Exploring the returns to scale in food preparation (baking penny buns at home)

We show that as household size increases, households substitute away from prepared foods and towards ingredients. They also devote more time to food preparation. These observations (1) are consistent with a simple model with home production, returns to scale in the time input to food preparation, and varieties of food that differ in the required time input; (2) support the idea that returns to scale in home production are an important source of returns to scale in consumption; and (3), mean that across household sizes, household market expenditures on food are not proportional to food consumption quantities. The latter may provide a partial explanation for a puzzle raised by Deaton and Paxson.Household returns to scale, home production, food preparation

The neutron charge form factor in helium-3

In order to measure the charge form factor of the neutron, $G^n_E(Q^2)$, one needs to use a neutron bound in a nuclear target. We calculate the change in the form factor for a neutron bound in $^3He$, with respect to the free case, using several versions of the quark meson coupling model. It is found that the form factor may be suppressed by as much as 12% at $Q^2 = 0.5{GeV}^2$ with respect to that of the free neutron.Comment: 13 pages including 2 ps figure

Quantum fluctuations and isotope effects in ab initio descriptions of water

Nuclear quantum effects, such as zero-point energy and tunneling, cause significant changes to the structure and dynamics of hydrogen bonded systems such as liquid water. However, due to the current inability to simulate liquid water using an exact description of its electronic structure, the interplay between nuclear and electronic quantum effects remains unclear. Here we use simulations that incorporate the quantum mechanical nature of both the nuclei and electrons to provide a fully ab initio determination of the particle quantum kinetic energies, free energy change upon exchanging hydrogen for deuterium and the isotope fractionation ratio in water. These properties, which selectively probe the quantum nature of the nuclear degrees of freedom, allow us to make direct comparison to recent experiments and elucidate how electronic exchange and correlation and nuclear quantum fluctuations determine the structure of the hydrogen bond in water.Comment: 8 pages, 2 figures, 2 table

Exploring the Returns to Scale in Food Preparation (Baking Penny Buns at Home)

We show that as household size increases, households substitute away from prepared foods and towards ingredients. They also devote more time to food preparation. These observations (1) are consistent with a simple model with home production, returns to scale in the time input to food preparation, and varieties of food that differ in the required time input; (2) support the idea that returns to scale in home production are an important source of returns to scale in consumption; and (3), mean that across household sizes, household market expenditures on food are not proportional to food consumption quantities. The latter may provide a partial explanation for a puzzle raised by Deaton and Paxson.household returns to scale; home production; food preparation

Exploring the Returns-to-Scale in Food Preparation

We show that as household size increases, households substitute away from prepared foods and towards ingredients. They also devote more time to food preparation. These observations (1) are consistent with a simple model with home production, returns to scale in the time input to food preparation, and varieties of food that differ in the required time input; (2) support the idea that returns to scale in home production are an important source of returns to scale in consumption; and (3), mean that across household sizes, household market expenditures on food are not proportional to food consumption quantities. The latter may provide a partial explanation for a puzzle raised by Deaton and Paxson.

An MDL approach to the climate segmentation problem

This paper proposes an information theory approach to estimate the number of changepoints and their locations in a climatic time series. A model is introduced that has an unknown number of changepoints and allows for series autocorrelations, periodic dynamics, and a mean shift at each changepoint time. An objective function gauging the number of changepoints and their locations, based on a minimum description length (MDL) information criterion, is derived. A genetic algorithm is then developed to optimize the objective function. The methods are applied in the analysis of a century of monthly temperatures from Tuscaloosa, Alabama.Comment: Published in at http://dx.doi.org/10.1214/09-AOAS289 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org