The association of Clostridium perfringens with foal diarrhoea

Several case reports of i>Clostridium perjringens involvement in equine enteric disease have not identified the prevalence and statistical association of these bacteria with foal diarrhoea. Each of five methods which favoured the recovery of C. perjringens in different physiological states were chosen to improve the sensitivity of isolation in a survey of foal diarrhoea for C. perjringens and other pathogens. C. perjringens was significantly associated with foal diarrhoea (isolated from 57% of 421 scouring anjmals but from only 33% of 222 controls; odds ratio 7.4; pCryptosporidium sp. and large numbers of Strongyloides westeri were the only other pathogens associated with diarrhoea although they were less prevalent than C. perjringens; Salmonella sp. was the only other pathogen associated with fatal diarrhoea. Enterotoxin production was detected by reverse passive latex agglutination test (RPLA) amongst isolates of C. perjringens from scouring and healthy foals. The enterotoxin gene from an equine strain was cloned and its sequence was essentially identical to that published for a human isolate. Less than 5% of C. perjringens isolated from scouring foals and 0.5% from controls were positive for the enterotoxin gene by polymerase chain reaction (PCR) (odds ratio 19.1; p<0.005). Presence of the enterotoxin gene was confirmed in representative isolates with a gene probe of chromosomal DNA and PCR product as well as neutralisation of cytotoxicity by antitoxin. Enterotoxigenicity of half ofRPLA positive isolates could not be confirmed in this way. Enterotoxigenic C. perjringens were a probable cause of foal diarrhoea. However, a greater proportion of the disease was associated with non-enterotoxigenic C. perjringens. There is now a need to identify molecular differences between non-enterotoxigenic C. perjringens strains from scouring and healthy foals which might be associated with pathogenicity

Exceptional points in optical systems: A resonant-state expansion study

Exceptional points (EPs) in open optical systems are rigorously studied using the resonant-state expansion (RSE). A spherical resonator, specifically a homogeneous dielectric sphere in a vacuum, perturbed by two point-like defects which break the spherical symmetry and bring the optical modes to EPs, is used as a worked example. The RSE is a non-perturbative approach encoding the information about an open optical system in matrix form in a rigorous way, and thus offering a suitable tool for studying its EPs. These are simultaneous degeneracies of the eigenvalues and corresponding eigenfunctions of the system, which are rigorously described by the RSE and illustrated for perturbed whispering-gallery modes (WGMs). An exceptional arc, which is a line of adjacent EPs, is obtained analytically for perturbed dipolar WGMs. Perturbation of high-quality WGMs with large angular momentum and their EPs are found by reducing the RSE equation to a two-state problem by means of an orthogonal transformation of a large RSE matrix. WGM pairs of opposite chirality away from EPs are shown to have the same chirality at EPs. This chirality can be observed in circular dichroism measurements, as it manifested itself in a squared-Lorentzian part of the optical spectra, which we demonstrate here analytically and numerically in the Purcell enhancement factor for the perturbed dipolar WGMs.Comment: 24 pages. 13 figures (3 in Appendix). To be submitted in Physical Review A. Authors: K S Netherwood (primary author), H Riley (initial concept work), E A Muljarov (theme leader

Modelling Wall Deformation and Fluid-Structure Interaction in Fluid-Conveying Elastic-Walled Tubes

The fluid-structure interaction arising from the ow through collapsible tubes plays an important biological role in the transportation and delivery of nutrients to tissues and organs. In this thesis, we focus on developing mathematical models for the wall deformation and fluid-structure interaction arising from the ow through an elastic-walled tube. Whittaker et al. (2010; Q. J. Mech. Appl. Math. 63(4): 465-496) developed a mathematical model for the wall deformations of an initially elliptical elastic-walled tube, which are induced by an azimuthally uniform transmural pressure. In Chapter 2, we expand on this model to allow arbitrary initial cross-sectional shapes and azimuthally non-uniform pressures. In Chapter 3, we re-visit the problem for the deformations of an initially elliptical tube and produce the first formal solution for the wall motion using an eigenfunction expansion method, which overcomes the need to invoke ad-hoc assumptions made by Whittaker et al. (2010; Q. J. Mech. Appl. Math.63(4): 465-496) in order to obtain their solution. In Chapter 4, we couple our results for the wall deformation from Chapter 3 to the asymptotic model for the ow through a rapidly oscillating elastic tube derived by Whittaker et al. (2010, J. Fluid. Mech. 648, 83{121). Our results provide a three-dimensional description of the fluid-structure interaction that arises from the ow through an initially elliptical elastic tube. In Chapter 5, we produce a formal solution for the wall deformation of an elastic-walled tube with an arbitrary initial cross-sectional shape. We then use this model to compute a family of initial cross-sectional shapes with the property that an azimuthally uniform transmural pressure will excite only a single deformation mode

A Nutritional Approach for the Management of Deoxynivalenol (DON) Toxicity in the Gastrointestinal Tract of Growing Chickens

It has been shown that DON has negative effects on the active transport of some nutrients in the small intestine of chickens. The plausible interactions between food contaminants and natural components could be high. The present study investigated the effects of DON on the presence or absence of dietary inulin on the electrophysiological response of the gut to glucose. Ussing chamber studies were conducted with isolated jejunal epithelia at the age of 35 days. Electrophysiology of the epithelia was recorded and the changes of the short-circuit current (Isc) were determined. The addition of d-glucose on the luminal side of the isolated mucosa increased (P < 0.05) the Isc in the control group and inulin supplemented group. The oligosaccharides did not increase glucose absorption in young healthy chickens compared with the controls. In the second experiment, after preincubation of tissues with DON, the addition of glucose did not increase the Isc in jejunum and colon in the control group (P > 0.05). However, in the dietary inulin supplemented group in both jejunum and colon, the addition of glucose after preincubation of tissues with DON increased the Isc, suggesting that the dietary inulin supplementation of the broilers regulated and improved the glucose absorption in the presence of DON and kept it at normal levels

Vortex beam lasing from III-V nanowires epitaxially grown on silicon-on-insulator

Photonic crystal lasers can be used to achieve high emission powers with exceptional beam quality. Vortex beams carrying orbital angular momentum have found applications in areas such as free space communication, optical trapping, and microscopy. In this paper, the growth and operation of an epitaxially grown InGaAs nanowire photonic crystal laser on silicon on insulator, emitting a vortex beam, are investigated. The device is composed of a honeycomb array of nanowires, with compressed and expanded configurations to make use of the band inversion phenomenon. The resulting bound-state-in-the-continuum modes are characterized using simulations and confirmed by measurement

Accidental and Regulated Cell Death in Yeast Colony Biofilms

The yeast species Saccharomyces cerevisiae is one of the most intensively studied organisms on the planet due to it being an excellent eukaryotic model organism in molecular and cell biology. In this work, we investigate the growth and morphology of yeast colony biofilms, where proliferating yeast cells reside within a self-produced extracellular matrix. This research area has garnered significant scientific interest due to its applicability in the biological and biomedical sectors. A central feature of yeast colony biofilm expansion is cellular demise, which is onset by one of two independent mechanisms: either accidental cell death (ACD) or regulated cell death (RCD). In this article, we generalise a continuum model for the nutrient-limited growth of a yeast colony biofilm to include the effects of ACD and RCD. This new model involves a system of four coupled nonlinear reaction–diffusion equations for the yeastcell density, the nutrient concentration, and two species of dead cells. Numerical solutions of the spatially one and two-dimensional governing equations reveal the impact that ACD and RCD have on expansion speed, morphology and cell distribution within the colony biofilm. Our results are in good qualitative agreement with our own experiments