ALBERT

Beschreibung: Charge generation in a typical intermediate connector, composed of “n-type doped layer/transition metal oxide (TMO)/hole transporting layer (HTL),” of a tandem organic light-emitting device (OLED) has recently been found to arise from charge transfer at the TMO/HTL interfaces. In this paper, we investigate the effect of hole injection barriers from intermediate connectors on the performance of tandem OLEDs. The hole injection barriers are caused by the offset of the highest occupied molecular orbital (HOMO) energy levels between HTLs contained in the intermediate connector and the top electroluminescence (EL) unit. We also find that although charge generation can occur at the interfaces between the TMO and a wide variety of HTLs of different HOMO values, an increase in the hole injection barrier however limits the electroluminescence efficiency of the top EL units. In the case of large hole injection barriers, significant charge accumulation in the HTLs makes the intermediate connector lose its functionality gradually over operating time, and limits device stability.

Beschreibung: Author(s): N. A. Sinitsyn We consider nonadiabatic transitions in explicitly time-dependent systems with Hamiltonians of the form Ĥ(t)=Â+B̂t+Ĉ/t, where t is time and Â, B̂, Ĉ are Hermitian N×N matrices. We show that in any model of this type, scattering matrix elements satisfy nontrivial exact constraints that follow fr... [Phys. Rev. A 90, 062509] Published Thu Dec 11, 2014

Beschreibung: Author(s): P. Szańkowski, M. Trippenbach, and J. Chwedeńczuk We demonstrate that memory in an N-qubit system subjected to decoherence, is a potential resource for the slowdown of the entanglement decay. We show that this effect can be used to retain the sub-shot-noise sensitivity of the parameter estimation in quantum interferometry. We calculate quantum Fish... [Phys. Rev. A 90, 063619] Published Thu Dec 11, 2014

Beschreibung: Author(s): J. Lam, C. J. Rennick, and T. P. Softley Near-threshold photodissociation of Br 2 from a supersonic beam produces slow bromine atoms that are trapped in the magnetic-field minimum formed between two opposing permanent magnets. Here we quantify the dominant trap-loss rate due to collisions with two sources of residual gas: the background lim... [Phys. Rev. A 90, 063419] Published Thu Dec 11, 2014

Beschreibung: Author(s): Y. Lutsyshyn, G. E. Astrakharchik, C. Cazorla, and J. Boronat We study the zero-temperature quantum phase transition between liquid and hcp solid 4 He. We use the variational method with a simple yet exchange-symmetric and fully explicit wave function. It is found that the optimized wave function undergoes spontaneous symmetry breaking and describes the quantum... [Phys. Rev. B 90, 214512] Published Thu Dec 11, 2014

Beschreibung: Author(s): L. Z. Deng, B. Lv, Z. Wu, Y. Y. Xue, W. H. Zhang, F. S. Li, L. L. Wang, X. C. Ma, Q. K. Xue, and C. W. Chu We report a detailed investigation on the superconductivity in eight 1–4 unit-cell (UC) FeSe films on SrTiO 3 substrates by measuring their magnetization and sheet resistance in a field between 5×10 −2 and 7×10 4  Oe over the last one and a half years as a function of temperature and frequency, from 2 t... [Phys. Rev. B 90, 214513] Published Thu Dec 11, 2014

Beschreibung: Author(s): Hiromi Otsuka We present an algorithm for Monte Carlo simulations of a nearest-neighbor spin-ice model based on its cluster representation. To assess its performance, we estimate a relaxation time, and find that, in contrast to the Metropolis algorithm, our algorithm does not develop spin freezing. Also, to demon... [Phys. Rev. B 90, 220406] Published Thu Dec 11, 2014

Beschreibung: Author(s): Hongbin Yao, Wei Guo, Mark R. Hoffmann, and Keli Han We demonstrate an efficient scheme for controlling the tunneling ionization of a H 2 + molecular ion. Our scheme is based on the idea that the tunneling ionization rate is highly dependent on the instantaneous magnitude of the electric field. By manipulating the relative phase of the synthesized 5-fs,... [Phys. Rev. A 90, 063418] Published Thu Dec 11, 2014

Beschreibung: Author(s): Wenkui Ding, Anqi Shi, J. Q. You, and Wenxian Zhang We numerically investigate the encoding and retrieval processes for quantum memory realized in a semiconductor quantum dot by focusing on the effect of inhomogeneously polarized nuclear spins whose polarization depends on the local hyperfine coupling strength. We find that the performance of quantum... [Phys. Rev. B 90, 235421] Published Thu Dec 11, 2014

Beschreibung: Author(s): Sam Morley-Short, Lawrence Rosenfeld, and Pieter Kok The study of quantum systems evolving from initial states to distinguishable, orthogonal final states is important for information processing applications such as quantum computing and quantum metrology. However, for most unitary evolutions and initial states the system does not evolve to an orthogo... [Phys. Rev. A 90, 062116] Published Thu Dec 11, 2014

Beschreibung: Author(s): Chaitanya Joshi, Patrik Öhberg, James D. Cresser, and Erika Andersson We investigate how to model Markovian evolution of coupled harmonic oscillators, each of them interacting with a local environment. When the coupling between the oscillators is weak, dissipation may be modeled using local Lindblad terms for each of the oscillators in the master equation, as is commo... [Phys. Rev. A 90, 063815] Published Thu Dec 11, 2014

Beschreibung: Author(s): Yoshihito Kuno, Keita Suzuki, and Ikuo Ichinose In this paper, we study an extended bosonic t-J model in an optical lattice, which describes two-component hard-core bosons with nearest-neighbor pseudospin interactions and, also, inter- and intraspecies dipole-dipole interactions. In particular, we focus on the case in which two-component hard-cor... [Phys. Rev. A 90, 063620] Published Thu Dec 11, 2014

Beschreibung: Author(s): Jixia Dai, Kristjan Haule, J. J. Yang, Y. S. Oh, S-W. Cheong, and Weida Wu Layered 5d transition metal dichalcogenide (TMD) IrTe 2 is distinguished from the traditional TMDs (such as NbSe 2 ) by the existence of multiple charge-density wave (CDW)-like stripe phases and superconductivity at low temperatures. Despite intensive studies, there is still no consensus on the physica... [Phys. Rev. B 90, 235121] Published Thu Dec 11, 2014

Beschreibung: Author(s): Martin Doškář, Jan Novák, and Jan Zeman The paper presents a concept to compress and synthesize complex material morphologies that is based on Wang tilings. Specifically, a microstructure is stored in a set of Wang tiles and its reconstruction is performed by means of a stochastic tiling algorithm. A substantial part of the study is devot... [Phys. Rev. E 90, 062118] Published Thu Dec 11, 2014

Beschreibung: Author(s): A. Le Yaouanc, L. Oliver, and J.-C. Raynal We pursue the group-theoretical method to study Isgur-Wise (IW) functions. We extend the general formalism, formerly applied to the baryon case j P =0 + (for Λ b →Λ c ℓν̅ ℓ ), to mesons with j P =1/2 - , i.e. B̅ →D(D (*) )ℓν. In this case, which is more involved from the angular momentum point of vi... [Phys. Rev. D 90, 114016] Published Thu Dec 11, 2014

Beschreibung: Author(s): D. Fuster, J. M. Conoir, and T. Colonius We study the influence of bubble-bubble interactions on the propagation of linear acoustic waves in bubbly liquids. Using the full model proposed by Fuster and Colonius [J. Fluid Mech. 688 , 253 (2011)JFLSA710.1017/jfm.2011.380], numerical simulations reveal that direct bubble-bubble interactions hav... [Phys. Rev. E 90, 063010] Published Thu Dec 11, 2014

Beschreibung: Author(s): Felix Yndurain Using ab initio methods based on the density functional theory, we study the magnetic properties of different point defects in graphene. We consider separately, atomic hydrogen, atomic fluorine, and single vacancies. The three defects have completely different magnetic properties. A local spin one-h... [Phys. Rev. B 90, 245420] Published Thu Dec 11, 2014

Beschreibung: Author(s): Kees Wapenaar In time-reversal acoustics, waves recorded at the boundary of a strongly scattering medium are sent back into the medium to focus at the original source position. This requires that the medium can be accessed from all sides. We discuss a focusing method for media that can be accessed from one side o... [Phys. Rev. E 90, 063202] Published Thu Dec 11, 2014

Beschreibung: Author(s): Alan Heavens, Raul Jimenez, and Licia Verde A measure of how galaxies are spatially distributed can be determined in a new, more robust way. [Phys. Rev. Lett. 113, 241302] Published Thu Dec 11, 2014

Beschreibung: Author(s): Ya-Bo Wu, Jun-Wang Lu, Wen-Xin Zhang, Cheng-Yuan Zhang, Jian-Bo Lu, and Fang Yu In the probe limit, we numerically construct a holographic p-wave superfluid model in the four-dimensional (4D) and five-dimensional (5D) anti-de Sitter black holes coupled to a Maxwell-complex vector field. We find that, for the condensate with the fixed superfluid velocity, the results are similar... [Phys. Rev. D 90, 126006] Published Thu Dec 11, 2014

Beschreibung: Author(s): Douglas Stanford and Leonard Susskind In this paper we refine a conjecture relating the time-dependent size of an Einstein-Rosen bridge (ERB) to the computational complexity of the dual quantum state. Our refinement states that the complexity is proportional to the spatial volume of the ERB. More precisely, up to an ambiguous numerical ... [Phys. Rev. D 90, 126007] Published Thu Dec 11, 2014

Beschreibung: Author(s): A. Ludwig, J. Maurer, B. W. Mayer, C. R. Phillips, L. Gallmann, and U. Keller We report the breakdown of the electric dipole approximation in the long-wavelength limit in strong-field ionization with linearly polarized few-cycle mid-infrared laser pulses at intensities on the order of 10 13   W/cm 2 . Photoelectron momentum distributions were recorded by velocity map imaging and ... [Phys. Rev. Lett. 113, 243001] Published Thu Dec 11, 2014

Beschreibung: Author(s): N. Y. Yao, C. R. Laumann, S. Gopalakrishnan, M. Knap, M. Müller, E. A. Demler, and M. D. Lukin Systems of strongly interacting dipoles offer an attractive platform to study many-body localized phases, owing to their long coherence times and strong interactions. We explore conditions under which such localized phases persist in the presence of power-law interactions and supplement our analytic... [Phys. Rev. Lett. 113, 243002] Published Thu Dec 11, 2014

Beschreibung: Spin-dependent transport properties in CoFe/MgO/n + -Si junctions were investigated by Hanle effect measurements and inelastic electron tunneling (IET) spectroscopy. The CoFe/MgO/n + -Si junctions examined in this study exhibited two different Hanle curves. In the low bias region, broad Hanle signals were mainly observed; in the high bias region, narrow Hanle signals were mainly observed. The d 2 I / dV 2 - V curves (which correspond to IET spectra) contain several peaks originating from phonon modes and other peaks originating from electron trap states. At the bias voltage where electron trap states are observed, Δ d 2 I / dV 2 depends on the magnetic field and the full width at half-maximum of the Δ d 2 I / dV 2 – H curves corresponds to that of the broad Hanle signals. These results indicate that electron trap states are located in the low energy region and cause a decrease in spin lifetime.

Beschreibung: We elucidate a strong room temperature stimulated emission (SE) of In 0.17 Ga 0.83 N epilayer grown by molecular beam epitaxy under the subpicosecond pulse excitation. The SE peak at 428 nm emerges on the higher energy side of the spontaneous emission in photoluminescence spectra when the excitation density exceeds the threshold of ∼3.68 mJ/cm 2 . Nondegenerate transient differential reflectivity measurements show that a multi-stage carrier thermalization from excited states to localized edge states and stimulated emission dominate the decay processes of photogenerated carriers under various excitation densities. Our results indicate that the existence of phonon bottleneck effect could result in a slow thermalization process in the InGaN material even under the condition of stimulated emission.

Beschreibung: The relationship between carrier concentration and donor atomic concentration has been determined in n -type Ge films doped with P. The samples were carefully engineered to minimize non-active dopant incorporation by using specially designed P(SiH 3 ) 3 and P(GeH 3 ) 3 hydride precursors. The in situ nature of the doping and the growth at low temperatures, facilitated by the Ge 3 H 8 and Ge 4 H 10 Ge sources, promote the creation of ultra-low resistivity films with flat doping profiles that help reduce the errors in the concentration measurements. The results show that Ge deviates strongly from the incomplete ionization expected when the donor atomic concentration exceeds N d  = 10 17  cm −3 , at which the energy separation between the donor and Fermi levels ceases to be much larger than the thermal energy. Instead, essentially full ionization is seen even at the highest doping levels beyond the solubility limit of P in Ge. The results can be explained using a model developed for silicon by Altermatt and coworkers, provided the relevant model parameter is properly scaled. The findings confirm that donor solubility and/or defect formation, not incomplete ionization, are the major factors limiting the achievement of very high carrier concentrations in n -type Ge. The commercially viable chemistry approach applied here enables fabrication of supersaturated and fully ionized prototypes with potential for broad applications in group-IV semiconductor technologies.

Beschreibung: We developed a T-gate technology based on selective wet etching yielding 200 nm wide T-gate structures used for fabrication of High Electron Mobility Transistors (HEMT). Major advantages of our process are the use of only standard photolithographic process and the ability to generate T-gate stacks. A HEMT fabricated on AlGaN/GaN/sapphire with gate length L g  = 200 nm and double-stacked T-gates exhibits 60 GHz cutoff frequency showing ten-fold improvement compared to 6 GHz for the same device with 2  μ m gate length. HEMTs with a double-level-T-gate (DLTG) structure exhibit up to 35% improvement of f max value compared to a single T-gate device. This indicates a significant reduction of skin effect losses in DLTG structure compared to its standard T-gate counterpart. These results agree with the theoretical predictions.

Beschreibung: This investigation analyzes the effect of vortex wakes on the Lagrangian displacement of particles induced by the passage of an obstacle in a two-dimensional incompressible and inviscid fluid. In addition to the trajectories of individual particles, we also study their drift and the corresponding total drift areas in the Föppl and Kirchhoff potential flow models. Our findings, which are obtained numerically and in some regimes are also supported by asymptotic analysis, are compared to the wakeless potential flow which serves as a reference. We show that in the presence of the Föppl vortex wake, some of the particles follow more complicated trajectories featuring a second loop. The appearance of an additional stagnation point in the Föppl flow is identified as a source of this effect. It is also demonstrated that, while the total drift area increases with the size of the wake for large vortex strengths, it is actually decreased for small circulation values. On the other hand, the Kirchhoff flow model is shown to have an unbounded total drift area. By providing a systematic account of the wake effects on the drift, the results of this study will allow for more accurate modeling of hydrodynamic stirring.

Beschreibung: The magnetic configuration of Mn 2 NiAl ribbon has been investigated. In contrast to Ni 2 MnAl, the compound Mn 2 NiAl with considerable disorder does exhibit ferromagnetism and, due to exchange interaction competition, both ferromagnetic and antiferromagnetic moment orientations can coexist between nearest neighbor Mn atoms. This is unexpected in Heusler alloys. Regarding the mechanism of the martensitic transformation in Mn 50 Ni 50− x Al x , it is found that increasing the Al content results in an unusual change in the lattice constant, a decrease of the transformation entropy change, and enhancement of the calculated electron localization. These results indicate that the p-d covalent hybridization between Mn (or Ni) and Al atoms gradually increases at the expense of the d-d hybridization between Ni and Mn atoms. This leads to an increased stability of the austenite phase and a decrease of the martensitic transformation temperature. For 11 ≤  x  ≤ 14, Mn 50 Ni 50− x Al x ferromagnetic shape memory alloys are obtained.

Beschreibung: Electrowetting (EW) has applications including displays, microactuation, miniaturized chemistry, adaptive optics, and energy harvesting—understanding the physics of EW junctions is of key importance. Here, the roles of semiconductor space-charge and electric double layer in continuous EW at an electrolyte-insulator-semiconductor junction are considered. A model is formulated in terms of experimental parameters—applied voltage, zero-bias wetting contact angle, semiconductor type and doping, insulator thickness and dielectric constant, and electrolyte concentration and dielectric constant. The model predicts, and experiments indicate, that the EW behavior is diminished for low concentration solutions (∼1–10 nM) and lowly doped silicon (10 14 –10 15  cm −3 ).

Beschreibung: The dynamics of the magnetic relaxation process during the sustainment of spheromak configurations at different helicity injection rates is studied. The three-dimensional activity is recovered using time-dependent resistive magnetohydrodynamic simulations. A cylindrical flux conserver with concentric electrodes is used to model configurations driven by a magnetized coaxial gun. Magnetic helicity is injected by tangential boundary flows. Different regimes of sustainment are identified and characterized in terms of the safety factor profile. The spatial and temporal behavior of fluctuations is described. The dynamo action is shown to be in close agreement with existing experimental data. These results are relevant to the design and operation of helicity injected devices, as well as to basic understanding of the plasma relaxation mechanism in quasi-steady state.

Beschreibung: The present experiments were performed on the PF-1000 plasma focus device at a current of 2 MA with the deuterium injected from the gas-puff placed in the axis of the anode face. The XUV frames showed, in contrast with the interferograms, the fine structure: filaments and spots up to 1 mm diameter. In the deuterium filling, the short filaments are registered mainly in the region of the internal plasmoidal structures and their number correlates with the intensity of neutron production. The longer filamentary structure was recorded close to the anode after the constriction decay. The long curve-like filaments with spots were registered in the big bubble formed after the pinch phase in the head of the umbrella shape of the plasma sheath. Filaments can indicate the filamentary structure of the current in the pinch. Together with the filaments, small compact balls a few mm in diameter were registered by both interferometry and XUV frame pictures. They emerge out of the dense column and their life-time can be greater than hundreds of ns.

Beschreibung: The radiation pressure acceleration of protons in the interaction of Gaussian laser pulses and surface modulated targets is examined by multi-dimensional particle-in-cell simulations. It is shown that strong longitudinal quasi-static magnetic field is generated on the modulated surface of the target, which significantly enhances the transverse diffusion of electrons. This is beneficial for suppressing the transverse Rayleigh-Taylor instability. Finally, the surface of the accelerated proton beams becomes smoother than that in the case of the planar target, and a final mono-energetic proton beam is obtained by using the surface modulated target.

Beschreibung: We have studied the impact dynamics of non-Newtonian droplets containing poly-(ethylene oxide) (PEO) by using a high speed camera. To get a deeper insight into the droplet-substrate interaction on droplet impact behavior, both the bare droplet and the liquid marbles have been investigated. The usually observed anti-rebound phenomenon caused by the PEO additives can be rejuvenated by enwrapment of droplets with nanoparticles. The presence of PEO in bare droplets greatly enhances the contact line friction and leads to irreversible impalement of the surface structure. Whereas for liquid marbles, the nanoparticle shell on the droplet surface inhibits the impalement. Our results clearly demonstrate that it is the droplet-substrate friction rather than the bulk rheological properties of the liquid that plays the essential role in the anti-rebound effect.

Beschreibung: Author(s): M. A. Reshchikov, D. O. Demchenko, A. Usikov, H. Helava, and Yu. Makarov In high-purity GaN grown by hydride vapor phase epitaxy, the commonly observed yellow luminescence (YL) band gives way to a green luminescence (GL) band at high excitation intensity. We propose that the GL band with a maximum at 2.4 eV is caused by transitions of electrons from the conduction band t... [Phys. Rev. B 90, 235203] Published Fri Dec 12, 2014

Beschreibung: Author(s): M. N. Achasov et al. The process e + e - →nn̅ has been studied at the VEPP-2000 e + e - collider with the SND detector in the energy range from threshold up to 2 GeV. As a result of the experiment, the e + e - →nn̅ cross section and effective neutron form factor have been measured. [Phys. Rev. D 90, 112007] Published Fri Dec 12, 2014

Beschreibung: Author(s): S. Mohammad Moosavi Nejad and Mahboobe Balali We calculate the O (α s ) radiative corrections to the spin-dependent differential decay rates of the process t→b+W + . These are needed to study the angular distribution of the energy of hadrons produced in polarized top quark decays at next-to-leading order. In our previous work, we studied the angular... [Phys. Rev. D 90, 114017] Published Fri Dec 12, 2014

Beschreibung: Author(s): Rui Xu, Daowei He, Yuhan Zhang, Bing Wu, Fengyuan Liu, Lan Meng, Jun-Fang Liu, Qisheng Wu, Yi Shi, Jinlan Wang, Jia-Cai Nie, Xinran Wang, and Lin He Very recently, it was demonstrated that the carrier mobility of a molecular monolayer dioctylbenzothienobenzothiophene (C 8 -BTBT) on boron nitride can reach 10 cm 2 /Vs, the highest among the previously reported monolayer molecular field-effect transistors. Here we show that the high-quality single cry... [Phys. Rev. B 90, 224106] Published Fri Dec 12, 2014

Beschreibung: Author(s): C. Oswald et al. (Belle Collaboration) [Phys. Rev. D 90, 119901] Published Fri Dec 12, 2014

Beschreibung: Author(s): T. Appelquist, R. C. Brower, G. T. Fleming, J. Kiskis, M. F. Lin, E. T. Neil, J. C. Osborn, C. Rebbi, E. Rinaldi, D. Schaich, C. Schroeder, S. Syritsyn, G. Voronov, P. Vranas, E. Weinberg, and O. Witzel (Lattice Strong Dynamics (LSD) Collaboration) We study an SU(3) gauge theory with N f =8 degenerate flavors of light fermions in the fundamental representation. Using the domain wall fermion formulation, we investigate the light hadron spectrum, chiral condensate ⟨ψ̅ ψ⟩ and electroweak S parameter. We consider a range of light fermion mass... [Phys. Rev. D 90, 114502] Published Fri Dec 12, 2014

Beschreibung: Author(s): D. Hove, D. V. Fedorov, H. O. U. Fynbo, A. S. Jensen, K. Riisager, N. T. Zinner, and E. Garrido Borromean nuclear cluster structures are expected at the corresponding drip lines. We locate the regions in the nuclear chart with the most promising constituents, it being protons and α particles and investigate in details the properties of the possible Borromean two-α systems in medium-heavy nucle... [Phys. Rev. C 90, 064311] Published Fri Dec 12, 2014

Beschreibung: Author(s): P. Doornenbal et al. The reduced transition probability B(E2)↑ of the first excited 2 + state in the nucleus 104 Sn was measured via Coulomb excitation in inverse kinematics at intermediate energies. A value of 0.173(28) e 2 b 2 was extracted from the absolute cross section on a Pb target. Feeding contributions in 104 Sn from... [Phys. Rev. C 90, 061302] Published Fri Dec 12, 2014

Beschreibung: Author(s): A. Göök, F.-J. Hambsch, and M. Vidali The spontaneous fission of 252 Cf serves as an excellent benchmark of prompt emission in fission since experimental data can be obtained without the need of an incident beam. With the purpose of providing experimental data on the prompt fission neutron properties in correlation with fission-fragment ... [Phys. Rev. C 90, 064611] Published Fri Dec 12, 2014

Beschreibung: Author(s): Orest Hrycyna, Marek Szydłowski, and Michał Kamionka We investigate observational constraints on the Brans-Dicke cosmological model using observational data coming from distant supernovae type Ia, the Hubble function H(z) measurements, information coming from the Alcock-Paczyński test, and baryon acoustic oscillations. Our analysis is based on the mod... [Phys. Rev. D 90, 124040] Published Fri Dec 12, 2014

Beschreibung: Author(s): V. Barger, Lingjun Fu, J. G. Learned, D. Marfatia, S. Pakvasa, and T. J. Weiler The Glashow resonance at E ν =6.3  PeV is a measure of the ν̅ e content of the astrophysical neutrino flux. The fractional ν̅ e content depends on the neutrino production model at the cosmic neutrino source, and the environment at the source. Thus, the strength of the Glashow resonance e... [Phys. Rev. D 90, 121301] Published Fri Dec 12, 2014

Beschreibung: Author(s): Atsushi Taruya, Takahiro Nishimichi, Francis Bernardeau, Takashi Hiramatsu, and Kazuya Koyama Based on the multipoint propagator expansion, we present resummed perturbative calculations for cosmological power spectra and correlation functions in the context of modified gravity. In a wide class of modified gravity models that have a screening mechanism to recover general relativity (GR) on sm... [Phys. Rev. D 90, 123515] Published Fri Dec 12, 2014

Beschreibung: Author(s): Victor T. Kim and Grigorii B. Pivovarov A new approach to computing the amplitudes of multiparticle processes in renormalizable quantum field theories is presented. Its major feature is a separation of the renormalization from the computation. Within the suggested approach, new computational rules are formulated. According to the new rule... [Phys. Rev. D 90, 125009] Published Fri Dec 12, 2014

Beschreibung: Author(s): H. Berrehrah, P. B. Gossiaux, J. Aichelin, W. Cassing, and E. Bratkovskaya In this study we evaluate the dynamical collisional energy loss of heavy quarks, their interaction rate, as well as the different transport coefficients (drag and diffusion coefficients, q̂, etc). We calculate these different quantities for (i) perturbative partons (on-shell particles in the vacuum ... [Phys. Rev. C 90, 064906] Published Fri Dec 12, 2014

Beschreibung: Author(s): H. Ness We suggest a generalization of the expression of the nonequilibrium (NE) density matrix obtained by Hershfield's method for the cases where both heat and charge steady-state currents are present in a quantum open system. The finite-size quantum system, connected to two temperature and particle reser... [Phys. Rev. E 90, 062119] Published Fri Dec 12, 2014

Beschreibung: Author(s): N. Panza, H. Rodrigues, D. Cocuroci, and J. A. Helayël-Neto In this paper, we analyze a curvature- and torsion-square quantum gravity action with an additional Holst term minimally coupled to a massive Dirac field in four dimensions. The main purpose here is to try to estimate and compare the value of the Barbero-Immirzi parameter with its currently known re... [Phys. Rev. D 90, 125007] Published Fri Dec 12, 2014

Beschreibung: Author(s): Moupriya Das The states of an overdamped Brownian particle confined in a two-dimensional bilobal enclosure are considered to correspond to two binary values: 0 (left lobe) and 1 (right lobe). An ensemble of such particles represents bits of entropic information. An external bias is applied on the particles, equa... [Phys. Rev. E 90, 062120] Published Fri Dec 12, 2014

Beschreibung: The dependence of divertor asymmetry and scrape-off layer (SOL) flow on heating power has been investigated in the Experimental Advanced Superconducting Tokamak (EAST). Divertor plasma exhibits an outboard-enhanced in-out asymmetry in heat flux in lower single null configuration for in reversed (ion ∇ B drift direction toward the upper X-point) field directions. Upper single null exhibits an inboard-favored asymmetry in low heating power condition, while exhibits an outboard-favored asymmetry when increasing the heating power. Double null has the strongest in-out asymmetry in heat flux, favoring the outer divertor. The in-out asymmetry ratios of q t , out / q t , in and P out / P total increase with the power across the separatrix P loss , which is probably induced by the enhanced radial particle transport due to a large pressure gradient. The characteristics of the measured SOL parallel flow under various discharge conditions are consistent with the Pfirsch-Schlüter (PS) flow with the parallel Mach number M ∥ decreasing with the line averaged density but increasing with P loss , in the same direction as the PS flow. The contributions of both poloidal E × B drift and parallel flow on poloidal particle transport in SOL on EAST are also assessed.

Beschreibung: Magnetic islands have been implemented in the gyrokinetic toroidal code to study the effects of the islands on microturbulence. The pressure profile flattening is verified in the simulation with the islands. Simulations of ion temperature gradient instability find that different toroidal modes are linearly coupled together and that toroidal spectra become broader when the island width increases. The real frequencies and growth rates of different toroidal modes approach each other with the averaged value independent of the island width. The linear mode structures are enhanced at the island separatrices and weakened at the island centers, consistent with the flattening of the pressure profile inside the islands.

Beschreibung: The slow motion of a circular cylinder in a plane Poiseuille flow in a microchannel is analyzed for a wide range of cylinder radii and positions across the channel. The cylinder translates parallel to the channel walls and rotates about its axis. The Stokes approximation is used and the problem is solved analytically using the Papkovich-Fadle eigenfunction expansion and the least-squares method. The stream function and the pressure distribution of the flow field are obtained as results. The force and moment exerted on the cylinder, and the pressure change far from the cylinder, are calculated and shown as functions of the size and location of the cylinder. The results confirm some reciprocal relations exactly. In particular, the translational and rotational velocities of the drifting cylinder in the existing Poiseuille flow are determined. The induced pressure change, when the cylinder drifts in the Poiseuille flow, is also calculated. Some typical streamline patterns, depending on the size and location of the cylinder, are shown and discussed. When the cylinder translates and/or rotates in the channel blocked at infinity, a series of Moffatt eddies appears far from the cylinder in the channel, as expected.

Beschreibung: Interactions between capillary and elastic effects are relevant to a variety of applications from micro- and nano-scale manufacturing to biological systems. In this work, we investigate capillary flows in flexible, millimeter-scale cylindrical elastic tubes. We demonstrate that surface tension can cause sufficiently flexible tubes to collapse and coalesce spontaneously through non-axisymmetric buckling, and develop criteria for the initial deformation and complete collapse of a circular tube. Experimental results for capillary rise and evaporation of a liquid in a flexible tube are presented, and several regimes are seen for the equilibrium state of a flexible tube deforming under capillary pressure. Deformations of the tube walls are measured in different regimes and compared with a shell theory model. Analysis and experimental results show that despite the complex and non-axisymmetric deformed shapes of cylindrical structures, the elastocapillary length used in previous literature for flat plates and sheets can be used to predict the behavior of flexible tubes.

Beschreibung: A study is presented for the oblique propagation of ion acoustic cnoidal waves in a magnetized plasma consisting of cold ions and two temperature superthermal electrons modelled by kappa-type distributions. Using the reductive perturbation method, the nonlinear Korteweg de-Vries equation is derived, which further gives the solutions with a special type of cnoidal elliptical functions. Both compressive and rarefactive structures are found for these cnoidal waves. Nonlinear periodic cnoidal waves are explained in terms of plasma parameters depicting the Sagdeev potential and the phase curves. It is found that the density ratio of hot electrons to ions μ significantly modifies compressive/refractive wave structures. Furthermore, the combined effects of superthermality of cold and hot electrons κ c , κ h , cold to hot electron temperature ratio σ , angle of propagation and ion cyclotron frequency ω ci have been studied in detail to analyze the height and width of compressive/refractive cnoidal waves. The findings in the present study could have important implications in understanding the physics of electrostatic wave structures in the Saturn's magnetosphere where two temperature superthermal electrons are present.

Beschreibung: A smart monitoring system for superconducting cable test is proposed with an adaptive current control of a superconducting transformer secondary. The design, based on Fuzzy Gain Scheduling, allows the controller parameters to adapt continuously, and finely, to the working variations arising from transformer nonlinear dynamics. The control system is integrated in a fully digital control loop, with all the related benefits, i.e., high noise rejection, ease of implementation/modification, and so on. In particular, an accurate model of the system, controlled by a Fuzzy Gain Scheduler of the superconducting transformer, was achieved by an experimental campaign through the working domain at several current ramp rates. The model performance was characterized by simulation, under all the main operating conditions, in order to guide the controller design. Finally, the proposed monitoring system was experimentally validated at European Organization for Nuclear Research (CERN) in comparison to the state-of-the-art control system [P. Arpaia, L. Bottura, G. Montenero, and S. Le Naour, “Performance improvement of a measurement station for superconducting cable test,” Rev. Sci. Instrum.83, 095111 (2012)] of the Facility for the Research on Superconducting Cables, achieving a significant performance improvement: a reduction in the system overshoot by 50%, with a related attenuation of the corresponding dynamic residual error (both absolute and RMS) up to 52%.

Beschreibung: This paper presents a method which uses the characteristics of the etch pits induced in a polyallyl-diglycol-carbonate (PADC) detector of the CR-39/PM-355 type to estimate particle energy. This method is based on the data provided by a semiautomatic system that selects tracks according to two parameters, crater diameters, and mean gray level values. In this paper we used the results of the calibration measurements that were obtained in our laboratory in the period 2000–2014. Combining the information on the two parameters it is possible to determine unambiguously the incident projectile energy values. The paper presents the results of an attempt to estimate the energy resolution of the method when analyzing the tracks produced in the CR-39/PM-355 detector by energetic ions such as alpha particles, protons, and deuterons. We discuss the energy resolution of the measurement of light charged particle energy which is based on the parameters (crater diameter and mean gray level value) of tracks induced in solid state nuclear track detectors of the PADC type.

Beschreibung: In this work, an automated apparatus for driving single electrostatic probes and acquiring the plasma-related data has been designed and fabricated. The voltage range of the present system is ±110 V with an adjustable voltage step as low as 3 mV. Voltage and current measurements are carried out with high resolution and high accuracy circuits, both based on 16 bit analog-to-digital converters. The code embedded in a micro-controller, schedules the operation of the device and transfers the experimental data to a personal computer. The modular design of the system makes possible its modification and thus increases its adaptability to different plasma setups. Finally, the reliable operation of the entire device is confirmed by tests in Electron Cyclotron Resonance plasma.

Beschreibung: For magnon spintronic applications, the detailed knowledge of spin wave (SW) beam dispersion, transmission (reflection) of SWs passing through (reflected from) interfaces, or borders or the scattering of SWs by inhomogeneities is crucial. These wave properties are decisive factors on the usefulness of a particular device. Here, we demonstrate, using micromagnetic simulations supported by an analytical model, that the Goos-Hänchen (GH) shift exists for SW reflecting from thin film edge and that with the effect becomes observable. We show that this effect will exist for a broad range of frequencies in the dipole-exchange range, with the magnetization degree of pinning at the film edge as the crucial parameter, whatever its nature. Moreover, we have also found that the GH effect can be accompanied or even dominating by a bending of the SW beam due to the inhomogeneity of the internal magnetic field. This inhomogeneity, created by demagnetizing field taking place at the film edge, causes gradual change of SWs refractive index. The refraction of the SW beams by the non-uniformity of the magnetic field enables the exploration of graded index magnonics and metamaterial properties for the transmission and processing of information at nanoscale.

Beschreibung: As a non-magnetic heavy metal is attached to a ferromagnet, a vertically flowing heat-driven spin current is converted to a transverse electric voltage, which is known as the longitudinal spin Seebeck effect (SSE). If the ferromagnet is a metal, this voltage is also accompanied by voltages from two other sources, i.e., the anomalous Nernst effect in both the ferromagnet and the proximity-induced ferromagnetic boundary layer. By properly identifying and carefully separating those different effects, we find that in this pure spin current circuit the additional spin current drawn by the heavy metal generates another significant voltage by the ferromagnetic metal itself which should be present in all relevant experiments.

Beschreibung: We introduce a confocal shift-interferometer based on optical fibers. The presented spectroscopy allows measuring coherence maps of luminescent samples with a high spatial resolution even at cryogenic temperatures. We apply the spectroscopy onto electrostatically trapped, dipolar excitons in a semiconductor double quantum well. We find that the measured spatial coherence length of the excitonic emission coincides with the point spread function of the confocal setup. The results are consistent with a temporal coherence of the excitonic emission down to temperatures of 250 mK.

Beschreibung: We demonstrate enhanced hydrogen generation rates at high pH using colloidal cadmium sulphide nanorods decorated with Pt nanoparticles. We introduce a simplified procedure for the decoration and subsequent hydrogen generation, reducing both the number of working steps and the materials costs. Different Pt precursor concentrations were tested to reveal the optimal conditions for the efficient hydrogen evolution. A sharp increase in hydrogen evolution rates was measured at pH 13 and above, a condition at which the surface charge transfer was efficiently mediated by the formation of hydroxyl radicals and further consumption by the sacrificial triethanolamine hole scavenger.

Beschreibung: Spatial gaps between grains and other grains, substrates, or electrodes in organic electronic devices are one of the causes of the reduction in the electrical characteristics. In this study, we demonstrate that cold isostatic pressing (CIP) is an effective method to crush the gaps and enhance the electrical characteristics. CIP of metal-free phthalocyanine (H 2 PC) films induced a decrease in the film thickness by 34%–40% because of the gap crush. The connection of smaller grains into a larger grain and planarization of the film surface were also observed in the CIP film. The crystal axes of the H 2 PC crystallites were rearranged from the a-axis to the c-axis of the α-phase crystal structure in a direction perpendicular to the substrate by CIP, indicating favorable hole injection and transport in this direction because of a better overlap of π orbitals. Thermally stimulated current measurements showed that deep hole traps disappeared and the total hole-trap density decreased after CIP. These CIP-induced changes of the film thicknesses, crystal axes and the hole traps lead to a marked increase in the hole mobility of the H 2 PC films from 2.0 × 10 −7 to 4.0 × 10 −4 cm 2 /V s by 2000 times in the perpendicular direction. We believe that these findings are important for unveiling the underlying carrier injection and transport mechanisms of organic films and for enhancing the performance of future organic electronic devices.

Beschreibung: Anomalous Hall effect (AHE) based ferromagnetic resonance (FMR) measurements were carried out on perpendicularly magnetized Co/Pt multilayer single dots of 0.4–3  μ m in diameter. The resonance behavior was measured by detecting the decrease of perpendicular magnetization component due to magnetization precession. Resonance behavior was observed as a clear decrease of Hall voltages, and the obtained resonance fields were consistent with the results of vector-network-analyzer FMR. Spin-waves with cylindrical symmetry became significant by decreasing the dot diameter, and quantized multiple resonances were observed in the dot of 0.4 μm in diameter. The AHE based FMR proposed here is a powerful method to approach magnetization dynamics including spin waves and non-linear behavior excited in a finite nanostructure.

Beschreibung: Author(s): James Schneeloch, Curtis J. Broadbent, and John C. Howell We postulate the existence of a universal uncertainty relation between the quantum and classical mutual informations between pairs of quantum systems. Specifically, we propose that the sum of the classical mutual information, determined by two mutually unbiased pairs of observables, never exceeds th... [Phys. Rev. A 90, 062119] Published Mon Dec 15, 2014

Beschreibung: Author(s): L. Gulyás, S. Egri, and T. Kirchner We study the process of single ionization of Li in collisions with H + and O 8+ projectile ions at 6-MeV and 1.5-MeV/amu impact energies, respectively. Using the frameworks of the independent-electron model and the impact parameter picture, fully (FDCS) and doubly (DDCS) differential cross sections ar... [Phys. Rev. A 90, 062710] Published Mon Dec 15, 2014

Beschreibung: Author(s): Fam Le Kien and A. Rauschenbeutel We study the propagation of nanofiber-guided light through an array of atomic cesium, taking into account the transitions between the hyperfine levels 6S 1/2 F=4 and 6P 3/2 F ′ =5 of the D 2 line. We derive the coupled-mode propagation equation, the input-output equation, the scattering matrix, the transfe... [Phys. Rev. A 90, 063816] Published Mon Dec 15, 2014

Beschreibung: Author(s): Yachin Ivry, Chung-Soo Kim, Andrew E. Dane, Domenico De Fazio, Adam N. McCaughan, Kristen A. Sunter, Qingyuan Zhao, and Karl K. Berggren Thin superconducting films form a unique platform for geometrically confined, strongly interacting electrons. They allow an inherent competition between disorder and superconductivity, which in turn enables the intriguing superconducting-to-insulating transition and is believed to facilitate the com... [Phys. Rev. B 90, 214515] Published Mon Dec 15, 2014

Beschreibung: Author(s): T. J. Davis and D. E. Gómez A complete theoretical methodology of the interactions between chiral molecules and the evanescent fields of localized surface plasmons generated in a metallic nanostructure of arbitrary shape. The calculations confirm various previous results on the enhancement of the absorption of light and subsequent circular dichroism by surface plasmons. They also predict a chirality-dependent absorption arising from the metallic nanostructure illuminated with linearly polarized light. [Phys. Rev. B 90, 235424] Published Mon Dec 15, 2014

Beschreibung: Author(s): Tobias Meng and Eran Sela We extend the coupled-wire construction of quantum Hall phases, and search for fractional topological insulating states in models of weakly coupled wires at zero external magnetic field. Focusing on systems beyond double copies of fractional quantum Hall states at opposite fields, we find that spin-... [Phys. Rev. B 90, 235425] Published Mon Dec 15, 2014

Beschreibung: Author(s): Carmine Ortix, Carlo Di Castro, and José Lorenzana We show that in layered systems with electronic phase separation tendency, the long-range Coulomb interaction can drive the spontaneous formation of unidirectional superlattices of electronic charge in a completely homogeneous crystalline background. In this self-organized electronic heterostructure... [Phys. Rev. B 90, 241110] Published Mon Dec 15, 2014

Beschreibung: Author(s): Jonathan D. Mar, Jeremy J. Baumberg, Xiulai Xu, Andrew C. Irvine, and David A. Williams We demonstrate the initialization of a single quantum-dot hole spin with high fidelity (lower bound 〉97%), on picosecond time scales, and without the need for magnetic fields. Using the initialization scheme based on rapid electric-field ionization of a resonantly excited exciton, this is achieve... [Phys. Rev. B 90, 241303] Published Mon Dec 15, 2014

Beschreibung: Author(s): Pranay Patil, Ishita Dasgupta, and Kedar Damle We study bond and spin correlations of the nearest-neighbor resonating valence bond (RVB) wave function for a SU(2) symmetric S=1/2 antiferromagnet on the honeycomb lattice. We find that spin correlations in this wave function are short ranged, while the bond energy correlation function takes on an ... [Phys. Rev. B 90, 245121] Published Mon Dec 15, 2014

Beschreibung: Author(s): J. H. Pixley, Aditya Shashi, and Andriy H. Nevidomskyy The antiferromagnetic spin-1 chain has a venerable history and has been thought to be well understood. Here, we show that inclusion of both next-nearest-neighbor (α) and biquadratic (β) interactions results in a rich phase diagram with a multicritical point that has not been observed before. We stud... [Phys. Rev. B 90, 214426] Published Mon Dec 15, 2014

Beschreibung: Author(s): Andrea Di Cicco, Keisuke Hatada, Erika Giangrisostomi, Roberto Gunnella, Filippo Bencivenga, Emiliano Principi, Claudio Masciovecchio, and Adriano Filipponi High intensity pulses obtained by modern extreme ultraviolet (EUV) and x-ray photon sources allows the observation of peculiar phenomena in condensed matter. Experiments performed at the Fermi@Elettra FEL-1 free-electron-laser source at 23.7, 33.5, and 37.5 eV on Al thin films, for an intermediate-f... [Phys. Rev. B 90, 220303] Published Mon Dec 15, 2014

Beschreibung: We introduce a method for generating rational extensions of time-dependent potentials, such that the associated Schrödinger equation admits solutions in terms of exceptional orthogonal polynomials. Our method is applicable to position-dependent Schrödinger equations, as well as to their conventional counterparts for constant mass.

Beschreibung: In this paper, we prove the existence of the Stark-Wannier quantum resonances for one-dimensional Schrödinger operators with smooth periodic potential and small external homogeneous electric field. Such a result extends the existence result previously obtained in the case of periodic potentials with a finite number of open gaps.

Beschreibung: Author(s): Eliot Gann, Anne Watson, John R. Tumbleston, Justin Cochran, Hongping Yan, Cheng Wang, Jaewook Seok, Michael Chabinyc, and Harald Ade The internal structures of thin films, particularly interfaces between different materials, are critical to system properties and performance across many disciplines, but characterization of buried interface topography is often unfeasible. In this work, we demonstrate that grazing resonant soft x-ra... [Phys. Rev. B 90, 245421] Published Mon Dec 15, 2014

Beschreibung: Author(s): P. N. Fountas, G. A. Souliotis, M. Veselsky, and A. Bonasera Detailed calculations of the yields of projectilelike fragments (with focus on the neutron-rich isotopes) are presented for the interaction of 86 Kr (15 MeV/nucleon) with 64 Ni, 58 Ni, and 124 Sn, 112 Sn, as well as 86 Kr (25 MeV/nucleon) with 124 Sn and compared with our recently published experimental da... [Phys. Rev. C 90, 064613] Published Mon Dec 15, 2014

Beschreibung: Author(s): G. A. Souliotis, P. N. Fountas, M. Veselsky, S. Galanopoulos, Z. Kohley, A. McIntosh, S. J. Yennello, and A. Bonasera The isoscaling of heavy projectile residues from peripheral heavy-ion reactions at 15–25 MeV/nucleon is employed to obtain information on the process of N/Z equilibration. Recent mass spectrometric data of projectile residues from the reactions of 86 Kr (15 MeV/nucleon) with 64,58 Ni and 124,112 Sn wer... [Phys. Rev. C 90, 064612] Published Mon Dec 15, 2014

Beschreibung: Author(s): Thomas Elghozi, William Nelson, and Mairi Sakellariadou We study the occurrence of cuspy events on a light string stretched between two Y-junctions with fixed heavy strings. We first present an analytic study and give a solid criterion to discriminate between cuspy and noncuspy string configurations. We then describe a numerical code, built to test this ... [Phys. Rev. D 90, 123517] Published Mon Dec 15, 2014

Beschreibung: We study four citrate synthase homodimeric proteins within a structure-based coarse-grained model. Two of these proteins come from thermophilic bacteria, one from a cryophilic bacterium and one from a mesophilic organism; three are in the closed and two in the open conformations. Even though the proteins belong to the same fold, the model distinguishes the properties of these proteins in a way which is consistent with experiments. For instance, the thermophilic proteins are more stable thermodynamically than their mesophilic and cryophilic homologues, which we observe both in the magnitude of thermal fluctuations near the native state and in the kinetics of thermal unfolding. The level of stability correlates with the average coordination number for amino acid contacts and with the degree of structural compactness. The pattern of positional fluctuations along the sequence in the closed conformation is different than in the open conformation, including within the active site. The modes of correlated and anticorrelated movements of pairs of amino acids forming the active site are very different in the open and closed conformations. Taken together, our results show that the precise location of amino acid contacts in the native structure appears to be a critical element in explaining the similarities and differences in the thermodynamic properties, local flexibility, and collective motions of the different forms of the enzyme.

Beschreibung: Author(s): Kazuyuki Sekizawa and Kazuhiro Yabana Background: The time-dependent Hartree-Fock (TDHF) theory has been successful in describing low-energy heavy ion collisions. Recently, we have shown that multinucleon transfer processes can be reasonably described in the TDHF theory combined with the particle-number projection technique. [Phys. Rev. C 90, 064614] Published Mon Dec 15, 2014

Beschreibung: Author(s): Sylvain Joubaud, Tess Homan, Y. Gasteuil, Detlef Lohse, and Devaraj van der Meer We describe direct measurements of the acceleration of an object impacting on a loosely packed granular bed under various pressures, using an instrumented sphere. The sphere acts as a noninvasive probe that measures and continuously transmits the acceleration as it penetrates into the sand, using a ... [Phys. Rev. E 90, 060201] Published Mon Dec 15, 2014

Beschreibung: Author(s): M. Borówko and W. Rżysko The phase behavior of Janus disks on a square lattice is studied using the Monte Carlo method. A particle is composed of two different parts, A and B. The interactions between neighboring particles depend on their orientations. To control the strength of the interactions, we use energy parameters ch... [Phys. Rev. E 90, 062308] Published Mon Dec 15, 2014

Beschreibung: Author(s): T. P. Bennett, G. D'Alessandro, and K. R. Daly We use homogenization theory to develop a multiscale model of colloidal dispersion of particles in nematic liquid crystals under weak-anchoring conditions. We validate the model by comparing it with simulations by using the Landau–de Gennes free energy and show that the agreement is excellent. We th... [Phys. Rev. E 90, 062505] Published Mon Dec 15, 2014

Beschreibung: Author(s): Chanyong Park, Do-Young Gwak, Bum-Hoon Lee, Yumi Ko, and Sunyoung Shin [Phys. Rev. D 90, 129902] Published Mon Dec 15, 2014

Beschreibung: Author(s): Matthias Punk We develop a method for multidimensional optimization using flow equations. This method is based on homotopy continuation in combination with a maximum entropy approach. Extrema of the optimizing functional correspond to fixed points of the flow equation. While ideas based on Bayesian inference such... [Phys. Rev. E 90, 063307] Published Mon Dec 15, 2014

Beschreibung: Author(s): Christopher J. Moore and Jonathan R. Gair Posterior distributions on parameters computed from experimental data using Bayesian techniques are only as accurate as the models used to construct them. In many applications, these models are incomplete, which both reduces the prospects of detection and leads to a systematic error in the parameter... [Phys. Rev. Lett. 113, 251101] Published Mon Dec 15, 2014

Beschreibung: Author(s): A. Boyarsky, O. Ruchayskiy, D. Iakubovskyi, and J. Franse An x-ray feature recently detected by different astronomy groups may be the long-awaited signature of dark matter. [Phys. Rev. Lett. 113, 251301] Published Mon Dec 15, 2014

Beschreibung: Author(s): Marco Baggio, Vasilis Niarchos, and Kyriakos Papadodimas We report an exact solution of 2- and 3-point functions of chiral primary fields in SU(2) N =2 super-Yang-Mills theory coupled to four hypermultiplets. It is shown that these correlation functions are nontrivial functions of the gauge coupling, obeying differential equations which take the form of th... [Phys. Rev. Lett. 113, 251601] Published Mon Dec 15, 2014

Beschreibung: We give an algorithm which produces a unique element of the Clifford group on n qubits ( C n ) from an integer 0 ≤ i 〈 C n (the number of elements in the group). The algorithm involves O ( n 3 ) operations and provides, in addition to a canonical mapping from the integers to group elements g , a factorization of g into a sequence of at most 4 n symplectic transvections. The algorithm can be used to efficiently select random elements of C n which are often useful in quantum information theory and quantum computation. We also give an algorithm for the inverse map, indexing a group element in time O ( n 3 ).

Beschreibung: Author(s): Sumesh P. Thampi, Ramin Golestanian, and Julia M. Yeomans Active turbulence in dense active systems is characterized by high vorticity on a length scale that is large compared to that of individual entities. We describe the properties of active turbulence as momentum propagation is screened by frictional damping. As friction is increased, the spacing betwe... [Phys. Rev. E 90, 062307] Published Mon Dec 15, 2014

Beschreibung: Author(s): J. Upadhyay, Do Im, S. Popović, A.-M. Valente-Feliciano, L. Phillips, and L. Vušković Plasma-based surface modification of niobium is a promising alternative to wet etching of superconducting radio frequency (SRF) cavities. We have demonstrated surface layer removal in an asymmetric nonplanar geometry, using a simple cylindrical cavity. The etching rate is highly correlated with the ... [Phys. Rev. ST Accel. Beams 17, 122001] Published Mon Dec 15, 2014

Beschreibung: We present laboratory experimental results demonstrating that librational forcing of an ellipsoidal container of water can produce intense motions through the mechanism of a libration driven elliptical instability (LDEI). These libration studies are conducted using an ellipsoidal acrylic container filled with water. A particle image velocimetry method is used to measure the 2D velocity field in the equatorial plane over hundreds libration cycles for a fixed Ekman number, E = 2 × 10 −5 . In doing so, we recover the libration induced base flow and a time averaged zonal flow. Further, we show that LDEI in non-axisymmetric container geometries is capable of driving both intermittent and saturated turbulent motions in the bulk fluid. Additionally, we measure the growth rate and amplitude of the LDEI induced excited flow in a fully ellipsoidal container at more extreme parameters than previously studied [Noir et al. , “Experimental study of libration-driven flows in nonaxisymmetric containers,” Phys. Earth Planet. Inter. 204-205 , 1 (2012); Cébron et al. , Phys. Fluids 24 , 061703, “Libration driven elliptical instability,” (2012)]. Excitation of bulk filling turbulence by librational forcing provides a mechanism for transferring rotational energy into turbulent fluid motion and thus can play an important role in the thermal evolution, interior dynamics, and magneto-hydrodynamics of librating bodies, as appear to be common in solar system settings [e.g., Comstock and Bills, “A solar system survey of forced librations in longitude,” J. Geophys. Res. Planets 108 , 1 (2003)].

Beschreibung: We numerically study the displacement flow of two iso-viscous Newtonian fluids in an inclined two-dimensional channel, formed by two parallel plates. The results are complementary to our previous studies on displacement flows in pipes and channels. The heavier displacing fluid moves the lighter displaced fluid in the downward direction. Three dimensionless groups largely describe these flows: the densimetric Froude number ( Fr ), the Reynolds number ( Re ), and the duct inclination (β). As a first order approximation, we are able to classify different flow regimes phenomenologically in a two-dimensional ( Fr ; Re cosβ/ Fr )-plane and provide leading order expressions for the transitions between different regimes. The stabilizing and/or de-stabilizing effects of the imposed mean flow on buoyant exchange flows (zero imposed velocity) are described for a broad range of dimensionless parameters.

Beschreibung: Compressible granular materials are involved in many applications, some of them being related to energetic porous media. Gas permeation effects are important during their compaction stage, as well as their eventual chemical decomposition. Also, many situations involve porous media separated from pure fluids through two-phase interfaces. It is thus important to develop theoretical and numerical formulations to deal with granular materials in the presence of both two-phase interfaces and gas permeation effects. Similar topic was addressed for fluid mixtures and interfaces with the Discrete Equations Method (DEM) [R. Abgrall and R. Saurel, “Discrete equations for physical and numerical compressible multiphase mixtures,” J. Comput. Phys. 186 (2), 361-396 (2003)] but it seemed impossible to extend this approach to granular media as intergranular stress [K. K. Kuo, V. Yang, and B. B. Moore, “Intragranular stress, particle-wall friction and speed of sound in granular propellant beds,” J. Ballist. 4 (1), 697-730 (1980)] and associated configuration energy [J. B. Bdzil, R. Menikoff, S. F. Son, A. K. Kapila, and D. S. Stewart, “Two-phase modeling of deflagration-to-detonation transition in granular materials: A critical examination of modeling issues,” Phys. Fluids 11 , 378 (1999)] were present with significant effects. An approach to deal with fluid-porous media interfaces was derived in Saurel et al. [“Modelling dynamic and irreversible powder compaction,” J. Fluid Mech. 664 , 348-396 (2010)] but its validity was restricted to weak velocity disequilibrium only. Thanks to a deeper analysis, the DEM is successfully extended to granular media modelling in the present paper. It results in an enhanced version of the Baer and Nunziato [“A two-phase mixture theory for the deflagration-to-detonation transition (DDT) in reactive granular materials,” Int. J. Multiphase Flow 12 (6), 861-889 (1986)] model as symmetry of the formulation is now preserved. Several computational examples are shown to validate and illustrate method’s capabilities.