Over the last decade, nanoparticles have been used more frequently in industrial applications and in consumer and medical products, and these applications of nanoparticles will likely continue to ...increase. Concerns about the environmental fate and effects of these materials have stimulated studies to predict environmental concentrations in air, water, and soils and to determine threshold concentrations for their ecotoxicological effects on aquatic or terrestrial biota. Nanoparticles can be added to soils directly in fertilizers orplant protection products or indirectly through application to land or wastewater treatment products such as sludges or biosolids. Nanoparticles may enter aquatic systems directly through industrial discharges or from disposal of wastewater treatment effluents or indirectly through surface runoff from soils. Researchers have used laboratory experiments to begin to understand the effects of nanoparticles on waters and soils, and this Account reviews that research and the translation of those results to natural conditions. In the environment, nanoparticles can undergo a number of potential transformations that depend on the properties both of the nanoparticle and of the receiving medium. These transformations largely involve chemical and physical processes, but they can involve biodegradation of surface coatings used to stabilize many nanomaterial formulations. The toxicity of nanomaterials to algae involves adsorption to cell surfaces and disruption to membrane transport. Higher organisms can directly ingest nanoparticles, and within the food web, both aquatic and terrestrial organisms can accumulate nanoparticles. The dissolution of nanoparticles may release potentially toxic components into the environment. Aggregation with other nanoparticles (homoaggregation) or with natural mineral and organic colloids (heteroaggregation) will dramatically change their fate and potential toxicity in the environment. Soluble natural organic matter may interact with nanoparticles to change surface charge and mobility and affect the interactions of those nanoparticles with biota. Ultimately, aquatic nanomaterials accumulate in bottom sediments, facilitated in natural systems by heteroaggregation. Homoaggregates of nanoparticles sediment more slowly. Nanomaterials from urban, medical, and industrial sources may undergo significant transformations during wastewater treatment processes. For example, sulfidation of silver nanoparticles in wastewater treatment systems converts most of the nanoparticles to silver sulfides (Ag2S). Aggregation of the nanomaterials with other mineral and organic components of the wastewater often results in most of the nanomaterial being associated with other solids rather than remaining as dispersed nanosized suspensions. Risk assessments for nanomaterial releases to the environment are still in their infancy, and reliable measurements of nanomaterials at environmental concentrations remain challenging. Predicted environmental concentrations based on current usage are low but are expected to increase as use increases. At this early stage, comparisons of estimated exposure data with known toxicity data indicate that the predicted environmental concentrations are orders of magnitude below those known to have environmental effects on biota. As more toxicity data are generated under environmentally-relevant conditions, risk assessments for nanomaterials will improve to produce accurate assessments that assure environmental safety.
Highly porous and hydrophobic silica aerogel is fabricated using fly ash and trona ore as the starting materials and the cost-effective ambient pressure drying technique. The optimal calcination ...parameters are determined as temperature of 850°C, holding time of 2h, and the trona ore/fly ash mass ratio of 1.4. The CO2 release mechanism during calcination is proposed and has been verified by the Thermogravimetric and Differential Scanning Calorimetry analysis (TG/DSC) and X-ray fluorescence (XRF) technique. The hydrogel is derived from reacting the calcination mixture with sulphuric acid solution, followed by filtration. The impurities can be effectively removed through water washing and solvent exchange processes. No ion exchange resin is used in this preparation method, and thus it is a safe, inexpensive and much more straightforward process. In order to minimize drying shrinkage, the hydrogel is first transformed into an alcogel by soaking in ethanol, after which the alcogel is surface modified with the hexane/ethanol/trimethylchlorosilane (hexane/ethanol/TMCS) mixture solution. It has been observed that the specific surface area, BJH desorption pore volume, and BJH desorption average pore diameter all first increase and then decrease so that reach to the maximum values once the heat treatment temperature approaches 500°C due to the oxidation of CH3 groups on the silica skeleton surface. The final product presents special characteristics including: (1) high thermal stability for maintaining hydrophobicity up to 476°C, (2) contact angle of the as-dried silica aerogel as high as 151°, (3) silica particle size of ca. 3–6nm, agreeing well with the model as reported, (4) and the 500°C heat treated sample possessing a large specific surface area of 856.2m2/g, a large pore volume of 2.92cm3/g, and a BJH desorption average pore diameter of 17.1nm. The proposed inexpensive approach produces silica aerogel with superior properties and is a scalable-manufacturing method for large-scale industrial production.
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•A novel and cost-effective aerogel is prepared using fly ash and trona ore.•The calcination parameters are determined and the mechanism is proposed.•The silica aerogel maintains high contact angle of 151° up to 476°C.•The silica aerogel has a large surface area of 856.2m2/g after 500°C calcination.
Modern observatories have revealed the ubiquitous presence of magnetohydrodynamic waves in the solar corona. The propagating waves (in contrast to the standing waves) are usually originated in the ...lower solar atmosphere which makes them particularly relevant to coronal heating. Furthermore, open coronal structures are believed to be the source regions of solar wind, therefore, the detection of MHD waves in these structures is also pertinent to the acceleration of solar wind. Besides, the advanced capabilities of the current generation telescopes have allowed us to extract important coronal properties through MHD seismology. The recent progress made in the detection, origin, and damping of both propagating slow magnetoacoustic waves and kink (Alfvénic) waves is presented in this review article especially in the context of open coronal structures. Where appropriate, we give an overview on associated theoretical modelling studies. A few of the important seismological applications of these waves are discussed. The possible role of Alfvénic waves in the acceleration of solar wind is also touched upon.
•Effects of subcore scale laminations were analyzed experimentally.•Sensitivity analysis via modeling shows the brine saturation is a dominant parameter.•A two-scale analysis of rock properties ...demonstrate the need to consider effects of laminations.
This study aims at understanding effects of sub-core scale petrophysical heterogeneity on CO2-brine multiphase flow properties during CO2 injection in samples of the Minnelusa Formation in Wyoming, representing differing lithofacies. Unsteady-state CO2-brine drainage tests were performed on a core sample from a dune deposit with laminated bedding and poorly sorted grain distribution. To highlight the role of low-porosity and low-permeability bedding layers (LLBL) on CO2 migration during CO2 injection, a contrasting coreflooding experiment was conducted on a sample of well-sorted sandstone collected from an interdune deposit. Assisted history matching was used to estimate the corresponding core-scale relative permeability curves, a procedure that reveals heterogeneity-dependent behavior. The simulated brine production from the optimal history matching case suggests that the main variation in multiphase flow properties could be attributed to internal permeability structures, i.e. sub-core scale LLBL, leading, in turn, to capillary pressure heterogeneity. CO2 sweep efficiency and distribution in heterogeneous Eolian sandstone are hard to estimate based solely on the limited number of coreflooding experiments, due to LLBL properties variability. Consequently, sensitivity analyses for the properties of sub-core scale LLBL on core-scale brine production were conducted using the developed model. Analyses indicate that the residual brine saturation and thickness of LLBL have a more significant effect on bulk brine production, whereas the impact of CO2 end-point relative permeability of LLBL on bulk brine production is negligible. In addition, comparison results show that ignoring the sub-core scale heterogeneity (e.g. sub-core scale relative permeability) during CO2 injection can create significant uncertainties in storage and fluid flow displacement in simulated results, due to important flow effects and thereby physically insightful responses. Overall, this study provides us with a deeper understanding of core-scale CO2-brine multiphase flow properties for CO2 geological storage in heterogeneous sandstones and gained us insights into CO2-brine multiphase flow upscaling in heterogeneous geological models. Our approach needs to be incorporated in upscaling procedures to avoid smearing key small-scale features, relevant to multiphase flow behaviour.
Abstract
Emergent color centers with accessible spins hosted by van der Waals materials have attracted substantial interest in recent years due to their significant potential for implementing ...transformative quantum sensing technologies. Hexagonal boron nitride (hBN) is naturally relevant in this context due to its remarkable ease of integration into devices consisting of low-dimensional materials. Taking advantage of boron vacancy spin defects in hBN, we report nanoscale quantum imaging of low-dimensional ferromagnetism sustained in Fe
3
GeTe
2
/hBN van der Waals heterostructures. Exploiting spin relaxometry methods, we have further observed spatially varying magnetic fluctuations in the exfoliated Fe
3
GeTe
2
flake, whose magnitude reaches a peak value around the Curie temperature. Our results demonstrate the capability of spin defects in hBN of investigating local magnetic properties of layered materials in an accessible and precise way, which can be extended readily to a broad range of miniaturized van der Waals heterostructure systems.
Solar flare emission is detected in all EM bands and variations in flux density of solar energetic particles. Often the EM radiation generated in solar and stellar flares shows a pronounced ...oscillatory pattern, with characteristic periods ranging from a fraction of a second to several minutes. These oscillations are referred to as quasi-periodic pulsations (QPPs), to emphasise that they often contain apparent amplitude and period modulation. We review the current understanding of quasi-periodic pulsations in solar and stellar flares. In particular, we focus on the possible physical mechanisms, with an emphasis on the underlying physics that generates the resultant range of periodicities. These physical mechanisms include MHD oscillations, self-oscillatory mechanisms, oscillatory reconnection/reconnection reversal, wave-driven reconnection, two loop coalescence, MHD flow over-stability, the equivalent LCR-contour mechanism, and thermal-dynamical cycles. We also provide a histogram of all QPP events published in the literature at this time. The occurrence of QPPs puts additional constraints on the interpretation and understanding of the fundamental processes operating in flares, e.g. magnetic energy liberation and particle acceleration. Therefore, a full understanding of QPPs is essential in order to work towards an integrated model of solar and stellar flares.
The ADAR RNA-editing enzymes deaminate adenosine bases to inosines in cellular RNAs. Aberrant interferon expression occurs in patients in whom ADAR1 mutations cause Aicardi-Goutières syndrome (AGS) ...or dystonia arising from striatal neurodegeneration. Adar1 mutant mouse embryos show aberrant interferon induction and die by embryonic day E12.5. We demonstrate that Adar1 embryonic lethality is rescued to live birth in Adar1; Mavs double mutants in which the antiviral interferon induction response to cytoplasmic double-stranded RNA (dsRNA) is prevented. Aberrant immune responses in Adar1 mutant mouse embryo fibroblasts are dramatically reduced by restoring the expression of editing-active cytoplasmic ADARs. We propose that inosine in cellular RNA inhibits antiviral inflammatory and interferon responses by altering RLR interactions. Transfecting dsRNA oligonucleotides containing inosine-uracil base pairs into Adar1 mutant mouse embryo fibroblasts reduces the aberrant innate immune response. ADAR1 mutations causing AGS affect the activity of the interferon-inducible cytoplasmic isoform more severely than the nuclear isoform.
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•Adar1 mutant mouse embryonic lethality is rescued in Adar1; Mavs double mutants•Aberrant antiviral responses in the Adar1 mutant are due to loss of RNA editing•Human ADAR1 mutations causing AGS affect primarily the interferon-inducible isoform•We propose that inosine helps innate immunity to distinguish cellular from viral RNA
Mice lacking Adar1 have a heightened immune response and stress-related apoptosis. Mannion et al. demonstrate that this mutation can be rescued to birth by generating a double mutant with Mavs, an innate immune gene, indicating the central role ADAR1 plays in innate immunity.
This first comprehensive analysis of the Third Reich's efforts to confiscate, loot, censor and influence art begins with a brief history of the looting of artworks in Western history. The artistic ...backgrounds of Adolf Hitler and Hermann Goring are examined, along with the various Nazi art looting organizations, and Nazi endeavors to both censor and manipulate the arts for propaganda purposes. Long-held beliefs about the Nazi destruction of "degenerate art" are examined, drawing on recently developed university databases, new translations of original documents and recently discovered information. Theft and destruction of artworks by the Allies and looting by Soviet trophy brigades are also documented.
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