bluuebunny/crossref_metadata_2025 huggingface dataset:
Bending‐like behavior of thin wedge‐shaped elastic fault blocks
Authors: Hu Yan , Wang Kelin
Published: June 2006

We derive an Airy stress function solution for a submarine or subareal, infinite or finite, elastic wedge with a frictional basal fault. The solution has a simple compact expression and has corrected errors present in earlier elastic wedge solutions. We use the solution to study frequently observed bending‐like behavior of relatively thin wedges, in which lateral tension and compression coexist but are vertically partitioned. Conditions to cause such coexistence are best understood by examining how the position of a neutral line changes in response to variations in basal traction, pore fluid pressure, and wedge geometry. We have used the example of the Mauna Loa–Kilauea rift flank in Hawaii to illustrate how the solution may be applied to geological problems. Our results generally support the concept of a “bent” elastic wedge previously proposed to explain coeval normal faulting in the upper part and reverse faulting in the lower part of the rift flank. However, we find that coexistence of tension and compression in a wedge of this type can occur over a much wider range of pore fluid pressure values and basal friction conditions than previously thought and does not require unusual geological processes.
Optimized smoothing of Gravity Recovery and Climate Experiment (GRACE) time‐variable gravity observations
Authors: Chen J. L. , Wilson C. R. , Seo K.‐W.
Published: June 2006

High‐degree and high‐order spherical harmonics of time‐variable gravity fields observed by the Gravity Recovery and Climate Experiment (GRACE) gravity mission are dominated by noise. We develop two smoothing methods that suppress these high‐degree and high‐order errors with results superior to more commonly used Gaussian smoothing. These optimized smoothing methods considerably improve signal‐to‐noise levels of GRACE terrestrial water storage estimates relative to residual signal and noise over the oceans and show significantly better spatial resolution and lower leakage error. On the basis of analysis using an advanced land surface model, the equivalent spatial resolution from these optimized smoothing estimates is about 500 km, compared to the roughly 800–1000 km Gaussian smoothing that is required to suppress high‐degree noise in the GRACE fields.
Accretionary prisms in subduction earthquake cycles: The theory of dynamic Coulomb wedge
Authors: Wang Kelin , Hu Yan
Published: June 2006

We expand the theory of critically tapered Coulomb wedge for accretionary prisms by considering stress changes in subduction earthquake cycles. Building on the Coulomb plasticity of the classical theory, we assume an elastic–perfectly Coulomb plastic rheology and derive exact stress solutions for stable and critical wedges. The new theory postulates that the actively deforming, most seaward part of an accretionary prism (the outer wedge) overlies the updip velocity‐strengthening part of the subduction fault, and the less deformed inner wedge overlies the velocity‐weakening part (the seismogenic zone). During great earthquakes, the outer wedge is pushed into a compressively critical state, with an increase in basal and internal stresses and pore fluid pressure. After the earthquake, the outer wedge returns to a stable state. The outer wedge geometry is controlled by the peak stress of the updip velocity‐strengthening part of the subduction fault achieved in largest earthquakes. The inner wedge generally stays in the stable regime throughout earthquake cycles, acting as an apparent backstop and providing a stable environment for the formation of forearc basins. The new theory has important implications for the studies of the updip limit of the seismogenic zone, the evolution of accretionary prisms and forearc basins, activation of splay faults and tsunami generation, evolution of the fluid regime, and mechanics of frontal prisms at margins dominated by tectonic erosion.
Flow of synthetic, wet, partially molten “granite” under undrained conditions: An experimental study
Authors: Rutter E. H. , Brodie K. H. , Irving D. H.
Published: June 2006

Major problems in experimental studies of the flow of partially molten granitic rocks are (1) maintaining control of the grain size of the matrix of solid grains, (2) controlling the melt fraction, and (3) controlling the melt viscosity (closely linked to water content). To overcome these problems, we used a synthetic “granitoid” comprising a solid matrix of quartz grains (50 μm grain size) mixed with an albite‐quartz melt prepared from oxides, with added water (2.5 wt %) dissolved in the melt phase (viscosity 9 × 104 Pa s). Experiments were performed undrained, with melt fractions of 0.1, 0.2, 0.25, and 0.3. Constant strain rate, creep, and stress relaxation experiments were carried out in a gas medium apparatus at 1273 and 1173 K, mostly at 300 MPa confining pressure, up to ∼15% shortening strain. Strain rates ranged between 10−4 to less than 10−7 s−1, and fully ductile mechanical behavior was observed. Melt fraction has a more profound effect on strength than water content, temperature, or total confining pressure. Low strain rate (<10−6 s−1) data were fitted to an empirical flow law of the form dɛ/dt = A exp(B ϕm) exp(−H/RT) σn with the parameters logA = −1.39, m = 3, n = 1.8, B = 192, H = 220 kJmol−1, where dɛ/dt is strain rate (s−1), σ is flow stress (MPa), ϕ is melt fraction, and T is temperature (K). Strength is expected to fall rapidly above about 0.4 melt fraction to levels characteristic of flow of the melt containing suspended crystallites. Extrapolation to geological strain rates using this flow law shows that in nature, migmatites bearing granitic melt will be extremely weak, much weaker than silicate rocks deforming by intracrystalline plasticity. Microstructural study shows grains remain equant at all strains, with no discernable formation of a grain flattening fabric nor a large strain contribution from microfracturing; thus bulk intracrystalline plasticity is of minor importance, and intergranular sliding is implied. The nonlinear flow observed is tentatively attributed to a combination of sintering of grain contacts and sliding failure of such contacts, with a substantial contribution from diffusive transfer processes.
Large Eddy Simulation of the ventilated wave boundary layer
Authors: Lohmann I. P. , Fredsøe J. , Sumer B. M. , Christensen E. D.
Published: June 2006

A Large Eddy Simulation (LES) of (1) a fully developed turbulent wave boundary layer and (2) case 1 subject to ventilation (i.e., suction and injection varying alternately in phase) has been performed, using the Smagorinsky subgrid‐scale model to express the subgrid viscosity. The model was found to reproduce experimental results well. However, in case 1, the near‐bed ensemble averaged velocity is underestimated during the acceleration stage, probably due to the Smagorinsky subgrid‐scale model not being able to capture the physics well in that region. Also, there is a general overestimation of the streamwise turbulence intensity, while an underestimation of the intensities in the two other directions. This may be an effect from the stretched computational mesh in the streamwise direction, since the Smagorinsky subgrid viscosity assumes proportionality to one scalar expressing the overall (local) grid size. The results indicate that the large eddies develop in the resolved scale, corresponding to fluid with an effective viscosity decided by the sum of the kinematic and subgrid viscosity. Regarding case 2, the results are qualitatively in accordance with experimental findings. Injection generally slows down the flow in the full vertical extent of the boundary layer, destabilizes the flow and decreases the mean bed shear stress significantly; whereas suction generally speeds up the flow in the full vertical extent of the boundary layer, stabilizes the flow and increases the mean bed shear stress significantly. Ventilation therefore results in a net current, even in symmetric waves.
Analysis of winter dust activity off the coast of West Africa using a new 24‐year over‐water advanced very high resolution radiometer satellite dust climatology
Authors: Evan Amato T. , Heidinger Andrew K. , Knippertz Peter
Published: June 2006

A 24‐year (1982–2005) winter daytime advanced very high resolution radiometer (AVHRR) data set has been processed utilizing a new over‐water dust detection algorithm. The dust data are for the oceanic regions surrounding West Africa and provide a long‐term remotely sensed continuous record of dustiness in the region. These AVHRR dust observations are comparable to dust records produced via the Total Ozone Mapping Spectrometer and Meteosat instruments. Strong positive correlations between the wintertime Jones North Atlantic Oscillation index and this dust record are observed across the entire oceanic region, corroborating earlier studies on the relationship between the two. Also consistent with previous investigations, we find more regional positive and negative correlations between dust and the wintertime Niño 3.4 index and summertime Sahelian precipitation, respectively. Also, unique to satellite studies of interannual dust variability over the North Atlantic, we develop a wintertime AVHRR normalized difference vegetation index time series for the Sahel region. A strong relationship is seen between tropical North Atlantic dustiness and this vegetation index, suggesting the possibility that vegetation changes in the Sahel play an important role in variability of downwind dustiness.
Deep convective influence on the Asian summer monsoon anticyclone and associated tracer variability observed with Atmospheric Infrared Sounder (AIRS)
Authors: Randel William J. , Park Mijeong
Published: June 2006

The Asian summer monsoon anticyclone is linked to climatological deep convection over Southeast Asia, and the coupling of circulation and convection strongly influences constituent behavior in the upper troposphere – lower stratosphere (UTLS). This work explores the variability of the Asian monsoon circulation and trace constituents linked to transient deep convection, on the basis of dynamical fields and outgoing longwave radiation (OLR) data, plus water vapor and ozone retrievals from the Atmospheric Infrared Sounder (AIRS) instrument. Within the monsoon region, transient deep convection varies with a timescale of ∼10–20 days, linked to active/break cycles in the monsoon circulation. We show that these convective events trigger variations of the anticyclone itself, with strong correlations between OLR and the area of low potential vorticity (PV) defining the anticyclone. Relatively high PV (stratospheric air) is also advected to low latitudes to the east of the anticyclone following enhanced convection. AIRS data show that the transient convective events are associated with the vertical transport of low ozone and high water vapor into the UTLS region, with significant effects over potential temperature levels 340–360 K (∼7–13 km). Idealized transport calculations are used to demonstrate that constituent anomalies are confined within the upper tropospheric anticyclone, and this confinement contributes to the climatological constituent patterns observed during summer.
Influences of man‐made emissions and climate changes on tropospheric ozone, methane, and sulfate at 2030 from a broad range of possible futures
Authors: Unger Nadine , Shindell Drew T. , Koch Dorothy M. , Amann Markus , Cofala Janusz , Streets David G.
Published: June 2006

We apply the Goddard Institute for Space Studies composition‐climate model to an assessment of tropospheric O3, CH4, and sulfate at 2030. We compare four different anthropogenic emissions forecasts: A1B and B1 from the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios and Current Legislation (CLE) and Maximum Feasible Reduction (MFR) from the International Institute for Applied Systems Analysis. The projections encompass a wide range of possible man‐made emissions changes. The A1B, B1, and CLE forecasts all suggest large increases in surface O3 and sulfate baseline pollution at tropical and subtropical latitudes, especially over the Indian subcontinent, where the pollution increases may be as large as 100%. The ranges of annual mean regional ground level O3 and sulfate changes across all scenarios are −10 to +30 ppbv and −1200 to +3000 pptv, respectively. Physical climate changes reduce future surface O3, but tend to increase ground level sulfate locally over North Africa because of an enhancement of aqueous‐phase SO2 oxidation. For all examined future scenarios the combined sum of the CH4, O3, and sulfate radiative forcings is positive, even for the MFR scenario, because of the large reduction in sulfate. For A1B the forcings are as much as half of that of the preindustrial to present‐day forcing for each species. For MFR the sign of the forcing for each species is reversed with respect to the other scenarios. At 2030, global changes in climate‐sensitive natural emissions of CH4 from wetlands, NOx from lightning, and dimethyl sulfide from the ocean appear to be small (<5%).
The 1452 or 1453 A.D. Kuwae eruption signal derived from multiple ice core records: Greatest volcanic sulfate event of the past 700 years
Authors: Gao Chaochao , Robock Alan , Self Stephen , Witter Jeffrey B. , Steffenson J. P. , Clausen Henrik Brink , Siggaard‐Andersen Marie‐Louise , Johnsen Sigfus , Mayewski Paul A. , Ammann Caspar
Published: June 2006

We combined 33 ice core records, 13 from the Northern Hemisphere and 20 from the Southern Hemisphere, to determine the timing and magnitude of the great Kuwae eruption in the mid‐15th century. We extracted volcanic deposition signals by applying a high‐pass loess filter to the time series and examining peaks that exceed twice the 31 year running median absolute deviation. By accounting for the dating uncertainties associated with each record, these ice core records together reveal a large volcanogenic acid deposition event during 1453–1457 A.D. The results suggest only one major stratospheric injection from the Kuwae eruption and confirm previous findings that the Kuwae eruption took place in late 1452 or early 1453, which may serve as a reference to evaluate and improve the dating of ice core records. The average total sulfate deposition from the Kuwae eruption was 93 kg SO4/km2 in Antarctica and 25 kg SO4/km2 in Greenland. The deposition in Greenland was probably underestimated since it was the average value of only two northern Greenland sites with very low accumulation rates. After taking the spatial variation into consideration, the average Kuwae deposition in Greenland was estimated to be 45 kg SO4/km2. By applying the same technique to the other major eruptions of the past 700 years our result suggests that the Kuwae eruption was the largest stratospheric sulfate event of that period, probably surpassing the total sulfate deposition of the Tambora eruption of 1815, which produced 59 kg SO4/km2 in Antarctica and 50 kg SO4/km2 in Greenland.
Identification of volcanic rootless cones, ice mounds, and impact craters on Earth and Mars: Using spatial distribution as a remote sensing tool
Authors: Bruno B. C. , Fagents S. A. , Hamilton C. W. , Burr D. M. , Baloga S. M.
Published: June 2006

This study aims to quantify the spatial distribution of terrestrial volcanic rootless cones and ice mounds for the purpose of identifying analogous Martian features. Using a nearest neighbor (NN) methodology, we use the statisticsR(ratio of the mean NN distance to that expected from a random distribution) andc(a measure of departure from randomness). We interpretRas a measure of clustering and as a diagnostic for discriminating feature types. All terrestrial groups of rootless cones and ice mounds are clustered (R: 0.51–0.94) relative to a random distribution. Applying this same methodology to Martian feature fields of unknown origin similarly yieldsRof 0.57–0.93, indicating that their spatial distributions are consistent with both ice mound or rootless cone origins, but not impact craters. Each Martian impact crater group hasR≥ 1.00 (i.e., the craters are spaced at least as far apart as expected at random). Similar degrees of clustering preclude discrimination between rootless cones and ice mounds based solely onRvalues. However, the distribution of pairwise NN distances in each feature field shows marked differences between these two feature types in skewness and kurtosis. Terrestrial ice mounds (skewness: 1.17–1.99, kurtosis: 0.80–4.91) tend to have more skewed and leptokurtic distributions than those of rootless cones (skewness: 0.54–1.35, kurtosis: −0.53–1.13). Thus NN analysis can be a powerful tool for distinguishing geological features such as rootless cones, ice mounds, and impact craters, particularly when degradation or modification precludes identification based on morphology alone.
Quasi‐electrostatic field analysis and simulation of Martian and terrestrial dust devils
Authors: Zhai Y. , Cummer S. A. , Farrell W. M.
Published: June 2006

Recent experimental and modeling studies show that large quasi‐static electric fields (2–20 kV/m) can be developed in a Martian or terrestrial dust devil as a result of contact electrification and charge separation of dust grains with different sizes and compositions. Electric discharging occurs when the maximum electric field reaches breakdown values (∼20 kV/m on Mars and ∼3 MV/m on Earth, at surface altitudes). We derive a maximum electric field in a dust devil and develop a two‐dimensional (2‐D) cylindrically symmetric finite element model for Martian and terrestrial dust devil simulations. Unlike previous models with unlimited field growth, the tribocharging process and the time evolution of the dust devil electric field are self‐consistently limited in our model and the saturated maximum electric fields in our simulations are comparable to past measurements. We study the saturated maximum electric fields for dust storms of different size, atmosphere conductivity and time rate of tribocharging. We also discuss the 2‐D cylindrical field structures surrounding a dust devil and the conductivity gradient effect to the field growth of large Martian dust storms.
Hydrological modeling in swelling/shrinking peat soils
Authors: Camporese M. , Ferraris S. , Putti M. , Salandin P. , Teatini P.
Published: June 2006

Peatlands respond to natural hydrologic cycles of precipitation and evapotranspiration with reversible deformations due to variations of water content in both the unsaturated and saturated zone. This phenomenon results in short‐term vertical displacements of the soil surface that superimpose to the irreversible long‐term subsidence naturally occurring in drained cropped peatlands because of bio‐oxidation of the organic matter. These processes cause changes in the peat structure, in particular, soil density and void ratio. The consequential changes in the hydrological parameters need to be incorporated in water flow dynamical models. In this paper, we present a new constitutive relationship for the soil shrinkage characteristic (SSC) in peats by describing the variation of porosity with moisture content. This model, based on simple physical considerations, is valid for both anisotropic and isotropic three‐dimensional peat deformations. The capability of the proposed SSC to accurately describe the deformation dynamics has been assessed by comparison against a set of laboratory experimental results recently published. The constitutive relationship has been implemented into a Richards' equation–based numerical code and applied for the simulation of the peat soil dynamics as observed in a peatland south of the Venice Lagoon, Italy, in an ad hoc field experiment where the relevant parameters are continuously measured. The modeling results match well a large set of field data encompassing a period of more than 50 days and demonstrate that the proposed approach allows for a reliable reproduction of the soil vertical displacement dynamics as well as the hydrological behavior in terms of, for example, water flow, moisture content, and suction.
Diagnosing model error in canopy‐atmosphere exchange using empirical orthogonal function analysis
Authors: Drewry Darren T. , Albertson John D.
Published: June 2006

The application of complex land surface models to long‐term estimation of water, energy, and CO2 exchange suffers from possible static parameterization of inherently time‐varying properties. This paper presents a method by which structural (i.e., spatial) patterns in model output errors can be identified and associated with errors in a single parameter or set of interacting parameters. We focus on CO2 concentration profiles as the observed quantity containing spatial information on model performance. The core of the method relies on the empirical orthogonal function (EOF) analysis of an ensemble of model error profiles produced by synthetically inducing parameter biases. EOF analyses of the error profiles associated with photosynthetic capacity, stomatal conductance, radiation interception, soil respiration, and turbulent mixing parameters concentrated greater than 94% of the error pattern variability in the first two EOFs, producing very compact (two member) basis sets. Application of the EOFs to the identification of parameter error sources was performed with three sets of synthetic tests. The method was broadly successful at identifying the primary error source when one or two error sources were present, using single‐parameter basis sets. Two‐parameter basis sets were able to identify strongly interacting parameter errors (i.e., errors of approximately equal magnitude). Environmental classification of photosynthetically active radiation and wind speed regimes was effective at untangling error influences for the tightly coupled photosynthetic, radiation, and stomatal conductance parameters. Data analysis of measured concentration profiles was used to derive the environmental classes.
Activation of lumbosacral 5‐HT2Creceptors induces bursts of rhythmic activity in sympathetic nerves to the vas deferens in male rats
Authors: Stafford Stuart A , Tang Kim , Coote John H
Published: June 2006

We previously demonstrated thatp‐chloroamphetamine (PCA) intravenously (i.v.) evokes a specific patterned bursting response in the vas deferens nerve (VDN) of anaesthetised male rats that is associated with contraction of the vas deferens, and ejaculation and contraction of the bulbospongiosus muscles. The present study used selective 5‐HT agonists to induce similar rhythmic bursting responses in the VDN in order to reveal the 5‐HT receptor subtypes involved.

The 5‐HT2Creceptor agonist (1.0 mg kg−1Ro600175 i.v.) evoked the characteristic bursting pattern responses in the VDN. The 5‐HT1Areceptor agonist (1.0 mg kg−18‐OH‐DPAT i.v.) failed to elicit any responses. However, 8‐OH‐DPAT coadministered in combination with Ro600175 induced a potentiation of the responses.

Responses were also evoked in rats with a mid‐thoracic spinalisation, with a more predictable response being observed following the combination of agonists. This suggests an action of both agonists in the lumbosacral spinal cord.

Responses were blocked by 0.5 mg kg−1SB206553 i.v. (5‐HT2B/Creceptor antagonist) or 0.5 mg kg−1WAY100635 i.v. (5‐HT1Areceptor antagonist), but not 0.1 or 1.0 mg kg−1SB269970 i.v. (5‐HT7receptor antagonist).

We suggest that activation of 5‐HT2Cand 5‐HT1Areceptor subtypes synergistically elicits contraction of the vas deferens through the activation of sympathetic preganglionic neurones in the spinal cord.

These data support the idea of a proejaculatory action of 5‐HT2Creceptors in the lumbosacral spinal cord, suggesting a descending 5‐HT excitatory pathway in addition to a 5‐HT inhibitory pathway. An excitatory action of 8‐OH‐DPAT at lumbosacral sites is also evident.

British Journal of Pharmacology(2006)148, 1083–1090. doi:10.1038/sj.bjp.0706814
Na+–K+–2Cl− cotransporter is implicated in gender differences in the response of the rat aorta to phenylephrine
Authors: Palacios Javier , Espinoza Francisco , Munita Carolina , Cifuentes Fredi , Michea Luis
Published: June 2006

Inhibition of the Na+–K+–2Cl− cotransporter (NKCC1) with bumetanide reduced contractile responses to phenylephrine (PE) in male rat aortas (129±4% of 60 mM KCl‐induced contraction control vs 108±7% bumetanide; PE 10−5 M; P<0.01) but did not change equivalent responses in female rat aortas. Removal of the endothelium blunted the effect of NKCC1 inhibition on the response to PE (10−5 M) in males, whereas in denuded aorta from female rats, bumetanide reduced this response (162±5% control vs 146±3% bumetanide; P<0.05).

NKCC1 basal activity did not show gender differences in intact aortic rings, but in the presence of PE, bumetanide‐sensitive 86Rb+/K+ uptake increased more in male than female aortas (179±8 in males vs 158±5 nmol 86Rb+/K+ min−1 (g aorta)−1 in females; P<0.05). PE did not stimulate NKCC1 activity in denuded aorta from male rats. However, in female rats, PE increased NKCC1 activity similarly in both denuded (169±11 nmol 86Rb+/K+ min−1 (g aorta)−1) and intact aortas.

Ovariectomy increased the bumetanide‐sensitive 86Rb+/K+ uptake increase elicited by PE (223±17 nmol 86Rb+/K+ min−1 (g aorta)−1) and hormone replacement with 17β‐estradiol prevented this effect (159±29 nmol 86Rb+/K+ min−1 (g aorta)−1).

Na+,K+‐ATPase basal activity, measured as ouabain‐sensitive 86Rb+/K+ uptake, was similar in male and female rats, but the effect of PE was significantly less in intact male aortas (232±16 in males vs 296±25 nmol 86Rb+/K+ min−1 (g aorta)−1 in females; P<0.05).

Our results suggest that PE induced activation of NKCC1 and Na+,K+‐ATPase in the rat aorta in a gender‐dependent way.

British Journal of Pharmacology (2006) 148, 964–972. doi:10.1038/sj.bjp.0706818
X-ray parabolic lenses made from glassy carbon by means of laser
Authors: Artemiev A. , Snigirev A. , Kohn V. , Snigireva I. , Artemiev N. , Grigoriev M. , Peredkov S. , Glikin L. , Levtonov M. , Kvardakov V. , Zabelin A. , Maevskiy A.
Published: June 2006

Parabolic planar compound refractive lenses (CRLs) made from glassy carbon by means of laser ablation are presented. They have radii of curvatures of 5 and 200μm and geometric apertures of 40 and 900μm, respectively. The numbers of biconcave elements in the CRLs were 4, 7, and 200. The planar lenses allow formation of a linear focus of length comparable with the depths of their profiles. Usage of two CRLs in a crossed geometry provides formation of two-dimensional focus. The lenses were tested at the European Synchrotron Radiation Facility at the bending magnet beam line BM-5. The minimum experimental size of the focus has been achieved as 1.4μm.
Graph transformation method for calculating waiting times in Markov chains
Authors: Trygubenko Semen A. , Wales David J.
Published: June 2006

We describe an exact approach for calculating transition probabilities and waiting times in finite-state discrete-time Markov processes. All the states and the rules for transitions between them must be known in advance. We can then calculate averages over a given ensemble of paths for both additive and multiplicative properties in a nonstochastic and noniterative fashion. In particular, we can calculate the mean first-passage time between arbitrary groups of stationary points for discrete path sampling databases, and hence extract phenomenological rate constants. We present a number of examples to demonstrate the efficiency and robustness of this approach.
Probability and Quantum Symmetries. II. The Theorem of Nœther in quantum mechanics
Authors: Albeverio S. , Rezende J. , Zambrini J.-C.
Published: June 2006

For the largest class of physical systems having a classical analog, a new rigorous, but not probabilistic, Lagrangian version of nonrelativistic quantum mechanics is given, in terms of a notion of regularized action function. As a consequence of the study of the symmetries of this action, an associated Nœther theorem is obtained. All the quantum symmetries resulting from the canonical quantization procedure follow in this way, as well as a number of symmetries which are new even for the case of the simplest systems. The method is based on the study of a corresponding Lie algebra and an analytical continuation in the time parameter of the probabilistic construction given in paper I of this work. Generically, the associated quantum first integrals are time dependent and the probabilistic model provides a natural interpretation of the new symmetries. Various examples illustrate the physical relevance of our results.
Iterative techniques for computing the linearized manifolds of quasiperiodic tori
Authors: Wysham Derin B. , Meiss James D.
Published: June 2006

We develop an iterative technique for computing the unstable and stable eigenfunctions of the invariant tori of diffeomorphisms. Using the approach of Jorba [NonlinearityNONLE5 14, 943 (2001)], the linearized equations are rewritten as a generalized eigenvalue problem. Casting the system in this light allows us to take advantage of the speed of eigenvalue solvers and create an efficient method for finding the first-order approximations to the invariant manifolds of the torus. We present a numerical scheme based on the power method that can be used to determine the behavior normal to such tori, and give some examples of the application of the method. We confirm the qualitative conclusions of the Melnikov calculations of Lomelí and Meiss [NonlinearityNONLE5 16, 1573 (2003)] for a volume-preserving mapping.
A global 12-dimensional ab initio potential energy surface and dynamical studies for the SiH4+H→SiH3+H2 reaction
Authors: Wang Manhui , Sun Xiaomin , Bian Wensheng , Cai Zhengting
Published: June 2006

A global 12-dimensional ab initio interpolated potential energy surface (PES) for the SiH4+H→SiH3+H2 reaction is presented. The ab initio calculations are based on the unrestricted quadratic configuration interaction treatment with all single and double excitations together with the cc-pVTZ basis set, and the modified Shepard interpolation method of Collins and co-workers [K. C. Thompson et al., J. Chem. Phys. 108, 8302 (1998); M. A. Collins, Theor. Chem. Acc. 108, 313 (2002); R. P. A. Bettens and M. A. Collins, J. Chem. Phys. 111, 816 (1999)] is applied. Using this PES, classical trajectory and variational transition state theory calculations have been carried out, and the computed rate constants are in good agreement with the available experimental data.
Capillary condensation and adsorption of binary mixtures
Authors: Weinberger B. , Darkrim-Lamari F. , Levesque D.
Published: June 2006

The adsorption of equimolar binary mixtures of hydrogen-carbon dioxide, hydrogen-methane, and methane-carbon dioxide in porous material models is determined by grand canonical Monte Carlo simulations. The material models have an adsorbent surface similar to that of nanofibers with a herringbone structure. Our main result, which is relevant for hydrogen purification and carbon dioxide capture, is that the adsorption selectivities calculated for the mixtures can differ significantly from those deduced from simulations of the adsorption of pure gases, in particular, when one of the adsorbed gases presents a capillary condensation induced by confinement within the pore network. A comparison of our data is also made with theoretical models used in the literature for predicting the properties of the mixture adsorption.
Comment on “Dynamic ion association in aqueous solutions of sulfate” [J. Chem. Phys. 123, 034508 (2005)]
Authors: Buchner R. , Rudolph W. W. , Hefter G. T.
Published: June 2006

The “dynamic exchange” model of ion association proposed by Watanabe and Hamaguchi, [J. Chem. Phys.123, 034508 (2005)] for aqueous solutions of MgSO4 is shown to be inconsistent with the extensive information available from Raman, relaxation, and thermodynamic studies, all of which can be explained by the Eigen equilibrium model.
Response to “Comment on ‘Ion association dynamics in aqueous solutions of sulfate salts as studied by Raman band shape analysis’ ” [J. Chem. Phys. 124, 247101 (2006)]
Authors: Watanabe Daisuke , Hamaguchi Hiro-o
Published: June 2006

In this Response, answers are given, respectively, to the questions raised in the Comment by Buchner et al. [J. Chem. Phys.(to be published)]. We believe that, in the analysis of vibrational spectra in the liquid phase, dynamic viewpoints are necessary in order to fully understand their band shapes.
Nonuniversality of commonly used correlation-energy density functionals
Authors: Katriel Jacob , Roy Sudip , Springborg Michael
Published: June 2006

The correlation energies of the helium isoelectronic sequence and of Hooke’s atom isoelectronic sequence have been evaluated using an assortment of local, gradient, and metagradient density functionals. The results are compared with the exact correlation energies, showing that while several of the more recent density functionals reproduce the exact correlation energies of the helium isoelectronic sequence rather closely, none is satisfactory for Hooke’s atom isoelectronic sequence. It is argued that the uniformly acceptable results for the helium sequence can be explained through simple scaling arguments that do not hold for Hooke’s atom sequence, so that the latter system provides a more sensitive testing ground for approximate density functionals. This state of affairs calls for further effort towards formulating correlation-energy density functionals that would be truly universal at least for spherically symmetric two-fermion systems.
Interfacial nematodynamics of heterogeneous curved isotropic-nematic moving fronts
Authors: Wincure Benjamin , Rey Alejandro D.
Published: June 2006

The early stages of liquid crystal phase ordering upon thermal quenches of isotropic phases into unstable and metastable temperature ranges is studied using two-dimensional (2D) computational solutions of the governing Landau-de Gennes (L-dG) equations for low molar mass nematic liquid crystals and analysis based on the corresponding interfacial nematodynamic model. The early phase ordering stage, for both unstable and metastable quenches of the isotropic phase, is shown to lead to highly textured nematic spherulites through a mechanism of interfacial defect nucleation. The underlying mechanisms of interface-driven texturing are elucidated using complementary 2D computational parametric studies of the bulk L-dG equation and analysis of the IN model. It is shown that for highly curved nanodomains and realistic elastic anisotropy, sharp interfacial transitions between uniaxial and biaxial states arise and are resolved by interfacial defect nucleation, which upon subsequent migration into the spherulite’s interior leads to strong texturing. This paper shows that texture formation in the early stages of phase ordering is interface driven, and due to low interface tension, elastic anisotropy, and large curvature. Interfacial defect shedding in highly curved, low tension, anisotropic interfaces is a significant defect nucleation mechanism that needs to be taken into account when considering texturing processes.
Towards uniform enhancement in solid-state cross polarization magnetic angle spinning NMR: A scheme incorporating cross polarization with rotational resonance
Authors: Hou Guangjin , Deng Feng , Ye Chaohui , Ding Shangwu
Published: June 2006

A recently proposed experimental scheme for achieving uniform cross polarization enhancement of low-γ nuclear species in solids under magic angle spinning, termed quantitative cross polarization (QUCP) [Hou et al., Chem. Phys. Lett. 421, 356 (2006)], is described, supported with comprehensive theoretical analysis, numerical simulation, and experimental investigation with both uniformly labeled and naturally abundant solids. This method combines cross polarization with dipolar-assisted rotational resonance (DARR) [Takegoshi et al., Chem. Phys. Lett. 344, 631 (2001)] broadband homonuclear recoupling technique to achieve quantitative CP spectra under fast magic angle spinning. In addition to the correct and systematical interpretation on the phenomenon we reported in the previous Letter, a number of general guidelines for performing QUCP experiments are presented in this work. It is firmly established that while the enhancement factor in QUCP depends on the CP contact time, uniform enhancement can nevertheless be realized for all types of carbon group. For natural abundance samples, the polarization transfer rate is generally slower than that in labeled samples, but quasiequilibrium among dilute spins in the mixing period can always be reached and uniform enhancement can be achieved albeit the DARR irradiation time needed can be much longer. For labeled samples, the time gain of QUCP experiment is almost the same as that of conventional CP. For natural abundance samples, it is generally much better than single-pulse experiment. Various representative systems, including uniformly C13-labeled DL-alanine and C13, N15 labeled L-tyrosine, as well as naturally abundant alanine, tyrosine, and monoethyl fumarate, are used to verify the validity of our theoretical analysis and numerical simulation and to demonstrate the utility and advantages of the present approach.
Irreversible extinction of ferroelectric polarization in P(VDF-TrFE) thin films upon melting and recrystallization
Authors: Park Youn Jung , Kang Seok Ju , Park Cheolmin , Kim Kap Jin , Lee Han Sup , Lee Moon Sook , Chung U-In , Park In Jun
Published: June 2006

We observed the irreversible extinction of ferroelectric polarization in spun coated poly(vinylidene fluoride-co-trifluoroethylene) thin films upon melting and recrystallization. We investigate the alteration of the ferroelectric properties correlated with the preferred polymer crystal orientation with respect to the electrodes using grazing incident scattering, spectroscopy, and electron microscopes. Heat treatment above melting point gave rise to the significant reduction of the ferroelectric performance mainly caused by the modification of molecular orientation of polymer crystals whose c and b axes are perpendicular and parallel to the electrode surface, respectively, leading to almost zero effective electric field.
InP-based quantum cascade detectors in the mid-infrared
Authors: Graf Marcel , Hoyler Nicolas , Giovannini Marcella , Faist Jérôme , Hofstetter Daniel
Published: June 2006

We present two InP-based quantum cascade detectors (QCDs) in the mid-infrared wavelength range. Their narrow band detection spectra are centered at 5.3 and 9μm. A vertical intersubband transition followed by a carefully designed extraction cascade, which is adapted to the LO-phonon energy, leads to 10K responsivities R of 3.2 and 9.0mA∕W and background limited detectivities DBLIP* of 2×108 and 3×109 Jones, for the 5.3 and the 9μm devices, respectively. Detection has been observed up to device temperatures of 300K (RT), albeit reasonable performance is restricted to temperatures below 150K (5.3μm) and 70K (9μm). Designed for zero bias operation, QCDs do not produce any dark current and therefore do not suffer from dark current noise and capacitance saturation at long integration times, making them ideal devices for large focal plane arrays.
The design and control of a three-dimensional piezoceramic tube scanner with an inertial slider
Authors: Chao Shih-Hui , Garbini Joseph L. , Dougherty William M. , Sidles John A.
Published: June 2006

Inertial sliders are often used to produce coarse relative positioning for scanning probe microscopes. This article describes the design, dynamic analysis, and control of a compact four-segment piezoceramic tube scanner employing an inertial slider. Velocity feedback control, implemented using two-segment piezoelectric sensing, was used to suppress undesired vibrations in the tube, and to improve scanner step uniformity. The control analysis was based on an empirical open-loop identification of the as-built tube behavior, which was also measured using the two-segment sensing technique. A reset integrator friction simulation predicted the overall system performance, and showed good agreement with experimental results.
Dynamic strength of metals in shock deformation
Authors: Kubota Alison , Reisman David B. , Wolfer Wilhelm G.
Published: June 2006

The Hugoniot and critical shear strength of shock-compressed metals can be obtained directly from molecular dynamics simulations without recourse to surface velocity profiles and their analyses. Results from simulations in aluminum containing an initial distribution of microscopic defects are shown to agree with experimental results.
Highly efficient solution processed blue organic electrophosphorescence with 14lm∕W luminous efficacy
Authors: Mathai Mathew K. , Choong Vi-En , Choulis Stelios A. , Krummacher Benjamin , So Franky
Published: June 2006

We report highly efficient solution processed blue electrophosphorescent organic light emitting diodes (PHOLEDs) utilizing a phosphorescent dye and a nonconjugated polymer host, molecularly doped with electron transporting molecules. Based on a bilayer device architecture blue PHOLEDs with luminous efficacy of 14lm∕W at luminous efficiency reaching 22cd∕A are demonstrated. Analysis of device performance indicates that this high efficiency is achieved by a combination of improved charge balance and light outcoupling efficiency. Our results demonstrate that simple solution processed devices can have efficiencies similar to those published to date for small molecule multilayer PHOLEDs based on the same emitter.
Evidence of oxygen vacancy enhanced room-temperature ferromagnetism in Co-doped ZnO
Authors: Hsu H. S. , Huang J. C. A. , Huang Y. H. , Liao Y. F. , Lin M. Z. , Lee C. H. , Lee J. F. , Chen S. F. , Lai L. Y. , Liu C. P.
Published: June 2006

The annealing effects on structure and magnetism for Co-doped ZnO films under air, Ar, and Ar∕H2 atmospheres at 250°C have been systematically investigated. Room-temperature ferromagnetism has been observed for the as-deposited and annealed films. However, the saturation magnetization (Ms) varied drastically for different annealing processes with Ms∼0.5, 0.2, 0.9, and 1.5μB∕Co for the as-deposited, air-annealed, Ar-annealed, and Ar∕H2-annealed films, respectively. The x-ray absorption spectra indicate all these samples show good diluted magnetic semiconductor structures. By comparison of the x-ray near edge spectra with the simulation on Zn K edge, an additional preedge peak appears due likely to the formation of oxygen vacancies. The results show that enhancement (suppression) of ferromagnetism is strongly correlated with the increase (decrease) of oxygen vacancies in ZnO. The upper limit of the oxygen vacancy density of the Ar∕H2-annealed film can be estimated by simulation to be about 1×1021cm−3.
Ruthenium gate electrodes on SiO2 and HfO2: Sensitivity to hydrogen and oxygen ambients
Authors: Pantisano L. , Schram T. , Li Z. , Lisoni J. G. , Pourtois G. , De Gendt S. , Brunco D. P. , Akheyar A. , Afanas’ev V. V. , Shamuilia S. , Stesmans A.
Published: June 2006

The incorporation of chemical species during annealing at the interface between the Ru gate electrode and the dielectric perturbs the electrostatic potential, thus affecting the effective work function of the metal. For both SiO2 and HfO2 gate dielectrics, O2 anneal at 550°C leads to Ru oxidation (i.e., to RuOx formation) at the Ru∕dielectric interface, resulting in a higher effective work function than that of metallic Ru. In turn, when RuOx is exposed to hydrogen, a work function reduction occurs, caused by either a reduction of RuOx into Ru or hydroxyl incorporation at the interface.
Versatile maskless microscope projection photolithography system and its application in light-directed fabrication of DNA microarrays
Authors: Naiser Thomas , Mai Timo , Michel Wolfgang , Ott Albrecht
Published: June 2006

We present a maskless microscope projection lithography system (MPLS), in which photomasks have been replaced by a Digital Micromirror Device type spatial light modulator (DMD™, Texas Instruments). Employing video projector technology high resolution patterns, designed as bitmap images on the computer, are displayed using a micromirror array consisting of about 786 000 tiny individually addressable tilting mirrors. The DMD, which is located in the image plane of an infinity corrected microscope, is projected onto a substrate placed in the focal plane of the microscope objective. With a 5× [0.25 NA (numerical aperture)] Fluar microscope objective, a fivefold reduction of the image to a total size of 9mm2 and a minimum feature size of 3.5μm is achieved. The ultrahigh pressure lamp of a video projector is a cheap, durable, and powerful alternative to the mercury arc lamps commonly used in lithography applications. The MPLS may be employed in standard photolithography. We have successfully produced patterns in 40μm films of SU-8 photoresist, with an aspect ratio of about 1:10. Our system can be used in the visible range as well as in the near UV (with a light intensity of up to 76mW∕cm2 around the 365nm Hg line). We developed an inexpensive and simple method to enable exact focusing and controlling of the image quality of the projected patterns. Our MPLS has originally been designed for the light-directed in situ synthesis of DNA microarrays. One requirement is a high UV intensity to keep the fabrication process reasonably short. Another demand is a sufficient contrast ratio over small distances (of about 5μm). This is necessary to achieve a high density of features (i.e., separated sites on the substrate at which different DNA sequences are synthesized in parallel fashion) while at the same time the number of stray light induced DNA sequence errors is kept reasonably small. We demonstrate the performance of the apparatus in light-directed DNA chip synthesis and discuss its advantages and limitations.
Enhanced luminescence in GaInNAsSb quantum wells through variation of the arsenic and antimony fluxes
Authors: Bank Seth R. , Yuen Homan B. , Bae Hopil , Wistey Mark A. , Moto Akihiro , Harris James S.
Published: June 2006

Photoluminescence efficiency was enhanced in molecular-beam-epitaxial-grown 1.55-μm GaInNAsSb single quantum wells through modulation of the arsenic and antimony fluxes. The arsenic-to-antimony flux ratio was found to be a key consideration at reduced group-V fluxes in maintaining the beneficial effects of antimony while reducing the number of point defects, most likely arsenic antisites. Samples were also characterized by high-resolution x-ray diffraction, secondary ion mass spectrometry, and low-temperature photoluminescence. These findings offer a means to substantially reduce dilute-nitride laser threshold current densities.
High-k and low-k nanocomposite gate dielectrics for low voltage organic thin film transistors
Authors: Kim Chang Su , Jo Sung Jin , Lee Sung Won , Kim Woo Jin , Baik Hong Koo , Lee Se Jong , Hwang D. K. , Im Seongil
Published: June 2006

Ce O 2 – Si O 2 nanocomposite films were used as the gate dielectrics in organic thin film transistors (OTFTs) with pentacene active semiconductor. CeO2–SiO2 composite films exhibited a high dielectric capacitance of 57nF∕cm2 with exceptionally low leakage current. Good device characteristics were obtained with saturation at low operating voltages (∼2V) and with a field effect mobility of 0.84cm2V−1s−1, a threshold voltage of ∼0.25V, an on/off current ratio of 103, and a subthreshold slope of 0.3V∕decade, whereas the gate leakage current density is considerably lowered. These results should therefore increase the prospects of using OTFTs in low power applications such as portable devices.
Parametric amplification in left-handed transmission line media
Authors: Kozyrev Alexander B. , Kim Hongjoon , van der Weide Daniel W.
Published: June 2006

We introduce active negative-index metamaterials based on left-handed nonlinear transmission line media and measure a greater than 10dB amplification of a weak signal wave at the output of the transmission line due to its parametric interaction with an intensive pump wave, by which energy in a pump wave at one frequency is transferred to the energy in a weak signal wave at another frequency.