bluuebunny/crossref_metadata_2025 huggingface dataset:
A molecular-dynamics simulation study of solvent-induced repulsion between C60 fullerenes in water
Authors: Li Liwei , Bedrov Dmitry , Smith Grant D.
Published: November 2005

Molecular-dynamics simulations of a single C60 fullerene and pairs of C60 fullerenes in aqueous solution have been performed for the purpose of obtaining improved understanding of the nature of solvent-induced interactions between C60 fullerenes in water. Our simulations reveal repulsive solvent-induced interactions between two C60 fullerenes in aqueous solution in contrast to the associative effects observed for conventional nonpolar solutes. A decomposition of the solvent-induced potential of mean force between fullerenes into entropy and energy (enthalpy) contributions reveals that the water-induced repulsion between fullerenes is energetic in origin, contrasting strongly to entropy-driven association observed for conventional nonpolar solutes. The dominance of energy in the solvent-induced interactions between C60 fullerenes arises primarily from the high atomic density of the C60 molecule, resulting in strong C60-water van der Waals attraction that is reduced upon association of the fullerenes. The water-induced repulsion is found to decrease with increasing temperature due largely to an increasing contribution from a relatively weak entropy-driven association.
Direct deperturbation analysis of the AΠ2∼BΣ+2 complex of LiAr7,6 isotopomers
Authors: Meshkov Vladimir V. , Pazyuk Elena A. , Zaitsevskii Andrei , Stolyarov Andrey V. , Brühl Rüdiger , Zimmermann Dieter
Published: November 2005

Direct deperturbation analysis of the highly accurate experimental rovibronic term values of the AΠ2∼BΣ+2 complex of LiAr [R. Brühl and D. Zimmermann, J. Chem. Phys. 114, 3035 (2001)] has been performed in the framework of inverted close-coupling approach implicitly adjusted to the unified treatment of the overall A∼B coupling effect without reducing the rovibrational dimensionality. The nonlinear fitting procedure was supported by the ab initio calculations on the spin-orbit and angular coupling matrix elements between the lowest XΣ+2, AΠ2, and BΣ+2 states. The analytical grid mapping based on the reduced variable representation of the radial coordinate r was used to improve the efficiency of the solution of the close-coupling radial equations near the dissociation limit. The mutual A∼X perturbation effect on the AΠ2 term values and spin-rotation splitting of the ground state were evaluated for both LiAr7,6 isotopomers. The resulting empirical potential-energy curves for the adiabatic AΠ2 and BΣ+2 states, along with the refined r-dependent nonadiabatic matrix elements, reproduce the total rovibronic structure of the LiAr7 complex with the standard deviation of 0.003cm−1. The mass invariance of the deperturbed electronic parameters was confirmed by the calculation of the rovibronic term values of the LiAr6 isotopomer which coincided with their experimental counterparts within 0.004cm−1.
Experimental evidences for two paths in the dissolution process of B clusters in crystalline Si
Authors: De Salvador D. , Napolitani E. , Bisognin G. , Carnera A. , Bruno E. , Mirabella S. , Impellizzeri G. , Priolo F.
Published: November 2005

We show that B clusters, produced by self-interstitial interaction with substitutional B in crystalline Si, dissolve under annealing according to two distinct paths with very different characteristic times. The two regimes generally coexist, but while the faster dissolution path is predominant for clusters formed at low B concentration (1×1019B∕cm3), the slower one is characteristic of clusters formed above the solubility limit and dominates the dissolution process at high B concentration (2×1020B∕cm3). The activation energies of both processes are characterized and discussed. It is showed that the faster path can be connected to mobile B direct emission from small clusters, while the slower path is demonstrated not to be self-interstitial limited and it is probably related to a more complex cluster dissolution process.
Near-UV photodissociation of oriented CH3I adsorbed on Cu(110)–I
Authors: Jensen E. T.
Published: November 2005

Methyl iodide adsorbed on a Cu(110)–I surface has been found to be highly orientationally ordered. We have exploited this orientation to select different CH3I excited states for photodissociation by using polarized near-UV light at wavelengths of 308, 248, and 222nm. Using p-polarized light at all three wavelengths, we find that dissociation proceeds largely via the Q03 state, consistent with the picture from gas-phase photolysis. In contrast, using s-polarized light we find contributions from the Q13 state at λ=308nm, the Q11 state at λ=248nm, and the (E,1) state at λ=222nm—the latter being a state that has not been implicated in gas-phase studies of CH3I A-band photolysis. We also note the contribution to surface photodissociation from low-energy photoelectrons causing dissociative electron attachment to adsorbed CH3I and have identified the promotion of direct photodissociation pathways during λ=308nm photolysis.
Ab initiocalculation of interatomic decay rates by a combination of the Fano ansatz, Green’s-function methods, and the Stieltjes imaging technique
Authors: Averbukh Vitali , Cederbaum Lorenz S.
Published: November 2005

A new computational technique is introduced for the ab initio calculation of the rates of interatomic and intermolecular nonradiative decay processes occurring due to electronic correlation. These recently discovered phenomena are described theoretically using the configuration-interaction formalism first introduced by Fano [Phys. Rev. 124, 1866 (1961)] and later adapted to an Auger decay by Howat et al. [J. Phys. B 11, 1575 (1978)]. The boundlike and the continuumlike components of the wave function of the decaying state are constructed using a Green’s-function method known as algebraic diagrammatic construction. A combination of atomic and distributed Gaussian basis sets is shown to provide an adequate description of both boundlike and continuumlike wave-function components. The problem of the normalization of the continuum (final state) wave function is addressed using the Stieltjes imaging technique. The new method is applied to the calculation of the rates of interatomic decay in alkaline-earth–rare-gas clusters. The obtained results help to verify our earlier conclusions [Phys. Rev. Lett. 93, 263002 (2004)] regarding the validity of the virtual-photon transfer model for the interatomic Coulombic decay. In addition, we demonstrate that the process of electron-transfer-mediated decay is responsible for the finite lifetimes of the outer valence vacancies in alkaline-earth–rare-gas clusters.
Raman spectroscopy of PbI2-filled double-walled carbon nanotubes
Authors: Sendova Mariana , Flahaut Emmanuel , DeBono Bryan
Published: November 2005

PbI 2 -filled double-walled carbon nanotubes (PbI2@DWCNTs) have been studied by Raman spectroscopy employing a 785 nm excitation wavelength and their spectra have been compared to those of pristine double-walled carbon nanotubes (DWCNTs). The DWCNTs were synthesized by catalytic chemical-vapor deposition. Assignment of the radial breathing modes and the tangential modes was done based on the one-dimensional electronic energy-band structure of carbon nanotubes. It was established that PbI2@DWCNTs can be unambiguously identified by the position of the second-order G′ band and its rate of downshift due to power-density increase of the excitation radiation. After laser-assisted disintegration of the PbI2@DWCNTs the PbI2 band has been detected and compared to those of the powder PbI2. The one-dimensional PbI2 crystal chains show downshifted Raman bands as compared to those of the powder material.
Surface plasmon routing along right angle bent metal strips
Authors: Weeber J.-C. , González M. U. , Baudrion A.-L. , Dereux A.
Published: November 2005

An efficient routing of surface plasmon polaritons (SPP) is of fundamental importance in the development of SPP-based photonics. This paper reports that microgratings acting as Bragg mirrors can guide SPP along metal stripes waveguides featuring 90° bents. The measurement of the mirrors efficiency, performed by means of photon scanning tunneling microscopy, shows that bent losses as low as 1.9dB can be achieved. Finally, we demonstrate operating SPP beamsplitters obtained by an appropriate design of the Bragg mirrors constituting elements.
Large eddy simulation of stably stratified open channel flow
Authors: Taylor John R. , Sarkar Sutanu , Armenio Vincenzo
Published: November 2005

Large eddy simulation has been used to study flow in an open channel with stable stratification imposed at the free surface by a constant heat flux and an adiabatic bottom wall. This leads to a stable pycnocline overlying a well-mixed turbulent region near the bottom wall. The results are contrasted with studies in which the bottom heat flux is nonzero, a difference analogous to that between oceanic and atmospheric boundary layers. Increasing the friction Richardson number, a measure of the relative importance of the imposed surface stratification with respect to wall-generated turbulence, leads to a stronger, thicker pycnocline which eventually limits the impact of wall-generated turbulence on the free surface. Increasing stratification also leads to an increase in the pressure-driven mean streamwise velocity and a concomitant decrease in the skin friction coefficient, which is, however, smaller than in the previous channel flow studies where the bottom buoyancy flux was nonzero. It is found that the turbulence in any given region of the flow can be classified into three regimes (unstratified, buoyancy-affected, and buoyancy-dominated) based on the magnitude of the Ozmidov length scale relative to a vertical length characterizing the large scales of turbulence and to the Kolmogorov scale. Since stratification does not strongly influence the near-wall turbulent production in the present configuration, the behavior of the buoyancy flux, turbulent Prandtl number, and mixing efficiency is qualitatively different from that seen in stratified shear layers and in channel flow with fixed temperature walls, and, furthermore, collapse of quantities as a function of gradient Richardson number is not observed. The vertical Froude number is a better measure of stratified turbulence in the upper portion of the channel where buoyancy, by providing a potential energy barrier, primarily affects the transport of turbulent patches generated at the bottom wall. The characteristics of free-surface turbulence including the kinetic energy budget and pressure-strain correlations are examined and found to depend strongly on the surface stratification.
Switching of submicron-sized, antiferromagnetically coupled CoFeB∕Ru∕CoFeB trilayers
Authors: Wiese N. , Dimopoulos T. , Rührig M. , Wecker J. , Reiss G.
Published: November 2005

This work reports on the magnetic reversal of submicron-sized elements consisting of an CoFeB∕Ru∕CoFeB artificial ferrimagnet (AFi). The elements were patterned into ellipses having a width of approximately 250–270 nm and a varying aspect ratio between 1.3 and 8. The coercivity was found to decrease with an increasing imbalance of the magnetic moment of the two antiferromagnetically coupled layers and is therefore strongly affected by an increase of effective anisotropy due to the antiferromagnetic coupling of the two layers. With respect to a single layer of amorphous CoFeB, patterned in comparable elements, the AFi has an increased coercivity. Switching asteroids comparable to single layers were only observed for samples with a high net moment.
Morphology-dependent exciton emission and energy transfer in fluorene-polymer-related fluorescent and phosphorescent composite films spin cast from a mixture of two dissimilar organic solvents
Authors: Wu Yue , Hu Bin , Howe Jane
Published: November 2005

We report morphology-dependent exciton emission and energy transfer in fluorene-conjugated polymer poly(9,9-dioctylfluorenyl-2,7-diyl)-related fluorescent and phosphorescent materials by using a mixture of two dissimilar organic solvents for spin-cast film formation. The electron microscopic characterizations revealed that the mixture of a high-boiling-point orthodichlorobenzene and a low-boiling-point chloroform results in a formation of both crystalline and amorphous morphological structures in fluorene-conjugated polymers. The UV-visible absorption and photoluminescence studies indicated that the low-energy crystalline phase domains, randomly distributed in the continuous high-energy amorphous phase, function as potential quantum wells. As a consequence, the mixture of two dissimilar organic solvents significantly affects the exciton emission from fluorescent fluorene-conjugated polymer and the energy transfer in phosphorescent composite of fluorene polymer and iridium complex molecules, presenting a pathway to control fluorescent and phosphorescent processes in polymer light-emitting materials.
6-H single-crystal silicon carbide thermo-optic coefficient measurements for ultrahigh temperatures up to 1273 K in the telecommunications infrared band
Authors: Riza Nabeel A. , Arain Muzzamil , Perez Frank
Published: November 2005

6H single-crystal silicon carbide (SiC) is an excellent optical material for extremely high temperature applications. Furthermore, the telecommunication infrared band (e.g., 1500–1600 nm) is an eye safe and high commercial maturity optical technology. With this motivation, the thermo-optic coefficient ∂n∕∂T for 6H single-crystal SiC is experimentally measured and analyzed from near room temperature to a high temperature of 1273 K with data taken at the 1550 nm wavelength. Specifically, the natural étalon behavior of 6-H single-crystal SiC is exploited within a simple polarization-insensitive hybrid fiber-free-space optical interferometric system to take accurate and rapid optical power measurements leading to ∂n∕∂T data. The reported results are in agreement with the previously reported research at the lower <600K temperatures.
Optical absorption properties of Mg-doped GaN nanocolumns
Authors: Iwanaga Takeshi , Suzuki Toshihiko , Yagi Shigeru , Motooka Teruaki
Published: November 2005

Optical properties of GaN nanocolumnar films with and without Mg doping are characterized in the visible and ultraviolet regions. Strong uniaxial anisotropy of dielectric constants is observed by ellipsometry. The complex dielectric functions determined from the reflectance and transmittance spectra showed that the ε2 value is found to be reduced by approximately 50% of that of the epitaxial-GaN film in the energy range above the band gap regardless of Mg doping. This anisotropy and reduction in dielectric constants are due to polarization fields of nanocolumnar crystallites and their interactions. The absorption in undoped GaN nanocolumnar film extends below the band gap of epitaxial GaN, probably due to defects in the nanocolumnar film. Further extension of the absorption tail by Mg doping can be attributed to the transition from a Mg-acceptor level detected in the cathodoluminescence spectra from Mg-doped samples.
Photonic band structure of ZnO photonic crystal slab laser
Authors: Yamilov A. , Wu X. , Cao H.
Published: November 2005

We recently reported on the realization of ultraviolet photonic crystal laser based on zinc oxide [Appl. Phys. Lett. 85, 3657 (2004)]. Here we present the details of structural design and its optimization. We develop a computational supercell technique that allows a straightforward calculation of the photonic band structure of ZnO photonic crystal slab on sapphire substrate. We find that despite the small index contrast between the substrate and the photonic layer, the low-order eigenmodes have predominantly transverse-electric (TE) or transverse-magnetic polarization. Because emission from ZnO thin film shows a strong TE preference, we are able to limit our consideration to TE bands, spectrum of which can possess a complete photonic band gap with an appropriate choice of structure parameters. We demonstrate that the geometry of the system may be optimized so that a sizable band gap is achieved.
Surface compositional gradients of InAs∕GaAs quantum dots
Authors: Biasiol G. , Heun S. , Golinelli G. B. , Locatelli A. , Mentes T. O. , Guo F. Z. , Hofer C. , Teichert C. , Sorba L.
Published: November 2005

With laterally resolved photoemission spectroscopy, we obtained In and Ga surface concentration maps of InAs∕GaAs quantum dots. Our data demonstrate that the dot composition is neither pure InAs nor homogeneous InxGa1−xAs, but presents an In concentration increasing from the borders to the center of the dots. Besides, our observations suggest strong In segregation (x∼0.9) on the surface of the dots and of the surrounding wetting layer. Such segregation, well known for two-dimensional InAs∕GaAs growth, had not been directly observed so far on the dots, and should be taken into account to model size and composition of GaAs-overgrown structures.
Low frequency noise in silicon nanogaps
Authors: Berg Jonas , Lundgren Per , Enoksson Peter , Bengtsson Stefan
Published: November 2005

Silicon nanogaps are contact structures for connecting organic molecules. An insulating layer is removed by etching, and this dramatically increases the current levels and the noise, which closely resembles a 1∕f law and scales with the square of the current. After etching, the noise level at 30Hz and 10nA is in the order of 10−21A2∕Hz, which is more than two orders of magnitude larger than before etching. We model the noisy behavior by several percolation paths in parallel at the etched surface between the electrodes, and compare it with soft breakdown in thin oxide.
Time-of-flight system with a movable ion detector for absolute measurement of cyclotron beam energy
Authors: Okumura S. , Kurashima S. , Miyawaki N. , Yoshida K. , Fukuda M.
Published: November 2005

A time-of-flight system for determining the absolute energy of ion beams has been developed for the azimuthally varying field (AVF) cyclotron at Japan Atomic Energy Agency (JAEA). Ion detectors, a microchannel-plate detector and a plastic scintillation detector, were applied to the system in order to achieve high time resolution measurement of the flight time and to cover a wide range of beam intensity in combination with a beam attenuator. The change of the flight length, performed by moving the plastic scintillation detector with flexible bellows, allows determination of the mean beam energy only from the relative measurement of the flight time and the flight length without knowing their absolute values. A maximum movable distance of 2m yields the difference in the time of flight from 16to94ns for the energy range of ion beams accelerated by the JAEA AVF cyclotron. The time-of-flight system even with the 2m change in the flight length achieves accurate energy determination of the order of 0.1%, since the relative measurement has an advantage of elimination of the uncertainties in determination of the time zero and the length zero. The time-of-flight measurement with the relative measurement also allows estimation of the beam energy spread without conventional expensive systems such as a magnetic spectrometer. By comparing the widths of the time-of-flight spectra of ions accumulated at different flight lengths, we have estimated the energy spread. In order to reduce the labor process of the coincidence detection of ions in the time-of-flight measurement, we have also accomplished a simple estimation method for mean beam energy determination with a beam bunch, naturally modulated with the acceleration RF of the cyclotron. The mean beam energy has been obtained from the shift of the beam bunch centroids at different flight lengths in the time-of-flight spectrum.
Large anisotropy of ferroelectric and dielectric properties for Bi3.15Nd0.85Ti3O12 thin films deposited on Pt∕Ti∕SiO2∕Si
Authors: Lu C. J. , Qiao Y. , Qi Y. J. , Chen X. Q. , Zhu J. S.
Published: November 2005

Polycrystalline Bi3.15Nd0.85Ti3O12 (BNdT) thin films of a-axis preferential orientation [α(100)=62%] and high c-axis orientation [α(001)=96%] were fabricated directly on Pt∕Ti∕SiO2∕Si substrates through a sol-gel process. We observed strong dependences of ferroelectric and dielectric properties on the film orientation, with a remanent polarization 2Pr of 39μC∕cm2 and dielectric constant εr of 343 at 100 kHz in the a-axis oriented film; 2Pr of 20μC∕cm2 and εr of 331 in the film of random orientation; and 2Pr of 13μC∕cm2,εr of 218 in the highly c-axis oriented film. Furthermore, the 2Pr value of a purely a-axis-oriented BNdT film can be predicted to be ∼51μC∕cm2. The large anisotropy of 2Pr and εr values demonstrates that the polarization vector of BNdT is close to the a axis.
Phonon localization in periodic uniaxially nanostructured silicon
Authors: Cloutier Sylvain G. , Guico Rodney S. , Xu Jimmy M.
Published: November 2005

Phonon spectroscopy of low-dimensional silicon nanostructures may help identify and understand their unique physical properties for potentially enabling new applications. High-resolution Raman spectroscopy reveals that fabrication of such nanostructures can lead to the creation of nanosize crystallites at the silicon interface due to the introduction of defect centers which is most likely responsible for local crystal-symmetry breaking and phonon localization. By examining these nanocrystallites created in periodic crystalline silicon nanodot arrays formed in silicon-on-insulator and their dispersive and power-dependent phonon spectra, we found clear evidence of spatial phonon localization, which in turn suggests a breaking of the fundamental phonon-selection rule limiting radiative recombination in silicon’s indirect band structure.
Predicting ionic conductivity of solid oxide fuel cell electrolyte from first principles
Authors: Pornprasertsuk Rojana , Ramanarayanan Panchapakesan , Musgrave Charles B. , Prinz Fritz B.
Published: November 2005

First-principles quantum simulations complemented with kinetic Monte Carlo calculations were performed to gain insight into the oxygen vacancy diffusion mechanism and to explain the effect of dopant composition on ionic conductivity in yttria-stabilized zirconia (YSZ). Density-functional theory (DFT) within the local-density approximation with gradient correction was used to calculate a set of energy barriers that oxygen ions encounter during migration in YSZ by a vacancy mechanism. Kinetic Monte Carlo simulations were then performed using Boltzmann probabilities based on the calculated DFT barriers to determine the dopant concentration dependence of the oxygen self-diffusion coefficient in (Y2O3)x(ZrO2)(1−2x) with x increasing from 6% to 15%. The results from the simulations suggest that the maximum conductivity occurs at 7–9mol% Y2O3 at 600–1500K and that the effective activation energy increases at higher Y doping concentrations in good agreement with previously reported literature data. The increase in the effective activation energy for migration arises from the higher-energy barrier for oxygen vacancy diffusion across an Y–Y common edge relative to diffusion across one with a Zr–Y common edge of two adjacent tetrahedra. The binding energies between oxygen vacancies and dopants were extracted up to the fourth nearest-neighbor interaction. Our results reveal that the binding energy is the strongest when the vacancy is in the second nearest-neighbor position relative to the Y dopant atom. The methodology was also applied to scandium-doped zirconia (SDZ). Preliminary results from quantum simulations of SDZ suggest that the effective activation energy for vacancy diffusion in SDZ is lower than that of YSZ, in agreement with experimental observations. The agreement with experimental studies on the two systems analyzed in this paper supports the use of this technique as a predictive tool on electrolyte systems not yet characterized experimentally.
Impact ionization in strained Si devices
Authors: Nicholas G. , Grasby T. J. , Parker E. H. C. , Whall T. E. , Skotnicki T.
Published: November 2005

Impact ionization in biaxial tensile strained Si n and p metal-oxide-semiconductor field-effect transistors is investigated. Despite the smaller band gap and higher carrier mobility in strained Si, no evidence for significantly increased impact ionization is found. This is attributed to the reduced density of states in strained Si, brought about by strain-induced band splitting, limiting the opportunities for scattering.
Formation and evolution of self-assembled crystalline Si nanorings on (001) Si mediated by Au nanodots
Authors: He J. H. , Wu W. W. , Chueh Y. L. , Hsin C. L. , Chen L. J. , Chou L. J.
Published: November 2005

The growth of high-density Si nanorings has been achieved on ultrathin Au films on silicon substrate. Nanorings, which are gold-free and epitaxially grown on (001) Si, had a narrow distribution of height and diameter of 1.4±0.3 and 24.9±4.0nm, with a density of 4.3×1010cm−2. In situ ultrahigh-vacuum transmission electron microscopy revealed that the formation of nanorings involves a mechanism mediated by Au nanodots and evaporation of Au-Si eutectic liquid droplets at high temperature. The process promises to be an effective nanofabrication technique to produce high-density and uniform-sized nanorings.
Oxygen segregation to dislocations in GaN
Authors: Hawkridge M. E. , Cherns D.
Published: November 2005

The structure and composition of threading dislocations in GaN grown by hydride vapor phase epitaxy have been examined by electron microscopy. Transmission electron microscopy showed that the core structure of screw dislocations varied widely, alternating irregularly between open core (“nanopipe”) and closed core structures, with evidence that the equilibrium structure was a closed core configuration. A combination of electron energy loss spectroscopy and atomic resolution imaging in the scanning transmission electron microscope showed that the surfaces of nanopipes had 1.7±0.3 monolayers of nitrogen substituted by oxygen, and that closed core dislocations showed little evidence of oxygen segregation. It is argued that these results support a model where nanopipe formation is controlled by the segregation of oxygen by surface diffusion to surface pits, rather than dislocations per se. The implications for understanding the electronic properties of dislocations in GaN are discussed.
Reversible electromechanical characteristics of individual multiwall carbon nanotubes
Authors: Semet V. , Binh Vu Thien , Guillot D. , Teo K. B. K. , Chhowalla M. , Amaratunga G. A. J. , Milne W. I. , Legagneux P. , Pribat D.
Published: November 2005

Here we report the reversible change in the nonlinear conductance of a multiwall carbon nanotube (MWNT) when it is bent longitudinally. As the nanotube is compressed and bent, its resistance decreases dramatically. This behavior is fully recoverable. The observed drop in resistance during bending must be the result of increasing number of conduction channels in the nanotube and parallel transport through them. Using this concept of parallel transport, we show that it is indeed possible to electrically model the behavior of the MWNT under compression. The reversible electrical characteristics of a MWNT under bending opens new possibilities for these structures to be applied as nanoscale displacement sensors.
Epitaxial, ferromagnetic Cu2−xMnxO films on (001) Si by near-room-temperature electrodeposition
Authors: Liu Y. L. , Harrington S. , Yates K. A. , Wei M. , Blamire M. G. , MacManus-Driscoll J. L. , Liu Y. C.
Published: November 2005

∼ 1 micron thick Cu2−xMnxO films were grown both on Au-coated and uncoated (001) Si from sulphate solutions at 60°C, several hundred degrees lower than normally used for growth of dilute magnetic semiconductors. The Mn concentration in the films was controlled very sensitively by controlling both the ratio of Mn:Cu in solution and the deposition potential. An optimum Mn concentration of 0.3% in the films produced saturation magnetization values of 0.6μB∕Mn at room temperature. The Cu2−xMnxO films were semiconducting with resistivitity value lower than the undoped film. Photoluminscence measurements showed that Mn substitutes on the Cu lattice sites.
Rectifying properties of the YBa2Cu3O7−δ∕SrTiO3:Nb heterojunction
Authors: Sun J. R. , Xiong C. M. , Zhang Y. Z. , Shen B. G.
Published: November 2005

A heterojunction has been fabricated by growing a YBa2Cu3O7−δ (YBCO) film of the thickness of 1000Å on a 0.5wt%Nb-doped SrTiO3 (STON) crystal, and its resistive behavior was experimentally studied. The strong asymmetry of the current-voltage (I–V) relation with respect to bias polarity indicates an excellent rectifying property of the junction in the whole temperature range studied. The superconducting transition of YBCO causes a visible reduction of diffusion potential, measured by the forward voltage corresponding to the current rush in the I–V curves, though the general rectifying behavior remains unchanged. This is possibly a result of the variation of the Fermi level of YBCO relative to that of STON, and suggests an alternative technique detecting the effects of superconducting transition in YBCO.
Synthesis of high-purity samples of CrO2 by a simple route
Authors: Bajpai A. , Nigam A. K.
Published: November 2005

Practical applications of the spintronic material CrO2 have been limited, primarily because of the difficulty in its synthesis, as it is not known to form in ambient pressures in a pure form. Here we show that CrO2 can be prepared by a simple route that bypasses the need to either apply any external pressure or measure and control it during synthesis. These samples not only exhibit saturation magnetization (MS) values close to the theoretical predicted one, but also exhibit a substantially enhanced grain size, at least an order of magnitude larger as compared to that reported prior to this work. In addition, the method provides some easy steps to tune the grain size and grain boundary density, thus enabling an investigation of this technologically important material in hitherto unexplored microstructural regimes.
Fabrication and characterization of electrostatic Si∕SiGe quantum dots with an integrated read-out channel
Authors: Sakr M. R. , Jiang H. W. , Yablonovitch E. , Croke E. T.
Published: November 2005

A nontraditional fabrication technique is used to produce quantum dots with read-out channels in silicon/silicon–germanium two-dimensional electron gases. The technique utilizes Schottky gates, placed on the sides of a shallow etched quantum dot, to control the electronic transport process. An adjacent quantum point contact gate is integrated to the side gates to define a read-out channel, and thus allow for noninvasive detection of the electronic occupation of the quantum dot. Reproducible and stable Coulomb oscillations and the corresponding jumps in the read-out channel resistance are observed at low temperatures. The fabricated dot combined with the read-out channel represents a step toward the spin-based quantum bit in Si∕SiGe heterostructures.
Corrigendum to: Recolonization by the mountain galaxias Galaxias olidus of a montane stream after the eradication of rainbow trout Oncorhynchus mykiss
Authors: Lintermans Mark
Published: November 2005

The introduced salmonid
Oncorhynchus mykiss was eradicated by use of the
piscicide rotenone from a section of small montane stream upstream of an
impassable barrier. Recolonization of the stream both above and below the
barrier by the native Galaxias olidus was monitored
annually for four successive years. Following trout eradication,
G. olidus recolonized the trout-free stream section
above the barrier but was never detected below the barrier where trout still
occurred. Initial colonization was by juvenile G. olidus
but a successful breeding population had established three years after trout
eradication. The implications of the use of barriers and targeted eradication
programmes are discussed for the management of small, threatened fish species.
The FAO definition of sustainable development and the Code of Conduct for Responsible Fisheries: an analysis of the related principles, criteria and indicators
Authors: Garcia Serge M.
Published: November 2005

In 1988, FAO adopted its definition of
sustainable development. In 1995 it adopted a Code of Conduct for Responsible
Fisheries, which offers an integrated comprehensive framework for the
sustainable development of fisheries and aquaculture. The paper analyses
briefly the correspondence between the principles contained in the definition
and the provisions contained in the Code. It shows that both texts represent a
sustainability framework (with different degree of detail) and identifies the
main criteria and indicators implicitly or explicitly called for in both the
FAO definition and Code of Conduct.
Corrigendum to: Ocean currents and the larval phase of Australian western rock lobster, Panulirus cygnus
Authors: Griffin David A. , Wilkin John L. , Chubb Chris F. , Pearce Alan F. , Caputi Nick
Published: November 2005

The return of Panulirus cygnus larvae to the coast of
Western Australia after nearly a year at sea and its modulation by ocean
currents were addressed with an individual-based larval-transport model. The
simulations implied that offshore wind-driven transport of larvae is balanced
by onshore geostrophic flow. Additional simulations revealed that vertical
migration behaviour was essential to larval survival through its impact on
advection. The six years simulated include two of high, two of low, and two of
average puerulus settlement. The most robust interannual difference of the
simulations was that, when coastal sea level was low and the Leeuwin Current
was weak, more early-stage larvae were lost to the north and west under the
influence of the wind. Conversely, many late-stage model larvae were carried
south of the fishery in years when the Leeuwin Current was strong. The
fraction of model larvae remaining or arriving offshore of the fishery and
metamorphosing was essentially constant from year to year, so the variation in
observed puerulus settlement was not explained by the model. The results imply
that the nonadvective effects of fluctuations in the Leeuwin (e.g., on
temperature and primary production) were primarily responsible for the high
variation in natural settlement.
Studies on Age, Growth, and Life History of the Pilchard, Sardinops neopilchardus (Steindachner), in Southern and Western Australia
Authors: Blackburn JM
Published: November 2005

The biology of the unexploited Australian pilchard, Sardinops neopilchardus (Steindachner), was studied from a limited material available from Victorian, Tasmanian, South Australian, and Western Australian waters. This completes the preliminary study of the species over almost the whole of its sub-continental range. In Victorian waters, the surface shoaling season is spring and summer, in South Australia, summer and autumn, and in southern Western Australia, autumn and winter; these are the spawning seasons for the respective areas. In New South Wales and Queensland waters, the shoaling season is autumn to spring, which is again a spawning period. The situation in Tasmania, where the species is rare, is probably similar to that in Victoria. On the west coast of Australia, where the species extends northward to the Tropic of Capricorn (as it also does in the east) the seasonal distribution is not clear. In all these areas pilchard occurrences are virtually limited to the bay and neritic waters. Victorian pilchards attain mean standard lengths of about 8.0, 10.5, 12.5, 14.0, and 15.5 cm. at the ages of one, two, three, four, and five years respectively. This growth rate is considerably lower than that in New South Wales. In southern Western Australia the growth rate is intermediate between the other two, but in South Australia it was not established. The average size of pilchards in the seasonal shoals appears to be greater in Western Australia
than elsewhere, but no fish over 19.5 cm. standard length (9.0 in. total length) has been encountered in any of the current Australian investigations. Sexual maturity occurs earlier in Victoria than in New South Wales, sometimes at one year of age. The ring pattern of Australian pilchard scales is complex, involving yearly, spawning, and secondary rings. A hypothesis to account for the formation of spawning rings is outlined, and an earlier hypothesis relating to yearly rings is abandoned. Secondary rings occur on most scales from the same fish. In all waters the season of ring formation coincides with that of surface availability of fish, but in Victoria it is also the growing season, which makes age determination particularly difficult. The fish-length/scale-length relationship for Victorian material is of the same linear type as for New South Wales, but there are differences in the size of scales taken from the same area of the body. The possible influences of distribution, size, and condition of fish on future economic exploitation are discussed.
The New South Wales Tiger Flathead, Neoplatycephalus macrodon (Ogilby). I. Biology and Age Determination
Authors: Fairbridge WS
Published: November 2005

In a previous paper the catch statistics of the east Australian trawl fishery (Fairbridge 1948) were discussed, and in the present work, the biology of the most important species, the tiger flathead, is examined in greater detail. An age determination technique is developed for this species, and the age composition of the catch of recent years is analysed. The sampling technique carried out at the Sydney Fishmarkets is described and tested. The results are given of the first experimental trawling in Australian waters using a fine-meshed cover on the codend. The biology of the species is studied, chiefly from the point of view of establishing the age determination technique and the final analysis of the catch. Spawning is protracted, lasting throughout the six warmer months, and takes place throughout the geographical range of the species. The males spawn first in their second year, the females in their third or fourth. The "condition" (K) of the gutted fish is lowest in February, after spawning. It is probable that there is a single, genetically uniform stock, with a single centre of maximum occurrence. The younger age-groups probably do not undertake extensive coastwise movement; as a result, local areas are liable to become relatively depopulated by heavy fishing. The method of collecting and reading the flathead otolith is described. The otolith is found to grow isauxetically above a fish-length of 10 cm., and the technique of back-calculation is therefore used as an aid in age determina- tion. The otolith in this species is certainly not as clear to interpret as that of the North Sea plaice, but is probably comparable with that of the cod or hake.
Races and Populations of the Australian Pilchard, Sardinops neopilchardus (Steindachner)
Authors: Blackburn M
Published: November 2005

The evidence of taxonomic differentiation in the Australian pilchard is reviewed. Three major groups (called races), located respectively in eastern, south-eastern, and south-western Australian waters, are distinguished by differences in growth rate. The boundary zone of the two former is near the New South Wales-Victoria bolder, but it is not certain to which of the two latter races the South Australian fish belong. The two former races are sukdivided into smaller, more or less separate stocks (populations), which are distinguished mainly by differences in mean number of vertebrae and in abundance fluctuations. There are at least two such groups in the eastern race, which meet between Port Jackson and Jervis Bay, and at least two in the south-eastern race. The pilchards of Cook Strait, New Zealand, are probably distinct from those of any Australian locality.
Stomach Contents of New Zealand Inland Shags
Authors: Dickinson P
Published: November 2005

Twenty-nine stomachs of the large black shag (Phalacrocorax carbo (Linn.)) and 61 of the white-throated or little pied shag (P. brevirostris (Gould)) from the Rotorua-Taupo area were examined. Techniques used to determine the state of digestion and the identification of otoliths are discussed. Stomach content analyses showed that the food of lake-feeding shags in July consisted almost entirely of fish and freshwater crayfish. Bullies (Gobiomorphus sp.) were the most important food fish. Salmonid fish were found in one stomach (P. carbo).
The New South Wales Tiger Flathead Neoplatycephalus macrodon (Ogilby). II. The Age Compositon of the Commercial Catch, Overfishing of the Stocks, and Suggested Conservation
Authors: Fairbridge WS
Published: November 2005

The commercial flathead catch is analysed into its component age-groups. The results are expressed in numbers and weight of each age-group caught in each month. The results indicate an absence of natural fluctuations in abundance of the year-groups during the series of years covered. The post-war decline in the catch of flathead is discussed in the light of this analysis. The catch has fallen from 5,700,000 lb. in 1944–45 to 2,100,000 lb. in 1948–49. The catch of flathead for a period between the wars is estimated at over 10,000,000 lb. per year. The stock of flathead has thus shown a failure to recover during the war-time rest, as well as a sudden fall with the inception of heavy fishing of recent years. Possible reasons for these changes in the flathead stock are discussed. It is suggested that the numbers of recruits are limited by the numbers of spawning adults. The results obtained from this work are fuller, but in entire agreement with those of the earlier paper on the trawlfishery as a xvliole. The adoption of conservation measures is urged. The trawlfishery is now dependent on two hitherto discarded species of poorer quality than the flathead, and the better of these is already showing a reduced catch per unit effort of fishing. The
most important conservation measure is that suggested in the earlier paper — a reduction of the fleet to the equivalent of 13 trawlers. It is regarded as probable that if this step is not taken, the annual trawlfish catch will continue to decline. Closure of the Botany fishing ground is suggested as a further, but not an alternative, measure.
Studies on the Ecology of the New Zealand Freashwater Eels. I. The Design and Use of an Electric Fishing Machine
Authors: Burnet AMR
Published: November 2005

A portable electric fishing machine using pulse-modulated D.C. has been developed. Short-finned eels have been shown to occur in three streams in which they have not been previously found. It has been shown that the river population of long-finned eels is not entirely female. Total population densities have been calculated and a comparison is made with the population densities as measured by the baited trap method.
The Toheroa, Amphidesma ventricosum Gray (Eulamellibranchiata), Development and Growth
Authors: Rapson AM
Published: November 2005

A short historical account of the toheroa of New Zealand is given, and its beach habitat is described. Development of the reproductive organs, spawning, and early development are described up to the stage when the free-swimming form settles on the beach. Types of sand and the particular character of the zone in which toheroa are found are described. Length
frequency data and shell zones are used to demonstrate differences in growth rate on the four principal beaches. Length frequency data are shown to give a much higher rate than shell zones indicate, probably because of the long spawning season. Growth of different parts by weight is studied. Of several hundred toheroa marked with a file, two were recovered after 6 weeks, giving a growth rate in agreement with that estimated. One small specimen kept in an aquarium for 8 weeks made no growth. The existence of off-shore stocks is briefly discussed.
The Ascidians of Australia. I. Stolidobranchiata Lahille and Phlebobranchiata Lahille
Authors: Kott P
Published: November 2005

An account is given of a collection of 85 species of simple ascidians from all parts of the Australian coast, including descriptions of 23 species new to science. Comprehensive keys for all species already described from the Australasian area accompany the account of each genus. There is a short discussion on the distribution of simple ascidians in Australia; and the Baudinian region, a new zoogeographic marine region in south Western Australia is proposed.
Tagging of School Shark, Galeorhinus australis (Macleay) (Carcharhanidae) in South-eastern Australian Waters
Authors: Olsen AM
Published: November 2005

In south-eastern Australian waters, 5835 school sharks have been tagged since 1947. The two techniques used and the effects of some of the tags on the fins and body walls are described. It was found that the percentage return from experiments using both internal and fin tags was three times that from experiments using only fin tags. No significant difference was found in the numbers of white and grey Petersen disc fin tags returned. No deterioration has been detected in these tags and the silver tagging wires have not shown any appreciable signs of wear. Under natural conditions the incision made in the body wall for this insertion of the internal tag has been found to have healed completely within 2 months. Often there is no sign of the scar after 12 months.
Three New Stomatopoda (Crustacea) from Eastern Australia
Authors: Stephenson W
Published: November 2005

The following new species are described and figured: Squilla granti from Moreton Bay, Queensland; S. terrareginensis from north Queensland; and S. meneilli from deep water off the New South Wales coast. Justifications are given for the elevation of S. scorpio var. immaculata Kemp 1913 to specific rank.
Further Results of Tagging Sea Mullet, Mugil cephalus Linnaeus, on the Eastern Australia Coast
Authors: Kesteven GL
Published: November 2005

An account is given of tagging operations in eastern Australian waters on sea mullet. The operations involved fish of wide age and size ranges in a variety of habitats and localities, in all months of the year except July. The recoveries from these operations are analysed for information on movement, growth, and mortality. The results show the movement of the tagged fish to be predominantly northwards and require a postulate that southward movement takes place among the young fish (and possibly eggs). The movement of individual fish can be quite rapid and cover long distances, and each fish probably migrates a number of times during its lifetime. The proportion of the population involved in these movements probably exceeds 50 per cent. The results show that there is on the coast one continuous stock of this species, of which the populations occupying the numerous rivers and lakes constantly intermingle. Confirmation was obtained of the earlier workeon the technique of scale reading in this species, and of the general results on average growth rate. Growth occurs chiefly in summer, but possibly also in the latter part of spring and the early part of autumn. The physiology of scale growth and trhe formation of annual "breaks" are discussed. Proportional recoveries from each operation are reported but these cannot serve well a s an index of intensity of fishing. On the other hand, the longevity of the tags serves to indicate the probable life expectancy of these groups of fish; this is estimated as slightly more than 3 yr.