Transformation of two and three-dimensional regions by elliptic systems

Grid smoothing and orthogonalization procedures were developed and implemented in the construction of two and three dimensional grids. The procedures are based on the variational methods of grid generation. The two-dimensional examples were computed using the MSU IRIS Graphics Workstation. It was demonstrated that the elliptic grid generation equations, with arbitrary forcing functions, can be solved, in their variational formulation, using a gradient method. Since gradient methods have a global convergence property, the divergence problems often encountered when using SOR iterative methods can be avoided. It is not to be concluded, however, that SOR methods should be abandoned, since gradient methods tend to converge very slowly. In fact, slow convergence was the major problem encountered in the three-dimensional grids. Further progress was made on the continuing effort to develop conservative interpolation formulas for overlapping grids

Kinetics and mechanism of the reaction between atomic chlorine and dimethyl selenide; comparison with the reaction between atomic chlorine and dimethyl sulfide

Dimethyl selenide is the most abundant gaseous selenium species in marine environments. In this work, the value of the rate coefficient for the gas-phase reaction between dimethyl selenide and Cl atoms has been determined for the first time. The value of the second-order rate coefficient obtained was (5.0±1.4)×10–10 cm3 molecule–1 s–1. The very fast nature of the reaction means that, when estimating the lifetime of dimethyl selenide in the atmosphere, loss due to reaction with Cl atoms should be considered along with loss due to reaction with O3 and with OH and NO3 radicals. Analysis of the available kinetic data suggests that at 760 Torr the dominant reaction pathway for the reaction of Cl atoms with dimethyl selenide will be the addition of Cl to the Se atom forming an adduct of the type CH3Se(Cl)CH3. Theoretical calculations, at the B3LYP/6-311++G(2df,p)//B3LYP/6-311++G(d,p) level of theory, show that at 298 K the value of rH for the formation of the adduct is –111.4 kJ mol–1. This value may be compared to –97.0 kJ mol–1, the value calculated for rH for the formation of the analogous sulfur adduct, CH3S(Cl)CH3, following the reaction between Cl atoms and dimethyl sulfide. Variational RRKM theory was used to predict the thermal decomposition rates of the two adducts back to starting materials. The estimated rate constant for the decomposition of the selenium adduct to the reactants is 5×10–5 s–1, compared to 0.02 s–1 in the case of the sulfur adduct. However, our calculations suggest that the CH3Se(Cl)CH3 adduct, which is initially formed highly excited, will not be stabilised under atmospheric conditions, but rather will decompose to yield CH3SeCl and CH3, a process that is calculated to be exothermic with respect to the initial reactants by 5.8 kJ mol–1. The formation of CH3SCl and CH3 from the sulfur adduct, on the other hand, is endothermic by 20.8 kJ mol–1 with respect to the initial reactants, and is thus not expected to occur

Hydrogen bonded complexes between nitrogen dioxide, nitric acid, nitrous acid and water with SiH3OH and Si(OH)4

The inter-conversion of nitrogen oxides and oxy acids on silica surfaces is of major atmospheric importance. As a preliminary step towards rationalising experimental observations, and understanding the mechanisms behind such reactions we have looked at the binding energies of NO2, N2O4, HNO3, HONO and H2O with simple proxies of a silica surface, namely SiH3OH and Si(OH)4 units. The geometries of these molecular clusters were optimised at both HF/6-311+G(d) and B3LYP/6-311+G(d) level of theory. The SCF energies of the species were determined at the HF/6-311++G(3df,2pd) and B3LYP/6-311++G(3df,2pd) level. The values indicate that nitric acid is by far the most strongly bound species, in agreement with experimental observations. It was also found that the dimer N2O4 is significantly more strongly bound to the Si(OH)4 and SiH3OH units than NO2 itself. The vibrational frequencies calculated for the hydrogen-bonded complexes are compared to the experimentally observed frequencies of the adsorbed species where possible

An Unbiased Survey of 500 Nearby Stars for Debris Disks: A JCMT Legacy Program

We present the scientific motivation and observing plan for an upcoming detection survey for debris disks using the James Clerk Maxwell Telescope. The SCUBA-2 Unbiased Nearby Stars (SUNS) Survey will observe 500 nearby main sequence and sub-giant stars (100 of each of the A, F, G, K and M spectral classes) to the 850 micron extragalactic confusion limit to search for evidence of submillimeter excess, an indication of circumstellar material. The survey distance boundaries are 8.6, 16.5, 22, 25 and 45 pc for M, K, G, F and A stars, respectively, and all targets lie between the declinations of -40 deg to 80 deg. In this survey, no star will be rejected based on its inherent properties: binarity, presence of planetary companions, spectral type or age. This will be the first unbiased survey for debris disks since IRAS. We expect to detect ~125 debris disks, including ~50 cold disks not detectable in current shorter wavelength surveys. A substantial amount of complementary data will be required to constrain the temperatures and masses of discovered disks. High resolution studies will likely be required to resolve many of the disks. Therefore, these systems will be the focus of future observational studies using a variety of observatories to characterize their physical properties. For non-detected systems, this survey will set constraints (upper limits) on the amount of circumstellar dust, of typically 200 times the Kuiper Belt mass, but as low as 10 times the Kuiper Belt mass for the nearest stars in the sample (approximately 2 pc).Comment: 11 pages, 7 figures (3 color), accepted by the Publications of the Astronomical Society of the Pacifi

27th Annual Midwest/Midsouth Estate Planning Institute

Materials from the 27th Annual Midwest/Midsouth Estate Planning Institute held by UK/CLE in July 2000

Weather and our food supply

The steep rate of increase in yield of grain crops in the United States since the mid-1950\u27s has resulted in the use of the term explosion in technology. Surplus grains piled up to such proportions after the 1960 · harvest that acreage control appeared. to be in order. But despite substantial reductions in acreages after 1960 the increased output per acre has just about compensated for acreage reductions. During this period of rapid increase in output per acre there has been a growing tendency to believe that technology has reduced the influence of weather on grain production so that we no longer need to fear shortages due to unfavorable weather. There is also a popular belief that acreage control$ fail to achieve the objective of production control, and that public funds are being wasted in storing surplus grains which we don\u27t need. There is increasing evidence, however, that a period of favorable weather interacted with technology to produce our recent high yields, and that perhaps half of the increase in yield per acre since 1950 has been due to a change to more favorable weather for grain crops. These findings have important implications in continued support for research in production technology and in the way in which we look at our surplus stocks of feed and food grains. If a period of favorable weather has been responsible for half of the increase in yields since 19501 then what can we expect if the weather trend reverses itself for a few years? Do we have periodicity in weather, and have we just passed through a run of favorable years that might be followed by a run of unfavorable years? Should we treat our surplus grains as reserves? How does our rate of growth in grain output compare with the needs of a growing world population? And of course I in the background of these questions is one big question -- how much of our recent high yields is really due to weather? To answer these important questions the Center for Agriculture and Economic Development invited outstanding authorities to present their ideas under three main headings: (1) Techniques for Evaluation of Weather Variables in Agricultural Production I (2) Periodicity in Weather Patterns: Implications in Agriculture I and (3) Weather Considerations in Agricultural Policy. The papers have been assembled in the order of their presentation under the general outline above.https://lib.dr.iastate.edu/card_reports/1021/thumbnail.jp

IMOS national reference stations: A continental-wide physical, chemical and biological coastal observing system

Sustained observations allow for the tracking of change in oceanography and ecosystems, however, these are rare, particularly for the Southern Hemisphere. To address this in part, the Australian Integrated Marine Observing System (IMOS) implemented a network of nine National Reference Stations (NRS). The network builds on one long-term location, where monthly water sampling has been sustained since the 1940s and two others that commenced in the 1950s. In-situ continuously moored sensors and an enhanced monthly water sampling regime now collect more than 50 data streams. Building on sampling for temperature, salinity and nutrients, the network now observes dissolved oxygen, carbon, turbidity, currents, chlorophyll a and both phytoplankton and zooplankton. Additional parameters for studies of ocean acidification and bio-optics are collected at a sub-set of sites and all data is made freely and publically available. Our preliminary results demonstrate increased utility to observe extreme events, such as marine heat waves and coastal flooding; rare events, such as plankton blooms; and have, for the first time, allowed for consistent continental scale sampling and analysis of coastal zooplankton and phytoplankton communities. Independent water sampling allows for cross validation of the deployed sensors for quality control of data that now continuously tracks daily, seasonal and annual variation. The NRS will provide multi-decadal time series, against which more spatially replicated short-term studies can be referenced, models and remote sensing products validated, and improvements made to our understanding of how large-scale, long-term change and variability in the global ocean are affecting Australia's coastal seas and ecosystems. The NRS network provides an example of how a continental scaled observing systems can be developed to collect observations that integrate across physics, chemistry and biology