930 resultados para Types of environments
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Thesis (Ph.D.)--University of Washington, 2016-08
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Thesis (Ph.D.)--University of Washington, 2016-08
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Stainless steels were developed in the early 20th century and are used where both the mechanical properties of steels and corrosion resistance are required. There is continuous research to allow stainless steel components to be produced in a more economical way and be used in more harsh environments. A necessary component in this effort is to correlate the service performance with the production processes. The central theme of this thesis is the mechanical grinding process. This is commonly used for producing stainless steel components, and results in varied surface properties that will strongly affect their service life. The influence of grinding parameters including abrasive grit size, machine power and grinding lubricant were studied for 304L austenitic stainless steel (Paper II) and 2304 duplex stainless steel (Paper I). Surface integrity was proved to vary significantly with different grinding parameters. Abrasive grit size was found to have the largest influence. Surface defects (deep grooves, smearing, adhesive/cold welding chips and indentations), a highly deformed surface layer up to a few microns in thickness and the generation of high level tensile residual stresses in the surface layer along the grinding direction were observed as the main types of damage when grinding stainless steels. A large degree of residual stress anisotropy is interpreted as being due to mechanical effects dominating over thermal effects. The effect of grinding on stress corrosion cracking behaviour of 304L austenitic stainless steel in a chloride environment was also investigated (Paper III). Depending on the surface conditions, the actual loading by four-point bend was found to deviate from the calculated value using the formula according to ASTM G39 by different amounts. Grinding-induced surface tensile residual stress was suggested as the main factor to cause micro-cracks initiation on the ground surfaces. Grinding along the loading direction was proved to increase the susceptibility to chloride-induced SCC, while grinding perpendicular to the loading direction improved SCC resistance. The knowledge obtained from this work can provide a reference for choosing appropriate grinding parameters when fabricating stainless steel components; and can also be used to help understanding the failure mechanism of ground stainless steel components during service.
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La culture sous abris avec des infrastructures de type grands tunnels est une nouvelle technologie permettant d’améliorer la production de framboises rouges sous des climats nordiques. L’objectif principal de ce projet de doctorat était d’étudier les performances de ces technologies (grands tunnels vs. abris parapluie de type Voen, en comparaison à la culture en plein champ) et leur effets sur le microclimat, la photosynthèse, la croissance des plantes et le rendement en fruits pour les deux types de framboisiers non-remontants et remontants (Rubus idaeus, L.). Puisque les pratiques culturales doivent être adaptées aux différents environnements de culture, la taille d’été (pour le cultivar non-remontant), l’optimisation de la densité des tiges (pour le cultivar remontant) et l’utilisation de bâches réfléchissantes (pour les deux types des framboisiers) ont été étudiées sous grands tunnels, abris Voen vs. en plein champ. Les plants cultivés sous grands tunnels produisent en moyenne 1,2 et 1,5 fois le rendement en fruits commercialisables que ceux cultivés sous abri Voen pour le cv. non-remontant ‘Jeanne d’Orléans’ et le cv. remontant ‘Polka’, respectivement. Comparativement aux framboisiers cultivés aux champs, le rendement en fruits des plants sous grands tunnels était plus du double pour le cv. ‘Jeanne d’Orléans’ et près du triple pour le cv. ‘Polka’. L’utilisation de bâches réfléchissantes a entrainé un gain significatif sur le rendement en fruits de 12% pour le cv. ‘Jeanne d’Orléans’ et de 17% pour le cv. ‘Polka’. La taille des premières ou deuxièmes pousses a significativement amélioré le rendement en fruits du cv. ‘Jeanne d’Orléans’ de 26% en moyenne par rapport aux framboisiers non taillés. Des augmentations significatives du rendement en fruits de 43% et 71% du cv. ‘Polka’ ont été mesurées avec l’accroissement de la densité à 4 et 6 tiges par pot respectivement, comparativement à deux tiges par pot. Au cours de la période de fructification du cv. ‘Jeanne d’Orléans’, les bâches réfléchissantes ont augmenté significativement la densité de flux photonique photosynthétique (DFPP) réfléchie à la canopée inférieure de 80% en plein champ et de 60% sous grands tunnels, comparativement à seulement 14% sous abri Voen. Durant la saison de fructification du cv. ‘Polka’, un effet positif de bâches sur la lumière réfléchie (jusqu’à 42%) a été mesuré seulement en plein champ. Dans tous les cas, les bâches réfléchissantes n’ont présenté aucun effet significatif sur la DFPP incidente foliaire totale et la photosynthèse. Pour le cv. ‘Jeanne d’Orléans’, la DFPP incidente sur la feuille a été atténuée d’environ 46% sous le deux types de revêtement par rapport au plein champ. Par conséquent, la photosynthèse a été réduite en moyenne de 43% sous grands tunnels et de 17% sous abris Voen. Des effets similaires ont été mesurés pour la DFPP incidente et la photosynthèse avec le cv. Polka. En dépit du taux de photosynthèse des feuilles individuelles systématiquement inférieur à ceux mesurés pour les plants cultivés aux champs, la photosynthèse de la plante entière sous grands tunnels était de 51% supérieure à celle observée au champ pour le cv. ‘Jeanne d’Orléans’, et 46% plus élevée pour le cv. ‘Polka’. Ces résultats s’expliquent par une plus grande (près du double) surface foliaire pour les plants cultivés sous tunnels, qui a compensé pour le plus faible taux de photosynthèse par unité de surface foliaire. Les températures supra-optimales des feuilles mesurées sous grands tunnels (6.6°C plus élevé en moyenne que dans le champ), ainsi que l’atténuation de la DFPP incidente (env. 43%) par les revêtements de tunnels ont contribué à réduire le taux de photosynthèse par unité de surface foliaire. La photosynthèse de la canopée entière était étroitement corrélée avec le rendement en fruits pour les deux types de framboisiers rouges cultivés sous grands tunnels ou en plein champ.
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Objectives: Mycological contamination of occupational environments can be a result of fungal spores’ dispersion in the air and on surfaces. Therefore, it is very important to assess it in both types of the samples. In the present study we assessed fungal contamination in the air and in the surface samples to show relevance of surfaces sampling in complementing the results obtained in the air samples. Material and Methods: In total, 42 settings were assessed by the analysis of air and surfaces samples. The settings were divided into settings with a high fungal load (7 poultry farms and 7 pig farms, 3 cork industries, 3 waste management plants, 2 wastewater treatment plants and 1 horse stable) and a low fungal load (10 hospital canteens, 8 college canteens and 1 maternity hospital). In addition to culture-based methods, molecular tools were also applied to detect fungal burden in the settings with a higher fungal load. Results: From the 218 sampling sites, 140 (64.2%) presented different species in the examined surfaces when compared with the species identified in the air. A positive association in the high fungal load settings was found between the presence of different species in the air and surfaces. Wastewater treatment plants constituted the setting with the highest number of different species between the air and surface. Conclusions: We observed that surfaces sampling and application of molecular tools showed the same efficacy of species detection in high fungal load settings, corroborating the fact that surface sampling is crucial for a correct and complete analysis of occupational scenarios.
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Understanding how biodiversity spatially distribute over both the short term and long term, and what factors are affecting the distribution, are critical for modeling the spatial pattern of biodiversity as well as for promoting effective conservation planning and practices. This dissertation aims to examine factors that influence short-term and long-term avian distribution from the geographical sciences perspective. The research develops landscape level habitat metrics to characterize forest height heterogeneity and examines their efficacies in modelling avian richness at the continental scale. Two types of novel vegetation-height-structured habitat metrics are created based on second order texture algorithms and the concepts of patch-based habitat metrics. I correlate the height-structured metrics with the richness of different forest guilds, and also examine their efficacies in multivariate richness models. The results suggest that height heterogeneity, beyond canopy height alone, supplements habitat characterization and richness models of two forest bird guilds. The metrics and models derived in this study demonstrate practical examples of utilizing three-dimensional vegetation data for improved characterization of spatial patterns in species richness. The second and the third projects focus on analyzing centroids of avian distributions, and testing hypotheses regarding the direction and speed of these shifts. I first showcase the usefulness of centroids analysis for characterizing the distribution changes of a few case study species. Applying the centroid method on 57 permanent resident bird species, I show that multi-directional distribution shifts occurred in large number of studied species. I also demonstrate, plain birds are not shifting their distribution faster than mountain birds, contrary to the prediction based on climate change velocity hypothesis. By modelling the abundance change rate at regional level, I show that extreme climate events and precipitation measures associate closely with some of the long-term distribution shifts. This dissertation improves our understanding on bird habitat characterization for species richness modelling, and expands our knowledge on how avian populations shifted their ranges in North America responding to changing environments in the past four decades. The results provide an important scientific foundation for more accurate predictive species distribution modeling in future.
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The ‘Microbial Cities’ vision of bacterial biofilms has dominated our understanding of the development and functioning of bacterial aggregations for the past 20 years, during which active sludge, clumps, colonies, flocs, mats, pellicles, rafts, slimes, zooglea, etc. have been largely forgotten or ignored. Although the medically inspired developmental model of human pathogen biofilms has merits including providing a rationale for the development of anti-biofilm therapeutics, it fails to provide links to other types of bacterial aggregation that are commonly found in a wide range of natural and man-made environments. Possibly as a result, applied and environmental microbiologists tend to avoid the term ‘biofilm’ and use others such as ‘microbial mats’ instead. Here we challenge the simplistic planktonic (independent and free-swimming bacteria)-biofilm (sessile and co-operative bacteria) dichotomy, and consider biofilms within the larger context of bacterial aggregations. By placing biofilms into context, which we see as a continuum of aggregations or communities with varying abiotic and biotic properties, fundamental physical, biological, and evolutionary ecological processes that effect community development and function can no longer be considered unique to biofilms, but may also be important in other aggregations that develop over time and change in nature depending on prevailing conditions. By doing this, we will be better able to distinguish those processes which govern bacterial colonisation and ecological success in a wider sense from those that are unique to particular environments and specialised strategies.
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Every year in the US and other cold-climate countries considerable amount of money is spent to restore structural damages in conventional bridges resulting from (or “caused by”) salt corrosion in bridge expansion joints. Frequent usage of deicing salt in conventional bridges with expansion joints results in corrosion and other damages to the expansion joints, steel girders, stiffeners, concrete rebar, and any structural steel members in the abutments. The best way to prevent these damages is to eliminate the expansion joints at the abutment and elsewhere and make the entire bridge abutment and deck a continuous monolithic structural system. This type of bridge is called Integral Abutment Bridge which is now widely used in the US and other cold-climate countries. In order to provide lateral flexibility, the entire abutment is constructed on piles. Piles used in integral abutments should have enough capacity in the perpendicular direction to support the vertical forces. In addition, piles should be able to withstand corrosive environments near the surface of the ground and maintain their performance during the lifespan of the bridge. Fiber Reinforced Polymer (FRP) piles are a new type of pile that can not only accommodate large displacements, but can also resist corrosion significantly better than traditional steel or concrete piles. The use of FRP piles extends the life of the pile which in turn extends the life of the bridge. This dissertation studies FRP piles with elliptical shapes. The elliptical shapes can simultaneously provide flexibility and stiffness in two perpendicular axes. The elliptical shapes can be made using the filament winding method which is a less expensive method of manufacturing compared to the pultrusion or other manufacturing methods. In this dissertation a new way is introduced to construct the desired elliptical shapes with the filament winding method. Pile specifications such as dimensions, number of layers, fiber orientation angles, material, and soil stiffness are defined as parameters and the effects of each parameter on the pile stresses and pile failure have been studied. The ANSYS software has been used to model the composite materials. More than 14,000 nonlinear finite element pile models have been created, each slightly different from the others. The outputs of analyses have been used to draw curves. Optimum values of the parameters have been defined using generated curves. The best approaches to find optimum shape, angle of fibers and types of composite material have been discussed.
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International audience
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Apparitions of empire and imperial ideologies were deeply embedded in the International Exhibition, a distinct exhibitionary paradigm that came to prominence in the mid-nineteenth century. Exhibitions were platforms for the display of objects, the movement of people, and the dissemination of ideas across and between regions of the British Empire, thereby facilitating contact between its different cultures and societies. This thesis aims to disrupt a dominant understanding of International Exhibitions, which forwards the notion that all exhibitions, irrespective of when or where they were staged, upheld a singular imperial discourse (i.e. Greenhalgh 1988, Rydell 1984). Rather, this thesis suggests International Exhibitions responded to and reflected the unique social, political and economic circumstances in which they took place, functioning as cultural environments in which pressing concerns of the day were worked through. Understood thus, the International Exhibition becomes a space for self-presentation, serving as a stage from which a multitude of interests and identities were constructed, performed and projected. This thesis looks to the visual and material culture of the International Exhibition in order to uncover this more nuanced history, and foregrounds an analysis of the intersections between practices of exhibition-making and identity-making. The primary focus is a set of exhibitions held in Glasgow in the late-1880s and early-1900s, which extends the geographic and temporal boundaries of the existing scholarship. What is more, it looks at representations of Canada at these events, another party whose involvement in the International Exhibition tradition has gone largely unnoticed. Consequently, this thesis is a thematic investigation of the links between a municipality routinely deemed the ‘Second City of the Empire’ and a Dominion settler colony, two types of geographic setting rarely brought into dialogue. It analyses three key elements of the exhibition-making process, exploring how iconographies of ‘quasi-nationhood’ were expressed through an exhibition’s planning and negotiation, its architecture and its displays. This original research framework deliberately cuts across strata that continue to define conceptions of the British Empire, and pushes beyond a conceptual model defined by metropole and colony. Through examining International Exhibitions held in Glasgow in the late-Victorian and Edwardian periods, and visions of Canada in evidence at these events, the goal is to offer a novel intervention into the existing literature concerning the cultural history of empire, one that emphasises fluidity rather than fixity and which muddles the boundaries between centre and periphery.
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My thesis consists of three essays that investigate strategic interactions between individuals engaging in risky collective action in uncertain environments. The first essay analyzes a broad class of incomplete information coordination games with a wide range of applications in economics and politics. The second essay draws from the general model developed in the first essay to study decisions by individuals of whether to engage in protest/revolution/coup/strike. The final essay explicitly integrates state response to the analysis. The first essay, Coordination Games with Strategic Delegation of Pivotality, exhaustively analyzes a class of binary action, two-player coordination games in which players receive stochastic payoffs only if both players take a ``stochastic-coordination action''. Players receive conditionally-independent noisy private signals about the normally distributed stochastic payoffs. With this structure, each player can exploit the information contained in the other player's action only when he takes the “pivotalizing action”. This feature has two consequences: (1) When the fear of miscoordination is not too large, in order to utilize the other player's information, each player takes the “pivotalizing action” more often than he would based solely on his private information, and (2) best responses feature both strategic complementarities and strategic substitutes, implying that the game is not supermodular nor a typical global game. This class of games has applications in a wide range of economic and political phenomena, including war and peace, protest/revolution/coup/ strike, interest groups lobbying, international trade, and adoption of a new technology. My second essay, Collective Action with Uncertain Payoffs, studies the decision problem of citizens who must decide whether to submit to the status quo or mount a revolution. If they coordinate, they can overthrow the status quo. Otherwise, the status quo is preserved and participants in a failed revolution are punished. Citizens face two types of uncertainty. (a) non-strategic: they are uncertain about the relative payoffs of the status quo and revolution, (b) strategic: they are uncertain about each other's assessments of the relative payoff. I draw on the existing literature and historical evidence to argue that the uncertainty in the payoffs of status quo and revolution is intrinsic in politics. Several counter-intuitive findings emerge: (1) Better communication between citizens can lower the likelihood of revolution. In fact, when the punishment for failed protest is not too harsh and citizens' private knowledge is accurate, then further communication reduces incentives to revolt. (2) Increasing strategic uncertainty can increase the likelihood of revolution attempts, and even the likelihood of successful revolution. In particular, revolt may be more likely when citizens privately obtain information than when they receive information from a common media source. (3) Two dilemmas arise concerning the intensity and frequency of punishment (repression), and the frequency of protest. Punishment Dilemma 1: harsher punishments may increase the probability that punishment is materialized. That is, as the state increases the punishment for dissent, it might also have to punish more dissidents. It is only when the punishment is sufficiently harsh, that harsher punishment reduces the frequency of its application. Punishment Dilemma 1 leads to Punishment Dilemma 2: the frequencies of repression and protest can be positively or negatively correlated depending on the intensity of repression. My third essay, The Repression Puzzle, investigates the relationship between the intensity of grievances and the likelihood of repression. First, I make the observation that the occurrence of state repression is a puzzle. If repression is to succeed, dissidents should not rebel. If it is to fail, the state should concede in order to save the costs of unsuccessful repression. I then propose an explanation for the “repression puzzle” that hinges on information asymmetries between the state and dissidents about the costs of repression to the state, and hence the likelihood of its application by the state. I present a formal model that combines the insights of grievance-based and political process theories to investigate the consequences of this information asymmetry for the dissidents' contentious actions and for the relationship between the magnitude of grievances (formulated here as the extent of inequality) and the likelihood of repression. The main contribution of the paper is to show that this relationship is non-monotone. That is, as the magnitude of grievances increases, the likelihood of repression might decrease. I investigate the relationship between inequality and the likelihood of repression in all country-years from 1981 to 1999. To mitigate specification problem, I estimate the probability of repression using a generalized additive model with thin-plate splines (GAM-TPS). This technique allows for flexible relationship between inequality, the proxy for the costs of repression and revolutions (income per capita), and the likelihood of repression. The empirical evidence support my prediction that the relationship between the magnitude of grievances and the likelihood of repression is non-monotone.
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Forested areas within cities host a large number of species, responsible for many ecosystem services in urban areas. The biodiversity in these areas is influenced by human disturbances such as atmospheric pollution and urban heat island effect. To ameliorate the effects of these factors, an increase in urban green areas is often considered sufficient. However, this approach assumes that all types of green cover have the same importance for species. Our aim was to show that not all forested green areas are equal in importance for species, but that based on a multi-taxa and functional diversity approach it is possible to value green infrastructure in urban environments. After evaluating the diversity of lichens, butterflies and other-arthropods, birds and mammals in 31 Mediterranean urban forests in south-west Europe (Almada, Portugal), bird and lichen functional groups responsive to urbanization were found. A community shift (tolerant species replacing sensitive ones) along the urbanization gradient was found, and this must be considered when using these groups as indicators of the effect of urbanization. Bird and lichen functional groups were then analyzed together with the characteristics of the forests and their surroundings. Our results showed that, contrary to previous assumptions, vegetation density and more importantly the amount of urban areas around the forest (matrix), are more important for biodiversity than forest quantity alone. This indicated that not all types of forested green areas have the same importance for biodiversity. An index of forest functional diversity was then calculated for all sampled forests of the area. This could help decision-makers to improve the management of urban green infrastructures with the goal of increasing functionality and ultimately ecosystem services in urban areas.
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Offshore structures with numerous applications in different environments throughout the world and used at different depths. Due to the expansion of marine industries, including offshore oil industry in Iran , particularly in the Persian Gulf region, in order to more accurately model these structures and to prevent incidents such as the Overturning of the platform serious damage to the South Pars Phase ١٣ was platforms, the use New Technic is essential technologies. One of the methods that are used in the construction of offshore wind turbines, using a pre-pile. In this method, a template is constructed with the dimensions specified in the workshop. After making templates using special vessels for placement in the desired location on the sea bed is carried, then the template is placed on the sea bed, Then, using a hammer for Pile Driving Operation Started Vibration hammer and fit the template of 3 or 4 piles of crushed within this template on the seabed . The next step piling, templates have been removed from the site And Jacket placed on piles. The system was installed on the deck on piles and Consequently Deck Load pile inserted on .It should be noted that the design of these types of platforms, base diameter of the pile diameter independent of the choice as one of the major advantages of this system is. This thesis examines a Template Fixed Platform in the oil Soroush Using the Pre-Piling and the Common Piling systems in the Persian Gulf were studied and the effect of different design compared to the Pre-Piling Platforms Persian Gulf were evaluated. The results suggest that Pre-Piling system compared with conventional systems piling in the Persian Gulf, as a more appropriate model structure and behavior Top Model economic efficiency is selected. It should be noted that all calculations and analyzes were performed using Software Abaqus.
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Part 15: Performance Management Frameworks
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This research is about producing recombinant Trichoderma reesei endoglucanase Cel7B by using Kluyveromyces lactis, transformed with chromosomally integrated Cel7B cDNA, as a host cell (K. lactis Cel7B). Cel7B is one of the glycoside hydrolyze family of proteins that are produced by T. reesei. Cel7B together with other endoglucanases, exoglucanases, and â-glucosidases hydrolyze cellulose to glucose, which can then be fermented to biofuels or other value-added products. The research objective of this MS project is to examine favorable fermentation conditions for recombinant Cel7B enzyme production and improved activity. Production of enzyme on different types of media was examined, and the activity of the enzyme was measured by using different tools or procedures. The first condition tested for was using different concentrations of galactose as a carbon and energy source; however galactose also acts as a potent promoter of recombinant Cel7B expression in K. lactis Cel7B. The purpose of this method is to determine the relationship between production of enzyme with increasing sugar concentration. The second culture condition test was using different types of media: a complex medium-yeast extract, peptone, galactose (YPGal); a minimal medium-yeast nitrogen base (YNB) with galactose; and a minimal medium with supplement-yeast nitrogen base with casamino acid (YBC), a nitrogen source, with galactose. The third condition was using different types of reactors or fermenters: a small reactor (shake flask) and a larger automated bioreactor (BioFlo 3000 fermenter). The purpose of this method is to determine the quantity of the protein produced by using different environments of production. Different tools to determine the presence and activity of Cel7B enzyme were used. For the presence of enzyme, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was used. Secondly, to detect enzyme activity, the carboxymethyl cellulose- 3,5-dinitrosalicylic acid (CMC- DNS) assay was employed. SDS-PAGE showed that the enzyme band was at 67 kDa, which is larger than native Cel7B (52 kDa.), likely due to over glycolylation during post-translational processing in K. lactis. For the different types of media used in our fermentation, recombinant Cel7B was produced from yeast extract peptone galactose (YPGal), and yeast nitrogen base with casamino acid (YBC), but was not produced and no activity was detected from yeast nitrogen base (YNB). This experiment concluded that the Cel7B production requires the amino acid resources as part of fermentation medium. In experiments where recombinant Cel7B net activity was measured at 1% galactose initial concentration in YPGal and YBC media, higher enzyme activity was detected for the complex medium YPGal. Higher activity of recombinant Cel7B was detected for flask culture in 2% galactose compared to 1% galactose for YBC medium. Two bioreactor experiments were conducted under these culture conditions at 30°C, pH 7.0, dissolved oxygen of 50% of saturation, and 250 rpm agitation (variable depending on DO control) K. lactis-Cel7B yeast growth curves were quite reproducible with maximum optical density (O.D) at 600 nm of between 7 and 8 (when factoring dilution of 10:1). Galactose was consumed rapidly during the first 15 hours of bioreactor culture and recombinant Cel7B started to appear in the culture at 10-15 hours and increased thereafter up to a maximum of between 0.9 and 1.6 mg/mL/hr in these experiments. These bioreactor enzyme activity results are much higher than comparable experiments conducted with flask-scale culture (0.5 mg/mL/hr). In order to achieve the highest recombinant Cel7B activity from batch culture of K. lactis-Cel7B, based on this research it is best to use a complex medium, 2% initial galactose concentration, and an automated bioreactor where good control of temperature, pH, and dissolved oxygen can be achieved.