In this study, generalized predictive models were developed to estimate KOA of four kinds of aromatic pollutants based on the calculated solvation free energy and taking the dimer effect into... Show moreIn this study, generalized predictive models were developed to estimate KOA of four kinds of aromatic pollutants based on the calculated solvation free energy and taking the dimer effect into account. Uncorrected log KOA values, which were directly estimated from the calculated solvation free energy of individual molecules, underestimated experimental values, and the deviation increased with increasing log KOA. Dimers were found to greatly affect the apparent KOA values of these aromatic pollutants, which were driven by π-π interactions. London dispersion and exchange-repulsion terms were identified to be dominant components of the underlying π-π interactions. It is interesting to find that the π-π interactions of polybrominated diphenyl ethers correlate with not only the molecular polarizability but also the size of opposing aromatic surfaces, which leads to a different trend of π-π interactions from other aromatic pollutants. A universal quantitative structure-activity relationship model was developed to estimate the proportion of dimers based on five molecular structural descriptors relevant to the π-π interactions. After calibration with the dimer effect, estimations of log KOA were consistent with experimental values. Therefore, the dimer effect should be taken into consideration when investigating the partition behavior of aromatic pollutants, and the solvation free energy model could be an alternative method for the prediction of KOA. Show less
Studies investigating different food processing techniques have shed light on the dietary habits and subsistence strategies adopted by prehistoric populations. They have shown that grinding cereals... Show moreStudies investigating different food processing techniques have shed light on the dietary habits and subsistence strategies adopted by prehistoric populations. They have shown that grinding cereals into flour has taken place since the Palaeolithic period, yet the grinding method employed has often not been investigated. The analysis presented here identified different types of use-wear traces associated with the dry-grinding and wet-grinding of cereals, which can be used to infer prehistoric grinding techniques. Applying this reference baseline to Jiahu, an early Neolithic site known for the earliest findings of domesticated rice in the central plain of China, reveals that dry-grinding rather than wet-grinding was employed for cereal (including rice) processing 9000 years ago. This grinding method could have been inherited from the earlier hunter-gatherers, but could also result from a broad-spectrum subsistence strategy adopted at Jiahu. By comparing the properties and ethnographic uses of different plant species, it is also suggested that cereals such as rice were a more sensible choice for the dry-grinding process. Show less
he site of Jiahu in the central plain of China is known for its early rice cultivation 9000 years ago. The preliminary starch analysis implies that the Jiahu grinding tools were used for processing... Show morehe site of Jiahu in the central plain of China is known for its early rice cultivation 9000 years ago. The preliminary starch analysis implies that the Jiahu grinding tools were used for processing various plants, including rice. This paper presents the use-wear analysis carried out on a sample of seventeen grinding tools from Jiahu, nine of which were previously analyzed for the presence of starch. Use-wear traces associated with processing cereal and wood-like material were identified. This result confirms important evidence of cereal processing in the early Neolithic period. It also reveals the diversity of functions in the grinding tool assemblage. Furthermore, the use-wear distribution indicates that grinding slabs without feet and cylindrical rollers were mainly associated with the processing of cereals while grinding slabs with feet were mainly related to the processing of wood-like material. Quantitative analysis of the starch data also indicates that grinding slabs without feet possess more starch grains than the grinding slabs with feet. Therefore, it is argued that specific types of grinding tools were used for processing specific kinds of material. This study highlights the different roles grinding tools may have played in early farming societies. Show less
