Chemical and Biomolecular Engineering - Research Publications
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ItemNo Preview AvailableOptimised start-up strategy for bioelectrochemical systems operating on hydrolysed human urine.(Elsevier BV, 2024-04-06)Key nutrients, such as nitrogen measured as total ammonium nitrogen (TAN), could be recycled from hydrolysed human urine back to fertiliser use. Bioelectrochemical systems (BESs) are an interesting, low-energy option for realising this. However, the high TAN concentration (> 5 g L-1) and pH (> 9) of hydrolysed urine can inhibit microbial growth and hinder the enrichment of an electroactive biofilm at the anode. This study investigated a new strategy for bioanode inoculation by mixing real hydrolysed urine with thickened waste activated sludge (TWAS) from a municipal wastewater treatment plant at different volumetric ratios. The addition of TWAS diluted the high TAN concentration of hydrolysed urine (5.2 ± 0.3 g L-1) to 2.6-5.1 g L-1, while the pH of the inoculation mixtures remained > 9 and soluble chemical oxygen demand (sCOD) at 5.6-6.7 g L-1. Despite the high pH, current generation started within 24 h for all reactors, and robust bioanodes tolerant of continuous feeding with undiluted hydrolysed urine were enriched within 11 days of start-up. Current output and Coulombic efficiency decreased with increasing initial hydrolysed urine fraction. The anodes inoculated with the highest sCOD-to-TAN ratio (2.1) performed the best, which suggests that high organics levels can protect microbes from inhibition even at elevated TAN concentrations.
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ItemNo Preview AvailableEffect of storage conditions on the characteristics of cryogenic hydrogen jet dispersion(Elsevier BV, 2024-05-20)
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ItemNo Preview AvailableBiofouling control in reverse osmosis membranes by concentrated free ammonia in hydrolysed urine(Elsevier BV, 2024-07-01)
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ItemThe Impact of Activating Agents on Non-Enzymatic Nucleic Acid Extension Reactions(Wiley, 2024-04-02)Non-enzymatic template-directed primer extension is increasingly being studied for the production of RNA and DNA. These reactions benefit from producing RNA or DNA in an aqueous, protecting group free system, without the need for expensive enzymes. However, these primer extension reactions suffer from a lack of fidelity, low reaction rates, low overall yields, and short primer extension lengths. This review outlines a detailed mechanistic pathway for non-enzymatic template-directed primer extension and presents a review of the thermodynamic driving forces involved in entropic templating. Through the lens of entropic templating, the rate and fidelity of a reaction are shown to be intrinsically linked to the reactivity of the activating agent used. Thus, a strategy is discussed for the optimization of non-enzymatic template-directed primer extension, providing a path towards cost-effective in vitro synthesis of RNA and DNA.
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ItemVacuum-Free Liquid-Metal-Printed 2D Semiconducting Tin Dioxide: The Effect of Annealing(American Chemical Society, 2024)Thin film transistors (TFTs) offer unparalleled opportunities for the fabrication of multifunctional electronic and optoelectronic devices. In this work, we report a vacuum-free liquid metal exfoliation technique for rapidly printing ∼2 nm-thick layer of oxide from molten tin. We explore the effect of rapid thermal annealing at 450 °C on the stoichiometry, morphology, and crystal structure of the resulting tin oxide nanosheets. The annealed samples exhibit a dominant SnO2 phase and a high degree of transparency (>99%) in the visible spectra. Field-effect transistors based on the two-dimensional (2D) SnO2 films show typical n-channel conduction with a field-effect mobility of ∼7.5 cm2 V–1 s–1. Photodetectors utilizing annealed tin dioxide demonstrate significant improvement in photoresponsivity reaching a value of 5.2 × 103 A W–1 compared to that found in an unannealed sample at an ultraviolet wavelength of 285 nm. We demonstrate that the improvement in device performance is due to nanocrystalline changes within the oxide layers during the annealing process. This work offers a straightforward and ambient air-compatible method for depositing ultrathin, large-area semiconducting oxides as potential candidates for enabling emerging applications in transparent nanoelectronics and optoelectronics.
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ItemExperimental investigation, numerical simulation and RSM modelling of the freezing and thawing of Mozzarella cheese(Elsevier, 2024-01)Freezing can be used to preserve functionality of Mozzarella cheese allowing export to distant markets but limited tools are available for prediction of freezing and thawing times as a function of composition and processing variables. Freezing and thawing processes were experimentally and numerically assessed for six Mozzarella samples, differing significantly in block size and composition. Numerical simulations using an enthalpy method were developed to build a validated and robust model for solving heat and mass transfer equations. A decrease in salt (NaCl) content from 1.34 % w/w to 0.07 % significantly altered the temperature of phase change from ∼–4.5 °C to –3 °C. Simulations showed minimal impact of salt migration on the salt in free moisture content deeper than ∼1–2 centimeters from the surface during freezing, with a slight increase of 8–10 % salt in free moisture at the block center. A response surface methodology (RSM) model was fit to the simulated data providing a useful tool for predicting freezing and thawing times for block sizes and a wider range of operating conditions enabling future process optimization. The RSM model indicated that increased salt content increased freezing time but decreased thawing time.
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ItemMachine learning for the prediction of proteolysis in Mozzarella and Cheddar cheese(Elsevier, 2024-03)Proteolysis is a complex biochemical event during cheese storage that affects both functionality and quality, yet there are few tools that can accurately predict proteolysis for Mozzarella and Cheddar cheese across a range of parameters and storage conditions. Machine learning models were developed with input features from the literature. A gradient boosting method outperformed random forest and support vector regression methods in predicting proteolysis for both Mozzarella (R2 = 92%) and Cheddar (R2 = 97%) cheese. Storage time was the most important input feature for both cheese types, followed by coagulating enzyme concentration and calcium content for Mozzarella cheese and fat or moisture content for Cheddar cheese. The ability to predict proteolysis could be useful for manufacturers, assisting in inventory management to ensure optimum Mozzarella functionality and Cheddar with a desired taste, flavor and texture; this approach may also be extended to other types of cheese.
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ItemNo Preview AvailableEnergy dissipation during homogeneous wetting of surfaces with randomly and periodically distributed cylindrical pillars(ACADEMIC PRESS INC ELSEVIER SCIENCE, 2024-04)HYPOTHESIS: Understanding contact angle hysteresis on rough surfaces is important as most industrially relevant and naturally occurring surfaces possess some form of random or structured roughness. We hypothesise that hysteresis can be described by the dilute defect model of Joanny & de Gennes [1] and that the energy dissipation occurring during the stick-slip motion of the contact line is key to developing a predictive equation for hysteresis. EXPERIMENTS: We measured hysteresis on surfaces with randomly distributed and periodically arranged microscopic cylindrical pillars for a variety of different liquids in air. The inherent (flat surface) contact angles tested range from lyophilic (θe=33.8°) to lyophobic (θe=112.0°). FINDINGS: A methodology for averaging the measured advancing and receding contact angles on random surfaces is presented. Based on these results correlations for roughness-induced energy dissipation are derived, and an equation for predicting the advancing and receding contact angles during homogeneous (Wenzel) wetting on random surfaces is presented. Equations that predict the onset of the alternate wetting conditions of hemiwicking, split-advancing, split-receding and heterogeneous (Cassie) wetting are also derived, thus defining the range of validity for the homogeneous wetting equation. A 'cluster' concept is proposed to explain the measurably higher hysteresis exhibited by structured surfaces compared to random surfaces.