The Steel Tomb

Non-fiction by David Hodg

Effects of potassium fertilization of fescue pastures on metabolism of magnesium, calcium and potassium in lactating beef cows

The objectives of this research were to determine what effects high K fertilization of fescue pastures had on plasma levels of Mg, Ca and K and on the metabolism of Mg. Ca and K In beef cows In early lactation. Balance trials were conducted using beef cows with young suckling calves In February and March, 1980 and 1981. Cows were placed on one of two adjacent fescue pastures. Both pastures were fertilized with N (112 kg/hectare) and P (169 kg/hectare). One pasture received no fertilization of K and the other, 224 kg/hectare. The Internal (acid-detergent 11gn1n)-external (Cr203) Indicator technique was used to determine fecal dry matter output and dry matter consumption of the cows. Urine volume was estimated using creatinine ratios. Milk production (calf-suckle technique) was estimated and sampled for all cows. Cows on the control pasture consumed more dry matter and Mg. Cows consuming the K-fertilized pastured had reduced urinary Mg excretion. Indicating reduced absorption of the Mg. Excretion of Mg In the milk remained the same regardless of treatment. Cows on the K-fertilized pasture tended to have depressed plasma Mg values with a higher Incidence of hypomagnesemia. Nine cows on the K-fertilized pasture were hypomagnesemic compared with only four on the control pasture, although no symptoms of grass tetany were seen. This rela-tionship suggests that In a tetany-prone year, the number of cases n nn of grass tetany could be higher because of pasture fertilization with K. There were no differences between treatment in plasma Ca values, but plasma K tended to be higher in cows on the K-fertilized pasture

Behavioral risk profiles of homeschooled adolescents in the United States: a nationally representative examination of substance use related outcomes

BACKGROUND: The homeschool population continues to grow in size and now accounts for 3.4% of all students in the United States. OBJECTIVE: Given the heterogeneous nature of the population, this study examines the relationship between different types of homeschoolers and a number of substance use related outcomes. METHODS: To conduct this study, we used pooled data (2002–2013) from the National Survey on Drug Use and Health (NSDUH). Respondents aged 12–17 who reported they had been homeschooled at any time during the previous 12 months were classified as homeschoolers (N = 1,321). Latent profile analysis (LPA) was conducted to identify latent subgroups of homeschoolers and multinomial regression was executed to assess the relationship between the subgroups and perceived substance use risk, availability, and past 12-month use. RESULTS: The LPA yielded four subgroups, which were summarized as (1) highly religious and engaged, (2) limited parental monitoring, (3) high parental warmth and support, and (4) secular permissive. Of these, the highly religious and engaged subgroup was the least likely to report using substances. CONCLUSION: The results underscore the variation that exists among homeschoolers and the importance of examining the relationship between different types of homeschoolers and outcomes of interest

On the asymptotic optimality of greedy index heuristics for multi-action restless bandits

The class of restless bandits as proposed by Whittle (1988) have long been known to be intractable. This paper presents an optimality result which extends that of Weber and Weiss (1990) for restless bandits to a more general setting in which individual bandits have multiple levels of activation but are subject to an overall resource constraint. The contribution is motivated by the recent works of Glazebrook et al. (2011a), (2011b) who discussed the performance of index heuristics for resource allocation in such systems. Hitherto, index heuristics have been shown, under a condition of full indexability, to be optimal for a natural Lagrangian relaxation of such problems in which a resource is purchased rather than constrained. We find that under key assumptions about the nature of solutions to a deterministic differential equation that the index heuristics above are asymptotically optimal in a sense described by Whittle. We then demonstrate that these assumptions always hold for three-state bandits

Focus rural land policies on ecosystem services, not agriculture.

Land policies around the world are weighted towards agricultural output. We argue that this leads to ineffective public expenditure, environmental harm and missed opportunities for use of rural resources. Applying ecosystems services thinking to the governance of rural land would secure greater social value