bluuebunny/crossref_metadata_2025 huggingface dataset:
TWO OUT OF THREE AIN'T BAD: A COMMENT ON “THE AMBIGUITY AVERSION LITERATURE: A CRITICAL ASSESSMENT”
Authors: Siniscalchi Marciano
Published: November 2009

Al-Najjar and Weinstein (2009) propose to scrutinize the implications of recent theories of ambiguity in dynamic settings. They conclude that such implications are so unreasonable as to cast doubts on the legitimacy of the theories under consideration. The present paper argues that the seemingly unreasonable implications highlighted by Al-Najjar and Weinstein can be understood as the result of basic trade-offs that arise naturally in the presence of ambiguity. In particular, Al-Najjar and Weinstein are uncomfortable with the possibility that an ambiguity-averse individual may reject freely available information; however, this phenomenon simply reflects a trade-off between the intrinsic value of information, which is positive even in the presence of ambiguity, and the value of commitment.
The effect of alcohol and nicotine abuse on gene expression in the brain
Authors: Flatscher-Bader Traute , Wilce Peter A.
Published: November 2009

Alcohol intake at levels posing an acute heath risk is common amongst teenagers. Alcohol abuse is the second most common mental disorder worldwide. The incidence of smoking is decreasing in the Western world but increasing in developing countries and is the leading cause of preventable death worldwide. Considering the longstanding history of alcohol and tobacco consumption in human societies, it might be surprising that the molecular mechanisms underlying alcohol and smoking dependence are still incompletely understood. Effective treatments against the risk of relapse are lacking. Drugs of abuse exert their effect manipulating the dopaminergic mesocorticolimbic system. In this brain region, alcohol has many potential targets including membranes and several ion channels, while other drugs, for example nicotine, act via specific receptors or binding proteins. Repeated consumption of drugs of abuse mediates adaptive changes within this region, resulting in addiction. The high incidence of alcohol and nicotine co-abuse complicates analysis of the molecular basis of the disease. Gene expression profiling is a useful approach to explore novel drug targets in the brain. Several groups have utilised this technology to reveal drug-sensitive pathways in the mesocorticolimbic system of animal models and in human subjects. These studies are the focus of the present review.
Long-term skill proceduralization in schizophrenia
Authors: RÉMILLARD SOPHIE , POURCHER EMMANUELLE , COHEN HENRI
Published: November 2009

Previous studies had revealed no specific effect under haloperidol (typical) and risperidone (atypical) neuroleptic (NLP) treatments for schizophrenia (SZ) on a variety of neurocognitive functions relying on the dopaminergic meso-cortico-limbic system (Rémillard et al., 2005, 2008). Considering the different affinities of D2dopamine receptors for typical and atypical NLPs, these drugs may differentially affect the functions of the striatum, a determinant brain structure involved in procedural learning. The influence of risperidone (2–6 mg) and haloperidol (2–40 mg) on a nonmotor procedural task involving semantically related pairs of words with inverted letters was investigated in this double-blind study. The performance of 26 patients with SZ, randomly assigned to risperidone or haloperidol, was compared to that of 18 healthy controls at baseline, 3, 6, and 12 months. Results revealed that all patients with SZ exhibited slower reading speed of the word pairs than healthy controls at all assessment periods. In addition, procedural learning – characterized as a significant decrease in the time taken to read aloud the target word pairs – was more impaired in the haloperidol- than in the risperidone-treated group at all assessment periods. Healthy controls showed steady improvement in reading speed over the 12 months of the study, in contrast to SZ patients, who reached a plateau in their capacity to improve mirror-reading skill over time. However, all SZ participants in the study showed near normal learning profiles from exposure to semantic associations embedded in the procedural memory task, providing evidence for the preservation of associative connections in the semantic network of these patients. The observed impairment in procedural learning in SZ may thus reflect, at least in part, the influence of neuroleptic medication on striatal functions. (JINS, 2010,16, 148–156.)
Sensitivity of the water resources of Rio Yaqui Basin, Mexico, to agriculture extensification under multiscale climate conditions
Authors: Muñoz‐Arriola Francisco , Avissar Roni , Zhu Chunmei , Lettenmaier Dennis P.
Published: November 2009

The Yaqui River Basin (YRB) is the most important wheat‐producing region in Mexico. The main source of irrigation water in the Yaqui basin (over 80%) is surface water. Crop production sustainability is therefore closely linked to YRB streamflow and potentially to its sensitivity to climate variability and land use changes. We study the sensitivity of streamflow to land cover change resulting primarily from conversion of natural vegetation to unirrigated agriculture within the basin. We also examine how this sensitivity is influenced by midscale (North American Monsoon) and large‐scale (El Niño–Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO)) climate regimes. Streamflow simulations using the variable Infiltration Capacity Model were performed in which current land use was altered incrementally within the three major subbasins of the YRB. In general, we found that the sensitivity of basin runoff to ENSO‐and PDO‐related variations in precipitation was much greater than to land cover–related changes and was highest during winter. Furthermore, climate and land cover runoff sensitivities appear to be related; in El Niño (generally wet) years the sensitivity of streamflow to land cover change can be four times higher than in La Niña (generally dry) years. The sensitivity of streamflow to PDO phase was smaller. Streamflow sensitivities to climate were the highest when PDO and ENSO were in phase. We conclude that climate variability exerts stronger controls on the surface hydrology than does land use change associated with the extensification of agriculture. For instance, flows in El Niño versus La Niña years differed by 76% in winter and 16% in summer, whereas maximum monthly (winter) flow changes were at most 4%.
A viscoelastic and afterslip postseismic deformation model for the 1964 Alaska earthquake
Authors: Suito Hisashi , Freymueller Jeffrey T.
Published: November 2009

We developed a 3‐D viscoelastic model, in concert with an afterslip model, to describe the postseismic deformation following the 1964 Alaska earthquake. Our model incorporates a realistic geometry including an elastic slab with very low dip angle. These geometric factors are important and require a reanalysis of the 1964 coseismic model. Our coseismic model differs from previous models in that the Montague Island splay fault extends farther along the Kenai Peninsula coast, and as a result, slip on the megathrust in that region is smaller. We computed postseismic deformation models using a range of mantle viscosities with Maxwell relaxation time τ of 1 to 50 years, with a best estimate of 20 years. The viscoelastic model explains most of the trenchward motion observed in the present velocity field but has little impact on cumulative 1965 to present uplifts. After removing the viscoelastic response, the largest residual cumulative uplifts were located downdip from areas of largest coseismic slip area, and we explain them using an afterslip model, constrained in space by the observed cumulative postseismic uplifts and in time by tide gauge records. No single mechanism can explain both the 30 years of cumulative uplift and the present velocities, but a combination of viscoelastic relaxation, afterslip, interseismic elastic deformation, and motion of southern Alaska relative to North America explains the first‐order features of the observations. Forty years after the earthquake, the present‐day velocities contain a significant component of postseismic deformation, so very long lived postseismic deformation plays an important role in the subduction zone earthquake cycle for great earthquakes.
Improved modeling of the Arctic halocline with a subgrid‐scale brine rejection parameterization
Authors: Nguyen A. T. , Menemenlis D. , Kwok R.
Published: November 2009

The halocline in the Arctic Ocean plays an important role in regulating heat exchange at the bottom of the mixed layer and it has a direct effect on the ocean sea ice energy balance and sea ice mass balance. Modeling the halocline, however, remains a challenge in current state‐of‐the‐art coupled ocean sea ice models including those that participated in the Arctic Ocean Model Intercomparison Project. In this study, we successfully reproduce a cold halocline in the Canada Basin by implementing a subgrid‐scale brine rejection parameterization in an ocean general circulation model. The brine rejection scheme improves the solution by redistributing surface salts rejected during sea ice formation to their neutral buoyancy depths. The depths are based on salt plume physics and published laboratory and numerical experiments. Compared with hydrographic data from 1993 to 2004, distribution of most of the rejected salt to the bottom of the mixed layer seems to yield the lowest model‐data misfits. We also show that the model's mixed layer depth is sensitive to the background diffusivity ν used in the k‐profile parameterization vertical mixing scheme. A background diffusivity of 10−6 m2/s in combination with brine rejection scheme described herein yield the best simulation of the Arctic halocline.
Modeling of high‐latitude spring freshet from AMSR‐E passive microwave observations
Authors: Yan Fenglin , Ramage Joan , McKenney Rose
Published: November 2009

Snowmelt runoff in high latitudes has significant impacts on global climatic and hydrologic systems. Snowmelt timing and snow water equivalent (SWE) from the Advanced Microwave Scanning Radiometer for EOS (AMSR‐E) are inputs to the new flux‐based SWEHydro model to simulate the spring streamflow without meteorological data for high‐latitude, snow‐dominated drainages. The model was developed for the Ross River (7250 km2) and tested on the Pelly River (49,000 km2), nested tributaries to the Yukon River. The model uses four parameters: snowmelt rate during and after the melt transition (as defined by passive microwave observations), and flow timing during and after the melt transition. A normalized mismatch function was used to calculate the error compared with observed discharge. Curves were ranked by lowest error in freshet timing, peak timing, and magnitude. Melt timing is a good predictor of freshet timing across years and basins. The system is most sensitive to the flow timing after the transition.
Thickness-induced resonance-based complex permittivity measurement technique for barium strontium titanate ceramics at microwave frequency
Authors: Xia Song , Xu Zhuo , Wei Xiaoyong
Published: November 2009

Thickness-induced resonance would be the major factor of uncertainty for complex permittivity measurement by using transmission/reflection method when the thickness of sample is several integer multiples of the half wavelength. A new technique for complex permittivity measurement was presented in this paper using the thickness-induced resonance for barium strontium titanate (BST) ceramics at microwave frequency. Simulated and experimental results show that there are some resonance peaks on the transmittance versus frequency curve and the complex permittivity can be calculated from the resonance.
On the application of a generalized dressing method to the integration of variable-coefficient coupled Hirota equations
Authors: Su Ting , Dai Hui-Hui , Geng Xianguo
Published: November 2009

Based on the generalized dressing method, we propose two variable-coefficient coupled Hirota equations and derive their Lax pairs. The generalized dressing method is applied to study these variable-coefficient coupled Hirota equations, from which explicit solutions of the two equations and their reductions are constructed.
High contrast chiral nematic liquid crystal device using negative dielectric material
Authors: Choi Su Seok , Castles Flynn , Morris Stephen M. , Coles Harry J.
Published: November 2009

A liquid crystal device is demonstrated using a short-pitch (260 nm) chiral nematic with negative dielectric anisotropy. Due to dielectric coupling, an in-plane electric field switches the liquid crystal between the standing-helix (field-off, “dark” state) and lying-helix (field-on, transmissive state) configurations. We report experimental results on the optical transmission as a function of the applied field, the response time (as short as 35 microseconds) and the contrast ratio (1000:1).
Superconducting tunneling spectroscopy of a carbon nanotube quantum dot
Authors: Dirks Travis , Chen Yung-Fu , Birge Norman O. , Mason Nadya
Published: November 2009

We report results on superconducting tunneling spectroscopy of a carbon nanotube quantum dot. Using a three-probe technique that includes a superconducting tunnel probe, we map out changes in conductance due to band structure, excited states, and end-to-end bias. The superconducting probe allows us to observe enhanced spectroscopic features, such as robust signals of both elastic and inelastic cotunneling. We also see evidence of inelastic scattering processes inside the quantum dot.
Tb
3
+
luminescence by energy transfer from Eu2+ in (Sr,Ba)2SiO4 phosphor
Authors: Hiramatsu Ryosuke , Ishida Kunio , Aiga Fumihiko , Fukuda Yumi , Matsuda Naotoshi , Asai Hironori
Published: November 2009

( Sr , Ba ) 2 SiO 4 phosphors co-doped with Tb3+ and Eu2+ were prepared by a conventional solid-state reaction method. Prepared (Sr,Ba)2SiO4:Tb,Eu phosphors had characteristic luminescent spectra excited under near-UV excitation in which both the broadband spectrum assigned to Eu2+ and the narrowband spectrum assigned to Tb3+ are observed, although Tb3+ is inactive with this photon energy in general. The sudden emergence of the Tb3+ luminescence shows that Eu2+–Tb3+ energy transfer is possible in the phosphor. We also studied the energy transfer mechanism in terms of the resonant energy transfer theory and found that the crystal structure of the host material Sr2SiO4 plays an important role in the luminescence properties of the phosphor. The Eu2+–Tb3+ energy transfer is ascribed to the overlap between the shorter Eu2+ luminescence band from the Sr2SiO4 crystal structure with two Sr sites and D54 energy level of Tb3+ ion. Therefore, this phosphor has a potential for application to white light-emitting diodes excited by near-UV light.
Magnetic properties of Fe–Cu alloys prepared by pulsed electrodeposition
Authors: Noce R. D. , Gomes O. D. M. , de Magalhães S. D. , Wolf W. , Guimarães R. B. , de Castro A. C. , Pires M. J. M. , Macedo W. A. A. , Givord D. , Barthem V. M. T. S.
Published: November 2009

Fe x Cu 100 − x metastable alloys were prepared by pulsed electrodeposition for 5<x<85. The Fe-rich alloys crystallize in the bcc structure of α-Fe and the Fe-poor ones in the fcc structure of Cu. The magnetic properties of the ferromagnetic Fe-rich alloys (x>50) are reminiscent of those observed in Fe–Cu alloys prepared by other methods. The Curie temperature decreases regularly with decreasing x. In the Fe-poor alloys (x≤30), the observed properties indicate that Fe-rich clusters form within a Cu-rich matrix. In the x=10 alloy, the Fe clusters are found to be superparamagnetic at room temperature, but a superferromagnetic order develops below a critical temperature of about 120 K. It is suggested that the intercluster coupling is mediated by Ruderman–Kittel–Kasuya–Yosida interactions which are predominantly positive due to the very short intercluster distances.
Recombination lifetimes in highly aluminum-doped silicon
Authors: Schmidt Jan , Thiemann Nils , Bock Robert , Brendel Rolf
Published: November 2009

We show that the recombination lifetimes measured in highly aluminum-doped p-type silicon (Al-p+) regions, fabricated by means of screen printing and firing of aluminum paste, are three orders of magnitude larger than the lifetimes expected from the extrapolation of the lifetime data measured on aluminum-doped Czochralski-grown silicon wafers. Solar cell simulations demonstrate that the lifetime of 130 ns measured in Al-p+ regions with an aluminum doping concentration of ∼2×1018 cm−3 enables solar cell open-circuit voltages of 670 mV and energy conversion efficiencies of 21% on n-type silicon wafers. These results prove that the efficiency potential of screen-printed Al-p+ emitters for the application to rear-junction n-type silicon solar cells is much higher than traditionally assumed.
One-dimensional quantum waveguide theory of Rashba electrons
Authors: Liu Duan-Yang , Xia Jian-Bai , Chang Yia-Chung
Published: November 2009

The ballistic spin transport in one-dimensional waveguides with the Rashba effect is studied. Due to the Rashba effect, there are two electron states with different wave vectors for the same energy. The wave functions of two Rashba electron states are derived, and it is found that their phase depend on the direction of the circuit and the spin directions of two states are perpendicular to the circuit, with the +π/2 and −π/2 angles, respectively. The boundary conditions of the wave functions and their derivatives at the intersection of circuits are given, which can be used to investigate the waveguide transport properties of Rashba spin electron in circuits of any shape and structure. The eigenstates of the closed circular and square loops are studied by using the transfer matrix method. The transfer matrix M(E) of a circular arc is obtained by dividing the circular arc into N segments and multiplying the transfer matrix of each straight segment. The energies of eigenstates in the closed loop are obtained by solving the equation det[M(E)−I]=0. For the circular ring, the eigenenergies obtained with this method are in agreement with those obtained by solving the Schrödinger equation. For the square loop, the analytic formula of the eigenenergies is obtained first. The transport properties of the AB ring and AB square loop and double square loop are studied using the boundary conditions and the transfer matrix method. In the case of no magnetic field, the zero points of the reflection coefficients are just the energies of eigenstates in closed loops. In the case of magnetic field, the transmission and reflection coefficients all oscillate with the magnetic field; the oscillating period is Φm=hc/e, independent of the shape of the loop, and Φm is the magnetic flux through the loop. For the double loop the oscillating period is Φm=hc/2e, in agreement with the experimental result. At last, we compared our method with Koga’s experiment.
Effect of indium content on performance and reliability of InGaN/GaN light-emitting diodes
Authors: Li Z. L. , Tripathy S. , Lai P. T. , Choi H. W.
Published: November 2009

While longer wavelength emission from InGaN/GaN light-emitting diodes (LEDs) can be achieved by increasing the indium (In) content in the quantum wells, the increased In content gives rise to side effects to the material and device performance and reliability. It was found that the induced strain in the wafer and the density of threading dislocations increase with increasing In content. From current-voltage and 1/f noise measurements, it was observed that the leakage currents, static resistance, and noise magnitudes rise monotonically with increasing emission wavelength (In composition), which can be attributed to higher defect concentrations. After undergoing a 1000 h reliability test, it was discovered that the optical degradation rates for the longer wavelength green LEDs were significantly higher than those of shorter wavelength.
Polarimetry and Schlieren diagnostics of underwater exploding wires
Authors: Fedotov-Gefen A. V. , Krasik Ya. E.
Published: November 2009

Nondisturbing laser-probing polarimetry (based on the Faraday and Kerr effects) and Schlieren diagnostics were used in the investigation of underwater electrical wire explosion. Measuring the polarization plane rotation angle of a probing laser beam due to the Faraday effect allows one to determine an axially resolved current flowing through the exploding wire, unlike commonly used current probes. This optical method of measuring current yields results that match those obtained using a current viewing resistor within an accuracy of 10%. The same optical setup allows simultaneous space-resolved measurement of the electric field using the Kerr effect. It was shown that the maximal amplitude of the electric field in the vicinity of the high-voltage electrode is ∼80 kV/cm and that the radial electric field is <1 MV/cm during the wire explosion. Finally, it was shown that the use of Schlieren diagnostics allows one to obtain qualitatively the density distribution behind the shock wave front, which is important for the determination of the energy transfer from the discharge channel to the generated water flow.
Impact of postgrowth annealing on spin-glass ordering and exchange bias in SrMn3O6−δ nanoribbons
Authors: Yu J. Y. , Tang S. L. , Zhai L. , Deng Y. , Shi Y. G. , Zhang X. K. , Du Y. W.
Published: November 2009

The magnetic properties of as-grown single-crystal SrMn3O6−δ nanoribbons synthesized by a simple molten-salt method can be significantly improved by a heat-treatment procedure, which enhances the ferromagnetism and spin-glass behavior. These enhanced properties might originate from a spin structure modulated by the thermodynamical equilibrium nonuniform oxygen distribution. Measurements of ac susceptibility prove the existence of a spin-glass phase in the postgrowth annealing SrMn3O6−δ nanoribbons, which differs from the only antiferromagnetic phase in the corresponding bulk material. Asymmetric magnetization hysteresis loops observed in applied magnetic fields H≤5 T are attributed to an exchange coupling between the spin-glass shell and the antiferromagnetic core of postgrowth annealing SrMn3O6−δ nanoribbons. Results suggest that the intrinsic phase inhomogeneity due to the surface effects of the nanostructural manganites may induce exchange anisotropy, which is of special interests for potential application in multifunctional spintronic devices.
The cooling field and the exchange bias in ferromagnet/antiferromagnet bilayers
Authors: Xu X. Y. , Tian H. Y. , Qian X. , Hu J. G.
Published: November 2009

The effect of the cooling field (hcf) on the exchange bias (hE) has been investigated in ferromagnet/antiferromagnet (FM/AFM) bilayers with the different types of interface exchange coupling. The results show that for the antiferromagnetic interface coupling, hE can change from negative values to positive ones with increasing hcf as the direction of cooling field approaches that of the AFM hard axis. However, hE is commonly positive when the cooling field is applied near along the AFM easy axis. On the other hand, for the ferromagnetic interface coupling, the system always exhibits a negative exchange bias while its magnitude depends slowly on hcf. Moreover, it is found that the sign of hE is determined by the interfacial spin configuration between the FM and the AFM after field cooling procedure. The cooling field may play a decisive role in the creation of the interfacial spin configuration for the exchange bias, not only by the interaction between the Zeeman energy of the spins in the external magnetic field and the antiferromagnetic coupling at the FM/AFM interface, but also by the effect of the uniaxial anisotropy of AFM. Particularly, our results highlight the important role of the direction of the hcf with respect to easy axis of the AFM.
Theoretical analysis of thermally tunable microring resonator filters made of dielectric-loaded plasmonic waveguides
Authors: Tsilipakos Odysseas , Yioultsis Traianos V. , Kriezis Emmanouil E.
Published: November 2009

Microring resonator filters, which are made of dielectric-loaded surface plasmon polariton waveguides and operate in the telecom spectral range, are thoroughly analyzed by means of vectorial three dimensional (3D) finite element method (FEM) simulations. The filters’ functional characteristics, such as the resonant frequencies where the transmission minima occur, the free spectral range, the extinction ratio, and the minima linewidth associated with the quality factor of the resonances, are investigated for different values of the key structural parameters, namely, the ring radius and the gap separating the bus waveguide from the ring. The rigorous 3D-FEM simulations are qualitatively complemented by a simplified model. Apart from the harmonic propagation simulations, the uncoupled microring is treated as an eigenvalue problem, and the frequencies of the resonances are compared with those of the transmission minima. Furthermore, the possibility of exploiting the thermally tuned microring resonator filter as a switching element is explored. The shift in the transmission minima is quantified when the ring’s refractive index is altered by virtue of Ohmic heating, and in addition to that, the temporal response is assessed by solving the transient problem.
Effects of Mn doping on dielectric and ferroelectric properties of (Pb,Sr)TiO3 films on (111) Pt/Ti/SiO2/Si substrates
Authors: Yang J. , Meng X. J. , Shen M. R. , Sun J. L. , Chu J. H.
Published: November 2009

A series of Mn doped Pb0.5Sr0.5TiO3 (PSMT) films with dopant concentrations from 0 to 10 mol % was fabricated on (111) Pt/Ti/SiO2/Si substrates by chemical solution deposition. Their microstructure, ferroelectric, and dielectric properties were investigated, and Mn doping was found to have a significant influence on the properties of (Pb,Sr)TiO3 film. The improved microstructure with increased grain size, remnant polarization, dielectric permittivity and its tunability by dc electric field, and reduced coercive field and dielectric loss was observed in the Mn doped samples. A PSMT film with 0.5 mol % Mn dopants exhibits the optimum characteristics with maximal remnant polarization (2Pr=25.28 μC/cm2), dielectric permittivity (1427) and tunability (74.5%, at 100 kHz), and minimal dielectric loss (0.015) at 1 kHz. The improvement was attributed to the improved microstructure, enhanced displacement of polar ions, and, most importantly, the suppression of oxygen-vacancy-induced ferroelectric domain pinning, which was well verified in terms of Rayleigh law. Finally, the evolution of oxygen-vacancy concentration modulated by the Mn doping in PSMT films was discussed.
The method of Ostrogradsky, quantization, and a move toward a ghost-free future
Authors: Nucci M C , Leach P G L
Published: November 2009

The method of Ostrogradsky has been used to construct a first-order Lagrangian, hence Hamiltonian, for the fourth-order field-theoretical model of Pais–Uhlenbeck with unfortunate results when quantization is undertaken since states with negative norm, commonly called “ghosts,” appear. We propose an alternative route based on the preservation of symmetry and this leads to a ghost-free quantization.
Pseudoduality between symmetric space sigma models
Authors: Sarisaman Mustafa
Published: November 2009

We study the pseudoduality transformation on the symmetric space sigma models. We switch the Lie group-valued pseudoduality equations to Lie algebra-valued ones, which leads to an infinite number of pseudoduality equations. We obtain an infinite number of conserved currents on the tangent bundle of the pseudodual manifold. We show that there can be mixing of decomposed spaces with each other, which leads to mixings of the following expressions. We obtain the mixing forms of curvature relations and one-loop renormalization group beta functions by means of these currents.
Capillary liquid bridges in atomic force microscopy: Formation, rupture, and hysteresis
Authors: Men Yumei , Zhang Xianren , Wang Wenchuan
Published: November 2009

Atomic force microscopy (AFM) can work in a variety of environment with different humidities. When the tip of AFM approaches a sample, the measured adhesion force would be significantly affected by the presence of nanometer-sized liquid bridge. The formation and rupture of liquid bridges can occur either through equilibrium or nonequilibrium process. In this work, the liquid bridges are assumed to be in thermodynamic equilibrium with the surrounding vapor medium. To study theoretically the stability of liquid bridge, a constraint is added into the lattice density functional theory to stabilize a series of bridges with different radii at a given tip-substrate distance. With the help of the constraint, we can identify not only stable and metastable states but also transition states for the formation and rupture of liquid bridges. Using this constrained method we calculate the energy barriers involved in the formation and rupture of the liquid bridges, respectively, and then discuss their stability as well as the origin of the hysteresis behavior observed with atomic force microscope measurements. On the whole, the calculated force-distance curves are found to be qualitatively in agreement with experimental observations. The energy barriers for the formation and rupture of liquid bridges are also analyzed as a function of tip-sample distance, humidity, and tip-fluid interaction.
Probing C–O bond activation on gas-phase transition metal clusters: Infrared multiple photon dissociation spectroscopy of Fe, Ru, Re, and W cluster CO complexes
Authors: Lyon Jonathan T. , Gruene Philipp , Fielicke André , Meijer Gerard , Rayner David M.
Published: November 2009

The binding of carbon monoxide to iron, ruthenium, rhenium, and tungsten clusters is studied by means of infrared multiple photon dissociation spectroscopy. The CO stretching mode is used to probe the interaction of the CO molecule with the metal clusters and thereby the activation of the C–O bond. CO is found to adsorb molecularly to atop positions on iron clusters. On ruthenium and rhenium clusters it also binds molecularly. In the case of ruthenium, binding is predominantly to atop sites, however higher coordinated CO binding is also observed for both metals and becomes prevalent for rhenium clusters containing more than nine atoms. Tungsten clusters exhibit a clear size dependence for molecular versus dissociative CO binding. This behavior denotes the crossover to the purely dissociative CO binding on the earlier transition metals such as tantalum.
Generalized log-likelihood functions and Bregman divergences
Authors: Wada Tatsuaki
Published: November 2009

Based on a two-parameter generalization of Gauss’ law of error, a generalized log-likelihood is related to a Bregman divergence. This relation is a two-parameter generalization of the well-known relation between log-likelihood and Kullback–Leibler divergence.
An ultralow noise preamplifier for low frequency noise measurements
Authors: Cannatà Gianluca , Scandurra Graziella , Ciofi Carmine
Published: November 2009

Low frequency noise measurements are among the most sensitive tools for the investigation of the quality and of the reliability of semiconductor devices. The sensitivity that can be obtained depends on the background noise of the low noise preamplifier coupled to the device under test (DUT) that, at very low frequencies, is dominated by flicker noise. The low frequency noise produced by the DUT, on the other end, is very often the most interesting signal to be detected and analyzed. In this work we propose a very simple topology for the realization of a general purpose low noise preamplifier whose noise performances, at very low frequencies (below 10 Hz), are significantly better than those that can be obtained by the most popular commercial instrumentation. Indeed, a gain of 80 dB with a pass band extending from a few tens of mHz up to a few kHz with an equivalent input voltage noise as low as 14 nV/√Hz (100 mHz), 1.4 nV/√Hz (1 Hz), 1.0 nV/√Hz (10 Hz), and 0.8 nV/√Hz (1 kHz) are consistently obtained by using quite standard electronic components and with no need for trimming and/or calibration steps. Moreover, the junction field-effect transistor input stage of the amplifier is characterized by an equivalent input current noise below 4 fA/√Hz in the entire bandwidth, resulting in negligible background noise degradation for DUT impedances in excess of 100 kΩ.
Electron density measurements of a field-reversed configuration plasma using a novel compact ultrastable second-harmonic interferometer
Authors: Brandi F. , Giammanco F. , Harris W. S. , Roche T. , Trask E. , Wessel F. J.
Published: November 2009

A compact high-sensitivity second-harmonic interferometer for line-integrated electron density measurements on a large plasma machine is presented. The device is based on a fiber coupled near-infrared continuous-wave Nd:YAG laser and is remotely controlled. The performances of the instrument are tested on the Irvine field-reversed configuration machine, and a sensitivity of few 1014 cm−2 in measuring line integrated electron density is demonstrated with a time resolution of a few microseconds. The interferometer is self calibrated, has an impressive stability, and it does not require any further alignment after proper installation. These features make this device a real turn-key system suitable for electron density measurement in large plasma machines.
Continuous wave terahertz wave spectrometer based on diode laser pumping: Potential applications in high resolution spectroscopy
Authors: Tanabe Tadao , Ragam Srinivasa , Oyama Yutaka
Published: November 2009

We constructed a high resolution terahertz (THz) spectroscopic system with an automatic scanning control using a continuous wave (cw) THz wave generator based on difference frequency generation method by excitation of phonon-polariton mode in GaP. The pump and signals lasers were compact, tunable external cavity laser, and distributed feedback (DFB) lasers, respectively. The generated THz waves were tuned automatically by changing the temperature of the DFB laser using a system control. We present the water vapor transmission characteristics of the THz wave and also absorption spectrum of a white polyethylene in the frequency range of 1.97–2.45 THz. The spectroscopic measurements performed at an output power level of 2 nW, which was obtained with a 15-mm-long GaP crystal at 2 THz. The advantage of this cw THz spectrometer is wide frequency tuning range (0.7–4.42 THz) with an estimated linewidth of full width at quarter maximum <8 MHz and this system has a potential application in high resolution spectroscopy.
Measurements of total peroxy and alkyl nitrate abundances in laboratory-generated gas samples by thermal dissociation cavity ring-down spectroscopy
Authors: Paul Dipayan , Furgeson Amanda , Osthoff Hans D.
Published: November 2009

A novel measurement technique, thermal dissociation cavity ring-down spectroscopy (TD-CRDS), for rapid (1 s time resolution) and sensitive (precision ∼100 parts per trillion by volume (10−12; pptv)) quantification of total peroxy nitrate (ΣPN) and total alkyl nitrate (ΣAN) abundances in laboratory-generated gas mixtures is described. The organic nitrates are dissociated in a heated inlet to produce NO2, whose concentration is monitored by pulsed-laser CRDS at 532 nm. Mixing ratios are determined by difference relative to a cold inlet reference channel. Conversion of laboratory-generated mixtures of AN in zero air (at an inlet temperature of 450 °C) is quantitative over a wide range of mixing ratios (0–100 parts per billion by volume (10−9, ppbv)), as judged from simultaneous measurements of NOy using a commercial NO–O3 chemiluminescence monitor. Conversion of PN is quantitative up to about 4 ppbv (at an inlet temperature of 250 °C); at higher concentrations, the measurements are affected by recombination reactions of the dissociation products. The results imply that TD-CRDS can be used as a generic detector of dilute mixtures of organic nitrates in air at near-ambient concentration levels in laboratory experiments. Potential applications of the TD-CRDS technique in the laboratory are discussed.
Design and characterization of a high-power ultrasound driver with ultralow-output impedance
Authors: Lewis George K. , Olbricht William L.
Published: November 2009

We describe a pocket-sized ultrasound driver with an ultralow-output impedance amplifier circuit (less than 0.05 Ω) that can transfer more than 99% of the voltage from a power supply to the ultrasound transducer with minimal reflections. The device produces high-power acoustical energy waves while operating at lower voltages than conventional ultrasound driving systems because energy losses owing to mismatched impedance are minimized. The peak performance of the driver is measured experimentally with a PZT-4, 1.54 MHz, piezoelectric ceramic, and modeled using an adjusted Mason model over a range of transducer resonant frequencies. The ultrasound driver can deliver a 100 Vpp (peak to peak) square-wave signal across 0–8 MHz ultrasound transducers in 5 ms bursts through continuous wave operation, producing acoustic powers exceeding 130 W. Effects of frequency, output impedance of the driver, and input impedance of the transducer on the maximum acoustic output power of piezoelectric transducers are examined. The small size, high power, and efficiency of the ultrasound driver make this technology useful for research, medical, and industrial ultrasonic applications.
Buoyancy-driven convection around exothermic autocatalytic chemical fronts traveling horizontally in covered thin solution layers
Authors: Rongy L. , De Wit A.
Published: November 2009

Spatial variations of concentrations and temperature across exothermic chemical fronts can initiate buoyancy-driven convection. We investigate here theoretically the spatiotemporal dynamics arising from such a coupling between exothermic autocatalytic reactions, diffusion, and buoyancy-driven flows when an exothermic autocatalytic front travels perpendicularly to the gravity field in a thin solution layer. To do so, we numerically integrate the incompressible Stokes equations coupled to evolution equations for the concentration of the autocatalytic product and temperature through buoyancy terms proportional to, respectively, a solutal RC and a thermal RT Rayleigh number. We show that exothermic fronts can exhibit new types of dynamics in the presence of convection with regard to the isothermal system. In the cooperative case (RC and RT are of the same sign), the dynamics asymptotes to one vortex surrounding, deforming, and accelerating the front much like in the isothermal case. However, persistent local stratification of heavy zones over light ones can be observed at the rear of the front when the Lewis number Le (ratio of thermal diffusivity over molecular diffusion) is nonzero. When the solutal and thermal effects are antagonistic (RC and RT of opposite sign), temporal oscillations of the concentration, temperature, and velocity fields can, in some cases, be observed in a reference frame moving with the front. The various dynamical regimes are discussed as a function of RC, RT, and Le.
Electroluminescence induced by photoluminescence excitation in GaInN/GaN light-emitting diodes
Authors: Schubert Martin F. , Dai Qi , Xu Jiuru , Kim Jong Kyu , Schubert E. Fred
Published: November 2009

Optical emission resulting from 405 nm selective photoexcitation of carriers in the GaInN/GaN quantum well (QW) active region of a light-emitting diode reveals two recombination channels. The first recombination channel is the recombination of photoexcited carriers in the GaInN QWs. The second recombination channel is formed by carriers that leak out of the GaInN QW active region, self-bias the device in forward direction, induce a forward current, and subsequently recombine in the GaInN active region in a spatially distributed manner. The results indicate dynamic carrier transport involving active, confinement, and contact regions of the device.
Nanowire-quantum-dot solar cells and the influence of nanowire length on the charge collection efficiency
Authors: Leschkies Kurtis S. , Jacobs Alan G. , Norris David J. , Aydil Eray S.
Published: November 2009

External quantum efficiency in solar cells based on junctions between PbSe quantum dots (QDs) and thin ZnO films is increased by replacing the ZnO films with a vertically oriented array of single-crystalline ZnO nanowires, and infiltrating this array with colloidal QDs. When illuminated with 100 mW/cm2 of simulated solar light, QD-nanowire solar cells exhibited power conversion efficiencies approaching 2%, approximately three times higher than that achieved with thin-film ZnO devices constructed with the same amount of QDs. Significant photocurrent and power conversion improvement with increasing nanowire length is consistent with higher exciton and charge collection efficiencies.
Highly efficient (Cs8V) superatom-based spin-polarizer
Authors: He Haiying , Pandey Ravindra , Reveles J. Ulises , Khanna Shiv N. , Karna Shashi P.
Published: November 2009

Quantum transport through molecules and the possibility to manipulate spin has generated tremendous excitement. Here, we demonstrate unusual spin transport through a molecule of two Cs8V magnetic superatoms. Calculations based on density functional theory and nonequilibrium Green’s function methods find a much higher current for the spin-down charge carriers relative to the spin-up carriers in the model Au–(Cs8V)–(Cs8V)–Au device system with almost 100% spin polarization, indicating a highly efficient spin polarizer. The new behavior is rooted in strong coupling of the localized magnetic core on V and the itinerant electrons of the Cs shell atoms leading to nearly full spin polarization.
Electrical behavior and oxygen vacancies in BiFeO3/[(Bi1/2Na1/2)0.94Ba0.06]TiO3 thin film
Authors: Wu Jiagang , Kang Guangqing , Wang John
Published: November 2009

Multiferroic bilayered thin films consisting of [(Bi1/2Na1/2)0.94Ba0.06]TiO3 (BNBT) and BiFeO3 (BFO) nanolayers were successfully grown on Pt/TiO2/SiO2/Si substrates via a combined sol-gel and radio frequency sputtering route. The bilayered BFO/BNBT thin film with (110) orientation and dense texture exhibits excellent ferroelectric and dielectric behavior (e.g., 2Pr∼79.7 μC/cm2, 2Ec∼772.6 kV/cm, εr∼178, and tan δ∼0.03), together with a long fatigue endurance up to 1×1010 switching cycles, while the desired magnetic behavior is well retained. Impedance study suggested that the second ionization of oxygen vacancies was involved in the conduction of the bilayered BFO/BNBT thin film.
Two-state competition in 1.3 μm multilayer InAs/InGaAs quantum dot lasers
Authors: Cao Q. , Yoon S. F. , Tong C. Z. , Ngo C. Y. , Liu C. Y. , Wang R. , Zhao H. X.
Published: November 2009

The competition of ground state (GS) and excited state (ES) is investigated from the as-grown and thermally annealed 1.3 μm ten-layer p-doped InAs/GaAs quantum dot (QD) lasers. The modal gain competition between GS and ES are measured and analyzed around the ES threshold characteristics. Our results show that two-state competition is more significant in devices with short cavity length operating at high temperature. By comparing the as-grown and annealed devices, we demonstrate enhanced GS and suppressed ES lasing from the QD laser annealed at 600 °C for 15 s.
Strong Tc dependence for strained epitaxial Ba(Fe1−xCox)2As2 thin films
Authors: Iida K. , Hänisch J. , Hühne R. , Kurth F. , Kidszun M. , Haindl S. , Werner J. , Schultz L. , Holzapfel B.
Published: November 2009

Ba ( Fe 1 − x Co x ) 2 As 2 superconducting thin films have been grown on SrTiO3, (La,Sr)(Al,Ta)O3, LaAlO3, and YAlO3 (YAO) single crystal substrates by pulsed laser deposition. All the films, except on YAO, have been grown epitaxially without buffer layers. The films deposited on YAO contained 45° in-plane rotated grains and showed a broad superconducting transition. The onset Tc of the films is observed to increase from 16.2 to 24.5 K with increasing c/a, mainly due to a slight distortion of the AsFe4 tetrahedron. From this correlation, we expect that higher superconducting transition temperatures than 24.5 K in a strained epitaxial film may be possible.
Effect of CO desorption and coadsorption with O on the phase diagram of a Ziff–Gulari–Barshad model for the catalytic oxidation of CO
Authors: Buendía G. M. , Machado E. , Rikvold P. A.
Published: November 2009

We study the effect of coadsorption of CO and O on a Ziff–Gulari–Barshad model with CO desorption for the reaction CO+O→CO2 on a catalytic surface. Coadsorption of CO at a surface site already occupied by an O is introduced by an Eley–Rideal-type mechanism that occurs with probability p, 0≤p≤1. We find that besides the well-known effect of eliminating the second-order phase transition between the reactive state and an O-poisoned state, the coadsorption step has a profound effect on the transition between the reactive state and the CO-poisoned state. The coexistence curve between these two states terminates at a critical value kc of the desorption rate k, which now depends on p. Our Monte Carlo simulations and finite-size scaling analysis indicate that kc decreases with increasing values of p. For p=1, there appears to be a sharp phase transition between the two states only for k at (or near) zero.
Gold adsorption induced surface alloying on Si(111)-√3×√3-Pb surface
Authors: Tang Lin , Guan Ze-Lei , Hao Dan , Jia Jin-Feng , Ma Xu-Cun , Xue Qi-Kun
Published: November 2009

The formation of surface Au/Pb alloys on a Pb-induced Si(111)-√3×√3 surface is investigated using scanning tunneling microscopy (STM). Two types of alloy islands, compact and loose islands, have been observed. The former shows a long-range ordered 3×3-Au/Pb reconstruction corresponding to an Au0.57Pb0.43 alloy, while the latter is not totally disordered with a short-range ordered structure. Based on the atomic structure of the substrate around the compact islands, Si atoms are excluded in the formation process of the Au/Pb surface alloys.
Peter William Gage 1937 - 2005
Authors: Adams D. J. , Barry P. H.
Published: November 2009

Peter William Gage (1937?2005) was recognised nationally and internationally as one of Australia's leaders in membrane physiology, biophysics and neuroscience. His research on neurotransmission, muscle and the structure?function of ion channels was extraordinarily productive, with over 7,000 citations. A gifted speaker with a great enthusiasm for research and for the introduction of cutting-edge technology, Peter Gage influenced and encouraged a great many research students, postdoctoral fellows and senior colleagues in their scientific careers.
Structural basis for specific recognition of multiple mRNA targets by a PUF regulatory protein
Authors: Wang Yeming , Opperman Laura , Wickens Marvin , Hall Traci M. Tanaka
Published: November 2009

Caenorhabditis elegans
fem-3
binding factor (FBF) is a founding member of the PUMILIO/FBF (PUF) family of mRNA regulatory proteins. It regulates multiple mRNAs critical for stem cell maintenance and germline development. Here, we report crystal structures of FBF in complex with 6 different 9-nt RNA sequences, including elements from 4 natural mRNAs. These structures reveal that FBF binds to conserved bases at positions 1–3 and 7–8. The key specificity determinant of FBF vs. other PUF proteins lies in positions 4–6. In FBF/RNA complexes, these bases stack directly with one another and turn away from the RNA-binding surface. A short region of FBF is sufficient to impart its unique specificity and lies directly opposite the flipped bases. We suggest that this region imposes a flattened curvature on the protein; hence, the requirement for the additional nucleotide. The principles of FBF/RNA recognition suggest a general mechanism by which PUF proteins recognize distinct families of RNAs yet exploit very nearly identical atomic contacts in doing so.