bluuebunny/crossref_metadata_2025 huggingface dataset:
Highly active and durable platinum-lead bimetallic alloy nanoflowers for formic acid electrooxidation
Authors: Gong Mingxing , Li Fumin , Yao Zhigang , Zhang Suqi , Dong Jingwen , Chen Yu , Tang Yawen
Published: February 2015

Pt84Pb16bimetallic alloy nanoflowers were synthesized by a simple hydrothermal method and exhibit an enhanced catalytic activity towards formic acid electrooxidation.
Cationic iridium-catalyzed C–H alkylation of 2-substituted pyridine N-oxides with acrylates
Authors: Shibata Takanori , Takano Hideaki
Published: February 2015

The reaction of 2-arylmethyl-, 2-aryl-, and 2-alkyl substituted pyridine N-oxides with acrylates proceeded in the presence of a cationic Ir-rac-BINAP catalyst under heating conditions.
Alkali and alkaline-earth metal complexes with tetraoxa[8]circulene sheet: a computational study by DFT and QTAIM methods
Authors: Karaush Nataliya N. , Baryshnikov Gleb V. , Minaev Boris F.
Published: February 2015

The optimized structure of the sandwich-type complexes [M(TOC)2]n+(M = K+, Ca2+).
Coaxial carbon nanofiber/NiO core–shell nanocables as anodes for lithium ion batteries
Authors: Park Seok-Hwan , Lee Wan-Jin
Published: February 2015

The CNF/NiO core–shell nanocables are prepared by electrospinning and electrophoretic deposition. The CNF/NiO nanocables deliver a high reversible capacity of 825 mA h g−1 at 200 mA g−1 after 50 charge–discharge cycles without showing obvious decay.
Novel supramolecular assemblies of repulsive DNA–anionic porphyrin complexes based on covalently modified multi-walled carbon nanotubes and cyclodextrins
Authors: Ning Jingheng , Wang Yufang , Wu Qi , Zhang Xuefeng , Lin Xianfu , Zhao Hongbin
Published: February 2015

A strategy for constructing novel DNA–anionic porphyrin supramolecular assemblies by “fixation” of CNTs and “inclusion” of CDs was reported.
Catalytic alcoholysis of urea to diethyl carbonate over calcined Mg–Zn–Al hydrotalcite
Authors: Wang Peixue , Liu Shimin , Zhou Feng , Yang Benqun , Alshammari Ahmad S. , Deng Youquan
Published: February 2015

The synthesis of diethyl carbonate (DEC) from urea and ethanol was carried out over Mg–Zn–Al composite oxide catalysts derived from hydrotalcites (HTs).
Low frequency ultrasound assisted sequential and co-precipitation syntheses of nanoporous RE (Gd and Sm) doped cerium oxide
Authors: Sathishkumar Panneerselvam , Mangalaraja Ramalinga Viswanathan , Pandiyarajan Thangaraj , Gracia-Pinilla M. A. , Escalona N. , Herrera C. , Garcia R.
Published: February 2015

Cerium oxide (CeO2), Ce0.9Gd0.1O1.95 and Ce0.9Sm0.1O1.95 nanostructures were synthesized using 42 kHz ultrasound assisted sequential and co-precipitation techniques.
Mechanical properties of structurally-defined magnetoactive polymer (co)networks
Authors: Mpekris Fotios , Achilleos Mariliz , Vasile Eugenia , Vasile Eugeniu , Krasia-Christoforou Theodora , Stylianopoulos Triantafyllos
Published: February 2015

Magnetic nanoparticle loading increases mechanical properties of structurally-defined magnetoactive polymer (co)networks.
Cathodic electrochemiluminescence behavior of an ammonolysis product of 3,4,9,10-perylenetetracarboxylic dianhydride in aqueous solution and its application for detecting dopamine
Authors: Lu Qiyi , Zhang Juanjuan , Wu Yuanya , Yuan Ruo , Chen Shihong
Published: February 2015

The preparation process and cathodic electrochemiluminescence behavior of an ammonolysis product of 3,4,9,10-perylenetetracarboxylic dianhydride in an aqueous solution.
Solution of coupled partial differential equations of a packed bed reactor for SO2 removal by lime using the finite element method
Authors: Moshiri H. , Nasernejad B. , Ale Ebrahim H. , Taheri M.
Published: February 2015

In the present work, the reaction of SO2 with a single pellet and also a packed bed reactor of conventional and macropore lime was simulated by applying the random pore model.
Voltammetric studies on the inter-relationship between the redox chemistry of TTF, TTF+˙, TTF2+ and HTTF+ in acidic media
Authors: Adeel Shaimaa , Abdelhamid Muhammad E. , Nafady Ayman , Li Qi , Martin Lisandra L. , Bond Alan M.
Published: February 2015

The chemistry of oxidized forms of TTF in acidified CH3CN has been established using electrochemical and spectroscopic techniques.
High-throughput imaging assay of multiple proteins via target-induced DNA assembly and cleavage
Authors: Zong Chen , Wu Jie , Liu Mengmeng , Yan Feng , Ju Huangxian
Published: February 2015

A versatile imaging strategy integrated with target-induced DNA assembly and cleavage was designed for an assay for multiple proteins.
Synthesis of graphene@Fe3O4@C core–shell nanosheets for high-performance lithium ion batteries
Authors: Zhang Zehui , Wang Fei , An Qiao , Li Wei , Wu Peiyi
Published: February 2015

Graphene@Fe3O4@C core–shell nanosheets are synthesized by a one-pot solvothermal method, which are promising candidates as anodes in LIB applications.
Multiformity and fluctuation of Cu ordering in Cu2Se thermoelectric materials
Authors: Lu Ping , Liu Huili , Yuan Xun , Xu Fangfang , Shi Xun , Zhao Kunpeng , Qiu Wujie , Zhang Wenqing , Chen Lidong
Published: February 2015

Ultra-low thermal conductivity resulting from multiformity and fluctuation of Cu ordering in Cu2Se thermoelectric materials.
Efficient solid-state white light-emitting electrochemical cells employing embedded red color conversion layers
Authors: Lu Jung-Sheng , Chen Hsiao-Fan , Kuo Jung-Chin , Sun Ray , Cheng Chia-Yu , Yeh Yun-Shiuan , Su Hai-Ching , Wong Ken-Tsung
Published: February 2015

White LECs containing embedded red color conversion layers exhibit EQE and power efficiency of up to 12.5% and 27 lm W−1, respectively.
Ionic liquid-assisted synthesis of ultralong nanowires of zinc octaethylporphyrin and their photoresponse
Authors: Lu Ying , Wang Feng-Xia , Yang Bo , Zhang Qing-Guo , Pan Ge-Bo
Published: February 2015

Ultralong nanowires of ZnOEP were fabricated by an IL-assisted solution-phase precipitative method and were directly used in the construction of a prototype photodetector, exhibiting excellent performance.
In situ synthesis of metal–organic frameworks in a porous polymer monolith as the stationary phase for capillary liquid chromatography
Authors: Yang Shengchao , Ye Fanggui , Zhang Cong , Shen Shufen , Zhao Shulin
Published: February 2015

In this study, HKUST-1 was synthesized in situ on the porous polymer monolith as the stationary phase for capillary liquid chromatography (cLC).
FT-MIR modelling enhancement for the quantitative determination of haemoglobin in human blood by combined optimization of grid-search LSSVR algorithm with different pre-processing modes
Authors: Chen Hua-Zhou , Ai Wu , Feng Quan-Xi , Tang Guo-Qiang
Published: February 2015

Combined optimization of grid-search LSSVR modelling with SNV-SGS pre-processing improves the predictive abilities of the FT-MIR analysis of human blood HGB.
Oxalic acid complexes: promising draw solutes for forward osmosis (FO) in protein enrichment
Authors: Ge Qingchun , Chung Tai-Shung
Published: February 2015

Efficient protein enrichment was achieved through novel oxalic acid complex promoted forward osmosis membrane technology.
Polymerase synthesis of DNA labelled with benzylidene cyanoacetamide-based fluorescent molecular rotors: fluorescent light-up probes for DNA-binding proteins
Authors: Dziuba Dmytro , Pohl Radek , Hocek Michal
Published: February 2015

Fluorescent molecular rotors are for the first time used as light-up probes for sensing of DNA–protein interaction.
Thermodynamics of nanoalloys
Authors: Calvo Florent
Published: February 2015

Nanoalloys exhibit composition- and size-dependent shapes that are influenced by temperature at equilibrium.
Edge reconstruction in armchair phosphorene nanoribbons revealed by discontinuous Galerkin density functional theory
Authors: Hu Wei , Lin Lin , Yang Chao
Published: February 2015

We use DGDFT based AIMD calculations to reveal that a 2 × 1 edge reconstruction appears in ACPNRs at room temperature.
Design and photovoltaic characterization of dialkylthio benzo[1,2-b:4,5-b′]dithiophene polymers with different accepting units
Authors: Ge Guidong , Gu Jinan , Yu Jiangsheng , Zhu Enwei , Hai Jiefeng , Bian Linyi , Zhang Fujun , Xu Zhongsheng , Ma Wanli , Tang Weihua
Published: February 2015

Three dialkylthio benzo[1,2-b:4,5-b′]dithiophene polymers were developed with tuned bandgaps exhibiting a highest PCE value of 5.63% obtained for the polymer solar cells.
Electron transfer and catalysis with high-valent metal-oxo complexes
Authors: Fukuzumi Shunichi
Published: February 2015

High-valent metal-oxo complexes are produced by thermal and photoinduced electron-transfer reactions, acting as catalysts for oxygenation of substrates using water or dioxygen as an oxygen source.
Microfluidic paper-based analytical devices fabricated by low-cost photolithography and embossing of Parafilm®
Authors: Yu Ling , Shi Zhuan Zhuan
Published: February 2015

The combination of photolithography-patterning and embossing of a Parafilm® can fabricate microfluidic paper-based analytical devices (μPADs) without the use of a wax printer, cutter plotter and wet-chemical processing of paper.
Nanoarchitectonics: a new materials horizon for nanotechnology
Authors: Ariga Katsuhiko , Ji Qingmin , Nakanishi Waka , Hill Jonathan P. , Aono Masakazu
Published: February 2015

A paradigm shift from nanotechnology to nanoarchitectonics has been proposed.
Identification of dopaminergic neurons of the substantia nigra pars compacta as a target of manganese accumulation
Authors: Robison Gregory , Sullivan Brendan , Cannon Jason R. , Pushkar Yulia
Published: February 2015

A combined approach of FluoroGold™ retrograde tracer injection and XRF imaging to performin situmeasurement of manganese content and distribution in dopaminergic cells of the rodent substantia nigra compacta.
Host–guest interaction of coumarin-derivative dyes and cucurbit[7]uril: leading to the formation of supramolecular ternary complexes with mercuric ions
Authors: Aliaga Margarita E. , García-Río Luis , Pessêgo Márcia , Montecinos Rodrigo , Fuentealba Denis , Uribe Iván , Martín-Pastor Manuel , García-Beltrán Olimpo
Published: February 2015

The interaction between the studied coumarin derivatives-cucurbit[7]uril complexes and mercuric ions displays a positive cooperative effect relative to the dyes alone.
Synthesis and magnetostructural studies of amine functionalized superparamagnetic iron oxide nanoparticles
Authors: Salunkhe A. B. , Khot V. M. , Ruso J. M. , Patil S. I.
Published: February 2015

Superparamagnetic iron oxide nanoparticles are synthesized through the co precipitation method by using the new generation base diisopropylamine (DIPA) which electrostatically complexes with the iron ions, reduces them and subsequently caps the nanoparticles.
Molecular level interactions in binary mixtures of 1-ethyl 3-methylimidazolium tetrafluoroborate and water
Authors: Marium Mayeesha , Rahman M. Muhibur , Mollah M. Yousuf A. , Susan Md. Abu Bin Hasan
Published: February 2015

NIR spectroscopic analysis and DLS measurements were carried out to study hydrogen bonding and aggregation in ionic liquid–water binary mixtures.
Silica microspheres containing high density surface hydroxyl groups as efficient epoxidation catalysts
Authors: Chandra Prakash , Doke Dhananjay S. , Umbarkar Shubhangi B. , Vanka Kumar , Biradar Ankush V.
Published: February 2015

Uniformly sized silica microspheres were synthesized by a hydrolysis–condensation method and very efficient for epoxidation of olefine using hydrogen peroxide as green oxidant.
Crystallographic sites of Eu2+ and Eu2+–Tb3+ energy transfer in Sr2LiSiO4F
Authors: Xie Mubiao , Li Dongyu , Pan Rongkai , Zhou Xiaoping , Zhu Guoxian
Published: February 2015

Eu2+ ions occupy two crystallographic sites with emission at 475 nm and 520 nm in Sr2LiSiO4F:Eu2+.
Stabilization and fabrication of microbubbles: applications for medical purposes and functional materials
Authors: Lee Mina , Lee Eun Yeol , Lee Daeyeon , Park Bum Jun
Published: February 2015

In this review, we discuss the controlled stability of microbubbles, recent developments in a variety of microbubble preparation techniques, and applications of bubbles for medicine and functional materials.
Correction: Inkjet printed paper based frequency selective surfaces and skin mounted RFID tags: the interrelation between silver nanoparticle ink, paper substrate and low temperature sintering technique
Authors: Sanchez-Romaguera Veronica , Wünscher Sebastian , Turki Badredin M. , Abbel Robert , Barbosa Silvia , Tate Daniel J. , Oyeka Dumtoochukwu , Batchelor John C. , Parker Edward A. , Schubert Ulrich S. , Yeates Stephen G.
Published: February 2015

Correction for ‘Inkjet printed paper based frequency selective surfaces and skin mounted RFID tags: the interrelation between silver nanoparticle ink, paper substrate and low temperature sintering technique' by Veronica Sanchez-Romaguera et al., J. Mater. Chem. C, 2015, DOI: 10.1039/c4tc02693d.
Microemulsions, modulated phases and macroscopic phase separation: a unified picture of rafts
Authors: Giang Ha , Shlomovitz Roie , Schick Michael
Published: February 2015

We consider two mechanisms that can lead to an inhomogeneous distribution of components in a multicomponent lipid bilayer: macroscopic phase separation and the formation of modulated phases. A simple model that encompasses both mechanisms displays a phase diagram that also includes a structured fluid, a microemulsion. Identifying rafts with the inhomogeneities of this structured fluid, we see how rafts are related to the occurrence of macroscopic phase separation or the formation of modulated phases in other systems, and focus our attention on specific differences between them.
Auditory Learning Using a Portable Real-Time Vocoder: Preliminary Findings
Authors: Casserly Elizabeth D. , Pisoni David B.
Published: February 2015

Purpose

Although traditional study of auditory training has been in controlled laboratory settings, interest has been increasing in more interactive options. The authors examine whether such interactive training can result in short-term perceptual learning, and the range of perceptual skills it impacts.

Method

Experiments 1 (
N
= 37) and 2 (
N
= 21) used pre- and posttest measures of speech and nonspeech recognition to find evidence of learning (within subject) and to compare the effects of 3 kinds of training (between subject) on the perceptual abilities of adults with normal hearing listening to simulations of cochlear implant processing. Subjects were given interactive, standard lab-based, or control training experience for 1 hr between the pre- and posttest tasks (unique sets across Experiments 1 & 2).

Results

Subjects receiving interactive training showed significant learning on sentence recognition in quiet task (Experiment 1), outperforming controls but not lab-trained subjects following training. Training groups did not differ significantly on any other task, even those directly involved in the interactive training experience.

Conclusions

Interactive training has the potential to produce learning in 1 domain (sentence recognition in quiet), but the particulars of the present training method (short duration, high complexity) may have limited benefits to this single criterion task.

Supplemental Material

https://doi.org/10.23641/asha.6170324
Approximate ergodic capacity of multiuser massive multiple input multiple output in a Rayleigh fading uplink channel with variance profile
Authors: Kazemi Mohammad , Aghaeinia Hassan
Published: February 2015

The effect of large‐scale fading variations over massive multiple input multiple output (MIMO) antenna array on sum‐capacity of massive MIMO system has not been thoroughly investigated in the literature. This study considers a multiuser massive MIMO system with a Rayleigh fading channel that takes into account large‐scale fading variations over base station antenna array. Two scenarios are investigated: distributed antenna base station and linear array base station. In both scenarios, the authors obtain an approximate closed‐form expressions for uplink ergodic sum‐capacity for both low and high signal‐to‐noise ratio (SNR) regimes. It is shown that the proposed closed‐form expressions are accurate in a wide range of practical SNRs; for example, the approximation error is below 10% for SNRs lower than −10 dB and higher than 17 dB for low‐SNR and high‐SNR closed‐form expressions, respectively. It is also shown that the proposed closed‐form expressions are not only valid for massive MIMO scenario but also for a system with a few number of base station antennas. The numerical results show that the proposed closed‐form expressions have much less computational complexity than previous works.
Optimum pattern synthesis of non‐uniform spherical arrays using the Euler rotation
Authors: Oraizi Homayoon , Soleimani Hadi
Published: February 2015

Method of least squares is employed for synthesis of non‐uniform spherical arrays using Euler rotation of coordinate axes for reduction of side‐lobe levels, controllability of 3‐db beam‐width of main‐lobe etc. It is useful for synthesis of conformal arrays, where pattern multiplication is not applicable and array synthesis is involved. This method for synthesis of spherical arrays is general that determines radius of sphere, longitude and latitude angles of elements and their current excitations (amplitudes and phases). The authors investigate several examples to demonstrate its capability. Studies on conformal arrays deal with non‐uniform excitation currents, leading to complicated input networks. Therefore the authors suggest non‐uniform spacing, which shows that array synthesis by variable element spacing will realise any specifications, same as non‐uniform excitations. An error function is constructed for pattern synthesis, which is a function of element spacing and excitations. The authors use combination of global and local minimisation algorithms. In examples of spherical array synthesis, 2.5 and 5.5 dB reduction of side‐lobe levels have been achieved in the E‐ and H‐plane patterns, respectively, relative to the available design data. In addition, reduction of beam‐width of main‐beams in E‐ and H‐planes has been obtained by 39% and 34%, respectively.
Estimation of transient surge energy transferred with associated time delays for individual components of surge protector circuits
Authors: James Sisira , Kularatna Nihal , Steyn‐Ross Alistair , Künnemeyer Rainer
Published: February 2015

Modern semiconductor technology is vulnerable to transient surges such as lightning. Transient voltage suppressor systems (TVSSs), which are installed to protect modern electronics, use non‐linear components such as varistors and transient voltage suppressor diodes in their design. In the case of low‐voltage (1000 V and less) AC power circuits, there is no clear approach to estimate the energy absorption and associated time delays in individual components in relation to the propagated transient surge. Numerical simulation techniques can be used to analyse the phenomenon of surge propagation within a TVSS and estimate the energy transferred to each component with associated time delays. Suitable mathematical models must be used for the non‐linear components. This study presents the development of reasonably accurate models for the non‐linear circuit elements and formulation of state equations for the TVSS, together with simulation results; results are experimentally validated using a lightning surge simulator. The method of analysing surge propagation presented here could be extended to analyse the phenomenon of surge propagation within power conversion stages which buffer the complex electronic circuits and the power source. The results discussed here indicate that the theoretical energy calculations are within 10% of the experimental results for the individual circuit elements.
Discrete‐time sliding‐mode‐based digital pulse width modulation control of a boost converter
Authors: Vidal‐Idiarte Enric , Marcos‐Pastor Adria , Garcia Germain , Cid‐Pastor Angel , Martinez‐Salamero Luis
Published: February 2015

In this study, a non‐linear digital control of a boost converter based on a sliding discrete‐time approximation is presented. The control strategy follows a classical cascade regulation scheme with the inner loop consisting in a non‐linear current‐control based on discrete‐time sliding mode, and the outer one being composed of a simple discrete‐time proportional‐integral (PI) controller for output voltage regulation. An analytical expression of the current control law is developed using a simplified discrete‐time small‐signal model of the boost converter. The discrete‐time PI compensator is designed from a discrete‐time small‐signal parametric model of the inner loop obtained by linearisation around the desired equilibrium point. The proposed method is initially based on the notion of discrete‐time sliding motion to eventually derive a pulse width modulation (PWM) controlled system. Thus, the reported approach can be categorised not only as a direct digital design technique for voltage regulation but also as a competitive method to design sliding‐mode‐based PWM controllers. Simulated and experimental results in a boost converter operating in continuous conduction mode verify the theoretical predictions.
Algorithm to eliminate the wind direction ambiguity from the monostatic high‐frequency radar backscatter spectra
Authors: Chu Xiaoliang , Zhang Jie , Wang Shuyao , Ji Yonggang
Published: February 2015

In this study, an algorithm is presented to eliminate the ambiguity of the wind direction from the monostatic radar. The true wind direction can be obtained by comparing three angles that reflect the differences between wind direction and three adjacent radar beams. The correlation coefficient and the root‐mean‐square (RMS) error between the inversion data and the anemometer data are 0.67 and 49.8°, respectively. When the data whose wind speed is greater than the threshold 4.67 m/s are used, the correlation coefficient and the RMS error are 0.93 and 24.6°. Therefore, the effect of the wind speed threshold on the radar measurements should be put into consideration in the data processing. The results make clear that the algorithm can remove the ambiguity of the wind direction effectively, and authors can utilise the algorithm to estimate the wind direction.
State-to-state reaction dynamics of 18O+32O2 studied by a time-dependent quantum wavepacket method
Authors: Xie Wenbo , Liu Lan , Sun Zhigang , Guo Hua , Dawes Richard
Published: February 2015

The title isotope exchange reaction was studied by converged time-dependent wave packet calculations, where an efficient 4th order split operator was applied to propagate the initial wave packet. State-to-state differential and integral cross sections up to the collision energy of 0.35 eV were obtained with 32O2 in the hypothetical j0 = 0 state. It is discovered that the differential cross sections are largely forward biased in the studied collision energy range, due to the fact that there is a considerable part of the reaction occurring with large impact parameter and short lifetime relative to the rotational period of the intermediate complex. The oscillations of the forward scattering amplitude as a function of collision energy, which result from coherent contribution of adjacent resonances, may be a sensitive probe for examining the quality of the underlying potential energy surface. A good agreement between the theoretical and recent experimental integral and differential cross sections at collision energy of 7.3 kcal/mol is obtained. However, the theoretical results predict slightly too much forward scattering and colder rotational distributions than the experimental observations at collision energy of 5.7 kcal/mol.
Impact of branching on the supramolecular assembly of thioethers on Au(111)
Authors: Murphy Colin J. , Shi Xuerong , Jewell April D. , McGuire Allister F. , Bellisario Darin O. , Baber Ashleigh E. , Tierney Heather L. , Lewis Emily A. , Sholl David S. , Sykes E. Charles. H.
Published: February 2015

Alkanethiolate monolayers are one of the most comprehensively studied self-assembled systems due to their ease of preparation, their ability to be functionalized, and the opportunity to control their thickness perpendicular to the surface. However, these systems suffer from degradation due to oxidation and defects caused by surface etching and adsorbate rotational boundaries. Thioethers offer a potential alternative to thiols that overcome some of these issues and allow dimensional control of self-assembly parallel to the surface. Thioethers have found uses in surface modification of nanoparticles, and chiral thioethers tethered to catalytically active surfaces have been shown to enable enantioselective hydrogenation. However, the effect of structural, chemical, and chiral modifications of the alkyl chains of thioethers on their self-assembly has remained largely unstudied. To elucidate how molecular structure, particularly alkyl branching and chirality, affects molecular self-assembly, we compare four related thioethers, including two pairs of structural isomers. The self-assembly of structural isomers N-butyl methyl sulfide and tert-butyl methyl sulfide was studied with high resolution scanning tunneling microscopy (STM); our results indicate that both molecules form highly ordered arrays despite the bulky tert-butyl group. We also investigated the effect of intrinsic chirality in the alkyl tails on the adsorption and self-assembly of butyl sec-butyl sulfide (BSBS) with STM and density functional theory and contrast our results to its structural isomer, dibutyl sulfide. Calculations provide the relative stability of the four stereoisomers of BSBS and STM imaging reveals two prominent monomer forms. Interestingly, the racemic mixture of BSBS is the only thioether we have examined to date that does not form highly ordered arrays; we postulate that this is due to weak enantiospecific intermolecular interactions that lead to the formation of energetically similar but structurally different assemblies. Furthermore, we studied all of the molecules in their monomeric molecular rotor form, and the surface-adsorbed chirality of the three asymmetric thioethers is distinguishable in STM images.
Lithium formate ion clusters formation during electrospray ionization: Evidence of magic number clusters by mass spectrometry and ab initio calculations
Authors: Shukla Anil , Bogdanov Bogdan
Published: February 2015

Small cationic and anionic clusters of lithium formate were generated by electrospray ionization and their fragmentations were studied by tandem mass spectrometry (collision-induced dissociation with N2). Singly as well as multiply charged clusters were formed in both positive and negative ion modes with the general formulae, (HCOOLi)nLi+, (HCOOLi)nLimm+, (HCOOLi)nHCOO−, and (HCOOLi)n(HCOO)mm−. Several magic number cluster (MNC) ions were observed in both the positive and negative ion modes although more predominant in the positive ion mode with (HCOOLi)3Li+ being the most abundant and stable cluster ion. Fragmentations of singly charged positive clusters proceed first by the loss of a dimer unit ((HCOOLi)2) followed by the loss of monomer units (HCOOLi) although the former remains the dominant dissociation process. In the case of positive cluster ions, all fragmentations lead to the magic cluster (HCOOLi)3Li+ as the most abundant fragment ion at higher collision energies which then fragments further to dimer and monomer ions at lower abundances. In the negative ion mode, however, singly charged clusters dissociated via sequential loss of monomer units. Multiply charged clusters in both positive and negative ion modes dissociated mainly via Coulomb repulsion. Quantum chemical calculations performed for smaller cluster ions showed that the trimer ion has a closed ring structure similar to the phenalenylium structure with three closed rings connected to the central lithium ion. Further additions of monomer units result in similar symmetric structures for hexamer and nonamer cluster ions. Thermochemical calculations show that trimer cluster ion is relatively more stable than neighboring cluster ions, supporting the experimental observation of a magic number cluster with enhanced stability.
Tolman length and rigidity constants of the Lennard-Jones fluid
Authors: Wilhelmsen Øivind , Bedeaux Dick , Reguera David
Published: February 2015

It is well-known that the surface tension of small droplets and bubbles deviates significantly from that at the planar interface. In this work, we analyze the leading corrections in the curvature expansion of the surface tension, i.e., the Tolman length and the rigidity constants, using a “hybrid” square gradient theory, where the local Helmholtz energy density is described by an accurate equation of state. We particularize this analysis for the case of the truncated and shifted Lennard-Jones fluid, and are then able to reproduce the surface tensions and Tolman length from recent molecular dynamics simulations within their accuracy. The obtained constants in the curvature expansion depend little on temperature, except in the vicinity of the critical point. When the bubble/droplet radius becomes comparable to the interfacial width at coexistence, the critical bubble/droplet prefers to change its density, rather than to decrease its size, and the curvature expansion is no longer sufficient to describe the change in surface tension. We find that the radius of the bubble/droplet in this region is proportional to the correlation length between fluctuations in the liquid-phase.
Crystallization in supercooled liquid Cu: Homogeneous nucleation and growth
Authors: E J. C. , Wang L. , Cai Y. , Wu H. A. , Luo S. N.
Published: February 2015

Homogeneous nucleation and growth during crystallization of supercooled liquid Cu are investigated with molecular dynamics simulations, and the microstructure is characterized with one- and two-dimensional x-ray diffraction. The resulting solids are single-crystal or nanocrystalline, containing various defects such as stacking faults, twins, fivefold twins, and grain boundaries; the microstructure is subject to thermal fluctuations and extent of supercooling. Fivefold twins form via sequential twinning from the solid-liquid interfaces. Critical nucleus size and nucleation rate at 31% supercooling are obtained from statistical runs with the mean first-passage time and survival probability methods, and are about 14 atoms and 1032 m−3s−1, respectively. The bulk growth dynamics are analyzed with the Johnson-Mehl-Avrami law and manifest three stages; the Avrami exponent varies in the range of 1–19, which also depends on thermal fluctuations and supercooling.
High second-order nonlinearity by p-n junction formation in plasma enhanced chemical vapor deposition deposited hydrogenated amorphous silicon thin films
Authors: Liu Qiming , Wu Guoxing , Wang Mingliang , Zhao Xiujian , Du Jincheng
Published: February 2015

High second-order nonlinearity as high as 115.9 pm/V was obtained through the formation of p-n junction using plasma-enhanced CVD deposition of hydrogenated amorphous silicon thin films on fused silica substrate without additional electrical poling to induce second harmonic generation in the isotropic amorphous materials. No second harmonic generation was observed for films deposited with only p or n type amorphous silicon. The built-in electrostatic field Edc of p-n junction was observed by measuring the I-V curve of the designed p-i-n layered films, and was found to be the main source of high second-order nonlinearity.
Active guiding of Dirac plasmons in graphene
Authors: Morozov Mikhail Yu. , Davoyan Artur R. , Moiseenko Ilya M. , Satou Akira , Otsuji Taiichi , Popov Vyacheslav V.
Published: February 2015

The Dirac plasmon propagation in active pristine graphene with the carrier population inversion created by the diffusion of the photoexcited carriers from a semiconductor substrate is studied theoretically. It is shown that an order of magnitude smaller pump power can be used for the diffusion pumping as compared to direct optical pumping of graphene for obtaining the same plasmon gain in graphene. We find that the field of the amplified plasmons remains strongly confined in the vicinity of graphene similarly to the case of the attenuated plasmons. Remarkably, the diffusion pumping is characterized by low insertion losses due to small photoexcited carrier concentration in the carrier-supplying semiconductor substrate in the region of the plasmon field confined near graphene.
Photoelectron spectra of CeO− and Ce(OH)2−
Authors: Ray Manisha , Felton Jeremy A. , Kafader Jared O. , Topolski Josey E. , Jarrold Caroline Chick
Published: February 2015

The photoelectron spectrum of CeO− exhibits what appears to be a single predominant electronic transition over an energy range in which numerous close-lying electronic states of CeO neutral are well known. The photoelectron spectrum of Ce(OH)2−, a molecule in which the Ce atom shares the same formal oxidation state as the Ce atom in CeO−, also exhibits what appears to be a single transition. From the spectra, the adiabatic electron affinities of CeO and Ce(OH)2 are determined to be 0.936 ± 0.007 eV and 0.69 ± 0.03 eV, respectively. From the electron affinity of CeO, the CeO− bond dissociation energy was determined to be 7.7 eV, 0.5 eV lower than the neutral bond dissociation energy. The ground state orbital occupancies of both CeO− and Ce(OH)2− are calculated to have 4f 6s2 Ce+ superconfigurations, with open-shell states having 4f5d6s superconfiguration predicted to be over 1 eV higher in energy. Low-intensity transitions observed at higher electron binding energies in the spectrum of CeO− are tentatively assigned to the 1Σ+ (Ω = 0) state of CeO with the Ce+2ߙ6s2 superconfiguration.
1D self-assembly of chemisorbed thymine on Cu(110) driven by dispersion forces
Authors: Temprano I. , Thomas G. , Haq S. , Dyer M. S. , Latter E. G. , Darling G. R. , Uvdal P. , Raval R.
Published: February 2015

Adsorption of thymine on a defined Cu(110) surface was studied using reflection-absorption infrared spectroscopy (RAIRS), temperature programmed desorption (TPD), and scanning tunnelling microscopy (STM). In addition, density functional theory (DFT) calculations were undertaken in order to further understand the energetics of adsorption and self-assembly. The combination of RAIRS, TPD, and DFT results indicates that an upright, three-point-bonded adsorption configuration is adopted by the deprotonated thymine at room temperature. DFT calculations show that the upright configuration adopted by individual molecules arises as a direct result of strong O–Cu and N–Cu bonds between the molecule and the surface. STM data reveal that this upright thymine motif self-assembles into 1D chains, which are surprisingly oriented along the open-packed [001] direction of the metal surface and orthogonal to the alignment of the functional groups that are normally implicated in H-bonding interactions. DFT modelling of this system reveals that the molecular organisation is actually driven by dispersion interactions, which cause a slight tilt of the molecule and provide the major driving force for assembly into dimers and 1D chains. The relative orientations and distances of neighbouring molecules are amenable for π-π stacking, suggesting that this is an important contributor in the self-assembly process.
Relaxation processes in a lower disorder order transition diblock copolymer
Authors: Sanz Alejandro , Ezquerra Tiberio A. , Hernández Rebeca , Sprung Michael , Nogales Aurora
Published: February 2015

The dynamics of lower disorder-order temperature diblock copolymer leading to phase separation has been observed by X ray photon correlation spectroscopy. Two different modes have been characterized. A non-diffusive mode appears at temperatures below the disorder to order transition, which can be associated to compositional fluctuations, that becomes slower as the interaction parameter increases, in a similar way to the one observed for diblock copolymers exhibiting phase separation upon cooling. At temperatures above the disorder to order transition TODT, the dynamics becomes diffusive, indicating that after phase separation in Lower Disorder-Order Transition (LDOT) diblock copolymers, the diffusion of chain segments across the interface is the governing dynamics. As the segregation is stronger, the diffusive process becomes slower. Both observed modes have been predicted by the theory describing upper order-disorder transition systems, assuming incompressibility. However, the present results indicate that the existence of these two modes is more universal as they are present also in compressible diblock copolymers exhibiting a lower disorder-order transition. No such a theory describing the dynamics in LDOT block copolymers is available, and these experimental results may offer some hints to understanding the dynamics in these systems. The dynamics has also been studied in the ordered state, and for the present system, the non-diffusive mode disappears and only a diffusive mode is observed. This mode is related to the transport of segment in the interphase, due to the weak segregation on this system.
Gradual wavelet reconstruction of the velocity increments for turbulent wakes
Authors: Keylock C. J. , Stresing R. , Peinke J.
Published: February 2015

This work explores the properties of the velocity increment distributions for wakes of contrasting local Reynolds number and nature of generation (a cylinder wake and a multiscale-forced case, respectively). It makes use of a technique called gradual wavelet reconstruction (GWR) to generate constrained randomizations of the original data, the nature of which is a function of a parameter, ϑ. This controls the proportion of the energy between the Markov-Einstein length (∼ 0.8 Taylor scales) and integral scale that is fixed in place in the synthetic data. The properties of the increments for these synthetic data are then compared to the original data as a function of ϑ. We write a Fokker-Planck equation for the evolution of the velocity increments as a function of spatial scale, r, and, in line with previous work, expand the drift and diffusion terms in terms up to fourth order in the increments and find no terms are relevant beyond the quadratic terms. Only the linear contribution to the expansion of the drift coefficient is non-zero and it exhibits a consistent scaling with ϑ for different flows above a low threshold. For the diffusion coefficient, we find a local Reynolds number independence in the relation between the constant term and ϑ for the multiscale-forced wakes. This term characterizes small scale structure and can be contrasted with the results for the Kolmogorov capacity of the zero-crossings of the velocity signals, which measures structure over all scales and clearly distinguishes between the types of forcing. Using GWR shows that results for the linear and quadratic terms in the expansion of the diffusion coefficient are significant, providing a new means for identifying intermittency and anomalous scaling in turbulence datasets. All our data showed a similar scaling behavior for these parameters irrespective of forcing type or Reynolds number, indicating a degree of universality to the anomalous scaling of turbulence. Hence, these terms are a useful metric for testing the efficacy of synthetic turbulence generation schemes used in large eddy simulation, and we also discuss the implications of our approach for reduced order modeling of the Navier-Stokes equations.
On the dynamic computation of the model constant in delayed detached eddy simulation
Authors: Yin Z. , Reddy K. R. , Durbin P. A.
Published: February 2015

The current work puts forth an implementation of a dynamic procedure to locally compute the value of the model constant CDES, as used in the eddy simulation branch of Delayed Detached Eddy Simulation (DDES). Former DDES formulations [P. R. Spalart et al., “A new version of detached-eddy simulation, resistant to ambiguous grid densities,” Theor. Comput. Fluid Dyn. 20, 181 (2006); M. S. Gritskevich et al., “Development of DDES and IDDES formulations for the k- ω shear stress transport model,” Flow, Turbul. Combust. 88, 431 (2012)] are not conducive to the implementation of a dynamic procedure due to uncertainty as to what form the eddy viscosity expression takes in the eddy simulation branch. However, a recent, alternate formulation [K. R. Reddy et al., “A DDES model with a Smagorinsky-type eddy viscosity formulation and log-layer mismatch correction,” Int. J. Heat Fluid Flow 50, 103 (2014)] casts the eddy viscosity in a form that is similar to the Smagorinsky, LES (Large Eddy Simulation) sub-grid viscosity. The resemblance to the Smagorinsky model allows the implementation of a dynamic procedure similar to that of Lilly [D. K. Lilly, “A proposed modification of the Germano subgrid-scale closure method,” Phys. Fluids A 4, 633 (1992)]. A limiting function is proposed which constrains the computed value of CDES, depending on the fineness of the grid and on the computed solution.
Size dependence of the polarizability and Haynes rule for an exciton bound to an ionized donor in a single spherical quantum dot
Authors: Feddi E. , Zouitine A. , Oukerroum A. , Dujardin F. , Assaid E. , Zazoui M.
Published: February 2015

We study the effect of an external electric field on an exciton bound to an ionized donor (D+, X) confined in a spherical quantum dot using a perturbative-variational method where the wave function and energy are developed in series of powers of the electric field strength. After testing this new approach in the determination of the band gap for some semiconductor materials, we generalize it to the case of (D+, X) in the presence of the electric field and for several materials ZnO, PbSe, and InAs, with significant values of the mass ratio. Three interesting results can be deduced: First, we show that the present method allows to determine the ground state energy in the presence of a weak electric field in a simple way (E = E0 − αf2) using the energy without electric field E0 and the polarizability α. The second point is that our theoretical predictions show that the polarizability of (D+, X) varies proportionally to R3.5 and follows an ordering αD0<αX<α(D+,X). The last point to highlight is that the Haynes rule remains valid even in the presence of a weak electric field.
Photoluminescence from silicon nanocrystals embedded in silicon nitride fabricated by low-pressure chemical vapor deposition followed by high-temperature annealing
Authors: Hafsi Nadjet , Bouridah Hachemi , Beghoul Mahmoud Riad , Haoues Hakim
Published: February 2015

The photoluminescence (PL) from silicon nanocrystals (Si-ncs) embedded in an amorphous silicon nitride matrix was examined both experimentally and through theoretical simulations. The film was prepared using low-pressure chemical vapor deposition with subsequent high-temperature annealing. The experimental parameters required for the PL modeling were determined using Raman spectroscopy. A novel method to estimate the nitrogen content, which allowed the determination of both the Urbach energy and the Tauc gap, was reported. The luminescence could be attributed to different origins, namely, Si-ncs, amorphous silicon nanodots, nitrogen and silicon defects, and amorphous matrix. A comparison between the experimental results and the modeling indicated that the existing models are unable to satisfactorily explain the observed PL.
Cutoff frequency of toroidal plasma waveguide
Authors: Zakeri-Khatir H. , Aghamir F. M.
Published: February 2015

The cutoff frequencies of E and H-modes of empty and plasma filled toroidal waveguides are evaluated. The effects of space curvature and plasma density on cutoff frequencies for both modes are investigated. Using a suitable variable change, a scalar wave equation in the direction of propagation was obtained. The study indicates that the curvature in the direction of wave propagation in toroidal waveguide has an analogous effect as a straight waveguide filled with anisotropic media. The Rayleigh-Schrodinger perturbation method was employed to solve for cutoff frequencies in the first order of approximation. In the limit of small space curvature, the toroidal waveguide cutoff frequencies for both E and H-modes approach those of TM and TE modes of empty cylindrical waveguide with a radius equal to toroidal waveguide minor radius. The analysis shows that the curvature in the direction of propagation in toroidal waveguides leads to the removal of the degeneracy between E and H-modes.
Quasiparticle band structures and thermoelectric transport properties of p-type SnSe
Authors: Shi Guangsha , Kioupakis Emmanouil
Published: February 2015

We used density functional and many-body perturbation theory to calculate the quasiparticle band structures and electronic transport parameters of p-type SnSe both for the low-temperature Pnma and high-temperature Cmcm phases. The Pnma phase has an indirect band gap of 0.829 eV, while the Cmcm has a direct band gap of 0.464 eV. Both phases exhibit multiple local band extrema within an energy range comparable to the thermal energy of carriers from the global extrema. We calculated the electronic transport coefficients as a function of doping concentration and temperature for single-crystal and polycrystalline materials to understand the previous experimental measurements. The electronic transport coefficients are highly anisotropic and are strongly affected by bipolar transport effects at high temperature. Our results indicate that SnSe exhibits optimal thermoelectric performance at high temperature when doped in the 1019–1020 cm−3 range.
Honeycomb superlattice pattern in a dielectric barrier discharge in argon/air
Authors: Zhu Ping , Dong Lifang , Yang Jing , Gao Yenan , Wang Yongjie , Li Ben
Published: February 2015

We report on a honeycomb superlattice pattern in a dielectric barrier discharge in argon/air for the first time. It consists of hexagon lattice and honeycomb framework and bifurcates from a hexagon pattern as the applied voltage increases. A phase diagram of the pattern as a function of the gas component and gas pressure is presented. The instantaneous images show that the hexagon lattice and honeycomb framework are ignited in turn in each half voltage cycle. The honeycomb framework is composed of filaments ignited randomly. The spatiotemporal dynamics of honeycomb superlattice pattern is discussed by wall charges.
Half metallic ferromagnetism in tri-layered perovskites Sr4T3O10(T = Co, Rh)
Authors: Ghimire Madhav Prasad , Thapa R. K. , Rai D. P. , Sandeep  , Sinha T. P. , Hu Xiao
Published: February 2015

First-principles density functional theory (DFT) is used to investigate the electronic and magnetic properties of Sr4Rh3O10, a member of the Ruddlesden-Popper series. Based on the DFT calculations taking into account the co-operative effect of Coulomb interaction (U) and spin-orbit couplings (SOC), Sr4Rh3O10 is found to be a half metallic ferromagnet (HMF) with total magnetic moment μtot = 12 μB per unit cell. The material has almost 100% spin-polarization at the Fermi level despite of sizable SOC. Replacement of Rh atom by the isovalent Co atom is considered. Upon full-replacement of Co, a low-spin to intermediate spin transition happens resulting in a HMF state with the total magnetic moment three-time larger (i.e., μtot = 36 μB per unit cell), compared to Sr4Rh3O10. We propose Sr4Rh3O10 and Sr4Co3O10 as candidates of half metals.