Flags of almost affine codes and the two-party wire-tap channel of type II

We describe a two-party wire-tap channel of type II in the framework of almost affine codes. Its cryptological performance is related to some relative profiles of a pair of almost affine codes. These profiles are analogues to relative generalized Hamming weights in the linear case.     

Large-scale finite-wavelength modulation within turbulent shear flows

We show that turbulent "spirals" and "spots" observed in Taylor-Couette and plane Couette flow correspond to a turbulence-intensity modulated finite-wavelength pattern which in every respect fits the phenomenology of coupled noisy Ginzburg-Landau (amplitude) equations with noise. This suggests the existence of a long-wavelength instability of the homogeneous turbulence regime.     

Noncovalent Modulation of Chemoselectivity in the Gas Phase Leads to a Switchover in Reaction Type from Heterolytic to Homolytic to Electrocyclic Cleavage

In the gas phase, thermal activation of supramolecular assemblies such as host–guest complexes leads commonly to noncovalent dissociation into the individual components. Chemical reactions, for example of encapsulated guest molecules, are only found in exceptional cases. As observed by mass spectrometry, when 1-amino-methyl-2,3-diazabicyclo[2.2.2]oct-2-ene (DBOA) is complexed by the macrocycle β-cyclodextrin, its protonated complex undergoes collision-induced dissociation into its components, the conventional reaction pathway. Inside the macrocyclic cavity of cucurbit[7]uril (CB7), a competitive chemical reaction of monoprotonated DBOA takes place upon thermal activation, namely a stepwise homolytic covalent bond cleavage with the elimination of N₂, while the doubly protonated CB7⋅DBOA complex undergoes an inner-phase elimination of ethylene, a concerted, electrocyclic ring-opening reaction. These chemical reaction pathways stand in contrast to the gas-phase chemistry of uncomplexed monoprotonated DBOA, for which an elimination of NH₃ predominates upon collision-induced activation, as a heterolytic bond cleavage reaction. The combined results, which can be rationalized in terms of organic-chemical reaction mechanisms and density-function theoretical calculations, demonstrate that chemical reactions in the gas phase can be steered chemoselectively through noncovalent interactions.     

Synthesis of complex oligosaccharides by using a mutated (1,3)-beta-D-glucan endohydrolase from barley

Complex oligosaccharides with newly formed (1,3)-beta-glycosidic linkages were obtained in good to excellent yields when substituted or unsubstituted alpha-laminaribiosyl fluorides, acting as donors, were condensed onto mono- and disaccharide beta-D-hexopyranoside acceptors by using a (1,3)-beta-D-glycosynthase. These linear and branched (1,3)-beta-linked oligosaccharides could prove to be important in a range of medical, pharmaceutical, and agricultural applications. Furthermore, the observation that the (1,3)-beta-D-glucan glycosynthase accommodates (1,3)-, (1,4),- and (1,6)-beta-oligosaccharides in its acceptor subsites suggests novel, yet unexpected physiological roles for the wild type (1,3)-beta-D-glucan endohydrolase from higher plants.