Tissue engineering of co-cultured skin substitutes using biocomposite membranes based on collagen and polycaprolactone

The preparation and characterisation of collagen: PCL, gelatin: PCL and gelatin/collagen:PCL biocomposites for manufacture of tissue engineered skin substitutes are reported. Films of collagen: PLC, gelatin: PCL (1:4, 1:8 and 1:20 w/w) and gelatin/collagen:PCL (1:8 and 1:20 w/w) biocomposites were prepared by impregnation of lyophilised collagen and/or gelatin mats by PCL solutions followed by solvent evaporation. In vitro assays of total protein release of collagen:PCL and gelatin: PCL biocomposite films revealed an expected inverse relationship between the collagen release rate and the content of synthetic polymer in the biocomposite samples that may be exploited for controlled presentation and release of biopharmaceuticals such as growth factors. Good compatibility of all biocomposite groups was proven by interaction with 3T3 fibroblasts, normal human epidermal keratinocytes (NHEK), and primary human epidermal keratinocytes (PHEK) and dermal fibroblasts (PHDF) in vitro respectively. The 1:20 collagen: PCL materials exhibiting good cell growth curves and mechanical characteristics were selected for engineering of skin substitutes in this work. The tissue-engineered skin model based on single-donor PHEK and PHDF with differentiated confluent epidermal layer and fibrous porous dermal layer was then developed successfully in vitro proven by SEM and immunohistochemistry assay. The following in vivo animal study on athymic mice revealed early complete wound healing in 10 days and good integration of co-cultured skin substitutes with adjacent mice skin structures. Thus the co-cultured skin substitutes based on 1:20 collagen: PCL biocomposite membranes was proven in principle. The approach to skin modelling reported here may find application in wound treatment, gene therapy and screening of new pharmaceuticals.

Microstructural analysis of surface and interface zones in concrete

Several of OPC paste and concrete specimens, with different mix proportions, were cast against CPF and impermeable formwork (IF) and the profiles of pore structure, microhardness and scratch hardness of the cover zone were established. The chloride ingress and the depth of carbonation of the surface zone of concrete cast against CPF and IF were investigated. The main mechanisms controlling the ECR processes and the factors affecting such treatment were critically reviewed. Subsequently, as a means of restoring passivation of steel embedded in carbonated concrete, such HCP specimens were subjected to ECR. The influence of ECR on the chemistry of the pore solution and the microstructure of the surface and the steel/cement past interface zones were also studied. The main findings of this investigation were as follows: (a) The thickness of the microstructure gradient of cover concrete is significantly decreased with increasing period of water curing but is relatively unaffected by curing temperature, w/e ratio and the use of cement replacement materials. (b) The scratch hardness technique was shown to be potentially useful for characterising the microstructure and microhardness gradients of the surface zone. (c) A relationship between the microstructure gradient and mass transport properties of the surface zone was established. (d) The use of CPF resulted in a significant reduction in porosity of both the cement paste matrix and the aggregate/cement paste transition zone, and a marked improvement in the resistance of the surface zone to carbonation and the ingress of chloride ions. (e) The ECR treatment resulted in a marked densification of the pore structure and in changes to the pore solution chemistry and the cement phases of near-surface and steel/cement paste transition zones. This effect was more pronounced with current density, period of treatment and particularly with the use of sodium phosphate as an electrolyte.

Chloride resistance and durability of cement paste and concrete containing metakaolin

Metakaolin (MK), a calcined clay, was included as a partial cement replacement material, at up to 20% by weight of binder, in cement pastes and concrete, and its influence on the resistance to chloride ingress investigated. Reductions in effective chloride diffusion coefficients through hardened cement paste were obtained for binary blends and by combining OPC, MK and a second cement replacement material of pulverised fuel ash or ground granulated blast furnace slag. Steady state oxygen diffusion measurements through hardened cement pastes measured using an electrochemical cell showed that the interaction between charged species and the pore surfaces is a major factor in determining chloride diffusion rate. Rheology of the binder, particularly at high MK replacement levels, was found to have a dramatic influence on the diffusion performance of cement pastes. It was concluded that plasticising admixtures are essential for adequate dispersion of MK in cement pastes. Chloride concentration profile analysis of the concrete cylinders, exposed to sodium chloride solution for one year, was employed to obtain apparent chloride diffusion coefficients for concrete specimens. MK was found to reduce the depth of chloride penetration into concrete when compared with that of unblended mixes. Corrosion rate and corrosion potential measurements were taken on steel bars embedded in concrete exposed to a saline environment under conditions of cyclic wetting and drying. The initiation time for corrosion was found to be significantly longer for MK blended mixes than for plain OPC systems. The aggregate-paste interfacial zone of MK blended systems was investigated by steady state diffusion of chloride ions through mortar containing glass beads as model aggregate. For the model aggregate specimens tested the work confirmed the hypothesis that properties of the bulk paste are the controlling factors in ionic diffusion through mortar.

The durability of glass fibre reinforced cements made with new cementitious matrices

Widespread use of glass fibre reinforced cement (GRC) has been impeded by concerns over its durability. Three degradation mechanisms are proposed - fibre corrosion, Ca(OHh precipitation and matrix densification - although their relative importance is debated. Matrices with reduced alkalinities and Ca(OH)2 contents are being developed; the aim of this study was to investigate their hydration and interaction with alkali-resistant fibres to determine the factors controlling their long-term durability, and assess the relevancy of accelerated ageing. The matrices studied were: OPC/calcium-sulphoaluminate cement plus metakaolin (C); OPC plus metakaolin (M); blast-furnace slag cement plus a micro-silica based additive (D); and OPC (O). Accelerated ageing included hot water and cyclic regimes prior to tensile testing. Investigations included pore solution expression, XRD, DTA/TG, SEM and optical petrography. Bond strength was determined from crack spacings using microstructural parameters obtained from a unique image analysis technique. It was found that, for the new matrices - pore solution alkalinities were lower; Ca(OH)2 was absent or quickly consumed; different hydrates were formed at higher immersion temperatures; degradation under 65°C immersion was an order of magnitude slower, and no interfilamental Ca(OH)2 was observed .It was concluded that: fibre weakening caused by flaw growth was the primary degradation mechanism and was successfully modelled on stress corrosion/static fatigue principles. OPC inferiority was attributed partly to its higher alkalinity but chiefly to the growth of Ca(OH)2 aggravating the degradation; and hot water ageing although useful in model formulation and contrasting the matrices, changed the intrinsic nature of the composites rather than simply accelerating the degradation mechanisms.

Metakaolin as a cement extender

The effect of 10% and 20% replacement metakaolin on a number of aspects of hydration chemistry and service performance of ordinary Portland cement pastes has been investigated. The analysis of expressed pore solutions has revealed that metakaolin-blended specimen pastes possess enhanced chloride binding capacities and reduced pore solution pH values when compared with their unblended counterparts. The implications of the observed changes in pore solution chemistry with respect to chloride induced reinforcement corrosion and the reduction in expansion associated with the alkali aggregate reaction are discussed. Differential thermal analysis, mercury intrusion porosimetry, and nuclear magnetic resonance spectroscopy have been employed in the analysis of the solid phase. It is suggested that hydrated gehlenite (a product of pozzolanic reaction) is operative in the removal and solid state binding of chloride ions from the pore solution of metakaolin-blended pastes. Diffusion coefficients obtained in a non-steady state chloride ion diffusion investigation have indicated that cement pastes containing 10% and 20% replacement metakaolin exhibit superior resistance to the penetration of chloride ions in comparison with those of plain OPC of the same water:cement ratio. The chloride induced corrosion behaviour of cement paste samples, of water:cement ratio 0.4, containing 0% , 10%, and 20% replacement metakaolin, has been monitored using the linear polarization technique. No significant corrosion of embedded mild steel was observed over a 200 day period.

Electrochemical chloride extraction to halt corrosion of reinforcement

This thesis presents results of experiments designed to study the effect of applying electrochemical chloride extraction (ECE) to a range of different hardened cement pastes. Rectangular prism specimens of hydrated cement paste containing sodium chloride at different concentrations were subjected to electrolysis between the embedded steel cathodes and external anodes of activated titanium mesh. The cathodic current density used was in the range of 1 to 5 A/m2 with treatment periods of 4 to 12 weeks. After treatment, the specimens were cut into sections which were subjected to pore-solution expression and analysis in order to determine changes in the distribution of free and total ionic species. The effect of the ECE treatment on the physical and microstructural properties of the cements was studied by using microhardness and MIP techniques. XRD was employed to look at the possibility of ettringite redistribution as a result of the accumulation of soluble sulphate ions in the cement matrix near the cathode during ECE. Remigration of chloride which remains after the ECE treatment and distribution of other ions were studied by analysing specimens which had been stored for several months, after undergoing ECE treatment. The potentials of the steel cathodes were also monitored over the period to detect any changes in their corrosion state. The main findings of this research were as follows: 1, ECE, as applied in this investigation, was capable of removing both free and bound chloride. The removal process occurred relatively quickly and an equilibrium between free and bound chlorides in the specimens was maintained throughout. At the same time, alkali concentrations in the pore solution near the steel cathode increased. The soluble sulphate ionic concentration near the cathode also increased due to the local increase in the pH of the pore solution. 2, ECE caused some changes in physical and microstructural of the cement matrix. However these changes were minimal and in the case of microhardness, the results were highly scattered. Ettringite in the bulk material well away from the cathode was found not to increase significantly with the increase in charge passed.3, Remigration of chloride and other ionic species occurred slowly after cessation of ECE with a resultant gradual increase in the Cl-/OH- ratio around the steel.4, The removal of chloride from blended cements was slower than that from OPC.

Pore structure and diffusional properties of hardened cement pastes

This study has investigated the inclusion of pulverised fuel ash (PFA) and blast furnace slag (BFS) into hardened cement pastes (HCP) in retarding the ingress of chloride ions and oxygen molecules from the external environment. The influence of environmental factors such as drying and carbonation on the pore structure and diffusional properties of OPC, OPC/30%PFA and OPC/65%BFS hardened pastes was investigated. Specimens were desorbed from a saturated surface dry condition to a near constant weight at 65% relative humidity (RH) while others were simultaneously exposed to a 65% RH atmosphere and a carbon dioxide atmosphere of up to 5% by volume until there were fully carbonated. The presence of the interfacial zone at the cement paste-aggregate interface was critically reviewed and identified. The influence of the interfacial zone on porosity and chloride ingress in assumed periodic composites of glass bead mortars was also studied. The investigations have demonstrated the following: (a) The use of fly ash and slag in blended cement pastes has resulted in a marked reduction in capillary porosity and rate of chloride ingress. (b) The ratio of oxygen to chloride diffusion coefficients increased from values close to 1 in permeable pastes, to values of around 15 in low-permeability blended fly ash and slag pastes. This supports the view that the diffusion of chloride ions is retarded by the surface charge of the hydrated cement gel in low-permeability pastes. (c) Compared with plain OPC pastes, the carbonation of blended fly ash and slag pastes resulted in a marked increase in the coarse capillary porosity and a corresponding increase in the oxygen and chloride diffusion rates.

The management of foreign exchange exposure on business contracts overseas

This thesis is a piece of applied research. It is the result of a joint project between the University of Aston Interdisciplinary Higher Degrees Scheme and International Aeradio plc (IAL). It considers the structure and organisation of overseas business and the effects that exchange rate movements have on financial performance. It looks in detail at a series of overseas contracts and factors which affect the monitoring and performance of those contracts. From this initial research is developed a series of conceptual models which attempt to capture the effects of foreign exchange rate movements on contract costing, the monitoring of performance on overseas contracts and a measure of company wide exposure. These models are then considered in the context of real IAL generated data and circumstances. The work is finally considered in the context of a survey of other companies with a similar mode of undertaking overseas business with the aim of placing the work in a general context.

Reduction of noise levels in vaccum cleaners

The work described in this thesis is directed towards the reduction of noise levels in the Hoover Turbopower upright vacuum cleaner. The experimental work embodies a study of such factors as the application of noise source identification techniques, investigation of the noise generating principles for each major source and evaluation of the noise reducing treatments. It was found that the design of the vacuum cleaner had not been optimised from the standpoint of noise emission. Important factors such as noise `windows', isolation of vibration at the source, panel rattle, resonances and critical speeds had not been considered. Therefore, a number of experimentally validated treatments are proposed. Their noise reduction benefit together with material and tooling costs are presented. The solutions to the noise problems were evaluated on a standard Turbopower and the sound power level of the cleaner was reduced from 87.5 dB(A) to 80.4 db(A) at a cost of 93.6 pence per cleaner.The designers' lack of experience in noise reduction was identified as one of the factors for the low priority given to noise during design of the cleaner. Consequently, the fundamentals of acoustics, principles of noise prediction and absorption and guidelines for good acoustical design were collated into a Handbook and circulated at Hoover plc.Mechanical variations during production of the motor and the cleaner were found to be important. These caused a vast spread in the noise levels of the cleaners. Subsequently, the manufacturing processes were briefly studied to identify their source and recommendations for improvement are made.Noise of a product is quality related and a high level of noise is considered to be a bad feature. This project suggested that the noise level be used constructively both as a test on the production line to identify cleaners above a certain noise level and also to promote the product by `designing' the characteristics of the sound so that the appliance is pleasant to the user. This project showed that good noise control principles should be implemented early in the design stage.As yet there are no mandatory noise limits or noise-labelling requirements for household appliances. However, the literature suggests that noise-labelling is likely in the near future and the requirement will be to display the A-weighted sound power level. However, the `noys' scale of perceived noisiness was found more appropriate to the rating of appliance noise both as it is linear and therefore, a sound level that seems twice as loud is twice the value in noys and also takes into consideration the presence of pure tones, which even in the absence of a high noise level can lead to annoyance.

User interface design support for the development of knowledge-based systems

The present scarcity of operational knowledge-based systems (KBS) has been attributed, in part, to an inadequate consideration shown to user interface design during development. From a human factors perspective the problem has stemmed from an overall lack of user-centred design principles. Consequently the integration of human factors principles and techniques is seen as a necessary and important precursor to ensuring the implementation of KBS which are useful to, and usable by, the end-users for whom they are intended. Focussing upon KBS work taking place within commercial and industrial environments, this research set out to assess both the extent to which human factors support was presently being utilised within development, and the future path for human factors integration. The assessment consisted of interviews conducted with a number of commercial and industrial organisations involved in KBS development; and a set of three detailed case studies of individual KBS projects. Two of the studies were carried out within a collaborative Alvey project, involving the Interdisciplinary Higher Degrees Scheme (IHD) at the University of Aston in Birmingham, BIS Applied Systems Ltd (BIS), and the British Steel Corporation. This project, which had provided the initial basis and funding for the research, was concerned with the application of KBS to the design of commercial data processing (DP) systems. The third study stemmed from involvement on a KBS project being carried out by the Technology Division of the Trustees Saving Bank Group plc. The preliminary research highlighted poor human factors integration. In particular, there was a lack of early consideration of end-user requirements definition and user-centred evaluation. Instead concentration was given to the construction of the knowledge base and prototype evaluation with the expert(s). In response to this identified problem, a set of methods was developed that was aimed at encouraging developers to consider user interface requirements early on in a project. These methods were then applied in the two further projects, and their uptake within the overall development process was monitored. Experience from the two studies demonstrated that early consideration of user interface requirements was both feasible, and instructive for guiding future development work. In particular, it was shown a user interface prototype could be used as a basis for capturing requirements at the functional (task) level, and at the interface dialogue level. Extrapolating from this experience, a KBS life-cycle model is proposed which incorporates user interface design (and within that, user evaluation) as a largely parallel, rather than subsequent, activity to knowledge base construction. Further to this, there is a discussion of several key elements which can be seen as inhibiting the integration of human factors within KBS development. These elements stem from characteristics of present KBS development practice; from constraints within the commercial and industrial development environments; and from the state of existing human factors support.

Tear analysis and lens-tear interactions:part II. Ocular lipids-nature and fate of meibomian gland phospholipids

Purpose: Published data indicate that the polar lipid content of human meibomian gland secretions (MGS) could be anything between 0.5% and 13% of the total lipid. The tear film phospholipid composition has not been studied in great detail and it has been understood that the relative proportions of lipids in MGS would be maintained in the tear film. The purpose of this work was to determine the concentration of phospholipids in the human tear film. Methods: Liquid chromatography mass spectrometry (LCMS) and thin layer chromatography (TLC) were used to determine the concentration of phospholipid in the tear film. Additionally, an Amplex Red phosphatidylcholine-specific phospholipase C (PLC) assay kit was used for determination of the activity of PLC in the tear film. Results: Phospholipids were not detected in any of the tested human tear samples with the low limit of detection being 1.3 µg/mL for TLC and 4 µg/mL for liquid chromatography mass spectrometry. TLC indicated that diacylglycerol (DAG) may be present in the tear film. PLC was in the tear film with an activity determined at approximately 15 mU/mL, equivalent to the removal of head groups from phosphatidylcholine at a rate of approximately 15 µM/min. Conclusions: This work shows that phospholipid was not detected in any of the tested human tear samples (above the lower limits of detection as described) and suggests the presence of DAG in the tear film. DAG is known to be at low concentrations in MGS. These observations indicate that PLC may play a role in modulating the tear film phospholipid concentration.

State-of-the-art in lean design engineering:a literature review on white collar lean

Lean is usually associated with the ‘operations’ of a manufacturing enterprise; however, there is a growing awareness that these principles may be transferred readily to other functions and sectors. The application to knowledge-based activities such as engineering design is of particular relevance to UK plc. Hence, the purpose of this study has been to establish the state-of-the-art, in terms of the adoption of Lean in new product development, by carrying out a systematic review of the literature. The authors' findings confirm the view that Lean can be applied beneficially away from the factory; that an understanding and definition of value is key to success; that a set-based (or Toyota methodology) approach to design is favoured together with the strong leadership of a chief engineer; and that the successful implementation requires organization-wide changes to systems, practices, and behaviour. On this basis it is felt that this review paper provides a useful platform for further research in this topic.

Textbook on contract law

This edition of the guide to the law of contract takes account of the implications of Internet contracting and includes discussion of the Consumer Protection (Distance Selling) Regulations 2000. Where appropriate, reference is made, for reasons of comparison, to the principles contained in thePrinciples of European Contract Law (PECL) and the UNIDROIT Principles of International Commercial Contracts.;Significant developments in contract law, both statutory and case law, are discussed, including the Contracts (Rights of Third Parties) Act 1999, the Electronic Communications Act 2000 andthe House of Lords' decisions in Alfred McAlpine Construction Ltd v Panatown Ltd and Attorney General V Blake. Other important decisions covered in this revised edition are Royal Bank of Scotland v Etridge, Barclays Bank Plc v Coleman, Barclays Bank Plc v Boulter, Avon Insurance v Swire, Zanzibar vBritish Aerospace (Lancsaster House) Ltd and Nutt v Read. In addition, there is discussion of the Unfair Terms in Consumer Contracts Regulations 1999 and the European Commission's Review of the Unfair Terms Directive, as well as coverage of Director General of Fair Trading v First National Bank. Other decisions on illegality, onerous terms, constructionand repudiation of contract are included.

1.14Tb/s DP-QPSK WDM polarization-diverse optical phase conjugation

Optical phase conjugation (OPC) of a polarization-multiplexed comb of 10x114Gb/s DP-QPSK signals has been demonstrated for the first time, occupying a spectral bandwidth of >1THz (~9nm). The nonlinear element employed for the OPC was highly nonlinear fiber (HNLF) optimized for the suppression of stimulated Brillouin scattering (SBS) and configured in a bi-directional loop offering polarization diversity. Pump power (each way about the loop) and input signal power to the OPC subsystem were optimized at 29.7dBm and + 3dBm respectively producing a Q2 penalty of ≤0.9dB over all conjugate wavelengths, polarizations and output OSNR (up to 20dB).

Extra compensation for inventive employees:is our system equitable, unbiased and motivating?

There is a presumption that invention is good. It provides us with innovative goods, services and ways of doing things leading to greater employment, wealth and health. This article looks at the two recent UK cases regarding statutory extra compensation that may be awarded to employee inventors under the Patents Act 1977. Most universities worldwide and many companies have individual inventor reward schemes. Researchers now work in teams made up of both industry and academic researchers who are often based in different countries where different legal regimes apply. Is leaving the decision to award employees extra financial compensation up to individual companies unfair, unequal and de-motivating? Is having differing legislative systems in different European countries counter productive and a barrier to economic growth? There must be a balance between the inventor and the innovator. Do we have it right and if not what should it be? Legislation: Patents Act 1977 s.39 , s.40 , s.41 Cases: Kelly v GE Healthcare Ltd [2009] EWHC 181 (Pat); [2009] R.P.C. 12 (Ch D (Patents Ct)) Shanks v Unilever Plc [2010] EWCA Civ 1283; [2011] R.P.C. 12 (CA (Civ Div))