An experiment-based model for the petrogenesis of high-alumina basalts

To understand magmatism at convergent margins, one must know the origin of their characteristic, plagioclase-rich, high-alumina basalts (HABs). Wet melting experiments on basalts at 3 kilobars yielded high-alumina liquids and a coexisting mineral assemblage with little or no plagioclase. An isothermal pressure drop to 1 kilobar caused 20 to 30 percent plagioclase crystallization in these melts, while mafic minerals underwent limited crystallization or even resorption. These results suggest that hydrous (>/=4 percent H(2)O) HAB liquids, presumably formed by fractionation of a hydrous basalt at depth, will precipitate voluminous plagioclase as pressure drops during ascent and eruption. Plagioclase accumulation is not necessarily required to explain the petrogenesis of plagioclase-rich HAB.     

Soft-tissue vessels and cellular preservation in Tyrannosaurus rex

Soft tissues are preserved within hindlimb elements of Tyrannosaurus rex (Museum of the Rockies specimen 1125). Removal of the mineral phase reveals transparent, flexible, hollow blood vessels containing small round microstructures that can be expressed from the vessels into solution. Some regions of the demineralized bone matrix are highly fibrous, and the matrix possesses elasticity and resilience. Three populations of microstructures have cell-like morphology. Thus, some dinosaurian soft tissues may retain some of their original flexibility, elasticity, and resilience.     

Comparative genomics of trypanosomatid parasitic protozoa

A comparison of gene content and genome architecture of Trypanosoma brucei, Trypanosoma cruzi, and Leishmania major, three related pathogens with different life cycles and disease pathology, revealed a conserved core proteome of about 6200 genes in large syntenic polycistronic gene clusters. Many species-specific genes, especially large surface antigen families, occur at nonsyntenic chromosome-internal and subtelomeric regions. Retroelements, structural RNAs, and gene family expansion are often associated with syntenic discontinuities that-along with gene divergence, acquisition and loss, and rearrangement within the syntenic regions-have shaped the genomes of each parasite. Contrary to recent reports, our analyses reveal no evidence that these species are descended from an ancestor that contained a photosynthetic endosymbiont.