22 research outputs found

    Towards a continuous manufacturing strategy for complex oral health formulations

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    The conversion of traditional batch operations into continuous processes represents an important goal towards process intensification. The rigorous design of continuous manufacturing operations poses several challenges, especially for processes involving complex fluids, whose rheological properties change during processing. The scope of this thesis is to provide a new approach for the development of a continuous process aimed at the production of a non-aqueous Carbopol gel used in oral health formulations. The dissertation addresses two main challenges related to the process: (i) in-line mixing of complex liquids and (ii) control over the Carbopol gelation. First, the impact of complex rheological properties on the mixing stage was investigated experimentally and numerically. Concentrations maps, obtained at different mixers lengths via Planar Laser Induced Fluorescence experiments, revealed that mixing of viscoelastic fluids reduces when the elastic rheological response becomes significant. To prevent these effects and better control the evolution of the rheological properties over the entire process, the kinetics of the gelation process was investigated via time-resolved rheometry and UV-Vis spectroscopy. This study yielded insights into the mechanism of gelation, leading to a kinetic relation to describe the time-evolution of the linear elastic properties of the Carbopol matrix. To further link the kinetic findings with the evolution of the flow properties, the rheological properties of Carbopol dispersions and the impact of different solvents on the swollen configuration of the microgels were investigated. In the presence of co-solvents, the kinetic aspect of the swelling process is critical in determining the final swollen state. Once the final particle dimension has been determined, a generalized scaling behaviour of the flow properties can be retrieved as function of the particle volume fraction. Finally, the scaling laws and the kinetic model were implemented in a computational fluid dynamic model to enable simulations of the gelating flow in different operating conditions

    Abrasive wear behaviour of steels and advanced HVOF-sprayed WC-M coatings

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    This thesis concerns a study of the three-body abrasive wear behaviour of two groups of materials with different abrasive particles using the Dry Sand Rubber Wheel (DSRW) test method. This investigation can be divided into three sections: In the first section, the abrasion of a range of steels with an ash from a biomass power station was compared with that observed for abrasion with a conventional silica abrasive. It was seen that the wear rate of the steels when abraded with silica increased in proportion to the applied load and decreased with the hardness of the steel. However, the bottom-ash was more friable than the silica abrasive, and as such, significantly more abrasive crushing was observed during the tests with the bottom-ash abrasive. It is proposed that the wear is dominated by abrasion by the larger particles in the distribution, and that damage is limited by the maximum load which the particles can sustain before failing. In the second section, the motion of particles in the DSRW test with silica abrasive against a range of steels, as a function of applied load and the hardness of the steels was studied. The results showed that particle rolling through the contact is favoured by low applied loads and low testpiece hardness whereas particle sliding through the contact is favoured by high applied loads and high testpiece hardness. A model was proposed to provide an analysis of the motion of particles in the DSRW test. The effect of hardness on particle rotation is well predicted by the model, but the effect of the applied load on particle motion observed experimentally is opposite to that which is predicted by the model. The shortcomings of the model are discussed, and the model has been qualitatively modified to account for this discrepancy. In the third section, five different WC-metal cermet powders were deposited as coatings by HVOF thermal spraying. These were a WC-nickel alloy, a WC-iron alloy and three types of WC-Co powders with different carbide grain sizes. Characterisation of the coatings showed decomposition of WC during spray process for all the coatings. The results show different solubilities of W and C in the binders and different precipitation characteristics. DSRW tests were performed to assess the wear resistance of the coatings with silica and alumina abrasives. It was found that the coatings had different wear rates and mechanisms when abraded with silica compared with alumina. The differences in the wear behaviour of the coatings are due to the differences in powder characteristics, the extent of reaction and decarburisation during spraying, and the subsequent development of the microstructure in the coating during splat solidification at high cooling rates

    Volume 3 – Conference

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    We are pleased to present the conference proceedings for the 12th edition of the International Fluid Power Conference (IFK). The IFK is one of the world’s most significant scientific conferences on fluid power control technology and systems. It offers a common platform for the presentation and discussion of trends and innovations to manufacturers, users and scientists. The Chair of Fluid-Mechatronic Systems at the TU Dresden is organizing and hosting the IFK for the sixth time. Supporting hosts are the Fluid Power Association of the German Engineering Federation (VDMA), Dresdner Verein zur Förderung der Fluidtechnik e. V. (DVF) and GWT-TUD GmbH. The organization and the conference location alternates every two years between the Chair of Fluid-Mechatronic Systems in Dresden and the Institute for Fluid Power Drives and Systems in Aachen. The symposium on the first day is dedicated to presentations focused on methodology and fundamental research. The two following conference days offer a wide variety of application and technology orientated papers about the latest state of the art in fluid power. It is this combination that makes the IFK a unique and excellent forum for the exchange of academic research and industrial application experience. A simultaneously ongoing exhibition offers the possibility to get product information and to have individual talks with manufacturers. The theme of the 12th IFK is “Fluid Power – Future Technology”, covering topics that enable the development of 5G-ready, cost-efficient and demand-driven structures, as well as individual decentralized drives. Another topic is the real-time data exchange that allows the application of numerous predictive maintenance strategies, which will significantly increase the availability of fluid power systems and their elements and ensure their improved lifetime performance. We create an atmosphere for casual exchange by offering a vast frame and cultural program. This includes a get-together, a conference banquet, laboratory festivities and some physical activities such as jogging in Dresden’s old town.:Group 8: Pneumatics Group 9 | 11: Mobile applications Group 10: Special domains Group 12: Novel system architectures Group 13 | 15: Actuators & sensors Group 14: Safety & reliabilit

    Cost modelling of rapid manufacturing based mass customisation system for fabrication of custom foot orthoses

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    PhD ThesisSolid freeform fabrication (SFF) or Additive manufacturing (AM) techniques have emerged in recent years as advanced manufacturing techniques. These techniques have demonstrated advantages particularly in situations where the demands for unique geometrical structured customer-specific products are high and the time to market is very short. Applications of these techniques in the medical sector in combination with the latest medical digital imaging technologies are growing quickly. The techniques have inherent advantages of compatibility with the output information of medical digitising techniques. Foot orthoses are medical devices used as shoe inserts in the treatment of foot disorders, injuries and diseases such as diabetes, rheumatoid arthritis, congenital defects and other foot related injuries. Currently custom foot orthoses are fabricated through manufacturing techniques which involve costly and based on lengthy trial and error manufacturing process. These techniques have limitations in terms of fabricating required geometries and incorporating complex design features in the custom-made orthoses. The novelty of this research is to explore the commercial scale application of rapid manufacturing techniques and to assess a rapid manufacturing based design and fabrication system for production of custom foot orthoses. The developed system is aimed at delivering the custom made orthoses at mass scale with improved fit, consistency, accuracy and increased product quality. The traditional design and fabrication process for production of custom foot orthoses was investigated and modelled with IDEF0 modelling methodology. The developed IDEF0 model was re-modelled and then the rapid manufacturing approach was integrated in the design and fabrication process. The main functions of foot geometry capture, orthoses design and manufacture of orthoses were modelled and evaluated individually with respect to time and cost and quality of the final product. Different well-established rapid manufacturing techniques were integrated in the current design and fabrication process. The results showed that the techniques have significant impacts on the overall design and fabrication process in terms of increased process efficiency, low lead-time, increased productivity and improved quality of the final product. An orthosis model was fabricated on an experimental basis using different well established rapid manufacturing techniques. The techniques were separately investigated and analysed in terms of orthoses fabrication cost and build time. The cost and lead-time in different techniques were modelled, analysed and evaluated for evaluation of commercial scale applications. The analysis and evaluation of the cost and lead-time modelled for different rapid manufacturing techniques showed that selective laser sintering technique is the better option for integrating the technique in fabrication of custom foot orthoses and that it has the potential to compete with conventional techniques

    Occupational respiratory diseases

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    Shipping list no.: 87-222-P."September 1986."S/N 017-033-00425-1 Item 499-F-2Also available via the World Wide Web.Includes bibliographies and index

    Textbook on Scar Management

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    This text book is open access under a CC BY 4.0 license. Written by a group of international experts in the field and the result of over ten years of collaboration, it allows students and readers to gain to gain a detailed understanding of scar and wound treatment – a topic still dispersed among various disciplines. The content is divided into three parts for easy reference. The first part focuses on the fundamentals of scar management, including assessment and evaluation procedures, classification, tools for accurate measurement of all scar-related elements (volume density, color, vascularization), descriptions of the different evaluation scales. It also features chapters on the best practices in electronic-file storage for clinical reevaluation and telemedicine procedures for safe remote evaluation. The second section offers a comprehensive review of treatment and evidence-based technologies, presenting a consensus of the various available guidelines (silicone, surgery, chemical injections, mechanical tools for scar stabilization, lasers). The third part evaluates the full range of emerging technologies offered to physicians as alternative or complementary solutions for wound healing (mechanical, chemical, anti-proliferation). Textbook on Scar Management will appeal to trainees, fellows, residents and physicians dealing with scar management in plastic surgery, dermatology, surgery and oncology, as well as to nurses and general practitioners ; Comprehensive reference covering the complete field of wounds and scar management: semiology, classifications and scoring Highly educational contents for trainees as well as professionals in plastic surgery, dermatology, surgery, oncology as well as nurses and general practitioners Fast access to information through key points, take home messages, highlights, and a wealth of clinical cases Book didactic contents enhanced by supplementary material and video

    Self-Assembling Peptides for Cartilage Regeneration

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    Loss of glycosaminoglycans (GAGs) in osteoarthritic (OA) cartilage contributes to a decrease in mechanical properties and function in vitro, and is considered to be a major contributor to disease progression. The aims of this investigation were to test the hypothesis that a combination of self-assembling peptides (SAPs) and chondroitin sulfate (glycosaminoglycan; GAG) would restore the biomechanical properties of GAG depleted porcine condylar cartilage, ideally to a level intrinsic to native porcine condylar cartilage. The SAPs investigated were members of the P11 series which have been designed to spontaneously self-assemble into three-dimensional fibrilar hydrogels, in response to physiological conditions. Initial studies were carried out to determine which of three peptides (P11-4, P11-8 and P11-12) demonstrated high ÎČ-sheet percentage, long-woven fibrilar networks and high stiffness; when mixed with chondroitin sulfate at two different GAG molar ratios (1:16 and 1:64) in physiological conditions, using FTIR analysis, transmission electron microscopy and rheology. The ÎČ-sheet percentage, dimensions of fibrils and stiffness were dependent upon the peptide, GAG molar ratio and Na2+ salt concentration. P11-4 and P11-8: GAG mixtures had high ÎČ-sheet percentage ranging from 50.6-91 % and 81.7-92 %, respectively. Fibril lengths of the P11-4 and P11-8: GAG mixtures were in the range 498- 3518 nm and the elastic shear modulus (G’) ranged from 4,479-10,720 Pa and 7,722-26,854 Pa, respectively. P11-4 and P11-8: GAG mixtures were selected for further investigation. In order to produce a GAG depleted cartilage model, porcine femoral condylar cartilage was subjected to three different methods of GAG depletion (1) coating the surface with chondroitinase ABC (2) injecting chondroitinase ABC into the cartilage (3) washing the condyles in sodium dodecyl sulfate (SDS). GAG depletion was successfully achieved following two 24 hour washes in 0.1 % (w/v) SDS and buffer washes. Histological analysis of safranin O stained sections revealed an absence of GAGs. Quantification of GAGs using the dimethylemethylene blue assay revealed that 75 % of GAGs had been removed. In order to assess the effects of peptide: GAG mixtures on the biomechanical properties of the GAG depleted porcine condylar cartilage a biomechanical test method was developed. A series of indentation tests using different loads, followed by finite element analysis of the data were performed on native and GAG depleted porcine condylar cartilage; to identify a suitable load for detection of a significant difference in the deformation, equilibrium elastic modulus and permeability between the native and GAG depleted porcine condylar cartilages. A load of 0.31 N was identified as the most appropriate. GAG depleted porcine condylar cartilage was injected with P11-4 and P11-8 alone, P11-4 and P11-8 : GAG mixtures at a molar ratio of 1:64 and chondroitin sulfate alone. The average percentage deformation of the medial condylar cartilage samples injected with P11-4 alone and P11-4: GAG mixture was 15.5 % and 8.7 % and for P11-8 alone and P11-8: GAG mixture was 11.4 % and 9.1 % respectively; compared to 6.3 % for the native cartilage and 12.6 % for the GAG depleted cartilage. The average equilibrium elastic modulus of the medial cartilage samples injected with P11-4 alone and P11-4: GAG mixture was 0.16 MPa and 0.43 MPa and for P11-8 alone and P11-8: GAG, 0.23 MPa and 0.35 MPa, respectively; compared to 0.49 MPa for the native cartilage and 0.21 MPa for the GAG depleted cartilage. Statistical analysis (ANOVA) showed that a mixture of P11-4: GAG, but not P11-8: GAG restored both the percentage deformation and equilibrium elastic modulus of the GAG depleted cartilage to levels that were not significantly different to the native cartilage. This study has shown that the use of P11-4 in combination with chondroitin sulfate has future potential for development as a minimally invasive treatment for early stage osteoarthritis

    Textbook on Scar Management

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    This text book is open access under a CC BY 4.0 license. Written by a group of international experts in the field and the result of over ten years of collaboration, it allows students and readers to gain to gain a detailed understanding of scar and wound treatment – a topic still dispersed among various disciplines. The content is divided into three parts for easy reference. The first part focuses on the fundamentals of scar management, including assessment and evaluation procedures, classification, tools for accurate measurement of all scar-related elements (volume density, color, vascularization), descriptions of the different evaluation scales. It also features chapters on the best practices in electronic-file storage for clinical reevaluation and telemedicine procedures for safe remote evaluation. The second section offers a comprehensive review of treatment and evidence-based technologies, presenting a consensus of the various available guidelines (silicone, surgery, chemical injections, mechanical tools for scar stabilization, lasers). The third part evaluates the full range of emerging technologies offered to physicians as alternative or complementary solutions for wound healing (mechanical, chemical, anti-proliferation). Textbook on Scar Management will appeal to trainees, fellows, residents and physicians dealing with scar management in plastic surgery, dermatology, surgery and oncology, as well as to nurses and general practitioners ; Comprehensive reference covering the complete field of wounds and scar management: semiology, classifications and scoring Highly educational contents for trainees as well as professionals in plastic surgery, dermatology, surgery, oncology as well as nurses and general practitioners Fast access to information through key points, take home messages, highlights, and a wealth of clinical cases Book didactic contents enhanced by supplementary material and video
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