bluuebunny/crossref_metadata_2025 huggingface dataset:
Band alignment of InGaZnO4/Si interface by hard x-ray photoelectron spectroscopy
Authors: Lee Kyeongmi , Nomura Kenji , Yanagi Hiroshi , Kamiya Toshio , Ikenaga Eiji , Sugiyama Takeharu , Kobayashi Keisuke , Hosono Hideo
Published: August 2012

Although amorphous InGaZnO4 has intensively been studied for a semiconductor channel material of thin-film transistors in next-generation flat-panel displays, its electronic structure parameters have not been reported. In this work, the electron affinities (χ) and the ionization potentials (Ip) of crystalline and amorphous InGaZnO4 (c-IGZO and a-IGZO) were measured using bulk-sensitive hard x-ray photoelectron spectroscopy. First, the χ and Ip values of c-IGZO and a-IGZO thin films were estimated by aligning the Zn 2p3/2 core level energies to a literature value for ZnO, which provided χ = 3.90 eV and Ip = 7.58 eV for c-IGZO and 4.31 eV and 7.41 eV for a-IGZO. It was also confirmed that the escape depth of the photoelectrons excited by the photon energy of 5950.2 eV is 3.3 nm for a-IGZO and large enough for directly measuring the interface electronic structure using a-IGZO/c-Si heterojunctions. It provided the valence band offset of ∼2.3 eV, which agrees well with the above data. The present results substantiate that the a-IGZO/c-Si interface follows well the Schottky-Mott rule.
Characterization of the transport topology in patient-specific abdominal aortic aneurysm models
Authors: Arzani Amirhossein , Shadden Shawn C.
Published: August 2012

Abdominal aortic aneurysm (AAA) is characterized by disturbed blood flow patterns that are hypothesized to contribute to disease progression. The transport topology in six patient-specific abdominal aortic aneurysms was studied. Velocity data were obtained by image-based computational fluid dynamics modeling, with magnetic resonance imaging providing the necessary simulation parameters. Finite-time Lyapunov exponent (FTLE) fields were computed from the velocity data, and used to identify Lagrangian coherent structures (LCS). The combination of FTLE fields and LCS was used to characterize topological flow features such as separation zones, vortex transport, mixing regions, and flow impingement. These measures offer a novel perspective into AAA flow. It was observed that all aneurysms exhibited coherent vortex formation at the proximal segment of the aneurysm. The evolution of the systolic vortex strongly influences the flow topology in the aneurysm. It was difficult to predict the vortex dynamics from the aneurysm morphology, motivating the application of image-based flow modeling.
Spacer and well pumping of InGaN vertical cavity semiconductor lasers with varying number of quantum wells
Authors: Debusmann R. , Brauch U. , Hoffmann V. , Weyers M. , Kneissl M.
Published: August 2012

We have investigated the dependence of the threshold pump power and slope efficiency of 415 nm (In)GaN vertical cavity surface emitting lasers on the wavelength of the pump source and the number of quantum wells. InGaN double quantum well resonant-periodic-gain structures with 6, 8, and 10 periods have been compared. By barrier and well pumping of the samples with a 375 nm dye laser, a nearly 10 times reduction of the laser threshold was observed compared to pumping with a 337 nm nitrogen laser source. The laser threshold was found to be independent of the number of quantum wells. The slope efficiency seems to be not affected by the pump wavelength and resonant-periodic-gain periods. The results are discussed with a rate equation model that takes into account the inhomogeneous pumping of the quantum wells and optical thickness variations in the resonant-periodic-gain structure.
Redox instability, mechanical deformation, and heterogeneous damage accumulation in solid oxide fuel cell anodes
Authors: Abdeljawad F. , Nelson G. J. , Chiu W. K. S. , Haataja M.
Published: August 2012

Mechanical integrity and damage tolerance represent two key challenges in the design of solid oxide fuel cells (SOFCs). In particular, reduction and oxidation (redox) cycles, and the associated large transformation strains have a notable impact on the mechanical stability and failure mode of SOFC anodes. In this study, the deformation behavior under redox cycling is investigated computationally with an approach that provides a detailed, microstructurally based view of heterogeneous damage accumulation behavior within an experimentally obtained nickel/yttria stabilized zirconia SOFC anode microstructure. Simulation results underscore the critical role that the microstructure plays in the mechanical deformation behavior of and failure within such materials.
Exciton states and oscillator strengths in a cylindrical quantum wire with finite potential under transverse electric field
Authors: Wu Shudong , Tomić Stanko
Published: August 2012

The effects of a transverse electric field on the electronic structure, exciton states, and oscillator strengths in a cylindrical quantum wire (QWR) are theoretically investigated. We consider a QWR made of GaAs material surrounded by a barrier of Al0.3Ga0.7As of finite depth potential. The electronic structure of the QWR, at the single electron level of theory, is obtained inside the effective mass approximation using the plane wave method, while the exciton states and transition oscillator strengths are calculated using the variational principle. The results show that the exciton oscillator strength is strongly enhanced due to the excitonic effect. The external electric field lifts the degeneracy of the electron or hole states. The energy levels of the electron and hole, exciton binding energy and exciton oscillator strength decrease with the increasing of the strength of the electric field. The stronger the electric field, the weaker the excitonic effect is. The influence of the electric field on exciton states and oscillator strengths becomes more significant for wide quantum wires. However, in sufficiently narrow wires, the influence of the electric field is also significant at small fields.
Relationship between variable range hopping transport and carrier density of amorphous In2O3–10 wt. % ZnO thin films
Authors: Makise Kazumasa , Shinozaki Bunju , Asano Takayuki , Mitsuishi Kazutaka , Yano Koki , Inoue Kazuyoshi , Nakamura Hiroaki
Published: August 2012

The electrical transport characteristics in amorphous Zn doped In2O3 films have been investigated in the range from 2 × 1017 cm−3 to 6 × 1020 cm−3 of the carrier concentration Ne. For films with Ne > 3 × 1020 cm−3, it is found that the Hall mobility μH is limited by ionized impurity scattering. However, for films with Ne < 1 × 1020 cm−3, the Ne dependence of μH is given by the relation of μH ∝ Ne1/3. The temperature T dependence of resistivity ρ(T) changes from exhibiting metallic behavior with dρ/dT > 0 to insulating behavior with dρ/dT < 0 near Ne≈1 × 1020 cm−3 with decreasing Ne. The transport mechanism of carriers in the high-resistivity region is discussed by considering a model based on the Ioffe-Regel criterion. For the film with highest resistivity with Ne ≈ (5 − 6) × 1017 cm−3 among the present films, the ρ(T) show a change from Mott variable-range hopping (ρ ∝ exp T−1/4) to ρ ∝ expT−1/2 at approximately 10 K with decreasing temperature.
Geodesic acoustic mode excitation by a spatially broad energetic particle beam
Authors: Qiu Z. , Zonca F. , Chen L.
Published: August 2012

Global radial eigenmodes of energetic-particle-induced geodesic acoustic mode are systematically studied, and their properties are found to depend on the nonuniformities of both the geodesic acoustic mode continuous spectrum and the energetic particle (EP) radial density profile. For a broad EP drive, the eigenmode equation valid for arbitrary EP drift orbit width is derived, and the excited energetic-particle-induced geodesic acoustic mode is shown to be strongly coupled to the geodesic acoustic mode continuous spectrum; resulting in a finite drive threshold in EP density. The cross-scale couplings between micro-, meso-, and macro-scales, discussed in this work, are mediated by the EP dynamics and have many interesting similarities with complex behaviors, expected in burning plasmas of fusion interest.
Experimental and computational study of complex shockwave dynamics in laser ablation plumes in argon atmosphere
Authors: Harilal S. S. , Miloshevsky G. V. , Diwakar P. K. , LaHaye N. L. , Hassanein A.
Published: August 2012

We investigated spatio-temporal evolution of ns laser ablation plumes at atmospheric pressure, a favored condition for laser-induced breakdown spectroscopy and laser-ablation inductively coupled plasma mass-spectrometry. The 1064 nm, 6 ns pulses from a Nd:YAG laser were focused on to an Al target and the generated plasma was allowed to expand in 1 atm Ar. The hydrodynamic expansion features were studied using focused shadowgraphy and gated 2 ns self-emission visible imaging. Shadowgram images showed material ejection and generation of shock fronts. A secondary shock is observed behind the primary shock during the time window of 100-500 ns with instabilities near the laser cone angle. By comparing the self-emission images obtained using fast photography, it is concluded that the secondary shocks observed in the shadowgraphy were generated by fast moving target material. The plume front estimates using fast photography exhibited reasonable agreement with data obtained from shadowgraphy at early times ≤400 ns. However, at later times, fast photography images showed plume confinement while the shadowgraphic images showed propagation of the plume front even at greater times. The structure and dynamics of the plume obtained from optical diagnostic tools were compared to numerical simulations. We have shown that the main features of plume expansion in ambient Ar observed in the experiments can be reproduced using a continuum hydrodynamics model which provided valuable insight into the expansion dynamics and shock structure of the plasma plume.
Extraction of negative ions from pulsed electronegative capacitively coupled plasmas
Authors: Agarwal Ankur , Rauf Shahid , Collins Ken
Published: August 2012

Charge buildup during plasma etching of dielectric features can lead to undesirable effects, such as notching, bowing, and twisting. Pulsed plasmas have been suggested as a method to achieve charge-free plasma etching. In particular, electronegative plasmas are attractive as the collapse of the plasma potential during the after-glow period of pulsed capacitively coupled plasmas (CCPs) can allow for extraction of negative ions into the feature. The extraction of negative ions in the after-glow of pulsed CCPs sustained in CF4 containing gas mixtures is computationally investigated. In this paper, the consequences of pulse frequency and gas chemistry on negative ion flux to the wafer are discussed. A low negative ion flux to the wafer was observed only in the late after-glow period of low pulse frequencies. The negative ion flux was found to significantly increase with the addition of highly electronegative gases (such as thermally attaching Cl2) even at a high pulse frequency of 10 kHz. As the production of negative ions during the after-glow diminishes, alternative strategies to enhance the flux were also pursued. The flux of negative ions was found to increase by the addition of a pulsed dc voltage on the top electrode that is 180° out-of-phase with the rf pulse.
Magnetic properties of Al doped TbMnO3 thin films grown by pulsed laser deposition
Authors: Perez-Osuna F. , Siqueiros J. M. , Durán A. , Cruz M. P. , Salamanca-Riba L. , Heiras J.
Published: August 2012

We report experimental results on the characterization of the structural, compositional, and magnetic properties of c-oriented Tb1 − xAlxMnO3 (x = 0, 0.05, and 0.10) thin films grown by pulsed laser deposition on SrTiO3 (001) substrates. Film thicknesses were 10, 25, 50, and 100 nm. X-ray diffraction analysis showed that films were single phase preferentially oriented in the (001) direction. The substrate-film strain highly increases the magnetization of the thinner films for samples with x ≤ 0.05. The introduction of Al in the films makes evident a magnetic anomaly at the temperature Tlock (∼27 K) of the TbMnO3 single crystal. Furthermore, the dopant causes the displacement of the transition temperatures TN1 due to the Mn+3 ordering and TN2 due to the Tb+3 ordering, toward higher temperatures for all samples. The most important effect of Al in the samples is to enhance the ferromagnetic behavior of the TbMnO3 thin films, improving the magnetic performance of this material, leading to a potential multiferroic with ferromagnetic ordering.
Observation of intriguing exchange bias in BiFeO3 thin films
Authors: Sung K. D. , Park Y. A. , Seo M. S. , Jo Y. , Hur N. , Jung J. H.
Published: August 2012

We have reported an intriguing exchange bias in BiFeO3 thin films on SrTiO3 substrates. While the field cooling temperature (∼300 K) is far below the Néel temperature of BiFeO3 (∼640 K), we clearly observe the exchange bias (∼−225 Oe) at 10 K. The exchange bias becomes strong with lowering temperature and depends on the applied magnetic field direction during cooling, irrespective of crystallographic directions. Magnetic force microscopy measurements reveal the existence of a ferri/ferromagnetic material, probably γ-Fe2O3, at the grain boundary of antiferromagnetic BiFeO3, forming a core-shell like structure. Based on the uncompensated spins and strong anisotropy of antiferromagnetic layer, we have explained the observed exchange bias.
Investigation into the formation of charge packets in polyethylene: Experiment and simulation
Authors: Zhao J. , Chen G. , Lewin P. L.
Published: August 2012

The phenomenon of charge packet has been reported in polymeric insulation materials under the application of dc electric fields in recent decades. It is noted that such charge packets could lead to substantial modification of local electric stress, which increases the possibility of failure of insulating materials. The physics of charge packets has not yet been revealed clearly. In this paper, the dynamics of positive charge packets in polyethylene is observed using the pulsed electro-acoustic technique. Negative differential mobility of positive charge carrier is found, which is believed to be crucial to the formation of charge packets. This negative differential mobility is introduced into a bipolar charge transport model to simulate the packet-like space charge in polymers. Simulation results show that not only the negative differential mobility but also weaker trapping characteristic are required to generate a positive charge packet in polyethylene under dc stress.
Characteristics of electric-field-induced polarization rotation in 〈001〉-poled Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals close to the morphotropic phase boundary
Authors: Peräntie J. , Hagberg J. , Uusimäki A. , Tian J. , Han P.
Published: August 2012

The special characteristics of polarization rotation and accompanying electric-field-induced ferroelectric-ferroelectric phase transitions in 〈001〉-poled Pb(Mg1/3Nb2/3)1−xTixO3 (x = 27.4, 28.8, and 30.7 mol. %) single crystals close to the morphotropic phase boundary region were studied by means of dielectric and thermal measurements as a function of a unipolar electric field at various temperatures. Discontinuous first-order-type phase transition behavior was evidenced by distinct and sharp changes in polarization and thermal responses with accompanying hysteresis as a function of the electric field. All compositions of crystals showed either one or two reversible discontinuities along the polarization rotation paths, which can be understood by electric-field-induced phase transition sequences to the tetragonal phase through different monoclinic phases previously observed along the polarization rotation path. Together with increasing polarization, a field-induced reversible decrease in temperature was observed with increasing electric field, indicating increased dipolar entropy during the electric-field-induced phase transitions. Constructed electric field-temperature phase diagrams based on the polarization and thermal data suggest that the complex polarization rotation path extends to a wider composition range than previously observed. The measured thermal response showed that a transition from the monoclinic to the tetragonal phase produced a greater thermal change in comparison with a transition within two monoclinic phases.
The influence of in-plane ferroelectric crystal orientation on electrical modulation of magnetic properties in Co60Fe20B20/SiO2/(011) xPb(Mg1/3Nb2/3)O3-(1 − x)PbTiO3 heterostructures
Authors: Zhu Guodong , Wong Kin. L. , Zhao J. , Amiri Pedram K. , Wang Kang L. , Hockel J. , Carman Gregory P. , Zhu J. , Krivorotov I.
Published: August 2012

(011) cut xPb(Mg1/3Nb2/3)O3-(1 − x)PbTiO3 (PMN-PT) ferroelectric crystal is usually used in ferroelectric/ferromagnetic (FE/FM) heterostructures due to its strong voltage-induced anisotropic in-plane strain. (011) PMN-PT crystal includes two in-plane crystal orientations, 〈100〉 and 〈01 − 1〉, with different piezoelectric strength resulting in anisotropic in-plane strain. Few systematic studies have been conducted to determine the influence of in-plane orientation on magnetoelectric (ME) coupling characteristic in ferroelectric/ferromagnetic composites. In this paper, we report our work to distinguish the contributions of in-plane orientations on electric modulation of magnetic properties. Magneto-optical Kerr effect and propagating spin wave spectroscopy are measured to define the influence of in-plane orientations on electric control of magnetic parameters and spin wave propagation. Magnetoelectric coupling coefficients and frequency modulation coefficients are also calculated.
Effect of electrode resistance on dielectric and transport properties of multiferroic superlattice: A Impedance spectroscopy study
Authors: Dussan Sandra , Kumar Ashok , Scott J. F. , Katiyar Ram S.
Published: August 2012

Fundamental microscopic processes that take place throughout of ferroelectric PbZr1−xTixO3 (x = 0.48) (PZT) and ferromagnetic La1−xSrxMnO3 (x = 0.33) (LSMO) superlattices (SLs) architecture including the influences of electrode on functional properties are analyzed using impedance spectroscopy technique (IS). Temperature and frequency dependence impedance and ac conductivity are investigated in the ranges of 100–600 K and 102–106 Hz suggesting a strong dependence between temperature and electrode contribution in the electrical properties. The results are interpreted using the alternative Z′ as a function of Z″/F representation, more commonly this representation applied in the cases when the complex impedance curves show overlapped arcs due to the relative small differences in relaxations frequencies. Activation energy is obtained from the Arrhenius plot of relaxation time and ac conductivity in order to identify the conduction mechanism present in the superlattices.
Simulation of current-filament dynamics and relaxation in the Pegasus Spherical Tokamak
Authors: O’Bryan J. B. , Sovinec C. R. , Bird T. M.
Published: August 2012

Nonlinear numerical computation is used to investigate the relaxation of non-axisymmetric current-channels from washer-gun plasma sources into “tokamak-like” plasmas in the Pegasus toroidal experiment [Eidietis et al. J. Fusion Energy 26, 43 (2007)]. Resistive MHD simulations with the NIMROD code [Sovinec et al. Phys. Plasmas 10(5), 1727–1732 (2003)] utilize ohmic heating, temperature-dependent resistivity, and anisotropic, temperature-dependent thermal conduction corrected for regions of low magnetization to reproduce critical transport effects. Adjacent passes of the simulated current-channel attract and generate strong reversed current sheets that suggest magnetic reconnection. With sufficient injected current, adjacent passes merge periodically, releasing axisymmetric current rings from the driven channel. The current rings have not been previously observed in helicity injection for spherical tokamaks, and as such, provide a new phenomenological understanding for filament relaxation in Pegasus. After large-scale poloidal-field reversal, a hollow current profile and significant poloidal flux amplification accumulate over many reconnection cycles.
Cd and Pb removal from contaminated environment by metal resistant bacterium Cupriavidus metallidurans CH34: importance of the complexation and competition effects
Authors: Hajdu Rita , Slaveykova Vera I.
Published: August 2012

Environmental contextLive bacteria are widely used to remove toxic metals from contaminated environments. We use the metal-resistant bacterium Cupriavidus metallidurans, in both model solutions and aqueous extracts of soils, to investigate the complexation and competition effects on Cd and Pb uptake. Accumulation of Cd was more affected by competition with Ca, Mg and Zn, whereas Pb accumulation was more influenced by complexation with humic acids. The study highlights the need to consider chemical site-specificity in the removal of metals from contaminated environments. AbstractThe present study aims to improve the understanding of the role of complexation and competition effects on Cd and Pb accumulation by the metal resistant bacterium Cupriavidus metallidurans largely used in bioremediation. Adsorbed and intracellular metal content in bacteria were determined in model exposure medium within a concentration range spanning from 10–9 to 5 × 10–5 M of Cd or Pb and water extracts from soils. In parallel, the free metal ion concentrations ([M2+]) were measured by an ion exchange technique. Obtained results demonstrated that Cd and Pb accumulation by C. metallidurans was related to [M2+] in the solution. The adsorbed and intracellular M fractions were significantly reduced by nitrilotriacetic acid, Elliot or Pahokee Peat humic acids, as well as by a large excess of Ca, Mg and Zn. No effect on Cd and Pb bioaccumulation was observed in the presence of Mn, Cu or Co at a 10-fold excess for bacteria exposed to 10–6 M of Cd or Pb. Adsorbed and intracellular metal determined when bacteria were exposed to water extracts of soil were in the same order as expected from the model experiments when complexation and competition effects are considered. The study emphasises the necessity of taking into account chemical site-specificity of soil solutions and water, including dissolved organic ligands, pH and the presence of other metals when developing metal removal technologies by living bacteria.
Mouse oocyte meiosis is disturbed by knockdown of Suv4-20h
Authors: Xiong Kai , Wu Wei , Wang Xuguang , Ma Xueshan , Chen Jie , Liu Honglin
Published: August 2012

Suv4-20h was initially characterised as a histone methyltransferase (HMTase) that catalyses lysine 20 of histone H4 dimethylation (H4K20me2) and trimethylation (H4K20me3). In the present study, using RNA interference (RNAi), we found that Suv4-20h activity is required for the fidelity of chromosome distribution during meiosis in the mammalian oocyte. Knockdown of Suv4-20h resulted in attenuation of H4K20me3 and the accumulation of H4K20me1. After Suv4-20h knockdown, oocytes exhibited an increasing percentage of aberrant chromosome alignment in MI, together with a decreasing percentage of polar body I extrusion. We conclude that Suv4-20h may be required for normal chromosome behaviour and that it is crucial for proper meiotic progression in mammalian oocytes.
Sexual health professionals’ evaluations of a prototype computer-based contraceptive planning intervention for adolescents: implications for practice
Authors: Brown K. E. , Abraham C. , Joshi P. , Wallace L. M.
Published: August 2012

Background
This paper aims to demonstrate how an online planning intervention to enhance contraceptive and condom use among adolescents was viewed by sexual health professionals. It identifies feedback that has facilitated improvement of the intervention both in terms of potential effectiveness and sustainability in practice. The data illustrate how professionals’ feedback can enhance intervention development. Method: Ten practitioners (two male; eight female) representing a range of roles in sexual health education and healthcare were given electronic copies of the prototype intervention. Interviews were conducted to elicit feedback. Transcripts of the interviews were subjected to thematic analysis. Results: Practitioners provided positive feedback about the intervention content, use of on-line media, the validity of planning techniques and the inclusion of males in contraceptive planning. Issues with rapport building, trust, privacy, motivation, and time and resources were raised, however, and the promotion of condom carrying was contentious. Conclusions: Professionals’ feedback provided scope for developing the intervention to meet practitioners’ concerns, thus enhancing likely feasibility and acceptability in practice. Ways in which particular feedback was generalisable to wider theory-based and online intervention development are explored. Some responses indicated that health practitioners would benefit from training to embed theory-based interventions into sexual health education and healthcare.
Promotion and uptake of a new online partner notification and retesting reminder service for gay men
Authors: Bourne Chris , Zablotska Iryna , Williamson Anthony , Calmette Yves , Guy Rebecca
Published: August 2012

Background In 2006, two new innovative features were added to a website called WhyTest which provided HIV/sexually transmissable infection (STI) information for gay men. The features were the ‘Tell them’ service allowing visitors to forward anonymous e-postcard or short message services (SMS) to sexual partners who may have been exposed to an STI, and the ‘Remind me’ service allowing visitors to register for a 3-, 6- or 12-monthly SMS reminder for a sexual health check. We describe the uptake of the new website functionality, and recognition of a health promotion campaign conducted in January–June 2007 to promote these new features. Methods: We used Poisson regression to assess trends in monthly partner notification messages and STI testing reminders sent in August 2007–June 2010. We also analysed 2007 Sydney Gay Community Periodic Survey data to measure recall of the campaign. Results: A total of 7923 partner notification messages were sent in the period August 2007–June 2010, with a significant increasing trend in monthly messages sent (P < 0001). Of the total messages sent, 7581 (96%) were by SMS and 342 (4%) by e-postcards. A total of 1023 STI testing reminders were sent in the same period, with a significant increasing trend in monthly reminders sent (P < 0.001); 516 reminders were by SMS (50.4%) and 507 by email (49.6%). The 2007 Sydney Gay Community Periodic Survey showed that 55% of the 2342 participants recognised the WhyTest image in the campaign. Conclusion: There was high awareness of WhyTest campaign images and the SMS partner notification service was more popular than the e-postcard feature.
Relative‐age effect on competition outcomes at the World Youth and World Junior Athletics Championships
Authors: Hollings Stephen C. , Hume Patria A. , Hopkins Will G.
Published: August 2012

The relative‐age effect refers to a higher frequency of athletes with birthdates earlier in the competitive year. Track and field athletics has a 2‐year competitive cycle at youth and junior levels that could make it particularly susceptible to the effect. We have therefore investigated the effect in athletics event finalists (first to eighth place) at the 2008 Junior Championships (men and women aged ≤ 19 years; n=1479) and the 2009 Youth Championships (boys and girls aged 16–17 years; n=1445). Counts of finalists differing in age by 1 year were estimated with Poisson regression and compared as factor effects (with ×/÷90% confidence limits and assessment of magnitude). The factor effects were: junior men 2.1 (×/÷1.4, large); junior women 1.7 (×/÷1.4, moderate); youth boys 3.7 (×/÷1.4, very large); youth girls 2.1 (×/÷1.3, large). Analysis by event group indicated the age effect was greatest in youth boys' sprints & hurdles (4.0, ×/÷1.7, very large), throws (7.2, ×/÷2.3, very large) and jumps (5.6, ×/÷1.9, very large), whereas it was smallest in junior men's throws (1.4, ×/÷1.4, small) and youth girls' jumps (1.4, ×/÷1.4, small). In conclusion, the marked relative‐age effects in athletics must exclude some talented younger athletes from youth and junior championships and presumably discourage them from continuing to senior championships. The consequences are a lower overall standard of performance and, for some athletes, termination of involvement in athletics before realising their full potential. An alternative structure and calendar is needed to make youth and junior athletics championships more equitable.
Mobility enhancement and highly efficient gating of monolayer MoS2 transistors with polymer electrolyte
Authors: Lin Ming-Wei , Liu Lezhang , Lan Qing , Tan Xuebin , Dhindsa Kulwinder S , Zeng Peng , Naik Vaman M , Cheng Mark Ming-Cheng , Zhou Zhixian
Published: August 2012

We report electrical characterization of monolayer molybdenum disulfide (MoS2) devices using a thin layer of polymer electrolyte (PE) consisting of poly(ethylene oxide) (PEO) and lithium perchlorate (LiClO4) as both a contact-barrier reducer and channel mobility booster. We find that bare MoS2 devices (without PE) fabricated on Si/SiO2 have low channel mobility and large contact resistance, both of which severely limit the field-effect mobility of the devices. A thin layer of PEO/LiClO4 deposited on top of the devices not only substantially reduces the contact resistance but also boost the channel mobility, leading up to three-orders-of-magnitude enhancement of the field-effect mobility of the device. When the PE is used as a gate medium, the MoS2 field-effect transistors exhibit excellent device characteristics such as a near ideal subthreshold swing and an on/off ratio of 106 as a result of the strong gate-channel coupling.
Design and measurement of a polarization convertor based on a truncated circular waveguide
Authors: Zhang Liang , Donaldson Craig R , He Wenlong
Published: August 2012

A polarization convertor based on a truncated circular waveguide is studied. It is simple to make and suitable for operating in the low terahertz frequency range. The bandwidth, machining tolerance and the nonlinear taper, used to reduce microwave reflection, are discussed. A W-band truncated polarization convertor was fabricated and its microwave properties were measured. An averaged transmission loss of −0.3 dB and a reflection of −30 dB were measured, which are in good agreement with the analytical calculation and numerical simulation presented in this paper.
Time-resolved optical emission spectroscopy of nanosecond pulsed discharges in atmospheric-pressure N2 and N2/H2O mixtures
Authors: van der Horst R M , Verreycken T , van Veldhuizen E M , Bruggeman P J
Published: August 2012

In this contribution, nanosecond pulsed discharges in N2 and N2/0.9% H2O at atmospheric pressure (at 300 K) are studied with time-resolved imaging, optical emission spectroscopy and Rayleigh scattering. A 170 ns high-voltage pulse is applied across two pin-shaped electrodes at a frequency of 1 kHz. The discharge consists of three phases: an ignition phase, a spark phase and a recombination phase. During the ignition phase the emission is mainly caused by molecular nitrogen (N2(C–B)). In the spark and recombination phase mainly atomic nitrogen emission is observed. The emission when H2O is added is very similar, except the small contribution of H
α
and the intensity of the molecular N2(C–B) emission is less.

The gas temperature during the ignition phase is about 350 K, during the discharge the gas temperature increases and is 1 µs after ignition equal to 750 K. The electron density is obtained by the broadening of the N emission line at 746 nm and, if water is added, the H
α
line. The electron density reaches densities up to 4 × 1024 m−3. Addition of water has no significant influence on the gas temperature and electron density.

The diagnostics used in this study are described in detail and the validity of different techniques is compared with previously reported results of other groups.
Inactivation of Gram-positive biofilms by low-temperature plasma jet at atmospheric pressure
Authors: Marchal F , Robert H , Merbahi N , Fontagné-Faucher C , Yousfi M , Romain C E , Eichwald O , Rondel C , Gabriel B
Published: August 2012

This work is devoted to the evaluation of the efficiency of a new low-temperature plasma jet driven in ambient air by a dc-corona discharge to inactivate adherent cells and biofilms of Gram-positive bacteria. The selected microorganisms were lactic acid bacteria, a Weissella confusa strain which has the particularity to excrete a polysaccharide polymer (dextran) when sucrose is present. Both adherent cells and biofilms were treated with the low-temperature plasma jet for different exposure times. The antimicrobial efficiency of the plasma was tested against adherent cells and 48 h-old biofilms grown with or without sucrose. Bacterial survival was estimated using both colony-forming unit counts and fluorescence-based assays for bacterial cell viability. The experiments show the ability of the low-temperature plasma jet at atmospheric pressure to inactivate the bacteria. An increased resistance of bacteria embedded within biofilms is clearly observed. The resistance is also significantly higher with biofilm in the presence of sucrose, which indicates that dextran could play a protective role.
The radial contraction of argon microwave plasmas studied by Thomson scattering
Authors: Carbone E A D , Hübner S , Palomares J M , van der Mullen J J A M
Published: August 2012

Radial electron density n
e(r) and temperature T
e(r) profiles of a microwave argon plasma at intermediate pressure were investigated by Thomson scattering. This method allows one to get n
e(r) and T
e(r) spatially resolved without any a priori assumption on the shape of the profile. Data were acquired in the pressure range 5–88 mbar where a transition from wall-stabilized to a radially contracted plasma mode was observed.

It was found that the fitting of the radial profile can be done with a Bessel function for which the boundary radius R defined by n
e(R) = 0 is a free parameter. For pressures above 20 mbar the electron density profile undergoes radial contraction, so R goes down from 3 mm at 5 mbar (wall position) to 2.09 mm at 88 mbar. The electron temperature T
e(r) on the other hand is flat in the centre and rises towards the wall. For low pressures, this rise is moderate but for pressures of 20 mbar and above the increase is more pronounced.
A note on periodic solutions of the delay differential equation 𝑥’(𝑡)=-𝑓(𝑥(𝑡-1))
Authors: Yu Jianshe
Published: August 2012

Consider the delay differential equation

x
′

(
t
)
=
−
f
(
x
(
t
−
1
)
)

x’(t)=-f(x(t-1))

, where

f
∈
C
(

R

,

R

)

f\in C(\mathbb {R}, \mathbb {R})

is odd and satisfies

x
f
(
x
)
>
0

xf(x)>0

for

x
≠
0

x\ne 0

. When

α
=

lim

x
→
0

f
(
x
)

x

\alpha =\lim _{x\to 0}\frac {f(x)}{x}

and

β
=

lim

x
→
∞

f
(
x
)

x

\beta =\lim _{x\to \infty }\frac {f(x)}{x}

exist, there is at least one Kaplan-Yorke periodic solution with period

4
4

if

min
{
α
,
β
}
>

π
2

>
max
{
α
,
β
}

\min \{\alpha ,\beta \}>\frac {\pi }{2}>\max \{\alpha ,\beta \}

. When this condition is not satisfied, we present several sufficient conditions on the existence/nonexistence of such periodic solutions. It is worthy of mention that some results are on the existence of at least two Kaplan-Yorke periodic solutions with period

4
4

and in some cases we do not require the limits

α
\alpha

and/or

β
\beta

to exist. Hence our results not only greatly improve but also complement existing ones. Moreover, some of the theoretical results are illustrated with examples.
On universal spaces for the class of Banach spaces whose dual balls are uniform Eberlein compacts
Authors: Brech Christina , Koszmider Piotr
Published: August 2012

For

κ
\kappa

being the first uncountable cardinal

ω
1

\omega _1

or

κ
\kappa

being the cardinality of the continuum

c

\mathfrak {c}

, we prove that it is consistent that there is no Banach space of density

κ
\kappa

in which it is possible to isomorphically embed every Banach space of the same density which has a uniformly Gâteaux differentiable renorming or, equivalently, whose dual unit ball with the weak

∗

^*

topology is a subspace of a Hilbert space (a uniform Eberlein compact space). This complements a consequence of results of M. Bell and of M. Fabian, G. Godefroy, and V. Zizler which says that assuming the continuum hypothesis, there is a universal space for all Banach spaces of density

κ
=

c

=

ω
1

\kappa =\mathfrak {c}=\omega _1

that have a uniformly Gâteaux differentiable renorming. Our result implies, in particular, that

β

N

∖

N

\beta \mathbb {N}\setminus \mathbb {N}

may not map continuously onto a compact subset of a Hilbert space with the weak topology of density

κ
=

ω
1

\kappa =\omega _1

or

κ
=

c

\kappa =\mathfrak {c}

and that a

C
(
K
)

C(K)

space for some uniform Eberlein compact space

K
K

may not embed isomorphically into

ℓ
∞

/

c
0

\ell _\infty /c_0

.
Primitive spherical systems
Authors: Bravi P.
Published: August 2012

A spherical system is a combinatorial object, arising in the theory of wonderful varieties, defined in terms of a root system. All spherical systems can be obtained by means of some general combinatorial procedures (such as parabolic induction and wonderful fiber product) from the so-called primitive spherical systems. Here we classify the primitive spherical systems. As an application, we prove that the quotients of a spherical system are in correspondence with the so-called distinguished subsets of colors.
Expression of Bacterial Blight Resistance in Brassica Leafy Greens Under Field Conditions and Inheritance of Resistance in a Brassica juncea Source
Authors: Wechter W. P. , Keinath A. P. , McMillan M. , Smith J. P. , Farnham M. W.
Published: August 2012

Brassica leafy greens are one of the most economically important vegetable commodity groups grown in the southeastern United States, and more than 28,000 metric tons of these crops are harvested in the United States annually. Collard and kale (Brassica oleracea Acephala group), mustard green (B. juncea), and turnip green (B. rapa) are the most commonly planted members of the brassica leafy greens group. In the last 10 years, numerous occurrences of bacterial blight on these leafy vegetables have been reported in several states. One of the pathogens responsible for this blight is designated Pseudomonas cannabina pv. alisalensis. Two B. rapa (G30710 and G30499) and two B. juncea (PI418956 and G30988) plant introductions (PIs) that exhibited moderate to high levels of resistance to this pathogen in greenhouse studies were tested for field resistance in comparison with eight commercial cultivar representatives of turnip green, mustard green, collard, and kale. The two B. juncea PIs and one of the B. rapa PIs (G30499) were found to have significantly less disease than all tested cultivars except ‘Southern Curled Giant’ mustard green (B. juncea) and ‘Blue Knight’ kale (B. oleracea). Inheritance of resistance studies performed with populations derived from the resistant G30988 and two susceptible PIs provided some evidence that resistance may be controlled by a single recessive gene.
Selection for Resistance to the Rhizoctonia-Bacterial Root Rot Complex in Sugar Beet
Authors: Strausbaugh Carl A. , Eujayl Imad A. , Foote Paul
Published: August 2012

The Rhizoctonia-bacterial root rot complex continues to be a concerning problem in sugar beet production areas. To investigate resistance to this complex in 26 commercial sugar beet cultivars, field studies and greenhouse studies with mature roots from the field were conducted with Rhizoctonia solani anastomosis group 2-2 IIIB strains and Leuconostoc mesenteroides. Based on means for the 26 cultivars in the 2010 and 2011 field studies, fungal rot ranged from 0 to 8%, bacterial rot ranged from 0 to 37%, total internal rot ranged from 0 to 44%, and surface rot ranged from 0 to 52%. All four rot variables resulted in significant (P < 0.0001) cultivar differences. Based on regression analysis, strong positive relationships (r2 from 0.6628 to 0.9320; P < 0.0001) were present among the rot variables. When ranking cultivars, the most consistent rot variable was surface rot, because 12 of 13 variable–year combinations had significant (P ≤ 0.05) correlations. When cultivar ranking in greenhouse assays was compared, there was frequently a positive correlation with storage data but no relationship with field results. Thus, the greenhouse assays will identify storage rot resistance but field screening will be required to find resistance to this rot complex in the field.
The Role of Aphid Abundance, Species Diversity, and Virus Titer in the Spread of Sweetpotato Potyviruses in Louisiana and Mississippi
Authors: Wosula E. N. , Davis J. A. , Clark C. A. , Smith T. P. , Arancibia R. A. , Musser F. R. , Reed J. T.
Published: August 2012

Sweet potato feathery mottle virus (SPFMV), Sweet potato virus G (SPVG), and Sweet potato virus 2 (SPV2) are sweetpotato (Ipomoea batatas) potyviruses nonpersistently transmitted by aphids. Our objective was to determine how aphid abundance, aphid species diversity, and virus titers relate to the spread of SPFMV, SPVG, and SPV2 in Louisiana and Mississippi sweetpotato fields. The most abundant aphid species were Aphis gossypii, Myzus persicae, Rhopalosiphum padi, and Therioaphis trifolii. Aphids were captured during the entire crop cycle but virus infection of sentinel plants occurred mainly during the months of June to August. SPFMV was more commonly detected than SPVG or SPV2 in sentinel plants. Virus titers for SPFMV were higher in samples beginning in late June. Because significant aphid populations were present during April to June when virus titers were low in sweetpotato and there was very little virus infection of sentinel plants, low virus titers may have limited aphid acquisition and transmission opportunities. This is the first study to comprehensively examine aphid transmission of potyviruses in sweetpotato crops in the United States and includes the first report of R. maidis and R. padi as vectors of SPFMV, though they were less efficient than A. gossypii or M. persicae.
First Report of Alfalfa mosaic virus Occurrence in Hydrangea in the United States
Authors: Lockhart B. , Mollov D. , Daughtrey M.
Published: August 2012

In spring of 2012, a previously unrecorded virus-like disease characterized by conspicuous yellow leaf blotching (calico symptoms) was observed in plants of Hydrangea macrophylla in a single location in Southampton, NY. Bacilliform and spherical particles resembling those of Alfalfa mosaic virus (AMV) were observed by transmission electron microscopy (TEM) in partially purified extracts from symptomatic leaf tissue. The identity of the virus was confirmed by immunosorbent electron microscopy (ISEM) (4) using antiserum to AMV (ATCC PVAS 92) that both trapped and decorated the virions. Three primer pairs designed from available AMV RNA 1, RNA 2, and RNA 3 genomic sequences were used to generate amplicons from the hydrangea AMV isolate. Reverse-transcription (RT)-PCR was done using total RNA extracted from symptomatic hydrangea leaf tissue with a Qiagen RNeasy kit, and Ready-to-Go RT-PCR beads (GE Healthcare). Amplicons of 1,049, 1,013, and 658 bp were obtained using the primer pairs AMV1F (5′-ATCCACCGATGCCAGCCTTA)/AMV1R (5′-TTCCGCCTCACTGCTGTCTG), AMV2F (5′-GATCGCCGGAAGTGATCCAG)/AMV2R (5′-TCACCGGAAGCAACAACGAA), and AMV3F (5′-GCCGGTTCTCCAAAGGGTCT)/AMV3R (5′-CGCGTCGAAGTCCAGACAGA), respectively. The PCR products were cloned using a TOPO TA cloning kit (Invitrogen) and three clones of each were sequenced. The sequences obtained from the hydrangea AMV RNA 1 (JX154090), RNA 2 (JX154091), and RNA 3 (JX154092) had 95 to 98% nucleotide sequence identity to homologous genomic sequences of known AMV isolates. To our knowledge, this is the first report of AMV occurrence in H. macrophylla in the United States. This virus has been reported to occur in H. macrophylla in British Columbia (3), but in a previous survey its presence was not detected in hydrangeas in the United States (1). A report of possible AMV infection in H. macrophylla in Italy (2) was based solely on symptomatology and cross-protection tests and therefore cannot be verified. The AMV-infected hydrangea plants were found by ISEM to also contain low concentrations of Hydrangea ringspot virus (HRSV) and Hydrangea chlorotic mottle virus (HdCMV). However, based on previous evidence of single and mixed infections (3), it is unlikely that the calico symptoms observed were influenced by the presence of HRSV and HdCMV. This report is of interest both because AMV, unlike HRSV and HdCMV, causes foliar symptoms that would render hydrangea plant unmarketable, and because the disease can be spread by a number of common aphid species that transmit AMV. It will also serve to alert growers and diagnosticians to the potential threat posed by AMV infection.

References: (1) T. C. Allen et al. Acta Hortic. 164:85, 1985. (2) G. Belli. Phytopathol. Mediterr. 7:70, 1968. (3) A. W. Chiko and S. E. Godkin. Plant Dis. 70:541, 1986. (4) B. E. L. Lockhart et al. Phytopathology 82:691, 1992.
First Report of Brown Spot Disease Caused by Neoscytalidium dimidiatum on Hylocereus undatus in Guangdong, Chinese Mainland
Authors: Lan G.-B. , He Z.-F. , Xi P.-G. , Jiang Z.-D.
Published: August 2012

Pitahaya or dragon fruit [Hylocereus undatus (Haw.) Britton & Rose] is one of the most popular tropical fruits in the world. In China, it is widely planted in Guangdong, Guangxi, Hainan, and Taiwan. In July 2011, a new pitahaya disease was found in Conghua City and Yunfu City, Guangdong Province, China, characterized by many small, circular, reddish brown spots over the diseased stems. The spots continuously expanded, and ultimately formed large areas of canker on stems. It is similar to pitahaya stem canker disease caused by Neoscytalidium dimidiatum in Taiwan (1). Pieces of tissues were collected from the lesion margins. After surface disinfestations with 1% sodium hypochloride for 1 min and rinsing in sterile water three times, the diseased tissues were placed on potato dextrose agar medium plates (PDA) and incubated at 28°C for 3 days. A dark, fast-growing fungus was isolated from all samples. For identification, single-spore cultures were grown on PDA in an incubator at 28°C. After 5 days, colonies with dark gray to black aerial mycelium formed. The colonies produced abundant conidia that occurred in arthric chains in aerial mycelium. The conidia were disarticulating, cylindrical-truncate, oblong-obtuse to doliform, dark brown, zero- to one-septate, and averaged 7.56 (5.46 to 10.30) × 6.20 (3.79 to 8.93) μm. The teleomorph was never observed in PDA culture. Based on these characteristics, the fungus was identified as N. dimidiatum (Penz.) Crous & Slippers (2). The internal transcribed spacer (ITS) regions of rDNAs from two isolates were amplified by primers ITS1 and ITS4 (3), and then sequenced. Both sequences were completely identical and 579 bp long (GenBank Accession Nos. JX128103 and JX128104), with 99% identity to that of N. dimidiatum previously deposited (Accession No. HQ439174). To confirm its pathogenicity, six healthy detached stems of pitahaya designed as two replicates were inoculated by injecting 10 μl of conidia suspension (1 × 106 conidia per ml). Three stems were inoculated with sterile water as controls. The inoculated stems were kept in an incubator at 28°C in dark. The stems exhibited the same symptoms as described above after 10 days post inoculation, whereas no symptoms developed on the control stems. The fungus was reisolated from the lesions of the inoculated stem. These results indicated that N. dimidiatum was the pathogen of pitahaya brown spot disease. To our knowledge, this is the first report of brown spot caused by N. dimidiatum on H. undatus on the Chinese mainland.

References: (1) M. F. Chuang et al. Plant Dis. 96:906, 2012. (2) P. W. Crous et al. Stud. Mycol. 55:235, 2006. (3) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, New York, 1990.