bluuebunny/crossref_metadata_2025 huggingface dataset:
Climate Change and Religious Response: The Case of Early Medieval China
Authors: Barrett T. H.
Published: April 2007

The following remarks were originally drafted to serve as the thirty-seventh Evans-Wentz Lecture in Asian Philosophy, Religion and Ethics at Stanford University in May 2006, and take therefore as their tacit point of departure the work of Walter Y Evans-Wentz (1878–1965). His Tibetan Book of the Dead, first published by Oxford University Press in 1927, long remained the most influential account of the way in which Buddhists confronted their future as mortal beings, though in this lecture the scope of my own inquiry is widened from the individual to encompass fears concerning the transience of human society as a whole. This broader approach, moreover, allows for a degree of innovation. Ever since the era of Evans-Wentz, if not earlier, the problem of presenting the impulses behind traditions as unfamiliar as those of South and East Asia without simply confirming their apparent ‘exoticism’ has been difficult to solve, but over recent years our greatly increased knowledge of the history of the planetary environment that we all inhabit has offered an unprecedented perspective on the widely shared hopes and fears of the past. This is because we now know that at times different regions of the planet were subjected to events caused by the same catastrophic upheavals in climate. By taking one of the best known of these in the sixth century CE – and the information given below by no means exhausts what has been discovered about this phenomenon – and looking at its impact in terms of the sense of foreboding it engendered, it is therefore possible to trace the extent to which Europe and East Asia reacted in similar ways.
Analysis of a potential “solar radiation dose–dimethylsulfide–cloud condensation nuclei” link from globally mapped seasonal correlations
Authors: Vallina S. M. , Simó R. , Gassó S. , de Boyer‐Montégut C. , del Río E. , Jurado E. , Dachs J.
Published: April 2007

The CLAW postulate states that an increase in solar irradiance or in the heat flux to the ocean can trigger a biogeochemical response to counteract the associated increase in temperature and available sunlight. This natural (negative) feedback mechanism would be based on a multistep response: first, an increase in seawater dimethylsulfide concentrations (DMSw) and therefore its fluxes to the atmosphere (DMSflux); second, an increase in the atmospheric cloud condensation nuclei (CCN) burden as a consequence of DMS oxidation to form biogenic CCN (CCNbio); and third, an increase in cloud albedo due to higher CCN numbers. Monthly global climatological fields of the solar radiation dose in the upper mixed layer (SRD), surface oceanic DMSw, model outputs of hydroxyl radical concentrations (OH), and satellite‐derived CCN numbers (CCNs) are analyzed in order to evaluate the proposed “solar radiation dose‐DMS‐CCN” link from a global point of view. OH is included as the main atmospheric oxidant of the estimated DMSflux to produce CCNbio. Global maps of seasonal correlations between the variables show that the solar radiation dose is highly (positively) correlated with seawater dimethylsulfide over most of the global ocean and that atmospheric DMS oxidation is highly (positively) correlated with CCNs over large regions. These couplings are stronger at high latitudes, whereas the regions with negative or no correlation are located at low latitudes around the equator. However, CCNbio estimates for 15 regions of the global ocean show that DMS oxidation can be an important contributor to the CCNs burden only over pollution‐free regions, while it would have a minor contribution over regions with high loads of continental aerosols. Globally, the mean annual contribution of CCNbio to total CCNs is estimated to be ≈30%. Our results support that an oceanic biogenic mechanism that modulates cloud formation and albedo can indeed occur, although its impact seems rather weak over regions under a strong influence of continental aerosols. Nevertheless, our approach does not fully rule out that the observed correlations are due to an independent seasonal variation of the studied variables; seasonal couplings are necessary but not sufficient conditions to prove the CLAW hypothesis.
Suggestive correlations between the brightness of Neptune, solar variability, and Earth's temperature
Authors: Hammel H. B. , Lockwood G. W.
Published: April 2007

Long‐term photometric measurements of Neptune show variations of brightness over half a century. Seasonal change in Neptune's atmosphere may partially explain a general rise in the long‐term light curve, but cannot explain its detailed variations. This leads us to consider the possibility of solar‐driven changes, i.e., changes incurred by innate solar variability perhaps coupled with changing seasonal insolation. Although correlations between Neptune's brightness and Earth's temperature anomaly—and between Neptune and two models of solar variability—are visually compelling, at this time they are not statistically significant due to the limited degrees of freedom of the various time series. Nevertheless, the striking similarity of the temporal patterns of variation should not be ignored simply because of low formal statistical significance. If changing brightnesses and temperatures of two different planets are correlated, then some planetary climate changes may be due to variations in the solar system environment.
Geological controls and tidal forcing of submarine groundwater discharge from a confined aquifer in a coastal sand dune system
Authors: Holliday D. , Stieglitz T. C. , Ridd P. V. , Read W. W.
Published: April 2007

Submarine groundwater discharge (SGD) into the ocean is increasingly recognized as an important component of land‐ocean interaction. Numerous geological settings may be the source of terrestrially derived SGD, including spatially extensive sand dune systems, which are a common coastal setting in tropical, subtropical, and temperate regions throughout the world. Within the catchment of the Great Barrier Reef lagoon, numerous large‐scale sand dune systems exist. Creeks and rivers draining these systems are largely absent; however, terrestrially derived groundwater discharges from discrete springs in the intertidal zone. The geological and hydrological controls of the discharge were investigated, using a combination of geological, geophysical, and hydrological methods. From sedimentary and geoelectric data it is inferred that a unit of sandy clay provides a confinement of the shallow aquifer system in the dune complex, with groundwater discharging where this layer is breached. Groundwater discharge flux was inversely correlated with tidal water level, but remained positive throughout the tidal cycle. A simple hydrological model indicates that the continuous discharge is the result of a change in hydraulic pressure of the confined aquifer in response to tidal forcing at the seaward limit of the aquitard, which is a previously undescribed effect of tidal modulation of SGD. The observed groundwater discharge is likely to have a significant effect on the biogeochemistry of the coastal environment, particularly in the absence of surface water drainage.
Numerical study of the dynamics of the Ryukyu Current system
Authors: Nakamura Hirohiko , Ichikawa Hiroshi , Nishina Ayako
Published: April 2007

Recent observations indicate that the Ryukyu Current system, part of the western boundary current of the North Pacific subtropical gyre on the eastern slope of the Ryukyu Islands, Japan, exhibits bottom intensification to the north of Okinawa Island and a nearly barotropic current to the south. We performed numerical experiments of this system using two primitive equation models that incorporate realistic and idealized topography, respectively, to identify the processes that act to maintain the Ryukyu Current system. The dynamics responsible for baroclinic structures of the Ryukyu Current system are examined in detail by diagnosing numerical solutions based on a characteristic equation derived from two‐layer planetary geostrophic equations. The diagnoses show that bottom intensification of the Ryukyu Current system is primarily formed along the characteristics due to the first baroclinic mode topographic Rossby wave that emanates from the Kuroshio in the Tokara Strait. This topographic wave depresses the main thermocline along the inshore slope area east of the Ryukyu Islands such that the passage of the wave over the barotropic northward flow along the slope establishes a state of no motion in the upper layer and bottom intensification of the northward current in the lower layer. The diagnoses also suggest that the characteristics that result from this topographic wave are expelled in the slope area south of Okinawa Island by the first baroclinic mode planetary Rossby wave that propagates westward from the North Pacific interior region, resulting in bottom intensification only in the northern slope area.
Mars equatorial mesospheric clouds: Global occurrence and physical properties from Mars Global Surveyor Thermal Emission Spectrometer and Mars Orbiter Camera limb observations
Authors: Clancy R. Todd , Wolff Michael J. , Whitney Barbara A. , Cantor Bruce A. , Smith Michael D.
Published: April 2007

We report the occurrence of a new type of cloud in the Mars dayside (1300–1400 Local Time) atmosphere, apparent as high‐altitude (60 to 80 km), vertically discrete aerosol scattering layers. Mars Global Surveyor (MGS) limb observations from the Thermal Emission Spectrometer (TES) visible channel indicate peak frequencies at the beginning and end of the aphelion northern summer season (LS = 30° and 150°), where they are confined to equatorial (15°S–15°N) latitudes and two longitude ranges (40°E–2°W and 50°W–120°W). Limb images from the MGS Mars Orbiter Camera (MOC) indicate significant horizontal variations in these Mars equatorial mesospheric (MEM) clouds on 20–50 km scales. On the basis of the distribution of projected limb heights, MEM clouds exhibit peak optical depths over 70–75 km altitudes, that are substantial (nadir τvis of order 0.01) for the low‐pressure region of formation (∼1 μbar). Averaged TES limb infrared spectral (5–40 μm) and solarband radiance profiles corresponding to MEM occurrence indicate dust aerosols (reff = 1.5–2.0 μm, τvis ∼ 0.4) at 0–25 km altitudes, capped by water ice clouds (reff = 1.5–2.0 μm, τvis ∼ 0.2) at 20–45 km altitudes. The lack of detectable infrared radiances at MEM cloud heights precludes distinction of water versus CO2 ice, but indicates ≤1 μm particle sizes for water or ≤1.5 μm for CO2 ice compositions. More recent Mars Express observations point toward Mars mesospheric CO2 clouds, although current dynamical and radiative models do not indicate sufficiently cold temperatures at MEM cloud locations to produce daytime CO2 saturation conditions.
Spatial and temporal complexity of the Amazon flood measured from space
Authors: Alsdorf Doug , Bates Paul , Melack John , Wilson Matt , Dunne Thomas
Published: April 2007

Floodplain processes are driven by water flows that seasonally change in direction and consist of a myriad of interacting streams of varying depth, velocity, source, sediment concentration and chemistry. Here we show, using spaceborne interferometric synthetic aperture radar (SAR) JERS‐1 measurements, the first spatially dense hydraulic mapping of the passage of a flood wave through a large, topographically complex floodplain. We find that temporal changes in flood water heights (∂h/∂t) are more complex than typically assumed. During the passage of a flood wave, sharp variations in ∂h/∂t are localized along some floodplain channels. These channels separate adjacent locations with different rates of infilling. Near the peak of the flood wave, some of the channels are no longer evident as controls on ∂h/∂t. During the passage of the flood wave, flow paths change from bathymetrically influenced to hydraulically controlled (and back again), thus it is difficult to know the flow path a‐priori from bathymetry alone.
Glutamatergic and GABAergic Neurotransmitter Cycling and Energy Metabolism in Rat Cerebral Cortex during Postnatal Development
Authors: Chowdhury Golam MI , Patel Anant B , Mason Graeme F , Rothman Douglas L , Behar Kevin L
Published: April 2007

The contribution of glutamatergic and γ-aminobutyric acid (GABA)ergic neurons to oxidative energy metabolism and neurotransmission in the developing brain is not known. Glutamatergic and GABAergic fluxes were assessed in neocortex of postnatal day 10 (P10) and 30 (P30) urethane-anesthetized rats infused intravenously with [1,6-13C2]glucose for different time intervals (time course) or with [2-13C]acetate for 2 to 3 h (steady state). Amino acid levels and 13C enrichments were determined in tissue extracts ex vivo using 1H-[13C]-NMR spectroscopy. Metabolic fluxes were estimated from the best fits of a three-compartment metabolic model (glutamatergic neurons, GABAergic neurons, and astroglia) to the 13C-enrichment time courses of amino acids from [1,6-13C2]glucose, constrained by the ratios of neurotransmitter cycling ( Vcyc)-to-tricarboxylic acid (TCA) cycle flux ( VTCAn) calculated from the steady-state [2-13C]acetate enrichment data. From P10 to P30 increases in total neuronal (glutamate plus GABA) TCA cycle flux (3×; 0.24±0.05 versus 0.71 ± 0.07 μmol per g per min, P < 0.0001) and total neurotransmitter cycling flux (3.1 to 5×; 0.07 to 0.11 (± 0.03) versus 0.34 ± 0.03 μmol per g per min, P < 0.0001) were approximately proportional. Incremental changes in total cycling (δ Vcyc(tot)) and neuronal TCA cycle flux (δ VTCAn(tot)) between P10 and P30 were 0.23 to 0.27 and 0.47 μmol per g per min, respectively, similar to the ∼ 1:2 relationship previously reported for adult cortex. For the individual neurons, increases in VTCAn and Vcyc were similar in magnitude (glutamatergic neurons, 2.7× versus 2.8 to 4.6×; GABAergic neurons, ∼ 5× versus ∼7×), although GABAergic flux changes were larger. The findings show that glutamate and GABA neurons undergo large and approximately proportional increases in neurotransmitter cycling and oxidative energy metabolism during this major postnatal growth spurt.
Proliferating Resident Microglia after Focal Cerebral Ischaemia in Mice
Authors: Denes Adam , Vidyasagar Rishma , Feng Jianghua , Narvainen Johanna , McColl Barry W , Kauppinen Risto A , Allan Stuart M
Published: April 2007

Cerebral ischaemia usually results in the rapid death of neurons within the immediate territory of the affected artery. Neuronal loss is accompanied by a sequence of events, including brain oedema, blood-brain barrier (BBB) breakdown, and neuroinflammation, all of which contribute to further neuronal death. Although the role of macrophages and mononuclear phagocytes in the expansion of ischaemic injury has been widely studied, the relative contribution of these cells, either of exogenous or intrinsic central nervous system (CNS) origin is still not entirely clear. The purpose of this study, therefore, was to use different durations of transient middle cerebral artery occlusion (tMCAo) in the mouse to investigate fully post-occlusion BBB permeability and cellular changes in the brain during the 72 h post-MCAo period. This was achieved using in vivo magnetic resonance imaging (MRI) and cell labelling techniques. Our results show that BBB breakdown and formation of the primary ischaemic damage after tMCAo is not associated with significant infiltration of neutrophils, although more are observed with longer periods of MCAo. In addition, we observe very few infiltrating exogenous macrophages over a 72 h period after 30 or 60 mins of occlusion, instead a profound increase in proliferating resident microglia cells was observed. Interestingly, the more severe injury associated with 60 mins of MCAo leads to a markedly reduced proliferation of resident microglial cells, suggesting that these cells may play a protective function, possibly through phagocytosis of infiltrating neutrophils. These data further support possible beneficial actions of microglial cells in the injured brain.
A nonlinear model for surface segregation and solute trapping during planar film growth
Authors: Han Xiaoying , Spencer Brian J.
Published: April 2007

Surface segregation and solute trapping during planar film growth is one of the important issues in molecular beam epitaxy, yet the study on surface composition has been largely restricted to experimental work. This paper introduces some mathematical models of surface composition during planar film growth. Analytical solutions are obtained for the surface composition during growth.
Relativistic breakdown in planetary atmospheres
Authors: Dwyer J. R.
Published: April 2007

In 2003, a new electrical breakdown mechanism involving the production of runaway avalanches by positive feedback from runaway positrons and energetic photons was introduced. This mechanism, which shall be referred to as “relativistic feedback,” allows runaway discharges in gases to become self-sustaining, dramatically increasing the flux of runaway electrons, the accompanying high-energy radiation, and resulting ionization. Using detailed Monte Carlo calculations, properties of relativistic feedback are investigated. It is found that once relativistic feedback fully commences, electrical breakdown will occur and the ambient electric field, extending over cubic kilometers, will be discharged in as little as 2×10−5s. Furthermore, it is found that the flux of energetic electrons and x rays generated by this mechanism can exceed the flux generated by the standard relativistic runaway electron model by a factor of 1013, making relativistic feedback a good candidate for explaining terrestrial gamma-ray flashes and other high-energy phenomena observed in the Earth’s atmosphere.
Temperature dependence of magnetotransport properties of Ni80Fe20∕Fe50Mn50∕Ni80Fe20 trilayers
Authors: Chui K. M. , Tripathy D. , Adeyeye A. O.
Published: April 2007

In this work, we have investigated the temperature dependence and effect of seed layer thickness on the exchange bias of a Ni80Fe20 (ts)∕Fe50Mn50 (20nm)∕Ni80Fe20 (20nm) trilayer, with ts varied systematically from 5to50nm. Room temperature hysteresis loops show that variation in ts strongly affects the exchange bias of both the seed and top Ni80Fe20 layers. Magnetotransport measurements were used to determine the temperature dependence of the overall exchange field (HE) and coercivity (HC) as a function of seed layer thickness.
Magnetic anisotropy and high coercivity of epitaxial Co-ferrite films prepared by pulsed laser deposition
Authors: Yin J. H. , Ding J. , Liu B. H. , Yi J. B. , Miao X. S. , Chen J. S.
Published: April 2007

Co Fe 2 O 4 films with different thicknesses (40–200nm) were prepared on sapphire using pulsed laser deposition at different substrate temperatures. The films on (0001) sapphire showed a (111) epitaxial structure even at a low deposition temperature of 150°C. The coercivity up to 8.8kOe could be achieved in the 40nm film on sapphire deposited at 550°C. By comparison, the 33nm film on quartz possesses a nanocrystalline structure with the grain size below 20nm as well as a strong (111) preferential texture. The highest coercivity (12.5kOe) up to now was obtained in the 33nm Co-ferrite films. The study also revealed that high coercivity and large perpendicular anisotropy of these Co-ferrite thin films may be related to the textured structure and large residual strain.
Size dependent magnetic properties and cation inversion in chemically synthesized MnFe2O4 nanoparticles
Authors: Chinnasamy C. N. , Yang Aria , Yoon S. D. , Hsu Kailin , Shultz M. D. , Carpenter E. E. , Mukerjee S. , Vittoria C. , Harris V. G.
Published: April 2007

Mn Fe 2 O 4 nanoparticles with diameters ranging from about 4to50nm were synthesized using a modified coprecipitation method. X-ray diffractograms revealed a pure phase spinel ferrite structure for all samples. Transmission electron microscopy showed that the particles consist of a mixture of both spherical (smaller) and cubic (larger) particles dictated by the reaction kinetics. The Néel temperatures (TN) of MnFe2O4 for various particle sizes were determined by using high temperature magnetometry. The ∼4nm MnFe2O4 particles showed a TN of about 320°C whereas the ∼50nm particles had a TN of about 400°C. The high Néel temperature, compared with the bulk MnFe2O4 TN of 300°C, is due to a change in cation distribution between the tetrahedral and octahedral sites of the spinel lattice. Results of extended x-ray absorption fine structure measurements indicate a systematic change in the cation distribution dependent on processing conditions.
High-resistivity nanogranular Co–Al–O films for high-frequency applications
Authors: Khalili Amiri Pedram , Zhuang Yan , Schellevis Hugo , Rejaei Behzad , Vroubel Marina , Ma Yue , Burghartz Joachim N.
Published: April 2007

This work presents a series of high-resistivity nanogranular Co–Al–O films with maximum resistivity of ∼110mΩcm. The films were deposited using pulsed dc reactive sputtering of a Co72Al28 target in an oxygen/argon ambient. The samples were characterized by scanning electron microscopy (SEM), M-H loop measurements, and s-parameter measurements on microstrip transmission lines with Co–Al–O magnetic cores. The high-frequency magnetic permeability profile was extracted from the microstrip measurements. Reduction of deposition power resulted in resistivity enhancement, as well as reduction of coercivity and permeability. SEM images reveal an average grain size of ∼80nm for films with the highest resistivity.
Effect of the temperature dependence of Hk in thermally assisted recording
Authors: Greaves S. J. , Muraoka H.
Published: April 2007

Simulations of thermally assisted recording were carried out to determine the effect of the temperature dependence of Hk and thermal gradients on the recording performance. Even in the absence of a head field gradient, it was possible to record sharp transitions in the media. The relationship between Ms(T) and Ku(T) and its influence on signal-to-noise ratio (SNR) was investigated, and it was discovered that media in which Ku(T)∝Ms3(T) had higher SNR and narrower written tracks than materials with Ku(T)∝Ms2(T).
Sasa-Satsuma (complex modified Korteweg–de Vries II) and the complex sine-Gordon II equation revisited: Recursion operators, nonlocal symmetries, and more
Authors: Sergyeyev Artur , Demskoi Dmitry
Published: April 2007

We present a new symplectic structure and a hereditary recursion operator for the Sasa-Satsuma equation which is widely used in nonlinear optics. Using an integrodifferential substitution relating this equation to a third-order symmetry flow of the complex sine-Gordon II equation enabled us to find a hereditary recursion operator and higher Hamiltonian structures for the latter equation. We also show that both the Sasa-Satsuma equation and the third-order symmetry flow for the complex sine-Gordon II equation are bi-Hamiltonian systems, and we construct several hierarchies of local and nonlocal symmetries for these systems.
Computationally efficient description of relativistic electron beam transport in collisionless plasma
Authors: Polomarov Oleg , Sefkow Adam B. , Kaganovich Igor , Shvets Gennady
Published: April 2007

A reduced approach to modeling the electromagnetic Weibel instability and relativistic electron beam transport in collisionless background plasma is developed. Beam electrons are modeled by macroparticles and the background plasma is represented by electron fluid. Conservation of generalized vorticity and quasineutrality of the plasma-beam system are used to simplify the governing equations. The method is suitable for modeling the nonlinear stages of collisionless beam-plasma interaction. A computationally efficient code based on this reduced description is developed and benchmarked against a standard particle-in-cell code. The full-scale two-dimensional numerical simulation of the Weibel instability saturation of a low-current electron beam is presented. Using the present approach, linear growth rates of the Weibel instability are derived for the cold and finite-temperature beams.
Relativistic two-component infinite order method for atomic core ionization potentials
Authors: Barysz Maria , Leszczyński Jerzy
Published: April 2007

In this paper the authors have applied the infinite-order two-component method (IOTC) to compute the valence and inner shell ionization potentials for the Ne, Ar, Kr, and Xe elements. The obtained results show the very good performance of the recently defined relativistic IOTC method. They also confirm the importance of the relativistic effects in the determination of the inner shell ionization potentials.
Ab initio study of the torsional potential energy surfaces of N2O3 and N2O4: Origin of the torsional barriers
Authors: Halpern Arthur M. , Glendening Eric D.
Published: April 2007

Intrinsic reaction coordinate (IRC) torsional potentials were calculated for N2O4 and N2O3 based on optimized B3LYP/aug-cc-pVDZ geometries of the respective 90°-twisted saddle points. These potentials were refined by obtaining CCSD(T)∕aug-cc-pVXZ energies [in the complete basis set (CBS) limit] of points along the IRC. A comparison is made between these ab initio potentials and an analytical form based on a two-term cosine expansion in terms of the N–N dihedral angle. The shapes of these two potential curves are in close agreement. The torsional barriers in N2O4 and N2O3 obtained from the CCSD(T)/CBS//B3LYP/aug-cc-pVDZ calculations are 2333 and 1704cm−1, respectively. For N2O4 the torsion fundamental frequency from the IRC potential is 87.06cm−1, which is in good agreement with the experimentally reported value of 81.73cm−1. However, in the case of N2O3 the torsional frequency found from the IRC potential, 144cm−1, is considerably larger than the reported experimental values 63–76cm−1. Consistent with this discrepancy, the torsional barrier obtained from several different calculations, 1417–1718cm−1, is higher than the value of 350cm−1 deduced from experimental studies. It is suggested that the assignment of the torsional mode in N2O3 should be reexamined. N2O4 and N2O3 exhibit strong hyperconjugative interactions of in-plane O lone pairs with the central N–N σ* antibond. Hyperconjugative stabilization is somewhat stronger at the planar geometries because 1,4 interactions of lone pairs on cis O atoms promote delocalization of electrons into the N–N antibond. Calculations therefore suggest that the torsional barriers in these molecules arise principally from a combination of 1,4 interactions and hyperconjugation.
Fast collisionless reconnection in electron-positron plasmas
Authors: Bessho Naoki , Bhattacharjee A.
Published: April 2007

Magnetic reconnection in electron-positron (pair) plasmas is studied by two-dimensional, electromagnetic, particle-in-cell simulations. In pair plasmas, the Hall current does not appear because there is no scale separation between ion and electron motion. Simulations show that fast reconnection is realized in both nonrelativistic and relativistic regimes. It is demonstrated that the divergence of the electron and positron pressure tensors essentially plays the role of an effective collisionless resistivity in realizing fast reconnection. Since there is no Hall current in pair plasmas, there is no quadrupolar structure in the out-of-plane magnetic field. Particle acceleration by reconnection is investigated. Major sites of particle acceleration are the regions in the vicinity of X lines, where ultrarelativistic particles are generated by the reconnection electric field.
Instabilities in buoyant flows under localized heating
Authors: Navarro M. C. , Mancho A. M. , Herrero H.
Published: April 2007

We study, from the numerical point of view, instabilities developed in a fluid layer with a free surface in a cylindrical container which is nonhomogeneously heated from below. In particular, we consider the case in which the applied heat is localized around the origin. An axisymmetric basic state appears as soon as a nonzero horizontal temperature gradient is imposed. The basic state may bifurcate to different solutions depending on vertical and lateral temperature gradients and on the shape of the heating function. We find different kinds of instabilities: extended patterns growing on the whole domain, which include those known as targets, and spiral waves. Spirals are present even for infinite Prandtl number. Localized structures both at the origin and at the outer part of the cylinder may appear either as Hopf or stationary bifurcations. An overview of the developed instabilities as functions of the dimensionless parameters is presented in this article.
Polarization separated Zeeman spectra from magnetic dipole transitions in highly charged argon in the large helical device
Authors: Iwamae A. , Atake M. , Sakaue A. , Katai R. , Goto M. , Morita S.
Published: April 2007

Visible spectral emission lines from magnetic dipole transitions in ArX, ArXI, ArXIV, and ArXV are observed from plasmas heated with neutral-beam injection (NBI) in the Large Helical Device [O. Motojima et al., Phys. Plasmas 6, 1843 (1999)]. Orthogonal linearly polarized components of the emission line profiles are observed with a polarization separation optical system and high-resolution spectrometer. Zeeman split profiles reveal polarization characteristics of magnetic dipole transitions. Ion temperatures and emission locations are estimated from the profiles with the magnetic field information on the lines of sight (LOS). The spatially resolved emissions are observed by the array of absolutely calibrated views. The time histories of line profiles and emission intensities at the poloidal view are presented. The observed line profiles and the intensity distribution at the poloidal view indicate the localization of these charge states in the edge region just inside the last closed flux surface. The emission line of ArX in the tangential observation indicates Doppler shifts of the Zeeman split profiles. The velocity components of ArX ion flow along the LOS at the tangential view are 7.7 and 2.0km∕s at the outer and inner edge plasmas, respectively, in the opposite direction to the NBI.
Application of the three omega method for the thermal conductivity measurement of polyaniline
Authors: Kaul Pankaj B. , Day Kevin A. , Abramson Alexis R.
Published: April 2007

The three omega method has proven to provide accurate and reliable measurements of thermal conductivity of thin films and other materials. However, if the films are soft and conductive, conventional methodologies to prepare samples for the measurement technique are challenging and often unachievable. Various modifications to the sample preparation to employ this technique for soft conducting films are reported in this paper including the use of shadow masks for metal heater deposition and a process for preparation of low temperature insulating films required between film and heater. In this work, thick (∼5μm) and ultrathin (∼110nm) films of polyaniline as well as a thin (∼300nm) film of low temperature plasma enhanced chemical vapor deposited SiO2 as a function of temperature were measured. Though not considered a soft material, the silicon dioxide film was utilized for comparison with previous data. Results indicate that the SiO2 film exhibits a thermal conductivity slightly lower than others’ data [S. M. Lee and D. G. Cahill, J. Appl. Phys. 81, 2590 (1997); H. Yan et al., Chem. Lett. 2000, 392; H. Yan et al., Anal. Calorim. 69, 881 (2002); J. E. de Albuquerque et al., Rev. Sci. Instrum. 74, 306 (2003)], which is likely due to the low temperature processing conditions that results in additional disorder in the film. The polyaniline films exhibit an increase in thermal conductivity with temperature, which is largely due to increasing heat capacity. The thick film thermal conductivity is many times the value corresponding to the thin film, which is likely due to significant phonon boundary scattering present in the ultrathin film.
Chemical origin of blue- and redshifted hydrogen bonds: Intramolecular hyperconjugation and its coupling with intermolecular hyperconjugation
Authors: Li An Yong
Published: April 2007

Upon formation of a H bond Y⋯H–XZ, intramolecular hyperconjugation n(Z)→σ*(X–H) of the proton donor plays a key role in red- and blueshift characters of H bonds and must be introduced in the concepts of hyperconjugation and rehybridization. Intermolecular hyperconjugation transfers electron density from Y to σ*(X–H) and causes elongation and stretch frequency redshift of the X–H bond; intramolecular hyperconjugation couples with intermolecular hyperconjugation and can adjust electron density in σ*(X–H); rehybridization causes contraction and stretch frequency blueshift of the X–H bond on complexation. The three factors—intra- and intermolecular hyperconjugations and rehybridization determine commonly red- or blueshift of the formed H bond. A proton donor that has strong intramolecular hyperconjugation often forms blueshifted H bonds.
Effect of liquid thickness on laser ablation efficiency
Authors: Kang Hyun Wook , Welch Ashley J.
Published: April 2007

The purpose of this study was to investigate the effect of liquid thickness on laser ablation efficiency. Both Q-switched Nd:YAG (yttrium aluminum garnet) and free-running Er:YAG lasers were used to ablate polymethyl-methacrylate samples in the presence of a water layer. The thickness of the liquid layer varied from 500μmto3mm. Ablation performance as a function of liquid thickness for both lasers was quantitatively measured by optical coherence tomography. For the Q-switched Nd:YAG laser, wet ablation produced up to three times greater ablation volume than dry ablation, and the ablation efficiency decreased with increase of liquid thickness. On the other hand, for the Er:YAG laser, wet ablation with a 500μm layer of water produced comparable ablation volume to dry ablation. Ablation performance decreased as the liquid layer thickness increased. Q-switched laser ablation assisted by a thin liquid layer efficiently augmented material removal, while ablation efficiency of a long-pulsed Er:YAG laser decreased as water thickness was increased.
Yield of electronically excited CN molecules from the dissociative recombination of HNC+ with electrons
Authors: Rosati Richard E. , Pappas Daphne , Johnsen Rainer , Golde Michael F.
Published: April 2007

The authors have studied CN(B-X) and CN(A-X) emissions produced by the dissociative recombination of HNC+ ions with thermal electrons in a flowing afterglow experiment. A separate drift tube study showed that the reaction Ar++HCN, the precursor reaction used in the flow-tube experiment, produces predominantly HNC+ rather than the more energetic HCN+ isomer. Models simulating the ion-chemical processes, diffusion, and gas mixing in the afterglow plasma were fitted to observed position dependent CN(A-X) and CN(B-X) band intensities. Absolute yields of CN(B) and CN(A) were then obtained by comparing the CN band intensities to those of CO bands produced by recombination of CO2+ ions. It was concluded that the 300K recombination coefficient of HNC+ is close to 2×10−7cm3s−1, that CN(B) is formed with a yield of 0.22±0.08 and CN(A) with a yield of 0.14±0.05. By comparison to synthetic spectra, the rotational temperature of CN(B) was estimated to be approximately 2500K. It was also found that recombination produces CN(B) and CN(A) with far greater vibrational excitation than would be expected from the “impulse model” of Bates [Mon. Not. R. Astron. Soc. 263, 369 (1993)].
Spectroscopic and microscopic study of vanadium oxide nanotubes
Authors: Gloskovskii A. , Nepijko S. A. , Schönhense G. , Therese H. A. , Reiber A. , Kandpal H. C. , Fecher G. H. , Felser C. , Tremel W. , Klimenkov M.
Published: April 2007

V 2 O 5 nanotubes synthesized via the sol-gel route has been studied by electron energy loss spectroscopy (EELS), x-ray absorption spectroscopy (XAS), and energy dispersive x-ray analysis, in order to understand the local structure of vanadium in the nanotubes. Contrary to our expectation, all the features of the XAS and EELS spectra of the V2O5 nanotubes are in line with that of bulk layered vanadium oxide revealing that vanadium is present in the 5+ oxidation state in the nanotubes. However, V2O5 nanotubes exhibit additional surface states in their electronic structure in comparison with bulk V2O5. A comparison of measured and calculated spectra allows us to distinguish single-wall from multiwall V2O5 nanotubes.
Jahn-Teller effect in CH3D+ and CD3H+: Conformational isomerism, tunneling-rotation structure, and the location of conical intersections
Authors: Wörner H. J. , Merkt F.
Published: April 2007

High-resolution pulsed-field-ionization zero-kinetic-energy photoelectron spectra of CH3D and CD3H have been recorded at rotational resolution from the adiabatic ionization energy up to 600cm−1 of internal energy of the respective cations. The spectra are characterized by the effects of a large-amplitude pseudorotational motion exchanging the equivalent nuclei in each molecule. With increasing internal energy, a transition from the tunneling regime with splittings of the order of 1–10cm−1 to the free pseudorotation regime is observed. A theoretical model that treats the simultaneous rotational and pseudorotational motions and incorporates the effects of the geometric phase has been developed. The model provides the appropriate rovibronic symmetries in the C3v(M) molecular symmetry group and reaches a near-quantitative agreement with the experimental data. The complete group-theoretical analysis of the rovibronic problem is also given. The analysis of the spectra has revealed the existence of two different isomers for both CH3D+ and CD3H+, which differ in the bond length between the carbon atom and the unique ligand atom. All isomers are subject to a fast pseudorotational motion between three equivalent minima with a period of 3–5ps in CH3D+ and 18–28ps in CD3H+. The analysis has also provided the ordering of the tunneling sublevels for each isomer, which enables the location of the twofold conical intersections on the potential energy surface that could not be determined from experiments on CH4+.
Hamiltonian formalism for two magnon scattering microwave relaxation: Theory and applications
Authors: Krivosik Pavol , Mo Nan , Kalarickal Sangita , Patton Carl E.
Published: April 2007

A two magnon scattering theory for microwave relaxation in magnetic systems is formulated in the framework of the Hamiltonian formalism. The paper provides general expressions for inhomogeneity coupling coefficients in the case of localized inhomogeneities. An approximate solution for the relaxation rate of the ferromagnetic resonance uniform mode relaxation rate is presented. Two examples of the application of the theory are presented, one for bulk polycrystalline ferrites and one for polycrystalline metallic thin films.
Orientation of pentacene molecules on SiO2: From a monolayer to the bulk
Authors: Zheng Fan , Park Byoung-Nam , Seo Soonjoo , Evans Paul G. , Himpsel F. J.
Published: April 2007

Near edge x-ray absorption fine structure (NEXAFS) spectroscopy is used to study the orientation of pentacene molecules within thin films on SiO2 for thicknesses ranging from monolayers to the bulk (150nm). The spectra exhibit a strong polarization dependence of the π* orbitals for all films, which indicates that the pentacene molecules are highly oriented. At all film thicknesses the orientation varies with the rate at which pentacene molecules are deposited, with faster rates favoring a thin film phase with different tilt angles and slower rates leading to a more bulklike orientation. Our NEXAFS results extend previous structural observations to the monolayer regime and to lower deposition rates. The NEXAFS results match crystallographic data if a finite distribution of the molecular orientations is included. Damage to the molecules by hot electrons from soft x-ray irradiation eliminates the splitting between nonequivalent π* orbitals, indicating a breakup of the pentacene molecule.
Rapid measurement of three-dimensional diffusion tensor
Authors: Cho H. , Ren X.-H. , Sigmund E. E. , Song Y.-Q.
Published: April 2007

In this article, the authors demonstrate a rapid NMR method to measure a full three-dimensional diffusion tensor. This method is based on a multiple modulation multiple echo sequence and utilizes static and pulsed magnetic field gradients to measure diffusion along multiple directions simultaneously. The pulse sequence was optimized using a well-known linear inversion metric (condition number) and successfully tested on both isotropic (water) and anisotropic (asparagus) diffusion systems.
Investigation of local charged defects within high-temperature annealed HfSiON∕SiO2 gate stacks by scanning capacitance spectroscopy
Authors: Naitou Y. , Ando A. , Ogiso H. , Kamiyama S. , Nara Y. , Yasutake K. , Watanabe H.
Published: April 2007

We studied the oxide charges and traps within nitrided Hf-silicate (HfSiON)∕SiO2 gate stacks processed with high-temperature annealing with a spectroscopic technique by using high spatial resolution scanning capacitance microscopy. Spectroscopy was performed by detecting the static capacitance (dC∕dZ) between a conductive probe and the sample while sweeping the sample bias. The dC∕dZ image and spatially resolved dC∕dZ-V spectrum revealed the existence of positive fixed charges within HfSiON and interface trap charges between the SiO2 underlayer and Si substrate. We also observed a transient electron trap process from the conductive probe to the HfSiON film as abrupt discontinuities in the dC∕dZ-V spectrum and with bias-induced topography change of the HfSiON surface. These oxide charges and trap sites distribute inhomogeneously within HfSiON∕SiO2 gate stacks, and the origin of these charged defects is ascribable to phase separation induced by high-temperature postdeposition annealing.
Inertial-subrange structures of isotropic incompressible magnetohydrodynamic turbulence in the Lagrangian renormalized approximation
Authors: Yoshida Kyo , Arimitsu Toshihico
Published: April 2007

The structures of isotropic incompressible magnetohydrodynamic (MHD) turbulence in the inertial subrange are studied within the Lagrangian renormalized approximation (LRA). It is confirmed that LRA derives the total energy spectrum which is consistent with the Iroshnikov-Kraichnan (IK) spectrum. The residual energy spectrum in LRA is found to obey k−2 scaling law, where k is the wave number. Given are the quantitative estimates of (i) the dimensionless constants in the total and residual energy spectra, (ii) contribution of triad interactions to the energy flux, and (iii) the eddy viscosity and the eddy magnetic diffusivity. A direct numerical simulation (DNS) of a forced quasi-isotropic incompressible MHD turbulence is performed to find that the obtained total energy spectrum is in good agreement with the one derived within LRA both in its scaling exponent and in the dimensionless constant. The residual energy spectrum obtained in the DNS agrees with that derived in LRA with respect to the scaling exponent and the sign of the dimensionless constant, which is negative, although the magnitude of the dimensionless constant is about four times larger.
Autoresonant ion cyclotron isotope separation
Authors: Rax J.-M. , Robiche J. , Fisch N. J.
Published: April 2007

A new isotope separation process based on selective cyclotron resonant interaction between ions and a tapered helicoidal magnetic structure is identified, analyzed, and evaluated. On the basis of a Hamiltonian analysis, the existence of a class of tapered magnetic modulation that provide a full conversion of linear momentum into angular momentum is discovered. The characteristics and parameters of this field configuration are analyzed and described. The dynamic of the nonresonant isotope is investigated in order to set up a separation criterion. This autoresonant ion cyclotron isotope separation mechanism provides an efficient alternative to other niches of enrichment process.
Vlasov-Maxwell plasma equilibria with temperature and density gradients: Weak inhomogeneity limit
Authors: Montagna C. , Pegoraro F.
Published: April 2007

Stationary self-consistent solutions of the Vlasov-Maxwell system in a magnetized plasma (so called Vlasov equilibria) with both density and temperature gradients are investigated analytically in the limit of weak inhomogeneities. These solutions provide a simple class of self-consistent equilibria that can be used as a convenient starting point for numerical studies such as the study of the effects of temperature gradient and temperature anisotropy on the nonlinear development of reconnection instabilities in a kinetic plasma regime.
Microstructure and dielectric relaxor properties for Ba0.5Sr0.5TiO3/La0.67Sr0.33MnO3 heterostructure
Authors: Miao J. , Tian H. Y. , Zhou X. Y. , Pang K. H. , Wang Y.
Published: April 2007

Ferroelectric and magnetoresistance heterostructure (Ba,Sr)TiO3/(La,Sr)MnO3 (BST/LSMO) heterostructure is deposited epitaxially on SrTiO3 (001) substrate by pulse laser deposition. The phase structures of the BST/LSMO heterostructure are characterized by x-ray diffraction. Cross-sectional transmission electron microscope shows a substantial interdiffusision between BST and LSMO layers. The dielectric properties and conductivity of BST/LSMO heterostructure is measured as a function of temperature, frequency, and electric field. The dielectric constant dependence on electric field, ε vs E, exhibits a strong nonlinear behavior in the temperature from 20 to 300 K, while ε(E=0) vs T relation shows a dielectric relaxor characteristic. Furthermore, the dielectric constant (E=0 kV/cm) and the dielectric tunability (E=200 kV/cm) are found to be similar temperature dependencies. Last, in the temperature regime where a semiconduction-type conduction became dominate, the activation thermal energy of BST/LSMO heterostructure is estimated to be 0.67 and 0.73 eV at 1 kHz and 1 MHz, respectively.
Long-range corrected density functional calculations of chemical reactions: Redetermination of parameter
Authors: Song Jong-Won , Hirosawa Tsuyoshi , Tsuneda Takao , Hirao Kimihiko
Published: April 2007

Chemical reaction calculations were carried out using the long-range correction (LC) scheme, which improves long-range exchange effects in density functional theory (DFT) [J. Chem. Phys. 115, 3540 (2001); 120, 8425 (2004)]. A new determination of the LC scheme parameter μ was made by a root mean square fit of the percent error in calculated atomization energies. As a result, the parameter μ was optimized as 0.47, which is higher than the previous one (μ=0.33). Using this new parameter μ, LC-DFT was firstly applied to geometry optimizations of the G2 benchmark set molecules. Consequently, this new LC-DFT gave more accurate bond lengths and bond angles than previous LC-DFT and hybrid B3LYP results. Following this result, the authors calculated reaction barrier height energies of benchmark reaction sets, which have been underestimated in conventional DFT calculations. Calculated results showed that LC-DFT provided much more accurate barrier height energies with errors less than half those of previous LC-DFT and B3LYP studies. To test the general validity of the new LC-DFT, the authors finally calculated reaction enthalpies. As a result, they found that the LC scheme using the new μ clearly improved the accuracy of calculated enthalpies. The authors therefore conclude that the insufficient inclusion of long-range exchange effects is responsible for the underestimation of reaction barriers in DFT calculations and that LC-DFT using the new parameter is a powerful tool for theoretically investigating chemical reactions.