Poly- and perfluoroalkyl substances (PFASs) comprise a group of synthetic organic surfactants with a wide range of industrial and commercial applications. A few PFASs such as perfluorooctane ...sulfonate (PFOS) and perfluorooctanoate (PFOA) are now known to be ubiquitously present in the aquatic environment. They have become a global concern because of the toxicity and bioaccumulative properties. With the increasing availability of high-resolution mass spectrometers, many novel PFASs have been identified. Studies published between 2009 and 2017 have discovered 455 new PFASs (including nine fully and 446 partially fluorinated compounds), 45%, 29%, 17%, and 8% of which are anions, zwitterions, cations, and neutrals, respectively. They have been identified in natural waters, fish, sediments, wastewater, activated sludge, soils, aqueous film-forming foams, and commercial fluoropolymer surfactants. This article integrates and critically evaluates what is known about these newly identified PFASs. It discusses the different aspects of detection methodologies. It also surveys the removal of these compounds during conventional and advanced drinking-water and wastewater treatment, predicts the relevant physicochemical properties by means of four software programs, and identifies major knowledge gaps. Notably, a number of these newly identified PFASs are potential precursor compounds of PFOS and PFOA. Studies are critically needed to understand the removal and transformation of these compounds in natural and engineered environmental systems and their contribution, if any, to the secondary formation of PFOS and PFOA in these systems.
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•Literature review of emerging PFASs.•More than 450 PFASs have been discovered.•Zwitterions and cations comprise a significant portion of novel PFASs.•Certain emerging PFASs have been detected at comparable levels to legacy PFASs.•Fate, effects, and removal of emerging PFASs remain understudied.
Zika virus (ZIKV) has become a public health threat due to its global transmission and link to severe congenital disorders. The host immune responses to ZIKV infection have not been fully elucidated, ...and effective therapeutics are not currently available. Herein, we demonstrated that cholesterol-25-hydroxylase (CH25H) was induced in response to ZIKV infection and that its enzymatic product, 25-hydroxycholesterol (25HC), was a critical mediator of host protection against ZIKV. Synthetic 25HC addition inhibited ZIKV infection in vitro by blocking viral entry, and treatment with 25HC reduced viremia and conferred protection against ZIKV in mice and rhesus macaques. 25HC suppressed ZIKV infection and reduced tissue damage in human cortical organoids and the embryonic brain of the ZIKV-induced mouse microcephaly model. Our findings highlight the protective role of CH25H during ZIKV infection and the potential use of 25HC as a natural antiviral agent to combat ZIKV infection and prevent ZIKV-associated outcomes, such as microcephaly.
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•CH25H and its enzymatic product, 25HC, inhibit ZIKV entry in vitro•25HC attenuates ZIKV-associated viremia and disease in mice and non-human primates•25HC prevents ZIKV infection in human cortical organoids•25HC protects fetal mice from microcephaly caused by ZIKV infection
Zika virus (ZIKV) presents a major challenge to the global health system. Li et al. find that 25-hydroxycholesterol (25HC) inhibits ZIKV infection in monkeys and human cortical organoids and protects mice from microcephaly. 25HC has potential as a first-line antiviral agent to combat a broad array of pathogenic species, including ZIKV.
Dimethyl sulfoxide (DMSO) is one of the most commonly applied organic solvents in chemical transformations and is utilized widely in industrial processes as well. During the past decades, numerous ...procedures using DMSO as a reaction reagent have been developed and published. In this review, the main developments on the employment of DMSO as sources of Me, SMe, SO2Me, as an oxidant etc. have been summarized and discussed.
The paper studies asynchronous consensus problems of continuous-time multi-agent systems with discontinuous information transmission. The proposed consensus control strategy is implemented based on ...the state information of each agent's neighbors at some discrete times. The asynchrony means that each agent's update times, at which the agent adjusts its dynamics, are independent of others'. Furthermore, it is assumed that the communication topology among agents is time-dependent and the information transmission is with bounded time-varying delays. If the union of the communication topology across any time interval with some given length contains a spanning tree, the consensus problem is shown to be solvable. The analysis tool developed in this paper is based on nonnegative matrix theory and graph theory. The main contribution of this paper is to provide a valid distributed consensus algorithm that overcomes the difficulties caused by unreliable communication channels, such as intermittent information transmission, switching communication topology, and time-varying communication delays, and therefore has its obvious practical applications. Simulation examples are provided to demonstrate the effectiveness of the theoretical results.
Although a number of reviews on catalytic carbonylations as well as on the synthesis of heterocycles already exist, no general summary on palladium-catalyzed carbonylative syntheses of heterocycles ...has been published so far. A summary of the main achievements in this area is presented.
Abstract
Aim
Ecological niche modelling (ENM) or species distribution modelling is increasingly used in decision‐making regarding land use and biodiversity conservation. Model accuracy is essential, ...but can be affected by modelling choices, including the critical and ubiquitous question of how to define a model training domain. Theories have suggested designing a training domain based on areas accessible to a species for improved model performance (here termed as species’ mobility hypothesis). However, we still lack direct quantitative evidence on whether this approach leads to optimal model performance. Here, I conducted a modelling experiment to investigate the species' mobility hypothesis.
Location
North and South America.
Taxon
Hummingbirds (Aves: Trochilidae).
Methods
The modelling experiment was based on 87 hummingbird species. A series of spatial buffers (from 5 to 5000 km with varying intervals) were created around occurrences, where background points were sampled and used as input for model calibration. The models calibrated with spatial buffers were compared with models calibrated with training domains that considered areas accessible to species, using Boyce index and sensitivity, specificity and true skill statistics.
Results
Model performance increased when the size of the training domain was larger, although the model performance reached saturation when size of the training domain passed a certain threshold. The threshold varied by species and evaluation method and was generally estimated to be below 200 km. The model performance based on areas accessible to species was comparable (e.g. non‐significant difference in sensitivity) to the saturation performance of models when spatial buffers were used.
Main conclusions
Positive evidence was found to support the species' mobility hypothesis that designing a training domain based on areas accessible to species could lead to optimal or near‐optimal model performance. When no information on the accessible area is available, modellers may use a tuning strategy to identify the size of the training domain for optimized model performance.
Supported metal nanoparticles are widely used as catalysts in the industrial production of chemicals, but still suffer from deactivation because of metal leaching and sintering at high temperature. ...In recent years, serious efforts have been devoted to developing new strategies for stabilizing metal nanoparticles. Recent developments for preparing sinter‐resistant metal‐nanoparticle catalysts via strong metal–support interactions, encapsulation with oxide or carbon layers and within mesoporous materials, and fixation in zeolite crystals, are briefly summarized. Furthermore, the current challenges and future perspectives for the preparation of highly efficient and extraordinarily stable metal‐nanoparticle‐based catalysts, and suggestions regarding the mechanisms involved in sinter resistance, are proposed.
Recent advancements in the design and application of sinter‐resistant metal nanoparticles are reviewed. Several strategies are proposed for stabilizing metal nanoparticle catalysts. The exciting progress of sinter‐resistant supported metal‐nanoparticle catalysts is achieved via various methodologies, including strong metal–support interactions, encapsulation with oxide or carbon layers and within mesoporous materials, and fixation in zeolite crystals.
Organoboron compounds are among the most versatile and useful building blocks in modern synthetic chemistry. The past decades have seen impressive developments in the direct C−H bond borylation of ...(hetero)arenes in which the applied catalysts are shifting from noble metals to metal‐free systems. This Highlight gives a brief summary on this evolution and focuses on recent elegant work in this field.
Impressive developments in the direct C−H bond borylation of (hetero)arenes have been achieved in the past decades. The applied catalysts are shifting from noble metals to metal‐free systems. This Highlight gives a brief summary of this evolution and focuses on recent elegant work in this field.
Thermal barrier coatings (TBCs) can effectively protect the alloy substrate of hot components in aeroengines or land-based gas turbines by the thermal insulation and corrosion/erosion resistance of ...the ceramic top coat. However, the continuous pursuit of a higher operating temperature leads to degradation, delamination, and premature failure of the top coat. Both new ceramic materials and new coating structures must be developed to meet the demand for future advanced TBC systems. In this paper, the latest progress of some new ceramic materials is first reviewed. Then, a comprehensive spalling mechanism of the ceramic top coat is summarized to understand the dependence of lifetime on various factors such as oxidation scale growth, ceramic sintering, erosion, and calcium-magnesium-aluminium-silicate (CMAS) molten salt corrosion. Finally, new structural design methods for high-performance TBCs are discussed from the perspectives of lamellar, columnar, and nanostructure inclusions. The latest developments of ceramic top coat will be presented in terms of material selection, structural design, and failure mechanism, and the comprehensive guidance will be provided for the development of next-generation advanced TBCs with higher temperature resistance, better thermal insulation, and longer lifetime.
Hypoxia and the Tumor Microenvironment Li, Yue; Zhao, Long; Li, Xiao-Feng
Technology in Cancer Research & Treatment,
2021, Letnik:
20
Book Review, Journal Article
Recenzirano
Odprti dostop
Hypoxia is an important feature of the tumor microenvironment, and is closely associated with cell proliferation, angiogenesis, metabolism and the tumor immune response. All these factors can further ...promote tumor progression, increase tumor aggressiveness, enhance tumor metastatic potential and lead to poor prognosis. In this review, these effects of hypoxia on tumor biology will be discussed, along with their significance for tumor detection and treatment.
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