bluuebunny/crossref_metadata_2025 huggingface dataset:
Aqueous dispersions of oligomer-grafted carbon nanomaterials with controlled surface charge and minimal framework damage
Authors: Hu Sheng , Chen Shu , Menzel Robert , Goode Angela D. , Ryan Mary P. , Porter Alexandra E. , Shaffer Milo S. P.
Published: September 2014

Functionalised carbon nanomaterials (CNMs), with an undamaged carbon framework and controlled physiochemical properties, are desirable for a wide range of scientific studies and commercial applications. The use of a thermochemical grafting approach provides a versatile means to functionalise both multi-walled carbon nanotubes (MWCNTs) and carbon black (CB) nanoparticles without altering their inherent structures. The functionalisation process was investigated by employing various types of grafting monomers; to improve water solubility, reagents were chosen that introduced an ionic character either intrinsically or after further chemical reactions. The degree of grafting for both MWCNTs and CB ranged from 3–27 wt%, as established by thermal gravimetric analysis (TGA). Raman spectroscopy confirmed that the structural framework of the MWCNTs was unaffected by the thermochemical treatment. The effectiveness of the surface modification was demonstrated by significantly improved dispersibility and stability in water, and further quantified by zeta-potential analysis. The concentration of stable, individualised and grafted MWCNTs in water ranged from ∼30 to 80 μg mL−1after centrifugation at 10 000 g for 15 min, whereas functionalised CB in water showed improved dispersibility up to ∼460 μg mL−1. The successful preparation of structurally identical but differently functionalised nanoparticle panels, with high water compatibility and minimal framework damage, is useful for controlled experiments. For example, they can be used to explore the relationship between toxicological effects and specific physiochemical properties, such as surface charge and geometry.
On characterization of anisotropic plant protein structures
Authors: Krintiras Georgios A. , Göbel Jesse , Bouwman Wim G. , Jan van der Goot Atze , Stefanidis Georgios D.
Published: September 2014

In this paper, a set of complementary techniques was used to characterize surface and bulk structures of an anisotropic Soy Protein Isolate (SPI)–vital wheat gluten blend after it was subjected to heat and simple shear flow in a Couette Cell.
Lactobacillus plantarum NCU116 improves liver function, oxidative stress and lipid metabolism in rats with high fat diet induced non-alcoholic fatty liver disease
Authors: Li Chuan , Nie Shao-Ping , Zhu Ke-Xue , Ding Qiao , Li Chang , Xiong Tao , Xie Ming-Yong
Published: September 2014

Possible mechanisms underlying how Lactobacillus plantarum NCU116 improves lipid metabolism in rats with high fat diet induced NAFLD.
One-step propylene formation from bio-glycerol over molybdena-based catalysts
Authors: Zacharopoulou Vasiliki , Vasiliadou Efterpi S. , Lemonidou Angeliki A.
Published: September 2014

A novel one-step process is explored for glycerol conversion to propene, over molybdena-based catalysts. Through hydro-deoxygenation reactions, glycerol is converted to 2-propenol, which is subsequently hydrogenated to form propene.
Synthesis of tetrazole compounds as a novel type of potential antimicrobial agents and their synergistic effects with clinical drugs and interactions with calf thymus DNA
Authors: Dai Ling-Ling , Zhang Hui-Zhen , Nagarajan Sangaraiah , Rasheed Syed , Zhou Cheng-He
Published: September 2014

A series of tetrazole derivatives were synthesized and characterized by NMR, IR, MS and HRMS spectroscopy.
Alkane oxidation with peroxides catalyzed by cage-like copper(ii) silsesquioxanes
Authors: Vinogradov Mikhail M. , Kozlov Yuriy N. , Bilyachenko Alexey N. , Nesterov Dmytro S. , Shul'pina Lidia S. , Zubavichus Yan V. , Pombeiro Armando J. L. , Levitsky Mikhail M. , Yalymov Alexey I. , Shul'pin Georgiy B.
Published: September 2014

Copper(ii) silsesquioxanes [(PhSiO1.5)12(CuO)4(NaO0.5)4] or [(PhSiO1.5)10(CuO)2(NaO0.5)2] are catalysts for alkane oxidation with H2O2ort-BuOOH.
Photoelectron spectroscopy of wet and gaseous samples through graphene membranes
Authors: Kraus Jürgen , Reichelt Robert , Günther Sebastian , Gregoratti Luca , Amati Matteo , Kiskinova Maya , Yulaev Alexander , Vlassiouk Ivan , Kolmakov Andrei
Published: September 2014

Due to the short electron mean free path in dense media samples in liquid or ambient pressure environment cannot be easily characterized by photoelectron spectroscopy. We overcome this limitation by employing electron transparent graphene membranes to separate the sample environment from the vacuum conditions in the electron spectrometer.
Diameter selective electron transfer from encapsulated ferrocenes to single-walled carbon nanotubes
Authors: Iizumi Yoko , Suzuki Hironori , Tange Masayoshi , Okazaki Toshiya
Published: September 2014

The diameter selective photoluminescence quenching of single-walled carbon nanotubes (SWCNTs) is observed upon ferrocene encapsulation, which can be attributed to electron transfer from the encapsulated ferrocenes to the SWCNTs.
Synthesis and characterization of bead-like poly(N-isopropylacrylamide) copolymers with double decker silsesquioxane in the main chains
Authors: Wei Kun , Wang Lei , Li Lei , Zheng Sixun
Published: September 2014

A bead-like PNIPAAm copolymer with double-decker silsesquioxane (DDSQ) in the main chain was synthesized via a reversible addition–fragmentation chain transfer polymerization (RAFT) approach.
Polymer grafted recyclable magnetic nanoparticles
Authors: Wang Lei , Cole Marcus , Li Junting , Zheng Yang , Chen Yung Pin , Miller Kristen P. , Decho Alan W. , Benicewicz Brian C.
Published: September 2014

The recyclable poly(methacrylic acid) grafted magnetic particles retained excellent aqueous phase dispersibility and high biological activity against bacteria when loaded with an antibiotic. The particles were removed from water solutions using a magnet after antimicrobial testing, thus avoiding nano-based pollution of the biological environment.
Novel thermo-sensitive hydrogels containing polythioether dendrons: facile tuning of LCSTs, strong absorption of Ag ions, and embedment of smaller Ag nanocrystals
Authors: Jiang Daoyi , Wang Gang , Zheng Feng , Han Jin , Wu Xuedong
Published: September 2014

Polythioether dendrons made tuning of the LCST of a thermo-sensitive hydrogel facile and the size of loaded Ag nanocrystals much smaller.
Antiproliferative and apoptosis-induction studies of a metallosurfactant in human breast cancer cell MCF-7
Authors: Riyasdeen Anvarbatcha , Senthilkumar Rajendran , Periasamy Vaiyapuri Subbarayan , Preethy Paul , Srinag Suresh , Zeeshan Mohammed , Krishnamurthy Hanumanthappa , Arunachalam Sankaralingam , Akbarsha Mohammad Abdulkader
Published: September 2014

The cytotoxic potential of the surfactant–cobalt(iii) complex (metallosurfactant) cis-[Co(trien)(C14H29NH2)Cl](ClO4)2 was tested on an MCF-7 breast cancer cell.
Textures of Au, Pt and Pd/PdO nanoparticles thermally dewetted from thin metal layers on fused silica
Authors: Kracker Michael , Wisniewski Wolfgang , Rüssel Christian
Published: September 2014

This article shows that multiple crystallographic textures coexist in thermally dewetted metal nano particles in contrast to the usually assumed or presented 111 texture.
Through-holes, cavities and perforations in polydimethylsiloxane (PDMS) chips
Authors: Silva Santisteban Tomas , Zengerle Roland , Meier Matthias
Published: September 2014

We present a method to fabricate through-holes between 10 to 180 μm between polydimethylsiloxane (PDMS) layers of microfluidic large-scale integration platforms.
Mechanistic insights into hydroacylation with non-chelating aldehydes
Authors: Murphy Stephen K. , Bruch Achim , Dong Vy M.
Published: September 2014

Rhodium catalysts with small-bite-angle diphosphines enable branched-selective hydroacylation of 2-vinylphenols via C–H activation of non-chelating aldehydes.
A strategy based on nucleotide specificity leads to a subfamily-selective and cell-active inhibitor of N6-methyladenosine demethylase FTO
Authors: Toh Joel D. W. , Sun Lingyi , Lau Lisa Z. M. , Tan Jackie , Low Joanne J. A. , Tang Colin W. Q. , Cheong Eleanor J. Y. , Tan Melissa J. H. , Chen Yun , Hong Wanjin , Gao Yong-Gui , Woon Esther C. Y.
Published: September 2014

The AlkB family of nucleic acid demethylases are of intense biological and medical interest. The discovery of a highly selective FTO inhibitor should greatly facilitate the study of these enzymes.
Synthesis of hollow organosiliceous spheres for volatile organic compound removal
Authors: Wang Hongning , Tang Mei , Han Lu , Cao Jianyu , Zhang Zhihui , Huang Weiqiu , Chen Ruoyu , Yu Chengzhong
Published: September 2014

Synthesized mesoporous hollow organosiliceous spheres exhibit the smallest water vapor adsorption capacity, the largest VOC removal capacity and the highest recyclability as compared to commercial silica gel and activated carbon.
Mechanofluorochromic behaviors of β-iminoenolate boron complexes functionalized with carbazole
Authors: Zhang Zhenqi , Xue Pengchong , Gong Peng , Zhang Gonghe , Peng Jiang , Lu Ran
Published: September 2014

New β-iminoenolate boron complexes exhibit different mechanofluorochromic properties due to the excimer and monomer transformation.
Circularly polarised printed antenna miniaturised using complementary split‐ring resonators and reactive pin loading
Authors: Gupta Saurabh , Mumcu Gokhan
Published: September 2014

A circularly polarised printed antenna, miniaturised by utilising a combination of complementary split‐ring resonators (CSRR) and reactive pin loadings, is presented. This design technique is shown to reduce the electrical size of the antenna diameter by 44% at 2.4 GHz. The antenna prototype, when radiating a right‐hand circularly polarised beam, displayed 4.1 dBic of broadside realised gain with 70% radiation efficiency. Specifically, it was demonstrated that the stand‐alone CSRR loading resulted in a size reduction of 30%. The addition of reactive pins enhances this factor up to 44% without causing any observable degradation in antenna performance.
High-resolution grazing-incidence grating spectrometer for temperature measurements of low-Z ions emitting in the 100–300 Å spectral band
Authors: Widmann K. , Beiersdorfer P. , Magee E. W. , Boyle D. P. , Kaita R. , Majeski R.
Published: September 2014

We have constructed a high-resolution grazing-incidence spectrometer designed for measuring the ion temperature of low-Z elements, such as Li+ or Li2 +, which radiate near 199 Å and 135 Å, respectively. Based on measurements at the Livermore Electron Beam Ion Trap we have shown that the instrumental resolution is better than 48 mÅ at the 200 Å setting and better than 40 mÅ for the 135-Å range. Such a high spectral resolution corresponds to an instrumental limit for line-width based temperature measurements of about 45 eV for the 199 Å Li+ and 65 eV for the 135 Å Li2 + lines. Recently obtained survey spectra from the Lithium Tokamak Experiment at the Princeton Plasma Physics Laboratory show the presence of these lithium emission lines and the expected core ion temperature of approximately 70 eV is sufficiently high to demonstrate the feasibility of utilizing our high-resolution spectrometer as an ion-temperature diagnostic.
Use of soft x-ray diagnostic on the COMPASS tokamak for investigations of sawteeth crash neighborhood and of plasma position using fast inversion methods
Authors: Imrisek M. , Weinzettl V. , Mlynar J. , Odstrcil T. , Odstrcil M. , Ficker O. , Pinzon J. R. , Ehrlacher C. , Panek R. , Hron M.
Published: September 2014

The soft x-ray diagnostic is suitable for monitoring plasma activity in the tokamak core, e.g., sawtooth instability. Moreover, spatially resolved measurements can provide information about plasma position and shape, which can supplement magnetic measurements. In this contribution, fast algorithms with the potential for a real-time use are tested on the data from the COMPASS tokamak. In addition, the soft x-ray data are compared with data from other diagnostics in order to discuss possible connection between sawtooth instability on one side and the transition to higher confinement mode, edge localized modes and productions of runaway electrons on the other side.
Edge electron density profiles and fluctuations measured by two-dimensional beam emission spectroscopy in the KSTAR
Authors: Nam Y. U. , Zoletnik S. , Lampert M. , Kovácsik Ákos , Wi H. M.
Published: September 2014

Beam emission spectroscopy (BES) system in Korea Superconducting Tokamak Advanced Research (KSTAR) has recently been upgraded. The background intensity was reduced from 30% to 2% by suppressing the stray lights. This allows acquisition of the relative electron density profiles on the plasma edge without background subtraction from the beam power modulation signals. The KSTAR BES system has its spatial resolution of 1 cm, the temporal resolution of 2 MHz, and a total 32 channel (8 radial × 4 poloidal) avalanche photo diode array. Most measurements were done on the plasma edge, r/a ∼ 0.9, with 8 cm radial measurement width that covers the pedestal range. High speed density profile measurements reveal temporal behaviors of fast transient events, such as the precursors of edge localized modes and the transitions between confinement modes. Low background level also allows analysis of the edge density fluctuation patterns with reduced background fluctuations. Propagation of the density structures can be investigated by comparing the phase delays between the spatially distributed channels.
Fully crystalline perovskite-perylene hybrid photovoltaic cell capable of 1.2 V output with a minimized voltage loss
Authors: Ishii Ayumi , Jena Ajay Kumar , Miyasaka Tsutomu
Published: September 2014

A fully crystalline heterojunction of organo-metal-halide perovskite, CH3NH3PbI3−xClx (X < 0.24), and perylene constitutes a planar photovoltaic cell that yields a photovoltage exceeding 1.2 V with a single junction cell absorbing up to 800 nm. Here, perylene not only works as a hole conductor but also contributes to photovoltage as a photoconductor. The crystalline plane orientation of perovskite prepared on TiO2 was controlled by thermal annealing such that the lead halide (110) plane that participates in carrier conduction is highly oriented to enhance the photovoltaic performance. The crystal orientation improves the heterojunction structure with perylene. For the best cell with high crystalline orientation, a total voltage loss is significantly minimized to 0.32 V with respect to the absorption band gap of 1.55 eV. The planar crystal cells generate high open-circuit voltages of 1.15–1.22 V, which is close to a theoretical maximal voltage (1.25–1.3 V) described by the Shockley-Queisser efficiency limit. The cell yielded energy conversion efficiency up to 4.96%.
High-speed imaging upgrade for a standard sample scanning atomic force microscope using small cantilevers
Authors: Adams Jonathan D. , Nievergelt Adrian , Erickson Blake W. , Yang Chen , Dukic Maja , Fantner Georg E.
Published: September 2014

We present an atomic force microscope (AFM) head for optical beam deflection on small cantilevers. Our AFM head is designed to be small in size, easily integrated into a commercial AFM system, and has a modular architecture facilitating exchange of the optical and electronic assemblies. We present two different designs for both the optical beam deflection and the electronic readout systems, and evaluate their performance. Using small cantilevers with our AFM head on an otherwise unmodified commercial AFM system, we are able to take tapping mode images approximately 5–10 times faster compared to the same AFM system using large cantilevers. By using additional scanner turnaround resonance compensation and a controller designed for high-speed AFM imaging, we show tapping mode imaging of lipid bilayers at line scan rates of 100–500 Hz for scan areas of several micrometers in size.
The role of radiative reabsorption on the electron energy distribution functions in H2/He plasma expansion through a tapered nozzle
Authors: D'Ammando Giuliano , Capitelli Mario , Esposito Fabrizio , Laricchiuta Annarita , Pietanza Lucia D. , Colonna Gianpiero
Published: September 2014

A collisional-radiative model for the H2/He plasma, coupled to a Boltzmann solver for the free electron kinetics is used to investigate the non-equilibrium conditions created in the expansion of an high-temperature plasma flow through a converging-diverging nozzle, starting from the steady state composition at T0=10 000 K and p0=1 atm in the reservoir. It is shown that the plasma optical thickness plays a major role on the evolution of macroscopic quantities and internal distributions along the nozzle axis. Structured electron energy distribution functions, characterized by long plateaux and humps, are created due to superelastic collisions of cold electrons and electronically excited atomic hydrogen. The magnitudes of the plateaux are orders of magnitude higher in an optically thick plasma compared with a thin plasma, while the electron-electron collisions play a role in smoothing the peaks created by superelastic collisions between cold electrons and H(n>2).
Spectral content of buried Ag foils at 1016 W/cm2 laser illumination
Authors: Huntington C. M. , Maddox B. R. , Park H.-S. , Prisbrey S. , Remington B. A.
Published: September 2014

Sources of 5–12 keV thermal Heα x-rays are readily generated by laser irradiation of mid-Z foils at intensities >1014 W/cm2, and are widely used as probes for inertial confinement fusion and high-energy-density experiments. Higher energy 17–50 keV x-ray sources are efficiently produced from “cold” Kα emission using short pulse, petawatt lasers at intensities >1018 W/cm2 [H.-S. Park, B. R. Maddox et al., “High-resolution 17–75 keV backlighters for high energy density experiments,” Phys. Plasmas 15(7), 072705 (2008); B. R. Maddox, H. S. Park, B. A. Remington et al., “Absolute measurements of x-ray backlighter sources at energies above 10 keV,” Phys. Plasmas 18(5), 056709 (2011)]. However, when long pulse (>1 ns) lasers are used with Z > 30 elements, the spectrum contains contributions from both K shell transitions and from ionized atomic states. Here we show that by sandwiching a silver foil between layers of high-density carbon, the ratio of Kα:Heα in the x-ray spectrum is significant increased over directly illuminated Ag foils, with narrower lines from K-shell transitions. Additionally, the emission volume is more localized for the sandwiched target, producing a more planar x-ray sheet. This technique may be useful for generating probes requiring spectral purity and a limited spatial extent, for example, in incoherent x-ray Thomson scattering experiments.
Sub-picowatt resolution calorimetry with niobium nitride thin-film thermometer
Authors: Dechaumphai Edward , Chen Renkun
Published: September 2014

High-resolution calorimetry has many important applications such as probing nanoscale thermal transport and studying the thermodynamics of biological and chemical systems. In this work, we demonstrated a calorimeter with an unprecedentedly high resolution at room temperature using a high-performance resistive thermometry material, niobium nitride (NbNx). Based on a theoretical analysis, we first showed that the heat flux resolution of a resistive-thermometry based calorimeter depends on the parasitic thermal conductance of the device and the temperature coefficient of resistance (TCR) of the thermometer, when the noise is limited by the Johnson noise. Based on this analysis, we then developed a calorimeter using NbNx as the thermometry material because it possesses both high TCR (∼0.67%/K) and a low thermal conductivity (k ∼ 1.1 W/m K). This calorimeter, when used with the modulated heating scheme, demonstrated an unprecedentedly high power resolution of 0.26 pW at room temperature. In addition, NbNx based resistive thermometry can also be extended to cryogenic temperature, where the TCR is shown to be significantly higher.
Nanometer-scale temperature imaging for independent observation of Joule and Peltier effects in phase change memory devices
Authors: Grosse Kyle L. , Pop Eric , King William P.
Published: September 2014

This paper reports a technique for independent observation of nanometer-scale Joule heating and thermoelectric effects, using atomic force microscopy (AFM) based measurements of nanometer-scale temperature fields. When electrical current flows through nanoscale devices and contacts the temperature distribution is governed by both Joule and thermoelectric effects. When the device is driven by an electrical current that is both periodic and bipolar, the temperature rise due to the Joule effect is at a different harmonic than the temperature rise due to the Peltier effect. An AFM tip scanning over the device can simultaneously measure all of the relevant harmonic responses, such that the Joule effect and the Peltier effect can be independently measured. Here we demonstrate the efficacy of the technique by measuring Joule and Peltier effects in phase change memory devices. By comparing the observed temperature responses of these working devices, we measure the device thermopower, which is in the range of 30 ± 3 to 250 ± 10 μV K−1. This technique could facilitate improved measurements of thermoelectric phenomena and properties at the nanometer-scale.
Transitions of tethered chain molecules under tension
Authors: Luettmer-Strathmann Jutta , Binder Kurt
Published: September 2014

An applied tension force changes the equilibrium conformations of a polymer chain tethered to a planar substrate and thus affects the adsorption transition as well as the coil-globule and crystallization transitions. Conversely, solvent quality and surface attraction are reflected in equilibrium force-extension curves that can be measured in experiments. To investigate these effects theoretically, we study tethered chains under tension with Wang-Landau simulations of a bond-fluctuation lattice model. Applying our model to pulling experiments on biological molecules we obtain a good description of experimental data in the intermediate force range, where universal features dominate and finite size effects are small. For tethered chains in poor solvent, we observe the predicted two-phase coexistence at transitions from the globule to stretched conformations and also discover direct transitions from crystalline to stretched conformations. A phase portrait for finite chains constructed by evaluating the density of states for a broad range of solvent conditions and tensions shows how increasing tension leads to a disappearance of the globular phase. For chains in good solvents tethered to hard and attractive surfaces we find the predicted scaling with the chain length in the low-force regime and show that our results are well described by an analytical, independent-bond approximation for the bond-fluctuation model for the highest tensions. Finally, for a hard or slightly attractive surface the stretching of a tethered chain is a conformational change that does not correspond to a phase transition. However, when the surface attraction is sufficient to adsorb a chain it will undergo a desorption transition at a critical value of the applied force. Our results for force-induced desorption show the transition to be discontinuous with partially desorbed conformations in the coexistence region.
Rapid low-temperature processing of metal-oxide thin film transistors with combined far ultraviolet and thermal annealing
Authors: Leppäniemi J. , Ojanperä K. , Kololuoma T. , Huttunen O.-H. , Dahl J. , Tuominen M. , Laukkanen P. , Majumdar H. , Alastalo A.
Published: September 2014

We propose a combined far ultraviolet (FUV) and thermal annealing method of metal-nitrate-based precursor solutions that allows efficient conversion of the precursor to metal-oxide semiconductor (indium zinc oxide, IZO, and indium oxide, In2O3) both at low-temperature and in short processing time. The combined annealing method enables a reduction of more than 100 °C in annealing temperature when compared to thermally annealed reference thin-film transistor (TFT) devices of similar performance. Amorphous IZO films annealed at 250 °C with FUV for 5 min yield enhancement-mode TFTs with saturation mobility of ∼1 cm2/(V·s). Amorphous In2O3 films annealed for 15 min with FUV at temperatures of 180 °C and 200 °C yield TFTs with low-hysteresis and saturation mobility of 3.2 cm2/(V·s) and 7.5 cm2/(V·s), respectively. The precursor condensation process is clarified with x-ray photoelectron spectroscopy measurements. Introducing the FUV irradiation at 160 nm expedites the condensation process via in situ hydroxyl radical generation that results in the rapid formation of a continuous metal-oxygen-metal structure in the film. The results of this paper are relevant in order to upscale printed electronics fabrication to production-scale roll-to-roll environments.
A two-step load-deflection procedure applicable to extract the Young's modulus and the residual tensile stress of circularly shaped thin-film diaphragms
Authors: Beigelbeck Roman , Schneider Michael , Schalko Johannes , Bittner Achim , Schmid Ulrich
Published: September 2014

We report on a novel two-step load-deflection (LD) formula and technique that enables an accurate extraction of the Young's modulus and the residual tensile stress from LD measurements on circularly shaped thin-film diaphragms. This LD relationship is derived from an adaptation of Timoshenko's plate bending theory, where the in-plane and out-of-plane deflections are approximated by series expansions. Utilizing the minimum total potential energy principle yields an infinite-dimensional system of equations which is solved analytically resulting in a compact closed-form solution. In the appendant measurement procedure, the whole transverse bending characteristic of the diaphragm as a function of the radial coordinate is recorded for different pressure loads and introduced into the novel LD equation in order to determine the elastomechanical parameters of interest. The flexibility of this approach is demonstrated by ascertaining the Young's modulus and the residual tensile stress of two disparate diaphragm materials made of either micromachined silicon or microfiltered buckypapers composed of carbon nanotube compounds.
Communication: A non-empirical correlation factor model for the exchange-correlation energy
Authors: Přecechtělová Jana , Bahmann Hilke , Kaupp Martin , Ernzerhof Matthias
Published: September 2014

A persistent challenge in density functional theory is the construction of a nonempirical correlation functional that is compatible with the exact exchange energy. To solve this problem, we develop a correlation factor approach in which an exchange hole model, yielding the exact exchange energy, is multiplied by a correlation factor that turns the exchange hole into an exchange-correlation hole. This results in an accurate correlation energy functional that is determined solely through physical constraints. Subject to the properties of the employed exchange hole model, the proposed correlation factor model to the exchange-correlation energy becomes exact in the high-density limit. In this limit, the exchange-correlation energy is dominated by exchange.
Tuning the thickness of electrochemically grafted layers in large area molecular junctions
Authors: Fluteau T. , Bessis C. , Barraud C. , Della Rocca M. L. , Martin P. , Lacroix J.-C. , Lafarge P.
Published: September 2014

We have investigated the thickness, the surface roughness, and the transport properties of oligo(1-(2-bisthienyl)benzene) (BTB) thin films grafted on evaporated Au electrodes, thanks to a diazonium-based electro-reduction process. The thickness of the organic film is tuned by varying the number of electrochemical cycles during the growth process. Atomic force microscopy measurements reveal the evolution of the thickness in the range of 2–27 nm. Its variation displays a linear dependence with the number of cycles followed by a saturation attributed to the insulating behavior of the organic films. Both ultrathin (2 nm) and thin (12 and 27 nm) large area BTB-based junctions have then been fabricated using standard CMOS processes and finally electrically characterized. The electronic responses are fully consistent with a tunneling barrier in case of ultrathin BTB film whereas a pronounced rectifying behavior is reported for thicker molecular films.
In-situ microscale through-silicon via strain measurements by synchrotron x-ray microdiffraction exploring the physics behind data interpretation
Authors: Liu Xi , Thadesar Paragkumar A. , Taylor Christine L. , Oh Hanju , Kunz Martin , Tamura Nobumichi , Bakir Muhannad S. , Sitaraman Suresh K.
Published: September 2014

In-situ microscale thermomechanical strain measurements have been performed in combination with synchrotron x-ray microdiffraction to understand the fundamental cause of failures in microelectronics devices with through-silicon vias. The physics behind the raster scan and data analysis of the measured strain distribution maps is explored utilizing the energies of indexed reflections from the measured data and applying them for beam intensity analysis and effective penetration depth determination. Moreover, a statistical analysis is performed for the beam intensity and strain distributions along the beam penetration path to account for the factors affecting peak search and strain refinement procedure.
Oxygen vacancies-induced metal-insulator transition in La2/3Sr1/3VO3 thin films: Role of the oxygen substrate-to-film transfer
Authors: Hu L. , Luo X. , Zhang K. J. , Tang X. W. , Zu L. , Kan X. C. , Chen L. , Zhu X. B. , Song W. H. , Dai J. M. , Sun Y. P.
Published: September 2014

Electrical transport properties of La2/3Sr1/3VO3 (LSVO) thin films grown on LaAlO3 (LAO) and SrTiO3 (STO) substrates have been investigated. It is found that the LSVO/LAO show metal-insulator transition when decreasing the temperature, while the LSVO/STO exhibit metallic behavior. The difference in transport properties of LSVO thin films has been discussed based on the variation of oxygen content and can be attributed to different oxygen substrate-to-film transfer. These results highlight the crucial role of oxygen stoichiometry in determining the physical properties of LSVO and the importance of oxygen-substrate contribution in LSVO thin films.
Magnetic and dielectric behavior of the spin-chain compound Er2BaNiO5 well below its Néel temperature
Authors: Basu Tathamay , Singh Kiran , Mohapatra N. , Sampathkumaran E. V.
Published: September 2014

We have recently reported that the Haldane spin-chain system, Er2BaNiO5, undergoing antiferromagnetic order below (TN=) 32 K, is characterized by the onset of ferroelectricity near 60 K due to magnetoelectric coupling induced by short-range magnetic-order within spin-chains. We have carried out additional magnetic and dielectric studies to understand the properties well below TN. We emphasize here on the following: (i) A strong frequency dependent behaviors of ac magnetic susceptibility and complex dielectric properties have been observed at much lower temperatures (<8 K), that is, “reentrant multiglass-like” phenomenon, naturally suggesting the existence of an additional transition well below TN. (ii) “Magnetoelectric phase coexistence” is observed at very low temperature (e.g., T = 2 K), where the high-field magnetoelectric phase is partially arrested on returning to zero magnetic field after a cycling through metamagnetic transition.
Ferroelectric-ferromagnetic multilayers: A magnetoelectric heterostructure with high output charge signal
Authors: Prokhorenko S. , Kohlstedt H. , Pertsev N. A.
Published: September 2014

Multiferroic composites and heterostructures comprising ferroelectric and ferromagnetic materials exhibit room-temperature magnetoelectric (ME) effects greatly exceeding those of single-phase magnetoelectrics known to date. Since these effects are mediated by the interfacial coupling between ferroic constituents, the ME responses may be enhanced by increasing the density of interfaces and improving their quality. A promising material system providing these features is a ferroelectric-ferromagnetic multilayer with epitaxial interfaces. In this paper, we describe theoretically the strain-mediated direct ME effect exhibited by free-standing multilayers composed of single-crystalline ferroelectric nanolayers interleaved by conducting ferromagnetic slabs. Using a nonlinear thermodynamic approach allowing for specific mechanical boundary conditions of the problem, we first calculate the polarization states and dielectric properties of ferroelectric nanolayers in dependence on the lattice mismatch between ferroic constituents and their volume fractions. In these calculations, the ferromagnetic component is described by a model which combines linear elastic behavior with magnetic-field-dependent lattice parameters. Then the quasistatic ME polarization and voltage coefficients are evaluated using the theoretical strain sensitivity of ferroelectric polarization and measured effective piezomagnetic coefficients of ferromagnets. For Pb(Zr0.5Ti0.5)O3−FeGaB and BaTiO3−FeGaB multilayers, the ME coefficients are calculated numerically as a function of the FeGaB volume fraction and used to evaluate the output charge and voltage signals. It is shown that the multilayer geometry of a ferroelectric-ferromagnetic nanocomposite opens the way for a drastic enhancement of the output charge signal. This feature makes biferroic multilayers advantageous for the development of ultrasensitive magnetic-field sensors for technical and biomedical applications.
First-principles electronic structure and formation energies of group V and VII impurities in the α-Fe2O3 alloys
Authors: Xia Congxin , Jia Yu , Zhang Qiming
Published: September 2014

Based on density functional theory, the electronic structures, formation energy, and transition level of the selected group V and VII impurities in α-Fe2O3 are investigated by means of first-principles methods. Numerical results show that the group V and VII atoms-doped α-Fe2O3 can be energetically favorable under the Fe-rich condition. Group V atom substituting O atom can induce the acceptor impurity level, while the deep donor impurity states are formed inside the band gap when group VII atom substitute O atom in the α-Fe2O3. Moreover, our results show that halogen atom F substituting O atom should be very easy in the α-Fe2O3. In addition, our results also show that for both group V and VII atom-doped α-Fe2O3, the upper sides of valence band are modified obviously, while the conduction band edge does not change.
Particle in cell simulations of Buneman instability of a current-driven plasma with q-nonextensive electron velocity distribution
Authors: Niknam A. R. , Roozbahani H. , Hashemzadeh M. , Komaizi D.
Published: September 2014

The nonlinear evolution of low frequency Buneman instability in an unmagnetized current-driven plasma with q-nonextensive electron velocity distribution is investigated using particle in cell simulation. Simulation results show that the generation of electron phase space holes and the counter-streaming current induced in the plasma strongly depend on the q-parameter. It is found that by increasing the nonextensive parameter, the distribution of electron density becomes highly peaked. This density steepening or grating-like pattern occurs at the saturation time. In addition, a generalized dispersion relation is obtained using the kinetic theory. Analysis of the dispersion relation and the temporal evolution of the electric field energy density reveal that the growth rate of instability increases by increasing the q-parameter. Finally, the results of Maxwellian and q-nonextensive velocity distributions have been compared and discussed.
Study of the electric field formation in a multi-cusped magnetic field
Authors: Liu Hui , Wu Huan , Zhao Yinjian , Yu Daren , Ma Chengyu , Wang Di , Wei Haoyu
Published: September 2014

The multi-cusped field thruster is a kind of electric thruster adopting a cusped magnetic field to achieve a potentially longer lifetime. It is observed in some experiments that the main electric potential drop forms near the exhaust plane, but the formation mechanism of the electric field in this kind of thrusters is not fully clear yet. Based on the analysis of the electron movement, a 2D Particle-in-Cell plus Monte Carlo model is built to reveal the difference of the constraint to electrons between the central leak path and the lateral region of the thruster. Electron trajectories from cathode are analyzed furthermore. It is found that the central leak path inside the discharge channel may play a significant role in the formation of the main electric potential drop near the exhaust plane.
The impact of trench defects in InGaN/GaN light emitting diodes and implications for the “green gap” problem
Authors: Massabuau F. C.-P. , Davies M. J. , Oehler F. , Pamenter S. K. , Thrush E. J. , Kappers M. J. , Kovács A. , Williams T. , Hopkins M. A. , Humphreys C. J. , Dawson P. , Dunin-Borkowski R. E. , Etheridge J. , Allsopp D. W. E. , Oliver R. A.
Published: September 2014

The impact of trench defects in blue InGaN/GaN light emitting diodes (LEDs) has been investigated. Two mechanisms responsible for the structural degradation of the multiple quantum well (MQW) active region were identified. It was found that during the growth of the p-type GaN capping layer, loss of part of the active region enclosed within a trench defect occurred, affecting the top-most QWs in the MQW stack. Indium platelets and voids were also found to form preferentially at the bottom of the MQW stack. The presence of high densities of trench defects in the LEDs was found to relate to a significant reduction in photoluminescence and electroluminescence emission efficiency, for a range of excitation power densities and drive currents. This reduction in emission efficiency was attributed to an increase in the density of non-radiative recombination centres within the MQW stack, believed to be associated with the stacking mismatch boundaries which form part of the sub-surface structure of the trench defects. Investigation of the surface of green-emitting QW structures found a two decade increase in the density of trench defects, compared to its blue-emitting counterpart, suggesting that the efficiency of green-emitting LEDs may be strongly affected by the presence of these defects. Our results are therefore consistent with a model that the “green gap” problem might relate to localized strain relaxation occurring through defects.
Spin-dependent recombination at arsenic donors in ion-implanted silicon
Authors: Franke David P. , Otsuka Manabu , Matsuoka Takashi , Vlasenko Leonid S. , Vlasenko Marina P. , Brandt Martin S. , Itoh Kohei M.
Published: September 2014

Spin-dependent transport processes in thin near-surface doping regions created by low energy ion implantation of arsenic in silicon are detected by two methods, spin-dependent recombination using microwave photoconductivity and electrically detected magnetic resonance monitoring the direct current through the sample. The high sensitivity of these techniques allows the observation of the magnetic resonance, in particular, of As in weak magnetic fields and at low resonance frequencies (40–1200 MHz), where high-field-forbidden transitions between the magnetic sublevels can be observed due to the mixing of electron and nuclear spin states. Several implantation-induced defects are present in the samples studied and act as spin readout partner. We explicitly demonstrate this by electrically detected electron double resonance experiments and identify a pair recombination of close pairs formed by As donors and oxygen-vacancy centers in an excited triplet state (SL1) as the dominant spin-dependent process in As-implanted Czochralski-grown Si.
Monolithic phosphor-free InGaN/GaN quantum dot wavelength converter white light emitting diodes
Authors: Jahangir Shafat , Pietzonka Ines , Strassburg Martin , Bhattacharya Pallab
Published: September 2014

We report the characteristics of phosphor-free self-organized InGaN/GaN quantum dot wavelength converter white light emitting diodes grown by plasma assisted molecular beam epitaxy. The exciting quantum dots, in which electrically injected carriers recombine, are blue-emitting and the converter dots are red-emitting. We have studied the effect of tuning the number of dot layers and the peak emission wavelength of the exciting and converter dots on the nature of the emitted white light, in terms of the chromaticity coordinates and correlated color temperature. Depending on the values of these wavelengths, color temperatures in the range of 4420–6700 K have been derived at a current density of 45 A/cm2 across multiple devices. The variation of the color temperature with change in injection current is found to be very small.
Temperature dependence of the dielectric function in the spectral range (0.5–8.5) eV of an In2O3 thin film
Authors: Schmidt-Grund R. , Krauß H. , Kranert C. , Bonholzer M. , Grundmann M.
Published: September 2014

We present the dielectric function of a bcc-In2O3 thin film in the wide spectral range from near-infrared to vacuum-ultraviolet and for temperatures 10 K–300 K, determined by spectroscopic ellipsometry. From the temperature dependence of electronic transition energies, we derive electron-phonon coupling properties and found hints that the direct parabolic band-band transitions involve In-d states. Further we discuss possible excitonic contributions to the dielectric function.
Fabrication of nanofluidic diodes with polymer nanopores modified by atomic layer deposition
Authors: Sheng Qian , Wang Lin , Wang Ceming , Wang Xinwei , Xue Jianming
Published: September 2014

Surface charge distribution is a crucial factor for the ionic transport properties inside nanopores. Modifying the surface charge inside a single conical nanopore can greatly affect the rectification behavior of the ionic current through the nanopore and afford nanofluidic diodes. In this work, we describe a new method to fabricate nanofluidic diodes by atomic layer deposition (ALD) on conical track-etched nanopores. Thorough investigation of the ionic transport behavior through ALD-modified polyethylene terephthalate (PET) nanopores is carried out. Our results demonstrate that ALD is a simple and effective method to modify the inner surface of the polymer nanopores for fabricating nanofluidic devices. In addition, we also investigate the stability of the ALD-modified nanopores, and the results suggest that the long-time stability could be compromised by high voltage applied along the nanopore.
Multichromophoric energy sensitization of C60 for organic photovoltaics
Authors: Bartynski Andrew N. , Trinh Cong , Kirlikovali Kent O. , Thompson Mark E.
Published: September 2014

In organic photovoltaics (OPVs), photocurrent generation is limited by absorption and exciton diffusion in the active layer. In this work, we describe the energy sensitization of C60 simultaneously by two chromophores at high volume concentrations (50%). This sensitization strategy takes advantage of the intense absorption of the sensitizers and the exceptional electron conduction and exciton diffusion length of C60 resulting in a 30% increase in photoresponse of the C60-based sensitized acceptor layer between λ = 450 nm and 670 nm and power conversion efficiency under simulated AM 1.5 G illumination. In (2,4-bis[4-(N,N-diphenylamino)-2,6-dihydroxyphenyl] squaraine)/C60 devices, sensitization results in an increase in JSC from 6.5 ± 0.2 mA/cm2 to 8.6 ± 0.2 mA/cm2 without compromising VOC or FF. These results demonstrate the robust nature of this sensitization scheme and its broad potential for application in OPVs.
Modelling the maximum potential of nitrogen deposition and requirements of lysine for broilers
Authors: Dorigam Juliano Cesar De Paula , Sakomura Nilva Kazue , Da Silva Edney Pereira , Fernandes João Batista Kochenborger
Published: September 2014

This study aimed to develop a dynamic model to estimate lysine (Lys) requirements based on the maximum theoretical potential of nitrogen deposition (NDmaxT) and metabolic bodyweight (MBW) of growing broilers. Three N balance trials were conducted (6–21, 22–37 and 38–53 days of age) at average ages of 14, 30 and 46 days, respectively, with 36 male broilers (Cobb 500) used in each trial. In each trial, the NDmaxT was estimated by exponential model fitting of daily N intake as a function of daily N deposition for the average age. The N deposition was obtained by application of the N balance technique. To model the NDmaxT in relation to MBW, the mean and standard deviation of NDmaxT was used to generate a new population. The critical exponential model was fitted to estimate the daily NDmaxT, resulting in the following model: NDmaxT = 1677 + (–1677 + 13810 × MBW) × (0.151MBW). The daily NDmaxT data so generated were used in the Goettingen model to calculate the daily Lys requirements for N retention response. Modelling of Lys requirements resulted in greater than recommended values, with an average difference of 1.05 times the recommendation of the management guide for the studied strain. According to the results obtained from this simulation, the model provided consistent estimates of Lys requirements and may enable nutritionists to provide nutritional strategies to optimise production of broilers based on the MBW.
Lanthanide-Based Polymers with Charged Ligand Backbones: Triple-Stranded Chain Structures and their DNA Cleavage Studies
Authors: Chen Ming , Tang Xiao-Yan , Chen Ming-Zhen , Chen Jin-Xiang , Chen Wen-Hua
Published: September 2014

Four rare-earth metal complexes, [Ln(Ccbp)3(H2O)3]n (Ln = La (1), Ce (2), Pr (3) and Nd (4)) are synthesised from the ligand H2CcbpBr (H2CcbpBr = 4-carboxy-1-(4-carboxybenzyl)pyridinium bromide) and the respective lanthanide metal ions. Complexes 1–4 are isostructural in that every three Ccbp– ligands juxtapose two Ln3+ ions in a monodentate coordination mode to form triple-stranded one-dimensional chain structures. Each central Ln3+ atom further associates with three H2O molecules, furnishing a monocapped square-antiprism geometry. Agarose gel electrophoresis studies indicate that 1–4 are capable of cleaving DNA in the presence of H2O2, most probably via an oxidative cleavage mechanism. Complexes 1 and 2 exhibited catalytic efficiencies (kmax/KM) of 37.69 and 34.11 h–1 mM–1, and are approx. 15- and 20-fold more effective than those of complexes 3 (kmax/KM = 1.75 h–1 mM–1) and 4 (kmax/KM = 2.21 h–1 mM–1).
Chitosan–Zinc Oxide Nanoparticles Combined with Dispersive Liquid–Liquid Microextraction for the Determination of BTEX in Water Samples
Authors: Khajeh Mostafa , Azarsa Leyla , Rakhshanipour Mansoureh
Published: September 2014

In this study, chitosan–zinc oxide nanoparticles were used as an adsorbent matrix for solid-phase extraction and combined with dispersive liquid–liquid microextraction (SPE–DLLME) for determination of benzene, toluene, ethylbenzene, and xylene isomers (BTEX) in water samples. The eluent of SPE was used as the dispersive solvent of the DLLME for further purification and enrichment of the BTEX prior to gas chromatography-flame ionization detector analysis. The effect of variables, including amount of adsorbent, sample and eluent flow rate, type and volume of extraction and dispersive solvent, salt concentration, and extraction time, was investigated and they were optimized. Under the optimum conditions, good linearity for all BTEX with determination coefficients in the range of 0.9993 < r2 < 0.9997, suitable precision (1.4 % < RSD <1.9 %; where RSD refers to relative standard deviation), and low detection limits (0.5–1.1 µg L–1) were achieved. The current chitosan–zinc oxide nanoparticles SPE–DLLME procedure combines the advantages of SPE and DLLME, and was applied for determination of BTEX in water samples and acceptable recoveries were obtained.