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The penultimate deglaciation was characterized by a sub-millennial-scale warm event in the Heinrich Stadial 11(HS11), termed the 134-ka event. However, its precise timing and structure remain poorly constrained due to the lack of high-resolution and precisely dated records. We present an oxygen isotope record of a speleothem with well-developed annual lamina from Zhangjia Cave, located on the north margin of the Sichuan Basin, characterizing Asian summer monsoon (ASM) changes in the 134-ka event, which included an increase excursion of ca. 149 years and decrease excursion of ca. 200 years, inferred from 3.3‰ δ18O variations. This event also divided the weak ASM interval-II (WMI-II), corresponding to HS11, into two stages, the WMI-IIa 132.8–134.1 ka and WMI-IIb 134.4–136.4 ka. With a comparable climatic pattern globally, the 134-ka event is essentially similar to the millennial-scale events in last glacial–deglacial period. Particularly, the observed weak-strong-weak ASM sequence (138.8–132.8 ka) is largely controlled by changes in the Atlantic Meridional Overturning Circulation (AMOC) forced by the meltwater of northern high-latitude ice sheets. Moreover, our results underpin that AMOC, rather than the global ice volume, is more critical to ASM variations during the last two deglaciations. [ABSTRACT FROM AUTHOR]

Abstract In addition to amyloid cascade hypothesis, ferroptosis – a recently identified cell death pathway associated with the accumulation of lipid hydroperoxides – was hypothesized as one of the main forms of cell death in Alzheimer's disease. Herein, a series of hydroxylated chalcones were designed and synthesized as dual-functional inhibitors to inhibit amyloid-β peptide (Aβ) aggregation as well as ferroptosis simultaneously. Thioflavin-T assay indicated trihydroxy chalcones inhibited Aβ aggregation better. In human neuroblastoma SH-SY5Y cells, cytoprotective chalcones 14a-c with three hydroxyl substituents exhibited a significant neuroprotection against Aβ 1-42 aggregation induced toxicity. In addition, chalcones 14a-c were found to be good inhibitors of ferroptosis induced by either pharmacological inhibition of the hydroperoxide-detoxifying enzyme Gpx4 using (1S, 3R)-RSL4 or cystine/glutamate antiporter system X c − inhibition by erastin through lipid peroxidation inhibition mechanism. Trihydroxy chalcone 14a was also able to completely subvert lipid peroxidation induced by Aβ 1-42 aggregation in SH-SY5Y cells indicating that they can reduce the neurotoxicity involved with oxidative stress. Compound 14a-c showed good ADMET properties and blood-brain barrier penetration in silico simulation software. From these data, a picture emerges wherein trihydroxy chalcones are potential candidates for the treatment of Alzheimer's disease by simultaneously inhibition of Aβ 1-42 aggregation and ferroptosis. Graphical abstract Image 1 Highlights • Hydroxylated chalcones were synthesized as dual-functional inhibitors. • Chalcones 14a-c inhibited amyloid-β aggregation at micromolar concentrations. • Chalcones 14a-c protected neural cells against Aβ aggregation induced toxicity. • Chalcones 14a-c protected cells from ferroptosis at micromolar concentrations. [ABSTRACT FROM AUTHOR]

Lipid oxidation is a major food safety issue for edible oils. The objective of this study was to develop a simple method for detecting lipid oxidation through the color change of a composite film. Schiff's reagent which can form color compound with lipid oxidation products—aldehydes was incorporated into polyvinyl alcohol (PVA) to form the composite film. The effects of PVA molecular weight (Mw), Schiff's reagent/PVA ratio and glycerol content on the response of the composite film to aldehyde were investigated. Sunflower seed oil with various extent of oxidation was used to evaluate the effectiveness of the composite film for lipid oxidation detection. The results showed that the composite film formed with lower PVA Mw turned from colorless to purple upon aldehyde exposure. Higher Schiff's reagent/PVA ratio and glycerol content led to shorter response time and larger color change after aldehyde exposure. The color change of the composite film was linearly (R2 = 0.96) related to aldehyde concentration. The oxidation status of four sunflower seed oil samples out of five were correctly identified by the composite film. Although the accuracy of this method was 80% in this study, it still shows great potential for lipid oxidation detection application. • A composite film was developed for detecting lipid oxidation in edible oils. • The film turned from colorless to purple when exposed to lipid oxidation product—aldehyde. • The film showed high efficiency in identifying highly oxidized edible oil samples. [ABSTRACT FROM AUTHOR]

Significant multi‐centennial climate oscillations have been documented in a number of well‐dated climate records across the Holocene epoch and left various imprints in human cultural history. In this study, we developed speleothem δ13C, δ18O, trace elements, and lamina thickness records from the Yunnan‐Guizhou Plateau (YGP). Our high‐resolution and precisely dated records show a significant ∼550‐yr cycle as the dominant pattern of regional temperature and vegetation variations between ∼5,870 and ∼3,670 years ago. The phase analyses of the 550‐yr cycles among our speleothem records, other Northern Hemisphere climate records, solar activity index, and Atlantic meridional overturning circulation (AMOC) variations suggest that this climate cycle has a large spatial extent, and may be causally linked to the AMOC changes through coupled oceanic‐atmospheric processes. Additionally, the first cold phase of the ∼550‐yr cycle in our records coincides with the major cultural development on the YGP at ∼5,500–5,000 years ago, suggesting a critical relationship between climate and prehistorical cultural changes in the region. Plain Language Summary: This study presents precisely dated speleothem isotope and lamina thickness records, which shows a ∼550‐yr periodicity of vegetation and temperature changes between ∼5,870 and ∼3,670 years ago in the Yunnan‐Guizhou Plateau (YGP), southwestern China. The phase analyses between our records and other Northern Hemisphere climate records suggest that these climate cycles have a large spatial scale in Northern Hemisphere and may be linked to the Atlantic meridional overturning circulation changes through coupled oceanic‐atmospheric processes. Besides, the records show that a cold phase during ∼5,500–5,000 years ago coincided with the period of development of YGP Neolithic production tools, suggesting a critical role of climate change in the prehistorical cultural evolution in the region. Key Points: A significant multi‐centennial temperature and vegetation oscillation of ∼550‐yr cycles occurred between ∼5,870 and ∼3,670 years ago in the Yunnan‐Guizhou Plateau (YGP)The climate cycles were likely linked to the Atlantic meridional overturning circulation variation through coupled oceanic‐atmospheric processesThe first cold phase of the ∼550‐yr cycles in our records coincided with a change of population and major cultural transform in the YGP at ∼5,500–5,000 years ago, implying a critical role of climate change and resource shortage in the prehistorical cultural evolution in the region [ABSTRACT FROM AUTHOR]

The 8.2 ka event has been extensively studied, whereas its structure is ambiguous in North China. Here we present a high‐resolution (∼1 year) δ18O record from annual laminated speleothem from Beijing to characterize the detailed variability across this event in North China. Our record indicates a dry 8.2 ka event spanning 8.254–8.107 ka BP with a two‐stage structure superimposed by three prominent high δ18O excursions. The identical structure of speleothem δ18O records between North and central China during the event suggests a common forcing/response in East China, whereas the progressively increased offset between their average values may reflect changes in moisture source or rainout effect. A close comparison with the Greenland ice core records suggests a strong linear response of the Asian summer monsoon to the North Atlantic climate changes across the early and middle stages of the event, but a different mechanism in the termination processes. Plain Language Summary: As the most pronounced abrupt climate event in the Holocene, the 8.2 ka event has been studied using various geological archives worldwide, but its detailed structure in North China and its link to other climate systems remain poorly understood. Since the Beijing speleothem δ18O, a proxy of the precipitation δ18O, is sensitive to the Asian summer monsoon (ASM) variations, it allows us to establish precise timing and structure of the 8.2 ka event and estimate the cause of it. Our new speleothem δ18O record from Beijing reveals a two‐stage structure superimposed by three "V‐shape" excursions during the event and almost exactly covaries with another published speleothem record from central China, suggesting coherent climate changes over the east ASM domain in response to the same forcing. The gradually increased offset between them probably results from the changed atmospheric circulations. Our results suggest a fast climatic signal propagation from the North Atlantic to the ASM domain during the early and middle 8.2 ka event, and another forcing mechanism in the termination processes. Key Points: Annual laminated speleothem δ18O record from North China manifests a two‐stage 8.2 ka event superimposed by three positive excursionsHigh consistency in speleothem records from North and central China on interdecadal to multidecadal timescales indicates a common driverThe climate forcing for the termination process is different from the early and middle stages of the 8.2 ka event [ABSTRACT FROM AUTHOR]

Speleothem isotope records have been widely used in the forefront of paleoclimate researches. Although the oxygen isotope (δ18O) records of speleothems remain the most commonly used hydroclimate proxy, the carbon isotope (δ13C) and trace element records of speleothem have also shown their unique advantages in charactering regional-local hydroclimate variations. In this study, we present two high-resolution (seasonal-monthly) and precisely dated speleothem δ13C records (NB2 and NB3) over the past 120 years from Niubi cave in Southeast China. Our analyses show that hydroclimate-induced changes in the regional vegetation coverage appear to be the primary control on the speleothem δ13C values over the past 120 years. However, during the late 1950s to early 1960s, a large high δ13C excursion is observed in the NB record, which is apparently linked to a special human activity in China's modern history, the so-called "Great Leap Forward in Iron and Steel". We suggest that the large degree of damages to regional vegetation occurred during the time period resulted in the observed high speleothem δ13C values, as the local precipitation remained in an ordinary state inferred from δ18O and trace element data. The persistent decreasing trend in the NB δ13C record during the 1980–2018 CE may be attributed to the increased vegetation effect via increases in precipitation, temperature and atmosphere CO 2 , as well as the decrease of δ13C of atmospheric CO 2. [ABSTRACT FROM AUTHOR]

During the Bronze and Iron Age, Sardinia was home of one of the most technologically advanced Mediterranean societies (the Nuragic culture). Given its key geographical location, the island was also the fulcrum of deep cultural exchanges. Toward the end of the Iron Age, Phoenicians, and especially Carthaginians and Romans, massively frequented Sardinia for different purposes. This marks an important cultural transition for the region, as the ancient Nuragic-related society terminated. At the same time, this impacted the subsistence and land use practices. Together with middle to late Holocene climate changes, the novel anthropic activities had a pivotal role in shaping the landscape around the island. However, high resolution climate and environmental records for these culturally important phases are still lacking in Sardinia. Thus, this paper explores palaeoenvironmental changes from the Bronze Age to post Iron Ages times by using carbonate speleothems from Suttaterra de Sarpis Cave (Urzulei, central east Sardinia), strategically located nearby the Or Murales Nuragic Village. U–Th ages (n = 20) indicate that five stalagmites comprehensively span the last ∼7000 years. Peculiarly, they all show an evident stratigraphic discontinuity. Age models attest that hiatuses can be at times associated with the discontinuities, spanning periods of ∼1200 to ∼200 years. Importantly, the discontinuities occurred from the Late Iron Age to the Roman period. Based on fabric observations, trace elements and δ13C- δ18O analyses, the discontinuities are primarily attributed to a progressive change of land use above the cave. We suppose that deforestation aimed to clearance for agriculture and livestock practices probably was the most impacting factor for infiltration dynamics and soil state, thus affecting the studied speleothems, although archaeological and historical data are absent for the specific study area. Instead, this is in line with the cultural transition occurring in Sardinia toward the end of the Iron Age, with novel agricultural practices imported by the overseas populations. The anthropic disturbance to the millennial-long karst equilibrium possibly overprinted the response of speleothem proxies to climate oscillations, although future higher resolution analyses are necessary to better investigate the evolution of climate during the Holocene as well as its role in the development of ancient civilizations. Indeed, this is the first speleothem-based Holocene palaeoenvironmental reconstruction accomplished in Sardinia. Considering the paucity of natural lakes in this key location, speleothems here demonstrate their potential in exploring human-driven palaeoenvironmental changes during times of cultural transitions within the Mediterranean context. • The first Holocene speleothem paleoenvironmental record from Sardinia (Italy). • Changes in geochemical and physical speleothems' properties point to variation of land use. • Land use variation is connected to cultural shifts during intra- and post-Nuragic period. [ABSTRACT FROM AUTHOR]

The 8.2 ka abrupt cooling event has been extensively studied, whereas the 7.2 ka event and their comparations rarely mentioned. Here, we present a high resolution (∼4 years) and precisely dated (±25 years) speleothem multi-proxy record from Zhangjia Cave (northern margin of Sichuan basin, China) spanning the 7.2 and 8.2 ka events within the transition of early to middle Holocene. The speleothem δ18O mainly reflects the dynamic facets of the East Asian summer monsoon (EASM) system, while its δ13C and trace elements ratios serve as an indicator of local hydrological conditions. Our results reveal intense dry conditions in southwest China during the 7.2 ka event, despite the 7.2 event was characterized by a relatively stronger monsoon compared to the 8.2 ka event. Furthermore, the hydrological conditions during the 7.2 ka event and the middle Holocene appear to exhibit "north flood and south drought" pattern when compared to different paleoclimate records in EASM domains, while it can be summarized as "spatially consistent drought" in the 8.2 ka event. These different hydrological conditions are a response to the weakening of the EASM, a phenomenon also observed in modern climatic observations and empirical simulations, which underpins our understanding that the speleothem δ18O variations are mainly dynamical manifestations of the EASM system, likely different with its thermodynamical appearances. • In the 7.2 ka event, we observed more intense dryness in southwest China compared to the 8.2 ka event, despite the 7.2 event having a relatively stronger monsoon. • The precipitation patterns differed between the 7.2 ka event, 8.2 ka event, as well as the Early and Middle Holocene. During the 7.2 ka event, hydrological conditions exhibited a "north flood and south drought" pattern, while the 8.2 ka event was characterized by "spatially consistent drought." • The varying precipitation patterns under similar East Asian Summer Monsoon (EASM) intensities enhance our understanding of speleothem δ18O. This suggests that speleothem δ18O primarily reflects the dynamics of the EASM system rather than the thermodynamics. [ABSTRACT FROM AUTHOR]

High-resolution and precisely dated hydroclimate records in the southeastern Tibetan Plateau (TP) remain sparse beyond the Holocene, which hampers our ability to understand the hydroclimate variability in this important Indian summer monsoon (ISM) fringe area and its global teleconnection. Here we present 3-y resolution δ18O and δ13C records from a laminated stalagmite (RG-3) from Rige Cave in the southeastern TP, spanning the Younger Dryas (YD). The records allow us to precisely characterize the timing, structure, and particularly centennial-scale events within the YD, and probe the control factors of precipitation δ18O (δ18O p) in the ISM fringe area. On centennial–millennial timescales, the Rige δ18O record shows coherent pattern with the East Asian summer monsoon (EASM) counterpart, combined with modeled δ18O p results and spatial analysis, suggesting that δ18O p in this part of the TP is largely controlled by the large-scale atmosphere circulation (or the ISM strength), and the altitude increase in the TP may not potentially result in an opposite δ18O p pattern at least in the monsoonal TP regime. We also found significant δ13C-δ18O covariation on the centennial timescale, suggesting a coincided ISM rainfall and biomass change during the YD. In the Rige records, one weak centennial-scale ISM event (namely the intra-Allerød cold period, IACP) and three strong centennial-scale ISM events within the YD (namely A1′-A2′-A3′) were prominent and occurred between ∼12,470 and 12,310 ± 14, ∼12,210–12,090 ± 12 and ∼12,010–11,920 ± 12 y BP (before present, where present = 1950 CE), respectively. Spectral analyses of Rige records also revealed a significant ∼200-y periodicity, which is nearly in-phase with observed centennial-scale variations of the North Atlantic temperature and mid-latitude westerly-jet during that time. These observations support the hypothesis that the solar de Vries cycle (207-y) triggered the centennial-scale climate variations in high northern latitude, leading to the ISM variations via fast atmospheric processes. • Precipitation δ18O and its millennial-centennial patterns in SE Tibet Plateau are controlled by large monsoon circulations • Centennial δ13C-δ18O covariations in Younger Dryas suggest a link of the local biomass to Indian summer monsoon rainfall • Centennial Indian summer monsoon events in Younger Dryas correlate precisely to the North Atlantic climate variations • Solar de Vries cycle (207-y) triggered centennial Indian summer monsoon variations via North Atlantic climate changes [ABSTRACT FROM AUTHOR]

Speleothem oxygen isotope (δ18O s) record as a climatic proxy in southeastern China is still in debate due to multifaceted influencing factors, a modern δ18O s record, which can be calibrated or compared with observational data, is critical to explore the interpretation of δ18O s proxy. Here we present a seasonally resolved δ18O s record spanning the interval of 1898–2018 CE from Niubi Cave, Guangdong Province, southeastern China. A comparison between the Niubi δ18O s and instrumental data reveals that the Niubi δ18O s variability is primarily controlled by changes in precipitation seasonality modulated by El Niño-Southern Oscillation on interannual to interdecadal timescales. Higher (lower) δ18O s values correspond to lower (higher) ratios of the East Asian summer monsoon/non-summer monsoon precipitation during the El Niño (La Niña) events associated with concomitant changes in the outgoing longwave radiation, wind field and Western Pacific Subtropical High. While ∼73% historical drought events correlate to positive anomalies in Niubi δ18O s values over the last 120 years, the rest of drought events associate with the negative δ18O s anomalies. This observation suggests two different mechanisms for the drought events with more and less diminution of rainfall amount in the East Asian summer monsoon relative to the non-summer monsoon precipitation, respectively. Additionally, our Niubi δ18O s record from southeastern China, together with other high-resolution speleothem and tree ring records, demonstrate a "tripole pattern" of summer precipitation during the last ∼100 years in eastern China. • δ18O s records from SEC is controlled by the precipitation seasonality modulated by the ENSO on interannual timescales. • Not all drought events correspond to the higher δ18O s in NB cave because of the effect of precipitation seasonality. • A "tripole pattern" of summer rainfall in eastern China can be observed in palaeoclimatic records over the past ∼100 years. [ABSTRACT FROM AUTHOR]