Experimental Study of the Role of Atomic Interactions on Quantum Transport

We report an experimental study of quantum transport for atoms confined in a periodic potential and compare between thermal and BEC initial conditions. We observe ballistic transport for all values of well depth and initial conditions, and the measured expansion velocity for thermal atoms is in excellent agreement with a single-particle model. For weak wells, the expansion of the BEC is also in excellent agreement with single-particle theory, using an effective temperature. We observe a crossover to a new regime for the BEC case as the well depth is increased, indicating the importance of interactions on quantum transport.Comment: 4 pages, 3 figure

Struggling to a monumental triumph : Re-assessing the final stages of the smallpox eradication program in India, 1960-1980

The global smallpox program is generally presented as the brainchild of a handful of actors from the WHO headquarters in Geneva and at the agency's regional offices. This article attempts to present a more complex description of the drive to eradicate smallpox. Based on the example of India, a major focus of the campaign, it is argued that historians and public health officials should recognize the varying roles played by a much wider range of participants. Highlighting the significance of both Indian and international field officials, the author shows how bureaucrats and politicians at different levels of administration and society managed to strengthen—yet sometimes weaken—important program components. Centrally dictated strategies developed at WHO offices in Geneva and New Delhi, often in association with Indian federal authorities, were reinterpreted by many actors and sometimes changed beyond recognition

Towards an interoperable metamodel suite: size assessment as one input

In recent years, many metamodels have been introduced in the software engi- neering literature and standards. These metamodels vary in their focus across, for example, process, product, organizational and measurement aspects of software development and have typically been developed independently of each other with shared concepts being only accidental. There is thus an increasing concern in the standards communities that possible conicts of structure and semantics between these various metamodels will hinder their widespread adoption. The complexity of these metamodels has also increased significantly and is another barrier in their appreciation. This complexity is compounded when more than one metamodel is used in the lifecycle of a software project. Therefore there is a need to have interoperable metamodels. As a first step towards engendering interoperability and/or possible mergers between metamodels, we examine the size and complexity of various meta- models. To do this, we have used the Rossi and Brinkkemper metrics-based approach to evaluate the size and complexity of several standard metamodels including UML 2.3, BPMN 2.0, ODM, SMM and OSM. The size and complexity of these metamodels is also compared with the previous version of UML, BPMN and Activity diagrams. The comparatively large sizes of BPMN 2.0 and UML 2.3 suggest that future integration with these metamodels might be more difficult than with the other metamodels under study (especially ODM, SSM and OSM)

OGLE-2017-BLG-0173Lb: Low-mass-ratio Planet in a "Hollywood" Microlensing Event

We present microlensing planet OGLE-2017-BLG-0173Lb, with planet–host mass ratio of either q ≃ 2.5 x 10^(-5) or q ≃ 6.5 x 10^(-5), the lowest or among the lowest ever detected. The planetary perturbation is strongly detected, Δχ^2 ~ 10000, because it arises from a bright (therefore, large) source passing over and enveloping the planetary caustic: a so-called "Hollywood" event. The factor ~2.5 offset in q arises because of a previously unrecognized discrete degeneracy between Hollywood events in which the caustic is fully enveloped and those in which only one flank is enveloped, which we dub "Cannae" and "von Schlieffen," respectively. This degeneracy is "accidental" in that it arises from gaps in the data. Nevertheless, the fact that it appears in a Δχ^2 = 10000 planetary anomaly is striking. We present a simple formalism to estimate the sensitivity of other Hollywood events to planets and show that they can lead to detections close to, but perhaps not quite reaching, the Earth/Sun mass ratio of 3 x 10(-6). This formalism also enables an analytic understanding of the factor ~2.5 offset in q between the Cannae and von Schlieffen solutions. The Bayesian estimates for the host mass, system distance, and planet–host projected separation are M = 0.39^(+0.40)_(-0.24) M⊙, D_L = 4.8^(+1.5)_(-1.8) kpc, and a⊥ = 3.8 ± 1.6 au, respectively. The two estimates of the planet mass are m_p = 3.3^(+3.8)_(-2.1) M⊕ and m_p = 8^(+11)_(-6) M⊕. The measured lens-source relative proper motion µ = 6 mas yr^(-1) will permit imaging of the lens in about 15 years or at first light on adaptive-optics imagers on next-generation telescopes. These will allow one to measure the host mass but probably will not be able to resolve the planet–host mass-ratio degeneracy

Rietveld refinements of the crystal structures of Rb2XSi5O12 (X = Mn, Ni)

Poster Number: CCG06 Synthetic analogues of the silicate framework mineral leucite (KAlSi2O6) with the stoichiometry Rb2XSi5O12 (X = Mn, Ni) have been prepared by high temperature solid-state synthesis. Ambient temperature X-ray powder diffraction data have been collected on these samples. Analysis of these powder diffraction data show that these samples both consist of single phases [1] isostructural with the Pbca cation-ordered framework leucite structure of Cs2CdSi5O12 [2]. Rietveld refinement [3] shows that for X = Mn this crystal structure has complete Mn and Si cation order over the tetrahredrally coordinated sites (T-sites) in the silicate framework. However, for X = Ni, Rietveld refinement suggests that there may be some Ni and Si cation T-site cation disorder

Bose-Einstein Condensate Driven by a Kicked Rotor in a Finite Box

We study the effect of different heating rates of a dilute Bose gas confined in a quasi-1D finite, leaky box. An optical kicked-rotor is used to transfer energy to the atoms while two repulsive optical beams are used to confine the atoms. The average energy of the atoms is localized after a large number of kicks and the system reaches a nonequilibrium steady state. A numerical simulation of the experimental data suggests that the localization is due to energetic atoms leaking over the barrier. Our data also indicates a correlation between collisions and the destruction of the Bose-Einstein condensate fraction.Comment: 7 pages, 8 figure

Colloidal Electrostatic Interactions Near a Conducting Surface

Charge-stabilized colloidal spheres dispersed in deionized water are supposed to repel each other. Instead, artifact-corrected video microscopy measurements reveal an anomalous long-ranged like-charge attraction in the interparticle pair potential when the spheres are confined to a layer by even a single charged glass surface. These attractions can be masked by electrostatic repulsions at low ionic strengths. Coating the bounding surfaces with a conducting gold layer suppresses the attraction. These observations suggest a possible mechanism for confinement-induced attractions.Comment: 4 pages, 2 figure

Local spinfoam expansion in loop quantum cosmology

The quantum dynamics of the flat Friedmann-Lemaitre-Robertson-Walker and Bianchi I models defined by loop quantum cosmology have recently been translated into a spinfoam-like formalism. The construction is facilitated by the presence of a massless scalar field which is used as an internal clock. The implicit integration over the matter variable leads to a nonlocal spinfoam amplitude. In this paper we consider a vacuum Bianchi I universe and show that by choosing an appropriate regulator a spinfoam expansion can be obtained without selecting a clock variable and that the resulting spinfoam amplitude is local.Comment: 12 page