Agricultural Prices, Food Consumption and the Health and Productivity of Farmers

Demand and Price Analysis, Farm Management, Food Consumption/Nutrition/Food Safety,

Estimating the Intrafamily Incidence of Health: Child Illness and Gender Inequality in Indonesian Households

In this paper, we demonstrate the difficulties of identifying both the own- and cross-effects of health on the allocation of time within a household, and develop and implement a method for estimating the effects of infant morbidity on the differential allocation of time by other family members based on discrete indicators of health and of activity participation commonly available in survey data. Estimates obtained from Indonesian household data indicate that inattention to problems of the measurement and endogeneity of health leads to a substantial underestimate of the effects of variations in child morbidity on the intrahousehold division of labor, and our estimates that take into account the "simultaneity" of health-activity associations indicate that increased levels of infant morbidity significantly exacerbate existing differentials in work-home time allocations across teenage boys and girls in Indonesia.Consumer/Household Economics, Health Economics and Policy,

The Selectivity of Fertility and the Determinants of Human Capital Investments: Parametric and Semi-Parametric Estimates

In this paper we assess the importance of heterogeneity and selective fertility in altering estimates and interpretations of the determinants of the human capital of children. We set out a sequential model of human capital investments in children incorporating endogenous fertility and heterogeneity in human capital endowments to illustrate the fertility selection problem and issues of identification. Empirical results based on parametric and semi-parametric estimates of selectivity models applied to data on birthweight and schooling in Malaysia indicate that the hypothesis of no fertility selection is strongly rejected, with mothers having higher birthweight children tending to have substantially lower birth probabilities (negative birth selectivity). As a consequence, the positive association between mother's schooling and birthweight is substantially underestimated and the positive effects of delaying childbearing overestimated when birth selectivity is not taken into account. The schooling results indicate strong rejection of the "efficient schooling" model, in which schooling is allocated efficiently across children, but only when the selectivity of fertility is taken into account.Labor and Human Capital,

The use of snowcovered area in runoff forecasts

Long-term snowcovered area data from aircraft and satellite observations have proven useful in reducing seasonal runoff forecast error on the Kern river watershed. Similar use of snowcovered area on the Kings river watershed produced results that were about equivalent to methods based solely on conventional data. Snowcovered area will be most effective in reducing forecast procedural error on watersheds with: (1) a substantial amount of area within a limited elevation range; (2) an erratic precipitation and/or snowpack accumulation pattern not strongly related to elevation; and (3) poor coverage by precipitation stations or snow courses restricting adequate indexing of water supply conditions. When satellite data acquisition and delivery problems are resolved, the derived snowcover information should provide a means for enhancing operational streamflow forecasts for areas that depend primarily on snowmelt for their water supply

Multiple duplications of yeast hexose transport genes in response to selection in a glucose-limited environment

When microbes evolve in a nutrient-limited environment, natural selection can be predicted to favor genetic changes that give cells greater access to limiting substrate. We analyzed a population of baker\u27s yeast that underwent 450 generations of glucose-limited growth. Relative to the strain used as the inoculum, the predominant cell type at the end of this experiment sustains growth at significantly lower steady-state glucose concentrations and demonstrates markedly enhanced cell yield per mole glucose, significantly enhanced high-affinity glucose transport, and greater relative fitness in pairwise competition. These changes are correlated with increased levels of mRNA hybridizing to probe generated from the hexose transport locus HXT6. Further analysis of the evolved strain reveals the existence of multiple tandem duplications involving two highly similar, high-affinity hexose transport loci, HXT6 and HXT7. Selection appears to have favored changes that result in the formation of more than three chimeric genes derived from the upstream promoter of the HXT gene and the coding sequence of HXT6. We propose a genetic mechanism to account for these changes and speculate as to their adaptive significance in the context of gene duplication as a common response of microorganisms to nutrient limitation

Novel Studies on the \eta' Effective Lagrangian

The effective Lagrangian for \eta' incorporating the effect of the QCD \theta-angle has been developed previously. We revisit this Lagrangian and carry out its canonical quantization with particular attention to the test function spaces of constraints and the topology of the \eta'-field. In this way, we discover a new chirally symmetric coupling of this field to chiral multiplets which involves in particular fermions. This coupling violates P and T symmetries. In a subsequent paper, we will evaluate its contribution to the electric dipole moment (EDM) of fermions. Our motivation is to test whether the use of mixed states restores P and T invariance, so that EDM vanishes. This calculation will be shown to have striking new physical consequences.Comment: 14 pages, 1 figure; V2: NEW TITLE; revised version to be published in JHEP; references adde

Navy composite maintenance and repair experience

The Navy has been a strong proponent of composites for aircraft structure. Fleet use of composites started with the F-14 in the early 1970's and has steadily increased. This experience base provides sufficient information to allow an evaluation of the maintenance performance of polymer composites in service. A summary is presented of the Navy's experience with maintenance of composite structure. The general types of damage experienced in the fleet as well as specific examples of composite damage to aircraft is described. The impact of future designs on supportability is also discussed

Energy Loss of a High Charge Bunched Electron Beam in Plasma

There has been much interest in the blowout regime of plasma wakefield acceleration (PWFA), which features ultra-high fields and nonlinear plasma motion. Using an exact analysis, we examine here a fundamental limit of nonlinear PWFA excitation, by an infinitesimally short, relativistic electron beam. The beam energy loss in this case is shown to be linear in charge even for nonlinear plasma response, where a normalized, unitless charge exceeds unity. The physical basis for this effect is discussed, as are deviations from linear behavior observed in simulations with finite length beams.Comment: Submitted to Physical Review Letter