Dinuclear complexes of a pseudocalixarene macrocycle: structural consequences of intramolecular hydrogen bonding

A series of dinuclear complexes of a pseudocalixarene macrocycle H6L containing two 2,2'-methylenediphenol groups have been synthesised and structurally characterised. Using divalent metal ions, complexes containing a common hyperbolic paraboloid (saddle) M2(H4L)2+ core are formed. The structure is controlled by two strong O-H-O interactions resulting from metal ion-promoted monodeprotonation of the methylenediphenol units. The metal ions are located in a cleft within which neutral or anionic guests can bind. Use of trivalent metal ions leads to complete deprotonation of the phenol groups and loss of the saddle conformation.     

Hölder Exponent for a Two-Parameter Lévy Process

We study the regularity of a two-parameter Lévy process in the neighbourhood of a fixed point and then we compute the Hölder exponent of such a process.     

A survey of the Szegő equation

Science China Mathematics - We survey the main properties of the cubic Szegő equation from the PDE viewpoint, emphasising global existence of smooth solutions, analytic regularity, growth of...     

Sluggish light for radio-frequency true-time-delay applications with a large time-bandwidth product

A new radio-frequency (RF) photonic technique for achieving large RF time delays has been experimentally demonstrated using femtosecond pulses modulated by an acousto-optic tunable filter in a frequency-mapped and Doppler-shifted modulation scheme. A short optical delay line with length of 240 mum produces nearly 3 micros RF time delay after optical heterodyne detection, resulting in an effective slow-light velocity of 86 m/s. A delay-to-pulse-width ratio of 20 based on this technique has been observed, with a larger fractional delay foreseeable.     

Lithium solvation and diffusion in the 1‐butyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquid

The Raman spectra of (1 − x)(BMITFSI), xLiTFSI ionic liquids, where 1‐butyl‐3‐methylimidazolium cation (BMI⁺) and bis(trifluoromethane‐sulfonyl)imide anion (TFSI⁻) are analyzed for LiTFSI mole fractions x < 0.4. As expected from previous studies on similar TFSI‐based systems, most lithium ions are shown to be coordinated within [Li(TFSI)₂]⁻ anionic clusters. The variation of the self‐diffusion coefficients of the ¹H, ¹⁹F, and ⁷Li nuclei, measured by pulsed‐gradient spin‐echo NMR (PGSE‐NMR) as a function of x, can be rationalized in terms of the weighted contribution of BMI⁺ cations, TFSI⁻ ‘free’ anions, and [Li(TFSI)₂]⁻ anionic clusters. This implies a negative transference number for lithium. Copyright © 2008 John Wiley & Sons, Ltd.     

Encapsulation of magnetic self-assembled systems in thermoreversible gels

We describe two different ways of encapsulating within the fibrils of thermoreversible polymer gels the filaments of a supermolecular polymer formed by self-assembly of a bicopper complex. Heterogeneous nucleation is brought about with gels made from isotactic poly(styrene) while compound formation occurs with gels made from poly(hexyl isocyanate). These ways depend upon the interaction between the wings of the supermolecular polymer and the side groups of the polymer. In all cases, the filaments retain their 1-D structure. Preliminary results from magnetic susceptibility measurements show a striking difference between the pure and the encapsulated supermolecular polymer.