Energy-based models for the design of cavities located in creeping media

This thesis uses an energy-based approach to develop new analytical solutions for the time-dependent creep response of deeply embedded cavities. The new models developed here can be used for the initial design of tunnels and for other applications such as underground storage caverns and problems outside the field of geomechanics. The objective of using this energy-based approach is to develop models that can provide a quick estimate of cavity closure and that can be applied to different design situations and material behaviour. For the first time a three-dimensional analytical solution has been developed for the time-dependent response of a cavity embedded in a viscoelastic medium. The cavity is excavated quasi-instantaneously from an infinite body with an initial isotropic stress field. The problem is three-dimensional due to the effect of a tunnel face. This new solution can predict the full interaction between the tunnel and the surrounding creeping rock and thus can be incorporated with field monitoring data in an expert system for tunnel design. The accuracy of this model is comparable with finite element analysis. A new class of thermodynamically consistent constitutive models have been developed, which couple viscoplasticity and damage, describing both the secondary and tertiary stages of creep behaviour. Models were derived for both frictionless and frictional materials within the framework of hyperplasticity. The frictional model provided a good fit to data obtained from the triaxial compression testing of sandstone, illustrating its capability of describing creeping rock. These new constitutive models were incorporated into the energy-based method for cavity analysis, using a two-dimensional plane strain cylindrical cavity for demonstration purposes. A parametric study was carried out and results were also compared with FE analysis. Findings show that the models successfully describe the secondary and tertiary stages of creep behaviour. These new solutions only require a simple text file as an input and need minimal skill to operate. The formation of an initial geometry or finite element mesh is not necessary. This is shown through the creation of a standalone program for the three-dimensional model. The new solutions can take into account a wide range of different material behaviour, both two-dimensional and three-dimensional problems and due to their thermodynamic consistency are able to simulate other time-dependent processes, such as relaxation. This shows the flexibility of this approach and its applicability to different geomechanics problems

Disease activity and cognition in rheumatoid arthritis : an open label pilot study

Acknowledgements This work was supported in part by NIHR Newcastle Biomedical Research Centre. Funding for this study was provided by Abbott Laboratories. Abbott Laboratories were not involved in study design; in the collection, analysis and interpretation of data; or in the writing of the report.Peer reviewedPublisher PD

Some reactions of sulphonylhydroxylamines leading to an investigation of sulphonylaminyloxides

Mercury (II) and lead (II) ions, but not mercury (l) and thallium (I), react with both the nitrosyIdisulphonate, ON(S0₃)₂₂- and the hydroxylaminedisulphonate dianions, ON(S0₃)₂²⁻-, to yield the corresponding metal sulphate and a mixture of sulphate and sulphite ions. Silver (I) ions are reduced to the metal by both anions, but reacts with potassium imidodisulphonate, HN(SO₃K)₂, and tripotassium imidodisulphonate, KN(S0₃K)₂, to yield trisilver imidodisulphonate, Ag₃NS₂O₆, and disilver potassium imidodisulphonate, Ag₂KNS₂O₆. The reaction of some related salts are also reported. Mechanisms for some of the decompositions, and stoichiometric equations are proposed. No metal salts of hydroxylaminedisulphonates, HON(SO₃M)₂ were isolated. The silver imidodisulphonate salts failed to react with both alkyl and aryl halides. A series of N, N-bis-(arylsulphonyl)hydroxylamines, (p-XC₆H₄S₂)₂N0, were synthesised (X = H, Me, MeO, Cl and F). The species (p-XC₆H₄S₂)₂N0, p-XC₆H₄S₂NO and p-XC₆H₄S₂ are proposed as intermediates during the oxidation of the bis-species with PbO₂, silver (I,III) oxide, AgO, MnO₂. Pb(O₂CMe)₄ or nitric acid to N, N, 0-tris-(arylsulphonyl)hydroxylamines, p-XC₆H₄S₂)₂N0S₂C₆H₄X-p and nitrate ion. A mechanism involving hydroxylamine is ruled out. I. r. and n.m.r. spectra show that the tris-species are hydroxylamines, R₂NOR, rather than amine oxides, R₃NO, and the structure is considered by a comparison with (CF208)₂NOH and (CF₃)₂NO. The e.s.r. spectra of the tris-species in benzene indicates the presence of a nitroxide radical. The bis-species are found to decompose to the tris-hydroxylamine and the corresponding arenesulphonic acid, while the tris-species decompose to the sulphonic acid. Oligomerisation of cyclohexene is observed during the oxidation of bis-hydroxylamines, while with bases, such as pyridine, the hydroxylamine is converted to a mixture of (RSO₂)₂NH pyridine-N-oxide and a pyridinium arylsulphonate. N, N, 0-tris-(Alkyl-sulphonyl) hydroxylamines could not be isolated. Nitrosylarene-sulphinates, p-XC₆H₄SO₂NO are proposed as intermediates but could not be isolated from the reactions of nitrosyl chloride and nitrogen (II) oxide with arylsulphonylhydroxylamines. p-XC₆H₄SO₂NHOH, (p-XC₆H₄SO₂)₂NOH and p-XC₆H₄SO₂NH₂ (X=H, CH₃) are all are converted by NOCl to p-XC₆H₄SO₂Cl, but (p-XC₆H₄S0₂)₂N0S0₂C₆H₄X-p and (p-XC₆H₄SO₂)₂NH are unaffected. Oxidation of C₆H₅SO₂NHOH by a range of oxidants yielded, C₆H₅SO₂Cl, C₆H₅SO₃H, or (C₆H₅SO₂)₂NOSO₂C₆H₅, but not C₆H₅SO₂NO. Diene cycloaddition products of p-XC₆H₄SO₂NO could not be isolated. p-CH₃C₆H₄SO₂Na is converted by nitrosyl chloride to p-CH₃C₆H₄SO₂Cl rather than to p-CH₃C₆H₄SO₂NO. (p-CH₃C₆H₄SO₂)₂NH is inert to a wide range of oxidants. Both (p-XC₆H₄S0₂)₂NOH and (p-XC₆H₄S0₂)₂N0S0₂C₆H₄X-p initiate free-radical halogenation by dichlorine and dibromine, but not by diiodine, of benzene and cyclohexane. Simple carboxyamides also initiate free-radical chlorination of the same substrates. (N-aryl-N-arylsulphonyl) hydroxylamines were oxidised by PbO₂ and Pb(0₂CMe)₄, but not MnO₂, to a mixture of the corresponding [N- aryl-N, O -bis(aryl sulphonyl)]hydroxylamine, nitrobenzene and azoxybenzene. The tris-species appears to contain the nitroxide radical, ArS0₂N(0)Ar¹. A similar mechanism to that for the oxidation of (p-XC₆H₄S0₂)₂N0H is proposed

The immunoregulatory and allergy-associated cytokines in the aetiology of the otitis media with effusion.

Inflammation in the middle ear mucosa, which can be provoked by different primary factors such as bacterial and viral infection, local allergic reactions and reflux, is the crucial event in the pathogenesis of otitis media with effusion (OME). Unresolved acute inflammatory responses or defective immunoregulation of middle inflammation can promote chronic inflammatory processes and stimulate the chronic condition of OME. Cytokines are the central molecular regulators of middle ear inflammation and can switch the acute phase of inflammation in the chronic stage and induce molecular-pathological processes leading to the histopathological changes accompanying OME. In this review we present cytokines identified in otitis media, immunoregulatory [interleukin (IL)-2, IL-10, transforming growth factor-beta]) and allergy associated (IL-4, IL-5, granulocyte-macrophage colony-stimulating factor), as crucial molecular regulators, responsible for chronic inflammation in the middle ear and the chronic condition of OME

Update on otitis media – prevention and treatment

Acute otitis media and otitis media with effusion are common childhood disorders, a source of significant morbidity, and a leading cause of antibiotic prescription in primary health care. Although effective treatments are available, some shortcomings remain, and thus better treatments would be welcome. Recent discoveries within the field of otitis media research relating to its etiology and pathogenesis have led to further investigation aimed at developing novel treatments. This article provides a review of the latest evidence relating to the understanding of acute otitis media and otitis media with effusion, current treatment strategies, their limitations, new areas of research, and novel strategies for treatment

Demonstrating an absolute quantum advantage in direct absorption measurement

Engineering apparatus that harness quantum theory promises to offer practical advantages over current technology. A fundamentally more powerful prospect is that such quantum technologies could out-perform any future iteration of their classical counterparts, no matter how well the attributes of those classical strategies can be improved. Here, for optical direct absorption measurement, we experimentally demonstrate such an instance of an absolute advantage per photon probe that is exposed to the absorbative sample. We use correlated intensity measurements of spontaneous parametric downconversion using a commercially available air-cooled CCD, a new estimator for data analysis and a high heralding efficiency photon-pair source. We show this enables improvement in the precision of measurement, per photon probe, beyond what is achievable with an ideal coherent state (a perfect laser) detected with 100% efficient and noiseless detection. We see this absolute improvement for up to 50% absorption, with a maximum observed factor of improvement of 1.46. This equates to around 32% reduction in the total number of photons traversing an optical sample, compared to any future direct optical absorption measurement using classical light

Evaluation of combinations of putative anti-biofilm agents and antibiotics to eradicate biofilms of Staphylococcus aureus and Pseudomonas aeruginosa

Objectives To evaluate potential anti-biofilm agents for their ability to enhance the activity of antibiotics for local treatment of localized biofilm infections. Methods Staphylococcus aureus and Pseudomonas aeruginosa in vitro biofilm models were developed. The putative antibiotic enhancers N-acetylcysteine, acetylsalicylic acid, sodium salicylate, recombinant human deoxyribonuclease I, dispersin B, hydrogen peroxide and Johnson’s Baby Shampoo (JBS) were tested for their anti-biofilm activity alone and their ability to enhance the activity of antibiotics for 7 or 14 days, against 5 day old biofilms. The antibiotic enhancers were paired with rifampicin and clindamycin against S. aureus and gentamicin and ciprofloxacin against P. aeruginosa. Isolates from biofilms that were not eradicated were tested for antibiotic resistance. Results Antibiotic levels 10× MIC and 100× MIC significantly reduced biofilm, but did not consistently eradicate it. Antibiotics at 100× MIC with 10% JBS for 14 days was the only treatment to eradicate both staphylococcal and pseudomonal biofilms. Recombinant human deoxyribonuclease I significantly reduced staphylococcal biofilm. Emergence of resistance of surviving isolates was minimal and was often associated with the small colony variant phenotype. Conclusions JBS enhanced the activity of antibiotics and several other promising anti-biofilm agents were identified. Antibiotics with 10% JBS eradicated biofilms produced by both organisms. Such combinations might be useful in local treatment of localized biofilm infections

Anti-confocal versus confocal assessment of the middle ear simulated by Monte Carlo methods

The ability to monitor the inflammatory state of the middle ear mucosa would provide clinical utility. To enable spectral measurements on the mucosa whilst rejecting background signal from the eardrum an anti-confocal system is investigated. In contrast to the central pinhole in a confocal system the anti-confocal system uses a central stop to reject light from the in-focus plane, the eardrum, with all other light detected. Monte Carlo simulations of this system show an increase in detected signal and improved signal-to-background ratio compared to a conventional confocal set-up used to image the middle ear mucosa. System parameters are varied in the simulation and their influence on the level of background rejection are presented

A model for reactive porous transport during re-wetting of hardened concrete

A mathematical model is developed that captures the transport of liquid water in hardened concrete, as well as the chemical reactions that occur between the imbibed water and the residual calcium silicate compounds residing in the porous concrete matrix. The main hypothesis in this model is that the reaction product -- calcium silicate hydrate gel -- clogs the pores within the concrete thereby hindering water transport. Numerical simulations are employed to determine the sensitivity of the model solution to changes in various physical parameters, and compare to experimental results available in the literature.Comment: 30 page