The peptidoglycan of many Gram-positive bacteria is densely functionalized with anionic glycopolymers called wall teichoic acids (WTAs). Recent studies have shown that these polymers play crucial roles in cell shape determination, regulation of cell division, and other fundamental aspects of Gram-positive bacterial physiology. Furthermore, in pathogens they are important in host infection and play key roles in antibiotic resistance. In many cases, precise mechanisms for WTA involvement in these processes have not been established. In order to better understand the roles of WTAs in the biology of the human pathogen Staphylococcus aureus, we sought to identify their interactions with other cellular pathways. By employing a transposon screen, we found that lipoteichoic acid (LTA) synthesis, D-alanylation of teichoic acids, cell wall stress sensors, CAAX-like proteases, and peptidoglycan biosynthesis were all synthetically lethal with depletion of WTAs in Staphylococcus aureus . Further investigations revealed that several genes required when WTAs were depleted were not essential when LTAs were removed. Unexpectedly, TA D-alanylation, became essential in the absence of WTAs, but not LTAs. Examination of terminal phenotypes following WTA depletion revealed that strains lacking LTA D-alanine esters died from envelope rupture during ongoing cell division whereas strains lacking LTAs were unable to form Z rings, stopped dividing, and had altered PG biosynthesis. Finally, we designed and implemented parallel, pathway-specific chemical screens to identify inhibitors that specifically kill mutants deficient in WTAs or D-alanylation of TAs. In addition to elucidating new interactions between cell envelope pathways, and establishing distinct roles LTAs and WTAs in the cell envelope of S. aureus, these experiments provide a list of potential targets and a strategy for identifying inhibitors for these targets, in compound combinations as therapeutics against antibiotic-resistant S. aureus infections.

This thesis examines the impact of social and economic change on the practice of "free mining" in the Forest of Dean between 1788 and 1886, asking how and why the free miners' "rights" altered over that period and what the consequences of their survival were for the development of trade unionism among the Forest miners. The thesis is divided into three parts. The first of them discusses the free miners' rights and argues that they should be seen as part of a group of uses, including commoning and the occupation of Crown land, which its inhabitants made of the Forest in the eighteenth century. These uses came under pressure between 1788 and 1841 from reforms in central government and the intrusion of strangers from outside the Forest into the mining industry. A series of Acts of Parliament between 1838 and 1841 consolidated the new order in the Forest but the bargaining which preceded that legislation resulted in the preservation - though in a diluted form - of the miners' rights and of commoning. Part two asks whether the partial survival of these customs acted as a socially conservative influence which might have explained the relative weakness of trade unionism among the Forest's colliers. It is argued that the instability of union may be explained by reference to the organization of the industry and its markets, to the method of work organization in the pits, which created divisions among the miners, and to the inadequacies of "national" miners' unionism. Though it is not necessary to invoke the peculiar local rights and customs to account for the weakness of unionism in Dean, Part three will contend that they remained important to many foresters. Renewed pressure from the Crown and from the large coalowners, on both the free miners and commoners, and the resistance of the foresters to change, are examined. The character of that resistance took colour from the assumptions and rhetoric of the union and in turn reinforced and helped to make successful, a campaign by the union for the separate representation of the working men in the Parliament.

The aim of this thesis is to investigate the effects of Mn content and alloying additions such as Cr and Mo, and various heat treatment procedures on both microstructure and mechanical properties of austenitic manganese (Hadfield) steels. For this purpose, steels with two different Mn content were considered (12-14 Mn, 16-18 Mn). First, five different heat treatment procedures were applied to the as-cast 12-14 Mn specimens to decide the procedure resulting the optimum tensile properties. Then, the specimens having various amounts of Mn, Cr and Mo were cast and heat-treated to investigate the effect of alloy modifications on austenitic manganese steels. Optical and scanning electron microscopies were used for microstructural investigation. To determine the mechanical properties, tensile tests and hardness tests were carried out. In addition to correlation between microstructure and mechanical properties, ultrasonic velocity measurements were also done. The results show that both composition and heat treatment affect the performance of hadfield steels extensively, and these changes also affect the propogation velocity of the ultrasonic waves.

Geostatistics and more specifically stochastic modeling of reservoir heterogeneities are being increasingly considered by reservoir analysts and engineers for their potential in generating more accurate reservoir models together with usable measures of spatial uncertainty. Geostatistics provides a probabilistic framework and a toolbox for data analysis with early integration of information. The uncertainty about the spatial distribution of critical reservoir parameters is modeled and transferred all the way to a risk conscious reservoir management. The stochastic imaging (modeling) algorithms allow the generation of multiple, equiprobable, unsmoothed reservoir models yet all honoring the data available. This thesis presents stochastic reserve estimation methods as related to the various stages of development of an oil field. Advances in technology are leading to better deterministic estimates as well as stochastic estimates with narrower ranges. Practices in the industry vary from complete dedication to deterministic or stochastic to a choice of the method depending on the stage of the development. In this study, reserves are calculated from the data available in Southeastern Turkey by using stochastic methods. Probability density functions, number of iterations are important statistical concepts. Increasing number of iterations leads to a normal distribution of histogram.

The effect of physical, chemical and mineralogical properties on reducibility of iron containing raw materials were studied with the use of two pellets, one sinter and one lump iron ore sample provided by Erdemir integrated iron and steel works. Although Erdemir lump iron ore contained hematite, it was found to be less reducible than Erdemir sinter since porous structures are easier to reduce and in general sinters have a higher porosity as compared to lump ores. Experimental findings indicated that Erdemir pellet with a code B had the highest reducibility. On the other hand, the results of Erdemir samples were compared with those results obtained from the projects carried out in the Metallurgical and Materials Engineering Department of METU in 1980&rsquo / s. In mentioned projects, samples of various lump iron ores and a concentrate, pellet and sinter from Turkish sources and imported lump iron ores of CVRD from Brazil and ISCOR from the Republic of South Africa were tested. Within the context of this thesis, a mathematical model that would fit to the reduction kinetics was studied and the porous solid model was found to be the best for Erdemir samples.

The most important criterion in industrial production processes is to control the required product quality and comply with the standards pre-described for the application during any stage of the process. This control begins from the entry of raw material to the plant and continues with pre-determined points. Mainly two different types of inspection and analyses are used to examine the material quality and content. These are physical and chemical analysis.In most of the production plants above mentioned analyses are made in related laboratories of the plant. Therefore, it is necessary to have &amp / #65533 / sample&amp / #65533 / to be analyzed. This &amp / #65533 / sample&amp / #65533 / should have a real &amp / #65533 / representative&amp / #65533 / property, which must carry all of the physical and chemical characteristics of the material at the point where this &amp / #65533 / sample&amp / #65533 / is taken.The present methods and systems used to take samples from any required point have some disadvantages and present some problems especially for not being &amp / #65533 / representative&amp / #65533 / . These problems are discussed in detail within this thesis study and aimed to reach a new concept and system with: - Low cost of investment - Low cost of operation - Less requirement of maintenance and calibration - The achievement of &amp / #65533 / correct&amp / #65533 / and &amp / #65533 / representative&amp / #65533 / sample As a result of the theoretical studies together with practical application works and experiments, a new concept in sampling, namely &amp / #65533 / Sampling System with Air Cannons&amp / #65533 / was introduced. The new system of sampling was tested to give better performance and practical use.

ABSTRACT MODELING A MODERN MARBLE PROCESSING PLANT BY USING PETRI NET Keser, &Ouml / zge M. Sc., Department of Mining Engineering Supervisor: Prof Dr. NeS&rsquo / e &Ccedil / elebi Co-Supervisor: Prof Dr. Tevfik G&uuml / yag&uuml / ler December 2003, 110 pages All developing countries need sufficient raw material resources to develop and to guarantee their future. Considering Turkish natural resources, marble has a great importance because of its demand on the market, reserve amount and quality. However, some effort is required to improve the existing marble production and processing efficiency. Petri nets (PNs) are the information models that control the flow for concurrent and synchronous systems. In this regard, PN application can be useful. However, its application is limited to the complex systems and no application of PN is available in mining sector. iii In this sense, this study aims to examine the applicability of PN to mining. This study examines the production system in order to optimize the process in case of two different types of marble product orders. Three case studies are applied to examine benefits and difficulties in implementation of PN to a marble processing plant. The study shows that PN can successfully be used as a tool for the optimization of total production time, simulation and modeling of the system. It provides to see the sequence of the processes, their time, remaining time of each transition and optimum total production times. The difficulties of PN implementation are found out as the determination of each path in the reachability graph, matrix representation with large quantity of place, etc.

In this work, nozzle clogging in the submerged entry nozzle in continuous casting of Al killed steels has been studied. The study has been based on low silicon Al killed SAE 1006 (1.2006) and SAE 1008 (1.2008) grades. In this study, castabilities of 75 heats for 1.2006 steel grades and 75 heats for 1.2008 steel grades have been investigated. Castabilities of the experimental heats have been found to be affected by Al content in oxide form (Aloxy) and Ca content of the liquid steel. Castabilities have been found to decrease with increase in Aloxy and to increase with increase in Ca content and Ca/Aloxy ratio. Reoxidation has been found not to affect the castability appreciably.

In this thesis, it is aimed to investigate and analyze the effect of meteorological conditions on airborne dust measured at Ovacik Open Pit Gold Mine. Meteorological data must be sound and reliable which are used mainly to design an air model to predict the effect of industrial sites on air quality during production. Wind speed, wind direction, airtemperature, air pressure, relative humidity, rainfall, evaporation and sunshine. are the parameters investigated in this study. In the thesis, the meteorological data observed are analyzed and discussed together with the airborne dust measured by MP101M Suspended Particulate Beta Gauge Monitor at Ovacik Gold Mine. In this study, the most significant meteorological parameter affecting airborne dust concentration is determined as air temperature. In this study, it is also determined through airborne dust measurements that neither the short-term limit nor the long-term limit has been exceeded. Therefore, the airborne dust concentrations at Ovacik Gold Mine comply with the Turkish Air Quality Control Regulation.

Discontinuity surfaces generally consist of undulations termed as roughness. It is well known that surface roughness plays an important role on the shear strength and shear behavior of discontinuities. However, the effect of roughness will not be the same when the direction of shearing changes. This effect causes variation of shear strength with shearing direction or in other words anisotropy on shear strength. In this thesis, an experimental study was performed to investigate the effect of roughness and anisotropy on shear strength. For this purpose, joint samples were prepared using a model material and direct shear tests were conducted at different normal stress levels and shearing directions.