bluuebunny/crossref_metadata_2025 huggingface dataset:
Origin of the deep Bering Sea nitrate deficit: Constraints from the nitrogen and oxygen isotopic composition of water column nitrate and benthic nitrate fluxes
Authors: Lehmann Moritz F. , Sigman Daniel M. , McCorkle Daniel C. , Brunelle Brigitte G. , Hoffmann Sharon , Kienast Markus , Cane Greg , Clement Jaclyn
Published: October 2005

On the basis of the normalization to phosphate, a significant amount of nitrate is missing from the deep Bering Sea (BS). Benthic denitrification has been suggested previously to be the dominant cause for the BS nitrate deficit. We measured water column nitrate 15N/14N and 18O/16O as integrative tracers of microbial denitrification, together with pore water‐derived benthic nitrate fluxes in the deep BS basin, in order to gain new constraints on the mechanism of fixed nitrogen loss in the BS. The lack of any nitrate isotope enrichment into the deep part of the BS supports the benthic denitrification hypothesis. On the basis of the nitrate deficit in the water column with respect to the adjacent North Pacific and a radiocarbon‐derived ventilation age of ∼50 years, we calculate an average deep BS (>2000 m water depth) sedimentary denitrification rate of ∼230 μmol N m−2 d−1 (or 1.27 Tg N yr−1), more than 3 times higher than high‐end estimates of the average global sedimentary denitrification rate for the same depth interval. Pore water‐derived estimates of benthic denitrification were variable, and uncertainties in estimates were large. A very high denitrification rate measured from the base of the steep northern slope of the basin suggests that the elevated average sedimentary denitrification rate of the deep Bering calculated from the nitrate deficit is driven by organic matter supply to the base of the continental slope, owing to a combination of high primary productivity in the surface waters along the shelf break and efficient down‐slope sediment focusing along the steep continental slopes that characterize the BS.
Climatic oscillations influence the flooding of Venice
Authors: Fagherazzi Sergio , Fosser Giorgia , D'Alpaos Luigi , D'Odorico Paolo
Published: October 2005

A detailed analysis of the tidal regime in Venice, Italy, during the last century shows that the frequency and magnitude of high tides are correlated to interdecadal climatic oscillations. The monthly high tide maxima and the average elevation of all high tides are negatively correlated to the North Atlantic Oscillation (NAO), to the Arctic Oscillation (AO), to the East Atlantic – West Russian oscillation (EA‐WR), and to the Polar Eurasia teleconnection (POL). The correlation is high during winter months for all four indices, whereas in the fall, when most of the city floods occur, the AO and the EA‐WR exert a stronger influence on the tidal regime. During negative phases of the climate indices both the average elevation of high tides and the frequency of flooding increase consistently, with negative effects on the city and its monuments.
An improved strategy to detect CO2 leakage for verification of geologic carbon sequestration
Authors: Lewicki J. L. , Hilley G. E. , Oldenburg C. M.
Published: October 2005

The long‐term storage of CO2 must be verified to ensure the success of geologic carbon sequestration projects. To detect subtle CO2 leakage signals, we present a strategy that integrates near‐surface measurements of CO2 fluxes or concentrations with an algorithm that enhances temporally‐ and spatially‐correlated leakage signals while suppressing random background noise. We assess the performance of this strategy using synthetic CO2 flux data sets and modeled surface CO2 leakage. These simulations provide a means of estimating the number of measurements required to detect a potential CO2 leakage signal of given magnitude and area. Results show that given a rigorous and well‐planned field sampling program, subtle surface CO2 leakage may be detected using the algorithm; however, leakage of very limited spatial extent or exceedingly small magnitude may be difficult to detect with a reasonable set of monitoring resources.
Integrating spatial patterns into a snow avalanche cellular automata model
Authors: Kronholm Kalle , Birkeland Karl W.
Published: October 2005

Snow avalanches are a major mountain hazard that kills hundreds of people and causes millions of dollars in damage worldwide annually. Yet, the relationship between the well‐documented spatial variability of the snowpack and the avalanche release process is not well understood. We utilize a cellular automata model to show that the spatial structure of shear strength may be critically important for avalanche fracture propagation. Fractures through weak layers with large‐scale spatial structure are much more likely to propagate over large areas than fractures through weak layers with smaller‐scale spatial structure. Our technique of integrating spatial structure into the model can improve many cellular automata models that aim to explain and predict other natural hazards, such as forest fires, landslides and earthquakes.
Magnetic minerals in the Martian crust
Authors: Dunlop David J. , Arkani‐Hamed Jafar
Published: October 2005

Using rock magnetism and thermal modeling, we evaluate the candidate minerals responsible for strong magnetic anomalies in the Terra Sirenum and Terra Cimmeria regions of Mars' southern highlands. We assume an early global dynamo field similar in strength to the present Earth's field, enduring about 500 Myr after accretion and core formation, and a basaltic crust containing no more than 4–7 weight% of magnetic minerals. Thermal evolution models with a wide variety of initial crustal thicknesses, distributions of radioactive elements, and thermal expansion coefficients all yield similar thermal histories for the crust: warming in the first ∼1000 Myr (due mainly to radioactive heating) followed by monotonic cooling for the remainder of Mars' history. Primary thermoremanent magnetization (TRM) acquired by intrusive and extrusive bodies during the first 500 Myr was in part thermally demagnetized by general crustal warming after the dynamo field disappeared, from 500 to 1000 Myr. The Curie point isotherms around 1000 Myr established the maximum depth of TRM‐bearing crust. Shock and heating due to impacts demagnetized the uppermost ∼10 km of the crust around the same time, resulting in potential magnetic layer thicknesses of 15–20 km for pyrrhotite, 40–50 km for magnetite, and 50–60 km for hematite. Other magnetic phases, such as iron and finely exsolved low‐Ti titanohematite, are possible but less likely in a basaltic crust under oxidizing conditions. The prime candidates, in order of likelihood, are single‐domain magnetite (0.2–0.4 volume% or 0.4–0.8 weight% required), single‐domain pyrrhotite (1–2 volume% or 2–4 weight%), and either multidomain (>15 μm) or 5–15 μm single‐domain hematite or a mixture of both (1.5–3 volume% or 3–6 weight%). A composite source with different combinations of these minerals at different depths is entirely possible. Viscous decay of TRM is difficult to assess without detailed knowledge of the distribution of minerals and blocking temperatures with depth but would increase the amounts of magnetic material required.
Critical History of the Acculturation Psychology of Assimilation, Separation, Integration, and Marginalization
Authors: Rudmin Floyd W.
Published: October 2005

The psychology of intercultural adaptation was first discussed by Plato. Many modern enculturation theories claim that ethnic minorities (including aboriginal natives, immigrants, refugees, and sojourners) can favor either the dominant culture, or their own minority culture, or both, or neither. Between 1918 and 1984, 68 such theories showed varied and inconsistent terminology, poor citation of earlier research, conflicting and poorly tested predictions of acculturative stress, and lack of logic, for example, 2 cultures in contact logically allow 16 types of acculturation, not just 4. Logic explains why assimilation = negative chauvinism = marginality, why measures of incompatible acculturative attitudes can be positively correlated, and why bicultural integration and marginalisation are confounded constructs. There is no robust evidence that biculturalism is most adaptive.
“I Know, you Know”: Epistemic Egocentrism in Children and Adults
Authors: Royzman Edward B. , Cassidy Kimberly Wright , Baron Jonathan
Published: October 2005

This article reviews the evidence and theory pertaining to a form of perspective-taking failure—a difficulty in setting aside the privileged information that one knows to be unavailable to another party. The authors argue that this bias (epistemic egocentrism, or EE) is a general feature of human cognition and has been tapped by 2 independent and largely uncommunicating research traditions: the theory-of-mind tradition in developmental psychology and, with more sensitive probes, the “heuristics and biases” tradition in the psychology of human judgment. This article sets the stage for facilitating communication between these traditions as well as for the recognition of EE's breadth and potential interdisciplinary significance: The authors propose a life-span account and a tentative taxonomy of EE; and they highlight the interdisciplinary significance of EE by discussing its implications for normative ethics.
Dimensions of Affect Relationships: Models and Their Integrative Implications
Authors: Reich John W. , Zautra Alex J. , Davis Mary
Published: October 2005

This article presents data from a number of areas of psychology that have dealt with the issue of whether positive and negative affects are independent—the bivariate view—or whether they operate inversely from each other—the unidimensional, bipolar view. Both models have extensive empirical support. A more integrative view, the Dynamic Model of Affect (DMA), specifies conditions under which both bivariate and bipolar models are valid. It is tailored to analyzing both affect systems functioning concurrently. The DMA is reviewed and then extended to show how 3 major areas of research can begin to incorporate the more integrative framework of analyzing co-occurring types of affect.
Stability of a supercritical fluid diffusing layer with mixed boundary conditions
Authors: Accary Gilbert , Raspo Isabelle , Bontoux Patrick , Zappoli Bernard
Published: October 2005

We consider a fluid close to its gas-liquid critical point in the Rayleigh-Bénard configuration. Owing to thermoacoustic effects, the bottom heating induces thermal boundary layers along both the lower and the upper horizontal plates. The hydrodynamic stability of these diffusing layers, whose bounding conditions are interchanged, is studied numerically in a two-dimensional (2D) approximation. As far as the convection onset criterion and the critical wave number are concerned, some discrepancies are found between the simulations and the predictions obtained by means of linear analysis. The extension of the study to three-dimensional configurations confirms the validity of the 2D approximation for the analysis of the hydrodynamic stability and shows its inadequacy when the layers become convection dominated.
Concerted and sequential Coulomb explosion processes of N2O in intense laser fields by coincidence momentum imaging
Authors: Ueyama Masakuni , Hasegawa Hirokazu , Hishikawa Akiyoshi , Yamanouchi Kaoru
Published: October 2005

The Coulomb explosion dynamics of N2O in intense laser fields (800nm, 60fs, ∼0.16PW∕cm2) is studied by the coincidence momentum imaging method. From the momentum correlation maps obtained for the three-body fragmentation pathway, N2O3+→N++N++O+, the ultrafast structural deformation dynamics of N2O prior to the Coulomb explosion is extracted. It is revealed that the internuclear N–N and N–O distances stretch simultaneously as the bond angle ∠N–N–O decreases. In addition, two curved thin distributions are identified in the momentum correlation maps, and are interpreted well as those originating from the sequential dissociation pathway, N2O3+→N++NO2+→N++N++O+.
Function group approach to unconstrained Hamiltonian Yang–Mills theory
Authors: Salmela Antti
Published: October 2005

Starting from the temporal gauge Hamiltonian for classical pure Yang–Mills theory with the gauge group SU(2) a canonical transformation is initiated by parametrizing the Gauss law generators with three new canonical variables. The construction of the remaining variables of the new set proceeds through a number of intermediate variables in several steps, which are suggested by the Poisson bracket relations and the gauge transformation properties of these variables. The unconstrained Hamiltonian is obtained from the original one by expressing it in the new variables and then setting the Gauss law generators to zero. This Hamiltonian turns out to be local and it decomposes into a finite Laurent series in powers of the coupling constant.
Jacobi structures in R3
Authors: Haas F.
Published: October 2005

The most general Jacobi brackets in R3 are constructed after solving the equations imposed by the Jacobi identity. Two classes of Jacobi brackets were identified, according to the rank of the Jacobi structures. The associated Hamiltonian vector fields are also constructed.
Fragmentation of HCN in optically selected mass spectrometry: Nonthermal ion cooling in helium nanodroplets
Authors: Lewis William K. , Bemish Raymond J. , Miller Roger E.
Published: October 2005

A technique that combines infrared laser spectroscopy and helium nanodroplet mass spectrometry, which we refer to as optically selected mass spectrometry, is used to study the efficiency of ion cooling in helium. Electron-impact ionization is used to form He+ ions within the droplets, which go on to transfer their charge to the HCN dopant molecules. Depending upon the droplet size, the newly formed ion either fragments or is cooled by the helium before fragmentation can occur. Comparisons with gas-phase fragmentation data suggest that the cooling provided by the helium is highly nonthermal. An “explosive” model is proposed for the cooling process, given that the initially hot ion is embedded in such a cold solvent.
Pseudopotential and electron propagator methods for the calculation of the photoelectron spectra of anionic silicon clusters: Predictions on Si10−
Authors: Tiznado William A. , Fuentealba P. , Ortiz J. V.
Published: October 2005

Photoelectron spectra of anionic clusters of silicon require reliable theoretical calculations for their assignment and interpretation. Electron propagator calculations in the outer valence Green’s-function approximation with two well-characterized, all-electron basis sets on vertical electron detachment energies (VEDEs) of anions are compared to similar calculations that employ Stuttgart pseudopotentials. Tests on Sin− clusters with n=3–7 exhibit an encouraging agreement between the all-electron and pseudopotentials results and between electron propagator predictions and experiments and values obtained from coupled-cluster calculations. To illustrate the capabilities of the new approach based on a Si pseudopotential and electron propagator methods, VEDE calculations on Si10− are presented.
Photodissociation of vanadium, niobium, and tantalum oxide cluster cations
Authors: Molek K. S. , Jaeger T. D. , Duncan M. A.
Published: October 2005

Transition-metal oxide clusters of the form MnOm+(M=V,Nb,Ta) are produced by laser vaporization in a pulsed nozzle cluster source and detected with time-of-flight mass spectrometry. Consistent with earlier work, cluster oxides for each value of n produce only a limited number of stoichiometries, where m>n. The cluster cations are mass selected and photodissociated using the second (532nm) or third (355nm) harmonic of a Nd:YAG (yttrium aluminum garnet) laser. All of these clusters require multiphoton conditions for dissociation, consistent with their expected strong bonding. Dissociation occurs by either elimination of oxygen or by fission, repeatedly producing clusters having the same specific stoichiometries. In oxygen elimination, vanadium species tend to lose units of O2, whereas niobium and tantalum lose O atoms. For each metal increment n, oxygen elimination proceeds until a terminal stoichiometry is reached. Clusters having this stoichiometry do not eliminate more oxygen, but rather undergo fission, producing smaller MnOm+ species. The smaller clusters produced as fission products represent the corresponding terminal stoichiometries for those smaller n values. The terminal stoichiometries identified are the same for V, Nb, and Ta oxide cluster cations. This behavior suggests that these clusters have stable bonding networks at their core, but additional excess oxygen at their periphery. These combined results determine that M2O4+, M3O7+, M4O9+, M5O12+, M6O14+, and M7O17+ have the greatest stability for V, Nb, and Ta oxide clusters.
Optical observation of the 3sσgFΠu3 Rydberg state of N2
Authors: Sprengers J. P. , Reinhold E. , Ubachs W. , Baldwin K. G. H. , Lewis B. R.
Published: October 2005

Using ultrahigh-resolution 1XUV+1UV two-photon ionization laser spectroscopy, the FΠu3←XΣg+1(0,0) transition of N2 has been optically observed for the first time, and the 3sσgFΠu3(υ=0) Rydberg level fully characterized with rotational resolution. The experimental spectroscopic parameters and predissociation level widths suggest strong interactions between the F state and the 3pπuGΠu3 Rydberg and C′Πu3 valence states, analogous to those well known in the case of the isoconfigurational Πu1 states.
Numerical simulation of two-dimensional steady granular flows in rotating drum: On surface flow rheology
Authors: Renouf M. , Bonamy D. , Dubois F. , Alart P.
Published: October 2005

The rheology of two-dimensional steady surface flow of cohesionless cylinders in a rotating drum is investigated through nonsmooth contact dynamics simulations. Profiles of volume fraction, translational and angular velocity, rms velocity, strain rate, and stress tensor are measured at the midpoint along the length of the surface-flowing layer, where the flow is generally considered as steady and homogeneous. Analysis of these data and their interrelations suggest the local inertial number—defined as the ratio between local inertial forces and local confinement forces—to be the relevant dimensionless parameter to describe the transition from the quasistatic part of the packing to the flowing part at the surface of the heap. Variations of the components of the stress tensor as well as the ones of rms velocity as a function of the inertial number are analyzed within both the quasistatic and the flowing phases. Their implications are discussed.
On the dielectric susceptibility spectra of supercooled o-terphenyl
Authors: Richert Ranko
Published: October 2005

Supercooled o-terphenyl has been the subject of many investigations including dielectric relaxation spectroscopy. Due to the low dielectric strength and the tendency to crystallize at elevated temperatures, a detailed shape analysis of the loss profile from the glass transition temperature Tg to ∼1.2Tg is not available for the neat glass former. Assessing the origin of the different temperature dependencies of translational and rotational motions in supercooled liquids and its possible connection to heterogeneity requires this knowledge regarding the possible changes in the relaxation-time distribution across the 100s–100ns relaxation-time range. This note provides this information for o-terphenyl on the basis of a master curve representation: time-temperature superposition applies with a constant stretching exponent of β=0.5 in the range of interest.
High-pressure equations of state of Al, Cu, Ta, and W
Authors: Chijioke Akobuije D. , Nellis W. J. , Silvera Isaac F.
Published: October 2005

We have generated 300-K isotherms to pressures as high as 300 GPa for Al, Cu, Ta, and W. Hugoniot data were reduced to isotherms using calculated thermal pressures. For these four metals, available experimental results permitted corrections of Hugoniot data for shock-induced strength as a function of shock pressure. High-pressure shock-wave data are extended to zero pressure using ultrasonically determined bulk moduli. For ease of evaluation of pressure-volume points, the isotherms are presented in the Vinet [J. Phys. C 19, L467 (1986)] form of the equation of state, along with isotherms for Mo and Au and Pt.
Dynamical diffraction artifacts in Laue microdiffraction images
Authors: Yan Hanfei , Noyan I. C.
Published: October 2005

Back-reflection images obtained from single-crystal semiconductor substrates using Laue microdiffraction with medium-to-high energy x rays (10–30keV) may contain double spots, one strong and one weak, for the higher-energy reflections. Some of the weaker spots originate from the back surface of the sample and are due to dynamic diffraction from a finite crystal. Others may be due to epitaxial thin films on the substrate. The intensity and position of the back-surface peaks depend on the x-ray energy, sample characteristics, and diffraction geometry. We provide a set of simple equations that can be used to calculate the separation of such peak pairs. These equations can be used to identify the peaks from the back surface of the sample.
Frequent Josephson junction decoupling is the main origin of ac losses in the superconducting state
Authors: Sarangi S. , Chockalingam S. P. , Bhat S. V.
Published: October 2005

The origins of ac losses in the high Tc superconductors are not addressed adequately in the literature. We found out that frequent Josephson junction (JJ) decoupling (both intergranular and interlayer) due to the flow of ac is one of the main origins of the ac losses in high Tc superconductors. We have determined the ac losses in superconductors in the rf range by measuring the absolute value of nonresonant rf power absorbed by the samples. Our data show that under certain conditions when both the number density of JJs present in the sample and the JJ critical current cross a threshold value, ac losses in the superconducting state keep on increasing with decreasing temperature below Tc. The underlying mechanism is an interesting interplay of JJ coupling energy and the amplitude of rf voltage applied to the sample. The effects of an applied magnetic field, variation of rf, and temperature were studied in detail. To find out the exact relation among the JJ coupling energy, JJ number density, applied ac frequency, the amplitude of ac, and the ac losses in superconductors, we have studied samples with different crystalline properties, different grain sizes, pressurized at different pressures, and sintered under different physical and chemical conditions. These results have important implications for the understanding of the origin of ac losses and the characterization of superconducting samples. In this paper we also extend the capability of the ac loss studies in superconductors for the characterization of materials for device applications.
Anomalous negative differential conductance in nanomechanical double barrier tunneling structures
Authors: Majima Yutaka , Azuma Yasuo , Nagano Kouhei
Published: October 2005

Anomalous negative differential conductance (NDC) is observed along with a Coulomb staircase in the tunneling current-voltage curves of a nanomechanical double barrier tunneling structure consisting of a scanning vibrating probe/vacuum/colloidal Au nanodot/1,6-hexanedithiol/Au substrate. The peak voltages in the NDC phenomena when the sample voltage is applied correspond well with that of the probe voltage. We discuss a candidate mechanism of the NDC phenomena by taking into account the modulation of the tunneling rate between the scanning probe and an Au nanodot due to the nanometer-scale probe vibration.
Measurement of Si 311 defect properties using x-ray scattering
Authors: Nordlund K. , Metzger T. H. , Malachias A. , Capello L. , Calvo P. , Claverie A. , Cristiano F.
Published: October 2005

The 311 defects play a crucial role in the damage healing and dopant redistribution which occurs during the annealing of an ion-beam-doped Si. Using grazing-incidence x-ray scattering we measure the type, length, and width of the 311 defects created with different annealing times. In particular, we show that measurements around (1.3 1.3 0) in reciprocal space can be used to determine all these quantities without the need for pristine reference samples. The results agree well with computer simulation predictions and transmission-electron-microscopy measurements, demonstrating that x-ray methods can be used as a nondestructive, rapid method to characterize the 311 defects.
Growth of SiOx nanowire bunches cocatalyzed with Ga and Ni
Authors: Cai X. M. , Djurišić A. B. , Xie M. H.
Published: October 2005

Si O x nanowire bunches were fabricated on Ni(NO3)2*6H2O solution-coated Si(111) substrates in a chemical vapor deposition system in the presence of Ga and under the flow of Ar and NH3 gases. The roles of nickel nitrate hydrate, gallium, and ammonia in the formation of SiOx nanowire bunches were investigated. It was found that Ni and Ga act as catalysts for the growth, while nickel nitrate hydrate also serves as a source of oxygen. The growth mechanisms of different nanowire structures obtained by varying the fabrication conditions are discussed.
Inequalities for experimental tests of the Kochen-Specker theorem
Authors: Nagata Koji
Published: October 2005

We derive inequalities for n-partite states under the assumption that the hidden-variable theoretical joint probability distribution for any pair of commuting observables is equal to the quantum mechanical one. Fine showed that this assumption is connected to the no-hidden-variables theorem of Kochen and Specker (KS theorem). These inequalities give a way to experimentally test the KS theorem. The fidelity to the Bell states which is larger than 1∕2 is sufficient for the experimental confirmation of the KS theorem. Hence, the Werner state is enough to test experimentally the KS theorem. Furthermore, it is possible to test the KS theorem experimentally using uncorrelated states. An n-partite uncorrelated state violates the n-partite inequality derived here by an amount that grows exponentially with n.
The formation of amorphous alloy oxides as barriers used in magnetic tunnel junctions
Authors: Yang J. Joshua , Yang Ying , Wu Kaisheng , Chang Y. Austin
Published: October 2005

The quality of a tunnel barrier is of critical importance for the success of a magnetic tunnel junction. An amorphous state of the precursor metal films is beneficial for the formation of an ultrasmooth and likely defect-free oxide tunnel barrier layer, thus leading to an improved performance of a magnetic tunnel junction. However, prior to oxidation, most sputter-deposited thin films of pure metals are polycrystalline instead of amorphous. In contrast, a sputter-deposited alloy thin film could have a better amorphous-forming ability than a pure metal. Using an Al–Zr binary as an example, the amorphous-forming ability of alloy thin films was investigated thermodynamically and experimentally. A thermodynamic model was formulated to predict the compositions of a binary alloy exhibiting favorable amorphous-forming abilities when sputter-deposited alloy thin films are made. The thermodynamically calculated compositions of Al–Zr alloys with great tendencies to form amorphous metallic thin films were confirmed experimentally. The sputter-deposited alloy thin films were characterized using transmission electron microscopy and x-ray diffraction. The thermodynamic argument, applicable to any binary systems, can serve as a guide to preselect alloy compositions of any selected metallic binary with high amorphous-forming ability as precursor metals to form an oxide tunnel barrier used in a magnetic tunnel junction.
Grain-boundary diffusion of Nd147 in nanocrystalline Nd2Fe14B
Authors: Sprengel W. , Herth S. , Barbe V. , Schaefer H-E. , Wejrzanowski T. , Gutfleisch O. , Würschum R.
Published: October 2005

The Nd self-diffusivity has been studied in nanocrystalline Nd-rich Nd2Fe14B. From the analysis of the diffusion profiles grain-boundary diffusion coefficients DGBNd are derived similar to the values observed recently for Fe59 diffusion in this material. Above the intergranular melting transition, a second diffusion path indicates rapid diffusion in the liquid intergranular phase.
Characteristics of laminar flow past a sphere in uniform shear
Authors: Kim Dongjoo , Choi Hyungseok , Choi Haecheon
Published: October 2005

Numerical simulations are performed to investigate the characteristics of laminar flow past a sphere in uniform shear. The Reynolds numbers considered are Re=300, 425, and 480 based on the inlet center velocity uc and sphere diameter d. The nondimensional shear rate K of inlet uniform shear is varied from 0 to 0.15, where K=∣∇u∣d∕uc (∣∇u∣) and ∣∇u∣ is the shear rate at inlet. For all Reynolds numbers investigated, the head of the hairpin vortex loop is always located on the high-velocity side in uniform shear. The flow maintains planar symmetry at Re=300. At Re=425 and 480, the temporal variation in the azimuthal angle of the hairpin vortex formation appearing in the uniform inlet flow is greatly reduced in uniform shear, but the flows still keep asymmetry for most inlet shear rates. However, in the cases of K=0.075 and 0.1, at Re=425, the flows become planar symmetric and their characteristics of formation and evolution of the hairpin vortex loops are different from those of asymmetric flows. In most cases, except the instances showing planar symmetry at Re=425, the Strouhal number and time-averaged drag and lift coefficients increase with increasing inlet shear rate. On the other hand, for K=0.075 and 0.1, showing planar symmetry at Re=425, three different vortices are shed in the wake, resulting in three distinct peak frequencies. Finally, a hysteresis phenomenon switching from planar symmetry to asymmetry (or vice versa) depending on the initial condition is observed at Re=425 and 450, implying that small variations in the flow or initial conditions change the flow field at these Reynolds numbers.
Kinetic Lagrange simulation of a source-driven magnetized oblique presheath
Authors: Sharma Devendra
Published: October 2005

A source driven magnetized oblique presheath is analyzed by means of a kinetic model and a detailed kinetic simulation using a backward-Lagrangian characteristics based simulation procedure. The four-dimensional ion phase-space distribution function and its associated moments, namely, density, flow velocity, and parallel and perpendicular temperatures are simulated. Extra simplification in the moment derivation results from the simulation procedure which facilitates the use of a structured distribution of nodes in the three-dimensional velocity space. Strong kinetic effects appear in the oblique geometry as the two temperatures are observed to drop preferentially in the limits of normal and grazing incidences. The effects are reflected also in the detailed behavior of flow velocity profiles which show a finite dependence on the angle of magnetic field’s incidence in the region of magnetized presheath. A comparison of the kinetic solutions with those obtained from the existing fluid models is also presented.
Improved emission stability of single-walled carbon nanotube field emitters by plasma treatment
Authors: Kim Won Seok , Lee Jeonghee , Jeong Tae Won , Heo Jung Na , Kong Byung Yoon , Jin Yong Wan , Kim J. M. , Cho Sung Hee , Park Jong Hwan , Choe D. H.
Published: October 2005

We investigated the effect of plasma treatment on single-walled carbon nanotube (SWCNT) field emitters, which were fabricated by printing a photoimageable SWCNT paste, to improve emission lifetime. The treatment was performed by applying a dc pulsed voltage between two electrodes, where the cathode was the SWCNT emitter to be treated and the anode was a bare indium-doped tin oxide glass, under inert gas (Xe∕Ne) atmosphere. With increasing applied voltage and treatment time, the stability of the emission current at a constant electric field is improved, while the field to reach a required emission current becomes high. We attribute the improved emission stability to the removal of a small portion of protruding emitters, which dominate initial emission characteristics. The elimination of small number of prominent emitters allows a greater number of emitters to be active on emission with a compensation for higher electric-field application. We expect that the plasma treatment introduced in this letter will provide a quick and easy way to improve emission lifetime, which is essential for the commercialization of field emission display.
Difference in formation of hydrogen and helium clusters in tungsten
Authors: Henriksson K. O. E. , Nordlund K. , Krasheninnikov A. , Keinonen J.
Published: October 2005

The experimentally observed large difference in the depths of hydrogen and helium clusters formed in tungsten still lacks a fundamental explanation. Using density functional theory calculations, molecular dynamics simulations, and kinetic Monte Carlo calculations, we show that the fundamental mechanism behind the different clustering depths is significantly different behaviors of interstitial H and He atoms in W: H–H states are unstable for small interatomic distances whereas He–He states are strongly bound.
Aluminum mobility and interfacial segregation in fully silicided gate contacts
Authors: Pezzi R. P. , Copel M. , Cabral C. , Baumvol I. J. R.
Published: October 2005

The mobility of aluminum implanted as a dopant of fully silicided nickel for advanced metal gates has been investigated following rapid thermal annealing at temperatures ranging from 160to700°C. Resonant nuclear reaction profiling using the Al27(p,γ)Si28 reaction was used for aluminum quantification and depth profiling. The results indicate that there is no significant aluminum loss in the whole annealing temperature interval. Furthermore, aluminum is seen to segregate near the interface with silicon oxide during metal silicidation, forming a stable layer of aluminum oxide.
Thermal conductivity and interfacial resistance in single-wall carbon nanotube epoxy composites
Authors: Bryning M. B. , Milkie D. E. , Islam M. F. , Kikkawa J. M. , Yodh A. G.
Published: October 2005

We report thermal conductivity measurements of purified single-wall carbon nanotube (SWNT) epoxy composites prepared using suspensions of SWNTs in N-N-Dimethylformamide (DMF) and surfactant stabilized aqueous SWNT suspensions. Thermal conductivity enhancement is observed in both types of composites. DMF-processed composites show an advantage at SWNT volume fractions between ϕ∼0.001 to 0.005. Surfactant processed samples, however, permit greater SWNT loading and exhibit larger overall enhancement (64±9)% at ϕ∼0.1. The enhancement differences are attributed to a ten-fold larger SWNT/solid-composite interfacial thermal resistance in the surfactant-processed composites compared to DMF-processed composites. The interfacial resistance is extracted from the volume fraction dependence of the thermal conductivity data using effective medium theory. [C. W. Nan, G. Liu, Y. Lin, and M. Li, Appl. Phys. Lett. 85, 3549 (2004)].
A note on irrotational viscous flow
Authors: Sirakov B. T. , Greitzer E. M. , Tan C. S.
Published: October 2005

This Brief Communication describes features of steady irrotational flow in a viscous fluid. The aim is to illustrate, in a simple manner, the different roles played by viscous forces (which are identically zero) and viscous stresses (which are not), the differences in behavior of stagnation pressure (which is constant along a streamline even in the presence of viscous dissipation) and stagnation enthalpy (which changes through the flow), and the role of viscous stresses on the boundary in creating these behaviors.
High-strength Ti-base ultrafine eutectic with enhanced ductility
Authors: Das J. , Kim K. B. , Baier F. , Löser W. , Eckert J.
Published: October 2005

( Ti 0.705 Fe 0.295 ) 100 − x Sn x (x=0 and 3.85) ultrafine eutectics were prepared by slow cooling from the melt through cold crucible casting. The addition of 3.85 at. % Sn to the binary Ti–Fe eutectic decreases the strength slightly but considerably improves the plastic deformability under uniaxial compressive loading from εf=2.1% to 9.6% strain to failure. The change in the morphology of the eutectic and the distribution of the FeTi phase are suggested as origin of the improvement of the mechanical properties.
Ohmic contacts to silicon carbide determined by changes in the surface
Authors: Mohammad F. A. , Cao Y. , Porter L. M.
Published: October 2005

In this study, we investigated the effects of the contact phases and the underlying SiC surface on the ohmic behavior of annealed Pt and Pt∕Si contacts to p-type 4H–SiC. The contacts were annealed at 1100 and 1000 °C, respectively, for 5 min in vacuum to form ohmic contacts. Our data show that although the formation of the PtSi phase was complete, and the only phase present in the Pt∕Si∕SiC samples annealed at 900 °C, the contacts did not become ohmic at this temperature. Removal of the annealed Pt and Pt∕Si contacts and their replacement with unannealed Ni contacts resulted in ohmic behavior that was nearly identical to that of the previous annealed contacts. In contrast, as-deposited Ni contacts on as-received p-type SiC resulted in rectifying contacts. The results of this study show that changes in the SiC substrate underneath the contacts dominate the electrical behavior, and that effects of the particular phase(s) formed are small.
Magnetic coupling between Cr atoms doped at bulk and surface sites of ZnO
Authors: Wang Q. , Sun Q. , Jena P. , Kawazoe Y.
Published: October 2005

Contrary to theoretical prediction that Cr-doped bulk ZnO is ferromagnetic, recent experiments on Cr-doped ZnO thin film reveal the coupling to be antiferromagnetic. Using first-principles calculations based on gradient corrected density functional theory, we show that a possible origin of this disagreement may be associated with the site preference of Cr. In bulk, when Cr substitutes Zn, bond contraction occurs and Cr atoms prefer to cluster around O atoms. The ferromagnetic coupling among Cr atoms is driven by Cr 3d and O 2p exchange interactions as in Cr2O cluster. However, when Cr atoms replace Zn on the surface, due to the different bonding environment, bonds expand preventing Cr atoms from clustering around O atoms. Consequently, the coupling between Cr atoms becomes antiferromagnetic.
Electrical contacts to carbon nanotubes down to 1nm in diameter
Authors: Kim Woong , Javey Ali , Tu Ryan , Cao Jien , Wang Qian , Dai Hongjie
Published: October 2005

Rhodium (Rh) is found similar to Palladium (Pd) in making near-Ohmic electrical contacts to single-walled carbon nanotubes (SWNTs) with diameters d>∼1.6nm. Non-negligible positive Schottky barriers (SBs) exist between Rh or Pd and semiconducting SWNTs (S-SWNTs) with d<∼1.6nm. With Rh and Pd contacts, the characteristics of SWNT field-effect transistors and SB heights at the contacts are largely predictable based on the SWNT diameters, without random variations among devices. Surprisingly, electrical contacts to metallic SWNTs (M-SWNTs) also appear to be diameter dependent especially for small SWNTs. Ohmic contacts are difficult for M-SWNTs with diameters ⩽∼1.0nm possibly due to tunnel barriers resulted from large perturbation of contacting metal to very small diameter SWNTs due to high chemical reactivity of the latter.
Characterization of magnetically actuated resonant cantilevers in viscous fluids
Authors: Vančura Cyril , Lichtenberg Jan , Hierlemann Andreas , Josse Fabien
Published: October 2005

The vibration behavior of magnetically actuated resonant microcantilevers immersed in viscous fluids has been studied. A dependence of the resonance frequency and the quality factor (Q factor) on the fluid properties, such as density and viscosity and on the cantilever geometry is described. Various cantilever geometries are analyzed in pure water and glycerol solutions, and the results are explained in terms of the added displaced fluid mass and the fluid damping force for both the resonance frequency and the quality factor. An in-depth knowledge and understanding of such systems is necessary when analyzing resonant cantilevers as biochemical sensors in liquid environments.
Low-temperature growth and interface characterization of BiFeO3 thin films with reduced leakage current
Authors: Lee Yi-Hsien , Wu Jenn-Ming , Chueh Yu-Lun , Chou Li-Jen
Published: October 2005

BiFeO 3 (BFO) thin films of pure perovskite phase were deposited on LaNiO3-buffered Pt∕TiOx∕SiO2∕Si (LNO) and Pt∕TiOx∕SiO2∕Si (Pt) substrates by RF magnetron sputtering. Highly (100)-oriented BFO film was coherently grown on LNO at a temperature as low as 300 °C. The crystal structure and the film/electrode interface of BFO films were characterized using x-ray diffraction and scanning transmission electron microscope high-angle annular dark-field imaging. The conventional problem of the leakage current was greatly reduced with remarkable improvement in the film/electrode interface, chemical homogeneity, crystallinity, and surface roughness of the BFO film.
All-fiber integrated chirped pulse amplification at 1.06μm using aircore photonic bandgap fiber
Authors: Kennedy R. E. , Taylor J. R.
Published: October 2005

We demonstrate all-fiber integrated chirped pulse amplification (CPA) at 1.06μm using an air-core photonic bandgap fiber (APBF). Prior to the CPA stage, 4.0 ps pulses from a modelocked fiber laser were compressed to 1.3 ps in an all fiber integrated pulse compressor based on spectral broadening in a holey fiber and compression in a 12.4 m length of APBF. The compressed 1.3 ps pulses were then stretched to ∼20ps in 125 m of single mode fiber, amplified in a large mode area YDFA and recompressed to 600 fs in 50 m of APBF, which was directly spliced to the amplifier output fiber. The 600 fs output pulses had an estimated peak power of 2.6 kW.
Coupling of photon energy via a multiwalled carbon nanotube array
Authors: Lu Qi , Rao Rahul , Sadanadan Bindu , Que William , Rao Apparao M. , Ke Pu Chun
Published: October 2005

Fluorescent beads were excited by a laser beam coupled through a multiwalled carbon nanotube array. The images of the fluorescent beads showed a distinctive dependence on the polarization direction of the laser beam owing to the surface plasmons induced from the metallic property of the array. The thickness of the array is 2μm as compared to the metallic films of tens of nanometers in thickness that are conventionally used for surface plasmon excitation. This remarkable photon coupling capacity of a multiwalled carbon nanotube array is attributed to the confinement of electrons in its outermost tube shells and ballistic transport.
Gap junction-mediated intercellular biochemical coupling in cochlear supporting cells is required for normal cochlear functions
Authors: Zhang Yanping , Tang Wenxue , Ahmad Shoab , Sipp James A. , Chen Ping , Lin Xi
Published: October 2005

Dysfunction of gap junctions (GJs) caused by mutations in connexin26 (Cx26) and Cx30 accounts for nearly half of all cases of hereditary nonsyndromic deafness cases. Although it is widely held that GJs connecting supporting cells in the organ of Corti mainly provide ionic pathways for rapid removal of K
+
around the base of hair cells, the function of GJs in the cochlea remains unknown. Here we show that GJs were not assembled in the supporting cells of the organ of Corti until 3 days after birth in mice and then gradually matured to connect supporting cells before the onset of hearing. In organotypic cochlear cultures that were confirmed to express GJs, GJs mediated the propagation of intracellular Ca
2+
concentration waves in supporting cells by allowing intercellular diffusion of inositol 1,4,5-trisphosphate. We found that a subset of structurally mild Cx26 mutations located at the second transmembrane region (V84L, V95M, and A88S) and a Cx30 mutation located at the first cytoplasmic segment (T5M) specifically affect the intercellular exchange of larger molecules but leave the ionic permeability intact. Our results indicated that Cx26 and Cx30 mutations that are linked to sensorineural deafness retained ionic coupling but were deficient in biochemical permeability. Therefore, GJ-mediated intercellular exchange of biochemically important molecules is required for normal cochlear functions.
Deep mantle structure and the postperovskite phase transition
Authors: Helmberger D. , Lay T. , Ni S. , Gurnis M.
Published: October 2005

Seismologists have known for many years that the lowermost mantle of the Earth is complex. Models based on observed seismic phases sampling this region include relatively sharp horizontal discontinuities with strong zones of anisotropy, nearly vertical contrasts in structure, and small pockets of ultralow velocity zones (ULVZs). This diversity of structures is beginning to be understood in terms of geodynamics and mineral physics, with dense partial melts causing the ULVZs and a postperovskite solid–solid phase transition producing regional layering, with the possibility of large-scale variations in chemistry. This strong heterogeneity has significant implications on heat transport out of core, the evolution of the magnetic field, and magnetic field polarity reversals.
Human infection patterns and heterogeneous exposure in river blindness
Authors: Filipe João A. N. , Boussinesq Michel , Renz Alfons , Collins Richard C. , Vivas-Martinez Sarai , Grillet María-Eugenia , Little Mark P. , Basáñez María-Gloria
Published: October 2005

Here we analyze patterns of human infection withOnchocerca volvulus(the cause of river blindness) in different continents and ecologies. In contrast with some geohelminths and schistosome parasites whose worm burdens typically exhibit a humped pattern with host age, patterns ofO. volvulusinfection vary markedly with locality. To test the hypothesis that such differences are partly due to heterogeneity in exposure to vector bites, we develop an age- and sex-structured model for intensity of infection, with parasite regulation within humans and vectors. The model is fitted to microfilarial data from savannah villages of northern Cameroon, coffee fincas of central Guatemala, and forest-dwelling communities of southern Venezuela that were recorded before introducing ivermectin treatment. Estimates of transmission and infection loads are compared with entomological and epidemiological field data. Host age- and sex-heterogeneous exposure largely explains locale-specific infection patterns in onchocerciasis (whereas acquired protective immunity has been invoked for other helminth infections). The basic reproductive number,R0, ranges from 5 to 8, which is slightly above estimates for other helminth parasites but well below previously presented values.