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"C-14"
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Cleopatra's daughter : from Roman prisoner to African queen
\"The first biography of one of the most fascinating yet long-neglected rulers of the ancient world: Cleopatra Selene, daughter of Antony and Cleopatra. Years ago, archaeologists excavating near Pompeii unearthed a hoard of Roman treasures, among them a bowl depicting a woman with thick, curly hair and sporting an elephant-scalp headdress. For decades, theories circulated about her identity-until, at last, she was ascertained to be Cleopatra Selene, the only surviving daughter of Roman Triumvir Marc Antony and Egyptian Queen Cleopatra VII. Using this discovery as her starting point and creating a narrative from mere fragments in the archaeological record, historian Jane Draycott reconstructs the exceptional life of this woman who, although born into royalty and raised in her mother's court, was held captive by Augustus Caesar and his sister, Octavia, after her parents' demise. Yet as Draycott shows, Cleopatra Selene was destined to emerge as an influential ruler in her own right, as queen, alongside King Juba II, of Mauretania, an ancient African kingdom. A long-overdue historical corrective, Cleopatra's Daughter reclaims a mighty regent-and her infamous family-for posterity\"-- Provided by publisher.
BOOK
Differential mobilization of terrestrial carbon pools in Eurasian Arctic river basins
Mobilization of Arctic permafrost carbon is expected to increase with warming-induced thawing. However, this effect is challenging to assess due to the diverse processes controlling the release of various organic carbon (OC) pools from heterogeneous Arctic landscapes. Here, by radiocarbon dating various terrestrial OC components in fluvially and coastally integrated estuarine sediments, we present a unique framework for deconvolving the contrasting mobilization mechanisms of surface vs. deep (permafrost) carbon pools across the climosequence of the Eurasian Arctic. Vascular plant-derived lignin phenol ¹₄C contents reveal significant inputs of young carbon from surface sources whose delivery is dominantly controlled by river runoff. In contrast plant wax lipids predominantly trace ancient (permafrost) OC that is preferentially mobilized from discontinuous permafrost regions, where hydrological conduits penetrate deeper into soils and thermokarst erosion occurs more frequently. Because river runoff has significantly increased across the Eurasian Arctic in recent decades, we estimate from an isotopic mixing model that, in tandem with an increased transfer of young surface carbon, the proportion of mobilized terrestrial OC accounted for by ancient carbon has increased by 3-6% between 1985 and 2004. These findings suggest that although partly masked by surface carbon export, climate change-induced mobilization of old permafrost carbon is well underway in the Arctic.
Journal Article
This time it's real
When seventeen-year-old Eliza Lin's entirely fictional essay about meeting her perfect boyfriend goes viral at her international school in Beijing, she has to make a deal with the handsome and charming Caz Song to play the part--but when the relationship starts to feel real all her career plans are suddenly threatened.
Book
Small Interannual Variability of Global Atmospheric Hydroxyl
The oxidizing capacity of the global atmosphere is largely determined by hydroxyl (OH) radicals and is diagnosed by analyzing methyl chloroform (CH₃CCl₃) measurements. Previously, large year-to-year changes in global mean OH concentrations have been inferred from such measurements, suggesting that the atmospheric oxidizing capacity is sensitive to perturbations by widespread air pollution and natural influences. We show how the interannual variability in OH has been more precisely estimated from CH₃CCl₃ measurements since 1998, when atmospheric gradients of CH₃CCl₃ had diminished as a result of the Montreal Protocol. We infer a small interannual OH variability as a result, indicating that global OH is generally well buffered against perturbations. This small variability is consistent with measurements of methane and other trace gases oxidized primarily by OH, as well as global photochemical model calculations.
Journal Article
A Complete Terrestrial Radiocarbon Record for 11.2 to 52.8 kyr B.P
Radiocarbon (¹⁴C) provides a way to date material that contains carbon with an age up to ~50,000 years and is also an important tracer of the global carbon cycle. However, the lack of a comprehensive record reflecting atmospheric ¹⁴C prior to 12.5 thousand years before the present (kyr B.P.) has limited the application of radiocarbon dating of samples from the Last Glacial period. Here, we report ¹⁴C results from Lake Suigetsu, Japan (35°35'N, 135°53'E), which provide a comprehensive record of terrestrial radiocarbon to the present limit of the ¹⁴C method. The time scale we present in this work allows direct comparison of Lake Suigetsu paleoclimatic data with other terrestrial climatic records and gives information on the connection between global atmospheric and regional marine radiocarbon levels.
Journal Article
Rational Design of Daunorubicin C-14 Hydroxylase Based on the Understanding of Its Substrate-Binding Mechanism
Doxorubicin is one of the most widely used antitumor drugs and is currently produced via the chemical conversion method, which suffers from high production costs, complex product separation processes, and serious environmental pollution. Biocatalysis is considered a more efficient and environment-friendly method for drug production. The cytochrome daunorubicin C-14 hydroxylase (DoxA) is the essential enzyme catalyzing the conversion of daunorubicin to doxorubicin. Herein, the DoxA from Streptomyces peucetius subsp. caesius ATCC 27952 was expressed in Escherichia coli, and the rational design strategy was further applied to improve the enzyme activity. Eight amino acid residues were identified as the key sites via molecular docking. Using a constructed screening library, we obtained the mutant DoxA(P88Y) with a more rational protein conformation, and a 56% increase in bioconversion efficiency was achieved by the mutant compared to the wild-type DoxA. Molecular dynamics simulation was applied to understand the relationship between the enzyme’s structural property and its substrate-binding efficiency. It was demonstrated that the mutant DoxA(P88Y) formed a new hydrophobic interaction with the substrate daunorubicin, which might have enhanced the binding stability and thus improved the catalytic activity. Our work lays a foundation for further exploration of DoxA and facilitates the industrial process of bio-production of doxorubicin.
Journal Article
The sterol C-14 reductase Erg24 is responsible for ergosterol biosynthesis and ion homeostasis in Aspergillus fumigatus
Ergosterol, a major lipid present in the fungal cell membrane, is considered as an effective antifungal drug target. A rational strategy for increasing drug reservoir relies on functionally validation of essential enzymes involved in fungal key biological pathway. Current knowledge regarding the essential genes in the ergosterol biosynthesis pathway is still limited in the opportunistic human pathogen Aspergillus fumigatus. In this study, we characterized two endoplasmic reticulum-localized sterol C-14 reductases encoded by both erg24A and erg24B homologs that are essential for the viability of A. fumigatus despite the fact that neither paralog is essential individually. Loss of one homolog of Erg24 impairs hyphal growth, conidiation, and virulence but has no effect on ergosterol biosynthesis. To investigate the functional significance of erg24, a conditional double mutant (Δerg24B niiA::erg24A) was constructed in the Δerg24B background. Strikingly, the conditional erg24 double mutant exhibited severe growth defects and accumulation of sterol intermediate. Moreover, the addition of metal ions and the overexpression of the corresponding ion transporters could rescue the growth defects of the erg24 double mutant in A. fumigatus, implying that the defective phenotype of the erg24 double mutant is tightly associated with dysregulation of ion homeostasis. Taken together, our results demonstrate the critical role of Erg24 in ergosterol biosynthesis and ion homeostasis in A. fumigatus, which may have important implications for antifungal discovery.Key points• We characterized two endoplasmic reticulum-localized sterol C-14 reductases Erg24A and Erg24B in A. fumigatus.• Erg24A and Erg24B in combination, but not individually, are required for the viability of A. fumigatus.• Inactivation of Erg24 leads to the disruption of ion homeostasis and affects ergosterol biosynthesis.
Journal Article
Simulating the integrated summertime d14CO2 signature from anthropogenic emissions over Western Europe
Radiocarbon dioxide (14CO2, reported in d14CO2) can be used to determine the fossil fuel CO2 addition to the atmosphere, since fossil fuel CO2 no longer contains any 14C. After the release of CO2 at the source, atmospheric transport causes dilution of strong local signals into the background and detectable gradients of d14CO2 only remain in areas with high fossil fuel emissions. This fossil fuel signal can moreover be partially masked by the enriching effect that anthropogenic emissions of 14CO2 from the nuclear industry have on the atmospheric d14CO2 signature. In this paper, we investigate the regional gradients in 14CO2 over the European continent and quantify the effect of the emissions from nuclear industry. We simulate the emissions and transport of fossil fuel CO2 and nuclear 14CO2 for Western Europe using the Weather Research and Forecast model (WRF-Chem) for a period covering 6 summer months in 2008. We evaluate the expected CO2 gradients and the resulting d14CO2 in simulated integrated air samples over this period, as well as in simulated plant samples. We find that the average gradients of fossil fuel CO2 in the lower 1200 m of the atmosphere are close to 15 ppm at a 12 km × 12 km horizontal resolution. The nuclear influence on d14CO2 signatures varies considerably over the domain and for large areas in France and the UK it can range from 20 to more than 500% of the influence of fossil fuel emissions. Our simulations suggest that the resulting gradients in d14CO2 are well captured in plant samples, but due to their time-varying uptake of CO 2, their signature can be different with over 3‰ from the atmospheric samples in some regions. We conclude that the framework presented will be well-suited for the interpretation of actual air and plant 14CO2 samples. © Author(s) 2014. CC Attribution 3.0 License.
Journal Article
SPATIAL VARIATION IN THE TEMPORAL RESOLUTION OF SUBTROPICAL SHALLOW-WATER MOLLUSCAN DEATH ASSEMBLAGES
Fossil assemblages are expected to be time-averaged as a result of biological and physical processes that mix skeletal remains. Our quantitative understanding of time-averaging derives primarily from actualistic studies, in which direct numerical dating of individual specimens is used to assess the scale and structure of age mixing in death assemblages (incipient fossil assemblages). Here we examine the age, and the time-averaging of Mactra shells (Bivalvia: Mollusca) gathered from surface mixed siliciclastic-bioclastic sands at three sites on a passive-margin subtropical shelf (the Southern Brazilian Shelf; ∼ 33°S). Sixty Mactra specimens were individually dated using amino acid racemization (AAR) calibrated using radiocarbon ages (n = 15). The time-averaging and the total age variability was based on a Bayesian approach that integrates the estimation errors and uncertainties derived from the posterior distribution associated with the AAR calibration average model. The 14C-calibrated AAR ages, pooled across all three sites, are strongly right-skewed with 97% of the individual mollusk shell age estimates ranging from 0 to 6 cal kyr BP. The magnitude of time-averaging varied inversely with the water depth, from < 15 yr at the deepest site (21 m) up to 1020–1250 yr at the shallowest site (7 m). The substantial variation in the temporal resolution across nearby sites, which are located in a seemingly homogenous depositional setting, indicates the presence of notable (if cryptic) spatial heterogeneities in local sedimentation, production, and exhumation, all increasing with water depth.
Journal Article
Paleoearthquake characteristics of the range-front Maidan Fault in the southwestern Tianshan
The Kalpin foreland thrust belt, which is in the southwestern Tianshan Mountains, has some of the most intense tectonic deformation and seismic activity on the continent. The range-front Maidan fault represents part of the boundary zone between the Tarim Basin and the southern Tianshan orogenic belt. In contrast with the other range-front faults in the Tianshan region that have been inactive during the late Quaternary, the Maidan fault displayed strong activity in the Holocene. Studying characteristics of paleoearthquake activity along the Maidan fault is highly important to understand the seismic risk and tectonic deformation in this area. On the basis of methods of remote sensing image interpretation, field surveys, trench excavation, and late Quaternary chronology determination, four paleoearthquake events were identified as follows: Event E1: (46.8 ± 4.2)-(49.0 ± 4.8) ka; Event E2: (13.1 ± 0.6)-(22.5 ± 1.7) ka; Event E3: (7.0 ± 0.6)-(7.7 ± 0.4) ka, and Event E4: after (5.1 ± 0.3) ka. Our results show that the range-front Maidan fault was still active during the late Quaternary and that several strong earthquake events ruptured the ground surface. This deformation pattern and strain distribution indicate that the range-front fault and frontal structure of the foreland thrust belt are both experiencing strong deformation, which highlights new challenges in studying paleoearthquake activity sequences and large earthquake risk analysis.
Journal Article