bluuebunny/crossref_metadata_2025 huggingface dataset:
Physikalisch‐chemische Untersuchungen tribomechanischer Vorgänge (Fragestellung, Ergebnisse, Aussichten)
Authors: Thießen P. A.
Published: September 2010

Die „Tribomechanik”︁ befaßt sich mit den submikroskopischen Vorgängen der Eingriffe in das Gefüge der Grenzflächen fester Körper. Alle Wechselwirkungen zwischen Werkzeug und Werkstück bei beliebigen mechanischen Bearbeitungen von Festkörpern beginnen mit tribomechanischen Prozessen. Erfolge ihrer molekular‐mechanischen Deutung sind in den letzten Jahren zunehmend auf den Einsatz physikalisch‐chemischer Methoden zurückzuführen. Die submikroskopische Zone der ersten Verformungsschritte stellt sich als ein Bereich dar, in dem für jeweils sehr kurze Zeiten neben stark zerstörtem Gefüge ein sehr heißes Plasma besteht. Bewegungsvorgänge, Veränderungen der Partner und ihrer Umgebung, optische, elektrische und chemische Vorgänge lassen sich aus einem submikroskopischen Verformungsmodell („Magma‐Plasma‐Modell”︁) herleiten, das nach einem synoptischen„ Verfahren der geringsten Widersprüche”︁ aufgestellt wurde.
Trennung und Reinigung von Makromolekülen und Partikeln durch multiplikative Verteilungsverfahren
Authors: Schwenke Klaus Dieter
Published: September 2010

Verfahren der multiplikativen Verteilung werden in zunehmendem Maße zur Lösung analytischer Probleme der makromolekularen Chemie herangezogen. Durch Benutzung geeigneter Zweiphasensysteme gelang es in letzter Zeit, hochmolekulare natürliche Polymere, wie Proteine und Nucleinsäuren, sowie Partikel, wie Zelltrümmer, ganze Zellen und Viren, anzureichern oder in reiner Form darzustellen. In einigen Fallen konnten auch synthetische Polymere durch Anwendung dieser Methodik wirksam fraktioniert werden.

Es wird eine Übersicht über die wichtigsten Beispiele der Trennung und Reinigung natürlicher und synthetischer Makromoleküle durch multiplikative Verteilung gegeben.
Die Mehrzentrenbindung im Modell der freien Elektronen
Authors: Müller Hans
Published: September 2010

Auf der Grundlage der Elektronengasmethode (FE‐Modell) wird für lineare und zyklische Strukturen die Quantenchemie der k‐Zentren‐Bindung (k = 2, 3, 4,…) entwickelt, die Bindungsfestigkeit und relative Stabilität der einzelnen Bindungstypen sowie ihre Elektronenverteilung diskutiert und ein Vergleich mit der LCAO‐MO‐Formulierung vorgenommen. An Hand einiger Beispiele werden die verschiedenen Bindungstypen erläutert.
Quantifying the vitamin D3 synthesizing potential of UVB lamps at specific distances over time
Authors: Schmidt Debra A. , Mulkerin Diane , Boehm Daniel R. , Ellersieck Mark R. , Lu Zhiren , Campbell Matthew , Chen Tai C. , Holick Michael F.
Published: September 2010

The purpose of this study was to quantify the ultraviolet B (UVB) output and in vitro previtamin D3 synthesis over time from various artificial light sources. Three incandescent lamps, T‐Rex Active UVHeat 160 watt spot, T‐Rex Active UVHeat 160 watt flood, and ZooMed PowerSun 160 watt flood, and two 1.2 m fluorescent lamps, Sylvania Blacklight 350 BL and ZooMed Reptisun 5.0, were studied. Total UVB irradiance and concentration of previtamin D synthesized using an in vitro ampoule model were quantified initially and at monthly intervals for 1 year. Incandescent lamps were measured at distances of 0.9 and 1.5 m while fluorescent lamps were measured at distances of 30.5 and 45.7 cm at the lamp's center, using both the radiometer and ampoules. Fluorescent lamp irradiance was also measured at the lamp's ends. Data were analyzed as a repeated measures split‐plot in time using SAS with all mean differences determined using Least Squares Means. Incandescent lamp irradiance differences were seen at various distances. The UVHeat lamps had consistently higher previtamin D3 production and irradiance readings compared with the PowerSun lamp. Reptisun 5.0 was consistently higher in UVB irradiance over Sylvania BL 350 at both 30.5 and 45.7 cm. However, there were no differences when comparing conversion of 7‐dehydrocholesterol to previtamin D3. Irradiance differences were detected between the centers and ends of the fluorescent lamps. Until UVB requirements for vitamin D3 synthesis in animals are determined, it is impossible to state that one light is superior to another. Zoo Biol 29:741–752, 2010. © 2010 Wiley‐Liss, Inc.
An Empirical Analysis of the Demand for Imports in three CARICOM Member Countries: An Application of the Bounds Test for Cointegration
Authors: Modeste Nelson C.
Published: September 2010

This paper provides fresh estimates of income and price elasticities of import demand in Guyana, Jamaica, and Trinidad and Tobago using a bounds test for cointegration. In addition, the paper also provides estimates of the consumption, investment, and exports elasticities of import demand. These latter elasticities were all found to be positive and statistically significant with values ranging from 0.16 to 0.55 in the long-run.
Predicted bacteriorhodopsin from Exiguobacterium sibiricum is a functional proton pump
Authors: Petrovskaya L.E. , Lukashev E.P. , Chupin V.V. , Sychev S.V. , Lyukmanova E.N. , Kryukova E.A. , Ziganshin R.H. , Spirina E.V. , Rivkina E.M. , Khatypov R.A. , Erokhina L.G. , Gilichinsky D.A. , Shuvalov V.A. , Kirpichnikov M.P.
Published: September 2010

The predicted Exigobacterium sibiricum bacterirhodopsin gene was amplified from an ancient Siberian permafrost sample. The protein bacteriorhodopsin from Exiguobacterium sibiricum (ESR) encoded by this gene was expressed in Escherichia coli membrane. ESR bound all‐trans‐retinal and displayed an absorbance maximum at 534 nm without dark adaptation. The ESR photocycle is characterized by fast formation of an M intermediate and the presence of a significant amount of an O intermediate. Proteoliposomes with ESR incorporated transport protons in an outward direction leading to medium acidification. Proton uptake at the cytoplasmic surface of these organelles precedes proton release and coincides with M decay/O rise of the ESR.
A disulfide driven domain swap switches off the activity of Shigella IpaH9.8 E3 ligase
Authors: Seyedarabi Arefeh , Sullivan James A. , Sasakawa Chihiro , Pickersgill Richard W.
Published: September 2010

MINT‐7993779: ipaH9.8 (uniprotkb:Q8VSC3) and ipaH9.8 (uniprotkb:Q8VSC3) bind (MI:0408) by X‐ray crystallography (MI:0114) MINT‐7993812: ipaH9.8 (uniprotkb:Q8VSC3) and ipaH9.8 (uniprotkb:Q8VSC3) bind (MI:0407) by affinity chromatography technology (MI:0004) MINT‐7993790: ipaH9.8 (uniprotkb:Q8VSC3) and ipaH9.8 (uniprotkb:Q8VSC3) bind (MI:0407) by blue native page (MI:0276)
The chaos game on a general iterated function system
Authors: BARNSLEY MICHAEL F. , VINCE ANDREW
Published: September 2010

The main theorem of this paper establishes conditions under which the ‘chaos game’ algorithm almost surely yields the attractor of an iterated function system. The theorem holds in a very general setting, even for non-contractive iterated function systems, and under weaker conditions on the random orbit of the chaos game than obtained previously.
What is a (global) polity?
Authors: CORRY OLAF
Published: September 2010

Despite sustained theoretical and empirical criticism of ‘statism’, a recognisablemodelof political structure other of hierarchy and anarchy (the models that underpin the state system-model) has long been lacking. Even many proponents of radical transformation of the international system often remain ‘post-international’, describing world politics essentially in terms of complications to the international system. This article agrees that a new point of departure is needed but offers a different model of political structure by redefining the term ‘polity’ – a term which is increasingly used to capture non-territorial political entities neither constituted by hierarchy nor by the lack of it. With the new definition building on Waltz's theory of theory as a ‘picture, mentally formed’ in order to simplify a domain, a  polity is deemed to exist when a set of subjects are oriented towards a common ‘governance-object’. The new polity model is applied illustratively to the idea of a global polity and a new polity research agenda of international relations is suggested.
FUNCTIONAL FORM MISSPECIFICATION IN REGRESSIONS WITH A UNIT ROOT
Authors: Kasparis Ioannis
Published: September 2010

We examine the limit properties of the nonlinear least squares (NLS) estimator under functional form misspecification in regression models with a unit root. Our theoretical framework is the same as that of Park and Phillips (2001,Econometrica69, 117–161). We show that the limit behavior of the NLS estimator is largely determined by the relative orders of magnitude of the true and fitted models. If the estimated model is of different order of magnitude than the true model, the estimator converges to boundary points. When the pseudo-true value is on a boundary, standard methods for obtaining rates of convergence and limit distribution results are not applicable. We provide convergence rates and limit theory when the pseudo-true value is an interior point. If functional form misspecification is committed in the presence of stochastic trends, the convergence rates can be slower and the limit distribution different than that obtained under correct specification.
A Novel Initial Alignment Scheme for Low-Cost INS Aided by GPS for Land Vehicle Applications
Authors: Han Songlai , Wang Jinling
Published: September 2010

This paper proposes a novel mechanism for the initial alignment of low-cost INS aided by GPS. For low-cost INS, the initial alignment is still a challenging issue because of the high noises from low-cost inertial sensors. In this paper, a two-stage Kalman Filtering mechanism is proposed for the initial alignment of low-cost INS. The first stage is designed for the coarse alignment. To solve the problems encountered by the general coarse alignment approach, an INS error dynamic accounting for unknown initial heading error is developed, and the corresponding observation equation, taking into account the unknown heading error, is also developed. The second stage is designed for the fine alignment, where the classical INS error dynamics based on small attitude error is used. Experimental results indicate that the proposed alignment approach can complete the initial alignment more quickly and more accurately compared with the conventional approach.
A Frequency-Domain INS/GPS Dynamic Response Method for Bridging GPS Outages
Authors: El-Diasty Mohammed , Pagiatakis Spiros
Published: September 2010

We develop a new frequency-domain dynamic response method to model integrated Inertial Navigation System (INS) and Global Positioning System (GPS) architectures and provide an accurate impulse-response-based INS-only navigation solution when GPS signals are denied (GPS outages). The input to such a dynamic system is the INS-only solution and the output is the INS/GPS integration solution; both are used to derive the transfer function of the dynamic system using Least Squares Frequency Transform (LSFT). The discrete Inverse Least Squares Frequency Transform (ILSFT) of the transfer function is applied to estimate the impulse response of the INS/GPS system in the time domain. It is shown that the long-term motion dynamics of a DQI-100 IMU/Trimble BD950 integrated system are recovered by 72%, 42%, 75%, and 40% for north and east velocities, and north and east positions respectively, when compared with the INS-only solution (prediction mode of the INS/GPS filter). A comparison between our impulse response model and the current state-of-the-art time-domain feed-forward neural network shows that the proposed frequency-dependent INS/GPS response model is superior to the neural network model by about 26% for 2D velocities and positions during GPS outages.
The Age of Sail: A Time when the Fortunes of Nations and Lives of Seamen Literally Turned with the Winds Their Ships Encountered at Sea
Authors: Carter William E. , Carter Merri S.
Published: September 2010

This paper examines the evidence to support the view that the inability of seamen to determine accurate longitude at sea in sailing ships was a major factor in the loss of ships and crews that was effectively solved by the introduction of the marine chronometer. It concludes that this was not the case and that a more compelling factor for the safety of ships was the introduction of mechanical propulsion systems.
A New Method For DGPS Ambiguity Resolution
Authors: Pieregentili Fabrizio , Cordelli Emiliano
Published: September 2010

This paper deals with the problem of determining the baseline vector between two GPS receivers in single frequency (L1) using the basic principles of interferometric Differential GPS, therefore using the interferometric relations between the two receivers and the satellites visible to both receivers. As a preliminary step, ambiguity identification was solved using the results provided by the Kalman filter; these results were optimized by evaluating the Dilution Of Precision indexes for satellites in view of the receivers. Results achieved by applying this first procedure to data collected are discussed. To increase the accuracy of the results, a new, computationally fast algorithm for carrier phase ambiguity resolution on data collected from static and dynamics acquisitions was developed, implemented and tested. The new algorithm permitted an increase of accuracy of about two orders of magnitude with respect to results given by filtered Double Difference in the resolution of baseline vector.
PLASTIC TREES AND GLADIATORS: LIBERALISM AND AESTHETIC REGULATION
Authors: Alexander Larry
Published: September 2010

The hallmark of modern liberalism is its embrace of the Millian harm principle and its antipathy to legal moralism. In this article I consider whether aesthetic regulations can be justified under the harm principle as that principle has been elaborated by Joel Feinberg. I conclude that aesthetic and other regulations that most liberals regard as unproblematic are actually instances of legal moralism.
FORMULAS IN MODAL LOGICS4
Authors: SASAKI KATSUMI
Published: September 2010

Here, we provide a detailed description of the mutual relation of formulas with finite propositional variablesp1, …,pmin modal logicS4. Our description contains more information onS4than those given in Shehtman (1978) and Moss (2007); however, Shehtman (1978) also treated Grzegorczyk logic and Moss (2007) treated many other normal modal logics. Specifically, we construct normal forms, which behave like the principal conjunctive normal forms in the classical propositional logic. The results include finite and effective methods to find a normal form equivalent to a given formulaAby clarifying the behavior of connectives and giving a finite method to list all exact models.
Wave mean flow interactions in the thermosphere induced by a major tsunami
Authors: Hickey M. P. , Walterscheid R. L. , Schubert G.
Published: September 2010

We investigate how the dynamics of the thermosphere is influenced by the dissipation of a tsunami‐driven gravity wave disturbance. Unlike typical lower atmospheric sources, the tsunami generates a spectrum entirely of fast gravity waves that can efficiently propagate to the upper atmosphere. This disturbance transports momentum into the thermosphere while dissipation due to molecular viscosity and thermal conduction drives a downward sensible heat flux within the thermosphere. The divergence of the momentum flux forces a change in velocity of 150–200 m/s between 200 and 300 km altitude. A tsunami propagating for ∼10 h before making landfall will produce a secular change in the wind and temperature field that extends as much as 8000 km along the direction of wave propagation. The induced winds should be observable through a variety of methods. The thermal effects driven by the divergence of the sensible heat flux are more modest and would be difficult to observe. These simulations show that large tsunami events could have a pronounced dynamical effect in the thermosphere until conditions relax to their undisturbed state.
Supraslab earthquake clusters above the subduction plate boundary offshore Sanriku, northeastern Japan: Seismogenesis in a graveyard of detached seamounts?
Authors: Uchida Naoki , Kirby Stephen H. , Okada Tomomi , Hino Ryota , Hasegawa Akira
Published: September 2010

Thousands of offshore repeating earthquakes with low‐angle thrust focal mechanisms occur along the subduction plate boundary of NE Japan. Double‐difference relocation methods using P‐ and S‐wave arrivals reveal clusters of events above these repeating events. To assure good depth control we restrict our study to events that are close to seismic stations. These “supraslab” earthquake clusters are regional features at depths of 25 to 50 km, and most of these clusters are below the depth of the forearc Moho, which we determined from converted waves. Seismicity over this depth range does not occur under the inland area of NE Japan except just below the vicinity of the arc volcanoes. Re‐entrants in the inner trench slope indicate that repeated collisions of seamounts have occurred in the past. Our preliminary interpretation of supraslab clusters is that they represent seismicity in seamounts detached from the Pacific plate during slab descent, driven by the resistance of seamounts to subduction. Detachment during slab descent probably occurs on the sedimented and hydrothermally altered seafloor on which seamounts were originally constructed since these are known as zones of weakness during active island growth. High fluid pressure produced during dehydration of clay minerals and other low‐temperature hydrous minerals could enable detachment at depths. Seamount crust is thus accreted to forearcs, possibly leading to a long‐term component of near‐coastal uplift. Supraslab earthquake clusters may be our most direct evidence of the fates of seamounts and suggest that tectonic underplating is actively occurring in this subduction system.
Creep of simulated reservoir sands and coupled chemical‐mechanical effects of CO2 injection
Authors: Hangx S. J. T. , Spiers C. J. , Peach C. J.
Published: September 2010

Geological storage of CO2 in clastic reservoirs and aquifers is expected to have a variety of coupled chemical‐mechanical effects. To investigate the effects of CO2 injection on creep phenomena, we performed uniaxial compaction experiments on granular aggregates of quartz and feldspar under both wet and dry control conditions. The experiments were performed in constant stress mode. Grain size, temperature, CO2 partial pressure, and effective stress were varied in order to determine their individual effect. Pore fluid pH was varied by the injection of CO2 and by addition of acidic and alkaline additives. Pore fluid salinity was increased by the addition of NaCl. Wet samples showed instantaneous compaction upon load application, followed by time‐dependent creep. From the mechanical data and microstructures, the main compaction mechanism was inferred to be chemically enhanced microcracking in both quartz and feldspar, with subcritical crack growth, i.e., stress corrosion cracking, controlling deformation in the creep stage. The injection of CO2 and the concomitant acidification of the pore fluid inhibited microcracking in both the quartz and feldspar samples in line with known effects of pH on stress corrosion cracking. We infer that the injection of CO2 into quartz‐ and plagioclase‐bearing sandstones will inhibit grain scale microcracking process and that related geomechanical effects, such as reservoir compaction and surface subsidence, will be negligible compared with the poroelastic response.
Effects of preexisting cyclonic eddies on upper ocean responses to Category 5 typhoons in the western North Pacific
Authors: Zheng Zhe‐Wen , Ho Chung‐Ru , Zheng Quanan , Lo Yao‐Tsai , Kuo Nan‐Jung , Gopalakrishnan Ganesh
Published: September 2010

This study examines the impacts of preexisting mesoscale cyclonic eddies (PCEs) on successive enhanced sea surface cooling in response to the passage of Super Typhoon Hai‐Tang in the western North Pacific in 2005, using numerical simulation methods. We have done two numerical experiments: one with the presence of these PCEs resolved by the Hybrid Coordinate Ocean Model/Navy Coupled Ocean Data Assimilation system (EXPHYC) and another with World Ocean Atlas 2001 climatology as initial conditions (EXPWOA). The results show that the cooling response simulated by EXPWOA is only half of that simulated by EXPHYC, which is close to satellite observations. This suggests that an accurate representation of the upper dynamic conditions is required to estimate the sea surface cooling to a typhoon accurately. Subsequently, the effects of the PCEs on successive cooling response to most major typhoons are evaluated by conducting a systematical analysis with a focus on Category 5 typhoons occurring in the region from 2003 to 2008. Satellite altimeter sea surface height anomaly data and merged Tropical Rainfall Measuring Mission Microwave Imager/Advanced Microwave Scanning Radiometer for EOS microwave sea surface temperatures (SST) are used to characterize PCEs and cooling responses to those typhoons. The results identify the relationship between PCEs and successive enhanced SST cooling for most strong typhoons in the western North Pacific.
Modification of inertial oscillations by the mesoscale eddy field
Authors: Elipot Shane , Lumpkin Rick , Prieto Germán
Published: September 2010

The modification of near‐surface near‐inertial oscillations (NIOs) by the geostrophic vorticity is studied globally from an observational standpoint. Surface drifter are used to estimate NIO characteristics. Despite its spatial resolution limits, altimetry is used to estimate the geostrophic vorticity. Three characteristics of NIOs are considered: the relative frequency shift with respect to the local inertial frequency; the near‐inertial variance; and the inverse excess bandwidth, which is interpreted as a decay time scale. The geostrophic mesoscale flow shifts the frequency of NIOs by approximately half its vorticity. Equatorward of 30°N and S, this effect is added to a global pattern of blue shift of NIOs. While the global pattern of near‐inertial variance is interpretable in terms of wind forcing, it is also observed that the geostrophic vorticity organizes the near‐inertial variance; it is maximum for near zero values of the Laplacian of the vorticity and decreases for nonzero values, albeit not as much for positive as for negative values. Because the Laplacian of vorticity and vorticity are anticorrelated in the altimeter data set, overall, more near‐inertial variance is found in anticyclonic vorticity regions than in cyclonic regions. While this is compatible with anticyclones trapping NIOs, the organization of near‐inertial variance by the Laplacian of vorticity is also in very good agreement with previous theoretical and numerical predictions. The inverse bandwidth is a decreasing function of the gradient of vorticity, which acts like the gradient of planetary vorticity to increase the decay of NIOs from the ocean surface. Because the altimetry data set captures the largest vorticity gradients in energetic mesoscale regions, it is also observed that NIOs decay faster in large geostrophic eddy kinetic energy regions.
Satellite Monitoring of Hazards: A Focus on Istanbul, Turkey
Authors: Walter T. R. , Manzo M. , Manconi A. , Solaro G. , Lanari R. , Motagh M. , Woith H. , Parolai S. , Shirzaei M. , Zschau J. , Baris S. , Ansal A.
Published: September 2010

Satellite remote sensing data can provide important information on ground displacement, which can help scientists better understand and monitor geohazards such as earthquakes, volcano unrest, or landslides. However, access to such data and their results often has been difficult or has occurred with significant delay. As a result, a remotely sensed assessment of ground displacements is often not available until months or years after the occurrence of a natural disaster.
Twentieth century warming in deep waters of the Gulf of St. Lawrence: A unique feature of the last millennium
Authors: Thibodeau Benoît , de Vernal Anne , Hillaire‐Marcel Claude , Mucci Alfonso
Published: September 2010

The impact of human activities on Earth's climate is still subject to debate and the pattern of a sharp recent global temperature increase contrasting with much lesser variable temperatures during preceding centuries has often been challenged, partly due to the lack of unquestionable evidence. In this paper, oxygen isotope compositions of benthic foraminifer shells recovered from sediments of the Lower St. Lawrence Estuary and the Gulf are used to reconstruct temperature changes in a water mass originating from ∼400 m deep North Atlantic waters. The data demonstrate that the 1.7 ± 0.3°C warming measured during the last century corresponds to a δ18O shift of 0.4 ± 0.05‰, encompassing the temperature effect and related change in the isotopic composition of the corresponding water mass. In contrast, δ18O values remained nearly constant over the last millennium, except for a small positive shift which we attribute to the Little Ice Age. We conclude that the 20th century warming of the incoming intermediate North Atlantic water has had no equivalent during the last thousand years.
Exploring Consumer Perceptions of Green Restaurants in the US
Authors: Schubert Franziska , Kandampully Jay , Solnet David , Kralj Anna
Published: September 2010

Consumer attitudes and behavioural intentions towards environmentally sustainable practices in restaurants is an under-explored area in the hospitality literature, despite the growing ‘green’ trend. This article analyses data collected from 455 restaurant customers across five casual dining restaurants to gain insight into consumer attitudes towards, and willingness to pay more for, restaurants that engage in ‘green’ practices. The findings illustrate that there is an unfilled market niche for ‘green’ restaurants, as customers care about restaurants protecting the environment and would be willing to pay more to offset any additional costs associated with ‘green’ practices.
Efficient evaluation of triple excitations in symmetry-adapted perturbation theory via second-order Møller–Plesset perturbation theory natural orbitals
Authors: Hohenstein Edward G. , Sherrill C. David
Published: September 2010

An accurate description of dispersion interactions is required for reliable theoretical studies of many noncovalent complexes. This can be obtained with the wave function-based formulation of symmetry-adapted perturbation theory (SAPT) provided that the contribution of triple excitations to dispersion is included. Unfortunately, this triples dispersion correction limits the applicability of SAPT due to its O(N7) scaling. The efficiency of the evaluation of this correction can be greatly improved by removing virtual orbitals from the computation. The error incurred from truncating the virtual space is reduced if second-order Møller–Plesset perturbation theory (MP2) natural orbitals are used in place of the canonical Hartree–Fock molecular orbitals that are typically used. This approximation is further improved if the triples correction to dispersion is scaled to account for the smaller virtual space. If virtual MP2 natural orbitals are removed according to their occupation numbers, in practice, roughly half of the virtual orbitals can be removed (with the aug-cc-pVDZ basis set) with negligible errors if the remaining triples dispersion contribution is scaled. This typically leads to speedups of 15–20 times for the cases considered here. By combining the truncated virtual space with the frozen core approximation, the triples correction can be evaluated approximately 50 times faster than the canonical computation. These approximations cause less than 1% error (or at most 0.02 kcal mol−1) for the cases considered. Truncation of greater fractions of the virtual space is possible for larger basis sets (leading to speedups of over 40 times before additional speedups from the frozen core approximation).
Fast plasma discharge capillary design as a high power throughput soft x-ray emission source
Authors: Wyndham E. S. , Favre M. , Valdivia M. P. , Valenzuela J. C. , Chuaqui H. , Bhuyan H.
Published: September 2010

We present the experimental details and results from a low energy but high repetition rate compact plasma capillary source for extreme ultraviolet and soft x-ray research and applications. Two lengths of capillary are mounted in two versions of a closely related design. The discharge operates in 1.6 and 3.2 mm inner diameter alumina capillaries of lengths 21 and 36 mm. The use of water both as dielectric and as coolant simplifies the compact low inductance design with nanosecond discharge periods. The stored electrical energy of the discharge is approximately 0.5 J and is provided by directly charging the capacitor plates from an inexpensive insulated-gate bipolar transistor in 1 μs or less. We present characteristic argon spectra from plasma between 30 and 300 Å as well as temporally resolved x-ray energy fluence in discrete bands on axis. The spectra also allow the level of ablated wall material to be gauged and associated with useful capillary lifetime according to the chosen configuration and energy storage. The connection between the electron beams associated with the transient hollow cathode mechanism, soft x-ray output, capillary geometry, and capillary lifetime is reported. The role of these e-beams and the plasma as measured on-axis is discussed. The relation of the electron temperature and the ionization stages observed is discussed in the context of some model results of ionization in a non-Maxwellian plasma.
Inversion layer carrier concentration and mobility in 4H–SiC metal-oxide-semiconductor field-effect transistors
Authors: Dhar S. , Haney S. , Cheng L. , Ryu S.-R. , Agarwal A. K. , Yu L. C. , Cheung K. P.
Published: September 2010

Free electron concentration and carrier mobility measurements on 4H–SiC metal-oxide-semiconductor inversion layers are reported in this article. The key finding is that in state-of-the-art nitrided gate oxides, loss of carriers by trapping no longer plays a significant role in the current degradation under heavy inversion conditions. Rather, it is the low carrier mobility (maximum∼60 cm2 V−1 s−1) that limits the channel current. The measured free carrier concentration is modeled using the charge-sheet model and the mobility is modeled by existing mobility models. Possible mobility mechanisms have been discussed based on the modeling results.
Size-dependent reversal of grains in perpendicular magnetic recording media measured by small-angle polarized neutron scattering
Authors: Lister S. J. , Thomson T. , Kohlbrecher J. , Takano K. , Venkataramana V. , Ray S. J. , Wismayer M. P. , de Vries M. A. , Do H. , Ikeda Y. , Lee S. L.
Published: September 2010

Polarized small-angle neutron scattering has been used to measure the magnetic structure of a CoCrPt–SiOx thin-film data storage layer, contained within a writable perpendicular recording media, at granular (<10 nm) length scales. The magnetic contribution to the scattering is measured as the magnetization is reversed by an external field, providing unique spatial information on the switching process. A simple model of noninteracting nanomagnetic grains provides a good description of the data and an analysis of the grain-size dependent reversal provides strong evidence for an increase in magnetic anisotropy with grain diameter.
Strongly coupled single quantum dot in a photonic crystal waveguide cavity
Authors: Brossard F. S. F. , Xu X. L. , Williams D. A. , Hadjipanayi M. , Hugues M. , Hopkinson M. , Wang X. , Taylor R. A.
Published: September 2010

Cavities embedded in photonic crystal waveguides offer a promising route toward large scale integration of coupled resonators for quantum electrodynamics applications. In this letter, we demonstrate a strongly coupled system formed by a single quantum dot and such a photonic crystal cavity. The resonance originating from the cavity is clearly identified from the photoluminescence mapping of the out-of-plane scattered signal along the photonic crystal waveguide. The quantum dot exciton is tuned toward the cavity mode by temperature control. A vacuum Rabi splitting of ∼140 μeV is observed at resonance.
Single crystal-like selection rules for unipolar-axis oriented tetragonal Pb(Zr,Ti)O3 thick epitaxial films
Authors: Nakajima Mitsumasa , Fujisawa Takashi , Ehara Yoshitaka , Yamada Tomoaki , Funakubo Hiroshi , Naganuma Hiroshi , Okamura Soichiro , Nishida Ken , Yamamoto Takashi , Osada Minoru
Published: September 2010

We investigated the polarized Raman spectra of a strain-free, unipolar-axis oriented tetragonal Pb(Zr,Ti)O3 thick epitaxial film. We evaluated the single crystal-like selection rules of the A1- and E-symmetry components, and found an anomalous behavior in the angular dependence of the A1(1TO)-mode intensity similar to that observed in high-Tc superconductor single crystals. Raman tensor analyses of the A1(1TO) mode revealed complex phases may exist between two independent Raman-tensor components even in the single 180° domain state.
Experimental and simulation study of breakdown voltage enhancement of AlGaN/GaN heterostructures by Si substrate removal
Authors: Visalli Domenica , Van Hove Marleen , Srivastava Puneet , Derluyn Joff , Das Johan , Leys Maarten , Degroote Stefan , Cheng Kai , Germain Marianne , Borghs Gustaaf
Published: September 2010

The breakdown mechanism in GaN-based heterostructures (HFETs) grown on silicon substrate is investigated in detail by TCAD simulations and silicon substrate removal technique. High-voltage electrical measurements show that the breakdown voltage saturates for larger gate-drain distances. This failure mechanism is dominated by the avalanche breakdown in the Si substrate. High-voltage TCAD simulations of AlGaN/GaN/Si substrate structures show higher impact ionization factor and electron density at the Si interface indicating a leakage current path where avalanche breakdown occurs. Experimentally, by etching off the Si substrate the breakdown voltage no longer saturates and linearly increases for all gate-drain gaps. We propose the silicon removal technique as a viable way to enhance the breakdown voltage of AlGaN/GaN devices grown on Si substrate.
Effects of the electroforming polarity on bipolar resistive switching characteristics of SrTiO3−δ films
Authors: Yan X. B. , Xia Y. D. , Xu H. N. , Gao X. , Li H. T. , Li R. , Yin J. , Liu Z. G.
Published: September 2010

The effects of the electroforming polarity on the bipolar resistive switching characteristics in SrTiO3−δ thin films have been investigated. The conduction mechanisms of high resistance state and low resistance state are Poole–Frenkel emission and tunneling, respectively. The temperature dependences of the resistance at high and low resistance state are both semiconductorlike. The impact of the polarity of the electroforming voltage on the resistive switching mechanism and the distribution of defects was discussed. A simple model describing the combination of bulk and the interface effect was proposed to explain the resistive switching in this material.
Effective reduction of interfacial traps in Al2O3/GaAs (001) gate stacks using surface engineering and thermal annealing
Authors: Chang Y. C. , Merckling C. , Penaud J. , Lu C. Y. , Wang W.-E. , Dekoster J. , Meuris M. , Caymax M. , Heyns M. , Kwo J. , Hong M.
Published: September 2010

To effectively passivate the technologically important GaAs (001) surfaces, in situ deposition of Al2O3 was carried out with molecular beam epitaxy. The impacts of initial GaAs surface reconstruction and post-deposition annealing have been systematically investigated. The corresponding interfacial state density (Dit) were derived by applying the conductance method at 25 and 150 °C on both p-type and n-type GaAs metal-oxide-semiconductor capacitors to establish the Dit spectra in proximity of the critical midgap region. We show that significant reduction of Dit near the midgap is achieved by applying an optimized thermal annealing on samples grown on a Ga-rich (4×6) reconstructed surface.
Photoluminescence quenching dynamics in cadmium telluride and gallium arsenide induced by ultrashort terahertz pulse
Authors: Liu Jingle , Kaur Gurpreet , Zhang X.-C.
Published: September 2010

The quenching dynamics of femtosecond-optical-pulse-induced photoluminescence in semiconductors under the influence of single-cycle terahertz pulses has been experimentally investigated. When electron kinetic energy gained from the terahertz field was comparable to or greater than initial excess electron energy, photoluminescence quenching was observed. Quenching in cadmium telluride (CdTe) and gallium arsenide (GaAs) is linearly proportional to the intensity of incident terahertz waves and reaches up to 17% and 4%, respectively, at a peak terahertz intensity of 13 MW/cm2. The photoluminescence measurement reveals that the ultrafast decay times of terahertz-pulse-induced quenching are 700±60 fs for CdTe and 350±30 fs for GaAs.
Emission characteristics of GaN-based blue lasers including a lattice matched Al0.83In0.17N optical blocking layer for improved optical beam quality
Authors: Castiglia A. , Carlin J.-F. , Feltin E. , Cosendey G. , Dorsaz J. , Grandjean N.
Published: September 2010

We demonstrate room-temperature continuous-wave operation of 425 nm InGaN-based blue laser diodes including a thin Al0.83In0.17N optical blocking layer. Structures are grown on c-plane GaN freestanding substrates with a lattice-matched AlInN layer positioned below an Al0.07Ga0.93N bottom cladding. Such devices are compared to standard InGaN based lasers looking at threshold current density, electrical characteristics, and far-field emission. Threshold current densities of 4 kA/cm2 and slope efficiencies of ∼0.6 W/A (for uncoated facets) have been achieved in AlInN containing devices. Lower mode leakage in the substrate is highlighted by a better transversal far-field pattern resulting in an improved beam quality.
Isolation, Purification, and Biological Activity of a Phytotoxin Produced by Stemphylium solani
Authors: Zheng Lu , Lv Rujing , Huang Junbin , Jiang Daohong , Hsiang Tom
Published: September 2010

Stemphylium solani, the causal agent of leaf blight of garlic (Allium sativum), produced phytotoxic metabolites in culture. A non-host-specific phytotoxin from culture filtrate of S. solani isolate DY-5, named SS-toxin, was extracted by ethyl acetate, isolated by bioassay-guided thin layer chromatography on silica gel, and purified by preparative liquid chromatography. SS-toxin produced necrotic lesions on detached garlic leaves, similar to that caused by S. solani. When wounded leaves were each treated with a 10-μl droplet of toxin, Changbanpo, a garlic cultivar susceptible to leaf blight, showed necrotic lesions at 11 μg/ml toxin, while a resistant cultivar, Qingganruanye, showed symptoms at 44 μg/ml. The effective doses causing 50% inhibition (EC50 values) of root growth and shoot elongation of the susceptible cultivar were 64.9 and 178.5 μg/ml, respectively. The SS-toxin significantly inhibited mitotic activity of root tip cells of the susceptible cultivar from 22 μg/ml and higher causing an abnormally high frequency of cells in interphase. Concentrations over 50 μg/ml of SS-toxin were found to be significantly toxic to total chlorophyll, both chlorophyll a and b, of the susceptible cultivar. The plasma membrane–cell wall interface, nuclear membranes, mitochondria, and chloroplasts were affected by SS-toxin in susceptible leaf cells. This is the first report of the purification and testing of a phytotoxin produced by S. solani.
Oxytetracycline Dynamics on Peach Leaves in Relation to Temperature, Sunlight, and Simulated Rain
Authors: Christiano R. S. C. , Reilly C. C. , Miller W. P. , Scherm H.
Published: September 2010

Oxytetracycline (OTC), a member of the tetracycline antibiotics, is used as a foliar spray to control Xanthomonas arboricola pv. pruni on stone fruits and Erwinia amylovora on pome fruits. We studied the dynamics of OTC residues on attached peach (Prunus persica) leaves treated with 300 ppm active ingredient of an agricultural OTC in relation to temperature, natural sunlight, and simulated rain. We further evaluated the potential of three ultraviolet (UV) protectants (lignin, titanium dioxide, and oxybenzone) and one sticker-extender (Nu Film-17) to prolong OTC longevity on the leaf surface. OTC residue was determined by high-pressure liquid chromatography (HPLC)-UV (C18 reversed-phase column). In controlled conditions in darkness, constant temperatures up to 40°C did not affect OTC degradation on leaves. In contrast, OTC residue decreased rapidly in natural sunlight in the absence of rain, declining, on average, by 43.8, 77.8, and 92.1% within 1, 2, and 4 days after application, respectively; 7 days after application, OTC levels were near the detection limit. Use of shade fabric with 10 and 40% sunlight transmittance, simulating overcast sky, reduced OTC degradation significantly but did not extend OTC persistence beyond 7 days. Areas under the OTC residue curve, summarizing OTC dynamics during the 7-day exposure period, were negatively and significantly correlated with solar radiation and UV radiation variables, but not with temperature. UV protectants and Nu Film-17 were ineffective in improving OTC persistence in outdoor conditions. Simulated rain at 44 mm h–1 drastically (by 67.2%) lowered OTC residue after 2 min, and levels were near the detection limit after 60 min of continuous rain, regardless of whether plants were exposed to rainfall 1 or 24 h after OTC application. In artificial inoculation experiments with X. arboricola pv. pruni on attached peach leaves, OTC concentrations ≥50 ppm active ingredient (corresponding to ≥0.06 μg OTC cm–2 leaf surface) were sufficient to suppress bacterial spot development. By extrapolation from our outdoor exposure experiments, similar OTC residues following application of labeled OTC rates would be reached after less than 2 days under full sunlight, after 4 days under overcast sky, or after 2 min of a heavy rainstorm.
First Report of Soft Rot of Potatoes Caused by Dickeya dadantii in Zimbabwe
Authors: Ngadze E. , Coutinho T. A. , van der Waals J. E.
Published: September 2010

A survey was carried out in the potato- (Solanum tuberosum L.) growing regions of Zimbabwe in April 2009 to assess the prevalence of bacterial soft rot. A total of 125 tubers with soft rot symptoms were collected. The disease caused severe economic losses ranging from 20 to 60% on tubers in the field and in storage. Affected tubers had symptoms that ranged from light vascular discoloration to complete seed piece decay. Infected tuber tissue was often cream colored and soft to the touch. In the field, plants showed severe wilting, often accompanied by a slimy, brown necrosis of the lower stems. Seventy-five of 125 isolations from diseased tubers yielded pectolytic bacteria on crystal violet pectate (CVP) medium and colonies were characterized after purification on King's B medium. All 75 isolates were gram-negative rods, oxidase negative, facultatively anaerobic, able to degrade pectate, and rot potato slices. They grew at 37°C, were sensitive to erythromycin, positive for phosphatase, indole production, cis-aconitate, lactose, d-arabinose, meso-tartrate, casein, d-melibiose, myo-inositol, and malonate utilization, while negative for acid production from trehalose, inuline, and α-methyl glucose. Dickeya dadantii (Erwinia chrysanthemi 3937 from the Scottish Research Institute) was included in all biochemical and pathogenicity tests. These characteristics are typical for two species, D. zeae and D. dadantii (2). Thus, the 75 isolates were further identified by PCR amplification with BOX and REP primers (3) and five isolates by gyrB sequence analysis (1). These analyses give support for the isolates being D. dadantii. Partial gyrB sequence analysis showed that the analyzed isolates had 96% sequence identity with the D. dadantii type strain Ech 586T (GenBank Accession No. CP001836.1). One-microliter suspensions (108 CFU per ml) of 20 samples were injected into the stolon end of potato tubers (S. tuberosum L.) cv. BP1. Each isolate was inoculated into three tubers, which were maintained at 25°C. Three control tubers were inoculated with sterile distilled water. Soft rot symptoms identical to those observed in the field and in storage appeared on all inoculated tubers 1 to 2 days after inoculation but not on the control tubers. A bacterium with identical characteristics to those described above was consistently reisolated from the rotted tissue of inoculated tubers. To our knowledge, this is the first report of soft rot on potato in Zimbabwe caused by D. dadantii, formerly referred to as E. chrysanthemi. This finding has implications for import and export of potato material into and out of Zimbabwe. Zimbabwe imports seed from various countries because of the current seed shortage and exports table potatoes to other African states.

References: (1) C. Brady et al. Int. J. Syst. Evol. Micobiol. 59:2339, 2009. (2) R. Samson et al. Int. J. Syst. Evol. Microbiol. 55:1415, 2005. (3) J. Versalovic et al. 1991. Nucleic Acids Res. 19:6823, 1991.
Detection and Frequency of Lily Viruses in Argentina
Authors: Chinestra S. C. , Facchinetti C. , Curvetto N. R. , Marinangeli P. A.
Published: September 2010

In a survey of lily growing fields in various regions of Argentina, three viruses, Lily symptomless virus (LSV), Lily mottle virus (LMoV), and Cucumber mosaic virus (CMV), were found in Longiflorum, Asiatic, Oriental, Longiflorum × Asiatic (LA), and Oriental × Trumpet (OT) hybrids. The areas surveyed were between latitude 26° 56′ S and 43° 03′ S, and longitude 65° 21′ W and 71° 29′ W. Virus detection was performed by double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) using polyclonal antiserum. In infected samples, viruses detected in decreasing order were LSV (60.5%), LMoV (51.0%), and CMV (28.7%) present in single or mixed infections. Virus infection varied among tested hybrids from 36.0% (Oriental Montecristo) to 94.7% (Lilium longiflorum Avita) in 2006 and from 38.9% (OT Yelloween) to 82.1% (LO Triumphator) in 2007, with an overall incidence of 64.1 and 70.7% in 2006 and 2007, respectively. A variation in virus incidence among localities was also observed. The highest virus incidence (89.6 and 87.6% in 2006 and 2007, respectively) was observed in Bahía Blanca (38° 44′ S, 62° 16′ W). The lowest virus incidences, detected in Trevellin (43° 03′ S, 71° 29′ W) and in Malargüe (35° 28′ S, 69° 35′ W), were 47.4 and 48.6% in 2006 and 2007, respectively. Moreover, a different distribution of each virus was observed between localities. The high occurrence of viruses infecting lily crops in Argentina could be due to both the use of infected bulbs for propagation and the lack of preventive virus vector control measures.