Bipartite Ramsey Numbers and Zarankiewicz Numbers

The bipartite Ramsey number b(m, n) is the minimum b such that any 2-coloring of Kb,b results in a monochromatic Km,m subgraph in the first color or a monochromatic Kn,n subgraph in the second color. The Zarankiewicz number z(m, n; s, t) is the maximum size among Ks,t-free subgraphs of Km,n. In this work, we discuss the intimate relationship between the two numbers as well as propose a new method for bounding the Zarankiewicz numbers. We use the better bounds to improve the upper bound on b(2, 5), in addition we improve the lower bound of b(2, 5) by construction. The new bounds are shown to be 17 ≤ b(2, 5) ≤ 18. Additionally, we apply the same methods to the multicolor case b(2, 2, 3) which has previously not been studied and determine bounds to be 16 ≤ b(2, 2, 3) ≤ 23

INVESTIGATING THE EFFECTS OF SHORT- AND LONG-TERM CLIMATIC VARIATION ON THE WATER USE OF THREE NORTHERN HARDWOOD TREE SPECIES

Many tree species are expected to decline in the northern Midwestern United States due to climate change increasing annual temperature 3-5º C by 2100. Sugar maple (Acer saccharum), an economically important timber and syrup species, is not expected to be sustainable in its current range under projected future climate, while trembling aspen (Populus tremuloides) and red maple (Acer rubrum) are expected to react more favorably to climate change. The success of individual tree species is dependent on how climate change will alter a species environment in regards to water use. Climate change could potentially reduce available soil moisture, reducing potential transpiration within a forest. This dissertation had three objectives; 1) to investigate the effects of experimental soil warming and irrigation on transpiration rates of sugar maple over three growing seasons, 2) to investigate the effects of environmental drivers on water use of trembling aspen and red maple, and to 3) investigate the effects of wounding on the accuracy of sap flux estimates in heat dissipation sensors. Overall, we found that drought effects due to climate change could potentially decrease sugar maple productivity on drier sites within its current range. Further, trembling aspen had higher rates of transpiration, growth and water use efficiency than red maple indicating that trembling aspen may not react as unfavorably to climate change as expected. Finally, we found wounding effects caused an underestimation in sap flux data in sugar maple and trembling aspen when probes remained in trees for two years

Venomous Spiders of the Southeastern US: An Unexpected Threat

Background: Environmental health specialists recommend that residents of the Southeastern US, including Georgia, have the ability to identify the three venomous spiders indigenous to this area. It is necessary to recognize the black widow, brown widow, and brown recluse spiders and to be familiar with the likely habitats of these insects and with the symptoms of bites. The primary author, who serves as an Environmental Health Specialist and is a hobbyist who works with distressed wood, frequently encounters all three of these spiders. Methods: A literature review supports the fact that these three venomous spiders are indigenous to Georgia. Results: Spiders, a common sight in rural and urban areas of Georgia, are often not considered as being especially dangerous. Three common species of spiders found in Georgia are, however, venomous. Conclusions: Recognition of spiders is particularly appropriate for the protection of food service workers, employees working in tourist accommodations, and hobbyists who routinely invade spider habitats. The evaluation of educational efforts may be assessed by the numbers of reported cases of spider bites among these populations

ARAS: an automated radioactivity aliquoting system for dispensing solutions containing positron-emitting radioisotopes.

BackgroundAutomated protocols for measuring and dispensing solutions containing radioisotopes are essential not only for providing a safe environment for radiation workers but also to ensure accuracy of dispensed radioactivity and an efficient workflow. For this purpose, we have designed ARAS, an automated radioactivity aliquoting system for dispensing solutions containing positron-emitting radioisotopes with particular focus on fluorine-18 ((18)F).MethodsThe key to the system is the combination of a radiation detector measuring radioactivity concentration, in line with a peristaltic pump dispensing known volumes.ResultsThe combined system demonstrates volume variation to be within 5 % for dispensing volumes of 20 μL or greater. When considering volumes of 20 μL or greater, the delivered radioactivity is in agreement with the requested amount as measured independently with a dose calibrator to within 2 % on average.ConclusionsThe integration of the detector and pump in an in-line system leads to a flexible and compact approach that can accurately dispense solutions containing radioactivity concentrations ranging from the high values typical of [(18)F]fluoride directly produced from a cyclotron (~0.1-1 mCi μL(-1)) to the low values typical of batches of [(18)F]fluoride-labeled radiotracers intended for preclinical mouse scans (~1-10 μCi μL(-1))

The Geographic Distribution of Bowhead Whales, Balaena mysticetus, in the Bering, Chukchi, and Beaufort Seas: Evidence from Whaleship Records, 1849–1914

We have extracted, digitized, and analyzed information about bowhead whales, Balaena mysticetus, contained in records of whaling cruises that were undertaken in the Bering, Chukchi, and Beaufort Seas from 1849 to 1914. Our database consists of 65,000 days of observations which provide insights into whether this bowhead stock may comprise more than one population