Lithic scatters and landscape: the Mesolithic, Neolithic and Early Bronze Age inhabitation of the lower Exe valley, Devon

This thesis examines the inhabitation of the lower Exe valley, between the Mesolithic and the Early Bronze Age through the evidence of a series of surface lithic scatters. Research draws on recent confident approaches to surface lithic scatters which view them as key data for understanding the inhabitation of prehistoric landscapes. Theoretically it draws on the dwelling perspective and proposes that both the contents of lithic scatters (the stone tools and debitage of which they are composed), and their contexts (the locations in which they are found) are inseparable parts of the same whole, and are implicated in the processes through which prehistoric populations came to understood and create their worlds. Research focuses on a small study area centred on the lower Exe valley, Devon. It is one of the most significant prehistoric landscapes in lowland southwest Britain and includes a large surface lithic collection spanning the Mesolithic to the Early Bronze Age. It also contains evidence for a number of contemporary monuments. Several methodologies are applied to the contents and contexts of the study area’s lithic assemblages. Methodologies utilised include lithic analysis, landscape phenomenology, LIDAR and vertical aerial photography, extensive geophysical survey and targeted excavation. Four themes are explored in relation to the study area’s archaeological record: • The character and composition of inhabitation • The temporality of inhabitation • Biographies of place • Scales of mobility and contact Results indicate the valley floor and its immediate western edge as a particular focus of activity during all periods. Against the background of increasing intensity and extent of inhabitation between the Mesolithic and Early Bronze Age, the repeated occupation of persistent places is noted. Repeated occupation of these locales is seen as key to the development of biographies of place which in turn act as anchors for subsequent acts of inhabitation and monument building. This thesis combines the analysis and interpretation of previously unpublished surface lithic assemblages, with the results of new archaeological fieldwork. At a regional level it has enhanced understanding of the prehistory of lowland Devon. In a wider context it offers a new theoretical and methodological approach to studying surface lithic scatters, and contributes to on going debates in landscape archaeology

Lithic scatters and landscape : the Mesolithic, Neolithic and Early Bronze Age inhabitation of the lower Exe valley, Devon

This thesis examines the inhabitation of the lower Exe valley, between the Mesolithic and the Early Bronze Age through the evidence of a series of surface lithic scatters. Research draws on recent confident approaches to surface lithic scatters which view them as key data for understanding the inhabitation of prehistoric landscapes. Theoretically it draws on the dwelling perspective and proposes that both the contents of lithic scatters (the stone tools and debitage of which they are composed), and their contexts (the locations in which they are found) are inseparable parts of the same whole, and are implicated in the processes through which prehistoric populations came to understood and create their worlds. Research focuses on a small study area centred on the lower Exe valley, Devon. It is one of the most significant prehistoric landscapes in lowland southwest Britain and includes a large surface lithic collection spanning the Mesolithic to the Early Bronze Age. It also contains evidence for a number of contemporary monuments. Several methodologies are applied to the contents and contexts of the study area’s lithic assemblages. Methodologies utilised include lithic analysis, landscape phenomenology, LIDAR and vertical aerial photography, extensive geophysical survey and targeted excavation. Four themes are explored in relation to the study area’s archaeological record: • The character and composition of inhabitation • The temporality of inhabitation • Biographies of place • Scales of mobility and contact Results indicate the valley floor and its immediate western edge as a particular focus of activity during all periods. Against the background of increasing intensity and extent of inhabitation between the Mesolithic and Early Bronze Age, the repeated occupation of persistent places is noted. Repeated occupation of these locales is seen as key to the development of biographies of place which in turn act as anchors for subsequent acts of inhabitation and monument building. This thesis combines the analysis and interpretation of previously unpublished surface lithic assemblages, with the results of new archaeological fieldwork. At a regional level it has enhanced understanding of the prehistory of lowland Devon. In a wider context it offers a new theoretical and methodological approach to studying surface lithic scatters, and contributes to on going debates in landscape archaeology.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

The temporal evolution of the tracer signal in the Deep Western Boundary Current, Tropical Atlantic

Four World Ocean Circulation Experiment (WOCE) repeat cruises (October 1990 to March 1994) in the tropical Atlantic off Brazil are used to study the spatial and temporal evolution of the chlorofluorocarbon (CFC) (components CFC-11 and CFC-12) and tritium signal in the upper North Atlantic Deep Water (NADW). Its shallowest part, located in the tropical Atlantic around 1600-m depth, is the shallow upper North Atlantic Deep Water (SUNADW). It is characterized by a distinct tracer maximum, which is presumably received through winter time convection in the subpolar North Atlantic. Here we discuss the tracer fields and the temporal evolution of the tracer signal of the SUNADW in the tropical Atlantic along two meridional sections at 44 degrees and 35 degrees W and two zonal sections at 5 degrees and 10 degrees S off Brazil. The spatial and temporal development of the tracer field in the tropical Atlantic as well as the correlation with hydrographic parameters show that the temporal tracer change being due to the arrival of "younger" water is disturbed by other processes. In particular, the impact of variable mixing and spreading pathways on the observed tracer variability in the SUNADW is evident in the observations

Network Structure Implied by Initial Axon Outgrowth in Rodent Cortex: Empirical Measurement and Models

The developmental mechanisms by which the network organization of the adult cortex is established are incompletely understood. Here we report on empirical data on the development of connections in hamster isocortex and use these data to parameterize a network model of early cortical connectivity. Using anterograde tracers at a series of postnatal ages, we investigate the growth of connections in the early cortical sheet and systematically map initial axon extension from sites in anterior (motor), middle (somatosensory) and posterior (visual) cortex. As a general rule, developing axons extend from all sites to cover relatively large portions of the cortical field that include multiple cortical areas. From all sites, outgrowth is anisotropic, covering a greater distance along the medial/lateral axis than along the anterior/posterior axis. These observations are summarized as 2-dimensional probability distributions of axon terminal sites over the cortical sheet. Our network model consists of nodes, representing parcels of cortex, embedded in 2-dimensional space. Network nodes are connected via directed edges, representing axons, drawn according to the empirically derived anisotropic probability distribution. The networks generated are described by a number of graph theoretic measurements including graph efficiency, node betweenness centrality and average shortest path length. To determine if connectional anisotropy helps reduce the total volume occupied by axons, we define and measure a simple metric for the extra volume required by axons crossing. We investigate the impact of different levels of anisotropy on network structure and volume. The empirically observed level of anisotropy suggests a good trade-off between volume reduction and maintenance of both network efficiency and robustness. Future work will test the model's predictions for connectivity in larger cortices to gain insight into how the regulation of axonal outgrowth may have evolved to achieve efficient and economical connectivity in larger brains

Temporal-Difference Reinforcement Learning with Distributed Representations

Temporal-difference (TD) algorithms have been proposed as models of reinforcement learning (RL). We examine two issues of distributed representation in these TD algorithms: distributed representations of belief and distributed discounting factors. Distributed representation of belief allows the believed state of the world to distribute across sets of equivalent states. Distributed exponential discounting factors produce hyperbolic discounting in the behavior of the agent itself. We examine these issues in the context of a TD RL model in which state-belief is distributed over a set of exponentially-discounting “micro-Agents”, each of which has a separate discounting factor (γ). Each µAgent maintains an independent hypothesis about the state of the world, and a separate value-estimate of taking actions within that hypothesized state. The overall agent thus instantiates a flexible representation of an evolving world-state. As with other TD models, the value-error (δ) signal within the model matches dopamine signals recorded from animals in standard conditioning reward-paradigms. The distributed representation of belief provides an explanation for the decrease in dopamine at the conditioned stimulus seen in overtrained animals, for the differences between trace and delay conditioning, and for transient bursts of dopamine seen at movement initiation. Because each µAgent also includes its own exponential discounting factor, the overall agent shows hyperbolic discounting, consistent with behavioral experiments

Analysis of Area-Specific Expression Patterns of RORbeta, ER81 and Nurr1 mRNAs in Rat Neocortex by Double In Situ Hybridization and Cortical Box Method

BACKGROUND: The mammalian neocortex is subdivided into many areas, each of which exhibits distinctive lamina architecture. To investigate such area differences in detail, we chose three genes for comparative analyses, namely, RORbeta, ER81 and Nurr1, mRNAs of which have been reported to be mainly expressed in layers 4, 5 and 6, respectively. To analyze their qualitative and quantitative coexpression profiles in the rat neocortex, we used double in situ hybridization (ISH) histochemistry and cortical box method which we previously developed to integrate the data of different staining and individuals in a standard three-dimensional space. PRINCIPAL FINDINGS: Our new approach resulted in three main observations. First, the three genes showed unique area distribution patterns that are mostly complementary to one another. The patterns revealed by cortical box method matched well with the cytoarchitectonic areas defined by Nissl staining. Second, at single cell level, RORbeta and ER81 mRNAs were coexpressed in a subpopulation of layer 5 neurons, whereas Nurr1 and ER81 mRNAs were not colocalized. Third, principal component analysis showed that the order of hierarchical processing in the cortex correlates well with the expression profiles of these three genes. Based on this analysis, the dysgranular zone (DZ) in the somatosensory area was considered to exhibit a profile of a higher order area, which is consistent with previous proposal. CONCLUSIONS/SIGNIFICANCE: The tight relationship between the expression of the three layer specific genes and functional areas were revealed, demonstrating the usefulness of cortical box method in the study on the cerebral cortex. In particular, it allowed us to perform statistical evaluation and pattern matching, which would become important in interpreting the ever-increasing data of gene expression in the cortex

Comparative and Joint Analysis of Two Metagenomic Datasets from a Biogas Fermenter Obtained by 454-Pyrosequencing

Biogas production from renewable resources is attracting increased attention as an alternative energy source due to the limited availability of traditional fossil fuels. Many countries are promoting the use of alternative energy sources for sustainable energy production. In this study, a metagenome from a production-scale biogas fermenter was analysed employing Roche's GS FLX Titanium technology and compared to a previous dataset obtained from the same community DNA sample that was sequenced on the GS FLX platform. Taxonomic profiling based on 16S rRNA-specific sequences and an Environmental Gene Tag (EGT) analysis employing CARMA demonstrated that both approaches benefit from the longer read lengths obtained on the Titanium platform. Results confirmed Clostridia as the most prevalent taxonomic class, whereas species of the order Methanomicrobiales are dominant among methanogenic Archaea. However, the analyses also identified additional taxa that were missed by the previous study, including members of the genera Streptococcus, Acetivibrio, Garciella, Tissierella, and Gelria, which might also play a role in the fermentation process leading to the formation of methane. Taking advantage of the CARMA feature to correlate taxonomic information of sequences with their assigned functions, it appeared that Firmicutes, followed by Bacteroidetes and Proteobacteria, dominate within the functional context of polysaccharide degradation whereas Methanomicrobiales represent the most abundant taxonomic group responsible for methane production. Clostridia is the most important class involved in the reductive CoA pathway (Wood-Ljungdahl pathway) that is characteristic for acetogenesis. Based on binning of 16S rRNA-specific sequences allocated to the dominant genus Methanoculleus, it could be shown that this genus is represented by several different species. Phylogenetic analysis of these sequences placed them in close proximity to the hydrogenotrophic methanogen Methanoculleus bourgensis. While rarefaction analyses still indicate incomplete coverage, examination of the GS FLX Titanium dataset resulted in the identification of additional genera and functional elements, providing a far more complete coverage of the community involved in anaerobic fermentative pathways leading to methane formation

Subcellular Location of PKA Controls Striatal Plasticity: Stochastic Simulations in Spiny Dendrites

Dopamine release in the striatum has been implicated in various forms of reward dependent learning. Dopamine leads to production of cAMP and activation of protein kinase A (PKA), which are involved in striatal synaptic plasticity and learning. PKA and its protein targets are not diffusely located throughout the neuron, but are confined to various subcellular compartments by anchoring molecules such as A-Kinase Anchoring Proteins (AKAPs). Experiments have shown that blocking the interaction of PKA with AKAPs disrupts its subcellular location and prevents LTP in the hippocampus and striatum; however, these experiments have not revealed whether the critical function of anchoring is to locate PKA near the cAMP that activates it or near its targets, such as AMPA receptors located in the post-synaptic density. We have developed a large scale stochastic reaction-diffusion model of signaling pathways in a medium spiny projection neuron dendrite with spines, based on published biochemical measurements, to investigate this question and to evaluate whether dopamine signaling exhibits spatial specificity post-synaptically. The model was stimulated with dopamine pulses mimicking those recorded in response to reward. Simulations show that PKA colocalization with adenylate cyclase, either in the spine head or in the dendrite, leads to greater phosphorylation of DARPP-32 Thr34 and AMPA receptor GluA1 Ser845 than when PKA is anchored away from adenylate cyclase. Simulations further demonstrate that though cAMP exhibits a strong spatial gradient, diffusible DARPP-32 facilitates the spread of PKA activity, suggesting that additional inactivation mechanisms are required to produce spatial specificity of PKA activity

Archeox: The Archaeology of East Oxford Project: Place Names Index Page

This is an index page for all Archeox Project placenames research data This is an index page for all Archeox Project placenames research dat