What Happens When We Randomly Assign Children to Families?

I use a new data set of Korean-American adoptees who, as infants, were randomly assigned to families in the U.S. I examine the treatment effects from being assigned to a high income family, a high education family or a family with four or more children. I calculate the transmission of income, education and health characteristics from adoptive parents to adoptees. I then compare these coefficients of transmission to the analogous coefficients for biological children in the same families, and to children raised by their biological parents in other data sets. Having a college educated mother increases an adoptee's probability of graduating from college by 7 percentage points, but raises a biological child's probability of graduating from college by 26 percentage points. In contrast, transmission of drinking and smoking behavior from parents to children is as strong for adoptees as for non-adoptees. For height, obesity, and income, transmission coefficients are significantly higher for non-adoptees than for adoptees. In this sample, sibling gender composition does not appear to affect adoptee outcomes nor does the mix of adoptee siblings versus biological siblings.

A study of dependency features of spike trains through copulas

Simultaneous recordings from many neurons hide important information and the connections characterizing the network remain generally undiscovered despite the progresses of statistical and machine learning techniques. Discerning the presence of direct links between neuron from data is still a not completely solved problem. To enlarge the number of tools for detecting the underlying network structure, we propose here the use of copulas, pursuing on a research direction we started in [1]. Here, we adapt their use to distinguish different types of connections on a very simple network. Our proposal consists in choosing suitable random intervals in pairs of spike trains determining the shapes of their copulas. We show that this approach allows to detect different types of dependencies. We illustrate the features of the proposed method on synthetic data from suitably connected networks of two or three formal neurons directly connected or influenced by the surrounding network. We show how a smart choice of pairs of random times together with the use of empirical copulas allows to discern between direct and un-direct interactions

Random Graphs Associated to some Discrete and Continuous Time Preferential Attachment Models

We give a common description of Simon, Barab\'asi--Albert, II-PA and Price growth models, by introducing suitable random graph processes with preferential attachment mechanisms. Through the II-PA model, we prove the conditions for which the asymptotic degree distribution of the Barab\'asi--Albert model coincides with the asymptotic in-degree distribution of the Simon model. Furthermore, we show that when the number of vertices in the Simon model (with parameter $\alpha$) goes to infinity, a portion of them behave as a Yule model with parameters $(\lambda,\beta) = (1-\alpha,1)$, and through this relation we explain why asymptotic properties of a random vertex in Simon model, coincide with the asymptotic properties of a random genus in Yule model. As a by-product of our analysis, we prove the explicit expression of the in-degree distribution for the II-PA model, given without proof in \cite{Newman2005}. References to traditional and recent applications of the these models are also discussed

Colonialism and Modern Income -- Islands as Natural Experiments

Using a new database of islands throughout the Atlantic, Pacific and Indian Oceans we examine whether colonial origins affect modern economic outcomes. We argue that the nature of discovery and colonization of islands provides random variation in the length and type of colonial experience. We instrument for length of colonization using wind direction and wind speed. Wind patterns which mattered a great deal during the age of sail do not have a direct effect on GDP today, but do affect GDP via their historical impact on colonization. The number of years spent as a European colony is strongly positively related to the island's GDP per capita and negatively related to infant mortality. This basic relationship is also found to hold for a standard dataset of developing countries. We test whether this link is directly related to democratic institutions, trade, and the identity of the colonizing nation. While there is substantial variation in the history of democratic institutions across the islands, such variation does not predict income. Islands with significant export products during the colonial period are wealthier today, but this does not diminish the importance of colonial tenure. The timing of the colonial experience seems to matter. Time spent as a colony after 1700 is more beneficial to modern income than years before 1700, consistent with a change in the nature of colonial relationships over time.

How Do Friendships Form?

We examine how people form social networks among their peers. We use a unique dataset that tells us the volume of email between any two people in the sample. The data are from students and recent graduates of Dartmouth College. First year students interact with peers in their immediate proximity and form long term friendships with a subset of these people. This result is consistent with a model in which the expected value of interacting with an unknown person is low (making traveling solely to meet new people unlikely), while the benefits from interacting with the same person repeatedly are high. Geographic proximity and race are greater determinants of social interaction than are common interests, majors, or family background. Two randomly chosen white students interact three times more often than do a black student and a white student. However, placing the black and white student in the same freshman dorm increases their frequency of interaction by a factor of three. A traditional "linear in group means" model of peer ability is only a reasonable approximation to the ability of actual peers chosen when we form the groups around all key factors including distance, race and cohort.

First passage times of two-correlated processes: analytical results for the Wiener process and a numerical method for diffusion processes

Given a two-dimensional correlated diffusion process, we determine the joint density of the first passage times of the process to some constant boundaries. This quantity depends on the joint density of the first passage time of the first crossing component and of the position of the second crossing component before its crossing time. First we show that these densities are solutions of a system of Volterra-Fredholm first kind integral equations. Then we propose a numerical algorithm to solve it and we describe how to use the algorithm to approximate the joint density of the first passage times. The convergence of the method is theoretically proved for bivariate diffusion processes. We derive explicit expressions for these and other quantities of interest in the case of a bivariate Wiener process, correcting previous misprints appearing in the literature. Finally we illustrate the application of the method through a set of examples.Comment: 18 pages, 3 figure

Sublingual sufentanil, a new opportunity for the improvement of postoperative pain management in Italy

Despite the availability of national and international guidelines, adequate postoperative pain (POP) management is still a challenge in Italy. One of the potential reasons for the high incidence of surgical patients complaining moderate to severe pain is the difficult application of the currently recommended analgesic techniques in clinical practice. In particular, morphine, the most commonly used systemic opioid in the POP treatment, has some unfavorable pharmacodynamic and pharmacokinetic characteristics for POP management, suggesting a potential relevant improvement by using different opioids. Many of sufentanil properties make it particularly suitable for POP control: a high affinity for the µ opioid receptor, the highest therapeutic index compared to any other opioid used in clinical practice and the absence of clinically relevant active metabolites. The elevated potency, together with the high lipophilicity of sufentanil, allow the preparation of a nanotablet, 3 mm of diameter and 0.75 mm of thickness, containing 15 µg of active drug. The sublingual route allows a longer time of drug plasmatic permanence in comparison to IV route, overcoming the need for continuous dosing. The patient-controlled system, considered in the present review, is preprogrammed to deliver one sublingual tablet of sufentanil with a 20-minute lockout period with a radiofrequency identification thumb tag allowing only the patient to activate the on demand button. Phase II and III studies have assessed the efficacy of this system in POP management, showing that it was considered more satisfactory than the IV PCA morphine system by both patients and nurses. The introduction of this simple and innovative system of patient-controlled analgesic administration could represent an opportunity for Italy to update the current practice in POP management