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京都大学 / 新制・課程博士 / 博士(農学) / 甲第24661号 / 農博第2544号 / 新制||農||1098(附属図書館) / 学位論文||R5||N5442(農学部図書室) / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 矢野 浩之, 教授 和田 昌久, 教授 今井 友也 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

Respirable coal mine dust (RCMD) still poses serious occupational health hazards to coal miners and can lead to incurable lung diseases such as coal workers' pneumoconiosis (CWP, also referred to as "black lung"). Further, CWP can develop into a more severe form known as progressive massive fibrosis (PMF). There has been a resurgence of PMF since the late 1990s. Coal miners are also exposed to crystalline silica, which can lead to a lung disease known as silicosis. While coal mining related disease is on the rise, the historic dust monitoring data does not indicate such a striking resurgence. As a result, there has been an increased interest in research surrounding RCMD to understand exposure as well as prevent health effects. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) is a powerful tool that can analyze RCMD on a particle-level. The images produced by the SEM can size and characterize morphology of micron and submicron-sized particles. In addition, the EDX can determine elemental content, which can be used to infer mineralogy. However, particle classification can be impacted by interferences due to particle loading density (PLD) and agglomeration. PLD refers to the number of particles per unit area of substrate, while agglomeration describes clustered or overlapping particles. This thesis includes two studies aimed at exploring the effects of both PLD and agglomeration on SEM-EDX analysis. Study 1 includes an investigation into the effect of PLD on RCMD classification by SEM-EDX analysis. Dust recovered from the sample parent filters under low and high PLD conditions were used to isolate the effect of PLD. The comparison between the low and high PLD filters was then used to establish modified classification criteria to correct for high PLD. When the modified criteria were then applied to RCMD particles analyzed direct-on-filter, minimal change was observed in the apparent mineralogy distributions for most samples. These results suggest that particle agglomeration may have substantial effects on the particle classification of respirable dust analyzed direct-on-filter. Study 2 includes an investigation into the effect of particle agglomeration on RCMD by SEM-EDX analysis. Automated and manual SEM-EDX analysis was performed on paired filters collected from a parent filter. The manual analysis targeted respirable silica containing agglomerates. Each pair consisted of a filter analyzed directly and a filter that underwent a recovery process to deposit dust particles onto a new filter. The mineralogy distributions from the automated analysis suggest that agglomeration affects sizing and particle classification. Based on the manual analysis, there was an apparent increase in independent silica and a decrease in respirable silica-containing agglomerates after the recovery process. A limited collection of passive samples revealed more agglomerates than on the filters that were collected using a pump and size-selector cyclone. The work in this thesis is relevant to the research efforts aimed at the resurgence of coal mining related lung diseases, as the use of SEM-EDX can characterize RCMD by geographic region, geology, and location within a mine. Future work in this area of study might look at methods to estimate PLD in the field, other dust recovery methods, and a comparison of sampling methods. / Master of Science / Respirable coal mine dust (RCMD) still poses serious occupational health hazards to coal miners and can lead to incurable lung diseases such as coal workers' pneumoconiosis (CWP, also referred to as "black lung"). Further, CWP can develop into a more severe form known as progressive massive fibrosis (PMF). There has been a resurgence of PMF since the late 1990s. Coal miners are also exposed to crystalline silica, which can lead to a lung disease known as silicosis. While coal mining related disease is on the rise, the historic dust monitoring data does not indicate such a striking resurgence. As a result, there has been an increased interest in research surrounding RCMD to understand exposure as well as prevent health effects. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) is a powerful tool that can analyze RCMD on a particle-level. SEM-EDX analysis can provide data on the size and elemental content of individual particles. The elemental content of each particle can be used to infer the mineralogy. However, the effectiveness of SEM-EDX analysis is dependent on sample conditions. Interference can occur if the samples are loaded with too many particles close together or clustered particles. In Study 1, a modified classification criteria to correct for overloading was created by using a dataset that consisted of paired filters with ideal loading and overloading. The modified criteria were applied to a second dataset, resulting in minimal change on the filters analyzed directly indicating that clustered particles may be present. Study 2 utilized automated and manual SEM-EDX analysis on paired filters, one filter was analyzed directly, and the other filter was dispersed using a recovery method. The automated results suggest that clustered particles can affect the sizing and particle classification. The manual analysis, which looked at clusters containing silica, revealed that less clusters were present on the filters that underwent the recovery process. A collection of passive samples exhibited more clustered particles compared to direct filters collected using a pump and size-selector. These findings are relevant to the research efforts aimed at the resurgence of coal mining related lung diseases, as the use of SEM-EDX analysis can characterize RCMD by geographic region, geology, and location within a mine.

Chapter 2 deals with a linear city model à la Hotelling where the two firms share linear transport costs with their customers. Mill pricing and uniform delivery pricing are special limiting cases. We characterize the conditions for the existence of a pure strategy equilibrium in the two-stage location-price game. These enable us to identify the causes for non-existence in the two limiting cases. We solve for the equilibrium of a location game between the duopolists with an exogenously given price. When the two firms are constrained to locate at the same central spot, we show the nonexistence of pure strategy equilibria, conjecture the existence of mixed strategy equilibria, and show that any such possible equilibria will always yield positive expected profits. Chapter 3 provides simulations as well as theoretical analysis of potential spatial separation of heterogeneous agents operating on a two-dimensional grid space that represents a city. Heterogeneity refers to a characteristic which is also a determinant of individual valuation of land. We study spatial separation with respect to the distinguishing characteristic and investigate the details of emerging spatial patterns. Simulations suggest that the process of interaction with little trade friction goes through stages which resemble its end-state with high trade friction. Several theoretical examples exhibit a distinguishing characteristic upon which the simulations are based. They reflect some of the causes for spatial separation. Examples for the absence of spatial separation are also given. In Chapter 4 simulations, in addition to some theory, are used to investigate certain aspects of a city formation process. The model assumes two types of economic agents, workers and employers, operating on a two-dimensional grid. The agents have simple preferences, positive for the opposite type and negative for the own type in the own location. In addition, they have positive or negative preference for agglomeration in the own location. The model helps build intuition about a potentially important factor for agglomeration formation, namely, the disparity between entrepreneurial and technical skills in localities. We also determine the minimum level of positive preference for agglomeration that leads to agglomeration formation. / Ph. D.

The CO dehydrogenase~linked ferredoxin from acetate-grown <i>Methanosarcina thermophiIa</i> was characterized to determine the structure and biochemical properties of the iron-sulfur clusters. Chemical and spectroscopic analyses indicated that the ferredoxin contained two [4Fe-4S] clusters per monomer of 6,790 Da, although a [3Fe-4S] species was also detected in the oxidized protein. The midpoint potentials of the [4Fe-4S] and [3Fe~4S] clusters at pH 7 were -407 m V and + 103 m V, respectively. Evidence from biochemical and spectroscopic studies indicated that the [3Fe-4S] species may have been formed from [4Fe-4S] clusters when ferredoxin was oxidized. The gene encoding the CO dehydrogenase-linked ferredoxin (<i>fdxA</i>) in <i>Ms. thermophila</i> had the coding capacity for a 6,230-Da protein which contained eight cysteines with spacings typical of 2[4Fe-4S] ferredoxins. A second open reading frame (ORF1) was also identified which had the potential to encode a 2[4Fe-4S] bacterial-like ferredoxin (5,850 Da). The deduced proteins from <i>fdxA</i> and ORF1 were 62% identical. <i>fdxA</i> and ORFI were present as single copies in the genome and each was transcribed on a monocistronic mRNA. Both <i>fdxA</i> and ORF1 were transcribed in cells grown on methanol and trimethylamine, but only the <i>fdxA</i> -specific transcript was detected in acetate-grown cells. The apparent transcriptional start sites of <i>fdxA</i> and ORFI were downstream of sequences which had high identity with the consensus methanogen promoter. The heterodisulfide of two cofactors unique to the methanogenic microorganisms, HS-HTP and HS-CoM, was enzymatically reduced in cell extracts of <i>Ms. thermophila</i> using electrons from the oxidation of either H₂ or CO. The homodisulfides of either HS-HTP or HS-CoM were not reduced under the same conditions. The results indicated that methane is formed by reductive demethylation of CH₃-S-CoM using HS-HTP as a reductant in <i>Ms. thermophila</i>. Coupling of CO oxidation with reduction of the heterodisulfide suggested that the CO dehydrogenase-linked ferredoxin may be involved, although the details of electron flow are not known. / Ph. D.

Previous studies have paid little attention to analyzing the impact of agglomeration externalities on a firm’s survival, especially for developing countries. This study applies various survival analysis methods to examine the relationship of three main types of agglomeration externalities: specialization, diversification (related variety and unrelated variety), and urbanization on the survival of firms in Vietnam, with respect to different types of firms ownership: state-owned firms, foreign-owned firms, and domestic private firms. This study confirms the positive role of specialization in reducing the exit probability for firms, especially for foreign-owned firms. The survival probability of foreign-owned firms and domestic private firms is insensitive to any type of diversification, and only related variety increases the survival chance for state-owned firms. In contrast, urbanization has a small negative impact on domestic private firms.

This article presents a framework within which the effects of demographic change on both agglomeration and growth of economic activities can be analyzed. I introduce an overlapping generation structure into a New Economic Geography model with endogenous growth due to learning spillovers and focus on the effects of demographic structures on long-run equilibrium outcomes and stability properties. First, life-time uncertainty is shown to decrease long-run economic growth perspectives. In doing so, it also mitigates the pro-growth effects of agglomeration resulting from the localized nature of learning externalities. Second, the turnover of generations acts as a dispersion force whose anti-agglomerative effects are, however, dampened by the growth-linked circular causality being present as long as interregional knowledge spillovers are not perfect. Finally, lifetime uncertainty also reduces the possibility that agglomeration is the result of a self-fulfilling prophecy. (author's abstract) / Series: Department of Economics Working Paper Series

A strong trend in Swedish retail has been and is that an increased amount of trade is moved to external shopping malls. Several city lines are negatively affected and lose purchasing power when shopping malls are established and attract customers. But what sets a store in a mall apart from a store in the middle of the city? In this study, we will examine how the customer bases differ between two similar stores that are located in the city centre and the shopping mall. The purpose of the study is to gain a greater understanding of how the customer bases at two similar stores differ depending on whether they are located in a shopping mall versus the city centre. The work must be able to report differences and similarities between shopping mall and the city retail customer base, as well as whether there are differences in price elasticity. The work will create a greater understanding of how customers differ and thus lead to information that can be useful for companies regarding decision-making regarding location and customer focus. This will be done through a comparative analysis of price elasticity and customer behaviour between the two stores. The study is based on a comparative case study with quantitative data collection to answer the study's purpose. The specific case being studied is the optics chain where two of their stores are being studied. The two analysis units are located in the city centre and the shopping centre, respectively. The data material collected consists of sales reports from each store. Calculation of price elasticity based on the collected data material and information about customers are studied and analysed. The results show that the customers in the city centre are less price sensitive than the customers for the store located in the shopping centre. The analysis links this to a difference in age groups among customers. 15–59 years are of a larger proportion in the city centre, which is the group that is most often professional and has a greater purchasing power. Larger agglomeration that occurs in shopping malls is also linked to the result. Greater purchasing power could also be demonstrated when the more exclusive arch groups were sold with a larger share in the city centre. The study shows that the stores complement each other. / En stark trend inom svensk detaljhandel har varit och är att en ökad mängd av handeln förflyttas till externa köpcentrum. Flera stadskärnor blir negativt påverkade och förlorar köpkraft då köpcentrum etableras och dra till sig kunder. Men vad är det som skiljer kunderna i köpcentrum från en butik mitt inne i staden? I den här studien ska vi undersöka hur kundbaserna skiljer sig mellan två likadana butiker som är belägna i stadskärnan respektive köpcentrum. Studiens syfte är att få en större förståelse om hur kundbaserna hos två liknande butiker skiljer sig beroende på om de är lokaliserade i ett köpcentrum kontra stadskärna. Arbetet ska kunna redovisa skillnader och likheter mellan köpcentrum och stadshandelns kundbas, samt om skillnader i priselasticiteten förekommer. Arbetet ska skapa en större förståelse för hur kunderna skiljer sig åt och därmed medföra information som kan vara till nytta för företag gällande beslutsfattning kring lokalisering och kundfokus. Detta kommer att göras genom en jämförande analys av priselasticitet och kundbeteende mellan de två butikerna. Studien grundar sig på en komparativ fallstudie med kvantitativ datainsamling för att svara på studiens syfte. Det specifika fallet som studeras är optikkedja där två av deras butiker studeras. De två analysenheterna är lokaliserade i stadskärnan respektive köpcentrum. Insamlade datamaterialet består av försäljningsrapporter från respektive butik. Beräkning av priselasticitet utifrån det insamlade datamaterialet samt info kring kunderna studeras och analyseras. Resultatet visar att kunderna i stadskärnan är mindre priskänsliga än kunderna för butiken lokaliserad i köpcentrum. Analysen kopplar detta till en skillnad i åldersgrupper hos kunderna. 15–59 år är av större andel i stadskärnan vilket är den grupp som oftast är yrkessamma och har en större köpkraft. Även större agglomeration som förekommer i köpcentrum kopplas till resultatet. Större köpkraft kunde även påvisas då de exklusivare båggrupperna såldes med större andel i stadskärnan. Studien kommer framtill att butikerna kompletterar varandra.