6 research outputs found

    Control strategies for power distribution networks with electric vehicles integration.

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    Controlled Delivery of Pan-PAD-Inhibitor Cl-Amidine Using Poly(3-Hydroxybutyrate) Microspheres.

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    This study deals with the process of optimization and synthesis of Poly(3-hydroxybutyrate) microspheres with encapsulated Cl-amidine. Cl-amidine is an inhibitor of peptidylarginine deiminases (PADs), a group of calcium-dependent enzymes, which play critical roles in a number of pathologies, including autoimmune and neurodegenerative diseases, as well as cancer. While Cl-amidine application has been assessed in a number of in vitro and in vivo models; methods of controlled release delivery remain to be investigated. P(3HB) microspheres have proven to be an effective delivery system for several compounds applied in antimicrobial, wound healing, cancer, and cardiovascular and regenerative disease models. In the current study, P(3HB) microspheres with encapsulated Cl-amidine were produced in a size ranging from ~4-5 µm and characterized for surface morphology, porosity, hydrophobicity and protein adsorption, in comparison with empty P(3HB) microspheres. Cl-amidine encapsulation in P(3HB) microspheres was optimized, and these were found to be less hydrophobic, compared with the empty microspheres, and subsequently adsorbed a lower amount of protein on their surface. The release kinetics of Cl-amidine from the microspheres were assessed in vitro and expressed as a function of encapsulation efficiency. There was a burst release of ~50% Cl-amidine in the first 24 h and a zero order release from that point up to 16 days, at which time point ~93% of the drug had been released. As Cl-amidine has been associated with anti-cancer effects, the Cl-amidine encapsulated microspheres were assessed for the inhibition of vascular endothelial growth factor (VEGF) expression in the mammalian breast cancer cell line SK-BR-3, including in the presence of the anti-proliferative drug rapamycin. The cytotoxicity of the combinatorial effect of rapamycin with Cl-amidine encapsulated P(3HB) microspheres was found to be 3.5% more effective within a 24 h period. The cells treated with Cl-amidine encapsulated microspheres alone, were found to have 36.5% reduction in VEGF expression when compared with untreated SK-BR-3 cells. This indicates that controlled release of Cl-amidine from P(3HB) microspheres may be effective in anti-cancer treatment, including in synergy with chemotherapeutic agents. Using controlled drug-delivery of Cl-amidine encapsulated in Poly(3-hydroxybutyrate) microspheres may be a promising novel strategy for application in PAD-associated pathologies

    Controlling the fate of stem cells through two-and three-dimensional scaffolds based on bioresorbable polymers and graphenen derivatives: a study towards nerve tissue regeneration.

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    184 p.Neurological disorders are the major cause of long-term impairment and the second largest cause of death worldwide. Hence, there is an urgent need for new treatments that allow the functional recovery of damaged tissue. Among the experimental treatments, bioresorbable polyesters are showing great results in preclinical and clinical trials due to their biocompatibility, tunable degradability, versatility and physicochemical and mechanical properties. In this PhD thesis nanostructured scaffolds based on bioresorbable polymers and graphene oxide were developed to study the attachment, aligned growth and migration of both murine and human stem cells, avoiding the use of extracellular matrix-like compounds coatings. The use of murine neural stem cells allowed to study the differentiation pattern of the cells over the nanostructuredscaffolds, focusing on the achievement of a balanced neuronal and glial support, for a long-term survival of the cultures in vitro. The use of a relatively new source of stem cells, now considered clinical waste, like the dental pulp stem cells, allowed to minimize the ethical concerns and provide an actual alternative for personalized medicine in future therapies. To test this alternative, the regeneration capabilities of the nanostructured scaffolds were studied after the impairment of the rostral migratory stream in a rodent model in vivo. And with the aim of addressing the enhanced restoration capabilities of the personalized advanced medical products combining polymeric materials and human stem cells, the regeneration of the rostral migratory stream was compared when grafting the dental pulp stem cells, alone or in combination with our nanostructured scaffolds.Finally, to better resemble the neural niche in vitro graphene derivatives-based three-dimensional scaffolds with tunable geometry, mechanical and electrical conductive features were fabricated and their effect studied on cell survival and differentiation. Afterward, cerium oxide nanoparticles were incorporated to provide enhanced antioxidant and neuroprotective features and their effect on the establishment of balanced neuronal and glial co-cultures studied.Overall, this thesis gives new insights into the design of polymeric materials based on graphene derivatives for future personalized advanced medical products in combination with human stem cells for the restoration of the nervous syste

    Controlled structures and properties of single-walled carbon nanotubes custom-produced by chemical vapor deposition method.

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    Single walled carbon nanotubes (SWNT) are considered as one of the most promising nanomaterials for a large variety of applications that require SWNTs with controlled structures and properties, which is the main focus of this dissertation. The first approach to tackle this problem is to develop appropriate methods to synthesize SWNTs of controlled structure. To achieve this goal, a number of techniques have been developed to selectively grow SWNTs on different support from porous silica to flat substrates. It is demonstrated that a precise control over chirality, diameter and bundle size can be obtained by tuning the reaction temperature in the growth of SWNT over Co-Mo/silica powder by CO disproportionation. In addition, a novel method for selective growth of SWNT on flat substrates has been developed. In this method, SWNTs can be grown either in random direction or vertical alignment on the surface under standard CoMoCATRTM reaction conditions. The second trust of this dissertation is to investigate the properties of as-produced SWNTS with their controlled structural parameters (i.e., diameter, bundle size, chirality, and alignment). Field emission measurements have been conducted to evaluate the dependence of the emission characteristics on the SWNT structure. For the nanotubes grown on flat substrates, the response of the vertically aligned SWNT to polarization of both X-rays (in XANES) and visible light (in Raman) clearly revealed the anisotropic optical properties of V-SWNT. Finally, efforts have been made to explore the growth mechanism of VSWNT on flat substrate. X-ray photoelectron spectroscopy and atomic force microscopy conducted on the flat surface with deposited catalyst gave detailed information about the chemical status of Co-Mo catalyst and their morphological distribution. The evolution of the growth of VSWNT with time was visualized by scanning electron the chemical status of Co-Mo catalyst and their morphological distribution. The evolution of the growth of VSWNT with time was visualized by scanning electron microscopy and clearly demonstrated a two-step process involving the formation of a crust layer followed by a concerted growth constrained by crust. Then a kinetic study with fitted growth data has been derived and the maximum growth rate estimated (i.e. 12.5 nm/sec). In addition to the growth of VSWNT, oxidation and transferring of VSWNT has been investigated for future applications

    Control of the Electron Energy Distribution Function (EEDF) in a Hall Thruster Plasma.

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    Further improvements to Hall-effect thruster (HET) efficiency in the low voltage regime will help enable more extensive space missions. HET efficiency depends on its ability to ionize and accelerate neutral propellant, which can be further improved when electrons with energies and trajectories that contribute to ionization are increased in the right locations. Therefore, electron energy distribution function (EEDF) tailoring is needed. However, predictive EEDF control in plasma devices is a challenging problem due to complex electromagnetic interactions that take place that lead to the turbulent nature of these plasmas. In an effort to control the HET’s EEDF to boost thruster efficiency, and to also uncover further insights into the operation and dynamics of these devices, various analyses were carried out. The last was a reverse-orientation cathode technique to control the EEDF by placing the cathode downstream and pointing towards the thruster to redirect high-energy electrons to a less circuitous path to ionization zones in the thruster’s channel. Total efficiency and its components were calculated from non-invasive thrust stand measurements and a suite of downstream thruster diagnostics respectively. For the test thruster’s nominal operating condition, total efficiency increased by 3 percentage points with the external, downstream cathode when compared to the standard, central cathode configuration; however, for an off-nominal condition, thruster efficiency decreased by 1 percentage point. For both operating conditions, the EEDFs revealed that external cathode electron temperatures were on average about half that of the corresponding central cathode values at the downstream data-taking locations. The results implied that the reverse-orientation cathode placed more control on directing high-energy electrons into the thruster channel since less were in downstream locations. These EEDF changes most likely correlated with an increase in efficiency for only the nominal condition due to larger ion beam divergence in the off-nominal condition. However, to confirm these inferences, internal ion current density and divergence measurements where thrust is produced are needed. Therefore, this EEDF control quest made clear the need for non-invasive, performance diagnostic measurements inside the channel to draw more direct conclusions not only about this method’s results, but also about thruster performance and dynamics in general.PHDApplied PhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/135858/1/kimtrent_1.pd

    Controlling soil erosion in a changing climate: evaluating suitable plant species in grassed waterway design.

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    Soil erosion is a global problem which needs mitigating due to the on-site and off- site impacts it causes. Soil erosion is set to become an even greater problem due to climate change. Climate change is likely to increase the intensity, frequency and duration of precipitation events. This change in precipitation will increase flow erosivity and thus increase the chance of soil detachment. Grass-based erosion mitigation features will have to be able to withstand a higher volume of water as runoff volumes will increase due to climate change. An increased surface runoff rate will increase sediment transport capacity leading to more soil erosion when coupled with an increased detachment rate therefore solutions for the future need to be researched. Grass-based erosion mitigation features such as swales, buffer strips and grassed water ways (GWWs) have been shown to be effective. In this study, Festulolium Bx511 (F2), Festulolium cv Prior (F1) and a mixture of Festuca rubra and Lolium perenne (C) were used in mixtures and monocultures to investigate their efficacy in mitigating erosion. Experiment 1 used growth rooms under different climatic conditions, a summer scenario (22°C) and an autumn scenario (15°C). There were also different rainfall scenarios, drought (No rainfall), normal (100 % rainfall based on average rainfall (1981 – 2010) average rainfall (1981 – 2010) data from the Met Office) and excess (200 % of average rainfall (1981 – 2010) based on data from the Met Office) to see how they would affect the plant traits needed for erosion control. For summer establishment conditions the normal rainfall value was 49.2 mm, and the excess rainfall was 98.4 mm. For autumn establishment conditions the normal rainfall was 81.9 mm, and the excess value was 163.8 mm. A plant trait ranking system was devised, the species which showed promise were taken forward and used within hydraulic flume experiments to assess actual soil erosion mitigation potential. Plant traits linked to erosion control include both above ground (% cover, plant height, number of stems, number of tillers, stem diameter (mm), stem area density (mm² mm-²), above ground biomass (g) and below ground traits (root total length (cm), root total surface area (cm² ), root diameter (mm) and total root length (cm) of ≤0.25 mm diameter. Climate change is likely to change how grass plant traits are manifest due to the differing climatic conditions. Therefore, any solutions currently promoted that utilise grass monocultures and mixtures for erosion mitigation features such as GWWs may need to be revised to mitigate for climate change. Conclusions from Experiment 1 include that species selection for soil erosion control features such as GWWs must consider potential rainfall and temperature conditions during the grass establishment for optimal erosion control. There were, however, two species combinations which could be considered as year-round candidates, Fest_1+Fest_2+C and C. Experiment 2 was a hydraulic flume experiment where the inflow rates used were 0.2 – 1.4 l s¯¹. Significant differences in the following plant traits; number of stems, number of tillers, stem diameter (mm), stem area density (mm² mm-²), total root length (≤0.25 mm ⌀), total root surface area (cm ² ), and root diameter (mm) were observed between different treatments. Conv had a significantly higher number of stems as compared to all other experimental treatments. Fest_1 had a significantly higher number of tillers, stem diameter and stem area density as compared to all other treatments. Fest_1+Fest_2+C had a significantly higher total root length (≤0.25 mm ⌀) as compared to Conv. Fest_1+2 had a significantly higher total root surface area than the Fest_1 and Fest_1+Fest_2+C experimental treatments. Fest_1+Fest_2 had a significantly higher root diameter as compared to the Fest_1+Fest_2+C experimental treatment. However, significant differences did not manifest in sediment concentration. In conclusion, it did not matter if grass species monocultures or mixtures were used as there were no significant differences in sediment concentration between the experimental grass treatments. Experiment 3 was also a hydraulic flume experiment where the inflow rates used were 0.2 – 2.6 l s¯¹. In this experiment there was a lowered seeding rate (L) and a recommended seeding rate used (N). There were significant differences in plant traits and also in sediment concentration. The critical thresholds for the Environment Agency (EA) major event classification of 1000 mg l¯¹ to be reached were determined for Experiment 3. There were several experimental grass treatments which did not breach the limit set out by the EA (Conv N, Fest_1+2 L, Fest_1 N and Conv L). In conclusion the Conv L, Fest_1 N and Fest_1+2 L species treatments should be recommended for farmers for use in soil erosion mitigation features such as grassed waterways. This thesis was made possible thanks to the soils training and research studentship centre for doctoral training (STARS CDT). It was funded by Biotechnology and Biological Sciences Research Council (BBSRC) and Natural Environment Research Council (NERC), Grant/Award Number: NE-R010218-1.PhD in Environment and Agrifoo
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