Engineering: Journal Articles
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Item Open Access The effect of HCl on the α-Ga2O3 thin films fabricated by third generation mist chemical vapor deposition(AIP Publishing, 2021) Yasuoka T; Liu L; Ozaki T; Asako K; Ishikawa Y; Fukue M; Dang, Giang; Kawaharamura Tα-Ga2O3 thin films were grown on a c-plane sapphire substrate by a third generation mist chemical vapor deposition system. The surface roughness was measured by atomic force microscopy, and the composition of Ga2O3 was measured by x-ray photoelectron spectroscopy. It was found that HCl affects the growth rate, purity, and surface roughness of α-Ga2O3 films. The growth rate increased with the HCl supply. The thickness, surface roughness, and chemical state analyses indicate that three growth modes occurred depending on the Ga supply rate and HCl/Ga supply ratio and the purity was improved by optimizing the HCl/Ga supply ratio and Ga supply rate.Item Open Access Constructing random matrices to represent real ecosystems(UNIV CHICAGO PRESS, 2015) James, Alex; Plank, Michael; Rossberg AG; Beecham J; Emmerson M; Pitchford JWModels of complex systems with n components typically have order n2 parameters because each component can potentially interact with every other. When it is impractical to measure these parameters, one may choose random parameter values and study the emergent statistical properties at the system level. Many influential results in theoretical ecology have been derived from two key assumptions: that species interact with random partners at random intensities and that intraspecific competition is comparable between species. Under these assumptions, community dynamics can be described by a community matrix that is often amenable to mathematical analysis. We combine empirical data with mathematical theory to show that both of these assumptions lead to results that must be interpreted with caution. We examine 21 empirically derived community matrices constructed using three established, independent methods. The empirically derived systems are more stable by orders of magnitude than results from random matrices. This consistent disparity is not explained by existing results on predator-prey interactions. We investigate the key properties of empirical community matrices that distinguish them from random matrices. We show that network topology is less important than the relationship between a species’ trophic position within the food web and its interaction strengths. We identify key features of empirical networks that must be preserved if random matrix models are to capture the features of real ecosystems.Item Open Access Observation and modeling of platelet ice fabric in McMurdo Sound, Antarctica(American Geophysical Union (AGU), 2010) Dempsey, David; Langhorne PJ; Robinson NJ; Williams MJM; Haskell TG; Frew RDDuring the annual growth of landfast ice in McMurdo Sound, Antarctica, an episodic flux of platelet ice crystals from the ocean contributes to the build up of a porous subice platelet layer, which is steadily incorporated into the sea ice cover as it thickens over winter. In November 2007, we examined the spatial variability of these processes by collecting sea ice cores, with simultaneous oceanographic observations, along an east-west transect in the sound. Previously identified draped and bladed platelet ice types were observed. In addition, we identify resumed columnar growth which appears to be a result of geometric selection from the subice platelet layer after the arrival of new platelet crystals from the ocean has ceased. A numerical model of mechanical platelet ice processes is developed that predicts crystal texture and c axis distributions, producing virtual incorporated platelet ice with known growth history. This model demonstrates how a disordered subice platelet layer arises from an initially flat interface and suggests that such a layer is more likely to form later in the growth season. The model also suggests how the grain boundary density in incorporated platelet ice responds to changes in the flux of loose platelet crystals from the ocean. Application of this result to our 2007 platelet ice observations indicates that sea ice in western McMurdo Sound is subject to larger and more persistent platelet fluxes than the ice in the east. This is consistent with the pattern of in situ supercooling just beneath the ocean surface. © 2010 by the American Geophysical Union.Item Open Access Modeling the effects of silica deposition and fault rupture on natural geothermal systems(American Geophysical Union (AGU), 2012) Dempsey, David; Rowland JV; Zyvoloski GA; Archer RANatural geothermal convection abounds within the Taupo Volcanic Zone (TVZ) of New Zealand's Central North Island. In many locations the highly porous eruptive products that blanket the landscape have been altered by the throughput of hydrothermal fluids and the consequent deposition of silica. We detail a numerical model that considers the evolution of a geothermal plume in the presence of silica deposition/dissolution that controls an evolving permeability distribution. Precipitation of silica occurs according to a gradient reaction regime, in which the dissolved silica concentration is controlled by the temperature dependent silica solubility. Over a period of 120 kyr, continuous geothermal circulation leads to the development of a low permeability cap-zone, approximately 200 m thick, above the main geothermal upflow zone. The cap-zone encourages lateral flow of rising fluids, increasing the area across which geothermal expression is observed. It also has an insulating effect on fluids below the cap, causing increases in temperature, enthalpy, and the reservoir potential of the field. A second model is constructed to consider the specific scenario of fault rupture through the impermeable cap-zone. Coseismic increases in permeability along the fault plane produce vigorous, renewed flow through the center of the geothermal field, temporarily reducing lateral flows. However, resealing of near surface permeability is rapid, and the restoration of lateral flows and recovery of the geothermal reservoir occurs within ∼10 kyr. These effects are discussed in the context of two TVZ geothermal fields: the extinct Ohakuri field, and Te Kopia, which is situated on a major active normal fault. Copyright 2012 by the American Geophysical Union.Item Open Access Nutrition in Abrupt Sunlight Reduction Scenarios: Envisioning Feasible Balanced Diets on Resilient Foods(MDPI AG, 2022) Pham , Alix; García Martínez, Juan B.; Brynych , Vojtech; Stormbjorne , Ratheka; Pearce , Joshua M.; Denkenberger, DavidAbrupt sunlight reduction scenarios (ASRS) following catastrophic events, such as a nuclear war, a large volcanic eruption or an asteroid strike, could prompt global agricultural collapse. There are low-cost foods that could be made available in an ASRS: resilient foods. Nutritionally adequate combinations of these resilient foods are investigated for different stages of a scenario with an effective response, based on existing technology. While macro-and micronutrient requirements were overall met, some—potentially chronic—deficiencies were identified (e.g., vitamins D, E and K). Resilient sources of micronutrients for mitigating these and other potential deficiencies are presented. The results of this analysis suggest that no life-threatening micronutrient deficiencies or excesses would necessarily be present given preparation to deploy resilient foods and an effective response. Careful preparedness and planning—such as stock management and resilient food production ramp-up—is indispensable for an effective response that not only allows for fulfilling people’s energy requirements, but also prevents severe malnutrition.Item Open Access Study on the pore and microstructure fractal characteristics of alkali-activated coal gangue-slag mortars(MDPI AG, 2020) Ma H; Sun J; Wu C; Yi C; Li, YuJust as it is regarding ordinary cement-based materials, the pore structure and microstructure of alkali-activated materials are disordered. It is essential to predict the macroscopic properties by studying the pore and microstructure fractal characteristics of materials. In this paper, the effects of slag content and alkali activator modulus on compressive strength, porosity, and microstructure of alkali-activated coal gangue-slag (AACGS) mortar were studied. Further, with the help of mercury intrusion porosimetry (MIP) data and the MATLAB programming, the pore and SEM photos fractal dimensions of AACGS mortar specimens were obtained, respectively, and the relationship between the microscopic fractal dimensions and the macroscopic strength and the structural characteristics of pores was established. The results show that the pore fractal dimension has a good linear relationship with the compressive strength and pore characteristic parameters (porosity, total pore area, and average pore diameter, etc.). With the increase of slag content, the SEM photos fractal dimension of AACGS mortar specimens increases, and the fractal dimension and compressive strength also show a significant positive linear relationship. The two fractal characterization methods can be used in the alkali-activated material system and have important guiding significance for predicting the macroscopic strength and pore characteristic parameters of the material.Item Open Access Enzyme Kinetics Analysis (EKA): an online tool for analysing enzyme initial rate data and teaching enzyme kinetics(Wiley, 2024) Mak D; Dunn S; Coombes D; Carere C; Allison JR; Nock, Volker; Hudson A; Dobson REnzymes are nature's catalysts, mediating chemical processes in living systems. The study of enzyme function and mechanism includes defining the maximum catalytic rate and affinity for substrate/s (among other factors), referred to as enzyme kinetics. Enzyme kinetics is a staple of biochemistry curricula and other disciplines, from molecular and cellular biology to pharmacology. However, because enzyme kinetics involves concepts rarely employed in other areas of biology, it can be challenging for students and researchers. Traditional graphical analysis was replaced by computational analysis, requiring another skill not core to many life sciences curricula. Computational analysis can be time‐consuming and difficult in free software (e.g., R) or require costly software (e.g., GraphPad Prism). We present Enzyme Kinetics Analysis (EKA), a web‐tool to augment teaching and learning and streamline EKA. EKA is an interactive and free tool for analyzing enzyme kinetic data and improving student learning through simulation, built using R and RStudio's ShinyApps. EKA provides kinetic models (Michaelis–Menten, Hill, simple reversible inhibition models, ternary‐complex, and ping‐pong) for users to fit experimental data, providing graphical results and statistics. Additionally, EKA enables users to input parameters and create data and graphs, to visualize changes to parameters (e.g., or number of measurements). This function is designed for students learning kinetics but also for researchers to design experiments. EKA provides a simple, interactive interface for teachers, students, and researchers to explore enzyme kinetics. It gives researchers the ability to design experiments and analyze data without specific software requirements.Item Open Access Accelerated crystallization kinetics of MFI zeolite via imidazolium-based synthesis(2024) Liu T; Li X; Shim J; Curnow O; Choi J; Yip, AlexIonic liquids (ILs), known for their low melting points and vast array of possible combinations of cations and anions, serve as an ideal template for zeolite synthesis. MFI zeolite, with the distinct three-dimensional porous network, has attracted wide interest in petrochemical processes and environmental applications. In this study, we used 1-butyl-3-methylimidazolium (BMIM)-based ILs for MFI-type zeolite synthesis, successfully achieving a highly crystallized MFI-type crystal within 18 h. To highlight the benefits of using ILs, ZSM-5 zeolite synthesized using the conventional template, tetrapropylammonium hydroxide, was prepared for comparative analysis. Parameters including ion variations, aging duration, and aluminate content on crystal phase growth were explored. Furthermore, seed-assisted synthesis was carried out to verify the impact of the IL on the nucleation step. The mechanism underlying the accelerated crystallization process was subsequently elucidated, revealing that the inclusion of BMIM in the synthesis gel significantly contributed to rapid nucleation. This was followed by the immediate formation of amorphous particles. These particles then experienced inward growth, culminating in the development of well-crystallized particles. This discovery underscores the promising potential of ionic liquids (ILs) for efficient zeolite synthesis.Item Open Access Design of the Height of Antiglare Panels along Concave Vertical Curves(Hindawi Limited, 2018) Liang G-H; Dong C-H; Li, Yu; Li G; Hu X-X; Cui L-ZThis study introduces a method for calculating the height of antiglare panels for concave vertical curves. The concave vertical curve is divided into a straight-slope section, transition section, and middle section. The height of the antiglare panels in the middle section is designed based on the glare distance. The height in the straight-slope section is designed based on the height calculation formula given by the Chinese standard. The height of the antiglare panels in the middle section is greater than that in the straight-slope section. There should be a gradual transition in the height difference of the antiglare panels in the transition section. The height gradient of the antiglare panels in the transition section must be designed to ensure visual continuity and comfort for drivers. In the transition section, the transition design is carried out on the height difference of the antiglare panels using the UC-Win/Road simulation software to determine the acceptable height difference for drivers. When the radius of the concave vertical curve does not exceed 30,000 m, the height of the antiglare panel is required to be designed, and the height difference should not exceed 6 cm.Item Open Access Performance evaluation of parameters as estimators of seismic site effects in northern South America(Elsevier BV, 2024) Mercado , Vicente; Díaz-Parra , Fernando J.; Pajaro , Cesar A.; Montejo , Julian; Posada , Gustavo; Arcila , Monica; Arteta , Carlos A.In this study, we investigate the performance of several parameters as estimators of seismic site effects for sites in northern South America. Investigated parameters include the conventional time-averaged shear wave velocity in the upper 30 m (VS30), the predominant period of the site, and horizontal-to-vertical spectral ratios. To assess the performance of these parameters, we estimate the amplification of seismic waves within shallow soil layers (i.e., site effects) at recording stations across northern South America. The site amplification is estimated by analyzing the residuals calculated from ground-motion records with respect to model predictions for hard-rock site conditions. Several functional forms were introduced to express the linear site amplification in terms of the explored parameters. We evaluate the efficacy of the parameters, as well as their advantages and limitations, by considering their impact in the site-to-site standard deviation of the residuals between observations and predictions using the introduced functional forms.Item Open Access A novel additive manufacturing method of cellulose gel(MDPI AG, 2021) Zadeh HN; Bowles D; Huber, Tim; Clucas, DonScreen-additive manufacturing (SAM) is a potential method for producing small intricate parts without waste generation, offering minimal production cost. A wide range of materials, including gels, can be shaped using this method. A gel material is composed of a three-dimensional cross-linked polymer or colloidal network immersed in a fluid, known as hydrogel when its main constituent fluid is water. Hydrogels are capable of absorbing and retaining large amounts of water. Cellulose gel is among the materials that can form hydrogels and, as shown in this work, has the required properties to be directly SAM, including shear thinning and formation of post-shearing gel structure. In this study, we present the developed method of SAM for the fabrication of complex-shaped cellulose gel and examine whether successive printing layers can be completed without delamination. In addition, we evaluated cellulose SAM without the need for support material. Design of Experiments (DoE) was applied to optimize the SAM settings for printing the novel cellulose-based gel structure. The optimum print settings were then used to print a periodic structure with micro features and without the need for support material.Item Open Access Enhancement of aromatics and syngas production by co-pyrolysis of biomass and plastic waste using biochar-based catalysts in microwave field(Elsevier BV, 2024) Wang B; Chen Y; Chen W; Hu J; Chang C; Pang, Shusheng; Li PIn this study, O-rich biomass (bamboo) was co pyrolyzed with H-rich plastic waste (PE) based on the biochar-based catalysts to investigate the yield and quality of pyrolysis oil and syngas. Focusing on the variations of aromatics and phenolics, to reveal the synergetic mechanism between biomass and PE in microwave field. Biomass is “rich in O and lack of H”, and waste plastics are “rich in C and rich in O” which can provide a lot of H radicals for catalytic pyrolysis of biomass, improve the quality of bio-oil. And the active factors of biomass effectively activated PE. The biochar-based catalysts further promoted deoxygenation and arylation reactions, intensifying the generation of aromatics and reducing oxygen 25 containing compounds (phenols, etc.). Bamboo: PE=1: 3 catalyzed by Zr-modified biochar-based catalysts resulted in aromatics yielded as high as 74.13%, while phenols yields was only 9.39%. Incorporation of the externally H-donor PE promoted the growth of carbon chains, and the microwave field activated free radicals which facilitated the cyclization and arylation of carbon. The biochar-based catalysts also promoted the generation of high-value monocyclic aromatics by utilizing the selective ability in the microwave field. Finally, the coupled synergistic mechanism of co-pyrolysis in microwave field was proposed.Item Open Access On-chip non-contact mechanical cell stimulation - quantification of SKOV-3 alignment to suspended microstructures(2024) Onal, Sevgi; Alkaisi, Maan; Nock, VolkerAlthough the accumulation of random genetic mutations have been traditionally viewed as the main cause of cancer progression, altered mechanobiological profiles of the cells and microenvironment also play a major role as a mutation-independent element. To probe the latter, we have previously reported a microfluidic cell-culture platform with an integrated flexible actuator and its application for sequential cyclic compression of cancer cells. The platform is composed of a control microchannel in a top layer for introducing external pressure, and a polydimethylsiloxane (PDMS) membrane from which a monolithically-integrated actuator protrudes downwards into a cell-culture microchannel. When actively actuated, the integrated actuator, referred to as micro-piston, transfers the pressure from the control channel as a mechanical force to the cells underneath. When not actuated, the micro piston remains suspended above cells, separated from the latter via a liquid-filled gap of ∼108 µm. Despite the lack of direct physical contact between the micro-piston and cells in the latter arrangement, we observed distinct alignment of SKOV-3 ovarian cancer cells to the piston shape. To charaterize this observation, micro-piston localization, shape, and size were adjusted and the directionality of a mono-layer of SKOV-3 cells relative to the suspended structure probed. Cell alignment analysis was performed in a novel, label-free approach by measuring elongation angles of whole cell bodies with respect to micro-piston peripheries. Alignment of SKOV-3 cells to the structure outline was significant for circular, triangular and square micro-piston when compared to control areas without micro-piston on the same chip. The effect was present irrespective of whether cells were loaded with micro-pistons in static position (∼108 µm gap) or actively retracted using vacuum (>108 µm gap). Similar alignment was not observed for MCF7 cancer cells and MCF10A non-cancerous epithelial cells. The reported observation of directional movement and growth of SKOV-3 cells towards the region under micro-pistons point towards a to-date unexplored mechanotactic behaviour of these cells, warranting future investigations regarding the mechanisms involved and the role these may play in cancer.Item Open Access Co-flow injection for serial crystallography at X-ray free-electron lasers(International Union of Crystallography (IUCr), 2022) Doppler D; Rabbani MT; Letrun R; Villarreal JC; Kim DH; Gandhi S; Egatz-Gomez A; Sonker M; Chen, J.; Koua FHM; Yang J; Youssef M; Mazalova V; Bajt S; Shelby MLSerial femtosecond crystallography (SFX) is a powerful technique that exploits X-ray free-electron lasers to determine the structure of macromolecules at room temperature. Despite the impressive exposition of structural details with this novel crystallographic approach, the methods currently available to introduce crystals into the path of the X-ray beam sometimes exhibit serious drawbacks. Samples requiring liquid injection of crystal slurries consume large quantities of crystals (at times up to a gram of protein per data set), may not be compatible with vacuum configurations on beamlines or provide a high background due to additional sheathing liquids present during the injection. Proposed and characterized here is the use of an immiscible inert oil phase to supplement the flow of sample in a hybrid microfluidic 3D-printed co-flow device. Co-flow generation is reported with sample and oil phases flowing in parallel, resulting in stable injection conditions for two different resin materials experimentally. A numerical model is presented that adequately predicts these flow-rate conditions. The co-flow generating devices reduce crystal clogging effects, have the potential to conserve protein crystal samples up to 95% and will allow degradation-free light-induced time-resolved SFX.Item Open Access An internet of things prototype to quantify the lateral wheel path distributions of local roads in New Zealand(Informa UK Limited, 2023) Li Y; van der Walt, Jacobus; Scheepbouwer, Eric; Guo, Hongwei; Patel TThe actual lateral wheel path distribution (LWD) on roads differs from the design assumptions. This leads to premature deterioration of chip-sealed pavements in the form of flushing and ravelling resulting in subsequent maintenance costs. The location of LWD is key to calibrating the variable-rate bitumen spray bar used to minimise flushing and ravelling during chip seal construction. Current methods used to estimate the location of LWD rely on visual inspection. This is subjective and reliant on individual expertise. This study aims to automate obtaining LWD by developing an Internet of Things (IoT) prototype to locate the LWDs. This prototype was tested by collecting LWDs from 22 locations in Christchurch, New Zealand. Results show that narrow roads exhibit a concentrated wheel path distribution. Specifically, increasing single lane carriageway width leads to a significant rise in the standard deviation (spread) and position of the LWDs among 22 locations investigated. Cycle lanes or parking bays significantly influence the location and distribution of LWD. There is no clear link between road camber and LWD. The findings can be used to improve the calibration of the variable-rate bitumen spray bar and inform pavement and traffic engineers to enhance construction and maintenance practices.Item Open Access Modification of Zeolite Morphology via NH4F Etching for Catalytic Bioalcohol Conversion(Wiley, 2023) Iadrat P; Prasertsab A; Limlamthong M; Choi J; Park HE; Wattanakit C; Yip, AlexVarious commercial zeolites, including FER, MOR, ZSM‐5, BEA, and FAU frameworks, were treated with NH4F aqueous solutions to study the effects of fluoride etching on different zeolite frameworks. NH4F‐treated small‐medium pore FER, MOR, and ZSM‐5 samples showed much higher mesoporosities than the untreated ones without alteration of the structural compositions and acidic properties. On the other hand, the 12‐membered ring zeolites BEA and FAU showed severe dissolution of the framework aluminosilicate structure after NH4F etching due to the high accessibility of fluoride species into the framework structures. The effect of NH4F concentration on the fluoride treatment of H‐ZSM‐5 zeolite was specifically studied. From the results, we observed that structural etching with 20 wt.% NH4F was optimal for fabricating open‐pore H‐ZSM‐5 zeolite and resulted in a high mesoporosity with comparable relative crystallinity and acidity with respect to the untreated H‐ZSM‐5. The catalytic activities of the open‐pore H‐ZSM‐5 were evaluated with acid‐catalyzed methanol and bioethanol conversions. Remarkably, the hierarchical open‐pore H‐ZSM‐5 zeolite fabricated via fluoride etching exhibited an enhanced catalytic performance in bioethanol conversion with >85% conversion over 34 h TOS and a higher catalytic stability in methanol conversion than the parent H‐ZSM‐5 (~50% of bioethanol conversion at 34 h TOS).Item Open Access Genetic parameters of essential-oil traits for Eucalyptus bosistoana(2023) Rajapaksha C; Apiolaza L; Squire M; Altaner, ClemensA Eucalyptus bosistoana breeding trial established in New Zealand to select plants with improved growth and wood properties was assessed for essential-oil traits. Mature leaves of 8-year-old E. bosistoana were collected from 1901 trees representing 85 families. Twenty compounds were quantified in these samples. Heritability estimates (h2 ) of the quantified essential-oil compounds ranged from 0.06 to 1.14, with the most abundant compounds 1,8-cineole, aromadendrene and the unidentified compound 8 showing the highest h2 of 0.78, 1.14 and 0.59, respectively. Total oil content of the leaves had moderate (0.25) heritability. The estimated negative correlation between total oil content and 1,8-cineole concentration at the phenotypic and genetic levels (rp = –0.44 and rg = –0.70, respectively) implies that families with higher-quality oil had less oil in the leaves. 1,8-cineole was genetically negatively correlated with myrcene (rg = –0.74), α-pinene (rg = –0.71), linalool (rg = –0.90), aromadendrene (rg = –0.94), trans-pinocarveol (rg = –0.75) and the unknown compounds 3 (rg = –0.91), 6 (rg = –0.83), 8 (rg = –0.88) and 9 (rg = –0.75). Seven of the 85 families had breeding values consistent with the standard commercial oil-quality requirement of over 70% 1,8-cineole. The results indicate that a breeding program could aid essential-oil production from E. bosistoana.Item Open Access Effective prevention of palladium metal particles sintering by histidine stabilization on silica catalyst support(2024) Cahyanto H; Chen X; Lam FLY; Iadrat P; Wattanakit C; Kidkhunthod P; Singh V; Brooker S; Pang S; Choi J; Yip, AlexA robust method for enhancing the dispersion and stabilization of small metal nanoparticles in heterogeneous catalysts is developed. It involves in situ complexation of palladium(II) by histidine, in water, prior to impregnation in fumed silica. TEM images show that the histidine facilitates dispersion of the Pd(II) into finer nanoscale particles (2 nm) uniformly distributed on the support, rather than the large clusters (5 nm) seen in the absence of histidine. After hydrogen reduction, assessments using CO chemisorption and propylene hydrogenation indicate that the coordinated histidine might obscure the active sites on the Pd particles. However, as histidine decomposes between 220-300°C in air, these materials were treated at 225°C in air for 48 h. Afterwards the Pd(II) particles remain the same size, but after hydrogen reduction, there is a 2.4- fold increase in CO gas adsorption, indicative of an expanded Pd surface area. Furthermore, superior catalyst stability (activity >200 h) is observed during propylene hydrogenation at 250°C. This is consistent with histidine use having generated widely spaced, uniformly small, Pd nanoparticles on the silica support which is expected to help prevent agglomeration (sintering) during catalysis. This is a convenient low-cost strategy for reducing metal content, preventing sintering and optimizing catalyst performance.Item Open Access Trace gas oxidation sustains energy needs of a thermophilic archaeon at suboptimal temperatures(Springer Science and Business Media LLC, 2024) Leung PM; Grinter R; Tudor-Matthew E; Lingford JP; Jimenez L; Lee HC; Milton M; Hanchapola I; Tanuwidjaya E; Kropp A; Peach HA; Carere, Carlo; Stott, Matthew; Schittenhelm RB; Greening CDiverse aerobic bacteria use atmospheric hydrogen (H2) and carbon monoxide (CO) as energy sources to support growth and survival. Such trace gas oxidation is recognised as a globally significant process that serves as the main sink in the biogeochemical H2 cycle and sustains microbial biodiversity in oligotrophic ecosystems. However, it is unclear whether archaea can also use atmospheric H2. Here we show that a thermoacidophilic archaeon, Acidianus brierleyi (Thermoproteota), constitutively consumes H2 and CO to sub-atmospheric levels. Oxidation occurs across a wide range of temperatures (10 to 70 °C) and enhances ATP production during starvation-induced persistence under temperate conditions. The genome of A. brierleyi encodes a canonical CO dehydrogenase and four distinct [NiFe]-hydrogenases, which are differentially produced in response to electron donor and acceptor availability. Another archaeon, Metallosphaera sedula, can also oxidize atmospheric H2. Our results suggest that trace gas oxidation is a common trait of Sulfolobales archaea and may play a role in their survival and niche expansion, including during dispersal through temperate environments.Item Open Access A genus in the bacterial phylum Aquificota appears to be endemic to Aotearoa-New Zealand(Springer Science and Business Media LLC, 2024) Power JF; Carere, Carlo; Welford HE; Hudson DT; Lee KC; Moreau JW; Ettema TJG; Reysenbach AL; Lee CK; Colman DR; Boyd ES; Morgan XC; McDonald IR; Craig Cary S; Stott, MatthewAllopatric speciation has been difficult to examine among microorganisms, with prior reports of endemism restricted to sub-genus level taxa. Previous microbial community analysis via 16S rRNA gene sequencing of 925 geothermal springs from the Taupō Volcanic Zone (TVZ), Aotearoa-New Zealand, revealed widespread distribution and abundance of a single bacterial genus across 686 of these ecosystems (pH 1.2-9.6 and 17.4-99.8 °C). Here, we present evidence to suggest that this genus, Venenivibrio (phylum Aquificota), is endemic to Aotearoa-New Zealand. A specific environmental niche that increases habitat isolation was identified, with maximal read abundance of Venenivibrio occurring at pH 4-6, 50-70 °C, and low oxidation-reduction potentials. This was further highlighted by genomic and culture-based analyses of the only characterised species for the genus, Venenivibrio stagnispumantis CP.B2T, which confirmed a chemolithoautotrophic metabolism dependent on hydrogen oxidation. While similarity between Venenivibrio populations illustrated that dispersal is not limited across the TVZ, extensive amplicon, metagenomic, and phylogenomic analyses of global microbial communities from DNA sequence databases indicates Venenivibrio is geographically restricted to the Aotearoa-New Zealand archipelago. We conclude that geographic isolation, complemented by physicochemical constraints, has resulted in the establishment of an endemic bacterial genus.