Although the mid-Cretaceous is considered to be a typical interval of greenhouse climate and high sea level, cooling events associated with regressions were inferred in recent years. We conducted a ...biostratigraphic, chemostratigraphic, sequence stratigraphic and cyclostratigraphic investigation of upper Turonian–lower Coniacian marine strata in the Tethyan Himalaya zone, to retrace the sea-level variations and to clarify their global correlations. According to the planktonic foraminiferal zonation, the studied interval is part of the late Turonian–early Coniacian Marginoruncana sigali and D. concavata Zones. The carbon isotope curve shows a good correlation to reference curves in the Boreal and western Tethys realms with all major and minor late Turonian δ13C events identified, indicating that the C-isotope curve provides an excellent tool for global stratigraphic correlation in the Turonian. Based on the lithological variations of clastic input and physical and chemical proxies, the succession is divided into two third order and eight fourth order sequences. Spectral analysis indicates that fourth order sea-level changes were linked to the astronomically stable 405-kyr eccentricity cycle. Comparison with classic global sea-level curves, we suggest that late Turonian–early Coniacian sea-level changes along the southeastern Tethyan margin were controlled by eustasy. The significant regressions during ∼90–89.8 Ma and ∼92–91.4 Ma, which are recorded in different continents, may be interpreted as the result of continental ice expansion, giving some support to the notion that ephemeral polar ice sheets existed even in the super-greenhouse world.
Based on the lithology assemblage, microfacies, and physical and chemical proxies, we reconstruct the relative sea-level curve of late Turonian-early Coniacian in Tethyan Himalaya. Spectral analysis indicates that fourth order sea-level changes were linked to the astronomically stable 405-kyr eccentricity cycle. By comparing with classic global sea-level curves, we suggest that late Turonian-early Coniacian sea-level changes in the southeastern Tethyan margin were controlled by eustasy. Two rapid and significant regressions during late Turonian, which are recorded in different continents, may be interpreted as the result of continental ice expansion, giving some support to the notion that ephemeral polar ice sheets existed even in the super-greenhouse world. Display omitted
•RG-I rich pectic polysaccharide were abundant in fruits and vegetables.•RG-I rich pectic polysaccharide were extracted by sequential mild treatment.•Blend gels showed improved gel properties in ...calcium-induced gelation.•Ca-bridges promoted the three-dimensional structure of blend gels.
RG-I rich pectic polysaccharide is common in fruit and vegetable and possesses health benefits. However, it is removed during commercial pectin production because of poor gelling properties. Synergistic gelation can improve rheological properties of RG-I pectic polysaccharide and expand its application in functional food hydrocolloids. In the study, RG-I rich pectic polysaccharides at different degree of esterification was extracted from citrus membrane by sequential mild acidic (0.4% HCl, 28 °C) and alkaline (0.6% NaOH, 32 °C) treatment. The pectic polysaccharide from acid water (PA) composes of 41% RG-I and 44% HG with DM of 45%, while the pectic polysaccharide from basic water (PB) composed of 63% RG-I and 19% HG with DM of 15%. PA/PB blend gel under CaCO3-glucono-δ-lactone system showed improved rheological properties compared with pure gels. Ca-bridges connected pectin aggregates and promoted the three-dimensional structure of PA/PB blend gels, while neutral sugar side-chains prompted hydrogen bonds and strengthened gel network.
Rhamnogalacturonan-I (RG-I) was considered to be incompatible with gel formation. Due to its important health benefits, our previous study reported synergistic gelation of RG-I enriched pectin from ...citrus membranes with sequential acidic and alkaline treatment. In the present study, we further fabricated RG-I enriched pectin-based emulsion gels with the synergistic gelation for hydrophobic bioactive encapsulation. The effect of oil fraction and interfacial compositions including pectin itself and Tween 20 on the physical properties and delivery characteristics of emulsion gels was investigated. As to interfacial compositions, pectin reduced syneresis and swelling ratio and increased water holding capacity. Oil fraction had no marked influence on syneresis and swelling ratio, but significantly increased water holding capacity. Particularly, all the emulsion gels showed an elastic behavior and a full structure recovery after shearing. Increase in pectin instead of Tween 20 onto the surface of oil droplets and oil fraction markedly improved their gel strength. Curcumin was encapsulated within the oil phase of emulsion gels. Improvement in gel strength provided enhanced protection of curcumin against heat-induced degradation. In vitro digestion revealed that interfacial compositions decelerated curcumin release by increasing the proportion of pectin onto the surface, but didn't change its bioaccessibility eventually. Increase in oil fraction accelerated curcumin release, but reduced its bioaccessibility. Overall, fabrication of RG-I enriched pectin-based emulsion gel with pectin itself as interfacial composition and low oil fraction would contribute to improving curcumin bioavailability for its sustained release, which should be further validated in vivo.
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•Rhamnogalacturonan-I enriched pectin-based emulsion gels were fabricated.•Interfacial compositions influenced strength of the emulsion gels.•Increase in oil fraction improved strength of the emulsion gels.•Curcumin was encapsulated within oil phase of the emulsion gels.•Protection and sustained release of curcumin were achieved.
The Cretaceous-Paleogene (K-Pg) boundary mass extinction is commonly attributed to the Chicxulub impact and/or the Deccan Traps (DT) volcanism, but the underlying trigger remains uncertain. The lack ...of detailed identification of the DT eruptive pluses impedes the full assessment of their relationship to the K-Pg boundary mass extinction. Here we present the first mercury (Hg) chemostratigraphy records on the paleo Asian plate, coupled with climatic and biotic data, to constrain the effects of the DT on the Late Cretaceous climate change and mass extinction. In northern China, a total Hg (THg) spike follows warming caused by the DT volcanism and corresponds to the significant species losses. Our study suggests that this most intense pulse of the DT (~50 kyr duration) occurred just before the K-Pg boundary and suggests that it contributed to the end-Cretaceous mass extinction in northern China.
•The first mercury (Hg) concentration and isotope record of the Cretaceous-Paleogene (K-Pg) boundary in the paleo Asian plate.•Hg anomaly close to the K-Pg boundary derived from a volcanic source coupling with biotic losses.•Deccan Traps LIP volcanism contributed to the end-Cretaceous mass extinction in northern China.
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•A ash database of the Jurassic and Cretaceous was compiled.•The values of ash concentration are higher near the arid provenance.•Greenhouse climate has lower ash concentration and ...lower dust deposition rate.
The study of dust deposition records in geological history is of great significance to the study of paleoclimate evolution during deep periods. Because dust can directly influence the biochemical processes and climate evolution of the Earth. However, the absence of quantitative data on dust limits the systematic and comprehensive study of paleoclimate evolution during deep periods. Prior to the Quaternary period, most quantitative studies on atmospheric dust have focused on the Permian era. However, in the entire Mesozoic era, there are still no quantitative data available on atmospheric dust deposition rates. We utilized the average concentration of inorganic matter in coal from the Jurassic and Cretaceous periods to depict the dust concentration and corresponding dust deposition rate in the atmospheric system during these periods. We also conducted a correlation analysis using the distribution of arid source areas. The results show that the values of ash concentration and dust deposition rates are higher near the arid provenance and lower far away from it. Furthermore, in this study, we have compared the latitudinal variation gradient of dust deposition rates under the icehouse and greenhouse climates by using the end of the Permian and Quaternary as representatives of icehouse climate and the Jurassic and Cretaceous periods as representatives of the greenhouse climate. Our findings indicate that there is a higher ash concentration, dust deposition rate, and dust deposition rate variation gradient in the air under the icehouse climate, while there is a lower ash concentration, dust deposition rate, and dust deposition rate gradient in the air under the greenhouse climate. We have also discussed the dust sources during the Mesozoic period, as well as the differences in ash data under greenhouse and icehouse conditions. This provides a strong basis for studying the atmospheric environment after the modern climate entered the ice age.
In this study, we synthesized a modified form of pectin know as sulfhydryl group (-SH) modified pectin (PSH) by linking cysteine's amino groups and pectin's carboxyl group through amide bonds. The ...-SH amounts varied from 517 μmol/g to 732 μmol/g. Pectin (PEC) modified with -SH groups showed no significant alteration in chain structure, monosaccharide composition and molecular weight. Compared to PEC, PSH had a stronger interaction with mucus, and the strength of this interaction increased with the -SH amounts. In vitro fermentation indicated that PSH was fermentable by human fecal microbiota, and the -SH modified can prolong the overall fermentation time of PEC from 48 h to 72 h, as evidenced by the variations in pH values, total sugar, molecular weight, monosaccharide consumption and short-chain fatty acids production. Furthermore, microbial analysis revealed that PSH significantly increased the abundance of Faecalibacterium and Bifidobacterium while decreasing the abundance of Klebsiella and Collinsella. These results provided a solid foundation for the potential use of -SH modified PEC as a mucoadhesive material for delivering active substances and regulating the effect of PEC on gut microbiota.
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•Pectin modified with -SH groups showed no significant alteration in molecular properties.•PSH had a stronger interaction with mucus, and the strength of this interaction increased with the -SH amounts.•PSH significantly increased the abundance of beneficial bacteria while decreasing the abundance of harmful bacteria.
In parallel with pronounced cooling in the oceans, vast areas of the continents experienced enhanced aridification and restructuring of vegetation and animal communities during the Late Miocene. ...Debate continues over whether pCO2-induced global cooling was the primary driver of this climate and ecosystem upheaval on land. Here we present an 8 to 5 Ma land surface temperatures (LST) record from East Asia derived from paleosol carbonate clumped isotopes and integrated with climate model simulations. The LST cooled by ~7 °C between 7.5 and 5.7 Ma, followed by rapid warming across the Miocene–Pliocene transition (5.5 to 5 Ma). These changes occurred synchronously with variations in alkenone and Mg/Ca-based sea surface temperatures and with hydroclimate and ecosystem shifts in East Asia, highlighting a global climate forcing mechanism. Our modeling experiments additionally demonstrate that pCO2-forced cooling would have altered moisture transfer and pathways and driven extensive aridification in East Asia. We, thus, conclude that the East Asian hydroclimate and ecosystem shift was primarily controlled by pCO2-forced global cooling between 8 and 5 Ma.
In parallel with pronounced cooling in the oceans, vast areas of the continents experienced enhanced aridification and restructuring of vegetation and animal communities during the Late Miocene. ...Debate continues over whether
CO
-induced global cooling was the primary driver of this climate and ecosystem upheaval on land. Here we present an 8 to 5 Ma land surface temperatures (LST) record from East Asia derived from paleosol carbonate clumped isotopes and integrated with climate model simulations. The LST cooled by ~7 °C between 7.5 and 5.7 Ma, followed by rapid warming across the Miocene-Pliocene transition (5.5 to 5 Ma). These changes occurred synchronously with variations in alkenone and Mg/Ca-based sea surface temperatures and with hydroclimate and ecosystem shifts in East Asia, highlighting a global climate forcing mechanism. Our modeling experiments additionally demonstrate that
CO
-forced cooling would have altered moisture transfer and pathways and driven extensive aridification in East Asia. We, thus, conclude that the East Asian hydroclimate and ecosystem shift was primarily controlled by
CO
-forced global cooling between 8 and 5 Ma.
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