bluuebunny/crossref_metadata_2025 huggingface dataset:
Product CFTs, gravitational cloning, massive gravitons and the space of gravitational duals
Authors: Kiritsis E.
Published: May 2007

The question of graviton cloning in the context of the bulk/boundary correspondence is considered. It is shown that multi‐graviton theories can be obtained from products of large‐N CFTs. No more than one interacting massless graviton is possible. There can be however, many interacting massive gravitons that can be arbitrarily light. This is achieved by coupling CFTs via multi‐trace marginal or relevant perturbations. The geometrical structure of the gravitational duals of such theories is that of product manifolds with their boundaries identified. The interpretation of such theories is discussed. Potential applications to massive gravity and cosmology are briefly suggested.
High‐power pure blue laser diodes
Authors: Ohta M. , Ohizumi Y. , Hoshina Y. , Tanaka T. , Yabuki Y. , Funato K. , Tomiya S. , Goto S. , Ikeda M.
Published: May 2007

We successfully developed high‐power and long‐lived pure blue laser diodes (LDs) having an emission wavelength of 440–450 nm. The pure‐blue LDs were grown by metalorganic chemical vapor deposition (MOCVD) on GaN substrates. The dislocation density was successfully reduced to ∼106 cm–2 by optimizing the MOCVD growth conditions and the active layer structure. The vertical layer structure was designed to have an absorption loss of 4.9 cm–1 and an internal quantum efficiency of 91%. We also reduced the operating current density to 6 kA/cm2 under 750 mW continuous‐wave operation at 35 °C by optimizing the stripe width to 12 µm and the cavity length to 2000 µm. The half lifetimes in constant current mode are estimated to be longer than 10000 h. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Recent progress of high efficiency white LEDs
Authors: Narukawa Yukio , Narita Junya , Sakamoto Takahiko , Yamada Takao , Narimatsu Hiroki , Sano Masahiko , Mukai Takashi
Published: May 2007

We fabricated three types of white light emitting diodes (LEDs). The first is the white LED, which has a high general color rendering index (Ra) of 97 and CRI‐No. 9 of 96. The CRI‐No. 9 denotes the color reproduction in the red region. These values are higher than those of a tri‐phosphor fluorescent lamp (Ra = 85 and CRI‐No. 9 = 8). The second is the high efficiency white LED fabricated from the small‐size high efficiency blue LED chip. The output power (Po), the external quantum efficiency (ηex) and wall‐plug efficiency (WPE) of the small‐size blue LED were 35.0 mW, 63.3% and 56.3%, respectively, at a forward‐bias current of 20 mA. The luminous flux (Φ), luminous efficiency (ηL) and WPE of the second white LED are 8.6 lm, 138 lm/W and 41.7%, respectively. The luminous efficiency is 1.5 times greater than that of a tri‐phosphor fluorescent lamp (90 lm/W). The third is the high power white LED fabricated from the larger‐size blue LED chip. Po, ηex and W.P.E. are 458 mW, 47.2% and 39.7%, respectively, at 350 mA. Φ, ηL and WPE of the third white LED are 106 lm, 91.7 lm/W and 27.7% at 350 mA, respectively. Moreover, Φ of 247 lm and 402 lm at 1 A and 2 A are obtained, respectively. Φ at 2 A is equivalent to the total flux of a 30 W incandescent lamp. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Atomic study of molecular wires composed of thiophene oligomers
Authors: Bai P. , Li E. P. , Ong E. A. , Collier P. , Loh K. P.
Published: May 2007

In this paper, we study the electron conductance of thiophene oligomers based molecular wires through atomic structures using the first principles method based on density functional theory and nonequilibrium Green's function. The molecular wires are built by sandwiching various thiophene oligomers between two metal electrodes via terminal groups at atomic levels. The effects of alkyl substituents on the thiophene oligomers are modelled by varying inter‐ring angles of the oligomers. Thiophene dimers, tetramers and hexamers are used to studied thiophene size effects. The projected orbitals, energy gaps, transmission functions and current–voltage characteristics of the molecular wires are calculated and analyzed. Results show that the molecular wires with the planar structures of thiophene oligomers have larger electron transmission functions, hence better electronic conductance than those with twist structures. The conductance of molecular wires decreases when the chain length of the thiophene oligomer increases. The results can provide guidance for design of thiophene molecular electronic wires and other devices. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Metabolite identification by data‐dependent accurate mass spectrometric analysis at resolving power of 60 000 in external calibration mode using an LTQ/Orbitrap
Authors: Lim Heng‐Keang , Chen Jie , Sensenhauser Carlo , Cook Kevin , Subrahmanyam Vangala
Published: May 2007

Performance evaluation of accurate mass measurement by the LTQ/Orbitrap, at a resolving power of 60 000 and in external calibration mode, indicated that the Orbitrap is capable of providing high mass accuracy of <2 ppm for over 24 h post‐calibration. This, together with limited trade‐off between sensitivity and resolving power plus a wide dynamic range for mass accuracy, suggested that the LTQ/Orbitrap is an ideal analytical tool for structural elucidation of metabolites. The application of the LTQ/Orbitrap to identification of human liver microsomal metabolites of carvedilol was evaluated, using parent mass list triggered data‐dependent multiple‐stage accurate mass analysis, at a resolving power of 60 000 in external calibration mode. A metabolite identification workflow was developed to utilize chemical formulas from high‐resolution accurate mass measurements to confirm structures of product ions of a drug proposed by Mass Frontier, illustrated by identification of structures used to establish lineage of product ions of carvedilol, which later served as a template for identification of its metabolites. A total of 58in vitrometabolites of carvedilol were detected using 5‐ppm mass tolerance filters for theoreticalm/zof protonated molecules of predicted metabolites in addition to product ions and neutral mass losses diagnostic of carvedilol. The chemical formulas with unsaturation numbers calculated from the accuratem/zof precursor and product ions can be used to assign, with a high degree of confidence, the structures of metabolites and the sites of metabolism. The mass accuracies obtained for all full scan MS and MSnspectra were <2 ppm. The majority of the metabolites identified agreed with those previously reported except for those that have not been reported before. For example, several glutathione conjugates of carvedilol were reported for the first time, which may explain the reported hepatotoxicity during clinical trials and recent clinical use. Copyright © 2007 John Wiley & Sons, Ltd.
Impact of approximating or ignoring within‐study covariances in multivariate meta‐analyses
Authors: Ishak K. Jack , Platt Robert W. , Joseph Lawrence , Hanley James A.
Published: May 2007

Multivariate meta‐analyses are used to derive summary estimates of treatment effects for two or more outcomes from a joint model. In addition to treatment effects, these models also quantify the correlations between outcomes across studies. To be fully specified, the model requires an estimate of the covariance or correlations between outcomes observed in each study. These are rarely available in published reports, so that analysts must either approximate
these or ignore correlations between effect estimates from the same studies. We examined the impact of errors in approximating within‐study covariances on the parameters of multivariate models in a simulation study. We found that treatment effect and heterogeneity estimates were not strongly affected by inaccurate approximations, but estimates of the correlation between outcomes were sometimes highly biased. The potential for error is greatest when the covariance between outcomes within‐ and between‐studies are of comparable scale. Copyright © 2007 John Wiley & Sons, Ltd.
A spatial structural equation modelling framework for health count responses
Authors: Congdon Peter , Almog Michael , Curtis Sarah , Ellerman Raymond
Published: May 2007

A structural equation model is proposed for the impact on area health referral counts of spatially correlated latent constructs. One type of construct is indicator based and represents the underlying morbidity or health need; such constructs are derived in a normal errors measurement model involving a set of observed socio‐economic indicators. Another set of residual constructs represents particularities of service configuration or spatially correlated risks that cannot be proxied by observed indicators. The structural model relates the referral outcomes to both types of construct in a Poisson regression. While multiple spatial factors based on measured socio‐economic indicators have already been proposed, the extension to include both indicator‐based and residual factors is novel. Further novel features are to represent spatially structured heterogeneity and nonlinearity in the impact of the indicator‐based constructs. A case study considers the modelling of a single indicator‐based morbidity construct (taken to represent a need for care) in 62 New York counties, with responses being psychiatric referrals to ambulatory and hospital care. Copyright © 2007 John Wiley & Sons, Ltd.
Ultrastructural effects of DDT, DDD, and DDE on neural cells of the chicken embryo model
Authors: Bornman M. S. , Pretorius E. , Marx J. , Smit E. , van der Merwe C. F.
Published: May 2007

Human exposure to environmental compounds with estrogenic activity and the potential effects on human health is the subject of ongoing scientific debates. Their potential effects raise concern regarding neurological development after prenatal exposure. Central to this debate is the pesticide 1,1,1‐trichloro‐2,2‐bis(4‐chlorophenyl)ethane (DDT). Although it has apparent low acute toxicity in mammals, DDT has a long residual persistence and laboratory research has indicated that it acts on the CNS by interfering with Na+/K+ pump mechanism of the neuronal membranes, causing disruption in Ca2+ homeostasis. Potentially this may lead to both apoptosis and necrosis. The present study investigates the effects of DDT and two of its metabolites DDD and DDE on the ultramorphology of neural cells, using a previously published chicken embryo model. Results indicate cellular swelling, budding, and increased membrane permeability for all three chemicals, accompanied by karyolysis in the DDE group (typical features of oncosis). These results support the finding of other researchers as well as the concerns of the WHO that DDT and its metabolites may cause neurotoxicity after prenatal exposure. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 328–336, 2007.
Predicting acute copper toxicity to valve closure behavior in the freshwater clam Corbicula fluminea supports the biotic ligand model
Authors: Liao Chung‐Min , Jou Li‐John , Lin Chieh‐Ming , Chiang Kuo‐Chin , Yeh Ching‐Hung , Chou Berry Yun‐Hua
Published: May 2007

The objective of this paper is to employ biotic ligand model (BLM) to link between acute copper (Cu) toxicity and its effect on valve closure behavior of freshwater clam Corbicula fluminea in order to further support for the BLM that potentially offers a rapid and cost‐effective method to conduct the acute toxicity tests for freshwater clam exposed to waterborne Cu. Reanalysis of published experimental data of C. fluminea closure daily rhythm and dose–response profiles based on the laboratory‐acclimated clams showed that a BLM‐based Hill model best described the free Cu2+‐activity‐valve closure response relationships. Our proposed Cu‐BLM‐Corbicula model shows that free ionic form of waterborne Cu binds specifically to a biotic ligand (i.e., clam gills) and impairs normal valve closure behavior, indicating that a fixed‐level of metal accumulation at a biotic ligand is required to elicit specific biological effects. With derived mechanistic‐based Cu‐BLM‐Corbicula model, we show that the site‐specific EC50(t) and valve closure behavior at any integrated time can be well predicted, indicating that our model has the potential to develop a biomonitoring system as a bioassay tool to on‐line measure waterborne Cu levels in aquatic systems. Our results confirm that BLM can be improved to analytically and rigorously describe the bioavailable fraction of metal causing toxicity to valve closure behavior in freshwater C. fluminea. We suggest that the Cu‐BLM‐Corbicula model can be used to assist in developing technically defensible site‐specific water quality criteria and performing ecological risk assessment and to promote more focused and efficient uses of resources in the regulation and control of metals and the protection of the aquatic ecosystems. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 295–307, 2007.
Premature ejaculation: (2) assessment and treatment
Authors: Bromage Stephen James , Pearce Ian
Published: May 2007

In part 1 of this article, the authors discussed the epidemiology and aetiology of premature ejaculation. Here, they provide a guide to assessment of the condition, discussing the treatment options available and those under development. Copyright © 2007 Wiley Interface Ltd
A homogenization result for a parabolic equation with Preisach hysteresis
Authors: Kopfová J.
Published: May 2007

In this paper we consider an initial boundary value parabolic problem [cu + 𝒫[u]]_t ‐ div(a ċ ν u) = f, with Preisach hysteresis 𝒫. The functions c, a, and the density function ψ of the Preisach operator are allowed to depend also on the space variable x. The equation is homogenized by considering a sequence of equations with spatially periodic data cϵ, aϵ, and ψϵ, where the spatial period ϵ converges to 0. Properties of hysteresis operators and the concept of two‐scale convergence are used to show the convergence of the corresponding solutions to the solution of the homogenized problem.
Numerical solutions of 2‐D steady incompressible flow in a driven skewed cavity
Authors: Erturk E. , Dursun B.
Published: May 2007

The benchmark test case for non‐orthogonal grid mesh, the “driven skewed cavity flow”, first introduced by Demirdžić et al. [5] for skew angles of α = 30° and α = 45°, is reintroduced with a more variety of skew angles. The benchmark problem has non‐orthogonal, skewed grid mesh with skew angle (α). The governing 2‐D steady incompressible Navier‐Stokes equations in general curvilinear coordinates are solved for the solution of driven skewed cavity flow with non‐orthogonal grid mesh using a numerical method which is efficient and stable even at extreme skew angles. Highly accurate numerical solutions of the driven skewed cavity flow, solved using a fine grid (512 × 512) mesh, are presented for Reynolds number of 100 and 1000 for skew angles ranging between 15° ⩽ α ⩽ 165°.
Antioxidative and prooxidative effects of quercetin on A549 cells
Authors: Robaszkiewicz Agnieszka , Balcerczyk Aneta , Bartosz Grzegorz
Published: May 2007

Quercetin, a common plant polyphenol, has been reported to show both antioxidant and prooxidant properties. We studied the effects of quercetin on A549 cells in in vitro culture. We found that low concentrations of the flavonoid stimulated cell proliferation and increased total antioxidant capacity (TAC) of the cells; while higher concentrations of the flavonoid decreased cell survival and viability, thiol content, TAC and activities of superoxide dismutase, catalase and glutathione S‐transferase. Quercetin decreased production of reactive oxygen species in the cells but produced peroxides in the medium. The cellular effects of quercetin are therefore complex and include both antioxidant effects and induction of oxidative stress due to formation of reactive oxygen species in the extracellular medium.
Comparison of a new device for blood sampling in cats with a vacuum tube collection system—Plasma biochemistry, haematology and practical usage assessment
Authors: Reynolds Brice S , Boudet Karine G , Faucher Mathieu R , Germain Claude , Geffre Anne , Lefebvre Herve P
Published: May 2007

Using paediatric devices to collect venous blood from a cephalic vein in cats offers numerous practical advantages over traditional jugular venepuncture and vacuum closed systems: minimal restraint is required; there is minimal risk of serious injury to the cat; the discomfort associated with venepuncture is reduced by the use of small diameter (25 gauge) needles; very small volumes (200 μl) of blood are extracted; and the risk of vein collapse or haematoma is low. The aim of this study was to compare the haematological and plasma chemistry results obtained from six healthy cats using the two sampling techniques. Five plasma biochemical analytes were measured and a complete haematological examination was performed on each specimen. No clinically relevant difference between the two blood sampling techniques was observed for any variable, indicating that paediatric devices provide a useful alternative to vacuum tubes for venous blood collection in the cat.
Mass of Saturn's magnetodisc: Cassini observations
Authors: Arridge C. S. , Russell C. T. , Khurana K. K. , Achilleos N. , André N. , Rymer A. M. , Dougherty M. K. , Coates A. J.
Published: May 2007

Saturn's ring current was observed by Pioneer 11 and the two Voyager spacecraft to extend 8–16 RS in the equatorial plane and appeared to be driven by stress balance with the centrifugal force. We present Cassini observations that show thin current sheets on the dawn flank of Saturn's magnetosphere, symptomatic of the formation of a magnetodisc. We show that the centrifugal force is the dominant mechanical stress in these current sheets, which reinforces a magnetodisc interpretation – the formation of the current sheet is fundamentally rotational in origin. The stress balance calculation is also used to estimate the mass density in the disc, which show good agreement with independent in‐situ measurements of the density. We estimate the total mass in the magnetodisc to be ∼106 kg.
Spatial distribution of ionization in the equatorial and low‐latitude ionosphere of the Indian sector and its effect on the pierce point altitude for GPS applications during low solar activity periods
Authors: Niranjan K. , Srivani B. , Gopikrishna S. , Rama Rao P. V. S.
Published: May 2007

The equatorial and low‐latitude ionosphere is characterized by dynamic changes in the spatial distribution of F region electron density. The in situ density data from Indian SROSS C2 satellite was used in conjunction with the international reference ionosphere (IRI) to demonstrate how the median models have limitations to represent the spatial gradients in the equatorial and subtropical latitudes in the Indian sector. The ground‐based ionosonde data was used to derive the bottomside electron density profiles which were matched with IRI to derive the complete F region electron density profile for different times to show the variability in the centroid of ionization mass distribution due to the equatorial plasma dynamics associated with Appleton ionization anomaly. The study brings out that a uniform ionospheric pierce point altitude cannot be assumed for GPS applications in this sector. However, during low sunspot activity periods, the GPS‐derived total electron content (TEC) using 2 × 2 grid point data indicates that spatial gradients in TEC are not too significant in meridian transects and that the assumption of homogeneous distribution is valid for the conversion of slant to vertical TEC even in the equatorial latitudes during solar minimum. Keeping this in view, a qualitative study has been carried out on the possible variability in ionospheric pierce point altitude at representative subtropical latitude in the Indian sector and the results are discussed in light of diurnal and seasonal features of the equatorial ionosphere.
Toward a direct combination of space‐geodetic techniques at the measurement level: Methodology and main issues
Authors: Coulot D. , Berio P. , Biancale R. , Loyer S. , Soudarin L. , Gontier A.‐M.
Published: May 2007

In the framework of the activities of the Combination Research Centers (CRC) of the International Earth Rotation and Reference Systems Service (IERS), the French Groupe de Recherche en Géodésie Spatiale (GRGS) studies the benefit of combining space‐geodetic techniques (Doppler orbitography and radiopositioning integrated by satellite, GPS, satellite laser ranging, and very long baseline interferometry) at the observational level. This combination aims to produce a global and consistent solution for Earth orientation parameters (EOPs), polar motionxpandyp, and universal timeUT1 with a 1‐day or a 6‐hour sampling, as well as weekly station positions. In this paper we present a methodology for multitechnique combination at the observational level. We process the measurements of the four techniques over a 1‐year period (the year 2002) in order to illustrate and validate our method. All techniques are processed with the same computational framework, thus with the same models and a priori values for parameters. By using the same software and conventions, we avoid inconsistencies in individual computations. We process each technique individually and inside the combination. The comparison between these solutions is a way of analyzing the power of our method even if the actual status of our software does not reproduce the state‐of‐the‐art analyses of each technique. However, we produce an analysis of the quality of our individual computations so that readers can get an informed appreciation of the current capabilities of our software. Finally, we present the capability of such combinations in terms of accuracy and precision, we underline the main issues of our method and propose solutions to solve them in the future.
An overview of the Mars Reconnaissance Orbiter (MRO) science mission
Authors: Zurek Richard W. , Smrekar Suzanne E.
Published: May 2007

The Mars Reconnaissance Orbiter (MRO) is the latest addition to the suite of missions on or orbiting Mars as part of the NASA Mars Exploration Program. Launched on 12 August 2005, the orbiter successfully entered Mars orbit on 10 March 2006 and finished aerobraking on 30 August 2006. Now in its near‐polar, near‐circular, low‐altitude (∼300 km), 3 p.m. orbit, the spacecraft is operating its payload of six scientific instruments throughout a one‐Mars‐year Primary Science Phase (PSP) of global mapping, regional survey, and targeted observations. Eight scientific investigations were chosen for MRO, two of which use either the spacecraft accelerometers or tracking of the spacecraft telecom signal to acquire data needed for analysis. Six instruments, including three imaging systems, a visible‐near infrared spectrometer, a shallow‐probing subsurface radar, and a thermal‐infrared profiler, were selected to complement and extend the capabilities of current working spacecraft at Mars. Whether observing the atmosphere, surface, or subsurface, the MRO instruments are designed to achieve significantly higher resolution while maintaining coverage comparable to the current best observations. The requirements to return higher‐resolution data, to target routinely from a low‐altitude orbit, and to operate a complex suite of instruments were major challenges successfully met in the design and build of the spacecraft, as well as by the mission design. Calibration activities during the seven‐month cruise to Mars and limited payload operations during a three‐day checkout prior to the start of aerobraking demonstrated, where possible, that the spacecraft and payload still had the functions critical to the science mission. Two critical events, the deployment of the SHARAD radar antenna and the opening of the CRISM telescope cover, were successfully accomplished in September 2006. Normal data collection began 7 November 2006 after solar conjunction. As part of its science mission, MRO will also aid identification and characterization of the most promising sites for future landed missions, both in terms of safety and in terms of the scientific potential for future discovery. Ultimately, MRO data will advance our understanding of how Mars has evolved and by which processes that change occurs, all within a framework of identifying the presence, extent, and role of water in shaping the planet's climate over time.
Precipitation measurements using VHF wind profiler radars: Measuring rainfall and vertical air velocities using only observations with a VHF radar
Authors: Campos Edwin F. , Fabry Frédéric , Hocking Wayne
Published: May 2007

In addition to a proper radar calibration, quantitative estimation of precipitation from radars also requires the extraction of the precipitation signal out of the Doppler spectra. It also requires the proper conversion of this precipitation signal into reflectivity factor. This study shows how the measurement of rainfall and vertical air velocities can be performed using only observations from a radar operating at the VHF band (i.e., meter wavelengths). We verify the assumption that the dielectric factor ∣K∣2 = 0.93 is valid for rain observations in the VHF band. We then derive, analytically and numerically, a more general version of the radar equation valid for vertically pointing radars with targets within a few kilometers range but still within the antenna far‐field region. Following this, we describe a new algorithm for extraction of rain signal out of VHF Doppler spectra. To validate our methods, we made colocated measurements of VHF Doppler spectra aloft and raindrop sizes at the ground. The analytical version of our radar equation compares well with similar equations available in current literature, and this validates the particular case of our numerically derived radar equation. We combine our numerical version of the radar equation and our algorithm for extracting precipitation signal. This combination allows us to obtain reflectivity factors (from rain signals) and vertical velocities (from air signals), these being simultaneous observations within the same sampling volume. From the data set collected, we found good agreement (linear correlation coefficient around 0.8) between the rain signals derived from VHF observations aloft and from drop sizes at ground level. Hence we are able to measure rainfall amounts and vertical air velocities in a simpler and more efficient way, using only observations from a VHF wind profiler. This represents a promising step toward the analysis of precipitation from large sets of radar data.
On the mechanism of hysteresis in conductance of point contacts to single ferromagnetic films
Authors: Konovalenko A. , Korenivski V. , Yanson I. K. , Naidyuk Yu. G. , Fisun V. V. , Balkashin O. P. , Triputen L. Yu.
Published: May 2007

Single nonmagnetic/ferromagnetic interfaces can exhibit magnetic excitations and hysteretic switching, provided that the current density traversing the interface is sufficiently high (≳108A∕cm2) and the flow regime is diffusive. We measure hysteretic switching in conductance induced by nominally unpolarized electron currents in nanocontacts to thin Co films and successfully model the effect for ∼20nm scale point contacts using micromagnetic simulations, which take into account an out of plane stress-induced magnetic anisotropy in the point contact region.
Synthesis and evaluation of magnetic active charcoals for removal of environmental endocrine disrupter and heavy metal ion
Authors: Nakahira A. , Nagata H. , Takimura M. , Fukunishi K.
Published: May 2007

In this study, alternative magnetic active charcoals (ACs) with magnetic responsibility for magnetic separations were synthesized by a chemical precipitation processing and subsequent heat treatments at 473K in H2 or air atmosphere. For various magnetic ACs, their adsorption abilities for bisphenol-A, methylene blue, and arsenic solution were evaluated. Magnetic AC with the same adsorption ability as normal AC could be collected and separated with a permanent magnet, demonstrating the successful synthesis of magnetic AC applicable to magnetic separations. Furthermore, magnetic AC heat treated in H2 possessed the high ability for arsenic removal.
Dynamics of a classical Hall system driven by a time-dependent Aharonov-Bohm flux
Authors: Asch J. , Šťovíček P.
Published: May 2007

We study the dynamics of a classical particle moving in a punctured plane under the influence of a homogeneous magnetic field, an electric background, and driven by a time-dependent singular flux tube through the hole. We exhibit a striking (de)localization effect: when the electric background is absent we prove that a linearly time-dependent flux tube opposite to the homogeneous flux eventually leads to the usual classical Hall motion: the particle follows a cycloid whose center is drifting orthogonal to the electric field; if the fluxes are additive, the drifting center eventually gets pinned by the flux tube whereas the kinetic energy is growing with the additional flux.
Second harmonic of nonlinear magnetoimpedance in amorphous magnetic wires with helical anisotropy
Authors: Seddaoui D. , Ménard D. , Ciureanu P. , Yelon A.
Published: May 2007

The axial magnetic field dependence of the second harmonic of giant magnetoimpedance in Co-rich amorphous wires with helical anisotropy has been measured to high field resolution in the current amplitude range of 2–14 mArms and frequency range of 200 kHz–3 MHz. We have found that the intensity of the inner peaks of the four-peak structure increases with current amplitude until a threshold value, and then begins to decrease without changing position, whereas the outer peaks decrease monotonically and move to higher field. When frequency is increased from 200 kHz to about 2 MHz, all of the four peaks increase in height and move to higher field. Beyond 2 MHz, all of the peaks move to lower field; the intensity of the inner peaks decreases while the outer peaks continue to increase. At low frequency and current, a third pair of peaks appears between the two inner peaks and disappears when the frequency increases. Using a simple quasistatic model, the four-peak and six-peak structures are explained qualitatively. The variation with the current amplitude is also understood. However, accurate determination of the second harmonic signal and its frequency dependence requires a more complete model.
Stimulated Raman scattering in tellurite glasses as a potential system for slow light generation
Authors: Qin Guanshi , Jose Rajan , Ohishi Yasutake
Published: May 2007

In this article, slow light generation via stimulated Raman scattering (SRS) in tellurite-based glasses is investigated based on characterization of Raman gain coefficients and an evaluation method of slow light generation we developed. The effects of different heavy metal oxides additions on slow light generation via SRS in tellurite-based glasses are also discussed. Our results show that designed tellurite-based glass is a promising candidate for slow light generation via SRS.
Electrical conductivity and relaxation in mixed alkali tellurite glasses
Authors: Ghosh S. , Ghosh A.
Published: May 2007

The authors have reported the electrical conductivity and the conductivity relaxation in mixed alkali tellurite glasses of compositions of 70TeO2−xNa2O−(30−x)Li2O in the frequency range from 10Hzto2MHz and in the temperature range from room temperature to just below the glass transition temperature. They have analyzed the relaxation data in the framework of different models. They have observed the mixed alkali effect in the dc and ac conductivities, the crossover frequency, and the conductivity relaxation frequency as well as in their respective activation energies in these glasses. They have also observed the mixed alkali effect in the decoupling index. The scaling property of the modulus spectra of these mixed alkali glasses shows that the conductivity relaxation in the mixed alkali tellurite glasses is independent of temperature but depends on the glass compositions.
Influence of vapor depletion on nucleation rate
Authors: Kožíšek Z. , Demo P.
Published: May 2007

During condensation in finite systems part of molecules is transformed from supersaturated mother phase to a new one and depletion of the mother phase occurs. Kinetic equations describing homogeneous nucleation process including decrease of supersaturation are solved numerically. It is shown that dependency of nucleation rate on nucleus size reaches some maximum, which decreases with time and moves to higher nucleus sizes. Nucleation rate is negative for undercritical size of nuclei.
Quantum effect of intramolecular high-frequency vibrational modes on diffusion-controlled electron transfer rate: From the weak to the strong electronic coupling regions
Authors: Zhu Wenjuan , Zhao Yi
Published: May 2007

The Sumi-Marcus theory is extended by introducing two approaches to investigate electron transfer reactions from weak-to-strong electronic coupling regime. One of these approaches is the quantum R-matrix theory, useful for dealing with the intramolecular vibrational motions in the whole electronic coupling domain. The other is the split operator approach that is employed to solve the reaction-diffusion equation. The approaches are then applied to electron transfer in the Marcus inverted regime to investigate the nuclear tunneling effect on the long time rate and the survival probabilities. The numerical results illustrate that the adiabatic suppression obtained from the R-matrix approach is much smaller than that from the Landau-Zener theory whereas it cannot be predicted by the perturbation theory. The jointed effects of the electronic coupling and solvent relaxation time on the rates are also explored.
Air-coupled acoustic method for testing and evaluation of microscale structures
Authors: Ricci Justin , Cetinkaya Cetin
Published: May 2007

A noncontact testing and characterization approach for microscale structures based on air-coupled acoustic excitation and optical sensing is proposed and demonstrated. Using an air-coupled transducer to externally excite and a laser Doppler vibrometer/interferometer to capture transient displacement wave forms, the experimental approach results in a technique to determine mechanical properties of microscale structural elements. The effectiveness of this method has been demonstrated on commercially available microcantilever beams and microscale rotational oscillators fabricated for this study. The resonance frequencies and mechanical properties (Young’s modulus and stiffness) extracted from the transient displacement wave forms have been compared, with good agreement, to computational and simplified analytical models for each case. It is also shown that the technique could serve to diagnose stiction problems of microscale structures. Some potential advantages of the approach described include the simplicity of the test setup, functionality at room conditions, noncontact and nondestructive operations, and repeatability and rapid turn-around time for the evaluation of modal parameters and mechanical properties of microscale structures.
Electrically switchable computer-generated hologram recorded in polymer-dispersed liquid crystals
Authors: Liu Y. J. , Sun X. W.
Published: May 2007

A computer-generated hologram (CGH) designed using the iterative Fourier transform algorithm was recorded in a cell filled with a polymer-dispersed liquid crystal material under a collimated He–Ne laser beam operating at 543nm. Due to the photopolymerization induced phase separation, an index modulation was formed between the polymer-rich and liquid-crystal-rich regions. The results showed a good reconstructed image. With a suitable voltage applied, the reconstructed image can be erased due to the index change between the polymer and liquid crystal. Such electrically switchable CGH is potentially useful in information storage and adaptive optical elements.
Highly precise experimental device for determining the heat capacity of liquids under pressure
Authors: González-Salgado D. , Valencia J. L. , Troncoso J. , Carballo E. , Peleteiro J. , Romaní L. , Bessières D.
Published: May 2007

An experimental device for making isobaric heat capacity measurements of liquids under pressure is presented. The device is an adaptation of the Setaram micro-DSC II atmospheric-pressure microcalorimeter, including modifications of vessels and a pressure line allowing the pressure in the measurement system to be set, controlled, and stabilized. The high sensitivity of the apparatus combined with a suitable calibration procedure allows very accurate heat capacity measurements under pressure to be made. The relative uncertainty in the isobaric molar heat capacity measurements provided by the new device is estimated to be 0.08% at atmospheric pressure and 0.2% at higher levels. The device was validated from isobaric molar heat capacity measurements for hexane, nonane, decane, undecane, dodecane, and tridecane, all of which were highly consistent with reported data. It also possesses a high sensitivity as reflected in its response to changes in excess isobaric molar heat capacity with pressure, which were examined in this work for the first time by making heat capacity measurements throughout the composition range of the 1-hexanol+n-hexane system. Finally, preliminary measurements at several pressures near the critical conditions for the nitromethane+2-butanol binary system were made that testify to the usefulness of the proposed device for studying critical phenomena in liquids under pressure.
Application of a fast electrical pulse in gated multichannel plate camera
Authors: Liu Jinyuan , Niu Lihong , Peng Wenda , Zhang Fengxia , Li Li , Ou Junfu , Yuan Huatao , Yang Qinlao , Niu Hanben , Long Jinghua
Published: May 2007

An eight-frame gated microchannel plate (MCP) camera and a gating electrical pulse are described in this article. The gating electrical pulse is obtained by first generating a high voltage fast step pulse using avalanche transistors in Marx bank configuration, and then shaping it using avalanche diodes. The high voltage fast step pulse is about 200ps in fall time and 4kV in amplitude. The gating pulse wave form with width of 160ps and amplitude of 2.5kV is achieved. Each frame photocathode coated with gold on the MCP is part of a 12Ω transmission line with open circuit end driven by the gating electrical pulse. The camera is tested by illuminating its photocathode with ultraviolet laser pulses, 266nm in wavelength, which shows exposure time as short as 120ps.
Structural investigations of epitaxial InN by x-ray photoelectron diffraction and x-ray diffraction
Authors: Hofstetter Daniel , Despont Laurent , Garnier M. Gunnar , Baumann Esther , Giorgetta Fabrizio R. , Aebi Philipp , Kirste Lutz , Lu Hai , Schaff William J.
Published: May 2007

The authors investigated a 1μm thick molecular beam epitaxy–grown InN film by means of full hemispherical x-ray photoelectron diffraction and high resolution x-ray diffraction. While x-ray diffraction reveals that this nominally hexagonal InN layer contains roughly 1% of cubic phase InN, a comparison between measured and simulated x-ray photoelectron diffraction data allowed them to directly determine the polarity of the crystal. Furthermore, the data indicate that the InN surface consists of a mosaic of domains oriented at an azimuth of 180° to each other, where the azimuth corresponds to the rotation angle around the [0001] axis.
Role of Polyhydroxybutyrate and Glycogen as Carbon Storage Compounds in Pea and Bean Bacteroids
Authors: Lodwig E. M. , Leonard M. , Marroqui S. , Wheeler T. R. , Findlay K. , Downie J. A. , Poole P. S.
Published: May 2007

Rhizobium leguminosarum synthesizes polyhydroxybutyrate and glycogen as its main carbon storage compounds. To examine the role of these compounds in bacteroid development and in symbiotic efficiency, single and double mutants of R. leguminosarum bv. viciae were made which lack poly-hydroxybutyrate synthase (phaC), glycogen synthase (glgA), or both. For comparison, a single phaC mutant also was isolated in a bean-nodulating strain of R. leguminosarum bv. phaseoli. In one large glasshouse trial, the growth of pea plants inoculated with the R. leguminosarum bv. viciae phaC mutant were significantly reduced compared with wild-type-inoculated plants. However, in subsequent glasshouse and growth-room studies, the growth of pea plants inoculated with the mutant were similar to wild-type-inoculated plants. Bean plants were unaffected by the loss of polyhydroxybutyrate biosynthesis in bacteroids. Pea plants nodulated by a glycogen synthase mutant, or the glgA/phaC double mutant, grew as well as the wild type in growth-room experiments. Light and electron micrographs revealed that pea nodules infected with the glgA mutant accumulated large amounts of starch in the II/III interzone. This suggests that glycogen may be the dominant carbon storage compound in pea bacteroids. Polyhydroxybutyrate was present in bacteria in the infection thread of pea plants but was broken down during bacteroid formation. In nodules infected with a phaC mutant of R. leguminosarum bv. viciae, there was a drop in the amount of starch in the II/III interzone, where bacteroids form. Therefore, we propose a carbon burst hypothesis for bacteroid formation, where polyhydroxybutyrate accumulated by bacteria is degraded to fuel bacteroid differentiation.
Probing the Sinorhizobium meliloti-Alfalfa Symbiosis Using Temperature-Sensitive and Impaired-Function Citrate Synthase Mutants
Authors: Grzemski Wojciech , Akowski James P. , Kahn Michael L.
Published: May 2007

To study the role of the decarboxylating leg of the bacterial TCA cycle in symbiotic nitrogen fixation, we used DNA shuffling and localized random polymerase chain reaction mutagenesis to construct a series of temperature-sensitive and impaired-function mutants in the Sinorhizobium meliloti Rm104A14 citrate synthase (gltA) gene. Reducing citrate synthase (CS) activity by mutation led to a corresponding decrease in the free-living growth rate; however, alfalfa plants formed fully effective nodules when infected with mutants having CS activities as low as 7% of the wild-type strain. Mutants with approximately 3% of normal CS activity formed nodules with lower nitrogenase activity and a mutant with less than 0.5% of normal CS activity formed Fix- nodules. Two temperature-sensitive (ts) mutants grew at a permissive temperature (25°C) with 3% of wild-type CS activities but were unable to grow on minimal medium at 30°C. Alfalfa plants that were inoculated with the ts mutants and grown with a root temperature of 20°C formed functional nodules with nitrogenase activities approximately 20% of the wild type. When the roots of plants infected with the ts mutants were transferred to 30deg;C, the nodules lost the ability to fix nitrogen over several days. Microscopic examination of these nodules revealed the loss of bacteroids and senescence, indicating that CS activity was essential for nodule maintenance.
Avoidance of Host Recognition by Alterations in the Repetitive and C-Terminal Regions of AvrXa7, a Type III Effector of Xanthomonas oryzae pv. oryzae
Authors: Yang Bing , Sugio Akiko , White Frank F.
Published: May 2007

avrXa7 is a member of the avrBs3/pthA gene family. The gene is a critical type III effector in several strains of Xanthomonas oryzae pv. oryzae (virulence activity), and in the presence of the Xa7 host gene for resistance, controls the elicitation of resistance in rice (avirulence activity). The ability of strains containing avrXa7 to adapt to the presence of Xa7 in the host population is dependent, in part, on the genetic plasticity of avrXa7. The potential for the conversion of avrXa7 to a virulence effector without Xa7-dependent elicitor activity was examined. Internal reorganization of avrXa7 by artificially deleting a portion of the central repetitive region resulted in gene pthXo4, which retained virulence activity and lost Xa7-dependent avirulence activity. Similarly, spontaneous rearrangements between repetitive regions of avrXa7 during bacterial culture gave rise to gene pthXo5, which also had virulence activity without Xa7-dependent avirulence activity. pthXo5 appeared to be the result of recombination between avrXa7 and a related gene in the genome. Loss of avirulence activity and retention of virulence activity also resulted from replacement of a portion of the C-terminal coding region of avrXa7 with the corresponding sequence from avrBs3. The results demonstrated the potential for a critical virulence effector to lose avirulence activity while retaining effector function. The results also demonstrated that features of both repetitive and nonrepetitive C-terminal regions of AvrXa7 are involved in avirulence specificity.
Regulation of Enteric Endophytic Bacterial Colonization by Plant Defenses
Authors: Iniguez A. Leonardo , Dong Yuemei , Carter Heather D. , Ahmer Brian M. M. , Stone Julie M. , Triplett Eric W.
Published: May 2007

Bacterial endophytes reside within the interior of plants without causing disease or forming symbiotic structures. Some endophytes, such as Klebsiella pneumoniae 342 (Kp342), enhance plant growth and nutrition. Others, such as Salmonella enterica serovar Typhimurium (S. typhimurium), are human pathogens that contaminate raw produce. Several lines of evidence are presented here to support the hypothesis that plant defense response pathways regulate colonization by endophytic bacteria. An ethyleneinsensitive mutant of Medicago truncatula is hypercolonized by Kp342 compared to the parent genotype. Addition of ethylene, a signal molecule for induced systemic resistance in plants, decreased endophytic colonization in Medicago spp. This ethylene-mediated inhibition of endophytic colonization was reversed by addition of the ethylene action inhibitor, 1-methylcyclopropene. Colonization of Medicago spp. by S. typhimurium also was affected by exogenous ethylene. Mutants lacking flagella or a component of the type III secretion system of Salmonella pathogenicity island 1 (TTSS-SPI1) colonize the interior of Medicago spp. In higher numbers than the wild type. Arabidopsis defense response-related genotypes indicated that only salicylic acid (SA)-independent defense responses contribute to restricting colonization by Kp342. In contrast, colonization by S. typhimurium is affected by both SA-dependent and -independent responses. S. typhimurium mutants further delineated these responses, suggesting that both flagella and TTSS-SPI1 effectors can be recognized. Flagella act primarily through SA-independent responses (compromising SA accumulation still affected colonization in the absence of flagella). Removal of a TTSS-SPI1 effector resulted in hypercolonization regardless of whether the genotype was affected in either SA-dependent or SA-independent responses. Consistent with these results, S. typhimurium activates the promoter of PR1, a SA-dependent pathogenesisrelated gene, while S. typhimurium mutants lacking the TTSS-SPI1 failed to activate this promoter. These observations suggest approaches to reduce contamination of raw produce by human enteric pathogens and to increase the number of growth-promoting bacteria in plants.
A New Cell-to-Cell Transport Model for Potexviruses
Authors: Verchot-Lubicz Jeanmarie
Published: May 2007

In the last five years, we have gained significant insight into the role of the Potexvirus proteins in virus movement and RNA silencing. Potexviruses require three movement proteins, named triple gene block (TGB)p1, TGBp2, andTGBp3, and the viral coat protein (CP) to facilitate viral cell-to-cell and vascular transport. TGBp1 is a multifunctional protein that has RNA helicase activity, promotes translation of viral RNAs, increases plasmodesmal size exclusion limits, and suppresses RNA silencing. TGBp2 and TGBp3 are embrane-binding proteins. CP is required for genome encapsidation and forms ribonucleoprotein complexes along with TGBp1 and viral RNA. This review considers the functions of the TGB proteins, how they interact with each other and CP, and how silencing suppression might be linked to viral transport. A new model of the mechanism for Potexvirus transport is proposed.