The shifting trajectory of growth in femur length during gestation

Bone size is a determinant of bone strength and tracks in its percentile of origin during childhood and adolescence. We hypothesized that the ranking of an individual's femur length (FL) is established in early gestation and tracks thereafter. Fetal FL was measured serially using 2D ultrasound in 625 Norwegian fetuses. Tracking was assessed using Pearson correlation, a generalized estimating equation model, and by calculating the proportion of fetuses whose FL remained within the same quartile. Baseline FL Z-score (weeks 10 to 19) and later measurements correlated, but more weakly as gestation advanced: r = 0.59 (weeks 20 to 26); r = 0.45 (weeks 27 to 33); and r = 0.32 (weeks 34 to 39) (p<0.001). Tracking within the same quartile throughout gestation occurred in 13% of fetuses. Of the 87% deviating, 21% returned to the quartile of origin, so 34% began and ended in the same quartile, 38% deviated by one quartile, and 28% deviated by two or more quartiles by the end of gestation. A standard deviation higher baseline FL Z-score, placental weight (150 g), maternal height (5 cm), and weight (10 kg), was associated with a 0.25, 0.15, 0.10, and 0.05 SD higher FL Z-score at the end of gestation, respectively (p ranging from <0.001 to 0.02). Tracking within the same percentile throughout the whole of gestation, as suggest by growth charts, is uncommon. Deviation from tracking is more common and is the result of changes in growth velocity within and between fetuses and is partly influenced by maternal, fetal, and placental factors. © 2010 American Society for Bone and Mineral Research

US foreign aid, interstate rivalry, and incentives for counterterrorism cooperation

A common strategy pursued by states targeted by international terrorism is to provide economic and military assistance to the states that host this activity. This is thought to increase their willingness and capacity to crack down on terrorism, but very little work to date has looked at whether this strategy actually leads to desirable outcomes. This article offers an explanation for why a strategy of foreign aid-for-counterterrorism can be successful in some contexts, but counterproductive in situations in which recipients have more pressing strategic priorities. Specifically, I argue that host states receiving US foreign aid that are involved in an ongoing interstate rivalry will use the aid to arm against their rival, rather than to undertake counterterrorism. These states thus have an incentive not to disarm terrorist groups, but rather to play-up the threat from terrorism in order to continue receiving aid concessions. Using data on US foreign aid and terrorist activity in recipient countries, I employ a series of duration and count models to demonstrate that, while US foreign aid can help to decrease terrorist activity in non-rivalrous states, the opposite is true in states with at least one rival