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Variation in the local motion statistics of real-life optic flow scenes
No full textOptic flow motion patterns can be a rich source of information about our own movement and about the structure of the environment we are moving in. We investigate the information available to the brain under real operating conditions by analysing video sequences generated by physically moving a camera through various typical human environments. We consider to what extent the motion signal maps generated by a biologically plausible, two-dimensional array of correlation-based motion detectors (2DMD) not only depend on egomotion, but also reflect the spatial setup of such environments. We analysed the local motion outputs by extracting the relative amounts of detected directions and comparing the spatial distribution of the motion signals to that of idealized optic flow. Using a simple template matching estimation technique, we are successfully able to extract the focus of expansion (FOE) and find relatively small errors that are distributed in characteristic patterns in different scenes. This shows that all types of scenes provide suitable motion information for extracting ego motion despite the substantial levels of noise affecting the motion signal distributions - attributed to the sparse nature of optic flow and the presence of camera jitter. However, there are large differences in the shape of the direction distributions between different types of scenes, in particular man-made office scenes are heavily dominated by directions in the cardinal axes, which is much less apparent in outdoors forest scenes. Further examination of motion magnitudes at different scales and the location of motion information in a scene revealed different patterns across different scene categories. This suggests that self-motion patterns are not only relevant for deducing heading direction and speed, but also provide a rich information source for scene structure and could be important for rapid formation of the gist of a scene under normal human locomotion
Data acquisition and readout system for the LUX dark matter experiment
No full textLUX is a two-phase (liquid/gas) xenon time projection chamber designed to detect nuclear recoils from interactions with dark matter particles. Signals from the LUX detector are processed by custom-built analog electronics which provide properly shaped signals for the trigger and data acquisition (DAQ) systems. The DAQ is composed of commercial digitizers with firmware customized for the LUX experiment. Data acquisition systems in rare-event searches must accommodate high rate and large dynamic range during precision calibrations involving radioactive sources, while also delivering low threshold for maximum sensitivity. The LUX DAQ meets these challenges using real-time baseline suppression that allows for a maximum event acquisition rate in excess of 1.5 kHz with virtually no deadtime. This paper describes the LUX DAQ and the novel acquisition techniques employed in the LUX experiment
Small epitaxial graphene devices for magnetosensing applications
No full textHall sensors with the width range from 0.5 to 20.0 μm have been fabricated out of a monolayer graphene epitaxially grown on SiC. The sensors have been studied at room temperature using transport and noise spectrum measurements. The minimum detectable field of a typical 10-μm graphene sensor is ≈2.5 μT/√Hz, making them comparable with state of the art semiconductor devices of the same size and carrier concentration and superior to devices made of CVD graphene. Relatively high resistance significantly restricts performance of the smallest 500-nm devices. Carrier mobility is strongly size dependent, signifying importance of both intrinsic and extrinsic factors in the optimization of the device performance
Cryptic Bumblebee Species: Consequences for Conservation and the Trade in Greenhouse Pollinators
No full textCommercial greenhouse growers in both Japan and China are increasingly using reared orange-tailed bumblebees known previously as Bombus hypocrita Perez as pollinators. Phylogenetic analysis of the DNA (COI) barcodes with Bayesian methods shows that this "species" is a long-standing confusion of two cryptic species. We find that the orange-tailed bumblebees in North China are actually part of the widespread Russian (otherwise white-tailed) B. patagiatus Nylander (as B. patagiatus ganjsuensis Skorikov, n. comb.), whereas the orange-tailed bees in Japan are true B. hypocrita. This situation has been further complicated because two other cryptic species from North China that were previously confused with the Russian B. patagiatus are now recognised as separate: B. lantschouensis Vogt n. stat. and B. minshanensis Bischoff n. stat.. As demand for pollination services by greenhouse growers inevitably increases, these bees are more likely to be transported between countries. In order to conserve genetic resources of pollinator species for their option value for future food security, we advocate preventing trade and movement of B. patagiatus from China into Japan and of B. hypocrita from Japan into China
Magnetic Coulomb Fields of Monopoles in Spin Ice and Their Signatures in the Internal Field Distribution
No full textFractionalization-the breaking up of an apparently indivisible microscopic degree of freedom-is one of the most counterintuitive phenomena in many-body physics. Here we study its most fundamental manifestation in spin ice, the only known fractionalized magnetic compound in 3D: we directly visualize the 1/r(2) magnetic Coulomb field of monopoles that emerge as the atomic magnetic dipoles fractionalize. We analyze the internal magnetic field distribution, relevant for local experimental probes. In particular, we present new zero-field NMR measurements that exhibit excellent agreement with the calculated line shapes, noting that this experimental technique can in principle measure directly the monopole density in spin ice. The distribution of field strengths is captured by a simple analytical form that exhibits a low density of low-field sites-in apparent disagreement with reported muon spin rotation results. Counterintuitively, the density of low-field locations decreases as the local ferromagnetic correlations imposed by the ice rules weaken
An Evaluation of ASEAN's Progress in Regional Community Building: Implications of Thailand's Bilateral Relations and the Extent of Civil Society Participation in Regionalism
No full textThis thesis seeks to evaluate the progress of regional community building in Southeast Asia, which has been undertaken by the Association of Southeast Asians (ASEAN). The thesis analyses the extent to which there has been a shift from policies and processes associated with “old regionalism” (state-security-economic centred regionalism) towards those which are associated with “new regionalism” and a regional community (the widening of regionalism to non-state actors, and expansion of regional cooperation into new areas, and regional solidarity). The first half of the thesis demonstrates the persistence of “old regionalism,” based on a tendency to differentiate others as an external security threat in Thailand’s bilateral relations. This tendency is driven by a deeply embedded historical legacy of differentiation, which is pursued by state actors for domestic political interests, as well as on-going bilateral disputes, and a militarised border. The second half of the thesis tests the significance of “new regionalism,” based on three case studies on civil society participation in regional community building. These case studies demonstrate how “new regionalism” is significant in form, rather than in substance, and how progress in community building is mainly driven by the more democratic ASEAN member states. Visible progress in community building includes the emergence of ASEAN-CSO meetings, an ASEAN Intergovernmental Commission on Human Rights (AICHR), and a transnational civil society network (TCSN), which is increasing society’s regional awareness and society’s participation in regionalism. However, substantive progress is lacking, due to the region’s political diversity and the prioritization of regional unity over the realization of a people-oriented ASEAN Community. Thus, ASEAN community building is empty in substance, due to the continuation of politically motivated differentiation and border insecurity, symbolic meetings between states and CSOs, a powerless regional human rights body, and the remaining gap between regional declarations and policy implementation
Investigation of Coherent Diffraction Radiation from a dual target system at CTF3 and its application for longitudinal bunch profile diagnostics.
No full textRising to the Adaptation Challenge? Responding to Global Environmental Change in eThekwini and Ugu Municipalities, South Africa.
No full textIn response to rising concerns about adverse global environmental change (GEC), or climate change (CC) impacts, adaptation and mitigation measures are being widely implemented. However, much still needs to be understood about how these measures manifest in reality at various scales and the drivers and barriers to action in specific contexts. This thesis uses multiple social science research methods to investigate responses to GEC/CC, with a particular emphasis on adaptation and underlying development contexts, within the neighbouring Ugu and eThekwini local government districts in KwaZulu-Natal province, South Africa. The study’s focus on local authorities and communities is pertinent given that many adaptation and some mitigation actions are ultimately undertaken at local scales. The thesis comprises two main layers of analysis: first, a comparative analysis of Ugu and eThekwini municipalities’ GEC/CC responses and an investigation of the relationship between these municipalities regarding environmental and GEC agendas, and the likely effect of collaboration or lack thereof on GEC adaptation initiatives. Second, incorporating these municipal-scale findings, I explore understandings and responses to climate variability and change and their likely effects within several diverse local study sites across rural-urban continua within both municipalities. The results show that, despite their close proximity, the two municipalities have responded to GEC in very different ways and that municipal authorities, together with their respective diverse local populations, have divergent adaptive capacities. The research also reveals that horizontal inter-municipal collaboration and vertical collaboration between multiple government spheres is weak. The thesis suggests that strengthening such collaboration within a multi-level governance framework can facilitate effective adaptation and address current divergent municipal adaptive capacities. The thesis also reveals the importance for GEC measures to account for the diversity of understandings, responses and vulnerabilities to GEC amongst local populations, shaped by multiple climatic and non-climatic stresses, including cultural beliefs
Congruency and typicality effects in lexical decision
No full textThis thesis describes basic research into visual word recognition and decision making. Determining the best matching lexical representation for a given stimulus involves interactions between representations. The standard task for studying these processes is the lexical decision task (LDT), but there is still debate regarding the factors that affect how individuals make lexical decisions. The nature of lexical interactions and the processes underlying lexical decision-making were addressed here by testing response congruency effects in the masked priming variant of the LDT.
The results of seven masked priming experiments showed a robust response congruency effect that depends on the difficulty of the word-nonword discrimination. This finding resolved apparent inconsistencies in previous research. The experiments were simulated using the Bayesian Reader and the Spatial Coding Model (SCM). The probability based Bayesian Reader model failed to accommodate the findings. However, a good fit to the data was provided by a modified version of the SCM in which the assumptions regarding the nature of lexical interactions were changed such that word nodes inhibit only (closely) related competitors. The model also assumes that the difficulty of the word-nonword discrimination affects the degree to which stimulus typicality informs lexical decisions.
A critical issue for these experiments involved the definition of orthographic typicality. An algorithm for measuring orthographic typicality and for generating nonwords with a specific level of orthographic typicality (OT3) was developed. An unprimed LDT experiment showed that OT3 affected decision latency even when other standard measures of orthographic typicality were controlled. Two additional masked priming experiments showed that highly typical primes lead to faster word responses and slower nonword responses than less typical primes. Overall, the results of this research enhance our understanding of the processes underlying visual word recognition and lexical decision making, and also have important methodological implications for the field
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