bluuebunny/crossref_metadata_2025 huggingface dataset:
Annealing effect on dislocations in SrTiO3∕LaAlO3 heterostructures
Authors: Su Dong , Yamada Tomoaki , Sherman Vladimir O. , Tagantsev Alexander K. , Muralt Paul , Setter Nava
Published: March 2007

Epitaxial SrTiO3 thin films were deposited on (001) LaAlO3 single crystals by pulsed laser deposition. The postannealing effect was studied by annealing the deposited films at 1100°C in O2 atmosphere for 4h. It was found that the postannealing treatment enhances the in-plane permittivity of the film. An analysis of the film lattice parameters from selected area electron diffraction and high-resolution electron microscopy shows a relaxation of the compressive strain by annealing. In addition, the density of threading dislocations is significantly reduced, and stacking faults with translation vector R=1∕2a⟨110⟩ resulting from the dissociation of threading dislocations are formed. Both structural and dielectric characterizations indicate that the enhancement of permittivity is mainly due to the relaxation of the misfit strain between the film and substrate. The reduction of the threading dislocation density by annealing may be beneficial to the reduction of the extrinsic dielectric loss in the film.
Electrical characterization of alpha radiation-induced defects in p-GaAs grown by metal-organic chemical-vapor deposition
Authors: Naz Nazir A. , Qurashi Umar S. , Iqbal M. Zafar
Published: March 2007

Investigations of the alpha particle irradiation-induced defects in low-pressure metal-organic chemical-vapor deposition grown p-GaAs have been carried out. By employing deep-level transient spectroscopy, at least seven radiation-induced deep-level defects have been observed in the lower half of the band gap in the temperature range of 12−475 K. Double-correlation deep-level transient spectroscopy measurements show three prominent levels: two known radiation-induced levels namely, Hα1 and Hα5, and one inadvertent center HSA, present before irradiation, to exhibit a significant dependence of thermal emission rate on the junction electric field. For Hα1 and HSA the field-enhanced emission data are well fitted with a Poole-Frenkel model, using a three-dimensional square-well potential with radius r=3.2 and 1.43 nm, respectively. The field effect for Hα5 has been explained by a square-well potential in combination with a phonon-assisted tunneling process. Detailed data on the carrier capture cross section for all three levels have been obtained. The hole capture cross section for the levels Hα1 and Hα5 are found to be temperature independent, while for HSA, the hole capture data show a dependence on temperature. The dependence of hole capture cross section of HSA on temperature has been explained in terms of multiphonon capture mechanism, yielding a capture barrier of 0.13 eV and σ(∞)=1.5×10−14 cm2. These analyses lead us to conclude that the levels Hα1 and HSA are associated with a charged center, while the level Hα5 is most likely a substitutional defect in GaAs.
Thermal conductivity improvement in carbon nanoparticle doped PAO oil: An experimental study
Authors: Shaikh S. , Lafdi K. , Ponnappan R.
Published: March 2007

The present work involves a study on the thermal conductivity of nanoparticle-oil suspensions for three types of nanoparticles, namely, carbon nanotubes (CNTs), exfoliated graphite (EXG), and heat treated nanofibers (HTT) with PAO oil as the base fluid. To accomplish the above task, an experimental analysis is performed using a modern light flash technique (LFA 447) for measuring the thermal conductivity of the three types of nanofluids, for different loading of nanoparticles. The experimental results show a similar trend as observed in literature for nanofluids with a maximum enhancement of approximately 161% obtained for the CNT-PAO oil suspension. The overall percent enhancements for different volume fractions of the nanoparticles are highest for the CNT-based nanofluid, followed by the EXG and the HTT. The findings from this study for the three different types of carbon nanoparticles can have great potential in the field of thermal management.
Electrochemical preparation of a rugate filter in silicon and its deviation from the ideal structure
Authors: Salem M. S. , Sailor M. J. , Sakka T. , Ogata Y. H.
Published: March 2007

Porous silicon single layers are formed by anodization of silicon in a hydrofluoric acid solution at different current densities. An accurate estimation of the etch rates and refractive indices is performed. The refractive index-depth profile of a porous silicon rugate filter (PSRF) prepared by sinusoidally modulating the current density during etch is investigated. The produced PSRF is found to have a periodic pseudo-sinusoidal variation of refractive index with depth. The sinusoidal current density waveform that was employed generates a nonideal refractive index-depth profile with an asymmetric period. It is found that this deformed refractive index profile affects the quality of the characteristic resonant peak of the rugate filter. A simple modification of the current density waveform can be implemented, which allows one to achieve a true sinusoidal refractive index-depth profile characteristic of a rugate filter. The modified current density waveform allows the generation of a PSRF with a low index contrast and a sharp resonant band. The ability of these structures to act as chemical vapor sensors is tested and compared with the existing literature. The filters exhibit a red-shift in the photonic feature upon exposure to saturated ethanol vapor. The modified signal does not impose a significant change on the filter sensitivity to ethanol vapor.
Temperature dependent characteristics of all polymer thin-film transistors based on poly(9,9-dioctylfluorene-co-bithiophene)
Authors: Yan Feng , Hong Yi , Migliorato Piero
Published: March 2007

Thin-film transistors based on poly(9,9-dioctylfluorene-co-bithiophene) have been studied in the temperature range from 130to300K. In this temperature range both the field effect mobility and the drain current show thermally activated behavior. From the bias and temperature dependence of the drain current we deduce the presence of an exponential distribution of states above the dominant transport level.
p
-type semiconducting α,ω-dihexylsexithiophene for an organic thin film transistor
Authors: Kwon Jae-Hong , Seo Jung-Hoon , Kang Hochul , Choi Dong Hoon , Ju Byeong-Kwon
Published: March 2007

End substitution of sexithiophene with hexyl groups, α,ω-dihexylsexithiophene (DH-6T), leads to a highly soluble conjugated oligomer. In this paper, we report on the synthesis of an air-stable p-type organic semiconductor, DH-6T. We also report on our analysis of its thermal, optical, and electrical properties. We obtained a stable characteristic curve. The field-effect performance had a mobility of 3.29×10−4cm2∕Vs, while the threshold voltage was about −19V. The current on/off ratio was greater than 106 when the gate voltage was scanned from −40to0V.
X
-valley leakage in GaAs-based midinfrared quantum cascade lasers: A Monte Carlo study
Authors: Gao X. , Botez D. , Knezevic I.
Published: March 2007

We present a detailed Monte Carlo simulation of electron transport incorporating both Γ- and X-valley states in GaAs-based quantum cascade lasers (QCLs). Γ states are calculated using the K⋅p method, while X states are obtained within the effective mass framework. All the relevant electron-phonon, electron-electron, and intervalley scattering mechanisms are included. We investigate the X-valley leakage in two equivalent-design GaAs/AlGaAs QCLs with 33% and 45% Al-barrier compositions. We find that the dominant X-valley leakage path in both laser structures is through interstage X→X intervalley scattering, leading to a parallel leakage current JX. The magnitude of JX depends on the temperature and occupation of the X subbands, which are populated primarily by the same-stage scattering from the Γ-continuum (Γc) states. At 77 K, JX is small up to very high fields in both QCLs. However, at room temperature the 33% QCL shows a much higher JX than the 45% QCL even at low fields. The reason is that in the 33% QCL the coupling between the Γ-localized (Γl) states and the next-stage Γc states is strong, which facilitates subsequent filling of the X states through efficient intrastage Γc→X scattering; with high X-valley population and high temperature, efficient interstage X→X scattering yields a large JX. In contrast, good localization of the Γl states in the 45% QCL ultimately leads to low X-valley leakage current up to high fields. Very good agreement with experiment is obtained at both cryogenic and room temperatures.
Orientational and translational dynamics in room temperature ionic liquids
Authors: Rivera A. , Brodin A. , Pugachev A. , Rössler E. A.
Published: March 2007

The authors investigate the dynamics of a series of room temperature ionic liquids, based on the same 1-butyl-3-methylimidazolium cation with different anions, by means of broadband (10−6–109Hz) dielectric spectroscopy and depolarized light scattering in the temperature range from 400K down to 35K. Typical ionic conductivity is observed above the glass transition temperature Tg. Below Tg the authors detect relaxation processes that exhibit characteristics of secondary relaxations, as typically observed in molecular glasses. At high temperatures, the characteristic times of cation reorientation, deduced from the light scattering data, are approximately equal to the electric modulus relaxation times related to ionic conductivity. In the supercooled regime and close to Tg, the authors observe decoupling of conductivity from structural relaxation. Overall, room temperature ionic liquids exhibit typical glass transition dynamics, apparently unaltered by Coulomb interactions.
Assembly of one-dimensional nanorods into Bi2S3 films with enhanced thermoelectric transport properties
Authors: Liufu Sheng-Cong , Chen Li-Dong , Yao Qin , Wang Chun-Fen
Published: March 2007

Bismuth sulfide thin films have been assembled by cross-linkage nanorods on surface-functionalized Si substrate with self-assembled monolayers. Results of transmission electron microscopy and electron diffraction revealed that highly crystalline Bi2S3 nanorods grow along c-axis direction. Electrical transport properties including resistivity (0.02Ωcm), thermopower (−755μVK−1), and carrier mobilities (1100cm2V−1s−1) of the Bi2S3 films at 300K are found superior to those of previously reported Bi2S3 samples. The Bi2S3 films exhibit a maximum thermoelectric power factor (3.97×10−3Wm−1K−2) at 450K. The enhancement of thermoelectric properties mainly originates from highly crystalline and oriented nanostructures embedded in the Bi2S3 films.
Doping dependence of thermopower and thermoelectricity in strongly correlated materials
Authors: Mukerjee Subroto , Moore Joel E.
Published: March 2007

The search for efficient semiconductor thermoelectrics has been greatly aided by theoretical modeling of electron and phonon transports in bulk materials and nanocomposites. Recent experiments have studied thermoelectric transport in thermoelectrics that are “strongly correlated” and derived by doping Mott insulators. Here a unified theory of electrical and thermal transport in the atomic and “Heikes” limit is applied to understand recent experiments on sodium cobaltate and other doped Mott insulators at room temperature and above. For optimal electron filling, a broad class of narrow-bandwidth correlated materials is shown to have thermoelectric power factors as high as in the best semiconductors.
Effects of rapid thermal annealing on the emission properties of highly uniform self-assembled InAs∕GaAs quantum dots emitting at 1.3μm
Authors: Yang Tao , Tatebayashi Jun , Aoki Kanna , Nishioka Masao , Arakawa Yasuhiko
Published: March 2007

The authors report the effects of rapid thermal annealing (RTA) on the emission properties of highly uniform self-assembled InAs quantum dots (QDs) emitting at 1.3μm grown on GaAs substrate by metal organic chemical vapor deposition. Postgrowth RTA experiments were performed under N2 flow at temperatures ranging from 600to900°C for 30s using GaAs proximity capping. Surprisingly, in spite of the capping, large blueshifts in the emission peak (up to about 380meV at 850°C) were observed (even at low annealing temperatures) along with enhanced integrated photoluminescence (PL) intensities. Moreover, pronounced peak broadenings occurred at low annealing temperatures (<700°C), indicating that RTA does not always cause peak narrowing, as is typically observed with traditional QDs with large inhomogeneous PL linewidths. The mechanism behind the large peak blueshift was studied and found to be attributed to the as-grown QDs with large size, which cause a larger dot-barrier interface and greater strain in and near the QD regions, thereby greatly promoting Ga–In intermixing across the interface during RTA. The results reported here demonstrate that it is possible to significantly shift the emission peak of the QDs by RTA without any additional procedures, even at lower annealing temperatures.
Multistable alignment states in nematic liquid crystal filled wells
Authors: Tsakonas C. , Davidson A. J. , Brown C. V. , Mottram N. J.
Published: March 2007

Two distinct, stable alignment states have been observed for a nematic liquid crystal confined in a layer with thickness of 12μm and in square wells with sides of length between 20 and 80μm. The director lies in the plane of the layer and line defects occur in two corners of the squares. The positions of the defects determine whether the director orientation is across the diagonal or is parallel to two opposite edges of the square. The device is multistable because both the diagonal and parallel states are stable when rotated by multiples of 90° in plane.
Spin-transfer-induced magnetization switching in tunnel junctions with nanocurrent channels
Authors: Zhang Yisong , Zhang Zongzhi , Liu Yaowen , Ma B. , Jin Q. Y.
Published: March 2007

Spin-transfer-induced magnetization switching processes are evidenced by the “snapshots” of magnetic configurations for junctions containing nanocurrent channels (NCCs). The switching behaviors are found to be closely related to the NCC size and its actual location. Both the switching time t and critical current density Jc decrease with the increase of NCC size. Faster switching and lower Jc are observed for NCC located in the center. This work suggests a reasonable design frame to efficiently manipulate the Jc reduction and fast switching in practical spin-transfer-switched devices.
Bamboolike carbon nitride nanotubes (C9N5H3): Atomic-scale construction, synthesis and lithium battery applications
Authors: Wu Changzheng , Zhu Xi , Wang Chengle , Sheng Hua , Yang Jinlong , Xie Yi
Published: March 2007

The authors constructed the finite cluster model of bamboolike carbon nitride nanotubes taking the C9N5H3 as an example. As desired, the C9N5H3 bamboolike nanotubes were prepared in a facile solvent-free system. Both x-ray photoelectron microscopy and elemental analysis give its formula of C9N5H3, while the UV-vis and Fourier transform infrared results agree well with the theoretical predictions. Due to the existence of pore structure in this carbon nitride tube wall, the lithium battery experimental results exhibit a much higher irreversible and reversible capacity than that of the theoretical capacity of graphite (372mAhg−1).
Microcantilever mechanics in flowing viscous fluids
Authors: Jana Anirban , Raman Arvind , Dhayal Babita , Tripp Steven L. , Reifenberger Ronald G.
Published: March 2007

Microcantilevers are often deployed in flowing fluids to measure local flow velocities or to detect rapidly the nanomechanical binding of trace quantities of target analytes. The authors investigate the flow-induced mechanics of microcantilevers by deriving a semianalytical theoretical model for the nanoscale deflections of an elastic microcantilever due to a laminar viscous flow incident upon it. Conversely, the model allows for the estimation of the local flow velocities based on measured microcantilever deflection. Careful experiments performed on silicon microcantilevers in flowing nitrogen confirm the theoretical predictions up to a critical flow rate, beyond which unsteady flow-induced vibrations are seen to occur.
Effect of enhanced C2 growth chemistry on nanodiamond film deposition
Authors: Teii Kungen , Ikeda Tomohiro
Published: March 2007

A route to high-purity nanocrystalline diamond films from C2 dimers and related mechanisms have been investigated by enhancing C2 growth chemistry in Ar-rich microwave plasmas. Efficient C2 production by direct dissociation from acetylene causes the micro- to nanocrystal transition with a low threshold Ar concentration of ∼70% and produces films of ∼20nm grains with a distinct visible-Raman peak of diamond. C2 grows nanodiamond on diamond surfaces but rarely initiates nucleation on foreign surfaces. The phase purity can be improved by increasing the dominance of nanodiamond growth from C2 over nondiamond growth from CHx(x=0–3) and large radicals.
Strain field in silicon on insulator lines using high resolution x-ray diffraction
Authors: Gailhanou M. , Loubens A. , Micha J.-S. , Charlet B. , Minkevich A. A. , Fortunier R. , Thomas O.
Published: March 2007

Symmetric and asymmetric reciprocal space maps (RSMs) of silicon on insulator (SOI) lines are obtained using high resolution x-ray diffraction. RSMs calculated from the displacement field simulated using finite element calculations show a good agreement with the experimental RSMs. These calculations indicate the large influence of the displacement field created by the silicon nitride cap and the sensitivity of the RSMs to the gradients of displacement at the edge of the SOI lines. They further show that the RSMs are influenced by local strains but also by local rotations of the crystal lattice connected with the strain distribution.
GaSb homojunctions for far-infrared (terahertz) detection
Authors: Jayaweera P. V. V. , Matsik S. G. , Perera A. G. U. , Paltiel Y. , Sher Ariel , Raizman Arie , Luo H. , Liu H. C.
Published: March 2007

A GaSb based homojunction interfacial work function internal photoemission far-infrared (>30μm) detector is presented. Metal-organic vapor phase epitaxy grown p-GaSb∕GaSb samples show 9.7A∕W peak responsivity and a peak detectivity of 5.7×1011 Jones with effective quantum efficiency of 33% at 36μm and 4.9K. The detector exhibits a 97μm (∼3THz) free carrier response threshold wavelength. Results indicate that p-GaSb homojunction internal work function internal photoemission detectors are promising candidates to be a competitor for terahertz applications.
Dynamic hysteresis and scaling behavior of hard lead zirconate titanate bulk ceramics
Authors: Yimnirun R. , Wongmaneerung R. , Wongsaenmai S. , Ngamjarurojana A. , Ananta S. , Laosiritaworn Y.
Published: March 2007

The scaling relation of ferroelectric hysteresis area ⟨A⟩ against frequency f and field amplitude E0 for the saturated loops of the hard lead zirconate titanate bulk ceramic takes the form of ⟨A⟩∝f−0.28E00.89, while that for the minor loops takes the form of ⟨A⟩∝f−0.43E03.19. In both cases, the scaling relations are similar to those of its soft counterpart. This indicates that the dynamic behaviors and scaling relations in bulk ceramics are mainly governed by the domain states and structures, while the distinct types of complex defects contribute mainly to the difference in the coercive field observed in hard and soft ceramics.
Excimer laser annealing of silicon nanowires
Authors: Misra Nipun , Xu Li , Pan Yaoling , Cheung Nathan , Grigoropoulos Costas P.
Published: March 2007

Nanowires can potentially be used with low-cost flexible plastic substrates for applications such as large-area displays and sensor arrays. However, high temperature processing steps such as thermal annealing that are incompatible with plastic substrates are still a major hindrance. Laser annealing permits localized energy input without affecting the underlying substrate and can help overcome this problem. In this study, the excimer laser annealing of silicon nanowires is demonstrated to be an efficient means of activating implanted dopants. The optical absorption of the nanowires is discussed and the effect of parameters such as fluence and number of pulses is investigated.
High quality Fe3−δO4∕InAs hybrid structure for electrical spin injection
Authors: Ferhat Marhoun , Yoh Kanji
Published: March 2007

Single crystalline Fe3−δO4 (0⩽δ⩽0.33) films have been epitaxially grown on InAs (001) substrates by molecular beam epitaxy using O2 as source of active oxygen. Under optimum growth conditions, in situ real time reflection high-energy electron diffraction patterns, along with ex situ atomic force microscopy, indicate that (001) Fe3−δO4 can be grown under step-flow-growth mode with a characteristic (2×2)R45 surface reconstruction. X-ray photoelectron spectroscopy demonstrates the possibility of obtaining iron oxides with compositions ranging from Fe3O4 to γ-Fe2O3. Measurements with a superconducting quantum interference device magnetometer at 300K show good magnetic properties, suggesting that iron-based oxides may be promising for spintronic applications.
Alpha-particle irradiation-induced defects in n-type germanium
Authors: Kolkovsky Vl. , Petersen M. Christian , Larsen A. Nylandsted
Published: March 2007

Deep level transient spectroscopy and high-resolution Laplace deep level transient spectroscopy were used to investigate alpha-particle irradiation-induced defects in n-type Ge. It is proposed that there is no electrically active divacancy level in the upper half of the band gap. A dominant peak has been observed at alpha-particle doses higher than about 6×1010cm−2. The electronic and annealing properties of the defect have been investigated. The defect is suggested to be a multivacancy complex.
Evidence of enhanced phonon-energy coupling in SiO2∕Si
Authors: Ong Pangleen , Chen Zhi
Published: March 2007

The authors designed special pn junctions to examine the recently discovered phonon-energy-coupling enhancement effect. They found that the breakdown voltage of the silicon substrate is increased by 0.3V after rapid thermal process (RTP), whereas it remains the same for diodes annealed in furnace with the same parameters as those in RTP. The increase in breakdown voltage of silicon is caused neither by dopant redistribution nor increased contact resistance after RTP but due to its intrinsic properties, i.e., stronger Si–Si bonds. The strengthening of Si–Si bonds is caused by coupling of the phonon energy from silicon to thin oxide.
Effects of (NH4)2Sx treatment on electrical properties of indium tin oxide/poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate)
Authors: Lin Yow-Jon , Chang Hsing-Cheng , Liu Bei-Yuan
Published: March 2007

The effects of (NH4)2Sx treatment on the current-voltage characteristics and interfacial properties of the indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT-PSS) samples have been investigated in this study. The authors found that (NH4)2Sx treatment could lead to the improvement of the interfacial stability of ITO/PEDOT-PSS samples. In addition, the current transport at the ITO/PEDOT-PSS interface is governed by the defects induced by interfacial reactions.
Channel width effect on the spin-orbit interaction parameter in a two-dimensional electron gas
Authors: Kwon Jae Hyun , Koo Hyun Cheol , Chang Joonyeon , Han Suk-Hee , Eom Jonghwa
Published: March 2007

The spin splitting energy obtained from the Shubnikov–de Haas oscillation increases with decreasing channel width (w) of the InAs-based heterostructure. Since the surface charge concentration depends only weakly on w, the channel width dependence of the spin splitting energy is attributed to variations in the spin-orbit interaction strength. The spin-orbit interaction parameter was found to be inversely proportional to w in the range of w=2–64μm. Our findings indicate that a strong spin-orbit interaction is induced in a narrow channel due to suppression of the spin precession length for a thin quantum well layer system.
Evaluating the double knockdown technique: sequence, application interval, and annual ryegrass growth stage
Authors: Borger Catherine P. , Hashem Abul
Published: March 2007

Applying glyphosate followed by a mixture of paraquat + diquat in the same season for pre-planting weed control may reduce the risk of developing resistance to either herbicide. Glasshouse and field experiments at Merredin and Beverly, Western Australia, were conducted over 2 seasons to determine the best herbicide application sequence, growth stage of annual ryegrass at which to apply the 2 herbicides, and application time and interval to be allowed between applications for optimum control of annual ryegrass (Lolium rigidum Gaud.). Annual ryegrass plants were treated at 3 growth stages with either glyphosate 540 g a.i./ha alone, paraquat + diquat 250 g a.i./ha alone, glyphosate followed by paraquat + diquat 250 g a.i./ha, or paraquat + diquat 250 g a.i./ha followed by glyphosate 540 g a.i./ha (the double knockdown treatment). The herbicides were applied at different times of the day, with varied intervals between herbicides when applied in sequence. The glasshouse experiment showed that herbicides in sequence more effectively killed annual ryegrass plants at the 3–6-leaf stage than a single application of either herbicide. Field experiments showed that applying glyphosate followed by paraquat + diquat provided 98–100% control of annual ryegrass plants when applied at the 3- or 6-leaf stage in 2002 and at all 3 growth stages in 2003. Generally, the sequence of paraquat + diquat followed by glyphosate was less effective than the reverse sequence, although the difference was not large. Averaged over 2 seasons, herbicides in sequence were most effective when the first herbicide was applied at the 3- or 6-leaf stage of annual ryegrass. An interval of 2–10 days between applications of herbicides was more effective than 1 day or less. The application time did not significantly affect the efficacy of double knockdown herbicides on annual ryegrass plants under field conditions.
Chemical ripeners increase early season sugar content in a range of sugarcane varieties
Authors: Morgan T. , Jackson P. , McDonald L. , Holtum J.
Published: March 2007

Ripening in sugarcane refers to an increase in sugar content on a fresh weight basis before commercial harvest. Certain chemicals are applied to cane in commercial fields in some countries to accelerate ripening and improve profitability of sugar production. However, responses have usually been reported to be variety and environment specific. We examined changes in the sucrose content in the juice extracted from 43 Australian sugarcane (Saccharum spp. hybrid) varieties in response to 4 ripener treatments in the Burdekin region in northern Queensland over 2 years. The 4 treatments applied were ethephon (as Ethrel®) + fluazifop-P butyl (as Fusilade®), Fusilade® alone, glyphosate (as Weedmaster® Duo), and haloxyfop-R methyl (as Verdict®). These treatments were applied in March–April each year and compared with an untreated control. Of particular interest was whether economic responses are possible for Australian varieties harvested in the May and June period when sugar content in cane is usually low. Increases in sucrose (measured by pol) levels in cane juice were observed after combined application of Ethrel + Fusilade (E+F) and after application of glyphosate, although the result for the latter varied between years. These results suggest that opportunities exist in the Australian industry to improve the profitability of early-harvested sugarcane crops, but further research is required to quantify effects on cane yield and responses in diverse environments.
Target and non-target effects on the invertebrate community of Vip cotton, a new insecticidal transgenic
Authors: Whitehouse M. E. A. , Wilson L. J. , Wilson G. A.
Published: March 2007

A new transgenic cotton producing the Vegetative Insecticidal Protein (Vip) is being developed to control Lepidopteran pests, especially Helicoverpa larvae. Before its introduction its efficacy against Helicoverpa larvae under field conditions needs to be confirmed, and any non-target effects it may have on the arthropod community need to be identified. We conducted field trials to compare the arthropod community in unsprayed conventional (Sicala 40) and Vip (Coker 312 Vip3A, event 102) cotton using visual searches, beatsheets, and suction samplers at 2 sites in Australia. At both sites, Vip controlled Helicoverpa larvae leading to much higher boll counts. There were no major differences in either species richness or diversity of the beneficial and non-target communities between Vip and conventional cotton, although cotton cultivar accounted for 2–7% of the variance in arthropod communities. There was no detrimental effect of Vip cotton on egg parasitoids. The number of predatory beetles and the pest mirid Creotiades dilutus (Stål) was higher in the Vip, although the increase in mirids was probably the result of more food (bolls) in the Vip crop. In a small plot experiment, we found higher numbers of whitefly in Vip, but this may be driven by differences in leaf hair between the cotton cultivars. Vip cotton appeared to have little effect on the arthropod community other than on Helicoverpa. As such it has the potential to be a useful tool in the management of Helicoverpa and may relieve resistance pressure on existing Bt cultivars (transgenic cotton containing genes for insecticidal Cry proteins), thereby increasing the durability of both technologies.
A review of the nutritional value of lupins for dairy cows
Authors: White C. L. , Staines V. E. , Staines M. vH.
Published: March 2007

Australia is the world’s leading source of lupin grain, producing ~1 million tonnes annually, of which 30% is used by the domestic livestock industry and the rest is exported for use in animal diets, including dairy cows. The domestic dairy industry uses ~70 000 tonnes annually, mainly as a supplementary feed source in pasture-based systems. Although much published information exists on the nutritive value of lupins for dairy cows, it tends to be fragmented and, in some important instances, exists only in the form of reports or publications outside the mainstream scientific journals. This paper aims to present a critical assessment of the current knowledge regarding the nutritional value of lupins as a feed for dairy cows, and offers recommendations for future research.
For cows grazing pasture or fed diets based on conserved pasture or cereal hay, the mean fractional response to lupin feeding was 0.53 kg milk/kg DM lupins, with a range of 0–0.97 kg/kg. The mean fractional forage substitution rate was 0.54 kg DM/kg lupins, and this appeared to be independent of the type of basal forage.
In experiments using cows fed iso-nitrogenous and iso-energetic total mixed rations, substituting oilseed protein such as soybean meal with cracked lupin grain had no significant effects on yield of milk, fat, and protein, but it reduced milk protein concentration and had mixed effects on fat concentration. There were no significant differences in milk yield or in fat or protein concentration when lupins were substituted for other pulse grains such as faba beans or peas. Treatment of lupin grain with heat or formaldehyde reduced lupin protein degradability in the rumen, but was not shown to have consistent benefits over untreated lupins in terms of increased milk yield.
Substitution of cereal grains with an equivalent weight of lupins in dairy concentrate rations generally resulted in increased yield of milk, fat, and protein, and a higher fat concentration. The higher yield responses in most cases could be explained on the basis of the higher metabolisable energy content of lupins compared with cereal grains, although the contribution from a potentially lower incidence of rumen lactic acidosis could not be discounted.
Feeding Lupinus albus lupins to cows significantly increased the concentration of C18 : 1 in milk and reduced that of C12 : 0–C16 : 0, thus shifting the fatty acid profile of milk towards national dietary guidelines for improved cardiovascular health in human populations.
Although the review lists some recommendations for improving the nutritive value of lupins, current commercially available cultivars possess characteristics that make them attractive as a feedstuff for dairy cows.
Assessment of clonal stability of in vitro regenerated shoots of Macadamia tetraphylla by RAPD analysis
Authors: Mulwa Richard M. S. , Bhalla Prem L.
Published: March 2007

Macadamia nuts constitute an important part of the world nut industry and are highly valued for their health-promoting properties. Macadamia is an open-pollinated crop that takes 8–12 years to bear fruit when multiplied via seeds. The yield and nut quality in seedling plantations are often highly variable, and grafting is currently the most common method for producing nursery trees with reduced variability. We have previously reported on the tissue-culture propagation of macadamia, and in the present study we assessed the clonal integrity of the regenerated shoots. The RAPD profiles of 3 macadamia stock plants and 10 in vitro regenerated lines from each stock plant were analysed to assess the clonal integrity of the shoots regenerated in vitro for micropropagation purposes. The extent of genetic variation between the stock plants and 9 randomly selected seedlings was also assessed. There was no difference in clonal identity between the stock plants and their micropropagated progeny, indicating that clonal micropropagation was possible using enhanced axillary proliferation in macadamia. In contrast, there was a large genetic variation among the seedlings and between the seedlings and stock plants, with genetic distance estimates ranging from 0.121 to 0.637 among seedlings, indicating rampant out-crossing of the macadamia plant.
The response of four perennial grass species to sodium chloride salinity when irrigated with saline waters
Authors: Rogers M. E.
Published: March 2007

The response of 4 temperate grass species (Lolium perenne cv. Victorian, Thinopyrum ponticum cv. Tyrell, Austrodanthonia richardsonii cv. Taranna, A. bipartita cv. Bunderra) to saline irrigated conditions was evaluated over 4 seasons at Tatura in northern Victoria. This experiment followed earlier research where the salt tolerance of ~20 species of grasses was evaluated in the greenhouse. Field plots were established under non-saline conditions and were irrigated with saline water at 1.6, 2.5, and 4.5 dS/m. Measurements made on these plots included dry-matter production, tissue ion (Na+, Cl–, K+, Mg2+, Ca2+) concentrations, in vitro dry-matter digestibility, root distribution, and soil chemistry. Soil salinity (EC1 : 5) and sodicity (SAR1 : 5) levels peaked at 0.30–0.60 m depth and reached 1.3 dS/m and 9.8, respectively, for the highest saline irrigation treatment. Cumulative plant dry-matter production was lower in T. ponticum compared with the Austrodanthonia species and L. perenne at all salinity levels, but in relative terms there was no difference in the salt tolerance among any of the 4 species (the reduction in dry weight at 4.5 dS/m was 10–15% for all species). Leaf tissue concentrations of Na+ and Cl– were significantly lower in A. richardsonii and A. bipartita compared with T. ponticum and L. perenne, and in vitro dry-matter digestibility tended to be greater in L. perenne under saline conditions than in the other 3 species. This research suggests that the 2 native Austrodanthonia species can be grown under moderately saline conditions—either under saline irrigation or in a dryland discharge area—in environments where perennial ryegrass may also be grown.
Effects of altitude on plant-species diversity and productivity in an alpine meadow, Qinghai - Tibetan plateau
Authors: Wang Chang Ting , Long Rui Jun , Wang Qi Ji , Ding Lu Ming , Wang Mei Ping
Published: March 2007

During the growing seasons of 2002 and 2003, biomass productivity and diversity were examined along an altitudinal transect on the south-western slope of Beishan Mountain, Maqin County (33°43′–35°16′N, 98°48′–100°55′E), Qinghai–Tibetan Plateau. Six altitudes were selected, between 3840 and 4435 m. Soil organic matter, soil available N and P and environmental factors significantly affected plant-species diversity and productivity of the alpine meadows. Aboveground biomass declined significantly with increasing altitude (P < 0.05) and it was positively and linearly related to late summer soil-surface temperature. Belowground biomass (0–10-cm depth) was significantly greater at the lowest and highest altitudes than at intermediate locations, associated with water and nutrient availabilities. At each site, the maximum belowground biomass values occurred at the beginning and the end of the growing seasons (P < 0.05). Soil organic matter content, and available N and P were negatively and closely related to plant diversity (species richness, Shannon–Wiener diversity index, and Pielou evenness index).
Casuarina ecology: factors limiting cone production in the drooping sheoak, Allocasuarina verticillata
Authors: Chapman Tamra F. , Paton David C.
Published: March 2007

Allocasuarina verticillata is an important species for biodiversity conservation on Kangaroo Island (South Australia) because it is the primary food source for the endangered glossy black-cockatoo, Calyptorhynchus lathami halmaturinus. Two potentially limiting factors, pollen and soil nutrients, were studied in the context of A. verticillata as foraging habitat for glossy black-cockatoos. Cone production was not limited by the amount of pollen available to female plants. The soils on which A. verticillata occurs on Kangaroo Island were low in nutrients. Available N, P and K were significantly increased via the application of slow-release fertiliser and the added nutrients resulted in a corresponding increase in the productivity of A. verticillata. The additional nutrients increased the number of cones produced on female branches, branch growth and potentially therefore, tree size. Since cone profitability appears to increase with tree size, the additional growth may also result in greater cone profitability in the long term. Adding slow-release fertiliser to small female A. verticillata trees and revegetation on sites with higher concentrations of soil nutrients would benefit the cockatoos. This is because other studies have shown that the cockatoos increase their foraging efficiency by cropping cones from large trees with greater cone profitability and branches with high densities of cones.
Burnt to blazes: landscape fires, resilience and habitat interaction in frequently burnt coastal heath
Authors: Myerscough Peter J. , Clarke Peter J.
Published: March 2007

Four fires burned vegetation on a sand plain on a 4-km stretch of Pleistocene beach ridges between 1980–1981 and 1998. Fires of 1980–81 and 1991 burned the whole area. Those of 1994 and 1998 burned only parts of it. Cover of individual species and bare ground was scored on permanent plots at intervals between 1990 and 1996. Ordination and generalised linear model analysis of the data showed strong spatial variation between dry and wet heaths, four transects and plots within transects. This was strictly conserved through time, owing to the rapid regrowth of abundant resprouting species, most of which, after 1 year, showed little change in cover with increasing time-since-fire. Vegetation of the dry and wet heaths showed no detectable convergence or divergence in similarity with time-since-fire or variation of interval between fires. Changes with time-since-fire were found, and some change with the length of fire interval, owing to variation in cover of obligate-seeder species, which increased steadily with time up to 10 years since fire, and showed some decrease when fire interval decreased to 3.75 years. At 10 years since fire, obligate-seeder species reached ~25% of the totalled cover scores for all species, with 75% from resprouting species. Dry and wet heath were broadly similar in their general pattern of regrowth after fire, but in dry heath bare ground was more slowly covered than in wet heath, and wet heath had a higher cover of monocotyledons, especially restiads and sedges. Wet heath was more flammable than dry heath in the patchy fire of 1998. The heaths observed appeared highly resilient to recent fire regimes. Resprouting species always dominated their canopy; none of their obligate-seeding species formed a dominant overstorey canopy.
Comparison of fungal endophyte communities in the invasive panicoid grass Hyparrhenia hirta and the native grass Bothriochloa macra
Authors: White Ian R. , Backhouse David
Published: March 2007

Communities of fungal endophytes from roots, stems and leaves of the introduced grass Hyparrhenia hirta (Coolatai grass) and the native species Bothriochloa macra (redgrass) were compared at two sites to identify characteristics that may be associated with invasiveness of H. hirta. The most frequently isolated fungi from both hosts were species of Nigrospora, Alternaria, Cladosporium, Phoma, Epicoccum, Fusarium and Periconia. Most of these occurred at a similar frequency in the two hosts, although Nigrospora sphaerica was much more frequently isolated from H. hirta at both sites. There was little support for the hypothesis that the introduced species (H. hirta) would have a less diverse endophyte community than the native species. There was a greater degree of dominance by the most frequent species in communities from H. hirta than from B. macra, leading to lower diversity indices, but no significant difference in species richness. Cluster analysis of the endophyte communities suggested that host had a greater influence than site on community structure, and that this was expressed mostly in the relative frequency of fungi isolated from stems and leaves, with very similar fungal communities present in the roots of both species at both sites. Analysis of co-occurrence showed no evidence that competition among fungi affected community structure within individual plants. The dominance of N. sphaerica in H. hirta was therefore due to fungus–plant interactions rather than fungus–fungus interactions. Interactions with N. sphaerica could potentially affect the population ecology of H. hirta.
Microtubule function in fibroblast spreading is modulated according to the tension state of cell–matrix interactions
Authors: Rhee Sangmyung , Jiang Hongmei , Ho Chin-Han , Grinnell Frederick
Published: March 2007

Mechanical and physical features of the extracellular environment dramatically impact cell shape. Fibroblasts interacting with 3D relaxed collagen matrices appear much different from cells on 2D collagen-coated surfaces and form dendritic cell extensions that contain microtubule cores and actin-rich tips. We found that interfering with cellular microtubules caused cells in relaxed matrices to remain round and unable to form dendritic extensions, whereas fibroblasts on coverslips formed lamellipodial extensions and were spread completely without microtubules but were unable to become polarized. Fibroblasts in relaxed collagen matrices lack stress fibers, focal adhesions, and focal adhesion signaling. Fibroblasts on collagen-coated coverslips that were unable to develop stress fibers and focal adhesions, because of either adding blebbistatin to the cells or use of soft coverslips, also formed microtubule-dependent dendritic extensions. Conversely, fibroblasts interacting with precontracted collagen matrices developed stress fibers and lamellipodial extensions and required microtubules for polarization but not spreading. Our findings demonstrate an unexpected relationship between the role of microtubules in cell spreading and the tension state of cell–matrix interactions. At a low tension state (absence of stress fibers and focal adhesions) typical of fibroblasts in relaxed collagen matrices, cells spread with dendritic extensions whose formation requires microtubules; at a high tension state (stress fibers and focal adhesions) typical of cells on coverslips, cells spread with lamellipodial extensions and microtubules are required for cell polarization but not for spreading.
A role for a complex between activated G protein-coupled receptors in yeast cellular mating
Authors: Shi Chunhua , Kaminskyj Susan , Caldwell Sarah , Loewen Michèle C.
Published: March 2007

Cell-cell fusion is a fundamental process that facilitates a wide variety of biological events in organisms ranging from yeast to humans. However, relatively little is actually understood with respect to fusion mechanisms. In the model organism
Saccharomyces cerevisiae
, mating of opposite-type cells is triggered by pheromone activation of the G protein-coupled receptors, α-factor receptor (Ste2p) and a-factor receptor (Ste3p), leading to mitogen-activated protein kinase signaling, growth arrest, and cellular fusion events. Herein we now provide evidence of a role for these receptors in the later cell fusion stage of mating.
In vitro
assays demonstrated the ability of the receptors to promote mixing of proteoliposomes containing phosphatidylserine, potentially based on a pheromone-dependent interaction between Ste2p and Ste3p that was confirmed by tandem affinity purification and cellular pull-down assays. The cellular mating activity of Ste2p was subsequently probed
in vivo
. Notably, a receptor-null yeast strain expressing N-terminally truncated Ste2p yielded a phenotype demonstrating wild-type signaling but arrested mating. The arrested prezygotes showed evidence of some cell wall erosion but no membrane juxtaposition at the fusion site. Further,
in vitro
analyses correlated this mutation with loss of the interaction between Ste2p and Ste3p and inhibition of related lipid mixing. Overall, these results support a role for a complex between activated yeast pheromone receptors in later cell fusion stages of mating, possibly mediating events at the level of cell wall digestion and membrane juxtaposition before membrane fusion.
Impaired clock output by altered connectivity in the circadian network
Authors: Fernández María de la Paz , Chu Jessie , Villella Adriana , Atkinson Nigel , Kay Steve A. , Ceriani María Fernanda
Published: March 2007

Substantial progress has been made in elucidating the molecular processes that impart a temporal control to physiology and behavior in most eukaryotes. In
Drosophila
, dorsal and ventral neuronal networks act in concert to convey rhythmicity. Recently, the hierarchical organization among the different circadian clusters has been addressed, but how molecular oscillations translate into rhythmic behavior remains unclear. The small ventral lateral neurons can synchronize certain dorsal oscillators likely through the release of pigment dispersing factor (PDF), a neuropeptide central to the control of rhythmic rest-activity cycles. In the present study, we have taken advantage of flies exhibiting a distinctive arrhythmic phenotype due to mutation of the potassium channel
slowpoke (slo)
to examine the relevance of specific neuronal populations involved in the circadian control of behavior. We show that altered neuronal function associated with the null mutation specifically impaired PDF accumulation in the dorsal protocerebrum and, in turn, desynchronized molecular oscillations in the dorsal clusters. However, molecular oscillations in the small ventral lateral neurons are properly running in the null mutant, indicating that
slo
is acting downstream of these core pacemaker cells, most likely in the output pathway. Surprisingly, disrupted PDF signaling by
slo
dysfunction directly affects the structure of the underlying circuit. Our observations demonstrate that subtle structural changes within the circadian network are responsible for behavioral arrhythmicity.