Attentional bias (AB) refers to the tendency to selectively attend to (orientation towards) and/or hold attention on (slowed disengagment from) disorder-relevant stimuli. Females with eating-related concerns are thought to preferentially process threatening stimuli, which in turn is thought to maintain and exacerbate eating concerns. The aim of the present thesis was to explore AB for threatening stimuli in females characterised by restrained, external or emotional eating, and those with high levels of (non-clinical) eating psychopathology. This was carried out with the intention of identifying cognitive processes that contribute to eating behaviours in females, in order to assess the relevance of an attention training (AT) programme for reducing such biases. A pilot study assessed orientation/slowed disengagement, for mood and food words amongst females with high/low levels of restraint. Forty females completed a modified Stroop task with three conditions. Food and mood conditions included sequences of five words ( target food/mood followed by four neutral). The neutral condition consisted of all neutral words. Performance did not significantly differ according to high/low restraint groups. All participants took longest to colour-name word position 2 (demonstrating slowed disengagement lasting one consecutive trial). However, this pattern was also found in the neutral condition. Methodological limitations were then addressed in study one. High/low restrained eaters (n=48) completed a modified Stroop where targets (food, interpersonal threat, animal) were presented prior to four neutral words. Participants were slow to disengage from targets (slowest for word position 2) in all conditions. Patterns of responding indicated that restrained eaters might take longer to disengage (i.e. the carry-over effect from the food word seemed to last longer than one trial). However, more neutral words in the sequence were needed to assess this. As slowed disengagement from animals also arose, a categorical effect may have occurred. Study two explored attention processing of food using modified Stroop and dot probe tasks. In the Stroop task targets (food, interpersonal threat, household objects) were presented prior to six matched neutral words. This task revealed no evidence of AB. No significant pattern of differences between restrained (n=29)/unrestrained eaters (n=31) emerged; however, binge eating scores were significantly negatively correlated with response times. A dot probe task with food/neutral picture pairs also revealed no evidence of AB. Both restrained/unrestrained eaters had negative mean interference scores indicating avoidance of food. None of the following eating behaviours significantly correlated with AB: restraint, disinhibition, external eating, emotional eating and non-clinical eating psychopathology. Study three employed a further modified dot probe task based on image ratings. There was no evidence of AB, and no significant relation between task performance and restrained, emotional or external eating. 2000ms bias scores (assessing disengagement) were significantly negatively correlated with eating psychopathology and age, suggesting that those with high levels of non-clinical eating psychopathology attentionally avoid food stimuli and that younger females are slower to disengage attention from food (although found within a limited age range). Study four employed further modified Stroop and dot probe tasks, and assessed whether AB mediates the negative mood-eating relationship. Participants were allocated to negative or neutral mood conditions. No evidence of AB was found with the dot probe, but greater levels of emotional eating were associated with slower responding. In the Stroop task, all participants displayed an orientation bias towards food. Emotional eating and drive for thinness (DFT) scores were significantly positively correlated with food word colour-naming times but only amongst participants in a negative mood. However, those with high levels of external eating showed greater AB towards food when in a neutral mood. Highly emotional eaters in a negative mood showed a greater desire to eat than those in a neutral mood but did not increase in food intake. Furthermore, those with a high DFT (in a negative mood) showed no evidence of increased desire to eat or food intake. AB was not significantly related to subjective appetite or food intake. Therefore, AB does not seem to mediate the negative-mood eating relationship. The present thesis provides important suggestions for modifications of Stroop and dot probe tasks targeting orientation and disengagement. A modified Stroop has been more sensitive at detecting food AB than the dot probe. Implications of biased attention processing are discussed in relation to the development of harmful eating behaviours, and the present findings have important implications for developing programmes to prevent eating disorders amongst at-risk females (e.g. through AT or training at-risk females how to effectively cope with negative mood).

Although Value Engineering (VE) studies are mandated by the Federal Highway Administration for large ($25 million or more) federal-aid highway projects, many state Departments of Transportation do not conduct voluntary VE studies on smaller projects. Those who have done so have seen project improvements and savings as a result. The success of the existing voluntary VE programs indicates that VE application to small transportation projects represents a significant opportunity for savings. The goal of this thesis work was to develop a methodology for conducting VE studies on small transportation projects that would make efficient use of available personnel and require little VE training. The author examined the results and procedures of several DOT VE programs, including some that conduct studies on projects as small as $1 million. The analyses revealed sources of past savings, trends and common methods in VE studies, and procedures and forms that are best suited to the types of project under study. Based on the research and analyses, the author developed a VE study methodology that is tailored to small transportation projects, including a workbook and both general and specific guidelines. This report proposes an approach to VE on small transportation projects using this methodology, which is characterized by conformance with accepted VE practice and FHWA guidelines, efficient use of personnel, and ease of use. In particular, these recommendations are intended for use by any state DOT with an existing but limited VE program, such as MassHighway, which currently conducts only mandated studies.

Cette thèse porte sur l'interaction lumière-matière au sein de nanostructures placées dans des cavités optiques à base de semi-conducteurs nitrures. A l'aide d'expériences de micro-photoluminescence dans l'ultra-violet, nous étudions les propriétés optiques de boîtes quantiques GaN/AlN dans des microcavités planaires et celles de puits quantiques GaN/AlN insérés dans des microdisques AlN.Afin d'améliorer la collection du faible signal de photoluminescence de boîtes quantiques uniques, nous utilisons des microcavités planaires pour modifier le diagramme d'émission d'une boîte quantique. Le dessin des microcavités est optimisé grâce à des simulations numériques basées sur la méthode des matrices de transfert en présence d'un émetteur. Nous montrons que, pour une microcavité nitrure à base de miroirs de Bragg AlN/AlGaN, la collection des photons émis par une boîte quantique peut être théoriquement améliorée d'un ordre de grandeur, ce qui est confirmé par nos mesures sur boîtes quantiques uniques, ouvrant ainsi la voie à des études avancées de corrélations de photons dans l'UV.La seconde partie des travaux est dédiée à la réalisation d'un micro-laser opérant dans l'UV profond et à température ambiante. En utilisant des puits quantiques GaN/AlN de 2,8 mono-couches, crûs sur substrat silicium et insérés dans des microdisques AlN, nous observons une émission laser à 275 nm sous pompage optique impulsionnel. Cette démonstration montre le fort potentiel des semi-conducteurs nitrures pour la nano-photonique UV sur silicium. / This thesis addresses the light-matter interaction in nitride nanostructures embedded in optical microcavities. By using micro-photoluminescence experiments, we study the optical properties of GaN/AlN quantum dots embedded in planar microcavities and those of GaN/AlN quantum wells in AlN microdisks.By placing quantum dots in planar microcavities, we are able to modify the emission diagram and increase the collection efficiency. The design of the microcavities is optimized by using numerical simulations based on transfer matrix method with an internal emitter. For an AlN microcavity with AlN/AlGaN Bragg mirrors, we show that the collection efficiency could be theoretical increase by one order of magnitude, which is confirmed by our micro-photoluminescence experiments on single quantum dots. This observation opens the way for advanced studies such as photon correlations experiments in the UV range.The second part of our work is devoted to the realization of a micro-laser operating in the deep-UV range at room-temperature. By using thin GaN/AlN quantum wells (2.8 monolayers), grown on silicon substrate and embedded in AlN microdisks, we observe a laser emission at 275 nm under pulsed optical pumping. This demonstration shows the strong potentiality for future developments of nitride-on-silicon nano-photonics.

There has been significant progress in the optical resolution of microscopes over the last two decades. However, the majority of currently used methods (e.g. STED, PALM, STORM) have a number of drawbacks, including high intensities of light that result in damage to living specimens in STED, and long data acquisition time leading to limitations on live-cell imaging. Therefore, there is a niche for faster image acquisition at lower intensities while maintaining resolution beyond the diffraction limit. Here, we have developed a new methodology - Quantum Dot-based Optical Spectral Separation (QDOSS) - which relies on using Quantum Dots (QDs) as fluorophores, and on their separation and localisation based on their spectral signatures. We utilise the key advantages of QDs over the usual organic fluorophores: broad excitation, narrow emission spectra and high resistance to photobleaching. Besides, since QDOSS is based on spectral differences for separation, QDs can be deterministically localised in a relatively short time - milliseconds and, potentially, microseconds. Last but not least, QDOSS is suitable for obtaining super-resolution images using a standard confocal fluorescence microscope equipped with a single laser excitation wavelength and capable of spectral signal separation (e.g. Leica TCS SP series or Zeiss LSM series). First, we demonstrated resolution down to 60 nm using triangular DNA origami as a reference. Furthermore, we labelled and imaged the alpha-tubulin structure in HEK293T cells. We showed that using a mixture of standard off-the-shelf QDs of different sizes, resolution down to 40 nm could be achieved via spectroscopic separation of QDs. Finally, we demonstrated that QDOSS could also be used for multicolour imaging of synaptic proteins distributed around synapsis in neurons within diffraction limit. All in all, we believe that these features of QDOSS make it a potential method for long-term live super-resolution imaging, which is going to have a high impact in biological sciences.

Test anxiety is an individual personality trait, which results in elevated state anxiety in situations of performance evaluation. For school-age children, high-stakes examinations occurring at the culmination of programmes of study are where they frequently experience such evaluation. Alongside its impact on an individual's wellbeing, heightened test anxiety has been reliably linked to deficits in performance on examinations and assessments. Attentional bias has been shown to be an aspect of many forms of anxiety and is considered to have role in the maintenance of state anxiety, though the mechanisms underlying this are not fully clear. However, Attentional Control Theory (Eysenck, Derakshan, Santos, & Calvo, 2007) implicates preferential allocation of attention to threat in its explanation of performance deficits associated with test anxiety. The presence of attentional bias in test anxiety appears theoretically plausible with some empirical support (e.g. Putwain, Langdale, Woods and Nicholson, 2011); however, its reliability is under question. This study aims to investigate the presence of attentional bias in test anxiety, with a view to further understanding its underlying mechanisms and informing the development of interventions to ameliorate its effects. To ensure ecological validity, this study was conducted in schools and colleges, with a sample of 16-18-year olds following high-stakes programmes of study. Full investigation of test anxiety requires individuals to experience heightened state anxiety through performance evaluation threat; hence, the Trier Social Stress Test (TSST) was modified to make it applicable to this context and population. This study was conducted in two experimental phases, both of which adopted a mixed methodological approach to provide quantitative and qualitative data. The preliminary phase evaluated the materials and anxiety manipulation protocols. The main phase employed the modified-TSST in collaboration with a dot-probe task to investigate participants' attentional bias when under high performance evaluation threat. No patterns of attentional bias were uncovered to indicate a consistent relationship to either trait test anxiety or attentional control. However, there was a level of congruence between how some individuals describe themselves in evaluative situations and the attentional bias they displayed. Further investigation employing mixed methodological approaches such as Single Case Experimental Design is recommended to identify and address attentional bias in test anxiety.

Tabagistas atendem seletivamente a estímulos ambientais relacionados ao cigarro, um processo cognitivo implícito denominado viés na atenção (VA). Contudo, não está claro se o VA persiste em ex-fumantes. Por isso, avaliou-se a influência do tempo de abstinência no VA em 62 ex-fumantes (de 50±11 anos) através de uma tarefa de atenção visual em computador. Independente do tempo de abstinência, os participantes evitaram as pistas associadas ao tabaco. Esta esquiva foi mais pronunciada em tempos de exposição maiores. Os ex-fumantes também atribuíram pouca valência emocional às imagens associadas ao cigarro e reportaram índices baixos de fissura antes e após a tarefa. O VA negativo e a menor valência emocional destas pistas podem constituir um processo de modulação da atenção típico da abstinência prolongada, no qual estratégias cognitivas são empregadas para manter este estado. Os resultados obtidos contribuem para a compreensão da cognição implícita na adição e sua importância no tratamento e prevenção do tabagismo. / Smokers selectively attend to smoking-related cues, an implicit cognitive process called attentional bias (AB). However, it is unclear whether former smokers present AB. Therefore, we evaluated the influence of abstinence time in VA in 62 exsmokers (50 ± 11 years-old) through a visual probe task. Participants avoided smoking cues despite of abstinence time. This avoidance was more pronounced in longer stimuli exposition. Former smokers also attributed little emotional valence to smoking cues and reported low craving rates both before and after the task. The negative AB and low emotional valence of smoking cues might constitute a process of attentional modulation typical of longer abstinence, in which cognitive strategies are employed to maintain this state. The results contribute to the understanding of implicit cognition in addiction and its importance to smoking treatment and prevention.

Terahertz (THz) technology is still currently a rapidly developing area of research with applications already demonstrated in the fields of biology, medicine, security, chemical/materials inspection and astrophysics to name a few. The diversity of applications which require the generation and measurement of THz or sub-millimeter (sub-mm) electromagnetic (EM) signals is the result of the vast number of chemical elements and compounds which exhibit molecular transitions and vibrational behavior that occur at frequency ranges corresponding to the so-called 'THz gap', roughly defined as 0.05-10 THz. The THz gap was named as such because of the relative difficulty in generating and analysing EM waves in this frequency band. This was due to the inherent challenges in generating either electrical signals with response periods below 1 picosecond (ps), or optical signals with wavelengths in the far-infrared (FIR) range. High absorption of THz signals in atmosphere via absorption by molecules such as H2O also impeded early developments and is a key issue in THz systems even today. There is now a wide variety of THz system solutions, each of which exhibits a different set of operational advantages and limitations. Arguably, the most well-established THz technique to date is based on the use of photoconductive antennas (PCAs) driven by ultrafast pulsed or dual-wavelength laser systems. This technique is the basis for the work presented in this thesis, which is an investigation into the potential utilisation of quantum dot (QD)-based semiconductor materials and devices in THz systems. This thesis discusses the work carried out in the development of a novel class of PCA devices which were postulated to enable efficient optical-to-THz signal conversion, whilst also overcoming several major limitations normally exhibited by PCA devices such as limited optical wavelength pumping range and thermal breakdown. To summarise briefly, these issues were addressed by considering: the additional pump absorption energy ranges enabled by the inclusion of multiple bandgap-engineered semiconductor materials and quantum-confined structures; the higher thermal conductivity and hence pump tolerance exhibited by relatively high-quality (low defect) absorption layers; and by simultaneously harnessing the ultrafast charge carrier modulation exhibited by the integrated QDs. Additionally, some work was carried out using QD-based lasers as pump sources, with the initial intention to explore the feasibility of a fully QD-based THz transceiver system and draw some conclusions as to the future potential for ultra-compact or even lab-on-chip THz systems, for example.

The increasing need for low power and stunningly fast devices in Complementary Metal Oxide Semiconductor Very large Scale Integration (CMOS VLSI) circuits, directs the stream towards scaling of the same. However scaling at sub-micro level and nano level pose quantum mechanical effects and thereby limits further scaling of CMOS circuits. Researchers look into new aspects in nano regime that could effectively resolve this quandary. One such technology that looks promising at nano-level is the quantum dot cellular automata (QCA). The basic operation of QCA is based on transfer of charge rather than the electrons itself. The wave nature of these electrons and their uncertainty in device operation demands a probabilistic approach to study their operation. The data is assigned to a QCA cell by positioning two electrons into four quantum dots. However the site in which the electrons settles is uncertain and depends on various factors. In an ideal state, the electrons position themselves diagonal to each other, through columbic repulsion, to a low energy state. The quantum cell is said to be polarized to +1 or -1, based on the alignment of the electrons. In this thesis, we put forth a probabilistic model to design sequential QCA in Bayesian networks. The timing constraints inherent in sequential circuits due to the feedback path, makes it difficult to assign clock zones in a way that the outputs arrive at the same time instant. Hence designing circuits that have many sequential elements is time consuming. The model presented in this paper is fast and could be used to design sequential QCA circuits without the need to align the clock zones. One of the major advantages of our model lies in its ability to accurately capture the polarization of each cell of the sequential QCA circuits. We discuss the architecture of some of the basic sequential circuits such as J-K flip flop (FF), RAM memory cell and s27 benchmark circuit designed in QCADesigner. We analyze the circuits using a state-of-art Dynamic Bayesian Networks (DBN). To our knowledge this is the first time sequential circuits are analyzed using DBN. For the first time, Estimated Posterior Importance Sampling Algorithm (EPIS) is used to determine the probabilistic values, to study the effect due to variations in physical dimension and operating temperature on output polarization in QCA circuits.

The problem of spin manipulation via the spin-orbit interaction in nonmagnetic semiconductors in the absence of magnetic fields is investigated in this work. We begin with a review of the literature on spin dynamics in semiconductors, then discuss the semi-empirical k ⋅ p method of calculating direct-gap semiconductor properties, which we use to estimate material parameters significant for manipulation of spin even in the absence of a magnetic field. The total effective magnetic fields and precession lengths are calculated for a variety of quantum well orientations, and a class of devices are proposed that will allow for all-electric arbitrary manipulation of spin orientations. The strain- and momentum-dependent spin splitting coefficient C3 has been calculated using a fourteen band Kane k⋅p model for a variety of III-V semiconductors as well as ZnSe and CdSe. It is observed that the spin-splitting parameters C3 and γ, corresponding to the strain-induced spin-orbit interaction and Dresselhaus coefficient, are sensitive to the value of the inter-band spin-orbit coupling Δ− between the p valence and p̄ second conduction band in all cases. The value of Δ− has therefore been recalculated in these materials using a tight-binding model and modern experimental values of the valence and second conduction band spin-orbit splittings. The total effective magnetic field and precession length of spins in strained quantum wells in the (001), (110), and (111) planes are derived with consideration for all known effective magnetic fields except those due to interface effects in non- common-atom heterostructures (native inversion asymmetry). The orientation of the k-linear Dresselhaus field and the strain-dependent fields vary strongly with the growth axis of the quantum well. The precession length in the (110) and (001) cases can achieve infinite anisotropy, while the precession length of (111) quantum wells is always isotropic. We find that the electronic spin rotation induced by drift transport around a closed path in a wide variety of nonmagnetic semiconductors at zero magnetic field depends solely on the physical path taken. Physical paths that produce any possible spin rotation due to transport around a closed path are constructed for electrons experiencing strain or electric fields in (001), (110), or (111)-grown zinc blende semiconductor quantum wells. Spin decoherence due to travel along the path is negligible compared to the background spin decoherence rate. The small size of the designed paths (< 100 nm scale in GaAs) may lead to applications in nanoscale spintronic circuits.

The thesis looks at the question asking for the computability of the dot-depth of star-free regular languages. Here one has to determine for a given star-free regular language the minimal number of alternations between concatenation on one hand, and intersection, union, complement on the other hand. This question was first raised in 1971 (Brzozowski/Cohen) and besides the extended star-heights problem usually refered to as one of the most difficult open questions on regular languages. The dot-depth problem can be captured formally by hierarchies of classes of star-free regular languages B(0), B(1/2), B(1), B(3/2),... and L(0), L(1/2), L(1), L(3/2),.... which are defined via alternating the closure under concatenation and Boolean operations, beginning with single alphabet letters. Now the question of dot-depth is the question whether these hierarchy classes have decidable membership problems. The thesis makes progress on this question using the so-called forbidden pattern approach: Classes of regular languages are characterized in terms of patterns in finite automata (subgraphs in the transition graph) that are not allowed. Such a characterization immediately implies the decidability of the respective class, since the absence of a certain pattern in a given automaton can be effectively verified. Before this work, the decidability of B(0), B(1/2), B(1) and L(0), L(1/2), L(1), L(3/2) were known. Here a detailed study of these classes with help of forbidden patterns is given which leads to new insights into their inner structure. Furthermore, the decidability of B(3/2) is proven. Based on these results a theory of pattern iteration is developed which leads to the introduction of two new hierarchies of star-free regular languages. These hierarchies are decidable on one hand, on the other hand they are in close connection to the classes B(n) and L(n). It remains an open question here whether they may in fact coincide. Some evidence is given in favour of this conjecture which opens a new way to attack the dot-depth problem. Moreover, it is shown that the class L(5/2) is decidable in the restricted case of a two-letter alphabet. / Die Arbeit beschaeftigt sich mit der Frage nach der Berechenbarkeit der Punkttiefe sternfreier regulaerer Sprachen. Dabei handelt es sich um die Aufgabe, zu einer gegebenen sternfreien regulaeren Sprache die minimal moegliche Anzahl von Wechseln zwischen den Operationen Konkatenation einerseits und Durchschnitt, Vereinigung, Komplement andererseits in einem sternfreien regulaeren Ausdruck fuer die gegebene Sprache zu bestimmen. Diese Frage wurde 1971 erstmals aufgeworfen (Brzozowski/Cohen) und gilt neben dem Problem der erweiterten Sternhoehe als eine der schwierigsten offenen Fragen der Theorie der regulaeren Sprachen. Formal fassen laesst sich das Problem der Punkttiefe durch Hierarchien von Klassen sternfreier regulaerer Sprachen B(0), B(1/2), B(1), B(3/2),...sowie L(0), L(1/2), L(1), L(3/2),.... die - ausgehend von einzelnen Buchstaben - mittels Alternierung zwischen Konkatenation und Booleschen Operationen definiert sind. Die Frage nach der Punkttiefe wird hier zur Frage nach der Entscheidbarkeit der Hierarchieklassen. In der Arbeit werden neue Fortschritte mittels sogenannter Verbotsmuster erzielt. Bei diesem Ansatz werden Klassen regulaerer Sprachen dadurch charakterisiert, dass in den zugehoerigen endlichen Automaten bestimmte Muster (Teilgraphen des Ueberfuehrungsgraphen) verboten werden. Gelingt eine solche Charakterisierung, folgt unmittelbar die Entscheidbarkeit der Klasse, da das Nichtvorhandensein eines Musters in einem gegebenen endlichen Automaten effektiv geprueft werden kann. Bisher war die Entscheidbarkeit von B(0), B(1/2), B(1) und L(0), L(1/2), L(1), L(3/2) bekannt. Mit Hilfe von Verbotsmustern erfolgt eine genaue Untersuchung dieser Klassen, die zu neuen Erkenntnissen ueber ihre innere Struktur fuehrt. Darueberhinaus gelingt der Nachweis der Entscheidbarkeit von B(3/2). Basierend auf diesen Ergebnissen wird eine Theorie der Verbotsmusteriteration entwickelt, die zur Einfuehrung von zwei neuen Hierarchien sternfreier regulaerer Sprachen fuehrt. Diese neuen Hierarchien sind zum einen entscheidbar, zum anderen stehen sie in enger Beziehung zu den Klassen B(n) und L(n). Es bleibt an dieser Stelle eine offene Frage, ob sie eventuell sogar mit ihnen uebereinstimmen. Fuer diese Vermutung werden einige Indizien gesammelt und somit ein neuer Weg fuer eine moegliche Loesung des Problems der Punkttiefe aufgezeigt. In diesem Zusammenhang erfolgt auch erstmals der Nachweis der Entscheidbarkeit der Klasse L(5/2) im eingeschraenkten Fall eines zweielementigen Alphabets.