TRIPLE OXYGEN ISOTOPES OF BIOMINERALS: A NEW PROXY FOR RECONSTRUCTING PALEOARIDITY, PALEOECOPHYSIOLOGY AND PALEO-CARBON-CYCLING

Over the past two decades, it has become widely recognized that triple oxygen isotope anomalies ("Δ'" 17O) in terrestrial materials have great significance in studying Earth surface processes. Of specific relevance to this dissertation, it has been shown that the "Δ'" 17O of water records environmental information related to aridity, and the "Δ'" 17O of atmospheric O2 is related to stratospheric photochemistry, the partial pressure of atmospheric CO2 (pCO2), and global primary productivity (GPP). Vertebrates incorporate the "Δ'" 17O signal of input water (drinking water, free food water, etc.) and atmospheric O2 into body water, and this signal is then preserved in the isotopic composition of biominerals. Hence, "Δ'" 17O of biominerals is an appealing tracer of paleoaridity and paleo-carbon-cycling. The major objective of this dissertation is to develop approaches to fully realize the potential of biomineral "Δ'" 17O in paleoclimate studies. To enable these studies, I contributed to the development of a new high-precision (±0.01‰, 1σ) method for "Δ'" 17O analysis of carbonates that allows subtle triple oxygen isotope variations to be resolved with unprecedented detail (Passey et al., 2014). In this dissertation, I develop a triple oxygen isotope mass balance body water model, examine the influence on animal body water "Δ'" 17O of numerous climatic, ecological, and isotopic variables, and evaluate the model against triple oxygen isotope data from modern and fossil animals. I then apply the analytical method to fossil dinosaurian eggshell of Jurassic and Cretaceous age, use the body water model to interpret the relationships between "Δ'" 17O of dinosaur body water and "Δ'" 17O of atmospheric O2 ["Δ'" 17O(O2)], and reconstruct the "Δ'" 17O of paleo-atmospheric O2. Cretaceous fossil samples indicate slightly lower or similar "Δ'" 17O(O2) values relative to modern days, pointing to slightly higher pCO2 or similar to slightly lower GPP. Late Jurassic samples indicate anomalously low "Δ'" 17O values, pointing to pCO2 several times higher than present (1490±780 ppm, when assuming present day GPP), reduced GPP, or a combination of both. In summary, this dissertation provides a fundamental triple oxygen isotope body water model for interpreting environmental and physiological influences, and a unique approach of using "Δ'" 17O to investigate pCO2 and carbon cycling of the past

Extreme enrichment in atmospheric 15N15N.

Molecular nitrogen (N2) comprises three-quarters of Earth's atmosphere and significant portions of other planetary atmospheres. We report a 19 per mil (‰) excess of 15N15N in air relative to a random distribution of nitrogen isotopes, an enrichment that is 10 times larger than what isotopic equilibration in the atmosphere allows. Biological experiments show that the main sources and sinks of N2 yield much smaller proportions of 15N15N in N2. Electrical discharge experiments, however, establish 15N15N excesses of up to +23‰. We argue that 15N15N accumulates in the atmosphere because of gas-phase chemistry in the thermosphere (>100 km altitude) on time scales comparable to those of biological cycling. The atmospheric 15N15N excess therefore reflects a planetary-scale balance of biogeochemical and atmospheric nitrogen chemistry, one that may also exist on other planets

The evaluation of biological productivity by triple isotope composition of oxygen trapped in ice-core bubbles and dissolved in ocean: a review

The 17O anomaly of oxygen (Δ17O, calculated from δ17O and δ18O) trapped in ice-core bubbles and dissolved in ocean has been respectively used to evaluate the past biosphere productivity at a global scale and gross oxygen production (GOP) in the mixed layer (ML) of ocean. Compared to traditional methods in GOP estimation, triple oxygen isotope (TOI) method provides estimates that ignore incubation bottle effects and calculates GOP on larger spatial and temporal scales. Calculated from TOI of O2 trapped in ice-core bubbles, the averaged global biological productivities in past glacial periods were about 0.83–0.94 of the present, and the longest time record reached 400 ka BP (thousand years before the present). TOI-derived GOP estimation has also been widely applied in open oceans and coastal oceans, with emphasis on the ML. Although the TOI method has been widely used in aquatic ecosystems, TOI-based GOP is assumed to be constant at a steady state, and the influence of physical transports below the ML is neglected. The TOI method applied to evaluate past total biospheric productivity is limited by rare samples as well as uncertainties related to O2 consumption mechanisms and terrestrial biosphere’s hydrological processes. Future studies should take into account the physical transports below the ML and apply the TOI method in deep ocean. In addition, study on the complex land biosphere mechanisms by triple isotope composition of O2 trapped in ice-core bubbles needs to be strengthened

Boosting oxygen evolution reaction by activation of lattice‐oxygen sites in layered Ruddlesden‐Popper oxide

Emerging anionic redox chemistry presents new opportunities for enhancing oxygen evolution reaction (OER) activity considering that lattice-oxygen oxidation mechanism (LOM) could bypass thermodynamic limitation of conventional metal-ion participation mechanism. Thus, finding an effective method to activate lattice-oxygen in metal oxides is highly attractive for designing efficient OER electrocatalysts. Here, we discover that the lattice-oxygen sites in Ruddlesden-Popper (RP) crystal structure can be activated, leading to a new class of extremely active OER catalyst. As a proof-of-concept, the RP Sr3(Co0.8Fe0.1Nb0.1)2O7-δ (RP-SCFN) oxide exhibits outstanding OER activity (eg, 334 mV at 10 mA cm−2 in 0.1 M KOH), which is significantly higher than that of the simple SrCo0.8Fe0.1Nb0.1O3-δ perovskite and benchmark RuO2. Combined density functional theory and X-ray absorption spectroscopy studies demonstrate that RP-SCFN follows the LOM under OER condition, and the activated lattice oxygen sites triggered by high covalency of metal-oxygen bonds are the origin of the high catalytic activity.This work was financially supported by the Australian Research Council (Discovery Early Career Researcher Award No. DE190100005)

Advances in reforming and partial oxidation of hydrocarbons for hydrogen production and fuel cell applications

One of the most attractive routes for the production of hydrogen or syngas for use in fuel cell applications is the reforming and partial oxidation of hydrocarbons. The use of hydrocarbons in high temperature fuel cells is achieved through either external or internal reforming. Reforming and partial oxidation catalysis to convert hydrocarbons to hydrogen rich syngas plays an important role in fuel processing technology. The current research in the area of reforming and partial oxidation of methane, methanol and ethanol includes catalysts for reforming and oxidation, methods of catalyst synthesis, and the effective utilization of fuel for both external and internal reforming processes. In this paper the recent progress in these areas of research is reviewed along with the reforming of liquid hydrocarbons, from this an overview of the current best performing catalysts for the reforming and partial oxidizing of hydrocarbons for hydrogen production is summarized

Depth profiles of dissolved O2 saturation and isotopologues from the R/V Yellowfin and R/V Kilo Moana from 2016-09-14 to 2017-08-28

Dataset: dissolved O2Seawater was sampled from Niskin bottles associated with CTD casts on each cruise. Water for these dissolved gas isotope samples was the first to be sampled from a given Niskin bottle. When possible, bottles from the same cast were sampled, but depth profiles often came from separate casts at the same site. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/753594NSF Division of Ocean Sciences (NSF OCE) OCE-1436590, NSF Division of Ocean Sciences (NSF OCE) OCE-1533501, NSF Division of Ocean Sciences (NSF OCE) OCE-1436326, NSF Division of Ocean Sciences (NSF OCE) OCE-1559004, NSF Division of Ocean Sciences (NSF OCE) OCE-155921

MiR-195-5p suppresses gastric adenocarcinoma cell progression via targeting OTX1

Gastric adenocarcinoma (GAC) caused by malignant transformation of gastric adenocytes is a malignancy with high incidence. MiR-195-5p modulates a variety of cancers. One of its target genes, orthodenticle homeobox 1 (OTX1), is believed to be a key modulator of tumor progression. We aim to analyze the mechanism of miR-195-5p and OTX1 in GAC. MiR195-5p and OTX1 mRNA levels in GAC cells were tested via qRT-PCR. OTX1 protein and EMT-related protein levels were examined through western blot. Several cell functional assays were designed to measure changes in cell malignant behaviors. Dual luciferase assay verified the targeting relation of miR-195-5p and OTX1. These experimental results showed significantly low miR-195-5p expression and significantly high OTX1 expression in GAC cells. Enforced miR-195-5p level repressed cell malignant progression and accelerated cell apoptosis in GAC. Increased OTX1 weakened the above-mentioned effect caused by overexpressing miR-195-5p. Thus, miR-195-5p restrained migration, proliferation, invasion and epithelial-mesenchymal transition process of GAC cells, and promoted cell apoptosis through regulating OTX1. A new insight is provided for searching for biomarkers or therapeutic targets of GAC

Multifunctional metal organic framework and carbon nanotube-modified filter for combined ultrafine dust capture and SO2 dynamic adsorption

© The Royal Society of Chemistry. Ultrafine dust and acid polar gas species (SO2, NOx, H2S, etc.) in the atmosphere have severe effects on human health. They are the most important indices for air quality evaluation. In this work, we developed a multifunctional, metal organic framework (MOF: UiO-66-NH2) and carbon nanotube (CNT)-modified filter for efficient ultrafine dust removal and acid gas adsorption. A thin layer of amine-functionalized CNTs was used to construct network skeletons on a polytetrafluoroethylene (PTFE) substrate and acted as an intermediate between the porous MOF nanoparticles and the PTFE substrate. The pore size of the filter was successfully regulated from 5.1 to 2.1 μm while the modified filter still had a high gas permeability of up to 402 m3 m−2 h−1 kPa−1. This well-designed multifunctional filter showed an extremely high capture efficiency (99.997%) for ultrafine dust (diameter ∼0.3 μm) and SO2 adsorption capacity in dynamic filtration. Our filter with hierarchical structures is very promising for indoor air purification