bluuebunny/crossref_metadata_2025 huggingface dataset:
Annunciation As Election
Authors: Work Telford
Published: January 2009

In his review of the historical tradition, James McClendon concludes that ‘the doctrine of election or predestination in Scripture viewed as a whole seems fully to warrant none of the paths ecclesiastical doctrine has so far taken’. He finds some hopeful signs, particularly in his own Radical Reformation tradition. Yet his redrawn contours of the doctrine rarely appeal to the tradition so far. ‘The old associations of the doctrine die so hard that (in my judgment) this part of Christian teaching is of litde present service. We do well to emphasize the rule of God in every effective way, while exercising great reserve with regard to this Augustinian deposit’.
Exogenous Shocks in Subsystem Adjustment and Policy Change: The Credit Crunch and Canadian Banking Regulation
Authors: WILLIAMS RUSSELL ALAN
Published: January 2009

This paper explores the impact of internationalization on the financial services policy subsystem in Canada. It uses subsystem adjustment as a concept to bring some analytical clarity to how exogenous factors like globalisation and international crises may impact existing policy regimes. Based on examination of globalisation-induced banking deregulation (1987–1991) and the current crisis of securitized banking, the paper argues that the strength of this approach is that it integrates endogenous effects of the existing subsystem in explaining policy changes in response to what are normally treated as exogenous shocks. Careful effort needs to be made to differentiate the processes of external systemic perturbations from subsystem spillovers as these two processes of adjustment and policy change can lead to different policymaking dynamics over the long term.
An alphavirus replicon-derived candidate vaccine against Rift Valley fever virus
Authors: HEISE M. T. , WHITMORE A. , THOMPSON J. , PARSONS M. , GROBBELAAR A. A. , KEMP A. , PAWESKA J. T. , MADRIC K. , WHITE L. J. , SWANEPOEL R. , BURT F. J.
Published: January 2009

Rift Valley fever virus (RVFV) is a mosquito-transmitted bunyavirus (genusPhlebovirus) associated with severe disease in livestock and fatal encephalitis or haemorrhagic fever in a proportion of infected humans. Although live attenuated and inactivated vaccines have been used in livestock, and on a limited scale in humans, there is a need for improved anti-RVFV vaccines. Towards this goal, Sindbis virus replicon vectors expressing the RVFV Gn and Gc glycoproteins, as well as the non-structural nsM protein, were constructed and evaluated for their ability to induce protective immune responses against RVFV. These replicon vectors were shown to produce the RVFV glycoproteins to high levelsin vitroand to induce systemic anti-RVFV antibody responses in immunized mice, as determined by RVFV-specific ELISA, fluorescent antibody tests, and demonstration of a neutralizing antibody response. Replicon vaccination also provided 100% protection against lethal RVFV challenge by either the intraperitoneal or intranasal route. Furthermore, preliminary results indicate that the replicon vectors elicit RVFV-specific neutralizing antibody responses in vaccinated sheep. These results suggest that alphavirus-based replicon vectors can induce protective immunity against RVFV, and that this approach merits further investigation into its potential utility as a RVFV vaccine.
Probabilistic reasoning with answer sets
Authors: BARAL CHITTA , GELFOND MICHAEL , RUSHTON NELSON
Published: January 2009

This paper develops a declarative language, P-log, that combines logical and probabilistic arguments in its reasoning. Answer Set Prolog is used as the logical foundation, while causal Bayes nets serve as a probabilistic foundation. We give several non-trivial examples and illustrate the use of P-log for knowledge representation and updating of knowledge. We argue that our approach to updates is more appealing than existing approaches. We give sufficiency conditions for the coherency of P-log programs and show that Bayes nets can be easily mapped to coherent P-log programs.
Deformation and eruptions at Mt. Etna (Italy): A lesson from 15 years of observations
Authors: Neri Marco , Casu Francesco , Acocella Valerio , Solaro Giuseppe , Pepe Susi , Berardino Paolo , Sansosti Eugenio , Caltabiano Tommaso , Lundgren Paul , Lanari Riccardo
Published: January 2009

Volcanoes deform as a consequence of the rise and storage of magma; once magma reaches a critical pressure, an eruption occurs. However, how the edifice deformation relates to its eruptive behavior is poorly known. Here, we produce a joint interpretation of spaceborne InSAR deformation measurements and volcanic activity at Mt. Etna (Italy), between 1992 and 2006. We distinguish two volcano‐tectonic behaviors. Between 1993 and 2000, Etna inflated with a starting deformation rate of ∼1 cm yr−1 that progressively reduced with time, nearly vanishing between 1998 and 2000; moreover, low‐eruptive rate summit eruptions occurred, punctuated by lava fountains. Between 2001 and 2005, Etna deflated, feeding higher‐eruptive rate flank eruptions, along with large displacements of the entire East‐flank. These two behaviors, we suggest, result from the higher rate of magma stored between 1993 and June 2001, which triggered the emplacement of the dike responsible for the 2001 and 2002–2003 eruptions. Our results clearly show that the joint interpretation of volcano deformation and stored magma rates may be crucial in identifying impending volcanic eruptions.
Modeling bimolecular reactions and transport in porous media
Authors: Edery Yaniv , Scher Harvey , Berkowitz Brian
Published: January 2009

We quantitatively account for the measured concentration profile from a laboratory experiment of bimolecular (A + B → C) reactive transport in a porous medium with a particle tracking (PT) model. The PT results are in contrast to the analytical solution of the continuum scale advection‐dispersion‐reaction equation, which results in an excess quantity of reaction product (C). The approaches differ in the treatment of the mixing zone, the fluctuations due to the low reactant concentrations, and the localized nature of the reaction. The PT can accommodate a range of transport modes with different temporal distributions. An exponential temporal distribution is equivalent to Fickian transport, which we use for the comparison to the laboratory data; a truncated power‐law (TPL) temporal distribution yields a non‐Fickian transport characteristic of heterogeneous media. We study the influence of disorder on the mixing zone and the product concentration profiles via these contrasting transport modes.
Variations of diurnal and inertial spectral peaks near the bi‐diurnal critical latitude
Authors: Xie Xiao‐Hui , Shang Xiao‐Dong , Chen Gui‐Ying , Sun Lu
Published: January 2009

Three sets of ADCP data obtained from the upper ocean are used to examine possible influence of parametric subharmonic instability (PSI) at ϕc ≈ 13–15°N. Both kinetic‐energy and shear spectra at ϕc reveal that significant peaks appear at subharmonic frequencies of diurnal internal tides. Especially, the 0.5 K1 (subharmonic of K1 tides) can be trapped poleward of its critical latitude (14.52°N), significantly distinguished from wind generated near‐inertial internal waves. Moreover, the enhanced 0.5 K1 motions are more or less subject to a fortnightly spring‐neap circle. Relative to a higher latitude (say 18°N), diurnal motions at ϕc are greatly weakened. In contrast, small vertical‐scale motions in the inertial band and the shear induced by these motions are significantly enhanced. Likely, PSI mechanism plays an important role in these observations, whilst trapped sub‐inertial waves (0.5 K1) may be associated with the presence of negative sub‐inertial eddies.
Seasonal and interannual variability of the surface circulation in the eastern Gulf of Cadiz (SW Iberia)
Authors: Criado‐Aldeanueva F. , García‐Lafuente J. , Navarro G. , Ruiz J.
Published: January 2009

An 11‐year (1996–2007) time series of current meter observations representative of the open sea circulation; a 4‐year (2001–2005) time series of current meter records over the continental shelf and in situ data during different seasons have been compared in order to study the seasonal and interannual variability of the surface circulation in the eastern Gulf of Cadiz. The open sea velocity observations indicate southeastward flow along the northern continental slope of the Gulf of Cadiz, compatible with anticyclonic circulation, during most of the year and more intense during summer months. Flow reversals (northwestward circulation) at seasonal time scales in late autumn and early winter (preferably December and January) are a rather recurrent feature with variable intensity depending on the year. Anticyclonic circulation is associated with westerlies, whereas flow reversals usually take place under easterly episodes, suggesting wind‐driven circulation. Negative North Atlantic Oscillation indices (indicative of southward displacement of the Azores high) are also linked to the reversals. Changes in this mainly wind‐driven large‐scale surface circulation are echoed by the shelf circulation: the coastal countercurrent that closes the mesoscale cyclonic cell over the eastern shelf in spring‐summer (upwelling season) is replaced by and eastward current in autumn and winter.
Density and temperatures of the upper Martian atmosphere measured by stellar occultations with Mars Express SPICAM
Authors: Forget François , Montmessin Franck , Bertaux Jean‐Loup , González‐Galindo Francisco , Lebonnois Sébastien , Quémerais Eric , Reberac Aurélie , Dimarellis Emmanuel , López‐Valverde Miguel A.
Published: January 2009

We present one Martian year of observations of the density and temperature in the upper atmosphere of Mars (between 60 and 130 km) obtained by the Mars Express ultraviolet spectrometer Spectroscopy for Investigation of Characteristics of the Atmosphere of Mars (SPICAM). Six hundred sixteen profiles were retrieved using stellar occultations technique at various latitude and longitude. The atmospheric densities exhibit large seasonal fluctuations due to variations in the dust content of the lower atmosphere which controls the temperature and, thus, the atmospheric scale height, below 50 km. In particular, the year observed by SPICAM was affected by an unexpected dust loading around Ls = 130° which induced a sudden increase of density above 60 km. The diurnal cycle could not be analyzed in detail because most data were obtained at nighttime, except for a few occultations observed around noon during northern winter. There, the averaged midday profile is found to slightly differ from the corresponding midnight profile, with the observed differences being consistent with propagating thermal tides and variations in local solar heating. About 6% of the observed mesopause temperatures exhibits temperature below the CO2 frost point, especially during northern summer in the tropics. Comparison with atmospheric general circulation model predictions shows that the existing models overestimate the temperature around the mesopause (above 80 to 100 km) by up to 30 K, probably because of an underestimation of the atomic oxygen concentration which controls the CO2 infrared cooling.
Rim uplift and crater shape in Meteor Crater: Effects of target heterogeneities and trajectory obliquity
Authors: Poelchau Michael H. , Kenkmann Thomas , Kring David A.
Published: January 2009

We have analyzed the rim structure of Meteor Crater, Arizona, in order to understand the mechanism of rim uplift in simple craters and the causes of the shape of polygonal impact craters. For this purpose, we systematically determined bedding orientation of the autochthonous crater wall and overturned flap and analyzed the kinematics of major radial faults. We found that rim uplift correlates with the crater shape and increases in the corners of the crater. The two main mechanisms of differential uplift are the formation of horizontal interthrust wedges, leading to the doubling of strata in the rim, and radial corner faults, or tear faults, that vertically displace bedrock. The development of Meteor Crater's quadrangular shape is caused by more effective crater excavation flow parallel to major joint sets. Additionally, we infer the impact direction with a newly developed technique, the two corners model, and review the arguments in favor of an oblique trajectory. While the data set is ambiguous, several indicators suggest an impact direction from the NNW. We conclude that oblique impacts should have an effect on early cratering and excavation flow, whereas target heterogeneities like joints start to play a prominent role in later stages when the stresses induced by the excavation flow are in the same order of strength as the material involved.
Aqueous and gaseous nitrogen losses induced by fertilizer application
Authors: Gu Chuanhui , Maggi F. , Riley W. J. , Hornberger G. M. , Xu T. , Oldenburg C. M. , Spycher N. , Miller N. L. , Venterea R. T. , Steefel C.
Published: January 2009

In recent years, concern has grown over the contribution of nitrogen (N) fertilizer use to nitrate (NO3−) water pollution and nitrous oxide (N2O), nitric oxide (NO), and ammonia (NH3) atmospheric pollution. Characterizing soil N effluxes is essential in developing a strategy to mitigate N leaching and emissions to the atmosphere. In this paper, a previously described and tested mechanistic N cycle model (TOUGHREACT‐N) was successfully tested against additional observations of soil pH and N2O emissions after fertilization and irrigation and before plant emergence. We used TOUGHREACT‐N to explain the significantly different N gas emissions and nitrate leaching rates resulting from the different N fertilizer types, application methods, and soil properties. The N2O emissions from NH4+‐N fertilizer were higher than from urea and NO3−‐N fertilizers in coarse‐textured soils. This difference increased with decreases in fertilization application rate and increases in soil buffering capacity. In contrast to methods used to estimate global terrestrial gas emissions, we found strongly nonlinear N2O emissions as a function of fertilizer application rate and soil calcite content. Speciation of predicted gas N flux into N2O and N2 depended on pH, fertilizer form, and soil properties. Our results highlighted the need to derive emission and leaching factors that account for fertilizer type, application method, and soil properties.
Monoterpene emissions and photoinhibition of “living fossil” trees grown under CO2enrichment in a simulated Cretaceous polar environment
Authors: Llorens L. , Llusià J. , Murchie E. H. , Peñuelas J. , Beerling D. J.
Published: January 2009

Polar forests populated high‐latitude landmasses during the Cretaceous and early Paleogene when the climate was warm and the atmospheric CO2concentration ([CO2]) was at least double that of the present‐day. We investigated emission rates and composition of monoterpenes in relation to photoinhibition and photoprotection of two evergreen and three deciduous “living fossil” tree species representative of these ancient forests, after growth in a simulated Cretaceous polar (75°N) environment at either ambient (400 ppm) or elevated (800 ppm) [CO2] for four years. Total monoterpene emission rates peaked during the polar summer, when prolonged periods of 24 h light would have been conducive to enhancing the formation and chemical lifetime of ozone, and hence its radiative forcing. During most of the growing season,α‐pinene was the main compound emitted, although the magnitude and chemical speciation of emissions was highly species specific. Growth at elevated [CO2] changed the composition of monoterpene emissions in evergreen and deciduous species, but only altered total leaf‐scale emission rates of the deciduous species. The continuous daylight (photon flux: 300–400μmol PAR m−2s−1) of the simulated polar summer (14.5 weeks) did not result in leaf photoinhibition or increased photoprotection via the xanthophyll cycle. Nevertheless, species with highα‐pinene emission rates showed also high values of photochemical efficiency at ambient [CO2], suggesting a possible function of this monoterpene in protecting the photosynthetic apparatus. We suggest that high monoterpene emissions from forests during the long polar summers may constitute a regional high‐latitude climatic feedback through alteration of tropospheric composition, and secondary organic aerosol formation. These biotic effects may be important to represent in Earth system models of ancient “greenhouse” climates.
Ontogenic increase of metabolic carbon in freshwater mussel shells (Pyganodon cataracta)
Authors: Gillikin David Paul , Hutchinson Kathryn A. , Kumai Yusuke
Published: January 2009

Incorporation of isotopically light metabolic carbon (CM) can obscure carbon isotope records of dissolved inorganic carbon from biogenic carbonates. Ontogenic increases of CM are common in marine bivalved mollusks, likely reflecting increasing absolute metabolism with increasing body size. Here we use shell aragonite from four specimens of Pyganodon cataracta to test if the same is true in freshwater bivalves. Annual δ18Oaragonite values were not different between individuals suggesting that the aragonite samples represent the same time interval. δ13Caragonite, however, showed an ontogenic decrease, with a strong linear relationship between shell height (H in mm) and %CM (R2 = 0.96; %CM = 0.23*H + 13.33), indicating that more CM is incorporated into larger shells. We estimate that between 15 and 35% of shell carbon is derived from metabolic CO2. Nevertheless, this vital effect does not exclude the use of δ13Caragonite records from freshwater shells as environmental proxies.
Equivalent stimulation of naive and memory CD8 T cells by DNA vaccination: a dendritic cell‐dependent process
Authors: Bedoui Sammy , Davey Gayle M , Lew Andrew M , Heath William R
Published: January 2009

CD8 T‐cell priming following DNA vaccination has been shown to confer protection against infections and tumors. These vaccines, however, have been disappointing in their ability to boost memory responses in prime‐boost settings. We recently found that migratory dendritic cell (DC) subsets inefficiently stimulate memory CD8 T cells, raising the possibility that the poor boosting capacity of DNA encoded antigens might relate to their presentation by subsets of DCs that are only capable of efficiently stimulating naive T cells. Here, we show that DCs are required for T‐cell priming in vivo following intradermal immunization with DNA‐encoded antigens and that epidermal Langerhans cells are relatively unimportant. We then provide evidence that naive and memory CD8 T cells respond equally to DNA‐encoded antigen. These findings show that immunization to DNA‐encoded antigens is strongly DC‐dependent and that the failure to boost memory T‐cell immunity efficiently is not a consequence of a differential capacity of this form of antigen to stimulate naive or memory T cells.
The second-meal phenomenon is associated with enhanced muscle glycogen storage in humans
Authors: Jovanovic Ana , Leverton Emily , Solanky Bhavana , Ravikumar Balasubramanian , Snaar Johanna E. M. , Morris Peter G. , Taylor Roy
Published: January 2009

The rise in blood glucose after lunch is less if breakfast has been eaten. The metabolic basis of this second-meal phenomenon remains uncertain. We hypothesized that storage of ingested glucose as glycogen could be responsible during the post-meal suppression of plasma NEFAs (non-esterified fatty acids; ‘free’ fatty acids). In the present study we determined the metabolic basis of the second-meal phenomenon. Healthy subjects were studied on two separate days, with breakfast and without breakfast in a random order. We studied metabolic changes after a standardized test lunch labelled with 3 g of 13C-labelled (99%) glucose. Changes in post-prandial muscle glycogen storage were measured using 13C magnetic resonance spectroscopy. The rise in plasma glucose after lunch was significantly less if breakfast had been taken (0.9±0.3 compared with 3.2±0.3 mmol/l, with and without breakfast respectively; P<0.001), despite comparable insulin responses. Pre-lunch NEFAs were suppressed after breakfast (0.13±0.03 compared with 0.51±0.04 mmol/l) and levels correlated positively with the maximum glucose rise after lunch (r=0.62, P=0.001). The increase in muscle glycogen signal was greater 5 h after lunch on the breakfast day (103±21 compared with 48±12 units; P<0.007) and correlated negatively with plasma NEFA concentrations before lunch (r=−0.48, P<0.05). The second-meal effect is associated with priming of muscle glycogen synthesis consequent upon sustained suppression of plasma NEFA concentrations.
A dynamic microindentation device with electrical contact detection
Authors: Reilly Matthew A. , Perry Gavin , Ravi Nathan
Published: January 2009

We developed a microindentation instrument that allows direct measurement of the point of contact for reasonably conductive samples. This is achieved in the absence of a contact load using a simple electrical circuit. Force is measured using an optical interrupter to measure the deflection of a cantilever beam. Displacement is achieved using a piezoelectric motor and is measured using an independent optical interrupter. Force and displacement measurements are accomplished in real time, allowing the specification of arbitrary waveforms. The instrument was rigorously validated by comparing mechanical property measurements from the indenter with results from traditional dynamic mechanical analysis. Details of the construction and feedback control schemes are given explicitly.
Coarse-grained models for fluids and their mixtures: Comparison of Monte Carlo studies of their phase behavior with perturbation theory and experiment
Authors: Mognetti B. M. , Virnau P. , Yelash L. , Paul W. , Binder K. , Müller M. , MacDowell L. G.
Published: January 2009

The prediction of the equation of state and the phase behavior of simple fluids (noble gases, carbon dioxide, benzene, methane, and short alkane chains) and their mixtures by Monte Carlo computer simulation and analytic approximations based on thermodynamic perturbation theory is discussed. Molecules are described by coarse grained models, where either the whole molecule (carbon dioxide, benzene, and methane) or a group of a few successive CH2 groups (in the case of alkanes) are lumped into an effective point particle. Interactions among these point particles are fitted by Lennard–Jones (LJ) potentials such that the vapor-liquid critical point of the fluid is reproduced in agreement with experiment; in the case of quadrupolar molecules a quadrupole-quadrupole interaction is included. These models are shown to provide a satisfactory description of the liquid-vapor phase diagram of these pure fluids. Investigations of mixtures, using the Lorentz–Berthelot (LB) combining rule, also produce satisfactory results if compared with experiment, while in some previous attempts (in which polar solvents were modeled without explicitly taking into account quadrupolar interaction), strong violations of the LB rules were required. For this reason, the present investigation is a step towards predictive modeling of polar mixtures at low computational cost. In many cases Monte Carlo simulations of such models (employing the grand-canonical ensemble together with reweighting techniques, successive umbrella sampling, and finite size scaling) yield accurate results in very good agreement with experimental data. Simulation results are quantitatively compared to an analytical approximation for the equation of state of the same model, which is computationally much more efficient, and some systematic discrepancies are discussed. These very simple coarse-grained models of small molecules developed here should be useful, e.g., for simulations of polymer solutions with such molecules as solvent.
Effect of subsurface Ti-interstitials on the bonding of small gold clusters on rutile TiO2(110)
Authors: Madsen Georg K. H. , Hammer Bjørk
Published: January 2009

The density functional theory is used to examine the electronic structure of small Au clusters, supported on rutile TiO2(110) surfaces having subsurface Ti-interstitials. The interstitials reduce the surface and we find that negatively charged gold clusters are stabilized with respect to the stoichiometric surface. The behavior of the open-shell gold clusters can be rationalized in terms of the highest occupied molecular orbitals and the resulting electron affinities. The relative stabilities of closed-shell gold clusters led to recent disagreements in the literature. We show that they are very dependent on the density functional used. As expected, a redshift in the CO stretch vibration is calculated for CO adsorbed on a negatively charged cluster. Somewhat surprisingly a larger redshift is found for CO adsorbed on an overall positively charged Au3 cluster. This is explained by CO being a local probe of the individual Au charges and one Au atom having an electron accumulation.
Compressible viscous flows generated by oscillating flexible cylinders
Authors: Van Eysden Cornelis A. , Sader John E.
Published: January 2009

The fluid dynamics of oscillating elastic beams underpin the operation of many modern technological devices ranging from micromechanical sensors to the atomic force microscope. While viscous effects are widely acknowledged to have a strong influence on these dynamics, fluid compressibility is commonly neglected. Here, we theoretically study the three-dimensional flow fields that are generated by the motion of flexible cylinders immersed in viscous compressible fluids and discuss the implications of compressibility in practice. We consider cylinders of circular cross section and flat blades of zero thickness that are executing flexural and torsional oscillations of arbitrary wave number. Exact analytical solutions are derived for these flow fields and their resulting hydrodynamic loads.
On the N=2 supersymmetric Camassa–Holm and Hunter–Saxton equations
Authors: Lenells J. , Lechtenfeld O.
Published: January 2009

We consider N=2 supersymmetric extensions of the Camassa–Holm and Hunter–Saxton equations. We show that they admit geometric interpretations as Euler equations on the superconformal algebra of contact vector fields on the 1∣2-dimensional supercircle. We use the bi-Hamiltonian formulation to derive Lax pairs. Moreover, we present some simple examples of explicit solutions. As a by-product of our analysis, we obtain a description of the bounded traveling-wave solutions for the two-component Hunter–Saxton equation.
The collisional depolarization of Σ2S+1 radicals by closed shell atoms: Theory and application to OH(A Σ2+)+Ar
Authors: Aoiz F. J. , Brouard M. , Eyles C. J. , Kłos J. , de Miranda M. P.
Published: January 2009

Classical and quantum mechanical expressions for the j-j′ vector correlation (also referred to as the rotational tilt) are presented for the situation in which the initial and final relative velocity directions are unresolved. The quantum mechanical expressions are compared with previous descriptions in the literature. It is shown that in the case of Σ2S+1 radicals in collision with closed shell species, a tensor opacity formalism can be employed in quasiclassical trajectory calculations to provide classical estimates of both open shell spin-rotation state and nuclear hyperfine state changing (or conserving) cross sections. Polarization parameters are also obtained from the same formalism. The method is applied to calculations on the OH(A Σ2+)–Ar system using a recently developed potential energy surface. The results of both the closed and open shell quasiclassical trajectory calculations are found to compare favorably with those from close-coupled closed and open shell quantum mechanical scattering calculations. The accompanying paper provides an experimental test of these calculations and of the potential energy surface they employ.
Investigation of Rayleigh–Taylor turbulence and mixing using direct numerical simulation with experimentally measured initial conditions. II. Dynamics of transitional flow and mixing statistics
Authors: Mueschke Nicholas J. , Schilling Oleg
Published: January 2009

A 1152×760×1280 direct numerical simulation (DNS) using initial conditions, geometry, and physical parameters chosen to approximate those of a transitional, small Atwood number, nonreacting Rayleigh–Taylor mixing experiment was presented in Paper I [Mueschke and Schilling, Phys. Fluids 21, 014106 (2009)]. In addition, the DNS model of the experiment was validated by comparing quantities from the simulation to experimental measurements, including large-scale quantities, higher-order statistics, and vertical velocity and density variance spectra. In Paper II of this study, other quantities not measured in the experiment are obtained from the DNS and discussed, such as the integral- and Taylor-scale Reynolds numbers, Reynolds stress and dissipation anisotropy, two-dimensional density and velocity variance spectra, hypothetical chemical product formation measures (similar to those used in reacting shear flow experiments), other local and global mixing parameters, and the statistical composition of mixed fluid. The integral- and Taylor-scale Reynolds numbers, together with visualizations of vertical and center plane slices of the density and vorticity fields, are used to elucidate the various evolutionary stages of the flow. It is shown that the early-time evolution retains a primarily two-dimensional character until the flow begins to transition to a more three-dimensional state at later times, as also observed in the experiment. The evolution of the three diagonal components of the anisotropy tensors showed that anisotropy persists to the latest times in the simulation. Compensated spectra at the latest time in the DNS suggest very short k−5/3 and k−5/4 inertial subrange scalings of the vertical velocity and density variance spectra, respectively. By interpreting the mixing between the two fluids as a hypothetical, infinitely fast, reversible chemical reaction between the species, the local formation of chemical product, equivalent product thickness, and other standard measures of mixing used in shear-driven turbulence are obtained from the DNS and discussed. Other measures of molecular mixing are shown to be qualitatively similar to the molecular mixing parameter θ on the center plane. Finally, the statistical composition of the mixed fluid is examined using the probability distribution function of the heavy-fluid volume fraction and the averaged composition of mixed fluid. Thus, DNS modeled closely after a physical Rayleigh–Taylor instability and mixing experiment can provide additional insights into the flow physics complementary to the experiment.
Size-dependent Curie transition of Ni nanocrystals
Authors: Lu H. M. , Li P. Y. , Huang Y. N. , Meng X. K. , Zhang X. Y. , Liu Q.
Published: January 2009

The mechanical spectroscopy and magnetization measurements are performed on Ni nanocrystals from room temperature to 650 K. It is found that the peak temperatures of internal friction are in agreement with the corresponding Curie temperatures of Ni nanocrystals obtained from the magnetization-temperature curves, showing that the traditional mechanical spectroscopy can also be employed to investigate the Curie transition of ferromagnetic nanocrystals. Moreover, the analytical model for size-dependent Curie temperature is proposed in terms of a size-dependent melting temperature model. The Curie temperature drops with decreasing grain size in Ni nanocrystals, which agrees with the corresponding experimental results.
Intense pulsed neutron emission from a compact pyroelectric driven accelerator
Authors: Tang V. , Meyer G. , Falabella S. , Guethlein G. , Sampayan S. , Kerr P. , Rusnak B. , Morse J. D.
Published: January 2009

Intense pulsed D–D neutron emission with rates of >1010 n/s during the pulse, pulse widths of approximately hundreds of nanoseconds and neutron yields of greater than 10 000 per pulse, are demonstrated in a compact pyroelectric accelerator. The accelerator consists of a small pyroelectric LiTaO3 crystal that provides the accelerating voltage and an independent compact spark plasma ion source. The crystal voltage versus temperature is characterized and compares well with theory. Results show neutron output per pulse that scales with voltage as V∼1.7. These neutron yields match a simple model of the system at low voltages but are lower than predicted at higher voltages due to charge losses not accounted for in the model. Interpretation of the data against modeling provides understanding of the accelerator and in general pyroelectric LiTaO3 crystals operated as charge limited negative high voltage targets. The findings overall serve as the proof of principle and basis for pyroelectric neutron generators that can be pulsed, giving peak neutron rates orders of magnitude greater than previous work and notably increase the potential applications of pyroelectric based neutron generators.
Phase mapping of domain kinetics in lithium niobate by digital holographic interferometry
Authors: Zhi Ya’nan , Liu De’an , Sun Jianfeng , Yan Aimin , Zhou Yu , Luan Zhu , Dai Enwen , Liu Liren , Qu Weijuan
Published: January 2009

The phase mapping of domain kinetics under the uniform steady-state electric field is achieved and investigated in the LiNbO3 crystals by digital holographic interferometry. We obtained the sequences of reconstructed three-dimensional and two-dimensional wave-field phase distributions during the electric poling in the congruent and near stoichiometric LiNbO3 crystals. The phase mapping of individual domain nucleation and growth in the two crystals are obtained. It is found that both longitudinal and lateral domain growths are not linear during the electric poling. The phase mapping of domain wall motions in the two crystals is also obtained. Both the phase relaxation and the pinning-depinning mechanism are observed during the domain wall motion. The residual phase distribution is observed after the high-speed domain wall motion. The corresponding analyses and discussions are proposed to explain the phenomena.
Influence of nonlinear effects in ZnTe on generation and detection of terahertz waves
Authors: Chen Xiaoshu , He Shan , Shen Zhen , Li Zhao Fu , Xu K. Y. , Wang Gang , Wang Reng , Dai Ning
Published: January 2009

Nonlinear effects, including two-photon absorption, Kerr effect, and terahertz related Kerr-like effect, are observed in one ZnTe crystal used as a terahertz emitter and detector. Experiment results show that nonlinear two-photon absorption of the probe beam, which adds to the difference signal, cannot be ignored. By removing the contribution of two-photon absorption, we demonstrate that the phase change in probe beam is due to Kerr effect and terahertz related Kerr-like effect. A phase sensitive time resolved z-scan method is introduced to study the relationship between Kerr effect and terahertz related Kerr-like nonlinear effect, and the latter one is proved not to be only the primary fact that causes phase change in probe beam in one ZnTe.
Design of high power radio frequency radial combiner for proton accelerator
Authors: Jain Akhilesh , Sharma Deepak Kumar , Gupta Alok Kumar , Hannurkar P. R.
Published: January 2009

A simplified design method has been proposed for systematic design of novel radio frequency (rf) power combiner and divider, incorporating radial slab-line structure, without using isolation resistor and external tuning mechanism. Due to low insertion loss, high power capability, and rigid mechanical configuration, this structure is advantageous for modern solid state rf power source used for feeding rf energy to superconducting accelerating structures. Analysis, based on equivalent circuit and radial transmission line approximation, provides simple design formula for calculating combiner parameters. Based on this method, novel 8-way and 16-way power combiners, with power handling capability of 4 kW, have been designed, as part of high power solid state rf amplifier development. Detailed experiments showed good performance in accordance with theory.
Strong and stable blue photoluminescence: The peapodlike SiOx@Al2O3 heterostructure
Authors: Chen Da-Yan , Shao Ming-Wang , Cheng Liang , Wang Xiu-Hua , Ma Dorothy Duo-Duo
Published: January 2009

Peapodlike heterostructure composed of SiOx particles orderly embedded in the high-crystalline α-Al2O3 nanoribbons was fabricated via a two-step thermal reaction route. The room temperature photoluminescence spectrum of the products showed a strong and stable blue emission centered at 467 nm under excitation at 320 nm, which was attributed to the especial heterostructure. This technique also provided a general and convenient approach for preparing even more complex heterostructures and would be useful in improving the properties of materials.
Jeans instability in a quantum dusty magnetoplasma
Authors: Salimullah M. , Jamil M. , Shah H. A. , Murtaza G.
Published: January 2009

Jeans instability in a homogeneous cold quantum dusty plasma in the presence of the ambient magnetic field and the quantum effect arising through the Bohm potential has been examined using the quantum magnetohydrodynamic model. It is found that the Jeans instability is significantly reduced by the presence of the dust-lower-hybrid wave and the ion quantum effect. The minimum wavenumber for Jeans stability depends clearly on ion quantum effect and the dust-lower-hybrid frequency also.
High-dielectric-permittivity high-elasticity three-component nanocomposites with low percolation threshold and low dielectric loss
Authors: Dang Zhi-Min , Xia Bing , Yao Sheng-Hong , Jiang Mei-Juan , Song Hong-Tao , Zhang Li-Qun , Xie Dan
Published: January 2009

Three-component high-elasticity nanocomposites consisting of methyl vinyl silicone rubber (VMQ) and nanosized barium titanate (BT) and carbon black (CB) were fabricated. Studies on dielectric property and elastic modulus of the CB-BT/VMQ nanocomposites showed that the composites had a low percolation threshold (fc=0.0355) due to the use of nanosized CB, and the maximum of dielectric permittivity was 960 at 103 Hz with a low dielectric loss (0.04). When the concentration of CB was close to fc, the dielectric permittivity was sensitive to the change in temperature. The present dielectric properties and excellent elasticity would satisfy the need in practical applications, especially in some fields of cable accessories and heat sensitive sensors.
Epitaxy of Ge–Sb–Te phase-change memory alloys
Authors: Braun Wolfgang , Shayduk Roman , Flissikowski Timur , Ramsteiner Manfred , Grahn Holger T. , Riechert Henning , Fons Paul , Kolobov Alex
Published: January 2009

The authors demonstrate the epitaxy of Ge–Sb–Te alloys close to the Ge2Sb2Te5 composition on GaSb(001). Using molecular beam epitaxy with elemental sources, amorphous films are obtained at growth temperatures below 120 °C and films with a cubic structure and a predominant cube-on-cube epitaxial relationship above 180 °C. Using a high-power pulsed laser, the epitaxial films are switched between the crystalline and the amorphous phases. Streaks in the diffraction data help to resolve the apparent ambiguity in interatomic distances between earlier x-ray absorption and powder diffraction measurements. The structural changes are confirmed by Raman spectroscopy.
Laser scanning confocal microscope with programmable amplitude, phase, and polarization of the illumination beam
Authors: Boruah B. R. , Neil M. A. A.
Published: January 2009

We describe the design and construction of a laser scanning confocal microscope with programmable beam forming optics. The amplitude, phase, and polarization of the laser beam used in the microscope can be controlled in real time with the help of a liquid crystal spatial light modulator, acting as a computer generated hologram, in conjunction with a polarizing beam splitter and two right angled prisms assembly. Two scan mirrors, comprising an on-axis fast moving scan mirror for line scanning and an off-axis slow moving scan mirror for frame scanning, configured in a way to minimize the movement of the scanned beam over the pupil plane of the microscope objective, form the XY scan unit. The confocal system, that incorporates the programmable beam forming unit and the scan unit, has been implemented to image in both reflected and fluorescence light from the specimen. Efficiency of the system to programmably generate custom defined vector beams has been demonstrated by generating a bottle structured focal volume, which in fact is the overlap of two cross polarized beams, that can simultaneously improve both the lateral and axial resolutions if used as the de-excitation beam in a stimulated emission depletion confocal microscope.
Determination of localized-state distributions in organic light-emitting diodes by impedance spectroscopy
Authors: Okachi Takayuki , Nagase Takashi , Kobayashi Takashi , Naito Hiroyoshi
Published: January 2009

A method for determining localized-state distributions in organic light-emitting diodes by impedance spectroscopy is proposed on the basis of a theory for single-injection space-charge-limited current. The method is sensitive and has high energy resolution. The applicability of the method is demonstrated in polyfluorene-based Green K (Sumation™) light-emitting polymer; the localized-state distributions in this polymer are mapped out in the energy range of 0.3–0.8 eV, both below the conduction-band mobility edge and above the valence-band mobility edge.
Lasing-induced reduction in core heating in high wall plug efficiency quantum cascade lasers
Authors: Hoffman Anthony J. , Braun Phillip X. , Escarra Matthew D. , Howard Scott S. , Franz Kale J. , Wang Xiaojun , Fan Jenyu , Gmachl Claire
Published: January 2009

Quantum cascade (QC) laser core heating is a primary impediment to high device wall plug efficiency (WPE). Here, we demonstrate that efficient photon generation produces a quantifiable reduction in heating of the QC laser core temperature. By superimposing low duty cycle current pulses on a core-heating dc baseline, we observe the instantaneous threshold current and current efficiency evolution as the dc input is varied. From these measurements we recover the laser core temperature Tcore. Results agree well with calculations of Tcore based on measured thermal resistance and WPE. Using the same thermal model for a laser with negligible WPE, we show that the large WPE of the measured device—24% for an 80 K heat sink—results in a core temperature reduction of ∼15 K.
TiN/Al Ohmic contacts to N-face n-type GaN for high-performance vertical light-emitting diodes
Authors: Jeon Joon-Woo , Seong Tae-Yeon , Kim Hyunsoo , Kim Kyung-Kook
Published: January 2009

We report on the electrical properties of TiN(30 nm)/Al(200 nm) Ohmic contacts to N-face n-type GaN for high-performance vertical light-emitting diodes and compare them with those of Ti(30 nm)/Al(200 nm) contacts. Both the as-deposited samples show Ohmic behaviors with contact resistivity of (6.0–7.2)×10−4 Ω cm2. However, annealing the samples at 300 °C causes the degradation of their electrical properties. Furthermore, unlike the TiN/Al contacts, the Ti/Al contacts suffer from aging degradation when exposed to air. Based on the x-ray photoemission spectroscopy and secondary ion mass spectrometry results, Ohmic formation and degradation mechanisms are briefly described and discussed.
Frequency-dependent reflection of spin waves from a magnetic inhomogeneity induced by a surface direct current
Authors: Neumann T. , Serga A. A. , Hillebrands B. , Kostylev M. P.
Published: January 2009

The reflectivity of a highly localized magnetic inhomogeneity is experimentally studied. The inhomogeneity is created by a direct current carrying wire placed on the surface of a ferrite film. The reflection of propagating dipole-dominated spin-wave pulses is found to be strongly dependent on the spin-wave frequency if the current locally increases the magnetic field. In the opposite case, the frequency dependence is negligible.
Room temperature negative differential resistance in DNA-based molecular devices
Authors: Jangjian Peng-Chung , Liu Tzeng-Feng , Li Mei-Yi , Tsai Ming-Shih , Chang Chia-Ching
Published: January 2009

A molecular device fabricated from metallic deoxyribonucleic acid (M-DNA) exhibits a negative differential resistance (NDR) behavior. When two gold electrodes were connected by Ni2+-chelated DNA, which was converted from λ-DNA, not only was the conductivity of DNA improved, but a NDR device was formed as a full cyclic voltage sweep was applied to measure its current versus voltage characteristics at room temperature and in an ambient environment. Such electronic characteristics of a M-DNA device may have been caused by the redox reactions of Ni ions. This finding provides a simple way to construct electrical nanodevices from biological molecules.
Time stretch enhanced recording oscilloscope
Authors: Gupta Shalabh , Jalali Bahram
Published: January 2009

Recording analog signals using photonic time-stretch technique in a mode which combines advantages of continuous signal capture, as in real-time analog-to-digital converters (ADCs), and very high bandwidth capability of (equivalent-time) sampling oscilloscopes, is proposed. It is shown that the eye diagrams of high speed serial data can be acquired at least 100 times faster than the fastest capture rates today. Unlike conventional sampling scopes, this technique can capture ultrafast dynamics of repetitive signals, nonrepetitive signals, and rare events. Experimentally, 45 Gbit/s data eye diagram measurement is demonstrated.
Tunable broadband antireflection structures for silicon at terahertz frequency
Authors: Chen Y. W. , Han P. Y. , Zhang X.-C.
Published: January 2009

We report enhanced transmission of broadband terahertz electromagnetic waves in the frequency range from 0.2 to 3.15 THz using silicon with micropyramid surface structures. We observe a maximum 89% reduction in reflectivity of terahertz power when the sample with 60-μm-period micropyramids is used, compared to a planar silicon substrate. By varying the period of micropyramid structures from 110 to 30 μm, the cutoff frequency of enhanced transmission is tuned from 0.74 to 2.93 THz and the bandwidth of enhancement increases from 0.91 to 3.15 THz, respectively.
Gold in graphene: In-plane adsorption and diffusion
Authors: Malola Sami , Häkkinen Hannu , Koskinen Pekka
Published: January 2009

We study the bonding and diffusion of Au in graphene vacancies using density-functional theory. Energetics show that Au adsorbs preferably to double vacancies, steadily in-plane with graphene. All diffusion barriers for the complex of Au in double vacancy are above 4 eV, whereas the barriers for larger vacancies are below 2 eV. Our results support the main results of a recent experiment [Y. Gan et al., Small 4, 587 (2008)] but suggest that the observed diffusion mechanism is not thermally activated but radiation enhanced.
Formation of compensated defects in zinc magnesium oxides assignable from diffusion coefficients and hard x-ray photoemission
Authors: Ohsawa Takeo , Sakaguchi Isao , Ohashi Naoki , Haneda Hajime , Ryoken Haruki , Matsumoto Kenji , Hishita Shunichi , Adachi Yutaka , Ueda Shigenori , Yoshikawa Hideki , Kobayashi Keisuke
Published: January 2009

We studied metastable (Zn1−xMgx)O alloy films having a high MgO fraction, e.g., x=0.47, in excess of its solubility limit (x≈0.15). Residual electron concentrations in the metastable films were close to those of the stable films having a smaller MgO fraction (x=0.07). In contrast to the electric conductivity, diffusivities of both cation and anion in the metastable films were surprisingly higher than those in the stable films, indicating that a high concentration of compensated defects were generated in the metastable alloy with a high MgO fraction. Photoemission spectroscopy confirmed the presence of ionized acceptors for charge compensation in the metastable (Zn1−xMgx)O.