Understanding the in vitro dissolution rate of glasses with respect to future clinical applications

Glass is a unique material with a long history. Several glass products are used daily in our everyday life, often unnoticed. Glass can be found not only in obvious applications such as tableware, windows, and light bulbs, but also in tennis rackets, windmill turbine blades, optical devices, and medical implants. The glasses used at present as implants are inorganic silica-based melt-derived compositions mainly for hard-tissue repair as bone graft substitute in dentistry and orthopedics. The degree of glass reactivity desired varies according to implantation situation and it is vital that the ion release from any glasses used in medical applications is controlled. Understanding the in vitro dissolution rate of glasses provides a first approximation of their behavior in vivo. Specific studies concerning dissolution properties of bioactive glasses have been relatively scarce and mostly concentrated to static condition studies. The motivation behind this work was to develop a simple and accurate method for quantifying the in vitro dissolution rate of highly different types of glass compositions with interest for future clinical applications. By combining information from various experimental conditions, a better knowledge of glass dissolution and the suitability of different glasses for different medical applications can be obtained. Thus, two traditional and one novel approach were utilized in this thesis to study glass dissolution. The chemical durability of silicate glasses was tested in water and TRIS-buffered solution at static and dynamic conditions. The traditional in vitro testing with a TRISbuffered solution under static conditions works well with bioactive or with readily dissolving glasses, and it is easy to follow the ion dissolution reactions. However, in the buffered solution no marked differences between the more durable glasses were observed. The hydrolytic resistance of the glasses was studied using the standard procedure ISO 719. The relative scale given by the standard failed to provide any relevant information when bioactive glasses were studied. However, the clear differences in the hydrolytic resistance values imply that the method could be used as a rapid test to get an overall idea of the biodegradability of glasses. The standard method combined with the ion concentration and pH measurements gives a better estimate of the hydrolytic resistance because of the high silicon amount released from a glass. A sensitive on-line analysis method utilizing inductively coupled plasma optical emission spectrometer and a flow-through micro-volume pH electrode was developed to study the initial dissolution of biocompatible glasses. This approach was found suitable for compositions within a large range of chemical durability. With this approach, the initial dissolution of all ions could be measured simultaneously and quantitatively, which gave a good overall idea of the initial dissolution rates for the individual ions and the dissolution mechanism. These types of results with glass dissolution were presented for the first time during the course of writing this thesis. Based on the initial dissolution patterns obtained with the novel approach using TRIS, the experimental glasses could be divided into four distinct categories. The initial dissolution patterns of glasses correlated well with the anticipated bioactivity. Moreover, the normalized surface-specific mass loss rates and the different in vivo models and the actual in vivo data correlated well. The results suggest that this type of approach can be used for prescreening the suitability of novel glass compositions for future clinical applications. Furthermore, the results shed light on the possible bioactivity of glasses. An additional goal in this thesis was to gain insight into the phase changes occurring during various heat treatments of glasses with three selected compositions. Engineering-type T-T-T curves for glasses 1-98 and 13-93 were stablished. The information gained is essential in manufacturing amorphous porous implants or for drawing of continuous fibers of the glasses. Although both glasses can be hot worked to amorphous products at carefully controlled conditions, 1-98 showed one magnitude greater nucleation and crystal growth rate than 13-93. Thus, 13-93 is better suited than 1-98 for working processes which require long residence times at high temperatures. It was also shown that amorphous and partially crystalline porous implants can be sintered from bioactive glass S53P4. Surface crystallization of S53P4, forming Na2O∙CaO∙2SiO2, was observed to start at 650°C. The secondary crystals of Na2Ca4(PO4)2SiO4, reported for the first time in this thesis, were detected at higher temperatures, from 850°C to 1000°C. The crystal phases formed affected the dissolution behavior of the implants in simulated body fluid. This study opens up new possibilities for using S53P4 to manufacture various structures, while tailoring their bioactivity by controlling the proportions of the different phases. The results obtained in this thesis give valuable additional information and tools to the state of the art for designing glasses with respect to future clinical applications. With the knowledge gained we can identify different dissolution patters and use this information to improve the tuning of glass compositions. In addition, the novel online analysis approach provides an excellent opportunity to further enhance our knowledge of glass behavior in simulated body conditions.

Design of Instrument for Knee Joint Kinematics Measurement

This thesis describes the process of design and modeling of instrument for knee joint kinematics measurement that can work for both in-vivo and in-vitro subjects. It is designed to be compatible with imaging machine in a sagittal plane. Due to the invasiveness of the imaging machine, the instrument is designed to be able to function independently. The flexibility of this instrument allows to measure anthropometrically different subject. Among the sixth degree of freedom of a knee, three rotational and one translational degree of freedom can be measured for both type of subject. The translational, proximal-distal, motion is stimulated by external force directly applied along its axis. These angular and linear displacements are measured by magnetic sensors and high precision potentiometers respectively

Pricing anomalies in the Finnish stock market

The aim of this thesis is to examine whether the pricing anomalies exists in the Finnish stock markets by comparing the performance of quantile portfolios that are formed on the basis of either individual valuation ratios, composite value measures or combined value and momentum indicators. All the research papers included in the thesis show evidence of value anomalies in the Finnish stock markets. In the first paper, the sample of stocks over the 1991-2006 period is divided into quintile portfolios based on four individual valuation ratios (i.e., E/P, EBITDA/EV, B/P, and S/P) and three hybrids of them (i.e. composite value measures). The results show the superiority of composite value measures as selection criterion for value stocks, particularly when EBITDA/EV is employed as earnings multiple. The main focus of the second paper is on the impact of the holding period length on performance of value strategies. As an extension to the first paper, two more individual ratios (i.e. CF/P and D/P) are included in the comparative analysis. The sample of stocks over 1993- 2008 period is divided into tercile portfolios based on six individual valuation ratios and three hybrids of them. The use of either dividend yield criterion or one of three composite value measures being examined results in best value portfolio performance according to all performance metrics used. Parallel to the findings of many international studies, our results from performance comparisons indicate that for the sample data employed, the yearly reformation of portfolios is not necessarily optimal in order to maximally gain from the value premium. Instead, the value investor may extend his holding period up to 5 years without any decrease in long-term portfolio performance. The same holds also for the results of the third paper that examines the applicability of data envelopment analysis (DEA) method in discriminating the undervalued stocks from overvalued ones. The fourth paper examines the added value of combining price momentum with various value strategies. Taking account of the price momentum improves the performance of value portfolios in most cases. The performance improvement is greatest for value portfolios that are formed on the basis of the 3-composite value measure which consists of D/P, B/P and EBITDA/EV ratios. The risk-adjusted performance can be enhanced further by following 130/30 long-short strategy in which the long position of value winner stocks is leveraged by 30 percentages while simultaneously selling short glamour loser stocks by the same amount. Average return of the long-short position proved to be more than double stock market average coupled with the volatility decrease. The fifth paper offers a new approach to combine value and momentum indicators into a single portfolio-formation criterion using different variants of DEA models. The results throughout the 1994-2010 sample period shows that the top-tercile portfolios outperform both the market portfolio and the corresponding bottom-tercile portfolios. In addition, the middle-tercile portfolios also outperform the comparable bottom-tercile portfolios when DEA models are used as a basis for stock classification criteria. To my knowledge, such strong performance differences have not been reported in earlier peer-reviewed studies that have employed the comparable quantile approach of dividing stocks into portfolios. Consistently with the previous literature, the division of the full sample period into bullish and bearish periods reveals that the top-quantile DEA portfolios lose far less of their value during the bearish conditions than do the corresponding bottom portfolios. The sixth paper extends the sample period employed in the fourth paper by one year (i.e. 1993- 2009) covering also the first years of the recent financial crisis. It contributes to the fourth paper by examining the impact of the stock market conditions on the main results. Consistently with the fifth paper, value portfolios lose much less of their value during bearish conditions than do stocks on average. The inclusion of a momentum criterion somewhat adds value to an investor during bullish conditions, but this added value turns to negative during bearish conditions. During bear market periods some of the value loser portfolios perform even better than their value winner counterparts. Furthermore, the results show that the recent financial crisis has reduced the added value of using combinations of momentum and value indicators as portfolio formation criteria. However, since the stock markets have historically been bullish more often than bearish, the combination of the value and momentum criteria has paid off to the investor despite the fact that its added value during bearish periods is negative, on an average.

Dynaamisen lämmönsiirtomallin kehittäminen

Dynaamisia simulointimalleja tarvitaan, jotta voidaan tarkastella järjestelmän käyttäytymistä ajan funktiona. Simulointimallilla voidaan simuloida järjestelmän lähtö erilaisilla herätteillä. Mallin avulla saadaan myös tarkempi käsitys järjestelmästä ja sen osa-alueista, koska simulointimallista voidaan tarkastella sellaisia asioita, jotka voivat olla oikeasta järjestelmästä vaikeasti mitattavia. Tässä työssä kehitetään LUT Energian hyötysuhdemittapaikan keskikokoista kalorimetriä approksimoiva dynaaminen lämmönsiirtomalli käyttäen Matlab® Simulink -ohjelmistoa. Kehitetyn lämmönsiirtomallin tarkkuutta arvioidaan todellisella järjestelmällä tehdyillä mittauksilla. Työssä käytetään karkeita approksimaatioita, jotka tulee korvata tarkemmilla matemaattisilla malleilla jatkokehitystä varten. Työssä kehitetty dynaaminen lämmönsiirtomalli approksimoi todellisen järjestelmän vastetta lämmitysvaiheessa keskimääräisenvirheen ±0,19 °C tarkkuudella.

Customer profitability measurement in a not-for-profit organization

The objective of this study was to find out the factors that affect customer profitability in the not-for-profit case company. The customer profitability was examined in two different segments of the customer base. The effects that price, cost and the amount of services provided have on the profit margin were studied. The distribution of profitability among the customers and the effect of certain characteristics, such as size of the customer measured in services purchased, on the profitability were analyzed. The theoretical framework was built around customer profitability and the use of customer profitability information in a not-for-profit organization. The present use of customer profitability information and the possibilities of using the results of this research in the case company were presented. Quantitative research methods were used in the empirical part of the study. The results indicate that the two customer segments have differences in their buying behaviors which affect the profitability and thus the measures taken to improve the profitability should be considered with the different characteristics of the customers in mind. Finally the limitations of the study were discussed as possible further research topics.

Design of an amplifier and an instrumentation setup for a harsh environment heat flux measurement application – case axial flux electric machine

Measurement is a tool for researching. Therefore, it is important that the measuring process is carried out correctly, without distorting the signal or the measured event. Researches of thermoelectric phenomena have been focused more on transverse thermoelectric phenomena during recent decades. Transverse Seebeck effect enables to produce thinner and faster heat flux sensor than before. Studies about transverse Seebeck effect have so far focused on materials, so in this Master’s Thesis instrumentation of transverse Seebeck effect based heat flux sensor is studied, This Master’s Thesis examines an equivalent circuit of transverse Seebeck effect heat flux sensors, their connectivity to electronics and choosing and design a right type amplifier. The research is carried out with a case study which is Gradient Heat Flux Sensors and an electrical motor. In this work, a general equivalent circuit was presented for the transverse Seebeck effect-based heat flux sensor. An amplifier was designed for the sensor of the case study, and the solution was produced for the measurement of the local heat flux of the electric motor to improve the electromagnetic compatibility.

Heat flux measurement inside internal combustion engine with gradient heat flux sensor.

This master’s thesis is devoted to study different heat flux measurement techniques such as differential temperature sensors, semi-infinite surface temperature methods, calorimetric sensors and gradient heat flux sensors. The possibility to use Gradient Heat Flux Sensors (GHFS) to measure heat flux in the combustion chamber of compression ignited reciprocating internal combustion engines was considered in more detail. A. Mityakov conducted an experiment, where Gradient Heat Flux Sensor was placed in four stroke diesel engine Indenor XL4D to measure heat flux in the combustion chamber. The results which were obtained from the experiment were compared with model’s numerical output. This model (a one – dimensional single zone model) was implemented with help of MathCAD and the result of this implementation is graph of heat flux in combustion chamber in relation to the crank angle. The values of heat flux throughout the cycle obtained with aid of heat flux sensor and theoretically were sufficiently similar, but not identical. Such deviation is rather common for this type of experiment.

Talousveden tuotannon ja jakelun tietohuollon kehittäminen julkisomisteisessa vesilaitoksessa

Vesilaitokset kuluttavat merkittäviä määriä energiaa, johon on alettu kiinnittää huomiota viime vuosina. Energiatehokkuuden edistämisen hidasteeksi on noussut puutteellinen tietohuolto sekä vesilaitosten yhteisten tunnuslukujen ja kriteerien puuttuminen. Diplomityön tavoitteena on selvittää tietohuollon ongelmia Tampereen Vedellä. Työn tavoitteena on myös tutkia veden tuotannon ja jakelun energiatehokkaiden ohjaustapojen löytämistä tietohuollon ja tunnuslukujen avulla. Työssä käytetyt metodologiat ovat Tampereen Veden työntekijöiden haastattelut, prototyypin analysointi sekä vedenottamoiden ominaisenergiaan liittyvien mittauspisteiden läpikäynti. Diplomityön tuloksena saatiin laaja kuva Tampereen Veden tietohuoltoon liittyvistä ongelmista. Merkittävimmät tietohuollon haasteet liittyvät työntekijöihin, järjestelmiin sekä mittauspisteiden puuttumiseen. Mittauspisteet ja niiden tallentuminen ovat edellytys tunnuslukujen luomiselle. Tunnuslukuja voidaan hyödyntää energiatehokkaiden ohjaustapojen löytämiseksi, mutta vesilaitosten yhteiset kriteerit tunnusluvuille puuttuvat. Energiatehokkuustunnuslukuja on tarve tutkia lisää ja kehittää yhteistyötä vesilaitosten välillä tunnuslukujen luomiseksi sekä vertailutietojen saamiseksi.

Performance measurement and management in a collaborative network

This study concerns performance measurement and management in a collaborative network. Collaboration between companies has been increased in recent years due to the turbulent operating environment. The literature shows that there is a need for more comprehensive research on performance measurement in networks and the use of measurement information in their management. This study examines the development process and uses of a performance measurement system supporting performance management in a collaborative network. There are two main research questions: how to design a performance measurement system for a collaborative network and how to manage performance in a collaborative network. The work can be characterised as a qualitative single case study. The empirical data was collected in a Finnish collaborative network, which consists of a leading company and a reseller network. The work is based on five research articles applying various research methods. The research questions are examined at the network level and at the single network partner level. The study contributes to the earlier literature by producing new and deeper understanding of network-level performance measurement and management. A three-step process model is presented to support the performance measurement system design process. The process model has been tested in another collaborative network. The study also examines the factors affecting the process of designing the measurement system. The results show that a participatory development style, network culture, and outside facilitators have a positive effect on the design process. The study increases understanding of how to manage performance in a collaborative network and what kind of uses of performance information can be identified in a collaborative network. The results show that the performance measurement system is an applicable tool to manage the performance of a network. The results reveal that trust and openness increased during the utilisation of the performance measurement system, and operations became more transparent. The study also presents a management model that evaluates the maturity of performance management in a collaborative network. The model is a practical tool that helps to analyse the current stage of the performance management of a collaborative network and to develop it further.

Communication Solutions for LVDC Island Networks

Production and generation of electrical power is evolving to more environmental friendly technologies and schemes. Pushed by the increasing cost of fossil fuels, the operational costs of producing electrical power with fossil fuels and the effect in the environment, like pollution and global warming, renewable energy sources gain con-stant impulse into the global energy economy. In consequence, the introduction of distributed energy sources has brought a new complexity to the electrical networks. In the new concept of smart grids and decen-tralized power generation; control, protection and measurement are also distributed and requiring, among other things, a new scheme of communication to operate with each other in balance and improve performance. In this research, an analysis of different communication technologies (power line communication, Ethernet over unshielded twisted pair (UTP), optic fiber, Wi-Fi, Wi-MAX, and Long Term Evolution) and their respective characteristics will be carried out. With the objective of pointing out strengths and weaknesses from different points of view (technical, economical, deployment, etc.) to establish a richer context on which a decision for communication approach can be done depending on the specific application scenario of a new smart grid deployment. As a result, a description of possible optimal deployment solutions for communication will be shown considering different options for technologies, and a mention of different important considerations to be taken into account will be made for some of the possible network implementation scenarios.

GIS assessing traditional and modern agricultural land use/land cover change. A case study 1959-2005: Rekijoki, Somero, SW-Finland

Finland’s rural landscape has gone through remarkable changes from the 1950’s, due to agricultural developments. Changed farming practices have influenced especially traditional landscape management, and modifications in the arable land structure and grasslands transitions are notable. The review of the previous studies reveal the importance of the rural landscape composition and structure to species and landscape diversity, whereas including the relevance in presence of the open ditches, size of the field and meadow patches, topology of the natural and agricultural landscape. This land-change study includes applying remote sensed data from two time series and empirical geospatial analysis in Geographic Information Systems (GIS). The aims of this retrospective research is to detect agricultural landscape use and land cover change (LULCC) dynamics and discuss the consequences of agricultural intensification to landscape structure covering from the aspects of landscape ecology. Measurements of LULC are derived directly from pre-processed aerial images by a variety of analytical procedures, including statistical methods and image interpretation. The methodological challenges are confronted in the process of landscape classification and combining change detection approaches with landscape indices. Particular importance is paid on detecting agricultural landscape features at a small scale, demanding comprehensive understanding of such agroecosystems. Topological properties of the classified arable land and valley are determined in order to provide insight and emphasize the aspect the field edges in the agricultural landscape as important habitat. Change detection dynamics are presented with change matrix and additional calculations of gain, loss, swap, net change, change rate and tendencies are made. Transition’s possibility is computed following Markov’s probability model and presented with matrix, as well. Thesis’s spatial aspect is revealed with illustrative maps providing knowledge of location of the classified landscape categories and location of the dynamics of the changes occurred. It was assured that in Rekijoki valley’s landscape, remarkable changes in landscape has occurred. Landscape diversity has been strongly influenced by modern agricultural landscape change, as NP of open ditches has decreased and the MPS of the arable plot has decreased. Overall change in the diversity of the landscape is determined with the decrease of SHDI. Valley landscape considered as traditional land use area has experienced major transitional changes, as meadows class has lost almost one third of the area due to afforestation. Also, remarkable transitions have occurred from forest to meadow and arable land to built area. Boundaries measurement between modern and traditional landscape has indicated noticeable proportional increase in arable land-forest edge type and decrease in arable land-meadow edge type. Probability calculations predict higher future changes for traditional landscape, but also for arable land turning into built area.

Creating risk measurement model to project portfolio management in construction company

This thesis was carried out as a case study of a company YIT in order to clarify the sev-erest risks for the company and to build a method for project portfolio evaluation. The target organization creates new living environment by constructing residential buildings, business premises, infrastructure and entire areas worth for EUR 1.9 billion in the year 2013. Company has noted project portfolio management needs more information about the structure of project portfolio and possible influences of market shock situation. With interviews have been evaluated risks with biggest influence and most appropriate metrics to examine. The major risks for the company were evaluated by interviewing the executive staff. At the same time, the most appropriate risk metrics were considered. At the moment sales risk was estimated to have biggest impact on company‟s business. Therefore project port-folio evaluation model was created and three different scenarios for company‟s future were created in order to identify the scale of possible market shock situation. The created model is tested with public and descriptive figures of YIT in a one-year-long market shock and the impact on different metrics was evaluated. Study was conducted using con-structive research methodology. Results indicate that company has notable sales risk in certain sections of business portfolio.

Entrepreneurship Education in Basic and Upper Secondary Education – Measurement and Empirical Evidence

The starting point of this study is to direct more attention to the teacher and those entrepreneurship education practices taking place in formal school to find out solutions for more effective promotion of entrepreneurship education. For this objective, the strategy-level aims of entrepreneurship education need to be operationalised into measurable and understandable teacher-level practices. Furthermore, to enable the effective development of entrepreneurship education in basic and upper secondary level education, more knowledge is needed of the state of affairs of entrepreneurship education in teaching. The purpose of the study is to increase the level of understanding of teachers’ entrepreneurship education practices, and through this to develop entrepreneurship education. This study builds on the literature on entrepreneurship education and especially those elements referring to the aims, resources, benefits, methods, and practises of entrepreneurship education. The study comprises five articles highlighting teachers’ role in entrepreneurship education. In the first article the concept of entrepreneurship and the teachers role in reflection upon his/hers approaches to entrepreneurship education are considered. The second article provides a detailed analysis of the process of developing a measurement tool to depict the teachers’ activities in entrepreneurship education. The next three articles highlight the teachers’ role in directing the entrepreneurship education in basic and upper secondary level education. Furthermore, they analyse the relationship between the entrepreneurship education practises and the teachers’ background characteristics. The results of the study suggest a wide range of conclusions and implications. First, in spite of many outspoken aims connected to entrepreneurship education, teachers have not set any aims for themselves. Additionally, aims and results seem to mix. However, it is possible to develop teachers’ target orientation by supporting their reflection skills, and through measurement and evaluation increase their understanding of their own practices. Second, applying a participatory action process it is possible to operationalise teachers’entrepreneurship education practices. It is central to include the practitioners’ perspective in the development of measures to make sure that the concepts and aims of entrepreneurship education are understood. Third, teachers’ demographic or tenure-related background characteristics do not affect their entrepreneurship education practices, but their training related to entrepreneurship education, participation in different school-level or regional planning, and their own capabilities support entrepreneurship education. Fourth, a large number of methods are applied to entrepreneurship education, and the most often used methods were different kinds of discussions, which seem to be an easy, low-threshold way for teachers to include entrepreneurship education regularly in their teaching. Field trips to business enterprises or inviting entrepreneurs to present their work in schools are used fairly seldom. Interestingly, visits outside the school are more common than visitors invited to the school. In line, most of the entrepreneurship education practices take place in a classroom. Therefore it seems to be useful to create and encourage teachers towards more in-depth cooperation with companies (e.g. via joint projects) and to network systematically. Finally, there are plenty of resources available for entrepreneurship education, such as ready-made materials, external stakeholders, support organisations, and learning games, but teachers have utilized them only marginally.