Stress concentrations in nanoscale defective graphene

Defect-free graphene nanosheets are the strongest material known but manufactured graphene tends to contain flaws of different forms and dimensions, leading to the degradation of mechanical performance. Here we report a quantitative mechanical approach to quantitatively evaluate the influence of defects within exfoliated pristine graphene sheets. Results indicate stress concentrations around defects within graphene sheets that lower strength. The description of stress concentration broadly follows a Griffith strength approach for continuum materials, despite the non-continuum structure of graphene, but has little impact on the Young’s modulus

Modulation of Actin Filament Dynamics by Inward Rectifying of Potassium Channel Kir2.1

Apart from its ion channel properties, the Kir2.1 channel has been found in tumors and cancer cells to facilitate cancer cell motility. It is assumed that Kir2.1 might be associated with cell actin filament dynamics. With the help of structured illumination microscopy (SIM), we show that Kir2.1 overexpression promotes actin filament dynamics, cell invasion, and adhesion. Mutated Kir2.1 channels, with impaired membrane expression, present much weaker actin regulatory effects, which indicates that precise Kir2.1 membrane localization is key to its actin filament remolding effect. It is found that Kir2.1 membrane expression and anchoring are associated with PIP2 affinity, and PIP2 depletion inhibits actin filament dynamics. We also report that membrane-expressed Kir2.1 regulates redistribution and phosphorylation of FLNA (filamin A), which may be the mechanism underlying Kir2.1 and actin filament dynamics. In conclusion, Kir2.1 membrane localization regulates cell actin filaments, and not the ion channel properties. These data indicate that Kir2.1 may have additional cellular functions distinct from the regulation of excitability, which provides new insight into the study of channel proteins

Immune escape mechanisms of severe fever with thrombocytopenia syndrome virus

Severe fever with thrombocytopenia syndrome (SFTS), which is caused by SFTS virus (SFTSV), poses a serious threat to global public health, with high fatalities and an increasing prevalence. As effective therapies and prevention strategies are limited, there is an urgent need to elucidate the pathogenesis of SFTS. SFTSV has evolved several mechanisms to escape from host immunity. In this review, we summarize the mechanisms through which SFTSV escapes host immune responses, including the inhibition of innate immunity and evasion of adaptive immunity. Understanding the pathogenesis of SFTS will aid in the development of new strategies for the treatment of this disease

A Simplified All-ZVS Strategy for High-Frequency Triple Active Bridge Converters with Designed Magnetizing Inductance

The triple active bridge (TAB) converters that integrates the on-board charger and the auxiliary power module is ideally suited for producing a high-power density electric vehicle (EV) charger. As the power coupling among each port complicates the TAB's mode analysis, it is challenging to avoid a compromise with high-efficient operation and the wide-applicability of soft-switching operation in the TAB modulation technique. In this work, the influence of the transformer's magnetizing inductance is introduced into the analysis of the TAB converter for simplifying the realization of zero voltage switching (ZVS), and in this way, the power conversion efficiency of TAB operating in high-frequency can be improved. Drawing on the working principles of a single dual active bridge (DAB) converter and the linear superposition theorem, a simplified four-phase modulation (FPM) scheme for the TAB converter is proposed in this article, which is computationally stress-free, featuring low switching and conduction loss characteristics. By combining the FPM scheme with the tuning of the magnetizing inductance value, the ZVS operation of all switches can be readily achieved without imposing extra computational burden. This is particularly advantageous for time-intensive scenarios such as those found in the application of EVs. In addition, the ZVS process of the TAB converter is thoroughly studied and unified to simplify the calculation of ZVS current and required dead time, enabling the identification of the optimal magnetizing inductance value. The proposed optimization solution is introduced, studied, validated, and benchmarked in a 2.5 kW/100 kHz SiC-based TAB prototype, whose operating parameters are tailored to EVs application and peak efficiency reaches 96.3% at a partial load.</p

An Integrated Power Decoupling Method for Single-Phase EV Onboard Charger in V2G Application

Instead of bulky passive filters, the active power decoupling (APD) method can be adopted to suppress the second-order ripple power in the dc bus of the single-phase electric vehicle onboard charging system. However, the traditional APD methods require additional power switches and energy storage devices, which increase the cost and significantly reduce the power conversion efficiency. To tackle these problems, an integrated method of utilizing the auxiliary power module to form a series-connected APD circuit is proposed in this article. Without additional switches and energy storage devices, the APD circuit only needs to compensate less than 10% of the rated power, while realizing soft-switching operation. In addition, the corresponding control method can further reduce the voltage stress of the switches on the high-voltage side of the converter, and increase the efficiency of the system. Finally, a 2-kW single-phase charging system prototype is built to verify the feasibility and effectiveness of the proposed method.</p

An Improved Combined Current Control for Single-Phase Operation Mode of Single-/Three-Phase EV Charging System with Voltage Ripple Suppression

In this article, the control stage of an interesting versatile single-/three-phase electric vehicle (EV) charging system is studied in details. Therein, a typical three-phase two-level voltage source rectifier can be reconfigured to operate as a single-phase rectifier where two phase-legs operate with a pulsewidth modulation interleaving method and the grid neutral is connected to the midpoint of the dc-bus capacitors with the third leg operating as an active power decoupling (APD) circuit to reduce the current stress in the capacitors. To improve the performance of the single-phase operation while considering external grid voltage disturbances, first, an improved hybrid current control method combining deadbeat prediction current control (DPCC) with repetitive control (RC) is proposed in this article, where a modified RC is adopted to suppress the influence of the internal dc-bus capacitor voltage disturbance and to improve the harmonic control performance. Thereafter, via introducing the weighting factor Kf of the DPCC and by multiplexing the filter of RC in the DPCC output, the stability of the current loop under the influence of grid voltage distortion and grid impedance can be improved remarkably. Moreover, a grid-frequency voltage ripple suppression function implementing zero-voltage-switching turn-on for the APD circuit is achieved, improving the reliability of the converter. Finally, a 7.4-kW single-phase ac-dc converter prototype is built to verify the feasibility and effectiveness of the proposed method in the single-/three-phase EV charging system.</p

Features of training specialists in the field of environmental safety in water resources management

The article substantiates the necessity of transforming the educational process to train specialists in the field of environmental safety in water resources management. The main peculiarity of labor functions performed by such specialists is in the randomness and secrecy of natural processes and the appearance of consequences from any type of activity over a long period of time. It is necessary to understand the cause-and-effect relationships between processes and the individual parameters that affect the speed of their realization in order to solve such problems. The result of the research was the development of the training concept, which allows the presentation of a task as a set of elementary actions that require particular resource support for their fulfillment. Potentially possible problems in their fulfillment are determined. It is recommended that models of “digital twins” of systems capable of imitating the reaction to certain influences be used to improve the efficiency of the educational process and perform highly specialized actions