidate the origin of the drift phenomenon. We highlight that the drift mechanism is ascribed to the removal of residual resonant-like bonding in the amorphous network, lowering the electronic component of the dielectric constant (ɛ∞) and leading to a progressive loosing of any medium-range order.
Diffusion in the presence of cylindrical obstacles arranged in a square lattice analyzed with generalized Fick-Jacobs equation
Authors: Dagdug Leonardo , Vazquez Marco-Vinicio , Berezhkovskii Alexander M. , Zitserman Vladimir Yu. , Bezrukov Sergey M.
Published: May 2012

The generalized Fick-Jacobs equation is widely used to study diffusion of Brownian particles in three-dimensional tubes and quasi-two-dimensional channels of varying constraint geometry. We show how this equation can be applied to study the slowdown of unconstrained diffusion in the presence of obstacles. Specifically, we study diffusion of a point Brownian particle in the presence of identical cylindrical obstacles arranged in a square lattice. The focus is on the effective diffusion coefficient of the particle in the plane perpendicular to the cylinder axes, as a function of the cylinder radii. As radii vary from zero to one half of the lattice period, the effective diffusion coefficient decreases from its value in the obstacle free space to zero. Using different versions of the generalized Fick-Jacobs equation, we derive simple approximate formulas, which give the effective diffusion coefficient as a function of the cylinder radii, and compare their predictions with the values of the effective diffusion coefficient obtained from Brownian dynamics simulations. We find that both Reguera-Rubi and Kalinay-Percus versions of the generalized Fick-Jacobs equation lead to quite accurate predictions of the effective diffusion coefficient (with maximum relative errors below 4% and 7%, respectively) over the entire range of the cylinder radii from zero to one half of the lattice period.
Electron scattering mechanisms in GZO films grown on a-sapphire substrates by plasma-enhanced molecular beam epitaxy
Authors: Liu H. Y. , Avrutin V. , Izyumskaya N. , Özgür Ü. , Yankovich A. B. , Kvit A. V. , Voyles P. M. , Morkoç H.
Published: May 2012

We report on the mechanisms governing electron transport using a comprehensive set of ZnO layers heavily doped with Ga (GZO) grown by plasma-enhanced molecular-beam epitaxy on a-plane sapphire substrates with varying oxygen-to-metal ratios and Ga fluxes. The analyses were conducted by temperature dependent Hall measurements which were supported by microstructural investigations as well. Highly degenerate GZO layers with n > 5 × 1020 cm−3 grown under metal-rich conditions (reactive oxygen-to-metal ratio <1) show relatively larger grains (∼20–25 nm by x-ray diffraction) with low-angle boundaries parallel to the polar c-direction. For highly conductive GZO layers, ionized-impurity scattering with almost no compensation is the dominant mechanism limiting the mobility in the temperature range from 15 to 330 K and the grain-boundary scattering governed by quantum-mechanical tunnelling is negligible. However, due to the polar nature of ZnO having high crystalline quality, polar optical phonon scattering cannot be neglected for temperatures above 150 K, because it further reduces mobility although its effect is still substantially weaker than the ionized impurity scattering even at room temperature (RT). Analysis of transport measurements and sample microstructures by x-ray diffraction and transmission electron microscopy led to a correlation between the grain sizes in these layers and mobility even for samples with a carrier concentration in the upper 1020 cm−3 range. In contrast, electron transport in GZO layers grown under oxygen-rich conditions (reactive oxygen-to-metal ratio >1), which have inclined grain boundaries and relatively smaller grain sizes of 10–20 nm by x-ray diffraction, is mainly limited by compensation caused by acceptor-type point-defect complexes, presumably (GaZn-VZn), and scattering on grain boundaries. The GZO layers with n <1020 cm−3 grown under metal-rich conditions with reduced Ga fluxes show a clear signature of grain-boundary scattering governed by the thermionic effect in the temperature-dependent mobility but with much higher RT mobility values compared to the samples grown under oxygen-rich conditions [34 vs. 7.5 cm2/V·s]. Properties of GZO layers grown under different conditions clearly indicate that to achieve highly conductive GZO, metal-rich conditions instead of oxygen-rich conditions have to be used.
Annealing effects on nanostructured gold-polymethylmethacrylate composites: Small-angle x-ray scattering analysis
Authors: Teixeira F. S. , Salvadori M. C. , Cattani M. , Brown I. G.
Published: May 2012

Composites formed of a polymer-embedded layer of sub-10 nm gold nanoclusters were fabricated by very low energy (49 eV) gold ion implantation into polymethylmethacrylate. We used small angle x-ray scattering to investigate the structural properties of these metal-polymer composite layers that were fabricated at three different ion doses, both in their original form (as-implanted) and after annealing for 6 h well above the polymer glass transition temperature (150 °C). We show that annealing provides a simple means for modification of the structure of the composite by coarsening mechanisms, and thereby changes its properties.
Effect of ZnS coatings on the enhancement of the photovoltaic properties of PbS quantum dot-sensitized solar cells
Authors: Hachiya Sojiro , Shen Qing , Toyoda Taro
Published: May 2012

We have studied the effect of ZnS coatings on the photovoltaic properties of PbS quantum dot-sensitized solar cells (QDSSCs). PbS QDs are suitable materials for QDSSCs because of their wide light absorption range; however, their high photochemical reactivity is a problem that needs to be overcome for solar cell applications. In this paper, a ZnS passivation layer was applied to PbS QDs adsorbed onto electrodes using a successive ionic layer adsorption and reaction (SILAR) method for different numbers of cycles in both aqueous and methanol solutions. It was demonstrated that, as a consequence of the low viscosity of methanol, the performance of the PbS QDSSCs was greatly enhanced when a methanol, rather than aqueous, solution was used in the SILAR method. The optical absorption properties of PbS QDs adsorbed on TiO2 electrodes with or without ZnS surface passivation were studied. An increase in size of the PbS QDs after coating with ZnS was confirmed by a red shift in the optical absorption spectra measured using photoacoustic spectroscopy. The photovoltaic properties of a sandwich structure of PbS QDSSCs were studied under “one sun” illumination using a polysulfide (S/S2−) redox system as the electrolyte and Cu2S on brass as the counter electrode. The short-circuit current density dramatically increased from 0.50 mA/cm2 to 11.2 mA/cm2 after the electrodes were modified with the ZnS coating. The maximum conversion efficiency that was achieved for PbS QDSSCs with a ZnS coating under one sun illumination was 1.92%.
Ultrafast photo-induced charge transfer unveiled by two-dimensional electronic spectroscopy
Authors: Bixner Oliver , Lukeš Vladimír , Mančal Tomáš , Hauer Jürgen , Milota Franz , Fischer Michael , Pugliesi Igor , Bradler Maximilian , Schmid Walther , Riedle Eberhard , Kauffmann Harald F. , Christensson Niklas
Published: May 2012

The interaction of exciton and charge transfer (CT) states plays a central role in photo-induced CT processes in chemistry, biology, and physics. In this work, we use a combination of two-dimensional electronic spectroscopy (2D-ES), pump-probe measurements, and quantum chemistry to investigate the ultrafast CT dynamics in a lutetium bisphthalocyanine dimer in different oxidation states. It is found that in the anionic form, the combination of strong CT-exciton interaction and electronic asymmetry induced by a counter-ion enables CT between the two macrocycles of the complex on a 30 fs timescale. Following optical excitation, a chain of electron and hole transfer steps gives rise to characteristic cross-peak dynamics in the electronic 2D spectra, and we monitor how the excited state charge density ultimately localizes on the macrocycle closest to the counter-ion within 100 fs. A comparison with the dynamics in the radical species further elucidates how CT states modulate the electronic structure and tune fs-reaction dynamics. Our experiments demonstrate the unique capability of 2D-ES in combination with other methods to decipher ultrafast CT dynamics.
Behavior of rate coefficients for ion-ion mutual neutralization, 300–550 K
Authors: Miller Thomas M. , Shuman Nicholas S. , Viggiano A. A.
Published: May 2012

Rate coefficients kMN have been measured for a number of anion neutralization reactions with Ar+ and Kr+ over the temperature range 300–550 K. For the first time, the data set includes anions of radicals and other short-lived species. In the present paper, we review these results and make note of correlations with reduced mass, electron binding energy of the anion (equivalent to the electron affinity of the corresponding neutral), and temperature, and compare with expectations from absorbing sphere models. An intriguing result is that the data for diatomic anions neutralized by Ar+ and Kr+ have kMN values close to 3 × 10−8 cm3 s−1 at 300 K, a figure which is lower than those for all of the polyatomic anions at 300 K except for SF5− + Kr+. For the polyatomic anions studied here, neutralized by Ar+ and Kr+, the reduced mass dependence agrees with theory, on average, but we find a stronger temperature dependence of T−0.9 than expected from the theoretical E−0.5 energy dependence of the rate coefficient at thermal energies. The kMN show a weak dependence on the electron binding energy of the anion for the polyatomic species studied.
Partial rectification of the plasmon-induced electrical tunnel current in discontinuous thin gold film at optical frequency
Authors: Yajadda M. M. A. , Müller K.-H. , Farrant D. I. , Ostrikov K.
Published: May 2012

The effect of plasmon oscillations, induced by pulsed laser irradiation, on the DC tunnel current between islands in a discontinuous thin gold film is studied. The tunnel current is found to be strongly enhanced by partial rectification of the plasmon-induced AC tunnel currents flowing between adjacent gold islands. The DC tunnel current enhancement is found to increase approximately linearly with the laser intensity and the applied DC bias voltage. The experimental data can be well described by an electron tunnelling model which takes the plasmon-induced AC voltage into account. Thermal heating seems not to contribute to the tunnel current enhancement.
Power generation from conductive droplet sliding on electret film
Authors: Yang Zhaochu , Halvorsen Einar , Dong Tao
Published: May 2012

Generating electrical power from low frequency vibration to power portable devices is a challenge that potentially can be met by nonresonant electrostatic energy harvesters. We propose a generator employing a conductive droplet sliding on a microfabricated electret film which is sputtered onto an interdigital electrode and charged already during deposition. Droplet motion causes a capacitance variation that is used to generate electric power. A prototype of the fluidic energy harvester demonstrated a peak output power at 0.18 µW with a single droplet having a diameter of 1.2 mm and sliding on a 2 -µm thick electret film.
A Rayleigh-Brillouin scattering spectrometer for ultraviolet wavelengths
Authors: Gu Ziyu , Vieitez M. Ofelia , van Duijn Eric-Jan , Ubachs Wim
Published: May 2012

A spectrometer for the measurement of spontaneous Rayleigh-Brillouin (RB) scattering line profiles at ultraviolet wavelengths from gas phase molecules has been developed, employing a high-power frequency-stabilized UV-laser with narrow bandwidth (2 MHz). The UV-light from a frequency-doubled titanium:sapphire laser is further amplified in an enhancement cavity, delivering a 5 W UV-beam propagating through the interaction region inside a scattering cell. The design of the RB-scattering cell allows for measurements at gas pressures in the range 0−4 bars and at stably controlled temperatures from −30 °C to 70 °C. A scannable Fabry-Perot analyzer with instrument resolution of 232 MHz probes the RB profiles. Measurements on N2 and SF6 gases demonstrate that the high signal-to-noise ratio is achievable with the instrument at the 1% level at the peak amplitude of the scattering profile.
Plasmon-polaritons on graphene-metal surface and their use in biosensors
Authors: Salihoglu Omer , Balci Sinan , Kocabas Coskun
Published: May 2012

We studied excitation of surface plasmon-polaritons on graphene-metal surface. The metal surface is functionalized by transfer printing of graphene grown by chemical vapor deposition on copper foils. Surface plasmon resonance characteristics of monolayer and multilayer graphene on the metal surface are presented. We were able to obtain the dispersion relation of graphene-metal surface which reveals the essential feature of the plasmon-polaritons. As an application, we fabricated a surface plasmon resonance sensor integrated with a microfluidic device to study nonspecific physical interaction between graphene layer and proteins.
Piezoresistive strain sensing using carbon nanotube forests suspended by Parylene-C membranes
Authors: Bsoul Anas , Sultan Mohamed Ali Mohamed , Nojeh Alireza , Takahata Kenichi
Published: May 2012

We present a strain gauge that uses a carbon nanotube (CNT) forest, partially embedded in a Parylene-C membrane, as a piezoresistor. The device exhibits high sensitivity with a gauge factor of 4.52 or higher for strains up to ∼1.5%, offering much higher sensitivity in the strain range than those reported for other types of CNT-forest/polymer composite piezoresistors. The gauge also shows a linear response to bending strains generated by forces applied perpendicularly to the membrane with a 55-ppm/mN sensitivity. These findings suggest promising characteristics for a variety of sensing applications of the CNT-forest/Parylene film.
Contributions of atomic diffusion and plastic deformation to the plasma surface activation assisted diffusion bonding of zirconium-based bulk metallic glass
Authors: Chen H. Y. , Cao J. , Song X. G. , Feng J. C.
Published: May 2012

A mathematical model was established to estimate the contributions of atomic diffusion and plastic deformation to the diffusion bonding of zirconium-based bulk metallic glasses. Additionally, the surface state was introduced into the model since oxide film is the main barrier to atomic bonding across interface. The model calculation displayed that the contribution of plastic deformation to void closure was six orders of magnitude higher than atomic diffusion. The joints with ion etching before bonding were achieved to verify the model. The experimental strength of joints had a sound fit with the theoretical strength calculated by the model.
Subthreshold characteristics of pentacene field-effect transistors influenced by grain boundaries
Authors: Park Jaehoon , Jeong Ye-Sul , Park Kun-Sik , Do Lee-Mi , Bae Jin-Hyuk , Sun Choi Jong , Pearson Christopher , Petty Michael
Published: May 2012

Grain boundaries in polycrystalline pentacene films significantly affect the electrical characteristics of pentacene field-effect transistors (FETs). Upon reversal of the gate voltage sweep direction, pentacene FETs exhibited hysteretic behaviours in the subthreshold region, which was more pronounced for the FET having smaller pentacene grains. No shift in the flat-band voltage of the metal-insulator-semiconductor capacitor elucidates that the observed hysteresis was mainly caused by the influence of localized trap states existing at pentacene grain boundaries. From the results of continuous on/off switching operation of the pentacene FETs, hole depletion during the off period is found to be limited by pentacene grain boundaries. It is suggested that the polycrystalline nature of a pentacene film plays an important role on the dynamic characteristics of pentacene FETs.
Formation of multilayered biopolymer microcapsules and microparticles in a multiphase microfluidic flow
Authors: Rondeau Elisabeth , Cooper-White Justin J.
Published: May 2012

This paper reports the development of a scalable continuous microfluidic-based method for the preparation of multilayered biopolymer microcapsules and microparticles, with a size range of 1 to 100 μm, in a single-layered polydimethylsiloxane-based device. This new approach has been utilised to produce polyethylene oxide (PEO)-based microparticles, layered with subsequent stage wise coatings of polylactide-based block copolymers and polyvinylpyrrolidone. The production process was shown to allow for on-chip encapsulation of protein and vitamin molecules in the biopolymer micro particles, without any further handling after collection from the device. We have studied the release profiles in the case of model molecules of distinctive molecular weights, namely, vitronectin, horse radish peroxidase, and vitamin B12. We compared the release properties of the microparticles to those from macro-gels of the same materials prepared off-chip. The results indicated that the microparticles have definitively different molecular weight cut-off characteristics, likely due to a denser microstructure within the microparticles compared to the bulk hydrogels. This difference suggests that significant benefits may exist in the use of this method to produce layered biopolymer microparticles in achieving improved controlled release and encapsulation.
Development of a magnetic immunosorbent for on-chip preconcentration of amyloid β isoforms: Representatives of Alzheimer’s disease biomarkers
Authors: Svobodova Zuzana , Reza Mohamadi Mohamad , Jankovicova Barbora , Esselmann Hermann , Verpillot Romain , Otto Markus , Taverna Myriam , Wiltfang Jens , Viovy Jean-Louis , Bilkova Zuzana
Published: May 2012

Determination of amyloid β (Aβ) isoforms and in particular the proportion of the Aβ 1-42 isoform in cerebrospinal fluid (CSF) of patients suspected of Alzheimer’s disease might help in early diagnosis and treatment of that illness. Due to the low concentration of Aβ peptides in biological fluids, a preconcentration step prior to the detection step is often necessary. This study utilized on-chip immunoprecipitation, known as micro-immunoprecipitation (μIP). The technique uses an immunosorbent (IS) consisting of magnetic beads coated with specific anti-Aβ antibodies organized into an affinity microcolumn by a magnetic field. Our goal was to thoroughly describe the critical steps in developing the IS, such as selecting the proper beads and anti-Aβ antibodies, as well as optimizing the immobilization technique and μIP protocol. The latter includes selecting optimal elution conditions. Furthermore, we demonstrate the efficiency of anti-Aβ IS for μIP and specific capture of 5 Aβ peptides under optimized conditions using various subsequent analytical methods, including matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), capillary electrophoresis, microchip electrophoresis, and immunoblotting. Synthetic Aβ peptides samples prepared in buffer and spiked in human CSF were analyzed. Finally, on-chip immunoprecipitation of Aβ peptides in human CSF sample was performed.
Aggregation kinetics of detonation nanocarbon
Authors: Bastea Sorin
Published: May 2012

We analyze the properties of diffusion-limited coagulation and associated energy release applicable to processes such as nanocarbon production in detonation or nanoaerosols growth. We introduce a physical model that yields the expected energy release by treating the aggregation kinetics as a quasi phase transformation with a nonlinear rate dependent on the size of the initial nuclei, thermodynamic conditions, and viscosity of the fluid matrix.
A multi-frequency sandwich type electromagnetic vibration energy harvester
Authors: Chen Jingdong , Chen Di , Yuan Tao , Chen Xiang
Published: May 2012

We proposed a multi-frequency sandwich type vibration energy harvester to widen the effective frequency range of vibration energy harvester. The harvester is composed of three resonant structures with different natural frequencies. The resonant structures are two cantilevers each with bi-layer coils and a plane spring with a magnet. The maximum peak-peak voltages of the three different frequencies are 172 mV, 104 mV, and 112 mV at the frequencies of 235 Hz, 330 Hz, and 430 Hz, respectively. The first maximum voltage is much higher than the others, because the coils in both cantilevers can produce voltages.
Tunable electron and hole doping in FeCl3 intercalated graphene
Authors: Nathaniel James , Wang Xiao-Qian
Published: May 2012

We have studied the electronic characteristics of FeCl3 intercalated bilayer graphene under a perpendicularly applied electric bias. Evolution of the electronic structure of FeCl3 intercalated bilayer graphene as a function of the applied electric bias is performed using first-principles density-functional theory including interlayer van der Waals interactions. The calculation results demonstrate that the hole-doped graphene layers associated with the high electronegativity of FeCl3 transform into electron-doped layers tuned by the applied bias. The implications of controllable electronic structure of intercalated graphene for future device applications are discussed.
Quantitative determination of Mn3+ content in LiMn1.5Ni0.5O4 spinel cathodes by magnetic measurements
Authors: Moorhead-Rosenberg Z. , Shin D. W. , Chemelewski K. R. , Goodenough J. B. , Manthiram A.
Published: May 2012

The magnetic properties of cation-disordered and cation-ordered LiMn1.5Ni0.5O4 spinel samples with different morphologies synthesized by hydrothermal and co-precipitation methods have been investigated. Extrapolation of the magnetization values measured below the ferrimagnetic ordering temperature to 0 K has been employed to quantitatively determine the Mn3+ content. The Mn3+ contents calculated on the basis of collinear spin ferrimagnetism from the extrapolated magnetic moment values at 0 K agree closely with those obtained from the capacity values in the 4 V region of lithium-ion cells. This study demonstrates that the magnetic method presented here could become a valuable tool to quantitatively determine the Mn3+ content in high-voltage spinel cathodes.
Spin-orbit field switching of magnetization in ferromagnetic films with perpendicular anisotropy
Authors: Wang D.
Published: May 2012

As an alternative to conventional magnetic field, the effective spin-orbit field in transition metals, derived from the Rashba field experienced by itinerant electrons confined in a spatial inversion asymmetric plane through the s-d exchange interaction, is proposed for the manipulation of magnetization. Magnetization switching in ferromagnetic thin films with perpendicular magnetocrystalline anisotropy can be achieved by current induced spin-orbit field, with small in-plane applied magnetic field. Spin-orbit field induced by current pulses as short as 10 ps can initiate ultrafast magnetization switching effectively, with experimentally achievable current densities. The whole switching process completes in about 100 ps.
An evaluation framework for non-medical prescribing research
Authors: Hale Andrew R. , Stowasser Danielle A. , Coombes Ian D. , Stokes Julie , Nissen Lisa
Published: May 2012

Without robust and credible evidence for the benefits in health outcomes of non-medical prescribing, widespread implementation will be challenging. Our aim is to develop a consistent evaluation framework that could be applied to non-medical prescribing research. An informal collaboration was initiated in 2008 by a group of pharmacists from Australia and New Zealand to assist in information sharing, pilot design, methodologies and evaluation for pharmacist prescribing. Different pilots used different models, methodologies and evaluation. It was agreed that the development of a consistent evaluation framework to be applied to future research on non-medical prescribing was required. The framework would help to align the outcomes of different research pilots and enable the comparison of endpoints to determine the effectiveness of a non-medical prescribing intervention. This article presents the results of a workshop held at The University of Queensland in January 2009. Participants were asked to consider how to evaluate the effectiveness of different models of pharmacist prescribing. What is known about the topic? Little is known about the effectiveness and safety of non-medical prescribing services due to a lack of robust evidence. What does this paper add? This paper adds a methodology for clinicians and healthcare managers to be able to evaluate any new service of non-medical prescribing, either in the pilot phase or once introduced as a new model of care. What are the implications for practitioners? The implication for practitioners is the ability to prove to healthcare providers that non-medical prescribing services are at least as effective as usual care, so informing whether a change should be introduced in the way healthcare is delivered to patients.
Breaking up is hard to do: why disinvestment in medical technology is harder than investment
Authors: Haas Marion , Hall Jane , Viney Rosalie , Gallego Gisselle
Published: May 2012

Healthcare technology is a two-edged sword - it offers new and better treatment to a wider range of people and, at the same time, is a major driver of increasing costs in health systems. Many countries have developed sophisticated systems of health technology assessment (HTA) to inform decisions about new investments in new healthcare interventions. In this paper, we question whether HTA is also the appropriate framework for guiding or informing disinvestment decisions. In exploring the issues related to disinvestment, we first discuss the various HTA frameworks which have been suggested as a means of encouraging or facilitating disinvestment. We then describe available means of identifying candidates for disinvestment (comparative effectiveness research, clinical practice variations, clinical practice guidelines) and for implementing the disinvestment process (program budgeting and marginal analysis (PBMA) and related techniques). In considering the possible reasons for the lack of progress in active disinvestment, we suggest that HTA is not the right framework as disinvestment involves a different decision making context. The key to disinvestment is not just what to stop doing but how to make it happen - that is, decision makers need to be aware of funding disincentives. What is known about this topic? Disinvestment is an increasingly popular topic amongst academics and policy makers. Most discussions focus on the need to increase disinvestment as a corollary of investment, the lack of overt disinvestment decisions and the use of a framework based on health technology assessment (HTA) to implement disinvestment. What does this paper add? This paper focusses on the difficulties associated with deciding which technologies to disinvest in, and the problems in using an HTA framework to make such decisions, when disinvestment involves a different decision making context from that of investment. What are the implications for practitioners? The key to disinvestment is not just what to stop doing but how to implement such decisions. Making it happen means being aware of funding disincentives.
Successfully reforming orthopaedic outpatients
Authors: Schoch Peter A. , Adair Lisa
Published: May 2012

Since 2005, Barwon Health has successfully reformed its orthopaedic outpatient service to address the following issues: increasing number of referrals, inefficient referral management and triage, long waiting times for non-urgent appointments, high ‘Did Not Attend’ (DNA) rates and poor utilisation of conservative therapies before referral to surgeon. Numerous strategies have been implemented including: waiting list audits, triage guidelines, physiotherapy-led clinics, a DNA policy, an orthopaedic lead nurse role and a patient-focussed booking system. There has been a 66% reduction in the number of patients waiting for their first appointment; an 87% reduction in the waiting time from referral to first appointment; a 10% reduction in new patient DNAs; and more efficient referral management and communication processes. Patients are now seen in clinically appropriate time frames and offered earlier access to a wider range of conservative treatments.

What is known about the topic?
Demand for public outpatient services continues to increase. New resource and budget availability is limited, so organisations must continually look for ways to utilise existing resources as efficiently and effectively as possible to deliver timely and appropriately patient care.

What does this paper add?
Further evidence that redesign work that addresses both the administrative and clinical aspects of outpatient services can achieve positive and sustainable outcomes. Alternative models of care such as physiotherapy-led screening clinics, which utilise the skills of a range of health professionals, can supplement traditional medical-led clinics to provide high quality patient care and reduce the workload on consultants. Administrative changes such as patient focussed bookings can be implemented without compromising patient care and may simultaneously reduce the administrative load for the organisation and encourage patients to become more active and responsible participants in their own care.

What are the implications for practitioners?
Redesign work needs to consider both the clinical and administrative aspects of outpatient care, in order to implement sustainable change that positively affects the patient journey. The effects of change on upstream and downstream providers needs to be considered before changes are made. Transparency of the change of management process is vital, no matter how confronting this may be for stakeholders, to ensure decisions are based on fact, rather than hearsay or historical practice.