169 research outputs found
3-D Tracking and Visualization of Hundreds of Pt-Co Fuel Cell Nanocatalysts During Electrochemical Aging
We present an electron tomography method that allows for the identification
of hundreds of electrocatalyst nanoparticles with one-to-one correspondence
before and after electrochemical aging. This method allows us to track, in
three-dimensions (3-D), the trajectories and morphologies of each Pt-Co
nanocatalyst on a fuel cell carbon support. The use of atomic-scale electron
energy loss spectroscopic imaging enables the correlation of performance
degradation of the catalyst with changes in particle/inter-particle
morphologies, particle-support interactions and the near-surface chemical
composition. We found that, aging of the catalysts under normal fuel cell
operating conditions (potential scans from +0.6 V to +1.0 V for 30,000 cycles)
gives rise to coarsening of the nanoparticles, mainly through coalescence,
which in turn leads to the loss of performance. The observed coalescence events
were found to be the result of nanoparticle migration on the carbon support
during potential cycling. This method provides detailed insights into how
nanocatalyst degradation occurs in proton exchange membrane fuel cells
(PEMFCs), and suggests that minimization of particle movement can potentially
slow down the coarsening of the particles, and the corresponding performance
degradation.Comment: Nano Letters, accepte
Assessment of the prognostic value of preoperative high-sensitive troponin T for myocardial injury and long-term mortality for groups at high risk for cardiovascular events following noncardiac surgery: a retrospective cohort study
BackgroundFew studies explored the association between high-sensitive cardiac troponin T (hs-cTnT) and long-term mortality for patients after surgery. This study was conducted to assess the association of hs-cTnT with long-term mortality and to investigate the extent to which this association is mediated via myocardial injury after noncardiac surgery (MINS).MethodsThis retrospective cohort study included all patients with hs-cTnT measurements who underwent non-cardiac surgery at Sichuan University West China Hospital. Data were collected from February 2018 and November 2020, with follow-up through February 2022. The primary outcome was all-cause mortality within 1 year. As secondary outcomes, MINS, length of hospital stay (LOS), and ICU admission were analyzed.ResultsThe cohort included 7,156 patients (4,299 [60.1%] men; 61.0 [49.0–71.0] years). Among 7,156 patients, there were 2,151 (30.05%) with elevated hs-cTnT(>14 ng/L). After more than 1 year of follow-up, more than 91.8% of mortality information was available. During one-year follow-up after surgery, there were 308 deaths (14.8%) with a preoperative hs-cTnT >14 ng/L, compared with 192 deaths (3.9%) with a preoperative hs-cTnT <=14 ng/L(adjusted hazard ratio [aHR] 1.93, 95% CI 1.58–2.36; p < 0.001). Elevated preoperative hs-cTnT was also associated with several other adverse outcomes (MINS: adjusted odds ratio [aOR] 3.01; 95% CI, 2.46–3.69; p < 0.001; LOS: aOR 1.48, 95%CI 1.34–1.641; p < 0.001; ICU admission: aOR 1.52, 95%CI 1.31–1.76; p < 0.001). MINS explained approximately 33.6% of the variance in mortality due to preoperative hs-cTnT levels.ConclusionPreoperative elevated hs-cTnT concentrations have a significant association with long-term mortality after noncardiac surgery, one-third of which may by accounted for by MINS
Interpretable machine learning-accelerated seed treatment by nanomaterials for environmental stress alleviation
Crops are constantly challenged by different environmental conditions. Seed
treatment by nanomaterials is a cost-effective and environmentally-friendly
solution for environmental stress mitigation in crop plants. Here, 56 seed
nanopriming treatments are used to alleviate environmental stresses in maize.
Seven selected nanopriming treatments significantly increase the stress
resistance index (SRI) by 13.9% and 12.6% under salinity stress and combined
heat-drought stress, respectively. Metabolomics data reveals that ZnO
nanopriming treatment, with the highest SRI value, mainly regulates the
pathways of amino acid metabolism, secondary metabolite synthesis, carbohydrate
metabolism, and translation. Understanding the mechanism of seed nanopriming is
still difficult due to the variety of nanomaterials and the complexity of
interactions between nanomaterials and plants. Using the nanopriming data, we
present an interpretable structure-activity relationship (ISAR) approach based
on interpretable machine learning for predicting and understanding its stress
mitigation effects. The post hoc and model-based interpretation approaches of
machine learning are combined to provide complementary benefits and give
researchers or policymakers more illuminating or trustworthy results. The
concentration, size, and zeta potential of nanoparticles are identified as
dominant factors for correlating root dry weight under salinity stress, and
their effects and interactions are explained. Additionally, a web-based
interactive tool is developed for offering prediction-level interpretation and
gathering more details about specific nanopriming treatments. This work offers
a promising framework for accelerating the agricultural applications of
nanomaterials and may profoundly contribute to nanosafety assessment.Comment: 30 pages, 6 figure
Establishment of Rab-11 Induced Inflammatory Regulation as Therapeutic Targets in Colon Cancer Progression
Colon cancer is the third-deadliest cancer in the United States. Better understanding the cancer microenvironment/niches is crucial to the development of successful therapeutic targets. An RNAi screening using enterocyte specific driver was performed in Drosophila melanogaster intestine to search for niches regulating the intestine stem cell homeostasis. A small GTPase, Rab11 caused strong intestine stem cell (ISC) proliferation and tissue hyperplasia upon knockdown, due to increased production of inflammatory cytokines and growth factors. Increased inflammatory cytokines and proliferation were also observed in mouse Rab11a knockout (KO) intestine, indicating Rab11 regulatory role in the inflammation-induced hyperplasia is evolutionarily conserved and may also apply to human. We hypothesized that Rab11 is required to maintain cytokines in an appropriate state and its expression is down regulated in cancers. We investigated dextran sulfate sodium and chemical induced mouse colon cancer. Rab11 was largely reduced/absent in cancer tissues whereas well present in the normal tissue. We also investigated the correlation of Rab11 level and human cancer progression by immunofluorescence staining, and found that close to 50% and 40% of the cases studied had reduced Rab11 level by 20% and 30%, respectively. The greater the reduction is, the higher chance it is associated with more progressed cancer. Rab11, therefore, functions to suppress cancer progression and can be potentially developed towards a better diagnosis and treatment target for colon cancer. We will screen FDA approved drugs for ISC proliferation regulation, using a fly intestine tumor model established by expressing a human activated RAFGOFgene and a luciferase gene in the fly gut precursor cells. Selected drugs will be applied to test the Rab11 induced hyperplasia in fly, and further validated by mouse and human organoids derived from Rab11 KO mouse or human colon cancer tissues
Breaking the Crowther Limit: Combining Depth-Sectioning and Tilt Tomography for High-Resolution, Wide-Field 3D Reconstructions
To date, high-resolution (< 1 nm) imaging of extended objects in
three-dimensions (3D) has not been possible. A restriction known as the
Crowther criterion forces a tradeoff between object size and resolution for 3D
reconstructions by tomography. Further, the sub-Angstrom resolution of
aberration-corrected electron microscopes is accompanied by a greatly
diminished depth of field, causing regions of larger specimens (> 6 nm) to
appear blurred or missing. Here we demonstrate a three-dimensional imaging
method that overcomes both these limits by combining through-focal depth
sectioning and traditional tilt-series tomography to reconstruct extended
objects, with high-resolution, in all three dimensions. The large convergence
angle in aberration corrected instruments now becomes a benefit and not a
hindrance to higher quality reconstructions. A through-focal reconstruction
over a 390 nm 3D carbon support containing over one hundred dealloyed and
nanoporous PtCu catalyst particles revealed with sub-nanometer detail the
extensive and connected interior pore structure that is created by the
dealloying instability
Polyploidy events shaped the expansion of transcription factors in Cucurbitaceae and exploitation of genes for tendril development
Cucurbitaceae is one of the most important plant families distributed worldwide. Transcription factors (TFs) regulate plant growth at the transcription level. Here, we performed a systematic analysis of 42 641 TFs from 63 families in 14 Cucurbitaceae and 10 non-cucurbit species. Whole-genome duplication (WGD) was the dominant event type in almost all Cucurbitaceae plants. The TF families were divided into 1 210 orthogroups (OGs), of which, 112 were unique to Cucurbitaceae. Although the loss of several gene families was detected in Cucurbitaceae, the gene families expanded in five species that experienced a WGD event comparing with grape. Our findings revealed that the recent WGD events that had occurred in Cucurbitaceae played important roles in the expansion of most TF families. The functional enrichment analysis of the genes that significantly expanded or contracted uncovered five gene families, AUX/IAA, NAC, NBS, HB, and NF-YB. Finally, we conducted a comprehensive analysis of the TCP gene family and identified 16 tendril-related (TEN) genes in 11 Cucurbitaceae species. Interestingly, the characteristic sequence changed from CNNFYFP to CNNFYLP in the TEN gene (Bhi06M000087) of Benincasa hispida. Furthermore, we identified a new characteristic sequence, YNN, which could be used for TEN gene exploitation in Cucurbitaceae. In conclusion, this study will serve as a reference for studying the relationship between gene family evolution and genome duplication. Moreover, it will provide rich genetic resources for functional Cucurbitaceae studies in the future
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The role of brevican in glioma: promoting tumor cell motility in vitro and in vivo
Background: Malignant glioma is a common primary tumor of the central nervous system. Brevican, an abundant extracellular matrix component in the adult brain, plays a critical role in the process of glioma. The mechanisms for the highly invasive behavior of gliomas are still poorly understood. The aim of this study was to examine whether brevican is a predictor of glioma and its roles in glioma cell motility. Methods: In this study, immunohistochemistry staining for brevican expression was performed in malignant gliomas and benign controls. We also explored the effects of brevican on cell adhesion and migration in brevican-overexpressed cells. Knockdown of brevican expression was achieved by stable transfection of U251 cells transduced with a construct encoding a short hairpin DNA directed against the brevican gene, which correspondingly, down-regulated the proliferation, invasion and spread of brevican-expressing cells. Moreover, the role of brevican in the growth and progression of glioma was demonstrated by in vivo studies. Results: Our results provide evidence for the molecular and cellular mechanisms that may underlie the motility-promoting role of brevican in the progression of glioma. The role of brevican as a target for immunotherapy might be taken into consideration in future studies. Conclusions: This study suggests that expression of brevican is associated with glioma cell adhesion, motility and tumor growth, and also is related to glioma cell differentiation, therefore it may be a marker for malignance degree of gliom
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