Direct imaging of a digital-micromirror device for configurable microscopic optical potentials

Programable spatial light modulators (SLMs) have significantly advanced the configurable optical trapping of particles. Typically, these devices are utilized in the Fourier plane of an optical system, but direct imaging of an amplitude pattern can potentially result in increased simplicity and computational speed. Here we demonstrate high-resolution direct imaging of a digital micromirror device (DMD) at high numerical apertures (NA), which we apply to the optical trapping of a Bose-Einstein condensate (BEC). We utilise a (1200 x 1920) pixel DMD and commercially available 0.45 NA microscope objectives, finding that atoms confined in a hybrid optical/magnetic or all-optical potential can be patterned using repulsive blue-detuned (532 nm) light with 630(10) nm full-width at half-maximum (FWHM) resolution, within 5% of the diffraction limit. The result is near arbitrary control of the density the BEC without the need for expensive custom optics. We also introduce the technique of time-averaged DMD potentials, demonstrating the ability to produce multiple grayscale levels with minimal heating of the atomic cloud, by utilising the high switching speed (20 kHz maximum) of the DMD. These techniques will enable the realization and control of diverse optical potentials for superfluid dynamics and atomtronics applications with quantum gases. The performance of this system in a direct imaging configuration has wider application for optical trapping at non-trivial NAs.Comment: 9 page

Benefits of federal community pastures on the prairies

Non-Peer ReviewedIn the wake of widespread soil erosion, during the 1930s, the federal governments passed the Prairie Farm Rehabilitation Administration (PFRA) act, establishing the agency, and through it a system of community pastures in the three prairie provinces. At present, PFRA operates 87 such pastures. The major motivation for this program was to reduce soil erosion through some careful land management practices, thereby enabling them to be a source of summer pasture for cattle grazing. This was seen as fostering greater economic security, stability and diversification in the region. Over time, many other uses of community pastures have emerged. Although grazing and breeding function has remained prominent, many other uses have become important enough so as not be totally ignored. Some of the notable uses include: wildlife and waterfowl habitats, recreational activity, preservation of biodiversity, preservation of fragile ecosystems, conservation of heritage sites, research activity, among others. In order to determine these uses, a survey of PFRA community pastures was undertaken during the summer of 2000. The results of this survey indicate that although grazing and breeding activities are still the major economic activities on these community pastures, the Canadian and the Prairie society benefits from these pastures in a significant manner. This study suggests that the PFRA community pastures are more than a place for farmers to leave their cattle for the summer period; they provide several benefits to local communities, and other members of the society through ecosystem functions, and other use and non-use related activities

Attitudes of cannabis growers to regulation of cannabis cultivation under a non-prohibition cannabis model

Background: How cannabis cultivation is dealt with under various examples of cannabis legalization or regulation is an important consideration in design of such schemes. This study aimed to (i) investigate support among current or recent cannabis growers, for various potential policy options for cannabis cultivation if prohibition were repealed, and (ii) explore the support for these options across countries, scale of growing operations, demographics, drug use and cannabis supply involvement variables. Methods: This study utilized data from the online web survey of largely 'small-scale' cannabis cultivators, aged 18. yrs and over, in eleven countries conducted by the Global Cannabis Cultivation Research Consortium (GCCRC). Data from 1722 current and recent cannabis growers in Australia, Denmark and the UK, who were all asked about policy, were included in the analysis. It investigated support for various frameworks for cultivation: (no regulation (. free market); adult only; growing licenses; restrictions on plant numbers; licensed business-only sale; approved commercial growing; etc.). Among current growers, support for these options were compared across countries, across scale of growing operations, and by demographics, drug use and crime variables. Results: Although there were some between country differences in support for the various policy options, what was striking was the similarity of the proportions for each of the eight most popular policy options. Among current growers, many of these positions were predicted by demographic, drug use and cannabis growing variables which were conceptually congruent with these positions. Conclusion: The results have relevance for the provisions regarding cannabis cultivation in the design of new non-prohibitionist models of cannabis which are increasingly under consideration. It should be of interest to policy makers, drug policy researchers, law enforcement and cannabis cultivators

Daisyworld: a review

Daisyworld is a simple planetary model designed to show the long-term effects of coupling between life and its environment. Its original form was introduced by James Lovelock as a defense against criticism that his Gaia theory of the Earth as a self-regulating homeostatic system requires teleological control rather than being an emergent property. The central premise, that living organisms can have major effects on the climate system, is no longer controversial. The Daisyworld model has attracted considerable interest from the scientific community and has now established itself as a model independent of, but still related to, the Gaia theory. Used widely as both a teaching tool and as a basis for more complex studies of feedback systems, it has also become an important paradigm for the understanding of the role of biotic components when modeling the Earth system. This paper collects the accumulated knowledge from the study of Daisyworld and provides the reader with a concise account of its important properties. We emphasize the increasing amount of exact analytic work on Daisyworld and are able to bring together and summarize these results from different systems for the first time. We conclude by suggesting what a more general model of life-environment interaction should be based on

Contributors to the Summer Issue/Notes

Notes by Louis F. DiGiovanni, E. A. Steffen, Jr., John L. Globensky, Lenton G. Sculthorp, William V. Phelan, and George Ratterman

Recent Decisions

Comments on recent decisions by Wilmer A. McLaughlin, Robert C. Enburg, Robert A. Layden, Lenton G. Sculthorp, Joseph T. Helling, John L. Globensky, Maurice J. Moriarty, Robert J. Affeldt, Louis J. Mustico, Donald John Tufts, Sidney Baker, and Edward J. VanTassel

Contributors to the Summer Issue/Notes

Notes by Louis F. DiGiovanni, E. A. Steffen, Jr., John L. Globensky, Lenton G. Sculthorp, William V. Phelan, and George Ratterman

Overeducation across British regions

This paper analyses levels of over-education and wage returns to education for males across eleven regions of the UK using Labour Force Survey data. Significant differences are found in the probability of being over-educated across regions; also, differences are found in the return to the ‘correct’ level of education in each region, in each case associated with flexibility of movement between and into particular regions, which determines the ease of job matching. Furthermore, evidence is found that, after controlling for the level of education acquired, there exists a premium to the ‘correct’ level of education, which varies across UK regions

Forecasting the underlying potential governing the time series of a dynamical system

Copyright © 2013 The Authors. Published by Elsevier B.V. All rights reserved.We introduce a technique of time series analysis, potential forecasting, which is based on dynamical propagation of the probability density of time series. We employ polynomial coefficients of the orthogonal approximation of the empirical probability distribution and extrapolate them in order to forecast the future probability distribution of data. The method is tested on artificial data, used for hindcasting observed climate data, and then applied to forecast Arctic sea-ice time series. The proposed methodology completes a framework for ‘potential analysis’ of tipping points which altogether serves anticipating, detecting and forecasting nonlinear changes including bifurcations using several independent techniques of time series analysis. Although being applied to climatological series in the present paper, the method is very general and can be used to forecast dynamics in time series of any origin.NERCAXA Research FundEuropean Commissio