The classical Poisson, geometric and negative binomial regression models for count data belong to the family of generalized linear models and are available at the core of the statistics toolbox in the R system for statistical computing. After reviewing the conceptual and computational features of these methods, a new implementation of zero-inflated and hurdle regression models in the functions zeroinfl() and hurdle() from the package pscl is introduced. It re-uses design and functionality of the basic R functions just as the underlying conceptual tools extend the classical models. Both model classes are able to incorporate over-dispersion and excess zeros - two problems that typically occur in count data sets in economics and the social and political sciences - better than their classical counterparts. Using cross-section data on the demand for medical care, it is illustrated how the classical as well as the zero-augmented models can be fitted, inspected and tested in practice. (author's abstract) / Series: Research Report Series / Department of Statistics and Mathematics

Text in Afrikaans / The purpose of this study was to determine the nature, origin and negative consequences of perfectionism and to set guidelines for the therapeutic handling of perfectionism. Two literature studies were done to investigate the phenomenon and therapeutic techniques with regards to perfectionsim. A questionnaire was developed as aid to the therapist to identify negative perfectionism and associated problem areas. An empirical study was done to investigate the effectivity of the questionnaire and to compose a program and guidelines for the therapist and perfectionist. Results of the study indicated that negative perfectionism resulted in affective, cognitive, interpersonal and behavioural consequences for the client. It further showed that it is necessary to find the origin of the client's perfectionism and to give them insight in their problem to enable the therapist to succesfully apply cognitive behavioral therapy. / Educational Studies / M. Ed. (Voorligting)

The classical Poisson, geometric and negative binomial regression models for count data belong to the family of generalized linear models and are available at the core of the statistics toolbox in the R system for statistical computing. After reviewing the conceptual and computational features of these methods, a new implementation of hurdle and zero-inflated regression models in the functions hurdle() and zeroinfl() from the package pscl is introduced. It re-uses design and functionality of the basic R functions just as the underlying conceptual tools extend the classical models. Both hurdle and zero-inflated model, are able to incorporate over-dispersion and excess zeros-two problems that typically occur in count data sets in economics and the social sciences-better than their classical counterparts. Using cross-section data on the demand for medical care, it is illustrated how the classical as well as the zero-augmented models can be fitted, inspected and tested in practice. (authors' abstract)

<p>Many cells spontaneously establish a polarity axis even in the absence of directional cues, a process called symmetry breaking. A central question concerns how cells polarize towards one, and only one, randomly oriented "front". The conserved Rhotype GTPase Cdc42p is an essential factor for both directed and spontaneous polarization in various organisms, whose local activation is thought to define the cell's front. We previously proposed that in yeast cells, a small stochastic cluster of GTP-Cdc42p at a random site on the cortex can grow into a large, dominating cluster via a positive feedback loop involving the scaffold protein Bem1p. As stochastic Cdc42p clusters could presumably arise at many sites, why does only one site become the dominating "front"? We speculated that competition between growing clusters for limiting factors would lead to growth of a single winning "front" at the expense of the others. Utilizing time-lapse imaging with high spatiotemporal resolution, we now document initiation of multiple polarized clusters that competed rapidly to resolve a winning cluster. Such multicluster intermediates are observed in wild-type yeast cells with functional directional cues, but the locations where they are initiated are biased by the spatial cues. In addition, we detected an unexpected oscillatory polarization in a majority of the cells breaking symmetry, in which polarity factors initially concentrated very brightly and then dimmed in an oscillatory manner, dampening down to a final intermediate level after 2-3 peaks. Dampened oscillation suggests that the polarity circuit contains an in-built negative feedback loop. Mathematical modeling predicts that negative feedback would confer robustness to the polarity circuit and make the kinetics of competition between polarity factor clusters relatively insensitive to polarity factor concentration.</p><p>We are trying to understand how competition between clusters occurs. We find that the yeast guanine-nucleotide dissociation inhibitor (GDI), Rdi1p, is needed for rapid competition between clusters. In the absence of Rdi1p the initial clustering of polarity</p><p>factors is slowed, and competition is also much slower: in some cases cells still have two clusters at the time of bud emergence and they form two buds. We suggest that in the absence of Rdi1p, the clusters compete for a limiting pool of Cdc42p, and that slow</p><p>exchange of Cdc42p on and off the membrane in the absence of Rdi1p leads to slow competition.</p> / Dissertation

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The purpose of this investigation is to determine the performance of an axial ow compressor operating in a closed loop helium cycle under high through- ow conditions. The GTHTR300 four-stage helium test compressor was chosen for this investigation. Limited information on the helium test compressor's blade pro les are available, therefore a mathematical model was developed to calculate the blade geometries based on the theory of Lieblein and Aungier. A locally available three-stage compressor was used to con rm whether the mathematical model calculated the blade pro le geometries correctly. The Stellenbosch University Compressor Code (SUCC), an axisymmetric inviscid through- ow code, was used to compare the performance of the calculated three-stage compressor blade geometries with available experimental data. Excellent correlation was obtained, thus it was concluded that the mathematical model as well as the SUCC could be used to predict the performance of an axial ow compressor. The blade geometries of the helium test compressor were calculated and the pressure ratio and e ciency predictions of the SUCC correlated well with the experimental data. The helium test compressor was simulated to verify the calculated blade geometries further using the Computational Fluid Dynamics (CFD) package NUMECA FINE /Turbo. The FINE /Turbo pressure ratio and e ciency predictions compared adequately with the SUCC and available experimental data, especially in the design region. At high mass ow rates the stator blade row experiences negative incidence stall which results in a large recirculation zone in the stator blade wake. / AFRIKAANSE OPSOMMING: Die doel van hierdie ondersoek is om vas te stel wat die werkverrigting is van 'n aksiale kompressor in 'n geslote lus helium siklus onderhewig aan hoë deurvloei kondisies. Die GTHTR300 vier-stadium helium toets kompressor is gekies vir die ondersoek. Daar is egter beperkte inligting oor die helium kompressor se lem geometrie, dus is 'n wiskundige model ontwikkel om dit te bereken gebaseer op die werk van Lieblein en Aungier. Om te bevestig dat die lem geometrie akkuraat was, was die lem geometrie van die 'n plaaslike beskikbare drie-stadium kompressor bereken. Die Stellenbosch University Compressor Code (SUCC), 'n aksisimmetriese nie-viskeuse deurvloei kode, is gebruik om die prestasie van die berekende lem geometrie met beskikbare eksperimentele data te vergelyk. Uitstekende korrelasie is verkry vir die drukverhouding en benuttingsgraad resultate, dus is die gevolgtrekking gemaak dat die wiskundige model sowel as die SUCC gebruik kon word om die lem geometrie en werkverrigting van aksiale kompressors te bereken en voorspel. Die helium toets kompressor is gesimuleer met behulp van die numeriese vloei-dinamika pakket NUMECA FINE /Turbo om die berkende lem geometrie verder te veri eer. Die FINE /Turbo drukverhouding en benuttingsgraad resultate het goed gekorreleer met beide die SUCC resultate en eksperimentele data, veral in die ontwerpsgebied. Teen hoë massa vloei tempo's vind daar groot wegbreking teen negatiewe invalshoek plaas in die stator lemry en dit veroorsaak 'n hersirkulasie sone in die naloop van die stator lem.

Breast cancer is one of the most common malignancy diagnosed in women and is the primary cause of cancer-related deaths in women worldwide. It is a heterogeneous group of diseases that have a different response, prognosis, and clinical outcomes. Estrogen, progesterone and HER2 negative breast cancer, known as triple negative breast cancer (TNBC), does not respond to hormonal therapy. Basal-like breast cancer (BLBC) has shorter overall survival rate among other subtypes. Tumors sharing both TNBC and BLBC are considered less responsive to currently available treatment. Chemoresistance to treatment has been a challenge in cancer biology and force investigation toward developing new targeted therapies, which selectively target specific subtypes. Sphingolipid metabolites have an important physiological role in determining cell fate. Sphingolipid metabolites, ceramide, sphingosine, and sphingosine-1-phosphate (S1P), are implicated in cancer. S1P exerts its functions via extracellular and intracellular targets. S1P synthesized inside the cell is exported outside and binds to G-protein coupled receptors, the sphingosine-1-phosphate receptors 1-5 (S1PR1-5). Although the intracellular function is not well defined, its suggested intracellular S1P promotes cell apoptosis. The S1P pathway has received great attention recently due its function in cell survival and death. This effect was reported to be concentration dependent. In this research, I focused on S1P effect on nine TNBC/BLBC cell lines. I examined the in-vitro effects of S1P on apoptosis, proliferation, and cytotoxicity in triple negative/ basal-like breast cancer cell lines. Moreover, I studied the co-administration of S1P with currently used chemotherapeutic agents in these cell lines. Data show that S1P can selectively induce cell death in TNBC/BLBC cell lines at a specific concentration. In this research, I found that the mechanism of cell death following treatment with different S1P concentrations was mainly due to apoptosis. Results show that S1P leads to cell shrinkage, rounding and detachment in the nine TNBC/BLBC cell lines. S1P combination with doxorubicin and docetaxel at different concentrations shows no beneficial effect of the combination compared to the chemotherapeuitc agent alone. In some cell lines, the combination showed a protective effect. Further studies are required to determine the mechanism by which S1P induces cell apoptosis, inhibits cell growth, and demonstrates lack of responsiveness in combination studies.

Bakgrunden till vår uppsats är att återkoppling behövs som verktyg på en arbetsplats för att få medarbetare att trivas. Detta har i grund och botten anknytning till vårt behov av att känna oss accepterade och av att känna samhörighet. Forskning har visat att bekräftelse från omvärlden är en viktig del för individens självbild. Särskilt i en projektorganisation är återkoppling betydelsefullt, eftersom projektgrupper ofta består av nya konstellationer av människor som snabbt måste lära sig att samarbeta. Om ett bra arbete med återkoppling sker kan detta få positiva effekter på arbetsprestationer. Problematiken kring att ge återkoppling handlar om att ge den på ett konstruktivt sätt som får mottagaren att ta åt sig. Genom att granska tidigare forskning undersökte vi varför det finns ett behov av återkoppling i pro-jektgrupper, vad forskningen säger att givaren bör tänka på när det handlar om återkoppling samt vad konsekvenserna och resultatet kan bli av återkoppling. Vårt syfte är att utifrån den forskning som idag finns undersöka hur arbetet med åter-koppling ser ut i praktiken för fem stycken projektledare. Vi ställde oss bland an-nat frågeställningarna: Ger projektledare återkoppling? På vilka sätt? Hur ser de på arbete med återkoppling? Vet de hur teorin ser ut kring ämnet? Arbetar de med att bli bättre på att ge återkoppling? För att undersöka frågeställningarna använde vi oss av en kvalitativ metod i form av semistrukturerade intervjuer. Projektle-darna arbetar alla inom samma bransch, fastighetsförvaltningsbranschen. Våra intervjudata bearbetades genom transkribering samt kodning efter förutbestämda teman. I vår analys jämförs den teoretiska bakgrunden med den empiriska datan vi insamlat. En matris med en sammanställning av det insamlade materialet återfinns i bilaga 2. Vår slutsats är bland annat att projektledare mest arbetar med positiv återkoppling och att negativ återkoppling kan vara problematiskt att ge. Vi fann även att projektledarna inte hade någon teoretisk kunskap om ämnet återkoppling utan de färdigheter de besatt hade de lärt sig genom erfarenhet. / The background of our paper is that feedback is needed as a tool on during work to make the individuals feel comfortable. This is basically related to our need of feeling accepted and to feel affinity. Research has demonstrated that the confirmation from the outside world is an important part of the individual's selfimage. In a project based environment, feedback is important, as project groups often consist of new constellations of people who quickly must learn to work together. If feed-back could be used successfully, this can have positive effects on work perfor-mance. The problem of providing feedback is how to give it in a constructive way so the receiver to take in the information and accept it. By examining past research, we examined why there is a need for feedback in project teams, what the research says that the giver should consider when it comes to feedback, and what consequences and results of feedback could be. Our purpose is, based on existing research, to examine how feedback is used in practice for five project managers. We asked ourselves following questions: Do project managers provide feedback? In what ways? How do they work with feedback? Do they know how the theory looks about the topic? How do they work to become better at giving feedback? To examine the issues, we used a qualitative approach in the form of semi-structured interviews. The interview subjects were all working in the same indus-try, the real estate industry. Our interview data were processed by transcribing and coding by predetermined themes. In our analysis we compared the theoretical background of the empirical data we collected. A matrix with a compilation of the collected data is presented in appendix 2. Our conclusion is that project managers mostly work with positive feedback and that giving negative feedback is perceived problematic. We also discovered that the project managers lacked a theo-retical knowledge about the subject and that the skills they possessed, had they learned through experience.

Literature Review: Anhedonia, the loss of interest or pleasure in usually pleasurable activities, is a core symptom of depression and is associated with a reduction in positive affect (PA). Repetitive negative thought (RNT) is implicated in the development and maintenance of psychiatric disorders. It has been hypothesised that RNT causally contributes to anhedonia. The aim of this review was to explore this relationship to answer two questions: Is there a relationship between RNT and anhedonia? Does RNT causally contribute to anhedonia? Review inclusion criteria were: studies using standardised measures to report a relationship between RNT and anhedonia or reduced PA. Results suggest that cross-sectional and longitudinal studies identify a relationship between RNT and anhedonia. Preliminary evidence from experimental studies shows that RNT causally contributes to anhedonia. Limitations within the field are that anhedonia is rarely measured directly or behaviourally. Future research is warranted to explore the relationship between RNT and anhedonia with a particular focus on direct and behavioural measures of anhedonia. Empirical Paper: It is hypothesised that repetitive negative thought (RNT) causally contributes to anhedonia. There is cross-sectional and longitudinal evidence of this relationship, but it has not previously been investigated directly using experimental methods. In the present study, student participants were randomly assigned to an unresolved goal (RNT) manipulation (n = 43) or resolved goal (control) manipulation (n =41) prior to completing a reward sensitivity task. This task has been reliably found to train a response bias towards the stimuli that is differentially positively reinforced, with both depression and self-reported anhedonia associated with a reduced response bias. The unresolved goal versus resolved goal manipulation was effective, with the unresolved condition producing significantly higher levels of RNT during the reward sensitivity task relative to the resolved condition. Inconsistent with study predictions, there was no significant difference between the conditions on response bias, although there were trend findings, which tentatively suggest that RNT may influence anhedonia. Potential accounts for the null findings and future research are discussed.

The objective of this research was to contribute to the discussion about LGBT-rights in Swedish politics. Some previous findings suggested that one political party in particular, the Swedish Democrats, had an opposing stance towards LGBT-persons. To investigate this, the first research question aimed to find out if there are in fact any notable differences between the different parties in the Swedish parliament in this regard. The second research question was designed in order to examine all related opinions of the parties in the light of positive and negative freedom. The third research question aimed to find out how the attitudes from the political parties could be understood within a perspective of tolerance. The analytical framework is based on the concept of tolerance, and the concepts of positive and negative freedom which were originally developed by Isiah Berlin. The study is a qualitative text-analysis with an abductive approach. Argumentation analysis has been applied when suitable. The study found that the Swedish Democrats was the most restrictive party in this context. Moreover, the studied policies were found to have characteristics of both negative and positive freedom, and they were generally approved upon by the political parties. Lastly, the Swedish Democrats and the Christian Democrats were argued to be tolerant towards these LGBT-policies, even though the policies were mostly disliked due to moral clashes against their core family values.

Protein sequences may evolve to avoid highly hydrophobic local regions of sequence, in part because such sequences promote nonnative aggregation. Hydrophobic local sequences are avoided in proteins even in buried regions, where native structure requirements tend to favor them. In this dissertation, I describe three explorations of this hydrophobic suppression. In Chapter 2, I examine the occurrence of hydrophobic and polar residues in completely buried β-strand elements, and find evidence for hydrophobic suppression that decreases as a β-strand becomes more exposed. In Chapter 3, I present a generalized study of the tendency of local sequences to deviate from the hydropathy (hydrophobicity) expected based on their solvent exposure. First, I examined the hydropathy of local and nonlocal sequence groups over a large range of solvent exposures, within folded protein domains in the ASTRAL Compendium database; second, I calculated the tendency of residues within 10 positions of a nonpolar or polar reference residue to deviate from the hydropathy expected based on their structural environment. Both analyses suggested that protein sequences exhibit 'local hydropathic balance' across a range of 6-7 residues, meaning that polar and nonpolar residues are more dispersed in the sequence than expected based on solvent exposure patterns. This balance occurs in all major fold classes, domain sizes and protein functions. An unexpected finding was that it partly arises from a tendency of buried or exposed residues to be flanked by polar or nonpolar residues, respectively. This relationship may result from evolutionary selection for folding efficiency, which might be enhanced by reduced local competition for buried or exposed sites during folding. Finally, in Chapter 4, I present several exploratory analyses, including a decision-tree approach, to visualize the influence of a large number of sequence-structure properties on residue hydrophobicity. Overall, the work in this dissertation confirms that hydrophobic suppression and local hydropathic balance in general are intrinsic properties of folded proteins. I speculate that local hydropathic balance results from selection for reduced aggregation propensity, increased folding efficiency and increased native state specificity. The concept of local hydropathic balance might be used to improve the properties of designed and engineered proteins.