A MODEL OF AGRICULTURAL INSURANCE IN EVALUATING ASYMMETRIC INFORMATION PROBLEMS

The main motivation for this paper is the recognition of the fact that asymmetric information is the form of moral hazard and adverse selection results in sizeable efficiency losses. These costs are passed back to producers in the form of excessively high premium rates and also passed back to the government via the crop insurance subsidy program. A secondary motivation stems from a recent debate in the literature regarding the specific effects of moral hazard on agricultural input use. Conventional wisdom suggests that moral hazard will induce producers to reduce input usage. A competing hypothesis has emerged which suggests that moral hazard may induce producers to increase their usage or risk increasing inputs. The main objective of this paper was to develop a model of agricultural insurance to understand why asymmetric information problems might exist and to compute and evaluate the relative program costs of agricultural insurance that can be attributed to moral hazard and adverse selection. These objectives are achieved by developing a theoretical model of agricultural insurance, and by conducting numerical simulations of the model. Simulation results indicated that insured farmers use less agricultural inputs than uninsured farmers in an attempt to maximize expected indemnities. Moral hazard was fould to be a significant problem only at higher coverage levels. Expected returns (in term of expected indemnities) to agricultural insurance were found to vary substantially between productivity (i.e., risk) types, and farmers were shown to recognize and respond to these differences. These results suggest that crop insurance is confronted with an adverse selection problem. Simulation results further indicated that program costs to a myopic insurer attributed to moral hazard and adverse selection could be substantial.Risk and Uncertainty,

THE ECONOMICS AND IMPLICATIONS OF EX-ANTE REGULATIONS IN ADDRESSING PROBLEMS OF MORAL HAZARD IN AGRICULTURAL INSURANCE

In this paper we develop a theoretical model of input supply by agricultural producers who purchase crop insurance and so who may engage in moral hazard. We show, through simulations, that a combination of partial insurance coverage combined with a minimum standard for input use may reduce substantially the problems associated with moral hazard. Partial insurance coverage creates an incentive for the producer to increase his use of inputs since the cost of lower output is partially borne by the producer, an outcome which would not be present under full coverage insurance. Partial monitoring of inputs, in the form of a minimum requirement for input use, has a direct effect on the reduction of moral hazard. We show that, rather than being substitute instruments, these are in fact complementary methods of encouraging a more efficient supply of inputs. Moreover, the minimum level of input use that must be required by regulation turns over to be substantially lower than the optimal or actual input level chosen by producers. Since the supply of inputs for crop production occurs in many stages over the pre-planting, planting and growing seasons, the fact that only a minimal input requirement is needed means that the cost of implementing such a regulation can be kept much lower than would be the case for a regulation of complete monitoring of input usage.Risk and Uncertainty,

Strain Hardening in Polymer Glasses: Limitations of Network Models

Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While traditional entropic network models can be fit to the total stress, their underlying assumptions are inconsistent with simulation results. There is a substantial energetic contribution to the stress that rises rapidly as segments between entanglements are pulled taut. The thermal component of stress is less sensitive to entanglements, mostly irreversible, and directly related to the rate of local plastic arrangements. Entangled and unentangled chains show the same strain hardening when plotted against the microscopic chain orientation rather than the macroscopic strain.Comment: 4 pages, 3 figure

Viscoplasticity and large-scale chain relaxation in glassy-polymeric strain hardening

A simple theory for glassy polymeric mechanical response which accounts for large scale chain relaxation is presented. It captures the crossover from perfect-plastic response to strong strain hardening as the degree of polymerization $N$ increases, without invoking entanglements. By relating hardening to interactions on the scale of monomers and chain segments, we correctly predict its magnitude. Strain activated relaxation arising from the need to maintain constant chain contour length reduces the $N$ dependence of the characteristic relaxation time by a factor $\sim \dot\epsilon N$ during active deformation at strain rate $\dot\epsilon$. This prediction is consistent with results from recent experiments and simulations, and we suggest how it may be further tested experimentally.Comment: The theoretical treatment of the mechanical response has been significantly revised, and the arguments for coherent relaxation during active deformation made more transparen

Renal biopsy findings among Indigenous Australians: a nationwide review

Australia's Indigenous people have high rates of chronic kidney disease and kidney failure. To define renal disease among these people, we reviewed 643 renal biopsies on Indigenous people across Australia, and compared them with 249 biopsies of non-Indigenous patients. The intent was to reach a consensus on pathological findings and terminology, quantify glomerular size, and establish and compare regional biopsy profiles. The relative population-adjusted biopsy frequencies were 16.9, 6.6, and 1, respectively, for Aboriginal people living remotely/very remotely, for Torres Strait Islander people, and for non-remote-living Aboriginal people. Indigenous people more often had heavy proteinuria and renal failure at biopsy. No single condition defined the Indigenous biopsies and, where biopsy rates were high, all common conditions were in absolute excess. Indigenous people were more often diabetic than non-Indigenous people, but diabetic changes were still present in fewer than half their biopsies. Their biopsies also had higher rates of segmental sclerosis, post-infectious glomerulonephritis, and mixed morphologies. Among the great excess of biopsies in remote/very remote Aborigines, females predominated, with younger age at biopsy and larger mean glomerular volumes. Glomerulomegaly characterized biopsies with mesangiopathic changes only, with IgA deposition, or with diabetic change, and with focal segmental glomerulosclerosis (FSGS). This review reveals great variations in biopsy rates and findings among Indigenous Australians, and findings refute the prevailing dogma that most indigenous renal disease is due to diabetes. Glomerulomegaly in remote/very remote Aboriginal people is probably due to nephron deficiency, in part related to low birth weight, and probably contributes to the increased susceptibility to kidney disease and the predisposition to FSGS

Fcc-bcc transition for Yukawa interactions determined by applied strain deformation

Calculations of the work required to transform between bcc and fcc phases yield a high-precision bcc-fcc transition line for monodisperse point Yukawa (screened-Couloumb) systems. Our results agree qualitatively but not quantitatively with previously published simulations and phenomenological criteria for the bcc-fcc transition. In particular, the bcc-fcc-fluid triple point lies at a higher inverse screening length than previously reported.Comment: RevTex4, 9 pages, 6 figures. Discussion of phase coexistence extended, a few other minor clarifications added, referencing improved. Accepted for publication by Physical Review

Co–Au core-shell nanocrystals formed by sequential ion implantation into SiO₂

Co–Au core-shell nanocrystals (NCs) were formed by sequential ion implantation of Au and Co into thin SiO₂. The NCs were investigated by means of transmission electron microscopy and extended x-ray absorption fine structure spectroscopy. The latter reveals a bond length expansion in the Co core compared to monatomic Co NCs. Concomitantly, a significant contraction of the bond length and a significant reduction of the effective Au–Au coordination number were observed in the Au shells. Increased Debye-Waller factors indicate significant strain in the NCs. These experimental results verify recent theoretical predictions.P.K. and M.C.R. thank the Australian Research Council for support. P.K., B.H., B.J., and M.C.R. were supported by the Australian Synchrotron Research Program, funded by the Commonwealth of Australia via the Major National Research Facilities Program

You spin me round: Measuring precession in the black hole population

Black holes: cosmic bodies of extreme gravity that nothing, not even light, can escape. Einstein first told the world about the existence of these enigmatic objects in his groundbreaking theory of General Relativity. It was not until 2015 that black holes were probed directly through the first observation of gravitational waves. The treasure trove of knowledge gleaned from this observation revolutionised our understanding of the cosmos. Since this Nobel prize winning observation, the LIGO Scientific, Virgo and KAGRA collaborations have observed fifty gravitational waves. The aim of this thesis has been to take advantage of the growing population of gravitational wave sources to answer the following fundamental question: do binary black holes undergo spin-induced orbital precession? This has significant implications on our understanding of how binary black holes form in nature. To answer this question, I first introduced a brand new formalisation for modelling a gravitational wave that originated from a precessing system. I then introduced the 'precession signal-to-noise ratio' which naturally followed from this unique description. This novel tool quantified, for the first time, the significance of precession in an observed gravitational wave. I then used the 'precession signal-to-noise ratio' to demonstrate a) that there is no evidence for precession in any of the binary black hole candidates from the first gravitational wave catalog and b) how this lack of precession allows us to constrain the properties of black holes. I then presented the properties of potentially the first neutron star-black hole binary observed -- a system which is most likely to have measurable precession as a result of the asymmetric component masses. I then calculated the 'precession signal-to-noise ratio' for all gravitational wave candidates observed in the first half of the third gravitational wave observing run, and demonstrated that three observed gravitational waves could have originated from precessing systems. I then used the gravitational wave data from the second gravitational wave catalog to determine the most likely spin distribution of black holes. By doing so, I was able to determine whether the population of binary black holes are likely to undergo spin-induced orbital precession. Finally, I presented a new and innovative software package to analyse, display and combine posterior samples. This package has become one of the major workhorses of the LIGO Scientific, Virgo and KAGRA collaborations and is widely distributed through the gravitational wave data analysis computing environment