bluuebunny/crossref_metadata_2025 huggingface dataset:
Simultaneous and accurate measurement of the dielectric constant at many frequencies spanning a wide range
Authors: Pérez-Aparicio Roberto , Crauste-Thibierge Caroline , Cottinet Denis , Tanase Marius , Metz Pascal , Bellon Ludovic , Naert Antoine , Ciliberto Sergio
Published: April 2015

We present an innovative technique which allows the simultaneous measurement of the dielectric constant of a material at many frequencies, spanning a four orders of magnitude range chosen between 10−2 Hz and 104 Hz. The sensitivity and accuracy are comparable to those obtained using standard single frequency techniques. The technique is based on three new and simple features: (a) the precise real time correction of the amplification of a current amplifier, (b) the specific shape of the excitation signal and its frequency spectrum, and (c) the precise synchronization between the generation of the excitation signal and the acquisition of the dielectric response signal. This technique is useful in the case of relatively fast dynamical measurements when the knowledge of the time evolution of the dielectric constant is needed.
The separation of vibrational coherence from ground- and excited-electronic states in P3HT film
Authors: Song Yin , Hellmann Christoph , Stingelin Natalie , Scholes Gregory D.
Published: April 2015

Concurrence of the vibrational coherence and ultrafast electron transfer has been observed in polymer/fullerene blends. However, it is difficult to experimentally investigate the role that the excited-state vibrational coherence plays during the electron transfer process since vibrational coherence from the ground- and excited-electronic states is usually temporally and spectrally overlapped. Here, we performed 2-dimensional electronic spectroscopy (2D ES) measurements on poly(3-hexylthiophene) (P3HT) films. By Fourier transforming the whole 2D ES datasets (S(λ1,T̃2,λ3)) along the population time (T̃2) axis, we develop and propose a protocol capable of separating vibrational coherence from the ground- and excited-electronic states in 3D rephasing and nonrephasing beating maps (S(λ1,ν̃2,λ3)). We found that the vibrational coherence from pure excited electronic states appears at positive frequency (+ν̃2) in the rephasing beating map and at negative frequency (−ν̃2) in the nonrephasing beating map. Furthermore, we also found that vibrational coherence from excited electronic state had a long dephasing time of 244 fs. The long-lived excited-state vibrational coherence indicates that coherence may be involved in the electron transfer process. Our findings not only shed light on the mechanism of ultrafast electron transfer in organic photovoltaics but also are beneficial for the study of the coherence effect on photoexcited dynamics in other systems.
Effect of adatom deposition on surface magnetism and exchange coupling parameter in (0001) SmCo5 slabs
Authors: Selva Chandrasekaran S. , Murugan P. , Saravanan P. , Kamat S. V.
Published: April 2015

First principles calculations are performed on 3d-transition metal atom deposited (0001) surface of SmCo5 to understand the magnetic properties and the improvement of Curie temperature (Tc). Various atomic sites are examined to identify the energetically feasible adsorption of adatom and it is found that the void site of Co-rich (0001) SmCo5 surface is the most favourable one to deposit. The surface magnetic moments of various adatom deposited SmCo5 surfaces are larger than the clean surface except for Cu and Zn. Eventually, the surface exchange coupling of clean and adatom deposited surface is found to increase for Mn, Fe, Co, Ni, and Cu deposited surfaces and this improvement results in the increase in Tc of SmCo5 slab.
Theoretical study on phase coexistence in ferroelectric solid solutions near the tricritical point
Authors: Lu Xiaoyan , Zheng Limei , Li Hui , Cao Wenwu
Published: April 2015

Phase coexistence in ferroelectric solid solutions near the tricritical point has been theoretically analyzed by using the Landau-Devonshire theory. Results revealed that different phases having similar potential wells could coexist in a narrow composition range near the tricritical point in the classical Pb(Zr1−xTix)O3 system. The potential barrier between potential wells increases with the decrease of temperature. Coexisting phases or different domains of the same phase can produce adaptive strains to maintain atomic coherency at the interfaces or domain walls. Such compatibility strains have influence on the energy potential as well as the stability of relative phases, leading to the appearance of energetically unfavorable monoclinic phases. Those competing and coexisting phases also construct an easy phase transition path with small energy barrier in between, so that very small stimuli can produce large response in compositions near the morphotropic phase boundary, especially near the tricritical point.
Dense nanoimprinted silicon nanowire arrays with passivated axial p-i-n junctions for photovoltaic applications
Authors: Zhang Peng , Liu Pei , Siontas Stylianos , Zaslavsky A. , Pacifici D. , Ha Jong-Yoon , Krylyuk S. , Davydov A. V.
Published: April 2015

We report on the fabrication and photovoltaic characteristics of vertical arrays of silicon axial p-i-n junction nanowire (NW) solar cells grown by vapor-liquid-solid (VLS) epitaxy. NW surface passivation with silicon dioxide shell is shown to enhance carrier recombination time, open-circuit voltage (VOC), short-circuit current density (JSC), and fill factor (FF). The photovoltaic performance of passivated individual NW and NW arrays was compared under 532 nm laser illumination with power density of ∼10 W/cm2. Higher values of VOC and FF in the NW arrays are explained by enhanced light trapping. In order to verify the effect of NW density on light absorption and hence on the photovoltaic performance of NW arrays, dense Si NW arrays were fabricated using nanoimprint lithography to periodically arrange the gold seed particles prior to epitaxial growth. Compared to sparse NW arrays fabricated using VLS growth from randomly distributed gold seeds, the nanoimprinted NW array solar cells show a greatly increased peak external quantum efficiency of ∼8% and internal quantum efficiency of ∼90% in the visible spectral range. Three-dimensional finite-difference time-domain simulations of Si NW periodic arrays with varying pitch (P) confirm the importance of high NW density. Specifically, due to diffractive scattering and light trapping, absorption efficiency close to 100% in the 400–650 nm spectral range is calculated for a Si NW array with P = 250 nm, significantly outperforming a blanket Si film of the same thickness.
Surface oxidation energetics and kinetics on MoS2 monolayer
Authors: KC Santosh , Longo Roberto C. , Wallace Robert M. , Cho Kyeongjae
Published: April 2015

In this work, surface oxidation of monolayer MoS2 (one of the representative semiconductors in transition-metal dichalcogenides) has been investigated using density functional theory method. Oxygen interaction with MoS2 shows that, thermodynamically, the surface tends to be oxidized. However, the dissociative absorption of molecular oxygen on the MoS2 surface is kinetically limited due to the large energy barrier at low temperature. This finding elucidates the air stability of MoS2 surface in the atmosphere. Furthermore, the presence of defects significantly alters the surface stability and adsorption mechanisms. The electronic properties of the oxidized surface have been examined as a function of oxygen adsorption and coverage as well as substitutional impurities. Our results on energetics and kinetics of oxygen interaction with the MoS2 monolayer are useful for the understanding of surface oxidation, air stability, and electronic properties of transition-metal dichalcogenides at the atomic scale.
Tunable permittivity and permeability of low loss Z + Y-type ferrite composites for ultra-high frequency applications
Authors: Su Zhijuan , Li Qifan , Wang Xian , Hu Bolin , Feng Zekun , Chen Yajie , Harris Vincent G.
Published: April 2015

A series of Z-type and Y-type ferrite composites with various phase fractions were studied for their RF properties including the measurement of permittivity to permeability spectra over a frequency range of 0.1–10 GHz. Phase identification of the ferrite composites' constituents was determined by X-ray diffraction. An effective medium approximation was used to predict the magnetic and dielectric behavior of the composites. The experiments indicated that the composite having 75 vol. % of Z-type ferrite demonstrated a permeability of ∼12 with a nearly equivalent permittivity, yielding a ratio (μ′/ε′) of 0.91 at a frequency range from 0.55 to 0.75 GHz. The dielectric loss (i.e., tan δε) and magnetic loss (i.e., tan δμ) were measured to be lower than 0.08 at f = 0.1–1 GHz and 0.29 at f = 0.1–0.7 GHz, respectively. Furthermore, the loss factors, as tan δε/ε′ and tan δμ/μ′, were calculated to be 0.003 and 0.02 at 0.65 GHz, respectively.
Model-independent measurement of the charge density distribution along an Fe atom probe needle using off-axis electron holography without mean inner potential effects
Authors: Migunov V. , London A. , Farle M. , Dunin-Borkowski R. E.
Published: April 2015

The one-dimensional charge density distribution along an electrically biased Fe atom probe needle is measured using a model-independent approach based on off-axis electron holography in the transmission electron microscope. Both the mean inner potential and the magnetic contribution to the phase shift are subtracted by taking differences between electron-optical phase images recorded with different voltages applied to the needle. The measured one-dimensional charge density distribution along the needle is compared with a similar result obtained using model-based fitting of the phase shift surrounding the needle. On the assumption of cylindrical symmetry, it is then used to infer the three-dimensional electric field and electrostatic potential around the needle with ∼10 nm spatial resolution, without needing to consider either the influence of the perturbed reference wave or the extension of the projected potential outside the field of view of the electron hologram. The present study illustrates how a model-independent approach can be used to measure local variations in charge density in a material using electron holography in the presence of additional contributions to the phase, such as those arising from changes in mean inner potential and specimen thickness.
A comparison of numerical simulations and analytical theory of the dynamics of interacting magnetic vortices
Authors: Asmat-Uceda Martin , Cheng Xuemei , Wang Xiao , Clarke David J. , Tchernyshyov Oleg , Buchanan Kristen S.
Published: April 2015

Magnetostatic interactions between vortices in closely spaced planar structures are important for applications including vortex-based magnonic crystals and spin torque oscillator networks. Analytical theories that include magnetostatic interaction effects have been proposed but have not yet been rigorously tested. Here, we compare micromagnetic simulations of the dynamics of magnetic vortices confined in three disks in an equilateral triangle configuration to analytical theories that include coupling. Micromagnetic simulations show that the magnetostatic coupling between the disks leads to splitting of the gyrotropic resonance into three modes and that the frequency splitting increases with decreasing separation. The temporal profiles of the magnetization depend on the vortex polarities and chiralities; however, the frequencies depend only on the polarity combinations and will fall into one of two categories: all polarities equal or one polarity opposite to the others, where the latter leads to a larger frequency splitting. Although the magnitude of the splitting observed in the simulations is larger than what is expected based on purely dipolar interactions, a simple analytical model that assumes dipole-dipole coupling captures the functional form of the frequency splitting and the motion patterns just as well as more complex models.
Superfluid response of two-dimensional parahydrogen clusters in confinement
Authors: Idowu Saheed , Boninsegni Massimo
Published: April 2015

We study by computer simulations the effect of confinement on the superfluid properties of small two-dimensional (2D) parahydrogen clusters. For clusters of fewer than twenty molecules, the superfluid response in the low temperature limit is found to remain comparable in magnitude to that of free clusters, within a rather wide range of depth and size of the confining well. The resilience of the superfluid response is attributable to the “supersolid” character of these clusters. We investigate the possibility of establishing a bulk 2D superfluid “cluster crystal” phase of p-H2, in which a global superfluid response would arise from tunnelling of molecules across adjacent unit cells. The computed energetics suggests that for clusters of about ten molecules, such a phase may be thermodynamically stable against the formation of the equilibrium insulating crystal, for values of the cluster crystal lattice constant possibly allowing tunnelling across adjacent unit cells.
Entry effects of droplet in a micro confinement: Implications for deformation-based circulating tumor cell microfiltration
Authors: Zhang Zhifeng , Chen Xiaolin , Xu Jie
Published: April 2015

Deformation-based circulating tumor cell (CTC) microchips are a representative diagnostic device for early cancer detection. This type of device usually involves a process of CTC trapping in a confined microgeometry. Further understanding of the CTC flow regime, as well as the threshold passing-through pressure, is a key to the design of deformation-based CTC filtration devices. In the present numerical study, we investigate the transitional deformation and pressure signature from surface tension dominated flow to viscous shear stress dominated flow using a droplet model. Regarding whether CTC fully blocks the channel inlet, we observe two flow regimes: CTC squeezing and shearing regime. By studying the relation of CTC deformation at the exact critical pressure point for increasing inlet velocity, three different types of cell deformation are observed: (1) hemispherical front, (2) parabolic front, and (3) elongated CTC co-flowing with carrier media. Focusing on the circular channel, we observe a first increasing and then decreasing critical pressure change with increasing flow rate. By pressure analysis, the concept of optimum velocity is proposed to explain the behavior of CTC filtration and design optimization of CTC filter. Similar behavior is also observed in channels with symmetrical cross sections like square and triangular but not in rectangular channels which only results in decreasing critical pressure.
Note: A simple vibrating orifice monodisperse droplet generator using a hard drive actuator arm
Authors: Kosch Sebastian , Ashgriz Nasser
Published: April 2015

We propose that the rotary voice coil actuators found in magnetic hard drives are fit to supercede loudspeakers as expedient vibration sources in the laboratory setting. A specific use case is the excitation of a liquid jet to induce controlled breakup into monodisperse droplets. Like loudspeakers, which are typically used for prototyping such devices, hard drive actuators are cheap and ubiquitous, but they are less unwieldy and supply greater amplitudes without producing noise. Frequencies between 0 and 17 kHz, and likely beyond, can be reproduced reliably. No machining tools or amplifying electronics are needed for the construction and operation of the presented droplet generator.
Defect-reduction mechanism for improving radiative efficiency in InGaN/GaN light-emitting diodes using InGaN underlayers
Authors: Armstrong Andrew M. , Bryant Benjamin N. , Crawford Mary H. , Koleske Daniel D. , Lee Stephen R. , Wierer Jonathan J.
Published: April 2015

The influence of a dilute InxGa1-xN (x ∼ 0.03) underlayer (UL) grown below a single In0.16Ga0.84N quantum well (SQW), within a light-emitting diode (LED), on the radiative efficiency and deep level defect properties was studied using differential carrier lifetime (DCL) measurements and deep level optical spectroscopy (DLOS). DCL measurements found that inclusion of the UL significantly improved LED radiative efficiency. At low current densities, the non-radiative recombination rate of the LED with an UL was found to be 3.9 times lower than the LED without an UL, while the radiative recombination rates were nearly identical. This suggests that the improved radiative efficiency resulted from reduced non-radiative defect concentration within the SQW. DLOS measurement found the same type of defects in the InGaN SQWs with and without ULs. However, lighted capacitance-voltage measurements of the LEDs revealed a 3.4 times reduction in a SQW-related near-mid-gap defect state for the LED with an UL. Quantitative agreement in the reduction of both the non-radiative recombination rate (3.9×) and deep level density (3.4×) upon insertion of an UL corroborates deep level defect reduction as the mechanism for improved LED efficiency.
Ferroelectric capped magnetization in multiferroic PZT/LSMO tunnel junctions
Authors: Kumar Ashok , Barrionuevo D. , Ortega N. , Shukla A. K. , Shannigrahi Santiranjan , Scott J. F. , Katiyar Ram S.
Published: April 2015

Self-poled ultra-thin ferroelectric PbZr0.52Ti0.48O3 (PZT) (5 and 7 nm) films have been grown by pulsed laser deposition technique on ferromagnetic La0.67Sr0.33MnO3 (LSMO) (30 nm) to check the effect of polar capping on magnetization for ferroelectric tunnel junction devices. PZT/LSMO heterostructures with thick polar PZT (7 nm) capping show nearly 100% enhancement in magnetization compared with thin polar PZT (5 nm) films, probably due to excess hole transfer from the ferroelectric to the ferromagnetic layers. Core-level x-ray photoelectron spectroscopy studies revealed the presence of larger Mn 3s exchange splitting and higher Mn3+/Mn4+ ion ratio in the LSMO with 7 nm polar capping.
Surface plasmon resonances of Ag-Au alloy nanoparticle films grown by sequential pulsed laser deposition at different compositions and temperatures
Authors: Verma Shweta , Rao B. T. , Detty A. P. , Ganesan V. , Phase D. M. , Rai S. K. , Bose A. , Joshi S. C. , Kukreja L. M.
Published: April 2015

We studied localized surface plasmon resonances (LSPR) at different compositions, substrate temperatures, and mass thicknesses of Ag-Au alloy nanoparticle films grown by sequential pulsed laser deposition. The LSPRs were pronounced at all compositions of the films grown at high substrate temperature of about 300 °C as compared to those grown at room temperature. The alloy formation and composition of the films were determined using X-ray photoelectron and energy dispersive spectroscopy. Films' mass thickness and compositional uniformity along the thickness were determined using X-ray reflectometry and secondary ion mass spectroscopy. Atomic force microscopic analysis revealed the formation of densely packed nanoparticles of increasing size with the number of laser ablation pulses. The LSPR wavelength red shifted with increasing either Au percentage or film mass thickness and corresponding LSPR tuning was obtained in the range of 450 to 690 nm. The alloy dielectric functions obtained from three different models were compared and the optical responses of the nanoparticle films were calculated from modified Yamaguchi effective medium theory. The tuning of LSPR was found to be due to combined effect of change in intrinsic and extrinsic parameters mainly the composition, morphology, particle-particle, and particle-substrate interactions.
Design of hybrid nanoheterostructure systems for enhanced quantum and solar conversion efficiencies in dye-sensitized solar cells
Authors: Kılıç Bayram , Telli Hakan , Tüzemen Sebahattin , Başaran Ali , Pirge Gursev
Published: April 2015

Dye sensitized solar cells (DSSCs) with an innovative design involving controlled-morphology vertically aligned (VA) ZnO nanowires within mesoporous TiO2 structures with ultrahigh surface area for implementation as photoanodes are herein reported. Although TiO2 nanostructures exhibit excellent power conversion efficiency, the electron transport rate is low owing to low electron mobility. To overcome this, ZnO nanowires with high electron mobility have been investigated as potential candidates for photoanodes. However, the power conversion efficiency of ZnO nanowires is still lower than that of TiO2 owing to their low internal surface area. Consequently, in this work, vertical growth of ZnO nanowires within mesoporous TiO2 structures is carried out to increase their solar power conversion efficiency. The photovoltaic performance of solar cells using ZnO nanowires, mesoporous TiO2, and TiO2/ZnO hybrid structures are compared. The VA TiO2/ZnO hybrid structures are found to provide direct electron transfer compared with the tortuous pathway of zero-dimensional nanostructures, resulting in an increased conversion efficiency. It is demonstrated that the light scattering of the photoanode film is increased and electron recombination is decreased when an appropriate amount of mesoporous TiO2 is used as a substrate for ZnO nanowires. The DSSC fabricated with the TiO2/ZnO hybrid photoanode prepared with 15.8 wt. % TiO2 showed the highest conversion efficiency of 7.30%, approximately 5%, 18%, and 40% higher than that of DSSCs fabricated with 3.99 wt. % TiO2, pure TiO2, and pure ZnO photoanodes, respectively.
Formation of a hybrid plasmonic waveguide mode probed by dispersion measurement
Authors: Saito H. , Kurata H.
Published: April 2015

Hybrid waveguides, i.e., dielectric waveguides combined with plasmonic waveguides, have great potential for concomitantly exhibiting subwavelength confinement and long range propagation, enabling a highly integrated photonic circuit. We report the characterization of hybrid waveguide modes excited in Si/SiO2/Al films, by dispersion measurement using angle-resolved electron energy-loss spectroscopy. This experiment directly verifies the formation of the hybrid waveguide mode with a strongly localized electromagnetic field in a 6-nm-thick SiO2 layer. The results clearly describe the characteristic behavior of the hybrid waveguide mode, which depends on the effective index of the constituent dielectric waveguide and the surface plasmon-polariton modes.
Atomistic origins of CH3NH3PbI3 degradation to PbI2 in vacuum
Authors: Deretzis I. , Alberti A. , Pellegrino G. , Smecca E. , Giannazzo F. , Sakai N. , Miyasaka T. , La Magna A.
Published: April 2015

We study the mechanisms of CH3NH3PbI3 degradation and its transformation to PbI2 by means of X-ray diffraction and the density functional theory. The experimental analysis shows that the material can degrade in both air and vacuum conditions, with humidity and temperature-annealing strongly accelerating such process. Based on ab initio calculations, we argue that even in the absence of humidity, a decomposition of the perovskite structure can take place through the statistical formation of molecular defects with a non-ionic character, whose volatility at surfaces should break the thermodynamic defect equilibria. We finally discuss the strategies that can limit such phenomenon and subsequently prolong the lifetime of the material.
Periodically distributed objects with quasicrystalline diffraction pattern
Authors: Wolny Janusz , Kuczera Pawel , Strzalka Radoslaw
Published: April 2015

It is possible to construct fully periodically distributed objects with a diffraction pattern identical to the one obtained for quasicrystals. These objects are probability distributions of distances obtained in the statistical approach to aperiodic structures distributed periodically. The diffraction patterns have been derived by using a two-mode Fourier transform—a very powerful method not used in classical crystallography. It is shown that if scaling is present in the structure, this two-mode Fourier transform can be reduced to a regular Fourier transform with appropriately rescaled scattering vectors and added phases. Detailed case studies for model sets 1D Fibonacci chain and 2D Penrose tiling are discussed. Finally, it is shown that crystalline, quasicrystalline, and approximant structures can be treated in the same way.
An experimental study of plasma aerodynamic actuation on a round jet in cross flow
Authors: Dai Sheng-ji , Xiao Yang , He Li-ming , Jin Tao , Zhang Qian , Hou Peng-hui , Zhao Zi-chen
Published: April 2015

The present paper is performed on the effect of plasma aerodynamic actuation on a round jet in cross flow field with a low Reynolds number by using smoke visualization. The actuator is constituted by an electrode pair separated by a dielectric Al2O3 sheet. Several AC supply conditions are utilized. The experimental result shows a closing-in tendency of the jet flow toward the wall after being induced by plasma aerodynamic actuation, and such tendency is increasingly intensified as the actuation voltage increases. Numerical simulation is also performed. The simulation results show that an induced vortex pair is generated by plasma aerodynamic actuation near the wall flow field. The rotation direction of the induced vortex pair reverses against the counter-rotating vortex pair generated by a round jet in a cross flow without plasma aerodynamic actuation. Then the strength and structural size of the counter-rotating vortex pair are significantly reduced, resulting in the intensified near-wall effect of the jet flow. Three electrode-typed actuators (straight, 150°-elliptic arc and 180°-elliptic arc with the same streamwise extent) are placed at the exit of round jet to research the influence of electrode structure on jet in cross flow. The result shows that the longer the arc electrode surrounding the hole, the stronger the induced jet that flow near the wall is.
Observation of longitudinal spin-Seebeck effect in cobalt-ferrite epitaxial thin films
Authors: Niizeki Tomohiko , Kikkawa Takashi , Uchida Ken-ichi , Oka Mineto , Suzuki Kazuya Z. , Yanagihara Hideto , Kita Eiji , Saitoh Eiji
Published: April 2015

The longitudinal spin-Seebeck effect (LSSE) has been investigated in cobalt ferrite (CFO), an exceptionally hard magnetic spinel ferrite. A bilayer of a polycrystalline Pt and an epitaxially-strained CFO(110) exhibiting an in-plane uniaxial anisotropy was prepared by reactive rf sputtering technique. Thermally generated spin voltage in the CFO layer was measured via the inverse spin-Hall effect in the Pt layer. External-magnetic-field (H) dependence of the LSSE voltage (VLSSE) in the Pt/CFO(110) sample with H ∥ [001] was found to exhibit a hysteresis loop with a high squareness ratio and high coercivity, while that with H∥[11̄0] shows a nearly closed loop, reflecting the different anisotropies induced by the epitaxial strain. The magnitude of VLSSE has a linear relationship with the temperature difference (ΔT), giving the relatively large VLSSE /ΔT of about 3 μV/K for CFO(110) which was kept even at zero external field.
Dangling DNA pinpoints a protein’s chemical groups
Authors: Miller Johanna L.
Published: April 2015

A short, single-stranded nucleic acid chain attached to the tip of an atomic force microscope can locate its complement with high resolution and specificity.
A newly found pair of stars appears destined to merge and explode
Authors: Wilson R. Mark
Published: April 2015

An analysis of their orbits and masses indicates that the pair is a plausible supernova progenitor.
Science envoys five years on
Authors: Kramer David
Published: April 2015

Prominent US scientists and engineers have been reaching out to strengthen ties and assist their colleagues in developing nations.
Resource use and environmental impacts from Australian export lamb production: a life cycle assessment
Authors: Wiedemann S. G. , Yan M.-J. , Murphy C. M.
Published: April 2015

This study conducted a life cycle assessment (LCA) investigating energy, land occupation, greenhouse gas (GHG) emissions, fresh water consumption and stress-weighted water use from production of export lamb in the major production regions of New South Wales, Victoria and South Australia. The study used data from regional datasets and case study farms, and applied new methods for assessing water use using detailed farm water balances and water stress weighting. Land occupation was assessed with reference to the proportion of arable and non-arable land and allocation of liveweight (LW) and greasy wool was handled using a protein mass method. Fossil fuel energy demand ranged from 2.5 to 7.0 MJ/kg LW, fresh water consumption from 58.1 to 238.9 L/kg LW, stress-weighted water use from 2.9 to 137.8 L H2O-e/kg LW and crop land occupation from 0.2 to 2.0 m2/kg LW. Fossil fuel energy demand was dominated by on-farm energy demand, and differed between regions and datasets in response to production intensity and the use of purchased inputs such as fertiliser. Regional fresh water consumption was dominated by irrigation water use and losses from farm water supply, with smaller contributions from livestock drinking water. GHG emissions ranged from 6.1 to 7.3 kg CO2-e/kg LW and additional removals or emissions from land use (due to cultivation and fertilisation) and direct land-use change (due to deforestation over previous 20 years) were found to be modest, contributing between –1.6 and 0.3 kg CO2-e/kg LW for different scenarios assessing soil carbon flux. Excluding land use and direct land-use change, enteric CH4 contributed 83–89% of emissions, suggesting that emissions intensity can be reduced by focussing on flock production efficiency. Resource use and emissions were similar for export lamb production in the major production states of Australia, and GHG emissions were similar to other major global lamb producers. The results show impacts from lamb production on competitive resources to be low, as lamb production systems predominantly utilised non-arable land unsuited to alternative food production systems that rely on crop production, and water from regions with low water stress.
Evaluating the feasibility of dual-purpose canola in a medium-rainfall zone of south-eastern Australia: a simulation approach
Authors: McCormick Jeffrey I. , Virgona Jim M. , Lilley Julianne M. , Kirkegaard John A.
Published: April 2015

Canola (Brassica napus L.) has recently been adopted as a dual-purpose crop (graze and grain) in the higher rainfall areas (>550 mm) of eastern Australia, but the feasibility in drier inland areas with a shorter growing season is uncertain. We modified the APSIM-Canola model by using observations from an irrigated grazing experiment, with the aim of using a simulation approach to investigate various aspects of dual-purpose canola production. Sowing opportunities, forage production for grazing and grain production were considered in the simulations, and effects of variables such as sowing date, cultivar type, plant density and nitrogen supply were investigated in simulations for 109 years of climate data from Wagga Wagga, NSW. APSIM-Canola predictions of vegetative growth and grain yield for recent varieties were inadequate when using existing parameters, but were improved by increasing the maximum leaf area parameter to reflect those of modern hybrid types. For grazed crops, APSIM-Canola overestimated the initial rate of regrowth, but accurately simulated biomass at flowering. Simulations of a range of management options to generate different pre-grazing biomass predicted that sowing before 15 May, using vigorous (hybrid) cultivars, high plant density (60–80 plants m–2) and adequate soil nitrogen, maximised biomass production. Assuming a rainfall-based sowing opportunity of 25 mm over 3 days and a minimum pre-grazing biomass of 1000 kg ha–1, grazing was possible in 53% of years, with 50% of those years providing grazing opportunities before 7 June at Wagga Wagga. Depending on stocking rate, crops could be grazed until early to mid-July, providing 400–1000 dry sheep equivalent days ha–1 of grazing, and allow regrowth to achieve a target biomass of 5000 kg ha–1 at flowering, which was required to maximise potential yield. The simulation analysis confirms significant opportunities to achieve valuable livestock grazing from canola crops sown in an early window (before May) without compromising potential yield, and the simulation framework developed can be readily applied to other regions.
The role and value of combining dual-purpose crops and lucerne in a mixed-enterprise farming system
Authors: Kingwell R. , Squibb L.
Published: April 2015

In Mediterranean-type environments, livestock productivity in mixed livestock and cropping enterprises often is limited by a period of feed scarcity that extends from late autumn, when dry residues of crops and pastures from the previous growing season are being exhausted, through to early winter when green feed is just commencing. Dual-purpose crops have been developed as a source of winter green feed, while still being a source of grain at harvest. These crops increase feed availability and boost livestock productivity. This study evaluates the role and value of dual-purpose wheat and canola crops, in combination with lucerne, in mixed-enterprise farming systems that experience a Mediterranean-type climate. Using bioeconomic modelling, the value of dual-purpose crops is assessed under a range of yield, price and technical assumptions. For an Australian study region, the robust finding is that the joint inclusion of dual-purpose crops and lucerne greatly increases the farming-system profits. Under standard assumptions when the farming system is operated to maximise profit, farm profit increases by AU$68 000 (or 88% over the base case) following the inclusion of both dual-purpose wheat and canola. The increase in profit is attributable to wool and sheep sales rising by 261%, yet the proportions of crop and pasture remain similar with or without the dual-purpose crops. Importantly, the proportion of the pasture area that is lucerne greatly increases to complement the increase in feed availability generated by the dual-purpose crops. The resultant large increase in feed availability in winter and summer allows the stocking rate to increase so sheep numbers and sheep turn-off become the main source of the increase in profit. Sensitivity analysis shows that even with significant commodity price fluctuations and further reduction in grain yield caused by grazing, and exclusion of lucerne, inclusion of dual-purpose crops in these farming systems still increases farm profit.
Small effects of deferment of annual pastures through grazing spring wheat crops in Western Australia can benefit livestock productivity
Authors: Thomas Dean T. , Moore Andrew D. , Norman Hayley C. , Revell Clinton K.
Published: April 2015

Grazing sheep on cereal crops in winter has become widely adopted in medium–high-rainfall zones of Australia. Interest in this practice has spread to the lower rainfall parts of the cereal–livestock zone where it is being applied to shorter season crop varieties. A farm-system modelling study was conducted to investigate the value of deferment of annual pastures by grazing spring wheat in their place. The biophysical simulation model, based on a representative wheat and sheep farming system in the wheatbelt of Western Australia, involved two grazing-management scenarios and used climate data for the period 1962–2011 for three locations in Western Australia representing low-, medium- and high-rainfall cropping regions: Merredin, Wickepin and Kojonup. The grazing-management policy of the main scenario, ‘crop grazing’, placed livestock on the crops only until the crop reached Zadoks growth stage 30, provided the green biomass of the farm’s annual pastures was <800 kg/ha. A second ‘shadow-grazing’ scenario was run in which a group of ewes identical to the main ewe flock was used to graze annual pastures simultaneously with the main ewe flock whenever the main flock grazed wheat crops. The difference between the two scenarios represented the pasture deferment value associated with grazing wheat crops.
Pasture deferment had little effect on total pasture production during the period when crops were grazed. However, there was a small benefit to feed supply through the accumulation of pasture during the period of crop grazing. This feed was available at a time of year when feed is scarce. This was reflected in improved animal production, with the weight of lambs at weaning being higher in the crop-grazing scenario than the shadow-grazing scenario. These results suggest that although increases in pasture productivity and feed supply associated with spring crop grazing are only marginal, grazing of spring wheat crops can still lead to changes in lamb production because this enterprise is sensitive to the feed supply in winter.
Forage canola (Brassica napus): spring-sown winter canola for biennial dual-purpose use in the high-rainfall zone of southern Australia
Authors: Paridaen Annieka , Kirkegaard John A.
Published: April 2015

European winter canola (Brassica napus L.) varieties adapted to the long, cool seasons in high-rainfall areas of southern Australia have recently been adopted as autumn-sown, grain-only and dual-purpose crops. A spring-sown winter canola could be used as a biennial dual-purpose crop, to provide additional forage for summer and autumn grazing before recovery to produce an oilseed crop. We report a series of field experiments demonstrating that European winter canola types have suitable phenological characteristics to allow for their use as biennial, spring-sown crops, providing significant forage (2.5–4 t ha–1) for grazing while remaining vegetative through summer and autumn, and recovering following vernalisation in winter to produce high seed yield (2.5–5.0 t ha–1). Sowing too early (September) in colder inland areas risked exposure of the crop to vernalising temperatures, causing the crop to bolt to flower in summer, whereas all crops sown from mid-October remained vegetative through summer. Crop stands thinned by 20–30% during summer, and this was exacerbated by grazing, but surviving stands of ~30 plants m–2 were sufficient to support high yields. Grazing had no effect on grain yield at one site, but reduced yield by 0.5 t ha–1 at a second site, although this was more than offset by the value of the grazed forage. The spring-sowing approach has potential to replace the existing forage rape–spring cereal sequence, or to add a further option to the existing autumn-sown winter canola in areas such as southern Victoria, where early autumn establishment can be problematic and spring-sown crops can better withstand pests and winter waterlogging, which limit yield of autumn-sown crops. Because these are the first known studies in Australia to investigate the use of spring-sown winter canola, further work is warranted to refine further the crop and grazing strategies to maximise productivity and profitability from this option.
Integrating dual-purpose wheat and canola into high-rainfall livestock systems in south-eastern Australia. 3. An extrapolation to whole-farm grazing potential, productivity and profitability
Authors: Bell L. W. , Dove H. , McDonald S. E. , Kirkegaard J. A.
Published: April 2015

Dual-purpose crops can provide valuable winter forage in livestock production systems and increase subsequent pasture availability. Using experimental measurements of sheep grazing on pasture only or dual-purpose crops of wheat, canola, and wheat and canola in combination, and their associated effects on subsequent pasture grazing, we estimated for two different years the whole-farm changes in whole-farm sheep grazing days (SGD), relative farm production and farm economic impact. The increased winter feed supply and higher grazing intensity on dual-purpose crops allowed 2–3 times the area of pasture to be spelled, which together enabled increases in potential year-round pasture stocking rate. Up to 20% of farm area could be allocated to dual-purpose crops while still obtaining the same number of SGD per farm ha with additional grain production (5.0–5.4 t wheat ha–1 and 1.9–3.6 t canola ha–1) adding significantly to farm profitability and production. Allocating 10–20% of the farm to a combination of dual-purpose wheat and canola grazed in sequence could increase whole-farm SGD by 10–15%, increase farm output by >25% and increase estimated farm profit margin by >AU$150 farm ha–1 compared with pasture-only livestock systems. The long crop-grazing period from wheat and canola in combination providing a large pasture-spelling benefit was a key factor enabling these economic and productivity increases. Introducing wheat or canola alone on up to 30% of the farm is likely to reduce SGD per farm ha, but still significantly increase whole-farm productivity (10–20%) and estimated profit margin ($50–100 farm ha–1). Over the two very different experimental growing seasons, the estimated relative changes in whole-farm productivity and estimated profit margin were similar, indicating that these benefits are likely to be consistent over a range of years. Together, these findings suggest that once whole-farm livestock feed-base effects are considered, large economic and productivity benefits can be attributed to dual-purpose crops when integrated into livestock production systems in Australia’s southern high-rainfall zone.
Optimising grain yield and grazing potential of crops across Australia’s high-rainfall zone: a simulation analysis. 1. Wheat
Authors: Bell Lindsay W. , Lilley Julianne M. , Hunt James R. , Kirkegaard John A.
Published: April 2015

Interest is growing in the potential to expand cropping into Australia’s high-rainfall zone (HRZ). Dual-purpose crops are suited to the longer growing seasons in these environments to provide both early grazing for livestock and later regrow to produce grain. Grain yield and grazing potential of wheats of four different maturity types were simulated over 50 years at 13 locations across Australia’s HRZ, and sowing date, nitrogen (N) availability and crop density effects were explored. Potential grazing days on wheat were obtained by simulating sheep grazing crops to Zadoks growth stage Z30 at 25 dry sheep equivalents (DSE)/ha. Optimal sowing dates for each maturity type at each location were matched to the flowering window during which risk of frost and heat stress was lowest. Overall, we found significant national potential for dual-purpose use of winter wheat cultivars across Australia’s HRZ, with opportunities identified in all regions. Simulated mean wheat yields exceeded 6 t/ha at most locations, with highest mean grain yields (8–10 t/ha) in southern Victoria, and lower yields (5–7 t/ha) in the south-west of Western Australia (WA) and central and northern New South Wales (NSW). Highest grazing days were from winter cultivars sown early (March–mid-April), which could provide 1700–3000 DSE-days/ha of grazing across HRZ locations; this was 2–3 times higher than could be obtained from grazing spring cultivars (200–800 DSE-days/ha). Sowing date was critical to maximise both grazing and grain yield potential from winter cultivars; each 1-week delay in sowing after 8 March reduced grazing by 200–250 DSE-days/ha and grain yield by 0.45 t/ha. However, in Mediterranean climates, a lower frequency of early sowing opportunities before mid-April (<30% of years) is likely to limit the potential to use winter cultivars. Prospects to graze shorter season spring cultivars that fit later sowing windows require further examination in south-west WA, the slopes of NSW and southern Queensland.
Forage and grain yield of diverse canola (Brassica napus) maturity types in the high-rainfall zone of Australia
Authors: Sprague S. J. , Kirkegaard J. A. , Graham J. M. , Bell L. W. , Seymour M. , Ryan M.
Published: April 2015

Cropping has recently expanded into arable areas of the high rainfall zone (HRZ) of Australia. We assessed the suitability of canola varieties of winter, winter × spring and spring-maturity at six sites across the south-eastern, northern and western HRZ of Australia for their suitability for dual-purpose production. Experiments measured potential forage production and the effect of defoliation or grazing on grain yield of crops sown from mid-March to mid-May. Overall, these experiments demonstrated the potential for dual-purpose canola across a wide area of the HRZ. In the south-eastern HRZ where winter conditions were sufficient for vernalisation and spring conditions were mild, winter and winter × spring types outperformed spring types as they provided an extended vegetative period for ‘safe’ grazing (prior to stem elongation), producing 3.0–6.8 t dry matter (DM) ha–1 of forage and recovered to produce 2.5–4.9 t ha–1 of grain yield. In the south-eastern region, early-sown winter types produced more forage than other canola types for grazing in late autumn and winter. In one experiment with four sowing times, consecutive delays in sowing of 2 weeks reduced forage available for grazing by 58%, 72% and 95% compared with the earliest sowing time of 10 March (6.1 t DM ha–1). Although spring types in this region provided some potential for grazing, the phenology was unsuitable for early sowing as the rapid onset of flowering reduced the period of safe grazing. Winter types were not suited to the western region, but the winter × spring and spring types produced >1.0 t DM ha–1 of forage and grain yield of 2.3 t ha–1. In the northern region, spring types produced the highest grain yield (>3.0 t ha–1) but suffered significant yield penalties associated with grazing. In other regions there was generally little or no effect of grazing on grain yield when crops were grazed or defoliated before stem elongation. These experimental studies confirm the potential for dual-purpose canola across all regions of the HRZ when suitable maturity types are sown, managed and grazed appropriately.
Resilience to climate change: complex relationships among wetland hydroperiod, larval amphibians and aquatic predators in temporary wetlands
Authors: Lowe Katrin , Castley J. Guy , Hero Jean-Marc
Published: April 2015

Amphibians that utilise temporary wetlands with unpredictable hydrology are living on the edge, maintaining viable populations under variable climatic conditions. Information on their breeding ecology will provide insight into their adaptive capacity and resilience to climate change. The environmental factors influencing breeding of a temporary wetland breeding frog (Litoria olongburensis) from eastern Australia were examined over two breeding seasons from August 2009 to March 2011. The influence of biotic and abiotic wetland characteristics on the abundance and seasonality of L. olongburensis aquatic larvae was quantified throughout the latitudinal range of the species. Substantial variation in yearly precipitation resulted in changes to the timing of breeding, and patterns of tadpole and predator abundance, which also varied along a hydroperiod gradient. Litoria olongburensis displayed adaptive strategies, including breeding when hydrological conditions were likely to last longest, and short time to hatching and metamorphosis. Concentrating breeding efforts early during wetland filling coincided with low predator densities. These pre-adaptations may reflect an adaptive capacity to predicted changes in frequency and reliability of precipitation as a result of climate change, and may apply to other temporary wetland species. Their conservation depends on preserving wetlands with a variety of hydroperiods within a landscape matrix.