bluuebunny/crossref_metadata_2025 huggingface dataset:
High quality mechanical and optical properties of commercial silicon nitride membranes
Authors: Zwickl B. M. , Shanks W. E. , Jayich A. M. , Yang C. , Bleszynski Jayich A. C. , Thompson J. D. , Harris J. G. E.
Published: March 2008

We have measured the optical and mechanical loss of commercial silicon nitride membranes. We find that 50nm thick, 1mm2 membranes have mechanical Q>106 at 293K, and Q>107 at 300mK, well above what has been observed in devices with comparable dimensions. The near-IR optical loss at 293K is less than 2×10−4. This combination of properties make these membranes attractive candidates for studying quantum effects in optomechanical systems.
Capacitive-based dilatometer cell constructed of fused quartz for measuring the thermal expansion of solids
Authors: Neumeier J. J. , Bollinger R. K. , Timmins G. E. , Lane C. R. , Krogstad R. D. , Macaluso J.
Published: March 2008

A dilatometer cell that can detect sub angstrom changes in the length of solid specimens in the temperature range 5K<T<350K is described. It is constructed entirely from fused quartz (silica). This is a capacitive-based technique, where the spacing between two metallized plates allows detection of changes in length. It is also a relative measurement in the sense that the capacitor plate spacing is determined by the relative thermal expansions of the cell and sample. The advantage of using fused quartz is that it has among the smallest known thermal expansions. As a result, for most measurements, the sample’s thermal expansion dominates the capacitance change. The construction and performance are described. It is directly compared to a dilatometer cell constructed of copper. Some thermometry and temperature control issues specific to dilatometry measurements are discussed.
On fully three-dimensional resistive wall mode and feedback stabilization computations
Authors: Strumberger E. , Merkel P. , Sempf M. , Günter S.
Published: March 2008

Resistive walls, located close to the plasma boundary, reduce the growth rates of external kink modes to resistive time scales. For such slowly growing resistive wall modes, the stabilization by an active feedback system becomes feasible. The fully three-dimensional stability code STARWALL, and the feedback optimization code OPTIM have been developed [P. Merkel and M. Sempf, 21st IAEA Fusion Energy Conference 2006, Chengdu, China (International Atomic Energy Agency, Vienna, 2006, paper TH/P3-8] to compute the growth rates of resistive wall modes in the presence of nonaxisymmetric, multiply connected wall structures and to model the active feedback stabilization of these modes. In order to demonstrate the capabilities of the codes and to study the effect of the toroidal mode coupling caused by multiply connected wall structures, the codes are applied to test equilibria using the resistive wall structures currently under debate for ITER [M. Shimada et al., Nucl. Fusion 47, S1 (2007)] and ASDEX Upgrade [W. Köppendörfer et al., Proceedings of the 16th Symposium on Fusion Technology, London, 1990 (Elsevier, Amsterdam, 1991), Vol. 1, p. 208].
Quantum reference frames and the classification of rotationally invariant maps
Authors: Boileau J.-C. , Sheridan L. , Laforest M. , Bartlett S. D.
Published: March 2008

We give a convenient representation for any map that is covariant with respect to an irreducible representation of SU(2), and use this representation to analyze the evolution of a quantum directional reference frame when it is exploited as a resource for performing quantum operations. We introduce the moments of a quantum reference frame, which serve as a complete description of its properties as a frame, and investigate how many times a quantum directional reference frame represented by a spin-j system can be used to perform a certain quantum operation with a given probability of success. We provide a considerable generalization of previous results on the degradation of a reference frame, from which follows a classification of the dynamics of spin-j system under the repeated action of any covariant map with respect to SU(2).
Stability of the boundary layer flow on a long thin rotating cylinder
Authors: Herrada M. A. , Del Pino C. , Fernandez-Feria R.
Published: March 2008

The development and stability of the boundary layer flow over a long thin cylinder aligned with the main flow and which rotates around its axis is considered. Numerical results show that the introduction of rotation has an important effect on the behavior of the basic flow. When the swirl increases, the shear stress at the wall also increases due to the changes in the pressure distribution along the cylinder surface. A nonparallel linear stability analysis of the basic flow is performed using parabolized stability equations. Even at moderately low rotation, we find the existence of unstable centrifugal modes, in addition to the shear ones found in previous stability analysis of the boundary layer flow on a cylinder with no rotation. These centrifugal instabilities develop at Reynolds numbers, based on the cylinder radius and external axial velocity, much smaller than those required for the growing of the shear instabilities. Our analysis shows that nonparallel effects play a key role in the onset and development of these instabilities, being the spiral mode with azimuthal wavenumber n=1, the first to become unstable as the Reynolds number is increased in most cases of interest. We characterize the critical Reynolds number for convective instability as a function of the axial distance to the leading edge for several values of the swirl parameter.
Magnetic field dependence of asymmetry-induced transport: A new approach
Authors: Eggleston D. L. , Williams J. M.
Published: March 2008

A new technique is used to experimentally study the dependence of asymmetry-induced radial particle flux Γ on an axial magnetic field B in a modified Malmberg–Penning trap. This dependence is complicated by the fact that B enters the physics in at least two places: in the asymmetry-induced first order radial drift velocity vr=Eθ∕B and in the zeroth order azimuthal drift velocity vθ=Er∕B. To separate these, it is assumed that the latter always enters the physics in the combination ω−lωR, where ωR(r)=vθ∕r is the column rotation frequency and ω and l are the asymmetry frequency and azimuthal mode number, respectively. Points where ω−lωR=0 are then selected from a Γ versus r versus ω data set, thus insuring that any function of this combination is constant. When the selected flux is plotted versus the density gradient ∇n, a roughly linear dependence is observed, showing that the assumption is valid and that the diffusive contribution to the transport has been isolated. The slope of a least-squares fitted line then gives the diffusion coefficient D0 for the selected flux. Varying the magnetic field, it is found that D0∝B−1.33±0.05. This does not match the scaling predicted by resonant particle transport theory.
The interfacial properties of MgCl2 thin films grown on Si(111)7×7
Authors: Karakalos Stavros , Siokou Angeliki , Dracopoulos Vasileios , Sutara Frantisek , Skala Tomas , Skoda Michal , Ladas Spyros , Prince Kevin , Matolin Vladimir , Chab Vladimir
Published: March 2008

Photoelectron spectroscopy with synchrotron radiation and low energy electron diffraction (LEED) were used in order to study the MgCl2∕Si(111) system. At submonolayer coverage of MgCl2, a new LEED pattern was observed corresponding to a (3×3)R30° overlayer superimposed on the underlying reconstructed Si(111)7×7. The surface species at this stage are mainly molecular MgCl2 and MgClx (x<2) or MgOxCly attached to the Si substrate through Cl bridges coexisting with monodentate SiCl. The interfacial interaction becomes more pronounced when the submonolayer coverage is obtained by annealing thicker MgCl2 layers, whereby desorption of molecular MgCl2 is observed leaving on the nonreconstructed silicon surface an ∼0.2 ML thick MgClx layer which again forms the (3×3)R30° superstructure.
Interaction of intense ultrashort pulse lasers with clusters
Authors: Petrov G. M. , Davis J.
Published: March 2008

The dynamics of clusters composed of different material irradiated by a high-intensity ultrashort pulse laser was studied using a fully relativistic three-dimensional molecular dynamics model. Key parameters of the cluster evolution such as particle positions, energy absorption, and cluster explosion were simulated. By a direct comparison of these parameters for clusters of equal initial radius but made of different material (deuterium, neon, argon, and xenon), the main stages and attributes of cluster evolution were elucidated. The simulations showed that clusters made of different material act alike, especially those of heavy elements. Clusters made of heavy elements (neon, argon, and xenon) differentiate from clusters made of light elements (deuterium) by the magnitude of the absorbed energy per cluster and the final mean energy of exploding ions. What most distinguishes clusters composed of different material is the amount of emitted radiation and its spectral range.
Postbuckling of circular rings: An analytical solution
Authors: Adams A. J.
Published: March 2008

The paper gives the analytical solution for postbuckling of an initially circular inextensible elastic ring under uniform external pressure.
Adiabatic intramolecular movements for water systems
Authors: Pedroza Luana S. , da Silva Antônio J. R.
Published: March 2008

An effective treatment of the intramolecular degrees of freedom is presented for water, where these modes are decoupled from the intermolecular ones, “adiabatically” allowing these coordinates to be positioned at their local minimum of the potential energy surface. We perform ab initio Monte Carlo simulations with the configurational energies obtained via density functional theory. We study a water dimer as a prototype system, and even in this simple case the intramolecular relaxations are very important to properly describe properties such as the dipole moment. We show that rigid simulations do not correctly sample the phase space, resulting in an average dipole moment smaller than the one obtained with the adiabatic model, which is closer to the experimental result.
Structurally frustrated polar nanoregions in BaTaO2N and the relationship between its high dielectric permittivity and that of BaTiO3
Authors: Withers R. L. , Liu Y. , Woodward P. , Kim Y.-I.
Published: March 2008

This letter presents direct evidence for the existence of the same inherently polar one-dimensional (1D), displacive disorder in BaTaO2N as occurs in paraelectric BaTiO3 as well as in doped BaTiO3 relaxor ferroelectric systems. The inherently polar, off-center and oppositely directed displacements of Ta and neighboring O∕N ions along ⟨001⟩ give rise to 1D polar nanoregions (PNRs) and are responsible for the dielectric properties of BaTaO2N. A bond valence sum analysis of the underlying crystal chemistry of BaTaO2N shows clearly that O∕N ordering is not directly responsible for inducing the observed 1D PNRs.
Low temperature thermal, thermoelectric, and thermomagnetic transport in indium rich Pb1−xSnxTe alloys
Authors: Jovovic V. , Thiagarajan S. J. , Heremans J. P. , Komissarova T. , Khokhlov D. , Nicorici A.
Published: March 2008

Galvanomagnetic and thermomagnetic data of single crystal indium rich Pb1−xSnxTe are analyzed, and electronic band parameters are calculated using nonparabolic band model. Transport properties at 80K are presented as a function of Sn (x=0–0.3) and In concentrations. Our results indicate pinning of Fermi level by indium impurity levels in these alloys. Effects of interaction of band with impurity level are investigated in terms of change in effective mass and energy scattering exponent. Indium doping slightly improves the thermoelectric properties of PbSnTe alloys.
Nematic ordering and defects on the surface of a sphere: A Monte Carlo simulation study
Authors: Bates Martin A.
Published: March 2008

We examine the ordering of hard rods on the surface of a sphere using computer simulations. As predicted by previous theories of thin nematic shells we observe four s=+1/2 defects. However, the predicted tetrahedral symmetry for the defects and the “baseball” director configuration is not observed. Instead the four defects are located, on average, on a great circle which splits the sphere into two hemispheres, each of which has a splay dominated director configuration. We argue that this result occurs as the bend elastic constant for hard rods is much larger than the splay elastic constant.
Electrophoretic size separation of particles in a periodically constricted microchannel
Authors: Cheng Kuang-Ling , Sheng Yu-Jane , Jiang Shaoyi , Tsao Heng-Kwong
Published: March 2008

The size separation of Brownian particles with the same free mobility in an electrophoretic microchannel with alternating thick regions and narrow constrictions is studied theoretically. The electrophoretic mobility is field dependent and generally increases with field strength. In weak fields, Brownian diffusion dominates and the migration is controlled by the entrance effect. Therefore, smaller particles migrate faster than larger ones. In strong fields, however, the particle tends to follow electric field lines. Smaller particles are susceptible to Brownian motion and thus influenced by the nonuniform electric field in the well significantly. As a result, larger particles possess higher mobilities. Our simulation results agree with the experimental observations and provide guidance for efficient nanofluidic separation.
Broadband optical absorbance spectroscopy using a whispering gallery mode microsphere resonator
Authors: Westcott Sarah L. , Zhang Jiangquan , Shelton Robert K. , Bruce Nellie M. K. , Gupta Sachin , Keen Steven L. , Tillman Jeremy W. , Wald Lara B. , Strecker Brian N. , Rosenberger A. T. , Davidson Roy R. , Chen Wei , Donovan Kevin G. , Hryniewicz John V.
Published: March 2008

We demonstrate the ability to excite and monitor many whispering gallery modes (WGMs) of a microsphere resonator simultaneously in order to make broadband optical absorbance measurements. The 340μm diameter microsphere is placed in a microfluidic channel. A hemispherical prism is used for coupling the WGMs into and out of the microsphere. The flat surface of the prism seals the microfluidic channel. The slight nonsphericity in the microsphere results in coupling to precessed modes whose emission is spatially separated from the reflected excitation light. The evanescent fields of the light trapped in WGMs interact with the surrounding environment. The change in transmission observed in the precessed modes is used to determine the absorbance of the surrounding environment. In contrast to our broadband optical absorbance measurements, previous WGM sensors have used only a single narrow mode to measure properties such as refractive index. With the microfluidic cell, we have measured the absorbance of solutions of dyes (lissamine green B, sunset yellow, orange G, and methylene blue), aromatic molecules (benzylamine and benzoic acid), and biological molecules (tryptophan, phenylalanine, tyrosine, and o-phospho-L-tyrosine) at visible and ultraviolet wavelengths. The microsphere surface was reacted with organosilane molecules to attach octadecyl groups, amino groups, and fluorogroups to the surface. Both electrostatic and hydrophobic interactions were observed between the analytes and the microsphere surface, as indicated by changes in the measured effective pathlength with different organosilanes. For a given analyte and coated microsphere, the pathlength measurement was repeatable within a few percent. Methylene blue dye had a very strong interaction with the surface and pathlengths of several centimeters were measured. Choosing an appropriate surface coating to interact with a specific analyte should result in the highest sensitivity detection.
Stripe sensor tomography
Authors: Barbic Mladen , Vltava Lvcian , Barrett Christopher P. , Emery Teresa H. , Scherer Axel
Published: March 2008

We introduce a general concept of tomographic imaging for the case of an imaging sensor that has a stripelike shape. We first show that there is no difference, in principle, between two-dimensional tomography using conventional electromagnetic or particle radiation and tomography where a stripe sensor is mechanically scanned over a sample at a sequence of different angles. For a single stripe detector imaging, linear motion and angular rotation are required. We experimentally demonstrate single stripe sensor imaging principle using an elongated inductive coil detector. By utilizing an array of parallel stripe sensors that can be individually addressed, two-dimensional imaging can be performed with rotation only, eliminating the requirement for linear motion, as we also experimentally demonstrate with parallel coil array. We conclude that imaging with a stripe-type sensor of particular width and thickness (where the width is much larger than the thickness) is resolution limited only by the thickness (smaller parameter) of the sensor. We give examples of multiple sensor families where this imaging technique may be beneficial such as magnetoresistive, inductive, superconducting quantum interference device, and Hall effect sensors, and, in particular, discuss the possibilities of the technique in the field of magnetic resonance imaging.
Specular Andreev reflection and magnetoresistance in graphene-based ferromagnet-superconductor double junctions
Authors: Bai Chunxu , Yang Yanling , Zhang Xiangdong
Published: March 2008

Spin-polarized transports of relativistic electrons through graphene-based ferromagnet-superconductor double junctions have been investigated theoretically. In the presence of specular Andreev reflection, some unusual properties are found. The oscillating negative magnetoresistance (MR) is not only observed, but the resonance peak of the MR also appears at a certain bias voltage due to the retroreflection crossing over to the specular Andreev reflection. This means that the MR can be tuned by external bias voltage, which benefits the spin-polarized electron device based on the graphene materials.
Magnetoelectric properties of BixCo2−xMnO4 (⩽x⩽0.3)
Authors: Rajeevan N. E. , Pradyumnan P. P. , Kumar Ravi , Shukla D. K. , Kumar S. , Singh A. K. , Patnaik S. , Arora S. K. , Shvets I. V.
Published: March 2008

We present the structural, dielectric and magnetization study of single phase polycrystalline BixCo2−xMnO4 (0⩽x⩽0.3), synthesized by a conventional solid state route. All the samples have the cubic spinel structure with Fd3m space group. Bi-substitution in Co2MnO4 stabilizes the ferroelectric transition at a temperature of ∼350K and enhances the dielectric constant with a relaxor behavior. The capacitance-voltage (C-V) measurements confirm the ferroelectric nature at room temperature. Ferrimagnetic nature of the Co2MnO4 is preserved in the Bi-substituted samples. Magnetocapacitive coupling proves candidature of these materials from an application point of view.
Subpicosecond timescale carrier dynamics in GaInAsSb∕AlGaAsSb double quantum wells emitting at 2.3μm
Authors: Rainò G. , Salhi A. , Tasco V. , Intartaglia R. , Cingolani R. , Rouillard Y. , Tournié E. , De Giorgi M.
Published: March 2008

We report the results of an extensive optical investigation by continuous-wave and time resolved photoluminescence experiments on double GaInAsSb∕AlGaAsSb quantum wells emitting at 2.3μm at room temperature. We have found that, at low temperature (<70K), the recombination is dominated by excitons trapped in disorder and interface defects. Whereas, at higher temperature, free-exciton recombination occurs. The observed temperature dependent photoluminescence quenching is ascribed to the ionization of bound exciton at low temperatures, while thermoionic emission of the hole out of the quantum well dominates photoluminescence quenching at high temperatures. The experimental results are supported by theoretical calculations.
Loss of phosphorus due to segregation at Si∕SiO2 interfaces: Experiments and modeling
Authors: Chang R. D. , Tsai J. R.
Published: March 2008

Phosphorus segregation at Si∕SiO2 interfaces was examined experimentally and by simulation, for phosphorus implanted at doses of 2×1013 and 7×1013cm−2. Reversible loss of implanted phosphorus was observed during annealing due to interface segregation. Two stages of dose recovery were observed in samples that were implanted at 7×1013cm−2. The surface concentration remains almost constant with rapid dose recovery during the early stage of annealing. The rate of dose recovery declines with the decay of the surface concentration after long-term annealing. Samples with implantation at 2×1013cm−2 exhibit only slow dose recovery. Slow dose recovery at low surface concentration was captured by simulation based on a conventional interface trap model. An interface clustering model was developed to simulate rapid dose recovery with an almost constant surface concentration. The interface clustering model assumes clustering reactions between phosphorus atoms at the interface while the interface trap model considers phosphorus trapping by individual interface defects. The difference between the segregation mechanisms is evidenced by the fact that the extracted segregation energy of the interface trap model greatly exceeds that of the interface clustering model.
Bulk moduli of wurtzite, zinc-blende, and rocksalt phases of ZnO from chemical bond method and density functional theory
Authors: Fan Changzeng , Wang Qiang , Li Lixiang , Zhang Suhong , Zhu Yan , Zhang Xinyu , Ma Mingzhen , Liu Riping , Wang Wenkui
Published: March 2008

The density functional theory based first-principles calculations and a recently proposed chemical bond method are used to investigate the elastic and compressibility properties of the rocksalt, wurtzite, and zinc-blende phases of ZnO. The calculated bulk moduli from these two means explain the discrepancy between the theoretical and experimental values of the bulk modulus of wurtzite ZnO as well as the scattered experimental data. The results suggest that further experimental efforts are needed in order to obtain the intrinsic bulk moduli of the three phases of ZnO.
Ultraviolet spectra of KPb2Cl5:Er3+
Authors: Jia Guohua , Tanner Peter A. , Tu Chaoyang , Li Jianfu , Lin Meng-Yeh , Cheng Bing-Ming
Published: March 2008

The vacuum ultraviolet excitation and ultraviolet-visible emission spectra are reported for the laser and upconverter material KPb2Cl5:Er3+. The low-phonon energies of the host lattice enable, in addition to the ten luminescent states of Er3+ in the visible and infrared spectral regions at room temperature, the observation of a further two luminescent multiplet terms in the ultraviolet spectral region at 10K. A careful distinction is made between 4f11–4f11 Er3+ transitions and the band to band and Pb2+ transitions.
Manganite thin film/ZnO nanowire (nanosheets) p-n junctions
Authors: Zhang Zhou , Sun Yinghui , Zhao Yonggang , Li Gongping , Wu Tom
Published: March 2008

We have fabricated p-type La0.7Sr0.3MnO3 thin film/n-type ZnO nanowires (nanosheets) heterostructures. A lower-temperature growth with Zn source and a higher-temperature growth with ZnO/graphite source led to the formations of nanowires and nanosheets, respectively. While the nanosheets showed an epitaxial relationship with the manganite film, the high processing temperature resulted in interfacial diffusion and reaction, which were reflected in the x-ray diffraction, magnetic, and electrical transport measurements. The manganite thin film/ZnO nanowires (nanosheets) p-n junctions exhibited good rectification behaviors. Such heterostructures are promising to find potential applications in electronic and spintronic devices.
Gold nanoparticle-pentacene memory transistors
Authors: Novembre Christophe , Guérin David , Lmimouni Kamal , Gamrat Christian , Vuillaume Dominique
Published: March 2008

We demonstrate an organic memory-transistor device based on a pentacene-gold nanoparticles active layer. Gold (Au) nanoparticles are immobilized on the gate dielectric (silicon dioxide) of a pentacene transistor by an amino-terminated self-assembled monolayer. Under the application of writing and erasing pulses on the gate, large threshold voltage shift (22V) and on/off drain current ratio of ∼3×104 are obtained. The hole field-effect mobility of the transistor is similar in the on and off states (less than a factor of 2). Charge retention times up to 4500s are observed. The memory effect is mainly attributed to the Au nanoparticles.
Resonance magnetoelectric interactions due to bending modes in a nickel-lead zirconate titanate bilayer
Authors: Chashin D. V. , Fetisov Y. K. , Kamentsev K. E. , Srinivasan G.
Published: March 2008

Resonance magnetoelectric (ME) effects due to bending oscillations have been investigated in bilayers of Ni and lead zirconate titanate (PZT). For nominal sample dimensions, such oscillations occur at a few kilohertz that are much smaller than radial or thickness acoustic modes and result in ME voltage coefficients of 1V∕cmOe for tangential magnetization. The mode frequencies can be controlled with proper choice for thicknesses of Ni and PZT. Theoretical estimates of mode frequencies are in very good agreement with the data. The resonator is potentially useful for realizing low-loss ME sensor networks for ac fields as low as 10μOe.
Electron beam induced current profiling of ZnO p-n homojunctions
Authors: Chernyak L. , Schwarz C. , Flitsiyan E. S. , Chu S. , Liu J. L. , Gartsman K.
Published: March 2008

Variable temperature electron beam induced current technique was employed for the profiling of ZnO p-n homojunctions and the extraction of minority electron diffusion length values in the Sb-doped p-type ZnO region. A thermally induced increase for diffusion length of minority electrons was determined to have an activation energy of ∼145meV. The latter parameter likely represents carrier delocalization energy and determines the increase of the diffusion length due to the reduction in recombination efficiency.
Fluorine plasma ion implantation in AlGaN∕GaN heterostructures: A molecular dynamics simulation study
Authors: Yuan L. , Wang M. J. , Chen K. J.
Published: March 2008

Fluoride-based plasma treatment is a robust technique that enables shallow implantation of fluorine ions into group III-nitride epitaxial structures. This technique has been used to achieve robust threshold voltage control of the AlGaN∕GaN high electron mobility transistors and led to the realization of self-aligned enhancement-mode devices. To reveal the atomic scale interactions and provide a modeling tool for process design and optimization, a molecular dynamics (MD) simulation is conducted for fluorine plasma ion implantation. Specific potential functions are applied to calculate the interactions among atoms and simulate the dynamic process of fluorine ions’ penetration and stopping in III-nitride materials. The MD simulation provides accurate information on dopant profiles that are verified by secondary-ion-mass-spectrum measurements. Defect formation and distributions, that are critical in process development, are also investigated.
Nearly lattice-matched n, i, and p layers for InGaN p-i-n photodiodes in the 365–500nm spectral range
Authors: Berkman E. A. , El-Masry N. A. , Emara A. , Bedair S. M.
Published: March 2008

We report on nearly lattice-matched grown InGaN based p-i-n photodiodes detecting in the 365–500nm range with tunable peak responsivity tailored by the i-layer properties. The growth of lattice matched i- and n-InGaN layer leads to improvement in the device performance. This approach produced photodiodes with zero-bias responsivities up to 0.037A∕W at 426nm, corresponding to 15.5% internal quantum efficiency. The peak responsivity wavelength ranged between 416 and 466nm, the longest reported for III-N photodiodes. The effects of InN content and i-layer thickness on photodiode properties and performance are discussed.
Segregation-controlled nanocrystallization in an Al–Ni–La metallic glass
Authors: Radiguet B. , Blavette D. , Wanderka N. , Banhart J. , Sahoo K. L.
Published: March 2008

The early stages of devitrification of Al89Ni6La5 metallic glass were investigated using three-dimensional atom probe. Even in the as-quenched amorphous state, nanometer-sized fluctuations of Ni and Al were observed. The Al-rich fluctuations act as nucleation sites for the crystallization at 443K in which α-Al clusters with a number density up to 5×1023m−3 nucleate and grow to nonspherical, 12nm large crystals. α-Al particles are almost pure in Al and are surrounded by a La-rich shell. It is concluded that La segregation controls the growth and limits the size of the α-Al nanocrystals.
Solvent mixtures for improving device efficiency of polymer photovoltaic devices
Authors: Chen Fang-Chung , Tseng Hsin-Chen , Ko Chu-Jung
Published: March 2008

In this work, we used solvent mixtures, consisting of 1-chloronaphthalene (Cl-naph), one solvent with a high boiling point, and o-dichlorobenzene, to prepare the polymer films for polymer photovoltaic devices. Because of the lower vapor pressure of the solvent mixtures, the polymer films dried slower. With higher Cl-naph concentration in the organic solvent, the polymer chains had longer time to self-organize themselves. As a result, the higher degree of crystalline led to lower device series resistance, thereby increasing the performance of the photovoltaic devices.
High-power semiconductor disk laser based on InAs∕GaAs submonolayer quantum dots
Authors: Germann T. D. , Strittmatter A. , Pohl J. , Pohl U. W. , Bimberg D. , Rautiainen J. , Guina M. , Okhotnikov O. G.
Published: March 2008

An optically pumped semiconductor disk laser using submonolayer quantum dots (SML QDs) as gain medium is demonstrated. High-power operation is achieved with stacked InAs∕GaAs SML QDs grown by metal-organic vapor-phase epitaxy. Each SML-QD layer is formed from tenfold alternate depositions of nominally 0.5 ML InAs and 2.3 ML GaAs. Resonant periodic gain from a 13-fold nonuniform stack design of SML QDs allows to produce 1.4W cw at 1034nm. The disk laser demonstrates the promising potential of SML-QD structures combining properties of QD and quantum-well gain media for high-power applications.
Ultrafast high strain rate acoustic wave measurements at high static pressure in a diamond anvil cell
Authors: Armstrong Michael R. , Crowhurst Jonathan C. , Reed Evan J. , Zaug Joseph M.
Published: March 2008

We have used subpicosecond laser pulses to launch ultrahigh strain rate (∼109s−1) nonlinear acoustic waves into a 4:1 methanol-ethanol pressure medium which has been precompressed in a standard diamond anvil cell. Using ultrafast interferometry, we have characterized acoustic wave propagation into the pressure medium at static compression of up to 24GPa. We find that the velocity is dependent on the incident laser fluence, demonstrating a nonlinear acoustic response which may result in a shock wave behavior. We compare our results to low strain rate acoustic data. This technique provides controlled access to regions of thermodynamic phase space that is otherwise difficult to obtain.
Anthrax lethal toxin and
Salmonella
elicit the common cell death pathway of caspase-1-dependent pyroptosis via distinct mechanisms
Authors: Fink Susan L. , Bergsbaken Tessa , Cookson Brad T.
Published: March 2008

Caspase-1 cleaves the inactive IL-1β and IL-18 precursors into active inflammatory cytokines. In
Salmonella
-infected macrophages, caspase-1 also mediates a pathway of proinflammatory programmed cell death termed “pyroptosis.” We demonstrate active caspase-1 diffusely distributed in the cytoplasm and localized in discrete foci within macrophages responding to either
Salmonella
infection or intoxication by
Bacillus anthracis
lethal toxin (LT). Both stimuli triggered caspase-1-dependent lysis in macrophages and dendritic cells. Activation of caspase-1 by LT required binding, uptake, and endosome acidification to mediate translocation of lethal factor (LF) into the host cell cytosol. Catalytically active LF cleaved cytosolic substrates and activated caspase-1 by a mechanism involving proteasome activity and potassium efflux. LT activation of caspase-1 is known to require the inflammasome adapter Nalp1. In contrast,
Salmonella
infection activated caspase-1 through an independent pathway requiring the inflammasome adapter Ipaf. These distinct mechanisms of caspase-1 activation converged on a common pathway of caspase-1-dependent cell death featuring DNA cleavage, cytokine activation, and, ultimately, cell lysis resulting from the formation of membrane pores between 1.1 and 2.4 nm in diameter and pathological ion fluxes that can be blocked by glycine. These findings demonstrate that distinct activation pathways elicit the conserved cell death effector mechanism of caspase-1-mediated pyroptosis and support the notion that this pathway of proinflammatory programmed cell death is broadly relevant to cell death and inflammation invoked by diverse stimuli.
Mutational load distribution analysis yields metrics reflecting genetic instability during pancreatic carcinogenesis
Authors: Tarafa Gemma , Tuck David , Ladner Daniela , Topazian Mark , Brand Randall , Deters Carolyn , Moreno Victor , Capella Gabriel , Lynch Henry , Lizardi Paul , Costa Jose
Published: March 2008

Considering carcinogenesis as a microevolutionary process, best described in the context of metapopulation dynamics, provides the basis for theoretical and empirical studies that indicate it is possible to estimate the relative contribution of genetic instability and selection to the process of tumor formation. We show that mutational load distribution analysis (MLDA) of DNA found in pancreatic fluids yields biometrics that reflect the interplay of instability, selection, accident, and gene function that determines the eventual emergence of a tumor. An
in silico
simulation of carcinogenesis indicates that MLDA may be a suitable tool for early detection of pancreatic cancer. We also present evidence indicating that, when performed serially in individuals harboring a p16 germ-line mutation bestowing a high risk for pancreatic cancer, MLDA may be an effective tool for the longitudinal assessment of risk and early detection of pancreatic cancer.
PPARδ-mediated antiinflammatory mechanisms inhibit angiotensin II-accelerated atherosclerosis
Authors: Takata Yasunori , Liu Joey , Yin Fen , Collins Alan R. , Lyon Christopher J. , Lee Chih-Hao , Atkins Annette R. , Downes Michael , Barish Grant D. , Evans Ronald M. , Hsueh Willa A. , Tangirala Rajendra K.
Published: March 2008

Activation of the nuclear hormone receptor peroxisome proliferator-activated receptor δ (PPARδ) has been shown to improve insulin resistance, adiposity, and plasma HDL levels. However, its antiatherogenic role remains controversial. Here we report atheroprotective effects of PPARδ activation in a model of angiotensin II (AngII)-accelerated atherosclerosis, characterized by increased vascular inflammation related to repression of an antiinflammatory corepressor, B cell lymphoma-6 (Bcl-6), and the regulators of G protein-coupled signaling (RGS) proteins RGS4 and RGS5. In this model, administration of the PPARδ agonist GW0742 (1 or 10 mg/kg) substantially attenuated AngII-accelerated atherosclerosis without altering blood pressure and increased vascular expression of Bcl-6, RGS4, and RGS5, which was associated with suppression of inflammatory and atherogenic gene expression in the artery.
In vitro
studies demonstrated similar changes in AngII-treated macrophages: PPARδ activation increased both total and free Bcl-6 levels and inhibited AngII activation of MAP kinases, p38, and ERK1/2. These studies uncover crucial proinflammatory mechanisms of AngII and highlight actions of PPARδ activation to inhibit AngII signaling, which is atheroprotective.
Vesicle association and exocytosis at ribbon and extraribbon sites in retinal bipolar cell presynaptic terminals
Authors: Zenisek David
Published: March 2008

Synaptic vesicles release neurotransmitter by following a process of vesicle docking and exocytosis. Although these steps are well established, it has been difficult to observe and measure these rates directly in living synapses. Here, by combining the direct imaging of single synaptic vesicles and synaptic ribbons, I measure the properties of vesicle docking and evoked and spontaneous release from ribbon and extraribbon locations in a ribbon-type synaptic terminal, the goldfish retinal bipolar cell. In the absence of a stimulus, captured vesicles near ribbons associate tightly and only rarely undock or undergo spontaneous exocytosis. By contrast, vesicle capture at outlier sites is less stable and spontaneous exocytosis occurs at a higher rate. In response to a stimulus, exocytic events cluster near ribbons, but show no evidence of clustering away from ribbon sites. Together, the results here indicate that, although vesicles can associate and fuse both near and away from synaptic sites, vesicles at synaptic ribbons associate more stably and fusion is more tightly linked to stimuli.
CAPON modulates cardiac repolarization via neuronal nitric oxide synthase signaling in the heart
Authors: Chang Kuan-Cheng , Barth Andreas S. , Sasano Tetsuo , Kizana Eddy , Kashiwakura Yuji , Zhang Yiqiang , Foster D. Brian , Marbán Eduardo
Published: March 2008

Congenital long- or short-QT syndrome may lead to life-threatening ventricular tachycardia and sudden cardiac death. Apart from the rare disease-causing mutations, common genetic variants in CAPON, a neuronal nitric oxide synthase (NOS1) regulator, have recently been associated with QT interval variations in a human whole-genome association study. CAPON had been unsuspected of playing a role in cardiac repolarization; indeed, its physiological role in the heart (if any) is unknown. To define the biological effects of CAPON in the heart, we investigated endogenous CAPON protein expression and protein–protein interactions in the heart and performed electrophysiological studies in isolated ventricular myocytes with and without CAPON overexpression. We find that CAPON protein is expressed in the heart and interacts with NOS1 to accelerate cardiac repolarization by inhibition of L-type calcium channel. Our findings provide a rationale for the association of CAPON gene variants with extremes of the QT interval in human populations.
Auxin transport inhibitors impair vesicle motility and actin cytoskeleton dynamics in diverse eukaryotes
Authors: Dhonukshe Pankaj , Grigoriev Ilya , Fischer Rainer , Tominaga Motoki , Robinson David G. , Hašek Jiří , Paciorek Tomasz , Petrášek Jan , Seifertová Daniela , Tejos Ricardo , Meisel Lee A. , Zažímalová Eva , Gadella Theodorus W. J. , Stierhof York-Dieter , Ueda Takashi , Oiwa Kazuhiro , Akhmanova Anna , Brock Roland , Spang Anne , Friml Jiří
Published: March 2008

Many aspects of plant development, including patterning and tropisms, are largely dependent on the asymmetric distribution of the plant signaling molecule auxin. Auxin transport inhibitors (ATIs), which interfere with directional auxin transport, have been essential tools in formulating this concept. However, despite the use of ATIs in plant research for many decades, the mechanism of ATI action has remained largely elusive. Using real-time live-cell microscopy, we show here that prominent ATIs such as 2,3,5-triiodobenzoic acid (TIBA) and 2-(1-pyrenoyl) benzoic acid (PBA) inhibit vesicle trafficking in plant, yeast, and mammalian cells. Effects on micropinocytosis, rab5-labeled endosomal motility at the periphery of HeLa cells and on fibroblast mobility indicate that ATIs influence actin cytoskeleton. Visualization of actin cytoskeleton dynamics in plants, yeast, and mammalian cells show that ATIs stabilize actin. Conversely, stabilizing actin by chemical or genetic means interferes with endocytosis, vesicle motility, auxin transport, and plant development, including auxin transport-dependent processes. Our results show that a class of ATIs act as actin stabilizers and advocate that actin-dependent trafficking of auxin transport components participates in the mechanism of auxin transport. These studies also provide an example of how the common eukaryotic process of actin-based vesicle motility can fulfill a plant-specific physiological role.
PPARδ regulates multiple proinflammatory pathways to suppress atherosclerosis
Authors: Barish Grant D. , Atkins Annette R. , Downes Michael , Olson Peter , Chong Ling-Wa , Nelson Mike , Zou Yuhua , Hwang Hoosang , Kang Heonjoong , Curtiss Linda , Evans Ronald M. , Lee Chih-Hao
Published: March 2008

Lipid homeostasis and inflammation are key determinants in atherogenesis, exemplified by the requirement of lipid-laden, foam cell macrophages for atherosclerotic lesion formation. Although the nuclear receptor PPARδ has been implicated in both systemic lipid metabolism and macrophage inflammation, its role as a therapeutic target in vascular disease is unclear. We show here that orally active PPARδ agonists significantly reduce atherosclerosis in apoE
−/−
mice. Metabolic and gene expression studies reveal that PPARδ attenuates lesion progression through its HDL-raising effect and anti-inflammatory activity within the vessel wall, where it suppresses chemoattractant signaling by down-regulation of chemokines. Activation of PPARδ also induces the expression of regulator of G protein signaling (RGS) genes, which are implicated in blocking the signal transduction of chemokine receptors. Consistent with this, PPARδ ligands repress monocyte transmigration and macrophage inflammatory responses elicited by atherogenic cytokines. These results reveal that PPARδ antagonizes multiple proinflammatory pathways and suggest PPARδ-selective drugs as candidate therapeutics for atherosclerosis.
A preclinical model for predicting drug response in soft-tissue sarcoma with targeted AAVP molecular imaging
Authors: Hajitou Amin , Lev Dina C. , Hannay Jonathan A. F. , Korchin Borys , Staquicini Fernanda I. , Soghomonyan Suren , Alauddin Mian M. , Benjamin Robert S. , Pollock Raphael E. , Gelovani Juri G. , Pasqualini Renata , Arap Wadih
Published: March 2008

Human sarcomas are rare but diverse malignant tumors derived from mesenchymal tissue. Clinical response to therapy is currently determined by the modified World Health Organization (WHO) criteria or the Response Evaluation Criteria in Solid Tumors (RECIST), but these standards correlate poorly with sarcoma patient outcome. We introduced ligand-directed particles with elements of AAV and phage (AAVP) to enable integration of tumor targeting to molecular imaging. We report drug-response monitoring and prediction in a nude rat model of human sarcoma by AAVP imaging. As a proof-of-concept, we imaged
Herpes simplex
thymidine kinase in a clinic-ready setting with PET to show that one can
a priori
predict tumor response to a systemic cytotoxic. Given the target expression in patient-derived sarcomas, this platform may be translated in clinical applications. Sarcoma-specific ligands and promoters may ultimately lead to an imaging transcriptome.
Distinct effects of the recurrent Mlh1
G67R
mutation on MMR functions, cancer, and meiosis
Authors: Avdievich Elena , Reiss Cora , Scherer Stefan J. , Zhang Yongwei , Maier Sandra M. , Jin Bo , Hou Harry , Rosenwald Andreas , Riedmiller Hubertus , Kucherlapati Raju , Cohen Paula E. , Edelmann Winfried , Kneitz Burkhard
Published: March 2008

Mutations in the human DNA mismatch repair (MMR) gene
MLH1
are associated with hereditary nonpolyposis colorectal cancer (Lynch syndrome, HNPCC) and a significant proportion of sporadic colorectal cancer. The inactivation of
MLH1
results in the accumulation of somatic mutations in the genome of tumor cells and resistance to the genotoxic effects of a variety of DNA damaging agents. To study the effect of
MLH1
missense mutations on cancer susceptibility, we generated a mouse line carrying the recurrent Mlh1
G67R
mutation that is located in one of the ATP-binding domains of Mlh1. Although the Mlh1
G67R
mutation resulted in DNA repair deficiency in homozygous mutant mice, it did not affect the MMR-mediated cellular response to DNA damage, including the apoptotic response of epithelial cells in the intestinal mucosa to cisplatin, which was defective in
Mlh1
−/−
mice but remained normal in

Mlh1
G67R/G67R

mice. Similar to
Mlh1
−/−
mice,

Mlh1
G67R/G67R

mutant mice displayed a strong cancer predisposition phenotype. However, in contrast to
Mlh1
−/−
mice,

Mlh1
G67R/G67R

mutant mice developed significantly fewer intestinal tumors, indicating that
Mlh1
missense mutations can affect MMR tumor suppressor functions in a tissue-specific manner. In addition,

Mlh1
G67R/G67R

mice were sterile because of the inability of the mutant Mlh1
G67R
protein to interact with meiotic chromosomes at pachynema, demonstrating that the ATPase activity of Mlh1 is essential for fertility in mammals.
The Day They Buried the Ayatollah
Authors: Fenton Tom
Published: March 2008

Note by Iranian Studies: Journalism has the potential to make a reporter feel at least as important as the subject of his or her reports. The temptation can be even stronger in global journalism, with reporters from the affluent nations covering the traumas of the people in more problem-ridden parts of the world. By contrast, in Tom Fenton's account of Ayatollah Khomeini's funeral in 1989, a seasoned reporter goes beyond the apparently chaotic and frenzied action by hundreds of thousands, if not millions, of Iranians to see the historic significance of the event and the man.

Thomas Trail Fenton, born 1930 in Baltimore, Maryland, retired from CBS in 2004 after a thirty-four year career. He graduated from Dartmouth College in 1952 and was an officer in the U.S. Navy from 1952 to 1961, serving in the Atlantic and the Mediterranean. Fenton began his career in journalism at The Baltimore Sun, where he worked until 1970, reporting from Europe and the Middle East, including the June 1967 Israeli-Arab war and the May 1968 student protests in France, which earned Fenton an award from the Overseas Press Club.

Fenton joined CBS News as a correspondent in the Rome Bureau in 1970, followed by assignments to the bureaus in Tel Aviv, Paris, London and Moscow. He became Senior European Correspondent in 1979. He reported on the Indo-Pakistani war of 1971, the 1973 Arab-Israeli war, and the 1974 Turkish invasion of Cyprus. After the fall of Mohammad Reza Shah in 1979, Fenton was the first western journalist to interview Ayatollah Khomeini. He later returned to Iran to report on the hostage crisis that had followed the occupation of the American Embassy in Tehran. During the 1990s, Fenton covered the break up of the Soviet Union, the wars in the Balkans, and the violence in the Middle East and Africa. After retiring, Fenton wrote Bad News: The Decline of Reporting, the Business of News, and the Danger to Us All in 2005.
Towards a ‘Pooled Sovereignty‘ in Community Planning in Scotland?
Authors: Lloyd M.G.
Published: March 2008

Integrated working in the public sector to achieve greater efficiencies and effectiveness in policy implementation is now a clear political objective. In practice integration of policy and institutional action requires vertical and horizontal synergies to realise its full potential. The question then arises as to how to secure these ambitions. Drawing on the experience of community planning in Scotland the paper explores the case for adopting a more formal and contractualised approach to integrated working based on devising operational agreements within the public sector.