bluuebunny/crossref_metadata_2025 huggingface dataset:
Black Hole Growth and Host Galaxy Morphology
Authors: Schawinski Kevin , Urry C. Megan , Virani Shanil , Coppi Paolo , Bamford Steven P. , Treister Ezequiel , Lintott Chris J. , Sarzi Marc , Keel William C. , Kaviraj Sugata , Cardamone Carolin N. , Masters Karen L. , Ross Nicholas P. ,   the Galaxy Zoo Team
Published: June 2010

We use data from large surveys of the local universe (SDSS+Galaxy Zoo) to show that the galaxy–black hole connection is linked to host morphology at a fundamental level. The fraction of early-type galaxies with actively growing black holes, and therefore the AGN duty cycle, declines significantly with increasing black hole mass. Late-type galaxies exhibit the opposite trend: the fraction of actively growing black holes increases with black hole mass.
Growing Supermassive Black Holes in Cosmological Simulations of Structure Formation
Authors: Sijacki Debora , Springel Volker , Haehnelt Martin G.
Published: June 2010

We discuss a numerical model for black hole (BH) growth and feedback that allows simultaneous tracking of the evolution of galaxies and their central BHs in fully cosmological simulations. After describing the main features of the numerical model adopted, we show how BHs in these simulations affect the properties of their host halos and how this in turn impacts the growth of the BHs themselves. We also present results from a set of simulations specifically designed to address the issue of BH assembly in the early Universe and discuss whether or not different extensions of the model, in particular rapidly spinning BHs and gravitational recoils, can hamper the formation of the first bright quasars.
The X-Ray AGN Bias Factor at Zero Redshift
Authors: Krivonos Roman A. , Revnivtsev Mikhail G.
Published: June 2010

Using an AGN sample from the INTEGRAL all-sky survey, we show that the density fluctuations of matter in the local universe translate linearly into the density fluctuations of accreting supermassive black holes. Our results imply that hard X-ray emitting AGNs are unbiased tracers of the galaxy population in the nearby universe and SMBH activity is independent of the density of galaxies.
Time‐lapse microgravity surveys reveal water storage heterogeneity of a karst aquifer
Authors: Jacob Thomas , Bayer Roger , Chery Jean , Le Moigne Nicolas
Published: June 2010

Time‐lapse microgravity surveying combined with absolute gravity measurements is used to investigate water storage changes in a karst aquifer of ∼100 km2 area. The survey consists of 40 gravity stations measured with a relative gravimeter; absolute gravity is measured at three stations for each survey. In total, four gravity surveys are performed over a 2 year time period during consecutive wet and dry periods. Survey precisions range between 2.4 and 5 μGal, enabling statistically significant detection of 10 μGal change, i.e., ∼0.25 m equivalent water level change. Observed gravity changes are coherent between consecutive survey periods, i.e., net water withdrawal and net water recharge is observed, reaching changes as high as 22 μGal. Observed gravity changes allow refining evapotranspiration estimates, which may serve to improve the water budget of the aquifer. High‐and low‐gravity amplitude zones characterize the karst system, demonstrating spatially variable storage behavior. Geomorphologic considerations are invoked to explain the location of preferential zones of water storage, and a conceptual model of water storage is discussed for the studied karst.
Relationship between ocean velocity and motionally induced electrical signals: 2. In the presence of sloping topography
Authors: Szuts Zoltan B.
Published: June 2010

Motionally induced electric fields and electric currents in the ocean depend to first order solely on the vertical dimension. We investigate the significance of two‐dimensional (2‐D) perturbations that arise in the presence of sloping topography. The full electric response is calculated for a schematic geometry that contains a topographic slope, has a two‐layer ocean with a layer of sediment beneath, and is described by five nondimensional parameters. When considered over the realistic ranges of topographic aspect ratio (the ratio of mean water depth to topographic width), topographic relief, sediment thickness, and sediment conductivity, velocity errors arising from 2‐D perturbations are found to be less than a few percent of the dominant one‐dimensional (1‐D) signal. All errors depend on the topographic aspect ratio to the power of 1.9 and have linear dependence on topographic relief and the depth of the surface jet. Depth‐uniform velocity errors are roughly proportional to the 1‐D sediment conductance ratio, whereas depth‐varying velocity errors are independent of sediment thickness or conductivity. Two‐dimensional perturbations decay with a half width of 0.2–1 times the 1‐D effective water depth. The magnitude of estimated errors is consistent with those found at a measurement location with strong 2‐D perturbations. This study extends the first‐order theory to the maximum expected aspect ratios for topography and finds small perturbations with simple dependencies. Overall, the 1‐D approximation is found to be adequate for interpreting observations at all but the most extreme locations.
Mineral dust observed with AERONET Sun photometer, Raman lidar, and in situ instruments during SAMUM 2006: Shape‐dependent particle properties
Authors: Müller D. , Ansmann A. , Freudenthaler V. , Kandler K. , Toledano C. , Hiebsch A. , Gasteiger J. , Esselborn M. , Tesche M. , Heese B. , Althausen D. , Weinzierl B. , Petzold A. , von Hoyningen‐Huene W.
Published: June 2010

Nearly pure Saharan dust was observed with an Aerosol Robotic Network (AERONET) Sun photometer, several Raman and high spectral resolution lidars, and airborne in situ instruments during the Saharan Mineral Dust Experiment (SAMUM) 2006 in Morocco. In the framework of a case study we present particle shape‐dependent dust properties, i.e., backscatter coefficients, extinction‐to‐backscatter (lidar) ratios, and linear particle depolarization ratios. These parameters can be inferred from AERONET's latest version of the mineral dust retrieval algorithm. The parameters can be measured with multiwavelength Raman/depolarization lidar without critical assumptions on particle shape. Lidar ratios inferred from the AERONET Sun photometer data tend to be larger than lidar ratios measured directly with lidar. Linear dust depolarization ratios were derived for several measurement wavelengths from the data products of the AERONET Sun photometer. The depolarization ratios tend to be smaller than the depolarization ratios measured with lidar. The largest differences exist in the near‐ultraviolet wavelength range. Particle axis ratios were determined with scanning electron microscopy. The axis ratio distribution differs significantly from the axis ratio distribution that is assumed in the AERONET retrievals. If the axis ratio distributions measured during SAMUM are used, the reproducibility of the lidar data products improves. The differences may in part be caused by an insufficient understanding of the light‐scattering model that is used in the AERONET algorithm. The results of the present study will be used to develop a dust light‐scattering model that will serve as the theoretical basis for the inversion of optical data into dust microphysical properties.
Analysis of Venusian steep‐sided domes utilizing stereo‐derived topography
Authors: Gleason Abigail L. , Herrick Robert R. , Byrnes Jeffrey M.
Published: June 2010

The morphology and topography of 23 Venusian steep‐sided domes are analyzed to examine possible emplacement mechanisms. Stereo radargrammetric techniques are used with Magellan synthetic aperture radar image data (∼100 m resolution) to generate digital elevation models for the domes (∼1 km horizontal resolution). Heights of the domes range from 390 to 1590 m, aspect ratios (height/diameter) range from 0.01 to 0.07, and volumes range from 73 to 1790 km3. Dome morphology varies along a continuous trend that is directly related to the aspect ratio. Domes with a low aspect ratio tend to be sunken in their centers, whereas domes with higher aspect ratios have flat to convex surfaces. Domes with the highest aspect ratios have central peaks. These trends are likely due to slight variations in the thickness of the crust and, possibly, effusion rates. Episodic emplacement is also inferred to be a significant process for the formation and growth of some of the domes in this sample.
Spontaneous transition to superrotation in warm climates simulated by CAM3
Authors: Caballero Rodrigo , Huber Matthew
Published: June 2010

Recent paleoclimate proxy reconstructions show that tropical surface temperatures may have been as high as 35°–40°C in the Early Cenozoic. Here, we study the tropical atmospheric circulation's response to temperatures in this range using a full‐complexity atmospheric general circulation model (AGCM). We find that when equatorial surface temperatures exceed ∼33°C, the model undergoes a transition to equatorial superrotation, a state with strong annual‐ and zonal‐mean westerlies on the equator. The transition is driven by zonal momentum convergence due to large‐amplitude transient eddies on the equator. These eddies have a structure similar to the observed Madden‐Julian Oscillation (MJO). The model's MJO variability is weaker than observed when simulating the modern climate but increases sharply with temperature, coming to dominate the tropical variability and mean state of the warmest climates.
An Analysis of Coexistence Curve Data for Several Binary Liquid Mixtures Near Their Critical Points
Authors: Stein A. , Allen G. F.
Published: June 2010

Experimental data on the coexistence curves for nine binary liquid systems, which meet strict criteria of precision, purity of components, and experimental method, are analyzed in the neighborhood of the critical point. The data are examined in terms of a general equation of state which is nonanalytic at the critical point. The results of the computer analysis using weighted non-linear least squares procedures present evidence that some symmetry features of classical equations of state remain; and within the experimental errors in the data all systems are consistent with the critical exponent β=0.34. The asymptotic behavior of the diameter is examined and evidence is provided for a curved diameter in some cases; however, it is concluded that the available data are not extensive enough to make a firm conclusion concerning the shape of the diameter. Experimental methods are briefly criticized and mention is made of the experimental direction that future work should take. Special attention is given to estimating the reliability of the conclusions that may be drawn from a given set of data.
Diffusion in Copper and Copper Alloys. Part I. Volume and Surface Self-Diffusion in Copper
Authors: Butrymowicz Daniel B. , Manning John R. , Read Michael E.
Published: June 2010

A survey, comparison, and critical analysis is presented of data compiled from the scientific literature concerning copper self-diffusion. Topics include volume diffusion, dislocation pipe diffusion, surface diffusion, sintering, electromigration, thermomigration, pressure effect on diffusion, strain-enhanced diffusion, nuclear magnetic resonance measurements of solid state diffusion and diffusion in molten copper. An extensive bibliography is presented along with figures, tabular presentation of data, and discussion of results.
Microwave Spectra of Molecules of Astrophysical Interest VI. Carbonyl Sulfide and Hydrogen Cyanide
Authors: Maki Arthur G.
Published: June 2010

All available data on the microwave spectra of carbonyl sulfide and hydrogen cyanide are critically reviewed and tabulated. Molecular data such as rotational constants, centrifugal distortion constants, dipole moments, hyperfine coupling constants, and structural parameters are also tabulated. All rotational transitions from 100 MHz to 300 GHz that are deemed likely to be of interest to radio astronomers are calculated and tabulated along with their estimated 95 percent confidence limits. Microwave measurements are tabulated for most isotopic species and for many of the lower vibrational states. For both carbonyl sulfide and hydrogen cyanide a bibliography is given which includes nearly all the spectroscopic work reported in the literature. For each molecule a bibliography of related astrophysical papers is also given.
Effects of nanoparticle layering on nanofluid and base fluid pool boiling heat transfer from a horizontal surface under atmospheric pressure
Authors: White Steven B. , Shih Albert J. , Pipe Kevin P.
Published: June 2010

Previous heat transfer studies of nanofluids have shown that suspended nanoparticles can affect thermal properties within a fluid and furthermore can affect surface roughness by depositing on a heater surface. Pool boiling studies of nanofluids have demonstrated either enhanced or diminished heat transfer, yet have been unable to distinguish the contributions of increased surface roughness and suppression of bubble transport by suspended particles because they have used base fluids on a clean boiling surface as a comparison. We resolve this uncertainty by studying the boiling performance of a surface exposed to a series of boiling tests that alternate between water and a water-based nanofluid with suspended 40 nm ZnO nanoparticles. We find that the performance for the water tests increases significantly, showing a 62% enhancement after four cycles. This increase correlates well with a surface roughness model for boiling that uses atomic force microscopy-measured surface data to quantify the layering of nanoparticles in intervening nanofluid boiling tests. We find that the performance of the ZnO nanofluid initially shows a 24% enhancement versus water on a clean (unroughened) surface, but then steadily declines in later tests as nanoparticle layering occurs, showing a measured trend that is opposite that of water. We ascribe this decrease to the suppression of bubble formation and motion by the suspended particles. The results demonstrate that the effect of increased surface roughness due to nanoparticle layering can be twofold, greatly enhancing boiling for the base fluid and slightly decreasing performance for the nanofluid.
Influence of in situ applied ultrasound during Si+ implantation in SiO2 on paramagnetic defect generation
Authors: Jivanescu M. , Romanyuk A. , Stesmans A.
Published: June 2010

Electron spin resonance (ESR) results are presented on the influence of in situ ultrasound treatment (UST) during implantation at 300 K of Si+ ions into thermal SiO2 on (100)Si before and after subsequent high-temperature (T) annealing (1100 °C) intended to promote the formation of embedded Si nanoparticles. The as-implanted state exhibits high densities of three prominent types of point defects, including the SiO2-specific S and E′γ O-vacancy type centers, and an unknown broad (≈20 G) signal at g≈2.0026 denoted IS. The high-intensity S signal shows demagnetization shape effects, pointing to a distribution of high local density of defects over a thin layer. UST is observed to effectuate a drastic reduction in S and E′γ centers, and elimination of IS beyond detection. This reveals a strong healing influence of in situ transferred ultrasound (US) energy on implantation-induced damage, here quantified and identified on atomic level in terms of mainly intrinsic paramagnetic point defects elimination, viz., Frenkel pair elimination, while all three initial signals disappear. Other types of defects surface after annealing of the non-US treated sample, including the SiO2-specific EX defect signal and Pb-type Si/SiO2 interface centers, the appearance of the latter providing direct ESR evidence for crystallization of the excess Si nanoparticles. The influence of the UST healing effect is kept up after subsequent annealing, now resulting in the absence of virtually all ESR-active centers. The drop in Pb-type centers below the detection level in the UST annealed sample indicates improvement of the nanocrystalline-Si/SiO2 interface quality. The combination of UST with high-T annealing emerges as a highly efficient means to eradicate ion implantation damage in terms of intrinsic point defects.
Broad-band ferromagnetic resonance characterization of lossy ferromagnetic metallic elements
Authors: Zagorodnii V. V. , Hutchison A. J. , Hansen S. , Chen Jue , Gatzen H. H. , Celinski Z.
Published: June 2010

We developed a method to analyze broad-band ferromagnetic resonance (FMR) data for rectangular ferromagnetic bars of micron and submicron thicknesses. This method allows one to determine the gyromagnetic ratio, the saturation magnetization, and the damping constant of the measured structures. The proposed technique can be used for nondestructive testing of the ferromagnetic elements of micro-electro-mechanical system sensors, actuators, and related devices without any special sample preparation. In the developed approach, an analysis of the FMR linewidth is not needed to determine the damping constant. This method rather utilizes the frequency dependence of the demagnetizing factors in the range of 1–40 GHz for the extraction of magnetic parameters. Its application is demonstrated using Ni81Fe19, Ni45Fe55, and Co35Fe65 specimens as examples.
Fast universal quantum computation with railroad-switch local Hamiltonians
Authors: Nagaj Daniel
Published: June 2010

We present two universal models of quantum computation with a time-independent, frustration-free Hamiltonian. The first construction uses 3-local (qubit) projectors and the second one requires only 2-local qubit-qutrit projectors. We build on Feynman’s Hamiltonian computer idea [R. Feynman, Optics News 11, 11 (1985)] and use a railroad-switch-type clock register. The resources required to simulate a quantum circuit with L gates in this model are O(L) small-dimensional quantum systems (qubits or qutrits), a time-independent Hamiltonian composed of O(L) local, constant norm, projector terms, the possibility to prepare computational basis product states, a running time O(L log2 L), and the possibility to measure a few qubits in the computational basis. Our models also give a simplified proof of the universality of 3-local adiabatic quantum computation.
Hypergolic fuel detection using individual single walled carbon nanotube networks
Authors: Desai S. C. , Willitsford A. H. , Sumanasekera G. U. , Yu M. , Tian W. Q. , Jayanthi C. S. , Wu S. Y.
Published: June 2010

Accurate and reliable detection of hypergolic fuels such as hydrazine (N2H4) and its derivatives is vital to missile defense, aviation, homeland security, and the chemical industry. More importantly these sensors need to be capable of operation at low temperatures (below room temperature) as most of the widely used chemical sensors operate at high temperatures (above 300 °C). In this research a simple and highly sensitive single walled carbon nanotube (SWNT) network sensor was developed for real time monitoring of hydrazine leaks to concentrations at parts per million levels. Upon exposure to hydrazine vapor, the resistance of the air exposed nanotubes (p-type) is observed to increase rapidly while that of the vacuum-degassed nanotubes (n-type) is observed to decrease. It was found that the resistance of the sample can be recovered through vacuum pumping and exposure to ultraviolet light. The experimental results support the electrochemical charge transfer mechanism between the oxygen redox couple of the ambient and the Fermi level of the SWNT. Theoretical results of the hydrazine-SWNT interaction are compared with the experimental observations. It was found that a monolayer of water molecules on the SWNT is necessary to induce strong interactions between hydrazine and the SWNT by way of introducing new occupied states near the bottom of the conduction band of the SWNT.
Effect of interlayer trapping and detrapping on the determination of interface state densities on high-k dielectric stacks
Authors: Castán H. , Dueñas S. , García H. , Gómez A. , Bailón L. , Toledano-Luque M. , del Prado A. , Mártil I. , González-Díaz G.
Published: June 2010

The influence of the silicon nitride blocking layer thickness on the interface state densities (Dit) of HfO2/SiNx:H gate-stacks on n-type silicon have been analyzed. The blocking layer consisted of 3 to 7 nm thick silicon nitride films directly grown on the silicon substrates by electron-cyclotron-resonance assisted chemical-vapor-deposition. Afterwards, 12 nm thick hafnium oxide films were deposited by high-pressure reactive sputtering. Interface state densities were determined by deep-level transient spectroscopy (DLTS) and by the high and low frequency capacitance-voltage (HLCV) method. The HLCV measurements provide interface trap densities in the range of 1011 cm−2 eV−1 for all the samples. However, a significant increase in about two orders of magnitude was obtained by DLTS for the thinnest silicon nitride barrier layers. In this work we probe that this increase is an artifact due to the effect of traps located at the internal interface existing between the HfO2 and SiNx:H films. Because charge trapping and discharging are tunneling assisted, these traps are more easily charged or discharged as lower the distance from this interface to the substrate, that is, as thinner the SiNx:H blocking layer. The trapping/detrapping mechanisms increase the amplitude of the capacitance transient and, in consequence, the DLTS signal that have contributions not only from the insulator/substrate interface states but also from the HfO2/SiNx:H interlayer traps.
The influence of interface roughness on the magnetic properties of exchange biased CoO/Fe thin films
Authors: Fleischmann C. , Almeida F. , Demeter J. , Paredis K. , Teichert A. , Steitz R. , Brems S. , Opperdoes B. , Van Haesendonck C. , Vantomme A. , Temst K.
Published: June 2010

We have investigated the correlation between magnetic and structural properties in exchange coupled polycrystalline CoO/Fe thin films. It has been found that an increase in interface roughness increases the exchange bias field as well as the coercivity. The magnetization reversal mechanism is also influenced by the interfacial morphology. Smooth interfaces are characterized by an asymmetric hysteresis loop, which is associated with domain wall motion for the first magnetization reversal after field cooling and spin rotation in all subsequent reversals. This asymmetry diminishes as the interface roughness increases, i.e., all magnetization reversals are dominated by spin rotation. Moreover, we have observed that the blocking temperature decreases with increasing interface roughness. We also report on a logarithmic time dependence of the magnetization which is different for both branches of the hysteresis loop of smooth CoO/Fe bilayers.
Investigations on terahertz radiation generated by two superposed femtosecond laser pulses
Authors: Malik Anil K. , Malik Hitendra K. , Kawata Shigeo
Published: June 2010

The generation of terahertz (THz) radiation based on tunnel ionization of a gas jet is analytically investigated when two superposed short pulse lasers with finite initial phase difference are focused on to it after passing through an axicon. The phase difference between these two lasers plays an important role for the optimization of rate of ionization, evolution of plasma density, and subsequently the residual current due to dipole oscillations. The directionality of the emitted THz radiation can be controlled by tuning initial phase difference between the two laser pulses. Since a nonuniform plasma is produced during the tunnel ionization, the effect of radial variation in the electron density in the plasma channel is studied on the frequency of the emitted THz radiation and on its power. Higher power THz radiation is obtained for the higher fields of the lasers. With optimum initial phase of the laser envelope and the channel width, the mechanism seems to be much more efficient than some of the other mechanisms.
Scalar relativistic explicitly correlated R12 methods
Authors: Bischoff Florian A. , Valeev Edward F. , Klopper Wim , Janssen Curtis L.
Published: June 2010

Combinations of explicitly correlated R12 wave functions with relativistic Douglas–Kroll–Hess (DKH) Hamiltonians are discussed. We considered several ways to incorporate the relativistic terms into the second-order Møller–Plesset R12 method and applied them to the helium isoelectronic series to investigate their accuracy and numerical stability. Among the approaches are the evaluation of the relativistic terms via double resolution-of-the-identity and the explicit evaluation of all terms up to O(c−4) using the Pauli Hamiltonian. Numerical collapse of the latter can be avoided if the R12 amplitudes are determined by Kato’s cusp condition. Closed formulas for new two-electron integrals that include the mass-velocity term have been derived and implemented into the LIBINT2 integral library. The proposed approaches are not restricted to DKH and can be combined with other one- and two-component relativistic Hamiltonians.
On the solvability of two dimensional semigroup gauge theories
Authors: Varga Péter
Published: June 2010

We study the solvability of two dimensional semigroup gauge theories by Migdal’s link elimination method. We determine certain conditions that ensure that the partition sum corresponding to the join of two plaquettes depends only on the holonomy around the boundary of the joined plaquettes. These conditions are checked for a few types of semigroups: 0-groups, cyclic, inverse symmetric, and Brandt semigroups.
Bias stress instability in organic transistors investigated by ac admittance measurements
Authors: Di Girolamo F. V. , Barra M. , Capello V. , Oronzio M. , Romano C. , Cassinese A.
Published: June 2010

In this paper, the bias stress effect (BSE) in organic field-effect transistors has been analyzed by an alternative experimental approach based on ac admittance (Y=G+jωC) measurements. conductance (C) and capacitance (G) curves have been recorded as a function of frequency at different times of the bias stress experiments and simultaneously fitted through a transmission line circuit, able to separately model the conducting properties of the channel and contact regions. The determination of the time behavior of the model fitting parameters is assumed as the starting point for a quantitative analysis of the BSE occurrence. This experimental procedure clarifies that both channel resistance (Rch) and contact resistance (Rc) are largely affected by the BSE, while the channel capacitance (Cch), related to the charge accumulation sheet, and the contact capacitance (Cc) result almost unchanged.
Communications: Making density functional theory and the quantum theory of atoms in molecules converse: A local approach
Authors: Tognetti Vincent , Joubert Laurent , Adamo Carlo
Published: June 2010

A first (local) bridge between Kohn–Sham density functional theory and the quantum theory of atoms in molecules of Bader is built by means of a second order reduced density gradient expansion of the exchange-correlation energy density at a given bond critical point. This approach leads to the definition of new “mixed” descriptors that are particularly useful for the classification of the chemical interactions for which the traditional atoms in molecules characterization reveals insufficient, as for instance the distinction between hydrogen and agostic bonds.
Analysis of the main optical mechanisms responsible for fragmentation of gold nanoparticles by femtosecond laser radiation
Authors: Videla F. A. , Torchia G. A. , Schinca D. C. , Scaffardi L. B. , Moreno P. , Méndez C. , Giovanetti L. J. , Ramallo Lopez J. M. , Roso L.
Published: June 2010

Studies of fragmentation process of gold nanoparticles (Nps) in deionized water after generation by femtosecond laser ablation were performed. To analyze the fragmentation process, direct IR ultrafast pulses or super-continuum (SC) radiation focused in the colloidal solution were used in separate steps. IR pulses and SC generated externally in a sapphire crystal or directly inside the water were applied under low fluence regime. In the latter cases, to evaluate the effect on fragmentation of the different spectral bands present in the SC, we have determined different efficiency regions characterized by means of the product between the spectral response and the optical extinction spectrum corresponding to the initial Nps solution. From the analysis of this product function, we can conclude that the main fragmentation mechanism is due to linear absorption in the visible region. Likewise, the SC generated in water resulted more efficient than the SC obtained externally by a sapphire crystal. This fact may be attributed to the blue broadening of the water SC spectrum (as compared with the sapphire SC) due to the large intensity used for its generation. Transmission electron microscopy and small angle x-ray scattering measurements support the results found from optical extinction spectroscopy.
Fermi level stabilization energy in cadmium oxide
Authors: Speaks D. T. , Mayer M. A. , Yu K. M. , Mao S. S. , Haller E. E. , Walukiewicz W.
Published: June 2010

We have studied the effects of high concentrations of native point defects on the electrical and optical properties of CdO. The defects were introduced by irradiation with high energy He+, Ne+, Ar+, and C+ ions. Increasing the irradiation damage with particles heavier than He+ increases the electron concentration until a saturation level of 5×1020 cm−3 is reached. In contrast, due to the ionic character and hence strong dynamic annealing of CdO, irradiation with much lighter He+ stabilizes the electron concentration at a much lower level of 1.7×1020 cm−3. A large shift of the optical absorption edge with increasing electron concentration in irradiated samples is explained by the Burstein–Moss shift corrected for electron-electron and electron-ion interactions. The saturation of the electron concentration and the optical absorption edge energy are consistent with a defect induced stabilization of the Fermi energy at 1 eV above the conduction band edge. The result is in a good agreement with previously determined Fermi level pinning energies on CdO surfaces. The results indicate that CdO shares many similarities with InN, as both materials exhibit extremely large electron affinities and an unprecedented propensity for n-type conductivity.
Fault-tolerance and thermal characteristics of quantum-dot cellular automata devices
Authors: Anduwan G. A. , Padgett B. D. , Kuntzman M. , Hendrichsen M. K. , Sturzu I. , Khatun M. , Tougaw P. D.
Published: June 2010

We present fault tolerant properties of various quantum-dot cellular automata (QCA) devices. Effects of temperatures and dot displacements on the operation of the fundamental devices such as a binary wire, logical gates, a crossover, and an exclusive OR (XOR) have been investigated. A Hubbard-type Hamiltonian and intercellular Hartree approximation have been used for modeling, and a uniform random distribution has been implemented for the defect simulations. The breakdown characteristics of all the devices are almost the same except the crossover. Results show that the success of any device is significantly dependent on both the fabrication defects and temperatures. We have observed unique characteristic features of the crossover. It is highly sensitive to defects of any magnitude. Results show that the presence of a crossover in a XOR design is a major factor for its failure. The effects of temperature and defects in the crossover device are pronounced and have significant impact on larger and complicated QCA devices.
Improvement of resistance switching characteristics in a thin FeOx transition layer of TiN/SiO2/FeOx/FePt structure by rapid annealing
Authors: Feng Li-Wei , Chang Chun-Yen , Chang Yao-Feng , Chang Ting-Chang , Wang Shin-Yuan , Chen Shih-Ching , Lin Chao-Cheng , Chen Shih-Cheng , Chiang Pei-Wei
Published: June 2010

In this paper, the influence of a 600 °C rapid thermal annealing for 60 s on the improvements of resistance switching behaviors in a TiN/SiO2/FeOx/FePt structure is reported. It is found that besides the distinct reduction in memory switching parameters in forming voltage, set/reset voltages, and their dispersions, the resistance ratio of high-resistance state to low-resistance state is also enlarged after annealing. The effects of annealing on improving the resistance switching properties are discussed by x-ray diffraction and x-ray photon-emission spectra depth profile results. Additionally, good retention characteristics are exhibited in the annealed TiN/SiO2/FeOx/FePt resistance switching memory.
Enhanced telecom wavelength single-photon detection with NbTiN superconducting nanowires on oxidized silicon
Authors: Tanner M. G. , Natarajan C. M. , Pottapenjara V. K. , O’Connor J. A. , Warburton R. J. , Hadfield R. H. , Baek B. , Nam S. , Dorenbos S. N. , Ureña E. Bermúdez , Zijlstra T. , Klapwijk T. M. , Zwiller V.
Published: June 2010

Superconducting nanowire single-photon detectors (SNSPDs) have emerged as a highly promising infrared single-photon detector technology. Next-generation devices are being developed with enhanced detection efficiency (DE) at key technological wavelengths via the use of optical cavities. Furthermore, new materials and substrates are being explored for improved fabrication versatility, higher DE, and lower dark counts. We report on the practical performance of packaged NbTiN SNSPDs fabricated on oxidized silicon substrates in the wavelength range from 830 to 1700 nm. We exploit constructive interference from the SiO2/Si interface in order to achieve enhanced front-side fiber-coupled DE of 23.2 % at 1310 nm, at 1 kHz dark count rate, with 60 ps full width half maximum timing jitter.
Oxygen vacancy formation and migration in Ce1−xZrxO2 catalyst: A DFT+U calculation
Authors: Chen Hsin-Tsung , Chang Jee-Gong
Published: June 2010

Spin-polarized density functional theory with the inclusion of on-site Coulomb correction (DFT+U) calculation is carried out to study the oxygen vacancy and migration of Ce1−xZrxO2 in a series of Ce/Zr ratios. Substitution of Zr4+ ion in CeO2 creates activated oxygen in Ce1−xZrxO2, leading to higher oxygen storage capacity (OCS) compared to CeO2 due to its structural and electronic modifications. It is found that the oxygen vacancy formation energy (Ef) is lowered even by small amounts of zirconia; the oxide with a content of 50% zirconia exhibits the lowest Ef and the best OCS. This indicates that the O vacancy is most easily created near the Zr centers. In addition, the activation energy calculations for oxygen vacancy migration around Zr dopant show facile oxygen migration through the Ce1−xZrxO2 materials, especially for 50% Zr-doped ceria. The detailed electronic analysis is also carried out to gain insights into the higher OCS of the Ce1−xZrxO2 catalyst.
Fate of the Julia set of higher dimensional maps in the integrable limit
Authors: Saito Satoru , Saitoh Noriko
Published: June 2010

By studying higher dimensional rational maps, we have shown, in our previous papers, that periodic points of integrable maps with sufficient number of invariants form invariant varieties of periodic points (IVPPs) different for each period. In this paper, we study the transition of a nonintegrable map to an integrable one. In particular, we investigate analytically where the Julia set goes and how it disappears when the map becomes integrable. We show that the behavior of the Julia set is different, depending on whether the map has an unstable variety of fixed point (UVFP), which becomes nonfixed in the integrable limit. If the map does not have an UVFP, all periodic points approach IVPP or fixed points of the integrable map. Otherwise, a large part of periodic points of all periods approach the UVFP and the UVFP itself becomes a variety of indeterminate points unless it disappears from the map. Moreover, we show that a map recovered by the singularity confinement generates the sequence of all IVPPs.
Molecular correlations and solvation in simple fluids
Authors: Barbosa Marco A. A. , Widom B.
Published: June 2010

We study the molecular correlations in a lattice model of a solution of a low-solubility solute, with emphasis on how the thermodynamics is reflected in the correlation functions. The model is treated in the Bethe–Guggenheim approximation, which is exact on a Bethe lattice (Cayley tree). The solution properties are obtained in the limit of infinite dilution of the solute. With h11(r), h12(r), and h22(r) the three pair correlation functions as functions of the separation r (subscripts 1 and 2 referring to solvent and solute, respectively), we find for r≥2 lattice steps that h22(r)/h12(r)≡h12(r)/h11(r). This illustrates a general theorem that holds in the asymptotic limit of infinite r. The three correlation functions share a common exponential decay length (correlation length), but when the solubility of the solute is low the amplitude of the decay of h22(r) is much greater than that of h12(r), which in turn is much greater than that of h11(r). As a consequence the amplitude of the decay of h22(r) is enormously greater than that of h11(r). The effective solute-solute attraction then remains discernible at distances at which the solvent molecules are essentially no longer correlated, as found in similar circumstances in an earlier model. The second osmotic virial coefficient is large and negative, as expected. We find that the solvent-mediated part W(r) of the potential of mean force between solutes, evaluated at contact, r=1, is related in this model to the Gibbs free energy of solvation at fixed pressure, ΔGp∗, by (Z/2)W(1)+ΔGp∗≡pv0, where Z is the coordination number of the lattice, p is the pressure, and v0 is the volume of the cell associated with each lattice site. A large, positive ΔGp∗ associated with the low solubility is thus reflected in a strong attraction (large negative W at contact), which is the major contributor to the second osmotic virial coefficient. In this model, the low solubility (large positive ΔGp∗) is due partly to an unfavorable enthalpy of solvation and partly to an unfavorable solvation entropy, unlike in the hydrophobic effect, where the enthalpy of solvation itself favors high solubility, but is overweighed by the unfavorable solvation entropy.
Critical behavior of static properties for nitrobenzene-alkane mixtures
Authors: Pérez-Sánchez Germán , Losada-Pérez Patricia , Cerdeiriña Claudio A. , Thoen Jan
Published: June 2010

We present experimental data of the isobaric heat capacity per unit volume Cp,xV−1 for mixtures containing nitrobenzene and an alkane (CNH2N+2, with N ranging from 6 to 15) upon approaching their liquid-liquid critical points along a path of constant composition. Values for the critical amplitude A+ have been determined. They have been combined with the previously reported ones for the leading term of the coexistence-curve width to obtain, with the aid of well-known universal relations, the critical amplitudes of the correlation length and of the osmotic susceptibility. The trends of all these critical parameters, which exhibit anomalous behavior in the low N region, are discussed in terms of particular microscopic phenomena characterizing NB-CNH2N+2 mixtures. The work is completed with an analysis of the analog of the Yang-Yang anomaly in liquid-liquid criticality: the behavior of the partial molar heat capacities of the two liquid components is found to illustrate previously uncovered asymmetry effects.
Characterization of electronic structure of silicon nanocrystals in silicon nitride by capacitance spectroscopy
Authors: Cho Chang-Hee , Kim Baek-Hyun , Kim Sang-Kyun , Park Seong-Ju
Published: June 2010

The electronic structure of silicon nanocrystals embedded in a silicon nitride insulating film is identified by using a capacitance spectroscopy. The tunneling capacitor device, which is used in this study, consists of a tunneling silicon nitride, an array of silicon nanocrystals embedded in a silicon nitride film, and a blocking silicon nitride deposited on p-type (100) Si substrate. The absolute position of the lowest conduction and the highest valence levels of the silicon nanocrystal is revealed and the band-gap energy of silicon nanocrystals estimated by the capacitance spectroscopy agrees well with that measured by photoluminescence spectroscopy.
The generalized Kupershmidt deformation for constructing new integrable systems from integrable bi-Hamiltonian systems
Authors: Yao Yuqin , Zeng Yunbo
Published: June 2010

Based on the Kupershmidt deformation for any integrable bi-Hamiltonian systems presented by Kupershmidt [Phys. Lett. A 372, 2634 (2008)], we propose the generalized Kupershmidt deformation to construct new systems from integrable bi-Hamiltonian systems, which provides a nonholonomic perturbation of the bi-Hamiltonian systems. The generalized Kupershmidt deformation is conjectured to preserve integrability. The conjecture is verified in a few representative cases: Korteweg–de Vries (KdV) equation, Boussinesq equation, Jaulent–Miodek equation, and Camassa–Holm equation. For these specific cases, we present a general procedure to convert the generalized Kupershmidt deformation into the integrable Rosochatius deformation of soliton equation with self-consistent sources, then to transform it into a t-type bi-Hamiltonian system. By using this generalized Kupershmidt deformation some new integrable systems are derived. In fact, this generalized Kupershmidt deformation also provides a new method to construct the integrable Rosochatius deformation of soliton equation with self-consistent sources.
Bihamiltonian structure of the two-component Kadomtsev–Petviashvili hierarchy of type B
Authors: Wu Chao-Zhong , Xu Dingdian
Published: June 2010

We employ a Lax pair representation of the two-component Kadomtsev–Petviashvili hierarchy of type B and construct its bihamiltonian structure with R-matrix techniques.
Suitability of umbrella- and overlap-sampling methods for calculation of solid-phase free energies by molecular simulation
Authors: Tan Tai Boon , Schultz Andrew J. , Kofke David A.
Published: June 2010

We examine the ability of two-stage free-energy perturbation methods to yield solid-phase free energies using a system of harmonically coupled particles as a reference. We consider two ways to construct a reference system, one based on derivatives of the intermolecular potential of the target system of interest (the conventional choice in lattice dynamics), and the other based on analysis of pairwise configurational correlations observed in simulations of the target system. For each case, we consider two perturbation techniques that compute the free energy difference between the target and reference systems while avoiding lengthy thermodynamic integration procedures. The methods are overlap sampling as optimized by Bennett, and umbrella sampling optimized in a similar fashion. Such methods require at most two simulations to yield a result, but they can fail if the target and reference do not share a sufficiently large set of relevant configurations. In particular, failure can be expected for large systems, and we examine the question of how large a system can be before this point is reached. Our test case is a face-centered cubic system of r−12 soft spheres, and we find that for systems of up to 108 particles the methods are accurate for all temperatures up to melting; for systems of 256 particles the methods begin to break down at about half the melting temperature. Significantly, we observe that the correction to the harmonic reference is only weakly dependent on system size, suggesting an N-hybrid technique in which perturbation is applied to a small system and the result added to a large-system harmonic reference to obtain a good estimate of the correct large-system free energy. We also examine these approaches, along with thermodynamic integration in temperature, with respect to their computational efficiency. We find that Bennett’s method using a derivative-based harmonic reference is the most efficient of all those examined, particularly when employed in the N-hybrid method.
Ion transport and storage of ionic liquids in ionic polymer conductor network composites
Authors: Liu Yang , Liu Sheng , Lin Junhong , Wang Dong , Jain Vaibhav , Montazami Reza , Heflin James R. , Li Jing , Madsen Louis , Zhang Q. M.
Published: June 2010

We investigate ion transport and storage of ionic liquids in ionic polymer conductor network composite electroactive devices. Specifically, we show that by combining the time domain electric and electromechanical responses, one can gain quantitative information on transport behavior of the two mobile ions in ionic liquids (i.e., cation and anion) in these electroactive devices. By employing a two carrier model, the total excess ions stored and strains generated by the cations and anions, and their transport times in the nanocomposites can be determined, which all depend critically on the morphologies of the conductor network nanocomposites.
Theoretical simulation on the variation in the transport behavior under pressure and magnetic field in La0.825Sr0.175MnO3
Authors: Wang Jing-Yi , Hu Chun-Lian , Jin Kui-Juan , Lu Hui-Bin , Wang Cong , Zhao Rui-Qiang , Yang Guo-Zhen
Published: June 2010

Based on phase separation model and breadth-first traversal algorithm, the spin-related electron transport property of La0.825Sr0.175MnO3 under hydrostatical pressure and magnetic field was systematically simulated. We find that the external hydrostatical pressure has a more important influence on the residual resistivity, high temperature resistivity coefficient, activation energy, and electron scattering of La0.825Sr0.175MnO3 than the external magnetic field. However, the Curie temperature and the magnon scattering are more sensitive to the external magnetic field than to the external hydrostatical pressure in La0.825Sr0.175MnO3.
Modeling the performance of magnetic nanoparticles in multimodal cancer therapy
Authors: Purushotham S. , Ramanujan R. V.
Published: June 2010

Composite magnetic nanoparticles (MNPs) consisting of an MNP core and drug loaded polymer shell can increase the efficacy of cancer therapy by overcoming several limitations of conventional hyperthermia and chemotherapy. Multimodal therapy consisting of simultaneous hyperthermia and chemotherapy can increase therapeutic efficiency compared to individual applications of these modalities. Factors influencing power output in an alternating magnetic field (AMF) for superparamagnetic γ-Fe2O3 and Fe3O4 iron oxide MNP were studied. The optimum MNP properties for in vivo magnetic hyperthermia were identified. For a 375 kHz AMF, 23 nm γ-Fe2O3 MNP and 12 nm Fe3O4 MNP produce maximum heating, heat generation is dependent primarily on Néel relaxation and is insensitive to polymer shell thickness. The heating of tumors by uniformly distributed magnetic clusters of optimized iron oxide MNP was modeled. The MNP mass required to heat tumors to hyperthermia temperatures was calculated, the Fe3O4 MNP concentration in the tumor required for hyperthermia was in the range of 0.12–2.2 g ml−1 for Fe3O4 and 0.06–1.7 g ml−1 for γ-Fe2O3 MNP respectively. In vitro drug release from doxorubicin loaded poly-n-isopropylacrylamide coated MNP was also modeled to understand the influence of shell thickness on thermoresponsive drug release. An increase in shell thickness or decrease in temperature resulted in decreased drug release rates. The MNP mass requirements for hyperthermia closely match the requirements for chemotherapy confirming the feasibility of these particles for combined hyperthermia and drug release applications.