TRACING CHEMICAL WEATHERING USING LITHIUM AND POTASSIUM ISOTOPES

Silicate weathering is one of the driving forces of element cycling between atmosphere, hydrosphere, lithosphere, modulating habitats on Earth’s surface for the biosphere. Lithium (Li) and potassium (K) isotope ratios (expressed as δ7Li and δ41K) have potentials to trace weathering processes as the isotopes are highly fractionated by fluid-mineral interactions. This dissertation focuses on Li and K isotope fractionations during chemical weathering based on experiments and field observations and their links to element cycles. Chapter 2 develops an improved protocol for chromatographic isolation of Li, enabling reliable Li isotope analysis. Chapter 3 provides a novel view on Li isotope behavior during clay adsorption, following a Rayleigh-type model in a closed system. Chapter 4 investigates K isotope fractionation during clay adsorption. Combined with synchrotron radiation, I highlight opposite K isotope fractionations during clay adsorption and incorporation. Chapter 5 investigates Li and K isotope fractionations during silicate dissolution, thus providing supplementary knowledge of weathering-driven isotope fractionation. Chapter 6 assesses the Li isotope composition in Hawaiian regoliths forming on distinct climate zones and addresses comparative contributions of external additions, native sources, and biogeochemical cycles. Chapter 7 evaluates the K isotope composition in Hawaiian regoliths on distinct climate zones and highlight the use of K isotopes for climate tracing. Chapter 8 leverages the use of K isotope in soils and plants to trace biological K utilization. In sum, this dissertation emphasizes and explains similarity and difference between Li and K isotope fractionation during weathering.Doctor of Philosoph

Elevated expression of Dickkopf-1 increases the sensitivity of human glioma cell line SHG44 to BCNU

<p>Abstract</p> <p>Background</p> <p>Studies have shown that Dickkopf-1 (DKK-1) is involved in tumorigenesis. Recently, we found that 9 out of 12 human glioma cell lines had high level of DKK-1 protein while the other 3 had very low or non-detectable level of DKK-1. The aim of this study is to further examine the function of DKK-1 in glioma cells.</p> <p>Materials and methods</p> <p>The glioma cell line SHG₄₄was obtained from a patient with grade II-III astrocytoma. SHG₄₄cells were transfected with a human DKK-1 gene. Transfection of the empty vector pcDNA3.1 was used as negative control. Sensitivity to BCNU was measured by Annexin-V staining. Expression of bax, bcl-2 and caspase-3 of three groups was determined by immunohistochemistry.</p> <p>Results</p> <p>The tranfection was confirmed by PCR, RT-PCR and Western blot. More apoptotic cell death was observed in the DKK-1 transfected cells, comparing to the non-transfected cells, or cells with empty vector. The expression of bax and caspase-3 of the SHG₄₄-DDK-1 increased, whereas the expression of bcl-2 decreased</p> <p>Conclusion</p> <p>Our results indicated that DKK-1 has a pro-apoptotic function of in glioma.</p

Adaptive Digital Twin for UAV-Assisted Integrated Sensing, Communication, and Computation Networks

In this paper, we study a digital twin (DT)-empowered integrated sensing, communication, and computation network. Specifically, the users perform radar sensing and computation offloading on the same spectrum, while unmanned aerial vehicles (UAVs) are deployed to provide edge computing service. We first formulate a multi-objective optimization problem to minimize the beampattern performance of multi-input multi-output (MIMO) radars and the computation offloading energy consumption simultaneously. Then, we explore the prediction capability of DT to provide intelligent offloading decision, where the DT estimation deviation is considered. To track this challenge, we reformulate the original problem as a multi-agent Markov decision process and design a multi-agent proximal policy optimization (MAPPO) framework to achieve a flexible learning policy. Furthermore, the Beta-policy and attention mechanism are used to improve the training performance. Numerical results show that the proposed method is able to balance the performance tradeoff between sensing and computation functions, while reducing the energy consumption compared with the existing studies.Comment: 14 pages, 11 figures

Graphene-analogues boron nitride nanosheets confining ionic liquids: a high-performance quasi-liquid solid electrolyte

Solid electrolytes are one of the most promising electrolyte systems for safe lithium batteries, but the low ionic conductivity of these electrolytes seriously hinders the development of efficient lithium batteries. Here, a novel class of graphene-analogues boron nitride (g-BN) nanosheets confining an ultrahigh concentration of ionic liquids (ILs) in an interlayer and out-of-layer chamber to give rise to a quasi-liquid solid electrolyte (QLSE) is reported. The electron-insulated g-BN nanosheet host with a large specific surface area can confine ILs as much as 10 times of the host's weight to afford high ionic conductivity (3.85 × 10−3 S cm−1 at 25 °C, even 2.32 × 10−4 S cm−1 at −20 °C), which is close to that of the corresponding bulk IL electrolytes. The high ionic conductivity of QLSE is attributed to the enormous absorption for ILs and the confining effect of g-BN to form the ordered lithium ion transport channels in an interlayer and out-of-layer of g-BN. Furthermore, the electrolyte displays outstanding electrochemical properties and battery performance. In principle, this work enables a wider tunability, further opening up a new field for the fabrication of the next-generation QLSE based on layered nanomaterials in energy conversion devices

Cell metabolism-based optimization strategy of CAR-T cell function in cancer therapy

Adoptive cell therapy (ACT) using chimeric antigen receptor (CAR)-modified T cells has revolutionized the field of immune-oncology, showing remarkable efficacy against hematological malignancies. However, its success in solid tumors is limited by factors such as easy recurrence and poor efficacy. The effector function and persistence of CAR-T cells are critical to the success of therapy and are modulated by metabolic and nutrient-sensing mechanisms. Moreover, the immunosuppressive tumor microenvironment (TME), characterized by acidity, hypoxia, nutrient depletion, and metabolite accumulation caused by the high metabolic demands of tumor cells, can lead to T cell “exhaustion” and compromise the efficacy of CAR-T cells. In this review, we outline the metabolic characteristics of T cells at different stages of differentiation and summarize how these metabolic programs may be disrupted in the TME. We also discuss potential metabolic approaches to improve the efficacy and persistence of CAR-T cells, providing a new strategy for the clinical application of CAR-T cell therapy

Intakes of magnesium, calcium and risk of fatty liver disease and prediabetes

Objective Obesity and insulin resistance play important roles in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Mg intake is linked to a reduced risk of metabolic syndrome and insulin resistance; people with NAFLD or alcoholic liver disease are at high risk of Mg deficiency. The present study aimed to investigate whether Mg and Ca intakes were associated with risk of fatty liver disease and prediabetes by alcohol drinking status. Design We analysed the association between Ca or Mg intake and fatty liver disease, prediabetes or both prediabetes and fatty liver disease in cross-sectional analyses. Setting Third National Health and Nutrition Examination Survey (NHANES III) follow-up cohort of US adults. Subjects Nationally representative sample of US adults in NHANES (n 13 489). Results After adjusting for potential confounders, Mg intake was associated with approximately 30 % reduced odds of fatty liver disease and prediabetes, comparing the highest intake quartile v. the lowest. Mg intake may only be related to reduced odds of fatty liver disease and prediabetes in those whose Ca intake is less than 1200 mg/d. Mg intake may also only be associated with reduced odds of fatty liver disease among alcohol drinkers. Conclusions The study suggests that high intake of Mg may be associated with reduced risks of fatty liver disease and prediabetes. Further large studies, particularly prospective cohort studies, are warranted to confirm the findings