•Developed a new method to construct the structure of amorphous SiO2.•Found the linear dependence of the TDE of O atoms on the Si–O–Si bond angles.•Discovered the increase of the attraction exerted ...on the central O atom as the Si–O–Si bond angle increases.•Predicted higher TDE values and higher radiation resistance of SiO2 at annealing temperature ranging from 3000 to 3500 K.
Amorphous SiO2 is a vital insulation or isolation material in modern silicon-based devices and chips, which is exposed to irradiations of energetic particles when working in space environment. In order to evaluate the radiation resistance of a-SiO2, the threshold displacement energy (TDE) with molecular dynamic simulations is calculated. We found a linear dependence of the TDE of O atoms on the Si–O–Si bond angles, which corresponds to a reduction in the stresses exerted on the central O atom as the bond angle increases. The further exploration about the oxide manufacturing process showed that the higher annealing temperature increases the probability of Si–O–Si bond angles in the range of 135°–155°. This work will shed light on the promotion of anti-radiation ability of silicon-based devices.
The vital role of electrocatalysts in determining the efficiency of renewable energy conversion inspired the uncovering of the relation between the catalytic efficiency and electronic structure, in ...which the volcano-type plot based on adsorption energies and d-band model has achieved great success. At the same time, catalysts with nontrivial topological electronic structures have received considerable attention because of their robust topological surface states and high-mobility electrons, which favor the electrons transfer processes in the heterogeneous catalysis reactions. Under the guidance of this theory, excellent catalysts were reported among topological materials. Inspired by the current development of catalyst and topological materials, we tried to extract a pure intrinsic physical parameter, projected Berry phase (PBP), that only depends on the bulk electronic structure. Applying this parameter to the well-known nonmagnetic transition-metal electrocatalysts, we found a linear relationship between PBP and catalytic efficiency of hydrogen evolution reaction (HER) after considering the symmetry constraint. This can be used as a descriptor for the prediction and designing of promising catalysts for HER, which is realized experimentally in Pt7Cu nanostructures. This work illustrates the importance of the pure bulk band structure effect on electrochemical activities and implies an effective way to understand the mechanism of HER catalysts.
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•Three new diketopiperazines were isolated from Aspergillus creber EN-602.•Compounds 1, 2, and 4 exhibited inhibitory activity against ACE in vitro.•Compounds 5 and 6 inhibited ...various aquatic bacteria in assay.•The intermolecular interaction of compounds 1–6 with ACE was investigated.
Thirteen alkaloids, which include three new diketopiperazines, namely, 3-hydroxyprotuboxepin K (4), 3,15-dehydroprotuboxepin K (5), and versiamide A (6), together with ten known alkaloid derivatives (1–3 and 7–13), were isolated from the marine red algal-derived fungus Aspergillus creber EN-602. Versiamide A (6) represents the first example of a naturally occurring quinazolinone alkaloid with a diketopiperazine ring that is derived from phenylalanine (Phe) and leucine (Leu). The structures of these compounds were elucidated by detailed interpretation of their 1D/2D NMR spectroscopic and mass spectrometric data, while the absolute configurations of compounds 1–6 were established on the basis of X-ray crystallographic analysis and time-dependent density functional (TDDFT) calculations of the ECD spectra. Compounds 1, 2, and 4 exhibited inhibitory activity against the angiotensin converting enzyme (ACE) with IC50 values of 11.2, 16.0, and 22.4 μM, respectively, and compounds 5 and 6 inhibited various aquatic bacteria with MIC values that ranged from 8 to 64 μg/mL. The intermolecular interactions and potential binding sites between compounds 1–6 and ACE were investigated via molecular docking simulations.
Nucleotide sequences from four plastid genes (rbcL, atpB, atpA, rps4) were used to infer relationships of Diplaziopsis and Rhachidosorus. The phylogenetic positions of these two Asian fern genera ...have been debated, and neither had been included in the most recent global molecular systematic studies of ferns. Our four plastid gene sequence analyses supported a sister relationship between Diplaziopsis, Rhachidosorus and the North American Homalosorus, the monophyletic group of the newly-examined genera is an early diverging lineage of Woodsiaceae, and far away from athyrioid ferns. The inferred relationships of Diplaziopsis and Rhachidosorus are not consistent with most recent treatments, while, some synapomorphic characteristics are shared with these two genera. Further studies on more morphological characters and gametophytes of these two genera are needed to test these relationship hypotheses.
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•New highly oxygenated and polycyclic andrastin-type meroterpenoids isolated from the cold seep-derived fungus were described.•Bialorastins A and B are rare 17-nor-andrastins with ...unique skeletons.•Bialorastin C exhibited significant proangiogenic activity in transgenic zebrafish.•Molecular dockings were performed to predict the intermolecular interaction of bialorastin C with VEGFR2.•Quantitative RT-PCR results indicated that bialorastin C could activate VEGFR2 and its downstream signaling pathways.
Six new highly oxygenated and polycyclic andrastin-type meroterpenoids, namely, bialorastins A–F (1–6), were discovered from the culture of Penicillium bialowiezense CS-283, a fungus isolated from the deep-sea cold seep squat lobster Shinkaia crosnieri. The planar structures and absolute configurations of these compounds were determined by detailed analysis of spectroscopic data, single crystal X-ray diffraction, and TDDFT-ECD calculations. Structurally, bialorastin A (1) represents a rare 17-nor-andrastin that possesses an unusual 2-oxaspiro4.5decane-1,4-dione moiety with a unique 6/6/6/6/5 polycyclic system, while bialorastin B (2) is also a 17-nor-andrastin featuring a gem-propane-1,2-dione moiety. Additionally, bialorastins C–E (3–5) possess a 6/6/6/6/5/5 fused hexacyclic skeleton, characterized by distinctive 3,23-acetal/lactone-bridged functionalities. All isolated compounds were evaluated for their proangiogenic activities in transgenic zebrafish. Compound 3 exhibited significant proangiogenic activity, which notably increased the number and length of intersegmental blood vessels in model zebrafish in a dose-dependent manner at concentrations of 20 and 40 μM. On a molecular scale, the tested compounds were modeled through molecular docking to have insight into the interactions with the possible target VEGFR2. Mechanistically, RT-qPCR results revealed that compound 3 could promote angiogenesis via activating VEGFR2 and subsequently activating the downstream PI3K/AKT and MAPK signaling pathways. These findings indicate that 3 could be a potential lead compound for developing angiogenesis agents.
Haze pollution caused by PM2.5 is the largest air
quality concern in China in recent years. Long-term measurements of
PM2.5 and the precursors and chemical speciation are crucially important
for ...evaluating the efficiency of emission control, understanding formation
and transport of PM2.5 associated with the change of meteorology, and
accessing the impact of human activities on regional climate change.
Here we reported long-term continuous measurements of PM2.5, chemical
components, and their precursors at a regional background station, the
Station for Observing Regional Processes of the Earth System (SORPES), in
Nanjing, eastern China, since 2011. We found that PM2.5 at the station
has experienced a substantial decrease (−9.1 % yr−1), accompanied by even
a very significant reduction of SO2 (−16.7 % yr−1), since the national
“Ten Measures of Air” took action in 2013. Control of open biomass
burning and fossil-fuel combustion are the two dominant factors that
influence the PM2.5 reduction in early summer and winter, respectively.
In the cold season (November–January), the nitrate fraction was significantly
increased, especially when air masses were transported from the north. More NH3
available from a substantial reduction of SO2 and increased oxidization
capacity are the main factors for the enhanced nitrate formation. The
changes of year-to-year meteorology have contributed to 24 % of the PM2.5
decrease since 2013. This study highlights several important implications on
air pollution control policy in China.
Abstract Objectives Malignant gliomas are common primary brain tumors with dismal prognosis. The blood–brain barrier and unacceptable systemic toxicity limit the employment of chemotherapeutic ...agents. BCNU-impregnated biodegradable polymers (Gliadel®) have been demonstrated to prolong the survival of patients with malignant gliomas. Until now, no biodegradable drug delivery system has been commercially available in China. In the present study, we evaluated the safety of implants with high-dose BCNU in Chinese patients with recurrent malignant gliomas. Patients and methods Adults with supratentorial recurrent malignant glioma were eligible. High-dose BCNU-loaded PLGA implants (20 mg of BCNU in each implant) were placed in the debulking cavity. The implants were investigated by a classical 3 + 3 design. Four levels of BCNU, up to 12 implants, were evaluated. Pharmacokinetic sampling was performed. The toxicity of the implants and the survival of patients were recorded. Results Fifteen recurrent patients were enrolled with 12 glioblastomas and 3 anaplastic gliomas. Among 15 patients, 3 were treated with 3 implants (60 mg of BCNU), 3 with 6 implants (120 mg), 3 with 9 implants (180 mg) and 6 with 12 implants (240 mg). No dose-limiting toxicity was observed in the cohort of patients. Subgaleal effusion was the most common adverse event, presenting in 7 patients (46.7%). The median overall survival (OS) was 322 days (95% CI, 173–471 days). The 6-month, 1-year and 2-year survival rates were 66.7%, 40% and 13.3%, respectively. Conclusions The high-dose BCNU-loaded PLGA implants were safe for Chinese patients with recurrent malignant gliomas and further investigation for efficacy is warranted.
This brief presents 2-D numerical simulation results of a single-event burnout (SEB) in a 4H-silicon carbide (SiC) junction termination extension (JTE) termination structure of a power ...metal-oxide-semiconductor field-effect transistor (MOSFET). Using the rated 1.5-kV JTE termination structure, the most sensitive ion's strike position to SEB is proved to be the edge of the P + /P − JTE region. Due to the severe punchthrough of the electric field, the source contact region is found to the most sensitive region to induce an SEB event. The SEB performance of the JTE termination structure with a single buffer layer or multilayer buffer is evaluated. The results show that the electric field distribution in four buffer layers (FBLs) is the most uniform to achieve the best SEB performance. Therefore, by adding an optimal FBL design to the termination region, the SEB threshold voltage can be increased to 1210 V instead of the common structure's 250 V. The SEB safe operating area of the power MOSFET with an optimal FBL can increase more than three times compared with the common one.
The psychological pressure of high strength, often cause teachers teaching dissatisfaction, absenteeism and employee turnover. The current study examined the impact of work stress on job burnout, ...mainly focused on confirmation of the mediator role of self-efficacy. A total of 387 middle school teachers were as participants involving in this research. Data were collected by using the Perceived Stress Scale, General Self-Efficacy Scale and Maslach Burnout Inventory-General Survey. The results revealed that both work stress and self-efficacy were significantly correlated with job burnout. Structural equation modeling indicated that self efficacy partially mediated work stress to job burnout. The final model also revealed significant both paths from work stress to job burnout through self efficacy. The findings extended prior researches and provided valuable evidence on how to promote mental health of teachers at the workplaces.
The Hierarchical Data Format (HDF) has been a data format standard in National Aeronautic and Space Administration (NASA)'s Earth Observing System Data and Information System since the 1990s. Its ...rich structure, platform independence, full-featured application programming interface (API), and internal compression make it very useful for archiving science data and utilizing them with a rich set of software tools. However, a key drawback for long-term archiving is the complex internal byte layout of HDF files, requiring one to use the API to access HDF data. This makes the long-term readability of HDF data for a given version dependent on long-term allocation of resources to support that version. Much of the data from NASA's Earth Observing System have been archived in HDF Version 4 (HDF4) format. To address the long-term archival issues for these data, a collaborative study between The HDF Group and NASA's Earth Science Data Centers (ESDCs) is underway. One of the first activities was an assessment of the range of HDF4-formatted data held by NASA to determine the capabilities inherent in the HDF format that were used in practice and for use in estimating the effort for full implementation across NASA's ESDCs. Based on the results of this assessment, methods for producing a map of the layout of the HDF4 files held by NASA were prototyped using a markup-language-based HDF tool. The resulting maps allow a separate program to read the file without recourse to the HDF API. To verify this, two independent tools based solely on the map files were developed and tested.
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