The Local Compressibility of Liquids near Non-Adsorbing Substrates: A Useful Measure of Solvophobicity and Hydrophobicity?

We investigate the suitability of the local compressibility chi(z) as a measure of the solvophobicity or hydrophobicity of a substrate. Defining the local compressibility as the derivative of the local one-body density w.r.t. the chemical potential at fixed temperature, we use density functional theory (DFT) to calculate chi(z) for a model fluid, close to bulk liquid-gas coexistence, at various planar substrates. These range from a `neutral' substrate with a contact angle of approximately 90 degrees, which favours neither the liquid nor the gas phase, to a very solvophobic, purely repulsive substrate which exhibits complete drying (i.e. contact angle 180 degrees). We find that the maximum in the local compressibility, which occurs within one-two molecular diameters of the substrate, and the integrated quantity chi_ex (the surface excess compressibility, defined below) both increase rapidly as the contact angle increases and the substrate becomes more solvophobic. The local compressibility provides a more pronounced indicator of solvophobicity than the density depletion in the vicinity of the surface which increases only weakly with increasing contact angle. When the fluid is confined in a parallel slit with two identical solvophobic walls, or with competing solvophobic and solvophilic walls, chi(z) close to the solvophobic wall is altered little from that at the single substrate. We connect our results with simulation studies of water near to hydrophobic surfaces exploring the relationship between chi(z) and fluctuations in the local density and between chi_ex and the mean-square fluctuation in the number of adsorbed molecules.Comment: 23 pages, 9 figures, submitted to Journal of Physics: Condensed Matter as a Special Issue Articl

Interactions of Applied Hormones in the Germination of Lepidium Virginicum Seeds

Author Institution: Department of Botany, The Ohio State UniversityTests of the germination response of light sensitive Lepidium virginicum seeds to applied gibberellic acid confirmed earlier reports that gibberellic acid can substitute for red light. Further tests indicated that promotion of germination by either red light or gibberellic acid can be nullified by abscisic acid. Dark incubation of the seeds in kinetin alone resulted in only slight promotion of germination. Combinations of suboptimal gibberellic acid plus kinetin did not enhance germination to a level greater than that for kinetin alone. Optimal concentrations of gibberellic acid plus kinetin can reverse inhibition of certain abscisic acid concentrations. A comparison of these responses with those of Grand Rapids variety of lettuce seed was made

First Canadian Breeding Record of the Dovekie (Alle alle)

The Dovekie (Alle alle) is the smallest and one of the most abundant alcids inhabiting the North Atlantic Ocean (Salomonsen, 1950; Brown et al., 1975; Roby et al., 1981). Until now there have been no documented breeding records of the Dovekie in the Canadian Arctic, though they are known to gather by the millions in northwest Baffin Bay during spring migration to breeding colonies in Northwest Greenland (Renaud et al., 1982). The Dovekie is well known to the Inuit of Baffin Island; it is called akpaliapik, in contradistinction to its larger relative, the akpa or Thick-billed Murre (uria lomvia). In August 1983, during a bowhead whale (Balaena mysticetus) study on the east coast of Baffin Island, Apak Qaqqasiq mentioned that Dovekies nested in at least two locations in Home Bay. With him and Josepi Tigullaraq, N.W.T. Wildlife Officer from Clyde, we visited one of these colonies by boat on 20 August. The colony was located on a small island (1 km long) called Abbajalik in Inuktitut (unnamed on maps), in northern Home Bay (69 02 N, 67 23 W) about 800 km south of the closest known Dovekie nesting locations in Northwest Greenland. ... The Dovekie colony appeared to be vacated and we were about to leave when Qaqqasiq detected a faint call from the moraine. After carefully moving a few boulders, we found two Dovekie eggs, and nearby an adult Dovekie. ..

Soil-Bentonite Slurry Trench Cutoff Wall Proposal

This is the proposal to the National Science Foundation for a soil-bentonite slurry trench cutoff wall. The proposal includes a project summary, description of the project, and the resources implemented on the project

Operation and Performance of a Shock Tube with Heated Driver

A shock tube was constructed with a driver section which could be heated with "Calrod" heaters to temperatures of approximately 300°C. This temperature rise increased the shock wave Mach number by about 40 per cent, or from values of 7.7 to 10 for pressure ratios of 2O,000 across the diaphragm. This increase is sufficient to produce partial dissociation of the oxygen molecules behind the shock wave. The flow behind the shock wave was as uniform as that produced by an unheated driver. A transition section was designed to enable the major portion of the low pressure chamber to be constructed of round Shelby tubing, while the test section still had a flat top and a flat bottom. The flat surfaces are advantageous for optical studies and for convenience in instrumenting the tube. Despite the fact that the transition was gradual, disturbances were present in the flow in the test section, 18 inches downstream of the transition section

National Science Foundation Soil-Bentonite cutoff Wall Award Abstract

This award abstract describes the purpose of constructing a soil-bentonite cutoff wall as well as the tests that were performed to analyze the performance of the wall