bluuebunny/crossref_metadata_2025 huggingface dataset:
Conductive silver inks and their applications in printed and flexible electronics
Authors: R. Venkata Krishna Rao , K. Venkata Abhinav , P. S. Karthik , Singh Surya Prakash
Published: August 2015

Conductive inks have been widely investigated in recent years due to their popularity in printed electronics (PE) and flexible electronics (FE).
Fe(OTs)3/SiO2: a novel catalyst for the multicomponent synthesis of dibenzodiazepines under solvent-free conditions
Authors: Tarannum Saima , Siddiqui Zeba N.
Published: August 2015

An Fe(OTs)3/SiO2catalyst was used as an efficient, recyclable, heterogeneous catalyst for the multicomponent synthesis of dibenzodiazepines.
Preparation of UV-curable functionalized phosphazene-containing nanotube/polyurethane acrylate nanocomposite coatings with enhanced thermal and mechanical properties
Authors: Qiu Shuilai , Li Siyu , Tao Youji , Feng Xiaming , Yu Bin , Mu Xiaowei , Xing Weiyi , Hu Yuan , Jie Ganxin
Published: August 2015

Poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) nanotubes with active hydroxyl groups were fabricated via an in situ template method under mild conditions, and then modified by acryloyl chloride to obtain the acryloyl-group functionalized PZS (f-PZS) nanotubes.
Convenient synthesis of organic-electronics-oriented building blocks via on-water and under-air homocoupling of (hetero)aryl iodides
Authors: Chen Yi-An , Liu Ching-Yuan
Published: August 2015

An on-water homocoupling reaction is developed for the alternative synthesis of various organic-electronically versatile bi(hetero)aryls. These multi-function building blocks are indispensable to polymer chemistry and modern organic electronics.
Synthesis, biological evaluation and molecular modeling of 1H-benzo[d]imidazole derivatives as novel anti-tubulin polymerization agents
Authors: Wang Fang , Wang Xue , Zhang Min-Xia , Yang Yong-Hua , Zhu Hai-Liang
Published: August 2015

A series of novel compounds (8a–21b) were designed and synthesized based on 2-phenyl-1H-benzo[d]imidazole. Compound 18b showed the most potent in vitro growth inhibitory activity and significant tubulin polymerization inhibitory activity.
Formation of lipid and polymer based gold nanohybrids using a nanoreactor approach
Authors: Witzigmann Dominik , Sieber Sandro , Porta Fabiola , Grossen Philip , Bieri Andrej , Strelnikova Natalja , Pfohl Thomas , Prescianotto-Baschong Cristina , Huwyler Jörg
Published: August 2015

Nanocarriers encapsulating gold nanoparticles hold tremendous promise for biomedical applications. The nanoreactor approach offers a versatile, efficient, and highly reproducible preparation technology.
Chromatographic selectivity of graphene capillary column pretreated with bio-inspired polydopamine polymer
Authors: Han Na , Qi Meiling , Ye Minghui , Fu Ruonong , Qu Liangti
Published: August 2015

Column fabrication by integration of graphene sheets on a polydopamine layer achieved improved column efficiency and chromatographic performance in capillary gas chromatographic separations.
A general electrodeposition-based method for in situ construction of resistive-type semiconductor film gas-sensor with excellent sensing performance
Authors: Pan Zizhao , Sun Fengqiang , Xu Shipu , Long Jinfeng , Chen Ying , Zhuang Zefeng
Published: August 2015

Based on an electrodeposition-based method, semiconductor film gas-sensors with excellent sensing performances were constructed in situ on a graphite-coating-covered ceramic tube.
Shape-dependent catalytic activity of Fe3O4 nanostructures under the influence of an external magnetic field for multicomponent reactions in aqueous media
Authors: Rafiee E. , Joshaghani M. , Ghaderi-Shekhi Abadi P.
Published: August 2015

Fe3O4 nanostructures were synthesized under external magnetic field, shown shape-dependent catalytic activity for the synthesis of imidazole derivatives in water.
Synthesis and characterization of Co(ii) and Fe(ii) peptide conjugates as hydrolytic cleaving agents and their preferential enantiomeric disposition for CT-DNA: structural investigation ofl-enantiomers by DFT and molecular docking studies
Authors: Parveen Sabiha , Usman Mohammad , Tabassum Sartaj , Arjmand Farukh
Published: August 2015

Molecular docked model of Co(ii) peptide conjugate with DNA and the mechanism of hydrolytic cleavage of pBR322 DNA.
Synthesis, characterization, and cure chemistry of high performance phosphate cyanate ester resins
Authors: Harvey Benjamin G. , Chafin Andrew C. , Garrison Michael D. , Cambrea Lee R. , Groshens Thomas J.
Published: August 2015

Three thermosetting cyanate ester resins with phosphate cores and potential fire-resistant applications have been synthesized and characterized. A trifunctional resin studied in this work (PhosCy3) has a Tg > 360 °C and a char yield of 67% in air.
The origin of the ligand-controlled regioselectivity in Rh-catalyzed [(2 + 2) + 2] carbocyclizations: steric vs. stereoelectronic effects
Authors: Crandell Douglas W. , Mazumder Shivnath , Evans P. Andrew , Baik Mu-Hyun
Published: August 2015

Density functional theory calculations demonstrate that the reversal of regiochemical outcome of the addition for substituted methyl propiolates in the rhodium-catalyzed [(2 + 2) + 2] carbocyclization with PPh3 and (S)-xyl-binap as ligands is both electronically and sterically controlled.
Dual stimuli-responsive coating designed through layer-by-layer assembly of PAA-b-PNIPAM block copolymers for the control of protein adsorption
Authors: Osypova A. , Magnin D. , Sibret P. , Aqil A. , Jérôme C. , Dupont-Gillain C. , Pradier C.-M. , Demoustier-Champagne S. , Landoulsi J.
Published: August 2015

We describe the construction, characteristics and interaction with proteins of stimuli-responsive nanostructured films prepared by layer-by-layer assembly of PAA-b-PNIPAM and PAH.
Mercaptophosphonic acids as efficient linkers in quantum dot sensitized solar cells
Authors: Aldakov Dmitry , Sajjad Muhammad T. , Ivanova Valentina , Bansal Ashu K. , Park Jinhyung , Reiss Peter , Samuel Ifor D. W.
Published: August 2015

New mercaptophosphonic linkers are presented for the attachment of ternary quantum dots to ZnO and TiO2 for photovoltaic applications.
One-pot synthesis of Au144(SCH2Ph)60 nanoclusters and their catalytic application
Authors: Liu Chao , Yan Chunyang , Lin Jizhi , Yu Changlin , Huang Jiahui , Li Gao
Published: August 2015

Here, we report the one-pot synthesis of atomically precise gold nanoclusters – Au144(SCH2Ph)60 with moderate efficiency (ca. 20% yield based on HAuCl4).
Facile preparation of graphene nanoribbon/cobalt coordination polymer nanohybrid for non-enzymatic H2O2 sensing by dual transduction: electrochemical and fluorescence
Authors: Ujjain Sanjeev K. , Ahuja Preety , Sharma Raj Kishore
Published: August 2015

A novel graphene nanoribbon (GNR)/cobalt coordination polymer (MCPs) composite (MCPs@GNR) is prepared by in situ reduction of graphene oxide nanoribbon (GONR) with simultaneous growth of MCPs nanoparticles on its surface demonstrating high H2O2 sensing.
Morphology and electromagnetic interference shielding effects of SiC coated carbon short fibers
Authors: Zhang Yi , Wang Zhou , Zhang Boliang , Zhou Chengjun , Zhao Guang-Lin , Jiang Jiechao , Guo S. M.
Published: August 2015

C–SiC core–shell short fiber fillers improve the electromagnetic interference shielding effectiveness in polymer composites.
Ag@Au hexagonal nanorings: synthesis, mechanistic analysis and structure-dependent optical characteristics
Authors: Lai Wei , Zhou Jun , Jia Zhenhong , Petti Lucia , Mormile Pasquale
Published: August 2015

Ag@Au hexagonal nanorings synthesized through a one-spot galvanic replacement route and their distinctive LSPR characteristics and SERS performance.
Ca3(BO3)2, a first wide waveband borate Raman laser crystal with strong Raman effects and outstanding anti-optical damage ability
Authors: Liu Yanqing , Zhang Fang , Wang Zhengping , Yu Fapeng , Wei Lei , Xu Xinguang , Zhao Xian
Published: August 2015

Borate crystals Ca3(BO3)2 are realized for stimulated Raman scattering from deep ultraviolet to near infrared.
Microstrip slow‐wave line for phase shifting cells
Authors: Gastaldi M. , Dragomirescu D. , Takacs A. , Armengaud V. , Rochette S.
Published: August 2015

The design, simulation and measurements of microstrip slow‐wave lines implemented in a 0.25 µm SiGe bipolar CMOS (BiCMOS) process is addressed for Ku‐band (10–15 GHz) applications. The simulation results and the measurements show better performances for the proposed microstrip slow‐wave line compared with the classical microstrip transmission line. These lines present very low insertion losses and a high phase constant.
84 GBd (168 Gbit/s) PAM‐4 3.7 Vpp power DAC in InP DHBT for short reach and long haul optical networks
Authors: Konczykowska A. , Jorge F. , Dupuy J‐Y. , Riet M. , Nodjiadjim V. , Aubry H. , Adamiecki A.
Published: August 2015

The architecture and performances of a multilevel driver for pulse amplitude modulation (PAM) formats, designed and fabricated in 0.7 µm InP double‐heterojunction bipolar transistor technology, are reported. The driver part is based on a power‐DAC architecture which is integrated with the multiplexing stage composed of three 2:1 selectors. Up to 100 GS/s operation was validated and PAM‐2, ‐4, ‐8 signals with high amplitude were measured. In particular, PAM‐4 at 84 GBd and PAM‐8 at 64 GBd operation was demonstrated with, respectively, a 3.7 and 4 Vpp differential output signal. This compact driver circuit is characterised by the highest merit factor in terms of high amplitude and the transmission capacity for an electronically generated multilevel signal.
Secrecy outage performance for partial relay selection schemes in cooperative systems
Authors: Zhou Yameng , Pan Gaofeng , Li Tingting , Liu Hequn , Tang Chaoqing , Chen Yunfei
Published: August 2015

In this study, secrecy outage performance is studied for partial relay selection (PRS) schemes in cooperative systems over Rayleigh fading channels. In the considered systems, there are one source (S), one destination (D), one eavesdropper, one jammer that can send interference to the eavesdropper, and N (N > 1) relay candidates, one of which is selected as the relay (R). By considering the practical scenarios and to protect the transmitted information over R–D link from being eavesdropped, the authors propose a new transmission scheme: let D send random information to R while S sending information to R. Then, R processes the messages from S and D by XOR operation in order to prevent the eavesdropper's interception while the information is delivered between R and D. They study the secrecy outage performance for two PRS schemes: (i) the optimal source–relay link (OSRL) scheme; and (ii) the optimal source–relay–destination link (OSRDL) scheme. The closed‐form expressions for the secrecy outage probability (SOP) of the two PRS schemes are derived, as well as the closed‐form upper bound for SOP under OSRL scheme and the lower bound for SOP under OSRDL scheme. Finally, simulation results are given to verify the presented analytical models and the proposed transmission scheme.
Performance analysis of zero‐forcing‐precoded scheduling system with adaptive modulation for multiuser‐multiple input multiple output transmission
Authors: Lee Donghun
Published: August 2015

In this study, the author presents performance analysis of a zero‐forcing (ZF)‐precoded scheduling system with adaptive modulation for multiuser‐multiple input multiple output transmission. The proposed scheduling system adapts the transmission rate and selects the best modulation to satisfy a given target bit error rate (BER). The author derive the tight closed‐form expressions of the ZF‐precoded system with adaptive modulation for the average spectral efficiency where user set non‐scheduling and user set scheduling methods are presented. The author also presents the tight closed‐form BER expressions of the non‐scheduling and scheduling systems with adaptive modulation for M‐ary quadrature amplitude modulation and M‐ary phase shift keying modulation. From the analytical results, the author shows that the proposed scheduling system provides performance improvement of the average spectral efficiency over the non‐scheduling system. Moreover, the proposed system provides the signal to noise ratio gain compared with the non‐scheduling system to satisfy the target BER regardless of modulation types. This is because the diversity order of the proposed system is superior to that of the non‐scheduling system by multi‐user diversity.
Localising low‐level short‐circuit faults on the windings of power transformers based on low‐frequency response measurement of the transformer windings
Authors: Mahvi Mojtaba , Behjat Vahid
Published: August 2015

Early detection and localisation of winding faults within the transformer can help make preventive actions and reduce potential damages to the transformer and the power system. This research work presents a new technique for sensitive detection and localisation of shorted turns on the windings of power transformers throughout low‐frequency response measurements of the transformer windings. To this end, using genetic algorithm, the detailed model of the damaged winding by the fault is estimated from the measured low‐frequency response data up to 10 kHz. The fault is localised along the winding by establishing the differences between the transfer functions of the healthy and faulty state of the winding units using statistical indicators. The experimental measurements which were made on a test transformer damaged by a low‐level short‐circuit fault proved that the newly developed method is sufficiently able and sensitive to detect and localise failures of only few shorted turns on the transformer windings.
Design of a hybrid hierarchical demand response control scheme for the frequency control
Authors: Bao Yu‐Qing , Li Yang , Hong Ying‐Yi , Wang Beibei
Published: August 2015

Conventionally, the frequency of the power system is controlled by matching the electric supply to the varying demand. Some recent studies demonstrated that demand response (DR) can also contribute to the frequency control. However, most of the research works focus on the overall control strategy of DR, whereas the DR parameters are usually randomised rather than carefully designed. In this study, a hybrid hierarchical DR control scheme is designed to support frequency control. The parameters settings are discussed in detail. Instead of randomising the parameters for individual DR controllers, this study proposes a systematic way to design the parameters such as frequency threshold and minimum off‐time for individual controllers, so that aggregation of DR can provide primary frequency control smoothly just like thermal generators. Furthermore, the control system is formulated as a multi‐objective optimisation problem. The parameters such as the recovery rate of DR and the integral gain of secondary frequency control is optimised so that the maximum deviation, overshoot and oscillations of the frequency can be properly minimised. The proposed method is verified on numerical examples.
Analysis of the global position system acquisition process in the presence of interference
Authors: Bek Mohammad K. , Shaheen Ehab M. , Elgamel Sherif A.
Published: August 2015

The objective of the acquisition process is to provide a rough estimate of Doppler and code delay of the received signal. The correlation process with a local replica generated by the receiver may have a peak that may cross the acquisition threshold. One of the threats that could interrupt such procedure is the presence of interfering signals which may severely cause an incorrect or no correlation peak during the acquisition process. To this end, this study investigates the performance of the global position system (GPS) signal acquisition process in the presence of different types of interfering signals such as: continuous wave interference, narrowband interference, partial band interference, broadband interference, matched spectrum interference and pulse interference. A novel classification to the interfering signals is presented. This classification is divided into two categories based on the interference contribution to the acquisition's output mean or variance values. Novel expressions of both false alarm and detection probabilities in the presence of noise along with different types of interfering signals are mathematically formulated. The comparison among the interfering signals based on the receiver operation characteristic is also performed. The impact of both coherent integration time and the phase shift between the GPS and the interfering signals on the acquisition performance is analysed.
Coplanar waveguide‐fed ultra‐wideband antenna with triple‐band notched design
Authors: Zhao Kun , Bai Dandan , Xia Yingqing , Wang Ying
Published: August 2015

A novel coplanar waveguide‐fed ultra‐wideband antenna with triple band‐notched function centred at 3.5, 5.5 and 7.5 GHz is proposed. It has small size of 26 × 26 mm2. This antenna consists of an elliptical radiator and a square ground plane with an elliptical slot on one side of the substrate. Besides, two circles with a radius of 2 mm were dug from the edge of the outer ellipse to realise the bandwidth requirement. To avoid interference from Worldwide Interoperability for Microwave Access, a single open‐ended elliptical arc‐shaped slot was etched on the top side of the ground. Moreover, another elliptical arc‐shaped slot notched at wireless local area network band was etched on the elliptical radiator and two systemically C‐shaped slots working at 7.3–7.7 GHz was embedded on the structure. Measured voltage standing wave ratio shows the working frequency range was from 3.1 to 13.5 GHz except for notched bands of 3.35–3.8, 5.1–5.9 and 7.35–7.8 GHz.
Unsaturated polyester resin/epoxy‐functionalised nanosilica composites constructed by in situ polymerisation
Authors: Yao Haiyang , Pan Hao , Li Rui Rui , Li Xiaohong , Zhang Zhijun
Published: August 2015

A reactable nanosilica surface capped with a silane coupling agent containing the epoxy group (denoted as RNS‐E) was allowed to participate in the in situ polycondensation reaction of unsaturated polyester resin (denoted as UPR) thereby affording the UPR/RNS‐E composite. The structure of the as‐prepared UPR/RNS‐E composites was investigated by means of Fourier transform infrared spectrometry, thermogravimetric analysis and scanning electron microscopy, and their tensile strength and impact strength were compared with those of pure UPR cured under the same condition and of UPR/RNS‐E composites prepared by mechanical blending. It was found that RNS‐E exhibits good strengthening effect and toughening effect for the in situ polymerised UPR/RNS‐E composite, which is attributed to the formation of a heterogeneous network structure in the cured UPR/RNS‐E composites via the chemical reaction among the epoxy group of RNS‐E and the hydroxyl (carboxyl) group of UPR. Particularly, the UPR/RNS‐E composite with 0.6% RNS‐E nanofiller has the highest tensile strength and impact strength, and it is much superior to the same composite obtained by mechanical blending.
Rayleigh-Taylor instability under an inclined plane
Authors: Brun P.-T. , Damiano Adam , Rieu Pierre , Balestra Gioele , Gallaire François
Published: August 2015

We revisit the canonical Rayleigh-Taylor instability and investigate the case of a thin film of fluid upon the underside of an inclined plane. The presence of a natural flow along the plane competes with the conventional droplet forming instability. In particular, experiments reveal that no drops form for inclinations greater than a critical value. These features are rationalized in the context of the absolute/convective analysis conducted in this article.
Explicit representations for multiscale Lévy processes and asymptotics of multifractal conservation laws
Authors: Górska K. , Woyczyński W. A.
Published: August 2015

Nonlinear conservation laws driven by Lévy processes have solutions which, in the case of supercritical nonlinearities, have an asymptotic behavior dictated by the solutions of the linearized equations. Thus, the explicit representation of the latter is of interest in the nonlinear theory. In this paper, we concentrate on the case where the driving Lévy process is a multiscale stable (anomalous) diffusion, which corresponds to the case of multifractal conservation laws considered in Biler et al. [J. Differ. Equations 148, 9 (1998); Stud. Math. 135, 231 (1999); Ann. Inst. Henri Poincare, Anal. Nonlineaire 18, 613 (2001); and Stud. Math. 148, 171 (2001)]. The explicit representations, building on the previous work on single-scale problems (see, e.g., Górska and Penson [Phys. Rev. E 83, 061125 (2011)]), are developed in terms of the special functions (such as Meijer G functions) and are amenable to direct numerical evaluations of relevant probabilities.
Turbulent mixing of passive scalar near turbulent and non-turbulent interface in mixing layers
Authors: Watanabe T. , Sakai Y. , Nagata K. , Ito Y. , Hayase T.
Published: August 2015

A direct numerical simulation of a temporally developing mixing layer with a passive scalar transport is performed for various Schmidt numbers (Sc = 0.25, 1, 4, and 8). Turbulent mixing is investigated near the turbulent/non-turbulent interface (TNTI), which is a layer consisting of the turbulent sublayer (TSL) and viscous superlayer (VSL). The irrotational boundary, which is close to the outer edge of the TNTI layer, is detected as the isosurface of small vorticity magnitude. The movement of fluid elements relative to the irrotational boundary movement is analyzed. Once the non-turbulent fluid is entrained into the VSL across the irrotational boundary by the viscous diffusion of vorticity, the fluid moves away from the irrotational boundary in the VSL in the normal direction of the irrotational boundary. After the fluid reaches the TSL, it is transported in the tangential direction of the irrotational boundary and is mixed with the fluid coming from the turbulent core (TC) region. The boundary between the TSL and VSL roughly separates the region (VSL) mostly consisting of the fluid entrained from the non-turbulent flow from the region (TSL) where the fluids from both the TC and non-turbulent regions coexist. Therefore, the scalar value in the VSL is close to the non-turbulent value especially for high Sc cases. Because of a large difference in the scalar between the TSL and VSL, a peak value of the conditional mean scalar dissipation rate appears near the boundary between the TSL and VSL independently of Sc.
Large-deviation joint statistics of the finite-time Lyapunov spectrum in isotropic turbulence
Authors: Johnson Perry L. , Meneveau Charles
Published: August 2015

One of the hallmarks of turbulent flows is the chaotic behavior of fluid particle paths with exponentially growing separation among them while their distance does not exceed the viscous range. The maximal (positive) Lyapunov exponent represents the average strength of the exponential growth rate, while fluctuations in the rate of growth are characterized by the finite-time Lyapunov exponents (FTLEs). In the last decade or so, the notion of Lagrangian coherent structures (which are often computed using FTLEs) has gained attention as a tool for visualizing coherent trajectory patterns in a flow and distinguishing regions of the flow with different mixing properties. A quantitative statistical characterization of FTLEs can be accomplished using the statistical theory of large deviations, based on the so-called Cramér function. To obtain the Cramér function from data, we use both the method based on measuring moments and measuring histograms and introduce a finite-size correction to the histogram-based method. We generalize the existing univariate formalism to the joint distributions of the two FTLEs needed to fully specify the Lyapunov spectrum in 3D flows. The joint Cramér function of turbulence is measured from two direct numerical simulation datasets of isotropic turbulence. Results are compared with joint statistics of FTLEs computed using only the symmetric part of the velocity gradient tensor, as well as with joint statistics of instantaneous strain-rate eigenvalues. When using only the strain contribution of the velocity gradient, the maximal FTLE nearly doubles in magnitude, highlighting the role of rotation in de-correlating the fluid deformations along particle paths. We also extend the large-deviation theory to study the statistics of the ratio of FTLEs. The most likely ratio of the FTLEs λ1 : λ2 : λ3 is shown to be about 4:1:−5, compared to about 8:3:−11 when using only the strain-rate tensor for calculating fluid volume deformations. The results serve to characterize the fundamental statistical and geometric structure of turbulence at small scales including cumulative, time integrated effects. These are important for deformable particles such as droplets and polymers advected by turbulence.
Large-eddy simulation of cavitating nozzle flow and primary jet break-up
Authors: Örley F. , Trummler T. , Hickel S. , Mihatsch M. S. , Schmidt S. J. , Adams N. A.
Published: August 2015

We employ a barotropic two-phase/two-fluid model to study the primary break-up of cavitating liquid jets emanating from a rectangular nozzle, which resembles a high aspect-ratio slot flow. All components (i.e., gas, liquid, and vapor) are represented by a homogeneous mixture approach. The cavitating fluid model is based on a thermodynamic-equilibrium assumption. Compressibility of all phases enables full resolution of collapse-induced pressure wave dynamics. The thermodynamic model is embedded into an implicit large-eddy simulation (LES) environment. The considered configuration follows the general setup of a reference experiment and is a generic reproduction of a scaled-up fuel injector or control valve as found in an automotive engine. Due to the experimental conditions, it operates, however, at significantly lower pressures. LES results are compared to the experimental reference for validation. Three different operating points are studied, which differ in terms of the development of cavitation regions and the jet break-up characteristics. Observed differences between experimental and numerical data in some of the investigated cases can be caused by uncertainties in meeting nominal parameters by the experiment. The investigation reveals that three main mechanisms promote primary jet break-up: collapse-induced turbulent fluctuations near the outlet, entrainment of free gas into the nozzle, and collapse events inside the jet near the liquid-gas interface.
Accelerated insulin aggregation under alternating current electric fields: Relevance to amyloid kinetics
Authors: Zheng Zhongli , Jing Benxin , Sorci Mirco , Belfort Georges , Zhu Yingxi
Published: August 2015

The time-dependent nucleation phase is critical to amyloid fibrillation and related to many pathologies, in which the conversion from natively folded amyloidogenic proteins to oligomers via nucleation is often hypothesized as a possible underlying mechanism. In this work, non-uniform AC-electric fields across two asymmetric electrodes were explored to control and examine the aggregation of insulin, a model amyloid protein, in aqueous buffer solution at constant temperature (20 °C) by fluorescence correlation spectroscopy and fluorescence microscopy. Insulin was rapidly concentrated in a strong AC-field by imposed AC-electroosmosis flow over an optimal frequency range of 0.5–2 kHz. In the presence of an AC-field, direct fibrillation from insulin monomers without the formation of oligomer precursors was observed. Once the insulin concentration had nearly doubled its initial concentration, insulin aggregates were observed in solution. The measured lag time for the onset of insulin aggregation, determined from the abrupt reduction in insulin concentration in solution, was significantly shortened from months or years in the absence of AC-fields to 1 min–3 h under AC-fields. The ability of external fields to alter amyloid nucleation kinetics provides insights into the onset of amyloid fibrillation.
Slowly moving test charge in two-electron component non-Maxwellian plasma
Authors: Ali S. , Eliasson B.
Published: August 2015

Potential distributions around a slowly moving test charge are calculated by taking into account the electron-acoustic waves in an unmagnetized plasma. Considering a neutralizing background of static positive ions, the supra-thermal hot and cold electrons are described by the Vlasov equations to account for the Kappa (power-law in velocity space) and Maxwell equilibrium distributions. Fourier analysis further leads to the derivation of electrostatic potential showing the impact of supra-thermal hot electrons. The test charge moves slowly in comparison with the hot and cold electron thermal speeds and is therefore shielded by the electrons. This gives rise to a short-range Debye-Hückel potential decaying exponentially with distance and to a far field potential decaying as inverse third power of the distance from the test charge. The results are relevant for both laboratory and space plasmas, where supra-thermal hot electrons with power-law distributions have been observed.
A diffuse interface approach to injection-driven flow of different miscibility in heterogeneous porous media
Authors: Chen Ching-Yao , Yan Pei-Yu
Published: August 2015

Miscible and immiscible injection flows in heterogeneous porous media, for which the permeability is characterized by a log Gaussian distribution, are simulated by a robust diffuse-interface formulation. The robust numerical method enables direct qualitative and quantitative comparisons regarding pattern formations in various fluid miscibility conditions. For miscible injections, the typical size of fingering structures depends strongly on the correlation length and forms tapered fingers with sharper tips. On the other hand, the typical size of immiscible fingers is affected less significantly by the permeability heterogeneity, and wide spreading tips are retained in the fingering patterns. Prominence of fingering instability is quantitatively evaluated by the channeling width and the interfacial length. The channeling width shows strong and monotonic dependences on the heterogeneous variance. On the contrary, maximum channeling width occurs at intermediate correlation length due to local resonant effect between the faster penetrating fingers and permeability heterogeneity. On the other hand, effects of the correlation length and the permeability variance on the interfacial lengths are generally consistent. Longer interfacial length is perturbed by smaller correlation length or higher variance. Interesting invariant evolutions of interfacial lengths are revealed regardless of the permeability variance in sufficiently large correlation length under all miscibility conditions. In addition, the regime of slower growth of interfacial length at later times experimentally observed in homogeneous miscible injection is verified in heterogeneous porous media as well.
Immiscible liquid–liquid pressure-driven flow in capillary tubes: Experimental results and numerical comparison
Authors: Soares Edson J. , Thompson Roney L. , Niero Debora C.
Published: August 2015

The immiscible displacement of one viscous liquid by another in a capillary tube is experimentally and numerically analyzed in the low inertia regime with negligible buoyancy effects. The dimensionless numbers that govern the problem are the capillary number Ca and the viscosity ratio of the displaced to the displacing fluids Nμ. In general, there are two output quantities of interest. One is associated to the relation between the front velocity, Ub, and the mean velocity of the displaced fluid, Ū2. The other is the layer thickness of the displaced fluid that remains attached to the wall. We compute these quantities as mass fractions in order to make them able to be compared. In this connection, the efficiency mass fraction, me, is defined as the complement of the mass fraction of the displaced fluid that leaves the tube while the displacing fluid crosses its length. The geometric mass fraction, mg, is defined as the fraction of the volume of the layer that remains attached to the wall. Because in gas–liquid displacement, these two quantities coincide, it is not uncommon in the literature to use mg as a measure of the displacement efficiency for liquid–liquid displacements. However, as is shown in the present paper, these two quantities have opposite tendencies when we increase the viscosity of the displacing fluid, making this distinction a crucial aspect of the problem. Results from a Galerkin finite element approach are also presented in order to make a comparison. Experimental and numerical results show that while the displacement efficiency decreases, the geometrical fraction increases when the viscosity ratio decreases. This fact leads to different decisions depending on the quantity to be optimized. The quantitative agreement between the numerical and experimental results was not completely achieved, especially for intermediate values of Ca. The reasons for that are still under investigation. The experiments conducted were able to achieve a wide range of Ca. We show that in the range 1 < Nμ < 2, wavy shape instabilities appear at the interface and that increasing capillary number the amplitude of those waves increases. A deeper investigation on the operation window where these instabilities occur is in order.
An effective medium approach for the elongational viscosity of non-colloidal and non-Brownian hard-sphere suspensions
Authors: Housiadas Kostas D.
Published: August 2015

An effective-medium fluid mechanics model based on the original idea first presented by Brinkman [“A calculation of the viscous force exerted by a flowing fluid on a dense swarm of particles,” Appl. Sci. Res. 1, 27-34 (1949)] for the viscous force exerted by a flowing fluid on a dense swarm of fixed spherical particles is utilized for the prediction of the elongational viscosity of a non-colloidal, non-Brownian hard-sphere suspension in an incompressible Newtonian matrix fluid. The same model was explored by Housiadas and Tanner [“A model for the shear viscosity of non-colloidal suspensions with Newtonian matrix fluids,” Rheol. Acta 53, 831-841 (2014)] for the derivation of an analytical formula for the bulk shear viscosity of the suspension as a function of the volume fraction of the solid phase, a formula which is in very good agreement with widely used semi-empirical relationships and available experimental data from the literature. In the present paper, it is assumed that a spherical particle is subject, in an average sense, to a far-field uniform uniaxial elongational flow and a suitable pressure gradient. Under steady, isothermal, creeping conditions, and imposing no-slip and no-penetration conditions at the surface of a particle in a stagnation point of the fluid and the far-field velocity and pressure profiles, the solution of the three-dimensional Brinkman equations is found analytically. The solution shows a faster decay of the velocity disturbances around a reference particle than the single-particle case. A volume average of the total stress tensor gives an analytical formula for the bulk elongational viscosity of the complex system as a function of the particle concentration. A significant increase of the elongation viscosity with increasing the particle concentration is predicted. The increase is larger than the corresponding increase of the shear viscosity, in qualitative accordance with the theoretical formula of Batchelor and Green [“The determination of the bulk stress in a suspension of spherical particles to order c2” J. Fluid Mech. 56(3), 401-427 (1972)]. The new formula reduces to Einstein’s expression in the infinite dilution limit and agrees well with other theoretical formulas in the semi-dilute regime. Moreover, the agreement of the new formula with recently developed semi-empirical formulas over the whole concentration regime is remarkable. Finally, the model predictions perform very well, and better than other formulas, when compared with a few experimental data for extensional measurements of hard-particle suspensions from the literature.
Grain-growth effect on dielectric nonlinearity of BaTiO3-based multi-layer ceramic capacitors
Authors: Yoon Seok-Hyun , Kim Mi-Yang , Nam Chan-Hee , Seo Jung-Wook , Wi Sung-Kwon , Hur Kang-Heon
Published: August 2015

A significant difference in dielectric nonlinearity was contrasted between fine- and coarse-grained BaTiO3-based multilayer ceramic capacitors. Grain growth resulted in a decrease in dielectric constant in low field but a steep increase with increase in alternating current field, which can be associated with a decrease in reversible and a significant increase in irreversible domain wall contribution from Preisach analysis. Fine-grained specimens showed almost cubic structure despite ferroelectric domain contrasts, which is anticipated to significantly reduce strain incompatibility during domain wall motion, and clean domain boundaries with no lattice defects. However, coarse-grained specimens with high aspect ratio of the tetragonal lattice should accompany lattice distortion with increased intergranular constraints during domain wall motion, and many lattice defects were observed near domain boundaries. These results demonstrate experimentally the presence of weak pinning centers in coarse-grained specimens, which inhibit domain wall motion in low alternating current fields. Long-range motion occurs beyond the threshold field and results in an abrupt increase in dielectric constant.
Harmonic strain-optical response revealed in the isotropic (liquid) phase of liquid crystals
Authors: Kahl P. , Baroni P. , Noirez L.
Published: August 2015

A strong optical birefringence is observed when applying a small amplitude oscillatory strain to the liquid phase of a liquid crystal. This unpredicted birefringence is found to oscillate at the same frequency as the driving frequency, with frequencies down to 0.01 Hz. This birefringence is visible up to 15 °C above the liquid crystal transition. This opto-dynamic property is interpreted as a result of a coupling of the orientational pretransitional fluctuations existing in the isotropic phase and long range elastic interactions recently identified in liquids. The conversion of the mechanical wave in an optical response is shapeable. Two examples of synchronized periodic signals are shown: the sine and the square waves. The optimization of the signal is analyzed using a Heaviside-step shear test. This optical property is immediately exploitable to design low energy on/off switching materials.
The ground-state potential energy curve of the radium dimer from relativistic coupled cluster calculations
Authors: Teodoro Tiago Quevedo , Haiduke Roberto Luiz Andrade , Dammalapati Umakanth , Knoop Steven , Visscher Lucas
Published: August 2015

The potential energy curve for the ground-state of radium dimer (Ra2) is provided by means of atomic and molecular relativistic coupled cluster calculations. The short-range part of this curve is defined by an equilibrium bond length of 5.324 Å, a dissociation energy of 897 cm−1, and a harmonic vibrational frequency of 20.5 cm−1. The asymptotic behavior at large interatomic distances is characterized by the van der Waals coefficients C6 = 5.090 × 103, C8 = 6.978 × 105, and C10 = 8.786 × 107 atomic units. The two regions are matched in an analytical potential to provide a convenient representation for use in further calculations, for instance, to model cold collisions between radium atoms. This might become relevant in future experiments on ultracold, optically trapped, radioactive radium atoms that are used to search for a permanent electric dipole moment.
Life-cycle assessment of five microalgae-to-biofuels processes of varying complexity
Authors: Adhikari Birendra , Pellegrino John
Published: August 2015

“Cradle-to-gate” life cycle analysis surrounding five algae-to-fuel/fuel precursor scenarios was studied. The different processes modeled were: an open pond producing either triacylglycerides (TAG) or free fatty acid methyl ester (FAME); a solar-lit photobioreactor producing either FAME or free fatty acids; and a light emitting diode irradiated (LED-lit) photobioreactor-producing TAG. These processes were chosen from amongst the simplest to most sophisticated approaches available in literature. The scenarios of production with open ponds are close to being sustainable environmentally. On the other hand, the production scenarios with solar-lit and LED-lit photobioreactors are both far from being sustainable. The reason for this is the higher embedded and operating life-cycle impacts associated with the materials in the growth reactor (and some other equipment) in these two types of production facilities, as well as the artificial photon source used in the latter. Many difficult-to-achieve improvements are required to make these processes less energy intensive. Algae strains with higher lipid productivity as well as changes in the number, the complexity, and energy expenditures in operation steps are always required to reduce overall life-cycle impacts when production of commodity fuels is the focus. An important perspective to keep in mind with algae-based processes is that there are currently no significant economies-of-scale with the environmental impacts for growth systems, since they are additive above a baseline production level.
Influence of intermolecular potentials on rarefied gas flows: Fast spectral solutions of the Boltzmann equation
Authors: Wu Lei , Liu Haihu , Zhang Yonghao , Reese Jason M.
Published: August 2015

The Boltzmann equation with an arbitrary intermolecular potential is solved by the fast spectral method. As examples, noble gases described by the Lennard-Jones potential are considered. The accuracy of the method is assessed by comparing both transport coefficients with variational solutions and mass/heat flow rates in Poiseuille/thermal transpiration flows with results from the discrete velocity method. The fast spectral method is then applied to Fourier and Couette flows between two parallel plates, and the influence of the intermolecular potential on various flow properties is investigated. It is found that for gas flows with the same rarefaction parameter, differences in the heat flux in Fourier flow and the shear stress in Couette flow are small. However, differences in other quantities such as density, temperature, and velocity can be very large.
Communication: Test of quantum chemistry in vibrationally hot hydrogen molecules
Authors: Niu M. L. , Salumbides E. J. , Ubachs W.
Published: August 2015

Precision measurements are performed on highly excited vibrational quantum states of molecular hydrogen. The v = 12, J = 0 − 3 rovibrational levels of H2 (X1Σg+), lying only 2000 cm−1 below the first dissociation limit, were populated by photodissociation of H2S and their level energies were accurately determined by two-photon Doppler-free spectroscopy. A comparison between the experimental results on v = 12 level energies with the best ab initio calculations shows a good agreement, where the present experimental accuracy of 3.5 × 10−3 cm−1 is more precise than theory, hence providing a gateway to further test theoretical advances in this benchmark quantum system.
Electrical conduction mechanism in Se90-xTe5Sn5Inx (x = 0, 3, 6 and 9) multi-component glassy alloys
Authors: Ram Indra Sen , Kumar Sunil , Singh Rajesh Kumar , Singh Prabhakar , Singh Kedar
Published: August 2015

Electrical conductivity of Se90-xTe5Sn5Inx (x = 0, 3, 6 and 9) glassy systems was studied employing impedance spectroscopic technique in the frequency range 100 Hz to 1 MHz and in the temperature range 308-388 K. The DC conductivity (σdc) at each temperature was evaluated from the low frequency plateau region for all the samples under investigation. The bulk conductivity for each sample was also evaluated from Nyquist impedance plots. The semicircle shape of Nyquist plot exhibit dipolar nature of samples. The activation energy for glassy, amorphous and crystalline region from the Arrhenius plot of the DC conductivity and bulk conductivity was evaluated. From the results it is found that activation energy varied from 0.091 to 0.194 eV in glassy, 0.686 to 0.002 eV in amorphous and 0.215 to 0.503 eV in crystalline region. The activation energy (ΔE) from DC conductivity and bulk conductivity found to be close in corresponding regions. The pre-exponential factor was also calculated for all three regions.
Note: Double-beveled multilayer stagger-split die for a large volume high-pressure apparatus
Authors: Wang Bolong , Li Mingzhe , Yang Yunfei , Liu Zhiwei
Published: August 2015

A high-pressure device with a large cavity was investigated using finite-element analysis. This device is called a double-beveled multilayer stagger-split die, and consists of two supported rings and a multilayer divided body assemblage. Each divided cylinder body has two bevels in the pressurized surface. We simulated the pressure capacity of this device according to different failure criteria. The results were compared with those of a multilayer stagger-split die and belt type die. The bearing capacity of the double-beveled multilayer stagger-split die was more than 7.3 GPa. A group of comparative experiments were conducted to validate the simulated results, and the experimental results show the actual pressure capacity was higher than the simulation.
Tuning the conductivity threshold and carrier density of two-dimensional electron gas at oxide interfaces through interface engineering
Authors: Ma H. J. Harsan , Zeng S. W. , Annadi A. , Huang Z. , Venkatesan T. , Ariando
Published: August 2015

The two-dimensional electron gas (2DEG) formed at the perovskite oxides heterostructures is of great interest because of its potential applications in oxides electronics and nanoscale multifunctional devices. A canonical example is the 2DEG at the interface between a polar oxide LaAlO3 (LAO) and non-polar SrTiO3 (STO). Here, the LAO polar oxide can be regarded as the modulating or doping layer and is expected to define the electronic properties of 2DEG at the LAO/STO interface. However, to practically implement the 2DEG in electronics and device design, desired properties such as tunable 2D carrier density are necessary. Here, we report the tuning of conductivity threshold, carrier density and electronic properties of 2DEG in LAO/STO heterostructures by insertion of a La0.5Sr0.5TiO3 (LSTO) layer of varying thicknesses, and thus modulating the amount of polarization of the oxide over layers. Our experimental result shows an enhancement of carrier density up to a value of about five times higher than that observed at the LAO/STO interface. A complete thickness dependent metal-insulator phase diagram is obtained by varying the thickness of LAO and LSTO providing an estimate for the critical thickness needed for the metallic phase. The observations are discussed in terms of electronic reconstruction induced by polar oxides.
Theoretical analysis of surface acoustic wave propagating properties of Y-cut nano lithium niobate film on silicon dioxide
Authors: Chen Jing , Zhang Qiaozhen , Han Tao , Zhou Liu , Tang Gongbin , Liu Boquan , Ji Xiaojun
Published: August 2015

The surface acoustic wave (SAW) propagating characteristics of Y-cut nano LiNbO3 (LN) film on SiO2/LN substrate have been theoretically calculated. The simulated results showed a shear horizontal (SH) SAW with enhanced electromechanical coupling factor K2 owing to a dimensional effect of the nanoscale LN film. However, a Rayleigh SAW and two other resonances related to thickness vibrations caused spurious responses for wideband SAW devices. These spurious waves could be fully suppressed by properly controlling structural parameters including the electrode layer height, thickness, and the Euler angle (θ) of the LN thin film. Finally, a pure SH SAW was obtained with a wide θ range, from 0° to 5° and 165° to 180°. The largest K2 achieved for the pure SH SAW was about 35.1%. The calculated results demonstrate the promising application of nano LN film to the realization of ultra-wideband SAW devices.