Analysis of testicular cell populations using flow cytometry

Studying testis is complex, because the tissue has a very heterogeneous cell composition and its structure changes dynamically during development. In reproductive field, the cell composition is traditionally studied by morphometric methods such as immunohistochemistry and immunofluorescence. These techniques provide accurate quantitative information about cell composition, cell-cell association and localization of the cells of interest. However, the sample preparation, processing, staining and data analysis are laborious and may take several working days. Flow cytometry protocols coupled with DNA stains have played an important role in providing quantitative information of testicular cells populations ex vivo and in vitro studies. Nevertheless, the addition of specific cells markers such as intracellular antibodies would allow the more specific identification of cells of crucial interest during spermatogenesis. For this study, adult rat Sprague-Dawley rats were used for optimization of the flow cytometry protocol. Specific steps within the protocol were optimized to obtain a singlecell suspension representative of the cell composition of the starting material. Fixation and permeabilization procedure were optimized to be compatible with DNA stains and fluorescent intracellular antibodies. Optimization was achieved by quantitative analysis of specific parameters such as recovery of meiotic cells, amount of debris and comparison of the proportions of the various cell populations with already published data. As a result, a new and fast flow cytometry method coupled with DNA stain and intracellular antigen detection was developed. This new technique is suitable for analysis of population behavior and specific cells during postnatal testis development and spermatogenesis in rodents. This rapid protocol recapitulated the known vimentin and γH2AX protein expression patterns during rodent testis ontogenesis. Moreover, the assay was applicable for phenotype characterization of SCRbKO and E2F1KO mouse models.

The role of management accounting systems and venture capital investors for start-up firms

The role of star-up firms in economy and the importance of venture capital investors for the growth of start-up firms have been highlighted in recent years. The growth challenges of start-up firms consist of fast changing environment, the availability of venture capital funding and the development of firm management in the growth phase. A growing number of studies have focused on management accounting systems and venture capital in start-up and growth firm context. In this thesis the role of management accounting systems and venture capital investors is considered in the growth phase of firm development. The theoretical objective of this thesis is to construct a theoretical framework in order to describe the importance of management accounting systems and venture capital investors in start-up firms. The practice orientated objective of this thesis is to study the application of management accounting systems and management accounting based information in start-up firms in high-technology industry as well as the impact of venture capital for management accounting system design. In addition, the growth challenges of start-up firms are studied in order to understand the context in which management accounting systems are used. The research approach of theoretical part is conceptual as the theoretical framework is constructed by combining literature on firm growth, management accounting and venture finance in order to analyse the phenomenon. The action-orientated research approach is appropriate for analysing and describing of the studied phenomenon through empirical evidence. The empirical evidence was collected through interviews with three experts in start-up firm accelerator centers, four representatives of start-up firms and one venture capital investor. The results indicate that the growth challenges of stat-up firms are not related to the development of management accounting systems. Managers of start-up firms expressed a positive attitude towards management accounting systems that improve efficiency of operations. In start-up firms flexible and adjustable management accounting practices, such as budgets, cash flow calculations and future-orientated analysis tools, are applied that support planning and coordination of operations. The results indicate that venture capital investors affect the provision and the quality of management accounting information during the investment process. In addition, venture capital investors enhance the use of management accounting information for internal coordination in start-up firms. By applying the theoretical framework in the analysis, it can be stated that by acting as support function management accounting systems facilitate start-up firms development.

Modeling of burden distribution in the blast furnace

The blast furnace is the main ironmaking production unit in the world which converts iron ore with coke and hot blast into liquid iron, hot metal, which is used for steelmaking. The furnace acts as a counter-current reactor charged with layers of raw material of very different gas permeability. The arrangement of these layers, or burden distribution, is the most important factor influencing the gas flow conditions inside the furnace, which dictate the efficiency of the heat transfer and reduction processes. For proper control the furnace operators should know the overall conditions in the furnace and be able to predict how control actions affect the state of the furnace. However, due to high temperatures and pressure, hostile atmosphere and mechanical wear it is very difficult to measure internal variables. Instead, the operators have to rely extensively on measurements obtained at the boundaries of the furnace and make their decisions on the basis of heuristic rules and results from mathematical models. It is particularly difficult to understand the distribution of the burden materials because of the complex behavior of the particulate materials during charging. The aim of this doctoral thesis is to clarify some aspects of burden distribution and to develop tools that can aid the decision-making process in the control of the burden and gas distribution in the blast furnace. A relatively simple mathematical model was created for simulation of the distribution of the burden material with a bell-less top charging system. The model developed is fast and it can therefore be used by the operators to gain understanding of the formation of layers for different charging programs. The results were verified by findings from charging experiments using a small-scale charging rig at the laboratory. A basic gas flow model was developed which utilized the results of the burden distribution model to estimate the gas permeability of the upper part of the blast furnace. This combined formulation for gas and burden distribution made it possible to implement a search for the best combination of charging parameters to achieve a target gas temperature distribution. As this mathematical task is discontinuous and non-differentiable, a genetic algorithm was applied to solve the optimization problem. It was demonstrated that the method was able to evolve optimal charging programs that fulfilled the target conditions. Even though the burden distribution model provides information about the layer structure, it neglects some effects which influence the results, such as mixed layer formation and coke collapse. A more accurate numerical method for studying particle mechanics, the Discrete Element Method (DEM), was used to study some aspects of the charging process more closely. Model charging programs were simulated using DEM and compared with the results from small-scale experiments. The mixed layer was defined and the voidage of mixed layers was estimated. The mixed layer was found to have about 12% less voidage than layers of the individual burden components. Finally, a model for predicting the extent of coke collapse when heavier pellets are charged over a layer of lighter coke particles was formulated based on slope stability theory, and was used to update the coke layer distribution after charging in the mathematical model. In designing this revision, results from DEM simulations and charging experiments for some charging programs were used. The findings from the coke collapse analysis can be used to design charging programs with more stable coke layers.