Modeling multiphase flow and substrate deformation in nanoimprint manufacturing systems

Nanopatterns found in nature demonstrate that macroscopic properties of a surface are tied to its nano-scale structure. Tailoring the nanostructure allows those macroscopic surface properties to be engineered. However, a capability-gap in manufacturing technology inhibits mass-production of nanotechnologies based on simple, nanometer-scale surface patterns. This gap represents an opportunity for research and development of nanoimprint lithography (NIL) processes. NIL is a process for replicating patterns by imprinting a fluid layer with a solid, nano-patterned template, after which ultraviolet cure solidifies the fluid resulting in a nano-patterned surface. Although NIL has been demonstrated to replicate pattern features as small as 4 nm, there are significant challenges in using it to produce nanotechnology. Ink-jet deposition methods deliver the small fluid volumes necessary to produce the nanopattern, and drop volumes can be tuned to what the pattern requires. However the drops trap pockets of gas as they merge and fill the template, and due to relatively slow gas dissolution, reduce processing throughput. Capillary forces that arise from the gas-liquid interfaces drive non-uniform gap closure and the resulting variations in residual layer reduces process yield or degrades product performance. This thesis develops reduced-order models for fluid flow and structural mechanics of the imprint process for NIL. Understanding key phenomena of gas trapping and residual layer non-uniformity drives model development to better understand how throughput and yield can be improved. Reynolds lubrication theory, the \textit{disperse} type of multiphase flow, and a lumped-parameter model of dissolution unite to produce a two-phase flow model for NIL simulations of 10,000 drops per $\text{cm}^2$. Qualitative agreement between simulation and experiment provides a modicum of validation of this model for flow in NIL simulations. The two-phase model simulations predicts that both dissolution and viscous resistance affect throughput. The coupling of a reduced-order model for 3D structural mechanics with the two-phase flow model enables simulations of drop merger on a free-span tensioned web. Challenges in improving the structural model lead to formulation of a 2D model for which sources of instability are more easily discovered and understood. Inextensible cylindrical shell theory and lubrication theory combine into a model for the elastohydrodynamics of a rolling-imprint modality of NIL. Foil-bearing theory describes the lubrication layer that forms between a thin, tensioned web moving past another surface. Reproduction of the results of foil-bearing theory validates this coupled model and reveals a highly predictable region of uniformity that provides low shear stress conditions ideal for UV-cure. These results show theoretical limitations that are used to construct a processing window for predicting process feasibility

The design and characterisation of miniature robotics for astronomical instruments

Micro robotics has the potential to improve the efficiency and reduce cost of future multi-object instruments for astronomy. This thesis reports on the development and evolution of a micro autonomous pick-off mirror called the Micro Autonomous Positioning System (MAPS) that can be used in a multi-object spectrograph. The design of these micro-autonomous pick-off mirrors is novel as they are capable of high precision positioning using electromagnetic propulsion through utilising non-conventional components and techniques. These devices are self-driven robotic units, which with the help of an external control system are capable of positioning themselves on an instruments focal plane to within 24 μm. This is different from other high precision micro robotics as they normally use piezoelectric actuators for propulsion. Micro robots have been developed that use electromagnetic motors, however they are not used for high precision applications. Although there is a plethora of literature covering design, functionality and capability of precision micro autonomous systems, there is limited research on characterisation methods for their use in astronomical applications. This work contributes not only to the science supporting the design of a micro-autonomous pick-off mirror but also presents a framework for characterising such miniature mechanisms. The majority of instruments are presented with a curved focal plane. Therefore, to ensure that the pick-off mirrors are aligned properly with the receiving optics, either the pick-off mirror needs to be tipped or the receiving optics repositioned. Currently this function is implemented in the beam steering mirror (i.e. the receiving optics). The travel range required by the beam steering mirror is relatively large, and as such, it is more difficult to achieve the positional accuracy and stability. By incorporating this functionality in the pick-off mirror, the instrument can be optimised in terms of size, accuracy and stability. A unique self-adjusting mirror (SAM) is thus proposed as a solution and detailed. As a proof-of-concepts both MAPS and SAM usability in multi-object spectrographs was evaluated and validated. The results indicate their potential to meet the requirements of astronomical instruments and reduce both the size and cost

hnRNP E1 and E2 have distinct roles in modulating HIV-1 gene expression

Pre-mRNA processing, including 5' end capping, splicing, and 3' end cleavage/polyadenylation, are events coordinated by transcription that can influence the subsequent export and translation of mRNAs. Coordination of RNA processing is crucial in retroviruses such as HIV-1, where inefficient splicing and the export of intron-containing RNAs are required for expression of the full complement of viral proteins. RNA processing can be affected by both viral and cellular proteins, and in this study we demonstrate that a member of the hnRNP E family of proteins can modulate HIV-1 RNA metabolism and expression. We show that hnRNP E1/E2 are able to interact with the ESS3a element of the bipartite ESS in tat/rev exon 3 of HIV-1 and that modulation of hnRNP E1 expression alters HIV-1 structural protein synthesis. Overexpression of hnRNP E1 leads to a reduction in Rev, achieved in part through a decrease in rev mRNA levels. However, the reduction in Rev levels cannot fully account for the effect of hnRNP E1, suggesting that hmRNP E1 might also act to suppress viral RNA translation. Deletion mutagenesis determined that the C-terminal end of hnRNP E1 was required for the reduction in Rev expression and that replacing this portion of hnRNP E1 with that of hnRNP E2, despite the high degree of conservation, could not rescue the loss of function

Irish Passage tombs : Neolithic images, contexts and beliefs

This thesis seeks to take the motifs on Irish Passage tombs beyond their traditional role as passive epiphenomenon and furthers understands them as performing active roles in the Neolithic. Rather than view the images through a textual representational analogy, I utilise visual cultural and neurological studies, set within a worldview perspective to paint a picture of the possible ambiguities of life and belief at some passage tomb locations. I explore the richness of evidence from the archaeological data and literature, to move beyond previous positions, and suggest new ways to deal with a past that develops multiple narratives. Such an account is thick with paradoxes, similarities, differences, tensions, emotions, life, death, pleasures and pain. Visions, context and belief layered together often generate ruptures in daily life that can facilitate new imaginings within the rhythms and sequences of images. Within such a perspective the Irish passage tomb motifs present fresh conditions for possibility and diverse understanding. In combining broader and more fine-grained analysis of particular passage tomb sites located in the north, east and south of Ireland, I demonstrate that social complexities operate at all scales. Magnified via cosmological perspectives, images on passage tombs interact with spectators through two-way intimate engagements. The assemblages that accompany the motifs are not static, instead they display notions of material animacy. Humans do not control all these interactions, for the motifs and objects are dynamic montages. These actions can be enhanced via process, such as the sequential nature of some images or by the application of liquid solutions, especially when conducted at particular times and places. With passage tombs acting as 'stages' and 'islandscapes', I construct interpretations that include both carnivalesque and axis mundi environments, which subvert, disrupt and perpetuate social beliefs. Such performances may have created dialogues and myths about the specialness of these places. These conversations would in turn factor and texture new illusions and simulations of the world, whilst creating fresh opportunities for experience.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Irish Passage tombs : Neolithic images, contexts and beliefs.

This thesis seeks to take the motifs on Irish Passage tombs beyond their traditional role as passive epiphenomenon and furthers understands them as performing active roles in the Neolithic. Rather than view the images through a textual representational analogy, I utilise visual cultural and neurological studies, set within a worldview perspective to paint a picture of the possible ambiguities of life and belief at some passage tomb locations. I explore the richness of evidence from the archaeological data and literature, to move beyond previous positions, and suggest new ways to deal with a past that develops multiple narratives. Such an account is thick with paradoxes, similarities, differences, tensions, emotions, life, death, pleasures and pain. Visions, context and belief layered together often generate ruptures in daily life that can facilitate new imaginings within the rhythms and sequences of images. Within such a perspective the Irish passage tomb motifs present fresh conditions for possibility and diverse understanding. In combining broader and more fine-grained analysis of particular passage tomb sites located in the north, east and south of Ireland, I demonstrate that social complexities operate at all scales. Magnified via cosmological perspectives, images on passage tombs interact with spectators through two-way intimate engagements. The assemblages that accompany the motifs are not static, instead they display notions of material animacy. Humans do not control all these interactions, for the motifs and objects are dynamic montages. These actions can be enhanced via process, such as the sequential nature of some images or by the application of liquid solutions, especially when conducted at particular times and places. With passage tombs acting as 'stages' and 'islandscapes', I construct interpretations that include both carnivalesque and axis mundi environments, which subvert, disrupt and perpetuate social beliefs. Such performances may have created dialogues and myths about the specialness of these places. These conversations would in turn factor and texture new illusions and simulations of the world, whilst creating fresh opportunities for experience

Challenges and Opportunities for CubeSat Detection for Space Situational Awareness using a CNN

The deployment of artificial neural networks (ANNs) on small satellites will improve space situational awareness (SSA) where scarce radio resources limits the interactions between space-born and ground-based systems. The application of ANNs in space is stymied by lack of curated datasets. This project addresses an ongoing problem of small spacecraft detection and identification. This paper will present the problem and the activities the team has taken to advance this field