Potential for Abrupt Changes in Atmospheric Methane

Methane (CH4) is the second most important greenhouse gas that humans directly influence, carbon dioxide (CO2) being first. Concerns about methane’s role in abrupt climate change stem primarily from (1) the large quantities of methane stored as solid methane hydrate on the sea floor and to a lesser degree in terrestrial sediments, and the possibility that these reservoirs could become unstable in the face of future global warming, and (2) the possibility of large-scale conversion of frozen soil in the high- latitude Northern Hemisphere to methane producing wetland, due to accelerated warming at high latitudes. This chapter summarizes the current state of knowledge about these reservoirs and their potential for forcing abrupt climate change

IMPLICATIONS OF TEMPERATURE-ACTIVATED POLYMER SEED COATING FOR CROP PRODUCTION IN THE NORTHERN CORN BELT

The value of an innovative new seed technology is evaluated in a discrete stochastic programming framework for a representative farm in the northern Corn Belt. Temperature-activated polymer coated seed has the potential to increase net returns by reducing yield loss due to delayed planting and by increasing the use of longer season varieties. A biophysical simulation model was used to estimate the impact of polymer coated seed on corn and soybean yields and on field day availability for five planting periods, two crop varieties and two tillage systems on two different soils under varying weather conditions. Results show that polymer coated seed increases net returns in corn by $2.50-$3.65 per acre and in soybeans by $4.50-$9.70 per acre.mathematical programming, biophysical simulation, corn, soybean, Crop Production/Industries,

Binding potentials for vapour nanobubbles on surfaces using density functional theory

We calculate density profiles of a simple model fluid in contact with a planar surface using density functional theory (DFT), in particular for the case where there is a vapour layer intruding between the wall and the bulk liquid. We apply the method of Hughes et al. [J. Chem. Phys. 142, 074702 (2015)] to calculate the density profiles for varying (specified) amounts of the vapour adsorbed at the wall. This is equivalent to varying the thickness $h$ of the vapour at the surface. From the resulting sequence of density profiles we calculate the thermodynamic grand potential as $h$ is varied and thereby determine the binding potential as a function of $h$. The binding potential obtained via this coarse-graining approach allows us to determine the disjoining pressure in the film and also to predict the shape of vapour nano-bubbles on the surface. Our microscopic DFT based approach captures information from length scales much smaller than some commonly used models in continuum mechanics.Comment: 15 pages, 15 figure

Calculation involving hydrogen-hydrogen(2) collisional cooling processes for use in astrophysics

This thesis will calculate the H-H2 cooling processes used in astrophysics. Cooling is critical to the formation of the first objects formed in the early universe, and other diverse phenomenon of interest to astrophysics. For instance, in order to collapse into objects, the gravitational potential energy of primordial density fluctuations must be radiated away. The most abundant element in the universe is hydrogen, and cooling processes involving hydrogen are important in several contexts. To calculate the cooling, the cross section for collisional excitation at constant energy were integrated over a Maxwellian velocity distribution to determine a rate coefficient. Then the equilibrium level populations will be solved for a given temperature and H density. Finally, the cooling and spectra are calculated from these equilibrium populations

The Upper Marine Limit in the Little Whale River Area, New Quebec

The relatively high land in places near the east coast of Hudson Bay in this area enables a more accurate estimate of direction and tilt of the upper marine limit plane to be made and thus to throw light on the emergence of this area after the last glaciation. The lower limit of perched boulders was used to indicate the height of the marine limit, for they represent the limit of wave action, whereas evidence given by the highest marine shells was inconclusive. The method of altimeter measurements and instrumental errors are stated. Analysis of data from 21 sites shows that the upper marine limit plane is tilted up toward 232 degrees ± 36 degrees(toward Hudson Bay); data from two points in the Richmond Bay area gave a tilt up toward 227 degrees ± 24 degrees. The varied isostatic readjustment indicates a major center of ice dispersal in the southern Hudson Bay/northern James Bay region during the Wisconsin glaciation.La limite supérieure de la transgression marine dans la région de la Petite rivière de la Baleine, Nouveau-Québec. À l'aide d'un altimètre, on a mesuré en 21 sites l'altitude de la limite supérieure de la transgression marine, indiquée par la limite inférieure des blocs perchés. L'analyse de ces cotes d'altitude indique que le plan de la limite supérieure est relevé vers 232º ± 36º. En ajoutant deux mesures géodésiques obtenues par Stanley en 1939, on arrive à un relèvement dirigé vers 277º ± 24º. On peut croire que ce rajustement isostatique variable indique la présence d'un centre majeur de dispersion glaciaire wisconsinienne au voisinage du sud de la mer d'Hudson et du nord de la baie de James

Self-insurance and self-protection in weed control: implications for nonpoint source pollution

This dissertation investigates producer\u27s weed control decisions in three papers. Using an endogenous risk framework, the papers model weed control decisions as they are affected by uncertainty and as they are affected by policies aimed at reducing nonpoint source pollution;The first paper adapts the theory of self protection and self insurance to weed control decisions in order to model substitutions between fertilizer and herbicides. Our results suggest that an increase in the probability of weed damage will generally decrease both herbicide and fertilizer application rates. We also show that increased probability of weed damage leads to use of less persistent herbicides and less fertilizer. Also, nonpoint pollution policies which restrict fertilizer quantities will tend to reduce herbicide rates and herbicide persistence, while policies which restrict herbicide rates or herbicide persistence will tend to reduce fertilizer rates;The second paper models weed control decisions using the concepts of self insurance and self protection to model substitutions among the types and quantities of herbicides used. Our results indicate that policies which restrict herbicide rates likely lead to use of more persistent herbicides, while policies which restrict the use of persistent herbicides likely lead to increased application rates. We also provide conditions to unambiguously sign the effects of increased application or effectiveness risk on optimal herbicide choices. Generally, risk leads to a tradeoff between herbicide rates and herbicide persistence;The third paper uses a biophysical modeling approach to construct and evaluate the environmental and economic effects of alternative nonpoint source pollution policies. Environmental and economic tradeoffs are compared for six sets of policies including five sets of tax policies and one set of bans. Generally, herbicide targeted tax policies which are based on groundwater exposure values are most cost-efficient for producing relatively small improvements in water quality, while broad-based policies such as flat taxes and bans are most cost-efficient for producing larger improvements in water quality

Quantum mechanical hydrogen-hydrogen collisional cross section calculation for astrophysics

The purpose of this work is to perform a quantum mechanical calculation of the collisional state-to-state cross sections for H-H2 required for astrophysical modeling. Previous quantum and semi-classical cooling rates computed from cross sections have shown unexplained discrepancies. This attempts to clarify the situation and provide reliable cross sections to the astrophysical community. As a side benefit of this calculation geometric phase effects in the H-H2 collision dynamics are investigated at higher energies than previously attempted. Cooling is critical to the formation of the first objects formed in the early universe, and other diverse phenomenon of interest to astrophysics. For instance, in order to collapse into objects, the gravitational potential energy of primordial density fluctuations must be radiated away. The most abundant element in the universe is hydrogen, and cooling processes involving hydrogen are important in several contexts