bluuebunny/crossref_metadata_2025 huggingface dataset:
Piping and woody plants in peatlands: Cause or effect?
Authors: Holden Joseph
Published: June 2005

This paper presents, for the first time, evidence to show that Calluna species are one causative factor of piping in blanket peat catchments. Ground‐penetrating radar survey on 960 plots illustrated that piping was prevalent throughout blanket peats. However, soil pipe occurrence was significantly higher where bare peat (149 pipes/km) or Calluna (87 pipes/km) were present compared to other species (67 pipes/km). A case study catchment where there was an altitudinal limit to Calluna provided some control over potential factors that may lead to an association between piping and Calluna. Under the controlled conditions of topographic index, peat depth, and water table, piping was greater under the Calluna‐covered peat than under other vegetation covers. Laboratory experiments demonstrated that 10 years worth of rainfall was enough to almost double the proportion of macropore flow occurring in recently colonized Calluna peatlands. This suggests that given enough water and time, the woody Calluna plants result in water being preferentially channeled through the upper peat. Improvements are therefore required in our understanding of the relationships between peatland plant nutrient and water supply and the feedbacks between ecosystem functioning and landform development. These results are also important given the propensity to encourage Calluna growth for game bird enhancement in many northern peatlands.
Arctic ozone loss and climate sensitivity: Updated three‐dimensional model study
Authors: Chipperfield M. P. , Feng W. , Rex M.
Published: June 2005

We have used a three‐dimensional (3D) chemical transport model (CTM) to investigate the variation in Arctic winter‐spring chemical ozone loss from 1991–2003, and its observed correlation with low temperatures. The CTM (SLIMCAT) has been updated based on recent field and laboratory results and contains improved treatments of transport, chemistry and denitrification. In contrast to previous model studies, the CTM now gives a good simulation of the observed O3 loss throughout the years studied. The model reproduces the large column loss of cold winters and also captures the shape of the ozone loss profile. The variation of O3 loss with interannual variations in temperature is also well reproduced. Hence we show that for the first time a 3D stratospheric model is able to reproduce the past climate sensitivity of Arctic ozone depletion on temperature. This new capability is an essential prerequisite for model predictions of the future of the Arctic ozone layer in a changing climate. With realistic transport, chemistry‐climate models with similar chemical modules should be able to reproduce polar chemical ozone depletion over the range of temperatures experienced so far.
Joint inversion of H/V ratios and dispersion curves from seismic noise: Estimating the S‐wave velocity of bedrock
Authors: Picozzi M. , Parolai S. , Richwalski S. M.
Published: June 2005

A joint inversion of phase velocity and H/V ratio curves, both obtained from seismic‐noise recordings, permits the retrieval of the shear‐wave velocity structure of local sedimentary cover. Our inversion scheme uses a genetic algorithm and considers the influence of higher modes on the data sets. Encouraged by the results published previously on joint inversion (Parolai et al., 2005) we went one step further. We found, using a synthetic data set, that the impedance contrast at the sediment‐bedrock interface has a strong influence on the shape of the H/V ratio curve, which therefore allows the bedrock S‐wave velocity to be well constrained in the joint‐inversion procedure. Our observations were further confirmed using a real data set.
Quantifying CO emissions from the 2004 Alaskan wildfires using MOPITT CO data
Authors: Pfister G. , Hess P. G. , Emmons L. K. , Lamarque J.‐F. , Wiedinmyer C. , Edwards D. P. , Pétron G. , Gille J. C. , Sachse G. W.
Published: June 2005

We present an inverse model analysis to quantify the emissions of wildfires in Alaska and Canada in the summer of 2004 using carbon monoxide (CO) data from the Measurements of Pollution in the Troposphere (MOPITT) remote sensing instrument together with the chemistry transport model MOZART (Model for Ozone and Related Chemical Tracers). We use data assimilation outside the region of the fires to optimally constrain the CO background level and the transport into that region. Inverse modeling is applied locally to quantify the fire emissions. Our a posteriori estimate of the wildfire emissions gives a total of 30 ± 5 Tg CO emitted during June–August 2004 which is of comparable order to the anthropogenic emissions for the continental US. The simulated CO fields have been evaluated by comparison with MOPITT and independent aircraft data.
Quantum Brownian motion with large friction
Authors: Ankerhold Joachim , Grabert Hermann , Pechukas Philip
Published: June 2005

Quantum Brownian motion in the strong friction limit is studied based on the exact path integral formulation of dissipative systems. In this limit the time-nonlocal reduced dynamics can be cast into an effective equation of motion, the quantum Smoluchowski equation. For strongly condensed phase environments it plays a similar role as master equations in the weak coupling range. Applications for chemical, mesoscopic, and soft matter systems are discussed and reveal the substantial role of quantum fluctuations.
Laser ablation of NaN3 and CsN3
Authors: Belau Leonid , Gorodetsky Jonathan , Haas Yehuda
Published: June 2005

Solid sodium azide and cesium azide crystals were irradiated by high power laser pulses; the ablation products were rapidly cooled by a supersonic expansion of helium and detected by a time of flight mass spectrometer. Neutral and positively charged species were separately recorded and analyzed using N15 isotopomers to help in their assignment. Cluster series of the sequences Na(NaN3)n [or Cs(CsN3)n] were observed, as well as clusters containing NaOH and NaCN; the origin of the C, H, and O atoms appears to be water and CO2 occluded in the salt. Addition of D2O increased the intensity of large clusters and added deuterated ones, whereas addition of chloroform leads to formation of clusters of a Na atom with (NaCl)n clusters. Possible mechanisms for the formation of these clusters are discussed.
Modeling disorder in polymer aggregates: The optical spectroscopy of regioregular poly(3-hexylthiophene) thin films
Authors: Spano Frank C.
Published: June 2005

Absorption and emission in polymer aggregates is studied theoretically, taking into account excitonic (intermolecular) coupling, exciton-phonon (EP) coupling, and disorder, all treated on equal footing within a generalized Holstein Hamiltonian with numerically generated eigenmodes and energies. The disorder is modeled as a Gaussian distribution of molecular transition frequency offsets of width σ and spatial correlation length l0. Both herringbone (HB) and lamellar aggregate morphologies are considered. The emission spectral line shape is shown to undergo marked changes in response to increasing disorder, with the intensity of the ac-polarized 0-0 emission peak generally increasing relative to the replica intensities (0-1,0-2,…) as σ increases and/or as l0 decreases. This is contrary to the behavior of the b-polarized component of the 0-0 intensity, which, in HB aggregates, decreases with increasing disorder. Comparisons are made to analogous trends in oligomer aggregates. Analytical results are obtained in the strong EP coupling regime appropriate for conjugated polymers while treating the disorder perturbatively. A method for uniquely determining σ and l0 from the emission and absorption spectra is presented. Applications are made to absorption and low-temperature emission in thin films of regioregular poly(3-hexylthiophene), with excellent agreement between theory and experiment obtained for a spatial correlation length of only 3–4 molecules.
Topological coarse graining of polymer chains using wavelet-accelerated Monte Carlo. I. Freely jointed chains
Authors: Ismail Ahmed E. , Rutledge Gregory C. , Stephanopoulos George
Published: June 2005

We introduce a new, topologically-based method for coarse-graining polymer chains. Based on the wavelet transform, a multiresolution data analysis technique, this method assigns a cluster of particles to a coarse-grained bead located at the center of mass of the cluster, thereby reducing the complexity of the problem by dividing the simulation into several stages, each with a fraction of the number of beads as the overall chain. At each stage, we compute the distributions of coarse-grained internal coordinates as well as potential functions required for subsequent simulation stages. In this paper, we present the basic algorithm, and apply it to freely jointed chains; the companion paper describes its applications to self-avoiding chains.
Measurements of molecular and thermal diffusion coefficients in ternary mixtures
Authors: Leahy-Dios Alana , Bou-Ali Mounir M. , Platten Jean K. , Firoozabadi Abbas
Published: June 2005

Thermal diffusion coefficients in three ternary mixtures are measured in a thermogravitational column. One of the mixtures consists of one normal alkane and two aromatics (dodecane-isobutylbenzene-tetrahydronaphthalene), and the other two consist of two normal alkanes and one aromatic (octane-decane-1-methylnaphthalene). This is the first report of measured thermal diffusion coefficients (for all species) of a ternary nonelectrolyte mixture in literature. The results in ternary mixtures of octane-decane-1-methylnaphthalene show a sign change of the thermal diffusion coefficient for decane as the composition changes, despite the fact that the two normal alkanes are similar. In addition to thermal diffusion coefficients, molecular diffusion coefficients are also measured for three binaries and one of the ternary mixtures. The open-end capillary-tube method was used in the measurement of molecular diffusion coefficients. The molecular and thermal diffusion coefficients allow the estimation of thermal diffusion factors in binary and ternary mixtures. However, in the ternaries one also has to calculate phenomenological coefficients from the molecular diffusion coefficients. A comparison of the binary and ternary thermal diffusion factors for the mixtures comprised of octane-decane-1-methylnaphthalene reveals a remarkable difference in the thermal diffusion behavior in binary and ternary mixtures.
Fabrication and characterization of multiterminal superconductor-insulator-normal metal-insulator-superconductor Josephson devices
Authors: Nevirkovets I. P. , Chernyashevskyy O. , Ketterson J. B. , Goldobin E.
Published: June 2005

We report the fabrication and basic characteristics of a multiterminal SINIS device which has electrical leads connected to the middle N layer; here S,I, and N denote a superconductor (Nb), an insulator (AlOx), and a normal metal (Al), respectively. We studied the behavior of the Josephson current through all layers on an injection current passing through one of the individual (NIS) junctions and along the N layer, as well as the influence of the injection current from one junction on the current–voltage characteristic of the other. In the latter case, a current gain and power gain, and good isolation between the input and output were observed.
The Perdew–Burke–Ernzerhof exchange-correlation functional applied to the G2-1 test set using a plane-wave basis set
Authors: Paier Joachim , Hirschl Robin , Marsman Martijn , Kresse Georg
Published: June 2005

Present local and semilocal functionals show significant errors, for instance, in the energetics of small molecules and in the description of band gaps. One possible solution to these problems is the introduction of exact exchange and hybrid functionals. A plane-wave-based algorithm was implemented in VASP (Vienna ab-initio simulation package) to allow for the calculation of the exact exchange. To systematically assess the precision of the present implementation, calculations for the 55 molecules of the G2-1 quantum chemical test set were performed applying the PBE and PBE0 functionals. Excellent agreement for both atomization energies and geometries compared with the results obtained by GAUSSIAN 03 calculations using large basis sets (augmented correlation consistent polarized valence quadruple zeta for the geometry optimization and augmented correlation-consistent polarized valence quintuple zeta for the energy calculations) was found. The mean absolute error for atomization energies between VASP and the experiment is 8.6 and 3.7kcal∕mol, as calculated with the PBE and PBE0 functionals, respectively. The mean deviations between VASP and GAUSSIAN are 0.46 and 0.49kcal∕mol for the PBE and PBE0 functionals, respectively.
Elastic electron scattering by C2F4
Authors: Winstead C. , McKoy V.
Published: June 2005

Recent measurements [R. Panajotovic, M. Jelisavcic, R. Kajita, T. Tanaka, M. Kitajima, H. Cho, H. Tanaka, and S. J. Buckman, J. Chem. Phys. 121, 4559 (2004)] and calculations [C. Trevisan, A. E. Orel, and T. N. Rescigno, Phys. Rev. A 70, 012704 (2004)] of the elastic electron cross section for C2F4 differ materially from our earlier calculations [C. Winstead and V. McKoy, J. Chem. Phys. 116, 1380 (2002)]. Some of the differences are readily attributed to approximations made in our computations, but an overall difference in cross section magnitude above ca. 10 eV was surprising. Here we report a reexamination of the electron-C2F4 elastic cross section. After eliminating or minimizing various possible sources of error, we continue to predict a substantially larger cross section at higher energies.
Asymmetric, nonbroadened large optical cavity waveguide structures for high-power long-wavelength semiconductor lasers
Authors: Ryvkin B. S. , Avrutin E. A.
Published: June 2005

We present a simple semianalytical model for evaluating the free-carrier loss in the waveguide layer of large-cavity semiconductor lasers, which proves that these losses may become an important factor at high bias currents. It is shown that nonbroadened asymmetric waveguide structures can significantly reduce these losses when compared to broadened symmetric waveguides, with little or no degradation in threshold, near- and far-field properties, and are thus a promising configuration for high-power lasers operating high above threshold.
Magnetic study of epitaxial Fe∕InGaAs∕InP(100) deposited by ion-beam sputtering
Authors: Richomme F. , Fnidiki A. , Eymery J. P.
Published: June 2005

Fe layers, 3, 6, 10, and 25 nm thick, were epitaxially deposited by ion-beam sputtering on InGaAs∕InP(100) wafers. For the 3-nm-thick layer, the sample shows a strong in-plane uniaxial magnetic anisotropy along the [110] direction between 5 and 300 K. The 6-nm film exhibits competition between the uniaxial magnetic anisotropy and the magnetic anisotropy of the bulk bcc Fe. The fourfold magnetic anisotropy of the bulk Fe dominates for the 10-nm Fe film. A decrease of the magnetization is observed for the thinner sample as compared to the bulk. This decrease is discussed in terms of Fe thickness, interface effect, diffusion effect, and possible phases at the interface with the semiconductor.
Electronic structure of a polymer nanowire on H-terminated Si(100)
Authors: Terada Yasuhiko , Miki Kazushi , Fujimori Masaaki , Heike Seiji , Suwa Yuji , Hashizume Tomihiro
Published: June 2005

We measured current–voltage (I–V) characteristics of individual conducting polymers, poly(3-hexylthiophene)s (P3HTs), fixed on hydrogen-terminated Si(100) using scanning tunneling microscopy (STM)∕spectroscopy. The I–V curves reveal rectification characteristics that are attributed to the shift of the energy level of the valence-band maximum of P3HT under bias. The current suppression at positive substrate bias results from the effect of differential charging of the polymer between the opposite bias polarities, indicating the possibility for doping of polymer nanowires by using a STM tip as a gate electrode.
On the use of optimal internal vibrational coordinates for symmetrical bent triatomic molecules
Authors: Zúñiga José , Picón José Antonio G. , Bastida Adolfo , Requena Alberto
Published: June 2005

The use of generalized internal coordinates for the variational calculation of excited vibrational states of symmetrical bent triatomic molecules is considered with applications to the SO2, O3, NO2, and H2O molecules. These coordinates depend on two external parameters which can be properly optimized. We propose a simple analytical method to determine the optimal internal coordinates for this kind of molecules based on the minimization with respect to the external parameters of the zero-point energy, assuming only quadratic terms in the Hamiltonian and no quadratic coupling between the optimal coordinates. The optimal values of the parameters thus obtained are shown to agree quite well with those that minimize the sum of a number of unconverged energies of the lowest vibrational states, computed variationally using a small basis function set. The unconverged variational calculation uses a basis set consisting of the eigenfunctions of the uncoupled anharmonic internal coordinate Hamiltonian. Variational calculations of the excited vibrational states for the four molecules considered carried out with an increasing number of basis functions, also evidence the excellent convergence properties of the optimal internal coordinates versus those provided by other normal and local coordinate systems.
Guided-mode effects in quantum-well infrared photodetectors integrated with light-emitting diode
Authors: Dupont E. , Byloos M. , Oogarah T. , Sproule I. , Liu H. C.
Published: June 2005

Mode-guiding effects on an infrared thermal-imaging device consisting of a quantum-well infrared photodetector integrated with a light-emitting diode have been observed. The photocurrent spectra and the integrated response are modulated even for a very large numerical aperture. In the range of device thickness explored the response changes by about 10%.
Water models based on a single potential energy surface and different molecular degrees of freedom
Authors: Saint-Martin Humberto , Hernández-Cobos Jorge , Ortega-Blake Iván
Published: June 2005

Up to now it has not been possible to neatly assess whether a deficient performance of a model is due to poor parametrization of the force field or the lack of inclusion of enough molecular properties. This work compares several molecular models in the framework of the same force field, which was designed to include many-body nonadditive effects: (a) a polarizable and flexible molecule with constraints that account for the quantal nature of the vibration [B. Hess, H. Saint-Martin, and H. J. C. Berendsen, J. Chem. Phys. 116, 9602 (2002), H. Saint-Martin, B. Hess, and H. J. C. Berendsen, J. Chem. Phys. 120, 11133 (2004)], (b) a polarizable and classically flexible molecule [H. Saint-Martin, J. Hernández-Cobos, M. I. Bernal-Uruchurtu, I. Ortega-Blake, and H. J. C. Berendsen, J. Chem. Phys. 113, 10899 (2000)], (c) a polarizable and rigid molecule, and finally (d) a nonpolarizable and rigid molecule. The goal is to determine how significant the different molecular properties are. The results indicate that all factors—nonadditivity, polarizability, and intramolecular flexibility—are important. Still, approximations can be made in order to diminish the computational cost of the simulations with a small decrease in the accuracy of the predictions, provided that those approximations are counterbalanced by the proper inclusion of an effective molecular property, that is, an average molecular geometry or an average dipole. Hence instead of building an effective force field by parametrizing it in order to reproduce the properties of a specific phase, a building approach is proposed that is based on adequately restricting the molecular flexibility and/or polarizability of a model potential fitted to unimolecular properties, pair interactions, and many-body nonadditive contributions. In this manner, the same parental model can be used to simulate the same substance under a wide range of thermodynamic conditions. An additional advantage of this approach is that, as the force field improves by the quality of the molecular calculations, all levels of modeling can be improved.
Weak Hopf algebras corresponding to Cartan matrices
Authors: Yang Shilin
Published: June 2005

We replace the group of grouplike elements of the quantized enveloping algebra Uq(g) of a finite dimensional semisimple Lie algebra g by some regular monoid and get the weak Hopf algebra wqd(g). It is a subclass of weak Hopf algebras but not Hopf algebras. Then we devote to constructing a basis of wqd(g) and determine the group of weak Hopf algebra automorphisms of wqd(g) when q is not a root of unity.
Kerr and four-wave mixing spectroscopy at the band edge of one-dimensional photonic crystals
Authors: Razzari Luca , Träger Denis , Astic Magali , Delaye Philippe , Frey Robert , Roosen Gérald , André Régis
Published: June 2005

Kerr and four-wave mixing spectroscopy is shown to be a powerful technique to quantify the strong enhancement of the third-order optical nonlinear susceptibilities at the band edge of photonic crystals. Local field factors of about 5 are demonstrated for crossed Kerr effect and a narrow resonance peak observed for the conjugate reflectivity. Moreover, a reduction of the effective nonlinear susceptibility of the four-wave mixing process with increasing pump intensities is measured, which is due to different Kerr-induced blueshifts of the band edge for forward and backward pump beams and signal and conjugate beams. This observation definitely demonstrates the need for considering all the nonlinear processes for the optimization of nonlinear photonic crystals for a given application in optical signal processing.
Lateral encroachment of Ni-silicides in the source/drain regions on ultrathin silicon-on-insulator
Authors: Seger J. , Hellström P.-E. , Lu J. , Malm B. G. , von Haartman M. , Östling M. , Zhang S.-L.
Published: June 2005

Lateral growth of Ni silicide towards the channel region of metal-oxide-semiconductor transistors (MOSFETs) fabricated on ultrathin silicon-on-insulator (SOI) is characterized using SOI wafers with a 20-nm-thick surface Si layer. With a 10-nm-thick Ni film for silicide formation, p-channel MOSFETs displaying ordinary device characteristics with silicided p+ source/drain regions were demonstrated. No lateral growth of NiSix under gate isolation spacers was found according to electron microscopy. When the Ni film was 20 nm thick, Schottky contact source/drain MOSFETs showing typical ambipolar characteristics were obtained. A severe lateral encroachment of NiSix into the channel region leading to an increased gate leakage was revealed, while no detectable voiding at the silicide front towards the Si channel was observed.
Long carrier lifetimes in GaN epitaxial layers grown using TiN porous network templates
Authors: Özgür Ü. , Fu Y. , Moon Y. T. , Yun F. , Morkoç H. , Everitt H. O. , Park S. S. , Lee K. Y.
Published: June 2005

Improved structural quality and radiative efficiency were observed in GaN thin films grown by metalorganic chemical vapor deposition on TiN porous network templates formed by in situ thermal annealing of Ti in ammonia. The room-temperature decay times obtained from biexponential fits to time-resolved photoluminescence data are longer than ever reported for GaN. The carrier lifetime of 1.86 ns measured for a TiN network sample is slightly longer than that for a 200 μm thick high-quality freestanding GaN. The linewidth of the asymmetric x-ray diffraction (XRD) (101¯2) peak decreases considerably with the use of TiN layer and with increasing in situ annealing time, indicating the reduction in threading dislocation density. However, no direct correlation is yet found between the decay times and the XRD linewidths, suggesting that point defect and impurity related nonradiative centers are the main parameters affecting the lifetime.
Footprints of deformation mechanisms during in situ x-ray diffraction: Nanocrystalline and ultrafine grained Ni
Authors: Budrovic Z. , Petegem S. Van , Derlet P. M. , Schmitt B. , Swygenhoven H. Van , Schafler E. , Zehetbauer M.
Published: June 2005

In situ x-ray diffraction demonstrates that in ultrafine grained Ni synthesized by high pressure torsion with a coherent scattering domain size of 80nm, a dislocation network is still built up during tensile deformation whereas this is not the case for electrodeposited nanocrystalline metals with a coherent scattering domain size of 30nm. Simultaneously, the technique shows for the first time important differences in macroscopic stress accommodation during plastic deformation between the nanocrystalline and ultrafine grained Ni, such as the origin of the reduction in flow stress.
Surface adsorption effects on the lattice expansion of copper nanocrystals
Authors: Champion Yannick , Bernard Frédéric , Millot Nadine , Perriat Pascal
Published: June 2005

Lattice expansion in nanocrystalline copper due to size and surface effect is reported. The lattice parameter is measured by in situ x-ray diffraction at various temperatures from −173°Cto150°C. The experiments are carried out on nanocrystalline copper powders having an average particle size of 40nm. The size effect on the lattice expansion is examined regarding a modified Laplace law, where a surface stress is considered instead of the usual scalar surface energy. The results are discussed taking into account oxidation state and the sorption of molecular species at the nanoparticles surface.
Ultrafast excitation cross-correlation photoconductivity in polyfluorene photodiodes
Authors: Gambetta A. , Virgili T. , Lanzani G.
Published: June 2005

Two-pulse excitation cross-correlation photocurrent is measured in single-layer poly(9,9 dioctylfluorene) light-emitting diodes. Off-resonant pulses show a three-photon resonance to a higher lying state responsible for charge generation, mediated by some low-lying excited singlet state S2 (of even symmetry). Resonant excitation shows a two-step transition to the charge generation states mediated by a vibrationally hot S1 state (of odd symmetry) which introduces an ultrafast timescale suitable for application. Basic knowledge on charge generation and excited state relaxation is obtained. Possible application to pulse characterization in the blue spectral region is also demonstrated.
Effect of antiphase boundaries on electrical transport properties of Fe3O4 nanostructures
Authors: Li Hongliang , Wu Yihong , Guo Zaibing , Wang Shijie , Teo Kie Leong , Veres Teodor
Published: June 2005

Fe 3 O 4 nanowires have been fabricated based on Fe3O4 thin films grown on α-Al2O3 (0001) substrates using the hard mask and ion milling technique. Compared with thin films, the Fe3O4 nanowire exhibits a slightly sharper Verwey transition but pronounced anisotropic magnetoresistance properties in the film plane at low magnetic field. Detailed bias-dependence study of both the conductance and magnetoresistance curves for both the thin films and nanowires suggests that the electrical conduction in magnetite near and above the Verwey transition temperature is dominated by a tunneling mechanism across antiphase boundaries.
In situ determination of the energy dependence of the high-frequency mobility in polymers
Authors: Hulea I. N. , Pronin A. V. , Brom H. B.
Published: June 2005

The high-frequency mobility (μhf) in disordered systems is governed by transport properties on mesoscopic length scales, which makes it a sensitive probe for the amount of local order. Here we present a method to measure the energy dependence of μhf by combining an electrochemically gated transistor with in situ quasioptical measurements in the subterahertz domain. We apply this method to poly([2-methoxy-5-(3′,7′-dimethylocyloxy)]-p-phenylene vinylene) and find a mobility at least as high as 0.1cm2V−1s−1.
Highly efficient top-emitting white organic electroluminescent devices
Authors: Hsu Shih-Feng , Lee Chung-Chun , Hwang Shiao-Wen , Chen Chin H.
Published: June 2005

We have developed highly efficient white top-emitting organic light-emitting devices with broad emission by modifying both the anode and cathode. To alleviate the undesirable microcavity effect and obtain “broad” white emission, a CFx-coated Ag anode and an index-matching layer (SnO2) capped on a thin Ca∕Ag cathode with a maximum transparency of 80% were employed. A top-emitting broad white-light device, based on the dual-layer architecture of light blue and yellow emitters with one of the highest EL efficiencies of 22.2cd∕A (9.6lm∕W) at 20mA∕cm2 and 7.3V with Commission Internationale d’Eclairage coordinates of (x=0.31,y=0.47), has been demonstrated.
Excessive broadening of hydrogen Balmer lines for discharge-surface interaction monitoring
Authors: Konjević N. , Majstorović G. Lj. , Šišović N. M.
Published: June 2005

A comparative study of the hydrogen Hα line shapes in titanium and stainless steel hollow cathode discharges, run with hydrogen or argon–hydrogen mixture illustrates the possibility of using the excessively broadened part of line profile for heavy particle-cathode surface interaction monitoring.
Gate oxide induced switch-on undershoot current observed in thin-film transistors
Authors: Yan Feng , Migliorato Piero , Hong Yi , Rana V. , Ishihara R. , Hiroshima Y. , Abe D. , Inoue S. , Shimoda T.
Published: June 2005

The transient drain current of the single-grain silicon thin-film transistor with gate oxide deposited by electron cyclotron resonance plasma-enhanced chemical vapor deposition has been measured by applying a square signal on the gate and a constant low voltage between source and drain. Switch-on undershoot current has been observed, which can be attributed to the motion of space charge in gate oxide. Assuming there are some mobile ions in the gate oxide, we find the drift kinetics of the ions is quite similar to the mobile protons in SiO2, as reported in the literature.
Viewpoint: Consideration of apoplastic water in plant organs: a reminder
Authors: Wardlaw Ian F.
Published: June 2005

The importance of apoplastic water was confirmed for the leaves of a range of species by a comparison of tissue solute concentrations determined by the extrapolation of water potential isotherms to 100% relative water content (symplastic solute concentration at full turgor) and concentrations derived more directly from frozen / thawed tissue, where there is dilution of the symplastic water fraction by the apoplastic water fraction. A thermocouple psychrometer was used for both water potential and solute potential measurements. Parallel measurements of the apoplastic water content, estimated by the extrapolation of pressure–volume curves to zero (1 / water potential) with a pressure chamber and measurements based on the dilution method, with a thermocouple psychrometer, showed that the two methods gave similar results. This lends support to the conclusion that water is lost from the symplast and not from the apoplast of leaves when these are subjected to increasing pressure in a pressure chamber. However, where tissues or organs are air-dried the loss of water occurs from both the symplast and apoplast. The overall data support the conclusion that the apoplastic water should not be ignored in plant water relations studies, particularly when estimating cell turgor indirectly from the difference between water potential and cell solute concentration based on the analysis of frozen / thawed tissue.
Boron response in wheat is genotype-dependent and related to boron uptake, translocation, allocation, plant phenological development and growth rate
Authors: Wimmer Monika A. , Bassil Elias S. , Brown Patrick H. , Läuchli André
Published: June 2005

Wheat genotypes often differ significantly in their response to low and high boron (B) supply, although the underlying mechanisms for such differences are poorly understood. The stable isotopes 10B and 11B were used to investigate the contribution of root retention, uptake rates, translocation and allocation of B within wheat (Triticum aestivum L.) genotypes known to differ in B response. At high B supply, the tolerant GREEK had reduced B concentrations in main shoot leaves associated with lower uptake rates and increased allocation of B to tillers. The equally tolerant BT-SCHOMBURGK exhibited high uptake rates, but accumulation was low because of rapid development, lower concentrations of soluble B in the cell sap and lower B translocation to the shoot. In WlMMC, high uptake rates, slow development, high translocation and allocation to main shoots resulted in high B accumulation and poor tolerance. Retention in roots was not substantial in any of the genotypes. The results suggest that B tolerance is multi-faceted and genotype specific. Mechanisms contributing to B tolerance include reduced uptake rates and differential translocation and allocation within plants. Additionally, plant growth rate and leaf morphology can influence B response by affecting tissue concentrations and allowing completion of plant maturation before B accumulation impairs growth. These mechanisms are expressed to different extents depending on the genotype.
Intermittent anoxia induces oxidative stress in wheat seminal roots: assessment of the antioxidant defence system, lipid peroxidation and tissue solutes
Authors: Goggin Danica E. , Colmer Timothy D.
Published: June 2005

The effects of continuous and intermittent anoxia on components of the antioxidant defence system were evaluated in the expanded zones of wheat seedling roots. Intermittent anoxia caused oxidative stress (measured by the proportion of reduced glutathione) after three cycles of anoxia–aeration. The concentration of glutathione and activities of glutathione reductase (GR) and catalase (CAT) were decreased by 50% under both continuous and intermittent anoxia. Ascorbate peroxidase (APX) activity was unaffected by anoxia but stimulated almost 2-fold during the aerated periods of intermittent anoxia. Superoxide dismutase activity was decreased by 20% under continuous anoxia but ultimately returned to aerated activities under intermittent anoxia. Membrane damage appeared to be negligible or reversible, as K+ concentrations recovered to original levels under intermittent anoxia and there was no increase in terminal lipid peroxidation products. Addition of 5 mm exogenous ascorbate to intermittently anoxic roots prevented oxidative stress and avoided the decreases in glutathione, GR and CAT. Therefore, it is likely that the oxidative stress resulted from inadequate levels of, or damage to, these two enzymes.
Performance of native and introduced grasses for low-input pastures. 1. Survival and recruitment
Authors: Waters C. M. , Garden D. L. , Smith A. B. , Friend D. A. , Sanford P. , Auricht G. C.
Published: June 2005

Differential survival and recruitment patterns are commonly ignored within plant selection and breeding programs, where attention is focused largely on selection of cultivars with high biomass and seed yields. However, in low-input situations, where fertiliser application is limited, the use of pasture species with superior survival and recruitment characteristics can offer the potential of cost-effective pasture establishment. We investigated the comparative survival and seedling recruitment of 62 native and introduced perennial grasses under low-fertility conditions within three agro-ecological zones of temperate Australia: the temperate high-rainfall pasture zone; drier mixed-farming areas and Mediterranean southern Australia. Plants were grown from seed in glasshouses and transplanted to the field as spaced plants within 6–8 weeks. At regular intervals, survival of transplanted plants and recruitment of new plants were recorded.
We found high mortality over a relatively short (24-month) period among both native and introduced grasses, despite good establishment. Frost damage at the cooler sites resulted in death of some C4 plants early in the experiment. Survival of some lines declined following the dry summer of 2000–01, and lines with best survival after this time were Eragrostis curvula cv. Consol, Austrodanthonia fulva (from Dalgety and Wagga, NSW) and Paspalidium jubiflorum (from Warren, NSW). C3 grasses, which generally had poor survival were a Microlaena stipoides selection from Nile, Tasmania, and two lines of Elymus scaber (Boorowa and Tumut, NSW). The C4 grasses Chloris truncata (Girilambone, NSW) and Dichanthium sericeum (Trangie, NSW) also exhibited poor survival, although there were exceptions at some sites.
The native lines A. caespitosa Tas2407, M. stipoides cv. Shannon and A. racemosa were the most successful recruiters. Introduced lines generally had lower recruitment, although two lines of D. glomerata from Spain recruited well at some sites. C4 lines generally had poor recruitment, including E. curvula cv. Consol, Bothriochloa macra, Themeda australis, Enteropogon acicularis, D. sericeum, P. jubiflorum and P. constrictum. The role of plants adapted to low-input situations is discussed, as well as the implications of the attributes of survival and recruitment for selection of new cultivars for these situations.
Performance of native and introduced grasses for low-input pastures. 2. Herbage production
Authors: Garden D. L. , Waters C. M. , Smith A. B. , Norton M. R. , Auricht G. C. , Kobelt E.
Published: June 2005

A total of 62 perennial grasses were evaluated for herbage production under low-fertiliser conditions at eight sites in the temperate zone of southern Australia from 1999 to 2001. A brief assessment of relative preference ranking by sheep was also made at the end of the experimental period. Four sites were in the high rainfall areas of south-east Australia, two in the drier mixed farming areas of western NSW, and two sites in Mediterranean southern Australia. Seven standard cultivars were included in the comparisons. Plants were grown from seed in glasshouses and transplanted to the field as spaced plants at 6–8 weeks age. Plants were harvested at irregular intervals by clipping to determine herbage production. Relative preference was determined by enclosing sheep in the experimental area at high stocking rates and estimating the amount of herbage grazed after 1, 3 and 5 days.
Herbage production data were analysed using a multi-environment trial approach in which the environments comprised all combinations of sites and sampling times over the 3-year period. Overall, 73.6% of the total genetic variation for herbage production was accounted for. Average seasonal comparisons revealed good herbage production from Eragrostis curvula cv. Consol in both winter and summer, but in spring, several Dactylis glomerata lines were the most productive. Consol was not generally preferred by sheep, while D. glomerata lines were. Apart from cv. Consol, C4 species, including Bothriochloa macra, Chloris truncata, Enteropogon acicularis and Dichanthium sericeum had low herbage production in winter and spring, and had low acceptability to grazing sheep. These particular grasses were also not highly ranked for production in summer, although other C4 lines, notably selections of Themeda australis, Paspalidium jubiflorum and P. constrictum were. Few native C3 grasses had superior herbage production, although selections of Elymus scaber, Austrodanthonia fulva and A. duttoniana showed good growth rates. When considering further evaluation, grasses with very high recruitment (e.g. A. caespitosa) may need to be included, and the acceptability of grasses to sheep should also be assessed.
Identification of superior native and introduced grasses for low-input pastures in temperate Australia
Authors: Sanford P. , Whalley R. D. B. , Garden D. L. , Norton M. R. , Waters C. M. , Smith A. B. , Mitchell M. L. , Kobelt E. , Friend D. A. , Hall E. , Auricht G.
Published: June 2005

This paper is the fifth in a series describing trials evaluating native and introduced grasses at eight locations across temperate Australia. In these trials, 62 perennial grass lines were assessed for herbage production, survival and recruitment under low fertiliser conditions using spaced plants produced in glass houses and transplanted into the field. Sites were grouped into three different climatic zones: Eastern Australian permanent pasture, Eastern Australian mixed farming and Mediterranean zone. For each of these zones, superior lines were identified and their potential use in permanent pastures or mixed farming discussed.
Among the C3 grasses tested, several lines of Dactylis glomerata from France on the Mediterranean coast near the Spanish border and from north-west maritime France proved to be superior lines in all zones and were better than the standard comparator cv. Currie with regard to the attributes assessed. In general, the D. glomerata lines were superior to the C3 native species except with respect to survival and recruitment.
The C4 introduced standard comparator Eragrostis curvula cv. Consol was outstanding with regard to its herbage production and survival in all climatic zones, although its recruitment was generally low. Native C4 lines of Themeda australis and Paspalidium jubiflorum yielded well in all climatic zones, and even produced more herbage than Consol in one zone. Survival rates of T. australis and P. jubiflorum were also very high but recruitment was low under the conditions of the trial.
In mixed pastures C4 grasses may reduce fluctuations in feed supply as well as increase water use. As a consequence mixtures of superior C3 and C4 lines identified in this study are likely to be suitable for pastures on infertile soils and in zones subjected to continuous or periodic drought.
Further work on the behaviour of these superior lines under sward conditions in association with forage legumes and their responses to grazing is needed; however, for the promising native lines, sward trials are not possible until suitable technology for commercial seed production and broad acre establishment of these lines has been developed.
Band Recoveries of the Magpie Goose, Anseranas semipalmata
Authors: Frith HJ
Published: June 2005

Recovery data from 107 magpie geese that had been banded near Darwin, mostly 15-20 years earlier, are summarized.

Some of the birds had dispersed throughout the subcoastal plains and to offshore islands, but there was a strong site attachment by individuals and 69% of them were recovered close to the banding place. There was evidence of considerable longevity; 11 birds were recovered more than 10 years after banding and two were recovered after almost 19 years.
Population genetic structure of the western spotted frog, Heleioporus albopunctatus (Anura:Myobatrachidae), in a fragmented landscape in south-western Australia
Authors: Davis Robert A. , Roberts J. Dale
Published: June 2005

We report on the genetic structuring of populations of a large burrowing frog, Heleioporus albopunctatus, from the central wheatbelt of Western Australia. This region has been highly fragmented by vegetation clearance for agriculture since the early 1900s. Genetic variation at four variable loci in 22 populations was analysed using cellulose acetate electrophoresis. Analysis across all populations showed a moderate, but significant, degree of subdivision (Fst = 0.087 ± 0.049, P < 0.05) and high levels of heterozygosity (H = 0.133, s.e. = 0.084). Several small populations had higher Fst values in pair-wise comparisons. A mantel test revealed no significant relationship between genetic distance and geographic distance (r = –0.136, P = 0.34) and this, combined with data from multidimensional scaling analyses, suggests that geographic isolation of populations is not a significant determinant of genetic structuring. Despite this, the presence of high levels of subdivision as a result of the erosion of genetic diversity indicates that regional persistence may be dependent on the maintenance of metapopulation structures that allow gene flow.
Swe1 regulation and transcriptional control restrict the activity of mitotic cyclins toward replication proteins in
Saccharomyces cerevisiae
Authors: Hu Fangfang , Aparicio Oscar M.
Published: June 2005

Cyclin-dependent kinases (CDKs) drive the cell cycle through the phosphorylation of substrates that function in genome duplication and cell division. The existence of multiple cyclin subunits and their distinct cell cycle-regulated expression suggests that cyclins impart unique specificities to CDK–substrate interactions that are critical for normal cellular function. This study shows that the combination of early cell cycle expression and deletion of the CDK inhibitor Saccharomyces Wee1 (Swe1) enables the mitotic B-type (Clb) cyclins Clb2, Clb3, and Clb4 of
Saccharomyces cerevisiae
to initiate S phase with similar effectiveness as the S-phase cyclin Clb5. Although
in vivo
analysis indicates preferential phosphorylation of a replication substrate by Clb5-Cdk1, this difference is relatively minor compared with the impact of transcriptional control and Swe1 regulation. Indeed, early expressed Clb2-Cdk1 can activate all essential Clb-Cdk substrates in a strain lacking all other Clbs and Swe1. Thus, Swe1 regulation and expression timing are key mechanisms that sequester the broad activity of Clb2-Cdk1 from critical substrates. Furthermore, the ability of Swe1 to inhibit the activity of different B-type cyclins in replication initiation correlates with the normal expression timing of those cyclins, with no apparent
in vivo
inhibition of Clb5 and Clb6, moderate inhibition of Clb3 and Clb4, and strong inhibition of Clb2. Hence, Swe1 appears to reinforce the temporal activity of cyclins established through transcriptional control. The conserved nature of CDK function suggests that similar mechanisms regulate CDK specificity in multicellular organisms.
Molecular electronics: Some views on transport junctions and beyond
Authors: Joachim Christian , Ratner Mark A.
Published: June 2005

The field of molecular electronics comprises a fundamental set of issues concerning the electronic response of molecules as parts of a mesoscopic structure and a technology-facing area of science. We will overview some important aspects of these subfields. The most advanced ideas in the field involve the use of molecules as individual logic or memory units and are broadly based on using the quantum state space of the molecule. Current work in molecular electronics usually addresses molecular junction transport, where the molecule acts as a barrier for incoming electrons: This is the fundamental Landauer idea of “conduction as scattering” generalized to molecular junction structures. Another point of view in terms of superexchange as a guiding mechanism for coherent electron transfer through the molecular bridge is discussed. Molecules generally exhibit relatively strong vibronic coupling. The last section of this overview focuses on vibronic effects, including inelastic electron tunneling spectroscopy, hysteresis in junction charge transport, and negative differential resistance in molecular transport junctions.
Scanning tunneling microscopy experiments on single molecular landers
Authors: Moresco Francesca , Gourdon André
Published: June 2005

Molecular landers are molecules comprising of a central rigid molecular wire maintained above a metallic surface by organic spacers, which allows specific ultrahigh vacuum-scanning tunneling microscopy experiments to be performed at the single-molecule level. The understanding of the molecule–surface interactions, intramolecular mechanics, and the possibility to perform extremely precise tip-induced manipulation permit these molecules to be brought in contact with a nanoelectrode and the resulting electronic interaction to be analyzed in well controlled conditions.