Re-examination of a proposed model for nonisothermal crystallization kinetics

This communication is a theoretical re-examination of the model proposed by Choe and Lee for the nonisothermal crystallization kinetics of semicrystalline polymers.     

Complex esters as antiwear agents

Diol centered complex esters using diethylene glycol, 1,3-butane diol, neopentyl glycol, polyethylene glycol (molecular weight 200–1000), 1-phenoxy 2,3 propane diol as centered diols and sebacic acid as dibasic acid with outer monohydric alcohols as 2-ethyl hexanol, 1-benzyloxy propanol-2 and methyl digol were prepared and assessed as antiwear agents in aviation turbine fuels, diesel fuels and light mineral oil. These types of complex esters, in general, were found to be effective antiwear agents.     

Detection of composite edges

The paper presents a new parametric model-based approach to high-precision composite edge detection using orthogonal Zernike moment-based operators. It deals with two types of composite edges: (a) generalized step and (b) pulse/staircase edges. A 2-D generalized step edge is modeled in terms of five parameters: two gradients on two sides of the edge, the distance from the center of the candidate pixel, the orientation of the edge and the step size at the location of the edge. A 2-D pulse/staircase edge is modeled in terms of two steps located at two positions within the mask, and the edge orientation. A pulse edge is formed if the steps are of opposite polarities whereas a staircase edge results from two steps having the same polarity. Two complex and two real Zernike moment-based masks are designed to determine parameters of both the 2-D edge models. For a given edge model, estimated parameter values at a point are used to detect the presence or absence of that type of edge. Extensive noise analysis is performed to demonstrate the robustness of the proposed operators. Experimental results with intensity and range images are included to demonstrate the efficacy of the proposed edge detection technique as well as to compare its performance with the geometric moment-based step edge detection technique and Canny's (1986) edge detector.     

Decrease in net mercury methylation rates following iron amendment to anoxic wetland sediment slurries

The rate of mercury methylation in anoxic wetland sediments is affected by the concentration of bioavailable complexes between Hg and sulfide. Previous research with pure bacterial cultures has shown that addition of ferrous iron reduces the net rate of mercury methylation by decreasing the concentration of dissolved sulfide. To assess the possibility of using this approach to decrease net mercury methylation in restored and constructed wetlands, laboratory experiments were conducted by adding Hg(II) and Fe(II) to sediments collected from six sites in five estuarine wetlands. Addition of 30 mM (0.07 mmol g(-1) or 3.9 mg g(-1)) Fe(II) decreased net mercury methylation relative to that of unamended controls by a factor of 2.1-6.6. In all cases, the observed decrease in net mercury methylation was accompanied by a decrease in the concentrations of sulfide and filterable mercury in the water overlying the sediments. When iron was added to one of the sediment samples at doses that were small relative to the concentration of sulfide present, net mercury methylation either increased slightly or was unaffected. Comparison of the results to speciation model predictions suggests that dissolved reduced sulfur-containing species play a role in the formation of uncharged, bioavailable Hg complexes. Although further research is needed to determine the long-term effect of iron amendment, these results suggest that iron addition decreases mercury methylation in authentic wetland sediments.     

Acoustic behavior of calcium soap solutions

The results of ultrasonic velocity for calcium soap solutions show that the adiabatic compressibility, intermolecular free length and solvation number decrease while the specific acoustic impedence, apparent molal compressibility, apparent molal volume and molar sound velocity increase with increasing soap concentration. The ultrasonic results are in agreement with the conductance measurements and confirm that calcium soaps behave as weak electrolytes in solutions.