169 research outputs found
Passiivisten bioreaktoreiden kehittäminen erityyppisten vähähiilisten jätevesien käsittelyyn kylmissä ilmasto-olosuhteissa
No full textAbstractWoodchip bioreactors have been used as an engineered solutions for mitigating nitrate from contaminated water. However, their year-round treatment performance and possible solutions for enhancing their removal efficiency under cold climate conditions still needs more research. In this thesis, we investigated nitrogen removal from aquaculture and mine-influenced water as an indoor and outdoor treatment system under several experimental conditions. This thesis attempts to identify design parameters (e.g., optimal hydraulic retention time (HRT) and nitrate removal rate) and enhancement solutions for woodchip bioreactors under cold climate conditions such as additional carbon source, hydraulic design and use of a floating aquatic as a hybrid system. The results show that woodchip bioreactors can successfully remove nitrate from recirculating aquaculture system (RAS) discharge and mine-influenced water under cold climate conditions. Two-year results from a full-scale woodchip bioreactor showed that selected design parameters from a laboratory-scale were sufficient to complete denitrification at the full-scale. The denitrification followed first-order reaction for RAS effluent and optimal HRT ranged between 1.5 to 2 d to achieve a nitrate removal rate of 25.8 g NO-3-N m-3d-1 and 74% removal efficiency. A layer of 50 cm of dry woodchips combined with snow cover (20‐30 cm) was sufficient to prevent frost, the water temperature never dropped lower than 7.3 °C during cold winter conditions (minimum air temperature = -24.7 ℃). Design of the hybrid unit was improved by inserting two inner plates along the water flow and adding floating hook-moss improved the hydraulic efficiency from poor (λ=0.06) to satisfactory (λ=0.51) which led to higher removal rates.Original papersOriginal papers are not included in the electronic version of the dissertation.Kiani, S., Kujala, K., T. Pulkkinen, J., Aalto, S. L., Suurnäkki, S., Kiuru, T., Tiirola, M., Kløve, B., & Ronkanen, A.-K. (2020). Enhanced nitrogen removal of low carbon wastewater in denitrification bioreactors by utilizing industrial waste toward circular economy. Journal of Cleaner Production, 254, 119973. https://doi.org/10.1016/j.jclepro.2020.119973Self-archived versionKiani, S., Lehosmaa, K., Kløve, B., & Ronkanen, A.-K. (2022). Nitrogen removal of mine-influenced water in a hybrid bioreactor with floating hook-moss (Warnstorfia fluitans) in cold climate conditions. Ecological Engineering, 177, 106562. https://doi.org/10.1016/j.ecoleng.2022.106562Self-archived versionPulkkinen, J. T., Ronkanen, A.-K., Pasanen, A., Kiani, S., Kiuru, T., Koskela, J., Lindholm-Lehto, P., Lindroos, A.-J., Muniruzzaman, M., Solismaa, L., Klöve, B., & Vielma, J. (2021). Start-up of a “zero-discharge” recirculating aquaculture system using woodchip denitrification, constructed wetland, and sand infiltration. Aquacultural Engineering, 93, 102161. https://doi.org/10.1016/j.aquaeng.2021.102161Self-archived versionKiani, S., Khan, U. A., T. Pulkkinen, J., Kujala, K., Kløve, B., Ronkanen, A.-K. (2022).
Design parameters of woodchip bioreactors under cold climate conditions (from laboratory to full scale). Manuscript in preparation.TiivistelmäPuuhakebioreaktoreita on käytetty puhdistusratkaisuna veden nitraattipitoisuuden vähentämiseksi. Niiden ympärivuotinen käsittelyteho ja mahdolliset ratkaisut poistotehokkuuden parantamiseksi kylmissä ilmasto-olosuhteissa vaativat kuitenkin lisätutkimuksia. Tässä opinnäytetyössä tutkittiin typenpoistoa vesiviljelyn ja kaivosten puhdistusta vaativista vesistä sisä- ja ulkokäsittelyjärjestelmänä useissa koeolosuhteissa. Tässä työssä tunnistettiin suunnitteluparametreja (esim. optimaalinen HRT ja nitraatinpoistonopeus) ja parannusratkaisuja puuhakebioreaktoreille kylmissä ilmasto-olosuhteissa, kuten lisähiililähde, hydraulinen suunnittelu ja kelluvan vesikasvattamon käyttö hybridijärjestelmänä. Tulosten perusteella puulastubioreaktoreilla voidaan onnistuneesti poistaa nitraattia sekä sisäisen kierron kalankasvattamojen (RAS) että kaivosten kuormittamasta vedestä kylmissä ilmasto-olosuhteissa. Kahden vuoden tulokset täysimittaisella puuhakebioreaktorilla osoittivat, että laboratoriomittakaavassa valitut suunnitteluparametrit riittivät täyteen denitrifikaatioon täysimittaisessa mittakaavassa. Denitrifikaatio noudatti ensimmäisen järjestyksen reaktiota RAS- järjestelmänjäteveden osalta, ja optimaalinen HRT-aika vaihteli 1,5 ja 2 päivän välillä, jotta saavutettiin 25,8 g NO-3-N m-3d-1 ja 74 prosentin poistotehokkuus. 50 cm:n kerros kuivaa puuhaketta yhdistettynä lumipeitteeseen (20‐30 cm) riitti estämään järjestelmänjäätymisen, eikä veden lämpötila laskenut kokeen aikana alle 7,3 °C:n kylmien talviolosuhteiden aikana (ilman alin lämpötila = -24,7 ℃). Hybridiyksikön suunnittelua parannettiin lisäämällä kaksi sisälevyä veden virtauksen suuntaisesti ja kelluvaa koukkusammalta lisäämällä parannettiin hydraulista tehokkuutta huonosta (λ=0,06) tyydyttävään (λ= 0,51), mikä johti suurempiin poistomääriin.OsajulkaisutOsajulkaisut eivät sisälly väitöskirjan elektroniseen versioon.Kiani, S., Kujala, K., T. Pulkkinen, J., Aalto, S. L., Suurnäkki, S., Kiuru, T., Tiirola, M., Kløve, B., & Ronkanen, A.-K. (2020). Enhanced nitrogen removal of low carbon wastewater in denitrification bioreactors by utilizing industrial waste toward circular economy. Journal of Cleaner Production, 254, 119973. https://doi.org/10.1016/j.jclepro.2020.119973Rinnakkaistallennettu versioKiani, S., Lehosmaa, K., Kløve, B., & Ronkanen, A.-K. (2022). Nitrogen removal of mine-influenced water in a hybrid bioreactor with floating hook-moss (Warnstorfia fluitans) in cold climate conditions. Ecological Engineering, 177, 106562. https://doi.org/10.1016/j.ecoleng.2022.106562Rinnakkaistallennettu versioPulkkinen, J. T., Ronkanen, A.-K., Pasanen, A., Kiani, S., Kiuru, T., Koskela, J., Lindholm-Lehto, P., Lindroos, A.-J., Muniruzzaman, M., Solismaa, L., Klöve, B., & Vielma, J. (2021). Start-up of a “zero-discharge” recirculating aquaculture system using woodchip denitrification, constructed wetland, and sand infiltration. Aquacultural Engineering, 93, 102161. https://doi.org/10.1016/j.aquaeng.2021.102161Rinnakkaistallennettu versioKiani, S., Khan, U. A., T. Pulkkinen, J., Kujala, K., Kløve, B., Ronkanen, A.-K. (2022).
Design parameters of woodchip bioreactors under cold climate conditions (from laboratory to full scale). Manuscript in preparation.Academic dissertation to be presented with the assent of the Doctoral Programme Committee of Technology and Natural Sciences of the University of Oulu for public defence in the Arina auditorium (TA105), Linnanmaa, on 8 December 2022, at 12 noonAbstract
Woodchip bioreactors have been used as an engineered solutions for mitigating nitrate from contaminated water. However, their year-round treatment performance and possible solutions for enhancing their removal efficiency under cold climate conditions still needs more research. In this thesis, we investigated nitrogen removal from aquaculture and mine-influenced water as an indoor and outdoor treatment system under several experimental conditions. This thesis attempts to identify design parameters (e.g., optimal hydraulic retention time (HRT) and nitrate removal rate) and enhancement solutions for woodchip bioreactors under cold climate conditions such as additional carbon source, hydraulic design and use of a floating aquatic as a hybrid system. The results show that woodchip bioreactors can successfully remove nitrate from recirculating aquaculture system (RAS) discharge and mine-influenced water under cold climate conditions. Two-year results from a full-scale woodchip bioreactor showed that selected design parameters from a laboratory-scale were sufficient to complete denitrification at the full-scale. The denitrification followed first-order reaction for RAS effluent and optimal HRT ranged between 1.5 to 2 d to achieve a nitrate removal rate of 25.8 g NO-3-N m-3d-1 and 74% removal efficiency. A layer of 50 cm of dry woodchips combined with snow cover (20‐30 cm) was sufficient to prevent frost, the water temperature never dropped lower than 7.3 °C during cold winter conditions (minimum air temperature = -24.7 ℃). Design of the hybrid unit was improved by inserting two inner plates along the water flow and adding floating hook-moss improved the hydraulic efficiency from poor (λ=0.06) to satisfactory (λ=0.51) which led to higher removal rates.Tiivistelmä
Puuhakebioreaktoreita on käytetty puhdistusratkaisuna veden nitraattipitoisuuden vähentämiseksi. Niiden ympärivuotinen käsittelyteho ja mahdolliset ratkaisut poistotehokkuuden parantamiseksi kylmissä ilmasto-olosuhteissa vaativat kuitenkin lisätutkimuksia. Tässä opinnäytetyössä tutkittiin typenpoistoa vesiviljelyn ja kaivosten puhdistusta vaativista vesistä sisä- ja ulkokäsittelyjärjestelmänä useissa koeolosuhteissa. Tässä työssä tunnistettiin suunnitteluparametreja (esim. optimaalinen HRT ja nitraatinpoistonopeus) ja parannusratkaisuja puuhakebioreaktoreille kylmissä ilmasto-olosuhteissa, kuten lisähiililähde, hydraulinen suunnittelu ja kelluvan vesikasvattamon käyttö hybridijärjestelmänä. Tulosten perusteella puulastubioreaktoreilla voidaan onnistuneesti poistaa nitraattia sekä sisäisen kierron kalankasvattamojen (RAS) että kaivosten kuormittamasta vedestä kylmissä ilmasto-olosuhteissa. Kahden vuoden tulokset täysimittaisella puuhakebioreaktorilla osoittivat, että laboratoriomittakaavassa valitut suunnitteluparametrit riittivät täyteen denitrifikaatioon täysimittaisessa mittakaavassa. Denitrifikaatio noudatti ensimmäisen järjestyksen reaktiota RAS- järjestelmänjäteveden osalta, ja optimaalinen HRT-aika vaihteli 1,5 ja 2 päivän välillä, jotta saavutettiin 25,8 g NO-3-N m-3d-1 ja 74 prosentin poistotehokkuus. 50 cm:n kerros kuivaa puuhaketta yhdistettynä lumipeitteeseen (20‐30 cm) riitti estämään järjestelmänjäätymisen, eikä veden lämpötila laskenut kokeen aikana alle 7,3 °C:n kylmien talviolosuhteiden aikana (ilman alin lämpötila = -24,7 ℃). Hybridiyksikön suunnittelua parannettiin lisäämällä kaksi sisälevyä veden virtauksen suuntaisesti ja kelluvaa koukkusammalta lisäämällä parannettiin hydraulista tehokkuutta huonosta (λ=0,06) tyydyttävään (λ= 0,51), mikä johti suurempiin poistomääriin
Fast Genetic Algorithm For Feature Selection — A Qualitative Approximation Approach
No full textWe propose a two-stage surrogate-assisted evolutionary approach to address the computational issues arising from using Genetic Algorithm (GA) for feature selection in a wrapper setting for large datasets. The proposed approach involves constructing a lightweight qualitative meta-model by sub-sampling data instances and then using this meta-model to carry out the feature selection task. We define "Approximation Usefulness" to capture the necessary conditions that allow the meta-model to lead the evolutionary computations to the correct maximum of the fitness function. Based on our procedure we create CHCQX a Qualitative approXimations variant of the GA-based algorithm CHC (Cross generational elitist selection, Heterogeneous recombination and Cataclysmic mutation). We show that CHCQX converges faster to feature subset solutions of significantly higher accuracy, particularly for large datasets with over 100K instances. We also demonstrate the applicability of our approach to Swarm Intelligence (SI), with results of PSOQX, a qualitative approximation adaptation of the Particle Swarm Optimization (PSO) method. A GitHub repository with the complete implementation is available2. This paper for the Hot-off-the-Press track at GECCO 2023 summarizes the original work published at [3].References[1] Mohammed Ghaith Altarabichi, Yuantao Fan, Sepideh Pashami, Peyman Sheikholharam Mashhadi, and Sławomir Nowaczyk. 2021. Extracting invariant features for predicting state of health of batteries in hybrid energy buses. In 2021 ieee 8th international conference on data science and advanced analytics (dsaa). IEEE, 1–6.[2] Mohammed Ghaith Altarabichi, Sławomir Nowaczyk, Sepideh Pashami, and Peyman Sheikholharam Mashhadi. 2021. Surrogate-assisted genetic algorithm for wrapper feature selection. In 2021 IEEE Congress on Evolutionary Computation (CEC). IEEE, 776–785.[3] Mohammed Ghaith Altarabichi, Sławomir Nowaczyk, Sepideh Pashami, and Peyman Sheikholharam Mashhadi. 2023. Fast Genetic Algorithm for feature selection—A qualitative approximation approach. Expert systems with applications 211 (2023), 118528.© 2023 Copyright held by the owner/author(s).</p
A pilot study to assess the potential of denitrifying bioreactors in treatment of aquaculture effluents
No full textHeterotrophic denitrification reactors are typical treatment units used to remove nitrate from aquaculture effluent. However, they face with limitation due to practical and economic reasons as a result of their requirement for external readily available organic carbon sources. In this study, four clear acrylic vertical columns (10cm × 32cm) with upward flow direction were constructed and packed packed with wood chips (from birch tree), and mixture of woodchips with three different carbon sources (potato peels from industrial process; dried sphagnum moss and biochar coals). The purification performance of bioreactors were investigated in treatment of aquaculture effluent under design hydraulic retention time (HRT) of 48-h and temperature of 15.35± 0.31°C (mean± SD) for 55 days.
The results of this study clearly showed the instant nitrate (NO₃-N) reduction in all bioreactors and stable removal efficiency after one week. As much as 94% of the nitrate was removed from aquaculture effluent with 35.5 mg NO₃-N L⁻¹ concentration, in bioreactor with woodchips. This removal efficiency corresponded to 21.6 g N m⁻³d⁻¹ removal rate. Reported removal rate and removal efficiency for 35.5 mg NO₃-N L⁻¹ inflow concentration, averaged (21.4 g N m⁻³d⁻¹, 92 %) for woodchips with potato peels, (20.7 g N m⁻³d⁻¹, 91.3 %) for woodchips with biochar and (19.2 g N m⁻³d⁻¹, 78.9 %) for woodchips with dried sphagnum moss (BR2). In addition, bioreactor with potato peels showed higher nitrate removal rate (29.2 g N m⁻³d⁻¹) for the inflow water with high concentration of NO₃-N (35th -55th day).
Reported nitrate removal rate in this study were relatively greater than measured in previous studies due to the selected sufficient HRT (48-h) combined with relatively high NO₃-N concentration of influent in the optimal temperature of 15.35± 0.31°C (mean± SD). Start-up leachate of organic carbon, ammonia and phosphorus for start-up period took place in all bioreactors, but with higher rate in bioreactor with potato peels. Rise in alkalinity took palace as an evidence of heterotrophic denitrification in all bioreactors expect bioreactor with potato peels.
Phosphorus reductions were observed after two weeks in woodchips bioreactor with biochar, bioreactor with dried sphagnum moss and woodchip bioreactor at the highest removal efficiency of 23%, 38% and 35%, respectively. While, Phosphorus reduction started in bioreactor with potato peels after nearly one month at the rate of 20%.
In summary, the master thesis demonstrated that woodchips bioreactors have potential of nitrate removal from aquaculture effluent even with low chemical oxygen demand (COD). Woodchips bioreactors can reach the stable performance within few weeks
Spaces of contestation: the everyday experiences of ten African migrants in Cape Town
No full textIncludes bibliographical references.Xenophobia in South Africa is so overt that it has take a covert form. The 'xenocide' events that took place in 2008 were called xenophobic acts. It is the recurrent denialism of xenophobia on an everyday basis that this project has explored through the narrative accounts of ten African migrants in Cape Town. The lived everyday experiences of ten African migrants have brought forward the central argument of this thesis. From the data, it is evident that as a reponse to everyday pressures of prejudices and xenophobia in social and physical spaces, African migrants have developed mutable, unsettled and vagrant identities in order to cope with everyday low level violence. This argument emerged as four key stressors have been identified as the components of a more substantial explanation of xenophobia in South Africa. The four key components are: the enforcement of identity (national and group), the demarcation of spaces of belonging, the experiences of economic insecurity, and lastly a 'culture of violence' in South Africa. This thesis argues that these four stressors are the result of an on-going active process of xenophobic attitudes
Rikastushiekka-altaan suotoveden keräysjärjestelmän arviointi : tapaustutkimus Kevitsan kaivos
No full textDevelopment of passive bioreactors treating different types of low carbon wastewater in cold climate conditions
No full textAbstract
Woodchip bioreactors have been used as an engineered solutions for mitigating nitrate from contaminated water. However, their year-round treatment performance and possible solutions for enhancing their removal efficiency under cold climate conditions still needs more research. In this thesis, we investigated nitrogen removal from aquaculture and mine-influenced water as an indoor and outdoor treatment system under several experimental conditions. This thesis attempts to identify design parameters (e.g., optimal hydraulic retention time (HRT) and nitrate removal rate) and enhancement solutions for woodchip bioreactors under cold climate conditions such as additional carbon source, hydraulic design and use of a floating aquatic as a hybrid system. The results show that woodchip bioreactors can successfully remove nitrate from recirculating aquaculture system (RAS) discharge and mine-influenced water under cold climate conditions. Two-year results from a full-scale woodchip bioreactor showed that selected design parameters from a laboratory-scale were sufficient to complete denitrification at the full-scale. The denitrification followed first-order reaction for RAS effluent and optimal HRT ranged between 1.5 to 2 d to achieve a nitrate removal rate of 25.8 g NO-3-N m-3d-1 and 74% removal efficiency. A layer of 50 cm of dry woodchips combined with snow cover (20‐30 cm) was sufficient to prevent frost, the water temperature never dropped lower than 7.3 °C during cold winter conditions (minimum air temperature = -24.7 ℃). Design of the hybrid unit was improved by inserting two inner plates along the water flow and adding floating hook-moss improved the hydraulic efficiency from poor (λ=0.06) to satisfactory (λ=0.51) which led to higher removal rates.Tiivistelmä
Puuhakebioreaktoreita on käytetty puhdistusratkaisuna veden nitraattipitoisuuden vähentämiseksi. Niiden ympärivuotinen käsittelyteho ja mahdolliset ratkaisut poistotehokkuuden parantamiseksi kylmissä ilmasto-olosuhteissa vaativat kuitenkin lisätutkimuksia. Tässä opinnäytetyössä tutkittiin typenpoistoa vesiviljelyn ja kaivosten puhdistusta vaativista vesistä sisä- ja ulkokäsittelyjärjestelmänä useissa koeolosuhteissa. Tässä työssä tunnistettiin suunnitteluparametreja (esim. optimaalinen HRT ja nitraatinpoistonopeus) ja parannusratkaisuja puuhakebioreaktoreille kylmissä ilmasto-olosuhteissa, kuten lisähiililähde, hydraulinen suunnittelu ja kelluvan vesikasvattamon käyttö hybridijärjestelmänä. Tulosten perusteella puulastubioreaktoreilla voidaan onnistuneesti poistaa nitraattia sekä sisäisen kierron kalankasvattamojen (RAS) että kaivosten kuormittamasta vedestä kylmissä ilmasto-olosuhteissa. Kahden vuoden tulokset täysimittaisella puuhakebioreaktorilla osoittivat, että laboratoriomittakaavassa valitut suunnitteluparametrit riittivät täyteen denitrifikaatioon täysimittaisessa mittakaavassa. Denitrifikaatio noudatti ensimmäisen järjestyksen reaktiota RAS- järjestelmänjäteveden osalta, ja optimaalinen HRT-aika vaihteli 1,5 ja 2 päivän välillä, jotta saavutettiin 25,8 g NO-3-N m-3d-1 ja 74 prosentin poistotehokkuus. 50 cm:n kerros kuivaa puuhaketta yhdistettynä lumipeitteeseen (20‐30 cm) riitti estämään järjestelmänjäätymisen, eikä veden lämpötila laskenut kokeen aikana alle 7,3 °C:n kylmien talviolosuhteiden aikana (ilman alin lämpötila = -24,7 ℃). Hybridiyksikön suunnittelua parannettiin lisäämällä kaksi sisälevyä veden virtauksen suuntaisesti ja kelluvaa koukkusammalta lisäämällä parannettiin hydraulista tehokkuutta huonosta (λ=0,06) tyydyttävään (λ= 0,51), mikä johti suurempiin poistomääriin
A pilot study to assess the potential of denitrifying bioreactors in treatment of aquaculture effluents
No full textHeterotrophic denitrification reactors are typical treatment units used to remove nitrate from aquaculture effluent. However, they face with limitation due to practical and economic reasons as a result of their requirement for external readily available organic carbon sources. In this study, four clear acrylic vertical columns (10cm × 32cm) with upward flow direction were constructed and packed packed with wood chips (from birch tree), and mixture of woodchips with three different carbon sources (potato peels from industrial process; dried sphagnum moss and biochar coals). The purification performance of bioreactors were investigated in treatment of aquaculture effluent under design hydraulic retention time (HRT) of 48-h and temperature of 15.35± 0.31°C (mean± SD) for 55 days.
The results of this study clearly showed the instant nitrate (NO₃-N) reduction in all bioreactors and stable removal efficiency after one week. As much as 94% of the nitrate was removed from aquaculture effluent with 35.5 mg NO₃-N L⁻¹ concentration, in bioreactor with woodchips. This removal efficiency corresponded to 21.6 g N m⁻³d⁻¹ removal rate. Reported removal rate and removal efficiency for 35.5 mg NO₃-N L⁻¹ inflow concentration, averaged (21.4 g N m⁻³d⁻¹, 92 %) for woodchips with potato peels, (20.7 g N m⁻³d⁻¹, 91.3 %) for woodchips with biochar and (19.2 g N m⁻³d⁻¹, 78.9 %) for woodchips with dried sphagnum moss (BR2). In addition, bioreactor with potato peels showed higher nitrate removal rate (29.2 g N m⁻³d⁻¹) for the inflow water with high concentration of NO₃-N (35th -55th day).
Reported nitrate removal rate in this study were relatively greater than measured in previous studies due to the selected sufficient HRT (48-h) combined with relatively high NO₃-N concentration of influent in the optimal temperature of 15.35± 0.31°C (mean± SD). Start-up leachate of organic carbon, ammonia and phosphorus for start-up period took place in all bioreactors, but with higher rate in bioreactor with potato peels. Rise in alkalinity took palace as an evidence of heterotrophic denitrification in all bioreactors expect bioreactor with potato peels.
Phosphorus reductions were observed after two weeks in woodchips bioreactor with biochar, bioreactor with dried sphagnum moss and woodchip bioreactor at the highest removal efficiency of 23%, 38% and 35%, respectively. While, Phosphorus reduction started in bioreactor with potato peels after nearly one month at the rate of 20%.
In summary, the master thesis demonstrated that woodchips bioreactors have potential of nitrate removal from aquaculture effluent even with low chemical oxygen demand (COD). Woodchips bioreactors can reach the stable performance within few weeks
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Examining the Diverse Pathological Consequences of Microglial Absence
No full textOur understanding of microglia, the principal immune cells of the central nervous system (CNS), continues to evolve as new models and approaches shift our perception of these intriguing cells. Previously envisioned as passive guardians of the brain, microglia have since been shown to play critical roles in development, neuroplasticity, and neurological disease (Hammond et al., 2018). Their range of functions spans immune-related activities but also extends to a wide variety of non-immune functions, many of which remain comparatively underexplored (Prinz et al., 2019). However, recent genome-wide association studies (GWAS) have provided a wealth of new clues, helping to spur a renaissance in our understanding of microglia biology. To date over 80 AD-linked loci have been identified (Jansen et al., 2019; Kunkle et al., 2019; Schwartzentruber et al., 2021), the great majority of which are associated with genes that are highly or exclusively expressed by microglia (Efthymiou and Goate, 2017; McQuade and Blurton-Jones, 2021). As researchers have begun to explore the function of these microglial risk genes, their findings have in turn underscored the importance of the multifaceted responses of microglia to AD pathologies including amyloid plaques and neurofibrillary tangles. To further understand the role of microglia in AD and the impact of microglial absence on the aging brain, my thesis studies utilized ‘FIRE mice’, a genetic model that lacks microglia. FIRE mice harbor a homozygous deletion within the Fms intronic regulatory element (FIRE) super-enhancer, leading to a loss of CSF1R expression and congenital absence of microglia. To examine the role of microglia in AD pathogenesis, I crossed FIRE mice with 5xfAD mice that develop robust beta-amyloid plaque pathology. Remarkably, I found that absence of microglia promotes the development of cerebral amyloid angiopathy (CAA), brain calcification, and cerebral hemorrhages in AD mice. Importantly, transplantation of wildtype microglia prevents each of these pathological changes (Chapter 1). To determine whether microglia absence alone can also induce pathological changes within the aging brain, I further examined 9-10 month-old FIRE mice in comparison to wildtype littermates and explored the impact of postnatal microglial transplantation, demonstrating that prolonged absence of microglia leads to the development of astrogliosis, calcification, and seizures, mimicking many of the pathological features of a rare human primary microgliopathy (Chapter 2). Taken together, my thesis studies have revealed important roles for microglia in protecting the brain against age- and disease-related development of vascular, and white matter pathologies. These findings not only deepen our understanding of microglia's roles in neurodegenerative diseases, but also provide initial evidence to support microglial transplantation as a viable therapeutic approach for a variety of neurodegenerative diseases
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