bluuebunny/crossref_metadata_2025 huggingface dataset:
Development, testing, and applications of site‐specific tsunami inundation models for real‐time forecasting
Authors: Tang L. , Titov V. V. , Chamberlin C. D.
Published: December 2009

The study describes the development, testing and applications of site‐specific tsunami inundation models (forecast models) for use in NOAA's tsunami forecast and warning system. The model development process includes sensitivity studies of tsunami wave characteristics in the nearshore and inundation, for a range of model grid setups, resolutions and parameters. To demonstrate the process, four forecast models in Hawaii, at Hilo, Kahului, Honolulu, and Nawiliwili are described. The models were validated with fourteen historical tsunamis and compared with numerical results from reference inundation models of higher resolution. The accuracy of the modeled maximum wave height is greater than 80% when the observation is greater than 0.5 m; when the observation is below 0.5 m the error is less than 0.3 m. The error of the modeled arrival time of the first peak is within 3% of the travel time. The developed forecast models were further applied to hazard assessment from simulated magnitude 7.5, 8.2, 8.7 and 9.3 tsunamis based on subduction zone earthquakes in the Pacific. The tsunami hazard assessment study indicates that use of a seismic magnitude alone for a tsunami source assessment is inadequate to achieve such accuracy for tsunami amplitude forecasts. The forecast models apply local bathymetric and topographic information, and utilize dynamic boundary conditions from the tsunami source function database, to provide site‐ and event‐specific coastal predictions. Only by combining a Deep‐ocean Assessment and Reporting of Tsunami‐constrained tsunami magnitude with site‐specific high‐resolution models can the forecasts completely cover the evolution of earthquake‐generated tsunami waves: generation, deep ocean propagation, and coastal inundation. Wavelet analysis of the tsunami waves suggests the coastal tsunami frequency responses at different sites are dominated by the local bathymetry, yet they can be partially related to the locations of the tsunami sources. The study also demonstrates the nonlinearity between offshore and nearshore maximum wave amplitudes.
Heat and turbulent kinetic energy budgets for surface layer cooling induced by the passage of Hurricane Frances (2004)
Authors: Huang Peisheng , Sanford Thomas B. , Imberger Jörg
Published: December 2009

Heat and turbulent kinetic energy budgets of the ocean surface layer during the passage of Hurricane Frances were examined using a three‐dimensional hydrodynamic model. In situ data obtained with the Electromagnetic‐Autonomous Profiling Explorer (EM‐APEX) floats were used to set up the initial conditions of the model simulation and to compare to the simulation results. The spatial heat budgets reveal that during the hurricane passage, not only the entrainment in the bottom of surface mixed layer but also the horizontal water advection were important factors determining the spatial pattern of sea surface temperature. At the free surface, the hurricane‐brought precipitation contributed a negligible amount to the air‐sea heat exchange, but the precipitation produced a negative buoyancy flux in the surface layer that overwhelmed the instability induced by the heat loss to the atmosphere. Integrated over the domain within 400 km of the hurricane eye on day 245.71 of 2004, the rate of heat anomaly in the surface water was estimated to be about 0.45 PW (1 PW = 1015 W), with about 20% (0.09 PW in total) of this was due to the heat exchange at the air‐sea interface, and almost all the remainder (0.36 PW) was downward transported by oceanic vertical mixing. Shear production was the major source of turbulent kinetic energy amounting 88.5% of the source of turbulent kinetic energy, while the rest (11.5%) was attributed to the wind stirring at sea surface. The increase of ocean potential energy due to vertical mixing represented 7.3% of the energy deposited by wind stress.
High‐frequency in situ optical measurements during a storm event: Assessing relationships between dissolved organic matter, sediment concentrations, and hydrologic processes
Authors: Saraceno John Franco , Pellerin Brian A. , Downing Bryan D. , Boss Emmanuel , Bachand Philip A. M. , Bergamaschi Brian A.
Published: December 2009

Dissolved organic matter (DOM) dynamics during storm events has received considerable attention in forested watersheds, but the extent to which storms impart rapid changes in DOM concentration and composition in highly disturbed agricultural watersheds remains poorly understood. In this study, we used identical in situ optical sensors for DOM fluorescence (FDOM) with and without filtration to continuously evaluate surface water DOM dynamics in a 415 km2 agricultural watershed over a 4 week period containing a short‐duration rainfall event. Peak turbidity preceded peak discharge by 4 h and increased by over 2 orders of magnitude, while the peak filtered FDOM lagged behind peak turbidity by 15 h. FDOM values reported using the filtered in situ fluorometer increased nearly fourfold and were highly correlated with dissolved organic carbon (DOC) concentrations (r2 = 0.97), providing a highly resolved proxy for DOC throughout the study period. Discrete optical properties including specific UV absorbance (SUVA254), spectral slope (S290–350), and fluorescence index (FI) were also strongly correlated with in situ FDOM and indicate a shift toward aromatic, high molecular weight DOM from terrestrially derived sources during the storm. The lag of the peak in FDOM behind peak discharge presumably reflects the draining of watershed soils from natural and agricultural landscapes. Field and experimental evidence showed that unfiltered FDOM measurements underestimated filtered FDOM concentrations by up to ∼60% at particle concentrations typical of many riverine systems during hydrologic events. Together, laboratory and in situ data provide insights into the timing and magnitude of changes in DOM quantity and quality during storm events in an agricultural watershed, and indicate the need for sample filtration in systems with moderate to high suspended sediment loads.
Analysis of soil carbon transit times and age distributions using network theories
Authors: Manzoni Stefano , Katul Gabriel G. , Porporato Amilcare
Published: December 2009

The long‐term soil carbon dynamics may be approximated by networks of linear compartments, permitting theoretical analysis of transit time (i.e., the total time spent by a molecule in the system) and age (the time elapsed since the molecule entered the system) distributions. We compute and compare these distributions for different network configurations, ranging from the simple individual compartment, to series and parallel linear compartments, feedback systems, and models assuming a continuous distribution of decay constants. We also derive the transit time and age distributions of some complex, widely used soil carbon models (the compartmental models CENTURY and Rothamsted, and the continuous‐quality Q‐Model), and discuss them in the context of long‐term carbon sequestration in soils. We show how complex models including feedback loops and slow compartments have distributions with heavier tails than simpler models. Power law tails emerge when using continuous‐quality models, indicating long retention times for an important fraction of soil carbon. The responsiveness of the soil system to changes in decay constants due to altered climatic conditions or plant species composition is found to be stronger when all compartments respond equally to the environmental change, and when the slower compartments are more sensitive than the faster ones or lose more carbon through microbial respiration.
Predictions of interplanetary shock arrivals at Earth: Dependence of forecast outcome on the input parameters
Authors: Smith Z. K. , Steenburgh R. , Fry C. D. , Dryer M.
Published: December 2009

Predictions of interplanetary shock arrivals at Earth are important to space weather because they are often followed by geomagnetic disturbances that disrupt human technologies. The success of numerical simulation predictions depends on the codes and on the inputs obtained from solar observations. The inputs are usually divided into the more slowly varying background solar wind, onto which short‐duration solar transient events are superposed. This paper examines the dependence of the prediction success on the range of values of the solar transient inputs. These input parameters are common to many 3‐D MHD codes. The predictions of the Hakamada‐Akasofu‐Fry version 2 (HAFv2) model were used because its predictions of shock arrivals were tested, informally in the operational environment, from 1997 to 2006. The events list and HAFv2's performance were published in a series of three papers. The third event set is used to investigate the success and accuracy of the predictions in terms of the input parameter ranges (considered individually). By defining three thresholds for the input speed, duration, and X‐ray class, it is possible to categorize the prediction outcomes by these input ranges. The X‐ray class gives the most successful classification. Above the highest threshold, 89% of the predictions were successful while below the lowest threshold, only 40% were successful. The accuracy, measured in terms of the time differences between the observed and predicted shock arrivals, also shows largest improvement for the X‐ray class. Guidelines are presented for space weather forecasters using the HAFv2 or other interplanetary simulation models.
Ordovician continental margin terranes in the Lachlan Orogen, Australia: Implications for tectonics in an accretionary orogen along the east Gondwana margin
Authors: Glen R. A. , Percival I. G. , Quinn C. D.
Published: December 2009

Four continental margin turbidite ± black shale terranes of the Lachlan Orogen in the southern Tasmanides of eastern Australia formed in two major systems along the east Gondwana margin and constrain the Ordovician assembly of this accretionary orogen. Key features are the dissimilar stratigraphies of the adjacent Bendigo and Melbourne terranes in the western system; the dissimilar stratigraphies of the adjacent Melbourne and Albury‐Bega terranes that reflect juxtaposition of the two systems during the Middle Devonian, and the presence of the Albury‐Bega Terrane both west and east of the Macquarie Arc in the eastern system that also includes the ocean floor Narooma Terrane and igneous ocean crust terrane(s). Repetition of the Albury‐Bega Terrane either side of the arc requires either rifting or orogen‐parallel, strike‐slip duplication of a once contiguous package. Terrane interactions began in the earliest Gisbornian with early docking, uplift, deformation, and exchange of detritus. Amalgamation occurred in the earliest Silurian Benambran Orogeny with accretion in the Middle Devonian. Over 40 Myr, discrete turbidite terranes aligned along the Gondwana margin in two systems were converted into a very wide orogen characterized by the along‐strike juxtaposition of superficially similar terranes.
An analytical probabilistic model of the quality efficiency of a sewer tank
Authors: Balistrocchi Matteo , Grossi Giovanna , Bacchi Baldassare
Published: December 2009

The assessment of the efficiency of a storm water storage facility devoted to the sewer overflow control in urban areas strictly depends on the ability to model the main features of the rainfall‐runoff routing process and the related wet weather pollution delivery. In this paper the possibility of applying the analytical probabilistic approach for developing a tank design method, whose potentials are similar to the continuous simulations, is proved. In the model derivation the quality issues of such devices were implemented. The formulation is based on a Weibull probabilistic model of the main characteristics of the rainfall process and on a power law describing the relationship between the dimensionless storm water cumulative runoff volume and the dimensionless cumulative pollutograph. Following this approach, efficiency indexes were established. The proposed model was verified by comparing its results to those obtained by continuous simulations; satisfactory agreement is shown for the proposed efficiency indexes.
Perceived Water Conservation Attitudes and Behaviours in Second-Home Island Settings
Authors: Gill Alison , Williams Peter , Thompson Shelagh
Published: December 2009

The availability and quality of water is an issue of increasing concern especially in small islands experiencing the pressures of second-home development. This article explores the perspectives and behaviours of permanent and second-home owner island residents with respect to their freshwater management practices on Mayne Island, British Columbia. It reports that although few differences exist in the stated water uses of these residents, discrepancies exist in the perceived contributions each group makes to this issue. These perceptual differences contribute to a lack of the collective social capital needed to implement an effective water management plan for the area. The findings recommend a variety of strategies for overcoming this problem.
Effect of oxidation and annealing on tunnel barrier structure and composition in IrMn/CoFe/TiOx/CoFe magnetic tunnel junctions
Authors: Kirk Daniel J. , Cockayne David J. H. , Petford-Long Amanda K. , Yi Ge
Published: December 2009

The effects of oxidation time and annealing conditions on sputter-deposited magnetic tunnel junctions with a TiOx barrier have been investigated. High resolution electron microscopy showed that longer oxidation times led to a significant increase in barrier layer width and to the formation of large volumes of oxides of Co and Fe. Annealing promoted extensive diffusion of Mn to the barrier region and the oxidation of Mn to MnOx concurrent with the reduction in oxides of Co and Fe. Annealing also increased the peak oxygen content of the barrier region and resulted in a distinct asymmetry in the barrier oxide structure.
Ultrasound holography for noninvasive imaging of buried defects and interfaces for advanced interconnect architectures
Authors: Shekhawat Gajendra , Srivastava Arvind , Avasthy Shraddha , Dravid Vinayak
Published: December 2009

Imaging high resolution subsurface defects nondestructively in advanced interconnect structures and devices is a challenge and no known metrology tools are available to identify such defects in a nondestructive way at nanometer level. Monitoring these defects necessitate the understanding of their growth mechanism of these interconnects as well as defect formation. We report here the application of scanning near field ultrasound holography by imaging buried defects in copper interconnects and low-K dielectric materials. Defects in these copper lines such as voids and delaminations appear as regions of dark contrast in ultrasound holography imaging due to large acoustic impedance mismatch at the voids. Identification of these buried defects in these interconnect architectures in a nondestructive way will open up unique opportunities in using this technique to detect subsurface defects and material imperfections.
Generation of local magnetic fields at megahertz rates for the study of domain wall propagation in magnetic nanowires
Authors: Bergman Bastiaan , Moriya Rai , Hayashi Masamitsu , Thomas Luc , Tyberg Christy , Lu Yu , Joseph Eric , Rothwell Mary-Beth , Hummel John , Gallagher William J. , Koopmans Bert , Parkin Stuart S. P.
Published: December 2009

We describe a technique for generating local magnetic fields at megahertz rates along magnetic nanowires. Local and global magnetic fields are generated from buried copper fine-pitch wires fabricated on 200mm silicon wafers using standard complementary metal-oxide-semiconductor back-end process technology. In combination with pump-probe scanning Kerr microscopy, we measure the static and dynamic propagation fields of domain walls in permalloy nanowires.
Atomically abrupt and unpinned Al2O3/In0.53Ga0.47As interfaces: Experiment and simulation
Authors: Kim Eun Ji , Chagarov Evgueni , Cagnon Joël , Yuan Yu , Kummel Andrew C. , Asbeck Peter M. , Stemmer Susanne , Saraswat Krishna C. , McIntyre Paul C.
Published: December 2009

III-V semiconductor field effect transistors require an insulator/channel interface with a low density of electrically active defects and a minimal interface dipole to avoid Fermi level pinning. We demonstrate that an atomically abrupt and unpinned interface can be formed between an In0.53Ga0.47As (100) channel and an Al2O3 dielectric layer grown by atomic layer deposition (ALD) when oxidation of the substrate surface is prevented before and during oxide deposition. X-ray photoelectron spectra and electron microscopy indicate that in situ desorption of a protective As2 layer on the In0.53Ga0.47As (100)−4×2 surface followed by ALD of Al2O3 produced an atomically abrupt interface without Fermi level pinning. Temperature-dependent and frequency-dependent capacitance-voltage and conductance-voltage analysis of the resulting Pt/Al2O3/InGaAs capacitors are consistent with movement of the Fermi level through the InGaAs band gap. Moreover, the nearly ideal flat band voltages observed for gate metals of widely varying work function indicate a small oxide/semiconductor interface dipole. Density functional theory calculations of the electronic structure of an ideal amorphous Al2O3/InGaAs (100) interface predict a weak perturbation of the InGaAs electronic structure if its oxidation is avoided, consistent with experiment.
Thermal desorption of C6H6 from surfaces of astrophysical relevance
Authors: Thrower J. D. , Collings M. P. , Rutten F. J. M. , McCoustra M. R. S.
Published: December 2009

The thermal desorption of C6H6 from two astrophysically relevant surfaces has been studied using temperature programmed desorption. Desorption from an amorphous SiO2 substrate was used as a mimic for bare interstellar grains, while multilayer films of amorphous solid water (ASW) were used to study the adsorption of C6H6 on grains surrounded by H2O dominated icy mantles. Kinetic parameters were obtained through a combination of kinetic modeling, leading edge analysis, and by considering a distribution of binding sites on the substrate. The latter is shown to have a significant impact on the desorption of small exposures of C6H6 from the amorphous SiO2 substrate. In the case of adsorption on ASW, dewetting behavior and fractional order desorption at low coverage strongly suggest the formation of islands of C6H6 on the H2O surface. The astrophysical implications of these observations are briefly outlined.
Higher-order symplectic integration in Born–Oppenheimer molecular dynamics
Authors: Odell Anders , Delin Anna , Johansson Börje , Bock Nicolas , Challacombe Matt , Niklasson Anders M. N.
Published: December 2009

The extended Lagrangian formulation of time-reversible Born–Oppenheimer molecular dynamics [A. M. N. Niklasson, C. J. Tymczak, and M. Challacombe, Phys. Rev. Lett. 100, 123004 (2008); Phys. Rev. Lett. 97, 123001 (2006)] enables the use of geometric integrators in the propagation of both the nuclear and the electronic degrees of freedom on the Born–Oppenheimer potential energy surface. Different symplectic integrators up to the sixth order have been adapted and optimized in the framework of ab initio self-consistent-field theory. It is shown how the accuracy can be significantly improved compared to a conventional Verlet integration at the same level of computational cost, in particular, for the case of very high accuracy requirements.
Fast reaction mechanism of a core(Al)-shell (Al2O3) nanoparticle in oxygen
Authors: Wang Weiqiang , Clark Richard , Nakano Aiichiro , Kalia Rajiv K. , Vashishta Priya
Published: December 2009

Atomistic mechanisms of oxidation in a laser flash heated core (Aluminum)-shell (Alumina) nanoparticle are investigated using multimillion-atom molecular dynamics simulations. We find a thermal-to-mechanochemical transition of oxidation mechanism when the initial core temperature is above 6000 K. The transition from thermal diffusion to mechanically enhanced diffusion to ballistic transport is accompanied by a change in the intermediate reaction products from Al rich Al2O to oxygen rich AlO2 clusters. Higher initial temperature of the core causes catastrophic failure of the shell, which provides direct oxidation pathways for core Al, resulting in faster energy release.
Optimization and calibration of atomic force microscopy sensitivity in terms of tip-sample interactions in high-order dynamic atomic force microscopy
Authors: Liu Yu , Guo Qiuquan , Nie Heng-Yong , Lau W. M. , Yang Jun
Published: December 2009

The mechanism of dynamic force modes has been successfully applied to many atomic force microscopy (AFM) applications, such as tapping mode and phase imaging. The high-order flexural vibration modes are recent advancement of AFM dynamic force modes. AFM optical lever detection sensitivity plays a major role in dynamic force modes because it determines the accuracy in mapping surface morphology, distinguishing various tip-surface interactions, and measuring the strength of the tip-surface interactions. In this work, we have analyzed optimization and calibration of the optical lever detection sensitivity for an AFM cantilever-tip ensemble vibrating in high-order flexural modes and simultaneously experiencing a wide range and variety of tip-sample interactions. It is found that the optimal detection sensitivity depends on the vibration mode, the ratio of the force constant of tip-sample interactions to the cantilever stiffness, as well as the incident laser spot size and its location on the cantilever. It is also found that the optimal detection sensitivity is less dependent on the strength of tip-sample interactions for high-order flexural modes relative to the fundamental mode, i.e., tapping mode. When the force constant of tip-sample interactions significantly exceeds the cantilever stiffness, the optimal detection sensitivity occurs only when the laser spot locates at a certain distance from the cantilever-tip end. Thus, in addition to the “globally optimized detection sensitivity,” the “tip optimized detection sensitivity” is also determined. Finally, we have proposed a calibration method to determine the actual AFM detection sensitivity in high-order flexural vibration modes against the static end-load sensitivity that is obtained traditionally by measuring a force-distance curve on a hard substrate in the contact mode.
Composition of β″ precipitates in Al–Mg–Si alloys by atom probe tomography and first principles calculations
Authors: Hasting Håkon S. , Frøseth Anders G. , Andersen Sigmund J. , Vissers Rene , Walmsley John C. , Marioara Calin D. , Danoix Frédéric , Lefebvre Williams , Holmestad Randi
Published: December 2009

The composition of β″ precipitates in an Al–Mg–Si alloy has been investigated by atom probe tomography, ab initio density functional calculations, and quantitative electron diffraction. Atom probe analysis of an Al-0.72% Si-0.58% Mg (at. %) alloy heat treated at 175 °C for 36 h shows that the β″ phase contains ∼20 at. % Al and has a Mg/Si-ratio of 1.1, after correcting for a local magnification effect and for the influence of uneven evaporation rates. The composition difference is explained by an exchange of some Si with Al relative to the published β″-Mg5Si6 structure. Ab initio calculations show that replacing the Si3-site by aluminum leads to energetically favorable compositions consistent with the other phases in the precipitation sequence. Quantitative electron nanodiffraction is relatively insensitive to this substitution of Al by Si in the β″-phase.
Dynamics of proton migration and dissociation in core-excited ethyne probed by multiple ion momentum imaging
Authors: Laksman J. , Céolin D. , Gisselbrecht M. , Canton S. E. , Sorensen S. L.
Published: December 2009

The study focuses on the rapid geometry change in ethyne excited near the carbon 1s edge. Core excitation and ionization lead to population of dicationic states in ethyne. We study three competing dissociation pathways associated with deprotonation in the linear ethyne molecule, and two cases of rapid proton migration. We investigate the alignment of the molecule in the excited state and find startling differences in these three cases. We present evidence for a strong anisotropy in the production of H2+/C2+ fragments through a rapid deformation of the molecule to a dibridged conformation with the transition dipole moment parallel to the polarization of the exciting radiation.
The geometric measure of entanglement for a symmetric pure state with non-negative amplitudes
Authors: Hayashi Masahito , Markham Damian , Murao Mio , Owari Masaki , Virmani Shashank
Published: December 2009

In this paper for a class of symmetric multiparty pure states, we consider a conjecture related to the geometric measure of entanglement: “for a symmetric pure state, the closest product state in terms of the fidelity can be chosen as a symmetric product state.” We show that this conjecture is true for symmetric pure states whose amplitudes are all non-negative in a computational basis. The more general conjecture is still open.
Properties of ZnO influenced by P concentration
Authors: Hu Guangxia , Gong Hao , Wang Yu , Liu H. F.
Published: December 2009

The properties of ZnO were found to be influenced by P concentration. Upon increasing P concentration in ZnO, up to small values of less than 0.1 at. %, the as-deposited ZnO is found to undergo a change from n-type to p-type character. The change is accompanied by a redshift of the optical band gap energy and an increase in the lattice constants of ZnO, which can be attributed to substitution of O by P. A further increase in P concentration, up to 0.4 at. %, leads to a decrease in both lattice constants and energy band gaps of the samples, compared to those of undoped ZnO. Additionally, the electrical conductivity of samples stopped increasing for high P concentrations and became an insulator at P=0.4 at. %. Possible mechanisms for these effects were investigated and discussed.
On alphabetic presentations of Clifford algebras and their possible applications
Authors: Toppan Francesco , Verbeek Piet W.
Published: December 2009

In this paper, we address the problem of constructing a class of representations of Clifford algebras that can be named “alphabetic (re)presentations.” The Clifford algebra generators are expressed as m-letter words written with a three-character or a four-character alphabet. We formulate the problem of the alphabetic presentations, deriving the main properties and some general results. At the end, we briefly discuss the motivations of this work and outline some possible applications.
Complete set of inner products for a discrete PT-symmetric square-well Hamiltonian
Authors: Znojil Miloslav
Published: December 2009

A discrete N-point Runge–Kutta version H(N)(λ) of one of the simplest non-Hermitian square-well Hamiltonians with real spectrum is studied. Its possible Hermitizations mediated by nontrivial (often called “non-Dirac”) metrics Θ≠I are considered as a source of nonequivalent standard probabilistic interpretations of this quantum model. A complete set of these alternative, multiparametric metrics Θ=Θ(a,b,…)(N)(λ) defining all the eligible Hamiltonian-dependent representations of the physical Hilbert space of states is constructed, in closed form, for any coupling λ∊(−1,1) and for any matrix dimension N.
Coupling atomistic and continuum hydrodynamics through a mesoscopic model: Application to liquid water
Authors: Delgado-Buscalioni Rafael , Kremer Kurt , Praprotnik Matej
Published: December 2009

We have conducted a triple-scale simulation of liquid water by concurrently coupling atomistic, mesoscopic, and continuum models of the liquid. The presented triple-scale hydrodynamic solver for molecular liquids enables the insertion of large molecules into the atomistic domain through a mesoscopic region. We show that the triple-scale scheme is robust against the details of the mesoscopic model owing to the conservation of linear momentum by the adaptive resolution forces. Our multiscale approach is designed for molecular simulations of open domains with relatively large molecules, either in the grand canonical ensemble or under nonequilibrium conditions.
A note on the logic of bounded quantum observables
Authors: Li Yuan , Sun Xiu-Hong
Published: December 2009

The set of bounded observables for a quantum system is represented by the set of bounded self-adjoint operators S(H) on a complex Hilbert space H, and the quantum effects for a physical system can be described by the set E(H) of positive contractive operators on a complex Hilbert space H. In this note, by the techniques of operator block and spectral, we give the simpler representation of A∧P and obtained the new necessary and sufficient conditions for A∨P, for A∊S(H) and P∊P(H), where P(H) is the set of all orthogonal projection operators on H. In particular, we get that if A∨P exists, then A∨P∊E(H) for A∊E(H) and P∊P(H). In addition, we consider the relations between the existence of A∨B, A−∨B−, and A+∨B+, where A+, B+, A−, and B− are the positive and negative parts of A,B∊S(H).
Some formulas for invariant phases of unitary matrices by Jarlskog
Authors: Suzuki Tatsuo
Published: December 2009

We describe a calculation of Jarlskog’s determinant in the case of n=4 in detail. Next, we investigate some formulas for invariant phases of unitary matrices and derive some explicit relations for them.
Carrier transfer and redistribution dynamics in vertically aligned stacked In0.5Ga0.5As quantum dots with different GaAs spacer thicknesses
Authors: Kwack Ho-Sang , Cho Yong-Hoon , Song Jin-Dong , Choi Won-Jun , Lee Jung-Il
Published: December 2009

We have investigated optical and structural properties of three-stacked InGaAs quantum dot (QD) structure with GaAs spacer thicknesses of 22, 35, and 88 nm (denoted by QD22, QD35, and QD88, respectively) grown by migration-enhanced molecular beam epitaxy. From temperature-dependent photoluminescence (PL) analysis, it is found that thermal carrier redistribution between vertically adjacent QD layers plays an important role as the thickness of GaAs spacer is reduced from 88 to 22 nm. Although the QD sizes of upper layers are quite similar to those of the first bottom layer, the QDs of the upper layers appear to emit at higher energies probably due to different alloy compositions caused by the strain-induced intermixing effect between InGaAs QDs and GaAs barriers with stacking. Especially for QD22 sample, we observed thermally assisted carriers transfer among vertically adjacent QD layers with increasing temperature by using time-resolved PL measurements, which is in good agreement with the temperature dependence of integrated PL intensity and peak energy position.
Pulsed laser deposited Y3Fe5O12 films: Nature of magnetic anisotropy I
Authors: Manuilov S. A. , Khartsev S. I. , Grishin A. M.
Published: December 2009

Recently we sintered by pulsed laser deposition (PLD) technique the epitaxial Fe-deficient yttrium iron garnet (YIG) films with ferromagnetic resonance (FMR) linewidth as narrow as 0.9 Oe, the uniaxial anisotropy as high as Hu=−880 Oe, and demonstrated them feasible for magnetostatic waves band pass filter application [Manuilov et al., J. Appl. Phys. 105, 033917 (2009)]. Here we explore the origin of unusually high noncubic magnetic anisotropy. Using the angular resolved FMR spectroscopy we found that in addition to strong uniaxial anisotropy, cubic magnetic anisotropy experienced almost fivefold reduction compared to standard YIG grown by liquid phase epitaxy. Molecular field theory was employed to calculate saturation magnetization 4πMs, cubic magnetocrystalline K1, and uniaxial anisotropy Ku in garnets with Fe vacancies. The modeling utilizes crystal field parameters that we revealed from earlier published experimental data on diamagnetic ion substituted Y3Fe5O12 and Fe-substituted isomorphous diamagnetic garnets. Consistent single ion anisotropy crystal field theory perfectly fits experimentally observed high saturation magnetization, reduction in cubic, and appearance of strong uniaxial anisotropy in PLD-grown Fe-deficient YIG films. The redistribution of Fe vacancies between different magnetic sublattices was quantified and confirmed that in YIG(111) films ferric ions preferentially leave vacant octahedrally coordinated sites. Simulation of growth induced anisotropy proves the ordering of Fe3+ vacancies within octahedral sites. At equal number of available ferric ions and vacancies, the latter populate the octahedrons with distortion axis perpendicular to the film surface with the probability equal to 0.67. Deformation blockage of octahedral complexes with distortion axes directed along the film surface reduces this probability down to 0.14.
Combined multiaxial deformation of polymers with in situ small angle and wide angle x-ray scattering techniques
Authors: Gurun B. , Thio Y. S. , Bucknall D. G.
Published: December 2009

A unique multiaxial deformation device has been designed and built specifically for simultaneous synchrotron small angle x-ray scattering (SAXS) and wide angle x-ray scattering (WAXS) measurements. The device can operate at strain rates of 0.0005–0.3 s−1 and induce strains up to stretch ratios of 5. Measurements can either be made at ambient or at elevated temperatures (up to ∼150 °C), the latter using a heating unit. The capabilities of the device coupled with simultaneous SAXS/WAXS measurements have been demonstrated by studying the morphological evolution of a number of polymers and their nanocomposites.
High intensity electron cyclotron resonance proton source for low energy high intensity proton accelerator
Authors: Roychowdhury P. , Chakravarthy D. P.
Published: December 2009

Electron cyclotron resonance (ECR) proton source at 50 keV, 50 mA has been designed, developed, and commissioned for the low energy high intensity proton accelerator (LEHIPA). Plasma characterization of this source has been performed. ECR plasma was generated with 400–1100 W of microwave power at 2.45 GHz, with hydrogen as working gas. Microwave was fed in the plasma chamber through quartz window. Plasma density and temperature was studied under various operating conditions, such as microwave power and gas pressure. Langmuir probe was used for plasma characterization using current voltage variation. The typical hydrogen plasma density and electron temperature measured were 7×1011 cm−3 and 6 eV, respectively. The total ion beam current of 42 mA was extracted, with three-electrode extraction geometry, at 40 keV of beam energy. The extracted ion current was studied as a function of microwave power and gas pressure. Depending on source pressure and discharge power, more than 30% total gas efficiency was achieved. The optimization of the source is under progress to meet the requirement of long time operation. The source will be used as an injector for continuous wave radio frequency quadrupole, a part of 20 MeV LEHIPA. The required rms normalized emittance of this source is less than 0.2 π mm mrad. The simulated value of normalized emittance is well within this limit and will be measured shortly. This paper presents the study of plasma parameters, first beam results, and the status of ECR proton source.
Direct measurement of local volume change in ion-irradiated and annealed SiC
Authors: Bae In-Tae , Weber William J. , Zhang Yanwen
Published: December 2009

Depth profiles of local volume expansions are precisely measured in 6H-SiC after irradiation at 150 K with 2 MeV Pt ions and following annealing at 770 K using transmission electron microscopy equipped with electron energy loss spectroscopy. It is found that the depth profile of local volume expansion from the as-implanted sample matches well with the depth profile of irradiation-induced local disorder measured by Rutherford backscattering spectrometry. Further, the local volume expansion increases linearly with local dose up to ∼10%. By systematically comparing the depth profiles of local volume expansion and local relative disorder, it is revealed that the atomic volume of amorphous SiC continues to increase until it saturates at ∼14% due to the increased chemical short-range disorder. This is believed to be one of the reasons for significant scatter in values of volume expansion previously reported for the irradiation-induced amorphous state of SiC.
The influence of ammonia on the electrical properties of detonation nanodiamond
Authors: Bevilacqua Mose , Chaudhary Aysha , Jackman Richard B.
Published: December 2009

Detonation nanodiamonds (DNDs) are an interesting class of materials for sensing applications, but little is currently understood about their electrical properties. Here, aggregated DNDs are explored with impedance spectroscopy and are found to offer near-to-ideal dielectric characteristics, which is intriguing given their nanostructure. When exposed to ammonia, two highly conductive pathways emerge through the material; these appear to be associated with grain boundary and grain interior processes, the latter potentially due to surface transfer doping. This process is reversible given modest temperature increases suggesting DNDs may offer a solid state electrical platform for ammonia sensing applications.
Surface and size effects on phase diagrams of ferroelectric thin films
Authors: Ma D. C. , Zheng Yue , Woo C. H.
Published: December 2009

Taking into account effects of the surface and depolarization field, we investigated the “misfit strain-temperature” phase diagrams of ferroelectric thin film by using the time-dependent Ginzburg–Landau theory. The simulation results show that the surface effect can shift the phase diagram to lower temperature. More importantly, effect of the depolarization field obviously shrinks the c-phase, and dominates the paraelectric and aa-phase in the phase diagram.
Generating higher-order Lie algebras by expanding Maurer–Cartan forms
Authors: Caroca R. , Merino N. , Perez A. , Salgado P.
Published: December 2009

By means of a generalization of the Maurer–Cartan expansion method, we construct a procedure to obtain expanded higher-order Lie algebras. The expanded higher-order Maurer–Cartan equations for the case G=V0⊕V1 are found. A dual formulation for the S-expansion multialgebra procedure is also considered. The expanded higher-order Maurer–Cartan equations are recovered from S-expansion formalism by choosing a special semigroup. This dual method could be useful in finding a generalization to the case of a generalized free differential algebra, which may be relevant for physical applications in, e.g., higher-spin gauge theories.
Ab initio study of EMIM-BF4 crystal interaction with a Li (100) surface as a model for ionic liquid/Li interfaces in Li-ion batteries
Authors: Valencia Hubert , Kohyama Masanori , Tanaka Shingo , Matsumoto Hajime
Published: December 2009

We examined the atomic and electronic structures of an interface between a 1-ethyl-3-methyl imidazolium tetrafluoroborate (EMIM-BF4) ionic-liquid crystal and a Li(100) surface by periodic density-functional calculations, as a model for a room-temperature ionic-liquid (RTIL) electrolyte/Li interface at a Li-ion battery electrode. Results are compared with our previous theoretical study of the EMIM-BF4 molecular adsorption on Li surfaces [H. Valencia et al., Phys. Rev. B 78, 205402 (2008)]. For the EMIM-BF4 crystal structure, the present projector augmented wave scheme with the generalized gradient approximation can reproduce rather correct intramolecular structures as well as satisfactory short-ranged intermolecular distances, while long-range intermolecular distances are overestimated due to the lack of correct description of long-range dispersive interactions. We constructed a coherent crystal/crystal interface model where four EMIM-BF4 pairs are stacked on a p(4×3) Li (100) surface cell so as to simulate RTIL-layer deposition on a Li surface. We observed significant attraction of surface Li ions toward contacting BF4− anions, counterbalanced by electron transfer toward EMIM+ cations near the interface, revealing the tendency of easy ionization of Li and Lix–BF4 cluster formation, coupled with the reduction of EMIM+. These features are similar to those observed in the EMIM-BF4 molecular adsorption, while these have been proved to occur in the crystal-layer adsorption. We examined the adhesive energy, wetability, and detailed electronic structure at the crystal/crystal interface.
A five-dimensional quantum dynamics study of the F(P2)+CH4 reaction
Authors: Chu Tianshu , Han Keli , Espinosa-Garcia Joaquin
Published: December 2009

By applying the semirigid vibrating rotor target (SVRT) model to the title reaction, five-dimensional wave packet quantum dynamics calculations have been carried out on the new potential energy surface PES-2006 [Espinosa-Garcia et al., J. Phys. Chem. A 111, 2761 (2007)]. The reaction probabilities have been calculated for total angular momentum J up to 105 to obtain the converged integral cross sections over a collision energy range of 0.01–0.345eV. With the polyatomic system initially in its ground rovibrational state |000⟩, no obvious resonance signature has been observed in the integral cross sections although it appears in the reaction probabilities for J⩽40. However, when the umbrella mode of the collision system is initially excited to να0=1 level, |001⟩ state, there is resonance signature in both the reaction probabilities with J⩽55 and the integral cross sections. In addition, rate constants are calculated by Boltzmann averaging of the |000⟩ integral cross sections over collision energy and compared with both the previous kinetic calculations and the experimental measurements. A reasonable agreement has been achieved over the investigated temperature range of 180–400K.
Limited-view photoacoustic imaging based on linear-array detection and filtered mean-backprojection-iterative reconstruction
Authors: Ma Songbo , Yang Sihua , Guo Hua
Published: December 2009

Most existing photoacoustic tomography techniques require collecting complete projection data that are acquired on a defined circle surrounding the object. However, in clinical application, the object can only be approached from a limited angle mostly. Furthermore, with the incomplete projection data acquired in limited view, the general filtered backprojection algorithm will streak image artifacts nearby the reconstructed location of absorbers. In this paper, we present a limited-view-scanning photoacoustic imaging system with a linear transducer array and develop a filtered mean-backprojection-iteration (FMBPI) algorithm to reconstruct the absorbed optical deposit distribution. The FMBPI algorithm combines the terseness of the filtered backprojection algorithm with the accuracy of the iterative reconstruction algorithm. Numerical simulation and experimental results validate that the algorithm can effectively reconstruct high-quality image with limited-view data. It is also demonstrated that with the FMBPI algorithm, the limited-view-scanning multielement photoacoustic imaging system has a great potential to be applied in fast noninvasive clinic diagnosis of breast cancer at the early stage.
Effects of conducting layers on surface acoustic wave in AlN films on diamond
Authors: Sung C. C. , Chiang Y. F. , Ro R. , Lee R. , Wu S.
Published: December 2009

The interdigital transducer (IDT)/AlN/conducting layer/diamond structures are investigated in this study to design surface acoustic wave (SAW) devices in the super high frequency band. Simulation results using the finite element method show that a thin conducting layer can effectively increase the coupling coefficient and, thus, broaden the bandwidth of SAW devices. For the Sezawa mode, it is illustrated that using a Ti layer with a layer thickness-to-wavelength ratio of 0.02 the maximum coupling coefficient is 2.546% and the associated SAW phase velocity is 10657 m/s at the AlN films’ thickness-to-wavelength ratio of 0.14. This coupling coefficient is 105% higher than that in the IDT/AlN/diamond structure. The research results can be applied to design SAW devices using diamond based structures in the super high frequency band.
Surface plasmon resonance in nanostructured metal films under the Kretschmann configuration
Authors: Leong Hai-Sheng , Guo Junpeng , Lindquist Robert G. , Liu Qing H.
Published: December 2009

We systematically investigated the surface plasmon resonance in one-dimensional (1D) subwavelength nanostructured metal films under the Kretschmann configuration. We calculated the reflectance, transmittance, and absorption for varying the dielectric fill factor, the period of the 1D nanostructure, and the metal film thickness. We have found that the small dielectric slits in the metal films reduce the surface plasmon resonance angle and move it toward the critical angle for total internal reflection. The reduction in surface plasmon resonance angle in nanostructured metal films is due to the increased intrinsic free electron oscillation frequency in metal nanostructures. Also we have found that the increasing the spatial frequency of the 1D nanograting reduces the surface plasmon resonance angle, which indicates that less momentum is needed to match the momentum of the surface plasmon-polariton. The variation in the nanostructured metal film thickness changes the resonance angle slightly, but mainly remains as a mean to adjust the coupling between the incident optical wave and the surface plasmon-polariton wave.
Anisotropic thermal transport in highly ordered TiO2 nanotube arrays
Authors: Guo Liying , Wang Jun , Lin Zhiqun , Gacek Sobieslaw , Wang Xinwei
Published: December 2009

This paper reports on the anisotropic thermal transport in highly ordered amorphous and anatase TiO2 nanotube arrays. Strong anisotropic thermal conductivity is observed: 0.617WK−1m−1 along the tube length direction and 0.077–0.102WK−1m−1 in the cross-tube direction for amorphous TiO2 nanotube arrays. The anatase TiO2 nanotube arrays are found to have a higher and anisotropic thermal conductivity, 1.12WK−1m−1 in the tube-length direction and 0.24WK−1m−1 in the cross-tube direction. The experimental results show that the density of the nanotube arrays is much lower than the value estimated from the geometry of the nanotube array, largely due to the existence of defects and loose contact among nanotubes. The thermal contact resistance between TiO2 nanotubes is characterized to be 15.1 and 20.6Km2W−1 for the two measured amorphous samples, and 5.90Km2W−1 for the anatase TiO2 nanotubes. This quantitatively proves that annealing of amorphous TiO2 nanotubes to transform them to anatase phase also improves the contact between nanotubes.
High-temperature lasing characteristics of randomly assembled SnO2 backbone nanowires coated with ZnO nanofins
Authors: Yang H. Y. , Yu S. F. , Liang H. K. , Mote Rakesh G. , Cheng C. W. , Fan H. J. , Sun T. , Hng H. H.
Published: December 2009

Lasing characteristics of randomly assembled SnO2 backbone nanowires coated with ZnO nanofins are investigated. It is shown that the hierarchical nanostructures can sustain ultraviolet random lasing action even at substrate temperature higher than 700 K and the corresponding characteristic temperature is found to be about 390 K. This is because the presence of ZnO nanofins improves heat transfer from the SnO2 backbone nanowires to the surrounding. Hence, some portion of the hierarchical nanostructures can be cooled down and the corresponding optical gain can be maintained even at high substrate temperature.