Lyman Break Analogs: Constraints on the Formation of Extreme Starbursts at Low and High Redshift

Lyman Break Analogs (LBAs), characterized by high far-UV luminosities and surface brightnesses as detected by GALEX, are intensely star-forming galaxies in the low-redshift universe ($z\sim 0.2$), with star formation rates reaching up to 50 times that of the Milky Way. These objects present metallicities, morphologies and other physical properties similar to higher redshift Lyman Break Galaxies (LBGs), motivating the detailed study of LBAs as local laboratories of this high-redshift galaxy population. We present results from our recent integral-field spectroscopy survey of LBAs with Keck/OSIRIS, which shows that these galaxies have the same nebular gas kinematic properties as high-redshift LBGs. We argue that such kinematic studies alone are not an appropriate diagnostic to rule out merger events as the trigger for the observed starburst. Comparison between the kinematic analysis and morphological indices from HST imaging illustrates the difficulties of properly identifying (minor or major) merger events, with no clear correlation between the results using either of the two methods. Artificial redshifting of our data indicates that this problem becomes even worse at high redshift due to surface brightness dimming and resolution loss. Whether mergers could generate the observed kinematic properties is strongly dependent on gas fractions in these galaxies. We present preliminary results of a CARMA survey for LBAs and discuss the implications of the inferred molecular gas masses for formation models.Comment: To appear in the proceedings of IAU Symposium 277, "Tracing the Ancestry of Galaxies on the Land of our Ancestors", eds. C. Carignan, K.C. Freeman, and F. Combe

Investment In An Unstable Tax Environment

While most of the capital budgeting situations are typically micro level problems, the introduction of this dual impact of the corporate tax rate on the project acceptance criterion provides an insight into potential tax regime decisions on long term investments in a given tax jurisdiction.  If we understand this dual behavior well enough, it might be possible for a tax regime to manipulate its corporate tax rate without necessarily jeopardizing acceptability status of capital projects to providers of capital. The present paper is an attempt to model this dual impact of the corporate tax rate on the NPV of projects within the tax regime, and study the implications of the results for policy makers and for corporations facing such policy makers

Cost of living, Healthy Food Acquisition, and the Supplemental Nutrition Assistance Program

We tested the hypothesis that high costs of living, such as from high housing rents, reduce the healthfulness of food acquisitions. Using the National Household Food Acquisition and Purchase Survey (2012-13), we examined the relationships between cost of living and food acquisition patterns among both SNAP participants and non-participants (N = 5,414 individuals from households participating in SNAP, 3,863 individuals from non-participating households \u3c185% of the federal poverty threshold, and 5,036 individuals from non-participating households \u3e185% of the federal poverty threshold). Indices for cost of living included county-level Regional Price Parities for major classes of expenditures and the geographic adjustment to the Supplemental Poverty Measure, which is based on rent prices. We regressed the cost of living indices against measures of food acquisitions per person per day in each of several standard food categories, controlling for individual-, household-, and county-level characteristics. Using endogenous treatment effects models to potentially address unmeasured confounders influencing both the propensity to live in high-cost areas and patterns of food acquisition, we observed that higher area-level costs of living were associated with less healthy food acquisitions, including significantly fewer acquisitions of vegetables, fruits, and whole grains, and significantly greater acquisitions of refined grains, fats and oils, and added sugars. Overall, living in a high-cost area was associated with an 11% reduction in the Healthy Eating Index—a composite nutritional index previously associated with obesity, type II diabetes, and all-cause mortality. Additionally, we found that SNAP participation was associated with a significantly improvement in the healthfulness of food acquisitions among persons living in high-cost counties

Mixed-integer bilevel representability

We study the representability of sets that admit extended formulations using mixed-integer bilevel programs. We show that feasible regions modeled by continuous bilevel constraints (with no integer variables), complementarity constraints, and polyhedral reverse convex constraints are all finite unions of polyhedra. Conversely, any finite union of polyhedra can be represented using any one of these three paradigms. We then prove that the feasible region of bilevel problems with integer constraints exclusively in the upper level is a finite union of sets representable by mixed-integer programs and vice versa. Further, we prove that, up to topological closures, we do not get additional modeling power by allowing integer variables in the lower level as well. To establish the last statement, we prove that the family of sets that are finite unions of mixed-integer representable sets forms an algebra of sets (up to topological closures)

The Effect of Tobacco Control Measures during a Period of Rising Cardiovascular Disease Risk in India: A Mathematical Model of Myocardial Infarction and Stroke

Background: We simulated tobacco control and pharmacological strategies for preventing cardiovascular deaths in India, the country that is expected to experience more cardiovascular deaths than any other over the next decade. Methods and Findings: A microsimulation model was developed to quantify the differential effects of various tobacco control measures and pharmacological therapies on myocardial infarction and stroke deaths stratified by age, gender, and urban/rural status for 2013 to 2022. The model incorporated population-representative data from India on multiple risk factors that affect myocardial infarction and stroke mortality, including hypertension, hyperlipidemia, diabetes, coronary heart disease, and cerebrovascular disease. We also included data from India on cigarette smoking, bidi smoking, chewing tobacco, and secondhand smoke. According to the model's results, smoke-free legislation and tobacco taxation would likely be the most effective strategy among a menu of tobacco control strategies (including, as well, brief cessation advice by health care providers, mass media campaigns, and an advertising ban) for reducing myocardial infarction and stroke deaths over the next decade, while cessation advice would be expected to be the least effective strategy at the population level. In combination, these tobacco control interventions could avert 25% of myocardial infarctions and strokes (95% CI: 17%–34%) if the effects of the interventions are additive. These effects are substantially larger than would be achieved through aspirin, antihypertensive, and statin therapy under most scenarios, because of limited treatment access and adherence; nevertheless, the impacts of tobacco control policies and pharmacological interventions appear to be markedly synergistic, averting up to one-third of deaths from myocardial infarction and stroke among 20- to 79-y-olds over the next 10 y. Pharmacological therapies could also be considerably more potent with further health system improvements. Conclusions: Smoke-free laws and substantially increased tobacco taxation appear to be markedly potent population measures to avert future cardiovascular deaths in India. Despite the rise in co-morbid cardiovascular disease risk factors like hyperlipidemia and hypertension in low- and middle-income countries, tobacco control is likely to remain a highly effective strategy to reduce cardiovascular deaths. Please see later in the article for the Editors' Summar