M?ssbauer spectroscopy: recent developments

In this review I have emphasized two basic points. First, M?ssbauer spectroscopy has been widely used as a tool for basic research in solid-state physics, chemical structure, and magnetism. Second, the technique has been applied to many analytical and materials science problems where the nature of the sample prevents the use of more traditional approaches. M?ssbauer spectroscopy research on frozen solutions, colloids, interface chemistry, and crystallographic transformations can be expected to increase rapidly in the next few years.     

Profile. The risks--and rewards--of war zone research

Gulu, about 4 hours north of here by car, is in an "upcountry" region torn by armed conflict. So upcountry clinical researchers like Matthew Lukwiya, a native of the Gulu district, play a critical role--and win high praise from their colleagues.     

Control of Aggregation in Dictyostelium discoideum by an External Periodic Pulse of Cyclic Adenosine Monophosphate

We have induced and controlled normal aggregation of Dictyostelium discoideum amoebas by electrophoretic release of pulses of cyclic adenosine monophosphate from a microelectrode. This has yielded information about the sequence of development of aggregation competences during interphase. We believe that modifications of the technique will have wide application in investigations of other developing systems.     

The effect of algal symbionts on the accuracy of Sr/Ca paleotemperatures from coral

The strontium-to-calcium ratio (Sr/Ca) of reef coral skeleton is commonly used as a paleothermometer to estimate sea surface temperatures (SSTs) at crucial times in Earth's climate history. However, these estimates are disputed, because uptake of Sr into coral skeleton is thought to be affected by algal symbionts (zooxanthellae) living in the host tissue. Here, we show that significant distortion of the Sr/Ca temperature record in coral skeleton occurs in the presence of algal symbionts. Seasonally resolved Sr/Ca in coral without symbionts reflects local SSTs with a temperature sensitivity equivalent to that of laboratory aragonite precipitated at equilibrium and the nighttime skeletal deposits of symbiotic reef corals. However, up to 65% of the Sr/Ca variability in symbiotic skeleton is related to symbiont activity and does not reflect water temperature.