Predicting the Orientation of Adsorbed Proteins Steered with Electric Fields Using a Simple Electrostatic Model.

Under the most common experimental conditions, the adsorption of proteins to solid surfaces is a spontaneous process that leads to a rather compact layer of randomly oriented molecules. However, controlling such orientation is critically important for the development of catalytic surfaces. In this regard, the use of electric fields is one of the most promising alternatives. Our work is motivated by experimental observations that show important differences in catalytic activity of a trypsin-covered surface, which depended on the applied potential during the adsorption. Even though adsorption results from the combination of several processes, we were able to determine that (under the selected conditions) mean-field electrostatics play a dominant role, determining the orientation and yielding a difference in catalytic activity. We simulated the electrostatic potential numerically, using an implicit-solvent model based on the linearized Poisson-Boltzmann equation. This was implemented in an extension of the code PyGBe that included an external electric field, and rendered the electrostatic component of the solvation free energy. Our model (extensions available at the Github repository) allowed estimating the overall affinity of the protein with the surface, and their most likely orientation as a function of the potential applied. Our results show that the active sites of trypsin are, on average, more exposed when the electric field is negative, which agrees with the experimental results of catalytic activity, and confirm the premise that electrostatic interactions can be used to control the orientation of adsorbed proteins.

The children of the missed pill.

We assess the impact of exogenous variation in oral contraceptives prices-a year-long decline followed by a sharp increase due to a documented collusion case-on fertility decisions and newborns' outcomes. Our empirical strategy follows an interrupted time-series design, which is implemented using multiple sources of administrative information. As prices skyrocketed (45% within a few weeks), the Pill's consumption plunged, and weekly conceptions increased (3.2% after a few months). We show large effects on the number of children born to unmarried mothers, to mothers in their early twenties, and to primiparae women. The incidence of low birth weight and fetal/infant deaths increased (declined) as the cost of birth control pills rose (fell). In addition, we document a disproportional increase in the weekly miscarriage and stillbirth rates. As children reached school age, we find lower school enrollment rates and higher participation in special education programs. Our evidence suggests these "extra" conceptions were more likely to face adverse conditions during critical periods of development.

Cost-benefit analysis of a micronutrient supplementation and early childhood stimulation program in Nicaragua.

This paper estimates the cost-benefit ratio for an integrated early childhood development program in Nicaragua (PAININ). Using longitudinal data, we estimate the average treatment effects of PAININ including micronutrient sprinkles on the prevalence of anemia and hemoglobin levels among disadvantaged children aged 6-36 months. We also estimate the effects of PAININ excluding sprinkles on cognitive outcomes among children aged 2.5-5 years. In the younger age group the program reduced anemia by 4 percentage points after 8 months and nearly 6 percentage points after 1 year; the latter is a 26% decrease in anemia. In the older age group, the program improved verbal and numeric memory after a year and a half, but the effects were modest (0.13 SD). When analyzing its potential impact on earnings, we conclude that the discounted annual costs of the program per child are less than the discounted annual increase in beneficiary earnings. Specifically, we estimate a cost-benefit ratio of 1.50 from the PAININ plus sprinkles package. Our sensitivity analysis suggests a range for this ratio between 1.30 and 2.30.

Economic perspectives on integrating early child stimulation with nutritional interventions.

There is a strongly held view that a narrow window exists for effective nutritional interventions and a widely known stylized depiction of age-dependent economic rates of returns to investments in cognitive and socioemotional development. Both indicate critical periods in early life. Moreover, the fact that both the physical and cognitive development of a child in these early years are highly dependent on childcare practices and on the characteristics of the caregivers motivates an interest in finding effective means to enhance stimulation in the context of nutritional programs, or vice versa. Nevertheless, there is relatively little evidence to date on how to align integrated interventions to these age-specific patterns and how to undertake benefit-cost analyses for integrated interventions. Thus, many core questions need further consideration in order to design integrated nutritional and stimulation programs. This paper looks at some of these questions and provides some guidelines as to how the economic returns from joint nutrition and stimulation programs might be estimated.

Do as You're Told! Facets of Agreeableness and Early Adult Outcomes for Inner-City Boys.

With data from the middle cohort of the Pittsburgh Youth Study, a prospective longitudinal study of inner-city boys, we examined whether Big Five agreeableness facets could be reliably recovered in this sample, and whether facets predicted educational, occupational, social, and antisocial life outcomes assessed a decade later. Caregivers described their adolescent boys' personalities using the Common California Q-Set; twelve years later, participants were interviewed and court records were obtained. Factor analyses recovered two facets: compliance and compassion. Compliance predicted more schooling and lower risk of unemployment, teenage fatherhood, and crime; compassion related to longer committed relationships. Findings highlight the value of studying personality at the facet level.

Testing the Correlated Random Coefficient Model.

The recent literature on instrumental variables (IV) features models in which agents sort into treatment status on the basis of gains from treatment as well as on baseline-pretreatment levels. Components of the gains known to the agents and acted on by them may not be known by the observing economist. Such models are called correlated random coe cient models. Sorting on unobserved components of gains complicates the interpretation of what IV estimates. This paper examines testable implications of the hypothesis that agents do not sort into treatment based on gains. In it, we develop new tests to gauge the empirical relevance of the correlated random coe cient model to examine whether the additional complications associated with it are required. We examine the power of the proposed tests. We derive a new representation of the variance of the instrumental variable estimator for the correlated random coefficient model. We apply the methods in this paper to the prototypical empirical problem of estimating the return to schooling and nd evidence of sorting into schooling based on unobserved components of gains.

Comparing IV With Structural Models: What Simple IV Can and Cannot Identify.

This paper compares the economic questions addressed by instrumental variables estimators with those addressed by structural approaches. We discuss Marschak's Maxim: estimators should be selected on the basis of their ability to answer well-posed economic problems with minimal assumptions. A key identifying assumption that allows structural methods to be more informative than IV can be tested with data and does not have to be imposed.

THE EDUCATION-HEALTH GRADIENT.

In this paper, we determine the role played by early cognitive, noncognitive, and health endowments. We identify the causal effect of education on health and health-related behaviors. We develop an empirical model of schooling choice and post-schooling outcomes, where both schooling and the outcomes determined in part by schooling are influenced by measured early family environments and latent capabilities (cognitive, noncognitive and health). We show that family background characteristics, and cognitive, noncognitive, and health endowments developed by age 10, are important determinants of labor market and health disparities at age 30. Not properly accounting for personality traits overestimates the importance of cognitive ability in determining adult health. Selection on factors determined early in life explains more than half of the observed difference by education in poor health, depression, and obesity. Education has an important causal effect in explaining differences in many adult outcomes and healthy behaviors. We uncover significant gender differences. We go beyond the current literature which typically estimates mean effects to compute distributions of treatment effects. We show how the health returns to education can vary among individuals who are similar with respect to their observed characteristics, and how a mean effect can hide gains and losses for different individuals. Our research highlights the important role played by the early years in producing health.

Measuring the Impact of Financial Intermediation: Linking Contract Theory to Econometric Policy Evaluation.

We study the impact that financial intermediation can have on productivity through the alleviation of credit constraints in occupation choice and/or an improved allocation of risk, using both static and dynamic structural models as well as reduced form OLS and IV regressions. Our goal in this paper is to bring these two strands of the literature together. Even though, under certain assumptions, IV regressions can recover accurately the true model-generated local average treatment effect, these are quantitatively different, in order of magnitude and even sign, from other policy impact parameters (e.g., ATE and TT). We also show that laying out clearly alternative models can guide the search for instruments. On the other hand adding more margins of decision, i.e., occupation choice and intermediation jointly, or adding more periods with promised utilities as key state variables, as in optimal multi-period contracts, can cause the misinterpretation of IV as the causal effect of interest.

Use of instrumental variables in the presence of heterogeneity and self-selection: an application to treatments of breast cancer patients.

Instrumental variable (IV) methods are widely used in the health economics literature to adjust for hidden selection biases in observational studies when estimating treatment effects. Less attention has been paid in the applied literature to the proper use of IVs if treatment effects are heterogeneous across subjects and individuals select treatments based on expected idiosyncratic gains or losses from treatments. In this paper we compare conventional IV analysis with alternative approaches that use IVs to estimate treatment effects in models with response heterogeneity and self-selection. Instead of interpreting IV estimates as the effect of treatment at an unknown margin of patients, we identify the marginal patients and we apply the method of local IVs to estimate the average treatment effect and the effect on the treated on 5-year direct costs of breast-conserving surgery and radiation therapy compared with mastectomy in breast cancer patients. We use a sample from the Outcomes and Preferences in Older Women, Nationwide Survey which is designed to be representative of all female Medicare beneficiaries (aged 67 or older) with newly diagnosed breast cancer between 1992 and 1994. Our results reveal some of the advantages and limitations of conventional and alternative IV methods in estimating mean treatment effect parameters.