Rank-based attachment leads to power law graphs

We investigate the degree distribution resulting from graph generation models based on rank-based attachment. In rank-based attachment, all vertices are ranked according to a ranking scheme. The link probability of a given vertex is proportional to its rank raised to the power -a, for some a in (0,1). Through a rigorous analysis, we show that rank-based attachment models lead to graphs with a power law degree distribution with exponent 1+1/a whenever vertices are ranked according to their degree, their age, or a randomly chosen fitness value. We also investigate the case where the ranking is based on the initial rank of each vertex; the rank of existing vertices only changes to accommodate the new vertex. Here, we obtain a sharp threshold for power law behaviour. Only if initial ranks are biased towards lower ranks, or chosen uniformly at random, we obtain a power law degree distribution with exponent 1+1/a. This indicates that the power law degree distribution often observed in nature can be explained by a rank-based attachment scheme, based on a ranking scheme that can be derived from a number of different factors; the exponent of the power law can be seen as a measure of the strength of the attachment

The domination number of on-line social networks and random geometric graphs

We consider the domination number for on-line social networks, both in a stochastic network model, and for real-world, networked data. Asymptotic sublinear bounds are rigorously derived for the domination number of graphs generated by the memoryless geometric protean random graph model. We establish sublinear bounds for the domination number of graphs in the Facebook 100 data set, and these bounds are well-correlated with those predicted by the stochastic model. In addition, we derive the asymptotic value of the domination number in classical random geometric graphs

Geometric protean graphs

We study the link structure of on-line social networks (OSNs), and introduce a new model for such networks which may help infer their hidden underlying reality. In the geo-protean (GEO-P) model for OSNs nodes are identified with points in Euclidean space, and edges are stochastically generated by a mixture of the relative distance of nodes and a ranking function. With high probability, the GEO-P model generates graphs satisfying many observed properties of OSNs, such as power law degree distributions, the small world property, densification power law, and bad spectral expansion. We introduce the dimension of an OSN based on our model, and examine this new parameter using actual OSN data. We discuss how the geo-protean model may eventually be used as a tool to group users with similar attributes using only the link structure of the network

User Interfaces and Difference Visualizations for Alternatives

Designers often create multiple iterations to evaluate alternatives. Todays computer-based tools do not support such easy exploration of a design space, despite the fact that such support has been advocated. This dissertation is centered on this. I begin by investigating the effectiveness of various forms of difference visualizations and support for merging changes within a system targeted at diagrams with node and edge attributes. I evaluated the benefits of the introduced difference visualization techniques in two user studies. I found that the basic side-by-side juxtaposition visualization was not effective and also not well received. For comparing diagrams with matching node positions, participants preferred the side-by-side option with a difference layer. For diagrams with non-matching positions animation was beneficial, but the combination with a difference layer was preferred. Thus, the difference layer technique was useful and a good complement to animation. I continue by investigating if explicit support for design alternatives better supports exploration and creativity in a generative design system. To investigate the new techniques to better support exploration, I built a new system that supports parallel exploration of alternative designs and generation of new structural combinations. I investigate the usefulness of my prototype in two user studies and interviews. The results and feedback suggest and confirm that supporting design alternatives explicitly enables designers to work more creatively. Generative models are often represented as DAGs (directed acyclic graphs) in a dataflow programming environment. Existing approaches to compare such DAGs do not generalize to multiple alternatives. Informed by and building on the first part of my dissertation, I introduce a novel user interface that enables visual differencing and editing alternative graphsspecifically more than two alternatives simultaneously, something that has not been presented before. I also explore multi-monitor support to demonstrate that the difference visualization technique scales well to up to 18 alternatives. The novel jamming space feature makes organizing alternatives on a 23 monitor system easier. To investigate the usability of the new difference visualization method I conducted an exploratory interview with three expert designers. The received comments confirmed that it meets their design goals

Biochemical Assay Optimization and Computational Screening Efforts to Identify Potential LuxS Inhibitors

Quorum sensing (QS) is a process of coordination of bacterial gene expression in response to cell population. System two QS is regulated by the small signaling molecule autoinducer-2 (AI-2) and is implicated in the infectious behaviors of various bacterial species. AI-2 is biosynthesized from S-ribosylhomocysteine (SRH) by the enzyme LuxS and induces interspecies cell-to-cell communication. Inhibition of LuxS would therefore inhibit interspecies QS. Herein, a search for novel molecular species that will competitively bind with SRH in the LuxS binding site is performed in silico. Computational screening results are then validated in vitro using an optimized LuxS inhibition assay

Measuring career anchors and investigating the role of career anchor congruence

This thesis empirically examines the career orientations inventory (COI) as a measure of career anchors and then, using this measure, it goes on to investigate the relationship between career anchor congruence and work related outcomes, specifically job satisfaction and organisational commitment. The psychometric properties of the 40 item COI (presented by Igbaria and Baroudi,\ud 1993) were explored by the administration of the measure to a sample of 658 individuals from 27 organisations in the UK. Through factor analysis an eight factor structure was demonstrated in line with that proposed by Schein (1993). The factor structure was replicated with a second sample. The COI demonstrated good levels of internal consistency (.59-.83) and test retest reliability (.68-.90). Similarly it was deemed to have acceptable levels of face validity and construct validity when compared to Mantech’s (1983) Work Values Questionnaire (WVQ). An analysis of the prevalence of career anchors and the demographic differences\ud within the current sample was undertaken. This analysis provided evidence to suggest that certain career anchors may be increasing in prevalence while others are\ud decreasing. These findings are in line with current research on the way in which workplace changes are impacting upon careers (Baruch, 2004). Evidence was found\ud that indicated gender differences in scores on the COI subscales. Specifically women were found to score higher on the lifestyle anchor and men to score higher on the general management anchor. Differences were also found between the age groups considered in this study in the general management, creativity, pure challenge and lifestyle anchors. Interaction effects for age and gender were found\ud for the general management and sense of service anchors.\ud The COI was then used to develop a commensurate measure of job career anchors. This job career anchor measure discriminated between jobs within one police\ud organisation. The measure was then used to explore the relationship between career anchors, career anchor congruence (congruence between individual and job\ud career anchors), job satisfaction and organisational commitment. Evidence was found to suggest that career anchors and career anchor congruence have a direct\ud effect on job satisfaction (predicting 10% and 4% of the variance respectively). The analysis also showed support for the role of career anchor congruence as a\ud moderator to the relationship between career anchors and job satisfaction. This thesis makes full consideration of the academic contributions and practical implications of the research presented whilst also considering its limitations. A number of suggestions for the direction of future research have been made

Expatriate academics and expatriate management in a South African higher education institution.

Doctor of Philosophy in Management. University of KwaZulu-Natal, Westville 2014.The main aim of the study is to examine the staffing trends of academics in SA higher education in order to compare South African academics to expatriate academics. A secondary aim of the study is to examine the international career experience of expatriate academics at University of KwaZulu-Natal (UKZN) from the perspective of expatriate academics concerning their reasons for relocating to South Africa as well as their experience of organisational and social support as well as from the perspective of organisational stakeholders, namely their academic line managers and human resource (HR) specialists at UKZN. Currently, SA is facing major skills and staffing shortages in terms of Science, Engineering and Agriculture. The Department of Higher Education and Training (DOHET) has provided funding to source international talent to allow SA universities to run programmes in scarce skills disciplines to create ‘home grown’ talent to overcome the staff and skills shortages. This type of international talent remains a largely under-researched group, as they have been labelled ‘self-initiated expatriates (SIEs)’. Many academics embark on international mobility in order to develop their careers and to improve their marketability and employability, therefore are part of this group and are called expatriate academics. The problem comes in when universities do not have formal policies in place to manage their international talent so as to retain this valuable human resource, they are managed no differently than their local colleagues despite facing a myriad of challenges in the form of general, work and interaction adjustment (Black and Gregersen, 1999). By examining expatriate academics experiences at UKZN, the aim of the study is to create a programme especially designed to assist expatriate academics to successfully adjust to life at UKZN and their communities in KwaZulu-Natal. This study has adopted a mixed methodology, using secondary data, quantitative and qualitative methods to extract the data required to examine expatriate academics in South African higher education and at UKZN. Firstly, an analysis of staffing trends in publically funded SA higher education institutions over the three years 2005/2010/2012 was conducted during the secondary data collection phase of the current study. Secondly, a self-reporting questionnaire consisting of questions covering the reasons for relocation and actual experience of expatriation was administered to expatriate academics at UKZN. Furthermore, the questionnaire incorporated the “Protean and Boundaryless Career Attitude Scales” (PBCA) which was developed by Briscoe, Hall and Demuth (2006:16).Thirdly, semi-structured interviews with academic line managers (heads of school, deans, discipline co-ordinators, supervisors) and HR specialists were conducted. This helped to provide the employer’s perspective, which is useful as a way of situating the faculty, school, discipline and administration’s viewpoint within the larger institution. The results of the secondary data collection phase results revealed that there were no significant differences in age between SA and expatriate academics nationally over the three years. However, when examining the age of academics (SA and expatriate), it is clear to see that it is a truly heterogeneous group of individuals. However, at UKZN over the three years there have been more female SA academics employed. A comparison of the academic qualifications of SA and expatriate academics over the three years indicates that expatriate academics are more highly qualified than their SA colleagues, as the majority of the former hold a doctoral degree. The majority of expatriate academics are recruited from SADC countries as well as other African countries. Interestingly enough, the next most frequent major supply region of expatriate academics to South Africa is Europe. WITS and UCT were consistently ranked first and second in terms of the number of expatriate academics employed over the three years. Both are among the leading five higher education institutions in South Africa in terms of their research outputs as well as the number of PhDs per member of staff. Secondly, an investigation into the motivation behind the expatriate academics’ decision to relocate was carried out. These findings suggest that there is no one primary motivation but rather a variety of motives at any given life stage or career stage that may together motivate expatriate academics in general. The motive Career appeared to be dominant among the respondents in this study, closely followed by Adventure/Travel and then Financial. Thirdly, the individual career experiences of expatriate academics in this study indicate that the majority are well adjusted in terms of their relationships with their host country colleagues and their relationships with family and friends back home as well as in terms of the fulfillment of their expectations regarding work. They did, however, indicate that their experience of organisational support could have been improved during their experience as well as during the pre-departure phase. Unlike previous studies, the results of this study indicate that expatriate academics do not share close ties with other expatriates or local South Africans in the university community or within the communities in which they lived. Fourthly, expatriate academics had to deal with many challenges during their career experience here in South Africa. These have been discussed across three levels, macro- (administrative), meso- (work adjustment) and micro-level (family and lifestyle adjustment). This proves that SIEs face many challenges that hinder their ability to expatriate and have positive career experiences. The PBCA scale was developed by Brisoe, Hall and Demuth (2006) and adapted for use in an academic setting. The results from the use of the scale in the current study indicate that respondents exhibit a protean career attitude which suggests that they are “able to develop a greater adaptability and self-awareness thereby ensuring a proactive smart employee” (Briscoe and Hall, 2006:16). These results confirm the results of the Expatriation Experience sub-scale in which it was found that the respondents were well adjusted to their work environment. The respondents in this study are best described ‘solid citizens’ in terms of the Career Profiles of Contemporary Career Agents (see Table 3.4) developed by Briscoe and Hall (2006). Fifthly, the major opportunities, according to management, presented by having expatriate academics at UKZN include access to subject matter expertise, diversity and a wealth of knowledge and experience. These academics also bring with them valuable social capital in the form of resources like networks of contacts, collaborative research opportunities and innovative curriculum development. Above all else, they serve as the solution to the critical skills shortages South Africa is facing particularly in the fields of science, engineering and mathematics. This study is a multi-disciplinary study, that is situated in a number of disciplines such as expatriate management, career management, migration as well as higher education studies. Therefore it adds to the existing body of knowledge by providing a multi-disciplinary approach to a concept that was previously exclusively dealt with in management studies in a business environment. This study is therefore unique as it highlights the perceptions of organisational support by expatriate academics to assess whether or not the organisation, in this case UKZN is doing enough to ensure the success of the international experience of expatriate academics