Measuring the Price Volatility of Certain Field Crops in South Africa using the ARCH/GARCH Approach

The conditional volatility in the daily spot prices of the crops traded on the South African Futures Exchange (yellow maize, white maize, wheat, sunflower seed and soybeans) is determined. The volatility in the prices of white maize, yellow maize and sunflower seed have been found to vary over time, suggesting the use of the GARCH approach in these cases. Using the GARCH approach, the conditional standard deviation is the measure of volatility, and distinguishes between the predictable and unpredictable elements in the price process. This leaves only the stochastic component and is hence a more accurate measure of the actual risk associated with the price of the crop. The volatility in the prices of wheat and soybeans was found to be constant over time; hence the standard error of the ARIMA process was used as the measure of volatility in the prices of these two crops. When comparing the medians of the conditional standard deviations in the prices of white maize, yellow maize and sunflower seed to the constant volatilities of wheat and soybeans, the price of white maize was found to be the most volatile, followed by yellow maize, sunflower seed, soybeans, and wheat respectively. These results suggest that the more risk-averse farmers will more likely produce wheat, sunflower seed and to a lesser extent soybeans, while maize producers are expected to utilise forward pricing methods, especially put options, at a high level to manage the higher volatility.Price volatility, field crops, SAFEX, time series analysis, ARCH/GARCH, Demand and Price Analysis,

The effects of immersion and navigation on the acquisition of spatial knowledge of abstract data networks

AbstractWith increasing frequency immersive virtual environments (IVEs) are being used to present multi-dimensional information visualizations. Networks and graphs are a common type of abstract data; in order to understand the varied relationships between entities in a network, it is crucial to acquire some spatial knowledge about the layout and connectivity of its components. While there is a good body of evidence for the benefits of IVE displays, most work on the effects of immersion and of navigation on the acquisition of spatial knowledge has been concerned with wayfinding in realistic environments; much less is known about how to leverage IVE technology to benefit a user’ss spatial understanding of (abstract) data networks. In this paper we present an empirical study designed to determine what effect level of immersion and navigation technique can have on a user’s acquisition of spatial knowledge of network data, specifically cell signaling pathways. For this CAVE study (CAVE Automatic Virtual Environment), the level of immersion is controlled by changing the Field-Of-Regard, while we also vary navigation between one egocentric and one exocentric technique. The results show that both immersion and navigation technique can affect the acquisition of spatial knowledge regarding abstract networks in an immersive virtual environment

Handbook for the analysis of micro-particles in archaeological samples

Horizon 2020(H2020)677576Bioarchaeolog

An initial key of starch grains from edible plants of the Eastern Mediterranean for use in identifying archaeological starches

Among archaeological micro-remains, starches can be used as a tool for reconstructing past environments, diets, and trade patterns through the identification of the plants collected and consumed by ancient populations. Starch grains preserved in dental calculus and on stone tools have been recovered from archaeological material from sites around the world. However, the ability to identify archaeological starch grains relies on having a broad (i.e., many taxa) and deep (i.e., many individuals from the same taxon) reference collection from modern plants. Only a small handful of such reference collections have been published, and thus far none have been created for taxa from the Eastern Mediterranean. This region is rich in plants that have been used for their starch-rich seeds and roots since prehistory, and many of the wild taxa are the progenitors of domesticated species that were cultivated in the Neolithic and remain economically important today. To help document the history of human interactions with these plant taxa, we present here a reference collection based on the analysis of 220 individual plant parts (e.g., seeds, tubers) from 188 modern Levantine plant species (both wild and domestic), and three non-native plants that are frequently found as modern contamination. Of the examined plant samples, 110 from 106 taxa (species and subspecies) contained starches. We also provide a key based on this collection to aid in the identification of archaeological starch remains.Horizon 2020(H2020)StG-677576Bioarchaeolog

Investigating biases associated with dietary starch incorporation and retention with an oral biofilm model

Dental calculus has proven to contain a wealth of information on the dietary habits of past populations. These insights have, to a large extent, been obtained by the extraction and identification of starch granules contained within the mineralised dental plaque from a wide range of regions and time periods. The scope of previous studies have been limited to microfossil extraction and identification to reconstruct dietary preferences from the archaeological record, and few studies have attempted to address the biases of starch retention in dental calculus. Those that have considered this problem have been limited to in vivo studies on modern humans and non-human primates. Here, we present a multispecies oral biofilm model, which allows experimental research on starch incorporation and retention to be conducted on in vitro dental calculus in a controlled laboratory setting. The biofilms were exposed to treatment solutions with known quantities of dietary starches (wheat and potato) during the 25 days growth period. After this, the starch granules were extracted from the mature biofilm (by dissolution in EDTA), and counted. We show that the granule counts extracted from the model dental calculus represented a low proportion (ranging from 0.06% to 0.16%) of the total number of granules exposed to the biofilms throughout the experiment. Additionally, we found that the ratios of granule sizes from the extracted starch granules differed from the original treatment solutions, with large granules (>20 μm) consistently being under-represented. We also found a positive correlation between the absolute granule counts and dry-weight of the biofilm (r = 0.659, 90%CI[0.463, 0.794]), meaning the absolute quantity of starch granules will increase as the size of the calculus deposit increases. A similar, but weaker correlation was found between the concentration (count per mg) of granules and dry-weight (r = 0.3, 90%CI[0.0618, 0.506]). Our results complement and reinforce previous in vivo studies suggesting that dental calculus presents a very small, and partly biased picture of the original dietary intake of starches, with an over-representation of plants producing granules smaller than 20 μm in size. The experimental model presented here is well-suited to address the need for further validation of methods and biases associated with dietary research on dental calculus.Horizon 2020(H2020)STG–677576Bioarchaeolog

The cost of gathering among the Baka Forager-Horticulturalists from southeastern Cameroon

What present-day foragers do for their living and what they eat have long been privileged areas for exploring human behavior, global health, and human evolution. While many studies have focused on hunting and meat acquisition, less attention has been given to gathering and plant foods. Despite evidence of variation in both nutritional quality and energetic costs of gathering different plants, the overall effort spent on gathering in relation to other subsistence tasks is still under explored. In the current context of economic, climate, and social changes, many forager societies also rely on other subsistence strategies, including agriculture and wage labor. In this study, we aim to explore the place of gathering in the livelihood of a mixed economy society, the Baka forager-horticulturalists of southeastern Cameroon, by comparing the involvement and the costs of activities related to food acquisition. From a pool of 153 adult participants (97 women and 56 men), we collected 246 daily records using a GPS (Global Positioning System) tracker combined with heart rate monitor and time allocation recalls. We compared the duration, distance traveled, and the intensity of work, measured by calculating the metabolic equivalent of task (MET), of subsistence activities related to food acquisition. Results from this work show that gathering activities, performed by both women and men, are energetically costly, with higher MET values than hunting and fishing activities. Furthermore, the MET values vary depending on the targeted plant foods. We discuss these insights in the overall framework of subsistence patterns, merging them with the socio-cultural and environmental factors that might explain Baka livelihood and subsistence strategy.Horizon 2020(H2020)677576Bioarchaeolog

European Society for the Study of Human Evolution 2017: old sites, new methods

Horizon 2020(H2020)ERC-STG 677576Bioarchaeolog

Charles Townsend Copeland Correspondence

Entries include a typed biography, a typed letter on The Walpole Inn stationery from Copeland\u27s secretary Provost, replying to a letter missing, likely destroyed, from the Maine State Library, a typed letter from Copeland\u27s secretary Felch, and a typed transcript of Copeland\u27s book inscription

The potential of dental calculus as a novel source of biological isotopic data

Stable isotope analysis has become an essential tool in investigations of ancient migration and paleodietary reconstruction. Because the biogeochemistry of bone collagen and apatite is well known, current methods rely almost exclusively on analyses of bones and teeth; however, dental calculus represents a potentially additional biological source of isotopic data from ancient skeletons. Dental calculus is a mineralized bacterial biofilm that forms on the surfaces of teeth. Sampling dental calculus does not damage the dentition and thus can be used in cases where it is not possible to perform destructive analyses of conventional mineralized tissues. Like bone and dentine, dental calculus contains both inorganic and organic components, allowing measurement of C, N, O, H, and Sr isotopes. Additionally, dental calculus forms as serial, non-remodeling laminar accretions on the tooth surface, opening up the possibility of analyzing discrete time points during the lifetime of an individual. However, as a microbial biofilm and not a human tissue, the biochemistry of dental calculus is complex, containing multiple calcium phosphate mineral phases, organic and inorganic food remains, hundreds of human and bacterial proteins, and diverse biomolecules from thousands of endogenous bacterial taxa. Isotopic investigation of dental calculus is still in its infancy, and many questions remain regarding its formation and processes of diagenesis. This chapter (1) reviews the unique advantages presented by dental calculus as a novel source of biological isotopic data, (2) critically evaluates published isotopic studies of dental calculus, and (3) explores the current challenges of dental calculus stable isotope analysis through a case study of an Ancient Puebloan Basketmaker II population from the American Southwest.Bioarchaeolog