bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural, electrochemical and photophysical properties of an exocyclic di-ruthenium complex and its application as a photosensitizer
Authors: Salpage Sahan R. , Paul Avishek , Som Bozumeh , Banerjee Tanmay , Hanson Kenneth , Smith Mark D. , Vannucci Aaron K. , Shimizu Linda S.
Published: May 2016

Structural, photophysical, and electrochemical characterization of a bridged exo-diruthenium compound [(bpy)2RuLRu(bpy)2]Cl4·6H2O and use as a recyclable SET catalyst.
Immobilization of polyoxometalates in crystalline solids for highly efficient heterogeneous catalysis
Authors: Ye Ji-Jie , Wu Chuan-De
Published: May 2016

The recently developed strategies on POM-based crystalline solids and their catalytic properties are summarized in this short review.
Probing spin–vibronic dynamics using femtosecond X-ray spectroscopy
Authors: Penfold T. J. , Pápai M. , Rozgonyi T. , Møller K. B. , Vankó G.
Published: May 2016

Ultrafast pump-probe spectroscopy within the X-ray regime is now possible owing to the development of X-ray Free Electrons Lasers (X-FELs) and is opening new opportunities for the direct probing of femtosecond evolution of the nuclei, the electronic and spin degrees of freedom. In this contribution we use wavepacket dynamics of the photoexcited decay of a new Fe(ii) complex, [Fe(bmip)2]2+ (bmip = 2,6-bis(3-methyl-imidazole-1-ylidine)pyridine), to simulate the experimental observables associated with femtosecond Fe K-edge X-ray Absorption Near-Edge Structure (XANES) and X-ray emission (XES) spectroscopy. We show how the evolution of the nuclear wavepacket is translated into the spectroscopic signal and the sensitivity of these approaches for following excited state dynamics.
Deriving the exact nonadiabatic quantum propagator in the mapping variable representation
Authors: Hele Timothy J. H. , Ananth Nandini
Published: May 2016

We derive an exact quantum propagator for nonadiabatic dynamics in multi-state systems using the mapping variable representation, where classical-like Cartesian variables are used to represent both continuous nuclear degrees of freedom and discrete electronic states. The resulting Liouvillian is a Moyal series that, when suitably approximated, can allow for the use of classical dynamics to efficiently model large systems. We demonstrate that different truncations of the exact Liouvillian lead to existing approximate semiclassical and mixed quantum–classical methods and we derive an associated error term for each method. Furthermore, by combining the imaginary-time path-integral representation of the Boltzmann operator with the exact Liouvillian, we obtain an analytic expression for thermal quantum real-time correlation functions. These results provide a rigorous theoretical foundation for the development of accurate and efficient classical-like dynamics to compute observables such as electron transfer reaction rates in complex quantized systems.
Electrochemistry at single bimetallic nanoparticles – using nano impacts for sizing and compositional analysis of individual AgAu alloy nanoparticles
Authors: Saw En Ning , Grasmik Viktoria , Rurainsky Christian , Epple Matthias , Tschulik Kristina
Published: May 2016

The increasing interest in producing bimetallic nanoparticles and utilizing them in modern technologies sets the demand for fast and affordable characterization of these materials. To date Scanning Transmission Electron Microscopy (STEM) coupled to energy dispersive X-ray spectroscopy is usually used to determine the size and composition of alloy nanoparticles, which is time-consuming and expensive. Here electrochemical single nanoparticle analysis is presented as an alternative approach to infer the particle size and composition of alloy nanoparticles, directly in a dispersion of these particles. As a proof of concept, 14 nm sized Ag0.73Au0.27 alloy nanoparticles are analyzed using a combination of chronoamperometric single nanoparticle analysis and cyclic voltammetry ensemble studies. It is demonstrated that the size, the alloying and the composition can all be inferred using this approach. Thus, the electrochemical characterization of single bimetallic alloy nanoparticles is suggested here as a powerful and convenient complement or alternative to TEM characterization of alloy nanoparticles.
Concluding remarks: progress toward the design of solid catalysts
Authors: Gates Bruce C.
Published: May 2016

The 2016 Faraday Discussion on the topic “Designing New Heterogeneous Catalysts” brought together a group of scientists and engineers to address forefront topics in catalysis and the challenge of catalyst design—which is daunting because of the intrinsic non-uniformity of the surfaces of catalytic materials. “Catalyst design” has taken on a pragmatic meaning which implies the discovery of new and better catalysts on the basis of fundamental understanding of the catalyst structure and performance. The presentations and discussion at the meeting illustrate the rapid progress in this understanding linked with improvements in spectroscopy, microscopy, theory, and catalyst performance testing. The following text includes a statement of recurrent themes in the discussion and examples of forefront science that evidences progress toward catalyst design.
Encapsulation of ascorbic acid promotes the reduction of Maillard reaction products in UHT milk
Authors: Troise Antonio Dario , Vitiello Daniele , Tsang Catherine , Fiore Alberto
Published: May 2016

The encapsulation of ascorbic acid can limit the reduction of available lysine and tune the formation of Maillard reaction products (MRPs).
Determination of trace impurities in advanced metallic nuclear fuels by inductively coupled plasma time-of-flight mass spectrometry (ICP-TOF-MS)
Authors: Saha Abhijit , Deb Sadhan Bijoy , Saxena Manoj Kumar
Published: May 2016

Development of a common analytical methodology for the determination of trace impurities in U–Ti, U–Zr and U–Mo alloy fuels by inductively coupled plasma mass spectrometry.
Palladium-catalysed directed C–H activation by anilides and ureas; water participation in a general base mechanism
Authors: Rauf Waqar , Brown John M.
Published: May 2016

A general-base pathway for CH-activation in anilides and ureas en route to palladacycles was developed through DFT calculations and fits available evidence.
Fast regioselective sulfonylation of pyridine/quinoline N-oxides induced by iodine
Authors: Wang Ruijia , Zeng Zebing , Chen Chuang , Yi Niannian , Jiang Jun , Cao Zhong , Deng Wei , Xiang Jiannan
Published: May 2016

We describe the unprecedented reaction between pyridine/quinoline N-oxides and sulfonyl hydroazides, which was completed in the presence of iodine.
Accelerated synthesis of MnO2 nanocomposites by acid-free hydrothermal route for catalytic soot combustion
Authors: Wang Lei , Wu Yang , Feng Nengjie , Meng Jie , Wan Hui , Guan Guofeng
Published: May 2016

MnO2 nanocomposites with porous structure were successfully synthesized by a facile hydrothermal route from KMnO4 without the addition of any acid.
Evaluation of kaolin floc characteristics during coagulation process: a case study with a continuous flow device
Authors: Wang Zhenbei , Nan Jun , Yao Meng , Ren Pengfei , Yang Yueming
Published: May 2016

This work investigates the influence of decreasing shear rate on temporal evolution of floc properties in continuous flow device.
Disposable (bio)chemical integrated optical waveguide sensors implemented on roll-to-roll produced platforms
Authors: Aikio Sanna , Zeilinger Martin , Hiltunen Jussi , Hakalahti Leena , Hiitola-Keinänen Johanna , Hiltunen Marianne , Kontturi Ville , Siitonen Samuli , Puustinen Jarkko , Lieberzeit Peter , Karioja Pentti
Published: May 2016

Demonstration of disposable multi-analyte polymeric integrated Young interferometers for analyte specific chemical- and biochemical sensing using biological and biomimetic recognition.
Effect of surfactants and halide ions on the adsorption and oxidation of homocysteine at the gold electrode
Authors: Wang Jianying , Zuo Shangshang , Lu Cui , Zu Yanbing , Chen Zuofeng
Published: May 2016

This study demonstrates how adsorptive species including a series of surfactants and halide ions affect the adsorption of Hcy on the electrode surface, as well as how the change of Hcy adsorption affects the oxidation of Hcy.
Design of micro–mesoporous zeolite catalysts for alkylation
Authors: Fu Xiaoqin , Sheng Xiaoli , Zhou Yuming , Fu Zhiwei , Zhao Shuo , Bu Xiaohai , Zhang Chao
Published: May 2016

The hierarchically micro–mesoporous zeolite Y provides preserved shape selectivity in combination with shorter diffusion pathways via the mesopores, leading to superior catalyst effectiveness.
A versatile in situ etching-growth strategy for synthesis of yolk–shell structured periodic mesoporous organosilica nanocomposites
Authors: Wei Yong , Li Xiaomin , Elzatahry Ahmed A. , Zhang Renyuan , Wang Wenxing , Tang Xueting , Yang Jianping , Wang Jinxiu , Al-Dahyan Daifallah , Zhao Dongyuan
Published: May 2016

A versatile “in situetching-growth” strategy has been proposed to synthesize mesoporous composites with yolk–shell structure and controlled PMO shell, by combing the etching process with the shell growth.
Degradation of 4-chlorophenol in a Fenton-like system using Au–Fe3O4magnetic nanocomposites as the heterogeneous catalyst at near neutral conditions
Authors: Liu Jie , Zhao Zhiwei , Ding Zhaoxia , Fang Zhendong , Cui Fuyi
Published: May 2016

The proposed mechanism for the generation of ˙OH and degradation of 4-CP in the Au–Fe3O4/H2O2system.
Slow and long-ranged dynamical heterogeneities in dissipative fluids
Authors: Avila Karina E. , Castillo Horacio E. , Vollmayr-Lee Katharina , Zippelius Annette
Published: May 2016

A two-dimensional bidisperse granular fluid is shown to exhibit pronounced long-ranged dynamical heterogeneities as dynamical arrest is approached.
Composite of few-layer MoO3nanosheets with graphene as a high performance anode for sodium-ion batteries
Authors: Sreedhara M. B. , Santhosha A. L. , Bhattacharyya Aninda J. , Rao C. N. R.
Published: May 2016

A composite anode comprising of a 3D network of few-layer MoO3nanosheets with an optimum amount of rGO exhibits excellent Na-ion cyclability over wide ranging values of operating current densities. Ultrathin nanosheets of MoO3are synthesized by oxidation of MoS2 nanosheets and are tagged with optimum amounts of rGO.
Endocrine Considerations of the Pediatric Organ Donor
Authors: Gupta Ronish , Dhanani Sonny
Published: May 2016

Patients determined to be neurologically deceased exhibit potentially harmful changes in various endocrine pathways due to disruptions of the body's neurohormonal control mechanisms. These deviations from endocrine homeostasis lead to hemodynamic, metabolic, and immunologic aberrations that are associated with reduced graft procurement and function for the purposes of organ donation. Existing literature has attempted to describe the pathophysiology that associates disruptions in endocrine pathways with organ dysfunction, both to increase understanding and to identify strategies to support the donor. For example, diabetes insipidus due to arginine vasopressin deficiency is commonly encountered, and should be anticipated. The significance of abnormalities in other pathways such as those involving cortisol and thyroid hormone is less established; however, there is increasing support for treating potential organ donors with combined hormonal therapies. While there are published documents aimed at guiding management of organ donors in general, many controversies exist and pediatric-specific literature is scarce. This article aims to review several of the important endocrine-specific aspects of managing the neurologically deceased organ donor, with an emphasis on pediatrics where information is available.
Kapillarmikroskopie
Authors: Sander O. , Dechant C. , Sunderkötter C. , Klein-Weigel P.
Published: May 2016

Die Kapillarmikroskopie spielt als bildgebendes Verfahren eine große Bedeutung in der Differenzialdiagnose mikrovaskulärer Pathologien der Haut. Bei Systemerkrankungen, insbesondere Kollagenosen werden hier spezifische Veränderungen gesehen. Zur Differenzierung eines Raynaud Syndroms ist sie unerlässlich. Diese interdisziplinär erstellte Arbeit bietet dem Leser eine aktuelle Übersicht der wichtigsten Anwendungsgebiete der Methode, Möglichkeiten, Grenzen der Kapillarmikroskopie und wagt einen Ausblick auf die zukünftige Entwicklung.
Grounded Design - a praxeological IS research perspective
Authors: Rohde Markus , Brödner Peter , Stevens Gunnar , Betz Matthias , Wulf Volker
Published: May 2016

In this paper, we propose Grounded Design - a particular design research (DR) approach rooted in a practice-theoretical tradition. It assesses the quality of information technology (IT) design through evaluation of emerging changes in social practices, which result from the appropriation and use of IT artifacts. The paper starts with a systematic analysis of the reasons for persistent limitations of traditional information systems DR, specifically in coping with problems of contingency and self-referentiality. Following this critique, the principles of Grounded Design are presented. Grounded Design is applied in case studies where we reconstruct the social practices observed before and during the design and appropriation of innovative IT artifacts. We call these context-specific research endeavors ‘design case studies.’ In conducting these case studies, Grounded Design builds upon well-established research methods such as ethnographical field studies, participatory design and action research. To support the transferability of its situated findings, Grounded Design suggests documenting increasing numbers of design case studies to create an extended, comparative knowledge base. Comparing cases allows for the emergence of bottom-up concepts dealing with the design and appropriation of innovative IT artifacts in social practice.
The HealthCare.gov project
Authors: Gogan Janis L , Davidson Elizabeth J , Proudfoot Jeffrey
Published: May 2016

This case describes the development of the HealthCare.gov website front-end, systems and databases supporting the implementation of the Affordable Care Act. In late October 2013, US Health and Human Services Secretary Kathleen Sebelius and US Centers for Medicare and Medicaid Services Administrator Marilyn Tavenner appear before a Congressional subcommittee to apologize about system glitches. The case gives students an opportunity to consider project risks that affected this huge systems development effort, and to consider how to ensure that millions of uninsured or underinsured Americans would be able to sign up for affordable health insurance.
Quantifying the economic impact of changes in energy demand for space heating and cooling systems under varying climatic scenarios
Authors: Hasegawa Tomoko , Park Chan , Fujimori Shinichiro , Takahashi Kiyoshi , Hijioka Yasuaki , Masui Toshihiko
Published: May 2016

The building sector is highly sensitive to climate change, where energy is used for numerous purposes such as heating, cooling, cooking and lighting. Space heating and cooling account for a large proportion of overall energy use, and the associated energy demand is also affected by climate change. Here, we project the economic impact of changes in energy demand for space heating and cooling under multiple climatic conditions. We use an economic model coupled with an end-use technology model to explicitly represent the investment costs for air-conditioning technologies, which influence the macroeconomy. We conclude that the negative effects on the economy from increases in the use of space cooling are sufficiently large to neutralize the positive impacts from reductions in space heating usage under climate change, which results in significant economic loss. The economic loss under the highest emissions scenario (RCP8.5) would correspond to a −0.34% (−0.39% to −0.18%) change in global gross domestic product (GDP) in 2100 compared with GDP without any climate change, while the impact under the lowest emissions scenario (RCP2.6) would result in a −0.03% (−0.07% to −0.01%) change in global GDP in 2100. The economic losses are mainly generated by incremental technological costs and not by changes in energy demand itself. The amount of economic loss can vary substantially based on assumptions of technological costs, population and income. To reduce the negative impacts of climate change measures for reducing the costs of air conditioning will be an important consideration for the building sector in the future.
Simple formalism for efficient derivatives and multi-determinant expansions in quantum Monte Carlo
Authors: Filippi Claudia , Assaraf Roland , Moroni Saverio
Published: May 2016

We present a simple and general formalism to compute efficiently the derivatives of a multi-determinant Jastrow-Slater wave function, the local energy, the interatomic forces, and similar quantities needed in quantum Monte Carlo. Through a straightforward manipulation of matrices evaluated on the occupied and virtual orbitals, we obtain an efficiency equivalent to algorithmic differentiation in the computation of the interatomic forces and the optimization of the orbital parameters. Furthermore, for a large multi-determinant expansion, the significant computational gain afforded by a recently introduced table method is here extended to the local value of any one-body operator and to its derivatives, in both all-electron and pseudopotential calculations.
Associative Yang-Baxter equation for quantum (semi-)dynamical R-matrices
Authors: Sechin Ivan , Zotov Andrei
Published: May 2016

In this paper we propose versions of the associative Yang-Baxter equation and higher order R-matrix identities which can be applied to quantum dynamical R-matrices. As is known quantum non-dynamical R-matrices of Baxter-Belavin type satisfy this equation. Together with unitarity condition and skew-symmetry it provides the quantum Yang-Baxter equation and a set of identities useful for different applications in integrable systems. The dynamical R-matrices satisfy the Gervais-Neveu-Felder (or dynamical Yang-Baxter) equation. Relation between the dynamical and non-dynamical cases is described by the IRF (interaction-round-a-face)-Vertex transformation. An alternative approach to quantum (semi-)dynamical R-matrices and related quantum algebras was suggested by Arutyunov, Chekhov, and Frolov (ACF) in their study of the quantum Ruijsenaars-Schneider model. The purpose of this paper is twofold. First, we prove that the ACF elliptic R-matrix satisfies the associative Yang-Baxter equation with shifted spectral parameters. Second, we directly prove a simple relation of the IRF-Vertex type between the Baxter-Belavin and the ACF elliptic R-matrices predicted previously by Avan and Rollet. It provides the higher order R-matrix identities and an explanation of the obtained equations through those for non-dynamical R-matrices. As a by-product we also get an interpretation of the intertwining transformation as matrix extension of scalar theta function likewise R-matrix is interpreted as matrix extension of the Kronecker function. Relations to the Gervais-Neveu-Felder equation and identities for the Felder’s elliptic R-matrix are also discussed.
Two distinct crystallization processes in supercooled liquid
Authors: Tane Masakazu , Kimizuka Hajime , Ichitsubo Tetsu
Published: May 2016

Using molecular dynamics simulations we show that two distinct crystallization processes, depending on the temperature at which crystallization occurs, appear in a supercooled liquid. As a model for glass-forming materials, an Al2O3 model system, in which both the glass transition and crystallization from the supercooled liquid can be well reproduced, is employed. Simulations in the framework of an isothermal-isobaric ensemble indicate that the calculated time-temperature-transformation curve for the crystallization to γ(defect spinel)-Al2O3 exhibited a typical nose shape, as experimentally observed in various glass materials. During annealing above the nose temperature, the structure of the supercooled liquid does not change before the crystallization, because of the high atomic mobility (material transport). Thus, the crystallization is governed by the abrupt crystal nucleation, which results in the formation of a stable crystal structure. In contrast, during annealing below the nose temperature, the structure of the supercooled liquid gradually changes before the crystallization, and the formed crystal structure is less stable than that formed above the nose temperature, because of the restricted material transport.
Novel pulsed particle accelerator for energy dependent positron re-emission experiments
Authors: Grill Niklas , Piochacz Christian , Zimnik Samantha , Hugenschmidt Christoph
Published: May 2016

We report on a novel device for particle acceleration based on elevation of the potential energy of beam pulses. This so-called energy elevator is particularly beneficial if both the particle source and the sample have to be near ground potential due to experimental constraints. We applied this new technique to enable depth dependent measurements of re-emitted positrons using the surface spectrometer at the NEPOMUC positron beam facility. First, a two-stage bunching system is used to generate positron pulses with a repetition rate of 5 MHz and a duration of 1.663(5) ns before their energy is raised to several keV. The whole system was shown to work with an exceptional efficiency of 88%. We demonstrated the usability of our setup by investigating the positron re-emission spectra of Ni and Pd as function of positron implantation energy. For Ni the positron work function could be determined to be ΦNi+=−1.4(2)eV. In addition, as predicted by theory, our experimental findings imply a positive positron work function for Pd.
Nanoscale current spreading analysis in solution-processed graphene oxide/silver nanowire transparent electrodes via conductive atomic force microscopy
Authors: Shaw Joseph E. , Perumal Ajay , Bradley Donal D. C. , Stavrinou Paul N. , Anthopoulos Thomas D.
Published: May 2016

We use conductive atomic force microscopy (CAFM) to study the origin of long-range conductivity in model transparent conductive electrodes composed of networks of reduced graphene oxide (rGOX) and silver nanowires (AgNWs), with nanoscale spatial resolution. Pristine networks of rGOX (1–3 monolayers-thick) and AgNWs exhibit sheet resistances of ∼100–1000 kΩ/□ and 100–900 Ω/□, respectively. When the materials are deposited sequentially to form bilayer rGOX/AgNW electrodes and thermally annealed at 200 °C, the sheet resistance reduces by up to 36% as compared to pristine AgNW networks. CAFM was used to analyze the current spreading in both systems in order to identify the nanoscale phenomena responsible for this effect. For rGOX networks, the low intra-flake conductivity and the inter-flake contact resistance is found to dominate the macroscopic sheet resistance, while for AgNW networks the latter is determined by the density of the inter-AgNW junctions and their associated resistance. In the case of the bilayer rGOX/AgNWs' networks, rGOX flakes are found to form conductive “bridges” between AgNWs. We show that these additional nanoscopic electrical connections are responsible for the enhanced macroscopic conductivity of the bilayer rGOX/AgNW electrodes. Finally, the critical role of thermal annealing on the formation of these nanoscopic connections is discussed.
High-speed digital holography for neutral gas and electron density imaging
Authors: Granstedt E. M. , Thomas C. E. , Kaita R. , Majeski R. , Baylor L. R. , Meitner S. J. , Combs S. K.
Published: May 2016

An instrument was developed using digital holographic reconstruction of the wavefront from a CO2 laser imaged on a high-speed commercial IR camera. An acousto-optic modulator is used to generate 1–25 μs pulses from a continuous-wave CO2 laser, both to limit the average power at the detector and also to freeze motion from sub-interframe time scales. Extensive effort was made to characterize and eliminate noise from vibrations and second-surface reflections. Mismatch of the reference and object beam curvature initially contributed substantially to vibrational noise, but was mitigated through careful positioning of identical imaging lenses. Vibrational mode amplitudes were successfully reduced to ≲1 nm for frequencies ≳50 Hz, and the inter-frame noise across the 128 × 128 pixel window which is typically used is ≲2.5 nm. To demonstrate the capabilities of the system, a piezo-electric valve and a reducing-expanding nozzle were used to generate a super-sonic gas jet which was imaged with high spatial resolution (better than 0.8 lp/mm) at high speed. Abel inversions were performed on the phase images to produce 2-D images of localized gas density. This system could also be used for high spatial and temporal resolution measurements of plasma electron density or surface deformations.
Analysis of limited-diffractive and limited-dispersive X-waves generated by finite radial waveguides
Authors: Fuscaldo Walter , Pavone Santi C. , Valerio Guido , Galli Alessandro , Albani Matteo , Ettorre Mauro
Published: May 2016

In this work, we analyze the spatial and temporal features of electromagnetic X-waves propagating in free space and generated by planar radiating apertures. The performance of ideal X-waves is discussed and compared to practical cases where the important effects related to the finiteness of the radiating aperture and the wavenumber dispersion are taken into account. In particular, a practical device consisting of a radial waveguide loaded with radiating slots aligned along a spiral path is considered for the practical case in the millimeter-wave range. A common mathematical framework is defined for a precise comparison of the spatiotemporal properties and focusing capabilities of the generated X-wave. It is clearly shown that the fractional bandwidth of the radiating aperture has a key role in the longitudinal confinement of an X-wave in both ideal and practical cases. In addition, the finiteness of the radiating aperture as well as the wavenumber dispersion clearly affect both the transverse and the longitudinal profiles of the generated radiation as it travels beyond the depth-of-field of the generated X-wave. Nevertheless, the spatiotemporal properties of the X-wave are preserved even in this “dispersive-finite” case within a defined region and duration related to the nondiffractive range and fractional bandwidth of the spectral components of the generated X-wave. The proposed analysis may open new perspectives for the efficient generation of X-waves over finite radiating apertures at millimeter waves where the dispersive behavior of realistic devices is no longer negligible.
Broadband absorption through extended resonance modes in random metamaterials
Authors: Hao J. , Niemiec R. , Burgnies L. , Lheurette É. , Lippens D.
Published: May 2016

The properties of disordered metamaterial absorbers are analyzed on the basis of numerical simulations and experimental characterizations. A broadening of the absorption spectrum is clearly evidenced. This effect is the consequence of both the coupling between nearby resonators leading to the occurrence of extended magnetic resonance modes and the interconnection of elementary particles yielding the definition of resonating clusters. The angular robustness of the absorbing structure under oblique incidence is also demonstrated for a wide domain of angles.
Nonextensive statistics and skin depth of transverse wave in collisional plasma
Authors: Hashemzadeh M.
Published: May 2016

Skin depth of transverse wave in a collisional plasma is studied taking into account the nonextensive electron distribution function. Considering the kinetic theory for charge particles and using the Bhatnagar-Gross-Krook collision model, a generalized transverse dielectric permittivity is obtained. The transverse dispersion relation in different frequency ranges is investigated. Obtaining the imaginary part of the wave vector from the dispersion relation, the skin depth for these frequency ranges is also achieved. Profiles of the skin depth show that by increasing the q parameter, the penetration depth decreases. In addition, the skin depth increases by increasing the electron temperature. Finally, it is found that in the high frequency range and high electron temperature, the penetration depth decreases by increasing the collision frequency. In contrast, by increasing the collision frequency in a highly collisional frequency range, the skin depth of transverse wave increases.
Viscosity of liquid Ag–In–Sb–Te: Evidence of a fragile-to-strong crossover
Authors: Orava J. , Weber H. , Kaban I. , Greer A. L.
Published: May 2016

The temperature-dependent viscosity η(T) is measured for the equilibrium liquid of the chalcogenide Ag–In–Sb–Te (AIST), the first time this has been reported for a material of actual interest for phase-change memory. The measurements, in the range 829–1254 K, are made using an oscillating-crucible viscometer, and show a liquid with high fragility and low viscosity, similar to liquid pure metals. Combining the high-temperature viscosity measurements with values inferred from crystal growth rates in the supercooled liquid allows the form of η(T) to be estimated over the entire temperature range from above the melting point down to the glass transition. It is then clear that η(T) for liquid AIST cannot be described with a single fragility value, unlike other phase-change chalcogenides such as liquid Ge–Sb–Te. There is clear evidence for a fragile-to-strong crossover on cooling liquid AIST, similar to that analyzed in Te85Ge15. The change in fragility associated with the crossover in both these cases is rather weak, giving a broad temperature range over which η(T) is near-Arrhenius. We discuss how such behavior may be beneficial for the performance of phase-change memory. Consideration of the fragile-to-strong crossover in liquid chalcogenides may be important in tuning compositions to optimize the device performance.
Management of light absorption in extraordinary optical transmission based ultra-thin-film tandem solar cells
Authors: Mashooq Kishwar , Talukder Muhammad Anisuzzaman
Published: May 2016

Although ultra-thin-film solar cells can be attractive in reducing the cost, they suffer from low absorption as the thickness of the active layer is usually much smaller than the wavelength of incident light. Different nano-photonic techniques, including plasmonic structures, are being explored to increase the light absorption in ultra-thin-film solar cells. More than one layer of active materials with different energy bandgaps can be used in tandem to increase the light absorption as well. However, due to different amount of light absorption in different active layers, photo-generated currents in different active layers will not be the same. The current mismatch between the tandem layers makes them ineffective in increasing the efficiency. In this work, we investigate the light absorption properties of tandem solar cells with two ultra-thin active layers working as two subcells and a metal layer with periodically perforated holes in-between the two subcells. While the metal layer helps to overcome the current mismatch, the periodic holes increase the absorption of incident light by helping extraordinary optical transmission of the incident light from the top to the bottom subcell, and by coupling the incident light to plasmonic and photonic modes within ultra-thin active layers. We extensively study the effects of the geometry of holes in the intermediate metal layer on the light absorption properties of tandem solar cells with ultra-thin active layers. We also study how different metals in the intermediate layer affect the light absorption; how the geometry of holes in the intermediate layer affects the absorption when the active layer materials are changed; and how the intermediate metal layer affects the collection of photo-generated electron-hole pairs at the terminals. We find that in a solar cell with 6,6-phenyl C61-butyric acid methyl ester top subcell and copper indium gallium selenide bottom subcell, if the periodic holes in the metal layer are square or polygon, total absorption remains approximately the same. However, the total absorption suffers significantly if the holes are triangle. The transmission spectra of incident light into the bottom subcell, and hence the absorption, change significantly for square and circle holes if the active materials change to cadmium selenide (CdSe) and cadmium telluride (CdTe) in the top and bottom subcells, respectively. Although the intermediate metal layer may induce electron-hole pair recombination due to surface defects, the short-circuit current density of an ultra-thin plasmonic solar cell with an intermediate metal layer with two-dimensional hole array is >9% of that of a structure without the intermediate metal layer.
Ion-implantation-induced amorphization of InxGa1−xP alloys as functions of stoichiometry and temperature
Authors: Hussain Z. S. , Wendler E. , Wesch W. , Schnohr C. S. , Ridgway M. C.
Published: May 2016

Rutherford Backscattering Spectrometry/Channeling and Extended X-ray Absorption Fine Structure measurements have been combined to investigate the amorphization of InxGa1−xP alloys at 15 and 300 K for selected stoichiometries representative of the entire stoichiometric range. The amorphization kinetics differs considerably for the two temperatures: at 15 K, the amorphization kinetics of InxGa1−xP is intermediate between the two binary extremes while at 300 K, InxGa1−xP is more easily amorphized than both InP and GaP. Direct impact and stimulated amorphization both contribute to the amorphization process at 15 K. Dynamic annealing via thermally induced Frenkel pair recombination reduces the influence of direct impact amorphization at 300 K such that the stimulated amorphization is dominant. At this temperature, stimulated amorphization in ternary InxGa1−xP alloys is supported by the structural disorder inherent from the bimodal bond length distribution.
Size modulated transition in the fluid–structure interaction losses in nano mechanical beam resonators
Authors: Vishwakarma S. D. , Pandey A. K. , Parpia J. M. , Verbridge S. S. , Craighead H. G. , Pratap R.
Published: May 2016

An understanding of the dominant dissipative mechanisms is crucial for the design of a high-Q doubly clamped nanobeam resonator to be operated in air. We focus on quantifying analytically the viscous losses—the squeeze film damping and drag force damping—that limit the net quality factor of a beam resonator, vibrating in its flexural fundamental mode with the surrounding fluid as air at atmospheric pressure. Specifically, drag force damping dominates at smaller beam widths and squeeze film losses dominate at larger beam widths, with no significant contribution from structural losses and acoustic radiation losses. The combined viscous losses agree well with the experimentally measured Q of the resonator over a large range of beam widths, within the limits of thin beam theory. We propose an empirical relation between the maximum quality factor and the ratio of maximum beam width to the squeeze film air gap thickness.
Synchrotron-based investigation of transition-metal getterability in n-type multicrystalline silicon
Authors: Morishige Ashley E. , Jensen Mallory A. , Hofstetter Jasmin , Yen Patricia X. T. , Wang Chenlei , Lai Barry , Fenning David P. , Buonassisi Tonio
Published: May 2016

Solar cells based on n-type multicrystalline silicon (mc-Si) wafers are a promising path to reduce the cost per kWh of photovoltaics; however, the full potential of the material and how to optimally process it are still unknown. Process optimization requires knowledge of the response of the metal-silicide precipitate distribution to processing, which has yet to be directly measured and quantified. To supply this missing piece, we use synchrotron-based micro-X-ray fluorescence (μ-XRF) to quantitatively map >250 metal-rich particles in n-type mc-Si wafers before and after phosphorus diffusion gettering (PDG). We find that 820 °C PDG is sufficient to remove precipitates of fast-diffusing impurities and that 920 °C PDG can eliminate precipitated Fe to below the detection limit of μ-XRF. Thus, the evolution of precipitated metal impurities during PDG is observed to be similar for n- and p-type mc-Si, an observation consistent with calculations of the driving forces for precipitate dissolution and segregation gettering. Measurements show that minority-carrier lifetime increases with increasing precipitate dissolution from 820 °C to 880 °C PDG, and that the lifetime after PDG at 920 °C is between the lifetimes achieved after 820 °C and 880 °C PDG.
Analysis of plasma-modes of a gated bilayer system in high electron mobility transistors
Authors: Bhardwaj Shubhendu , Rajan Siddharth , Volakis John L.
Published: May 2016

We present rigorous analytical and computational models to study the plasma-waves in a gated-bilayer system present in a double-channel high electron mobility transistor. By analytically deriving the dispersion relations, we have identified the optical and acoustic modes in such systems. We find that the presence of the metal gate selectively modifies the optical plasmons of an ungated-bilayer, while the acoustic plasmons remain largely unchanged. Analysis shows that these modified optical plasmons could be advantageous for resonant and non-resonant plasma-wave devices. The paper further serves to verify our analytical formulae using a full-wave hydrodynamic numerical solver, based on finite difference time domain algorithm. Using the solver, we examine these modes in the gated/ungated bilayers under a plane wave excitation. We observe that, most incident power couples to the optical mode for such an excitation. Nevertheless, acoustic modes can also be excited, if the discontinuity dimensions are optimized accordingly. These observations are also explained using 2D field-plots for the first time, thus providing intuitive understanding of the plasmon excitation in the bilayers.
The impact of new Geant4-DNA cross section models on electron track structure simulations in liquid water
Authors: Kyriakou I. , Šefl M. , Nourry V. , Incerti S.
Published: May 2016

The most recent release of the open source and general purpose Geant4 Monte Carlo simulation toolkit (Geant4 10.2 release) contains a new set of physics models in the Geant4-DNA extension for improving the modelling of low-energy electron transport in liquid water (<10 keV). This includes updated electron cross sections for excitation, ionization, and elastic scattering. In the present work, the impact of these developments to track-structure calculations is examined for providing the first comprehensive comparison against the default physics models of Geant4-DNA. Significant differences with the default models are found for the average path length and penetration distance, as well as for dose-point-kernels for electron energies below a few hundred eV. On the other hand, self-irradiation absorbed fractions for tissue-like volumes and low-energy electron sources (including some Auger emitters) reveal rather small differences (up to 15%) between these new and default Geant4-DNA models. The above findings indicate that the impact of the new developments will mainly affect those applications where the spatial pattern of interactions and energy deposition of very-low energy electrons play an important role such as, for example, the modelling of the chemical and biophysical stage of radiation damage to cells.
Observation of dust acoustic shock wave in a strongly coupled dusty plasma
Authors: Sharma Sumita K. , Boruah A. , Nakamura Y. , Bailung H.
Published: May 2016

Dust acoustic shock wave is observed in a strongly coupled laboratory dusty plasma. A supersonic flow of charged microparticles is allowed to perturb a stationary dust fluid to excite dust acoustic shock wave. The evolution process beginning with steepening of initial wave front and then formation of a stable shock structure is similar to the numerical results of the Korteweg-de Vries-Burgers equation. The measured Mach number of the observed shock wave agrees with the theoretical results. Reduction of shock amplitude at large distances is also observed due to the dust neutral collision and viscosity effects. The dispersion relation and the spatial damping of a linear dust acoustic wave are also measured and compared with the relevant theory.
Harmonic phonon theory for calculating thermal conductivity spectrum from first-principles dispersion relations
Authors: Shiga Takuma , Aketo Daisuke , Feng Lei , Shiomi Junichiro
Published: May 2016

In recent years, nanostructuring of dielectric and semiconducting crystals has enhanced controllability of their thermal conductivity. To carry out computational materials search for nanostructured materials with desirable thermal conductivity, a key property is the thermal conductivity spectrum of the original single crystal, which determines the appropriate length scale of nanostructures and mutual adaptability of different kinds of nanostructures. Although the first-principles phonon transport calculations have become accessible, the anharmonic lattice dynamics calculations are still expensive to scan many materials. To this end, we have developed an empirical model that describes the thermal conductivity spectrum in terms only of harmonic phonon properties and bulk thermal conductivity. The model was tested for several crystals with different structures and thermal conductivities, and was confirmed to reproduce the overall profiles of thermal conductivity spectra and their accumulation functions obtained by the first-principles anharmonic calculations.
Genetic study of visual scores and hip height at different ages in Nelore cattle
Authors: Silveira D. D. , De Vargas L. , Roso V. M. , Campos G. S. , Souza F. R. P. , Boligon A. A.
Published: May 2016

The objective of the present study was to evaluate the genetic variability of visual scores used as selection criteria in Nelore cattle, as well as their associations with yearling hip height (YH) and mature hip height (MH), to determine whether the selection considered would change the hip height of animals. (Co)variance components were obtained by two-trait animal model using Gibbs sampling, including YH or MH in each analysis. Breeding values for YH and MH were used to obtain the response to selection. The posterior mean of the heritability estimates for conformation, finishing precocity (or body condition) and muscling at weaning (WC: 0.21 ± 0.02; WP: 0.21 ± 0.02; and WM: 0.18 ± 0.02 respectively) were lower than those obtained for the same traits at yearling (YC: 0.34 ± 0.02; YP: 0.37 ± 0.02; and YM: 0.38 ± 0.02 respectively). Heritability estimates for YH and MH were 0.28 ± 0.01 and 0.33 ± 0.03 respectively. The results suggested that these traits should respond to selection process, but in different magnitudes. Positive and high genetic correlations were estimated between WC and YH and YC and YH (0.80 ± 0.03 and 0.76 ± 0.03 respectively), and lower values between these scores and MH (0.48 ± 0.09 and 0.36 ± 0.07 respectively). Weak genetic associations were obtained between finishing precocity score and YH and muscling score and YH (ranging from 0.05 ± 0.05 to 0.18 ± 0.06). Moreover, negative and favourable genetic associations between each of WP, WM, YP and YM, and MH (ranging from –0.21 ± 0.07 to –0.12 ± 0.09) were estimated. Correlated responses are expected to be unfavourable for hip height, measured at yearling and at maturity, when animals better genetically evaluated for conformation in relation to finishing precocity and muscling scores are selected. Genetic changes obtained for YH and MH were null (–0.02 cm/year and 0.03 cm/year respectively). It can be explained, in part, by smaller weights in the selection index for conformation rather than finishing precocity and muscling, as applied in the studied herds. However, in herds of beef cattle not evaluated and selected for finishing precocity and muscling scores or that have cows with larger size than acceptable, the adoption of mature hip height as one of the selection criteria can be one alternative for obtaining females with a desirable size.
Separating species and environmental determinants of leaf functional traits in temperate rainforest plants along a soil-development chronosequence
Authors: Turnbull Matthew H. , Griffin Kevin L. , Fyllas Nikolaos M. , Lloyd Jon , Meir Patrick , Atkin Owen K.
Published: May 2016

We measured a diverse range of foliar characteristics in shrub and tree species in temperate rainforest communities along a soil chronosequence (six sites from 8 to 120 000 years) and used multilevel model analysis to attribute the proportion of variance for each trait into genetic (G, here meaning species-level), environmental (E) and residual error components. We hypothesised that differences in leaf traits would be driven primarily by changes in soil nutrient availability during ecosystem progression and retrogression. Several leaf structural, chemical and gas-exchange traits were more strongly driven by G than E effects. For leaf mass per unit area (MA), foliar [N], net CO2 assimilation and dark respiration rates and foliar carbohydrate concentration, the G component accounted for 60–87% of the total variance, with the variability associated with plot, the E effect, much less important. Other traits, such as foliar [P] and N : P, displayed strong E and residual effects. Analyses revealed significant reductions in the slopes of G-only bivariate relationships when compared with raw relationships, indicating that a large proportion of trait–trait relationships is species based, and not a response to environment per se. This should be accounted for when assessing the mechanistic basis for using such relationships in order to make predictions of responses of plants to short-term environmental change.
Actions of activin A, connective tissue growth factor, hepatocyte growth factor and teratocarcinoma-derived growth factor 1 on the development of the bovine preimplantation embryo
Authors: Kannampuzha-Francis Jasmine , Tribulo Paula , Hansen Peter J.
Published: May 2016

The reproductive tract secretes bioactive molecules collectively known as embryokines that can regulate embryonic growth and development. In the present study we tested four growth factors expressed in the endometrium for their ability to modify the development of the bovine embryo to the blastocyst stage and alter the expression of genes found to be upregulated (bone morphogenetic protein 15 (BMP15) and keratin 8, type II (KRT8)) or downregulated (NADH dehydrogenase 1 (ND1) and S100 calcium binding protein A10 (S100A10)) in embryos competent to develop to term. Zygotes were treated at Day 5 with 0.01, 0.1 or 1.0 nM growth factor. The highest concentration of activin A increased the percentage of putative zygotes that developed to the blastocyst stage. Connective tissue growth factor (CTGF) increased the number of cells in the inner cell mass (ICM), decreased the trophectoderm : ICM ratio and increased blastocyst expression of KRT8 and ND1. The lowest concentration of hepatocyte growth factor (HGF) reduced the percentage of putative zygotes becoming blastocysts. Teratocarcinoma-derived growth factor 1 increased total cell number at 0.01 nM and expression of S100A10 at 1.0 nM, but otherwise had no effects. Results confirm the prodevelopmental actions of activin A and indicate that CTGF may also function as an embryokine by regulating the number of ICM cells in the blastocyst and altering gene expression. Low concentrations of HGF were inhibitory to development.