bluuebunny/crossref_metadata_2025 huggingface dataset:
Active micromixer based on artificial cilia
Authors: Khatavkar Vinayak V. , Anderson Patrick D. , den Toonder Jaap M. J. , Meijer Han E. H.
Published: August 2007

We propose a design for an active micromixer that is inspired by the motion of ciliated micro-organisms occurring in nature. The conceptual design consists of an array of individually addressable artificial cilia in the form of microactuators covering the channel wall. The microactuators can be set into motion by an external stimulus such as an electric or a magnetic field, inducing either a primary or secondary motion in the surrounding fluid. To validate the concept and to help to design the precise mixer configuration, we developed a computational fluid-structure model. This model is based on a fictitious domain method that couples the microactuator motion to the concomitant fluid flow, fully capturing the mutual fluid-structure interactions. The simulated flow patterns resulting from the motion of single and multiple actuated elements (in a microchannel filled with a Newtonian fluid) under the action of a time-periodic forcing function are analyzed using dynamical systems theory to quantify the mixing efficiency. The results show that with a proper actuation scheme, two microactuators placed on the same wall of a microchannel can indeed induce effective mixing by chaotic advection; their distance should be small, but collisions should be avoided, and they can be actuated in a rather broad regime around 90° out of phase. Placing actuators on opposite walls also induces exponential stretching in the fluid, but if their length is relatively small, of the order of 20% of the channel height, mixing effectiveness is higher when they are arranged on the same wall.
Double-peak switching current in soft ferroelectric lead zirconate titanate
Authors: Kamel Talal M. , de With Gijsbertus
Published: August 2007

Switching current measurements have been carried out on a soft lead zirconate titanate (PXE52, donor doped, modified proprietary composition with the overall formula PbZr0.415Ti0.585O3). The experiments showed a single switching current peak during the application of electric field to a nonpoled (virgin) sample. However, an unusual double peak for the switching current was observed upon reversing the electric field polarity. The pyrocurrent for a forward and reverse poled sample showed a related behavior. A single pyropeak is observed in the forward poled case and broadened peak was observed in case of a reverse poled sample. This behavior is attributed to non-180° domain switching during the reverse poled case as a result of residual stresses developed during the forward poling.
Classical Becchi-Rouet-Stora-Tyutin charge for nonlinear algebras
Authors: Buchbinder I. L. , Lavrov P. M.
Published: August 2007

We study the construction of the classical nilpotent canonical Becchi-Rouet-Stora-Tyutin (BRST) charge for the nonlinear gauge algebras, where a commutator (in terms of Poisson brackets) of the constraints is a finite order polynomial of the constraints. Such a polynomial is characterized by the coefficients forming a set of higher order structure constraints. Assuming the set of constraints to be linearly independent, we find the restrictions on the structure constraints when the nilpotent BRST charge can be written in a simple and universal form. In the case of quadratically nonlinear algebras, we find the expression for third order contribution in the ghost fields to the BRST charge without the use of any additional restrictions on the structure constants.
Self-consistent effective local potentials
Authors: Izmaylov Artur F. , Staroverov Viktor N. , Scuseria Gustavo E. , Davidson Ernest R.
Published: August 2007

An effective local potential (ELP) is a multiplicative operator whose deviation from a given nonlocal potential has the smallest variance evaluated with a prescribed single-determinant wave function. ELPs are useful in density functional theory as alternatives to optimized effective potentials (OEPs) because they do not require special treatment in finite basis set calculations as OEPs do. We generalize the idea of variance-minimizing potentials by introducing the concept of a self-consistent ELP (SCELP), a local potential whose deviation from its nonlocal counterpart has the smallest variance in terms of its own Kohn-Sham orbitals. A semi-analytical method for computing SCELPs is presented. The OEP, ELP, and SCELP techniques are applied to the exact-exchange-only Kohn-Sham problem and are found to produce similar results for many-electron atoms.
Electroluminescence from lattice defects of photonic crystal slabs in blue-light-emitting diodes
Authors: Kim Keunjoo , Choi Jaeho , Park Jong Bae , Jeon Sang Cheol , Kim Jin Soo , Lee Hee Mok
Published: August 2007

Lattice defect structures embedded into perfect photonic crystal slabs have been fabricated onto the GaN surfaces of InGaN/GaN multi-quantum-well light-emitting diodes. The photonic crystal slab with a triangular lattice constant of 230 nm showed suppressed light extraction for the electroluminescence at a peak of 464 nm, but the light radiated through lattice defects. The perfect photonic crystal slab shows the cooperative phenomenon of a light scattering similar to Wood’s anomaly in a metallic grating, and lattice defects result in the leaky modes of light extractions by breaking the symmetry of cooperative light scattering.
Direct water photoelectrolysis with patterned n-GaN
Authors: Waki Ichitaro , Cohen Daniel , Lal Rakesh , Mishra Umesh , DenBaars Steven P. , Nakamura Shuji
Published: August 2007

Direct photoelectrolysis of water was observed using a structured n-GaN photoanode, aqueous NaOH solution, and platinum cathode. The structured n-GaN was formed by selective area regrowth using metal stripes defined by photolithography. Gas evolution from both the n-GaN anode and the platinum cathode was observed under UV irradiation without external bias. The metal stripes eliminated current crowding and the n-GaN regrowth increased specific surface area. As a result, distinct improvements in photocurrent were achieved. The origin of the photocurrent and the conversion efficiency are discussed based on water-splitting reactions and etching reactions.
Radio-frequency magnetron sputtering and wet thermal oxidation of ZnO thin film
Authors: Liu H. F. , Chua S. J. , Hu G. X. , Gong H. , Xiang N.
Published: August 2007

The authors studied the growth and wet thermal oxidation (WTO) of ZnO thin films using a radio-frequency magnetron sputtering technique. X-ray diffraction reveals a preferred orientation of [101¯0]ZnO(0002)∕∕[112¯0]Al2O3(0002) coexisted with a small amount of ZnO (101¯1) and ZnO (101¯3) crystals on the Al2O3 (0001) substrate. The ZnO (101¯1) and ZnO (101¯3) crystals, as well as the in-plane preferred orientation, are absent from the growth of ZnO on the GaAs(001) substrate. WTO at 550 °C improves the crystalline and the photoluminescence more significantly than annealing in air, N2 and O2 ambient; it also tends to convert the crystal from ZnO (101¯1) and ZnO (101¯3) to ZnO (0002). The evolution of the photoluminescence upon WTO and annealing reveals that the green and orange emissions, centered at 520 and 650 nm, are likely originated from oxygen vacancies and oxygen interstitials, respectively; while the 420 nm emission, which is very sensitive to the postgrowth thermal processing regardless of the substrate and the ambient gas, is likely originated from the surface-state related defects.
Structural phase transition and ferromagnetism in monodisperse 3 nm FePt particles
Authors: Rong Chuan-bing , Poudyal Narayan , Chaubey Girija S , Nandwana Vikas , Skomski R. , Wu Y. Q. , Kramer M. J. , Liu J. Ping
Published: August 2007

FePt nanoparticles with a size of 3 nm and thermally stable room-temperature ferromagnetism are investigated. The monodisperse nanoparticles were prepared by chemical synthesis and a salt-matrix annealing technique. Structural and magnetic characterizations confirmed the phase transition from the disordered face-centered cubic structure to the L10 structure with the chemical ordering parameter of 0.62±0.05. Analysis in blocking temperature and fitting of temperature dependence of switching field reveals that the transformed 3 nm nanoparticles have a magnetic anisotropy constant of (2.8±0.2)×106 J∕m3, smaller than those for the bigger particles and the fully ordered L10 bulk phase.
Temperature dependence of exciton transfer in hybrid quantum well/nanocrystal heterostructures
Authors: Rohrmoser Stefan , Baldauf Julia , Harley Richard T. , Lagoudakis Pavlos G. , Sapra Sameer , Eychmüller Alexander , Watson Ian M.
Published: August 2007

The authors investigate the temperature dependence of exciton transfer from a single InGaN quantum well (QW) donor to colloidal CdS nanocrystal quantum dot acceptors and obtain an optimum transfer efficiency of 65% at 60K. Time and spectrally resolved measurements reveal that the transfer efficiency is dominated by the interplay between exciton localization and nonradiative recombination intrinsic to the QW.
Formation mechanisms of low-resistance and thermally stable Pd∕Ni∕Pd∕Ru Ohmic contacts to Mg-doped Al0.15Ga0.85N
Authors: Jang Ja-Soon , Seong Tae-Yeon , Jeon Seong-Ran
Published: August 2007

The authors report on the formation of low-resistance and thermally stable Pd∕Ni∕Pd∕Ru Ohmic contacts to Mg-doped AlGaN. The contacts become Ohmic with a contact resistivity of (1.4±0.3)×10−5Ωcm2 upon annealing at 600°C for 1min in a N2 ambient. The samples do not experience significant degradation of the specific contact resistance and the surface roughness even after annealing at 600°C for 60min. Based on x-ray photoelectron spectroscopy depth profile results, atomic force microscopy, and contact resistivity-temperature data, possible Ohmic formation and carrier transport mechanisms are described and discussed.
Vacancy-impurity complexes and diffusion of Ga and Sn in intrinsic and p-doped germanium
Authors: Riihimäki I. , Virtanen A. , Rinta-Anttila S. , Pusa P. , Räisänen J. , ISOLDE Collaboration The
Published: August 2007

The charge state of mobile vacancy-impurity complexes in germanium was studied via the effect of p-type (Ga) doping on Ga and Sn diffusions. Tin diffusion retards significantly as a function of doping concentration suggesting diffusion dominated by negatively charged vacancy-Sn complexes. Gallium diffusion is practically unaffected by doping, suggesting diffusion dominated by vacancy-Ga complexes having the same charge state as isolated, negatively charged Ga ions. The evident two orders of magnitude higher diffusivity of group V elements in germanium than of group III and IV elements can be well explicated by means of the present findings.
Effects of nitrogen in Stone-Wales defect on the electronic transport of carbon nanotube
Authors: Wei Jianwei , Hu Huifang , Zeng Hui , Wang Zhiyong , Wang Lei , Peng Ping
Published: August 2007

The effects of nitrogen substitutional doping in Stone-Wales (SW) defect on the transport properties of single-walled nanotubes are simulated by using density functional theory and nonequilibrium Green’s functions. It is found that the nitrogen in SW produces half-filled band near the Fermi level in which the electron effective mass varies with the changing of the position of nitrogen. The total transmission coefficients nearby the Fermi level increase and the others decrease after doping. The nitrogen doping and SW defect enhance the transport property of semiconducting (8, 0) and weaken that of quasimetallic (9, 0).
Chirality dependence of the energetic stability of 4Å carbon nanotubes
Authors: Chen J. , Liu H. J.
Published: August 2007

First-principles pseudopotential method is used to study the stability of three kinds of 4Å single-wall carbon nanotubes, which have been recently fabricated inside zeolite channels. The minimum energy path for unrolling the tube into a flat ribbon is calculated by the nudged elastic band technique. Our calculations suggest that all the three kinds of 4Å tubes are stable when the zeolite framework is dissolved by acid, and the relative stability depends strongly on their chiralities. It is expected that the majority of the grown sample is (3,3) tube in free space.
Random lasing emission from a red fluorescent dye doped polystyrene film containing dispersed polystyrene nanoparticles
Authors: Zhang Dingke , Wang Yanping , Ma Dongge
Published: August 2007

The authors report a random lasing emission from 4-(dicy-anomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran doped polystyrene thin films by introducing polystyrene nanoparticles. The aspects of concentration and diameter of polystyrene nanoparticles have been intensively investigated and found that the lasing occurs due to the scattering role of polystyrene nanoparticles. The devices emit a resonance multimode peak centered at a wavelength of 630nm with a mode linewidth of less than 0.35nm and exhibit threshold excitation intensity of as low as 0.06mJpulse−1cm−2. The microscopic laser cavities formed by multiple scattering have been captured. The demonstration of random laser opens up the possibility of using organic scattering as alternative sources of coherent light emission.
Development of a parallel detection and processing system using a multidetector array for wave field restoration in scanning transmission electron microscopy
Authors: Taya Masaki , Matsutani Takaomi , Ikuta Takashi , Saito Hidekazu , Ogai Keiko , Harada Yoshihito , Tanaka Takeo , Takai Yoshizo
Published: August 2007

A parallel image detection and image processing system for scanning transmission electron microscopy was developed using a multidetector array consisting of a multianode photomultiplier tube arranged in an 8×8 square array. The system enables the taking of 64 images simultaneously from different scattered directions with a scanning time of 2.6s. Using the 64 images, phase and amplitude contrast images of gold particles on an amorphous carbon thin film could be separately reconstructed by applying respective 8 shaped bandpass Fourier filters for each image and multiplying the phase and amplitude reconstructing factors.
Variation in lattice parameters of 6H-SiC irradiated to extremely low doses
Authors: Jiang W. , Nachimuthu P. , Weber W. J. , Ginzbursky L.
Published: August 2007

Irradiation of 6H-SiC single crystals was performed using 4MeV H+ ions at 340 and 210K. The changes in lattice parameters in the basal plane and along the c axes were measured as a function of dose using high-resolution x-ray diffraction. The c-axis lattice parameter increases monotonically with the increasing dose, while a-axis lattice parameter decreases at extremely low doses. An initial volumetric contraction of the unit cell is observed. The decrease in the a parameter may originate from the irradiation-induced vacancies and the possible formation of antisite defects that cause the lattice structure on the basal plane to shrink.
Boron deactivation in preamorphized silicon on insulator: Efficiency of the buried oxide as an interstitial sink
Authors: Hamilton J. J. , Kirkby K. J. , Cowern N. E. B. , Collart E. J. H. , Bersani M. , Giubertoni D. , Gennaro S. , Parisini A.
Published: August 2007

Preamorphization of ultrashallow implanted boron in silicon on insulator is optimized to produce an abrupt boxlike doping profile with negligible electrical deactivation and significantly reduced transient enhanced diffusion. The effect is achieved by positioning the as-implanted amorphous/crystalline interface close to the buried oxide interface to minimize interstitials while leaving a single-crystal seed to support solid-phase epitaxy. Results support the idea that the interface between the Si overlayer and the buried oxide is an efficient interstitial sink.
Vertical organic light emitting transistor
Authors: Xu Zheng , Li Sheng-Han , Ma Liping , Li Gang , Yang Yang
Published: August 2007

The authors demonstrate a vertical organic light emitting transistor achieved by stacking a capacitor on top of an organic light emitting diode (OLED). This unique device has dual functions, emitting light as an OLED and switching current as a transistor. When the capacitor is under bias, the storage charges on the thin electrode shared by two cells modulate the charge injection of the OLED active cell, hence controlling the current flow and subsequently tuning the light emission. Due to the vertical integration, this device can be operated at low voltage, which provides a solution for OLED display applications.
Unipolar accumulation-type transistor configuration implemented using Si nanowires
Authors: Shan Yinghui , Ashok S. , Fonash Stephen J.
Published: August 2007

A unipolar accumulation-type field effect transistor (FET) is proposed, fabricated, and characterized. The device, which uses a single doping type and Ohmic contacts, relies on the nanoscale to force the only possible source-drain path to pass through an accumulated (on state) or depleted (off state) region. The transistor is demonstrated using silicon nanowires (SiNWs) grown on glass with our nanochannel-template-guided “grow-in-place” approach. The resulting SiNW FETs exhibit an on-off ratio of 106 and a subthreshold slope of 130mV/decade. These transistors can allow unique design flexibility; for example, a NAND gate can be achieved in a uniformly doped nanowire with four contacts.
In situ electrical impedance spectroscopy under high pressure on diamond anvil cell
Authors: He Chunyuan , Gao Chunxiao , Ma Yanzhang , Li Ming , Hao Aimin , Huang Xiaowei , Liu Bingguo , Zhang Dongmei , Yu Cuiling , Zou Guangtian , Li Yanchun , Li Hui , Li Xiaodong , Liu Jing
Published: August 2007

The effect of grain boundary on electrical transportation properties is a basic physical problem and also a subject of material science and technology. In situ electrical measurement of powdered materials under high pressure provides a chance to figure out the electrical properties of grain boundaries. In this letter, the authors report an in situ impedance spectroscopy method used in conjunction with a diamond anvil cell for electrical property research of grain boundaries under high pressure. Powdered CdS was pressed up to 23GPa and an impedance arc corresponding to the grain boundary was detected. It was found that the electrical property of the grain boundary changed with pressure and could be determined by the resistance and the relaxation frequency. Pressure decreases the effective scattering section of the grain boundary to charge carriers, and finally leads to the decrease of resistance and activation energy of the grain boundary.
Fabrication, dynamics, and electrical properties of insulated scanning probe microscopy probes for electrical and electromechanical imaging in liquids
Authors: Rodriguez B. J. , Jesse S. , Seal K. , Baddorf A. P. , Kalinin S. V. , Rack P. D.
Published: August 2007

Insulated cantilever probes with a high aspect ratio conducting apex have been fabricated and their dynamic and electrical properties analyzed. The cantilevers were coated with silicon dioxide and a via was fabricated through the oxide at the tip apex and backfilled with tungsten to create an insulated probe with a conducting tip. The stiffness and Q factor of the cantilevers increased after the modifications and their resonances shifted to higher frequencies. The coupling strength between the cantilever and the coating are determined. Electromechanical imaging of ferroelectric domains, current voltage probing of a gold surface, and a probe apex repair process are demonstrated.
Comparison of the low-frequency predicitons of Biot’s and de Boer’s poroelasticity theories with Gassmann’s equation
Authors: Gurevich Boris
Published: August 2007

Predictions of Biot’s theory (BT) of poroelasticity [J. Acoust. Soc. Am. 28, 168 (1956)] and de Boer’s theory of porous media (TPM) [Theory of Porous Media (Springer, Berlin, 2000)] for the low-frequency bulk modulus of a fluid-saturated porous medium are compared with the Gassmann equation [Vierteljahrsschr. Naturforsch. Ges. Zur. 96, 1 (1951)]. It is shown that BT is consistent with the Gassmann equation, whereas TPM is not. It is further shown that the bulk modulus of a suspension of solid particles in a fluid as predicted by TPM is only correct if the particles are incompressible.
Structural and lasing characteristics of ultrathin hexagonal ZnO nanodisks grown vertically on silicon-on-insulator substrates
Authors: Yu Dingshan , Chen Yujie , Li Baojun , Chen Xudong , Zhang Mingqiu , Zhao Fuli , Ren Shan
Published: August 2007

Hexagonal ZnO nanodisks were grown on silicon-on-insulator substrates by vapor-transport method without catalysts. The resulting nanodisks possess ultrathin thickness (10–20nm) and most of them present vertical orientation on the substrate surface. Under optical excitation, these ultrathin nanodisks exhibit ultraviolet lasing emission with the excitation threshold of 205μJ∕cm2 and emission lifetime of 2ps at room temperature. The detailed lasing analysis indicates that whispering-gallery-mode lasing may occur in the ZnO nanodisks.
Misoriented domains in (0001)-GaN/(111)-Ge grown by molecular beam epitaxy
Authors: Zhang Y. , McAleese C. , Xiu H. , Humphreys C. J. , Lieten R. R. , Degroote B. , Borghs G.
Published: August 2007

Structural characterization has been performed on (0001)-GaN epilayers grown on (111)-Ge substrates using plasma assisted molecular beam epitaxy. By combining high-resolution x-ray diffraction, transmission electron microscopy, and scanning transmission electron microscopy, it has been shown that the GaN epilayer consists of misoriented domains. The domains are rotated about the GaN-[0001] (Ge-[111]) zone axis by 8° with respect to each other and by ±4° with respect to the Ge substrate. These domains need to be eliminated to reduce grain boundary defects and improve GaN crystal quality.
Crystalline SiGe films grown on Si substrates using laser-assisted plasma-enhanced chemical vapor deposition at low temperature
Authors: Lee Ching-Ting , Cheng Jun-Hung , Lee Hsin-Ying
Published: August 2007

Compared with conventional plasma-enhanced chemical vapor deposition, laser-assisted plasma-enhanced chemical vapor deposition (LAPECVD) can be used to deposit crystalline SiGe films on Si substrates at low temperature. In the LAPECVD system, a CO2 laser with a wavelength of 10.6μm was utilized to assist the pyrolytical decomposition of SiH4 and GeH4 reactant gases. The resultant Si0.78Ge0.22 films were obtained and verified through the use of the Auger electron spectroscopy measurement. As the diffraction pattern of a glancing incident angle X-ray diffraction measurement had indicated, several significant diffraction peaks corresponding to a diamond-cubic structure at (111), (220), and (311) were clearly observed. Crystalline SiGe films were also identified by the electron diffraction pattern of high-resolution transmission electron microscopy images.
The development of a PCR-based marker for PSY1 from Hordeum chilense, a candidate gene for carotenoid content accumulation in tritordeum seeds
Authors: Atienza S. G. , Avila C. M. , Martín A.
Published: August 2007

Hexaploid tritordeums are the amphiploids derived from the cross between the wild barley Hordeum chilense and durum wheat. Tritordeums are characterised by higher yellow pigment content in their seeds than their durum wheat progenitors due to certain H. chilense genes located on the α arm of chromosome 7Hch. In this work a candidate gene approach based on the phytoene synthase gene (PSY) was followed to investigate whether PSY1 may be responsible for the high carotenoid content in tritordeum and to develop a diagnostic marker for H. chilense PSY. This gene codes for the first step in the carotenoid biosynthetic pathway. It was first demonstrated that PSY is duplicated in H. chilense, Triticum urartu, and durum wheat (PSY1 and PSY2), and subsequently a diagnostic cleaved amplified polymorphism (CAP) marker able to differentiate between H. chilense and durum wheat PSY1 was developed. Using this CAP marker and a set of H. chilense-common wheat addition lines it was found that PSY1 is located on the α arm of chromosome 7Hch, where the gene(s) for yellow pigment content are located. PSY1 is located on chromosomes 7A and 7B of durum wheat as demonstrated using Langdon substitution lines. Furthermore, synteny between rice and wheat indicates that PSY1 should be located on the long arms of chromosomes 7A and 7B, in agreement with QTL data for yellow pigment content. Together, these results suggest that PSY1 may be a good candidate gene for further work with yellow pigment content in both durum wheat and tritordeum. In addition, the diagnostic CAP marker developed will be used in our breeding program to transfer H. chilense genes to durum wheat, to evaluate their potential for durum wheat improvement.
Tolerance of cotton expressing a 2,4-D detoxification gene to 2,4-D applied in the field
Authors: Charles Graham W. , Constable Greg A. , Llewellyn Danny J. , Hickman Mark A.
Published: August 2007

The tolerance to 2,4-dichlorophenoxy acetic acid (2,4-D) of a genetically modified (transgenic) cotton (Gossypium hirsutum) expressing a 2,4-D detoxification gene was compared with conventional (non-transgenic) cotton over 2 seasons. The 2,4-D was applied over-the-top of cotton in the field at 7–17 nodes of crop growth at rates of 0.004–1.12 kg a.i./ha. The transgenic cotton displayed better tolerance to 2,4-D than conventional cotton at all growth stages and herbicide rates. Some damage was apparent on both types of cotton at 2,4-D rates of 0.07 kg/ha and above, with damage most pronounced when the plants were exposed at 7 nodes. The transgenic cotton also had some tolerance to MCPA. Commercial use of transgenic, 2,4-D-tolerant cotton has the potential to greatly reduce problems of 2,4-D damage in cotton from accidental spray drift and herbicide residues in spraying equipment, where plants are predominantly exposed to low rates of 2,4-D.
Yield-limiting potential of Beet western yellows virus in Brassica napus
Authors: Jones R. A. C. , Coutts B. A. , Hawkes J.
Published: August 2007

Losses in seed yield and quality caused by infection with Beet western yellows virus (BWYV) alone or in combination with direct feeding damage by Myzus persicae (green peach aphid) were quantified in field experiments with Brassica napus (canola, oilseed rape) in the ‘grainbelt’ region of south-western Australia. Plants infected with BWYV and infested with M. persicae were introduced into plots early to provide infection sources and spread BWYV to B. napus plants. Insecticides were applied as seed dressings and/or foliar applications to generate a wide range of BWYV incidences in plots. Colonisation by vector aphids and spread of BWYV infection were recorded in the plots of the different treatments. At sites A (Medina) and B (Badgingarra) in 2001, foliar insecticide applications were applied differentially at first, but, later, ‘blanket’ insecticide sprays were applied to all plots to exclude any direct feeding damage by aphids. When BWYV infection at sites A and B reached 96% and 100% of plants, it decreased seed yield by up to 46% and 37%, respectively. Also, variation in BWYV incidence explained 95% (site A) and 96% (site B) of the variation in yield gaps, where for each 1% increase in virus incidence there was a yield decrease of 12 (site A) and 6 (site B) kg/ha. At both sites, this yield decline was entirely because fewer seeds formed on infected plants. At site B, BWYV infection significantly diminished oil content of seeds (up to 3%), but significantly increased individual seed weight (up to 11%) and erucic acid content (up to 44%); significant increases in seed protein content (up to 6–11%) were recorded at both sites. In field experiments at sites B and C (Avondale) in 2002, insecticides were applied as seed dressings or foliar sprays. At site B, when BWYV incidence reached 98%, the overall yield loss caused by BWYV and direct M. persicae feeding damage combined was 50%. At site C, when BWYV incidence reached 97%, the overall combined yield decline caused by BWYV and direct feeding damage was 46%. This research under Australian conditions shows that, when aphids spread it to B. napus plantings such that many plants become infected at an early growth stage, BWYV has substantial yield-limiting potential in B. napus crops. Although the results represent a worst case scenario, the losses were greater than those reported previously in Europe and are cause for concern for the Australian B. napus industry. When applied at 525 g a.i./100 kg of seed, imidacloprid seed dressing controlled insecticide-resistant M. persicae and effectively suppressed spread of BWYV for 2.5 months and increased seed yield by 84% at site B and 88% at site C. Therefore, provided that mixing the insecticide with seed is sufficiently thorough, dressing seed with imidacloprid before sowing provides good prospects for control of BWYV and M. persicae in B. napus crops.
Wheat genotypes differ in potassium efficiency under glasshouse and field conditions
Authors: Damon P. M. , Rengel Z.
Published: August 2007

A novel approach to the sustainable management of potassium (K) resources in agro-ecosystems is through better exploitation of genetic differences in the K efficiency of crop plants. Potassium efficiency is a measure of genotypic tolerance to soils with low potassium availability and can be quantified as the K efficiency ratio (the ratio of growth at deficient and adequate K supply). This study investigated the magnitude of variation in K efficiency among wheat (Triticum aestivum L.) genotypes grown in a glasshouse and in the field.
Genotypes differed significantly in response to low soil K availability in terms of shoot biomass during the vegetative growth phase and grain yield at maturity under glasshouse (144 genotypes) and field (89 genotypes) conditions. K-efficient and K-inefficient genotypes were identified. The main factor determining K efficiency for grain yield was the capacity of genotypes to maintain a high harvest index (grain yield/total shoot weight) at deficient K supply. Genotypes that had reduced harvest index under deficient K supply were K-inefficient. Capacity to tolerate low concentrations of K in shoot tissue where K supply was deficient was also important in determining K efficiency for grain yield. Potassium-efficient genotypes have the potential to enhance the productivity and sustainability of cereal cropping systems.
Proteome-wide identification of family member-specific natural substrate repertoire of caspases
Authors: Ju Wujian , Valencia C. Alexander , Pang Hao , Ke Yan , Gao Weiyi , Dong Biao , Liu Rihe
Published: August 2007

Caspases are proteolytic enzymes that are essential for apoptosis. Understanding the many discrete and interacting signaling pathways mediated by caspases requires the identification of the natural substrate repertoire for each caspase of interest. Using an amplification-based protein selection technique called mRNA display, we developed a high-throughput screen platform for caspase family member specific substrates on a proteome-wide scale. A large number of both known and previously uncharacterized caspase-3 substrates were identified from the human proteome. The proteolytic features of these selected substrates, including their cleavage sites and specificities, were characterized. Substrates that were cleaved only by caspase-8 or granzyme B but not by caspase-3, were readily selected. The method can be widely applied for efficient and systematic identification of the family member specific natural substrate repertoire of any caspase in an organism of interest, in addition to that of numerous other proteases with high specificity.
A metabolic pathway leading to mannosylfructose biosynthesis in
Agrobacterium tumefaciens
uncovers a family of mannosyltransferases
Authors: Torres Leticia L. , Salerno Graciela L.
Published: August 2007

A metabolic pathway for biosynthesis of the nonreducing disaccharide mannosylfructose (β-fructofuranosyl-α-mannopyranoside), an important osmolyte in
Agrobacterium tumefaciens
, was discovered. We have identified and functionally characterized two ORFs that correspond to genes (named
mfpsA
and
mfppA
) encoding the rare enzymes mannosylfructose-phosphate synthase and mannosylfructose-phosphate phosphatase, an associated phosphohydrolase. The
mfpsA
and
mfppA
genes are arranged in an operon structure, whose transcription is up-regulated by NaCl, resulting in the accumulation of mannosylfructose in the cells. Not only is the biosynthesis of mannosylfructose mechanistically similar to that of sucrose, but the corresponding genes for the biosynthesis of both disaccharides are also phylogenetic close relatives. Importantly, a protein phylogeny analysis indicated that mannosylfructose-phosphate synthase defines a unique group of mannosyltransferases.
Parents' and speech and language therapists' explanatory models of language development, language delay and intervention
Authors: Marshall Julie , Goldbart Juliet , Phillips Julie
Published: August 2007

Background: Parental and speech and language therapist (SLT) explanatory models may affect engagement with speech and language therapy, but there has been dearth of research in this area. This study investigated parents' and SLTs' views about language development, delay and intervention in pre‐school children with language delay.

Aims: The aims were to describe, explore and explain the thoughts, understandings, perceptions, beliefs, knowledge and feelings held by: a group of parents from East Manchester, UK, whose pre‐school children had been referred with suspected language delay; and SLTs working in the same area, in relation to language development, language delay and language intervention.

Methods & Procedures: A total of 24 unstructured interviews were carried out: 15 with parents whose children had been referred for speech and language therapy and nine with SLTs who worked with pre‐school children. The interviews were transcribed verbatim and coded using Atlas/ti. The data were analysed, subjected to respondent validation, and grounded theories and principled descriptions developed to explain and describe parents' and SLTs' beliefs and views.

Outcomes & Results: Parent and SLT data are presented separately. There are commonalities and differences between the parents and the SLTs. Both groups believe that language development and delay are influenced by both external and internal factors. Parents give more weight to the role of gender, imitation and personality and value television and videos, whereas the SLTs value the ‘right environment’ and listening skills and consider that health/disability and socio‐economic factors are important. Parents see themselves as experts on their child and have varied ideas about the role of SLTs, which do not always accord with SLTs' views. The parents and SLTs differ in their views of the roles of imitation and play in intervention. Parents typically try strategies before seeing an SLT.

Conclusions: These data suggest that parents' ideas vary and that, although parents and SLTs may share some views, there are some important differences. These views have implications for the provision of appropriate services. Although this is a small sample from one group in the UK, the results indicate the need to investigate the views of other groups of parents.
Language and communication difficulties in juvenile offenders
Authors: Bryan Karen , Freer Jackie , Furlong Cheryl
Published: August 2007

Background: Studies of the prison population suggest that the numbers of prisoners with language and communication disorders is higher than that of the overall population. However, the prison population is heterogeneous and it is important to focus on specific areas of the population. This study focuses on juvenile offenders.

Aims: The study aimed to screen language and communication skills in half the population of an establishment for juvenile offenders aged 15–17 years.

Methods & Procedures: A total of 58 participants were selected at random and screened on the oral subtests of the Test of Adolescent and Adult Language, 3rd Edn (TOAL‐3), the British Picture Vocabulary Scale (BPVS‐II) and the Test for Reception of Grammar: Version 2 (TROG‐2). Literacy and numeracy information was also obtained.

Outcomes & Results: The mean age of the group was 17 years; 19 were looked‐after children; and 90% had ceased to attend school before age 16. On the TOAL‐3 subtests, 66–90% of juvenile offenders in the sample had below average language skills, with 46–67% of these being in the poor or very poor group. None of the participants reached their age equivalence on the BPVS, but most of them reached the 12‐year and above threshold on the TROG. A total of 62% of the sample had not achieved Level 1 in literacy. The findings suggest that these young people may not have the necessary skills to cope with verbally mediated interventions aimed at reducing re‐offending.

Conclusions: The results suggest that speech and language therapy assessment should be available to juvenile offenders with speech and language therapy intervention available to those found to have language and communication difficulties. There are also implications for speech and language therapy provision to young people who are not engaged within the education system. The TOAL‐3 appears to be a useful screening instrument for this population, but a number of issues around the suitability of assessments for this population are discussed.
Assertive and responsive conversational skills of Italian‐speaking late talkers
Authors: Bonifacio Serena , Girolametto Luigi , Bulligan Manuela , Callegari Monica , Vignola Sandra , Zocconi Elisabetta
Published: August 2007

Background: Previous research on the pragmatic abilities of late talkers at 24 months of age indicates that they have difficulties initiating conversational interactions, but possess intact responsiveness skills. This study uses a parent‐administered questionnaire for evaluating the conversational skills of late talkers and suggesting pragmatic intervention goals.

Aim: To examine the conversational assertiveness and responsiveness of late talkers at 2 years of age.

Methods & Procedures: A parent report measure, The Social Conversational Skills Rating Scale–Italian version, was administered to 30 parents of late talkers, 30 parents of typically developing children matched for age, and 30 parents of younger, typically developing children matched for vocabulary size.

Outcomes & Results: The late talkers received significantly lower ratings for both assertiveness and responsiveness in comparison with their age‐matched peers. They did not differ significantly from the younger, vocabulary‐matched group. Assertiveness and responsiveness mean ratings were positively correlated with vocabulary size for the age‐matched group, but not for either of the other two groups.

Conclusions: This study confirms a delay in the development of late talkers' social–conversational skills. An investigation of individual profiles suggests that some late talkers may require goals for vocabulary development as well as independent goals for developing pragmatic skills.
Beyond scale separation in gyrokinetic turbulence
Authors: Garbet X. , Sarazin Y. , Grandgirard V. , Dif-Pradalier G. , Darmet G. , Ghendrih Ph. , Angelino P. , Bertrand P. , Besse N. , Gravier E. , Morel P. , Sonnendrücker E. , Crouseilles N. , Dischler J.-M. , Latu G. , Violard E. , Brunetti M. , Brunner S. , Lapillonne X. , Tran T.-M. , Villard L. , Boulet M.
Published: August 2007

This paper presents the results obtained with a set of gyrokinetic codes based on a semi-Lagrangian scheme. Several physics issues are addressed, namely, the comparison between fluid and kinetic descriptions, the intermittent behaviour of flux driven turbulence and the role of large scale flows in toroidal ITG turbulence. The question of the initialization of full-F simulations is also discussed.
Hyperosmotic Stress Signaling to the Nucleus Disrupts the Ran Gradient and the Production of RanGTP
Authors: Kelley Joshua B. , Paschal Bryce M.
Published: August 2007

The RanGTP gradient depends on nucleocytoplasmic shuttling of Ran and its nucleotide exchange in the nucleus. Here we show that hyperosmotic stress signaling induced by sorbitol disrupts the Ran protein gradient and reduces the production of RanGTP. Ran gradient disruption is rapid and is followed by early (10–20 min) and late (30–60 min) phases of recovery. Results from SB203580 and siRNA experiments suggest the stress kinase p38 is important for Ran gradient recovery. NTF2 and Mog1, which are transport factors that regulate the nuclear localization of Ran, showed kinetics of delocalization and recovery similar to Ran. Microinjection of a nuclear localization signal reporter protein revealed that sorbitol stress decreases the rate of nuclear import. Sorbitol stress also slowed RCC1 mobility in the nucleus, which is predicted to reduce RCC1 dissociation from chromatin and RanGTP production. This was tested using a FRET biosensor that registers nuclear RanGTP levels, which were reduced in response to sorbitol stress. Although sorbitol alters nucleotide levels, we show that inverting the GTP/GDP ratio in cells is not sufficient to disrupt the Ran gradient. Thus, the Ran system is a target of hyperosmotic stress signaling, and cells use protein localization–based mechanisms as part of a rapid stress response.
Two LIM Domain Proteins and UNC-96 Link UNC-97/PINCH to Myosin Thick Filaments inCaenorhabditis elegansMuscle
Authors: Qadota Hiroshi , Mercer Kristina B. , Miller Rachel K. , Kaibuchi Kozo , Benian Guy M.
Published: August 2007

By yeast two-hybrid screening, we found three novel interactors (UNC-95, LIM-8, and LIM-9) for UNC-97/PINCH in Caenorhabditis elegans. All three proteins contain LIM domains that are required for binding. Among the three interactors, LIM-8 and LIM-9 also bind to UNC-96, a component of sarcomeric M-lines. UNC-96 and LIM-8 also bind to the C-terminal portion of a myosin heavy chain (MHC), MHC A, which resides in the middle of thick filaments in the proximity of M-lines. All interactions identified by yeast two-hybrid assays were confirmed by in vitro binding assays using purified proteins. All three novel UNC-97 interactors are expressed in body wall muscle and by antibodies localize to M-lines. Either a decreased or an increased dosage of UNC-96 results in disorganization of thick filaments. Our previous studies showed that UNC-98, a C2H2 Zn finger protein, acts as a linkage between UNC-97, an integrin-associated protein, and MHC A in myosin thick filaments. In this study, we demonstrate another mechanism by which this linkage occurs: from UNC-97 through LIM-8 or LIM-9/UNC-96 to myosin.
Phosphatidylinositol 4,5-Bisphosphate Mediates the Targeting of the Exocyst to the Plasma Membrane for Exocytosis in Mammalian Cells
Authors: Liu Jianglan , Zuo Xiaofeng , Yue Peng , Guo Wei
Published: August 2007

The exocyst is an evolutionarily conserved octameric protein complex that tethers post-Golgi secretory vesicles at the plasma membrane for exocytosis. To elucidate the mechanism of vesicle tethering, it is important to understand how the exocyst physically associates with the plasma membrane (PM). In this study, we report that the mammalian exocyst subunit Exo70 associates with the PM through its direct interaction with phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2). Furthermore, we have identified key conserved residues at the C-terminus of Exo70 that are crucial for the interaction of Exo70 with PI(4,5)P2. Disrupting Exo70-PI(4,5)P2interaction abolished the membrane association of Exo70. We have also found that wild-type Exo70 but not the PI(4,5)P2-binding–deficient Exo70 mutant is capable of recruiting other exocyst components to the PM. Using the ts045 vesicular stomatitis virus glycoprotein trafficking assay, we demonstrate that Exo70-PI(4,5)P2interaction is critical for the docking and fusion of post-Golgi secretory vesicles, but not for their transport to the PM.
Saccharomyces cerevisiae CWH43Is Involved in the Remodeling of the Lipid Moiety of GPI Anchors to Ceramides
Authors: Umemura Mariko , Fujita Morihisa , Yoko-o Takehiko , Fukamizu Akiyoshi , Jigami Yoshifumi
Published: August 2007

The glycosylphosphatidylinositol (GPI)-anchored proteins are subjected to lipid remodeling during their biosynthesis. In the yeast Saccharomyces cerevisiae, the mature GPI-anchored proteins contain mainly ceramide or diacylglycerol with a saturated long-fatty acid, whereas conventional phosphatidylinositol (PI) used for GPI biosynthesis contains an unsaturated fatty acid. Here, we report that S. cerevisiae Cwh43p, whose N-terminal region contains a sequence homologous to mammalian PGAP2, is involved in the remodeling of the lipid moiety of GPI anchors to ceramides. In cwh43 disruptant cells, the PI moiety of the GPI-anchored protein contains a saturated long fatty acid and lyso-PI but not inositolphosphorylceramides, which are the main lipid moieties of GPI-anchored proteins from wild-type cells. Moreover, the C-terminal region of Cwh43p (Cwh43-C), which is not present in PGAP2, is essential for the ability to remodel GPI lipids to ceramides. The N-terminal region of Cwh43p (Cwh43-N) is associated with Cwh43-C, and it enhanced the lipid remodeling to ceramides by Cwh43-C. Our results also indicate that mouse FRAG1 and C130090K23, which are homologous to Cwh43-N and -C, respectively, share these activities.
The ZebrafishfleerGene Encodes an Essential Regulator of Cilia Tubulin Polyglutamylation
Authors: Pathak Narendra , Obara Tomoko , Mangos Steve , Liu Yan , Drummond Iain A.
Published: August 2007

Cilia and basal bodies are essential organelles for a broad spectrum of functions, including the development of left-right asymmetry, kidney function, cerebrospinal fluid transport, generation of photoreceptor outer segments, and hedgehog signaling. Zebrafish fleer (flr) mutants exhibit kidney cysts, randomized left-right asymmetry, hydrocephalus, and rod outer segment defects, suggesting a pleiotropic defect in ciliogenesis. Positional cloning flr identified a tetratricopeptide repeat protein homologous to the Caenorhabditis elegans protein DYF1 that was highly expressed in ciliated cells. flr pronephric cilia were shortened and showed a reduced beat amplitude, and olfactory cilia were absent in mutants. flr cilia exhibited ultrastructural defects in microtubule B-tubules, similar to axonemes that lack tubulin posttranslational modifications (polyglutamylation or polyglycylation). flr cilia showed a dramatic reduction in cilia polyglutamylated tubulin, indicating that flr encodes a novel modulator of tubulin polyglutamylation. We also found that the C. elegans flr homologue, dyf-1, is also required for tubulin polyglutamylation in sensory neuron cilia. Knockdown of zebrafish Ttll6, a tubulin polyglutamylase, specifically eliminated tubulin polyglutamylation and cilia formation in olfactory placodes, similar to flr mutants. These results are the first in vivo evidence that tubulin polyglutamylation is required for vertebrate cilia motility and structure, and, when compromised, results in failed ciliogenesis.
Parental age difference and offspring count in humans
Authors: Fieder Martin , Huber Susanne
Published: August 2007

Preferences for certain age characteristics of partners are reported across cultures: men prefer mates who are younger and women prefer mates older than themselves. To examine whether these age preferences entail fitness effects for men and women, we investigated the association among age differences between partners and offspring count. On the basis of a sample of approximately 10 000 post-reproductive Swedish men and women who did not change their partner between the birth of their first and last child, we find maximum offspring count in men if their partner is approximately 6 years younger, and in women if their partner is approximately 4 years older. We further find that after separation, on average, both men and women shift to a partner younger than the first, albeit in women the new partner is still older than the female herself. We conclude that the age preference for the partner yields fitness benefits for both men and women and may thus be an evolutionarily acquired trait.