Defect engineering is an effective way to modulate the electric states and provide active sites for electrocatalytic reactions. However, most studied oxygen vacancies are unstable and susceptible ...under the oxygen circumstance. Here, we fabricated cobalt-defected Co3–x O4 in situ for an efficient oxygen evolution reaction (OER). XAFS and PALS characterizations show that the crystals have abundant Co vacancies and a distorted structure. DFT calculations indicate that the metal defects lead to obvious electronic delocalization, which enhances the carrier transport to participate in water-splitting reactions along the defective conducting channels and the water adsorption/activation on the catalyst surface. Therefore, cobalt-defected Co3–x O4 shows remarkably high OER activity by delivering a much lower overpotential of 268 mV@10 mA cm–2 (with a small Tafel slope of 38.2 mV/dec) for OER in KOH electrolyte, in comparison with normal Co3O4 (376 mV), IrO2 (340 mV), and RuO2 (276 mV). This work opens up a promising approach to construct electronic delocalization structures in metal oxides for high-performance electrochemical catalysts.
Load frequency control (LFC) is widely employed to keep smart grids stable and secure. This paper proposes an adaptive resilient LFC scheme for sub-systems of smart grids under denial-of-service ...(DoS) attacks with energy constraint. Firstly, a resilient triggering communication scheme is introduced, where the triggering condition includes the uncertainty item induced by DoS attacks. Secondly, an adaptive resilient event-triggering LFC scheme is proposed to further reduce the communication burden and defeat the DoS attacks, where the event-triggering parameter can be dynamically adjusted. Third, a stability criterion is derived for Proportional Integral-based LFC systems by employing Lyapunov theory. Finally, to validate the proposed control scheme, case studies are carried out based on three different LFC power generation systems including one-area, two-area and three-area models. The simulation results clearly demonstrate that the proposed adaptive resilient LFC scheme can reduce the communication burden while defeating DoS attacks by comparing with resilient event-triggering LFC scheme and event-triggering LFC scheme in term of defense effect and average triggering period.
Efficient catalytic hydrogenation of nitroarenes to anilines with molecular hydrogen at room temperature is still a challenge. In this study, this transformation was achieved by using a photocatalyst ...of SiC-supported segregated Pd and Au nanoparticles. Under visible-light irradiation, the nitrobenzene hydrogenation reached a turnover frequency as high as 1715 h–1 at 25 °C and 0.1 MPa of H2 pressure. This exceptional catalytic activity is attributed to a synergistic effect of Pd and Au nanoparticles on the semiconducting SiC, which is different from the known electronic or ensemble effects in Pd–Au catalysts. This kind of synergism originates from the plasmonic electron injection of Au and the Mott–Schottky contact at the interface between Pd and SiC. This three-component system changes the electronic structures of the SiC surface and produces more active sites to accommodate the active hydrogen that spills over from the surface of Pd. These active hydrogen species have weaker interactions with the SiC surface and thus are more mobile than on an inert support, resulting in an ease in reacting with the NO bonds in nitrobenzene absorbed on SiC to produce aniline.
Microbial polyhydroxyalkanoates (PHA) containing short‐ and medium/long‐chain‐length monomers, abbreviated as SCL‐co‐MCL/LCL PHAs, generate suitable thermal and mechanical properties. However, ...SCL‐co‐MCL/LCL PHAs with carbon chain longer than nine are difficult to synthesize due to the low specificity of PHA synthase PhaC and the lack of either SCL‐ or MCL/LCL monomer precursor fluxes. This study succeeds in reprogramming a β‐oxidation weakened Pseudomonas entomophila containing synthesis pathways of SCL 3‐hydroxybutyryl‐CoA (3HB) from glucose and MCL/LCL 3‐hydroxyalkanoyl‐CoA from fatty acids with carbon chain lengths from 9 to 18, respectively, that are polymerized under a low specificity PhaC61‐3 to form P(3HB‐co‐MCL/LCL 3HA) copolymers. Through rational flux‐tuning approaches, the optimized recombinant P. entomophila accumulates 55 wt% poly‐3‐hydroxybutyrate in 8.4 g L−1 cell dry weight. Combined with weakened β‐oxidation, a series of novel P(3HB‐co‐MCL/LCL 3HA) copolymers with over 60 wt% PHA in 9 g L−1 cell dry weight have been synthesized for the first time. P. entomophila has become a high‐performing platform to generate tailor‐made new SCL‐co‐MCL/LCL PHAs.
A high‐performing bacterial platform for customized SCL‐co‐MCL/LCL PHA synthesis is developed via rational fine‐tuning approaches, based on which, a series of P(3HB‐co‐MCL/LCL 3HA) copolymers are generated with 3HA ranging from 9 to 18 carbon atoms. The PHA copolymer family is thus further expanded, generating various novel material properties and broader prospects for value‐added applications.
Nuclear localization of PTEN is essential for its tumor suppressive role, and loss of nuclear PTEN is more prominent than cytoplasmic PTEN in many kinds of cancers. However, nuclear PTEN-specific ...regulatory mechanisms were rarely reported. Based on the finding that nuclear PTEN is more unstable than cytoplasmic PTEN, here we identify that F-box only protein 22 (FBXO22) induces ubiquitylation of nuclear but not cytoplasmic PTEN at lysine 221, which is responsible for the degradation of nuclear PTEN. FBXO22 plays a tumor-promoting role by ubiquitylating and degrading nuclear PTEN. In accordance, FBXO22 is overexpressed in various cancer types, and contributes to nuclear PTEN downregulation in colorectal cancer tissues. Cumulatively, our study reports the mechanism to specifically regulate the stability of nuclear PTEN, which would provide the opportunity for developing therapeutic strategies aiming to achieve complete reactivation of PTEN as a tumor suppressor.
AbstractThe dynamic effect of structures under column removal scenarios is investigated by conducting comparative experiments on two identical steel frames with concrete slabs. One frame suffers from ...a static edge-column loss, while the other is subjected to a dynamic column loss that is simulated by imposing an impact on a three-hinged column. The vertical deflections at the column-removal location of the two frames are reported and compared. The stress measurements at key locations of the frame in the static test are also presented. Numerical models are created and validated against experimental results. To quantify the dynamic effect of structures under a sudden edge-column loss, a dynamic amplification factor (DAF) is analytically determined based on the principle of energy conservation and is verified against validated numerical analyses. Parametric studies are also conducted on DAFs for various deflections and stiffness ratios. The experimental results suggest that the two orthogonal steel beams intersecting at the column-removal location deform linearly. The double-span beam after column loss suffers more external loads than the cantilever beam perpendicular to it. The positive yield lines diagonally distribute at the slab bottom, extending from the column-removal location to the corners of the slab. It is found that, owing to the dynamic effect, the ultimate bearing capacity of the frame in the test decreases by approximately 25.6% under a sudden edge-column loss scenario. The discrepancies between the dynamic and static deflections are intensified when the initially imposed gravity loads increase. The DAF at the ultimate limit state of composite frame structures due to a sudden edge-column loss can range from 1.15 to 1.4. Ignoring the enhancement of membrane and catenary action to the resistance can result in an underestimation of the dynamic effect of frames at large deflections. The method for calculating DAFs proposed by Department of Defense is not conservative in practical safety design since a monotonously decreasing value is designated.
Automatic identification of sleep stage is an important step in a sleep study. In this paper, we propose a hybrid automatic sleep stage scoring approach, named HyCLASSS, based on single channel ...electroencephalogram (EEG). HyCLASSS, for the first time, leverages both signal and stage transition features of human sleep for automatic identification of sleep stages. HyCLASSS consists of two parts: A random forest classifier and correction rules. Random forest classifier is trained using 30 EEG signal features, including temporal, frequency, and nonlinear features. The correction rules are constructed based on stage transition feature, importing the continuity property of sleep, and characteristic of sleep stage transition. Compared with the gold standard of manual scoring using Rechtschaffen and Kales criterion, the overall accuracy and kappa coefficient applied on 198 subjects has reached 85.95% and 0.8046 in our experiment, respectively. The performance of HyCLASS compared favorably to previous work, and it could be integrated with sleep evaluation or sleep diagnosis system in the future.
Polyhydroxyalkanoates (PHA) are a family of diverse biopolyesters synthesized by bacteria. PHA diversity, as reflected by its monomers, homopolymers, random and block copolymers, as well as ...functional polymers, can now be generated by engineering the three basic synthesis pathways including the acetoacetyl-CoA pathway, in situ fatty acid synthesis, and/or β-oxidation cycles, as well as PHA synthase specificity. It is now possible to tailor the PHA structures via genome editing or process engineering. The increasing PHA diversity and maturing PHA production technology should lead to more focused research into their low-cost and/or high-value applications.
Covering: 2000 to 2020
Triptolide is a bioactive diterpene triepoxide isolated from
Tripterygium wilfordii
Hook F, a traditional Chinese medicinal plant whose extracts have been used as ...anti-inflammatory and immunosuppressive remedies for centuries. Although triptolide and its analogs exhibit potent bioactivities against various cancers, and inflammatory and autoimmune diseases, none of them has been approved to be used in the clinic. This review highlights advances in material sourcing, molecular mechanisms, clinical progress and new drug design strategies for triptolide over the past two decades, along with some prospects for the future course of development of triptolide.
This review highlights advances in material sourcing, molecular mechanisms, clinical progress and new drug design strategies for triptolide from a Chinese medicinal herb, along with some prospects for the future course of development of triptolide.
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