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Catalytic ethylene oligomerization is a well understood industrially viable process. The large majority of scientific literature and patents concerning this process has been developed with the use of chromium catalysts. Commercial systems producing selective tri/tetramerization, non-selective oligomerization and polymerization are all based on this metal with the exception of a few systems based on other transition metals (Zr, Ti, Ni etc.). This versatility raises interesting questions about chromium’s unique behaviour. Essentially, selective or non-selective oligomerization and polymerization processes could be regarded as belonging to the same category of C-C bond forming reactions, though different mechanisms are involved. The first part of this thesis explores a variety of chromium complexes for ethylene oligomerization purposes. In order to gather further information about the unique behaviour of chromium, we have explored a variety of nitrogen and phosphorus containing ligands. We started with a simple bi-dentate anionic amidophosphine (NP) ligand and assessed the role of the ligand’s negative charge and number of donor atoms in determining the type of catalytic behaviour in relation to the metal oxidation state. This ligand proved capable of generating a series of chromium dimeric, tetrameric or polymeric and even heterobimetallic chromium-aluminate complexes in different valence states. This allowed us to isolate a “single component” self activating Cr(II) complex as well as a rare example of mixed valence Cr(I)/Cr(II) species. Additionally, each of these species acted as switchable catalyst depending on the type of co-catalyst

Magistro darbe tiriama žėlimo ypatumai grynuose pušynuose po neplynųjų atvejinių kirtimų Liepynės, Meros, Nemenčinės, Purviniškių girininkijose. Darbo objektas – V.Į. Nemenčinės miškų urėdijos Liepynės, Meros, Nemenčinės, Purviniškių girininkijų 2006–2012 metais neplynaisiais (atvejiniais) kirtimais iškirstos brandžių pušynų kirtavietės. Darbo metodai – Tyrimai vykdyti 1–7 metų minėtų girininkijų neplynųjų atvejinių kirtimų pušynų kirtavietėse 2012–2013 metais. Siekiant įvertinti žėlinių kokybę ir atlikti jų apskaitą tiriamų kirtaviečių apskaitos aikštelės buvo tolygiai išdėstytos sąlyginai – vienodais atstumais sklypų įstrižainių kryptimis. Nuo žėlinių tankumo priklausėšių stačiakampių apskaitos aikštelių plotas.Kai žėliniai buvo vidutinio tankumo (2–8 tūkst. vnt./ha) – 10 m2, kai reti (< 2 tūkst. vnt./ha) – 20 m2. Apskaitos aikštelių kiekis priklausė nuo kirtavietės ploto. Mažesniuose kaip 1 ha sklypuose buvo išdėstytos penkios aikštelės, 1–3 ha – išdėstytos aštuonios ir didesniuose kaip 3 ha – dešimt ir daugiau apskaitos aikštelių.Kiekvienoje apskaitos aikštelėje atlikti tokie vertinimai: savaiminukų gausa ir rūšis, savaiminukų gyvybingumas, žolinės dangos agresyvumo laipsnis, pažeidimai ir galimos priežastys. Darbo rezultatai – tirtose 20 neplynųjų kirtimų kirtaviečių vidutinis žėlinių tankis – 2270 vnt./ha, vidutinė žėlinių rūšinė sudėtis – 6P4B. Liepynės girininkijos – 3750 vnt./ha, 8P2B. Meros – 1210 vnt./ha,7B3P. Nemenčinės – 2070 vnt./ha,6P4B. Purviniškių – 1500 vnt... [toliau žr. visą tekstą] / The present Master’s thesis examines the growth peculiarities of pure pine forests after selective shelterwood cutting in Liepynė, Mera, Nemenčinė, Purviniškės forestries. Object of the thesis – cutting areas of mature pine forests, cut by selective (shelterwood) cutting, in Liepynė, Mera, Nemenčinė, Purviniškių forestries of Nemenčinė Forest Enterprise during the period of 2006–2012. Methods of the research – research was carried out in selective cutting areas of pine forests of aforementioned forestries in 1-7 years, during the period of 2012-2013. Seeking to assess the quality of sprouts and make the inventory, inventory sites of researched cutting areas were divided into relatively equal distances between areas at diagonal direction. The area of rectangular inventory sites depended on density of sprouts. In case of average density (2–8 thousandunits/ha) – 10 m2, and in case of low density (< 2 thousand units/ha) – 20 m2. The number of inventory sites depended on area of cutting zone. There were five sites in smaller than 1 ha plots, while there were eight sites in plots of 1–3 ha, and there were ten and more inventory sites in 3 ha plots. The following assessments were made in each inventory site: abundance and species of wildings, viability of wildings, aggressiveness degree of grass cover, its damage and possible causes. Results of the thesis– average density of sprouts in 20 researched selective cutting areas is2270 units/ha, average species composition of sprouts –... [to full text]

Human vision is remarkable. By limiting the main concentration of high-acuity photoreceptors to the eye's central fovea region, we efficiently view the world by redirecting the fovea between points of interest using eye movements called <em>saccades</em>. <br /><br /> Part I describes a saccadic vision system prototype design. The dual-resolution saccadic camera detects objects of interest in a scene by processing low-resolution image information; it then revisits salient regions in high-resolution. The end product is a dual-resolution image in which background information is displayed in low-resolution, and salient areas are captured in high-acuity. This lends to a resource-efficient active vision system. <br /><br />Part II describes CMOS image sensor designs for active vision. Specifically, this discussion focuses on methods to determine regions of interest and achieve high dynamic range on the sensor.

This thesis concerns selective attention in the context of the Stroop task (identify the colour) and Reverse Stroop task (identify the word). When a person is asked to select and identify one dimension of a bidimensional stimulus (e. g. , the word RED printed in green) the typical finding is that the word influences colour identification (i. e. , the Stroop effect) but the colour does not influence word identification (i. e. , no Reverse Stroop effect). A major account of performance in these tasks posits that one dimension interferes with the other only when a translation occurs (e. g. , Roelofs, <i>Psychological Review, 2003</i>; Sugg & McDonald, <i>Journal of Experimental Psychology: Human Perception & Performance, 1994</i>; Virzi & Egeth, <i>Memory & Cognition, 1985</i>). This translation assumption is implicit in virtually all work in the field. The first part of this thesis completely undermines the translation assumption. In a series of four experiments (two unique paradigms), I demonstrate that interference from the colour in a Reverse Stroop task occurs in the absence of a translation. The second part of this thesis contains two additional experiments designed to discriminate between translation effects and response conflict effects. The results of these experiments confirm that a translation was not required because no stimulus conflict effect, the most likely locus of a translation effect, was observed. However, response conflict effects were observed. The third part of this thesis implements a computational model based on the principle that the strength of association (Cohen, Dunbar, & McClelland, <i>Psychological Review, 1990</i>) between a specific stimulus and its response (Logan, </i>Psychological Review, 1988</i>) is important in determining the influence of the irrelevant dimension. This model has no translation mechanism. A final experiment was conducted to test this model; the model accounted for over 98% of the variance in RTs and 92% of the variance in interference and facilitation scores in both the Stroop and Reverse Stroop tasks independent of whether a translation was required.

Due to the nature of the condition, research into selective mutism has tended towards quantitative analyses or individual case studies. This study aimed to explore the personal experiences of adolescents with selective mutism whilst considering the threats to validity that exist in previous qualitative studies. In a series of case studies (n=6), methods of eliciting data derived from Personal Construct Psychology were employed. Experience Cycle Methodology was used to explore the process of construing, whilst the Repertory Grid Technique enabled an exploration of the structure of construing. It was hoped that these methods might identify obstacles to change and inform appropriate interventions. Results suggested that mutism may be ‘chosen’ because it may enable greater anticipation of their interpersonal relationships than does speaking. Furthermore, there were suggestions that selective mutism may be a way of avoiding possible invalidation. Further research into sociality and systemic discourse was proposed in order to understand this condition further.

Gastrointestinal parasitism in grazing lambs adversely affects animal performance and welfare, causing significant production losses for the sheep industry. Control of gastrointestinal parasitism using chemotherapeutic treatment is under threat due to the emergence of anthelmintic resistance, thus stimulating research into alternative control strategies. Whilst investigating control strategies experimentally can be costly and time consuming, using a mathematical modelling approach can reduce such constraints. A previously developed model which describes the impact of host nutrition, genotype and gastrointestinal parasitism in a growing lamb, provided an appropriate starting point to explore control strategies and their impact on host-parasite interactions. Two contrasting mechanisms have previously been proposed to account for the occurrence of anorexia during parasitism. These were reductions in either intrinsic growth rate or relative food intake. Thus, the existing individual lamb model was modified to evaluate these mechanisms by exploring the relationship between anorexia and food composition (Chapter 2). For foods that did not constrain food intake, published data was found to be consistent with the predictions that arose from anorexia being modelled as a reduction in relative food intake. Reported genetic parameter estimates for resistance and performance traits appear to vary under differing production environments. In order to explore the impact of epidemiological effects and anthelmintic input on genetic parameter estimates the model was extended to simulate a population of lambs in a grazing scenario (Chapter 3). Whilst estimates of heritabilities and genetic correlations for drenched lambs remained constant, for lambs given no anthelmintic treatment, the heritability of empty body weight (EBW) reduced and the genetic correlation between faecal egg count (FEC) and EBW became increasingly negative with increasing exposure to infective larvae. Thus differences in anthelmintic input and pasture larval contamination (PC) may provide plausible causes for the variation in genetic parameter estimates previously reported. To investigate the interactions between host resistance and epidemiology (Chapter 4) a population of 10,000 lambs were simulated and FEC predictions used to assign the 1,000 lambs with the highest and lowest predicted FEC to ‘susceptible’ (S) and ‘resistant’ (R) groups, respectively. R and S groups were then simulated to graze separate pastures over 3 grazing seasons. The average FEC and PC predictions of these groups diverged during the first 2 grazing seasons and stabilised during the third, such that the difference in FEC predictions between R and S groups were double those predicted when grazed with the population. This was found to be consistent with experimental data. Further, anthelmintic treatment and grazing strategies were predicted to have no impact on the EBW of resistant lambs, suggesting that control strategies should be targeted towards susceptible animals. Targeted selective anthelmintic treatment (TST) has been proposed to reduce risks of anthelmintic resistance with minimal impacts on performance. To describe the short- and long-term impacts of TST and drenching frequency on sheep production and the emergence of anthelmintic resistance, the model was extended to include a description of anthelmintic resistance genotypes within the nematode population (Chapter 5). Reducing the proportion of treated animals was predicted to increase the duration of anthelmintic efficacy, whilst reducing the drenching frequency increased the long-term benefits of anthelmintic on sheep production. Various determinant criteria for use in TST regimes were compared (Chapter 5) including performance traits such as live weight and growth rate, and parasitological traits such as FEC. Using FEC as the TST criterion was predicted to allow the greatest reduction in the number of anthelmintic treatments administered whilst maintaining the highest average EBW, whilst live weight and growth rate were predicted to give little to no improvement in comparison to selecting animals at random for TST. Using estimated breeding values (EBVs) for FEC as the determinant criterion for TST regimes was compared to using measured FEC (Chapter 6). The EBV for true FEC across the entire growth period, akin to perfect genomic selection, was predicted to be a better criterion than measured time-specific FEC (including a sampling error) for a TST regime. EBVs calculated using measured time-specific FEC showed little benefit compared to measured FEC. The information gained from these simulation studies increases our understanding of control strategies and their impact on host-parasite interactions under various scenarios that may not have been possible using experimental methods. It is important to remember that the aim of alternative or complimentary control strategies is to maintain the sustainability of sheep production systems, and as such the production gain of any control strategy needs to be weighed against the financial, labour and time costs involved in implementation.

Active learning reduces annotation costs for supervised learning by concentrating labelling efforts on the most informative data. Most active learning methods assume that the model structure is fixed in advance and focus upon improving parameters within that structure. However, this is not appropriate for natural language processing where the model structure and associated parameters are determined using labelled data. Applying traditional active learning methods to natural language processing can fail to produce expected reductions in annotation cost. We show that one of the reasons for this problem is that active learning can only select examples which are already covered by the model. In this thesis, we better tailor active learning to the need of natural language processing as follows. We formulate the Unreliable Parameter Principle: Active learning should explicitly and additionally address unreliably trained model parameters in order to optimally reduce classification error. In order to do so, we should target both missing events and infrequent events. We demonstrate the effectiveness of such an approach for a range of natural language processing tasks: prepositional phrase attachment, sequence labelling, and syntactic parsing. For prepositional phrase attachment, the explicit selection of unknown prepositions significantly improves coverage and classification performance for all examined active learning methods. For sequence labelling, we introduce a novel active learning method which explicitly targets unreliable parameters by selecting sentences with many unknown words and a large number of unobserved transition probabilities. For parsing, targeting unparseable sentences significantly improves coverage and f-measure in active learning.

Selective eating (SE) refers to an individual narrowing their range of preferred foods, resulting in a restricted food intake, high levels of rigidity and food refusal (Bryant-Waugh, 2000). SE is encompassed in the new Diagnostic and Statistical Manual of Mental Disorders 5th Edition (DSM-V) (American Psychiatric Association, 2013) category avoidant restrictive food intake disorder (ARFID). Such difficulties are common in children with an autism spectrum disorder (ASD) (Raiten & Massaro, 1986) and neuropsychological differences have been found in children with ASD (Hill, 2004). This research aimed to be the first to investigate whether a distinct neuropsychological profile exists in children and adolescents with SE and furthermore, whether aspects of the profile vary depending on whether the child or adolescent displays elevated autistic traits. A case series of 10 children between the ages of 8 to 13 years old were recruited. A well-established neuropsychological test battery, the Ravello Profile (Rose, Frampton & Lask, 2012), was modified and administered to assess visuospatial processing, central coherence, executive functions (including cognitive flexibility, inhibition and planning) and theory of mind abilities. The results demonstrated a high degree of variability across the group in terms of visuospatial processing and theory of mind, weak central coherence across all participants and otherwise relatively intact abilities in executive function domains. There were no substantive findings in relation to those children with elevated autistic traits although a trend toward visuospatial processing differences did emerge. This exploratory case series was the first attempt to describe a neuropsychological profile in SE, however the small sample size and high variability in the data meant that a distinct neuropsychological profile did not emerge. The results did however provide an initial indication of possible trends in strengths and weaknesses across neuropsychological domains in SE. These findings have implications for the assessment and treatment of SE difficulties.

A number of studies have indicated that violent video gameplay is associated with higher levels of aggression, and desensitization to violent content contributes to this association. Utilizing a rapid serial visual presentation (RSVP) task, the current study used event-related potentials (ERPs) to investigate selective attention (N1 activation), cognitive control (N2 activation), and desensitization (P3 activation) as neurocognitive mechanisms potentially underlying the association between gameplay and subtypes of aggression. Results showed video game players and non-players differed significantly in brain activation when engaged with violent imagery. N1 and P3 amplitude moderated the association between gameplay and pleasure-oriented aggression. Follow-up analyses further revealed that individuals who play games for many hours and show large N1 activation (high selective attention) in the face of violence have small P3 activation (heightened desensitization). Thus, our results suggest that selective attention to violent content and subsequent desensitization effects moderate the association between video gameplay and aggression.