The Law of the Minimum and Sources of Nonzero Skewness for Crop Yield Distributions

Crop yields are not commonly found to be normally distributed, but the cause of the non-normal distribution is unclear. The non-normality might be due to weather variables and/or an underlying von Liebig law of the minimum (LoM) production function. Our objective is to determine the degree to which an underlying linear response stochastic plateau production function can explain the skewness of Oklahoma wheat yields at varied nitrogen rates. We use farm-level wheat data from a long-term experiment in Oklahoma, which is a unique data set to the literature. The Tembo et al. (2008) production function provides negative skewness at all levels of nitrogen with skewness near zero for both very high and very low levels of nitrogen. Observed skewness for wheat yields, however, is positive. The variation in the plateau by year shows positive skewness. Skewness in yield potential related to weather should be considered as a possible explanation of skewness.linear plateau model, non-normal distributions, skewness, wheat, yield distribution, Production Economics, Risk and Uncertainty, Q10,

Economics of Pre-Plant, Topdress, and Variable Rate Nitrogen Application in Winter Wheat

Past research about the efficiency of nitrogen application in winter wheat (Triticum aestivum L.) based on source and timing has produced inconsistent results. The majority of the literature used data from few locations over short time periods. This study used a unique data set of yields and nitrogen quantities from 2002-2009 at ten different locations in Oklahoma, USA. The objective of this research was to determine wheat yield response for granular pre-plant, uniform foliar topdress, and variable rate foliar topdress. Topdress liquid nitrogen had a 19% higher NUE than pre-plant urea, and was the most profitable source of nitrogen.linear stochastic plateau, nitrogen use efficiency, profitability, wheat, Crop Production/Industries,

The Astronomy of Africa’s Health Systems Literature During the MDG Era: Where Are the Systems Clusters?

The volume of literature on health systems in sub-Saharan Africa has been expanding since the 2000 MDG era. Focus has remained generally on categorical health themes rather than systems concepts. Topics such as scaling-up, organizational development, data use for decision making, logistics, and financial planning remain underrepresented. And quite surprisingly, implementation science remains something of a “black hole.” But bibliometric evidence suggests there is a shift in focus that may soon address these gaps

Assessing model performance for counterfactual predictions

Counterfactual prediction methods are required when a model will be deployed in a setting where treatment policies differ from the setting where the model was developed, or when the prediction question is explicitly counterfactual. However, estimating and evaluating counterfactual prediction models is challenging because one does not observe the full set of potential outcomes for all individuals. Here, we discuss how to tailor a model to a counterfactual estimand, how to assess the model's performance, and how to perform model and tuning parameter selection. We also provide identifiability results for measures of performance for a potentially misspecified counterfactual prediction model based on training and test data from the same (factual) source population. Last, we illustrate the methods using simulation and apply them to the task of developing a statin-na\"{i}ve risk prediction model for cardiovascular disease

Intersection of chronic pain treatment and opioid analgesic misuse: causes, treatments, and policy strategies

Treating chronic pain in the context of opioid misuse can be very challenging. This paper explores the epidemiology and potential treatments for chronic pain and opioid misuse and identifies educational and regulation changes that may reduce diversion of opioid analgesics. We cover the epidemiology of chronic pain and aberrant opioid behaviors, psychosocial influences on pain, pharmacological treatments, psychological treatments, and social treatments, as well as educational and regulatory efforts being made to reduce the diversion of prescription opioids. There are a number of ongoing challenges in treating chronic pain and opioid misuse, and more research is needed to provide strong, integrated, and empirically validated treatments to reduce opioid misuse in the context of chronic pain

Copper(0)-mediated radical polymerisation in a self-generating biphasic system

Herein, we demonstrate the synthesis of well-defined poly(n-alkyl acrylate)s via copper(0)-mediated radical polymerisation in a self-generating biphasic system. During the polymerisation of n-butyl acrylate in DMSO, the polymer phase separates to yield a polymer-rich layer with very low copper content (ICP-MS analysis: 0.016 wt%). The poly(n-butyl acrylate) has been characterized by a range of techniques, including GPC, NMR and MALDI-TOF, to confirm both the controlled character of the polymerisation and the end group fidelity. Moreover, we have successfully chain extended poly(n-butyl acrylate) in this biphasic system several times with n-butyl acrylate to high conversion without intermediate purification steps. A range of other alkyl acrylates have been investigated and the control over the polymerisation is lost as the hydrophobicity of the polymer increases due to the increase in alkyl chain length indicating that it is important for the monomer to be soluble in the polar solvent

(E)-Methyl 2-[(2S,3S,12bR)-3-ethyl-8-meth­oxy-1,2,3,4,6,7,12,12b-octa­hydro­indolo[2,3-a]quinolizin-2-yl]-3-methoxy­acrylate ethanol solvate

In the title compound, C23H30N2O4·C2H6O, the indole derivative has four fused rings, forming an indolo[2-3a]quinolizine system, in which one six-membered ring is directly connected to the indole unit and has a distorted chair conformation. The fourth ring is also a six-membered ring, depicting a regular chair conformation. In the crystal, the mol­ecules are linked by N—H⋯O and O—H⋯N inter­actions, forming a C(7) chain

Dibaryon Spectroscopy

The AdS/CFT correspondence relates dibaryons in superconformal gauge theories to holomorphic curves in Kaehler-Einstein surfaces. The degree of the holomorphic curves is proportional to the gauge theory conformal dimension of the dibaryons. Moreover, the number of holomorphic curves should match, in an appropriately defined sense, the number of dibaryons. Using AdS/CFT backgrounds built from the generalized conifolds of Gubser, Shatashvili, and Nekrasov (1999), we show that the gauge theory prediction for the dimension of dibaryonic operators does indeed match the degree of the corresponding holomorphic curves. For AdS/CFT backgrounds built from cones over del Pezzo surfaces, we are able to match the degree of the curves to the conformal dimension of dibaryons for the n'th del Pezzo surface, n=1,2,...,6. Also, for the del Pezzos and the A_k type generalized conifolds, for the dibaryons of smallest conformal dimension, we are able to match the number of holomorphic curves with the number of possible dibaryon operators from gauge theory.Comment: 30 pages, 6 figures, corrected refs; v3 typos correcte

The child survival impact of the Ghana Essential Health Interventions Program: A health systems strengthening plausibility trial in Northern Ghana

Background: The Ghana Health Service in collaboration with partner institutions implemented a five-year primary health systems strengthening program known as the Ghana Essential Health Intervention Program (GEHIP). GEHIP was a plausibility trial implemented in an impoverished region of northern Ghana around the World Health Organizations (WHO) six pillars combined with community engagement, leadership development and grassroots political support, the program organized a program of training and action focused on strategies for saving newborn lives and community-engaged emergency referral services. This paper analyzes the effect of the GEHIP program on child survival. Methods: Birth history data assembled from baseline and endline surveys are used to assess the hazard of child mortality in GEHIP treatment and comparison areas prior to and after the start of treatment. Difference-in-differences (DiD) methods are used to compare mortality change over time among children exposed to GEHIP relative to children in the comparison area over the same time period. Models test the hypothesis that a package of systems strengthening activities improved childhood survival. Models adjusted for the potentially confounding effects of baseline differentials, secular mortality trends, household characteristics such as relative wealth and parental educational attainment, and geographic accessibility of clinical care. Results: The GEHIP combination of health systems strengthening activities reduced neonatal mortality by approximately one half (HR = 0.52, 95% CI = 0.28,0.98, p = 0.045). There was a null incremental effect of GEHIP on mortality of post-neonate infants (from 1 to 12 months old) (HR = 0.72; 95% CI = 0.30,1.79; p = 0.480) and post-infants (from 1 year to 5 years old) -(HR = 1.02; 95% CI = 0.55–1.90; p = 0.940). Age-specific analyses show that impact was concentrated among neonates. However, effect ratios for post-infancy were inefficiently assessed owing to extensive survival history censoring for the later months of childhood. Children were observed only rarely for periods over 40 months of age. Conclusion: GEHIP results show that a comprehensive approach to newborn care is feasible, if care is augmented by community-based nurses. It supports the assertion that if appropriate mechanisms are put in place to enable the various pillars of the health system as espoused by WHO in rural impoverished settings where childhood mortality is high, it could lead to accelerated reductions in mortality thereby increasing survival of children. Policy implications of the pronounced neonatal effect of GEHIP merit national review for possible scale-up

Integrated Conceptual Ecosystem Model Development for the Southeast Florida Coastal Marine Ecosystem

The overall goal of the MARES (MARine and Estuarine goal Setting) project for South Florida is “to reach a science-based consensus about the defining characteristics and fundamental regulating processes of a South Florida coastal marine ecosystem that is both sustainable and capable of providing the diverse ecosystem services upon which our society depends.” Through participation in a systematic process of reaching such a consensus, science can contribute more directly and effectively to the critical decisions being made both by policy makers and by natural resource and environmental management agencies. The document that follows briefly describes MARES overall and this systematic process. It then describes in considerable detail the resulting output from the first step in the process, the development of an Integrated Conceptual Ecosystem Model (ICEM) for the third subregion to be addressed by MARES, the Southeast Florida Coast (SEFC). What follows with regard to the SEFC relies upon the input received from more than 60 scientists, agency resource managers, and representatives of environmental organizations during workshops held throughout 2009–2012 in South Florida