Viral respiratory tract infections and asthma in early life: cause and effect?

Interactions between viral respiratory tract infections in infancy and childhood, and asthma development and exacerbation, are complex and intriguing. This review aims to unravel some of these complexities. Does severe respiratory viral infection early in life predispose to later asthma development, or is it indicative of a predisposition to allergic respiratory disease? How could variables such as age and severity of viral infection affect the interaction between respiratory viral infections and asthma? How could respiratory viral infection drive allergic sensitization? Here, we review the evidence surrounding these questions, and discuss current and future research and therapeutic approaches targeting the interplay between viral respiratory tract infection and asthma.

27Al multiple-quantum MAS NMR of mechanically treated bayerite (alpha-Al(OH)3) and silica mixtures.

Two-dimensional 27Al multiple-quantum magic angle spinning (MQMAS) NMR experiments are used to study mixtures of bayerite (alpha-Al(OH)3) with either silicic acid (SiO2.nH2O) or silica gel (SiO2) that have been ground together for varying lengths of time. This mechanical treatment produces changes in the 27Al MAS and MQMAS NMR spectra that correspond to the formation of new Al species. Mean values of the quadrupolar interaction (PQ) and isotropic chemical shift (deltacs) are extracted from the two-dimensional 27Al NMR spectra for each of these species. The presence of significant distributions of both 27Al quadrupolar and chemical shift parameters is demonstrated and the effect of grinding duration on the magnitudes of these distributions is discussed.

Effect of lanthanides on the relaxation rates of 89Y and 29Si in yttrium silicon oxynitride phases.

Additions of paramagnetic lanthanides are found to increase the relaxation rates of both 89Y and 29Si in the yttrium silicon oxynitride compounds Y2Si3N4O3 (N-melilite) and Y4Si2O7N2 (J-phase), allowing the observation of previously unreported 89Y magic-angle spinning nuclear magnetic resonance spectra of these phases. The dependence of the 89Y and 29Si relaxation rates was determined as a function of Yb3+ and Gd3+ concentration. Both the 29Si and 89Y resonances become broader with increasing Yb concentration, but at all lanthanide concentrations the 89Y spectrum of J-phase is broader than that of N-melilite, possibly due to a greater distribution of Y site geometries in the former. At concentrations below about 360 mumol g-1, the lanthanide ions appear to be incorporated in the lattice, but are not involved in covalent bonding to Y or Si. The effect of a series of lanthanides on the 89Y and 29Si relaxation rates and line widths is presented in terms of the lanthanide spin quantum numbers and magnetic moments. The most effective lanthanide was found to be Eu3+, giving fast relaxation (particularly for 89Y) and sharp lines.

Titanium carbide, nitride and carbonitrides: a 13C, 14N, 15N and 47,49Ti solid-state nuclear magnetic resonance study.

The first 47,49Ti, 13C, 14N and 15N solid-state nuclear magnetic resonance (NMR) spectra of titanium carbide, nitride and a series of cubic carbonitrides have been obtained under both static and magic-angle spinning (MAS) conditions. The 15N samples were isotopically enriched by gas-solid exchange at 1000 degrees C in a closed system. The Ti spectra of the carbide and nitride are sharp, reflecting the well defined cubic symmetry of these compounds, but become considerably broadened in the carbonitride series, with the spectra being approximately the sum of TiC and TiN together with some small electric field gradient (EFG) effects. The resonance positions and widths of all the NMR spectra change as carbon is progressively replaced by nitrogen. A relationship is observed between the 13C chemical shift and the nitrogen content of the carbonitrides, suggesting a possible NMR method for estimating the composition of these compounds. Although electron paramagnetic resonance (EPR) spectra of all these compounds show typically metallic behaviour, the NMR spectra show few effects attributable to conduction electrons, probably due to the lack of s-orbital contributions to the conduction band.