bluuebunny/crossref_metadata_2025 huggingface dataset:
Apparatus for material tests using an internal loading system in high-pressure gas at room temperature
Authors: Imade M. , Fukuyama S. , Yokogawa K.
Published: July 2008

A new type of apparatus for material tests using an internal loading system in high-pressure gas up to 100MPa at room temperature without conventional material testing equipment was developed. The apparatus consists of a high-pressure control system and a pressure vessel, in which a piston is installed in the cylinder of the pressure vessel. The load caused by the pressure difference between spaces separated by the piston in the vessel cylinder is applied on the specimen connected to the piston in the vessel cylinder. The actual load on the specimen is directly measured by an external load cell and the displacement of the specimen is also measured by an external extensometer. As an example of the application of the apparatus, a tensile test on SUS316 stainless steel the Japanese Industrial Standard (JIS) G4303, which is comparable to the type 316 stainless steel ASTM A276, was conducted in 90MPa hydrogen and argon. Hydrogen showed a marked effect on the tensile property of the material. The hydrogen gas embrittlement of the material was briefly discussed.
Cryogenic gas loading in a Mao–Bell-type diamond anvil cell for high pressure-high temperature investigations
Authors: Sekar M. , Kumar N. R. Sanjay , Sahu P. Ch. , Chandra Shekar N. V. , Subramanian N.
Published: July 2008

A simple system for loading argon fluid at cryogenic temperatures in a Mao–Bell-type diamond anvil cell (DAC) has been developed. It is done in a two step process in which the piston-cylinder assembly alone is submerged in the cryogenic chamber for trapping the liquefied inert gas. Liquid nitrogen is used for condensing the argon gas. This system is now being efficiently used for loading liquid argon in the DAC for high pressure–high temperature experiments. The success rate of trapping liquefied argon in the sample chamber is about 75%. The performance of the gas loading system is successfully tested by carrying out direct conversion of pyrolitic graphite to diamond under high pressure-high temperature using laser heated DAC facility.
Application of fall-line mix models to understand degraded yield
Authors: Welser-Sherrill L. , Cooley J. H. , Haynes D. A. , Wilson D. C. , Sherrill M. E. , Mancini R. C. , Tommasini R.
Published: July 2008

Mixing between fuel and shell material is an important topic in the inertial confinement fusion community, and is commonly accepted as the primary mechanism for neutron yield degradation. Typically, radiation hydrodynamic simulations that lack mixing (clean simulations) tend to considerably overestimate the neutron yield. This paper presents a series of yield calculations based on a variety of fall-line inspired mix models. The results are compared to a series of OMEGA experiments which provide total neutron yields and time-dependent yield rates.
Drying of salt solutions in porous materials: Intermediate-time dynamics and efflorescence
Authors: Guglielmini Laura , Gontcharov Alexandre , Aldykiewicz Antonio J. , Stone Howard A.
Published: July 2008

Drying of salt solutions leads to the accumulation of salt at any surface where evaporation occurs. When this drying occurs within porous media, the precipitation of salts or efflorescence is generally to be avoided. A one-dimensional model for the drying processes in initially saturated porous materials was presented by Huinink et al. [Phys. Fluids 14, 1389 (2002)] and analytical results were obtained for short times when the concentration distribution evolves diffusively. Here, we present analytical results for intermediate times when convective and diffusive fluxes balance. Moreover, the approach is extended to symmetrical geometries and is generalized for porous objects with arbitrary shape, which highlights the role of the surface area to volume ratio. Estimates for the Peclet number dependence of the maximum salt concentration at the surface are obtained and the conditions that allows to avoid efflorescence are characterized.
Electronic level alignment at the deeply buried absorber/Mo interface in chalcopyrite-based thin film solar cells
Authors: Bär M. , Nishiwaki S. , Weinhardt L. , Pookpanratana S. , Shafarman W. N. , Heske C.
Published: July 2008

We have investigated the electronic structure of the absorber/back contact interface for S-free [Cu(In,Ga)Se2 (“CIGSe”)] and S-containing [Cu(In,Ga)(S,Se)2 (“CIGSSe”)] chalcopyrites with direct and inverse photoemission. Comparison of the electronic levels of the cleavage planes reveals a pronounced cliff in the conduction band at the CIG(S)Se∕Mo interface. For the valence band, we find a flat alignment and a small spike for the CIGSe- and CIGSSe-based structures, respectively.
Monitoring crack-induced changes in elasticity with resonant spectroscopy
Authors: Zadler Brian J. , Scales John A.
Published: July 2008

The presence and nature of fractures can have a profound impact on the elastic and mechanical properties of materials. Whether it is a fracture-induced loss of strength or the creation of a long-wavelength anisotropy, being able to infer the presence and properties of fractures in a material has many applications. Detecting changes in the spectra of mechanical resonances due to the presence of fractures is not difficult. A more interesting issue is which elastic moduli are sensitive to the presence of these fractures and how are these moduli related to the stiffness of the material? Resonant ultrasound spectroscopy was performed on acrylic cylinders with internal cracks. Inversions were performed for both isotropic and anisotropic moduli. Good agreement was obtained between isotropic moduli and projected (optimal isotropic moduli obtained from anisotropic moduli) for nonverlapping cracks. The same projections yielded poorer agreement for the sample with overlapping cracks. The results also show that the degree of anisotropy depends upon the amount of crack overlap, and that the isotropic shear modulus is a reliable measure of decreasing stiffness.
Magnetophotoluminescence and energy-dependent circular polarization from CdMnS nanowires
Authors: Oh Eunsoon , Choi Jung Ho , Oh Dong Keun , Park Jeonghee
Published: July 2008

We measured the Zeeman shift and the circular polarization of the magnetophotoluminescence from CdMnS nanowires. The circular polarization of the CdMnS nanowires reaches up to 5% at 5K, the polarization being dependent upon photon energies. The relatively small circular polarization is explained by the fact that the carriers are not in states with well defined angular momentum due to the nature of the wurtzite structure. The strong photon energy dependence of the circular polarization is attributed to the energy relaxation process via phonon emission, rather than by the variation of the nanowire diameters or by the Mn concentrations.
A “tabletop” electrostatic ion storage ring: Mini-Ring
Authors: Bernard J. , Montagne G. , Brédy R. , Terpend-Ordacière B. , Bourgey A. , Kerleroux M. , Chen L. , Schmidt H. T. , Cederquist H. , Martin S.
Published: July 2008

We report on the design, construction, and commissioning of a novel electrostatic ion storage ring of small dimensions—in the following referred to as “Mini-Ring.” Mini-Ring consists of four horizontal parallel-plate deflectors and two conical electrostatic mirrors. Ions are injected through the two deflectors on the injection side and off axis with respect to the conical mirrors which face each other. The first injection deflector, originally at zero voltage, is switched to its set value such that the ions after one turn follow stable trajectories of lengths of roughly 30cm. This design reduces the number of electrodes necessary to guide the ion beam through the ring in stable orbits. The six elements (deflectors and mirrors) are placed on a common grounded plate—the tabletop. Here, we present the design, ion trajectory simulations, and results of the first test experiments demonstrating the successful room-temperature operation of Mini-Ring at background pressures of 10−6–10−7mbar.
Paths of Friedmann–Robertson–Walker brane models
Authors: Szydłowski Marek , Hrycyna Orest
Published: July 2008

The dynamics of brane-world models of dark energy is reviewed. We demonstrate that simple dark energy brane models can be represented as two-dimensional dynamical systems of a Newtonian type. Hence a fictitious particle moving in a potential well characterizes the model. We investigate the dynamics of the brane models using methods of dynamical systems. The simple brane-world models can be successfully unified within a single scheme—an ensemble of brane dark energy models. We characterize generic models of this ensemble as well as exceptional ones using the notion of structural stability (instability). Then due to the Peixoto theorem we can characterize the class of generic brane models. We show that the global dynamics of the generic brane models of dark energy is topologically equivalent to the concordance ΛCDM model. We also demonstrate that the bouncing models or models in which acceleration of the universe is only transient phenomenon are nongeneric (or exceptional cases) in the ensemble. We argue that the adequate brane model of dark energy should be a generic case in the ensemble of Friedmann–Robertson–Walker dynamical systems on the plane.
Bright-matter solitons in a uniformly feeded Bose–Einstein condensate with expulsive harmonic potential
Authors: Dikandé Alain Moïse
Published: July 2008

The Gross–Pitaevskii equation, which describes the dynamics of a one-dimensional uniformly feeded attractive Bose–Einstein condensate in an expulsive potential of arbitrary harmonic shape −a2x2+a1x, is solved analytically following the inverse scattering transform method. Within this approach, bright-matter waves are obtained as exact envelope-soliton solutions of the nonlinear Schrödinger equation with a complex harmonic potential. The envelope shapes mimic double-lump pulses of unequal amplitudes symmetric with respect to the potential maximum, moving simultaneously at nonconstant accelerations with amplitudes that vary in time.
Temperature-dependent photoluminescence study of 1.3μm undoped InAs∕InGaAs∕GaAs quantum dots
Authors: Ngo C. Y. , Yoon S. F. , Lim D. R. , Wong Vincent , Chua S. J.
Published: July 2008

In As ∕ In Ga As ∕ Ga As quantum dot (QD) structures are commonly employed for 1.3μm emission. However, reduction in the thermal stability of the undoped InAs∕InGaAs∕GaAs QD lasers has been observed upon inclusion of the InxGa1−xAs strain-reducing layer. In this work, the effect of QD growth temperature on the temperature-dependent photoluminescence of the 1.3μm undoped InAs∕InGaAs∕GaAs QD samples was investigated. Due to higher confining potential of QD samples grown at lower growth temperature, enhancement in the thermal stability was observed. We believe that our findings will be beneficial to those working on improving the uncooled performance of 1.3μm undoped InAs∕InGaAs∕GaAs QD photonic devices.
Temperature of systems out of thermodynamic equilibrium
Authors: Garden J.-L. , Richard J. , Guillou H.
Published: July 2008

Two phenomenological approaches are currently used in the study of the vitreous state. One is based on the concept of fictive temperature introduced by Tool [J. Res. Natl. Bur. Stand. 34, 199 (1945)] and recently revisited by Nieuwenhuizen [Phys. Rev. Lett. 80, 5580 (1998)]. The other is based on the thermodynamics of irreversible processes initiated by De Donder at the beginning of the last century [L’Affinité (Gauthier-Villars, Paris, 1927)] and recently used by Möller et al. for a thorough study of the glass transition [J. Chem. Phys. 125, 094505 (2006)]. This latter approach leads to the possibility of describing the glass transition by means of the freezing-in of one or more order parameters connected to the internal structural degrees of freedom involved in the vitrification process. In this paper, the equivalence of the two preceding approaches is demonstrated, not only for glasses but in a very general way for any system undergoing an irreversible transformation. This equivalence allows the definition of an effective temperature for all systems departed from equilibrium generating a positive amount of entropy. In fact, the initial fictive temperature concept of Tool leads to the generalization of the notion of temperature for systems out of thermodynamic equilibrium, for which glasses are just particular cases.
Minimax approximation for the decomposition of energy denominators in Laplace-transformed Møller–Plesset perturbation theories
Authors: Takatsuka Akio , Ten-no Seiichiro , Hackbusch Wolfgang
Published: July 2008

We implement the minimax approximation for the decomposition of energy denominators in Laplace-transformed Møller–Plesset perturbation theories. The best approximation is defined by minimizing the Chebyshev norm of the quadrature error. The application to the Laplace-transformed second order perturbation theory clearly shows that the present method is much more accurate than other numerical quadratures. It is also shown that the error in the energy decays almost exponentially with respect to the number of quadrature points.
Improvement of transparent organic thin film transistor performance by inserting a lithium fluoride buffer layer
Authors: Lin Yu-Ju , Li Yu-Chang , Wen Ten-Chin , Huang Li-Ming , Chen Ying-Kuo , Yeh Hong-Jian , Wang Yeong-Her
Published: July 2008

Pentacene-based highly transparent thin-film transistors which are fabricated by inserting a thin insulating lithium fluoride layer between pentacene and transparent source/drain electrodes are presented. Through this method, device performance can be enhanced dramatically with an average transmittance of as high as 69.72% in the visible region, indicating that the LiF layer is not responsible for optical transmission. For example, there is a significant improvement of a few times with the introduction of the 1-nm-thick LiF layer, the maximum saturation drain current and the field-effect mobility. These improvements are attributed to the energy band realignment and the tunneling process.
Analytical expression for the quantum dot contribution to the quasistatic capacitance for conduction band characterization
Authors: Buda Ma , Iordache G. , Mokkapati S. , Fu Lan , Jolley G. , Tan H. H. , Jagadish C , Buda Mi
Published: July 2008

This paper demonstrates an analytical expression for the quasistatic capacitance of a quantum dot layer embedded in a junction, where the reverse bias is used to discharge the initially occupied energy levels. This analysis can be used to determine the position and the Gaussian homogeneous broadening of the energy levels in the conduction band, and is applied for an InGaAs/GaAs quantum dot structure grown by metal organic chemical vapor deposition. It is shown that the Gaussian broadening of the conduction band levels is significantly larger than the broadening of the interband photoluminescence (PL) transitions involving both conduction and hole states. The analysis also reveals a contribution from the wetting layer both in PL and modeled C-V profiles which is much stronger than in typical molecular beam epitaxy grown dots. The presence of a built-in local field oriented from the apex of the dot toward its base, contrary to the direction expected for a strained dot with uniform composition (negative dipole), is also derived from fitting of the C-V experimental data.
High-temperature poling of ferroelectrics
Authors: Kounga Alain B. , Granzow Torsten , Aulbach Emil , Hinterstein Manuel , Rödel Jürgen
Published: July 2008

The poling behavior of a lead-zirconate-titanate piezoelectric ceramic is investigated by measurements of the ferroelectric hysteresis, the longitudinal piezoelectric coefficient, and field-cooling poling experiments. At high temperatures, the decrease in the coercive field facilitates poling at lower electric fields, resulting in higher values of the longitudinal piezoelectric coefficient. However, there exists a threshold field of about 150 V/mm, below which fully poled samples cannot be obtained even when field cooling from temperatures above the transition. Further, a temperature regime below the Curie temperature is observed, where a polarization under field can be measured, but a remanent polarization is not stable. The results are discussed with respect to the phase transition behavior.
Piezoresistance in p-type silicon revisited
Authors: Richter J. , Pedersen J. , Brandbyge M. , Thomsen E. V. , Hansen O.
Published: July 2008

We calculate the shear piezocoefficient π44 in p-type Si with a 6×6 k⋅p Hamiltonian model using the Boltzmann transport equation in the relaxation-time approximation. Furthermore, we fabricate and characterize p-type silicon piezoresistors embedded in a (001) silicon substrate. We find that the relaxation-time model needs to include all scattering mechanisms in order to obtain correct temperature and acceptor density dependencies. The k⋅p results are compared to results obtained using a recent tight-binding (TB) model. The magnitude of the π44 piezocoefficient obtained from the TB model is a factor of 4 lower than experimental values; however, the temperature and acceptor density dependencies of the normalized values agree with experiments. The 6×6 Hamiltonian model shows good agreement between the absolute value of π44 and the temperature and acceptor density dependencies when compared to experiments. Finally, we present a fitting function of temperature and acceptor density to the 6×6 model that can be used to predict the piezoresistance effect in p-type silicon.
10
mJ
class femtosecond optical parametric amplifier for generating soft x-ray harmonics
Authors: Takahashi Eiji J. , Kanai Tsuneto , Nabekawa Yasuo , Midorikawa Katsumi
Published: July 2008

Power scaling of an infrared (IR) parametric amplifier chain, pumped at 800nm by a terawatt Ti:sapphire laser system has been reported. A total output energy exceeding 10mJ with 40fs pulse duration has been achieved in the IR region, which is the highest energy and peak power ever reported for an ultrafast optical parametric amplifier scheme. By applying the developed IR pulses to high-order harmonic generation, we have observed a significant cutoff extension compared to the case of 800nm driving wavelength. This source suits as a driver laser for extending high-order harmonic photon energy into the kiloelectronvolts region.
Phase transitions and dielectric properties in Bi(Zn1/2Ti1/2)O3−BaTiO3 perovskite solid solutions
Authors: Huang Chien-Chih , Cann David P.
Published: July 2008

( 1 − x ) Bi ( Zn 1 / 2 Ti 1 / 2 ) O 3 − x BaTiO 3 polycrystalline ceramics were obtained via solid state processing techniques. The perovskite structure was found to be stable for compositions containing x=0.66 or greater. Based on x-ray diffraction data, a morphotropic phase boundary between tetragonal and rhombohedral perovskite phases was observed at x≈0.9. For compositions rich in BaTiO3, the symmetry of the perovskite phase was tetragonal but with increased Bi(Zn1/2Ti1/2)O3 content, the rhombohedral phase appeared. Dielectric characterization revealed that as Bi(Zn1/2Ti1/2)O3 content increased, the transition temperature decreased and the transition peak became very diffused. A comparison of the dielectric behavior with other Bi(Zn1/2Ti1/2)O3-based solid solutions is also discussed.
Improved electronic interfaces for AT-cut quartz crystal microbalance sensors under variable damping and parallel capacitance conditions
Authors: Arnau A. , García J. V. , Jimenez Y. , Ferrari V. , Ferrari M.
Published: July 2008

A new configuration of automatic capacitance compensation (ACC) technique based on an oscillatorlike working interface, which permits the tracking of the series resonant frequency and the monitoring of the motional resistance and the parallel capacitance of a thickness-shear mode quartz crystal microbalance sensor, is introduced. The new configuration permits an easier calibration of the system which, in principle, improves the accuracy. Experimental results are reported with 9 and 10 MHz crystals in liquids with different parallel capacitances which demonstrate the effectiveness of the capacitance compensation. Some frequency deviations from the exact series resonant frequency, measured by an impedance analyzer, are explained by the specific nonideal behavior of the circuit components. A tentative approach is proposed to solve this problem that is also common to previous ACC systems.
How large is the static electric (hyper)polarizability anisotropy in HXeI?
Authors: Maroulis George
Published: July 2008

An extensive conventional ab initio and density functional theory investigation reveals that HXeI is a polar molecule with large multipole moments and highly anisotropic (hyper)polarizability. At the CCSD(T) level of theory our best values for the mean (hyper)polarizability are α¯∕e2a02Eh−1=101.46, β¯∕e3a03Eh−2=−850.7, and γ¯∕e4a04Eh−3=18.7×103. The corresponding anisotropies are Δα∕e2a02Eh−1=119.66, Δβ∕e3a03Eh−2=−2518.7, Δ1γ∕e4a04Eh−3=−249.1×103, and Δ2γ∕e4a04Eh−3=−99.6×103. The longitudinal components of the (hyper)polarizability are dominant. Our value for the anisotropy of the dipole polarizability is considerably larger than the recent empirical estimate of 22.9e2a02Eh−1 [N. H. Nahler et al., J. Chem. Phys. 119, 224 (2003)]. The results of the insertion of Xe into HI are quantified by the calculation of the differential (hyper)polarizability at the MP2 level of theory: α¯diff≡α¯(HXeI)−α(HI)−α¯(Xe)=36.29e2a02Eh−1 and γ¯diff≡γ¯(HXeI)−γ¯(HI)−γ¯(Xe)=18.1×103e4a04Eh−3.
Shell transitions between metastable states of Yukawa balls
Authors: Käding S. , Block D. , Melzer A. , Piel A. , Kählert H. , Ludwig P. , Bonitz M.
Published: July 2008

Spherical dust clusters composed of several concentric shells are experimentally investigated with particular interest on transitions between different configurations and transitions of particles between different shells. Transitions between different ground and metastable configurations are frequently observed. The experimental analysis allows us to derive the energy differences of different configurations from particles traveling between shells. The observed transitions and transition probabilities are compared to molecular dynamics simulations.
Laser annealing induced high Ge concentration epitaxial SiGe layer in Si1−xGex virtual substrate
Authors: Ong C. Y. , Pey K. L. , Li X. , Wang X. C. , Ng C. M. , Chan L.
Published: July 2008

Graded silicon germanium (Si1−yGey) epilayer with a thin layer of high Ge concentration (∼36%) near the surface is obtained by laser thermal annealing (LTA). The graded Si1−yGey layer is formed during a liquid phase regrowth after LTA. The relaxation in this graded Si1−yGey epilayer is insignificant; therefore it can be integrated into the source/drain of the p-type metal-oxide-semiconductor field effect transistor to induce high compressive strain to the Si channel. The thickness of the graded Si1−yGey epilayer and the concentration of the Ge near the surface can be controlled by the laser fluence, which in turn changes the strain induced to the Si channel of strained devices.
Two-dimensional dynamics of relativistic solitons in cold plasmas
Authors: Lehmann G. , Laedke E. W. , Spatschek K. H.
Published: July 2008

The two-dimensional dynamics of solitons appearing during relativistic laser-plasma interaction is investigated. The analysis starts from known soliton models in one space-dimension (1D). Some of the soliton solutions are already unstable in 1D, and all suffer from transverse instability in two dimensions (2D). The most unstable modes are calculated. They give a hint to the 2D structures which appear because of transversal effects. The linear stability considerations are supplemented by full 2D nonlinear simulations.
Effect of freestream isotropic turbulence on heat transfer from a sphere
Authors: Bagchi Prosenjit , Kottam Kirit
Published: July 2008

We consider direct numerical simulation (DNS) based on pseudospectral methods to study the heat transfer around a stationary sphere held at a constant temperature and subject to an ambient turbulent velocity and temperature condition. The sphere Reynolds number is in the range of 63–400, and the sphere diameter (d) varies from one to eight times the Kolmogorov scale (η). The ambient turbulent field is isotropic, and the Taylor microscale Reynolds number Rλ varies from 38 to 240. Results from two sets of DNS are presented. In the first set, the ambient velocity field is turbulent, but the ambient temperature is held constant. In the second set of simulations, both the ambient velocity and the temperature fields are turbulent. These two sets of simulations allow us to isolate the role of freestream velocity fluctuations and temperature fluctuations in modifying the mean and time-dependent heat transfer from the sphere. The mean Nusselt number is observed to be independent of Rλ. It is shown that the freestream turbulence does not have any significant effect on the mean Nusselt number, and the available correlations for a steady and uniform ambient can predict the mean Nusselt number under the turbulent ambient condition. The instantaneous Nusselt number, however, can differ significantly from the mean, and can be negative in case of large temperature fluctuation in the far field. The instantaneous Nusselt number obtained from the DNS is analyzed and compared with the analytical expression for the unsteady thermal response of a sphere. It is shown that the thermal added-mass effect is small for d/η≈1 but introduces spurious oscillation at higher d. The thermal history effect is shown to be insignificant for all d/η. Properties of the thermal wake in the presence of the turbulent velocity and temperature fields are studied. The mean thermal wake is observed to be shorter in streamwise direction and wider in crossflow direction in a turbulent ambient than that in a steady and uniform ambient. The mean thermal wake is shown to behave like a self-preserving laminar wake. It is also shown that the fluctuation in the ambient temperature is damped out in the sphere wake, and the large variation observed in the instantaneous Nusselt number arises from the variation in the local heat transfer near the front stagnation area of the sphere rather than the wake.
Reaction enhancement of isolated scalars by vortex stirring
Authors: Crimaldi John P. , Cadwell Jillian R. , Weiss Jeffrey B.
Published: July 2008

The effect of vortex stirring on reaction rate enhancement is investigated for two reactive scalars initially separated by a third nonreactive scalar. The presence of the intervening scalar precludes reactions at early times. Vortex stirring accelerates the coalescence of the reactive scalars relative to pure diffusion and enhances the resulting reaction rates. Analytical and numerical results for reactive stirring by a single point vortex are shown for a range of Péclet (Pe) and Damköhler (Da) numbers. At low Da and high Pe, nondimensional reaction rates grow as Pe1/3, and peak reaction times decrease as Pe−2/3. Reaction rates scale linearly with Da for slow reactions, but this scaling breaks down for fast reactions due to reactant depletion. The stirring-induced reaction rate enhancement is shown to be relatively insensitive to initial placement of scalars within the point vortex. The study provides mechanistic insights into more general mixing and reaction problems involving initially isolated scalars.
Chalcogenide thin-film transistors using oxygenated n-type and p-type phase change materials
Authors: Song Ki-Bong , Sohn Sung-Won , Kim JunHo , Kim Kyung-Am , Cho Kyuman
Published: July 2008

A technique for chalcogenide thin-film transistors (ChG-TFT) using oxygenated (Ox) n-type and p-type phase change materials is developed. By the oxygen doping into Ge2Sb2Te5 (GST) in a range of 10%–35%, the oxygen impurities induced by destabilization of the electron killers in GST and resultantly n-type Ox-GST was realized. For a p-type Ox-GST, by GeTe deposition with GeTe/Ox-GST ratio more than 0.3 and subsequent thermal diffusion, the diffused film showed the p-type conductivity. With n-type and p-type Ox-GST films, the doped ChG-TFTs were developed. The rectification ratio was ∼103 at +5 V, and was increased by the p-n junction structure.
Electron temperature and density determination in a nonequilibrium laser induced plasma by means of self-reversed-line spectroscopy
Authors: Karabourniotis D. , Ribiere M. , Cheron B. G.
Published: July 2008

A method is presented for determining excited-level temperature (Tp), electron temperature (Tel) and density (nel) by comparing a self-reversed line emitted from high electron-density plasma with the computed Stark-broadened line shape. These parameters are simultaneously determined from the analysis of a resonance line of aluminum emitted at delay times of 109ns in the early plasma arising from the laser ablation of aluminum. Substantial deviation from excitation equilibrium is evident from the large difference in Tp (≈8900K) and Tel (⩾13500K).
The time-dependent melting failure in flip chip lead-free solder interconnects under current stressing
Authors: Yang D. , Chan Y. C. , Tu K. N.
Published: July 2008

The melting failure in flip chip Sn3.5Ag1.0Cu solder interconnects was investigated under a current density of 2.3×104A∕cm2 at 125°C, which was attributed to the accumulated effect of void propagation, chemical dissolution, and Al electromigration. The velocity of void growth in the solder varied from 0.2to0.5μm∕h in earlier stages. The chemical dissolution in the Al pad also played the important role in failure. In the final stage, the depletion in the Al trace due to the electromigration exhibited a linear relationship with time. The rate of resistance change was estimated to be 0.9%h−1.
The great improvement effect of pores on ZT in Co1−xNixSb3 system
Authors: He Qinyu , Hu Shejun , Tang Xingui , Lan Yucheng , Yang Jian , Wang Xiaowei , Ren Zhifeng , Hao Qing , Chen Gang
Published: July 2008

In this paper, the Co1−xNixSb3+y system (x=0.1,0.2; y=0, 0.05) has been prepared by direct current induced hot press and annealing. Pores were made by annealing pressed Co1−xNixSb3.05 pellets into Co1−xNixSb3 pellets during annealing. It was found that from room temperature to 500°C, the pores with diameter larger than 1μm has significantly increased the Seebeck coefficient, considerably decreased the thermal conductivity, almost maintained the electrical conductivity constant, and therefore markedly improved the dimensionless figure of merit (ZT) of Co1−xNixSb3 system. By comparing the samples, we conclude that inducing pores into skutterudites is an effective route to greatly improve the ZT.
A direct measurement of the local resistances in a ZnO tetrapod by means of impedance spectroscopy: The role of the junction in the overall resistance
Authors: Huh Junghwan , Kim Gyu-Tae , Lee Jong Soo , Kim Sangtae
Published: July 2008

We have measured the local resistances in the arms and at the junction in a ZnO tetrapod separately by means of ac impedance spectroscopy. The resistance at the junction is found to be even greater than that in the arms although a volume fraction of the junction is negligibly small compared to that of the arms. This result clearly demonstrates that the junction plays a decisive role in the overall electrical property of the ZnO-tetrapod and thus determines the functionality of the ZnO tetrapod electronic devices.
A representation theorem of infimum of bounded quantum observables
Authors: Weihua Liu , Junde Wu
Published: July 2008

In 2006, Gudder introduced a logic order on the bounded quantum observable set S(H). In 2007, Pulmannova and Vincekova proved that for each subset D of S(H), the infimum of D exists with respect to this logic order. In this paper, we present a representation theorem for the infimum of D.
Detection of particles of explosives via backward coherent anti-Stokes Raman spectroscopy
Authors: Portnov Alexander , Rosenwaks Salman , Bar Ilana
Published: July 2008

Coherent anti-Stokes Raman scattering spectroscopy (CARS) was used for detection of solid particles of explosives and related compounds. The CARS spectra were recorded in the fingerprint region and were shown to exhibit the strong characteristic features of spontaneous Raman spectra of the respective compounds. This study demonstrates the applicability of narrowband backward-CARS spectroscopy for detection of explosives and specifically of its preference over spontaneous Raman scattering. This method has the potential to be applied to remote sensing of hazardous materials.
Conductance of gold nanojunctions thinned by electromigration
Authors: Hoffmann R. , Weissenberger D. , Hawecker J. , Stöffler D.
Published: July 2008

We investigate nanocontact formation by thermally assisted electromigration of gold nanowires. An automatic cycling process allows us to follow a line of constant power dissipated at the nanocontact up to resistances corresponding to 10–20 conductance quanta. The contacts are thinned in a controlled way by voltage-induced heating. In the ballistic regime, oscillations of the conductance histograms show oscillations typical for atomic discreteness.
Enhanced thermoelectric property originating from additional carrier pocket in skutterudite compounds
Authors: Liu Wei-Shu , Zhao Li-Dong , Zhang Bo-Ping , Zhang Hai-Long , Li Jing-Feng
Published: July 2008

The effect of additional carrier pocket (ACP) on the thermoelectric property is investigated based on the multiband model, indicating that an ACP indeed enhances the power factor, and hence the thermoelectric figure of merit. The established model can be used to well explain the experimental observations in skutterudite compounds that a small addition of Ni or Pd significantly enhances power factor. However, the ACP effect works only when the edge energy difference EΔ between major carrier pocket and ACP is less than 5kBT.
Noncontact inspection technique for electrical failures in semiconductor devices using a laser terahertz emission microscope
Authors: Yamashita Masatsugu , Otani Chiko , Kawase Kodo , Nikawa Kiyoshi , Tonouchi Masayoshi
Published: July 2008

We have proposed and demonstrated a novel technique for the noncontact inspection of electrical failures in semiconductor devices using a laser terahertz emission microscope. It was found that the waveforms of the terahertz pulses, emitted by exciting p-n junctions in semiconductor circuits with focused ultrafast laser pulses, depend on the interconnection structures of the circuits. We successfully distinguished damaged silicon metal-oxide-semiconductor field effect transistor circuits with disconnected wires from normal ones by comparing the images of terahertz emission amplitudes between a normal chip and a defective one.
Probing coherently excited optical phonons by extreme ultraviolet radiation with femtosecond time resolution
Authors: Papalazarou E. , Boschetto D. , Gautier J. , Garl T. , Valentin C. , Rey G. , Zeitoun Ph. , Rousse A. , Balcou Ph. , Marsi M.
Published: July 2008

We present a pump-probe experimental approach to study time-resolve coherent optical phonons using light pulses in the extreme ultraviolet wavelength range with femtosecond time resolution. Using this technique, a Bi (111)-oriented single crystal was excited by near-infrared (1.55eV) pulses and probed by a high-order harmonic generation source, whose intrinsic flux instability was reduced by making use of a normalization procedure. This unconventional approach allowed us to perform measurements in a previously inaccessible range of phonon wavevectors within the Brillouin zone.
Observation of negative capacitances in metal-insulator-metal devices based on a-BaTiO3:H
Authors: El Kamel F. , Gonon P. , Jomni F. , Yangui B.
Published: July 2008

We study capacitance dispersion in hydrogen-doped amorphous barium titanate (a-BaTiO3:H). Negative values of capacitance are observed at very low frequencies (<10 Hz). This behavior is shown to be related to proton and oxygen vacancy conductions. A qualitative model is proposed to explain negative capacitances. It involves the modification of the Schottky barrier at the metal-dielectric interface upon accumulation of mobile protons and oxygen vacancies at electrodes.
Large electric tunability in poly(vinylidene fluoride-trifluoroethylene) based polymers
Authors: Lu S. G. , Neese B. , Chu B. J. , Wang Y. , Zhang Q. M.
Published: July 2008

A tunability as high as 86% was obtained at the Curie temperature in poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] 55/45 copolymers when a 100 MV/m dc electric field was applied. The tunability was much higher than that in P[VDF-TrFE-chlorofluoroethylene (CFE)] 64.3/27.6/8.1 terpolymers, which demonstrated only 49% in a 50 MV/m electric field and at the phase transition temperature. The large difference was regarded to come from the domain size change when CFE was introduced into the copolymers, and the polymer changed from normal ferroelectric for copolymers to the relaxor ferroelectric for terpolymers.
Room temperature single ion detection with Geiger mode avalanche diode detectors
Authors: Seamons J. A. , Bielejec E. , Carroll M. S. , Childs K. D.
Published: July 2008

We report on the fabrication and performance of a novel single ion Geiger mode avalanche (SIGMA) diode detector that senses single ions with ∼100% detection efficiency at room temperature for 250 keV protons. The SIGMA diode detector utilizes Geiger mode operation of avalanche photodiodes, which can be sensitive to single electron-hole (e-h) pairs induced by the ion stopping. The SIGMA diode detector takes advantage of a complementary metal oxide semiconductor foundry allowing for future integration with silicon nanostructures to build novel single atom modified devices. SIGMA diode detector offers potential improvement in current integrated ion detector approaches that have noise floors in the order of 103 e-h pairs.
Correlation of tellurium inclusions and carrier lifetime in detector grade cadmium zinc telluride
Authors: Elshazly Ezzat S. , Tepper Gary
Published: July 2008

Carrier lifetimes and tellurium inclusion densities in detector grade cadmium zinc telluride crystals grown by the high pressure Bridgman method were optically measured using pulsed laser microwave cavity perturbation and infrared microscopy. Excess carriers were produced in the material using a pulsed laser with a wavelength of 1064 nm and pulse width of 7 ns, and the electronic decay was measured at room temperature. Spatial mapping of lifetimes and defect densities in cadmium zinc telluride was performed to determine the relationship between tellurium defect density and trapping. A strong correlation was found between the volume fraction of tellurium inclusions and the carrier trapping time.
Lifetimes and Auger coefficients in type-II W interband cascade lasers
Authors: Bewley W. W. , Lindle J. R. , Kim C. S. , Kim M. , Canedy C. L. , Vurgaftman I. , Meyer J. R.
Published: July 2008

Lifetimes and Auger coefficients for type-II W interband cascade lasers are deduced from correlations of the experimental threshold current densities and slope efficiencies with calculated threshold carrier densities and optical gains. The room-temperature Auger coefficients for a number of low-threshold devices emitting at wavelengths from 2.9 to 4.1 μm fall in the narrow range of (3–5)×10−28 cm6/s, which represents a much stronger suppression of Auger decay than was implied by most earlier experiments and theoretical projections. The Auger coefficient is nearly independent of the thicknesses and compositions of the layers in the W active region.
A tangled tale of topological fluids
Authors: McLeish Tom
Published: July 2008

Whether a large polymer is linear, simply branched like a star, or multiply branched dramatically affects how it moves through a densely entangled polymer soup
Acoustic design of music rehearsal rooms
Authors: Ryherd Erica
Published: July 2008

An architectural acoustician relies on the physics of sound propagation, material properties, and noise control to craft a desired soundscape.
Light-activated DNA binding in a designed allosteric protein
Authors: Strickland Devin , Moffat Keith , Sosnick Tobin R.
Published: July 2008

An understanding of how allostery, the conformational coupling of distant functional sites, arises in highly evolvable systems is of considerable interest in areas ranging from cell biology to protein design and signaling networks. We reasoned that the rigidity and defined geometry of an α-helical domain linker would make it effective as a conduit for allosteric signals. To test this idea, we rationally designed 12 fusions between the naturally photoactive LOV2 domain from
Avena sativa
phototropin 1 and the
Escherichia coli trp
repressor. When illuminated, one of the fusions selectively binds operator DNA and protects it from nuclease digestion. The ready success of our rational design strategy suggests that the helical “allosteric lever arm” is a general scheme for coupling the function of two proteins.
ESAT-6-specific CD4 T cell responses to aerosolMycobacterium tuberculosisinfection are initiated in the mediastinal lymph nodes
Authors: Reiley William W. , Calayag Mark D. , Wittmer Susan T. , Huntington Jennifer L. , Pearl John E. , Fountain Jeffrey J. , Martino Cynthia A. , Roberts Alan D. , Cooper Andrea M. , Winslow Gary M. , Woodland David L.
Published: July 2008

CD4+T cell responses to aerosolMycobacterium tuberculosis(Mtb) infection are characterized by the relatively delayed appearance of effector T cells in the lungs. This delay in the adaptive response is likely critical in allowing the bacteria to establish persistent infection. Because of limitations associated with the detection of low frequencies of naïve T cells, it had not been possible to precisely determine when and where naïve antigen-specific T cells are first activated. We have addressed this problem by using early secreted antigenic target 6 (ESAT-6)-specific transgenic CD4 T cells to monitor early T cell activationin vivo. By using an adoptive transfer approach, we directly show that T cell priming to ESAT-6 occurs only after 10 days of infection, is initially restricted to the mediastinal lymph nodes, and does not involve other lymph nodes or the lungs. Primed CD4 T cells rapidly differentiated into proliferating effector cells and ultimately acquired the ability to produce IFN-γ and TNF-αex vivo. Initiation of T cell priming was enhanced by two full days depending on the magnitude of the challenge inoculum, which suggests that antigen availability is a factor limiting the early CD4 T cell response. These data define a key period in the adaptive immune response to Mtb infection.
Poxvirus ankyrin repeat proteins are a unique class of F-box proteins that associate with cellular SCF1 ubiquitin ligase complexes
Authors: Sonnberg Stephanie , Seet Bruce T. , Pawson Tony , Fleming Stephen B. , Mercer Andrew A.
Published: July 2008

F-box proteins direct the degradation of an extensive range of proteins via the ubiquitin-proteasome system. Members of this large family of proteins are typically bipartite. They recruit specific substrates through a substrate-binding domain and, via the F-box, link these to core components of a major class of ubiquitin ligases (SCF1). F-box proteins thus determine the specificity of SCF1-mediated ubiquitination. F-box-like motifs were recently detected in poxvirus ankyrin repeat (ANK) proteins but clear compositional differences to typical F-box proteins raise questions regarding the classification and function of the motif. Here we show that all five ANK proteins of a representative poxvirus, Orf virus, interact
in vivo
with core components of the SCF1 ubiquitin ligase complex. Interaction is dependent on the poxviral F-box-like motif and the adaptor subunit of the complex (SKP1). The viral protein does not block enzymatic activity of the complex. These observations identify the poxviral motif as a functional F-box. They also identify a new class of F-box that in contrast to cellular counterparts is truncated, has an extreme C-terminal location and is paired with an ANK protein-binding domain. ANK proteins constitute the largest family of poxviral proteins but their function and the significance of their abundance have remained an enigma. We propose that poxviruses use these unique ANK/F-box proteins to dictate target specificity to SCF1 ubiquitin ligases and thereby exploit the cell's ubiquitin-proteasome machinery.
Death receptor 5 mediated-apoptosis contributes to cholestatic liver disease
Authors: Takeda Kazuyoshi , Kojima Yuko , Ikejima Kenichi , Harada Kenichi , Yamashina Shunhei , Okumura Kyoko , Aoyama Tomonori , Frese Steffen , Ikeda Hiroko , Haynes Nicole M. , Cretney Erika , Yagita Hideo , Sueyoshi Noriyoshi , Sato Nobuhiro , Nakanuma Yasuni , Smyth Mark J. , Okumura Ko
Published: July 2008

Chronic cholestasis often results in premature death from liver failure with fibrosis; however, the molecular mechanisms contributing to biliary cirrhosis are not demonstrated. In this article, we show that the death signal mediated by TNF-related apoptosis-inducing ligand (TRAIL) receptor 2/death receptor 5 (DR5) may be a key regulator of cholestatic liver injury. Agonistic anti-DR5 monoclonal antibody treatment triggered cholangiocyte apoptosis, and subsequently induced cholangitis and cholestatic liver injury in a mouse strain-specific manner. TRAIL- or DR5-deficient mice were relatively resistant to common bile duct ligation-induced cholestasis, and common bile duct ligation augmented DR5 expression on cholangiocytes, sensitizing mice to DR5-mediated cholangitis. Notably, anti-DR5 monoclonal antibody-induced cholangitis exhibited the typical histological appearance, reminiscent of human primary sclerosing cholangitis. Human cholangiocytes constitutively expressed DR5, and TRAIL expression and apoptosis were significantly elevated in cholangiocytes of human primary sclerosing cholangitis and primary biliary cirrhosis patients. Thus, TRAIL/DR5-mediated apoptosis may substantially contribute to chronic cholestatic disease, particularly primary sclerosing cholangitis.
Endothelial Notch4 signaling induces hallmarks of brain arteriovenous malformations in mice
Authors: Murphy Patrick A. , Lam Michael T. Y. , Wu Xiaoqing , Kim Tyson N. , Vartanian Shant M. , Bollen Andrew W. , Carlson Timothy R. , Wang Rong A.
Published: July 2008

Brain arteriovenous malformations (BAVMs) can cause devastating stroke in young people and contribute to half of all hemorrhagic stroke in children. Unfortunately, the pathogenesis of BAVMs is unknown. In this article we show that activation of Notch signaling in the endothelium during brain development causes BAVM in mice. We turned on constitutively active Notch4 (
int3
) expression in endothelial cells from birth by using the tetracycline-regulatable system. All mutants developed hallmarks of BAVMs, including cerebral arteriovenous shunting and vessel enlargement, by 3 weeks of age and died by 5 weeks of age. Twenty-five percent of the mutants showed signs of neurological dysfunction, including ataxia and seizure. Affected mice exhibited hemorrhage and neuronal cell death within the cerebral cortex and cerebellum. Strikingly,
int3
repression resolved ataxia and reversed the disease progression, demonstrating that
int3
is not only sufficient to induce, but also required to sustain the disease. We show that
int3
expression results in widespread enlargement of the microvasculature, which coincided with a reduction in capillary density, linking vessel enlargement to Notch's known function of inhibiting vessel sprouting. Our data suggest that the Notch pathway is a molecular regulator of BAVM pathogenesis in mice, and offer hope that their regression might be possible by targeting the causal molecular lesion.