Aspects of the Middle and Upper Pleistocene of the Upper Ouse Basin

The thesis undertakes a lithostratigraphical examination of terrace and fluvioglacial gravels of the Upper Great Ouse basin, and part of the Nene basin, in order to provide a foundation for a Middle and Upper Pleistocene stratigraphy of a relatively little-researched area. Pebble-counts are used as a basis for Stratigraphie interpretation following the work of Green and McGregor on the terrace gravels of the Proto-Thames. The thesis first examines the characteristics of the study area which influence superficial deposits. This is followed by a discussion of previous research in surrounding areas so that comparisons and correlations may subsequently be made. Field and laboratory methods employed are discussed, and each site sampled is described. The analysis of the gravel is divided into two parts. Firstly the lithological composition of each sample is ascertained. Each lithology present is described and the probable source geology discussed. Secondly the lithological composition of all samples is compared in order to determine the spatial patterns (using trend surface analysis) and the stratigraphical patterns (using cluster analysis) among the samples. The statistical tests involved are discussed and the results of the analyses are described and interpreted with particular reference to the source geology. At Stoke Goldington, an interglacial deposit of richly-organic clay is reported which contains a wide range of fauna and flora. Associated with the clay are two separate suites of gravel. A description of the site is presented together with a preliminary report on the biological evidence. Finally, the lithostratigraphic results, together with the biological evidence from Stoke Goldington, and evidence from the literature of the Ouse basin and surrounding areas are brought together, and a succession incorporating all the available evidence is presented. Correlations with the surrounding regions are suggested.<p

Increasing Light Absorption and Collection Using Engineered Structures

In recent years we have witnessed an explosion of interest in two dimensional (2D) materials, due to their unique physical properties. Excitement surrounds the promise of replacing conventional bulk photodetectors with devices based on 2D materials, allowing better integration, flexibility and potentially improving performance. However, the low inherent light absorption of 2D materials is an outstanding issue to be solved. In this chapter we review two independent approaches to tackling this problem, which have the potential to be combined to find a robust solution. The first approach involves patterning the substrate with a rod-type photonic crystal (PhC) cavity structure, which is shown to increase the light absorption into a 2D material flake coupled spatially to the cavity mode. Secondly, we review 2D–compatible solid immersion lenses (SILs) and their ability to increase both the optical magnification of the structures they encapsulate, and the longevity of the material. SILs have been shown to reduce the requirements for complex optics in the implementation of 2D materials in optoelectronic devices, and also in preserving the photodetector’s optical performance over long periods of time. Finally, we show how by combining rod-type PhC cavities with SILs, we can improve the performance of 2D material-based photodetectors

Solid Waste Management (SWM) Options: The Economics of Variable Cost and Conventional Pricing Systems in Maine

Solid waste management has been influenced by the growing trend to apply market-based incentives to environmental problems. The impetus to reform solid waste management procedures in part stems from the increasing costs associated with solid waste disposal, thus encouraging municipalities to seek innovative ways to reduce solid waste generation. One method adopted by numerous municipalities in Maine is known as variable cost pricing. Alternatively, this system is referred to as unit pricing, volume-based fees, and pay-by-the-bag (PB). Under this system, waste collection fees are based on the volume of solid waste disposal. A household\u27s solid waste disposal costs change with the number of bags of waste disposed since each bag is assessed a fee. As a result, the less trash set out for disposal, the lower the cost to the resident

Mapping the e-Learning Assessment Domain: Concept Maps for Orientation and Navigation

Concept or Topic Maps have long been used as a method of categorizing and organizing information about a domain. Building them can help people conceptualize an area and spot trends or gaps, and as a presentation method they quickly provide an overview and general impression of a space. We are currently constructing a Reference Model of the Assessment Domain that takes the form of a highly interlinked dynamic website. This represents the assessment domain via the software, projects, standards and use cases of which it is composed. In this paper we present our efforts to create complimentary concept maps of the assessment domain, not as an overview, but for navigation and orientation within the domain. These concept maps, which model resources and activities independently, have been corroborated with practitioners in the e-learning community

Photonic crystals for enhanced light extraction from 2D materials

In recent years, a range of two-dimensional (2D) transition metal dichalcogenides (TMDs) have been studied, and remarkable optical and electronic characteristics have been demonstrated. Furthermore, the weak interlayer Van der Waals interaction allows TMDs to adapt to a range of substrates. Unfortunately, the photons emitted from these TMD monolayers are difficult to efficiently collect into simple optics, reducing the practicality of these materials. The realization of on-chip optical devices for quantum information applications requires structures that maximize optical extraction efficiently whilst also minimizing substrate loss. In this work we propose a photonic crystal cavity based on silicon rods that allows maximal spatial and spectral coupling between TMD monolayers and the cavity mode. Finite difference time domain (FDTD) simulations revealed that TMDs coupled to this type of cavity have highly directional emission towards the collection optics, as well as up to 400% enhancement in luminescence intensity, compared to monolayers on flat substrates. We consider realistic fabrication tolerances and discuss the extent of the achievable spatial alignment with the cavity mode field maxima

Increasing quantum light extraction from TMDC's

Much of the recent explosion of research into 2D semiconductor materials has focused on direct bandgap materials such as monolayers of transition metal dichalcogenides (TMDCs), which show great promise in optoelectronic devices such as ultra-thin LEDs [1, 2]. Extraction of light out of these structures can be enhanced in the near field through the integration of these monolayers into waveguides, cavities, or photonic crystals [3]; however these methods are not ideal as they require costly and time consuming processing. Furthermore none of these methods allow you to observe the light directly, therefore are unhelpful in certain applications, such as quantum unique devices [4]. The research we present demonstrates a solution to this problem by encapsulating a range of two-dimensional materials in Solid Immersion Lenses (SILs), dynamically-shaped from UV cure epoxy. We show that the advantages of using SILs formed in this way are numerous, with the most prominent being they can be deterministically placed and directly tuned, to ensure the extraction efficiency is maximised. We will also present detailed photoluminescence maps showing how the reduction of laser spot size caused by focusing through a SIL can allow for very detailed mapping of WSe2 multilayer structures

Engineering of Chinese Hamster Ovary Cells With NDPK-A to Enhance DNA Nuclear Delivery Combined With EBNA1 Plasmid Maintenance Gives Improved Exogenous Transient Reporter, mAb and SARS-CoV-2 Spike Protein Expression

Transient gene expression (TGE) in mammalian cells is a method of rapidly generating recombinant protein material for initial characterisation studies that does not require time-consuming processes associated with stable cell line construction. High TGE yields are heavily dependent on efficient delivery of plasmid DNA across both the plasma and nuclear membranes. Here, we harness the protein nucleoside diphosphate kinase (NDPK-A) that contains a nuclear localisation signal (NLS) to enhance DNA delivery into the nucleus of CHO cells. We show that co-expression of NDPK-A during transient expression results in improved transfection efficiency in CHO cells, presumably due to enhanced transportation of plasmid DNA into the nucleus via the nuclear pore complex. Furthermore, introduction of the Epstein Barr Nuclear Antigen-1 (EBNA-1), a protein that is capable of inducing extrachromosomal maintenance, when coupled with complementary oriP elements on a transient plasmid, was utilised to reduce the effect of plasmid dilution. Whilst there was attenuated growth upon introduction of the EBNA-1 system into CHO cells, when both NDPK-A nuclear import and EBNA-1 mediated technologies were employed together this resulted in enhanced transient recombinant protein yields superior to those generated using either approach independently, including when expressing the complex SARS-CoV-2 spike (S) glycoprotein

Relatively low-temperature processing and its impact on device performance and reliability

Non-silicon, large-area/flexible electronics for the internet of things (IoT) has acquired substantial attention in recent years. Key electron devices to enable this technology include metal-oxide-semiconductor field effect transistors (MOSFETs), where ultra-thin and/or low-dimensional (i.e., 2D to a few layers) semiconductor materials may be required, like those found in thin-film transistors (TFTs) and transition metal dichalcogenide (TMD) FETs [1,2]. Whether TFT or TMDFET, a relatively low-temperature process commensurate with large-area/flex applications to enable large (i.e., greater than 300 mm) and/or flexible substrate fabrication is required. Furthermore, TMD materials may be implemented as the channel semiconductor to function as an ultra-thin body to mitigate short channel effects and extend further scaling as the future progresses in CMOS scaling. In addition, the gate dielectric insulator is another vital component of any MOSFET that requires investigation as part of the MOS stack in these types of transistors. Lastly, semiconductor materials mentioned herein do not have a universally accepted way to introduce dopants to form sources and drains. Thus, metal-semiconductor contacts are employed where the interface region of the contact plays a critical role in determining the conductivity/resistivity of the contact. Moreover, how the metal-semiconductor interface are formed also impacts the quality of the contact. Therefore, exploration of low-temperature processing, interfaces, and their impact on device performance and reliability will be critical to eventual implementation in future technologies. To ascertain the impact of low-temperature fabrication and critical interfaces, several process approaches and electrical characterization methods were employed [1-6]. In one case, for a TMD FET contact study, an oxygen plasma exposure in the contact region on MoS2 (a TMD material) is done prior to titanium deposition. The results demonstrate that contaminants and photoresist residue that still reside after development can noticeably impact electrical performance (Fig. 1). The O2 plasma removes the residue present at the surface of MoS2 without the use of a high temperature anneal, and subsequently improves the device performance significantly (Fig. 1) [1]. In another case, for a MOS-based TFT study, an investigation of low-temperature (\u3e 115°C) deposited zinc-based semiconductors was executed (Fig. 2). For ZnO and IGZO, saturation mobilities of 14.4 and 8.4 cm2/V-s, along with threshold voltages of 2.2 V and 2.0 V were obtained, respectively, demonstrating robust devices that also have an on/off ratio \u3e 108, with IOFF lower than 10-12 A. Furthermore, a hot carrier stress methodology demonstrated threshold voltage (VTH) shifts of 0.4 V and 1.8 V for ZnO and IGZO, respectively, after stress (Fig. 2) [2]. Continued research is required to ascertain the electrically active defects responsible for the VTH shift. Please click Additional Files below to see the full abstract