Quantification of dislocation nucleation stress in TiN through high-resolution in situ indentation experiments and first principles calculations

Through in situ indentation of TiN in a high-resolution transmission electron microscope, the nucleation of full as well as partial dislocations has been observed from {001} and {111} surfaces, respectively. The critical elastic strains associated with the nucleation of the dislocations were analyzed from the recorded atomic displacements, and the nucleation stresses corresponding to the measured critical strains were computed using density functional theory. The resolved shear stress was estimated to be 13.8 GPa for the partial dislocation 1/6 <110> {111} and 6.7 GPa for the full dislocation ½ <110> {110}. Such an approach of quantifying nucleation stresses for defects via in situ high-resolution experiment coupled with density functional theory calculation may be applied to other unit processes.

Magnesium and the acute physician

Magnesium deficiency, and to a lesser extent magnesium excess, is commonly encountered in patients admitted to the Acute Medical Unit. It is important that acute physicians are able to identify those at risk of these states and initiate appropriate investigation and treatment. This article aims to provide the reader with a sound understanding of magnesium physiology and its effect at a cellular level. The causes, symptoms and treatment of magnesium disorders are discussed along with a review of evidence regarding the therapeutic use of magnesium.

Transforming insulating rutile single crystal into a fully ordered nanometer-thick transparent semiconductor

Rutile single crystals treated with ion-beam preferential etching (IBPE) are investigated with electrical transport and transmission electron microscopy. The initially insulating single crystals show the formation of an oxygen vacancy-rich, highly ordered, thin conducting layer, below a crystalline rutile TiO(2) surface layer. Carrier concentrations of 10(19) cm(-3) and very high mobilities of the order of 300 cm(2) V(-1) s(-1) are observed in the nanolayers. The observations indicate that rutile single crystals can be effectively transformed into controlled conducting material using IBPE for creating a new breakthrough in transparent conducting media.

Limitations of typhoid vaccination for travellers

Around one-third of travellers to endemic areas receive pre-travel typhoid vaccination, increasingly with the new parenteral vaccination Typhim Vi (Mérieux). More than 200 cases of Salmonella typhi and S. paratyphi infection are imported into the UK each year. Despite the widespread use of immunisation, non-specialist clinicians and the travelling public do not appear to fully appreciate the limitations of currently available vaccination. These limitations are not adequately highlighted in either the Green Book of Immunisation against Infectious Diseases (HMSO, 1992) or the new handbook Health Information for Overseas Travel (HMSO, 1995) which are important sources of reference for clinicians and practice nurses. This may delay consideration of diagnosis and presentation for treatment in immunised travellers.