X-ray photometry

I describe a method for synthesizing photometric passbands for use with current and future X-ray instruments. The method permits the standardisation of X-ray passbands and thus X-ray photometry between different instruments and missions. The method is illustrated by synthesizing a passband in the XMM-Newton EPIC pn which is similar to the ROSAT PSPC 0.5-2 keV band.Comment: Accepted for publication in MNRA

An exploratory study of creating dementia-friendly businesses in the visitor economy : Evidence from the UK

© 2019 Published by Elsevier Ltd.Many governments have promoted the development of a civil society to encourage citizen involvement in addressing many of the grand social challenges such as the growing prevalence of dementia, as ageing becomes a major trend in developed societies. One outcome has been the development of Dementia Friendly Communities, created via Dementia Action Alliances (DAAs) in England, to enhance awareness, care and the experience of people with dementia in accessing services and facilities. These initiatives are based on engaging the business community and yet no research studies have examined this theme to date. Given the growing significance of leisure and tourism activities that people with dementia and family members engage in, this study examines the experience of business engagement with DAAs in the visitor economy in England. The notion of shared value articulated by Porter and Kramer (2011) is used as a basis for understanding the type of business engagement.Peer reviewedFinal Published versio

An English language interface for constrained domains

The Multi-Satellite Operations Control Center (MSOCC) Jargon Interpreter (MJI) demonstrates an English language interface for a constrained domain. A constrained domain is defined as one with a small and well delineated set of actions and objects. The set of actions chosen for the MJI is from the domain of MSOCC Applications Executive (MAE) Systems Test and Operations Language (STOL) directives and contains directives for signing a cathode ray tube (CRT) on or off, calling up or clearing a display page, starting or stopping a procedure, and controlling history recording. The set of objects chosen consists of CRTs, display pages, STOL procedures, and history files. Translation from English sentences to STOL directives is done in two phases. In the first phase, an augmented transition net (ATN) parser and dictionary are used for determining grammatically correct parsings of input sentences. In the second phase, grammatically typed sentences are submitted to a forward-chaining rule-based system for interpretation and translation into equivalent MAE STOL directives. Tests of the MJI show that it is able to translate individual clearly stated sentences into the subset of directives selected for the prototype. This approach to an English language interface may be used for similarly constrained situations by modifying the MJI's dictionary and rules to reflect the change of domain

The astacin metalloprotease moulting enzyme NAS-36 is required for normal cuticle ecdysis in free-living and parasitic nematodes

Nematodes represent one of the most abundant and species-rich groups of animals on the planet, with parasitic species causing chronic, debilitating infections in both livestock and humans worldwide. The prevalence and success of the nematodes is a direct consequence of the exceptionally protective properties of their cuticle. The synthesis of this cuticle is a complex multi-step process, which is repeated 4 times from hatchling to adult and has been investigated in detail in the free-living nematode, Caenorhabditis elegans. This process is known as moulting and involves numerous enzymes in the synthesis and degradation of the collagenous matrix. The nas-36 and nas-37 genes in C. elegans encode functionally conserved enzymes of the astacin metalloprotease family which, when mutated, result in a phenotype associated with the late-stage moulting defects, namely the inability to remove the preceding cuticle. Extensive genome searches in the gastrointestinal nematode of sheep, Haemonchus contortus, and in the filarial nematode of humans, Brugia malayi, identified NAS-36 but not NAS-37 homologues. Significantly, the nas-36 gene from B. malayi could successfully complement the moult defects associated with C. elegans nas-36, nas-37 and nas-36/nas-37 double mutants, suggesting a conserved function for NAS-36 between these diverse nematode species. This conservation between species was further indicated when the recombinant enzymes demonstrated a similar range of inhibitable metalloprotease activities

The cuticle

The nematode cuticle is an extremely flexible and resilient exoskeleton that permits locomotion via attachment to muscle, confers environmental protection and allows growth by molting. It is synthesised five times, once in the embryo and subsequently at the end of each larval stage prior to molting. It is a highly structured extra-cellular matrix (ECM), composed predominantly of cross-linked collagens, additional insoluble proteins termed cuticlins, associated glycoproteins and lipids. The cuticle collagens are encoded by a large gene family that are subject to strict patterns of temporal regulation. Cuticle collagen biosynthesis involves numerous co- and post-translational modification, processing, secretion and cross-linking steps that in turn are catalysed by specific enzymes and chaperones. Mutations in individual collagen genes and their biosynthetic pathway components can result in a range of defects from abnormal morphology (dumpy and blister) to embryonic and larval death, confirming an essential role for this structure and highlighting its potential as an ECM experimental model system

Optimizing the Throughput of Particulate Streams Subject to Blocking

Filtration, flow in narrow channels and traffic flow are examples of processes subject to blocking when the channel conveying the particles becomes too crowded. If the blockage is temporary, which means that after a finite time the channel is flushed and reopened, one expects to observe a maximum throughput for a finite intensity of entering particles. We investigate this phenomenon by introducing a queueing theory inspired, circular Markov model. Particles enter a channel with intensity $\lambda$ and exit at a rate $\mu$. If $N$ particles are present at the same time in the channel, the system becomes blocked and no more particles can enter until the blockage is cleared after an exponentially distributed time with rate $\mu^*$. We obtain an exact expression for the steady state throughput (including the exiting blocked particles) for all values of $N$. For $N=2$ we show that the throughput assumes a maximum value for finite $\lambda$ if $\mu^*/\mu < 1/4$. The time-dependent throughput either monotonically approaches the steady state value, or reaches a maximum value at finite time. We demonstrate that, in the steady state, this model can be mapped to a previously introduced non-Markovian model with fixed transit and blockage times. We also examine an irreversible, non-Markovian blockage process with constant transit time exposed to an entering flux of fixed intensity for a finite time and we show that the first and second moments of the number of exiting particles are maximized for a finite intensity.Comment: 20 pages, 13 figure

Factors affecting low temperature performance of zirconia gas sensors.

A reduction in the operation temperature of zirconia ceramic gas sensors is highly desirable for a number of practical reasons. This work seeks to investigate the factors that prevent a reduction in operation temperature and propose methods by which these may be resolved. A novel approach to sensor fabrication has been developed and employed with the advantage of reduced device complexity that should lead to subsequent cost and reliability benefits. Leakage rates in these devices have been shown to be small and electrochemical in origin. Leakage was greater than reported for gold seal devices, partly due to increased electrode activity. The flexibility of device configuration allows a variety of sensor geometries and functions to be realised. This flexibility led to the characterisation of sensors at the upper and lower ends of measurement range and the identification of deviations from theoretical performance. These deviations have been reconciled with theory extended to cover these limits. Such sensors are known to be sensitive to reducible gas species such as CO2 and H2O with a second limiting plateau allowing quantification of these gases. Such analysis capabilities have been found to be extended by incorporating a second pair of electrodes. These effects have not previously been reported. Sensors have been shown to be more sensitive to H2O than to CO2. To investigate the low temperature response of sensors, a variety of techniques and analyses have been developed and are employed with varying success. Impedance spectroscopy was by far the most useful and revealing tool but this is a function of the highly developed hardware and sophisticated control and analysis software bought as a complete system. Gas step changes and current / voltage sweeps were also useful as comparative techniques but could not separate out component mechanisms. Scanning electron microscopy proved to be a vital tool as it allowed vital information to be obtained concerning electrode and electrolyte microstructure. Again this is a function of a highly developed and sophisticated instrument. The techniques of pressure and concentration modulation were limited in terms of ease of use, measurement range and results interpretation. The main drawbacks were limited frequency ranges and laborious data collection and analysis. They do both however show large potential for improvement. Both amperometric and potentiometric sensors response rates were analysed with a variety of noble metal electrodes using each technique. Electrode material proved to have a marked effect on sensor performance with the best results obtained with silver and electro-deposited platinum. Scanning electron microscopy of silver showed that a finely divided and openly porous electrode was not required for high performance contrary to expectations. This is thought to be due to the solubility of oxygen in this metal. With platinum however, the improved microstructure is thought to be a signifîcant factor in electro-deposited and cermet electrode performance. Response rates in amperometric sensors did not show any significant temperature dependence although a restriction in measurement range was observed. Response rates were suspected to be mainly influenced by sensor geometry whilst measurement range was a function of sensor geometry, electrolyte conductivity and electrode activity. Improved electrolytes will provide improvements and may come in the form of attention to the YSZ system or by employing an alternative ion conductor such as ceria. Close attention to sensor dimensions provides possibility for enhancements. In amperometric devices for instance a long, thin diffusion barrier is required leading to a small internal cavity with a large electrode surface area and a thin electrolyte membrane

A glance beyond the quantum model

One of the most important problems in Physics is how to reconcile Quantum Mechanics with General Relativity. Some authors have suggested that this may be realized at the expense of having to drop the quantum formalism in favor of a more general theory. However, as the experiments we can perform nowadays are far away from the range of energies where we may expect to observe non-quantum effects, it is difficult to theorize at this respect. Here we propose a fundamental axiom that we believe any reasonable post-quantum theory should satisfy, namely, that such a theory should recover classical physics in the macroscopic limit. We use this principle, together with the impossibility of instantaneous communication, to characterize the set of correlations that can arise between two distant observers. Although several quantum limits are recovered, our results suggest that quantum mechanics could be falsified by a Bell-type experiment if both observers have a sufficient number of detectors