Effects of large induced superconducting gap on semiconductor Majorana nanowires

With the recent achievement of extremely high-quality epitaxial interfaces between InAs nanowires and superconducting Al shells with strong superconductor-semiconductor tunnel coupling, a new regime of proximity-induced superconductivity in semiconductors can be explored where the induced gap may be similar in value to the bulk Al gap (large gap) with negligible subgap conductance (hard gap). We propose several experimentally relevant consequences of this large-gap strong-coupling regime for tunneling experiments, and we comment on the prospects of this regime for topological superconductivity. In particular, we show that the advantages of having a strong spin-orbit coupling and a large spin g-factor in the semiconductor nanowire may both be compromised in this strongly coupled limit, and somewhat weaker interface tunneling may be necessary for achieving optimal proximity superconductivity in the semiconductor nanowire. We derive a minimal, generic theory for the strong-coupling hard-gap regime obtaining good qualitative agreement with the experiment and pointing out future directions for further progress toward Majorana nanowires in hybrid semiconductor-superconductor structures.Comment: 8 pages, 5 figures; published versio

The programmable spring: towards physical emulators of mechanical systems

The way motion is generated and controlled in robotics has traditionally been based on a philosophy of rigidity, where movements are tightly controlled and external influences are ironed out. More recent research into autonomous robots, biological actuation and human machine interaction has uncovered the value of compliant mechanisms in both aiding the production of effective, adaptive and efficient behaviour, and increasing the margins for safety in machines that operate alongside people. Various actuation methods have previously been proposed that allow robotic systems to exploit rather than avoid the influences of external perturbations, but many of these devices can be complex and costly to engineer, and are often task specific. This thesis documents the development of a general purpose modular actuator that can emulate the behaviour of various spring damping systems. It builds on some of the work done to produce reliable force controlled electronic actuators by developing a low cost implementation of an existing force actuator, and combining it with a novel high level control structure running in software on an embedded microcontroller. The actuator hardware with its embedded software results in a compact modular device capable of approximating the behaviour of various mechanical systems and actuation devices. Specifying these behaviours is achieved with an intuitive user interface and a control system based on a concept called profile groups. Profile group configurations that specify complex mechanical behaviours can be rapidly designed and the resulting configurations downloaded for a device to emulate. The novel control system and intuitive user interface developed to facilitate the rapid prototyping of mechanical behaviours are explained in detail. Two prototype devices are demonstrated emulating a number of mechanical systems and the results are compared to mechanical counterparts. Performance issues are discussed and some solutions proposed alongside general improvements to the control system. The applications beyond robotics are also explored

Novel insights into the asexual life-cycle of the wheat-leaf pathogen Zymoseptoria tritici

Zymoseptoria tritici, the causal agent of Septoria tritici blotch (STB), is the most economically important pathogen of wheat in temperate climates. EU spending on the control of STB is estimated at more than € 1.3 billion per annum, even when tolerant cultivars are used. This thesis comprises 5 data chapters each looking to ascertain reasons for the success of Z. tritici. Using mainly in vitro methods combined with confocal microscopy, this thesis explores asexual spore submergence in rain, epiphytic development, the potential triggers for pycnidiation, low-nutrient ex planta survival, and soil treatments as a novel method of control. Novel findings include that (i) submergence leads to a form of spore dormancy, (ii) epiphytic development is more extensive than previously thought with hyphal growth and sporulation both occurring readily over a 21 day period, (iii) pycnidiation is a rapid, deterministic developmental process, triggered by contents of lysed plant cells, (iv) asexual spores have the capacity to survive for many weeks in low-nutrient environments, and finally (v) that treating soil-borne environmental spores may be a novel way to reduce field inoculum levels before a new crop is sown. Collectively these results provide many new insights in to the behaviour of Z. tritici during its disease cycle. This thesis proposes an updated version of the life cycle for this devastating fungal pathogen and argues that current methods of control are not adequate long-term

The impact of management ability and market structure on the performance of agricultural banks in Iowa

The effects of management ability and market structure on the performance of agricultural banks are assessed using observations on 444 Iowa banks from the years 1976 and 1978. Management ability is measured by the ratio of assets to employees, market structure is measured by a Herfindahl index and a market share variable, and bank performance is represented by the ratio of loans to total assets and the ratio of time and savings deposits to total deposits. Ordinary least squares analysis indicates that market structure strongly influences the ratio of time and savings deposits to total deposits but does not influence the ratio of loans to total assets. Management ability strongly influences the ratio of time and savings deposits to total deposits and weakly influences the ratio of loans to total assets. Two-stage and three-stage least squares analyses indicate that coefficients on market structure variables are not invariant to estimation method, but there is no strong evidence that market structure variables should be treated as endogenous rather than exogenous variables. A Chow test reveals that market structure variables do not measure market concentration in single bank communities and multiple bank communities equally well when banks from both types of communities are contained in the sample. Empirical results also indicate that Production Credit Associations influence the ratio of time and savings deposits to total deposits at agricultural banks but do not influence the ratio of loans to total assets;Changes in banking market structure that result from financial deregulation apparently will affect the liability side of agricultural bank balance sheets more strongly than the asset side. In order to mitigate the negative impacts of financial deregulation, bank owners and managers should seek ways of improving management ability. Future research should continue to explore the relationship between management ability and agricultural bank performance, but that research must be preceded by, or include, development of innovative measures of banking market concentration and exploration of relationships between Production Credit Association activities and bank performance

Digital zero noise extrapolation for quantum error mitigation

Zero-noise extrapolation (ZNE) is an increasingly popular technique for mitigating errors in noisy quantum computations without using additional quantum resources. We review the fundamentals of ZNE and propose several improvements to noise scaling and extrapolation, the two key components in the technique. We introduce unitary folding and parameterized noise scaling. These are digital noise scaling frameworks, i.e. one can apply them using only gate-level access common to most quantum instruction sets. We also study different extrapolation methods, including a new adaptive protocol that uses a statistical inference framework. Benchmarks of our techniques show error reductions of 18X to 24X over non-mitigated circuits and demonstrate ZNE effectiveness at larger qubit numbers than have been tested previously. In addition to presenting new results, this work is a self-contained introduction to the practical use of ZNE by quantum programmers.Comment: 11 pages, 7 figure

Proclamation for Primary Election

https://digitalmaine.com/arc_executive_proclamations_1950/1034/thumbnail.jp

An Act Relating to the Administration of the State

https://digitalmaine.com/arc_executive_proclamations_1950/1031/thumbnail.jp

Increase of Capital Stock of Bangor Gas Light Company

https://digitalmaine.com/arc_executive_proclamations_1950/1019/thumbnail.jp