bluuebunny/crossref_metadata_2025 huggingface dataset:
On the motion of laminar wing wakes in a stratified fluid
Authors: Spalart Philippe R.
Published: May 2006

We present numerical solutions for two-dimensional laminar symmetric vortex systems descending in a stably stratified fluid, within the Boussinesq approximation. Three types of flows are considered: (I) tight vortices; (II) those deriving from an elliptical wing lift distribution; and (III) those deriving from a ‘high-lift’ distribution, with a part-span flap on the wing. The non-dimensional stratification ranges from zero to moderate, as it does for airliners. For Types I and II, with high Reynolds numbers and weak stratification, the solutions confirm the theory of Scorer & Davenport (1970) (their article lacks a crucial link which we provide, equivalent to one of Crow (1974)). Contrary to common conceptions and observations in small-scale experiments, the descent velocity increases exponentially with time, as the distance between vortices decreases and the circulation of the vortices proper is conserved. With moderate stratification, wakes with sufficient energy also attain the accelerating régime, until the vortex cores make contact. However, they first experience a rebound, which is both of practical importance and out of reach of simple formulas. Type III wakes produce two durable vortex pairs which tumble, and mitigate the buoyancy effect by exchanging fluid with the surroundings. These phenomena are obscured by low wing aspect ratios, Reynolds numbers below about 105, or appreciable surrounding turbulence; this may explain why neither a clear rebound nor an acceleration can be reconciled with experiments to date. We argue that airliner wakes have very little inherent diffusion, and that a rapid end to the wake's descent must reveal effects other than simple buoyancy. In particular, stratification promotes the Crow instability.
Formation of a pointed drop in Taylor's four-roller mill
Authors: Antanovskii Leonid K.
Published: May 2006

The paper addresses the mathematical modelling of the formation of a pointed drop in a four-roller mill, observed by Taylor (1934) in the Cavendish Laboratory. Since the experiments were carried out with drops of small diameter compared to the mill size, the method of matched asymptotic expansions is applicable. A two-dimensional Stokes flow generated by the rotating rollers in the mill but with no drop effect (outer problem) is computed numerically by a boundary-element method. The local expansion of that flow at the centre of the mill, where the drop is to be positioned, is used as a far field for the flow around the drop in unbounded fluid (inner problem). Employing a plane-flow model and using complex-variable techniques, the explicit solutions previously obtained by the author are adapted to the inner problem. It is proved that, with an increasing rotation rate of the rollers, the drop does develop two apparent cusps on the interface, and its shapes have striking similarities with Taylor's experiments. Response diagrams showing the drop distortion versus the elongational strain demonstrate that these are one-to-one function of each other if the drop diameter is greater than a critical value determined by the size of the mill but cease to be one-to-one otherwise. This behaviour is identified with a sudden transition from a rounded drop to a cusped one at a critical strain.
Motion of observed structures calculated from multi‐point magnetic field measurements: Application to Cluster
Authors: Shi Q. Q. , Shen C. , Dunlop M. W. , Pu Z. Y. , Zong Q.‐G. , Liu Z. X. , Lucek E. , Balogh A.
Published: May 2006

A new method is described which calculates the velocity of observed, quasi‐stationary structures at every moment in time from multi‐point magnetic field measurements. Once the magnetic gradient tensor G = ∇ and the time variation of the magnetic field have been estimated at every moment, the velocity can then be determined, in principle, as a function of time. One striking property of this method is that we can calculate the velocity of structures for any dimensionality: for three‐dimensional structures, all three components of the velocity vector can be calculated directly; for two‐dimensional (or one‐dimensional) structures, we can calculate the velocity along two (or one) directions. The advantage of this method is that the velocity is determined instantaneously, point by point through any structure, and so we can see the time variation of the velocity as the spacecraft traverse the structure. In this paper, the feasibility of the method is tested by calculating the motion velocity of a three‐dimensional, near cusp structure and a two‐dimensional magnetotail current sheet. The results for one‐dimensional structures in the magnetopause and cusp boundaries are compared to calculations for the standard techniques for analyzing discontinuities.
Response of tropical Pacific interannual variability to decadal entrainment temperature change in a hybrid coupled model
Authors: Zhang Rong‐Hua , DeWitt David G.
Published: May 2006

The role of decadal changes in ocean thermal structure, as observed in the tropical Pacific in the late 1970s, in modulating El Niño/Southern Oscillation (ENSO) is examined using a hybrid coupled model (HCM), consisting of an atmospheric general circulation model (AGCM; ECHAM4.5) and an intermediate ocean model (IOM) with an empirical parameterization for the temperature of subsurface water entrained into the mixed layer (Te), which is constructed via a singular value decomposition (SVD) analysis of historical data. A standard HCM run produces irregularity of ENSO. Two perturbation runs are conduced by introducing the decadal changes in Te estimated from two subperiods before and after the climate shift (Te63–79and Te80–96), respectively. Together with previous studies using an intermediate coupled model (ICM) consisting of the same IOM, different modulating effects of Te in the ocean and stochastic forcing in the atmosphere are demonstrated on the properties of ENSO. The former is responsible for changes in the phase propagation of ENSO, while the latter can contribute to the amplitude and period modulation.
New boundary conditions for the West Antarctic Ice Sheet: Subglacial topography of the Thwaites and Smith glacier catchments
Authors: Holt John W. , Blankenship Donald D. , Morse David L. , Young Duncan A. , Peters Matthew E. , Kempf Scott D. , Richter Thomas G. , Vaughan David G. , Corr Hugh F. J.
Published: May 2006

Airborne radar sounding over the Thwaites Glacier (TG) catchment and its surroundings provides the first comprehensive view of subglacial topography in this dynamic part of the West Antarctic Ice Sheet (WAIS) and reveals that TG is underlain by a single, broad basin fed by a dendritic pattern of valleys, while Smith Glacier lies within an extremely deep, narrow trench. Subglacial topography in the TG catchment slopes inland from a broad, low‐relief coastal sill to the thickest ice of the WAIS and makes deep connections to both Pine Island Glacier and the Ross Sea Embayment enabling dynamic interactions across the WAIS during deglaciation. Simple isostatic rebound modeling shows that most of this landscape would be submarine after deglaciation, aside from an island chain near the present‐day Ross‐Amundsen ice divide. The lack of topographic confinement along TG's eastern margin implies that it may continue to widen in response to grounding line retreat.
Rotationally driven quasi‐periodic radio emissions in the Jovian magnetosphere
Authors: Morioka A. , Nozawa H. , Misawa H. , Tsuchiya F. , Miyoshi Y. , Kimura T. , Kurth W.
Published: May 2006

The occurrence characteristics of Jovian multiple quasi‐periodic (QP) bursts are investigated based on Galileo spacecraft observations. Multiple QP bursts recurrently appeared in a group with a planetary spin period of 10 hours. Their appearance was synchronized with the planetary rotation, i.e., they were preferably excited when Jupiter had a particular spin phase angle with respect to the Sun (at a subsolar longitude of System III around 260–320°). We also found that the burst groups were activated during magnetospheric disturbances probably caused by solar wind pressure variations. The rotationally driven polar disturbances accompanying quasi‐periodic particle accelerations and radio wave bursts are discussed as being one of the daily unloading processes of planetary rotational energy.
Attenuation models (QP and QS) in three dimensions of the southern California crust: Inferred fluid saturation at seismogenic depths
Authors: Hauksson Egill , Shearer Peter M.
Published: May 2006

We analyze high dynamic range waveform spectra to determine t* values for both P and S waves from earthquakes in southern California. We invert the t* values for three‐dimensional (3‐D) frequency‐independent QP and QS regional models of the crust. The models have 15 km horizontal grid spacing and an average vertical grid spacing of 4 km, down to 22 km depth, and extend from the U.S.‐Mexico border to the Coast Ranges in the south and Sierra Nevada in the north. In general, QP and QS increase rapidly with depth, consistent with crustal densities and velocities. The 3‐D QP and QS models image the major tectonic structures and to a much lesser extent the thermal structure of the southern California crust. The near‐surface low QP and QS zones coincide with major sedimentary basins such as the San Bernardino, Chino, San Gabriel Valley, Los Angeles, Ventura, and Santa Maria basins and the Salton Trough. In contrast, at shallow depths beneath the Peninsular Ranges, southern Mojave Desert, and southern Sierras, we image high QP and QS zones, which correspond to the dense and high‐velocity rocks of the mountain ranges. Several clear transition zones of rapidly varying QP and QS coincide with major late Quaternary faults and connect regions of high and low QP and QS. At midcrustal depths, the QP and QS exhibit modest variation in slightly higher and lower QP or QS zones, which is consistent with reported crustal reflectivity. In general, for the southern California crust, QS/QP is greater than 1.0, suggesting partially fluid‐saturated crust. A few limited regions of QS/QP less than 1.0 correspond to areas mostly outside the major sedimentary basins, including areas around the San Jacinto fault, suggesting a larger reduction in the shear modulus compared to the bulk modulus or almost complete fluid saturation.
Marine particle nucleation: Observation at Bodega Bay, California
Authors: Wen Jian , Zhao Yongjing , Wexler Anthony S.
Published: May 2006

A TSI nano‐SMPS was installed in a lab at Bodega Bay, about 50 m from the coastline and 5 m above sea level. On the basis of measurements conducted from June to December 2001 and from January to June 2003, we have observed two kinds of nucleation events, i.e., long‐term (a few hours) and short‐term (a few minutes) particle bursts. The long‐term events mostly occur during daytime in the summer, lasting from 0.5 to 8 hours. Narrow spikes (short‐term events) that occur year‐round, both day and night, last only a few minutes to a half hour but contain particle number concentrations comparable to some of the long‐term events. Wind direction and speed affect the occurrence and intensity of the particle burst. Nucleation mostly takes place during northwesterly onshore wind for both long‐ and short‐term events, and the probability of nucleation occurrence is higher at higher wind speed. However, in contrast to what has been observed at Mace Head, Ireland, nucleation at Bodega Bay does not correlate with tidal height. Instead, the seasonal and interannual variations of ultrafine particle number concentration N3–10nm appear to correlate with ocean upwelling, a characteristic of currents along the west coast of the United States that brings up nutrients from subsurface waters, promoting plant productivity. Simultaneous measurements of nucleation at the coast and 1.6 km out suggest that nucleation is a coastal phenomenon, supporting the contention that it is related to direct or biogenic emission of precursor gases from the coastal area during the sea upwelling periods.
A climatology of equatorial plasma bubbles from DMSP 1989–2004
Authors: Gentile L. C. , Burke W. J. , Rich F. J.
Published: May 2006

After examining evening sector plasma density measurements from polar‐orbiting Defense Meteorological Satellite Program (DMSP) spacecraft for 1989–2004, we have established a statistical database of more than 14,400 equatorial plasma bubble (EPB) observations. EPBs are irregular plasma density depletions in the postsunset ionosphere that degrade communication and navigation signals. In general, the DMSP observations support Tsunoda's (1985) hypothesis that EPB rates peak when the terminator is aligned with the Earth's magnetic field, but unpredicted offsets are also evident in many longitude sectors. Plots of EPB rates for solar cycle phases: maximum 1989–1992 and 1999–2002, minimum 1994–1997, and transition years 1993, 1998, and 2003 reveal significant differences in the climatologies for solar maximum and minimum, between the two solar maxima, and in the transition years. To assess local time effects on EPB rates, we also compare observations from F12, F14, F15, and F16 at slightly different postsunset local times for 2000–2004. This study was undertaken to facilitate improvements in ionospheric models in preparation for the Communication/Navigation Outage Forecasting System (C/NOFS) mission.
Changes in the molecular weight distribution of dissolved organic carbon within a Precambrian shield stream
Authors: Kothawala D. N. , Evans R. D. , Dillon P. J.
Published: May 2006

Dissolved organic carbon (DOC) is of environmental and biological significance to Precambrian shield streams. Our objective was to determine the extent of transformations to the concentration and molecular weight distribution (MWD) of DOC along the length of Harp 4A stream, from the headwater swamp to the outflow into Harp Lake. The average MWD shifted to a smaller weight by 0.48 kDa. A rapid decline in the concentration and MWD of DOC was observed within 120 m from the main DOC source, a headwater swamp. The most significant decline in concentration and MWD was observed within the first of a series of three beaver ponds. DOC within waters downstream of the beaver ponds was resistant to further changes in concentration and MWD. The MWD within each of four stream sections with Hp 4a remained stable over 6 months, from May to October 2001.
Recent changes in the fire regime across the North American boreal region—Spatial and temporal patterns of burning across Canada and Alaska
Authors: Kasischke Eric S. , Turetsky Merritt R.
Published: May 2006

We used historic records from 1959–99 to explore fire regime characteristics at ecozone scales across the entire North American boreal region (NABR). Shifts in the NABR fire regime between the 1960s/70s and the 1980s/90s were characterized by a doubling of annual burned area and more than a doubling of the frequency of larger fire years because of more large fire events (>1,000 km2). The proportion of total burned area from human‐ignited fires decreased over this same time period, while the proportion of burning during the early and late‐ growing‐seasons increased. Trends in increased burned area were consistent across the NABR ecozones, though the western ecozones experienced greater increases in larger fire years compared to the eastern ecozones. Seasonal patterns of burning differed among ecozones. Along with the climate warming, changes in the fire regime characteristics may be an important driver of future ecosystem processes in the NABR.
Gravity‐driven advective transport during deep geological disposal of contaminants
Authors: Selvadurai A. P. S.
Published: May 2006

The paper presents a mathematical model for the study of the advective transport problem where gravity‐induced entry of chemicals takes place from open regions of lined boreholes and fracture‐type cavities that are deeply located in porous geological media. A characteristic feature of a gravity driven deep geological disposal concept is the presence of time‐dependent advective flow velocities in the system. It is shown that certain exact closed‐form solutions can be developed to describe the gravity‐driven transport of a contaminant into a fluid‐saturated host porous geologic medium.
Cerebral Perfusion Response to Hyperoxia
Authors: Bulte Daniel P , Chiarelli Peter A , Wise Richard G , Jezzard Peter
Published: May 2006

Graded levels of supplemental inspired oxygen were investigated for their viability as a noninvasive method of obtaining intravascular magnetic resonance image contrast. Administered hyperoxia has been shown to be effective as a blood oxygenation level-dependent contrast agent for magnetic resonance imaging (MRI); however, it is known that high levels of inspired fraction of oxygen result in regionally decreased perfusion in the brain potentially confounding the possibility of using hyperoxia as a means of measuring blood flow and volume. Although the effects of hypoxia on blood flow have been extensively studied, the hyperoxic regime between normoxia and 100% inspired oxygen has been only intermittently studied. Subjects were studied at four levels of hyperoxia induced during a single session while perfusion was measured using arterial spin labelling MRI. Reductions in regional perfusion of grey matter were found to occur even at moderate levels of hyperoxia; however, perfusion changes at all oxygen levels were relatively mild (less than 10%) supporting the viability of hyperoxia-induced contrast.
Hydrogen bond dynamics and microscopic structure of confined water inside carbon nanotubes
Authors: Hanasaki Itsuo , Nakatani Akihiro
Published: May 2006

We have investigated the density and temperature dependences of microscopic structure and hydrogen bond dynamics of water inside carbon nanotubes (CNTs) using molecular dynamics simulation. The CNTs are treated as rigid, and smoothly truncated extended simple point charge water model is adopted. The results show that as the overall density increases, the atomic density profiles of water inside CNTs become sharper, the peaks shift closer to the wall, and a new peak of hydrogen atomic density appears between the first (outermost) and second layer. The intermittent hydrogen bond correlation function CHB(t) of water inside CNTs decays slower than that of bulk water, and the rate of decay decreases as the tube diameter decreases. CHB(t) clearly decays more slowly for the first layer of water than for other regions inside CNTs. The CHB(t) of the interlayer hydrogen bonds decays faster than those of the other regions and even faster than that of the bulk water. On the other hand, the hydrogen bond lifetimes of the first layer are shorter than those of the inner layer(s). Interlayer hydrogen bond lifetimes are clearly shorter than those of the constituent layers. As a whole, the hydrogen bond lifetimes of water inside CNTs are shorter than those of bulk water, while the relaxation of CHB(t) is slower for the confined water than for bulk water. In other words, hydrogen bonds of water inside CNTs break more easily than those of bulk water, but the water molecules remain in each other’s vicinity and can easily reform the bonds.
Quantum entanglement and geometry of determinantal varieties
Authors: Chen Hao
Published: May 2006

Quantum entanglement was first recognized as a feature of quantum mechanics in the famous paper of Einstein, Podolsky, and Rosen. Recently it has been realized that quantum entanglement is a key ingredient in quantum computation, quantum communication, and quantum cryptography. In this paper, we introduce algebraic sets, which are determinantal varieties in the complex projective spaces or the products of complex projective spaces, for the mixed states on bipartite or multipartite quantum systems as their invariants under local unitary transformations. These invariants are naturally arised from the physical consideration of measuring mixed states by separable pure states. Our construction has applications in the following important topics in quantum information theory: (1) separability criterion, it is proved that the algebraic sets must be a union of the linear subspaces if the mixed states are separable; (2) simulation of Hamiltonians, it is proved that the simulation of semipositive Hamiltonians of the same rank implies the projective isomorphisms of the corresponding algebraic sets; (3) construction of bound entangled mixed states, examples of the entangled mixed states which are invariant under partial transpositions (thus PPT bound entanglement) are constructed systematically from our new separability criterion.
Gyrokinetic simulations of off-axis minimum-q profile corrugations
Authors: Waltz R. E. , Austin M. E. , Burrell K. H. , Candy J.
Published: May 2006

Quasiequilibrium radial “profile corrugations” in the electron temperature gradient are found at lowest-order singular surfaces in global gyrokinetic code simulations of both monotonic-q and off-axis minimum-q discharges. The profile corrugations in the temperature and density gradients are time-averaged components of zonal flows. The m∕n=2∕1 electron temperature gradient corrugation is measurably large and appears to trigger an internal transport barrier as the off-axis minimum-q=2 surfaces enter the plasma.
Effects of pressure gradient on existence of Alfvén cascade modes in reversed shear tokamak plasmas
Authors: Fu G. Y. , Berk H. L.
Published: May 2006

It is shown analytically that pressure gradient effects are favorable to the existence of Alfvén cascade (AC) modes in a tokamak plasma with reversed shear. What is crucial for obtaining the improved existence criterion of ACs is the averaged normal curvature. This term depends on the Shafranov shift, which contains a pressure gradient term that at sufficiently low frequency causes a cancellation in the mode existence criterion of all terms quadratic in the pressure gradient. The favorable criterion is then found to be proportional to the product of the pressure gradient and the inverse aspect ratio. Near the rational surface, there is one-to-one correspondence between Mercier stability and the AC mode existence. When the averaged curvature is favorable to Mercier modes, it is also favorable to the existence of AC. However, at higher frequencies the α2 term can be unfavorable to mode existence. We show that when α>3ϵ, that as qmin decreases from m∕n, the cascade mode can easily satisfy its existence criterion at lower frequencies, but the existence criterion will fail before the frequency reaches the toroidal Alfvén eigenmode (TAE) gap, which occurs when qmin approaches (m−1∕2)∕n.
Computational study of ZrSiO4 polymorphs
Authors: Korkin Anatoli , Kamisaka Hideyuki , Yamashita Koichi , Safonov Andrey , Bagatur’yants Alexander
Published: May 2006

Using the density functional theory in a local density approximation and generalized gradient approximation (GGA) with a plane wave basis set we have revealed eight new polymorphs of ZrSiO4 within the energy range ∼1eV above the most stable zircon which have higher and lower density than experimentally known zircon and reidite. Two structures, which have both silicon and zirconium atoms sixfold coordinated, orthorhombic AlTaO4-like (alumotantite), and monoclinic PbWO4-like (raspite), have similar energies at a GGA level ∼0.35eV above reidite and density intermediate between zircon and reidite. Among two low-density structures, which can be potentially revealed experimentally in the nanocrystalline thin films, the orthorhombic CaSO4-like form has an energy similar to reidite but with much lower density.
Quasiferromagnetism in semiconductors
Authors: Dubroca T. , Hack J. , Hummel R. E. , Angerhofer A.
Published: May 2006

Ferromagnetic hysteresis has been observed at room temperature in materials not consisting of elements commonly associated with ferromagnetism, such as Co, Ni, Fe, or Mn-containing alloys. In particular, we report on magnetic hysteresis seen in silicon prepared by two different techniques: ion implantation (Si and Ar) and neutron irradiation. Because the material investigated contains no ferromagnetic elements, we tentatively call it “quasiferromagnetic.” The paramagnetic defects present in these materials were investigated using electron paramagnetic resonance. We suggest that these defects are one of the factors responsible for the observed macroscopic magnetic hysteresis loop.
Thermally stable Schottky contacts on n-type GaN using ZrB2
Authors: Oder T. N. , Martin P. , Lin J. Y. , Jiang H. X. , Williams J. R. , Isaacs-Smith T.
Published: May 2006

The electrical properties and thermal stability of ZrB2 Schottky contacts deposited on n-type GaN have been studied. As-deposited contacts had a barrier height of 0.80eV, which decreased to 0.7eV after annealing at 300°C, and to 0.6eV after additional annealing at 400°C in nitrogen for 20min. However, the barrier height remained at about 0.6eV even when the diodes were annealed at 600°C for 20min. The Rutherford backscattering spectra of annealed contacts showed no reaction at the ZrB2∕GaN interface. These results make ZrB2∕GaN Schottky contacts attractive for high temperature device applications.
Critical length of electromigration for eutectic SnPb solder stripe
Authors: Wei C. C. , Chen Chih
Published: May 2006

The critical length of eutectic SnPb solder was investigated using solder stripes. By employing focus ion beam, solder stripes of various lengths, including 5, 10, 15, 20, 30, 100, and 200μm, can be fabricated. Length-dependent electromigration behavior was observed, which implies that there may be back stress under stressing. The critical length was determined to be between 10 and 15μm under stressing by 2×104A∕cm2 at 100°C, and the corresponding critical product was between 20 and 30A∕cm. Both values show good agreement with their theoretical values.
Structural and optical properties of GaInAs∕GaAs and GaInNAs∕GaNAs multiple quantum wells upon postgrowth annealing
Authors: Liu H. F. , Xiang N. , Chua S. J. , Pessa M.
Published: May 2006

We have investigated structural and optical properties of Ga1−xInxAs∕GaAs and Ga1−xInxNyAs1−y∕GaNzAs1−z multiple quantum wells. The evolution of x-ray diffraction rocking curves during thermal treatment of the samples indicates that there is observable Ga∕In interdiffusion across the heterointerfaces at high sample temperatures. X-ray diffraction also indicates that the diffusion length of the atoms decreases with an increase in nitrogen concentration, while the interface roughness, which exhibits remarkable changes for the two different quantum wells, only plays a minor role in diffusion. Structural stability of the Ga1−xInxNyAs1−y∕GaNzAs1−z quantum wells against temperature variations is better than that of the Ga1−xInxAs∕GaAs quantum wells. These observations can be accounted for by assuming that nitrogen has a tendency to suppress Ga∕In interdiffusion across the heterojunctions.
Fused Supracyclopentadienyl Ligand Precursors. Synthesis, Structure, and Some Reactions of 1,3-Diphenylcyclopenta[l]phenanthrene-2-one, 1,2,3-Triphenylcyclopenta[l]phenanthrene-2-ol, 1-Chloro-1,2,3-triphenylcyclopenta[l]phenanthrene, 1-Bromo-1,2,3-triphenylcyclopenta[l]phenanthrene, and 1,2,3-Triphenyl-1H-cyclopenta[l]phenanthrene
Authors: Dennis Glen D. , Edwards-Davis David , Field Leslie D. , Masters Anthony F. , Maschmeyer Thomas , Ward Antony J. , Buys Irmi E. , Turner Peter
Published: May 2006

The photochemical reaction of 1,3-diphenylcyclopenta[l]phenanthrene-2-one 5 (phencyclone) with oxygen in acetone leads to the formation of 1,2,3-trihydro-1,2,3-triphenylcyclo-penta[l]phenanthrene 7 (9,10-dibenzoylphenanthrene) along with a trace of the lactone 1,4-diphenylcyclo-3-pyran[l]phenanthrene-2-one 8. An independent synthesis of 8 was achieved by the reaction of 5 with FeCl3 in CHCl3. The treatment of 5 with phenyllithium yields 1,2,3-triphenylcyclopenta[l]phenanthrene-2-ol 9-OH in good yield. Subsequent reaction of 9-OH with SOCl2 or SOBr2 in pyridine leads to the formation of the halo-analogues 1-chloro-1,2,3-triphenylcyclopenta[l]phenanthrene 9-Cl and 1-bromo-1,2,3-triphenylcyclopenta[l]phenanthrene 9-Br, respectively. Treatment of 9-OH with HBr in acetic acid affords the rearranged product 1,1,3-triphenylcyclopenta[l]phenanthrene-2-one 10 with a trace of 9-Br. Treatment of 9-Cl or 9-Br with zinc in acetic acid affords 1,2,3-tri-phenyl-1H-cyclopenta[l]phenanthrene 9-H. 9,10-Phenanthrenediylbis(phenyl)methanone 7 is formed in good yield upon treatment of 9-OH with HI in acetic acid followed by heating with H2PO4. Compounds 7, 8, 9-Cl, 9-Br, and 10 have been structurally characterized using X-ray crystallography.
New Heterocycle-Based Organic Molecule with Two-Photon Induced Blue Fluorescent Emission
Authors: Shao Pin , Li Zhen , Qin Jingui , Gong Hongmei , Ding Sha , Wang Ququan
Published: May 2006

A new heterocycle-based quadrupolar molecule containing 2,5-diphenyl-1,3,4-oxadiazole as the π-centre and two carbazoles as end units has been synthesized. It exhibits two-photon induced blue emission, and its two-photon absorption cross section in the femtosecond region is measured to be 239 × 10−50 cm4 s photon−1 at a wavelength of 788 nm.
Synthesis of Azobenzenophanes with a Large Molecular Cavity
Authors: Rajakumar Perumal , Senthilkumar Beeran , Srinivasan Kannupal
Published: May 2006

The design and synthesis of four large-cavity azobenzenophanes, capable of forming photochemically controllable complexes with organic guest molecules, are described. These azobenzenophanes, possessing m-terphenyl, aromatic carbonyl, and chiral BINOL spacers, were synthesized from the corresponding bisphenols and dibromides using simple O-alkylation methodology. A preliminary photochemical study was carried out on the aromatic carbonyl spacer containing azobenzenophane, and the isosbestic points for the cis–trans isomerization process appeared at 319 and 419 nm.
New Coordination Architectures of Dithioether Ligand with Silver Salts: Effect of Anions on Complex Structures
Authors: Xie Ya-Bo , Li Jian-Rong , Bu Xian-He
Published: May 2006

Reactions of a flexible dithioether ligand, 2,3-bis(5-methyl-1,3,4-thiadiazole-2-thiomethyl)quinoxaline (L), with AgX (X = ClO4ˉ or PF6ˉ) lead to the formation of two new one-dimensional (1D) silver(i) complexes: {[AgL](ClO4)}∞ 1 and {[Ag2L(CH3OH)](PF6)2(CH3OH)}∞ 2, which have been characterized by elemental analysis, IR spectroscopy, and X-ray crystallography. Although 1 and 2 are synthesized under the same conditions, they take different structures due to the difference in anions in the silver salts. In 1, each ligand supplies three N-donors to bridge two silver atoms to result in a chain structure, and all silver atoms in the chain possess the same coordination geometry. In 2, each ligand gives six N-donors to coordinate to two silver atoms of different geometries, forming a 1D chain. The changes in counteranions affect the coordination mode of the ligand and the geometry of the Ag(i) centre, and consequently give rise to complexes with different structures. The coordination features of the ligand have also been primarily investigated through density functional theory calculations.
Synthesis and Radiolabelling of Ipratropium and Tiotropium for Use as PET Ligands in the Study of Inhaled Drug Deposition
Authors: Issa Fatiah , Kassiou Michael , Chan Hak-Kim , McLeod Malcolm D.
Published: May 2006

Ipratropium bromide [(1R,3r,5S,8r,2′RS)-3-(3′-hydroxy-2′-phenylpropionyloxy)-8-isopropyl-8-methyl-8-azabicyclo[3.2.1]octan-8-ium bromide] and tiotropium bromide [(1R,2R,4S,5S,7s)-7-[2′-hydroxy-2′,2′-di(thiophen-2′′-yl)acetoxy]-9,9-dimethyl-9-aza-3-oxatricyclo[3.3.1.02,4]nonan-9-ium bromide] are inhaled drugs used in the treatment of chronic obstructive pulmonary disease (COPD) and asthma. Tertiary amine precursors have been synthesized and radiolabelled with carbon-11 by N-alkylation with [11C]CH3I. The [11C]ipratropium and [11C]tiotropium positron emission tomography (PET) ligands are obtained with high radiochemical purity, in 0.3 and 0.5% non-decay corrected yields based on [11C]CO2 at end-of-synthesis and specific activities of 11 and 18 GBq μmol−1, respectively, calculated at end-of-synthesis. These PET radioligands can be used in the study of inhaled drug deposition.
Enzyme Electrochemistry — Biocatalysis on an Electrode
Authors: Bernhardt Paul V.
Published: May 2006

Oxidoreductase enzymes catalyze single- or multi-electron reduction/oxidation reactions of small molecule inorganic or organic substrates, and they are integral to a wide variety of biological processes including respiration, energy production, biosynthesis, metabolism, and detoxification. All redox enzymes require a natural redox partner such as an electron-transfer protein (e.g. cytochrome, ferredoxin, flavoprotein) or a small molecule cosubstrate (e.g. NAD(P)H, dioxygen) to sustain catalysis, in effect to balance the substrate/product redox half-reaction. In principle, the natural electron-transfer partner may be replaced by an electrochemical working electrode. One of the great strengths of this approach is that the rate of catalysis (equivalent to the observed electrochemical current) may be probed as a function of applied potential through linear sweep and cyclic voltammetry, and insight to the overall catalytic mechanism may be gained by a systematic electrochemical study coupled with theoretical analysis. In this review, the various approaches to enzyme electrochemistry will be discussed, including direct and indirect (mediated) experiments, and a brief coverage of the theory relevant to these techniques will be presented. The importance of immobilizing enzymes on the electrode surface will be presented and the variety of ways that this may be done will be reviewed. The importance of chemical modification of the electrode surface in ensuring an environment conducive to a stable and active enzyme capable of functioning natively will be illustrated. Fundamental research into electrochemically driven enzyme catalysis has led to some remarkable practical applications. The glucose oxidase enzyme electrode is a spectacularly successful application of enzyme electrochemistry. Biosensors based on this technology are used worldwide by sufferers of diabetes to provide rapid and accurate analysis of blood glucose concentrations. Other applications of enzyme electrochemistry are in the sensing of macromolecular complexation events such as antigen–antibody binding and DNA hybridization. The review will include a selection of enzymes that have been successfully investigated by electrochemistry and, where appropriate, discuss their development towards practical biotechnological applications.
A Simple Dyad Exhibiting Microsecond Charge-Separation in Non-Polar Solvents
Authors: Ghiggino Kenneth P. , Hutchison James A. , Langford Steven J. , Latter Melissa J. , Lee Marcia A.-P. , Takezaki Makoto
Published: May 2006

A simple photovoltaic device in which two chromophoric components are assembled by Zn–N coordination yields a charge-separated state with microsecond lifetime upon photoexcitation in non-polar solvents. Characterization of the electron transfer dynamics using time-resolved fluorescence and transient absorption spectroscopy suggests that the unusual longevity is due to charge recombination occurring between states with different electron spin character. Control of electron spin may provide a novel paradigm for optimizing light-induced charge-separation processes.
Artificial Molecular Motors Powered by Light
Authors: Credi Alberto
Published: May 2006

The bottom-up construction and operation of machines and motors of molecular size is a topic of great interest in nanoscience, and a fascinating challenge of nanotechnology. The problem of the energy supply to make molecular motors work is of the greatest importance. Research in the last ten years has demonstrated that light energy can indeed be used to power artificial nanomotors by exploiting photochemical processes in appropriately designed systems. More recently, it has become clear that under many aspects light is the best choice to power molecular motors; for example, systems that show autonomous operation and do not generate waste products can be obtained. This review is intended to discuss the design principles at the basis of light-driven artificial nanomotors, and provide an up-to-date overview on the prototype systems that have been developed.
Synthesis of 1-Hydroxypyrrolidin-2,5-dione Derivatives of the Phosphonic - Hydroxamic Acid Antibiotic SF-2312
Authors: Owotoki Wamuyu , Geffken Detlef , Kurz Thomas
Published: May 2006

Analogues of the antibiotic SF-2312 with a 3-substituted 1-hydroxypyrrolidine moiety have been prepared from 1-benzyloxy-3-bromopyrrolidin-2,5-dione (1) through Michaelis–Arbusov reaction with various trialkyl phosphites and subsequent alkylation of ring position 3. Cleavage of phosphonic esters 3 by TMSBr afforded the corresponding phosphonic acids 7, which were treated with ethanolamine to give the monosalts 8. Finally, hydrogenolysis furnished 1-hydroxypyrrolidin-2,5-diones 9.
Direct Synthesis of Deep Cavity p-Phenylcalix[4]arene in Poly(Ethylene Glycol), and its Self-Association in the Solid State
Authors: Makha Mohamed , Raston Colin L. , Sobolev Alexandre N.
Published: May 2006

p-Phenylcalix[4]arene is formed directly from p-phenylphenol in 66% yield (50% isolated yield) using poly(ethylene glycol) as the reaction medium, with crystallization of the pure cavitand from toluene mediated by p-carborane. The solid-state structure comprises interlocking columnar arrays.
Removal of Iodinated X-Ray Contrast Media During Drinking Water Treatment
Authors: Seitz Wolfram , Jiang Jia-Qian , Weber Walter H. , Lloyd Barry J. , Maier Matthias , Maier Dietrich
Published: May 2006

Environmental Context.In recent years, many micro-organic pollutants, e.g. pharmaceuticals and personal care products (PPCP), have been observed to be persisting through wastewater treatment and occurring in the environment. Persistent micropollutants are of particular concern owing to the fact that some of them have been found in drinking water, and iodinated X-ray contrast media (ICM) are one group of such pollutants.
Abstract.The present study investigates the removal of five iodinated X-ray contrast media (ICM) during drinking water production from surface water at a full-scale water works, which comprises coagulation/flocculation, intermediate ozonation, in-line filtration and adsorption with activated carbon. The elimination rates over all treatment units for the non-ionic ICM (iomeprol, iopromide, iohexol and iopamidol) were determined to be approximately 70%. In particular, intermediate ozonation can remove 30% on average of the non-ionic ICM, whereas it cannot remove the ionic diatrizoic acid, and the granulated activated carbon filters can achieve a further 50% removal of non-ionic ICM. However, over 100 ng L−1 of ionic diatrizoic acid and 40–100 ng L−1 of non-ionic ICM were found in the produced drinking water.
Flow Analysis Techniques for Spatial and Temporal Measurement of Nutrients in Aquatic Systems
Authors: Gray Sarah , Hanrahan Grady , McKelvie Ian , Tappin Alan , Tse Florence , Worsfold Paul
Published: May 2006

Environmental Context.Eutrophication is a growing problem globally, and it has significant ecological and socio-economic consequences. Understanding the causes of eutrophication requires a knowledge of nutrient biogeochemistry in aquatic systems. Owing to the high spatial and temporal variability of nutrients in these systems, there is a need for autonomous in situ measurement techniques with rapid response and the ability to collect long-term data. Flow injection analysis is one technique that meets these demands.

Abstract.Flow analysis offers a versatile and powerful approach to monitoring of the aquatic environment. The present review highlights the drivers for determining macro- and micro-nutrients in marine and fresh waters, and outlines the instrumental requirements for in situ instrumentation. The principles of flow analysis, specifically flow injection and derivative techniques, and the chemical bases for macro- and micro-nutrient detection are discussed, and key examples of suitable approaches are considered. The successful deployment of flow analysis nutrient monitoring systems for spatial and temporal measurements is illustrated by specific examples relating to surface transects, depth profiles and temporal deployments. Finally, the challenges and imperatives of research in this area are outlined.
Sorption of the Herbicide Terbumeton and its Metabolites onto Soils. Influence of Copper(II)
Authors: Abiven David , Boudesocque Stéphanie , Guillon Emmanuel , Couderchet Michel , Dumonceau Jacques , Aplincourt Michel
Published: May 2006

Environmental Context.Agrochemicals have contributed greatly to modern agriculture, allowing better yields and lower costs. However, their extensive use has led to frequent contamination of underground and surface water. A better knowledge of the fate of pesticides from the sprayer to the water that would take into account the diversity of the physical and chemical properties of the various molecules and environmental conditions should help in the challenge of protecting and restoring natural water quality.
Abstract.The intensive use of terbumeton (N-(1,1-dimethyl)-N′-ethyl-6-methoxy-1,3,5-triazine-2,4-diamine) has resulted in its widespread presence, together with its main metabolites, in surface- and groundwater. To estimate the fate of these compounds, their adsorption and desorption properties were studied in vineyard soils. The values of the organic carbon normalized adsorption coefficient (KOC) for terbumeton (34.6 and 39.2 L g−1) were significantly higher than those of its metabolites (between 6.8 and 21.1 L g−1). Terbumeton exhibited a higher adsorption capacity and a lower desorption potential as compared with the metabolites. An important hysteresis was observed in all cases. The Freundlich isotherms exhibited a linear shape, which was interpreted as non-specific interaction. The influence of copper(II), a ubiquitous metal cation in vineyard soils, on pesticide sorption was also studied. Copper significantly decreased the amount of adsorbed terbumeton when present in a high concentration (2 ×10−4 M).
On-line Removal of Sulfide Interference in Phosphate Determination by Flow Injection Analysis
Authors: Grace Michael , Udnan Yuthapong , McKelvie Ian , Jakmunee Jaroon , Grudpan Kate
Published: May 2006

Environmental Context.Effective management of eutrophication and resultant major algal blooms requires accurate assessment of the importance of internal (sediment-based) as well as external, sources of phosphorus to susceptible aquatic ecosystems. The high spatial variability in pore water filterable reactive phosphorus (FRP) necessitates extensive sampling, and rapid flow injection methods overcome many of the difficulties in maintaining sample integrity. A simple flow injection manifold has been developed to prevent major sulfide interference with FRP determination and therefore enable accurate phosphate measurements.
Abstract.Simple on-line sulfide removal using potassium permanganate (KMnO4) was incorporated into a spectrophotometric flow injection (FI) system for phosphate determination using molybdenum blue with ascorbic acid as the reductant. Excess KMnO4 was reduced before the sample zone passed through the detector and the method effectively removed all sulfide interference. Without this removal, sulfide interference caused major errors in filterable reactive phosphorus (FRP) analyses. Some model organic phosphates were tested with the permanganate manifold and there was no conversion to phosphate. With the KMnO4 carrier, the calibration plot was linear over the tested range (0–1000 μg L−1 P), with a detection limit of 38 μg L−1 P. Precision was typically better than 2.5%, based on triplicate injections. FRP determinations on anoxic, estuarine pore water samples were in excellent agreement with the conventional batch method with prior acidification and sparging, but avoided sample pretreatment and the generation of toxic H2S. Samples spiked with phosphate gave recoveries of 93–104%. Given the simplicity of modifying conventional FI manifolds to incorporate the improvements described here, it is recommended that all FRP measurements by FI replace water as the carrier with 0.01 M KMnO4 whenever the presence of sulfide is suspected.
Temporal change in fish assemblages in the lower Goulburn River, south-eastern Australia: comment on Pollino et al. (2004)
Authors: Crook David A. , Koster Wayne M.
Published: May 2006

A recent analysis of fish assemblages in the Goulburn River, south-eastern Australia, used fish survey data collected between 1970 and 2002 to examine spatial patterns in the compositions and relative abundances of fish assemblages in the catchment. Based on this analysis, it was concluded that the native fish fauna of the Goulburn River is in a stressed condition and that introduced species dominate the fish assemblages. Fish survey data collected in 1982–1983 are compared with data collected in 2003–2004 to examine whether fish assemblages in the lower Goulburn River were stable at the temporal scale at which the data were aggregated in the previous analysis. The results show significant differences in fish assemblage composition between the two surveys, suggesting that fish assemblage structure in the lower Goulburn River did not remain stable between 1982–1983 and 2003–2004. The aggregation of data collected over several decades has the potential to confound analysis of spatial variations in fish assemblages and is unlikely to provide a reliable means of assessing their current condition.
A revision of Cassinia (Asteraceae: Gnaphalieae) in Australia. 5. Additional taxa in Section Leptocephalae
Authors: Orchard A. E.
Published: May 2006

Additional collections and re-examination of previous specimens allow the description of new taxa in Cassinia. Cassinia sect. Leptocephalae is divided into three series: ser. Leptocephaleae, which comprises the C. leptocephala / C. cunninghamii / C. decipiens group; ser. Macrocephaleae Orchard, ser. nov. to accommodate C. macrocephala and C. denticulata; and ser. Compactae Orchard, ser. nov., to accommodate the C. compacta group of five brown-headed species. Further evidence is presented to support the suggestion that the lack of paleae in those Cassinia species with few florets is an artefact, and that the innermost ‘phyllaries’ are in fact paleae. Two new subspecies of C. macrocephala are described: subsp. petrapendula Orchard, subsp. nov. and subsp. storyi Orchard, subsp. nov., plus one new species, Cassinia furtiva Orchard, sp. nov.
Polianthion, a new genus of Rhamnaceae (Pomaderreae) from Western Australia and Queensland
Authors: Kellermann Jürgen , Rye Barbara L. , Thiele Kevin R.
Published: May 2006

Recent phylogenetic studies have revealed that four species of Australian Rhamnaceae, tribe Pomaderreae Reissek ex Endl., should be assigned to a new genus. This paper describes Polianthion K.R.Thiele, including one new species, P. collinum Rye, and makes the relevant combinations for P. bilocularis (A.S.George) Kellermann, P. wichurae (Nees ex Reissek) K.R.Thiele and P. minutiflorum (E.M.Ross) K.R.Thiele. The genus is defined by having two carpels, a characteristic dense stellate indumentum on both vegetative and floral parts of the plant, free stipules, long-pedicellate flowers and fruitlets dehiscent for their full length. Three species are found in the south-west of Western Australia and one in eastern Queensland.