bluuebunny/crossref_metadata_2025 huggingface dataset:
PROGESTERONE RECEPTOR (PR) ANTAGONISM OF THE INFLAMMATORY SIGNALS LEADING TO LABOUR
Authors: HARDY DANIEL B , MENDELSON CAROLE R
Published: November 2006

The incidence of preterm birth in developed countries has steadily increased over the past two decades and now approaches 12.5% of all live births in the U.S. This is due, in part, to our incomplete understanding of the pathways that maintain uterine quiescence throughout pregnancy, as well as those that promote increased uterine contractility and cervical ripening leading to labour. It is clear that uterine quiescence throughout most of pregnancy is maintained by progesterone acting through its nuclear receptor (PR). Furthermore, there is increasing evidence that both preterm and term labour are associated with activation of inflammatory response pathways in the pregnant uterus and cervix. In this article, we will consider the factors that induce the inflammatory response leading to term and preterm labour. We also will review findings to support the novel concept that the maintenance of uterine quiescence vs. induction of uterine contractility is exquisitely controlled by the cross-repressive effect of progesterone/PR and inflammatory transcription factors, such as nuclear factor κB (NF-κB).
Reproducing board game positions: Western Chess and African Bao
Authors: de Voogt Alexander J.
Published: November 2006

Cognitive experimental research on experts has been dominated by research on Chess masters. De Groot’s work on Chess masters ( de Groot 1946/1965 ) started a tradition of Chess research concentrating on perception, memory and problem-solving expertise (e.g. Chase & Simon, 1973 ; de Groot & Gobet, 1996 ; Newell & Simon, 1972 ). In later years, this research was replicated by research on board games other than Chess. Experiments on players of Gomoku, Go ( Eisenstadt & Kareev, 1977 ; Reitman, 1976 ) and Othello ( Billman & Shaman, 1990 ; Wolff, Mitchell, & Frey, 1984 ) largely confirmed the findings on Chess masters. In board games research the effect of “cultural” variables has not been studied or even considered. Despite the presence of Japanese, Russian, Dutch and recently African players or games, the results of the experiments have been compared as if there is one “board game culture”. As long as the results of the experiments do not upset the results of Chess research, one could claim that this cultural background is irrelevant and that cognitive experiments on experts concern a level of thinking which is universal in humans. However, recent research on Bao experts - a board game played in East Africa - contradicted some of the results in Chess ( de Voogt, 1995 ). In this instance, the role of “culture” became an issue in two ways. Is the difference between Bao and Chess players related to the differences in playing context or are the experiments designed for Chess not comparable or not applicable to Bao?
Ra isotopes in trees: Their application to the estimation of heartwood growth rates and tree ages
Authors: Hancock Gary J. , Murray Andrew S. , Brunskill Gregg J. , Argent Robert M.
Published: November 2006

The difficulty in estimating growth rates and ages of tropical and warm‐temperate tree species is well known. However, this information has many important environmental applications, including the proper management of native forests and calculating uptake and release of atmospheric carbon. We report the activities of Ra isotopes in the heartwood, sapwood and leaves of six tree species, and use the radial distribution of the 228Ra/226Ra activity ratio in the stem of the tree to estimate the rate of accretion of heartwood. A model is presented in which dissolved Ra in groundwater is taken up by tree roots, translocated to sapwood in a chemically mobile (ion‐exchangeable) form, and rendered immobile as it is transferred to heartwood. Uptake of 232Th and 230Th (the parents of 228Ra and 226Ra) is negligible. The rate of heartwood accretion is determined from the radioactive decay of 228Ra (half‐life 5.8 years) relative to long‐lived 226Ra (half‐life 1600 years), and is relevant to growth periods of up to 50 years. By extrapolating the heartwood accretion rate to the entire tree ring record the method also appears to provide realistic estimates of tree age. Eight trees were studied (three of known age, 72, 66 and 35 years), including three Australian hardwood eucalypt species, two mangrove species, and a softwood pine (P. radiata). The method indicates that the rate of growth ring formation is species and climate dependent, varying from 0.7 rings yr−1 for a river red gum (E. camaldulensis) to around 3 rings yr−1 for a tropical mangrove (X. mekongensis).
Coral‐based climate variability in the Western Pacific Warm Pool since 1867
Authors: Quinn Terrence M. , Taylor Frederick W. , Crowley Thomas J.
Published: November 2006

We have generated monthly resolved, stable isotope (δ18O and δ13C) and Sr/Ca time series from a massive Porites coral from Rabaul (4°S, 152°E): a site located in the warmest sector of the Western Pacific Warm Pool (WPWP). The coral δ18O and Sr/Ca time series are well correlated to each other and positive excursions in both records coincide with times of ENSO warm phase events. These time series contain abundant interannual variability that exhibits the well‐recognized pattern of low amplitude ENSO variation between ∼1920–1960 and high amplitude ENSO variation between 1880–1920 and 1960–1997. The ENSO‐filtered coral δ18O and Sr/Ca time series are well matched to each other (r = 0.73) and to similarly filtered coral δ18O records from Papua New Guinea (r > 0.56). There is no long‐term trend in the coral δ18O record, but there is a long‐term trend of increasing coral Sr/Ca from 1867 to 1997. This trend in coral Sr/Ca suggests a cooling of ∼0.7°C, which is rather unlikely and implies that factors other than SST may be influencing the coral Sr/Ca record. The trend in coral Sr/Ca is not an analytical artifact, nor a product of time varying riverine input, nor a product of skeletal diagenesis, nor the results of kinetic effects, but may reflect surface‐water variability in Sr/Ca. Despite the presence of a nonclimatic trend in coral Sr/Ca, the Rabaul coral records contain abundant interannual‐ to multidecadal‐scale variability, much of which is coherent with other proxy records from the WPWP and with instrumental records of ENSO variability.
Aerosol inputs enhance new production in the subtropical northeast Atlantic
Authors: Duarte Carlos M. , Dachs Jordi , Llabrés Moira , Alonso‐Laita Patricia , Gasol Josep M. , Tovar‐Sánchez Antonio , Sañudo‐Wilhemy Sergio , Agustí Susana
Published: November 2006

Atmospheric deposition is an important source of limiting nutrients to the ocean, potentially stimulating oceanic biota. Atmospheric inputs can also deliver important amounts of organic matter, which may fuel heterotrophic activity in the ocean. The effect of atmospheric dry aerosol deposition on the metabolic balance and net production of planktonic communities remains unresolved. Here we report high inputs of aerosol‐bound N, Si, P, Fe and organic C to the subtropical NE Atlantic and experimentally demonstrate these inputs to stimulate autotrophic abundance and metabolism far beyond the modest stimulation of heterotrophic processes, thereby enhancing new production. Aerosol dry deposition was threefold to tenfold higher in the coastal ocean than in the open ocean, and supplied high average (±SE) inputs of organic C (980 ± 220 μmol C m−2 d−1), total N (280 ± 70 μmol N m−2 d−1), Si (211 ± 39 μmol Si m−2 d−1), and labile Fe (1.01 ± 0.19 μmol Fe m−2 d−1), but low amounts of total P (8 ± 1.6 μmol P m−2 d−1) to the region during the study. Experimental aerosol inputs to oceanic planktonic communities from the studied area resulted, at the highest doses applied, in a sharp increase in phytoplankton biomass (sevenfold) and production (tenfold) within 4 days, with the community shifting from a dominance of picocyanobacteria to one of diatoms. In contrast, bacterial abundance and production showed little response. Primary production showed a much greater increase in response to aerosol inputs than community respiration did, so that the P/R ratio increased from around 0.95 in the ambient waters, where communities were close to metabolic balance, to 3.3 at the highest nutrient inputs, indicative of a high excess production and a potential for substantial net CO2 removal by the community in response to aerosol inputs. These results showed that aerosol inputs are major vectors of nutrient and carbon inputs, which can, during high depositional events, enhance new production in the NE subtropical Atlantic Ocean.
Convection electric field in the near‐Earth tail during the super magnetic storm of November 20–21, 2003
Authors: Hori Tomoaki , Lui A. T. Y. , Ohtani S. , Brandt P. C. , Mauk B. H. , McEntire R. W. , Maezawa K. , Mukai T. , Kasaba Y. , Hayakawa H.
Published: November 2006

We examine the electric field observations made by the Geotail spacecraft in the magnetotail during the intense magnetic storm of November 20–21, 2003. During this storm, Geotail traversed the magnetotail at R ∼ 9–12 Re from dusk to dawn through the midnight sector at ∼17 UT on November 20 and observed the convection electric field in the near‐Earth plasma sheet for the main phase and early recovery phase. While the electric field in the plasma sheet during the storm interval shows highly turbulent characteristics in a wide range of local time, the average intensity of the duskward electric field is not so different in magnitude from those observed during other small to moderate level storms. A comparison with those calculated using the empirical models reveals that the independent behavior of the tail convection intensity with regard to the storm driver intensity still holds for an intense storm case. These results give a further support to the hypothesis suggested by our previous study that the tail convection supplies the ring current particles rather constantly regardless of the solar wind condition.
A novel technique for measuring the rate of turbulent dissipation in the marine environment
Authors: Wiles Philip J. , Rippeth Tom P. , Simpson John H. , Hendricks Peter J.
Published: November 2006

We present a new technique for the estimation of profiles of the rate of dissipation of turbulent kinetic energy (ɛ, TKE) in the marine environment using a standard acoustic Doppler current profiler (ADCP). The technique is based on the structure function method used in radar meteorology. The new method is validated through comparisons of ɛ estimates from a structure function with simultaneous measurements of profiles of ɛ made using a freefall profiler, and estimates of the rate of production of TKE using the ADCP variance method. There is a good agreement between the estimates, although some differences in absolute values. A difference in ɛ estimates between the upstream and downstream beams is attributed to the presence of a significant Reynolds stress.
Tropical Atlantic moisture availability and precipitation over West Africa: Application to DEMETER hindcasts
Authors: Rogel Philippe , Tourre Yves M. , Benoit Vincent , Jarlan Lionel
Published: November 2006

From rainfall analysis over West Africa (rotated empirical orthogonal functions, Varimax criterion), significant leading modes are identified: i.e., along the Gulf of Guinea, the Senegal/west Mali area, and the central Sahel. Using the moisture convergence/divergence (MCD) parameter derived from ERA‐40, three leading empirical orthogonal function modes are extracted. They are respectively linked to the Intertropical Convergence Zone position, the equatorial Atlantic upper‐ocean thermal conditions (center and west), and significantly correlated with identified rainfall modes. Linkages between temporal variability of the above modes and that of the tropical Atlantic upper‐ocean thermal are highlighted. A new statistico‐dynamical probabilistic model for West African rainfall prediction is thus built using MCD as predictors diagnosed from the DEMETER hindcasts. The model takes advantage of both identified statistical linkages, and conditional probabilities between precipitation occurrence and MCD values. It is found that new probabilistic scores for precipitation predictions, are significantly improved when compared to those which were obtained directly from DEMETER precipitation forecasts.
Martian dust storms as a possible sink of atmospheric methane
Authors: Farrell W. M. , Delory G. T. , Atreya S. K.
Published: November 2006

Recent laboratory tests, analog studies and numerical simulations all suggest that Martian dust devils and larger dusty convective storms generate and maintain large‐scale electric fields. Such expected E‐fields will have the capability to create significant electron drift motion in the collisional gas and to form an extended high energy (u ≫ kT) electron tail in the distribution. We demonstrate herein that these energetic electrons are capable of dissociating any trace CH4 in the ambient atmosphere thereby acting as an atmospheric sink of this important gas. We demonstrate that the methane destruction rate increases by a factor of 1012 as the dust storm E‐fields, E, increase from 5 to 25 kV/m, resulting in an apparent decrease in methane stability from ∼ 1010 sec to a value of ∼1000 seconds. While destruction in dust storms is severe, the overall methane lifetime is expected to decrease only moderately due to recycling of products, heterogeneous effects from localized sinks, etc. We show further evidence that the electrical activity anticipated in Martian dust storms creates a new harsh electro‐chemical environment.
Closed loop GPR data inversion for soil hydraulic and electric property determination
Authors: Lambot S. , Slob E. C. , Vanclooster M. , Vereecken H.
Published: November 2006

We propose an integrated electromagnetic‐hydrodynamic inverse modeling approach for identifying field‐scale unsaturated soil hydraulic properties and electric profiles from off‐ground time‐lapse ground‐penetrating radar data. Hydrodynamic modeling based on the one‐dimensional Richards' equation with homogeneous soil hydraulic parameters is used to physically constrain the full‐wave radar electromagnetic inverse problem in a closed loop. Significant effects can be observed of water dynamics on the time‐lapse radar data and numerical studies demonstrate the uniqueness of the inverse solution. The results suggest that the method is promising for non‐invasive characterization of the shallow subsurface and monitoring of its dynamics.
Parameter extraction of source plasma from observed particle velocity distribution
Authors: Lui A. T. Y.
Published: November 2006

Plasma measurements in the Earth's magnetotail have revealed occasional existence of multiple plasma components containing a fast flowing beam embedded within a stationary population during dynamic episodes. We present here a quantitative procedure to extract plasma parameters at the source location of a fast flowing beam from the observed 3D velocity distribution. These parameters include the magnetic field at the source location of the beam as well as total electric potential drop experienced by the beam. This procedure is based on the Liouville's Theorem and the nonlinear least square Levenberg‐Marquardt fitting method, under the assumptions of gyrotropic distribution and constant phase space density for a given magnetic moment in the ensemble. We demonstrate this technique with an event observed by Geotail 3D plasma measurements. The result shows that the fast‐flowing beam population originated generally from a location with a magnetic field strength much less than that measured locally, had similar thermal properties as the local stationary population, and had undergone substantial electric field acceleration before detection at the observing site.
Intercomparison of four global precipitation data sets and their correlation with increased Eurasian river discharge to the Arctic Ocean
Authors: Pavelsky Tamlin M. , Smith Laurence C.
Published: November 2006

Recent increases in Eurasian river discharge to the Arctic Ocean have attracted considerable scientific attention but remain poorly understood. Previous studies have examined fire frequency, permafrost thaw, and dam construction as potential mechanisms. Here we focus on precipitation as a driver, using 198 dam‐free Eurasian river basins ranging from 151 to 897,000 km2. Using R‐ArcticNet monthly discharge data and four observational and reanalysis precipitation products from the University of Delaware (UDel), University of Washington (UW), NCEP/NCAR (NCEP), and ECMWF (ERA‐40), we (1) assess which precipitation data sets best capture spatially realistic patterns as inferred from agreement with river discharge (198 basins; 1958–1989); and (2) determine to what extent observed discharge trends follow Udel precipitation changes (66 basins; 1936–1999). Results from the precipitation intercomparison show for the 74 (of 198) basins displaying statistically significant discharge trends (24 positive, 50 negative; −74% to +89%, mean = −1%), interpolated precipitation products significantly outperform reanalysis data sets, perhaps owing to the fine‐scale resolutions examined here. Agreement between discharge and precipitation is 42–86% and 42–97% for UDel and UW, respectively, but approaches zero for NCEP and ERA‐40. Comparison of precipitation and discharge trends suggests that precipitation increases play a significant role in observed long‐term discharge increases. For the 40 (of 66) basins displaying statistically significant trends in discharge (32 positive, 8 negative; −23% to +50%, mean = +11%), 29 display corresponding trends in precipitation with 35–62% agreement between discharge and precipitation trend. Comparison of discharge trends with basin permafrost properties indicates a possible, but not strong role for permafrost thaw in the observed increases.
Dielectric, magnetic, and magnetoelectric properties of laminated PbZr0.52Ti0.48O3∕CoFe2O4 composite ceramics
Authors: Zhou Jian-ping , He Hong-cai , Shi Zhan , Liu Gang , Nan Ce-Wen
Published: November 2006

Multiferroic laminated composites of PbZr0.52Ti0.48O3(PZT)∕CoFe2O4(CFO)∕PbZr0.52Ti0.48O3 were prepared by conventional ceramic processing. The interdiffusion of the elements between different layers occurred, altering material properties. The dielectric behavior of such a sandwiched ceramic was dominated by the relative thickness of the different layers because of the high dielectric constant of the PZT layer and the low dielectric constant of the CFO layer. The magnetoelectric behaviors were strongly dependent on the relative thickness of the CFO layer, dc magnetic field, ac magnetic frequency, and the angle θ between the magnetic field and polarization direction. The maximal magnetoelectric-induced voltage coefficient of the composites reaches up to about 27mV∕Oe, close to what was reported previously. The magnetoelectric effect of the laminated composites was also simulated with the finite-element method. The reasons for the difference between experiment and simulation were discussed.
Preparation and thermoelectric properties of sintered Fe1−xCoxTe2 (≤x≤0.4)
Authors: Kishimoto Kengo , Kondo Kento , Koyanagi Tsuyoshi
Published: November 2006

Polycrystalline samples of FeTe2 substituted with Co were prepared by powder metallurgy, and their thermoelectric properties were investigated. When the substitution amount x increased to 0.4, their electrical conductivity increased to approximately 2000 S∕cm at room temperature and their lattice thermal conductivity decreased to 10 mW cm−1 K−1 at high temperatures. A maximum dimensionless figure of merit of 0.13 was obtained for Fe0.8Co0.2Te2 at 700 K. The electronic structure of FeTe2 was also calculated, and the possibility of improving its thermoelectric performance of FeTe2 is discussed.
Cosmic dust-ion-acoustic waves, spherical modified Kadomtsev-Petviashvili model, and symbolic computation
Authors: Gao Yi-Tian , Tian Bo
Published: November 2006

The spherical modified Kadomtsev-Petviashvili (smKP) model is hereby derived with symbolic computation for the dust-ion-acoustic waves with zenith-angle perturbation in a cosmic dusty plasma. Formation and properties of both dark and bright smKP nebulons are obtained and discussed. The relevance of those smKP nebulons to the supernova shells and Saturn’s F-ring is pointed out, and possibly observable nebulonic effects for the future cosmic plasma experiments are proposed. The difference of the smKP nebulons from other types of nebulons is also analyzed.
Efficient organic photovoltaic devices using a combination of exciton blocking layer and anodic buffer layer
Authors: Chan M. Y. , Lee C. S. , Lai S. L. , Fung M. K. , Wong F. L. , Sun H. Y. , Lau K. M. , Lee S. T.
Published: November 2006

By using bathophenanthroline (BPhen) as an exciton blocking layer (EBL) at the organic/cathode contact of a standard copper phthalocyanine/C60 organic photovoltaic (OPV) device, power conversion efficiency was substantially increased from 0.86% to 2.64%. The BPhen-based devices showed a 45% increase in power conversion efficiency over that of an equivalent device with an EBL of bathocuproine. The performance improvement was analyzed in terms of the electron energy levels, optical transparencies and electron mobilities of the two EBLs. Based on these results, the roles of and requirements for an effective EBL were discussed. Combining the use of BPhen and a WO3 anodic buffer layer further increased the power conversion efficiency of the OPV device to 3.33%.
Extended multicanonical method combined with thermodynamically optimized potential: Application to the liquid-crystal transition of silicon
Authors: Yoshimoto Yoshihide
Published: November 2006

A novel method is proposed to study first-order phase transition in real materials. It is applied to the liquid-crystal transition of silicon successfully. It consists of two parts: a direct simulation of the transition by an extended multicanonical ensemble with an order parameter defined with structure factors that characterize the transition, and optimization of a model interatomic potential in terms of the ensemble from an accurate one. These provide a principle to project a first-principles approach on a model-based approach conserving thermodynamic properties of multiple phases.
Interaction of metallophthalocyanines (MPc,M=Co,Ni) on Au(001): Ultraviolet photoemission spectroscopy and low energy electron diffraction study
Authors: Ellis Trinity S. , Park Kenneth T. , Ulrich Marc D. , Hulbert Steven L. , Rowe Jack E.
Published: November 2006

Thin films of metallophthalocyanine (MPc,M=Co,Ni) evaporated onto a “5×20” reconstructed Au(001) substrate at room temperature have been investigated by employing low energy electron diffraction (LEED) and ultraviolet photoelectron spectroscopy (UPS). The LEED images from NiPc thin films show that the overlayers are highly ordered with a square unit cell of 12.8×12.8Å2 aligned along the ⟨110⟩ and ⟨11¯0⟩ axes of the Au(001) substrate. For CoPc, the LEED pattern reveals the superposition of multiple rotationally equivalent domains of a 12.9×12.9Å2 square lattice which are rotated by 16° with respect to each other. The contrast between NiPc and CoPc on Au(001) is further demonstrated in the interfacial electronic structure. UPS studies of the interfacial layers of NiPc deposited on the hexagonally reconstructed gold substrate indicate that NiPc physisorbs on the gold surface as evidenced by a uniform molecular orbital (MO) shift. The CoPc MO’s, on the other hand, indicates a charge transfer at the interface, evidenced by the 13a1g MO interacting with the Au surface.
Dependence of the vibronic emission on self-absorption and reemission processes in conjugated polymers
Authors: Cury L. A. , Guimarães P. S. S.
Published: November 2006

Photoluminescence spectra from the edge of thin films of a conjugated polymer were obtained by varying the self-absorption level at different temperatures. This technique together with the use of a Franck-Condon analysis enabled a clear identification of the vibrational relaxation processes, providing a way to recognize the participating vibrational modes. The higher order vibronic bands were observed to shift to lower energies than those predicted theoretically. This was interpreted as an effect of self-absorption processes, which lead to the loss of energy by intramolecular interactions due to the increase of thermal disorder.
Photon kinetic modeling of laser pulse propagation in underdense plasma
Authors: Reitsma A. J. W. , Trines R. M. G. M. , Bingham R. , Cairns R. A. , Mendonça J. T. , Jaroszynski D. A.
Published: November 2006

This paper discusses photon kinetic theory, which is a description of the electromagnetic field in terms of classical particles in coordinate and wave number phase space. Photon kinetic theory is applied to the interaction of laser pulses with underdense plasma and the transfer of energy and momentum between the laser pulse and the plasma is described in photon kinetic terms. A comparison is made between a one-dimensional full wave and a photon kinetic code for the same laser and plasma parameters. This shows that the photon kinetic simulations accurately reproduce the pulse envelope evolution for photon frequencies down to the plasma frequency.
Spherically and system-averaged pair density functional theory
Authors: Nagy Á.
Published: November 2006

In a couple of recent papers Gori-Giorgi and Savin [Phys. Rev. A 71, 032513 (2005)] proposed a theory that provides simple radial equations to generate the spherically and system averaged pair density. In a recent density matrix functional theory [Á. Nagy, Phys. Rev. A 66, 022505 (2002)] it was shown that the problem of an arbitrary system can be reduced to a two-particle problem. Based on this theory, via a double adiabatic connection, it is rigorously derived that the square root of the ground-state spherically and system averaged pair density is the solution of a simple radial equation, that is, contrary to the theory of Gori-Giorgi and Savin only a single equation has to be considered.
Combined nonadiabatic transition-state theory and ab initio molecular dynamics study on selectivity of the α and β bond fissions in photodissociation of bromoacetyl chloride
Authors: Zhang Feng , Ding Wan-Jian , Fang Wei-Hai
Published: November 2006

The selectivity of the α C–Cl and β C–Br bond fissions upon n→π* excitation of bromoacetyl chloride has been investigated with combined nonadiabatic Rice-Ramsperger-Kassel-Marcus theory and ab initio molecular dynamics calculations, which are based on the potential energy profiles calculated with the complete active space self-consistent field and multireference configuration interaction methods. The Zhu-Nakamura [J. Chem. Phys. 101, 10630 (1994); 102, 7448 (1995)] theory is chosen to calculate the nonadiabatic hopping probability. It is found that nonadiabatic effect plays an important role in determining selective dissociations of the C–Cl and C–Br bonds. The calculated rate constants are close to those from experimentally inferred values, but the branching ratio of the α C–Cl and β C–Br bond fissions is different from the experimental findings. The direct molecular dynamics calculations predict that fission of the C–Cl bond occurs on a time scale of picoseconds and cleavage of the β C–Br bond proceeds with less probability within the same period. This reveals that the initial relaxation dynamics is probably another important factor that influences the selectivity of the C–Cl and C–Br bond fissions in photodissociation of BrCH2COCl at 248nm.
Classical line shapes based on analytical solutions of bimolecular trajectories in collision induced emission
Authors: Reguera David , Birnbaum George
Published: November 2006

The classical theory of collision induced emission (CIE) from pairs of dissimilar atoms is studied. This radiation emitted by accelerating dipoles is produced essentially by their overlap and exchange interaction at short range. This classical calculation is based on exact collinear solutions of the trajectories of two spherical particles in a head-on collision under the influence of a Morse potential with a well of arbitrary depth. Without too restrictive conditions a variety of simple solutions in closed form is obtained that illustrates the connection between collision dynamics and CIE. Depending on the well depth and energy of the particles, they may radiate in the far infrared to infrared or visible and shorter wavelength regions. The results are characterized by a fixed total energy. Nevertheless, a connection is demonstrated between the line shape in CIE computed through the trajectory and that based on the emission of a thermally equilibrated system.
Molecular dynamics investigation with the time resolved optical Kerr effect on the CS2–C6H6 mixtures
Authors: Heisler Ismael A. , Correia Ricardo R. B. , Cunha Silvio L. S.
Published: November 2006

An investigation of the molecular dynamics in pure liquids and in mixtures through the technique of time resolved optical Kerr effect is performed. The samples studied were the mixtures of carbon disulfide (CS2) with benzene (C6H6). The molecular dynamics of the pure liquids is briefly discussed while the main results are obtained for the mixtures. A slow dynamics component is observed for the optical heterodyne detected optical Kerr effect transient decaying exponentially with time constants on picosecond time scale. The fast subpicosend time relaxations are analyzed in terms of the nondiffusive component of the spectral response that is associated with the molecular dynamics. The modifications of the spectrum are quantified, and the explanation of the observed changes is given in terms of the structural interaction configurations that produced changes in the intermolecular potential within which the molecules execute librational motions.
Spatial distribution of fluorescent light emitted from neon and nitrogen excited by low energy electron beams
Authors: Morozov A. , Krücken R. , Ulrich A. , Wieser J.
Published: November 2006

Side-view intensity profiles of fluorescent light were measured for neon and nitrogen excited with 12keV electron beams at gas pressures from 250to1400hPa. The intensity profiles were compared with theoretical profiles calculated using the CASINO program which performs Monte Carlo simulations of electron scattering. It was assumed that the spatial distribution of fluorescent intensity is directly proportional to the spatial distribution of energy loss by primary electrons. The comparison shows good correlation of experimental data and the results of numeric simulations.
Effects of bias stress on ZnO nanowire field-effect transistors fabricated with organic gate nanodielectrics
Authors: Ju Sanghyun , Janes David B. , Lu Gang , Facchetti Antonio , Marks Tobin J.
Published: November 2006

The effects of bias stress (gate stress or drain stress) on nanowire field-effect transistor (NW-FET) stability were investigated as a function of stress bias and stress time. The n-channel NW-FETs used a nanoscopic self-assembled organic gate insulator, and each device contained a single ZnO nanowire. Before stress, the off current is limited by a leakage current in the 1nA range, which increases as the gate to source bias becomes increasingly negative. The devices also exhibited significant changes in threshold voltage (Vth) and off current over 500 repeated measurement sweeps. The leakage current was significantly reduced after gate stress, but not after drain stress. Vth variations observed upon successive bias sweeps for devices following gate stress or drain stress were smaller than the Vth variation of unstressed devices. These observations suggest that gate stress and drain stress modify the ZnO nanowire-gate insulator interface, which can reduce electron trapping at the surface and therefore reduce the off current levels and variations in Vth. These results confirm that gate and drain stresses are effective means to stabilize device operation and provide high performance transistors with impressive reliabilities.
Growth and optical and structural characterizations of GaN on freestanding GaN substrates with an (Al,In)N insertion layer
Authors: Bejtka K. , Martin R. W. , Watson I. M. , Ndiaye S. , Leroux M.
Published: November 2006

The effects of lattice-matched (Al,In)N insertion layers on the optical and structural properties of GaN films grown epitaxially on freestanding GaN substrates are described. The intensities and energetic positions of the GaN excitonic transitions in the photoluminescence from material grown above (Al,In)N show that high material quality and low strain have been preserved. The free exciton energies of the overgrown GaN, measured by reflectivity and photoluminescence, are 3.477, 3.482, and 3.500eV for A, B, and C excitons, respectively, corresponding to strain-free GaN. The spectra are compared with those of a similar heterostructure grown on sapphire and of GaN-on-sapphire templates.
Dielectric spectroscopy analysis of CaCu3Ti4O12 polycrystalline systems
Authors: Bueno P. R. , Ramírez M. A. , Varela J. A. , Longo E.
Published: November 2006

Dielectric spectroscopy was used in this study to examine CaCu3Ti4O12 polycrystalline samples. The analysis involved systems presenting low non-Ohmic properties, and the grain’s internal domain was evaluated separately from the contribution of barrier-layer capacitances associated with Schottky-type barriers in this type of material. The effect of oxygen-rich atmosphere and high cooling rate was evaluated, revealing a strong increase in the dielectric properties of the CaCu3Ti4O12 system under these conditions. This effect was attributed to a chemical change in the grain’s internal domain, which may be considered an internal barrier-layer capacitance of the polycrystalline material.
Generalized planar fault energies and twinning in Cu–Al alloys
Authors: Kibey S. , Liu J. B. , Johnson D. D. , Sehitoglu H.
Published: November 2006

We report ab initio density functional theory calculations of generalized planar fault energies of fcc Cu–xAl (x=0, 5.0, and 8.3at.%) alloys. We investigate the effects of substitutional solute Al on the unstable intrinsic γus and twin γut stacking fault energies (SFEs). Our results reveal an increased tendency of Cu–Al to deform preferentially by twinning with increasing Al content, consistent with experiment. We attribute this mechanical behavior to appreciable lowering of the twinning barrier γut, along with the stable intrinsic and twin SFEs.
X
-valley leakage in GaAs∕AlGaAs quantum cascade lasers
Authors: Gao X. , Botez D. , Knezevic I.
Published: November 2006

The authors present a Monte Carlo simulation of GaAs∕Al0.33Ga0.67As and GaAs∕Al0.45Ga0.55As quantum cascade lasers (QCLs) that incorporates both Γ- and X-valley transport. The dominant X-valley leakage path in both lasers is interstage X→X scattering. The leakage current is much higher in the 33%-Al QCL, as strong coupling of its weakly localized Γ-valley states to the next-stage continuum Γ states (Γc), followed by strong same-stage Γc→X scattering, ensures high X-valley population and subsequent high X→X leakage current at 300K, even at low fields. Very good agreement with experiment is obtained at both cryogenic and room temperatures.
Investigation of Cr- and Al-based metals for the reflector and Ohmic contact on n-GaN in GaN flip-chip light-emitting diodes
Authors: Hsueh Kuang-Po , Chiang Kuo-Chun , Hsin Yue-Ming , Wang Charles J.
Published: November 2006

This letter investigates three composite metals used as a reflector and Ohmic contact on n-GaN to simplify the process in a flip-chip light-emitting diode (FCLED). The investigated composite metals were Ti∕Al∕Ti∕Au, Cr∕Al∕Cr∕Au, and Cr∕Ti∕Au. The specific contact resistivities of the Ti∕Al∕Ti∕Au, Cr∕Al∕Cr∕Au, and Cr∕Ti∕Au Ohmic contacts on n-GaN were changed from 1.4×10−4, 1.7×10−4, and 1.9×10−4Ωcm2 to 1.3×10−4, 1.1×10−4, and 3.3×10−5Ωcm2, respectively, after 500h of thermal stress. The corresponding operating voltages of FCLEDs with different composite metals were changed by less than 1%. After 96h of thermal stress, the luminous intensities of the three structures decreased by 6.2%, 11.1%, and 1.4%, respectively. The GaN FCLED that was fabricated with Cr∕Ti∕Au as a reflector and an Ohmic contact on n-GaN exhibits good thermal stability and luminous intensity.
Quasi-phase-matched adhered ridge waveguide in LiNbO3
Authors: Kurimura Sunao , Kato Yuji , Maruyama Masayuki , Usui Yusuke , Nakajima Hirochika
Published: November 2006

Uniform periodically poled domains were demonstrated in an insulator-sandwiched structure with z-cut lithium niobate wafers for an adhered ridge waveguide. Efficient quasi-phase-matched second harmonic generation was achieved in a mechanically defined ridge waveguide. Strong confinement in the waveguide produced second-harmonic-generation normalized conversion efficiency of 370%∕Wcm2 in the 1.5μm wavelength region.
Ultralow threshold on-chip microcavity nanocrystal quantum dot lasers
Authors: Min Bumki , Kim Sungjee , Okamoto Koichi , Yang Lan , Scherer Axel , Atwater Harry , Vahala Kerry
Published: November 2006

Chemically synthesized nanocrystal, CdSe∕ZnS (core/shell), quantum dots are coated on the surface of an ultrahigh-Q toroidal microcavity and the lasing is observed at room and liquid nitrogen temperature by pulsed excitation of quantum dots, either through tapered fiber or free space. Use of a tapered fiber coupling substantially lowered the threshold energy when compared with the case of free space excitation. The reason for the threshold reduction is attributed to the efficient delivery of pump pulses to the active gain region of the toroidal microcavity. Further threshold reduction was possible by quantum dot surface-coverage control. By decreasing the quantum dot numbers on the surface of the cavity, the threshold energy is further decreased down to 9.9fJ.
John Maxwell Cowley 1923 - 2004
Authors: Moodie A. F. , Spence J. C. H.
Published: November 2006

John Cowley contributed significantly to all of the fields that relate to electron diffraction and electron microscopy, and helped to found not a few of them. His name is associated in particular with n-beam dynamical theory, high-resolution electron microscopy, scanning transmission electron microscopy, instrumental design, and the application of the techniques of electron scattering to structure analysis. His experimental work was not, however, confined to the scattering of electrons: to take but one instance, his seminal work on the theory of short-range order was stimulated initially by his experiments using X-rays, and it was only later that he extended the technique to include electron diffraction. Finally, to all those who practise the techniques of scattering electrons, X-rays, or neutrons in the study of solids, liquids or gases, his book Diffraction Physics remains not only eminently readable but authoritative.
Organic carbon partitioning in soil and litter in subtropical woodlands and open forests: a case study from the Brigalow Belt, Queensland
Authors: Roxburgh S. H. , Mackey B. G. , Dean C. , Randall L. , Lee A. , Austin J.
Published: November 2006

A woodland–open forest landscape within the Brigalow Belt South bioregion of Queensland, Australia, was surveyed for soil organic carbon, soil bulk density and soil-surface fine-litter carbon. Soil carbon stocks to 30 cm depth across 14 sites, spanning a range of soil and vegetation complexes, ranged from 10.7 to 61.8 t C/ha, with an overall mean of 36.2 t C/ha. Soil carbon stocks to 100 cm depth ranged from 19.4 to 150.5 t C/ha, with an overall mean of 72.9 t C/ha. The standing stock of fine litter ranged from 1.0 to 7.0 t C/ha, with a mean of 2.6 t C/ha, and soil bulk density averaged 1.4 g/cm3 at the soil surface, and 1.6 g/cm3 at 1 m depth. These results contribute to the currently sparse database of soil organic carbon and bulk density measurements in uncultivated soils within Australian open forests and woodlands. The estimates of total soil organic carbon stock calculated to 30 cm depth were further partitioned into resistant plant material (RPM), humus (HUM), and inert organic matter (IOM) pools using diffuse mid-infrared (MIR) analysis. Prediction of the HUM and RPM pools using the RothC soil carbon model agreed well with the MIR measurements, confirming the suitability of RothC for modelling soil organic carbon in these soils. Methods for quantifying soil organic carbon at landscape scales were also explored, and a new regression-based technique for estimating soil carbon stocks from simple field-measured soil attributes has been proposed. The results of this study are discussed with particular reference to the difficulties encountered in the collection of the data, their limitations, and opportunities for the further development of methods for quantifying soil organic carbon at landscape scales.
Fragmentation of Australian rangelands: processes, benefits and risks of changing patterns of land use
Authors: Stokes C. J. , McAllister R. R. J. , Ash A. J.
Published: November 2006

Pastoral development of Australian rangelands has been accompanied by fragmentation of land use, which has changed the scale at which humans and livestock access patchily-distributed resources in landscapes. These changes have tended to be targeted towards achieving narrowly defined policy or land management objectives, and have ignored the broader consequences for land use. We describe the processes of rangeland fragmentation, the factors that have driven these changing patterns of land use, and current trends towards enterprise consolidation and intensification, which continue to reshape the way humans and livestock use rangelands. Although there is growing interest in intensified systems of rangeland management, some of the benefits are uncertain, and there are several risks that serve as a caution against overoptimism: (i) intensification involves multiple simultaneous changes to enterprise operations and the benefits and trade offs of each component need to be better understood; (ii) if intensification proceeds without addressing constraints to implementing these management options sustainably then overutilisation and degradation of rangelands is likely to occur; (iii) further fragmentation of rangelands (from increased internal fencing) could compromise potential benefits derived from landscape heterogeneity in connected landscapes. Adaptation by the pastoral industry continues to reshape the use of rangelands. A broad-based approach to changes in land use that incorporates risks together with expected benefits during initial planning decisions would contribute to greater resilience of rangeland enterprises.
The effects of vegetation structure on the birds in a tropical savanna woodland in north-eastern Australia
Authors: Tassicker A. L. , Kutt A. S. , Vanderduys E. , Mangru S.
Published: November 2006

Management of the dynamics of woody vegetation in Australia’s tropical savannas is a vexing issue for both pastoralists and conservation biologists. In savanna regions around the world, increasing density of woody vegetation contributes to declines in pastoral productivity, but its effects on native fauna are largely unknown. In this paper we examine the avifauna in savanna woodlands of varying structure in the Desert Uplands bioregion, Queensland. Vegetation cover maps derived from aerial photographs were used to choose 60 sites, across 4 cattle stations. We sampled sites mapped at 30–45% and 45–60% foliage cover, and areas which previously had these levels of cover but had been mechanically modified, both by broad scale clearing and selective thinning. Between May and June 2004, we measured a range of habitat variables and sampled the birds at each site. Bird species composition varied significantly between treatments. Bird richness and frequency was greatest in intact vegetation. Thirteen species of birds were most frequently encountered in sites with 30–45% canopy cover, compared with 10 species in the 45–60% cover sites, 4 species in the thinned sites and 7 in the cleared sites. Our results suggest that increasing density of woody vegetation in savanna woodland may be to the advantage of some savanna bird species. Mechanical modification to reduce woody vegetation appears to also benefit some common, widespread species, but has a generally negative overall effect on bird species richness.
Distribution and cone production in Allocasuarina diminuta and A. gymnanthera (Casuarinaceae) in central New South Wales
Authors: Cameron Matt
Published: November 2006

Allocasuarina diminuta (L. Johnson) and A. gymnanthera (L. Johnson) are critical food resources of the threatened glossy black-cockatoo (Calyptorhynchus lathami) in central New South Wales. The distribution and cone production in these species was investigated as part of a broader study on the foraging ecology of the glossy black-cockatoo. Both Allocasuarina species were closely associated with vegetation communities occurring on the ridges and upper slopes. Cone production appeared to be linked to rainfall, with fewer cones produced in dry years. Rainfall during autumn–spring appeared to be especially important. Drought conditions resulted in the failure of plants to produce seed and caused the death of significant numbers of plants. Any decrease in moisture balance or increase in drought frequency/length due to global warming is likely to have negative consequences for Allocasuarina and glossy black-cockatoo populations.
Artefact discard and accumulated patterns in stone artefact assemblage composition in surface archaeological deposits from Pine Point and Langwell Stations, western New South Wales
Authors: Shiner J. I.
Published: November 2006

This paper addresses the potential of deflated surface archaeological deposits to contribute to our understanding of human use of the southern periphery of the semi-arid Barrier Range of western New South Wales. Radiocarbon determinations from heat retainer hearths are used to establish occupational contexts for the surface deposits near the confluence of 2 creeks. This demonstrates a 2000 year discontinuous record of occupation on the eroded surfaces adjacent to the creeks. The reduction and use of raw materials is compared between stone artefact assemblages from these surfaces. The results of the stone artefact analysis indicate both similarities and differences in the formation of the stone artefact assemblages. These patterns are related to the temporal character of human occupation across the landscape. Assemblages that represent a greater intensity of raw material reduction are indicative of extended occupation. The discontinuous occupational chronology from the region suggests that synchronic settlement pattern models underestimate the temporal variation evident in human – environment relationships.