bluuebunny/crossref_metadata_2025 huggingface dataset:
Milestones in graphical bioinformatics
Authors: Randić Milan , Novič Marjana , Plavšić Dejan
Published: June 2013

After reviewing the field of graphical bioinformatics, we have selected two dozen of the most significant publications that represent milestones of graphical bioinformatics. These publications can be viewed as forming the backbone of graphical bioinformatics, the branch of bioinformatics that initiates analysis of DNA, RNA, and proteins by considering various graphical representations of these sequences. Graphical bioinformatics, a division of bioinformatics that analyzes sequences of DNA, RNA, proteins, and proteomics maps by developing and using tools of discrete mathematics and graph theory in particular, has expanded since the year 2000, although pioneering contributions date back to Hamory (1983) and Jeffrey (1990). We chronologically follow the development of graphical bioinformatics, without assuming that readers are familiar with discrete mathematics or graph theory. Readers unfamiliar with graph theory may even have some advantage over those who have been only superficially exposed to graph theory, inview of wide misconceptions and misinformation about chemical graph theory among quantum chemists, physical chemists, and medicinal chemists in past decades. © 2013 Wiley Periodicals, Inc.
A robust smart card‒based anonymous user authentication protocol for wireless communications
Authors: Wen Fengtong , Susilo Willy , Yang Guomin
Published: June 2013

Anonymous user authentication is an important but challenging task for wireless communications. In a recent paper, Das proposed a smart card‒based anonymous user authentication protocol for wireless communications. The scheme can protect user privacy and is believed to be secure against a range of network attacks even if the secret information stored in the smart card is compromised. In this paper, we reanalyze the security of Das' scheme, and show that the scheme is in fact insecure against impersonation attacks. We then propose a new smart card‒based anonymous user authentication protocol for wireless communications. Compared with the existing schemes, our protocol uses a different user authentication mechanism, which does not require different entities to maintain a synchronized clock. We show that the proposed new protocol can provide stronger security and better efficiency and scalability than previous schemes.
Rainfall extremes, excesses, and intensity‐duration‐frequency curves: A unified asymptotic framework and new nonasymptotic results based on multifractal measures
Authors: Veneziano Daniele , Yoon Seonkyoo
Published: June 2013

We present a unified asymptotic theory of rainfall extremes including annual maxima, excesses above high thresholds, and intensity‐duration‐frequency (IDF) curves that builds on previous findings and derive new nonasymptotic results. The analysis is based on stationary multifractal representations of rainfall and produces extensions of the familiar results from extreme value (EV) and extreme excess (EE) theories. The latter results apply to theT‐yr maximum asT→∞ and the excess abovezasz→∞. By exploiting the scaling relationship among the distributions of rainfall intensity for different averaging durationsd, the multifractal asymptotics include, in addition, results in the small‐scale limitsd→0 andwithα > 0. In all cases, the maximum distributions are of the generalized extreme value (GEV) type, but the indexkdepends on the limit considered. Multifractal models also produce asymptotic scaling results for the IDF curves. For the nonasymptotic case (dandTfinite), we obtain accurate approximations of the IDF curves and derive a semitheoretical formula for the indexkof the GEV model that best approximates the distribution of the annual maximum over a finite range of return‐period intensities. The nonasymptotic analysis explains several observed deviations of rainfall extremes from the asymptotic predictions, such as the tendency ofkto decrease as the averaging durationdincreases and the tendency of the IDF curves to converge asdor the return periodTincrease.
Warming effects in the western Antarctic Peninsula ecosystem: the role of population dynamic models for explaining and predicting penguin trends
Authors: Lima Mauricio , Estay Sergio A.
Published: June 2013

The western Antarctica Peninsula and Scotia Sea ecosystems appear to be driven by complex links between climatic variables, primary productivity, krill and Avian predators. There are several studies reporting statistical relationships between climate, krill and Penguin population size. The Adélie (Pygoscelis adeliae), Chinstrap (P. antarctica) and Gentoo (P. papua) penguins appear to be influenced by interannual variability in sea‐ice extent and krill biomass. In this paper we developed simple conceptual models to decipher the role of climate and krill fluctuations on the population dynamics of these three Pygoscelis penguin species inhabiting the Antarctic Peninsula region. Our results suggest that the relevant processes underlying the population dynamics of these penguin species at King George Island (South Shetland Islands) are intra‐specific competition and the combined effects of krill abundance and sea‐ice cover. Our results using population theoretical models appear to support that climate change, specifically regional warming on the western Antarctic Peninsula, represents a major driver. At our study site, penguins showed species‐specific responses to climate change. While Chinstrap penguins were only influenced by krill abundance, the contrasting population trends of Adélie and Gentoo penguins appear to be better explained by the “sea‐ice hypothesis”. We think that proper population dynamic modeling and theory are essential for deciphering and proposing the ecological mechanisms underlying dynamics of these penguin populations.
Time-based comparative transcriptomics in engineered xylose-utilizing Saccharomyces cerevisiae identifies temperature-responsive genes during ethanol production
Authors: Ismail Ku Syahidah Ku , Sakamoto Takatoshi , Hasunuma Tomohisa , Kondo Akihiko
Published: June 2013

Agricultural residues comprising lignocellulosic materials are excellent sources of pentose sugar, which can be converted to ethanol as fuel. Ethanol production via consolidated bioprocessing requires a suitable microorganism to withstand the harsh fermentation environment of high temperature, high ethanol concentration, and exposure to inhibitors. We genetically enhanced an industrial Saccharomyces cerevisiae strain, sun049, enabling it to uptake xylose as the sole carbon source at high fermentation temperature. This strain was able to produce 13.9 g/l ethanol from 50 g/l xylose at 38 °C. To better understand the xylose consumption ability during long-term, high-temperature conditions, we compared by transcriptomics two fermentation conditions: high temperature (38 °C) and control temperature (30 °C) during the first 12 h of fermentation. This is the first long-term, time-based transcriptomics approach, and it allowed us to discover the role of heat-responsive genes when xylose is the sole carbon source. The results suggest that genes related to amino acid, cell wall, and ribosomal protein synthesis are down-regulated under heat stress. To allow cell stability and continuous xylose uptake in order to produce ethanol, hexose transporter HXT5, heat shock proteins, ubiquitin proteins, and proteolysis were all induced at high temperature. We also speculate that the strong relationship between high temperature and increased xylitol accumulation represents the cell’s mechanism to protect itself from heat degradation.
THE EFFECTS OF INPUT ENHANCEMENT ON GRAMMAR LEARNING AND COMPREHENSION
Authors: Winke Paula M.
Published: June 2013

In his 2007 study “Effects of Textual Enhancement and Topic Familiarity on Korean EFL Students’ Reading Comprehension and Learning of Passive Form,” Lee demonstrated that learners were better able to correct written sentences that contained incorrect English passive forms after exposure to texts flooded with enhanced (versus nonenhanced) passive forms. But with enhanced forms, learners did worse on comprehension tests, which arguably demonstrated a trade-off: More attention to forms resulted in less to meaning. In this study, a conceptual replication of Lee’s using eye-movement data, I assessed how English passive construction enhancement affects English language learners’ (a) learning of the form (via pre- and posttest gains on passive construction tests) and (b) text comprehension. In contrast to Lee’s results, I found enhancement did not significantly increase form correction gain scores, nor did enhancement significantly detract from comprehension. There was no trade-off effect. Form learning and comprehension did not correlate. By recording learners’ eye movements while reading, I found enhancement significantly impacted learners’ noticing of the passive forms through longer gaze durations and rereading times. Thus, enhancement in this study functioned as intuitively and originally (Sharwood Smith, 1991, 1993) proposed; it promoted noticing, but, in this case, without further explicit instruction, it appeared to have done little else.
Should the trade of hazardous waste be uniformly regulated? An empirical analysis of export demand for ‘waste and scrap’
Authors: Ichinose Daisuke , Higashida Keisaku , Shinkuma Takayoshi , Kojima Michikazu
Published: June 2013

We examine the substitutability of waste and scrap exported from different countries by estimating the export demand functions of China. In particular, we focus on the export of other ferrous waste and scrap (HS code 720449) and other waste, parings and scrap of plastics (HS code 391590). It is shown that the substitutability of these wastes and scraps is weak among the exporting countries. Our empirical results imply that a uniform ban on trading hazardous waste, represented by the Basel Ban, could be an inefficient environmental policy.
Alternative selection rules for one- and two-photon transitions in tribenzotetraazachlorin: Quasi-centrosymmetrical π-conjugation pathway of formally non-centrosymmetrical molecule
Authors: Makarov Nikolay S. , Drobizhev Mikhail , Wicks Geoffrey , Makarova Elena A. , Lukyanets Evgeny A. , Rebane Aleksander
Published: June 2013

We compare the two-photon absorption (2PA) spectra of non-centrosymmetrical metal-free tribenzo-tetraazachlorin (H2TBTAC) and analogous symmetrical tetra-tert-butyl-phthalocyanine (H2TtBuPc). Surprisingly, despite formal lack of center of inversion, the 2PA spectrum of H2TBTAC displays a two-photon allowed transition at 935 nm, similar to gerade–gerade (g–g) transitions observed in H2TtBuPc and in other symmetrical phthalocyanines. This transition is even better resolved in the singlet–singlet excited-state absorption spectrum. We tentatively explain the survival of the g–g transition in H2TBTAC by assuming that the main π-electron conjugation pathway in the tetraaza-substituted tetrapyrrole macrocycle bypasses the outer parts of the two oppositely located isoindole rings and thus renders the optically responsive core of the chromophore quasi-centrosymmetrical. By using the independently measured ground- and excited-state absorption extinction coefficients, we also show that the two-photon absorptivity can be quantitatively explained by a simple three-level model with the lowest energy Q1 state serving as an intermediate level.
Zinc oxide nanotubes: An ab initio investigation of their structural, vibrational, elastic, and dielectric properties
Authors: Lacivita V. , Erba A. , Noël Y. , Orlando R. , D’Arco Ph. , Dovesi R.
Published: June 2013

Structural, vibrational, elastic, and dielectric properties of ZnO single-walled nanotubes are investigated theoretically. Calculations are carried out by using a Gaussian basis set and the B3LYP hybrid functional as implemented in the periodic ab initio CRYSTAL code. Nanotubes with increasing radius display asymptotic limits to the infinite monolayer. One soft phonon mode is recognized, whose vibration frequency is shown to be connected to the elastic constant C11 of the monolayer as the 1D → 2D transition is approached. The value of Young's elastic modulus of the nanotubes denotes a remarkable flexibility. Electronic and ionic contributions to the polarizability turn out to be comparable in magnitude. In particular, geometry relaxations at increasing radii show large influence on the transverse vibrational polarizability.
Vibrational and structural properties of amorphous n-butanol: A complementary Raman spectroscopy and X-ray diffraction study
Authors: Hédoux Alain , Guinet Yannick , Paccou L. , Derollez P. , Danède F.
Published: June 2013

Raman spectroscopy and X-ray diffraction experiments were performed in the liquid, undercooled liquid, and glassy states of n-butanol. Clear correlated signatures are obtained below the melting temperature, from both temperature dependences of the low-wavenumber vibrational excitations and the intermediate-range order characterized by a prepeak detected in the different amorphous states. It was found that these features are related to molecular associations via strong hydrogen bonds, which preferentially develop at low temperature, and which are not compatible with the long-range order of the crystal. This study provides information on structural heterogeneities developing in hydrogen-bonded liquids, associated to the undercooled regime and the inherent glass transition. The analysis of the isothermal abortive crystallization, 2 K above the glass transition temperature, has given the opportunity to analyze the early stages of the crystallization and to describe the origin of the frustration responsible for an uncompleted crystallization.
Entrainment of noise-induced and limit cycle oscillators under weak noise
Authors: Mitarai Namiko , Alon Uri , Jensen Mogens H.
Published: June 2013

Theoretical models that describe oscillations in biological systems are often either a limit cycle oscillator, where the deterministic nonlinear dynamics gives sustained periodic oscillations, or a noise-induced oscillator, where a fixed point is linearly stable with complex eigenvalues, and addition of noise gives oscillations around the fixed point with fluctuating amplitude. We investigate how each class of models behaves under the external periodic forcing, taking the well-studied van der Pol equation as an example. We find that when the forcing is additive, the noise-induced oscillator can show only one-to-one entrainment to the external frequency, in contrast to the limit cycle oscillator which is known to entrain to any ratio. When the external forcing is multiplicative, on the other hand, the noise-induced oscillator can show entrainment to a few ratios other than one-to-one, while the limit cycle oscillator shows entrain to any ratio. The noise blurs the entrainment in general, but clear entrainment regions for limit cycles can be identified as long as the noise is not too strong.
Metric solutions in torsionless gauge for vacuum conformal gravity
Authors: Fabbri Luca
Published: June 2013

In a recent paper we have established the form of the metric-torsional conformal gravitational field equations, and in the present paper we study their vacuum configurations; we will consider a specific situation that will enable us to look for the torsionless limit: two types of special exact solutions are found eventually. A discussion on general remarks will follow.
Recording of self-induced waveguides in lithium niobate at 405 nm wavelength by photorefractive–pyroelectric effect
Authors: Popescu S. T. , Petris A. , Vlad V. I.
Published: June 2013

We characterize the process of soliton waveguides (SWGs) recording at 405 nm wavelength using pyroelectric effect in lithium niobate (LN) crystals. We experimentally study and discuss the influence of the input irradiance, the polarization of the signal beam, and the crystal temperature change on the waveguide writing time and mode-profile. These characteristics significantly change when changing the recording wavelength. The advantages of recording SWGs in LN by using blue-violet light and pyroelectric field are emphasised. The generation of radiation at 405 nm wavelength by inexpensive laser diodes, the fast recording at this wavelength, and the convenient way to produce a static electric field inside the crystal by heating it with few degrees leads to a next step in the soliton waveguides recording process with applications in 3D integrated optical circuits.
The use of mould-templated surface structures for high-quality uniform-lying-helix liquid-crystal alignment
Authors: Outram B. I. , Elston S. J. , Tuffin R. , Siemianowski S. , Snow B.
Published: June 2013

The chiral-flexoelectrooptic effect in a Uniform Lying Helix (ULH) configuration provides a sub-millisecond in-plane rotation of the optic axis with the application of a transverse field. This enables displays with a wide viewing angle without costly in-plane-type electrodes. The salient challenge is one of alignment of the ULH, which is not topologically compatible with uniform alignment surface treatments. Here, we create a micro-grooved surface structure with features on the micron scale by using a replica-moulding technique. When the cell is assembled, the micro-grooves create channels, and using surface-energy considerations, we explain how and show experimentally that the channels align a cholesteric material in the ULH geometry with the helicoidal axis oriented parallel to the channels. The resultant alignment provides a high level of contrast between crossed polarizers and exhibits an electrooptic response with a switching time of the order of tens of microseconds.
Note: Investigation on the influences of gripping methods on elastic modulus by a miniature tensile device and in situ verification
Authors: Ma Z. C. , Zhao H. W. , Wang K. T. , Zhou X. Q. , Hu X. L. , Lu S. , Cheng H. B.
Published: June 2013

In this paper, by gripping the specimen on various positions, including the gripping section, stress concentration transition section, and gauge length section, theoretical analysis on the influences of gripping methods on tensile elastic modulus calculation was investigated with a group of equations. Then, an image-based displacement measurement system was implemented, and the experimental verification via in situ tensile testing was carried out to verify the feasibility of the theoretical analysis by a miniature tensile device integrated with a metallographic microscope. The stress-strain curves of 2026 aluminum alloy were also obtained by gripping the specimens on various positions to illustrate the influences of gripping methods. The influence of gripping methods on elongation measurement was also investigated. This paper showed a modular calculation method of elastic modulus for the tensile testing of typical plate specimens.
Radiation hardness of graphene and MoS2 field effect devices against swift heavy ion irradiation
Authors: Ochedowski O. , Marinov K. , Wilbs G. , Keller G. , Scheuschner N. , Severin D. , Bender M. , Maultzsch J. , Tegude F. J. , Schleberger M.
Published: June 2013

We have investigated the deterioration of field effect transistors based on two-dimensional materials due to irradiation with swift heavy ions. Devices were prepared with exfoliated single layers of MoS2 and graphene, respectively. They were characterized before and after irradiation with 1.14 GeV U28+ ions using three different fluences. By electrical characterization, atomic force microscopy, and Raman spectroscopy, we show that the irradiation leads to significant changes of structural and electrical properties. At the highest fluence of 4 × 1011 ions/cm2, the MoS2 transistor is destroyed, while the graphene based device remains operational, albeit with an inferior performance.
Dirac-Schrödinger transformations in contacted graphene structures
Authors: Dragoman Daniela
Published: June 2013

At an interface between contacts and graphene, the mathematical equation that governs the propagation of electrons transforms from the Schrödinger to the Dirac equation. The condition of current probability conservation at such an interface does not determine uniquely the boundary conditions for the quantum wavefunction. We discuss the possible form of boundary conditions, determine its influence on the transmission coefficient of a contacted graphene structure, and suggest that optical experiments on photonic crystals with Dirac points can help identifying, under certain circumstances, the proper boundary condition at graphene/electrode interfaces.
Impedance response and dielectric relaxation in co-precipitation derived ferrite (Ni,Zn)Fe2O4 ceramics
Authors: Chen D. G. , Tang X. G. , Liu Q. X. , Jiang Y. P. , Ma C. B. , Li R.
Published: June 2013

Dielectric spectra and magnetization hysteresis loops were used to investigate the grain size effect with temperature on the electrical and magnetic response of co-precipitation derived spinel (Ni0.5Zn0.5)Fe2O4 (NZFO) ceramics. Remarkable dielectric relaxation phenomena of non-Debye type have been observed in each NZFO ceramics as confirmed by two kinds of Cole-Cole plots of the 1100 °C sintered samples, mainly due to the electron-hopping mechanism between n-type and p-type carriers and interfacial ion effect when applied an increase of temperature. The high and low response of grain and grain-boundary regions were determined by modeling the impedance experimental results on two equivalent RC circuits taking into account grain deep trap states. By employing the modified Arrhenius equation, activation energy values of different sintering temperatures were calculated and analyzed in combination with oxygen vacancy. In addition, the magnetization of various sintering temperature samples is dominated by cation distribution and surface effect in different particle ranges.
Chaotic flow in an aortic aneurysm
Authors: Parashar Abhinav , Singh Rahul , Panigrahi P. K. , Muralidhar K.
Published: June 2013

Oscillatory flow in straight and deformed geometries is seen in various biomedical applications. The nature of flow plays a significant role in the pathogenesis of an abdominal aortic aneurysm. The present study examines the onset of chaotic flow inside a bulged tube under oscillating flow conditions. An experimental facility is set up for generating the oscillatory flow field inside the model. A fusiform shaped model is hollowed out in a rectangular silicone model. A mixture of water and glycerin is used as the working liquid. Two-camera imaging system placed at right angles is used for three-component velocity measurement of a spherical particle inside the model. Images recorded as a time sequence are analyzed by a particle tracking algorithm. The particle trajectories in space and instantaneous velocities within the bulge have been obtained from experiments as well as numerical simulation. The frequency of oscillation considered is 1.2 Hz and the peak Reynolds numbers are in the range of 650–1200 (experiments) and 1000–3500 (simulation). The dimensionless frequency defined by the Womersely number is in the range of 10–12. Velocity signals obtained from the experiment have been analyzed to study chaotic behavior of fluid flow. Chaos is quantified in terms of the largest Lyapunov exponent, positive values being a signature of chaos. The Lyapunov exponent increases with Reynolds number and is significantly higher in the bulged geometry compared to that of the straight tube. The signature of chaotic flow is also seen in power spectra and Poincaré plots.
Nonspecific detection of lead ions in water using a simple integrated optical polarimetric interferometer
Authors: Lu Dan-feng , Li Jinyang , Qi Zhi-mei
Published: June 2013

Real-time detection of heavy metal ions in water was implemented by using a composite optical waveguide (COWG) based polarimetric interferometer. The COWG was made by local deposition of a tapered nanometric layer of high-index materials onto a single-mode slab glass waveguide, and it is a low-cost robust waveguide with a locally large modal birefringence. The COWG-based polarimetric interferometer operates with a single incident laser beam and uses the transverse electric and transverse magnetic modes as the sensing and reference beams, respectively, and it can easily detect 0.1 ppm lead(II) ions in water via nonspecific adsorption on the tapered layer of TiO2. The excellent linearity was obtained between the lead(II) concentration and the ratio of concentration to the phase-difference change (Δϕ), suggesting that adsorption of lead(II) ions on the TiO2 film follows the Langmuir isotherm model. The saturation adsorption leads to Δϕmax = 7.485π. By use of the eigenvalue equations for a homogeneous waveguide to fit the measured refractive-index (RI) sensitivity of the interferometer, the equivalent thickness of Teq = 26.05 nm for the tapered TiO2 layer used was achieved. With Teq = 26.05 nm and Δϕmax = 7.485π and the thickness of 0.264 nm for the lead(II) adlayer, the adlayer RI was derived to be nad ≈ 1.945 at the maximum coverage.
Triple-band polarization-insensitive wide-angle ultra-thin planar spiral metamaterial absorber
Authors: Huang Xiaojun , Yang Helin , Yu Shengqing , Wang Jixin , Li Minhua , Ye Qiwei
Published: June 2013

The design, fabrication, and measurement of a triple-band metamaterial absorber are presented. The proposed absorber consists of a metallic planar spiral layer and a metallic ground plane separated by a dielectric layer. Experimental results show that the proposed absorber can perform absorption peaks at three resonant frequencies 9.86 GHz, 12.24 GHz, and 15.34 GHz with the absorption of 99.4%, 96.7%, and 99.1%, respectively. In addition, the absorber with the thickness of λ/35 at the lowest fundamental resonant frequency can operate at a wide range of incident angles under both transverse electric and transverse magnetic polarizations.
Instability of amorphous hafnium-indium-zinc-oxide thin film transistors under negative-bias-illumination stress
Authors: Chul Park Jae , Ahn Seung-Eon , Jung Kim Chang , Lee Ho-Nyeon , Im Seongil
Published: June 2013

In this study, the degradation mechanism and location of defect creation (whether the source or the drain side) of amorphous hafnium-indium-zinc-oxide thin film transistors under negative-bias-illumination stress was investigated. Most of the electrical characteristics—such as threshold voltage, subthreshold slope, and mobility—deteriorated remarkably due to defects generated in the deep-level and tail bands of the semiconductor bandgap. (The extent of hysteresis due to damage reflects the amount of defects generated.) As the drain voltage was increased—whilst under stress and with the gate voltage fixed—the electrical properties of thin film transistors got progressively worse. This indicates that the drain region was more seriously affected (compared to the source region), most likely because the drain region was placed under a higher negative field in the active layer.
Magnonic crystal wave guide with large spin-wave propagation velocity in CoFeB
Authors: Schwarze T. , Grundler D.
Published: June 2013

Propagating spin-wave spectroscopy is reported for two-dimensional CoFeB antidot lattices (ADLs) with perpendicular-to-plane magnetization. The magnonic crystals consist of square lattices of 190 nm diameter holes with different periods p. At p = 600 nm, the velocity vg of long wavelength spin-waves is reduced compared to the unpatterned reference film by up to about 30%. However, a large vg is regained when we leave out a column of nanoholes in the ADLs. Such a magnonic crystal wave guide is found to support faster spin waves than a CoFeB stripe of the same geometrical width, making the finding interesting for spin-wave guiding in integrated magnonics.
Equilibrium large vortex state in ferromagnetic disks
Authors: Metlov Konstantin L.
Published: June 2013

Magnetic vortices in soft ferromagnetic nano-disks have been extensively studied for at least several decades both for their applied (non-volatile information storage) as well as fundamental value. Here, it is shown that there is another vortex ground state with large radius-dependent core profile in nano-scale ferromagnetic disks of several exchange lengths in size. Its energy is computed numerically and its stability is studied analytically, which allows to plot it on magnetic phase diagram. Large vortices may exist on par with the classical ones, while being separated by an energy barrier, controllable by tuning the geometry and material of ferromagnetic disk.
Temporally, spatially, and spectrally resolved barrier discharge produced in trapped helium gas at atmospheric pressure
Authors: Chiper Alina Silvia , Popa Gheorghe
Published: June 2013

Experimental study was made on induced effects by trapped helium gas in the pulsed positive dielectric barrier discharge (DBD) operating in symmetrical electrode configuration at atmospheric pressure. Using fast photography technique and electrical measurements, the differences in the discharge regimes between the stationary and the flowing helium are investigated. It was shown experimentally that the trapped gas atmosphere (TGA) has notable impact on the barrier discharge regime compared with the influence of the flowing gas atmosphere. According to our experimental results, the DBD discharge produced in trapped helium gas can be categorized as a multi-glow (pseudo-glow) discharge, each discharge working in the sub-normal glow regime. This conclusion is made by considering the duration of current pulse (few μs), their maximum values (tens of mA), the presence of negative slope on the voltage-current characteristic, and the spatio-temporal evolution of the most representative excited species in the discharge gap. The paper focuses on the space-time distribution of the active species with a view to better understand the pseudo-glow discharge mechanism. The physical basis for these effects was suggested. A transition to filamentary discharge is suppressed in TGA mode due to the formation of supplementary source of seed electrons by surface processes (by desorption of electrons due to vibrationally excited nitrogen molecules, originated from barriers surfaces) rather than volume processes (by enhanced Penning ionisation). Finally, we show that the pseudo-glow discharge can be generated by working gas trapping only; maintaining unchanged all the electrical and constructive parameters.
Plasma-surface interaction in heptane
Authors: Hamdan A. , Kosior F. , Noel C. , Henrion G. , Audinot J.-N. , Gries T. , Belmonte T.
Published: June 2013

The main processes related to discharges between pin and plate electrodes in hydrocarbon liquid (heptane) are modelled for micro-gap (from 10 to 100 μm) conditions. When a plasma channel hits the surface, a micro-crater is created. The different phenomena controlling the geometry (shape and dimension) of a single crater are described and included in a theoretical model developed for the specific case of pure aluminium. The influence of the most important parameters affecting the geometry of the crater is discussed. Among them, one finds the pressure exerted by the plasma on the liquid metal. It is found that the distribution of the pressure applied on the liquid pool changes significantly the way the plasma shapes the pool. It is assumed that at high charges, the pressure profile is tilted from the channel axis, leading to the formation of a central protrusion. On the other hand, we demonstrate that Thomson-Marangoni forces play an important role for crater diameters smaller than 5 μm. Then, the choice of the first derivative of the surface tension with respect to the temperature is a key factor. This effect is strongly related to the way convection displaces matter in the liquid pool. Finally, the quenching step is sufficiently fast to freeze the liquid shape as soon as the plasma vanishes.
Laser-machined ultra-high-Q microrod resonators for nonlinear optics
Authors: Del'Haye Pascal , Diddams Scott A. , Papp Scott B.
Published: June 2013

Optical whispering-gallery microresonators are useful tools in microphotonics and non-linear optics at very low threshold powers. Here, we present details about the fabrication of ultra-high-Q whispering-gallery-mode resonators made by CO2-laser lathe machining of fused-quartz rods. The resonators can be fabricated in less than 1 min and the obtained optical quality factors exceed Q = 1 × 109. Demonstrated resonator diameters are in the range between 170 μm and 8 mm (free spectral ranges between 390 GHz and 8 GHz). Using these microresonators, a variety of optical nonlinearities are observed, including Raman scattering, Brillouin scattering, and four-wave mixing.
New software for hybrid renewable energy assessment for ten locations in Saudi Arabia
Authors: Eltamaly Ali M. , Addoweesh Khaled E. , Bawah Umar , Mohamed Mohamed A.
Published: June 2013

This paper introduces a design and optimization methodology for autonomous hybrid photovoltaic (PV)/wind/battery energy system. The main function of the proposed methodology is to determine the optimum size of each component of the energy system for the lowest cost of kWh generated and the best loss of load probability. This methodology uses the hourly wind speed, hourly radiation, and hourly load power with many different types of wind turbines and PV module types to get the optimum size of each component and the minimum cost of kWh generated at highest reliability. This methodology changes the share ratio of wind/PV with certain increments and calculates the required size of all components and the optimum battery size to get the predefined lowest acceptable probability. This methodology is implemented using a new computer program in flexible fashion which is not available in any market available software, such as homer or retscreen software. Actual data for ten Saudi sites are used with this computer program. The results obtained from the proposed program are compared with homer software. The proposed computer program performed the optimal design steps in very short time and with accurate results. Very valuable results can be extracted from the new computer program that could help researchers and decision makers. The results obtained from the proposed computer program have established the economic feasibility of installing hybrid energy systems in many sites of Saudi Arabia.
Lamb waves in two-dimensional phononic crystal slabs with neck structures
Authors: Yu Kunpeng , Chen Tianning , Wang Xiaopeng , Li Yinggang
Published: June 2013

In this paper, a new structure of two-dimensional phononic crystals consisting of one or more rows of parallel rectangular rods placed periodically in a homogenous slab, in which the rods are not connected directly but linked through neck structures with the slab, is proposed, and the Lamb wave propagation in this structure is investigated with numerical analysis. The dispersion relations and the power transmission spectra are studied using the finite-element method. In contrast to the phononic crystals where the rods and the slab are completely in contact, the proposed structure with necks are proved to display band gaps at much lower frequencies. The displacement fields of the eigenmodes of the band edges are computed and analyzed to clarify the mechanism for the generation of the low-frequency band gaps. It is found that the low-frequency band gaps are attributed to the interaction between the local resonance of the rod inclusion connected with the neck and the Lamb modes of the four plates which are formed by the introduction of the neck. Furthermore, the influences of the geometry parameters of the neck on the band gaps are discussed. Numerical results show that band gaps are significantly dependent upon the width and the position of the necks while insensitive to the neck length. These properties of Lamb waves can potentially be applied to optimize band gaps, generate filters, and design acoustic devices.
Stress-induced transformation behaviors at low temperatures in Ti-51.8Ni (at. %) shape memory alloy
Authors: Niitsu K. , Omori T. , Kainuma R.
Published: June 2013

Martensitic transformation behaviors at low temperatures in polycrystalline Ti-51.8Ni (at. %) alloy were investigated with compressive stress. Superelasticity with almost complete shape recovery was confirmed at temperatures of 40–180 K. In stress-induced transformation at fixed temperatures, while the reverse transformation finishing stress monotonically decreased with decreasing test temperature, the forward transformation starting stress changed from decrease to increase at about 125 K. Forward and reverse transformation temperatures evaluated under constant stresses of 50 and 750 MPa were generally coincident with the results determined at the constant temperatures, where “heating-induced forward transformation” was confirmed under a stress of 750 MPa.
Phase transition and huge ferroelectric polarization observed in BiFe1−xGaxO3 thin films
Authors: Yan Jingdan , Gomi Manabu , Yokota Takeshi , Song Huaihe
Published: June 2013

We prepared the chemical-solution deposited films of BiFe1−xGaxO3, which was previously only possibly synthesized under high-pressure and high-temperature. The thin films crystallized in rhombohedral perovskite structure (R3c) up to x = 0.05 and in tetragonal-like monoclinic structure (Cm) above x = 0.2. The coexistence of R3c and Cm phases was observed at x = 0.1. It is found that Bi-based film with coexistence phase exhibits a huge ferroelectric polarization of 230 μC cm−2, which can be attributed to the presence of the morphotropic phase boundary.
Mechanism of crystal-symmetry dependent deformation in ferroelectric ceramics: Experiments versus model
Authors: Li Y. W. , Zhou X. L. , Miao H. C. , Cai H. R. , Li F. X.
Published: June 2013

In this paper, we investigate the mechanism of crystal-symmetry dependent deformation in ferroelectrics both experimentally and theoretically. We fabricated three types of Pb(ZrxTi1-x)O3 ceramics including the tetragonal (PZT45/55), the rhombohedral (PZT60/40), and the morphotropic (PZT52/48), where the tetragonal and rhombohedral phases coexist. X-ray diffraction and piezoresponse force microscopy were performed to characterize the crystal structures and domain patterns. Deformation of both poled and unpoled PZT ceramics was tested under bipolar electric fields and uniaxial compression, respectively. It is found that in both loading cases, the deformation of the morphotropic PZT is obviously larger than that of the tetragonal and rhombohedral PZT. As to the latter two, the electric field induced strain in the tetragonal PZT is smaller than that in the rhombohedral PZT, while the compression induced strains show the opposite tendency. To explore the observed crystal-symmetry deformation mechanism, we employed a previously proposed optimization-based constrained domain-switching model to simulate the experimental results. Domain switching in this model is realized by an optimization process to minimize the free energy of each grain. The constraint from neighboring grains is considered in an Eshelby inclusion manner, which is inherently crystal-symmetry dependent. The simulation results fit well with our experimental results without any fitting parameters, which indicate that the constrained domain-switching is responsible for the crystal-symmetry dependent deformation mechanism in ferroelectric ceramics.
Boltzmann expansion in a radiofrequency conical helicon thruster operating in xenon and argon
Authors: Charles C. , Boswell R. , Takahashi K.
Published: June 2013

A low pressure (∼0.5 mTorr in xenon and ∼1 mTorr in argon) Boltzmann expansion is experimentally observed on axis within a magnetized (60 to 180 G) radiofrequency (13.56 MHz) conical helicon thruster for input powers up to 900 W using plasma parameters measured with a Langmuir probe. The axial forces, respectively, resulting from the electron and magnetic field pressures are directly measured using a thrust balance for constant maximum plasma pressure and show a higher fuel efficiency for argon compared to xenon.
Communication: Extension of a universal explicit electron correlation correction to general complete active spaces
Authors: Haunschild Robin , Cheng Lan , Mukherjee Debashis , Klopper Wim
Published: June 2013

We present the extension of a recently proposed universal explicit electron correlation (F12) correction for multi-reference perturbation theories to general complete active spaces and arbitrary choices of complete active space self-consistent field (CASSCF) orbitals. This F12 correction is applied to Mukherjee's multi-reference second-order perturbation theory (Mk-MRPT2). Pilot examples show the expected reduction of the basis sets incompleteness error of about two cardinal numbers.
Large negative magnetoresistance in reactive sputtered polycrystalline GdNx films
Authors: Mi W. B. , Guo Z. B. , Duan X. F. , Zhang X. J. , Bai H. L.
Published: June 2013

Polycrystalline ferromagnetic GdNx films were fabricated at different N2 flow rates (fN2) to modify N-vacancy concentration so as to study its influence on electrotransport. Metal-semiconductor transition appears at Curie temperature (TC) of ∼40 K. Temperature-dependent magnetoresistance (MR) shows a peak at TC. The films at fN2 = 5, 10, 15, and 20 sccm show MR of −38%, −42%, −46%, and −86% at 5 K and 50 kOe, respectively. Above 15 K, MR is from colossal MR and from both colossal and tunneling MR below 15 K. The enhanced MR at fN2 = 20 sccm is attributed to large spin polarization of half-metallicity in GdNx with low N vacancies.
Communication: Substrate induced dehydrogenation: Transformation of octa-ethyl-porphyrin into tetra-benzo-porphyrin
Authors: van Vörden D. , Lange M. , Schmuck M. , Schaffert J. , Cottin M. C. , Bobisch C. A. , Möller R.
Published: June 2013

Individual molecules of octa-ethyl-porhphyrin-iron(III)-chloride adsorbed on a Cu(111) surface are studied by scanning tunneling microscopy. Upon moderate heating the molecules are found to transform into Fe-tetra-benzo-porphyrin at a surprisingly low temperature of 380 K. If the annealing is interrupted, the different steps of the transformation can be imaged. By evaluating the ratio of transformed molecules as function of annealing temperature, an approximate activation energy of 1.2 eV ± 0.1 eV could be determined.
Aging effect evolution during ferroelectric-ferroelectric phase transition: A mechanism study
Authors: Feng Zuyong , Cheng Zhenxiang , Shi Dongqi , Dou Shixue
Published: June 2013

Aging can significantly modify the dielectric, piezoelectric, and ferroelectric performance of ferroelectrics. However, little attention has been paid to the aging effect during ferroelectric-ferroelectric phase transitions that is essentially correlated with real applications. In this letter, the authors report the aging effect evolution between two ferroelectric phases in an acceptor-doped piezoceramics. The results show that aging-induced double hysteresis loops were exhibited in different ferroelectric phases, but disappeared during ferroelectric-ferroelectric phase transitions, suggesting the mechanism that the intrinsic restoring force for the reversible switching of domains caused by the alignment of defect dipoles was weakened due to ferroelectric dipole reorientation.
Evolution of nanoripples on silicon by gas cluster-ion irradiation
Authors: Lozano Omar , Chen Q. Y. , Tilakaratne B. P. , Seo H. W. , Wang X. M. , Wadekar P. V. , Chinta P. V. , Tu L. W. , Ho N. J. , Wijesundera D. , Chu W. K.
Published: June 2013

Si wafers of (100), (110) and (111) orientations were bombarded by gas cluster ion beam (GCIB) of 3000 Ar-atoms/cluster on average at a series of angles. Similar surface morphology ripples developed in different nanoscales. A simple scaling functional satisfactorily describe the roughness and wavelength of the ripple patterns as a function of dosage and angle of incidence. The ripples are formed orthogonal to the incident cluster-ions at large off-normal angles. An ellipsoidal pattern was created by two consecutive irradiations incident in mutually orthogonal directions with unequal exposure times between each irradiation, from 7:1 to 10:1, beyond which the original ripple imprints would be over-written. This work was inspired by use of the ripples to seed growth of controlled nanostructures without patterning by lithography or predeposition of catalysts.
Brush-like SnO2/ZnO hierarchical nanostructure: Synthesis, characterization and application in UV photoresponse
Authors: Dai Jun , Xu Chunxiang , Guo Jiyuan , Xu Xiaoyong , Zhu Gangyi , Lin Yi
Published: June 2013

Brush-like hierarchical SnO2/ZnO nanostructure with high surface to volume ratio was synthesized by a two-step growth method. In the first growth stage, SnO2 nanowires were fabricated by vapor transport method. In the second growth stage, ZnO nanorods were hydrothermally grown up around the SnO2 nanowires to form brush-like SnO2/ZnO hierarchical structure. The structure morphology was characterized by X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy. The oxygen vacancy related photoluminescence from the nanostructure was investigated based on the XPS result. A UV photodetector was realized using the brush-like SnO2/ZnO nanostructure as active layer. The device showed good reversibility and response speed.
Numerical estimation on free electrons generated by shielded radioactive materials under various gaseous environments
Authors: Kim D. S. , Lee W. S. , So J. H. , Choi E. M.
Published: June 2013

We report simulation results on generation of free electrons due to the presence of radioactive materials under controlled pressure and gases using a general Monte Carlo transport code (MCNPX). A radioactive material decays to lower atomic number, simultaneously producing high energy gamma rays that can generate free electrons via various scattering mechanisms. This paper shows detailed simulation works for answering how many free electrons can be generated under the existence of shielded radioactive materials as a function of pressure and types of gases.
Self-biased magnetic left-handed material
Authors: Gu Yan , Wu Rui-xin , Yang Yan , Poo Yin , Chen Ping , Lin Zhifang
Published: June 2013

We present experimental demonstrations that the material consists of self-biased Sr-ferrite rods is the lower loss left-handed material (LHM). Clear negative refractions are observed in refraction experiments with the wedge shaped samples made from this material, and negative effective refractive index n = −1 is measured. The attenuation of the sample is about 0.55 dB/cm obtained from transmission measurements much lower than other known LHMs. Our configuration avoids the bias magnetic fields required for LHMs made of soft magnetic materials and extremely high permittivity needed for making LHMs with purely dielectrics, which greatly improves its impedance mismatch with the air.
Habitat preference of the Australian water rat (Hydromys chrysogaster) in a coastal wetland and stream, Two Peoples Bay, south-western Australia
Authors: Speldewinde Peter C. , Close Paul , Weybury Melissa , Comer Sarah
Published: June 2013

This study provides a preliminary investigation of the home range and habitat selection of the Australian water rat (Hydromys chrysogaster) in Two Peoples Bay Nature Reserve near Albany, Western Australia. Six individuals were captured (trap success 1.9%) from 810 trap-nights. This low number suggests that the water rat population in Two Peoples Bay Nature Reserve is much smaller than anecdotal evidence would suggest. Home-range size (neighbour-linkage method) averaged 18.9 ha (±11.6). Individuals preferentially utilised wetland habitats characterised by dense, low-lying vegetation (0–30 cm from ground), low-density canopy cover and shallow, narrow water bodies.