bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthetic possibility of polystyrene functionalization based on hydroxyl groups of graphene oxide as nucleophiles
Authors: Yu Rongbing , Zhang Shupeng , Luo Yuting , Bai Ruofei , Zhou Jiangfang , Song Haiou
Published: April 2015

The successful wet chemical functionalization of graphene oxide with polystyrene offered the possibility of nucleophilic substitution in heterogeneous phase reactions.
Time-dependent biodistribution, clearance and biocompatibility of magnetic fibrin nanoparticles: an in vivo study
Authors: Prabu Periyathambi , Vedakumari Weslen S. , Sastry Thotapalli P.
Published: April 2015

Recently, bioretention and toxicity of injected nanoparticles in the body has drawn much attention in biomedical research.
Automated quantitative image analysis of nanoparticle assembly
Authors: Murthy Chaitanya R. , Gao Bo , Tao Andrea R. , Arya Gaurav
Published: April 2015

Automated quantitative image analysis tool for characterizing structural properties of nanoparticle clusters during assembly from experimental images.
Ultrarapid and ultrasensitive electrical detection of proteins in a three-dimensional biosensor with high capture efficiency
Authors: Kim Bo-Yeong , Sohn Il-yung , Lee Doowon , Han Gill Sang , Lee Won-Il , Jung Hyun Suk , Lee Nae-Eung
Published: April 2015

A bio-FET using 3D sensing channel structures composed of ZnO nanorods and graphene demonstrates the capability of achieving ultrarapid and ultrasensitive immunodetection.
Sulfur poisoning of emergent and current electrocatalysts: vulnerability of MoS2, and direct correlation to Pt hydrogen evolution reaction kinetics
Authors: Tan Shu Min , Sofer Zdeněk , Pumera Martin
Published: April 2015

The impacts of sulfur poisoning on both MoS2 and Pt were examined through comparisons between their HER electrocatalytic activities before and after poisoning. In particular, the poisoning of Pt was directly correlated to its HER performance.
Polypyrrole nanoparticles for tunable, pH-sensitive and sustained drug release
Authors: Samanta Devleena , Meiser Jana L. , Zare Richard N.
Published: April 2015

Charged drug molecules from nanoparticles are released by changing the pH of the surroundings and fine-tuned by adding appropriate amphiphiles.
Dithienosilole-benzothiadiazole-based ternary copolymers with a D1–A–D2–A structure for polymer solar cells
Authors: Huang Xuelong , Zhang Guichuan , Zhou Cheng , Liu Liqian , Jin Yaocheng , Liu Shengjian , Ying Lei , Huang Fei , Cao Yong
Published: April 2015

A series of regularly alternating D1–A–D2–A type of ternary copolymers were synthesized for the application in polymer solar cells.
Photo-induced conversion from supramolecular to covalently linked polymers based on anthracene-appended amphiphiles
Authors: Zhang Xun , Gao Yuxia , Lin Yuan , Hu Jun , Ju Yong
Published: April 2015

A photo-induced conversion from supramolecular to covalent polymers was achieved based on anthracene-appended amphiphiles.
A novel artificial red blood cell substitute: grafted starch-encapsulated hemoglobin
Authors: Xu Ruifen , Zhang Jianwei , Zhou Panghu , Yang Rui , Feng Xuyang , Xu Lixian
Published: April 2015

GSEHb induced no histological variations of the main organs including the hearts, kidneys, lungs and livers of the control and GSEHb treated rats in rat model with hemorrhagic shock.
Dithieno[3,2-a:2′,3′-c]phenazine-based chemical probe for anions: a spectroscopic study of binding
Authors: El-Assaad Tarek H. , Shiring Stephen B. , Getmanenko Yulia A. , Hallal Kassem M. , Brédas Jean-Luc , Marder Seth R. , Al-Sayah Mohammad H. , Kaafarani Bilal R.
Published: April 2015

The synthesis and binding studies ofN,N′-(2,5-bis(4-(tert-butyl)phenyl)dithieno[3,2-a:2′,3′-c]phenazine-9,10-diyl)bis(4-methylbenzenesulfonamide) (1) are reported.
Synthesis and properties of a nano-silica modified environmentally friendly polyurethane adhesive
Authors: Jia-Hu Guo , Yu-Cun Liu , Tao Chai , Su-Ming Jing , Hui Ma , Ning Qin , Hua Zhou , Tao Yan , Wei-Ming He
Published: April 2015

In this study, a nano-SiO2 modified waterborne polyurethane (WPU) adhesive with remarkably low VOC content and high adhesion performance was successfully synthesized via in situ polymerization.
Propylphosphonium hydrogen carbonate ionic liquid supported on nano-silica as a reusable catalyst for the efficient multicomponent synthesis of fully substituted pyridines and bis-pyridines
Authors: Rahmani Fahime , Mohammadpoor-Baltork Iraj , Khosropour Ahmad R. , Moghadam Majid , Tangestaninejad Shahram , Mirkhani Valiollah
Published: April 2015

An efficient method for the synthesis of fully substituted pyridines and bis-pyridines in the presence of propylphosphonium hydrogen carbonate supported on nano-silica (PPHC–nSiO2) as a reusable catalyst under solvent-free conditions is reported.
AgPd nanoparticles supported on zeolitic imidazolate framework derived N-doped porous carbon as an efficient catalyst for formic acid dehydrogenation
Authors: Feng Cheng , Hao Yunhui , Zhang Li , Shang Ningzhao , Gao Shutao , Wang Zhi , Wang Chun
Published: April 2015

A metal nanoparticle functionalized N-decorated nanoporous carbon (NPC) was fabricated and used as an efficient formic acid dehydrogenation catalyst for the first time.
Identification of dabigatran etexilate major degradation pathways by liquid chromatography coupled to multi stage high-resolution mass spectrometry
Authors: Amrani Fatma , Secrétan Philippe-Henri , Sadou-Yayé Hassane , Aymes-Chodur Caroline , Bernard Mélisande , Solgadi Audrey , Yagoubi Najet , Do Bernard
Published: April 2015

The major degradation mechanisms of dabigatran etexilate were deduced in the context of stress testing. Under hydrolytic stress conditions, O-dealkylation may occur along with formation of benzimidic acid derivatives.
Synthesis of 2-trifluoromethyl indoles via visible-light induced intramolecular radical cyclization
Authors: Dong Xichang , Hu Yumin , Xiao Tiebo , Zhou Lei
Published: April 2015

A visible-light induced intramolecular radical cyclization is described. The reaction allows the rapid construction of 2-trifluoromethyl-3-acylindoles in a sequential C–C and C–O bond formation process under mild conditions.
Morphological and structural characterisation of sol–gel electrospun Co3O4nanofibres and their electro-catalytic behaviour
Authors: George Gibin , Elias Liju , Hegde A. Chitharanjan , Anandhan S.
Published: April 2015

Evolution of hydrogen and oxygen are a crucial part of many renewable energy systems.
Controlling the activity of quorum sensing autoinducers with light
Authors: Van der Berg J. P. , Velema W. A. , Szymanski W. , Driessen A. J. M. , Feringa B. L.
Published: April 2015

Bacteria use Quorum Sensing (QS) to organize into communities and synchronize gene expression. Here we report on a method to externally interfere with QS system using light.
Diastereodivergent organocatalysis for the asymmetric synthesis of chiral annulated furans
Authors: Verrier Charlie , Melchiorre Paolo
Published: April 2015

Stereoselective methods to prepare chiral annulated furans are reported. Complementary organocatalytic systems ensure access to all possible stereoisomeric products.
Directed self-assembly of cylinder-forming diblock copolymers on sparse chemical patterns
Authors: Yang Yong-Biao , Choi Young Joo , Kim Sang Ouk , Kim Jaeup U.
Published: April 2015

Pattern multiplication and directed self-assembly of block copolymer films deposited on sparsely patterned substrates.
pH-Tunable wormlike micelles based on an ultra-long-chain “pseudo” gemini surfactant
Authors: Feng Yujun , Chu Zonglin
Published: April 2015

Rheological properties of wormlike micelles formed by a pseudo gemini surfactant EAMA and of those without the “gemini” character formed by UC22AMPM in the presence of hydrochloric acid (named EAHCl) have been investigated.
Morphological changes and electrochemical response of mixed nickel manganese oxides as charge storage electrodes
Authors: Nguyen Tuyen , Boudard Michel , Rapenne Laetitia , Carmezim M. João , Montemor M. Fátima
Published: April 2015

Controlling the surface morphology of mixed nickel manganese oxides prepared by electrodeposition and thermal annealing for use as charge storage electrodes.
Mesoporous silica nanoparticles for glutathione-triggered long-range and stable release of hydrogen sulfide
Authors: Sun Xiaotian , Kong Biao , Wang Wenshuo , Chandran Paurnami , Selomulya Cordelia , Zhang Huili , Zhu Kai , Liu Ye , Yang Wuli , Guo Changfa , Zhao Dongyuan , Wang Chunsheng
Published: April 2015

A mesoporous silica-based glutathione-triggered delivery system has been fabricated for long-range and stable release of hydrogen sulfide.
Phase angle spectroscopy on transparent conducting polymer electrodes for real-time measurement of epithelial barrier integrity
Authors: Löffler S. , Richter-Dahlfors A.
Published: April 2015

A PEDOT:PSS based sensor for continuous electronic monitoring of epithelial barrier formation and disruption compatible with microscopy.
Ion conductive properties in ionic liquid crystalline phases confined in a porous membrane
Authors: Uchida Y. , Matsumoto T. , Akita T. , Nishiyama N.
Published: April 2015

The anisotropic ion conductivity and phase transition behaviours of ionic liquid crystalline samples confined in aluminum oxide membranes with cylindrical pores were demonstrated.
Ladder-type conjugated oligomers prepared by the Scholl oxidative cyclodehydrogenation reaction: synthesis, characterization and application in field effect transistors
Authors: Huang Wei , Zhang Hejian , Ma Ji , Chen Moyun , Zhu Haoyun , Wang Weizhi
Published: April 2015

Two promising ladder-type oligomers are synthesized by the Scholl reaction. The top-gate FET devices fabricated with the obtained oligomers as the semiconductor show excellent performance.
Well-designed metal nanostructured arrays for label-free plasmonic biosensing
Authors: Li Wanbo , Zhang Li , Zhou Jianhua , Wu Hongkai
Published: April 2015

Well-designed metal nanostructured arrays hold great advantages for on-chip label-free plasmonic biosensing, meeting the need for portable and rapid diagnosis.
Colored, see-through perovskite solar cells employing an optical cavity
Authors: Lee Kyu-Tae , Fukuda Masanori , Joglekar Suneel , Guo L. Jay
Published: April 2015

Optical cavity-integrated perovskite solar cells capable of creating distinctive semitransparent colors with high efficiencies are demonstrated.
One-pot synthesis of hydrophobic and enhanced red-emitting CaCO3:Eu3+ phosphors
Authors: Sun Yidi , Zou Haifeng , Zhang Bowen , Zhou Xiuqing , Huo Qisheng , Sheng Ye
Published: April 2015

Hydrophobic and enhanced red-emitting CaCO3:Eu3+ phosphors were in situ prepared using the carbonization method in the presence of sodium oleate.
Interlayer coupling and optoelectronic properties of ultrathin two-dimensional heterostructures based on graphene, MoS2 and WS2
Authors: Huo Nengjie , Wei Zhongming , Meng Xiuqing , Kang Joongoo , Wu Fengmin , Li Shu-Shen , Wei Su-Huai , Li Jingbo
Published: April 2015

Graphene–WS2 heterostructures exhibit strong interlayer coupling with stiffening phonon modes, as well as ambipolar, gate-tunable rectification and enhanced photo-switching behavior.
Effects of multi-walled carbon nanotube structures on the electrical and mechanical properties of silicone rubber filled with multi-walled carbon nanotubes
Authors: Li Yuling , Li Mingjun , Pang Minglei , Feng Shengyu , Zhang Jie , Zhang Changqiao
Published: April 2015

The specific surface area is a key factor that determines both the electrical and mechanical properties of silicone rubber/MWCNTs.
Electrochemical processes and mechanistic aspects of field-effect sensors for biomolecules
Authors: Huang Weiguo , Diallo Abdou Karim , Dailey Jennifer L. , Besar Kalpana , Katz Howard E.
Published: April 2015

Electronic biosensing is a leading technology for determining concentrations of biomolecules.
Abnormal oscillatory conductance and strong odd–even dependence of a perfect spin-filtering effect in a carbon chain-based spintronic device
Authors: Zeng Jing , Chen Ke-Qiu
Published: April 2015

By using nonequilibrium Green's functions in combination with the density functional theory, the transport properties of a carbon chain-based spintronic device are investigated.
Achieving efficient Tb3+ dual-mode luminescence via Gd-sublattice-mediated energy migration in a NaGdF4 core–shell nanoarchitecture
Authors: Ding Mingye , Chen Daqin , Wan Zhongyi , Zhou Yang , Zhong Jiasong , Xi Junhua , Ji Zhenguo
Published: April 2015

Efficient dual-mode luminescence from identical Tb3+ in single NaGdF4 nanoparticles has been successfully realized for the first time with the help of Gd-sublattice-mediated energy migration and core–shell engineering techniques.
Human exonuclease 1 (EXO1) activity characterization and its function on flap structures
Authors: Keijzers Guido , Bohr Vilhelm A. , Rasmussen Lene Juel
Published: April 2015

Human exonuclease 1 (EXO1) is involved in multiple DNA metabolism processes, including DNA repair and replication. Most of the fundamental roles of EXO1 have been described in yeast. Here, we report a biochemical characterization of human full-length EXO1. Prior to assay EXO1 on different DNA flap structures, we determined factors essential for the thermodynamic stability of EXO1. We show that enzymatic activity and stability of EXO1 on DNA is modulated by temperature. By characterization of EXO1 flap activity using various DNA flap substrates, we show that EXO1 has a strong capacity for degrading double stranded DNA and has a modest endonuclease or 5′ flap activity. Furthermore, we report novel mechanistic insights into the processing of flap structures, showing that EXO1 preferentially cleaves one nucleotide inwards in a double stranded region of a forked and nicked DNA flap substrates, suggesting a possible role of EXO1 in strand displacement.
Hybrid inductive and active filtering method for damping harmonic resonance in distribution network with non‐linear loads
Authors: Li Yong , Liu Fang , Saha Tapan Kumar , Krause Olav , Cao Yijia
Published: April 2015

In this study, a hybrid inductive and active filtering (HIAF) method is proposed to dampen the harmonic resonance in distribution network with non‐linear loads. At a first, a new topology of energy conversion system with active technique, which includes an inductively filtered converter transformer, fully‐tuned branches and a controlled voltage source inverter (VSI), is proposed for large‐power non‐linear loads. The working principle of such a new topology is described, and the advantage of damping harmonic resonance of the distribution network is revealed by means of mathematical modelling and theoretical analysis. Then, the control system of VSI is designed with the multiple purposes of damping harmonic resonance from the grid side and isolating harmonic currents from the non‐linear load side. A case study is carried out to validate theoretical results. By comparing with the traditional hybrid active filtering method and the passive filtering method, it indicates that the proposed HIAF method is more effective to dampen harmonic resonance in the distribution network and at the same time is able to significantly reduce the harmonic contents in the grid winding, which is good to both the public network and the energy conversion system connected with large‐power non‐linear loads.
Practical implementation of stripmap Doppler imaging
Authors: Garry Joseph Landon , Smith Graeme Edward , Baker Christopher John
Published: April 2015

Doppler imaging is a technique that can generate fine two‐dimensional (2D) imagery in the absence of large bandwidths. Radar imaging has traditionally consisted of combining wide bandwidth waveforms with aperture synthesis. Wide bandwidth waveforms provide high resolution in down‐range (line‐of‐sight), whereas aperture synthesis enables high resolution in the orthogonal direction. However, in today’s increasingly congested spectral environment, using wide bandwidths waveforms is becoming less and less attractive. Consequently, imaging techniques that require only narrow bandwidth waveforms offer very attractive and practical advantages. An approach, examined here, is to use phase in conjunction with aperture synthesis to achieve high resolution in down‐range while using narrowband waveforms. This method has the added benefit of using the same collection geometry as traditional stripmap synthetic aperture radar imaging. Therefore Doppler imaging is compatible with use in spectrally congested environments where wide bandwidth waveforms might be prohibited. In this study, the basic Doppler imaging concept is explained, a simple framework for its operation is introduced and resolution limits are examined. Results are presented from both simulations and full‐scale experiments, which demonstrate range resolutions as fine as 23 cm using an 8.9 GHz CW waveform and 2 m long synthetic aperture.
Reduced complexity generalised likelihood ratio detector for digital video broadcasting terrestrial‐based passive radar
Authors: Bolvardi Hasan , Derakhtian Mostafa , Sheikhi Abbas
Published: April 2015

The high resolution of the digital video broadcasting terrestrial (DVB‐T) signals leads to a dramatically large number of observation samples in an integration time of a DVB‐T‐based passive radar. Hence, because of the high computational complexity (CC), applying extensive cancellation algorithm and generalised likelihood ratio (GLR) detector seems to be impractical in the DVB‐T‐based passive radars. In this study, the authors derive a reduced complexity GLR detector for the DVB‐T‐based passive radar in the presence of the clutter, the interfering targets and the noise. The proposed detector employs the split received signal to reduce the CC substantially compared with the methods that process the whole signal at once. Moreover, the CC reduction in the proposed method does not lead to a degradation in Doppler resolution and the detection performance. Simulation results are also corroborated with the theoretical analysis.
Magnetohydrodynamically generated velocities in confined plasma
Authors: Morales Jorge A. , Bos Wouter J. T. , Schneider Kai , Montgomery David C.
Published: April 2015

We investigate by numerical simulation the rotational flows in a toroid confining a conducting magnetofluid in which a current is driven by the application of externally supported electric and magnetic fields. The computation involves no microscopic instabilities and is purely magnetohydrodynamic (MHD). We show how the properties and intensity of the rotations are regulated by dimensionless numbers (Lundquist and viscous Lundquist) that contain the resistivity and viscosity of the magnetofluid. At the magnetohydrodynamic level (uniform mass density and incompressible magnetofluids), rotational flows appear in toroidal, driven MHD. The evolution of these flows with the transport coefficients, geometry, and safety factor are described.
Periodic solution for a non-isentropic compressible Navier-Stokes equations in a bounded domain
Authors: Jin Chunhua
Published: April 2015

This paper is concerned with a non-isentropic compressible Navier-Stokes equations with time-dependent external force in a bounded domain of ℝ3. We first consider the existence of a global solution to the corresponding initial-value problem, and proved a stability result, then, by the stability result, we showed the existence of a time-periodic solution when the external force is a time periodic function.
Isotopic dependence of the predissociations of the E1Π state of CO
Authors: Lefebvre-Brion H. , Majumder M.
Published: April 2015

The predissociations of the E1Π state of CO are again studied. They include both the background predissociation attributed to the continuum of the A1Π state and the accidental predissociation due to the k3Π state. They are calculated using a coupled equations method. The three components of the k state are introduced. These predissociations are studied for different isotopologues and are shown to decrease with increasing reduced mass, in agreement with the experimental results of Ubachs et al. [J. Chem. Phys. 113, 547 (2000)].
Investigation of point and extended defects in electron irradiated silicon—Dependence on the particle energy
Authors: Radu R. , Pintilie I. , Nistor L. C. , Fretwurst E. , Lindstroem G. , Makarenko L. F.
Published: April 2015

This work is focusing on generation, time evolution, and impact on the electrical performance of silicon diodes impaired by radiation induced active defects. n-type silicon diodes had been irradiated with electrons ranging from 1.5 MeV to 27 MeV. It is shown that the formation of small clusters starts already after irradiation with high fluence of 1.5 MeV electrons. An increase of the introduction rates of both point defects and small clusters with increasing energy is seen, showing saturation for electron energies above ∼15 MeV. The changes in the leakage current at low irradiation fluence-values proved to be determined by the change in the configuration of the tri-vacancy (V3). Similar to V3, other cluster related defects are showing bistability indicating that they might be associated with larger vacancy clusters. The change of the space charge density with irradiation and with annealing time after irradiation is fully described by accounting for the radiation induced trapping centers. High resolution electron microscopy investigations correlated with the annealing experiments revealed changes in the spatial structure of the defects. Furthermore, it is shown that while the generation of point defects is well described by the classical Non Ionizing Energy Loss (NIEL), the formation of small defect clusters is better described by the “effective NIEL” using results from molecular dynamics simulations.
Gadolinium metallo nanocongregates as potential magnetosensors for detecting early stage cancers
Authors: Dutta Ranu , Pandey Avinash C.
Published: April 2015

Gadolinium chelates and gadolinium based inorganic nanoparticles have been extensively studied, because of the high magnetic moment of gadolinium. Here, metallic gadolinium nanocongregates have been developed. Upon injecting these nanoparticles in the mice, they initially circulate in the blood stream and are localized at the cancer site, which could be visualized upon application of magnetic field hence acting as small magnetic nanosensors searching for even small cancers, detecting cancers at a very early stage.
Spin reorientation in multiferroic spinel Co0.5Fe0.5Cr2O4 with Mössbauer spectroscopy
Authors: Myoung Bo Ra , Kim Chul Sung
Published: April 2015

We studied the magnetic properties of multiferroic spinel Co0.5Fe0.5Cr2O4, especially focusing on the spin-ordering, spin-reorientation, and charge re-distribution effects. From the Rietveld refinement analysis, the crystal structure was identified to be a normal cubic spinel of Fd-3m. Based on the temperature-dependent measurements of the magnetization and magnetic hyperfine field (Hhf), Curie temperature (TC) of Co0.5Fe0.5Cr2O4 was determined to be around 86 K where Hhf  ≅  0. From the change of slope in the M-T curve, the conical-spiral magnetic ordering temperature was determined to be 20 K, which coincides with Hhf measurement. Also, we have observed the decrease in the slope of the electric quadrupole splitting (ΔEQ) curve above 20 K, suggesting that the change in ΔEQ around TS is originated from charge redistribution due to the spin-relocation associated with the distortion of each tetrahedral site around Fe2+ ion above TS. This indicates that Co0.5Fe0.5Cr2O4 has the noncollinear conical-spiral spin ordering with incommensurate spin structure below TS, while above TS, it has ferrimagnetic spin ordering with commensuration in the collinear state. In addition, the Jahn-teller distortion temperature is measured to be around 155 K, since both ΔEQ and Δ1 of 5T2g band decrease rapidly with increasing temperature and disappear around 155 K.
Gyrokinetic studies of core turbulence features in ASDEX Upgrade H-mode plasmas
Authors: Navarro A. Bañón , Happel T. , Görler T. , Jenko F. , Abiteboul J. , Bustos A. , Doerk H. , Told D. ,   ASDEX Upgrade Team
Published: April 2015

Gyrokinetic validation studies are crucial for developing confidence in the model incorporated in numerical simulations and thus improving their predictive capabilities. As one step in this direction, we simulate an ASDEX Upgrade discharge with the GENE code, and analyze various fluctuating quantities and compare them to experimental measurements. The approach taken is the following. First, linear simulations are performed in order to determine the turbulence regime. Second, the heat fluxes in nonlinear simulations are matched to experimental fluxes by varying the logarithmic ion temperature gradient within the expected experimental error bars. Finally, the dependence of various quantities with respect to the ion temperature gradient is analyzed in detail. It is found that density and temperature fluctuations can vary significantly with small changes in this parameter, thus making comparisons with experiments very sensitive to uncertainties in the experimental profiles. However, cross-phases are more robust, indicating that they are better observables for comparisons between gyrokinetic simulations and experimental measurements.
Influence of renormalization shielding on the electron-impact ionization process in dense partially ionized plasmas
Authors: Song Mi-Young , Yoon Jung-Sik , Jung Young-Dae
Published: April 2015

The renormalization shielding effects on the electron-impact ionization of hydrogen atom are investigated in dense partially ionized plasmas. The effective projectile-target interaction Hamiltonian and the semiclassical trajectory method are employed to obtain the transition amplitude as well as the ionization probability as functions of the impact parameter, the collision energy, and the renormalization parameter. It is found that the renormalization shielding effect suppresses the transition amplitude for the electron-impact ionization process in dense partially ionized plasmas. It is also found that the renormalization effect suppresses the differential ionization cross section in the peak impact parameter region. In addition, it is found that the influence of renormalization shielding on the ionization cross section decreases with an increase of the relative collision energy. The variations of the renormalization shielding effects on the electron-impact ionization cross section are also discussed.
Non-ferroelectric nature of the conductance hysteresis in CH3NH3PbI3 perovskite-based photovoltaic devices
Authors: Beilsten-Edmands J. , Eperon G. E. , Johnson R. D. , Snaith H. J. , Radaelli P. G.
Published: April 2015

We present measurements of conductance hysteresis on CH3NH3PbI3 perovskite thin films, performed using the double-wave method, in order to investigate the possibility of a ferroelectric response. A strong frequency dependence of the hysteresis is observed in the range of 0.1 Hz to 150 Hz, with a hysteretic charge density in excess of 1000 μC cm−2 at frequencies below 0.4 Hz—a behaviour uncharacteristic of a ferroelectric response. We show that the observed hysteretic conductance, as well as the presence of a double arc in the impedance spectroscopy, can be fully explained by the migration of mobile ions under bias on a timescale of seconds. Our measurements place an upper limit of ≈1 μC cm−2 on any intrinsic frequency-independent polarisation, ruling out ferroelectricity as the main cause of current-voltage hysteresis and providing further evidence of the importance of ionic migration in modifying the efficiency of CH3NH3PbI3 devices.
Design for size and weight reduction of lap-winding type three-phase variable inductor
Authors: Nakamura Kenji , Honma Koya , Ohinata Takashi , Arimatsu Kenji , Ichinokura Osamu
Published: April 2015

Variable inductors have a simple structure that consists of only magnetic core and primary dc and secondary ac windings, but can control effective inductance of the secondary ac winding by the primary dc current due to magnetic saturation effect. Hence, the variable inductors can be applied as a var compensator in electric power systems. In a previous paper, a lap-winding type three-phase variable inductor, which has the primary dc and secondary ac windings concentrically arranged on the same leg, was presented. It has a good controllability and low distortion current. This paper describes size and weight reduction of the lap-winding type three-phase variable inductor by focusing on the leg width. First, an initial design method of the leg width considering the influence of the dc-biased magnetization is presented. Next, a detailed design of the leg width for the size and weight reduction of the proposed variable inductor is described. Finally, characteristics of the size- and weight-reduced variable inductor were compared to those of the previous variable inductor. It is demonstrated that the core diameter is reduced by about 6% and the weight is decreased by about 50% in comparison with the previous variable inductor.
Time-resolved detection of propagating Lamb waves in thin silicon membranes with frequencies up to 197 GHz
Authors: Grossmann Martin , Ristow Oliver , Hettich Mike , He Chuan , Waitz Reimar , Scheer Elke , Gusev Vitalyi , Dekorsy Thomas , Schubert Martin
Published: April 2015

Guided acoustic waves are generated in nanopatterned silicon membranes with aluminum gratings by optical excitation with a femtosecond laser. The spatial modulation of the photoacoustic excitation leads to Lamb waves with wavelengths determined by the grating period. The excited Lamb waves are optically detected for different grating periods and at distances up to several μm between pump and probe spot. The measured frequencies are compared to the theoretical dispersion relation for Lamb waves in thin silicon membranes. Compared to surface acoustic waves in bulk silicon twice higher frequencies for Lamb waves (197 GHz with a 100 nm grating) are generated in a membrane at equal grating periods.
Thermal effects on the magnetic properties of titanium modified cobalt ferrite
Authors: Nlebedim I. C. , Jiles D. C.
Published: April 2015

The temperature dependence of the magnetic properties of titanium modified cobalt ferrite is presented. The change of maximum magnetization obtained at H ≈ 2.4 MA/m between any two temperatures increases systematically with composition, which is desirable for applications in devices. Variation in magnetocrystalline anisotropy and coercivity were different from previous studies on cation substituted cobalt ferrite. At lower concentrations, the effect of lower thermal energy dominated the effect of non-magnetic cation substitutions in controlling the anisotropy. The reverse was the case at higher concentrations. The temperature dependence of coercivity is dominated by the contribution of magnetocrystalline anisotropy to coercivity, while the compositional dependence of coercivity is dominated by microstructural contribution through the pinning of domain walls.
Microwave and millimeter wave dielectric permittivity and magnetic permeability of epsilon-gallium-iron-oxide nano-powders
Authors: Chao Liu , Afsar Mohammed N. , Ohkoshi Shin-ichi
Published: April 2015

In millimeter wave frequency range, hexagonal ferrites with high uniaxial anisotropic magnetic fields are used as absorbers. These ferrites include M-type barium ferrite (BaFe12O19) and strontium ferrite (SrFe12O19), which have natural ferromagnetic resonant frequency range from 40 GHz to 60 GHz. However, the higher frequency range lacks suitable materials that support the higher frequency ferromagnetic resonance. A series of gallium-substituted ε-iron oxides (ε-GaxFe2−xO3) are synthesized, which have ferromagnetic resonant frequencies appearing over the frequency range of 30 GHz to 150 GHz. The ε-GaxFe2−xO3 is synthesized by the sol-gel method. The particle sizes are observed to be smaller than 100 nm. In this paper, in-waveguide transmission and reflection method and the free space magneto-optical approach have been employed to study these newly developed ε-GaxFe2−xO3 particles in millimeter waves. These techniques enable to obtain precise transmission spectra to determine the dielectric and magnetic properties of both isotropic and anisotropic ferrites in the microwave and millimeter wave frequency range from single set of direct measurements. The complex dielectric permittivity and magnetic permeability spectra of ε-GaxFe2−xO3 are shown in this paper. Strong ferromagnetic resonances at different frequencies determined by the x parameter are found.
Tuning of the microwave magnetization dynamics in CoZr-based thin films by Nd-doping
Authors: Xu Zhan , Yin Yuan , Xu Feng , Xu Qingyu , Wang Dunhui , Li Shandong
Published: April 2015

To enhance the damping of microwave magnetization dynamics, we investigate the effect of Nd-doping (0–3.0 at. %) into CoZr thin films. The saturation magnetization decreases with Nd-doping. The coercivities generally decrease in the case of 1.5 at. % Nd-doping, while increase in the case of 3.0 at. % Nd-doping. The magnetization dynamics is characterized with the permeability spectra, which are determined by the ferromagnetic resonance behavior at the microwave range. The permeability spectra are analyzed through the fittings with Landau-Lifshitz-Gilbert equation. From the fittings, both the dynamic magnetic anisotropy field and the damping factor increase, due to the enhanced spin-orbital coupling by Nd-doping.
Investigating nanoparticle interactions from interparticle-to-nanocomposite
Authors: Desautels R. D. , Skoropata E. , Rowe M. , van Lierop J.
Published: April 2015

A series of core/shell Fe-oxide/SiO2 nanoparticles were produced to form Fe-oxide (1:1 Fe3O4 and γ-Fe2O3) cores with diameters of approximately 4.6 nm and shell thicknesses ranging from 3.6 to 5.4 nm. Hot press sintering of core/shell nanoparticles created a nanocomposite of Fe-oxide nanoparticles in a SiO2 matrix. The presence of an iron-orthosilicate at the core-shell interface defines the intrinsic magnetic properties of the nanoparticle systems, resulting in an increase in magnetic anisotropy with thicker SiO2 shell. We find that dipole-dipole interactions are mediated by the overall SiO2 shell, and that these interactions are coupling neighbouring particles' magnetization with increasing correlation lengths. When the nanoparticles from a composite material, packing significantly increases the interaction strengths, altering the overall magnetization of the system so that the iron-oxide cores present an approximate 25% increase in (saturation) magnetization to a bulk-like (∼80 emu/g) value.
On the equivalence of LIST and DIIS methods for convergence acceleration
Authors: Garza Alejandro J. , Scuseria Gustavo E.
Published: April 2015

Self-consistent field extrapolation methods play a pivotal role in quantum chemistry and electronic structure theory. We, here, demonstrate the mathematical equivalence between the recently proposed family of LIST methods [Wang et al., J. Chem. Phys. 134, 241103 (2011); Y. K. Chen and Y. A. Wang, J. Chem. Theory Comput. 7, 3045 (2011)] and the general form of Pulay’s DIIS [Chem. Phys. Lett. 73, 393 (1980); J. Comput. Chem. 3, 556 (1982)] with specific error vectors. Our results also explain the differences in performance among the various LIST methods.
Note: A three-dimension active vibration isolator for precision atom gravimeters
Authors: Zhou Min-Kang , Xiong Xin , Chen Le-Le , Cui Jia-Feng , Duan Xiao-Chun , Hu Zhong-Kun
Published: April 2015

An ultra-low frequency active vibration isolator, simultaneously suppressing three-dimensional vibration noise, is demonstrated experimentally. The equivalent natural period of the isolator is 100 s and 12 s for the vertical and horizontal direction, respectively. The vibration noise in the vertical direction is about 50 times reduced during 0.2 and 2 Hz, and 5 times reduced in the other two orthogonal directions in the same frequency range. This isolator is designed for atom gravimeters, especially suitable for the gravimeter whose sensitivity is limited by vibration couplings.
Perspectives for imaging single protein molecules with the present design of the European XFEL
Authors: Ayyer Kartik , Geloni Gianluca , Kocharyan Vitali , Saldin Evgeni , Serkez Svitozar , Yefanov Oleksandr , Zagorodnov Igor
Published: April 2015

The Single Particles, Clusters and Biomolecules & Serial Femtosecond Crystallography (SPB/SFX) instrument at the European XFEL is located behind the SASE1 undulator and aims to support imaging and structure determination of biological specimen between about 0.1 μm and 1 μm size. The instrument is designed to work at photon energies from 3 keV up to 16 keV. Here, we propose a cost-effective proof-of-principle experiment, aiming to demonstrate the actual feasibility of a single molecule diffraction experiment at the European XFEL. To this end, we assume self-seeding capabilities at SASE1 and we suggest to make use of the baseline European XFEL accelerator complex—with the addition of a slotted-foil setup—and of the SPB/SFX instrument. As a first step towards the realization of an actual experiment, we developed a complete package of computational tools for start-to-end simulations predicting its performance. Single biomolecule imaging capabilities at the European XFEL can be reached by exploiting special modes of operation of the accelerator complex and of the SASE1 undulator. The output peak power can be increased up to more than 1.5 TW, which allows to relax the requirements on the focusing efficiency of the optics and to reach the required fluence without changing the present design of the SPB/SFX instrument. Explicit simulations are presented using the 15-nm size RNA Polymerase II molecule as a case study. Noisy diffraction patterns were generated and they were processed to generate the 3D intensity distribution. We discuss requirements to the signal-to-background ratio needed to obtain a correct pattern orientation. When these are fulfilled, our results indicate that one can achieve diffraction without destruction with about 0.1 photons per Shannon pixel per shot at 4 Å resolution with 1013 photons in a 4 fs pulse at 4 keV photon energy and in a 0.3 μm focus, corresponding to a fluence of 1014 photons/μm2. We assume negligible structured background. At this signal level, one needs only about 30 000 diffraction patterns to recover full 3D information. At the highest repetition rate manageable by detectors at European XFEL, one will be able to accumulate these data within a fraction of an hour, even assuming a relatively low hit probability of about a percent.
Non-resonant below-bandgap two-photon absorption in quantum dot solar cells
Authors: Li Tian , Dagenais Mario
Published: April 2015

We study the optically nonlinear sub-bandgap photocurrent generation facilitated by an extended tailing distribution of states in an InAs/GaAs quantum dots (QDs) solar cell. The tailing states function as both the energy states for low energy photon absorption and the photocarriers extraction pathway. One of the biggest advantages of our method is that it can clearly differentiate the photocurrent due to one-photon absorption (1PA) process and two-photon absorption (2PA) process. Both 1PA and 2PA photocurrent generation efficiency in an InAs/GaAs QD device operated at 1550 nm have been quantitatively evaluated. A two-photon absorption coefficient β = 5.7 cm/GW is extracted.
Evidence for the role of hydrogen in the stabilization of minority carrier lifetime in boron-doped Czochralski silicon
Authors: Nampalli N. , Hallam B. , Chan C. , Abbott M. , Wenham S.
Published: April 2015

This study demonstrates that the presence of a hydrogen source during fast-firing is critical to the regeneration of B-O defects and that is it not a pure thermally based mechanism or due to plasma exposure. Boron-doped p-type wafers were fired with and without hydrogen-rich silicon nitride (SiNx:H) films present during the fast-firing process. After an initial light-induced degradation step, only wafers fired with the SiNx:H films present were found to undergo permanent and complete recovery of lifetime during subsequent illuminated annealing. In comparison, wafers fired bare, i.e., without SiNx:H films present during firing, were found to demonstrate no permanent recovery in lifetime. Further, prior exposure to hydrogen-rich plasma processing was found to have no impact on permanent lifetime recovery in bare-fired wafers. This lends weight to a hydrogen-based model for B-O defect passivation and casts doubt on the role of non-hydrogen species in the permanent passivation of B-O defects in commercial-grade p-type Czochralski silicon wafers.
Optimal generation dispatch incorporating wind power and responsive loads: A chance-constrained framework
Authors: Khazali Amirhossein , Kalantar Mohsen
Published: April 2015

This paper presents a novel probabilistic framework for solving the security constrained generation dispatch problem in the presence of wind power and responsive loads. The proposed framework is capable of decreasing the probability or preventing any constraint violations in real time for different combinations of uncertain variables while minimizing the desired objective functions. The presented framework is formulated as a chance constrained problem using the point estimate method to calculate the probabilistic characteristics of output variables. The objective functions which are studied in this work are total operation costs, emissions, and security indexes. Also a probabilistic multi-objective framework is developed to optimize all objective functions concurrently. To study the effect of responsive loads, two different cases are studied neglecting and regarding demand response resources. The proposed method is studied on the IEEE 30-bus system and the results are presented and compared with results obtained from the deterministic generation dispatch framework.
A Carbon Nanodots-Based Fluorescent Turn-On Probe for Iodide
Authors: Wang Qi , Wu Yuehuan
Published: April 2015

The human body requires iodine to develop and maintain proper metabolic balance. Worldwide, iodine deficiency affects two billion people and is the leading preventable cause of intellectual disability. Small amounts of iodine are needed for good health. However, large doses can eventually cause iodide goitre, hypothyroidism or myxedema. Children are especially sensitive to the effects of iodine. Because humans can be exposed to iodide via several different food chains, the development of on-site, real-time and reliable sensors for iodide is of great interest to ensure early diagnosis and improve management. We propose here a simple and low cost, yet sensitive and selective fluorescent ‘turn-off-on’ assay for rapid determination of iodide based on a combined carbon nanodots (CDs) and Hg2+ system. The fluorescence of CDs that was quenched by Hg2+ was restored and ‘turned on’ in the presence of iodide, which triggered a competitive reaction among CDs, Hg2+ and iodide. The recovered fluorescence intensity varied linearly with the concentration of iodide in the range of 0.05–5 μmol L–1, with a limit of detection as low as 46 nmol L–1. This approach shows excellent selectivity for iodine over the other anions.
A coupled modelling approach to assess the effect of fuel treatments on post-wildfire runoff and erosion
Authors: Sidman Gabriel , Guertin D. Phillip , Goodrich David C. , Thoma David , Falk Donald , Burns I. Shea
Published: April 2015

The hydrological consequences of wildfires are among their most significant and long-lasting effects. As wildfire severity affects post-fire hydrological response, fuel treatments can be a useful tool for land managers to moderate this response. However, current models focus on only one aspect of the fire–watershed linkage (fuel treatments, fire behaviour, fire severity, watershed responses). This study outlines a spatial modelling approach that couples three models used sequentially to allow managers to model the effects of fuel treatments on post-fire hydrological responses. Case studies involving a planned prescribed fire at Zion National Park and a planned mechanical thinning at Bryce Canyon National Park were used to demonstrate the approach. Fuel treatments were modelled using FuelCalc and FlamMap within the Wildland Fire Assessment Tool (WFAT). The First Order Fire Effects Model (FOFEM) within WFAT was then used to evaluate the effectiveness of the fuel treatments by modelling wildfires on both treated and untreated landscapes. Post-wildfire hydrological response was then modelled using KINEROS2 within the Automated Geospatial Watershed Assessment tool (AGWA). This coupled model approach could help managers estimate the effect of planned fuel treatments on wildfire severity and post-wildfire runoff or erosion, and compare various fuel treatment scenarios to optimise resources and maximise mitigation results.
Myosin light chain kinase regulates cell polarization independently of membrane tension or Rho kinase
Authors: Lou Sunny S. , Diz-Muñoz Alba , Weiner Orion D. , Fletcher Daniel A. , Theriot Julie A.
Published: April 2015

Cells polarize to a single front and rear to achieve rapid actin-based motility, but the mechanisms preventing the formation of multiple fronts are unclear. We developed embryonic zebrafish keratocytes as a model system for investigating establishment of a single axis. We observed that, although keratocytes from 2 d postfertilization (dpf) embryos resembled canonical fan-shaped keratocytes, keratocytes from 4 dpf embryos often formed multiple protrusions despite unchanged membrane tension. Using genomic, genetic, and pharmacological approaches, we determined that the multiple-protrusion phenotype was primarily due to increased myosin light chain kinase (MLCK) expression. MLCK activity influences cell polarity by increasing myosin accumulation in lamellipodia, which locally decreases protrusion lifetime, limiting lamellipodial size and allowing for multiple protrusions to coexist within the context of membrane tension limiting protrusion globally. In contrast, Rho kinase (ROCK) regulates myosin accumulation at the cell rear and does not determine protrusion size. These results suggest a novel MLCK-specific mechanism for controlling cell polarity via regulation of myosin activity in protrusions.
FOXO1 differentially regulates both normal and diabetic wound healing
Authors: Zhang Chenying , Ponugoti Bhaskar , Tian Chen , Xu Fanxing , Tarapore Rohinton , Batres Angelika , Alsadun Sarah , Lim Jason , Dong Guangyu , Graves Dana T.
Published: April 2015

Healing is delayed in diabetic wounds. We previously demonstrated that lineage-specific Foxo1 deletion in keratinocytes interfered with normal wound healing and keratinocyte migration. Surprisingly, the same deletion of Foxo1 in diabetic wounds had the opposite effect, significantly improving the healing response. In normal glucose media, forkhead box O1 (FOXO1) enhanced keratinocyte migration through up-regulating TGFβ1. In high glucose, FOXO1 nuclear localization was induced but FOXO1 did not bind to the TGFβ1 promoter or stimulate TGFβ1 transcription. Instead, in high glucose, FOXO1 enhanced expression of serpin peptidase inhibitor, clade B (ovalbumin), member 2 (SERPINB2), and chemokine (C-C motif) ligand 20 (CCL20). The impact of high glucose on keratinocyte migration was rescued by silencing FOXO1, by reducing SERPINB2 or CCL20, or by insulin treatment. In addition, an advanced glycation end product and tumor necrosis factor had a similar regulatory effect on FOXO1 and its downstream targets and inhibited keratinocyte migration in a FOXO1-dependent manner. Thus, FOXO1 expression can positively or negatively modulate keratinocyte migration and wound healing by its differential effect on downstream targets modulated by factors present in diabetic healing.
The source of matrix-degrading enzymes in human cancer: Problems of research reproducibility and possible solutions
Authors: Madsen Daniel H. , Bugge Thomas H.
Published: April 2015

Matrix degradation is central to tumor pathogenesis. Enzymes that degrade extracellular matrix are abundant in tumors. But which out of the complex mixture of cells that form a tumor produces them? Surprisingly, several hundred studies devoted to this question have provided confusion rather than clarity. Our analysis of these studies identifies likely reasons as to why this may be the case, which has implications for the broader issue of research reproducibility.