The melting temperature (Tm) of iron at megabar pressures constrains the Earth's core temperature structure and dynamics. Previous experimental studies demonstrated large discrepancies in Tm at high ...pressures. We used the intrinsic resistance discontinuity across solid‐liquid transition as a melting criterion to study the melting behavior of iron in laser‐heated diamond anvil cells. The resistance jump is sensitive to the incipient melting, capable of detecting the emergence of less than 2 vol.% melts. We found a high melting curve of iron at 30–135 GPa, but a relatively low‐transition temperature of the slow‐fast recrystallization. The determined Tm of iron is 4306(±300) K at the core‐mantle boundary (CMB) pressure in good agreement with the static and shockwave experimental results by Anzellini et al. (2013, https://doi.org/10.1126/science.1233514) and Li et al. (2020, https://doi.org/10.1029/2020gl087758). The high melting point of iron implies a high and steep geothermal gradient and influences a heat flow across the CMB.
Plain Language Summary
The melting of iron is fundamental to constrain the thermal structure, solidification, heat flux, and evolution of the Earth's core. Here, we propose a sensitive melting criterion, the resistance discontinuity across the phase transition, which is capable of detecting 2 vol.% melting of the bulk sample. Using this criterion, we determined the melting temperature of iron up to 135 GPa. The new melting curve of iron reconciles with the most recent shockwave and static experimental results, indicating a melting temperature of 4306(±300) K at the Earth's core‐mantle boundary. Large discrepancies existing in the melting of iron are unlikely caused by varying melting criteria, while chromatic aberrations should be one of the major reasons resulting from refractive optical lens in the temperature measurement system.
Key Points
The criterion of an electrical resistance jump is sensitive to detect 1%–2% melt fraction of bulk iron to 135 GPa in diamond anvil cells
The slopes in the temperature‐resistance profile are changed across the solid‐solid and slow‐fast recrystallization transitions of iron
The melting temperature of iron is ∼4306 K at core‐mantle boundary pressure, consistent with latest static and shockwave experiments
•Synthesis of new mesoporous carbon nitride (MCN-7) with cage type pores.•The pore diameter of these mesoporous carbon nitrides can be tuned.•Nitrogen content of the MCN-7 is much higher than the MCN ...with 1D structure.•MCN-7 exhibits a higher CO2 adsorption capacity than pure mesoporous carbon.
Mesoporous carbon nitrides with well-ordered 3D porous structure and large, tuneable cage-type mesopores (MCN-7) have been prepared through a straightforward polymerization of ethylenediamine (EDA) and carbon tetrachloride (CTC) inside the pore channels of FDU-12 with different pore diameters. The obtained MCN-7 were characterized using small angle X-ray diffraction, N2 adsorption, high resolution transmission electron microscopy (HRTEM), high resolution scanning electron microscopy (FE SEM), Fourier transform infra-red, electron energy loss and X-ray photoelectron spectroscopy, and CHN analysis. The characterization results reveal that the structure of the MCN-7 is highly ordered and the pore structure of the templates are perfectly replicated into the carbon nitrides (CN). Nitrogen adsorption results indicate that the pore diameter of MCN-7 is directly controlled by the pore diameter of the template and can be tuned with a simple adjustment of the pore size of the template. The XPS and FT-IR data confirm that the wall structure of the samples are composed of CN framework with terminal amine groups that are exposed on the surface and are important for the capture of CO2 molecules. MCN-7 with different pore diameters and specific surface area are used as adsorbents for the capture of CO2 molecules at different high pressures (0–30bar) and temperatures (0–25°C). The MCN-7 materials show excellent affinity towards CO2 molecules because of the strong acid base interactions. It is found that the amount of the CO2 adsorbed over the MCN-7 is mainly dependent on the BET surface area, and the structural order, and pore diameter of the adsorbent. MCN-7 with the highest specific surface area shows higher CO2 adsorption capacity than that of other materials including MCN with one dimensional structure.
Display omitted
•A first of its kind review on use of experimental designs in HPLC method development and validation.•Deals with recent advances in mathematical modeling, screening and optimization ...designs.•Discusses various applications of chemometry in sample preparation, dissolution studies, stability-indicating assays.•Demonstrates complex multi component UPLC and LC–MS separations with improved reliability.•Describes the quality by design paradigm and the six sigma practices as quality indicators.
Chemometric approaches have been increasingly viewed as precious complements to high performance liquid chromatographic practices, since a large number of variables can be simultaneously controlled to achieve the desired separations. Moreover, their applications may efficiently identify and optimize the significant factors to accomplish competent results through limited experimental trials. The present manuscript discusses usefulness of various chemometric approaches in high and ultra performance liquid chromatography for (i) methods development from dissolution studies and sample preparation to detection, considering the progressive substitution of traditional detectors with tandem mass spectrometry instruments and the importance of stability indicating assays (ii) method validation through screening and optimization designs. Choice of appropriate types of experimental designs so as to either screen the most influential factors or optimize the selected factors’ combination and the mathematical models in chemometry have been briefly recalled and the advantages of chemometric approaches have been emphasized. The evolution of the design of experiments to the Quality by Design paradigm for method development has been reviewed and the Six Sigma practice as a quality indicator in chromatography has been explained. Chemometric applications and various strategies in chromatographic separations have been described.
Innovative food processing technologies including ultrasound, microwave and high-pressure treatment have been widely applied for preservation and valorization of nutrients in food resources with high ...efficiency. However, these treatments are also reported to induce modifications and interactions of food components. The impact and interaction mechanism of food components under additional treatments by innovative technologies has not been well-discussed in the present literatures.
This study aims to summarize recently available information regarding the impact of innovative food processing technologies on several main food components (i.e. protein, polysaccharide and polyphenol), as well as their interactions or complexation with other natural products in model systems. In this regard, the data published in literatures were retrieved and the effects of ultrasound, microwave, high pressure homogenization and high hydrostatic pressure on food components were mainly presented.
Ultrasound, microwave and high-pressure treatments can modify the physicochemical and functional properties of food components with different effects, depending on processing parameters, conditions and food matrix. The modification of food components induced by innovative technologies treatment may be promising or unwilling. By processing conditions monitoring and adjusting, interaction of food components can be promoted without destroying the primary structures of the compounds.
Display omitted
•Recent advances on the application of innovative technologies in food processing were focused in this review.•The modification of food components induced by ultrasound, microwave and high-pressure treatment was compared.•Impact of different innovative technologies on the interactions of food components was summarized.
•SiO2 stishovite in a water-saturated system underwent in situ X-ray observation using a multi-anvil apparatus.•Large excess volume was observed at 600 °C and below but was judged to occur ...metastably.•Pure SiO2 stishovite cannot be a major water transporter in Earth's deep mantle.
The stability of minerals that can hold water is important for understanding the distribution and transportation of water in the Earth's deep interior. Water distribution in the lower mantle depends on the stability of water-bearing minerals in the subducting slab because minerals in the surrounding lower mantle have low water solubility. Recent studies have reported that pure SiO2 high-pressure phases can hold large amounts of water (>3 wt%) however, their experimental results are contradictory regarding stability. In this study, the stability of hydrous SiO2 stishovite in a water-saturated system was investigated at pressures of 10–30 GPa and temperatures reaching 1300 °C by in situ X-ray observation using a multi-anvil apparatus. The experiments revealed that the unit-cell volume of stishovite was significantly greater than that of anhydrous stishovite (by 3.8 % at the maximum) below 700 °C in the studied range of pressure, suggesting a high water content in stishovite (up to 5.4 wt% H2O). However, the excess volume decreased rapidly at higher temperatures and the volume was approximately identical to anhydrous stishovite above 800 °C. Time-resolved measurements at constant temperatures of 450 and 500 °C, where water-induced excessive volume was observed, showed that the unit-cell volume shrank with time. This indicates that the dissolution of water in stishovite is a metastable phenomenon. These results indicate that SiO2 stishovite in crustal materials subducting into the lower mantle is unlikely to retain >1 wt% of water as a stable phase.
The polymer polydimethylsiloxane (PDMS) is widely used to build microfluidic devices compatible with cell culture. Whilst convenient in manufacture, PDMS has the disadvantage that it can absorb small ...molecules such as drugs. In microfluidic devices like “Organs-on-Chip”, designed to examine cell behavior and test the effects of drugs, this might impact drug bioavailability. Here we developed an assay to compare the absorption of a test set of four cardiac drugs by PDMS based on measuring the residual non-absorbed compound by High Pressure Liquid Chromatography (HPLC). We showed that absorption was variable and time dependent and not determined exclusively by hydrophobicity as claimed previously. We demonstrated that two commercially available lipophilic coatings and the presence of cells affected absorption. The use of lipophilic coatings may be useful in preventing small molecule absorption by PDMS.
Display omitted
•Binding of different compounds to PDMS varies greatly.•Previous reported correlations of absorption and LogP values could not be repeated.•Topological polar surface area possibly related to compound absorption.•A lipid based coating partially obviates compound absorption.•Presence of cultured cells affects free drug concentration, but less than substrate.
The spatiotemporal variability and three-dimensional structures of mesoscale convective systems (MCSs) east of the U.S. Rocky Mountains and their large-scale environments are characterized across all ...seasons using 13 years of high-resolution radar and satellite observations. Long-lived and intense MCSs account for over 50% of warm season precipitation in the Great Plains and over 40% of cold season precipitation in the southeast. The Great Plains has the strongest MCS seasonal cycle peaking in May–June, whereas in the U.S. southeast MCSs occur year-round. Distinctly different large-scale environments across the seasons have significant impacts on the structure of MCSs. Spring and fall MCSs commonly initiate under strong baroclinic forcing and favorable thermodynamic environments. MCS genesis frequently occurs in the Great Plains near sunset, although convection is not always surface based. Spring MCSs feature both large and deep convection, with a large stratiform rain area and high volume of rainfall. In contrast, summer MCSs often initiate under weak baroclinic forcing, featuring a high pressure ridge with weak low-level convergence acting on the warm, humid air associated with the low-level jet. MCS genesis concentrates east of the Rocky Mountain Front Range and near the southeast coast in the afternoon. The strongest MCS diurnal cycle amplitude extends from the foothills of the Rocky Mountains to the Great Plains. Summer MCSs have the largest and deepest convective features, the smallest stratiform rain area, and the lowest rainfall volume. Last, winter MCSs are characterized by the strongest baroclinic forcing and the largest MCS precipitation features over the southeast. Implications of the findings for climate modeling are discussed.
The geometric transformation of a descending plate, such as from steep to flat subduction in response to a change from normal to overthickened oceanic crust during subduction, is a common and ...important geological process at modern or fossil convergent margins. However, the links between this process and the metamorphic evolution of the exhumation of oceanic (ultra)high‐pressure eclogites are poorly understood. Here we report detailed petrological, mineralogical, phase equilibria, and secondary ion mass spectrometry zircon and rutile U‐Pb age data for the Dong Co eclogites at the western segment of the Bangong‐Nujiang suture zone, central Tibet. Our data reveal that the Dong Co eclogites experienced peak eclogite‐facies metamorphism (T = 610–630°C, P = 2.4–2.6 GPa) and underwent multiple stages of retrograde metamorphism. P‐T pseudosections and compositional isopleths of garnet define a complex clockwise P‐T‐t path (including two stages of decompression‐dominated P‐T path and one of isobaric heating), suggesting varying exhumation velocities. Combining previous studies with our new results, we suggest that the transformation from rapid to slow exhumation is dominated by the transition from steep to flat subduction. The flat‐slab segment, caused by subduction of buoyant oceanic plateau, led to an extremely slow exhumation and a strong overprinting of HP granulite facies at a depth of ~50 km at ~177 Ma. The slab rollback that followed in response to a substantial density increase of the eclogitized oceanic plateau resulted in another rapid exhumation process at ~168 Ma and triggered the formation of abundant near‐simultaneous or later magmatic rocks.
Key Points
HP‐UHP eclogites from western segment of the Bangong‐Nujiang suture zone, central Tibet
Multistage retrograde metamorphism, phase equilibria, and SIMS zircon and rutile U‐Pb ages
Granulite facies overprinting during the exhumation of eclogites linked to flat‐slab subduction
PDF
