Optical preparation and measurement of atomic coherence at gigahertz bandwidth

We detail a method for the preparation of atomic coherence in a high density atomic medium, utilising a coherent preparation scheme of gigahertz bandwidth pulses. A numerical simulation of the preparation scheme is developed, and its efficiency in preparing coherent states is found to be close to unity at the entrance to the medium. The coherence is then measured non-invasively with a probe field.Comment: 7 pages, 5 figure

Dark Green Color Index as a Method of Real-time In-season Corn Nitrogen Measurement and Fertilization

Corn (Zea mays L.) requires higher rates of nitrogen fertilizer than any other major U.S. crop partly because N fertilizers are subject to loss through various mechanisms. Because of this, corn may suffer from inadequate nitrogen fertilization or producers may over-apply nitrogen to compensate for early-season nitrogen losses. A timely, accurate, and precise method for measuring in-season corn N status is needed to allow producers to keep nitrogen use efficiency high within a growing season. Using appropriate software, hue, saturation, and brightness values of digital images can be combined in a dark green color index (DGCI) which is closely associated with leaf nitrogen concentration. Our objectives were: (1) to develop quantitative relationships among yield, corn leaf nitrogen concentration, and DGCI measurements taken in the mid-vegetative stages of growth development;; and (2) to determine the amount of nitrogen to apply to recover yield based upon DGCI measurements on 6-leaf corn (V6). Various corn hybrids were planted across two years in Arkansas. A wide range of N applications were made at emergence and at V6 stage. SPAD, DGCI, and leaf nitrogen measurements were taken prior to V6 application and again at tasseling. Leaf nitrogen concentrations, DGCI, and SPAD were found to be closely associated. Crops with varying early-season N deficiencies demonstrated a non-linear, quadratic response to V6 N applications. Combining the responses of yield to V6 N application amounts with concurrent mid-season DGCI measurements allowed for the development of calibration equations. These calibrations equations allow corrective, mid-season N applications to be made based on an observed DGCI value, which allows for the recovery of 90 or 95% of the crop\u27s yield potential

Faraday Rotation of Pulsed and Continuous-wave Light in Atomic Vapour

The absorptive and dispersive properties of a Doppler-broadened vapour of rubidium atoms is investigated. A detailed model of the atom-light interaction is developed and found to be in excellent agreement with experiment in the regime where the interacting light field is sufficiently weak such that it does not significantly alter the medium through which it propagates. The importance of using a weak beam to probe atomic systems is discussed, and a method of characterising how weak such a beam has to be is provided. The theoretical model is applied to both situations of illumination by continuous-wave and pulsed light, the latter situation providing a demonstration of the slow light effect. This phenomenon is a manifestation of the dispersive properties of the medium and is shown to exist over a particularly large frequency range, compared to the absorption spectrum, in thermal vapours. Off-resonant interactions are studied, in which incident laser-light is detuned from resonance to such a degree that Doppler-broadening can be neglected. We quantify the extent to which the light needs to be detuned to be in this regime, and provide approximations to the line-shape function developed in earlier parts of the thesis. The approximate line-shapes are much easier to manipulate and allow a more intuitive understanding of the atom-light interaction. In the second part of the thesis we study the Faraday effect and related phenomena which are an expression of the birefringent properties of the atom-light system. Beginning with a theoretical and experimental investigation of the Faraday rotation of a weak continuous-wave beam, we move on to the consideration of pulsed light. Optically-induced birefringence via the application of an intense continuous-wave pumping field is demonstrated experimentally, and the theoretical plausibility of controlling the polarisation state of a weak pulsed field mediated via intense pulsed light is shown

Yay or Neigh? Frederic Remington’s Bronco Buster, Public Art, and Socially-Engaged Art History Pedagogy

This article outlines a collaborative, community-based project developed for two undergraduate art history courses at a large state university. The exercise focused on Frederic Remington’s 1894-95 sculpture, the Bronco Buster, a large bronze image of a cowboy whipping a bucking bronco with the goal of taming it. An enlarged replica of Remington’s sculpture was installed recently in the downtown district of this university town, raising questions about how it was selected and funded, as well as what message the sculpture sent about the town to its visitors. As we discussed our frustration with both the iconography and the selection process of the Bronco Buster, we wondered if we could translate it into powerful learning experiences for our art history students, tying their real-world, local experiences to the critical skills and historical knowledge that we teach in the classroom. In this essay, we describe and evaluate the semester-long collaborative learning experience that we designed and implemented. We discuss engaged scholarship and community interaction, consider the relevance of art history to contemporary life and politics, confront the pedagogical challenges posed by regionally, politically, and racially diverse student bodies, and generate a model for others invested in the connections between academic and everyday life

SMILE: the creation of space for interaction through blended digital technology

Interactive Learning Environments at Sussex University is a course in which students are given mobile devices (XDAs) with PDA functionality and full Internet access for the duration of the term. They are challenged to design and evaluate learning experiences, both running and evaluating learning sessions that involve a blend of technologies. Data on technology usage was collected via backups, email and web-site logging as well as video and still photography of student-led sessions. Initial analysis indicates that large amounts of technical support, solid pedagogical underpinning and a flexible approach to both delivery context and medium are essential. The project operated under the acronym SMILE – Sussex Mobile Interactive Learning Environment

Whether it's M-learing or E-learning, it must be ME learning: a case study of mobile learning in Higher Education

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Large eddy simulation of subsurface phytoplankton dynamics: an optimum condition for chlorophyll patchiness induced by Langmuir circulations

Phytoplankton patchiness occurs on a plethora of spatial and temporal scales which can be extremely patchy in both horizontal and vertical directions. This patchiness directly affects the dynamics of the overall bloom, so understanding the mechanisms for patchiness to occur on each scale is therefore integral to the understanding of plankton bloom dynamics as a whole. This modelling study aims to introduce a mechanism for patch formations which has had very little exposure, but is ubiquitous to the oceanic mixed layer – patchiness induced by the interaction between the nutrient upwelling and Langmuir circulations. By combining a Large-Eddy Simulation which resolves Langmuir circulations, with a Nutrient-Phytoplankton-Zooplankton biological model, one can examine the horizontal and vertical patchiness which results from a flux of nutrients into the bottom of the mixed layer. Here, phytoplankton form significant horizontal patchiness in a depth interval where vertical currents from Langmuir cells are apparent and turbulent mixing is not; this comprises the lower region of the surface mixed layer. Aggregations have frequently been observed in lower regions of the surface mixed layer and have been attributed to the high nutrient flux associated with the pycnocline. This modelling study also shows patches occurring in this region and it is hypothesised that Langmuir cells are a catalyst for patchiness. The results clearly demonstrate that for certain levels of wind forcing, which are strong enough to introduce turbulent mixing only to the upper part of the mixed layer whilst inducing deeper Langmuir circulation, patchiness is greatly enhanced

How accurate are forecasts of costs of energy? A methodological contribution

Forecasts of the cost of energy are typically presented as point estimates; however forecasts are seldom accurate, which makes it important to understand the uncertainty around these point estimates. The scale of the differences between forecasts and outturns (i.e. contemporary estimates) of costs may have important implications for government decisions on the appropriate form (and level) of support, modelling energy scenarios or industry investment appraisal. This paper proposes a methodology to assess the accuracy of cost forecasts. We apply this to levelised costs of energy for different generation technologies due to the availability of comparable forecasts and contemporary estimates, however the same methodology could be applied to the components of levelised costs, such as capital costs. The estimated “forecast errors” capture the accuracy of previous forecasts and can provide objective bounds to the range around current forecasts for such costs. The results from applying this method are illustrated using publicly available data for on- and off-shore wind, Nuclear and CCGT technologies, revealing the possible scale of “forecast errors” for these technologies

Canine Insulinoma

Canine insulinoma is the neoplastic growth of the beta cells of the pancreas. in man 90% of the growths are found to be benign while in the dog reports say 69-81% of the growths are malignant (2,7). A malignant canine insulinoma denotes a functional neoplasm secreting excessive amounts of insulin or what some authors term inappropriate release of insulin