bluuebunny/crossref_metadata_2025 huggingface dataset:
Triggered dynamics in a model of different fault creep regimes
Authors: Kostić Srđan , Franović Igor , Perc Matjaž , Vasović Nebojša , Todorović Kristina
Published: June 2014

The study is focused on the effect of transient external force induced by a passing seismic wave on fault motion in different creep regimes. Displacement along the fault is represented by the movement of a spring-block model, whereby the uniform and oscillatory motion correspond to the fault dynamics in post-seismic and inter-seismic creep regime, respectively. The effect of the external force is introduced as a change of block acceleration in the form of a sine wave scaled by an exponential pulse. Model dynamics is examined for variable parameters of the induced acceleration changes in reference to periodic oscillations of the unperturbed system above the supercritical Hopf bifurcation curve. The analysis indicates the occurrence of weak irregular oscillations if external force acts in the post-seismic creep regime. When fault motion is exposed to external force in the inter-seismic creep regime, one finds the transition to quasiperiodic- or chaos-like motion, which we attribute to the precursory creep regime and seismic motion, respectively. If the triggered acceleration changes are of longer duration, a reverse transition from inter-seismic to post-seismic creep regime is detected on a larger time scale.
Generation of the SCN1A epilepsy mutation in hiPS cells using the TALEN technique
Authors: Chen Wanjuan , Liu Jingxin , Zhang Longmei , Xu Huijuan , Guo Xiaogang , Deng Sihao , Liu Lipeng , Yu Daiguan , Chen Yonglong , Li Zhiyuan
Published: June 2014

Human induced pluripotent stem cells (iPSC) can be used to understand the pathological mechanisms of human disease. These cells are a promising source for cell-replacement therapy. However, such studies require genetically defined conditions. Such genetic manipulations can be performed using the novel Transcription Activator-Like Effector Nucleases (TALENs), which generate site-specific double-strand DNA breaks (DSBs) with high efficiency and precision. Combining the TALEN and iPSC methods, we developed two iPS cell lines by generating the point mutation A5768G in the SCN1A gene, which encodes the voltage-gated sodium channel Nav1.1 α subunit. The engineered iPSC maintained pluripotency and successfully differentiated into neurons with normal functional characteristics. The two cell lines differ exclusively at the epilepsy-susceptibility variant. The ability to robustly introduce disease-causing point mutations in normal hiPS cell lines can be used to generate a human cell model for studying epileptic mechanisms and for drug screening.
Scissor-based fluorescent detection of pepsin using lysozyme-stabilized Au nanoclusters
Authors: Li Wei , Gao Zhao , Su Rongxin , Qi Wei , Wang Libing , He Zhimin
Published: June 2014

Highly selective and sensitive detection of pepsin was developed through peptic hydrolysis of lysozyme-stabilized gold nanoclusters at pH 3.
Sensitive quantification and visual detection of bacteria using CdSe/ZnS@SiO2 nanoparticles as fluorescent probes
Authors: Wang Renjie , Xu Yi , Jiang Yan , Chuan Na , Su Xi , Ji Jingou
Published: June 2014

Hydrophobic CdSe/ZnS was incorporated into SiO2 spheres, and amine-modified CdSe/ZnS@SiO2 nanoparticles were used for a quantitative and visual determination of bacteria.
Oligoamine-tethered low generation polyamidoamine dendrimers as potential nucleic acid carriers
Authors: Bansal Ruby , Singh Manju , Gupta Kailash Chand , Kumar Pradeep
Published: June 2014

Oligoamine-tethered low generation PAMAM dendrimers (mG2–mG4) have been synthesized, which showed significantly higher transfection efficiency with minimal cytotoxicity in vitro.
Optical control over bioactive ligands at supramolecular surfaces
Authors: Voskuhl J. , Sankaran S. , Jonkheijm P.
Published: June 2014

Addressing whole protein and bacterial immobilization and their optical control on a β-cyclodextrin supramolecular platform.
2D conglomerate crystallization of heptahelicene
Authors: Seibel Johannes , Zoppi Laura , Ernst Karl-Heinz
Published: June 2014

Two-dimensional homochiral nucleation and conglomerate crystallization of an unsubstituted all-carbon helicene on a metal surface is observed for the first time.
Tip-induced C–H activation and oligomerization of thienoanthracenes
Authors: Dinca L. E. , MacLeod J. M. , Lipton-Duffin J. , Fu C. , Ma D. , Perepichka D. F. , Rosei F.
Published: June 2014

The tip of a scanning tunneling microscope (STM) can be used to dehydrogenate freely-diffusing tetrathienoanthracene (TTA) molecules on Cu(111), trapping the molecules into metal-coordinated oligomeric structures.
Polygermanes: bandgap engineering via tensile strain and side-chain substitution
Authors: Fa Wei , Zeng Xiao Cheng
Published: June 2014

Polygermanes: bandgap engineering by strain and side-chain substitution.
pH-responsive inorganic–organic hybrid supramolecular hydrogels with jellyfish-like switchable chromic luminescence
Authors: Wei Haibing , Shi Nan , Zhang Jinlong , Guan Yan , Zhang Jie , Wan Xinhua
Published: June 2014

A novel hybrid hydrogel, based on electrostatic co-assembly of polyoxometaltate and the ABA triblock copolymers shows both sol–gel transition and luminescence variation in response to pH change.
Palladium-catalyzed oxidative CH/CH cross-coupling of pyridine N-oxides with five-membered heterocycles
Authors: Liu Wei , Yu Xin , Li Yahui , Kuang Chunxiang
Published: June 2014

Using Ag2CO3 as an additive, we developed the Pd-catalyzed intermolecular C–H/C–H cross-coupling of pyridine N-oxides with five-membered heterocycles such as 1-benzyl-1,2,3-triazoles, thiophens and furans.
Polymeric one- and two-dimensional copper(i) iodide complexes showing photoluminescence tunable by azaaromatic ligands
Authors: Kitada Nobuo , Ishida Takayuki
Published: June 2014

Photoluminescent properties of four low-dimensional [(CuI)xL]n complexes were investigated in the solid state at ambient temperature. A photoluminescence quantum yield of 73% was recorded for [(CuI)2(46dmpm)]n.
Photophysical, amplified spontaneous emission and charge transport properties of oligofluorene derivatives in thin films
Authors: Choi E. Y. , Mazur L. , Mager L. , Gwon M. , Pitrat D. , Mulatier J. C. , Monnereau C. , Fort A. , Attias A. J. , Dorkenoo K. , Kwon J. E. , Xiao Y. , Matczyszyn K. , Samoc M. , Kim D.-W. , Nakao A. , Heinrich B. , Hashizume D. , Uchiyama M. , Park S. Y. , Mathevet F. , Aoyama T. , Andraud C. , Wu J. W. , Barsella A. , Ribierre J. C.
Published: June 2014

We investigate the charge transport, photophysical and amplified spontaneous emission properties of a series of monodisperse solution-processable oligofluorenes functionalized with hexyl chains at the C9 position of each fluorene unit.
Dynamics of photodissociation of XeF2 in organic solvents
Authors: Dunning Greg T. , Preston Thomas J. , Orr-Ewing Andrew J. , Greaves Stuart J. , Greetham Gregory M. , Clark Ian P. , Towrie Michael
Published: June 2014

This article explores photodissociation of XeF2 in solution, using femtosecond pump probe spectroscopy to follow the fates of photoproducts following cleavage of one Xe–F bond.
Fully solution processed all inorganic nanocrystal solar cells
Authors: Townsend Troy K. , Foos Edward E.
Published: June 2014

Robust all inorganic solar cells showing 1.7% efficiency were fabricated entirely from solution in air onto non-conductive glass using solution soluble nanocrystal inks.
Heteroatom-doped graphene materials: syntheses, properties and applications
Authors: Wang Xuewan , Sun Gengzhi , Routh Parimal , Kim Dong-Hwan , Huang Wei , Chen Peng
Published: June 2014

Heteroatom doping endows graphene with new or improved properties and greatly enhances its potential for various applications.
Cobalt mediated C–H bond functionalization: emerging tools for organic synthesis
Authors: Tilly David , Dayaker Gandrath , Bachu Prabhakar
Published: June 2014

This review provides a perspective on C–H bond functionalization mediated by cobalt complexes used in either stoichiometric or catalytic amounts, without the contribution of any other transition metal, for organic synthesis applications.
Hydrocarbon oxidation catalyzed by a cheap nonheme imine-based iron(ii) complex
Authors: Olivo Giorgio , Arancio Giorgio , Mandolini Luigi , Lanzalunga Osvaldo , Di Stefano Stefano
Published: June 2014

An imine-based iron complex, prepared in situ from iron(ii), pyridine-2-carbaldehyde and 2-aminomethylpyridine, effectively catalyzes hydrocarbon oxidation at low loadings.
The role of reversibility in the enantioselective conjugate addition of α,α-disubstituted aldehydes to nitro-olefins catalyzed by primary amine thioureas
Authors: Ji Yining , Blackmond Donna G.
Published: June 2014

Identification of intermediates in the asymmetric conjugate addition of aldehdyes to nitro-olefins catalyzed by primary amine thioureas add mechanistic insight.
1,3,5,7-Tetrakis(tetrazol-5-yl)-adamantane: the smallest tetrahedral tetrazole-functionalized ligand and its complexes formed by reaction with anhydrous M(ii)Cl2(M = Mn, Cu, Zn, Cd)
Authors: Boldog Ishtvan , Domasevitch Konstantin V. , Sanchiz Joaquín , Mayer Peter , Janiak Christoph
Published: June 2014

Porous [M4Cl4L2] framework complexes with gismondine zeolite topology, manifesting a tetrahedral ligand ‘imprinting’, which stimulates the realization of effectively tetrahedral metal-tetrazolato/chlorido clusters, are in the focus of the report.
A spectrophotometric study of Am(iii) complexation with nitrate in aqueous solution at elevated temperatures
Authors: Tian Guoxin , Shuh David K.
Published: June 2014

The complexation of americium(iii) with nitrate was studied at temperatures from 10 to 85 °C in 1 M HNO3–HClO4 by spectrophotometry.
Hybrid photocatalysts using graphitic carbon nitride/cadmium sulfide/reduced graphene oxide (g-C3N4/CdS/RGO) for superior photodegradation of organic pollutants under UV and visible light
Authors: Pawar Rajendra C. , Khare Varsha , Lee Caroline Sunyong
Published: June 2014

Schematic of the electron transport from g-C3N4to the CdS nanoparticles and RGO sheets during RhB photodegradation.
From C,N- and N,N-chelated chloroboranes to substituted 1H-2,1-benzazaboroles and 1H-pyrrolo[1,2-c][1,3,2]diazaborolidines: a straightforward route to five-membered rings containing the B–N or N–B–N moiety
Authors: Hejda Martin , Lyčka Antonín , Jambor Roman , Růžička Aleš , Dostál Libor
Published: June 2014

The reaction of C,N- and N,N-chelated boranes with lithium reagents resulted in the formation of substituted 1H-2,1-benzazaboroles and 1H-pyrrolo[1,2-c][1,3,2]diazaborolidines.
Red wine extract decreases pro-inflammatory markers, nuclear factor-κB and inducible NOS, in experimental metabolic syndrome
Authors: Janega Pavol , Klimentová Jana , Barta Andrej , Kovácsová Mária , Vranková Stanislava , Cebová Martina , Čierna Zuzana , Matúsková Zuzana , Jakovljevic Vladimir , Pechánová Olga
Published: June 2014

Alibernet red wine extract (AWE) decreased p65 NF-κB and iNOS expressions elevated due to the development of metabolic syndrome in SHR/N-cp rats.
Propagating longitudinal contractions in the ileum of the rabbit – Efficiency of advective mixing
Authors: Fullard Luke , Lammers Willem , Wake Graeme C. , Ferrua Maria J.
Published: June 2014

The flow and mixing of viscous fluids in the small intestine for various types of longitudinal motility.
Efficient one-step preparation of γ-aminobutyric acid from glucose without an exogenous cofactor by the designed Corynebacterium glutamicum
Authors: Zhang Rongzhen , Yang Taowei , Rao Zhiming , Sun Hongmei , Xu Meijuan , Zhang Xian , Xu Zhenghong , Yang Shangtian
Published: June 2014

Efficient one-step production of γ-aminobutyric acid from glucose without an exogenous cofactor pyridoxal-5′-phosphate was realized by the designedCorynebacterium glutamicum.
Enzymatic synthesis of ionic responsive lignin nanofibres through surface poly(N-isopropylacrylamide) immobilization
Authors: Gao Guangzheng , Karaaslan Muzaffer A. , Kadla John F. , Ko Frank
Published: June 2014

Surface modification of electrospun lignin nanofibres with poly(N-isopropylacrylamide) (PNIPAM) was conducted through surface-initiated atom transfer radical polymerization (ATRPase) using various biocatalysts under aqueous conditions.
Highly efficient and reversible CO2 adsorption by amine-grafted platelet SBA-15 with expanded pore diameters and short mesochannels
Authors: Zhou Lingyun , Fan Jing , Cui Guokai , Shang Xiaomin , Tang Qinghu , Wang Jianji , Fan Maohong
Published: June 2014

Amine-grafted mesoporous silica materials with short channels and large pore diameters have been prepared and used to adsorb CO2 efficiently.
Insect–Human Hybrid Eye (IHHE): an adaptive optofluidic lens combining the structural characteristics of insect and human eyes
Authors: Wei Kang , Zeng Hansong , Zhao Yi
Published: June 2014

An optofluidic device named the “Insect–Human Hybrid Eye” (IHHE), which combines the architectural merits of both human camera eyes and insect compound eyes, is presented to implement imaging with a large angle of view and adaptive focusing along any direction within the field.
Synthesis of copper–isonicotinate metal–organic frameworks simply by mixing solid reactants and investigation of their adsorptive properties for the removal of the fluorescein dye
Authors: Tella Adedibu C. , Owalude Samson O. , Ojekanmi Christianah A. , Oluwafemi Oluwatobi S.
Published: June 2014

The copper–isonicotinate metal–organic frameworks [Cu(INA)2] (INA = isonicotinate) (MOFs) has been prepared by a highly efficient and environmentally benign technique involving mixing and heating of solid reactants without milling. The adsorption of fluorescein dye on the as-synthesised [Cu(INA)2] was also investigated.
A cyano-bridged copper(ii)–copper(i) mixed-valence coordination polymer as a source of copper oxide nanoparticles with catalytic activity in C–N, C–O and C–S cross-coupling reactions
Authors: Trivedi Manoj , Ujjain Sanjeev kumar , Sharma Raj Kishore , Singh Gurmeet , Kumar Abhinav , Rath Nigam P.
Published: June 2014

A cyano-bridged Cu(ii)–Cu(i) complex was synthesized and transformed into CuO nanoparticles. Their catalytic activity in C–N, C–O, and C–S cross-coupling reactions was explored.
Fabrication and electrochemical characterization of Zn–halloysite nanotubes composite coatings
Authors: Ranganatha S. , Venkatesha T. V.
Published: June 2014

Zinc–halloysite nanotube (HNT) composite coatings through electrodeposition technique were successfully fabricated on mild steel substrate.
The preferred radical scavenging mechanisms of fisetin and baicalein towards oxygen-centred radicals in polar protic and polar aprotic solvents
Authors: Dimitrić Marković Jasmina M. , Milenković Dejan , Amić Dragan , Mojović Miloš , Pašti Igor , Marković Zoran S.
Published: June 2014

The flavonoids fisetin and baicalein have been investigated for their ability to scavenge certain anion radicals.
Morphology controlling of calcium carbonate by self-assembled surfactant micelles on PET substrate
Authors: Li Zhenyou , Xing Li , Xiang Junhui , Liang Xiaohong , Zhao Chunlin , Sai Huazheng , Li Fei
Published: June 2014

In the present work, spherical and hexagonal CaCO3 were fabricated on different surfactant micelle-modified PET substrates at liquid–liquid interfaces. The results revealed a same nanoparticle-mediate self-organization process in which the surfactants act not only as regulators but also as templates.
3D printed tactile pattern formation on paper with thermal reflow method
Authors: Jo Wonjin , Kim Do Hyun , Lee Jeong Sim , Lee Heon Ju , Moon Myoung-Woon
Published: June 2014

The combination of 3D FDM printing method and thermal reflow technique was applied to fabricate tactile patterns for visually impaired people. The size controllable 3D tactile patterns were significantly improved in surface smoothness and adhesion strength on papers.
NHC catalysed direct addition of HMF to diazo compounds: synthesis of acyl hydrazones with antitumor activity
Authors: António João P. M. , Frade Raquel F. M. , Santos Fábio M. F. , Coelho Jaime A. S. , Afonso Carlos A. M. , Gois Pedro M. P. , Trindade Alexandre F.
Published: June 2014

Synthesis and evaluation of HMF derived N-acyl hydrazone with antitumor activity.
Temperature-dependent photoluminescence properties of Mn:ZnCdS quantum dots
Authors: Zheng Jinju , Cao Sheng , Wang Lin , Gao Fengmei , Wei Guodong , Yang Weiyou
Published: June 2014

We report the temperature-dependent photoluminescence of Mn:ZnCdS QDs with a high PL QY of 65% at 360 K.
Base-catalyzed retro-Claisen condensation: a convenient esterification of alcohols via C–C bond cleavage of ketones to afford acylating sources
Authors: Xie Feng , Yan Fengxia , Chen Mengmeng , Zhang Min
Published: June 2014

The base-catalyzed esterification of alcohols via retro-Claisen condensation has been demonstrated for the first time.
Effect of carbonate anions on Bi-doped Ca2Ru2O7 pyrochlores that are potential cathode catalysts for low temperature carbonate fuel cells
Authors: Hancock Cathryn A. , Ong Ai Lien , Varcoe John R.
Published: June 2014

This ex situ electrochemical study investigates how the oxygen reduction reaction (ORR) on Bi-doped Ca2Ru2O7 pyrochlore catalysts is affected by the addition of carbonate to the aqueous KOH (1 mol dm−3) electrolyte.
Shooting in a foam
Authors: Le Goff Anne , Quéré David , Clanet Christophe
Published: June 2014

We study the motion of a solid sphere after its fast impact on a bath of liquid foam.
Phase segregation of sulfonate groups in Nafion interface lamellae, quantified via neutron reflectometry fitting techniques for multi-layered structures
Authors: DeCaluwe Steven C. , Kienzle Paul A. , Bhargava Pavan , Baker Andrew M. , Dura Joseph A.
Published: June 2014

Advanced neutron reflectometry techniques demonstrate that phase separation of fluorocarbons from sulfonates accompanies the interfacial lamellar ordering of humidified Nafion, and is partially retained upon dehydration.
Crystallised mesoporous TiO2(A)–VO2(M/R) nanocomposite films with self-cleaning and excellent thermochromic properties
Authors: Chen Zhang , Cao Chuanxiang , Chen Shi , Luo Hongjie , Gao Yanfeng
Published: June 2014

A “two-step” method was developed for the preparation of crystallised TiO2(A)–VO2(M/R) nanocomposite mesoporous films with self-cleaning properties and excellent thermochromic performance.
Improved electrochemical performance of Li1.2Mn0.54Ni0.13Co0.13O2 by Mg doping for lithium ion battery cathode material
Authors: Xu Hongjie , Deng Shengnan , Chen Guohua
Published: June 2014

The electrochemical performance of Li1.2Mn0.54Ni0.13Co0.13O2 is improved by partially replacing Li with Mg.
DJ-1 interacts with RACK1 and protects neurons from oxidative-stress-induced apoptosis
Authors: Ma Jun , Wu Rong , Zhang Qiang , Wu Jun-bing , Lou Jizhong , Zheng Zheng , Ding Jian-qing , Yuan Zengqiang
Published: June 2014

PD (Parkinson's disease) is a complex disorder that is associated with neuronal loss or dysfunction caused by genetic risks, environmental factors and advanced aging. It has been reported that DJ-1 mutations rendered neurons sensitive to oxidative damage, which led to the onset of familiar PD. However, the molecular mechanism is still unclear. In the present study we show that DJ-1 interacts with RACK1 (receptor of activated C kinase 1) and increases its dimerization and protein stability. The DJ-1 transgene protects cortical neurons from H2O2-induced apoptosis, and this protective effect is abrogated by knocking down RACK1. Similarly, deletion of DJ-1 in cortical neurons increases the sensitivity to H2O2, and the damage can be significantly rescued by DJ-1 or DJ-1/RACK1 co-transfection, but not by RACK1 alone. We observed further that the interaction of DJ-1 and RACK1 is disrupted by H2O2 or MPP+ (1-methyl-4-phenylpyridinium) treatment, and the protein levels of DJ-1 and RACK1 decreased in neurodegenerative disease models. Taken together, the DJ-1–RACK1 complex protects neurons from oxidative stress-induced apoptosis, with the implication that DJ-1 and RACK1 might be novel targets in the treatment of neurodegenerative diseases.
Regulation of PKA activity by an autophosphorylation mechanism in Saccharomyces cerevisiae
Authors: Solari Clara Andrea , Tudisca Vanesa , Pugliessi Marcelo , Nadra Alejandro Daniel , Moreno Silvia , Portela Paula
Published: June 2014

PKA (cAMP-dependent protein kinase) activity, as well as that of other AGC members, is regulated by multiple phosphorylations of its catalytic subunits. In Saccharomyces cerevisiae, the PKA regulatory subunit is encoded by the gene BCY1, and the catalytic subunits are encoded by three genes: TPK1, TPK2 and TPK3. Previously, we have reported that, following cAMP/PKA pathway activation, Tpk1 increases its phosphorylation status. Now, in vivo genetic and in vitro experiments indicate an autophosphorylation mechanism for Tpk1. Using array peptides derived from Tpk1, we identified Ser179 as a target residue. Tpk1 is phosphorylated on Ser179in vivo during glucose stimulus. Reduction of the activation loop Thr241 phosphorylation increases Ser179 autophosphorylation. To evaluate the role of phosphorylation on Ser179, we made strains expressing tpk1S179A or tpk1S179D as the sole PKA kinase source. Our results suggest that Ser179 phosphorylation increases the reactivity towards the substrate without affecting the formation of the holoenzyme. Phenotypic readout analysis showed that Ser179 phosphorylation increases in vivo PKA activity, reducing cell survival, stress and lifespan. Ser179 phosphorylation increases Tpk1 cytoplasmic accumulation in glucose-grown cells. These results describe for the first time that an autophosphorylation mechanism on Tpk1 controls PKA activity in response to glucose availability.
Prevention of age-related endothelial dysfunction by habitual aerobic exercise in healthy humans: possible role of nuclear factor κB
Authors: Walker Ashley E. , Kaplon Rachelle E. , Pierce Gary L. , Nowlan Molly J. , Seals Douglas R.
Published: June 2014

Habitual aerobic exercise prevents age-related impairments in endothelium-dependent dilation (EDD). We have hypothesized that the pro-inflammatory transcription factor nuclear factor κB (NF-κB) impairs EDD with sedentary aging, and habitual aerobic exercise prevents this age-related suppression of EDD by NF-κB. To test this hypothesis, we have inhibited NF-κB signalling via oral salsalate administration in healthy older aerobic exercise-trained adults (OT, n=14, 58±2 years), older non-exercising adults (ON, n=16, 61±1 years) and young non-exercising controls (YN, n=8, 23±1 years). Salsalate reduced endothelial cell expression of NF-κB p65 by ~25% in ON (P<0.05) but did not significantly change expression in OT or YN (P>0.05). EDD, assessed by brachial artery flow-mediated dilation (FMD), was improved by salsalate in ON (4.0±0.7% compared with 6.8±0.7%, placebo compared with salsalate, P<0.001) but did not change with salsalate in OT or YN (OT: 7.2±0.7% compared with 7.7±0.6%; YN: 7.6±0.9% compared with 8.1±0.8%; placebo compared with salsalate, P>0.05). Endothelium-independent dilation was not affected by salsalate in any group (P>0.05). In ON, vitamin C infusion improved FMD by ~30% during placebo (P<0.001) but had no affect during salsalate (P>0.05). In OT and YN, vitamin C infusion did not affect FMD during either placebo or salsalate (P>0.05). Salsalate reduced endothelial cell nitrotyrosine content by ~25% and NADPH oxidase p47phox expression by ~30% in ON (P<0.05) but had no effect in OT or YN (P>0.05). Our results suggest that endothelial NF-κB signalling is associated with oxidative stress-related impairment of EDD in healthy non-exercising but not aerobically exercising older adults. This may be a key mechanism by which regular aerobic exercise preserves endothelial function and reduces cardiovascular risk with aging.
Analysis and design of high‐order wideband bandstop filters with sharp rejection
Authors: Feng Wenjie , Che Wenquan , Xue Quan
Published: June 2014

High‐order wideband bandstop filters (BSFs) with sharp rejection based on transversal signal‐interference techniques are analysed and designed. By choosing different open stubs and open/shorted coupled lines, third/fifth/seventh‐order wideband BSFs with six transmission zeros from 0 GHz to 2f0 (f0 is the centre frequency of the stopband) can be achieved, respectively, due to the superposition of signals from the two transmission paths. The bandwidths of the three high selectivity wideband BSFs can be easily adjusted by changing the characteristic impedance of the resonant structures of the two transmission paths. Three wideband BSF prototypes with 3 dB fractional bandwidths of 113% (1.74–6.26 GHz), 115% (1.85–6.45 GHz) and 112.3% (1.76–6.25 GHz) are designed and fabricated for demonstration. The theoretical and measured results are in good agreement and show good in‐band filtering performance and high selectivity.
Quantum fields with classical perturbations
Authors: Dereziński Jan
Published: June 2014

The main purpose of these notes is a review of various models of Quantum Field Theory (QFT) involving quadratic Lagrangians. We discuss scalar and vector bosons, spin \documentclass[12pt]{minimal}\begin{document}$\frac{1}{2}$\end{document}12 fermions, both neutral and charged. Beside free theories, we study their interactions with classical perturbations, called, depending on the context, an external linear source, mass-like term, current or electromagnetic potential. The notes may serve as a first introduction to QFT.
A geometric approach to the Landauer-Büttiker formula
Authors: Sâad R. Ben , Pillet C.-A.
Published: June 2014

We consider an ideal Fermi gas confined to a geometric structure consisting of a central region – the sample – connected to several infinitely extended ends—the reservoirs. Under physically reasonable assumptions on the propagation properties of the one-particle dynamics within these reservoirs, we show that the state of the Fermi gas relaxes to a steady state. We compute the expected value of various current observables in this steady state and express the result in terms of scattering data, thus obtaining a geometric version of the celebrated Landauer-Büttiker formula.
Fully coupled Pauli-Fierz systems at zero and positive temperature
Authors: Møller Jacob Schach
Published: June 2014

These notes provide an introduction to the spectral analysis of Pauli-Fierz systems at zero and positive temperature. More precisely, we study finite dimensional quantum systems linearly coupled to a single reservoir, a massless scalar quantum field. We emphasize structure results valid at arbitrary system-reservoir coupling strength. The notes contain a mixture of known, refined, and new results and each section ends with a discussion of open problems.
Repeated interactions in open quantum systems
Authors: Bruneau Laurent , Joye Alain , Merkli Marco
Published: June 2014

Analyzing the dynamics of open quantum systems has a long history in mathematics and physics. Depending on the system at hand, basic physical phenomena that one would like to explain are, for example, convergence to equilibrium, the dynamics of quantum coherences (decoherence) and quantum correlations (entanglement), or the emergence of heat and particle fluxes in non-equilibrium situations. From the mathematical physics perspective, one of the main challenges is to derive the irreversible dynamics of the open system, starting from a unitary dynamics of the system and its environment. The repeated interactions systems considered in these notes are models of non-equilibrium quantum statistical mechanics. They are relevant in quantum optics, and more generally, serve as a relatively well treatable approximation of a more difficult quantum dynamics. In particular, the repeated interaction models allow to determine the large time (stationary) asymptotics of quantum systems out of equilibrium.
X-ray digital industrial radiography (DIR) for local liquid velocity (VLL) measurement in trickle bed reactors (TBRs): Validation of the technique
Authors: Mohd Salleh Khairul Anuar , Rahman Mohd Fitri Abdul , Lee Hyoung Koo , Al Dahhan Muthanna H.
Published: June 2014

Local liquid velocity measurements in Trickle Bed Reactors (TBRs) are one of the essential components in its hydrodynamic studies. These measurements are used to effectively determine a reactor's operating condition. This study was conducted to validate a newly developed technique that combines Digital Industrial Radiography (DIR) with Particle Tracking Velocimetry (PTV) to measure the Local Liquid Velocity (VLL) inside TBRs. Three millimeter-sized Expanded Polystyrene (EPS) beads were used as packing material. Three validation procedures were designed to test the newly developed technique. All procedures and statistical approaches provided strong evidence that the technique can be used to measure the VLL within TBRs.
Slip velocity of rigid fibers in turbulent channel flow
Authors: Zhao L. , Marchioli C. , Andersson H. I.
Published: June 2014

In this study, the slip velocity between rigid fibers and a viscous carrier fluid is investigated for the reference case of turbulent channel flow. The statistical moments of the slip velocity are evaluated modelling fibers as prolate spheroids with Stokes number, St, ranging from 1 to 100 and aspect ratio, λ, ranging from 3 to 50. Statistics are compared one-to-one with those obtained for spherical particles (λ = 1) to highlight effects due to fiber elongation. Comparison is also made at different Reynolds numbers (Reτ =150, 180, and 300 based on the fluid shear velocity) to discuss effects due to an increase of turbulent fluctuations. Results show that elongation has a quantitative effect on slip velocity statistics, particularly evident for fibers with small St. As St increases, differences due to the aspect ratio tend to vanish and the relative translational motion between individual fibers and surrounding fluid is controlled by fiber inertia through preferential concentration. A clear manifestation of inertial effects is the different distribution of slip velocities for fibers trapped in sweep/ejection events and for fibers segregated in near-wall fluid streaks. The corresponding conditional probability distribution functions, shown here for the streamwise and wall-normal slip velocity components, are found to be non-Gaussian, thus suggesting that fiber motion relative to the fluid in high-shear flow regions may not be modelled as a pure diffusion process with constant diffusion coefficient. For the range of simulation parameters investigated, no significant Reynolds number effects are observed, indicating that fiber dynamics exhibit a scaling behavior with respect to the shear velocity up to Reτ =300.
What is the fate of runaway positrons in tokamaks?
Authors: Liu Jian , Qin Hong , Fisch Nathaniel J. , Teng Qian , Wang Xiaogang
Published: June 2014

Massive runaway positrons are generated by runaway electrons in tokamaks. The fate of these positrons encodes valuable information about the runaway dynamics. The phase space dynamics of a runaway position is investigated using a Lagrangian that incorporates the tokamak geometry, loop voltage, radiation and collisional effects. It is found numerically that runaway positrons will drift out of the plasma to annihilate on the first wall, with an in-plasma annihilation possibility less than 0.1%. The dynamics of runaway positrons provides signatures that can be observed as diagnostic tools.
Asymptotic solution of light transport problems in optically thick luminescent media
Authors: Şahin-Biryol Derya , Ilan Boaz
Published: June 2014

We study light transport in optically thick luminescent random media. Using radiative transport theory for luminescent media and applying asymptotic and computational methods, a corrected diffusion approximation is derived with the associated boundary conditions and boundary layer solution. The accuracy of this approach is verified for a plane-parallel slab problem. In particular, the reduced system models accurately the effect of reabsorption. The impacts of varying the Stokes shift and using experimentally measured luminescence data are explored in detail. The results of this study have application to the design of luminescent solar concentrators, fluorescence medical imaging, and optical cooling using anti-Stokes fluorescence.
Development of a combined portable x-ray fluorescence and Raman spectrometer for in situ analysis
Authors: Guerra M. , Longelin S. , Pessanha S. , Manso M. , Carvalho M. L.
Published: June 2014

In this work, we have built a portable X-ray fluorescence (XRF) spectrometer in a planar configuration coupled to a Raman head and a digital optical microscope, for in situ analysis. Several geometries for the XRF apparatus and digital microscope are possible in order to overcome spatial constraints and provide better measurement conditions. With this combined spectrometer, we are now able to perform XRF and Raman measurements in the same point without the need for sample collection, which can be crucial when dealing with cultural heritage objects, as well as forensic analysis. We show the capabilities of the spectrometer by measuring several standard reference materials, as well as other samples usually encountered in cultural heritage, geological, as well as biomedical studies.
Calculation of state-to-state differential and integral cross sections for atom-diatom reactions with transition-state wave packets
Authors: Zhao Bin , Sun Zhigang , Guo Hua
Published: June 2014

A recently proposed transition-state wave packet method [R. Welsch, F. Huarte-Larrañaga, and U. Manthe, J. Chem. Phys. 136, 064117 (2012)] provides an efficient and intuitive framework to study reactive quantum scattering at the state-to-state level. It propagates a few transition-state wave packets, defined by the eigenfunctions of the low-rank thermal flux operator located near the transition state, into the asymptotic regions of the reactant and product arrangement channels separately using the corresponding Jacobi coordinates. The entire S-matrix can then be assembled from the corresponding flux-flux cross-correlation functions for all arrangement channels. Since the transition-state wave packets can be defined in a relatively small region, its transformation into either the reactant or product Jacobi coordinates is accurate and efficient. Furthermore, the grid/basis for the propagation, including the maximum helicity quantum number K, is much smaller than that required in conventional wave packet treatments of state-to-state reactive scattering. This approach is implemented for atom-diatom reactions using a time-dependent wave packet method and applied to the H + D2 reaction with all partial waves. Excellent agreement with benchmark integral and differential cross sections is achieved.
Ponderomotive self-focusing of Gaussian laser beam in warm collisional plasma
Authors: Jafari Milani M. R. , Niknam A. R. , Farahbod A. H.
Published: June 2014

The propagation characteristics of a Gaussian laser beam through warm collisional plasma are investigated by considering the ponderomotive force nonlinearity and the complex eikonal function. By introducing the dielectric permittivity of warm unmagnetized plasma and using the WKB and paraxial ray approximations, the coupled differential equations defining the variations of laser beam parameters are obtained and solved numerically. Effects of laser and plasma parameters such as the collision frequency, the initial laser intensity and its spot size on the beam width parameter and the axis laser intensity distribution are analyzed. It is shown that, self-focusing of the laser beam takes place faster by increasing the collision frequency and initial laser spot size and then after some distance propagation the laser beam abruptly loses its initial diameter and vastly diverges. Furthermore, the modified electron density distribution is obtained and the collision frequency effect on this distribution is studied.
Extension and evaluation of the multilevel summation method for fast long-range electrostatics calculations
Authors: Moore Stan G. , Crozier Paul S.
Published: June 2014

Several extensions and improvements have been made to the multilevel summation method (MSM) of computing long-range electrostatic interactions. These include pressure calculation, an improved error estimator, faster direct part calculation, extension to non-orthogonal (triclinic) systems, and parallelization using the domain decomposition method. MSM also allows fully non-periodic long-range electrostatics calculations which are not possible using traditional Ewald-based methods. In spite of these significant improvements to the MSM algorithm, the particle-particle particle-mesh (PPPM) method was still found to be faster for the periodic systems we tested on a single processor. However, the fast Fourier transforms (FFTs) that PPPM relies on represent a major scaling bottleneck for the method when running on many cores (because the many-to-many communication pattern of the FFT becomes expensive) and MSM scales better than PPPM when using a large core count for two test problems on Sandia's Redsky machine. This FFT bottleneck can be reduced by running PPPM on only a subset of the total processors. MSM is most competitive for relatively low accuracy calculations. On Sandia's Chama machine, however, PPPM is found to scale better than MSM for all core counts that we tested. These results suggest that PPPM is usually more efficient than MSM for typical problems running on current high performance computers. However, further improvements to MSM algorithm could increase its competitiveness for calculation of long-range electrostatic interactions.
Quasi-energies, parametric resonances, and stability limits in ac-driven PT-symmetric systems
Authors: D'Ambroise Jennie , Malomed Boris A. , Kevrekidis P. G.
Published: June 2014

We introduce a simple model for implementing the concepts of quasi-energy and parametric resonances (PRs) in systems with the PT symmetry, i.e., a pair of coupled and mutually balanced gain and loss elements. The parametric (ac) forcing is applied through periodic modulation of the coefficient accounting for the coupling of the two degrees of freedom. The system may be realized in optics as a dual-core waveguide with the gain and loss applied to different cores, and the thickness of the gap between them subject to a periodic modulation. The onset and development of the parametric instability for a small forcing amplitude (V1) is studied in an analytical form. The full dynamical chart of the system is generated by systematic simulations. At sufficiently large values of the forcing frequency, ω, tongues of the parametric instability originate, with the increase of V1, as predicted by the analysis. However, the tongues following further increase of V1 feature a pattern drastically different from that in usual (non-PT) parametrically driven systems: instead of bending down to larger values of the dc coupling constant, V0, they maintain a direction parallel to the V1 axis. The system of the parallel tongues gets dense with the decrease of ω, merging into a complex small-scale structure of alternating regions of stability and instability. The cases of ω→0 and ω→∞ are studied analytically by means of the adiabatic and averaging approximation, respectively. The cubic nonlinearity, if added to the system, alters the picture, destabilizing many originally robust dynamical regimes, and stabilizing some which were unstable.
Modeling intrinsic defects in LiNbO3 within the Slater-Janak transition state model
Authors: Li Yanlu , Sanna Simone , Schmidt Wolf Gero
Published: June 2014

Intrinsic point defects in LiNbO3, i.e., isolated Nb antisites and Li as well Nb vacancies, are investigated from first-principles within the Slater-Janak transition state model. Thereby the electronic structure of the investigated defects is calculated with hybrid exchange-correlation functionals. This approach allows for the calculation of charge transition levels without comparing the total energies of differently charged supercells. The obtained results are in agreement with previous hybrid density-functional theory calculations based on total-energy differences. Li and Nb vacancies can be formed in the \documentclass[12pt]{minimal}\begin{document}$\mathrm{V}_\mathrm{Li}^-$\end{document}V Li − and \documentclass[12pt]{minimal}\begin{document}$\mathrm{V}_\mathrm{Nb}^{5-}$\end{document}V Nb 5− charge states only, as long as the host is not strongly p-type or n-type, respectively. NbLi antisites may capture one or two electrons, forming the defect states often referred to as small bound polaron and bi-polaron.
The effect of concentration- and temperature-dependent dielectric constant on the activity coefficient of NaCl electrolyte solutions
Authors: Valiskó Mónika , Boda Dezső
Published: June 2014

Our implicit-solvent model for the estimation of the excess chemical potential (or, equivalently, the activity coefficient) of electrolytes is based on using a dielectric constant that depends on the thermodynamic state, namely, the temperature and concentration of the electrolyte, ε(c, T). As a consequence, the excess chemical potential is split into two terms corresponding to ion-ion (II) and ion-water (IW) interactions. The II term is obtained from computer simulation using the Primitive Model of electrolytes, while the IW term is estimated from the Born treatment. In our previous work [J. Vincze, M. Valiskó, and D. Boda, “The nonmonotonic concentration dependence of the mean activity coefficient of electrolytes is a result of a balance between solvation and ion-ion correlations,” J. Chem. Phys. 133, 154507 (2010)], we showed that the nonmonotonic concentration dependence of the activity coefficient can be reproduced qualitatively with this II+IW model without using any adjustable parameter. The Pauling radii were used in the calculation of the II term, while experimental solvation free energies were used in the calculation of the IW term. In this work, we analyze the effect of the parameters (dielectric constant, ionic radii, solvation free energy) on the concentration and temperature dependence of the mean activity coefficient of NaCl. We conclude that the II+IW model can explain the experimental behavior using a concentration-dependent dielectric constant and that we do not need the artificial concept of “solvated ionic radius” assumed by earlier studies.
Study on the Ge1−xSnx/HfO2 interface and its impacts on Ge1−xSnx tunneling transistor
Authors: Qiu Yingxin , Wang Runsheng , Huang Qianqian , Huang Ru
Published: June 2014

In this paper, we employ first-principle calculation to investigate the Ge1−xSnx/HfO2 interface, and then evaluate its impacts on Ge1−xSnx tunneling field-effect transistor (TFET). First-principle calculations of Ge1−xSnx/HfO2 interfaces in the oxygen-rich process atmosphere indicate that the interface states originate from the Ge and Sn dangling bond, rather than Hf-bond. The total density of state shows that there are more interface states in the semiconductor bandgap with increasing Sn fraction. By further incorporating the material and interface parameters from density functional theory calculation into advanced device simulation, the electrical characteristics of Ge1−xSnx TFET are investigated. Removing the Sn atom from the first atom layer of Ge1−xSnx in device processes is found to be beneficial to reduce the degradations. For the degradation mechanisms, the trap-assisted-tunneling is the dominant mechanism at the low Sn fraction, and enhanced Shockley-Read-Hall recombination induced by traps becomes the dominant mechanism with increasing Sn fraction. The results are helpful for the interface optimization of Ge1−xSnx TFET.
Piezoelectric surface acoustical phonon amplification in graphene on a GaAs substrate
Authors: Nunes O. A. C.
Published: June 2014

We study the interaction of Dirac Fermions in monolayer graphene on a GaAs substrate in an applied electric field by the combined action of the extrinsic potential of piezoelectric surface acoustical phonons of GaAs (piezoelectric acoustical (PA)) and of the intrinsic deformation potential of acoustical phonons in graphene (deformation acoustical (DA)). We find that provided the dc field exceeds a threshold value, emission of piezoelectric (PA) and deformation (DA) acoustical phonons can be obtained in a wide frequency range up to terahertz at low and high temperatures. We found that the phonon amplification rate RPA,DA scales with TBGS−1 (S=PA,DA), TBGS being the Block−Gru¨neisen temperature. In the high-T Block−Gru¨neisen regime, extrinsic PA phonon scattering is suppressed by intrinsic DA phonon scattering, where the ratio RPA/RDA scales with ≈1/n, n being the carrier concentration. We found that only for carrier concentration n≤1010cm−2, RPA/RDA>1. In the low-T Block−Gru¨neisen regime, and for n=1010cm−2, the ratio RPA/RDA scales with TBGDA/TBGPA≈7.5 and RPA/RDA>1. In this regime, PA phonon dominates the electron scattering and RPA/RDA<1 otherwise. This study is relevant to the exploration of the acoustic properties of graphene and to the application of graphene as an acoustical phonon amplifier and a frequency-tunable acoustical phonon device.
Characteristics of intermediate state related to anti-Stokes luminescence of ZnO single crystals
Authors: Fujii Katsushi , Goto Takenari , Yao Takafumi
Published: June 2014

Anti-Stokes luminescence from ZnO is supposed to be a two-step two-photon absorption process with an intermediate state. The intermediate state is assumed to be a localized state with two different excited and relaxed states. One of the localized states is believed to be the well-known 2.4 eV green luminescence; the other is difficult to observe experimentally. We found an interesting 2.25 eV deep luminescence from ZnO, which has been shown to relate to anti-Stokes luminescence. The 2.25 eV yellow luminescence was observable only below the band gap excitation and through a time-resolved observation after the excitation light was turned off. The intermediate states were found to be a photo-excited donor-acceptor pair and its lattice relaxation state. The characteristics and the role of the intermediate state of ZnO related to the anti-Stokes luminescence are discussed.
Note: A vortex cross-correlation flowmeter with enhanced turndown ratio
Authors: Venugopal A. , Agrawal Amit , Prabhu S. V.
Published: June 2014

In the present study, a novel dual sensor vortex cross correlation technique is suggested and implemented to extend the lower operating range of the flowmeter. The first sensor located at an optimum streamwise location of 0.85 times the width of the bluff body is employed to compute the vortex shedding frequency under high Reynolds number conditions. Under low Reynolds number conditions, when the strength of the vortex signal is poor, the outputs from the two piezoelectric sensors are correlated to compute the vortex convection velocity. This vortex convection velocity is used to compute the volume flow rate. This novel dual flow rate estimation technique has demonstrated its robustness under low Reynolds number flow conditions with a remarkable turndown ratio of 1:66 as compared to 1:20 for conventional vortex flowmeters.
Note: Multi channel Doppler tuned spectrometer to study highly charged ions
Authors: Karn Ranjeet K. , Mishra C. N. , Ahmad Nissar , Saini S. K. , Safvan C. P. , Nandi T.
Published: June 2014

We describe the design and implementation of a multi channel Doppler tuned spectrometer setup to study physics of highly charged ions at high resolution in a direct way. A unique Soller slit assembly coupled with a long one dimensional position sensitive proportional counter enables us to get distinct x-ray peaks at different angles, which allows us to cover large number of angle in one shot. By using this setup, 1s2s 3S1 - 1s2 1S0 M1 transition in He-like Fe has been resolved from its satellite line \documentclass[12pt]{minimal}\begin{document}$1s2s2p {\,}^4\!P^0_{5/2}$\end{document}1s2s2p4P5/20 - 1s22s 2S1/2 M2 transition in Li-like Fe and measured the lifetime of their respective upper levels with high precision.