Characterizing plasmin-induced lag phase and application of PDMS microfluidics to detection of fibrinolytic activity

Physical trauma is responsible for over six million deaths annually, and of these roughly 40 percent result from acute traumatic coagulopathy (ATC) occurring in the first few hours of incidence. Patients who have developed ATC have significantly improved survivability when treated with tranexamic acid (TXA), a chemical inhibitor of the clot lysing enzyme plasmin. Current methods of detecting ATC are inadequate, lacking in either efficient speed, sensitivity, or cost. Hyperfibrinolysis (HF) is a key component of ATC and can be a result of excess plasmin activity. The following study observes effects of plasmin on hemostasis, and explores the use of silicon-based polydimethylsiloxane (PDMS) microfluidics measuring changes in electrical resistance as a method to detect HF. Coagulation was characterized by measuring turbidity of solutions containing fibrinogen and thrombin, and plasmin was incorporated to observe fibrinolysis and other plasmin-induced effects. It was found that high concentrations of plasmin caused a delay in the turbidity increase during coagulation. This lag phase may be a contributing factor to HF and ultimately ATC. Finally, the use of PDMS microfluidics to measure changes in electrical resistance to detect coagulation and fibrinolysis activity was supported. Resistance change adhered closely to traditional substrate-enzyme kinetics and plasmin-induced effects mimicked those which were observed in turbidity measurements. Further investment and development of this method of measurement could provide a faster, more accurate, and more inexpensive alternative to current techniques for measuring fibrinolysis

Guidelines to select suitable parameters for contour method stress measurements

The contour method is one of the promising techniques for the measurement of residual stresses in engineering components. In this method, the cut surfaces deform, owing to the relaxation of residual stresses. The deformations of the two cut surfaces are then measured and used to back calculate the 2-dimensional map of original residual stresses normal to the plane of the cut. Thus, it involves four main steps; specimen cutting, surface contour measurement, data analysis and finite element simulation. These steps should perform in a manner that they do not change the underlying features of surface deformation especially where the residual stress distribution varies over short distances. Therefore, to carefully implement these steps, it is important to select appropriate parameters such as surface deformation measurement spacing, data smoothing parameters (‘knot spacing’ for example cubic spline smoothing) and finite element mesh size. This research covers an investigation of these important parameters. A simple approach for choosing initial parameters is developed based on an idealised cosine displacement function (giving a self-equilibrated one-dimensional residual stress profile). In this research, guidelines are proposed to help the measurer to select the most suitable choice of these parameters based on the estimated wavelength of the residual stress field

Measurement of true ileal calcium digestibility of feed ingredients for broiler chickens : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Institute of Veterinary, Animal and Biomedical Science (IVABS), Massey University, Palmerston North, New Zealand

Listed in 2017 Dean's List of Exceptional ThesesThe recent interest towards the use of digestible phosphorus (P) in poultry feed formulations necessitates the measurement of true calcium (Ca) digestibility of feed ingredients because of the close relationship between these two minerals for their absorption and post absorptive utilisation. When this thesis research was initiated, no published data were available on Ca digestibility of feed ingredients for broiler chickens. The major objective of the studies reported in this thesis was to determine the true Ca digestibility of feed ingredients for broiler chickens. In total, nine studies were conducted. The first study (Chapter 4) was conducted to determine the effect of methodology on ileal endogenous Ca losses. Three methods, namely feeding a Ca- and P-free diet, maize gluten meal based diet and egg albumen based diet, were used. Ileal endogenous Ca losses differed among different methodologies. The highest ileal endogenous losses of 125 mg/kg dry matter intake (DMI) were recorded on the Ca- and P-free diet, followed by 77 and 43 mg/kg DMI on maize gluten meal and egg albumen diets, respectively. In the second and third studies (Chapters 5 and 6), regression and direct methods, respectively, were used to determine the true Ca digestibility of meat and bone meal (MBM). The true Ca digestibility coefficient of MBM samples were ranged from 0.41 to 0.60. No difference was observed between true Ca digestibility coefficients of MBM determined by regression and direct methods. Since the direct method is less laborious and cost effective compared to regression method, this method was used in subsequent studies (Chapters 7 to 10) to determine the true Ca digestibility of a range of Ca sources. In fourth and fifth studies (Chapters 7 and 8), the influence of dietary P, particle size and Ca to non-phytate P ratio was investigated on the true Ca digestibility of limestone for broiler chickens. The true Ca digestibility of three limestone samples varied from 0.56 to 0.62. Supplementation with recommended dietary P (4.5 g/kg) increased the true Ca digestibility of limestone when compared to diets without P. An increase in particle size from <0.5 to 1-2mm improved the true ileal Ca digestibility of limestone. Widening the Ca to non-phytate P ratio reduced the true Ca digestibility of limestone for broiler chickens. The sixth study (Chapter 9) was conducted to determine the effect of Ca source and particle size on the true Ca digestibility and total tract retention. Limestone and oyster shell were used as Ca sources. No difference was observed between the true Ca digestibility of limestone and oyster shell. An increase in particle size from <0.5 to 1-2 mm increased both the Ca digestibility and retention of both Ca sources, and increased the Ca concentration of gizzard contents. The study reported in Chapter 10 was conducted to determine the true Ca digestibility of dicalcium phosphate (DCP), monocalcium phosphate (MCP), canola meal, poultry by-product meal and fish meal, and to compare the effect of dietary adaptation length on true Ca digestibility of DCP and MCP. The true Ca digestibility coefficients of these feed ingredients were lower than MBM, limestone and oyster shell, and ranged from 0.24 to 0.33. It was speculated that the length of adaption to the assay diets may be responsible for the lower than expected estimates. The effect of dietary adaptation length (24, 48 or 72 hrs) was subsequently examined, but had no effect on true Ca digestibility of DCP and MCP. In the final study (Chapter 11), the true Ca digestibility of DCP was determined using different methodologies (regression, difference and direct methods). The true Ca digestibility coefficients of DCP were 0.34 and 0.21 with direct and different methods, respectively. A very low digestibility coefficient of 0.13 was determined by the regression method. In conclusion, the true Ca digestibility coefficient of major Ca sources (limestone, oyster shell and MBM) is not high and varied from 0.40 to 0.70. Particle size of limestone and oyster shell influenced Ca digestibility, with coarser particles having higher digestibility. The direct method appears to be suitable for the determination of true Ca digestibility of limestone, oyster shell and MBM, but may not be appropriate for other Ca sources with intrinsic imbalance of Ca and P

The pathogenesis of Acanthamoeba infections: current status and future implications

Acanthamoeba are opportunistic protozoan parasites that can cause painful, visionthreatening keratitis. However the pathogenesis and pathophysiology of Acanthamoeba keratitis remain incompletely understood. Most cases of Acanthamoeba keratitis develop as a result of poor hygiene in contact lens care but it is unclear how amoebae transmigrate from the environment into the cornea leading to inflammation, photophobia and blindness. Acanthamoeba keratitis has become increasingly important in the past few decades due to increasing populations of contact lens users. The mechanisms associated with the pathogenesis of Acanthamoeba are highly complex, depending on the virulence properties of the parasite, host susceptibility and the environmental conditions. Complete understanding of Acanthamoeba pathogenesis and its associated risks factors should allow us to design strategies for disease prevention and for the rational development of therapeutic interventions against these devastating infections. Acanthamoeba keratitis has become a significant problem in recent years, especially in contact lens wearers exposed to contaminated water

Diabetic microvascular complications as simple indicators of risk for cardiovascular outcomes and heart failure

No abstract available

Cardiovascular and mortality risks in migrant South Asians with type 2 diabetes: are we winning the battle?

Purpose of Review: We seek to describe the relationship between diabetes mellitus and cardiovascular risk in migrant South Asians compared to native white Europeans, and to determine the temporal change in this relationship over recent years. Recent Findings: Recent evidence suggests that the excess mortality risk associated with diabetes is lower in the migrant South Asian population compared with white Europeans. By contrast, South Asians continue to demonstrate elevated cardiovascular morbidity compared to white Europeans, although to a lesser extent than was observed in previous decades. Summary: The excess mortality previously observed in South Asian migrants has attenuated with a lower mortality risk compared to white Europeans observed in several recent studies. We speculate that these findings may relate in part to earlier diabetes diagnosis and more prolonged exposure to cardiovascular risk factor management in the South Asian population. Further study is required to confirm these hypotheses

Ethnic entrepreneurs and online home-based businesses

Objectives The study considers how online home-based businesses offer opportunities for ethnic entrepreneurs to ‘break out’ of the traditional highly competitive and low margin sectors they are often associated with. Prior Work Previous studies have found a positive association between ethnic minorities high levels of entrepreneurship (Levie, 2007) and between home computer use and entrepreneurship in ethnic groups (Fairlie, 2006). Despite these associations, no previous studies have explored the formation of home-based or other online businesses by ethnic entrepreneurs. This study seeks to address this gap by exploring how online home-based businesses provide opportunities for ethnic entrepreneurs to form and operate businesses outside traditional sectors (Rath, 2002; Kloosterman, 2010). Approach The study adopts mixed embeddedness (Kloosterman et al, 1999) as a theoretical lens to guide interviews with 22 ethnic entrepreneurs who have started online home-based businesses in the UK. All interviews are recorded, fully transcribed and analysed by thematic coding using NVivo software. Results Our findings suggest two distinct groups of online home-based business ventures. The first consist of mainly entrepreneurs who have good IT qualifications and are using the internet to leverage these, such as running web design or networking businesses or selling computer hardware online. The second group had no IT expertise and saw the web as an opportunity to start a business based on retailing, design skills or other interests. The informants were emphatic that the unique characteristics offered by an online home-based business were instrumental in their decision and ability to form a business. We use the findings of the study to argue that the theory of mixed embeddedness should include notions of choice and agency by ethnic entrepreneurs and also that the entrepreneurs are not only subject to social, economic and institutional forces, but that their actions can positively influence these forces. Implications The findings suggest that online home-based businesses can offer new opportunities to ethnic entrepreneurs that allow them to move beyond being the passive subjects of social, economic and institutional forces. Value The study is of benefit to ethnic entrepreneurs seeking to start new ventures and provides a valuable evidence base for wider social debates about the role and contribution of ethnic groups to the economic and social fabric of the UK. The research also has important policy implications, for example, the efficacy and sustainability of entrepreneurship visas