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Rationale: The Δ36S standard deviation measured in a conventional isotope ratio mass spectrometer such as MAT 253 is ca 0.1‰ to 0.3‰. At this precision, it is difficult to resolve the origin of non‐mass‐dependent sulfur isotope fractionation in tropospheric sulfate aerosol and in Martian meteorites or small deviations from the canonical mass‐dependent fractionation laws. Interfering ions with m/z at 131 of 36SF5+ are suggested by the community as the cause of the poor precision, but the exact ion species has not been identified or confirmed. Methods: Here we examined the potential interfering ions by using a Thermo Scientific ultrahigh‐resolution isotope ratio mass spectrometer to measure SF6 working gas and SF6 gases converted from IAEA‐S1/2/3 Ag2S reference materials. Results: We found that there are two resolvable peaks to the right of the 36SF5+ peak when a new filament was installed, which are 186WF42+ followed by 12C3F5+. However, only the 12C3F5+ interference peak was observed after more than three days of filament use. 12C3F5+ is generated inside the instrument during the ionization process. Avoiding the interfering signals, we were able to achieve a Δ36S standard deviation of 0.046‰ (n = 8) for SF6 zero‐enrichment and 0.069‰ (n = 8) for overall measurement start from silver sulfide IAEA‐S1. Conclusions: Aging the filament with SF6 gas can avoid the interference of 186WF42+. Minimizing the presence of carbon‐bearing compounds and avoiding the interfering signals of 12C3F5+ from 36SF5+, we can improve Δ36S measurement accuracy and precision, which helps to open new territories for research using quadruple sulfur isotope composition. [ABSTRACT FROM AUTHOR]

Low temperature superconducting vacuum tube maglev is one of the ultra-high-speed transportation methods that a lot of countries are competing to develop. At present, the research is in its infancy, and it is necessary to evaluate the dynamic performance of its route lines. In this paper, taking the maglev test line from Changsha to Hengyang as an example, a vehicle-route coupling model of the low-temperature superconducting electric levitation system was established, the dynamic performances of the maglev vehicle were determined. Firstly, the vertical and lateral acceleration of the carbody, levitation and guidance force were calculated. Secondly, the frequency histograms of the dynamic performance indicators were drawn, and the distributions of these indicators in different intervals was analyzed. Thirdly, the influence of the different curve radius on the dynamic performance index was obtained. The research shows that when the maglev vehicle travels across the Changsha-Hengyang line, the calculated vertical and lateral accelerations of the carbody are lower than the comfort threshold, and the dynamic performance meets the requirements. From the perspective of vehicle dynamic performance, the transition curve length of 1 400 m is reasonable. When the curve radius is 20 000 m, the vehicle speed 1 000 km/h and the cross slope of 16° match the best dynamic performances. The results in the article can provide references for the design of ultra high speed maglev lines. [ABSTRACT FROM AUTHOR]

The global biosphere is commonly assumed to have been less productive before the rise of complex eukaryotic ecosystems than it is today.sup.1. However, direct evidence for this assertion is lacking. Here we present triple oxygen isotope measurements ([increment].sup.17O) from sedimentary sulfates from the Sibley basin (Ontario, Canada) dated to about 1.4 billion years ago, which provide evidence for a less productive biosphere in the middle of the Proterozoic eon. We report what are, to our knowledge, the most-negative [increment].sup.17O values (down to -0.880/00) observed in sulfates, except for those from the terminal Cryogenian period.sup.2. This observation demonstrates that the mid-Proterozoic atmosphere was distinct from what persisted over approximately the past 0.5 billion years, directly reflecting a unique interplay among the atmospheric partial pressures of CO.sub.2 and O.sub.2 and the photosynthetic O.sub.2 flux at this time.sup.3. Oxygenic gross primary productivity is stoichiometrically related to the photosynthetic O.sub.2 flux to the atmosphere. Under current estimates of mid-Proterozoic atmospheric partial pressure of CO.sub.2 (2-30 times that of pre-anthropogenic levels), our modelling indicates that gross primary productivity was between about 6% and 41% of pre-anthropogenic levels if atmospheric O.sub.2 was between 0.1-1% or 1-10% of pre-anthropogenic levels, respectively. When compared to estimates of Archaean.sup.4-6 and Phanerozoic primary production.sup.7, these model solutions show that an increasingly more productive biosphere accompanied the broad secular pattern of increasing atmospheric O.sub.2 over geologic time.sup.8.Triple oxygen isotope measurements of 1.4-billion-year-old sedimentary sulfates reveal a unique mid-Proterozoic atmosphere and demonstrate that gross primary productivity in the mid-Proterozoic was between 6% and 41% of pre-anthropogenic levels., Author(s): Peter W. Crockford [sup.1] [sup.2] [sup.3] , Justin A. Hayles [sup.4] [sup.5] , Huiming Bao [sup.5] [sup.6] , Noah J. Planavsky [sup.7] , Andrey Bekker [sup.8] , Philip W. [...]

Rationale: The oxygen isotope composition of phosphate (δ18OPO4) is widely employed for reconstructing paleotemperature and tracing biogeochemical phosphorus cycling. However, existing phosphate purification protocols do not work well for igneous rocks and igneous weathering profiles (IWPs). A reliable purification method is needed for measuring δ18OPO4 in these materials. Methods: Our phosphate purification method includes two steps of cation exchange resin treatment separated by a step of calcium phosphate precipitation (R‐Ca‐R method). In addition, the silver phosphate precipitation in our procedure is featured by slow evaporation to crystallization until the appearance of ammonium nitrate or silver nitrate crystals. We evaluated our methods on weathered and pristine igneous rocks, phosphorite rocks, KH2PO4, and (NH4)2HPO4 solutions. Results: Our purification method converted over 99.9% phosphate in solution to calcium phosphate, which can be easily decalcified by cation resin. The improved silver phosphate precipitation method produced high phosphate yields (97.1%–99.5%) and retained original δ18OPO4 within analytical uncertainty (2σ = 0.6‰). We applied the purification and precipitation method on five igneous rocks and IWPs, and obtained δ18OPO4 values ranging from 6.4‰ to 8.0‰. Duplicate phosphate extractions yielded δ18OPO4 values differing by less than 0.3‰. Conclusions: We developed a new phosphate purification method that is applicable to phosphate extraction in igneous rocks and IWPs. We also proposed a reliable indicator for the termination of silver phosphate precipitation. Our method can achieve high phosphate yield and reproducible δ18OPO4 value. [ABSTRACT FROM AUTHOR]

Two cap carbonates overlying Cryogenian panglacial deposits are found in North‐East Svalbard of which the younger (635 Ma) forms the base of the Ediacaran Period. It is represented by a transgressive succession in which laminated dolostone, typically around 20 m thick (Member D1), is succeeded transitionally by a similar thickness of impure carbonates (Member D2). In Spitsbergen, there is evidence of microbially influenced sediment stabilisation and carbonate precipitation in the lower part of D1, whilst the upper part of D1 and D2 show centimetre‐decimetre‐scale graded units with undulatory lamination interpreted as evidence of storm activity. Carbonate originated as possible freshwater whitings, as well as microbial precipitates. Exhumed and eroded hardgrounds display replacive 10–30 μm dolomite crystals with cathodoluminescence characteristics consistent with early diagenetic manganese and iron reduction. Regionally, carbon isotope values consistently decrease by around 2‰ from around −3‰ over 30 m of section which is both a temporal and a bathymetric signal, but not a global one. An exponential decline in carbonate production predicted by box models is fitted by a semi‐quantitative sedimentation model. A mass‐anomalous 17O depletion in carbonate‐associated sulphate in dolomite, inherited from precursor calcite, decreases from −0.6 to −0.3‰ in the basal 15 m of section and then approaches background values. The post‐glacial anomalous 17O depletion in carbonate‐associated sulphate and barite elsewhere has been interpreted in terms of ultra‐high pCO2 at the onset of deglaciation. Such anomalies, with larger amplitude, have been reported in Svalbard from underlying lacustrine and tufaceous limestones representing a hyperarid glacial environment. The anomalous sulphate could be produced contemporarily, or the internally drained landscape may have continued to release 17O‐anomalous sulphate as it was transgressed during cap carbonate deposition. The late Cryogenian to earliest Ediacaran record in Svalbard provides the most complete record of the basal 17O‐depletion event in the world. [ABSTRACT FROM AUTHOR]

Motion control of truck-mounted concrete pump booms is an important part of concrete construction work. The quality of the boom movement will affect the efficiency and safety of construction operations. To make the boom move quickly and steadily, its hydraulic control system needs to be improved. In this article, we firstly combine independent metering control (IMC) and active disturbance rejection control (ADRC). The hydraulic system that controls the boom is meliorated by replacing the traditional proportional directional spool valve with four cartridge flow control valves to realize IMC. Meanwhile, a fuzzy linear ADRC algorithm is proposed for a new IMC hydraulic system where ADRC is linearized and combined with fuzzy logic to achieve better motion control performance of boom sections. According to the results of experiments conducted using all six boom sections, compared with the PID control algorithm, the fuzzy linear active disturbance rejection control (FLADRC) proposed in this article can improve the stability and rapidity of valves controlled by hydraulic cylinders by 10.0% to 66.7% in different working conditions. [ABSTRACT FROM AUTHOR]

Barite in basal Ediacaran cap carbonates in South China shows distinct, non-mass-dependent depletion in [sup.17]O, a signal most likely reflecting an extremely high pC[O.sub.2] atmosphere during Marinoan glacial meltdown. The precise geological context of the barite within the cap carbonate was not defined, however, and such information is crucial to an accurate interpretation of the anomalous [sup.17}O signal. Based on an extensive field survey of Marinoan cap carbonates in South China and detailed sedimentological, petrographic, and isotope data, we propose here a unified sequence of events that followed the deposition of the Nantuo diamictite: the cap dolostone was first deposited and later uplifted due to isostatic rebound, undergoing karstic dissolution in both shallow platform and transitional facies of the Yangtze Block; subsequent transgression initiated a consistent sequence of mineral deposition on karstic surfaces or within cavities. The [sup.17]O-depleted barite, either visible on outcrops or identifiable in thin sections, is among the first minerals precipitated when the transgression flooded the karstified cap dolostone. The calcite with extremely negative [delta][sup.13]C values occurs at the last stage of the cavity filling, well after the deposition of cap dolostone and the [sup.17]O-depleted barite, suggesting that the signal of methane hydrate was registered much later in the cap dolostone. A similar recognition of karstic dissolution and subsequent barite deposits in cap dolostones in northwest Africa and northwest Canada suggest that deposition of the [sup.17]O-depleted barites may be a global event, recording an atmospheric-biological-hydrological condition shortly (within 0-1.6 m.y.) after the initial meltdown of the Marinoan snowball Earth. doi: 10.1130/G31224.1

Volcanic eruptions release a large amount of sulphur dioxide (S[O.sub.2]) into the atmosphere (1,2). S[O.sub.2] is oxidized to sulphate and can subsequently form sulphate aerosol (3), which can affect the Earth's radiation balance, biologic productivity and high-altitude ozone concentrations, as is evident from recent volcanic eruptions (4). S[O.sub.2] oxidation can occur via several different pathways that depend on its flux and the atmospheric conditions (3). An investigation into how S[O.sub.2] is oxidized to sulphate--the oxidation product preserved in the rock record--can therefore shed light on past volcanic eruptions and atmospheric conditions. Here we use sulphur and triple oxygen isotope measurements of atmospheric sulphate extracted from tuffaceous deposits to investigate the specific oxidation pathways from which the sulphate was formed. We find that seven eruption-related sulphate aerosol deposition events have occurred during the mid-Cenozoic era (34 to 7 million years ago) in the northern High Plains, North America. Two extensively sampled ash beds display a similar sulphate mixing pattern that has two distinct atmospheric secondary sulphates. A three-dimensional atmospheric sulphur chemistry and transport model study reveals that the observed, isotopically discrete sulphates in sediments can be produced only in initially alkaline cloudwater that favours an ozone-dominated S[O.sub.2] oxidation pathway in the troposphere. Our finding suggests that, in contrast to the weakly acidic conditions today (5), cloudwater in the northern High Plains may frequently have been alkaline during the mid-Cenozoic era. We propose that atmospheric secondary sulphate preserved in continental deposits represents an unexploited geological archive for atmospheric S[O.sub.2] oxidation chemistry linked to volcanism and atmospheric conditions in the past., A close temporal correlation between large igneous provinces and major mass extinction events over the last 300 million years implies a potentially causal relationship between the two (6). There has [...]

Rationale: When isotope composition is measured in dual‐inlet mode with an isotope ratio mass spectrometer (IRMS), reference gas may be gradually enriched in heavy isotopes due to preferential loss of light ones from the bellows over time. Quantifying the degree of isotopic enrichment of the reference gas is imperative for high‐precision isotopic analysis (i.e. at per meg level). Methods: O2 and CO2 leaking experiments were performed with the dual‐inlet system of an IRMS (Thermo Fisher® MAT 253 Plus). During each experiment, the drop of gas pressure in the bellows with time was recorded and isotope ratios of residual gas at various time intervals were analyzed. Results: Isotopic enrichment of residual O2 gas could be as large as 1‰ for δ18O when a large fraction (>75%) of initial gas was lost. The evolution of isotope compositions of the remaining gas can be well described by a pressure‐dependent Rayleigh fractionation equation. When the pressure in the bellows is within 10–50 mBar, the isotope fractionation factor (α18O) for O2 leaking ranges from 0.99911 to 0.99982 and the characteristic relationship of α17O and α18O is from 0.5123 to 0.5124. Conclusions: Isotope fractionation associated with capillary leaking from bellows is pressure‐dependent. We recommend that the reference gas should be reloaded frequently, especially after a measurement with a low analyzing pressure for the analysis of small amounts of sample. [ABSTRACT FROM AUTHOR]

In the laboratory, barite precipitated from a solution with a high nitrate/sulfate ratio can have a significant amount (up to 28% by weight) of nitrate occluded in barite crystals that cannot be simply washed away. The impurity poses a serious problem for an accurate measurement of the oxygen isotope compositions for atmospheric sulfate, since atmospheric nitrate bears extremely positive [[DELTA].sup.17]O and [[delta].sup.18]O values. Currently available methods for removing the occluded nitrate are either ineffective or not tested for oxygen isotope exchange. Here, I report a DTPA (a chelating solution) dissolution and reprecipitation (DDARP) method that is simple and effective in removing nitrate and other contaminants in barite. A series of barite dissolution and reprecipitation experiments that utilize 170-anomalous solutions or barite crystals is conducted to examine the effect on oxygen isotopes during various treatments. It is established that no oxygen isotope exchange occurs between sulfate and water during DDARP treatment at two experimental temperatures (21 and 70[degrees]C). Occlusion of DTPA itself in barite is negligible. Upon acidification, barite reprecipitation from a DTPA solution is quantitative (~100%). Partially extracted barite may have slightly lower [[delta].sup.18]O or [[delta].sup.34]S values than the originals but no effect on [[DELTA].sup.17]O values. It is also demonstrated that heavily nitrate-contaminated barite samples are free of nitrate occlusion after two dissolution-reprecipitation cycles.

Author(s): Huiming Bao (corresponding author) [1]; Douglas A. Campbell [1]; James G. Bockheim [2]; Mark H. Thiemens [1] The dry valleys of Antarctica are some of the oldest terrestrial surfaces [...]

With the observation of mass-independent isotopic anomalies in numerous atmospheric molecules, the ability to measure both (delta)(super 17)O and (delta)(super 18) in a range of samples is needed. Sulfate oxygen isotopic studies conventionally report only (delta)(super 18)O values. Recent findings indicate that sulfate (delta)(super 17)O and (delta)(super 18) values, particularly the (Delta)(super 17)O value (= (delta)(super 17)O - (0.52)((delta)(super 18)O)), can provide independent information on the origin, mixing, and transformation of sulfate in the atmospheric and surface environments, which is not resolvable by only (delta)(super 18)O measurements. Existing methods for analyzing sulfate (delta)(super 17)O and (delta)(super 18) are extremely laborious and demand high-purity BrF(sub 5). Here we report a novel method of generating O(sub 2) directly from Barite (BaSO(sub 4)) for simultaneous analysis of (delta)(super 18)O and (delta)(super 17)by isotope ratio mass spectrometry (IRMS). The method utilizes a CO(sub 2) - laser fluorination system that can also be used to quantitatively generate O(sub 2) from silicates and oxides. Partial but consistent oxygen yields from BaSO(sub 4) are obtained for samples >4 mg. Correction factors of +9.4% for (delta)(super 18)O and 4.89% for (delta)(super 17)O are obtained, and there is no deviation in the (Delta)(super 17)O value due to the nonquantitative O(sub 2) generation. The system may process more than a dozen samples per working day, with analytical error of +/- 0.05% and +/- 0.8% for (Delta)(super 17)O and (delta)(super 18)O, respectively. This new method is ideal for studies emphasizing an accurate sulfate (Delta)(super 17)O value.