Spatial distribution of manganese in enamel and coronal dentine of human primary teeth

Emerging evidence indicates that excessive exposure to manganese (Mn) during the prenatal period and early childhood may result in neurodevelopmental deficits. However, accurate exposure biomarkers are not well established, limiting our understanding of exposure-response relationships over these susceptible periods of development. Naturally shed deciduous teeth are potentially a useful biomarker of environmental exposure to Mn. However, the uptake and distribution of Mn in human teeth has not been studied in detail.Mn distribution was measured at high resolution (~ 20 μm) in eight human primary teeth using laser ablation-inductively coupled plasma-mass spectrometry. A bio-imaging methodology was applied to construct detailed elemental maps of three incisors, and bone meal (NIST SRM 1486) was used to validate the analyses.The distribution of Mn in enamel and coronal dentine showed a distinct and reproducible pattern. In enamel, the ⁵⁵Mn:⁴³Ca ratio was highest at the outer edge of enamel (range = 0.57 to 4.74) for approximately 20-40 μm but was substantially lower in deeper layers (range = 0.005 to 0.013). The highest levels of Mn were observed in dentine immediately adjacent the pulpal margin (⁵⁵Mn:⁴³Ca range = 2.27 to 6.95). Importantly, a clearly demarcated high Mn zone was observed in dentine at the incisal end of the teeth. Using confocal laser scanning microscopy to visualize the neonatal line, this region was identified as being in the prenatally formed dentine.The high-resolution map of the spatial distribution of Mn in human primary teeth highlighted specific reproducible patterns of Mn distribution in enamel and coronal dentine.     

ADSORPTION OF ASPHALTS AND THEIR SIZE EXCLUSION CHROMATOGRAPHY FRACTIONS ON AGGREGATE SURFACES

The adsorption behavior of two asphalts and their size exclusion chromatography (SEC) fractions from toluene solution onto aggregate was investigated. The effect of the differences in chemistry and molecular size of the asphalt samples on their adsorption behavior on silica, granite and greywacke was determined. The adsorption of asphalts and SEC fractions on SI-1000 silica was well-represented by the Toth model, while the Radke-Prausnitz model better described their adsorption behavior on both granite and greywacke. Combining the adsorption models with the Gibbs adsorption equation of state gave the spreading pressure of each adsorbate species adsorbed on the aggregate surfaces. The spreading pressure predicted the competitive adsorptive edge of the asphalt fractions. The SEC I fractions, containing molecules of larger molecular size and higher heteroatom contents, showed higher spreading pressures than the SEC II fractions, which contained molecules of smaller molecular size and fewer heteroatoms. The asphalts yielded intermediate spreading pressures for SI-1000 silica and granite, but they gave the highest spreading pressure values for greywacke.     

Magnetic separations in biotechnology—a review

Magnetic separation technology has a broad range of potential applications in both small and large scale biotechnology. This review considers a selection of magnetic techniques and their possible uses.     

Maximal sub-triangulation in pre-processing phylogenetic data

In order to help infer an evolutionary tree (phylogeny) from experimental data, we propose a new method for pre-processing the corresponding dissimilarity matrix, which is related to the property that the distance matrix of a phylogeny (called an additive matrix) describes a sandwich family of chordal graphs. As experimental data often yield distance values which are known to be under-estimated, we address the issue of correcting the data by increasing the distances which are incorrect. This is done by computing, for each graph of the sandwich family, a maximal chordal subgraph.     

Mathematical Modeling of Encapsulated Buffer Performance in Sand Columns

A one-dimensional mathematical model was developed to simulate pH control using an encapsulated phosphate buffer during denitrification in a sand column. The parameters required for the model were obtained from direct physical measurement, from a tracer study to characterize the dispersion coefficient in the column, and from batch experiments designed to obtain an empirical expression describing the variation of the first-order rate constant for the encapsulated buffer core release with pH. First-order kinetic constants describing the rates of denitrification and ethanol biodegradation were obtained by fitting the model to column runs without the encapsulated buffer. With these parameters, the model was subsequently used to predict the performance of column runs containing the encapsulated buffer. Since denitrification was essentially complete in the sand columns, an increase in the effluent pH was observed. This pH increase was counteracted by the controlled release of the acidic core of the encapsulated buffers added in the columns. The model reasonably predicted the release of the encapsulated buffer core and the performance of the encapsulated buffer for controlling pH in the column.     

Gender-Typed Play and Amniotic Testosterone.

Sex differences in play are apparent in a number of mammalian species, including humans. Prenatal testosterone may contribute to these differences. The authors report the first attempt to correlate gender-typed play in a normative sample of humans with measurements of amniotic testosterone (aT). Testosterone was measured in the amniotic fluid of 53 children (31 boys and 22 girls). A strong sex difference was observed in aT and, at ages 4.75 to 5.8 years, on a modified version of the Child Game Participation Questionnaire. Hierarchical regression analyses on the entire group and within-sex correlations suggested that variations in aT did not contribute to individual differences in game participation as reported by the mother. A critique of explanations for this finding is presented. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Seeking medical care for a breast cancer symptom: Determinants of intentions to engage in prompt or delay behavior.

Examined the cognitive structures underlying women's intentions to seek medical care for a breast cancer symptom. 134 women imagined that they had discovered a change in their breast and chose between 2 alternatives based on I. Ajzen and M. Fishbein's (1980) theory of reasoned action: immediately calling the doctor (prompt behavior) or monitoring the breast change on one's own (delay behavior). Results show that intentions to delay were positively associated with favorable attitudes toward delay (FATDs) and with perceived social pressure to delay. The attitudinal factor was more influential than the social factor in determining intentions. Underlying FATDs were beliefs that delay would result in maintaining control and avoiding disruption, without negative health outcomes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)