The combinatorics of the Baer-Specker group

Denote the integers by Z and the positive integers by N. The groups Z^k (k a natural number) are discrete, and the classification up to isomorphism of their (topological) subgroups is trivial. But already for the countably infinite power Z^N of Z, the situation is different. Here the product topology is nontrivial, and the subgroups of Z^N make a rich source of examples of non-isomorphic topological groups. Z^N is the Baer-Specker group. We study subgroups of the Baer-Specker group which possess group theoretic properties analogous to properties introduced by Menger (1924), Hurewicz (1925), Rothberger (1938), and Scheepers (1996). The studied properties were introduced independently by Ko\v{c}inac and Okunev. We obtain purely combinatorial characterizations of these properties, and combine them with other techniques to solve several questions of Babinkostova, Ko\v{c}inac, and Scheepers.Comment: To appear in IJ

Appetite self-regulation: Environmental and policy influences on eating behaviors

Objective: Appetite regulation is influenced by the environment, and the environment is shaped by food-related policies. This review summarizes the environment and policy research portion of an NIH Workshop (Bethesda, MD, 2015) titled “Self-Regulation of Appetite—It's Complicated.”. Methods: In this paper, we begin by making the case for why policy is an important tool in efforts to improve nutrition, and we introduce an ecological framework that illustrates the multiple layers that influence what people eat. We describe the state of the science on how policies influence behavior in several key areas: the federal food programs, schools, child care, food and beverage pricing, marketing to youth, behavioral economics, and changing defaults. Next, we propose novel approaches for multidisciplinary prevention and intervention strategies to promote breastfeeding, and examine interactions between psychology and the environment. Results: Policy and environmental change are the most distal influences on individual-level appetite regulation, yet these strategies can reach many people at once by changing the environment in which food choices are made. We note the need for more research to understand compensatory behavior, reactance, and how to effectively change social norms. Conclusions: To move forward, we need a more sophisticated understanding of how individual psychological and biological factors interact with the environment and policy influences

Children\u27s Consumption of Fruits and Vegetables: Do School Environment and Policies Affect Choices at School and Away from School?

School environment and policies may affect children\u27s ability to make healthy food choices both at and away from school. Using data from the third School Nutrition Dietary Assessment Study conducted in 2005 we estimate the effect of environment and policies on children\u27s fruit and vegetable intakes. We use an instrumental variable approach to control for the endogeneity of participation in the National School Lunch Program (NSLP). On an average school day, school lunch participants consume more fruits and vegetables, including relatively more at school and less away from school compared to nonparticipants. Meal policies had little effect on NSLP participation itself. Policies that restrict high fat milks or desserts and restrict the sale of competitive foods are associated with greater fruit and/or vegetable intake at school; some policies affected consumption at home as well

Prenatal Particulate Air Pollution and DNA Methylation in Newborns: An Epigenome-Wide Meta-Analysis

BACKGROUND: Prenatal exposure to air pollution has been associated with childhood respiratory disease and other adverse outcomes. Epigenetics is a suggested link between exposures and health outcomes. OBJECTIVES: We aimed to investigate associations between prenatal exposure to particulate matter (PM) with diameter [Formula: see text] ([Formula: see text]) or [Formula: see text] ([Formula: see text]) and DNA methylation in newborns and children. METHODS: We meta-analyzed associations between exposure to [Formula: see text] ([Formula: see text]) and [Formula: see text] ([Formula: see text]) at maternal home addresses during pregnancy and newborn DNA methylation assessed by Illumina Infinium HumanMethylation450K BeadChip in nine European and American studies, with replication in 688 independent newborns and look-up analyses in 2,118 older children. We used two approaches, one focusing on single cytosine-phosphate-guanine (CpG) sites and another on differentially methylated regions (DMRs). We also related PM exposures to blood mRNA expression. RESULTS: Six CpGs were significantly associ

The Economics of Brazil's Ethanol-Sugar Markets, Mandates, and Tax Exemptions

Sugarcane in Brazil is processed into sugar and/or ethanol, often in flex plants that can switch between the two products. We develop an economic model of flex plants, export demands, and two domestic fuel demand curves for a blend of ethanol with gasoline consumed by conventional cars, and ethanol consumed only by flex cars. We analyze the market impacts of the following policies: the blend mandate; fixing gasoline prices below world prices; the high gasoline tax; and a higher tax exemption for ethanol blended with gasoline. Because Brazilian and U.S. ethanol prices have become linked, a change in Brazilian ethanol policy or a shock in world sugar markets can now impact U.S. ethanol and corn prices. We show that in theory, each policy analyzed has an ambiguous impact on ethanol and sugar prices. Empirically, however, a low gasoline tax and a high tax exemption for ethanol used in the fuel blend reduce ethanol and sugar prices; this contradicts conventional wisdom. Overall, we find that policy reforms implemented in 2010 offset the ethanol price increase by about 27% due to outward shifts in fuel transportation and sugar export demand curves, and due to a reduced sugarcane supply caused by bad weather. Our model illustrates the importance of Brazil's ethanol policies on world commodity markets; it also provides insight into how the Brazilian government can adjust policies to better control domestic inflation while minimizing impacts on investment

An Economic Model of Brazil’s Ethanol-Sugar Markets and Impacts of Fuel Policies

We develop an economic model of flex plants, export demands and two domestic fuel demand curves: E25, a 25 percent blend of ethanol with gasoline consumed by conventional cars, and E100, ethanol consumed only by flex cars. This allows us to analyze the market impacts of specific policies, namely the E25 blend mandate, fixing gasoline prices below world prices, the high gasoline tax, and a higher tax exemption for ethanol used in E25. Because Brazilian and U.S. ethanol prices have become linked, a change in Brazilian ethanol policy or a shock in world sugar markets can now impact U.S. ethanol and corn prices. Because of two demand curves, with flex car owners switching between fuels depending on relative prices, and because the mandate is for E25 only, the impact of each Brazilian policy in theory has an ambiguous impact on ethanol and sugar prices. Conventional wisdom is that a higher level of the mandate, gasoline tax exemptions for ethanol and gasoline price, and a lower gasoline tax, all help the ethanol industry. But for two policies, a low gasoline tax and a high tax exemption for ethanol used in E25, our empirical results show ethanol and sugar prices decline. Overall, we find that the package of policy reforms implemented in 2010 offset the ethanol price increase due outward shifts in fuel transportation and sugar export demand curves, and reduced sugarcane supply due to bad weather, by about 27 percent. Our model illustrates the importance of Brazil’s ethanol policies on world commodity markets and provides insights on how the Brazilian government can adjust policies to better control domestic inflation while minimizing impacts on investment