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Metabolic engineering of Rhodotorula toruloides for the production of linalool
No full textLinalool is widely used in foods, pharmaceuticals, and cosmetics. Microbial production offers a sustainable alternative to current plant extraction and chemical synthesis. In the present study, the oleaginous yeast Rhodotorula toruloides was metabolically engineered for linalool production. Overall, an integrated strategy involving linalool synthase selection, promoter screening, and pathway enhancement was implemented. The linalool biosynthesis baseline was established by using a 51 aa-truncated linalool synthase from Mentha citrate (t51McLIS). The linalool titer was increased to 249.7 mg/L by optimizing the expression of critical enzymes with native promoters. Then, it was improved to 790.2 mg/L by manipulating the mevalonate pathway and further elevated to 845.1 mg/L (42.3 mg/g glucose) by optimizing the fermentation conditions in shake flasks. Finally, the linalool production was enhanced to 2.59 g/L and 26.9 mg/g glucose in a 3 L bioreactor. The results demonstrated the potential of R. toruloides for the microbial production of monoterpenes
Longer wing bones in warmer climates suggest a role of thermoregulation in bird wing evolution
No full textAim
The tendency for animals in warmer climates to be longer-limbed (Allen's Rule) is widely attributed to the demands of thermoregulation. The role of thermoregulation in structuring bird wings, however, has been overshadowed by the selective demands placed on wings by flight. We test whether occurrence in warmer climates is associated with longer wing bones.
Location
Global.
Time Period
Current.
Major Taxa Studied
Aves: Passeriformes.
Methods
Using computer vision, we measure wing-bone length from photographs of museum skeletal specimens for 1520 species of passerine birds. We then model the relationship between wing-bone length and temperature, accounting for allometry, the demands of flight efficiency and manoeuvrability, and a range of ecological and environmental variables.
Results
Wing bones are longer in warmer climates. Our models, largely as a result of allometric effects, explain nearly all the variation in wing-bone length in our data, with a marginal R2 = 0.80 and a conditional R2 > 0.99.
Main Conclusions
Across 1520 species of birds, higher temperatures are associated with longer wing bones, as predicted by Allen's Rule. The vascularised musculature along these bones is maximally uncovered when birds actively hold their wings away from their bodies to aid in cooling or during flight. Conversely, the musculature along the wing bones is insulated by feathering when at rest, such that wings play a minor role in heat exchange when individuals are less active and may need to retain heat. While our analyses do not directly establish the mechanistic basis underlying the pattern we recover, given the asymmetry in the role of wings in thermoregulation, we interpret the positive relationship between temperature and wing-bone length to reflect increased demand for heat dissipation in warmer climates. Our findings highlight the role of thermoregulation in shaping even the most critical features of vertebrate anatomy
Dynamic nanodomains dictate macroscopic properties in lead halide perovskites
No full textLead halide perovskites have emerged as promising materials for solar energy conversion and X-ray detection owing to their remarkable optoelectronic properties. However, the microscopic origins of their superior performance remain unclear. Here we show that low-symmetry dynamic nanodomains present in the high-symmetry average cubic phases, whose characteristics are dictated by the A-site cation, govern the macroscopic behaviour. We combine X-ray diffuse scattering, inelastic neutron spectroscopy, hyperspectral photoluminescence microscopy and machine-learning-assisted molecular dynamics simulations to directly correlate local nanoscale dynamics with macroscopic optoelectronic response. Our approach reveals that methylammonium-based perovskites form densely packed, anisotropic dynamic nanodomains with out-of-phase octahedral tilting, whereas formamidinium-based systems develop sparse, isotropic, spherical nanodomains with in-phase tilting, even when crystallography reveals cubic symmetry on average. We demonstrate that these sparsely distributed isotropic nanodomains present in formamidinium-based systems reduce electronic dynamic disorder, resulting in a beneficial optoelectronic response, thereby enhancing the performance of formamidinium-based lead halide perovskite devices. By elucidating the influence of the A-site cation on local dynamic nanodomains, and consequently, on the macroscopic properties, we propose leveraging this relationship to engineer the optoelectronic response of these materials, propelling further advancements in perovskite-based photovoltaics, optoelectronics and X-ray imaging
Multiplicative dynamic mode decomposition
No full textKoopman operators are infinite-dimensional operators that linearize nonlinear dynamical systems, facilitating the study of their spectral properties and enabling the prediction of the time evolution of observable quantities. Recent methods have aimed to approximate Koopman operators while preserving key structures. However, approximating Koopman operators typically requires a dictionary of observables to capture the system’s behavior in a finite-dimensional subspace. The selection of these functions is often heuristic, may result in the loss of spectral information, and can severely complicate structure preservation. This paper introduces multiplicative dynamic mode decomposition (MultDMD), which enforces the multiplicative structure inherent in the Koopman operator within its finite-dimensional approximation. Leveraging this multiplicative property, we guide the selection of observables and define a constrained optimization problem for the matrix approximation, which can be efficiently solved. MultDMD presents a structured approach to finite-dimensional approximations and can more accurately reflect the spectral properties of the Koopman operator. We elaborate on the theoretical framework of MultDMD, detailing its formulation, optimization strategy, and convergence properties. The efficacy of MultDMD is demonstrated through several examples, including the nonlinear pendulum, the Lorenz system, and fluid dynamics data, where we demonstrate its remarkable robustness to noise
Using the helium triplet as a tracer of the physics of giant planet outflows
No full textHydrodynamic outflows, such as those observed escaping close-in gas giant planets, are not isothermal in structure. Their highly ionized nature allows them to cool adiabatically at distances beyond several planetary radii. The contrast between the hottest gas temperatures at around 10,000K and the coldest at around 1,000K triggers an excess population of the observable helium triplet. This excess is caused by the suppression of collisional de-excitation from the triplet state at cool temperatures. Using radiation-hydrodynamic simulations, we show that this helium triplet excess may explain the excess broadening seen in HD 189733b’s observed transmission spectrum, demonstrating adiabatic cooling of its outflow, confirming its hydrodynamic nature on scales of several planetary radii. However, further observations are required to confirm this conclusion. Furthermore, we explore a range of electron transitions for neutral helium which were not considered in the previous literature. We find that the He21S state is unavailable as a potential reservoir for He23S electrons. Additionally, the de-excitation to the ground state must be considered for stellar spectra later than K2 in predicting the correct helium triplet population. Importantly, since triplet helium inherits momentum from ionized helium as it is generated by recombination, it is significantly less prone to fractionation than ground-state neutral helium. However at separations of ≳ 0.05 au, ionization at the flow base and drag on helium weaken, leading to significant fractionation of the then mostly neutral helium. This in turn, can cause a suppression of the Helium transit depth, even though the helium line width remains large
The influence of hydroxylamine on Fe coagulation when treating NOM and TC from real-world waters
No full textCoagulation occurs everywhere in natural aquatic environment and is widely used in water treatment. However, the influence of reducing substances on coagulation has long been overlooked. And one limitation of coagulation is its low efficiency in removing organics of low molecular weight (MW). In this study, we investigated the influence of hydroxylamine (HA), a representative reducing substance, on iron (Fe) coagulation when treating natural organic matter (NOM) and tetracycline (TC); the latter selected as a representative low MW micro-pollutant. It was found that HA enhanced the removal of organics from the effluent water (the Olympic Park Lake water, OP) and surface water (the Jingmi River water, JM) employed in the experiments. Also, the simultaneous enhanced removal of NOM and TC was achieved in the coagulation process. In addition, HA not only enhanced the removal of TC of low MW, but also improved the NOM removal of low MW components. The integration results of size exclusion chromatography (SEC) showed that HA increased the NOM removal of Fe(III) and Fe(II) from 10.1 %, 0–14.2 %, 15.2 % and 7.0 %, 5.3–11.0 %, 13.7 % for 1.5–2.5 K MW in OP and JM, respectively. The reasons for the enhanced performance were that, in addition to the reducing effect of HA on Fe redox revealed by cyclic voltammetry, beneficial Fe species were generated, resulting in a greater combination between Fe and organics. In general, this study has provided detailed information about the influence of HA on Fe coagulation when treating NOM and low MW micro-pollutants
SpaceKG: towards exploiting Knowledge Graphs in space systems
No full textSpace systems consist of a vast quantity of deeply interconnected and time-evolving elements. This complexity has been steadily increasing in recent years, prompting the development of intelligent tools capable of managing information in such a scenario and transforming it into actionable knowledge. This paper aims to combine deductive artificial intelligence with space engineering, integrating space project activities with Knowledge Graphs’ semantics and operational dynamics. We propose SpaceKG, a real-time, data-driven, dynamically evolving cognitive digital twin that enables digital continuity throughout the life cycle and across the disciplines of space systems. While traditional Model Based Systems Engineering approaches focus on Knowledge Representation, they struggle with rapid adaptation to change. In contrast, our solution offers a dynamic framework to deal with faster interactions with domain experts and evolving requirements. We showcase and validate the effectiveness of the proposed approach in a specific case study for detecting failure events in the Space Shuttle Main Engine. To this aim, we leverage Vadalog, a high-performance deductive reasoning language that provides full transparency and explainability over the portion of the space system more comprehensively and flexibly than existing approaches
Aerosol dynamics on hot exoplanets: the role of radiation pressure
No full textAerosols appear to be ubiquitousin exoplanetary atmospheres. However, because our understanding of the physical processesthat
govern aerosols is incomplete, their presence makes the measurement of atmospheric properties, such as molecular abundance
ratios, difficult. We show that aerosol particles in highly irradiated exoplanets experience an additional acceleration due to stellar
radiation pressure. The strength of this radiative acceleration often exceeds the planet’s gravity and can approach values of
∼ 10–20× gravity’s for low-density planets (typically sub-Saturns) hosting ∼0.1–1μm aerosols. Since these highly irradiated,
low-density planets are often the best targets for atmospheric characterization with current instrumentation, radiation pressure is
likely an important process when considering aerosol dynamics. We find that radiation pressure accelerates hazes produced by
photochemistry at high altitudes to faster terminal velocities, causing them to grow more slowly. Hence, the particles are smaller
and have lower mass concentrations in the presence of radiation pressure. By simulating haze-like aerosols in a 2D equatorial
band model, we show that radiation pressure steepens optical slopes in transmission spectra, resulting in less muted molecular
features in the Near-IR and gives rise to a correlation between the strength of radiation pressure and the molecular feature
amplitude. Furthermore, the interaction of zonal winds and radiation pressure impacts both the optical slopes and amplitudes on
the individual morning and evening terminators
Predictive modelling of the solid-liquid solubility and chemical equilibrium of amino acids and oligopeptides: Exploring the influence of charges within a group-contribution framework
No full textThe accurate prediction of thermodynamic properties of amino-acid and peptide solutions is critical in the pharmaceutical industry, where amino acids and oligopeptides are gaining increasing prominence as active pharmaceutical ingredients (APIs). A major challenge in this regard is the development of predictive models with broad applicability, parameter transferability, and minimal reliance on system-specific experimental data. In this thesis, this challenge is addressed by developing group-contribution (GC) thermodynamic models to predict the solubility of amino acids and oligopeptides across a wide range of solvent systems and thermodynamic conditions, with a particular focus on the complex effects of pH-dependent speciation and charge interactions.
The SAFT-γ Mie GC equation of state (EoS) is employed to describe solid–liquid equilibria in systems containing amino acids and oligopeptides. Parameter optimisation is carried out using experimental data from chemically related systems, demonstrating the high degree of transferability and reducing the dependency on direct solubility measurements. Chemical-equilibrium equations are coupled with phase-equilibrium equations to capture speciation effects accurately. Additionally, an exploratory molecular simulation study benchmarks the treatment of electrostatic interactions in ionic systems using the expanded-ensemble method, providing critical insights into modelling ionic chains within primitive-model expressions.
The resulting model delivers accurate solubility predictions for a wide variety of systems, underscoring its robustness and potential for application in drug development. However, the study also highlights the limitations imposed by the scarcity and inconsistency of experimental data, especially for melting properties and solid–liquid solubility. The molecular simulation study provides important insights into the treatment of electrostatic interactions in ionic-chain molecules, providing potential directions for future improvements to the primitive-model expressions used within the model.Open Acces
Pore-scale investigation of two-phase flow hysteresis in hydrogen storage using micro-ct imaging
No full textWith increasing interest in hydrogen as a clean energy carrier, understanding its behaviour in subsurface porous media is essential for optimising geological storage systems. This PhD thesis investigates the pore-scale dynamics of hydrogen-brine systems, focusing on hysteresis, capillary pressure, and the role of Ostwald ripening in gas retention and connectivity. Traditional models-largely based on hydrocarbon systems-tend to overlook gas redistribution mechanisms like Ostwald ripening. This research addresses that gap by employing high-resolution X-ray tomography combined with the computation of Minkowski functionals to examine hydrogen behaviour in Bentheimer sandstone, offering new insights into gas-phase connectivity and trapping. The work comprises three experimental investigations. The first study examined hydrogen and brine distribution during repeated injection and waterflooding cycles, with a 16-hour storage period. Results showed preferential hydrogen accumulation in larger pores and demonstrated that Ostwald ripening enhanced gas connectivity even in the absence of external flow. The second experiment focused on capillary pressure and saturation changes across three injection–flooding cycles. Residual gas saturation decreased from 40% in the first cycle to less than 18% by the third, suggesting reduced hysteresis relative to conventional expectations and reinforcing the significance of Ostwald ripening in mobilising trapped gas. The final study extended the storage period to four days to observe longer-term effects on hydrogen distribution and connectivity. Using both hydrophilic and hydrophobic porous plates, contact angle measurements confirmed the water-wet nature of Bentheimer sandstone. Observations revealed a decrease in gas saturation from 85% after initial hydrogen injection to 22% after the third brine injection. These findings further highlight that hydrogen storage hysteresis is less pronounced than predicted by classical models. By advancing the understanding of pore-scale fluid topology and gas connectivity, this thesis contributes important insights toward the design and optimisation of subsurface hydrogen storage systems, supporting the transition to cleaner energy solutions.Open Acces