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Lightning strikes on aircraft are mainly due to self-triggered bidirectional leader discharges. Understanding the physical processes of lightning strikes is the basis for designing appropriate lightning protection measures. For this purpose, the development processes of bidirectional leaders triggered by a floating conductor were studied in a laboratory. In this paper, an experimental platform for the observation of bidirectional leader discharges is established through a reasonable gap arrangement. The discharge processes were recorded by a high-speed camera with up to 504 000 f/s. The effects of negative streamer discharges on the positive leader propagation speed as well as brightness during the bidirectional leader discharge at different electric field rise rates were mainly studied and quantitatively analyzed by introducing incremental coefficients. The experimental results show that the discharge development at the negative end of the floating conductor lags behind that at the positive end, and there is a coupling phenomenon between the positive and the negative discharge. At low electric field rise rates, when a negative streamer discharge occurs, it causes a positive corona burst, resulting in a sharp increase in brightness, while on the contrary the leader speed change is not as pronounced as the brightness change. As the rate of rise of the electric field increases, the effect of the discharge at the negative end on the positive end gradually decreases. This work could provide a theoretical basis for understanding the physical process of lightning strikes on aircraft. [ABSTRACT FROM AUTHOR]

The stepwise development of positive lightning leaders is still not well understood. A recent laboratory study indicated, at high absolute humidity, positive leaders can do steps due to the merging of a separate luminous structure and the primary leader channel, similar to the steps of negative leaders. The humidity may play a key role in the formation of positive leader steps, however, the humidity effect on the positive leader steps has never been explored. In this paper, we examine numerous positive long spark discharges at different humidity levels with the synchronized discharge current and high‐speed camera frames recording the evolution of leader channel. The positive leader propagation manners at different humidity levels are compared both morphologically and electrically. The effect of humidity on steps is further analyzed statistically. We found that the positive leader steps characterized by steep‐rise current pulse and abrupt channel elongation, which may be led by separate luminous structures, only appear under the condition that high absolute humidity is above a certain threshold. As the ambient humidity increases, these positive leader steps occur more frequently. Plain Language Summary: Lightning is driven by the propagation of positively and negatively charged, thermally‐ionized plasma channels, known as positive and negative leaders. Leaders propagate in a continuous or stepwise manner, characterized by intense reilluminations and abrupt elongations. The physics underlying the positive leaders is still mysterious. Previously, it was commonly accepted that the physics underlying the positive and negative leader steps differed. Recently, researchers found that, at least at high absolute humidity, positive leaders can form steps due to the merging of a separate luminous structure and the primary leader channel, similar to the steps of negative leaders. It seems that humidity plays an important role in the formation of positive leader steps, but the humidity effect on the positive leader steps has never been explored. In this paper, we reported the effect of humidity on the steep‐rise type steps. We found that the positive leader steps characterized by steep‐rise current pulse and abrupt channel elongation, which may be led by separate luminous structures, only appear under the condition that high absolute humidity is above a certain threshold. As the ambient humidity increases, these positive leader steps occur more frequently. Key Points: Humidity plays a key role in the formation of positive leader stepsThese steps only occur under high humidity above a certain thresholdAs the ambient humidity increases, these positive leader steps occur more frequently [ABSTRACT FROM AUTHOR]

Discharges of different polarities develop in different modes, resulting in different guiding effects by femtosecond laser filaments. Knowledge of the contribution of laser filaments to positive and negative discharges is the basis of the laser-guided long-air-gap discharge technique. This study presents a direct comparison of the inception, propagation, and breakdown characteristics of discharges of both polarities. Long-air-gap discharge experiments under the switching impulses of both polarities are carried out under the same experimental conditions. Discharge modes and phases are also considered. The statistical results show that positive discharge inception voltages are transformed from a Weibull distribution into an exponential distribution under the influence of laser filaments, but there is little effect on the negative discharge inception voltage. The guidance probability of a positive discharge reaches 15% at most during the dark period stage, leading to little effect on the breakdown discharge probability. However, for negative discharges, the guidance probability can exceed 95%. An investigation of the filament contributions to both polarity discharges shows that the different migration directions of photoelectrons lead to a difference in the effects of laser filaments on inception voltages, and the difference in the connection of the two discharge passages leads to a difference in the guidance probability. Through the results of a simulation model, it is speculated that the connection condition for positive discharges is that the positive leader overlaps with the laser filaments, and, for negative discharges, the rod electrode is connected to the laser filaments through bi-directional discharge propagation. [ABSTRACT FROM AUTHOR]

High‐speed video frames and discharge current records of 34 long laboratory sparks were examined. Two consecutive frames of the breakthrough phase, depicting the evolution of the common streamer zone, were obtained in five events, all presented in this study. Two types of luminous structures were observed inside the common streamer zone just before the return stroke phase: the floating luminous segment and the luminous channel linking the opposite polarity leaders. The luminous structure served as a selected route for the return stroke channel. These results demonstrate that the transformation of high‐impedance common streamer zone into a hot plasma channel may involve two main features: the common streamer zone shrinking and the dominant development of the selected route. Plain Language Summary: The breakthrough phase is the final stage of the attachment process in cloud‐to‐ground lightning and begins with the establishment of high‐impedance region (called common streamer zone) between tips of two oppositely charged channels (called leaders) developing from thundercloud and grounded object. The evolution of the breakthrough phase is still not fully understood and very rarely captured in optical images. Many basic lightning phenomena and mechanisms were discovered in long laboratory sparks. Here, we investigated the breakthrough phase in laboratory long sparks generated by rod‐to‐rod air gaps, using a high‐speed video camera and a synchronized electrical parameter measurement system. Two consecutive frames of the breakthrough phase, showing detailed evolution of the common streamer zone, were recorded for five events. Two types of unexpected luminous structures were captured between the two approaching oppositely charged leaders during the breakthrough phase, providing a new insight into the evolution of the breakthrough phase and improving our understanding of the lightning attachment process. Key Points: Two consecutive frames showing the breakthrough phase of attachment process were observed in five sparksLuminous structures were observed inside the common streamer zone just prior to the return stroke frameThe observed luminous structure exhibits as the floating segment or the route linking the positive and negative leaders [ABSTRACT FROM AUTHOR]

Positive leader steps are currently not well understood. Many recent findings challenge the previous understanding of the positive leader steps occurring in continuous leader development. In this work, we investigate the stepping propagation of positive leaders in laboratory spark discharge by using a high‐speed video camera and a synchronized electrical parameter measurement system. Two types of steps were distinguished in the positive leader continuous development process based on the current pulse features. One type of step exhibits a bell‐shaped current pulse, while the other type of step exhibits a steep current rise. The former type vanishes when the rising rate of the ambient electric field increases, whereas the latter type, which could be led by a separate luminous structure, does not. Plain Language Summary: Lightning is one of the most impressive, commonly experienced geophysical phenomena, driven by the propagation of positively and negatively charged, thermally‐ionized plasma channels, known as positive and negative leaders. Leaders propagate in a continuous or stepwise manner. Knowledge of leader steps is critical to understanding the radio‐frequency electromagnetic radiation and even the high energy physical phenomenon. Based on natural or triggering lightning observations, laboratory‐scale discharge experiments, and numerical simulations, some important insights (like the spontaneous emergence of space stems and the bi‐directional development of the space leaders) about negative leader steps have been given by researchers. Positive leader steps are more mysterious. We investigate positive leader steps by performing laboratory spark discharge experiments. Using a high‐speed video camera and a synchronized electrical parameter measurement system, two types of steps were distinguished in the positive leader continuous development process based on the current pulse features. One type of step exhibits a bell‐shaped current, while the other type of step exhibits a steep current rise. The former type vanishes when the rising rate of the ambient electric field increases, whereas the latter type, which could be led by a floating luminous formation, does not. Key Points: Positive leader steps superimposed on the continuous leader propagation are classified into two types based on the current featuresThe steep‐rise type steps are accompanied by the abrupt leader channel elongation, while the bell type steps maybe notThe bell type steps will disappear with the rising rate increase of the ambient electric field, while the steep‐rise type steps do not [ABSTRACT FROM AUTHOR]

A three-stage-five-coil inductive power transfer (IPT) system which is based on cylindrical solenoid coupler (CSC) is proposed in this article. The shape and parameters of the CSC are optimized. The five litz coils compensated by series capacitors are considered to form an IPT system based on equivalent CLC/S/CLC compensation topology with constant voltage characteristics. The mutual inductance between compensation auxiliary coil (CAC) and power transfer coil could be changed by moving the position of CAC, and the freedom of parameter design is enhanced. Mathematical model and loss model of the system are established, and power transfer characteristics of the system are analyzed. The system is considered to be used as a power source for state detection equipment of high-voltage (HV) device to achieve long-distance IPT, the effect of the coupler on the HV electric field is verified. Finally, a prototype with a length of 1.54 m was built. Based on the platform, output voltage and dc–dc power transfer efficiency curves with changed input voltage and load are obtained. The maximum efficiency of the dc–dc system can reach about 60%. [ABSTRACT FROM AUTHOR]

This work mainly studies the interfacial behaviors of scutellarin on a newly developed emulsion and establishes a three-phase distribution model. The results showed that the concentration of scutellarin could decrease the interfacial tension and the gel-liquid crystal phase transition temperature of phospholipids. By observing the micromorphology of the emulsion, it is inferred that the drug exists on the emulsion interface. The distribution of drugs in three phases at different pH was calculated. The results showed that when pH was in the range of 3.0–8.0, the content of scutellarin in the oil phase was less than 0.25%; when pH < 7.4, more than 88% of the drugs were on the interface; when pH > 7.4, the drugs were mainly distributed in the aqueous phase. Therefore, the behavior of emulsions (pH 6.0) in vitro and in vivo is mainly composed of the behavior of drugs on the interface. The study above can explain some properties of the emulsions after loading scutellarin. Including the decrease of particle size and stability constant Ke, the increase of zeta potential, and the decreased chemical stability after the pH value went higher. [ABSTRACT FROM AUTHOR]

An ideal tumor treatment is supposed to eliminate the primary tumor and simultaneously trigger the host antitumor immune responses to prevent tumor recurrence and metastasis. Herein, a liposome encapsulating phosphoinositide 3‐kinase gamma (PI3Kγ) inhibitor IPI‐549 and photosensitizer chlorin e6 (Ce6), denoted by LIC, is prepared for colon cancer treatment. LIC internalized into CT26 cells generates reactive oxygen species (ROS) under laser irradiation to cause immunogenic tumor cell death, during which immunostimulatory signals such as calreticulin are released to further induce T lymphocyte‐mediated tumor cell killing. Meanwhile, IPI‐549 transported by liposome can inhibit PI3Kγ in the myeloid‐derived suppressive cells (MDSCs), resulting in downregulation of arginase 1 (Arg‐1) and ROS to promote MDSCs apoptosis and reduce their immunosuppressive activity to CD8+ T cells. LIC‐mediated immunogenic photodynamic therapy synergizes with MDSCs‐targeting immunotherapy, which significantly inhibits tumor growth via facilitating the dendritic cell maturation and tumor infiltration of CD8+ T cells while decreasing the tumor infiltration of immunosuppressive regulatory T cells, MDSCs, and M2‐like tumor‐associated macrophages. Moreover, the synergistic therapy increases the number of effector memory T cells (TEM) in spleen, which suggests a favorable immune memory to prevent tumor recurrence and metastasis. The Ce6 and IPI‐549‐coloaded multifunctional nanodrug demonstrates high efficacy in colon cancer treatment. [ABSTRACT FROM AUTHOR]

Knowledge of leader corona is the basis for long spark discharge modelling, which is critical to understand the underlying physics of lightning flashes and dielectric breakdown of long air gap widely utilized in power systems. This paper presents an accurate observation of the leader corona. The morphology of the leader corona region during the discharge was obtained using a high-speed camera and an image-enhanced charge-coupled device camera. Statistical results showed that the morphology of the streamer region varied at different discharge sub-phases. The first corona was a conical region with the average apex angle of 118.91°; the leader corona region behaved as a cone with an average vertex angle of 75.87° during the leader propagation process; the streamer area in the final jump was a combination of a cylinder and a cone with the average vertex angle of 82.61°. Noting that the obtained cone apex angle of the leader corona during the leader propagation phase was significantly smaller than that in photographical reports, and the observation results were related to the selected temporal resolution of the optical image apparatus. The discussion on the effect of the single-frame exposure time on observation results found that the average vertex angle of the conical streamer region gradually decreased with the decrease of the single-frame exposure time, and eventually tended to a stable value of about 75.96°. For comparison purposes, discharge experiments under two gap-distances demonstrated that on the premise of stable leader, the statistical distribution characteristics of the leader corona vertex angle were consistent, indicating the universal applicability to the simulation researches. Finally, it is found that the distortion of the electric field caused by the space charge explained the variation of the streamer area during the discharge process. [ABSTRACT FROM AUTHOR]

Under the slow varying ambient electric field, positive leader propagation exhibits steps characterized by intense reilluminations and abrupt elongations. These steps are currently not well understood. In this work, we investigate these steps in laboratory atmospheric discharges, using a high‐speed video camera and a synchronized electrical parameter measurement system. The discharge, emitting weak light and preceding the intense reillumination, is discovered. This finding suggests that the leader channel actually restarts and extends forward before the intense reillumination, which deepens our understanding of the dynamic process of the positive leader step. The discharge before the intense reillumination contributes to the corona inception from the electrode, leading to the intense reillumination of the leader channel and the emergence of an intense corona streamer burst from the leader tip. Plain Language Summary: Lightning is a positive or negative super long spark discharge between the cloud and ground or cloud and cloud. The propagation of positively and negatively charged plasma channels, termed, respectively, positive and negative leaders, is the physical nature of lightning development. Under the slow varying ambient electric field, positive leader propagation is not continuous and exhibits steps with waiting time of tens of microseconds punctuated by sudden elongations and intense reilluminations. These steps are currently not fully understood. Leader discharges can also be simulated in a laboratory. Important insights about natural lightning phenomena have come emerging from explorations of laboratory‐scale atmospheric discharges. Here, we investigate the positive leader steps under the slow varying ambient electric field in long laboratory spark discharges, using a high‐speed video camera and a synchronized electrical parameter measurement system. A discharge that precedes the intense leader channel reillumination is discovered, which provides a new understanding of the dynamic process of positive leader steps and provides new insights into positive stepped lightning leaders under the slow varying ambient electric field. Key Points: This letter presents a discharge that precedes the intense reillumination in the positive leader stepThe positive leader restarts and extends forward before the intense reillumination in the positive leader stepThe newfound discharge contributes to the intense leader channel reillumination [ABSTRACT FROM AUTHOR]

Nanostructured functional materials have demonstrated their great potentials in medical applications, attracting increasing attention because of the opportunities in cancer therapy and the treatment of other ailments. This article reviews the problems and recent advances in the development of magnetic NPs for drug delivery. [ABSTRACT FROM AUTHOR]

Service lifetime estimation for earth grounding grids as a problem or a task faced by the industry is presented. A mathematical model based on Freschi's semianalytical model to determine the performance of the earth grounding grid at a certain year after being buried is proposed. The mathematical model can also explain the performance degradation of the earth grounding grid in principle and mathematically. According to the model, a scheme to estimate the service life of the earth grounding grid is proposed. A case study is given to illustrate how the scheme works. If the estimated service life of an earth grounding grid is not satisfactory, some measures, such as cathodic protection, should be considered to extend the service lifetime of the earth grounding grid. [ABSTRACT FROM AUTHOR]

Background: Onco-immunogenic molecule CD155 is overexpressed in various tumor microenvironments (TME) including in colorectal cancer (CRC). Tumor-associated macrophages (TAMs) are the most abundant immune cells in CRC TME and play a vital role in CRC progression and metastasis. Most studies have focused on investigating the role of CRC cell-specific CD155 on CRC progression, while the contribution of TAMs-specific CD155 is still unknown. Here, we sought to investigate the expression pattern of CD155 in CRC TAMs and its role in tumor immunity and progression., Methods: CD155 expression patterns in CRC TAMs and macrophages in paratumor or adjacent normal tissue were analyzed in 50 patients with CRC using flow cytometry and in 141 patients with CRC using immunohistochemistry. The correlation of CD155 expression level in TAMs with M1 and M2 phenotypic transition was analyzed. The role of macrophage-specific CD155 in CRC progression and tumor immune response was investigated in vitro and in vivo. We further analyzed the effect of CRC cells on the regulation of CD155 expression in macrophages., Results: CRC TAMs from clinical samples showed robustly higher expression of CD155 than macrophages from paratumor and adjacent normal tissues. The CD155 expression level was higher in TAMs of CRC at III/IV stages compared with the I/II stages and was negatively associated with the survival of patients with CRC. CD155 + TAMs showed an M2 phenotype and higher expression of interleukin (IL)-10 and transforming growth factor (TGF)-β. CD155 + macrophages promoted CRC cell migration, invasion, and tumor growth supporting the findings from the clinical tissue analysis. This effect was mainly regulated by TGF-β-induced STAT3 activation-mediated release of matrix metalloproteinases (MMP)2 and MMP9 in CRC cells. CD155 -⁄- bone marrow transplantation in wild-type mice, as well as CD155- macrophages treatment, promoted the antitumor immune response in the mice ectopic CRC model. Additionally, CRC cells released IL-4 to trigger CD155 expression in macrophages indicating the regulatory role of CRC cells in the development of CD155 + TAMs., Conclusions: These findings indicated that CD155 + TAMs are responsible for the M2-phenotype transition, immunosuppression, and tumor progression in CRC. The specific localization of CD155 + TAMs in CRC tissue could turn into a potential therapeutic target for CRC treatment., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)