bluuebunny/crossref_metadata_2025 huggingface dataset:
Light driven growth of silver nanoplatelets on 2D MoS2nanosheet templates
Authors: Daeneke T. , Carey B. J. , Chrimes A. F. , Ou J. Zhen , Lau D. W. M. , Gibson B. C. , Bhaskaran M. , Kalantar-zadeh K.
Published: April 2015

This work investigates a novel synthesis strategy for the functionalisation of 2D MoS2nanosheets with silver. Direct excitation of the MoS2bandgap was found to lead to the photodeposition and eventual planar growth of metallic silver on the 2D MoS2nanosheet templates.
Highly improved electro-actuation of dielectric elastomers by molecular grafting of azobenzenes to silicon rubber
Authors: Zhang Ling , Wang Dongrui , Hu Penghao , Zha Jun-Wei , You Feng , Li Sheng-Tao , Dang Zhi-Min
Published: April 2015

Electromechanical deformation of silicone rubbers was efficiently improved by chemically grafting with strong polar azobenzenes.
In situ synthesis of a highly crystalline Tb-doped YAG nanophosphor using the mesopores of silica monoliths as a template
Authors: Aboulaich Abdelhay , Caperaa Nathalie , El Hamzaoui Hicham , Capoen Bruno , Potdevin Audrey , Bouazaoui Mohamed , Chadeyron Geneviève , Mahiou Rachid
Published: April 2015

This report describes the first synthesis of a highly crystalline YAG:Tb nanophosphor inside the pores of a mesoporous silica monolith (MSM).
Undernutrition during pregnancy in mice leads to dysfunctional cardiac muscle respiration in adult offspring
Authors: Beauchamp Brittany , Thrush A. Brianne , Quizi Jessica , Antoun Ghadi , McIntosh Nathan , Al-Dirbashi Osama Y. , Patti Mary-Elizabeth , Harper Mary-Ellen
Published: April 2015

Intrauterine growth restriction (IUGR) is associated with an increased risk of developing obesity, insulin resistance and cardiovascular disease. However, its effect on energetics in heart remains unknown. In the present study, we examined respiration in cardiac muscle and liver from adult mice that were undernourished in utero. We report that in utero undernutrition is associated with impaired cardiac muscle energetics, including decreased fatty acid oxidative capacity, decreased maximum oxidative phosphorylation rate and decreased proton leak respiration. No differences in oxidative characteristics were detected in liver. We also measured plasma acylcarnitine levels and found that short-chain acylcarnitines are increased with in utero undernutrition. Results reveal the negative impact of suboptimal maternal nutrition on adult offspring cardiac energy metabolism, which may have life-long implications for cardiovascular function and disease risk.
Diverging biological roles among human monocyte subsets in the context of tuberculosis infection
Authors: Balboa Luciana , Barrios-Payan Jorge , González-Domínguez Erika , Lastrucci Claire , Lugo-Villarino Geanncarlo , Mata-Espinoza Dulce , Schierloh Pablo , Kviatcovsky Denise , Neyrolles Olivier , Maridonneau-Parini Isabelle , Sánchez-Torres Carmen , Sasiain María del Carmen , Hernández-Pando Rogelio
Published: April 2015

Circulating monocytes (Mo) play an essential role in the host immune response to chronic infections. We previously demonstrated that CD16pos Mo were expanded in TB (tuberculosis) patients, correlated with disease severity and were refractory to dendritic cell differentiation. In the present study, we investigated whether human Mo subsets (CD16neg and CD16pos) differed in their ability to influence the early inflammatory response against Mycobacterium tuberculosis. We first evaluated the capacity of the Mo subsets to migrate and engage a microbicidal response in vitro. Accordingly, CD16neg Mo were more prone to migrate in response to different mycobacteria-derived gradients, were more resistant to M. tuberculosis intracellular growth and produced higher reactive oxygen species than their CD16pos counterpart. To assess further the functional dichotomy among the human Mo subsets, we carried out an in vivo analysis by adapting a hybrid mouse model (SCID/Beige, where SCID is severe combined immunodeficient) to transfer each Mo subset, track their migratory fate during M. tuberculosis infection, and determine their impact on the host immune response. In M. tuberculosis-infected mice, the adoptively transferred CD16neg Mo displayed a higher lung migration index, induced a stronger pulmonary infiltration of murine leucocytes expressing pro- and anti-inflammatory cytokines, and significantly decreased the bacterial burden, in comparison with CD16pos Mo. Collectively, our results indicate that human Mo subsets display divergent biological roles in the context of M. tuberculosis infection, a scenario in which CD16neg Mo may contribute to the anti-mycobacterial immune response, whereas CD16pos Mo might promote microbial resilience, shedding light on a key aspect of the physiopathology of TB disease.
Electricity price forecasting using a new data fusion algorithm
Authors: Darudi Ali , Bashari Masoud , Javidi Mohammad Hossein
Published: April 2015

Accurate price forecasting is crucial for all market participants in electricity markets. This study presents a hybrid price forecasting framework based on a new data fusion algorithm. Owing to the complexity and distinct nature of the electricity price, a single forecast engine cannot capture all different patterns of the price signals. Hence, this study focuses on a hybrid forecasting method to extract the advantages of several forecasting engines. In the proposed method, artificial neural network, adaptive neuro‐fuzzy inference system and autoregressive moving average are employed as primary forecast engines (agents) which provide three independent price forecasts. Then, a new data fusion algorithm, the modified ordered weighted average (modified OWA), is proposed to combine the three forecasts to generate a single unified price forecast. Hopefully, the fusion's output outperforms all the agents’ forecasts. The author's proposed fusion algorithm, unlike conventional OWA, uses the feedback from the agents’ error. The proposed framework is evaluated on the Spanish electricity market. The results confirm the ability of the proposed fusion framework to provide more accurate forecasts compared with the input agents forecasts. Results are also compared with some of the recent electricity price forecasting methods.
Congestion management through rotor stress controlled optimal transmission switching
Authors: Nasrolahpour Ehsan , Ghasemi Hassan
Published: April 2015

Security constrained optimal transmission switching (SC‐OTS) can be an essential part of future smart grids with flexible topologies. Transmission switching, however, can have adverse impact on generators because of creating excessive torque on their rotor shafts. In this study, SC‐OTS as an effective tool is applied to relieve congestion while considering AC constraints and generator rotor shaft impact caused by switching. As opposed to previously used simplified models based on standing phase angle, this study utilises dynamic response of generators to accurately calculate the actual stresses on rotors because of switching. In addition, network N‐1 security criterion is taken into account. In the proposed model, OTS actions are obtained through a bi‐level process. In the upper level, OTS set is determined and the applicability of each action is checked in the lower level. The proposed methodology leads to a mixed integer non‐linear programming problem, which is formulated and solved based on Benders decomposition. Test results for the IEEE 57 and 118‐bus systems illustrate the effectiveness of the method in removing congestion while ensuring that destructive switching manoeuvres are avoided.
Coordinated control strategy for doubly‐fed induction generator with DC connection topology
Authors: Nian Heng , Yi Xilu
Published: April 2015

With the development of wind power generation system and requirement of large‐scale and long‐distance power transmission, it is greatly important for wind farm to achieve the high effective DC grid connection technology. This study presents a novel grid connection topology for doubly‐fed induction generator (DFIG) connected to a DC‐link, in which a stator side converter and rotor side converter fed by a common DC bus are employed. Coordinated control method for the converters is proposed to regulate the electromagnetic torque directly based on the air‐gap flux orientation technique. Compared with the traditional grid connection system, the proposed system has a lot of advantages such as simpler structure, lower requirement for the converter capacity and higher power transmission efficiency. The power distribution between stator side converter and rotor side converter is analysed based on the proposed grid connection topology. Finally, DFIG‐based experimental system is developed to validate the correctness and availability of the proposed DC grid connection topology and control strategy.
Investigation of penetration using atomic force microscope: potential biomarkers of cell membrane
Authors: Yang Runhuai , Liu Lianqing , Zhang Changlin , Xi Ning , Yang Jie
Published: April 2015

The penetration of cell membrane using atomic force microscope (AFM) is studied. The penetration is monitored by AFM, and the penetration force is measured for three types of cells. The dissipated energy of the cell membrane before and after drug treatment is also calculated and analysed. Experimental results indicate that AFM is an efficient tool for measuring and monitoring the penetration of the cell membrane. Results also show that the penetration force differs significantly from each type of cells, indicating that the penetration force is a potential biomarker of cell membrane to distinguish different types of cells. Moreover, the dissipated energy of cell membrane is studied to be a biomarker to indicate the condition of the cell membrane. After the cell membrane is treated with dimethyl sulfoxide, the dissipated energy of cell membrane decreases.
Effects of Zinc Supplementation on Markers of Insulin Resistance and
Lipid Profiles in Women with Polycystic Ovary Syndrome: a Randomized,
Double-blind, Placebo-controlled Trial
Authors: Foroozanfard F. , Jamilian M. , Jafari Z. , Khassaf A. , Hosseini A. , Khorammian H. , Asemi Z.
Published: April 2015

Objective: This study was conducted to evaluate the effects of zinc
supplementation on glucose homeostasis parameters and lipid concentrations in
PCOS women. We are aware of no study evaluating the effects of zinc
supplementation on metabolic profiles of patients with polycystic ovary syndrome
(PCOS).

Methods: This randomized, double-blind, placebo-controlled trial was
conducted among 52 women diagnosed with PCOS and aged 18–40 years old.
Participants were randomly divided into 2 groups to receive 220 mg zinc sulfate
(containing 50 mg zinc) supplements (n=26) or placebo (n=26) per day for 8
weeks. Fasting blood samples were taken at baseline and after 8 weeks’
intervention to quantify glucose, insulin and lipid concentrations.

Results: After 8 weeks of intervention, subjects who received zinc
supplements had significantly increased serum zinc levels (+15.6±21.8 vs.
−4.1±16.7 mg/dL, P=0.001) compared with placebo. In addition, zinc-supplemented
patients had reduced fasting plasma glucose (FPG) (−4.3±9.6 vs. +0.5±6.0 mg/dL,
P=0.03), serum insulin levels (−3.0±2.9 vs. +1.5±8.4 µIU/mL, P=0.01),
homeostasis model of assessment-insulin resistance (HOMA-IR) (−0.8±0.8 vs.
+0.3±1.9, P=0.006), homeostatic model assessment-Beta cell function (HOMA-B)
(−10.6±9.5 vs. +4.9±32.1, P=0.02) and increased quantitative insulin sensitivity
check index (QUICKI) (+0.02±0.02 vs. −0.004±0.05, P=0.03) compared with placebo.
Additionally, a significant reduction in serum triglycerides (−15.6±40.3 vs.
+14.5±25.3 mg/dL, P=0.002) and VLDL-cholesterol concentrations (−3.2±8.1 vs.
+2.9±5.1 mg/dL, P=0.002) was observed following the administration of zinc
supplements compared with placebo.

Conclusion: Taken together, 220 mg zinc sulfate supplementation per day
for 8 weeks among PCOS women had beneficial effects on metabolic profiles.
The contribution of radio-frequency rectification to field-aligned losses of high-harmonic fast wave power to the divertor in the National Spherical Torus eXperiment
Authors: Perkins R. J. , Hosea J. C. , Jaworski M. A. , Ahn J.-W. , Diallo A. , Bell R. E. , Bertelli N. , Gerhardt S. , Gray T. K. , Kramer G. J. , LeBlanc B. P. , McLean A. , Phillips C. K. , Podestà M. , Roquemore L. , Sabbagh S. , Taylor G. , Wilson J. R.
Published: April 2015

The National Spherical Torus eXperiment (NSTX) can exhibit a major loss of high-harmonic fast wave (HHFW) power along scrape-off layer (SOL) field lines passing in front of the antenna, resulting in bright and hot spirals on both the upper and lower divertor regions. One possible mechanism for this loss is RF sheaths forming at the divertors. Here, we demonstrate that swept-voltage Langmuir probe characteristics for probes under the spiral are shifted relative to those not under the spiral in a manner consistent with RF rectification. We estimate both the magnitude of the RF voltage across the sheath and the sheath heat flux transmission coefficient in the presence of the RF field. Although precise comparison between the computed heat flux and infrared (IR) thermography cannot yet be made, the computed heat deposition compares favorably with the projections from IR camera measurements. The RF sheath losses are significant and contribute substantially to the total SOL losses of HHFW power to the divertor for the cases studied. This work will guide future experimentation on NSTX-U, where a wide-angle IR camera and a dedicated set of coaxial Langmuir probes for measuring the RF sheath voltage directly will quantify the contribution of RF sheath rectification to the heat deposition from the SOL to the divertor.
Parametric study of broadband terahertz radiation generation based on interaction of two-color ultra-short laser pulses
Authors: Moradi S. , Ganjovi A. , Shojaei F. , Saeed M.
Published: April 2015

In this work, using a two-dimensional kinetic model based on particle in cell-Monte Carlo collision simulation method, the influence of different parameters on the broadband intense Terahertz (THz) radiation generation via application of two-color laser fields, i.e., the fundamental and second harmonic modes, is studied. These two modes are focused into the molecular oxygen (O2) with uniform density background gaseous media and the plasma channels are created. Thus, a broadband THz pulse that is around the plasma frequency is emitted from the formed plasma channel and co-propagates with the laser pulse. For different laser pulse shapes, the THz electric field and its spectrum are both calculated. The effects of laser pulse and medium parameters, i.e., positive and negative chirp pulse, number of laser cycles in the pulse, laser pulse shape, background gas pressure, and exerted DC electric field on THz spectrum are verified. Application of a negatively chirped femtosecond (40 fs) laser pulse results in four times enhancement of the THz pulse energy (2 times in THz electric field). The emission of THz radiation is mostly observed in the forward direction.
Interaction between periodic structures of object and X-ray standing wave generated by wavefront-division interferometer
Authors: Suzuki Yoshio
Published: April 2015

An x-ray imaging method that utilizes interaction between standing wave and periodic structure of object is proposed. When a periodic object is placed in a standing wave field, the interaction is modulated by relation between the periodic structure of object and the standing wave period. Then, the structure of object can be observed as a modulation of transmission image, and the existence of fine periodic structures can be detected with an imaging detector of low spatial resolution. Feasibility studies have been performed using a standing wave generated by a wavefront-division x-ray interferometer with refractive prism optics.
The effect of beam pre-bunching on the excitation of terahertz plasmons in a parallel plane guiding system
Authors: Sharma Suresh C. , Malik Pratibha
Published: April 2015

The excitation of terahertz (THz) plasmons by a pre-bunched relativistic electron beam propagating in a parallel plane semiconducting guiding system is studied. It is found that the n-InSb semiconductor strongly supports the confined surface plasmons in the terahertz frequency range. The growth rate and efficiency of the THz surface plasmons increase linearly with modulation index and show the largest value as modulation index approaches unity. Moreover, the growth rate of the instability scales as one-third power of the beam density and inverse one-third power of the THz radiation frequency.
Experiments on the structure and stability of mode-2 internal solitary-like waves propagating on an offset pycnocline
Authors: Carr M. , Davies P. A. , Hoebers R. P.
Published: April 2015

The structure and stability of mode-2 internal solitary-like waves is investigated experimentally. A rank-ordered train of mode-2 internal solitary waves is generated using a lock release configuration. The pycnocline is centred either on the mid-depth of the water column (the 0% offset case) or it is offset in the positive vertical direction by a fraction of 5%, 10%, or 20% of the total fluid depth. It is found that offsetting the pycnocline has little effect on the basic wave properties (e.g., wave speed, wave amplitude, and wavelength) but it does significantly affect wave stability. Instability takes the form of small K-H-like billows in the rear of the wave and small scale overturning in the core of the wave. In the 0% offset case, instability occurs on both the upper and lower interfaces of the pycnocline and is similar in extent and vigour over the two interfaces. As the offset percentage is increased, however, instability is more pronounced on the lower interface with little or no evidence of instability being observed on the upper interface. In the 20% offset case, a mode-1 tail is associated with the wave and the wave characteristics resemble qualitatively the recent field observations of Shroyer et al. [“Mode 2 waves on the continental shelf: Ephemeral components of the nonlinear internal wavefield,” J. Geophys. Res. 115, C07001, doi:10.1029/2009JC005605 (2010)].
Semianalytical study of the propagation of an ultrastrong femtosecond laser pulse in a plasma with ultrarelativistic electron jitter
Authors: Jovanović Dušan , Fedele Renato , Belić Milivoj , De Nicola Sergio
Published: April 2015

The interaction of a multi-petawatt, pancake-shaped laser pulse with an unmagnetized plasma is studied analytically and numerically in a regime with ultrarelativistic electron jitter velocities, in which the plasma electrons are almost completely expelled from the pulse region. The study is applied to a laser wakefield acceleration scheme with specifications that may be available in the next generation of Ti:Sa lasers and with the use of recently developed pulse compression techniques. A set of novel nonlinear equations is derived using a three-timescale description, with an intermediate timescale associated with the nonlinear phase of the electromagnetic wave and with the spatial bending of its wave front. They describe, on an equal footing, both the strong and the moderate laser intensity regimes, pertinent to the core and to the edges of the pulse. These have fundamentally different dispersive properties since in the core the electrons are almost completely expelled by a very strong ponderomotive force, and the electromagnetic wave packet is imbedded in a vacuum channel, thus having (almost) linear properties. Conversely, at the pulse edges, the laser amplitude is smaller, and the wave is weakly nonlinear and dispersive. New nonlinear terms in the wave equation, introduced by the nonlinear phase, describe without the violation of imposed scaling laws a smooth transition to a nondispersive electromagnetic wave at very large intensities and a simultaneous saturation of the (initially cubic) nonlocal nonlinearity. The temporal evolution of the laser pulse is studied both analytically and by numerically solving the model equations in a two-dimensional geometry, with the spot diameter presently used in some laser acceleration experiments. The most stable initial pulse length is estimated to exceed ≳1.5–2 μm. Moderate stretching of the pulse in the direction of propagation is observed, followed by the development of a vacuum channel and of a very large electrostatic wake potential, as well as by the bending of the laser wave front.
Complex network based techniques to identify extreme events and (sudden) transitions in spatio-temporal systems
Authors: Marwan Norbert , Kurths Jürgen
Published: April 2015

We present here two promising techniques for the application of the complex network approach to continuous spatio-temporal systems that have been developed in the last decade and show large potential for future application and development of complex systems analysis. First, we discuss the transforming of a time series from such systems to a complex network. The natural approach is to calculate the recurrence matrix and interpret such as the adjacency matrix of an associated complex network, called recurrence network. Using complex network measures, such as transitivity coefficient, we demonstrate that this approach is very efficient for identifying qualitative transitions in observational data, e.g., when analyzing paleoclimate regime transitions. Second, we demonstrate the use of directed spatial networks constructed from spatio-temporal measurements of such systems that can be derived from the synchronized-in-time occurrence of extreme events in different spatial regions. Although there are many possibilities to investigate such spatial networks, we present here the new measure of network divergence and how it can be used to develop a prediction scheme of extreme rainfall events.
Formation of H2 from internally heated polycyclic aromatic hydrocarbons: Excitation energy dependence
Authors: Chen T. , Gatchell M. , Stockett M. H. , Delaunay R. , Domaracka A. , Micelotta E. R. , Tielens A. G. G. M. , Rousseau P. , Adoui L. , Huber B. A. , Schmidt H. T. , Cederquist H. , Zettergren H.
Published: April 2015

We have investigated the effectiveness of molecular hydrogen (H2) formation from Polycyclic Aromatic Hydrocarbons (PAHs) which are internally heated by collisions with keV ions. The present and earlier experimental results are analyzed in view of molecular structure calculations and a simple collision model. We estimate that H2 formation becomes important for internal PAH temperatures exceeding about 2200 K, regardless of the PAH size and the excitation agent. This suggests that keV ions may effectively induce such reactions, while they are unlikely due to, e.g., absorption of single photons with energies below the Lyman limit. The present analysis also suggests that H2 emission is correlated with multi-fragmentation processes, which means that the [PAH-2H]+ peak intensities in the mass spectra may not be used for estimating H2-formation rates.
Prediction of the critical reduced electric field strength for carbon dioxide and its mixtures with copper vapor from Boltzmann analysis for a gas temperature range of 300 K to 4000 K at 0.4 MPa
Authors: Li Xingwen , Guo Xiaoxue , Zhao Hu , Jia Shenli , Murphy Anthony B.
Published: April 2015

The influence of copper vapor mixed in hot CO2 on dielectric breakdown properties of gas mixture at a fixed pressure of 0.4 MPa for a temperature range of 300 K–4000 K is numerically analyzed. First, the equilibrium composition of hot CO2 with different copper fractions is calculated using a method based on mass action law. The next stage is devoted to computing the electron energy distribution functions (EEDF) by solving the two-term Boltzmann equation. The reduced ionization coefficient, the reduced attachment coefficient, and the reduced effective ionization coefficient are then obtained based on the EEDF. Finally, the critical reduced electric field (E/N)cr is obtained. The results indicate that an increasing mole fraction of copper markedly reduces (E/N)cr of the CO2–Cu gas mixtures because of copper's low ionization potential and large ionization cross section. Additionally, the generation of O2 from the thermal dissociation of CO2 contributes to the increase of (E/N)cr of CO2–Cu hot gas mixtures from about 2000 K to 3500 K.
Magnetic control of the inclination of biogenic guanine crystals fixed on a substrate
Authors: Mizukawa Yuri , Iwasaka Masakazu
Published: April 2015

In the present study, we describe the fabrication and manipulation of a micro-mirror system similar to the iridophores of neon tetra that allow microstructural light control. Biogenic guanine crystals as micro-mirrors were adhered to a glass substrate with flexible DNA joints under a vertical magnetic field of 480 mT. We then observed the movement of the micro-mirrors under sub-Tesla horizontal magnetic fields. Under ambient fields, the orientation of the guanine micro-mirrors did not change. Appling a horizontal magnetic field of approximately 400 mT generated by an electromagnet induced motion and width changes of the guanine micro-mirrors, which were observed by an optical microscope. However, the inclination of the micro-mirrors recovered upon removal of the magnetic field. The developed guanine micro-mirrors on a glass substrate demonstrate the remote control of microstructural diamagnetic materials, and may show promise for use as an underwater microactuator for microfluidic systems.
Néel temperature of Cr2O3 in Cr2O3/Co exchange-coupled system: Effect of buffer layer
Authors: Pati Satya Prakash , Shimomura Naoki , Nozaki Tomohiro , Shibata Tatsuo , Sahashi Masashi
Published: April 2015

The lattice parameter dependence of the Néel temperature TN of thin Cr2O3 in a Cr2O3/Co exchange-coupled system is investigated. Lattice-mismatch-induced strain is generated in Cr2O3 by using different buffer layers. The lattice parameters are determined from out-of-plane and in-plane X-ray diffraction measurements. The Néel temperature is detected by direct temperature-dependent magnetization measurement as well as the temperature-dependent interface exchange coupling energy. It is observed that in-plane lattice contraction can enhance TN in Cr2O3, which is consistent with theoretical calculations.
The fabrication and characterization of stable core-shell superparamagnetic nanocomposites for potential application in drug delivery
Authors: Sharifabad M. Eizadi , Mercer T. , Sen T.
Published: April 2015

Two systems of core-shell superparamagnetic nanoparticles in the size range of 45–80 nm have been fabricated by the coating of bare magnetite particles with either mesoporous silica or liposomes and the loading/release of the anti-cancer drug Mitomycin C (MMC) from their surfaces has been investigated. The magnetic cores of size ∼10 nm were produced by a co-precipitation method in aqueous solution, with the silica coating containing an unstructured network of pores of size around 6 nm carried out using a surfactant-templating approach and the liposome coating achieved by an evaporation-immersion technique of the particles in a lipid solution. Stability measurements using a scanning column magnetometry technique indicated that the lipid-coating of the particles halts the sedimentation otherwise apparent in <1 h for the bare magnetite to produce an ultra-stable system and thereby overcome one of the main barriers to potential in-vivo applications. Whilst an increase in stability was also observed in the silica-coated system, it was still unstable over a few hours and will require further investigation. Magnetization curves of the coated systems were indicative of superparamagnetic behavior whilst the in vitro loading and release of MMC resulted in two distinctly different outcomes for the two systems: (i) the silica-coated particles saturated in <4 h to a loading of around 7 μg/mg of material, releasing about 6% at a near constant rate over 48 h whilst (ii) the lipid-coated particles saturated to around only 4 μg/mg over the same time period but with a subsequent rapid release rate over the first 3 h to 27% then rising near-linearly to a value of about 45% at the 48 h mark. This gives scope for systems' to be tuned to the appropriate rate and load delivery as required by clinical need with further investigations underway.
Large perpendicular magnetic anisotropy of single Co atom on MgO monolayer: A first-principles study
Authors: Shao Bin , Shi Wu-Jun , Feng Min , Zuo Xu
Published: April 2015

Realizing the magnetic bit with a single atom is the ultimate goal for magnetic storage. Based on density functional theory, the magnetic anisotropy (MA) of single Co atom on MgO monolayer has been investigated. Results show that this two dimensional system possesses a large perpendicular MA, about 5.8 meV per Co atom. Besides, there exists remarkable unquenched orbital moments for different magnetization directions, which can be attributed to the reduction of coordination number in two dimensional system and is responsible for the enhanced MA. The Bloch pseudo-wavefunction and band structure of Co d-orbitals have been calculated to elucidate the origin of the perpendicular MA.
Continuous wave vertical cavity surface emitting lasers at 2.5 μm with InP-based type-II quantum wells
Authors: Sprengel S. , Andrejew A. , Federer F. , Veerabathran G. K. , Boehm G. , Amann M.-C.
Published: April 2015

A concept for electrically pumped vertical cavity surface emitting lasers (VCSEL) for emission wavelength beyond 2 μm is presented. This concept integrates type-II quantum wells into InP-based VCSELs with a buried tunnel junction as current aperture. The W-shaped quantum wells are based on the type-II band alignment between GaInAs and GaAsSb. The structure includes an epitaxial GaInAs/InP and an amorphous AlF3/ZnS distributed Bragg reflector as bottom and top (outcoupling) mirror, respectively. Continuous-wave operation up to 10 °C at a wavelength of 2.49 μm and a peak output power of 400 μW at −18 °C has been achieved. Single-mode emission with a side-mode suppression ratio of 30 dB for mesa diameters up to 14 μm is presented. The long emission wavelength and current tunability over a wavelength range of more than 5 nm combined with its single-mode operation makes this device ideally suited for spectroscopy applications.
Nonlinear time-series analysis revisited
Authors: Bradley Elizabeth , Kantz Holger
Published: April 2015

In 1980 and 1981, two pioneering papers laid the foundation for what became known as nonlinear time-series analysis: the analysis of observed data—typically univariate—via dynamical systems theory. Based on the concept of state-space reconstruction, this set of methods allows us to compute characteristic quantities such as Lyapunov exponents and fractal dimensions, to predict the future course of the time series, and even to reconstruct the equations of motion in some cases. In practice, however, there are a number of issues that restrict the power of this approach: whether the signal accurately and thoroughly samples the dynamics, for instance, and whether it contains noise. Moreover, the numerical algorithms that we use to instantiate these ideas are not perfect; they involve approximations, scale parameters, and finite-precision arithmetic, among other things. Even so, nonlinear time-series analysis has been used to great advantage on thousands of real and synthetic data sets from a wide variety of systems ranging from roulette wheels to lasers to the human heart. Even in cases where the data do not meet the mathematical or algorithmic requirements to assure full topological conjugacy, the results of nonlinear time-series analysis can be helpful in understanding, characterizing, and predicting dynamical systems.
Pressure optimization of high harmonic generation in a differentially pumped Ar or H2 gas jet
Authors: Sayrac M. , Kolomenskii A. A. , Anumula S. , Boran Y. , Hart N. A. , Kaya N. , Strohaber J. , Schuessler H. A.
Published: April 2015

We experimentally studied the dependence of high harmonic generation in argon and molecular hydrogen on pressure changes in a gas jet that cause variations of the phase matching conditions and absorption. The study was performed at a peak laser intensity of ∼1.5 × 1014 W/cm2. To enable measurements over a wide range of pressures, we employed differential pumping with an additional cell (∼20 cm3 volume) enclosing the gas jet. By increasing the pressure in the gas jet up to a maximum of 1.5 bars with argon or 0.5 bars with hydrogen, we observed an increase in the high harmonic (HH) yield until an optimum pressure of 0.2 bars was reached for Ar, beyond which the output began decreasing. For H2, we observed an increase of the HH output up to the maximum pressure of 0.5 bars. This pressure-dependence study allowed us to achieve a tenfold enhancement in the high harmonic yield at the optimum pressure.
The cumulative energy effect for improved ignition timing
Authors: Markhotok A.
Published: April 2015

A technique capable of improving timing in ignition applications is proposed. It is based on the use of shock waves propagating in a specific medium that allows achieving extremely high speeds and energies. The model uses the energy cumulation effect in the presence of the shock wave refraction on an interface with plasma. The problem was solved analytically and the effects were demonstrated for a cylindrically symmetrical geometry. Numerical results show very quick and uneven acceleration of different portions of the shock front. Its strong distortions lead to formation of a sharply focused jet near the axis of symmetry. The ability of the shock to achieve extremely high speeds and energies can be useful in design of efficient combustors for hypersonic systems, and possibly offers an alternative way of construction of a nuclear fusion reactor. Recommendations are given in terms of adjustment parameters and can be applied at any problem scale and for various combinations of the strengths of the effects involved in the problem.
Influence of epitaxial BiFeO3 on superparamagnetic behavior of CoFeB thin film
Authors: Zhang Q. T. , You L. , Wan C. H. , Yuan Z. H. , Zhang X. , Wang J. , Han X. F.
Published: April 2015

Superparamagnetic behavior of ultrathin CoFeB film grown on epitaxial BiFeO3 (BFO) thin film was investigated by using anomalous Hall effect (AHE) at different temperatures. A transition from superparamagnetism to blocked state was observed for CoFeB grown directly on SrTiO3 (STO) substrate, but absent for CoFeB grown on BFO from 30 K to 300 K. By fitting normalized AHE data with Langevin equation, average grain sizes of the superparamagnetic CoFeB grown on STO and BFO were estimated. Considering the relationship between volume of nanoparticle and blocking temperature (TB), TB of CoFeB grown on BFO was above 30 K which was not observed experimentally, indicating that in addition to surface roughness or oxidation, interfacial exchange coupling also played a role in the suppression of TB. By taking the interfacial exchange coupling between BFO and superparamagnetic CoFeB as an effective field, Bloch equations were introduced to study the relaxation process of superparamagnetic CoFeB. This suppression of TB was proposed to be attributed to a cooperative effect of interfacial exchange coupling as well as roughness or oxidation between BFO and superparamagnetic CoFeB.
Effect of nonthermal electrons on the shock formation in a laser driven plasma
Authors: Nicolaï Ph. , Feugeas J.-L. , Nguyen-bui T. , Tikhonchuk V. , Antonelli L. , Batani D. , Maheut Y.
Published: April 2015

In the laser-driven inertial fusion schemes and specifically in the shock ignition concept, non thermal electrons may be generated. By depositing their energy far from the origin, they can significantly modify the target hydrodynamics. It is shown in this paper that these electrons may affect the laser-driven shock formation and its propagation through the target. These changes are induced by the target heating and depend on the electron energy spectrum. Furthermore, results of some passive diagnostic may be misinterpreted, indicating an apparent different pressure.
Plasma sputtering robotic device for in-situ thick coatings of long, small diameter vacuum tubes
Authors: Hershcovitch A. , Blaskiewicz M. , Brennan J. M. , Custer A. , Dingus A. , Erickson M. , Fischer W. , Jamshidi N. , Laping R. , Liaw C.-J. , Meng W. , Poole H. J. , Todd R.
Published: April 2015

A novel robotic plasma magnetron mole with a 50 cm long cathode was designed, fabricated, and operated. The reason for this endeavor is to alleviate the problems of unacceptable resistive heating of stainless steel vacuum tubes in the BNL Relativistic Heavy Ion Collider (RHIC). The magnetron mole was successfully operated to copper coat an assembly containing a full-size, stainless steel, cold bore, RHIC magnet tubing connected to two types of RHIC bellows, to which two additional pipes made of RHIC tubing were connected. To increase the cathode lifetime, a movable magnet package was developed, and the thickest possible cathode was made, with a rather challenging target to substrate (de facto anode) distance of less than 1.5 cm. Achieving reliable steady state magnetron discharges at such a short cathode to anode gap was rather challenging, when compared to commercial coating equipment, where the target to substrate distance is 10's cm; 6.3 cm is the lowest experimental target to substrate distance found in the literature. Additionally, the magnetron developed during this project provides unique omni-directional uniform coating. The magnetron is mounted on a carriage with spring loaded wheels that successfully crossed bellows and adjusted for variations in vacuum tube diameter, while keeping the magnetron centered. Electrical power and cooling water were fed through a cable bundle. The umbilical cabling system is driven by a motorized spool. Excellent coating adhesion was achieved. Measurements indicated that well-scrubbed copper coating reduced secondary electron yield to 1, i.e., the problem of electron clouds can be eliminated. Room temperature RF resistivity measurement indicated that a 10 μm copper coated stainless steel RHIC tube has a conductivity close to that of pure copper tubing. Excellent coating adhesion was achieved. The device details and experimental results are described.
Highly conductive indium nanowires deposited on silicon by dip-pen nanolithography
Authors: Kozhukhov Anton , Klimenko Anatoliy , Shcheglov Dmitriy , Volodin Vladimir , Karnaeva Natalya , Latyshev Alexander
Published: April 2015

In this paper, we developed a new dip-pen nanolithography (DPN) method. Using this method, we fabricated conductive nanowires with diameters of 30–50 nm on silicon substrates. To accomplish this, indium was transferred from an atomic force microscopy tip to the surface by applying a potential difference between the tip and substrate. The fabricated indium nanowires were several micrometers in length. Unlike thermal DPN, our DPN method hardly oxidized the indium, producing nanowires with conductivities from 5.7 × 10−3 to 4 × 10−2 Ω cm.
Acid inhibition during anaerobic digestion of biodegradable kitchen waste
Authors: Dai Benlin , Xu Jiming , He Yulong , Xiong Peng , Wang Xinfeng , Deng Yuanfang , Wang Yixian , Yin Zhiming
Published: April 2015

The aim of this work was to investigate the acid inhibition during the anaerobic digestion of kitchen waste. Four biodegradable substrates of soybean, fat meat, rice, and celery cane were considered in this paper. A series of anaerobic co-digestion tests were performed on the four substrates at the load of 1.0 gVS/(l·day) and anaerobic granular sludge. The results show that the acid inhibition was occurred at the load of 1.0 gVS/(l·day) for the soybean and rice; the corresponding pH values at the lowest acidification points were 5.03 and 3.73, respectively. There was no acid inhibition during the whole digestion period for the celery cane substrate. And the results also reveal that the order of the cumulative gas yields for different substrates from highest to lowest is: celery cane > soybean > fat meat > rice; while the order of the average methane (CH4) percentage from highest to lowest is: celery cane > fat meat > soybean > rice. Finally, the method to calculate the lowest acidification points of the four substrates was provided by the least squares method, and it is verified by the measured data, and good agreement is found.
Description of the ideality factor of a-Si:H photovoltaic cells under different illumination intensity levels
Authors: Tarabsheh A. Al
Published: April 2015

This paper presents a closed form for the behavior of the ideality factor n of amorphous silicon (a-Si:H) photovoltaic cells under different illumination intensity Φ levels and applied voltage V. The advantage of this model, over other existing models, is its effectiveness of describing the dependency of n on both V and Φ even without evaluating n itself. Therefore, the errors of calculating n using various existing methods are minimized in this paper. The variations of the current voltage J/V data under different levels of Φ are monitored where the illumination intensity dependence of parallel resistance Rp(Φ) is taken into account. The resulting model is a first order differential equation with non-constant coefficients whose solution expresses the variations of n in V- and Φ-domain. From the solution of the differential equation, it is found that n increases as V or Φ increases.
Room-temperature zero thermal expansion in a cubic perovskite oxide SrCu3Fe4−xMnxO12
Authors: Yamada Ikuya , Marukawa Shohei , Hayashi Naoaki , Matsushita Masafumi , Irifune Tetsuo
Published: April 2015

A zero thermal expansion in a wide temperature range including room temperature has been achieved in a cubic perovskite oxide SrCu3Fe4−xMnxO12 for x = 1.5. Partial substitution of Mn for Fe in SrCu3Fe4O12 systematically changes the linear thermal expansion coefficient from negative [−6.4(2), −5.7(5), and −1.88(11) ppm/K for x = 0.5, 1, and 1.25, respectively] to almost zero [0.67(15) ppm/K for x = 1.5] to positive [2.97(17) ppm/K for x = 1.75] and the operational temperature window shifts to higher temperature ranges above room temperature. Crystal structure analysis and Mössbauer spectroscopy reveal that the zero thermal expansion for x = 1.5 composition is induced by intermetallic charge transfer between Cu and (Fe,Mn) ions. These results display the high potential of SrCu3Fe4−xMnxO12 for the development of zero thermal expansion materials.
Microsecond-range optical shutter for unpolarized light with chiral nematic liquid crystal
Authors: Mohammadimasoudi Mohammad , Shin Jungsoon , Lee Keechang , Neyts Kristiaan , Beeckman Jeroen
Published: April 2015

A fast electro-optic shutter is fabricated and demonstrated. The device works independently of the polarization state of the incoming light beam. Modulation between 3% transmission and 60% transmission is obtained within a wavelength range of 50 nm with a response time of 20 μs. The device consists of two partly polymerized chiral nematic liquid crystal layers separated by a half wave plate. The transmission modulation is due to a 50 nm wavelength shift of the photonic band gap of the chiral liquid crystal realized by applying an electric field over a mixture of photo-polymerized LC and non-reactive nematic LC containing a chiral dopant. The shutter features high reflectivity in the photonic band gap. We investigate the influence of the amplitude of the applied voltage on the width and the depth of the reflection band.
Nickel stimulates copper uptake by nickel-hyperaccumulator plants in the genus Alyssum
Authors: Ghasemi Rasoul , Ghaderian S. Majid , Ebrazeh Sahar
Published: April 2015

The greatest number of nickel (Ni)-hyperaccumulator plants belonging to the genus Alyssum originate from serpentine soils. They possess physiological mechanisms that enable them tolerate very high internal concentrations of Ni. The specificity of these traits has still not been fully clarified; however, by studying the interactions of different metals, some clues may be given. In the present study, the tolerance, uptake, accumulation and interactions of Ni and copper (Cu) were assessed in a range of Alyssum species. A. bracteatum (Harsin and Paveh populations) and A. inflatum were selected as Ni hyperaccumulators from western Iran. A. montanum and A. saxatile were selected as non-accumulators originating from the Mediterranean region, now being used as ornamental plants. Different concentrations of Ni (0, 100 and 250 µM for hyperaccumulators and 0, 10 and 25 µM for the non-accumulator plants), and Cu (0.5, 1 and 2.5 µM) were employed as treatments in a hydroponic growth experiment with a fully randomised factorial design. No tolerance to high concentrations of Cu was observed in any of the species tested. In the presence of Ni, an increased Cu concentration was observed in both roots and shoots of the Ni-hyperaccumulator plants, but not in the non-accumulators. Furthermore, no negative interaction was detected between Ni and Cu in metal uptake by roots, suggesting that different uptake mechanisms are involved. Stimulation of Cu uptake by Ni in the Ni hyperaccumulators hints that this particular feature may be among the characteristics that enable them to hyperaccumulate Ni, unlike their congeneric non-accumulators.
TAGLN2 regulates T cell activation by stabilizing the actin cytoskeleton at the immunological synapse
Authors: Na Bo-Ra , Kim Hye-Ran , Piragyte Indre , Oh Hyun-Mee , Kwon Min-Sung , Akber Uroos , Lee Hyun-Su , Park Do-Sim , Song Woo Keun , Park Zee-Yong , Im Sin-Hyeog , Rho Mun-Chual , Hyun Young-Min , Kim Minsoo , Jun Chang-Duk
Published: April 2015

The formation of an immunological synapse (IS) requires tight regulation of actin dynamics by many actin polymerizing/depolymerizing proteins. However, the significance of actin stabilization at the IS remains largely unknown. In this paper, we identify a novel function of TAGLN2—an actin-binding protein predominantly expressed in T cells—in stabilizing cortical F-actin, thereby maintaining F-actin contents at the IS and acquiring LFA-1 (leukocyte function-associated antigen-1) activation after T cell receptor stimulation. TAGLN2 blocks actin depolymerization and competes with cofilin both in vitro and in vivo. Knockout of TAGLN2 (TAGLN2−/−) reduced F-actin content and destabilized F-actin ring formation, resulting in decreased cell adhesion and spreading. TAGLN2−/− T cells displayed weakened cytokine production and cytotoxic effector function. These findings reveal a novel function of TAGLN2 in enhancing T cell responses by controlling actin stability at the IS.
A role for disulfide bonding in keratin intermediate filament organization and dynamics in skin keratinocytes
Authors: Feng Xia , Coulombe Pierre A.
Published: April 2015

We recently reported that a trans-dimer, homotypic disulfide bond involving Cys367 in keratin 14 (K14) occurs in an atomic-resolution structure of the interacting K5/K14 2B domains and in keratinocyte cell lines. Here we show that a sizable fraction of the K14 and K5 protein pools participates in interkeratin disulfide bonding in primary cultures of mouse skin keratinocytes. By comparing the properties of wild-type K14 with a completely cysteine-free variant thereof, we found that K14-dependent disulfide bonding limited filament elongation during polymerization in vitro but was necessary for the genesis of a perinuclear-concentrated network of keratin filaments, normal keratin cycling, and the sessile behavior of the nucleus and whole cell in keratinocytes studied by live imaging. Many of these phenotypes were rescued when analyzing a K14 variant harboring a single Cys residue at position 367. These findings establish disulfide bonding as a novel and important mechanism regulating the assembly, intracellular organization, and dynamics of K14-containing intermediate filaments in skin keratinocytes.