Weather Cycles, Production Yields and Georgia's Muscadine

This paper looks at the relationship between weather, crop yield, and market price of muscadines using a dynamic panel data that spans from the 2000 to 2005 and across the state of Georgia. We use a Generalized Methods of Moments technique to estimate the impact of weather on the price of muscadines with the yield per acre as the instrumented variable. The results suggest that there is a relationship between the price and weather for muscadines, which provide important implications for the potential relevance of a weather derivative for muscadine production.muscadines, weather cycles, price, production yields, Georgia, Generalized Method of Moments, Farm Management, Risk and Uncertainty,

Studies of Unexplained Inflammation in Haemodialysis and the Role of Endotoxin

Clinical outcomes for patients with end-stage kidney disease on haemodialysis remain poor and have similar mortality risk to some cancers. A significant proportion of haemodialysis patients have chronic unexplained inflammation – the pathophysiology of this syndrome is unclear but is associated with poor quality of life and survival. A large number of studies have proposed that circulating endotoxin, fragments of gram negative bacterial cell wall, plays a key role in driving chronic inflammation in dialysis patients in the absence of clinical infection. However, interpretation of published literature is difficult for several reasons. Firstly, reports have mainly been cross-sectional in nature. Secondly, various different types of endotoxin detection assays have been used and reported blood endotoxin levels in clinically stable non-infected patients were exceedingly high which is incompatible with the clinical state. Additionally, nearly all studies used endotoxin detection assays that could be also be activated by (1-3)-β-D glucan, a cell wall constituent of cereals, yeast and fungi. This is a particularly important given that materials used to construct some dialyser membranes are known to leach (1-3)-β-D glucan. The doctoral research project had two central hypotheses requiring investigation. Firstly, that endotoxin and other exogenous molecules in the gut including (1-3)-β-D glucan are contributors to unexplained inflammation in patients with chronic kidney disease. Second, that their presence in blood is a result of translocation from the gut due to increased gastrointestinal permeability in the uraemic state. The clinical importance of these hypotheses is that if the relationship between presence of endotoxin and (1-3)-β-D glucan in blood of patients with chronic kidney disease and inflammation were clarified, and a positive association was confirmed, this would justify embarking on endotoxin or (1-3)-β-D glucan lowering interventional studies such as extracorporeal endotoxin adsorption therapy or exploring therapies to modify gut flora. In order to address these hypotheses systematically, the studies were designed with the following specific aims: 1. To determine the prevalence of chronic unexplained inflammation in patients receiving haemodialysis to determine the scope and extent of the clinical problem. 2. To determine the optimum endotoxin assay, in terms of accuracy and precision, for measurement of endotoxin in uraemic human blood and to limit interference of other factors in the assay such as presence of (1-3)-β-D glucan. 3. To determine the relationship of blood levels of endotoxin measured with an optimised assay and (1-3)-β-D glucan in patients with chronic kidney disease with patient symptoms and inflammation both cross-sectionally and longitudinally. 4. To determine factors influencing the presence of endotoxin and (1-3)-β-D glucan in the blood of patients requiring haemodialysis to determine whether increased gut permeability, potentially induced by intravascular volume depletion during dialysis, is a potential contributor. To determine the extent of unexplained inflammation, a retrospective study was performed of 444 prevalent haemodialysis patients at the East and North Herts NHS Trusts in which medical records and serial CRP measurements over 3 months were reviewed. Specific potential causes of inflammation were sought for each patient. 64.8% of patients had evidence of elevated CRP >5mg/L on at least two occasions one month apart and 23.4% of the study population had chronic unexplained inflammation. To determine the optimum blood endotoxin detection assay, a literature review was conducted to identify candidate assays for testing. All published endotoxin studies in dialysis patients used variations of assays based on the Limulus Amoebocyte Lysate (LAL) assay. The kinetic turbidimetric, kinetic chromogenic LAL and Endotoxin Scattering Photometry assay were compared in a direct head-to-head study in terms of accuracy and precision. The kinetic turbidimetric LAL assay was found to have the best performance and used for blood endotoxin detection in clinical studies. In a study of 40 haemodialysis patients, blood samples were measured simultaneously for endotoxin and (1-3)-β-D glucan. Endotoxin signals correlated significantly with (1-3)-β-D glucan. However, on modifying the kinetic turbidimetric LAL assay with a blocker which prevents assay activation by (1-3)-β-D glucan, all previously detected signals were extinguished and true endotoxemia in haemodialysis patients in this study was low, contrary to findings from previous studies. ‘Endotoxin’ signals detected using LAL assays suffer from significant false positive interference from elevated (1-3)-β-D glucan in haemodialysis patients. Given the low prevalence of endotoxemia detected, haemodialysis patients were further studied during clinical states that were hypothesised to increase endotoxin influx including during exercise and after haemodialysis. Blood samples were collected from 10 haemodialysis patients before and after haemodialysis and intra-dialytic exercise. Similarly, after modifying the LAL assay with a blocker to prevent false activation from (1-3)-β-D glucan, only one sample tested positive for endotoxin whereas 43% of samples had elevated (1-3)-β-D glucan. The relationship between (1-3)-β-D glucan with kidney function, inflammation and endotoxin levels were further studied in a study of 60 haemodialysis patients (30 with high-risk features including chronic unexplained inflammation, hypotension during haemodialysis or high ultrafiltration requirements and 30 low-risk patient [no inflammation, hypotension and low ultrafiltration requirement], 15 peritoneal dialysis patients, 20 patients with CKD 4-5, 20 patients with CKD 1-3 and 20 healthy controls. Similarly, while endotoxin signals were highest in haemodialysis patients, most signals disappeared after modifying the LAL assay with a (1-3)-β-D glucan blocking buffer. Low level endotoxemia was found in only 3 haemodialysis patients. BG levels increased with worsening CKD stage and were highest in haemodialysis patients, 22% having significantly elevated levels. (1-3)-β-D glucan correlated strongly with endotoxin signals (r=0.545, p<0.001) suggesting that previous reports of elevated endotoxin may be artefactual due to raised blood (1-3)-β-D glucan in renal impairment. (1-3)-β-D glucan correlated strongly with markers of inflammation and were associated with higher depression and kidney disease related symptoms scores. Intestinal barrier dysfunction and increased intestinal permeability has been proposed as a source of inflammation in haemodialysis patients and the haemodialysis procedure has been suggested to exacerbate intestinal permeability due to the large blood volume changes that occur during treatment. Intestinal permeability has not been studied directly in haemodialysis patients since conventional assays rely on measurement of probes in urine but this method cannot be applied to anuric dialysis patients. Using a novel intestinal permeability assay which measures probes in plasma instead, intestinal permeability was measured in 10 haemodialysis patients before and after haemodialysis treatment and compared with 5 healthy controls. Direct comparison of intestinal permeability between haemodialysis patients and healthy controls was difficult since concentration of probes in plasma was influenced by level of kidney function, although there was a suggestion that small intestinal permeability was increased in haemodialysis patients. However, intestinal permeability was not significantly affected by the haemodialysis procedure. The main finding of this work is that endotoxemia is relatively uncommon in dialysis patients and hence unlikely to be the sole cause of unexplained chronic inflammation in these patients. Previous reports of apparent high levels of blood endotoxin in dialysis patients were due, in part at least, to false positive interference of LAL assays by elevated (1-3)-β-D glucan present in the blood of patients with kidney disease. The work presented in this thesis supports this. Furthermore, the clinical studies carried out did not demonstrate a convincing association between endotoxin and inflammation. In contrast, this work has demonstrated a progressive increase in levels of (1-3)-β-D glucan with worsening degree of kidney disease and an association of these levels with inflammation, higher depression and kidney-disease related symptom scores. The cause of elevated (1-3)-β-D glucan in dialysis patients is unclear and warrants further study, though an intestinal source is a possibility. The direct intestinal permeability studies carried out in dialysis patients suggest impaired intestinal barrier function, although until an accurate method of assessing intestinal permeability in vivo in uraemic patients is available, this hypothesis remains to be proven

Octahedron-based Projections as Intermediate Representations for Computer Imaging: TOAST, TEA, and More

This paper defines and discusses a set of rectangular all-sky projections that have no singular points, notably the Tesselated Octahedral Adaptive Spherical Transformation (or TOAST) developed initially for the WorldWide Telescope. These have proven to be useful as intermediate representations for imaging data where the application transforms dynamically from a standardized internal format to a specific format (projection, scaling, orientation, etc.) requested by the user. TOAST is strongly related to the Hierarchical Triangular Mesh pixelization and is particularly well adapted to situations where one wishes to traverse a hierarchy of images increasing in resolution. Because it can be recursively computed using a very simple algorithm it is particularly adaptable to use with graphical processing units

Cone Penetration Test in Unsaturated Soil with Matric Suction Measurement

This research consists of two main studies. In the first half of this dissertation, the research findings regarding the use of 3D scanner for shrinkage limit testing of soils are presented; the second half of this dissertation presents the findings related to the chamber tests conducted which measures the matric suction of the unsaturated soil during cone penetration tests. Part I: Shrinkage curve Evaluation using a 3D scanner A procedure is proposed for conducting shrinkage limit tests using a 3D scanner. Shrinkage limit tests were conducted on 13 different soils of various plasticity. Shrinkage curves for each material were obtained by curve fitting a shrinkage model to the measured dataset. Using linear regression analysis, an empirical correlation was developed to reasonably relate parameter csh from the shrinkage model to the ratio of the plastic and liquid limits. The shrinkage curves produced based on the model have an average difference of ~1.2% in terms of measured void ratio and predicted void ratio. The method was demonstrated to be robust for materials of low, medium, and high plasticity. The proposed methodology also presents a means of estimating a shrinkage curve in its entirety based solely on the volume of an air-dried sample, the specific gravity and Atterberg limits of the specimen. This effectively reduces the amount of work needed to derive the shrinkage curve and could potentially reduce the time for a shrinkage limit test by half or more. Part II: Cone Penetration Testing in Unsaturated Silt with Matric Suction measurements Most empirical correlations used to interpret cone penetration test (CPT) results have been developed from and for saturated soils, so the applicability of CPTs to unsaturated soils remains in question. This paper presents experimental results for CPTs conducted in a chamber instrumented with four rapid-response tensiometers and filled with an unsaturated silt: one test with silt at one water content and three tests with two layers of silt at different water contents (drier layer overlying the wetter layer). Two pore pressure dissipation (PPD) tests were conducted after 400 to 500 mm penetration in each layer. Negative pore-water pressures (matric suction) were monitored during advancement of the cone and the PPD tests; cone resistance, sleeve friction, and pore-water pressure were also recorded. CPT results indicate the built-in pore-water pressure transducer cannot provide useful information regarding pore pressure and hydraulic properties of the unsaturated soil. Hence, tensiometers ought to be used to obtain pore pressure measurements during and after penetration. Tensiometer readings can also be used to characterize the unsaturated soil in terms of the in situ soil water characteristic curve (SWCC), unsaturated hydraulic conductivity, in situ pore-water pressure profile, and in situ effective stress. Existing empirical correlations used to interpret the results of PPD tests and soil behaviour type (SBT) are reviewed. Using a spherical cavity expansion solution, a method is proposed to estimate the frictional parameters of the unsaturated silt

Resourcing Defense Innovation: The role of organizational values

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