The Dynamic Geometry of Interaction Machine: A Call-by-Need Graph Rewriter

Girard's Geometry of Interaction (GoI), a semantics designed for linear logic proofs, has been also successfully applied to programming language semantics. One way is to use abstract machines that pass a token on a fixed graph along a path indicated by the GoI. These token-passing abstract machines are space efficient, because they handle duplicated computation by repeating the same moves of a token on the fixed graph. Although they can be adapted to obtain sound models with regard to the equational theories of various evaluation strategies for the lambda calculus, it can be at the expense of significant time costs. In this paper we show a token-passing abstract machine that can implement evaluation strategies for the lambda calculus, with certified time efficiency. Our abstract machine, called the Dynamic GoI Machine (DGoIM), rewrites the graph to avoid replicating computation, using the token to find the redexes. The flexibility of interleaving token transitions and graph rewriting allows the DGoIM to balance the trade-off of space and time costs. This paper shows that the DGoIM can implement call-by-need evaluation for the lambda calculus by using a strategy of interleaving token passing with as much graph rewriting as possible. Our quantitative analysis confirms that the DGoIM with this strategy of interleaving the two kinds of possible operations on graphs can be classified as "efficient" following Accattoli's taxonomy of abstract machines

Identical sequences found in distant genomes reveal frequent horizontal transfer across the bacterial domain

Horizontal Gene Transfer (HGT) is an essential force in microbial evolution. Despite detailed studies on a variety of systems, a global picture of HGT in the microbial world is still missing. Here, we exploit that HGT creates long identical DNA sequences in the genomes of distant species, which can be found efficiently using alignment-free methods. Our pairwise analysis of 93 481 bacterial genomes identified 138 273 HGT events. We developed a model to explain their statistical properties as well as estimate the transfer rate between pairs of taxa. This reveals that long-distance HGT is frequent: our results indicate that HGT between species from different phyla has occurred in at least 8% of the species. Finally, our results confirm that the function of sequences strongly impacts their transfer rate, which varies by more than 3 orders of magnitude between different functional categories. Overall, we provide a comprehensive view of HGT, illuminating a fundamental process driving bacterial evolution

Multi-touch interaction with stereoscopically rendered 3D objects

Anfänglich hauptsächlich im 2D Kontext betrachtet, gewinnen Multi-Touch Interfaces immer mehr an Bedeutung im Bereich dreidimensionaler Umgebungen und, in den letzten Jahren, auch im Zusammenhang mit stereoskopischen Visualisierungen. Dennoch führt die Touch-basierte Interaktion mit stereoskopisch dargestellten Objekten zu Problemen, da die Objekte in der nahen Umgebung der Displayoberfläche schweben, während die Berührungspunkte nur bei direktem Kontakt mit dem Display robust detektiert werden können. In dieser Arbeit werden die Probleme bei Touch-Interaktion in stereoskopischen Umgebungen näher untersucht und Interaktionskonzepte in diesem Kontext entwickelt. Insbesondere wird die Anwendbarkeit unterschiedlicher Wahrnehmungsillusionen für 3D Touch-Interaktion mit stereoskopisch dargestellten Objekten in einer Reihe psychologischer Experimente untersucht. Basierend auf die Experimentdaten werden einige praktische Interaktionstechniken entwickelt und auf ihre Anwendbarkeit überprüft.While touch technology has proven its usability for 2D interaction and has already become a standard input modality for many devices, the challenges to exploit its applicability with stereoscopically rendered content have barely been studied. In this thesis we exploit different hardware and perception based techniques to allow users to touch stereoscopically displayed objects when the input is constrained to a 2D surface. Therefore we analyze the relation between the 3D positions of stereoscopically displayed objects and the on-surface touch points, where users touch the interactive surface, and we have conducted a series of experiments to investigate the user’s ability to discriminate small induced shifts while performing a touch gesture. The results were then used to design practical interaction techniques, which are suitable for numerous application scenarios. <br

Primary Teachers' Understandings Of The Nature Of Science And The Purposes Of Science Education

With the introduction of the National Curriculum in English primary schools in the late 1980s, the status of science changed from discretionary option, taught to the teacher’s strengths, to mandated core subject with tightly defined curriculum. During the first few years, teachers’ initial uncertainty gave way to growing feelings of competence and confidence, which local, national and international evidence from the mid- 1990s onwards shows were not entirely misplaced. Meanwhile, however, a series of studies consistently showed apparently severe gaps in primary teachers’ science knowledge – so what was it that was changing? Teachers themselves hold the key to understanding how science has been accommodated into primary practice: this research looks at some teachers’ views of the nature of science and the purposes of teaching it, the manifestation of such views in planning and teaching; changes in views over time: and the accommodation of science teaching into their professional identities. Drawing on a 1996 pilot study, the research involves case studies of five teachers - biographical and semi-structured interviews, protocol analysis, and lesson observations, over eighteen months from early 1998, a questionnaire survey of a broader sample; and triangulation between case studies and survey. Various factors that may underlie a teacher’s view of the nature of science are proposed - scientism, naive empiricism, new-age-ism, constructivism, pragmatism, and scepticism. It is suggested that teachers’ accommodation of science into their practice can involve its structural and organisational interweaving into the fabric of their professional identities. A tentative hypothetical model is outlined, of the emergence of professional identity from an autopoietic network involving auto-biography; values; dispositions; beliefs; personal theories; self-image; knowledge of and relationships and discourse with children and colleagues; curriculum, subject and pedagogic knowledge: images of teaching and learning; the exercise of agency in practice; and reflexive connections between, and reflection upon, these

An investigation into whether the use of funds by section 21 schools improves the quality of teaching and learning in Mthatha District of Education in the eastern Cape Province

This study investigated whether the funding of section 21 schools improves the quality of teaching and learning in six schools in the Mthatha Education District, in the Eastern Cape Province of South Africa. Despite the large funds that are pumped into schools by the Department of Education, the schools appear to be under resourced, underdeveloped and therefore underperforming. The researcher used the theories of school improvement to ground this study and to investigate whether the schools improve or not, and are offered support where necessary, as they are continuously being funded by the Department of Education. The study had these objectives: To investigate how the funds are spent by Section 21 schools in the Mthatha district of Education: to assess whether the SGB manages the spending of funds and whether there is any collaboration between the Principal and the SGB in financial issues and: to evaluate whether Procurement procedures are followed when purchasing. Systematic random sampling, amongst 6 schools, has been conducted. A questionnaire was administered to the school Principals, 2 Finance committe members, 1 Educator and 1 learner and SGB chairpersons from each of the 6 schools. Thus, both qualitative and quantitative methods of inquiry were used in this study. 3 Junior Secondary and 3 Senior Secondary schools were considered in the sample. The findings that emerged were a lack of capacity, on the part of SGBs to monitor recurrent allocations as stipulated in the South African Schools Act (No 84 of 1996). Another factor that emerged was that schools still need training and workshops on procurement procedures. Also evident was that there appeared to be little evidence of collaboration between principals and SGBs, especially in financial matters. Finally, recommendations and suggestions were made that schools need to be provided with a series of workshops on procurement procedures and policies. SGBs were to be capacitated so that they could be on board on financial management. The principals were to be encouraged to cooperate and be transparent on financial matters especially since, as stipulated in SASA, as an official of the Department of Education, the principal has a responsibility to advise the governing body when they issue instructions or act in a manner that contravenes departmental instructions or policy

Epithelial ovarian cancer. Population-based cohort studies. The NOWAC Study and Postgenome biobank

Important gaps in population-based epidemiological research on ovarian cancer include understanding how risk factors relate to cancer subtypes and anatomical sites, identifying safe and effective preventive measures, and getting a more detailed picture of the continuum of events during ovarian carcinogenesis. This thesis used prospective exposure information from the Norwegian Women and Cancer (NOWAC) Study and blood samples from the NOWAC Postgenome biobank to explore topics within these gaps. On the topic of risk factors, subtypes and anatomical sites, previous studies have shown that serous carcinomas of the ovary and fallopian tube cancers have similar risk factors. This thesis compared risk factors between the ovary/fallopian tube and uterine corpus. One risk factor association separated serous carcinomas of these sites, while no differences in risk factor associations were found for endometrioid and clear cell carcinomas. Possible alternative explanations of this result include few observations in the analysis of endometrioid and clear cell carcinomas, and histological misclassification of high-grade endometrioid carcinomas. Among preventive measures, combined oral contraceptives reduce the risk of both ovarian and uterine carcinoma. Current trends in female contraception include an increase in use of progestin-only long-acting reversible contraceptives, such as the levonorgestrel-releasing intrauterine system (LNG-IUS). In the NOWAC cohort, ever use of LNG-IUS reduced the risk of ovarian carcinoma by 53% (95% CI: 22% – 68%) and the risk of uterine carcinoma by 78% (95% CI: 60% – 87%) compared to never use. These results extend current knowledge to include postmenopausal women in a sample of the general population. The association with breast cancer was also investigated and discussed. To investigate the continuum of events during ovarian carcinogenesis, this thesis explores gene expression in peripheral blood in the years preceding ovarian cancer diagnosis. The presented study did not find strong associations. This could be because there is little association between ovarian cancer and prediagnostic gene expression in blood, but could also be due to a small sample size, or the analytic approach that was used.  Kreft i eggstokkene er forholdsvis sjelden kreftform, som har høy dødelighet. Denne doktoravhandlingen bygger på spørreskjema fra 172000 kvinner i Kvinner og kreft-studien, og på blodprøver fra 50000 av deltakerne. Blodprøvene utgjør en unik biobank med bevart genuttrykk fra de hvite blodlegemene. Fra før vet man at kvinner som har brukt p-piller har lavere risiko for eggstokkreft. I dag har mange kvinner, også de yngre, begynt å bruke hormonspiral. Det er lite kunnskap om hvorvidt kvinner som bruker hormonspiral har lavere risiko for eggstokkreft slik som p-pillebrukerne. Blant de noe eldre deltakerne i Kvinner og kreft hadde kvinner som noen gang har brukt hormonspiral en halvert risiko for eggstokkreft. Fordi det var få tilfeller, har anslaget en usikkerhet som tilsvarer mellom 10% og 70% lavere risiko. Blodprøvene i biobanken gir mulighet til å undersøke endringer i genuttrykk i immunceller opptil sju år før diagnosen ble stilt, i håp om å forstå mer om sykdomsutviklingen. Vi gjorde en utforskende analyse av blodprøver fra kvinner som hadde fått eggstokkreft, men fant ikke entydige endringer i genuttrykket

Towards open-ended crowd-powered data processing: a case study of clustering and counting

Due to the widespread use and importance of crowdsourcing in gathering training data at scale, the data management community has devoted its efforts in understanding and optimizing fundamental primitives like filters and joins. These primitive boolean operations, where the human responses come from a small, finite space of possible answers, are inadequate for a number of data analysis tasks, especially those involving images, videos and maps. There is, thus, a need for open-ended crowdsourcing in order to get more fine-grained information from humans that can be used in developing sophisticated AI systems. In this thesis, we study two popular open-ended crowdsourcing problems. The first, clustering, is the problem of organizing a collection of objects (images, videos) by allowing workers to form as many clusters as they would like and organize items across them. The second, counting, is the problem of counting objects in images. In this thesis, we develop models to reason about human behavior for both problems, and use these models to design provably cost-efficient algorithms that provide high-quality results, as compared to currently available approaches