Single- and dual-porosity modelling of flow in reclaimed mine soil cores with embedded lignitic fragments

Lignitic mine soils represent a typical two-scale dual-porosity medium consisting of a technogenic mixture of overburden sediments that include lignitic components as dust and as porous fragments embedded within a mostly coarse-textured matrix. Flow and transport processes in such soils are not sufficiently understood to predict the course of soil reclamation or of mine drainage. The objective of this contribution is to identify the most appropriate conceptual model for describing small-scale heterogeneity effects on flow on the basis of the physical structure of the system. Multistep flow experiments on soil cores are analyzed using either mobile–immobile or mobile–mobile type 1D dual-porosity models, and a 3D numerical model that considers a local-scale distribution of fragments. Simulations are compared with time series' of upward infiltration and matric potential heads measured at two depths using miniature tensiometers. The 3D and the 1D dual-permeability models yielded comparable results as long as pressure heads are in local equilibrium; however, could describe either the upward infiltration or the matric potential curves but not both at the same time. The mobile–immobile type dual-porosity model failed to describe the data. A simultaneous match with pressure heads and upward infiltration data could only be obtained with the 1D dual-permeability model (i.e., mobile–mobile) by assuming an additional restriction of the inter-domain water transfer. These results indicate that for unsaturated flow conditions at higher matric potential heads (i.e., here >− 40 hPa), water in a restricted part of the fragment domain must be more mobile as compared to water in the sandy matrix domain. Closer inspections of the pore system and first neutron radiographic imaging support the hypothesis that a more continuous pore region exists at these pressure heads in the vicinity of the lignitic fragments possibly formed by fragment contacts and a lignitic dust interface-region between the two domains. The results suggest that the small-scale structure is too complex as to be represented by weighted contributions of individual components alone.     

Mutations and the conformational stability of globular proteins

The elucidation of the three-dimensional structure of now over 100 proteins provides the basis for describing the nature of interactions stabilizing native protein structure. To understand the forces responsible for maintaining the native structure, it is necessary to analyze the contributions of the specific forces like a hydrogen bond, a salt bridge or a hydrophobic interaction to the overall stability of a protein. Using mutant proteins carrying a single amino acid substitution, specific interactions in a protein can be altered and the effect can be studied. In this paper the results of such studies on stability variants of human haemoglobin and of T4 phage lysozyme are described.     

Reproductive Stages Limiting Productivity of the Endangered Attwater's Prairie Chicken

An important concern of conservation biologists is determining what conditions most limit the number of individuals in endangered populations. Because time is a constraint, narrowing the search for such factors is beneficial. Toward this end we used broad spatial and temporal data, to test the hypothesis that reproductive success (as measured by juvenile-to-adult ratios) of the endangered Attwater's Prairie Chicken ( Tympanuchus cupido attwateri ) was not equal to that of the nonendangered Greater Prairie Chicken ( T. c. pinnatus ). We then tested the hypotheses that mean clutch size, egg hatchability, nesting success, and number of chicks per brood prior to brood breakup for Attwater's Prairie Chicken were not equal to those of the Greater Prairie Chicken. We found that the mean ratio of juveniles to adults among Attwater's Prairie Chicken was less than that of the Greater Prairie Chicken ( p < 0.011), as would be predicted if reproductive success controls proportional changes in prairie-grouse numbers among years. Mean nesting success (32.2%) and number of chicks per brood prior to brood breakup (4.2) of Attwater's Prairie Chicken were both less than those of the Greater Prairie Chicken (49.5 %, p = 0.0425, and 6.0 p = 0.0001, respectively). We suggest that researchers focus on determining what proportion of Attwater's Prairie Chicken broods survive and why Attwater's Prairie Chicken nesting and brood-rearing success are so poor relative to those of the Greater Prairie Chicken.     

Cooling water use patterns at US nonutility electric generating facilities

Cooling water is used by many industrial facilities. The largest user of cooling water is the electric power industry, although other significant users include the pulp and paper, chemical, iron and steel, aluminum, and petroleum refining industries. The US Environmental Protection Agency (EPA) is currently developing regulations to implement section 316(b) of the Clean Water Act, which deals with cooling water intake structures. The EPA will examine cooling water use patterns at various industries. Data pertaining to cooling water use patterns at utility plants are readily available; however, no information has been assembled for cooling water use at electric power generating facilities owned or operated by entities other than utilities (nonutilities). This paper presents data concerning cooling water use from two subsets of the nonutility sector and focuses on plants using once-through cooling systems. The first subset includes 123 nonutility plants that each generate at least 150 MW of power. Collectively, they represent 41,494 MW of generating capacity, or about 56% of the total nonutility generating capacity. Approximately 17% of the installations within that subset utilize once-through cooling water. The second subset includes 58 waste-to-energy facilities, which individually produce less than 80 MW but collectively generate about 2200 MW. Only 11% of this subset of plants uses once-through cooling water. The total 15,372 MW generated by once-through nonutilities is equivalent to only 6% of the 258,906 MW generated by utilities utilizing once-through cooling. From a national perspective this share may appear relatively insignificant. However, in some states, the nonutility once-through total is equivalent to a more significant percentage of the utility once-through total.     

Molecular structures and associations of humic substances in the terrestrial environment

Here we show, for the first time, evidence of the primary molecular structures in humic substances (HS), the most abundant naturally occurring organic molecules on Earth, and their associations as mixtures in terrestrial systems. Multi-dimensional nuclear magnetic resonance (NMR) experiments show us that the major molecular structural components in the mixtures operationally defined as HS are aliphatic acids, ethers, esters and alcohols; aromatic lignin derived fragments; polysaccharides and polypeptides. By means of diffusion ordered spectroscopy, distinct diffusion coefficients consistent with relatively low molecular weight molecules were observed for all the components in the mixtures, and saccharides were the largest single class of component present. Liquid chromatography NMR confirmed that HS components can be easily separated and nuclear Overhauser effect (NOE) enhancements support the finding that the components are of relatively low molecular weight <~2,000 Da. The widely recognized properties of HS, i.e., characteristics indicative of crosslinked, macromolecular networks, can now be explained as aggregation of mixtures, most likely instigated by complexation with metal cations.