Quantitative modeling of near-field interactions incorporating polaritonic and electrostatic effects.

As scattering-scanning near-field optical microscopy (s-SNOM) continues to grow in prominence, there has been great interest in modeling the near-field light-matter interaction to better predict experimental results. Both analytical and numerical models have been developed to describe the near-field response, but thus far models have not incorporated the full range of phenomena accessible. Here, we present a finite element model (FEM), capable of incorporating the complex physical and spatial phenomena that s-SNOM has proved able to probe. First, we use electromagnetic FEM to simulate the multipolar response of the tip and illustrate the impact of strong coupling on signal demodulation. We then leverage the multiphysics advantage of FEM to study the electrostatic effect of metallic tips on semiconductors, finding that THz s-SNOM studies are most impacted by this tip-induced band-bending. Our model is computationally inexpensive and can be tailored to specific nanostructured systems and geometries of interest.

Time-dependence of nuclear magnetic resonance quadrupole interactions for polymers under shear.

We consider the problem of performing NMR spectroscopy under conditions of flow, a central issue in Rheo-NMR. By way of example, the effects of rotational motion on the deuterium NMR spectrum are considered for Couette cell experiments involving deformation of polymers under shearing conditions. The polymer was modelled as a power law fluid and for each streamline, the spin Hamiltonian evolved to allow for flow reorientation. The gap-integral spectra are compared with the 'ideal' spectra for a polymer under shear, but without reorientation. It is found that flow does affect the shape of the deuterium spectra, as well as slightly perturbing the splittings.

Denture satisfaction and clinical performance in a paediatric population.

OBJECTIVES: The objectives of this study were to investigate the clinical performance of partial upper dentures in children and to assess reported denture satisfaction in this young population. DESIGN: This was a retrospective study using patients' dental records in conjunction with a postal questionnaire. SETTING: The Paediatric Dentistry Clinic, School of Clinical Dentistry, Sheffield. SAMPLE AND METHODS: Fifty-eight children (aged 7-17 years) who had been provided with a partial upper denture to replace one or more missing permanent incisors were included in the study. The patients' dental records were examined for the following details: tooth type missing, presence of retained incisor roots, aetiology of tooth absence, age at which the denture was first provided, total time period dentures had been worn, and frequency and type of any denture repairs or replacements. Next a short questionnaire was sent to each child, which sought an evaluation of several parameters of denture satisfaction including: overall attitude towards wearing a denture, denture appearance, ease of eating, comfort and perceived degree of teasing from peers. Visual analogue scales (VAS) were employed to provide a graded response. RESULTS: 70.7% of subjects had a single missing incisor and trauma was the most common cause of tooth loss (77.3%). The mean age at which patients started wearing a denture was 11.6 years and the mean length of time dentures had been worn, at the time of the investigation, was 2.1 years. A 'T-shaped' denture was most commonly employed (77.5% of dentures). Overall, 36.2% of subjects had required at least one denture repair, 28.2% presenting within a year of denture provision. One or more denture replacements had been received by 60.3% of the patients, and 43.6% had required this within a year. Component failure was highest for the denture tooth (40% of repairs) and a change in the patient's dentition necessitated a denture remake in 66% of cases. VAS scores for parameters of denture satisfaction indicated an overall positive evaluation of the dentures, with the most positive response relating to ease of eating. However, the reported degree of teasing was high and increased with time. The only significant difference for denture satisfaction according to gender was for mastication: girls reportedly found eating easier than did boys. CONCLUSION: Children are generally accepting of upper partial dentures, but their poor clinical performance is of concern and there is need for improvement.