Thesis

Thesis (MA (Philosophy))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: This thesis consists of two essays, each focussing on a current topic in aesthetics in the tradition of analytic philosophy. First paper (On depiction) Given broad consensus that resemblance theories do not do well at explaining depiction, two alternative approaches have dominated the literature in recent decades: (1) Perceptual accounts try to ground depiction in the phenomenology of our pictorial experiences; (2) Structural accounts understand pictures as symbols in pictorial symbol systems. I follow Dominic Lopes in granting that the two approaches, often interpreted as each other’s rivals, both have merit and are successful in answering divergent questions about depiction. After taking stock of the most influential theories from both approaches, I turn to John Kulvicki’s recent work. He has made surprising progress as a proponent of the structural approach. His attempt to define depiction in structural terms is groundbreaking and, for the most part, successful. The paper measures some of his suggestions on picture structure and perception against the well-established “twofoldness”-thesis of the perceptual theorist on depiction, Richard Wollheim. Wollheim’s theory is defended and suggestions made to adapt Kulvicki’s theory accordingly. Second paper (On expression) Since Frank Sibley’s early papers in the mid-twentieth century, analytic aesthetics has broadened its field of inquiry to extend past the traditional focus on judgements of beauty or aesthetic merit, to peripheral terms, concepts, properties and judgements (e.g. of grace, elegance, garishness, daintiness, dumpiness, etc.). Nick Zangwill gives a traditionalist report of what binds the new, broad and heterogeneous category of the aesthetic together. He argues that purely evaluative aesthetic judgements of beauty or ugliness (i.e. “verdicts”) are fundamental. All other aesthetic judgements derive their evaluative aesthetic nature from them. In this essay it is argued that Zangwill’s defence of beauty’s supremacy in the category of the aesthetic, does not do justice to ostensible instances of non-evaluative judgements that ascribe expressive properties to artworks. Nelson Goodman’s cognitivist theory of expression in art is used as a foil for Zangwill’s claims.AFRIKAANSE OPSOMMING: Hierdie tesis bestaan uit twee essays, elk oor ’n aktuele onderwerp in estetika in die tradisie van die analitiese filosofie. Eerste essay (Oor uitbeelding, oftewel “piktoriale representasie”) Gegewe ’n algemene konsensus dat ooreenkoms-teorieë nie slaag daarin om uitbeelding (“depiction”) te verklaar nie, is daar twee alternatiewe benaderings wat die onlangse literatuur oor die onderwerp oorheers: (1) die perseptuele benadering probeer uitbeelding begrond in die fenomenologie van ons piktoriale ervaringe; (2) die strukturele benadering verstaan beelde as simbole in piktoriale simboolsisteme. In navolging van Dominic Lopes neem ek aan dat dié twee benaderings, wat normaalweg as mekaar se opponente beskou word, altwee meriete dra en onderskeidelik sukses behaal in die beantwoording van heel uiteenlopende vrae oor die aard van uitbeelding. Na ’n bestekopname van die mees invloedryke teorieë onder beide benaderings, word John Kulvicki se onlangse werk oorweeg. Hy maak verrassende vooruitgang as ondersteuner van die strukturele benadering. Sy poging om uitbeelding in strukturele terme te definiëer is revolusionêr en bied stof vir nadenke. In hierdie essay word sommige van sy voorstelle oor beeld-struktuur en -waarneming gemeet aan die gevestigde “twofoldness”-tesis van Richard Wollheim. Wollheim se perseptuele teorie word verdedig en ’n voorstelle word gemaak om Kulvicki se teorie daarvolgens aan te pas. Tweede essay (Oor uitdrukking) Sedert Frank Sibley se vroeë essays in die middel van die twintigste eeu het die analitiese estetika sy visier verbreed om verby die tradisionele fokus op oordele van skoonheid en estetiese waarde te kyk, na perifere terme, begrippe, eienskappe en oordele (van bv. grasie, delikaatheid, balans, strakheid, elegansie, ens., ens.). Nick Zangwill gee ’n tradisionalistiese verslag van wat die nuwe, breë en heterogene kategorie van die estetiese saambind. Hy argumenteer dat suiwer evaluerende oordele van skoonheid fundamenteel bly. Alle ander estetiese oordele se estetiese aard word daarvan afgelei. In hierdie essay argumenteer ek dat Zangwill se verdediging van skoonheid (of estetiese waarde) as fundamenteel tot die kategorie van die estetiese, nie laat reg geskied aan aantoonbare gevalle van nie-evaluerende oordele, naamlik dié wat ekspressiewe eienskappe aan kunswerke toeskryf, nie. Nelson Goodman se kognitiewe teorie van van uitdrukking in kuns word gebruik as teenhanger en wegspringplek vir kritiek op Zangwill se aansprake

Convex treemaps with bounded aspect ratio

Treemaps are a popular technique to visualize hierarchical data. The input is a weighted tree T where the weight of each node is the sum of the weights of its children. A treemap for T is a hierarchical partition of a rectangle into simply connected regions, usually rectangles. Each region represents a node of T and the area of each region is proportional to the weight of the corresponding node. An important quality criterium for treemaps is the aspect ratio of its regions. Unfortunately, one cannot bound the aspect ratio if the regions are restricted to be rectangles. Hence Onak and Sidiropoulos introduced polygonal partitions, which use convex polygons. We are the first to obtain convex partitions with optimal aspect ratio O(depth(T )). We also consider the important special case that depth(T ) = 1, that is, single-level treemaps. We show how to construct convex single-level treemaps that use only four simple shapes for the regions and have aspect ratio at most 34/7

Bias-based modeling and entropy analysis of PUFs

Physical Unclonable Functions (PUFs) are increasingly becoming a well-known security primitive for secure key storage and anti-counterfeiting. For both applications it is imperative that PUFs provide enough entropy. The aim of this paper is to propose a new model for binary-output PUFs such as SRAM, DFF, Latch and Buskeeper PUFs, and a method to accurately estimate their entropy. In our model the measurable property of a PUF is its set of cell biases. We determine an upper bound on the ‘extractable entropy’, i.e. the number of key bits that can be robustly extracted, by calculating the mutual information between the bias measurements done at enrollment and reconstruction. In previously known methods only uniqueness was studied using information-theoretic measures, while robustness was typically expressed in terms of error probabilities or distances. It is not always straightforward to use a combination of these two metrics in order to make an informed decision about the performance of different PUF types. Our new approach has the advantage that it simultaneously captures both of properties that are vital for key storage: uniqueness and robustness. Therefore it will be possible to fairly compare performance of PUF implementations using our new method. Statistical validation of the new methodology shows that it clearly captures both of these properties of PUFs. In other words: if one of these aspects (either uniqueness or robustness) is less than optimal, the extractable entropy decreases. Analysis on a large database of PUF measurement data shows very high entropy for SRAM PUFs, but rather poor results for all other memory-based PUFs in this database

An International Study of the Ability and Cost-Effectiveness of Advertising Methods to Facilitate Study Participant Self-Enrolment Into a Pilot Pharmacovigilance Study During Early Pregnancy

Knowledge of the fetal effects of maternal medication use in pregnancy is often inadequate and current pregnancy pharmacovigilance (PV) surveillance methods have important limitations. Patient self-reporting may be able to mitigate some of these limitations, providing an adequately sized study sample can be recruited.To compare the ability and cost-effectiveness of several direct-to-participant advertising methods for the recruitment of pregnant participants into a study of self-reported gestational exposures and pregnancy outcomes.The Pharmacoepidemiological Research on Outcomes of Therapeutics by a European Consortium (PROTECT) pregnancy study is a non-interventional, prospective pilot study of self-reported medication use and obstetric outcomes provided by a cohort of pregnant women that was conducted in Denmark, the Netherlands, Poland, and the United Kingdom. Direct-to-participant advertisements were provided via websites, emails, leaflets, television, and social media platforms.Over a 70-week recruitment period direct-to-participant advertisements engaged 43,234 individuals with the study website or telephone system; 4.78% (2065/43,234) of which were successfully enrolled and provided study data. Of these 90.4% (1867/2065) were recruited via paid advertising methods, 23.0% (475/2065) of whom were in the first trimester of pregnancy. The overall costs per active recruited participant were lowest for email (€23.24) and website (€24.41) advertisements and highest for leaflet (€83.14) and television (€100.89). Website adverts were substantially superior in their ability to recruit participants during their first trimester of pregnancy (317/668, 47.5%) in comparison with other advertising methods (P<.001). However, we identified international variations in both the cost-effectiveness of the various advertisement methods used and in their ability to recruit participants in early pregnancy.Recruitment of a pregnant cohort using direct-to-participant advertisement methods is feasible, but the total costs incurred are not insubstantial. Future research is needed to identify advertising strategies capable of recruiting large numbers of demographically representative pregnant women, preferentially in early pregnancy

Distance Estimation Is Influenced by Encoding Conditions

Background:\ud It is well established that foveating a behaviorally relevant part of the visual field improves localization performance as compared to the situation where the gaze is directed elsewhere. Reduced localization performance in the peripheral encoding conditions has been attributed to an eccentricity-dependent increase in positional uncertainty. It is not known, however, whether and how the foveal and peripheral encoding conditions can influence spatial interval estimation. In this study we compare observers' estimates of a distance between two co-planar dots in the condition where they foveate the two sample dots and where they fixate a central dot while viewing the sample dots peripherally.\ud \ud Methodology/Principal Findings:\ud Observers were required to reproduce, after a short delay, a distance between two sample dots based on a stationary reference dot and a movable mouse pointer. When both sample dots are foveated, we find that the distance estimation error is small but consistently increases with the dots-separation size. In comparison, distance judgment in peripheral encoding condition is significantly overestimated for smaller separations and becomes similar to the performance in foveal trials for distances from 10 to 16 degrees.\ud \ud Conclusions/Significance:\ud Although we find improved accuracy of distance estimation in the foveal condition, the fact that the difference is related to the reduction of the estimation bias present in the peripheral conditon, challenges the simple account of reducing the eccentricity-dependent positional uncertainty. Contrary to this, we present evidence for an explanation in terms of neuronal populations activated by the two sample dots and their inhibitory interactions under different visual encoding conditions. We support our claims with simulations that take into account receptive fields size differences between the two encoding conditions

Modified iterative versus Laplacian Landau gauge in compact U(1) theory

Compact U(1) theory in 4 dimensions is used to compare the modified iterative and the Laplacian fixing to lattice Landau gauge in a controlled setting, since in the Coulomb phase the lattice theory must reproduce the perturbative prediction. It turns out that on either side of the phase transition clear differences show up and in the Coulomb phase the ability to remove double Dirac sheets proves vital on a small lattice.Comment: 14 pages, 8 figures containing 23 graphs, v2: 2 figures removed, 2 references adde

Political stringency, infection rates, and higher education students' adherence to government measures in the Nordic countries and the UK during the first wave of the COVID-19 outbreak

Understanding predictors of adherence to governmental measures to prevent the spread of the COVID-19 is fundamental to guide health communication. This study examined whether political stringency and infection rates during the first wave of the pandemic were associated with higher education students' adherence to COVID-19 government measures in the Nordic countries (Denmark, Finland, Norway, Iceland, and Sweden) and the United Kingdom. Both individual- and country-level data were used in present study. An international cross-sectionalsubsample (n = 10,345) of higher-education students was conducted in May–June 2020 to collect individual-level information on socio-demographics, study information, living arrangements, health behaviors, stress, and COVID-19-related concerns, including adherence to government measures. Country-level data on political stringency from the Oxford COVID-19 Government Response Tracker and national infection rates were added to individual-level data. Multiple linear regression analyses stratified by country were conducted. Around 66% of students reported adhering to government measures, with the highest adherence in the UK (73%) followed by Iceland (72%), Denmark (69%), Norway (67%), Finland (64%) and Sweden (49%). Main predictors for higher adherence were older age, being femaleand being worried about getting infected with COVID-19 (individual-level), an increase in number of days since lockdown, political stringency, and information about COVID-19 mortality rates (country-level). However, incidence rate was an inconsistent predictor, which may be explained by imperfect data quality during the onset of the pandemic. We conclude that shorter lockdown periods and political stringency are associated with adherence to government measures among higher education students at the outset of the COVID-19 pandemic.Peer reviewe