bluuebunny/crossref_metadata_2025 huggingface dataset:
Elastic wave amplitudes in shock-compressed thin polycrystalline aluminum samples
Authors: Winey J. M. , LaLone B. M. , Trivedi P. B. , Gupta Y. M.
Published: October 2009

Thin polycrystalline aluminum (1050 and 6061-T6 alloys) samples were shocked to 4 GPa to examine elastic wave attenuation not observed in thicker samples (1–10 mm). Using laser interferometry in plate impact experiments, particle velocity histories were obtained for 0.08–1 mm thick samples, thinned from bulk material. Unlike past work on thicker samples, thin 1050 Al samples reveal large and rapidly attenuating elastic wave amplitudes, indicating a time-dependent elastic-plastic response. Extrapolation of measured elastic wave amplitudes to larger sample thicknesses agrees well with previously observed amplitudes for thicker 1050 and 1060 Al samples. Thus, all of the results for relatively pure polycrystalline Al can be reconciled into a single consistent picture: elastic wave attenuation, due to time-dependent elastic-plastic response, is confined to material close to the impact surface. In contrast to the 1050 Al results, thin 6061-T6 Al samples reveal an elastic wave amplitude of ∼0.7 GPa with no attenuation, in quantitative agreement with previous results for thick 6061-T6 Al samples. The lack of elastic wave attenuation even in thin samples suggests that elastic wave amplitudes in shocked 6061-T6 Al are governed by different plastic deformation mechanisms than those for shocked pure Al.
Femtosecond pump-probe photoionization-photofragmentation spectroscopy: Photoionization-induced twisting and coherent vibrational motion of azobenzene cation
Authors: Ho Jr-Wei , Chen Wei-Kan , Cheng Po-Yuan
Published: October 2009

We report studies of ultrafast dynamics of azobenzene cation using femtosecond photoionization-photofragmentation spectroscopy. In our experiments, a femtosecond pump pulse first produces an ensemble of azobenzene cations via photoionization of the neutrals. A delayed probe pulse then brings the evolving ionic system to excited states that ultimately undergo ion fragmentation. The dynamics is followed by monitoring either the parent-ion depletion or fragment-ion formation as a function of the pump-probe delay time. The observed transients for azobenzene cation are characterized by a constant ion depletion modulated by a rapidly damped oscillatory signal with a period of about 1 ps. Theoretical calculations suggest that the oscillation arises from a vibration motion along the twisting inversion coordinate involving displacements in CNNC and phenyl-ring torsions. The oscillation is damped rapidly with a time constant of about 1.2 ps, suggesting that energy dissipation from the active mode to bath modes takes place in this time scale.
Fabrication and photovoltaic property of ordered macroporous silicon
Authors: Peng Kui-Qing , Wang Xin , Wu Xiaoling , Lee Shuit-Tong
Published: October 2009

Wafer-scale highly ordered macroporous silicon (macro-PSi) has been fabricated by the combination of lithography and metal-catalyzed Si etching in hydrofluoric acid. The periodicity and dimensions of the pores can be controlled by the lithography and the etching conditions. Significantly, this catalytic etching method is capable of creating uniform pores on Si substrates of any type of conductivity. Photovoltaic application results showed that the as-prepared macro-PSi samples are photoactive, and became more effective in solar energy conversion via surface modification with metal particles. The present fabrication method of macroporous Si structures could open potential applications in solar cells, photonic crystals, sensors, and batteries.
Conductive versus capacitive coupling for cell electroporation with nanosecond pulses
Authors: French David M. , Uhler Michael D. , Gilgenbach Ronald M. , Lau Y. Y.
Published: October 2009

Experiments and simulations were performed to determine the difference between capacitive coupling and conductive connection for the electroporation of cells. The pulses used in the experiments have a peak voltage of 24 kV, 0.6 ns rise time, and 1.6 ns full width at half maximum. Experiments performed compare the conductive connection of the cell suspension versus a capacitively coupled cell suspension. The magnitude of the electric field was 16 kV/cm in both cases; however, the pulse shape is different. For the conductively connected case the cells located between the electrodes experienced an electric field in one direction only, whereas cells located between the electrodes in the capacitive coupling case were subject to an electric field that reverses direction. For the capacitively coupled case the bipolar pulse leads to no net cell charging. The conductive connection case is different, in that cells are left with a net polarization after the pulse is applied. Experimentally, only cells subject to the pulse with conductive connection demonstrated electroporation with the drug Bleomycin.
Parameter survey of the performance of a noncontact ultrasonic motor
Authors: Cheng L. P. , Zhang S. Y.
Published: October 2009

Acoustic streaming was proposed to drive rotary motors, where a gas layer exists between the stator and the rotor. With numerical simulations for this kind of noncontact ultrasonic motors, the influences of the parameters of the air flow on the performance of the motors are calculated and analyzed. The results show that the replacement of invariant viscosity by the temperature-dependent viscosity decreases the rotor velocity by ∼11%. Heat conduction is found to play a trivial role. It is also revealed that the rotor velocity increases more and more rapidly as the thickness of the air gap becomes smaller and smaller. Most importantly, we demonstrated that this kind of motor is very stable, and the rotor velocity is insensitive to the working temperature of the environment.
Computation for the canonical measures of a colored disordered lattice gas and spectral gap
Authors: Halim Zeghdoudi , Hacène Boutabia
Published: October 2009

In this work we deal with spectral gap and canonical measures related to a model called colored disordered lattice gas. We consider the approach used in the work of Dermoune and Heinrich [“A small step towards the hydrodynamic limit of a colored disordered lattice gas,” C. R. Math. Acad. Sci. 339, 507–511 (2004)]. We suggest a new computation for the canonical measures. Also, we propose the explicit form of the spectral gap for colored disordered lattice gas of exclusion processes which plays an important role in the study of hydrodynamic limit.
Predicting the lifetime of copper/barrier/dielectric systems: Insights for designing better barriers for reducing copper ion drift/diffusion into the dielectric
Authors: Achanta Ravi S. , Gill William N. , Plawsky Joel L.
Published: October 2009

Our previous drift/diffusion model describing the effect of the transport and accumulation of copper ions on the time to failure of dielectrics was extended here to include metallic barriers and the effect of an elastic drift term. The results of the model were compared with experimental data on the time to failure of SiO2 dielectrics that included Ru(P) and TaN barriers. Excellent agreement was found, and the success of the Ru(P) compared to the TaN barrier was attributed to the former’s lower copper ion solubility and diffusivity. There is a change in the value of the field acceleration parameter (γ) with barriers that leads to an increase in the projected lifetime. We link this change in γ to a number of factors including the transport of oxidizing species through the barrier responsible for copper ion formation, and the injection and motion of electrons and holes, which are altered in the presence of a barrier between the metal and dielectric.
Descriptions of a linear device developed for research on advanced plasma imaging and dynamics
Authors: Chung J. , Lee K. D. , Seo D. C. , Nam Y. U. , Ko W. H. , Lee J. H. , Choi M. C.
Published: October 2009

The research on advanced plasma imaging and dynamics (RAPID) device is a newly developed linear electron cyclotron resonance (ECR) plasma device. It has a variety of axial magnetic field profiles provided by eight water-cooled magnetic coils and two dc power supplies. The positions of the magnetic coils are freely adjustable along the axial direction and the power supplies can be operated with many combinations of electrical wiring to the coils. A 6 kW 2.45 GHz magnetron is used to produce steady-state ECR plasmas with central magnetic fields of 875 and/or 437.5 G (second harmonic). The cylindrical stainless steel vacuum chamber is 300 mm in diameter and 750 mm in length and has eight radial and ten axial ports including 6-in. and 8-in. viewing windows for heating and diagnostics. Experimental observation of ECR plasma heating has been recently carried out during the initial plasma operation. The main diagnostic systems including a 94 GHz heterodyne interferometer, a high-resolution 25 channel one-dimensional array spectrometer, a single channel survey spectrometer, and an electric probe have been also prepared. The RAPID device is a flexible simulator for the understanding of tokamak edge plasma physics and new diagnostic system development. In this work, we describe the RAPID device and initial operation results.
Ab initio quantum Monte Carlo study of the positronic hydrogen cyanide molecule
Authors: Kita Yukiumi , Maezono Ryo , Tachikawa Masanori , Towler Mike , Needs Richard J.
Published: October 2009

Quantum Monte Carlo methods are used to investigate the binding of a positron to the hydrogen cyanide (HCN) and lithium hydride (LiH) molecules. Our value of the adiabatic positron affinity (PA) of LiH of 1.010(3) eV is very close to the best theoretical value of 1.005 eV, obtained from variational calculations using explicitly correlated Gaussian basis sets [K. Strasburger, J. Chem. Phys. 114, 00615 (2001)]. We have obtained a reliable estimate of 0.0378(48) eV for the PA of the HCN molecule, which is almost 20 times larger than that obtained at the Hartree–Fock level, and strongly supports the binding of a positron in the electrostatic field of the HCN molecule. Our results show the importance of correlation effects for describing weakly bound positronic molecular complexes.
Bandgap characteristics of one-dimensional plasma photonic crystal
Authors: Yin Yan , Xu Han , Yu M. Y. , Ma Yan-yun , Zhuo Hong-bin , Tian Cheng-lin , Shao Fu-qiu
Published: October 2009

When two pump laser pulses intersect in an underdense plasma, plasma Bragg grating (PBG) is induced by the slow-varying ponderomotive force [Z. M. Sheng et al., Appl. Phys. B: Lasers Opt. 77, 673 (2003)]. Such a PBG can be considered as a one-dimensional (1D) plasma photonic crystal (PPC). Here the bandgap characteristic of 1D PPC composed of plasma layers of different densities is investigated theoretically and numerically. It is found that when the maximum density is lower than the critical density of the pump laser, there is only one normal-incidence bandgap. When the maximum density is higher than the critical density of the pump laser, high-order bandgaps are found. The theoretical results are verified by 1D particle-in-cell simulations.
Lasing characteristics of a Limaçon-shaped microcavity laser
Authors: Yi Chang-Hwan , Kim Myung-Woon , Kim Chil-Min
Published: October 2009

We investigate lasing characteristics of a Limaçon-shaped InGaAsP semiconductor microcavity laser. When the cavity is pumped with dc current, the laser generates directional emissions. Near the threshold a series of modes with equidistantly spaced resonant frequencies emit. From the mode spacing we confirm the emission of whispering gallery-type resonance modes. As the injection current increases, a single resonance mode becomes dominant with directional emission. The quality factor of the single mode is obtained near the threshold, which is larger than 22 000.
Coupled chirped vertical gratings for on-chip group velocity dispersion engineering
Authors: Tan D. T. H. , Ikeda K. , Fainman Y.
Published: October 2009

Coupled chirped vertical gratings are proposed for on-chip group velocity dispersion engineering. The device circumvents the need for directional couplers or circulators to redirect compensated data. Finite difference time domain simulations and experimental verification of fabricated devices are performed. Dispersion values of up to 8.4×105 ps/nm/km are demonstrated.
The molecular dissociation of formaldehyde at medium photoexcitation energies: A quantum chemistry and direct quantum dynamics study
Authors: Araújo Marta , Lasorne Benjamin , Magalhães Alexandre L. , Worth Graham A. , Bearpark Michael J. , Robb Michael A.
Published: October 2009

The mechanisms of radiationless decay involved in the photodissociation of formaldehyde into H2 and CO have been investigated using complete active space self-consistent field (CASSCF) calculations and direct dynamics variational multiconfiguration Gaussian (DD-vMCG) quantum dynamics in the S1, T1, and S0 states. A commonly accepted scheme involves Fermi Golden Rule internal conversion from S1 followed by dissociation of vibrationally hot H2CO in S0. We recently proposed a novel mechanism [M. Araujo et al., J. Phys. Chem. A 112, 7489 (2008)] whereby internal conversion and dissociation take place in concert through a seam of conical intersection between S1 and S0 after the system has passed through an S1 transition barrier. The relevance of this mechanism depends on the efficiency of tunneling in S1. At lower energy, an alternative scheme to internal conversion involves intersystem crossing via T1 to regenerate the reactant before the S0 barrier to dissociation. We propose here a previously unidentified mechanism leading directly to H2 and CO products via T1. This channel opens at medium energies, near or above the T1 barrier to dissociation and still lower than the S1 barrier, thus making T1 a possible shortcut to molecular dissociation.
A 1 A laser driver in 0.35 μm complementary metal oxide semiconductor technology for a pulsed time-of-flight laser rangefinder
Authors: Nissinen Jan , Kostamovaara Juha
Published: October 2009

An integrated complementary metal oxide semiconductor (CMOS) current pulse generator is presented which achieves an ampere-scale peak current pulse with a rise time and pulse width of less than 1 and 2.5 ns (pulse width at half maximum), respectively. The generator is implemented in a 0.35 μm CMOS process and consists of four parallel n-type metal oxide semiconductor transistors driven by a scaled buffer chain to achieve fast switching.
Midinfrared intersubband absorption in GaN/AlGaN superlattices on Si(111) templates
Authors: Kandaswamy P. K. , Machhadani H. , Bougerol C. , Sakr S. , Tchernycheva M. , Julien F. H. , Monroy E.
Published: October 2009

We report on the observation of midinfrared intersubband absorption in Si-doped GaN/AlGaN superlattices grown by plasma-assisted molecular-beam epitaxy on semi-insulating GaN-on-Si(111) templates. TM-polarized absorption attributed to transition between the first two electronic levels in the quantum wells peaked in the range from 2 to 9 μm. The relative spectral width remains around 20% in the whole midinfrared spectral range. Doping is predicted to have a large influence on the intersubband absorption energy due to screening of polarization-induced internal electric field.
Low temperature magnetocaloric effect in polycrystalline BiFeO3 ceramics
Authors: Ramachandran B. , Rao M. S. Ramachandra
Published: October 2009

We report on the structural, thermal, and magnetic properties of polycrystalline BiFeO3 synthesized by sol-gel route. Powder x-ray diffraction data of the BiFeO3 sample was refined with rhombohedral structure with space group R3c. Magnetization and coercive field measurements showed weak ferromagnetic nature below 10 K. We also investigated the low temperature magnetocaloric effect in polycrystalline BiFeO3 ceramics. The anomalies observed in the magnetic entropy change of the BiFeO3 ceramics were close to that of low temperature phase transitions. The combined relative errors in the magnetic entropy change are found to vary from 4% to 15% with increase in temperature.
High temperature ferroic phase transitions and evidence of paraelectric cubic phase in the multiferroic 0.8BiFeO3–0.2BaTiO3
Authors: Singh Anar , Patel Jay Prakash , Pandey Dhananjai
Published: October 2009

We present here results of a powder x-ray diffraction study on the multiferroic 0.8BiFeO3–0.2BaTiO3 in the temperature range of 300–925 K. Our results provide unambiguous evidence for paraelectric cubic phase. We do not find any evidence for intermediate β-phase in our studies. The rhombohedral to cubic phase transition is shown to be of first order as revealed by the coexistence of cubic and rhombohedral phases over 100 K range and a discontinuous change in the unit cell volume. An anomaly in the unit cell volume at the magnetic transition temperature indicative of the magnetoelastic coupling is also reported.
Penning ionization and ion fragmentation of formamide HCONH2 by He∗, Ne∗, and Ar∗ in molecular beams
Authors: Madison Tamika A. , Siska P. E.
Published: October 2009

Mass spectra from Penning ionization by metastable atom bombardment (MAB) in the title system at kinetic energies near 1 kcal/mol are reported. The experiments employ a supersonic excited noble gas beam crossing an effusive beam of formamide vapor. Product ions are extracted perpendicular to the plane of the beams, analyzed by a quadrupole mass filter, and counted by a scintillation-type ion counter. Relative to 70 eV electron impact, the He∗ and Ne∗ spectra show more extensive breakage of C–N and C–H bonds despite the smaller available energy, while the Ar∗ spectrum shows only the molecular ion (m/z 45), H atom elimination (44), and the decarbonylation products CO+NH3+ (17). Fragmentation in the latter system has been analyzed using a combination of ab initio calculations and Rice–Ramsperger–Kassel–Marcus theory with tunneling correction; good agreement with the experimental 45/44/17 intensity ratio 100/6.8±0.7/6.2±1.7 is obtained. 15% of m/z 17 and 50% of m/z 44 is attributed to tunneling. The ab initio decarbonylation reaction path yields a hydrogen bonded H2N–HCO+ transition state, which transfers a proton while proceeding downhill to the observed products, while both the path and the energetics support the earlier conclusion that the lowest lying electronically excited state of the ion (2π or 2a″) crosses the ground state early along the reaction path, thereby dominating the dynamics of decarbonylation.
Two-well terahertz quantum-cascade laser with direct intrawell-phonon depopulation
Authors: Kumar Sushil , Chan Chun Wang I. , Hu Qing , Reno John L.
Published: October 2009

We report the simplest quantum-cascade laser (QCL) to-date with only two quantum wells per QCL period, and at low temperatures, only three subband levels participate in electron transport. The lower laser level is directly depopulated via intrawell longitudinal-optical phonon scattering, which is in contrast with all the previously demonstrated terahertz QCLs, and maintains an ultrashort lower level lifetime under all operating bias and temperatures. Optical gain is due to a diagonal photon-assisted tunneling transition. Laser operation at 4.6 THz is obtained up to a heat-sink temperature of 121 K with a low-temperature threshold current density of 350 A/cm2. Due to the simplicity of a two-well design, its electrical transport behavior could be analyzed in greater detail. A thermally activated carrier leakage due to higher-energy parasitic levels is speculated to be the most likely cause of a steep rise in the lasing threshold current density with temperature.
Effects of gas flow rate on the length of atmospheric pressure nonequilibrium plasma jets
Authors: Li Qing , Li Jiang-Tao , Zhu Wen-Chao , Zhu Xi-Ming , Pu Yi-Kang
Published: October 2009

Effects of gas flow rate on the length of atmospheric pressure plasma jets have been investigated using a capillary dielectric barrier discharge configuration. For the discharge in only downstream region, three distinguishable modes of plasma jet length versus argon gas flow rate, namely, laminar, transition, and turbulent jet mode, have been identified. For the case of discharge in both downstream and upstream regions, the curve of length versus flow rate has significant “dent” in the laminar jet mode for pure helium, neon, and argon flow gas spraying into air ambient.
Spatially controlled reversible colloidal self-assembly
Authors: Fernandes Gregory E. , Beltran-Villegas Daniel J. , Bevan Michael A.
Published: October 2009

We studied the localized self-assembly of colloidal crystals on a topographically patterned substrate. A competition between particle and pattern interactions provided the ability to reversibly assemble quasi-two-dimensional colloidal crystals on a periodic landscape. The assembly process was visualized and controlled in real-space and real-time using video microscopy. Independent measurements and computer simulations were used to quantify all interactions controlling self-assembly. Steady-state studies characterized spatially inhomogeneous, coexisting fluid and crystal microstructures at various stages of assembly. Microstructures arise from a balance of local sedimentation equilibria within potential energy features and a tunable pairwise depletion attraction between colloids. Transient colloidal crystal self-assembly occurred via a quasiequilibrium process as characterized by continuously evolving spatial profiles of local density, bond orientational order, and self-diffusivities.
Atomic structure of functional interfaces in Sr2RuO4/Sr3Ru2O7 eutectic crystals
Authors: Ciancio R. , Pettersson H. , Börjesson J. , Lopatin S. , Fittipaldi R. , Vecchione A. , Kittaka S. , Maeno Y. , Pace S. , Olsson E.
Published: October 2009

Sr 2 RuO 4 / Sr 3 Ru 2 O 7 eutectic system is investigated by transmission electron microscopy (TEM) and high angle annular dark field scanning TEM (STEM). The Sr2RuO4/Sr3Ru2O7 lamellar structure allows studying tunneling and proximity effects between spin-triplet superconductor Sr2RuO4 and metamagnetic normal metal Sr3Ru2O7. Our analyses reveal two typologies of interfaces within the eutectic: interfaces parallel to the growth direction are sharp and defect-free whereas interfaces perpendicular to the growth direction appear wavy and decorated with Ru precipitates. These results indicate that interfaces parallel to the growth direction are the best candidates for Sr2RuO4/Sr3Ru2O7 natural junctions to study the unusual superconductivity of Sr2RuO4.
A stretchable temperature sensor based on elastically buckled thin film devices on elastomeric substrates
Authors: Yu Cunjiang , Wang Ziyu , Yu Hongyu , Jiang Hanqing
Published: October 2009

Stretchable electronics and sensors have been attracting significant attention due to their unique characteristics and wide applications. This letter presents a prototype of a fully stretchable temperature sensor on an elastomeric substrate. The sensor was fabricated on a silicon-on-insulator wafer and then transferred to a prestrained elastomeric polydimethylsiloxane substrate. Releasing the prestrain on the substrates led to the formation of the microscale, periodic, wavy geometries of the sensor. The thin wavy sensor device can be reversibly bent and stretched up to 30% strain without any damage or performance degradation. A theoretical analysis was also developed to estimate the wavy profile.
Temperature-dependent transition from injection-limited to space-charge-limited current in metal-organic diodes
Authors: Zheng Yi , Wee Andrew T. S. , Troadec Cedric , Chandrasekhar N.
Published: October 2009

Based on the assumption that the contact barrier height determines the current flow in organic semiconductor-based electronic devices, charge injection at metal-organic (MO) interfaces has been extensively investigated, while space-charge conduction in organic bulk is generally overlooked. Recent theoretical modeling and simulation have pointed out that such a simplification is questionable due to the hopping nature of charge injection and hopping-related space-charge conduction. Here we show experimentally that charge transport in MO diodes is a complex interplay between injection-limited current (ILC) and space-charge-limited current (SCLC). We report the experimental observation of ILC-to-SCLC transition in Ag/pentacene/Ag diodes as a function of temperature.
Atomic charge densities generated using an iterative stockholder procedure
Authors: Lillestolen Timothy C. , Wheatley Richard J.
Published: October 2009

A simple computational technique is introduced for generating atomic electron densities using an iterated stockholder procedure. It is proven that the procedure is always convergent and leads to unique atomic densities. The resulting atomic densities are shown to have chemically intuitive and reasonable charges, and the method is used to analyze the hydrogen bonding in the minimum energy configuration of the water dimer and charge transfer in the borazane molecule.
Azimuthally correlated ablation between z-pinch wire cores
Authors: Zier J. C. , Douglass J. D. , Blesener I. C. , Blesener K. S. , Chalenski D. A. , Gilgenbach R. M. , Greenly J. B. , Hammer D. A. , Knapp P. F. , Kusse B. R. , Lau Y. Y. , McBride R. D. , Syed W. , Yu E. P.
Published: October 2009

Azimuthally correlated wire core ablation was compared for closely spaced versus widely spaced wires in a 1 MA Z-pinch. X-ray point-projection diagnostics revealed that 240 μm spaced wires exhibited a correlation coefficient approaching unity in both real space and in k-space. This correlated ablation between wires at a fixed axial location is believed to occur due to an enhanced, localized Joule heating. Wires separated by 2.47 mm or greater were uncorrelated in real space, but correlated in k-space, indicating the ablation structure between wires was shifted in phase.
Electrical bistability of copper (I) sulfide nanocrystals blending with a semiconducting polymer
Authors: Tang Aiwei , Teng Feng , Qian Lei , Hou Yanbing , Wang Yongsheng
Published: October 2009

Electrically bistable devices were fabricated based on blends of n-dodecanethiol capped copper (I) sulfide (Cu2S) nanocrystals and a semiconducting polymer using a simple spin-coating method. Reproducible electrical bistability and negative differential resistance effects were observed in current-voltage characteristics. A large ON/OFF current ratio of 104 at negative voltages could be obtained by applying different amplitude of sweeping voltages and varying the mass ratios of Cu2S nanocrystals to polymer. The observed conductance switching was speculated to be resulted from electric-filed-induced charge transfer between the nanocrystals and polymer, and negative differential resistance behavior could be attributed to the charge trapping in the nanocrystals.
A simple wall-layer model for large eddy simulation with immersed boundary method
Authors: Roman F. , Armenio V. , Fröhlich J.
Published: October 2009

A wall-layer model is proposed for large eddy simulation of high Reynolds number turbulent flows in conjunction with immersed boundaries. The model is based on two main steps: the reconstruction of the velocity field at the first grid point off the immersed body and the modelization of the actual wall shear stress at the immersed boundary through imposition of a Reynolds averaged Navier–Stokes-like eddy viscosity obtained by means of analytical considerations. The model is tested in a turbulent plane channel flow with walls reproduced by immersed boundaries considering both Cartesian and curvilinear grids. Even with coarse and distorted grids the proposed methodology is able to reproduce accurately both first- and second-order turbulent statistics.
Impact of Si growth rate on coherent electron transport in Si:P delta-doped devices
Authors: Goh K. E. J. , Simmons M. Y.
Published: October 2009

We address the impact of Si growth rate on electron transport in Si:P δ-doped devices encapsulated by low temperature Si molecular beam epitaxy. Si growth rates ranging from 0.05 to 2.2 Å s−1 were used in conjunction with 250 °C Si overgrowth. Using a combination of scanning tunneling microscopy and 4.2 K magnetotransport measurements, we find that high growth rates tend to degrade the crystal quality of the Si cap layer resulting in shorter electron mean free path and phase coherence length in such devices.
Magnetoelectric voltage gain effect in a long-type magnetostrictive/piezoelectric heterostructure
Authors: Wang Yaojin , Zhao Xiangyong , Di Wenning , Luo Haosu , Or Siu Wing
Published: October 2009

We report a large voltage gain of 130, together with a high magnetoelectric voltage coefficient of 7.6 V/Oe, in a long-type heterostructure made by combining a coil-wound, length-magnetized magnetostrictive Tb0.3Dy0.7Fe1.92 (Terfenol-D) alloy plate and a length-polarized piezoelectric 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 single-crystal plate along the length direction. The observed voltage gain is found to originate from the product effect of the electromagnetic induction in the coil and the resonance magnetoelectric effect in the heterostructure.
Correlation between structural relaxation and shear transformation zone volume of a bulk metallic glass
Authors: Pan D. , Yokoyama Y. , Fujita T. , Liu Y. H. , Kohara S. , Inoue A. , Chen M. W.
Published: October 2009

The effect of structural relaxation on shear transformation zones (STZs) in a Zr70Ni16Cu6Al8 glassy alloy is evaluated. Upon annealing, the measured STZ size dramatically decreases with moderate augment of mass density caused by the increase of icosahedra short-range orders. The greater atomic packing density gives rise to involvement of lesser atoms in the formation of STZs and thereby degradation of ductility. This study demonstrates that STZ volume is a key parameter reflecting the intrinsic relationship between atomic structure and mechanical properties of metallic glasses.
Millimeter wave notch filters based on ferromagnetic resonance in hexagonal barium ferrites
Authors: Song Young-Yeal , Ordóñez-Romero César L. , Wu Mingzhong
Published: October 2009

A hexagonal ferrite-based millimeter wave notch filter was demonstrated. The filter consists of an M-type BaFe12O19 (BaM) slab sitting on top of a stripline. The band-stop filtering response originates from the ferromagnetic resonance absorption in the BaM slab. The BaM slab has an in-plane uniaxial anisotropy field of 17 kOe. This anisotropy field facilitates the operation of the filter beyond 50 GHz without a need of high external fields. The operating frequency increases linearly with the external field, while the bandwidth versus field profile shows a U-shaped response. The physical mechanisms for these responses were discussed.
Shadows on the Path: Negotiating Geopolitics on an Urban Section of Britain's South West Coast Path
Authors: Sidaway James D
Published: October 2009

The challenge of producing geographical narrative has recently been enhanced through work under the banners of affect and nonrepresentational theory. This has been registered in a range of topics in cultural, social, and political geography, and impacted in work on landscape. Such work has antecedents in several decades of humanistic geography and is immersed in more recent writings on performance and subjectivity and the critical rethinking of being, dwelling, movement, and place. With those and allied works in mind, this paper interrogates such literatures through writing about walking an urban section (through the port of Plymouth) of Britain's South West Coast Path; one of the few places where any of the twenty demarcated national trails and long-distance routes in the UK intersects a city. The existence of a rich literature on strolling in urban space opens up possibilities and connections. However the approach here is deliberately eclectic and also draws on works from/about geopolitics, natural history, and urban studies. My purpose here is to bring such literatures into closer and productive dialogue, through an account that shifts geographical and temporal scales and perspectives. This is done through the device of an evening's walk along a section of the path: negotiating spaces of capital and sovereignty. Military geography and security/insecurity emerge as master keys to how topography has been shaped here and the paper draws a series of connections between landscape, life, death, and military activities, both near and far. What the paper aims to do, therefore, is to illustrate how geopolitics affects us—to illustrate how the repercussions of militarism, war, and death are folded into the textures of an everyday urban fabric. This has implications for how other landscapes, places, and paths might be understood.
The Relative Importance of Visual, Auditory, and Haptic Information for the User's Experience of Mechanical Switches
Authors: Mortensen Ditte H , Bech Søren , Begault Durand R , Adelstein Bernard D
Published: October 2009

While the use of hand tools and other everyday manually controlled devices is naturally accompanied by multisensory feedback, the deployment of fully multimodal virtual interfaces requires that haptic, acoustic, and visual cues be synthesised. The complexity and character of this synthesis will depend on a thorough understanding of the multimodal perceptual experience, including the interrelations between the individual sensory channels during manual interaction. In this study seventy participants were asked to rank the manual operation of ten electromechanical switches according to preference. The participants were randomly assigned in groups of ten to one of seven sensory presentation conditions. These conditions comprised six bimodal and unimodal sensory combinations created by selectively restricting the flow of haptic, auditory, and visual information, plus one condition in which ful sensory information was available. A principal components analysis on the obtained ranking data indicated that the sensory conditions with unimpeded haptic information were clearly distinct from those in which the haptic cues were impeded. The analysis also showed that, for switch use, the unimodal haptic condition most closely approached the condition with combined haptic, auditory, and visual feedback, compared with all of the conditions where haptic feedback was restricted.
Word Recognition Processes Modulate the Naso-Temporal Asymmetry of the Human Visual Field
Authors: Lavidor Michal , Alexander Tim , McGraw Paul V
Published: October 2009

Many visual tasks display a well-documented naso-temporal asymmetry (NTA), where sensitivity is greater to stimuli presented in the temporal hemifield. Four-letter strings were presented at various eccentricities under monocular vision conditions, and observers were asked to classify the stimuli as ‘words’ or ‘non-words’ in a lexical decision task (experiment 1). In experiment 2, the same observers had to classify the stimuli as ‘darker’ or ‘lighter’ (contrast discrimination). Apart from the task, the visual conditions and stimuli were identical in both experiments. The typical temporal hemifield advantage was found for a contrast discrimination task in both English and Hebrew readers, but only for lexical decision judgments in Hebrew readers. The lack of the expected NTA in English readers that was observed only for a reading but not a low-level visual task indicates that language lateralisation and reading-related learning can override fundamental, anatomically based, visual asymmetries.
The Relevance of Symmetry in Line Length Perception
Authors: Charras Pom , Lupiáñez Juan
Published: October 2009

The length of a whole line is overestimated in comparison to the sum of its parts (Künnapas, 1955 Journal of Experimental Psychology49 134–140). This has been considered to be true for many years, although recent studies have demonstrated that it is not always so. The perception of the length of a whole line is highly dependent on the configuration of its two parts. More precisely, whereas a whole line is perceived as longer than the sum of symmetrically bisected line parts, this overestimation decreases when compared to the sum of the lengths of asymmetrically bisected line parts. Furthermore, the extent of overestimation depends on the degree of asymmetry, so that when the two parts are greatly asymmetric in length, the whole is no longer overestimated (Wolfe et al, 2005 Perception & Psychophysics67 967–979). Here, two experiments are reported in which a vertical/horizontal line length comparison task was used to investigate how line bisection affects length estimation. The results give rise to a new general principle characterising the mechanisms of visual perception: the sum of the lengths of two asymmetrically bisected parts is perceived as greater than that of two symmetrically bisected parts. Also bisection plays a critical role in length perception by preventing vertical bias.
The interaction of TIGIT with PVR and PVRL2 inhibits human NK cell cytotoxicity
Authors: Stanietsky Noa , Simic Hrvoje , Arapovic Jurica , Toporik Amir , Levy Ofer , Novik Amit , Levine Zurit , Beiman Meirav , Dassa Liat , Achdout Hagit , Stern-Ginossar Noam , Tsukerman Pinhas , Jonjic Stipan , Mandelboim Ofer
Published: October 2009

NK cell cytotoxicity is controlled by numerous NK inhibitory and activating receptors. Most of the inhibitory receptors bind MHC class I proteins and are expressed in a variegated fashion. It was recently shown that TIGIT, a new protein expressed by T and NK cells binds to PVR and PVR-like receptors and inhibits T cell activity indirectly through the manipulation of DC activity. Here, we show that TIGIT is expressed by all human NK cells, that it binds PVR and PVRL2 but not PVRL3 and that it inhibits NK cytotoxicity directly through its ITIM. Finally, we show that TIGIT counter inhibits the NK-mediated killing of tumor cells and protects normal cells from NK-mediated cytoxicity thus providing an “alternative self” mechanism for MHC class I inhibition.
Tumor-associated and microbial proteases compromise host IgG effector functions by a single cleavage proximal to the hinge
Authors: Brezski Randall J. , Vafa Omid , Petrone Diane , Tam Susan H. , Powers Gordon , Ryan Mary H. , Luongo Jennifer L. , Oberholtzer Allison , Knight David M. , Jordan Robert E.
Published: October 2009

The successful elimination of pathogenic cells and microorganisms by the humoral immune system relies on effective interactions between host immunoglobulins and Fcγ receptors on effector cells, in addition to the complement system. Essential Ig motifs that direct those interactions reside within the conserved IgG lower hinge/CH2 interface. We noted that a group of tumor-related and microbial proteases cleaved human IgG1s in that region, and the “nick” of just one of the heavy chains profoundly inhibited IgG1 effector functions. We focused on IgG1 monoclonal antibodies (mAbs) since IgG1 is the most abundant human subclass and demonstrates robust Fc-mediated effector functions. The loss of Fc-mediated cell killing activities was correlated with diminished binding to the Fcγ family of receptors, but a similar decrease in affinity was not observed toward the FcRn receptor that maintains IgG in circulation. Endogenous human IgG cleavage products of comparable size to mAbs with the single cleavage were detected by Western blot analysis in synovial fluid from patients with rheumatoid arthritis and in breast carcinoma extracts. Their detection is problematic under physiological conditions, since there is no loss of structure, and antigen-binding capability is unaffected. These findings suggest that within the hostile proteolytic microenvironments associated with many diseases, key effector functions of host IgGs, or therapeutic Abs, may be compromised.
The crystal structure of sphingosine-1-phosphate in complex with a Fab fragment reveals metal bridging of an antibody and its antigen
Authors: Wojciak Jonathan M. , Zhu Norman , Schuerenberg Karen T. , Moreno Kelli , Shestowsky William S. , Hiraiwa Masao , Sabbadini Roger , Huxford Tom
Published: October 2009

The pleiotropic signaling lipid sphingosine-1-phosphate (S1P) plays significant roles in angiogenesis, heart disease, and cancer. LT1009 (also known as sonepcizumab) is a humanized monoclonal antibody that binds S1P with high affinity and specificity. Because the antibody is currently in clinical trials, it is important to confirm by structural and biochemical analyses that it binds its target in a predictable manner. Therefore, we determined the structure of a complex between the LT1009 antibody Fab fragment and S1P refined to 1.90 Å resolution. The antibody employs unique and diverse strategies to recognize its antigen. Two metal ions bridge complementarity determining regions from the antibody light chain and S1P. The coordination geometry, inductively coupled plasma spectroscopy, surface plasmon resonance spectroscopy, and biochemical assays suggest that these are Ca
2+
. The amino alcohol head group of the sphingosine backbone is recognized through hydrogen bonding interactions from 1 aa side chain and polypeptide backbone atoms of the antibody light and heavy chains. The S1P hydrophobic tail is almost completely enclosed within a hydrophobic channel formed primarily by the heavy chain. Both treatment of the complex with metal chelators and mutation of amino acids in the light chain that coordinate the metal atoms or directly contact the polar head group abrogate binding, while mutations within the hydrophobic cavity also decrease S1P binding affinity. The structure suggests mechanistic details for recognition of a signaling lipid by a therapeutic antibody candidate. Moreover, this study provides direct structural evidence that antibodies are capable of using metals to bridge antigen:antibody complexes.
β-Adrenergic signaling accelerates and synchronizes cardiac ryanodine receptor response to a single L-type Ca2+channel
Authors: Zhou Peng , Zhao Yan-Ting , Guo Yun-Bo , Xu Shi-Ming , Bai Shu-Hua , Lakatta Edward G. , Cheng Heping , Hao Xue-Mei , Wang Shi-Qiang
Published: October 2009

As the most prototypical G protein-coupled receptor, β-adrenergic receptor (βAR) regulates the pace and strength of heart beating by enhancing and synchronizing L-type channel (LCC) Ca2+influx, which in turn elicits greater sarcoplasmic reticulum (SR) Ca2+release flux via ryanodine receptors (RyRs). However, whether and how βAR-protein kinase A (PKA) signaling directly modulates RyR function remains elusive and highly controversial. By using unique single-channel Ca2+imaging technology, we measured the response of a single RyR Ca2+release unit, in the form of a Ca2+spark, to its native trigger, the Ca2+sparklet from a single LCC. We found that acute application of the selective βAR agonist isoproterenol (1 μM, ≤20 min) increased triggered spark amplitude in an LCC unitary current-independent manner. The increased ratio of Ca2+release flux underlying a Ca2+spark to SR Ca2+content indicated that βAR stimulation helps to recruit additional RyRs in synchrony. Quantification of sparklet-spark kinetics showed that βAR stimulation synchronized the stochastic latency and increased the fidelity (i.e., chance of hit) of LCC-RyR intermolecular signaling. The RyR modulation was independent of the increased SR Ca2+content. The PKA antagonists Rp-8-CPT-cAMP (100 μM) and H89 (10 μM) both eliminated these effects, indicating that βAR acutely modulates RyR activation via the PKA pathway. These results demonstrate unequivocally that RyR activation by a single LCC is accelerated and synchronized during βAR stimulation. This molecular mechanism of sympathetic regulation will permit more fundamental studies of altered βAR effects in cardiovascular diseases.
Epstein-Barr virus LMP2A bypasses p53 inactivation in a MYC model of lymphomagenesis
Authors: Bieging Kathryn T. , Amick Alexandra C. , Longnecker Richard
Published: October 2009

Although Epstein-Barr virus (EBV) is linked to Burkitt's lymphoma (BL), the role of the virus in lymphomagenesis is unclear. LMP2A, encoded by EBV, can be detected in BL biopsies and has prosurvival functions. We generated mice expressing MYC and LMP2A in B cells. LMP2A/λ-
MYC
mice show greatly accelerated tumor onset. Similar to previous work, we found p53 mutations in λ-
MYC
tumors; however, we detected no mutations in the rapidly arising LMP2A/λ-
MYC
tumors. We further demonstrate that the p53 pathway is functionally intact in LMP2A/λ-
MYC
tumors, which have increased levels of PUMA and sensitivity to p53 activation by Nutlin. This work shows that LMP2A can permit tumorigenesis in the presence of an intact p53 pathway, identifying an important contribution of EBV to BL.
Temporomandibular joint formation requires two distinct hedgehog-dependent steps
Authors: Purcell Patricia , Joo Brian W. , Hu Jimmy K. , Tran Pamela V. , Calicchio Monica L. , O'Connell Daniel J. , Maas Richard L. , Tabin Clifford J.
Published: October 2009

We conducted a genetic analysis of the developing temporo-mandibular or temporomandi-bular joint (TMJ), a highly specialized synovial joint that permits movement and function of the mammalian jaw. First, we used laser capture microdissection to perform a genome-wide expression analysis of each of its developing components. The expression patterns of genes identified in this screen were examined in the TMJ and compared with those of other synovial joints, including the shoulder and the hip joints. Striking differences were noted, indicating that the TMJ forms via a distinct molecular program. Several components of thehedgehog(Hh) signaling pathway are among the genes identified in the screen, includingGli2, which is expressed specifically in the condyle and in the disk of the developing TMJ. We found that mice deficient inGli2display aberrant TMJ development such that the condyle loses its growth-plate-like cellular organization and no disk is formed. In addition, we used a conditional strategy to removeSmo, a positive effector of the Hh signaling pathway, from chondrocyte progenitors. This cell autonomous loss ofHhsignaling allows for disk formation, but the resulting structure fails to separate from the condyle. Thus, these experiments establish that Hh signaling acts at two distinct steps in disk morphogenesis, condyle initiation, and disk–condyle separation and provide a molecular framework for future studies of the TMJ.
Theoretical examination of quantum coherence in a photosynthetic system at physiological temperature
Authors: Ishizaki Akihito , Fleming Graham R.
Published: October 2009

The observation of long-lived electronic coherence in a photosynthetic pigment–protein complex, the Fenna–Matthews–Olson (FMO) complex, is suggestive that quantum coherence might play a significant role in achieving the remarkable efficiency of photosynthetic electronic energy transfer (EET), although the data were acquired at cryogenic temperature [Engel GS, et al. (2007) Evidence for wavelike energy transfer through quantum coherence in photosynthetic systems.
Nature
446:782–786]. In this paper, the spatial and temporal dynamics of EET through the FMO complex at physiological temperature are investigated theoretically. The numerical results reveal that quantum wave-like motion persists for several hundred femtoseconds even at physiological temperature, and suggest that the FMO complex may work as a rectifier for unidirectional energy flow from the peripheral light-harvesting antenna to the reaction center complex by taking advantage of quantum coherence and the energy landscape of pigments tuned by the protein scaffold. A potential role of quantum coherence is to overcome local energetic traps and aid efficient trapping of electronic energy by the pigments facing the reaction center complex.