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Low cost printed circuit board (PCB) electrochemical biosensors for rapid and label free detection of Streptococcus pneumoniae
No full textSevere sepsis presents a critical healthcare challenge where rapid pathogen identification is vital for timely intervention. Current diagnostic methods, however, remain inadequate, often delaying targeted treatment. Using readily available printed circuit board (PCB) electrodes, we address this need by developing a low-cost electrochemical DNA biosensor for rapid detection of Streptococcus pneumoniae using the lytA gene as a biomarker. Through systematic evaluation of commercial and custom PCB designs (P1–P4), gold-plated PCB P4 was found as the optimal platform, demonstrating sensitive detection of lytA sequences (20 bp at 4.50 pM limit of detection in buffer) and clinically relevant 235 bp polymerase chain reaction (PCR) amplicons in 100% human serum (1.0–100 pM) within 15 min at room temperature using electrochemical impedance spectroscopy. The performance of the biosensor originates from the optimized electrode geometry, surface properties, and robust self-assembled monolayer functionalization, enabling specific recognition of bacterial DNA without sample pretreatment. This work establishes PCB-based biosensors as a promising solution for point-of-care sepsis diagnostics, offering significant advantages in speed, cost, and operational simplicity compared to conventional methods
Design of transient plasma photonic structure mirrors for high-power lasers using deep kernel Bayesian optimisation
Get PDFUltra-high power lasers are becoming important tools for advancing high-field physics and fusion research. However, their development is constrained by the damage thresholds of conventional optical components; it is challenging to design optical elements capable of withstanding high powers without them becoming impractically large. Here we show that transient plasma photonic structures, formed by the interaction of intercepting laser pulses in gas, can act as compact and robust reflective elements. Because these structures evolve in space and time, and rely on many interdependent parameters, designing optical components using traditional trial-and-error design methods is challenging. We show that machine learning can efficiently explore this complex parameter space to rapidly design robust, high reflectivity plasma mirrors. Moreover, this design process unexpectedly discovers a regime where unchirped laser pulses are compressed. This work demonstrates machine learning as a powerful tool for design, discovery and development of ultra-compact optical components for next-generation lasers
Hydroelastic performance of a flexible pontoon-type floating breakwater embedded with multiple oscillating-water-column devices
Get PDFCombining Wave Energy Converters (WECs) with a long-flexible floating breakwater is a plausible pathway to the engineering application of wave energy technologies, which not only enhances energy capture capability but also improves structural stability of breakwater. This study proposes a multi-module flexible pontoon-type floating breakwater integrated with oscillating water column (OWC) units. Each chamber features an independent power take-off (PTO) system for energy capture. A coupled fluid-structure interaction model, integrating Computational Fluid Dynamics (CFD) with Finite Element Method (FEM), is developed to investigate the hydroelastic response. The bi-directional coupled process is realized by satisfying constant boundary conditions between fluid velocity and pressure, and structural node displacements at each time step. Parametric studies demonstrate that flexible structures offer superior adaptability to wave loading compared to rigid counterparts, effectively reducing wave-induced forces while maintaining energy capture. Further analysis reveal that increased structural stiffness enhances internal resonance within chambers, significantly improving capture factors, whereas excessive flexibility can trigger complex multimode radiated wave interactions, adversely affecting energy conversion efficiency. Additionally, incorporating a bottom opening strengthens wave resonance within the chamber, thereby increasing energy dissipation. These findings highlight practical advantages of multi-module flexible floating breakwaters, providing valuable guidelines for design and optimization in engineering applications
Near-net-shape wire-arc additive manufacturing (WAAM) of bimetallic P22 steel and Inconel 625 : microstructure–property correlations
Get PDFWire-arc additive manufacturing (WAAM) is a state-of-the-art near net shape manufacturing technology for manufacturing structures with tailored mechanical properties. However, the process typically requires minor post-processing (e.g., machining) to achieve the desired surface finish and dimensional accuracy. This study investigates the mechanical properties and the concomitant microstructural evolution in a WAAM bimetallic comprising of a low alloy carbon steel (P22) and Inconel 625 nickel alloy (IN625) using gas metal arc welding (GMAW). Microstructural examination revealed distinct microstructural features, including bainite-ferrite morphology in P22 steel and a dendritic γ-austenite matrix in IN625 with intermetallic Laves phase precipitates. The interface exhibited a defect-free metallurgical bond, characterised by martensitic laths within the P22 region, primarily due to rapid cooling, and columnar grains in the IN625 region due to directional solidification. Tensile and Charpy impact tests revealed that IN625 exhibited superior mechanical properties, whereas the bimetallic component displayed moderate strength with reduced ductility. In these tests, fractures appeared to consistently occur on the P22 side, due to the presence of Mn-rich inclusions. Crystallographic texture analysis showed near random texture for the P22 steel, governed by recrystallisation and phase transformation dynamics. In contrast, the texture of the IN625 deposit cannot be concluded due to the small number of directionally grown grains during WAAM
Offshore wind support structures – evaluation of size effects and influencing factors on the fatigue performance of butt-welded joints using an updated database
Get PDFOffshore wind turbine support structures, such as monopiles, require high fatigue resistance at welded connections, particularly around the circumferential welds. This paper reviews the influence of plate thickness on the fatigue performance of welded butt joints and presents a statistical evaluation of relevant fatigue test data. The analysis combines the European fatigue database (DASt Database) with newly available data related to welded offshore wind structures to ensure representativeness for modern monopile structures. The unfiltered European fatigue database contains more than 4700 data points for butt welds, but its heterogeneity in materials, welding processes, and specimen geometries produces a large scatter. After filtering for offshore wind-relevant conditions, by including thick plates (t ≥ 25 mm), various sub-grades of S355 structural steel, double-sided butt welds, submerged arc welding, axial loading condition, and load ratios of R ≥ 0 the dataset reduces drastically but yields consistent results based on relevant test data. In this subset, the characteristic fatigue resistance corresponds to FAT 90, while the inverse slope of the S–N curve increased to m ≈ 3.45, which is higher than the EN 1993-1-9 standard assumption of m = 3 but in excellent agreement with the monopile-specific D curve in DNV-RP-C203 standard. The newly added offshore wind related datasets, particularly for plate thicknesses of 40 mm and 50 mm, confirm these findings. They demonstrate a fatigue life reduction trend with increasing the plate thickness for t ≥ 25 mm, while the thickness correction formulation in EN 1993-1-9 standard has been found to produce a trend that falls at the lower bound of the scatter. Moreover, the variations in the load ratios of R ≥ 0 and the yield strength in various sub-grades of S355 steel were found to have no significant influence on fatigue resistance. Overall, the results demonstrate that targeted filtering and integration of offshore wind-specific data provide a more realistic basis for fatigue design and life assessment of monopile support structures
Evaluating tidal and offshore wind as a sustainable solution for remote off-grid communities
Get PDFLocating renewable energy systems in remote areas with extreme conditions is challenging due to weather variability and past deployment failures. This study assesses tidal and offshore wind resources for application in off-grid communities, focusing on data accuracy and site viability. Tidal energy, being highly predictable, is analysed using ADCP measurements and the FES2014c model at sites in the North Atlantic, including the FoW (Orkney, Scotland) and the Nares Strait (Canadian Archipelago), to understand any limitations with the use of FES2014c in the area evaluated. Strong correlations (R2 = 83%–89%) were found, although bathymetry-related errors were noted in shallow areas. FES2014c was then used to evaluate Nunavut locations where tidal or offshore wind energy could be used to reach net-zero targets. In Nunavut, Canada, correlations between the MERACAN Atlas and the FES model varied widely (R2 = 19%–95%), with skill scores between 39%–94%. The FES model showed deviations from 1.12 ms-1 to 0.03 ms-1, while tidal amplitude remained reliable, aiding site identification. A site in Naujaat was identified as a suitable location for the deployment of both tidal and offshore wind energy, with estimated capacity factors of 38% for tidal and 28% for wind. The combined annual energy production is approximately 1791.8 MWh. However, for offshore wind development only, no suitable locations were found where bathymetric conditions matched with capacity factors. In contrast, tidal stream analysis identified at least four viable turbine sites, each with a capacity factor exceeding 20%
Surface wave source with a multistage depressed collector - designing a high-power THz source
Get PDFTerahertz (THz) radiation, encompassing millimetre/submillimetre wavelengths (0.3THz-10THz), is one of the most desirable ranges of electromagnetic (EM) radiation. While sources capable of generating coherent THz radiation are continuously developing and subjects of exciting R&D programs, a significant frequency band from approximately 0.5THz to 5THz is still practically unbridged, with only occasional "steppingstones" appearing to support a limited number of research and industrial applications. This is specifically true for high power (>100W) compact and energy efficient (> 10%) sources of THz radiation. The project, stimulated by market research conducted and led by UKAEA, is to explore opportunities to construct high efficient (>10%) THz source potentially capable of generating >100W of coherent THz radiation (0.5 THz to 5 THz) in pulsed and CW regimes. The results of the market research based on more than 20 interviews will be also presented and discussed
"The net that catches the most fish" : fishing, innovation, and law in the Gold Coast Colony (Ghana), c. 1898–1923
Get PDFBetween 1898 and 1923, a series of disputes erupted among fishing communities in the British Gold Coast Colony (modern-day Ghana) following the introduction of larger and more productive sea fishing nets. All along the coast, fishers debated the environmental and economic consequences of adopting the nets, which debates shifted across African and colonial forums. Focusing on these disputes, this article interrogates the ways in which sites of fishing innovations and experimentation became sites of intense conflict and negotiation throughout the Gold Coast Colony as different groups debated and contested technological change. In the process, voices advocating for caution within the fishing industry were effectively marginalised through the manoeuvring of net advocates while the introduction of colonial arbitration within the realm of fisheries offered new challenges to the authority of African leaders within the marine space
Effects of pulse repetition rate on active species production for nanosecond spark discharges in air
Get PDFNanosecond pulsed discharges are capable of producing highly transient nonequilibrium plasma in gases which are characterized by high electron temperatures and relatively low rotational and vibrational temperatures. These conditions enable the formation of unstable molecules, namely radicals, which are beneficial to a wide range of biomedical and environmental applications including air and water purification, bio-decontamination, and advanced oxidation processes. This research investigates the effects of repetition rate of ns discharges in static air and the average power delivered into the plasma on the production of the hydroxyl radical (OH ⋅ ) and the nitric oxide radical (NO ⋅ ) through optical emission spectroscopy (OES). Plasma pulses were generated with voltage pulses with a constant voltage rate of rise (dV/dt) of 9 kV/ μ s resulting in the formation of a spark discharge with current impulse duration of 16 ns. These pulses were applied at repetition rates from 5 thousand pulses per second (kpps) to 38 kpps. The individual discharge energy was observed to decrease as a result of increasing pulse repetition rate, showing a drop from 1.17 mJ per pulse to 0.28 mJ per pulse at 5 and 38 kpps, respectively. Despite this decrease, the average power delivered into the plasma increased as a result of pulse repetition rate from 5.80 to 11.56 W. The optical emission spectra from both the OH ⋅ and NO ⋅ radicals, and atomic oxygen showed a strong dependence on pulse repetition rate for low repetition rates, followed by a clear correlation with power delivered into the plasma for repetition rates over 15 kpps. The plasma rotational and vibrational temperatures were obtained using 3 methods, with a high resolution N2 second positive system (SPS) measurement used to evaluate the baseline temperatures. This was compared with a low resolution N2 SPS measurement using a local thermal equilibrium (LTE) assumption, which showed an error of over 1000 K between the LTE Tvib and the actual Tvib , proving the limitations of the LTE assumption with relation to transient spark discharges. The rotational temperature of OH ⋅ was evaluated and found to follow a non-Boltzmann behavior, resulting in an error in Trot of up to 189% as compared to the N2 SPS Trot . This study provides clear insights into the optimization of nanosecond pulsed plasma systems for efficient active species production, with wide ranging implications for biomedical, environmental, and industrial applications. The findings provide further insights into the characterization of transient plasmas, advancing the understanding of nonequilibrium plasmas
Impact of solvent choice during microfluidic manufacture on the in vivo performance of liposomal doxorubicin
No full textMicrofluidics offers a reproducible approach to liposome manufacture; however, the impact of solvent choice on formulation performance remains underexplored. Here, we investigated whether solvent selection during microfluidic manufacturing influences liposome performance by assessing its effect on the drug release and biodistribution of liposomal doxorubicin, using rotary evaporation as a conventional method of comparison. PEGylated liposomes (DSPC:Chol:DSPE-PEG2000, 3:1:1 w/w) were prepared using a staggered herringbone microfluidic mixer, with lipids dissolved in either ethanol or Transcutol, and compared with liposomes produced by rotary evaporation and extrusion. All formulations were actively loaded with doxorubicin via an ammonium sulphate gradient, purified by tangential flow filtration, and characterised for size, polydispersity, and drug loading. The three formulations (two microfluidic (ethanol vs Transcutol) and one rotary evaporation control) were intravenously administered to Sprague–Dawley rats (1 mg/kg), and doxorubicin concentrations in plasma and tissues were quantified using LC–MS. Although solvent choice produced liposomes with broadly comparable physicochemical properties (~ 100–120 nm, PDI 90%), Transcutol-based microfluidic liposomes showed prolonged and higher concentrations of doxorubicin within the plasma and tissue samples compared with liposomes produced by ethanol microfluidics and rotary evaporation. By contrast, the manufacturing method alone (microfluidics using ethanol as the solvent versus rotary evaporation) did not significantly influence biodistribution. These findings highlight solvent selection as an important parameter in microfluidic liposome manufacture, demonstrating that matching standard critical quality attributes and in vitro release behaviour alone may be insufficient to ensure comparable in vivo performance
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