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Selenium (Se) is an essential element for aquatic organisms as well as humans. It can be toxic to organisms depending on its concentration and chemical speciation; thus, considerable efforts have been made to unravel the biogeochemical cycling of Se in aquatic systems. Mathematical models provide an important tool to better understand the fate of Se in different environment compartments. However, a comprehensive review of modeling Se in aquatic systems with current challenges and opportunities is missing. To fill this gap, we firstly summarize the processes governing Se cycling in aquatic systems, including particle adsorption and desorption, diffusion, biological uptake, redox reactions, and volatilization. Then, we critically review the available models, identifying the compartments modelled, environmental factors considered, and the Se species and geochemical processes used in each model, providing an assessment of their advantages and limitations. Data availability for modeling studies is investigated, highlighting how to better quantify the redox reactions, estimate of Se loadings, and mass balance. For the modeling of Se cycling in aquatic systems, the ability of the models to link sources to biota concentrations under a range of hydrodynamic conditions and with mechanistic representations of transport, transformation, and uptake processes is required. The majority of the current models can conduct this task; however, to better present the uptake processes of Se in the food web, two-way coupling of the Se cycling model with a food web model is recommended.

Carbon nanotubes (CNTs) possess unique mechanical, physical, electrical and absorbability properties coupled with their nanometer dimensional scale that renders them extremely valuable for applications in many fields including nanotechnology and chromatographic separation. The aim of this review is to provide an updated overview about the applications of CNTs in chiral and achiral separations of pharmaceuticals, biologics and chemicals. Chiral single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) have been directly applied for the enantioseparation of pharmaceuticals and biologicals by using them as stationary or pseudostationary phases in chromatographic separation techniques such as high-performance liquid chromatography (HPLC), capillary electrophoresis (CE) and gas chromatography (GC). Achiral MWCNTs have been used for achiral separations as efficient sorbent objects in solid-phase extraction techniques of biochemicals and drugs. Achiral SWCNTs have been applied in achiral separation of biological samples. Achiral SWCNTs and MWCNTs have been also successfully used to separate achiral mixtures of pharmaceuticals and chemicals. Collectively, functionalized CNTs have been indirectly applied in separation science by enhancing the enantioseparation of different chiral selectors whereas non-functionalized CNTs have shown efficient capabilities for chiral separations by using techniques such as encapsulation or immobilization in polymer monolithic columns.

Deepfakes have emerged as one of the most significant developments in contemporary computational media, representing a sophisticated convergence of machine learning, computer vision, and audiovisual synthesis. Enabled primarily by deep neural networks such as generative adversarial networks (GANs) and transformer-based architectures, Deepfakes are realistic video fabrications through sound and image alteration and substitution that synthesises human likeness, speech, and behaviours. Deepfakes function simultaneously as creative tools, political instruments, security risks, and epistemic disruptors. They have generated widespread scholarly, regulatory, and public concern by contributing to the reshaping of visual communication and posing significant challenges to established norms of authenticity. This entry defines Deepfakes, outlines their technological foundations, synthesises insights from current research and assesses implications for media industries, journalism, documentary, disinformation, governance, and digital culture.

Environmental contextArsenic’s effect on rice plant health is a critical environmental issue. This study reveals that rice plants absorb inorganic arsenic and dimethylarsenic differently, with dimethylarsenic posing a greater threat to rice plant health. These findings contribute to our understanding of arsenic toxicity in plants, highlighting the need for further research into detoxification strategies for dimethylarsenic.RationaleArsenic toxicity in plants, particularly the effects of different arsenic species, is not well understood. This study investigated the response of juvenile rice plants, grown hydroponically, to prolonged exposure to inorganic and dimethyl arsenic species. The hydroponic system removed complexity by eliminating soil processes.MethodologyThe accumulation of inorganic As (Asi) and dimethylarsenic (DMA) in hydroponically grown rice was monitored for plants exposed to different As concentrations (0–6.7 µmol L−1). Dose–response experiments were conducted to compare the effects of As species on plant health in terms of growth.ResultsPlants absorb Asi and DMA linearly, with faster Asi uptake than DMA. Asi exposure leads to higher As concentrations in roots and shoots than DMA. Despite more Asi in roots, its translocation to shoots is lower. Asi and DMA accumulation in shoots remains relatively constant at lower As concentrations. At the highest As concentration, more Asi and DMA accumulate in shoots. Exceeding 1.6 µmol L−1, Asi and DMA reduce plant height and biomass. Asi-exposed plants show little health differences except at the highest concentrations. DMA-exposed plants show more unhealthy instances above 1.6 µmol L−1.DiscussionDMA’s lower uptake rate aligns with other rice species results, as do lower shoot and root translocation factors. Near constant As concentrations in shoots at low Asi concentrations suggest an Asi exposure threshold before plants lose their As sequestration ability, resulting in reduced growth. DMA exposure increases the number of unhealthy plants, suggesting a greater potential effect on plant health and fitness, differing from Asi-induced stress.

Environmental contextSeveral predators that eat Antarctic krill may be unintentionally ingesting toxic substances. Studying aspects of krill life to understand the effects of potential increases in Antarctic mercury (Hg) availability revealed that seasons, locations and individual size influence krill Hg concentration. Despite increasing human presence (potential Hg sources) in Antarctica, krill Hg content remains stable, and evidence suggests that Hg accumulates in predators by both short (krill-based) and longer food chains.RationaleMercury (Hg) is passively assimilated from the water by phytoplankton, accumulated by lower trophic levels species, and biomagnified along food chains. Any increases in its bioavailability in Antarctic waters could endanger the survival of vulnerable top predators. With Antarctic food webs reliant on krill, we must understand the temporal, spatial and biological variability in their Hg concentration to forecast ecosystem-wide impacts of rising Hg levels.MethodologyWe sampled krill fortnightly from South Georgia, South Orkney Islands and West Antarctic Peninsula between December 2013 and September 2019 (excluding October and November months). Individuals were weighed, sexed and analysed for Hg. We assessed the importance of biological (krill size, sex and life stage) and environmental (location, time and chlorophyll-a concentration) parameters on krill Hg concentrations with generalised linear models, analyses of variance, Gaussian linear models and vector autoregressive modelling.ResultsTemporal variation explained most of the differences in krill Hg concentrations, with location and individual size also contributing to the variability. Subsurface chlorophyll-a concentrations and the affinity of methylmercury to sulfhydryl groups of some proteins, rather than krill fatty acid content, were likely the drivers of observed annual cycles.DiscussionAntarctic krill Hg concentrations have remained stable since the 1990s, although our measurements were lower than most. Such a historic baseline is indispensable for continued monitoring of Antarctic ecosystems. Krill is considered a key prey species, but our findings and those of biomagnification studies suggest that there may be a gap in our understanding of trophic transfer and accumulation of Hg in some top predators. Future biomagnification studies would benefit from conducting mass balance models.

The fate of selenium (Se) inputs from coal-fired power station operations in a marine dominated estuary, Lake Macquarie NSW, is explored, as well as Se toxicity, including sublethal and population effects. Selenium is rapidly adsorbed to sediments, and food webs are based on benthic food sources. Selenium is remobilised from sediments by volatilisation and diffusional processes following bioturbation. It is then transferred into food chains via benthic microalgae, deposit feeders and filter-feeding organisms processing suspended sediments. Historically, Se has been found to accumulate in fish to levels above those considered safe for human consumption. After the remediation of a major ash dam in 1995, Se inputs to Lake Macquarie have declined, and the Se concentrations of sediments have also reduced partially due to the deposition of cleaner sediment but also due to the formation of volatile dimethyl selenide. Bioturbation of oxidised surface sediments also results in the release of inorganic Se. In response to decreases in sediment Se concentrations, molluscs and fish Se concentrations have also reduced below deleterious levels, with most fish now being safe for human consumption. Selenium cycling involves the transformation of inorganic species (Se0, SeII, SeIV, SeVI) in sediments and the water column to dimethylselenide and dimethyl diselenide by bacteria with the accumulation of organic Se species in plant detritus (selenomethionine) and animals (selenomethionine and selenocysteine). Dissolved Se concentrations in Lake Macquarie, except near ash dam inputs, have always been well below those that cause toxicity. There is evidence based on Se sediment-spiking studies, however, that Se is probably causing sublethal effects. When undertaking risk assessments of Se, careful consideration should be given to understanding the fate of Se inputs and remobilisation into food webs as not all systems act in accordance with published studies that generally have high Se concentrations in the water column and phytoplankton-based food webs.

To investigate the release and degradation of arsenolipids present in the marine brown macroalga Ecklonia radiata, tissues were collected in various stages of decomposition from intertidal environments, while tissues were also decomposed in laboratory-based microcosms prepared using combinations of autoclaved and natural (non-autoclaved) seawater and sand. Field collected macroalgae samples contained 20–120 μg g−1 total As of which 1–10% were arsenolipids comprising mainly an arsenic hydrocarbon (AsHC; 3–13% of total arsenolipids) and four di-acyl arsenic phospholipids (AsPLs; 86–95%). Additionally, a mono-acyl AsPL was found in all water-column decomposing samples. Arsenolipid concentrations in live tissues were similar to those in tissues decomposing in the water-column (1.3–2.9 μg g−1 dry mass), which were both up to four times higher than those in decomposing tissues collected from intertidal environments (0.7–1.3 μg g−1 dry mass). In the microcosm experiments, the arsenolipid content of E. radiata decreased substantially as decomposition proceeded. In the majority of microcosms, more than 75% of the arsenolipids present initially disappeared within 5 days with only the AsHC persisting until day 60 (the length of the experiment). This study demonstrates that the habitat in which decomposition occurs influences the release and degradation of arsenolipids with the greatest losses occurring when tissues decompose in intertidal environments. Microbial diversity, biomass, and overall activity are thus likely to play important roles in the persistence of arsenolipids in decomposing algae.

Rationale. The uptake of arsenate by algae from oceanic waters and its transformation to arsenosugars and arsenolipids is well established, but the biosynthetic pathways remain largely unknown. Methodology. We investigated these pathways by using time-series experiments over 48 h to follow the formation of organoarsenic species from arsenate-enriched medium (15 µg As L−1) by the unicellular alga Dunaliella tertiolecta cultured under batch and continuous culture conditions. We used complementary mass spectrometry methods for the determination and quantification of 14 arsenic species; an additional three species could be quantified but remained unidentified. Results. The alga rapidly methylated the arsenate to dimethylarsinate (DMA), which then served as the precursor to arsenosugars and arsenolipids; the concentrations of these complex organoarsenicals increased throughout the experiments accompanied by a concomitant reduction in DMA concentrations. The pattern of compounds formed by the alga was similar for both batch and continuous cultures, but the concentrations were 2–3-fold higher in the continuous culture samples and the increases with time were much clearer. Discussion. The data suggest that the arsenosugars and the arsenolipids were mostly formed simultaneously from DMA, although there was an indication that the arsenic phospholipids were at least partly also being formed from the arsenosugars. Overall, the data are consistent with a direct biosynthesis of DMA from arsenate by D. tertioleta, and thereafter a non-specific incorporation of DMA into commonly available alga metabolites encompassing various sugars and lipids.

A 28-year-old woman who was undergoing treatment with eculizumab for paroxysmal nocturnal hemoglobinuria presented to the hospital with fevers, chills, headache, and a swollen left index finger. Blood cultures returned positive for Neisseria gonorrhoeae. We report the second case of disseminated gonococcal infection associated with the use of eculizumab.

This study investigated whether selenium species in wheat grains could be altered by exposure to different combinations of nitrogen (N) and sulphur (S) fertilisers in an agronomic biofortification experiment. Four Australian wheat cultivars (Mace, Janz, Emu Rock and Magenta) were grown in a glasshouse experiment and exposed to 3 mg Se kg −1 soil as selenate (Se VI ). Plants were also exposed to 60 mg N kg −1 soil as urea and 20 mg S kg −1 soil as gypsum in a factorial design (N + S + Se; N + Se; S + Se; Se only). Plants were grown to maturity with grain analysed for total Se concentrations via ICP-MS and Se species determined via HPLC-ICP-MS. Grain Se concentrations ranged from 22 to 70 µg Se g −1 grain (dry mass). Selenomethionine (SeMet), Se-methylselenocystine (MeSeCys), selenohomolanthionine (SeHLan), plus a large concentration of uncharacterised Se species were found in the extracts from grains. SeMet was the major Se species identified accounting for between 9 and 24 µg Se g −1 grain. Exposure to different N and S fertiliser combinations altered the SeMet content of Mace, Janz and Emu Rock grain, but not that of Magenta. MeSeCys and SeHLan were found in far lower concentrations (<4 µg Se g −1 grain). A large component of the total grain Se was uncharacterisable (>30 % of total grain Se) in all samples. When N fertiliser was applied (with or without S), the proportion of uncharacterisable Se increased between 60 and 70 % of the total grain Se. The data presented here indicate that it is possible to alter the content of individual Se species in wheat grains via biofortification combined with manipulation of N and S fertiliser regimes. This has potential significance in alleviating or combating both Se deficiency and Se toxicity effects in humans.