Transfer of mercury and methylmercury along macroinvertebrate food chains in a floodplain lake of the Beni River, Bolivian Amazonia

We have evaluated the mercury and methylmercury transfers to and within the macroinvertebrate communities of a floodplain lake of the Beni River basin, Bolivia, during three hydrological seasons and in two habitats (open water and vegetation belt). Using the stable isotopes δ¹³C and δ¹⁵N, six trophic chains were identified during a previous study. Four are based on only one source: seston, organic matter from the bottom sediment, periphyton and macrophytes. Two are based on mixed sources (seston and periphyton in one case, periphyton and macrophytes in the other). During sampling, we found only one taxon that had surface sediment organic matter as food source and very few taxa whose trophic source was constituted by macrophytes. The periphyton was the most important source during all seasons; it produced the longest chain, with three trophic positions. Whatever the season and trophic source, all collected macroinvertebrates contained methyl mercury and the latter was biomagnified in all trophic chains that we identified. The biomagnification of methylmercury through invertebrate trophic chains accurately reflected the existence and length of these chains. Biomagnification was virtually non-existent in the sediment-based chain, low and restricted to the dry season in the macrophyte-based chain. It was significant in the seston-based chain, but limited by the existence of only two trophic levels and restricted to the wet season. Finally, it was very effective in the periphyton-based chain, which offers the highest rate of contamination of the source but, above all, the largest number of trophic levels.     

Identification of the genetic variants of κ-casein in milk by isoelectric focusing electrophoresis

The genetic variants of κ-casein (κ-CN) A and B were analysed in milk from Holstein–Friesian (HF) and Jersey cows by means of isoelectric focusing (IEF) electrophoresis. Milk samples were obtained in triplicate from pure-breed HF and Jersey cows (three of each) to estimate the protein content, casein and purify κ-CN. The protein and casein contents in the milk from both breeds were statistically different ( P <  0.05). The κ-CN A migrates first with an isoelectric point (pI) of 7.2–7.3 and then B with a pI of 7.5–7.7. Differences in the expression proportion of both variants were detected.     

Adulthood functioning: the joint effects of parental alcoholism, gender and childhood socio-economic stress

The popular literature has publicized the adjustment difficulties of adult children of an alcohol-dependent parent (ACOAs); however, empirical studies do not provide consistent support. We examined the impact of parental alcoholism, degree of childhood socio-economic stress and gender on three broad categories of adulthood functioning (psychopathology, socio-economic attainment and marital stability). These effects were investigated with a heterogeneous sample of 400 men and 226 women participating in studies at the University of Michigan Alcohol Research Center. Parental alcoholism and childhood socio-economic stress exerted significant independent effects on most adulthood functioning measures. Men and women differed substantially only on socio-economic attainment measures, and effects of parental alcoholism and childhood economic stress on men and women were generally similar. For marital stability, parental alcoholism and childhood socio-economic stress interacted. These results suggest that researchers who study the impact of family history for alcoholism on psychological functioning should consider other aspects of the family of origin that promote wellbeing. In addition, results of this study point to the need for more research on gender differences, protective factors that promote good adjustment and outcome measures reflecting general life adaptation.     

Knowledge-based spatiotemporal linear abstraction

We present a theoretical framework and a case study for reusing the same conceptual and computational methodology for both temporal abstraction and linear (unidimensional) space abstraction, in a domain (evaluation of traffic-control actions) significantly different from the one (clinical medicine) in which the method was originally used. The method, known asknowledge-based temporal abstraction, abstracts high-level concepts and patterns from time-stamped raw data using a formal theory of domain-specific temporal-abstraction knowledge. We applied this method, originally used to interpret time-oriented clinical data, to the domain of traffic control, in which the monitoring task requires linear pattern matching along both space and time. First we reused the method for creation of unidimensional spatial abstractions over highways, given sensor measurements along each highway measured at the same time point. Second, we reused the method to create temporal abstractions of the traffic behaviour, for the same space segments, but during consecutive time points. We defined the corresponding temporal-abstraction and spatial-abstraction domain-specific knowledge. Our results suggest that (1) the knowledge-base temporal-abstraction method is reusable over time and unidimensional space as well as over significantly different domains; (2) the method can be generalised into a knowledge-based linear-abstraction method, which solves tasks requiring abstraction of data along any linear distance measure; and (3) a spatiotemporal-abstraction method can be assembled, from two copies of the generalised method and a spatial-decomposition mechanism, and is applicable to tasks requiring abstraction of time-oriented data into meaningful spatiotemporal patterns over a linear, decomposable space, such as traffic over a set of highways.     

Characterisation of the casein fraction of Ibérico cheese by electrophoretic techniques

The physicochemical characteristics of Ibérico cheese, a semi‐hard Spanish variety manufactured from mixtures of cow's, ewe's and goat's milk, were studied. The casein fraction and breakdown products of 6‐month‐old cheeses were characterised by various electrophoretic techniques: urea polyacrylamide gel electrophoresis (urea‐PAGE) at alkaline pH, isoelectric focusing (IEF) and two‐dimensional polyacrylamide gel electrophoresis (2DE). Proteins were separated in 2DE according to their charge/mass ratio by urea‐PAGE at alkaline pH in the first dimension and according to their isoelectric point by IEF in the second dimension. Some individual bands considered homogeneous by urea‐PAGE at alkaline pH (ie different grades of phosphorylation of α_s1‐casein and α_s2‐casein) or by IEF (ie overlapping of several bands of α_s2‐casein with γ‐casein bands) were found to be complex mixtures of casein components by 2DE. The two‐dimensional electrophoretic pattern was characteristic of the milk of each animal species included in Ibérico cheese. Capillary electrophoresis (CE) was also used to study the Ibérico cheeses. The high resolution of this technique allowed the identification of the main caseins of the different species (ie para‐κ‐casein, β‐casein, γ₂‐casein and γ₃‐casein). © 2002 Society of Chemical Industry     

Bayesian and regularization methods for hyperparameter estimationin image restoration

In this paper, we propose the application of the hierarchical Bayesian paradigm to the image restoration problem. We derive expressions for the iterative evaluation of the two hyperparameters applying the evidence and maximum a posteriori (MAP) analysis within the hierarchical Bayesian paradigm. We show analytically that the analysis provided by the evidence approach is more realistic and appropriate than the MAP approach for the image restoration problem. We furthermore study the relationship between the evidence and an iterative approach resulting from the set theoretic regularization approach for estimating the two hyperparameters, or their ratio, defined as the regularization parameter. Finally the proposed algorithms are tested experimentally.     

Analytical I–E response for several multistep potential techniques applied to an electrocatalytic process at mediator modified electrodes

General analytical and explicit equations for the transient and stationary I–E responses of electrocatalytic process of soluble solution species at mediator modified electrodes, valid for any reversibility degree of the charge transfer and for any multipotential pulse technique, are presented. These expressions have been applied to staircase voltammetry (SCV) and linear sweep voltammetry (LSV), and also to their corresponding differential and derivative modalities. The value of the chemical rate constant can be easily obtained from a cathodic plateau of the SCV curves under transient and stationary conditions. Easy methods for determining other characteristic parameters of the process are proposed. The theoretical predictions have been experimentally tested.     

Guanidinium-based potentiometric SO2 gas sensor

An SO2 gas sensor was developed by using a hydrogen sulfite-selective electrode positioned behind a gas-permeable membrane (GPM). The hydrogen sulfite-selective electrode was prepared by incorporating a multicyclic guanidinium ionophore in a plasticized poly(vinyl chloride) membrane. This gas sensor presents important advantages over the conventional Severinghaus-type SO2 gas sensor that contains a pH electrode immersed in an internal solution behind the GPM. The Severinghaus gas sensor suffers interferences from weak acids that can cross the GPM as gases and change the pH of the internal solution. In contrast, in the proposed sensor, the excellent selectivity of the HSO3- electrode and the ability of the GPM to discriminate gaseous from nongaseous species combine to generate the most selective potentiometric SO2 gas sensor reported to date.