bluuebunny/crossref_metadata_2025 huggingface dataset:
Silver
Authors: Bury Nic. R.
Published: July 2014

Silver uptake and metabolism is linked to that of copper. Ag(I) is taken up via the copper transporter 1 (CTR1), binds to copper chaperones and is trafficked to the trans-Golgi network (TGN), where it is imported via a Cu-ATPase. The Ag(I)-laden TGN vesicles travel to the membrane and Ag(I) is exported from the cell. Ag(I) has been shown to replace Cu(I) in a number of cuproenzymes. Unlike Cu(I), Ag(I) is not involved in Fenton–Haber–Weiss chemistry, yet it can be reduced to Ag(0), a reaction that would use up cellular reducing capacity. In addition, silver can interfere with mitochondrial function resulting in reactive oxygen species (ROS) production and oxidative damage, and it also affects membrane integrity and DNA synthesis. Ag is exceptionally toxic to bacteria and aquatic organisms, but is generally thought to be relatively benign to humans. This property has seen a rise in the use of Ag as an antimicrobial agent, and in recent years the production and use of Ag-nanoparticles (Ag-NPs) has expanded rapidly. Ag-NPs are known to cause cytotoxicity and accumulate in tissues, but it is uncertain whether humans or wildlife are exposed to concentrations that are sufficient to pose a health risk. The chapter will discuss the cellular transport process, intracellular handling and toxicity of Ag(I) and Ag-NP and mechanisms of bacterial Ag resistance.
Gold
Authors: Soncini Fernando C. , Checa Susana K.
Published: July 2014

There is growing evidence that an active biogeochemical cycle for gold (Au) exists, and that this process is responsible for the solubilization and dissemination of gold throughout the environment. It has been shown that soluble gold, in its ionic forms or in complexes, can enter cells by non-specific intake and that it accumulates in plants, fungi and fish. Recent observations have demonstrated the presence of bacterial biofilms on gold nuggets and that these can contribute to its mobilization in the environment. Bacteria such as Salmonella enterica and Cupriavidus metallidurans use Au-specific transcriptional regulators that detect its presence and control the expression of specific resistance factors. Their presence allows these microorganisms to cope with the toxic effects of gold ions. This chapter will address the biological influence of the cycling of gold, focusing primarily on the current understanding of the regulatory proteins involved in its detection and the induced mechanisms that alleviate toxicity in bacteria caused by Au. In addition, gold has been used in medicine from ancient times. Before the discovery of antibiotics and because of its toxicity, gold was used to treat infections and a number of diseases. Currently, Au(I) and Au(III) compounds are being designed for treatment of cancers, rheumatoid arthritis and viral and parasitic diseases.
Actinides in Biological Systems
Authors: Geipel Gerhard , Viehweger Katrin
Published: July 2014

Actinides are radioactive heavy elements with atomic numbers between 89 and 103. Based on their occurrence, they can be separated into two groups: naturally occurring and synthetic elements. However, the line between them is not a sharp one. This is due to human activities in using and testing nuclear power and nuclear weapons as well as to a smaller degree due to natural nuclear reactors in the Proterozoic era. Thorium, protactinium, uranium and, in much smaller amounts, plutonium are the naturally occurring elements. Neptunium and all elements with atomic numbers (AN) larger than 94 are synthetic elements. The isotopes of elements beginning with einsteinium (AN=99) have relatively short lifetimes of radioactive decay (<472 d for 252Es) and their availability is very limited. Therefore, no information about their behaviour in biological systems has been published until recently. Especially uranium, neptunium, plutonium and to some extent americium can exist in different oxidation states. Therefore, for these elements redox reactions in biological systems are of great significance. Actinides can accumulate in the human body. However, the target accumulating organs differ. While protactinium mainly accumulates in the kidneys and bone, plutonium is incorporated in lung, liver and bone. All actinides have long residence times in the human body. Therefore, it is sometimes not straightforward to distinguish between chemical toxicity and radio-toxicity. Most of the scientific literature deals with monitoring of radioactivity and calculation of doses in living systems; however, this aspect will not be the focus of this chapter. Several bodies of data are available, dealing with questions of decontamination of actinides inhaled or ingested into the human body. Lanthanides (elements of the 4f series) show similar chemical behaviour to actinides in the same oxidation state. The behaviour of actinides in biosystems that are of common interest includes pathways of uptake and excretion, plus strategies of protection and defence employed by organisms. The long-living elements thorium and uranium mainly show heavy metal effects; this behaviour changes within the actinide series, starting with neptunium where radiological effects also have to be taken into account.
Aluminium
Authors: Exley Christopher
Published: July 2014

Aluminium is the most abundant metal in the Earth's crust and yet, paradoxically, it has no known biological function. Aluminium is biochemically reactive, it is simply that it is not required for any essential process in extant biota. Since there is evidence of neither element-specific nor evolutionarily conserved aluminium biochemistry, it could be surmised that there are no ligands or chaperones for its transport, there are no transporters or channels to facilitate its passage across membranes, there are no intracellular storage proteins and there are no pathways to enable its metabolism and excretion. Of course, aluminium is found in every compartment of every cell of every organism, from virus through to Man, and herein I have investigated each of the “silent” pathways and metabolic events, which together constitute a form of aluminium homeostasis in biota, identifying and evaluating as far as is possible what is known and, equally importantly, what is unknown about its uptake, transport, storage and excretion.
Voltammetric pH sensing using carbon electrodes: glassy carbon behaves similarly to EPPG
Authors: Lu Min , Compton Richard G.
Published: July 2014

Developing and building on recent work based on a simple sensor for pH determination using unmodified edge plane pyrolytic graphite (EPPG) electrodes.
Determination of butyltin and phenyltin analogues in sea products by Grignard derivatization and gas chromatography-triple quadrupole tandem mass spectrometry
Authors: Cui Zongyan , Qian Yunkai , Ge Na , Zhang Jinjie , Liu Yongming , Cao Yanzhong
Published: July 2014

A GC MS/MS method was development with high sensitivity and selectivity for organotin speciation in sea products.
Differentiating crack cocaine from regular cocaine in whole blood samples in drugs and driving cases
Authors: Hackett Jeffery , Elian Albert A.
Published: July 2014

In this study, the procedure for analyzing cocainic drugs and metabolites (anhydroecgnonine, anhydroecgnonine methyl ester, benzoylecgonine, cocaine, cocaethylene, ecgnonine ethyl ester, and ecgnonine methyl ester) in whole blood samples obtained from drugs and driving cases using a mixed mode solid phase extraction (SPE) C8/SCX cartridge (Clean Screen DAU206), is described.
A facile synthetic route to poly(p-phenylene terephthalamide) with dual functional groups
Authors: Du Shuming , Wang Wenbin , Yan Yan , Zhang Jie , Tian Ming , Zhang Liqun , Wan Xinhua
Published: July 2014

Claisen rearrangement reaction introduces simultaneously allyl and hydroxyl groups to PPTA chains, and improves the interface structure and interfacial adhesion of Kevlar fiber reinforced composites.
g-C3N4 quantum dots: direct synthesis, upconversion properties and photocatalytic application
Authors: Wang Wanjun , Yu Jimmy C. , Shen Zhurui , Chan Donald K. L. , Gu Ting
Published: July 2014

g-C3N4 quantum dots were synthesized and can be used as general energy-transfer components in photocatalytic systems to harness the Vis-NIR spectrum of sunlight.
The extraordinary catalytic ability of peroxiredoxins: a combined experimental and QM/MM study on the fast thiol oxidation step
Authors: Zeida Ari , Reyes Anibal M. , Lebrero Mariano C. G. , Radi Rafael , Trujillo Madia , Estrin Darío A.
Published: July 2014

A combination of kinetic experiments and QM/MM simulations on the peroxiredoxin's reaction mechanism, unravelling the molecular basis of the remarkable catalytic effects of these enzymes.
A label-free double-amplification system for sensitive detection of single-stranded DNA and thrombin by liquid chromatography-mass spectrometry
Authors: Zhao Wenbo , Qin Zhen , Zhang Chengsen , Zhao Meiping , Luo Hai
Published: July 2014

A label-free double amplification system has been developed by using a ternary DNA probe containing the poly(adenine-thymine) sequence assisted by exonuclease III degradation.
The glyco-stereoisomerism effect on hydrogelation of polymers interacting via dynamic covalent bonds
Authors: Lin Mingchang , Sun Pengfei , Chen Guosong , Jiang Ming
Published: July 2014

This work explores, for the first time, the stereoisomerism effect of sugar units of glycopolymers on hydrogelation.
A quantum chemical study on gas phase decomposition pathways of triethylgallane (TEG, Ga(C2H5)3) and tert-butylphosphine (TBP, PH2(t-C4H9)) under MOVPE conditions
Authors: Stegmüller Andreas , Rosenow Phil , Tonner Ralf
Published: July 2014

Gas phase decomposition products of MOVPE precursor molecules TEG and TBP were identified via thermodynamic and kinetic data from a catalogue of 61 elementary reactions as calculated by quantum chemical methods.
Syntheses, crystal structures, and optical properties of five metal complexes constructed from a V-shaped thiophene-containing ligand and different dicarboxylate ligands
Authors: Shi Zhi-Qiang , Guo Zi-Jian , Zheng He-Gen
Published: July 2014

Five new metal complexes constructed from the V-shaped ligand 2,8-di(1H-imidazol-1-yl)dibenzothiophene (DIDP) and different aromatic dicarboxylic acids have been synthesized and structurally characterized in detail. All these complexes show optical semiconductive properties.
Comparison of microsublimation and ion exchange chromatography for boron isolation preceding its isotopic analysis via multi-collector ICP-MS
Authors: Van Hoecke K. , Devulder V. , Claeys P. , Degryse P. , Vanhaecke F.
Published: July 2014

Two boron isolation methods, microsublimation and ion exchange chromatography, were compared in terms of B recovery, procedural blank, matrix removal efficiency, accuracy and precision of δ11B, labor intensiveness and costs.
Catalytic control over the formation of supramolecular materials
Authors: Eelkema Rienk , van Esch Jan H.
Published: July 2014

Catalytic formation of self-assembling building blocks provides control over the morphology, mechanical properties and spatial distribution of soft supramolecular materials.
A high-performance photovoltaic small molecule developed by modifying the chemical structure and optimizing the morphology of the active layer
Authors: Ni Wang , Li Miaomiao , Wan Xiangjian , Feng Huanran , Kan Bin , Zuo Yi , Chen Yongsheng
Published: July 2014

High performance organic solar cell (8.26% PCE) developed through modifying the chemical structure of molecule and optimizing the morphology of active layer.
Processing of plasma-modified and polymer-grafted hydrophilic PET surfaces, and study of their aging and bioadhesive properties
Authors: Perez-Roldan Maria Jesus , Debarnot Dominique , Poncin-Epaillard Fabienne
Published: July 2014

In this work, poly(ethylene terephthalate) (PET) films were treated by oxygen and helium plasmas and their chemistry and morphology were studied.
Examination of the topic-specific nature of pedagogical content knowledge in teaching electrochemical cells and nuclear reactions
Authors: Aydin Sevgi , Friedrichsen Patricia M. , Boz Yezdan , Hanuscin Deborah L.
Published: July 2014

The purpose of this study was to examine experienced chemistry teachers' pedagogical content knowledge (PCK) for two different topics in chemistry to better understand how PCK is specific to topic, including whether all components of PCK are topic-specific and to what degree. To explore the topic-specific nature of PCK, we examined two experienced teachers' PCK using a case study methodology. Multiple data collection strategies were used, including a card-sorting activity, Content Representation (CoRe), semi-structured interviews, observations, and field notes. The data collected were analyzed both deductively and inductively. Results revealed that the teachers used more content-based and teacher-centered instruction to teach electrochemistry, whereas their instruction was less teacher-centered, and included Science–Technology–Society–Environment discussions and implicit NOS instruction to teach nuclear reactions. The teachers also varied in the extent of their knowledge of learners and curriculum in comparing their PCK for each topic. In regard to assessment, the teachers' assessment practices were at the general PK level; they lacked topic-specific PCK for either topic. We provided recommendations for professional development programs, pre-service teacher education programs, and curriculum developers to support teachers in developing topic-specific PCK.
Controlling the number of dendrimers in dendrimicelle nanoconjugates from 1 to more than 100
Authors: Wang Junyou , Voets Ilja K. , Fokkink Remco , van der Gucht Jasper , Velders Aldrik H.
Published: July 2014

The study presents a facile strategy to controllably build up dendrimicelles by self-assembly of anionic PAMAM dendrimers with cationic–neutral diblock copolymers.
Compact bandpass filter with improved upper stopband
Authors: Nie Wei , Luo Sha , Guo Yongxin , Fan Yong
Published: July 2014

A compact bandpass filter (BPF) with a wide upper stopband using a short‐circuited microstrip coupled‐line hairpin resonator is presented. The equivalent transmission‐line circuit model is developed to analyse the performances of the proposed filter. The feeding lines are capacitively coupled to the resonator at the point which divides the fingers of the hairpin into two segments at a ratio of 1:2. As a result, the first harmonic appears at the frequency which is five times the fundamental frequency. In the final design with a grounding via hole, three transmission zeros are generated to improve the skirt effect. Therefore, a compact BPF with a wide upper stopband could be achieved. Finally, the proposed filter is fabricated to verify the design principles, and the measured results agree well with the predicted ones.
Constant twiddle factor multiplier sharing in multipath delay feedback parallel pipelined FFT processors
Authors: Yang Seung‐Won , Lee Jong‐Yeol
Published: July 2014

A new constant twiddle factor multiplier sharing method in parallel pipelined fast Fourier transform (FFT) processors based on a multi‐path delay feedback architecture which consists of multiple single‐path delay feedback datapaths is presented. The proposed method exploits constant twiddle factor multiplier relocation which moves a constant twiddle factor multiplier into a feedback path based on twiddle factor decomposition. By relocating a twiddle factor multiplier, the timing of twiddle factor multiplications is changed so that the multiplications with a twiddle factor are performed at different clock cycles in two datapaths, which makes it possible that the two datapaths share a multiplier operating with the twiddle factor. A reduction of 50% in the number of constant twiddle factor multipliers in the first two stages of a 128‐point four‐parallel pipelined FFT processor is achieved using the proposed method.
3D imaging using narrowband bistatic MIMO radar
Authors: Yang Jianchao , Su Weimin , Gu Hong
Published: July 2014

A new method for three‐dimensional (3D) imaging via a narrowband bistatic multiple‐input–multiple‐output (MIMO) radar with two uniform rectangular arrays is presented. After matched filtering and phase compensation, the method utilises the 2D cross‐range images measured by the transmit and receive arrays to reconstruct the 3D image of the target. Compared with the 3D wideband monostatic MIMO imaging, lower hardware cost can be achieved since the narrowband waveforms are employed. In addition, the range alignment in wideband imaging can be avoided for the poor range resolution of the narrowband waveforms.
Design of ternary clock generator
Authors: Lang Yan‐Feng , Shen Ji‐Zhong , Geng Liang , Yao Mao‐Qun
Published: July 2014

A ternary clock generator (TCG) is proposed to settle its shortage. The TCG is implemented at the switch level with a simple structure of 24 MOS transistors and simulated at the layout level using the HSPICE software with TSMC 0.18 μm CMOS technology, showing that it works properly. The analyses show that the proposed TCG not only can output a ternary clock of high quality, meeting the clock's design requirements, but also can be fabricated with standard CMOS technology.
Shifted dispersion‐induced RF‐fading based continuously tunable optoelectronic oscillator
Authors: Li Liwei , Paolino Liana , Yi Xiaoke , Huang Thomas
Published: July 2014

A new continuously tunable optoelectronic oscillator based on shifted dispersion‐induced RF‐fading is proposed and experimentally demonstrated. The design provides wideband continuously all‐optical tunability by incorporating the shifted RF‐fading based on a Mach‐Zehnder structure in an optoelectronic feedback loop. By simply varying the path difference between the two arms of the Mach‐Zehnder configuration via an adjustable variable delay line, the fundamental frequency of the oscillator can achieve extremely high and continuous tuning with a frequency upper bound dependent on the delay properties of the variable optical delay line.
Three-dimensional simulation of scanning tunneling microscopy for semiconductor carrier and impurity profiling
Authors: Fukuda K. , Nishizawa M. , Tada T. , Bolotov L. , Suzuki K. , Satoh S. , Arimoto H. , Kanayama T.
Published: July 2014

Scanning tunneling microscopy for semiconductor carrier profiling is simulated in three dimensions. By solving the tunnel currents between a probe tip and a sample consistently with the current continuity equations, current–voltage characteristics in good agreement with measurements are obtained. Critical differences from potential-based calculations are observed under depletion and inversion conditions. By preparing a current–concentration table from samples with uniform concentrations, the carrier profile in p-n junction samples can be extracted by estimating the concentrations at each position. It is revealed that the tunnel current is spread around the depletion region of a p-n junction, which affects the results dramatically. When a proposed simulation is iteratively used with measurements, impurity profile extraction is possible even in the depletion region.
Dynamics of H2 Eley-Rideal abstraction from W(110): Sensitivity to the representation of the molecule-surface potential
Authors: Pétuya R. , Larrégaray P. , Crespos C. , Busnengo H. F. , Martínez A. E.
Published: July 2014

Dynamics of the Eley-Rideal (ER) abstraction of H2 from W(110) is analyzed by means of quasi-classical trajectory calculations. Simulations are based on two different molecule-surface potential energy surfaces (PES) constructed from Density Functional Theory results. One PES is obtained by fitting, using a Flexible Periodic London-Eyring-Polanyi-Sato (FPLEPS) functional form, and the other by interpolation through the corrugation reducing procedure (CRP). Then, the present study allows us to elucidate the ER dynamics sensitivity on the PES representation. Despite some sizable discrepancies between both H+H/W(110) PESs, the obtained projectile-energy dependence of the total ER cross sections are qualitatively very similar ensuring that the main physical ingredients are captured in both PES models. The obtained distributions of the final energy among the different molecular degrees of freedom barely depend on the PES model, being most likely determined by the reaction exothermicity. Therefore, a reasonably good agreement with the measured final vibrational state distribution is observed in spite of the pressure and material gaps between theoretical and experimental conditions.
The complex chemical Langevin equation
Authors: Schnoerr David , Sanguinetti Guido , Grima Ramon
Published: July 2014

The chemical Langevin equation (CLE) is a popular simulation method to probe the stochastic dynamics of chemical systems. The CLE’s main disadvantage is its break down in finite time due to the problem of evaluating square roots of negative quantities whenever the molecule numbers become sufficiently small. We show that this issue is not a numerical integration problem, rather in many systems it is intrinsic to all representations of the CLE. Various methods of correcting the CLE have been proposed which avoid its break down. We show that these methods introduce undesirable artefacts in the CLE’s predictions. In particular, for unimolecular systems, these correction methods lead to CLE predictions for the mean concentrations and variance of fluctuations which disagree with those of the chemical master equation. We show that, by extending the domain of the CLE to complex space, break down is eliminated, and the CLE’s accuracy for unimolecular systems is restored. Although the molecule numbers are generally complex, we show that the “complex CLE” predicts real-valued quantities for the mean concentrations, the moments of intrinsic noise, power spectra, and first passage times, hence admitting a physical interpretation. It is also shown to provide a more accurate approximation of the chemical master equation of simple biochemical circuits involving bimolecular reactions than the various corrected forms of the real-valued CLE, the linear-noise approximation and a commonly used two moment-closure approximation.
Development of horn antenna mixer array with internal local oscillator module for microwave imaging diagnostics
Authors: Kuwahara D. , Ito N. , Nagayama Y. , Yoshinaga T. , Yamaguchi S. , Yoshikawa M. , Kohagura J. , Sugito S. , Kogi Y. , Mase A.
Published: July 2014

A new antenna array is proposed in order to improve the sensitivity and complexity of microwave imaging diagnostics systems such as a microwave imaging reflectometry, a microwave imaging interferometer, and an electron cyclotron emission imaging. The antenna array consists of five elements: a horn antenna, a waveguide-to-microstrip line transition, a mixer, a local oscillation (LO) module, and an intermediate frequency amplifier. By using an LO module, the LO optics can be removed, and the supplied LO power to each element can be equalized. We report details of the antenna array and characteristics of a prototype antenna array.
Boundary displacement measurements using multi-energy soft x-rays
Authors: Tritz K. , Diallo A. , LeBlanc B. P. , Sabbagh S. , Stutman D.
Published: July 2014

The Multi-Energy Soft X-ray (ME-SXR) system on NSTX provides radial profiles of soft X-ray emission, measured through a set of filters with varying thickness, which have been used to reconstruct the electron temperature on fast time scales (∼10 kHz). In addition to this functionality, here we show that the ME-SXR system can be used to measure the boundary displacement of the NSTX plasma with a few mm spatial resolution during magnetohydrodyamic (MHD) activity. Boundary displacement measurements can serve to inform theoretical predictions of neoclassical toroidal viscosity, and will be used to investigate other edge phenomena on NSTX-U. For example, boundary measurements using filtered SXR measurements can provide information on pedestal steepness and dynamic evolution leading up to and during edge localized modes (ELMs). Future applications include an assessment of a simplified, filtered SXR edge detection system as well as its suitability for real-time non-magnetic boundary feedback for ELMs, MHD, and equilibrium position control.
Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET
Authors: Jacobsen A. S. , Salewski M. , Eriksson J. , Ericsson G. , Hjalmarsson A. , Korsholm S. B. , Leipold F. , Nielsen S. K. , Rasmussen J. , Stejner M. ,   JET-EFDAContributors
Published: July 2014

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR.
Differential cross sections for intermediate-energy electron scattering from α-tetrahydrofurfuryl alcohol: Excitation of electronic-states
Authors: Chiari L. , Duque H. V. , Jones D. B. , Thorn P. A. , Pettifer Z. , da Silva G. B. , Limão-Vieira P. , Duflot D. , Hubin-Franskin M.-J. , Delwiche J. , Blanco F. , García G. , Lopes M. C. A. , Ratnavelu K. , White R. D. , Brunger M. J.
Published: July 2014

We report on measurements of differential cross sections (DCSs) for electron impact excitation of a series of Rydberg electronic-states in α-tetrahydrofurfuryl alcohol (THFA). The energy range of these experiments was 20–50 eV, while the scattered electron was detected in the 10°–90° angular range. There are currently no other experimental data or theoretical computations against which we can directly compare the present measured results. Nonetheless, we are able to compare our THFA DCSs with earlier cross section measurements for Rydberg-state electronic excitation for tetrahydrofuran, a similar cyclic ether, from Do et al. [J. Chem. Phys. 134, 144302 (2011)]. In addition, “rotationally averaged” elastic DCSs, calculated using our independent atom model with screened additivity rule correction approach are also reported. Those latter results give integral cross sections consistent with the optical theorem, and supercede those from the only previous study of Milosavljević et al. [Eur. Phys. J. D 40, 107 (2006)].
On the Debye–Hückel effect of electric screening
Authors: Campos L. M. B. C. , Lau F. J. P.
Published: July 2014

The paper considers non-linear self-consistent electric potential equation (Sec. I), due to a cloud made of a single species of electric charges, satisfying a Boltzmann distribution law (Sec. II). Exact solutions are obtained in a simple logarithmic form, in three cases: (Sec. III) spherical radial symmetry; (Sec. IV) plane parallel symmetry; (Sec. V) a special case of azimuthal-cylindrical symmetry. All these solutions, and their transformations (Sec. VI), involve the Debye-Hückel radius; the latter was originally defined from a solution of the linearized self-consistent potential equation. Using an exact solution of the self-consistent potential equation, the distance at which the potential vanishes differs from the Debye-Hückel radius by a factor of 2. The preceding (Secs. II–VI) simple logarithmic exact solutions of the self-consistent potential equations involve no arbitrary constants, and thus are special or singular integrals not the general integral. The general solution of the self-consistent potential equation is obtained in the plane parallel case (Sec. VII), and it involves two arbitrary constants that can be reduced to one via a translation (Sec. VIII). The plots of dimensionless potential (Figure 1), electric field (Figure 2), charge density (Figure 3), and total charge between ζ and infinity (Figure 4), versus distance normalized to Debye-Hückel radius ζ ≡ z/a, show that (Sec. IX) there is a continuum of solutions, ranging from a charge distribution concentrated inside the Debye-Hückel radius to one spread-out beyond it. The latter case leads to the limiting case of logarithmic potential, and stronger electric field; the former case, of very concentrated charge distribution, leads to a fratricide effect and weaker electric field.
Improved time response for large area microchannel plate photomultiplier tubes in fusion diagnostics
Authors: Milnes J. S. , Horsfield C. J. , Conneely T. M. , Howorth J.
Published: July 2014

Fusion diagnostics that utilise high speed scintillators often need to capture a large area of light with a high degree of time accuracy. Microchannel plate (MCP) photomultiplier tubes (PMTs) are recognised as the leading device for capturing fast optical signals. However, when manufactured in their traditional proximity focused construction, the time response performance is reduced as the active area increases. This is due to two main factors: the capacitance of a large anode and the difficulty of obtaining small pore MCPs with a large area. Collaboration between Photek and AWE has produced prototype devices that combine the excellent time response of small area MCP-PMTs with a large active area by replacing the traditional proximity-gap front section with an electro-optically focused photocathode to MCP. We present results from both single and double MCP devices with a 40 mm diameter active area and show simulations for the 100 mm device being built this year.
Higher than 60% internal quantum efficiency of photoluminescence from amorphous silicon oxynitride thin films at wavelength of 470 nm
Authors: Zhang Pengzhan , Chen Kunji , Dong Hengping , Zhang Pei , Fang Zhonghui , Li Wei , Xu Jun , Huang Xinfan
Published: July 2014

We reported the study on the photoluminescence internal quantum efficiency (PL IQE) and external quantum efficiency (PL EQE) from the amorphous silicon oxynitride (a-SiNO) films, which were fabricated by plasma-enhanced chemical vapor deposition followed by in situ plasma oxidation. We employed the direct measurement of absolute quantum efficiency within a calibrated integration sphere to obtain the PL EQE. Then, we calculated the PL IQE by combing the measured EQE and optical parameters of light extraction factor, reflectivity, and transmittance of the a-SiNO thin films. We also derived the PL QE through investigating the characteristic of the temperature dependent PL. These results show that the PL IQE as high as 60% has been achieved at peak wavelength of about 470 nm, which is much higher than that of Si nanocrystal embedded thin films.
Spectral light separator based on deep-subwavelength resonant apertures in a metallic film
Authors: Büyükalp Yasin , Catrysse Peter B. , Shin Wonseok , Fan Shanhui
Published: July 2014

We propose to funnel, select, and collect light spectrally by exploiting the unique properties of deep-subwavelength resonant apertures in a metallic film. In our approach, each aperture has an electromagnetic cross section that is much larger than its physical size while the frequency of the collected light is controlled by its height through the Fabry-Pérot resonance mechanism. The electromagnetic crosstalk between apertures remains low despite physical separations in the deep-subwavelength range. The resulting device enables an extremely efficient, subwavelength way to decompose light into its spectral components without the loss of photons and spatial coregistration errors. As a specific example, we show a subwavelength-size structure with three deep-subwavelength slits in a metallic film designed to operate in the mid-wave infrared range between 3 and 5.5 μm.
Magnetization and magnetoelastic behavior of a functionally graded rectangular superconductor slab
Authors: Yang Yumei , Wang Xingzhe
Published: July 2014

The magnetoelastic stress and magnetostriction induced by flux-pinning in a functionally graded rectangular superconductor slab are investigated analytically. Two material graded indexes α and β are introduced for indicating the critical current state and the elastic property of the inhomogeneous superconductor. Based on an extended exponent model, the magnetic field distributions are analytically obtained under the zero-field cooling process. The magnetoelastic strain/stress state and the magnetostriction behavior induced by flux-pinning forces are then evaluated, and the maximum stress variation inside the superconductor slab is highlighted. Results show that the maximum flux-pinning stress is increased with the superconductor inhomogeneity, and the maximum magnetostriction of the slab is independent on the maximum applied magnetic field after the slab is completely trapped. The inhomogeneity of the material is a considerable factor to affect the electromagnetic properties and its mechanical behavior significantly for the graded superconductor slab.
Advantage of suppressed non-Langevin recombination in low mobility organic solar cells
Authors: Stolterfoht Martin , Philippa Bronson , Armin Ardalan , Pandey Ajay K. , White Ronald D. , Burn Paul L. , Meredith Paul , Pivrikas Almantas
Published: July 2014

Photovoltaic performance in relation to charge transport is studied in efficient (7.6%) organic solar cells (PTB7:PC71BM). Both electron and hole mobilities are experimentally measured in efficient solar cells using the resistance dependent photovoltage technique, while the inapplicability of classical techniques, such as space charge limited current and photogenerated charge extraction by linearly increasing voltage is discussed. Limits in the short-circuit current originate from optical losses, while charge transport is shown not to be a limiting process. Efficient charge extraction without recombination can be achieved with a mobility of charge carriers much lower than previously expected. The presence of dispersive transport with strongly distributed mobilities in high efficiency solar cells is demonstrated. Reduced non-Langevin recombination is shown to be beneficial for solar cells with imbalanced, low, and dispersive electron and hole mobilities.
Meandering of overgrown v-shaped defects in epitaxial GaN layers
Authors: Weidlich P. H. , Schnedler M. , Portz V. , Eisele H. , Dunin-Borkowski R. E. , Ebert Ph.
Published: July 2014

The meandering of v-shaped defects in GaN(0001) epitaxial layers is investigated by cross-sectional scanning tunneling microscopy. The spatial position of v-shaped defects is mapped on (101¯0) cleavage planes using a dopant modulation, which traces the overgrown growth front. Strong lateral displacements of the apex of the v-shaped defects are observed. The lateral displacements are suggested to be induced by the meandering of threading dislocations present in the v-shaped defects. The meandering of the dislocation is attributed to interactions with inhomogeneous strain fields.
Nonlinear harmonic distortion effect in magnetoelectric laminate composites
Authors: Xu Hao , Pei Yongmao , Fang Daining , Wang Panding
Published: July 2014

Magnetoelectric (ME) harmonic distortion behavior in layered piezoelectric/magnetostrictive composites was investigated in this study. Taking into account the quadratic magnetostrictive effect, a nonlinear distortion coefficient was proposed to quantitatively describe the distortion of ME frequency response. It was revealed that the ME distortion was the competition result of linear piezomagnetic and quadratic magnetostrictive effect. Theoretical predictions of their dependences on dc bias field and frequency of ac drive field showed good agreement with experiment. Moreover, the diagram of competition mechanism for these two effects was established, demonstrating that the nonlinear distortion could be tuned by interplay between frequency doubling and mechanical resonance effect, which was significant for the development of tunable nonlinear ME devices.
Significant tuning of band structures of magneto-mechanical phononic crystals using extraordinarily small magnetic fields
Authors: Yang Aichao , Li Ping , Wen Yumei , Lu Caijiang , Peng Xiao , Zhang Jitao , He Wei , Wang Decai , Yang Chao
Published: July 2014

Tuning band structures of a magneto-mechanical phononic crystal (PnC) (containing elastic plates bonded with magnets) is demonstrated by applying a small static magnetic field (Hdc). Due to magnetic torque effect, the markedly altered coupling between Bragg scattering (related to lattice constants) and local resonances of plates occurs. Consequently, significant tuning of band structures is observed under a greatly small Hdc. Experiments show that an additional passband occurs in band structures when Hdc ≥ 130 Oe. This threshold (130 Oe) is ∼1/100 as large as that of the conventional PnC using magnetostrictive materials. The adjusted maximum of passband bandwidth is 0.57 kHz under 0–600 Oe.
Fluctuations of DNA mobility in nanofluidic entropic traps
Authors: Wu Lingling , Levy Stephen
Published: July 2014

We studied the mobility of DNA molecules driven by an electric field through a nanofluidic device containing a periodic array of deep and shallow regions termed entropic traps. The mobility of a group of DNA molecules was measured by fluorescent video microscopy. Since the depth of a shallow region is smaller than the DNA equilibrium size, DNA molecules are trapped for a characteristic time and must compress themselves to traverse the boundary between deep and shallow regions. Consistent with previous experimental results, we observed a nonlinear relationship between the mobility and electric field strength, and that longer DNA molecules have larger mobility. In repeated measurements under seemingly identical conditions, we measured fluctuations in the mobility significantly larger than expected from statistical variation. The variation was more pronounced for lower electric field strengths where the trapping time is considerable relative to the drift time. To determine the origin of these fluctuations, we investigated the dependence of the mobility on several variables: DNA concentration, ionic strength of the solvent, fluorescent dye staining ratio, electroosmotic flow, and electric field strength. The mobility fluctuations were moderately enhanced in conditions of reduced ionic strength and electroosmotic flow.
Ultraviolet random lasing from a diamond nanoparticle film
Authors: Niyuki Ryo , Takashima Hideaki , Fujiwara Hideki , Sasaki Keiji
Published: July 2014

We demonstrated ultraviolet random lasing from a diamond nanoparticle film, in which commercially available diamond nanoparticles with an average size of 25 nm acted as the gain medium and scatterers. By optically exciting the diamond nanoparticle film at an excitation wavelength of 355 nm, discrete sharp peaks, superposed on a collapsed broad emission spectrum, randomly appeared at wavelengths around the broad emission maximum (∼382 nm) when the excitation intensity exceeded the threshold. From the dependence of lasing peak intensities measured at different locations as a function of excitation intensity, the threshold was estimated to be approximately several tens of MW/cm2.
Interaction between jets during laser-induced forward transfer
Authors: Patrascioiu A. , Florian C. , Fernández-Pradas J. M. , Morenza J. L. , Hennig G. , Delaporte P. , Serra P.
Published: July 2014

Simultaneous two-beam laser-induced forward transfer (LIFT) was carried out for various inter-beam separations, analyzing both the resulting printing outcomes and the corresponding liquid transfer dynamics. In a first experiment, droplets of an aqueous solution were printed onto a substrate at different inter-beam distances, which proved that a significant departure from the single-beam LIFT dynamics takes places at specific separations. In the second experiment, time-resolved imaging analysis revealed the existence of significant jet-jet interactions at those separations; such interactions proceed through a dynamics that results in remarkable jet deflection for which a possible onset mechanism is proposed.
AlGaN composition dependence of the band offsets for epitaxial Gd2O3/AlxGa1−xN (0 ≤ x ≤ 0.67) heterostructures
Authors: Ihlefeld Jon F. , Brumbach Michael , Allerman Andrew A. , Wheeler David R. , Atcitty Stanley
Published: July 2014

Gd2O3 films were prepared on (0001)-oriented AlxGa1−xN (0 ≤ x ≤ 0.67) thin film substrates via reactive molecular-beam epitaxy. X-ray diffraction revealed that these films possessed the cubic bixbyite structure regardless of substrate composition and were all 111-oriented with in-plane rotations to account for the symmetry difference between the oxide film and nitride epilayer. Valence band offsets were characterized by X-ray photoelectron spectroscopy and were determined to be 0.41 ± 0.02 eV, 0.17 ± 0.02 eV, and 0.06 ± 0.03 eV at the Gd2O3/AlxGa1−xN interfaces for x = 0, 0.28, and 0.67, respectively.
Resonant tunneling and magnetoresistance effect in magnetically modulated graphene
Authors: Lu Wei-Tao
Published: July 2014

We study resonant tunneling through a magnetic barrier structure in graphene, on the basis of Fabry-Pérot interference effect. For parallel structure, the Fabry-Pérot resonance displays symmetric distribution in (E, ky) space, and the transmission range is shrunk rapidly with the increased magnetic barrier or period number. For antiparallel structure, there exists a complex resonant tunneling caused by the combined effect of Fabry-Pérot resonance and line-type resonance, which are related to resonant states in the vector potential barriers and wells, respectively. Such a transmission difference leads to a giant magnetoresistance ratio which can be effectively controlled by adjusting the magnetic field.
Enhanced graphene plasmon waveguiding in a layered graphene−metal structure
Authors: Lin I-Tan , Liu Jia-Ming
Published: July 2014

In this Letter, a graphene-based terahertz plasmonic waveguide is proposed. The proposed structure benefits from the enhanced confinement and increased attenuation length of graphene surface plasmon by placing the graphene sheet in proximity of metal layers. For a graphene-based slab waveguide, our data show a 20% increase in the plasmonic attenuation length and a 97% increase in the attenuation length normalized to the plasmonic wavelength, thus significantly increasing the propagation distance of the surface plasmon. Further, improvement is possible by optimizing dielectric mismatch, graphene−metal distance, waveguide width, and the Fermi energy of graphene.
Recruiting general practitioners for surveys and other research: additional lessons learned
Authors: McKenzie Suzanne , Larkins Sarah , Spillman Margaret
Published: July 2014

This letter acknowledges the work of Parkinson et al. ‘Recruiting general practitioners for surveys: reflections on the difficulties and some lessons learned’ (Australian Journal of Primary Health, 2015, 21(2), 254–258), but contributes additional reflections and lessons learned from a successful practice-based research network.
Differential gene-expression profiles from canine cumulus cells of ovulated versus in vitro-matured oocytes
Authors: Cho Su-Jin , Lee Kyeong-Lim , Kim Yu-Gon , Kim Dong-Hoon , Yoo Jae-Gyu , Yang Byoung-Chul , Park Jin-Ki , Kong Il-Keun
Published: July 2014

We compared the nuclear maturation status and gene-expression profiles of canine cumulus cells (CCs) derived from cumulus–oocyte complexes (COCs) that were spontaneously ovulated versus those that were matured in vitro. Cumulus–oocyte complexes were retrieved from uteri by surgical flushing (after spontaneous ovulation) or by ovariectomy follicle aspiration and in vitro maturation. The objective of Experiment 1 was to investigate the nuclear maturation status of in vivo- versus in vitro-matured oocytes. The objective of Experiment 2 was to compare gene-expression profiles of CCs derived from in vivo- versus in vitro-matured COCs. Genes analysed are related to cell maturation, development and apoptosis, including GDF9, MAPK1, PTX3, CX43, Bcl2 and BAX; mRNA expression for all of these genes, except for GDF9, differed (P < 0.05) between in vivo- and in vitro-matured CCs. In conclusion, we found that gene-expression profiles are related to the quality of CCs and therefore posit that monitoring gene expression could be a useful strategy to guide attempts to improve in vitro culture systems.
Structural basis for cooperative interactions of substituted 2-aminopyrimidines with the acetylcholine binding protein
Authors: Kaczanowska Katarzyna , Harel Michal , Radić Zoran , Changeux Jean-Pierre , Finn M. G. , Taylor Palmer
Published: July 2014

Significance

Heretofore, ligand recognition at each subunit interface of the acetylcholine binding protein (AChBP) has been found to be independent of the other interfaces, representing a disconnection between the properties of the AChBP and the full receptor that it is intended to model. These results comprise the first examples of cooperative binding with the extracellular domain, providing insights into the structural basis for interactions between subunits. Within a single series of congeneric molecules, both positively and negatively cooperative behaviors toward AChBP are manifest. Hence, a distinct mode of binding to the agonist-competitive antagonist site is established in the AChBP protein.
The preference of probability over negative values in action selection
Authors: Neyedli Heather F. , Welsh Timothy N.
Published: July 2014

It has previously been found that when participants are presented with a pair of motor prospects, they can select the prospect with the largest maximum expected gain (MEG). Many of those decisions, however, were trivial because of large differences in MEG between the prospects. The purpose of the present study was to explore participants' preferences when making non-trivial decisions between two motor prospects. Participants were presented with pairs of prospects that: 1) differed in MEG with either only the values or only the probabilities differing between the prospects; and 2) had similar MEG with one prospect having a larger probability of hitting the target and a higher penalty value and the other prospect a smaller probability of hitting the target but a lower penalty value. In different experiments, participants either had 400 ms or 2000 ms to decide between the prospects. It was found that participants chose the configuration with the larger MEG more often when the probability varied between prospects than when the value varied. In pairs with similar MEGs, participants preferred a larger probability of hitting the target over a smaller penalty value. These results indicate that participants prefer probability information over negative value information in a motor selection task.