Properties of Chaotic and Regular Boundary Crisis in Dissipative Driven Nonlinear Oscillators

The phenomenon of the chaotic boundary crisis and the related concept of the chaotic destroyer saddle has become recently a new problem in the studies of the destruction of chaotic attractors in nonlinear oscillators. As it is known, in the case of regular boundary crisis, the homoclinic bifurcation of the destroyer saddle defines the parameters of the annihilation of the chaotic attractor. In contrast, at the chaotic boundary crisis, the outset of the destroyer saddle which branches away from the chaotic attractor is tangled prior to the crisis. In our paper, the main point of interest is the problem of a relation, if any, between the homoclinic tangling of the destroyer saddle and the other properties of the system which may accompany the chaotic as well as the regular boundary crisis. In particular, the question if the phenomena of fractal basin boundary, indeterminate outcome, and a period of the destroyer saddle, are directly implied by the structure of the destroyer saddle invariant manifolds, is examined for some examples of the boundary crisis that occur in the mathematical models of the twin-well and the single-well potential nonlinear oscillators.     

NMR detection of intermolecular NH.OP hydrogen bonds between guanidinium protons and bisposphonate moieties in an artificial arginine receptor

Hydrogen bonding plays a major role in the selective recognition of guanidinium groups by receptor molecules. The present NMR investigation provides direct experimental evidence of hydrogen bonds in an artificial arginine receptor complex consisting of alpha-N-benzoylarginine ethyl ester and a bisphosphonate tweezers molecule. trans-Hydrogen bond 2hJHP couplings between the phosphonate moieties and individual guanidinium protons as well as the amide proton have been detected by [1H,31P]-HMBC and [31P,1H]-INEPT experiments. The detected hydrogen bonding network in the investigated artificial arginine receptor shows a symmetrical end-on interaction of the guanidinium moiety, which enables concerted rotations and deviates from the structure proposed for the biological arginine fork.     

Synthetic infrared spectra

We have designed, microfabricated, and characterized a diffractive optical element that reproduces the infrared spectrum of HF from 3600 to 4300 cm(-1) . The reflection-mode diffractive optic consists of 4096 lines, each 4.5mum wide, at 16 discrete depths relative to the substrate from 0 to 1.2 mum and was fabricated upon a silicon wafer by anisotropic reactive ion-beam etching in a four-mask-level process. We envisage the use of diffractive optical elements of this type as the basis for a new class of miniaturized, remote chemical sensor systems based on correlation spectroscopy.