bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanoscale characterization of PM2.5 airborne pollutants reveals high adhesiveness and aggregation capability of soot particles
Authors: Shi Yuanyuan , Ji Yanfeng , Sun Hui , Hui Fei , Hu Jianchen , Wu Yaxi , Fang Jianlong , Lin Hao , Wang Jianxiang , Duan Huiling , Lanza Mario
Published: July 2015

In 2012 air pollutants were responsible of seven million human death worldwide and among them particulate matter with an aerodynamic diameter of 2.5 micrometers or less (PM2.5) are the most hazardous because they are small enough to invade even the smallest airways and penetrate to the lungs. During the last decade the size, shape, composition, sources and effect of these particles on human health have been studied. However, the noxiousness of these particles not only relies on their chemical toxicity, but particle morphology and mechanical properties affect their thermodynamic behavior, which has notable impact on their biological activity. Therefore, correlating the physical, mechanical and chemical properties of PM2.5airborne pollutants should be the first step to characterize their interaction with other bodies but, unfortunately, such analysis has never been reported before. In this work, we present the first nanomechanical characterization of the most abundant and universal groups of PM2.5airborne pollutants and, by means of atomic force microscope (AFM) combined with other characterization tools, we observe that fluffy soot aggregates are the most sticky and unstable. Our experiments demonstrate that such particles show strong adhesiveness and aggregation, leading to a more diverse composition and compiling all possible toxic chemicals.
Promoter-level expression clustering identifies time development of transcriptional regulatory cascades initiated by ErbB receptors in breast cancer cells
Authors: Mina Marco , Magi Shigeyuki , Jurman Giuseppe , Itoh Masayoshi , Kawaji Hideya , Lassmann Timo , Arner Erik , Forrest Alistair R. R. , Carninci Piero , Hayashizaki Yoshihide , Daub Carsten O. ,   the FANTOM Consortium, Okada-Hatakeyama Mariko , Furlanello Cesare
Published: July 2015

The analysis of CAGE (Cap Analysis of Gene Expression) time-course has been proposed by the FANTOM5 Consortium to extend the understanding of the sequence of events facilitating cell state transition at the level of promoter regulation. To identify the most prominent transcriptional regulations induced by growth factors in human breast cancer, we apply here the Complexity Invariant Dynamic Time Warping motif EnRichment (CIDER) analysis approach to the CAGE time-course datasets of MCF-7 cells stimulated by epidermal growth factor (EGF) or heregulin (HRG). We identify a multi-level cascade of regulations rooted by the Serum Response Factor (SRF) transcription factor, connecting the MAPK-mediated transduction of the HRG stimulus to the negative regulation of the MAPK pathway by the members of the DUSP family phosphatases. The finding confirms the known primary role of FOS and FOSL1, members of AP-1 family, in shaping gene expression in response to HRG induction. Moreover, we identify a new potential regulation of DUSP5 and RARA (known to antagonize the transcriptional regulation induced by the estrogen receptors) by the activity of the AP-1 complex, specific to HRG response. The results indicate that a divergence in AP-1 regulation determines cellular changes of breast cancer cells stimulated by ErbB receptors.
Ca2+/Calmodulin-Dependent Protein Kinase IV Promotes Interplay of Proteins in Chromatoid Body of Male Germ Cells
Authors: Wang Guishuan , Zhang Huijuan , Wang Lu , Wang Yuan , Huang Hefeng , Sun Fei
Published: July 2015

The chromatoid body is a granule-like structure of male germ cells, containing many proteins and RNAs and is important for spermatogenesis. However, the molecular mechanisms for the formation and function of the chromatoid body are still elusive. Here, we report that Ca2+/calmodulin-dependent protein kinase IV (CaMKIV) accumulates in the chromatoid body by immunofluorescence staining, indicating that CaMKIV is a new component of the chromatoid body. Furthermore, we find that CaMKIV can interplay with the other components of the chromatoid body by immunoprecipitation: mouse VASA homologue (MVH), mouse homologue of PIWI, PIWIL1 (MIWI) and kinesin KIF17b. Importantly, interplay between KIF17b and MVH or MIWI can be potentially regulated by CaMKIV. These results imply that CaMKIV plays a role in maintenance the structure of chromatoid body by regulating the associations of proteins in it.
Earliest evidence of dental caries manipulation in the Late Upper Palaeolithic
Authors: Oxilia Gregorio , Peresani Marco , Romandini Matteo , Matteucci Chiara , Spiteri Cynthianne Debono , Henry Amanda G. , Schulz Dieter , Archer Will , Crezzini Jacopo , Boschin Francesco , Boscato Paolo , Jaouen Klervia , Dogandzic Tamara , Broglio Alberto , Moggi-Cecchi Jacopo , Fiorenza Luca , Hublin Jean-Jacques , Kullmer Ottmar , Benazzi Stefano
Published: July 2015

Prehistoric dental treatments were extremely rare and the few documented cases are known from the Neolithic, when the adoption of early farming culture caused an increase of carious lesions. Here we report the earliest evidence of dental caries intervention on a Late Upper Palaeolithic modern human specimen (Villabruna) from a burial in Northern Italy. Using Scanning Electron Microscopy we show the presence of striations deriving from the manipulation of a large occlusal carious cavity of the lower right third molar. The striations have a “V”-shaped transverse section and several parallel micro-scratches at their base, as typically displayed by cutmarks on teeth. Based on in vitro experimental replication and a complete functional reconstruction of the Villabruna dental arches, we confirm that the identified striations and the associated extensive enamel chipping on the mesial wall of the cavity were produced ante-mortem by pointed flint tools during scratching and levering activities. The Villabruna specimen is therefore the oldest known evidence of dental caries intervention, suggesting at least some knowledge of disease treatment well before the Neolithic. This study suggests that primitive forms of carious treatment in human evolution entail an adaptation of the well-known toothpicking for levering and scratching rather than drilling practices.
Design and improvement of artificial redox modules by molecular fusion of flavodoxin and flavodoxin reductase from Escherichia coli
Authors: Bakkes Patrick J. , Biemann Stefan , Bokel Ansgar , Eickholt Marc , Girhard Marco , Urlacher Vlada B.
Published: July 2015

A variety of fusion proteins between the versatile redox partners flavodoxin (FldA) and flavodoxin reductase (Fpr) from Escherichia coli was constructed with the aim to improve the electron transfer properties. The order in which FldA and Fpr were fused and the linker region between them was varied in a systematic manner. A simple molecular tool, designated “DuaLinX”, was developed that facilitated the parallel introduction of flexible glycine-rich and rigid proline-rich linkers between the fusion partners in a single cloning event. The fusion constructs were tested for their ability to transfer electrons to cytochrome c and cytochrome P450 109B1 from Bacillus subtilis. With CYP109B1, the performance of the constructs showed, independent of the domain order, a strong dependency on linker length, whereas with cytochrome c this phenomenon was less pronounced. Constructs carrying linkers of ≥15 residues effectively supported the CYP109B1-catalysed hydroxylation of myristic acid. Constructs carrying proline-rich linkers generally outperformed their glycine-rich counterparts. The best construct, FldA-Fpr carrying linker ([E/L]PPPP)4, supported CYP109B1 activity equally well as equivalent amounts of the non-fused redox partners, while cytochrome c reductase activity was ~2.7-fold improved. Thus, to functionally connect redox partners, rigid proline-rich linkers may be attractive alternatives to the commonly used flexible glycine-rich linkers.
Versatile MoS2 Nanosheets in ITO-Free and Semi-transparent Polymer Power-generating Glass
Authors: Hu Xiaotian , Chen Lie , Tan Licheng , Zhang Yong , Hu Lin , Xie Bing , Chen Yiwang
Published: July 2015

Chemical exfoliated ultra-thin MoS2 nanosheets (NSs) with well 2D structure were demonstrated for interfacial layers and Ag nanowires composite transparent electrode in polymer solar cells (PSCs). The smooth and uniform n-type and p-type (after the plasma treatment) MoS2 NSs could improve fill factor of devices and light absorption in active layer. The optimized Ag nanowires–MoS2 NSs (AgNW-MoS2 NSs) transparent electrode presented a low sheet resistance of 9.8 Ω sq−1 and the corresponding transmittance also exhibited a high value of 93.1% at 550 nm. As a result, ITO-free PSCs based on AgNW-MoS2 NSs/n-MoS2 NSs cathode and p-MoS2 NSs/Ag anode achieved a highest PCE of 8.72%. Furthermore, a high efficiency (6.55%), large area and low cost semi-transparent power-generating glass was obtained, after reducing the thickness of top Ag electrode from 100 nm to 30 nm. To our best knowledge, it is the highest performance for semi-transparent PSCs devices reported up to now. The novel semi-transparent power-generating glass showed good performance and color purity for commercial applications in the near future.
Strong phylogenetic signals and phylogenetic niche conservatism in ecophysiological traits across divergent lineages of Magnoliaceae
Authors: Liu Hui , Xu Qiuyuan , He Pengcheng , Santiago Louis S. , Yang Keming , Ye Qing
Published: July 2015

The early diverged Magnoliaceae shows a historical temperate-tropical distribution among lineages indicating divergent evolution, yet which ecophysiological traits are phylogenetically conserved and whether these traits are involved in correlated evolution remain unclear. Integrating phylogeny and 20 ecophysiological traits of 27 species, from the four largest sections of Magnoliaceae, we tested the phylogenetic signals of these traits and the correlated evolution between trait pairs. Phylogenetic niche conservatism (PNC) in water-conducting and nutrient-use related traits was identified and correlated evolution of several key functional traits was demonstrated. Among the three evergreen sections of tropical origin, Gwillimia had the lowest hydraulic-photosynthetic capacity and the highest drought tolerance compared with Manglietia and Michelia. Contrastingly, the temperate centred deciduous section, Yulania, showed high rates of hydraulic conductivity and photosynthesis at the cost of drought tolerance. This study elucidated the regulation of hydraulic and photosynthetic processes in the temperate-tropical adaptations for Magnoliaceae species, which led to strong phylogenetic signals and PNC in ecophysiological traits across divergent lineages of Magnoliaceae.
Analysis of ATP and AMP binding to a DNA aptamer and its imidazole-tethered derivatives by surface plasmon resonance
Authors: Zhao Jing , Katsube Satoshi , Yamamoto Junpei , Yamasaki Kazuhiko , Miyagishi Makoto , Iwai Shigenori
Published: July 2015

The tethering of imidazole to the ATP-binding DNA aptamer increased its affinity for ATP, almost independently of the linker structure or the modification site.
Control of the photoluminescence properties of single-walled carbon nanotubes by alkylation and subsequent thermal treatment
Authors: Maeda Yutaka , Takehana Yuya , Yamada Michio , Suzuki Mitsuaki , Murakami Tatsuya
Published: July 2015

Alkylation and subsequent thermal treatment of SWNTs induces a new bright PL peak in the NIR region.
1,3-Diiodobenzene on Cu(111) – an exceptional case of on-surface Ullmann coupling
Authors: Rastgoo Lahrood Atena , Björk Jonas , Heckl Wolfgang M. , Lackinger Markus
Published: July 2015

Ullmann coupling of 1,3-diiodobenzene is studied on Cu(111) surfaces in ultra-high vacuum (UHV).
Crystal engineering of cadmium coordination polymers decorated with nitro-functionalized thiophene-2,5-dicarboxylate and structurally related bis(imidazole) ligands with varying flexibility
Authors: Xue Li-Ping , Li Zhao-Hao , Ma Lu-Fang , Wang Li-Ya
Published: July 2015

Five bis(imidazole) ligand modulated cadmium coordination polymers based on a new nitro-functionalized thiophene-2,5-dicarboxylate ligand or 4-nitro-thiophene-2-carboxylic acid involving in situ ligand synthesis.
Charge-switchable gold nanoparticles for enhanced enzymatic thermostability
Authors: Shankar Shiv , Soni Sarvesh K. , Daima Hemant K. , Selvakannan P. R. , Khire Jayant M. , Bhargava Suresh K. , Bansal Vipul
Published: July 2015

Zwitterionic amino acids allow the synthesis of charge-switchable metal nanoparticles, which support efficient immobilization of enzymes on nanoparticles, leading to high thermal stability and enzymatic efficiency.
Physical properties of the hybrid lipid POPC on micrometer-sized domains in mixed lipid membranes
Authors: Shimokawa Naofumi , Nagata Mariko , Takagi Masahiro
Published: July 2015

In a DPPC/DOPC/POPC ternary mixture, hybrid lipids are localized at the solid-ordered domain boundary. On the other hand, in a DPPC/DOPC/POPC/Chol four-component mixture, they are included in the liquid-ordered domain and disturb the chain ordering of lipids in the domain.
Facile synthesis of S, N co-doped carbon dots and investigation of their photoluminescence properties
Authors: Zhang Yue , He Junhui
Published: July 2015

Carbon dots with stable down and up conversion fluorescence were synthesized and a unique photoluminescence mechanism is proposed.
A first-principles examination of conducting monolayer 1T′-MX2(M = Mo, W; X = S, Se, Te): promising catalysts for hydrogen evolution reaction and its enhancement by strain
Authors: Putungan Darwin Barayang , Lin Shi-Hsin , Kuo Jer-Lai
Published: July 2015

We investigated the application of 1T′-MX2(M = Mo, W; X = S, Se, Te) 2D materials as hydrogen evolution reaction (HER) catalysts using density functional theory.
Downstream processing of Isochrysis galbana: a step towards microalgal biorefinery
Authors: Gilbert-López Bienvenida , Mendiola José A. , Fontecha Javier , van den Broek Lambertus A. M. , Sijtsma Lolke , Cifuentes Alejandro , Herrero Miguel , Ibáñez Elena
Published: July 2015

An algae-based biorefinery relies on the efficient use of algae biomass through its fractionation in several valuable/bioactive compounds that can be used in industry.
Stability analysis of chemically modified mRNA using micropattern-based single-cell arrays
Authors: Ferizi Mehrije , Leonhardt Carolin , Meggle Christian , Aneja Manish K. , Rudolph Carsten , Plank Christian , Rädler Joachim O.
Published: July 2015

Micro-structured arrays allow highly parallel assessment of single-cell mRNA-mediated dsGFP-expression time courses. Fits to the individual expression kinetics yield mRNA life-time distribution, which are compared for differently stabilized mRNA constructs.
Division time-based amplifiers for stochastic gene expression
Authors: Wang Haohua , Yuan Zhanjiang , Liu Peijiang , Zhou Tianshou
Published: July 2015

While cell-to-cell variability is a phenotypic consequence of gene expression noise, sources of this noise may be complex – apart from intrinsic sources such as the random birth/death of mRNA and stochastic switching between promoter states, there are also extrinsic sources of noise such as cell division where division times are either constant or random.
Near infrared light-actuated gold nanorods with cisplatin–polypeptide wrapping for targeted therapy of triple negative breast cancer
Authors: Feng Bing , Xu Zhiai , Zhou Fangyuan , Yu Haijun , Sun Qianqian , Wang Dangge , Tang Zhaohui , Yu Haiyang , Yin Qi , Zhang Zhiwen , Li Yaping
Published: July 2015

Gold nanorods with cisplatin–polypeptide wrapping were developed for combinational photothermal therapy and chemotherapy of triple negative breast cancer.
The biomolecular corona of nanoparticles in circulating biological media
Authors: Pozzi D. , Caracciolo G. , Digiacomo L. , Colapicchioni V. , Palchetti S. , Capriotti A. L. , Cavaliere C. , Zenezini Chiozzi R. , Puglisi A. , Laganà A.
Published: July 2015

The structure and composition of the liposome–protein corona are dependent on the incubation protocol (i.e. dynamic vs. static incubation).
A novel single walled carbon nanotube (SWCNT) functionalization agent facilitating in vivo combined chemo/thermo therapy
Authors: Zhang Liwen , Rong Pengfei , Chen Minglong , Gao Shi , Zhu Lei
Published: July 2015

A new single walled carbon nanotube (SWCNT) dispersion agent is reported. The new functionalized SWCNT is promising for effective ablation of tumors by combined therapy.
Colorful surface architectures with three different types of dynamic covalent bonds: integration of anthocyanins, tritylium ions and flavins
Authors: Zhang Kang-Da , Sakai Naomi , Matile Stefan
Published: July 2015

Complex systems with three different types of dynamic covalent bonds are probed for emergent properties.
Well-defined colloidal crystal films from the 2D self-assembly of core–shell semi-soft nanoparticles
Authors: Sabouri Hadi , Ohno Kohji , Perrier Sébastien
Published: July 2015

Silica core–polymer shell particles are obtained from surface mediated RAFT polymerisation and assembled into ordered 2D colloidal crystals.
A new paradigm of copper oxide nanoparticles catalyzed reactions: synthesis of 1,2,3-triazoles through oxidative azide-olefin cycloaddition
Authors: Gangaprasad D. , Raj J. Paul , Kiranmye T. , Sadik S. Sagubar , Elangovan J.
Published: July 2015

Oxidative [3 + 2] cycloaddition of activated olefins and azides is reported with readily available CuO nanoparticles. 1,4-Disubsitituted and 1,4,5-trisubstituted 1,2,3-triazoles have been achieved without use of base or additives in a shorter time.
Synthesis and adsorption application of amine shield-introduced-released porous chitosan hydrogel beads for removal of acid orange 7 from aqueous solutions
Authors: Li Tingting , Liu Yunguo , Wang Shufan , Zeng Guangming , Zheng Bohong , Wang Hui , Zhang Mingming , Guo Fangying , Zeng Xiaoxia
Published: July 2015

An effective and low-cost adsorbent named amine shield-introduced-released porous chitosan hydrogel beads (APCB) was synthesized and used for the removal of acid orange 7 from aqueous solutions.
A polynuclear hetero atom containing molecular organic scaffold to detect Al3+ ion through a fluorescence turn-on response
Authors: Ali Rashid , Razi Syed S. , Srivastava Priyanka , Shahid Mohammad , Misra Arvind
Published: July 2015

A simple polynuclear hetero atom (N and O) containing molecular organic scaffold/probe, 3 has been designed and synthesized and explored as a potential chemosensor to detect Al3+ (22 nM; ∼0.6 ppb) ion in a HEPES buffer.
A core–shell TiO2@C nano-architecture: facile synthesis, enhanced visible photocatalytic performance and electrochemical capacitance
Authors: Hou Linrui , Hua Hui , Cao Hui , Zhu Siqi , Yuan Changzhou
Published: July 2015

A mesoporous core–shell TiO2@C nanohybrid exhibited remarkable photocatalytic degradation efficiency and stability for methylene blue under visible light irradiation, and attractive electrochemical behaviors for electrochemical capacitors.
Surface-modified TS-1 with enhanced activity for cyclohexanone ammoximation in a Pickering emulsion and increased stability in hot aqueous ammonia
Authors: Xu Lei , Lv Guojun , Li Hang , Shen Yu , Cai Wangfeng , Wang Fumin , Zhang Xubin
Published: July 2015

Hydrophobilized TS-1, with moderate wettability, has an enhanced activity in cyclohexanone ammoximation in Pickering emulsion stabilized by it, and increased stability to endure hot aqueous ammonia.
Copper catalyzed synthesis of unsymmetrical diaryl sulfones from an arenediazonium salt and sodium p-toluenesulfinate
Authors: Gund Sitaram Haribhau , Shelkar Radheshyam Suresh , Nagarkar Jayashree Milind
Published: July 2015

Aryl sulfones have been synthesized by the reaction of sodium p-toluenesulfinate and arenediazonium salts using a CuI catalyzed homogeneous system.
Simple route for the generation of differently functionalized PVC@graphene–polyaniline fiber bundles for the removal of Congo red from wastewater
Authors: Kumar Rajeev , Ansari Mohd Omaish , Parveen Nazish , Barakat Mohamed A. , Cho Moo Hwan
Published: July 2015

This paper reports a simple route for the generation of fibrous polyvinyl chloride (PVC) and graphene (GN) fibers (PVC@GN).
Fluorescent selectivity for small molecules of three Zn-MOFs with different topologies based on a tetracarboxylate ligand
Authors: Yang Jie , Zhang Liangliang , Wang Xiaoqing , Wang Rongming , Dai Fangna , Sun Daofeng
Published: July 2015

Three Zn-MOFs depended on solvent conditions have been obtained. The guest-free forms demonstrate luminescent sensor for small molecules.
Improvement of electroactive β phase nucleation and dielectric properties of WO3·H2O nanoparticle loaded poly(vinylidene fluoride) thin films
Authors: Thakur Pradip , Kool Arpan , Bagchi Biswajoy , Hoque Nur Amin , Das Sukhen , Nandy Papiya
Published: July 2015

Electroactive β phase nucleation mechanism and promising dielectric properties of WO3·H2O nanoparticle loaded PVDF thin films.
A new single-phase white-light-emitting CaWO4:Dy3+ phosphor: synthesis, luminescence and energy transfer
Authors: Zhang Yang , Gong Weitao , Yu Jingjie , Pang Hongchang , Song Qiang , Ning Guiling
Published: July 2015

A new single-phase white-emitting CaWO4:Dy3+ phosphor has been successfully synthesized and the photoluminescence properties and energy-transfer mechanism have been carefully investigated.
Full-molar-ratio synthesis and enhanced lithium storage properties of CoxFe1−xCO3composites with an integrated lattice structure and an atomic-scale synergistic effect
Authors: Zhao Shiqiang , Wang Yuxi , Liu Rui , Yu Yue , Wei Shanshan , Yu Faqi , Shen Qiang
Published: July 2015

Hydrothermally synthesized CoxFe1−xCO3composites with an integrated lattice structure show enhanced lithium storage properties due to the atomic-scale synergistic effect between Co- and Fe-based components.
Synthesis and in vivo toxicity assessment of CdSe:ZnS quantum dots functionalized with EDTA-Bis-Cysteamine
Authors: Bag Narmada , Mathur Rashi , Hussain Firasat , Indracanti Namita , Singh Sweta , Singh Shivani , Chauhan Ram Prakash , Chuttani Krishna , Mishra Anil Kumar
Published: July 2015

Synthesis and in vivo toxicity assessment of radiolabeled Bis-ligand functionalized core shell quantum dot.
Cleft Missions: Don't Miss the Opportunity: A Special Opinion Piece
Authors: Peterson-Falzone Sally J.
Published: July 2015

Missions to developing countries to provide surgical care for children and adults with cleft lip and palate constitute unique opportunities for speech-language pathologists (SLPs). The SLP helps determine if a patient will actually benefit from a planned procedure, and occasionally has the chance to perform short-term therapy. The clinical experience gained on a 2-week mission is invaluable.
Mouth Matters: Scientific and Clinical Applications of Speech Movement Analysis
Authors: Green Jordan R.
Published: July 2015

New techniques for recording and analyzing speech movements have the potential to radically change existing approaches to speech assessment and management. Advances in motion capture hardware and software are now enabling a critical mass of researchers to comprehensively investigate speech motor performance in healthy and disordered populations. Although this technology is currently almost exclusively used for research, promising clinical applications are now emerging. In this paper, I briefly discuss the technological progression of current technologies used to record speech movements. I also highlight research in the Speech and Feeding Disorders Lab that is exploring ways to leverage this technology to assist with the assessment and management of motor speech disorders.
Improving the road network performance with dynamic route guidance by considering the indifference band of road users
Authors: Vreeswijk Jaap D. , Landman Ramon L. , van Berkum Eric C. , Hegyi Andreas , Hoogendoorn Serge P. , van Arem Bart
Published: July 2015

When applying dynamic route guidance to improve the road network performance, the interests of the road authorities and the road users are likely to conflict. Road users are normally aiming at minimising their travel times by choosing the time‐shortest route, whereas the authorities might want to send road users to a time‐longer alternative to prevent phenomena like capacity drop and spill‐back. In this study, the authors demonstrate how, in such a situation, bounded rationality and indifference bands (IB) of road users can be used to improve the network performance, such that the road users will not experience being disadvantaged by the advice. An interpretation and utilisation of the IBs in a route guidance control approach is proposed, which degrades the routes such that the network performance deterioration is prevented while the IBs of road users are respected. By means of a simulation test case, the potential gain in network performance of different IBs is evaluated. Results show a reduction in total travel time of 5% compared with user equilibrium, in case of an IB of 4 min for a trip of ∼22 min, and up to 14% in case of an IB of 10 min.
Quantum field theory of classically unstable Hamiltonian dynamics
Authors: Strauss Y. , Horwitz L. P. , Levitan J. , Yahalom A.
Published: July 2015

We study a class of dynamical systems for which the motions can be described in terms of geodesics on a manifold (ordinary potential models can be cast into this form by means of a conformal map). It is rigorously proven that the geodesic deviation equation of Jacobi, constructed with a second covariant derivative, is unitarily equivalent to that of a parametric harmonic oscillator, and we study the second quantization of this oscillator. The excitations of the Fock space modes correspond to the emission and absorption of quanta into the dynamical medium, thus associating unstable behavior of the dynamical system with calculable fluctuations in an ensemble with possible thermodynamic consequences.
Understanding the changes in ductility and Poisson's ratio of metallic glasses during annealing from microscopic dynamics
Authors: Wang Z. , Ngai K. L. , Wang W. H.
Published: July 2015

In the paper K. L. Ngai et al., [J. Chem. 140, 044511 (2014)], the empirical correlation of ductility with the Poisson's ratio, νPoisson, found in metallic glasses was theoretically explained by microscopic dynamic processes which link on the one hand ductility, and on the other hand the Poisson's ratio. Specifically, the dynamic processes are the primitive relaxation in the Coupling Model which is the precursor of the Johari–Goldstein β-relaxation, and the caged atoms dynamics characterized by the effective Debye–Waller factor f0 or equivalently the nearly constant loss (NCL) in susceptibility. All these processes and the parameters characterizing them are accessible experimentally except f0 or the NCL of caged atoms; thus, so far, the experimental verification of the explanation of the correlation between ductility and Poisson's ratio is incomplete. In the experimental part of this paper, we report dynamic mechanical measurement of the NCL of the metallic glass La60Ni15Al25 as-cast, and the changes by annealing at temperature below Tg. The observed monotonic decrease of the NCL with aging time, reflecting the corresponding increase of f0, correlates with the decrease of νPoisson. This is important observation because such measurements, not made before, provide the missing link in confirming by experiment the explanation of the correlation of ductility with νPoisson. On aging the metallic glass, also observed in the isochronal loss spectra is the shift of the β-relaxation to higher temperatures and reduction of the relaxation strength. These concomitant changes of the β-relaxation and NCL are the root cause of embrittlement by aging the metallic glass. The NCL of caged atoms is terminated by the onset of the primitive relaxation in the Coupling Model, which is generally supported by experiments. From this relation, the monotonic decrease of the NCL with aging time is caused by the slowing down of the primitive relaxation and β-relaxation on annealing, and vice versa.
Regular and chaotic dynamics of a piecewise smooth bouncer
Authors: Langer Cameron K. , Miller Bruce N.
Published: July 2015

The dynamical properties of a particle in a gravitational field colliding with a rigid wall moving with piecewise constant velocity are studied. The linear nature of the wall's motion permits further analytical investigation than is possible for the system's sinusoidal counterpart. We consider three distinct approaches to modeling collisions: (i) elastic, (ii) inelastic with constant restitution coefficient, and (iii) inelastic with a velocity-dependent restitution function. We confirm the existence of distinct unbounded orbits (Fermi acceleration) in the elastic model, and investigate regular and chaotic behavior in the inelastic cases. We also examine in the constant restitution model trajectories wherein the particle experiences an infinite number of collisions in a finite time, i.e., the phenomenon of inelastic collapse. We address these so-called “sticking solutions” and their relation to both the overall dynamics and the phenomenon of self-reanimating chaos. Additionally, we investigate the long-term behavior of the system as a function of both initial conditions and parameter values. We find the non-smooth nature of the system produces novel bifurcation phenomena not seen in the sinusoidal model, including border-collision bifurcations. The analytical and numerical investigations reveal that although our piecewise linear bouncer is a simplified version of the sinusoidal model, the former not only captures essential features of the latter but also exhibits behavior unique to the discontinuous dynamics.
Anomalous temperature dependent magneto-conductance in organic light-emitting diodes with multiple emissive states
Authors: Zhao Chen-xiao , Jia Wei-yao , Huang Ke-Xun , Zhang Qiao-ming , Yang Xiao-hui , Xiong Zu-hong
Published: July 2015

The temperature dependence of the magneto-conductance (MC) in organic electron donor-acceptor hybrid and layer heterojunction diodes was studied. The MC value increased with temperature in layer heterojunction and in 10 wt. % hybrid devices. An anomalous decrease of the MC with temperature was observed in 25 wt. %–50 wt. % hybrid devices. Further increasing donor concentration to 75 wt. %, the MC again increased with temperature. The endothermic exciplex-exciton energy transfer and the change in electroplex/exciton ratio caused by change in charge transport with temperature may account for these phenomena. Comparative studies of the temperature evolutions of the IV curves and the electroluminescence and photoluminescence spectra back our hypothesis.
Bi-layer metamaterials as fully functional near-perfect infrared absorbers
Authors: Adomanis Bryan M. , Watts Claire M. , Koirala Machhindra , Liu Xianliang , Tyler Talmage , West Kevin G. , Starr Tatiana , Bringuier Jonathan N. , Starr Anthony F. , Jokerst Nan Marie , Padilla Willie J.
Published: July 2015

In this letter, we discuss the design, fabrication, and experimental characterization of a bi-layer fully functional near-perfect metamaterial absorber (MMA) in the long-wavelength infrared (LWIR), which is broadband and generally insensitive to polarization up to a 60° incidence angle. A spectral absorptance of ≥99% was attained simultaneously at multiple LWIR wavelengths, with a bandwidth of 2 μm where the absorptance is ≥90%. This remarkable behavior is attributed to the strong mixing of coupling modes between the two resonators and the ground plane in the presence of a lossy dielectric, in which single layer structures do not exhibit. Furthermore, we show, by comparing two different MMA structures, how the absorption can be tailored by design within and across several IR subdivisions through a slight change in geometrical parameters. The bi-layer MMA has the immediate application of a functionally versatile, low-profile thermal sensor or emitter.
Understanding the effects of strain on morphological instabilities of a nanoscale island during heteroepitaxial growth
Authors: Feng Lu , Wang Jing , Wang Shibin , Li Linan , Shen Min , Wang Zhiyong , Chen Zhenfei , Zhao Yang
Published: July 2015

A comprehensive morphological stability analysis of a nanoscale circular island during heteroepitaxial growth is presented based on continuum elasticity theory. The interplay between kinetic and thermodynamic mechanisms is revealed by including strain-related kinetic processes. In the kinetic regime, the Burton-Cabrera-Frank model is adopted to describe the growth front of the island. Together with kinetic boundary conditions, various kinetic processes including deposition flow, adatom diffusion, attachment-detachment kinetics, and the Ehrlich-Schwoebel barrier can be taken into account at the same time. In the thermodynamic regime, line tension, surface energy, and elastic energy are considered. As the strain relief in the early stages of heteroepitaxy is more complicated than commonly suggested by simple consideration of lattice mismatch, we also investigate the effects of external applied strain and elastic response due to perturbations on the island shape evolution. The analytical expressions for elastic fields induced by mismatch strain, external applied strain, and relaxation strain are presented. A systematic approach is developed to solve the system via a perturbation analysis which yields the conditions of film morphological instabilities. Consistent with previous experimental and theoretical work, parametric studies show the kinetic evolution of elastic relaxation, island morphology, and film composition under various conditions. Our present work offers an effective theoretical approach to get a comprehensive understanding of the interplay between different growth mechanisms and how to tailor the growth mode by controlling the nature of the crucial factors.
Latent heat induced rotation limited aggregation in 2D ice nanocrystals
Authors: Bampoulis Pantelis , Siekman Martin H. , Kooij E. Stefan , Lohse Detlef , Zandvliet Harold J. W. , Poelsema Bene
Published: July 2015

The basic science responsible for the fascinating shapes of ice crystals and snowflakes is still not understood. Insufficient knowledge of the interaction potentials and the lack of relevant experimental access to the growth process are to blame for this failure. Here, we study the growth of fractal nanostructures in a two-dimensional (2D) system, intercalated between mica and graphene. Based on our scanning tunneling spectroscopy data, we provide compelling evidence that these fractals are 2D ice. They grow while they are in material contact with the atmosphere at 20 °C and without significant thermal contact to the ambient. The growth is studied in situ, in real time and space at the nanoscale. We find that the growing 2D ice nanocrystals assume a fractal shape, which is conventionally attributed to Diffusion Limited Aggregation (DLA). However, DLA requires a low mass density mother phase, in contrast to the actual currently present high mass density mother phase. Latent heat effects and consequent transport of heat and molecules are found to be key ingredients for understanding the evolution of the snow (ice) flakes. We conclude that not the local availability of water molecules (DLA), but rather them having the locally required orientation is the key factor for incorporation into the 2D ice nanocrystal. In combination with the transport of latent heat, we attribute the evolution of fractal 2D ice nanocrystals to local temperature dependent rotation limited aggregation. The ice growth occurs under extreme supersaturation, i.e., the conditions closely resemble the natural ones for the growth of complex 2D snow (ice) flakes and we consider our findings crucial for solving the “perennial” snow (ice) flake enigma.
Tuned range separated hybrid functionals for solvated low bandgap oligomers
Authors: de Queiroz Thiago B. , Kümmel Stephan
Published: July 2015

The description of charge transfer excitations has long been a challenge to time dependent density functional theory. The recently developed concept of “optimally tuned range separated hybrid (OT-RSH) functionals” has proven to describe charge transfer excitations accurately in many cases. However, describing solvated or embedded systems is yet a challenge. This challenge is not only computational but also conceptual, because the tuning requires identifying a specific orbital, typically the highest occupied one of the molecule under study. For solvated molecules, this orbital may be delocalized over the solvent. We here demonstrate that one way of overcoming this problem is to use a locally projected self-consistent field diagonalization on an absolutely localized molecular orbital expansion. We employ this approach to determine ionization energies and the optical gap of solvated oligothiophenes, i.e., paradigm low gap systems that are of relevance in organic electronics. Dioxane solvent molecules are explicitly represented in our calculations, and the ambiguities of straightforward parameter tuning in solution are elucidated. We show that a consistent estimate of the optimal range separated parameter (ω) at the limit of bulk solvation can be obtained by gradually extending the solvated system. In particular, ω is influenced by the solvent beyond the first coordination sphere. For determining ionization energies, a considerable number of solvent molecules on the first solvation shell must be taken into account. We demonstrate that accurately calculating optical gaps of solvated systems using OT-RSH can be done in three steps: (i) including the chemical environment when determining the range-separation parameter, (ii) taking into account the screening due to the solvent, and (iii) using realistic molecular geometries.
A mechanical-magneto-thermal model for the tunability of band gaps of epoxy/Terfenol-D phononic crystals
Authors: Zhang Shunzu , Shi Yang , Gao Yuanwen
Published: July 2015

A way based on the temperature effect is investigated to adjust the longitudinal wave band gaps of one-dimensional epoxy/Terfenol-D phononic crystals. For both the cases (with and without consideration of demagnetization effect), the dependences of component materials' effective parameters on temperature are obtained by applying a nonlinear mechanical-magneto-thermal coupling constitutive model and fitting the experimental data, respectively. Further, the influence of temperature on the band structure of wave propagation in phononic crystals consisting of epoxy and Terfenol-D is discussed in detail. Meanwhile, the effects of magnetic field, pre-stress, and filling fraction are studied. Numerical results show that temperature has a significant influence on the band structure of wave propagation in phononic crystals: As temperature rises from −40 °C to 40 °C, the widths of the first, second, and fourth band gaps increase, while that of the third band gap decreases. In addition, the demagnetization effect should not be ignored under a low magnetic field.
Cylindrical plasmas generated by an annular beam of ultraviolet light
Authors: Thomas D. M. , Allen J. E.
Published: July 2015

We investigate a cylindrical plasma system with ionization, by an annular beam of ultraviolet light, taking place only in the cylinder's outer region. In the steady state, both the outer and inner regions contain a plasma, with that in the inner region being uniform and field-free. At the interface between the two regions, there is an infinitesimal jump in ion density, the magnitude approaching zero in the quasi-neutral (λD → 0) limit. The system offers the possibility of producing a uniform stationary plasma in the laboratory, hitherto obtained only with thermally produced alkali plasmas.
Interpenetration and deflection phenomena in collisions between supersonic, magnetized, tungsten plasma flows diagnosed using high resolution optical Thomson scattering
Authors: Swadling G. F. , Lebedev S. V. , Harvey-Thompson A. J. , Rozmus W. , Burdiak G. , Suttle L. , Patankar S. , Smith R. A. , Bennett M. , Hall G. N. , Suzuki-Vidal F. , Bland S. , Yuan J.
Published: July 2015

An optical Thomson scattering diagnostic has been used to investigate collisions between supersonic, magnetized plasma flows, in particular the transition from collisionless to collisional interaction dynamics. These flows were produced using tungsten wire array z-pinches, driven by the 1.4 MA 240 ns Magpie generator at Imperial College London. Measurements of the collective-mode Thomson scattering ion-feature clearly indicate that the ablation flows are interpenetrating at 100 ns (after current start), and this interpenetration continues until at least 140 ns. The Thomson spectrum at 150 ns shows a clear change in the dynamics of the stream interactions, transitioning towards a collisional, shock-like interaction of the streams near the axis. The Thomson scattering data also provide indirect evidence of the presence of a significant toroidal magnetic field embedded in the “precursor” plasma near the axis of the array over the period 100–140 ns; these observations are in agreement with previous measurements [Swadling et al., Phys. Rev. Lett. 113, 035003 (2014)]. The Thomson scattering measurements at 150 ns suggest that this magnetic field must collapse at around the time the dense precursor column begins to form.
Rheology and morphology of no-slip sheared polymer nanocomposite under creep condition
Authors: Mortezapour Saba , Eslami Hossein , Nedaaee Oskoee Ehsan
Published: July 2015

Dissipative particle dynamics simulations are performed on wet polymer nanocomposite blends under the discrete imposed velocity profile and no-slip boundary conditions. To be able to study the chain length dependency of the rheological properties, a number of blends of mono-disperse polymer chains of lengths varying from 10 to 100 repeat units and nanoparticles of diameters 2.5 and 5 have been simulated. The wall velocity was imposed on a thin polymer layer (the no-slip layer). Linear velocity profiles for polymer confined in the pore were observed at the steady state. We found that the flow has a shear thinning effect on the chains with a radius of gyration less than the filler radius. Long chains (with a radius of gyration longer than the filler’s radius), however, obey the Newtonian behavior over a much wider shear rate than that which causes shear thinning in short chains. The effect of particle-monomer interactions, polymer entanglements, chain morphology, and link formation on the shear rate dependency of the viscosity coefficient has been studied. Our results show that the particle-polymer interactions have no effect on shear thinning behavior of the blend. In contrast, the long range polymer-polymer interactions and the chain length have considerable effects on the rheological behavior of the blend. Finally, the phase diagram of the rheological properties of polymer nanocomposite as a function of strain rate and the chain length is extracted.
Roothaan’s approach to solve the Hartree-Fock equations for atoms confined by soft walls: Basis set with correct asymptotic behavior
Authors: Rodriguez-Bautista Mariano , Díaz-García Cecilia , Navarrete-López Alejandra M. , Vargas Rubicelia , Garza Jorge
Published: July 2015

In this report, we use a new basis set for Hartree-Fock calculations related to many-electron atoms confined by soft walls. One- and two-electron integrals were programmed in a code based in parallel programming techniques. The results obtained with this proposal for hydrogen and helium atoms were contrasted with other proposals to study just one and two electron confined atoms, where we have reproduced or improved the results previously reported. Usually, an atom enclosed by hard walls has been used as a model to study confinement effects on orbital energies, the main conclusion reached by this model is that orbital energies always go up when the confinement radius is reduced. However, such an observation is not necessarily valid for atoms confined by penetrable walls. The main reason behind this result is that for atoms with large polarizability, like beryllium or potassium, external orbitals are delocalized when the confinement is imposed and consequently, the internal orbitals behave as if they were in an ionized atom. Naturally, the shell structure of these atoms is modified drastically when they are confined. The delocalization was an argument proposed for atoms confined by hard walls, but it was never verified. In this work, the confinement imposed by soft walls allows to analyze the delocalization concept in many-electron atoms.
Probing the anisotropic behaviors of black phosphorus by transmission electron microscopy, angular-dependent Raman spectra, and electronic transport measurements
Authors: Lu Wanglin , Ma Xiaomeng , Fei Zhen , Zhou Jianguang , Zhang Zhiyong , Jin Chuanhong , Zhang Ze
Published: July 2015

In this study, we correlated the angular dependence of the Raman response of black phosphorus to its crystallographic orientation by using transmission electron microscopy and Raman spectroscopy. It was found that the intensity of the Ag2 mode reached a maximum when the polarization direction of the incident light was parallel to the zigzag crystallographic orientation. Notably, it was further confirmed that the zigzag crystallographic direction exhibited superior conductance and carrier mobility. Because of the lattice extension along the armchair direction, an intensification of the anisotropic Raman response was observed. This work provides direct evidence of the correlation between anisotropic properties and crystallographic direction and represents a turning point in the discussion of the angular-dependent electronic properties of black phosphorus.
A large electrochemical setup for the anodization of aluminum towards highly ordered arrays of cylindrical nanopores
Authors: Assaud Loïc , Bochmann Sebastian , Christiansen Silke , Bachmann Julien
Published: July 2015

A new electrochemical setup and the associated procedures for growing ordered anodic aluminum oxide pore arrays on large surfaces are presented. The typical size of the samples is 14 × 14 cm2. The most crucial experimental parameters that allow for the stabilization of the high-field procedures are a very efficient cooling of sample and electrolyte, as well as the initial ramping up of the voltage at an accurately defined rate. The morphology of the cylindrical, parallel alumina pores is similar to those obtained on smaller scales with standard setups. Our setup facilitates the availability of porous anodic alumina as a template system for a number of applications.
Remarks on the room temperature impurity band conduction in heavily Al+ implanted 4H-SiC
Authors: Parisini A. , Gorni M. , Nath A. , Belsito L. , Rao Mulpuri V. , Nipoti R.
Published: July 2015

The processing parameters which favour the onset of an impurity band conduction around room temperature with a contemporaneous elevated p-type conductivity in Al+ implanted 4H-SiC are highlighted by comparing original and literature results. In the examined cases, Al is implanted at 300–400 °C, in concentrations from below to above the Al solubility limit in 4H-SiC (2 × 1020 cm−3) and post implantation annealing temperature is ≥1950 °C. Transport measurements feature the onset of an impurity band conduction, appearing at increasing temperature for increasing Al implant dose, until this transport mechanism is enabled around room temperature. This condition appears suitable to guarantee a thermal stability of the electrical properties. In this study, the heaviest doped and less resistive samples (Al implanted concentration of 5 × 1020 cm−3 and resistivity of about 2 × 10−2 Ω cm) show a carrier density above the Al solubility limit, which is consistent with at least a 50% electrical activation for a 15% compensation. The model of Miller and Abrahams well describes the resistivity data of the lower doped sample, whereas a deviation from the behaviour predicted by such a model is observed in the higher doped specimens, consistent with the occurrence of a variable range hopping at low temperature.