Trapping of a particle in a short-range harmonic potential well

Eigenstates of a particle in a localized and unconfined harmonic potential well are investigated. Effects due to the variation of the potential parameters as well as certain results from asymptotic expansions are discussed. © 2012 Springer Science+Business Media, LLC.

Bright solitons in a quasi-one-dimensional reduced model of a dipolar Bose-Einstein condensate with repulsive short-range interactions

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influence of a co-substituted A-site on structural characteristics and ferroelectricity of (Pb, Ba, Ca)TiO3 complex perovskites: analysis of local-, medium- and long-range order

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Fingerprints of short-range and long-range structure in BaZr1-xHfxO3 solid solutions: an experimental and theoretical study

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Local order and magnetic field effects on the electronic properties of disordered binary alloys in the quantum site percolation limit

Electronic properties of disordered binary alloys are studied via the calculation of the average Density of States (DOS) in two and three dimensions. We propose a new approximate scheme that allows for the inclusion of local order effects in finite geometries and extrapolates the behavior of infinite systems following finite-size scaling ideas. We particularly investigate the limit of the Quantum Site Percolation regime described by a tight-binding Hamiltonian. This limit was chosen to probe the role of short range order (SRO) properties under extreme conditions. The method is numerically highly efficient and asymptotically exact in important limits, predicting the correct DOS structure as a function of the SRO parameters. Magnetic field effects can also be included in our model to study the interplay of local order and the shifted quantum interference driven by the field. The average DOS is highly sensitive to changes in the SRO properties and striking effects are observed when a magnetic field is applied near the segregated regime. The new effects observed are twofold: there is a reduction of the band width and the formation of a gap in the middle of the band, both as a consequence of destructive interference of electronic paths and the loss of coherence for particular values of the magnetic field. The above phenomena are periodic in the magnetic flux. For other limits that imply strong localization, the magnetic field produces minor changes in the structure of the average DOS. © World Scientific Publishing Company.

Physikalische Eigenschaften kolloidaler Festkörper

In dieser Arbeit wird das Phasenverhalten fluid-kristallin und kristallin-amorph, die elastischen Eigenschaften, das Nukleationsverhalten und das diffusive Verhalten ladungsstabilisierter Kolloide aus sphärischen Polystyrol- und Polytetrafluorethylenpartikeln in wässerigen Dispersionsmitteln bei sehr geringem Fremdionengehalt systematisch untersucht. Die dazugehörigen Messungen werden an einer neuartigen selbstkonstruierten Kombinationslichtstreuapparatur durchgeführt, die die Meßmethoden der dynamischen Lichtstreuung, statischen Lichtstreuung und Torsionsresonanzspektroskopie in sich vereint. Die drei Meßmethoden sind optimal auf die Untersuchung kolloidaler Festkörper abgestimmt. Das elastische Verhalten der Festkörper kann sehr gut durch die Elastizitätstheorie atomarer Kristallsysteme beschrieben werden, wenn ein Debye-Hückel-Potential im Sinne des Poisson-Boltzmann-Cell Modells als Wechselwirkungspotential verwendet wird. Die ermittelten Phasengrenzen fluid-kristallin stehen erstmalig in guter Übereinstimmung mit Ergebnissen aus molekulardynamischen Simulationen, wenn die in der Torsionsresonanzspektroskopie bestimmte Wechselwirkungsenergie zu Grunde gelegt wird. Neben der Gleichgewichtsstruktur sind Aussagen zur Verfestigungskinetik möglich. Das gefundene Nukleationserhalten kann gut durch die klassische Nukleationstheorie beschrieben werden, wenn bei niedriger Unterkühlung der Schmelze ein Untergrund heterogener Keimung berücksichtigt wird. PTFE-Partikel zeigen auch bei hohen Konzentrationen nur geringfügige Mehrfachstreuung. Durch ihren Einsatz ist erstmals eine systematische Untersuchung des Glasübergangs in hochgeladenen ladungsstabilisierten Systemen möglich. Ladungsstabilisierte Kolloide unterscheiden sich vor allem durch ihre extreme Kristallisationstendenz von früher untersuchten Hartkugelsystemen. Bei hohen Partikelkonzentrationen (Volumenbrüche größer 10 Prozent) kann ein glasartiger Festkörper identifiziert werden, dessen physikalisches Verhalten die Existenz eines Bernalglases nahe legt. Der Glasübergang ist im Vergleich mit den in anderen kolloidalen Systemen und atomaren Systemen beobachteten Übergängen von sehr unterschiedlichem Charakter. Im verwendeten PTFE-System ist auf Grund der langreichweitigen stark repulsiven Wechselwirkung kein direkter Zugang des Glaszustandes aus der übersättigten Schmelze möglich. Der amorphe Festkörper entsteht hier aus einer nanokristallinen Phase. Die Keimrate steigt im zugänglichen Meßbereich annähernd exponentiell mit der Partikelanzahldichte, so daß man feststellen kann, daß der Glaszustand nicht durch Unterdrückung der Nukleation, sondern durch eine Forcierung derselben erreicht wird.

Search for a spin-dependent short-range force between nucleons with a 3 He, 129 Xe clock-comparison experiment

Light pseudoscalar bosons, such as the axion that was originally proposed as a solution of the strong CP problem, would cause a new spin-dependent short-range interaction. In this thesis, an experiment is presented to search for axion mediated short-range interaction between a nucleon and the spin of a polarized bound neutron. This interaction cause a shift in the precession frequency of nuclear spin-polarized gases in the presence of an unpolarized mass. To get rid of magnetic field drifts co-located, nuclear spin polarized 3He and 129Xe atoms were used. The free nuclear spin precession frequencies were measured in a homogeneous magnetic guiding field of about 350nT using LTc SQUID detectors. The whole setup was housed in a magnetically shielded room at the Physikalisch Technische Bundesanstalt (PTB) in Berlin. With this setup long nuclear spin-coherence times, respectively, transverse relaxation times of 5h for 129Xe and 53h for 3He could be achieved. The results of the last run in September 2010 are presented which give new upper limits on the scalar-pseudoscalar coupling of axion-like particles in the axion-mass window from 10^(-2) eV to 10^(-6) eV. The laboratory upper bounds were improved by up to 4 orders of magnitude.

Measurement of long-range pseudorapidity correlations and azimuthal harmonics in √s_NN=5.02 TeV proton-lead collisions with the ATLAS detector

Measurements of two-particle correlation functions and the first five azimuthal harmonics, v 1 to v 5 , are presented, using 28 nb −1 of p+Pb collisions at a nucleon-nucleon center-of-mass energy of √s NN=5.02 TeV measured with the ATLAS detector at the LHC. Significant long-range “ridgelike” correlations are observed for pairs with small relative azimuthal angle (|Δϕ|<π/3 ) and back-to-back pairs (|Δϕ|>2π/3 ) over the transverse momentum range 0.4

range correlations is Fourier decomposed to obtain the harmonics v n as a function of p T and event activity. The extracted v n values for n=2 to 5 decrease with n . The v 2 and v 3 values are found to be positive in the measured p T range. The v 1 is also measured as a function of p T and is observed to change sign around p T ≈1.5 –2.0 GeV and then increase to about 0.1 for p T >4 GeV. The v 2 (p T ) , v 3 (p T ) , and v 4 (p T ) are compared to the v n coefficients in Pb+Pb collisions at √s NN=2.76 TeV with similar event multiplicities. Reasonable agreement is observed after accounting for the difference in the average p T of particles produced in the two collision systems.

Improving the low-wind performance of the AERMOD atmospheric dispersion model for predicting short-range impacts of livestock ammonia emissions.

Short-range impacts to sensitive ecosystems as a result of ammonia emitted by livestock farms are often assessed using atmospheric dispersion modelling systems such as AERMOD. These assessments evaluate mean annual atmospheric concentrations of ammonia and nitrogen deposition rates at the ecosystem location for comparison with ecosystem damage thresholds. However, predictions of mean annual atmospheric concentrations can be dominated by periods of stable night-time conditions, which can contribute significantly to mean concentrations. AERMOD has been demonstrated to overestimate concentrations in certain stable low-wind conditions and so the model could potentially overestimate the short-range impacts of livestock ammonia emissions. This paper tests several modifications to the parameterisation of AERMOD (v12345) that aim to improve model predictions in low-wind conditions. The modifications are first described and then are applied to three pig farm case studies in the USA, Denmark and Spain to assess whether the modifications improve long-term mean ammonia concentration predictions through improved model performance. For these three case studies, most of the modifications tested improved model performance as a result of reducing the long-term mean concentration predictions, with the largest effect for low- or ground-level sources (e.g. slurry lagoons or naturally ventilated housing).

CtBP-dependent activities of the short-range Giant repressor in the Drosophila embryo

There are at least three short-range gap repressors in the precellular Drosophila embryo: Krüppel, Knirps, and Giant. Krüppel and Knirps contain related repression motifs, PxDLSxH and PxDLSxK, respectively, which mediate interactions with the dCtBP corepressor protein. Here, we present evidence that Giant might also interact with dCtBP. The misexpression of Giant in ventral regions of transgenic embryos results in the selective repression of eve stripe 5. A stripe5-lacZ transgene exhibits an abnormal staining pattern in dCtBP mutants that is consistent with attenuated repression by Giant. The analysis of Gal4-Giant fusion proteins identified a minimal repression domain that contains a sequence motif, VLDLS, which is conserved in at least two other sequence-specific repressors. Removal of this sequence from the native Giant protein does not impair its repression activity in transgenic embryos. We propose that Giant-dCtBP interactions might be indirect and mediated by an unknown bZIP subunit that forms a heteromeric complex with Giant. We also suggest that the VLDLS motif recruits an as yet unidentified corepressor protein.

Correspondence between long-range and short-range spin glasses

We compare the critical behavior of the short-range Ising spin glass with a spin glass with long-range interactions which fall off as a power σ of the distance. We show that there is a value of σ of the long-range model for which the critical behavior is very similar to that of the short range model in four dimensions. We also study a value of σ for which we find the critical behavior to be compatible with that of the three-dimensional model, although we have much less precision than in the four-dimensional case.

Short-range public transportation improvements. Final report.

Urban Mass Transportation Administration, Washington, D.C.

Short-range transit planning.

Mode of access: Internet.