Effect of the polyurethane crystalline interphase formed at an Al surface on water‐vapor absorption

Water‐vapor absorption of polyurethane/Al bonds was studied, and the weight gain of samples after water‐vapor exposure was measured to examine the effect of the polyurethane crystalline interphase formed at the Al surface on water‐vapor absorption. Water‐vapor absorption was found to be independent of the crosslink density of the polyurethanes. Instead, it was found that the microstructural characteristics of the spherulitic interphase, a mixture of crystallites and amorphous material formed on the Al surface, strongly affects water‐vapor absorption: As the area fraction and the size of spherulites for the films increases, the amount of absorbed water vapor initially increases rapidly and then remained constant. The water vapor absorbed and condensed at spherulite boundaries consisting of voids and defects was created due to volume contraction during polymer crystallization.© 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1417–1422, 2003     

A combined single crystal X-ray diffraction and electron diffraction study of the T2phase in Al-Li-Cu alloys

Both single crystal X-ray diffraction techniques and convergent beam electron diffraction have been employed to examine the structure of theT ₂ (Al₆CuLi₃) phase in three particular Al-Li-Cu alloys. It is shown thatT ₂ displays icosahedral symmetry both in a high purity laboratory melt and in two impure alloys which had been processed industrially. Possible reasons for the five-fold symmetry ofT ₂ are discussed.     

An automatic liver segmentation algorithm based on grow cut and level sets

Organ segmentation is often a first step in medical diagnostic. In this paper a fully automatic three-dimensional method for liver segmentation is presented. It is based on voxel density analysis with use of automated grow cut method. Obtained segmentation is then refined by active contours model.     

Exploratory Analysis of the Effects of Particulate Characteristics on the Variation in Partitioning of Nonpolar Organic Contaminants to Marine Sediments

The partitioning of nonpolar organic contaminants to marine sediments is considered to be controlled by the amount of organic carbon present. However, several studies propose that other characteristics of sediments may affect the partitioning of contaminants. For this exploratory analysis, we measured 19 sediment characteristics from five marine sediments and 11 characteristics of humic acids extracted from the sediments. These characteristics included elemental composition, grain size, soot carbon, polarity indices and molar ratios. Each individual characteristic and combinations of these characteristics were then used to normalize partition coefficients (K_p) generated for three organic contaminants: lindane, fluoranthene and a tetrachlorinated biphenyl (PCB). A coefficient of variation (CV) was then calculated for each contaminant to determine which normalization characteristic (individually or in combination) resulted in the lowest variability in partitioning between study sediments. For lindane and the PCB, normalization by the amount of sediment organic carbon resulted in the lowest variability in partition coefficients with CVs of 16.2% and 37.7%, respectively. However, normalization of fluoranthene by silt content resulted in lower CVs than those generated by organic carbon normalization: 31.0% vs. 37.6%. Normalization of contaminants K_p's by combined values of sediment characteristics resulted in lower CVs but only by a few percent. Using humic acid characteristics, humic organic carbon reduced variability between sediments most effectively. But only the normalized fluoranthene values had a CV (i.e., 25.4%) lower than the one based on normalization by sediment characteristics. When combined, humic acid characteristics resulted in lower CVs than normalization by individual or combinations of sediment characteristics for fluoranthene and the PCB with CVs of 19.3% and 28.7%, respectively. This analysis indicates variability associated with the partitioning of some organic contaminants to marine sediments can be further reduced when normalization by sediment characteristics other than organic carbon are utilized.     

Determination of Young's Modulus in Chemically Vapor-Deposited SiC Coatings

Young's modulus of CVD and SiC coatings was measured in situ (on the substrate) using strain gage/flexure and dynamic resonance techniques. The average Young's moduli of CVD SiC from these techniques were 446 and 415 Gpa, respectively, and were considered to be in good agreement. The determination of a representative coating thickness and cross section is critical in order to accurately estimate Young's modulus of coatings.     

Genetic algorithm application in image segmentation

In consideration of living organisms’ ability to endure for years, and their ability to adapt to surrounding environment, the mechanism of evolution is the inspiration for creating a new genetic algorithm. The goal of this paper is to examine possibilities of genetic algorithm application for segmentation of digital image data, implementation of this algorithm, and to create tools for its testing. The next goal is to examine possible choices of algorithm’s parameters, and to compare quality of the results with other segmentation methods within various image data.     

Calculation and evaluation of the gibbs energies of formation of Cr3C2, Cr7C3, and Cr23C6

A thermodynamic analysis of chemical composition data for a series of iron alloys containing chromium and carbon has been completed. These data were obtained from literature compilations for alloys equilibrated for extended times at 700 °C under neutral atmospheres. The results of this analysis, when supplemented with thermochemical data from the literature, permitted the calculation of the standard Gibbs energies of formation for the chromium carbides Cr₇C₃ and Cr₂₃C₆ over the range 600 to 1000 °C. These standard Gibbs energies were compared to data for these carbides from other sources. Available Gibbs energy data for the third pure chromium carbide, Cr₃C₂, were also evaluated. For each of these three compounds, a separation of the values for the Gibbs energy of formation into two distinct groups was observed. Each of these groups can be classed according to the nature of the experimental study used, whether it be a high temperature solid-gas equilibration involving a system of a carbide-chromic oxide-carbon (or chromium) with carbon monoxide, on one hand, or a series of investigations concerned mainly with electrolytic cell measurements, plus the work on which the present study is based. It is suggested that the differences in the Gibbs energies of formation for the respective carbides are associated with 1) the nonstoichiometric nature of these carbides and 2) possible dissolution of oxygen in the carbides during the equilibration studies.     

A transpubic approach for reconstructive surgery of genitourinary injuries and congenital malformations

Four children were operated on by the transpubic approach for injury to the vagina or urethra and to correct malformations within the pelvis minor. One boy had posttraumatic stricture of the urethra, and a girl presented with disruption of the urethra and vagina. One of two boys who had congenital malformations was treated for epispadias and incontinence; the other for a large urethral diverticulum caused by anal atresia. Total reconstruction was achieved, and no complications of symphysis restoration were observed.