bluuebunny/crossref_metadata_2025 huggingface dataset:
A generalized Omori's law for earthquake aftershock decay
Authors: Shcherbakov Robert , Turcotte Donald L. , Rundle John B.
Published: June 2004

Earthquake aftershock sequences have been found to approximately satisfy three empirical scaling relations: i) the Gutenberg‐Richter frequency‐magnitude scaling, ii) Båth's law for the difference in the magnitude of a mainshock and its largest aftershock, and iii) the modified Omori's law for the temporal decay of aftershock rates. The three laws are incorporated to give a generalized Omori's law for aftershock decay rates that depend on several parameters specific for each given seismogenic region. It is shown that the characteristic time c, first introduced in the modified Omori's law, is no longer a constant but scales with a lower magnitude cutoff and a mainshock magnitude. The generalized Omori's law is tested against earthquake catalogs for the aftershock sequences of the Landers, Northridge, Hector Mine, and San Simeon earthquakes.
On the relationship between ion upflow events and cusp auroral transients
Authors: Moen J. , Oksavik K. , Carlson H. C.
Published: June 2004

In this paper we present a one‐to‐one relationship between poleward moving auroral forms (PMAFs) and ion upflows in the cusp. Ion upflows have the same quasi‐periodic nature as cusp auroral transients, which are believed to be a signature of flux‐transfer events. This new observation corroborates the idea that low energy particle precipitation is the dominant source of energy for ion upflows. Some events were lacking elevated Ti which indicates that frictional heating is not required. The ion upflow events broadened with altitude in characteristic V‐shape. We suggest that each PMAF was associated with an inverted V‐ potential structure moving over the radar.
Source characteristics and radiation mechanism of Jovian anomalous continuum
Authors: Morioka A. , Yuasa T. , Miyoshi Y. S. , Tsuchiya F. , Misawa H.
Published: June 2004

We investigate the characteristics of the Jovian anomalous continuum (JAC) in interplanetary space and in the magnetosheath, using Ulysses observations. Some new source characteristics of JAC were obtained in addition to those found by previous authors [e.g., Kaiser, 1998]. JAC tends to occur when the solar wind dynamic pressure decreases after a rapid increase. We confirm and show more concretely that the commencement of JAC has significant dependence on local time, i.e., its appearance is most likely when the System III longitude of the subsolar point is near 270°. The periodic appearance of JAC is not due to its intensity modulation but to its repeated individual excitation. JAC exhibited an abrupt amplitude change across the bow shock, possibly suggesting a mode conversion from quasi‐electrostatic to electromagnetic waves at the bow shock. We also evaluate possible sources of JAC and hypothesize that its origin is Langmuir waves excited at the magnetopause by energetic particles such as quasiperiodic bursts ejected from the polar magnetosphere. The relation of magnetospheric disturbances to the generation of JAC is also discussed.
Pharmacological‐based translational induction of transgene expression in mammalian cells
Authors: Boutonnet Christel , Boijoux Olivier , Bernat Sandra , Kharrat Abdelhakkim , Favre Gilles , Faye Jean‐Charles , Vagner Stéphan
Published: June 2004

In the quest for the development of pharmacological switches that control gene expression, no system has been reported that regulates at the translational level. To permit small‐molecule control of transgene translation, we have constructed a farnesyl transferase inhibitor‐responsive translation initiation factor. This artificial protein is a three‐component chimaera consisting of the ribosome recruitment core of the eIF4G1 eukaryotic translation initiation factor, the RNA‐binding domain of the R17 bacteriophage coat protein and the plasma membrane localization CAAX motif of farnesylated H‐Ras. This membrane‐delocalized translation factor is inactive unless liberated in the cytosol. Farnesyl transferase inhibitor FTI‐277 prevents the membrane association of the CAAX motif and thus increases the cytoplasmic levels of the eIF4G fusion protein, which is then capable of inducing translation of the second cistron of a bicistronic messenger RNA containing an R17‐binding site in its intercistronic space. Such direct translational control by farnesyl transferase inhibitors provides a system for fast, graded and reversible regulation of transgene expression.
Recommended Critical Temperatures. Part II. Aromatic and Cyclic Hydrocarbons
Authors: Owczarek Iwona , Blazej Krystyna
Published: June 2004

This study presents 41 recommended experimental and 52 calculated values of critical temperatures of aromatic and cyclic hydrocarbons. Additionally this work includes 93 recommended normal boiling point temperatures for these two groups of compounds. This is Part II in a series dealing with recommended critical data for organic compounds; Part I dealt with aliphatic hydrocarbons. For 33 aromatic and 19 cyclic compounds there is a significant lack of critical temperature values. Values have been provided by means of prediction methods and previously critically evaluated values, based on a recommended experimental database. One reason for the creation of this database was for the purpose of evaluation the accuracy of prediction methods applied in this study.
An experimental study of Faraday waves formed on the interface between two immiscible liquids
Authors: Tipton C. R. , Mullin T.
Published: June 2004

We report results of an experimental study of Faraday waves that were formed on the interface between two immiscible liquids in a cylindrical cell when it was oscillated vertically. The effects of the volume filling ratio ψ on the bifurcation set associated with the onset of the fundamental axisymmetric mode was investigated systematically. In particular, results are presented for the subharmonic regime of the control parameter space where the response was greatest. Both super- and subcritical bifurcations are uncovered, with hysteresis in the latter case. The extent of the hysteresis is observed to strongly depend on ψ, suggesting that nonlinear damping effects are influenced by this parameter. At large drive amplitudes, a precessional periodic motion was found to develop via a Hopf bifurcation. This mode was observed to disappear catastrophically at an excitation frequency equal to 1.853±0.006 times the natural frequency of the resonant mode.
A drift-kinetic approach to neoclassical transport theory for plasmas with large toroidal rotation
Authors: Wong S. K. , Chan V. S.
Published: June 2004

A formulation of the neoclassical transport theory for tokamak plasmas with large toroidal velocities that can be comparable to the ion thermal velocity is presented using the drift kinetic equation. In this formulation, the motion of the guiding centers is the same as in the small rotation theory, but the radial electric field is considered stronger: the ordering Er/Bθ∼v̄i is adopted where Bθ is the poloidal magnteic field and v̄i the ion thermal velocity. A complete set of transport coefficients for both electrons and ions is calculated in the large-aspect-ratio limit in the banana regime for flux surfaces of arbitrary shape. The calculation utilizes a recently developed method of matched asymptotic expansions for particle and energy fluxes and a regular perturbation for the angular momentum flux. The consistent application of perturbation for large-aspect-ratio provides a satisfactory explanation why the angular momentum flux is much smaller than the ion energy flux.
Fluid elastic instability of a small circular cylinder in the shear layer of a two-dimensional jet
Authors: Yu Ming-huei , Yu Che-ming , Chen Kuei-hsiung
Published: June 2004

Fluid elastic instability of a long, small-diameter circular cylinder in the shear layer of a two-dimensional air jet is investigated experimentally. A metal wire 0.23 mm in diameter, used as a small circular cylinder, was flexibly mounted along the span-wise direction of the two-dimensional jet, and in the shear layer region where the shear layer thickness is much larger than the wire diameter. The motion of the metal wire was monitored by a two-channel vibration measurement system, and the flow data of the jet were documented by a hot-wire anemometer. Stability of the wire was examined in the experimental ranges of Reynolds number from 8 to 120, reduced velocity from 100 to 1400, and shear parameter from 0 to 0.14. The local flow velocity at the wire location and the wire diameter were chosen as the characteristic velocity and length, respectively, for the three non-dimensional parameters. It is illustrated that in the experimental ranges the wire is unstable and induced to vibrate if initially mounted in a shear layer with sufficient high flow velocity and velocity gradient, while the wire is stable in uniform cross flow. Fluid elastic instability is identified to be responsible for the flow induced vibration. The critical condition for the onset of the instability is determined from amplitude diagrams. It is found that on the critical condition the reduced velocity R and the shear parameter K approximately satisfy the relation RK1.44=5.0 for the small circular cylinder in the airflow with a mass ratio of 5112. Past the critical condition, the amplitude of the wire vibration increases significantly to the scale of the shear layer thickness. By analyses of the vibration amplitudes, spectral data, and orbits of the wire, it is illustrated that the wire vibration in the shear layer of the two-dimensional jet is self-excited through a Hopf bifurcation to a limit cycle state.
Turbulent diffusion of momentum and suspended particles: A finite-mixing-length theory
Authors: Nielsen Peter , Teakle Ian A. L.
Published: June 2004

A finite-mixing-length theory is presented for turbulent mixing. This theory contains Fickian diffusion as the limiting case for lm/L→0, where lm is the mixing length and L is the scale of the distribution under consideration. The new model is of similar generality to that of Taylor (1921), “Diffusion by continuous movements.” However, while Taylor’s model, being strictly Lagrangian, is difficult to apply to inhomogeneous scenarios, the new model is Eulerian and easily applicable to bottom boundary layers and other inhomogeneous flows. When applied to steady suspended sediment concentrations c(z), the theory predicts the observed trend of apparent Fickian diffusivities εFick=−wsc/(dc/dz) being larger for particles with larger settling velocity ws, in a given flow. The corresponding nature of the ratios between apparent Fickian sediment diffusivities and eddy viscosities, β=εFick/vt, for different particles in the same flow, is also revealed. That is, β is an increasing function of the particle settling velocity and may be greater or smaller than unity depending on the relative magnitude of the vertical scales for concentrations Lc and for horizontal velocity Lu. Applied to the case of wave motion over ripples, even the observed trend of fine sand indicating decreasing εFick(z) while coarse sand shows increasing εFick(z) can be modelled with realistic turbulence parameters. Different Fickian diffusivities displayed by different species like density, heat, and salinity in a given turbulent flow may also be qualitatively explainable in terms of finite-mixing-length effects.
Universality of probability density distributions in the overlap region in high Reynolds number turbulent boundary layers
Authors: Lindgren Björn , Johansson Arne V. , Tsuji Yoshiyuki
Published: June 2004

The probability density functions (PDFs) of the streamwise mean velocity in high Reynolds number turbulent boundary layers have been studied. The hypothesis of self-similar, normalized with the root mean square velocity, PDFs has been tested using the KTH database of high Reynolds number zero pressure-gradient turbulent boundary layer flow. The self-similarity was tested using the Kullback–Leibler divergence measure and it was found that the region of self-similar PDFs extends from about 160 viscous wall units to about 0.3 boundary layer thicknesses (in δ95). This region is somewhat larger than the universal overlap region. The PDF shape in the universal overlap region is close to Gaussian allowing for a Gram–Charlier expansion approximation of the measured PDFs. A remarkable collapse was found for 57 normalized PDF distributions for different positions within the universal overlap region and Reynolds numbers based on the momentum-loss thickness between 4300 and 12 600, strongly indicating a high degree of flow universality within the universal overlap region. Within the range studied, the Gram–Charlier expansion coefficients (related to the PDF moments) show no Reynolds number trend further supporting the self-similarity hypothesis.
Dynamics of ultrasound-induced cavitation bubbles in non-Newtonian liquids and near a rigid boundary
Authors: Brujan E. A. , Ikeda T. , Matsumoto Y.
Published: June 2004

The dynamics of ultrasound-induced cavitation bubbles situated in non-Newtonian liquids and near a rigid boundary are investigated experimentally by acoustic measurements and high-speed photography with up to 4 million frames/s. The non-Newtonian liquids consist of a 0.5% polyacrylamide (PAM) aqueous solution with a strong elastic component and a 0.5% carboxymethylcellulose aqueous solution with a weak elastic component. The maximum velocity of the re-entrant liquid jet and the pressure amplitude of the acoustic transients emitted during first bubble collapse are diminished by the polymer additives. The most significant reduction was found in the elastic PAM solution. It might be caused by an increased resistance to extensional flow which is conferred upon the liquid by the polymer additive. The results are discussed with respect to the mechanisms of cavitation erosion of rigid materials. The material presented may also be useful for comparison with future numerical work.
A model for the condensation of a dusty plasma
Authors: Bellan P. M.
Published: June 2004

A model for the condensation of a dusty plasma is constructed by considering the spherical shielding layers surrounding a dust grain test particle. The collisionless region less than a collision mean free path from the test particle is shown to separate into three concentric layers, each having distinct physics. The method of matched asymptotic expansions is invoked at the interfaces between these layers and provides equations which determine the radii of the interfaces. Despite being much smaller than the Wigner–Seitz radius, the dust Debye length is found to be physically significant because it gives the scale length of a precipitous cut-off of the shielded electrostatic potential at the interface between the second and third layers. Condensation is predicted to occur when the ratio of this cut-off radius to the Wigner–Seitz radius exceeds unity and this prediction is shown to be in good agreement with experiments.
Harmonic generation in clusters
Authors: Fomyts’kyi Mykhailo V. , Breizman Boris N. , Arefiev Alexey V. , Chiu Charles
Published: June 2004

A model is presented for the nonlinear response of a small cluster, with a size much smaller than the wavelength, at the third harmonic of the laser frequency. The model involves collective modes of a cold electron core confined within a positively charged ion background. The response of the electron core to the laser field is similar to that of a weakly nonlinear oscillator driven by an external force. In particular, there is a resonant enhancement of the third harmonic when the frequency of the applied field is close to one third of the core eigenfrequency. It is shown that density nonuniformity or nonspherical shape of the ion background is necessary for harmonic generation. Particle-in-cell simulations have been performed to model the time evolution of the third harmonic response as the ion density profile changes due to cluster expansion. The simulation results are consistent with the predictions of the cold electron core model. In addition, the code quantifies the role of stochastic electron heating, an alternative harmonic generation mechanism.
The complete set of Casimir constants of the motion in magnetohydrodynamics
Authors: Hameiri Eliezer
Published: June 2004

A set of functional equations that all Casimir constants of the motion must satisfy is derived. A simple technique is developed that can be used to obtain partial information on the functional dependence of the Casimirs on the state variables. Together with additional known information, this is sufficient to determine all the Casimirs for a magnetohydrodynamic plasma with nested magnetic flux surfaces, as well as for some other magnetic configurations.
Scaling, spectra and zonal jets in beta-plane turbulence
Authors: Danilov Sergey , Gurarie David
Published: June 2004

A beta-plane approximation of the two-dimensional quasigeostrophic model describes a single layer (barotropic) fluid subjected to a latitudinally varying Coriolis parameter or topography. Rhines (1975) initiated the study of beta-plane turbulence. He predicted the inverse energy cascade into predominantly zonal modes, hence an array of eastward–westward jets, and estimated the jet number (celebrated Rhines scale). He also proposed a k−5 scaling law of zonal energy spectra. Our paper re-examines scaling, spectra, and zonal structure of beta-plane turbulence, based on theoretical predictions and numeric experiments. We show that the inverse cascade gives rise to strong organized zonal jets that evolve a peculiar frontal-band (“saw-tooth”) vorticity profile. Such structure affects all spectral properties of the system, by creating organized sequences of spectral peaks, and thus confounds any putative “scaling behavior.” The frontal-band structure appears consistently in all stochastically forced beta-plane flows, independent of dissipation and/or other details. But the resulting turbulent quasiequilibrium is not unique, its gross parameters (jets number, mean vorticity gradient) retain memory of the initial state and/or history.
Inverse scattering problem in nuclear physics—Optical model
Authors: Isozaki Hiroshi , Nakazawa Hideo , Uhlmann Gunther
Published: June 2004

We consider the inverse scattering problem for the Schrödinger operator with optical potential introduced in nuclear physics to study the scattering of nucleons by nuclei. We show that the corresponding spin–orbit interaction and the complex matrix potential can be uniquely reconstructed from the scattering amplitude at fixed energy.
On an integrable hierarchy derived from the isentropic gas dynamics
Authors: Brunelli J. C. , Das Ashok
Published: June 2004

In this paper we study a new hierarchy of equations derived from the system of isentropic gas dynamics equations where the pressure is a nonlocal function of the density. We show that the hierarchy of equations is integrable. We construct the two compatible Hamiltonian structures and show that the first structure has three distinct Casimirs while the second has one. The existence of Casimirs allows us to extend the flows to local ones. We construct an infinite series of commuting local Hamiltonians as well as three infinite series (related to the three Casimirs) of nonlocal charges. We discuss the zero curvature formulation of the system where we obtain a simple expression for the nonlocal conserved charges, which also clarifies the existence of the three series from a Lie algebraic point of view. We point out that the nonlocal hierarchy of Hunter–Zheng equations can be obtained from our nonlocal flows when the dynamical variables are properly constrained.
Observed Abundance Features and their Implications for Chemical Evolution
Authors: Tsujimoto Takuji , Shigeyama Toshikazu
Published: June 2004

We describe the star formation histories of the Milky Way dwarf spheroidal galaxy and the globular cluster ω Centauri in terms of an inhomogeneous chemical evolution model developed for the Galactic halo. The observed abundance trends seen in neutron-capture elements together with α-elements constrain our models to shed light on the histories of these nearby galaxies and ω Cen. The origin of low-α stars and a new picture of the globular cluster formation scenario induced by cloud–cloud collisions are also presented.
Modelling Galaxies with a 3D Multi-Phase ISM
Authors: Harfst Stefan , Theis Christian , Hensler Gerhard
Published: June 2004

We present a modified TREE-SPH code to model galaxies in three dimensions. The model includes a multi-phase description of the interstellar medium which combines two numerical techniques. A diffuse warm/hot gas phase is modelled by SPH, whereas a cloudy medium is represented by a sticky particle scheme. Interaction processes (such as star formation and feedback), cooling, and mixing by condensation and evaporation, are taken into account. Here we apply our model to the evolution of a Milky Way type galaxy. After an initial stage, a quasi-equilibrium state is reached. It is characterised by a star formation rate of ∼1 M⊙ yr–1. Condensation and evaporation rates are in balance at 0.1–1 M⊙ yr–1.
Solar Neighbourhood Age–Metallicity Relation Based on Hipparcos Data
Authors: Ibukiyama Akihiko
Published: June 2004

We derive age–metallicity relations (AMRs) and orbits for the 1658 solar neighbourhood stars for which accurate distances are measured by the Hipparcos satellite. The sample comprises 1382 thin disk stars, 229 thick disk stars, and 47 halo stars according to their orbital parameters. We find a considerable scatter for thin disk AMRs along the one-zone Galactic chemical evolution (GCE) model. Orbits and metallicities of thin disk stars show no clear relation to each other. The scatter along the AMR exists even if stars with the same orbits are selected. We examine simple extensions of one-zone GCE models which account for inhomogeneity in the effective yield and inhomogeneous star formation rate in the Galaxy. Both extensions of the one-zone GCE model cannot account for the scatter in the age–[Fe/H]–[Ca/Fe] relation simultaneously. We conclude, therefore, that the scatter along the thin disk AMR is an essential feature in the formation and evolution of the Galaxy. The AMR for thick disk stars shows that star formation terminated 8 Gyr ago in the thick disk. As previously reported, thick disk stars are more Ca-rich than thin disk stars with the same [Fe/H]. We find that thick disk stars show a vertical abundance gradient. These three facts — AMR, vertical gradient, and [Ca/Fe]–[Fe/H] relation — support monolithic collapse and/or accretion of satellite dwarf galaxies as likely thick disk formation scenarios.
Multiple Supernova Explosions in a Forming Galaxy
Authors: Mori Masao , Umemura Masayuki , Ferrara Andrea
Published: June 2004

Ultra-high resolution hydrodynamic simulations using 10243 grid points are performed of a very large supernova burst in a forming galaxy, with properties similar to those inferred for Lyman Break Galaxies (LBGs). Explosions produce kpc-sized expanding hot bubbles enclosed by cool, dense shells, and the engulfed gas is polluted with freshly-synthesised heavy elements. We show that the resultant inhomogeneous mixing produces a large spread ([Fe/H] ≈ –1 to –5) of metallicities, which affects the subsequent galactic chemical evolution and leaves its imprint on metal-poor stars. By combining a spectral synthesis model with the numerical results, we predict Lyα emission from such galaxy at z = 3. We find that the simulated galaxy, whose peak star formation rate is ≈200 M⊙ yr–1, produces a Lyα luminosity Lα = 9.7 × 1042 erg s–1. This value favorably matches the observed one, but some discrepancies are left for the Lyα line width, the metallicity, and X-ray properties. Since the results of the simulation is applicable only at the very early epoch of the galaxy formation, the metallicity is still lower than that of LBGs. However, the analysis presented here demonstrates a way to enable a systematic comparison with observational data.

It is concluded that LBGs are optimal objects to scrutinise the early self-enrichment in forming galaxies. In the future, the predicted bubbly structure carved by SNe may be directly detected by high resolution observations with JWST.
On the Shape of the Galactic Dark Matter Halo
Authors: Helmi Amina
Published: June 2004

The confined nature of the debris from the Sagittarius dwarf to a narrow trail on the sky has recently prompted the suggestion that the dark matter halo of our Galaxy should be nearly spherical (Ibata et al. 2001; Majewski et al. 2003). This would seem to be in strong contrast with predictions from cold dark matter (CDM) simulations, where dark halos are found to have typical density axis ratios of 0.6 to 0.8. Here I present numerical simulations of the evolution of a system like the Sagittarius dSph in a set of Galactic potentials with varying degrees of flattening. These simulations show that the Sagittarius streams discovered so far are too young dynamically to be sensitive to the shape of the dark halo of the Milky Way. The data presently available are entirely consistent with a Galactic dark matter halo that could either be oblate or prolate, with density axis ratios c/a that range from 0.6 to 1.6 within the region of the halo probed by the orbit of the Sagittarius dwarf.
White clover (Trifolium repens) and associated viruses in the subalpine region of south-eastern Australia: implications for GMO risk assessment
Authors: Godfree R. C. , Chu P. W. G. , Woods M. J.
Published: June 2004

Over the past several years, increased emphasis has been placed on conducting comprehensive ecological-risk assessments of virus-resistant genetically modified organisms (GMOs) prior to their release into the environment. In this paper we report on the first stage in our assessment of the level of risk posed by virus-resistant transgenic Trifolium repens L. (white clover) to native plant communities in south-eastern Australia. We investigated the distribution, abundance and phytosociological characteristics of naturalised T. repens populations in two areas in the subalpine region of New South Wales (NSW) and the Australian Capital Territory (ACT), and determined the distribution and abundance of Alfalfa mosaic virus, Clover yellow vein virus and White clover mosaic virus in 31 populations of white clover in this region. We found that T. repens is a significant component of Poa grasslands and Eucalyptus–Poa woodlands in the subalpine region, but is absent or rare in Eucalyptus species forests and Carex–Poa species bogs. Clover yellow vein virus was by far the most common virus in the study area, being present in 18% of T. repens plants across a wide range of plant communities. Alfalfa mosaic virus and White clover mosaic virus were each recorded in only one white-clover population growing in a native plant community. We conclude that white clover is a significant constituent of subalpine grasslands and woodlands in the region studied, and that of the viruses investigated, Clover yellow vein virus is the most abundant and widespread.
Tree growth rates in north Australian savanna habitats: seasonal patterns and correlations with leaf attributes
Authors: Prior L. D. , Eamus D. , Bowman D. M. J. S.
Published: June 2004

We demonstrate a significant relationship between leaf attributes and growth rates of mature trees under natural conditions in northern Australia, a pattern that has not been widely reported before in the literature. Increase in diameter at breast height (DBH) was measured every 3 months for 2 years for 21 tree species from four habitats near Darwin: Eucalyptus open forest, mixed eucalypt woodland, Melaleuca swamp and dry monsoon rainforest. Assimilation rates and foliar chlorophyll, nitrogen and phosphorus concentrations were positively correlated with growth rate and negatively correlated with leaf mass per area. For most species, increases in DBH were confined to the wet-season (summer) period between November and May. Average annual increases in DBH were larger in the dry monsoon rainforest (0.87 cm) and the Melaleuca swamp (0.65 cm) than in the woodland (0.20 cm) and the open forest (0.16 cm), and were larger in non-Myrtaceous species (0.53 cm) than in Myrtaceous species (0.25 cm). These results are discussed in relation to the frequent fire regime prevailing over much of northern Australia which causes the marked contrast between the small pockets of fire-tender closed monsoon rainforest and large expanses of fire-tolerant savanna.
Effects of individual fire events on the flower production of fruit-bearing tree species, with reference to Aboriginal people's management and use, at Kalumburu, North Kimberley, Australia
Authors: Vigilante T. , Bowman D. M. J. S.
Published: June 2004

This study used a number of landscape-scale natural experiments to investigate the influence of individual fire events on the reproductive output of key fruit-bearing woody species [Buchanania obovata Engl. (two leaf forms), Persoonia falcata R.Br., Planchonia careya (F.Muell.) Knuth, Syzygium eucalyptoides (F.Muell.) B.Hyland, Syzygium suborbiculare (Benth.) T.Hartley & Perry. and Terminalia cunninghamii C.Gardner] around Kalumburu, North Kimberley, Australia. Flowering level was used as an estimate of reproductive success as sampling was done prior to fruit development.Terminalia cunninghamii was found to flower earlier and more prolifically in areas burnt in the early dry season of 1999 than in areas left unburnt; however, there was no significant difference between these treatments in 2000. Flowering levels were significantly reduced in burnt treatments (from early to mid-dry season fires) for Buchanania obovata (large-leafed form), Persoonia falcata, Planchonia careya, Syzygium eucalyptoides and Syzygium suborbiculare. Positive correlations occurred between the minimum foliage height and total tree height of Buchanania obovata small-leafed form (r = 0.78, y = 0.61x + 0.003), large-leafed form (r = 0.87, y = 0.59x + 0.10) and Syzygium suborbiculare (r = 0.76, y = 0.43x + 0.54). Above a height of 2 m, most trees have the majority of their foliage located in the top half of the tree. In all cases, flowering levels increased with foliage height intervals.The results indicate that fire events and their timing can have an impact on the reproductive cycle of fruit-tree species. Indigenous people have managed these resources through the careful use of fire. The conservation of fruit-tree species and frugivorous-animal species could benefit from (i) the careful management of areas with high densities of fruit-bearing species, and (ii) spatially and temporally diverse fire regimes across broader landscape units.
A new species of Glaphyromorphus (Reptilia : Scincidae) from Mt Elliot, north-eastern Queensland
Authors: Hoskin Conrad J. , Couper Patrick J.
Published: June 2004

Glaphyromorphus clandestinus, sp. nov., is described from granite-slab habitat on Mt Elliot, north-eastern Queensland. This species can be distinguished from its congeners by a combination of the following characters: large size (SVL 72 mm), adpressed limbs of adult separated by noticeably more than the length of the forelimb, 26 mid-body scale rows, and flanks patterned with dark flecks forming a series of longitudinal lines. The distribution, habitat preferences and habits of this species are poorly known. Currently G. clandestinus is known from a single locality where individuals have been found in an exposed area of exfoliating granite, set in a mosaic of rainforest and eucalyptus woodland. The discovery of this species brings to three the number of vertebrate species known to be endemic to Mt Elliot and highlights the evolutionary significance of this southerly outlier to the mountainous rainforest of the Wet Tropics.
Formation of a central supramolecular activation cluster is not required for activation of naive CD8+T cells
Authors: O'Keefe James P. , Blaine Kelly , Alegre Maria-Luisa , Gajewski Thomas F.
Published: June 2004

Although both naive and effector T lymphocytes interact with antigen-expressing cells, the functional outcome of these interactions is distinct. Naive CD8+T cells are activated to proliferate and differentiate into effector cytolytic T lymphocytes (CTL), whereas CTL interact with specific targets, such as tumor cells, to induce apoptotic death. We recently observed that several molecules linked to actin cytoskeleton dynamics were up-regulated in effector vs. naive CD8+T cells, leading us to investigate whether T cell differentiation is accompanied by changes in actin-dependent processes. We observed that both naive and effector CD8+T cells underwent T cell receptor capping and formed stable conjugates with antigen-specific antigen-presenting cells. However, the characteristics of the immunological synapse were distinct. Whereas accumulation of signaling molecules at the T cell/antigen-presenting cell contact site was detectable in both naive and effector CD8+T cells, only effector cells developed a central supramolecular activation cluster as defined by punctate focusing of PKCθ, phospho-PKCθ, and phospho-ZAP70. Extended kinetics, CD28 costimulation, and high-affinity antigenic peptide did not promote PKCθ focusing in naive cells. Nonetheless, naive CD8+T cells polarized the microtubule organizing center, produced IL-2, proliferated, and differentiated into effector cells. Our results suggest that the formation of a central supramolecular activation cluster is not required for activation of naive CD8+T cells and support the notion that one role of an organized immune synapse is directed delivery of effector function.
Phosphoprotein inhibitor CPI-17 specificity depends on allosteric regulation of protein phosphatase-1 by regulatory subunits
Authors: Eto Masumi , Kitazawa Toshio , Brautigan David L.
Published: June 2004

Inhibition of myosin phosphatase is critical for agonist-induced contractility of vascular smooth muscle. The protein CPI-17 is a phosphorylation-dependent inhibitor of myosin phosphatase and, in response to agonists, Thr-38 is phosphorylated by protein kinase C, producing a >1,000-fold increase in inhibitory potency. Here, we addressed how CPI-17 could selectively inhibit myosin phosphatase among other protein phosphatase-1 (PP1) holoenzymes. PP1 in cell lysates was separated by sequential affinity chromatography into at least two fractions, one bound specifically to thiophospho-CPI-17, and another bound specifically to inhibitor-2. The MYPT1 regulatory subunit of myosin phosphatase was concentrated only in the fraction bound to thiophospho-CPI-17. This binding was eliminated by addition of excess microcystin-LR to the lysate, showing that binding at the active site of PP1 is required. Phospho-CPI-17 failed to inhibit glycogen-bound PP1 from skeletal muscle, composed primarily of PP1 with the striated muscle glycogen-targeting subunit (G
M
) regulatory subunit. Phospho-CPI-17 was dephosphorylated during assay of glycogen-bound PP1, not MYPT1-associated PP1, even though these two holoenzymes have the same PP1 catalytic subunit. Phosphorylation of CPI-17 in rabbit arteries was enhanced by calyculin A but not okadaic acid or fostriecin, consistent with PP1-mediated dephosphorylation. We propose that CPI-17 binds at the PP1 active site where it is dephosphorylated, but association of MYPT1 with PP1C allosterically retards this hydrolysis, resulting in formation of a complex of MYPT1·PP1C·P-CPI-17, leading to an increase in smooth muscle contraction.
A unified approach to polyene macrolides: Synthesis of candidin and nystatin polyols
Authors: Kadota Isao , Hu Yueqing , Packard Garrick K. , Rychnovsky Scott D.
Published: June 2004

Polyene macrolide antibiotics are naturally occurring antifungal agents. Members of this class include amphotericin B, which has been used widely to treat systemic fungal infections. A general synthetic strategy has been devised to prepare polyol chains associated with the polyene macrolides. Cyanohydrin acetonide alkylations were used to assemble the carbon skeleton, and a simple modification of the strategy allowed an advanced intermediate to be converted to either the candidin polyol or the nystatin polyol. The candidin polyol was further elaborated to a protected candidin aglycone. This strategy will be applicable to other members of the polyene macrolide natural products.
Identification of an outer membrane protein required for the transport of lipopolysaccharide to the bacterial cell surface
Authors: Bos Martine P. , Tefsen Boris , Geurtsen Jeroen , Tommassen Jan
Published: June 2004

Lipopolysaccharide (LPS), also known as endotoxin due to its severe pathophysiological effects in infected subjects, is an essential component of the outer membrane (OM) of most Gram-negative bacteria. LPS is synthesized in the bacterial inner membrane, a process that is now well understood. In contrast, the mechanism of its transport to the outer leaflet of the OM has remained enigmatic. We demonstrate here that the OM protein, known as increased membrane permeability (Imp) or organic solvent tolerance protein, is involved in this process. An Imp-deficient mutant of
Neisseria meningitidis
was viable and produced severely reduced amounts of LPS. The limited amount of LPS that was still produced was not accessible to LPS-modifying enzymes expressed in the OM or added to the extracellular medium. We conclude therefore that Imp mediates the transport of LPS to the cell surface. The role of Imp in LPS biogenesis and its high conservation among Gram-negative bacteria make it an excellent target for the development of novel antibacterial compounds.
Phylogenetic expression of Galα1-4Gal on avian glycoproteins: Glycan differentiation inscribed in the early history of modern birds
Authors: Suzuki Noriko , Laskowski, Michael , Lee Yuan C.
Published: June 2004

Glycoproteins containing Galα1-4Gal (galabiose) had been rarely found in vertebrates, except in a few species of birds and amphibians. We had previously reported that pigeon (
Columba livia
) egg white and serum glycoproteins are rich in N-glycans with Galα1-4Gal at nonreducing termini. To investigate the origin of Galα1-4Gal expression in avian evolution, we examined the presence of Galα1-4Gal glycoproteins in egg whites from 20 orders, 88 families, 163 genera, and 181 species of birds, as probed by Western blot with
Griffonia simplicifolia
-I lectin (terminal α-Gal/GalNAc-specific) and anti-P
1
mAb (Galα1-4Galβ1-4GlcNAcβ1-specific). One of the significant observations is the total absence of Galα1-4Gal glycoproteins in Struthioniformes (four species), Tinamiformes (three species), Craciformes (two species), Galliformes (14 species), and Anseriformes (10 species), which are phylogenetically separated from other orders at earlier stage of modern bird diversification (100-65 million years ago). The presence or absence of Galα1-4Gal glycoproteins in other avian orders varied by the species (104 species positive, and 44 species negative), even though some of them belong to the same order or family. Our results revealed that the expression of Galα1-4Gal glycoproteins is not rare among avians, and is correlated with the phylogeny. The expression was most likely differentiated at earlier stage of diversification in modern birds, but some birds might have lost the facility for the expression relatively recently.
The Parkinson's disease protein DJ-1 is neuroprotective due to cysteine-sulfinic acid-driven mitochondrial localization
Authors: Canet-Avilés Rosa M. , Wilson Mark A. , Miller David W. , Ahmad Rili , McLendon Chris , Bandyopadhyay Sourav , Baptista Melisa J. , Ringe Dagmar , Petsko Gregory A. , Cookson Mark R.
Published: June 2004

Loss-of-function
DJ-1
mutations can cause early-onset Parkinson's disease. The function of DJ-1 is unknown, but an acidic isoform accumulates after oxidative stress, leading to the suggestion that DJ-1 is protective under these conditions. We addressed whether this represents a posttranslational modification at cysteine residues by systematically mutating cysteine residues in human DJ-1. WT or C53A DJ-1 was readily oxidized in cultured cells, generating a pI 5.8 isoform, but an artificial C106A mutant was not. We observed a cysteine-sulfinic acid at C106 in crystalline DJ-1 but no modification of C53 or C46. Oxidation of DJ-1 was promoted by the crystallization procedure. In addition, oxidation-induced mitochondrial relocalization of DJ-1 and protection against cell death were abrogated in C106A but not C53A or C46A. We suggest that DJ-1 protects against neuronal death, and that this is signaled by acidification of the key cysteine residue, C106.
Caenorhabditis
phylogeny predicts convergence of hermaphroditism and extensive intron loss
Authors: Kiontke Karin , Gavin Nicholas P. , Raynes Yevgeniy , Roehrig Casey , Piano Fabio , Fitch David H. A.
Published: June 2004

Despite the prominence of
Caenorhabditis elegans
as a major developmental and genetic model system, its phylogenetic relationship to its closest relatives has not been resolved. Resolution of these relationships is necessary for studying the steps that underlie life history, genomic, and morphological evolution of this important system. By using data from five different nuclear genes from 10
Caenorhabditis
species currently in culture, we find a well resolved phylogeny that reveals three striking patterns in the evolution of this animal group: (
i
) Hermaphroditism has evolved independently in
C. elegans
and its close relative
Caenorhabditis briggsae
; (
ii
) there is a large degree of intron turnover within
Caenorhabditis
, and intron losses are much more frequent than intron gains; and (
iii
) despite the lack of marked morphological diversity, more genetic disparity is present within this one genus than has occurred within all vertebrates.
Knock-in human rhodopsin-GFP fusions as mouse models for human disease and targets for gene therapy
Authors: Chan Fung , Bradley Allan , Wensel Theodore G. , Wilson John H.
Published: June 2004

The human rhodopsin gene is the locus for numerous alleles linked to the neurodegenerative disease retinitis pigmentosa. To facilitate the study of retinal degeneration and to test reagents designed to alter the structure and function of this gene, we have developed strains of mice whose native rhodopsin gene has been replaced with the corresponding human DNA modified to encode an enhanced GFP fusion at the C terminus of rhodopsin. The human rhodopsin-GFP fusion faithfully mimics the expression and distribution of wild-type rhodopsin in heterozygotes and serves as a sensitive reporter of rod-cell structure and integrity. In homozygotes, however, the gene induces progressive retinal degeneration bearing many of the hallmarks of recessive retinitis pigmentosa. When the gene is flanked by recognition sites for Cre recombinase, protein expression is reduced ≈5-fold despite undiminished mRNA levels, suggesting translation inhibition. GFP-tagged human rhodopsin provides a sensitive method to monitor the development of normal and diseased retinas in dissected samples, and it offers a noninvasive means to observe the progress of retinal degeneration and the efficacy of gene-based therapies in whole animals.
Dietary intervention with the probioticsLactobacillus acidophilus145 andBifidobacterium longum913 modulates the potential of human faecal water to induce damage in HT29clone19A cells
Authors: Oberreuther-Moschner Daniela L , Jahreis Gerhard , Rechkemmer Gerhard , Pool-Zobel Beatrice L
Published: June 2004

Probiotics reduce the risk of colon cancer by inhibiting carcinogen-induced DNA damage in animals, but there are no analogous data in human subjects. To enhance knowledge of the effects of probiotics in human subjects, we have investigated the genotoxicity of faecal water after dietary intervention with standard yoghurt or with probiotic yoghurt, which included the strainsLactobacillus acidophilus145 andBifidobacterium longum913. Faeces were collected from nine healthy volunteers after intervention with probiotic yoghurt or standard yoghurt. Faecal water was isolated and incubated with human colon tumour cells HT29clone19A. DNA strand breaks, oxidised DNA bases and damage after challenge with H2O2were determined by micro-gel-electrophoresis. Faecal water was genotoxic in comparison with NaCl, but protected against H2O2-induced DNA strand breaks. The intervention with probiotic yoghurt significantly lowered faecal water genotoxicity compared with standard yoghurt. However, probiotic intervention also increased oxidative damage; this either reflected prooxidative activity or stimulation of endogenous defence systems. Altogether, the balance of effects favoured protection, since faecal water from the probiotic group reduced overall genetic damage. Thus, there was a reduction of strand break-inducing compounds in human faeces after dietary intervention with probiotic bacteria. This protection reflected results from previous studies in carcinogen-exposed animals where probiotics reduced DNA damage in colon cells.
Functional dichotomy: glutathione and vitamin E in homeostasis relevant to primary open-angle glaucoma
Authors: Veach John
Published: June 2004

Primary open-angle glaucoma (POAG) is a complex chronic neurological disease that can result in blindness. The goal of understanding the aetiology of POAG is to be able to target effective treatment to individuals who will eventually go blind without it. Epidemiological studies of POAG have not specifically addressed the possibility that nutrition may play a role in the development of POAG. A handful of papers have considered that nutrition may have an impact on POAG patients. POAG is not believed to be a ‘vitamin-deficiency disease’. The concept of ‘vitamin-deficiency diseases’ and the recommended daily allowances have not kept pace with the growing understanding of the cellular and molecular functions of vitamins and other micronutrients. The aetiology of POAG remains a mystery. Discoveries in cell physiology can be assimilated from the literature and applied to known homeostatic mechanisms of the eye. In this way the possible roles of nutritional components involved in the aetiology of POAG can be described. The mechanisms may be subject to many influences in ways that have yet to be defined. Two distinct changes in the trabecular meshwork can be identified: trabecular meshwork changes that cause intra-ocular pressure to increase and trabecular meshwork changes that are directly correlated to optic nerve atrophy. Compelling evidence suggests that collagen trabecular meshwork extracellular matrix (ECM) remodelling is correlated to increased intraocular pressure in POAG. Elastin trabecular meshwork ECM remodelling is correlated to POAG optic nerve atrophy. There appear to be two different pathways of ECM remodelling and apoptosis induction in POAG. The pathway for collagen remodelling and apoptosis induction seems to be exogenously influenced by water-soluble antioxidants, for example, glutathione. The pathway for elastin remodelling and apoptosis induction seems to be influenced by endogenous lipid-soluble antioxidants, for example, vitamin E. Roles can be defined for antioxidants in the two different pathways of ECM remodelling and apoptosis induction. This suggests that antioxidants are important in maintaining cellular homeostasis relevant to the aetiology of POAG.