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Physics of Fluids : Chaotic motions of a forced droplet-droplet os...

By: D. M. Slater, C. A. López, A. H. Hirsa, and P. H. Steen

Description: A model for the motion of two coupled spherical-cap droplets subject to periodic forcing is studied. The inviscid unforced model is a conservative second-order system, similar to Duffing’s equation. Surface tension resists the inertia of deformations from the spherical shape. Steady states of the system are parametrized by the total combined volume of the two droplet caps. The family of equilibria exhibits a classical pitchfork bifurcation, where a single le...

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Journal of Applied Physics : Ultraviolet light in glow discharges

By: Loic Ledernez, Fethi Olcaytug, Hirotsugu Yasuda, and Gerald Urban

Description: The use of ultraviolet light has prevailed in investigation of gas breakdown phenomena since Townsend developed the model of gas breakdown discharge carrying his name because ultraviolet light creates the supposedly necessary electrons in the interelectrode space. However, the ultraviolet light influences the gas breakdown characteristics. Therefore, the extent of the influence of the ultraviolet light on the prebreakdown current, the breakdown current, the ...

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Physics of Plasmas : Toroidal self-consistent modeling of drift ki...

By: Yueqiang Liu, M. S. Chu, I. T. Chapman, and T. C. Hender

Description: A self-consistent kinetic model is developed to study the stability of the resistive wall mode in toroidal plasmas. This model is compared with other models based on perturbative approaches. The degree of the kinetic modification to the stability of the mode depends on the plasma configurations. Both stabilizing and destabilizing kinetic effects are observed. The nonperturbative approach, with a self-consistent inclusion of the eigenfunctions and the eigenva...

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Applied Physics Letters : Measurement and evaluation of the interf...

By: Heng-Chieh Chien, Da-Jeng Yao, and Cheng-Ting Hsu

Description: We used a sandwiched film structure of dielectric, metal, and dielectric to measure and also to estimate theoretically the metal-dielectric interfacial thermal resistance. In this structure, a metal layer with a thickness of about 10 nm, including chromium, titanium, aluminum, nickel, and platinum, is sandwiched between two SiO2 layers with a thickness of 100 nm prepared by plasma enhanced chemical vapor deposition. The estimates, 10−10–10−9 m2 K W−1, calcul...

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Physics of Fluids : Measurements of the steady streaming flow arou...

By: Florian Otto, Emmalee K. Riegler, and Greg A. Voth

Description: Granular particles vibrated in a fluid have been found to exhibit self-organization with attractive and repulsive interactions between the particles. These interactions have been attributed to the steady streaming flow around oscillating particles. Here we examine the steady streaming flow surrounding a vertically oscillating sphere using three-dimensional particle tracking velocimetry. We present measurements of the flow with the sphere far from boundaries,...

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Journal of Applied Physics : Nanomechanical properties of piezores...

By: Paul R. Wilkinson, William S. Klug, Brandon Van Leer, and James K. Gimzewski

Description: Concise analytical expressions for the effective spring constant, resonance frequency, and effective mass are derived using elementary beam theory for cantilevers, which exhibit a basic rectangular cross section modified by a rectangular hole centered at the base, which is a typical case for piezoresistive cantilevers. The results demonstrate that each of these mechanical properties can be represented as the property of the same cantilever in the absence of ...

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Review of Scientific Instruments : Digital control of force micros...

By: Jonathan P. Jacky, Joseph L. Garbini, Matthew Ettus, and John A. Sidles
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Applied Physics Letters : Restoration of high spatial frequency at...

By: Du Hyun Beak, Jin Woo Yoon, Jae Sung Shin, and Hong Jin Kong

Description: We have found experimentally that it is possible to restore the high spatial frequency of optical images by using stimulated Brillouin scattering (SBS) with a prepulse. The Stokes wave usually has to lose the high spatial frequency because of the necessary energy to generate the acoustic grating. However, this problem has been resolved by using a prepulse method. We have achieved an amplitude increase of ~41% compared to the normal SBS scheme at a spatial ...

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Review of Scientific Instruments : Design of a double diaphragm sh...

By: Ingo Stotz, Grazia Lamanna, Harald Hettrich, Bernhard Weigand, and Johan Steelant

Description: A double diaphragm shock tube facility for studying liquid-spray atomization and combustion-related phenomena at elevated pressures and temperatures is described. The present shock tube is specifically intended for the investigation of fundamental processes related to fluid disintegration and mixing under realistic engine conditions. Special features of the facility include a variable-area driver section to compensate for shock attenuation, a square test sec...

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Applied Physics Letters : Spin precession induced by an effective ...

By: Genhua Liu, Yonghai Chen, Caihong Jia, and Zhanguo Wang

Description: We theoretically study the spatial behaviors of the spin precession in a two-dimensional electron system with spin-orbit interaction. Through analysis of interaction between the spin and the effective magnetic field in the system, we obtain the general conditions to generate a persistent spin helix and predict a persistent spin helix pattern in [001] -grown quantum wells. Particularly, we demonstrate that the phase of spin can be locked to propagate in a qu...

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Journal of Applied Physics : Direct evidence of detwinning in poly...

By: Z. H. Nie, R. Lin Peng, S. Johansson, E. C. Oliver, Y. Ren et al

Description: In situ time-of-flight neutron diffraction and high-energy x-ray diffraction techniques were used to reveal the preferred reselection of martensite variants through a detwinning process in polycrystalline Ni–Mn–Ga ferromagnetic shape memory alloys under uniaxial compressive stress. The variant reorientation via detwinning during loading can be explained by considering the influence of external stress on the grain/variant orientation-dependent distortion ener...

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The Journal of Chemical Physics : The Alzheimer ß-amyloid (Aß1–39)...

By: Priya Anand, Fateh S. Nandel, and Ulrich H. E. Hansmann

Description: Oligomers of Aβ peptides are suspected as the underlying cause of Alzheimer disease. Knowledge of their structural properties could therefore lead to a deeper understanding of the mechanism behind the outbreak of this disease. As a step in this direction we have studied Aβ dimers by all-atom molecular dynamics simulations. Equilibrated structures at 300 K were clustered into different families with similar structural features. The dominant cluster has parall...

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Journal of Applied Physics : Effect of compensation and of metalli...

By: Joris Libal, Sara Novaglia, Maurizio Acciarri, Simona Binetti, Roman Petres et al

Description: In this work we present a study of a p-type Czochralski-grown Si ingot which was grown using 10% solar grade silicon (SoG-Si). As the SoG-Si contains a relatively high concentration of impurities including phosphorus, the electrical properties of the as-grown wafers from this ingot are affected by both the compensating dopants and other impurities. Measurements of the minority charge carrier lifetime in the as-grown material reveal very low values (4–8 μs). ...

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Journal of Applied Physics : Microstructures and the corresponding...

By: V. G. Prokhorov, Y. H. Hyun, J. S. Park, J. B. Kim, G. H. Kim et al

Description: The microstructural and magnetic properties of amorphous, nanoclustered, and self-organized bilayer Nd0.5Sr0.5MnO3 films, prepared by rf magnetron sputtering, are investigated. The amorphous film was found to be a typical paramagnet with free motion of the individual Mn spins, and the magnetic properties are well described on the basis of the Curie–Weiss approximation. The nanoclustered film manifests magnetic properties mimicking those of superparamagnetic ...

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Journal of Applied Physics : Thermal phonon resonance observed wit...

By: Yasuo Minami and Keiji Sakai

Description: We observed resonating thermal phonons in a cavity. The combination of our millisecond Brillouin scattering technique and this phonon resonance observation enables the determination of phonon velocity with an accuracy of 10−4 within an observation time of 30 ms. In the experiment, phonon propagation in a confined space filled with liquid toluene was observed. The observed phonon resonance spectra agree with theoretical predictions.

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Journal of Applied Physics : Subwavelength imaging based on freque...

By: Stanislav Maslovski, Pekka Alitalo, and Sergei Tretyakov

Description: A new principle of subwavelength imaging based on frequency scanning is considered. It is shown that it is possible to reconstruct the spatial profile of an external field exciting an array (or coupled arrays) of subwavelength-sized resonant particles with a frequency scan over the whole band of resonating array modes. During the scan it is enough to measure and store the values of the near field at one or at most two points. After the scan the distribution ...

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Applied Physics Letters : ZnO nanowire arrays: Optical scattering ...

By: Ramón Tena-Zaera, Jamil Elias, and Claude Lévy-Clément

Description: Arrays of ZnO nanowires with different lengths (0.5–2 μm) and diameters (100–330 nm) were electrodeposited to study the influence of the nanowire dimensions on light scattering. The nanowire length and diameter were found to be major parameters in modifying the intensity and the wavelength of the scattered radiation, respectively. A significant scattering for the whole visible wavelength range was attained in arrays of ZnO nanowires of ∼ 1.5 μm in length and...

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Applied Physics Letters : Reduced hole mobility due to the presenc...

By: J. Y. Song, N. Stingelin, W. P. Gillin, and T. Kreouzis

Description: The hole mobility in poly-(3-hexylthiophene) samples is measured by the dark injection transient technique in both hole only and ambipolar devices. By applying a small offset bias prior to the voltage step, electronic excited states are generated in the ambipolar but not in the hole only devices. The presence of excited states reduces the room temperature hole mobility (typically 5×10−5 cm2 V−1 s−1) by as much as 15% compared to that measured without offset,...

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Physics of Plasmas : Structure based statistical theory of intermi...

By: Eun-jin Kim and Johan Anderson

Description: A general statistical theory of the intermittency in turbulence based on short-lived coherent structures (instantons) is presented. The probability density functions (PDFs) of the flux R are shown to have an exponential scaling P(R)∝exp(−cRs) in the tails, with the exponent s = (n+1)/m. Here, n and m are the order of the highest nonlinear interaction term and moments for which the PDFs are computed, respectively; c is constant depending on spatial profile of...

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The Journal of Chemical Physics : First-principles study of therma...

By: Jun-Ho Lee, Ji Young Lee, and Jun-Hyung Cho

Description: Using first-principles density-functional calculations, we investigate the reaction of acetone on the Si(001) surface, which exhibits the conversion from a kinetically controlled reaction to thermodynamically controlled one by means of thermal anneal or the highly confined electron beam of the scanning tunneling microscopy (STM) tip. We identified the four different reaction pathways forming not only two kinds of di-σ structures on top of a single Si dimer (...

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