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Numerous optodes, with fluorophores as the chemical sensing element and optical fibres for light delivery and collection, have been fabricated for minimally invasive endoscopic measurements of key physiological parameters such as pH. These flexible miniaturised optodes have typically attempted to maximize signal-to-noise through the application of high concentrations of fluorophores. We show that high-density attachment of carboxyfluorescein onto silica microspheres, the sensing elements, results in fluorescence energy transfer, manifesting as reduced fluorescence intensity and lifetime in addition to spectral changes. We demonstrate that the change in fluorescence intensity of carboxyfluorescein with pH in this “high-density” regime is opposite to that normally observed, with complex variations in fluorescent lifetime across the emission spectra of coupled fluorophores. Improved understanding of such highly loaded sensor beads is important because it leads to large increases in photostability and will aid the development of compact fibre probes, suitable for clinical applications. The time-resolved spectral measurement techniques presented here can be further applied to similar studies of other optodes.

PurposeThe relentless rise in antimicrobial resistance is a major societal challenge and requires, as part of its solution, a better understanding of bacterial colonization and infection. To facilitate this, we developed a highly efficient no-wash red optical molecular imaging agent that enables the rapid, selective, and specific visualization of Gram-positive bacteria through a bespoke optical fiber–based delivery/imaging endoscopic device.MethodsWe rationally designed a no-wash, red, Gram-positive-specific molecular imaging agent (Merocy-Van) based on vancomycin and an environmental merocyanine dye. We demonstrated the specificity and utility of the imaging agent in escalating in vitro and ex vivo whole human lung models (n = 3), utilizing a bespoke fiber–based delivery and imaging device, coupled to a wide-field, two-color endomicroscopy system.ResultsThe imaging agent (Merocy-Van) was specific to Gram-positive bacteria and enabled no-wash imaging of S. aureus within the alveolar space of whole ex vivo human lungs within 60 s of delivery into the field-of-view, using the novel imaging/delivery endomicroscopy device.ConclusionThis platform enables the rapid and specific detection of Gram-positive bacteria in the human lung.

Physiological sensing deep in tissue remains a clinical challenge. Here a flexible miniaturised sensing optrode providing a platform to perform minimally invasive in vivo in situ measurements is reported. Silica microspheres covalently coupled with a high density of ratiometrically configured fluorophores were deposited into etched pits on the distal end of a 150 µm diameter multicore optical fibre. With this platform, photonic measurements of pH and oxygen concentration with high precision in the distal alveolar space of the lung are reported. We demonstrated the phenomenon that high-density deposition of carboxyfluorescein covalently coupled to silica microspheres shows an inverse shift in fluorescence in response to varying pH. This platform delivered fast and accurate measurements (±0.02 pH units and ±0.6 mg/L of oxygen), near instantaneous response time and a flexible architecture for addition of multiple sensors.

PV systems are frequently used in a stand-alone configuration. In a solar PV-based energy-producing system, power fluctuation is a natural occurrence. Alternative sources of energy, including such hybrid grid-tied or energy storage systems, could be discovered when solar PV systems run off-grid to satisfy regional power demands for reliable power supply. This research uses an unusual PV system that can function in both grid-connected and stand-alone states to propose an efficient approach for the power generation challenge in the residential segment. A block of storage battery with sufficient dimensions is included in the system to make sure the constant power supply of such a residential building with an average electricity demand of 10 kWh. An atypical 3.2 kWp PV system and a 19.2 kWh storage battery brick was determined to be capable of meeting the house’s whole daily energy requirements, as well as the defined electrical shutdown times, to simulate the system, which took into account the day load profile, network cutoff times, and monthly radiation from the sun. The collected simulation results showed that during 9 months of each year, the generated PV energy surpasses the load needs, resulting in a maximum battery state-of-charge (SOC) in the range of 74-85%. The generated PV energy is an approximately proportional requirement as during 3 months of minimum solar irradiance (Dec-Feb), whereas the sequence’s SOC differs between 40 and 49%, demonstrating the validity of the proposed photovoltaic system. In January and July, the PV service’s daily energy produced ranges between 2.6 and 5.4 kWh/kWp, corresponding to a conversion efficiency of 90% and 66.25%, correspondingly.

The reduced performance of a diesel engine with biodiesel can be overcome by inclusion of nanoparticles. This study uses a novel binary mixture of Prosopis juliflora biodiesel (PJB) and 200 ppm of metal-based nanoparticles [cerium oxide (CeO 2 ), manganese dioxide (MnO 2 ), and titanium dioxide (TiO 2 )], to operate and examine the behaviour of a four-stroke, one-cylinder, naturally aspirated, water-cooled diesel engine. The work comprises a new comparison of energy, exergy, and sustainability performance through energy distribution and utilisation inside the engine using first and second laws of thermodynamics for the fuel samples PJB0, PJB100, PJB100Ce, PJB100Mn, and PJB100Ti. The boundary conditions for the analysis are set to a compression ratio of 17.5, an engine speed of 1500 rpm, and injection timing of 23° crank angle bTDC. The addition of various nanoparticles into the pure PJB fuel increased the energy and exergy efficiency by 6.1–7.3%, the exergy performance coefficient by 9.9–14.6%, and the sustainability index by 3.6–6.8% and reduced the exergy destruction by 3.5–6.4% at full engine load. Among the various blends analysed, PJB100Ti performed superiorly as compared to others. From the detailed analysis, energy, exergy, and sustainability provide insightful information about the engine’s operation and its impact on the engine system. The adoption of nanoparticle-enhanced biodiesel is not only a promising alternative in the search for cleaner but also more effective energy sources. This study suggests more investigation and development in the areas of alternative fuels, engine optimization, and the development of sustainable energy solutions. Graphical abstract

The alveolar space forms the distal end of the respiratory tract where chemoreceptor driven gas exchange processes occur. In healthy humans, the physiological state within the alveoli is tightly regulated by normal homeostatic mechanisms. However, pulmonary abnormalities such as chronic obstructive pulmonary disease may induce significant perturbation of the homeostatic baselines of physiology as well as cause host tissue damage. Therefore, physiological parameters (pH, glucose, oxygen tension) within the alveolar space provide a key biomarker of innate defence. Here, we discuss an endoscope-deployable fibre-optic optrode for sensing pH in the alveolar space. In order to circumvent the unwanted Raman signal generated within the fibre, the optrode consists of a custom asymmetric dual-core optical fibre designed for spatially separated optical pump delivery and SERS signal collection. pH sensing is achieved using the surface enhanced Raman spectroscopy (SERS) signal generated from functionalised gold nanoshell sensors. We show a ∼ 100-fold increase in SERS signal-to-fibre background ratio and demonstrate multiple site pH sensing in the alveoli of an ex vivo ovine lung model with a measurement accuracy of ± 0.07 pH unit.

Conversion of methane to higher hydrocarbons by its low-temperature activation without forming undesirable carbon oxides is of great scientific and practical importance. Methane can be highly activated, yielding high rates of conversion to higher hydrocarbons and aromatics (10 to 45 percent) at low temperatures (400° to 600°C), by its reaction over H-galloaluminosilicate ZSM-5 type (MFI) zeolite in the presence of alkenes or higher alkanes. The methane activation results from its hydrogen-transfer reaction with alkenes.

Nano-additives are being employed in successive generations of biodiesels to increase the performance characteristics and output of diesel engines. In this study, the impact of mixing carbon nanotubes (CNT) with three different generations of biodiesel in a diesel engine is assessed. With 100 ppm of CNT nanoparticles mixed together, pure biodiesels made from first-generation oil (soybean), second-generation oil (neem), and third-generation oil ( Nannochloropsis oculata microalgae) are used for the analysis. With an engine load ranging from 0 to 100%, a one-cylinder, four-stroke, direct injection diesel engine is employed. The engine has a water-cooling system, a compression ratio of 17.5:1, and a fuel injection angle of 23° before TDC. The evaluated engines’ improved performance and lower emissions serve as proof of the outcomes. The results are evidenced by the lower emissions and higher performance of the tested engines. The biodiesel containing CNT nanoparticles enhanced the cylinder pressure by 0.8–10.69%, the heat release rate (HRR) by 6.38–21.69%, and the brake thermal efficiency (BTE) by 0.32–1.62%. Subsequently, it reduced the brake-specific fuel consumption (BSFC) by 2.53–8.13%, the brake-specific energy consumption (BSEC) by 1.07–3.77%, the smoke opacity (BSN) by 6.26–12.85%, the particulate matter (PM) emissions by 11.04–18.33%, and the carbon dioxide (CO 2 ) emissions by 2.53–8.14% at full engine load. However, an increase in 13.62–18.37% nitrogen emissions (NOx) emissions is also observed with the addition of CNT at 100% load. The investigation supports the use of CNT nano-additives in diesel engines for improved performance and reduced emissions. Graphical Abstract

This paper presents a thermodynamic and sustainability analysis for an experimentally developed solar water heater-with water treatment. The parabolic trough collector (PTC) is employed to capture thermal energy from the sun, which is subsequently utilized to increase the temperature of water. “Experimental and numerical” investigations are divided into two cases. Case 1: PTC with a glass cover and case 2: PTC without glass cover. Using an experimental analysis, data are collected, such as solar insolation and water outlet temperature. The collected data are utilized to analyse the thermodynamic performance of the proposed system. The first law of thermodynamics helps to quantify the system’s performance, called energy analysis, whereas the second law of thermodynamics provides qualitative performance, called exergy analysis. The maximum energy and exergy efficiency achieved by the proposed system are 69.5% and 6.15%, respectively. Simultaneously, an exergy-based sustainability analysis is proposed, which shows how effectively the fuel exergy is utilized with the proposed system. The maximum sustainability index for case 1 is 1.07, and for case 2, it is 1.08. At the end of the experimental investigation, a slight decrease in total dissolved solid (TDS) was detected, indicating that if we enhance the performance of the PTC system, by changing the reflector material and installing evacuated tubes, the quality of the water may improve. Graphical abstract

The future of diesel engines is greatly influenced by ongoing research on alternative fuels. Renewable fuels have been researched and adopted by several nations to encourage the production and use of biodiesel. This study examines the energy conversion of waste plastic biodiesel and Spirulina microalgae biodiesel at a 20% blending ratio to analyze the behavior of a one-cylinder, 4-stroke diesel engine running at 1500 rpm with a compression ratio of 17.5. The authors evaluated, analyzed, and compared the engine’s combustion, performance, and emission at an incremental engine load of 25% from 25 to 100%. The findings demonstrated that the biodiesel fuel samples generated somewhat poorer efficiency but reduced emissions from the engine. At 100% load, the percentage differences between the diesel and blended fuel samples ranged from 2.4 to 7.3% for BTE, 2.9 to 16.5% for BSFC, and 1.0 to 4.62% for BSEC; however, the PM, SO 2 , and CO 2 emissions were reduced by 1.6–28.8% except for NO x emissions, which are increased by up to 9.4%. Pure diesel exhibits the best performance characteristics; however, pure biodiesel exhibits the best emission characteristics. The 20% blended fuels showed promising results, as they exhibited comparable or slightly improved BTE values compared to their respective pure biodiesel fuels. The findings indicate that Spirulina microalgae biodiesel and waste plastic biodiesel have the potential to be utilized as substitute fuels for diesel engines; however, for the greatest performance and lowest emissions, their blending ratios and engine operating conditions must be optimized. Graphical abstract