bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical properties of ZnO and ZnO:In nanorods assembled by sol-gel method
Authors: Chen Y. W. , Liu Y. C. , Lu S. X. , Xu C. S. , Shao C. L. , Wang C. , Zhang J. Y. , Lu Y. M. , Shen D. Z. , Fan X. W.
Published: September 2005

Self-assembled zinc oxide (ZnO) and indium-doping zinc oxide (ZnO:In) nanorod thin films were synthesized on quartz substrates without catalyst in aqueous solution by sol-gel method. The samples were characterized by x-ray diffraction (XRD), scanning electron microscope (SEM), Raman-scattering spectroscopy, room-temperature photoluminescence (PL) spectra, and temperature-dependent PL spectra measurements. XRD and Raman spectra illustrated that there were no single In2O3 phase in ZnO lattice after indium doping. The PL spectra of ZnO showed a strong UV emission band located at 394nm and a very weak visible emission associated with deep-level defects. Indium incorporation induced the shift of optical band gap, quenching of the near-band-edge photoluminescence and enhanced LO mode multiphonon resonant Raman scattering in ZnO crystals at different temperatures. Abnormal temperature dependence of UV emission integrated intensity of ZnO and ZnO:In samples is observed. The local state emission peak of ZnO:In samples at 3.37eV is observed in low-temperature PL spectra. The near-band-edge emission peak at room temperature was a mixture of excitons and impurity-related transitions for both of two samples.
Diagnosing broken ergodicity using an energy fluctuation metric
Authors: de Souza Vanessa K. , Wales David J.
Published: September 2005

The Mountain and Thirumalai energy fluctuation metric, Ω(t), has been used to study the effective ergodicity of 60- and 256-atom binary Lennard-Jones mixtures in order to determine the reliability of the calculated diffusion constants at different energies. A plot of Ω(t) against 1∕time allows the identification of two distinct regimes: ergodic supercooled liquids, where Ω(t) approaches zero, and nonergodic glassy states, where Ω(t) asymptotically approaches a nonzero value on the molecular dynamics time scale. This approach seems to be more appropriate than attempting to define a threshold value for Ω(t)∕Ω(0). The behavior of systems between these two limits, which are nonergodic on the time scale considered but may be approaching ergodicity, was examined for a range of simulation times. The calculated diffusion constants change as effective ergodicity is approached, moving closer to the Vogel-Tammann-Fulcher fit defined by higher-energy systems that are already considered to be effectively ergodic. Using the form of the decay of the metric as a measure of ergodicity, we have been able to reproduce the trend in fragility obtained by Sastry for a 256-atom system [Nature (London) 409, 164 (2001)], correcting some of our earlier results [J. Chem. Phys. 120, 8314 (2004)].
A reweighted random series method for stereographic projection path integrals
Authors: Curotto E.
Published: September 2005

A set of general reweighted random series methods for metric affine spaces is developed. The extension of the theorems to metric affine spaces demands the introduction of a configuration-independent reference metric tensor; this geometric object is used to treat the path expansion coefficients beyond the core path, in both the partial averaging and the reweighted random series approach. Numerical tests are conducted by simulating a particle in a ring. The reweighted random series results show better convergence properties and better statistical quality at a fraction of the cost compared with the related partial averaging simulation.
The effect of proton disorder on the structure of ice-Ih: A theoretical study
Authors: Kuo Jer-Lai , Klein Michael L. , Kuhs Werner F.
Published: September 2005

A precise and accurate measurement of the crystal structure of ice-Ih is hindered by its disordered H-bond network. In this work, we carried out first-principle calculations to study the effects of H-bond topology on the structure of ice-Ih with emphasis on the molecular geometry of water and the distortion in oxygen lattice. An analytic algorithm based on group and graph theory is employed to enumerate all possible configurations in a given unit cell and to select a set of structures for detailed examinations. In total we have studied more than 60 ice-Ih structures in a hexagonal unit cell of 48 water molecules by quantum-chemical methods and found a significant amount of static distortion in the oxygen positions from their crystallographic positions which is in good agreements with highly significant higher-order terms obtained from both x-ray and neutron-diffraction data. Much debated structural information such as H–O–H angle and O–H bond length is found to be 106.34±0.36° and 0.9997±0.0008Å, compared to experimental value of 106.6±1.5° and 0.986±0.005Å. Detailed benchmarking calculations were carried out to gauge the influence of using different exchange and correlation functionals, pseudopotentials, and unit-cell sizes. Our results have proven that first-principle methods are useful complementary tools to experiments, especially for cases in which experimental accuracy is limited by intrinsic orientational disorder.
Multiscale coarse graining of liquid-state systems
Authors: Izvekov Sergei , Voth Gregory A.
Published: September 2005

A methodology is described to systematically derive coarse-grained (CG) force fields for molecular liquids from the underlying atomistic-scale forces. The coarse graining of an interparticle force field is accomplished by the application of a force-matching method to the trajectories and forces obtained from the atomistic trajectory and force data for the CG sites of the targeted system. The CG sites can be associated with the centers of mass of atomic groups because of the simplicity in the evaluation of forces acting on these sites from the atomistic data. The resulting system is called a multiscale coarse-grained (MS-CG) representation. The MS-CG method for liquids is applied here to water and methanol. For both liquids one-site and two-site CG representations without an explicit treatment of the long-ranged electrostatics have been derived. In addition, for water a two-site model having the explicit long-ranged electrostatics has been developed. To improve the thermodynamic properties (e.g., pressure and density) for the MS-CG models, the constraint for the instantaneous virial was included into the force-match procedure. The performance of the resulting models was evaluated against the underlying atomistic simulations and experiment. In contrast with existing approaches for coarse graining of liquid systems, the MS-CG approach is general, relies only on the interatomic interactions in the reference atomistic system.
The vibration-rotation emission spectrum of hot BeF2
Authors: Yu Shanshan , Shayesteh Alireza , Bernath Peter F. , Koput Jacek
Published: September 2005

The high-resolution infrared emission spectrum of BeF2 vapor at 1000°C was rotationally analyzed with the assistance of large-scale ab initio calculations using the coupled-cluster method including single and double excitations and perturbative inclusion of triple excitations, in conjunction with correlation-consistent basis sets up to quintuple-zeta quality. The ν3 fundamental band, the ν1+ν2, ν1+ν3, and 2ν2+ν3 combination bands, and 18 hot bands were assigned. The symmetric stretching (ν1), bending (ν2), and antisymmetric stretching (ν3) mode frequencies were determined to be 769.0943(2), 342.6145(3), and 1555.0480(1)cm−1, respectively, from the band origins of the ν3, ν1+ν3, and ν1+ν2 bands. The observed vibrational term values and B rotational constants were fitted simultaneously to an effective Hamiltonian model with Fermi resonance taken into account, and deperturbed equilibrium vibrational and rotational constants were obtained for BeF2. The equilibrium rotational constant (Be) was determined to be 0.235354(41)cm−1, and the associated equilibrium bond distance (re) is 1.3730(1)Å. The results of our ab initio calculations are in remarkably good agreement with those of our experiment, and the calculated value was 1.374Å for the equilibrium bond distance (re). As in the isoelectronic CO2 molecule, the Fermi resonance in BeF2 is very strong, and the interaction constant k122 was found to be 90.20(4)cm−1.
Type-IV phase behavior in fluids with an internal degree of freedom
Authors: Schöll-Paschinger Elisabeth , Kahl Gerhard
Published: September 2005

We have identified a fourth archetype of phase diagram in binary symmetrical mixtures, which is encountered when the ratio of the interaction between the unlike and the like particles is sufficiently small. This type of phase diagram is characterized by the fact that the λ line (i.e., the line of the second-order demixing transition) intersects the first-order liquid-vapor curve at densities smaller than the liquid-vapor critical density.
The peptide-chain size dependence of positive dissociation energy effect in metallized and protonated polydentate oligoglycine peptides
Authors: Ai Hongqi , Bu Yuxiang , Li Ping , Yan Shihai
Published: September 2005

The dependence of the positive dissociation energy (PDE) on the size of both protonated and various metal cationized (M+∕2+=Na+, K+, Mg2+, and Ca2+) oligoglycines GnHM (G=glycine; n=1–5, and including 6 for GnHK) in the gas phase has been first determined at the B3LYP level with different basis sets. Results show that these PDEs become negative ones when n⩾5 for GnHNa, n⩾6 for GnHK, n⩾2 for GnHMg, and n⩾3 for GnHCa. Moreover, the PDE effect decreases gradually along the increase of oligoglycine size for all these PDE systems. More charge transfer to the ambient ligand and large electrostatic effect of the two divalent cation (Mg2+ and Ca2+) involved systems make them lose the PDE effect more rapidly, and hold more compact and oblate shapes than the monovalent ones. Differently, polydentate GnHK prefers a spherical to oblate shape along with the increase of oligoglycine size.
Quantum observable homotopy tracking control
Authors: Rothman Adam , Ho Tak-San , Rabitz Herschel
Published: September 2005

This paper presents a new tracking method where the target observable ⟨O(s,T)⟩ at the final dynamical time T follows a predefined track P(s) with respect to a homotopy tracking variable s⩾0. The procedure calculates the series of control fields E(s,t) required to accomplish observable homotopy tracking by solving a first-order differential equation in s for the evolution of the control field. Controls produced by this technique render the desired track for all s without encountering field singularities. This paper also extends the technique to the case where the field-free Hamiltonian and dipole moment operator change with s in order to explore the control of new physical systems along the track. Several simulations are presented illustrating the various uses for this quantum tracking control technique.
Torsional potential of 4,4′-bipyridine: Ab initio analysis of dispersion and vibrational effects
Authors: Pérez-Jiménez Ángel J. , Sancho-García Juan C. , Pérez-Jordá José M.
Published: September 2005

Ab initio calculations using restricted Hartree-Fock, second-order Møller-Plesset perturbation theory (MP2), density-functional theory (DFT), and coupled-cluster methods have been done to obtain the torsional potential-energy profile of the aza-aromatic molecule 4,4′-bipyridine. The torsional potential is evaluated adiabatically by fixing the normalized sum of the dihedral angles through the C–C inter-ring bond at several values along the torsional path and relaxing the remaining degrees of freedom. Previous discrepancies between MP2 and DFT internal rotation barrier heights are removed, and seen to be mostly due to the underestimation of the dispersion energy in the coplanar conformer by MP2 when using relatively small basis sets. The calculations indicate that the barrier height between the twisted global minimum and the 0° conformer is around 1.5–1.8kcalmol−1 while that corresponding to the 90° one is about 2.0–2.2kcalmol−1. This same relative energy ordering of the coplanar and perpendicular conformers was experimentally derived from nuclear magnetic resonance (NMR) measurements of H1 dipolar couplings on 4,4′-bipyridine solutions in a nematic liquid crystal, although the barrier heights are much lower than those estimated from NMR experiments in the gas phase. The DFT infrared spectrum and zero-point vibrational energy corrections to the torsional energy profile have also been calculated, the latter having a small influence on the torsional potential-energy profiles.
Unusual magnetic properties of mixed-valence system: Multiconfigurational method theoretical study on Mn2+ cation
Authors: Wang Bingwu , Chen Zhida
Published: September 2005

The geometry structure, dissociation energy, vibrational frequencies, and low-lying spin-state energy spectrum of Mn2+ are investigated by using ab initio CASSCF/ECP10MDF, complete active space self-consistent field/atomic natural orbital basis sets (CASSCF/ANO-s), CASPT2/ECP10MDF, and second-order perturbation theory with CASSCF reference function/atomic natural orbital basis sets (CASPT2/ANO-s) levels of theory. For the ground state the dissociation energy of 1.397eV calculated at the CASPT2/ANO-s level supports Jarrlod’s experimental value of 1.39eV. The equilibrium bond length and vibrational frequency are 2.940Å calculated at the CASPT2/ANO-s level of theory and 214.4cm−1 calculated at the CASSCF/ANO-s level of theory, respectively. On the basis of the mixed-valence model, the Heisenberg exchange constant J(−71.2cm−1) and the double-exchange constant B(647.7cm−1) are extracted explicitly from the low-lying energy spectrum calculated at the higher levels of theory. The magnetic competition between the weaker Heisenberg exchange interactions and the stronger double-exchange interactions makes the ground state a Σg+12 state, consistent with electron paramagnetic resonance experimental observation, which explains unusual magnetic properties of Mn2+, quite different from the antiferromagnetic ground state of Mn2 and Cr2. On the other hand, the results calculated at the higher levels of theory show the consistent antiferromagnetic Heisenberg exchange interactions between 3d−3d for Cr2, Mn2+, and Mn2
InGaN nanorings and nanodots by selective area epitaxy
Authors: Chen P. , Chua S. J. , Wang Y. D. , Sander M. D. , Fonstad C. G.
Published: September 2005

An integrated process to fabricate controllable arrays of semiconductor nanorings and nanodots on patterned surfaces is presented. This approach is based on pattern transfer of nanopores to a SiO2 layer, followed by selective epitaxial growth of InGaN onto an underlying GaN substrate using metalorganic chemical vapor deposition. Using this approach, crystalline InGaN nanorings and nanodots ∼80nm in diameter have been grown on GaN surfaces. The formation mechanism of the nanorings and nanodots is described based on the initial stage of selective growth and restricted atom migration in a confined hole. Strong photoluminescence obtained at room temperature from the noncapped nanorings indicates strong confinement of the excitons in the nanostructures. This approach enables fabrication of dense, uniform arrays of epitaxial nanostructures and is potentially applicable to a variety of materials systems.
Einstein relation for disordered semiconductors: A dimensionless analysis
Authors: Nguyen Thanh H. , O’Leary Stephen K.
Published: September 2005

We present a generalized Einstein relation analysis, applicable for disordered semiconductors with exponential distributions of tail states and square-root distributions of band states. The results of this analysis, a series of plots for the ratio between the diffusion coefficient and the mobility, are cast in a dimensionless form. This will allow the experimentalist to simply “look up” the required results without the need for further analysis.
Saturated voids in interconnect lines due to thermal strains and electromigration
Authors: Zhang Zhen , Suo Zhigang , He Jun
Published: September 2005

Thermal strains and electromigration can cause voids to grow in conductor lines on semiconductor chips. This long-standing failure mode is exacerbated by the recent introduction of low-permittivity dielectrics. We describe a method to calculate the volume of a saturated void (VSV), attained in a steady state when each point in a conductor line is in a state of hydrostatic pressure, and the gradient of the pressure along the conductor line balances the electron wind. We show that the VSV will either increase or decrease when the coefficient of thermal expansion of the dielectric increases and will increase when the elastic modulus of the dielectric decreases. The VSV will also increase when porous dielectrics and ultrathin liners are used. At operation conditions, both thermal strains and electromigration make significant contributions to the VSV. We discuss these results in the context of interconnect design.
Unidirectional compression of electrorheological fluids in electric fields
Authors: Meng Yonggang , Filisko Frank E.
Published: September 2005

A series of unidirectional compression tests on electrorheological fluids has been carried out with different plate sizes, initial plate separations, and applied voltages. Experimental results of compression pressure were compared with the continuum non-Newtonian squeeze-flow theory in a normalized form. It was found that the compression resistance of the electrorheological fluid in an electric field was much higher than that predicted by the theory when the fluid was compressed to some extent and/or when the initial plate separation was relatively small. Characteristics of the pressure variation with the reduction in electrode gap width have been analyzed, and the compression behaviors under different experimental conditions have been discussed in terms of the morphology of particle aggregations under compression.
Thermal-expansion anomaly and spontaneous magnetostriction of Nd2AlFe15Mn compound
Authors: Hao Yanming , Zhao Miao , Zhou Yan
Published: September 2005

The structure and magnetic properties of Nd2AlFe15Mn compound have been investigated by means of x-ray diffraction and magnetization measurements. The Nd2AlFe15Mn compound has a rhombohedral Th2Zn17-type structure. The small thermal-expansion coefficient of Nd2AlFe15Mn compound was found by x-ray diffraction in temperature range of 103–342 K. Especially in the 282–342 K, the small thermal-expansion coefficient is nearly equal to zero. An anisotropic and strong positive spontaneous magnetostriction exists in Nd2AlFe15Mn compound. The magnetostrictive deformations were discussed.
Huge magnetoresistance in ultrathin La0.7Ca0.3MnO3 films: The role of superparamagnetic clusters and domain walls
Authors: Colino J. M. , de Andrés A.
Published: September 2005

The magnetic behavior of epitaxial La0.7Ca0.3MnO3 (LCMO) films grown on SrTiO3, with thickness down to 2.4nm, has been analyzed and correlated to the magnetoresistance (MR). Below about 10nm the canonical ferromagnetic order switches to a distribution of superparamagnetic clusters. These ultrathin films show a huge MR (4000%) at Tc and, at 5K, the MR is 300 times that of the ferromagnetic films’ value. Metallic conductivity is observed below Tc down to the blocking temperature (TB≈65K) but a strong upturn appears below TB. These findings can be explained by the ordering of uncoupled superparamagnetic clusters and their blocking at lower temperature, together with the collapse of the magnetic domain walls which are substituted by very small Mn magnetic clusters (few Mn) probably localized at the structural domain boundaries.
Influence of oxygen on optical properties of Si nanocrystallites
Authors: Ramos L. E. , Furthmüller J. , Bechstedt F.
Published: September 2005

The influence of oxygen on optical absorption spectra, radiative lifetimes, and localization of states is analyzed within the quasiparticle formalism based on the GW approximation for defect-free Si nanocrystallites. Passivation with hydroxyls and oxide coverage have significant influence on the spatial distribution of the highest-occupied and lowest-unoccupied molecular orbitals as well as on the radiative lifetimes. Oxidation blueshifts the onset of absorption, whereas oxide coverage and passivation with hydroxyls tend to redshift it. The indirect-gap nature of the optical transitions in Si bulk is transferred to the Si nanocrystallites independently of the oxygen contents.
45° polymer-based total internal reflection coupling mirrors for fully embedded intraboard guided wave optical interconnects
Authors: Wang Li , Wang Xiaolong , Jiang Wei , Choi Jinho , Bi Hai , Chen Ray
Published: September 2005

An array of 50μm×50μm polymer waveguides with 45° total internal reflection (TIR) wideband coupling mirrors were fabricated by soft molding to achieve fully embedded boardlevel optoelectronic interconnects. The 45° TIR coupling mirrors were formed at the ends of the waveguides to provide surface normal light coupling between waveguides and optoelectronic devices. Three-dimensional optoelectronic interconnects were replicated in one-step transfer by the soft molding technique. The measured propagation loss of the multimode waveguide was 0.16dB∕cm at 850nm wavelength. The coupling efficiency of the silver-coated 45° micromirrors buried under the top cladding was 92% with low polarization sensitivity.
Synthesis of silicon nanocones using rf microplasma at atmospheric pressure
Authors: Shirai H. , Kobayashi T. , Hasegawa Y.
Published: September 2005

We report the synthesis of silicon nanocones using the rf microplasma discharge at atmospheric pressure. The products formed underneath the tube electrode on Fe-coated crystalline silicon were constituted mainly of silicon and silicon oxide despite the use of a methane-argon mixture. Carbon nanotubes and silicon nanowires were also formed around the silicon nanocones. The number density and average size of silicon nanocones increased with the plasma exposure time accompanied by the enlargement of their surface distribution. The growth mechanism of silicon nanocones is discussed in terms of the catalytic growth via diffusion of silicon with nanocrystalline Si particle through FeSix nanoclusters, and enhanced Si oxidation by the plasma heating.
High-efficiency laser-diodes-pumped microthickness Yb:Y3Al5O12 slab laser
Authors: Sueda K. , Takahashi H. , Kawato S. , Kobayashi T.
Published: October 2005

A high-efficiency and high-power Yb:Y3Al5O12 oscillator was developed based on the microthickness slab structure with high aspect ratio to obtain one-dimensional temperature gradient and to reduce the temperature increase in the crystal. Laser output power of 257W was obtained in cw oscillation with 42% optical conversion efficiency at a pump power of 608W.
Corrigendum to: Soil water extraction and biomass production by lucerne in the south of Western Australia
Authors: Dolling P. J. , Latta R. A. , Ward P. R. , Robertson M. J. , Asseng S.
Published: September 2005

To understand the factors involved in lucerne reducing drainage below the root-zone and influencing lucerne biomass production and water extraction were analysed in the south of Western Australia. The lucerne was grown for 3 years before removal. The factors investigated as part of the water extraction analysis included the rate of advance of the extraction front or extraction front velocity (EFV, mm/day), the soil plant-available water-holding capacity (PAWC, mm/m soil), and the temporal change in soil water deficit (drainage buffer, mm). The drainage buffer is related to the EFV and PAWC.
A site with deep sand had the highest EFV (mean of 9.2�mm/day) but the lowest PAWC (mean of 32�mm/m soil) to a depth of 4�m. In the duplex soils the EFV was 18.34% of the deep sand EFV and the PAWC was 60.222% higher than the deep sand PAWC to a depth of 1.6.2.1�m. The EFV was reduced by the higher clay content and sodicity in the B horizon of the duplex soils. The highest drainage buffer measurements occurred in the deep sand site and the better structured duplex soils and therefore these soils will have the greater effect on reducing drainage below the root-zone. However, lucerne was able to create a drainage buffer to at least a depth of 1.5�m over 3 years and therefore contribute to a reduced drainage even on the most sodic and saline sites. Low soil pH did not affect the drainage buffer as much as soil texture and structure.
Variation in biomass production of lucerne-based pastures was positively related to rainfall and water use (taking into account soil water storage and drainage losses) across sites, explaining approximately 50% of the biomass variation. Rainfall and water use could therefore be used for predicting lucerne biomass production in Western Australia. Biomass water use efficiency was highest in spring (15 kg/ha.mm) and least during autumn (4.5 kg/ha.mm).
Corrigendum to: Influence of gibberellic acid and N6-benzyladenine on the development of seed and shot berries in the seedless grape (Vitis vinifera L.) cv. Perlette
Authors: Usha K. , Kashyap D. , Singh B.
Published: September 2005

Gibberellins have been used to improve quality of grapes in several cases. However, gibberellic acid (GA) alone is not enough to improve the quality in Perlette. A field experiment was conducted on 3-year-old grape cv. Perlette trained on pergolas, to investigate the effect of bunch dipping with GA3 and N6-benzyladenine (BA) on reducing the problem of shot berries and improving the productivity of grapevines. Our observations proved that the stage of application of GA3 and BA is crucial to avoiding seed formation in seedless varieties such as Perlette for table grapes. The results showed that BA at low (10 �L/L) or high concentration (30 �L/L) at 50% of full bloom caused seed development in the seedless grape cv. Perlette, whereas no seed was formed when BA was used later at the fruit set stage. Based on our studies, we found that bunch dipping with 30 �L/L GA3 (at 50% of full bloom) and 10�L/L BA (at pea size) significantly reduced the problem of shot berries, and improved the yield and quality in grape cv. Perlette.
Deep drainage and land use systems. Model verification and systems comparison
Authors: Paydar Zahra , Huth Neil , Ringrose-Voase Anthony , Young Rick , Bernardi Tony , Keating Brian , Cresswell Hamish
Published: September 2005

Deep drainage or drainage below the bottom of the profile usually occurs when rain infiltrates moist soil with insufficient capacity to store the additional water. This drainage is believed to be contributing to watertable rise and salinity in some parts of the Liverpool Plains catchment in northern New South Wales. The effect of land use on deep drainage was investigated by comparing the traditional long fallow system with more intense ‘opportunity cropping’. Long fallowing (2 crops in 3 years) is used to store rainfall in the soil profile but risks substantial deep drainage. Opportunity cropping seeks to lessen this risk by sowing whenever there is sufficient soil moisture. Elements of the water balance and productivity were measured under various farming systems in a field experiment for 4 years in the southern part of the catchment. The experimental results were used to verify APSIM (Agricultural Production Systems Simulator) by comparing them with predictions of production, water storage, and runoff. The verification procedure also involved local farmers and agronomists who assessed the credibility of the predictions and suggested modifications. APSIM provided a realistic simulation of common farming systems in the region and could capture the main hydrological and biological processes. APSIM was then used for long-term (41 years) simulations to predict deep drainage under different systems and extrapolate experimental results. The results showed large differences between agricultural systems mostly because differences in evapotranspiration contributed to differences in profile moisture when it rained. The model predicted that traditional long fallow farming systems (2 crops in 3 years) are quite ‘leaky’, with average annual deep drainage of 34 mm. However, by planting crops in response to the depth of moist soil (opportunity or response cropping), APSIM predicted a much smaller annual drainage rate of 6 mm. Opportunity cropping resulted in overall greater water use and increased production compared with long fallowing. Furthermore, modelling indicated that average annual deep drainage under continuous sorghum (3 mm) is much less than under either long fallow cropping or continuous wheat (39 mm), demonstrating the importance of including summer cropping, as well as increasing cropping frequency, to reducing deep drainage.
Linking physiological and genetic analyses of the control of leaf growth under changing environmental conditions
Authors: Tardieu François , Reymond Matthieu , Muller Bertrand , Granier Christine , Simonneau Thierry , Sadok Walid , Welcker C.
Published: September 2005

Decrease in leaf growth rate under water deficit can be seen as an adaptive process. The analysis of its genetic variability is therefore important in the context of drought tolerance. Several mechanisms are widely believed to drive the reduction in leaf growth rate under water deficit, namely leaf carbon balance, incomplete turgor maintenance, and decrease in cell wall plasticity or in cell division rate, with contributions from hormones such as abscisic acid or ethylene. Each of these mechanisms is still controversial, and involves several families of genes. It is argued that gene regulatory networks are not feasible for modelling such complex systems. Leaf growth can be modelled via response curves to environmental conditions, which are considered as ‘meta-mechanisms’ at a higher degree of organisation. Response curves of leaf elongation rate to meristem temperature, atmospheric vapour pressure deficit, and soil water status were established in recombinant inbred lines (RILs) of maize in experiments carried out in the field and in the greenhouse. A quantitative trait locus (QTL) analysis was conducted on the slopes of these responses. Each parameter of the ecophysiological model could then be computed as the sum of QTL effects, allowing calculation of parameters of new RILs, either virtual or existing. Leaf elongation rates of new RILS were simulated and were similar to measurements in a growth chamber experiment. This opens the way to the simulation of virtual genotypes, known only by their alleles, in any climatic scenario. Each genotype is therefore represented by a set of response parameters, valid in a large range of conditions and deduced from the alleles at QTLs.
Grasstree (Xanthorrhoea preissii) recovery after fire in two seasons and habitats
Authors: Korczynskyj Dylan , Lamont Byron B.
Published: October 2005

To distinguish fire-stimulated growth from the underlying growth patterns imposed by season, we measured leaf production of Xanthorrhoea preissii Endl. (Xanthorrhoeaceae). We compared unburnt with spring- and autumn-burnt sites in forest and woodland habitats. Following fire, X. preissii responded with accelerated leaf production, regardless of season. Rapid leaf production during the initial flush of growth was partly at the expense of starch reserves in the stem, at least after autumn fire. Although this initial flush was relatively short-lived after fire in both seasons (12–32 weeks), the effect of fire on leaf production was sustained for up to 20 months, accompanied by a significant reduction in leaf longevity. Mean maximum leaf production rate was higher for spring-burnt grasstrees (up to 6.1 leaves day–1) than those burnt in autumn (up to 4.5 leaves day–1), associated with seasonally optimal growing conditions in late spring–early summer. Similarly, the timing of autumn burns in relation to declining temperature with the approach of winter appeared to dictate how rapidly grasstrees recovered. The consequences of fire season could have implications for the reproductive success of X. preissii.
The systematics of the south-east Asian genus Fangensis Rambla (Opiliones:Cyphophthalmi:Stylocellidae)
Authors: Schwendinger Peter J. , Giribet Gonzalo
Published: September 2005

The hitherto monotypic opilionid genus Fangensis Rambla, 1994 is re-evaluated from new material collected in northern, western and southern Thailand. The original description of F. leclerci Rambla (type material not traceable) was based on specimens belonging to at least three distinct species. Fangensis leclerci is thus redefined and the binomen restricted to specimens from a cave in northern Thailand only. Three new species are described, F. spelaeus, sp. nov. and F. cavernarus, sp. nov. from two caves in western Thailand and F. insulanus, sp. nov. from forests on two islands in southern Thailand. Taxonomic characters are discussed and relationships among Fangensis species and between Fangensis and other cyphophthalmids are evaluated using morphological data and ~4 Kb of molecular data from three loci, two nuclear ribosomal genes and a mitochondrial coding gene. Overall, data indicate monophyly of Stylocellidae and morphological and ribosomal data suggest monophyly of Fangensis, which is in turn divided into two clades, one composed of the three species from northern and western Thailand and the other represented by the species from southern Thailand. Observations on mating in F. leclerci are provided.
Attentional integration between anatomically distinct stimulus representations in early visual cortex
Authors: Haynes John-Dylan , Tregellas Jason , Rees Geraint
Published: September 2005

Vision often requires attending to, and integrating information from, distant parts of the visual field. However, the neural basis for such long-range integration is not clearly understood. Here, we demonstrate a specific neural signature of attentional integration between stimuli in different parts of the visual field. Using functional MRI, we found that a task requiring the integration of information between two attended but spatially separated stimuli actively modulated the degree of functional integration (in terms of effective connectivity) between their retinotopic representations in visual cortical areas V1, V2, and V4. Spatial attention enhanced long-distance coupling between distinct neuronal populations that represented the attended visual stimuli, even at the earliest stages of cortical processing. In contrast, unattended stimulus representations were decoupled both from attended representations and particularly strongly from each other. Furthermore, enhanced functional integration between cortical representations was associated with enhanced behavioral performance. Attention may thus serve to “bind” together cortical loci at multiple levels of the visual hierarchy that are commonly involved in processing attended stimuli, promoting integration between otherwise functionally isolated cortical loci.
Structures of microfilament destabilizing toxins bound to actin provide insight into toxin design and activity
Authors: Allingham John S. , Zampella Angela , D'Auria Maria Valeria , Rayment Ivan
Published: September 2005

Marine macrolides that disrupt the actin cytoskeleton are promising candidates for cancer treatment. Here, we present the actin-bound x-ray crystal structures of reidispongiolide A and C and sphinxolide B, three marine macrolides found among a recently discovered family of cytotoxic compounds. Their structures allow unequivocal assignment of the absolute configuration for each compound. A comparison of their actin-binding site to macrolides found in the trisoxazole family, as well as the divalent macrolide, swinholide A, reveals the existence of a common binding surface for a defined segment of their macrocyclic ring. This surface is located on a hydrophobic patch adjacent to the cleft separating domains 1 and 3 at the barbed-end of actin. The large area surrounding this surface accommodates a wide variety of conformations and designs observed in the macrocyclic component of barbed-end-targeting macrolides. Conversely, the binding pocket for the macrolide tail, located within the cleft itself, shows very limited variation. Functional characterization of these macrolides by using
in vitro
actin filament severing and polymerization assays demonstrate the necessity of the
N
-methyl-vinylformamide moiety at the terminus of the macrolide tail for toxin potency. These analyses also show the importance of stable interactions between the macrocyclic ring and the hydrophobic patch on actin for modifying filament structure and how this stability can be compromised by subtle changes in macrolactone ring composition. By identifying the essential components of these complex natural products that underlie their high actin affinity, we have established a framework for designing new therapeutic agents.
Pomegranate fruit juice for chemoprevention and chemotherapy of prostate cancer
Authors: Malik Arshi , Afaq Farrukh , Sarfaraz Sami , Adhami Vaqar M. , Syed Deeba N. , Mukhtar Hasan
Published: September 2005

Prostate cancer is the most common invasive malignancy and the second leading cause of cancer-related deaths among U.S. males, with a similar trend in many Western countries. One approach to control this malignancy is its prevention through the use of agents present in diet consumed by humans. Pomegranate from the tree
Punica granatum
possesses strong antioxidant and antiinflammatory properties. We recently showed that pomegranate fruit extract (PFE) possesses remarkable antitumor-promoting effects in mouse skin. In this study, employing human prostate cancer cells, we evaluated the antiproliferative and proapoptotic properties of PFE. PFE (10-100 μg/ml; 48 h) treatment of highly aggressive human prostate cancer PC3 cells resulted in a dose-dependent inhibition of cell growth/cell viability and induction of apoptosis. Immunoblot analysis revealed that PFE treatment of PC3 cells resulted in (
i
) induction of Bax and Bak (proapoptotic); (
ii
) down-regulation of Bcl-X
L
and Bcl-2 (antiapoptotic); (
iii
) induction of WAF1/p21 and KIP1/p27; (
iv
) a decrease in cyclins D1, D2, and E; and (
v
) a decrease in cyclin-dependent kinase (cdk) 2, cdk4, and cdk6 expression. These data establish the involvement of the cyclin kinase inhibitor-cyclin-cdk network during the antiproliferative effects of PFE. Oral administration of PFE (0.1% and 0.2%, wt/vol) to athymic nude mice implanted with androgen-sensitive CWR22Rν1 cells resulted in a significant inhibition in tumor growth concomitant with a significant decrease in serum prostate-specific antigen levels. We suggest that pomegranate juice may have cancer-chemopreventive as well as cancer-chemotherapeutic effects against prostate cancer in humans.
Dynamics of sleep-wake cyclicity in developing rats
Authors: Blumberg Mark S. , Seelke Adele M. H. , Lowen Steven B. , Karlsson Karl Æ.
Published: September 2005

Adult mammals cycle between periods of sleep and wakefulness. Recent assessments of these cycles in humans and other mammals [Lo, C. C., Amaral, L. A. N., Havlin, S., Ivanov, P. Ch., Penzel, T., Peter, J. H. & Stanley, H. E. (2002)
Europhys. Lett.
57, 625-631 and Lo, C. C., Chou, T., Penzel, T., Scammell, T. E., Strecker, R. E., Stanley, H. E. & Ivanov, P. Ch. (2004)
Proc. Natl. Acad. Sci.
101, 17545-17548] indicate that sleep bout durations exhibit an exponential distribution, whereas wake bout durations exhibit a power-law distribution. Moreover, it was found that wake bout distributions, but not sleep bout distributions, exhibit scale invariance across mammals of different body sizes. Here we test the generalizability of these findings by examining the distributions of sleep and wake bout durations in infant rats between 2 and 21 days of age. In agreement with Lo
et al
., we find that sleep bout durations exhibit exponential distributions at all ages examined. In contrast, however, wake bout durations also exhibit exponential distributions at the younger ages, with a clear power-law distribution only emerging at the older ages. Further analyses failed to find substantial evidence either of short- or long-term correlations in the data, thus suggesting that the durations of current sleep and wake bouts evolve through time without memory of the durations of preceding bouts. These findings further support the notion that bouts of sleep and wakefulness are regulated independently. Moreover, in light of recent evidence that developmental changes in sleep and wake bouts can be attributed in part to increasing forebrain influences, these findings suggest the possibility of identifying specific neural circuits that modulate the changing complexity of sleep and wake dynamics during development.
Lymphoid neogenesis in chronic rejection: Evidence for a local humoral alloimmune response
Authors: Thaunat Olivier , Field Anne-Christine , Dai Jianping , Louedec Liliane , Patey Natacha , Bloch Marie-Françoise , Mandet Chantal , Belair Marie-France , Bruneval Patrick , Meilhac Olivier , Bellon Blanche , Joly Etienne , Michel Jean-Baptiste , Nicoletti Antonino
Published: September 2005

Recent advances indicate that, in various chronic inflammatory disorders, the activation of the immune system is triggered locally rather than in lymphoid organs. In this study, we have evaluated whether the humoral alloimmune response involved in chronic rejection is elicited within the graft. We used the rat aortic interposition model and microdissected the adventitia of the graft. Over time, the T cell infiltrate shifted toward a B helper phenotype. B lymphocyte clusters were detected and were the site of intense proliferation and apoptosis. Simultaneously, adventitial vascular endothelium acquired a high endothelial venule phenotype. Similar features were evidenced in the interstitium of chronically allografts (hearts and kidneys). Strikingly, ganocultured graft interstitial tissue was found to be the site of production of antibodies directed against donor MHC-I molecules. These findings, therefore, document the appearance of germinal centers in chronically rejected tissues. This lymphoid neogenesis implies that the graft is not only the target of the alloimmune response but also a site where this response actually develops, so as to optimize the communication between the targeted tissue and the immune effectors.
RelA repression of RelB activity induces selective gene activation downstream of TNF receptors
Authors: Jacque Emilie , Tchenio Thierry , Piton Guillaume , Romeo Paul-Henri , Baud Véronique
Published: September 2005

TNF-α is a potent proinflammatory cytokine that regulates immune and inflammatory responses and programmed cell death. TNF-α stimulation causes nuclear translocation of several NF-κB dimers, including RelA/p50 and RelB/p50. However, contrary to RelA, RelB entering the nucleus in response to TNF-α cannot bind to DNA in mouse embryonic fibroblasts, strongly suggesting that RelB DNA-binding activity is modulated by additional nuclear mechanisms. Here, we demonstrate that TNF-α promotes the association of RelA with RelB in the nucleus and that TNF-α-induced RelA/RelB heterodimers do not bind to κB sites. Remarkably, we show that RelA serine-276, the phosphorylation of which is induced by TNF receptor ligation, is crucial for RelA/RelB complex formation and subsequent inhibition of RelB DNA binding. In the absence of RelA phosphorylation on serine-276, TNF-α stimulation leads to a strong increase in the expression of endogenous NF-κB-responsive genes, such asBcl-xL, whose transcriptional up-regulation is mainly controlled by RelB. Our findings demonstrate that RelA has a major regulatory role serving to dampen RelB activity in response to TNF-α and define a previously unrecognized mechanism that represents an essential step leading to selective NF-κB target gene expression.
Host-plant finding by the asparagus fly, Plioreocepta poeciloptera (Diptera: Tephritidae), a monophagous, monovoltine tephritid
Authors: Thibout É , Pierre D. , Mondy N. , Lecomte C. , Biémont J.C. , Auger J.
Published: September 2005

The role of various olfactory and visual stimuli was studied in host-plant finding by the asparagus fly Plioreocepta poeciloptera (Schrank), a monophagous monovoltine tephritid causing serious damage to asparagus spears. Volatiles released by asparagus plants were extracted by diethyl ether after cryotrapping concentration, and identified by gas chromatography–mass spectrometry. Twelve of the 13 compounds identified were tested using electroantennography to measure the response of the fly. Behavioural response was analysed using two different flight tunnels according to circadian rhythm, age and sex of adults, presence of the plant and of different coloured lures, presence of a male congener, or exposure to four pure asparagus odour compounds that elicited responses in electroantennography, i.e. hexanal, (E)-2-hexenal, (Z)-2-hexen-1-ol and decanal. Data showed that males locate the host plant more quickly than females. Females are attracted mainly by the blend of plant odour and male pheromone. Both sexes respond to a complex of stimuli only during the afternoon. These findings will be helpful in developing new and effective approaches to control this pest insect.
Hybridization between Helicoverpa armigera and Helicoverpa assulta (Lepidoptera: Noctuidae): development and morphological characterization of F1 hybrids
Authors: Zhao X.-C. , Dong J.-F. , Tang Q.-B. , Yan Y.-H. , Gelbic I. , Van Loon J.J.A. , Wang C.-Z.
Published: September 2005

Reciprocal hybridizations between Helicoverpa armigera (Hübner) and Helicoverpa assulta (Guenée) were studied. The cross between females of H. armigera and males of H. assulta yielded only fertile males and sterile individuals lacking an aedeagus, valva or ostium bursae. A total of 492 larvae of the F1 generation were obtained and 374 of these completed larval development and pupated. Only 203 pupae were morphologically normal males, the remaining 171 pupae were malformed. Larvae and pupae that gave rise to morphologically abnormal adults exhibited longer development times. Sterility was not only associated with malformed external sex organs, but also a range of abnormalities of the internal reproductive system: (i) loss of internal reproductive organs, (ii) with one to three copies of an undeveloped bursa copulatrix; or (iii) with one or two undeveloped testes. Normal male hybrid adults showed higher flight activity in comparison with males of both species. In contrast, the cross between females of H. assulta and males of H. armigera yielded morphologically normal offspring (80 males and 83 females). The interaction of the Z-chromosome from H. assulta with autosomes from H. armigera might result in morphological abnormalities found in hybrids and backcrosses, and maternal-zygotic incompatibilities might contribute to sex bias attributed to hybrid inviability.