bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiband polarisation insensitive metamaterial absorber based on circular fractal structure
Authors: Jiang Hao , Xue Zhenghui , Li Weiming , Ren Wu
Published: May 2016

In this study, the authors present a geometrically symmetrical fractal structure called circular fractal structure. The iterative process of the geometric construction is illustrated and the dimension of the proposed circular fractal structure is 1.5729 based on the similarity dimension. Then, a polarisation insensitive multiband perfect metamaterial absorber (MMA) is proposed based on the circular fractal structure. The proposed MMA has three near‐perfect absorption bands for both transverse electric (TE) and transverse magnetic (TM) polarisations based on the theory of the fractal geometry. The current distribution on the top and bottom surfaces of the MMA are presented to preferably understand the physical mechanism behind the multiband absorption. The simulated results match the experimental results well. For both TE and TM polarisations, the three absorption frequencies are f1 = 2.29 GHz, f2 = 4.28 GHz, and f3 = 11.71 GHz, with the absorptivity of 98.7, 99.4, and 99.5%. Both experimental and simulated results indicate that the proposed circular fractal MMA is a promising candidate for absorbing elements in scientific and military applications.
Miniaturisation of microstrip patch antenna using an artificial planar magneto‐dielectric meta‐substrate
Authors: Kumar Saurabh , Vishwakarma Dinesh Kumar
Published: May 2016

In this communication, a practically realisable artificial planar magneto‐dielectric (MD) meta‐substrate is proposed and investigated for microstrip patch antenna miniaturisation. The meta‐substrate employs cross‐coupled twisted metallic split‐ring resonator ring pairs to achieve effective permeability (μeff) and permittivity (ɛeff) greater than that of the host dielectric which leads to antenna miniaturisation. Electromagnetic simulation and analysis of effective material parameters are performed to characterise it, which shows nearly equal enhanced effective permeability and permittivity (μeff ≃ ɛeff) at 2.35 GHz with low loss‐factor level not achievable from natural materials. An inset fed microstrip patch antenna is designed on the proposed MD meta‐substrate to test and validate its performance. The performances of the miniaturised patch antenna loaded with proposed dispersive MD meta‐substrate, non‐dispersive homogenous MD substrate, and high‐permittivity substrates (lossy and loss‐free) are compared with the conventional patch antenna on host dielectric. It is found that dispersive nature of the meta‐substrate plays a critical role in the antenna performance. The antenna on proposed meta‐substrate occupying an overall volume of 0.250λ0 × 0.344λ0 × 0.009λ0 at 2.35 GHz is 74.83% miniaturised as compared with the conventional antenna on host dielectric. To ensure the practicability, the designed antenna is fabricated and measured.
Increased inflammation in sanctuary sites may explain viral blips in HIV infection
Authors: Cardozo E. Fabian , Piovoso Michael J. , Zurakowski Ryan
Published: May 2016

Combined antiretroviral therapy (cART) suppress HIV‐1 viral replication, such that viral load in plasma remains below the limit of detection in standard assays. However, intermittent episodes of transient viremia (blips) occur in a set of HIV‐patients. Given that follicular hyperplasia occurs during lymphoid inflammation as a normal response to infection, it is hypothesised that when the diameter of the lymph node follicle (LNF) increases and crosses a critical size, a viral blip occurs due to cryptic viremia. To study this hypothesis, a theoretical analysis of a mathematical model is performed to find the conditions for virus suppression in all compartments and different scenarios of LNF size changes are simulated. According to the analysis, blips with duration of around 30 days arise when the diameter rise rate is between 0.02 and 0.03 days−1. Moreover, the final diameter of the site is directly related to the steady states of the virus load after the occurrence of a blip. When the value of R 0 is around 2.1, to have a steady‐state below the limit of detection after the viral blip, the maximum final diameters should be greater than 0.7 mm so that there is a relative loss of connection between compartments.
The ν6 fundamental frequency of the Ã state of formaldehyde and Coriolis perturbations in the 3ν4 level
Authors: Park G. Barratt , Krüger Bastian C. , Meyer Sven , Schwarzer Dirk , Schäfer Tim
Published: May 2016

Formaldehyde is the smallest stable organic molecule containing the carbonyl functional group and is commonly considered to be a prototype for the study of high-resolution spectroscopy of polyatomic molecules. The a-axis Coriolis interaction between the near-degenerate ν4 and ν6 (out-of-plane and in-plane wagging modes, respectively) of the ground electronic state has received extensive attention and is thoroughly understood. In the first excited singlet Ã 1A2 electronic state, the analogous Coriolis interaction does not occur, because the Ã state suffers from a pseudo-Jahn-Teller distortion, which causes a double-well potential energy structure in the q4′ out-of-plane coordinate, and which dramatically reduces the effective ν4′ frequency. The ν4′ frequency is reduced by such a great extent in the Ã state that it is the 3ν4′ overtone which is near degenerate with ν6′. In the current work, we report the precise ν6′ fundamental frequency in the Ã state, and we determine the strength of the a-axis Coriolis interaction between 3ν4′ and ν6′. We also provide a rotational analysis of the ν4′+ν6′ combination band, which interacts with 3ν4′ via an additional c-axis Coriolis perturbation, and which allows us to provide a complete deperturbed fit to the 3ν4′ rotational structure. Knowledge of the Coriolis interaction strengths among the lowest-lying levels in the Ã state will aid the interpretation of the spectroscopy and dynamics of many higher-lying band structures, which are perturbed by analogous interactions.
Chemical speciation of U, Fe, and Pu in melt glass from nuclear weapons testing
Authors: Pacold J. I. , Lukens W. W. , Booth C. H. , Shuh D. K. , Knight K. B. , Eppich G. R. , Holliday K. S.
Published: May 2016

Nuclear weapons testing generates large volumes of glassy materials that influence the transport of dispersed actinides in the environment and may carry information on the composition of the detonated device. We determine the oxidation state of U and Fe (which is known to buffer the oxidation state of actinide elements and to affect the redox state of groundwater) in samples of melt glass collected from three U.S. nuclear weapons tests. For selected samples, we also determine the coordination geometry of U and Fe, and we report the oxidation state of Pu from one melt glass sample. We find significant variations among the melt glass samples and, in particular, find a clear deviation in one sample from the expected buffering effect of Fe(II)/Fe(III) on the oxidation state of uranium. In the first direct measurement of Pu oxidation state in a nuclear test melt glass, we obtain a result consistent with existing literature that proposes Pu is primarily present as Pu(IV) in post-detonation material. In addition, our measurements imply that highly mobile U(VI) may be produced in significant quantities when melt glass is quenched rapidly following a nuclear detonation, though these products may remain immobile in the vitrified matrices. The observed differences in chemical state among the three samples show that redox conditions can vary dramatically across different nuclear test conditions. The local soil composition, associated device materials, and the rate of quenching are all likely to affect the final redox state of the glass. The resulting variations in glass chemistry are significant for understanding and interpreting debris chemistry and the later environmental mobility of dispersed material.
Full-dimensional quantum dynamics study of the H2 + C2H → H + C2H2 reaction on an ab initio potential energy surface
Authors: Chen Liuyang , Shao Kejie , Chen Jun , Yang Minghui , Zhang Dong H.
Published: May 2016

This work performs a time-dependent wavepacket study of the H2 + C2H → H + C2H2 reaction on a new ab initio potential energy surface (PES). The PES is constructed using neural network method based on 68 478 geometries with energies calculated at UCCSD(T)-F12a/aug-cc-pVTZ level and covers H2 + C2H↔H + C2H2, H + C2H2 → HCCH2, and HCCH2 radial isomerization reaction regions. The reaction dynamics of H2 + C2H → H + C2H2 are investigated using full-dimensional quantum dynamics method. The initial-state selected reaction probabilities are calculated for reactants in eight vibrational states. The calculated results showed that the H2 vibrational excitation predominantly enhances the reactivity while the excitation of bending mode of C2H slightly inhibits the reaction. The excitations of two stretching modes of C2H molecule have negligible effect on the reactivity. The integral cross section is calculated with J-shift approximation and the mode selectivity in this reaction is discussed. The rate constants over 200-2000 K are calculated and agree well with the experimental measured values.
Far-field coupling in nanobeam photonic crystal cavities
Authors: Rousseau Ian , Sánchez-Arribas Irene , Carlin Jean-François , Butté Raphaël , Grandjean Nicolas
Published: May 2016

We optimized the far-field emission pattern of one-dimensional photonic crystal nanobeams by modulating the nanobeam width, forming a sidewall Bragg cross-grating far-field coupler. By setting the period of the cross-grating to twice the photonic crystal period, we showed using three-dimensional finite-difference time-domain simulations that the intensity extracted to the far-field could be improved by more than three orders of magnitude compared to the unmodified ideal cavity geometry. We then experimentally studied the evolution of the quality factor and far-field intensity as a function of cross-grating coupler amplitude. High quality factor (>4000) blue (λ = 455 nm) nanobeam photonic crystals were fabricated out of GaN thin films on silicon incorporating a single InGaN quantum well gain medium. Micro-photoluminescence spectroscopy of sets of twelve identical nanobeams revealed a nine-fold average increase in integrated far-field emission intensity and no change in average quality factor for the optimized structure compared to the unmodulated reference. These results are useful for research environments and future nanophotonic light-emitting applications where vertical in- and out-coupling of light to nanocavities is required.
Review on heat-utilization processes and heat-exchange equipment in biogas engineering
Authors: Han Ruiping , Hagos Kiros , Ji Xiaoyan , Zhang Shaopeng , Chen Jingjing , Yang Zhuhong , Lu Xiaohua , Wang Changsong
Published: May 2016

With the increasing demand for environmental protection and renewable energy, bioenergy technology has been attracting considerable attention. Anaerobic digestion (AD) is the process to convert the low-grade biomass into bioenergy, in which both heat-recovery and -recycling should be treated carefully in order to improve the process efficiency. In this work, the heat-recovery and its utilization processes were reviewed, and different types of heat exchangers as well as their advantages in biogas engineering were surveyed. It shows that the recovery and utilization of the waste heat from biogas plants with an internal system, such as slurry effluent unit, the combined heat and power unit, the sanitation unit, and the internal recycle unit, are important for improving the AD efficiency of biogas production. For example, the recovery and recycling of waste heat from the effluent can result in a 2–3 °C temperature increase for the inlet manure slurry. For thermophilic AD, the heat recovery from effluent can save about 50% of the total heat requirement. The external heating process is more suitable for large- and medium-scale biogas plants, and the heat transfer coefficient of external heating (850–1000 W/m2 K−1) is almost two-times higher than that of the internal heating (300–400 W/m2 K−1). To utilize the waste heat in biogas plants, heat exchangers have been designed for biogas slurry. However, further improvement on the heat exchangers with anti-blockage, anti-fouling, high efficiency, and low investment is still needed. Moreover, the heat exchanger suitable for a low-temperature-difference system is specially needed in China, but the development is still in its infancy. Therefore, to tailor to the Chinese national conditions, special external heating processes should be designed and reoriented to the diversity of biomass, the climatic environmental conditions, and the renewable Chinese policies.
An absolute instrument for determination of the speed of sound in water
Authors: Li Zhiwei , Zhu Junchao , Li Tao , Zhang Baofeng
Published: May 2016

An apparatus for the absolute determination of the sound speed in water based on the time-of-flight technique is described. The time measurement is realized by hardware circuits and the distance measurement by a double-beam plane-mirror interferometer. A highly accurate time chip, with a resolution of approximately 90 ps, is employed for time measurements. The acoustic path length is adjustable and can be measured directly. Two transducers are used for transmitting and receiving ultrasonic signals without reflection. The transducers are immersed in a thermostatic vessel that maintains bath temperature with high stability. The speed of sound in pure water was measured at ambient pressure and at the temperatures 308 K, 303 K, 298 K, and 293 K. The achieved measurement uncertainties are 2 mK for temperature and 0.045 m/s for speed of sound. The results are compared to data from the literature, equation of state models, and measurements by two commercial sensors in the same experiment, showing excellent agreement among them.
High accuracy calibration of a dynamic vapor sorption instrument and determination of the equilibrium humidities using single salts
Authors: Rörig-Dalgaard Inge , Svensson Staffan
Published: May 2016

We present a procedure for accurately calibrating a dynamic vapor sorption (DVS) instrument using single salts. The procedure accounts for and tailors distinct calibration tests according to the fundamental properties of each salt. Especially relevant properties influencing the calibration are the heat of solution, heat of condensation, and the kinetics connected to the salt phase transition, as these influence the microclimate surrounding the salts during calibration. All these issues were dealt with to obtain precise calibration results. The DVS instrument comprises two control modes to generate and measure the relative humidity (RH). Both control modes were separately examined and combined to overcome the shortcomings of each of the two control modes and thereby obtain the most accurate results. Repeated calibration testing with the single salts (LiCl, MgCl2, Mg(NO3)2, NaCl, and KNO3) enables five discrete sorption isotherm measurements within the range of 11%–93%RH. The equilibrium RH of the solution for LiCl, MgCl2, Mg(NO3)2, NaCl, and KNO3 was determined with a standard deviation of 0.06%-0.15% (0.45% for KNO3) RH. By comparing the measured calibration values with the well-known equilibrium RH of each salt solution, the presented method’s results are both accurate with significant agreement and precise with small variation.
Entanglement entropy of electronic excitations
Authors: Plasser Felix
Published: May 2016

A new perspective into correlation effects in electronically excited states is provided through quantum information theory. The entanglement between the electron and hole quasiparticles is examined, and it is shown that the related entanglement entropy can be computed from the eigenvalue spectrum of the well-known natural transition orbital (NTO) decomposition. Non-vanishing entanglement is obtained whenever more than one NTO pair is involved, i.e., in the case of a multiconfigurational or collective excitation. An important implication is that in the case of entanglement it is not possible to gain a complete description of the state character from the orbitals alone, but more specific analysis methods are required to decode the mutual information between the electron and hole. Moreover, the newly introduced number of entangled states is an important property by itself giving information about excitonic structure. The utility of the formalism is illustrated in the cases of the excited states of two interacting ethylene molecules, the conjugated polymer para-phenylene vinylene, and the naphthalene molecule.
Push it to the limit: Characterizing the convergence of common sequences of basis sets for intermolecular interactions as described by density functional theory
Authors: Witte Jonathon , Neaton Jeffrey B. , Head-Gordon Martin
Published: May 2016

With the aim of systematically characterizing the convergence of common families of basis sets such that general recommendations for basis sets can be made, we have tested a wide variety of basis sets against complete-basis binding energies across the S22 set of intermolecular interactions—noncovalent interactions of small and medium-sized molecules consisting of first- and second-row atoms—with three distinct density functional approximations: SPW92, a form of local-density approximation; B3LYP, a global hybrid generalized gradient approximation; and B97M-V, a meta-generalized gradient approximation with nonlocal correlation. We have found that it is remarkably difficult to reach the basis set limit; for the methods and systems examined, the most complete basis is Jensen’s pc-4. The Dunning correlation-consistent sequence of basis sets converges slowly relative to the Jensen sequence. The Karlsruhe basis sets are quite cost effective, particularly when a correction for basis set superposition error is applied: counterpoise-corrected def2-SVPD binding energies are better than corresponding energies computed in comparably sized Dunning and Jensen bases, and on par with uncorrected results in basis sets 3-4 times larger. These trends are exhibited regardless of the level of density functional approximation employed. A sense of the magnitude of the intrinsic incompleteness error of each basis set not only provides a foundation for guiding basis set choice in future studies but also facilitates quantitative comparison of existing studies on similar types of systems.
CH3NH3PbBr3 is not pyroelectric, excluding ferroelectric-enhanced photovoltaic performance
Authors: Rakita Yevgeny , Meirzadeh Elena , Bendikov Tatyana , Kalchenko Vyacheslav , Lubomirsky Igor , Hodes Gary , Ehre David , Cahen David
Published: May 2016

To experimentally (dis)prove ferroelectric effects on the properties of lead-halide perovskites and of solar cells, based on them, we used second-harmonic-generation spectroscopy and the periodic temperature change (Chynoweth) technique to detect the polar nature of methylammonium lead bromide (MAPbBr3). We find that MAPbBr3 is probably centrosymmetric and definitely non-polar; thus, it cannot be ferroelectric. Whenever pyroelectric-like signals were detected, they could be shown to be due to trapped charges, likely at the interface between the metal electrode and the MAPbBr3 semiconductor. These results indicate that the ferroelectric effects do not affect steady-state performance of MAPbBr3 solar cells.
Microfluidics made easy: A robust low-cost constant pressure flow controller for engineers and cell biologists
Authors: Mavrogiannis Nicholas , Ibo Markela , Fu Xiaotong , Crivellari Francesca , Gagnon Zachary
Published: May 2016

Over the last decade, microfluidics has become increasingly popular in biology and bioengineering. While lab-on-a-chip fabrication costs have continued to decrease, the hardware required for delivering controllable fluid flows to the microfluidic devices themselves remains expensive and often cost prohibitive for researchers interested in starting a microfluidics project. Typically, microfluidic experiments require precise and tunable flow rates from a system that is simple to operate. While many labs use commercial platforms or syringe pumps, these solutions can cost thousands of dollars and can be cost prohibitive. Here, we present an inexpensive and easy-to-use constant pressure system for delivering flows to microfluidic devices. The controller costs less than half the price of a single syringe pump but can independently switch and deliver fluid through up to four separate fluidic inlets at known flow rates with significantly faster fluid response times. It is constructed of readily available pressure regulators, gauges, plastic connectors and adapters, and tubing. Flow rate is easily predicted and calibrated using hydraulic circuit analysis and capillary tubing resistors. Finally, we demonstrate the capabilities of the flow system by performing well-known microfluidic experiments for chemical gradient generation and emulsion droplet production.
Skyrmion-induced bound states on the surface of three-dimensional topological insulators
Authors: Andrikopoulos Dimitrios , Sorée Bart , De Boeck Jo
Published: May 2016

The interaction between the surface of a 3D topological insulator and a skyrmion/anti-skyrmion structure is studied in order to investigate the possibility of electron confinement due to the skyrmion presence. Both hedgehog (Néel) and vortex (Bloch) skyrmions are considered. For the hedgehog skyrmion, the in-plane components cannot be disregarded and their interaction with the surface state of the topological insulator (TI) has to be taken into account. A semi-classical description of the skyrmion chiral angle is obtained using the variational principle. It is shown that both the hedgehog and the vortex skyrmion can induce bound states on the surface of the TI. However, the number and the properties of these states depend strongly on the skyrmion type and the skyrmion topological number NSk. The probability densities of the bound electrons are also derived where it is shown that they are localized within the skyrmion region.
Bifurcations and degenerate periodic points in a three dimensional chaotic fluid flow
Authors: Smith L. D. , Rudman M. , Lester D. R. , Metcalfe G.
Published: May 2016

Analysis of the periodic points of a conservative periodic dynamical system uncovers the basic kinematic structure of the transport dynamics and identifies regions of local stability or chaos. While elliptic and hyperbolic points typically govern such behaviour in 3D systems, degenerate (parabolic) points also play an important role. These points represent a bifurcation in local stability and Lagrangian topology. In this study, we consider the ramifications of the two types of degenerate periodic points that occur in a model 3D fluid flow. (1) Period-tripling bifurcations occur when the local rotation angle associated with elliptic points is reversed, creating a reversal in the orientation of associated Lagrangian structures. Even though a single unstable point is created, the bifurcation in local stability has a large influence on local transport and the global arrangement of manifolds as the unstable degenerate point has three stable and three unstable directions, similar to hyperbolic points, and occurs at the intersection of three hyperbolic periodic lines. The presence of period-tripling bifurcation points indicates regions of both chaos and confinement, with the extent of each depending on the nature of the associated manifold intersections. (2) The second type of bifurcation occurs when periodic lines become tangent to local or global invariant surfaces. This bifurcation creates both saddle–centre bifurcations which can create both chaotic and stable regions, and period-doubling bifurcations which are a common route to chaos in 2D systems. We provide conditions for the occurrence of these tangent bifurcations in 3D conservative systems, as well as constraints on the possible types of tangent bifurcation that can occur based on topological considerations.
Optical and vibrational properties of (ZnO)k In2O3 natural superlattice nanostructures
Authors: Margueron Samuel , Pokorny Jan , Skiadopoulou Stella , Kamba Stanislav , Liang Xin , Clarke David R.
Published: May 2016

A thermodynamically stable series of superlattices, (ZnO)kIn2O3, form in the ZnO-In2O3 binary oxide system for InO1.5 concentrations from about 13 up to about 33 mole percent (m/o). These natural superlattices, which consist of a periodic stacking of single, two-dimensional sheets of InO6 octahedra, are found to give rise to systematic changes in the optical and vibrational properties of the superlattices. Low-frequency Raman scattering provides the evidence for the activation of acoustic phonons due to the folding of Brillouin zone. New vibrational modes at 520 and 620 cm−1, not present in either ZnO or In2O3, become Raman active. These new modes are attributed to collective plasmon oscillations localized at the two-dimensional InO1.5 sheets. Infrared reflectivity experiments, and simulations taking into account a negative dielectric susceptibility due to electron carriers in ZnO and interface modes of the dielectric layer of InO2, explain the occurrence of these new modes. We postulate that a localized electron gas forms at the ZnO/InO2 interface due to the electron band alignment and polarization effects. All our observations suggest that there are quantum contributions to the thermal and electrical conductivity in these natural superlattices.
Progress on electrocaloric multilayer ceramic capacitor development
Authors: Hirose Sakyo , Usui Tomoyasu , Crossley Sam , Nair Bhasi , Ando Akira , Moya Xavier , Mathur Neil D.
Published: May 2016

A multilayer capacitor comprising 19 layers of 38 μm-thick 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 has elsewhere been shown to display electrocaloric temperature changes of 2.2 K due to field changes of 24 V μm−1, near ∼100 °C. Here we demonstrate temperature changes of 1.2 K in an equivalent device with 2.6 times the thermal mass, i.e., 49 layers that could tolerate 10.3 V μm−1. Breakdown was compromised by the increased number of layers, and occurred at 10.5 V μm−1 near the edge of a near-surface inner electrode. Further optimization is required to improve the breakdown strength of large electrocaloric multilayer capacitors for cooling applications.
Sizeable Kane–Mele-like spin orbit coupling in graphene decorated with iridium clusters
Authors: Qin Yuyuan , Wang Siqi , Wang Rui , Bu Haijun , Wang Xuefeng , Wang Xinran , Song Fengqi , Wang Baigeng , Wang Guanghou
Published: May 2016

The spin-orbit coupling strength of graphene can be enhanced by depositing iridium nanoclusters. Weak localization is intensely suppressed near zero fields after the cluster deposition, rather than changing to weak anti-localization. Fitting the magnetoresistance gives the spin relaxation time, which increases by two orders with the application of a back gate. The spin relaxation time is found to be proportional to the electronic elastic scattering time, demonstrating the Elliot–Yafet spin relaxation mechanism. A sizeable Kane–Mele-like coupling strength of over 5.5 meV is determined by extrapolating the temperature dependence to zero.
Formulation of the Rice-Walsh equation of state based on Shock Hugoniot data for porous metals
Authors: Nagayama K.
Published: May 2016

The dimensionless material parameter R introduced by Wu and Jing into the Rice-Walsh equation of state (EOS) has been deduced from the LASL shock Hugoniot data for porous Al and Cu. It was found that the parameter R/p decays smoothly with shock pressure p and displays small experimental scatter in the high pressure region. This finding led to the conclusion that the parameter has only a weak temperature dependence and is well approximated by a function of pressure alone, and the Grüneisen parameter should be temperature dependent under compression. The thermodynamic formulation of the Rice-Walsh EOS for Al and Cu was realized using the empirically determined function R(p) for each material and their known shock Hugoniot. It was then possible to reproduce porous shock Hugoniot for these metals. For most degrees of porosity, agreement between the porous data and the calculated Hugoniots using the empirical function described was very good. However, slight discrepancies were seen for Hugoniots with very high porosity. Two new thermal variables were introduced after further analysis, which enabled the calculation of the cold compression curve for these metals. The Grüneisen parameters along full-density and porous Hugoniot curve were calculated using a thermodynamic identity connecting R and the Grüneisen parameter. It was shown that the Grüneisen parameter is strongly temperature dependent. The present analysis suggested that the Rice-Walsh type EOS is a preferable choice for the analysis with its simple form, pressure-dependent empirical Wu-Jing parameter, and its compatibility with porous shock data.
Electricity sector transformation in New Zealand: A sustainability assessment approach
Authors: Suomalainen K. , Sharp B.
Published: May 2016

New Zealand has a long history in producing a major part of its electricity from low-carbon resources. A major transition from a state owned and operated electricity sector to an open electricity market model and the policies adopted during this period have shaped the generation mix of New Zealand to its current form. Currently, domestic fossil fuel resources offer opportunity for economic growth, while renewable energy resources are significant and present opportunities for green growth in both domestic and global markets. What is particular about the New Zealand case is the “middle out” approach of the national renewable energy strategy, rather than the common top-down approach of many other countries. Consenting is done on a case by case basis at regional level, allowing for wide community and stakeholder participation. This paper describes the transitions in the electricity sector and renewable energy policy of New Zealand, and presents an assessment using sustainability indicators to study the impact of this transition on the level of sustainability of the country's electricity supply system. Although the electricity mix has seen a transition from hydropower towards gas, geothermal, and wind energy, there has been no significant change in the overall sustainability index of the New Zealand electricity supply. This is because the system remains based on renewable sources and gas, which scores relatively high in the model we have applied. Using the country-specific values for the indicators would give a more reliable model to assess the sustainability of the electricity system in detail from its economic, social, and environmental aspects.
Measuring contact angles of small spherical particles at planar fluid interfaces by Light Extinction
Authors: Horváth Imre T. , Colinet Pierre , Vetrano Maria Rosaria
Published: May 2016

An experimental technique is introduced for measuring the contact angle of small colloidal particles at planar fluid interfaces. The presented light scattering-based method relies on performing two spectral transmittance measurements: one on a particle monolayer standing at the fluid interface and the other on a dispersion of the same particles in a homogeneous medium. The observed shift between the two transmitted spectra is explained in terms of the phase shift parameter, which is then used to determine the particle position relative to the interface and hence the contact angle. The applicability of the technique is demonstrated through simulations and experiments.
Plasmonic engineering of metal-oxide nanowire heterojunctions in integrated nanowire rectification units
Authors: Lin Luchan , Zou Guisheng , Liu Lei , Duley Walt W. , Zhou Y. Norman
Published: May 2016

We show that irradiation with femtosecond laser pulses can produce robust nanowire heterojunctions in coupled non-wetting metal-oxide Ag-TiO2 structures. Simulations indicate that joining arises from the effect of strong plasmonic localization in the region of the junction. Strong electric field effects occur in both Ag and TiO2 resulting in the modification of both surfaces and an increase in wettability of TiO2, facilitating the interconnection of Ag and TiO2 nanowires. Irradiation leads to the creation of a thin layer of highly defected TiO2 in the contact region between the Ag and TiO2 nanowires. The presence of this layer allows the formation of a heterojunction and offers the possibility of engineering the electronic characteristics of interfacial structures. Rectifying junctions with single and bipolar properties have been generated in Ag-TiO2 nanowire circuits incorporating asymmetrical and symmetrical interfacial structures, respectively. This fabrication technique should be applicable for the interconnection of other heterogeneous metal-oxide nanowire components and demonstrates that femtosecond laser irradiation enables interfacial engineering for electronic applications of integrated nanowire structures.
Interface induced high temperature superconductivity in single unit-cell FeSe on SrTiO3(110)
Authors: Zhou Guanyu , Zhang Ding , Liu Chong , Tang Chenjia , Wang Xiaoxiao , Li Zheng , Song Canli , Ji Shuaihua , He Ke , Wang Lili , Ma Xucun , Xue Qi-Kun
Published: May 2016

We report high temperature superconductivity in one unit-cell (1-UC) FeSe films grown on SrTiO3 (STO)(110) substrate by molecular beam epitaxy. By in-situ scanning tunneling microscopy measurement, we observe a superconducting gap as large as 17 meV on the 1-UC FeSe films. Transport measurements on 1-UC FeSe/STO(110) capped with FeTe layers reveal superconductivity with an onset transition temperature (TC) of 31.6 K and an upper critical magnetic field of 30.2 T. We also find that TC can be further increased by external electric field although the effect is weaker than that on STO(001) substrate.
Electrochemical control of the phase transition of ultrathin FeRh films
Authors: Jiang M. , Chen X. Z. , Zhou X. J. , Cui B. , Yan Y. N. , Wu H. Q. , Pan F. , Song C.
Published: May 2016

We investigate the electrical manipulation of the phase transition in ultrathin FeRh films through a combination of ionic liquid and oxide gating. The 5 nm-thick FeRh films show an antiferromagnetic-ferromagnetic transition at around 275 K with in-plane magnetic field of 70 kOe. A negative gate voltage seriously suppresses the transition temperature to ∼248 K, while a positive gate voltage does the opposite but with a smaller tuning amplitude. The formation of electric double layer associated with a large electric field induces the migration of oxygen ions between the oxide gate and the FeRh layer, producing the variation of Fe moments in antiferromagnetic FeRh accompanied by the modulation of the transition temperature. Such a modulation only occurs within several nanometers thick scale in the vicinity of FeRh surface. The reversible control of FeRh phase transition by electric field might pave the way for non-volatile memories with low power consumption.
Defect dipole induced large recoverable strain and high energy-storage density in lead-free Na0.5Bi0.5TiO3-based systems
Authors: Cao Wenping , Li Weili , Feng Yu , Bai Terigele , Qiao Yulong , Hou Yafei , Zhang Tiandong , Yu Yang , Fei Weidong
Published: May 2016

In this letter, we propose an effective route to obtain large recoverable strain, purely electrostrictive effects and high energy-storage density by inducing defect dipoles into Na0.5Bi0.5TiO3 (NBT)-based relaxor ferroelectrics. It has been found that pinched and double polarization hysteresis loops with high maximum polarization (Pmax) and negligible remanent polarization (Pr) can be observed due to the presence of acceptor-induced defect dipoles. A large recoverable strain of 0.24% with very little hysteresis and high electrostriction coefficient of 0.022 m4 C2 with purely electrostrictive characteristics were acquired when 11 mol. ‰ Mn-doped. Meanwhile, a high recoverable energy density of 1.06 J/cm3 with excellent temperature stability was obtained at the same composition owing to the enlarged value of Pmax-Pr (36.8 μC/cm2) and relatively high electric field (95 kV/cm). Our achievement can open up the exciting opportunities for ferroelectric materials in high-precision positioning devices and high electric power pulse energy storage applications.
Predictive direct power control of multilevel direct current link converter for grid connected battery energy storage systems
Authors: Lee Sze Sing , Heng Yeh En
Published: May 2016

This paper proposes the adoption of a multilevel dc link converter for a grid connected battery energy storage system in low voltage applications. The multilevel dc link converter is the simple upgrade of a typical two level voltage source converter with the incorporation of some cascaded modular chopper cells which constitute a switched-battery circuit. With the additional chopper cells, more candidates of voltage vectors are available for switching vector selection in power control. Compared to two level voltage source converter using a look-up-table direct power control or finite control set model predictive direct power control, the multilevel dc link converter which employed the latter power control tracks the reference power with much lower power ripple, as well as results in much lower total harmonic distortion in grid current. Therefore, the power quality can be improved significantly. Simulation results are presented to verify that a 3 level dc link converter is more effective than a two level voltage source converter for the grid-connected battery energy storage systems in both generating mode and charging mode.
Infrared absorption of hydrogen-related defects in ammonothermal GaN
Authors: Suihkonen Sami , Pimputkar Siddha , Speck James S. , Nakamura Shuji
Published: May 2016

Polarization controlled Fourier transform infrared (FTIR) absorption measurements were performed on a high quality m-plane ammonothermal GaN crystal grown using basic chemistry. The polarization dependence of characteristic absorption peaks of hydrogen-related defects at 3000–3500 cm−1 was used to identify and determine the bond orientation of hydrogenated defect complexes in the GaN lattice. Majority of hydrogen was found to be bonded in gallium vacancy complexes decorated with one to three hydrogen atoms (VGa-H1,2,3) but also hydrogenated oxygen defect complexes, hydrogen in bond-center sites, and lattice direction independent absorption were observed. Absorption peak intensity was used to determine a total hydrogenated VGa density of approximately 4 × 1018 cm−3, with main contribution from VGa-H1,2. Also, a significant concentration of electrically passive VGa-H3 was detected. The high density of hydrogenated defects is expected to have a strong effect on the structural, optical, and electrical properties of ammonothermal GaN crystals.
Electroanalytical Opportunities Derived from Ion Transfer at Interfaces between Immiscible Electrolyte Solutions
Authors: Arrigan Damien W. M. , Alvarez de Eulate Eva , Liu Yang
Published: May 2016

This review presents an introduction to electrochemistry at interfaces between immiscible electrolyte solutions and surveys recent studies of this form of electrochemistry in electroanalytical strategies. Simple ion and facilitated ion transfers across interfaces varying from millimetre scale to nanometre scales are considered. Target detection strategies for a range of ions, inorganic, organic, and biological, including macromolecules, are discussed.
Prenatally administered dexamethasone impairs folliculogenesis in spiny mouse offspring
Authors: Hułas-Stasiak Monika , Dobrowolski Piotr , Tomaszewska Ewa
Published: May 2016

This study was designed to determine whether prenatal dexamethasone treatment has an effect on follicular development and atresia in the ovary of spiny mouse (Acomys cahirinus) offspring. Dexamethasone (125 µg kg–1 bodyweight per day) was administered to pregnant spiny mice from Day 20 of gestation to parturition. The processes of follicle loss were analysed using classical markers of apoptosis (terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling reaction, active caspase-3) and autophagy (Lamp1). The present study indicated that dexamethasone reduced the pool of healthy primordial follicles. Moreover, the oocytes from these follicles showed intensive caspase-3 and Lamp1 staining. Surprisingly, dexamethasone caused an increase in the number of secondary follicles; however, most of these follicles were characterised by extensive degeneration of the oocyte and caspase-3 and Lamp1 labelling. Western-blot analysis indicated that the glucocorticoid receptor as well as apoptosis and autophagy markers were more strongly expressed in the DEX-treated group than in the control. On the basis of these findings, we have concluded that dexamethasone impairs spiny mouse folliculogenesis and enhances follicular atresia through induction of autophagy or combined autophagy and apoptosis.
Gelatinases and their tissue inhibitors are associated with oxidative stress: a potential set of markers connected with male infertility
Authors: Kratz Ewa M. , Kałuża Anna , Ferens-Sieczkowska Mirosława , Olejnik Beata , Fiutek Renata , Zimmer Mariusz , Piwowar Agnieszka
Published: May 2016

The expression and activity of matrix metalloproteinases (MMPs) may be regulated by oxidative stress in various pathophysiological processes; therefore, the aim of the present study was to analyse the associations between the expression of the gelatinases MMP-9 and MMP-2 and their tissue inhibitors TIMP-1, TIMP-2 and levels of total antioxidant capacity (TAC) and advanced oxidation protein products (AOPP) in seminal plasma prepared for artificial insemination. Levels of MMPs and TIMPs were evaluated using ELISA, whereas TAC and AOPP in the seminal plasma of 131 childless men and 38 fertile volunteers were determined spectrophotometrically. Seminal MMP-9 expression was higher in childless men than in fertile subjects, whereas there was no significant differences in MMP-2 expression between the analysed seminal groups. TIMP-1 and TIMP-2 expression was similar in all groups. However, TAC expression was significantly higher in infertile normozoospermic and oligozoospermic men and AOPP expression was higher in astheno-, oligo- and normozoospermic infertile patients than in fertile men. High AOPP, together with an increased MMP-9 : TIMP-1 ratio alters the oxidative–antioxidative balance of the ejaculate, thereby reducing male fertility, and therefore these parameters may serve as additional diagnostic markers of semen quality and male reproductive potential.
Optogenetic toolkit reveals the role of Ca
2+
sparklets in coordinated cell migration
Authors: Kim Jin Man , Lee Minji , Kim Nury , Heo Won Do
Published: May 2016

Significance

In this article, we present a pioneering experimental approach for studying cell migration and more broadly establish representative guidelines for applying an optogenetic approach in biological studies. Using recently developed optogenetic tools, we identified local Ca
2+
influx as a major source of Ca
2+
for gradient formation and established the functional importance of polarized chemistry in highly coordinated cell migration. These findings provide strong evidence for a mechanism that addresses fundamental questions about front–rear Ca
2+
gradients in migrating cells and suggest a previously unidentified role of voltage-dependent Ca
2+
channels in the directional migration of nonexcitable cells.
Role of
Plasmodium vivax
Duffy-binding protein 1 in invasion of Duffy-null Africans
Authors: Gunalan Karthigayan , Lo Eugenia , Hostetler Jessica B. , Yewhalaw Delenasaw , Mu Jianbing , Neafsey Daniel E. , Yan Guiyun , Miller Louis H.
Published: May 2016

Significance

Duffy-null Africans were thought to be resistant to
Plasmodium vivax
infection. Recently,
P. vivax
infection was observed in Duffy-null Africans. This parasite adaptation is potentially a serious public health problem as the majority of African populations are Duffy-null. This article is aimed at understanding whether mutations or DNA expansion in Duffy-binding protein (DBP) contributes to
P. vivax
Duffy-null infection. Importantly,
P. vivax
infection in Squirrel monkey has an ability to use an invasion pathway that is independent of the DBPs. Thus,
P. vivax
may use a different ligand–receptor pair for its infection in Duffy-null Africans, or some Duffy-negative Africans are not null but express a low level of Duffy blood group antigen.
A combination of soy isoflavones and cello-oligosaccharides changes equol/O-desmethylangolensin production ratio and attenuates bone fragility in ovariectomized mice
Authors: Fujii Shungo , Takahashi Nobuyuki , Inoue Hirofumi , Katsumata Shin-ichi , Kikkawa Yuji , Machida Makoto , Ishimi Yoshiko , Uehara Mariko
Published: May 2016

We examined the cooperative effects of isoflavones and cello-oligosaccharides on daidzein metabolism and bone fragility in ovariectomized mice. Cello-oligosaccharides increased urinary equol and decreased O-desmethylangolensin. A combination of isoflavones and cello-oligosaccharides attenuated decreases in bone breaking force and stiffness caused by ovariectomy. Combination treatment with isofalvones and cello-oligosaccharides increases urinary equol/O-desmethylangolensin production ratio and prevents ovariectomy-induced abnormalities in bone strength.
Microstructure and mechanical properties of Al-6061-T6 alloy welded by a new hybrid FSW/SSW joining process
Authors: Hajihashemi M. , Shamanian M. , Niroumand B.
Published: May 2016

In this study for the first time, the effects of decrease in heat inflow to the weld metal in friction stir process by utilising semisolid processing and decreasing the pin rotational speed as well as increasing the pin transverse speed were examined. As a result, the characteristic loss of hardness and strength in the weld zone were eliminated. The results showed that by approaching the ultrafine microstructure in the weld zone through the hybrid FSW/SSW process, the hardness and elongation values reached to 90 Hv and 8.88%, respectively. These are only slightly different from those of the base metal of the welded samples. Furthermore, the ultimate tensile strength of the samples welded by the hybrid technique was found to be about 167 MPa that was higher than those of the samples welded by friction stir welding (151 MPa) and semisolid welding (114 MPa) techniques.
Gas metal arc brazing of galvannealed steel sheets
Authors: Makwana P. , Shome M. , Goecke Sven-F. , De A.
Published: May 2016

An advanced gas metal arc welding technique with controlled short-circuiting mode of metal transfer and arcing at low power was employed for brazing of galvannealed steels using CuSi3 filler wire. The brazed joints showed the presence of an interface layer with Fe–Si intermetallic compounds (IMC). Increase in heat input resulted in an increase of the interface layer thickness. The maximum failure load of 2.5 kN was achieved for a heat input of 105 J mm−1 with the corresponding interface layer thickness of 2.7 µm. Heat inputs beyond 105 J mm−1 led to excessive spatter of zinc and increase in interface layer thickness with hard Si-rich IMC. In contrast, heat input values lower than 80 J mm−1 produced inadequate wetting of the steel surface by the molten filler wire deposit and resulted in low joint strength.
Modelling of bead hump formation in high speed gas metal arc welding
Authors: Xu Guoxiang , Cao Qingnan , Hu Qingxian , Zhang Weiwei , Liu Peng , Du Baoshuai
Published: May 2016

Without any presupposed mechanism, a unified three-dimensional model is developed to predict the formation of humping bead in high speed gas metal arc welding, which considers the three phase coupling of solid, liquid and gas and the effect of shear stress exerting on weld pool surface caused by arc plasma. A strong backward fluid flow in weld pool is identified as the major factor for bead hump formation. The generation of thin liquid transition zone and its premature solidification are two conditions responsible for the occurrence of humped weld. In case of low inner contact angle between the liquid metal and workpiece surface, the bead hump is still generated. With increasing welding current, the bead hump can be suppressed.