bluuebunny/crossref_metadata_2025 huggingface dataset:
Interface reaction kinetics in SiGe oxidation
Authors: Li Xiuyan , Noma Yusuke , Song Woojin , Nishimura Tomonori , Toriumi Akira
Published: December 2019

The oxidation of SiGe is very different from that of Si or Ge, leading to poor interface quality in oxidized SiGe gate stacks. In this work, SiGe oxidation kinetics and its effects on the generation of interface defects are discussed by considering the GeO desorption as well as Ge precipitation. Unlike GeO2/Ge, no GeO desorption associated with the reaction between GeO2 and Ge is detected in GeO2/SiGe below 700 °C. Instead, GeO desorption related to a reaction between GeO2 and Si is observed above 800 °C; however, it is suppressed by inserting a thin SiO2 layer on the SiGe surface. Based on experimental results and thermodynamic calculations, the SiGe oxidation kinetics is reconsidered in conjunction with the interface properties in SiGe gate stacks. The present results provide clear insights into a viable solution for high performance SiGe gate stacks.
An interface-compressed diffuse interface method and its application for multiphase flows
Authors: Zhang Tongwei , Wu Jie , Lin Xingjian
Published: December 2019

In this paper, an interface-compressed diffuse interface method is proposed for simulating multiphase flow with a large density ratio. In this method, an interface-compression term is introduced into the Cahn-Hilliard equation to suppress the interface dispersion caused by the numerical and modeling diffusion. The additional term only takes effect in the region of phase interface and works normal to the interface. The compression rate can be adjusted synchronously according to the local gradient of normal velocity at the interface. Numerical validations of the proposed method are implemented by simulating Rayleigh-Taylor instability, bubble deformation in shear flow, bubble merging, and bubble rising with a density ratio of 1000 and a viscosity ratio of 100. Good agreement of interface shapes and flow properties has been achieved as compared with both analytical solutions and published data in the literature. The obtained results also show that the present method makes great improvement of interface sharpness and avoids the occurrence of unphysical phenomenon. Meanwhile, the tiny interfacial structures can be captured effectively.
Enhancement of the electronic thermoelectric properties of bulk strained silicon-germanium alloys using the scattering relaxation times from first-principles calculations
Authors: Murphy-Armando F.
Published: December 2019

We use first-principles electronic structure methods to calculate the electronic thermoelectric properties (i.e., due to electronic transport only) of single-crystalline bulk n-type silicon-germanium alloys vs Ge composition, temperature, doping concentration, and strain. We find excellent agreement to available experiments for the resistivity, mobility, and Seebeck coefficient. These results are combined with the experimental lattice thermal conductivity to calculate the thermoelectric figure of merit ZT, finding very good agreement with experiments. We predict that 3% tensile hydrostatic strain enhances the n-type ZT by 50% at carrier concentrations of n=1020cm−3 and a temperature of T=1200K. These enhancements occur at different alloy compositions due to different effects: at 50% Ge composition, the enhancements are achieved by a strain induced decrease in the Lorenz number, while the power factor remains unchanged. These characteristics are important for highly doped and high temperature materials, in which up to 50% of the heat is carried by electrons. At 70% Ge, the increase in ZT is due to a large increase in the electrical conductivity produced by populating the high mobility Γ conduction band valley, lowered in energy by strain.
Mechanical properties of monolayer ternary transitional metal dichalogenides MoS2xTe2(1 − x): A molecular dynamics study
Authors: Ying Penghua , Zhang Jin , Zhong Zheng
Published: December 2019

In this paper, the mechanical behaviors of recently synthesized monolayer ternary transitional metal dichalogenides (TMDs) MoS2xTe2(1 − x) (0 < x < 1) under tensile loading are studied by classical molecular dynamics simulations. Particular attention is paid to the fundamental mechanical properties such as Young's modulus and fracture behaviors of monolayer MoS2xTe2(1 − x). Our results show that Young's modulus of monolayer MoS2xTe2(1 − x) remains almost unchanged when the stoichiometric coefficient x is in the range of 0–0.4 but increases apparently when x increases from 0.4 to 1. In terms of their fracture behaviors, the alloyed ternary TMDs are found to show a ductile fracture feature, which is distinctly different from the brittle fracture behavior observed in their pristine binary TMD counterparts. The ultimate strength of alloyed ternary TMDs is found to be much lower than that of the pristine binary TMDs, which is attributed to the unaccommodated deformation caused by the stress concentration between Te atoms and nearby S atoms. The influence of loading direction and temperature on the aforementioned mechanical properties is also examined. It is found that Young's modulus and the ultimate strength of monolayer MoS2xTe2(1 − x) generally decrease with increasing temperature due to the temperature-induced softening effect. In the biaxial tensile test, Young's modulus and ultimate strength are found to be isotropic. The aforementioned mechanical parameters of monolayer MoS2xTe2(1 − x) under biaxial loading are significantly smaller than those under uniaxial loading. The present work is expected to significantly expand the knowledge of the mechanics of ternary TMDs and facilitate their applications in bandgap engineering.
Instabilities of particle-laden layers in the stably stratified environment
Authors: Chou Yi-Ju , Cheng Che-Jung , Chern Ruey-Lin , Hung Chen-Yen
Published: December 2019

The stability of the interface formed by fine suspended particles is studied through linear stability analysis. Our derivation using the regular perturbation expansion with respect to the particle’s settling velocity shows that the unstable modes are independent of the gravitational settling of individual particles. These modes can be obtained from the six-order ordinary differential equation obtained from the analysis of zero-order quantities. In addition to the four boundary conditions applied at the interface in the traditional Rayleigh-Taylor problem in the semi-infinite domain, two conditions based on the continuity of the concentration of the background stratification agent and its gradient are introduced. Our stability results show transition of modes from a small value in a regime of Rayleigh-Taylor instability to the large values of double-diffusive convection when the background density stratification becomes increasingly significant. In the latter case, our analysis shows growth of small perturbations with dominant wavelengths scaled by the double-diffusion length scale. The transition of unstable modes depends on the density ratio, the Prandtl number of the stratification agent, and the viscosity ratio between the two fluid layers. The analysis is further confirmed by the results from the direct numerical simulation.
Determination of the excited argon states densities in high-frequency capacitive discharge
Authors: Kovalev A. S. , Kurchikov K. A. , Proshina O. V. , Rakhimova T. V. , Vasilieva A. N. , Voloshin D. G.
Published: December 2019

An experimental measurement of the density of excited argon states 1s5, 1s4, 1s3, and 1s2 was carried out for an rf capacitive discharge in argon at a frequency of 13.56 MHz and 81 MHz for two pressures of 50 and 100 mTorr in a wide range of discharge applied power. A collision-radiative model was developed to calculate the densities of 1s states from the known electron density and the electron energy distribution function. The electron energy distribution function is obtained from a self-consistent discharge simulation based on the Particle in cell with Monte Carlo collisions model. It is shown that the calculated densities of the metastable states of argon are in good agreement with the experimentally measured ones. The calculated resonance state densities are underestimated.
Thermal boundary resistance predictions with non-equilibrium Green's function and molecular dynamics simulations
Authors: Chu Yuanchen , Shi Jingjing , Miao Kai , Zhong Yang , Sarangapani Prasad , Fisher Timothy S. , Klimeck Gerhard , Ruan Xiulin , Kubis Tillmann
Published: December 2019

The nonequilibrium Green's function (NEGF) method with Büttiker probe scattering self-energies is assessed by comparing its predictions for the thermal boundary resistance with molecular dynamics (MD) simulations. For simplicity, the interface of Si/heavy-Si is considered, where heavy-Si differs from Si only in the mass value. With Büttiker probe scattering parameters tuned against MD in homogeneous Si, the NEGF-predicted thermal boundary resistance quantitatively agrees with MD for wide mass ratios. Artificial resistances that the unaltered Landauer approach yields at virtual interfaces in homogeneous systems are absent in the present NEGF approach. Spectral information results from NEGF in its natural representation without further transformations. The spectral results show that the scattering between different phonon modes plays a crucial role in thermal transport across interfaces. Büttiker probes provide an efficient and reliable way to include anharmonicity in phonon related NEGF. NEGF including the Büttiker probes can reliably predict phonon transport across interfaces and at finite temperatures.
Scattering in non-ideal classical plasmas: Scattering length and zero-energy resonances
Authors: Karmakar Akashdip , Ghoshal Arijit
Published: December 2019

A fully quantum mechanical calculation has been performed to investigate the scattering of charged particles in nonideal classical plasmas (NICPs). Interactions among the charged particles in NICP have been depicted by a pseudopotential, derived from a sequential solution of Bogolyubov's chain equations. The Schwinger variational method (SVM) has been employed in the momentum space to compute the scattering phase shifts accurately for various plasma parameters. A detailed study has been made on the dynamics of electron-electron (e-e) and electron-proton (e-p) scattering in NICP for a wide range of plasma parameters. Special attention is paid to explore the scattering dynamics at low incident energies. In particular, scattering length and zero-energy resonances have been investigated in detail. Furthermore, effects of nonideality of plasma on the total cross section and transport cross section have also been studied.
A consistent reduction of the two-layer shallow-water equations to an accurate one-layer spreading model
Authors: Fyhn Eirik Holm , Lervåg Karl Yngve , Ervik Åsmund , Wilhelmsen Øivind
Published: December 2019

The gravity-driven spreading of one fluid in contact with another fluid is of key importance to a range of topics. These phenomena are commonly described by the two-layer shallow-water equations (SWE). When one layer is significantly deeper than the other, it is common to approximate the system with the much simpler one-layer SWE. It has been assumed that this approximation is invalid near shocks, and one has applied additional front conditions to correct the shock speed. In this paper, we prove mathematically that an effective one-layer model can be derived from the two-layer equations that correctly capture the behavior of shocks and contact discontinuities without additional closure relations. The result shows that simplification to an effective one-layer model is justified mathematically and can be made without additional knowledge of the shock behavior. The shock speed in the proposed model is consistent with empirical models and identical to front conditions that have been found theoretically by von Kármán and Benjamin. This suggests that the breakdown of the SWE in the vicinity of shocks is less severe than previously thought. We further investigate the applicability of the SW framework to shocks by studying one-dimensional lock-exchange/-release. We derive expressions for the Froude number that are in good agreement with the widely employed expression by Benjamin. The equations are solved numerically to illustrate how quickly the proposed model converges to solutions of the full two-layer SWE. We also compare numerical results from the model with results from experiments and find good agreement.
Low temperature anomalies and room temperature magnetism in In0.95Fe0.05Sb dilute magnetic semiconducting film
Authors: Agrawal Naveen , Sarkar Mitesh , Ganesan V.
Published: December 2019

We report the results of structural, electrical, surface morphological, and magnetic studies on the undoped and dilute Fe (0.05) doped InSb films (In0.95Fe0.05Sb) using the grazing angle X-ray diffraction technique, the quantum design physical property measurement system, atomic force microscopy (AFM), magnetic force microscopy (MFM), and the quantum design magnetic property measurement system. The In0.95Fe0.05Sb film of 500 nm thickness is grown on the silicon (Si) substrate using the thermal evaporation technique. A systematic investigation of electrical resistivity as a function of temperature and magnetic field is embarked. The electrical resistivity of the respective sample exhibits an upturn at approximately 15 K in the ferrimagnetic region. This theory explains the anomalous behavior of the electrical resistivity based on electron-electron, electron-phonon, electron-magnon, and Kondo-like spin-dependent scattering. The high-temperature data above 300 K are interpreted using the adiabatic small polaron hopping model. The AFM study shows the uniform particle size distribution, whereas the magnetic interaction at the surface is seen through MFM. The zero-field cooled magnetization measurement shows the transition at ∼65 K. The hysteresis curve at 10 K shows the ferrimagnetic behavior of the In0.95Fe0.05Sb film with coercivity and residual magnetization values of ∼100 Oe and 6.8811 emu, respectively.
Escape of
α
-particle from hot-spot for inertial confinement fusion
Authors: Li Kai , Lan Ke
Published: December 2019

Escape of α-particles from a burning or an ignited burning deuterium-tritium (DT) hot-spot with temperature up to more than tens of kilo-electron-volts is very important in inertial confinement fusion, which can significantly influence not only the hot-spot dynamics but also the energy gain. In this paper, we study the α-particle escape from a burning or an ignited burning DT hot-spot by considering the modifications, including the α-particle stopping by both DT ions and electrons with their Maxwellian average stopping weights, the relativity effect on electron distribution, and the modified Coulomb logarithm of the DT-α particle collisions. As a result, the escape effect from our modified model is obviously stronger than those from the traditional models. A fitted expression is presented to calculate the escape factor, which can be applied to a burning hot-spot with a temperature of 1–150 keV and an areal density of 0.04–3 g/cm2 with an accuracy within ±0.02. Finally, we discuss the α-particle escape effect on hot-spot dynamics and thermonuclear energy gain by comparing the results with escape factors from different models.
Experimental simulation of hybrid quantum systems and entanglement on a quantum computer
Authors: Mazhandu Farai , Mathieson Kayleigh , Coleman Christopher , Bhattacharyya Somnath
Published: December 2019

We propose the utilization of the IBM Quantum Experience quantum computing system to simulate different scenarios involving common hybrid quantum system components, the nitrogen vacancy center (NV center), and the flux qubit. We perform a series of simulation experiments and demonstrate properties of a virtual hybrid system, including its spin relaxation rate and state coherence. In correspondence with experimental investigations, we look at the scalability of such systems and show that increasing the number of coupled NV centers decreases the coherence time. We also establish the main error rate as a function of the number of control pulses in evaluating the fidelity of the four qubit virtual circuit with the simulator. Our results show that the virtual system can attain decoherence and fidelity values comparable to what has been reported for experimental investigations of similar physical hybrid systems, observing a coherence time at 0.35 s for a single NV center qubit and fidelity in the range of 0.82. This work thus establishes an effective simulation protocol to test and evaluate different technologies as a supplementary measure that complements their experimental operation.
Common surface structures of graphene and Au(111): The effect of rotational angle on adsorption and electronic properties
Authors: Yortanlı Merve , Mete Ersen
Published: December 2019

Graphene adsorption on the Au(111) surface was explored to identify its common surface structures by means of van der Waals corrected density functional theory calculations. The alignment of graphene in the form of certain rotational angles on the gold surface has an important role in lattice matching, which causes Moiré patterns, and in the electronic properties of the resulting common cell structures. Dispersive weak interactions between carbon and gold layers lead to a downward shift of Fermi energy of the adsorption system with respect to the Dirac point of graphene showing a p-type doping character. Moreover, the shift was shown to depend on the rotational angle of graphene on Au(111).
Modulation of spin-charge conversion in silicon
Authors: Weng Yi-Chien , Liang C.-T. , Lin Jauyn Grace
Published: December 2019

Silicon (Si) is an important material for the application of spintronics because its spin lifetime is relatively long compared to those of metals, and it is the well-studied semiconductor in term of its electronic properties. However, as a potential spintronic material, the complete knowledge about the spintronic properties of Si is still not established yet. In this work, the technique of ferromagnetic resonance driven spin pumping is adopted to accurately determine several critical parameters, including the spin lifetime (τs), the spin diffusion length (λs), and the spin Hall angle (θISHE) of Si. By changing the type (n- and p-type) of carrier and the carrier concentration (1 × 1013 to 1.7 × 1019 cm−3), a correlation between λs  and  θISHE is found, suggesting an effective route to tune the efficiency of spin-charge conversion in Si.
Optical probing of extended defects in CdTe virtual substrates via isolated emitters produced by weakly perturbed fragments of partial dislocations
Authors: Krivobok V. S. , Chentsov S. I. , Nikolaev S. N. , Chernopitssky M. A. , Onishchenko E. E. , Pruchkina A. A. , Martovitskiy V. P. , Bagaev V. S. , Ikusov D. G. , Marin D. V. , Mikhailov N. N. , Yakushev M. V.
Published: December 2019

It is shown that, at helium temperatures, relaxed CdTe films reveal isolated emitters, the properties of which indicate their relation with a weakly perturbed fragment of the Shockley dislocation core. The polarization and spatial distribution of such emitters in CdTe/Si and CdTe/GaAs virtual substrates contain information on the structure of extended defects in a relaxed CdTe layer, which are important for HgCdTe epitaxy.
Deep learning optimized single-pixel LiDAR
Authors: Radwell Neal , Johnson Steven D. , Edgar Matthew P. , Higham Catherine F. , Murray-Smith Roderick , Padgett Miles J.
Published: December 2019

Interest in autonomous transport has led to a demand for 3D imaging technologies capable of resolving fine details at long range. Light detection and ranging (LiDAR) systems have become a key technology in this area, with depth information typically gained through time-of-flight photon-counting measurements of a scanned laser spot. Single-pixel imaging methods offer an alternative approach to spot-scanning, which allows a choice of sampling basis. In this work, we present a prototype LiDAR system, which compressively samples the scene using a deep learning optimized sampling basis and reconstruction algorithms. We demonstrate that this approach improves scene reconstruction quality compared to an orthogonal sampling method, with reflectivity and depth accuracy improvements of 57% and 16%, respectively, for one frame per second acquisition rates. This method may pave the way for improved scan-free LiDAR systems for driverless cars and for fully optimized sampling to decision-making pipelines.
Energy transfer speed of polymer network and its scaling-law of elastic modulus—New insights
Authors: Li Ziqian , Liu Zishun
Published: December 2019

The elastic modulus E of a solvent-absorbable polymer network and its polymer-fraction ϕ (or, conversely, water content) obey a scale-law E∼ϕν. In particular, for a polymer network paired with a good solvent, ν = 2.3. We now provide a fresh look at this problem from the perspective of energy transfer speed defined for a complex fractal network. Two core algorithms are designed, showing that the elastic modulus actually stands for the ability to transfer energy within a certain matter. Our algorithms can directly give the scaling exponent of ν=2.3. It is much easier to understand the scaling law E∼ϕν from the perspective of energy transfer speed.
Spatio-temporal behavior of magnetohydrodynamic fluctuations with cross-helicity and background magnetic field
Authors: Lugones R. , Dmitruk P. , Mininni P. D. , Pouquet A. , Matthaeus W. H.
Published: December 2019

We study the spatiotemporal behavior of the Elsässer variables describing magnetic and velocity field fluctuations, using direct numerical simulations of three-dimensional magnetohydrodynamic turbulence. We consider cases with relatively small, intermediate, and large values of a mean background magnetic field and with null, small, and high cross-helicity (correlations between the velocity and the magnetic field). Wavenumber-dependent time correlation functions are computed for the different simulations. From these correlation functions, the decorrelation time is computed and compared with different theoretical characteristic times: the local nonlinear time, the random-sweeping time, and the Alfvénic time. It is found that decorrelation times are dominated by sweeping effects for low values of the mean magnetic field and for low values of the cross-helicity, while for large values of the background field or of the cross-helicity and for wave vectors sufficiently aligned with the guide field, decorrelation times are controlled by Alfvénic effects. Finally, we observe counterpropagation of Alfvénic fluctuations due to reflections produced by inhomogeneities in the total magnetic field. This effect becomes more prominent in flows with large cross-helicity, strongly modifying the propagation of waves in turbulent magnetohydrodynamic flows.
Statistics of temperature and thermal energy dissipation rate in low-Prandtl number turbulent thermal convection
Authors: Xu Ao , Shi Le , Xi Heng-Dong
Published: December 2019

We report the statistical properties of temperature and thermal energy dissipation rate in low-Prandtl number turbulent Rayleigh-Bénard convection. High resolution two-dimensional direct numerical simulations were carried out for the Rayleigh number (Ra) of 106 ≤ Ra ≤ 107 and the Prandtl number (Pr) of 0.025. Our results show that the global heat transport and momentum scaling in terms of Nusselt number (Nu) and Reynolds number (Re) are Nu = 0.21Ra0.25 and Re = 6.11Ra0.50, respectively, indicating that scaling exponents are smaller than those for moderate-Prandtl number fluids (such as water or air) in the same convection cell. In the central region of the cell, probability density functions (PDFs) of temperature profiles show stretched exponential peak and the Gaussian tail; in the sidewall region, PDFs of temperature profiles show a multimodal distribution at relatively lower Ra, while they approach the Gaussian profile at relatively higher Ra. We split the energy dissipation rate into contributions from bulk and boundary layers and found the locally averaged thermal energy dissipation rate from the boundary layer region is an order of magnitude larger than that from the bulk region. Even if the much smaller volume occupied by the boundary layer region is considered, the globally averaged thermal energy dissipation rate from the boundary layer region is still larger than that from the bulk region. We further numerically determined the scaling exponents of globally averaged thermal energy dissipation rates as functions of Ra and Re.
Broadband absorption enhancement of graphene in the ultraviolet range based on metal-dielectric-metal configuration
Authors: Guo Yongbo , Wang Shuqi , Zhou Yuanguo , Chen Chengying , Zhu Jinfeng , Wang Ren , Cai Yijun
Published: December 2019

Light absorption of suspended monolayer graphene in the ultraviolet range is relatively low, which impedes the potential applications for graphene-based optoelectronic devices. To enhance the light-matter interaction in a wide spectral range, we propose two plasmonic structures based on a metal-dielectric-metal configuration. After rigorous optimization of geometric parameters, broadband and enhanced ultraviolet light absorption of graphene can be achieved. The bandwidth above 30% absorption rate can reach up to 245 nm (from 240 nm to 485 nm), while the relative bandwidth can reach up to 68%. The optimal absorption peak is as high as 54%. Besides, the absorption spectrum can be tuned by adjusting the geometric parameters. Physical insight is revealed with electric and magnetic field distributions. Furthermore, the tolerance for the incident angle is demonstrated, and the dependence of the polarization angle is discussed. Our approach shows promising potential for novel graphene-based applications in the ultraviolet range.
Model helps optimize energy sustainability in China
Authors: Gasparini Allison
Published: December 2019

Researchers use a system-dynamics approach to predict how electric power substitution policy will affect energy supply and demand in China.
Infrared spectroscopy of CO2 transformation by group III metal monoxide cations
Authors: Yang Dong , Su Ming-zhi , Zheng Hui-jun , Zhao Zhi , Kong Xiang-tao , Li Gang , Xie Hua , Zhang Wei-qing , Fan Hong-jun , Jiang Ling
Published: December 2019

Infrared photodissociation spectroscopy of mass-selected [MO(CO2)n]+ (M=Sc, Y, La) complexes indicates that the conversion from the solvated structure into carbonate one can be achieved by the ScO+ cation at n=5 and by the YO+ cation at n=4, while only the solvated structures are observed for the LaO+ cation. These findings suggest that both the ScO+ and YO+ cations are able to fix CO2 into carbonate. Quantum chemical calculations are performed on [MO(CO2)n]+ to identify the structures of the low-lying isomers and to assign the observed spectral features. Theoretical analyses show that the [YO(CO2)n]+ complex has the smallest barrier for the conversion from the solvated structure into carbonate one, while [LaO(CO2)n]+ exhibits the largest conversion barrier among the three metal oxide cations. The present system affords a model in clarifying the effect of different metals in catalytic CO2 transformation at the molecular level.
Physical cosmology wins a share of the Nobel Prize in Physics
Authors: Berkowitz Rachel
Published: December 2019

James Peebles developed a mathematical framework that describes how the universe evolved. Decades of empirical evidence later, it still holds up.
Half of Nobel Prize in Physics honors exoplanet trailblazers
Authors: Grant Andrew
Published: December 2019

By discovering an extrasolar planet orbiting a sunlike star, the laureates helped launch a field that explores a diverse set of worlds and their potential to host life.
Structures of 1:1 Mononuclear Adducts of Zinc(II) Halides, ZnX2 (X=Cl, Br, I) and of New Hydrates of 1:1 Adducts of Zinc(II) Nitrate and Sulfate with Aromatic N,N′′-Bidentate Base Derivatives of Pyridine (bpy, phen)
Authors: Bowmaker Graham A. , Kim Yang , Skelton Brian W. , Sobolev Alexandre N. , White Allan H.
Published: November 2019

Single crystal X-ray structure determinations have been executed for several title compounds of the mononuclear form [LMX2], namely [(bpy)ZnX2], X=Cl, Br; [(phen)ZnX2], X=Cl, Br, I (bpy=2,2′-bipyridine; phen=1,10-phenanthroline). Also reported are the crystal structures of ZnSO4/bpy/H2O (1:1:5) (≡ [(bpy)Zn(OH2)4](SO4)·H2O) and Zn(NO3)2/bpy/H2O (1:1:3) (≡ [(bpy)Zn(OH2)3(ONO2)](NO3)). The sulfate complex completes the array [LM(OH2)4]2+, L=bpy, phen, M=Zn, Cd, while the nitrate is the first nitrate example for [LM(OH2)3(OX)](+) (OX=ONO2, OSO3). In all examples of the sulfate and nitrate forms here and previously defined, the metal atoms are six-coordinate, with any anionic donors lying in axial coordination sites (i.e. M–O (quasi-) normal to the LM plane). The structures of [LHg(SCN)2] (L=phen, tpy) (tpy=2,2′:6′,2′-terpyridine), [(tpy)(CdBr2], and [Zn(tpy)2](NO3)2·2H2O are also recorded.
Spatial variability and sources of platinum in a contaminated harbor – tracing coastal urban inputs
Authors: Abdou Melina , Schäfer Jörg , Gil-Díaz Teba , Tercier-Waeber Mary-Lou , Catrouillet Charlotte , Massa Francesco , Castellano Michela , Magi Emanuele , Povero Paolo , Blanc Gérard
Published: December 2019

Environmental contextEmerging contaminants such as platinum are continuously released into aquatic environments. Analytical challenges, however, have restricted information on their geochemical cycles. We examine the potential use of platinum as a tracer of anthropogenic inputs in a model industrial/urban site (Genoa Harbor, Italy), and provide a first estimate of dissolved platinum baseline concentrations in the northern Mediterranean coast. AbstractBiogeochemical cycles that include processes to control platinum (Pt) distribution remain widely unknown in aquatic environments, especially in coastal systems. Dissolved Pt concentrations in coastal seawater (PtD) and in suspended particulate matter (SPM, PtP) were measured, together with master variables comprising dissolved oxygen, dissolved and particulate organic carbon, chlorophyll-a, turbidity, and ammonium levels, along two longitudinal profiles in the industrial Genoa Harbor (north-west Italy). Concentrations and spatial distribution of PtD and PtP levels reflect distinct concentration gradients that were attributed to different Pt sources such as hospital, domestic and industrial wastewater, atmospheric deposition, and/or road runoff. Concentrations reaching up to 0.18ngL−1 PtD and 14ngg−1 PtP reflect the impact of Pt urban inputs to coastal sites. These first data highlight considerable anthropogenic contamination in a confined harbor compared with the proposed reference value for the western Mediterranean surface seawater measured at external sites. Identified correlations between Pt levels and human pollution signals suggest the potential use of Pt as a new tracer of anthropogenic inputs that can be applied to other urbanised coastal systems. Biogeochemical processes that induce changes in the partitioning and fate of Pt in coastal seawater reflect a spatial variability and highlight the need for comprehensive environmental monitoring at an appropriate spatial scale.
118 Semen quality and fertilization ability of myostatin-knockout boars
Authors: Xuan M.-F. , Han S.-Z. , Quan B.-H. , Yin X.-J. , Kang J.-D.
Published: December 2019

Myostatin-knockout (MSTN−/−) pigs may provide a source of healthy lean protein for human consumption. However, little is known about the effect of this knockout on semen quality, which is important if these pigs are used for production. The purpose of this study is to evaluate the semen quality and fertility of MSTN−/− boars. We generated MSTN−/− boars from Duroc-Landrace-Yorkshire hybrid pig cell lines by somatic cell nuclear transfer, and all 12 boars showed sexual maturation with an obvious “double muscling” phenotype. Semen was collected randomly from three MSTN−/− boars using the gloved-hand technique by one technician and then tested by computer-assisted semen analysis. Semen acrosomal integrity and deformity were measured using Coomassie blue- and eosin-stained smears, respectively. Sperm plasma membrane integrity and mitochondrial activity were evaluated by Hoechst 33342, propidium iodide, and JC-1 multiple staining. The reproductive performance of MSTN−/− boars was evaluated by IVF and by AI. All data were analysed by Student's t-tests. The results showed that the semen color, odor, and pH had no abnormalities. The concentration, motility, plasma membrane integrity, deformity, acrosome integrity, and mitochondrial activity of the semen presented no significant differences from those of the control semen (Duroc). The ejaculation volume of the MSTN−/− boars was significantly lower than that of the control (168.78±6.70 and 223.11±21.21mL, respectively), although the total sperm number was not significantly different. The rate of cleavage and blastocyst formation (247 to 254 oocytes per boar) was not significantly different from those of the control (69.1±0.7 vs. 65.2±1.6%, and 20.2±1.2 vs. 22.8±1.4%, respectively). Seventeen healthy offspring were successfully produced from three sows through AI using semen from one MSTN−/− boar. However, the genotype of piglets has not been tested at present. Thus, MSTN−/− boar may be used as sires, and these pigs are expected to be developed to provide new super-lean meat varieties in the future.
12 Assessment of oocyte and embryo production in senescent beef cows
Authors: Alvarez R. H. , Bayeux B. M. , Watanabe Y. F. , Joaquim D. A. , Duarte K. M. R. , Pugliesi G.
Published: December 2019

Fertility associated with age has been poorly documented in cattle. There is evidence that more than 50% of cows became infertile (failure to bear a calf for two successive years) at the age of 15. The causes of infertility in cows have been attributed to poor oocyte quality and/or follicle depletion. The present study aimed to compare the rates of oocyte and invitro embryo production of fertile cows older than 15 years. Sixteen Nellore cows (Bos taurus indicus) 200.3±4.9 months old were submitted to two ovum pickup series (OPU1 and OPU2) at a 2-year (2017 and 2019) interval. Before the OPU1 of each series, the cows were prepared with an IM injection of 2mg estradiol benzoate and 0.15mg prostaglandin F2α analogue and a progesterone-releasing intravaginal device (1g). After five days, the progesterone-releasing intravaginal device was withdrawn and the OPU1 was performed. The second OPU (OPU2) was performed 5 days later to aspirate only the growing follicles. The number and morphologic quality of recovered cumulus-oocyte complexes were registered. After IVM (tissue culture medium 199) and fertilization (Tyrode's solution) of cumulus-oocyte complexes, the presumptive zygotes were cultured in synthetic oviductal fluid with amino acids to assess developmental rates to blastocyst. Data were analysed by chi-squared and Wilcoxon test. The number of oocytes recovered at OPU1 was higher in 2107 than in 2019 (27.8±6.6 vs. 10.8±4.2; P<0.01), whereas in OPU2 the production of oocytes was not different (14.7±3.3 vs. 10.9±3.1). In OPU1, eight cows in 2017 and four in 2019 produced more than 20 oocytes, compared with only one cow in OPU2 of both years (P=0.02). Although there was no significant difference in the proportion of viable oocytes in OPU1 (83.6% and 87.2%) and OPU2 (85.5 and 68.0%), more viable oocytes were produced at OPU1 of 2017 (23.2±5.8) compared with OPU1 of 2019 (9.4±4.1), OPU2 of 2017 (12.6±2.7) and OPU2 of 2019 (7.4±2.4), respectively (P<0.05). There was no significant difference in the proportion of cleaved oocytes in OPU1 (74.2 and 75.1%) and OPU2 (68.9 and 79.8%). Two cows in 2017 (12.5%) and five in 2019 (31.2%) did not produce embryos in both OPUs. Cows produced more embryos (blastocysts) in OPU1 at 2017 (7.3±1.6) than 2019 (2.8±0.6; P<0.05), whereas in OPU2 there was no difference (4.1±0.8 and 3.1±0.8). In conclusion, senescent fertile cows decreases the number of oocytes and embryos as they approach 20 years of age; however, the quality of oocytes does not appear to be compromised.
Financial support was provided by FAPESP (proc. 2018/07450-5).
123 Nerve growth factor-induced ovulation in llamas: Evidence of hypothalamic refractoriness to nerve growth factor during the declining phase of the luteinising hormone surge
Authors: Carrasco R. , Adams G.
Published: December 2019

Nerve growth factor (NGF) in semen is responsible for triggering ovulation after copulation in camelids. Interaction of NGF with its cognate receptors results in a preovulatory luteinising hormone (LH) surge that leads to ovulation, but the pharmacokinetics of NGF and the mechanism by which it mediates LH release are unknown. In an effort to elucidate the site and mechanism of action involved, the objective of this study was to determine whether the decline in the LH surge occurs as a result of pituitary depletion (i.e. diminished response to gonadotrophin-releasing hormone (GnRH)) or as an obtunded response at the level of the hypothalamus (diminished GnRH). Adult nonpregnant, nonlactating llamas (n=18) were synchronized by the administration of an ovulatory dose of a GnRH analogue (100μg IM; Fertiline, Vetoquinol). At 10 to 14 days later, the ovaries were examined to confirm the presence of a dominant follicle measuring ≥ 7mm, and a jugular catheter was put in place. The following day, a pretreatment blood sample was taken, and llamas were treated intravenously with 1mg of purified NGF from llama seminal plasma. Blood samples were taken every 30min for 7h from the time of NGF treatment. After the last blood sample was taken, llamas were treated with NGF (n=6; 1mg IV), GnRH (n=5; 100μg IV), or saline (Sal; IV; n=6), and blood samples were taken every 30min for another 7h. The ovaries were examined 48h after initial NGF treatment, via transrectal ultrasonography, to detect ovulation. Plasma was harvested and stored for analysis of LH concentration by radioimmunoassay. Data were compared using ANOVA for repeated measures, and single-point data were analysed using paired t-tests. As expected, most llamas ovulated in response to the initial NGF treatment (5 out of 5 in NGF-GnRH; 5 of 6 in NGF-NGF; 5 of 6 in NGF-Sal). Compared with pretreatment values, all llamas showed a 4-fold increase in plasma LH concentrations within 2h of the initial NGF treatment (P<0.05). Plasma LH concentrations peaked at 3h after initial NGF treatment and began to decline 4.5 to 5h after treatment (P<0.05). Plasma LH concentrations continued to decline following the second dose of NGF or Sal, whereas a transient elevation of LH was detected in llamas treated with GnRH (P<0.05). The LH concentration returned to basal levels (pretreatment) 8, 12, and 13h after NGF treatment in llamas treated with NGF-Sal, NGF-GnRH, and NGF-NGF, respectively. We conclude that the lack of LH response to the second dose of NGF is not because of pituitary depletion but rather due to diminished GnRH. The latter may be attributed to either a downregulation of NGF receptors within the hypothalamus or to temporary depletion of GnRH at the nerve terminals within the median eminence.
Research was supported by the Natural Sciences and Engineering Research Council of Canada.
124 Ovarian follicular development and steroid secretion during oestrous cycle of Lohi sheep
Authors: Younis M. , Irfan-ur-Rehman Khan M. , Murtaza A. , Abbas M. , Tahir M. Z. , Javed K. , Mohsin I. , Shahzad M.
Published: December 2019

Pakistan has 30.9 million heads of sheep; however, little information is available on their reproductive aspects. The objective of this study was to document ovarian physiology and endocrinology of Lohi ewes during the oestrous cycle. Nine Lohi ewes, synchronized by administering single prostaglandin F2α (PGF2a; Cyclomate, Star Laboratories), were monitored for ovarian follicular dynamics using transrectal ultrasonography (7.5MHz, HS-1500, Honda) for two consecutive oestrous cycles during the breeding season (September to November 2018). Changes in plasma progesterone and oestradiol-17β concentrations of ewes (n=9) were also determined during the oestrous cycle using radioimmunoassay. The interovulatory interval of Lohi ewes averaged 17.0±0.1 days, and the duration of follicular and luteal phases was 4.6±0.2 and 11.3±0.2 days, respectively. Follicles emerged in either 3- or 4-wave patterns, but the frequency of the 3-wave pattern was higher than that of the 4-wave (87 vs. 13%, respectively; P=0.05). Following ovulation (Day 0), follicles (=3mm) in 3-wave cycles (n=14) emerged on Days 0.7, 5.2, and 10.5, whereas in 4-wave cycles (n=2) follicles emerged on Days 0.1, 4, 8.5, and 11.5. The maximum diameter of preovulatory follicles and corpora lutea (CL) were 5.4±0.3 and 10.4±0.3mm, respectively. Regardless of the wave pattern, single ovulation occurred in each cycle. The CL was first detectable on Day 4±0.1, it reached maximum diameter on Day 9±0.1, and luteolysis began on Day 12.2±0.2 of the cycle. The peak plasma oestradiol-17β concentration (42.5±2.6 pgmL−1) was observed 48h before ovulation and correlated with the diameter of the preovulatory follicle during the follicular phase (r=0.84; P<0.05). The peak plasma progesterone concentration (11.8±1.7ngmL−1) was observed on Day 9±0.1 and coincided with the diameter of CL throughout the oestrous cycle (r=0.93; P<0.05). In conclusion, the majority of oestrous cycles in Lohi ewes had a 3-wave pattern and were mono-ovulatory in nature.
129 Ovarian dynamics and gonadotropins during selection of the dominant follicle in postpartum lactating versus non-postpartum cycling mares
Authors: Pastorello M. , Gastal M. O. , Piquini G. K. , Godoi D. B. , Gastal E. L.
Published: December 2019

The mare, compared to other livestock, has the shortest interval from partum to the first ovulation. In monovulatory species, the follicle deviation process in a wave is characterised by the continued growth of the dominant follicle (DF) and regression of the subordinate follicle. Although follicle diameter deviation, a key event of follicle selection, has been investigated during the oestrous and menstrual cycles, the occurrence of this phenomenon before the first postpartum ovulation seems to be unclear in all species. This study aimed to compare the follicular dynamics and gonadotropin profiles around the follicle diameter deviation day in postpartum lactating (PP Lactating; n=24) versus non-postpartum cycling (NPP Cycling; n=15) mares. On the day of parturition, every PP Lactating mare was paired with an NPP Cycling mare, and ovarian follicles (>4mm) were tracked daily by transrectal ultrasonography, and blood samples were collected. Data were analysed in the PP Lactating group according to the length of the partum-ovulation interval (POI; ≤22 and >22 days) and the postpartum interovulatory interval (PPIOI), and in the NPP Cycling group during two interovulatory intervals (1st and 2nd IOI). In addition, regardless of group, all four intervals were compared. We performed the FSH and LH assays using radioimmunoassay. Ovarian and hormonal parameters were analysed using ANOVA for sequential data. The day and diameter of the DF at the deviation (overall mean: 14.9±2.5 days; 21.7±0.4mm, respectively) were not different (P>0.05) between PP Lactating and NPP Cycling mares. However, when considering the length of POI, follicle deviation occurred 4.4±0.8 days earlier (P<0.001) in mares with POI ≤ 22 days than in mares with POI>22 days. No difference was found between PP Lactating and NPP Cycling mares within and between groups for the intervals from deviation to maximum diameter of the DF (10.4±0.4 days), for the intervals from deviation to ovulation (12.1±0.5 days), or for the growth rates of the DF from deviation to maximum diameter (2.6±0.1mm per day). The growth rate of the DF from deviation to ovulation (2.4±0.1mm per day) did not differ between PP Lactating and NNP Cycling mares; however, this growth rate was lower (P<0.03) in the POI, PPIOI, and 1st IOI compared with the 2nd IOI. The mean diameter of the DF around deviation (days −3 to 3; 22.5±0.3mm), and systemic FSH (days −4 to 4; 10.3±0.2ngmL−1) were not different between PP Lactating and NPP Cycling mares. Level of LH was lower (P<0.0001) around deviation (days −4 to 4) in the PP Lactating (0.7±0.0ngmL−1) versus the NPP Cycling mares (1.8±0.1ngmL−1). Results demonstrated that a partum effect occurs only on the day of deviation in mares during the foal heat (POI ≤ 22 days) and that low levels of LH during both intervals in PP Lactating mares were not detrimental to prevent ovulation.
130 Increased antral follicle population at 60 days of gestation in Holstein cows with low antral follicle count
Authors: Droher R. G. , Morotti F. , Guidugli Lindquist A. , Fonseca Zangirolamo A. , Marcondes Seneda M.
Published: December 2019

The antral follicle count (AFC) has been pointed out as one of the main factors that influence the efficiency of reproductive biotechniques. Thus, AFC is considered a fertility marker, which has high repeatability in the same animal. The objective of this study was to evaluate AFC in cows at AI (nonpregnant) and at two moments of gestation (30 and 60 days). For this, 35 pregnant cows, aged 23 to 99 months, confined in a freestall system, kept in the same environmental conditions (24°46'28”S, 49°56'42”W) and under the same feeding conditions, were selected for this study. The same technician performed the AI of the females, after detection of natural or induced oestrus, with 25mg of Dinoprost (Lutalyse) intramuscularly (IM). We established AFC (antral follicles ≥3mm diameter) using a convex intravaginal transducer at the time of AI and at 30 and 60 days of pregnancy. Females were distributed in groups of low (≤18 follicles, n=11), intermediate (≥24 and ≤28 follicles, n=11), or high AFC (≥30 follicles, n=13). Data were analysed using a generalized linear mixed model (Minitab version 18.1), with significance declared at P ≤ 0.05. In the low AFC group, there was an increase in the mean number of antral follicles in relation to gestation, presenting 14.82±1.36 at the time of AI and 23.45±2.31 and 35.18±3.17 at 30 and 60 days of pregnancy, respectively (P<0.0001). Similarly, the intermediate group presented an increase in mean AFC, from 24.64±0.76 at the time of AI and 29.27±3.32 at 30 days to 43.36±5.91 at 60 days of gestation (P=0.001). There was no difference in the high AFC group at different moments, as these presented 41.92±3.50 at the time of AI, 38.31±3.96 at 30 days, and 50.92±5.49 at 60 days of pregnancy. Although mean AFCs differed (P<0.0001) between the low, intermediate, and high AFC groups at time of AI and at 30 days of gestation, there were no differences in AFC between the three groups at 60 days of gestation (P=0.329). In conclusion, low AFC females presented an increase in the number of antral follicles at gestation moments 30 and 60 days from AI. This finding reinforces the strategy of using this category more efficiently for ovum pickup at the beginning of gestation.