Nanoscale Equilibrium Crystal Shapes

The finite size and interface effects on equilibrium crystal shape (ECS) have been investigated for the case of a surface free energy density including step stiffness and inverse-square step-step interactions. Explicitly including the curvature of a crystallite leads to an extra boundary condition in the solution of the crystal shape, yielding a family of crystal shapes, governed by a shape parameter c. The total crystallite free energy, including interface energy, is minimized for c=0, yielding in all cases the traditional PT shape (z x3/2). Solutions of the crystal shape for c≠0 are presented and discussed in the context of meta-stable states due to the energy barrier for nucleation. Explicit scaled relationships for the ECS and meta-stable states in terms of the measurable step parameters and the interfacial energy are presented.Comment: 35 page

Profile scaling in decay of nanostructures

The flattening of a crystal cone below its roughening transition is studied by means of a step flow model. Numerical and analytical analyses show that the height profile, h(r,t), obeys the scaling scenario dh/dr = F(r t^{-1/4}). The scaling function is flat at radii r<R(t) \sim t^{1/4}. We find a one parameter family of solutions for the scaling function, and propose a selection criterion for the unique solution the system reaches.Comment: 4 pages, RevTex, 3 eps figure

The profile of a decaying crystalline cone

The decay of a crystalline cone below the roughening transition is studied. We consider local mass transport through surface diffusion, focusing on the two cases of diffusion limited and attachment-detachment limited step kinetics. In both cases, we describe the decay kinetics in terms of step flow models. Numerical simulations of the models indicate that in the attachment-detachment limited case the system undergoes a step bunching instability if the repulsive interactions between steps are weak. Such an instability does not occur in the diffusion limited case. In stable cases the height profile, h(r,t), is flat at radii r<R(t)\sim t^{1/4}. Outside this flat region the height profile obeys the scaling scenario \partial h/\partial r = {\cal F}(r t^{-1/4}). A scaling ansatz for the time-dependent profile of the cone yields analytical values for the scaling exponents and a differential equation for the scaling function. In the long time limit this equation provides an exact description of the discrete step dynamics. It admits a family of solutions and the mechanism responsible for the selection of a unique scaling function is discussed in detail. Finally we generalize the model and consider permeable steps by allowing direct adatom hops between neighboring terraces. We argue that step permeability does not change the scaling behavior of the system, and its only effect is a renormalization of some of the parameters.Comment: 25 pages, 18 postscript figure

Dewetting of an ultrathin solid film on a lattice-matched or amorphous substrate

An evolution partial differential equation for the surface of a non-wetting single-crystal film in an attractive substrate potential is derived and used to study the dynamics of a pinhole for the varying initial depth of a pinhole and the strengths of the potential and the surface energy anisotropy. The results of the simulations demonstrate how the corresponding parameters may lead to complete or partial dewetting of the film. Anisotropy of the surface energy, through faceting of the pinhole walls, is found to most drastically affect the time to film rupture. In particular, the similations support the conjecture that the strong anisotropy is capable of the complete suppression of dewetting even when the attractive substrate potential is strong.Comment: Submitted to PR

Aerosol-assisted CVD synthesis, characterisation and gas-sensing application of gold-functionalised tungsten oxide

Tungsten oxide nanoneedles (NNs) functionalised with gold nanoparticles (NPs) have been integrated with alumina gas-sensor platforms using a simple and effective co-deposition method via aerosol-assisted chemical vapour deposition (AACVD) utilising a novel gold precursor, (NH4)AuCl4. The gas-sensing results show that gold NP functionalisation of tungsten oxide NNs improves the sensitivity of response to ethanol, with sensitivity increasing and response time decreasing with increasing amount of gold

Percutaneous coronary intervention in Europe 1992-2003

peer reviewedAims: The purpose of this registry is to collect data on trends in interventional cardiology within Europe. Special interest focuses on relative increases and ratios in newer revascularization approaches and its distribution in different regions in Europe. We report the data of the year 2003 and give an overview of the development of coronary interventions since 1992, when the first data collection was performed. Methods and results: Questionnaires were distributed yearly to delegates of all national societies of cardiology represented in the European Society of Cardiology to collect the case numbers of all local institutions and operators. The overall numbers of coronary angiographies increased from 1992 to 2003 from 684,000 to 1,993,000 (from 1,250 to 3,500 per million inhabitants). The respective numbers for percutaneous coronary interventions (PCI-coronary angioplasty) and coronary stenting procedures increased from 184,000 to 733,000 (from 335 to 1,300) and from 3,000 to 610,000 (from 5 to 1,100), respectively. Germany has been the most active country for the past years with 653,000 angiographies (7,800), 222,000 angioplasties (2,500), and 180,000 stenting procedures (2,200) in 2003. The indication has shifted towards acute coronary syndromes, as demonstrated by raising rates of interventions for acute myocardial infarction over the last decade. The procedures are more readily performed and safer, as shown by increasing rate of “ad hoc” PCI and decreasing need for emergency coronary artery bypass surgery (CABG). In 2003, use of drug-eluting stents had further increased. However, an enormous variability is reported with the highest rate in Portugal (55%). Conclusion: Interventional cardiology in Europe is still expanding, mainly but not exclusively due to rapid growth in the eastern European countries. A number of new coronary revascularization procedures introduced over the years have all but disappeared. Only stenting has experienced an exponential growth. The same can be forecast for drug-eluting stenting