bluuebunny/crossref_metadata_2025 huggingface dataset:
On the relationship between satellite‐retrieved surface temperature fronts and chlorophyll a in the western South Atlantic
Authors: Saraceno Martin , Provost Christine , Piola Alberto R.
Published: November 2005

The time‐space distribution of chlorophyll a in the southwestern Atlantic is examined using 6 years (1998–2003) of sea surface color images from Sea‐viewing Wide Field of View Sensor (SeaWiFS). Chlorophyll a (chl a) distribution is confronted with sea surface temperature (SST) fronts retrieved from satellite imagery. Histogram analysis of the color, SST, and SST gradient data sets provides a simple procedure for pixel classification from which eight biophysical regions in the SWA are identified, including three new regions with regard to Longhurst (1998) work: Patagonian Shelf Break (PSB), Brazil Current Overshoot, and Zapiola Rise region. In the PSB region, coastal‐trapped waves are suggested as a possible mechanism leading to the intraseasonal frequencies observed in SST and chl a. Mesoscale activity associated with the Brazil Current Front and, in particular, eddies drifting southward is probably responsible for the high chl a values observed throughout the Brazil Current Overshoot region. The Zapiola Rise is characterized by a local minimum in SST gradient magnitudes and shows chl a maximum values in February, 3 months later than the austral spring bloom of the surroundings. Significant interannual variability is present in the color imagery. In the PSB, springs and summers with high chl a concentrations seem associated with stronger local northerly wind speed, and possible mechanisms are discussed. Finally, the Brazil‐Malvinas front is detected using both SST gradient and SeaWiFS images. The time‐averaged position of the front at 54.2°W is estimated at 38.9°S and its alongshore migration of about 300 km.
The mean circulation of the southwestern Mediterranean Sea: Algerian Gyres
Authors: Testor P. , Send U. , Gascard J.‐C. , Millot C. , Taupier‐Letage I. , Béranger K.
Published: November 2005

This is a study about the general circulation of the southwestern Mediterranean Sea based on observations of currents carried out in the southwestern Mediterranean Sea in the framework of the Mass Transfer and Ecosystem Response (MATER) program (EEC/MAST3 program). From July 1997 to August 2002, profiling floats (MEDPROF experiment), isobaric floats (LIWEX experiment), and moored current meters (ELISA experiment) give evidence of two large‐scale barotropic cyclonic circulations, the here‐called Western and Eastern Algerian Gyres, centered around [3730′N, 230′E] and [3830′N, 600′E], respectively. These gyres have typical horizontal scales of 100–300 km and are characterized by orbital velocities of about 5 cm/s corresponding to rotational periods of about 4 months. They are strongly related to the bottom topography of the basin and to the planetary vorticity gradient: closed f/H isocontours (f is the planetary vorticity, H the water depth) correspond to the locations of the gyres and favor such circulations as free geostrophic modes. A linear and barotropic model is used to investigate the possibility of wind driving, but the results suggest that the wind stress is not responsible for establishing such circulations. The boundary currents flowing along the continental slope of Africa, Sardinia, and the Balearic Islands are proposed to be the main drivers of these gyres.
A mean field model of the decrease of the specific surface area of dry snow during isothermal metamorphism
Authors: Legagneux Loïc , Domine Florent
Published: November 2005

The surface area of snow that is accessible to gases is an essential parameter for quantifying the exchange of trace gases between the snowpack and the atmosphere and is called the specific surface area (SSA). Snow SSA decreases during metamorphism, but this is not described in current snow models owing to the complexity of the physics and geometry of snow. In this paper, we test whether it is possible to model snow SSA changes during isothermal metamorphism without accounting for all the complexity of the three‐dimensional (3‐D) structure of real snow. We have developed a mean field model of snow metamorphism under isothermal conditions, grounded in the theoretical framework of transient Ostwald ripening and representing snow as a distribution of spherical particles. Analytical expressions of the growth rates of these spheres are obtained, and the evolution of two measurable parameters that characterize snow geometry, the SSA and the distribution of radii of curvature (DRC), are simulated and compared to experimental data obtained by X‐ray tomography. The qualitative effects of temperature, snow density, and the condensation coefficient on the rate of SSA decrease are examined. The model predicts very well the rate of evolution of the particle size distribution, which validates our physical description of isothermal metamorphism. In particular, we find that vapor phase diffusion is rate limiting. However, the calculation of the SSA from the DRC appears delicate and evidences too crude approximations in our description of the 3‐D geometry of snow. Finally, it is stressed that the initial DRC can greatly influence the rate of SSA decrease, while experimental measurements of the rate of SSA decrease suggest that all snow types evolve in a similar way. It is thus proposed that most natural fresh snows have similar DRCs.
Generation and verification of theoretical rating curves in the Whitewater River basin, Kansas
Authors: Kean Jason W. , Smith J. Dungan
Published: November 2005

A new method for generating stage‐discharge relations (rating curves) for geomorphically stable channels is presented and applied to two streams in the Whitewater River basin, Kansas. The approach converts measurements of stage into discharge using a fluid mechanically based model. The model does not use empirical roughness coefficients, such as Manning coefficients, but rather determines channel roughness from field measurements of the (1) channel geometry, (2) the physical roughness of the bed, banks, and floodplain, and (3) the vegetation density on the banks and floodplain. These measurements are used to calculate explicitly the drag on the small‐scale topographic features on the boundary, the drag on the stems and branches of woody vegetation, and the friction on the bed, banks, and floodplain. The theoretical rating curves produced by the model for two study reaches, which are near U.S. Geological Survey (USGS) streamflow‐gauging stations, are in good agreement with direct measurements of discharge made by the USGS. Our method has the potential of providing accurate estimates of stream flows less expensively than conventional gauging methods. In addition, the method can be used to obtain more accurate discharge estimates than conventional indirect methods for determining discharge, which are based on estimates of Manning's coefficient.
Posterior distributions of a statistic of propagation loss inferred from radar sea clutter
Authors: Rogers L. Ted , Jablecki Michael , Gerstoft Peter
Published: November 2005

The generation of a posteriori distribution of a statistic of propagation loss conditioned on observed radar sea clutter is described. The statistic u is the 20th percentile level of the two‐way propagation loss at a 5‐m height over the 10–60 km range interval. A discrete implementation of the Bayesian paradigm is employed. The forward mapping from the space of environmental parameters into the space of radar clutter incorporates a random process model such that many realizations of modeled clutter are generated for each environmental refractivity parameter combination. The algorithm is adjusted such that over a series of simulated inversion runs, it is seen that for intervals between percentile levels (e.g., between the 20th and 80th percentile levels), a posteriori distributions of u contain the ground truth values of u the correct percentage of the time (60% for the used interval). For real data cases, it is observed that the a posteriori distributions are too narrow. The inversion algorithm is used to examine the behavior of the a posteriori distribution as the noise floor is raised. An abrupt reduction in the information obtained from the clutter (indicated by a widening of the a posteriori distribution) occurs when peak clutter levels over the ranges of 25–50 km drop below about 15 dB for both simulated and real data cases.
Scattering layer statistics from space borne GLAS observations
Authors: Bréon F. M. , O'Brien D. M. , Spinhirne J. D.
Published: November 2005

Cloud and aerosol layers detected by the space borne Geoscience Laser Altimeter System (GLAS) are used to derive statistics of clear and almost clear atmospheres, the latter defined to be those with some scattering material but total optical thickness less than 0.2. Such statistics are needed to evaluate the potential coverage of NASA's forthcoming Orbital Carbon Observatory. The global fraction of clear cases is approximately 15%, with large scale spatial structures similar to those found by passive sensors. The spatial distribution of almost clear cases is similar to that for clear, with global fraction approximately 20%. The mean altitude of optically thin scattering layers is generally below one kilometer, indicating that they are composed mostly of boundary layer aerosol rather than high altitude cloud. The spatial correlation function of clear cases is accurately reproduced by the analytical function F(d) = exp[−(d/d0)0.5], where d0 is a correlation scale length. Between 60N and 60S, d0 shows little zonal variation, and its average value is 320 km. Over the Arctic d0 falls to 250 km, but rises to 450 km over the Antarctic.
Initial results of the Netlander imaging ground‐penetrating radar operated on the Antarctic Ice Shelf
Authors: Berthelier J. J. , Bonaimé S. , Ciarletti V. , Clairquin R. , Dolon F. , Le Gall A. , Nevejans D. , Ney R. , Reineix A.
Published: November 2005

The objective of the Netlander mission was to land 4 small geophysical stations on the surface of Mars to study the deep interior, subsurface, surface and atmosphere of the planet. Included in the payload was a ground penetrating radar (GPR) designed to retrieve not only the distance but also the direction of the reflectors, thus providing a simplified 3D imaging of the subsurface. In this paper we report initial results obtained during the RANETA campaign on the Antarctic ice shelf. Data from two soundings of the ice‐bed rock interface are analyzed, demonstrating the capability of the radar to disentangle echoes from different reflecting facets of the bed rock.
Flow of the West Antarctic Ice Sheet on the continental margin of the Bellingshausen Sea at the Last Glacial Maximum
Authors: Ó Cofaigh Colm , Larter Rob D. , Dowdeswell Julian A. , Hillenbrand Claus‐Dieter , Pudsey Carol J. , Evans Jeffrey , Morris Peter
Published: November 2005

Geophysical data show that during the last glaciation the West Antarctic Ice Sheet (WAIS) drained to the continental shelf edge of the Bellingshausen Sea through a cross‐shelf bathymetric trough (Belgica Trough) as a grounded, fast flowing, ice stream. The drainage basin feeding this ice stream probably encompassed southwestern Palmer Land, parts of southern Alexander Island, and the Bryan Coast of Ellsworth Land, with an area exceeding 200,000 km2. On the inner continental shelf, streamlined bedrock and drumlins mapped by swath bathymetry show that the ice stream was fed by convergent ice flow draining from Eltanin Bay and bays to the east, as well as by ice draining the southern part of the Antarctic Peninsula Ice Sheet through the Ronne Entrance. The presence of a paleoice stream in Belgica Trough is indicated by megascale glacial lineations formed in soft till and a trough mouth fan on the continental margin. Grounding zone wedges on the inner and midshelf record ice marginal stillstands during deglaciation and imply a staggered pattern of ice sheet retreat. These new data indicate an extensive WAIS at the Last Glacial Maximum (LGM) on the Bellingshausen Sea continental margin, which advanced to the shelf edge. In conjunction with ice sheet reconstructions from the Antarctic Peninsula and Pine Island Bay, this implies a regionally extensive ice sheet configuration during the LGM along the Antarctic Peninsula, Bellingshausen Sea, and Amundsen Sea margins, with fast flowing ice streams draining the WAIS and Antarctic Peninsula Ice Sheet to the continental shelf edge.
Quantifying grain size distribution of pedogenic magnetic particles in Chinese loess and its significance for pedogenesis
Authors: Liu Qingsong , Torrent José , Maher Barbara A. , Yu Yongjae , Deng Chenglong , Zhu Rixiang , Zhao Xixi
Published: November 2005

Quaternary glacial/interglacial cycles have been imprinted on the Chinese loess/paleosol sequences through pedogenesis. In order to accurately decode the paleoclimatic signals carried by these pedogenic particles it is essential to quantify the pedogenically produced magnetic particles in terms of mineralogy as well as grain size distribution (GSD). To date, the GSD has not been accurately determined because of the dearth of available means for analyzing extremely fine grained (nanometer‐scale) pedogenic magnetic particles. Using low‐temperature techniques, we systematically investigated the temperature dependency of χfd (defined as χ1Hz − χ10Hz, where χ1Hz and χ10Hz are AC magnetic susceptibility measured at 1 and 10 Hz, respectively) from two characteristic loess profiles, one located at the western Chinese Loess Plateau and the other in the central plateau. On the basis of Néel theory for a shape anisotropy dominant grain and experimental analysis at low temperatures, a quantitative GSD for pedogenic particles in Chinese loess/paleosols was constructed. We found that the dominant magnetic grain size lies just above the superparamagnetic/single‐domain threshold (∼20–25 nm) and that the GSD is almost independent of the degree of pedogenesis. This observation agrees well with other constraints from previous studies. This new GSD model improves our understanding of the pedogenic processes in Chinese loess, enabling further explicit linkage of environmental magnetism to paleoclimate changes.
Atmospheric and oceanic contributions to Chandler wobble excitation determined by wavelet filtering
Authors: Seitz F. , Schmidt M.
Published: November 2005

Fluctuations of Earth rotation are associated with the redistribution and motion of mass elements in the Earth system. On seasonal to interannual timescales, the largest effects are due to mass redistributions within atmosphere and oceans. In order to study the Earth's reaction on geophysical excitations, the dynamic Earth system model DyMEG has been developed. It is based on the balance of angular momentum in the Earth system. The model is forced by consistent atmospheric and oceanic angular momenta from reanalysis data and a global ocean circulation model. As rotational deformations of the Earth are regarded, forced variations of Earth rotation due to atmospheric and oceanic excitations influence the free polar motion (Chandler wobble) of DyMEG. The comparison of the numerical model results with geodetic observations reveals a good agreement in both the annual and the Chandler frequency band. In order to support the presumption that the excitation energy of atmospheric and oceanic angular momenta within a spectral band around the Chandler frequency is sufficient to reproduce the observed Chandler wobble, the excitation series are band‐pass filtered. For consistent filtering and signal analysis, wavelet techniques based on the Morlet function are applied. When DyMEG is forced with the filtered excitations, the resulting polar motion resembles the actually observed Chandler oscillation, which is determined from geodetic observations applying the same filtering method. Between 1980 and 2002 the correlation coefficient between the unconstrained model result and the observed Chandler wobble amounts to 0.99 and the root‐mean‐square difference is 16 milliarc seconds.
Cross sections and thermal rate constants for the isotope exchange reaction: D(S2)+OH(Π2)→OD(Π2)+H(S2)
Authors: Atahan Sule , Alexander Millard H. , Rackham Edward J.
Published: November 2005

We report state-to-state and overall thermal rate constants for the isotope exchange reaction D(S2)+OH(Π2)→OD(Π2)+H(S2) for 0 K<T<500K. The reaction cross sections were determined by a statistical capture model which includes the electronic degrees of freedom of the OH(OD) radical. Both the D+OH and OD+H channels are described by four ab initio potential-energy surfaces (A′1,3 and A″1,3). All electronic and spin-orbit couplings are included. We predict a reaction rate constant of 14.22×10−11cm3molecule−1s−1 at T=100K and 10.78×10−11cm3molecule−1s−1 at T=300K. At lower temperatures, around 50 K, the value rises to k(T)=15×10−11cm3molecule−1s−1. The predicted rate constants confirm the earlier theoretical and experimental results. A negative temperature dependence in the rate constant is observed. The state-resolved cross sections and rate constants predict a significant propensity toward the formation of the OD (A′)Λ-doublet level and the ground spin-orbit manifold F1.
Large-scale molecular-dynamics simulation of nanoscale hydrophobic interaction and nanobubble formation
Authors: Koishi Takahiro , Yasuoka Kenji , Ebisuzaki Toshikazu , Yoo S. , Zeng X. C.
Published: November 2005

We performed large-scale molecular-dynamics simulation of nanoscale hydrophobic interaction manifested by the formation of nanobubble between nanometer-sized hydrophobic clusters at constrained equilibrium. Particular attention is placed on the tendency of formation and stability of nanobubbles in between model nanoassemblies which are composed of hydrophobic clusters (or patches) embedded in a hydrophilic substrate. On the basis of physical behavior of nanobubble formation, we observed a change from short-range molecular hydrophobic interaction to midrange nanoscopic interaction when the length scale of hydrophobe approaches to about 1 nm. We investigated the behavior of nanobubble formation with several different patterns of nonpolar-site distribution on the nanoassemblies but always keeping a constant ratio of nonpolar to polar monomer sites. Dynamical properties of confined water molecules in between nanoassemblies are also calculated.
Soldered bundle background for the de Sitter top
Authors: Armenta J. , Nieto J. A.
Published: November 2005

We prove that the mathematical framework for the de Sitter top system is the de Sitter fiber bundle. In this context, the concept of soldering associated with a fiber bundle plays a central role. We comment on the possibility that our formalism may be of particular interest in different contexts including MacDowell-Mansouri theory, two time physics, and oriented matroid theory.
Electric field stabilization for temperature driven variation of permittivity in ferroelectric devices
Authors: Prudan A. M. , Kozyrev A. B. , Osadchy V. N. , Kosmin D. M. , Kaydanova T. , Ginley D.
Published: November 2005

The Ginzburg–Devonshire phenomenological approach is used to define the correlation between temperature and electric field magnitudes required to keep permanent values of permittivity of ferroelectrics in rather broad range of operating temperatures. The existence of a crossover of the electric field dependencies for ε at different temperatures is demonstrated theoretically. It makes it possible to establish the upper limit of electrical field strength necessary to provide the thermal stability of ferroelectric devices. Theoretical results have been confirmed experimentally with (Ba,Sr)TiO3 thin film measurements.
Evaluation of tantalum silicon alloy systems as gate electrodes
Authors: Luan H. , Alshareef H. N. , Lysaght P. S. , Harris H. R. , Wen H. C. , Choi K. , Senzaki Y. , Majhi P. , Lee B.-H.
Published: November 2005

The effect of Si concentration on the effective work function of tantalum silicon (Ta–Si) alloy systems as gate electrodes in direct contact with SiO2 and HfSiOx gate dielectrics has been studied extensively. It was found that the Si concentration in the Ta–Si electrodes (⩾60at.% Si) has a strong effect on the effective work function, and three discrete composition-dependent phases (tantalum metal, tantalum silicide, and silicon) coexist in the films. The film resistivity and density also change dramatically as a function of Si concentration. Physical analysis shows that these Si-rich Ta–Si electrodes are amorphous at room temperature and crystallize with a 1000°C, 5-s anneal. Finally, an effective work function value of 3.98eV has been achieved by arsenic implantation of a capacitor electrode layer in Ta–Si∕HfSiOx film systems, thereby producing a potential n-type metal gate electrode in conjunction with high-k gate dielectrics.
Potential of submicrometer thickness Cu(In,Ga)Se2 solar cells
Authors: Gloeckler Markus , Sites James R.
Published: November 2005

Thin-film solar cells based on Cu(In,Ga)Se2 absorbers with thicknesses similar to or below their optical absorption length are investigated with numerical simulations. The key issue for cells with thicknesses below 1.0μm is to limit back-contact recombination, which can be accomplished by the choice of back-contact material, surface modifications, or inclusion of Ga∕(Ga+In) grading. Unlike in thicker cells, the benefit of grading is maximized if it is limited to a narrow region at the back contact, where it acts as an electron reflector. The potential for optical improvement is evaluated considering variations in back-contact reflectivity and light trapping. Back-contact passivation combined with improved back-contact reflectivity should allow for thinning of the absorber material from 3 to 0.3μm with efficiencies above 17%. A sensitivity analysis with respect to material parameters illustrates that very thin cells suffer substantially stronger from nonuniformities.
Critical exponents of the La0.7Sr0.3MnO3, La0.7Ca0.3MnO3, and Pr0.7Ca0.3MnO3 systems showing correlation between transport and magnetic properties
Authors: Taran Subhrangsu , Chaudhuri B. K. , Chatterjee Sandip , Yang H. D. , Neeleshwar S. , Chen Y. Y.
Published: November 2005

From the low-temperature (down to 10K) dc-magnetization data of the La0.7Sr0.3MnO3 (LSM), La0.7Ca0.3MnO3 (LCM), and Pr0.7Ca0.3MnO3 (PCM) systems, we estimated the critical exponents β, γ, and hence δ from the analysis of the modified Arrot plots. The exponent β estimated for the LCM system is less than that predicted by Heisenberg model and resides within the zone predicted by Ising model while for the LSM sample, β is higher than that predicted from the Heisenberg model which is considered to be due to the presence of dipole-dipole interaction arising from the large spin moment in the LSM system. The magnetization data of the PCM system cannot be fitted to the modified Arrot plots, which suggest highly inhomogeneous ground state even under 5T magnetic field. Both LSM and LCM have almost equal values of γ. Seebeck coefficient data indicate a crossover from higher-temperature n-type to lower-temperature p-type conductivity behavior in both LSM and LCM systems, while the semiconducting PCM system shows p-type conductivity throughout the temperature range (300–80K). It is noticed that for LSM system TC (Curie temperature) and TMI (metal-insulator transition temperature) are almost equal (∼360K), whereas for the LCM system there exist a large difference between TC and TMI (TC∼245K and TMI∼265K), which may give some idea regarding the critical behavior of the respective samples.
Two-dimensional wave dynamics in thin films. I. Stationary solitary pulses
Authors: Saprykin Sergey , Demekhin Evgeny A. , Kalliadasis Serafim
Published: November 2005

We consider two-dimensional stationary solitary pulses in a falling film by using the two-dimensional generalized Kuramoto-Sivashinsky equation as a model system. We numerically construct solitary wave solutions of this equation as a function of the dispersion parameter. We obtain an analytical estimate for the speed of these waves in the strongly dispersive case by using a perturbation from the Korteweg-de Vries limit. An impulse response analysis in which the nonlinearity is replaced with a delta function leads to an approximate analytical solution for the shape of two-dimensional solitary waves. The analytical predictions are in excellent agreement with numerical results for the speed and shape of these waves.
Modulated optical reflectance measurements on La2∕3Sr1∕3MnO3 thin films
Authors: Méchin Laurence , Flament Stéphane , Perry Andy , Almond Darryl P. , Chakalov Radoslav A.
Published: November 2005

The modulated optical reflectance (MOR) measurement technique was applied to colossal magnetoresistive materials, in particular, La2∕3Sr1∕3MnO3 (LSMO) thin films. The contactless measurement scheme is prospective for many applications spanning from materials’ characterization to devices such as reading heads for magnetically recorded media. A contrasted room-temperature surface scan of a 100-μm-wide and 400-μm-long bridge patterned into LSMO film provided preliminary information about the film homogeneity. Then the temperature was varied between 240 and 400K, i.e., through the ferromagnetic to paramagnetic transition. A clear relation between the MOR signal measured as a function of the temperature and the relative derivative of the resistivity up to the Curie temperature was observed. This relationship is fundamental for the MOR technique and its mechanism was explored in the particular case of LSMO. Analysis in the framework of the Drude model showed that, within certain conditions, the measured MOR signal changes are correlated to the changes in the charge-carrier concentration.
Nonclassical gasdynamic region of selected fluorocarbons
Authors: Guardone A. , Argrow B. M.
Published: November 2005

The nonclassical gasdynamic region of fluorinated substances belonging to the PP, FC, and E series is investigated using different thermodynamic models of increasing complexity. Thermodynamic models range from the simple van der Waals equation of state to the more complex Martin-Hou model and include the Redlich-Kwong, Clausius-II, Soave-Redlich-Kwong, and Peng-Robinson equations, under both the polytropic (constant isochoric specific heat in the dilute gas limit) and nonpolytropic approximations. The possibility of observing nonclassical gasdynamic behavior for a given fluid is confirmed to increase with the molecular weight of the substance times the specific heat at constant volume in the dilute gas limit and at the critical temperature, but to be almost insensitive to the nonpolytropic behavior of the fluid; the dependence on the compressibility at the critical point is also weak. A strong dependence on the acentric factor of the substance is revealed, which points to fluids made of nonpolar molecules with nearly spheroidal shapes as the most favorable to exhibit nonclassical gasdynamic behavior. In this respect, the fluorinated cyclic compounds of the PP series are singled out as the most promising candidates for the experimental verification of the existence of nonclassical phenomena in the vapor phase and for nonclassical gasdynamic applications.
Thermal and optical properties of bulk GaN crystals fabricated through hydride vapor phase epitaxy with void-assisted separation
Authors: Oshima Yuichi , Suzuki Takayuki , Eri Takeshi , Kawaguchi Yusuke , Watanabe Kazutoshi , Shibata Masatomo , Mishima Tomoyoshi
Published: November 2005

The fundamental material parameters associated with GaN, which are important for the design of devices such as light-emitting diodes and laser diodes, were investigated using large high-quality GaN single crystals fabricated through hydride vapor phase epitaxy using the void-assisted separation method. The thermal-expansion coefficients (298–573K) along the C[0001], A[112¯0], and M[101¯0] axes (αC, αA, and αM) were measured. Thermal expansion in each direction, approximately proportional to the temperature, was observed throughout the measured temperature range. Although the thermal-expansion coefficients in the high-temperature range, i.e., αC(573K)=7.2±0.02×10−6∕K, αA(573K)=5.7±0.2×10−6∕K, and αM(573K)=5.8±0.2×10−6∕K,were relatively close to the reported values, the thermal-expansion coefficients along the C axis in the low-temperature range, i.e., αC(298K)=5.3±0.02×10−6∕K, was significantly larger than the reported values. Thermal conductivities parallel and perpendicular to the C axis were almost the same, i.e., 2.0±0.1Wcm−1K−1. This value is close to the values reported on the low-dislocation density part of epitaxially laterally overgrown GaN. This could indicate that the defect density of our crystals is very low and that the defects are distributed uniformly throughout the volume. The wavelength dependence of the refractive index and the optical-absorption coefficient was also investigated.
2
μ
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lasing from highly thulium doped tellurite glass microsphere
Authors: Wu Jianfeng , Jiang Shibin , Qua Tiequn , Kuwata-Gonokami Makoto , Peyghambarian N.
Published: November 2005

A single mode microsphere laser at 2μm is demonstrated from a highly thulium doped tellurite glass microsphere. Glass samples with various doping concentrations are fabricated and characterized to choose the material with the highest pump efficiency. The laser wavelength is redshifted from the emission peak of thulium ions at 1800 nm due to the different mode distribution inside the microsphere. The laser line width (full width at half maximum) is measured as 115 MHz.
Organic bistable memory characteristics with a photochromic diarylethene layer
Authors: Tsujioka Tsuyoshi , Shimizu Masato , Ishihara Eiji
Published: November 2005

Device structure dependence of the recording efficiency of organic bistable molecular memory using photochromic diarylethene (DAE) was studied. Devices with a thicker memory layer showed faster current decrease, that is, shorter writing time. This was attributed to effective isomerization at the many carrier traps in the memory layer. The device with an electron transport layer that consisted of a Silole derivative showed fast writing speed. The device with an Alq3 electron transport layer showed electroluminescence. This indicates the holes were transported through the DAE layer without contribution for isomerization. DAE molecules with good receptivity for both carriers should be developed for obtaining high speed memory.
Josephson effect in MgB2∕Pd∕Fe∕Nb Josephson junctions
Authors: Malisa A.
Published: November 2005

MgB 2 ∕ Pd ∕ Fe ∕ Nb Josephson junctions were fabricated and characterized. The junctions exhibited the Josephson effect. A supercurrent was observed across the magnetically active layer formed at the Pd and Fe interface and also across the magnetic metal Fe itself. Shapiro steps and fractional Shapiro steps were observed when microwave fields were applied to the junctions. Modulation of the critical currents of the junctions was observed when an external magnetic field was applied in the plane of the junctions. The maxima of the magnetic field dependence of the critical current (Ic−B) did not occur at zero fields but at small positive fields of about 3.7μT. The magnetic field of 3.7μT increased the critical current by 100% when it was applied in the plane of the junction or perpendicular to the junction plane. The effect disappeared when the polarity of the field was reversed.
Photoluminescence from impurity codoped and compensated Si nanocrystals
Authors: Fujii Minoru , Yamaguchi Yasuhiro , Takase Yuji , Ninomiya Keiichi , Hayashi Shinji
Published: November 2005

Photoluminescence (PL) properties of B and P codoped and compensated Si nanocrystals were studied. The compensation of carriers in nanocrystals was confirmed by the annihilation of confined-carrier optical absorption in the infrared region. In the PL spectra obtained under the resonant excitation condition, the codoped samples did not exhibit structures related to momentum-conserving phonons, which were clearly observed for pure Si nanocrystals. The result strongly suggests that in impurity codoped Si nanocrystals, nonphonon quasidirect optical transition is the dominant recombination path for electron-hole pairs, and thus impurity codoping is a possible approach to further improving PL efficiency of Si nanocrystals.
Energy structures and chemical reactions at the Al∕LiF∕Alq3 interfaces studied by synchrotron-radiation photoemission spectroscopy
Authors: Wu Chih-I , Lee Guan-Ru , Pi Tun-Wen
Published: November 2005

The chemical properties and energy levels of Al∕LiF∕Alq3 were investigated via high-resolution synchrotron-radiation photoemission spectroscopy. No clear chemical reaction was found with LiF deposited on Alq3. The core-level spectra show that Li+ ion and Alq3 anion are created only after Al is deposited on LiF∕Alq3 surfaces. Combined with the increase of the electron concentrations indicated by the Fermi-level position in valence-band spectra, the results provide direct evidence of the proposed chemical reaction, 3LiF+Al+3Alq3→AlF3+3Li+Alq3−, which leads to the excellent electron injection efficiency in Al∕LiF∕Alq3.
Spontaneous formation of nanometric multilayers of metal-carbon films by up-hill diffusion during growth
Authors: Corbella C. , Echebarria B. , Ramírez-Piscina L. , Pascual E. , Andújar J. L. , Bertran E.
Published: November 2005

We report the spontaneous formation of multilayer structures with nanometric periodicity during Ti–C thin-film growth by reactive magnetron sputtering. Their characterization was performed by transmission electron microscopy, x-ray photoelectron spectroscopy, x-ray diffraction, and secondary ion mass spectrometry. We discuss film structure and morphology as a function of metal content, and propose surface-directed spinodal decomposition as the mechanism responsible for the segregation of species in separated layers by up-hill diffusion.
Photoelectrochemical deoxyribonucleic acid sensing on a nanostructured TiO2 electrode
Authors: Tokudome Hiromasa , Yamada Yoko , Sonezaki Shuji , Ishikawa Hiroshi , Bekki Makoto , Kanehira Koki , Miyauchi Masahiro
Published: November 2005

A nanostructured TiO2 electrode chemisorbed with probe deoxyribonucleic acid (DNA) can photoelectrochemically detect a dye-labeled target DNA molecule. After the hybridization between the probe and target DNA molecules, light irradiation generates electrons in the dye molecules, and these electrons are injected into the TiO2 electrode. The resulting photocurrent can be measured and corresponds to the concentration of target DNA. This sensor can quantitatively detect target DNA at lower than nanomolar concentrations. In addition, by utilizing two different dyes, different DNA sequences can be detected on the TiO2 electrode.
Four-point measurements of n- and p-type two-dimensional systems fabricated with cleaved-edge overgrowth
Authors: Grayson M. , Roth S. F. , Xiang Y. , Fischer F. , Schuh D. , Bichler M.
Published: November 2005

We demonstrate a contact design that allows four-terminal magnetotransport measurements of cleaved-edge overgrown two-dimensional electron and hole systems. By lithographically patterning and etching a bulk-doped surface layer, finger-shaped leads are fabricated, which contact the two-dimensional systems on the cleave facet. Both n- and p-type two-dimensional systems are demonstrated at the cleaved edge, using Si as either donor or acceptor, dependent on the growth conditions. Four-point measurements of both gated and modulation-doped samples yield fractional quantum Hall features for both n and p types, with several higher-order fractions evident in n-type modulation-doped samples.
Doping of phosphorus in chemical-vapor-deposited silicon carbide layers: A theoretical study
Authors: Hornos T. , Gali A. , Devaty R. P. , Choyke W. J.
Published: November 2005

Ab initio supercell calculations have been carried out to investigate the doping of phosphorus in chemical-vapor-deposited (CVD) silicon carbide (SiC) layers. We simulated the CVD conditions by using the appropriate chemical potentials for hydrogen and phosphorus (P). We find that the site selection of P is not affected by the presence of hydrogen, and hydrogen does not practically passivate the P donors. We find that the most abundant defect is P at the Si-site followed by P at the C-site. The calculated concentrations of the P donors and free carriers in CVD grown SiC agree with the experimental findings.
Characterization of luminous-cubic boron-nitride single-crystals doped with Eu3+ and Tb3+ ions
Authors: Nakayama Atsuko , Taniguchi Takashi , Kubota Yoichi , Watanabe Kenji , Hishita Shunichi , Kanda Hisao
Published: November 2005

Incorporation of Eu3+ and Tb3+ ions into single crystals of cubic boron nitride (c-BN) has been performed by mixing these fluorides into a solvent for crystal growth of c-BN under high pressure. This method consequently brings luminous features into c-BN. The doped c-BN single crystals show no discernible structural changes in their matrices, while their elements are incorporated into the whole of crystals in atomic scale. Photoluminescence spectra of c-BN:Eu and c-BN:Tb exhibit the intra-4f electron transitions of Eu3+ and Tb3+ ions, starting from their excitation levels, D05 and D45, respectively.
Electrical transport in passivated Pt∕TiO2∕Ti Schottky diodes
Authors: Dittrich Th. , Zinchuk V. , Skryshevskyy V. , Urban I. , Hilt O.
Published: November 2005

Pt ∕ Ti O 2 ∕ Ti Schottky diodes were investigated by current-voltage analysis, photoresponse, and transient photocurrent (PC) in a wide temperature range. The compact TiO2 as well as the SiO2 passivation layers were prepared by the sol-gel technique. The Schottky-barrier height (1.2–1.3eV) was equal to the difference of the work functions of Pt and Ti. The temperature dependence of the ideality factor was interpreted in terms of a Gaussian distribution of barrier heights [J. H. Werner and H. H. Güttler, J. Appl. Phys. 69, 1522 (1991)]. Space-charge-limited currents under the presence of defects with an exponential distribution were observed. Under zero-potential condition, the PC transients were practically independent of temperature and the electron drift mobility amounted to 2×10−4cm2∕(Vs). A screening dipole layer at the Pt∕TiO2 junction was formed under low forward and reverse potentials. Defects were generated under electron injection.
Improvement of retention loss in Pb(Zr,Ti)O3 capacitors using Ir∕SrRuO3 top electrodes
Authors: Kim Sukpil , Koo Junemo , Shin Sangmin , Park Youngsoo
Published: November 2005

We investigated the retention behavior of Pb(Zr,Ti)O3 (PZT) capacitors with Ir∕SrRuO3 (SRO) top electrodes. The capacitors with Pt and Ir∕IrO2 top electrodes were also prepared for comparison. The opposite state retention characteristic of the PZT capacitor was significantly improved by using an Ir∕SRO top electrode structure. The nonvolatile polarization of the opposite state retention was kept at 96% of its initial value even after a 100h baking test at 150°C, while those of Pt and Ir∕IrO2 were 36 and 59%, respectively. The retention enhancement is attributed to the effective inhibition of defect generation on the interface between PZT and SRO.
Femtosecond investigation of the non-instantaneous third-order nonlinear suceptibility in liquids and glasses
Authors: Burgin J. , Guillon C. , Langot P.
Published: November 2005

The symmetry of the noninstantaneous Kerr susceptibility is investigated in different liquids and glasses using a time-resolved two-beam energy transfer technique with pulses in the 100–15 fs range. The pulse duration dependence of the ratio of the isotropic χxxxx(3) to anisotropic χxyyx(3) tensor elements is demonstrated in liquid CS2 and in silica, showing that the elementary mechanisms mediating the observed optical beam energy transfers are modified for short pulses. This effect is ascribed to alteration of the nuclear contribution and increasing influence of the electronic one.
Near-infrared electroluminescent devices using single-wall carbon nanotubes thin flms
Authors: Kazaoui S. , Minami N. , Nalini B. , Kim Y. , Takada N. , Hara K.
Published: November 2005

We have fabricated near-infrared electroluminescent (EL) devices utilizing single-wall carbon nanotubes (SWNTs) finely dispersed in a polymer, such as poly[2-methoxy-5-(2′-ethylhexyloxy]-1,4-phenylenevinylene (MEHPPV). Al/SWNT-MEHPPV/indium tin oxide thin-film devices exhibit a very promising EL response over a broad spectrum, including the range of 900–1600nm. From the analysis of the optical absorption, photoluminescence and EL spectra, as well as the current-voltage characteristics, we demonstrate that those devices exploit the intrinsic near-infrared light-emitting properties of semiconducting SWNTs and the electronic transport properties of SWNT-doped MEHPPV. Those achievements are essential for the future development of thin-film SWNT optoelectronic devices.
Investigation on Underwater Fouling. II. The Biology of Fouling in Australia: Results of a Year's Research
Authors: Allen FE , Wood EJ Ferguson
Published: November 2005

The results of the first year of work on a continuing investigation on the fouling of submerged surfaces are outlined, with some preliminary conclusions to be drawn therefrom. The work represents a study of glass plates exposed to fouling by marine growth in the south-east of Australia. Only the more abundant fouling organisms are listed and their seasonal
abundance is shown.
The Bacteriology of Shark Spoilage
Authors: Wood EJ Ferguson
Published: November 2005

The spoilage of shark is considered on present evidence to be due to autolysis and bacterial action, but the relative importance of each is not known. Spoilage is regarded as due to production of ammonia from urea and other nitrogenous bodies present in shark flesh, as well as to the formation of less volatile substances. The genera Corynebacterium, Micrococcus, Sarcina, Pseudomonus, Bacillus, Enterobacter, and Mycoplana are recorded as well as a Torula. The flora is regarded as a modified marine flora in which the Gram-positive elements have been greatly epriched, with the Gram-negative of little importance. It resembles a mud flora rather than one from sea-water.
Shell Movements of the Freshwater Mussel, Hyridella australis Lam. (Lamellibranchiata)
Authors: Hiscock ID
Published: November 2005

An analysis of about 4,500 hours of shell movement tracings of the freshwater mussel, Hyridella australis Lam., is presented. Nine series of experiments have been conducted, representing variations in light and temperature conditions. It has been found that, as well as shell movements, shell position or degree of openness must be considered. The shells may be closed (phase 1), completely open (phase 3), or stationary, intermediate between the two (phase 2), for the validity of which position mathematical proof has been found. The characteristics of each phase have been outlined. Temperature, within the range 17 to 27°C shows no well-definded influence on shell movements or the degree of openness. The influence of light, especially in regard to phase 2, is discussed. A diurnal light rhythm is associated with a diurnal feeding rhythm; under continuous illumination the shells tend to remain apart but in phase 2, darkness suppresses shell movements and feeding. The shell movements during ovulation are discussed.
Studies in Australian Estuarine Hydrology. I. Introdutory and Comparative Features
Authors: Rochford DJ
Published: November 2005

In this paper is presented an introduction to the methods involved in the collection, analysis, and interpretation of Australian estuarine hydrological data collected by the Division of Fisheries, C.S.I.R.O. The chief features of the circulation and mixing exchanges in such systems have been discussed. A review of the zonal distribution of the principal hydrological properties of estuarine waters, and of certain selected chemical properties of the bottom deposits, has led to the establishment of a schematic zonal diagram by which the hydrological classification of estuarine systems can be attempted. An examination of the zonal composition of certain estuarine systems has been attempted, and on the basis of such composition and the volume of water, a theory of zonal dominance has been developed. The development of conflicts
of hydrological properties, by reason of tidal rise and fall of water level, has been examined, and some idea of the range of this derived property demonstrated by an examination of the diurnal range of chlorinity in certain estuarine systems. Some general aspects of the productivity of estuarine waters and bottom deposits have been examined and a number of hypotheses concerning the role of phosphates in their respective productivity levels have been postulated. An examination of the chemical interaction between the water and its associated bottom deposit has been made. The relation of these studies to oyster cultivation and methods of mud flat enrichment for promotion of oyster growth has been discussed.
Growth and Habits of the Sea Mullet, Mugil dobula Gnnther, in Western Australia
Authors: Thomson JM
Published: November 2005

Morphologically and physiologically, the sea mullet of Western Australia seems to be identical with that of the eastern Australian coast. No raciation can be detected either within Western Australian waters or between the stocks of eastern and Western Australia. However, the mean growth rate varies from one estuary to another and from year to year within any particular river system. Growth is isometric and shows considerable individual variation though tending to a mean rate. Increase in length is seasonal, practically stopping in midwinter and reaching a peak in midsummer. The seasons of fish and scale growth are contemporaneons. The annuli form at the end of September or the beginning of October, when growth recommences after the winter cessation. Mullet mature at a size of 31–35 cm. (12 1/2-13 3/4 in. length to caudal fin) at the end of their third year. The movement of mullet from the fishing grounds as they increase in size leads to an incomplete sampling of the population so that Petersen's method of age determination is inappIicable owing to the apparent nonprogression of the modes. Of 7110 mullet tagged, only 97 or 1.35 per cent. were returned. The return for separate tagging operations varied from nil to 25 per cent. and according to localities from nil to 16 per cent. Only three fish were retaken outside the rivers in which they were tagged. These showed a northerly movement. Inside the rivers the young fish spread out over the estuary and into the fresh water; but the older age-groups remain in the slightly brackish or fresh water except during the migration season, when they pass through the saline estuaries on the way to the sea.
A Preliminary Study of the Limnology of Lake Hayes
Authors: Jolly VH
Published: November 2005

A general description is given of Lake Hayes, a freshwater lake in the South Island of New Zealand, with a brief analysis of its physical conditions. Preliminary samplings from a variety of lakes showed that Lake Hayes possesses a comparatively rich zooplankton, noteworthy for the fact that its bulk is made up of few species, chiefly entomostracan Crustacea. The greatest number of organisims occur in the upper 6 fathoms but there is a vertical distribution through the complete range. Seasonal fluctuations are marked, the phytoplankton showing greatest productivity in spring, while summer and autumn peaks are dominated respectively by cladocera and copepods. The Entomostraca manifest a diurnal vertical migration. There is a concentration of the population in the surface waters at dawn and dusk. During the day, tile migrants desert the upper waters, while at night the numbers assume average proportions but no peak periods occur. It appears that the Entomostraca of Lake Hayes exhibit n facultative phototropism with a negative reaction to direct sunlight but a positive reaction to weak light.