Research on pressure sensors for biomedical instruments

The development of a piezo-resistive pressure transducer is discussed suitable for recording pressures typically encountered in biomedical applications. The pressure transducer consists of a thin silicon diaphragm containing four strain-sensitive resistors, and is fabricated using silicon monolithic integrated-circuit technology. The pressure transducers can be as small as 0.7 mm outer diameter, and are, as a result, suitable for mounting at the tip of a catheter. Pressure-induced stress in the diaphragm is sensed by the resistors, which are interconnected to form a Wheatstone bridge

Excitation Chains at the Glass Transition

The excitation-chain theory of the glass transition, proposed in an earlier publication, predicts diverging, super-Arrhenius relaxation times and, {\it via} a similarly diverging length scale, suggests a way of understanding the relations between dynamic and thermodynamic properties of glass-forming liquids. I argue here that critically large excitation chains play a role roughly analogous to that played by critical clusters in the droplet model of vapor condensation. The chains necessarily induce spatial heterogeneities in the equilibrium states of glassy systems; and these heterogeneities may be related to stretched-exponential relaxation. Unlike a first-order condensation point in a vapor, the glass transition is not a conventional phase transformation, and may not be a thermodynamic transition at all.Comment: 4 pages, no figure

Some Finite Size Effects in Simulations of Glass Dynamics

We present the results of a molecular dynamics computer simulation in which we investigate the dynamics of silica. By considering different system sizes, we show that in simulations of the dynamics of this strong glass former surprisingly large finite size effects are present. In particular we demonstrate that the relaxation times of the incoherent intermediate scattering function and the time dependence of the mean squared displacement are affected by such finite size effects. By compressing the system to high densities, we transform it to a fragile glass former and find that for that system these types of finite size effects are much weaker.Comment: 12 pages of RevTex, 4 postscript figures available from W. Ko

Slow Dynamics in Ion-Conducting Sodium Silicate Melts: Simulation and Mode-Coupling Theory

A combination of molecular-dynamics (MD) computer simulation and mode-coupling theory (MCT) is used to elucidate the structure-dynamics relation in sodium-silicate melts (NSx) of varying sodium concentration. Using only the partial static structure factors from the MD as an input, MCT reproduces the large separation in relaxation time scales of the sodium and the silicon/oxygen components. This confirms the idea of sodium diffusion channels which are reflected by a prepeak in the static structure factors around 0.95 A^-1, and shows that it is possible to explain the fast sodium-ion dynamics peculiar to these mixtures using a microscopic theory.Comment: 4 pages, 4 figure

Exploring the Grocery Store Satisfaction of England's Older Population: An Evaluation of Antecedents and Consequences Using Structural Equation Modelling

The number of people aged 60 years and above is increasing in the UK. In total, this age group represents 22% of the population with estimates indicating a rise to 29% by 2050 (United Nations, 2009). One market sector that is extremely important to the health and wellbeing of older people is grocery retail (Khan, 1981). However, little previous research has addressed how older people rate the service delivered by their grocery provider, particularly in regard to satisfaction. To reconcile this gap in theoretical understanding, a sequential transformative mixed-method research design was specified using 36 qualitative interviews and quantitative questionnaires with 524 subjects. A model including both drivers and consequences of satisfaction was formulated using past research. As such, an antecedent scale for grocery store image was developed via procedures suggested in the extant literature (e.g. DeVellis, 2003). Pre-existing scales (i.e. commitment and loyalty) representing exemplary reliability and validity were borrowed and specified as consequences. The scales were modified and integrated into a ‘structural equation model’. Older people were found to place a high level of importance in aspects of merchandise, store environment, personnel and services. Price/promotions and clientele were found to be insignificant in driving satisfaction. Differences in factor mean scores and structural parameters were then analysed using ‘finite mixture structural equation modelling’ to identify segments of similar respondents (Jedidi et al, 1997). Using posterior probabilities, the emerging segments were subjected to profiling using personal and behavioural variables (Hahn et al, 2002). Market Segmentation showed three groups of similar respondents in the sample population, differing in factor mean scores and psychological operationalisation of satisfaction. Nonetheless, only several differences in personal and behavioural characteristics were found between the segments. Whilst, the results show that segmenting this group is necessary when measuring satisfaction, basing this purely on a priori descriptive variables might be erroneous given the inherent levels of unobserved heterogeneity. The model developed and tested in this study is considered the most up-to-date available in the literature

Private Accounts and Social Security: The Issue of Risk

Robert J. Angell, DBA, is a professor of finance. Department of Business Administration, North Carolina Agricultural and Technical State University, Greensboro, North Carolina 27411

Interface free energies in p-spin glass models

The replica method has been used to calculate the interface free energy associated with the change from periodic to anti-periodic boundary conditions in finite-dimensional p-spin glass models in the phase which at mean-field level has one-step replica symmetry breaking (1RSB). In any finite dimension the interface free energy is exponentially small for a large system. This result implies that in finite dimensions, the 1RSB state does not exist, as it is destroyed by thermal excitation of arbitrarily large droplets. The implications of this for the theory of structural glasses are discussed.Comment: 4 page