bluuebunny/crossref_metadata_2025 huggingface dataset:
Faktorenanalyse von 57 Variablen der visuellen Worterkennung
Authors: Graf Ralf , Nagler Markus , Jacobs Arthur M.
Published: October 2005

Zusammenfassung. Unter Bezug auf aktuelle theoretische Modelle der visuellen Wortverarbeitung werden 57 Variablen ausgewählt, die als Determinanten der Worterkennungsleistung in Benennungsaufgaben und lexikalischen Entscheidungsaufgaben gelten und auf Wort-, Subkomponenten- und Buchstabenebene in Zusammenhang mit der Erklärung von Frequenz-, Nachbarschafts- und Konsistenzeffekten stehen. Eine Faktorenanalyse zweiter Ordnung dieser Variablen anhand von 1175 deutschen einsilbigen vier- bis sechsbuchstabigen Wörtern ergab sechs orthogonale Faktoren, die als (F1) Allgemeine Worthaftigkeit, (F2) Wortmittefaktor, (F3) Wortanfangsfaktor, (F4) Feedbackkonsistenzfaktor des Wortendes, (F5) Frequenz- und Nachbarschaftsfaktor des Wortendes und (F6) Feedforwardkonsistenzfaktor des Wortendes interpretiert werden. Vier Regressionsstudien belegen die Relevanz dieser Faktoren zur Varianzaufklärung von Reaktionszeiten. Hierdurch kann in Experimenten, die nicht genuin Fragestellungen der visuellen Worterkennung verfolgen, verwendetes Wortmaterial vereinfacht kontrolliert werden sowie der Rahmen für einen auf Invarianten basierenden Ansatz innerhalb der visuellen Wortverarbeitung geschaffen werden.
Heute haben wir Hitler im Kino gesehen:
Authors: Hofmann Wilhelm , Baumert Anna , Schmitt Manfred
Published: October 2005

Zusammenfassung. Wir evaluierten die Wirkung des Films “Der Untergang“ (2004), der die letzten Tage von Hitlers Diktatur und den Kampf um die Stadt Berlin schildert, auf Schüler/innen der neunten und zehnten Klasse Gymnasium und Hauptschule. Verglichen mit Schüler/inne/n, die nicht im Film waren, und unter Einbezug einer Reihe von Kontrollvariablen, gaben Filmgänger/innen weniger negative Emotionen gegenüber Hitler an, nahmen ihn eher als Menschen wahr, lehnten Sanktionen gegen Deutschland eher ab und zeigten erhöhte Identifikation mit der eigenen Nation. Keine Unterschiede ließen sich hingegen für die Wahrnehmung der deutschen Bevölkerung als ‘Opfer‘ feststellen sowie für die eingeschätzte Notwendigkeit von Geschichtsaufarbeitung. Es zeigte sich eine Reihe bedeutsamer Wechselwirkungen des Films mit Autoritarismus, Patriotismus, Schulbildung und der bisherigen Beschäftigung mit der Geschichte des Nationalsozialismus.
Correlating seismicity parameters and subsidence in the Tokai region, central Japan
Authors: Wiemer Stefan , Yoshida Akio , Hosono Kohji , Noguchi Shin‐ichi , Takayama Hiromi
Published: October 2005

We demonstrate that transients in subsidence rate in the Tokai area of central Japan correlate with changes in the rate and size distribution of earthquakes. Three largely independent seismic catalogs cover this region: National Research Institute for Earth Science and Disaster Prevention (NIED), Japanese Meteorological Agency (JMA), and Japan University Network Catalog (JUNEC). Comparing seismicity patterns between these three data sets offers a unique opportunity to verify seismicity anomalies based on independent sources. A study of data quality, magnitude reporting consistency, and consistency across the three data sources reveals that the NIED data for the period 1981–2002 are best suited for seismicity analysis. We spatially and temporally map seismicity rates, finding that a significant decrease in the earthquake rate of M ≥ 2.0 events coincides with an accelerated subsidence period; however, this anomaly disappears when including smaller magnitudes in the analysis. This relative quiescence of larger events can readily be explained when interpreting the transient in seismicity in the framework of a change in the earthquake size distribution, or b value. The background b value of about 0.8 increased in the period 1987.5–1989.5 to a value of b = 1.2, a highly significant change that can be confirmed in all three data sets. The correlation between subsidence and b value change is significant. Stress tensor inversions of focal mechanism data for the anomalous period show an increase in thrusting‐type earthquakes. While a unique interpretation of the relationship between subsidence and b value is not possible, we propose that an increase in the locking stress, a “slow stick event,” is consistent with all observations.
Electron signatures of active merging sites on the magnetopause
Authors: Maynard N. C. , Burke W. J. , Scudder J. D. , Ober D. M. , Weimer D. R. , Siebert K. D. , Russell C. T. , Lester M. , Mozer F. S. , Sato N.
Published: October 2005

Near magnetopause current layers the Polar satellite often detects field‐aligned fluxes of >0.5 keV electrons that carry heat flux away from merging sites along inner/outer separatrices between newly opened and closed/interplanetary magnetic flux. Close to separator lines, electron gyrotropy weakens to break trapping on closed field lines of the outer plasma sheet followed by attachment to newly opened flux at random pitch angles. Energetic electrons in the “tails” of distribution functions quickly move great distances along separatrices to act as surgical indicators of active merging. If IMF BY is large, field rotation in the magnetopause current layer can be ≪180°, obscuring relationships between merging sources and separatrices. Suprathermal electrons and accelerated ions moving along nearby inner and outer edges of moderate shear current layers are remote signatures of merging at widely separate locations. Detecting accelerated ions at a moderate shear magnetopause is insufficient evidence for component merging occurring near a spacecraft. During magnetopause‐skimming passes Polar sampled electron tail events characteristic of inner and outer separatrices that typically lasted from a few tens of seconds to several minutes. The 557.7‐nm emissions observed at cusp boundaries suggest that their sources operate on similar timescales and are active simultaneously at multiple locations. The magnetic conjugacy of inner separatrices with cusp boundaries as well as the similar timescales of electron tail and 557.7‐nm emission events strongly indicates that they are causally connected. Combining the two types of measurements offers an effective technique for separating temporal and spatial variability in magnetopause dynamics.
Modeling the radiation belt electrons with radial diffusion driven by the solar wind
Authors: Barker A. B. , Li X. , Selesnick R. S.
Published: October 2005

On the basis of the correlation between the solar wind and radiation belt electron fluxes, we develop a model to simulate the MeV electron phase space density variations from L = 3 to L = 8 by extending the Li et al. (2001) radial diffusion model for geosynchronous electrons. We add L dependence to the Li et al. model and allow for comparison with measurements at more than one L shell while retaining a similar form of their diffusion coefficient. The extended model achieves a prediction efficiency (PE) of 0.61 at L = 4 and 0.52 at L = 6 when the phase space density is converted to differential flux and compared with orbit‐averaged Polar 2 MeV measurements at L = 4 and daily averaged LANL 0.7–1.8 MeV geosynchronous measurements for the year 1998. These results indicate that radial diffusion plays a strong role in the enhancement of radiation belt electrons yet leaves a significant portion of the variance unaccounted for. We have also tuned parameters to model the electron fluxes during four individual geomagnetic storms during 1998 and found that the parameter values must differ from those of the long term and from each other to achieve the best PE. This suggests that the different solar wind drivers have varying degrees of influence on the MeV electron variations during different magnetic storms. This model can be used to forecast the MeV electron variations inside geosynchronous orbit with a reasonably good PE on the basis of real‐time solar wind measurements only.
Groundwater contaminant flux reduction resulting from nonaqueous phase liquid mass reduction
Authors: Jawitz J. W. , Fure A. D. , Demmy G. G. , Berglund S. , Rao P. S. C.
Published: October 2005

This work presents a stream tube–based analytical approach to evaluate reduction in groundwater contaminant flux resulting from partial mass reduction in a nonaqueous phase liquid (NAPL) source zone. The reduction in contaminant flux, Rj, discharged from the source zone is a remediation performance metric that has a direct effect on the fundamental drivers of remediation: protection of human health and the environment. Closed form expressions are provided for analyzing remediation performance under conditions of joint spatial variability of both groundwater flow and NAPL content. The performance measures derived here are expressed in terms of measurable parameters. Spatial variability is described within a Lagrangian framework where aquifer hydrodynamic heterogeneities are characterized using nonreactive travel time distributions, while NAPL spatial distribution heterogeneity can be similarly described using reactive travel time distributions. The combined statistics of these distributions are used to evaluate the relationship between reduction in contaminant mass, Rm, and Rj. A portion of the contaminant mass in the source zone is assumed to be removed via in situ flushing remediation, with the initial and final conditions defined as steady state natural gradient groundwater flow through the contaminant source zone. The combined effects of aquifer and NAPL heterogeneities are shown to be captured in a single parameter, reactive travel time variability, which was determined to be the most important factor controlling the relationship between Rm and Rj. It is shown that as heterogeneity in aquifer properties and NAPL spatial distribution increases, less mass reduction is required to achieve a given flux reduction, although the overall source longevity increases. When rate‐limited dissolution is important, the efficiency of remediation, in terms of both mass and flux reduction, is reduced. However, at many field sites the combined effects of field‐scale heterogeneities and site aging will result in favorable relationships between mass reduction and flux reduction.
Carbon dioxide and methane emissions and the carbon budget of a 10‐year old tropical reservoir (Petit Saut, French Guiana)
Authors: Abril Gwenaël , Guérin Frédéric , Richard Sandrine , Delmas Robert , Galy‐Lacaux Corinne , Gosse Philippe , Tremblay Alain , Varfalvy Louis , Dos Santos Marco Aurelio , Matvienko Bohdan
Published: October 2005

The emissions of carbon dioxide (CO2) and methane (CH4) from the Petit Saut hydroelectric reservoir (Sinnamary River, French Guiana) to the atmosphere were quantified for 10 years since impounding in 1994. Diffusive emissions from the reservoir surface were computed from direct flux measurements in 1994, 1995, and 2003 and from surface concentrations monitoring. Bubbling emissions, which occur only at water depths lower than 10 m, were interpolated from funnel measurements in 1994, 1997, and 2003. Degassing at the outlet of the dam downstream of the turbines was calculated from the difference in gas concentrations upstream and downstream of the dam and the turbined discharge. Diffusive emissions from the Sinnamary tidal river and estuary were quantified from direct flux measurements in 2003 and concentrations monitoring. Total carbon emissions were 0.37 ± 0.01 Mt yr−1 C (CO2 emissions, 0.30 ± 0.02; CH4 emissions, 0.07 ± 0.01) the first 3 years after impounding (1994–1996) and then decreased to 0.12 ± 0.01 Mt yr−1 C (CO2, 0.10 ± 0.01; CH4, 0.016 ± 0.006) since 2000. On average over the 10 years, 61% of the CO2 emissions occurred by diffusion from the reservoir surface, 31% from the estuary, 7% by degassing at the outlet of the dam, and a negligible fraction by bubbling. CH4 diffusion and bubbling from the reservoir surface were predominant (40% and 44%, respectively) only the first year after impounding. Since 1995, degassing at an aerating weir downstream of the turbines has become the major pathway for CH4 emissions, reaching 70% of the total CH4 flux. In 2003, river carbon inputs were balanced by carbon outputs to the ocean and were about 3 times lower than the atmospheric flux, which suggests that 10 years after impounding, the flooded terrestrial carbon is still the predominant contributor to the gaseous emissions. In 10 years, about 22% of the 10 Mt C flooded was lost to the atmosphere. Our results confirm the significance of greenhouse gas emissions from tropical reservoir but stress the importance of: (1) considering all the gas pathways upstream and downstream of the dams and (2) taking into account the reservoir age when upscaling emissions rates at the global scale.
Effects of temperature on Mg/Ca in neogloboquadrinid shells determined by live culturing
Authors: von Langen Peter J. , Pak Dorothy K. , Spero Howard J. , Lea David W.
Published: October 2005

New culturing protocols allowed the development of a Mg/Ca temperature calibration equation for Neogloboquadrina pachyderma (d.). When cultured between 9°C and 19.2°C, Mg/Ca in N. pachyderma (d.) shell calcite exhibits a clear dependence on temperature. Shell calcite Mg/Ca increased exponentially with temperature: Mg/Ca = 0.51−0.15+0.23 * exp(0.10±0.02*T). Limited data suggest N. dutertrei exhibit similar elemental temperature relationships to N. pachyderma (d.). We applied the temperature relationship established by culturing to Mg/Ca in neogloboquadrinid shells collected using plankton tows. Compared to measured SST, the calculated temperatures were within ±2°C for Mg/Ca (95% CI). Multiple samples from single tows generally had calculated temperatures that ranged from near‐surface values to temperatures consistent with calcification depths down to ∼70 m. Our work indicates that Mg/Ca temperature calibration equations for temperate and polar foraminiferal species have a similar exponential constant but a higher pre‐exponential constant than those for surface‐dwelling tropical species. Therefore accurate paleotemperature reconstructions from temperate and polar species require the use of an equation distinct from those used for tropical species.
On the use of ICESAT‐GLAS measurements for MODIS and SEVIRI cloud‐top height accuracy assessment
Authors: Naud Catherine , Muller Jan‐Peter , de Valk Paul
Published: October 2005

This study reports on the first attempt to use cloud boundary and optical depth retrievals from the GLAS lidar to assess the accuracy of cloud‐top heights obtained with MODIS (onboard NASA‐TERRA and AQUA) and SEVIRI (onboard METEOSAT‐8). Over the period from 25 September to 18 November 2003, MODIS‐GLAS coincidences were only found in the Polar Regions, whilst SEVIRI‐GLAS coincidences were available for a larger range of latitudes. For both passive instruments, cloud‐top heights were overestimated by about 300–400 m when clouds were low and opaque. For high and thin clouds, MODIS and SEVIRI cloud‐top heights were underestimated, and the bias increased with decreasing optical depth. For optical depths below 0.3, the number of misdetections increased significantly and the bias in cloud‐top height increased from 1 to 2 km. The bias was found to be larger when lower cloud layers were present.
Detection of external influence on sea level pressure with a multi‐model ensemble
Authors: Gillett N. P. , Allan R. J. , Ansell T. J.
Published: October 2005

Over the past fifty years, December–February mean sea level pressure has decreased markedly over both poles, corresponding to a trend toward strengthened westerlies in both hemispheres. In this study we compare observed sea level pressure trends with those simulated in response to natural and anthropogenic influence in a suite of eight up‐to‐date coupled general circulation models. A global analysis indicates that sea level pressure trends may be attributed to external influence. However, while simulated Southern Hemisphere sea level pressure trends are consistent with those observed, simulated Northern Hemisphere sea level pressure trends are not: Observations show a large negative trend in the Arctic and a positive trend over the subtropical North Atlantic and Mediterranean which is not reproduced in the simulations.
Response of diatoms distribution to global warming and potential implications: A global model study
Authors: Bopp L. , Aumont O. , Cadule P. , Alvain S. , Gehlen M.
Published: October 2005

Using a global model of ocean biogeochemistry coupled to a climate model, we explore the effect of climate change on the distribution of diatoms, a key phytoplankton functional group. Our model results suggest that climate change leads to more nutrient‐depleted conditions in the surface ocean and that it favors small phytoplankton at the expense of diatoms. At 4xCO2, diatoms relative abundance is reduced by more than 10% at the global scale and by up to 60% in the North Atlantic and in the subantarctic Pacific. This simulated change in the ecosystem structure impacts oceanic carbon uptake by reducing the efficiency of the biological pump, thus contributing to the positive feedback between climate change and the ocean carbon cycle. However, our model simulations do not identify this biological mechanism as a first‐order process in the response of ocean carbon uptake to climate change.
Empirical downscaling of wind speed probability distributions
Authors: Pryor S. C. , Schoof J. T. , Barthelmie R. J.
Published: October 2005

This paper presents a novel approach to developing empirically downscaled estimates of near‐surface wind speed and energy density and results from application of the technique to multiple stations in northern Europe. The downscaling takes a probabilistic approach in that it uses the mean and standard deviation of relative vorticity at 500 hPa and mean sea level pressure gradients computed using output from the ECHAM4/OPYC3 atmosphere‐ocean general circulation model as the predictors and parameters of the wind speed probability distribution at surface stations as the predictands. We demonstrate that this approach generates accurate depictions of the wind climate during the conditioning period and then apply the downscaling technique to examine changes between 1961–1990 and 2071–2100, which are compared to the results of dynamical downscaling. The empirically downscaled results for 1961–1990 and 2071–2100 show some evidence for small decreases in mean wind speed, 90th percentile wind speed, and energy density in 2071–2100 relative to 1961–1990. The projected changes are larger than the mean errors in the training period but smaller than current interannual variability. Rossby Centre regional climate model (RCM)–derived grid cell mean wind speeds exhibit a high degree of agreement with the empirically downscaled station wind speeds. However, in contrast to the empirical downscaling, simulations conducted using the Rossby Centre RCM indicate evidence for a small increase in the annual wind energy resource over northern Europe between the end of the 20th century and the end of the 21st century.
The circadian cycle: daily rhythms from behaviour to genes
Authors: Merrow Martha , Spoelstra Kamiel , Roenneberg Till
Published: October 2005

The daily recurrence of activity and rest are so common as to seem trivial. However, they reflect a ubiquitous temporal programme called the circadian clock. In the absence of either anatomical clock structures or clock genes, the timing of sleep and wakefulness is disrupted. The complex nature of circadian behaviour is evident in the fact that phasing of the cycle during the day varies widely for individuals, resulting in extremes colloquially called ‘larks’ and ‘owls’. These behavioural oscillations are mirrored in the levels of physiology and gene expression. Deciphering the underlying mechanisms will provide important insights into how the circadian clock affects health and disease.
A nonisospectral extension of the Volterra hierarchy to 2+1 dimensions
Authors: Gordoa P. R. , Pickering A. , Zhu Z. N.
Published: October 2005

We give a new nonisospectral generalization of the Volterra lattice equation to 2+1 dimensions. We use this to construct a new nonisospectral lattice hierarchy in 2+1 dimensions, along with its underlying linear problem. Reductions yield a variety of new integrable hierarchies, including generalizations of known discrete Painlevé hierarchies, all along with their corresponding linear problems. This represents an extension of previously developed techniques to the discrete case.
Monte Carlo calculations for the intrinsic viscosity of several dendrimer molecules
Authors: Freire Juan J. , Rodríguez Esteban , Rubio Ana M.
Published: October 2005

We have performed Monte Carlo simulations to reproduce the intrinsic viscosity corresponding to different generation of several types of dendrite molecules: polyamidoamine dendrimers with an ethylendiamine core, polypropylene-imine with a diaminobutane core, and monodendrons and tridendrons of polybenzylether. With this end, we have employed coarse-grained idealizations of the molecules constituted by only two beads in each repeat unit (one in a branching or end unit and one intermediate along the repeat unit) and a simple hard-sphere potential between non-neighboring beads. Our goal is to investigate if this simple model is able to provide a reasonable description of some differences between these systems that have been observed experimentally, in particular, the location of the maximum in the intrinsic viscosity as a function of the generation number. Experimental radii of gyration in a given solvent are reproduced by a fit of the hard-sphere potential diameter. Subsequently, intrinsic viscosities are calculated by the variational approach of Fixman, which yields an accurate lower-bound value with an additional hydrodynamic interaction parameter (the friction radius of the beads). The results show a pronounced variation of the maximum location with the value of the friction radius and the structural details that cannot be mimicked with simpler models. The initial conformations for the Monte Carlo procedure are taken from atomistic configurations thermalized by means of a molecular dynamics.
Studies of collisional selection rules in thioformaldehyde (H2CS) by microwave-optical double resonance
Authors: Barnett M. , Ramsay D. A. , Zhu Q.
Published: October 2005

Individual rotational levels in the ÃA21,v4=1 state of thioformaldehyde (H2CS) are excited by a cw laser and microwave transitions in the region of 8–12GHz are measured. Some of the microwave frequencies are found to be characteristic of rotational levels other than the level being pumped. Since the microwave frequencies are characteristic of individual rotational levels in the excited state and the excited-state lifetime is ∼170μs, information is obtained concerning rotational selection rules during collisions. It is found that J can change by several units and Ka by 0, ±2, ±4, and ±6. The latter result confirms that o-H2CS is not converted to p-H2CS by collisions. Observation of Ka doublets indicates that there are no appreciable differences between the two components.
Limits of strain relaxation in InGaAs∕GaAs probed in real time by in situ wafer curvature measurement
Authors: Lynch C. , Chason E. , Beresford R. , Freund L. B. , Tetz K. , Schwarz K. W.
Published: October 2005

In situ stress measurements during molecular-beam epitaxy growth of InxGa1−xAs∕GaAs provide insight into the relaxation behavior of thin films grown on mismatched substrates. Strain relaxation in the materials studied occurs due to the formation and glide of dislocations. Measurements of additional relaxation during growth interruptions show that relaxation is kinetically limited during the early stages of growth. In thicker films, the residual strain is not significantly affected by growth conditions. We find that relaxation in thick layers does not proceed as far as predicted by models which consider the formation of dislocation arrays or dislocation blocking, and we discuss this discrepancy between theory and experiment. We discuss the effect of a nonuniform dislocation array configuration on the overall relaxation behavior. Results from dislocation dynamics simulations are presented which provide evidence that nonuniform dislocation array distributions limit the extent of plastic relaxation.
Study of diffusion length in two-dimensional HgCdTe avalanche photodiodes by optical beam induced current
Authors: Liu Mingguo , Wang Shuling , Campbell Joe C. , Beck Jeffrey D. , Wan Chang-Feng , Kinch Michael A.
Published: October 2005

Optical beam induced current (OBIC) imaging has been used to measure the diffusion length of HgCdTe avalanche photodiodes (APDs) having a cylindrical structure. We show that the effective diffusion length extracted from current profiles is dependent on the electrode size and shape and the distance between electrode and excitation spot. To obtain the bulk diffusion length, a two-dimensional diffusion model was developed. The simulations provide good fits to experiment and indicate a bulk diffusion length of 70μm at room temperature.
A simplified relativistic time-dependent density-functional theory formalism for the calculations of excitation energies including spin-orbit coupling effect
Authors: Wang Fan , Ziegler Tom
Published: October 2005

In the present work we have proposed an approximate time-dependent density-functional theory (TDDFT) formalism to deal with the influence of spin-orbit coupling effect on the excitation energies for closed-shell systems. In this formalism scalar relativistic TDDFT calculations are first performed to determine the lowest single-group excited states and the spin-orbit coupling operator is applied to these single-group excited states to obtain the excitation energies with spin-orbit coupling effects included. The computational effort of the present method is much smaller than that of the two-component TDDFT formalism and this method can be applied to medium-size systems containing heavy elements. The compositions of the double-group excited states in terms of single-group singlet and triplet excited states are obtained automatically from the calculations. The calculated excitation energies based on the present formalism show that this formalism affords reasonable excitation energies for transitions not involving 5p and 6p orbitals. For transitions involving 5p orbitals, one can still obtain acceptable results for excitations with a small truncation error, while the formalism will fail for transitions involving 6p orbitals, especially 6p1∕2 spinors.
A density-functional model of the dispersion interaction
Authors: Becke Axel D. , Johnson Erin R.
Published: October 2005

We have recently introduced [J. Chem. Phys. 122, 154104 (2005)] a simple parameter-free model of the dispersion interaction based on the instantaneous in space, dipole moment of the exchange hole. The model generates remarkably accurate interatomic and intermolecular C6 dispersion coefficients, and geometries and binding energies of intermolecular complexes. The model involves, in its original form, occupied Hartree-Fock or Kohn-Sham orbitals. Here we present a density-functional reformulation depending only on total density, the gradient and Laplacian of the density, and the kinetic-energy density. This density-functional model performs as well as the explicitly orbital-dependent model, yet offers obvious computational advantages.
Hydrogen storage capacity of different carbon nanostructures in ambient conditions
Authors: Jang Jae Won , Lee Cheol Eui , Oh Chan Ick , Lee Cheol Jin
Published: October 2005

The hydrogen storage capacity of bamboo-shaped multiwalled carbon nanotubes (BS-MWNTs) in ambient conditions was studied by means of the volumetric method, and compared with those of single-walled carbon nanotubes (SWNTs) and multiwalled carbon nanotubes (MWNTs). The BS-MWNTs, whose herringbonelike structure was characterized by the transmission electron microscopy, showed the greatest hydrogen storage capacity with about 0.4wt% at atmospheric pressure. The SWNTs showed a comparable hydrogen storage capacity, whereas the MWNTs were insensitive to the pressure change. Our work indicates that the herringbone carbon nanotube structure is more capable of hydrogen storage than the herringbone graphite nanofiber structure.
Optical models for radio-frequency-magnetron reactively sputtered AlN films
Authors: Easwarakhanthan T. , Assouar M. B. , Pigeat P. , Alnot P.
Published: October 2005

The optical properties of aluminum nitrate (AlN) films reactively sputtered on Si substrates using radio-frequency (rf) magnetron have been studied in this work from multiwavelength spectroscopic ellipsometry (SE) measurements performed over the 290–615nm wavelength range. The SE modeling carried out with care to adhere as much to the ellipsometric fitting qualities is also backed up with atomic force microscopy and x-ray-diffraction measurements taken on these films thus grown to nominal thicknesses from 40to150nm under the same optimized experimental conditions. It follows that the model describing the optical properties of the thicker AlN films should consist at least in three layers on the Si substrate: an almost roughnessless smooth surface overlayer that is presumed essentially of Al2O3, a bulk AlN layer, and an AlN interface layer that has a refractive index dispersion falling in the range from 2.04 [312nm] to 1.91 [615nm] on the average and is fairly distinguishable from the slightly higher bulk layer index which drops correspondingly from 2.12 to 1.99. These index values imply that, beneath the partly or mostly oxidized surface AlN layer, the films comprise a polycrystalline-structured bulk AlN layer above a less-microstructurally-ordered interface layer that extends over 40–55nm from the substrate among thicker films. This ellipsometric evidence indicating the existence of the interface layer is consistent with those interface layers confirmed through electron microscopy in some previous works. However, the ellipsometrically insufficient thinner AlN films may be only modeled with the surface layer and an AlN layer. The film surface oxide layer thickness varies between 5 and 15nm among samples. The refractive index dispersions, the layer thicknesses, and the lateral thickness variation of the films are given and discussed regarding the optical constitution of these films and the ellipsometric validity of these parameters.
Double-wave-front reversal of dipole-exchange spin waves in yttrium-iron garnet films
Authors: Melkov G. A. , Vasyuchka V. I. , Chumak A. V. , Slavin A. N.
Published: October 2005

The effect of double-wave-front reversal in the system of dipolar and dipole-exchange spin waves propagating in a ferrite film is studied experimentally and theoretically with the goal of development of a nonlinear microwave signal processor. In the proposed processor microwave signal pulse supplied to the input antenna excites in the ferrite film a long-wavelength dipolar spin wave (magnetostatic wave), which in the course of propagation is scattered on the film inhomogeneities and is transformed into short-wavelength long-lifetime dipole-exchange spin waves. Then, a sequence of two high-power double-frequency parametric pumping pulses, supplied to the film through an open dielectric resonator with a certain time delay between them, performs first, and then second, wave-front reversal for all the spin waves created by the input signal in the ferrite film. As a result of this double wave-front reversal process microwave output pulses with either reversed (input antenna) or nonreversed (output antenna) time profiles delayed by different time intervals appear at the antennae of the signal processor. The maximum delay time of the pulsed microwave input signal obtained as a result of the double-wave-front reversal was around 3μs with insertion losses below 25dB∕μs.
Nanoelectromechanical switches with vertically aligned carbon nanotubes
Authors: Jang J. E. , Cha S. N. , Choi Y. , Amaratunga Gehan A. J. , Kang D. J. , Hasko D. G. , Jung J. E. , Kim J. M.
Published: October 2005

Electromechanical switching devices have been fabricated successfully employing vertically grown multiwalled carbon nanotubes (MWCNTs) from the prepatterned catalyst dots on the patterned device electrodes. The devices show various interesting switching characteristics depending on the length and the number of MWCNTs used. The device design not only simplifies the fabrication process, but also improves the integration density greatly. The device has a great potential in realizing technically viable nanoelectromechanical systems, such as switch, memory, fingers, or grippers.
Split donor centers and split excitons in a semiconductor heterostructure
Authors: Gribnikov Z. S. , Haddad G. I.
Published: October 2005

The first subject considered in the article is a donor center embedded in a thin heterostructural barrier separating a semiconductor medium into two halves. As a result of the small thickness of this barrier, the wave function of an electron bound by the donor center shifts almost completely into both halves of the surrounding semiconductor medium. The ground and first excited electron states of such a donor center are separated from each other by a narrow energy gap determined by the symmetric-antisymmetric tunnel splitting. Such structures can be implemented in both GaAs∕AlXGa1−XAs and Si∕GeXSi1−X material systems. The second considered subject is an exciton formed in analogous heterostructures when the staggered band alignment takes place between the heterobarrier and semiconductor medium. As a result of such band alignment, the hole participating in the exciton creation is located in the formed quantum well and the electron, which is the hole’s opponent, is separated into halves (on different sides of the quantum well) as before. Unlike the donor center, the exciton can be shifted and localized in arbitrary positions along the staggered “barrier-well” boundary by inhomogeneous electric fields of external controlling gates.
Magnetic tunnel transistor with a silicon hot-electron emitter
Authors: LeMinh P. , Gokcan H. , Lodder J. C. , Jansen R.
Published: October 2005

We report on a modified magnetic tunnel transistor having a silicon tunnel emitter. The device has the structure Si∕Al2O3∕base∕Si with a spin-valve metal base, a Schottky barrier collector, but a silicon emitter separated from the base by a thin tunnel oxide. The energy of the hot electrons injected from the Si emitter into the base can be tuned by the emitter bias, which drops partly over the Si depletion region. Compared to a magnetic tunnel transistor with a metal emitter, the voltage drop over the thin tunnel oxide is reduced, enabling stable device operation at higher biasing conditions. We fabricated devices with a magnetocurrent up to 166% and a steeply enhanced transfer ratio reaching 6×10−4 at an emitter current of 200mA.
Magnetic reconnection with anomalous resistivity in two-and-a-half dimensions. I. Quasistationary case
Authors: Malyshkin Leonid M. , Linde Timur , Kulsrud Russell M.
Published: October 2005

In this paper quasistationary, “two-and-a-half-dimensional” magnetic reconnection is studied in the framework of incompressible resistive magnetohydrodynamics. A new theoretical approach for the calculation of the reconnection rate is presented. This approach is based on the local analytical derivations in a thin reconnection layer, and it is applicable to the case when resistivity is anomalous and is an arbitrary function of the electric current and the spatial coordinates. It is found that a quasistationary reconnection rate is fully determined by a particular functional form of the anomalous resistivity and by the local configuration of the magnetic field just outside the reconnection layer. It is also found that, in the special case of constant resistivity, reconnection is Sweet-Parker [Electromagnetic Phenomena, edited by B. Lehnert (Cambridge University Press, New York, 1958), p. 123; Astrophys. J., Suppl. 8, 177 (1963)] and not Petschek [AAS-NASA Symposium on Solar Flares NASA SP5 (National Aeronautics and Space Administration, Washington, D.C., 1964), p. 425].
Plasma-maser effect in inhomogeneous plasma in the presence of drift wave turbulence
Authors: Singh M. , Deka P. N.
Published: October 2005

A theoretical study is made on the generation mechanism of Bernstein-mode wave through plasma-maser effect in the presence of drift wave turbulence field. The drift wave turbulence field is taken as low-frequency resonant-mode field and plasma is considered to be spatially inhomogeneous to support the drift wave turbulence field. The growth rate of the test high-frequency Bernstein-mode wave is obtained with the involvement of the spatial density gradient parameter. A comparative study on the role of the density gradient for the generation of Bernstein mode on the basis of the plasma-maser effect is presented.
Analysis of waves in the plasma guided by a periodical vane-type slow wave structure
Authors: Wu T. J. , Kou C. S.
Published: October 2005

In this study, the dispersion relation has been derived to characterize the propagation of the waves in the plasma guided by a periodical vane-type slow wave structure. The plasma is confined by a quartz plate. Results indicate that there are two different waves in this structure. One is the plasma mode that originates from the plasma surface wave propagating along the interface between the plasma and the quartz plate, and the other is the guide mode that originally travels along the vane-type slow wave structure. In contrast to its original slow wave characteristics, the guide mode becomes a fast wave in the low-frequency portion of the passband, and there exists a cut-off frequency for the guide mode. The vane-type guiding structure has been shown to limit the upper frequency of the passband of the plasma mode, compared with that of the plasma surface wave. In addition, the passband of the plasma mode increases with the plasma density while it becomes narrower for the guide mode. The influences of the parameters of the guiding structure and plasma density on the propagation of waves are also presented.
Near-infrared transparent electrodes for precision Teng–Man electro-optic measurements: In2O3 thin-film electrodes with tunable near-infrared transparency
Authors: Wang Lian , Yang Yu , Marks Tobin J. , Liu Zhifu , Ho Seng-Tiong
Published: October 2005

Highly near-infrared (NIR) transparent In2O3 thin films have been grown by ion-assisted deposition at room temperature, and the optical and electrical properties characterized. NIR transparency and the plasma edge frequency can be engineered by control of the film deposition conditions. As-deposited In2O3 thin films were employed as transparent electrodes for direct thin film electro-optic (EO) characterization measurements via the Teng–Man technique. Using LiNbO3 as the standard, the relationship between electrode NIR transparency and Teng–Man EO measurement accuracy was evaluated. It is found that In2O3 electrodes can be tailored to be highly NIR transparent, thus providing far more accurate Teng–Man EO coefficient quantification than tin-doped indium oxide. In addition, the EO coefficients of stilbazolium-based self-assembled superlattice thin films were directly determined for the first time using an optimized In2O3 electrode. EO coefficients r33 of 42.2, 13.1, and 6.4pm∕V are obtained at 633, 1064, and 1310 nm, respectively.
On the local equilibrium of the subgrid scales: The velocity and scalar fields
Authors: da Silva Carlos B. , Pereira José C. F.
Published: October 2005

Direct numerical simulations of homogeneous isotropic turbulence are used to analyze the local equilibrium assumption between large and small scales of motion in the context of large-eddy simulations. The local imbalance, between grid/subgrid scales transfer (of kinetic energy and scalar variance) and molecular dissipation, increases with the Reynolds and Schmidt numbers and with the filter size. It is shown that the correlations between SGS production and dissipation (for the velocity and scalar fields) are higher in regions dominated by strain and where vorticity and strain are comparably large, and smaller in regions where vorticity dominates.
Piezoelectrically induced resistance modulations in La0.7Sr0.3MnO3∕Pb(Zr,Ti)O3 field effect devices
Authors: Thiele C. , Dörr K. , Schultz L. , Beyreuther E. , Lin W.-M.
Published: October 2005

Epitaxial ferroelectric-ferromagnetic field effect devices of PbZr0.52Ti0.48O3∕La0.7Sr0.3MnO3 (PZT∕LSMO) with narrow manganite channels (⩽7nm) show butterflylike hysteretic resistance modulations (ΔR) which are commensurate with strain variation from inverse piezoelectric effect of PZT. Based on the type of observed resistance hysteresis loops, contributions from electric field effect and strain effect have been distinguished for devices with varied channel thickness. The strain-induced ΔR decreases with increasing channel thickness. The ΔR from field effect is low in the LSMO channels with 30% Sr doping.
Self-aligned self assembly of multi-nanowire silicon field effect transistors
Authors: Black C. T.
Published: October 2005

We demonstrate the efficacy of diblock copolymer self assembly for solving key fabrication challenges of aggressively scaled silicon field effect transistors. These materials spontaneously form nanometer-scale patterns that self-align to larger-scale lithography, enabling construction of sub-lithographic semiconducting transistor channels composed of arrays of parallel nanowires with critical dimensions (15 nm width, 40 nm pitch) defined by self assembly. The number of nanowires in the arrays is readily adjusted, greatly reducing the complexity associated with width-scaling of nanowire transistors. We measured Schottky source/drain multi-nanowire n-channel devices comprised of 6, 8, 10, and 16 nanowires, with current drives of ∼5μA∕wire and current on/off ratios of ∼105.
Screening effects in InAs quantum-dot structures observed by photoluminescence and capacitance-voltage spectra
Authors: Lüttjohann Stephan , Meier Cedrik , Lorke Axel , Reuter Dirk , Wieck Andreas D.
Published: October 2005

We have performed photoluminescence spectroscopy as well as capacitance-voltage spectroscopy on an ensemble of self-assembled InAs quantum dots that are embedded in a field-effect-transistor structure. By investigating the charging spectra as a function of excitation power density, we are able to demonstrate a buildup of a transient positive charge in the heterostructure that leads to a screening of the electric field inside the structure. Moreover, by taking photoluminescence and capacitance spectra simultaneously, we can correlate the charging state of the dots with the interband transitions of s- and p-shell. We find that the observation of photoluminescence from higher orbital states in such field-effect-transistor structures is not only a consequence of Pauli-blocking but also of the accumulation of holes inside the structure. Also, we are able to determine the energy shift between the higher-charged excitonic states X2− and X3− to be ΔE=2.6meV.
Single-electron transistor mediated by C60 insertion inside a carbon nanotube
Authors: Yu H. Y. , Lee D. S. , Lee S. H. , Kim S. S. , Lee S. W. , Park Y. W. , Dettlaff-Weglikowskaand U. , Roth S.
Published: October 2005

Electrical properties of C60 encapsulated peapod are investigated at various temperatures from room temperature down to T=1.8K. The current behavior induced by the applied gate and source-drain voltage shows that C60 peapods exhibit single-electron transistor properties. Gate-dependent conductance is enhanced at negative gate voltage and is suppressed and oscillate at positive gate voltage. This behavior is ascribed to the modulation of density of states by the insertion of C60s inside a carbon nanotube.
Great improvement of phase controlling of the entirely independent stimulated Brillouin scattering phase conjugate mirrors by balancing the pump energies
Authors: Lee Seong Ku , Kong Hong Jin , Nakatsuka Masahiro
Published: October 2005

For developing a beam combination laser with the stimulated Brillouin scattering-phase conjugate mirrors (SBS-PCMs), the phase control of the backward SBS waves is essentially required. We proposed a new effective and practical technique in previous works, in which entirely independent SBS-PCMs are used, so that there is no limit of the number of the beams for the beam combination laser. In this letter, we show that in the proposed technique, the phase of the SBS wave significantly depends on the pump energy and it can be stabilized—although the independently separate SBS-PCMs are used—provided that the pump energies are balanced under the density modulation. In this experimental work, the standard deviation of the relative phase difference between the SBS waves has been reduced less than λ∕30 by the amplitude dividing method to provide the pump beams with the nearly same energies.
Urban Wild Things: A Cosmopolitical Experiment
Authors: Hinchliffe Steve , Kearnes Matthew B , Degen Monica , Whatmore Sarah
Published: October 2005

Cities are inhabited by all manner of things and made up of all manner of practices, many of which are unnoticed by urban politics and disregarded by science. In this paper we do two things. First, we add to the sense that urban living spaces involve much more than human worlds and are often prime sites for human and nonhuman ecologies. Second, we experiment with what is involved in taking these nonhuman worlds and ecologies seriously and in producing a politics for urban wilds. In order to do this we learn how to sense urban wildlife. In learning new engagements we also learn new things and in particular come to see urban wilds as matters of controversy. For this reason we have borrowed and adapted Latour's language to talk of wild things. Wild things become more rather than less real as people learn to engage with them. At the same time, wild things are too disputed, sociable, and uncertain to become constant objects upon which a stable urban politics can be constructed. So a parliament of wild things might be rather different from the house of representatives that we commonly imagine. It may be closer to what Stengers (1997, Power and Invention University of Minnesota Press, Minneapolis, MN) has characterised as cosmopolitics, a politics that is worked out without recourse to old binaries of nature and society. Using empirical work with urban wildlife-trust members we muddy the clean lines of representational politics, and start to grapple with issues that a reconvened wild politics might involve.
‘King of Fish’ or ‘Feral Peril’: Tasmanian Atlantic Salmon and the Politics of Belonging
Authors: Lien Marianne E
Published: October 2005

The focus of this paper is Tasmanian Atlantic salmon, and the ways in which this object has served historically to enact, to produce, and to challenge key boundaries and continuities in the construction of Tasmania as a distinct place in the world. Tracing the object and its trajectories in time and space, I shall argue that the making of place involves practices, images, and experiences that connect and disconnect a place to significant places elsewhere. It is argued that both species and the spaces they inhabit are sustained by hybrid networks which stretch across time and space and thus escape the timeless boundedness and genealogical purity inherent in contemporary visions of nature.