Features of the normal choriocapillaris with OCT-angiography: Density estimation and textural properties

The main objective of our work is to perform an in depth analysis of the structural features of normal choriocapillaris imaged with OCT Angiography. Specifically, we provide an optimal radius for a circular Region of Interest (ROI) to obtain a stable estimate of the subfoveal choriocapillaris density and characterize its textural properties using Markov Random Fields. On each binarized image of the choriocapillaris OCT Angiography we performed simulated measurements of the subfoveal choriocapillaris densities with circular Regions of Interest (ROIs) of different radii and with small random displacements from the center of the Foveal Avascular Zone (FAZ). We then calculated the variability of the density measure with different ROI radii. We then characterized the textural features of choriocapillaris binary images by estimating the parameters of an Ising model. For each image we calculated the Optimal Radius (OR) as the minimum ROI radius required to obtain a standard deviation in the simulation below 0.01. The density measured with the individual OR was 0.52 ± 0.07 (mean ± STD). Similar density values (0.51 ± 0.07) were obtained using a fixed ROI radius of 450 μm. The Ising model yielded two parameter estimates (β = 0.34 ± 0.03; γ = 0.003 ± 0.012; mean ± STD), characterizing pixel clustering and white pixel density respectively. Using the estimated parameters to synthetize new random textures via simulation we obtained a good reproduction of the original choriocapillaris structural features and density. In conclusion, we developed an extensive characterization of the normal subfoveal choriocapillaris that might be used for flow analysis and applied to the investigation pathological alterations

Entrepreneurial experience and opportunity identification : the role of intuition and cognitive versatility

The issue of “why, when and how” some people, but not others, discover opportunities is central to our understanding of entrepreneurship. Although there is a growing body of research in this area, opportunity identification remains an ongoing phenomenon of interest as many questions remain unanswered. One important question concerns the effects of experience on opportunity identification. Research suggests that entrepreneurs become more adept at identifying opportunities as they gain experience, but the cognitive processes underlying this relationship remain unclear. This study explores this gap in the literature by addressing the following research question: To what extent can the relationship between entrepreneurial experience and opportunity identification be explained by cognitive strategy? Guided by sound theoretical principles (Cognitive-Experiential Self- Theory) and by a critical review of the scholarly literature, this study argued first, that intuition is a key process that links experience to an enhanced ability for opportunity identification, and second that intuition is most effective when used together with analysis in a versatile cognitive strategy – an approach characterised by high levels of both intuition and analysis, and an ability to switch between them as needed. Building on these arguments, this study develops and tests a model in which intuition and cognitive versatility are hypothesised to mediate the relationship between experience and opportunity identification. Seventy-four technology-entrepreneurs completed a think-aloud protocol analysis exercise in which they generated potential business ideas for three innovative technologies. In addition, they completed an online survey that was designed to control for factors which may influence intuition, cognitive versatility and/or opportunity identification, namely cognitive style, risk perception, risk propensity, and entrepreneurial experience. The model was tested by integrating the survey data with the coded and quantified protocol data in a series of regression and mediation analyses. Consistent with prior research, this study found that experienced entrepreneurs are more proficient than novices at identifying opportunities. Extending previous research, this study shows that intuition and cognitive versatility mediate the relationship between experience and opportunity identification. Not only do experienced entrepreneurs use their intuition to help them identify potentially lucrative opportunities, they also employ a process of analysis to complement their intuition and to ensure that this intuition is not leading them astray. Overall, these results suggest that scholars need to consider cognitive versatility, rather than simply looking at intuition or analysis in isolation, and to think about how this can be shaped to benefit opportunity identification

Offal and beef demand in Indonesia and Australia's trade prospects (a case study of Makassar City)

Understanding meat demand and its characteristics are important in giving a more accurate evaluation of the factors that govern consumers’ willingness to pay for meat products, and in understanding the relationship and responsiveness between variables. Demand for meat, including beef and beef offal is continuously increasing in Indonesia, and studies in meat demand have been conducted extensively. However, most of those studies did not consider offal products. This study focuses only on the consumption of offal and beef, considering that domestic production has not met the domestic demand. In addition, some problems still appear as the beef self-sufficiency program has not yielded the maximum desired results. This study has five main purposes. Firstly, it provides up to date information about the determinants of social-demographic factors for offal and beef expenditures with probit model analysis. Secondly, it estimates the demand elasticities for offal and beef (local and imported) by using the linear approximate of almost ideal demand system (LA/AIDS) model with the inclusion of Inverse Mill Ratio (IMR). Thirdly, this study estimates the potential impact of socioeconomic and demographic factors, product attributes (quality and affordability) and market factor (availability) on the willingness to pay (WTP) for imported offal with the hedonic price model approach. Fourthly, this study examines the actual WTP for imported offal and calculates the marginal implicit price (marginal willingness to pay) by using the hedonic price model approach. Finally, this study explores Australia’s trade prospects for imported offal in Indonesia based on the LA/AIDS, WTP and descriptive analyses. Research findings show that several important factors such as age, income, ethnicity, occupation, family size and level of education significantly affect the expenditure for local and imported offal, and local and imported beef. Offal and beef are classified as necessity goods in Makassar, and consumers rely heavily on offal and beef products. This result is supported by the positive expenditure elasticity of the study, where consumer income increases the demand for local and imported offal and beef. The WTP analysis reveals that if the price of imported offal on the market increases, the willingness to pay for the product will decrease. Therefore, the availability of the products in the market should be a large focus of the Indonesian Government, including local and international firms. Maintaining the sustainability of meat products in the country, including with efficient trade policies of imported offal and beef is crucial. Australia as a major exporter of live cattle and beef products in Indonesia could gain more insight from this perspective. The research contributes to the literature of the demand and practice studies, especially in assisting producers, marketers and policy makers in developing effective supply, including the market share of offal and beef in Makassar City. The results of this study will have important implications and better understanding of beef and offal industries in Indonesia

The Economics of Tobacco Production and Feasible Alternatives in Uganda

Tobacco control policies are credited with contributing to the well-being of society. But for tobacco producers, such polices can present pitfalls, especially in rural contexts where households are dependent on tobacco leaf production. This study focuses on the adjustment strategies open to tobacco-growing households particularly on Article 17 of the FCTC which is a strategic policy guideline that supports economically viable alternatives to the production of tobacco. The central hypothesis of the study is the consideration of farm household decision-making structures as requisites to FCTC supply policies. The study uses the agricultural household framework to examine tobacco supply and relative farm efficiency. This framework is applied to a farm survey dataset collected from the West Nile sub-region of Uganda. The study used a probability sampling method to sample households. A sampling frame was provided by the district agricultural offices from the study area. The study developed a bivariate model to examine economic and noneconomic incentives to tobacco supply. Relative farm efficiencies are examined with data envelopment analysis. A Tobit model is further used to estimate farm inefficiency among tobacco and other farm households. The findings demonstrate that there is a clear variation in profitability between tobacco farms and other farms, with alternative farms posting better farm profits. There is considerable evidence in the data that tobacco farmers are capable of responding to staple food and cash crop prices, production value, and other non-economic incentives, as implicitly expected by economic theory. The tobacco output supply is strongly associated with economic incentives such as an export or cash crop price as opposed to a staple food price. This could be that with a cash crop price, tobacco farmers are able to produce at a point where marginal cost is equal to marginal revenue. Efficiency results reveal that subsistence food crops do not offer a viable alternative to tobacco in West Nile, Uganda. A crop such as coffee can have some potential as a specialised cash crop in West Nile, but none of the grains or pulses do when grown as mono-crops. A balanced mixed of grains and pulses, that includes some coffee, can vii certainly compete with tobacco in West Nile. Vertically integrated farmers are at the mercy of powerful buyers/processors who are generally very prescriptive about quantities while at the same time controlling prices so that farmers have very little room to manoeuvre. Overall, it is important to note that both tobacco leaf and alternative farms are too small, and therefore experience increasing returns to scale. Tobacco-specialised farms are overcapitalised and suffer from inefficient management practices. Relying on agricultural support is beneficial to farm efficiency. Three policy implications are considered. A realistic price strategy in a comprehensive package of government action is required to ensure a sound agricultural base for the development of alternative farming. This would also include a crop diversification strategy to support a broad spectrum of alternative crops. A package of these changes would work well with an improvement in agricultural support, and for this reason the government of Uganda needs to develop an agricultural support framework. The thesis contributes to the empirical, field research and some methodology towards Article 17, and to research on the economics of tobacco production and alternative livelihoods

The Spatial and Temporal Ecology of Seed Dispersal by Gorillas in Lopé National Park, Gabon: Linking Patterns of Disperser Behavior and Recruitment in an Afrotropical Forest

Western lowland gorillas: Gorilla g. gorilla) consume large quantities of fruit and disperse a great number of seeds. The majority these seeds are dispersed intact and viable in the dung. Dung is often deposited around the rim of a night nest or at a nest-site. Gorillas often construct nests in areas that have a sparse canopy, flattening the ground vegetation. These locations can be beneficial to the growth and survival of the seed species they disperse. Thus, not only are gorillas effective in terms of depositing seeds great distances from parent plants, away from the highest seed rain densities, they are also effective in directing seeds to potentially beneficial microsites. The objective of this research was to develop an understanding of the spatial and temporal patterns in fruit availability, seed deposition, and adult plants, and to test whether these patterns relate to the ecology of seed dispersal by gorillas. Results suggest that gorilla foraging and nesting behavior in particular, impose both spatial and temporal limitations to the distribution of dispersed seeds. In addition, temporal variation in the gorilla diet and factors that affect defecation rates and locations promote variation in the combinations: composition and abundance) of the seed species dispersed to different microsites. The clustered distribution of nest-sites leads to clumped and spatially restricted seed deposition patterns. Recruitment in gorilla-dispersed seed species corresponds with the aggregated: clumped) distribution of nest-sites. Gorillas have a long-lasting effect on the spatial structure and floristic composition of the forests they inhabit, particularly in large-seeded species

Spatial pattern modeling and discovery in biological images

Studying spatial arrangement and relationships in full tissue samples can improve our understanding of the various developmental/pathological processes that underlie proper organ or organism function. In particular, it has been found that neuronal or vascular structures are pervasive in many tissues, and oftentimes are spatially correlated with other cells. This work aims to discover those relationships, by extracting biological knowledge from cellular and sub-cellular imaging using spatial point process methods.In this dissertation, we present discoveries on spatial distributions and attributes of dendritic spines and retinal astrocytes, two crucial elements in the mammalian nervous system. Although little is known about the spatial distributions of either respective to their surroundings and attributes, this thesis attempts to pose some possible biological hypotheses based on strong statistical evidence, as well as further extend the tools used for spatial analysis. In particular, we develop a multitype version of the linear network K-function, a summary function used for measuring clustering or repulsion of point features existing on a linear network

Handbook of Mathematical Geosciences

This Open Access handbook published at the IAMG's 50th anniversary, presents a compilation of invited path-breaking research contributions by award-winning geoscientists who have been instrumental in shaping the IAMG. It contains 45 chapters that are categorized broadly into five parts (i) theory, (ii) general applications, (iii) exploration and resource estimation, (iv) reviews, and (v) reminiscences covering related topics like mathematical geosciences, mathematical morphology, geostatistics, fractals and multifractals, spatial statistics, multipoint geostatistics, compositional data analysis, informatics, geocomputation, numerical methods, and chaos theory in the geosciences

Untangling hotel industry’s inefficiency: An SFA approach applied to a renowned Portuguese hotel chain

The present paper explores the technical efficiency of four hotels from Teixeira Duarte Group - a renowned Portuguese hotel chain. An efficiency ranking is established from these four hotel units located in Portugal using Stochastic Frontier Analysis. This methodology allows to discriminate between measurement error and systematic inefficiencies in the estimation process enabling to investigate the main inefficiency causes. Several suggestions concerning efficiency improvement are undertaken for each hotel studied.info:eu-repo/semantics/publishedVersio