Loss Characteristics of TeraHertz Surface Waves on Laser Micromachined Textured Metals

For the application of geometrically-induced THz surface wave technology for communication and sensing, a critical analysis of the propagation characteristics (i.e. dispersion and attenuation) for different textured surfaces should be studied and benchmarked. For the broadband characterisation of archetypal textured surfaces (e.g. corrugated plane, two-dimensional array of blind holes and bed of nails) supporting THz transverse magnetic (i.e., p-polarized) surface waves, we employ time-domain spectroscopy and edge-diffraction coupling methods. Measurements of laser micromachined prototypes demonstrate strong frequency-dependent dispersion and the large impact that surface roughness of the order of few μm has on the path loss, increasing it by a factor ranging from 1.6 to 4.3 compared to smooth textured surfaces. Together with numerical modelling, we disentangle all loss mechanisms (namely, ohmic, scattering, propagation divergence and phase mismatch) and highlight the challenge of loss estimation due to surface roughness in highly confined THz surface waves

Loss Characteristics of TeraHertz Surface Waves on Laser Micromachined Textured Metals

For the application of geometrically-induced THz surface wave technology for communication and sensing, a critical analysis of the propagation characteristics (i.e. dispersion and attenuation) for different textured surfaces should be studied and benchmarked. For the broadband characterisation of archetypal textured surfaces (e.g. corrugated plane, two-dimensional array of blind holes and bed of nails) supporting THz transverse magnetic (i.e., p-polarized) surface waves, we employ time-domain spectroscopy and edge-diffraction coupling methods. Measurements of laser micromachined prototypes demonstrate strong frequency-dependent dispersion and the large impact that surface roughness of the order of few μm has on the path loss, increasing it by a factor ranging from 1.6 to 4.3 compared to smooth textured surfaces. Together with numerical modelling, we disentangle all loss mechanisms (namely, ohmic, scattering, propagation divergence and phase mismatch) and highlight the challenge of loss estimation due to surface roughness in highly confined THz surface waves

Microwave dielectric sensing of free-flowing, single, living cells in aqueous suspension

Dielectric measurements offer the possibility of highly sensitive detection of physical cell properties, and are of interest for clinical applications due to their non-destructive nature and the lack of need for cell labelling. Here we report sensitive measurements on single, living, free-flowing cells (not electrostatically or dielectrophoretically trapped, cultured or fixed directly on sensing elements) in aqueous medium at ~9.8 GHz taken using a coupled dielectric-split ring resonator assembly. Inductive coupling between the two resonators enabled separation of microfluidic chips from RF connectors and allowed for time-resolved continuous-wave measurements on flowing single cells via the coaxial ports of a dielectric-loaded microwave cavity. Analysis via an equivalent circuit model showed that the novel resonator assembly maintained the permittivity-dependent sensitivity of a split ring resonator while operating at quality factors >1000 with lossy aqueous media (typically ~1900). Using a microfluidic channel with a 300 x 300 μm cross section, at a water-loaded resonant amplitude of ~-22 dB at 0 dBm input power level, shifts in amplitude due to individual cells passing through the sensing region of up to -0.0015 dB were observed. Correlations between averaged amplitude shifts and cell size as well as material properties demonstrate the diagnostic potential of this technique

Weber and church governance: religious practice and economic activity

The debate about the relationship between religion and economic activity in the wake of Weber has been cast largely in terms of belief and values. This article suggests an alternative focus on practice. It argues that taken for granted practices of church governance formed to-hand resources for the organization of economic activity. The argument is developed through an examination of the historical development of church governance practices in the Presbyterian Church of Scotland, with particular emphasis on the way in which theological belief gave rise to practices of accountability and record keeping. In turn such practices contributed to a ‘culture of organization’ which had implications for economic activity. A focus on governance practices can help to illuminate enduring patterns of difference in the organization of economic activity

Creating and curating an archive: Bury St Edmunds and its Anglo-Saxon past

This contribution explores the mechanisms by which the Benedictine foundation of Bury St Edmunds sought to legitimise and preserve their spurious pre-Conquest privileges and holdings throughout the Middle Ages. The archive is extraordinary in terms of the large number of surviving registers and cartularies which contain copies of Anglo-Saxon charters, many of which are wholly or partly in Old English. The essay charts the changing use to which these ancient documents were put in response to threats to the foundation's continued enjoyment of its liberties. The focus throughout the essay is to demonstrate how pragmatic considerations at every stage affects the development of the archive and the ways in which these linguistically challenging texts were presented, re-presented, and represented during the Abbey’s history