RESUMEN
The self-assembly and self-organization of water molecules are relevant in many fields of research. When water spontaneously reacts with 2,2,6,6-tetra-methyl-piperidine (TMP) to form colourless and crystalline discrete needles, only in the exact ratio of 2:1, it is important to understand the phenomenon. Single-crystal X-ray and neutron diffraction data have unveiled that TMP self-assembles around columns of water molecules, and as such, the resulting adduct may be described as a series of molecular water pipes.
RESUMEN
A simple method for the preparation of bromoferrocenes from stannylferrocenes is described: the preparation of 1,1'-dibromoferrocene is used as an example. Stannylferrocenes are reacted with bromine directly in dichloromethane to give bromoferrocenes in a self-indicating titration reaction. Also, an enhanced method of removal of the highly soluble organotin tin by-products formed in the preparation of 1,1'-diiodoferrocene from 1,1'-tri-n-butylstannylferrocene is reported allowing the preparation of large-scale quantities of 1,1'-diiodoferrocene, which is one of the most important starting materials in ferrocene chemistry.
RESUMEN
During 2015-2016, record temperatures triggered a pan-tropical episode of coral bleaching, the third global-scale event since mass bleaching was first documented in the 1980s. Here we examine how and why the severity of recurrent major bleaching events has varied at multiple scales, using aerial and underwater surveys of Australian reefs combined with satellite-derived sea surface temperatures. The distinctive geographic footprints of recurrent bleaching on the Great Barrier Reef in 1998, 2002 and 2016 were determined by the spatial pattern of sea temperatures in each year. Water quality and fishing pressure had minimal effect on the unprecedented bleaching in 2016, suggesting that local protection of reefs affords little or no resistance to extreme heat. Similarly, past exposure to bleaching in 1998 and 2002 did not lessen the severity of bleaching in 2016. Consequently, immediate global action to curb future warming is essential to secure a future for coral reefs.
