The feasibility of performing a randomised controlled trial of therapeutic hypothermia for neuroprotection after paediatric cardiac arrest in the UK

Cardiac arrest in paediatric patients often results in death or survival with severe brain injury. Therapeutic hypothermia, lowering of core body temperature to 32 to 34⁰C may reduce injury to the brain in the period after circulation has been restored. This thesis comprises studies related to the feasibility of performing a randomised controlled trial (RCT) of therapeutic hypothermia for neuroprotection after cardiac arrest in the UK. A systematic Cochrane review of paediatric evidence finds no published RCTs supporting or refuting the use of therapeutic hypothermia after cardiac arrest. Four on-going RCTs are identified which will add to the future evidence base; however, a future UK RCT is recommended. Additional support for a RCT is demonstrated by two UK surveys of paediatric intensive care and emergency care clinicians. Current UK practice is varied and clinical equipoise exists regarding post cardiac arrest temperature management. A national, retrospective study of all admissions to paediatric intensive care after out of hospital (OHCA) and in hospital cardiac arrest (IHCA) shows an overall survival of 76 and 50% respectively. Important differences between IHCA and OHCA populations are identified, recommending separation in a RCT. The incidence rate of cardiac arrest admissions to PICU in the UK is too low to recruit to a UK only RCT, after consideration of sample size requirements. A large, multi-centre, retrospective, observational study of OHCA patients identified multiple factors associated with survival. A survival prediction model, incorporating: pupillary reaction, blood lactate level and duration of cardiac arrest, is described. The model could be used as a tool for stratified randomisation within a RCT. Finally, therapeutic hypothermia is retrospectively compared with standard, normothermic temperature management after OHCA. In a limited population, no difference in survival is found; however, important information on application, logistics and safety of the intervention are evaluated

Mathematical Formulas for Calculating Net Returns from Participation in Government Farm Programs: Provisions of the Food, Agricultural, Conservation and Trade Act of 1990

Agricultural and Food Policy, Agricultural Finance,

Reheating the Universe After Multi-Field Inflation

We study in detail (p)reheating after multi-field inflation models with a particular focus on N-flation. We consider a variety of different couplings between the inflatons and the matter sector, including both quartic and trilinear interactions with a light scalar field. We show that the presence of multiple oscillating inflatons makes parametric resonance inefficient in the case of the quartic interactions. Moreover, perturbative processes do not permit a complete decay of the inflaton for this coupling. In order to recover the hot big bang, we must instead consider trilinear couplings. In this case we show that strong nonperturbative preheating is possible via multi-field tachyonic resonance. In addition, late-time perturbative effects do permit a complete decay of the condensate. We also study the production of gauge fields for several prototype couplings, finding similar results to the trilinear scalar coupling. During the course of our analysis we develop the mathematical theory of the quasi-periodic Mathieu equation, the multi-field generalization of the Floquet theory familiar from preheating after single field inflation. We also elaborate on the theory of perturbative decays of a classical inflaton condensate, which is applicable in single-field models also.Comment: 46+1 pages, 19 figure

Phenomenology of a Pseudo-Scalar Inflaton: Naturally Large Nongaussianity

Many controlled realizations of chaotic inflation employ pseudo-scalar axions. Pseudo-scalars \phi are naturally coupled to gauge fields through c \phi F \tilde{F}. In the presence of this coupling, gauge field quanta are copiously produced by the rolling inflaton. The produced gauge quanta, in turn, source inflaton fluctuations via inverse decay. These new cosmological perturbations add incoherently with the "vacuum" perturbations, and are highly nongaussian. This provides a natural mechanism to generate large nongaussianity in single or multi field slow-roll inflation. The resulting phenomenological signatures are highly distinctive: large nongaussianity of (nearly) equilateral shape, in addition to detectably large values of both the scalar spectral tilt and tensor-to-scalar ratio (both being typical of large field inflation). The WMAP bound on nongaussianity implies that the coupling, c, of the pseudo-scalar inflaton to any gauge field must be smaller than about 10^{2} M_p^{-1}.Comment: 45 pages, 7 figure

MATHEMATICAL FORMULAS FOR CALCULATING NET RETURNS FROM PARTICIPATION IN GOVERNMENT PROGRAMS, CRP, AND CROP INSURANCE ALTERNATIVES

The purpose of this report is to provide a revised version of the publication, "Mathematical Formulas for Calculating Net Returns from Participation in Government Commodity Programs including Marketing Loans" (Williams and Barnaby, 1994). The change in design of the government commodity programs and development of several crop insurance alternatives has been significant since the previous paper was published. The formulas for calculating net returns incorporate provisions from the Farm Security and Rural Investment Act of 2002 and several crop insurance designs developed in the 1990s. Individuals conducting research or education programs will be able to use this revision for reference when estimating net returns for producers under current commodity program and crop insurance plan provisions.Agricultural Finance,

Reduction of Yield and Income Risk Under Alternative Crop Insurance and Disaster Assistance Plans

This study compares the effectiveness of five crop insurance/disaster assistance plans: an individual farm yield insurance plan similar to the current FCIC multi-peril program ; two area yield insurance plans; a farm yield disaster assistance plan; and an area yield disaster assistance plan. These methods are examined for reduction in yield and gross income variability with and without participation in the government deficiency payment programs using farm-level yield data from 98 dryland wheat farms and 38 dryland corn farms in Kansas . Although individual farm yield insurance is complex, suffers from moral hazard and adverse selection problems, and is likely to be the most expensive to administer , it provides more yield and gross income risk reduction than any of the alternative insurance/disaster assistance plans.Crop Insurance, Crop Disaster Assistance, Risk, Wheat, Corn, Risk and Uncertainty,

Diffraction-limited polarimetric imaging of protoplanetary disks and mass-loss shells with VAMPIRES

Both the birth and death of a stellar system are areas of key scientific importance. Whether it's understanding the process of planetary formation in a star's early years, or uncovering the cause of the enormous mass-loss that takes place during a star's dying moments, a key to scientific understanding lies in the inner few AU of the circumstellar environment. Corresponding to scales of 10s of milli-arcseconds, these observations pose a huge technical challenge due to the high angular-resolutions and contrasts required. A major stumbling block is the problem of the Earth's own atmospheric turbulence. The other difficulty is that precise calibration is required to combat the extremely high contrast ratios and high resolutions faced. By taking advantage of the fact that starlight scattered by dust in the circumstellar region is polarized, differential polarimetry can help achieve this calibration. Spectral features can also be utilized