bluuebunny/crossref_metadata_2025 huggingface dataset:
Ferromagnetic and optical properties of Co doped ZnO hexagonal bipods
Authors: Guo Ting , Zhang Yujung , Luo Yidong , Nan Ce-Wen , Lin Yuan-Hua
Published: October 2012

ZnO hexagonal bipods have been synthesized by a hydrothermal method using NaAOT as template. Co-doped ZnO bipods show obvious room temperature ferromagnetic behaviours. Phase composition, microstructure, and x-ray photoemission spectra analysis indicate that there is no Co cluster exsisting in the samples, and the ferromagnetism observed in Co-doped ZnO bipods should be intrinsic. Photoluminescence spectra indicate there exist a large amount of oxygen vacancies in the ZnO bipods. The ferromagnetism can be tuned by the content of Co ions, which should be closely realted to the magnetic coupling interaction between the Co2+ 3d spins and the electrons trapped at oxygen vacancies.
Stochastic mapping of first order reaction networks: A systematic comparison of the stochastic and deterministic kinetic approaches
Authors: Lente Gábor
Published: October 2012

Stochastic maps are developed and used for first order reaction networks to decide whether the deterministic kinetic approach is appropriate for a certain evaluation problem or the use of the computationally more demanding stochastic approach is inevitable. On these maps, the decision between the two approaches is based on the standard deviation of the expectation of detected variables: when the relative standard deviation is larger than 1%, the use of the stochastic method is necessary. Four different systems are considered as examples: the irreversible first order reaction, the reversible first order reaction, two consecutive irreversible first order reactions, and the unidirectional triangle reaction. Experimental examples are used to illustrate the practical use of the theoretical results. It is shown that the maps do not only depend on particle numbers, but the influence of parameters such as time, rate constants, and the identity of the detected target variable is also an important factor.
Noncolliding Brownian motion with drift and time-dependent Stieltjes-Wigert determinantal point process
Authors: Takahashi Yuta , Katori Makoto
Published: October 2012

Using the determinantal formula of Biane, Bougerol, and O’Connell, we give multitime joint probability densities to the noncolliding Brownian motion with drift, where the number of particles is finite. We study a special case such that the initial positions of particles are equidistant with a period a and the values of drift coefficients are well-ordered with a scale σ. We show that, at each time t > 0, the single-time probability density of particle system is exactly transformed to the biorthogonal Stieltjes-Wigert matrix model in the Chern-Simons theory introduced by Dolivet and Tierz. Here, one-parameter extensions (θ-extensions) of the Stieltjes-Wigert polynomials, which are themselves q-extensions of the Hermite polynomials, play an essential role. The two parameters a and σ of the process combined with time t are mapped to the parameters q and θ of the biorthogonal polynomials. By the transformation of normalization factor of our probability density, the partition function of the Chern-Simons matrix model is readily obtained. We study the determinantal structure of the matrix model and prove that, at each time t > 0, the present noncolliding Brownian motion with drift is a determinantal point process, in the sense that any correlation function is given by a determinant governed by a single integral kernel called the correlation kernel. Using the obtained correlation kernel, we study time evolution of the noncolliding Brownian motion with drift.
Solvated dissipative electro-elastic network model of hydrated proteins
Authors: Martin Daniel R. , Matyushov Dmitry V.
Published: October 2012

Elastic network models coarse grain proteins into a network of residue beads connected by springs. We add dissipative dynamics to this mechanical system by applying overdamped Langevin equations of motion to normal-mode vibrations of the network. In addition, the network is made heterogeneous and softened at the protein surface by accounting for hydration of the ionized residues. Solvation changes the network Hessian in two ways. Diagonal solvation terms soften the spring constants and off-diagonal dipole-dipole terms correlate displacements of the ionized residues. The model is used to formulate the response functions of the electrostatic potential and electric field appearing in theories of redox reactions and spectroscopy. We also formulate the dielectric response of the protein and find that solvation of the surface ionized residues leads to a slow relaxation peak in the dielectric loss spectrum, about two orders of magnitude slower than the main peak of protein relaxation. Finally, the solvated network is used to formulate the allosteric response of the protein to ion binding. The global thermodynamics of ion binding is not strongly affected by the network solvation, but it dramatically enhances conformational changes in response to placing a charge at the active site of the protein.
Realigning random states
Authors: Aubrun Guillaume , Nechita Ion
Published: October 2012

We study how the realignment criterion (also called computable cross-norm criterion) succeeds asymptotically in detecting whether random states are separable or entangled. We consider random states on Cd⊗Cd obtained by partial tracing a Haar-distributed random pure state on Cd⊗Cd⊗Cs over an ancilla space Cs. We show that, for large d, typically, the realignment criterion is successful in detecting entanglement if and only if \documentclass[12pt]{minimal}\begin{document}$s \leqslant (\frac{8}{3\pi })^2 d^2$\end{document}s⩽(83π)2d2. In this sense, the realignment criterion is asymptotically weaker than the partial transposition criterion.
Tailoring thermal expansion in metal matrix composites blended by antiperovskite manganese nitrides exhibiting giant negative thermal expansion
Authors: Takenaka K. , Hamada T. , Kasugai D. , Sugimoto N.
Published: October 2012

We controlled thermal expansion of metal matrix composites (MMCs) that had been blended using antiperovskite manganese nitrides with giant negative thermal expansion (NTE). The NTE of the manganese nitrides, which is isotopic, is greater than −30 ppm K−1 in α (coefficient of linear thermal expansion), which is several or ten times as large as that of conventional NTE materials. These advantages of nitrides are desirable for practical application as a thermal-expansion compensator, which can suppress thermal expansion of various materials including metals and even plastics. Powder metallurgy using pulsed electric current sintering enables us to reduce temperatures and times for fabrication of MMCs. Consequently, chemical reactions between matrix (Al, Ti, Cu) and filler can be controlled and even high-melting-point metals can be used as a matrix. Thermal expansion of these MMCs is tunable across widely various α values, even negative ones, with high reproducibility. These composites retain a certain amount of voids. Formation of rich and stable interfacial bonding, overcoming large mismatch in thermal expansion, remains as a problem that is expected to hinder better composite performance.
Global existence and nonrelativistic limit for the Vlasov-Maxwell-Chern-Simons system
Authors: Huh Hyungjin , Lee Ho
Published: October 2012

The Vlasov-Maxwell-Chern-Simons system is studied. Global existence of classical solutions is proved, and then its nonrelativistic limit is investigated. When the speed of light tends to infinity, it is proved that solutions of the Vlasov-Maxwell-Chern-Simons system converge to solutions of the Vlasov-Yukawa system in a suitable sense.
Arbitrary order El'yashevich–Wilson B tensor formulas for the most frequently used internal coordinates in molecular vibrational analyses
Authors: Hollman David S. , Schaefer Henry F.
Published: October 2012

In recent years, internal coordinates have become the preferred means of expressing potential energy surfaces. The ability to transform quantities from chemically significant internal coordinates to primitive Cartesian coordinates and spectroscopically relevant normal coordinates is thus critical to the further development of computational chemistry. In the present work, general nth order formulas are presented for the Cartesian derivatives of the five most commonly used internal coordinates—bond stretching, bond angle, torsion, out-of-plane angle, and linear bending. To compose such formulas in a reasonably understandable fashion, a new notation is developed that is a generalization of that which has been used previously for similar purposes. The notation developed leads to easily programmable and reasonably understandable arbitrary order formulas, yet it is powerful enough to express the arbitrary order B tensor of a general, N-point internal coordinate, as is done herein. The techniques employed in the derivation of such formulas are relatively straightforward, and could presumably be applied to a number of other internal coordinates as needed.
Debye-diffraction-based concentric energy analysis on two-photon photoluminescence imaging of gold nanorods under radial polarization illumination
Authors: Kang Hong , Gu Min
Published: October 2012

Gold nanorods have been identified to be useful contrast agents as they exhibit pronounced two-photon photoluminescence under laser illumination of appropriate intensity and polarization configurations. In this paper, the two-photon photoluminescence imaging of three-dimensionally randomly oriented gold nanorods under linear and radial polarization illumination is investigated through a concentric energy analysis based on the Debye diffraction theory. Consequently, the effect of the numerical aperture and the apodization function of an objective on the polarization distribution in the focal region can be analyzed to form an important part in the understanding on the efficient excitation of gold nanorods. It is demonstrated that the radially polarized beam is an effective laser mode in generating strong two-photon imaging of nanorods in the presence of objectives with high numerical aperture and large annular obstruction sizes.
Negative residual infrared photoconduction in the p-SiGe/Si heterostructures with selectively doped quantum wells
Authors: Gudenko Yu. N. , Vainberg V. V. , Vasetskii V. M. , Poroshin V. N. , Sarbey O. G. , Chirchik S. V.
Published: October 2012

In the p-Si0.88Ge0.12/Si heterostructures with quantum wells delta-doped by boron, the decay kinetics of the lateral infrared photoconduction has been studied at low temperatures (15 to 50 K). Photoconduction was excited in the impurity spectral range by a CO2-laser pulse radiation. After switching off the light, both positive and negative residual photoconductions are observed. It is positive at low temperatures, but it changes to the negative one at T > 25 K. The higher the temperature and electric field are, the faster is the decay of the negative residual photoconduction. Qualitative explanation and quantitative description of the photoconduction relaxation take into account the competition between the recombination of free holes on the impurity levels and their thermal excitation from barrier traps into subbands of the quantum well. If the recombination time is much smaller than the excitation time from the traps, the negative residual photoconduction appears.
Structural and optical properties of ZnCdO/ZnO multiple quantum wells grown on sapphire substrates using pulsed laser deposition
Authors: Jiang J. , Zhu L. P. , He H. P. , Li Y. , Guo Y. M. , Cao L. , Li Y. G. , Wu K. W. , Zhang L. Q. , Ye Z. Z.
Published: October 2012

High quality Zn0.92Cd0.08O/ZnO multiple quantum wells with smooth interfaces have been prepared on c-plane sapphire substrates by pulsed laser deposition. The periodic structure has been characterized by scanning transmission electron microscope and energy dispersive x-ray spectroscopy line scans. The temperature dependent photoluminescence of Zn0.92Cd0.08O/ZnO exhibits an inconspicuous S-shaped property due to a combined effect of the slightly disordered ZnCdO alloy. We can observe both quantum confinement effects and quantum-confinement Stark effect in the quantum wells. We can modulate the well emission energy from 2.90 to 3.085 eV by varying the well thickness at room temperature.
Effects of fluid properties and laser fluence on jet formation during laser direct writing of glycerol solution
Authors: Yan Jingyuan , Huang Yong , Xu Changxue , Chrisey Douglas B.
Published: October 2012

Laser-induced forward transfer (LIFT) has been widely studied to print various structures. It is important to investigate the jet and droplet formation process under different LIFT operating conditions. The resulting knowledge will help to better control the resulting printing quality and feature resolution. This study aims to better understand the effects of fluid properties and laser fluence on the jet formation process using time resolved imaging analysis during LIFT of glycerol solutions. It is found that if the laser fluence is too low and/or the glycerol concentration is too high, it is less likely for a bubble to fully form and/or grow before it diminishes. If the laser fluence is too high and/or the glycerol concentration is too low, it is also difficult to form a well-developed jet since dramatic bubble expansion may lead to a bulgy shape and even splashing. Only under certain combinations of glycerol concentration and laser fluence, can a well-defined jet form. When a jetting fluid is given, its jettability (J) can be characterized as the inverse of the Ohnesorge number. It is observed that a good jet forms at 0.86 ≤ J ≤ 2.49 (corresponding to 75%–85% glycerol solutions) when the laser fluence is 717 ± 45 mJ/cm2.
Heat capacity and entropy of a GaAs quantum dot with Gaussian confinement
Authors: Boyacioglu B. , Chatterjee A.
Published: October 2012

The heat capacity and entropy effects in a GaAs quantum dot with Gaussian confinement are calculated in the presence of a magnetic field and its interaction with the electron spin using the canonical ensemble approach. It is shown that the heat capacity shows a Schottky-like anomaly at a low temperature, while it approaches a saturation value 2kB as the temperature increases. As a function of the magnetic field, the heat capacity shows a maximum and then reduces to zero. Also the width of the maximum becomes wider with temperature. It is also shown that the heat capacity remains constant up to a certain value of the confinement length beyond which it displays a monotonic increase. However as a function of the confinement strength, though the heat capacity initially shows a significant drop, it remains constant thereafter. At low temperatures like T = 10 and 20 K, the entropy is found to decrease with increasing magnetic field, but at higher temperatures, it remains almost independent of the magnetic field. At high temperatures, entropy shows a monotonic increase with temperature, but at a sufficiently low temperature as the magnetic field decreases, the entropy is found to develop a shoulder which becomes more and more pronounced with decreasing magnetic field.
Electron back-scattering coefficient below 5 keV: Analytical expressions and surface-barrier effects
Authors: Cazaux J.
Published: October 2012

Simple analytical expressions for the electron backscattering coefficient, η, are established from published data obtained in the ∼0.4-5 keV range for 21 elements ranging from Be to Au. They take into account the decline in η with a decrease in energy E° for high-Z elements and the reverse behavior for low-Z elements. The proposed expressions for η (E°) lead to crossing energies situated in the 0.4-1 keV range and they may be reasonably extended to any of the other elements—via an interpolation procedure—to metallic alloys and probably to compounds. The influence of the surface barrier on the escape probability of the back-scattered electrons is next evaluated. This evaluation provides a theoretical basis to explain the observed deviation between various published data as a consequence of surface contamination or oxidation. Various practical applications and strategies are deduced for the η-measurements in dedicated instruments as well for the image interpretation in low voltage scanning electron microscopy based on the backscattered electron detection. In this microscopy, the present investigation allows to generalize the scarce contrast changes and contrast reversals previously observed on multi elemental samples and it suggests the possibility of a new type of contrast: the work function contrast.
Time growth rate and field profiles of hybrid modes excited by a relativistic elliptical electron beam in an elliptical metallic waveguide with dielectric rod
Authors: Jazi B. , Rahmani Z. , Heidari-Semiromi E. , Abdoli-Arani A.
Published: October 2012

The dispersion relation of guided electromagnetic waves propagating in an elliptical metallic waveguide with a dielectric rod driven by relativistic elliptical electron beam (REEB) is investigated. The electric field profiles and the growth rates of the waves are numerically calculated by using Mathieu functions. The effects of relative permittivity constant of dielectric rod, accelerating voltage, and current density of REEB on the growth rate are presented.
Analytical calculations of intense Gaussian laser beam propagating in plasmas with relativistic collision correction
Authors: Wang Ying , Yuan Chengxun , Gao Ruilin , Zhou Zhongxiang
Published: October 2012

Theoretical investigations of a Gaussian laser beam propagating in relativistic plasmas have been performed with the WKB method and complex eikonal function. We consider the relativistic nonlinearity induced by intense laser beam, and present the relativistically generalized forms of the plasma frequency and electron collision frequency in plasmas. The coupled differential equations describing the propagation variations of laser beam are derived and numerically solved. The obtained simulation results present the similar variation tendency with experiments. By changing the plasma density, we theoretically analyze the feasibility of using a plasmas slab of a fixed thickness to compress the laser beam-width and acquire the focused laser intensity. The present work complements the relativistic correction of the electron collision frequency with reasonable derivations, promotes the theoretical approaching to experiments and provides effective instructions to the practical laser-plasma interactions.
Near-coincident K-line and K-edge energies as ionization diagnostics for some high atomic number plasmas
Authors: Pereira N. R. , Weber B. V. , Phipps D. G. , Schumer J. W. , Seely J. F. , Carroll J. J. , Vanhoy J. R. , Słabkowska K. , Polasik M.
Published: October 2012

For some high atomic number atoms, the energy of the K-edge is tens of eVs higher than the K-line energy of another atom, so that a few eV increase in the line's energy results in a decreasing transmission of the x-ray through a filter of the matching material. The transmission of cold iridium's ≃63.287 keV Kα2 line through a lutetium filter is 7% lower when emitted by ionized iridium, consistent with an energy increase of Δε≃10±1 eV associated with the ionization. Likewise, the transmission of the Kβ1 line of ytterbium through a near-coincident K-edge filter changes depending on plasma parameters that should affect the ionization. Systematic exploration of filter-line pairs like these could become a unique tool for diagnostics of suitable high energy density plasmas.
Magnetocaloric properties of La0.7Ca0.3Mn16O3 and La0.7Ca0.3Mn18O3 manganites and their “sandwich”
Authors: Aliev A. M. , Gamzatov A. G. , Kamilov K. I. , Kaul A. R. , Babushkina N. A.
Published: October 2012

The effect of 16О → 18О isotope substitution on specific heat and magnetocaloric effect of polycrystalline La0.7Ca0.3MnO3 manganite is studied. Mainly the effect of isotope substitution for the specific heat and magnetocaloric effect is only the reduction of temperatures of anomalies. ΔTad values at magnetic field change ΔH = 18 kOe are equal to ΔTad = 2.41 K and 2.60 K for La0.7Ca0.3Mn16O3 (LCMO16) and La0.7Ca0.3Mn18O3 (LCMO18), respectively. The sandwich of the LCMO16 and LCMO18 samples was produced for direct measurement of ΔTad. The use of sandwich from materials with near similar magnetocaloric properties increases the relative cooling power by about 20%.
Stress evaluation in thin strained-Si film by polarized Raman spectroscopy using localized surface plasmon resonance
Authors: Hashiguchi Hiroki , Takei Munehisa , Kosemura Daisuke , Ogura Atsushi
Published: October 2012

We evaluated the stress in a thin strained-Si film on relaxed SiGe on a surface-oxidized Si substrate using surface enhanced Raman scattering (SERS). The strained-Si peak was enhanced by the SERS technique. However, the strained-Si peak shifted toward a higher wavenumber while the peaks from the Si substrate were unchanged. We performed Raman measurement under the optical geometry in LO and TO phonon active conditions. From these measurements, it was clarified that the peak shift was attributed to the TO phonon peak that appeared, which was caused by the excitation of the z polar component in the near-field light.
Hard x-ray photoelectron spectroscopy study on band alignment at poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/ZnO interface
Authors: Nagata T. , Oh S. , Yamashita Y. , Yoshikawa H. , Hayakawa R. , Kobayashi K. , Chikyow T. , Wakayama Y.
Published: October 2012

We used hard x-ray photoelectron spectroscopy to investigate the interfacial electronic states of a poly(styrenesulfonate) doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) contact on a ZnO single crystal. An understanding of the interfacial band structure is useful for putting the organic contact to practical use. We observed upward band bending of the ZnO layer a few nanometers from the interface. The detected ZnO bulk region exhibited a flat band structure, meaning that the PEDOT:PSS does not greatly deplete the ZnO layer. The band bending caused the charge injection barrier formation with the result that the contact exhibited the Schottky property.
Effect of wake potential on Coulomb crystallization in the presence of magnetic field
Authors: Bhattacharjee Saurav , Das Nilakshi
Published: October 2012

The formation of dust crystal in plasma under the influence of repulsive Yukawa (Debye-Hückel) potential is a well known phenomenon. The regular structure of dust particles is affected by anisotropic ion flow near the sheath region. The bombardment of the ions over dust grains distorts their Debye sphere by overshielding the dust cloud and gives rise to an attractive oscillatory wake potential. In this paper, we have obtained an expression for wake potential along with the Yukawa type of potential in a complex plasma in the presence of magnetic field, for subsonic ion flow towards the plasma sheath. In the presence of magnetic field, interaction potential gets modified and becomes anisotropic. We have studied the combined effect of the attractive wake potential as well as repulsive Yukawa potential on a 2D dust crystal, both in the presence and absence of magnetic field, using molecular dynamic simulation.
Self-healing of optical functions by molecular metabolism in a swollen elastomer
Authors: Saito Mitsunori , Nishimura Tatsuya , Sakiyama Kohei , Inagaki Sota
Published: October 2012

Optical functions of organic dyes, e.g., fluorescence or photochromism, tend to degrade by light irradiation, which causes a short lifetime of photonic devices. Self-healing of optical functions is attainable by metabolizing bleached molecules with nonirradiated ones. A polydimethylsiloxane elastomer provides a useful matrix for dye molecules, since its flexible structure with nano-sized intermolecular spaces allows dye diffusion from a reservoir to an operation region. Swelling the elastomer with a suitable solvent promotes both dissolution and diffusion of dye molecules. This self-healing function was demonstrated by an experiment in which a photochromic elastomer exhibited improved durability against a repeated coloring-decoloring process.
Ion-Pair Recognition by Metal - Salophen and Metal - Salen Complexes
Authors: Mihan Francesco Yafteh , Bartocci Silvia , Bruschini Michele , De Bernardin Paolo , Forte Gianpiero , Giannicchi Ilaria , Cort Antonella Dalla
Published: October 2012

The development of heteroditopic receptor systems that can simultaneously bind cationic and anionic species is one of the most challenging research topics in supramolecular chemistry, attracting the attention of a large number of research groups worldwide. Such an interest is due especially to the fact that the overall receptor–ion-pair complex is neutral and this can be advantageous in many situations, such as salt solubilization and extraction, and membrane-transport applications. Receptors designed for ion-pair complexation are molecules comprising well-known anion-binding motifs and familiar cation-binding sites. An important family of compounds that can use metal Lewis-acidic centres for anion recognition and that can be easily derivatized to introduce an additional binding site for the cation is metal–salophen and metal–salen complexes. This short review shows that the high versatility of salen and salophen ligands and of the corresponding metal complexes allows, through simple modifications of the basic skeleton, the obtention of highly efficient receptors for ion pairs.
Stop interfering: Stroop task conflict independence from informational conflict and interference
Authors: Kalanthroff Eyal , Goldfarb Liat , Usher Marius , Henik Avishai
Published: October 2012

Performance of the Stroop task reflects two conflicts—informational (between the incongruent word and ink colour) and task (between relevant colour naming and irrelevant word reading). This is supported by findings showing that the anterior cingulate cortex is more activated by congruent and incongruent stimuli than by nonword neutral stimuli. Previously, researchers demonstrated behavioural evidence for task conflict—a reverse facilitation effect under a reduced task conflict control condition. The boundary conditions of this Stroop reverse facilitation effect are not yet clear. The current study aimed to investigate whether task conflict arises, and task control is needed, whenever there are two possible tasks, even if the irrelevant task cannot mislead one to give erroneous responses (i.e., stimuli do not contain an informational conflict). To this end, in both experiments no incongruent stimuli were presented. In Experiment 1, participants conducted a Stroop task with a high proportion of nonword neutrals and with a neutral/congruent cue in 50% of the trials. In Experiment 2, the nonword neutral was replaced by a real non-colour-word. We found the reverse facilitation effect in the noncued trials of Experiment 1. Moreover, as expected, this effect was eliminated when a noncolour neutral word that induced task conflict was used (Experiment 2). We conclude that task conflict control is reactively activated whenever there are at least two possible tasks, even in the absence of any possibility of informational conflict.
Executive Summary: Clinical Practice Guideline for the Diagnosis and Management of Group A Streptococcal Pharyngitis: 2012 Update by the Infectious Diseases Society of America
Authors: Shulman Stanford T. , Bisno Alan L. , Clegg Herbert W. , Gerber Michael A. , Kaplan Edward L. , Lee Grace , Martin Judith M. , Van Beneden Chris
Published: October 2012

The guideline is intended for use by healthcare providers who care for adult and pediatric patients with group A streptococcal pharyngitis. The guideline updates the 2002 Infectious Diseases Society of America guideline and discusses diagnosis and management, and recommendations are provided regarding antibiotic choices and dosing. Penicillin or amoxicillin remain the treatments of choice, and recommendations are made for the penicillin-allergic patient, which now include clindamycin.
First Report of Bacterial Spot Caused by Xanthomonas campestris pv. vesicatoria on Sweet Pepper (Capsicum annuum L.) in Saudi Arabia
Authors: Ibrahim Y. , Al-Saleh M.
Published: October 2012

In the summer of 2009 and 2010, 18 sweet pepper fruit with blister-like, raised, rough lesions were collected from four greenhouses (total of 0.1 ha) in the Al-Kharj region of Saudi Arabia. All samples were collected from commercial crops of the sweet pepper cv. California Wonder. Disease incidence was ≤5%. Isolations were made from all diseased fruits. A small piece (3 mm2) of symptomatic tissue from pepper fruit was placed in a sterile mortar and macerated in sterile distilled water with a pestle. A loopful of bacterial suspension from each sample was streaked onto Tween B agar medium (3). Plates were incubated at 28°C for 48 h. Single yellow, circular, butyrous, shiny colonies were picked from the plates and transferred to nutrient agar plates containing 5% D+ glucose agar (NGA). Gram-negative, rod-shaped bacteria were consistently isolated from the fruit and 10 of the isolates were identified as Xanthomonas campestris pv. vesicatoria on the basis of morphological, physiological, and biochemical tests (1,2). The isolates were oxidase positive and levan negative, arginine-dihydrolase positive, and did not macerate potato discs. The isolates were also non-fluorescent, grew at 37 and 4°C but not at 40°C, did not liquefy gelatine or starch, but did produce H2S. The identity of the 10 bacterial strains was confirmed by PCR assay using primers RST65 and RST69 (4). Four-week old pepper plants (cv. California Wonder) were inoculated by spraying five potted plants with each isolate using a bacterial suspension (108 CFU/ml). Sterile distilled water was sprayed on an additional five plants as a negative control treatment. The bacterial isolates caused necrotic lesions, each with a yellow halo, on leaves of inoculated plants. Bacteria reisolated from the necrotic lesions using the technique previously described were identical to the original strains according to the morphological, cultural, and biochemical tests described above. Negative control plants inoculated with sterile distilled water did not show symptoms and no bacterial colonies were recovered from them. To our knowledge, this is the first report of bacterial spot on pepper fruits in Saudi Arabia.

References: (2) R. F. Bradbury. Genus II Xanthomonas Dowson 1939. In: Bergey's Manual of Systematic Bacteriology, Vol. 1, Krieg, R., Holt, J. G. (Eds.), Williams & Wilkins Co., Baltimore, MD, 1987. (3) R. A. Lelliott and D. E. Stead. Methods for the Diagnosis of Bacterial Diseases of Plants. Blackwell Scientific Publications, Oxford, UK. (1) R. G. McGuire et al. Plant Dis 70:887, 1986. (4) A. Obradovic et al. Eur. J. Plant Pathol. 110:285, 2004.
Qubit purification speed-up for three complementary continuous measurements
Authors: Ruskov Rusko , Combes Joshua , Mølmer Klaus , Wiseman Howard M.
Published: October 2012

We consider qubit purification under simultaneous continuous measurement of the three non-commuting qubit operators

,

,

. The purification dynamics is quantified by (i) the average purification rate and (ii) the mean time of reaching a given level of purity, 1−
ε
. Under ideal measurements (detector efficiency
η
=1), we show in the first case an asymptotic mean purification speed-up of 4 when compared with a standard (classical) single-detector measurement. However, by the second measure—the mean time of first passage

of the purity—the corresponding speed-up is only 2. We explain these speed-ups using the isotropy of the qubit evolution that provides an equivalence between the original measurement directions and three simultaneous measurements, one with an axis aligned along the Bloch vector and the other with axes in the two complementary directions. For inefficient detectors,
η
=1−
δ
<1, the mean time of first passage

increases because qubit purification competes with an isotropic qubit dephasing. In the asymptotic high-purity limit (
ε
,
δ
≪1), we show that the increase possesses a
scaling behaviour
:

is a function only of the ratio
δ
/
ε
. The increase

is linear for small arguments, but becomes exponential

for
δ
/
ε
large.
Non-abelian Weyl commutation relations and the series product of quantum stochastic evolutions
Authors: Evans D. Gwion , Gough John E. , James Matthew R.
Published: October 2012

We show that the series product, which serves as an algebraic rule for connecting state-based input–output systems, is intimately related to the Heisenberg group and the canonical commutation relations. The series product for quantum stochastic models then corresponds to a non-abelian generalization of the Weyl commutation relation. We show that the series product gives the general rule for combining the generators of quantum stochastic evolutions using a Lie–Trotter product formula.
The quantum trajectory approach to quantum feedback control of an oscillator revisited
Authors: Doherty Andrew C. , Szorkovszky A. , Harris G. I. , Bowen W. P.
Published: October 2012

We revisit the stochastic master equation approach to feedback cooling of a quantum mechanical oscillator undergoing position measurement. By introducing a rotating wave approximation for the measurement and bath coupling, we can provide a more intuitive analysis of the achievable cooling in various regimes of measurement sensitivity and temperature. We also discuss explicitly the effect of backaction noise on the characteristics of the optimal feedback. The resulting rotating wave master equation has found application in our recent work on squeezing the oscillator motion using parametric driving and may have wider interest.
Reliable polarization switching of BiFeO
3
Authors: Baek S. H. , Eom C. B.
Published: October 2012

As a room temperature multi-ferroic with coexisting anti-ferromagnetic, ferroelectric and ferroelastic orders, BiFeO
3
has been extensively studied to realize magnetoelectric devices that enable manipulation of magnetic ordering by an electric field. Moreover, BiFeO
3
is a promising candidate for ferroelectric memory devices because it has the largest remanent polarization (
P
r
>100 μC cm
−2
) of all ferroelectric materials. For these applications, controlling polarization switching by an electric field plays a crucial role. However, BiFeO
3
has a complex switching behaviour owing to the rhombohedral symmetry: ferroelastic (71
°
, 109
°
) and ferroelectric (180
°
) switching. Furthermore, the polarization is switched through a multi-step process: 180
°
switching occurs through three sequential 71
°
switching steps. By using monodomain BiFeO
3
thin-film heterostructures, we correlated such multi-step switching to the macroscopically observed reliability issues of potential devices such as retention and fatigue. We overcame the retention problem (i.e. elastic back-switching of the 71
°
switched area) using monodomain BiFeO
3
islands. Furthermore, we suppressed the fatigue problem of 180
°
switching, i.e. loss of switchable polarization with switching cycles, using a single 71
°
switching path. Our results provide a framework for exploring a route to reliably control multiple-order parameters coupled to ferroelastic order in other rhombohedral and lower-symmetry materials.
Giant flexoelectric effect through interfacial strain relaxation
Authors: Lee Daesu , Noh Tae Won
Published: October 2012

Interfacial strain gradients in oxide epitaxial thin films provide an interesting opportunity to study flexoelectric effects and their potential applications. Oxide epitaxial thin films can exhibit giant and tunable flexoelectric effects, which are six or seven orders of magnitude larger than those in conventional bulk solids. The strain gradient in an oxide epitaxial thin film can generate an electric field above 1 MV m
−1
by flexoelectricity, large enough to affect the physical properties of the film. Giant flexoelectric effects on ferroelectric properties are discussed in this overview of recent experimental observations.
Phase engineering in oxides by interfaces
Authors: Fiebig Manfred
Published: October 2012

Optical second harmonic generation and piezoresponse force microscopy are used to investigate manifestations of ordered states directly related to the presence of an oxide interface. Three examples, each with a very different scope, are reviewed in order to highlight the richness of interface-related phenomena in oxides. (i) The orbital states involved in the emergence of an interfacial conducting state in LaAlO
3
/SrTiO
3
heterostructures are investigated, which reveal a surprising decoupling of orbital and transport properties; (ii) the distribution of ferroelectric and antiferromagnetic domains in epitaxial films of the multiferroic hexagonal manganites is investigated, which reveals striking differences to the corresponding bulk crystals; and (iii) the distribution of trimerization–polarization domains in the hexagonal manganites is investigated, which reveals the presence of topologically protected domain walls with properties different from the bulk.
Insights from the study of high-temperature interface superconductivity
Authors: Pereiro J. , Bollinger A. T. , Logvenov G. , Gozar A. , Panagopoulos C. , Božović I.
Published: October 2012

A brief overview is given of the studies of high-temperature interface superconductivity based on atomic-layer-by-layer molecular beam epitaxy (ALL-MBE). A number of difficult materials science and physics questions have been tackled, frequently at the expense of some technical tour de force, and sometimes even by introducing new techniques. ALL-MBE is especially suitable to address questions related to surface and interface physics. Using this technique, it has been demonstrated that high-temperature superconductivity can occur in a single copper oxide layer—the thinnest superconductor known. It has been shown that interface superconductivity in cuprates is a genuine electronic effect—it arises from charge transfer (electron depletion and accumulation) across the interface driven by the difference in chemical potentials rather than from cation diffusion and mixing. We have also understood the nature of the superconductor–insulator phase transition as a function of doping. However, a few important questions, such as the mechanism of interfacial enhancement of the critical temperature, are still outstanding.
Effects of agricultural policy reforms and farm characteristics on income risk in Swiss agriculture
Authors: El Benni Nadja , Finger Robert , Mann Stefan
Published: October 2012

Purpose

The purpose of this study is to examine the effects of agricultural policy reform – specifically the change from market to direct payment support – on income variability of Swiss farming households. In addition, the observed heterogeneity in income risks across farms and time is explained in terms of farm and regional characteristics.

Design/methodology/approach

Unbalanced farm‐level panel data of the Swiss farm accountancy network (FADN) are used to construct coefficients of variation of five‐year overlapping time intervals for total household income and gross farm revenues over the period 1992 to 2009. Linear fixed effect models are applied to measure the effect of specialization, off‐farm income, direct payments, farm size, and liquidity on the variability of gross farm revenues and household income in the valley, hill, and mountain regions.

Findings

The switch from market‐based support to direct payments has decreased the variability of farm revenues and household income. The strong reliance on direct payments serves as insurance for most farmers and reduces both household income and revenue risk. Off‐farm income can be used by farmers to reduce household income risk but it increases revenue risk in the valley regions. In all of the regions considered, farm size has a positive effect on household income risk and a negative effect on revenue risk. A high degree of specialization increases both gross revenue and household income risk. Potential revenue insurance contracts should specify farmers' off‐farm employment, the degree of specialization, farm size, and regional specific risk profiles.

Originality/value

This paper assesses the complementary effects of specific farm characteristics and risk management strategies with regard to both farm revenue and household income risk. Influences of agricultural policy changes on income risks are also empirically assessed at different spatial scales.
The role of an agribusiness index in a modern portfolio
Authors: Clark Benjamin M. , Detre Joshua D. , D'Antoni Jeremy , Zapata Hector
Published: October 2012

Purpose

The purpose of this research is to develop a composite agribusiness stock index and then compare the returns and volatility to other broad‐based market indices. The paper then evaluates the diversification potential of agribusiness stocks in the context of an investment portfolio.

Design/methodology/approach

This agribusiness index (AGB Index) is market‐capitalization weighted. Only firms traded on the NYSE, AMEX, or NASDAQ and meeting ERS SIC classification for industries related to agriculture are included in the index. The paper then uses standard financial metrics to measure the historical risk, return, and correlation.

Findings

Until recent years, the AGB Index has historically exhibited lower returns than the market indices. The AGB Index has also exhibited lower risk and correlation with treasury securities than broad market indices.

Practical implications

In recent years, portfolio managers and large investors have invested considerably in asset classes like farmland for stable returns, an inflation hedge, and diversification tool. This agribusiness index may further this trend and lead to the development of an alternative Exchange Traded Fund (ETF). This product would make investment in agriculture possible for virtually all investors.

Originality/value

Despite increasing popularity, very little research exists on the performance of agricultural stocks in an investment portfolio. This study develops a large‐cap agribusiness stock price index to help fill this void in the literature.
Effects of crop acreage and aggregation level on price‐yield correlations
Authors: Finger Robert
Published: October 2012

Purpose

The purpose of this paper is to analyze the effects of data aggregation and farm‐level crop acreage on the level of natural hedge, i.e. the level of price‐yield correlations, which is an important issue in risk modeling and management.

Design/methodology/approach

Swiss FADN data for five crops covering the period 2002‐2009 are used to estimate price‐yield correlations at the farm‐ as well as on an aggregated level. Tobit regressions are used to estimate empirical relationships between the level of natural hedge and the underlying crop acreage.

Findings

Price‐yield correlations differ significantly between farm‐ and aggregated‐level. More specifically, the natural hedge observed at the farm‐level is much smaller, i.e. correlations are closer to zero. Taking correlations from aggregated levels thus leads to an underestimation of farm‐level revenue variability. Furthermore, it is found that larger farms have a stronger natural hedge. For instance, a 1 percent increase in area under maize and intensive barley leads to a change in the correlation by −0.02 and −0.08, respectively.

Practical implications

The natural hedge is often approximated with correlations observed at more aggregated levels, e.g. the county level. The results show that this implies errors in risk assessment and modeling as well as insurance applications. Thus, farm‐level estimates should be used. The here presented relationship between price‐yield correlations and farm‐level crop acreage can be used to derive better information on levels of the natural hedge.

Originality/value

Even though the effects of data aggregation on price‐yield correlations have been discussed in earlier research, this paper is the first to also account for on‐farm effects of underlying crop acreage on levels of natural hedge. It is found that this simple relationship can be useful in risk management and modeling applications.
Hedging weather risk on aggregated and individual farm‐level
Authors: Erec Heimfarth Leif , Finger Robert , Musshoff Oliver
Published: October 2012

Purpose

Since the 1990s, there has been a discussion about the use of weather index‐based insurance, also called weather derivatives, as a new instrument to hedge against volumetric risks in agriculture. It particularly differs from other insurance schemes by pay‐offs being related to objectively measurable weather variables. Due to the absence of individual farm yield time series, the hedging effectiveness of weather index‐based insurance is often estimated on the basis of aggregated farm data. The authors expect that there are differences in the hedging effectiveness of insurance on the aggregated level and on the individual farm‐level. The purpose of this paper is to estimate the magnitude of bias which occurs if the hedging effectiveness of weather index‐based insurance is estimated on aggregated yield data.

Design/methodology/approach

The study is based on yield time series from individual farms in central Germany and weather data provided by the German Meteorological Service. Insurance is structured as put‐option on a cumulated precipitation index. The analysis includes the estimation of the hedging effectiveness of insurance on aggregated level and on individual farm‐level. The hedging effectiveness is measured non‐parametrically regarding the relative reduction of the standard deviation and the value at risk of wheat revenues.

Findings

Findings indicate that the hedging effectiveness of a weather index‐based insurance estimated on aggregated level is considerably higher than the realizable hedging effectiveness on the individual farm‐level. This refers to: hedging effectiveness estimated on the aggregated level is higher than the mean of realized hedging effectiveness on the individual farm‐level and almost every evaluated individual farm in the analysis realizes a lower hedging effectiveness than estimated on the aggregated level of the study area. Nevertheless, weather index‐based insurance designed on the aggregated level can lead to a notable risk reduction for individual farms.

Originality/value

To the authors’ knowledge, this paper is the first that analyzes the influence of crop yield aggregation with regard to the hedging effectiveness of weather index‐based insurance.
The influence of labelling on consumers' evaluations of fresh and thawed cod fillets in England
Authors: Altintzoglou Themistoklis , Helen Nøstvold Bjørg , Carlehög Mats , Heide Morten , Østli Jens , Egeness Finn‐Arne
Published: October 2012

Purpose

The purpose of this study was to investigate the effect of information on English consumers' evaluation of fresh and thawed cod fillets which in English retail stores is referred to as “chilled” seafood.

Design/methodology/approach

After the exploration of consumers' impressions of thawed fish, this study followed a pair‐wise comparison approach in a central location consumer test. Fish fillets were evaluated on liking, smell and texture by means of a questionnaire with additional behavioural and attitudinal questions.

Findings

This study showed that consumers in England may prefer thawed over fresh cod fillets without information. However, consumers' evaluations increased for labelled fresh cod fillets and decreased for thawed. Finally, consumers reported positive expectations about fillets labelled “fresh” or “frozen at sea”.

Research limitation/implications

This study involved testing cod fillets in a central location test. Consumers do not usually evaluate cod fillets in this way in their daily life. The quality of the two types of fillets made especially for this test may vary compared to the ones usually sold and consumed.

Practical implications

This study can inform producers and retailers about what to expect by means of sales of fresh and thawed cod products with or without information.

Social implications

It was shown that consumers are positively influenced by information and are willing to consume more fish if they know that the fish is fresh or thawed properly.

Originality/value

This is the first paper to present English consumers' evaluations of thawed cod.