京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21373号 / 工博第4532号 / 新制||工||1706(附属図書館) / 京都大学大学院工学研究科化学工学専攻 / (主査)教授 前 一廣, 教授 河瀬 元明, 教授 佐野 紀彰 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Firing the Canon is written in conjunction with is namesake exhibition, prepared as a culmination of work leading to the master of fine arts degree. In an attempt to help viewers better understand my body of work, I discuss herein: events contributing to my personal narrative, major themes and their origins and pertinent sources of artistic and non-artistic inspiration.

Prescribed fire is a common land management tool in the southeastern United States. Historical fires occurred primarily in the growing season, but modern day prescribed fire is commonly restricted to the dormant season. Plant community responses to various fire regimes are relatively unknown, and managers require information on how fire regimes impact plant communities. To address these limitations, I studied the impacts of March and June fire on plant communities. Results indicated various woody midstory species respond differently to fire season and community response is driven by species composition. In another study, I examined impacts of February, May-June, and September-October backing and heading fires on midstory and understory vegetation. Results indicated May-June fires maximized midstory mortality and growing-season fires maximized herbaceous understory coverage while dormant-season fire promoted resprouting woody species. Managers can use this information to tailor fire prescriptions to specific properties to better meet management objectives.

Co-firing is a combustion process in which more than one type of fuel is used. In many cases, co-firing reduces fuel costs and/or reduces the environmental impact. The objective of this research was to test the hypothesis that adding biogas to be co-fired with biomass in a traditional cookstove reduces indoor air pollution and increases the combustion efficiency. The impact of co-firing on indoor air pollution is assessed by comparing the concentrations of carbon monoxide and particulate matter in the exhaust stream of a co-fired cookstove to a cookstove fueled with biomass alone. The concentrations of each of these pollutants were measured using a portable emissions monitoring system. Combustion efficiency is defined as the ratio of energy released by combustion to energy in the fuel. Instead of combustion efficiency, the impact of co-firing was assessed on the modified combustion efficiency, which is defined as CO2/(CO2+CO) on a molar basis. This is because CO and CO2 concentrations can be measured. In addition, the impact of cofiring on other parameters such as thermal efficiency, specific fuel consumption rate, and specific emission of CO, CO2, and PM were assessed. Previous investigation of biomass combustion in traditional cookstoves indicates that power harvested using a thermoelectric generator can be used to drive a fan and increase the amount of air flowing into the combustion zone. The impact of using a fan on indoor air pollution and combustion efficiency was also assessed. It was found that co-firing biomass with optimum amount of biogas reduced the emission of CO by 32 % and PM by 33 % and increased the modified combustion efficiency by 1.3 %. It was found that using a fan reduced the emission of CO by 35 % and PM by 39 % and increased the modified combustion efficiency by 1.1 %. Finally, the combination of co-firing and use of a fan reduced the emission of CO by 58 % and PM by 71 % and increased the modified combustion efficiency by 2.8 %.

Syfte: Syftet med föreliggande studie är att undersöka färgstabiliteten hos manuellt färginfiltrerad högtranslucent zirkonia efter upprepade bränningar.   Material och metod: Fem provkroppar av respektive fabrikat; Prettau® Zirconia (PZ) och M+W Zircon HT (MW) kapades fram ur ofärgade zirkonia-diskar. Provkropparna färgades in manuellt med färgen A3 och torkades därefter under en infraröd lampa. Provkropparna sintrades enligt fabrikanternas anvisningar och en första färgmätning utfördes med en spektrofotometer (VITA Easyshade Advance 4.0) mot en matt grå bakgrund. Där efter utfördes bränningar av provkropparna i fyra cykler. Efter varje cykel utfördes färgmätningar.Medelvärdena för L*a*b*c*h* registrerades. Formlerna CIE76 (∆E*ab) och CIEDE2000 (∆E*00) användes för att räkna ut färgskillnader efter bränncyklerna. Värdena registrerades i SPSS och analyserades med One-way ANOVA, Tukey’s test med en signifikansnivå på α=0,05.   Resultat: Statistiskt signifikanta skillnader (p<0,05) i färgförändring hittades både inom och mellan de båda grupperna (MW och PZ). Färgskillnaderna som uppmättes befann sig inom ramen för vad som anses som en acceptabel (∆E*ab≤2,7 och ∆E*00≤1,8) eller mycket god färgmatchning (∆E*ab≤1,2 och ∆E*00≤0,8).   Slutsats: Inom ramen för studiens begränsningar kan följande slutsatser dras: Upprepade bränningar påverkar färgen hos manuellt färginfiltrerad högtranslucent zirkonia. De färgförändringar som sker är inom ramen för vad som räknas som en ”acceptabel färgmatchning” eller ”mycket god färgmatchning” enligt aktuella gränsvärden. Färgförändringarna som sker är inte iögonfallande och har ringa betydelse kliniskt. Färgen och färgskillnader hos manuellt färginfiltrerad högtranslucent zirkonia är beroende av fabrikat. / Purpose: The purpose of this study is to investigate color stability in manually color infiltrated high translucent zirconia after repeated firings. Material and methods: Five specimens of each manufacturer; Prettau® Zirconia (PZ) and M+W Zircon HT (MW) were cut from uncolored zirconia discs. The specimens were manually colored with shade A3, and dried. The specimens were sintered and a first color measurement was performed with a spectrophotometer (VITA Easyshade Advance 4.0) against a matte gray background. Firings of the specimens were performed in four cycles. After each cycle, color measurements were performed. The mean values for L*a*b*c*h* ​​were registered. The formulas CIE76 (∆E*ab) and CIEDE2000 (∆E*00) were used to calculate color differences after firing cycles. The values were registered and analyzed with One-way ANOVA, Tukey's test with a level of significance at α=0.05.  Results: Statistically significant color differences (p<0.05) were found within and between groups (PZ and MW). The color differences measured were within the range of what is considered an acceptable match (∆E*ab≤2.7 and ∆E*00≤1.8) or a perfect match (∆E*ab≤1.2 and ∆E*00≤0.8).   Conclusion: Within the limitations of this study, the following conclusions can be drawn: Repeated firings affect the color in manually color infiltrated high translucent zirconia. The color changes that occur are within the range of what is considered an “acceptable match” or “perfect match” according to current thresholds. The color changes are not conspicuous and of little importance clinically. The color and color differences in manually color infiltrated high translucent zirconia are dependent on the brand.

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The subiculum is a structure that forms a bridge between the hippocampus and the entorhinal cortex (EC) in the brain, and plays a major role in the memory consolidation process. It consists of different types of pyramidal neurons. Based on their firing behavior, these excitatory neurons are classified into strong burst firing (SBF), weak burst firing (WBF) and regular firing (RF) neurons. In the first part of the work, morphological differences in the different neuronal subtypes was explored by biocytin staining after classifying the neurons based on the differences in electrophysiological properties. Detailed morphological properties of these three neuronal subtypes were analyzed using Neurolucida neuron reconstruction method. Unlike the differences in their electrophysiological properties, no difference was found in the morphometric properties of these neuronal subtypes. In the second part of the thesis, experimental results on spike- timing- dependent plasticity (STDP) at the proximal excitatory inputs on the subicular pyramidal neurons of the juvenile (P15-P19) rat are described. The STDP was studied in the WBF and RF neurons. Causal pairing of a single EPSP with a single back propagating action potential (bAP) at a time interval of 10 ms failed to induce plasticity. However, increasing the number of bAPs in such EPSP-bAP pair to three at 50 Hz (bAP burst) induced LTD in both, the RF, as well as the WBF neurons. Increasing the frequency of action potentials to 150 Hz in the bAP burst during causal pairing also induced LTD in both the neuronal subtypes. However, all other STDP related experiments were performed only with the bAP bursts consisting of 3 bAPs evoked at 50 Hz. Amplitude of the causal pairing induced LTD decreased with increasing time interval between EPSP and the bAP burst. Reversing the order of the EPSP and the bAP burst in the pair induced LTP only with a short time interval of 10 ms. This finding is in contrast to most of the reports on excitatory synapses, wherein the pre-before post (causal) pairing induced LTP and vice-versa. The results of causal and anti-causal pairing were used to plot the STDP curve for the WBF neurons. In the STDP curve observed in these synapses, LTD was observed upto a causal time interval of 30 ms, while LTP was limited to 10 ms time interval. Hence, the STDP curve was biased towards LTD. These results reaffirm the earlier observations that the relative timing of the pre- and postsynaptic activities can lead to multiple types of STDP curves. Next, the mechanism of non-Hebbian LTD was studied in both, the RF and WBF neurons. The involvement of calcium in the postsynaptic neuron in plasticity induction was studied by chelating intracellular calcium with BAPTA. The results indicate that the LTD induction in WBF neurons required postsynaptic calcium, while LTD induction in the RF neurons was independent of postsynaptic calcium. Paired pulse ratio (PPR) experiments suggested the involvement of a presynaptic mechanism in the induction of LTD in the RF neurons, and not in the WBF neurons since the PPR was unaffected by the induction protocol only in the WBF neurons. LTD induction in the WBF neurons required activity of the NMDA receptors since LTD was not observed in the presence of the NMDA receptor blocker in the WBF neurons, while it was unaffected in the RF neurons. However, the RF neurons required the activity of L-type calcium channels for plasticity induction, since LTD was affected in the presence of the L-type calcium channel blockers, although the WBF neurons did not require the L-type calcium channel activity for plasticity induction. Hence, in addition to a non-Hebbian STDP curve, a novel mechanism of LTD induction has been reported, where L-type calcium channels are involved in a synaptic plasticity that is expressed via change in the release probability. The findings on the STDP in subicular pyramidal neurons may have strong implications in the memory consolidation process owing to the central role of the subiculum and LTD in it.

Chip-firing is a deceptively simple game played on the vertices of a graph, which was independently discovered in probability theory, poset theory, graph theory, and statistical physics. In recent years, chip-firing has been employed in the development of a theory of divisors on graphs analogous to the classical theory for Riemann surfaces. In particular, Baker and Norin were able to use this set up to prove a combinatorial Riemann-Roch formula, whose classical counterpart is one of the cornerstones of modern algebraic geometry. It is now understood that the relationship between divisor theory for graphs and algebraic curves goes beyond pure analogy, and the primary operation for making this connection precise is tropicalization, a certain type of degeneration which allows us to treat graphs as “combinatorial shadows” of curves. The development of this tropical relationship between graphs and algebraic curves has allowed for beautiful applications of chip-firing to both algebraic geometry and number theory. In this thesis we continue the combinatorial development of divisor theory for graphs. In Chapter 1 we give an overview of the history of chip-firing and its connections to algebraic geometry. In Chapter 2 we describe a reinterpretation of chip-firing in the language of partial graph orientations and apply this setup to give a new proof of the Riemann-Roch formula. We introduce and investigate transfinite chip-firing, and chip-firing with respect to open covers in Chapters 3 and 4 respectively. Chapter 5 represents joint work with Arash Asadi, where we investigate Riemann-Roch theory for directed graphs and arithmetical graphs, the latter of which are a special class of balanced vertex weighted graphs arising naturally in arithmetic geometry.

Pesquisas in vivo e in vitro, têm estabelecido uma correlação entre alterações na morfologia dendrítica e a epilepsia. No entanto, ainda não se conhecem em detalhe as consequências dessas modificações, sobre a eletrofisiologia e o padrão de disparo. Também existe um fenômeno que não tem sido completamente explicado, conhecido como o paradoxo do dendrito epiléptico, no qual neurônios piramidais, mesmo com a diminuição dramática do principal lugar de inervação glutamatérgica (como consequência de, por exemplo, uma redução do diâmetro e comprimento das árvores dendríticas), inesperadamente apresentam um estado de hiperexcitabilidade crônica. Nesta pesquisa foram aproveitadas as vantagens de uma abordagem neurocomputacional, para induzir sistematicamente alterações na arquitetura dendrítica do mesmo tipo às observadas na epilepsia, e avaliar os seus efeitos sobre a eletrofisiologia e o padrão de disparo. Para isso foi construído um modelo computacional biologicamente realista, de um neurônio piramidal do neocórtex. O código-fonte do modelo está na linguagem do NEURON, e foi baseado em dados eletrofisiológicos (i.e. propriedades da membrana e condutâncias iônicas) e morfométricos, obtidos in vitro previamente por outros pesquisadores. A análise foi feita com base em parâmetros eletrofisiológicos do padrão de disparo. O nosso modelo sugere uma influencia muito forte da morfologia dendrítica sobre a eletrofisiologia, a geração de potencias de ação e o padrão de disparo. Os resultados obtidos mostram que, mesmo mantendo constantes todos parâmetros biofísicos (que têm a ver com as dinâmicas elétricas dos canais iônicos), é possível induzir um aumento grande no comportamento elétrico e na geração de potenciais de ação, a partir da redução do diâmetro e comprimento das ramificações das árvores dendríticas. Estes resultados, também permitem contribuir no fornecimento de uma explicação para o paradoxo mencionado. / In vivo and in vitro studies had found a correlation between dendritic morphology alterations and epilepsy. Nevertheless, it has not been established in detail the consequences of those modifications, over the electrophysiology and firing pattern. There is also a phenomenon still not completely understood, known as the epileptic dendrite paradox, in which pyramidal neurons with a dramatic reduction in the principal place of glutamatergic innervation (due to, for example, a loss in dendritic trees\' diameter and length), unexpectedly present a chronic hyperexcitable state. In this study we took advantage of a neurocomputational approach, to systematically induce dendritic alterations of the same type as observed in Epilepsy, and evaluate their effect over the electrophysiology and firing behavior. With that purpose in mind, we constructed a biologically realistic computational model of a pyramidal neuron of the neocortex. For this model, it was implemented the programming language (hoc) of the NEURON software, and was elaborated based on electrophysiological data (i.e. membrane properties and ionic conductances), and morphological measurements, taken in vitro previously by other investigators. The analysis was done from electrophysiological parameters of the firing pattern. Our model suggests a great influence of dendritic morphology over the electrophysiology, spike generation and firing pattern. The results obtained show that, even when all the biophysical parameters involved in ion channel dynamics are maintained constant, it is possible to induce a strong increase in electric behavior and spike firing, from a reduction in the length and diameter of the dendritic trees\' ramifications. These results, also contribute to a explanation of the mentioned paradox.