Rates of solar angles for two-axis concentrators

The Sun's position by the azimuth and elevation angles and its rate of change at any time of day are determined to design 2 axis tracking mechanisms of solar concentrators. The Sun's angles and their rates for selected months of the year (March, June, September and December) and for seven selected atitudes (0, + or - 30, + or - 60, + or - 90) covering both the northern and southern hemispheres were studied. The development of the angle and angle rate analytical expressions for any month, hour of day, and latitude provides the solar concentrator designer with a quantitative determination of the limiting Sun's position and angle rates for an accurate automatic tracking mechanism

Dynamical Electron Mass in a Strong Magnetic Field

Motivated by recent interest in understanding properties of strongly magnetized matter, we study the dynamical electron mass generated through approximate chiral symmetry breaking in QED in a strong magnetic field. We reliably calculate the dynamical electron mass by numerically solving the nonperturbative Schwinger-Dyson equations in a consistent truncation within the lowest Landau level approximation. It is shown that the generation of dynamical electron mass in a strong magnetic field is significantly enhanced by the perturbative electron mass that explicitly breaks chiral symmetry in the absence of a magnetic field.Comment: 5 pages, 1 figure, published versio

Multi-Qubit Gates in Arrays Coupled by 'Always On' Interactions

Recently there has been interest in the idea of quantum computing without control of the physical interactions between component qubits. This is highly appealing since the 'switching' of such interactions is a principal difficulty in creating real devices. It has been established that one can employ 'always on' interactions in a one-dimensional Heisenberg chain, provided that one can tune the Zeeman energies of the individual (pseudo-)spins. It is important to generalize this scheme to higher dimensional networks, since a real device would probably be of that kind. Such generalisations have been proposed, but only at the severe cost that the efficiency of qubit storage must *fall*. Here we propose the use of multi-qubit gates within such higher-dimensional arrays, finding a novel three-qubit gate that can in fact increase the efficiency beyond the linear model. Thus we are able to propose higher dimensional networks that can constitute a better embodiment of the 'always on' concept - a substantial step toward bringing this novel concept to full fruition.Comment: 20 pages in preprint format, inc. 3 figures. This version has fixed typos and printer-friendly figures, and is to appear in NJ

Greening Rail Infrastructure for Carbon Benefits

© 2017 The Authors. Metropolitan Sydney has a network of rail corridors almost 400 kilometers in length, which vary in width from narrow cuttings to wide easements. With an appropriate selection of vegetation species, these corridors can be used to offset carbon emissions from railway operations. Simultaneously, the plantings will improve air quality, reduce pollution and storm water flows, ameliorate urban heating deliver biodiversity gains and improve urban design and property values. A pilot study was carried out on a representative section of one of the major rail lines in Sydney in 2016. A detailed inventory of vegetation on the selected site was obtained through a field survey and a variety of tools were used including i-Tree Eco to benchmark current carbon sequestration and storage (CS & S) levels. Study outcomes include the existing carbon capacity of the rail corridor's above-ground (and substrate) biomass and air pollution reduction. It also presents estimates of CS & S potential by identifying future planting areas within the pilot study corridor. These results are valuable for infrastructure policy formulation directed towards carbon emissions as well as securing the co-benefits noted above

Greening Rail Infrastructure for Carbon Benefits

© 2017 The Authors. Metropolitan Sydney has a network of rail corridors almost 400 kilometers in length, which vary in width from narrow cuttings to wide easements. With an appropriate selection of vegetation species, these corridors can be used to offset carbon emissions from railway operations. Simultaneously, the plantings will improve air quality, reduce pollution and storm water flows, ameliorate urban heating deliver biodiversity gains and improve urban design and property values. A pilot study was carried out on a representative section of one of the major rail lines in Sydney in 2016. A detailed inventory of vegetation on the selected site was obtained through a field survey and a variety of tools were used including i-Tree Eco to benchmark current carbon sequestration and storage (CS&S) levels. Study outcomes include the existing carbon capacity of the rail corridor's above-ground (and substrate) biomass and air pollution reduction. It also presents estimates of CS&S potential by identifying future planting areas within the pilot study corridor. These results are valuable for infrastructure policy formulation directed towards carbon emissions as well as securing the co-benefits noted above

Reply to “Comment by A. Appleby, D. Lilian and H. B. Singh on ‘Atmospheric halocarbons: A discussion with emphasis on chloroform’”

No abstract

Agricultural Perturbations of the Nitrogen Cycle and Related Impact on Atmospheric N_2O and Ozone

The available data are employed to identify the fate of agricultural nitrogen in the environment. Best estimates predict denitrification of nearly 50% of fertilizer nitrogen in less than 10 years after application. We also discuss in detail the expected demand curve for agricultural N. If population growth continues at projected levels, between 100 and 200 M tons/yr of agricultural N will be needed by the year 2000. We estimate that as a result, atmospheric N_2O could be more than doubled by 2050, and that perturbations of O_3 at that time could range from 10 to more than 20%. Major uncertainties remain however, and we emphasize the importance of further experimental research into the nitrogen cycle

Exoplanet Atmospheres and Photochemistry

Over 150 extrasolar planets are known to orbit sun-like stars. A growing number of them (9 to date) are transiting “hot Jupiters” whose physical characteristics can be measured. Atmospheres of two of these planets have already been detected. We summarize the atmosphere detections and useful upper limits, focusing on the MOST albedo upper limit and II exosphere detection for IID 209458b as the most relevant for photochemical models. We describe our photochemical model for hot Jupiters and present a summary explanation of the main results: a low gas-phase abundance of hydrocarbons; an absence of hydrocarbon hazes; and a large reservoir of II atoms in the upper atmospheres of hot Jupiters. We conclude by relating these model results to the relevant observational data