On Density-Critical Matroids

For a matroid $M$ having $m$ rank-one flats, the density $d(M)$ is $\tfrac{m}{r(M)}$ unless $m = 0$, in which case $d(M)= 0$. A matroid is density-critical if all of its proper minors of non-zero rank have lower density. By a 1965 theorem of Edmonds, a matroid that is minor-minimal among simple matroids that cannot be covered by $k$ independent sets is density-critical. It is straightforward to show that $U_{1,k+1}$ is the only minor-minimal loopless matroid with no covering by $k$ independent sets. We prove that there are exactly ten minor-minimal simple obstructions to a matroid being able to be covered by two independent sets. These ten matroids are precisely the density-critical matroids $M$ such that $d(M) > 2$ but $d(N) \le 2$ for all proper minors $N$ of $M$. All density-critical matroids of density less than $2$ are series-parallel networks. For $k \ge 2$, although finding all density-critical matroids of density at most $k$ does not seem straightforward, we do solve this problem for $k=\tfrac{9}{4}$.Comment: 16 page

High-speed induction motor with an integrated gearbox for propulsion

Induction motors with a planetary gear are a viable option for the transportation industry as they are a relatively inexpensive electric drive solution. Designing a prototype of a high-speed induction motor with a planetary gear is the focus of this project. This will be the proof of concept, to demonstrate a compact and cost-efficient electric drive solution, when compared to electric drives with lower speeds and no gearbox. Using a high-speed electric motor and gearing it down will provide a high torque density and power. A prototype with a high power density and efficiency will provide a competitive alternative to other electric drive solutions. The design choices of the prototype are covered. 3D modeling software is used for the mechanical design that integrates the planetary gear and the induction motor. Finite Element Method (FEM) simulations are completed to determine the final design. The geometry and properties of the induction motor are optimized using FEM. Electromagnetics, torque, and the losses of the induction motor are analyzed. The prototype design presented in this thesis is analyzed to determine the overall efficiency, cost, and feasibility for the transportation industry. The design allows for future development by ensuring easy changes and additions that can be made to the prototype. The development of the high-speed motor should continue with the use of models and design presented in this thesis. The design presented in this thesis is another step towards the final prototype production. The possibilities for future thesis topics and improvements will be discussed at the end of this thesis. One possibility for future development is the use of additive manufacturing to build the induction motor

Ownership Structure and the Operating Performance of Hungarian Firms

This paper uses firm-level data on 162 large Hungarian enterprises to analyse the relationship between ownership structure and corporate performance in 1998 and 1999. Cross-sectional regressions are run for each of these years using the return on assets (ROA) as the measure of performance. Both after-tax profits and operating profits are used to produce the ROA variable. The signs of the regression coefficients and their significance levels are consistent across the different measures of profit, and also across the two years. The results of the regressions suggest that the presence of foreign ownership may positively affect performance while the existence of continuing State ownership has the opposite effect. Neither of these relationships, however, is statistically significant. Two variables have a significant impact on performance that is consistent across different constructions of the regression models: firm size and capital intensity. The smaller firms in the sample outperform the larger firms, which suggests that the greater monitoring and agency costs likely to be incurred by larger firms negatively impact their performance. The more capital intensive a firm (measured by the log of total assets to employees) the greater is its performance. This positive relationship suggests that high capital intensity may impose a barrier to entry and strengthen the competitive position of companies within their industries. The export intensity of a company (exports to sales revenue) is also positively and significantly related to performance, which suggests that the discipline of competing in foreign markets has a positive impact. However, the inclusion of an industry dummy variable to the regression equations results in the export intensity variable losing its significance

The use of Sphingomyelin to protect against UV induced DNA damage in Human Keratinocytes

Non melanoma skin cancer (NMSC) is a serious condition caused by chronic ultraviolet (UV) exposure that leads to DNA damage in skin. UV radiation has the potential to lead to DNA damage, which triggers biochemical pathways within a cell. The result is that the cell either undergoes cell cycle arrest, giving the cell time to repair DNA damage, or apoptosis. Sunscreen is the most commonly used treatment for preventing UV induced skin damage, but it involves a number of undesirable and toxic side effects including damaging the dermis, premature aging of skin and underweight child births. This has led to interest in finding safer alternatives to prevent UV damage without the negative side effects of sunscreen. In particular, bovine milk sphingomyelin (SM) is a compound that has the potential to protect against UV damage without any of the dangerous side effects of sunscreen. Here we present the use of SM for UV protection of human keratinocytes (KRTs) to prevent DNA mutations that result from UV exposure. In particular, analysis of the expression of DNA damage biomarkers p21 and p53 was done to determine the potential of SM to prevent DNA damage associated with UV exposure. Both non-SM treated KRTs and KRTs treated with 0.1% SM media 24 hours prior to UV radiation were fixed and IF-stained at 24 hours following 40 mJ/cm2 of UV exposure. Significant differences in both p21 and p53 were observed between the SM treated and non-SM treated cells at the UV dosage level (via t-test;

The Role of Technology Licensing in the International Business Operations of UK Multinationals

This thesis explores the nature of the international licensing activities of UK-based multinational companies (MNCs). It is concerned with the outward licensing of technology, in the form of patents and know-how, and it assesses the relative importance of a number of variables that motivate MNCs to license their technology to overseas companies rather than to use the more common methods of international business, foreign direct investment (FDI) and exporting. The thesis analyses the extent of international licensing activity among UK-based MNCs, and its significance in relation to the other two major international business methods. It also describes the characteristics of the technology licensed and of the MNCs involved in licensing, and tests a number of hypotheses about these characteristics that are drawn from a variety of sources in the literatures on the the MNC, FDI, international licensing, technology transfer and transaction cost theory. The research is broadly deductive in nature as it assesses the validity of various explanations found in the above literatures. Most of the data was collected by means of a mailed questionnaire directed at a carefully selected survey population of 322 UK-based MNCs in 1984, from which 86 useable responses were received. The statistical analysis utilises mainly non-parametric procedures as most of the data is of an ordinal nature, although parametric procedures are also used. The analysis of government statistics on FDI, exports and royalties over the period 1964 to 1984 revealed that the proportions of the UK's total foreign sales which arose from licensing were consistently lower than those which arose from FDI and exports, but were nevertheless sufficiently large (6.7% in 1984) to merit serious attention. The analysis of the determinants of the licensing decision using the questionnaire survey data revealed that licensing was viewed by the vast majority of UK MNCs as a 'strategic' decision, in the sense that it was more often than not evaluated against FDI and exporting. Government-created market imperfections were found to be important reasons behind the decision to opt for licensing at the expense of FDI or exporting. The intercorrelations between the variables listed in the questionnaire were subjected to factor analysis to determine whether a smaller group of key factors could be used to account for the decision of UK MNCs to adopt licensing, and this exercise was successful in isolating a number of such factors. The technique of multiple linear regression analysis was also employed to determine the extent to which nine key corporate characteristics were associated with the level of licensing activity of the sample of UK MNCs. The intellectual property content of the licensing agreements possessed by the sample were analysed using standard nonparametric tests to determine if their characteristics differed according to whether the agreements were with unrelated or related overseas companies. It was anticipated that differences would exist due to the greater transaction costs that are assumed to arise in unrelated agreements. The results were generally consistent with expectations. In summary, the key contributions to knowledge made by this study are as follows: firstly, it provides evidence that the licensing decision is not simply a by-product of the FDI and exporting decisions but is often a first-best choice; secondly, it provides insights into the factors which influence the licensing decision and their relative weightings; and, thirdly, it produces evidence which is broadly supportive of the transaction cost school of thought through its examination of the intellectual property characteristics of licensing agreements

Re-imagining Christian Education for Millennials in an African American Pentecostal Assemblies Context

It seems many Christian Pentecostal churches are struggling to disciple and retain a millennial population. According to a recent Gallup Poll, 57% of religious millennials have church membership, and this represents the lowest percentage among current generations as overall church membership and participation trends downward from 76% in 1948 to 52% in 2018 (Jones, 2019). The factors contributing to the poll must be explored both from outside and inside of the church. One may wonder if the church is providing the proper education and training to attract and retain millennials. The purpose of this qualitative exploratory case study research design will be to explore current pedagogical methodologies and ICT use in Christian education among pastors and teachers in the Gates of Heaven Assembly of Churches (GOHAOC) and to assess the current level of satisfaction with and participation in Christian education ministry activities of the GOHAOC among the millennial members of the church community. At this stage in the research, ICT is defined as a “diverse set of technological tools and resources used to communicate and to create, disseminate, store, and manage information. These technologies include computers, the Internet, broadcasting technologies (radio and television), and telephony” (Amin, 2018, p.2). Pastors, Christian educators, and millennials will be interviewed and surveyed to explore contributing factors to the target group\u27s discipleship practices. The qualitative methodology was chosen to analyze the practices surrounding the research problem. Research findings and recommendations from this research will contribute to the body of literature on discipling millennials

Principals\u27 Perceptions of Teacher Academy for Preparation and Pedagogy Teachers (Tapp) And Traditionally Certified Teachers

Georgia\u27s alternative certification program, Teacher Academy for Preparation and Pedagogy (TAPP), is producing approximately 20% of the teacher pool in Georgia although minimal research exists about the performance of TAPP teachers in Georgia classrooms compared to traditionally certified teachers. Principals that employ TAPP teachers and traditionally certified teachers are responsible for performance evaluations and; therefore, they are a valid source for providing comparisons between the two types of teacher preparation. In an effort to gain a better understanding of principals\u27 perceptions of TAPP teachers and traditionally certified teachers, the researcher used a previously validated formal survey constructed by Dr. Michael Nusbaum in 2002. The survey was sent electronically to 40 principals in an east Georgia RESA district that currently employ a first year TAPP teacher. The survey focused on three constructs of teaching: content knowledge, classroom management and instructional planning. A random group of principals from the RESA district were also interviewed to obtain further understanding of the survey results. The researcher\u27s findings confirmed that principals\u27 perceive TAPP teachers\u27 content knowledge to be equal to traditionally certified teachers. However, principals\u27 reported that traditionally certified teachers are more adept at classroom management than TAPP teachers. Principals also perceived that TAPP teachers initially struggle with instructional planning, but eventually learn the skill by collaborating with experienced teachers

Conservation evo-devo: preserving biodiversity by understanding its origins

Unprecedented rates of species extinction increase the urgency for effective conservation biology management practices. Thus, any improvements in practice are vital and we suggest that conservation can be enhanced through recent advances in evolutionary biology, specifically advances put forward by evolutionary developmental biology (i.e., evo-devo). There are strong overlapping conceptual links between conservation and evo-devo whereby both fields focus on evolutionary potential. In particular, benefits to conservation can be derived from some of the main areas of evo-devo research, namely phenotypic plasticity, modularity and integration, and mechanistic investigations of the precise developmental and genetic processes that determine phenotypes. Using examples we outline how evo-devo can expand into conservation biology, an opportunity which holds great promise for advancing both fields