The Effects of Isolation and Acid Mine Drainage on Fish and Macroinvertebrate Communities of Monday Creek, Ohio, USA

Isolated headwater streams in mined watersheds may have good water quality and fish habitat, yet be disconnected from immigration sources by stream segments impaired by acid mine drainage (AMD). Studies of fish and macroinvertebrate communities, habitat, and a number of hydrochemical parameters in Monday Creek, Ohio, show that AMD eliminates fish communities and severely limits macroinvertebrate communities in directly affected tributaries. Isolated headwaters in the heavily mined Monday Creek watershed have relatively good water quality and habitat, but poor fish communities. Comparison of isolated Monday Creek headwaters with non-isolated reaches in unmined watersheds indicates that differences in fish communities are attributable to isolation. Fish communities in isolated headwaters have lower Indices of Biotic Integrity (IBI) than comparable non-isolated communities, reduced species numbers, and lower numbers of individuals, despite suitable habitat as measured by the Qualitative Habitat Evaluation Index (QHEI). Comparison of macroinvertebrate communities shows higher Invertebrate Community Indices (ICI), and no apparent species loss, which can be attributed to the obligate flight stage in the life cycle of many macroinvertebrates, which enables them to overcome aquatic barriers. The implication of this research is that there is an opportunity for recovery of depleted fish communities in large AMD-isolated areas with good water quality, suitable habitat, and intact macroinvertebrate communities, by downstream treatment or source control of AMD to create aquatic corridors for fish immigration.     

Interfacial tension of polyethylene/polyethylene terephthalate with various compatibilizing agents

The effect of 12 different potential compatibilizing agents on the interfacial tension of polyethylene (PE) and polyethylene terephthalate (PET) is described. A wide range of compatibilizing agents based upon ethylene and a second comonomer were devised and used. They were divided into three categories. The first category (I) includes block polymers. The second category (II) includes random copolymers. The third category (III) includes reactive copolymers that should form graft copolymers during mixing with PET. The addition of various potential compatibilizing agents to the PE/PET binary system results in lowered interfacial tension. The efficiency of the different compatibilizing agents in reducing the interfacial tension is discussed. © 1996 John Wiley & Sons, Inc.     

Investigation of a Unique Commonality from a Wide Range of Natural Materials as Viewed from the Maillard Reaction Perspective

Based on the characteristics of a wide range of natural products, a more comprehensive understanding of the role of the Maillard reaction has been developed which describes a molecular basis for the production of a common set of flavourful, volatile aromatic compounds from the reactions between amino acids and sugars at elevated temperature (pressure cooking). By employing a variety of natural products, a clearer knowledge of the common mechanisms for the production of many important flavourants and odourants has been established. Regardless of the starting natural product the same qualitative profile of volatile materials is produced upon ‘pressure cooking’ an aqueous extract of the natural product. The notable differences in aroma arise not from significant differences in the qualitative nature of the materials but from variations in the quantitative distribution of the volatile materials produced.     

Influence of Monoglycerides of Different Chain Lengths on Texture and Flavor of Breads Made with Waxy Cornstarch

The addition of monoglycerides (MGs) monolaurin (ML), monomyristin (MM), monopalmitin (MP), and monostearin (MS)) to a model system bread made from waxy cornstarch was studied for their effects on delaying staling. The model system breads containing 0.5% of a MG and a control bread containing no MG were prepared five different times and stored at room temperature for 1, 3, and 6 days. A sensory panel measured changes in firmness, stale flavor, and moistness, and an Instron universal testing machine (model 1122) was used to indicate firmness of the samples. The volumes of the loaves were measured on day 1 for the five replications. Results indicated that the addition of MGs to the model system breads decreased firmness and stale flavor and increased moistness compared with the control bread. Breads containing MM and MP were rated significantly (p<0.05) less firm and less stale on days 1 and 6 and more moist on day 1 than the breads containing MS and the control bread. In general, as the molecular weight (MW) of the MGs increased, the firmness (by Instron) of the breads also increased, and the volume of the loaves decreased. The control bread had the highest Instron firmness value and the lowest volume when compared with the breads containing MGs.     

Variation of lipid and tocopherol composition in three strains of channel catfish (Ictalurus punctatus)

Three strains of channel catfish (Ictalurus punctatus), which were designated as ‘AQUA’, ‘LSU’ and ‘MSU’, were examined for their lipid and tocopherol composition to delineate if genetic strains exhibited the potential to vary in their susceptibility to lipid oxidation. Since age, diet and environmental conditions were similar for all strains, growth and compositional differences were ascribed to genetic factors. Significant differences were noted between strains in their muscle tissue for triacylglycerol (TG) levels, fatty acid composition, and tocopherol levels. The largest quantity of TG was found in the LSU strain whereas the smallest quantity was found in the AQUA strain. Levels of polyunsaturated fatty acids (PUFA) in the TG and total lipid (TL) fraction were highest in the AQUA strain and lowest in the MSU strain. Similarly, a peroxidizability index, which took into account the differences in susceptibility of unsaturated fatty acids to oxidize, was highest in AQUA and lowest in MSU for the TG and TL fractions. The peroxidizability index for the phospholipid fraction did not vary between strains. Adopting a relative antioxidant effectiveness value of 0.31 for γ-tocopherol, the LSU, MSU and AQUA catfish strains were calculated to contain 37.72, 22.79 and 42.49 nmol of α-tocopherol equivalents, respectively. The MSU catfish strain exhibited the highest ratio (nmol PUFA/nmol α-tocopherol equivalents) suggesting that its tissue would be the least stable to oxidation.     

Microbiological survey of tofu sold in a rural Illinois county.

The purpose of this study was to determine the microbial status of tofu sold in a rural Illinois county and assess the factors contributing to the safety of tofu. Six brands of tofu from eight different stores (60 total samples) were purchased and analyzed for temperature, pH, total aerobic bacteria, and the presence of coliforms. Relationships between age, temperature, pH of tofu, and total aerobic bacteria were tested. An analysis of variance was also performed to test for differences in total bacterial counts among the brands. Mean aerobic bacterial counts ranged from 0 to 7.76 x 10(7) CFU/g. Fifty-five percent of the tofu tested fell within the excellent range for freshness as delineated by the standards developed by the Soyfoods Association of North America, 6.7% fell within the acceptable range, 6.7% within the marginal range, and 28% within the unacceptable range. Sixteen percent of the samples contained coliform bacteria. No significant correlation was found between variables, except pH with total aerobic bacterial counts (r = -0.51) and pH with eosin-methylene blue agar counts (r = -0.67). Most of the tofu was displayed at unsafe temperatures (>5 degrees C) for potentially hazardous foods. This study confirmed the concerns regarding safety of tofu sold in the grocery stores. Based on these results, special training on tofu storage and handling is recommended for grocery stores selling this food product.     

Residual stress distribution modification caused by weathering in polypropylene and polystyrene

A study has been made of changes in residual stress distributions caused by weathering in polypropylene and polystyrene. Chemi-crystallization has a major effect in polypropylene and an analysis based on the volumetric changes that occur on crystallization has been developed. Close to the surface, fractional crystallinity changes up to 4% are caused by photodegradation (X-ray measurements by Rabello and White (18)). It is estimated that this would cause a tensile residual stress of ～2MNm^?2 to form at the surface if there were no preexisting residual stresses; in the case examined here, the effect of this shrinkage stress was to reduce the compressive residual stress to a small value (<1MNm^?2). Additional changes caused by stress relaxation prior to completion of chemi-crystallization resulted in net tensile stresses near to the surface of the photo-degraded polypropylene. The changes occur almost symmetrically in polypropylene even if the molding is exposed on one surface only. A similar analysis has been made for thermoplastics in which the changes occur only at the exposed surface, comparing the results with measurements made on a glass fiber reinforced grade of polypropylene. In this case the analysis predicts that the stress changes by 2–3MNm^?2 near the surface, enough to develop tensile stresses up to 2MNm^?2 there if the compressive residual stress at the beginning is fairly small, in fairly good agreement with observed changes. Glass fiber reinforced polypropylene does not relax as readily as unfilled polypropylene and better agreement is to be expected without any allowance for stress relaxation. The analysis for one-sided chemi-crystallization allows calculation of the resulting distortion in terms of the curvature: this was estimated at 0.33m^?1, compared to the measured value of 0.44 m^?1. Volumetric changes also occur in noncrystalline polymers and a similar analysis based on data obtained with polystyrene (17) confirms that these changes can explain the observed development of tensile residual stresses on weathering. In the example studied here surface stress changes of 2–3MNm^?2 are predicted and this accounts for a large proportion of the change in residual stress obtained by direct measurement.