Combined release of platelet-rich plasma and 3D-mesenchymal stem cell encapsulation in alginate hydrogels modified by the presence of silica

We report the modified release of platelet-rich plasma from alginate platelet-rich plasma hydrogels altered by the presence of silica. These PRP–alginate–silica compositions can be used as injectable carriers for viable mesenchymal stem cells

Electric superbike racing: the design and construction of a championship winning electric superbike

The electric superbikes recently developed at The University of Nottingham have to be considered as a high performance vehicles, competing with its internal combustion engine driven counterparts. This paper presents the motivations for this work as well the design decisions taken to maximize performance in race conditions, along with modelling undertaken to gain an insight into the system interaction as a whole. Data recorded during races and on a rolling road are presented to validate the simulation work

Design, Manufacture and Properties of Cr-Re Alloys for Apllication in Satellite Thrusters.

Aquesta tesi ha consistit en el disseny, fabricació i estudi de les propietats d'aleacions Cr-Re destinades a substituir els aliatges base Pt utilitzats en els motors d'apogeu i de correcció orbital de satél.lits i ha estat recolzada pel Centre de Recerca d'EADS en col.laboració amb la Universitat Politècnica de Catalunya. Els aleatges de Cr-Re han estat objecte d'alguns estudis en el passat que indicaven una millora de les propietats mecàniques amb addicions de fins un 35% de Re. Malhauradament aquests estudis de caire fonamental no incluïen la investigació de la influència del Re en altres proprietats importants per aplicacions estructurals. En aquesta tesi s'ha dissenyat un métode de fabricació semi-industrial pels aliatges Cr-18at%Re i Cr-35at%Re i s'ha estudiat les propietats mecàniques, químiques i tèrmiques rellevants a l'aplicació potencial dels aliatges en càmeres de combustió de motors de satél.lit Un métode de fabricació pulvimetal.lúrgic ha estat dissenyat per la producció d'aliatges prototip i s'ha desenvolupat un métode de fabricació per fosa mitjançant arc eléctric en cressol fred per produir els aliatges d'alta puresa. Per millorar l'homogeneïtat dels aliatges Cr-18Re s'ha implementat un métode d'inoculació de la fosa amb Cr, Pr i Sc. Els aliatges produits per aquest métode presenten una alta puresa i homogeneïtat.Les proprietats mecàniques dels aliatges milloren amb percentatges de Re creixents. Els aliatges Cr-35Re produits en fase líquida presenten les millors propietats mecàniques amb un límit elàstic de 800 MPa a temperatura ambient i una deformació a la ruptura del 5% en tracció. A 1400°C el límit elàstic en tracció i compressió és superior a 140MPa. El Cr-35Re presenta fractura en mode mixte intergranular-transgranular fins a 1200°C i intergranular a temperatura més elevada, això limita la seva plasticitat a alta temperatura. La ductilitat màxima, amb una deformació en tracció del 10% s'assoleix en mode intergranular entre 600 i 1000°C. La resistència dels aliatges Cr-18Re i Cr-35Re a l'oxidació i a la nitruració va ser assajada fins a 1500°C. L'estabilitat dels Cr-35Re a alta temperatura és molt bona i la influència de l'exposició a alta temperatura en la ductilitat és limitada. Els aliatges Cr-18Re presenten una resistència a temperatures elevades mediocre, caracteritzada per la la segregació del Cr a les boreres gra durant l'exposició i la seva evaporació.Com era previsible les addicions de Re al Cr disminueixen la conductivitat tèrmica i elèctrica, ja que els àtoms de Re distorsionen la simetria cristal.lina de l'aliatge. La disminució de la conductivitat térmica unida a la millora de les propietats mecàniques fa difícil fer una estimació sobre la resitència de l'aliatge al xoc tèrmic. Per aquesta raó es va decidir comprovar experimentalment la resistència dels aliatges als gradients térmics característics de l'aplicació. La cinètica d'escalfament de 500K/s i el gradient térmic geomètric de 500K/mm van ser impossibles de reproduir amb equips comercials i va ser necessàri dissenyar una instal.lació específica basada en un forn d'arc eléctric. Els aliatges de Cr-35Re donen la millor resposta en xoc i gradient tèrmic, presentant micro fissures de menys de 150µm a la superfície després de 100 cícles i cap fissuració interna, mentre que els aleatges de Cr-18Re presenten fissuració a les boreres de gra de la superfícies fins a una findària de 200µm.La millora de les propietats mecàniques, químiques i de ciclatge tèrmic de l'aleatge contenint un 35% de Re es significativa i indica que s'adequa a l'aplicació. L'estudi ha resultat en la fabricació d'un motor de 22N que serà assajat a les instal.lacions de EADS Space a Lampoldhausen, Alemanya.The manufacturing process and properties of various Cr-Re alloys have been investigated in this work to replace Pt alloys used currently in the satellite thruster combustion chambers. This Thesis has been supported by the Corporate Research Center of EADS and tutored by the Technical University of Catalonia. The studies carried out in the past on the Re effect on the mechanical properties of refractory alloys resulted in the industrial application of Mo-Re and W-Re alloys. Cr-Re alloys have been studied at a fundamental level indicating an improvement of the mechanical properties of the alloys containing Re. Other properties related to its potential application in satellite thrusters were not characterized and an industrial manufacturing process for Cr-Re alloys does not exist, hence the motivation for this PhD. In this work Cr-Re alloys were manufactured initially by means of powder metallurgy. Their mechanical properties improved with increasing Re content verifying the results of the few literature references available. High purity Cr-18at%Re and Cr-35at%Re alloys were produced by melting and casting by a specific procedure. Heterogeneity problems in Cr-18Re alloys were reduced by inoculation of the melt with Ce, Pr and Sc. Mechanical properties of the high purity Cr-Re alloys improve significantly over the powder metallurgical alloys. Compressive elastic limit of both Cr-18 and Cr-35Re alloys at room temperature is over 800 MPa and compressive deformation is possible up to 70% without formation of surface cracks. Elastic limit at 1400°C is over 140 MPa both under compression and tension. Fracture under tension is mixed transgranular and intergranular up to 1200°C. Above this fracture becomes intergranular, characterized by very little plasticity. Best ductility under tension is obtained between 600 and 1000°C with a deformation to fracture of about 10%.Resistance of the alloys to oxidation and nitruration was characterized up to 1700 °C. Tests revealed that Cr-18Re alloys are not capable of building a stable protective layer during exposure to air or nitrogen at the test temperature. They also present a grain boundary instability caused by Cr segregation and evaporation during exposure. Cr-35Re alloys create a stable protective layer of Cr oxide that protects the substrate against light element diffusion. In nitrogen atmosphere Cr-35Re builds a stable layer that is not protective against diffusion of nitrogen. The investigation of the plasticity of the samples after exposure shows that diffused nitrogen does not affect significantly the plasticity of Cr-35Re however there is some scatter in the results due to the small sample cross section relative to grain size. Exposure to vacuum at 1700 °C verified that the grain boundary instability of Cr-18Re was not related to any reaction with the atmosphere as it also takes place in vacuum. Cr-35Re alloys did not present any significant sublimation at this temperature and no grain growth could be detected after exposure. Additions of Re to Cr reduce the thermal and electric conductivity of the alloys as the symmetry of the lattice is distorted by the Re atoms. This, coupled to the improvement of the mechanical properties makes a prediction of the thermal shock resistance of the alloys difficult. For this reason it was decided to build an installation reproducing the thermal shocks and thermal gradients, of 500K/s and 500K/mm respectively, characteristic of the application. When cycled, Cr-18Re alloys suffered also from the grain boundary instability and fractured up to a depth of 200µm. Cr-35Re alloys showed minor cracks and accommodated the linear thermal gradient by means of twinning. The mechanical, chemical and thermal cycling properties of the Cr-35Re alloys indicate that it is suitable for the application. This work resulted in the construction of a 22N satellite thruster with Cr-35Re alloy that will be tested in EADS Space Transportation in Lampoldshausen

Layered Al2O3-SiO2 and Al2O3-Ta2O5 thin-film composites for high dielectric strength, deposited by pulsed direct current and radio frequency magnetron sputtering

Multilayer thin films have the potential to act as high dielectric strength insulation for wire and microelectronics. In this study, films consisting of 2, 4 or 8 layers, composed of Al2O3 with SiO2 or Ta2O5, were prepared via pulsed direct current and radio frequency magnetron sputtering to a thickness of between 152 and 236 nm. The dielectric strengths of all films exceeded the 310 Vμm−1 achieved for PDC Al2O3. Maximum dielectric strengths were obtained for four layer composites; Al2O3-SiO2-Al2O3-SiO2 (466 Vμm−1) and Al2O3-Ta2O5-Al2O3-Ta2O5 (513 Vμm−1), each containing two PDC-Al2O3 and two RF-SiO2/Ta2O5 layers. Whilst the average dielectric strength was higher in the Ta2O5 composites, they suffered from higher leakage prior to breakdown with ca. 6.5 nA compared to ca. 0.1 nA for SiO2 composites. The mechanical properties of the composites were poorer due to increased intrinsic coating stress. Samples exhibited complete interfacial delamination with maximum coating adhesion strengths of 22 and 25 MPa. The variance resulted from larger coefficient of thermal expansion for Ta2O5 compared to SiO2. Sputtered composites of Al2O3 and either SiO2 or Ta2O5 had high breakdown strength with reasonable adhesion and could be suitable for insulating copper conductors in the aerospace and automotive industries

Mejora de los procesos del sistema de garantía interna de la calidad de la EINA

La EINA dispone de un Sistema de Garantía Interna de la Calidad certificado que, al igual que el resto de su actividad, precisa de mejora continua. En este contexto se propone el presente TFG cuyas actividades principales serán las siguientes: - Revisión del SGIC, Establecimiento de un mapa de indicadores actualizado. - Definición e implementación de una sistemática de actualización automática de dichos indicadores. - Actualización del plan de mejora continua

Degradation and characterization of resorbable phosphate-based glass thin-film coatings applied by radio-frequency magnetron sputtering

Quinternary phosphate-based glasses of up to 2.67 μm, deposited by radio-frequency magnetron sputtering, were degraded in distilled water and phosphate-buffered saline (PBS) to investigate their degradation characteristics. Magnetron- sputtered coatings have been structurally compared to their compositionally equivalent melt-quenched bulk glass counterparts. The coatings were found to have structurally variable surfaces to melt-quenched glass such that the respective bridging oxygen to nonbridging oxygen bonds were 34.2% to 65.8% versus 20.5% to 79.5%, forming metaphosphate (PO3)−(Q2) versus less soluble (P2O7)4− (Q1) and (PO4)3− (Q0), respectively. This factor led to highly soluble coatings, exhibiting a t1/2 degradation dependence in the first 2 h in distilled water, followed by a more characteristic linear profile because the subsequent layers were less soluble. Degradation was observed to preferentially occur, forming voids characteristic of pitting corrosion, which was confirmed by the use of a focused ion beam. Coating degradation in PBS precipitated a (PO3)−metaphosphate, an X-ray amorphous layer, which remained adherent to the substrate and seemingly formed a protective diffusion barrier, which inhibited further coating degradation. The implications are that while compositionally similar, sputter-deposited coatings and melt-quenched glasses are structurally dissimilar, most notably, with regard to the surface layer. This factor has been attributed to surface etching of the as-deposited coating layer during deposition and variation in the thermal history between the processes of magnetron sputtering and melt quenching

In vitro degradation and mechanical properties of PLA-PCL copolymer unit cell scaffolds generated by two-photon polymerization

The manufacture of 3D scaffolds with specific controlled porous architecture, defined microstructure and an adjustable degradation profile was achieved using two-photon polymerization (TPP) with a size of 2  ×  4  ×  2 mm3. Scaffolds made from poly(D,L-lactide-co-ɛ-caprolactone) copolymer with varying lactic acid (LA) and ɛ -caprolactone (CL) ratios (LC16:4, 18:2 and 9:1) were generated via ring-opening-polymerization and photoactivation. The reactivity was quantified using photo-DSC, yielding a double bond conversion ranging from 70% to 90%. The pore sizes for all LC scaffolds were see 300 μm and throat sizes varied from 152 to 177 μm. In vitro degradation was conducted at different temperatures; 37, 50 and 65 °C. Change in compressive properties immersed at 37 °C over time was also measured. Variations in thermal, degradation and mechanical properties of the LC scaffolds were related to the LA/CL ratio. Scaffold LC16:4 showed significantly lower glass transition temperature (T g) (4.8 °C) in comparison with the LC 18:2 and 9:1 (see 32 °C). Rates of mass loss for the LC16:4 scaffolds at all temperatures were significantly lower than that for LC18:2 and 9:1. The degradation activation energies for scaffold materials ranged from 82.7 to 94.9 kJ mol−1. A prediction for degradation time was applied through a correlation between long-term degradation studies at 37 °C and short-term studies at elevated temperatures (50 and 65 °C) using the half-life of mass loss (Time (M1/2)) parameter. However, the initial compressive moduli for LC18:2 and 9:1 scaffolds were 7 to 14 times higher than LC16:4 (see 0.27) which was suggested to be due to its higher CL content (20%). All scaffolds showed a gradual loss in their compressive strength and modulus over time as a result of progressive mass loss over time. The manufacturing process utilized and the scaffolds produced have potential for use in tissue engineering and regenerative medicine applications

Assessing the life cycle environmental impacts of titania nanoparticle production by continuous flow solvo/hydrothermal synthesis

Continuous-flow hydrothermal and solvothermal syntheses offer substantial advantages over conventional processes, producing high quality materials from a wide range of precursors. In this study, we evaluate the “cradle-to-gate” life cycle environmental impacts of alternative titanium dioxide (TiO₂) nanoparticle production parameters, considering a range of operational conditions, precursors, material properties and production capacities. A detailed characterisation of the nano-TiO₂ products allows us, for the first time, to link key nanoparticle characteristics to production parameters and environmental impacts, providing a useful foundation for future studies evaluating nano-TiO₂ applications. Five different titanium precursors are considered, ranging from simple inorganic precursors, like titanium oxysulphate (TiOS), to complex organic precursors such as titanium bis(ammonium-lactato)dihydroxide (TiBALD). Synthesis at the laboratory scale is used to determine the yield, size distribution, crystallinity and phase of the nanoparticles. The specifications and operating experience of a full scale plant (>1000 t per year) are used to estimate the mass and energy inputs of industrial scale production for the life cycle assessment. Overall, higher process temperatures are linked to larger, more crystalline nanoparticles and higher conversion rates. Precursor selection also influences nano-TiO₂ properties: production from TiOS results in the largest particle sizes, while TiBALD achieves the smallest particles and narrowest size distribution. Precursor selection is the main factor in determining cradle-to-gate environmental impacts (>80% in some cases), due to the production impact of complex organic precursors. Nano-TiO2 production from TiOS shows the lowest global warming potential (GWP) (<12 kg CO₂-eq. per kg TiO₂) and cumulative energy demand (CED) (<149 MJ kg¯¹ TiO₂) due to the low environmental impact of the precursor, the use of water as a solvent and its high yield even at lower temperatures. Conversely, the TiBALD precursor shows the highest impact (86 kg CO₂-eq. per kg TiO₂ and 1952 MJ kg¯¹ TiO₂) due to the need for additional post-synthesis steps and complexity of precursor manufacturing. The main purpose of this study is not a direct comparison of the environmental impacts of TiO₂ nanoparticles manufactured utilizing various precursors under different conditions, but to provide an essential foundation for future work evaluating potential applications of nano-TiO₂ and their life cycle environmental impacts

In vitro degradation and mechanical properties of PLA-PCL copolymer unit cell scaffolds generated by two-photon polymerization

The manufacture of 3D scaffolds with specific controlled porous architecture, defined microstructure and an adjustable degradation profile was achieved using two-photon polymerization (TPP) with a size of 2 × 4 × 2 mm3. Scaffolds made from poly(D,L-lactide-co-ε-caprolactone) copolymer with varying lactic acid (LA) and ε -caprolactone (CL) ratios (LC16:4, 18:2 and 9:1) were generated via ring-opening-polymerization and photoactivation. The reactivity was quantified using photo-DSC, yielding a double bond conversion ranging from 70% to 90%. The pore sizes for all LC scaffolds were see 300 μm and throat sizes varied from 152 to 177 μm. In vitro degradation was conducted at different temperatures; 37, 50 and 65°C. Change in compressive properties immersed at 37°C over time was also measured. Variations in thermal, degradation and mechanical properties of the LC scaffolds were related to the LA/CL ratio. Scaffold LC16:4 showed significantly lower glass transition temperature (T g) (4.8°C) in comparison with the LC 18:2 and 9:1 (see 32°C). Rates of mass loss for the LC16:4 scaffolds at all temperatures were significantly lower than that for LC18:2 and 9:1. The degradation activation energies for scaffold materials ranged from 82.7 to 94.9 kJ mol-1. A prediction for degradation time was applied through a correlation between long-term degradation studies at 37°C and short-term studies at elevated temperatures (50 and 65°C) using the half-life of mass loss (Time (M1/2)) parameter. However, the initial compressive moduli for LC18:2 and 9:1 scaffolds were 7 to 14 times higher than LC16:4 (see 0.27) which was suggested to be due to its higher CL content (20%). All scaffolds showed a gradual loss in their compressive strength and modulus over time as a result of progressive mass loss over time. The manufacturing process utilized and the scaffolds produced have potential for use in tissue engineering and regenerative medicine applications

Continuous synthesis of dispersant-coated hydroxyapatite plates

A continuous flow hydrothermal synthetic route which allows the direct “in situ” capping/coating of hydroxyapatite nanoplates with functional dispersants in a single stage is reported. The methodology induced crystallisation by rapid mixing of streams of preheated water and solutions of reagents in water, whilst the hydrophobic surface modification of the HA platelets was achieved without morphological disruption. The effect of adding the hydrocarbon either before or after the HA platelet formation point has also been assessed, proving that the presence of surfactant at the reaction site does not interfere with the formation of HA and allows for a more efficient binding and extraction of the inorganic materials. The coupling mechanisms between the surfactant and the HA surface have been proposed to be a mixture of covalent and electrostatic interactions (i.e. all forms of chemisorption). This synthesis route is fully scalable to pilot (10 tons per year) and industrial (1000 tons per year) scales