bluuebunny/crossref_metadata_2025 huggingface dataset:
Quadrupole lamp furnace for high temperature (up to 2050K) synchrotron powder x-ray diffraction studies in air in reflection geometry
Authors: Sarin P. , Yoon W. , Jurkschat K. , Zschack P. , Kriven W. M.
Published: September 2006

A four-lamp thermal image furnace has been developed to conduct high temperature x-ray diffraction in reflection geometry on oxide ceramic powder samples in air at temperatures ⩽2050K using synchrotron radiation. A refractory crucible made of Pt20%Rh alloy was used as a specimen holder. A material with well characterized lattice expansion properties was used as an internal crystallographic thermometer to determine the specimen temperature and displacement. The performance of the apparatus was verified by measurement of the thermal expansion properties of CeO2, MgO, and Pt which were found to be within ±3% of the acceptable values. The advantages, limitations, and important considerations of the instrument developed are discussed.
Band anticrossing in GaNxSb1−x
Authors: Jefferson P. H. , Veal T. D. , Piper L. F. J. , Bennett B. R. , McConville C. F. , Murdin B. N. , Buckle L. , Smith G. W. , Ashley T.
Published: September 2006

Fourier transform infrared absorption measurements are presented from the dilute nitride semiconductor GaNSb with nitrogen incorporations between 0.2% and 1.0%. The divergence of transitions from the valence band to E− and E+ can be seen with increasing nitrogen incorporation, consistent with theoretical predictions. The GaNSb band structure has been modeled using a five-band k∙p Hamiltonian and a band anticrossing fitting has been obtained using a nitrogen level of 0.78eV above the valence band maximum and a coupling parameter of 2.6eV.
Self-similar solutions for a nonlinear radiation diffusion equation
Authors: Garnier Josselin , Malinié Guy , Saillard Yves , Cherfils-Clérouin Catherine
Published: September 2006

This paper considers the hydrodynamic equations with nonlinear conduction when the internal energy and the opacity have power-law dependences in the density and in the temperature. This system models the situation in which a dense solid is brought into contact with a thermal bath. It supports self-similar solutions that depend on the surface temperature. The self-similar solution can exhibit a shock wave followed by an ablation front if the surface temperature does not increase too fast in time, but it can exhibit a heat front followed by an isothermal shock otherwise. These flows are carefully studied in order to clarify the role of the initial solid density in the energy absorption and the ablation process. Comparisons with numerical simulations show excellent agreement.
A comparative study of the properties of polar and nonpolar solvent/solute/polystyrene solutions in microwave fields via molecular dynamics
Authors: Purdue Mark J. , MacElroy J. M. D. , O’Shea D. F. , Okuom Macduff O. , Blum Frank D.
Published: September 2006

The influence of an applied microwave field on the dynamics of methylamine-dichloromethane (DCM) mixtures bound within atactic polystyrene (a-PS) over a range of polymer densities from 30to94wt% polymer was examined using atomistic molecular dynamics simulations. This study is an extension of previous studies on methylamine transport in relatively polar polystyrene solutions of methanol and dimethylformamide [M. J. Purdue et al., J. Chem. Phys. 124, 204904 (2006)]. A direct comparison is made across the three types of polystyrene solutions. Consideration is given to both solvent and reagent transport within the polymer solutions under zero-field conditions and in an external electromagnetic field in the canonical ensemble (NVT) at 298.0K. Various frequencies up to 104GHz and a rms electric field intensity of 0.1V∕Å were applied. The simulation studies were validated by comparison of the simulated zero-field self-diffusion coefficients of DCM in a-PS with those obtained using pulsed-gradient spin-echo NMR spectrometry. Athermal effects of microwave fields on solute transport behavior within polymer solutions are discussed.
Two-component membrane material properties and domain formation from dissipative particle dynamics
Authors: Illya G. , Lipowsky R. , Shillcock J. C.
Published: September 2006

The material parameters (area stretch modulus and bending rigidity) of two-component amphiphilic membranes are determined from dissipative particle dynamics simulations. The preferred area per molecule for each species is varied so as to produce homogeneous mixtures or nonhomogeneous mixtures that form domains. If the latter mixtures are composed of amphiphiles with the same tail length, but different preferred areas per molecule, their material parameters increase monotonically as a function of composition. By contrast, mixtures of amphiphiles that differ in both tail length and preferred area per molecule form both homogeneous and nonhomogeneous mixtures that both exhibit smaller values of their material properties compared to the corresponding pure systems. When the same nonhomogeneous mixtures of amphiphiles are assembled into planar membrane patches and vesicles, the resulting domain shapes are different when the bending rigidities of the domains are sufficiently different. Additionally, both bilayer and monolayer domains are observed in vesicles. We conclude that the evolution of the domain shapes is influenced by the high curvature of the vesicles in the simulation, a result that may be relevant for biological vesicle membranes.
Vibrational anharmonicity effects in electronic tunneling through molecular bridges
Authors: Brisker Daria , Peskin Uri
Published: September 2006

Effects of anharmonic bridge vibrations on electronic tunneling in donor-bridge-acceptor complexes are studied using a model of anharmonic bridge vibration coupled nonlinearly to an electronic degree of freedom. An anharmonicity parameter is introduced, enabling to reproduce the standard harmonic model with linear coupling as a limiting case. The frequency of electronic tunneling oscillations between the donor and acceptor sites is shown to be sensitive to the nuclear anharmonicity, where stretching and compression modes have an opposite effect on the electronic frequency. This phenomenon, that cannot be accounted for within the harmonic approximation, is analyzed and explained.
Two-color reduced-Doppler ion imaging
Authors: Huang Cunshun , Li Wen , Hwa Kim Myung , Suits Arthur G.
Published: September 2006

We demonstrate a two-color reduced-Doppler probe for ion imaging that, in many applications, offers advantages over conventional 2+1 resonance-enhanced multiphoton ionization detection. Using counterpropagating beams of two different colors, one of which is broadband 266nm, we achieve convenient and sensitive D atom detection without the need for Doppler scanning. We demonstrate the approach using 224nm photodissociation of DBr. This method improves the sensitivity and signal-to-noise ratio and presents advantages and opportunities for use in the other systems.
A variational approach to the stochastic aspects of cellular signal transduction
Authors: Lan Yueheng , Wolynes Peter G. , Papoian Garegin A.
Published: September 2006

Cellular signaling networks have evolved to cope with intrinsic fluctuations, coming from the small numbers of constituents, and the environmental noise. Stochastic chemical kinetics equations govern the way biochemical networks process noisy signals. The essential difficulty associated with the master equation approach to solving the stochastic chemical kinetics problem is the enormous number of ordinary differential equations involved. In this work, we show how to achieve tremendous reduction in the dimensionality of specific reaction cascade dynamics by solving variationally an equivalent quantum field theoretic formulation of stochastic chemical kinetics. The present formulation avoids cumbersome commutator computations in the derivation of evolution equations, making the physical significance of the variational method more transparent. We propose novel time-dependent basis functions which work well over a wide range of rate parameters. We apply the new basis functions to describe stochastic signaling in several enzymatic cascades and compare the results so obtained with those from alternative solution techniques. The variational Ansatz gives probability distributions that agree well with the exact ones, even when fluctuations are large and discreteness and nonlinearity are important. A numerical implementation of our technique is many orders of magnitude more efficient computationally compared with the traditional Monte Carlo simulation algorithms or the Langevin simulations.
Stress development of germanium nanocrystals in silicon oxide matrix
Authors: Choi W. K. , Chew H. G. , Zheng F. , Chim W. K. , Foo Y. L. , Fitzgerald E. A.
Published: September 2006

The authors demonstrate from their Raman and transmission electron microscopy results that the annealing ambient, temperature, and duration play a significant role in the formation, the evolution, and the crystallinity of Ge nanocrystals in silicon oxide matrix. With careful etching experiments, the authors established that the compressive stress experienced by the nanocrystals in the oxide matrix is intimately linked to the density, the size, and the quality of the Ge nanocrystals.
Formation of supramolecular permethrin/β-cyclodextrin nanorods
Authors: Yang Guang-Fu , Wang Hong-Bo , Yang Wen-Chao , Gao Daquan , Zhan Chang-Guo
Published: September 2006

Molecular dynamics simulations along with scanning tunneling microscopy (STM) imaging demonstrate the formation of a novel type of nanorods, with a stable [permethrin(β-CD)2]n structure in which the host:guest ratio is 2:1 and n=21–27 giving a length of ∼30.0–38.5nm and an average diameter of ∼1.5nm, self-assembled from an inclusion complex composed of permethrin and biocompatible β-cyclodextrin.
Room temperature epitaxial growth of AlGaN on ZnO by pulsed laser deposition
Authors: Kobayashi Atsushi , Ohta Jitsuo , Kawaguchi Yuji , Fujioka Hiroshi
Published: September 2006

The authors have grown Al0.1Ga0.9N films on atomically flat ZnO substrates at room temperature (RT) by pulsed laser deposition. Epitaxial growth of AlGaN at RT proceeds in the layer-by-layer mode, and the films show atomically flat stepped and terraced surfaces. On the other hand, growth at 600°C proceeds three dimensionally, and the films suffer from degradation in their crystalline quality and from rough surface morphology. These results indicate that suppression of the formation of interfacial layers between AlGaN and ZnO by reducing the growth temperature is inherently important in order to take advantage of the nearly lattice-matched ZnO substrates. They have also found that high-quality AlGaN films can be obtained under highly N-rich conditions at reduced growth temperatures, which provides a striking contrast to the case of molecular beam epitaxy.
Effect of surface free energy in gate dielectric in pentacene thin-film transistors
Authors: Chou Wei-Yang , Kuo Chia-Wei , Cheng Horng-Long , Chen Yi-Ren , Tang Fu-Ching , Yang Feng-Yu , Shu Dun-Yin , Liao Chi-Chang
Published: September 2006

The surface free energy of a dielectric has a strong influence on the performance of pentacene thin-film transistors. Research shows that by matching surface free energy in the interface of the dielectric and the orthorhombic thin-film phase of pentacene film, the field-effect mobility of transistors is enhanced reaching above 2.0cm2∕Vs. The authors suggested that a more complete first monolayer of pentacene was formed upon the gate dielectric surface with almost identical surface free energy, benefiting carrier transportation. The research also discusses the mechanism of surface free energy effects on the crystalline size and structural disorder in pentacene film.
Anomalous behavior in the third harmonic generation z response through dispersion induced shape changes and matching χ(3)
Authors: Pillai Rajesh S. , Brakenhoff G. J. , Müller M.
Published: September 2006

The third harmonic generation (THG) axial response in the vicinity of an interface formed by two isotropic materials of normal dispersion is typically single peaked, with the maximum intensity at the interface position. Here it is shown experimentally that this THG z response may show anomalous behavior—being double peaked with a dip coinciding with the interface position—when the THG contributions from both materials are of similar magnitude. The observed anomalous behavior is explained, using paraxial Gaussian theory, by considering dispersion induced shape changes in the THG z response.
Simple good approximations for the special elliptic functions in standard Fowler-Nordheim tunneling theory for a Schottky-Nordheim barrier
Authors: Forbes Richard G.
Published: September 2006

The discovery is reported of simple, good approximate formulas for special elliptic functions that appear in the standard theory of Fowler-Nordheim (FN) [Proc. R. Soc. London, Ser. A 119, 173 (1914)] tunneling through an image-rounded Schottky-Nordheim [W. Schottky, Z. Phys. 15, 872 (1923); L. W. Nordheim, Proc. R. Soc. London, Ser. A 121, 626 (1928)] barrier and in the standard FN equation. The FN-exponent correction factor v can be written as v(y)≈1−y2+(1∕3)y2lny, where y is the Nordheim parameter. This formula has a respectable mathematical basis, predicts exact values of v(y) to within 0.33% in 0⩽y⩽1, and can be rewritten to give (after nearly 80years) a simple, reliable algebraic formula for the explicit dependence of v on barrier field. Significant consequences are expected.
Influence of phonon, geometry, impurity, and grain size on Copper line resistivity
Authors: Plombon J. J. , Andideh Ebrahim , Dubin Valery M. , Maiz Jose
Published: September 2006

The authors report on the resistivity of submicron copper lines ranging from 75to500nm linewidths as a function of temperature in the 10Kto380K interval. Their estimate of the contributions to electron scattering at 20K for the narrowest line (75nm linewidth) is 29% from copper surfaces, 25% from grain boundaries, and 30% from impurities, with the bulk resistivity making up the remaining 16%. It should be noted that at 300K, the contribution of electron-phonon scattering is about 60% illustrating the benefit of studying different scattering mechanisms at cryogenic temperatures.
Adaptive stochastic output feedback control of resistive wall modes in tokamaks
Authors: Sun Z. , Sen A. K. , Longman R. W.
Published: September 2006

An adaptive optimal stochastic output feedback control is developed to stabilize the resistive wall mode (RWM) instability in tokamaks. The system dynamics is experimentally determined via the extended least square method with an exponential forgetting factor and covariance resetting. The optimal output feedback controller is redesigned online periodically based on the system identification. The output measurements and past control inputs are used to construct new control inputs. The adaptive output controller can stabilize the time dependent RWM in a slowly evolving tokamak discharge. This is accomplished within a time delay of roughly three times the inverse of the growth rate. The design procedure is simpler and the computation time is shorter than the state feedback method reported earlier in Sun, Sen, and Longman [Phys. Plasmas13, 012512 (2006)].
Integration of fiber-coupled high-Q SiNx microdisks with atom chips
Authors: Barclay Paul E. , Srinivasan Kartik , Painter Oskar , Lev Benjamin , Mabuchi Hideo
Published: September 2006

Micron scale silicon nitride (SiNx) microdisk optical resonators are demonstrated with Q=3.6×106 and an effective mode volume of 15(λ∕n)3 at near-visible wavelengths. A hydrofluoric acid wet etch provides sensitive tuning of the microdisk resonances, and robust mounting of a fiber taper provides efficient fiber optic coupling to the microdisks while allowing unfettered optical access for laser cooling and trapping of atoms. Measurements indicate that cesium adsorption on the SiNx surfaces significantly red detunes the microdisk resonances. Parallel integration of multiple (10) microdisks with a single fiber taper is also demonstrated.
Conductivity scaling with bundle length and diameter in single walled carbon nanotube networks
Authors: Hecht David , Hu Liangbing , Grüner George
Published: September 2006

Transparent single walled carbon nanotube (SWNT) networks were printed on plastic substrates. Nanotubes in the network form small bundles, and the authors evaluated the dc conductivity (σdc) as a function of the average bundle length (Lav) in the network. They find σdc to vary as σdc∼Lav1.46 for bundles of the same diameter and give a qualitative argument for why this agrees with a model where the resistance between SWNT bundles dominates the overall network resistance.
Impact of film properties of atomic layer deposited HfO2 resulting from annealing with a TiN capping layer
Authors: Triyoso D. H. , Tobin P. J. , White B. E. , Gregory R. , Wang X. D.
Published: September 2006

Atomic layer deposited HfO2 films void and exhibit poor electrical characteristics when annealed at high temperature unless a TiN capping layer is used. The TiN is removed prior to characterization of the dielectric. The authors find that capped HfO2 films annealed at 1000°C by rapid thermal process are smooth and void-free. The microstructure of HfO2 is modified from fully monoclinic to a mixed monoclinic and tetragonal phase when the capping layer is used. Conducting atomic force microscopy performed on these films shows fewer areas with high leakage current. Mo∕HfO2 capacitors show improved CV characteristics and lower leakage current density.
Atomic rearrangements in HfO2∕Si1−xGex interfaces
Authors: Cho Deok-Yong , Oh S.-J. , Park Tae Joo , Hwang Cheol Seong
Published: September 2006

Atomic exchanges across the interface between a HfO2 thin film and strained semiconducting Si1−xGex (x=0.1, 0.2, and 0.3) was investigated by extended x-ray absorption fine structures. Atomic layer deposition of HfO2 films on epitaxial Si1−xGex produces a Hf-silicate (Hf–O–Si bond) phase at the interface. Also O atoms diffuse into the Si1−xGex alloy to form Ge oxide in a segregated phase. This tendency becomes evident when the Ge concentration of the substrate becomes higher or when HfO2 is deposited and these samples are compared to the pure Si1−xGex substrates which have been exposed to ambient atmosphere.
Cathodoluminescence of rare earth implanted AlInN
Authors: Wang K. , Martin R. W. , Nogales E. , Edwards P. R. , O’Donnell K. P. , Lorenz K. , Alves E. , Watson I. M.
Published: September 2006

AlInN layers implanted with europium and erbium ions are systematically studied and compared with similarly implanted GaN. Cathodoluminescence from four series of annealed samples shows that the Eu∕Er emissions from AlInN are considerably broader than those from GaN, while the peak positions only change slightly. The rate of increase of cathodoluminescence intensity with annealing temperature, up to 1300°C, is analyzed for all four series. For Eu the increase exceeds 10× in both hosts. Although some decomposition is observed for annealing at 1200°C, well above the growth temperature, AlInN is shown to be a surprisingly robust host for rare earth ions.
Concentration dependence of carrier localization in InN epilayers
Authors: Shu G. W. , Wu P. F. , Lo M. H. , Shen J. L. , Lin T. Y. , Chang H. J. , Chen Y. F. , Shih C. F. , Chang C. A. , Chen N. C.
Published: September 2006

The authors studied the concentration dependence of carrier localization in InN epilayers using time-resolved photoluminescence (PL). Based on the emission-energy dependence of the PL decays and the PL quenching in thermalization, the localization energy of carriers in InN is found to increase with carrier concentration. The dependence of carrier concentration on the localization energy of carriers in InN can be explained by a model based on the transition between free electrons in the conduction band and localized holes in the deeper tail states. They suggest that carrier localization originates from the potential fluctuations of randomly located impurities.
Parametric modulation of an atomic magnetometer
Authors: Li Zhimin , Wakai Ronald T. , Walker Thad G.
Published: September 2006

The authors report on a rubidium atomic magnetometer designed for use in a shielded environment. Operating in the spin-exchange relaxation-free regime, the magnetometer utilizes parametric modulation of the z-magnetic field to suppress noise associated with airflow through the oven and to simultaneously detect x- and y-field components, using a single probe beam, with minimal loss of sensitivity and bandwidth. A white noise level of 60fT∕(Hz)1∕2 was achieved.
In
Sb
∕
Al
x
In
1
−
x
Sb
quantum-well light-emitting diodes with high internal quantum efficiencies
Authors: Mirza B. I. , Nash G. R. , Smith S. J. , Haigh M. K. , Buckle L. , Emeny M. T. , Ashley T.
Published: September 2006

The properties of InSb∕AlxIn1−xSb quantum-well light-emitting diodes have been investigated as a function of temperature from 300to15K. Over the whole range, the peak emission occurred at significantly higher energies than the band gap of InSb but below the band gap of the AlxIn1−xSb barriers, confirming that emission is from the quantum wells. Maximum internal quantum efficiencies of 65% and 85% were measured at 15K for diodes containing 40 and 20nm quantum wells, respectively.
Low-voltage-driven top-gate ZnO thin-film transistors with polymer/high-k oxide double-layer dielectric
Authors: Lee Kimoon , Kim Jae Hoon , Im Seongil , Kim Chang Su , Baik Hong Koo
Published: September 2006

The authors report on the fabrication of a low-voltage-driven top-gate ZnO thin-film transistor with a polymer/high-k oxide double-layer dielectric. Hybrid double-layer dielectric (k=∼9.8) was formed on patterned ZnO through sequential deposition processes: spin casting of 45-nm-thin poly-4-vinylphenol and e-beam evaporation of 50-nm-thick amorphous high-k oxide (CeO2–SiO2 mixture). Room-temperature-deposited ZnO channel exhibits much rougher surfaces compared to that of 100°C deposited ZnO, so that enhanced device performances were achieved from a ZnO thin-film transistor (TFT) prepared with 100°C deposited ZnO: ∼0.48cm2∕Vs for field-effect mobility and ∼5×103 for on/off current ratio. Adopting our top-gate ZnO-TFT, a load-resistance inverter was set up and demonstrated decent static and dynamic operations at 3V.
Enhanced microwave absorption in nickel/hexagonal-ferrite/polymer composites
Authors: Li Bao-Wen , Shen Yang , Yue Zhen-Xing , Nan Ce-Wen
Published: September 2006

Ni/hexagonal-ferrite (Co2Z or Zn2Y barium ferrites)/polymer composites were prepared for electromagnetic interference (EMI) shielding materials. In comparison with the hexagonal-ferrite/polymer or Ni/polymer composites, such three-phase composites exhibit excellent microwave absorption properties in the X-band frequency range, strongly depending on the combination of these three phases. For the Ni∕Co2Z/polymer composites with volume fraction ratio of Ni/ferrite equal to 0.70∕0.30, the EMI shielding effectiveness (SE) of the composites with a thickness of 2mm can be as high as ∼67dB. The high EMI SE of the composites and much larger contribution to total EMI SE from absorption than from reflection suggest that these composites would be very promising for applications as thinner and lighter EMI absorption materials.
Two-dimensional tungsten oxide nanowire networks
Authors: Zhao Y. M. , Li Y. H. , Ahmad I. , McCartney D. G. , Zhu Y. Q. , Hu W. B.
Published: September 2006

The authors report the synthesis and characterization of two-dimensional (2D) single crystalline nanonetworks consisting of tungsten oxide nanowires with diameters of ca. 20nm. The 2D networks are believed to result from the nanowire growth along the four crystallographic equivalent directions of ⟨110⟩ in the tetragonal WO2.9 structure. These 2D tungsten oxide networks may be potential precursors for creating 2D networks comprising WS2 nanotubes.
Interpenetrating multiwall carbon nanotube electrodes for organic solar cells
Authors: Miller Anthony J. , Hatton Ross A. , Silva S. Ravi P.
Published: September 2006

Low concentrations of multiwall carbon nanotubes (MWCNTs) (∼1wt%) uniformly distributed within the donor layer of a heterojunction organic solar cell are shown to be an effective means of greatly reducing cell series resistance without compromising cell shunt resistance, resulting in an increase in cell fill factor of 50–60%. By chemically functionalizing MWCNTs with polar surface moieties, it is also possible to manipulate device open circuit voltage. The results of this study demonstrate that MWCNTs have excellent potential as a versatile interpenetrating electrode material for organic solar cells.
Development of textured MgO templates on nonmetallic flexible ceraflex
Authors: Lu Rongtao , Vallejo Ronald N. , Fisher Daniel W. , Wu Judy Z.
Published: September 2006

Reducing ac loss has become a critical issue in the development of high-Tc superconductor coated conductors (HTSCCs). One scheme is to replace the metallic substrates employed currently for HTSCCs with nonmetallic ones. The flexible ceramic polycrystalline ceraflex is a promising candidate while its rough surface presents a tough challenge in the development of textured templates needed for HTSCCs. By developing a surface smoothening process, high-quality biaxially textured MgO templates have been achieved on ceraflex. This work has overcome the major difficulties in texturing ceraflex surface for HTSCCs, which may provide a viable scheme for low ac loss HTSCC applications.
Critical electric field for maximum tunability in nonlinear dielectrics
Authors: Akdogan E. K. , Safari A.
Published: September 2006

The authors develop a self-consistent thermodynamic theory to compute the critical electric field at which maximum tunability is attained in a nonlinear dielectric. They then demonstrate that the stored electrostatic free energy functional has to be expanded at least up to the sixth order in electric field so as to define the critical field, and show that it depends solely on the fourth and sixth order permittivities. They discuss the deficiency of the engineering tunability metric in describing nonlinear dielectric phenomena, introduce a critical field renormalized tunability parameter, and substantiate the proposed formalism by computing the critical electric field for prototypical 0.9Pb(Mg1∕3,Nb2∕3)–0.1PbTiO3 and Ba(Ti0.85,Sn0.15)O3 paraelectrics.
Microwave transmission through metallic hole arrays: Surface electric field measurements
Authors: Hou Bo , Hang Zhi Hong , Wen Weijia , Chan C. T. , Sheng Ping
Published: September 2006

The authors investigate the enhanced microwave transmission through a metal plate perforated by a square lattice of subwavelength holes, predicted to occur as a structure factor resonance phenomenon [F. J. Gracía de Abajo and J. J. Sáenz, Phys. Rev. Lett. 95, 233901 (2005)]. By probing the surface electric field on the metallic plate at the peak transmission frequency, they establish the similarities and differences between the structure factor resonance and surface plasmon.
Pasture and sheep responses to lime application in a grazing experiment in a high-rainfall area, south-eastern Australia. I. Pasture production
Authors: Li G. D. , Helyar K. R. , Welham S. J. , Conyers M. K. , Castleman L. J. C. , Fisher R. P. , Evans C. M. , Cullis B. R. , Cregan P. D.
Published: September 2006

‘Managing Acid Soils Through Efficient Rotations (MASTER)’ is a long-term pasture–crop rotation experiment commenced in 1992. One of the objectives was to demonstrate the extent of crop, pasture, and animal responses to lime on a typical acidic soil in the 500–800 mm rainfall zone in south-eastern Australia. Two types of pastures (perennial v. annual pastures) with or without lime application were established in 1992. This paper presents the results of the pasture dry matter (DM) responses to lime application over 6 years from 1992 to 1997. Results showed that both perennial and annual pastures responded positively to lime on a highly acidic soil on the south-west slopes of New South Wales. Averaged across pasture types and 5 growing seasons, the limed pastures produced 18% more pasture DM (520 kg/ha, P < 0.05) than the unlimed pastures. Significant responses to lime were detected on perennial pastures (610 kg DM/ha, P < 0.05), but not on annual pastures, although the limed annual pastures produced more DM (420 kg/ha, P = 0.20) than the unlimed annual pastures. There was a large seasonal variation in pasture growth rate with the significant lime responses in winter and spring on both perennial pastures (P < 0.05) and annual pastures (P < 0.10 in winter and P < 0.05 in spring), but no responses in autumn and summer on either perennial or annual pastures. The extra growth in winter is of importance as winter is the period when feed is normally inadequate and limits stocking rates. It is recommended that perennial-based pastures should be promoted for the purposes of productivity, in terms of increasing pasture production and improving feed quality, and for the environmental benefits in terms of alleviating the soil acidity problem and reducing the risk of dryland salinity in the high-rainfall zone in south-eastern Australia.
Pasture and sheep responses to lime application in a grazing experiment in a high-rainfall area, south-eastern Australia. II. Liveweight gain and wool production
Authors: Li G. D. , Helyar K. R. , Conyers M. K. , Castleman L. J. C. , Fisher R. P. , Poile G. J. , Lisle C. J. , Cullis B. R. , Cregan P. D.
Published: September 2006

‘Managing Acid Soils Through Efficient Rotations (MASTER)’ is a long-term pasture–crop rotation experiment commenced in 1992. One of the objectives was to demonstrate the extent of crop, pasture, and animal responses to lime application on a typical acidic soil in the 500–800 mm rainfall zone of south-eastern Australia. Two types of pastures (perennial v. annual pastures) with or without lime application were established in 1992. Fifteen- to eighteen-month-old Merino hoggets were used as test animals and were changed annually. This paper reports the results of sheep responses to liming from the 4 continuous pasture treatments over 6 years from 1992 to 1997. The stocking rate was the same on all plots within a treatment during each rotation period, but was varied between treatments based on the pasture availability and sheep body condition. The most important findings from this study are that the limed treatments carried 29% and 27% more stock (up to 4 DSE/ha) than the unlimed treatments for perennial and annual pastures, respectively. As a result, the limed perennial pastures produced 27% more liveweight gain (62 kg/ha.year) and 28% more greasy wool (13 kg/ha.year) than unlimed perennial pastures, whereas the limed annual pastures produced 34% more liveweight gain (77 kg/ha.year) and 24% more greasy wool (11 kg/ha.year) than unlimed annual pastures. The significant responses to lime in liveweight and wool production were detected from the second growing season after the pastures were established. The increased sheep productivity on the limed treatment was due to a combination of increased pasture production and improved pasture quality. Perennial pastures showed a slight advantage in wool production, but not in liveweight gain. However, the seasonal variation of liveweight was greater on annual pastures than on perennial pastures. The larger variation in liveweight change could lead to more adverse effects on wool quality especially at high grazing pressures. Grazing management can be used to manipulate pasture and animal productivity to increase profits from lime use.
Flour yield QTLs in three Australian doubled haploid wheat populations
Authors: Lehmensiek A. , Eckermann P. J. , Verbyla A. P. , Appels R. , Sutherland M. W. , Martin D. , Daggard G. E.
Published: September 2006

Flour yield quantitative trait loci (QTLs) were identified in 3 Australian doubled haploid populations, Sunco × Tasman, CD87 × Katepwa, and Cranbrook × Halberd. Trial data from 3 to 4 sites or years were available for each population. QTLs were identified on chromosomes 2BS, 4B, 5AL, and 6BL in the Sunco × Tasman population, on chromosomes 4B, 5AS, and 6DL in the CD87 × Katepwa population, and on chromosomes 4DS, 5DS, and 7AS in the Cranbrook × Halberd population. In the Sunco × Tasman cross the highest genetic variance was detected with the QTL on chromosome 2B (31.3%), in the CD87 × Katepwa cross with the QTL on chromosome 4B (23.8%), and in the Cranbrook × Halberd cross with the QTL on chromosome 5D (18%). Only one QTL occurred in a similar location in more than one population, indicating the complexity of the flour yield character across different backgrounds.
Variation in feed intake of grazing crossbred ewes and genetic correlations with production traits
Authors: Fogarty N. M. , Lee G. J. , Ingham V. M. , Gaunt G. M. , Cummins L. J.
Published: September 2006

Feed for maintenance of the ewe flock is a major cost in lamb production systems and a reduction in these feed requirements could have an effect on carrying capacity and both biological and economic efficiency in sheep flocks. Inclusion of feed intake in breeding programs requires knowledge of its genetic variation and genetic relationships with other production traits. This study reports on the variation in relative digestible dry matter intake (rDDMI) of 2528 mature, non-pregnant, crossbred ewes that are the progeny of 91 rams of various maternal breeds. Feed intake of pasture under grazing conditions was estimated using the faecal marker dilution technique with chromium sesquioxide controlled-release devices. There was significant variation in intake associated with liveweight, liveweight gain, prior reproductive status, fat depth, and muscle depth of the ewes. Sire breed was not significant for rDDMI, although there was a considerable range of >30% across sire progeny groups within most sire breeds, and rDDMI had an estimated heritability of 0.41 ±  0.07 (s.e.). The genetic correlations with a range of production traits (growth, carcass, wool, and reproduction) were all close to zero. The potential for inclusion of genetic improvement of efficiency of feed utilisation in breeding programs for sheep is discussed.
Root characteristics of vigorous wheat improve early nitrogen uptake
Authors: Liao Mingtan , Palta Jairo A. , Fillery Ian R. P.
Published: September 2006

Root growth is important for the acquisition of nitrogen (N) and water in deep sandy soil profiles with high leaching potential. Root growth characteristics and the N uptake of wheat genotypes differing in early vigour were investigated in 2 glasshouse experiments. In both experiments the vigorous breeding lines Vigor18 and B18 and the well-adapted commercial cultivar Janz were grown in glass-walled growth boxes in a controlled-temperature glasshouse up to the onset of stem elongation. In Expt 1, rooting parameters and detailed measurements of root growth and proliferation were made at 2-day intervals using a root mapping technique. In Expt 2 the glass-walled growth boxes were segmented into upper (0–0.2 m), middle (0.2–0.7 m), and bottom (0.7–1.0 m) soil layers, and the contribution of N fertiliser uptake by roots from each soil layer to the total plant N uptake was determined by applying 15N-urea to a single soil layer each time. The accumulated total root length across the soil profile from the 1-leaf stage to the onset of stem elongation was 33–83% higher in the vigorous lines Vigor18 and B18 than in Janz. The roots of the 3 genotypes grew vertically down the soil profile at a similar rate, but the roots of vigorous lines branched earlier and grew horizontally faster and more extensively than those of cv. Janz, resulting in a greater root-length density and root number in the top 0.7-m soil layer. Uptake of N fertiliser by roots in the upper 0–0.2 m of the soil profile was 60–68% higher in the vigorous lines than in Janz. Roots of the vigorous lines located in the segment 0.2–0.7 m of the soil profile captured twice as much N fertiliser than those of Janz. Uptake of N fertiliser by roots in the lower 0.7–1.0 m of the soil profile was similar in the vigorous lines and Janz. This indicates that the early and more extensive horizontal growth of the roots in the 0.2–0.7 m of the soil profile was responsible for the superior uptake of N by the vigorous lines. The implications of these genotypic differences in root growth and proliferation and their relationship with the early acquisition of N are discussed with emphasis on their role in improving the efficiency of N fertiliser uptake and reducing nitrate leaching, particularly in the sandy soils of the Mediterranean climatic region of Australia.
Towards optimal designs for hedgerow olive orchards
Authors: Connor David J.
Published: September 2006

An analysis of row height, row width, canopy slope, and alley width of hedgerow olive orchards was conducted to identify combinations that maximise productivity while allowing access to machinery for management. This objective requires maximising both the interception of incident solar radiation and its distribution over the canopy surface for productivity. For maximum productivity, all foliage must be illuminated above threshold values for the critical step in the shoot growth – floral initiation – flowering – fruit formation – fruit filling reproductive sequence. The key sites for adequate illumination are the bases of the canopy walls. For canopies with row height and alley width combinations that provide threshold illumination at the bases of the canopy walls, the area of productive foliage per unit orchard area is inversely related to row width because incident radiation received by broad canopy tops is better spread at smaller irradiance over more canopy wall. The analysis revealed that canopies of equal productivity can be formed with a range of combinations of height, slope, and alley width, and that optimal combinations are responsive to threshold values in the range 20–30% of incident radiation. Research is required to establish threshold values and the limits to row height and row width consistent with year-to-year production of reproductive shoots. The latter requires attention to cost and performance of machinery, the growth habit of the tree, and its response to pruning.
The high molecular weight glutenin subunit composition in old and modern bread wheats cultivated in Iran
Authors: Shahnejat-Bushehri Ali-Akbar , Gomarian Masoud , Yazdi-Samadi Bahman
Published: September 2006

All current and old wheat cultivars grown in Iran were characterised by sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE). The high-molecular-weight glutenin subunit (HMW-GS) banding patterns for each cultivar were assigned a Glu-1 quality score, a theoretical quality score based on Payne’s Glu-1 quality assignments. At the Glu-A1 loci, HMW-GS subunit compositions N, 7 + 8, 2 + 12 and 2*, 7 + 8, 2 + 12 were found to be predominant being expressed in 24 and 15 cultivars, respectively, out of 95. Eighteen different alleles were identified for the 3 loci studied: Glu-A1 (3), Glu-B1 (9), and Glu-D1 (6). The glutenin quality scores of Iranian wheat ranged from 4 to 10, with an average of 7.4. It was found that some cultivars were heterogeneous in HMW-GS composition. In cv. Cooleh, only one glutenin subunit at the Glu-B1 locus was present. HMW-GS 2*** + 12′ was found in 6 cultivars and biotypes. The results obtained here describing the allelic composition of bread wheat commonly grown in Iran may be useful in wheat breeding programs selecting for good quality parameters.
Effects of high temperature on the growth and composition of sugarcane internodes
Authors: Bonnett G. D. , Hewitt M. L. , Glassop D.
Published: September 2006

Sugarcane grown in the Ord River district of Western Australia has lower sucrose content than expected from earlier trials and experience in other irrigated districts. High temperatures have been hypothesised as a possible cause. The effects of high temperature (above 32°C) on growth and carbon partitioning were investigated. A temperature regime of (25–38°C) was compared with (23–33°C). In one experiment, 7-month-old plants of cvv. Q117 and Q158 were subjected to the treatments for 2 months. In another experiment, the plants were allowed to regrow (ratoon) for 6 months. In both experiments, the higher temperature resulted in more, shorter internodes and higher moisture content. Most internodes from plants in the higher temperature treatment had lower sucrose content than internodes from the lower temperature. On a dry mass basis the internodes from the plants in the higher temperature had proportionately more fibre and hexoses but lower sucrose. Combined with an increased number of nodes in a stem of similar or shorter length this would result in higher stalk fibre and lower sucrose content. The data provided evidence that sugarcane partitions less carbon to stored sucrose when grown under high compared with low temperatures. The two cultivars partitioned carbon between soluble (sugars) and insoluble (fibre) fractions to different degrees. These experiments also indicate that the current models describing leaf appearance and perhaps sugarcane growth at temperatures above 32°C, in general, need revision.
Genomic analysis of the hierarchical structure of regulatory networks
Authors: Yu Haiyuan , Gerstein Mark
Published: September 2006

A fundamental question in biology is how the cell uses transcription factors (TFs) to coordinate the expression of thousands of genes in response to various stimuli. The relationships between TFs and their target genes can be modeled in terms of directed regulatory networks. These relationships, in turn, can be readily compared with commonplace “chain-of-command” structures in social networks, which have characteristic hierarchical layouts. Here, we develop algorithms for identifying generalized hierarchies (allowing for various loop structures) and use these approaches to illuminate extensive pyramid-shaped hierarchical structures existing in the regulatory networks of representative prokaryotes (
Escherichia coli
) and eukaryotes (
Saccharomyces cerevisiae
), with most TFs at the bottom levels and only a few master TFs on top. These masters are situated near the center of the protein–protein interaction network, a different type of network from the regulatory one, and they receive most of the input for the whole regulatory hierarchy through protein interactions. Moreover, they have maximal influence over other genes, in terms of affecting expression-level changes. Surprisingly, however, TFs at the bottom of the regulatory hierarchy are more essential to the viability of the cell. Finally, one might think master TFs achieve their wide influence through directly regulating many targets, but TFs with most direct targets are in the middle of the hierarchy. We find, in fact, that these midlevel TFs are “control bottlenecks” in the hierarchy, and this great degree of control for “middle managers” has parallels in efficient social structures in various corporate and governmental settings.
Tail-interacting protein TIP47 is a connector between Gag and Env and is required for Env incorporation into HIV-1 virions
Authors: Lopez-Vergès Sandra , Camus Grégory , Blot Guillaume , Beauvoir Roxane , Benarous Richard , Berlioz-Torrent Clarisse
Published: September 2006

The presence of the envelope glycoprotein Env in HIV-1 virions is essential for infectivity. To date, the molecular mechanism by which Env is packaged into virions has been largely unknown. Here, we show that TIP47 (tail-interacting protein of 47 kDa), which has been shown to interact with Env, also binds the MA (matrix) domain of HIV-1 Gag protein and that these three proteins form a ternary complex. Mutations in Gag that abrogate interaction with TIP47 inhibit Env incorporation and virion infectivity as well as colocalization between Gag and Env. We also show that TIP47 silencing impairs Env incorporation and infectivity and abolishes coimmunoprecipitation of Gag with Env. In contrast, overexpression of TIP47 increases Env packaging. Last, we demonstrate that TIP47 can interact simultaneously with Env and Gag. Taken together, our results show that TIP47 is a cellular cofactor that plays an essential role in Env incorporation, allowing the encounter and the physical association between HIV-1 Gag and Env proteins during the viral assembly process.
Structural and mutational studies of the amino acid-editing domain from archaeal/eukaryal phenylalanyl-tRNA synthetase
Authors: Sasaki Hiroshi M. , Sekine Shun-ichi , Sengoku Toru , Fukunaga Ryuya , Hattori Motoyuki , Utsunomiya Yukiko , Kuroishi Chizu , Kuramitsu Seiki , Shirouzu Mikako , Yokoyama Shigeyuki
Published: September 2006

To achieve accurate aminoacylation of tRNAs with their cognate amino acids, errors in aminoacylation are corrected by the “editing” mechanism in several aminoacyl-tRNA synthetases. Phenylalanyl-tRNA synthetase (PheRS) hydrolyzes, or edits, misformed tyrosyl-tRNA with its editing domain in the β subunit. We report the crystal structure of an N-terminal fragment of the PheRS β subunit (PheRS-β
N
) from the archaeon,
Pyrococcus horikoshii
, at 1.94-Å resolution. PheRS-β
N
includes the editing domain B3/4, which has archaea/eukarya-specific insertions/deletions and adopts a different orientation relative to other domains, as compared with that of bacterial PheRS. Surprisingly, most residues constituting the editing active-site pocket were substituted between the archaeal/eukaryal and bacterial PheRSs. We prepared Ala-substituted mutants of
P. horikoshii
PheRS for 16 editing-pocket residues, of which 12 are archaea/eukarya-specific and four are more widely conserved. On the basis of their activities, Tyr-adenosine was modeled on the B3/4-domain structure. First, the mutations of Leu-202, Ser-211, Asp-234, and Thr-236 made the PheRS incorrectly hydrolyze the cognate Phe-tRNA
Phe
, indicating that these residues participate in the Tyr hydroxy group recognition and are responsible for discrimination against Phe. Second, the mutations of Leu-168 and Arg-223, which could interact with the tRNA 3′-terminal adenosine, reduced Tyr-tRNA
Phe
deacylation activity. Third, the mutations of archaea/eukarya-specific Gln-126, Glu-127, Arg-137, and Asn-217, which are proximal to the ester bond to be cleaved, also reduced Tyr-tRNA
Phe
deacylation activity. In particular, the replacement of Asn-217 abolished the activity, revealing its absolute requirement for the catalysis.
FLASH is an essential component of Cajal bodies
Authors: Barcaroli D. , Dinsdale D. , Neale M. H. , Bongiorno-Borbone L. , Ranalli M. , Munarriz E. , Sayan A. E. , McWilliam J. M. , Smith T. M. , Fava E. , Knight R. A. , Melino G. , De Laurenzi V.
Published: September 2006

Cajal bodies are small nuclear organelles with a number of nuclear functions. Here we show that FLICE-associated huge protein (FLASH), originally described as a component of the apoptosis signaling pathway, is mainly localized in Cajal bodies and is essential for their structure. Reduction in FLASH expression by short hairpin RNA results in disruption of the normal architecture of the Cajal body and relocalization of its components. Because the function of FLASH in the apoptosis receptor signaling pathway has been strongly questioned, we have now identified a clear function for this protein.