bluuebunny/crossref_metadata_2025 huggingface dataset:
Plateau‐style accumulation of deformation: Southern Altiplano
Authors: Elger Kirsten , Oncken Onno , Glodny Johannes
Published: August 2005

Employing surface mapping of syntectonic sediments, interpretation of industry reflection‐seismic profiles, gravity data, and isotopic age dating, we reconstruct the tectonic evolution of the southern Altiplano (∼20–22°S) between the cordilleras defining its margins. The southern Altiplano crust was deformed between the late Oligocene and the late Miocene with two main shortening stages in the Oligocene (33–27 Ma) and middle/late Miocene (19–8 Ma) that succeeded Eocene onset of shortening at the protoplateau margins. Shortening rates in the southern Altiplano ranged between 1 and 4.7 mm/yr with maximum rates in the late Miocene. Summing rates for the southern Altiplano and the Eastern Cordillera, we observe an increase from Eocene times to the late Oligocene to some 8 mm/yr, followed by fluctuation around this value during the Miocene prior to shutoff of deformation at 7–8 Ma and transfer of active shortening to the sub‐Andean fold and thrust belt. Shortening inverted early Tertiary graben and half graben systems and was partitioned in three fault systems in the western, central, and eastern Altiplano, respectively. The east vergent fault systems of the western and central Altiplano were synchronously active with the west vergent Altiplano west flank fault system. From these data and from section balancing, we infer a kinematically linked western Altiplano thrust belt that accumulated a minimum of 65 km shortening. Evolution of this belt contrasts with the Eastern Cordillera, which reached peak shortening rates (8 mm/yr) in between the above two stages. Hence local shortening rates fluctuated across the plateau superimposed on a general trend of increasing bulk rate with no trend of lateral propagation. This observation is repeated at the shorter length and time scales of individual growth structures that show evidence for periods of enhanced local rates at a timescale of 1–3 Myr. We interpret this irregular pattern of deformation to reflect a plateau‐style of shortening related to a self‐organized state of a weak crust in the central South American back arc with a fault network that fluctuated around the critical state of mechanical failure. Tuning of this state may have occurred by changes in plate kinematics, during the Paleogene, initially reactivating crustal weak zones and by thermal weakening of the crust with active magmatism mainly in the Neogene stage.
Paleomagnetism of the Gran Sasso range salient (central Apennines, Italy): Pattern of orogenic rotations due to translation of a massive carbonate indenter
Authors: Satolli Sara , Speranza Fabio , Calamita Fernando
Published: August 2005

We report on the paleomagnetism (39 new sites) of Gran Sasso, an indenter‐controlled salient of the external central Apennines formed by two orthogonal limbs. We find that Gran Sasso is a complex salient, paleomagnetically corresponding to neither a nonrotating nor an oroclinal end‐member. Data from the core of the arc show that the indenter itself did not undergo any rotation. Conversely, rotations of variable magnitude and sign are observed along the curve‐shaped thrust fronts. Rotations are virtually absent at both end points of the arc. Moving toward the apex, progressively greater counterclockwise (CCW) and clockwise (CW) rotations occur along the E‐W and N‐S fronts, respectively. The rotations increase continuously and more than linearly, reaching their maximum values (∼80° CCW and ∼50° CW) around the apex. Here, the more strongly CCW and CW rotated fronts are separated by a domain characterized by local block rotations. The inequality between the maximum CCW and CW rotation values is likely a consequence of the asymmetry of the indenter displacement direction (N70°E) with respect to the preorogenic trends of its margins (E‐W and N‐S). From an oroclinal point of view, the fronts close to the end points virtually define a nonrotating arc, while the pattern around the apex is similar to that of an orocline. We conclude that close to end points, nonrotational thrusting normal to the indenter margins occurred, while in the vicinity of the apex, the peritidal carbonates acted as an “ice breaker”, pushing apart (and strongly rotating) the weaker multilayer located ahead.
Growth and composition of high‐Mg calcite in the skeleton of a Bermudian gorgonian (Plexaurella dichotoma): Potential for paleothermometry
Authors: Bond Zoë A. , Cohen Anne L. , Smith Struan R. , Jenkins William J.
Published: August 2005

We used a secondary ion mass spectrometry (SIMS) ion microprobe to analyze magnesium‐to‐calcium (Mg/Ca) and strontium‐to‐calcium (Sr/Ca) ratios of high‐Mg calcite loculi within the skeleton of a shallow water gorgonian, Plexaurella dichotoma, from Bermuda. A cross section of the gorgonian skeleton reveals loculi embedded within proteinaceous gorgonin arranged in concentric rings about the axial core. Viewed in cross section, the loculi are fan‐shaped, 10–140 μm in diameter, and composed of bundles of needle‐shaped crystals that appear to radiate out from a calcification center. Discrete sample spots, each 20 μm diameter, were sputtered from successive loculi along a sample track 3 mm long. Over this distance, 25 bands of high‐low density gorgonin couplets were encountered, estimated to represent the period 1963 to 1988. Mg/Ca ratios show an overall, positive correlation with annual sea surface temperatures (SSTs) that is strongest in the autumn months (October–December). High‐resolution analyses along the growth axes of individual loculi reveal low variability and no trend, consistent with our interpretation of seasonal growth of these calcite inclusions. The sensitivity of Mg/Ca to interannual changes in average autumn temperatures is 0.47 mmol/mol per °C. Conversely, interannual variability in calcite Sr/Ca does not follow the interannual variability in SST and may be influenced primarily by growth rate.
Determination of multiple element/calcium ratios in foraminiferal calcite by quadrupole ICP‐MS
Authors: Yu Jimin , Day Jason , Greaves Mervyn , Elderfield Henry
Published: August 2005

A method has been developed for rapid and precise simultaneous determination of nine element/Ca ratios in foraminiferal tests directly from intensity ratios using external, matrix‐matched standards on a quadrupole inductively coupled plasma–mass spectrometer (ICP‐MS). All quantification isotopes are determined in pulse mode to avoid cross‐calibration. Small argide (40Ar26Mg) interferences on 66Zn are corrected by using two additional Mg and Zn standards. A stable signal, conducive for high‐precision measurements, is obtained by cone conditioning. Variable calcium concentration has negligible effect on Li, Al, Mn, and Sr, but Ca concentrations for standards and samples need to be constrained at a similar level for precise measurements of Zn, Cd, and U. Aliquots of samples are first analyzed for Ca concentrations on an inductively coupled plasma–atomic emission spectrometer (ICP‐AES), and the remaining solutions are diluted to Ca concentration of 100 ppm for ratio measurements to assure data quality. The long‐term reproducibility of the method yielded precisions of Li/Ca = 2.4%, B/Ca = 4.2%, Mg/Ca = 1.4%, Al/Ca = 14%, Mn/Ca = 0.9%, Zn/Ca = 2.8% (1.2∼7.8 μmol/mol) and 5.1% (0.5∼1.2 μmol/mol), Sr/Ca = 0.9%, Cd/Ca = 2.4% (0.07∼0.24 μmol/mol) and 4.8% (0.01∼0.07 μmol/mol), and U/Ca = 2.5% for foraminiferal samples as small as 60 μg.
The El Niño–Southern Oscillation and daily temperature extremes in east Asia and the west Pacific
Authors: Nicholls N. , Baek H.‐J. , Gosai A. , Chambers L. E. , Choi Y. , Collins D. , Della‐Marta P. M. , Griffiths G. M. , Haylock M. R. , Iga N. , Lata R. , Maitrepierre L. , Manton M. J. , Nakamigawa H. , Ouprasitwong N. , Solofa D. , Tahani L. , Thuy D. T. , Tibig L. , Trewin B. , Vediapan K. , Zhai P.
Published: August 2005

The numbers of warm nights and hot days, across most of the east Asia – west Pacific region, increase substantially in the year after the onset of an El Niño event. The number of cool days and cold nights tend to decrease, although the relationship with El Niño is weaker for these variables. The relationship is confounded, for warm nights and hot days, by a strong increasing trend in the numbers of extremes not matched by a trend in the El Niño. Removal of this trend leads to even stronger correlations with the El Niño. Strong correlations exist between some of the extremes indices and an index of the El Niño – Southern Oscillation in months prior to the occurrence of the extremes, indicating that predictions of the frequency of extreme temperatures across the region should be feasible.
On the sensitivity of undeformed Arctic sea ice to its vertical salinity profile
Authors: Vancoppenolle Martin , Fichefet Thierry , Bitz Cecilia M.
Published: August 2005

The temporal evolution of sea ice salinity affects the temperature profile and vertical growth and decay of the ice cover, as well as many other important properties. Here, we use a one‐dimensional thermodynamic sea ice model to explore the sensitivity to the vertical profile of ice salinity of (1) Arctic first‐year and equilibrium multiyear sea ice thickness, and (2) the salt/freshwater flux at the ice/ocean interface. Results indicate that increasing the mean salinity induces a higher thermal inertia reducing summer melt and finally increasing ice thickness. The shape of the profile is also important, since low salinity at the surface must be captured to produce enough surface melt. This study gives accurate hints on what the minimum complexity of a parameterization of the temporal evolution of sea ice salinity should be.
Determination of the ion-drag force in a complex plasma
Authors: Yaroshenko V. , Ratynskaia S. , Khrapak S. , Thoma M. H. , Kretschmer M. , Höfner H. , Morfill G. E. , Zobnin A. , Usachev A. , Petrov O. , Fortov V.
Published: August 2005

The ion-drag force acting on dust particles in the positive column of a dc discharge is measured in the pressure range of 20–120 Pa. The force is obtained by a method which does not require a priori knowledge of the particle charge, but uses the charge gradient determined from the same experiment. The method depends only on two experimentally determined quantities: the particle drift velocity and the electric field. The comparison of experimental results with theoretical models is presented and discussed.
Critical point of electrolyte mixtures
Authors: Hynninen Antti-Pekka , Dijkstra Marjolein , Panagiotopoulos Athanassios Z.
Published: August 2005

The critical behavior of electrolyte mixtures was studied using grand canonical Monte Carlo simulations. Mixtures consist of large multivalent macroions and small monovalent co- and counterions. The system can be viewed as a binary mixture of macroions (with their counterions) and salt (co- and counterion pair). The primitive model description was used, in which the ions are point charges with a hard core and the solvent is treated as a uniform dielectric continuum. The grand canonical simulations are based on insertions and removals of neutral molecules: macroion with its counterions or coions and a counterion. We propose a distance biasing method that enables direct grand canonical simulations up to charge asymmetry of 10:1. We calculated the critical loci that connect the salt-free state, which consists of only macroions and counterions, with the pure salt state using mixed-field finite-size scaling with no pressure mixing. The critical parameters are determined for macroion to counterion charge asymmetries of 2:1, 3:1, and 10:1. Our results suggest that binary electrolyte mixtures are type-I mixtures, where the two components mix continuously.
Characteristic two-dimensional IR spectroscopic features of antiparallel and parallel β-sheet polypeptides: Simulation studies
Authors: Hahn Seungsoo , Kim Seong-Soo , Lee Chewook , Cho Minhaeng
Published: August 2005

The antiparallel and parallel β sheets are two of the most abundant secondary structures found in proteins. Although various spectroscopic methods have been used to distinguish these two different structures, the linear spectroscopic measurements could not provide incisive information for distinguishing an antiparallel β sheet from a parallel β sheet. After carrying out quantum-chemistry calculations and model simulations, we show that the polarization-controlled two-dimensional (2D) IR photon echo spectroscopy can be of critical use in distinguishing these two different β sheets. Particularly, the ratio between the diagonal peak and the cross peak is found to be strongly dependent on the quasi-2D array of the amide I local-mode transition dipole vectors. The relative intensities of the cross peaks in the 2D difference spectrum of an antiparallel β sheet are significantly larger than those of the diagonal peaks, whereas the cross-peak amplitudes in the 2D difference spectrum of a parallel β sheet are much weaker than the main diagonal-peak amplitudes. A detailed discussion on the origin of the diagonal- and cross-peak intensity distributions of both the antiparallel and parallel β sheets is presented by examining vibrational exciton delocalization, relative angles between two different normal-mode transition dipoles, and natures of the cross peaks in the 2D difference spectrum.
Influences of the thermal electron motion and the magnetic field on surface wave discharges
Authors: Cho Suwon
Published: August 2005

The magnetic field and the electron thermal motion are considered to study their effects on propagation and damping of the electromagnetic surface waves and the axial structure of discharges sustained by these waves. The analytic expression for the plasma column resonance frequency is obtained for a magnetized plasma using the electrostatic approximation and it is verified by comparison with the exact numerical solutions of the electromagnetic equation. The electron temperature modifies the dispersion characteristics and the axial structure more significantly at a higher magnetic field when the pressure is relatively low, but its effects are negligible when the electron cyclotron frequency is close to or higher than the wave frequency. For unmagnetized or weakly magnetized plasmas the thermal influence is strong at a moderately high pressure due to the strong inhomogeneity of the radial profile.
Direct calculation of the binding free energies of FKBP ligands
Authors: Fujitani Hideaki , Tanida Yoshiaki , Ito Masakatsu , Jayachandran Guha , Snow Christopher D. , Shirts Michael R. , Sorin Eric J. , Pande Vijay S.
Published: August 2005

Direct calculations of the absolute free energies of binding for eight ligands to FKBP protein were performed using the Fujitsu BioServer massively parallel computer. Using the latest version of the general assisted model building with energy refinement (AMBER) force field for ligand model parameters and the Bennett acceptance ratio for computing free-energy differences, we obtained an excellent linear fit between the calculated and experimental binding free energies. The rms error from a linear fit is 0.4kcal∕mol for eight ligand complexes. In comparison with a previous study of the binding energies of these same eight ligand complexes, these results suggest that the use of improved model parameters can lead to more predictive binding estimates, and that these estimates can be obtained with significantly less computer time than previously thought. These findings make such direct methods more attractive for use in rational drug design.
Dynamical exchanges in facilitated models of supercooled liquids
Authors: Jung YounJoon , Garrahan Juan P. , Chandler David
Published: August 2005

We investigate statistics of dynamical exchange events in coarse-grained models of supercooled liquids in spatial dimensions d=1, 2, and 3. The models, based upon the concept of dynamical facilitation, capture generic features of statistics of exchange times and persistence times. Here, distributions for both times are related and calculated for cases of strong and fragile glass formers over a range of temperatures. Exchange-time distributions are shown to be particularly sensitive to the model parameters and dimensions, and exhibit more structured and richer behavior than persistence-time distributions. Mean exchange times are shown to be Arrhenius, regardless of models and spatial dimensions. Specifically, ⟨tx⟩∼c−2, with c being the excitation concentration. Different dynamical exchange processes are identified and characterized from the underlying trajectories. We discuss experimental possibilities to test some of our theoretical findings.
Enhanced luminescence of SiO2:Eu3+ by energy transfer from ZnO nanoparticles
Authors: Bang Jungsik , Yang Heesun , Holloway Paul H.
Published: August 2005

ZnO nanoparticles embedded into SiO2 by an ex situ method were shown to result in stable green emission with a peak at 510 nm compared to the normal peak at 495 nm from micron-sized ZnO powders. Green emission from ZnO nanoparticles was completely suppressed when they were embedded in SiO2 doped with Eu3+. Instead, the f-f emissions from Eu3+ were enhanced 5–10 times by energy transfer from the embedded ZnO nanoparticles to Eu3+. The Eu3+ luminescence increased as the Eu3+ concentration increased from 1 vs 5 mole % (for 10 mole % ZnO). In addition, the intensity increased as the embedded ZnO nanoparticles concentration increased up to 10 mole % (for 5 mole % Eu3+). The effects of phonon mediated energy transfer, quenching by activator interactions between Eu3+ ions, and energy back-transfer from Eu3+ ions to ZnO nanoparticles were discussed.
A generalized bead-rod model for Brownian dynamics simulations of wormlike chains under strong confinement
Authors: Wang Jizeng , Gao Huajian
Published: August 2005

This paper is aimed to develop a Brownian dynamics simulation method for strongly confined semiflexible polymers where numerical simulation plays an indispensable role in complementing theory and experiments. A wormlike chain under strong confinement is modeled as a string of virtual spherical beads connected by inextensible rods with length varying according to the confinement intensity of the chain measured by the Odijk deflection length. The model takes hydrodynamic interactions into account. The geometrical constraints associated with the inextensible rods are realized by the so-called linear constraint solver. The model parameters are studied by quantitatively comparing the simulated properties of a double-stranded DNA chain with available experimental data and theoretical predictions.
Ab Initio simulations of nonstoichiometric CdxTe1−x liquids
Authors: Ko Eunjung , Alemany M. M. G. , Derby Jeffrey J. , Chelikowsky James R.
Published: August 2005

We present ab initio molecular-dynamics simulations for CdxTe1−x liquids where the composition is nonstoichiometric. The simulations are performed following Born-Oppenheimer molecular dynamics. The required forces are obtained from a solution of the Kohn-Sham equation using ab initio pseudopotentials. We consider stoichiometries of the form: CdxTe1−x, where x=0.2, 0.4, 0.6, and 0.8. For each composition of the melt, we consider a range of temperatures near the experimentally determined liquid temperatures. We examine the microstructural properties of the melt, the viscosity, and self-diffusion properties of the liquid as a function of the stoichiometry and temperature. We also perform an analysis of the distribution of the electronic density of states in these liquids. We find that structural changes in the local order, experimentally predicted to occur when the concentration of Cd is increased, are closely related to changes in the electronic properties of the melt.
Calculation of the Maxwell stress tensor and the Poisson-Boltzmann force on a solvated molecular surface using hypersingular boundary integrals
Authors: Lu Benzhuo , Cheng Xiaolin , Hou Tingjun , McCammon J. Andrew
Published: August 2005

The electrostatic interaction among molecules solvated in ionic solution is governed by the Poisson-Boltzmann equation (PBE). Here the hypersingular integral technique is used in a boundary element method (BEM) for the three-dimensional (3D) linear PBE to calculate the Maxwell stress tensor on the solvated molecular surface, and then the PB forces and torques can be obtained from the stress tensor. Compared with the variational method (also in a BEM frame) that we proposed recently, this method provides an even more efficient way to calculate the full intermolecular electrostatic interaction force, especially for macromolecular systems. Thus, it may be more suitable for the application of Brownian dynamics methods to study the dynamics of protein/protein docking as well as the assembly of large 3D architectures involving many diffusing subunits. The method has been tested on two simple cases to demonstrate its reliability and efficiency, and also compared with our previous variational method used in BEM.
Surface entropy of rare-gas clusters
Authors: Prasalovich S. , Hansen K. , Kjellberg M. , Popok V. N. , Campbell E. E. B.
Published: August 2005

Abundances of ArN+ and XeN+ clusters produced in a supersonic expansion source are inverted to find relative dissociation energies. The values around the shell and subshell closings at N=55, 71, and 147 differ from theoretical values derived from ground-state energies of Lennard-Jones clusters. A significant part of the difference can be accounted for by the conformational entropies of surface atoms and vacancies.
Study of thermomechanical properties of Si∕SiGe superlattices using femtosecond transient thermoreflectance technique
Authors: Ezzahri Y. , Dilhaire S. , Grauby S. , Rampnoux J. M. , Claeys W. , Zhang Y. , Zeng G. , Shakouri A.
Published: August 2005

Using a Femtosecond Transient Thermoreflectance (FTT) technique, we studied the thermomechanical properties of two Si∕SiGe superlattices. A theoretical model is presented which agrees well with the experimental results and allows us to determine the cross-plan thermal conductivity of the superlattices at room temperature. We also show that, from the experimental curve, we can extract the thickness of the metallic film, the longitudinal sound velocity and the refractive index of the superlattice using acoustic echoes and Brillouin oscillation data.
The potential (iz)m generates real eigenvalues only, under symmetric rapid decay boundary conditions
Authors: Shin Kwang C.
Published: August 2005

We consider the non-Hermitian eigenvalue problems −u″(z)±(iz)mu(z)=λu(z),m⩾3, under every rapid decay boundary condition that is symmetric with respect to the imaginary axis in the complex z plane. We prove that the eigenvalues λ are all real and positive.
Phase-space overlap measures. II. Design and implementation of staging methods for free-energy calculations
Authors: Wu Di , Kofke David A.
Published: August 2005

We consider staged free-energy calculation methods in the context of phase-space overlap relations, and argue that the selection of work-based methods should be guided by consideration of the phase-space overlap of the systems of interest. Stages should always be constructed such that work is performed only into a system that has a phase-space subset relation with the starting system. Thus multiple stages are required if the systems of interest are not such that one forms a phase-space subset with the other. Three two-stage methods are possible, termed umbrella sampling, overlap sampling, and funnel sampling. The last is appropriate for cases in which the subset relation holds, but only in the extreme, meaning that one system’s important phase space constitutes a very small portion of the others. Umbrella sampling is most suitable for nonoverlap systems, and overlap sampling is appropriate for systems exhibiting partial phase-space overlap. We review recently introduced metrics that characterize phase-space overlap, showing that the performance of the single- and two-stage methods is consistent with the phase-space picture. We also demonstrate that a recently introduced bias-detection measure is effective in identifying inaccuracy in single- and multistage calculations. The examples used are the chemical-potential calculation for a Lennard-Jones liquid at moderate and at high densities, the same for model water at ambient conditions, and a process of charging a neutral ion in water.
The stability of ballooning modes in tokamaks with internal transport barriers
Authors: Webster A. J. , Szwer D. J. , Wilson H. R.
Published: August 2005

Modern tokamaks can produce transport barriers (TBs)—localized regions with an increased energy confinement. Previous studies have been unable to examine the stability of internal TBs to radially extended short-wavelength magnetohydrodynamic instabilities (“ballooning modes”), for the usual case with a sheared plasma flow and a magnetic shear that passes through zero near the TB. An established technique is adapted to study this situation, finding instability if (1) there is a low-pressure gradient, and if (2) the nearest “resonant surface” at which a Fourier mode is resonant, is sufficiently close. Surprisingly, flow shear is no more stabilizing than for magnetic shears of order one. This is explained. Without a strongly stabilizing mechanism, ballooning modes will fundamentally limit a TB's radial extent, preventing them from extending across the entire plasma radius.
Electrical breakdown characteristics of an atmospheric pressure rf capacitive plasma source
Authors: Li Shou-Zhe , Kang Jung G. , Uhm Han S.
Published: August 2005

The electrical breakdown characteristics of the rf capacitive plasma source are investigated theoretically and experimentally. The plasma source is the electrode type consisting of the concentric cylinders for generating nonequilibrium plasma at atmospheric pressure. The theoretical model based on the diffusion-controlled breakdown mechanism is proposed to analyze the electrical breakdown phenomenon in this rf capacitive plasma source of the coaxial cylinders. The electron temperature at the electrical breakdown is calculated from the theoretical model, thereby evaluating the electrical breakdown voltages. The experimental data of the electrical breakdown voltage are measured with respect to the variation of the geometric parameters of plasma source, the gas temperature, and the concentration of the foreign reactive gases (oxygen and nitrogen) mixed in the helium gas. The theoretical results of the electrical breakdown voltage agree remarkably well with experimental data. This indicates that not only the electron temperature is important in determining the electrical breakdown voltage, but also the geometric variables, the gas temperature, and the scattering cross sections of molecules play significant roles.
Prediction of protein crystallization based on interfacial and diffusion kinetics
Authors: Jia Yanwei , Liu Xiang-Yang
Published: August 2005

The interfacial kinetics of protein crystallization was studied via the kinetics of protein two-dimensional self-assembly. The competition between the protein volume transport and surface integration determines whether single crystals or amorphous aggregation will occur. A kinetic coefficient was found to provide an effective and reliable criterion to predict protein crystallization conditions. This criterion has been applied to lysozyme, concanavalin A and BSA crystallization, and it turned out to be very successful and more reliable than the second virial coefficient criterion.
Characteristics of field-effect devices with gate oxide modification by DNA
Authors: Xuan G. , Kolodzey J. , Kapoor V. , Gonye G.
Published: August 2005

Current-voltage characterization was used to investigate the behavior of silicon field-effect devices with DNA solutions of various concentrations and molecular states deposited on the gate oxide. These devices were similar to conventional transistors but without gate metal, and no surface treatments or agents were used to immobilize the DNA. With increasing micromolar concentration, significant changes were produced in the device response. The current decreased with increasing ratios of double-to-single stranded populations produced by mixing complementary sequences, and by thermal denaturing. The device characteristics were reproducible. Modeling suggested a mechanism of modifications to the device carrier density induced by variations in the electrochemical properties of the DNA located within a charge screening length of the gate oxide surface. These results showed that field-effect devices may be useful for the real time monitoring of nucleic acids, without binding agents or label tags.
Influence of superlattice and antiphase domain boundaries on dielectric loss in Ba[Mg1∕3(Nbx∕4Ta(4−x)∕4)2∕3]O3 ceramics
Authors: Lin Chen-Fu , Lu Horng-Hwa , Chang Tien-I , Huang Jow-Lay
Published: August 2005

The Ba[Mg1∕3(Nbx∕4Ta(4−x)∕4)2∕3]O3 ceramics (x=0, 1, 2, 3, and 4) synthesized by a solid reaction method were sintered at 1650 °C for 9 h. The quality factor (Q,∼1∕tanδ,tanδ: dielectric loss) and superlattice structure were investigated by the cavity method and high-resolution electron microscopy. The excellent Q value of 17 600 obtained at appropriate Nb content (x=1). The disorder structure (superlattice modulation∼0.41nm), 1:2 ordering structure (superlattice modulation∼0.71nm) and antiphase domain boundary (APB) were revealed in Ba[Mg1∕3(Nbx∕4Ta(4−x)∕4)2∕3]O3 ceramics. The formation of extra ordering structure (superlattice modulation∼1.24nm) on the APBs contributed to the improved Q value with the stabilization of ordering-induced domain boundaries.
Photonic band gaps in nanowire superlattices
Authors: Chen L. , Towe E.
Published: August 2005

This paper examines how a complete photonic band gap in a semiconductor nanowire superlattice can be achieved. By choosing the nanowire superlattice periodicity and its radius, a photonic band gap can be localized below the single optical mode cut-off frequency of the nanowire waveguide. We show that Bragg mirrors with near-unity reflectivity as well as high quality factor single defect cavities can be designed in a nanowire even by using dielectric stack materials with a low index contrast.
An Integrated Macroeconomic Model for Assessing Urban Sustainability
Authors: Fung Manson , Kennedy Christopher A
Published: August 2005

A macrolevel approach for integrating regional economic models with urban metabolism models is developed. Challenges with consistency and aggregation persist in the integration of urban models between socioeconomic and environmental systems, and between the micro and macro scale. Using an econometric model as a foundation offers a flexible structure, with low data requirements, that might potentially be integrated with microlevel process models. Such an econometric model is developed and verified for the economy of the Toronto region. The economic model is integrated with a greenhouse gas emission model that simulates emissions from the residential, transportation, and solid waste sectors. Emissions are simulated to 2010 for optimistic and pessimistic exogenous economic climates. In the absence of technological change, emissions will increase in the order of 30%, largely as a result of population growth (22%–23%), which is relatively insensitive to economic growth. The potential to decrease emissions through changing land-use development and increased recycling of solid waste is examined.
Predicting Ecological Connectivity in Urbanizing Landscapes
Authors: Bierwagen Britta G
Published: August 2005

Nearly half the world's population lives in urban centers, and these areas are increasingly important components of regional and global land cover. However, their ecological attributes are often overlooked, despite the presence of species, ecosystem services, and risks associated with the spread of pests or threatening processes such as fire. Movement and dispersal of organisms contribute to species persistence in urban landscapes; however, landscape patterns that promote ecological connectivity may also facilitate the spread of undesirable organisms or processes. I investigate how urban form can be used to predict ecological connectivity and assist in prioritizing urban landscapes for conservation activities and risk management. I examine the value of qualitative and quantitative descriptions of urban morphology as predictors of ecological connectivity by comparing sixty-six cities in the USA. Results show that qualitative categories are not adequate for describing ecological connectivity; multivariate descriptions are much better predictors, with urban area, number of urban patches, urban patch extent, level of aggregation, and perimeter area fractal dimension composing the significant synthetic variables. The dominance of area as a differentiating variable led to the development of a new urban connectivity index using a combination of urban area and state population size. This metric, based on readily available aspatial data, explains 78% of variation in ecological connectivity. These results provide a simple but novel tool for beginning to understand the role of urban morphology in promoting desirable environmental outcomes and managing environmental risks in urbanizing landscapes.
Exploration of Spatial Scale Sensitivity in Geographic Cellular Automata
Authors: Ménard André , Marceau Danielle J
Published: August 2005

Cellular automata (CA) are individual-based models in which states, time, and space are discrete. Spatiotemporal dynamics emerge from the simple and local interactions of the cells. When using CA in a geographic context, nontrivial questions have to be answered about the choice of spatial scale, namely cell size and neighbourhood configuration. However, the spatial scale decisions involved in the elaboration of geographic cellular automata (GCA) are often made arbitrarily or in relation to data availability. The objective of this study is to evaluate the sensitivity of GCA to spatial scale. A stochastic GCA was built to model land-cover change in the Maskoutains region (Quebec, Canada). The transition rules were empirically derived from two Landsat-TM (30 m resolution) images taken in 1999 and 2002 that have been resampled to four resolutions (100, 200, 500, 1000 m). Six different neighbourhood configurations were considered (Moore, Von Neumann, and circular approximations of 2, 3, 4, and 5 cell radii). Simulations were performed for each of the thirty spatial scale scenarios. Results show that spatial scale has a considerable impact on simulation dynamics in terms of both land-cover area and spatial structure. The spatial scale domains present in the results reveal the nonlinear relationships that link the spatial scale components to the simulation results.
Influence of Physical Characteristics of Routes on Distance Cognition in Virtual Environments
Authors: Cubukcu Ebru , Nasar Jack L
Published: August 2005

Discrepanices between perceived and actual distance may affect people's spatial behavior. In a previous study Nasar, using self report of behavior, found that segmentation (measured through the number of buildings) along the route affected choice of parking garage and path from the parking garage to a destination. We recreated that same environment in a three-dimensional virtual environment and conducted a test to see whether the same factors emerged under these more controlled conditions and to see whether spatial behavior in the virtual environment accurately reflected behavior in the real environment. The results confirmed similar patterns of response in the virtual and real environments. This supports the use of virtual reality as a tool for predicting behavior in the real world and confirms increases in segmentation as related to increases in perceived distance.
Pulsars and Gravitational Wave Detection
Authors: Hobbs George
Published: August 2005

The number of known millisecond pulsars has dramatically increased in the last few years. Regular observations of these pulsars may allow gravitational waves with frequencies ∼10−9 Hz to be detected. A ‘pulsar timing array’ is therefore complimentary to other searches for gravitational waves using ground-based or space-based interferometers that are sensitive to much higher frequencies. In this review we describe (1) the basic methods for using an array of pulsars as a gravitational wave detector, (2) the sources of the potentially detectable waves, (3) current limits on individual sources and a stochastic background, and (4) the new project recently started using the Parkes radio telescope.
Science Programs for a 2-m Class Telescope at Dome C, Antarctica: PILOT, the Pathfinder for an International Large Optical Telescope
Authors: Burton M. G. , Lawrence J. S. , Ashley M. C. B. , Bailey J. A. , Blake C. , Bedding T. R. , Bland-Hawthorn J. , Bond I. A. , Glazebrook K. , Hidas M. G. , Lewis G. , Longmore S. N. , Maddison S. T. , Mattila S. , Minier V. , Ryder S. D. , Sharp R. , Smith C. H. , Storey J. W. V. , Tinney C. G. , Tuthill P. , Walsh A. J. , Walsh W. , Whiting M. , Wong T. , Woods D. , Yock P. C. M.
Published: August 2005

The cold, dry, and stable air above the summits of the Antarctic plateau provides the best ground-based observing conditions from optical to sub-millimetre wavelengths to be found on the Earth. Pathfinder for an International Large Optical Telescope (PILOT) is a proposed 2 m telescope, to be built at Dome C in Antarctica, able to exploit these conditions for conducting astronomy at optical and infrared wavelengths. While PILOT is intended as a pathfinder towards the construction of future grand-design facilities, it will also be able to undertake a range of fundamental science investigations in its own right. This paper provides the performance specifications for PILOT, including its instrumentation. It then describes the kinds of projects that it could best conduct. These range from planetary science to the search for other solar systems, from star formation within the Galaxy to the star formation history of the Universe, and from gravitational lensing caused by exo-planets to that produced by the cosmic web of dark matter. PILOT would be particularly powerful for wide-field imaging at infrared wavelengths, achieving near diffraction-limited performance with simple tip–tilt wavefront correction. PILOT would also be capable of near diffraction-limited performance in the optical wavebands, as well be able to open new wavebands for regular ground-based observation, in the mid-IR from 17 to 40 μm and in the sub-millimetre at 200 μm.
Tidal Tails and the Shape of the Dark Matter Halo
Authors: Lewis Geraint F. , Ibata Rodrigo A.
Published: August 2005

Cold dark matter cosmologies successfully accounts for the distribution of matter on large scales. On smaller scales, these cosmological models predict that galaxies like our own Milky Way should be enveloped in massive dark matter halos. Furthermore, these halos should be significantly flattened or even triaxial. Recent observational evidence, drawn from the demise of the Sagittarius dwarf galaxy as it is cannibalized by our own, indicates that the potential of the Milky Way must be close to spherical. While the precise interpretation of the observational evidence is under debate, an apparently spherical halo may signify a pronounced failing of dark matter models, and may even indicate a failure in our fundamental understanding of gravity.
Recurrent ∼24 h Periods in RXTE ASM Data
Authors: Farrell Sean A. , O'Neill Paul M. , Sood Ravi K.
Published: August 2005

Analysis of data from the Rossi X-ray Timing Explorer satellite's All Sky Monitor (ASM) instrument for several X-ray binary sources has identified a recurrent ∼24 h period. This period is sometimes highly significant, giving rise to the possibility of it being identified as an orbital or super-orbital period. Further analysis has revealed the same period in a number of other X-ray sources. As a result this period has been discounted as spurious, described variously as arising from daily variations in background levels, the scheduling of ASM observations and beating between the sampling period and long-term secular trends in the light curves. We present here an analysis of the spurious periods and show that the dominant mechanism is in fact spectral leakage of low-frequency power present in the light curves.
A Damped Lyα Absorption-Line System in an Apparent Void at Redshift 2.38
Authors: Godfrey Leith E. H. , Francis Paul J.
Published: August 2005

We study the contents of an apparent void in the distribution of Lyα emitting galaxies at redshift 2.38. We show that this void is not empty, but contains a damped Lyα absorption-line system, seen in absorption against background QSO 2138-4427. Imaging does not reveal any galaxy associated with this absorption-line system, but it contains metals (Fe/H ∼ −1.3), and its large velocity range (∼180 km s−1) implies a significant mass.
Intra-Pixel Sensitivity Variation and Charge Transfer Inefficiency — Results of CCD Scans
Authors: Toyozumi Hiroyuki , Ashley Michael C. B.
Published: August 2005

The efficiency with which a charge-coupled device (CCD) detects photons depends, amongst other factors, on where within a pixel the photon hits. To explore this effect we have made detailed scans across a pixel for a front-illuminated three-phase EEV05-20 CCD using the standard astronomical B, V, R, and I colour filters. Pixel response functions and photometric sensitivity maps are derived from the scan images. Nonlinear charge transfer inefficiency (CTI) effects were observed and corrected for. The resulting images clearly show the intra-pixel sensitivity variations (IPSVs) due to the CCD electrode structure, and its dependence on wavelength. We briefly comment on the implications of IPSVs and CTI for high-precision photometry and astrometry.
Cosmology Under Milne's Shadow
Authors: Chodorowski Michał J.
Published: August 2005

Based on the magnitude–redshift diagram for the sample of supernovae Ia analyzed by Perlmutter et al. (1999), Davis & Lineweaver (2004) ruled out the special relativistic interpretation of cosmological redshifts at a confidence level of 23σ. Here, we critically reassess this result. Special relativity is known to describe the dynamics of an empty universe, by means of the Milne kinematic model. Applying only special relativistic concepts, we derive the angular diameter distance and the luminosity distance in the Milne model. In particular, in this model we do not use the underlying metric in its Robertson–Walker form, so our exposition is useful for readers without any knowledge of general relativity. We do however, explicitly use the special relativistic Doppler formula for redshift. We apply the derived luminosity distance to the magnitude–redshift diagram for supernovae Ia of Perlmutter et al. (1999) and show that special relativity fits the data much better than that claimed by Davis & Lineweaver. Specifically,using these data alone, the Milne model is ruled out only at a 2σ level. Alhough not a viable cosmological model, in the context of current research on supernovae Ia it remains a useful reference model when comparing predictions of various cosmological models.
Second Data Release of the 6dF Galaxy Survey
Authors: Jones D. Heath , Saunders Will , Read Michael , Colless Matthew
Published: August 2005

The 6dF Galaxy Survey is measuring around 150 000 redshifts and 15 000 peculiar velocities from galaxies over the southern sky at |b| > 10°. When complete, it will be the largest survey of its kind by more than an order of magnitude. Here we describe the characteristics of the Second Incremental Data Release and provide an update of the survey. This follows earlier data made public in 2002 December and 2004 March. A total of 83 014 sources now have their spectra, redshifts, and near-infrared and optical photometry available online and searchable through an Structured Query Language database at www-wfau.roe.ac.uk/6dFGS/.
Pollen of the Spermacoce (Rubiaceae) species from the Northern Territory of Australia: morphology and taxonomic significance
Authors: Dessein S. , Harwood R. , Smets E. , Robbrecht E.
Published: August 2005

Complementary to the revision of the genus Spermacoce in the Northern Territory of Australia, pollen morphology of 48 of the 53 native Spermacoce species from the Northern Territory has been investigated by scanning electron and light microscopy. There is considerable variation for most diagnostic pollen characters. The average equatorial diameter (E) ranges from 10.5 to 41.7 µm. Grains are invariably colporate with the apertures situated at the equator (being zonocolporate). The number of apertures varies from 3 to 17. The endoaperture is generally an endocingulum, often with a secondary thinning at the ectocolpus; one species has endocolpi. The sexine is usually perforate, but psilate, foveolate, and (micro)reticulate patterns were also found. Supratectal elements are present as granules or microspines scattered over the whole surface or confined to a region around the ectoapertures. The inner nexine surface is granular, often with irregular grooves (endocracks).
The pollen morphological variation observed allows the distinction of four pollen types. Three of these types are not yet recorded in other palynological studies of Spermacoce. Pollen characters are often useful to delimit species and groups of related species.
An investigation of phyllode variation in Acacia verniciflua and A. leprosa (Mimosaceae), and implications for taxonomy
Authors: Gardner Stuart K. , Murphy Daniel J. , Newbigin Edward , Drinnan Andrew N. , Ladiges Pauline Y.
Published: August 2005

Acacia verniciflua A.Cunn. and A. leprosa Sieber ex DC. are believed to be closely related, although strict interpretation of the current sectional classification of subgenus Phyllodineae places them in separate sections based on main nerve number. Six populations, comprised of the common and the southern variants of A. verniciflua and the large phyllode variant of A. leprosa, were sampled to test the value of nerve number as a taxonomic character and the current delimitation of these geographically variable species. Morphometrics, microscopy and the AFLP technique were used to compare and contrast populations. Phyllode nerve development was investigated and the abaxial nerve was found to be homologous with the mid-rib of a simple leaf. Three taxa were differentiated, two that are consistently two-nerved and one taxon that is variably one-nerved, two-nerved or both within a single plant. The first two-nerved taxon, characterised by smaller phyllodes, matches the type specimen of A. verniciflua. The second two-nerved taxon, characterised by large phyllodes, is apparently endemic to Mt William. The third taxon, with variable main nerve number, also has large phyllodes, and combines large phyllode variant A. leprosa (Wilhelmina Falls) and southern variant A. verniciflua (Kinglake) individuals. The number of main nerves per face in phyllodes is not a useful taxonomic character for sectional classification of Acacia. Although it has clearly proved functional in some instances, the character appears too variable to reliably define natural monophyletic groups. Anatomical features such as cell number of resinous glands and staining patterns proved to be informative.