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Circular dichroism and cross polarization conversion using chiral metasurface
Get PDFThis paper presents a novel dual-mode chiral metasurface (CM) designed to achieve strong circular dichroism (CD) in both transmission and reflection mode within the Ku-band. The proposed dual-mode CM demonstrates CD i.e., an efficient conversion of linearly polarized (LP) electromagnetic (EM) waves into circularly polarized (CP) waves, both within a broader spectrum as well as at single frequencies in both transmission and reflection mode, exhibiting asymmetric transmission (AT) response. This is achieved through a judiciously designed unit cell structure, which eliminates the requirement for intricate supercell configurations or active circuitry. The metasurface comprises a circular ring structure embedded with intelligently placed angle-induced slot and a metallic strip, fabricated using the cost-effective FR-4 substrate. The structure on the front side of the dual-mode CM is replicated on the back side of the substrate with a 90° rotation to achieve a chiral configuration. Under the forward-propagating y-polarized incident wave, the dual-mode CM demonstrates the capability to convert LP wave into right-handed circularly polarized (RHCP) wave at 14.064 GHz. Additionally, in transmission mode, it converts LP waves to left-handed circularly polarized (LHCP) wave over a wider frequency range of 16.60 -17.03 GHz with AT response. In reflection mode, the dual-mode CM converts LP wave into RHCP wave at 12.048 GHz when subject to x-polarized incident wave propagating in the backward direction
Pseudo-planar Ge-on-Si Avalanche Photodiode with >100 Gain and Low Excess Noise
Get PDFThere is significant interest in short-wave infrared (SWIR) avalanche photodiodes (APDs) for imaging and optical communications. SWIR detection enables long-range, eye-safe LIDAR with improved transmission through obscurants and also compatibility with telecoms networks operating around λ=1550nm. Si-based platforms are cost-effective and integrate with CMOS electronics but are limited to wavelengths <1μm. Ge absorber layers extend detection to SWIR wavelengths but typical mesa-based designs typically have edge effects that limit available gain. Here we demonstrate the benefits of a pseudo-planar design that mitigates these effects and enables high gains of 101 to be demonstrated in surface normal APDs with low excess noise factors of 3.1 at a gain of 20; a record for Ge-on-Si devices. Devices have a unity-gain responsivity of 0.41A/W at λ=1550nm wavelength
Bond behaviour of BFRP bars embedded in concrete under harsh conditions: a comprehensive review
No full textBasalt fibre-reinforced polymer (BFRP) bars are notable for their high strength-to-weight ratio, corrosion resistance, and environmental sustainability, making them a viable alternative to traditional steel reinforcements. The bond performance of BFRP bars in concrete is essential for the longevity and safety of marine infrastructure, especially under extreme conditions like chemical and moisture exposure, freeze-thaw cycles and high temperatures. For example, 80-90% bond strength reductions have been reported for FRP bars at 300°C, compared to only 38% for steel. This review summarises recent advancements in understanding how these environmental factors affect the bond behaviour of BFRP bars. The findings reveal the impact of environmental stresses on the mechanical properties of BFRP bars, deterioration mechanisms at the bar-concrete interface, and the effectiveness of mitigation strategies. The paper also highlights the need for further research into the long-term behaviour of BFRP-reinforced concrete structures
CtrlAer: programmable real-time execution of scientific experiments using a domain specific language for the Raspberry Pi Pico/Pico 2
No full textAutomated laboratory experimentation is increasingly dependent on synchronized operation of a heterogeneous hardware setups according to arbitrarily complex user-defined timing, but there is a lack of accessible, vendor-neutral options for reliable generation of these control signals. We present, CtrlAer, a domain-specific language for describing activation signals on a synchronized parallel timeline via a simple syntax containing only a handful of primitives. Embedded within MicroPython, CtrlAer programs are directly executable on the widely available and inexpensive Raspberry Pi Pico/Pico 2 and the wide ecosystem of open hardware development boards built around the RP2040/RP2350 microcontrollers. CtrlAer allows arbitrarily long and complex control sequences to be generated on up to 16 fully synchronized parallel channels at up to 10.7 MHz on the RP2350 (8.9 MHz on the RP2040), scaling to the needs of scientific experiments in a variety of disciplines
Zeitgeist and Ortgeist: time and place in institutional creation
Get PDFHow are institutions created is one of the most interesting questions in institutional theory. Some strands of literature favour heroic explanations: mythologizing individuals with vision, tenacity and drive and putting these individuals on the pedestal of the institution. Institutional work literature advocates a more diffuse model whereby the collective effort of institutional actors over time contributes to institutional creation. Drawing on our ethnographic study of the Scottish Parliament, we examined the roles of different institutional actors through the theoretical lens of materiality. We focused on the material base for the institution, the building that houses the Parliament. We asked two questions: How do institutional actors interact with the material nature of the building in institutional creation? And how do these institutional actors, individually and collectively, create the spirit of the place in a new building? We identified some mechanisms in which institutional actors interact with the material nature of the building: mythologizing the institution, searching for discursive legitimacy, accentuating differentiation from other institutions and making incremental changes in the fabric of the building. While acknowledging the importance of the heroic narratives in institutional creation, we draw analytic attention to the collective effort by institutional actors who create the institution and its building over time
Semipermeable membrane-mediated hydrogen bonding interface for fabricating high-performance pure PEDOT:PSS hydrogels
No full textConductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) hydrogels are potential bioelectronic interface materials because of their favorable mechanical properties and tunable electrochemical performances. Owing to intrinsic core-shell colloidal microstructure composed of insulative phase and conductive phase, inducing phase separation via diverse methods are proposed to improve their performances. However, fabrication of high-performance pure PEDOT:PSS hydrogels via a simple, mild strategy remains challenges. Here, we report a straightforward strategy to yield high-performance pure PEDOT:PSS hydrogels via the formation of semipermeable membrane-mediated hydrogen bonding interface. In this method, ethanol-attracted PSS is free to accumulate at the man-made interface provided by the semipermeable membrane, to realize controllable hierarchical PEDOT and PSS two-phase distribution. The separated PEDOT aggregates via π–π conjugation, followed by the removal of rearranged insulative PSS phase easily, to form PEDOT:PSS hydrogels with satisfactory mechanical and electrochemical performances. This work presents a universal, effective, and controlled strategy to design conductive hydrogels for bioelectronic applications
Do post-pandemic policies support green recovery?
No full text15 May 2025: David Clelland and Fabrice Renaud from the School of Social and Environmental Sustainability share insights from their research on how policies for post-pandemic recovery balanced economic, social and environmental goals, and what this might mean for future approaches to promoting sustainable development
Art
No full textIn the wake of the so-called ‘aesthetic’ or ‘visual’ turns, constructivist, post-structuralist, feminist and queer scholars have become increasingly attuned to the ways in which visual media shape global ideas, norms, identities, and practices. The last twenty years have thus seen an ever-widening range of scholarship exploring the relationship between art and world politics. This entry identifies and outlines four broad and interrelated ways of conceptualising this relationship. First, there is scholarship that looks to art as a critical or affective stimulus. Second, there is work that looks to art as a discursive site of identity-construction and norm-contestation. Third, there is work that looks at the art world itself as an object of global-political contestation. Finally, some IR scholars have begun to incorporate artistic methods into their teaching and research practice. The entry ends by identifying three underexplored areas of enquiry
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