bluuebunny/crossref_metadata_2025 huggingface dataset:
I
−
⋅
CH
3
X
(X=Cl,Br,I) photodetachment: The effect of electron-molecule interactions in cluster anion photodetachment spectra and angular distributions
Authors: Van Duzor Matthew , Wei Jie , Mbaiwa Foster , Mabbs Richard
Published: October 2010

The electron kinetic energy dependence of the photoelectron spectra and angular distributions of I−⋅CH3X (X=Cl,Br,I) cluster anions are measured via velocity mapped imaging at wavelengths between 350 and 270 nm. Processes analogous to those encountered in free CH3X-electron interactions are revealed. In particular, the presence and energies of resonances associated with a low lying σ∗ state have a marked effect on the results of I−⋅CH3X photoexcitation. These effects (vibrational excitation, product anion production, and alteration of the photoelectron angular distribution) are far more prominent for I−⋅CH3I. However, in the vicinity of the P21/2 threshold there is a sharp deviation in the P23/2 channel angular distribution and an enhancement of the P23/2 channel vibrational structure of all three cluster anions. These latter effects are specific to the cluster anion environment through the relaxation of the partner excited I atom and subsequent electronic autodetachment.
Vertical detachment energies of anionic thymidine: Microhydration effects
Authors: Kim Sunghwan , Schaefer Henry F.
Published: October 2010

Density functional theory has been employed to investigate microhydration effects on the vertical detachment energy (VDE) of the thymidine anion by considering the various structures of its monohydrates. Structures were located using a random searching procedure. Among 14 distinct structures of the anionic thymidine monohydrate, the low-energy structures, in general, have the water molecule bound to the thymine base unit. The negative charge developed on the thymine moiety increases the strength of the intermolecular hydrogen bonding between the water and base units. The computed VDE values of the thymidine monohydrate anions are predicted to range from 0.67 to 1.60 eV and the lowest-energy structure has a VDE of 1.32 eV. The VDEs of the monohydrates of the thymidine anion, where the N1H hydrogen of thymine has been replaced by a 2′-deoxyribose ring, are greater by ∼0.30 eV, compared to those of the monohydrates of the thymine anion. The results of the present study are in excellent agreement with the accompanying experimental results of Bowen and co-workers [J. Chem. Phys. 133, 144304 (2010)].
Influence of dipolar interactions on hyperthermia properties of ferromagnetic particles
Authors: Serantes D. , Baldomir D. , Martinez-Boubeta C. , Simeonidis K. , Angelakeris M. , Natividad E. , Castro M. , Mediano A. , Chen D.-X. , Sanchez A. , Balcells LI. , Martínez B.
Published: October 2010

We show both experimental evidences and Monte Carlo modeling of the effects of interparticle dipolar interactions on the hysteresis losses. Results indicate that an increase in the intensity of dipolar interactions produce a decrease in the magnetic susceptibility and hysteresis losses, thus diminishing the hyperthermia output. These findings may have important clinical implications for cancer treatment.
Negative ions of transition metal-halogen clusters
Authors: Pradhan Kalpataru , Gutsev Gennady L. , Jena Purusottam
Published: October 2010

A systematic density functional theory based study of the structure and spectroscopic properties of neutral and negatively charged MXn clusters formed by a transition metal atom M (M=Sc,Ti,V) and up to seven halogen atoms X (X=F,Cl,Br) has revealed a number of interesting features: (1) Halogen atoms are bound chemically to Sc, Ti, and V for n≤nmax, where the maximal valence nmax equals to 3, 4, and 5 for Sc, Ti, and V, respectively. For n>nmax, two halogen atoms became dimerized in the neutral species, while dimerization begins at n=5, 6, and 7 for negatively charged clusters containing Sc, Ti, and V. (2) Magnetic moments of the transition metal atoms depend strongly on the number of halogen atoms in a cluster and the cluster charge. (3) The number of halogen atoms that can be attached to a metal atom exceeds the maximal formal valence of the metal atom. (4) The electron affinities of the neutral clusters abruptly rise at n=nmax, reaching values as high as 7 eV. The corresponding anions could be used in the synthesis of new salts, once appropriate counterions are identified.
Self-organized, gratinglike nanostructures in polymer films with embedded metal nanoparticles induced by femtosecond laser irradiation
Authors: Loeschner K. , Seifert G. , Heilmann A.
Published: October 2010

The self-organized formation of periodic superstructures in thin plasma polymer films containing noble metal nanoparticles upon femtosecond laser irradiation has been studied in detail. By applying several hundred laser pulses on average per spot, the nanostructure of the metal layer is persistently changed into an approximate line grating with periodical changes in particle size and shape as observed by scanning and transmission electron microscopy. The formation of the structures is only possible within rather narrow ranges of laser intensity and metal content. The orientation of the lines is given by the laser polarization, while their spatial periodicity depends on laser wavelength and incidence angle. These observations give evidence that interference of incident light with light scattered into the film plane is the main mechanism controlling the nanostructure formation. We also discuss the optical spectra of the irradiated regions, in particular the observed dichroism and its relation to the prepared periodic structures.
Global potential energy surface, vibrational spectrum, and reaction dynamics of the first excited (Ã A2′) state of HO2
Authors: Li Anyang , Xie Daiqian , Dawes Richard , Jasper Ahren W. , Ma Jianyi , Guo Hua
Published: October 2010

The authors report extensive high-level ab initio studies of the first excited (Ã A2′) state of HO2. A global potential energy surface (PES) was developed by spline-fitting 17 000 ab initio points at the internal contracted multireference configuration interaction (icMRCI) level with the AVQZ basis set. To ascertain the spectroscopic accuracy of the PES, the near-equilibrium region of the molecule was also investigated using three interpolating moving least-squares-based PESs employing dynamically weighted icMRCI methods in the complete basis set limit. Vibrational energy levels on all four surfaces agree well with each other and a new assignment of some vibrational features is proposed. In addition, the dynamics of both the forward and reverse directions of the H+O2(ã Δ1g)↔OH+O reaction (J=0) were studied using an exact wave packet method. The reactions are found to be dominated by sharp resonances.
Dynamic phase transformation of crystalline silicon under the dry and wet impact studied by molecular dynamics simulation
Authors: Chen Ruling , Luo Jianbin , Guo Dan , Lei Hong
Published: October 2010

Molecular dynamics simulation is applied in analyzing quantitatively the dynamic phase transformation of crystalline silicon under the dry and wet impact, respectively. At the impact loading stage, the phase transformation between fourfold silicon atoms and fivefold or threefold silicon atoms is affected only by the local pressure. The influence of the local temperature or the contact area on the phase transformation will emerge from the impact unloading stage. And the dynamic process of phase transformation between fourfold atoms and fivefold or threefold atoms will obey the Boltzmann distribution law by stages. The variance of the number of fivefold or fourfold atoms at impact loading stage is almost the same as the impact unloading stage. Furthermore, the dynamic residence time of fivefold or threefold atoms formed during the impact process will be about 250 fs. The half-life of these atoms is about 50 fs.
Noncontact ultrasonic spectroscopy applied to the study of polypropylene ferroelectrets
Authors: Gómez Álvarez-Arenas T. E. , Calás H. , Cuello J. Ealo , Fernández A. Ramos , Muñoz M.
Published: October 2010

Noncontact ultrasonic spectroscopy (NCUS) is used to excite and sense thickness resonances in films of polypropylene ferroelectrets. From the comparison of these measurements with theoretical calculations it is possible to extract some material properties: film thickness and density, velocity, and attenuation of ultrasounds and variation in these two magnitudes with the frequency. Hence elastic compliance and acoustic impedance are worked out. Observed variation in the attenuation with the frequency exhibits classical viscoelastic behavior which can be used to investigate the underlaying physical mechanism. In addition, the influence of the metallization on the film response is studied. A modification of the NCUS method is proposed on the basis of the piezoelectric response of these films, which give rise to an alternative characterization method. Consistency of both methods is verified.
Adsorption-driven tuning of the electrical resistance of nanoporous gold
Authors: Wahl Patrick , Traußnig Thomas , Landgraf Stephan , Jin Hai-Jun , Weissmüller Jörg , Würschum Roland
Published: October 2010

The electrical resistance of nanoporous gold prepared by dealloying is tuned by charging the surfaces of the porous structure in an electrolyte. Reversible variations in the resistance up to approximately 4% and 43% occur due to charging in the regimes of double layer charging and specific adsorption, respectively. Charging-induced variations in the electron density or of the volume cannot account for the resistance variation, indicating that this variation is primarily caused by charge-induced modifications of the charge carrier scattering at the solid-electrolyte interface. The relative resistance variation in nanoporous Au with surface charging is found to be much higher than reported for porous nanocrystalline Pt. This is due to the lesser resistance contribution from internal grain boundaries. The resistance variation in nanoporous Au is also higher than that found in thin films owing to the stronger surface scattering in the ligament structure compared to plan surfaces. We argue that the strong resistance variation in up to 43% in the regime of specific adsorption is due to the reversible formation of a chemisorbed surface layer acting as scattering centers for the charge carriers.
Blue-green and white color tuning of monolithic light emitting diodes
Authors: Damilano B. , Demolon P. , Brault J. , Huault T. , Natali F. , Massies J.
Published: October 2010

A blue light emitting diode (LED) is grown on top of a (Ga, In)N/GaN multiple quantum well (QW) acting as a light converter from blue to green-yellow wavelength. The blue light is produced by electrical injection, while the green-yellow emitting QWs are optically pumped by the blue photons. It is shown that the final color of the LED is strongly dependent on the blue pumping wavelength, the absorption and the internal quantum efficiency of the light converter. Depending on these parameters, blue to green LEDs or even white LEDs can be obtained. In addition, the injection current dependence of the LED electroluminescence is measured and analyzed. A very low blueshift is observed as a function of the injection current. It is explained by the fact that the carrier density per QW in the light converter stays relatively low compared to the case of classical current-injected green LEDs.
Cr-doped TiO2 (rutile): Ferromagnetism in bulk form?
Authors: Koohpayeh S. M. , Williams A. J. , Abell J. S. , Lim J. , Blackburn E.
Published: October 2010

Cr-doped rutile samples in powder and single crystal form have been prepared and studied with particular emphasis on their compositional, structural, and magnetic properties. Both powders and single crystals were characterized using x-ray diffractometry and vibrating sample magnetometry, while crystals were also studied using the x-ray Laue technique, scanning electron microscopy, and energy dispersive x-ray analysis. The results indicate weak ferromagnetic behavior at room temperature (RT) in Cr-doped TiO2 powders having 2 at. % Cr, while powders with higher amounts of Cr (e.g., 8 or 12 at. %) showed no evidence of ferromagnetism. Following successful floating zone crystal growth of Cr-doped rutile crystals in argon, magnetic measurements taken from the as-grown crystals revealed no indication of RT ferromagnetism over the composition range 2 to 12 at. % Cr. A solubility limit for Cr into the rutile matrix of 3 at. % Cr at RT is suggested.
Design of a top mirror for the n-GaAs homojunction far-infrared/terahertz detectors
Authors: Deng G. G. , Zhang Y. H. , Shen W. Z.
Published: October 2010

The top mirror of the resonant cavity enhanced homojunction interfacial workfunction internal photoemission (HIWIP) far-infrared (FIR)/terahertz (THz) detector is investigated. Aiming at an existing half-optimized n-GaAs HIWIP FIR/THz detector, two designs of the top mirror are investigated to increase the quantum efficiency. The genuine or equivalent single layer is proved to be unqualified as the top mirror. A design based on the two-dimensional (2D) periodical reversed pyramidal structure of intrinsic GaAs is proposed as the top mirror. The resulted quantum efficiency can be as high as 29.0%. Some elementary thoughts and a tentative fabricating solution of this 2D periodical reversed pyramidal intrinsic GaAs top mirror are suggested. The designing ideas of this kind of top mirror may also be applied to other FIR/THz devices for reference.
Contact resistivity and current flow path at metal/graphene contact
Authors: Nagashio K. , Nishimura T. , Kita K. , Toriumi A.
Published: October 2010

The contact properties between metal and graphene were examined. The electrical measurement on a multiprobe device with different contact areas revealed that the current flow preferentially entered graphene at the edge of the contact metal. The analysis using the cross-bridge Kelvin (CBK) structure suggested that a transition from the edge conduction to area conduction occurred for a contact length shorter than the transfer length of ∼1 μm. The contact resistivity for Ni was measured as ∼5×10−6 Ω cm2 using the CBK. A simple calculation suggests that a contact resistivity less than 10−9 Ω cm2 is required for miniaturized graphene field effect transistors.
Fracture of electrodes in lithium-ion batteries caused by fast charging
Authors: Zhao Kejie , Pharr Matt , Vlassak Joost J. , Suo Zhigang
Published: October 2010

During charging or discharging of a lithium-ion battery, lithium is extracted from one electrode and inserted into the other. This extraction-insertion reaction causes the electrodes to deform. An electrode is often composed of small active particles in a matrix. If the battery is charged at a rate faster than lithium can homogenize in an active particle by diffusion, the inhomogeneous distribution of lithium results in stresses that may cause the particle to fracture. The distributions of lithium and stress in a LiCoO2 particle are calculated. The energy release rates are then calculated for the particle containing preexisting cracks. These calculations predict the critical rate of charging and size of the particle, below which fracture is averted.
Strain effects in GaN epilayers grown on different substrates by metal organic vapor phase epitaxy
Authors: Zhang L. , Cheng K. , Degroote S. , Leys M. , Germain M. , Borghs G.
Published: October 2010

For practical applications, it is important to control strain by carefully tuning growth conditions for stress modification. Strain can have a pronounced impact on device behavior and is caused by extrinsic thermal stress and a tunable intrinsic growth stress. The impact of strain on GaN epilayers was investigated by photoluminescence and high resolution x-ray diffraction (XRD). The GaN samples were grown by metal organic vapor phase epitaxy, on sapphire, 4H–SiC, freestanding GaN and Si (111) substrates. Both free and bound exciton transitions were observed at low temperature, and their energy shift was analyzed with respect to the strain values derived from XRD. We also characterized the valence band split and the GaN bandgap as a function of the strain at 4 K.
High-performance n-type organic field-effect transistors with ionic liquid gates
Authors: Ono S. , Minder N. , Chen Z. , Facchetti A. , Morpurgo A. F.
Published: October 2010

High-performance n-type organic field-effect transistors were developed with ionic-liquid gates and N,N″-bis(n-alkyl)-(1,7 and 1,6)-dicyanoperylene-3,4:9,10-bis(dicarboximide)s single-crystals. Transport measurements show that these devices reproducibly operate in ambient atmosphere with negligible gate threshold voltage and mobility values as high as 5.0 cm2/V s. These mobility values are essentially identical to those measured in the same devices without the ionic liquid, using vacuum or air as the gate dielectric. Our results indicate that the ionic-liquid and n-type organic semiconductor interfaces are suitable to realize high-quality n-type organic transistors operating at small gate voltage, without sacrificing electron mobility.
Equation of state and anharmonicity of carbon dioxide phase I up to 12 GPa and 800 K
Authors: Giordano Valentina M. , Datchi Frédéric , Gorelli Federico A. , Bini Roberto
Published: October 2010

We present an extended investigation of phase I of carbon dioxide by x-ray diffraction and spectroscopic techniques at simultaneous high pressure and high temperature, up to 12 GPa and 800 K. Based on the present and literature data, we show that a Mie–Grüneisen–Debye model reproduces within experimental uncertainties the equation of state of CO2 over the entire range of stability of phase I. Using infrared and Raman spectroscopy, we have determined the frequencies of the zone-center lattice modes as a function of pressure and temperature. We have then extracted the volume and temperature dependencies of the optical lattice mode frequencies and their respective Grüneisen parameters. We find a large difference between the thermodynamic Grüneisen parameter obtained from the P-V-T data and those associated with the optical lattice modes. This suggests, within the quasiharmonic approximation, that acoustic modes have a dominant contribution to the anharmonicity of the system.
Effective numbers of modes applied to analysis of internal dynamics of weakly bound clusters
Authors: Rybakov A. A. , Belega E. D. , Trubnikov D. N.
Published: October 2010

The dependence of the volume of the chaotic component in the internal dynamics of triatomic van der Waals clusters on the angular momentum is calculated using the Monte Carlo and molecular dynamics methods. It has been found that this dependence is nonmonotonic and that its functional form varies for different values of the total energy. The effective number of rotational modes was used to clarify why a change in the volume of chaotic component of the phase space happens for certain values of the angular momentum. We conclude that a large fraction of regular trajectories in relation to all trajectories appears only when there is a possibility for the regular motion to perform a rotation different from that for a chaotic motion. When such difference is small, the regular motion disappears. The effective number of rotational modes can be used to estimate the difference in the type of rotation and is a convenient parameter which controls changes in the dynamics of the system.
Quantum efficiency of energy transfer in noncovalent carbon nanotube/porphyrin compounds
Authors: Roquelet C. , Garrot D. , Lauret J. S. , Voisin C. , Alain-Rizzo V. , Roussignol Ph. , Delaire J. A. , Deleporte E.
Published: October 2010

We report on the quantum yield of excitation energy transfer in noncovalently bound nanotube/porphyrin compounds. Evidence for energy transfer is gained from photoluminescence excitation experiments. We perform a quantitative evaluation of the transfer quantum yield in the case of (6,5) nanotubes through three independent methods: quantitative photoluminescence excitation measurements, evaluation of the luminescence quenching of the donor (porphyrin) and ultrafast transient absorption measurements. The latter shows a tremendous increase in the porphyrin recovery rate upon incorporation in the compound. All these measurements consistently lead to an exceptional quantum yield: η∼1(10−5<1−η<10−3).
The characteristics of atmospheric radio frequency discharges with frequency increasing at a constant power density
Authors: Zhang Yuan Tao , Li Qing Quan , Lou Jie , Li Qing Min
Published: October 2010

A computational model is used to investigate the characteristics of atmospheric radio frequency discharges by increasing frequency from 20 to 100 MHz at a constant power density. The simulation results show that increasing frequency can effectively enhance electron density before the transition frequency but after it the ignition is quenched then the electron density decreases. However this simulation also indicates the maximum time-averaged electron energy reduces monotonically with the excitation frequency increasing at a constant power density.
Spin-orbit density functional and ab initio study of HgXn (X=F, Cl, Br, and I; n=1, 2, and 4)
Authors: Kim Joonghan , Ihee Hyotcherl , Lee Yoon Sup
Published: October 2010

Quantum chemical calculations of HgXn (X=F, Cl, Br, and I; n=1, 2, and 4) in the gas phase are performed using the density functional theory (DFT), two-component spin-orbit (SO) DFT, and high-level ab initio method with relativistic effective core potentials (RECPs). Molecular geometries, vibrational frequencies, and various thermochemical energies are calculated and compared with available experimental results. We assess the performances of DFT functionals for calculating various molecular properties. The PBE0 functional is generally reasonable for the molecular geometries and the vibrational frequencies, but the M06 functional is more appropriate for estimating thermochemical energies. Both shape-consistent and energy-consistent RECPs correctly describe the SO effect.
An integrated microfluidic cell array for apoptosis and proliferation analysis induction of breast cancer cells
Authors: Song Huixue , Chen Tan , Zhang Baoyue , Ma Yifan , Wang Zhanhui
Published: October 2010

In vitro sensitivity testing of tumor cells could rationalize and improve the choice of chemotherapy and hormone therapy. In this report, a microfluidic device made from poly(dimethylsiloxane) and glass was developed for an assay of drug induced cytotoxicity. We evaluated the apoptotic and proliferation-inhibitory effects of anticancer drugs mitomycin C (MMC) and tamoxifen (TAM) using MCF-7 breast cancer cells. MMC and TAM both induced apoptosis and inhibited proliferation of MCF-7 cells in a concentration-dependent manner. MMC caused the expression of antiapoptotic protein Bcl-2 a dose-dependent reduction in MCF-7 cells. The expression of Bcl-2 did not change significantly in MCF-7 cells treated by TAM. The results in the microfluidic device were correlated well with the data obtained from the parallel experiments carried out in the conventional culture plates. The developed microfluidic device could be a potential useful tool for high content screening and high throughput screening research.
Tensor powers of 2-positive maps
Authors: Størmer Erling
Published: October 2010

By studying tensor powers ϕ⊗n of a positive map ϕ of B(K) into B(H) for finite dimensional Hilbert spaces K and H, we give conditions for a map ϕ, such that ϕ⊗n 2-positive for all n to be nondistillable and completely positive.
Tensile strained island growth at step-edges on GaAs(110)
Authors: Simmonds P. J. , Lee M. L.
Published: October 2010

We report the growth of tensile strained GaP islands on a GaAs(110) surface. Three-dimensional island formation proceeds via a step-edge nucleation process. To explain the dislocation-free nature of these islands, we consider the kinetics of strain relief within the context of a model for dislocation glide as a function of surface orientation and sign of strain.
Tilt grain boundaries in a diblock copolymer ordered nanocomposite lamellar phase
Authors: Thompson Russell B.
Published: October 2010

A hybrid self-consistent field theory/density functional theory method is applied to predict tilt (kink) grain boundary structures between lamellar domains of a symmetric diblock copolymer with added spherical nanoparticles. Structures consistent with experimental observations are found and theoretical evidence is provided in support of a hypothesis regarding the positioning of nanoparticles. Some particle distributions are predicted for situations not yet examined by experiment.
Electronic states of MgO: Spectroscopy, predissociation, and cold atomic Mg and O production
Authors: Maatouk A. , Ben Houria A. , Yazidi O. , Jaidane N. , Hochlaf M.
Published: October 2010

We used multiconfigurational methods and a large basis set to compute the potential energy curves of the valence and valence-Rydberg electronic states of MgO molecule. New bound electronic states are found. Using these highly correlated wave functions, we evaluated their mutual spin-orbit couplings and transition moment integrals. For the bound electronic states of MgO, we deduced an accurate set of spectroscopic constants that agree remarkably well with experimental results. Moreover, our potentials, transition moments, and spin-orbit coupling evolutions are incorporated into Fermi golden rule calculations to deduce the radiative lifetimes of MgO(B Σ1+) rovibrational levels and the natural lifetimes of MgO(A Π1) vibrational levels, where a good agreement is found with experimental values. Finally, we suggest new routes for the production of cold Mg and O atoms and cold MgO molecules.
A boron-containing molecule as an efficient electron-transporting material with low-power consumption
Authors: Shizu Katsuyuki , Sato Tohru , Tanaka Kazuyoshi , Kaji Hironori
Published: October 2010

We theoretically propose a boron-containing molecule, hexaboracyclophane (HBCP), as an electron-transporting (ET) material with low-power loss. We calculate the vibronic coupling of HBCP, comparing them with those of other ET materials, tris-(8-hydroxyquinoline) aluminum(III) (Alq3) and tris[3-(3-pyridyl)mesityl]borane (3TPYMB). Using the nonequilibrium Green’s function method to evaluate their single molecular ET properties, we show that HBCP exhibits more efficient and lower-power consumption than Alq3 and 3TPYMB. HBCP has suitable highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels as an electron-transport layer when Alq3 is employed as an emitter.
Communication: Thermodynamics of water modeled using ab initio simulations
Authors: Weber Valéry , Asthagiri D.
Published: October 2010

We regularize the potential distribution framework to calculate the excess free energy of liquid water simulated with the BLYP-D density functional. Assuming classical statistical mechanical simulations at 350 K model the liquid at 298 K, the calculated free energy is found in fair agreement with experiments, but the excess internal energy and hence also the excess entropy are not. The utility of thermodynamic characterization in understanding the role of high temperatures to mimic nuclear quantum effects and in evaluating ab initio simulations is noted.
Reduction of gate hysteresis above ambient temperature via ambipolar pulsed gate sweeps in carbon nanotube field effect transistors for sensor applications
Authors: Mattmann Moritz , Bechstein Daniel , Roman Cosmin , Chikkadi Kiran , Hierold Christofer
Published: October 2010

We investigate the hysteresis behavior in carbon nanotube (CNT) field effect transistors (CNFETs) upon pulsed gate voltages (Vg) above ambient temperature within 300–390 K. Assuming charge trapping near the CNT channel to be the major mechanism behind gate hysteresis, we perform charge trapping experiments based on Vg pulses and find that CNFET charge trapping is increasing with temperature. We assess the impact of thermally enhanced charge trapping on the hysteresis reduction performance of two different pulsed Vg sweeps. One of the two sweeps, consisting of alternating polarity pulses, is shown to essentially eliminate gate hysteresis in the studied temperature range.
Observation of hydrophobic-like behavior in geometrically patterned hydrophilic microchannels
Authors: Parikesit G. O. F. , Vrouwe E. X. , Blom M. T. , Westerweel J.
Published: October 2010

We present our observation of meta-hydrophobicity, where geometrically patterned surfaces make hydrophilic microchannels exhibit hydrophobic-like behaviors. We analyze the wetting-induced energy decrease that results from the surface geometries and experimentally demonstrate how those geometries can modulate the dynamics of capillary-driven wetting and evaporation-driven drying of microfluidic systems. Our results also show that the modulated wetting dynamics can be employed to generate regulated patterns of microbubbles.
1.54

μ
m
emitters based on erbium doped InGaN p-i-n junctions
Authors: Dahal R. , Ugolini C. , Lin J. Y. , Jiang H. X. , Zavada J. M.
Published: October 2010

We present here on the growth, fabrication and electroluminescence (EL) characteristics of light emitting diodes (LEDs) based on Er-doped InGaN active layers. The p-i-n structures were grown using metal organic chemical vapor deposition and processed into 300×300 μm2 mesa devices. The LEDs exhibit strong emissions at 1.0 and 1.54 μm, due to Er intra-4f transitions, under forward bias conditions. The emitted EL intensity increases with applied input current without exhibiting saturation up to 70 mA. The integrated power over the near infrared emission, measured at room temperature from the top of a bare chip, is about 2 μW. The results represent a significant advance in the development of current injected, chip-scale emitters and waveguide amplifiers based on Er doped semiconductors.
Density functional theory study of 3R– and 2H–CuAlO2 under pressure
Authors: Liu Qi-Jun , Liu Zheng-Tang , Feng Li-Ping , Tian Hao , Liu Wen-Ting , Yan Feng
Published: October 2010

We present a first-principles density-functional theory based study of the impact of pressure on the structural and elastic properties of bulk 3R– and 2H–CuAlO2. The ground state properties of 3R– and 2H–CuAlO2 are obtained, which are in good agreement with previous experimental and theoretical data. The analysis of enthalpy variation with pressure indicates the phase transition pressure between 3R and 2H is 15.4 GPa. The independent elastic constants of 3R– and 2H–CuAlO2 are calculated. As the applied pressure increases, the calculations show the presences of mechanical instability at 26.2 and 27.8 GPa for 3R– and 2H–CuAlO2, which are possibly related with the phase transitions.
rf plasma oxidation of Ni thin films sputter deposited to generate thin nickel oxide layers
Authors: Hoey Megan L. , Carlson J. B. , Osgood R. M. , Kimball B. , Buchwald W.
Published: October 2010

Nickel oxide (NiO) layers were formed on silicon (Si) substrates by plasma oxidation of nickel (Ni) film lines. This ultrathin NiO layer acted as a barrier layer to conduction, and was an integral part of a metal-insulator-metal (MIM) diode, completed by depositing gold (Au) on top of the oxide. The electrical and structural properties of the NiO thin film were examined using resistivity calculations, current-voltage (I-V) measurements and cross-sectional transmission electron microscopy (XTEM) imaging. The flow rate of the oxygen gas, chamber pressure, power, and exposure time and their influence on the characteristics of the NiO thin film were studied.
The interaction of hybrid nanoparticles inserted within surfactant bilayers
Authors: Constantin Doru
Published: October 2010

We determine by small-angle x-ray scattering the structure factor of hydrophobic particles inserted within lamellar surfactant phases for various particle concentrations. The data are then analyzed by numerically solving the Ornstein–Zernicke equation, taking into account both the intra- and interlayer interactions. We find that particles within the same layer repel each other and that the interaction potential (taken as independent of the concentration) has a contact value of 2.2kBT and a range of about 10 Å. If the amplitude is allowed to decrease with increasing concentration, the contact value in the dilute limit is about 5kBT for a similar range.
Properties of alkali-halide salt solutions about polarizable nanoparticle solutes for different ion models
Authors: Wynveen Aaron , Bresme Fernando
Published: October 2010

We investigate the distributions of various salts about large hydrophobic polarizable solutes in aqueous electrolyte solutions. The solutes are modeled as nanometer-sized cylindrical objects, a scale relevant to biomolecules and nanomaterials, and particularly high aspect ratio nanoparticles. Interactions, including image charge forces arising from the finite polarizability of the solute, between explicit solvent/ions and the solute are computed explicitly using a molecular dynamics simulation methodology we have recently introduced. Comparisons are made between several salt species and different models of the force fields for each ionic component of the salt. We find evidence that both small cations, Li+, and large anions, I−, adsorb at hydrophobic interfaces. Our results indicate that the ion structure about the solute is strongly dependent on the force field investigated, suggesting that ion selectivity is quite sensitive to the respective parameters defining the ion’s size and binding energy as well as to the polarizability of the solute.
Curvature modulates the self-assembly of amphiphilic molecules
Authors: Tian Falin , Luo Yu , Zhang Xianren
Published: October 2010

In this work, we used lattice Monte Carlo simulations and theoretical model calculations to show how the self-assembly of adsorbed amphiphilic molecules is affected by the local curvature of solid surfaces. It is found that, beyond a critical curvature value, solid surface geometry governs the spatial ordering of aggregates and may induce the morphological transitions. The simulation results show how the curvature of solid surfaces modulates the distribution of aggregates: the anisotropy in local curvature along and perpendicular to the cylindrical surfaces tends to generate orientationally ordered cylindrical micelles. To account for the morphological transitions induced by the local curvature of solid surfaces, we constructed a theoretical model which includes the Helfrich bending energy, the deformation energy of aggregates induced by solid surfaces, and the adsorption energy. The model calculations indicate that on highly curved solid surfaces the bending energy for bilayer structure sharply increases with surface curvature, which in turn induces the morphological transition from bilayer to cylindrical structure. Our results suggest that the local curvature provides a means of controlling the spatial organization of amphiphilic molecules.
Continuously tunable monomode mid-infrared vertical external cavity surface emitting laser on Si
Authors: Khiar A. , Rahim M. , Fill M. , Felder F. , Hobrecker F. , Zogg H.
Published: October 2010

A tunable PbTe based mid-infrared vertical external cavity surface emitting laser is described. The active part is a ∼1 μm thick PbTe layer grown epitaxially on a Bragg mirror on the Si-substrate. The cavity is terminated with a curved Si/SiO Bragg top mirror and pumped optically with a 1.55 μm laser. Cavity length is <100 μm in order that only one longitudinal mode is supported. By changing the cavity length, up to 5% wavelength continuous and mode-hop free tuning is achieved at fixed temperature. The total tuning extends from 5.6 to 4.7 μm at 100–170 K operation temperature.
A New Equation of State for Carbon Dioxide Covering the Fluid Region from the Triple-Point Temperature to 1100 K at Pressures up to 800 MPa
Authors: Span Roland , Wagner Wolfgang
Published: October 2010

This work reviews the available data on thermodynamic properties of carbon dioxide and presents a new equation of state in the form of a fundamental equation explicit in the Helmholtz free energy. The function for the residual part of the Helmholtz free energy was fitted to selected data of the following properties: (a) thermal properties of the single-phase region (pρT) and (b) of the liquid-vapor saturation curve (ps, ρ′, ρ″) including the Maxwell criterion, (c) speed of sound w and (d) specific isobaric heat capacity cp of the single phase region and of the saturation curve, (e) specific isochoric heat capacity cv, (f) specific enthalpy h, (g) specific internal energy u, and (h) Joule–Thomson coefficient μ. By applying modern strategies for the optimization of the mathematical form of the equation of state and for the simultaneous nonlinear fit to the data of all these properties, the resulting formulation is able to represent even the most accurate data to within their experimental uncertainty. In the technically most important region up to pressures of 30 MPa and up to temperatures of 523 K, the estimated uncertainty of the equation ranges from ±0.03% to ±0.05% in the density, ±0.03% to ±1% in the speed of sound, and ±0.15% to ±1.5% in the isobaric heat capacity. Special interest has been focused on the description of the critical region and the extrapolation behavior of the formulation. Without a complex coupling to a scaled equation of state, the new formulation yields a reasonable description even of the caloric properties in the immediate vicinity of the critical point. At least for the basic properties such as pressure, fugacity, and enthalpy, the equation can be extrapolated up to the limits of the chemical stability of carbon dioxide. Independent equations for the vapor pressure and for the pressure on the sublimation and melting curve, for the saturated liquid and vapor densities, and for the isobaric ideal gas heat capacity are also included. Property tables calculated from the equation of state are given in the appendix.
Internal dynamics, the state, and recourse to external aid: towards a historical sociology of the peasant movement inSenegal since the 1960s
Authors: Hrabanski Marie
Published: October 2010

The paper presents a historical sociology of the peasant movement in Senegal through three successive periods from its emergence until its internationalisation. The analysis shows that recourse to external aid has been an integral part of the Senegalese peasant movement, in that the movement has developed within a multi-level political space where the government of Senegal and external donors play a decisive role. However, the peasant movement is also a product of its own dynamics and has adjusted its strategies according to the national and international political environment.
Peasant struggles in Mali: from defending cotton producers’ interests to becoming part of the Malian power structures
Authors: Roy Alexis
Published: October 2010

This article describes how the organisation and representation of cotton growers in Mali developed from the mid 1970s to the current day, from the setting up of Village Associations through to the privatisation of the cotton industry. The research focused most closely on the relationships between the growers’ organisations and the state-owned cotton company, as well as on the different struggles throughout this period. It can be seen that at the same time as peasant participation was increasing, a ‘cotton elite’ also emerged. Far from reshaping the power structures operating in the cotton sector, this elite appropriated them.
Claiming workers' rights in the Democratic Republic of Congo: the case of the Collectif des ex-agents de la Gécamines
Authors: Rubbers Benjamin
Published: October 2010

Within the context of its strategy for the reform of public companies in Africa, the World Bank became involved in redundancies of questionable legality. In the Democratic Republic of Congo, for example, the Bank arranged and financed a voluntary severance programme in 2003, whereby 10,000 employees of the mining company Gécamines, some 45% of its workforce, left in return for an arbitrarily fixed lump-sum payment. Based on ethnographic research, this paper discusses the history of the protest movement which emerged from this mass redundancy programme, the arguments deployed by the movement and the resources available to it. On the basis of this case study, the paper goes on to offer some thoughts on the conditions for social criticism in a transitional regime, heir to an authoritarian tradition of long standing, and operating under the tutelage of foreign donors.
West African social movements ‘against the high cost of living’: from the economic to the political, from the global to the national
Authors: Maccatory Bénédicte , Oumarou Makama
                      Bawa , Poncelet Marc
Published: October 2010

The globalisation of the market for basic consumer goods, speculation, and the success of biofuels production all underlie a recent return to the international agenda of the issues of food security, food sovereignty and the right to food. In 2008, the ‘high cost of living’ phenomenon sparked off numerous collective, urban, African protests movements: these challenged and took the governments in power by surprise, impelling them to react in different ways. This article describes and analyses the social movements brought into being by activist organisations (including unions, human rights organisations, and consumer associations) in two countries, Niger and Burkina Faso, and demonstrates how important it is to situate the movements in local temporalities and circumstances. One of the main issues highlighted by the findings of the research is the importance of local governance issues: the measures taken in relation to the price rises were aimed more at the symptoms than at the underlying causes, and had only short-term effects. The different temporalities of world events hence played a very minor role, despite the connection of a number of the actors, especially in Niger, to the international sphere via anti-globalisation movements.
The extraversion of protest: conditions, history and use of the ‘international’ in Africa
Authors: Pommerolle Marie-Emmanuelle
Published: October 2010

The growing number of international causes and an intensification in the establishment of transnational networks in Africa are expanding a chain of interdependency which links an ever-larger and more diverse set of actors from North and South. It therefore seems relevant to revisit the debates of the 1990s concerning the dependency of ‘African civil society’ with regard to the North, through the concept of ‘extraversion’ within the political spaces of sub-Saharan Africa. First, it is argued that the conditions and effects of this internationalisation of protest actors are contradictory. Access to the international sphere is subject to two forms of competition: social and political. While universally determined by socially selective skills, such access also provides a vehicle for social ascension. Meanwhile, in the specifically African context, it is the object of intense political battles, representing as such both a ‘refuge’ and a resource, as well as a new source of coercion. Secondly, it is suggested that the specific modalities of relationships between actors from North and South tend to reproduce existing inequalities, with the effect that northern models of protest (in terms of both themes and tools) ultimately win out in African spaces. Finally, similarities in modalities of implementation, in vocabulary, in the skills demanded by internationalised mobilisations, and in the political and economic reforms introduced by external actors, lead to the hypothesis that these transnational mobilisations contribute to a reforming authoritarianism, that is to say to the implementation of reforms which depoliticise social and political issues and reproduce the established order. By repositioning mobilisations with access to the international sphere within the history of African political spaces, the concept of extraversion thus allows consideration of their impact as agent of both emancipation and domination.
Another dragon in the kitchen: Psychological experiences of hepatitis C treatment among HIV‐hepatitis C co‐infected gay men
Authors: Sinclair Michael , McPherson Susan , Bor Robert , Orban Lisa
Published: October 2010

Background:Increasing numbers of HIV‐infected gay men acquire hepatitis C virus (HCV) co‐infection, which causes serious medical consequences. Treatment for HCV is associated with many severe side effects, in some cases psychological, and many patients subsequently fail to adhere, even when psychological services are utilised, to improve treatment adherence.Objective:This qualitative study aimed to explore the experiences of HIV‐infected gay men undergoing treatment for HCV in order to inform psychological services to better meet specific treatment needs of this population.Methods:Thirteen HIV‐infected gay men who had undergone HCV treatment were interviewed and a qualitative analysis was conducted. Participants described HCV and its treatments in the context of their relationships and lifestyles.Findings:Four domains emerged: HCV diagnosis and treatment; HCV treatment education; change in sense of self; and sexual risk‐taking. Adhering to treatment was a significant challenge for all participants and emerged across all domains.Discussion:Psychological services for this population of co‐infected gay men should assist this clinical population not only with adherence to hepatitis C treatment but should also be available at an earlier stage in the process to help patients make informed choices about whether or not to begin a course of treatment. Assessing factors such as coping strategies, treatment readiness and knowledge, self‐awareness, and level of risk‐taking, can guide clinicians in tailoring treatment and adherence planning for HIV/HCV‐co‐infected gay men.
Bridging the gap between research and practice in counselling and psychotherapy training: Learning from trainees
Authors: Moran Patricia
Published: October 2010

Aim: This study set out to examine trainee practitioners' perceptions of research training, and to explore ways in which training might be developed to facilitate the integration of research and practice. Method: Fourteen trainees on a doctoral programme in counselling psychology and psychotherapy participated in two focus groups, and verbatim transcripts were analysed using the Framework approach. Findings: The findings indicate that while participants appreciated the value of research, most found it challenging and anxiety provoking. Participants identified a number of ways in which training approaches could be adapted to enhance motivation to engage with research, and enable integration of research and clinical practice. Conclusions/implications: The findings are discussed in terms of the implications for the way research is incorporated into clinical training, as well as the type of research taught in the context of wider debates about evidence.
Naming digits in a semantic blocking paradigm
Authors: Herrera Amparo , Macizo Pedro
Published: October 2010

It is widely agreed that word numerals are processed similar to other words, and, thus, they can be named without semantic mediation. However, there is no consensus about Arabic digits. Although digits seem to have a preferential link to magnitude representation, there is some evidence indicating a possible asemantic route to access phonological information. In the present study, we used a semantic blocking paradigm to explore this question. In Experiment 1, participants were asked to name digits and pictures or numeral words and name of objects in a semantic blocked context and in a mixed context. For both types of numerical notation we found facilitation in the blocked condition relative to the mixed condition. In Experiment 2, participants named two-digit numbers in a blocked condition (short numerical distance) or in a mixed condition (large numerical distance). Again, facilitation was found for the blocked condition relative to the mixed condition. This pattern of results seems to indicate that Arabic digits, like number words, might be named through an asemantic route.