The aim of this thesis is to enhance the extracellular electron transfer rates (exoelectrogenesis) in cyanobacteria, to be utilised for photo-bioelectricity generation in biophotovoltaics (electrochemical cell). An initial cross comparison of the cyanobacterium Synechococcus elongatus PCC7942 against other exoelectrogenic cultures showed a hindered exoelectrogenic capacity. Nonetheless, in mediatorless biophotovoltaics, it outperformed the microalgae Chlorella vulgaris. Furthermore, the performance of S. elongatus PCC7942 was improved by constructing a more efficient design (lower internal resistance), which was fabricated with carbon fibres and nitrocellulose membrane, both inexpensive materials. To strategically obtain higher exoelectrogenic rates, S. elongatus PCC7942 was conditioned by iron limitation and CO2 enrichment. Both strategies are novel in improving cyanobacteria exoelectrogenesis. Iron limitation induced unprecedented rates of extracellular ferricyanide reduction (24-fold), with the reaction occurring favourably around neutral pH, different to the cultural alkaline pH. Iron limited cultures grown in 5% and 20% CO2 showed increased exoelectrogenic rates in an earlier stage of growth in comparison to air grown cultures. Conveniently, the cultural pH under enriched CO2 was around neutral pH. Enhanced photo-bioelectricity generation in ferricyanide mediated biophotovoltaics was demonstrated. Power generation was six times higher with iron limited cultures at neutral pH than with iron sufficient cultures at alkaline pH. The enhanced performance was also observed in mediatorless biophotovoltaics, especially in the dark phase. Exoelectrogenesis was mainly driven by photosynthetic activity. However, rates in the dark were also improved and in the long term it appeared that the exoelectrogenic activity under illumination tended to that seen in the dark. Proteins participating in iron uptake by an alleged reductive mechanism were overexpressed (2-fold). However, oxidoreductases in the outer membrane remain to be identified. Furthermore, electroactive regions in biofilms of S. elongatus PCC7942 were established using cyclic voltammetry. Double step potential chronoamperometry was also successfully tested in the biofilms. Thus, the electrochemical characterisation of S. elongatus PCC7942 was demonstrated, implying that the strategies presented in this thesis could be used to screen for cyanobacteria and/or electrode materials to further develop systems for photo-bioelectricity generation.

In this dissertation, we investigate coupling between axons in a tract, when the tract has an arbitrary cross-section, with the coupling being mediated by currents as well as electric fields. Under the current mediated setting, we develop a new master equation which captures the relative axonal geometry, specifically, the axon inclinations θi and the inter-axon distances Wip and perform a number of simulations. We observe synchronization in our simulations of axons with differing diameters and separation-dependent coupling delays in the case of non-trivial tract geometries. For the field-mediated interaction setting, we determine the electric near-field of a firing axon’s node of Ranvier - its strength and direction - by a volume conduction approach as well as a more microscopic, dipole-based approach. We obtain field strengths of about 105V/m at a few hundred micron distance from the source at the node. With the field levels having been found significant enough to cause 100 mV voltage drops across 1 micron-diameter axons, we develop an alternate, field-mediated model for synchronization between axons based on the dipole fields generated during action potential propagation. This model shows that synchronization between action potentials on differing axons depends on the phases of the synchronizing action potentials and not merely their separation. Since synchronization takes place in both settings, but currents are generated by fields, when constrained to a specific direction, we find that the field picture is a generalization of the presently prevalent current mediated picture for interaction between axons.

No description available.

La fermentation sombre et les piles à combustible microbiennes (MFC) sont deux technologies émergentes respectivement pour la conversion biologique de l'énergie chimique des composés organiques en hydrogène (H2) et en électricité. En raison des avantages cinétiques et thermodynamiques, la température élevée peut être la clé pour augmenter à la fois la production d'H2 de fermentation sombre et la production d'électricité dans les MFC. Par conséquent, cette thèse se concentre sur la manière dont la température influence la production biologique de H2 et d'électricité à partir d'eaux usées contenant du carbone organique. Deux inocula traités thermiquement (à boues activées fraîches et digérées) ont été comparés pour la production de H2 à partir de xylose à 37, 55 et 70 °C. A la fois à 37 et 55 °C, on obtient un meilleur rendement en H2 par les boues activées fraîches comparé aux boues digérées tandis qu'un très faible rendement en H2 est obtenu par les deux inocula à 70 °C. Ensuite, quatre prétraitements d'inoculum différents (chocs acides, alcalins, thermiques et de congélation) ont été évalués pour créer une efficace communauté productrice de H2 mésophile (37 °C) ou thermophile (55 °C). Les chocs acides et alcalins ont sélectionné des micro-organismes producteurs de H2, appartenant aux Clostridiaceae, au détriment des bactéries produisant du lactate, ce qui a donné respectivement le rendement en H2 le plus élevé à 37 et 55 °C. Bien que le choc thermique ait abouti à un faible rendement en H2 dans un seul lot, il a été montré que la production de H2 par les boues activées fraîches traitées thermiquement augmentait dans l'expérience avec quatre cycles consécutifs. Des boues activées fraîches et traitées thermiquement ont été sélectionnées comme inoculum pour la production continue de H2 à partir d'une eau usée synthétique contenant du xylose dans un réacteur à lit fluidisé (FBR) mésophile (37 °C) et thermophile (55-70 °C, augmenté par étapes). Un rendement en H2 plus élevé a été obtenu dans le FBR thermophile que dans le FBR mésophile. En outre, la production de H2 à 70 °C, qui a échoué dans l'étude précédente, a été couronnée de succès dans le FBR, avec un rendement stable de 1.2 mol H2 mol-1 xylose. La température de fonctionnement de 70 °C s'est également révélée optimale pour la production de H2 à partir d'eaux usées thermomécaniques (TMP) dans un incubateur à gradient de température, car la culture en batch à 70 ° C. Une approche de l'ARN a été utilisée pour étudier la structure et le rôle des communautés microbiennes attachées à l'anode, attachées à la membrane et planctoniques dans un MFC mésophile (37 °C) et thermophile (55 °C) alimenté au xylose. Une communauté anodine dominée par Geobacteraceae a soutenu la production d'électricité à 37 °C, alors que l'établissement de micro-organismes méthanogènes et H2 oxydants a entraîné une faible production d'électricité à 55 °C. Cependant, le développement d'une communauté exoélectrogène thermophile peut être favorisé en appliquant une stratégie de démarrage qui comprend l'imposition d'un potentiel négatif à l'anode et l'inhibition chimique des méthanogènes. Une communauté exoélectrogénique mésophile a également été montré pour produire de l'électricité à partir d'eaux usées de TMP dans un MFC à flux ascendant exploité à 37 °C. En conclusion, une production de H2 plus élevé et plus stable peut être obtenu dans une fermentation sombre thermophile plutôt que mésophile. La fermentation sombre à 70 °C est particulièrement appropriée pour le traitement des eaux usées de TMP car elle est libérée à haute température (50-80 °C) et pourrait être traitée sur site. Les eaux usées de TMP peuvent également être utilisées comme substrat pour la production d'électricité dans les MFC mésophiles. La production d'électricité dans les MFC thermophiles est faisable, mais l'enrichissement des micro-organismes exoélectrogènes thermophiles peut nécessiter une longue période de démarrage / Dark fermentation and microbial fuel cells (MFCs) are two emerging technologies for biological conversion of the chemical energy of organic compounds into hydrogen (H2) and electricity, respectively. Due to kinetic and thermodynamic advantages, high temperature can be the key for increasing both dark fermentative H2 production and electricity production in MFCs. Therefore, this thesis focuses on delineating how temperature influences biological production of H2 and electricity from organic carbon-containing wastewaters. Two heat-treated inocula (fresh and digested activated sludge) were compared, for H2 production from xylose at 37, 55 and 70 °C. At both 37 and 55 °C, a higher H2 yield was achieved by the fresh than digested activated sludge, whereas a very low H2 yield was obtained by both inocula at 70 °C. Then, four different inoculum pretreatments (acidic, alkaline, heat and freezing shocks) were evaluated for creating an efficient mesophilic (37 °C) or thermophilic (55 °C) H2 producing community. Acidic and alkaline shocks selected known H2 producing microorganisms belonging to Clostridiaceae at the expenses of lactate producing bacteria, resulting in the highest H2 yield at 37 and 55 °C, respectively. Although a heat shock resulted in a low H2 yield in a single batch, H2 production by the heat-treated fresh activated sludge was shown to increase in the experiment with four consecutive batch cycles.Heat-treated fresh activated sludge was selected as inoculum for continuous H2 production from a xylose-containing synthetic wastewater in a mesophilic (37 °C) and a thermophilic (55-70 °C, increased stepwise) fluidized bed reactor (FBR). A higher H2 yield was obtained in the thermophilic than in the mesophilic FBR. Furthermore, H2 production at 70 °C, which failed in the earlier batch study, was successful in the FBR, with a stable yield of 1.2 mol H2 mol-1 xyloseadded. Operation temperature of 70 °C was also found optimal for H2 production from thermomechanical pulping (TMP) wastewater in a temperature gradient incubator assay.A RNA approach was used to study the structure and role of the anode-attached, membrane-attached and planktonic microbial communities in a mesophilic (37 °C) and a thermophilic (55 °C) two-chamber, xylose-fed MFC. An anode attached community dominated by Geobacteraceae sustained electricity production at 37 °C, whereas the establishment of methanogenic and H2 oxidizing microorganisms resulted in a low electricity production at 55 °C. However, the development of a thermophilic exoelectrogenic community can be promoted by applying a start-up strategy which includes imposing a negative potential to the anode and chemical inhibition of methanogens. A mesophilic exoelectrogenic community was also shown to produce electricity from TMP wastewater in an upflow MFC operated at 37 °C. In conclusion, a higher and more stable H2 yield can be achieved in thermophilic rather than mesophilic dark fermentation. Dark fermentation at 70 °C is particularly suitable for treatment of TMP wastewater as it is released at high temperature (50-80 °C) and could be treated on site. TMP wastewater can be also used as substrate for electricity production in mesophilic MFCs. Electricity production in thermophilic MFCs is feasible, but enrichment of thermophilic exoelectrogenic microorganisms may require a long start-up period

<p>Bioelectricity, or endogenous electrical signaling mediated by the dynamic distribution of charged molecules, is an ancient signaling mechanism conserved across living organisms. Increasing evidence has revealed that bioelectric signals play a critical role in many diverse aspects of biology such as embryonic development, cell migration, regeneration, cancer, and other diseases. However, direct visualization and manipulation of bioelectricity during development are lacking. Neuroscience has developed tools such as GEVIs (genetically encoded voltage indicators) and chemogenetics like DREADDs (designer receptor exclusively activated by designer drugs) which allow for real–time voltage monitoring and activation of mutated receptors by inert molecules for perturbing membrane potential (Vm). To uncover bioelectric activity during development, we generated a whole-zebrafish transgenic GEVI reporter line and characterized the electrical signaling during early embryogenesis using light sheet microscopy (LSM). Additionally, we generated tissue-specific transgenic lines that combined GEVIs and chemogenetic DREADD tools to manipulate Vm. We found zebrafish embryos display stage-specific characteristic bioelectric signals during the cleavage, blastula, gastrula, and segmentation periods. Furthermore, activation of DREADDs was able to alter cell-specific GEVI fluorescence intensity and could cause a melanophore hyperpigmentation phenotype. Ultimately, these results provide the first real-time systematic analysis of endogenous bioelectricity during vertebrate embryonic development. Additionally, we generated and tested zebrafish transgenic lines for simultaneous visualization and chemogenetic manipulation of Vm during development. These results provide a better understanding of developmental bioelectricity and new tools for future studies, which could eventually help uncover the cellular electric mechanisms behind tissue patterning and disease.</p>

<p>  </p> <p>Electroporation uses puled electric fields to permeabilize cell membranes to either introduce exogeneous molecules into cells through normally impermeable membranes or completely lysing cells to induce cell death. This thesis examines electroporation in combination with a natural product for microorganism inactivation and pulsed magnetic fields for inducing pain remediation. Motivated by previous studies using curcumin with pulsed electric fields for cancer treatment, we hypothesized that this combined treatment modality could also enhance microorganism inactivation. The experiments did not indicate any synergistic benefit from combining curcumin and pulsed electric fields for microorganism inactivation. We also hypothesized that a pulsed magnetic field treatment could permeabilize neuron membranes to block action potentials to reduce pain without requiring drugs or direct intervention with the electric pulses. This thesis explored Sim4Life, a commercial software that coupled electromagnetic solvers with models of organisms to assess the interaction of pulsed magnetic fields with tissues. We designed and simulated a device for generating a pulsed magnetic field with different geometries to assess electric and magnetic field generation. These studies only considered pulsed magnetic fields and not specifically time-dependent currents or DC magnetic fields that could be benchmarked to standard analytic solutions. The process outlined here will enable future benchmarking for Multiphysics, multiscale simulations of pulsed magnetic fields, AC magnetic fields, or novel electromagnetic waveforms. The results for this thesis provide a starting point for future experiments coupling electroporation with natural products for microorganism inactivation and for assessing in vivo effects of external electromagnetic fields. </p>

A tecnologia da biodigestão anaeróbia tem sido comprovada como uma das mais eficientes no tratamento dos dejetos de suínos, esta tecnologia, encontra-se num crescimento tímido em Angola facilitando assim uma poluição maior dos Rios, solos e o ar atmosférico, por falta de tratamento adequado da biomassa produzida por milhares de suínos existentes neste País. O emprego do biogás como fonte de energia para o funcionamento dos equipamentos ainda encontra limitações de ordem tecnológica e por falta de informação, organização e em muitos casos apoios tecnológicos e de instituições governamentais ou Não Governamentais. Este trabalho avaliou a viabilidade técnica, na implantação de Biodigestores na Região de Icolo Bengo em Angola. Foi estudada a implantação de Biodigestores, Modelo Indiano, na fazenda Menga assim como o potencial de geração de energia elétrica existente na produção de Biogás. O tratamento anaeróbio dos resíduos de Suínos como fonte renovável de energia, dentro de um conceito de desenvolvimento sustentável e de racionalização da produção sem agressão ao Meio-Ambiente também são referenciados mostrando que esta tecnologia pode ser apropriada como estratégia de conservação e uso eficiente da energia elétrica que é muito escasso em Angola. O emprego da biodigestão anaeróbia neste caso é possível e desejável, uma vez que contribui para preservação do Meio Ambiente, viabiliza os modernos sistemas de confinamento e reduz o custo da produção assim como ajuda na produção de energia elétrica e de fertilizantes. Um sistema integrado foi proposto e será aplicado na Fazenda Menga, como um dos projetos pioneiros em Angola. / The technology of anaerobic digestion has been proven as one of the most effective in the treatment of pig slurry, In Angola this technology is growing in a shy, so faculties a greater pollution of rivers, soil and atmospheric air for lack of adequate treatment of biomass produced by thousands of pigs in this country. The uses of biogas as an energy source for the operation of the equipment still meets the technological, and for lack of information, organization and often support technological and governmental institutions or NGOs. This study evaluated the technical feasibility, for implementation of the Biodigestors in Icolo-Bengo in Angola. We studied the implementation of Biodigestors, Indian Model, at Menga farm as well as potentially generating power existing in the production of biogas. The anaerobic treatment of swine waste as a renewable source of energy, within the concept of sustainable development and rationalization of production without aggression to the Environment are also referred to showing that this technology may be appropriate as conservation and energy efficiency electricity that is not much in this country. The use of anaerobic digestion in this case is possible and desirable, as it contributes to preservation of the environment, makes possible the modern systems of containment and reduces the cost of production as well as help in the production of electricity and fertilizers. An integrated system was proposed and will be implemented at the Menga farm, as one of the pioneer projects in Angola.

The medical field has been a part of the smart textile area for quite some time. With time come technological advancement and the two fields converge on more and more areas. One such area is that of using textile electrodes, textrodes, for measuring bioelectrical activity, such as heart rate for ECG analysis. There are many components that make for a successful textile electrode and though many studies have been made in the subject there are several aspects that still are difficult. By using textile electrodes the problem with skin irritation from electrolyte gels, commonly used for conventional electrodes, is avoided, however dry textrodes create disturbances in the output signal (heart rate) while subjected to movement and internal dimensional changes. The addition of moisture to a textrode has shown to decrease these intermittent disturbances but the knowledge about fundamental textile structural influence in the matter has not been fully investigated. This study investigates a flat, a 2-thread fleece and an open structure, and their relation to moisture both as textile structures and as textrodes. This way the possibilities of utilising moisture to increase performance in a textrode purpose can be examined and to what extent the textile structure plays a part in that exploitation. The material composition of textile structures also affects their properties The introduction of assistive materials, polyester and viscose, into the Shieldex (conductive yarn) structures is done to test core moisture management properties such as surface tension, absorption and moisture content, and correlate them to electrical properties necessary for textrode function. In the end the gap between textile structure and end product in form of a textrode is closed as the impedance and microclimate of the textrodes are studied. This is mainly to tie together the fundamental textile structures with a complex textile construction. In conclusion the complexity is also confirmed as structural, materialistic and external influences has an impact on the results. The influence of moisture on lowered resistance and impedance in the structures is confirmed but the impact of textile structure can also be seen. The 2-thread fleece and open structures often has a more positive impact on results and therefore has the possibility of enhancing performance of a textrode for bioelectrical signal monitoring. With these results a more effective way of producing long-lasting, patient-friendly, textrodes can be derived and in the future lead to better care in the medical areas.

A tecnologia da biodigestão anaeróbia tem sido comprovada como uma das mais eficientes no tratamento dos dejetos de suínos, esta tecnologia, encontra-se num crescimento tímido em Angola facilitando assim uma poluição maior dos Rios, solos e o ar atmosférico, por falta de tratamento adequado da biomassa produzida por milhares de suínos existentes neste País. O emprego do biogás como fonte de energia para o funcionamento dos equipamentos ainda encontra limitações de ordem tecnológica e por falta de informação, organização e em muitos casos apoios tecnológicos e de instituições governamentais ou Não Governamentais. Este trabalho avaliou a viabilidade técnica, na implantação de Biodigestores na Região de Icolo Bengo em Angola. Foi estudada a implantação de Biodigestores, Modelo Indiano, na fazenda Menga assim como o potencial de geração de energia elétrica existente na produção de Biogás. O tratamento anaeróbio dos resíduos de Suínos como fonte renovável de energia, dentro de um conceito de desenvolvimento sustentável e de racionalização da produção sem agressão ao Meio-Ambiente também são referenciados mostrando que esta tecnologia pode ser apropriada como estratégia de conservação e uso eficiente da energia elétrica que é muito escasso em Angola. O emprego da biodigestão anaeróbia neste caso é possível e desejável, uma vez que contribui para preservação do Meio Ambiente, viabiliza os modernos sistemas de confinamento e reduz o custo da produção assim como ajuda na produção de energia elétrica e de fertilizantes. Um sistema integrado foi proposto e será aplicado na Fazenda Menga, como um dos projetos pioneiros em Angola. / The technology of anaerobic digestion has been proven as one of the most effective in the treatment of pig slurry, In Angola this technology is growing in a shy, so faculties a greater pollution of rivers, soil and atmospheric air for lack of adequate treatment of biomass produced by thousands of pigs in this country. The uses of biogas as an energy source for the operation of the equipment still meets the technological, and for lack of information, organization and often support technological and governmental institutions or NGOs. This study evaluated the technical feasibility, for implementation of the Biodigestors in Icolo-Bengo in Angola. We studied the implementation of Biodigestors, Indian Model, at Menga farm as well as potentially generating power existing in the production of biogas. The anaerobic treatment of swine waste as a renewable source of energy, within the concept of sustainable development and rationalization of production without aggression to the Environment are also referred to showing that this technology may be appropriate as conservation and energy efficiency electricity that is not much in this country. The use of anaerobic digestion in this case is possible and desirable, as it contributes to preservation of the environment, makes possible the modern systems of containment and reduces the cost of production as well as help in the production of electricity and fertilizers. An integrated system was proposed and will be implemented at the Menga farm, as one of the pioneer projects in Angola.

Ion channels and pumps play critical roles during sea urchin development including mediating the blocks to polyspermy, regulating left-right and dorsal-ventral axis specification, directing ventral PMC migration, and controlling biomineralization of the larval skeleton. We performed a screen of pharmacological ion channel inhibitors, and we chose two inhibitors to investigate further. First, we found that tricaine, a potent inhibitor of voltage-gated sodium channels (VGSCs), induces aberrant skeletal patterning in Lytechinus variegatus larvae. The larval skeleton is secreted by the primary mesenchyme cells (PMCs), which migrate within the blastocoel into a stereotypical pattern. We show that VGSC activity is required for normal PMC migration and skeletal patterning. Timed inhibitor studies identified VGSC activity as specifically required from early gastrula to the onset of late gastrula for normal skeletal patterning. Tricaine inhibits the voltage-gated sodium channel LvScn5a which is strongly expressed in the developing nervous system in pluteus larvae. We found that exogenous expression of an anesthetic-insensitive version of LvScn5a is sufficient to rescue hallmark tricaine-mediated skeletal patterning defects, demonstrating the specificity of the inhibitor. LvScn5a exhibits a ventrolateral ectodermal expression domain in gastrulating embryos that is spatiotemporally congruent with triradiate formation in the ventrolateral PMC clusters at the onset of skeletogenesis. This ectodermal territory normally expresses the patterning cue Wnt5, and we find that the expression of Wnt5 is dramatically spatially expanded by tricaine treatment. We also observe ectopic PMC clusters in tricaine-treated embryos. We found that knockdown of Wnt5 expression is sufficient to rescue tricaine-mediated skeletal patterning defects. These results are consistent with a model in which LvScn5a activity in the ventrolateral ectoderm functions to spatially restrict the expression of the ectodermal patterning cue Wnt5 that in turn induces PMC cluster formation. Together, these findings show that spatially restricted sodium channel activity regulates ectodermal cue expression that, in turn, regulates PMC differentiation and skeletal morphogenesis. Second, we show that V-type H⁺ ATPase (VHA) activity is required for specification of the dorsal-ventral (DV) axis. DV specification is controlled by the TGF-β signal Nodal that specifies the ventral territory and indirectly activates dorsal specification via induction of BMP 2/4 expression. Nodal expression occurs downstream of p38 MAPK, which is transiently, asymmetrically inactive on the presumptive dorsal side of the blastula embryo. VHA activity is required for that transient inactivation of p38 MAPK, and it is required for the subsequent spatial restriction of Nodal expression. We show that VHA inhibition is sufficient to induce global Nodal expression during the blastula stage, resulting in ventralization of the embryo. We show that this phenotype can be rescued by experimentally imposing asymmetric Nodal expression at the 4-cell stage. We discover a VHA-dependent voltage gradient across the DV axis and find that VHA activity is required for hypoxia inducible factor (HIF) activation. We show that neither hyperpolarization nor HIF activation is sufficient to perturb DV specification, which implicates a third unknown pathway connecting VHA activity and p38 MAPK symmetry breaking. These results are consistent with a model in which dorsal VHA activity is required to inhibit Nodal expression and signaling, potentially via dorsal p38 MAPK inhibition. Together, these studies demonstrate that ion channels are required for both DV specification and for normal skeletal patterning.