bluuebunny/crossref_metadata_2025 huggingface dataset:
Coverage-dependent quantum versus classical scattering of thermal neon atoms from Li/Cu(100)
Authors: MacLaren D. A. , Huang C. , Levi A. C. , Allison W.
Published: September 2008

We show that subtle variations in surface structure can enhance quantum scattering and quench atom-surface energy transfer. The scattering of thermal energy neon atoms from a lithium overlayer on a copper substrate switches between a classical regime, dominated by multiphonon interactions, and a quantum regime, dominated by elastic diffraction. The transition is achieved by simple tailoring of the lithium coverage and quantum scattering dominates only in the narrow coverage range of θ=0.3–0.6 ML. The results are described qualitatively using a modified Debye–Waller model that incorporates an approximate quantum treatment of the adsorbate-substrate vibration.
Piezoelectric properties of low-temperature sintered Li-modified (Na, K)NbO3 lead-free ceramics
Authors: Wang Ke , Li Jing-Feng , Liu Nan
Published: September 2008

LiNbO 3 -doped (Na, K)NbO3 lead-free piezoceramics were prepared by conventional sintering at a temperature as low as 950 °C using excess Na2O additives. The crystal structure changed from orthorhombic to tetragonal with increasing LiNbO3 amount since the phase transition temperature TO−T shifted downward. In the region of two-phase coexistence, enhanced piezoelectric constant d33 (280 pC/N) and electromechanical coupling factor kp (48.3%) with a high Curie temperature TC (475 °C) were obtained in the nominal composition 0.92(Na0.535K0.48)NbO3–0.08LiNbO3. Our results open up the way to low-temperature sintering of (Na, K)NbO3-based lead-free piezoceramics with high performance.
Bias and temperature dependence of the escape processes in quantum dots-in-a-well infrared photodetectors
Authors: Höglund L. , Holtz P. O. , Pettersson H. , Asplund C. , Wang Q. , Almqvist S. , Smuk S. , Petrini E. , Andersson J. Y.
Published: September 2008

The performance of quantum dots-in-a-well infrared photodetectors (DWELL IPs) has been studied by means of interband and intersubband photocurrent measurements as well as dark current measurements. Using interband photocurrent measurements, substantial escape of electrons from lower lying states in the DWELL structure at large biases was revealed. Furthermore, a significant variation in the escape probability from energy states in the DWELL structure with applied bias was observed. These facts can explain the strong temperature and bias dependence of both photocurrent and dark currents in DWELL IPs.
Fluid-flow characterization with nuclear spins without magnetic resonance
Authors: Crawford C. W. , Xu Shoujun , Siegel Eric J. , Budker Dmitry , Pines Alexander
Published: September 2008

A technique for noninvasive monitoring of flow inside metallic enclosures using laser-based atomic magnetometry is introduced. The analyte is labeled via nuclear magnetization by magnets, thereby combining the polarization and encoding steps. No radiofrequency or audiofrequency pulses are involved. We demonstrate detection of flow inside an aluminum pipe with an inner diameter of 4.9 mm that has a constriction with a diameter of 1.6 mm and a length of 6.4 mm. The results agree with a model of spin density and relaxation indicating that our technique allows for fast, quantitative, and noninvasive diagnostics of flow with potential applications discussed below.
Ballistic nanoindentation of polymers
Authors: Gotsmann B. , Rothuizen H. , Duerig U.
Published: September 2008

Indentation of a sharp (20 nm) cantilevered silicon tip into a polymer (SU8) surface is analyzed experimentally and through finite-element simulations. A rate effect on the microsecond scale that eases indentation is found, in contrast to the commonly observed hardening at high strain rates. The observed rate effect is discussed in terms of adiabatic heating and inertial force overshoot. The estimated magnitude of adiabatic heating is marginal, but the force overshoot itself is large enough to explain the data. The data imply that topographic patterning of a polymer at megahertz rates is feasible.
A multisized piezoelectric microcantilever biosensor array for the quantitative analysis of mass and surface stress
Authors: Shin Sanghun , Kim Jun Pyo , Sim Sang Jun , Lee Jaichan
Published: September 2008

A multisized piezoelectric microcantilever biosensor array with scaling down in two dimensions is presented as a multifunctional resonant cantilever-based sensor platform. The multisized microcantilever array allowed simultaneous sensing of the surface stress as well as mass. The adsorption-induced surface stress and resulting spring constant change were analyzed in the multisized microcantilever array, and a mass sensitivity in the femtogram regime was demonstrated. The array sensor was used to immobilize human IgG on its cantilever surface, suggesting that the dynamic and simultaneous analysis of both adsorption-induced mass and the surface stress is feasible.
Limiting nature of continuum generation in silicon
Authors: Koonath Prakash , Solli Daniel R. , Jalali Bahram
Published: September 2008

Spectral broadening in silicon through self-phase modulation is studied numerically and experimentally in the normal dispersion regime. Temporal dynamics of the free carriers generated during the propagation of optical pulses, through the process of two-photon absorption, affect the amplitude and phase of the optical pulses, thereby determining the nature and extent of the generated spectral continuum. Experimental results are obtained by propagating picosecond optical pulses in a silicon waveguide for intensities that span two orders of magnitude (1–150GW∕cm2). These results validate the conclusions drawn from numerical simulations that the continuum generation has a self-limiting nature in silicon.
Magnetic and magneto-optical properties of Fe-doped SrTiO3 films
Authors: Kim Hyun-Suk , Bi Lei , Dionne G. F. , Ross C. A.
Published: September 2008

Epitaxial films of magnetically doped SrTi1−xFexO3 (x⩽0.5) were grown on (001) LaAlO3 substrates by pulsed laser deposition. Structural and magnetic studies indicate that the observed ferromagnetism is intrinsic rather than from an impurity phase. The higher transparency with Fe doping is attributed to charge compensation resulting from hole doping by Fe incorporation into the SrTiO3 lattice. SrTi0.6Fe0.4O3 has a reasonably high Faraday rotation of 0.078deg∕μm accompanied by low optical loss (0.07dB∕μm), which makes it a promising candidate for integrated waveguide isolator applications.
Directional emission control and increased light extraction in GaN photonic crystal light emitting diodes
Authors: McGroddy K. , David A. , Matioli E. , Iza M. , Nakamura S. , DenBaars S. , Speck J. S. , Weisbuch C. , Hu E. L.
Published: September 2008

Limitations in extraction efficiency of gallium nitride (GaN) photonic crystal (PhC) light emitting diodes (LEDs) are addressed by implementing an LED design using both two-dimensional PhCs in-plane and index guiding layers (IGLs) in the vertical direction. The effects of PhCs on light extraction and emission directionality from GaN LEDs are studied experimentally. Angular-resolved electroluminescence clearly shows the combined effect of controlling the vertical mode profile with the IGLs and tailoring the emission profile with the periodicity of the PhC lattice. Increases in directional emission as high as 3.5 times are achieved by taking advantage of this directionality and guided mode control.
Carrier dynamics and erbium sensitization in silicon-rich nitride nanocrystals
Authors: Li R. , Schneck J. R. , Warga J. , Ziegler L. D. , Dal Negro L.
Published: September 2008

Ultrafast two-color pump-probe measurements, time-resolved photoluminescence (TRPL), and photoluminescence excitation measurements were performed on Si-rich nitride (SRN) and Er doped SRN (Er:SRN) nanocrystals samples. Transient absorption data were compared with picosecond TRPL and excited state absorption cross (ESA) sections σ were measured at different wavelengths. Our data show that σ in Er:SRN, which is approximately 10−19cm2 at 1.54μm, does not scale with the ∼λ2 behavior predicted by simple free carrier absorption models. Finally, our data demonstrate that in Er:SRN efficient energy transfer to Er ions occurs on the nanosecond time scale with reduced ESA compared to Er-doped oxide-based systems.
Hybrid metamaterials enable fast electrical modulation of freely propagating terahertz waves
Authors: Chen Hou-Tong , Palit Sabarni , Tyler Talmage , Bingham Christopher M. , Zide Joshua M. O. , O’Hara John F. , Smith David R. , Gossard Arthur C. , Averitt Richard D. , Padilla Willie J. , Jokerst Nan M. , Taylor Antoinette J.
Published: September 2008

We demonstrate fast electrical modulation of freely propagating terahertz waves at room temperature using hybrid metamaterial devices. The devices are planar metamaterials fabricated on doped semiconductor epitaxial layers, which form hybrid metamaterial—Schottky diode structures. With an applied ac voltage bias, we show modulation of terahertz radiation at inferred frequencies over 2MHz. The modulation speed is limited by the device depletion capacitance which may be reduced for even faster operation.
Theory of grain boundary diffusion induced by the Kirkendall effect
Authors: Yu Hui-Chia , Van der Ven A. , Thornton K.
Published: September 2008

A set of coupled diffusion equations is numerically solved to demonstrate that grain boundary diffusion is significantly enhanced when diffusing atomic species have dissimilar atomic hop frequencies in the bulk. The model is based on a rigorous treatment of two-component substitutional diffusion where vacancies are treated as an additional species. By examining the concentration fields and the eigenvalues of the diffusivity matrix, the origin of the enhanced grain boundary diffusion is explained in terms of the Kirkendall effect.
Improved effective mass theory for silicon nanostructures
Authors: Nehari K. , Lannoo M. , Michelini F. , Cavassilas N. , Bescond M. , Autran J. L.
Published: September 2008

Effective mass theory is known to fail for nanostructures of indirect band gap materials such as silicon. We show that this situation can be remedied by going beyond the conventional second order expansion in the wave vector k. The method including fourth order terms is developed for the conduction band of silicon and applied to the ⟨100⟩-oriented wells, wires, and dots. The energy minima, their shift in k-space, as well as the variation in the effective mass with size are fully predicted from analytical equations containing only bulk parameters. This approach opens the way for accurate simulations of realistic quantum devices avoiding heavy calculations.
Enhanced optical response in doubly waveguided plasmonic gratings
Authors: Zhang Xinping , Feng Shengfei , Liu Hongmei , Wang Li
Published: September 2008

A waveguide fabricated on top of a bottom-waveguided gold-nanowire grating device excites additional resonance modes through interaction between the two waveguides, which overlaps the “intrinsic” resonance mode of the bottom waveguide. Thus, the TE polarized (parallel to the gold nanowires) waveguide mode and TM polarized (perpendicular to the nanowires) coupled mode between the waveguide mode and the particle plasmon resonance of the gold nanowires are enhanced significantly in a tunable spectral band. The top waveguide also extends considerably the spectral tuning range of this optical filter device.
On-chip Si/SiOx microtube refractometer
Authors: Bernardi A. , Kiravittaya S. , Rastelli A. , Songmuang R. , Thurmer D. J. , Benyoucef M. , Schmidt O. G.
Published: September 2008

The authors fabricate rolled up microtubes consisting of Si/SiOx on Si substrate and analyze the possibility to use them as a refractometric sensor. An aqueous sugar solution is inserted into the microtube, which leads to a change in refractive index and, as a result, to a detectable spectral shift of the whispering gallery modes. Experimental results can fit well with finite-difference time-domain simulations, which are used to determine the sensitivity of this tube refractometer. The ratio of spectral sensitivity to channel cross-sectional area of the refractometer is particularly striking and allows analysis of fluid volumes in the range of femtoliters. A comparative discussion with other existing refractometer schemes concludes this work.
Conversion of surface plasmon polaritons to light by a surface step
Authors: Yamamoto Naoki , Suzuki Takahiro
Published: September 2008

A focused electron beam in a transmission electron microscope can excite a surface plasmon polariton (SPP) at any position on a metal surface as a point source. The excited SPP is converted into light at a surface step and the emission intensity depends on the beam position, photon energy, and emission angle. A spectrum image was obtained by scanning the electron beam across a step on a silver surface with a fixed emission angle, demonstrating a characteristic fringe pattern. The dispersion relation of the SPP on a silver surface is derived by analyzing the spectrum image.
Evolution of electric field amplitude dependent scaling behaviors in ferroelectric films over a broad temperature range
Authors: Yang J. , Meng X. J. , Shen M. R. , Gao C. , Sun J. L. , Chu J. H.
Published: September 2008

The evolution of the electric field amplitude (V0) dependent scaling of dynamic hysteresis area (A∝V0α) with the temperature in Mn doped (Pb,Sr)TiO3 film was analyzed. α exhibited different values under three temperature regions, where (1) the intrinsic ferroelectric domain nucleation, growth, and reversal, (2) the competition between the polar nanoregions and mobile defects, and (3) the Joule loss during long range movement of oxygen vacancies were demonstrated. This study provides a quantitative criterion to distinguish the intrinsic ferroelectric hysteresis from artificial one.
An integrated double half-wave organic Schottky diode rectifier on foil operating at 13.56 MHz
Authors: Myny Kris , Steudel Soeren , Vicca Peter , Genoe Jan , Heremans Paul
Published: September 2008

We demonstrate an integrated organic double half-wave rectifier for use in organic radio frequency identification (RFID) tags. This rectifier comprises two organic Schottky diodes, each followed by a capacitor, integrated on the same foil. This rectifier delivers approximately twice the dc voltage of single half-wave rectifiers. Its offset voltage is merely 2 V. It is able to generate voltages of 10–14 V, which are necessary for driving current organic RFID multibit code generators, from an ac-input voltage of only 8–10 V amplitude, which are generated at rf magnetic fields of 0.9–1.3 A/m. Such fields are below the minimum required rf magnetic field strength set by standards.
Highly efficient electron beam generation in a wide-aperture discharge in helium
Authors: Belskaya E. V. , Bokhan P. A. , Zakrevsky Dm. E.
Published: September 2008

The paper deals with a gas discharge having electron beam generation efficiency η≃100% at a voltage U>300 V. The discharge has been realized in helium in a cell with a cathode diameter of 19.5 cm. The discharge features are a higher η as compared to other discharges, the presence of reverse bends in the voltage-current characteristics including the occurrence of a falling section, and nonmonotony in η(U) and its growth with increasing He pressure. The discharge peculiarities are explained by its photoemissive nature. The basic contribution to the photoemission is made by the emission from the resonance state excited in the secondary processes.
Polarization-switchable single photon source using the Stark effect
Authors: Rakher M. T. , Stoltz N. G. , Coldren L. A. , Petroff P. M. , Bouwmeester D.
Published: September 2008

A polarization-switchable single photon source is demonstrated by embedding a self-assembled quantum dot in a high-quality, electrically gated, oxide-apertured micropillar cavity. Due to the noncircular aperture, the polarization degeneracy of the fundamental cavity mode is lifted, leaving two linearly polarized Q≈20 000 modes separated by 194 μeV. An intracavity electric field generated by an applied bias enables Stark shift tuning of the quantum dot emission over a frequency range containing both polarization modes, switching the dominant single photon polarization through the Purcell effect. We measure polarization switching up to 300 kHz, limited by the RC time constant of the device.
Terahertz emission from a large-area GaInAsN emitter
Authors: Peter Falk , Winnerl Stephan , Schneider Harald , Helm Manfred , Köhler Klaus
Published: September 2008

A large-area interdigitated terahertz emitter based on molecular-beam epitaxy grown GaInAsN with an additional AlGaAs heterostructure is investigated as a terahertz source for excitation wavelengths between 1.1 and 1.5 μm. The optical and electrical properties of the emitter material exhibit absorption up to a wavelength of 1.5 μm and have a resistivity of 550 kΩ cm. Terahertz waves were detected by electro-optical sampling with a bandwidth exceeding 2 THz. Best performance is found for excitation wavelengths below 1.35 μm. Furthermore the emission properties for several excitation powers are investigated, showing a linear increase in terahertz emission.
Spectral bandwidth and phase effects of resonantly excited ultrafast surface plasmon pulses
Authors: Yalcin S. E. , Wang Y. , Achermann M.
Published: September 2008

We report on the detailed analysis of femtosecond surface plasmon polariton (SPP) pulse generation under resonant excitation. Using prism coupling technique we excite femtosecond SPP pulses at a gold/air interface with ultrafast laser pulses. We show that the photon-SPP coupling is a resonant process with a finite spectral bandwidth that causes a spectral phase shift and a narrowing of the SPP pulse spectrum. Both effects result in a temporal pulse broadening and, therefore, set a lower limit on the duration of ultrafast SPP pulses with consequences for ultrafast SPP applications.
A capillary microgripper based on electrowetting
Authors: Vasudev Abhay , Zhe Jiang
Published: September 2008

An electrowetting based capillary microgripper, which can pick up and release micro-objects, is presented. Electrowetting was utilized to dynamically change the contact angle between the liquid bridge and the gripper surface to control the capillary lifting forces. A coplanar interdigitated gold electrode pair was employed to simplify the microfabrication. The lifting force generated by the microgripper was experimentally characterized. The pickup and release routine was demonstrated for various micro glass beads whose weight ranges from 77 to 136 μN. The design, microfabrication, and testing of the microgripper are presented.
Improved performance of Schottky diodes on pendeoepitaxial gallium nitride
Authors: Zheleva T. , Derenge M. , Ewing D. , Shah P. , Jones K. , Lee U. , Robins L.
Published: September 2008

We designed experiments to investigate the role of dislocation density on the performance of Schottky diodes fabricated on a GaN material grown conventionally and by pendeo-epitaxy. Devices of varying geometries were fabricated on low defect density GaN regions grown selectively via pendeo-epitaxy. In addition, corresponding devices were fabricated on the conventional GaN material with a high density of dislocations. Schottky diodes fabricated on pendeo-material showed nearly two orders of magnitude lower leakage current and displayed improved ideality factor, while diodes built on a conventional material displayed nonideal characteristics.
Nanobelts in multicomponent aluminum alloys
Authors: Jia Z. H. , Arnberg L.
Published: September 2008

High density of nanobeltlike precipitates has been observed in an Al–Si–Mg–Hf–Y alloy after heat treatments. Quantitative analysis in scanning transmission electron micrscopy (TEM) shows that the precipitates contain Hf, Si, and some Al. The precipitates have an orthorhombic structure which has been revealed by high-resolution TEM and electron diffraction. The precipitates have been identified to be of the Si2Hf-type phase.
On the Crooks fluctuation theorem and the Jarzynski equality
Authors: Chen L. Y.
Published: September 2008

The Jarzynski equality (JE) and the undergirding Crooks fluctuation theorem (CFT) have generated intense interest recently among researchers in physical and biological sciences. It has been held that the CFT has wider applicability than the JE. This note shows that the two are equally applicable and that their applicability is possibly limited to near-equilibrium processes, where the linear fluctuation-dissipation theorem holds.
Order of magnitude enhancement in neutron emission with deuterium-krypton admixture operation in miniature plasma focus device
Authors: Verma Rishi , Lee P. , Lee S. , Springham S. V. , Tan T. L. , Rawat R. S. , Krishnan M.
Published: September 2008

The effect of varied concentrations of deuterium-krypton (D2–Kr) admixture on the neutron emission of a fast miniature plasma focus device was investigated. It was found that a judicious concentration of Kr in D2 can significantly enhance the neutron yield. The maximum average neutron yield of (1±0.27)×104 n/shot for pure D2 filling at 3 mbars was enhanced to (3.14±0.4)×105 n/shot with D2+2% Kr admixture operation, which represents a >30-fold increase. More than an order of magnitude enhancement in the average neutron yield was observed over the broader operating range of 1–4 mbars for D2+2% Kr and D2+5% Kr admixtures.
Study of spin fluctuations in Ni3±xAl1∓x using point contact Andreev reflection spectroscopy
Authors: Mukhopadhyay Sourin , Dhar Sudesh Kumar , Raychaudhuri Pratap
Published: September 2008

We report point contact Andreev reflection (PCAR) spectroscopy studies on Ni3±xAl1∓x with composition range spanning the ferromagnetic to paramagnetic phase boundary. PCAR studies performed using Nb tip as counterelectrode reveal that the superconducting quasiparticle lifetime (τ) and superconducting energy gap (Δ) decrease with increasing spin fluctuation in the normal metal electrode. Our study reveals that PCAR could be a useful probe to study spin fluctuations in systems that are on the verge of magnetic instability.
Terahertz Bloch oscillations in periodic graphene structures
Authors: Dragoman D. , Dragoman M.
Published: September 2008

In periodic graphene structures formed by mechanical undulation or by patterning an array of metallic electrodes on graphene, Bloch oscillations up to tens of terahertz can be generated due to ballistic transport and the low scattering rate.
Solvent-dependent electrical characteristics and stability of organic thin-film transistors with drop cast bis(triisopropylsilylethynyl) pentacene
Authors: Kim Chang Su , Lee Stephanie , Gomez Enrique D. , Anthony John E. , Loo Yueh-Lin
Published: September 2008

The solvent from which the active layer is drop cast dramatically influences the electrical characteristics and electrical stability of thin-film transistors comprising bis(triisopropylsilylethynyl) pentacene. Casting from high boiling solvents allows slower crystallization; devices cast from toluene and chlorobenzene thus exhibit mobilities >0.1 cm2/V s and on/off ratios of ∼106. More importantly, the solvent choice influences the device stability. Devices from toluene exhibit stable characteristics, whereas devices from chlorobenzene show hystereses on cycling, with dramatic threshold voltage shifts toward positive voltages. The instability in chlorobenzene devices is attributed to the migration of water and solvent impurities to the charge transport interface on repetitive testing.
Control of carbon nanotube geometry via tunable process parameters
Authors: Cullinan Michael A. , Culpepper Martin L.
Published: September 2008

We present a method for selecting fabrication process parameters (temperature, catalyst film thickness, and hydrocarbon concentration) that may be used to grow multiwalled carbon nanotubes (CNTs) with desired outer diameter D and number of walls Nw. This capability enables the control of rigidity, which in turn makes it possible to control a CNT’s lateral vibration behavior and bending stiffness. A growth model was generated and used to link D and Nw to the process parameters. Experimental results showed that the models predicted D and Nw with less than 6% and 7% error, respectively.
Video rate atomic force microscopy using low stiffness, low resonant frequency cantilevers
Authors: Howard-Knight J. P. , Hobbs J. K.
Published: September 2008

High speed atomic force microscopy (AFM) images have been collected at 25 ms/frame using “passive mechanical feedback,” in which the cantilever is forced to respond to the sample surface at frequencies considerably greater than its resonant frequency. Through finite element modeling of the cantilever as it responds to the sample surface, the simulated trajectory and full transient response of the cantilever have been obtained. The resultant simulated image is found to agree well with the experimental high speed AFM images, showing that cantilever imaging at these high frequencies can be well understood in terms of continuum mechanics.
Reversed scheme of thin foil acceleration
Authors: Borodziuk S. , Kasperczuk A. , Pisarczyk T. , Ullschmied J. , Krousky E. , Masek K. , Pfeifer M. , Rohlena K. , Skala J. , Pisarczyk P.
Published: September 2008

An alternative concept for accelerating thin foils to high velocity has been proposed and tested. The thin (10 μm) Al foil has been accelerated by the ablative plasma generated by means of the third harmonic (λ=0.438 μm, τ=250 ps) of the iodine laser pulse of the energies of 75 and 190 J irradiating a massive Cu target. Two separation distances of the foil from the massive target of 100 and 500 μm were used. It has been shown that this method of an indirect, two-step acceleration, named as the reversed acceleration scheme, can be more effective than the classic, direct-drive approach. The Al flyer foil has reached a velocity of ∼1.3×107 cm/s, i.e., significantly higher than that in the comparable “classic” ablative acceleration experiment.
High-intensity nanosecond-pulsed laser-induced plasma in air, water, and vacuum: A comparative study of the early-stage evolution using a physics-based predictive model
Authors: Wu Benxin
Published: September 2008

A comparative study has been performed for properties (temperature, density, and electron Coulomb coupling constant) of plasma induced by high-intensity (∼GW∕cm2) nanosecond laser-metal interactions in air, water, and vacuum. The study is for early-stage (t≲30ns) plasma evolution, where the above plasma properties are very difficult to measure experimentally and hence a comparative property study has been rarely reported in literature. In this paper a physics-based predictive model is used as the investigation tool. The model was verified based on experimental measurements for the early-stage plasma pressure and front propagation and the late-stage (t≳30ns) plasma temperature and electron number density, which are relatively easy to measure. Therefore, the experimentally verified model can provide reasonably accurate information on the difficult-to-measure plasma temperature and density in the early-stage at least in the semiquantitative sense, and the information will be very useful for the fundamental laser plasma study and relevant laser applications. It has been found that plasma with very different temperatures and densities can be created in different media.
Highly efficient tandem p-i-n organic light-emitting diodes adopting a low temperature evaporated rhenium oxide interconnecting layer
Authors: Leem Dong-Seok , Lee Jae-Hyun , Kim Jang-Joo , Kang Jae-Wook
Published: September 2008

High quality interconnection units (ICUs) with a high transparency and superior charge generating capability for tandem organic light-emitting diodes (OLEDs) are developed. The ICUs of rubidium carbonate-doped 4,7-diphenyl-1,10-phenanthroline/rhenium oxide (ReO3)-doped N,N′-diphenyl-N,N′-bis(1,1′-biphenyl)-4,4′-diamine layers with or without an additional ReO3 interlayer produce high transmittance (88%–92% at 420–700nm) and spontaneous internal charge generation properties. A very high efficiency of ∼129cd∕A has been demonstrated from only two stacked green p-i-n OLEDs by employing the developed ICUs. The relationship between the device efficiency and internal charge generation within the ICUs is further described by means of the capacitance measurements.
Vacancy formation during oxidation of silicon crystal surface
Authors: Suezawa M. , Yamamoto Y. , Suemitsu M. , Usami N. , Yonenaga I.
Published: September 2008

To study the formation of interstitials and vacancies during oxidation of silicon crystals, we applied a quenching method, namely, oxidation at high temperatures in mixed gases of water vapor and H2 followed by the quenching into water. Contrary to our expectation, the vacancy concentration was higher than that of the thermal equilibrium during the short duration of oxidation.
Cathodoluminescence spectroscopy of ambipolar diffusion in (Al,Ga)As barriers and capture of nonequilibrium carriers in GaAs quantum wells
Authors: Fujiwara K. , Jahn U. , Grahn H. T.
Published: September 2008

Ambipolar vertical diffusion of carriers generated in an Al0.3Ga0.7As barrier is investigated by cathodoluminescence (CL) spectroscopy in a system containing a sequence of GaAs-based quantum wells (QWs). The intensity distribution of the CL line scan exhibits a single exponential decay for the first QW of the sequence, reflecting a pure diffusion-limited transport. However, the CL line scans of the second, third, and fourth QWs are governed by diffusion only for large separations between the electron beam and the corresponding QW. For smaller distances, the CL intensity distribution is significantly influenced by the carrier capture into the intervening QWs.
A microwave nonlinear phase shifter
Authors: Ustinov Alexey B. , Kalinikos Boris A.
Published: September 2008

A microwave nonlinear phase shifter is described. It is a device producing a power-dependent phase shift of microwave signals. The device is fabricated with a ferrite film which serves as a waveguide for magnetostatic spin waves. A nonlinear phase shift of the carrier spin waves appearing under increasing their power is the key phenomenon in the device operation. A theoretical model for the nonlinear phase shifter is presented. The model provides a good description for the experimentally obtained performance characteristics of the device.
Ultrafast carrier dynamics and terahertz conductivity of photoexcited GaAs under electric field
Authors: Zhou Qing-li , Shi Yulei , Jin Bin , Zhang Cunlin
Published: September 2008

The ultrafast carrier dynamics and terahertz conductivity in semi-insulating GaAs have been investigated under electric field (E) by using optical pump-terahertz probe technique. The measurements indicate that the terahertz transmission change induced by the pump pulses at high E is smaller than that without E. We attribute this phenomenon to carrier scattering into the L valley, which leads to a drop in carrier mobility. The calculated transient photoconductivities fit well with the Drude–Smith model, being consistent with our intervalley scattering model.
Theory of the relaxation matrix and its relation to microwave transient phenomena. II. Semiclassical calculations for systems of OCS and nonpolar collisions partners
Authors: Liu Wing-Ki , Marcus R. A.
Published: September 2008

JCPSA,63,290,1975
MTOC translocation modulates IS formation and controls sustained T cell signaling
Authors: Martín-Cófreces Noa B. , Robles-Valero Javier , Cabrero J. Román , Mittelbrunn María , Gordón-Alonso Mónica , Sung Ching-Hwa , Alarcón Balbino , Vázquez Jesús , Sánchez-Madrid Francisco
Published: September 2008

The translocation of the microtubule-organizing center (MTOC) toward the nascent immune synapse (IS) is an early step in lymphocyte activation initiated by T cell receptor (TCR) signaling. The molecular mechanisms that control the physical movement of the lymphocyte MTOC remain largely unknown. We have studied the role of the dynein–dynactin complex, a microtubule-based molecular motor, in the process of T cell activation during T cell antigen–presenting cell cognate immune interactions. Impairment of dynein–dynactin complex activity, either by overexpressing the p50-dynamitin component of dynactin to disrupt the complex or by knocking down dynein heavy chain expression to prevent its formation, inhibited MTOC translocation after TCR antigen priming. This resulted in a strong reduction in the phosphorylation of molecules such as ζ chain–associated protein kinase 70 (ZAP70), linker of activated T cells (LAT), and Vav1; prevented the supply of molecules to the IS from intracellular pools, resulting in a disorganized and dysfunctional IS architecture; and impaired interleukin-2 production. Together, these data reveal MTOC translocation as an important mechanism underlying IS formation and sustained T cell signaling.
Cardiolipin defines the interactome of the major ADP/ATP carrier protein of the mitochondrial inner membrane
Authors: Claypool Steven M. , Oktay Yavuz , Boontheung Pinmanee , Loo Joseph A. , Koehler Carla M.
Published: September 2008

Defined mutations in the mitochondrial ADP/ATP carrier (AAC) are associated with certain types of progressive external ophthalmoplegia. AAC is required for oxidative phosphorylation (OXPHOS), and dysregulation of AAC has been implicated in apoptosis. Little is known about the AAC interactome, aside from a known requirement for the phospholipid cardiolipin (CL) and that it is thought to function as a homodimer. Using a newly developed dual affinity tag, we demonstrate that yeast AAC2 physically participates in several protein complexes of distinct size and composition. The respiratory supercomplex and several smaller AAC2-containing complexes, including other members of the mitochondrial carrier family, are identified here. In the absence of CL, most of the defined interactions are destabilized or undetectable. The absence of CL and/or AAC2 results in distinct yet additive alterations in respiratory supercomplex structure and respiratory function. Thus, a single lipid can significantly alter the functional interactome of an individual protein.
To flip or not to flip: lipid–protein charge interactions are a determinant of final membrane protein topology
Authors: Bogdanov Mikhail , Xie Jun , Heacock Phil , Dowhan William
Published: September 2008

The molecular details of how lipids influence final topological organization of membrane proteins are not well understood. Here, we present evidence that final topology is influenced by lipid–protein interactions most likely outside of the translocon. The N-terminal half of Escherichia coli lactose permease (LacY) is inverted with respect to the C-terminal half and the membrane bilayer when assembled in mutants lacking phosphatidylethanolamine and containing only negatively charged phospholipids. We demonstrate that inversion is dependent on interactions between the net charge of the cytoplasmic surface of the N-terminal bundle and the negative charge density of the membrane bilayer surface. A transmembrane domain, acting as a molecular hinge between the two halves of the protein, must also exit from the membrane for inversion to occur. Phosphatidylethanolamine dampens the translocation potential of negative residues in favor of the cytoplasmic retention potential of positive residues, thus explaining the dominance of positive over negative amino acids as co- or post-translational topological determinants.
Receptor trafficking controls weak signal delivery: a strategy used by c-Met for STAT3 nuclear accumulation
Authors: Kermorgant Stéphanie , Parker Peter J.
Published: September 2008

C-Met, the receptor of hepatocyte growth factor (HGF), through overexpression or mutation, is a major protooncogene that provides an attractive molecular target for cancer therapy. HGF/c-Met–induced tumorigenesis is dependent, in part, on the transcription factor and oncogene signal transducer and activator of transcription 3 (STAT3), which is believed to be activated by the receptor at the plasma membrane and then to travel to the nucleus where it acts. We demonstrate that although the robust signal to STAT3 elicited from the cytokine oncostatin-M does indeed support this mechanism of STAT3 action, for the weaker STAT3 signal emanating from c-Met, the activated receptor itself needs to be delivered to a perinuclear endosomal compartment to sustain phosphorylated STAT3 in the nucleus. This is signal specific because c-Met–induced extracellular signal-regulated kinase nuclear accumulation does not require receptor trafficking to the perinuclear compartment. This response is triggered from peripheral endosomes. Thus, control of growth factor receptor traffic determines the nature of the signal output, providing novel opportunities for intervention.
Survival of the weakest: signaling aided by endosomes
Authors: McShane Marisa P. , Zerial Marino
Published: September 2008

The tyrosine kinase receptor c-Met plays a key role in cell proliferation, morphogenesis, and motility in response to hepatocyte growth factor. C-Met is often altered in cancer and is a major target for therapeutic intervention. Despite knowing a great deal of the molecular machinery downstream of this receptor tyrosine kinase, the spatiotemporal regulation of c-Met signaling still remains elusive. In this issue of the Journal of Cell Biology, Kermorgant and Parker (Kermorgant, S. and P.J. Parker. 2008. J. Cell Biol. 182:855–863) provide evidence for a model in which the c-Met–activated STAT3 signal is mediated by endosomal trafficking. This study elegantly highlights how weak signals can be effectively transmitted to the nucleus by exploiting endosomal compartments, raising important mechanistic implications for the signaling research community.
The acoustic diversity of the seabed based on the similarity index computed from Chirp seismic data
Authors: Lee Gwang H. , Kim Han J. , Kim Dae C. , Yi Bo Y. , Nam Seong M. , Khim Boo K. , Lim Moon S.
Published: September 2008

Lee, G. H., Kim, H. J., Kim, D. C., Yi, B. Y., Nam, S. M., Khim, B. K., and Lim, M. S. 2009. The acoustic diversity of the seabed based on the similarity index computed from Chirp seismic data. – ICES Journal of Marine Science, 66: 227–236. The similarity index (SI), computed from the singular value decomposition of seabed-echo envelopes recorded in Chirp seismic data, was tested in mapping the acoustic diversity of the seabed in Suyong Bay, Busan, Korea. Rocky bottom is characterized by low SI values, indicating acoustic heterogeneity, and sedimentary seabed by high SI values, also indicating acoustic homogeneity. Isolated areas of low SI values, not identified as rocky bottom in Chirp profiles, may suggest a shallow basement. The gradual seaward change of the substratum from coarse-grained to relatively poorly sorted, finer-grained sediments also corresponds to an overall seaward decrease in the SI value. The straightforward and quick computation of the SI makes it possible to assess the gross acoustic diversity of the seabed in almost real time.
Mixtures of Two Argentinean Wheat Cultivars of Different Quality: A Study on Breadmaking Performance
Authors: Ponzio N. R. , Puppo M. C. , Ferrero C.
Published: September 2008

Commercial Argentinean wheat flours are commonly composed of at least two wheat cultivars to obtain products of constant quality. Flours from two different wheats (Buck Pronto [BP] and Klein Escudo [KE]) with different protein profiles and breadmaking performance were assayed. Glu‐1 alleles are expressed in BP with 2, 7+8, 5+10 HMW glutenins subunits, while in KE 2, 7+9, 5+10 HMW glutenins subunits are present. Different sample blends (BP and KE) of 100:0, 75:25, 50:50, 25:75, and 0:100 were analyzed to relate composition of blends to the characteristics of dough and breads obtained from them. Physicochemical assays, alveograms, farinograms, and the SDS sedimentation test (SDSS test) were applied to characterize pure flours and blends. Rheological behavior of dough was studied by texture profile analysis (TPA) and dynamic assays. Scanning electron microscopy (SEM) was used to analyze dough microstructure. Alveographic W and farinographic stability values of blends with ≤50% KE were higher than expected. The same behavior was observed in SDSS‐test values, hardness (TPA), and rheometric assays. These results indicate that the performance of a cultivar like BP, rendering strong flours, would not be affected when a less strong flour is incorporated up to a certain proportion. However, bread quality of BP was superior to that of KE and BP‐KE blends. The decrease in bread quality was particularly evident in the increase in the shape ratio (W/H). Correlations could be established among some textural parameters of dough (hardness and elasticity) and certain quality attributes of bread (crumb and crust hardness).
Effect on Dough Functional Properties of Partial Fractionation, Redistribution, and In Situ Deposition of Wheat Flour Gluten Proteins Exposed to Water, Ethanol, and Aqueous Ethanol
Authors: Robertson G. H. , Cao T. K. , Orts W. O.
Published: September 2008

The application of the cold‐ethanol laboratory fractionation method to the bulk separation of wheat starch and gluten is accompanied by incidental dissolution, removal, or redeposition of a small part of the functional gliadin protein. The new distribution resulting from process incidental redeposition of soluble components or by purposeful add‐back of soluble and leached components can lead to differences in functionality and more difficult recovery of native properties. To assess this issue, we exposed several wheat flour types to ethanol and water (50–90% v/v) solutions, water, and absolute ethanol at 22°C and –12°C. The exposure was mass conserving (leached components returned to substrate by evaporation of the solvent without separation of phases) or mass depleting (leached components not returned to substrate). The result of the mass‐conserving contact would be flour with altered protein distributions and intermolecular interactions. The result of the mass‐depleting contact would also include altered protein content. Furthermore, the mass‐conserving contact would model an industrial outcome for a cold‐ethanol process in which leached components would be added back from an alcohol solution. The leaching result was monitored by mixography of the flour, nitrogen analysis, and capillary zone electrophoresis of extracts. Although dough rheology was generally like that of the source flour, there were notable differences. The primary change for mass‐conserving contact was an increase in the time to peak resistance and a decrease in the rate of loss of dough resistance following peak resistance. These changes were in direct proportion to the amount of protein mobilized by the solvent. Leaching at 22°C, prevented dough formation for most aqueous ethanol concentrations and greatly reduced gliadin protein content. Minimal changes were noted for solvent contact at –12°C regardless of the ethanol concentration. The data suggested that 1) the conditions applied in cold‐ethanol enrichment of protein from wheat will generally preserve vital wheat gluten functionality, 2) functionality losses can be recovered by returning the solubilized fractions, and 3) the flour to which the gluten is added may require more mixing.
Physical and Sensory Properties of Regular and Reduced‐Fat Pound Cakes with Added Amaranth Flour
Authors: Capriles Vanessa Dias , Almeida Eveline Lopes , Ferreira Reinaldo Eduardo , Arêas José Alfredo Gomes , Steel Caroline Joy , Chang Yoon Kil
Published: September 2008

The sum of wheat flour and corn starch was replaced by 10, 20, or 30% whole amaranth flour in both conventional (C) and reduced fat (RF) pound cakes, and the effects on physical and sensory properties of the cakes were investigated. RF presented 33% fat reduction. The increasing amaranth levels darkened crust and crumb of cakes, which decreased color acceptability. Fresh amaranth‐containing cakes had similar texture characteristics to the controls, evaluated both instrumentally and sensorially. Sensory evaluation revealed that replacement by 30% amaranth flour decreased C cakes overall acceptability scores, due to its lower specific volume and darker color. Amaranth flour levels had no significant effect on overall acceptability of RF cakes. Hence, the sum of wheat flour and corn starch could be successfully replaced by up to 20% amaranth flour in C and up to 30% in RF pound cakes without negatively affecting sensory quality in fresh cakes. Moisture losses for all the cakes were similar, ≈1% per day during storage. After six days of storage, both C and RF amaranth‐containing cakes had higher hardness and chewiness values than control cakes. Further experiments involving sensory evaluation during storage are necessary to determine the exact limit of amaranth flour replacement.
FTIR and Raman Signatures of Wheat Grain Peripheral Tissues
Authors: Barron C. , Rouau X.
Published: September 2008

Hand‐dissection of mature grains from three common wheat cultivars (Triticum aestivum L.: Caphorn, Crousty, and Recital) and one durum wheat (T. durum Desf., Ardente) was performed to obtain pure samples of aleurone layer, hyaline layer, outer pericarp, and a composite layer made up of testa+inner pericarp. Vibrational spectral signatures were collected on both sides of the layers by ATR‐FTIR and Raman spectroscopy. Spectra were compared with biochemical analysis on the same samples which allowed identification of specific composition patterns in each tissue regardless of the cultivar. Considering the low penetration depth of ATR‐FTIR signal, the cuticles were evidenced on the external sides of outer pericarp, hyaline layer, and testa. Spectra from testa of red and white wheats were clearly distinguished. FTIR spectroscopy, combined with statistical analysis, was successful in identifying the specific spectral signature for each peripheral tissue of wheat grains. In the 1500–800 cm‐1 spectral region, multivariate models allowed accurate prediction of the histological origin of the pericarp, hyaline, and aleurone layers regardless of the analyzed side, and the testa but with a lower performance.
Content and Molecular Weight Distribution of Oat β‐Glucan in Oatrim, Nutrim, and C‐Trim Products
Authors: Kim Sanghoon , Inglett George E. , Liu Sean X.
Published: September 2008

The soluble fiber, β‐glucan, in oat products is an active hypolipidemic component that is responsible for lowering plasma lipids. Quantitative analysis of β‐glucan in oat hydrocolloids such as Oatrim, Nutrim, and C‐Trim was performed to measure the total β‐glucan content and molecular weight distribution. For the measurement of total β‐glucan content, both modified flow‐injection analysis (FIA) method and the standard AACC enzymatic method were employed. FIA method uses the enhanced fluorescence produced when β‐glucan forms complexes with Calcofluor. Experimental results of both the modified FIA method and the standard AACC enzymatic method revealed very good coincidence with each other. This result confirms the applicability of either technique for the quantitative evaluation of β‐glucan in hydrocolloids. Molecular weight (MW) distribution of β‐glucan was determined by size‐exclusion chromatography with postcolumn detection. Experimental results revealed that the molecular weight of β‐glucan in the Trim products was decreased during the manufacturing process. This result was ascribed to the rigorous processing condition of jet‐cooking.