339 research outputs found
Data for the publication "Statistical Reproducibility of Selective Area Grown InAs Nanowire Devices"
No full textNew approaches such as selective area growth, where crystal growth is lithographically controlled, allow the integration of bottom-up grown semiconductor nanomaterials in large-scale classical and quantum nanoelectronics. This calls for assessment and optimization of the reproducibility between individual components. We quantify the structural and electronic statistical reproducibility within large arrays of nominally identical selective area growth InAs nanowires. The distribution of structural parameters is acquired through comprehensive atomic force microscopy studies and transmission electron microscopy. These are compared to the statistical distributions of the cryogenic electrical properties of individual SAG nanowire field effect transistors addressed using cryogenic multiplexer circuits. Correlating measurements between successive thermal cycles allows distinguishing between the contributions of surface impurity scattering and fixed structural properties to device reproducibility. The results confirm the potential of SAG nanomaterials, and the methodologies for quantifying statistical metrics are essential for further optimization of reproducibility. The .zip file contains the AFM and electrical transport data that was used to support the findings in the associated publication. The AFM data is available in .asc format and can be opened with FOSS software such as Gwyddion or read via python. The transport data is arranged into python dictionaries for easy navigation. A jupyter notebook is included describing the dictionary structure and providing example code for accessing the data. -- Methods, materials and software: AFM, InAs, Gwyddion, pythonPeer reviewe
Initial Plant Growth in Sand Mine Spoil Amended with Peat Moss and Fertilizer Under Greenhouse Conditions: Potential Species for Use in Reclamation
No full textThe Great Lakes Basin exhibits the largest collection of freshwater sand dunes in the world. Sand dunes are ecologically important and support a unique assemblage of flora and fauna. Sand dunes are also economically valuable. However, when sand dunes are mined, soil quality is drastically reduced. Therefore, soil quality improvements followed by revegetation maybe necessary for successful reclamation. This study evaluates the germination and initial growth of 2 legume species, sundial lupine (Lupinus perennis) and Illinois bundleflower (Desmanthus illinoensis), and 2 warm-season grass species, Indian grass (Sorghastrum nutans) and little bluestem (Schizachyrium scoparium), in the presence of 2 soil amendments (inorganic fertilizer and sphagnum peat moss) added to spoil from a local sand mine. We sowed species in pots and propagated them under greenhouse conditions. Results indicate that sundial lupine and Illinois bundleflower exhibited the greatest germination and growth among species. Peat moss had the greatest overall impact on germination and growth while the addition of fertilizer positively affected initial growth. Based on these results, sundial lupine is recognized as a primary candidate for sand mine reclamation, while Illinois bundleflower is also recommended as an appropriate species for revegetation efforts. We recommend using soil amendments that are functionally equivalent to peat in increasing soil water holding capacity. We further suggest that fertilization may be accomplished by including legumes in plant species mixes used for revegetation. Results presented here may help to identify appropriate species and soil amendments for the reclamation of former sand mines or restoration of freshwater sand dunes
Scale-Dependent Growth Modes of Selective Area Grown III-V Nanowires
No full textDue to their flexible geometry, in-plane selective area grown (SAG) nanowires (NWs) encompass the advantages of vapor-liquid-solid NWs and planar structures. The complex interplay of growth kinetics and NW dimensions provides new pathways for crystal engineering; however, their growth mechanisms remain poorly understood. We analyze the growth mechanisms of GaAs(Sb) and InGaAs/GaAs(Sb) in-plane SAG NWs using molecular beam epitaxy (MBE). While GaAs(Sb) NWs consistently follow a layer-by-layer growth, the InGaAs/GaAs(Sb) growth transitions from step-flow to layer-by-layer and layer-plus-island depending on the InGaAs thickness and the NW dimensions. We extract the diffusion lengths of Ga adatoms along the [11̅0] and [110] directions under As2 during GaAs(Sb) growth. Our results indicate that Sb may inhibit the layer-by-layer to step-flow transition. Our findings show that different growth modes can be achieved in the MBE of in-plane SAG NWs grown on the same substrate and highlight the importance of the interplay with NW dimensions
Statistical Reproducibility of Selective Area Grown InAs Nanowire Devices
No full textNew approaches such as selective area growth (SAG), where crystal growth is lithographically controlled, allow the integration of bottom-up grown semiconductor nanomaterials in large-scale classical and quantum nanoelectronics. This calls for assessment and optimization of the reproducibility between individual components. We quantify the structural and electronic statistical reproducibility within large arrays of nominally identical selective area growth InAs nanowires. The distribution of structural parameters is acquired through comprehensive atomic force microscopy studies and transmission electron microscopy. These are compared to the statistical distributions of the cryogenic electrical properties of 256 individual SAG nanowire field effect transistors addressed using cryogenic multiplexer circuits. Correlating measurements between successive thermal cycles allows distinguishing between the contributions of surface impurity scattering and fixed structural properties to device reproducibility. The results confirm the potential of SAG nanomaterials, and the methodologies for quantifying statistical metrics are essential for further optimization of reproducibility
The role of leishmania proteophosphoglycans in sand fly transmission and infection of the Mammalian host.
No full textLeishmania are transmitted by the bite of their sand fly vector and this has a significant influence on the virulence of the resulting infection. From our studies into the interaction between parasite, vector, and host we have uncovered an important missing ingredient during Leishmania transmission. Leishmania actively adapt their sand fly hosts into efficient vectors by secreting Promastigote Secretory Gel (PSG), a proteophosphoglycan (PPG)-rich, mucin-like gel which accumulates in sand fly gut and mouthparts. This has the effect of blocking the fly, such that during bloodfeeding both parasites and gel are co-transmitted in an act of regurgitation. We are discovering that this has further implications for the mammalian infection, again, in favor of the parasite. Experimentally, PSG exacerbates cutaneous and visceral leishmaniasis and can promote the chronicity of Leishmania infection, even in mouse strains normally capable of controlling leishmaniasis. The underlying mechanism of PSG's action is a major focus of our ongoing work. This review aims to synthesize what is known about the role and action of PSG and its constituent proteophosphoglycans, for parasite colonization of the sand fly, transmission, and mammalian infection. Lastly, we discuss potential exploitation of this important vector-transmitted product and future avenues of research
Cryogenic performance of field-effect transistors and amplifiers based on selective area grown InAs nanowires
No full textIndium-arsenide nanowire field-effect transistors (NWFETs) are promising platforms for high-speed, low-power nanoelectronics operating at cryogenic conditions, relevant for quantum information processing. We use selective area growth of nanowires to realize scalable and planar nanowire device geometries that are compatible with standard semiconductor processing techniques. NWFETs are fabricated, and their low temperature characteristics, including I ON / I OFF ratios, threshold voltages, sub-threshold slope, interfacial trap density, hysteresis, and mobility, are characterized. The NWFETs operate effectively in integrated circuitry relying on saturation-mode operation. In sub-threshold applications such as amplifiers, we find bandwidths exceeding our cryostat wiring, but the gate hysteresis presents challenges for precise tuning of the amplifier operating point. We discuss the role of crystal imperfections and fabrication processes on the transistor characteristics and propose strategies for further improvements.Peer reviewe
A Two-Dimensional Superconducting Electron Gas in Freestanding LaAlO<sub>3</sub>/SrTiO<sub>3</sub> Micromembranes
No full textFreestanding oxide membranes constitute an intriguing material platform for new functionalities and allow integration of oxide electronics with technologically important platforms such as silicon. Sambri et al. recently reported a method to fabricate freestanding LaAlO3/SrTiO3 (LAO/STO) membranes by spalling of strained heterostructures. Here, we first develop a scheme for the high-yield fabrication of membrane devices on silicon. Second, we show that the membranes exhibit metallic conductivity and a superconducting phase below ∼200 mK. Using anisotropic magnetotransport we extract the superconducting phase coherence length ξ ≈ 36-80 nm and establish an upper bound on the thickness of the superconducting electron gas d ≈ 17-33 nm, thus confirming its two-dimensional character. Finally, we show that the critical current can be modulated using a silicon-based backgate. The ability to form superconducting nanostructures of LAO/STO membranes, with electronic properties similar to those of the bulk counterpart, opens opportunities for integrating oxide nanoelectronics with silicon-based architectures
Tolerance of the widespread cyanobacterium Nostoc commune to extreme temperature variation (-269 to105 degress C), pH and salt stress
No full textThe light of the eye : doctrine, piety and reform in the works of Thomas Sherlock, Hannah More and Jane Austen
No full textBibliography: leaves 376-401.This thesis investigates the ways in which three eighteenth-century writers, Bishop Thomas Sherlock, Hannah More and Jane Austen embody orthodox Anglican doctrine according to their individual perceptions of the enlightening properties of Protestant Christianity. After situating them in their respective gender, literary and ecclesiastical contexts, I examine some of their key doctrines and analyse excerpts from their works. My selection of passages from Sherlock's works is fairly comprehensive, but in the case of More and Austen, where there is already a formidable body of literary criticism, it is more selective. Thus, I focus on doctrine in More's tracts, Strictures on the System of Female Education, An Essay on St Paul and most especially Coelebs in Search of a Wife and in the case of Austen, on her prayers and select passages from Sense and Sensibility and Mansfield Park. I conclude that, although diverse in their particular kind of Anglicanism (High, Evangelical and Median) and in their choice of genre, transparency or obscurity (anonymity and pseudonymity) and the various narratological strategies some of them invoke to circumvent certain taboos, Sherlock, More and Austen champion the same central orthodox doctrines, defend them against current alternatives to orthodoxy such as Latitudinarianism, Deism and various forms of Freethinking, and promote similar moral and ecclesiastical reforms. However, indirectly (through female characters who resist male representation or control) the women writers subject their ostensibly authorially-endorsed male narrators/characters to scrutiny and sometimes (when the males objectify the women) subversion
Field experiments at three sites to investigate the effects of age on steel piles driven in sand
No full textThis paper investigates the influences that steel type, in-situ soil properties, water table depth, pile diameter, roughness and driving procedures have on the ageing behaviour of piles driven in sand. Tension tests have been performed on fifty-one, 48 to 60mm, outside diameter open-ended steel micro-piles driven at well-established research sites at Larvik in Norway, Dunkirk in France and Blessington in Ireland to better understand the processes that control axial capacity set-up trends in the field. Mild steel, stainless and galvanised steel micro-piles were driven and left to age undisturbed for periods of between 2 hours and 696 days before being subjected to first-time axial tension load tests. In addition to reporting and interpreting these experiments, further investigations of the sites’ geotechnical profiles are reported, including new piezocone and seismic cone penetration soundings as well as laboratory tests. Integration with earlier ageing studies at the same sites with larger (340 to 508mm outside diameter) open-ended steel piles driven to 7 to 20m embedment’s and experiments that varied the piles’ initial surface roughness shows that corrosion, pile-scale, roughness, the bonding of soil particles and the driving process can all be highly significant. New insights are gained into the mechanisms that control the axial capacity of piles driven in sand
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