PHIDL: Python CAD layout and geometry creation for nanolithography

Computer-aided design (CAD) has become a critical element in the creation of nanopatterned structures and devices. In particular, with the increased adoption of easy-to-learn programming languages like Python there has been a significant rise in the amount of lithographic geometries generated through scripting and programming. However, there are currently unaddressed gaps in usability for open-source CAD tools -- especially those in the GDSII design space -- that prevent wider adoption by scientists and students who might otherwise benefit from scripted design. For example, constructing relations between adjacent geometries is often much more difficult than necessary -- spacing a resonator structure a few micrometers from a readout structure often requires manually-coding the placement arithmetic. While inconveniences like this can be overcome by writing custom functions, they are often significant barriers to entry for new users or those less familiar with programming. To help streamline the design process and reduce barrier to entry for scripting designs, we have developed PHIDL, an open-source GDSII-based CAD tool for Python 2 and 3

Ultrafast Electric Field-induced Phase Transition in Bulk Bi0.5Na0.5TiO3 under High Intensity Terahertz Irradiation

“This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Photonics, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://pubs.acs.org/doi/10.1021/acsphotonics.0c01559”Ultrafast polarization switching is being considered for the next generation of ferroelectric based devices. Recently, the dynamics of the field-induced transitions associated with this switching have been difficult to explore, due to technological limitations. The advent of terahertz (THz) technology has now allowed for the study of these dynamic processes on the picosecond (ps) scale. In this paper, intense terahertz (THz) pulses were used as a high-frequency electric field to investigate ultrafast switching in the relaxor ferroelectric, Bi0.5Na0.5TiO3. Transient atomic-scale responses, which were evident as changes in reflectivity, were captured by THz probing. The high energy THz pulses induce an increase in reflectivity, associated with an ultrafast field-induced phase transition from a weakly polar phase (Cc) to a strongly polar phase (R3c) within 20 ps at 200 K. This phase transition was confirmed using X-ray powder diffraction and by electrical measurements which showed a decrease in the frequency dispersion of relative permittivity at low frequencies

Orthotic management of instability of the knee related to neuromuscular and central nervous system disorders: qualitative interview study of patient perspectives

Objectives: Adults with knee instability related to neuromuscular disorders or central nervous conditions often experience mobility problems and rely on orthoses to improve function and mobility. Patient views of device effectiveness and acceptability are underexplored. Our study aimed to elicit device users’ perspectives regarding fitting, acceptability, effectiveness and use of orthoses, and identify important treatment outcomes. / Design: Qualitative descriptive study using in-depth semistructured interviews. Interview transcriptions were coded and thematically analysed, using ‘Framework’. / Setting and participants: A purposive sample of 24 adult users of orthotic devices. Nineteen patients were recruited across three National Health Service sites, and five people through charities/patient support groups in England. Half of the participants had been diagnosed with poliomyelitis, and the remainder with multiple sclerosis, Charcot-Marie-Tooth disease, spinal injury or spina bifida, and stroke. The median age of participants was 64.5 years (range 36–80 years). / Results: Patients’ medical condition impacted significantly on daily life. Participants relied on orthotic devices to enable engagement in daily activities. Patient goals for mobility were linked to individual circumstances. Desired treatment outcomes included reduction in pain, trips and falls, with improved balance and stability. Effectiveness, reliability, comfort and durability were the most valued features of orthoses and associated with reported use. Obtaining suitable footwear alongside orthotic devices was a significant concern. Time pressures during device fitting were viewed negatively. / Conclusions: Orthotic devices for knee instability play a crucial role in promoting, maintaining and enhancing physical and psychological health and well-being, enabling patients to work, engage in family life and enjoy social activities. Future research should consider how best to measure the impact of orthotic devices on patient quality of life and daily functioning outside the clinic setting, as well as device use and any adverse effects. / Trial registration number: This qualitative study was retrospectively registered as Current Controlled Trials ISRCTN65240228

A superconducting-nanowire 3-terminal electronic device

In existing superconducting electronic systems, Josephson junctions play a central role in processing and transmitting small-amplitude electrical signals. However, Josephson-junction-based devices have a number of limitations including: (1) sensitivity to magnetic fields, (2) limited gain, (3) inability to drive large impedances, and (4) difficulty in controlling the junction critical current (which depends sensitively on sub-Angstrom-scale thickness variation of the tunneling barrier). Here we present a nanowire-based superconducting electronic device, which we call the nanocryotron (nTron), that does not rely on Josephson junctions and can be patterned from a single thin film of superconducting material with conventional electron-beam lithography. The nTron is a 3-terminal, T-shaped planar device with a gain of ~20 that is capable of driving impedances of more than 100 k{\Omega}, and operates in typical ambient magnetic fields at temperatures of 4.2K. The device uses a localized, Joule-heated hotspot formed in the gate to modulate current flow in a perpendicular superconducting channel. We have characterized the nTron, matched it to a theoretical framework, and applied it both as a digital logic element in a half-adder circuit, and as a digital amplifier for superconducting nanowire single-photon detectors pulses. The nTron has immediate applications in classical and quantum communications, photon sensing and astronomy, and its performance characteristics make it compatible with existing superconducting technologies. Furthermore, because the hotspot effect occurs in all known superconductors, we expect the design to be extensible to other materials, providing a path to digital logic, switching, and amplification in high-temperature superconductors

Lessons from the evaluation of the UK's NHS R&D Implementation Methods Programme

Background: Concern about the effective use of research was a major factor behind the creation of the NHS R&D Programme in 1991. In 1994, an advisory group was established to identify research priorities in research implementation. The Implementation Methods Programme (IMP) flowed from this, and its commissioning group funded 36 projects. In 2000 responsibility for the programme passed to the National Co-ordinating Centre for NHS Service Delivery and Organisation R&D, which asked the Health Economics Research Group (HERG), Brunel University, to conduct an evaluation in 2002. By then most projects had been completed. This evaluation was intended to cover: the quality of outputs, lessons to be learnt about the communication strategy and the commissioning process, and the benefits from the projects. Methods: We adopted a wide range of quantitative and qualitative methods. They included: documentary analysis, interviews with key actors, questionnaires to the funded lead researchers, questionnaires to potential users, and desk analysis. Results: Quantitative assessment of outputs and dissemination revealed that the IMP funded useful research projects, some of which had considerable impact against the various categories in the HERG payback model, such as publications, further research, research training, impact on health policy, and clinical practice. Qualitative findings from interviews with advisory and commissioning group members indicated that when the IMP was established, implementation research was a relatively unexplored field. This was reflected in the understanding brought to their roles by members of the advisory and commissioning groups, in the way priorities for research were chosen and developed, and in how the research projects were commissioned. The ideological and methodological debates associated with these decisions have continued among those working in this field. The need for an effective communication strategy for the programme as a whole was particularly important. However, such a strategy was never developed, making it difficult to establish the general influence of the IMP as a programme. Conclusion: Our findings about the impact of the work funded, and the difficulties faced by those developing the IMP, have implications for the development of strategic programmes of research in general, as well as for the development of more effective research in this field

Production of highly-polarized positrons using polarized electrons at MeV energies

The Polarized Electrons for Polarized Positrons experiment at the injector of the Continuous Electron Beam Accelerator Facility has demonstrated for the first time the efficient transfer of polarization from electrons to positrons produced by the polarized bremsstrahlung radiation induced by a polarized electron beam in a high-$Z$ target. Positron polarization up to 82\% have been measured for an initial electron beam momentum of 8.19~MeV/$c$, limited only by the electron beam polarization. This technique extends polarized positron capabilities from GeV to MeV electron beams, and opens access to polarized positron beam physics to a wide community.Comment: 5 pages, 4 figure