Dissecting amygdala cell types in fear and extinction

The mammalian brain consists of billions of neurons; Individual neurons serve as building blocks (Cajal 1911, translation Swanson and Swanson 1995). However, studying individual neurons is simply insufficient to understand how the brain works. A promising approach is the cell-type-specific approach, an effort to classify neurons that perform the same function as a single cell type (functional definition, see (Luo et al., 2008)) and to understand their roles in information processing and behavioral outputs. Nevertheless, the limitation of this definition is that we barely know the precise functions or roles of neurons, and even in very well-characterized neurons such as retinal ganglion cells, there would likely be remaining unknown functions. Thus, as an operational definition to drive neuroscience forward, defining cell types using genetic tools that allow us to access specific subsets of neurons was suggested and widely accepted in an almost implicit manner. This consensus is based on an optimistic view that, at some point, the operational genetic definition and the ultimate functional definition would converge. In this thesis, having this philosophy in mind, I try to match several operationally defined amygdala cell types with their distinct functions/roles in the context of fear and extinction learning. In Project 1, I demonstrate that a cell-type in the amygdala complex defined by molecular marker expression exerts essential functions in fear and extinction by composing a unique mutual inhibition circuit motif. In Project 2, I find that a cell-type in the basolateral amygdala defined by di-synaptic downstream target show unprecedented functional specificity in fear learning. Finally, in Project 3, I aim to characterize functions and roles of cell types in the basolateral amygdala defined by dynamic, neuronal activity-dependent gene expression upon learning. Collectively, this thesis serves as an important stepping stone to achieving the convergence between definitions of a cell type

Moisture conditions in external timber cladding : field trials and their design implications

This thesis describes the development of technical guidance on timber facade design. The study involved a state-of-the-art review; an exposure trial of external cladding made from Sitka spruce (Picea sitchensis) and the production of construction details and associated information. It was undertaken because timber is an increasingly common cladding material in the UK, being used on low-rise residential buildings and for medium-rise and non-domestic buildings. The risks have, therefore, increased but this is not reflected in published guidance. Sitka spruce was used due to its availability in the UK and its similarity to Norway spruce (P. abies) which is widely used for cladding in Scandinavia. The exposure trial indicated that the moisture content range in timber facades is wider than accepted. The minimum moisture content of around 10% appears to be similar for all types of timber cladding and all species. The maximum appears to vary between species according to their fibre saturation point and is influenced by construction detailing and workmanship. A preliminary model of these interactions is proposed. From a theoretical standpoint, the moisture conditions observed in the trial mean that the (commonly quoted) mean moisture content is all but irrelevant. The mode is a more representative statistic as in most cases the data are skewed towards the fibre saturation point for the species concerned. Most detailing combinations had a moisture content near to the fibre saturation point throughout the winter. Sitka spruce is, therefore, only suitable as external cladding in the UK if preservative treated. Around 40 construction details were produced. They integrate, for the first time, all of the performance requirements applicable to low- and medium-rise timber facades in the UK. The work's key benefit is that the guidance arising from this study rationalises and improves facade design. Further research is, however, needed to validate the moisture content model and extend it to other timber species.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Moisture conditions in external timber cladding: field trials and their design implications

This thesis describes the development of technical guidance on timber facade design. The study involved a state-of-the-art review; an exposure trial of external cladding made from Sitka spruce (Picea sitchensis) and the production of construction details and associated information. It was undertaken because timber is an increasingly common cladding material in the UK, being used on low-rise residential buildings and for medium-rise and non-domestic buildings. The risks have, therefore, increased but this is not reflected in published guidance. Sitka spruce was used due to its availability in the UK and its similarity to Norway spruce (P. abies) which is widely used for cladding in Scandinavia. The exposure trial indicated that the moisture content range in timber facades is wider than accepted. The minimum moisture content of around 10% appears to be similar for all types of timber cladding and all species. The maximum appears to vary between species according to their fibre saturation point and is influenced by construction detailing and workmanship. A preliminary model of these interactions is proposed.From a theoretical standpoint, the moisture conditions observed in the trial mean that the (commonly quoted) mean moisture content is all but irrelevant. The mode is a more representative statistic as in most cases the data are skewed towards the fibre saturation point for the species concerned. Most detailing combinations had a moisture content near to the fibre saturation point throughout the winter. Sitka spruce is, therefore, only suitable as external cladding in the UK if preservative treated.Around 40 construction details were produced. They integrate, for the first time, all of the performance requirements applicable to low- and medium-rise timber facades in the UK. The work’s key benefit is that the guidance arising from this study rationalises and improves facade design. Further research is, however, needed to validate the moisture content model and extend it to other timber species