The search for medieval parallels and for medieval roots in New World history has become a fascinating genre. My own university has produced one of the major figures in this field, Lynn White, Jr., and has recently honored another, Luis Weckmann. With the Columbus centennial rushing toward us, we may expect more exercises in their spirit. Such an approach is not farfetched or whimsical. We are the heirs of medieval technology and mentalities. In both, as White has reminded us, the United States may be “closer to the Middle Ages than is Europe.“ And the great historian Shelomo Goitein, after spending most of his working life in pre-Nazi Germany and then in Israel, upon moving to the United States was startled to recognize the medieval flavor of our social structures and mentalities; as a lifelong student of the Middle Ages, he found that “one feels quite at home“ here.

The growth kinetics of cholesterol gallstones have been studied by growing crystals from melted gallstones. The resulting microstructures are spherulitic which is essentially the same as the structures seen in natural gallstones prior to melting. The cholesterol crystals when observed in hot stage microscopy emerge from a unique nucleation center growing radially in the [001] direction with constant rate. The DSC thermograph of a natural gallstone is initially similar to that of cholesterol monohydrate. Upon melting, cholesterol monohydrate changes to anhydrous cholesterol; both forms are crystalline and exhibit polymorphic transformations. Synthetic stones grown from cholesterol were anhydrous and have a phase change at temperatures close to human body temperature. Optical microscopy established that this phase transformation cracks the spherulitic crystals perpendicular to the fast growth direction. Thermal expansion measurements demonstrate that upon heating, the low density, low temperature phase is transformed to a high density phase. This phase transformation and repeated cracking may prove to be useful in destroying natural gallstones, while suppressing this transformation and its associated cracking might aid in securing other solid cholesterol deposits within the human body.

Thermal conductivity measurements were performed on several amorphous rare earth transition metal thin films of varying microstructure. The thermal conductivity perpendicular to the plane of the film, measured by the thermal comparator method, was compared with the thermal conductivity value measured parallel to the plane of the film. The latter value was obtained by converting electrical conductivity values to thermal conductivity via the Wiedemann–Franz relationship. As expected, the columnar microstructure induced during the sputter deposition of the thin films causes an anisotropy in the thermal conductivity values, with the in-plane values consistently lower than the out-of-plane values. The effect is most pronounced for the more columnar films deposited at higher pressure, for which the in-plane thermal conductivity, 0.3 W/mK, is an order of magnitude lower than the out-of-plane thermal conductivity, 4.3 W/mK. The thermal conductivity out of the plane of the film decreased with increasing deposition pressure, due to the decreasing film density.