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Remote ischemic postconditioning (RIPostC) has been demonstrated to protect the myocardium against ischemia/reperfusion (I/R) injury; however, the mediator and underlying mechanisms remain to be elucidated. It has been confirmed that aldehyde dehydrogenase 2 (ALDH2) is involved in the remote ischemic preconditioning pathway, but whether it is involved in RIPostC remains unknown. The aim of the present study was to determine whether increased ALDH2 expression levels were involved in the cardioprotective effect evoked by RIPostC via the phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathway. Male Sprague Dawley rats (n=48) were randomly allocated into the following four groups: Sham group, I/R group, RIPostC group, and RIPostC plus wortmannin group (RIPostC+Wort). With the exception of the Sham group, the anesthetized rats underwent 45 min of coronary artery occlusion followed by 180 min of reperfusion to mimic an I/R injury model. Hemodynamic parameters, including the mean arterial pressure and heart rate, were recorded, the infarct size was determined and the plasma lactate dehydrogenase (LDH) content and creatine kinase (CK) activity levels were measured. The expression levels of Bcl-2 and Bax at the mRNA level and ALDH2, Akt, phospho-Akt (p-Akt), caspase-3 and cleaved caspase-3 at the protein level in the left anterior myocardium were assessed. In the RIPostC group, the infarct size was reduced versus that of the I/R group. The plasma LDH content and CK activity levels were also reduced. The expression levels of ALDH2 protein were elevated, accompanied with increases in the levels of Bcl-2/Bax and p-Akt/Akt and a reduction in the levels of cleaved caspase-3. When the PI3K inhibitor wortmannin was administered at reperfusion, the p-Akt/Akt ratio was markedly reduced and associated with a reduction in the ALDH2 and Bcl-2/Bax levels, and the cleaved caspase-3 expression levels were elevated. In conclusion, ALDH2 may be an important mediator in the cardioprotection of RIPostC through the PI3K/Akt-dependent signaling pathway. [ABSTRACT FROM AUTHOR]

To observe the changes of lung injury when diabetic rats were treated with low concentration of ethanol (EtOH) and analyze the related mechanisms, male Sprague-Dawley (SD) rats were divided into control, diabetic (DM), and EtOH+DM groups. Diabetic rat was mimicked by injection of streptozotocin intraperitoneally. Fasting blood glucose (FBG) level, lung weight (LW), body weight (BW), and LW/BW were measured. The changes of lung tissue and Type II alveolar cell were detected. Pulmonary malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were measured; meanwhile, ALDH2 mRNA and protein expressions were detected by RT-PCR and western blotting, respectively. Compared with control group, in DM group, SOD activity was decreased; FBG level, LW/BW,MDA content, ALDH2 mRNA, and protein expressions were decreased. Compared with DM group, in EtOH+DM group, SOD activity, ALDH2 mRNA, and protein expressions were increased; LW/BW and MDA content were decreased. The structures of lung tissue and lamellar bodies were collapsed in DM group; the injury was attenuated in EtOH+DM group. Our findings suggested that, in diabetic rat, pulmonary ALDH2 expression was decreased accompanying lung injury. EtOH at low concentration decreased diabetes induced lung injury through activating ALDH2 expression. [ABSTRACT FROM AUTHOR]

As the population of transformers in service increases and their operating time extends, much attention has been focused on their availability and reliability. However, insufficient research work concentrates on how to evaluate transformer's aging condition, although huge progress has been made on the techniques of fault diagnosis and condition assessment of transformer in past decades. This paper presents the concept of Aging Index (AI), which is a practical tool that combines the results of routine inspections, and site and laboratory testing to estimate the aging condition of oil-immersed transformers. Further, frequency domain spectroscopy (FDS) as a novel non-destructive testing technique to estimate remained life expectancy is included in aging evaluation system. Moreover, a software system based on transformer's electrical and thermal parameters is developed correspondingly, by using a multi-parameters analytic approach. This system would dedicate to decision-making and replacement planning and has good application prospects. [ABSTRACT FROM AUTHOR]

Surface discharges of dielectric window seriously limit the generation and transmission of high-power microwaves (HPMs), which block the development of microwave technology. An S-band (2.856-GHz) HPM experimental system is established. Several kinds of dielectric window materials, i.e., polyethylene, polytetrafluoroethylene, and polymethyl methacrylate, are investigated under S-band HPMs in vacuum, and the characteristics of destroyed dielectric samples are analyzed with macroscopic and microcosmic observation. Treelike breakdown channels are found on the upstream face of dielectric window along the direction of microwave electric field, and a breakdown development model with an increase of cumulative breakdown times is proposed. Dielectric surface breakdown suppression technologies are also studied, i.e., surface-polishing and surface-notching treatments. The experimental results show that the polishing treatment on the dielectric surface can decrease breakdown degree and increase surface breakdown threshold. The surface grooves that are parallel to the direction of electric field will reduce the surface breakdown threshold, while the grooves that are perpendicular to the direction of electric field can suppress the surface breakdown obviously. The effect is influenced by the depth and width of grooves on the dielectric surface, and correlative theoretical analysis is discussed. [ABSTRACT FROM AUTHOR]

Surface breakdown of dielectric window seriously limits the transmission of high power microwave (HPM), which blocks the development of microwave technology. Under Xband HPM with the power level of 1 GW at 9.4 GHz, dielectric breakdown experiments were conducted with several dielectric window materials including polytetrafluoroethylene (PTFE), low-density polyethylene (LDPE), high-density polyethylene (HDPE) and polymethyl methacrylate (PMMA) in vacuum. The influence of different surface treatments for PTFE with notching and polishing on its breakdown characteristics is also studied. After breakdown, the photographs of damaged dielectric samples are analyzed with macroscopic and microcosmic observations. There are obvious tree-like breakdown phenomena occurred on the upstream face of the dielectric window along the direction of microwave electric field. The damage is significantly affected by the different surface treatments. It is considered that the treelike breakdown channels are closely related to the applied microwave field. Based on in-depth observation on the tree failure inside the transparent PMMA sample, it was found that, the tree developed along the surface and also inside of the material. A physical model is proposed to describe the dielectric window breakdown under HPM. It is suggested that the electric field results in the tree developing along the material surface. Possible reason for the tree invading into the material is analyzed. Moreover, several kinds of possible manners are presented to describe the tree initiation and development inside the dielectric window. [ABSTRACT FROM AUTHOR]

Before flashover across an insulator under high electric field in vacuum, there are charging phenomena occurring on the insulator surface, which significantly affect the developing process of flashover. Based on the secondary-electron-emission- avalanche model and by using the Monte Carlo method, a 2-D analysis of surface charge density on cylindrical and conical insulators prior to flashover in vacuum has been performed under unipolar voltage. Different materials are employed, i.e., alumina ceramic, PTFE, PMMA, and PI. The influences of materials, voltage amplitudes, and coning angles on charge distribution are investigated. The results reveal that negative charges exist in a small surface region near the cathode, while the surface charges positive in a larger region away from the cathode. With increasing applied voltage, both the negative charge density and region decrease, and even vanish, whereas both the positive charge density and region increase, and the peaks of both regions move toward the cathode. For the conical insulator with a negative angle, the positive charge density is greater than that with a positive angle, and the simulation describes well experimental data relating the coning angle, the surface charge, and the flashover voltage. [ABSTRACT FROM AUTHOR]

The electrical strength of the surface of low-temperature melting machinable glass ceramic, prepared by using several different methods, is investigated before and after treatment with diluted hydrofluoric acid (HF). Using the surface potential decay method, the surface trap density and the energy of each sample are measured. The influence of acid treatment on the trap distribution is analyzed. Concurrent optical and electrical measurements allow surface flashover phenomena in vacuum under impulse voltage to be investigated, along with the influence of surface trapping parameters on flashover performance. It is shown that the glass phase on the surface of machinable ceramic greatly influences the shallow traps, which in turn degrade the flashover characteristics. Removing the glass phase with HF treatment reduces the concentration of shallow traps and stabilizes the flashover voltage. [ABSTRACT FROM AUTHOR]

Nonthermal plasma generated by parallel-plate dielectric-barrier discharge with 60-kHz high-voltage power was used to sterilize the bacteria in atmospheric air. Two kinds of typical bacteria, gram-negative E. coli (ATCC8099) and gram-positive S. aureus (ATCC6S38), were used as test strains. Bacteria cells held by cover-glass were placed on the bottom electrode. By adjusting the applied voltage, gap spacing, and treatment time, the effects of plasma and electric field on bacteria inactivation were investigated. The transmission electron microscope was used to observe the damage of cells treated by plasma. The concentrations of K+, protein, and nucleic acid leaked from cells were measured for detecting the cytoplasm status after plasma treatment. Experimental results showed that almost 100% of S. aureus and E. coli strains were killed in less than 10- and 7-s plasma treatment, respectively. It is concluded that the reactive oxygen species (ROS) in plasma play a dominant role in the inactivation process but not the electric field. It is supposed that the ROS can oxidize the cell membrane and then damage the protein and nucleic acid inside the cells and, thus, kill the bacteria. [ABSTRACT FROM AUTHOR]

A dielectric barrier discharge was used to generate low-temperature plasma to treat Candida albicans. When the gap spacing was 3 mm, the killing log value (KLV) of the plasma on Candida albicans within 20 s of exposure was more than five, and for 4 and 5 mm gap spacing, the KLV within 25 s was more than five. With the extension of exposure time, the decrease in velocity of the number of living Candida albicans was fastest for the gap spacing of 3 mm, and then for 4 and 5 mm spacing. With 60 s of electric field treatment, as the applied voltage increases, the survival number of Candida albicans has no significant difference from that of the control sample. As for the inactivation mechanism of plasma on Candida albicans on the molecular microbiology side, transmission electron microscopic examination and the results of protein, nucleic acid and K+ detection in the extracellular environment showed that the plasma destroyed the outer structure of Candida albicans. Cytoplasm was also released, which caused Candida albicans to be dead. On the plasma physics side, the role of the electric field during Candida albicans inactivation by plasma is considered negligible. Therefore, charged particles and reactive species in plasma might play a dominant role in the process of destroying the outer structure of Candida albicans. [ABSTRACT FROM AUTHOR]

As well known, the surface conditions of solid materials strongly affect the flashover phenomena under high electric field. The artificial doping ingredients could change the energy distribution and the density of electron and hole traps. The trapping parameters in the surface layer have some influences on the surface insulation strength. In order to adjust different trapping parameters, the composite materials of epoxy resin intermingled with aluminum hydroxide are prepared. The trapping parameters of the samples with different filler concentrations are investigated through the method of measuring the surface potential based on the isothermal current theory. The surface insulation performance in vacuum of each sample is tested according to the flashover voltage under pulsed excitation. Based on the experiment, the correlation between the trapping parameters and surface insulation strength is discussed and some novel models are presented. [ABSTRACT FROM AUTHOR]

Charge accumulation phenomenon on gas–solid interface greatly restricts the development of HVDC energy transmission system. In this study, the surface charge transport behavior and flashover performance on alumina/epoxy spacer coated by SiC/epoxy composites are experimentally investigated under DC stress. SiC/epoxy composites with varied SiC particle size are fabricated and deposited on spacer surface. Nearly a charge free surface is achieved especially at smaller SiC particle size, even when metallic wires are adhered on spacer surface and connected to high voltage electrode. The DC flashover voltage increases with the decrease of SiC particle size. On the one hand, smaller SiC particle size exhibits more outstanding nonlinear conductivity characteristics, contributing to accelerating charge dissipation, whereas on the other hand, it would introduce plenty of shallow traps due to the increased interfacial regions between SiC particle and epoxy matrix, resulting in aggravating charge accumulation. A theoretical model is proposed to reveal the control mechanism of SiC/epoxy coating with different SiC particle size on flashover performance. The validity of this model can be confirmed based on the surface trap distribution, carrier mobility and our previous investigations on gas–solid interface flashover development process. [ABSTRACT FROM AUTHOR]

Near-infrared spectroscopy (NIRS) is a rapid and non-destructive detection method for component determination and quantitative analysis with broad applications in numerous fields. In recent years, NIRS has started to be used in the aging condition assessment of power transformers. However, the real applications of NIRS are constrained by the lack of evaluation database and accurate prediction algorithms. In this paper, we aim at comparing different NIRS modeling methods and improving diagnostic accuracy. We build the evaluation database via the preparation of 230 specimens derived from three typical types of insulating paper. Calibration models are established by linear method-partial least squares (PLS) and nonlinear method-back propagation neural network (BPNN) to map the relationship between spectra and the degree of polymerization (DP). The DP prediction results show that using full NIR spectra as the input of the PLS model does not ensure a high prediction accuracy, and it is improved by competitive adaptive reweighted sampling (CARS) that selects the optimal wavelength combinations. Prediction precisions given by BPNN and CARS-BPNN models are shown to be less satisfactory than that of CARS-PLS. We process the original spectra with principal component analysis (PCA) as the input of BPNN and the PCA-BPNN model realizes high prediction precision for three types of paper (RMSE  ⩽  24, r  =  0.99). With the identification of paper type by the k-nearest neighbors (KNN) method before prediction, the KNN-PCA-BPNN model solves the problem of the low prediction precision for mixed (unknown) paper samples (RMSE  =  36, r  =  0.98), which facilitates future field tests as well as related applications in practice. [ABSTRACT FROM AUTHOR]

Surface discharge in a vacuum occurs under an intense external field, also called a flashover. The flashover threshold over which the surface flashover occurs is of vital importance in the vacuum–solid interface. It is widely assumed that the flashover is initiated by a single surface multipactor and develops as a plasma discharge along a dielectric surface, namely the secondary electron emission avalanche (SEEA). Yet the SEEA model is not versatile for all practical vacuum–solid interfaces and there remain experiment results contradicting the theory predictions without a resolute answer. Here we further expand on previous theories and consider the conventional SEEA model under arbitrary field distributions. The example of a conical insulator is then given to test the validity of the SEEA model under an arbitrary field. It is found that the obtained flashover threshold is only consistent with the experiment at low cone angles where the field near the cathode triple junction is strong, while remarkable discrepancies appear when the anode field is significantly enhanced. The discrepancies can be understood if a different discharge model, i.e. an anode-initiated flashover (AIF) is included. Both particle-in-cell simulation and optical diagnostics are employed to visualize this unique discharge, which are then formalized on theoretical grounds to elucidate the early stage of the AIF. The transition between two flashover phases is then clarified. The plasma–surface interaction and sheath dynamics during the discharge are analyzed theoretically, showing distinct sheath evolutions in two flashover models. Additionally, a new factor reflecting field distortion is introduced to estimate the discharge threshold under an SEEA framework. [ABSTRACT FROM AUTHOR]

Secondary electron emission (SEE) induced by interaction between positive ion and dielectric surface is essential physical process for maintaining sustained discharge and controlling the characteristics of atmospheric pressure dielectric barrier discharge (DBD). In this work, SEE is described based on Auger neutralization theory. Dielectric energy band structure and defect energy level, including hole and electron trap energy levels, are taken into account to build a hypothetical relationship γi  =  f (σ) between secondary electron emission coefficient γi and surface charge density σ. With the introduction of γi  =  f (σ) in DBD model, the characteristics of DBD are discussed in both first and steady discharges. It is found that, in steady discharge, γi has higher value during the beginning and development state of discharge pulse of DBD, and γi decreases in extinction stage. The negatively charged dielectric surface enhances SEE before discharge, which benefits the formation of diffuse discharge, compared with DBD of constant γi. Moreover, the increase of energy band gap of dielectric reduces γi, leading to the contractive discharge in DBD. The relationship between γi and σ can be further applied to study the influences of defect energy level parameters on SEE and DBD characteristics. [ABSTRACT FROM AUTHOR]

Surface charge accumulation on insulators becomes an important bottleneck to restrain the development of a DC energy transmission system. This study investigates the effects of SiC/epoxy coating on surface charge behaviors and flashover performance of alumina/epoxy spacers. A nonlinear conductive coating consisting of different contents of SiC fillers and epoxy matrix was fabricated and sprayed on only half surface of the spacers. The dependence of surface charges on the contents of SiC fillers is characterized by three stages. Surface charge accumulation is aggravated at deterioration stage, then almost unaltered at balance stage and inhibited at suppression stage. These three stages are determined by the competition between the increased surface trap density from interface region and the improved surface conductivity from SiC fillers. The variation trend of flashover in air and SF6/N2 mixtures is distinguished by three stages as well. Flashover voltage decreases at descent stage where deficient contents of SiC fillers are appended and then goes up at improved stage with moderate supply of SiC fillers. Finally, it ends up with drastically collapse at degenerated stage when affluent SiC fillers are brought in. The theoretical analysis is proposed based on surface trap distribution and conductivity measurement results to reveal the regulation mechanism of SiC/epoxy coating on surface charge behavior and flashover performance. [ABSTRACT FROM AUTHOR]

Polymer materials usually present lower surface flashover strength compared with their bulk breakdown strength, particuarly in a vacuum. Flashover along the solid insulation surface may pose a significant challenge to the safety of electrical equipment. In this paper, two kinds of polymers, epoxy resin and polyethylene, have been modified with F2/N2 fluorination to decrease the secondary electron yield (SEY) and further improve the surface electric withstanding strength. Experimental results have proved the effectiveness of this method in overall perspectives. The surface properties of modified samples are evaluated by comprehensive methods, i.e. surface roughness, scanning electron microscopy, charge trap characteristics and x-ray photoelectron spectroscopy. It is considered that physical factors such as roughness and chemical factors such as fluorine groups play a significant role in the modified mechanism. Reduction of SEY is linked with flashover voltage quantitively using multipactor and outgassing theory. In addition, we perform a simulation to illustrate multipactor dynamics in the presence of a surface barrier which represents specific surface roughness. The influence of trap characteristics is also analyzed theoretically to corroborate the experiment results. It is concluded that SEY is influenced by surface roughness and shallow traps. The reduction of SEY is directly linked with improvement of flashover voltage. Trap characteristics are changed by introducing fluorine groups. A comprehensive model of fluorination-based flashover mitigation is proposed considering the above features. [ABSTRACT FROM AUTHOR]

The potential antitumor application of low-temperature plasma (LTP) has attracted wide attention from researchers. The mechanism of plasma antitumor action may be related to LTP-induced reactive oxygen and nitrogen species. The aim of this study was to identify the apoptotic effects of plasma on melanoma cells (B16) in vivo and in vitro. For this purpose, a helium atmospheric-pressure plasma jet (APPJ) was used to generate the plasma-activated saline and medium (PAS and PAM). The PAS was injected subcutaneously to treat B16-tumor bearing mice in vivo and the PAM was used to treat B16 cells in vitro. Catalase (CAT) was added into the PAM to degrade H2O2 as the intervention group. The tumor nodules’ weight, cryosections, B16 cell viability, apoptosis, DNA damage, p53 pathway-related protein and the concentration of H2O2 in PAM were detected. The in vivo results showed that PAS could inhibit tumor growth and induce apoptosis. The in vitro results revealed the concentration of H2O2 in the PAM increased as LTP treatment time was longer, while the cell viability decreased as APPJ irradiation time was increased. Flow cytometry results showed that, compared with the control group, all PAM treatment groups showed a higher apoptotic rate. A single cell gel assay and an 8-OHdG assay showed that the PAM could induce DNA damage. A western blotting assay indicated that the PAM could increase the expressions of p53, p53-induced gene 8 protein, PIG3, cytoplasmic cytochrome c, cleaved-caspase-9 and -3. However, CAT could alleviate all these changes effectively. These findings suggested that plasma exerted an apoptotic effect on B16 cells mainly by activating the p53/PIGs/caspase pathway. [ABSTRACT FROM AUTHOR]

An investigation is conducted regarding the influence of surface roughness on the flashover strength of an insulator in vacuum. A series of experiments is first presented, showing the relationship between surface roughness and flashover voltage, combined with measurement of surface potential distribution. It is found that surface charging on a roughened dielectric is suppressed remarkably; also the flashover voltage threshold depicts a rise-and-fall trend with roughness increasing, exhibiting a voltage summit at a certain roughness value. In addition, optical observation is implemented to draw a parallel with an electron trajectory in vacuum. A proposal can therefore be made that multipactor expansion tends to be mitigated as electron bombardment on a dielectric occurs with a lower secondary electron yield. Then a theoretical model considering the microscopic physical process is established to explain the above phenomena, consisting of an internal charge migration layer, an interfacial electron absorption layer and an external electron obstruction layer. The validity of this theoretical model can be confirmed by obtaining the surface trap distribution, microscopic morphology and net secondary electron yield. [ABSTRACT FROM AUTHOR]

Much attention has been paid to different localisation algorithms to locate partial discharge (PD) sources in power transformers using the acoustic emission (AE) technique. Due to total reflection, AE sensors cannot always detect the signal of a direct wave. As a result, localisation algorithms based on an indirect wave can be more accurate. But little research has addressed arrival time (AT) methods of indirect PD signals. In this paper, a double-threshold (DT) method is introduced, and its improvement based on short-time energy and a zero-crossing rate is described. Because an indirect wave arrives earlier and has lower energy than a direct wave, current AT methods, such as the energy criterion, cross-correlation, and linear prediction residual methods, cannot determine its AT. However, the proposed DT method can determine the AT precisely. Moreover, a localisation experiment was conducted on a 35 kV transformer, and localisation results were calculated employing various AT methods and different localisation algorithms, such as the Chan, genetic, imperial competition, and improved-propagation-route-search algorithms. Characteristics of the proposed AT methods were compared and analysed to show their feasibility and accuracy. [ABSTRACT FROM AUTHOR]

We propose a novel theoretical formula to estimate the surface flashover threshold in vacuum using the intrinsic properties of dielectric material as well as dielectric-vacuum configuration. The method is based on an above-surface model called secondary electron emission avalanche (SEEA), where flashover development can be divided into multipactor discharge, outgassing and an ionization avalanche which eventually leads to a plasma discharge. The transition from SEE-dominated regime to discharge plasma is supposed to be of significance where gas breakdown takes place within a nonuniform desorbed gas cloud in the vicinity of dielectric surface. Flashover occurs when specific space charge multiplication is achieved, yielding the critical pressure and breakdown voltage. The depiction of previous stages involves the secondary electron emission of dielectric materials, desorption and diffusion of adsorbed gas, ambient temperature, electrode structure, etc. Both particle-in-cell simulation and experiment data can corroborate the obtained theoretical results. [ABSTRACT FROM AUTHOR]

The discharge mode and photoelectric characteristics of Ar/NH3 DBD (dielectric barrier discharge) are studied to discuss the stability of the discharge under the influence of Penning ionization and attachment reaction. There are three discharge modes, including stable uniform glow discharge, unstable glow discharge and unstable columnar discharge. Discharge instability, including nonuniform discharge and discharge channel split, occurs under low (<0.10%) or high (>0.35%) volume fractions of NH3, which are understood to be caused by an insufficiently strong Penning effect or a strong attachment reaction, respectively. The attachment reaction of NH3 can also lead to a weaker emission intensity for Ar/NH3 DBD, in particular regarding the emission of OH(A2Σ+). Ar/NH3 and He/N2 DBDs are also compared. In He/N2 DBD, the emission intensity of OH(A2Σ+) changes less with increasing N2 volume fraction, which may be attributed to the lack of attachment reaction. Compared with Ar/NH3 DBD, the single discharge channel in He/N2 DBD is narrower, but the discharge area is wider, which should be induced by the higher Townsend ionization coefficient nonlinearity of He/N2 and the absence of attachment reaction in He/N2, respectively. In the end, a one-dimensional fluid model of Ar/NH3 DBD is built to verify the explanation of experimental results. [ABSTRACT FROM AUTHOR]

Plasma distribution of atmospheric dielectric barrier discharge (DBD) can be modified by different applied electrical sources. In this paper, a 37-kHz ac DBD in air is employed to investigate plasma distribution characteristics at different applied voltages. By experimentally observed optical phenomena of microdischarge patterns, the obvious "memory" and "repulsion" effects of microdischarges are analyzed. [ABSTRACT FROM AUTHOR]

Optical investigation of flashover phenomena across silicon is performed in vacuum. A pulse waveform of ~0.4/ 2.5 µs is employed as stimulation source. The p100-type silicon wafers are the samples. The images of flashover growing are recorded by intensified charge couple device, and the corresponding waveforms of voltage and current are given. The results primarily suggest that the flashover across p-type silicon begins with the distortion of electric field at the edge of anode. Injection of minors may play an important role in the formation process of filament current. It is regarded that the plasma produced by ionized desorbed gas will appear at the final stage of surface flashover. [ABSTRACT FROM AUTHOR]

The plasma sheath is the non-neutral space charge region that isolates bulk plasma from a boundary. Radio-frequency (RF) sheaths are formed when applying RF voltage to electrodes. Generally, applied bias is mainly consumed by a RF sheath, which shields an external field. Here we report evidence that an intense boundary emission destroys a normal RF sheath and establishes a type of RF plasma where external bias is consumed by bulk plasma instead of a sheath. Ions are naturally confined while plasma electrons are unobstructed, generating a strong RF current in the entire plasma, combined with a unique particle and energy balance. The proposed model offers the possibility for ion erosion mitigation of a plasma-facing component. It also inspires techniques for reaction rate control in plasma processing and wave mode conversion. [ABSTRACT FROM AUTHOR]