bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantum cluster equilibrium model of N-methylformamide–water binary mixtures
Authors: von Domaros Michael , Jähnigen Sascha , Friedrich Joachim , Kirchner Barbara
Published: February 2016

The established quantum cluster equilibrium (QCE) approach is refined and applied to N-methylformamide (NMF) and its aqueous solution. The QCE method is split into two iterative cycles: one which converges to the liquid phase solution of the QCE equations and another which yields the gas phase. By comparing Gibbs energies, the thermodynamically stable phase at a given temperature and pressure is then chosen. The new methodology avoids metastable solutions and allows a different treatment of the mean-field interactions within the gas and liquid phases. These changes are of crucial importance for the treatment of binary mixtures. For the first time in a QCE study, the cis-trans-isomerism of a species (NMF) is explicitly considered. Cluster geometries and frequencies are calculated using density functional theory (DFT) and complementary coupled cluster single point energies are used to benchmark the DFT results. Independent of the selected quantum-chemical method, a large set of clusters is required for an accurate thermodynamic description of the binary mixture. The liquid phase of neat NMF is found to be dominated by the cyclic trans-NMF pentamer, which can be interpreted as a linear trimer that is stabilized by explicit solvation of two further NMF molecules. This cluster reflects the known hydrogen bond network preferences of neat NMF.
Critical density of a soliton gas
Authors: El G. A.
Published: February 2016

We quantify the notion of a dense soliton gas by establishing an upper bound for the integrated density of states of the quantum-mechanical Schrödinger operator associated with the Korteweg–de Vries soliton gas dynamics. As a by-product of our derivation, we find the speed of sound in the soliton gas with Gaussian spectral distribution function.
Observation and characterization of the smallest borospherene, B28− and B28
Authors: Wang Ying-Jin , Zhao Ya-Fan , Li Wei-Li , Jian Tian , Chen Qiang , You Xue-Rui , Ou Ting , Zhao Xiao-Yun , Zhai Hua-Jin , Li Si-Dian , Li Jun , Wang Lai-Sheng
Published: February 2016

Free-standing boron nanocages or borospherenes have been observed recently for B40− and B40. There is evidence that a family of borospherenes may exist. However, the smallest borospherene is still not known. Here, we report experimental and computational evidence of a seashell-like borospherene cage for B28− and B28. Photoelectron spectrum of B28− indicated contributions from different isomers. Theoretical calculations showed that the seashell-like B28− borospherene is competing for the global minimum with a planar isomer and it is shown to be present in the cluster beam, contributing to the observed photoelectron spectrum. The seashell structure is found to be the global minimum for neutral B28 and the B28− cage represents the smallest borospherene observed to date. It is composed of two triangular close-packed B15 sheets, interconnected via the three corners by sharing two boron atoms. The B28 borospherene was found to obey the 2(n + 1)2 electron-counting rule for spherical aromaticity.
Multiplexed infrared photodetection using resonant radio-frequency circuits
Authors: Liu R. , Lu R. , Roberts C. , Gong S. , Allen J. W. , Allen M. S. , Wenner B. R. , Wasserman D.
Published: February 2016

We demonstrate a room-temperature semiconductor-based photodetector where readout is achieved using a resonant radio-frequency (RF) circuit consisting of a microstrip split-ring resonator coupled to a microstrip busline, fabricated on a semiconductor substrate. The RF resonant circuits are characterized at RF frequencies as function of resonator geometry, as well as for their response to incident IR radiation. The detectors are modeled analytically and using commercial simulation software, with good agreement to our experimental results. Though the detector sensitivity is weak, the detector architecture offers the potential for multiplexing arrays of detectors on a single read-out line, in addition to high speed response for either direct coupling of optical signals to RF circuitry, or alternatively, carrier dynamics characterization of semiconductor, or other, material systems.
Identifying the influence of the intrinsic defects in Gd-doped ZnO thin-films
Authors: Flemban T. H. , Sequeira M. C. , Zhang Z. , Venkatesh S. , Alves E. , Lorenz K. , Roqan I. S.
Published: February 2016

Gd-doped ZnO thin films were prepared using pulsed laser deposition at different oxygen pressures and varied Gd concentrations. The effects of oxygen deficiency-related defects on the Gd incorporation, optical and structural properties, were explored by studying the impact of oxygen pressure during deposition and post-growth thermal annealing in vacuum. Rutherford Backscattering Spectrometry revealed that the Gd concentration increases with increasing oxygen pressure for samples grown with the same Gd-doped ZnO target. Unexpectedly, the c-lattice parameter of the samples tends to decrease with increasing Gd concentration, suggesting that Gd-defect complexes play an important role in the structural properties. Using low-temperature photoluminescence (PL), Raman measurements and density functional theory calculations, we identified oxygen vacancies as the dominant intrinsic point defects. PL spectra show a defect band related to oxygen vacancies for samples grown at oxygen deficiency.
Highly stretchable wrinkled gold thin film wires
Authors: Kim Joshua , Park Sun-Jun , Nguyen Thao , Chu Michael , Pegan Jonathan D. , Khine Michelle
Published: February 2016

With the growing prominence of wearable electronic technology, there is a need to improve the mechanical reliability of electronics for more demanding applications. Conductive wires represent a vital component present in all electronics. Unlike traditional planar and rigid electronics, these new wearable electrical components must conform to curvilinear surfaces, stretch with the body, and remain unobtrusive and low profile. In this paper, the piezoresistive response of shrink induced wrinkled gold thin films under strain demonstrates robust conductive performance in excess of 200% strain. Importantly, the wrinkled metallic thin films displayed negligible change in resistance of up to 100% strain. The wrinkled metallic wires exhibited consistent performance after repetitive strain. Importantly, these wrinkled thin films are inexpensive to fabricate and are compatible with roll to roll manufacturing processes. We propose that these wrinkled metal thin film wires are an attractive alternative to conventional wires for wearable applications.
Decoupled electron and phonon transports in hexagonal boron nitride-silicene bilayer heterostructure
Authors: Cai Yongqing , Pei Qing-Xiang , Zhang Gang , Zhang Yong-Wei
Published: February 2016

Calculations based on the density functional theory and empirical molecular dynamics are performed to investigate interlayer interaction, electronic structure and thermal transport of a bilayer heterostructure consisting of silicene and hexagonal boron nitride (h-BN). In this heterostructure, the two layers are found to interact weakly via a non-covalent binding. As a result, the Dirac cone of silicene is preserved with the Dirac cone point being located exactly at the Fermi level, and only a small amount of electrons are transferred from h-BN to silicene, suggesting that silicene dominates the electronic transport. Molecular dynamics calculation results demonstrate that the heat current along h-BN is six times of that along silicene, suggesting that h-BN dominates the thermal transport. This decoupled role of h-BN and silicene in thermal and electronic transport suggests that the BN-silicene bilayer heterostructure is promising for thermoelectric applications.
Universal spin-momentum locked optical forces
Authors: Kalhor Farid , Thundat Thomas , Jacob Zubin
Published: February 2016

Evanescent electromagnetic waves possess spin-momentum locking, where the direction of propagation (momentum) is locked to the inherent polarization of the wave (transverse spin). We study the optical forces arising from this universal phenomenon and show that the fundamental origin of recently reported non-trivial optical chiral forces is spin-momentum locking. For evanescent waves, we show that the direction of energy flow, the direction of decay, and the direction of spin follow a right hand rule for three different cases of total internal reflection, surface plasmon polaritons, and HE11 mode of an optical fiber. Furthermore, we explain how the recently reported phenomena of lateral optical force on chiral and achiral particles are caused by the transverse spin of the evanescent field and the spin-momentum locking phenomenon. Finally, we propose an experiment to identify the unique lateral forces arising from the transverse spin in the optical fiber and point to fundamental differences of the spin density from the well-known orbital angular momentum of light. Our work presents a unified view on spin-momentum locking and how it affects optical forces on chiral and achiral particles.
High-quality graphene grown on polycrystalline PtRh20 alloy foils by low pressure chemical vapor deposition and its electrical transport properties
Authors: Yang He , Shen Chengmin , Tian Yuan , Bao Lihong , Chen Peng , Yang Rong , Yang Tianzhong , Li Junjie , Gu Changzhi , Gao Hong-Jun
Published: February 2016

High-quality continuous uniform monolayer graphene was grown on polycrystalline PtRh20 alloy foils by low pressure chemical vapor deposition. The morphology of graphene was investigated by Raman spectroscopy, scanning electron microscopy, and atomic force microscopy. Analysis results confirm that high quality single-layer graphene was fabricated on PtRh20 foil at 1050 °C using a lower flux of methane under low pressure. Graphene films were transferred onto the SiO2/Si substrate by the bubbling transfer method. The mobility of a test field effect transistor made of the graphene grown on PtRh20 was measured and reckoned at room temperature, showing that the carrier mobility was about 4000 cm2 V−1 s−1. The results indicate that desired quality of single-layer graphene grown on PtRh20 foils can be obtained by tuning reaction conditions.
Precise rainbow trapping for low-frequency acoustic waves with micro Mie resonance-based structures
Authors: Zhou Chen , Yuan Baoguo , Cheng Ying , Liu Xiaojun
Published: February 2016

We have realized the acoustic rainbow trapping in the low frequency region (200–500 Hz) through micro Mie resonance-based structures. The structure has eight channels with a high refractive index obtained by coiling space, that can excite strong interactions with incident waves and support various orders of multipoles due to the Mie resonances of the microstructure. By utilizing the structure, the precise spatial modulation of the acoustic wave is demonstrated both theoretically and experimentally. The effect of trapping broadband acoustic waves and spatially separating different frequency components are ascribed to the monopolar Mie resonances of the structures. The trapping frequency is derived and the trapping positions can be tuned arbitrarily. With enhanced wave-structure interactions and tailored frequency responses, such micro structures show precise spectral-spatial control of acoustic waves and open a diverse venue for high performance acoustic wave detection, sensing, filtering, and a nondestructive test.
Ultrahigh-sensitive optical temperature sensing based on ferroelectric Pr3+-doped (K0.5Na0.5)NbO3
Authors: Tang Wei , Wang Shaochen , Li Zhenglin , Sun Ye , Zheng Limei , Zhang Rui , Yang Bin , Cao Wenwu , Yu Miao
Published: February 2016

Optical temperature sensing based on the variation of the fluorescence intensity ratio of rare-earth materials has become appealing due to the multiple superiorities over the electrical temperature sensing. However, confined by the largest energy separation of two thermally linked levels of rare-earth ions, the highest sensitivity of such temperature sensing is essentially smaller than 2878/T2, as reported previously from diverse systems. In this work, we demonstrate that ultrahigh-sensitive temperature sensing can be achieved from Pr3+-doped (K0.5Na0.5)NbO3 based on the intensity ratio of the 1D2-3H4 emission to the 3P0-3H4 emission. The ratio can be increased as high as 18-fold when temperature rises from room temperature to 456 K, nicely fitting a thermally linked-levels-like equation and showing an ultrahigh sensitivity of 7997/T2. The striking change of the ratio is attributed to the interaction between the two emission levels and the intervalence charge transfer state. This work may have provided a distinct route in the field of optical temperature sensing utilizing rare-earth-doped materials. In addition, the resultant product also possesses excellent photoluminescence and ferroelectric properties, showing promising potentials in multifunctional devices for practical applications.
Microfluidic platform for photodynamic therapy cytotoxicity analysis of nanoencapsulated indocyanine-type photosensitizers
Authors: Jastrzębska Elżbieta , Bazylińska Urszula , Bułka Magdalena , Tokarska Katarzyna , Chudy Michał , Dybko Artur , Wilk Kazimiera Anna , Brzózka Zbigniew
Published: February 2016

The application of nanotechnology is important to improve research and development of alternative anticancer therapies. In order to accelerate research related to cancer diagnosis and to improve the effectiveness of cancer treatment, various nanomaterials are being tested. The main objective of this work was basic research focused on examination of the mechanism and effectiveness of the introduction of nanoencapsulated photosensitizers to human carcinoma (A549) and normal cells (MRC-5). Newly encapsulated hydrophobic indocyanine-type photosensitizer (i.e., IR-780) was subjected to in vitro studies to determine its release characteristics on a molecular level. The photosensitizers were delivered to carcinoma and normal cells cultured under model conditions using multiwell plates and with the use of the specially designed hybrid (poly(dimethylsiloxane) (PDMS)/glass) microfluidic system. The specific geometry of our microsystem allows for the examination of intercellular interactions between cells cultured in the microchambers connected with microchannels of precisely defined length. Our microsystem allows investigating various therapeutic procedures (e.g., photodynamic therapy) on monoculture, coculture, and mixed culture, simultaneously, which is very difficult to perform using standard multiwell plates. In addition, we tested the cellular internalization of nanoparticles (differing in size, surface properties) in carcinoma and normal lung cells. We proved that cellular uptake of nanocapsules loaded with cyanine IR-780 in carcinoma cells was more significant than in normal cells. We demonstrated non cytotoxic effect of newly synthesized nanocapsules built with polyelectrolytes (PEs) of opposite surface charges: polyanion—polysodium-4-styrenesulphonate and polycation—poly(diallyldimethyl-ammonium) chloride loaded with cyanine IR-780 on human lung carcinoma and normal cell lines. However, the differences observed in the photocytotoxic effect between two types of tested nanocapsules can result from the type of last PE layer and their different surface charge.
Communication: Isotopic effects on tunneling motions in the water trimer
Authors: Videla Pablo E. , Rossky Peter J. , Laria D.
Published: February 2016

We present results of ring polymer molecular dynamics simulations that shed light on the effects of nuclear quantum fluctuations on tunneling motions in cyclic [H2O]3 and [D2O]3, at the representative temperature of T = 75 K. In particular, we focus attention on free energies associated with two key isomerization processes: The first one corresponds to flipping transitions of dangling OH bonds, between up and down positions with respect to the O–O–O plane of the cluster; the second involves the interchange between connecting and dangling hydrogen bond character of the H-atoms in a tagged water molecule. Zero point energy and tunneling effects lead to sensible reductions of the free energy barriers. Due to the lighter nature of the H nuclei, these modifications are more marked in [H2O]3 than in [D2O]3. Estimates of the characteristic time scales describing the flipping transitions are consistent with those predicted based on standard transition-state-approximation arguments.
Effects of cross-section on mechanical properties of Au nanowire
Authors: Vazinishayan Ali , Yang Shuming , Duongthipthewa Anchalee , Wang Yiming
Published: February 2016

The aim of this paper is study of the effects of multiple cross-section of Au nanowire on mechanical properties. Different cross-section models of Au nanowires including circular, hexagonal, pentagonal and rectangular were simulated by finite element modeling using ABAQUS. In this study, the bending technique was applied so that both ends of the model were clamped with mid-span under loading condition. The cross-sections had the length of 400 nm and the diameter of 40 nm, except the circular cross-section while the rest of the cross-sections had an equivalent diameter. Von Misses stresses distribution were used to define the stress distribution in the cross-section under loading condition, and elastic deformation was analyzed by the beam theory. The results disclosed that the circular and the rectangular models had highest and lowest strengths against plastic deformation, respectively.
Dynamic coherent backscattering mirror
Authors: Zeylikovich I. , Xu M.
Published: February 2016

The phase of multiply scattered light has recently attracted considerable interest. Coherent backscattering is a striking phenomenon of multiple scattered light in which the coherence of light survives multiple scattering in a random medium and is observable in the direction space as an enhancement of the intensity of backscattered light within a cone around the retroreflection direction. Reciprocity also leads to enhancement of backscattering light in the spatial space. The random medium behaves as a reciprocity mirror which robustly converts a diverging incident beam into a converging backscattering one focusing at a conjugate spot in space. Here we first analyze theoretically this coherent backscattering mirror (CBM) phenomenon and then demonstrate the capability of CBM compensating and correcting both static and dynamic phase distortions occurring along the optical path. CBM may offer novel approaches for high speed dynamic phase corrections in optical systems and find applications in sensing and navigation.
Ultra-soft magnetic properties and correlated phase analysis by 57Fe Mössbauer spectroscopy of Fe74Cu0.8Nb2.7Si15.5B7 alloy
Authors: Manjura Hoque S. , Liba S. I. , Anirban A. , Choudhury Shamima , Akhter Shireen
Published: February 2016

A detailed study of magnetic softness has been performed on FINEMENT type of ribbons by investigating the BH loop with maximum applied field of 960 A/m. The ribbon with the composition of Fe74Cu0.8Nb2.7Si15.5B7 was synthesized by rapid solidification technique and the compositions volume fraction was controlled by changing the annealing condition. Detail phase analysis was performed through X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Vibrating sample magnetometer (VSM) and Mössbauer spectroscopy in order to correlate the ultrasoft magnetic properties with the volume fraction of amorphous and α-Fe(Si) soft nano composites. Bright (BF) and dark field (DF) image with selective area diffraction (SAD) patterns by the transmission electron microscopy (TEM) of the sample annealed for the optimized annealed condition at 853 K for 3 min reveals nanocrystals with an average size between 10-15 nm possessing the bcc structure which matches with the grain size revealed by the X-ray diffraction. Kinetics of crystallization of α-Fe(Si) phases has been determined by DSC curves. Extremely small coercivity of 30.9 A/m and core loss of 2.5 W/Kg for the sample annealed at 853 K for 3 min was found. Similar values for other crystalline conditions were determined by using BH loop tracer with a maximum applied field of around 960 A/m. Mössbauer spectroscopy was used to determine chemical shift, hyperfine field distribution (HFD), and peak width of different phases. The volume fractions of the relative amount of amorphous and crystalline phases are also determined by Mössbauer spectroscopy. High saturation magnetization along with ultrasoft magnetic properties exhibits very high potentials technological applications.
Unipolar resistive switching with forming-free and self-rectifying effects in Cu/HfO2/n-Si devices
Authors: Wang M. J. , Gao S. , Zeng F. , Song C. , Pan F.
Published: February 2016

One of the most effective methods integrating self-rectifying RRAM is alleviating sneak current in crossbar architecture. In this work, to investigate RRAMs with excellent properties of self-rectifying effect, simple Cu/HfO2/n-Si tri-layer devices are fabricated and investigated through I − V characteristic measurement. The experimental results demonstrate that the device exhibits forming-free behavior and a remarkable rectifying effect in low resistance state (LRS) with rectification ratio of 104 at ±1 V, as well as considerable OFF/ON ratio (resistive switching window) of 104 at 1 V. The formation and annihilation of localized Cu conductive filament plays a key role in the resistive switching between low resistance state (LRS) and high resistance state (HRS). In addition, intrinsic rectifying effect in LRS attributes to the Schottky contact between Cu filament and n-Si electrode. Furthermore, satisfactory switching uniformity of cycles and devices is observed. As indicated by the results, Cu/HfO2/n-Si devices have a high potential for high-density storage practical application due to its excellent properties.
Modelling enteric methane abatement from earlier mating of dairy heifers in subtropical Australia by improving diet quality
Authors: Christie K. M. , Harrison M. T. , Trevaskis L. M. , Rawnsley R. P. , Eckard R. J.
Published: February 2016

Milking cows typically dominate dairy farm greenhouse gas (GHG) emissions, but replacement heifers also contribute to farm emissions and can increase the emission intensity of milk production. In northern Australia, heifers generally graze poorer-quality subtropical pastures and in the absence of energy-dense supplementary feed during periods of low pasture growth, liveweight (LW) gain can be restricted. This modelling study examined the time required and enteric methane (CH4) emissions produced in raising dairy heifers to a target LW for first mating by feeding a diet assuming either constant (static) or variable (dynamic) nutritive values. Using a static approach (Australian Feeding Standards methodology), and assuming a target mating LW of 360 kg, growing heifers reached their target LW at ~18 months of age while consuming C4 grasses with a constant metabolisable energy content of 9.5 MJ/kg dry matter (DM) or 11 months of age on a diet of 11.0 MJ/kg DM. Enteric CH4 emissions were 1.2 and 0.8 t of carbon dioxide equivalents/heifer over the 18- and 11-month periods, respectively. To explore the extent with which climatic conditions influence seasonal pasture availability and nutritive value with a dynamic approach, we used a whole-farm biophysical model (SGS pasture model) to simulate diets with mean metabolisable energy values of 9.5 and 10.9 MJ/ kg DM. On average (±s.d.), heifers required 22 ± 4 and 17 ± 1 months, respectively, to reach target LW, with cumulative enteric CH4 emissions of 1.22 ± 0.20 and 0.72 ± 0.04 t carbon dioxide equivalents, respectively. The dynamic approach resulted in slower LW gain due to the variable nutritive value of the diet throughout the year, resulting in seasonal periods of LW plateauing or decline. Maintaining heifers on high-quality diets in subtropical northern Australia should result in increased daily LW gain, lower enteric CH4 emissions to mating LW and earlier calving. Together, these factors reduce their lifetime emission intensity of milk production.
Genetic and genomic relationship between methane production measured in breath and fatty acid content in milk samples from Danish Holsteins
Authors: Lassen J. , Poulsen N. A. , Larsen M. K. , Buitenhuis A. J.
Published: February 2016

In this study the objective was to estimate the genetic and genomic relationship between methane-related traits and milk fatty acid profiles. This was done using two different estimation procedures: a single nucleotide polymorphism-based genomic relationship matrix and a classical pedigree-based relationship matrix. Data was generated on three Danish Holstein herds and a total of 339 cows were available for the study. Methane phenotypes were generated in milking robots during milking over a weekly period and the milk phenotypes were quantified from milk from one milking. Genetic and genomic parameters were estimated using a mixed linear model. Results showed that heritability estimates were comparable between models, but the standard error was lower for genomic heritabilities compared with genetic heritabilities. Genetic as well as genomic correlations were highly variable and had high standard errors, reflecting a similar pattern as for the heritability estimates with lower standard errors for the genomic correlations compared with the pedigree-based genetic correlations. Many of the correlations though had a magnitude that makes further studies on larger datasets worthwhile. The results indicate that genotypes are highly valuable in studies where limited number of phenotypes can be recorded. Also it shows that there is some significant genetic association between methane in the breath of the cow and milk fatty acids profiles.
How can grass-based dairy farmers reduce the carbon footprint of milk?
Authors: O'Brien D. , Geoghegan A. , McNamara K. , Shalloo L.
Published: February 2016

The Irish dairy industry aims to increase milk production from grass-based farms following the removal of the EU milk-quota system, but is also required to minimise greenhouse gas (GHG) emissions to meet European reduction targets. Consequently, the sector is under increasing pressure to reduce GHG emissions per unit of milk, or carbon footprint (CF). Therefore, the goal of the present study was to determine the main sources of the CF of grass-based milk production and to identify mitigation strategies that can be applied to reduce farm footprints. In total, the CF of milk was estimated for 62 grass-based dairy farms in 2014. The method used to quantify GHG emissions was a life cycle assessment (LCA), independently certified to comply with the British standard for LCA (PAS 2050). The LCA method was applied to calculate annual on- and off-farm GHG emissions associated with dairy production until milk was sold from the farm in CO2-equivalent (CO2-eq). Annual GHG emissions computed using LCA were allocated to milk on the basis of the economic value of dairy products and expressed per kilogram of fat- and protein-corrected milk to estimate CF. Enteric methane was the main source of the CF of milk (46%), followed by emissions from inorganic N fertilisers (16%), manure (16%) and concentrate feedstuffs (8%). The mean CF of milk from the 62 farms was 1.26 kg of CO2-eq per kilogram of fat- and protein-corrected milk, but varied from 0.98 kg to 1.67 kg as measured using the 95% confidence interval. The CF of milk was correlated with numerous farm attributes, particularly N-fertiliser, the percentage of grazed grass in the diet, and production of milk solids. Grass-based dairy farmers can significantly improve these farm attributes by increasing herd genetic merit, extending the length of the grazing season and optimising N fertiliser use and, thereby, reduce the CF of milk.
Measuring methane from grazing dairy cows using GreenFeed
Authors: Waghorn G. C. , Jonker A. , Macdonald K. A.
Published: February 2016

The GreenFeed (GF; C-lock Inc.) system for estimating methane (CH4) and carbon dioxide emissions from cows enables data to be acquired from a grazing herd, where individuals are unencumbered by equipment associated with sampling respired breath. Cows choose when or if they want to visit a GF. Confidence in CH4 measurements from this system requires information on individual cow use, patterns of visits and data need to be accumulated over several days or weeks. The effect of stocking rate (SR) on CH4 and carbon dioxide emissions was examined in herds of 28 and 40 dairy cows, each grazing an 11-ha self-contained farmlet (Low SR and High SR), in four measurement periods over a lactation. Emissions were measured for up to 3 weeks in each period; CH4 averaged 331 and 305 g/cow.day, with 19.6 and 16.5 kg milk/cow.day during the measurements for the Low and High SR, respectively. Values for CH4 were similar to estimates derived from calculated feed intakes, and daily carbon dioxide emissions averaged 10.8 and 10.0 kg/day for cows in Low and High SR treatments, respectively. Data from the GF system distinguished effects of SR, but only ~20 cows from each farmlet were regular (daily) users, despite feed restrictions for the High SR cows. Visits by ‘users’ averaged 1.6 and 1.1 cows/h for Low and High SR herds, respectively, and were spread over 24 h with a small circadian variation in emission rates. The GF can be integrated into intensive pasture-based dairying and estimates of CH4 emissions are in line with expectations associated with feed availability and stage of lactation, however the variation between cows in number of visits to the GF has not been explained.
Modelling the influence of soil carbon on net greenhouse gas emissions from grazed pastures
Authors: Meyer Rachelle , Cullen Brendan R. , Eckard Richard J.
Published: February 2016

Sequestering carbon (C) in soil organic matter in grassland systems is often cited as a major opportunity to offset greenhouse gas (GHG) emissions. However, these systems are typically grazed by ruminants, leading to uncertainties in the net GHG balance that may be achieved. We used a pasture model to investigate the net balance between methane (CH4), nitrous oxide (N2O) and soil C in sheep-grazed pasture systems with two starting amounts of soil C. The net emissions were calculated for four soil types in two rainfall zones over three periods of 19 years. Because of greater pasture productivity, and consequent higher sheep stocking rates, high-rainfall sites were associated with greater GHG emissions that could not be offset by C sequestration. On these high-rainfall sites, the higher rate of soil organic carbon (SOC) increase on low-SOC soils offset an average of 45% of the livestock GHG emissions on the modelled chromosol and 32% on the modelled vertosol. The slow rate of SOC increase on the high-SOC soils only offset 2–4% of CH4 and N2O emissions on these high-rainfall sites. On low-rainfall sites, C sequestration in low-SOC soils more than offset livestock GHG emissions, whereas the modelled high-C soils offset 75–86% of CH4 and N2O emissions. Greater net emissions on high-C soils were due primarily to reduced sequestration potential and greater N2O emissions from nitrogen mineralisation and livestock urine. Annual variation in CH4 and N2O emissions was low, whereas annual SOC change showed high annual variation, which was more strongly correlated with weather variables on the low-rainfall sites compared with the high-rainfall sites. At low-soil C concentrations, with high sequestration potential, there is an initial mitigation benefit that can in some instances offset enteric CH4 and direct and indirect N2O emissions. However, as soil organic matter increases there is a trade-off between diminishing GHG offsets and increasing ecosystem services, including mineralisation and productivity benefits.
Relationships between milk fatty acid profiles and enteric methane production in dairy cattle fed grass- or grass silage-based diets
Authors: Dijkstra J. , van Gastelen S. , Antunes-Fernandes E. C. , Warner D. , Hatew B. , Klop G. , Podesta S. C. , van Lingen H. J. , Hettinga K. A. , Bannink A.
Published: February 2016

We quantified relationships between methane production and milk fatty acid (FA) profile in dairy cattle fed grass- or grass silage-based diets, and determined whether recent prediction equations for methane, based on a wide variety of diets, are applicable to grass- and grass silage-based diets. Data from three studies were used, encompassing four grass herbage and 14 grass silage treatments and 132 individual cow observations. Methane production was measured using respiration chambers and milk fatty acids (FAs) analysed using gas chromatography. The proportion of grass or grass silage (dry matter (DM) basis) was 0.80 ± 0.037. Methane yield averaged 22.3 ± 2.10 g/kg DM intake (DMI) and 14.2 ± 2.90 g/kg fat- and protein-corrected milk (FPCM). Mixed model univariate regression including a random study effect on intercept was applied to predict methane yield, with individual milk FA concentrations (g/100 g FA) as fixed effects. Of the 42 milk FAs identified, no single FA had a strong positive correlation (r; strong correlation defined as |r| ≥ 0.50) with methane yield (g/kg DMI), and cis-12 C18:1 and cis-9,12,15 C18:3 had a strong negative correlation with methane yield (g/kg DMI). C14:0 iso, C15:0, C15:0 iso, C15:0 anteiso, C16:0, C20:0, cis-11,14 C20:2, cis-5,8,11,14 C20:4, C22:0, cis-7,10,13,16,19 C22:5 and C24:0 had a strong positive correlation with methane yield (g/kg FPCM), and trans-15+cis-11 C18:1, cis-9 C18:1, and cis-11 C20:1 had a strong negative correlation with methane yield (g/kg FPCM). Observed methane yield was compared with methane yield predicted by the equations of van Lingen et al. (2014; Journal of Dairy Science 97, 7115–7132). These equations did not accurately predict methane yield as grams per kilogram DMI (concordance correlation coefficient (CCC) = 0.13) or as grams per kilogram FPCM (CCC = 0.22), in particular related to large differences in standard deviation between predicted and observed values. In conclusion, quantitative relationships between milk FA profile and methane yield in cattle fed grass- or grass silage-based diets differ from those determined for other types of diets.
The concordance between greenhouse gas emissions, livestock production and profitability of extensive beef farming systems
Authors: Harrison Matthew T. , Cullen Brendan R. , Tomkins Nigel W. , McSweeney Chris , Cohn Philip , Eckard Richard J.
Published: February 2016

Here we examine the concordance among emissions, production and gross margins of extensive beef farming systems by modelling a range of scenarios for herd management, animal genotype and pasture nutritive quality. We based our simulations on a case-study farm in central Queensland, Australia, and studied the influence of interventions designed for emissions mitigation, increasing productivity, or increasing gross margin. Interventions included replacing urea supplementation with nitrate, finishing cattle on the perennial forage leucaena (L), herd structure optimisation (HO), higher female fecundity (HF), and a leucaena finishing enterprise that had net farm emissions equal to the baseline (leucaena equal emissions; LEE). The HO intervention reduced the ratio of breeding cows relative to steers and unmated heifers, and lowered the ratio of costs to net cattle sales. Gross margin of the baseline, nitrate, L, LEE, HO and HF scenarios were AU$146 000, AU$91 000, AU$153 000, AU$170 000, AU$204 000 and AU$216 000, respectively. Enterprises with early joining of maiden heifers as well as HO and HF further increased gross margin (AU$323 000), while systems incorporating all compatible interventions (HO, HF, early joining, LEE) had a gross margin of AU$315 000. We showed that interventions that increase liveweight turnoff while maintaining net farm emissions resulted in higher gross margins than did interventions that maintained liveweight production and reduced net emissions. A key insight of this work was that the relationship between emissions intensity (emissions per unit liveweight production) or liveweight turnoff with gross margin were negative and positive, respectively, but only when combinations of (compatible) interventions were included in the dataset. For example, herd optimisation by reducing the number of breeding cows and increasing the number of sale animals increased gross margin by 40%, but this intervention had little effect on liveweight turnoff and emissions intensity. However, when herd optimisation was combined with other interventions that increased production, gross margins increased and emissions intensity declined. This is a fortuitous outcome, since it implies that imposing more interventions with the potential to profitably enhance liveweight turnoff allows a greater reduction in emissions intensity, but only when each intervention works synergistically with those already in place.
Use of dietary nitrate to increase productivity and reduce methane production of defaunated and faunated lambs consuming protein-deficient chaff
Authors: Nguyen S. H. , Barnett M. C. , Hegarty R. S.
Published: February 2016

The effects of dietary nitrate supplementation and defaunation on methane (CH4) emission, microbial protein outflow, digesta kinetics and average daily gain were studied in lambs fed chaff containing 4.1% crude protein in dry matter. Twenty ewe lambs were randomly allocated in a 2 × 2 factorial experiment (0% or 3.1% calcium nitrate supplementation and defaunated or faunated protozoal state). Nitrate supplementation increased blood methaemoglobin concentration (P < 0.05), rumen volatile fatty acids, ammonia concentration, dry matter intake, microbial protein outflow, average daily gain, dry matter digestibility, clean wool growth and wool fibre diameter (P < 0.01). Nitrate increased CH4 production (g/day) due to greater dry matter intake, but did not affect CH4 yield (g/kg dry matter intake). Nitrate-supplemented lambs had a shorter total mean retention time of digesta in the gut (P < 0.05). Defaunation reduced CH4 production and CH4 yield by 43% and 47%, but did not cause changes in dry matter intake, microbial protein outflow, average daily gain or clean wool growth. Defaunation decreased total volatile fatty acids and the molar percentage of propionate, but increased the molar percentage of acetate (P < 0.05). Interactions were observed such that combined treatments of defaunation and nitrate supplementation increased blood methaemoglobin (P = 0.04), and decreased CH4 yield (P = 0.01).
Milk production and composition, and methane emissions from dairy cows fed lucerne hay with forage brassica or chicory
Authors: Williams S. R. O. , Moate P. J. , Deighton M. H. , Hannah M. C. , Wales W. J. , Jacobs J. L.
Published: February 2016

Forage brassica and chicory crops provide an alternative to perennial grass pastures as a forage supply for grazing dairy cows during summer, but there is little information about their effects on milk production and methane (CH4) emissions. Thirty-two Holstein–Friesian cows were fed for 10 days on a diet of lucerne cubes (750 g/kg DM) and grain (250 g/kg DM) (CON) or diets in which forage brassica (410 g/kg DM, FBR) or reproductive-stage chicory (410 g/kg DM, RCH) were offered with lucerne cubes (340 g/kg DM) and grain (250 g/kg DM). Cows offered the FBR diet produced more energy-corrected milk (25.4 kg/day) than did cows offered the CON diet (22.7 kg/day, P = 0.001), even though DM intake was not different for cows between the two groups (20.6 kg/day on average). In contrast, cows offered the RCH diet produced less energy-corrected milk (19.3 kg/day) than did cows in the other two groups (P = 0.001), reflecting the lower DM intake by cows offered the RCH diet (17.7 kg/day, P < 0.01). Methane yield (g CH4/kg DMI) was lower (P < 0.01) on the CON (21.0) and FBR (20.5) diets than on the RCH diet (26.1). Methane intensity (g/kg energy-corrected milk) was different (P < 0.01) for all diets, with CON (19.4) being intermediate, FBR (17.3) lowest and RCH (23.8) the greatest. Diet type was associated with differences in the proportions of only a small number of specific milk fatty acids, and differences in proportions of specific fatty acids were not related to CH4 emissions.
Smart livestock feeding strategies for harvesting triple gain – the desired outcomes in planet, people and profit dimensions: a developing country perspective
Authors: Makkar Harinder P. S.
Published: February 2016

Of the total greenhouse gas emission from the livestock sector, 45% relates to feed production and processing. Enteric methane (35%), land-use change (9%) and manure nitrous oxide and manure methane together (9.5%) are the other sources of greenhouse gas emissions, which to a large extent depend on feed types. Inefficient use of feeds reduces profitability. Increasing future feed demand and food-feed-fuel competition have environmental and social impacts. The growth for demand in livestock products comes with social, economic and environmental challenges. This paper argues that the efficient utilisation of feed resources and application of appropriate feeding strategies are vital for strengthening the three conventional pillars of sustainability (environment, social and economic). Towards this end, it identifies and explores a series of promising innovations and practices in feed production and feeding including balanced and phased feeding; increase in the quality and level of use of forages in diets; reduction in use of grains; harvesting forages when nutrient availability per unit of land is maximum; targeted mineral feeding; reduction in feed losses; use of straw-based densified feed blocks; better recycling of human food wastes and human-inedible food components to feed; new business models for production and use of urea-ammoniated straws, urea-molasses blocks, forages and silages in smallholder farms; and use of underutilised locally available feed crops linked with strengthening of seed development and distribution infrastructure. The development of simple tools and on-site assays for correcting nutritional imbalances also offers interesting opportunities. Collection of data on feed availability at the national level, and generation of sound chemical composition and nutritional value data of feeds, are a prerequisite to innovate. The focus of the discussion will be on low-input livestock systems in developing world. A large number of livestock are found in such systems and small improvements can have high global impact. In addition to the technological aspects, policy and institutional building options required to realise large impact are also discussed.
Effects of Tithonia diversifolia on in vitro methane production and ruminal fermentation characteristics
Authors: Terry S. A. , Ribeiro R. S. , Freitas D. S. , Delarota G. D. , Pereira L. G. R. , Tomich T. R. , Maurício R. M. , Chaves A. V.
Published: February 2016

The present study examined the effects of Tithonia diversifolia on in vitro methane (CH4) production and ruminal fermentation characteristics. The experiment was conducted as a completely randomised design (CRD) using a control (0% T. diversifolia) and three treatment groups with different concentrations (6.9%, 15.2%, 29.2%) of T. diversifolia, which replaced up to 15.2% and 14% dry matter (DM) of fresh sugarcane and concentrates, respectively. Ruminal fluid was obtained from two ruminally cannulated non-lactating Holstein × Zebu heifers maintained on a diet consisting of T. diversifolia, fresh sugarcane and 4 kg of concentrates. The inclusion of T. diversifolia had no effect (P ≥ 0.15) on cumulative gas production (mL, mL/g incubated DM, mL/g digested DM) or in vitro DM disappearance (%). Carbon dioxide (%, mL, mL/g incubated DM) linearly decreased (P ≤ 0.001) and CH4 (%, mL, mL/g incubated DM) quadratically increased (P ≤ 0.01) with increasing concentrations of T. diversifolia replacing fresh sugarcane and concentrates. The total volatile fatty acids (mM) and acetate (A) proportion of total volatile fatty acids (mmol/100 mmol) linearly increased (P < 0.01) with the increasing inclusion of T. diversifolia. Butyrate (mmol/100 mmol) increased quadratically (P ≤ 0.02), while propionate (P; mmol/100 mmol) decreased quadratically (P < 0.02). The A : P ratio increased linearly (P < 0.0001) with increasing amounts of T. diversifolia in the diet. These results indicated that increasing the amount of Tithonia diversifolia in the substrate DM increased the A : P ratio, which resulted in a six-fold increase of CH4 production when fresh sugarcane and concentrates were replaced at up to 15.2% and 14% (DM basis), respectively.
Mathematical formulae for accurate estimation of in vitro CH4 production from vented bottles
Authors: Hannah M. C. , Moate P. J. , Alvarez Hess P. S. , Russo V. M. , Jacobs J. L. , Eckard R. J.
Published: February 2016

A widely used method for the in vitro measurement of fermentation parameters, total gas and methane (CH4) production (mL/g) from feed samples employs AnkomRF Technology with vented bottles, initially flushed with carbon dioxide (CO2). The volumes of gas accumulated between ventings, and the volumes vented, are calculated from the headspace pressure data. By using these data, it is possible to infer mathematically the quantity of CH4 produced, given just a single measurement of the CH4 mixing ratio measured in the headspace at the termination of fermentation. However, this calculation requires an additional assumption. Two possibilities for this are considered. We present mathematical formulae arising from each, and describe their sensitivity to violations of their respective assumptions. Also considered is a formula based on using N2 instead of CO2 as the flushing gas. It appears that, in practice, all three formulae are suitable for estimating CH4 production, with errors less than 3%.