bluuebunny/crossref_metadata_2025 huggingface dataset:
Intercomparison of oxygenated volatile organic compound measurements at the SAPHIR atmosphere simulation chamber
Authors: Apel E. C. , Brauers T. , Koppmann R. , Bandowe B. , Boßmeyer J. , Holzke C. , Tillmann R. , Wahner A. , Wegener R. , Brunner A. , Jocher M. , Ruuskanen T. , Spirig C. , Steigner D. , Steinbrecher R. , Gomez Alvarez E. , Müller K. , Burrows J. P. , Schade G. , Solomon S. J. , Ladstätter‐Weißenmayer A. , Simmonds P. , Young D. , Hopkins J. R. , Lewis A. C. , Legreid G. , Reimann S. , Hansel A. , Wisthaler A. , Blake R. S. , Ellis A. M. , Monks P. S. , Wyche K. P.
Published: October 2008

This paper presents results from the first large‐scale in situ intercomparison of oxygenated volatile organic compound (OVOC) measurements. The intercomparison was conducted blind at the large (270 m3) simulation chamber, Simulation of Atmospheric Photochemistry in a Large Reaction Chamber (SAPHIR), in Jülich, Germany. Fifteen analytical instruments, representing a wide range of techniques, were challenged with measuring atmospherically relevant OVOC species and toluene (14 species, C1 to C7) in the approximate range of 0.5–10 ppbv under three different conditions: (1) OVOCs with no humidity or ozone, (2) OVOCs with humidity added (r.h. ≈ 50%), and (3) OVOCs with ozone (≈60 ppbv) and humidity (r.h. ≈ 50%). The SAPHIR chamber proved to be an excellent facility for conducting this experiment. Measurements from individual instruments were compared to mixing ratios calculated from the chamber volume and the known amount of OVOC injected into the chamber. Benzaldehyde and 1‐butanol, compounds with the lowest vapor pressure of those studied, presented the most overall difficulty because of a less than quantitative transfer through some of the participants' analytical systems. The performance of each individual instrument is evaluated with respect to reference values in terms of time series and correlation plots for each compound under the three measurement conditions. A few of the instruments performed very well, closely matching the reference values, and all techniques demonstrated the potential for quantitative OVOC measurements. However, this study showed that nonzero offsets are present for specific compounds in a number of instruments and overall improvements are necessary for the majority of the techniques evaluated here.
Surface BRDF estimation from an aircraft compared to MODIS and ground estimates at the Southern Great Plains site
Authors: Knobelspiesse Kirk D. , Cairns Brian , Schmid Beat , Román Miguel O. , Schaaf Crystal B.
Published: October 2008

Surface albedo, which quantifies the amount of solar radiation reflected by the ground, is an important component of climate models. However, it can be highly heterogeneous, so obtaining adequate measurements are challenging. Global measurements require orbital observations, such as those provided by the Moderate Resolution Imaging Spectroradiometer (MODIS). Satellites estimate the surface bidirectional reflectance distribution function (BRDF), a surface inherent optical property, by correcting observed radiances for atmospheric effects and accumulating measurements at many viewing and solar geometries. The BRDF is then used to estimate albedo, an apparent optical property utilized by climate models. Satellite observations are often validated with ground radiometer measurements. However, spatial and temporal sampling differences mean that direct comparisons are subject to substantial uncertainties. We attempt to bridge the resolution gap using an airborne radiometer, the Research Scanning Polarimeter (RSP). RSP was flown at low altitude in the vicinity of the Department of Energy's Southern Great Plains Central Facility (SGP CF) in Oklahoma during the Aerosol Lidar Validation Experiment (ALIVE) in September, 2005. The RSP's scanning radiometers estimate the BRDF in seconds, rather than days required by MODIS, and utilize the Ames Airborne Tracking Sunphotometer (AATS‐14) for atmospheric correction. Our comparison indicates that surface albedo estimates from RSP and MODIS agree with Best Estimate Radiation Flux (BEFLUX) ground radiometer observations at the SGP CF. Since the RSP is an airborne prototype of the Aerosol Polarimetery Sensor (APS), due to be launched into orbit in 2009, these techniques could form the basis for routine BRDF validation.
Probabilistic trend of anomalous summer rainfall in Beijing: Role of interdecadal variability
Authors: Wei Fengying , Xie Yu , Mann Michael E.
Published: October 2008

The interdecadal variability of summer precipitation in Beijing from 1724 to 2005 is analyzed using a filter, keeping the true trends at time series ends. A probability distribution, Pearson type III, was applied to the summer precipitation series to estimate the probability of anomalous rainfall. This study includes the correlation between the interdecadal variations of the summer precipitation in Beijing and those of the indices of Northern Atlantic Oscillation (NAO), Southern Oscillation (SOI), Pacific Decadal Oscillation (PDO), and summer monsoon (SMS) of East Asia indices are computed. A methodology is thus developed to forecast the probable distribution of precipitation intensities in Beijing. Results show that the probability of drought in Beijing has greatly increased since the middle of the 1960s. The interdecadal variability of NAO, PDO, and SMS are extremely important for the low‐frequency forecast of anomalous summer rainfall in Beijing. The method developed here seems appropriate to estimate the probability of future anomalous summer rainfall.
Psychological Climate and Psychological Empowerment: An Exploration in a Luxury UK Hotel Group
Authors: Amenumey Edem K. , Lockwood Andrew
Published: October 2008

The purpose of this study was to identify aspects of employees' work environment that were related to their feelings of psychological empowerment in a luxury hotel group. Data were collected through the administration of a self-completed questionnaire. Exploratory and confirmatory factors analyses were run to purify the scales measuring the two constructs before testing the relationship using structural equation modelling. The results here, which form part of a larger study, suggest that the four dimensions of psychological climate identified (Managerial Support, Customer Orientation, Internal Service, and Information/Communication) positively influenced employees' feelings of psychological empowerment, conceptualised as a three-dimensional construct (Meaning, Influence, and Competence), with clear implications for managerial policy and practice.
The Kramers problem with accommodative boundary conditions for quantum Fermi gases
Authors: Kostikov A. A. , Latyshev A. V. , Yushkanov A. A.
Published: October 2008

The Kramers problem of isothermal slip of a quantum Fermi gas with Cercignani boundary conditions is solved analytically. The velocity of isothermal slip is obtained as a function of the accommodation coefficient and the reduced chemical potential—the ratio of the chemical potential to the product of Boltzmann’s constant and the absolute temperature. The distribution function of the molecules is presented in explicit form.
Thermomagnetic instability and features of the dynamic response of superconducting films
Authors: Kuzovlev Yu. E. , Medvedev Yu. V.
Published: October 2008

A simple model of magnetic flux dynamics in a superconducting film strip is proposed. The model combines the classical phenomenology of temperature-dependent pinning and vortex motion, on the one hand, and an exact expression for the current distribution in the film in terms of the distribution of vortex density, on the other, and the diffusion of vortices is also taken into account. The model clearly reveals the features of the evolution of magnetic flux in the film due to the plane two-dimensional geometry of the film and the corresponding features of the dynamic response of the film, and it finds agreement with experiments.
Features of the conformational structures of 2′-deoxyuridine, matrix isolated in Ar and Kr
Authors: Ivanov A. Yu.
Published: October 2008

The conformational equilibrium of molecules of the nucleoside 2′-deoxyuridine (dU) in Ar and Kr low-temperature matrices is investigated with the aid of low-temperature matrix-isolation FTIR spectroscopy and quantum calculations by the DFT and MP2 methods. It is found that in the low-temperature matrices the dominant forms are two anti-conformers of dU with different structures of the sugar ring: C2′-endo and C3′-endo. The main syn-confomer is stabilized by intramolecular hydrogen bond O5′H—O2, while C2′-endo is the dominant conformation of its deoxyribose ring in Ar and Kr low-temperature matrices. The possibility that minor syn-conformers without the intramolecular hydrogen bond O5′H—O2 are present in the matrix samples is also demonstrated. An influence of the matrix on the orientation of the hydroxyl group O3′H of the sugar ring of the main syn-conformer is found.
Effect of a magnetic field on the dynamics of dislocations in normal metals with a high impurity concentration at low temperatures
Authors: Malashenko B. B.
Published: October 2008

The dependence of the dislocation stopping force on the dislocation velocity and the magnetic field intensity in a normal metal at low temperatures is investigated. It is shown that the dependence of this force on the dislocation velocity is a nonmonotonic function with a local minimum and maximum. The positions of the maximum and minimum of the stopping force are, respectively, independent of and dependent on the strength of the magnetic field. Dislocation motion is unstable in the velocity range where dF∕dv<0, F and v being the dislocation stopping force and velocity, repectively.
Optical properties of MoO3 containing tellurite glasses
Authors: Jose Rajan , Arai Yusuke , Ohishi Yasutake
Published: October 2008

It was observed that P2O5 generates TeO5+δ groups in tellurite glasses that have a profound influence on their optical properties. The presence of TeO5+δ groups in phosphotellurite glass made MoO3 behave in a different way compared to other tellurite glass systems that do not contain P2O5. The refractive index measurements and Raman spectroscopy were combined to show that the addition of MoO3 in a phosphotellurite glass generates TeO3+1 polyhedron, whereas it generates TeO3 trigonal bipyramids in other glass systems. The MoO3 system showed absorption bands corresponding to Mo5+ ion in phosphotellurite glasses, whereas no similar bands were observed for other glasses.
Photodissociation of NO2 in the (2)B22 state: A slice imaging study and reinterpretation of previous results
Authors: Wilkinson Iain , Whitaker Benjamin J.
Published: October 2008

The photodissociation dynamics of nitrogen dioxide have been probed above the second dissociation limit at photolysis wavelengths close to 226 nm. The O(P3J)+NO(Π2Ω) product channel has been examined using direct current slice velocity map imaging of the O(P3J) and NO(Π2Ω) fragments. Mass-resolved resonantly enhanced multiphoton ionization spectroscopy and velocity map imaging have been used to probe directly the rovibrational population distributions of the NO fragments. We also examine possible interference from the dissociation of N2O4 by investigating the effect of the sample temperature on the O(P3J) fragment energy distributions. The O(P3J)+NO(Π2Ω) dissociation channel has been found to favor the production of vibrationally cold, highly rotationally excited NO(Π2Ω) products with all three oxygen spin-orbit components. Other minor dissociation channels which produce O(P3J) atoms have also been identified. We discuss the significance of these dissociation channels and present a reinterpretation of previous studies of NO2 dissociation on excitation to the (2)B22 state.
Exact analysis of surface field reduction due to field-emitted vacuum space charge, in parallel-plane geometry, using simple dimensionless equations
Authors: Forbes Richard G.
Published: October 2008

This paper reports (a) a simple dimensionless equation relating to field-emitted vacuum space charge (FEVSC) in parallel-plane geometry, namely 9ζ2θ2−3θ−4ζ+3=0, where ζ is the FEVSC “strength” and θ is the reduction in emitter surface field (θ=field-with/field-without FEVSC), and (b) the formula j=9θ2ζ/4, where j is the ratio of emitted current density JP to that predicted by Child’s law. These equations apply to any charged particle, positive or negative, emitted with near-zero kinetic energy. They yield existing and additional basic formulas in planar FEVSC theory. The first equation also yields the well-known cubic equation describing the relationship between JP and applied voltage; a method of analytical solution is described. Illustrative FEVSC effects in a liquid metal ion source and in field electron emission are discussed. For Fowler–Nordheim plots, a “turn-over” effect is predicted in the high FEVSC limit. The higher the voltage-to-local-field conversion factor for the emitter concerned, then the higher is the field at which turn over occurs. Past experiments have not found complete turn over; possible reasons are noted. For real field emitters, planar theory is a worst-case limit; however, adjusting ζ on the basis of Monte Carlo calculations might yield formulae adequate for real situations.
Dynamics of protein-protein encounter: A Langevin equation approach with reaction patches
Authors: Schluttig Jakob , Alamanova Denitsa , Helms Volkhard , Schwarz Ulrich S.
Published: October 2008

We study the formation of protein-protein encounter complexes with a Langevin equation approach that considers direct, steric, and thermal forces. As three model systems with distinctly different properties we consider the pairs barnase:barstar, cytochrome c-cytochrome c peroxidase, and p53:MDM2. In each case, proteins are modeled either as spherical particles, as dipolar spheres, or as collection of several small beads with one dipole. Spherical reaction patches are placed on the model proteins according to the known experimental structures of the protein complexes. In the computer simulations, concentration is varied by changing box size. Encounter is defined as overlap of the reaction patches and the corresponding first passage times are recorded together with the number of unsuccessful contacts before encounter. We find that encounter frequency scales linearly with protein concentration, thus proving that our microscopic model results in a well-defined macroscopic encounter rate. The number of unsuccessful contacts before encounter decreases with increasing encounter rate and ranges from 20 to 9000. For all three models, encounter rates are obtained within one order of magnitude of the experimentally measured association rates. Electrostatic steering enhances association up to 50-fold. If diffusional encounter is dominant (p53:MDM2) or similarly important as electrostatic steering (barnase:barstar), then encounter rate decreases with decreasing patch radius. More detailed modeling of protein shapes decreases encounter rates by 5%–95%. Our study shows how generic principles of protein-protein association are modulated by molecular features of the systems under consideration. Moreover it allows us to assess different coarse-graining strategies for the future modeling of the dynamics of large protein complexes.
Comparison of cholesterol and its direct precursors along the biosynthetic pathway: Effects of cholesterol, desmosterol and 7-dehydrocholesterol on saturated and unsaturated lipid bilayers
Authors: Róg Tomasz , Vattulainen Ilpo , Jansen Maurice , Ikonen Elina , Karttunen Mikko
Published: October 2008

Despite extensive studies, the remarkable structure-function relationship of cholesterol in cellular membranes has remained rather elusive. This is exemplified by the fact that the membrane properties of cholesterol are distinctly different from those of many other sterols. Here we elucidate this issue through atomic-scale simulations of desmosterol and 7-dehydrocholesterol (7DHC), which are immediate precursors of cholesterol in its two distinct biosynthetic pathways. While desmosterol and 7DHC differ from cholesterol only by one additional double bond, we find that their influence on saturated lipid bilayers is substantially different from cholesterol. The capability to form ordered regions in a saturated (dipalmitoyl-phosphatidylcholine) membrane is given by cholesterol>7DHC>desmosterol, indicating the important role of cholesterol in saturated lipid environments. For comparison, in an unsaturated (dioleoyl-phosphatidylcholine) bilayer, the membrane properties of all sterols were found to be essentially identical. Our studies indicate that the different membrane ordering properties of sterols can be characterized by a single experimentally accessible parameter, the sterol tilt. The smaller the tilt, the more ordered are the lipids around a given sterol. The molecular level mechanisms responsible for tilt modulation are found to be related to changes in local packing around the additional double bonds.
Multicenter structure of the optical spectra and the charge-compensation mechanisms in Nd:SrWO4 laser crystals
Authors: Lupei A. , Lupei V. , Gheorghe C. , Gheorghe L. , Achim A.
Published: October 2008

An analysis of the high resolution optical spectra (10 and 300 K) of the self-stimulated Raman scattering active Nd:SrWO4 crystal was performed. Crystals doped only with low concentrations of Nd or codoped with Na+ or Nb5+ grown in N2 or air atmosphere were investigated. The single Nd-doped crystals show five main centers, whereas codoping with Na+ in the ratio Na/Nd=3/1 (in melt) simplifies considerably the spectra. Codoping with Nb5+ does not lead to a dominant center and introduces a new one. Growth in air revealed the role of the oxygen in the charge compensation and multicenter structure of the spectra. The spectral characteristics of the nonequivalent centers (levels, intensities, and polarization) function on concentration of Nd3+ and of codoping ions and growth conditions were analyzed. The polarization data show that only one center has ideal local symmetry S4. Based on the crystal structure, previous results, and the new spectral data, an attempt to connect various spectral nonequivalent centers to the charge compensators (Sr2+ vacancies, interstitial oxygen, Na+, and Nb5+) is made and structural models for various centers are proposed. The implications of these findings on the laser emission characteristics and on the selection of the pumping transitions are also discussed.
Experimental realization of graded L1-FePt/Fe composite media with perpendicular magnetization
Authors: Goll D. , Breitling A. , Gu L. , van Aken P. A. , Sigle W.
Published: October 2008

A concept is suggested and experimentally realized to fabricate graded media for ultrahigh density magnetic recording where the material parameters vary gradually in the interfacial region between the hard magnetic part and the soft magnetic part of epitaxial L10-FePt/Fe exchange spring nanocomposites with perpendicular magnetization. A graded interface between the L10-FePt phase and the Fe phase is formed by depositing part of the Fe layer at elevated temperatures. The existence of the graded interface is verified by electron energy-loss spectroscopy. The influence of the character of the graded interface on the magnetic properties is studied. With increasing thickness of the graded interface the coercivity continuously decreases, which can be used for a fine tuning of the coercivity of exchange spring composite media.
Two dimensional mesoscale simulations of projectile instability during penetration in dry sand
Authors: Dwivedi S. K. , Teeter R. D. , Felice C. W. , Gupta Y. M.
Published: October 2008

To gain insight into the instability and trajectory change in projectiles penetrating dry sand at high velocities, two dimensional plane strain mesoscale simulations were carried out using representative models of a particulate system and of a small projectile. A program, ISP-SAND, was developed and used to generate the representative particulate system with mean grain sizes of 60 and 120 μm as well as ±30% uniform size distribution from the mean. Target porosities ranged from 30% to 40%. The penetration of ogive nose steel projectiles with caliber radius head of 3.5 and length-to-diameter (l/d) ratio of 3.85 was simulated using the updated Lagrangian explicit parallel finite element code ISP-TROTP. Deformation of the projectile and individual sand grains was analyzed using a nonlinear elastic-inelastic model for these materials. Grain-grain and grain-projectile interactions were analyzed using a contact algorithm with and without friction. Projectile instability was quantified and compared using the lateral displacement of the center of mass, lateral force acting on the projectile, and its rotational momentum about the center of mass. The main source of projectile instability and the ensuing trajectory change in the penetration simulations was found to be the inhomogeneous loading of the projectile due to the heterogeneities and randomness inherent in a particulate media like sand. The granularity of the media has not been considered explicitly in previous work. Projectile instability increased with impact velocity, as expected. However, it also increased for the case of elastic impactor that preserved the nose shape, with an increase in grain size, and for uniform grain sizes. Moreover, friction, inherently present in geologic materials, was found to be a major contributor to instability. Conclusions derived from one projectile depth simulations were confirmed by two deeper penetration simulations considering up to three full lengths of penetration (requiring a larger sand target). The deep penetration simulation predicted considerable instability with a trajectory change of approximately 45° when friction was considered in the dry sand medium. An overall conclusion of this work is that projectile penetration studies in geologic materials need to explicitly consider the heterogeneous or particulate nature of these materials.
Optical trapping and surgery of living yeast cells using a single laser
Authors: Ando Jun , Bautista Godofredo , Smith Nicholas , Fujita Katsumasa , Daria Vincent Ricardo
Published: October 2008

We present optical trapping and surgery of living yeast cells using two operational modes of a single laser. We used a focused laser beam operating in continuous-wave mode for noninvasive optical trapping and manipulation of single yeast cell. We verified that such operational mode of the laser does not cause any destructive effect on yeast cell wall. By changing the operation of the laser to femtosecond-pulsed mode, we show that a tightly focused beam dissects the yeast cell walls via nonlinear absorption. Lastly, using the combined technique of optical microsurgery and trapping, we demonstrate intracellular organelle extraction and manipulation from a yeast cell. The technique established here will be useful as an efficient method for both surgery and manipulation of living cells using a single laser beam.
Modes coupling of shear acoustic waves polarized along a one-dimensional corrugation on the surfaces of an isotropic solid plate
Authors: Valier-Brasier Tony , Potel Catherine , Bruneau Michel
Published: October 2008

This paper aims at providing an analytical model, suitable to highlight the mode coupling due to scattering on small one-dimensional irregularities (parallel ridges) of the surfaces of isotropic solid plates, when shear horizontal waves polarized along the ridges propagate perpendicularly to them. An impedancelike boundary condition at the interface between the teeth (the ridges) and the inner plate (bounded outwardly by the ridges) accounts for the inertia of the teeth to describe the roughness. Using the integral formulation, the displacement field is expressed as a coupling between eigenmodes of the inner regular-shaped plate.
Fourier transform white-light interferometry based spatial frequency-division multiplexing of extrinsic Fabry–Pérot interferometric sensors
Authors: Jiang Yi , Tang Caijie
Published: October 2008

We have investigated the multiplexing technique of Fourier transform white-light interferometry recently reported by [Jiang IEEE Photon. Technol. Lett. 20, 75 (2008)]. Two extrinsic Fabry–Pérot interferometric sensors are spatially frequency-division multiplexed, and no cross talk is found in the experiment. Besides, an improvement was made to achieve a resolution of 1 nm, which is much better than the previous result, 300 nm.
Raman and dielectric study of Ba0.4Sr0.6TiO3–MgAl2O4 tunable microwave composite
Authors: Zhang Jingji , Zhai Jiwei , Jiang Haitao , Yao Xi
Published: October 2008

( 1 − x ) Ba 0.4 Sr 0.6 TiO 3 – x MgAl 2 O 4 (x=0.00, 0.05, 0.10, 0.20, and 0.30) composite ceramics have been synthesized by the solid-state reaction, and its structural and dielectric properties have been systematically characterized. Two crystalline phases, a cubic perovskite structure Ba0.4Sr0.6TiO3 (BST) and a face-centered-cubic spinel structure MgAl2O4 (MA), are clearly visible for x≥0.05. As the MA content increases, the composite ceramics show an increased degree of deviation from the Curie–Weiss law and an increased diffuseness of the dielectric peak. Meanwhile, the tunability of composite ceramics increases. Raman analysis clearly indicates that the incorporation of MA lowers the permittivity and degrades the quality factor of BST composites, which is ascribed to the deterioration on B-site ordering of ABO3 perovskite structure.
Stabilization of PbSe quantum dots by ultrathin EuTe and SrTe barrier layers
Authors: Abtin L. , Springholz G.
Published: October 2008

Overgrowth of self-assembled quantum dots usually changes their shape and composition due to surface exchange reactions and redistribution of adatoms. As shown for PbSe dots, this can be completely suppressed by covering the dots with ultrathin EuTe or SrTe barrier layers, based on the large EuTe and SrTe binding energies. The model is supported by annealing experiments that show that these barrier layers also suppress the usual coarsening and Ostwald ripening process.
Interfacial thermal conductance between silicon and a vertical carbon nanotube
Authors: Hu Ming , Keblinski Pawel , Wang Jian-Sheng , Raravikar Nachiket
Published: October 2008

Molecular simulations are used to evaluate thermal resistance between crystalline silicon and a vertically oriented carbon nanotube (CNT). Without chemical bonds between CNT and Si the thermal resistance is high and its values are consistent with that measured in experiment on vertical CNT arrays. With chemical bonds the thermal resistance is reduced by two orders of magnitude demonstrating significant potential of CNT arrays for thermal management applications. The underlying mechanism for the very large effect of chemical bonding is revealed by simulations of individual phonon scattering across the interface and understood within an analytical solution of a simple spring-mass chain model.
Separating the roles of electrons and holes in the organic magnetoresistance of aluminum tris(8-hydroxyquinoline) organic light emitting diodes
Authors: Rolfe N. , Desai P. , Shakya P. , Kreouzis T. , Gillin W. P.
Published: October 2008

Measurements of the effect of a magnetic field on the photocurrent in an aluminum tris(8-hydroxyquinolate) based organic light emitting diode have shown that it is possible to identify the contribution to the organic magnetoresistance of both electrons and holes. For holes the effect of a magnetic field is to decrease the mobility, whereas for electrons the magnetic field appears to increase the mobility. These changes are suggested to be brought about through the magnetic field dependence of the scattering of electrons and holes with excited states within the device.
Instability of plane Poiseuille flow in a fluid-porous system
Authors: Liu Rong , Liu Qiu Sheng , Zhao Si Cheng
Published: October 2008

The instability of Poiseuille flow in a fluid-porous system is investigated. The system consists of a fluid layer overlying porous media and is subjected to a horizontal plane Poiseuille flow. We use Brinkman’s model instead of Darcy’s law to describe the porous layer. The eigenvalue problem is solved by means of a Chebyshev collocation method. We study the influence of the depth ratio d̂ and the Darcy number δ on the instability of the system. We compare systematically the instability of Brinkman’s model with the results of Darcy’s model. Our results show that no satisfactory agreement between Brinkman’s model and Darcy’s model is obtained for the instability of a fluid-porous system. We also examine the instability of Darcy’s model. A particular comparison with early work is made. We find that a multivalued region may present in the (k,Re) plane, which was neglected in previous work. Here k is the dimensionless wavenumber and Re is the Reynolds number.
Superconducting single photon detectors with minimized polarization dependence
Authors: Dorenbos S. N. , Reiger E. M. , Akopian N. , Perinetti U. , Zwiller V. , Zijlstra T. , Klapwijk T. M.
Published: October 2008

Superconducting single photon detectors are usually fabricated in such a way that a polarization dependence of the quantum efficiency is inevitable. Their meandering nanowire leads to a preferential polarization absorption, this is undesired in experiments where the polarization degree of freedom is used. We have designed two new geometries for which the polarization dependence is minimized: a detector with two meander-type parts oriented perpendicular with respect to each other and a spiraling detector. Focusing on individual parts of the detectors shows polarization dependent quantum efficiency. When the detectors are illuminated uniformly, the maximum polarization dependent quantum efficiency cannot be achieved, however, the polarization dependence of the quantum efficiency is minimized.
High-purity white light from a simple single dopant host-guest white organic light-emitting diode architecture
Authors: Anzenbacher Pavel , Montes Victor A. , Takizawa Shin-ya
Published: October 2008

White light with good color properties (color rendering index=82–87) is generated in a simple organic light-emitting diode comprising an emissive layer, composed of an undoped tris(4-methyl-8-quinolinato)aluminum (Almq3) sublayer and region doped with an orange-red phosphorescent dopant, bis(2-phenyl-1-quinoline)iridium acetylacetonate (Ir(pq)2acac). Electron-hole recombination in a thin spacing Almq3 layer results in blue-green fluorescence, while the formed triplet excitons diffuse to the doped region and are harvested by the dopant to emit orange-red phosphorescence. The combination of blue-green and orange lights results in warm white light. This approach takes advantage of efficient migration of triplet excitons while being less demanding in terms of fabrication and color matching.
Aberration-free imaging for light and electrons
Authors: Fluegel B. , Mascarenhas A.
Published: October 2008

The equations for refraction of either the extraordinary wave of light or the wavefunction of an electron at a planar boundary between two misoriented uniaxially anisotropic materials are shown via raytracing to yield a transverse displacement of the object point. The displacement is independent of ray incidence angle and is thus free from spherical aberration, yielding a perfect virtual image which can have applications in birefringent optics. The general conditions for this aberration-free imaging are found to be identical to those required for amphoteric total refraction.
Polaron recombination in pristine and annealed bulk heterojunction solar cells
Authors: Deibel C. , Baumann A. , Dyakonov V.
Published: October 2008

We determined the dominant polaron recombination loss mechanism in pristine and annealed polythiophene:fullerene blend solar cells by applying the photoinduced charge extraction by linearly increasing voltage method in dependence on temperature. In pristine samples, we find a strongly temperature-dependent bimolecular polaron recombination rate, which is reduced as compared to the Langevin theory. For the annealed sample, we observe a polaron decay rate which follows a third order of carrier concentration almost temperature independently.
HIV rebounds from latently infected cells, rather than from continuing low-level replication
Authors: Joos Beda , Fischer Marek , Kuster Herbert , Pillai Satish K. , Wong Joseph K. , Böni Jürg , Hirschel Bernard , Weber Rainer , Trkola Alexandra , Günthard Huldrych F. ,   The Swiss HIV Cohort Study
Published: October 2008

Rapid rebound of plasma viremia in patients after interruption of long-term combination antiretroviral therapy (cART) suggests persistence of low-level replicating cells or rapid reactivation of latently infected cells. To further characterize rebounding virus, we performed extensive longitudinal clonal evolutionary studies of HIVenvC2-V3-C3 regions and exploited the temporal relationships of rebounding plasma viruses with regard to pretreatment sequences in 20 chronically HIV-1-infected patients having undergone multiple 2-week structured treatment interruptions (STI). Rebounding virus during the short STI was homogeneous, suggesting mono- or oligoclonal origin during reactivation. No evidence for a temporal structure of rebounding virus in regard to pretreatment sequences was found. Furthermore, expansion of distinct lineages at different STI cycles emerged. Together, these findings imply stochastic reactivation of different clones from long-lived latently infected cells rather than expansion of viral populations replicating at low levels. After treatment was stopped, diversity increased steadily, but pretreatment diversity was, on average, achieved only >2.5 years after the start of STI when marked divergence from preexisting quasispecies also emerged. In summary, our results argue against persistence of ongoing low-level replication in patients on suppressive cART. Furthermore, a prolonged delay in restoration of pretreatment viral diversity after treatment interruption demonstrates a surprisingly sustained evolutionary bottleneck induced by punctuated antiretroviral therapy.
Modulation of potassium channel function confers a hyperproliferative invasive phenotype on embryonic stem cells
Authors: Morokuma Junji , Blackiston Douglas , Adams Dany S. , Seebohm Guiscard , Trimmer Barry , Levin Michael
Published: October 2008

Ion transporters, and the resulting voltage gradients and electric fields, have been implicated in embryonic development and regeneration. These biophysical signals are key physiological aspects of the microenvironment that epigenetically regulate stem and tumor cell behavior. Here, we identify a previously unrecognized function for KCNQ1, a potassium channel known to be involved in human Romano–Ward and Jervell–Lange–Nielsen syndromes when mutated. Misexpression of its modulatory wild-type β-subunit XKCNE1 in the
Xenopus
embryo resulted in a striking alteration of the behavior of one type of embryonic stem cell: the pigment cell lineage of the neural crest. Depolarization of embryonic cells by misexpression of KCNE1 non-cell-autonomously induced melanocytes to overproliferate, spread out, and become highly invasive of blood vessels, liver, gut, and neural tube, leading to a deeply hyperpigmented phenotype. This effect is mediated by the up-regulation of
Sox10
and
Slug
genes, thus linking alterations in ion channel function to the control of migration, shape, and mitosis rates during embryonic morphogenesis. Taken together, these data identify a role for the KCNQ1 channel in regulating key cell behaviors and reveal the molecular identity of a biophysical switch, by means of which neoplastic-like properties can be conferred upon a specific embryonic stem cell subpopulation.
SPDL-1 functions as a kinetochore receptor for MDF-1 in Caenorhabditis elegans
Authors: Yamamoto Takaharu G. , Watanabe Sonoko , Essex Anthony , Kitagawa Risa
Published: October 2008

The spindle assembly checkpoint (SAC) ensures faithful chromosome segregation by delaying anaphase onset until all sister kinetochores are attached to bipolar spindles. An RNA interference screen for synthetic genetic interactors with a conserved SAC gene, san-1/MAD3, identified spdl-1, a Caenorhabditis elegans homologue of Spindly. SPDL-1 protein localizes to the kinetochore from prometaphase to metaphase, and this depends on KNL-1, a highly conserved kinetochore protein, and CZW-1/ZW10, a component of the ROD–ZW10–ZWILCH complex. In two-cell–stage embryos harboring abnormal monopolar spindles, SPDL-1 is required to induce the SAC-dependent mitotic delay and localizes the SAC protein MDF-1/MAD1 to the kinetochore facing away from the spindle pole. In addition, SPDL-1 coimmunoprecipitates with MDF-1/MAD1 in vivo. These results suggest that SPDL-1 functions in a kinetochore receptor of MDF-1/MAD1 to induce SAC function.
Molecular Typing ofMycobacterium chelonaeIsolates From a Pseudo-outbreak Involving an Automated Bronchoscope Washer
Authors: Chroneou Alexandra , Zimmerman Sarah K. , Cook Steven , Willey Sandra , Eyre-Kelly Jane , Zias Nikolaos , Shapiro Daniel S. , Beamis John F. , Craven Donald E.
Published: October 2008

We describe a pseudo-outbreak ofMycobacterium chelonaeinfection in bronchoalveolar lavage fluid from 9 patients that was traced to contamination of an automated bronchoscope washer. Molecular typing using repetitive extragenic palindromic polymerase chain reaction was helpful in confirming epidemiologic and clinical findings.
Nosocomial Infection After Septic Shock Among Intensive Care Unit Patients
Authors: Landelle Caroline , Lepape Alain , Français Adrien , Tognet Eve , Thizy Hélène , Voirin Nicolas , Timsit Jean François , Monneret Guillaume , Vanhems Philippe
Published: October 2008

Objectives.

To measure the incidence of nosocomial infection (NI) among patients with septic shock according to the place of septic shock acquisition and to evaluate the increase in the risk of pulmonary infection associated with septic shock.

Design.

Prospective cohort study.

Setting.

TWO intensive care units (ICUs) of a French university hospital.

Patients and Methods.

The study included a total of 209 septic shock patients during the period December 1, 2001 through April 30, 2005. The place of septic shock acquisition for 108 patients was the community; for 87, the hospital; and for 14, the ICU. To evaluate the impact of septic shock on the development of pulmonary infection, a competitive and adjusted hazard ratio (aHR) model was applied to nontrauma ICU patients.

Results.

Among the 209 study patients, 48 (23%) experienced 66 NIs after septic shock. There was no significant difference in the NI attack rates according to place of acquisition: for the community acquisition group, 24 cases per 100 patients (95% confidence interval [CI], 16-32); for the hospital acquisition group, 20 cases per 100 patients (95% CI, 11-28); and for the ICU acquisition group, 36 cases per 100 patients (95% CI, 11-61) (P = .3). For nontrauma ICU patients, the presence of community-acquired septic shock was found to be independently associated with a higher incidence of pulmonary infection, compared with the absence of septic shock (aHR, 2.12 [95% CI, 1.08-4.16]; P = .03).

Conclusions.

The risk of NI did not differ by the place of septic shock acquisition. The risk of pulmonary infection was higher for ICU patients with community-acquired septic shock who were admitted for underlying nontrauma disease. Studies are needed to investigate the pathogenic mechanisms that facilitate pulmonary infection in this population, taking into account exposure to invasive devices and immunosuppression after the initial phase of septic shock.
Efficacy of Pre-harvest Fungicide Applications and Cold Storage for Postharvest Control of Botrytis Fruit Rot (Gray Mold) on Red Raspberry
Authors: Ellis M. A. , Madden L. V. , Wright S. R. , Wilson L. L.
Published: October 2008

Applications of the fungicides Elevate 50WG and Switch 62.5WG to red raspberry prior to harvest were evaluated for post-harvest control of fruit rot, caused by Botrytis cinerea. Fungicides were applied three times during bloom only, three times pre-harvest (post-bloom) only, or six times full season (bloom through harvest), and symptomless fruit (at harvest) were incubated for 8 days in either cold storage (4°C) or at room temperature (23°C). Without fungicide, between 6 and 29% of the fruit had rot symptoms after 2 days of storage at room temperature over the 2 years of testing; after 8 days, 74 and 85% of the fruit had symptoms at room temperature. Zero and 12% of fruit had symptoms with 2 days of cold storage when plants were not treated with fungicide, and rot incidence increased to 9 and 60% at 8 days of cold storage over the 2 years. All fungicide treatments significantly reduced post-harvest fruit rot compared to the control (six water sprays). Applications of fungicide only at bloom generally had higher fruit rot incidence than found for the pre-harvest and full season fungicide programs. Results indicate that pre-harvest (post-bloom) fungicide sprays are beneficial for control of post-harvest Botrytis fruit rot, especially when coupled with cold-temperature storage.

Accepted for publication 8 August 2008. Published 15 October 2008.
Transcriptomic and Reverse Genetic Analysesof Branched-Chain Fatty Acid and Acyl Sugar Production inSolanum pennelliiandNicotiana benthamiana
Authors: Slocombe Stephen P. , Schauvinhold Ines , McQuinn Ryan P. , Besser Katrin , Welsby Nicholas A. , Harper Andrea , Aziz Naveed , Li Yi , Larson Tony R. , Giovannoni James , Dixon Richard A. , Broun Pierre
Published: October 2008

Acyl sugars containing branched-chain fatty acids (BCFAs) are exuded by glandular trichomes of many species in Solanaceae, having an important defensive role against insects. From isotope-feeding studies, two modes of BCFA elongation have been proposed: (1) fatty acid synthase-mediated two-carbon elongation in the high acyl sugar-producing tomato species Solanum pennellii and Datura metel; and (2) α-keto acid elongation-mediated one-carbon increments in several tobacco (Nicotiana) species and a Petunia species. To investigate the molecular mechanisms underlying BCFAs and acyl sugar production in trichomes, we have taken a comparative genomic approach to identify critical enzymatic steps followed by gene silencing and metabolite analysis in S. pennellii and Nicotiana benthamiana. Our study verified the existence of distinct mechanisms of acyl sugar synthesis in Solanaceae. From microarray analyses, genes associated with α-keto acid elongation were found to be among the most strongly expressed in N. benthamiana trichomes only, supporting this model in tobacco species. Genes encoding components of the branched-chain keto-acid dehydrogenase complex were expressed at particularly high levels in trichomes of both species, and we show using virus-induced gene silencing that they are required for BCFA production in both cases and for acyl sugar synthesis in N. benthamiana. Functional analysis by down-regulation of specific KAS I genes and cerulenin inhibition indicated the involvement of the fatty acid synthase complex in BCFA production in S. pennellii. In summary, our study highlights both conserved and divergent mechanisms in the production of important defense compounds in Solanaceae and defines potential targets for engineering acyl sugar production in plants for improved pest tolerance.
DISTANCE DATA REVISITED
Authors: FARRIS JAMES S.
Published: October 2008

Abstract— Objections to my earlier demonstration, that the branch lengths of trees fitted to distance matrices have no physical interpretation, are shown to be ill‐founded. In particular the contention of Felsenstein, that fitted lengths estimate expectations of amounts of change, is shown to lead to a paradox. A method is introduced for constructing multiple trees of optimal or near‐optimal fit to distance data, and this is found to give better performance than previous methods. Most published trees based on distances have been poorly chosen. Consensus trees of several trees with near‐optimal fit are found to be quite poorly resolved, and it appears that molecular distances seldom provide much useful information on phylogenetic relationships.
THE EUKARYOTIC KINGDOMS
Authors: LIPSCOMB DIANA L.
Published: October 2008

Abstract—Cladistic analysis of data from ultrastruetural and other cell biological studies indicates that neither the classical two kingdom nor the commonly accepted five kingdom classifications accurately represent the cellular diversity of eukaryotes. The resulting cladogram indicates instead that there are nine major groups of eukaryotes.
INTERRELATIONSHIPS OF THE SPANISH MACKERELS (PISCES: SCOMBRIDAE: SCOMBEROMORUS) AND THEIR COPEPOD PARASITES
Authors: COLLETTE BRUCE B. , RUSSO JOSEPH L.
Published: October 2008

Abstract— A cladistic analysis of the eighteen species of Spanish mackerels (Scomberomorus) was conducted using the double‐lined mackerel (Grammatorcynus) as the outgroup. Based on fifty‐eight osteological and morphological characters, six species groups are recognized. Comparisons of the cladogram for the regalis species group were made with a cladogram of the nine species of parasitic copepods that infest the six members of the regalis group. Incongruences were analyzed. The parasite tree was then “forced” onto the host cladogram to determine which evolutionary events of the parasites could be explained by evolutionary events of the hosts. Hypotheses of coevolution are supported in some cases, hypotheses of dispersal are proposed in others.
A LIKELIHOOD JUSTIFICATION OF PARSIMONY
Authors: SOBER ELLIOTT
Published: October 2008

Abstract—A connection is established between maximally parsimonious cladograms and trees of highest likelihood. The assumptions needed to prove this are derivable from the structure of evolutionary theory and are independent of the frequency of homoplasy. The bearing of this justification on alternative methods of phylogenetic inference and on Felsenstein's (1978) proof that parsimony and other phylogenetic methods can be statistically inconsistent is discussed.
ONTOGENY AND THE HIERARCHY OF TYPES
Authors: RIEPPEL OLIVIER
Published: October 2008

Abstract— The long history of belief in a parallelism between ontogeny and a hierarchical order of natural things is reviewed. The meaning of von Baerian recapitulation is analyzed and its implications for cladistic methodology are discussed at two levels: ontogeny and homology. The basic problem inherent in the purported parallelism is that the order of natural things (i.e., the taxic approach to homology) is part of the “world of being” of Platonic ideas, whereas ontogeny and phylogeny (i.e., the transformational approach to homology) belong to Plato's “world of becoming.” These two “genera of existence,” as Plato put it, being and becoming, are incompatible but complementary views of nature.
TESTING METHODS OF EVOLUTIONARY TREE CONSTRUCTION
Authors: PENNY DAVID , HENDY M. D.
Published: October 2008

Abstract— Evaluating the reliability of methods for reconstructing evolutionary trees is discussed under the four headings of: evaluating criteria for an optimal tree, finding the optimal tree for the criterion selected, detecting reliable and unreliable data, and estimating the error range for the final tree. It is shown with five data sets (protein sequences) that, in general, the minimal tree is a better estimate of phylogeny than a longer tree. However, for each data set, the minimal tree was no longer the shortest when the sequences were combined. An objective weighting of columns (characters) can lead to an improved tree by giving less weight to columns that are closer to a random order. The weighting of characters is derived from the ratio of the observed to expected number of incompatabilities for each column. Several forms of weighting give better trees as measured by both the increase in correlation between lengths of trees with different subsets of data, and by an increase in the similarity between minimal trees found with disjoint subsets of data. Increasing the size of randomly selected subsets, and measuring the increased similarity of the results, can lead to an estimate of the minimum number of trees that need to be considered as possibly the correct historical tree. A measure of the ‘treeness’ of the data is described that estimates the extent to which a binary tree is a good description of the data.