Cephalodiones A–D (1–4), the first example of C19‐norditerpenoid dimers, were isolated and fully characterized from a Cephalotaxus plant. These new skeletal natural products shared a unique ...tricyclo6.4.1.12,7tetradeca‐3,5,9,11‐tetraene‐13,14‐dione core that was capped in both ends with rigid multicyclic ring systems either C2‐symmetrically or asymmetrically. Compounds 1–4 were proposed to be biosynthetically produced by the 6+6‐cycloaddition of two identical C19‐norditerpenoid troponoids, which was validated by the semisyntheses of dimers 2–4. Moreover, some compounds showed significant inhibition on Th17 cell differentiation.
Chemical study on a Cephalotaxus plant led to the characterization of four unprecedented C19‐norditerpenoid dimers, named cephalodiones A–D (1–4). These compounds were proposed to be biosynthetically formed through 6+6‐cycloaddition of two C19‐norditerpenoid troponoids either C2‐symmetrically or asymmetrically, which was validated by the semisyntheses of 2–4. Some compounds showed significant inhibition on Th17 cell differentiation.
We make a comparison for ten typical, popular dark energy models according to their capabilities of fitting the current observational data. The observational data we use in this work include the JLA ...sample of type Ia supernovae observation, the Planck 2015 distance priors of cosmic microwave background observation, the baryon acoustic oscillations measurements, and the direct measurement of the Hubble constant. Since the models have different numbers of parameters, in order to make a fair comparison, we employ the Akaike and Bayesian information criteria to assess the worth of the models. The analysis results show that, according to the capability of explaining observations, the cosmological constant model is still the best one among all the dark energy models. The generalized Chaplygin gas model, the constant
w
model, and the
α
dark energy model are worse than the cosmological constant model, but still are good models compared to others. The holographic dark energy model, the new generalized Chaplygin gas model, and the Chevalliear–Polarski–Linder model can still fit the current observations well, but from an economically feasible perspective, they are not so good. The new agegraphic dark energy model, the Dvali–Gabadadze–Porrati model, and the Ricci dark energy model are excluded by the current observations.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The development of highly efficient electrocatalysts for complete oxidation of ethylene glycol (EG) in direct EG fuel cells is of decisive importance to hold higher energy efficiency. Despite some ...achievements, their progress, especially electrocatalytic selectivity to complete oxidated C1 products, is remarkably slower than expected. In this work, we developed a facile aqueous synthesis of Ir‐doped CuPd single‐crystalline mesoporous nanotetrahedrons (Ir‐CuPd SMTs) as high‐performance electrocatalyst for promoting oxidation cleavage of C−C bond in alkaline EG oxidation reaction (EGOR) electrocatalysis. The synthesis relied on precise reduction/co‐nucleation and epitaxial growth of Ir, Cu and Pd precursors with cetyltrimethylammonium chloride as the mesopore‐forming surfactant and extra Br− as the facet‐selective agent under ambient conditions. The products featured concave nanotetrahedron morphology enclosed by well‐defined (111) facets, single‐crystalline and mesoporous structure radiated from the center, and uniform elemental composition without any phase separation. Ir‐CuPd SMTs disclosed remarkably enhanced electrocatalytic activity and excellent stability as well as superior selectivity of C1 products for alkaline EGOR electrocatalysis. Detailed mechanism studies demonstrated that performance improvement came from structural and compositional synergies, which kinetically accelerated transports of electrons/reactants within active sites of penetrated mesopores and facilitated oxidation cleavage of high‐energy‐barrier C−C bond of EG for desired C1 products. More interestingly, Ir‐CuPd SMTs performed well in coupled electrocatalysis of anode EGOR and cathode nitrate reduction, highlighting its high potential as bifunctional electrocatalyst in various applications.
Ir‐doped CuPd single‐crystalline mesoporous nanotetrahedrons (Ir‐CuPd SMTs) were facilely prepared through an aqueous surfactant‐templating epitaxial growth strategy. With mesoporous channels and multi‐compositions, Ir‐CuPd SMTs delivered remarkable C−C bond cleavage of electrocatalytic ethylene glycol oxidation (EGOR) to C1 products. The Ir‐CuPd SMTs performed perfectly in coupled electrocatalysis of EGOR and nitrate reduction.
Accumulating evidence indicated that dysregulated circular RNAs (circRNAs) could play pivotal roles in cancer biology. A recent study demonstrated that circ_0030235 expression is upregulated in human ...pancreatic ductal adenocarcinoma (PDAC) by high-throughput circRNA microarray. In the current work, we aimed to elucidate the clinical significance, prognostic value, functional roles and mechanism of circ_0030235 in PDAC. Quantitative real time-PCR was used to detect circ_0030235 expression in PDAC tissue specimens and cell lines. The clinical significance of circ_0030235 was evaluated by Fisher's exact test, Kaplan-Meier curves, and Cox regression analysis. Cell growth, apoptosis, and metastatic properties were then explored after circ_0030235 knockdown/overexpression. Dual luciferase reporter assay was applied to detect the mechanisms of circ_0030235. As a result, the data documented that circ_0030235 was upregulated in PDAC cell lines and cancerous tissues compared with HPDE and matched normal tissue specimens, respectively. Overexpression of circ_0030235 in tumor samples is related to higher tumor stage and positive lymph node invasion. Additionally, analyses documented that high expression of circ_0030235 was associated with poor prognosis for PDAC patients. Knockdown of circ_0030235 by siRNAs inhibited cell growth, migratory and invasive potential, and promoted cell apoptosis. On the contrary, overexpression of circ_0030235 caused the opposite effect. Mechanistically, circ_0030235 directly sponges miR-1253 and miR-1294 in PDAC cells. What's more, the oncogenic properties of circ_0030235 was partly dependent on its suppression on miR-1253 and miR-1294. Overall, the results showed that circ_0030235 might act as an effective therapeutic target and indicate dismal prognosis for PDAC.
•Circ_0030235 is upregulated in PDAC tissues and cells.•Circ_0030235 expression is associated with PDAC patients' clinical severity.•Circ_0030235 exerts oncogenic properties in PDAC cells.•Circ_0030235 could directly sponge miR-1253 and miR-1294.•The oncogenic role of circ_0030235 is partly dependent on its regulation on miR-1253 and miR-1294.
The strained cyclopropane and/or cyclobutane subunits occurred in many complex natural products including terpenoids, steroids and alkaloids. Natural products with cyclopropane and/or cyclobutane ...motifs not only furnished fascinating structures, but also exhibited versatile biological activities, such as cytotoxic, anti-HIM antimicrobial, antiviral, and immunosuppressive effects. This review covered a large array of structurally unique natural products with strained cyclopropane and/or cyclobutane motifs and summarized their structural features, distributions, biological activities, as well as biogenetic considerations.
Combinations of climatic zones and human activities (A and B denote types of conservation and exploitation activities respectively) well correspond to the nine water-sediment co-varying trends (S, D, ...and I represent stable, decrease and increase trends respectively) in the world’s large rivers distributed globally.
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Water and sediment transport from rivers to oceans is of primary importance in global geochemical cycle. Against the background of global change, this study examines the changes in water and sediment fluxes and their drivers for 4307 large rivers worldwide (basin area ≥1000 km2) based on the longest available records. Here we find that 24% of the world’s large rivers experienced significant changes in water flux and 40% in sediment flux, most notably declining trends in water and sediment fluxes in Asia’s large rivers and an increasing trend in suspended sediment concentrations in the Amazon River. In particular, nine binary patterns of changes in water-sediment fluxes are interpreted in terms of climate change and human impacts. The change of precipitation is found significantly correlated to the change of water flux in 71% of the world’s large rivers, while dam operation and irrigation rather control the change of sediment flux in intensively managed catchments. Globally, the annual water flux from rivers to sea of the recent years remained stable compared with the long-time average annual value, while the sediment flux has decreased by 20.8%.
Hepatocellular carcinoma (HCC) is one of the most lethal tumours worldwide. However, the effects of first-line sorafenib treatment in advanced HCC fail to prolong patients' survival due to the highly ...heterogeneous characteristics of HCC etiology. Cyclin-dependent kinase 9 (CDK9) is an important target in the continuous development of cancer therapy. Here, we demonstrate that CDK9 is closely associated with the progression of HCC and can serve as an HCC therapeutic target by modulating the recovery of wild-type p53 (wt-p53) function. We prove that mouse double minute 2 homologue (MDM2) and Sirtuin 1 (SIRT1) are phosphorylated by CDK9 at Ser166 and Ser47, respectively. Inhibition of CDK9 not only reduces the MDM2-mediated ubiquitination and degradation of wt-p53 but also increases wt-p53 stability by suppressing deacetylase activity of SIRT1. Thus, inhibition of CDK9 promotes the wt-p53 stabilization and prevents HCC progression. However, excessive inhibition by high concentrations of specific CDK9 inhibitors counteracts the promotion of p53 stability and reduces their anti-HCC activity because of extreme general transcription repression. The effects of a novel CDK9 inhibitor named oroxylin A (OA) from Scutellaria baicalensis are explored, with the results indicating that OA shows moderate and controlled inhibition of CDK9 activity and expression, and stabilizes wt-p53 by inhibiting CDK9-regulated MDM2 and SIRT1 signaling. These outcomes indicate the high therapeutic potential of OA against HCC and its low toxicity in normal tissue. This study demonstrates a novel mechanism for the regulation of wt-p53 by CDK9 and indicates that OA is a potential candidate for HCC therapy.
Rhodium (Rh)‐based catalysts may solve the long‐standing inefficient oxidation of ethanol for direct ethanol fuel cells (DEFCs); however, the performance of ethanol oxidation reaction (EOR) on ...existing Rh‐based catalysts are far limited. Herein, the Rh–Pb catalysts are synthesized by building Pb and Pb oxide around Rh nanodomain, which shows highly efficient splitting CC bond and facile further oxidation of as‐generated C1 intermediates (COad and CHx fragments). It exhibits an ever‐highest EOR peak mass activity of ≈2636 mA mg−1Rh among Rh‐based catalysts in alkaline media. Meanwhile, its anodic current remains ≈50% even after a 4 h durability test at 0.53 V versus RHE. As for the C1‐pathway selectivity, in situ infrared adsorption spectral (IRAS) results demonstrate that it could significantly improve the production of CO2. More directly, the apparent faraday efficiency of EOR C1 pathway is estimated to be as high as 20% (at 0.53 V versus RHE). This Rh–Pb catalyst could hold great promise for developing the commercial DEFCs.
The Rh–Pb bifunctional catalysts efficiently break ethanol CC bond at Rh domains and further quickly oxidize COad and CHx intermediates by OHad species provided by Pb and/or Pb oxide, thus exhibiting a superior ethanol electrooxidation activity of ≈2636 mA mg−1Rh in alkaline media and an apparent C1 pathway faraday efficiency up to 20%.
Understanding the mechanisms controlling downstream water‐level variations after the operation of the Three Gorges Dam is important for riverine flood and drought management. However, our ...quantitative understanding of the multiple controls of river morphology, vegetation, and floodplain resistance on water levels in the Middle Yangtze River (MYR) remains limited. Here, we analyze changes in river channels and floodplain resistance in the MYR using 450 cross‐sectional profiles as well as data on discharge, water levels, sediment, and satellite images from 2003 to 2015. Results show an overall decline in low‐flow water‐levels (at a given small discharge) due to severe incisions of low‐flow channels caused by a sharp reduction of ∼90% in sediment loads from 1950–2002 to 2003–2020. In contrast, high‐flow water‐levels (at a given large discharge) display minor changes. Our analysis shows that the notably increased floodplain resistance due to vegetation growth is likely the dominant factor elevating flood water‐levels, followed by riverbed coarsening and greater fluctuations in the river longitudinal profiles. Our findings further the understanding of downstream geomorphic response to dam operation and their impacts on water levels and have important implications for riverine flood management in dammed river systems.
Key Points
Hungry‐water‐driven channel erosion causes the sharp reduction in low‐flow water‐levels
Floodplain resistance increase dominates the minor change in high‐flow water‐levels, followed by riverbed coarsening and greater fluctuations in the river longitudinal profile
Floodplain resistance increase mainly caused by vegetation expansion in floodplain and channel bars due to the reduced floodplain submerged frequency
Abstract
Achieving healthy active‐material microenvironment (ME@AM) for stable and efficient electron/ion transport around each active‐material particle is crucial for high‐performance battery ...electrodes. However, this goal has been proved extremely challenging for most high‐capacity AMs such as sulfur, owing to its notable volume change and severe shuttle effect. Here, a multifunctional hybrid material with zein protein reinforced catalytic single Cu atom/carbon composite (Cu─C) (zein/Cu─C) is coated onto sulfur/carbon (SC) particle, to prepare the advanced zein/Cu─C@SC core–shell particle. Similar to the multifunctional cell membrane well‐known in biology, this multifunctional zein/Cu─C coating helps build a healthy and stable ME@AM within sulfur cathode. Specifically, it can simultaneously provide robust protective shell for the AM particle, adsorption and catalyst function to the dissolved polysulfides, and AM surface treatment to improve AM/conductive agent interface. All these functions are the keys to build and maintain a healthy ME@AM in sulfur cathode. This study not only brings effective solutions to the challenges in volume‐change high‐capacity sulfur active materials and beyond, but also helps achieve comprehensive understanding of the key factors controlling the structuring and final quality of ME@AM.
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