Part I. Chromatography using ultra-stable metal oxide-based stationary phases for HPLC

The first part of the review contrasts the main drawbacks of silica-based packings such as their relative thermal and chemical instability with excellent stability of metal oxides. The paper concerns mainly ZrO2, TiO2 and Al2O3. Methods of preparation of spherical particles for HPLC are described. Surface chemistry of the oxides is, however, very different from that of silica. Ability of the oxides to ion- and ligand exchange is discussed from a chromatographic point of view.     

Studies on pyridazine azide cyclisation reactions

Reaction of sodium azide with 4-methyl-3,5,6-tribromopyridazine results in the formation of 3,5,6-triazide intermediate which could cyclise to give two possible bicyclic products while ab initio calculations show that the formation of a tricyclic compound is extremely energetically unfavourable. However, experimentally, only one major product is isolated. The structure of this unstable product has been conclusively established by X-ray crystallography as 3,5-diazido-4-methyl[1,5-b]tetrazolopyridazine confirming theoretical predictions.     

Polaroid operators and Weyl's theorem

``Polaroid elements" represent an attempt to abstract part of the condition, ``Weyl's theorem holds" for operators.

     

Uniqueness of travelling waves for nonlocal monostable equations

We consider a nonlocal analogue of the Fisher-KPP equation

0 ~{\rm on}~(0,1),\end{displaymath}">

and its discrete counterpart , , and show that travelling wave solutions of these equations that are bounded between and are unique up to translation. Our proof requires finding exact a priori asymptotics of a travelling wave. This we accomplish with the help of Ikehara's Theorem (which is a Tauberian theorem for Laplace transforms).

     

Self-assembly of chiral DNA nanotubes

A system of DNA "tiles" that is designed to assemble to form two-dimensional arrays is observed to form narrow ribbons several micrometers in length. The uniform width of the ribbons and lack of frayed edges lead us to propose that they are arrays that have curled and closed on themselves to form tubes. This proposal is confirmed by the observation of tubes with helical order.     

Forward scattering of pulses from a rough sea surface by Fourier synthesis of parabolic equation solutions

A variable depth step implementation of the range-dependent acoustic model (RAM) is applied to the modeling of forward scattering from a rough sea surface. The sea surface is treated within RAM simply as an internal interface between a water layer and an air upper halfspace. A comparison with a numerically exact integral equation is undertaken for the scattering of single frequencies from Pierson-Moskowitz sea surfaces. The method is extended to model the variability of linear frequency modulated pulses from a series of frozen sea surfaces in a shallow water waveguide. The subsequent effect of rough boundary scattering on the replica correlation process is investigated.     

A combined 14N/27Al nuclear magnetic resonance and powder X-ray diffraction study of impurity phases in beta-sialon ceramics

Beta-sialons are ceramic phases occurring in the SiO(2)-Si(3)N(4)-AlN-Al(2)O(3) system. A series of samples with differing compositions has been investigated by magic-angle spinning nuclear magnetic resonance (NMR) spectroscopy and powder X-ray diffraction (XRD). Although the constituent nitrogen nuclei occupy positions of low symmetry in the beta-sialon structure, 14N NMR spectra could be recorded for the samples examined. The origin of the 14N signal could be traced to the presence of an aluminium nitride (AlN) impurity phase with the help of 27Al NMR and XRD results. Similarly, the existence of Al(2)O(3) grains could be readily detected for a number of samples. Thus, the combination of 14N and 27Al NMR is shown to be an especially effective tool in identifying and characterizing impurity phases in sialon ceramics, complementing the results obtained from standard XRD analysis.     

Xenon clusters in intense VUV laser fields

A simple model is developed that quantitatively describes intense interactions of a vacuum ultraviolet (VUV) laser pulse with a xenon cluster. We find good agreement with a recent experiment [Nature (London) 420, 482 (2002)]]. In particular, the large number of VUV photons absorbed per atom, at intensities significantly below 10(16) W/cm(2), is now understood.