bluuebunny/crossref_metadata_2025 huggingface dataset:
Supramolecular grafting of doped polyaniline leads to an unprecedented solubility enhancement, radical cation stabilization, and morphology transformation
Authors: Maity Nabasmita , Dawn Arnab , Kuila Atanu , Nandi Arun K.
Published: May 2018

Polyaniline supramolecularly grafted with polyethylene glycol coupled with β-cyclodextrin forming a pseudorotaxane structure shows an extremely high solubility, higher degree of doping, and highly efficient radical cation stabilization.
Potential detection of cancer with fluorinated silicon nanoparticles in 19F MR and fluorescence imaging
Authors: Li Sha , Yuan Yaping , Yang Yuqi , Li Conggang , McMahon Michael T. , Liu Maili , Chen Shizhen , Zhou Xin
Published: May 2018

Novel fluorinated silicon nanoparticles with strong fluorescence, high 19F-MRI sensitivity and excellent aqueous solubility have been successfully developed.
Progress in organic molecular/ferromagnet spinterfaces: towards molecular spintronics
Authors: Sun Meifang , Mi Wenbo
Published: May 2018

The characteristics of organic molecular/ferromagnet spinterfaces are highlighted, including hybrid interface states, magnetic anisotropy, magnetic exchange interaction, etc.
Al-Doped SiC nanowires wrapped by the nanowire network: excellent field emission property and robust stability at high current density
Authors: Li Z. J. , Li K. H. , Song G. Y. , Qiu G. H. , Yang L. N. , Meng A. L.
Published: May 2018

Al-Doped SiC nanowires wrapped by the nanowire network were synthesized by a simple one-step calcination method.
A rigid ringlike molecule: large second-order nonlinear optical performance, good temporal and thermal stability, and ideal spherical structure conforming to the “site isolation” principle
Authors: Chen Pengyu , Liu Guangchao , Zhang Huanyu , Jin Meng , Han Mengmeng , Cheng Ziyao , Peng Qian , Li Qianqian , Li Zhen
Published: May 2018

Ringlike molecule R1 containing two FTC moieties exhibited excellent EO performance (d33 = 562 pm V−1 @1950 nm, T80% = 145 °C).
High photoluminescence quantum yield of 18.7% by using nitrogen-doped Ti3C2 MXene quantum dots
Authors: Xu Quan , Ding Lan , Wen Yangyang , Yang Wenjing , Zhou Hongjun , Chen Xingzhu , Street Jason , Zhou Aiguo , Ong Wee-Jun , Li Neng
Published: May 2018

Quantum dots, derived from two-dimensional (2D) materials, have shown promising applications in bioimaging, photocatalysis, biosensors and white light emission devices (W-LEDs).
Therapeutic effects of simvastatin on Galectin-3 and oxidative stress parameters in endotoxemic lung tissue
Authors: Yorulmaz Hatice , Ozkok Elif , Kaptan Engin , Ates Gulten , Tamer Sule
Published: May 2018

Galectins constitute of a soluble mammalian β-galactoside binding lectin family, which play homeostatic roles in the regulation of the cell cycle, and apoptosis, in addition to their inflammatory conditions. Galectin-3 has an important role in the regulation of various inflammatory conditions including endotoxemia, and airway inflammation. Statins, the key precursor inhibitors of 3-hydroxyl-3-methyl coenzyme A (HMG-CoA) reductase, may prevent the progression of inflammation in sepsis after prior statin treatment. Endotoxemia leads to the formation of oxidative stress parameters in proteins, carbohydrates, and DNA. In the present study, we aimed to show the effects of simvastatin on Galectin-3, and glutathione reductase (GR), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and thiobarbituric acid reactive substances (TBARS) levels in lung tissue of rats which were treated with lipopolysaccharides (LPS) during the early phase of sepsis. Rats were divided into four groups as the control, LPS (20 mg/kg), simvastatin (20 mg/kg), and simvastatin+LPS group. Galectin-3 expression in formalin-fixed paraffin-embedded lung tissue sections was demonstrated by using the immunohistochemistry methods. There were reduced densities, and the decreased number of Galectin-3 immunoreactivities in the simvastatin+LPS group compared with the LPS group in the pneumocytes, and in the bronchial epithelium of lung tissue. In the LPS group, GR, GSH-Px, and SOD were found lower than the levels in simvastatin-treated LPS group (P<0.05, P<0.01, P<0.01 respectively) in the lung tissue. However, TBARS decreased in the simvastatin+LPS group compared with the levels in LPS group (P<0.001). Simvastatin attenuates LPS-induced oxidative acute lung inflammation, oxidative stress, and suppresses LPS-induced Galectin-3 expression in the lung tissue.
Sub‐optimal low‐complexity detector for generalised quadrature spatial modulation
Authors: Neelakandan R.
Published: May 2018

Quadrature spatial modulation (QSM) is one of the recently emerging transmission schemes to improve the throughput of the multi‐input multi‐output systems. QSM transmits an M‐ary complex symbol whose real and imaginary parts activate an antenna index independently thus provides an extra spatial dimension compared to conventional spatial modulation (SM). A generalised QSM (GQSM) transmission is considered in which a set of M‐ary complex symbols activate multiple antennas to transmit their real and imaginary parts separately, which offers higher throughput in terms of bits per channel use (bpcu) than other SM techniques. A detector is proposed, ordering‐based structured orthogonal matching pursuit for GQSM using compressive sensing (CS), which performs very close to the maximum likelihood detector with significantly lesser complexity. Also, the proposed algorithm performs superior to other CS‐based detectors and offers a better trade‐off between complexity and performance.
Impact of stress in ICP‐CVD SiNx passivation films on the leakage current in AlGaN/GaN HEMTs
Authors: Cho S.‐J. , Li X. , Guiney I. , Floros K. , Hemakumara D. , Wallis D.J. , Humphreys C. , Thayne I.G.
Published: May 2018

The impact of the stress in room temperature inductively coupled plasma chemical vapour deposited (ICP‐CVD) SiNx surface passivation layers on off‐state drain (IDS‐off) and gate leakage currents (IGS) in AlGaN/GaN high electron mobility transistors (HEMTs) is reported. IDS‐off and IGS in 2 μm gate length devices were reduced by up to four orders of magnitude to ∼10 pA/mm using a compressively stressed bilayer SiNx passivation scheme. In addition, Ion/Ioff of ∼1011 and subthreshold slope of 68 mV/dec were obtained using this strain engineered surface passivation approach.
Modified root MUSIC for co‐prime linear arrays
Authors: Liu Aihua , Yang Qiang , Zhang Xin , Deng Weibo
Published: May 2018

The direction of arrival (DOA) estimation problem using co‐prime linear arrays is studied. By analysing the special array geometry of the co‐prime array, the co‐prime array is taken as a filled uniform linear array where some elements are omitted, then a modified root‐multiple signal classification (MUSIC) algorithm is developed, which avoids the matching process by obtaining the true DOAs without phase ambiguity. In addition, it can detect more sources by making full use of the degrees of freedom provided by the co‐prime array. Simulation results are provided to verify the effectiveness of the proposed algorithm.
Self‐balanced non‐isolated hybrid modular DC–DC converter for medium‐voltage DC grids
Authors: Elserougi Ahmed A. , Massoud Ahmed M. , Abdelsalam Ibrahim , Ahmed Shehab
Published: May 2018

Here, a new bi‐directional hybrid modular non‐isolated DC–DC converter is proposed where it consists of a boost converter (BC) fed from the high‐voltage (HV) side. At the BC output stage, a certain number of half bridge submodules (HB‐SMs) is connected across the BC switch. During the turn‐on period of BC switch, the HB‐SMs are connected sequentially to the low‐voltage (LV) side, which results in charging/discharging their capacitors from/into the LV side. While, during the turn‐off period, the LV side is bypassed and the HB‐SMs capacitors are connected in series across the BC output stage, which results in discharging/charging them into/from the HV side. The power flow is controlled in both directions by controlling the duty cycle. The proposed configuration provides self‐balancing operation thanks to the sequential connection of HB‐SMs capacitors, and it also provides the ability to operate with high conversion ratios. Illustration and analysis of the proposed converter and its closed‐loop controller are presented. A full design of the values and ratings of the involved components are presented. Simulation study for a 2.5 MW (25 kV/10 kV) DC–DC converter is presented. Finally, experimental results for a downscaled prototype are presented for validation.
Miniaturisation of switched beam array antenna using phase delay properties of CSRR‐loaded transmission line
Authors: Rao Patnam H. , Sajin Jaykumari Sajeevan , Kudesia Kushal
Published: May 2018

The application of phase delay property of complementary split‐ring resonator (CSRR)‐loaded transmission line in the miniaturisation of Butler matrix beam forming network is proposed. The design of left‐handed transmission line and the influence of the capacitive stubs in the phase delay properties of the CSRR‐loaded transmission line with a gap are presented. The CSRR‐loaded transmission line with a 7 mm capacitive stub provides 93° more phase delay than the CSRR‐loaded transmission line without the stubs. CSRR‐loaded transmission line with capacitive stubs is applied to the phase compensating lines of 4 × 4 Butler matrix configurations, without disturbing the 90° hybrids and crossovers. The CSRR‐loaded configuration exhibits a size reduction of 48% of the footprint of the conventional Butler matrix. The output of the miniaturised Butler matrix is connected to a linear microstrip antenna array of four radiating elements and its radiation parameters (beam pointing direction, beamwidth and sidelobe levels) are compared with that of an unloaded conventional 4 × 4 Butler matrix. The miniaturised switched beam‐steering antenna exhibits similar radiation characteristics as that of a conventional switched beam antenna.
Nanofluid‐based transformer oil: effect of ageing on thermal, electrical and physicochemical properties
Authors: Maharana Mrutyunjay , Bordeori Moon Moon , Nayak Sisir Kumar , Sahoo Niranjan
Published: May 2018

The development of nanofluids is necessary to replace the conventional transformer oil used in power and distribution transformers. A stable nanofluid has been prepared to verify its insulating and heat transfer performance in oxidative ageing environment. Due to the superior thermal and electrical properties of a nanoparticle (NP), its dispersion in mineral oil (MO) is expected to improve the dielectric and cooling properties of the nanofluid. This study presents a comparative assessment of the pre‐ and post‐ageing effects on MO and nanofluids. An open beaker, single temperature oxidative thermal ageing experiment is performed at 115°C for different ageing times, i.e. 164, 328, and 492 h. A concentration of 0.01 wt% of NP for both titanium oxide and exfoliated hexagonal boron nitride (Eh‐BN) is dispersed into a base fluid, i.e. MO, to prepare nanofluids. The important thermal, electrical and physicochemical properties of all the three insulating oils are analysed. The superior thermal, electrical and physicochemical performance of Eh‐BN/MO‐nanofluid is observed to be superior. Higher thermal conductivity, insulation and hydrophobic Eh‐BN NPs on dispersion with MO provide better cooling and insulation even after an ageing, thus confirm its usability as a novel nanofluid‐based transformer oil.
Optimally convergent hybridizable discontinuous Galerkin method for fifth-order Korteweg-de Vries type equations
Authors: Chen Yanlai , Dong Bo , Jiang Jiahua
Published: May 2018

We develop and analyze the first hybridizable discontinuous Galerkin (HDG) method for solving fifth-order Korteweg-de Vries (KdV) type equations. We show that the semi-discrete scheme is stable with proper choices of the stabilization functions in the numerical traces. For the linearized fifth-order equations, we prove that the approximations to the exact solution and its four spatial derivatives as well as its time derivative all have optimal convergence rates. The numerical experiments, demonstrating optimal convergence rates for both the linear and nonlinear equations, validate our theoretical findings.
Coordinated decision-making on manufacturer’s EPQ-based and buyer’s period review inventory policies with stochastic price-sensitive demand: A credit option approach
Authors: Jazinaninejad Mona , Seyedhosseini Seyed Mohammad , Hosseini-Motlagh Seyyed-Mahdi , Nematollahi Mohammadreza
Published: May 2018

Pricing and replenishment decisions are no longer internal issues within organizations and it is of high significance to coordinate such primary decisions from a supply chain (SC) perspective. In this study, for the first time, we develop a new method based on credit option to coordinate production, pricing, and periodic review policy decisions considering a manufacturer-buyer chain under price-sensitive stochastic demand. In the studied SC, the buyer applies a periodic review order-up-to level inventory policy and its decision variables are order-up-to level, selling price and review period. In this case, the manufacturer follows an economic production quantity (EPQ) policy and decides on production multiplier. Firstly, exact algorithms in addition to concavity analysis are addressed to find optimal decisions in centralized and decentralized structures. Afterwards, a credit option mechanism is proposed to obtain mutually acceptable decisions and create a win–win situation for the manufacturer and buyer. Numerical examples and sensitivity analysis along with a real case study are carried out to show the applicability and performance of the credit option contract. The results reveal the capability of the proposed credit option contract in coordinating pricing, production, and periodic review replenishment decisions; thereby encouraging both sides to accept the coordination mechanism. Moreover, the results indicate that the proposed credit option contract can even improve the SC profit more than centralized model under some circumstances.
Average covering number for some graphs
Authors: Doğan Durgun D. , Bagatarhan Ali
Published: May 2018

The interconnection networks are modeled by means of graphs to determine the reliability and vulnerability. There are lots of parameters that are used to determine vulnerability. The average covering number is one of them which is denoted by $ \overline{\beta }(G)$, where G is simple, connected and undirected graph of order n ≥ 2. In a graph G = (V(G), E(G)) a subset

$ {S}_v\subseteq V(G)$

of vertices is called a cover set of G with respect to v or a local covering set of vertex v, if each edge of the graph is incident to at least one vertex of Sv. The local covering number with respect to v is the minimum cardinality of among the Sv sets and denoted by βv. The average covering number of a graph G is defined as

β̅(G) = 1/|v(G)| ∑ν∈v(G)βν

In this paper, the average covering numbers of kth power of a cycle
$ {C}_n^k$ and Pn □ Pm, Pn □ Cm, cartesian product of Pn and Pm, cartesian product of Pn and Cm are given, respectively.
Time Dependence of Whole Blood Aggregation in Response to Platelet Activating Factor (PAF)
Authors: Taylor R R , Strophair J , Sturm M , Vandongen R , Beilin L J
Published: May 2018

The aggregation/adhesion response to platelet activating factor (PAF) was studied in diluted whole blood by impedance aggregometry. The extent of aggregation varied directly with the interval between blood sampling and aggregation measurement over the first 30 minutes from sampling, then remained stable for the next 60 minutes of observation. This is an effect opposite to that described for aggregation to PAF in platelet rich plasma which, however, cannot be studied soon after sampling. Time dependence of aggregation is important and comparative measurements should be made during the period of stable aggregability.
Predictors of Knee Arthrofibrosis and Outcomes after Arthroscopic Lysis of Adhesions following Ligamentous Reconstruction: A Retrospective Case–Control Study with Over Two Years' Average Follow-Up
Authors: Bodendorfer Blake M. , Keeling Laura E. , Michaelson Evan M. , Shu Henry T. , Apseloff Nicholas A. , Spratt James D. , Malone Patrick S. , Argintar Evan H.
Published: May 2018

Arthrofibrosis can be a devastating complication after ligamentous knee reconstruction. Beyond early range of motion (ROM), manipulation under anesthesia (MUA) and arthroscopic lysis of adhesions (LOAs) are the most frequently employed interventions for the condition. There is a paucity of data regarding predictive factors of arthrofibrosis requiring MUA and LOA, and even less data regarding changes in validated patient-reported outcome measures following the procedure. A retrospective case–control study was performed at an academic, urban Level I trauma center of patients that developed arthrofibrosis requiring MUA and LOA following ligamentous reconstruction. The indication for LOA was failure to achieve a 90° arc of ROM by 6 weeks. Seventeen cases and 141 controls were identified. Follow-up for cases was 26.9 ± 17.1 months (mean ± standard deviation). Time from initial reconstruction to LOA was 75.2 ± 27.9 days. Cases had higher body mass indices by a mean of 2.9 (p = 0.024). The most significant risk factors for stiffness were concomitant anterior cruciate ligament, posterior cruciate ligament, and posterolateral corner/lateral collateral ligament injury (odds ratio [OR], 17.08), knee dislocation (OR, 12.84), and use of an external fixator (OR, 12.81, 95% confidence interval [CI], 3.03–54.20) (all p < 0.0026). Mean Knee Injury and Osteoarthritis Outcome Scores, Western Ontario and McMaster Universities Osteoarthritis Indices, and International Knee Documentation Committee scores improved by 47.5, 50.5, and 47.3% (all p < 0.0038), respectively. All patients reported improvement in pain, with maximum daily pain scores improving by a mean of 4.1 points on the Numeric Pain Rating Scale (p < 0.001). Mean ROM arc improved by 38.8° (p < 0.001). All 17 cases were satisfied with the procedure. Twelve cases (70.59%) reported a full return to preinjury level of activity. No factors were identified that predicted success from the procedure, likely due to inadequate sample size. Arthrofibrosis following knee injury and ligamentous reconstruction can be predicted by the severity of injury and early intervention with MUA and arthroscopic LOA can lead to a satisfactory outcome for the patient.
Contrast-Enhanced Ultrasound and Near-Infrared Spectroscopy of the Neonatal Bowel: Novel, Bedside, Noninvasive, and Radiation-Free Imaging for Early Detection of Necrotizing Enterocolitis
Authors: Al-Hamad Suzanne , Hackam David , Goldstein Seth , Huisman Thierry , Darge Kassa , Hwang Misun
Published: May 2018

Despite extensive research and improvements in the field of neonatal care, the morbidity and mortality associated with necrotizing enterocolitis (NEC) have remained unchanged over the past three decades. Early detection of ischemia and necrotic bowel is vital in improving morbidity and mortality associated with NEC; however, strategies for predicting and preventing NEC are lacking. Contrast-enhanced ultrasound (CEUS) and near-infrared spectroscopy (NIRS) are novel techniques in pediatrics that have been proven as safe modalities. CEUS has benefits over conventional ultrasound (US) by its improved real-time evaluation of the micro- and macrovascularities of normally and abnormally perfused tissue. US has been implemented as a useful adjunct to X-ray for earlier evaluation of NEC. NIRS is another noninvasive technique that has shown promise in improving early detection of NEC. The purpose of this article is to review the current understanding of changes in bowel perfusion in NEC, discuss the accuracy of abdominal US in detecting NEC, and explain how the use of CEUS and NIRS will enhance the precise and early detection of altered/pathological bowel wall perfusion in the initial development and course of NEC.
Comparison of Serum and Cervical Cytokine Levels throughout Pregnancy between Preterm and Term Births
Authors: Ashford Kristin , Chavan Niraj , Wiggins Amanda , Sayre Molly , McCubbin Andrea , Critchfield Agatha , O'Brien John
Published: May 2018

Objective To assess differences in cytokine levels in cervicovaginal fluid (CVF) and serum across trimesters between women with preterm births (PTBs) and full-term births.

Study Design This multicenter study enrolled 302 women with a singleton gestation. CVF and serum cytokines, interleukin 1α (IL-1α), IL-1β, IL-6, IL-8, IL-10, C-reactive protein (CRP), tumor necrosis factor (TNF)-α, and matrix metalloproteinase (MMP)-8, were measured. Women with at least one cytokine assessment and noted PTB status in their medical record were retained in the study (N = 272). Data were analyzed using mixed modeling (main effects of PTBs and time/trimester).

Results For the CVF values of IL-6, IL-8, IL-10, TNF-α, and CRP, and serum MMP-8, those who delivered preterm had significantly higher values than the full-term group regardless of trimester. For the serum values of IL-1β, IL-6, and TNF-α, those delivering preterm had significantly lower values than those delivering full-term regardless of trimester. For IL-1β in CVF, the cytokine was significantly higher in the PTB group for second and third trimesters only, relative to the full-term group.

Conclusion For each CVF cytokine that differed by birth status, values were higher for PTB than term, averaged over trimester. Numerous cytokine profiles varied across trimesters in women delivering term versus preterm in both CVF and serum.
Validation of the kinetic-turbulent-neoclassical theory for edge intrinsic rotation in DIII-D
Authors: Ashourvan Arash , Grierson B. A. , Battaglia D. J. , Haskey S. R. , Stoltzfus-Dueck T.
Published: May 2018

In a recent kinetic model of edge main-ion (deuterium) toroidal velocity, intrinsic rotation results from neoclassical orbits in an inhomogeneous turbulent field [T. Stoltzfus-Dueck, Phys. Rev. Lett. 108, 065002 (2012)]. This model predicts a value for the toroidal velocity that is co-current for a typical inboard X-point plasma at the core-edge boundary (ρ ∼ 0.9). Using this model, the velocity prediction is tested on the DIII-D tokamak for a database of L-mode and H-mode plasmas with nominally low neutral beam torque, including both signs of plasma current. Values for the flux-surface-averaged main-ion rotation velocity in the database are obtained from the impurity carbon rotation by analytically calculating the main-ion—impurity neoclassical offset. The deuterium rotation obtained in this manner has been validated by direct main-ion measurements for a limited number of cases. Key theoretical parameters of ion temperature and turbulent scale length are varied across a wide range in an experimental database of discharges. Using a characteristic electron temperature scale length as a proxy for a turbulent scale length, the predicted main-ion rotation velocity has a general agreement with the experimental measurements for neutral beam injection (NBI) powers in the range PNBI < 4 MW. At higher NBI power, the experimental rotation is observed to saturate and even degrade compared to theory. TRANSP-NUBEAM simulations performed for the database show that for discharges with nominally balanced—but high powered—NBI, the net injected torque through the edge can exceed 1 Nm in the counter-current direction. The theory model has been extended to compute the rotation degradation from this counter-current NBI torque by solving a reduced momentum evolution equation for the edge and found the revised velocity prediction to be in agreement with experiment. Using the theory modeled—and now tested—velocity to predict the bulk plasma rotation opens up a path to more confidently projecting the confinement and stability in ITER.
2D discontinuous piecewise linear map: Emergence of fashion cycles
Authors: Gardini L. , Sushko I. , Matsuyama K.
Published: May 2018

We consider a discrete-time version of the continuous-time fashion cycle model introduced in Matsuyama, 1992. Its dynamics are defined by a 2D discontinuous piecewise linear map depending on three parameters. In the parameter space of the map periodicity, regions associated with attracting cycles of different periods are organized in the period adding and period incrementing bifurcation structures. The boundaries of all the periodicity regions related to border collision bifurcations are obtained analytically in explicit form. We show the existence of several partially overlapping period incrementing structures, that is, a novelty for the considered class of maps. Moreover, we show that if the time-delay in the discrete time formulation of the model shrinks to zero, the number of period incrementing structures tends to infinity and the dynamics of the discrete time fashion cycle model converges to those of continuous-time fashion cycle model.
Electromagnetically Induced Transparency (EIT) and Autler-Townes (AT) splitting in the presence of band-limited white Gaussian noise
Authors: Simons Matthew T. , Kautz Marcus D. , Holloway Christopher L. , Anderson David A. , Raithel Georg , Stack Daniel , St. John Marc C. , Su Wansheng
Published: May 2018

We investigate the effect of band-limited white Gaussian noise (BLWGN) on electromagnetically induced transparency (EIT) and Autler-Townes (AT) splitting, when performing atom-based continuous-wave (CW) radio-frequency (RF) electric (E) field strength measurements with Rydberg atoms in an atomic vapor. This EIT/AT-based E-field measurement approach is currently being investigated by several groups around the world as a means to develop a new International System of Units traceable RF E-field measurement technique. For this to be a useful technique, it is important to understand the influence of BLWGN. We perform EIT/AT based E-field experiments with BLWGN centered on the RF transition frequency and for the BLWGN blue-shifted and red-shifted relative to the RF transition frequency. The EIT signal can be severely distorted for certain noise conditions (bandwidth, center frequency, and noise power), hence altering the ability to accurately measure a CW RF E-field strength. We present a model to predict the line shifts and broadenings in the EIT signal in the presence of noise. This model includes AC Stark shifts and on resonance transitions associated with the noise source. The results of this model are compared to the experimental data, and we find very good agreement between the two.
Au147 nanoparticles: Ordered or amorphous?
Authors: Tarrat Nathalie , Rapacioli Mathias , Spiegelman Fernand
Published: May 2018

Structural aspects of the Au147 cluster have been investigated through a density functional based tight binding global optimization involving a parallel tempering molecular dynamics scheme with quenching followed by geometries relaxation at the Density Functional Theory (DFT) level. The focus is put on the competition between relaxed ordered regular geometries and disordered (or amorphous) structures. The present work shows that Au147 amorphous geometries are relevant low energy candidates and are likely to contribute in finite temperature dynamics and thermodynamics. The structure of the amorphous-like isomers is discussed from the anisotropy parameters, the atomic coordinations, the radial and pair distribution functions, the IR spectra, and the vibrational DOS. With respect to the regular structures, the amorphous geometries are shown to be characterized by a larger number of surface atoms, a less dense volume with reduced coordination number per atom, a propensity to increase the dimension of flat facets at the surface, and a stronger anisotropy. Moreover, all amorphous clusters have similar IR spectra, almost continuous with active frequencies over the whole spectral range, while symmetric clusters are characterized by a few lines with large intensities.
Fractal attractors in economic growth models with random pollution externalities
Authors: La Torre Davide , Marsiglio Simone , Privileggi Fabio
Published: May 2018

We analyze a discrete time two-sector economic growth model where the production technologies in the final and human capital sectors are affected by random shocks both directly (via productivity and factor shares) and indirectly (via a pollution externality). We determine the optimal dynamics in the decentralized economy and show how these dynamics can be described in terms of a two-dimensional affine iterated function system with probability. This allows us to identify a suitable parameter configuration capable of generating exactly the classical Barnsley's fern as the attractor of the log-linearized optimal dynamical system.
Carbonization temperature controlled thermal conductivity of graphitic carbon nanoparticles and their polymer composites
Authors: Zhu Weiwei , Meng Xianrui , Zhan Yanshan , Li Hanmei , Ma Jie , Liu Junxia , Zhai Cuiping , Zhang Wenkai , Fang Xiaomin , Ding Tao
Published: May 2018

Carbon materials as versatile fillers have drawn increasing attention in thermal conductive polymer composites, however, the thermal conductivity (TC) regulation of them remains challenging. Herein, the tunable lattice thermal conductivity is reported for glucose derived graphitic carbon nanoparticles (GCPs) and their polymer composites. Both the in-plane (La) and out-of-plane (Lc) coherence lengths of GCPs increase with carbonization temperature in the range of 700 °C to 1300 °C. The intrinsic TC of GCPs film is directly extracted from the dependence of the Raman G peak frequency on the excitation laser power and the first order temperature coefficient. It is found that the in-plane lattice TC increases exponentially with both of the increasing La and decreasing defect concentration. The GCPs are then used as highly processible fillers to fabricate thermoset composites based on reactive benzoxazine (BA-a). The total TC of the poly(BA-a)/GCPs are found increase monotonically from 0.27 W·m-1·K-1 to 0.34 W·m-1·K-1 with the increasing graphitization levels of GCPs, and a clear signature of thermal percolation threshold at 6 vol% GCPs loadings is also observed.
Electrical leakage phenomenon in heteroepitaxial cubic silicon carbide on silicon
Authors: Pradeepkumar Aiswarya , Zielinski Marcin , Bosi Matteo , Verzellesi Giovanni , Gaskill D. Kurt , Iacopi Francesca
Published: May 2018

Heteroepitaxial 3C-SiC films on silicon substrates are of technological interest as enablers to integrate the excellent electrical, electronic, mechanical, thermal, and epitaxial properties of bulk silicon carbide into well-established silicon technologies. One critical bottleneck of this integration is the establishment of a stable and reliable electronic junction at the heteroepitaxial interface of the n-type SiC with the silicon substrate. We have thus investigated in detail the electrical and transport properties of heteroepitaxial cubic silicon carbide films grown via different methods on low-doped and high-resistivity silicon substrates by using van der Pauw Hall and transfer length measurements as test vehicles. We have found that Si and C intermixing upon or after growth, particularly by the diffusion of carbon into the silicon matrix, creates extensive interstitial carbon traps and hampers the formation of a stable rectifying or insulating junction at the SiC/Si interface. Although a reliable p-n junction may not be realistic in the SiC/Si system, we can achieve, from a point of view of the electrical isolation of in-plane SiC structures, leakage suppression through the substrate by using a high-resistivity silicon substrate coupled with deep recess etching in between the SiC structures.
Leakage current and charging/discharging processes in barrier-type anodic alumina thin films for use in metal-insulator-metal capacitors
Authors: Hourdakis E. , Koutsoureli M. , Papaioannou G. , Nassiopoulou A. G.
Published: May 2018

Barrier-type anodic alumina thin films are interesting for use in high capacitance density metal-insulator-metal capacitors due to their excellent dielectric properties at small thickness. This thickness is easily controlled by the anodization voltage. In previous papers we studied the main parameters of interest of the Al/barrier-type anodic alumina/Al structure for use in RF applications and showed the great potential of barrier-type anodic alumina in this respect. In this paper, we investigated in detail charging/discharging processes and leakage current of the above dielectric material. Two different sets of metal-insulator-metal capacitors were studied, namely, with the top Al electrode being either e-gun deposited or sputtered. The dielectric constant of the barrier-type anodic alumina was found at 9.3. Low leakage current was observed in all samples studied. Furthermore, depending on the film thickness, field emission following the Fowler-Nordheim mechanism was observed above an applied electric field. Charging of the anodic dielectric was observed, occurring in the bulk of the anodic layer. The stored charge was of the order of few μC/cm2 and the calculated trap density ∼2 × 1018 states/cm3, the most probable origin of charge traps being, in our opinion, positive electrolyte ions trapped in the dielectric during anodization. We do not think that oxygen vacancies play an important role, since their existence would have a more important impact on the leakage current characteristics, such as resistive memory effects or significant changes during annealing, which were not observed. Finally, discharging characteristic times as high as 5 × 109 s were measured.
Resonance dynamics of DCO (X̃ A′2) simulated with the dynamically pruned discrete variable representation (DP-DVR)
Authors: Larsson Henrik R. , Riedel Jens , Wei Jie , Temps Friedrich , Hartke Bernd
Published: May 2018

Selected resonance states of the deuterated formyl radical in the electronic ground state X̃ A′2 are computed using our recently introduced dynamically pruned discrete variable representation [H. R. Larsson, B. Hartke, and D. J. Tannor, J. Chem. Phys. 145, 204108 (2016)]. Their decay and asymptotic distributions are analyzed and, for selected resonances, compared to experimental results obtained by a combination of stimulated emission pumping and velocity-map imaging of the product D atoms. The theoretical results show good agreement with the experimental kinetic energy distributions. The intramolecular vibrational energy redistribution is analyzed and compared with previous results from an effective polyad Hamiltonian. Specifically, we analyzed the part of the wavefunction that remains in the interaction region during the decay. The results from the polyad Hamiltonian could mainly be confirmed. The C=O stretch quantum number is typically conserved, while the D—C=O bend quantum number decreases. Differences are due to strong anharmonic coupling such that all resonances have major contributions from several zero-order states. For some of the resonances, the coupling is so strong that no further zero-order states appear during the dynamics in the interaction region, even after propagating for 300 ps.
A theoretical investigation of the influence of the second critical micelle concentration on the solubilization capacity of surfactant micelles
Authors: Bergström L. M.
Published: May 2018

The solubilization of hydrophobic components by surfactants that form microemulsion droplets has been investigated from a theoretical point of view. By means of combining thermodynamics of self-assembly to form small systems with bending elasticity theory, we have been able to demonstrate a strong correlation between the second critical micelle concentration (CMC2) of surfactant micelles and their solubilization capacity (σ). The correlation may be rationalized as a consequence of all three bending elasticity constants spontaneous curvature (H0), bending rigidity (kc) and saddle-splay constant (k¯c) showing similar trends with respect to the two quantities, i.e. σ increases and CMC2 decreases with decreasing values of kcH0 and increasing values of kc and k¯c, respectively. As a result, we demonstrate that the solubilization capacity is predicted to always be higher for a gemini surfactant with CMC2 = 11 mM as compared with a gemini surfactant with CMC2 = 18 mM. The predicted correlation between solubilization capacity and CMC2 agrees with experimental observations showing that surfactants forming larger micelles in general have better solubilization capacity than surfactants forming smaller micelles. The theory also demonstrates, in agreement with experiments, that σ is raised in the entire range of surfactant concentrations, below as well as above CMC2, regardless of micelle size. Consequently, our theory predicts that small micelles formed below CMC2 increase in size, whereas large rodlike or wormlike micelles formed above CMC2 decrease in size, as a hydrophobic solubilizate is added to a micellar solution.
In vitro models of molecular and nano-particle transport across the blood-brain barrier
Authors: Hajal Cynthia , Campisi Marco , Mattu Clara , Chiono Valeria , Kamm Roger D.
Published: May 2018

The blood-brain barrier (BBB) is the tightest endothelial barrier in humans. Characterized by the presence of tight endothelial junctions and adherens junctions, the primary function of the BBB is to maintain brain homeostasis through the control of solute transit across the barrier. The specific features of this barrier make for unique modes of transport of solutes, nanoparticles, and cells across the BBB. Understanding the different routes of traffic adopted by each of these is therefore critical in the development of targeted therapies. In an attempt to move towards controlled experimental assays, multiple groups are now opting for the use of microfluidic systems. A comprehensive understanding of bio-transport processes across the BBB in microfluidic devices is therefore necessary to develop targeted and efficient therapies for a host of diseases ranging from neurological disorders to the spread of metastases in the brain.
Kinetics of pattern formation in symmetric diblock copolymer melts
Authors: Ren Yongzhi , Müller Marcus
Published: May 2018

In equilibrium, copolymers self-assemble into spatially modulated phases with long-range order. When the system is quenched far below the order-disorder transition temperature, however, such an idealized, defect-free structure is difficult to obtain in experiments and simulations, instead a fingerprint-like structure forms. The relaxation toward long-range order is very protracted because it involves numerous thermally activated processes, and the rugged free-energy landscape has been likened to that of glass-forming systems. Using large-scale particle-based simulations of high-aspect-ratio, quasi-two-dimensional systems with periodic boundary condition, we study the kinetics of structure formation in symmetric, lamella-forming diblock copolymers after a quench from the disordered state. We characterize the ordering process by the correlation length of the lamellar structure and its Euler characteristic and observe that the growth of the correlation length and the rate of change of the Euler characteristic significantly slow down in the range of incompatibilities, 15 ≤ χN ≤ 20, studied. The increase of the time scale of ordering is, however, gradual. The density fields of snapshots of the particle-based simulations are used as starting values for self-consistent field theory (SCFT) calculations. The latter converge to the local, metastable minimum of the free-energy basin. This combination of particle-based simulations and SCFT calculations allows us to relate an instantaneous configuration of the particle-based model to a corresponding metastable free-energy minimum of SCFT—the inherent morphology—and we typically observe that a change of a free-energy basin is associated with a change of the Euler characteristic of the particle-based morphology, i.e., changes of free-energy basins are correlated to changes of the domain topology. Subsequently, we employ the string method in conjunction with SCFT to study the minimum free-energy paths (MFEPs) of changes of the domain topology. Since the time scales of relaxing toward the inherent morphology within a free-energy basin and jumps between free-energy basins are not well separated, the MFEP may overestimate the barriers encountered in the course of ordering.
Electrostatic shock structures in dissipative multi-ion dusty plasmas
Authors: Elkamash I. S. , Kourakis I.
Published: May 2018

A comprehensive analytical model is introduced for shock excitations in dusty bi-ion plasma mixtures, taking into account collisionality and kinematic (fluid) viscosity. A multicomponent plasma configuration is considered, consisting of positive ions, negative ions, electrons, and a massive charged component in the background (dust). The ionic dynamical scale is focused upon; thus, electrons are assumed to be thermalized, while the dust is stationary. A dissipative hybrid Korteweg–de Vries/Burgers equation is derived. An analytical solution is obtained, in the form of a shock structure (a step-shaped function for the electrostatic potential, or an electric field pulse) whose maximum amplitude in the far downstream region decays in time. The effect of relevant plasma configuration parameters, in addition to dissipation, is investigated. Our work extends earlier studies of ion-acoustic type shock waves in pure (two-component) bi-ion plasma mixtures.
Improving performance of Si/CdS micro-/nanoribbon p-n heterojunction light emitting diodes by trenched structure
Authors: Huang Shiyuan , Wu Yuanpeng , Ma Xiangyang , Yang Zongyin , Liu Xu , Yang Qing
Published: May 2018

Realizing high performance silicon based light sources has been an unremitting pursuit for researchers. In this letter, we propose a simple structure to enhance electroluminescence emission and reduce the threshold of injected current of silicon/CdS micro-/nanoribbon p-n heterojunction visible light emitting diodes, by fabricating trenched structure on silicon substrate to mount CdS micro-/nanoribbon. A series of experiments and simulation analysis favors the rationality and validity of our mounting design. After mounting the CdS micro-/nanoribbon, the optical field confinement increases, and absorption and losses from high refractive silicon substrate are effectively reduced. Meanwhile the sharp change of silicon substrate near heterojunction also facilitates the balance between electron current and hole current, which substantially conduces to the stable amplification of electroluminescence emission in CdS micro-/nanoribbon.
Analysis of the coupled electron-ripplon oscillations resonance spectra in the Wigner solid at different temperatures and modeling of the excitation process
Authors: Syvokon V. E. , Sharapova I. V.
Published: May 2018

The spectrum of coupled electron-ripplon oscillations in a Wigner crystal on the surface of superfluid helium at various temperatures and excitation voltages, leading to spectrum distortion, was studied experimentally. It was shown that at all temperatures, increasing excitation voltage leads to the appearance of non-axisymmetric vibrational modes, which indicates distortions of the crystal lattice. The possibility of excitation of the non-axisymmetric modes in a cell was demonstrated by modeling electronic crystal oscillations using the molecular dynamics method. At several fixed frequencies, the amplitudes of the response of the electronic crystal to external excitation were measured as a function of the magnitude of excitation voltage, and jumps were detected at certain critical voltages. Using the Lindemann criterion, a correlation was found between the critical stress and stability limit of the crystal lattice. It was concluded that when the critical voltage is reached, dynamic melting of the electronic crystal occurs.
Energy migration processes in phosphate nanocrystals: Size and dimensionality dependence
Authors: Kononets N. V. , Seminko V. V. , Maksimchuk P. O. , Bespalova I. I. , Klochkov V. K. , Malyukin Yu. V.
Published: May 2018

Peculiarities of electronic excitation energy migration in phosphate nanocrystals with three-dimensional (EuPO4) and one-dimensional (EuP3O9) arrangement of regular ions under variation of concentration of both energy traps (Nd3+ ions) and scattering centres (La3+ ions) are discussed in the paper. Processes of energy migration in both EuPO4 and EuP3O9 nanocrystals are phonon-assisted ones due to absence of resonance between energy levels of adjacent Eu3+ ions. The distance of energy migration for both EuPO4 and EuP3O9 nanocrystals was found to be equal to tens of nanometres, however, for EuPO4 nanocrystals energy migration leads to stronger quenching of Eu3+ luminescence. For 10 nm EuPO4 nanocrystals sufficient hampering of energy migration is observed due to the depletion of the low-energy phonon spectrum as a result of the phonon confinement effect.
Antiferromagnetic resonance in a GdCr3(BO3)4 crystal
Authors: Bludov A. N. , Savina Yu. O. , Kobets M. I. , Pashchenko V. A. , Gnatchenko S. L. , Kuzmin N. N. , Mal'tsev V. V. , Leonyuk N. I.
Published: May 2018

An experimental study of AFMR in a GdCr3(BO3)4 single crystal within the frequency range of 17–38 GHz, at the temperature 4.2 K, was performed. The determined value of the energy gap in spin-wave spectrum equals (25.5 ± 0.5). It was shown that the high-frequency properties of gadolinium chromium borate are well defined within the framework of a two-sublattice antiferromagnet model with “easy-plane” anisotropy.
Higher harmonic waveforms are revealed in nonlinear structures of magnetized plasma
Authors: Agner Mary Alexandra
Published: May 2018

Newly found characteristics of nonlinear streamer structures in magnetized plasma include self-coupled higher harmonics, plus a relation between the streamer’s envelope and the mediator’s waveform.
Dependency parsing of learner English
Authors: Huang Yan , Murakami Akira , Alexopoulou Theodora , Korhonen Anna
Published: May 2018

Current syntactic annotation of large-scale learner corpora mainly resorts to “standard parsers” trained on native language data. Understanding how these parsers perform on learner data is important for downstream research and application related to learner language. This study evaluates the performance of multiple standard probabilistic parsers on learner English. Our contributions are three-fold. Firstly, we demonstrate that the common practice of constructing a gold standard – by manually correcting the pre-annotation of a single parser – can introduce bias to parser evaluation. We propose an alternative annotation method which can control for the annotation bias. Secondly, we quantify the influence of learner errors on parsing errors, and identify the learner errors that impact on parsing most. Finally, we compare the performance of the parsers on learner English and native English. Our results have useful implications on how to select a standard parser for learner English.
The development of phrasal complexity in German intermediate learners of English
Authors: Kreyer Rolf , Schaub Steffen
Published: May 2018

On the basis of a longitudinal corpus of English produced by German intermediate learners, the present paper explores how noun phrase (NP) complexity develops in terms of global measures of complexity (length, number of modifiers per 1,000 words) in learner data on an intermediate level of competence and describes how the use of individual NP-modification structures changes as learners progress through their three final years of secondary school. An additional objective is to testBiber et al.’s (2011)hypothesized stages of acquisition against our data of intermediate learner English, complementing the data of advanced learner English provided byParkinson & Musgrave (2014). Our results show that global measures of NP complexity remain stable as learners progress from grades 10 to 12. Zooming in on individual learners and features, the results lend tentative support toBiber et al.’s (2011)stages of acquisition. However, individual variation influences the frequency of noun-phrasal modifiers.