1. Introduction. In [5] Mazur constructed a homotopy 4-sphere which looked like one of the strongest candidates for a counterexample to the 4-dimensional Poincaré Conjecture. In this paper we show that Mazur's example is in fact a true 4-sphere after all. This raises the odds in favour of the 4-dimensional Poincaré Conjecture. The proof involves a smooth knot of S2 in S4 with unusual properties.

Crystal engineering is discussed, along with its three key concepts: crystal packing; the design of solids; and physical and chemical properties.

Carbon is a major player in the evolutionary scheme of the universe because of its abundance and its ability to form complex species. It is also a key element in the evolution of prebiotic molecules. The different forms of cosmic carbon are reviewed ranging from carbon atoms and carbon-bearing molecules to complex, solid-state, carbonaceous structures. The current state of knowledge is assessed...

a National Engineering Laboratory of Soil Nutrient Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China b Soil Erosion and Degradation Research Group, Department of Geography, University of Valencia, Valencia, Spain c Soil Physics and Land Management Group, Wageningen University, Droevendaalsesteeg 4, 6708PB Wageningen, The Netherlands d University of Ch...

We generalize graded Hecke algebras to include a twisting twococycle for the associated finite group. We give examples where the parameter spaces of the resulting twisted graded Hecke algebras are larger than that of the graded Hecke algebras. We prove that twisted graded Hecke algebras are particular types of deformations of a crossed product.

The vast majority of protein sequences are aperiodic; they do not have any strong bias in the amino acid composition, and they use a subtle mixture of all or most of the 20 amino acid residues to code a great number of various structures and functions. In this context, homorepeats, runs of a single amino acid residue, represent unusual, eye-catching motifs in proteins. Despite the sequence simp...

Oligostatins C, D and E, three new antibiotics were found in the culture filtrate of Streptomyces myxogenes nov. sp. SF-1130. Their spectral and chemical properties suggested that oligostatins were basic oligosaccharide antibiotics. They exhibited not only antibacterial activity but also strong amylase inhibitory activity.