bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficacy of electronet fencing for excluding coyotes: A case study for enhancing production of black‐footed ferrets
Authors: Matchett Marc R. , Breck Stewart W. , Callon John
Published: October 2013

Reducing coyote (Canis latrans) predation can be an important management objective. Here, we evaluated the efficacy of electronet fencing for excluding coyotes from focal areas on black tailed prairie dog (Cynomys ludovicianus) colonies, measured the effect of fencing on wild‐born black‐footed ferret (Mustela nigripes) kit survival, and modeled costs and benefits of fencing. From 27 July to 2 October 2010 in north‐central Montana, USA, we erected and maintained 7.7 km of electronet that enclosed 108 ha on portions of 2 prairie dog colonies. We monitored 2 female ferrets and 6 kits inside exclosures and 3 females and 12 kits outside of exclosures. Percent of coyote sightings in the protected areas was 6 times less than expected during the exclosure period (42% pre‐exclosure, 7% exclosure, 47% post‐exclosure). We conclude that the electronet fencing was effective for dramatically decreasing coyote activity in focal areas where black‐footed ferret litters were being raised. We found evidence that survival of kits living primarily in protected areas was 22% higher, but we qualify this finding because of low sample sizes and because our monitoring activity on the study site may have influenced coyote activity. We estimated one‐time costs for fencing to be US$4,464/km and operation and/or maintenance costs for the 68 days of fence operation to be US$641/km. If fencing increased survival by 20–30%, then total cost per ferret kit not lost to coyote predation would range between US$5,400 and $3,600, or US$2,550 and $1,700 if fence set‐up–take‐down labor and use of an all‐terrain vehicle were donated. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.
Polyphenolic substrates and dyes degradation by yeasts from 25 de Mayo/King George Island (Antarctica)
Authors: Rovati José I. , Pajot Hipólito F. , Ruberto Lucas , Mac Cormack Walter , Figueroa Lucía I. C.
Published: October 2013

Antarctica offers a range of extreme climatic conditions, such as low temperatures, high solar radiation and low nutrient availability, and constitutes one of the harshest environments on Earth. Despite that, it has been successfully colonized by 'cold‐loving' fungi, which play a key role in decomposition cycles in cold ecosystems. However, knowledge about the ecological role of yeasts in nutrient or organic matter recycling/mineralization remains highly fragmentary. The aim of this work was to study the yeast microbiota in samples collected on 25 de Mayo/King George Island regarding the scope of their ability to degrade polyphenolic substrates such as lignin and azo dyes. Sixty‐one yeast isolates were obtained from 37 samples, including soil, rocks, wood and bones. Molecular analyses based on rDNA sequences revealed that 35 yeasts could be identified at the species level and could be classified in the genera Leucosporidiella, Rhodotorula, Cryptococcus, Bullera and Candida. Cryptococcus victoriae was by far the most ubiquitous species. In total, 33% of the yeast isolates examined showed significant activity for dye decolorization, 25% for laccase activity and 38% for ligninolytic activity. Eleven yeasts did not show positive activity in any of the assays performed and no isolates showed positive activity across all tested substrates. A high diversity of yeasts were isolated in this work, possibly including undescribed species and conspicuous Antarctic yeasts, most of them belonging to oligotrophic, slow‐growing and metabolically diverse basidiomycetous genera. Copyright © 2013 John Wiley & Sons, Ltd.
Multi‐shaped Amorphous Alloy Ni‐B: Ultrasonically Aided Complexing‐reduction Preparation, Catalytic Ability for NaBH4 Hydrolysis Yielding H2 Gas
Authors: Zhang Jun , Li Chengxuan , Li Lili , Du Xigang , Song Bangcai , Xu Hang
Published: October 2013

The multi‐shaped amorphous alloy (Ni‐B) powders were prepared by complexing reduction route using sodium borohydride (NaBH4) as reductant with assistance of ultrasonic wave. The selected complexants, i.e. water, ammonia, salicylic acid, and ethylene diamine tetraacetic acid (EDTA) possess sequentially escalating complexation ability. The chemical composition and shapes of the product samples obtained under different conditions were characterized by X‐ray powder differaction, selected area electron diffraction, and transmission electron microscope. The influence of reaction conditions such as the types of Ni‐B, temperatures, NaBH4 concentrations, and sodium hydroxide (NaOH) content on the hydrogen generation rate of hydrolysis of NaBH4 solution were investigated in detail. The results show that the as‐prepared Ni‐B powders all belong to amorphous alloy with variable element contents, and the Ni‐B sample prepared from EDTA complexation, possessing the best fineness and dispersity, has the strongest catalytic activity. The mean apparent activation energy of the hydrolysis reaction is 64.90 kJ·mol–1. The NaBH4 concentration has little impact on hydrogen generation rate, implying that the catalytic hydrolysis of NaBH4 solution should be the pseudo zero‐order reaction. Keeping the NaOH content at below 5 % could inhibit the hydrolysis of NaBH4 solution, but the NaOH contents from 10 % to 15 % will significantly promote the hydrolysis rate of NaBH4. The hydrolysis reaction mechanisms, especially the effect of NaOH content on the hydrolysis reaction were also analyzed.
Microphase Separation with Small Amphiphilic Molecules: Crystal Structure of Preservatives Sodium Benzoate (E 211) and Potassium Benzoate (E 212)
Authors: Butterhof Christian , Martin Thomas , Milius Wolfgang , Breu Josef
Published: October 2013

In the pharmaceutical industry many new active pharmaceutical ingredients (APIs) are marketed as carboxylic salts because of enhanced solubility and dissolution rates. These salts are, however, often hard to crystallize and/or exhibit a low degree of crystallinity. The reason may be found in the largely differing sizes of small inorganic cations and large organic anions in conjunction with the 1:1 stoichiometry, which makes it difficult to satisfy the coordination needs of the cations. Even rather small amphiphilic molecules like the widely used preservatives sodium benzoate (NaBz) and potassium benzoate (KBz) suffer of the same obstacle to crystallization. Both of these industrial products are marketed in semi‐crystalline forms and no crystal structures were known up to now despite their industrial relevance. By applying long term annealing at 420 °C for 5 months we obtained tiny needle‐like crystals of NaBz, which were nevertheless suitable for single crystal structure determination. Interestingly, the number of symmetry independent units in the crystal structure is exceptionally high (Z′ = 5), reflecting the difficulties in satisfying the coordination. Moreover, the small amphiphilic molecule undergoes a microphase separation into tubes with a hydrophilic core and a hydrophobic corona made up by the phenyl moieties. The tubes are arranged into a distorted hexagonal dense packing. Such microphases are well established with surfactants and block‐copolymers, and it seems that even small amphiphilic molecules follow the same modes of crystallization. Interestingly, simply by changing the cation to KBz a competing microphase structure is realized. KBz crystallizes in a lamellar arrangement.
CLA‐Rich Soy Oil Margarine Production and Characterization
Authors: Shah Utkarsh , Patel Ashok R. , Van de Walle Davy , Rajarethinem Pravin S. , Proctor Andrew , Dewettinck Koen
Published: October 2013

A heterogeneous catalysis method to produce 20 % conjugated linoleic acid (CLA)‐rich food‐grade soy oil in 2 h without solvents or gases was recently developed. The objective of this study was to produce and characterize CLA‐rich soy oil margarine relative to a soy oil control and commercial margarine. CLA‐rich soy oil was used to prepare margarine. The samples were characterized for firmness, rheology, thermal behavior, solid fat content (SFC) and microstructure and compared with a soy oil control and commercial margarine. The CLA‐rich oil margarine firmness and rheological properties were similar to commercial margarine and provided a better texture relative to the soy oil control margarine. However, SFC, droplet size distribution and melting behavior of CLA‐rich oil margarine were similar to control soy oil margarine and dissimilar to the commercial product. This suggests that hardness and rheological properties of margarine are not solely dependent on SFC and melting behavior. Lipid composition, polymorphism and microstructure differences in CLA‐rich oil margarine may play an important role on the texture and rheological properties. A 7‐g typical serving of the CLA‐rich oil margarine will provide 0.6 g CLA. Thus five servings will provide 3.2 g/day of CLA and 185 calories/day, which is well within the maximum recommended 700–980 fat calories/day.
Drainage Basin Delineation and Quantitative Analysis of Panamaram Watershed of Kabani River Basin, Kerala Using Remote Sensing and GIS
Authors: Joji V. S. , Nair A. S. K. , Baiju K. V.
Published: October 2013

The morphometric analysis was carried out to determine the drainage characteristics of Panamaram watershed (PW) of Kabani river basin, Kerala, India with emphasis on fourth order sub-basins (FOSBs) using Geocoded imageries of IRS-IC LISS III FCCs (1997) of 1:50,000 scale, aerial photographs (1990) of 1:15,000 scale and Survey of India toposheets (1968) on 1: 50,000 scale. The main idea was to examine the stream properties based on the measurement of various stream attributes. The different drainage parameters studied and the measurements related to perimeter, area of sub-basins, basin length and number of rivers were determined by using Map Info 6.5 techniques. The drainage pattern of the PW is dendritic, a sixth order stream. There are 587, 135, 36 and 12 first, second, third and fourth order Hortonian streams, respectively in PW. The mean bifurcation ratio indicates that the drainage pattern is not much influenced by geological structures. The shape parameters reveal the elongation of the basin and sub-basins. The applicability of Horton’s Laws on Stream numbers, Stream lengths and Stream areas is tested by using the theory of regression by estimating theoretically bifurcation ratio, length ratio and area ratio. For the fourth order sub-basins of 1, 2, 4, 5 and 8 of PW, a second degree polynomial equation seems to be a better model than the Hortonian model.
Effect of Mining on Geochemistry of Groundwater in Permo-carboniferous Gondwana Coalfields: Raniganj Basin, India
Authors: Adhikari K. , Sadhu K. , Chakroborty B. , Gangopadhyay A.
Published: October 2013

Lack of proper reclamation strategy and indiscriminate mining of various economic resources, particularly coal from Permo-carboniferous Gondwana coalfields affects the groundwater quality of the concerned regions. Leaching from mine-tailings along with seasonal fluctuation of water table caused a significant change in groundwater geochemistry of Raniganj coalfield area. Gondwana sequences, developed in intracratonic rift basin, are characterized by numerous longitudinal and cross faults. This results in the formation of many small aquifer systems which may be interconnected laterally as well as vertically providing the conduit for homogenization of aquifers. Although the predominance of major cations (Ca>Na>Mg>K) and anions (HCO3>Cl>SO4>NO3) remain same irrespective of season, the dominance of Na and SO4 have significantly increased in post-monsoon season. The types of groundwater in pre-monsoon and post-monsoon seasons are CaMgCl and CaHCO3 respectively. Leaching of SO4 from surface sources (mine tailings) has increased TDS in post-monsoon. Base exchange (direct and reverse) reactions have taken place between aquifer materials and groundwater.
Communication intensity, goal congruence, and uncertainty in buyer–supplier new product development
Authors: Yan Tingting , Dooley Kevin J.
Published: October 2013

Manufacturers involve suppliers in new product development in order to access knowledge and resources, but these benefits only occur with effective project‐level integration. Adopting a contingency theory view, we develop hypotheses concerning how two integrative devices, intensive communication and congruent goals, influence project performance under various conditions of uncertainty. We test our theoretical model with a sample of 214 buyer–supplier joint new product development projects. Results suggest that communication intensity is positively associated with project performance when either task or relational uncertainty is high, but is also negatively associated with performance when task uncertainty is low. Goal congruence is positively associated with project performance, especially when either task uncertainty is low or relational uncertainty is high. We discuss the implications of these findings for theory and practice.
The atomic and electronic structures of NiO(001)/Au(001) interfaces
Authors: Visikovskiy A. , Mitsuhara K. , Hazama M. , Kohyama M. , Kido Y.
Published: October 2013

The atomic and electronic structures of NiO(001)/Au(001) interfaces were analyzed by high-resolution medium energy ion scattering (MEIS) and photoelectron spectroscopy using synchrotron-radiation-light. The MEIS analysis clearly showed that O atoms were located above Au atoms at the interface and the inter-planar distance of NiO(001)/Au(001) was derived to be 2.30 ± 0.05 Å, which was consistent with the calculations based on the density functional theory (DFT). We measured the valence band spectra and found metallic features for the NiO thickness up to 3 monolayer (ML). Relevant to the metallic features, electron energy loss analysis revealed that the bandgap for NiO(001)/Au(001) reduced with decreasing the NiO thickness from 10 down to 5 ML. We also observed Au 4f lines consisting of surface, bulk, and interface components and found a significant electronic charge transfer from Au(001) to NiO(001). The present DFT calculations demonstrated the presence of an image charge beneath Ni atoms at the interface just like alkali-halide/metal interface, which may be a key issue to explain the core level shift and band structure.
Probing the origins of two-state folding
Authors: Lane Thomas J. , Schwantes Christian R. , Beauchamp Kyle A. , Pande Vijay S.
Published: October 2013

Many protein systems fold in a two-state manner. Random models, however, rarely display two-state kinetics and thus such behavior should not be accepted as a default. While theories for the prevalence of two-state kinetics have been presented, none sufficiently explain the breadth of experimental observations. A model, making minimal assumptions, is introduced that suggests two-state behavior is likely for any system with an overwhelmingly populated native state. We show two-state folding is a natural consequence of such two-state thermodynamics, and is strengthened by increasing the population of the native state. Further, the model exhibits hub-like behavior, with slow interconversions between unfolded states. Despite this, the unfolded state equilibrates quickly relative to the folding time. This apparent paradox is readily understood through this model. Finally, our results compare favorable with measurements of folding rates as a function of chain length and Keq, providing new insight into these relations.
Spherulitic crystallization in binary thin films under solvent-vapor annealing. I. A sharp-interface theory
Authors: Jabbour Michel , Man Chi-Sing , Paroni Roberto
Published: October 2013

We present a thermodynamically consistent theory for solvent-vapor induced spherulitic crystallization in binary thin-film blends, including those which consist of polymeric or organic small-molecule semiconductors. Under the proposed theory, spherulitic growth is interface driven, with no diffusion of any species. The thermodynamic driving force at the interface between the spherulite and amorphous phase is identified, and a kinetic relation that delivers a constant growth rate is proposed.
Collective effects due to dipolar fields as the origin of the extremely random behavior in hyperpolarized NMR maser: A theoretical and numerical study
Authors: Henner Victor , Desvaux Hervé , Belozerova Tatyana , Marion Denis J. Y. , Kharebov Petr , Klots Andrey
Published: October 2013

Numerical simulations based on microscopic approach are used to explore the spin dynamics encountered in the recently reported hyperpolarized 129Xe NMR maser [D. J. Y. Marion, G. Huber, P. Berthault, and H. Desvaux, ChemPhysChem 9, 1395–1401 (2008)] where series of amplitude modulated rf emissions are observed. The integration of the dynamic features of the electronic detection circuit in the present simulations, based on non-linear Maxwell-Bloch differential equations with dipole-dipole interactions, allows us to prove that the experimentally observed extremely random amplitude modulations crucially require the long-distance dipolar couplings between the nuclear spins with the feedback field acting as an amplifier. The massive dipolar couplings act, when the magnetization is largely tilted off the longitudinal axis, as an apparent transverse self-relaxation mechanism which destroys coherence. This, in particular, explains why the final magnetization after emissions can still be opposite to the magnetic field direction, i.e., being in an unstable state.
Modeling of time-dependent non-uniform dielectric breakdown using a clustering statistical approach
Authors: Wu Ernest Y. , Li Baozhen , Stathis James H.
Published: October 2013

We report a time-dependent clustering model for non-uniform dielectric breakdown. Its area scaling and low-percentile scaling properties are rigorously investigated. While at high percentiles non-uniform area scaling dominates, the model restores the weakest-link characteristics at low percentiles relevant for reliability projection. As a result, we develop a comprehensive methodology for the parameter extraction and projection methodology for non-uniform dielectric breakdown. Excellent agreement is obtained between the model and the experimental data of back-end-of-line low-k dielectrics and front-end-of-line gate dielectrics, suggesting a wide range of applications of this model in the field of dielectric breakdown reliability.
A periodic charge-dipole electrostatic model. II. A kinetic-exchange-correlation correction
Authors: Bodrenko I. V. , Della Sala F.
Published: October 2013

We extend the periodic charge-dipole electrostatic model, see I. V. Bodrenko, M. Sierka, E. Fabiano, and F. Della Sala, J. Chem. Phys. 137, 134702 (2012), to include a kinetic-exchange-correlation (KXC) correction. The KXC correction is approximated by means of an extended-Hückel-type formula, it is exact in the infinite jellium model and it is also computationally efficient as it requires only the computation of overlap integrals. Tests on the linear response of silver slabs to an external electrostatic perturbation show that the KXC correction yields a very accurate description of induced dipole and of the whole induced charge density profile. We also show that the KXC parameters are quite transferable and related to the atomic polarizability.
Optical fiber-based force transducer for microscale samples
Authors: V. Seshagiri Rao R. , Kalelkar Chirag , Pullarkat Pramod A.
Published: October 2013

We discuss the design, instrumentation, and calibration of a versatile force transducer with feedback control, called the Micro-Extensional Rheometer (MER). A force range of eight decades (1–108 pN) and a displacement range of four decades (10–105 nm) with a spatial resolution of the order of nanometers are accessible with the instrument. A feedback-loop algorithm is used to control the commanded force or the extensional strain on the sample and implement different rheometric protocols such as step-strain, step-force, exponential strain, among others. The device may also be used to measure the forces exerted by active suspensions, pulling neurons, etc.
Three-dimensional electromagnetic breathers in carbon nanotubes with the field inhomogeneity along their axes
Authors: Zhukov Alexander V. , Bouffanais Roland , Fedorov Eduard G. , Belonenko Mikhail B.
Published: October 2013

We study the propagation of extremely short electromagnetic three-dimensional bipolar pulses in an array of semiconductor carbon nanotubes. The heterogeneity of the pulse field along the axis of the nanotubes is accounted for the first time. The evolution of the electromagnetic field and the charge density of the sample are described by Maxwell's equations supplemented by the continuity equation. Our analysis reveals for the first time the possibility of propagation of three-dimensional electromagnetic breathers in CNTs arrays. Specifically, we found that the propagation of short electromagnetic pulse induces a redistribution of the electron density in the sample.
Local hyperdynamics
Authors: Kim Soo Young , Perez Danny , Voter Arthur F.
Published: October 2013

We present a new formulation of the hyperdynamics method in which the biasing effect is local, making it suitable for large systems. In standard hyperdynamics, the requirement that the bias potential be zero everywhere on the dividing surface bounding the state has the consequence that as the system size increases the boost factor decays to unity, regardless of the form of the bias potential. In the new method, the bias force on each atom is obtained by differentiating a local bias energy that depends only on the coordinates of atoms within a finite range of this atom. This bias force is thus independent of the bias force in distant parts of the system, providing a method that gives a constant boost factor, independent of the system size. We demonstrate for some realistic atomistic systems that the method gives escape rates in excellent agreement with direct molecular dynamics simulations.
First-principles study of doping-induced half-metallicity at the (001) surface of full-Heusler alloy Co2VGa
Authors: Han Hongpei , Dong Yongqiang , Fan Libo , Yao K. L.
Published: October 2013

We investigate the structural, electronic, and magnetic properties of the (001) surfaces and the pure V-terminated surface with V-doping for Co2VGa with L21 structure. It is shown from the present density of states that the pure V-terminated surface preserves the bulk half-metallicity although the half-metallic character is destroyed at both Co- and VGa-terminated surfaces. We also find the atomic magnetic moments at the considered three surfaces are greatly different from the bulk values due to the well-known surface effect. Our calculated results indicate the pure V-terminated surface can be more favorable to the applications of spintronic devices.
Accuracy and precision of reconstruction of complex refractive index in near-field single-distance propagation-based phase-contrast tomography
Authors: Gureyev Timur , Mohammadi Sara , Nesterets Yakov , Dullin Christian , Tromba Giuliana
Published: October 2013

We investigate the quantitative accuracy and noise sensitivity of reconstruction of the 3D distribution of complex refractive index, n(r)=1−δ(r)+iβ(r), in samples containing materials with different refractive indices using propagation-based phase-contrast computed tomography (PB-CT). Our present study is limited to the case of parallel-beam geometry with monochromatic synchrotron radiation, but can be readily extended to cone-beam CT and partially coherent polychromatic X-rays at least in the case of weakly absorbing samples. We demonstrate that, except for regions near the interfaces between distinct materials, the distribution of imaginary part of the refractive index, β(r), can be accurately reconstructed from a single projection image per view angle using phase retrieval based on the so-called homogeneous version of the Transport of Intensity equation (TIE-Hom) in combination with conventional CT reconstruction. In contrast, the accuracy of reconstruction of δ(r) depends strongly on the choice of the “regularization” parameter in TIE-Hom. We demonstrate by means of an instructive example that for some multi-material samples, a direct application of the TIE-Hom method in PB-CT produces qualitatively incorrect results for  δ(r), which can be rectified either by collecting additional projection images at each view angle, or by utilising suitable a priori information about the sample. As a separate observation, we also show that, in agreement with previous reports, it is possible to significantly improve signal-to-noise ratio by increasing the sample-to-detector distance in combination with TIE-Hom phase retrieval in PB-CT compared to conventional (“contact”) CT, with the maximum achievable gain of the order of 0.3δ/β. This can lead to improved image quality and/or reduction of the X-ray dose delivered to patients in medical imaging.
Optical absorptance measurement of an individual multiwall carbon nanotube using a T type thermal probe method
Authors: Li Qin-Yi , Liu Jin-Hui , Wang Hai-Dong , Zhang Xing , Takahashi Koji
Published: October 2013

Optical absorptance is an important property of carbon nanotubes for practical applications but has rarely been accurately measured. We developed a T type thermal probe method to measure the optical absorptance of an individual multiwall carbon nanotube. In this method, one end of the carbon nanotube (CNT) is attached to the center of a platinum nanofilm in a T shape and the Pt nanofilm acts as a thermometer. A laser beam irradiates at the CNT and the absorbed laser power can be determined by measuring the average temperature rise of the Pt nanofilm based on the temperature dependence of the electric resistance. Experimental results showed that a 100-nm-diameter multiwall CNT could absorb 13.2% of the 514-nm-wavelength laser power with the laser spot diameter being 1 μm. This method is useful for determining the optical absorptance of CNTs and other one-dimensional nanostructures such as Si/Ge nanowires for various optical wavelengths in their photovoltaic, photoelectrolysis and other optical applications.
Dynamics of pulsed laser ablation in high-density carbon dioxide including supercritical fluid state
Authors: Urabe Keiichiro , Kato Toru , Stauss Sven , Himeno Shohei , Kato Satoshi , Muneoka Hitoshi , Baba Motoyoshi , Suemoto Tohru , Terashima Kazuo
Published: October 2013

To gain a better understanding of pulsed laser ablation (PLA) processes in high-density fluids, including gases, liquids, and supercritical fluids (SCFs), we have investigated the PLA dynamics in high-density carbon dioxide (CO2) using a time-resolved shadowgraph (SG) observation method. The SG images revealed that the PLA dynamics can be categorized into two domains that are separated by the gas-liquid coexistence curve and the Widom line, which forms a border between the gaslike and liquidlike domains of an SCF. Furthermore, a cavitation bubble observed in liquid CO2 near the critical point exhibited a particular characteristic: the formation of an inner bubble and an outer shell structure. The results indicate that the thermophysical properties of the reaction field generated by PLA can be dynamically tuned by controlling the solvent temperature and pressure, particularly near the critical point.
Thrust and efficiency model for electron-driven magnetic nozzles
Authors: Little Justin M. , Choueiri Edgar Y.
Published: October 2013

A performance model is presented for magnetic nozzle plasmas driven by electron thermal expansion to investigate how the thrust coefficient and beam divergence efficiency scale with the incoming plasma flow and magnetic field geometry. Using a transformation from cylindrical to magnetic coordinates, an approximate analytical solution is derived to the axisymmetric two-fluid equations for a collisionless plasma flow along an applied magnetic field. This solution yields an expression for the half-width at half-maximum of the plasma density profile in the far-downstream region, from which simple scaling relations for the thrust coefficient and beam divergence efficiency are derived. It is found that the beam divergence efficiency is most sensitive to the density profile of the flow into the nozzle throat, with the highest efficiencies occurring for plasmas concentrated along the nozzle axis. Increasing the expansion ratio of the magnetic field leads to efficiency improvements that are more pronounced for incoming plasmas that are not concentrated along the axis. This implies that the additional magnet required to increase the expansion ratio may be worth the added complexity for plasma sources that exhibit poor confinement.
Modeling of plasma processes in the slowly diverging magnetic fields at the exit of an applied-field magnetoplasmadynamic thruster
Authors: Li Min , Tang Hai-Bin , Ren Jun-Xue , York Thomas M.
Published: October 2013

The performance of plasma thrusters with applied electric and magnetic fields can be enhanced by increasing the magnetic field strength, which is applied in the thrust chamber and the exit region propulsive plume. The ejected plasma which passes through a slowly diverging magnetic field will expand but can be restricted within the magnetic nozzle fields. To examine in detail the processes that occur, a new method with Particle-in-cell calculations is applied here. A two-dimensional axisymmetric particle dynamic code is used to model an AF-MPDT (Applied-field Magnetoplasmadynamic Thruster) for which extensive experimental data are available; it used Ar propellant and had applied magnetic coils of 101.5 mm radius and 153 mm length. From the results of the simulation study, it is found that total thrust increases linearly with magnetic field strength in the range of 0–0.1 T, but it decreases with increasing applied magnetic field up to 0.6 T. Thrust efficiency is found to increase to a maximum of 8.4% when B = 0.1 T; further, the peak value of nozzle efficiency reaches 91% at a moderate magnetic field (0.3 T). In detail, it is found that distributions of plasma density (1014–1015 m−3) that form in the magnetic nozzle demonstrate a significant pattern of concentration up to fields of B = 0.3 T where ions begin to be magnetized. However, azimuthal velocities of ions behave differently with different degrees of magnetization, i.e., weakly magnetized ions follow rotating electrons in a right-handed direction, while fully magnetized ions revolve in left-handed direction due to electromagnetic forces. Notably, a feedback effect on total magnetic field due to plasma motion identified in other studies is not found to be present in the working conditions of the AF-MPDT examined here.
Fully absorptive 3D IR spectroscopy using a dual mid-infrared pulse shaper
Authors: Mukherjee Sudipta S. , Skoff David R. , Middleton Chris T. , Zanni Martin T.
Published: October 2013

This paper presents the implementation of 3D IR spectroscopy by adding a second pump beam to a two-beam 2D IR spectrometer. An independent mid-IR pulse shaper is used for each pump beam, which can be programmed to collect its corresponding dimension in either the frequency or time-domains. Due to the phase matching geometry employed here, absorptive 3D IR spectra are automatically obtained, since all four of the rephasing and non-rephasing signals necessary to generate absorptive spectra are collected simultaneously. Phase cycling is used to isolate the fifth-order from the third-order signals. The method is demonstrated on tungsten hexacarbonyl (W(CO)6) and dicarbonylacetylacetonato rhodium (I), for which the eigenstates are extracted up to the third excited state. Pulse shaping affords a high degree of control over 3D IR experiments by making possible mixed time- and frequency-domain experiments, fast data acquisition and straightforward implementation.
Flexible and lightweight thermoelectric generators composed of carbon nanotube–polystyrene composites printed on film substrate
Authors: Suemori Kouji , Hoshino Satoshi , Kamata Toshihide
Published: October 2013

A flexible thermoelectric generator (TEG) was fabricated on a polyethylene naphthalate film substrate using a printing process. The thermoelectric material used in this study, a composite material consisting of carbon nanotubes (CNTs) and polystyrene, contained approximately 35 vol. % of voids. Because of the reduction in the density of the CNT–polystyrene composite caused by the voids, the TEG was remarkably lightweight (weight per unit area: ≈15.1 mg/cm2). The TEG generated approximately 55 mW/m2 of power at a temperature difference of 70 °C.
Role of molecule flexibility on the nucleation of dislocations in molecular crystals
Authors: Munday Lynn B. , Mitchell Robert L. , Knap Jaroslaw , Chung Peter W.
Published: October 2013

We show that a molecule's flexibility described by changes to its conformation and orientation during deformation is vital for the proper representation of dislocation nucleation in molecular crystals. This is shown for the molecular crystal hexahydro-1,3,5-trinitro-s-triazine (RDX) by comparing direct atomistic simulations to two alternate forms of a continuum dislocation nucleation model for a crack tip loaded in pure shear. The atomistic simulations show the emission of partial dislocations. These are compared to continuum dislocation nucleation models based on generalized stacking fault (GSF) energy surfaces where the molecules are allowed to be either rigid or flexible. The rigid molecules are unable to represent the partial dislocations whereas the flexible molecules agree with the direct atomistic model to within 17% of the stress intensity factor for emission of the first partial dislocation and to within 1% for the second partial. This agreement first indicates that the molecule flexibility serves a critical role in the ductile behavior of the molecular crystal and, second, the continuum dislocation nucleation model represents the correct atomistic behavior, showing two partial dislocations connected by a stacking fault, when parameterized with GSF energy surfaces that account for the molecule flexibility.
Electron spin resonance parameters of cation vacancies in tin dioxide doped with fluorine and hydrogen
Authors: Golovanov Viacheslav , Golovanova Viktoria , Kuisma Mikael , Rantala Tapio T.
Published: October 2013

The spin Hamiltonian parameters of intrinsic defects in tin dioxide (SnO2) doped with fluorine or hydrogen are examined through the first-principles electronic structure calculations based on density functional theory (DFT). The electron paramagnetic resonance signals with g-tensor value in the range of 1.89–1.94 were found for tin vacancy (VSn) and its complex with oxygen vacancy (VSn-VO) associated with a donor like interstitial hydrogen or fluorine, substituting oxygen. The calculated parameters are consistent with experimental observations, which indicate that Sn vacancies may be present in SnO2 at essentially higher concentration than it is predicted by DFT based on the formation energies calculations. Within the second coordination shell of the tin vacancy, the VO may stabilize in the singly ionized charge state, which is otherwise considered to be unstable for isolated oxygen vacancy in the bulk of SnO2.
Ballistic thermoelectric properties in boron nitride nanoribbons
Authors: Xie Zhong-Xiang , Tang Li-Ming , Pan Chang-Ning , Chen Qiao , Chen Ke-Qiu
Published: October 2013

Ballistic thermoelectric properties (TPs) in boron nitride nanoribbons (BNNRs) are studied using the nonequilibrium Green's function atomistic simulation of electron and phonon transport. A comparative analysis for TPs between BNNRs and graphene nanoribbons (GNRs) is made. Results show that the TPs of BNNRs are better than those of GNRs stemming from the higher power factor and smaller thermal conductance of BNNRs. With increasing the ribbon width, the maximum value of ZT (ZTmax) of BNNRs exhibits a transformation from the monotonic decrease to nonlinear increase. We also show that the lattice defect can enhance the ZTmax of these nanoribbons strongly depending on its positions and the edge shape.
Behaviour of sand during release from a shocked state
Authors: Braithwaite C. H. , Perry J. I. , Taylor N. E. , Jardine A. P.
Published: October 2013

The dynamic response of granular materials to an applied shockwave is of wide ranging importance. While the shock Hugoniot has been studied, the shock-release of granular systems has never been experimentally characterised. Here, we present a simple approach to such measurements and present a series of plate impact experiments providing release data for a well characterised dry sand. We discuss the origin of the release behaviour, which we support with further measurements on a weakly bound sandstone.
Percolation of high-density polymer regions in nanocomposites: The underlying property for mechanical reinforcement
Authors: Padmanabhan Venkat
Published: October 2013

Polymer nanocomposites have shown to exhibit improved mechanical properties compared to their pure host polymers. These property changes have been primarily attributed to the nature of polymer/nanoparticle interactions. Molecular dynamics simulations of model polymer nanocomposites have provided new insights into the molecular origin of property-changes in these nanocomposites. It was observed that addition of nanoparticles, induced adsorption of monomer segments onto the surface of nanoparticles creating high-density regions of polymer segments in the interfacial zones. A closer look into the morphology of these regions surrounding the nanoparticles revealed that mechanical reinforcement and changes in flow properties may be attributed to the formation of a percolated network of these high-density regions.
Mapping electrostatic profiles across axial p-n junctions in Si nanowires using off-axis electron holography
Authors: Gan Zhaofeng , Perea Daniel E. , Yoo Jinkyoung , Tom Picraux S. , Smith David J. , McCartney Martha R.
Published: October 2013

Si nanowires (NWs) with axial p-n junctions were grown by the vapor-liquid-solid method. Transmission electron microscopy and electron holography were used to characterize the microstructure and electrostatic properties. Measurement of the potential profile showed the presence of a p-n junction with a height of 1.0 ± 0.3 V. A Schottky barrier was observed at the end of the NW due to the Au catalyst particle. Comparison with simulations indicated dopant concentrations of 1019 cm−3 for donors and 1017 cm−3 for acceptors. These results confirm the benefit of combining off-axis electron holography with simulations for determining localized information about the electrically active dopant distributions in nanowire structures.
Foundations of ab initio simulations of electric charges and fields at semiconductor surfaces within slab models
Authors: Krukowski Stanisław , Kempisty Paweł , Strąk Paweł
Published: October 2013

Semiconductor surfaces were divided into charge categories, i.e., surface acceptor, donor, and neutral ones that are suitable for simulations of their properties within a slab model. The potential profiles, close to the charged surface states, accounting for explicit dependence of the point defects energy, were obtained. A termination charge slab model was formulated and analyzed proving that two control parameters of slab simulations exist: the slope and curvature of electric potential profiles which can be translated into a surface and volumetric charge density. The procedures of slab model parameter control are described and presented using examples of the DFT simulations of GaN and SiC surfaces showing the potential profiles, linear or curved, depending on the band charge within the slab. It was also demonstrated that the field at the surface may affect some surface properties in a considerable degree proving that verification of this dependence is obligatory for a precise simulation of the properties of semiconductor surfaces.
Numerical investigation of electron self-injection in the nonlinear bubble regime
Authors: Benedetti C. , Schroeder C. B. , Esarey E. , Rossi F. , Leemans W. P.
Published: October 2013

The process of electron self-injection in the nonlinear bubble wake generated by a short and intense laser pulse propagating in a uniform underdense plasma is studied by means of fully self-consistent particle-in-cell simulations and test-particle simulations. We consider a wake generated by a non-evolving laser driver traveling with a prescribed velocity, which then sets the structure and the velocity of the wake, so the injection dynamics is decoupled from driver evolution, but a realistic structure for the wakefield is retained. We show that a threshold for self-injection into a non-evolving bubble wake exists, and we characterize the dependence of the self-injection threshold on laser intensity, wake velocity, and plasma temperature for a range of parameters of interest for current and future laser-plasma accelerators.
Time frequency property for a micro resonant gas sensor
Authors: Xu Lizhong , Yang Qing
Published: October 2013

In this paper, combining dynamics equation of the resonant cantilever with kinetic equation of the adsorption reaction between coatings and the measured gas, a mechanical chemical coupled dynamics equation is proposed. Using the method of multiple scales, the mechanical chemical coupled dynamics equation is resolved. From the solution, using Hilbert transform, changes of the resonant frequency along with time are obtained. The time frequency property of the resonant cantilever during gas adsorption reaction is investigated. Results show that different gases can be distinguished from each other by means of the different time frequency property. Using the method, the measured time is short and there is not special requirement for adsorption reaction rate between coatings and the measured gas. It explores a novel idea for micro resonant chemical sensors.
Periodic defects lines in liquid crystal cell guided by polarization holograms at an aligning surface
Authors: Lysenko D. , Pagliusi P. , Provenzano C. , Reznikov Yu. , Slyusarenko K. , Cipparrone G.
Published: October 2013

Defect lines arrays are created in liquid crystal exploiting periodic arrangements of twisted domains with opposite handedness. The defect lines self-organize in a planar cell guided by a polarization hologram recorded in one aligning substrate that provides planar periodic alignment. Depending on the relationship between the cell thickness d and the hologram pitch Λ, the array period can be either Λ or 2Λ. An external voltage enables to switch the spatial periodicity of the defect lines from 2Λ to Λ and also to control their shape and location. A modeling of the observed twisted arrangements is reported.
Fiber-based pulse stretcher for narrowband terahertz pulse generation with a chirped-pulse beating method
Authors: Yoshida Tetsuya , Kamada Shohei , Murata Shuhei , Aoki Takao
Published: October 2013

We theoretically show that it is possible to generate chirp-free terahertz (THz) pulses with a chirped-pulse beating method by using an optical fiber as a pulse stretcher. Proper choices of the core radius and the dopant fraction of the core material of a step-index single-mode optical fiber eliminate the third-order spectral phase of the fiber, thus giving the pump laser pulse a purely linear chirp. We also show that even a standard commercial single-mode optical fiber can give THz pulses of lower chirp than the lower limit for a grating pair. We perform experiments to verify our theory.
Magneto- and electroinduced effects in optical second-harmonic generation from a planar Au/Co/Si nanostructure
Authors: Mitryukovskiy S. I. , Nikulin A. A. , Stognij A. I. , Murzina T. V.
Published: October 2013

Optical second-harmonic (SH) generation in planar Au/Co/Si(111) nanostructures under application of static magnetic and electric fields is studied experimentally. The crystallographic, magneto- and electroinduced contributions to the SH intensity reveal strong azimuthal anisotropy peculiar to the Si(111) surface. The transient times characterizing the electroinduced quadratic response are found to exceed 1 s. Relative amplitudes and phases of the magneto- and electroinduced constituents of the SH signal are estimated from the measurements data.
Inactivation effects of neutral reactive-oxygen species on Penicillium digitatum spores using non-equilibrium atmospheric-pressure oxygen radical source
Authors: Hashizume Hiroshi , Ohta Takayuki , Fengdong Jia , Takeda Keigo , Ishikawa Kenji , Hori Masaru , Ito Masafumi
Published: October 2013

The effectiveness of atomic and excited molecular oxygen species at inactivating Penicillium digitatum spores was quantitatively investigated by measuring these species and evaluating the spore inactivation rate. To avoid the effects of ultraviolet light and charged species, a non-equilibrium atmospheric-pressure radical source, which supplies only neutral radicals, was employed. Ground-state atomic oxygen (O(3Pj)) and excited molecular oxygen (O2(1Δg)) species were measured using vacuum ultraviolet absorption spectroscopy. The inactivation rate of spores was evaluated using the colony count method. The lifetimes of O(3Pj) and O2(1Δg) in an argon gas ambient at atmospheric pressure were found to be about 0.5 ms and much more than tens of ms, and their spore inactivation rates were about 10−17 cm3 s−1 and much lower than 10−21 cm3 s−1, respectively.
Magnetic anisotropy and order parameter in nanostructured CoPt particles
Authors: Komogortsev S. V. , Iskhakov R. S. , Zimin A. A. , Filatov E. Yu. , Korenev S. V. , Shubin Yu. V. , Chizhik N. A. , Yurkin G. Yu. , Eremin E. V.
Published: October 2013

The correlation of magnetic anisotropy energy with order parameter in the crystallites of CoPt nanostructured particles prepared by thermal decomposition and further annealing has been studied by investigation of the approach magnetization to saturation curves and x-ray powder diffraction pattern profiles. It is shown that magnetic anisotropy energy value in partially ordered CoPt crystallite could be described as an intermediate case between two extremes, corresponding to either single or several c-domains of L10 phase in crystallite.
Characterization of charge injection and photovoltaic effects of hybrid inorganic-organic GaN/pentacene heterostructures
Authors: Slawinski M. , Weingarten M. , Axmann S. , Urbain F. , Fahle D. , Heuken M. , Vescan A. , Kalisch H.
Published: October 2013

This work investigates the electrical and optical properties of hybrid GaN/pentacene heterostructures. We identify bipolar transport in GaN/pentacene by I-V and C-V measurements. Further results show a much stronger photocurrent under AM1.5 illumination of GaN/pentacene/Au structures than that of simple GaN/Au Schottky diodes. The higher photocurrent can be explained with the additional absorption of low-energy photons by pentacene. We introduce an interface model describing the behaviour of photogenerated charge carriers pairs for the case of Ga-polar n-GaN and pentacene. These results demonstrate the enhancement of inorganic device performance by integration of organic semiconductors.
Note: Accurate determination of thickness of multiple layers of thin film deposited on a piezoelectric quartz crystal
Authors: Wajid Abdul
Published: October 2013

Modern day piezoelectric quartz crystal microbalances for thin film deposition control are based on Z-match equation, which is mathematically valid for deposition of a single material on a given quartz crystal. When multiple layers are deposited, thickness and deposition rate errors accumulate due to mismatch of acoustic impedance of different materials. Here we present a novel method, based on the acoustic transfer matrix formalism, for accurate determination of thickness of an arbitrary number of layers of dissimilar materials deposited on a quartz crystal. Laboratory data show excellent accuracy of the method compared to conventional Z-match equation.