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The characteristics of spray, combustion, and soot emissions of the diesel engine fueled with biodiesel-diesel blends and diesel are numerically simulated using AVL-FIRE software to illustrate the suppression effect of biodiesel on in-cylinder soot. The model was validated by comparison with experimental cylinder pressure and smoke for the baseline engine at rated power. The results indicate the spray penetration distance of the blends is farther than that diesel. Compared with that of diesel, the evaporated fuel mass of 10 and 20% (vol) biodiesel blending with diesel (donated as B10 and B20) are almost the same. The Sauter mean diameter (SMD) of the blends is greater than that of diesel from 11° before top dead center (BTDC) to 7° BTDC, and then SMD of the blends is less than that of diesel. The equivalence ratio of the blends is lower that that diesel except at the end of injection, leading to the tendency of sooting. The ignition timing advances as the percent of biodiesel in the blend increases, helpful to reduce soot formation. The soot mass fraction for B20 decreases by 35.5% at exhaust valve opening, while it for B10 and 50% (vol) biodiesel blending with diesel (B50), decreases by 14.9 and 14.1%, respectively. The mean soot diameter and particle number of diesel give the bimodal distribution while those of the blends do trimodal distribution. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 282-288, 2015 [ABSTRACT FROM AUTHOR]

Particles which contain soluble organic fraction (SOF), soot, and inorganic salt are mainly the result from an incomplete combustion or pyrolysis of fossil fuels and other organic materials. In a diesel engine, the poor mixing of fuel and air creates fuel-rich zones that support particle formation at high temperatures. Numerous studies show that they are harmful to human health when inhaled and may cause cancer. For that reason, it is important to reduce the formation or at least the emission of particles to the environment. Meanwhile, the strict regulations for particulate matter emission have been enforced in many developed countries. A diesel particulate filter (DPF) is currently the dominant diesel particulate emissions control technology to meet stringent air quality standards, however, the oxidation ability of particles is important to the regeneration of the filter bed in DPF. Temperature has a great influence on the oxidation process of particles. Many physical and chemical changes of particles happen at a high temperature, leading to porosity formation of particles during oxidation. The porosity structure of particles is important to the oxidation ability of particles. The micro-orifice uniform deposition impactor (MOUDI) is a favorable apparatus for obtaining the particle size distribution and collecting the particles in different size ranges after classification. Thermogravimetric analysis (TGA) has been widely used as an analytical method for investigating the relationship between the material weight and temperature under the condition of programming a temperature rise. The curve of the sample weight then can be obtained with the temperature. A derivative thermal gravimetry (DTG) curve, the first order differential to a TG curve, can reveal the features of mass variation with the temperature. Small-angle X-ray scattering (SAXS) is a widely used diffraction method for studying the structure of the sample. In this study, the micro-orifice uniform deposit impactor was used to collect particle samples; the thermal gravimetric analysis was used to investigate the ignition of particles as a basis for determining the oxidation temperature; and the change rules of porosity structure parameters, porosity quantities, and size distribution of particles in the oxidation process were investigated by synchrotron (SAXS). The results of the thermogravimetric analysis showed that the ignition temperature of diesel particles was 487°C, and the oxidation temperature range should be set up under 400°C for study on the porosity structure of particles during oxidation. The results of small-angle X-ray scattering showed that the electron density difference of combustion particles increased, and the size of particles reduced the fractal dimension, average radius, gyration radius, and axial length all significantly increased as the oxidation temperature increased. The tightness of the porosity structure decreased, and the number and size of porosity all increased with increasing oxidation temperature. The porosity size of particles at 100°C was mainly distributed in a range of 6-7 nm. The porosity size of particles at 200°C was mainly distributed in a range of 8-9nm. The porosity size of particles at 400°C was mainly distributed in a range of 12-13 nm. The study provided valuable information on mechanisms of particle oxidation. [ABSTRACT FROM AUTHOR]

This paper presents the concept of preheating the intake air to reduce cold-start emissions from gasoline engines. The effects of intake air temperature on emissions from a gasoline engine were studied by using an air heater based on spark ignition. A light-duty vehicle test of cold-start emissions was carried out at an ambient temperature of−7°C according to New European Driving Cycle for Euro 3 and Euro 4 exhaust emission legislations. The results showed that preheating the intake air could effectively reduce both hydrocarbon (HC) and carbon monoxide (CO) emissions and improve fuel economy during a cold start. During idling conditions, the key phase of the HC and CO emissions was the first 40 s. With the aid of the air heater, cold-start HC and CO emissions from the vehicle were lower than the limit values in the Euro 3 and Euro 4 regulations. [ABSTRACT FROM AUTHOR]

Water has been found to be useful to reduce NOx emissions. In this research, numerical investigations are conducted to understand the effect of air humidity on NOx and soot emissions. A modeling study was carried out by using KIVA-3V code with the Zeldovich thermal NOx model and an improved soot oxidation model based on oxygen and OH oxidation. Good agreement between predictions and measurements of engine-out NOx and soot emissions was achieved. The computations confirm that air humidity allows significant NOx reduction with a little soot penalty except heavy and full load conditions. The computations show that air humidity with small level of (e.g., 2%) can significantly reduce 30% NOx production while increasing soot formation levels appreciably at light and middle loads. When the equivalence relative humidity is 6%, the NOx reduction of more than 70% can be achieved while the engine-out soot emissions increase by more than 30%. The reduction in NOx emissions by air humidity does not totally depend on the lower in-cylinder mean temperature. However, the in-cylinder temperature has direct effect on the formation of O radicals, and has significant effect on the NOx emissions. On the whole, humidity has dual effects on soot formation. [ABSTRACT FROM AUTHOR]

Abstract: Three-dimensional numerical simulation of NOx and soot emissions in a diesel engine was carried out using the KIVA code. In this paper, the NOx and soot models were Zeldovich thermal NOx model and the improved soot oxidation model based on oxygen and hydroxyl oxidation, respectively. The effects of pre-injection schemes on NOx and soot emissions were presented. The results indicate that NOx emissions greatly decrease while soot emissions increases according to the advance of the pre-injection timing and the decrease in the pre-injection amount. With increasing the spacing between the pre-injection and main injection, the NOx emissions decrease while the soot emissions increase. The cases with 25% of the pre-injection amount are reasonable for simultaneously reducing NOx and soot emission. At this ratio, the NOx emission can decrease by 30.9% without the penalty on the soot emission. [Copyright &y& Elsevier]

The chromium (Cr) isotope system is an important redox proxy for understanding Earth's oxygenation history. However, quantitative application of this proxy is hindered by a lack of clear understanding of the global Cr isotope mass balance. Estuarine environments potentially play important roles in influencing the global oceanic Cr mass balance because riverine Cr derived from continental weathering must first travel through estuaries before entering the open ocean. We collected water, suspended particulate matter, and sediment samples across a salinity gradient in the Mobile Bay Estuary located in the Northern Gulf of Mexico, with a purpose of evaluating whether Cr behaves conservatively in estuarine environments. A simple conservative mixing model between the fresh Mobile River water and Gulf of Mexico seawater alone was insufficient to explain the Cr concentration and isotope data, suggesting that Cr behaves non-conservatively in this estuary system. A model incorporating conservative mixing, partial Cr(VI) reduction and partial scavenging of the produced Cr(III) is developed to reproduce the observed data. Our data and modeling exercise suggest that up to 60% of Cr(VI) is reduced to Cr(III) in the Mobile Bay Estuary with a Cr isotope fractionation factor of −1.2‰, and 40% of the produced Cr(III) is removed from solution. Although these parameters may not be the sole solution to the system of equations involved, they are consistent with previous estimates. Future redox-specific Cr isotope data in estuarine environments are needed to place finer constraints on these parameters in estuaries, which is critical for estimating global marine Cr isotope mass balance using riverine Cr concentration and isotope data. [ABSTRACT FROM AUTHOR]

The chromium (Cr) stable isotope system is an increasingly used redox proxy for studying the oxygenation history of Earth's ocean-atmosphere system, but understanding of Cr isotope fractionation in modern seawater is still nascent. A linear relationship has been found between the isotope composition and the logarithmic concentration of total dissolved Cr in the global ocean. Such relationship was used to extract an 'effective' Cr isotope fractionation factor of ca. 0.7‰ associated with the removal of Cr from seawater. However, there is a statistically significant proportion of data that deviate from the global linear array, and the proportion of data plotting below the array is higher than that plotting above the array. Such scattering and skewing patterns are present even after excluding data that may have been caused by freshwater influences and potential inconsistency in methods used to purify Cr from seawater. A simple numerical exercise was conducted to demonstrate that the observed data scattering and skewing could be explained by parallel removal pathways with 'intrinsic' Cr isotope fractionation factors ranging from −0.8‰ to −1.6‰ combined with the presence of variable amount of dissolved Cr(III) in seawater. These results based on global seawater Cr isotope data are consistent with previous conclusions based on individual oceanographic sites. • This is significant scattering around the global δ53Cr vs. Ln[Cr total ] linear array. • Data are skewed below the global linear array (23% plotted below vs 17% above). • The scattering and skewness can be reproduced by Monte Carlo numerical simulations. • Parallel Cr removal pathways and dissolved Cr(III) can explain the data patterns. [ABSTRACT FROM AUTHOR]

This has now been corrected in both the PDF and HTML versions of the Article. The original version of this Article contained an error in the spelling of the author L. David Sibley, which was incorrectly given as David L. Sibley. [Extracted from the article]

Establishing the nickel (Ni) isotopic composition of the upper continental crust (UCC) is crucial for using the Ni isotope system to trace biogeochemical processes and understand crust-mantle interactions. This study reports the Ni isotopic composition of eighty-four well-characterized upper crustal samples, including granites, granodiorites, tonalite-trondhjemite-granodiorite (TTG), loess, river sediments and glacial diamictites, to constrain the Ni isotopic composition of the UCC. Significant variations in δ60Ni are revealed for I-type (0.02–0.26‰), A-type (−0.05–0.08‰) and S-type (0.08–0.36‰) granites for the first time. These Ni isotopic variations are attributed to magmatic differentiation for I- and A- type granites and source heterogeneity for S-type granites. The δ60Ni values of fine-grained clastic sediments (including loess, river sediments and glacial diamictites) range from −0.01‰ to 0.23‰. Such δ60Ni variations cannot be explained by Ni isotopic fractionation during chemical weathering because there are no clear correlations between δ60Ni and Ni/Al 2 O 3 , or the chemical index of alteration (CIA). Instead, the δ60Ni variations in fine-grained clastic sediments are likely inherited from source rocks. The δ60Ni values of our samples for 3.2–3.5 Ga TTGs (0.00–0.13‰), 2.4–2.5 Ga TTGs (0.04–0.13‰) and < 0.4 Ga granites (excluding S-type granites) are statistically indistinguishable (P < 0.05, student's t -test), implying limited variation of δ60Ni in the felsic igneous UCC since 3.5 Ga. Similarly, the δ60Ni values of glacial diamictites suggest insignificant temporal variation in the weathered UCC since 2.4 Ga. The data gathered in this study combined with literature data yields an arithmetic mean δ60Ni value of 0.12 ± 0.15‰ (2SD) for the UCC (ranging from −0.07‰ to 0.36‰). And the weighted average δ60Ni is estimated to be 0.07 ± 0.10‰ (2SD) or 0.11 ± 0.09‰ (2SD) depending on the assumed δ60Ni of the metamorphic rocks. Thus, a lithology-weighted average δ60Ni needs to be further determined by future studies when the δ60Ni values of metamorphosed sedimentary rocks in the UCC are constrained. [ABSTRACT FROM AUTHOR]

• Regulations on marine diesel engine emissions are listed and compared. • The contribution of marine diesel engine emissions to regional emissions is given. • The emission levels of marine diesel engines are reviewed. • Integrated multi-pollutant aftertreatment technologies are reviewed. Marine diesel engines, which provide main power source for ships, mainly contribute to air pollution in ports and coastal areas. Thus there is an increasing demand on tightening the emission standards for marine diesel engines, which necessitates the research on various emission reduction strategies. This review covers emission regulations and emission factors (EFs), environmental effects and available emission reduction solutions for marine diesel engines. Not only the establishment of the emission control areas (ECAs) in the regulations but also many experiments show high concerns about the sulfur limits in fuels, sulfur oxides (SOx) and nitrogen oxides (NOx) emissions. Research results reveal that NOx emissions from marine diesel engines account for 50% of total NOx in harbors and coastal regions. Sulfur content in fuel oil is an important parameter index that determines the development direction of emission control technologies. Despites some issues, biodiesel, methanol and liquefied nature gas (LNG) play their important roles in reducing emissions as well as in replacing fossil energy, being promising fuels for marine diesel engines. Fuel-water emulsion (FWE) and exhaust gas recirculation (EGR) are effective treatment option for NOx emissions control. Common rail fuel injection is an effective fuel injection strategy to achieve simultaneous reductions in particulate matter (PM) and NOx. Selective catalytic reduction (SCR) and wet scrubbing are the most mature and effective exhaust aftertreatment methods for marine diesel engines, which show 90% De-NOx efficiency and 95% De-SOx efficiency. It can be concluded that the integrated multi-pollutant treatment for ship emissions holds great promise. [ABSTRACT FROM AUTHOR]

The selenium (Se) isotope system has been proposed as a redox proxy in environmental and paleoceanographic studies. However, Se isotope exchange among various Se species can potentially interfere with redox-related isotope signatures, and is still poorly understood. In this work, we investigated Se isotope exchange kinetics and equilibrium fractionations between aqueous Se(IV) and Se(VI) under various experimental conditions. At pH = 7, low-Se concentration experiments (0.026 mM Se(IV) and 0.026 mM Se(VI)) at 25 °C, 38 °C and 60 °C were conducted for 900 days, while high-Se concentrations (0.13 mM Se (IV) and 0.14 mM Se(VI); 1.3 mM Se(IV) and 1.4 mM Se(VI)) at 60 °C were conducted for 1547 days. All experiments did not reach isotopic equilibrium, with observed Se isotope fractionations <0.20‰. Adding an electronic shuttle (Anthraquinone-2, 6-disulfonate) did not increase the isotope exchange rate. These results show that under the experimental conditions examined, the isotope exchange reaction between aqueous Se(IV) and Se(VI) is extremely slow. The exchange kinetics between Se(IV) and Se(VI) were also investigated using a 82Se tracer. The exchange rates (R) at 0.13 mM Se(IV) and 0.13 mM Se(VI) at 25 °C, 38 °C and 60 °C were determined to be ≤6.34 × 10−10 M day−1, ≤1.12 × 10−09 M day−1 and ≤1.17 × 10−09 M day−1, respectively. Using the upper bound for the isotope exchange rate at 25 °C and theoretically calculated equilibrium fractionations, and assuming a first order isotope exchange reaction between Se(IV) and Se(VI) by analogy to the sulfur system, the timescale of isotope exchange between aqueous Se (IV) and Se (VI) in a natural lake (Sweitzer Lake, Colorado, USA) was estimated. The minimum half-time (t 1/2 , time to reach 50% isotopic equilibrium) and the minimum time for detectable isotope exchange (t min) are ≥440,000 and ≥18,000 years, respectively. In the modern oceans, t 1/2 and t min are ≥51 million and ≥3.6 million years, respectively. These timescales are much longer than the residence time of Se in Sweizer Lake (2.4 years) and the modern ocean (26,000 years). Therefore, when using Se isotopes to trace the biogeochemical cycle of Se in lakes and oceans, the effect caused by isotope exchange between aqueous Se(IV) -Se(VI) systems is insignificant. [ABSTRACT FROM AUTHOR]

Correction for 'High-precision measurement of Cd isotopes in ultra-trace Cd samples using double spike-standard addition MC-ICP-MS' by Hui Chang et al., J. Anal. At. Spectrom., 2023, 38, 950–962, https://doi.org/10.1039/D3JA00047H. [ABSTRACT FROM AUTHOR]

The stable chromium isotope system has been widely used as a redox proxy to reconstruct the oxygenation history of ocean atmosphere systems. However, the Cr isotope mass balance in modern oceans (i.e., inputs and outputs) remains poorly constrained. To investigate the influence of seawater‐peridotite reaction on the global marine Cr isotope mass balance, we report high‐precision Cr isotope data (δ53Cr) on a series of fresh and altered abyssal peridotites from the Gakkel Ridge and the Southwest Indian Ridge (SWIR). The least altered peridotites give a δ53Cr value of −0.08 ± 0.06‰ (2SD, n = 4) for the oceanic mantle which is consistent with the established δ53Cr of the Bulk Silicate Earth. Compared to fresh peridotites, a subset of altered peridotites exhibit a loss of isotopically light Cr with relatively positive δ53Cr values (up to 0.04‰). These altered peridotites are characterized by significant Cr loss and likely have been subject to serpentinization. By contrast, seafloor weathering has limited influence on the Cr concentrations and isotopic compositions of the altered peridotites. Monte Carlo (MC) simulations of marine alteration suggest a net Cr flux into seawater from altered abyssal peridotites of ∼3.5 × 108 mol/yr, which is on the same order of magnitude as the riverine input flux of 108–109 mol/yr. Furthermore, the MC results suggest that the peridotite‐sourced net Cr flux has a negative δ53Cr signature (−0.33 ± 0.21‰, 2SD). Thus, seawater‐peridotite interactions must be considered when evaluating the modern oceanic Cr isotope mass balance. Plain Language Summary: The stable chromium isotope system is an emerging paleoredox proxy for tracing Earth's atmospheric oxygenation over geological timescales. However, accurately inferring past Earth's atmospheric oxygenation levels using chromium isotopes requires a more precise understanding of the elemental and isotopic cycling of chromium, particularly within the oceans. By studying abyssal peridotites which are rocks found beneath the oceanic crust, we find that specific types of alterations in these rocks, particularly the process of serpentinization, have an impact on the chromium isotopes. These findings provide insights into the mechanisms involved in transporting chromium from the deep Earth mantle to the oceans. We discover that these altered rocks release a flux of isotopically light chromium into the ocean, which is comparable to the amount coming from rivers. Our study sheds new light on the complex interactions between seawater and abyssal peridotites, which potentially exert a profound impact on the global marine Cr isotope mass balance. Key Points: The first data set of stable Cr isotopic compositions for abyssal peridotitesSeafloor weathering has insignificant impact on the Cr isotopic compositions of abyssal peridotitesSeafloor alteration exerts a key control on the Cr isotopic composition of seawater [ABSTRACT FROM AUTHOR]

Uranium (U) associated with coal can be an important source of U and result in environmental pollution during coal combustion. In this study, we developed a method for measurement of U isotope ratios in coals using multiple‐collector inductively coupled plasma‐mass spectrometry. The 233U‐236U double‐spike was utilised to calibrate the instrumental isotopic fractionation. High‐pressure bomb and dry ashing were adopted to digest the coal samples. The δ238UCRM‐145 values obtained from the two different digestion procedures were in good agreement. The δ238UCRM‐145 of seven coal and one fly ash reference materials are reported. Furthermore, the results of fly ash, bottom ash and feed coal samples reveal that the combustion processes lead to relatively small U isotopic fractionation between the samples within the same coal‐fired power plant, indicating that U isotope data can be used as a tracer for heavy metal pollution resulting from coal combustion. The U isotope measurement method of coal established in this study provides technical support to understand the behaviour of U during coal formation and combustion. [ABSTRACT FROM AUTHOR]

Particulate matter (PM) emission from diesel engines has been a critical issue due to its environmental impact. The soot size and number density inside the cylinder can severely affect the size and mass of PM emission emitted from the diesel exhaust pipe. In the present study, the temporal and spatial variations of the mean and instantaneous in-cylinder soot size and number density in a single cylinder direct injection diesel engine have been simulated numerically at different operating conditions, injection system parameters, fuel types and piston bowl geometry using AVL-FIRE code. The results show that the engine load has great effects on the mean soot particle size and number density with crank angle while the engine speed and the fuel injection system parameters have no obvious effects on them. It is observed that there is an obvious shift to larger particles at higher load. The mean soot number densities firstly increase with the increase of loads, but decrease at later crank angle. The in-cylinder soot size distribution shows a unimodal shape at different crank angle under all operating conditions. The soot particle numbers are concentrated from the start of combustion to 40 °CA after top dead center (ATDC). The spatial soot particle size distribution in the combustion chamber is closely related to engine load, impinging angle and airflow motion. The piston bowl diameter has large effect on the mean soot size and number density during the latter phase of the expansion stroke. The results also indicate that both in-cylinder mean soot size and number from biodiesel-diesel blends are affected not only by the oxygen content, but also engine operating conditions. [ABSTRACT FROM AUTHOR]

Sperm motility is crucial to reproductive success in sexually reproducing organisms. Impaired sperm movement causes male infertility, which is increasing globally. Sperm are powered by a microtubule-based molecular machine—the axoneme—but it is unclear how axonemal microtubules are ornamented to support motility in diverse fertilization environments. Here, we present high-resolution structures of native axonemal doublet microtubules (DMTs) from sea urchin and bovine sperm, representing external and internal fertilizers. We identify >60 proteins decorating sperm DMTs; at least 15 are sperm associated and 16 are linked to infertility. By comparing DMTs across species and cell types, we define core microtubule inner proteins (MIPs) and analyze evolution of the tektin bundle. We identify conserved axonemal microtubule-associated proteins (MAPs) with unique tubulin-binding modes. Additionally, we identify a testis-specific serine/threonine kinase that links DMTs to outer dense fibers in mammalian sperm. Our study provides structural foundations for understanding sperm evolution, motility, and dysfunction at a molecular level. [Display omitted] • Structures of native axonemal doublet microtubules from sea urchin and bovine sperm • Identification of >60 proteins decorating sperm doublet microtubules • Identification of microtubule-associated proteins with unique tubulin-binding modes • Analysis of the evolution and structural diversity of the tektin bundle Cryo-EM analysis of native axonemal doublet microtubules from sea urchin and bovine sperm provides molecular insights into sperm evolution, motility, and dysfunction. [ABSTRACT FROM AUTHOR]

Thermoelectric power generation (TEG) technology can be used to recover exhaust waste heat, but its effective application is restricted by bulky size and low thermoelectric conversion efficiency. The compactness evaluation of thermoelectric devices characterized by the power density is lacking. In this paper, a three-dimensional thermal flow and thermoelectricity multi-physics field model of a sandwich flat plate TEG device with multi-layer thermoelectric modules (TEMs) was established. An engine thermoelectric recovery bench test was carried out to verify the model and present the thermal parameters and output performance. The thermal, flow and electrical field distributions of the TEG device, as well as voltage, power and conversion efficiency with engine loads, and power density, were presented. The results show that the hot side temperatures, voltages and powers for each thermoelectric module (TEM) are greatly affected by the position occupied by the TEMs and engine loads. At full load and the coolant flow of 8.5 L/min, the device achieves the peak values of the power of 80.9 W and thermoelectric efficiency of 2.1 %, respectively. The device shows good compactness with the power density of 19.8 kW/m3, attributed to the reasonable arrangement of the collectors, coolers, and TEMs. This work can provide some insights of the relationship between the structural form and size, thermal parameters, electrical parameters and conversion efficiency of the sandwich type TEG device. [ABSTRACT FROM AUTHOR]

Purpose: CD81 deficiency is an extremely rare primary immunodeficiency disease characterized by severe and recurrent infections, IgA-related nephropathy, and profound hypogammaglobulinemia. Only one patient has been reported so far, and the pathogenesis remains unclear. Here, we identified a new case of CD81 deficiency and described its pathogenesis. Methods: We analyzed the clinical, genetic, and immunological features of the patient with CD81 deficiency, and explored the pathogenesis of her antibody deficiencies. Results: The major manifestation of this patient was unexpectedly not recurrent infections but IgA nephropathy with aberrant serum galactose-deficient IgA1. Whole-exome sequencing revealed novel biallelic mutations in CD81 gene that abolished the surface expression of CD81. B cells from the patient lack membrane CD19 and showed reduced switched memory B cells and transitional B cells. Decreased expression of key molecules pY and pBTK in BCR signaling were demonstrated by confocal microscopy. RNA sequencing revealed that genes associated with BCR signaling and immunoglobulins were downregulated in CD81-deficient B cells. In addition, the patient showed increased frequency of T follicular helper cells that biased to Th1-like subsets. Conclusion: We reported the second patient with CD81 deficiency in the world and illustrated aberrant BCR signaling in the patient, therefore helping to unravel the mechanism of antibody deficiency in CD81-deficient patients. [ABSTRACT FROM AUTHOR]

Pulses of the Ediacaran ocean oxygenation were inferred from strong enrichments of redox-sensitive elements (RSEs; particularly Mo, V, U, Re) and negative pyrite sulfur isotopes (δ34S py) in black shales of the Doushantuo Formation in South China. These oceanic oxygenation events (OOEs) have been challenged by the lack of comparable RSE enrichments in correlative strata of northwestern Canada. Here we report four positive chromium isotope (δ53Cr) excursions with peak values (+0.79 ± 0.03‰ to +1.45 ± 0.06‰; 2SD) close to the average δ53Cr value of the modern ocean (+1.0 ± 0.3‰) at the intervals of OOEs, which are separated by low δ53Cr values close to that of the bulk silicate Earth (BSE, −0.124 ± 0.101‰). The positive δ53Cr excursions could be explained by episodic input of oxygenated water from the open ocean to the restricted Nanhua basin, or pulses of ocean oxygenation during the Ediacaran-early Cambrian. The two interpretations can explain the majority of the geochemical data available from the Wuhe section, but both have limitations. The first interpretation implies that the open ocean was more oxygenated than the Nanhua basin during the entire Ediacaran-early Cambrian period, which is not supported by the currently available data from other Ediacaran successions. The second interpretation has difficulties to explain the thallium isotope (ε205Tl) data from the same section, pending confirmation of the OOEs from other successions globally. The data from the Wuhe section highlight the complexity of interpreting the redox history of the global ocean from geochemical results of a single section. Nonetheless, the synchronous changes of multiproxy records—including positive δ53Cr excursions, RSE peaks, negative δ34S py and molybdenum isotope (δ98Mo) excursions—at the same stratigraphic intervals do support a more oxygenated ocean at ~635 Ma, ~580 Ma, ~560 Ma, and early Cambrian, regardless of the degree of restriction of the Nanhua basin from the open ocean. [ABSTRACT FROM AUTHOR]

Adsorption plays an important role in the biogeochemical cycling of selenium (Se) in natural environments and Se isotope fractionation during adsorption is a significant but poorly studied part of Se isotope system. This paper examined Se(IV) and Se(VI) adsorption onto four naturally occurring metal oxides (hematite, manganese dioxide (β-MnO 2), and α and γ-alumina oxides) and revealed Se isotope fractionation as a function of the absorbents used, Se species adsorbed, exposure time, and pH. The results show that Se(IV)/(VI) adsorption was initially rapid and was accompanied with kinetic isotope fractionations as large as 3‰, but slowed down as adsorption equilibrium was approached, eventually approaching isotopic equilibrium. The Se(IV) adsorption onto the studied metal oxides took at least 12 h to reach adsorption equilibrium, longer than Se(VI) adsorption (<60 min). At adsorption equilibrium, Se(IV) adsorption onto Fe and Mn oxides induces significant isotope fractionation, with lighter Se isotopes preferentially adsorbed, whereas Se(IV) adsorption onto Al oxides causes only small fractionation: Δ82/76Se dissolved-adsorbed = δ82/76Se dissolved − δ82/76Se adsorbed is 0.87 ± 0.12 ‰ for hematite, 1.24 ± 0.05 ‰ for β-MnO 2 , 0.08 ± 0.10 ‰ for α-alumina, and 0.05 ± 0.09 ‰ for γ-alumina at pH 5. In contrast to Se(IV) adsorption, Se(VI) adsorption does not induce detectable Se isotope fractionation. The contrasting Se isotope fractionation between Se(IV) and Se(VI) adsorption is likely related to the mechanism of adsorption onto metal oxides, which causes a structural difference between dissolved and adsorbed Se(IV)/Se(VI). In addition, pH had a strong influence on Se isotope fractionation during Se(IV) adsorption onto β-MnO 2 : Δ82/76Se dissolved-adsorbed varied from 1.24‰ to −0.08‰ as pH increased from 5 to 8. However, there was little pH effect on Se isotope fractionation during adsorption onto Fe (consistently at 0.7–0.9‰) and Al oxide (consistently at ∼0‰). Our findings show that, beside abiotic and biotic reduction, Se(IV) adsorption onto Fe-Mn oxides is potentially another important process that can induce Se isotope fractionation in Earth's surface environments. This moves an important step toward correctly reconstructing the Se isotopic composition of seawater using Fe-Mn nodules or crusts. [ABSTRACT FROM AUTHOR]

Hydroxyproline-rich glycoproteins (HRGPs) are a ubiquitous class of protein in the extracellular matrices and cell walls of plants and algae, yet little is known of their native structures or interactions. Here, we used electron cryomicroscopy (cryo-EM) to determine the structure of the hydroxyproline-rich mastigoneme, an extracellular filament isolated from the cilia of the alga Chlamydomonas reinhardtii. The structure demonstrates that mastigonemes are formed from two HRGPs (a filament of MST1 wrapped around a single copy of MST3) that both have hyperglycosylated poly(hydroxyproline) helices. Within the helices, O -linked glycosylation of the hydroxyproline residues and O -galactosylation of interspersed serine residues create a carbohydrate casing. Analysis of the associated glycans reveals how the pattern of hydroxyproline repetition determines the type and extent of glycosylation. MST3 possesses a PKD2-like transmembrane domain that forms a heteromeric polycystin-like cation channel with PKD2 and SIP, explaining how mastigonemes are tethered to ciliary membranes. [Display omitted] • Cryo-EM reveals the composition and structure of an algal mastigoneme filament • MST3 anchors mastigonemes to ciliary membranes via a PKD-like domain aided by SIP • O -linked hydroxyproline glycosylation sheaths PPII helices in a carbohydrate casing • Serine galactosylation hydrogen bonds with the poly(hydroxyproline) backbone Structure of the native C. reinhardtii mastigoneme allows visualization of the glycan patterns associated with different types of proline repetition in two different hydroxyproline-rich glycoproteins, providing insight into the hydroxyproline glycosylation code. The structure also provides an explanation for how mastigonemes are tethered to ciliary membranes. [ABSTRACT FROM AUTHOR]

Mg-Li hybrid batteries (MLHBs) are regarded as promising candidates for electrical energy devices because they can combine the high capacity as well as fast ion transfer advantages of cathodes in lithium-ion batteries (LIBs) and the great safety feature of Mg metal anode in MLHBs. Here, we report a core-shell nanocomposite cathode material (T-Nb 2 O 5 @C-PZS) for MLHB application, where heteroatoms-doped carbon layer is wrapped on T-Nb 2 O 5 microparticles. Owning to the excellent pseudocapacitive performance from T-Nb 2 O 5 core and the abundant N, S and P heteroatoms from the carbon shell, the T-Nb 2 O 5 @C-PZS cathode shows a high discharge capacity (198 mAh g−1 at 0.1 A g−1), excellent rate performance (100 mAh g−1 at 2 A g−1) and outstanding cyclic stability (a capacity retention rate of 85% after 5000 cycles at 1.0 A g−1), when the Mg metal is used as the anode. The advantages of the preparation, microstructure as well as electrochemical performance of T-Nb 2 O 5 @C-PZS make it a promising cathode for MLHBs. [Display omitted] • A core-shell composite cathode material (T-Nb 2 O 5 @C-PZS) is an ideal cathode material having excellent pseudocapacitive performance from T-Nb 2 O 5 core and the abundant N, P and S heteroatoms from the carbon shell for MLHBs. • T-Nb 2 O 5 @C-PZS shows a high discharge capacity (198 mAh g−1 at 0.1 A g−1), excellent rate performance (100 mAh g−1 at 2 A g−1) and outstanding cyclic stability (a capacity retention rate of 85% after 5000 cycles at 1.0 A g−1). [ABSTRACT FROM AUTHOR]

Abstract We measured U/Ca ratios, 4He concentrations, 234U/238U, and 238U/235U in a subset of well-preserved aragonitic scleractinian fossil corals previously described by Gothmann et al. (2015). Comparisons of measured fossil coral He/U ages with the stratigraphic age demonstrate that well-preserved coral aragonite retains most or all of its radiogenic He for 10's of millions of years. Such samples must be largely or entirely free of alteration, including neomorphism. Measurements of 234U/238U and 238U/235U further help to characterize the fidelity with which the original U concentration has been preserved. Analyses of fossil coral U/Ca show that the seawater U/Ca ratio rose by a factor of 4–5 between the Early Cenozoic and today. Possible explanations for the observed increase include (1) the stabilization of U in seawater due to an increase in seawater [CO 3 2−], and a resulting increase in UO 2 -CO 3 complexation as originally suggested by Broecker (1971); (2) a decrease in the rate of low-temperature hydrothermal alteration from Early Cenozoic to present, leading to a diminished U sink and higher seawater [U]; or (3) a decrease in uranium removal in reducing sediments, again leading to higher seawater [U]. [ABSTRACT FROM AUTHOR]

Highlights • The RuO 2 /MWCNT anode was prepared using a facile precipitation method. • The anode showed high specific capacity and good rate performance. • Advanced LIHCs were successfully constructed with RuO 2 /MWCNT anode and APDC cathode. • The LIHCs exhibited high energy/power densities, with excellent cyclic stability. Abstract Here, the porous ruthenium oxide/multi-walled carbon nanocomposite (RuO 2 /MWCNT) was prepared using a facile precipitation method. The RuO 2 /MWCNT showed high specific capacity, outstanding rate performance and long cycling stability under a Li-ion organic electrolyte. Thus, advanced Li-ion hybrid capacitors (LIHCs) were successfully constructed with RuO 2 /MWCNT anode and activated ployaniline derived carbon (APDC) cathode under a Li-ion organic electrolyte. The LIHCs exhibited a highest energy density of 146 Wh kg−1 and a highest power densities of 33 kW kg−1, with excellent cyclic stability (∼100% at 2.0 A g−1 after 15,000 cycles), which exhibited better performance than other LIHCs systems. [ABSTRACT FROM AUTHOR]