bluuebunny/crossref_metadata_2025 huggingface dataset:
Localized versus delocalized excitations just above the 3d threshold in krypton clusters studied by Auger electron spectroscopy
Authors: Tchaplyguine M. , Kivimäki A. , Peredkov S. , Sorensen S. L. , Öhrwall G. , Schulz J. , Lundwall M. , Rander T. , Lindblad A. , Rosso A. , Svensson S. , Mårtensson N. , Björneholm O.
Published: September 2007

We present Auger spectroscopy studies of large krypton clusters excited by soft x-ray photons with energies on and just above the 3d5∕2 ionization threshold. The deexcitation spectra contain new features as compared to the spectra measured both below and far above threshold. Possible origins of these extra features, which stay at constant kinetic energies, are discussed: (1) normal Auger process with a postcollision interaction induced energy shift, (2) recapture of photoelectrons into high Rydberg orbitals after Auger decay, and (3) excitation into the conduction band (or “internal” ionization) followed by Auger decay. The first two schemes are ruled out, hence internal ionization remains the most probable explanation.
Gaussian-4 theory using reduced order perturbation theory
Authors: Curtiss Larry A. , Redfern Paul C. , Raghavachari Krishnan
Published: September 2007

Two modifications of Gaussian-4 (G4) theory [L. A. Curtiss et al., J. Chem. Phys. 126, 084108 (2007)] are presented in which second- and third-order perturbation theories are used in place of fourth-order perturbation theory. These two new methods are referred to as G4(MP2) and G4(MP3), respectively. Both methods have been assessed on the G3/05 test set of accurate experimental data. The average absolute deviation from experiment for the 454 energies in this test set is 1.04kcal∕mol for G4(MP2) theory and 1.03kcal∕mol for G4(MP3) theory compared to 0.83kcal∕mol for G4 theory. G4(MP2) is slightly more accurate for enthalpies of formation than G4(MP3) (0.99 versus 1.04kcal∕mol), while G4(MP3) is more accurate for ionization potentials and electron affinities. Overall, the G4(MP2) method provides an accurate and economical method for thermochemical predictions. It has an overall accuracy for the G3/05 test set that is much better than G3(MP2) theory (1.04 versus 1.39kcal∕mol) and even better than G3 theory (1.04 versus 1.13kcal∕mol). In addition, G4(MP2) does better for challenging hypervalent systems such as H2SO4 and for nonhydrogen species than G3(MP2) theory.
First principles study of magnetism in nanographenes
Authors: Jiang De-en , Sumpter Bobby G. , Dai Sheng
Published: September 2007

Magnetism in nanographenes [also known as polycyclic aromatic hydrocarbons (PAHs)] is studied with first principles density functional calculations. We find that an antiferromagnetic (AFM) phase appears as the PAH reaches a certain size. This AFM phase in PAHs has the same origin as the one in infinitely long zigzag-edged graphene nanoribbons, namely, from the localized electronic state at the zigzag edge. The smallest PAH still having an AFM ground state is identified. With increased length of the zigzag edge, PAHs approach an infinitely long ribbon in terms of (1) the energetic ordering and difference among the AFM, ferromagnetic, and nonmagnetic phases and (2) the average local magnetic moment at the zigzag edges. These PAHs serve as ideal targets for chemical synthesis of nanographenes that possess magnetic properties. Moreover, our calculations support the interpretation that experimentally observed magnetism in activated carbon fibers originates from the zigzag edges of the nanographenes.
Protein phase behavior and crystallization: Effect of glycerol
Authors: Sedgwick H. , Cameron J. E. , Poon W. C. K. , Egelhaaf S. U.
Published: September 2007

Glycerol is widely used as an additive to stabilize proteins in aqueous solution. We have studied the effect of up to 40wt% glycerol on the crystallization of lysozyme from brine. As the glycerol concentration increased, progressively larger amounts of salt were needed to crystallize the protein. Like previous authors, we interpret this as evidence for glycerol changing the interaction between lysozyme molecules. We quantitatively model the interprotein interaction using a Derjaguin-Landau-Verwey-Overbeek potential. We find that the effect of glycerol can be entirely accounted for by the way it modifies the dielectric constant and refractive index of the solvent. Quantifying the interprotein interaction by the second virial coefficient, B2, we find a universal crystallization boundary for all glycerol concentrations.
Toward a statistical mechanical theory for water: Analytical theory for a short-ranged reference system
Authors: Jirsák Jan , Nezbeda Ivo
Published: September 2007

Starting from a realistic Hamiltonian and making use of recent findings that the properties of associating fluids are determined primarily by short-ranged interactions, this methodology has been implemented using statistical mechanical approaches and thermodynamic perturbation theory for the TIP4P model of water. We focus on the short-range reference system for which an analytic expression for the Helmholtz free energy is derived. It is found that the model (reference system) exhibits, in addition to a faithful representation of the structure of water, the same features that are characteristic for real water, namely, (i) the temperature of the density maximum and its pressure dependence, including the inflection point at high pressures and (ii) the temperature minima of the constant pressure heat capacity and the coefficient of isothermal compressibility.
Enlarged atomic force microscopy scanning scope: Novel sample-holder device with millimeter range
Authors: Sinno A. , Ruaux P. , Chassagne L. , Topçu S. , Alayli Y. , Lerondel G. , Blaize S. , Bruyant A. , Royer P.
Published: September 2007

We propose a homemade sample-holder unit used for nanopositionning in two dimensions with a millimeter traveling range. For each displacement axis, the system includes a long range traveling stage and a piezoelectric actuator for accurate positioning. Specific electronics is integrated according to metrological considerations, enhancing the repeatability performances. The aim of this work is to demonstrate that near-field microscopy at the scale of a chip is possible. For this we chose to characterize highly integrated optical structures. For this purpose, the sample holder was integrated into an atomic force microscope. A millimeter scale topographical image demonstrates the overall performances of the combined system.
Experimental study on the characteristics of low power microwave plasma jet within local vacuum environment
Authors: Yang Juan , Xu Ying Qao , Zhu Bing , Mao Gen Wang , Zhu Liang Ming
Published: September 2007

A microwave plasma jet based on a coaxial cavity can be generated in atmosphere and vacuum environments. It is shown that with argon gas and a power range of 53–60W, cavity efficiency ranges from 54% to 68%. The electron density distribution and the microwave return loss of the confined plasma jet adjacent to a metal object and their dependency on argon mass flow rate and power have been studied by applying emission/Langmuir probe and spatial reflected wave diagnostic equipments in a low scatter vacuum environment. The results show that the electron density ranges from 8.8×1014to7.53×1016∕m3, and the electron density on the centerline of the jet decreases exponentially from the nozzle exit plane, but its distribution off the centerline is in an upheaved curve. Increasing mass flow rate at constant power and increasing power at constant mass flow rate increase electron density mildly. From typical measurements of microwave return loss, it is noted that the plasma jet attenuates microwaves in a 6to8GHz range.
Isochronous extension of the Hamiltonian describing free motion in the Poincaré half-plane: Classical and quantum treatments
Authors: Calogero F. A. , Leyvraz F.
Published: September 2007

We modify (in two different manners) the Hamiltonian describing motions in the Poincaré half-plane so that the modified Hamiltonians thereby obtained are entirely isochronous: indeed, in the classical context, all the motions they entail are periodic with the same period. We then investigate suitably quantized versions of these systems and show that their spectra are equispaced.
The friction factor of a rarefied gas flow in a circular tube
Authors: Valougeorgis Dimitris
Published: September 2007

An expression for the estimation of the Poiseuille number for internal rarefied flows is developed. The derived formula is given in terms of dimensionless quantities, which are obtained by the solution of the flow based on kinetic theory. The formulation is applied to the fully developed flow of a gas in a circular tube, and tabulated results of the Poiseuille number are presented in the whole range of the Knudsen number and for various values of the accommodation coefficient. Also, in the slip regime, a closed-form expression for the Poiseuille number is derived and a brief discussion on the proper estimation of the viscous slip coefficient is provided.
Peculiarities of neutron-transmutation phosphorous doping of Si30 enriched SiC crystals: Electron paramagnetic resonance study
Authors: Baranov P. G. , Ber B. Ya. , Ilyin I. V. , Ionov A. N. , Mokhov E. N. , Muzafarova M. V. , Kaliteevskii M. A. , Kop’ev P. S. , Kaliteevskii A. K. , Godisov O. N. , Lazebnik I. M.
Published: September 2007

We have obtained a high concentration of P donor dopants in 6H-SiC enriched with Si30 and irradiated with thermal neutrons. It was established that annealing at a relatively low temperature of 1300°C, i.e., 500–600°C lower than that used for annealing SiC with the natural isotope composition after neutron-transmutation doping, gives rise to an electron paramagnetic resonance (EPR) signal corresponding to three different shallow P (sP) donors with large hyperfine interactions. The correlated changes of these sP centers in all the annealing experiments and the similarities to the spectra of shallow N donors demonstrate that these sites have shallow donor levels and a similar electronic structure and that they belong to different lattice sites: two quasicubic and hexagonal. The phosphorus at these three sites is suggested to occupy the C position. Simultaneously the low-temperature EPR signal from another set of P-related donor centers having a small, strongly anisotropic hyperfine interaction is observed. It is suggested that phosphorus in these centers occupies the Si position. Annealing at 1800°C yields opposite changes in the concentrations of the two types of P-related donor centers: The EPR signals of sP centers disappear, while the intensity of the low-temperature EPR spectra of P donors considerably increases. Thus, the phosphorus at the C position is established to be unstable and annealing above 1700°C causes P at the C site to move to the Si site. This process is vacancy mediated, as the temperature of this process is shown to depend on the thermal stability of intrinsic defects produced by neutron irradiation, whose concentration is proportional to the neutron irradiation dose.
Magnetic properties of MnxTi1−xN thin films grown by plasma-assisted molecular beam epitaxy
Authors: Wu S. X. , Xia Y. Q. , Yu X. L. , Liu Y. J. , Li S. W.
Published: September 2007

High-quality MnxTi1−xN thin films were grown on MgO(001) substrates using plasma-assisted molecular beam epitaxy. Magnetic measurements evidence the presence of ferromagnetism with Curie temperature exceeding 380K. X-ray photoelectron spectroscopy indicates that the Mn ions are in a divalent state and uniformly substitute on Ti cation sites, consistent with the ferromagnetism that correlates with Mn substitution on Ti sites. The origin of the ferromagnetism might be attributed to itinerant-carrier mediated Rudermann-Kittel-Kasuya-Yosida (RKKY)-type long-range coupling which allows for arbitrary itinerant-carrier spin polarization and dynamic correlations.
Mechanical alloying of Co and P: Structural and photoacoustic studies
Authors: Souza S. M. , Trichês D. M. , de Lima J. C. , Grandi T. A. , Campos C. E. M.
Published: September 2007

A mixture of elemental Co and P powders with nominal CoP3 composition was investigated by the mechanical alloying technique. For milling times greater than 26h, the measured x-ray diffraction (XRD) patterns revealed the coexistence of the skutterudite CoP3, the orthorhombic CoP, and Co2P phases. The structural and photoacoustic properties of as-milled powders were studied by the XRD and photoacoustic spectroscopy (PAS) techniques. The thermal diffusivity parameter of the as-milled sample was measured from fitting the PAS signal phase. The thermoelastic bending process is the main contribution to the PAS signal amplitude.
Magnetic circular dichroism in Co1−xPtx nanowire bundles at the Co L2,3 edges
Authors: Li Wuxia , Zhang Jun , Thompson Jamie , Shen Tiehan H. , Arenholz Elke , Morton Simon A. , Ellerby Mark
Published: September 2007

Co 1 − x Pt x nanowire arrays embedded in anodic aluminum oxide templates were fabricated by an electrochemical route. X-ray magnetic circular dichroism (XMCD) measurements were conducted at the Co L2,3 edges on samples with an array of nanowire bundles at the substrate surfaces. The ratios between the orbital and the spin moments R were estimated to be about 0.19 (±0.03) and 0.07 (±0.03) for 20nm Co and 14nm Co91Pt9 nanowires, respectively. A strong temperature dependence of the R value was observed. The x-ray absorption spectra also indicated the presence of CoO, which did not contribute to the XMCD signals.
Dissociative recombination of H3+ in the ground and excited vibrational states
Authors: dos Santos Samantha Fonseca , Kokoouline Viatcheslav , Greene Chris H.
Published: September 2007

The article presents calculated dissociative recombination (DR) rate coefficients for H3+. The previous theoretical work on H3+ was performed using the adiabatic hyperspherical approximation to calculate the target ion vibrational states and it considered just a limited number of ionic rotational states. In this study, we use accurate vibrational wave functions and a larger number of possible rotational states of the H3+ ground vibrational level. The DR rate coefficient obtained is found to agree better with the experimental data from storage ring experiments than the previous theoretical calculation. We present evidence that excited rotational states could be playing an important role in those experiments for collision energies above 10meV. The DR rate coefficients calculated separately for ortho- and para-H3+ are predicted to differ significantly at low energy, a result consistent with a recent experiment. We also present DR rate coefficients for vibrationally excited initial states of H3+, which are found to be somewhat larger than the rate coefficient for the ground vibrational level.
Improved dielectric properties of Al2O3-doped Pb0.6Ba0.4ZrO3 thin films for tunable microwave applications
Authors: Wu Lin-Jung , Wu Jenn-Ming
Published: September 2007

The effect of doping Al2O3 on the Pb0.6Ba0.4ZrO3 thin films was investigated. With increasing Al2O3 content, the dielectric constant, tunability, and dissipation factor decrease while the figure of merit (FOM) increases. After doping with the optimal content of 1.5at.% Al2O3, the Pb0.6Ba0.4ZrO3 films have a dielectric constant of 190, a tunability of 30%, a dissipation factor of 0.0067, a FOM value of 49, and a temperature coefficient of capacitance value of 1.13×10−4. The loss mechanism is discussed in order to provide information, which could be useful for further improvement of the material performance.
Demonstration of a laser vorticity probe in turbulent boundary layers
Authors: Su W-J. , Stepaniuk V. , Ötügen M. V.
Published: September 2007

A laser-based probe for the nonintrusive measurement of velocity gradient and vorticity was demonstrated in turbulent boundary layers. Unlike most other optical methods, the current technique provides an estimate of the velocity gradient, without having to first measure velocity at multiple points. The measurement principle is based on the heterodyne of coherent light scattered from two adjacent particles. The beat frequency of the heterodyne is directly proportional to the velocity gradient. The probe is assembled from commercially available, inexpensive optical components. A laser Doppler velocimeter (LDV) processor is used to analyze the heterodyne signal. A component of vorticity is obtained by using two appropriately aligned velocity gradient probes. The optical probes developed were used in turbulent boundary layers to measure local, time-frozen velocity gradients ∂u∕∂y, ∂v∕∂x, and ∂v∕∂y, as well as the spanwise vorticity. The measurements were compared to those inferred from LDV measurements in the same facility and to data available in the literature.
Control of tip-to-sample distance in atomic force microscopy: A dual-actuator tip-motion control scheme
Authors: Jeong Younkoo , Jayanth G. R. , Menq Chia-Hsiang
Published: September 2007

The control of tip-to-sample distance in atomic force microscopy (AFM) is achieved through controlling the vertical tip position of the AFM cantilever. In the vertical tip-position control, the required z motion is commanded by laser reading of the vertical tip position in real time and might contain high frequency components depending on the lateral scanning rate and topographical variations of the sample. This paper presents a dual-actuator tip-motion control scheme that enables the AFM tip to track abrupt topographical variations. In the dual-actuator scheme, an additional magnetic mode actuator is employed to achieve high bandwidth tip-motion control while the regular z scanner provides the necessary motion range. This added actuator serves to make the entire cantilever bandwidth available for tip positioning, and thus controls the tip-to-sample distance. A fast programmable electronics board was employed to realize the proposed dual-actuator control scheme, in which model cancellation algorithms were implemented to enlarge the bandwidth of the magnetic actuation and to compensate the lightly damped dynamics of the cantilever. Experiments were conducted to illustrate the capabilities of the proposed dual-actuator tip-motion control in terms of response speed and travel range. It was shown that while the bandwidth of the regular z scanner was merely a small fraction of the cantilever’s bandwidth, the dual-actuator control scheme led to a tip-motion control system, the bandwidth of which was comparable to that of the cantilever, where the dynamics overdamped, and the motion range comparable to that of the z scanner.
Effects of process parameters on the electrochemical etching of sharp metallic tips with an attached mass
Authors: Kim Pilkyu , Jeong Sungho , Jeong Mun Seok , Ko Do-Kyeong , Lee Jongmin
Published: September 2007

The electrochemical etching of a metal wire with an attached mass at the end of the immersed wire is a new technique to enhance the yield rate of sharp tips. Unlike conventional electrochemical etching, the yield rate of sharp tips with subhundred nanometer apex could be increased up to around 60% with the attached mass method. In this article, the effects of the magnitude of attached mass and the taping material used for attachment on the yield rate and tip shape are investigated. Also, the variation of tip shape with respect to the temporal shape of applied electric field, constant or pulsed dc, is examined.
Type II InAs∕GaSb strain layer superlattice detectors with p-on-n polarity
Authors: Plis E. , Rodriguez J. B. , Kim H. S. , Bishop G. , Sharma Y. D. , Dawson L. R. , Krishna S. , Lee S. J. , Jones C. E. , Gopal Vishnu
Published: September 2007

We report on high operating temperature midwave infrared detectors based on type II InAs∕GaSb superlattices (SLs) with a p-on-n polarity. All InAs∕GaSb SLs photodiodes reported so far have a n-on-p polarity with a thin InAs n-type top contact, that is incompatible with most present day readout integrated circuits. Current-voltage measurements reveal dark current densities of ∼5×10−7A∕cm2 (82K) and 0.18A∕cm2 (240K) at −0.1V. R0A products were equal to ∼1×105Ωcm2 (82K) and 0.24Ωcm2 (240K). Zero-biases D* were estimated to be 2×1012 and 2×109 Jones at 82 and 240K, respectively.
Metal-insulator-metal capacitors’ current instability improvement using dielectric stacks to prevent oxygen vacancies formation
Authors: Manceau J.-P. , Bruyere S. , Jeannot S. , Sylvestre A. , Gonon P.
Published: September 2007

Current instability in metal-oxide-semiconductor and metal-insulator-metal (MIM) capacitors has been previously reported to be a potential reliability issue. This letter intends to study a particular way to reduce these current instabilities with time in high-κ MIM capacitors. It consists in the introduction of a stable dielectric layer between the high-κ dielectric and the electrodes in order to prevent oxygen vacancy formation at interfaces. When applied to Ta2O5 capacitors, the deposition of a thin layer of Al2O3 in the range of a few tens of angstroms enables the strong reduction of current instabilities while maintaining good electrical performances.
Identification of atomic-scale defect structure involved in the negative bias temperature instability in plasma-nitrided devices
Authors: Campbell J. P. , Lenahan P. M. , Krishnan A. T. , Krishnan S.
Published: September 2007

We utilize a very sensitive electron spin resonance technique called spin-dependent tunneling to identify defect centers involved in the negative bias temperature instability in plasma-nitrided p-channel metal-oxide-silicon field-effect transistors. The defect’s Si29 hyperfine spectrum identifies it as a K center which we refer to as KN. The generation of KN centers provides an explanation for the instability’s enhancement in nitrided devices.
Magnetic multilayers on porous anodized alumina for percolated perpendicular media
Authors: Rahman M. Tofizur , Shams Nazmun Nahar , Wu Yun-Chung , Lai Chih-Huang , Suess Dieter
Published: September 2007

Co ∕ Pt multilayers deposited on anodized alumina substrates are introduced as percolated perpendicular media. The pores act as pinning sites due to variations of thickness and anisotropy direction around the perimeters. Coercivity, domain size, and switching field can be engineered by controlling pore density. The media exhibit strong perpendicular anisotropy and the switching field remains unchanged at its minimum up to an angular deviation of 50° from the easy axis. A better tolerance of switching-field distributions can thus be achieved, which may help to achieve a high signal-to-noise ratio. The thermal stability of the proposed media is investigated by micromagnetic simulations.
Doped gallium oxide nanowires with waveguiding behavior
Authors: Nogales Emilio , García José Ángel , Méndez Bianchi , Piqueras Javier
Published: September 2007

Er and Cr doped β-Ga2O3 nano- and microwires have been grown by thermal treatments of Ga2O3 powder containing a fraction of Er2O3 powder or in the presence of Cr2O3 powder, respectively. Doping gives rise to the characteristic red photoluminescence (PL) of Cr3+ ions at about 700nm and to green emission of Er3+ at about 555nm. Waveguiding of the ion related PL light excited in the wires has been studied for wires with different sizes. Waveguide behavior for incident visible light of different wavelengths was demonstrated.
Ultrafast optical image processing based on third-harmonic generation in organic thin films
Authors: Fuentes-Hernandez Canek , Tseng Shuo-Yen , Owens Daniel , Kippelen Bernard
Published: September 2007

We report on the use of the noncollinear third-harmonic generation in an amorphous polymer film operating in the eye safe and telecommunication compatible near-infrared range to perform ultrafast all-optical two-dimensional (2D) image processing at 1550nm using 100fs pulses. The background-free and nondegenerate outputs at 517nm are easily spatially filtered and detected with low cost electronic components. We describe this Fourier transform based technique and demonstrate its application to the classical problem of 2D image recognition.
Cu films containing insoluble Ru and RuNX on barrierless Si for excellent property improvements
Authors: Chu J. P. , Lin C. H. , John V. S.
Published: September 2007

This letter reports superior properties of Ru- and RuNX-bearing Cu films deposited by cosputtering on barrierless Si substrates. After annealing at temperatures up to 680°C for 1h, low resistivity of ∼3μΩcm and minimal leakage currents as well as no detectable reaction at the Cu∕Si interface have confirmed the excellent thermal stability of these Cu(Ru) and Cu(RuNX) films. Furthermore, the highly stable Cu(RuNX) film exhibits an outstanding adhesion property, proving to be a very promising candidate for the barrierless Cu metallization.
Blue-light (488nm)-irradiation-induced photoactivation of the photoactivatable green fluorescent protein
Authors: Testa Ilaria , Mazza Davide , Barozzi Sara , Faretta Mario , Diaspro Alberto
Published: September 2007

We experimentally demonstrate the photoactivatable green fluorescent protein (paGFP) photoactivation in a wavelength range where the molecule barely absorbs. The photoactivation is induced at the same wavelength used to visualize the activated form of paGFP. This can be an obstacle in the intensity evaluation in photoactivation experiments. Power and kinetics based characterization of the effect was performed in model and cell systems. This study shows an operative threshold in which paGFP is not subjected to significant photoconversion. 488nm photoactivation is in tune with the broadening of the paGFP two-photon activation spectrum, indicating that multiple interactions lead to modifications of the molecular structure and alterations of its photophysical properties.
Direct synthesis of sp-bonded carbon chains on graphite surface by femtosecond laser irradiation
Authors: Hu A. , Rybachuk M. , Lu Q.-B. , Duley W. W.
Published: September 2007

Microscopic phase transformation from graphite to sp-bonded carbon chains (carbyne) and nanodiamond has been induced by femtosecond laser pulses on graphite surface. UV/surface enhanced Raman scattering spectra and x-ray photoelectron spectra displayed the local synthesis of carbyne in the melt zone while nanocrystalline diamond and trans-polyacetylene chains form in the edge area of gentle ablation. These results evidence possible direct “writing” of variable chemical bonded carbons by femtosecond laser pulses for carbon-based applications.
The effect of endophyte infection on persistence of tall fescue (Festuca arundinacea Schreb.) populations in two climatically contrasting Italian locations
Authors: Pecetti L. , Romani M. , Carroni A. M. , Annicchiarico P. , Piano E.
Published: September 2007

Endophytic fungi may reportedly improve summer persistence in tall fescue (Festuca arundinacea Schreb.). The objective of this study was assessing whether endophytes contributed to better persistence in 2 climatically contrasting Italian locations (Sanluri, Mediterranean climate, 382 mm average rainfall; Lodi, subcontinental climate, 802 mm average rainfall). Twelve populations from Sardinia were evaluated for 4 years in each site with or without nitrogen application. The populations hosted either of 2 endophyte forms (long-conidia, Neotyphodium coenophialum; short-conidia, FaTG-2 group) and belonged to the European race of fescue (hosting N. coenophialum) or the Mediterranean race (hosting FaTG-2). Three European-race commercial varieties (hosting N. coenophialum) were included as controls. The evaluated material was present both in the endophyte-infected and the endophyte-free (after chemical treatment) status. Stand persistence was recorded at the end of each year. The effect of the endophyte presence on persistence was nil in the Mediterranean site and slightly positive in the subcontinental location. Populations of the 2 geographic races had contrasting behaviour in the 2 sites irrespective of their endophyte status. The Mediterranean-race populations persisted well in the Mediterranean environment but not in the subcontinental one, and the reverse occurred for the European-race germplasm (including the controls). The results suggest that Mediterranean conditions may be too extreme for any enhancement of persistence to be solely provided by the endophyte, and highlight the overwhelming importance of the physiological adaptation of the grass germplasm to target environment.
CXCR7 (RDC1) promotes breast and lung tumor growth
in vivo
and is expressed on tumor-associated vasculature
Authors: Miao Zhenhua , Luker Kathryn E. , Summers Bretton C. , Berahovich Rob , Bhojani Mahaveer S. , Rehemtulla Alnawaz , Kleer Celina G. , Essner Jeffrey J. , Nasevicius Aidas , Luker Gary D. , Howard Maureen C. , Schall Thomas J.
Published: September 2007

Chemokines and chemokine receptors have been posited to have important roles in several common malignancies, including breast and lung cancer. Here, we demonstrate that CXCR7 (RDC1, CCX-CKR2), recently deorphanized as a chemokine receptor that binds chemokines CXCL11 and CXCL12, can regulate these two common malignancies. Using a combination of overexpression and RNA interference, we establish that CXCR7 promotes growth of tumors formed from breast and lung cancer cells and enhances experimental lung metastases in immunodeficient as well as immunocompetent mouse models of cancer. These effects did not depend on expression of the related receptor CXCR4. Furthermore, immunohistochemistry of primary human tumor tissue demonstrates extensive CXCR7 expression in human breast and lung cancers, where it is highly expressed on a majority of tumor-associated blood vessels and malignant cells but not expressed on normal vasculature. In addition, a critical role for CXCR7 in vascular formation and angiogenesis during development is demonstrated by using morpholino-mediated knockdown of CXCR7 in zebrafish. Taken together, these data suggest that CXCR7 has key functions in promoting tumor development and progression.
Finite deformation mechanics in buckled thin films on compliant supports
Authors: Jiang Hanqing , Khang Dahl-Young , Song Jizhou , Sun Yugang , Huang Yonggang , Rogers John A.
Published: September 2007

We present detailed experimental and theoretical studies of the mechanics of thin buckled films on compliant substrates. In particular, accurate measurements of the wavelengths and amplitudes in structures that consist of thin, single-crystal ribbons of silicon covalently bonded to elastomeric substrates of poly(dimethylsiloxane) reveal responses that include wavelengths that change in an approximately linear fashion with strain in the substrate, for all values of strain above the critical strain for buckling. Theoretical reexamination of this system yields analytical models that can explain these and other experimental observations at a quantitative level. We show that the resulting mechanics has many features in common with that of a simple accordion bellows. These results have relevance to the many emerging applications of controlled buckling structures in stretchable electronics, microelectromechanical systems, thin-film metrology, optical devices, and others.
Direct observation of ligand transfer and bond formation in cytochrome
c
oxidase by using mid-infrared chirped-pulse upconversion
Authors: Treuffet Johanne , Kubarych Kevin J. , Lambry Jean-Christophe , Pilet Eric , Masson Jean-Baptiste , Martin Jean-Louis , Vos Marten H. , Joffre Manuel , Alexandrou Antigoni
Published: September 2007

We have implemented the recently demonstrated technique of chirped-pulse upconversion of midinfrared femtosecond pulses into the visible in a visible pump–midinfrared probe experiment for high-resolution, high-sensitivity measurements over a broad spectral range. We have succeeded in time-resolving the CO ligand transfer process from the heme Fe to the neighboring Cu
B
atom in the bimetallic active site of mammalian cytochrome
c
oxidase, which was known to proceed in <1 ps, using the full CO vibrational signature of Fe–CO bond breaking and Cu
B
–CO bond formation. Our differential transmission results show a delayed onset of the appearance of the Cu
B
-bound species (200 fs), followed by a 450-fs exponential rise. Trajectories calculated by using molecular-dynamics simulations with a Morse potential for the Cu
B
–C interaction display a similar behavior. Both experimental and calculated data strongly suggest a ballistic contribution to the transfer process.
Hypomorphic CEP290/NPHP6 mutations result in anosmia caused by the selective loss of G proteins in cilia of olfactory sensory neurons
Authors: McEwen Dyke P. , Koenekoop Robert K. , Khanna Hemant , Jenkins Paul M. , Lopez Irma , Swaroop Anand , Martens Jeffrey R.
Published: September 2007

Cilia regulate diverse functions such as motility, fluid balance, and sensory perception. The cilia of olfactory sensory neurons (OSNs) compartmentalize the signaling proteins necessary for odor detection; however, little is known regarding the mechanisms of protein sorting/entry into olfactory cilia. Nephrocystins are a family of ciliary proteins likely involved in cargo sorting during transport from the basal body to the ciliary axoneme. In humans, loss-of-function of the cilia–centrosomal protein CEP290/NPHP6 is associated with Joubert and Meckel syndromes, whereas hypomorphic mutations result in Leber congenital amaurosis (LCA), a form of early-onset retinal dystrophy. Here, we report that CEP290–LCA patients exhibit severely abnormal olfactory function. In a mouse model with hypomorphic mutations in CEP290 [retinal dystrophy-16 mice (
rd16
)], electro-olfactogram recordings revealed an anosmic phenotype analogous to that of CEP290–LCA patients. Despite the loss of olfactory function, cilia of OSNs remained intact in the
rd16
mice. As in wild type, CEP290 localized to dendritic knobs of
rd16
OSNs, where it was in complex with ciliary transport proteins and the olfactory G proteins G
olf
and Gγ
13
. Interestingly, we observed defective ciliary localization of G
olf
and Gγ
13
but not of G protein-coupled odorant receptors or other components of the odorant signaling pathway in the
rd16
OSNs. Our data implicate distinct mechanisms for ciliary transport of olfactory signaling proteins, with CEP290 being a key mediator involved in G protein trafficking. The assessment of olfactory function can, therefore, serve as a useful diagnostic tool for genetic screening of certain syndromic ciliary diseases.
Φ-Value analysis of a three-state protein folding pathway by NMR relaxation dispersion spectroscopy
Authors: Neudecker Philipp , Zarrine-Afsar Arash , Davidson Alan R. , Kay Lewis E.
Published: September 2007

Experimental studies of protein folding frequently are consistent with two-state folding kinetics. However, recent NMR relaxation dispersion studies of several fast-folding mutants of the Fyn Src homology 3 (SH3) domain have established that folding proceeds through a low-populated on-pathway intermediate, which could not be detected with stopped-flow experiments. The dispersion experiments provide precise kinetic and thermodynamic parameters that describe the folding pathway, along with a detailed site-specific structural characterization of both the intermediate and unfolded states from the NMR chemical shifts that are extracted. Here we describe NMR relaxation dispersion Φ-value analysis of the A39V/N53P/V55L Fyn SH3 domain, where the effects of suitable point mutations on the energy landscape are quantified, providing additional insight into the structure of the folding intermediate along with per-residue structural information of both rate-limiting transition states that was not available from previous studies. In addition to the advantage of delineating the full three-state folding pathway, the use of NMR relaxation dispersion as opposed to stopped-flow kinetics to quantify Φ values facilitates their interpretation because the obtained chemical shifts monitor any potential structural changes along the folding pathway that might be introduced by mutation, a significant concern in their analysis. Φ-Value analysis of several point mutations of A39V/N53P/V55L Fyn SH3 establishes that the β
3
–β
4
-hairpin already is formed in the first transition state, whereas strand β
1
, which forms nonnative interactions in the intermediate, does not fully adopt its native conformation until after the final transition state. The results further support the notion that on-pathway intermediates can be stabilized by nonnative contacts.
Molecular basis for passive immunotherapy of Alzheimer's disease
Authors: Gardberg Anna S. , Dice Lezlee T. , Ou Susan , Rich Rebecca L. , Helmbrecht Elizabeth , Ko Jan , Wetzel Ronald , Myszka David G. , Patterson Paul H. , Dealwis Chris
Published: September 2007

Amyloid aggregates of the amyloid-β (Aβ) peptide are implicated in the pathology of Alzheimer's disease. Anti-Aβ monoclonal antibodies (mAbs) have been shown to reduce amyloid plaques
in vitro
and in animal studies. Consequently, passive immunization is being considered for treating Alzheimer's, and anti-Aβ mAbs are now in phase II trials. We report the isolation of two mAbs (PFA1 and PFA2) that recognize Aβ monomers, protofibrils, and fibrils and the structures of their antigen binding fragments (Fabs) in complex with the Aβ(1–8) peptide DAEFRHDS. The immunodominant EFRHD sequence forms salt bridges, hydrogen bonds, and hydrophobic contacts, including interactions with a striking WWDDD motif of the antigen binding fragments. We also show that a similar sequence (AKFRHD) derived from the human protein GRIP1 is able to cross-react with both PFA1 and PFA2 and, when cocrystallized with PFA1, binds in an identical conformation to Aβ(1–8). Because such cross-reactivity has implications for potential side effects of immunotherapy, our structures provide a template for designing derivative mAbs that target Aβ with improved specificity and higher affinity.
Do foreign language learners also have constructions?
Authors: Gries Stefan Th. , Wulff Stefanie
Published: September 2007

In Construction Grammar, the ultimate grammatical unit is the construction, a conventionalized form-meaning pairing. We present interrelated evidence from three different methods, all of which speak in favor of attributing an ontological status to constructions for non-native speakers of English. Firstly, in a sentence-fragment completion study with German learners of English, we obtained a significant priming effect between constructions. Secondly, these priming effects correlate strongly with the verb-construction preferences in native speaker corpora: verbs which are strongly associated with one construction resist priming to another semantically compatible construction; more importantly, the priming effects do not correlate with verb-construction preferences from German translation equivalents, ruling out a translational explanation. Thirdly, in order to rule out an alternative account in terms of syntactic rather than constructional priming, we present semantic evidence obtained by a sorting study, showing that subjects exhibited a strong tendency towards a construction-based sorting, which even reflects recent explanations of how constructions are related.
The construal of simultaneity in English with special reference to as-clauses
Authors: Broccias Cristiano
Published: September 2007

This paper investigates how simultaneity between two events, a main clause event and a subordinate clause event, is coded in English. It focuses on as-clauses but also contrasts them with while-clauses. It argues that as-clauses evoke path events, i.e. events susceptible to change. It also points out that as-clauses define a family resemblance network in that different, though related, variants can be recognised. While-clauses are argued to generally evoke larger and more stable temporal configurations, e.g. properties. The different behaviour of as-clauses and while-clauses is related to the different lexical status of as vs. while. The former is analysed as a subordinator unspecified for temporality whereas the latter is regarded as a temporal subordinator by default. Finally, the use of progressive aspect is discussed. It is argued to function as a “slow motion” marker in as-clauses and/or to signal a contrast between the temporal expanses of the main and as-clauses. By contrast, it takes on a transience-highlighting function in while-clauses.
Nominalization as an ‘interpersonally-driven’ system
Authors: Heyvaert Liesbet
Published: September 2007

This paper analyzes different types of deverbal -er nominals and factive nominalizations and argues that they can only be fully described and generalized across if, in addition to their ideational properties, the interpersonal categories which they realize are also considered. It is shown that interpersonal functions such as Subject/person deixis, finite/non-finite grounding and the Mood-relation between them are not exclusively clausal categories, but that they are equally operative at word level and in the nominal group. In factive and -er nominalizations, they set us on the track of the systems’ basic grammatico-semantic characteristics: the link which deverbal -er nominalizations establish between an entity and a process turns out to be strikingly similar to that realized by the Subject and the Finite at clause level; the analysis of the internal, interpersonal properties of that-factives, the fact that-constructions and gerundive factives confirms their downranked or ‘nominal’ nature and enables us to define factivity more accurately.
The syntactic motor system
Authors: Roy Alice C. , Arbib Michael A.
Published: September 2007

The human brain has mechanisms that can support production and perception of language. We ground the evolution of these mechanisms in primate systems that support manual dexterity, especially the mirror system that integrates execution and observation of hand movements. We relate the motor theory of speech perception to the mirror system hypothesis for language and evolution; explore links between manual actions and speech; contrast “language” in apes with language in humans; show in what sense the “syntax” implemented in Broca’s area is a “motor syntax” far more general than the syntax of linguistics; and relate communicative goals to sentential form.
Wincenty Lutosławski (1863–1954)
Authors: Pawłowski Adam , Pacewicz Artur
Published: September 2007

La stylométrie est une branche de la linguistique qui se donne pour objet la description quantitative des particularités stylistiques des textes. Dans certains cas, cette description permet, entre autres, d’identifier les auteurs de textes anonymes et de déterminer la chronologie des textes d’un auteur sur la base de leurs traits stylistiques. En analysant le parcours historique de la stylométrie, il serait difficile de nommer l’auteur qui, par ses travaux, aurait donné l’impact décisif à son développement. La lecture des monographies qui décrivent l’histoire de la stylométrie prouve que la plupart des auteurs utilisent les données historiques de manière sélective, en distinguant certains chercheurs et et en demeurant muet sur d’autres. Wincenty Lutosławski (1863–1954) est un bon exemple de chercheur oublié (ou du moins sous-estimé) par les chercheurs contemporains. C’est pourtant lui qui, à la fin du XIXe siècle, a inventé le terme de ‘stylométrie’ et a défini les principes de cette ‘nouvelle science’. Dans notre article, nous présentons et discutons les points suivants : l’importance de la chronologie pour l’interprétation de la philosophie platonicienne, la définition de l’objet de la stylométrie, les chronologies platoniciennes les plus importantes, la description et l’évaluation de l’apport de Lutosławski au développement de la méthode stylométrique, et l’origine de la stylométrie. En conclusion, nous essayons de redéfinir la place occupée par Lutosławski dans l’histoire des sciences du langage.
Disciplining women?
Authors: Percy Carol
Published: September 2007

On the basis of an analysis of works for children published by Ellenor Fenn (1743–1813) in the 1780s, an argument is offered concerning the significance of English grammar to the domestic education of elite boys and girls. The topic is contextualized in overviews of the high social value of grammar and of the maternal educator, idealized for her ‘civilizing’ influence, especially on men. Some elite mothers were criticized by Fenn and her contemporaries for preferring public life to domestic responsibility or for indulging their children. While acknowledging the difficulties of child-rearing and the challenges to women’s domestic authority, Fenn and others spell out the consequences of failing to train young males in particular. The author argues that educational toys and age-graded books like Fenn’s encouraged loving mothers to socialize their children while simul­taneously displaying their wealth. Grammar, because of its associations with order, was central to this domestic curriculum. While not overtly challenging conventional gender roles, Fenn represented ‘sprightly’ young females not as intellectually superficial but as naturally quick to learn and playfully able to teach young males and females. Their pedagogical duties justified young women’s education and granted women educators domestic authority and public importance.
Using graphics to support comprehension of dynamic information in texts
Authors: Lowe Richard K. , Promono Harto
Published: September 2007

Little is known about the influence of micro-level design factors on the effectiveness with which static and animated graphics support comprehension of dynamic information. Graphics are frequently used as adjuncts to written and spoken text with the aim of addressing any potential ambiguities that may arise during interpretation. When used to depict information about temporal change, graphics can present the situational dynamics with varying degrees of explicitness. With static graphics, viewer interpretation is reliant on some degree of inference; whereas with animated graphics, the dynamics can be presented in a direct, analog form. The effectiveness of static and animated graphics for portraying dynamic subject matter appears to be closely related to fine-grained aspects of the interaction between the graphic and its user that may be missed if a largely intuitive approach to design is adopted. Selected findings from empirical research into the effects of content, cues, background knowledge and attentional influences are discussed as a basis for suggesting a more principled approach to the design of adjunct graphics.
Constructing meaning from multiple information sources as a function of personal epistemology
Authors: Braten Ivar , Stromso Helge
Published: September 2007

Ten student teachers having naïve epistemological beliefs and nine having sophisticated beliefs read seven texts about Attention Deficit Hyperactivity Disorder, representing partly conflicting views on the topic. The results indicated that students with sophisticated beliefs were better at melding information from multiple perspectives. Moreover, they suggested that the students attained this advantage by engaging in more active use of deeper level text-processing strategies. In terms of practical implications, this research suggests that students working with multiple texts should be given the opportunity to reflect on their epistemological stances and also be taught how they can strategically construct meaning in this complex task environment.