Creation and characterization of vortex clusters in atomic Bose-Einstein condensates

We show that a moving obstacle, in the form of an elongated paddle, can create vortices that are dispersed, or induce clusters of like-signed vortices in 2D Bose-Einstein condensates. We propose new statistical measures of clustering based on Ripley's K-function which are suitable to the small size and small number of vortices in atomic condensates, which lack the huge number of length scales excited in larger classical and quantum turbulent fluid systems. The evolution and decay of clustering is analyzed using these measures. Experimentally it should prove possible to create such an obstacle by a laser beam and a moving optical mask. The theoretical techniques we present are accessible to experimentalists and extend the current methods available to induce 2D quantum turbulence in Bose-Einstein condensates.Comment: 9 pages, 9 figure

Notes on a collection of birds from Mindoro Island, Philippines

The 1954 Yale Peabody Museum-Silliman University Mindoro Zoological Expedition, headed by D. S. Rabor, stayed in the field from March 21 until June 7, 1954….https://elischolar.library.yale.edu/peabody_museum_natural_history_bulletin/1012/thumbnail.jp

New birds from Palawan and Culion Islands, Philippines

The Palawan Expedition of 1962 was sponsored jointly by the Yale Peabody Museum, the Entomology Section of the U. S. Army Medical Research and Development Command of the Office of the Surgeon General

Dynamic quantum clustering: a method for visual exploration of structures in data

A given set of data-points in some feature space may be associated with a Schrodinger equation whose potential is determined by the data. This is known to lead to good clustering solutions. Here we extend this approach into a full-fledged dynamical scheme using a time-dependent Schrodinger equation. Moreover, we approximate this Hamiltonian formalism by a truncated calculation within a set of Gaussian wave functions (coherent states) centered around the original points. This allows for analytic evaluation of the time evolution of all such states, opening up the possibility of exploration of relationships among data-points through observation of varying dynamical-distances among points and convergence of points into clusters. This formalism may be further supplemented by preprocessing, such as dimensional reduction through singular value decomposition or feature filtering.Comment: 15 pages, 9 figure

Agricultural development in the north Kimberley : terms, conditions and farm size recommendations

There are approximately 1,250,000 hectares of land in this area of Kimberley which may be sown to pastures such as Townsville Stylo, other Stylosanthes species or to other introduced pastures. The report recommends that grazing properties comprising 10,000 ha. of land capable of growing improved pastures, together with 60,000 ha. of native pasture land, should be established in the area. The economic size of the farm unit is 5,300 adult cattle equivalents

Visit of working party on North Kimberley Agricultural Development to the area in July 1977

Report suggests that the area of land suitable for Townsville Stylo in the North Kimberley above the 750 mm rainfall isohyet is about 1.25 million hectares. The regions in which land suitable for Stylosanthes can be found are shown. A brief description of the suitability of the land systems of the region for Stylosanthes is given

Shaping the future of our training

Peer reviewedPublisher PD

Two-dimensional supersolidity in a planar dipolar Bose gas

We investigate the crystalline stationary states of a dipolar Bose-Einstein condensate in a planar trapping geometry. Our focus is on the ground state phase diagram in the thermodynamic limit, where triangular, honeycomb and stripe phases occur. We quantify the superfluid fraction by calculating the non-classical translational inertia, which allows us to identify favorable parameter regimes for observing supersolid ground states. We develop two simplified theories to approximately describe the ground states, and consider the relationship to roton softening in the uniform ground state. This also allows us to extend the phase diagram to the low density regime. While the triangular and honeycomb states have an isotropic superfluid response tensor, the stripe state exhibits anisotropic superfluidity.Comment: 10 pages, 8 figure

Spatially embedded random networks

Many real-world networks analyzed in modern network theory have a natural spatial element; e.g., the Internet, social networks, neural networks, etc. Yet, aside from a comparatively small number of somewhat specialized and domain-specific studies, the spatial element is mostly ignored and, in particular, its relation to network structure disregarded. In this paper we introduce a model framework to analyze the mediation of network structure by spatial embedding; specifically, we model connectivity as dependent on the distance between network nodes. Our spatially embedded random networks construction is not primarily intended as an accurate model of any specific class of real-world networks, but rather to gain intuition for the effects of spatial embedding on network structure; nevertheless we are able to demonstrate, in a quite general setting, some constraints of spatial embedding on connectivity such as the effects of spatial symmetry, conditions for scale free degree distributions and the existence of small-world spatial networks. We also derive some standard structural statistics for spatially embedded networks and illustrate the application of our model framework with concrete examples