bluuebunny/crossref_metadata_2025 huggingface dataset:
In situ real-time spectroscopic ellipsometry measurement for the investigation of molecular orientation in organic amorphous multilayer structures
Authors: Yokoyama Daisuke , Adachi Chihaya
Published: June 2010

To investigate molecular orientation in organic amorphous films, in situ real-time spectroscopic ellipsometry measurements were performed during vacuum deposition. Three materials with different molecular shapes were adopted to confirm the generality of the molecular orientation. In all three cases, more than 200 000 values for the ellipsometric parameters measured during deposition were well simulated simultaneously over the entire spectral range and measurement period using a simple model where the films possessed homogeneous optical anisotropy. This demonstrated the homogeneity of the molecular orientation in the direction of film thickness. The molecular orientation can be controlled by the substrate temperature even in multilayer structures. It is also demonstrated that a “multilayer structure” can be fabricated using only one material, where each layer has different optical and electrical properties.
Luminescence enhancement and quenching in ZnS:Mn by Au nanoparticles
Authors: Ma Lun , Chen Wei
Published: June 2010

Au/silica/ZnS:Mn core-shell nanostructures were synthesized and their luminescence behaviors were investigated in comparison with that of silica-coated ZnS:Mn nanoparticles. The extinction peak of Au nanoparticles is at 520 nm which is from the surface plasmon. After silica coating, the surface plasmon extinction peak is red-shifted to 535 nm. Transmission electron microscopy observations show that some ZnS:Mn nanoparticles are adhered on the Au/silica surfaces. ZnS:Mn nanoparticles have two emissions. The emission at 442 nm is from surface defects or donor-acceptor (D-A) pairs and the emission at 600 nm is from the T41–A61 transition of Mn2+. For the first time, we observed that the Mn2+ emission at 600 nm was quenched but the D-A emission at 442 nm was enhanced by Au nanoparticles. This phenomenon can be explained reasonably by the radiation plasmon model that surface plasmon resonance scattering may enhance the emission while surface plasmon resonance absorption quenches the emission.
Hysteresis-free electron currents in poly(p-phenylene vinylene) derivatives
Authors: Craciun N. I. , Zhang Y. , Palmaerts A. , Nicolai H. T. , Kuik M. , Kist R. J. P. , Wetzelaer G. A. H. , Wildeman J. , Vandenbergh J. , Lutsen L. , Vanderzande D. , Blom P. W. M.
Published: June 2010

The interpretation of electron currents in conjugated polymers is strongly hindered by the occurrence of hysteresis. We investigate the transport of electrons in electron-only devices based on derivatives of poly(p-phenylene vinylene) (PPV) for various hole-blocking bottom electrodes as well as purification of the polymer. The use of a variety of hole blocking bottom contacts, as metallic electrodes and n-type doped polymers, did not give any improvement in the observed hysteresis. By purification of the PPV, hysteresis free electron-only currents can be obtained. The deep traps responsible for hysteresis, with a concentration in the 1016 cm−3 range, are not responsible for the trap-limited electron transport as observed in purified PPV.
Molecular dynamics simulation study of friction force and torque on a rough spherical particle
Authors: Kohale Swapnil C. , Khare Rajesh
Published: June 2010

Recent developments in techniques of micro- and nanofluidics have led to an increased interest in nanoscale hydrodynamics in confined geometries. In our previous study [S. C. Kohale and R. Khare, J. Chem. Phys. 129, 164706 (2008)], we analyzed the friction force experienced by a smooth spherical particle that is translating in a fluid confined between parallel plates. The magnitude of three effects—velocity slip at particle surface, the presence of confining surfaces, and the cooperative hydrodynamic interactions between periodic images of the moving particle—that determine the friction force was quantified in that work using molecular dynamics simulations. In this work, we have studied the motion of a rough spherical particle in a confined geometry. Specifically, the friction force experienced by a translating particle and the torque experienced by a rotating particle are studied using molecular dynamics simulations. Our results demonstrate that the surface roughness of the particle significantly reduces the slip at the particle surface, thus leading to higher values of the friction force and hence a better agreement with the continuum predictions. The particle size dependence of the friction force and the torque values is shown to be consistent with the expectations from the continuum theory. As was observed for the smooth sphere, the cooperative hydrodynamic interactions between the images of the sphere have a significant effect on the value of the friction force experienced by the translating sphere. On the other hand, the torque experienced by a spherical particle that is rotating at the channel center is insensitive to this effect.
Electrical transport characteristics of superconducting MgB2–MgO composite near continuous percolation
Authors: Zhang Yi Bing , Zhou Di Fan , Lv Zhen Xing , Deng Zhen Yan , Cai Chuan Bing , Zhou Shi Ping
Published: June 2010

Superconducting MgB2–MgO composite with about 75% mole concentration of MgO was synthesized in situ by a single-replacement reaction. The resistance versus temperature curve shows that the composite has a high superconducting transition temperature to 38.0 K and metallic transport behavior with low resistivity and highly residual resistance ratio comparable to a pure MgB2 sample. These characteristics are explained by using the statistical percolation model and a conductivity expression with temperature for the metal–insulator MgB2 composite is given in this paper. The results indicate that MgB2 superconductor can tolerance a high content of insulating contamination and this metal–insulator MgB2–MgO composite can be utilized for the superconducting fault current limiter.
Size dependent dynamic analysis of nanoplates
Authors: Assadi Abbas , Farshi Behrooz , Alinia-Ziazi Ali
Published: June 2010

Determination of accurate behavior of nanostructures is important in nanoelectromechanical systems in view of the shortcoming of classical theories of mechanics. In this study size-dependent transverse vibration of nanoplates is investigated. Surface properties which include surface elasticity and residual stresses are taken into account. Elasticity modulus of the bulk part is considered dependent on size as well as temperature. Kirchhoff theory of laminated plates is used to derive the governing differential equation of nanoplate structure.
Thermoelectrical manipulation of nanomagnets
Authors: Kadigrobov A. M. , Andersson S. , Radić D. , Shekhter R. I. , Jonson M. , Korenivski V.
Published: June 2010

We investigate the interplay between the thermodynamic properties and spin-dependent transport in a mesoscopic device based on a magnetic multilayer (F/f/F), in which two strongly ferromagnetic layers (F) are exchange-coupled through a weakly ferromagnetic spacer (f) with the Curie temperature in the vicinity of room temperature. We show theoretically that the Joule heating produced by the spin-dependent current allows a spin-thermoelectronic control of the ferromagnetic-to-paramagnetic (f/N) transition in the spacer and, thereby, of the relative orientation of the outer F-layers in the device (spin-thermoelectric manipulation of nanomagnets). Supporting experimental evidence of such thermally-controlled switching from parallel to antiparallel magnetization orientations in F/f(N)/F sandwiches is presented. Furthermore, we show theoretically that local Joule heating due to a high concentration of current in a magnetic point contact or a nanopillar can be used to reversibly drive the weakly ferromagnetic spacer through its Curie point and thereby exchange couple and decouple the two strongly ferromagnetic F-layers. For the devices designed to have an antiparallel ground state above the Curie point of the spacer, the associated spin-thermionic parallel to antiparallel switching causes magnetoresistance oscillations whose frequency can be controlled by proper biasing from essentially dc to GHz. We discuss in detail an experimental realization of a device that can operate as a thermomagnetoresistive switch or oscillator.
Relativistic four- and two-component calculations of parity violation effects in chiral tungsten molecules of the form NWXYZ (X, Y, Z=H, F, Cl, Br, or I)
Authors: Figgen Detlev , Saue Trond , Schwerdtfeger Peter
Published: June 2010

Parity violation (PV) effects to the electronic ground state structure for a series of chiral tungsten molecules of the type NWXYZ (X, Y, Z=H, F, Cl, Br, or I) are compared using four- (Dirac) and two- (X2C) component relativistic Hartree–Fock and density functional theories. The results show the computationally more affordable two-component X2C approach yields accurate results for all molecules investigated. The PV energy differences between the two enantiomers range from as little as 0.4 Hz for NWClBrI to 140 Hz for NWHClI using a generalized gradient approximation including exact exchange (B3LYP). The WN stretching mode in these molecules lies in the experimentally favorable CO2 laser frequency range, and we therefore investigated PV effects in vibrational transitions using a single normal mode analysis. Here the PV frequency shift between the two enantiomers ranges from 1.6 mHz for NWFBrI to 710 mHz for NWHClI. Thus these types of molecules could be useful for the future detection of PV effects in chiral molecules.
Fractional dissipative standard map
Authors: Tarasov Vasily E. , Edelman M.
Published: June 2010

Using kicked differential equations of motion with derivatives of noninteger orders, we obtain generalizations of the dissipative standard map. The main property of these generalized maps, which are called fractional maps, is long-term memory. The memory effect in the fractional maps means that their present state of evolution depends on all past states with special forms of weights. Already a small deviation of the order of derivative from the integer value corresponding to the regular dissipative standard map (small memory effects) leads to the qualitatively new behavior of the corresponding attractors. The fractional dissipative standard maps are used to demonstrate a new type of fractional attractors in the wide range of the fractional orders of derivatives.
Quantum well infrared photodetectors hardiness to the nonideality of the energy band profile
Authors: Lhuillier Emmanuel , Péré-Laperne Nicolas , Ribet-Mohamed Isabelle , Rosencher Emmanuel , Patriarche Gilles , Buffaz Amandine , Berger Vincent , Nedelcu Alexandru , Carras Mathieu
Published: June 2010

We report results on the effect of a nonsharp and disordered potential in quantum well infrared photodetectors (QWIP). Scanning electronic transmission microscopy is used to measure the alloy profile of the structure which is shown to present a gradient of composition along the growth axis. Those measurements are used as inputs to quantify the effect on the detector performance (peak wavelength, spectral broadening, and dark current). The influence of the random positioning of the doping is also studied. Finally we demonstrate that QWIP properties are quite robust with regard to the nonideality of the energy band profile.
General no-go condition for stochastic pumping
Authors: Maes Christian , Netočný Karel , Thomas Simi R.
Published: June 2010

The control of chemical dynamics requires understanding the effect of time-dependent transition rates between states of chemomechanical molecular configurations. Pumping refers to generating a net current, e.g., per period in the time dependence, through a cycle of consecutive states. The work of artificial machines or synthesized molecular motors depends on it. In this paper we give short and simple proofs of no-go theorems, some of which appeared before but here with essential extensions to non-Markovian dynamics, including the study of the diffusion limit. It allows to exclude certain protocols in the working of chemical motors where only the depth of the energy well is changed in time and not the barrier height between pairs of states. We also show how pre-existing steady state currents are, in general, modified with a multiplicative factor when this time dependence is turned on.
Heat-driven and electric-field-driven bistable devices using dye-doped nematic liquid crystals
Authors: Kim Jin Ki , Van Le Khoa , Dhara Surajit , Araoka Fumito , Ishikawa Ken , Takezoe Hideo
Published: June 2010

We have demonstrated memory and rewritable bistable devices based on an anchoring transition of a nematic liquid crystal on a perfluoropolymer surface. Spontaneous orientation changes between planar and homeotropic occur on cooling and heating with a large temperature hysteresis. Photo (heat) addressing is possible from homeotropic to planar using dye-doped samples. For a coumarin dye, photoaddressed images are preserved even after heating up the sample to the isotropic temperature, whereas, for a 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran dye the images can be erased by decreasing the temperature out of the thermal hysteresis. Orientation switching also occurs by applying an electric field with a response time of several milliseconds depending on the field strength.
Surface-directed spinodal decomposition in the pseudobinary alloy (HfO2)x(SiO2)1−x
Authors: Liu J. , Wu X. , Lennard W. N. , Landheer D. , Dharma-Wardana M. W. C.
Published: June 2010

Hf silicate films (HfO2)0.25(SiO2)0.75 with thicknesses in the range 4–20 nm were grown on silicon substrate by atomic layer deposition at 350 °C. Hf distributions in as-grown and 800 °C annealed films were investigated by high resolution transmission electron microscopy (HRTEM), angle-resolved x-ray photoelectron spectroscopy (ARXPS), and medium energy ion scattering (MEIS). HRTEM images show a layered structure in films thinner than 8 nm. The ARXPS data also reveal a nonuniform distribution of Hf throughout the film depth. Diffusion of SiO2 to the film surface after a longer time anneal was observed by MEIS. All these observations provide evidence for surface-directed spinodal decomposition in the pseudobinary (HfO2)x(SiO2)1−x alloy system.
Wurtzite structure Sc1−xAlxN solid solution films grown by reactive magnetron sputter epitaxy: Structural characterization and first-principles calculations
Authors: Höglund Carina , Birch Jens , Alling Björn , Bareño Javier , Czigány Zsolt , Persson Per O. Å. , Wingqvist Gunilla , Zukauskaite Agne , Hultman Lars
Published: June 2010

AlN(0001) was alloyed with ScN with molar fractions up to ∼22%, while retaining a single-crystal wurtzite (w-) structure and with lattice parameters matching calculated values. Material synthesis was realized by magnetron sputter epitaxy of thin films starting from optimal conditions for the formation of w-AlN onto lattice-matched w-AlN seed layers on Al2O3(0001) and MgO(111) substrates. Films with ScN contents between 23% and ∼50% exhibit phase separation into nanocrystalline ScN and AlN, while ScN-rich growth conditions yield a transformation to rocksalt structure Sc1−xAlxN(111) films. The experimental results are analyzed with ion beam analysis, x-ray diffraction, and transmission electron microscopy, together with ab initio calculations of mixing enthalpies and lattice parameters of solid solutions in wurtzite, rocksalt, and layered hexagonal phases.
Optical evaluation of multichannel radiative transitions originating from G45/2 level of Sm3+ in heavy-metal-gallate glasses
Authors: Zhang J. , Yang D. L. , Pun E. Y. B. , Gong H. , Lin H.
Published: June 2010

Conventional visible and novel infrared (IR) emissions of Sm3+ in heavy-metal-gallate glasses (Li2O–K2O–BaO–PbO–Bi2O3–Ga2O3, LKBPBG for short) with low phonon energy have been observed. Judd–Ofelt parameters Ω2 (3.00×10−20 cm2), Ω4 (5.19×10−20 cm2), and Ω6 (1.69×10−20 cm2) indicate a higher asymmetry and stronger covalent environment in the optical glasses. For the visible fluorescence bands peaked at 564, 601, 648, and 710 nm, the maximum stimulated emission cross-sections (σe) were derived to be 1.35×10−22, 9.21×10−22, 9.58×10−22, and 3.91×10−22 cm2, respectively, the values are larger than those in phosphate, oxyfluoroborate, tellurite, and calibo glasses obviously. The observed 1185 nm IR emission lies in the low-loss window of telecommunication system, and the maximum value of σe for this band was obtained to be 6.09×10−23 cm2. The characterization of multichannel radiative transitions of Sm3+ in LKBPBG glasses is beneficial in exposing its potential applications in visible and IR optoelectronic devices.
Electrokinetic framework of dielectrophoretic deposition devices
Authors: Burg Brian R. , Bianco Vincenzo , Schneider Julian , Poulikakos Dimos
Published: June 2010

Numerical modeling and experiments are performed investigating the properties of a dielectrophoresis-based deposition device, in order to establish the electrokinetic framework required to understand the effects of applied inhomogeneous electric fields while moving particles to desired locations. By capacitively coupling electrodes to a conductive substrate, the controlled large-scale parallel dielectrophoretic assembly of nanostructures in individually accessible devices at a high integration density is accomplished. Thermal gradients in the solution, which give rise to local permittivity and conductivity changes, and velocity fields are solved by coupling electric, thermal, and fluid-mechanical equations. The induced electrothermal flow (ETF) causes vortices above the electrode gap, attracting particles, such as single-walled carbon nanotubes (SWNTs), before they are trapped by the dielectrophoretic force and deposit across the electrodes. Long-range carbon nanotube transport is governed by hydrodynamic effects, while local trapping is dominated by dielectrophoretic forces in low concentration SWNT dispersions. Results show that by decreasing the ac frequency ac electroosmosis on the metallic electrodes occurs due to the emergence of an electric double layer, disturbing the initial flow pattern of the system. By superimposing a dc potential offset, a generated tangential electroosmotic fluid flow in the dielectric electrode gap also disrupts the ETF. Capacitive coupling is most efficient in the high frequency regime where it is the dominating impedance contribution. Understanding the occurrence and interaction of these different effects, including a self-limiting integration mechanism for individual nanostructures, allows an increased deposition yield at overall lower electric field strengths through a prudent choice of electric field parameters. The findings provide important avenues toward gentler particle handling, without direct current throughput, a relevant aspect for limiting process effects during device fabrication, all while increasing dielectrophoretic deposition efficiency in nanostructured networks.
Modeling of threshold voltage in pentacene organic field-effect transistors
Authors: Ou-Yang Wei , Weis Martin , Taguchi Dai , Chen Xiangyu , Manaka Takaaki , Iwamoto Mitsumasa
Published: June 2010

To understand the physical meaning of threshold voltage in organic field-effect transistors (OFETs), we studied the threshold voltage (shift) dependence on gate-insulator thickness as well as active-layer thickness, by using pentacene OFETs with and without a dipole interlayer between pentacene active layer and SiO2 gate insulator. Results showed that the presence of dipole monolayer caused a large threshold voltage shift and there was a linear relationship between the threshold voltage shift and the layer thickness of pentacene as well as SiO2. Assuming the pentacene film is a dielectric layer and the threshold voltage in pentacene OFET is determined from a zero-electric-field condition at the gate insulator interface, we propose a model based on compensation of the local electric field in the vicinity of semiconductor and gate insulator interface. The model well accounts for both the large negative threshold voltage shift and the linear relation. These findings reveal the importance of interfacial electric field for analyzing organic devices.
Energy barrier, charge carrier balance, and performance improvement in organic light-emitting diodes
Authors: Benor Amare , Takizawa Shin-ya , Pérez-Bolivar C. , Anzenbacher Pavel
Published: June 2010

The charge injection properties of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate anodes are crucial for performance of organic photovoltaics and organic light-emitting diodes (OLEDs). A simple method for tuning hole injection efficiency using UV-ozone is shown to change anode work-function and optimized carriers balance in the devices and improved efficiency in OLEDs. The optimum time of treatment and work-function differs with device architecture.
Coexistence of sign reversal of both magnetization and exchange bias field in the core-shell type La0.2Ce0.8CrO3 nanoparticles
Authors: Manna P. K. , Yusuf S. M. , Shukla R. , Tyagi A. K.
Published: June 2010

We report an extraordinary coexistence of sign reversal of both magnetization and exchange bias field in the La0.2Ce0.8CrO3 nanoparticles. From the high resolution transmission electron microscopy image, and field dependence of thermoremanent and isothermoremanent magnetization measurements, the nanoparticles are found to be of core-shell nature. The core-shell configuration with an antiferromagnetic core of the Cr3+ and Ce3+ spins and a disordered shell with the uncompensated spins, explains the sign reversal of both magnetization and exchange bias field. The present study shows an excellent way of tuning the sign of both magnetization and exchange bias field in a single magnetic system.
Group-theoretical approach to Bloch electron in magnetic field problem
Authors: Ćosić Marko
Published: June 2010

In this paper magnetic-translation group theory is extended to include full rotational symmetry of Hamiltonian. Proper generalization of small representation and star of the representation concepts are derived. Irreducible representations of magnetic-translation group and magnetic-space group are presented. Correct form of symmetrized basis function is derived, reflecting symmetry of the magnetic-point group. From viewpoint of group theory reduction of Hamiltonian symmetry group caused by magnetic field and splitting of energy levels is investigated.
Impact of N- and Ga-face polarity on the incorporation of deep levels in n-type GaN grown by molecular beam epitaxy
Authors: Arehart A. R. , Homan T. , Wong M. H. , Poblenz C. , Speck J. S. , Ringel S. A.
Published: June 2010

Deep levels in N-face and Ga-face n-type GaN grown by plasma-assisted molecular beam epitaxy were detected, analyzed and compared using deep level optical spectroscopy (DLOS) and conventional thermal deep level transient spectroscopy (DLTS), which together enable deep level detection throughout the GaN band gap. A redistribution of band gap states was observed between the two GaN crystal growth polarities but with a similar total trap density. Most significant was a tenfold concentration increase in a trap at EC-0.25 eV that is likely related to nitrogen vacancies for the N-face polarity material, with no significant change for the Ga-vacancy-related level at EC-2.60 eV. The DLOS results suggest that carbon impurities, which generate several GaN band gap states, appear to incorporate differently for both crystal polarities with the potential carbon interstitial at EC-1.28 eV being undetected for N-face material. Finally, low concentrations of several new levels in the N-face n-GaN not previously observed in Ga-face n-GaN were observed.
Current bistability and carrier transport mechanisms of organic bistable devices based on hybrid Ag nanoparticle-polymethyl methacrylate polymer nanocomposites
Authors: Kim Won Tae , Jung Jae Hun , Kim Tae Whan , Son Dong Ick
Published: June 2010

The current bistability and the carrier transport mechanisms of organic bistable devices (OBDs) using Ag nanoparticle-polymethyl methacrylate (PMMA) nanocomposites have been investigated. Current-voltage measurements at 300 K on the Al/Ag nanoparticles embedded in the PMMA layer/indium-tin-oxide devices exhibit a current bistability with an ON/OFF ratio of 103. Write-read-erase-read sequence results demonstrate the switching characteristics of the OBD. The cycling endurance number of the ON/OFF switching for the OBD is above 7×104. The current bistability and carrier transport mechanisms of the OBD fabricated utilizing hybrid Ag nanoparticle-PMMA polymer nanocomposites are described on the basis of the experimental data.
Infrared-wave number-dependent metal–insulator transition in vanadium dioxide nanoparticles
Authors: Lee Kyu Won , Kweon Jin Jung , Lee Cheol Eui , Gedanken A. , Ganesan R.
Published: June 2010

We have studied the metal–insulator transition (MIT) taking place at 340 K in vanadium dioxide nanoparticles. A peculiar nanosize effect on the 10-nm-sized VO2 nanoparticles is reported. While the infrared transmittance at high wave numbers displayed a broad transition behavior, the magnetic susceptibility and infrared transmittance at low wave numbers showed a sharp first-order MIT. Our results suggest that the size effect on the MIT is due to the surface region while the core region undergoes the same MIT as that in the bulk.
Enhancement of ferroelectricity in Cr-doped Ho2Ti2O7
Authors: Dong X. W. , Dong S. , Wang K. F. , Wan J. G. , Liu J.-M.
Published: June 2010

A series of polycrystalline pyrochlore rare-earth titanate Ho2−xCrxTi2O7 are synthesized in order to enhance the ferroelectricity of pyrochlore Ho2Ti2O7. A giant enhancement of polarization P from 0.54 μC/m2 at x=0 up to ∼660 μC/m2 at x=0.4 is obtained, accompanied with an increment of ferroelectric transition point Tc from Tc∼60 K up to Tc∼140 K. A magnetic anomaly at Tc∼140 K together with the polarization response to magnetic field is identified, implying the multiferroic effect in Ho2−xCrxTi2O7.
Metal-cavity surface-emitting microlaser at room temperature
Authors: Lu Chien-Yao , Chang Shu-Wei , Chuang Shun Lien , Germann Tim D. , Bimberg Dieter
Published: June 2010

We propose and realize a substrate-free metal-cavity surface-emitting microlaser with both top and sidewall metal and a bottom distributed Bragg reflector as the cavity structure. The transfer-matrix method is used to design the laser structure based on the round-trip resonance condition inside the cavity. The laser is 2.0 μm in diameter and 2.5 μm in height, and operates at room temperature with continuous-wave mode. Flip-bonding the device to a silicon substrate with a conductive metal provides efficient heat removal. A high characteristic temperature about 425 K is observed from 10 to 27 °C.
Positioning and stretching of actin filaments by electric fields
Authors: Wigge Christoph , Hinssen Horst , Reiss Günter , Herth Simone
Published: June 2010

The alignment of biological filaments on surfaces offers a high potential for controllable geometries in lab-on-a-chip-structures and micrototal analysis systems. Actin is a polar filamentous protein with a diameter of 7–8 nm that can be manipulated with strong electric fields. It is demonstrated that with the use of microelectrodes or nanoelectrodes and electric fields of 20 kV/m single actin filaments can be manipulated, stretched, and positioned between gold electrodes.
Communications: The fractional Stokes–Einstein equation: Application to water
Authors: Harris Kenneth R.
Published: June 2010

Previously [K. R. Harris, J. Chem. Phys. 131, 054503 (2009)] it was shown that both real and model liquids fit the fractional form of the Stokes–Einstein relation [fractional Stokes–Einstein (FSE)] over extended ranges of temperature and density. For example, the self-diffusion coefficient and viscosity of the Lennard-Jones fluid fit the relation (D/T)=(1/η)t with t=(0.921±0.003) and a range of molecular and ionic liquids for which high pressure data are available behave similarly, with t values between 0.79 and 1. At atmospheric pressure, normal and heavy water were also found to fit FSE from 238 to 363 K and from 242 to 328 K, respectively, but with distinct transitions in the supercooled region at about 258 and 265 K, respectively, from t=0.94 (high temperature) to 0.67 (low temperature). Here the recent self-diffusion data of Yoshida et al. [J. Chem. Phys. 129, 214501 (2008)] for the saturation line are used to extend the high temperature fit to FSE to 623 K for both isotopomers. The FSE transition temperature in bulk water can be contrasted with much lower values reported in the literature for confined water.
Unusual metallic-like transport near the percolation threshold
Authors: Bhatia Ravi , Suchand Sangeeth C. S. , Prasad V. , Menon Reghu
Published: June 2010

In multiwall carbon nanotube (MWNT)—polystyrene (PS) composites, a weak temperature dependence of conductivity has been observed at a percolation threshold of 0.4 wt %. The power law [σ(T)∝T0.3] behavior indicates metallic-like behavior, unlike the usual activated transport for systems near the percolation threshold. The low field positive magnetoconductance follows H2 dependence, due to the weak localization in disordered metallic systems. The marginal metallic nature of MWNT-PS at percolation threshold is further verified from the negligible frequency dependence of conductivity, in the temperature range of 300 to 5 K.
A theoretical analysis of time-dependent fragment momenta in indirect photofragmentation
Authors: Henriksen Niels E.
Published: June 2010

We study theoretically diatomic molecules which are prepared in a superposition of quasibound resonance states by a femtosecond laser pulse. An analytical (Landau–Zener-like) result is derived for the momentum distribution of the atomic fragments in the asymptotic force-free region after a single passage of a curve crossing. Furthermore, at later times, simple analytical expressions show how the emerging structures in the momentum distribution are related to the energies of the resonance states.
Temperature-dependent Rabi rotation in semiconductor quantum dots
Authors: Hung K.-M. , Hong W.-J. , Su K.-J. , Shieh T.-H. , Wu K.-Y. , Cheng H. H.
Published: June 2010

The dynamics of exciton coupling to photons and LO-phonons in a three-level quantum-dot system is studied using the Wigner–Weisskopf approach. An analytical solution to the system for a rectangular driving pulse is derived, and the wave function of an exciton is found to form a unit vector directed to the surface of an S2 Bloch hemisphere. For long decoherence times, the vector traces out a temperature (T)-dependent Rabi circle with increase pulse area. An increase in T does not deform the Rabi circle but shrinks its radius. Accordingly, a diverse representational scheme is proposed. These properties expand scenarios to T-dependent regimes.
Magnetodielectric effect in EuZrO3
Authors: Kolodiazhnyi T. , Fujita K. , Wang L. , Zong Y. , Tanaka K. , Sakka Y. , Takayama-Muromachi E.
Published: June 2010

Following recent report on antiferromagnetic ordering in EuZrO3 we performed dielectric measurements of this material as a function of temperature and magnetic field. Dielectric constant of dense EuZrO3 ceramics is 30.1 at 300 K. It gradually decreases upon cooling without any quantum paraelectric behavior; however, below TN=4.1 K it shows a pronounced drop that qualitatively resembles that observed in EuTiO3. We report that dielectric constant of EuZrO3 is magnetic field dependent. The magnitude of the magnetodielectric effect in both EuTiO3 and EuZrO3 is discussed in the light of the recently proposed coupling of the Eu–O–Eu superexchange interactions with electrons involved in partially covalent Ti(Zr)–O bond.
Navigation in New Terrain with Familiar Maps: Masterminding Sociospatial Equality through Resource-Oriented Innovation Policy
Authors: Kasa Sjur , Underthun Anders
Published: June 2010

We explore how political struggles influence innovation policy through a Norwegian case study on the formation of a state-funded research and development program for utilizing natural gas feedstock from the North Sea. Despite the apparent dominance of business, specialized branches of the state, and R&D institutions in the realm of innovation policy, the key argument is that labor unions and regional interests exert considerable influence in shaping national innovation policy, in particular when reflexively exploiting new forms of state accumulation strategies while retaining a defensive stance against deindustrialization. First, we argue that the struggle for state funding to natural-gas-based R&D was particularly effective because appropriate strategic political networks and alliances were mobilized. Second, the construction of strategic arguments to accommodate the social corporatist heritage of state intervention on the one hand and the competition-oriented language of flexible specialization on the other, proved crucial for acceptance as a state strategy. We engage a strategic–relational approach to state theory and argue that this is a useful starting point when studying how particular contexts affect how and why certain innovation policies emerge. In so doing, we also address the lack of political analysis in innovation studies.
Diversity or Disadvantage? Putnam, Goodhart, Ethnic Heterogeneity, and Collective Efficacy
Authors: Twigg Liz , Taylor Joanna , Mohan John
Published: June 2010

Recent debates have suggested that increasing social diversity within Western economies is associated with adverse social consequences such as loss of community and decline of civic society, including an erosion of collective efficacy (ie shared expectations of and mutual engagement by residents in social control). In the UK and US, these debates have been given impetus by concerns about the effects of growing ethnic heterogeneity on community life. Here there is an assumption that heterogeneity undermines social cohesion and makes the established population less willing to share resources, trust fellow citizens, so that it eventually ‘hunkers down’ and withdraws from collective life. To date there are few studies that have examined this in detail across England at the small-area level. The research presented here explores this terrain by exploiting information from the British Crime Survey on two recognised dimensions of collective efficacy: namely, social cohesion and trust, and informal social control. Multivariate, multilevel models were used to determine the importance of individual and area characteristics in the possible explanation of these outcomes, and particular attention was paid to the relative importance of neighbourhood disadvantage over and above neighbourhood diversity. Results suggest that both diversity and disadvantage are statistically associated with reduced levels of social cohesion and trust, and informal social control, but greater substantive importance is attached to neighbourhood disadvantage.
Notions of Materiality and Linearity: The Challenges of Marketing the Hadrian's Wall Place ‘Product’
Authors: Warnaby Gary , Medway Dominic , Bennison David
Published: June 2010

This paper provides a detailed examination of the marketing of Hadrian's Wall in northern England. The focus of this case is built around two themes which encapsulate the complexities and challenges of marketing such a place entity: (1) the Wall's existence as an historical monument of diminished materiality, and (2) its linearity and spatial diffuseness. These themes emphasise the fact that marketing Hadrian's Wall is different from usual place-marketing activity, which is typically focused on more tangible and easily delineated place entities. Hadrian's Wall, by contrast, represents a ‘fuzzy’ place, and the implications of this are explored in relation to jurisdictional, functional, and strategic ‘fissures’ in the place product.
Bridges: a tool for identifying local similarities in long sequences
Authors: Kondrashov Alexey S. , Assis Raquel
Published: June 2010

Summary: Bridges is a heuristic search tool that uses short word matches to rapidly identify local similarities between sequences. It consists of three stages: filtering input sequences, identifying local similarities and post-processing local similarities. As input sequence data are released from memory after the filtering stage, genome-scale datasets can be efficiently compared in a single run. Bridges also includes 20 parameters, which enable the user to dictate the sensitivity and specificity of a search.

Availability: Bridges is implemented in the C programming language and can be run on all platforms. Source code and documentation are available at http://github.com/rassis/bridges.

Contact:  kondrash@umich.edu
Catalyst supports for polymer electrolyte fuel cells
Authors: Subban Chinmayee , Zhou Qin , Leonard Brian , Ranjan Chinmoy , Edvenson Heather M. , DiSalvo F. J. , Munie Semeret , Hunting Janet
Published: June 2010

A major challenge in obtaining long-term durability in fuel cells is to discover catalyst supports that do not corrode, or corrode much more slowly than the current carbon blacks used in today’s polymer electrolyte membrane fuel cells. Such materials must be sufficiently stable at low pH (acidic conditions) and high potential, in contact with the polymer membrane and under exposure to hydrogen gas and oxygen at temperatures up to perhaps 120°C. Here, we report the initial discovery of a promising class of doped oxide materials for this purpose: Ti1−xMxO2, where M=a variety of transition metals. Specifically, we show that Ti0.7W0.3O2is electrochemically inert over the appropriate potential range. Although the process is not yet optimized, when Pt nanoparticles are deposited on this oxide, electrochemical experiments show that hydrogen is oxidized and oxygen reduced at rates comparable to those seen using a commercial Pt on carbon black support.
Turning carbon dioxide into fuel
Authors: Jiang Z. , Xiao T. , Kuznetsov V. L. , Edwards P. P.
Published: June 2010

Our present dependence on fossil fuels means that, as our demand for energy inevitably increases, so do emissions of greenhouse gases, most notably carbon dioxide (CO
2
). To avoid the obvious consequences on climate change, the concentration of such greenhouse gases in the atmosphere must be stabilized. But, as populations grow and economies develop, future demands now ensure that energy will be one of the defining issues of this century. This unique set of (coupled) challenges also means that science and engineering have a unique opportunity—and a burgeoning challenge—to apply their understanding to provide sustainable energy solutions. Integrated carbon capture and subsequent sequestration is generally advanced as the most promising option to tackle greenhouse gases in the short to medium term. Here, we provide a brief overview of an alternative mid- to long-term option, namely, the capture and conversion of CO
2
, to produce sustainable, synthetic hydrocarbon or carbonaceous fuels, most notably for transportation purposes.

Basically, the approach centres on the concept of the large-scale re-use of CO
2
released by human activity to produce synthetic fuels, and how this challenging approach could assume an important role in tackling the issue of global CO
2
emissions. We highlight three possible strategies involving CO
2
conversion by physico-chemical approaches: sustainable (or renewable) synthetic methanol, syngas production derived from flue gases from coal-, gas- or oil-fired electric power stations, and photochemical production of synthetic fuels. The use of CO
2
to synthesize commodity chemicals is covered elsewhere (

Arakawa
et al.
 2001

Chem. Rev.
101
, 953–996); this review is focused on the possibilities for the conversion of CO
2
to fuels. Although these three prototypical areas differ in their ultimate applications, the underpinning thermodynamic considerations centre on the conversion—and hence the utilization—of CO
2
. Here, we hope to illustrate that advances in the science and engineering of materials are critical for these new energy technologies, and specific examples are given for all three examples.

With sufficient advances, and institutional and political support, such scientific and technological innovations could help to regulate/stabilize the CO
2
levels in the atmosphere
and
thereby extend the use of fossil-fuel-derived feedstocks.
Building a mechanistic understanding of predation with GPS-based movement data
Authors: Merrill Evelyn , Sand Håkan , Zimmermann Barbara , McPhee Heather , Webb Nathan , Hebblewhite Mark , Wabakken Petter , Frair Jacqueline L.
Published: June 2010

Quantifying kill rates and sources of variation in kill rates remains an important challenge in linking predators to their prey. We address current approaches to using global positioning system (GPS)-based movement data for quantifying key predation components of large carnivores. We review approaches to identify kill sites from GPS movement data as a means to estimate kill rates and address advantages of using GPS-based data over past approaches. Despite considerable progress, modelling the probability that a cluster of GPS points is a kill site is no substitute for field visits, but can guide our field efforts. Once kill sites are identified, time spent at a kill site (handling time) and time between kills (killing time) can be determined. We show how statistical models can be used to investigate the influence of factors such as animal characteristics (e.g. age, sex, group size) and landscape features on either handling time or killing efficiency. If we know the prey densities along paths to a kill, we can quantify the ‘attack success’ parameter in functional response models directly. Problems remain in incorporating the behavioural complexity derived from GPS movement paths into functional response models, particularly in multi-prey systems, but we believe that exploring the details of GPS movement data has put us on the right path.
Temporal autocorrelation functions for movement rates from global positioning system radiotelemetry data
Authors: Boyce Mark S. , Pitt Justin , Northrup Joseph M. , Morehouse Andrea T. , Knopff Kyle H. , Cristescu Bogdan , Stenhouse Gordon B.
Published: June 2010

Autocorrelation has been viewed as a problem in telemetry studies because sequential observations are not independent in time or space, therefore violating assumptions for statistical inference. Yet nearly all ecological and behavioural data are autocorrelated in both space and time. We argue that there is much to learn about the structure of ecological and behavioural data from patterns of autocorrelation. Such patterns include periodicity in movement and patchiness in spatial data, which can be characterized by an autocorrelogram, semivariogram or spectrum. We illustrate the utility of temporal autocorrelation functions (ACFs) for analysing step-length data from GPS telemetry of wolves (
Canis lupus
), cougars (
Puma concolor
), grizzly bears (
Ursus arctos
) and elk (
Cervus elaphus
) in western Alberta. ACFs often differ by season, reflecting differences in foraging behaviour. In wilderness landscapes, step-length ACFs for predators decay slowly to apparently random patterns, but sometimes display strong daily rhythms in areas of human disturbance. In contrast, step lengths of elk are consistently periodic, reflecting crepuscular activity.
Nocardiopsis arvandica sp. nov., isolated from sandy soil
Authors: Hamedi Javad , Mohammadipanah Fatemeh , Pötter Gabriele , Spröer Cathrin , Schumann Peter , Göker Markus , Klenk Hans-Peter
Published: June 2010

An actinomycete strain, HM7T, was isolated from sandy soil from the banks of the Arvand River, Khoramshahr, Iran. In a study conducted using a polyphasic taxonomic approach, it was found that this strain represented a novel species in the genus Nocardiopsis. Strain HM7T had long, branched substrate mycelia and the aerial mycelium completely fragmented to long chains of rod-shaped spores. The cell wall of strain HM7T contained meso-diaminopimelic acid, galactose and ribose. The predominant phospholipids were phosphatidylglycerol, phosphatidylethanolamine diphosphatidylglycerol, and phosphatidylcholine. The main menaquinones were MK-10(H2), MK-10(H4), MK-10(H0) and MK-9(H2). Strain HM7T showed the highest degree of 16S rRNA gene sequence similarity with Nocardiopsis sinuspersici UTMC 00102T (99.8 %) and Nocardiopsis quinghaiensis YIM 28A4T (99.3 %), but differed significantly from these type strains based on DNA–DNA hybridization data (37.6 and 38.9 % relatedness, respectively). Physiological, biochemical and phenotypic characteristics allowed strain HM7T to be differentiated from related species. On the basis of results from phenotypic and phylogenetic analyses, strain HM7T is considered to represent a novel species of the genus Nocardiopsis, for which the name Nocardiopsis arvandica sp. nov. is proposed; the type strain of this species is HM7T ( = UTMC 00103T = DSM 45278T = CCUG 58831T).
Arabidopsis ROOT UVB SENSITIVE2/WEAK AUXIN RESPONSE1Is Required for Polar Auxin Transport
Authors: Ge L. , Peer W. , Robert S. , Swarup R. , Ye S. , Prigge M. , Cohen J.D. , Friml J. , Murphy A. , Tang D. , Estelle M.
Published: June 2010

Auxin is an essential phytohormone that regulates many aspects of plant development. To identify new genes that function in auxin signaling, we performed a genetic screen for Arabidopsis thaliana mutants with an alteration in the expression of the auxin-responsive reporter DR5rev:GFP (for green fluorescent protein). One of the mutants recovered in this screen, called weak auxin response1 (wxr1), has a defect in auxin response and exhibits a variety of auxin-related growth defects in the root. Polar auxin transport is reduced in wxr1 seedlings, resulting in auxin accumulation in the hypocotyl and cotyledons and a reduction in auxin levels in the root apex. In addition, the levels of the PIN auxin transport proteins are reduced in the wxr1 root. We also show that WXR1 is ROOT UV-B SENSITIVE2 (RUS2), a member of the broadly conserved DUF647 domain protein family found in diverse eukaryotic organisms. Our data indicate that RUS2/WXR1 is required for auxin transport and to maintain the normal levels of PIN proteins in the root.
The Molecular Basis for Distinct Pathways for Protein Import into Arabidopsis Chloroplasts
Authors: Inoue Hitoshi , Rounds Caleb , Schnell Danny J.
Published: June 2010

The translocons at the outer envelope membrane of chloroplasts (TOCs) initiate the import of thousands of nucleus-encoded proteins into the organelle. The identification of structurally and functionally distinct TOC complexes has led to the hypothesis that the translocons constitute different import pathways that are required to coordinate the import of sets of proteins whose expression varies in response to organelle biogenesis and physiological adaptation. To test this hypothesis, we examined the molecular basis for distinct TOC pathways by analyzing the functional diversification among the Toc159 family of TOC receptors. We demonstrate that the N-terminal A-domains of the Toc159 receptors regulate their selectivity for preprotein binding. Furthermore, the in vivo function of the two major Toc159 family members (atToc159 and atToc132) can be largely switched by swapping their A-domains in transgenic Arabidopsis thaliana. On the basis of these results, we propose that the A-domains of the Toc159 receptors are major determinants of distinct pathways for protein import into chloroplasts.