bluuebunny/crossref_metadata_2025 huggingface dataset:
Site location of Co in β-FeSi2
Authors: Dézsi I. , Fetzer Cs. , Kiss M. , Degroote S. , Vantomme A.
Published: October 2005

In order to reveal cationic site preference in β-FeSi2, Co-substituted samples synthesized by various techniques such as molecular beam epitaxy, ion implantation, and chemical vapor transport were investigated by Fe57 conversion electron Mössbauer (CEM) as well as Co57 Mössbauer emission (ME) spectroscopy. Literature on the structure of β-FeSi2 is somewhat contradictory, especially on the point of the population of the two iron sites in the orthorhombic structure. Co57 ME and Fe57 CEM spectra both showed two quadrupole split spectral components in the crystalline phase. Hyperfine parameters indicate that Co atoms substitute Fe in both Fe positions in the orthorhombic lattice. The aim of the present study was to get reliable results on the relative population of the two iron sites and determine the substitution of the iron sites by Co atoms in the β-FeSi2 lattice. The relative intensities of the two components in the absorption and emission Mössbauer spectra were found to be very similar for the samples prepared by different techniques, indicating a homogeneous distribution of Co on both Fe sites.
Optical properties and structure characterization of sapphire after Ni ion implantation and annealing
Authors: Xiang X. , Zu X. T. , Bao J. W. , Zhu S. , Wang L. M.
Published: October 2005

Implantation of 64keV Ni ions to sapphire was conducted at room temperature to 1×1017ions∕cm2 with a current density of 5 or 10μA∕cm2. Metallic Ni nanoparticles were formed with the 5μA∕cm2 ion current and the NiAl2O4 compound was formed with the 10μA∕cm2 ion current. The crystals implanted with both current densities were annealed isochronally for 1h at temperatures up to 1000°C in steps of 100°C in an ambient atmosphere. Optical absorption spectroscopy, x-ray diffraction, transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy have been utilized to characterize the samples. The surface plasmon resonance (SPR) absorption band peaked at 400nm due to the Ni nanoparticles shifted toward the longer wavelength gradually with the annealing temperature increasing from 400to700°C. The SPR absorption band disappeared after the annealing temperature reached 800°C. NiO nanoparticles were formed at the expense of Ni nanoparticles with an increasing annealing temperature. The TEM analyses revealed that the nanoparticles grew to 6–20nm and migrated toward the surface after annealing at 900°C. The absorption band at 430nm from Ni2+ cations in NiAl2O4 did not shift with the increasing annealing temperature.
Vacancy formation in GaAs under different equilibrium conditions
Authors: Bondarenko V. , Gebauer J. , Redmann F. , Krause-Rehberg R.
Published: October 2005

Defect properties of undoped semiinsulating and silicon doped n-type GaAs annealed at different arsenic vapor pressures have been studied by means of positron annihilation and Hall effect measurements. In both types of samples, formation of monovacancylike defects during annealing was observed. The concentration of these defects increases in GaAs:Si and decreases in undoped GaAs when the arsenic pressure increases. In GaAs:Si, the defect was earlier identified as SiGa–VGa complex, however, in undoped GaAs arsenic vacancies are formed, which are part of defect complex.
Thermocapillary instability of core-annular flows
Authors: Wei Hsien-Hung
Published: October 2005

Thermocapillary instability of a core-annular flow is asymptotically examined in the thin annulus limit. Two sets of scalings are established to study the interplays between base flows, interfacial tension, and thermocapillary effects. For each scaling case, an interfacial evolution equation is derived for describing the leading order stability of the system. Both linear and weakly nonlinear stabilities are examined. When the core fluid is warmer (cooler) than the wall, thermocapillarity linearly stabilizes (destabilizes) the system, and hence suppresses (promotes) the capillary instability. For a moderate thermocapillary force and a strong capillary force, the linear instability can be arrested within the weakly nonlinear regime. For a weak thermocapillary force and a moderately strong interfacial tension, the weakly nonlinear evolution is governed by a modified Kuramoto-Sivashinsky equation. The influence of thermocapillarity on the route to chaos is discussed.
A model of cusp magnetic-field compression by an expanding plasma fireball
Authors: Parks P. B.
Published: October 2005

The outward expansion of a hot plasma fireball initiated by a laser-driven pellet microexplosion in a spindle-cusp magnetic-field configuration is studied. The cusp magnetic field can protect the first wall of future inertial fusion energy containment vessels from the hot plasma ions and divert the expanded charged particles (waste energy) out of the system along open field lines. Closed-form solutions are derived for the compressed magnetic field in the case of a quasispherical expansion, and the maximum (stopping) radius of the field-free plasma cavity is calculated. For a 100-MJ-charged particle energy release per laser pulse, a rather low magnetic-field strength in the line cusp of 0.1 T can protect the first wall by stopping the fireball at a radius slightly less than the 6 m radius of the (spherical) target chamber wall.
Controlled growth of helium nanodroplets from a pulsed source
Authors: Yang Shengfu , Brereton Scott M. , Ellis Andrew M.
Published: October 2005

Factors affecting the size of liquid-helium droplets produced by a pulsed nozzle are described. The shape of the nozzle orifice is found to be important in allowing control of the size of the droplets. With an appropriate choice of nozzle geometry, the average droplet size is shown to be continuously variable over nearly two orders of magnitude by adjustment of the helium gas stagnation pressure and/or temperature. A scaling law similar to, but not identical with, that found for helium droplets produced by continuous supersonic expansion sources is found for the pulsed source. The pulsed nozzle described in this article has been used to make helium droplets ranging in size from a few thousand atoms up to nearly 105 helium atoms.
Characterization of a flow-through microcalorimeter for measuring the heat production of cardiac trabeculae
Authors: Taberner A. J. , Hunter I. W. , Kirton R. S. , Nielsen P. M. F. , Loiselle D. S.
Published: October 2005

The energy consumption of isolated cardiac trabeculae can be inferred from measurements of their heat production. Once excised from the heart, to remain viable, trabeculae require continuous superfusion with an oxygen- and nutrient-rich solution. Flow-through calorimeters enable trabeculae to be maintained in a stable and controlled environment for many hours at a time. In this paper we describe and characterize a flow-through microcalorimeter, with sensitivity in the 1μW range, for measuring the heat output of 10μg cardiac trabeculae. The device uses infrared-sensitive, thin-film thermopile sensors to provide a noncontact method for measuring temperature differences. The sensors are capable of resolving 5μK temperature differences within the superfusing fluid. The microcalorimeter has a sensitivity of 2.56V∕W at a flow rate of 1μl∕s, with a time constant of approximately 3.5 s. The sensitivity and time constant are strongly dependent upon the flow rate. Predictions of a finite-element model of the calorimeter’s characteristics compare favorably with measured data over a wide range of flow rates.
Control of penetration and mixing of an excited supersonic jet into a supersonic cross stream
Authors: Murugappan S. , Gutmark E. , Carter C.
Published: October 2005

Rayleigh/Mie scattering (from flow-field ice crystals) was used to study mixing and penetration of a forced supersonic jet in a supersonic Mach (M)-2 cross stream. Instantaneous images—using image planes along (side-view) and normal (end-view) to the flow axis—were used to study the dynamical structures in the jet whereas ensemble images provide information regarding the jet trajectory. Standard deviation images reveal information about the large-scale mixing/entrainment. Probability density functions were used to evaluate the mixing along the time-average jet interface. Forced cases indicate the presence of periodic formation of large-scale eddies in the jet/free stream interface. The eddies were bigger in size and more convoluted in the forced cases as compared to the baseline. These provided high penetration of the jet into the free stream. Forced cases also show a larger region involved in small scale and/or bulk mixing in both the side—and end-views. Different metrics such as total area contained in the jet (A90), total area involved in fluctuations of ⩾30% within the jet boundary (Aσ,30) and the interfacial contact at the jet free stream interface (S) were used to quantify the mixing of the forced cases. Analysis of averaged and standard deviation of end-view images indicates that these parameters were higher for the forced cases as compared to the baseline case.
Contactless measurement of electrical conductivity of Si wafers independent of wafer thickness
Authors: Ju Yang , Hirosawa Yo , Soyama Hitoshi , Saka Masumi
Published: October 2005

A method for contactless measurement of electrical conductivity of Si wafers independent of wafer thickness is presented. The effective region within which this proposed technique can be used is discussed in detail, and an equation to determine the boundary of the effective region is introduced. Three groups of Si wafers with different thicknesses were used as samples. A compact microwave instrument working at 94 GHz was used to measure the samples without contact. The reflection coefficient of the microwave signal was obtained and used to determine the electrical conductivity of the wafers. The electrical conductivities of the wafers thus measured were in good agreement with values obtained using a conventional four-point-probe method. This indicates that the proposed technique is a powerful tool for contactless measurement of electrical conductivity of Si as well as other semiconductor wafers independent of wafer thickness.
Organic solid-state ultraviolet-laser based on spiro-terphenyl
Authors: Spehr T. , Siebert A. , Fuhrmann-Lieker T. , Salbeck J. , Rabe T. , Riedl T. , Johannes H. H. , Kowalsky W. , Wang J. , Weimann T. , Hinze P.
Published: October 2005

We report on organic semiconductor lasers based on spiro-terphenyl as active gain medium in a second-order distributed feedback (DFB) structure. In contrast to neat p-terphenyl, the spiro-linked compound forms vitreous amorphous films—an essential prerequisite for low loss laser structures. Spiro-terphenyl shows amplified spontaneous emission in the ultraviolet part of the spectrum at 381 nm. Thin-film lasers with DFB grating periods between 200 and 230 nm exhibit emission wavelengths between 361.9 and 393.8 nm. The minimum threshold energy density under optical pumping is as low as 8.9μJ∕cm2 (383 nm). Therefore, the novel spiro-linked compound paves the way for low-threshold, widely tunable organic semiconductor lasers advancing into the ultraviolet spectral region.
Electron-beam-induced current and cathodoluminescence studies of thermally activated increase for carrier diffusion length and lifetime in n-type ZnO
Authors: Lopatiuk O. , Chernyak L. , Osinsky A. , Xie J. Q. , Chow P. P.
Published: October 2005

Temperature dependence of the minority carrier diffusion length and lifetime in bulk n-type ZnO was studied using electron-beam-induced current and cathodoluminescence techniques. The diffusion length was observed to increase exponentially over the temperature range from 25 °C to 125 °C, yielding activation energy of 45±2meV. Concomitant decrease of the cathodoluminescence intensity for the near-band-edge transition was also observed. The activation energy determined by optical measurements was 58±7meV. The larger minority carrier diffusion length and smaller luminescence intensity are attributed to the increased lifetime of nonequilibrium holes in the valence band at elevated temperatures.
Capacitance-voltage characteristics of ZnO∕GaN heterostructures
Authors: Oh D. C. , Suzuki T. , Kim J. J. , Makino H. , Hanada T. , Yao T. , Ko H. J.
Published: October 2005

We have investigated the electrical properties of ZnO∕GaN heterostructures by capacitance-voltage (C-V) measurements. ZnO∕GaN heterostructures are fabricated on Ga-polar GaN templates by plasma-assisted molecular-beam epitaxy. The ZnO∕GaN heterostructures exhibit a plateau region of 6.5V in the C-V curves measured at 10kHz and room temperature. Moreover, it is found that a large electron density is accumulated at the interface of ZnO∕GaN, where the concentration approaches ∼1018cm−3. The distinct C-V characteristics are ascribed to large conduction-band discontinuity at the ZnO∕GaN heterointerface. It is suggested that the ZnO∕GaN heterostructure is a very promising material for the application to heterojunction transistors.
Sodium hydroxide/aluminum bilayer cathode for enhancing the performance of blue polymer light-emitting diodes
Authors: Ma Liang , Xie Zhiyuan , Liu Jun , Yang Junwei , Cheng Yanxiang , Wang Lixiang , Wang Fosong
Published: October 2005

Sodium hydroxide/aluminum (NaOH∕Al) bilayer cathode has been developed for improving the performance of blue polymer light-emitting diodes (PLEDs) based on poly(9,9-dioctylfluorene). In comparison to the control device with Ca∕Al as the cathode, the performance of the PLED with NaOH∕Al cathode, including driving voltage, light-emitting efficiency, and color purity, is significantly improved. For achieving a luminance of 500cd∕m2, the driving voltage is reduced from 8.3to5.3V and the light-emitting efficiency is increased from 0.46to0.67cd∕A. Moreover, the device with NaOH∕Al cathode showed a pure blue emission with Commission Internationale de l’Eclairage coordinates of (0.17, 0.09) as compared to that of (0.18, 0.13) for control device operated at same condition. These improvements are attributed to the use of an efficient bilayer NaOH∕Al electron injection contact that also prevents the formation of Ca-induced fluorenone occurred in PLEDs with Ca∕Al cathode.
Effect of native defects on optical properties of InxGa1−xN alloys
Authors: Li S. X. , Haller E. E. , Yu K. M. , Walukiewicz W. , Ager J. W. , Wu J. , Shan W. , Lu Hai , Schaff William J.
Published: October 2005

The energy position of the optical-absorption edge and the free-carrier populations in InxGa1−xN ternary alloys can be controlled using high-energy He+4 irradiation. The blueshift of the absorption edge after irradiation in In-rich material (x>0.34) is attributed to the band-filling effect (Burstein-Moss shift) due to the native donors introduced by the irradiation. In Ga-rich material, optical-absorption measurements show that the irradiation-introduced native defects are inside the band gap, where they are incorporated as acceptors. The observed irradiation-produced changes in the optical-absorption edge and the carrier populations in InxGa1−xN are in excellent agreement with the predictions of the amphoteric defect model.
Thickness-dependent electronic structure of ultrathin SrRuO3 films studied by in situ photoemission spectroscopy
Authors: Toyota D. , Ohkubo I. , Kumigashira H. , Oshima M. , Ohnishi T. , Lippmaa M. , Takizawa M. , Fujimori A. , Ono K. , Kawasaki M. , Koinuma H.
Published: October 2005

In situ thickness-dependent photoemission spectroscopy (PES) has been performed on SrRuO3 (SRO) layers deposited on SrTiO3 substrates to study the structure-induced evolution of the electronic structure. The PES spectra showing the existence of two critical film thicknesses reveal that a metal-insulator transition occurs at a film thickness of 4–5 monolayers (ML) and the evolution of Ru 4d-derived states around the Fermi level (EF) saturates at about 15 ML. The observed spectral behavior well matches the electric and magnetic properties and thickness-dependent evolution of surface morphology of the ultrathin SRO films. These experimental results suggest the importance of the disorder associated with the unique growth-mode transition in SRO films.
Optical nonlinearity versus mechanical anharmonicity contrast in dynamic mode apertureless scanning near-field optical microscopy
Authors: Bek Alpan , Vogelgesang Ralf , Kern Klaus
Published: October 2005

We show that the contrast mechanism in dynamic mode apertureless scanning near-field optical microscopy is in general a combination of both spatially nonlinear optical interaction and temporally anharmonic mechanical cantilever motion. Mechanical factors are found experimentally to easily overshadow the optical signal, leading to artifacts not yet well documented in the literature. Our algebraic analysis provides a systematic framework to identify and control the relative influence of the competing contrast origins.
Using market research to understand the adoption of irrigation management strategies in the stone and pome fruit industry
Authors: Kaine G. , Bewsell D. , Boland A. , Linehan C.
Published: October 2005

Market research was conducted to develop an extension program targeting the specific irrigation management needs of growers in the stone and pome fruit industry within the Goulburn Valley, Victoria. The process of integrating market research with extension practice proved challenging, as it required the development of an extension program that was fundamentally different from what was originally envisaged. However, it was essential to achieve this integration in order to meet the original objectives for the extension program as set by the funding body. We found, in most cases, that the motivation for stone and pome fruit growers in the Goulburn Valley to change orchard irrigation management practices was not because they needed to save water, or to increase water use efficiency. Instead, growers were changing practices in order to save time irrigating, improve the scope for managerial flexibility in the orchard, or when redeveloping their orchard to a closer planting design. These findings suggest that growers in the Goulburn Valley are more likely to respond to an extension program consistent with these motivations rather than a program promoting water use efficiency.
The ability of Merino ewes and lambs to reunite after separation, as affected by divergent selection for ewe multiple rearing capacity
Authors: Cloete S. W. P. , Scholtz A. J. , Cloete J. J. E. , van Wyk J. B.
Published: October 2005

Lambs and ewes from 2 Merino lines that had been selected divergently from the same base population for (High line) or against (Low line) multiple rearing success, were assessed for their ability to reunite after temporary separation. Selection in the lines began in 1986, and data for this study were obtained from 1998 to 2002. Postnatal lamb mortality for lambs born during 1998–2002 were generally lower (P<0.05) in high line lambs than in low line contemporaries. When tethered 20 m away from their dams at 1 day of age, lambs in the High line tended (P<0.10) to be more likely to bleat and tug on the tethering rope than Low line contemporaries. Dams of lambs in the high line were quicker (P<0.05) to reunite with a tethered lamb than low line ewes. They were also quicker (P<0.05) to establish contact with the full litter after separation of multiples. In an experiment conducted in pens at an age of 3 days, no line difference was found for the ability of ewes to reunite with their lambs or litters when confronted by a choice of 3. When lambs were assessed in the same way, 89% was able to reunite with their dams within 5 min, with no evident line difference (P>0.05). When released from the pens, the dams of 95% of single lambs returned for their lambs, the proportion tending (P<0.10) to be higher in the High line than in the Low line. The dams of multiple lambs returned for 73% of the lambs tested, with no clear line difference. Lambs in the High line were more (P<0.01) likely to follow next to the front legs or midside of their dams than Low line lambs. Line differences in some behavioural patterns in favour of the High line are considered to be conducive to lamb survival when compared with Low line performance.
Changes in diazinon concentrations during shower and plunge dipping of Merino sheep
Authors: Lund R. D. , Levot G. W. , Black R.
Published: October 2005

The rate of removal of diazinon from solution (stripping) during dipping of adult short wool Merino sheep was similar in a standard and modified Buzacott 60R shower dip. During 12 min showering, dip concentration fell from about 100 mg/L to about 20 mg/L. Addition of insecticide concentrate (reinforcement) and sufficient fresh solution to re-establish original sump volume (topping up or replenishment) at this point restored dip concentration but was contrary to product label instructions. Adherence to the label directions to reinforce and top up after the sump was depleted by 25% (after 2 pens of sheep in the case of the standard dip) caused dip concentration to drop below the limit of quantification (10 mg/L). Similarly, current directions for continuous replenishment (commonly referred to as constant replenishment) shower dipping failed to offset diazinon stripping. Continuous replenishment plunge dipping with diazinon for the control of lice on sheep is an off-label use of the product; however, we demonstrated that a working concentration of about 100 mg diazinon /L (the nominal rate for lice control) was maintained in a 5000 L non-draining dip if charged and replenished at 200 mg diazinon/L. By maintaining 100 mg/L, this regimen was more likely to eradicate lice from sheep. This work also identified, by calculation, large and potentially significant variations in the dose of diazinon applied per sheep due to the application method, reinforcement practice and whether the sheep were treated early or late in the dipping sequence.
The northern Australian beef industry, a snapshot. 2. Breeding herd performance and management
Authors: Bortolussi G. , McIvor J. G. , Hodgkinson J. J. , Coffey S. G. , Holmes C. R.
Published: October 2005

Breeding herd performance and husbandry were surveyed on 375 northern Australian beef properties in 8 regions during 1996 and 1997. Mean branding rates ranged from 62.6% in the Northern Territory to 77.1% in the Maranoa South West regions of Queensland with considerable variation within regional herds.
The proportion of herds using controlled mating was highest in the Central Coastal, Central Highlands and Maranoa South West. Mean mating period across all regions varied from 5.6 to 11.8 months. Calving was seasonal with peak activity in the August–December period. Calving commenced earlier in the south (August) than it did in northern regions (September–November). Rainfall influenced the timing of commencement of calving and peak calving activity. The use of pregnancy testing was widespread but selective and often not all females were pregnancy tested.
About 97% of properties used weaning strategies with a peak in calf weaning in April–July, and a minor peak in September–October. Although mean weaner ages were similar across regions (5.9–6.9 months), mean weaner liveweight varied markedly with weaners in the more northern regions being lightest (<190 kg) while those in southern regions tended to be >200 kg.
Culling criteria for cows and heifers focused on temperament, conformation and reproductive failure; age was also important for cows with a common culling age of 10 years. Bulls were more commonly culled at 7–8 years of age. In addition to age, bulls were culled for physical defects, reproductive problems, temperament and poor quality/performing calves. Four to 5 criteria were commonly used to select bulls. Structural soundness and temperament ranked highest followed by conformation, weight for age, Breedplan and colour. Producers using Breedplan tended to use structural soundness and temperament also as selection criteria. The results suggest that producers associated increasing turn-off weight or decreasing turn-off age more with pasture improvement than with bulls of higher genetic merit for growth.
Supplementation of the breeding herd increased in the last half of the calendar year. Supplements containing molasses, urea, phosphate source, salt, and sulphate of ammonia were the most commonly supplied supplementary nutrients. Vaccination for botulism was quite common (>30% of regional survey groups) in all regions except Central Coastal and Maranoa South West regions of Queensland.
Comparisons with previous surveys show that there have been marked improvements in breeding herd performance and management over an extended period. The results are discussed in relation to scientific developments over the last 2 decades and future development of the northern Australian beef industry.
Grain yield and cadmium concentration of a range of grain legume species grown on two soil types at Merredin, Western Australia
Authors: Brennan R. F. , French R. J.
Published: October 2005

Five grain legumes species, narrow-leafed lupin (Lupinus angustifolius L.), field pea (Pisum sativum L.), faba bean (Vicia faba L.), chickpea (Cicer arietinum L.), and yellow lupin (Lupinus luteus L.), were grown on 2 soil types, a red clay and red duplex soil, in the < 400 mm rainfall district of Western Australia. The study showed that chickpea, field pea and faba bean accumulated less cadmium (Cd) in dried shoots and grain than narrow-leafed lupin. Yellow lupin had Cd concentrations ~3 times higher in dried shoots and ~9 times higher in grain than narrow-leafed lupin. For both experiments, the ranking (lowest to highest) of mean Cd concentration (mg Cd/kg) in the grain was: chickpea (0.017) < field pea (0.024) = faba bean (0.024) < narrow-leafed lupin (0.033) < yellow lupin (0.300).
Effect of Verticillium dahliae, pH, rootstocks and different sources of iron application on the chlorophyll and iron concentration in the leaves of peach trees
Authors: Tsipouridis C. , Thomidis T.
Published: October 2005

The aim of this study was to examine inexpensive techniques to control iron chlorosis. It was found that soil applications with Fe-EDDHA, FeSO4, K2SO4, KNO3, citric acid, Agrobiosol and FeSO4 + cow manure significantly increased the leaf iron concentration 90 days after application. Increased iron concentrations were found only in the leaves of trees supplied with K2SO4 and FeSO4 + 11–15–15, 150 days after application. Foliar applications with Micro-A-Fe, FeSO4, Micro-A-Fe + FeSO4, Mix Fyt + FeSO4, Biomin, Lysodin, FeSO4 + citric acid, FeSO4 + NH2CONH2 + citric acid, FeSO4 + KNO3 + citric acid increased significantly the leaf iron concentration 150 days after application. This study also investigated the effect of pH (in nutrient solution), rootstocks and Verticillium dahliae on iron chlorosis. The response of peach rootstocks was dependent on the pH — the highest iron concentration was found at pH 4 and the lowest at pH 7. Data were also obtained on the susceptibility of the important for the peach industry rootsocks to iron chlorosis. The rootstock St. Julien 655/2 had the highest iron concentration, while no significant differences were found between the rootstocks GF677, MRS 2/5, Seedling and Antafuel the lowest. Verticillium dahliae had no affect on the chlorophyll concentration of peach trees.
Variation in colonisation of Lolium rigidum by isolates of Dilophospora alopecuri, an antagonist of the causal organisms of annual ryegrass toxicity
Authors: Yan G. , Riley I. T.
Published: October 2005

The ability of 31 isolates of Dilophospora alopecuri to colonise Lolium rigidum co-inoculated with Anguina funesta and grown in pots outdoors was tested over 2 years. The isolates were collected from 3 grass hosts from sites across the southern mainland states of Australia. Marked variation among isolates of different host and regional origins was found. Isolates from L. rigidum showed the greatest colonisation with a mean of 16 infected inflorescences per 240 mm pot containing 32 plants. Isolates from the other hosts, Avena sativa, Holcus lanatus and Polypogon monspeliensis, only resulted in means of 1.9, 7.7 and 1.3 infected inflorescences per pot, respectively. The data allow selection of an aggressive isolate for dissemination for antagonism of A. funesta, one of the causal agents for annual ryegrass toxicity.
The northern Australian beef industry, a snapshot. 5. Land and pasture development practices
Authors: Bortolussi G. , McIvor J. G. , Hodgkinson J. J. , Coffey S. G. , Holmes C. R.
Published: October 2005

The land and pasture development practices of 375 northern Australian beef properties in 8 regions were surveyed during 1996–97. These properties represented a broad cross-section of the beef industry in terms of geographical location, enterprise and herd size, and ownership structures.
Both tree clearing and killing were more common in Queensland than in the Northern Territory or northern Western Australia. In all regions where trees were poisoned, native pasture was more widely used than sowing introduced grass and/or legume species. In contrast, tree clearing was most often accompanied by sowing pastures (either an introduced grass only or introduced grass and legume species together), rather than using native pastures. Central coastal Queensland had the highest use of poisoning trees for pasture development. Tree clearing and using native pasture was most important in central Queensland regions and the Maranoa South West. Sowing introduced pasture species under live trees was more commonly practiced in northern Queensland, the Northern Territory and northern Western Australia than in other regions.
A considerable number of introduced grass and legume species were sown by producers. Most of the sown species were grasses. Many of the sown grass and legume species were spreading naturally. Buffel grass was spreading in all areas with < 1000 mm average annual rainfall, but most sown species were spreading only in wetter regions. Stylosanthes spp. were the most commonly spreading legume species in regions with > 500 mm average annual rainfall.
The results are discussed in relation to contemporary natural resource management issues and how this may affect land and pasture development activities in the future.
New sources of resistance in Trifolium subterraneum to rust (Uromyces trifolii-repentis)
Authors: Barbetti M. J. , Nichols P. G. H.
Published: October 2005

Fifty-seven genotypes, including 10 cultivars, of Trifolium subterraneum var. subterraneum and var. yanninicum were screened in the field for resistance to rust (Uromyces trifolii-repentis) using artificial inoculation. There was outstanding resistance among the var. yanninicum, types with all but 1 genotype showing no rust symptoms. Several var. subterraneum genotypes also showed only a low rust incidence (≤3.5 on a 0–10 scale) with little or no leaf collapse from rust infection, including 83S19–07, CPI 103906F, EP132Sub-E, 84S20–02, and 84S20–01. Several other lines had a significant incidence of rust, while little leaf collapse from the disease was evident. Several highly susceptible lines were identified, including cultivars Green Range, Seaton Park and York, all with 100% of leaves affected by rust and extensive leaf collapse. There was excellent positive correlation between rust incidence and leaf collapse across the genotypes tested (R2 = 0.91). The excellent rust resistance observed in the majority of var. yanninicum lines and the good resistance in some var. subterraneum lines, indicates that these are useful sources of resistance that can be exploited, either directly as new cultivars to minimise leaf collapse from this disease or as parents in breeding programmes to develop more rust-resistant cultivars.
A negative elongation factor for human RNA polymerase II inhibits the anti-arrest transcript-cleavage factor TFIIS
Authors: Palangat Murali , Renner Dan B. , Price David H. , Landick Robert
Published: October 2005

Formation of productive transcription complexes after promoter escape by RNA polymerase II is a major event in eukaryotic gene regulation. Both negative and positive factors control this step. The principal negative elongation factor (NELF) contains four polypeptides and requires for activity the two-polypeptide 5,6-dichloro-1-β-
d
-ribobenzimidazole-sensitivity inducing factor (DSIF). DSIF/NELF inhibits early transcript elongation until it is counteracted by the positive elongation factor P-TEFb. We report a previously undescribed activity of DSIF/NELF, namely inhibition of the transcript cleavage factor TFIIS. These two activities of DSIF/NELF appear to be mechanistically distinct. Inhibition of nucleotide addition requires ≥18 nt of nascent RNA, whereas inhibition of TFIIS occurs at all transcript lengths. Because TFIIS promotes escape from promoter-proximal pauses by stimulating cleavage of back-tracked nascent RNA, TFIIS inhibition may help DSIF/NELF negatively regulate productive transcription.
Genetic evidence for a mammalian retromer complex containing sorting nexins 1 and 2
Authors: Griffin Courtney T. , Trejo JoAnn , Magnuson Terry
Published: October 2005

We have previously shown that the putative mammalian retromer components sorting nexins 1 and 2 (
Snx1
and
Snx2
) result in embryonic lethality when simultaneously targeted for deletion in mice, whereas others have shown that
Hβ58
(also known as
mVps26
), another retromer component, results in similar lethality when targeted for deletion. In the current study, we address the genetic interaction of these mammalian retromer components in mice. Our findings reveal a functional interaction between Hβ58, SNX1, and SNX2 and strongly suggest that SNX2 plays a more critical role than SNX1 in retromer activity during embryonic development. This genetic evidence supports the existence of mammalian retromer complexes containing SNX1 and SNX2 and identifies SNX2 as an important mediator of retromer biology. Moreover, we find that mammalian retromer complexes containing SNX1 and SNX2 have an essential role in embryonic development that is independent of cation-independent mannose 6-phosphate receptor trafficking.
Massive sequence perturbation of a small protein
Authors: Campbell-Valois F.-X. , Tarassov K. , Michnick S. W.
Published: October 2005

Most protein topologies rarely occur in nature, thus limiting our ability to extract sequence information that could be used to predict structure, function, and evolutionary constraints on protein folds. In principle, the sequence diversity explored by a given protein topology could be expanded by introducing sequence perturbations and selecting variant proteins that fold correctly. However, our capacity to explore sequence space is intrinsically limited by the enormous number of sequences generated from the 20 amino acids and the limited number of variants likely to fold. Here we sought to test whether the sequence space for naturally existing proteins can be explored by simple, sequential degeneration of a complete set of short sequence segments of a model protein, without long-range covariation. Using the Raf
ras
binding domain as a model of a small protein capable of autonomous folding, we degenerated 72 of 76 positions of the primary structure for the 20 amino acids in segments of four to seven residues defined by secondary structure and selected the folded species for interaction with
h-ras
by using an
in vivo
survival-selection assay. The methodology presented allowed for rigorous statistical analysis and comparison of sequence diversity. The ensemble of sequence variants of Raf
ras
binding domain obtained have recaptured the diversity observed for the ubiquitin-roll topology. A signature sequence for this fold and the implication of this strategy to protein design and structure prediction are discussed.
The Ca
2
+-induced methyltransferase xPRMT1b controls neural fate in amphibian embryo
Authors: Batut Julie , Vandel Laurence , Leclerc Catherine , Daguzan Christiane , Moreau Marc , Néant Isabelle
Published: October 2005

We have previously shown that an increase in intracellular Ca
2+
is both necessary and sufficient to commit ectoderm to a neural fate in
Xenopus
embryos. However, the relationship between this Ca
2+
increase and the expression of early neural genes has yet to be defined. Using a subtractive cDNA library between untreated and caffeine-treated animal caps, i.e., control ectoderm and ectoderm induced toward a neural fate by a release of Ca
2+
, we have isolated the arginine
N
-methyltransferase,
xPRMT1b
, a Ca
2+
-induced target gene, which plays a pivotal role in this process. First, we show in embryo and in animal cap that
xPRMT1b
expression is Ca
2+
-regulated. Second, overexpression of
xPRMT1b
induces the expression of early neural genes such as
Zic3
. Finally, in the whole embryo, antisense approach with morpholino oligonucleotide against
xPRMT1b
impairs neural development and in animal caps blocks the expression of neural markers induced by a release of internal Ca
2+
. Our results implicate an instructive role of an enzyme, an arginine methyltransferase protein, in the embryonic choice of determination between epidermal and neural fate. The results presented provide insights by which a Ca
2+
increase induces neural fate.
Signal propagation from membrane messengers to nuclear effectors revealed by reporters of phosphoinositide dynamics and Akt activity
Authors: Ananthanarayanan Bharath , Ni Qiang , Zhang Jin
Published: October 2005

Among various second messengers, phosphatidylinositol 3,4,5-triphosphate (PIP
3
) and phosphatidylinositol 3,4-bisphosphate [PI(3,4)P
2
] regulate a variety of cellular processes, such as cell survival, polarization, and proliferation. Many of these functions are achieved via activation of serine/threonine kinase Akt. To investigate the spatiotemporal regulation of these lipids, we constructed a genetically targetable phosphoinositide (PI) indicator by sandwiching pleckstrin homology (PH) domain of Akt and a “pseudoligand” containing acidic amino acid residues, between cyan and yellow mutants of GFP. In living cells, elevations in PIP
3
and PI(3,4)P
2
by growth factor-induced activation of phosphatidylinositol 3-kinase (PI3K) resulted in a change in fluorescence resonance energy transfer (FRET) between the fluorescent proteins, increasing yellow to cyan emission ratios by 10–30%. This response can be reversed by inhibiting PI3K and abolished by mutating the critical residues responsible for PI binding. Differential dynamics of PIs were observed at plasma membrane of NIH 3T3 cells, stimulated by various growth factors. On the other hand, the nuclear targeted indicator showed no response within an hour after platelet-derived growth factor stimulation, suggesting that no appreciable amounts of accessible PIP
3
and PI(3,4)P
2
were produced in the nucleus. Furthermore, simultaneous imaging of a plasma membrane-targeted PI indicator and a nuclear-targeted Akt activity reporter revealed a gradual and sustained accumulation of Akt activity in the nucleus after rapid and transient production of PIP
3
and PI(3,4)P
2
at plasma membrane in the same cell. Thus, signal propagation from the lipid messengers at plasma membrane to the effectors in the nucleus is precisely controlled by kinases as well as lipid and protein phosphatases.
Transposon-mediated insertional mutagenesis revealed the functions of animal cellulose synthase in the ascidian
Ciona intestinalis
Authors: Sasakura Yasunori , Nakashima Keisuke , Awazu Satoko , Matsuoka Terumi , Nakayama Akie , Azuma Jun-ichi , Satoh Nori
Published: October 2005

Tunicates are the only animals that perform cellulose biosynthesis. The tunicate gene for cellulose synthase,
Ci-CesA
, was likely acquired by horizontal transfer from bacteria and was a key innovation in the evolution of tunicates. Transposon-based mutagenesis in an ascidian,
Ciona intestinalis
, has generated a mutant,
swimming juvenile
(
sj
).
Ci-CesA
is the gene responsible for the
sj
mutant, in which a drastic reduction in cellulose was observed in the tunic. Furthermore, during metamorphosis, which in ascidians convert the vertebrate-like larva into a sessile filter feeder,
sj
showed abnormalities in the order of metamorphic events. In normal larvae, the metamorphic events in the trunk region are initiated after tail resorption. In contrast,
sj
mutant larvae initiated the metamorphic events in the trunk without tail resorption. Thus,
sj
larvae show a “swimming juvenile” phenotype, the juvenile-like trunk structure with a complete tail and the ability to swim. It is likely that ascidian cellulose synthase is required for the coordination of the metamorphic events in the trunk and tail in addition to cellulose biosynthesis.
Rab11a and myosin Vb are required for bile canalicular formation in WIF-B9 cells
Authors: Wakabayashi Yoshiyuki , Dutt Parmesh , Lippincott-Schwartz Jennifer , Arias Irwin M.
Published: October 2005

Hepatocytes polarize by forming functionally distinct sinusoidal (basolateral) and canalicular (apical) plasma membrane domains. Two distinct routes are used for delivery of membrane proteins to the canaliculus. Proteins having glycosylphosphatidylinositol anchors or single transmembrane domains are targeted to the sinusoidal plasma membrane from where they transcytose to the canalicular domain. In contrast, apical ATP-binding-cassette (ABC) transporters, which are required for energy-dependent biliary secretion of bile acids (ABCB11), phospholipids (ABCB4), and nonbile acid organic anions (ABCC2), lack initial residence in the basolateral plasma membrane and traffic directly from Golgi membranes to the canalicular membrane. While investigating mechanisms of apical targeting in WIF-B9 cells, a polarized hepatic epithelial cell line, we observed that rab11a is required for canalicular formation. Knockdown of rab11a or overexpression of the rab11a-GDP locked form prevented canalicular formation as did overexpression of the myosin Vb motorless tail domain. In WIF-B9 cells, which lack bile canaliculi, apical ABC transporters colocalized with transcytotic membrane proteins in rab11a-containing endosomes and, unlike the transcytotic markers, did not distribute to the plasma membrane. We propose that polarization of hepatocytes (i.e., canalicular biogenesis) requires recruitment of rab11a and myosin Vb to intracellular membranes that contain apical ABC transporters and transcytotic markers, permitting their targeting to the plasma membrane. In this model, polarization is initiated upon delivery of rab11a-myosin Vb-containing membranes to the surface, which causes plasma membrane at the site of delivery to differentiate into apical domain (bile canaliculus).
The UGT73C5 of
Arabidopsis thaliana
glucosylates brassinosteroids
Authors: Poppenberger Brigitte , Fujioka Shozo , Soeno Kazuo , George Gilu L. , Vaistij Fabián E. , Hiranuma Sayoko , Seto Hideharu , Takatsuto Suguru , Adam Gerhard , Yoshida Shigeo , Bowles Dianna
Published: October 2005

Steroid hormones are essential for development, and the precise control of their homeostasis is a prerequisite for normal growth. UDP-glycosyltransferases (UGTs) are considered to play an important regulatory role in the activity of steroids in mammals and insects. This study provides an indication that a UGT accepting plant steroids as substrates functions in brassinosteroid (BR) homeostasis. The UGT73C5 of
Arabidopsis thaliana
catalyses 23-
O
-glucosylation of the BRs brassinolide (BL) and castasterone. Transgenic plants overexpressing UGT73C5 displayed BR-deficient phenotypes and contained reduced amounts of BRs. The phenotype, which was already apparent in seedlings, could be rescued by application of BR. In feeding experiments with BL, wild-type seedlings converted BL to the 23-
O
-glucoside; in the transgenic lines silenced in UGT73C5 expression, no 23-
O
-glucoside was detected, implying that this UGT is the only enzyme that catalyzes BL-23-
O
-glucosylation in seedlings. Plant lines in which UGT73C5 expression was altered also displayed hypocotyl phenotypes previously described for seedlings in which BR inactivation by hydroxylation was changed. These data support the hypothesis that 23-
O
-glucosylation of BL is a function of UGT73C5
in planta
, and that glucosylation regulates BR activity.
Crystal structure of the archaeal ammonium transporter Amt-1 from
Archaeoglobus fulgidus
Authors: Andrade Susana L. A. , Dickmanns Antje , Ficner Ralf , Einsle Oliver
Published: October 2005

Ammonium transporters (Amts) are integral membrane proteins found in all kingdoms of life that fulfill an essential function in the uptake of reduced nitrogen for biosynthetic purposes. Amt-1 is one of three Amts encoded in the genome of the hyperthermophilic archaeon
Archaeoglobus fulgidus
. The crystal structure of Amt-1 shows a compact trimer with 11 transmembrane helices per monomer and a central channel for substrate conduction in each monomer, similar to the known crystal structure of AmtB from
Escherichia coli
. Xenon derivatization has been used to identify apolar regions of Amt-1, emphasizing not only the hydrophobicity of the substrate channel but also the unexpected presence of extensive internal cavities that should be detrimental for protein stability. The substrates ammonium and methylammonium have been used for cocrystallization experiments with Amt-1, but the identification of binding sites that are distinct from water positions is not unambiguous. The well ordered cytoplasmic C terminus of the protein in the Amt-1 structure has allowed for the construction of a docking model between Amt-1 and a homology model for its physiological interaction partner, the P
II
protein GlnB-1. In this model, GlnB-1 binds tightly to the cytoplasmic face of the transporter, effectively blocking conduction through the three individual substrate channels.
Predicting the energetics of osmolyte-induced protein folding/unfolding
Authors: Auton Matthew , Bolen D. Wayne
Published: October 2005

A primary thermodynamic goal in protein biochemistry is to attain predictive understanding of the detailed energetic changes that are responsible for folding/unfolding. Through use of recently determined free energies of side-chain and backbone transfer from water to osmolytes and Tanford's transfer model, we demonstrate that the long-sought goal of predicting solvent-dependent cooperative protein folding/unfolding free-energy changes (
m
values) can be achieved. Moreover, the approach permits dissection of the folding/unfolding free-energy changes into individual contributions from the peptide backbone and residue side chains.
p600, a unique protein required for membrane morphogenesis and cell survival
Authors: Nakatani Yoshihiro , Konishi Hiroaki , Vassilev Alex , Kurooka Hisanori , Ishiguro Keiichiro , Sawada Jun-ichi , Ikura Tsuyoshi , Korsmeyer Stanley J. , Qin Jun , Herlitz Anna M.
Published: October 2005

In this article, we identify and characterize p600, a unique 600-kDa retinoblastoma protein- and calmodulin-binding protein. In the nucleus, p600 and retinoblastoma protein seem to act as a chromatin scaffold. In the cytoplasm, p600 and clathrin form a meshwork structure, which could contribute to cytoskeletal organization and membrane morphogenesis. Reduced expression of p600 with interference RNA abrogates integrin-mediated ruffled membrane formation and, furthermore, prevents activation of integrin-mediated survival pathways. Consequently, knockdown of p600 sensitizes cells to apoptosis induced by cell detachment. These findings provide mechanistic insight into the regulation of membrane-proximal events in tumorigenesis.