Arkansas Landlord Selection of Land-Leasing Contract Type and Terms

Land leasing is a major source of the land input to production agriculture. Responses from a survey of landlords leasing crop land in Arkansas are analyzed to better understand those factors motivating landlords in the type of lease they select and the terms of those leases. Probit models are estimated to determine the relative importance of variables representing credit constraint, agency problem, and risk aversion factors. Regression models then estimate the impact of site, landlord, and tenant characteristics on contract terms – the percentage of crop and cost sharing arrangements between landlord and tenant. Probit results suggest credit constraint factors influence lease-type selection. Risk aversion, managerial ability, and social capital factors are also supported. Regression models show that land and crop characteristics are significant determinants of contract terms.Land leasing, Probit, Contract, Production agriculture, Land Economics/Use,

CONTRACT CHOICE SELECTION WITH LAND-LEASING AGREEMENTS

This study tests cropland contract hypotheses utilizing a landlord data set. Ordered probit and classical regression models are estimated and presented identifying factors that affect the contract type selection and terms. Results suggest credit constraints are a viable land-leasing hypothesis. Risk aversion, managerial ability, and social capital are also supported.Land Economics/Use,

Digitally-produced image comparison of three, 90 diopter-equivalent lenses: Subjective and objective findings

Purpose: To evaluate the image quality of retinal structures as obtained by three high plus lenses manufactured by the Yolk company to determine if any of the lens types provided a better quality of digital image. Methods: Digital images of two different patients\u27 left and right optic nerve heads (ONH) and left and right maculae (MAC) were obtained with three high plus lenses in conjunction with a biomicroscope. One of each of the following three lenses were used during the study: 90 Diopter Classic (90D), Super Field (SF) and Digital Wide Field (DWF). A total of 10 optometric physicians, who were faculty of an accredited school of optometry at the time of the study, were then asked to view 30 pairs of simultaneously presented photographs and select the image of higher quality. The paired photographs consisted of images of either the same optic nerve head or same macula of the one specific patient, as taken with two different lenses. Three sets of identical images were randomly presented to screen for left- or righthandedness. The digital images were also evaluated by Adobe Photoshop for color and luminosity values within a defined area. Results: Objective results showed that there was no statistically significant difference between mean color and luminosity of the ONH and MAC images as produced by the 90D, SF and DWF lenses: p = 0.542, p = 0.587, p = 0.232 and p = 0.186. Subjective results were statistically significant for selecting the 90D lens as producing the better ONH image quality 1 (p == 0.041). While not statistically significant (p == 0.165), the subjects followed a similar trend in choosing the 90D lens as having better quality of the MAC images. Conclusions: The 90D lens appears to produce subjectively better quality in digital images of the posterior pole

The Large-scale J=3-2 and J=2-1 CO Emission from M17 and its Implications for Extragalactic CO Observations

We observed a 10x20 pc region of the molecular cloud M17 in the 12CO and 13CO J=3-2 and J=2-1 transitions to determine their global behavior and to assess the reliability of using ratios of CO line intensities integrated over an entire cloud to determine the physical conditions within the cloud. Both the 12CO/13CO J=2-1 and J=3-2 line ratios correlate with the 13CO integrated intensity, with smaller line ratios observed at locations with large integrated intensities. This correlation is likely due to variations in the column density from one position to another within M17. The 12CO and 13CO (J=3-2/J=2-1) line ratios show no significant variation from place to place within M17, even on the peak of the photon-dominated region. A Large Velocity Gradient analysis of globally averaged line ratios gives results in reasonable agreement with the results obtained for individual lines-of-sight through the cloud, which suggests that the typical physical conditions in a molecular cloud can be determined using CO line ratios integrated over the entire cloud. There appears to be a clear trend of increasing 12CO/13CO J=2-1 and J=3-2 line ratios as one moves from Galactic molecular cloud cores to entire Galactic molecular clouds to normal galaxies. The most likely explanation of the high line ratios for normal galaxies is a significant contribution to the CO emission by low column density material, such as diffuse molecular clouds or the outer envelopes of giant molecular clouds.Comment: 26 pages, 6 figures, 2 tables. Accepted for publication in Ap

Anderson Localization, Non-linearity and Stable Genetic Diversity

In many models of genotypic evolution, the vector of genotype populations satisfies a system of linear ordinary differential equations. This system of equations models a competition between differential replication rates (fitness) and mutation. Mutation operates as a generalized diffusion process on genotype space. In the large time asymptotics, the replication term tends to produce a single dominant quasispecies, unless the mutation rate is too high, in which case the populations of different genotypes becomes de-localized. We introduce a more macroscopic picture of genotypic evolution wherein a random replication term in the linear model displays features analogous to Anderson localization. When coupled with non-linearities that limit the population of any given genotype, we obtain a model whose large time asymptotics display stable genotypic diversityComment: 25 pages, 8 Figure

Intense physical activity is associated with cognitive performance in the elderly

Numerous studies have reported positive impacts of physical activity on cognitive function. However, the majority of these studies have utilised physical activity questionnaires or surveys, thus results may have been influenced by reporting biases. Through the objective measurement of routine levels of physical activity via actigraphy, we report a significant association between intensity, but not volume, of physical activity and cognitive functioning. A cohort of 217 participants (aged 60–89 years) wore an actigraphy unit for 7 consecutive days and underwent comprehensive neuropsychological assessment. The cohort was stratified into tertiles based on physical activity intensity. Compared with individuals in the lowest tertile of physical activity intensity, those in the highest tertile scored 9%, 9%, 6% and 21% higher on the digit span, digit symbol, Rey Complex Figure Test (RCFT) copy and Rey Figure Test 30-min recall test, respectively. Statistically, participants in the highest tertile of physical activity intensity performed significantly better on the following cognitive tasks: digit symbol, RCFT copy and verbal fluency test (all P<0.05). The results indicate that intensity rather than quantity of physical activity may be more important in the association between physical activity and cognitive function