bluuebunny/crossref_metadata_2025 huggingface dataset:
Localization of Kv1.5 channels in rat and canine myocyte sarcolemma
Authors: Eldstrom Jodene , Van Wagoner David R. , Moore Edwin D. , Fedida David
Published: October 2006

Voltage‐gated potassium (Kv) channel subtypes localize to the plasma membrane of a number of cell types, and the sarcolemma in myocytes. Because many signaling molecules concentrate in subdomains of the plasma membrane, the localization of Kv channels to these sites may have important implications for channel function and regulation. In this study, the association of the voltage‐gated potassium channel Kv1.5 with a specific subtype of lipid rafts, caveolae, in rat and canine cardiac myocytes has been investigated. Interactions between caveolin‐3 and β‐dystroglycan or eNOS, as well as between Kv1.5 and α‐actinin were readily detected in co‐immunoprecipitation experiments, whereas no association between Kv1.5 and caveolin‐3 was evident. Wide‐field microscopy and deconvolution techniques revealed that the percent co‐localization of Kv1.5 with caveolin‐3 was extremely low in atrial myocytes from rat and canine hearts (8 ± 1% and 12.2 ± 2%, respectively), and limited in ventricular myocytes (11 ± 4% and 20 ± 3% in rat and canine, respectively). Immunoelectron microscopic imaging of rat atrial and ventricular tissues showed that Kv1.5 and caveolin‐3 labeling generally did not overlap. In HEK293 cells stably expressing the channel, Kv1.5 did not target to the low buoyant density raft fraction along with flotillin but instead fractionated along with the non‐raft associated transferrin receptor. Taken together, these results suggest that Kv1.5 is not present in caveolae of rat and canine heart.
The antimicrobial peptide parabutoporin competes with p47phox as a PKC‐substrate and inhibits NADPH oxidase in human neutrophils
Authors: Remijsen Quinten F.M. , Fontayne Alexandre , Verdonck Fons , Clynen Elke , Schoofs Liliane , Willems Jean
Published: October 2006

We investigated parabutoporin (PP), an antimicrobial scorpion peptide, to understand its inhibition on NADPH oxidase in human PMN. We show that PP is a good substrate for all PKC‐isotypes, implicated in the activation of NADPH oxidase, and acts as a potent competitive inhibitor of in vitro p47phox‐phosphorylation by PKC‐α, ‐βI, ‐βII and ‐δ, but not PKC‐ζ. In PMN, PP also inhibits the PMA‐stimulated phosphorylation of p47phox and its subsequent translocation. In contrast, PP affects the PKC‐independent activation to a much lesser degree. This indicates that PP inhibits the activation of NADPH oxidase at submicromolar concentrations in a strongly PKC‐dependent manner.
Phospholipase D protects ECV304 cells against TNFα‐induced apoptosis
Authors: Birbes Helene , Zeiller Caroline , Komati Hiba , Némoz Georges , Lagarde Michel , Prigent Annie-France
Published: October 2006

Tumor necrosis factor α (TNFα), a pleiotropic cytokine, activates both apoptotic and pro‐survival signals depending on the cell model. Using ECV304 cells, which can be made TNFα‐sensitive by cycloheximide (CHX) co‐treatment, we evaluated the potential roles of ceramide and phospholipase D (PLD) in TNFα‐induced apoptosis. TNFα/CHX induced a robust increase in ceramide levels after 16 h of treatment when cell death was maximal. PLD activity was increased at early time point (1 h) whereas both PLD activity and PLD1 protein were strongly decreased after 24 h. TNFα/CHX‐induced cell death was significantly lowered by exogenous bacterial PLD and phoshatidic acid, and in cells overexpressing PLD1. Conversely, cells depleted in PLD proteins by small interference RNA (siRNA) treatment exhibited higher susceptibility to apoptosis. These results show that PLD exerts a protective role against TNFα‐induced cell death.
Power as Nostalgia: the Bolshoi Ballet in the New Russia
Authors: Sporton Gregory
Published: October 2006

The economic and political transition of the old Soviet Union into Putin's Russia has been given plenty of attention over the past few years, with emphasis on free markets and democratic choice much in evidence. In this essay Gregory Sporton discusses the less often considered difficulties of the social transition towards a New Russia. The role of ballet in the culture of the Soviet Union occasionally leads to some embarrassment for those who think the arts represent freedom; and here the symbolic power of the nation's most political theatre, the Bolshoi, is examined at the point of its renovation. How the company has adapted to the new political realities, to the challenge of attracting audiences, and to its own complicity with the old regime is observed against the backdrop of May Day celebrations in 2004. Gregory Sporton is Director of the Visualisation Research Unit in the Department of Art at the Birmingham Institute of Art and Design. Since 2004 he has been a frequent visitor to Russia, studying a range of aspects of Russian culture under the Soviets from ballet to architecture, education and the visual arts. His study trip in 2004 was funded by the Elisabeth Barker Fund from the British Academy.
Community dynamics during early secondary succession in Mexican tropical rain forests
Authors: van Breugel Michiel , Martínez-Ramos Miguel , Bongers Frans
Published: October 2006

Stand structure dynamics during early secondary forest succession were related to mortality, growth and recruitment rates, and the dependence of these demographic processes on fallow age and initial stand structure attributes was evaluated. In 11 secondary tropical rain-forest sites (1.5–19 y) in Chiapas, Mexico, one plot of 10 × 50 m was established. Diameter and height were measured for all trees ≥ 1 cm dbh, and their survival, growth and recruitment was monitored over a 2-y period. Changes in stand structure were especially fast in the first 5 y of succession, and decreased rapidly afterwards, which resulted from similar stand-level changes in relative mortality, growth and recruitment rates. Demographic processes were negatively related with initial stand basal area, but independent of initial tree density. Basal area was a better explanatory variable of the among-stand variability in these rates than fallow age. Results suggest that asymmetric competition and resulting patterns of tree-thinning are major driving forces determining secondary forest successional pathways. Fallow age per se is a compound variable reflecting community organization at a certain point along the successional axis, while community structure drives succession. Sudden mass mortality among dominant species in some stands showed that early secondary forest succession is not always a gradual and unidirectional process.
Impact of life-history traits on response of seedlings of five tree species of tropical dry forest to shade
Authors: Khurana E. , Singh J. S.
Published: October 2006

Seedling growth under three shade levels was studied at Varanasi, India, for five tree species of tropical dry forest, which differed in life-history traits. Three of these were small-seeded pioneer (Albizia procera, Acacia nilotica and Phyllanthus emblica) and the other two were large-seeded non-pioneer (Terminalia arjuna and Terminalia chebula) species. Seedlings of all the species were subjected to three light levels (80–100%, 20–30% and 3–7% of full sunlight) comparable to sunlit gaps and shaded microsites in the dry forest. After 4 mo of shade treatment, height, basal area, biomass and other growth traits, viz. RGR (relative growth rate), NAR (net assimilation rate), and SLA (specific leaf area) were determined. Etiolation and plasticity indices were calculated. Reduction in seedling height, biomass and relative growth rates and enhancement in SLA due to shade was greater for small-seeded pioneer species. Seedlings from large-seeded non-pioneer species exhibited a stronger etiolation response to shade than seedlings from small-seeded species. Phenotypic plasticity indices for basal area, plant biomass and relative growth rate were greater for the three small-seeded early successional species (A. procera, A. nilotica and P. emblica), indicating their specialization in a more favourable light environment such as large gaps and forest peripheries. The non-pioneer and pioneer species differed only in the degree of shade tolerance, and we suggest that dry forest species cannot be strictly categorized into two distinct groups (shade tolerant vs. intolerant), rather shade preference and gap preference would be the more expressive terms. Marked environmental heterogeneity in terms of irradiance and the phenology of dry tropical trees permits coexistence of species of varying ecological traits, contributing to the maintenance of diversity in the dry forest.
Worker size and seed size selection in ‘seed’-collecting ant ensembles (Hymenoptera: Formicidae) in primary rain forests on Borneo
Authors: Pfeiffer Martin , Nais Jamili , Linsenmair K. Eduard
Published: October 2006

‘Size matching’ of forager size and prey size is an ecological mechanism that should partition diets both within ant colonies and ensembles. We studied the relationship between ant body size and food size in tropical leaf-litter ant ensembles at different levels. In three plots of primary rain forest in Sabah, Malaysia, we observed altogether 50 species of 18 genera of ants (e.g. Pheidole, Recurvidris, Lophomyrmex, Paratrechina, Odontoponera) that harvested seed particles from baits of milled rice of various particle size. At colony level ‘size matching’ of individual foragers with their load was found only in one of 12 tested species, viz. Pheidole lucioccipitalis. However, ant species differed considerably with respect to ‘seed’ size used: on average, foragers of larger species transported significantly larger ‘seed’ fragments. This was highly significant in a subset of ant species with at least 12 records of size choice per species. But when we investigated resource partitioning within each of the three ant ensembles with a null model, analysis proved that there was a significant overlap in seed size selection of species at two of the sites, thus indicating that food size choice of foragers had little influence on niche patterns and community structure of ants. Ant species with workers that were not matched with their seed resources (viz. Oligomyrmex or Pheidologeton) engaged in cooperative ‘seed’ transport, mass recruitment to and in situ mastication of rice fragments. Mean ‘seed’ transport distance was 38.4 cm.
Bird assemblages in isolated Ficus trees in Kenyan farmland
Authors: Eshiamwata G. W. , Berens D. G. , Bleher B. , Dean W. R. J. , Böhning-Gaese K.
Published: October 2006

Over the last few decades a rapid and extensive conversion of tropical forests to agricultural land has taken place resulting in mosaics of fragmented forest patches, pastures and farmland. While the effects of forest fragmentation on biodiversity have been intensively studied within the remaining forests, relatively little is known about the biodiversity in tropical farmland (Daily et al. 2001, Pimentel et al. 1992). Frugivorous birds are an important group of species in tropical farmland ecosystems. Frugivorous birds are significant seed dispersers and can play a prominent role in transporting seeds into disturbed areas and setting the stage for the regeneration of these systems. Isolated fleshy-fruited trees in agricultural landscapes have been shown to attract birds, leading to an increased seed rain and seedling establishment under their canopies (Carrière et al. 2002, Duncan & Chapman 1999, Guevara et al. 1986, 2004; Slocum & Horvitz 2000).
Getting to the root of tree neighbourhoods: hectare-scale root zones of a neotropical fig
Authors: Silman Miles R. , Krisel Carolyn
Published: October 2006

Sessile organisms interact locally on the scale of their body sizes, and one of the great advances in population and community ecology is the use of individual-based models to examine species interactions (Biondini 2001, Bolker & Pacala 1999, Pacala & Deutschman 1995, Pacala & Silander 1985, 1987; Silander & Pacala 1985). Canopies are often taken as a proxy for body size in the plant literature, even though roots can make up substantial amounts of a plant's biomass, have productivity that equals or exceeds the above-ground parts, and are critical in both competition and mutualisms involving nutrient capture and water balance (Biondini 2001, Casper & Jackson 1997, Casper et al. 2003, Rajaniemi & Reynolds 2004, Robinson 2004). Root zones, however, are seldom incorporated in plant ecological studies because they are exceptionally difficult to measure, and the importance of intra- and interspecific root interactions is little known (Schenk & Jackson 2002).
Cross-language perception of word-final stops in Thai and English
Authors: TSUKADA KIMIKO
Published: October 2006

This study examined Australian English (AE) and Thai–English bilingual (TE) speakers' ability to perceive word-final stops in their native and non-native languages. In the perception experiment, the TE listeners were able to discriminate stop contrasts differing only in place of articulation (/p/–/t/, /p/–/k/, /t/–/k/) in both English and Thai accurately, but the AE listeners' discrimination was accurate only for English. The listeners' discrimination accuracy was differentially influenced by the type of stop contrast they heard. The Thai /p/–/t/ contrast was most discriminable for both groups of listeners, in particular, the AE listeners. Acoustic analyses of the Thai stimuli presented in the perception experiment were conducted in order to search for cues that led to different response patterns for the AE and TE listeners. There was a clear effect of the final stop on the formant trajectories of /a/ and /u/, suggesting that these acoustic differences may be audible to the listeners. The results provide further evidence that first language (L1) transfer alone is insufficient to account for listeners' response patterns in cross-language speech perception and that it is necessary to take into account phonetic realization of sounds and/or the amount of acoustic information contained in the speech signal to predict accuracy with which sound contrasts are discriminated.
Mixing state of elemental carbon and non‐light‐absorbing aerosol components derived from in situ particle optical properties at Xinken in Pearl River Delta of China
Authors: Cheng Ya Fang , Eichler Heike , Wiedensohler Alfred , Heintzenberg Jost , Zhang Yuan Hang , Hu Min , Herrmann Hartmut , Zeng Li Min , Liu Shang , Gnauk Thomas , Brüggemann Erika , He Ling Yan
Published: October 2006

The aerosol mixing state was investigated with an optical closure study at Xinken, Pearl River Delta of China in 2004. On the basis of in situ aerosol microphysical and chemical measurements and a two‐component aerosol optical model an internal consistency algorithm was developed to model the mass ratio (r) of externally mixed elemental carbon (EC) to total EC, which minimized the discrepancies between measured and calculated optical properties. The rest of EC was assumed to be internally mixed. A time series ofrwas retrieved. Good agreement between model and observation was found, on the order of ±15% for total/back scattering coefficients and ±10% for absorption coefficient. The EC mixing state was strongly dependent on the local wind patterns. When north/northeasterly winds prevailed, the air came from the urban and industrial areas of mainland China, and EC was mainly externally mixed with an averagerof 85 ± 12%. When the airflow was controlled by a weak local wind system, the mixing state showed a pronounced diurnal variation. During daytime the wind speed was nearly zero. This favored the increase of local pollution, and the averagerwas about 95%. However, during nighttime the EC mixing state transformed to be internally mixed apparently with an averagerof 53 ± 15%, which can be explained by a more aged air mass. The south/southeasterly winds coming from the sea were found to have the most important effect on the transformation of EC mixing state in the night, but fairly rapid local aging processing was also observed. The uncertainties of the model were explored by a Monte Carlo simulation.
Time-resolved characterization of Hohlraum radiation temperature via interferometer measurement of quartz shock velocity
Authors: Olson R. E. , Bradley D. K. , Rochau G. A. , Collins G. W. , Leeper R. J. , Suter L. J.
Published: October 2006

A new technique for time-resolved measurement of Hohlraum radiation temperature has been successfully tested in Hohlraums with radiation temperatures in the range of 90–170eV. In these experiments, Hohlraum radiation fields produced ablatively driven shock waves in quartz samples. A line-imaging velocity interferometer was used to track the quartz shock velocity as a function of time, and an empirical relationship (determined in these experiments) was used to relate the measured shock velocity to the Hohlraum radiation temperature. The test experiments were performed at the Omega facility [J. M. Soures et al., Phys. Plasmas 3, 2108 (1996)] at the University of Rochester Laboratory for Laser Energetics. The technique should also be useful for Hohlraum temperature measurements at other DOE/NNSA high energy density experimental facilities, such as the Z facility [R. B. Spielman et al., Phys. Plasmas 5, 2105 (1998)] at Sandia National Laboratories and the National Ignition Facility [E. I. Moses, Fusion Sci. Technol. 44, 11 (2003)] at Lawrence Livermore National Laboratory.
Design challenges and analysis of the ITER core LIDAR Thomson scattering system
Authors: Walsh M. J. , Beurskens M. , Carolan P. G. , Gilbert M. , Loughlin M. , Morris A. W. , Riccardo V. , Xue Y. , Huxford R. B. , Walker C. I.
Published: October 2006

The maximum temperature expected in ITER is in the region of 40keV and the minimum average density of approximately 3×1019m−3 is also expected. The proven capability, convenience, and port occupancy of the LIDAR Thomson scattering approach, demonstrated on JET, makes it an excellent candidate for ITER. Nonetheless, there are formidable design challenges in realizing such a diagnostic system. The expected high temperature presents its own problem of a very large relativistic blueshift of the scattered spectrum (e.g., λ∕λ0∼0.35 for Te=40keV), impacting on the laser choice and spectrometer/detector system. The combination of coupling high power lasers to the plasma and broadband wavelength detection has been examined in terms of minimizing the operational risk to the overall system, while optimizing the diagnostic performance. Part of the exercise has also included identifying the present critical components, and reducing their impact, e.g., on diagnostic reliability and performance, and attempt to make the design compatible with possible long term developments and operational requirement. Issues such as redundancy of key operational components, e.g., lasers are explored.
H
α
measurements and neutral particle transport in Heliotron J
Authors: Kobayashi S. , Yabutani H. , Nakashima Y. , Higashizono Y. , Nagasaki K. , Mizuuchi T. , Okada H. , Sano F. , Cappa A. , Kondo K. , Nakamura Y. , Suzuki Y.
Published: October 2006

A multichannel system of the Hα-line emission detector is developed in order to investigate the neutral particle transport in the Heliotron J plasma. The application of a multianode photomultiplier tube to the filter measurement system enables us to observe the Hα emission profile with 32 chords. The absolute calibration with a standard lamp is performed and the cross-talk between each of the adjoining channels is evaluated to be less than 6%, while the photomultiplier tube has a typical cross-talk of 3% in nominal value. The temporal and spatial profiles of the Hα emission are measured in detail in the plasma breakdown by electron cyclotron heating (ECH). The Hα emission profile in the ECH plasma is calculated by the Monte Carlo simulation using a three-dimensional mesh model. The fueling rates of the wall recycling and the gas puffing are estimated by means of the simulation and the measurement.
Nonadiabatic coupling in the 3Π3 and 4Π3 states of NaK
Authors: Miles R. D. , Morgus L. , Kashinski D. O. , Huennekens J. , Hickman A. P.
Published: October 2006

The excited 3Π3 and 4Π3 electronic states of the NaK molecule exhibit an avoided crossing, leading to the anomalous behavior of many features of the rovibrational energy levels belonging to each state. A joint experimental and theoretical investigation of these states has been carried out. Experimental measurements of the vibrational, rotational, and hyperfine structure of numerous levels of the 3Π3 state were recently obtained using the Doppler-free, perturbation-facilitated optical-optical double resonance technique. Additional measurements for the 4Π3 state as well as bound-free emission spectra from selected 3Π3, 4Π3, and mixed 3Π3∼4Π3 rovibrational levels are reported here. A model is also presented for calculating the mixed rovibrational level energies of the coupled 3Π3-4Π3 system, starting from a 2×2 diabatic electronic Hamiltonian. The 3Π3 and 4Π3 potential curves and the coupling between them are simultaneously adjusted to fit the observed rovibrational levels of both states. The energy levels of the potential curves determined by the fit are in excellent agreement with experiment. The nonadiabatic coupling is sufficiently strong to cause an overall shift of 2–3cm−1 for many rovibrational levels as well as somewhat larger shifts for certain pairs of 3Π3∼4Π3 levels that would otherwise be very close together.
Single photon ionization of van der Waals clusters with a soft x-ray laser: (CO2)n and (CO2)n(H2O)m
Authors: Heinbuch S. , Dong F. , Rocca J. J. , Bernstein E. R.
Published: October 2006

Pure neutral (CO2)n clusters and mixed (CO2)n(H2O)m clusters are investigated employing time of flight mass spectroscopy and single photon ionization at 26.5eV. The distribution of pure (CO2)n clusters decreases roughly exponentially with increasing cluster size. During the ionization process, neutral clusters suffer little fragmentation because almost all excess cluster energy above the vertical ionization energy is taken away by the photoelectron and only a small part of the photon energy is deposited into the (CO2)n cluster. Metastable dissociation rate constants of (CO2)n+ are measured in the range of (0.2–1.5)×104s−1 for cluster sizes of 5⩽n⩽16. Mixed CO2–H2O clusters are studied under different generation conditions (5% and 20% CO2 partial pressures and high and low expansion pressures). At high CO2 concentration, predominant signals in the mass spectrum are the (CO2)n+ cluster ions. The unprotonated cluster ion series (CO2)nH2O+ and (CO2)n(H2O)2+ are also observed under these conditions. At low CO2 concentration, protonated cluster ions (H2O)nH+ are the dominant signals, and the protonated CO2(H2O)nH+ and unprotonated (H2O)n+ and (CO2)(H2O)n+ cluster ion series are also observed. The mechanisms and dynamics of the formation of these neutral and ionic clusters are discussed.
Development of neutron measurement system for nd∕nt fuel ratio measurement in ITER experiments
Authors: Okada K. , Kondo K. , Sato S. , Nishitani T. , Nomura K. , Okamoto A. , Iwasaki T. , Kitajima S. , Sasao M.
Published: October 2006

The possibility of measurement of fuel ratio from the DT/DD reaction ratio with a neutron spectrometer in the International Thermonuclear Experimental Reactor was studied. The results of neutron transport calculations using the Monte Carlo N-particle [MCNP, a general Monte Carlo N-particle transport code, version 4C, LA-13709, edited by J. F. Briesmeister, Los Alamos National Laboratory, 2000] code system indicated the possibility of DD spectrum separation from the scattered/energy-degraded neutrons derived from DT neutrons by selection of the measurement location and collimator design. A time-of-flight spectrometer was used in this study. An experiment using DD and DT neutrons from an accelerator was conducted at the Japan Atomic Energy Agency Fusion Neutronics Source facility. Using a sophisticated circuit with three discriminators for the first detector, separation of DD and DT neutron components of the spectrum in the megahertz region was confirmed experimentally.
Strong synergistic effects in the combustion of propellants in H2 Plasmas
Authors: Valliere Rodney , Blumenthal Rik
Published: October 2006

Electrothermal chemical (ETC) or plasma ignition of propellants has been investigated by observing the interactions of individual and combinations of the individual components of an ETC pulse with a thin film of propellant. Adjusting the applied dc bias of high-density hydrogen and argon plasmas, ions or electrons may be drawn to the film surface with defined energies and resulting in erosion of the film. Strong synergistic effects are observed between reactive hydrogen atoms and ion bombardment, and a physical model of the process is presented. These synergistic effects may be directly related to the short, highly reproducible ignition delay that characterizes the ETC ignition technology.
Classification of integrable Hamiltonian hydrodynamic chains associated with Kupershmidt’s brackets
Authors: Ferapontov E. V. , Khusnutdinova K. R. , Marshall D. G. , Pavlov M. V.
Published: October 2006

We characterize a class of integrable Hamiltonian hydrodynamic chains, based on the necessary condition for the integrability provided by the vanishing of the Haantjes tensor. We prove that the vanishing of the first few components of the Haantjes tensor is already sufficiently restrictive, and allows a complete description of the corresponding Hamiltonian densities. In each of the cases we were able to explicitly construct a generating function for conservation laws, thus establishing the integrability.
Ordered arrays of Ag nanoparticles grown by constrained self-organization
Authors: Sharma Pradeep , Liu C. Y. , Hsu Chen-Feng , Liu N. W. , Wang Y. L.
Published: October 2006

In a postdeposition annealing process, the Ag deposited at low temperature on a Si(100) substrate aggregates to regions that have been exposed to adequate dose of energetic ions. By patterning an array of such aggregation centers on the substrate, using a 50keV focused Ga+ ion beam, the migration of Ag on the patterned area during the subsequent annealing is constrained and ordered arrays of Ag nanoparticles with uniform size distribution are formed spontaneously. The mechanism and the optimum conditions for constraining the self-organization of Ag on Si by focused-ion-beam patterning are discussed.
Cubic phases of block copolymers under shear and electric fields by cell dynamics simulation. I. Spherical phase
Authors: Pinna Marco , Zvelindovsky Andrei V. , Todd S. , Goldbeck-Wood G.
Published: October 2006

Cell dynamics simulation is used to investigate pathways of sphere-to-cylinder transition in block copolymer melt under applied simple shear flow and electric field. Both fields can induce the transition when their strength is above some critical value. At weak fields the spherical phase is preserved, with spheres being deformed into ellipsoids. Weak shear flow is found to improve order in the spherical phase. Observed sliding of layers of spheres under shear is very similar to the experimental finding by Hamley et al. [J. Chem. Phys. 108, 6929 (1998)]. The kinetic pathways are sensitive to the degree of microphase separation in the system and hence affected by temperature. The details of the pathways are described by means of Minkowski functionals.
Relaxation time and elasticity during polymerization with DER 332
Authors: Venkateshan K. , Johari G. P.
Published: October 2006

To complement a study of the dielectric relaxation time’s relation with the velocity of propagation of hypersound wave in a polymerizing liquid [K. Venkateshan and G. P. Johari J. Chem. Phys.125, 014907 (2006)], we report results of an analogous study by using the same diglycidylether of bisphenol-A that had been used for measuring the velocity. The data show that the logarithmic relaxation time increases linearly with the square of the velocity of propagation of transverse hypersound wave.
Comment on “Identification of low order manifolds: Validating the algorithm of Maas and Pope” [Chaos 9, 108–123 (1999)]
Authors: Flockerzi Dietrich , Heineken Wolfram
Published: October 2006

It is claimed by Rhodes, Morari, and Wiggins [Chaos 9, 108–123 (1999)] that the projection algorithm of Maas and Pope [Combust. Flame 88, 239–264 (1992)] identifies the slow invariant manifold of a system of ordinary differential equations with time-scale separation. A transformation to Fenichel normal form serves as a tool to prove this statement. Furthermore, Rhodes, Morari, and Wiggins [Chaos 9, 108–123 (1999)] conjectured that away from a slow manifold, the criterion of Maas and Pope will never be fulfilled. We present two examples that refute the assertions of Rhodes, Morari, and Wiggins. In the first example, the algorithm of Maas and Pope leads to a manifold that is not invariant but close to a slow invariant manifold. The claim of Rhodes, Morari, and Wiggins that the Maas and Pope projection algorithm is invariant under a coordinate transformation to Fenichel normal form is shown to be not correct in this case. In the second example, the projection algorithm of Maas and Pope leads to a manifold that lies in a region where no slow manifold exists at all. This rejects the conjecture of Rhodes, Morari, and Wiggins mentioned above.
Response to “Comment on ‘Identification of low order manifolds: Validating the algorithm of Maas and Pope'” [Chaos 16, 048101 (2006)]
Authors: Rhodes Carl , Morari Manfred , Wiggins Stephen
Published: October 2006

Flockerzi and Heineken [Chaos 16, 048101 (2006)] present two examples with the goal of elucidating issues related to the Maas and Pope method for identifying low dimensional “slow” manifolds in systems with a time-scale separation. The goal of their first example is to show that the result claimed by Rhodes et al. [Chaos 9, 108-123 (1999)] that the Maas and Pope algorithm identifies the slow invariant manifold in the situation in which there is finite time-scale separation is incorrect. We show that their arguments result from an incomplete understanding of the situation and that, in fact, their example supports, and is completely consistent with, the result in Rhodes et al.. Their second example claims to be a counterexample to a conjecture in Rhodes et al. that away from the slow manifold the criterion of Maas and Pope [Combust. Flame 88, 239-264 (1992)] will never be fulfilled. While this conjecture may indeed be false, we argue that it is not clear that the example presented by Flockerzi and Heineken is indeed a counterexample.
Solid–liquid transitions of sodium chloride at high pressures
Authors: An Qi , Zheng Lianqing , Fu Rongshan , Ni Sidao , Luo Sheng-Nian
Published: October 2006

We investigate solid–liquid transitions in NaCl at high pressures using molecular dynamics simulations, including the melting curve and superheating/supercooling as well as solid–solid and liquid–liquid transitions. The first-order B1–B2 (NaCl–CsCl type) transition in solid is observed at high pressures besides continuous liquid structure transitions, which are largely analogous to the B1–B2 transition in solid. The equilibrium melting temperatures (Tm) up to megabar pressure are obtained from the solid–liquid coexistence technique and the superheating–supercooling hysteresis method. Lindemann’s vibrational and Born’s mechanical instabilities are found upon melting. The Lindemann frequency is calculated from the vibrational density of states. The Lindemann parameter (fractional root-mean-squared displacement) increases with pressure and approaches a constant asymptotically, similar to the Lennard-Jones system. However, the Lindemann melting relation holds for both B1 and B2 phases to high accuracy as for the Lennard-Jonesium. The B1 and B2 NaCl solids can be superheated by 0.18Tm and 0.24Tm, and the NaCl liquid, supercooled by 0.22Tm and 0.32Tm, respectively, at heating or cooling rates of 1 K/s and 1 K/ps. The amount of maximum superheating or supercooling and its weak pressure dependence observed for NaCl are in accord with experiments on alkali halides and with simulations on the Lennard-Jones system and Al.
Parallelization of the integral equation formulation of the polarizable continuum model for higher-order response functions
Authors: Ferrighi Lara , Frediani Luca , Fossgaard Eirik , Ruud Kenneth
Published: October 2006

We present a parallel implementation of the integral equation formalism of the polarizable continuum model for Hartree-Fock and density functional theory calculations of energies and linear, quadratic, and cubic response functions. The contributions to the free energy of the solute due to the polarizable continuum have been implemented using a master-slave approach with load balancing to ensure good scalability also on parallel machines with a slow interconnect. We demonstrate the good scaling behavior of the code through calculations of Hartree-Fock energies and linear, quadratic, and cubic response function for a modest-sized sample molecule. We also explore the behavior of the parallelization of the integral equation formulation of the polarizable continuum model code when used in conjunction with a recent scheme for the storage of two-electron integrals in the memory of the different slaves in order to achieve superlinear scaling in the parallel calculations.
Optical oscillator strengths for valence-shell and Br-3d inner-shell excitations of HCl and HBr
Authors: Li Wen-Bin , Zhu Lin-Fan , Yuan Zhen-Sheng , Liu Xiao-Jing , Xu Ke-Zun
Published: October 2006

Absolute optical oscillator strength density spectra for valence-shell excitations of HCl and HBr, as well as for Br-3d inner-shell excitations of HBr, have been determined by high-resolution electron-energy-loss-spectroscopy method in the dipole limit. Absolute optical oscillator strengths for the discrete transitions of HCl and HBr are reported and compared with the previous results determined by the photoabsorption method.
A justification for a nonadiabatic surface hopping Herman-Kluk semiclassical initial value representation of the time evolution operator
Authors: Wu Yinghua , Herman Michael F.
Published: October 2006

A justification is given for the validity of a nonadiabatic surface hopping Herman-Kluk (HK) semiclassical initial value representation (SC-IVR) method. The method is based on a propagator that combines the single surface HK SC-IVR method [J. Chem. Phys. 84, 326 (1986)] and Herman’s nonadiabatic semiclassical surface hopping theory [J. Chem. Phys. 103, 8081 (1995)], which was originally developed using the primitive semiclassical Van Vleck propagator. We show that the nonadiabatic HK SC-IVR propagator satisfies the time-dependent Schrödinger equation to the first order of ℏ and the error is O(ℏ2). As a required lemma, we show that the stationary phase approximation, under current assumptions, has an error term ℏ1 order higher than the leading term. Our derivation suggests some changes to the previous development, and it is shown that the numerical accuracy in applications to Tully’s three model systems in low energies is improved.
Canonical quantization of lattice Higgs-Maxwell-Chern-Simons fields: Krein Self-adjointness
Authors: Bowman Daniel A. , Challifour John L.
Published: October 2006

It is shown how techniques from constructive quantum field theory may be applied to indefinite metric gauge theories in Hilbert space for the case of a Higgs-Maxwell-Chern-Simons theory on a lattice. The Hamiltonian operator is shown to be Krein essentially self-adjoint by means of unbounded but Krein unitary transformations relating the Hamiltonian to an essentially maximal accretive operator.
Photoinduced spin alignment of the magnetic ions in (Ga,Mn)As
Authors: Sun Baoquan , Jiang Desheng , Sun Zheng , Ruan Xuezhong , Deng Jiajun , Zhao Jianhua , Ji Yang , Xu Zhongying
Published: October 2006

Time-resolved Kerr rotation measurement in the (Ga,Mn)As diluted magnetic semiconductor allows direct observation of the dynamical properties of the spin system of the magnetic ions and the spin-polarized holes. Experimental results show that the magnetic ions can be aligned by the polarized holes, and the time scales of spin alignment and relaxation take place in tens and hundreds of picoseconds, respectively. The Larmor frequency and effective g factor obtained in the Voigt geometry show an unusual temperature dependence in the vicinity of the Curie temperature due to the exchange coupling between the photoexcited holes and magnetic ions. Such a spin coherent precession can be amplified or destructed by two sequential excitation pulses with circularly copolarized or oppositely polarized helicity, respectively.
Comparing the kinetics of bias stress in organic field-effect transistors with different dielectric interfaces
Authors: Ng Tse Nga , Marohn John A. , Chabinyc Michael L.
Published: October 2006

The kinetics of trap formation and dissociation is investigated in organic field-effect transistors to understand how the dielectric surface affects device stability. Devices with surface treatment of octadecyl-trichlorosilane (OTS) show faster trapping rates than an untreated oxide dielectric. Trap release is also quicker from the OTS interface compared to the untreated interface, thus implying that traps have lower barriers in the OTS interface than in the untreated interface. Images of trap distribution are obtained by electric force microscopy for polyfluorenethiophene transistors, but the traps in polythiophene transistors could not be imaged due to shielding charges.
Improved dielectric properties of bismuth-doped LaAlO3
Authors: Zylberberg Joel , Ye Zuo-Guang
Published: October 2006

Bismuth-doped LaAlO3 was prepared in the form of solid solution, La(1−x)BixAlO3 (0⩽x⩽0.2), by solid-state reactions. The materials were characterized by x-ray diffraction and dielectric spectroscopy. With increasing bismuth amount (x), the dielectric constant increases from 31.6 for pure LaAlO3 to 34.6 for x=0.2, while the loss tangent drops from 0.03 to 0.004 (f=100Hz). The frequency dispersion of the dielectric constant is attenuated. The improved dielectric properties in the Bi-doped LaAlO3 are attributed to the high polarizability of Bi3+ ion with a lone electron pair.
Studies of minority carrier diffusion length increase in p-type ZnO:Sb
Authors: Lopatiuk-Tirpak O. , Chernyak L. , Xiu F. X. , Liu J. L. , Jang S. , Ren F. , Pearton S. J. , Gartsman K. , Feldman Y. , Osinsky A. , Chow P.
Published: October 2006

Minority electron diffusion length was measured in p-type, Sb-doped ZnO as a function of temperature using the electron beam induced current technique. A thermally induced increase of electron diffusion length was determined to have an activation energy of 184±10meV. Irradiation with a low energy (5kV) electron beam also resulted in an increase of diffusion length with a similar activation energy (219±8meV). Both phenomena are suggested to involve a SbZn–2VZn acceptor complex. Saturation and relaxation dynamics of minority carrier diffusion length are explored. Details of a possible mechanism for diffusion length increase are presented.
Modeling global vector fields of chaotic systems from noisy time series with the aid of structure-selection techniques
Authors: Xu Daolin , Lu Fangfang
Published: October 2006

We address the problem of reconstructing a set of nonlinear differential equations from chaotic time series. A method that combines the implicit Adams integration and the structure-selection technique of an error reduction ratio is proposed for system identification and corresponding parameter estimation of the model. The structure-selection technique identifies the significant terms from a pool of candidates of functional basis and determines the optimal model through orthogonal characteristics on data. The technique with the Adams integration algorithm makes the reconstruction available to data sampled with large time intervals. Numerical experiment on Lorenz and Rössler systems shows that the proposed strategy is effective in global vector field reconstruction from noisy time series.
Coexistence of inertial competitors in chaotic flows
Authors: Benczik I. J. , Károlyi G. , Scheuring I. , Tél T.
Published: October 2006

We investigate the dynamics of inertial particles immersed in open chaotic flows. We consider the generic problem of competition between different species, e.g., phytoplankton populations in oceans. The strong influence from inertial effects is shown to result in the persistence of different species even in cases when the passively advected species cannot coexist. Multispecies coexistence in the ocean can be explained by the fact that the unstable manifold is different for each advected competitor of different size.
Study of the interaction between diffusive and avalanche-like transport in near-critical dissipative-trapped-electron-mode turbulence
Authors: Mier J. A. , García L. , Sánchez R.
Published: October 2006

The change in properties of turbulent transport is explored, in the context of dissipative-trapped-electron-mode (DTEM) turbulence, as a function of the relative strength of a (subdominant) diffusive transport channel to the turbulent one. If the diffusive channel is totally absent and the system is slowly driven, transport exhibits many features characteristic of self-organized-critical (SOC) systems. This finding is consistent with those reported by several authors in other situations, such as pressure-gradient-driven or ion-temperature-gradient turbulence. But we also find that the temporal persistence and spatial self-similarity characteristic of the SOC state remain present, at a level much higher than what one would naively expect, as the strength of the diffusive channel is increased. This observation, which has been previously made for numerical sandpile models, may give a partial answer to the question of why SOC features are so frequently observed in turbulent experimental data and numerical simulations in spite of the fact that the experimental conditions appear to be quite far from those required by the strict definition of the SOC state.
First-principles study of the atomic and electronic structures of Pb on Si(001)
Authors: Zhu Y. , Ye L. , Wang X.
Published: October 2006

The atomic and electronic structures of the Si(001)2×2-Pb and Si(001)2×1-Pb surfaces are investigated using the first-principles total energy calculations. The atomic structures consist of rows of Pb ad-dimers, which are buckled on Si(001)2×2-Pb but symmetric on Si(001)2×1-Pb, verifying previous experimental results. The calculated electronic densities of states and band structures of the optimized Si(001)2×2-Pb and Si(001)2×1-Pb surfaces coincide qualitatively with the previous experimental observations.
Room temperature photoluminescence from ZnO quantum wells grown on (0001) sapphire using buffer assisted pulsed laser deposition
Authors: Misra P. , Sharma T. K. , Porwal S. , Kukreja L. M.
Published: October 2006

Efficient room temperature (RT) photoluminescence (PL) is achieved on ZnO multiple quantum wells (MQWs) grown on sapphire by pulsed laser deposition using a buffer assisted growth scheme. Absorption spectra of these MQWs at RT showed the excitonic features entwined with the band edges, which pointed to the excitonic nature of the PL transitions. At RT the band edge of these MQWs shifted from ∼3.36to3.78eV on decreasing the well layer thickness from ∼4to1nm. In the range from 10K to RT, the PL spectral linewidth increased and the peak shifted monotonically towards red with increasing temperature.
Intrinsic ferromagnetic properties of Ti0.94Fe0.06O2∕Ti0.94Mn0.06O2 superlattice films for dilute magnetic semiconductor applications
Authors: Seong Nak-Jin , Yoon Soon-Gil , Jo Young-Hun , Jung Myung-Hwa , Cho Chae-Ryong , Yang Jun-Mo , Park Dong-Jun , Lee Jae-Wook , Lee Jeong-Yong
Published: October 2006

Superlattice films have been proposed to get dilute magnetic semiconductor (DMS) with an intrinsic room-temperature ferromagnetism. For a TiO2-based DMS superlattice structure, each layer was alternately doped by two different transition metals (Fe and Mn) and deposited to a thickness of approximately 2.7Å on r-Al2O3(1102) substrates by pulsed laser deposition. Samples of Ti0.94Fe0.06O2 (TiFeO), Ti0.94Mn0.06O2 (TiMnO), and Ti0.94(Fe0.03Mn0.03)O2 show a low remanent magnetization and coercive field, as well as superparamagnetic features at room temperature. On the other hand, superlattice films (TiFeO∕TiMnO) show a high remanent magnetization and coercive field, resulting in intrinsic ferromagnetic properties. The superlattice films composed of alternating layers of Ti0.94Fe0.06O2 and Ti0.94Mn0.06O2 exhibit intrinsic ferromagnetic properties for dilute magnetic semiconductor applications.
A variational approach for calculating Franck-Condon factors including mode-mode anharmonic coupling
Authors: Luis Josep M. , Kirtman Bernard , Christiansen Ove
Published: October 2006

We have implemented our new procedure for computing Franck-Condon factors utilizing vibrational configuration interaction based on a vibrational self-consistent field reference. Both Duschinsky rotations and anharmonic three-mode coupling are taken into account. Simulations of the first ionization band of ClO2 and C4H4O (furan) using up to quadruple excitations in treating anharmonicity are reported and analyzed. A developer version of the MIDASCPP code was employed to obtain the required anharmonic vibrational integrals and transition frequencies.
Influence of carrier injection on resistive switching of TiO2 thin films with Pt electrodes
Authors: Kim Kyung Min , Choi Byung Joon , Jeong Doo Seok , Hwang Cheol Seong , Han Seungwu
Published: October 2006

The influence of electron injection on the electric-pulse-induced resistive switching of Pt∕TiO2 thin film/Pt structure was studied by current-voltage (I-V) measurements. The electron injection was increased by annealing the sample in a N2 atmosphere or measuring the I-V characteristics at high temperatures (>100°C). The switching from the high-resistance state (HRS) to the low-resistance state by a filamentary mechanism was suppressed when the carrier injection by Schottky emission or space-charge-limited conduction (SCLC) was excessive. Interfacial potential barrier played a crucial role in determining the carrier injection. Switching was observed (not observed) when the HRS resistance was low (high) although SCLC was observed.
Visible light emission from single layer Si nanodots fabricated by laser irradiation method
Authors: Cen Zhanhong , Xu Jun , Liu Yansong , Li Wei , Xu Ling , Ma Zhongyuan , Huang Xinfan , Chen Kunji
Published: October 2006

A single layer of dense (>1011cm−2) Si nanodots on an insulating a-SiN layer was fabricated by the method combining the laser irradiation on the ultrathin amorphous Si films and subsequent thermal annealing. Raman scattering spectroscopy, planar and cross-section transmission electron microscopy were employed to characterize the formation of Si nanodots. It was found that the size of formed Si nanodots is strongly influenced by the initial amorphous Si film thickness. Visible light emission was observed from the obtained Si nanodots at room temperature and the luminescence peak is varied from 660to725nm with increasing the amorphous Si film thickness. The variable luminescence can be attributed to the interface state assisted radiative recombination rather than the quantum size effect.
Superconducting memory based on ferromagnetism
Authors: Held R. , Xu J. , Schmehl A. , Schneider C. W. , Mannhart J. , Beasley M. R.
Published: October 2006

Answering to the need for dense superconducting memories, the authors propose a memory concept that combines ferromagnetic dots for the storage of the data and Josephson junctions for their readout. Good scalability is expected for large scale integration. Exploratory memory cells have been implemented using 3μm Nb technology and Permalloy dots. Nonvolatile data storage at 300K was demonstrated.