Fresnel phasing of segmented mirror telescopes

Shack-Hartmann (S-H) phasing of segmented telescopes is based upon a physical optics generalization of the geometrical optics Shack-Hartmann test, in which each S-H lenslet straddles an intersegment edge. For the extremely large segmented telescopes currently in the design stages, one is led naturally to very large pupil demagnifications for the S-H phasing cameras. This in turn implies rather small Fresnel numbers F for the lenslets; the nominal design for the Thirty Meter Telescope calls for F=0.6. For such small Fresnel numbers, it may be possible to eliminate the lenslets entirely, replacing them with a simple mask containing a sparse array of clear subapertures and thereby also eliminating a number of manufacturing problems and experimental complications associated with lenslets. We present laboratory results that demonstrate the validity of this approach.     

Development of a new indicator of pollutant loads and its application to the Chesapeake Bay watershed

Pollutant load reductions are often required to restore aquatic ecosystems experiencing eutrophication. Loads can be estimated using watershed models or data from monitoring stations, however data availability can limit the timeliness or comprehensiveness of the load estimates. We developed an approach to address this challenge that used watershed model results to estimate the proportion of annual nonpoint source nitrogen (N), phosphorus (P) and sediment (Sed) loads derived from unmonitored catchments. This proportion was multiplied by the nonpoint portion of United States Geological Survey (USGS) estimated annual river loads to account for annual variation in hydrologic conditions. Total loads were calculated as the sum of measured river loads, reported point sources from unmonitored areas and the estimated nonpoint source loads from unmonitored catchments. We applied this approach to the Chesapeake Bay because of its socio‐economic and ecological importance. Median watershed loads for N, P and Sed were 140, 6.4 and 3030 Mg year^?1, respectively (1990–2004). Nonpoint source loads from the monitored areas constituted the greatest source of N, P and Sed (55, 47 and 74% respectively) to the Bay. The high N, P and Sed yield rates (7.3, 0.38 and 99 kg ha^?1 year^?1, respectively) from nonpoint loads originating from unmonitored areas near the Bay resulted in 25, 32 and 26% (N, P and Sed, respectively) of the Bay's total loads (excluding direct atmospheric deposition, shoreline erosion and oceanic inputs). Disproportionately high loads of P and Seds were associated with years that experienced elevated discharge whereas N loads were directly related to discharge. Error estimates indicated that our methods were most reliable for N (±6%) but reasonable for P (±22%) and provide an effective technique for the timely estimation of pollutant loads from watersheds with unmonitored catchments. Management strategies that decrease N deposition and reduce runoff to control P and Sed transport will effectively reduce pollutant loads. Published in 2010 by John Wiley & Sons, Ltd.     

Pre-emptive glycopyrrolate 0.2 mg and bradycardia during gynaecological laparoscopy with mivacurium

In a prospective, randomized, double-blind, placebo-controlled trial, the effect of pre-emptive glycopyrrolate 0.2 mg given intravenously on the incidence of bradycardia in patients undergoing elective gynaecological laparoscopy with mivacurium neuromuscular blockade was investigated. Seven out of 32 (21.6%) control patients developed bradycardia (heart rate < 50 min-1), compared with 3 of 31 (9.6%) patients receiving glycopyrrolate (P = 0.4). Glycopyrrolate 0.2 mg, given immediately before induction in gynaecological laparoscopy with mivacurium, did not significantly reduce the incidence of intraoperative bradycardia.     

Embodied and Operational Energy Consumption in the City

This study shows how estimates of energy consumption can be extracted from existing data sets and efficiently related to characteristics of the real property making up the discrete areas of the city. The study suggests that embodied energy consumption may be more significant than previously thought and suggests how estimates of embodied and operational energy may be used as a development control tool in the planning system.     

Thermal Effects on Skewed Steel Highway Bridges and Bearing Orientation

An investigation is conducted to characterize and quantify external effects in composite steel highway bridges under thermal loading. Based on the results of a literature review, including thermal and thermoelastic analyses as well as current design code provisions, a simple but realistic thermal loading is developed for winter and summer conditions for AASHTO load and resistance factor design (LRFD) Zone 3. Three cases of bearing orientation, representative of current design practice, are examined. Parametric studies are then conducted. Hypothetical bridges are designed for a range of different span lengths, section depths, widths, and skews. Each bridge model is tested under all three constraint cases and both winter and summer thermal loading. Variations in structural response with each parameter are plotted, and the relative influence of each parameter is discussed. Design equations to predict the observed displacements and restraint forces at the bearings are then developed by a systematic regression procedure. The applicability of these proposed design equations is demonstrated by examples.     

Multipixel techniques for frequency-domain photon migration imaging

The ability to map interior optical properties of a highly scattering medium from exterior measurements of light propagation is afforded by optical tomography. In this communication, we describe the problem of optical tomography, the techniques of photon migration measurements necessary to accomplish it, and the development of multipixel measurements for rapid collection of optical signals. These multipixel measurements are shown to provide detection of contrast owing to the optical properties of absorption and fluorescence associated with dye-laden heterogeneities embedded in a tissue-like scattering medium. From these rapid measurements, successful reconstruction of an interior optical property map may now be possible with clinically realistic data acquisition times. Applications for the technology arise for biomedical optical imaging for the in vivo detection of disease and the diagnosis of tissue (bio-) chemistry.     

Evaluating graphics displays for complex 3D models

This article summarizes a user study of viewing 3D geometry on large-screen display devices. The geometry models the structure of a complex physical object. Our results show that the crispness of a display device (intraframe performance) must be considered along with the speed at which new frames can be computed (interframe performance). It's important to consider crispness from the user's perspective, using values that aren't often published in device specifications. Equally important is the framework for different types of 3D data and the categorization of display technology and techniques