Experiments with calibrated digital sideband separating downconversion

This article reports on the first step in a focused program to re-optimize radio astronomy receiver architecture to better take advantage of the latest advancements in commercial digital technology. Specifically, an L-Band sideband-separating downconverter has been built using a combination of careful (but ultimately very simple) analog design and digital signal processing to achieve wideband downconversion of an RFI-rich frequency spectrum to baseband in a single mixing step, with a fixed-frequency Local Oscillator and stable sideband isolation exceeding 50 dB over a 12 degree C temperature range.Comment: 10 pages, 12 figures, to be published in PAS

Full Open Population Capture-Recapture Models with Individual Covariates

Traditional analyses of capture-recapture data are based on likelihood functions that explicitly integrate out all missing data. We use a complete data likelihood (CDL) to show how a wide range of capture-recapture models can be easily fitted using readily available software JAGS/BUGS even when there are individual-specific time-varying covariates. The models we describe extend those that condition on first capture to include abundance parameters, or parameters related to abundance, such as population size, birth rates or lifetime. The use of a CDL means that any missing data, including uncertain individual covariates, can be included in models without the need for customized likelihood functions. This approach also facilitates modeling processes of demographic interest rather than the complexities caused by non-ignorable missing data. We illustrate using two examples, (i) open population modeling in the presence of a censored time-varying individual covariate in a full robust-design, and (ii) full open population multi-state modeling in the presence of a partially observed categorical variable

Fat Taxes and Thin Subsidies: Distributional Impacts and Welfare Effects

The extant literature on fat taxes and thin subsidies tends to focus on the overall effectiveness of such fiscal instruments in altering diets and improving health. However, little is known about the welfare impacts of fiscal food policies on society. This paper fills a gap in the literature by assessing the distributional impacts and welfare effects resulting from a tax-subsidy combination on different food groups. Using the methods derived from marginal tax reform theory, a formal welfare economics framework is developed allowing the calculation of the distributional characteristics of various food groups and approximate welfare measures of prices changes caused by a tax-subsidy combination. The distributional characteristics reveal that many of the food groups target by a fat tax are consumed in greater concentration by low-income households than higher-income households. The overall welfare effect of a fat tax and thin subsidy combination is found to be negative, meaning that the thin subsidy is not enough to compensate for the negative impacts of the fat tax.distributional characteristic, fat tax, obesity, thin subsidy, welfare., Health Economics and Policy, D30, D60, H20, I10, I30.,

The Impacts of Fat Taxes and Thin Subsidies on Nutrient Intakes

This paper examines the health effects of a fiscal food policy based on a combination of fat taxes and thin subsidies. The fat tax is based on the saturated fat content of food items while the thin subsidy is applied to select fruit and vegetable items. The policy is designed to be revenue neutral so the subsidy exactly offsets the revenue from the fat tax. A model of food demand is estimated using Bayesian methods that accounts for censoring and infrequency of purchase (the problem of unit values is also discussed). The estimated demand elasticities are used to compute nutrient elasticities which demonstrate how consumption of specific nutrients changes based on price changes in particular foods from the fiscal policy. Results show that although the fat tax decreases saturated fat intake, consumption of other important nutrients is also decreased, which may lead to negative health outcomes.fat tax, nutrient elasticities, obesity, thin subsidy, Food Consumption/Nutrition/Food Safety, D30, D60, H20, I10, I30,

A Relative Position Code for Saccades in Dorsal Premotor Cortex

Spatial computations underlying the coordination of the hand and eye present formidable geometric challenges. One way for the nervous system to simplify these computations is to directly encode the relative position of the hand and the center of gaze. Neurons in the dorsal premotor cortex (PMd), which is critical for the guidance of arm-reaching movements, encode the relative position of the hand, gaze, and goal of reaching movements. This suggests that PMd can coordinate reaching movements with eye movements. Here, we examine saccade-related signals in PMd to determine whether they also point to a role for PMd in coordinating visual–motor behavior. We first compared the activity of a population of PMd neurons with a population of parietal reach region (PRR) neurons. During center-out reaching and saccade tasks, PMd neurons responded more strongly before saccades than PRR neurons, and PMd contained a larger proportion of exclusively saccade-tuned cells than PRR. During a saccade relative position-coding task, PMd neurons encoded saccade targets in a relative position code that depended on the relative position of gaze, the hand, and the goal of a saccadic eye movement. This relative position code for saccades is similar to the way that PMd neurons encode reach targets. We propose that eye movement and eye position signals in PMd do not drive eye movements, but rather provide spatial information that links the control of eye and arm movements to support coordinated visual–motor behavior

On the Eikonal Approximation in AdS Space

We explore the eikonal approximation to graviton exchange in AdS_5 space, as relevant to scattering in gauge theories. We restrict ourselves to the regime where conformal invariance of the dual gauge theory holds, and to large 't Hooft coupling where the computation involves pure gravity. We give a heuristic argument, a direct loop computation, and a shock wave derivation. The scalar propagator in AdS_3 plays a key role, indicating that even at strong coupling, two-dimensional conformal invariance controls high-energy four-dimensional gauge-theory scattering.Comment: 22 pages, 2 figures; published version: updated references and several clarifying remarks adde

Impact of Income on Calorie and Nutrient Intakes: A Cross-Country Analysis

The relationship between income and nutrient intake is explored. Nonparametric, panel, and quantile regressions are used. Engle curves for calories, fat, and protein are approximately linear in logs with carbohydrate intakes exhibiting diminishing elasticities as incomes increase. Elasticities range from 0.10 to 0.25, with fat having the highest elasticities. Countries in higher quantiles have lower elasticities than those in lower quantiles. Results predict significant cumulative increases in calorie consumption which are increasingly composed of fats. Though policies aimed at poverty alleviation and economic growth may assuage hunger and malnutrition, they may also exacerbate problems associated with obesity.calorie and nutrient consumption, food and nutrition policy, income elasticities, nonparametric, panel, quantile regression., Agricultural and Food Policy, Food Consumption/Nutrition/Food Safety, Food Security and Poverty, International Development, Research Methods/ Statistical Methods, C11, C14, C21, C23, O10, O47, Q18,