bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantifying the importance of the atmospheric sink for polychlorinated dioxins and furans relative to other global loss processes
Authors: Lohmann Rainer , Jurado Elena , Dachs Jordi , Lohmann Ulrike , Jones Kevin C.
Published: November 2006

Previous attempts to establish global mass balances for polychlorinated dioxins and furans (PCDD/Fs) have focused on the terrestrial sink, thereby neglecting deposition to the oceans and atmospheric losses. In this study, the atmospheric sink of polychlorinated dioxins and furans (PCDD/Fs) was calculated on the basis of their presence in soils. OH radical ([OH]) depletion reactions compete with atmospheric deposition fluxes for the fate of atmospheric PCDD/Fs. Three different steady state scenarios were considered: scenario A was a one‐box atmosphere with globally averaged [OH], temperature (T), atmospheric lifetime (tlife), and a constant gas‐particle partitioning (Φ); in scenario B, [OH], T, and Φ were averaged in a multibox atmosphere, with a constant tlife; and in scenario C, tlife was varied. In scenario A the strength of the atmospheric sink was 2400–2800 kg/yr; in scenario B it was ∼2100 kg/yr; in scenario C, it was ∼1,800 kg/yr (tlife = 5.4 days) to ∼2,800 kg/yr (tlife = 14 days). The majority of the atmospheric sink was due to the depletion of Cl4DFs (1300–1400 kg/yr), followed by Cl4DDs (360–380 kg/yr) and Cl5DFs (230–240 kg/yr). On a global scale, major sinks for PCDD/Fs are the deposition to terrestrial soils and the oceans. For Cl6–8DDs, deposition to soils outweighs depletion reactions in the atmosphere and ocean uptake. The more volatile Cl4–5DD/Fs, however, are true “multimedia” compounds, with their estimated atmospheric sink being roughly as important as the terrestrial sink (in the case of Cl5DD/Fs) or outweighing it (e.g., Cl4DD/Fs).
Using object‐oriented classification and high‐resolution imagery to map fuel types in a Mediterranean region
Authors: Arroyo Lara A. , Healey Sean P. , Cohen Warren B. , Cocero David , Manzanera José A.
Published: November 2006

Knowledge of fuel load and composition is critical in fighting, preventing, and understanding wildfires. Commonly, the generation of fuel maps from remotely sensed imagery has made use of medium‐resolution sensors such as Landsat. This paper presents a methodology to generate fuel type maps from high spatial resolution satellite data through object‐oriented classification. Fuel maps were derived from QuickBird imagery, which offers a panchromatic and four multispectral bands ranging from 0.61 to 2.44 m resolution. The image used for this paper dated from July 2002 and is located in the NW region of Madrid, Spain. The Prometheus system, a fuel type classification adapted to the ecological characteristics of the European Mediterranean basin, was adopted for this study. Viewed with high‐resolution imagery, fuel‐related features are often aggregations of pixels exhibiting a variety of spectral properties. Correct identification and classification of these objects requires an explicit consideration of spatial context. We used an object‐oriented approach, which allowed context consideration during the classification process, as a complement to traditional pixel‐based methods. The map created with this approach was assessed to have greater than 80% accuracy for the prediction of six fuel classes. Results suggested that object‐oriented classification of high‐resolution imagery has the potential to create accurate and spatially precise fuel maps.
Along‐ridge petrological segmentation of the mantle in the Oman ophiolite
Authors: Monnier Christophe , Girardeau Jacques , Le Mée Laurent , Polvé Mireille
Published: November 2006

Oman ophiolite mantle has been sampled over a distance of about 400 km, all along the paleo‐ridge axis. Primary phases have been analyzed in 174 peridotites (mainly harzburgites) and major and trace element contents measured in 90 and 156 samples, respectively. Most samples display depleted characteristics with very low incompatible element bulk rocks and very low HREE contents. On the basis of the spinel Cr# and in agreement with Yb concentrations in the bulk rocks, an average of 16.5% (Fmax) of melt extraction is estimated. These rocks show light REE enrichments marked by high LREE/MREE ratios that well correlate with the extent of melting. The light REE were possibly gained during the latest stage of melting in an open‐system melting model, or through interaction with influxed fluid after melting. Chemical data have been processed Fourier Transforms to study the along‐ridge variations, which gives results similar to those obtained using the seven point running average (Le Mée et al., 2004). When plotted along ridge, spinel Cr# display variations with two types of wavelengths, defining four 50–100 km long segments (70 km in average) and numerous 10–20 km shorter ones making undulations within the longer ones. All segments have a center marked by high values of spinel Cr# (≈ Fmax) and edges with the lowest values. The large, 50–100 km segments (70 km in average) may correspond to large asthenospheric mantle upwellings between major deep mantle discontinuities, while the smaller ones possibly relate more superficial mantle instabilities similar to the structural diapirs of Nicolas et al. (1988a). We consider that the variation in degree of melting in the short‐scale instabilities relates fluid/melt flux melting variations. By comparison with mid‐oceanic ridge models, the long Oman segments can correspond to second‐order segments and the smallest to third‐ to fourth‐order ones. Our data on the geometry of the melting zones will constrain models of the dynamics of the mantle beneath ridges. They provide a new perspective for further characterization of the segments in the Oman ophiolite.
Influence of large scale topography on gravitational rock mass movements: New insights from physical modeling
Authors: Bachmann D. , Bouissou S. , Chemenda A.
Published: November 2006

Gravitational slope failures and associated rock mass movements can be observed at various scales in the same area. It seems obvious that the different movement scales should be interrelated, but their relationships are poorly understood. We address this problem using 3‐D physical modeling. Experiments were conducted with mechanically homogeneous models with two‐scale topographic features. A large scale corresponds to the whole mountain (several kilometers), and a smaller one to a part of a mountain slope (∼one kilometer). Results show that large scale relief induces large‐scale (large volume) gravitational movements. Introduction of small‐scale topographic features results not only in the generation of smaller‐scale landslides, but also in considerable changes in the deformation pattern. The various‐scale processes occur simultaneously and affect each other. To predict the evolution of a landslide, it is therefore necessary to take into account the topography and deformation pattern at various scales.
Evidence of the solar cycle in the tropical troposphere
Authors: Salby Murry L. , Callaghan Patrick F.
Published: November 2006

An analysis of low‐frequency variability in the National Centers for Environmental Prediction record reveals a decadal oscillation inside the tropical troposphere, one that operates coherently and in phase with the 11‐year variation of solar irradiance. The oscillation represents a robust signature of solar variability, achieving higher levels of significance than have previously been required. Characterized by symmetric latitudinal structure, the oscillation involves anomalous temperature that maximizes over the equator and anomalous zonal wind that maximizes in the tropics of each hemisphere. Its deep vertical structure, in concert with the horizontal distribution of anomalous temperature, suggests the involvement of organized convection, as well as a direct radiative influence at upper levels, inside the tropical tropopause layer.
Application of three‐dimensional solar radiative transfer to mountains
Authors: Chen Y. , Hall A. , Liou K. N.
Published: November 2006

We developed a three‐dimensional radiative transfer model simulating solar fluxes over mountain surfaces precisely given distributions of atmospheric scatterers and absorbers. The model quantifies direct, diffuse, terrain‐reflected, and coupling (i.e., photons reflected and scattered more than once) fluxes. We applied it to a midlatitude mountainous surface to study these components' diurnal, seasonal, and geographical variability under clear skies. Domain‐averaged direct and diffuse fluxes together comprise over 96% of the flux year‐round, with diffuse fluxes' relative importance varying inversely with that of direct radiation. Direct fluxes generally account for at least 80% of the total. However, the domain‐averaged diffuse flux proportion increases to nearly 40% at high zenith angles, and approaches 100% when neighboring slopes obscure the surface from the Sun. Terrain‐reflected and coupling components each account for less than 1% throughout much of the year. However, together they comprise ∼3% when surface albedo increases during winter and are similarly nonnegligible in deep valleys all year. We also studied controls on geographical variations in flux components: The sky view factor, a conventional predictor of diffuse fluxes, is surprisingly weakly correlated with them, posing a parameterization challenge. Terrain‐reflected and coupling fluxes may be easier to parameterize given topography. Finally, we assessed shortwave errors in General Circulation Models with smoothed topography by comparing results with the mountainous surface to identical calculations for a flat surface with the same mean elevation. The differences range from 5 to 20 W/m2 and arise because the atmosphere absorbs a different amount of sunshine when underlying topography is smoothed.
Aerosol variability in the Adriatic Sea from automated optical field measurements and Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS)
Authors: Mélin F. , Clerici M. , Zibordi G. , Bulgarelli B.
Published: November 2006

The aerosol optical properties in the Adriatic Sea are presented using a 9‐year time series (1996–2005) of automated measurements collected on the Acqua Alta Oceanographic Tower (AAOT) in the northern part of the basin and a coincident satellite record obtained from an atmospheric correction scheme adapted for European seas and applied to the Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS). At AAOT, the overall averages of aerosol optical thicknessτaat 500 nm and Ångström exponentαare 0.29 ± 0.21 and 1.51 ± 0.34, respectively. The average single scattering albedo varies from 0.957 at 440 nm to 0.910 at 1020 nm. The aerosol size distribution derived by optical data inversion exhibits an increase of the radius of the accumulation mode withτa. From 402 coincident data records, the agreement between satellite and fieldτais remarkable, with mean absolute percentage differences of 17–20% in the 412–870 nm spectral range. On the other hand, the satellite record tends to filter out occurrences of highτa. The satellite‐derived products are used to analyze the seasonal cycle over the Adriatic basin, showing minima in winter and maxima in summer (τa(500) from 0.06 to 0.23). Then, the results of radiative transfer simulations are combined with the satellite‐derived seasonal cycles ofτaand cloud fraction to determine the clear‐sky aerosol direct radiative effect for the Adriatic Sea. At the surface, the aerosol load results in a monthly average cooling effect ranging from −1 W m−2in winter up to −9.6 W m−2in August and a corresponding atmospheric warming from 0.5 to 4.6 W m−2.
Characteristics of InGaPN∕GaAs heterostructures investigated by photoreflectance spectroscopy
Authors: Wang T. S. , Lin K. I. , Hwang J. S.
Published: November 2006

Photoreflectance (PR) spectra at various temperatures and photoluminescence (PL) spectra and high-resolution x-ray rocking curve (XRC) measurements are used to investigate the band alignment, epitaxial-strain, and atomic-ordering effects in In0.54Ga0.46P1−yNy∕GaAs (y=0%–2.0%) heterostructures. The existence of additional peaks in PR spectra at higher levels of nitrogen (N) incorporation implies that the band alignment switches from type I to type II, due to the lowering of the conduction band. The electric field at the interface is determined and is discussed with the N content. Redshifts of the PR and PL peaks indicate that the band gap of InGaPN is dramatically reduced as N is incorporated. The valence-band splitting (VBS) and the spin-orbit splitting of InGaPN are obtained from PR spectra. High-resolution XRC measurements indicate that as the N content increases, the lattice mismatch and the compressive strain between the epilayer and GaAs substrate decrease while the VBS increases, which implies an increase in the degree of ordering in InGaPN caused by the transition from a cubic zinc blende structure to a [111] CuPt structure. The order parameter η of InGaPN deduced from the VBS ranges from 0.256 to 0.498, indicating that the InGaPN epilayer becomes more ordered with increasing N incorporation.
Operating longevity of organic light-emitting diodes with perylene derivatives as aggregating light-emitting-layer additives: Expansion of the emission zone
Authors: Jarikov Viktor V. , Young Ralph H. , Vargas J. Ramon , Brown Christopher T. , Klubek Kevin P. , Liao Liang-Sheng
Published: November 2006

We describe aggregating perylene derivatives as light-emitting-layer (LEL) additives in organic light-emitting diodes (OLEDs). These molecules readily form emissive aggregates when added to the LEL. In the resulting devices, the aggregates show moderate external quantum efficiencies of 0.9%–1.7%, which can be improved to 2.7%–4.0% by further adding a proper dopant. Importantly, addition of these polycyclic aromatic hydrocarbons increases the half-life (t50) of undoped and doped OLEDs by 30–150 times. Thus, 11cd∕A green and 5.2cd∕A red devices are produced that have pure color, Commission Internationale de l'Eclairage 1931 2° color chromaticity coordinates (CIEx,y) 0.32, 0.63 and 0.64, 0.36, respectively, and t50 of 30 000 and 200 000h, respectively, upon operation at 40mA∕cm2. A possible link between the thickness of the emission zone and the lifetime increase is illustrated by comparing aluminum 8-hydroxyquinoline chelate (Alq3) as an LEL host versus an Alq3+dibenzo[b,k]perylene mixed host using C545T as an emissive probe. The comparison suggests that the emission zone and probably the electron-hole recombination zone are expanded for the mixed host.
Freezing shape and composition of Ge∕Si(001) self-assembled islands during silicon capping
Authors: De Seta M. , Capellini G. , Di Gaspare L. , Evangelisti F. , D’Acapito F.
Published: November 2006

We use atomic force microscopy, x-ray photoemission spectroscopy, and x-ray absorption spectroscopy to study the effect of the deposition of a Si cap layer by chemical vapor deposition on the morphology and composition of a Ge island layer grown at 600°C. We found that the capping of self-assembled Ge islands under a silicon layer results in high-quality, atomically flat layer only at deposition temperature above 700°C. On the other hand at this temperature Ge–Si intermixing and island coarsening are greatly enhanced, resulting in an increased average island volume. Here we show that the predeposition at low temperature of a thin cap layer preserves island shape, size, and composition when the capped islands undergo a subsequent process at higher temperature up to 750°C. It is shown, therefore, that with a two-step capping process it is possible to combine the benefit of a low temperature capping, which reduces island alloying and coarsening, with that of a high temperature capping which is needed to recover a flat surface.
Simulation studies of self-assembly of end-tethered nanorods in solution and role of rod aspect ratio and tether length
Authors: Horsch Mark A. , Zhang Zhenli , Glotzer Sharon C.
Published: November 2006

We present temperature versus concentration phase diagrams for “shape amphiphiles” comprised of tethered moderate and low aspect ratio rods. Simulations of moderate aspect ratio rods (first reported by Horsch et al. [Phys. Rev. Lett. 95, 056105 (2005)]) predict their self-assembly into spherical micelles with bcc order, long micelles with nematic order, a racemic mixture of hexagonally ordered chiral cylinders, two perforated phases: one with tetragonal order and one with hexagonal order, and a smectic C lamellar phase. In contrast, we predict here that small aspect ratio tethered rods self-assemble into bcc ordered spherical micelles, hexagonally ordered cylinders, and a smectic C lamellar phase. We compare and contrast the phases obtained for the two aspect ratios and examine in further detail several unusual phases. Our simulations also reveal that for moderate aspect ratio rods there is a tendency toward phases with decreasing interfacial curvature with decreasing coil size, including a double gyroid phase. In addition, we investigate the role of tether length on the assembled structures. Our results are applicable to short rod-coil block copolymers and rodlike nanoparticles with polymer tethers, and to colloidal building blocks comprised of a flexible string of colloids tethered to a rigid string of colloids, with the interactions scaled appropriately.
Synthesis and optical properties of ZnSe∕95SiO2–5B2O3 nanocomposites by sol-gel method
Authors: Hao Haiyan , Yao Xi , Wang Mingqiang , Li Haiyan
Published: November 2006

Zn Se ∕ 95 Si O 2 – 5 B 2 O 3 nanocomposites were prepared by a sol-gel method and in situ growth technique. X-ray diffraction patterns showed the typical interplanar spacing corresponding to the cubic phase of ZnSe. Transmission electron microscopy studies indicated that an average particle size of the ZnSe nanocrystals is around 5.0nm. UV-visible spectroscopy was carried out to determine the band gap of the ZnSe nanocrystals and a blueshift was observed as compared to that of the ZnSe bulk materials. A single-beam Z-scan measurement showed that the nanocomposites have two-photon absorption (TPA) and a negative nonlinear refraction at the wavelength of 532nm; the TPA coefficient β and the nonlinear refractive index n2 are 19.94cm∕GW and 1.0×10−10esu, respectively. The nonlinearity of the nanocomposites is higher than that of the ZnSe bulk materials due to special surface structure and high surface activity of the ZnSe nanocrystals.
Low-temperature heat capacity of fullerite C60 doped with nitrogen
Authors: Gurevich A. M. , Terekhov A. V. , Kondrashev D. S. , Dolbin A. V. , Cassidy D. , Gadd G. E. , Moricca S. , Sundqvist B.
Published: November 2006

The heat capacity Cm of polycrystalline fullerite C60 doped with nitrogen is measured in the temperature interval 2–13K. The contributions to the heat capacity from translational lattice vibrations (Debye contribution), from orientational vibrations of the C60 molecules (Einstein contribution), and from the motion of the N2 molecules in the octahedral cavities of the C60 lattice are estimated. However, no indications of the first-order phase transformation detected earlier in a dilatometric investigation of the N2–C60 orientational glass are found (beyond the experimental error limits). A possible explanation for this fact is proposed.
Stoichiometry control of sputtered CuCl thin films: Influence on ultraviolet emission properties
Authors: Natarajan Gomathi , Rajendra Kumar R. T. , Daniels S. , Cameron D. C. , McNally P. J.
Published: November 2006

We demonstrate that the chemical composition of the sputtered CuCl thin films could be finely controlled by adjusting the bias to the substrate. The films deposited without any intentional bias were Cl rich (CuCl1+x), a bias of −22V yielded stoichiometric CuCl, and a further increase in the negative bias resulted in Cl deficient films (CuCl1−x). The crystalline and optical properties were found to be associated with the chemical composition. Cl rich films showed a deep level green emission at around 515nm in addition to ultraviolet (UV) excitonic emission. The stoichiometric films have higher optical quality, exhibiting a sharp UV emission at around 385nm at room temperature, compared to nonstoichiometric samples. Visible luminescence related to deep level defects was not observed in the stoichiometric films. Changes in energy of the flux from the target and the subsequent ion bombardment on the substrate surface are correlated with the variations in chemical composition and their impact on the film microstructure and UV emission.
Surface order-disorder phase transitions and percolation
Authors: Giménez M. C. , Nieto F. , Ramirez-Pastor A. J.
Published: November 2006

In the present paper, the connection between surface order-disorder phase transitions and the percolating properties of the adsorbed phase has been studied. For this purpose, four lattice-gas models in the presence of repulsive interactions have been considered. Namely, monomers on honeycomb, square, and triangular lattices, and dimers (particles occupying two adjacent adsorption sites) on square substrates. By using Monte Carlo simulation and finite-size scaling analysis, we obtain the percolation threshold θc of the adlayer, which presents an interesting dependence with w∕kBT (w, kB, and T being the lateral interaction energy, the Boltzmann constant, and the temperature, respectively). For each geometry and adsorbate size, a phase diagram separating a percolating and a nonpercolating region is determined.
Submolecular imaging of chloronitrobenzene isomers on Cu(111)
Authors: Niemi Eeva , Simic-Milosevic Violeta , Morgenstern Karina , Korventausta Antti , Paavilainen Sami , Nieminen Jouko
Published: November 2006

We compare computer simulations to experimental scanning tunneling microscopy (STM) images of chloronitrobenzene molecules on a Cu(111) surface. The experiments show that adsorption induced isomerization of the molecules takes place on the surface. Furthermore, not only the submolecular features can be seen in the STM images, but different isomers can also be recognized. The Todorov-Pendry approach to tunneling produces simulated STM images which are in good accordance with the experiments. Alongside with STM simulations in a tight-binding basis, ab initio calculations are performed in order to analyze the symmetry of relevant molecular orbitals and to consider the nature of tunneling channels. Our calculations show that while the orbitals delocalized to the phenyl ring create a relatively transparent tunneling channel, they also almost isolate the orbitals of the substitute groups at energies which are relevant in STM experiments. These features of the electronic structure are the key ingredients of the accurate submolecular observations.
Ion attachment mass spectrometry of nonequilibrium atmospheric-pressure pulsed remote plasma for SiO2 etching
Authors: Iwasaki Masahiro , Ito Masafumi , Uehara Tsuyoshi , Nakamura Megumi , Hori Masaru
Published: November 2006

An etching process for SiO2 that employs atmospheric-pressure pulsed remote plasma with a mixture gas (CF4∕Ar) has been demonstrated. The etch rate increased by increasing the pulse frequency and also increased rapidly with the addition of a small amount of O2 gas. A SiO2 etch rate of 400nm∕min was obtained without any bias supplied to the substrate, and more than 8μm∕min was obtained with H2O addition. The exhaust gas from the plasma source was investigated using ion attachment mass spectrometry (IAMS). With IAMS, the polymerized species were measured without the generation of fragment ions. The results suggest that HF molecules are generated by H2O addition to CF4 and that the etch rate of SiO2 depends on the density of HF molecules.
Kinetic Alfvén wave and associated current drive at the center of tokamaks
Authors: Chu M. S. , Chan V. S. , Politzer P. A. , Brennan D. P. , Choi M. , Lao L. L. , St. John H. E. , Turnbull A. D.
Published: November 2006

The possibility of kinetic Alfvén wave current drive at the center of tokamaks is proposed. The amount of driven current could be substantial and strongly affect the dynamics of the plasma central region. The relevance of this mechanism to present day and future tokamaks operating in the hybrid regime is discussed.
Influence of the flow field in curtain coating onto a prewet substrate
Authors: Marston J. O. , Simmons M. J. H. , Decent S. P. , Kirk S. P.
Published: November 2006

The onset of air entrainment for curtain coating onto a surface prewetted with the coating fluid was studied. The substrate used was a polished, scraped steel wheel and coating was performed over ranges of dimensionless parameters observed in commercial coating processes (Reynolds number, 0.14<Re=ρQ∕μ<33.02; Capillary number, 0.19<Ca=μU∕σ<25.07). The substrate velocity for the onset of air entrainment was obtained as a function of the curtain flow rate per unit width of curtain (1<Q<9cm2s−1), fluid dynamic viscosity (0.0326<μ<0.878Pas), curtain height (0.035<h<0.095m), and thickness of the prewet film (1×10−7<c<3×10−5m). A remarkable and strong dependence of the onset of air entrainment on curtain flow rate was observed (hydrodynamic assist) and the general features of the hydrodynamics were very similar to those observed for previous works onto dry substrates. However, the presence of the prewet film led to higher maximum substrate velocities at the onset of air entrainment than observed for dry substrates. For high liquid viscosities, the air entrainment curve bifurcates; under these conditions, the maximum substrate velocity is no longer inversely proportional to the fluid viscosity and stable coating is possible at higher substrate velocities than would be predicted by conventional theory. This “intense assist” exhibits a complex relationship with the prewet film thickness. The results presented in this paper demonstrate that hydrodynamic assist is not exclusive to wetting, but is a generic phenomenon of fluid flows.
Two size regimes of methanol clusters produced by adiabatic expansion
Authors: Bergersen H. , Abu-samha M. , Lindblad A. , Marinho R. R. T. , Öhrwall G. , Tchaplyguine M. , Børve K. J. , Svensson S. , Björneholm O.
Published: November 2006

Free neutral methanol clusters produced by adiabatic expansion have been studied by photoelectron spectroscopy and line shape modeling. The results show that clusters belonging to two distinct size regimes can be produced by changing the expansion conditions. While the larger size regime can be well described by line shapes calculated for clusters consisting of hundreds of molecules, the smaller size regime corresponds to methanol oligomers, predominantly of cyclic structure. There is little contribution from dimers to the spectra.
Enhancement of light extraction from a silicon quantum dot light-emitting diode containing a rugged surface pattern
Authors: Kim Kyung-Hyun , Shin Jae-Heon , Park Nae-Man , Huh Chul , Kim Tae-Youb , Cho Kwan-Sik , Hong Jong Cheol , Sung Gun Yong
Published: November 2006

The enhancement in light extraction efficiency from a periodic micron-scale rugged surface pattern on Si quantum dot light-emitting-diode (Si-QD LED) structures was investigated, both numerically and experimentally. Micron-scale rugged surface patterns were fabricated on the top layer of the Si-QD LED to increase the extraction of light from the active layer. The optimum light extraction condition for a Si-QD LED corresponded to a pattern size/period ratio of ∼0.7. In experiments, the luminescent powers of a Si-QD LED with/without micron-scale surface patterns increase linearly with current density, and the efficiency of light extraction was enhanced by a factor of 2.8.
La
B
6
tip-modified multiwalled carbon nanotube as high quality field emission electron source
Authors: Wei Wei , Jiang Kaili , Wei Yang , Liu Peng , Liu Kai , Zhang Lina , Li Qunqing , Fan Shoushan
Published: November 2006

An effective field emitter has been developed by modifying an individual multiwalled carbon nanotube (MWCNT) tip with LaB6. The modified emitter possesses the merits of both the MWCNT and LaB6, which presents a significant low turn-on voltage, good emission properties, and long lifetime. As a result, a total current of 70μA has been reached at a very low electric field of only 1.2V∕μm for an individual modified MWCNT emitter, which is also expected to have advantages of high brightness and coherence, clearly indicating great promise for practical applications such as electron guns or cathodes for field emission flat panel display.
Hollow core photonic crystal fiber surface-enhanced Raman probe
Authors: Yan He , Gu Claire , Yang Changxi , Liu Jie , Jin Guofan , Zhang Jiatao , Hou Lantian , Yao Yuan
Published: November 2006

The authors demonstrate a hollow core photonic crystal fiber (HCPCF) surface-enhanced Raman probe consisting of a HCPCF with Au nanoparticles coated on the inner surface of the air holes serving as the substrate of surface-enhanced Raman scattering (SERS). The experimental results indicate that the confinement of light inside the HCPCF and the coating of nanoparticles/analyte inside the air holes of the HCPCF offer a large area for the light to interact with the SERS particles. An optimized design of the HCPCF is provided to further improve the probe sensitivity.
Structure Determination of Butlerin A, B and C—Three New Lichen p-Terphenyls
Authors: Elix JA , Elix JA , Gaul KL , Gaul KL , Hockless DCR , Hockless DCR , Wardlaw JH , Wardlaw JH
Published: November 2006

The structures of butlerin A (1) (3′,4,4″,6′-tetramethoxy[1,1′:4′,1″-terphenyl]-2′-yl acetate), butlerin B (2) (3′,4,4″,5′-tetramethoxy[1,1′:4′,1″-terphenyl]-2′-yl acetate) and butlerin C (5) (3′,4,4″-trimethoxy[1,1′:4′,1″-terphenyl]-2′,6′-diyl acetate), three para-terphenyls from the lichen Relicina connivens, have been established by X-ray analysis of crystals of butlerins A and B and spectroscopic comparisons. Crystals of a mixture of butlerins A and B are orthorhombic, Pbcn, a 22.388(3), b 13.525(2), c 7.082(3) Ǻ; Z 4. Refinement of 1049 data with I > 3σ(I) gave conventional R factors of 0.043 and 0.042.
The Stereochemistry of Organometallic Compounds. XLII. The Preparation of [2,1-b]Quinazolines Involving Rhodium-Catalysed Hydroformylation of 2-Amino-N-Alkenylbenzylamines
Authors: Campi EM , Habsuda J , Jackson WR , Jonasson CAM , Mccubbin QJ
Published: November 2006

Rhodium-catalysed reactions of 2-amino-N-alkenylbenzylamines with H2/CO give hexahydro-pyrrolo- and hexahydropyrido -[2,1-b] quinazolines. Reactions of N-allyl derivatives give a single regioisomer, and reactions of but-3-enyl analogues give mixtures of pyrrolo and pyrido derivatives. Some reactions give significant amounts (10-30%) of tetrahydro derivatives. The origin of these compounds remains unclear.
Influence of benzimidazole fungicides on incidence of Botrytis allii infection of onion leaves and subsequent incidence of onion neck rot in storage in Tasmania, Australia
Authors: Chilvers M. I. , Hay F. S. , Hills J. , Dennis J. J. C. , Wilson C. R.
Published: November 2006

Neck rot of onion caused by Botrytis spp., including B. allii, has previously been controlled in Australia with the fungicide Benlate (benomyl). Production of Benlate has recently ceased, therefore a field trial was conducted to examine the efficacy of alternative benzimidazoles fungicides. The trial compared 2 carbendazim fungicides (Marvel and Spin Flo) at 3 rates of application with Benlate applied at commercial rates and to non-treated plots in a randomised complete block design with 4 replicate plots per treatment. Fungicides were applied at 89, 96, 112 and 119 days after sowing. Plots were sprayed with inoculum consisting of a suspension of B. allii conidia 103 days after sowing. The incidence of B. allii infection in leaves was estimated 10 times during the season by collection and incubation of leaf samples. Fifty-six days after inoculum application the mean incidence of B. allii in leaves from fungicide treatments ranged from 0 to 10%, significantly lower (P<0.05) than that of non-treated plots (28.8%). The mean incidence of neck rot in bulb samples after 3 months of storage ranged from 1.0 to 9.9% in fungicide treatments, significantly (P<0.05) lower than that of non-treated plots (63.4%). The incidence of B. allii leaf infection in plots sampled at different times during the season and the incidence of neck rot in storage were all significantly correlated (r = 0.42–0.61, P<0.01), except prior to application of inoculum.
Brian John Robinson 1930 - 2004
Authors: Whiteoak J. B. , Sim H. L.
Published: November 2006

In a half-century involvement in radio astronomy, Brian Robinson achieved international recognition and received many honours. During a forty-year career at CSIRO Division of Radiophysics, he undertook leading research, headed the Astrophysics Group, and contributed significantly in the Australia Telescope planning and funding campaign. Internationally, he distinguished himself in radio astronomy committees and negotiations to protect radio astronomy observations from interference from telecommunication transmissions.
A new approach to grassland management for the arid Aletai region in Northern China
Authors: Guo Zheng Gang , Liang Tian Gang , Liu Xing Yuan , Niu Fu Jun
Published: November 2006

Land degradation in the arid Aletai Region in northern China is not only detrimental to animal production, but also reduces the ability to conserve water resources by destabilising the catchments of rivers which affects runoff, thus, threatening the sustainable use of these grasslands. A new approach to grassland management based on carrying capacity and ecological services value of grassland types, using an index of classification management (ICG), was designed to ensure the sustainability of grassland ecosystems. In this approach, grassland is classified into 3 management sectors. The first is conservation grassland, which is mainly devoted to ecological and social values; the second is the moderately productive grassland, dedicated to multiple benefits by rational use; and the third is intensively productive grassland, focusing on maximum economic effect. For the arid Aletai region, no intensively productive grassland was available. Conservation grassland occupied 2.5 million ha, accounted for 25.4% of grassland area, and included alpine meadow, mountain meadow, mountain meadow steppe, mountain steppe and flat meadow. In these grasslands, grazing should be eliminated to allow restoration of degenerated areas, protect grasslands with important ecological values from destruction, and to further improve the environment. Moderately productive grassland covered 7.3 million ha, and the grassland types were alpine steppe, mountain desert steppe, plain desert steppe, steppe desert, and plain desert. Agricultural measures, such as fertiliser and irrigation application, should be used to enhance the productivity of these grasslands.
Aboriginal perspectives on kangaroo management in South Australia
Authors: Thomsen D. A. , Muir K. , Davies J.
Published: November 2006

Kangaroos are culturally significant to Aboriginal people but Aboriginal people are generally not involved in kangaroo management or in the kangaroo industry. Our research has provided the first opportunity for Aboriginal people in South Australia to present their perspectives on the commercial harvest of kangaroos. Research methods were qualitative, involving consultations with authoritative Aboriginal people about their perspectives, aspirations, and how they see their rights and interests in relation to the commercial harvest of kangaroos. We found diverse views on this topic from Aboriginal research participants. For some Aboriginal people, strict cultural protocols preclude any involvement in the commercial harvest, but for people from other regions where the cultural laws concerning kangaroos are quite different, there is interest in developing enterprises based on kangaroo harvest. Despite the diversity of views about commercial kangaroo harvest, Aboriginal people across South Australia highly value kangaroos, and want to be included in decision-making processes for kangaroo management. There is potential for appropriate engagement of Aboriginal people in kangaroo management through improved communication, greater understanding and respect for the diversity of Aboriginal perspectives and protocols regarding native wildlife.
Effect of visibility on time allocation and escape decisions in crimson rosellas
Authors: Boyer Jennifer S. , Hass Laura L. , Lurie Matthew H. , Blumstein Daniel T.
Published: November 2006

Most studies of antipredator behaviour have focused on a single behaviour at a time, but ubiquitous factors may simultaneously influence a variety of activities. Habitat structure influences visibility, which influences both the ability of prey to detect and respond to their predators. We studied how habitat visibility influenced time allocation and escape decisions of crimson rosellas (Playcercus elegans). We examined the effect of visibility on time allocated to looking, locomotion and foraging. We measured escape decisions by experimentally approaching rosellas until they fled. We measured visibility by standing 12 m away from a 1-m2 white sheet containing 36 points and counting the number of points that were visible. As measured, visibility influenced time allocated to both foraging and locomotion. However, there was no effect of visibility on flight-initiation distance or two other related measures of escape (a measure of the latency to detect an approaching threat or the latency to flee once the threat was detected). Therefore, crimson rosellas modified their behaviour as a function of visibility, but this did not influence their decision to flee from an approaching human. We infer that they are sensitive to variation in visibility, but that this does not influence their overall perception of risk as we measured it. These two stages of antipredator behaviour may thus be largely independent; ubiquitous factors need not have ubiquitous effects on different aspects of antipredator behaviour.
A single chromoprotein with triple chromophores acts as both a phytochrome and a phototropin
Authors: Kanegae Takeshi , Hayashida Emi , Kuramoto Chihiro , Wada Masamitsu
Published: November 2006

Plants sense their environmental light conditions by using three photoreceptors that absorb in the UV, blue/near UV, and red/far-red spectral ranges. These photoreceptors have specific chromophore components corresponding to their absorption spectra. Phytochrome, a red/far-red light receptor, has phytochromobilin as its chromophore, whereas the blue/near UV photoreceptors cryptochrome and phototropin have a pair of flavin derivatives. Plants use these various photoreceptors to assess the surrounding light environment. Phytochrome 3 (PHY3) is a red light receptor found in some ferns, which preferentially grow under weak light. PHY3 is composed of a phytochrome chromophore-binding domain in its N-terminal portion and an almost full-length phototropin in its C-terminal half. This unusual domain organization implies that two different light-sensing systems coexist in this single photoreceptor, although these light-sensing systems usually reside in independent photoreceptors. Here, we show that PHY3 acts as a dual-channel photoreceptor that possesses both the red light-sensing system of phytochrome and the blue light-sensing system of phototropin. Furthermore, red- and blue-light signals perceived by PHY3 are processed synergistically within this single chromoprotein. These unusual properties might confer an enhanced light sensitivity on PHY3, allowing ferns to grow under a low-light canopy.
Asymptotically increasing compliance of genomes with Chargaff's second parity rules through inversions and inverted transpositions
Authors: Albrecht-Buehler Guenter
Published: November 2006

Chargaff's second parity rules for mononucleotides and oligonucleotides (CIImonoand CIIoligorules) state that a sufficiently long (>100 kb) strand of genomic DNA that containsNcopies of a mono- or oligonucleotide, also containsNcopies of its reverse complementary mono- or oligonucleotide on the same strand. There is very strong support in the literature for the validity of the rules in coding and noncoding regions, especially for the CIImonorule. Because the experimental support for the CIIoligorule is much less complete, the present article, focusing on the special case of trinucleotides (triplets), examined several gigabases of genome sequences from a wide range of species and kingdoms including organelles such as mitochondria and chloroplasts. I found that all genomes, with the only exception of certain mitochondria, complied with the CIItripletrule at a very high level of accuracy in coding and noncoding regions alike. Based on the growing evidence that genomes may contain up to millions of copies of interspersed repetitive elements, I propose in this article a quantitative formulation of the hypothesis that inversions and inverted transposition could be a major contributing if not dominant factor in the almost universal validity of the rules.
Atomic structures of peptide self-assembly mimics
Authors: Makabe Koki , McElheny Dan , Tereshko Valentia , Hilyard Aaron , Gawlak Grzegorz , Yan Shude , Koide Akiko , Koide Shohei
Published: November 2006

Although the β-rich self-assemblies are a major structural class for polypeptides and the focus of intense research, little is known about their atomic structures and dynamics due to their insoluble and noncrystalline nature. We developed a protein engineering strategy that captures a self-assembly segment in a water-soluble molecule. A predefined number of self-assembling peptide units are linked, and the β-sheet ends are capped to prevent aggregation, which yields a mono-dispersed soluble protein. We tested this strategy by using
Borrelia
outer surface protein (OspA) whose single-layer β-sheet located between two globular domains consists of two β-hairpin units and thus can be considered as a prototype of self-assembly. We constructed self-assembly mimics of different sizes and determined their atomic structures using x-ray crystallography and NMR spectroscopy. Highly regular β-sheet geometries were maintained in these structures, and peptide units had a nearly identical conformation, supporting the concept that a peptide in the regular β-geometry is primed for self-assembly. However, we found small but significant differences in the relative orientation between adjacent peptide units in terms of β-sheet twist and bend, suggesting their inherent flexibility. Modeling shows how this conformational diversity, when propagated over a large number of peptide units, can lead to a substantial degree of nanoscale polymorphism of self-assemblies.
The twin-arginine translocation pathway is a major route of protein export in
Streptomyces coelicolor
Authors: Widdick David A. , Dilks Kieran , Chandra Govind , Bottrill Andrew , Naldrett Mike , Pohlschröder Mechthild , Palmer Tracy
Published: November 2006

The twin-arginine translocation (Tat) pathway is a protein transport system for the export of folded proteins. Substrate proteins are targeted to the Tat translocase by N-terminal signal peptides harboring a distinctive R-R-x-Φ-Φ “twin-arginine” amino acid motif. Using a combination of proteomic techniques, the protein contents from the cell wall of the model Gram-positive bacterium
Streptomyces coelicolor
were identified and compared with that of mutant strains defective in Tat transport. The proteomic experiments pointed to 43 potentially Tat-dependent extracellular proteins. Of these, 25 were verified as bearing bona fide Tat-targeting signal peptides after independent screening with a facile, rapid, and sensitive reporter assay. The identified Tat substrates, among others, include polymer-degrading enzymes, phosphatases, and binding proteins as well as enzymes involved in secondary metabolism. Moreover, in addition to predicted extracellular substrates, putative lipoproteins were shown to be Tat-dependent. This work provides strong experimental evidence that the Tat system is used as a major general export pathway in
Streptomyces
.
An efficient promoter trap for detection of patterned gene expression and subsequent functional analysis in
Drosophila
Authors: Larsen Camilla , Franch-Marro Xavier , Hartenstein Volker , Alexandre Cyrille , Vincent Jean-Paul
Published: November 2006

Transposable elements have been used in
Drosophila
to detect gene expression, inactivate gene function, and induce ectopic expression or overexpression. We have combined all of these features in a single construct. A promoterless GAL4 cDNA is expressed when the construct inserts within a transcriptional unit, and GAL4 activates a GFP-encoding gene present in the same transposon. In a primary screen, patterned gene expression is detected as GFP fluorescence in the live progeny of dysgenic males. Many animals expressing GFP in distinct patterns can be recovered with relatively little effort. As expected, many insertions cause loss of function. After insertion at a genomic location, specific parts of the transposon can be excised by FLP recombinase, thus allowing it to induce conditional misexpression of the tagged gene. Therefore, both gain- and loss-of-function studies can be carried out with a single insertion in a gene identified by virtue of its expression pattern. Using this promoter trap approach, we have identified a group of cells that innervate the calyx of the mushroom body and could thus define a previously unrecognized memory circuit.
The spine neck filters membrane potentials
Authors: Araya Roberto , Jiang Jiang , Eisenthal Kenneth B. , Yuste Rafael
Published: November 2006

Dendritic spines receive most synaptic inputs in the forebrain. Their morphology, with a spine head isolated from the dendrite by a slender neck, indicates a potential role in isolating inputs. Indeed, biochemical compartmentalization occurs at spine heads because of the diffusional bottleneck created by the spine neck. Here we investigate whether the spine neck also isolates inputs electrically. Using two-photon uncaging of glutamate on spine heads from mouse layer-5 neocortical pyramidal cells, we find that the amplitude of uncaging potentials at the soma is inversely proportional to neck length. This effect is strong and independent of the position of the spine in the dendritic tree and size of the spine head. Moreover, spines with long necks are electrically silent at the soma, although their heads are activated by the uncaging event, as determined with calcium imaging. Finally, second harmonic measurements of membrane potential reveal an attenuation of somatic voltages into the spine head, an attenuation directly proportional to neck length. We conclude that the spine neck plays an electrical role in the transmission of membrane potentials, isolating synapses electrically.
On Dinur’s proof of the PCP theorem
Authors: Radhakrishnan Jaikumar , Sudan Madhu
Published: November 2006

Probabilistically checkable proofs are proofs that can be checked probabilistically by reading very few bits of the proof. In the early 1990s, it was shown that proofs could be transformed into probabilistically checkable ones with only a modest increase in their length. The initial transformations, though elementary, were a little too complex. A recent work due to Irit Dinur gives a dramatically simple (and radically new) construction of probabilistically checkable proofs. This article explains the notion of a probabilistically checkable proof, presents the formal definition and then introduces the reader to Dinur’s work along with some of the context.