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This thesis is concerned with so-called higher derivative terms which arise in low energy approximations to certain physical models. In particular, the aim is to investigate the role that such terms play in low energy N=2 supersymmetric gauge theories in 4 dimensions, with gauge group SU(2).Chapter one serves as an introduction to the notions of supersymmetry and superfields. The problem of constructing an effective action which describes the low energy dynamics is introduced, and the construction of the Wilsonian action in terms of light and heavy modes is developed. The concept on a derivative expansion is also described. Chapter two introduces N=2 supersymmetric gauge theories with spontaneous symmetry breaking. It is observed that such systems always have a Bogomolnyi bound, and the consequences are discussed. We then develop a derivative expansion of this system in terms of N=2 superfields, drawing particular attention to the next-to- leading order derivative term (that is, those with 4 derivatives/8 fermions). The duality properties of such a term are reviewed, and their impact on the mass formula discussed. Conclusions are drawn as to their influence on the results of Seiberg and Witten. Chapter three deals with a non-renormalisation theorem for the next-to-leading order higher derivative term proposed by Dine and Seiberg. This states that instanton contributions to such a term in massless N=2 SU(N(_c)) gauge theories vanish when the number of flavours N(_f) = 2N(_c). We prove this result using the ADHM formalism for multi-instantons in the case N(_c) = 2.

Veiksmo pavadinimo konstrukcijos – būdingi šiuolaikinių technologijų, mokslo, teisės verslo ir daugelio kitų sričių kalbos bruožai. Šie žodžiai suteikia pavadinimą įvairiems procesams, procedūroms, metodams ir kt., todėl jie plačiai vartojami įvairiuose oficialiuose dokumentuose, ir būtent šie dokumentai dažnai apibūdinami kaip turintys bene daugiausia veiksmų pavadinimų konstrukcijų. Šiais laikais žmonės, kalbantys skirtingomis kalbomis, nuolat turi bendrauti, ir todėl dažnai atsiranda būtinybė versti oficialius dokumentus iš vienos kalbos į kitą. Taigi, pagrindinė keliama hipotezė, kad vertėjai, versdami oficialius dokumentus, vartoja tam tikrus žodžius, kurie apibrėžia skirtingus veiksmus, ir jie verčia šiuos žodžius pasitelkdami pačias produktyviausias priemones, t.y. produktyviausias priesagas anglų ir lietuvių kalbose, tuo tarpu kitas priesagas vartodami labai retai. Šio magistrinio darbo tema – „Veiksmo pavadinimo konstrukcijos dalykinio stiliaus tekstuose” (lyginamoji analizė). Nors praeityje daugelis mokslininkų tyrinėjo veiksmo pavadinimo konstrukcijas tiek anglų, tiek lietuvių kalboje, šios konstrukcijos dar nebuvo nagrinėjamos oficialiuose dokumentuose bei lyginamos tarpusavyje. Magistrinio darbo tikslas – atskleisti būdus, kaip yra sudaromi veiksmų pavadinimai, ir kaip jie yra verčiami anglų ir lietuvių kalbų dalykinio stiliaus tekstuose, atsižvelgiant tiek į jų formą, tiek į prasmę. Šiame darbe buvo apibrėžta veiksmo sąvoka, išskirta derivacinės morfologijos... [toliau žr. visą tekstą] / Action defining words are characteristic features of the modern language style of technology, science, law, business and many other fields. They create an individual subgroup of naming units in the vocabulary inventory. From the point of view of terminological use, action defining words may designate processes, procedures, methods, ways of processing materials and administration acts. Such words are widely used in different formal documents, and, therefore, the texts are characterized as having a great many of action defining words. Nowadays, as different language speakers regularly communicate, formal documents are facing the necessity to be translated from one language to another. Thus, the main hypothesis of the research is suggested by the fact that in formal texts translators use a determined set of words which define actions and consequently their translations often are performed in a particular manner: they use the most productive English and Lithuanian suffixes leaving aside other linguistic means. In other words, translators do not vary and choose the easiest ways how to express the action in the process of translating. Although there are many research studies carried out on the action defining words by the English and Lithuanian linguists, such as Quirk (1972), Holvoet (2006), Keinys (1999), Pakerys (2006), comparative investigations on the issue of the action defining words in English and Lithuanian are not widespread. This Master thesis aims at revealing the means... [to full text]

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Flying fruit flies (Drosophila melanogaster) locate a concealed appetitive odour source most accurately in environments containing vertical visual contrasts (Frye et al, 2003). To investigate how visuomotor and olfactory responses interact to cause this phenomenon, I implement a tracking system capable of recording flies’ flight trajectories in three dimensions. I examine free-flight behaviour in three different visual environments, with and without food odour present. While odour localisation is facilitated by a random chequerboard pattern compared to a horizontally striped one, a single vertical landmark also facilitates odour localisation, but only if the odour source is situated close to the landmark. I implement a closed-loop systems-level model of visuomotor control consisting of three parallel subsystems which use wide-field optic flow cues to control flight behaviour. These are: an optomotor response to stabilise the model fly’s yaw orientation; a collision avoidance system to initiate rapid turns (saccades) away from looming obstacles; and a speed regulation system. This model reproduces in simulation many of the behaviours I observe in flies, including distinctive visually mediated ‘rebound’ turns following saccades. Using recordings of real odour plumes, I simulate the presence of an odorant in the arena, and investigate ways in which the olfactory input could modulate visuomotor control. In accordance with the principle of Occam’s razor, I identify the simplest mechanism of crossmodal integration that reproduces the observed pattern of visual effects on the odour localisation behaviour of flies. The resulting model uses the change in odour intensity to regulate the sensitivity of collision avoidance, resulting in visually mediated chemokinesis. Additionally, it is necessary to amplify the optomotor response whenever odour is present, increasing the model fly’s tendency to steer towards features of the visual environment. This could be viewed as a change in behavioural context brought about by the possibility of feeding. A novel heterogeneous visual environment is used to validate the model. While its predictions are largely borne out by experimental data, it fails to account for a pronounced odour-dependent attraction to regions of exclusively vertical contrast. I conclude that visual and olfactory responses of Drosophila are not independent, but that relatively simple interaction between these modalities can account for the observed visual dependence of odour source localisation.