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The interaction between an atmospheric pressure plasma jet (APPJ) and an aqueous solution has great application prospects in biomedicine and many other fields. Reactive species adjacent to a water surface is critical to the activation of APPJ-treated water, which is affected by both the water evaporation and the admixture of ambient air. In this paper, taking He APPJ as an example, a two-dimensional (2D) cylindrically symmetric fluid model is developed to obtain the spatial distributions of gas components before discharging, and a series of global models are developed for the discharge in the boundary gas layer adjacent to the water surface. The interfacial distributions of reactive species and their fluxes onto the water surface are quantified. It is found that the electron density is 1016–1017 m−3 and it shows an annular distribution in the boundary gas layer. The density distributions of most reactive species there reveal ring-like shapes as well. The dominant cation and anion in such a boundary layer are H3O+ and OH−, respectively. The most abundant metastable is O2(a1Δ), the most abundant reactive oxygen species are H2O2 and OH, and the most abundant reactive nitrogen species are NO and HNO2. The species of H2O2, OH, HO2, and HNO2 are reportedly to have significant biological effects, and in our simulation, their fluxes onto the water surface are remarkable, higher than 1017 m−2 s−1. In addition, the effects of radial gas velocity and water evaporation on the particle flux distributions are also revealed.

Abstract A continuous risk from microbial infections poses a major environmental and public health challenge. As an emerging strategy for inhibiting bacterial infections, plasma‐activated water (PAW) has proved to be highly effective, environmental‐friendly, and non‐drug resistant to a broad range of microorganisms. However, the relatively short lifetime of reactive oxygen and nitrogen species (RONS) and the high spreadability of liquid PAW inevitably limit its real‐life applications. In this study, plasma‐activated hydrogel (PAH) is developed to act as reactive species carrier that allow good storage and controlled slow‐release of RONS to achieve long‐term antibacterial effects. Three hydrogel materials, including hydroxyethyl cellulose (HEC), carbomer 940 (Carbomer), and acryloyldimethylammonium taurate/VP copolymer (AVC) are selected, and their antibacterial performances under different plasma activation conditions are investigated. It is shown that the composition of the gels plays the key role in determining their biochemical functions after the plasma activation. The antimicrobial performance of AVC is much better than that of PAW and the other two hydrogels, along with the excellent stability to maintain the antimicrobial activity for more than 14 days. The revealed mechanism of the antibacterial ability of the PAH identifies the unique combination of short‐lived species (1O2, ∙OH, ONOO− and O2−) stored in hydrogels. Overall, this study demonstrates the efficacy and reveals the mechanisms of the PAH as an effective and long‐term disinfectant capable of delivering and preserving antibacterial chemistries for biomedical applications.

Abstract Sulphur hexafluoride (SF6) is widely used in gas insulation, and its decomposition products can be used to diagnose potential insulation failures. Quick and accurate detection of decomposition products can help to understand equipment‐operating conditions in time. In this study, the decomposition products of SF6/air gas mixtures under different pulsed discharge voltages were studied. It was found that the main products were SOF2, SO2F2, SO2, CF4 and SOF4, and the yields of SOF2, SO2F2, SO2 and SOF4 increased with the number of discharge pulse. The productive rate of SOF2, SO2 and SOF4 were positively correlated with the discharge voltage, and when the discharge voltage increased from 5 to 15 kV, their yields after 50,000 discharges increased by 49%, 120% and 1100%, respectively. The productive rate of SOF2 and SO2 were positively correlated with the proportion of air in the gas mixtures while that of SOF4 was opposite. When the proportion of air increases from 0% to 90%, their yields after 50,000 discharges became 270%, 3169% and 10% of the originals, respectively. In addition, the productive rate of SO2F2 was not affected by discharge voltage and the proportion of air in the gas mixtures. SO2F2, SOF2, SOF4 and SO2 can be used as the basis for judging the discharge failures and the discharge degree of power equipment.

Due to their good dielectric properties and low global warming potential, C4F7N–CO2 and C4F7N–N2 mixtures have shown promising potential to replace SF6 in high voltage gas insulated equipment. However, during manufacturing, installation, and transportation of power equipment, burs and metal particles can be inevitably left inside, and they can cause corona discharge. Fundamental investigation of the corona discharge mechanism is essential to monitor partial discharge signals in environmentally friendly power equipment. This paper applies the fluid model to investigate the discharge mechanism of C4F7N–CO2 and C4F7N–N2 mixtures in negative point-plane corona discharge. A 2D axisymmetric model combines the drift-diffusion equations for electrons, positive ions, and negative ions and Poisson’s equation to study the process of dynamics. The gas is a mixture of C4F7N (5%, 7%, or 13%) and CO2 or N2 (95%, 93%, or 87%). The rise time of the first discharge pulse in C4F7N–CO2 and C4F7N–N2 mixtures is about 0.1 ns. The interval time between the first and the second pulse in the 5% C4F7N–95%CO2 mixture is about 1.5 times longer than that in the 5% C4F7N–95% N2 mixture. When the C4F7N content is 7% and 13%, the interval time between the first and second pulses in C4F7N–CO2 mixtures is about 2 and 3 times longer than those in C4F7N–N2 mixtures, respectively. The suppression regions in C4F7N–CO2 mixtures are larger than those in corresponding C4F7N–N2 mixtures. The total number of electrons, positive ions, and negative ions in C4F7N–CO2 mixtures is higher than that in C4F7N–N2 mixtures, while the reduced electric field in C4F7N–CO2 mixtures is smaller than that in C4F7N–N2 mixtures.

Infection can hinder the process of wound healing, so it is important to begin antibacterial treatment quickly after a wound forms. Plasma activated water (PAW) can inactivate a variety of common wound infection bacteria. In this study, we compared the effects of PAW prepared with portable surface discharge plasma equipment and medical alcohol on wound healing in a mouse full-thickness skin wound model. The effectiveness of wound healing processes in mice was ranked accordingly: PAW treatment group > medical alcohol treatment group > control group. In order to further understand the mechanism of PAW in promoting wound healing, we tested the expression levels of the pro-inflammatory factors interleukin (IL)-1β and IL-6, the anti-inflammatory factor IL-10, and vascular endothelial growth factor (VEGF). The results showed that PAW promoted the release of pro-inflammatory factors and anti-inflammatory factors from the wounds in mice, which allowed the mice in the treatment group to transition out of the inflammatory period early and enter the next stage of wound healing. The expression level of VEGF in the wounds of mice in the PAW treatment group was higher, which indicates that the microvessels around the wound in the PAW treatment group proliferated faster, and thus the wound healed faster. PAW biosafety experiments showed that PAW did not significantly affect the appearance, morphology, or tissue structure of internal organs, or blood biochemical indicators in mice. In general, PAW prepared via portable devices is expected to become more widely used given its convenience, affordability, and lack of side effects in promoting wound healing.

Abstract Metal–organic frameworks (MOFs) are a class of hybrid materials with many promising applications. In recent years, lots of investigations have been oriented toward applications of MOFs in electronic and photoelectronic devices. While many high-quality reviews have focused on synthesis and mechanisms of electrically conductive MOFs, few of them focus on their photophysical properties. Herein, we provide an in-depth review on photoconductive and photoluminescent properties of conductive MOFs together with their corresponding applications in solar cells, luminescent sensing, light emitting, and so forth. For integration of MOFs with practical devices, recent advances in fabrication of photoactive MOF thin films are also summarized.

Abstract Background It was reported that tumor-expressed dickkopf-related (DKK) proteins affect micro-environment. However, the influence of DKK1 on colorectal cancer (CRC) liver oligometastases (CRCLOM) remains unclear. Methods CRC cases after resection of liver oligometastases were enrolled in Sun Yat-Sen University Cancer Center with intact clinical data. Serum DKK1 was detected by ELISA assay. Immunofluorescent staining examination for CD3 and CD8 in slices were also conducted. Results Among 65 patients included, the recurrence-free survival (RFS) and overall survival (OS) were significantly better in the low serum DKK1 group (RFS: P = 0.021; OS: P = 0.043). DKK1 was overexpressed in stage IV CRC patients in TCGA data. The number of CD8+ tumor-infiltrating lymphocytes (TILs) in invasive margin of CRC liver oligometastases was significantly higher in low serum DKK1 group (P = 0.042). Conclusion Elevated serum DKK1 level was associated with poorer RFS and OS, and less CD8+ TILs in invasive margin in CRC liver oligometastases. DKK1 might serve as a supplementalprognostic factor for clinical risk score and a potential target for immunotherapy.

Plasma-activated liquid (PAL) can effectively and selectively kill various types of cancer cells both in superficial and deeper tumors. As a promising novel approach to oncotherapy, the safety of PAL is essential in the clinic but has not been thoroughly assessed. In myeloma and blood tumors, the pathogenesis is in the bone marrow cavity. We have therefore evaluated the safety of PAL in New Zealand rabbits by intra-bone marrow injection, and provide a basis of further clinical research and application of PALs. In this study, both a plasma jet and plasma surface were used to treat saline solution, phosphate-buffered solution, and cell culture medium, to produce PAL. Then, oscillograms and optical emission spectra were evaluated to characterize the plasma discharge. Acute toxicity tests and safety evaluation studies were conducted by intra-bone marrow injection of PAL into New Zealand rabbits, while control rabbits received saline only. Body weight, vital organ coefficient, organ appearance, organ histopathology, blood cell and hemoglobin parameters, and blood biochemical indicators were tested on the 30th day after injection. We found that there was no mortality or loss of mobility throughout the experimental period. Acute toxicity tests showed that there were no PAL-related side effects in rabbits receiving the maximum dose of 700 μL PAL. PAL treatments did not affect body weight, organ coefficient, organ appearance, organ histopathology, or blood biochemical indicators. However, the percentage of lymphocytes decreased while the percentage of neutrophil granulocytes increased compared with the control group. In summary, our results indicate that PAL can be safely injected into bone marrow of New Zealand rabbits without significant toxicity.

Plasma–liquid interaction is a critical area of plasma science, mainly because much remains unknown about the physicochemical processes occurring at the plasma–liquid interface. Besides a lot of experimental studies toward the interaction, a few fluid models have also been reported in recent years. However, the interfacial boundary conditions in the models are different and the Henry’s law constants therein are uncertain; hence, the accuracy and robustness of the simulation results are doubtable. In view of this, three 1D fluid models are developed for the interaction between a plasma jet and deionized water, each of which has a unique interfacial boundary condition as reported in the literature. It is found that the density distribution of reactive species is nearly independent of the interfacial boundary conditions in both the gas and liquid phases, except for that in the interfacial gas layer with a thickness of several tens of micrometers above water. The densities of the reactive species with high Henry’s law constants (H > 104) are much different in such gas layers among the interfacial boundary conditions. Moreover, some Henry’s law constants are changed in the models according to their uncertainty reported in the literature, and only the reactive species with low Henry’s law constants (H < 1) have their aqueous densities following the change. These densities are very low in the plasma-activated water. It could be concluded that the simulation of plasma–liquid interaction is generally independent of the interfacial boundary conditions and the uncertainty in Henry’s law constants.

Cold atmospheric plasma, including plasma jet and surface plasma, can promote the apoptosis of cancer cells without causing significant damage to surrounding normal cells, which was hopeful to be applied to the clinical cancer therapy. However, experimental plasma devices used directly to clinical experiments has challenges in technology and methods, especially the difference in killing tumor cells efficiency of these two common plasma sources. Therefore, it is great necessity to explore the differences in treating tumors between different plasma sources. This paper achieved good killing efficiency by using two kinds of cold atmospheric plasma generating devices, namely plasma jet and surface plasma treatment along acute myeloid leukemia (AML). The results showed that the He plasma jet kills leukemia cells more efficiently than surface plasma with the same voltage and frequency and the same time. By GC-TOFMS and metabolomics analysis, this paper compared the differential metabolites of leukemia cells treated by two plasma devices and the key metabolic pathways closely related to differential metabolites. Simultaneously, we found alanine, aspartate and glutamate metabolism was most correlated with a key differential metabolite, glutamine. It was found that the glutaminase activity of He plasma jet group was lower than that of surface plasma group, which might be a reason for He plasma jet group to kill tumor cells better. It was also worth noting that relative quantity of glucose metabolites of plasma jet treatment group was lower than that of surface plasma treatment group. This study provides the basis for clinical trials for future.

Background Dickkopf 1 (DKK1) is associated with tumor progression. However, whether DKK1 influences the tumor response to programmed cell death protein 1 (PD-1) blockade in colorectal cancers (CRCs) with deficient mismatch repair (dMMR) or microsatellite instability (MSI) has never been clarified.Methods Tumor tissues from 80 patients with dMMR CRC were evaluated for DKK1 expression and immune status via immunohistochemistry. Serum DKK1 was measured in another set of 43 patients who received PD-1 blockade therapy. CT26 cells and dMMR CRC organoids were cocultured with T cells, and CT26-grafted BALB/c mice were also constructed. T-cell cytotoxicity was assessed by apoptosis assays and flow cytometry. The pathway through which DKK1 regulates CD8+ T cells was investigated using RNA sequencing, and chromatin immunoprecipitation and luciferase reporter assays were conducted to determine the downstream transcription factors of DKK1.Results Elevated DKK1 expression was associated with recurrence and decreased CD8+ T-cell infiltration in dMMR CRCs, and patients with high-serum DKK1 had a poor response to PD-1 blockade. RNA interference or neutralization of DKK1 in CRC cells enhanced CD8+ T-cell cytotoxicity, while DKK1 decreased T-bet expression and activated GSK3β in CD8+ T cells. In addition, E2F1, a downstream transcription factor of GSK3β, directly upregulated T-bet expression. In organoid models, the proportion of apoptotic cells was elevated after individual neutralization of PD-1 or DKK1 and was further increased on combined neutralization of PD-1 and DKK1.Conclusions DKK1 suppressed the antitumor immune reaction through the GSK3β/E2F1/T-bet axis in CD8+ T cells. Elevated serum DKK1 predicted poor tumor response to PD-1 blockade in dMMR/MSI CRCs, and DKK1 neutralization may restore sensitivity to PD-1 blockade.

Abstract Background Acute myeloid leukemia (AML) is a typically fatal malignancy and new drug and treatment need to be developed for a better survival outcome. Cold atmospheric plasma (CAP) is a novel technology, which has been widely applied in biomedicine, especially in various of cancer treatment. However, the changes in cell metabolism after CAP treatment of leukemia cells have been rarely studied. Methods In this study, we investigated the metabolite profiling of plasma treatment on leukemia cells based on Gas Chromatography Tandem Time-of-Flight Mass Spectrometry (GC-TOFMS). Simultaneously, we conducted a series of bioinformatics analysis of metabolites and metabolic pathways with significant differences after basic data analysis. Results 800 signals were detected by GC–TOF mass-spectrometry and then evaluated using PCA and OPLS-DA. All the differential metabolites were listed and the related metabolic pathways were analyzed by KEGG pathway. The results showed that alanine, aspartate and glutamate metabolism had a significant change after plasma treatment. Meanwhile, d-glutamine and d-glutamate metabolism were significantly changed by CAP. Glutaminase activity was decreased after plasma treatment, which might lead to glutamine accumulation and leukemia cells death. Conclusions We found the above two metabolic pathways vulnerable to plasma treatment, which might result in leukemia cells death and might be the cornerstone of further exploration of plasma treatment targets.

Metal–organic frameworks with highly ordered porosity have been studied extensively. In this paper, the effect of framework (pore) disorder on the gas sorption of azole-based isoreticular Cu(II) MOFs with rtl topology and characteristic 1D tubular pore channels is investigated for the first time. In contrast to other isoreticular rtl metal–organic frameworks, the Cu(II) metal–organic framework based on 5-(1H-imidazol-1-yl)isophthalate acid has a crystallographically identifiable disordered framework without open N-donor sites. The framework provides a unique example for investigating the effect of pore disorder on gas sorption that can be systematically evaluated. It exhibits remarkable temperature-dependent hysteretic CO2 sorption up to room temperature, and shows selectivity of CO2 over H2, CH4 and N2 at ambient temperature. The unique property of the framework is its disordered structure featuring distorted 1D tubular channels and DMF-guest-remediated defects. The results imply that structural disorder (defects) may play an important role in the modification of the performance of the material.

Abstract Background Despite new progress of chemotherapy in multiple myeloma (MM) clinical treatment, MM is still a refractory disease and new technology is needed to improve the outcomes and prolong the survival. Cold atmospheric plasma is a rapidly developed technology in recent years, which has been widely applied in biomedicine. Although plasma could efficiently inactivate various tumor cells, the effects of plasma on tumor cell metabolism have not been studied yet. Methods In this study, we investigated the metabolite profiling of He plasma treatment on myeloma tumor cells by gas-chromatography time-of-flight (GC-TOF) mass-spectrometry. Meanwhile, by bioinformatic analysis such as GO and KEGG analysis we try to figure out the metabolism pathway that was significantly affected by gas plasma treatment. Results By GC-TOF mass-spectrometry, 573 signals were detected and evaluated using PCA and OPLS-DA. By KEGG analysis we listed all the differential metabolites and further classified into different metabolic pathways. The results showed that beta-alanine metabolism pathway was the most significant change after He gas plasma treatment in myeloma cells. Besides, propanoate metabolism and linoleic acid metabolism should also be concerned during gas plasma treatment of cancer cells. Conclusions Cold atmospheric plasma treatment could significantly alter the metabolite profiling of myeloma tumor cells, among which, the beta-alanine metabolism pathway is the most susceptible to He gas plasma treatment.

Systemic infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are life-threatening due to their strong multidrug resistance, especially since the biofilms formed by MRSA are more difficult to inactivate by antibiotics, causing long term recurrence of infection. Plasma-activated saline (PAS), a derived form of cold atmospheric-pressure plasma, can effectively inactivate bacteria and cancer cells and has been applied to sterilization and cancer treatment. Previous studies have demonstrated that the pretreatment of MRSA with PAS could promote the action of antibiotics. Here, the PAS was used as an antibiotic adjuvant to promote the inactivation of MRSA biofilms by rifampicin and vancomycin, and the combined treatment reduced approximately 6.0-log10 MRSA cells in biofilms. The plasma-activated saline and rifampicin synergistically and effectively reduced the systemic infection in the murine model. The histochemical analysis and the blood hematological and biochemical test demonstrated that the combined treatment with plasma-activated saline and rifampicin improved the blood hematological and biochemical parameters of infected mice by reducing the infection. Therefore, PAS based on plasma technology represents a new strategy for the treatment of infectious disease caused by multidrug-resistant bacteria and alleviating antibiotic resistance.

Biofilm infections in wounds seriously delay the healing process, and methicillin-resistant Staphylococcus aureus is a major cause of wound infections. In addition to inactivating micro-organisms, low-temperature gas plasma can restore the sensitivity of pathogenic microbes to antibiotics. However, the combined treatment has not been applied to infectious diseases. In this study, low-temperature gas plasma treatment promoted the effects of different antibiotics on the reduction of S. aureus biofilms in vitro. Low-temperature gas plasma combined with rifampicin also effectively reduced the S. aureus cells in biofilms in the murine wound infection model. The blood and histochemical analysis demonstrated the biosafety of the combined treatment. Our findings demonstrated that low-temperature gas plasma combined with antibiotics is a promising therapeutic strategy for wound infections.

Biofilms formed by multidrug-resistant bacteria are a major cause of hospital-acquired infections. Cold atmospheric-pressure plasma (CAP) is attractive for sterilization, especially to disrupt biofilms formed by multidrug-resistant bacteria. However, the underlying molecular mechanism is not clear. In this study, CAP effectively reduced the living cells in the biofilms formed by methicillin-resistant Staphylococcus aureus, and 6 min treatment with CAP reduced the S. aureus cells in biofilms by 3.5 log10. The treatment with CAP caused the polymerization of SaFtsZ and SaClpP proteins in the S. aureus cells of the biofilms. In vitro analysis demonstrated that recombinant SaFtsZ lost its self-assembly capability, and recombinant SaClpP lost its peptidase activity after 2 min of treatment with CAP. Mass spectrometry showed oxidative modifications of a cluster of peaks differing by 16 Da, 31 Da, 32 Da, 47 Da, 48 Da, 62 Da, and 78 Da, induced by reactive species of CAP. It is speculated that the oxidative damage to proteins in S. aureus cells was induced by CAP, which contributed to the reduction of biofilms. This study elucidates the biological effect of CAP on the proteins in bacterial cells of biofilms and provides a basis for the application of CAP in the disinfection of biofilms.

Reactive oxygen and reactive nitrogen species (RONS) are believed to play a key role in biomedical applications, which means that RONS must reach the target tissue to produce a therapeutic effect. Existing methods (electron spin spectrometry and microplate reading) to determine the RONS concentration are not suitable for experimental real-time measurements because they require adding an indicating reagent to the plasma-treated medium, which may alter the chemical composition of the medium. In this paper, we propose a method to measure the long-lived RONS concentration in plasma-activated water (PAW) by using UV absorption spectroscopy. Based on an analysis and fit of the absorption spectra of standard solutions (H2O2, NaNO2, and NaNO3), we propose a detailed fitting procedure that allows us to calculate the concentrations of simplex H2O2, NO2−, and NO3−. The results show that the pH and the cross reactivity between RONS in PAW correlate strongly with the absorption spectra. To confirm the accuracy of the calculations, we also use a microplate reader and add chemical reagents to measure the concentrations of H2O2, NO2−, and NO3−. The results show that the concentrations calculated by the proposed fitting method are relatively accurate and that the error range is acceptable. Additionally, the time-dependent diffusion of RONS in PAW is measured and analyzed at different depths in the PAW. This fitting approach constitutes a nonintrusive approach to measure RONS at different depths in PAW.

Cold atmospheric plasma (CAP) is a rapidly developed technology that has been widely applied in biomedicine especially in cancer treatment. Due to the generation of various active species in plasma, CAP could induce various tumor cells death and showed a promising potential in cancer therapy. To enhance the biological effects of gas plasma, changing the discharging parameters is the most commonly used method, yet increasing discharging power will lead to a higher possibility of simultaneously damage surrounding tissues. In this study, by adding nontoxic concentration of additional nitrite and nitrate in the medium, we found that anti-tumor effect of CAP treatment was enhanced in the same discharging parameters. By microplate reader and cell flow cytometer we measured several extracellular and intracellular RONS and found that ONOO- was mostly correlated with the enhanced cancer cell killing effect. We proposed that more nitrogen supplies such as nitrite and nitrate could increase the production of RNS especially ONOO- and resulted in a better killing effect to cancer cells. Our results provided a new strategy to enhance the antitumor effect by plasma jet treatment without changing the discharging parameters.

Immunotherapy is reportedly effective in a subset of colorectal cancers (CRCs) with high microsatellite instability (MSI-H). Exploring the expression patterns and clinical values of immunologic molecules is critical in defining the specific responsive candidates. Here, we performed comprehensive molecular profiling of the B7 and TNFR family genes across 6 CRC datasets with over 1,000 patients’ details using cBioPortal TCGA data. About 20% of patients had B7 and TNFR family gene alterations. The frequency of B7 gene mutations (2.2%–5%) were similar to copy number alterations (0.53%–5.46%). TNFR amplifications were relatively more common (5.45–11.32%) than that of B7 (0.09–2.73%). B7 and TNFR gene mRNAs were upregulated in 26% of cases (102/379) and 16% of cases (61/379), respectively. The mRNA levels of B7 and TNFR genes were inversely correlated with promoter methylation status. Clinically, both B7-H3 and TNFSF7 mRNA overexpression were associated with unfavorable clinical outcomes, and the B7-H3 expression was increased gradually in cases with gene amplifications. Moreover, patients with MSI-H had significantly higher PD-L1 or PD-1 expression. Most importantly, in MSI-H group, patients with PD-L1 or PD-1 upregulation had poorer survivals than those with PD-L1/PD-1 downregulation. This is the first study drawing the immune landscapes of the co-stimulator B7 and TNFR families in CRC and showing that MSI-H patients with PD-1/PD-L1 upregulation are associated with poor clinical outcomes, providing potential markers to stratify patients responsive to immune checkpoint therapy.

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of serious nosocomial infections, and recurrent MRSA infections primarily result from the survival of persister cells after antibiotic treatment. Gas plasma, a novel source of ROS (reactive oxygen species) and RNS (reactive nitrogen species) generation, not only inactivates pathogenic microbes but also restore the sensitivity of MRSA to antibiotics. This study further found that sublethal treatment of MRSA with both plasma and plasma-activated saline increased the antibiotic sensitivity and promoted the eradication of persister cells by tetracycline, gentamycin, clindamycin, chloramphenicol, ciprofloxacin, rifampicin, and vancomycin. The short-lived ROS and RNS generated by plasma played a primary role in the process and induced the increase of many species of ROS and RNS in MRSA cells. Thus, our data indicated that the plasma treatment could promote the effects of many different classes of antibiotics and act as an antibiotic sensitizer for the treatment of antibiotic-resistant bacteria involved in infectious diseases.

The paper presents the results of a numerical simulation of the effects of N2 on the characteristics of Trichel pulses in SF6 at 0.4 MPa. The simulation was performed in a 2D axisymmetric geometry assuming a three species discharge model for the applied voltage on the discharge electrode to be −25 kV. Three drift-diffusion equations coupled with Poisson's equation are considered to determine the dynamic behavior of Trichel pulses and the temporal and spatial distributions of charged species. The reduced ionization coefficient, the reduced attachment coefficient, the electron mobility, and the electron diffusion coefficient of SF6/N2 mixtures are obtained by solving the two-term Boltzmann equations. The content of N2 varies from 20% to 80%. The distribution of three charged species and the reduced electric field at the discharge tip are presented at different instants of time to explain the formation mechanism of the Trichel pulses in SF6/N2 mixtures. The time-dependent current, the total number of electrons, the positive ions, and the negative ions as well as the reduced electric field at the discharge tip under different SF6/N2 mixtures are analyzed to investigate the sensitivities of these properties to the N2 content. [ABSTRACT FROM AUTHOR]

Background: A large number of studies have been conducted to investigate associations between genetic variants and esophageal cancer risk in the past several decades. However, findings from these studies have been generally inconsistent. We aimed to provide a summary of the current understanding of the genetic architecture of esophageal cancer susceptibility. Methods: We performed a comprehensive field synopsis and meta-analysis to evaluate associations between 95 variants in 70 genes or loci and esophageal cancer risk using data from 304 eligible publications, including 104,904 cases and 159,797 controls, through screening a total of 21,328 citations. We graded levels of cumulative epidemiologic evidence of a significant association with esophageal cancer using the Venice criteria and false-positive report probability tests. We constructed functional annotations for these variants using data from the Encyclopedia of DNA Elements Project and other databases. Results: Thirty variants were nominally significantly associated with esophageal cancer risk. Cumulative epidemiologic evidence of a significant association with overall esophageal cancer, esophageal squamous cell carcinoma, or esophageal adenocarcinoma was strong for 13 variants in or near 13 genes (ADH1B, BARX1, CDKN1A, CHEK2, CLPTM1L, CRTC1, CYP1A1, EGF, LTA, MIR34BC, PLCE1, PTEN, and PTGS2). Bioinformatics analysis suggested that these variants and others correlated with them might fall in putative functional regions. Conclusions: Our study summarizes the current literature on the genetic architecture of esophageal cancer susceptibility and identifies several potential polymorphisms that could be involved in esophageal cancer susceptibility. Impact: These findings provide direction for future studies to identify new genetic factors for esophageal cancer. [ABSTRACT FROM AUTHOR]

Cold atmospheric plasmas are reportedly capable of enhancing the percutaneous absorption of drugs, which is a development direction of plasma medicine. This motivated us to study how the enhancement effect was realized. In this letter, gelatin gel films were used as surrogates of human tissues, NaNO2 was used as a representative of small-molecule drugs, and cross-field and linear-field plasma jets were used for the purpose of enhancing the penetration of NaNO2 through the gelatin gel films. The permeability of gelatin gel films was quantified by measuring the NO2– concentration in water which was covered by those films. It was found that the gas flow and electric field of cold plasmas played a crucial role in the permeability enhancement of the model tissues, but the effect of gas flow was mainly confined in the surface layer, while the effect of the electric field was holistic. Those effects might be attributed to the localized squeezing of particles by gas flow and the weakening of the ion-dipole interaction by the AC electric field. The enhancement effect decreases with the increasing mass fraction of gelatin because the macromolecules of gelatin could significantly hinder the penetration of small molecules in the model tissues. [ABSTRACT FROM AUTHOR]

Although the formation and propagation of plasma plume for atmospheric pressure plasmas have been intensively studied, how does the plasma plume terminate is still little known. In this letter, helium plasma plumes are generated in a long quartz tube by pulsed voltages and a constant gas flow. The voltages have a variable pulse width (PW) from 0.5μs to 200μs. It is found that the plasma plume terminates right after the falling edge of each voltage pulse when PW<20μs, whereas it terminates before the falling edge. When PW is larger than 30 μs, the duration of plasma plume starts to decrease, and the termination is found to occur at the current zero moment of the discharge current through the high-voltage electrode, which is much different from that through the ground electrode. This indicates that part of the discharge current is shunted by the plasma plume to its downstream gas region. An equivalent circuit model is developed, from which the surface charge deposited on the quartz tube is found crucial for accelerating the termination of a plasma plume when PW>30μs. [ABSTRACT FROM AUTHOR]

A surface micro-discharge in atmospheric pressure He + N2 mixtures is studied in this paper with an emphasis on the discharge modes. With the N2 admixture increasing from 0.1% to 20%, the discharge evolves from a spatially diffuse mode to a filamentary mode during positive half-cycles of the applied voltage. However during the negative half-cycles, an additional patterned mode emerges between the diffuse and the filamentary modes, which has not been reported before to exist in surface micro-discharges. In the diffuse and patterned modes, the plasmas cover almost the entirety of the mesh area during one cycle after plasma ignition in all mesh elements, and the discharge power increases linearly with the applied voltage. In contrast, plasma coverage of the mesh area is only partial in the filamentary mode and the plasma is more unstable with the discharge power increasing exponentially with the applied voltage. As the surface micro-discharge evolves through the three modes, the density of excited species changes significantly, for instance, the density of N2+(B) drops by ∼20-fold from [N2] = 0.2% to 20%. The N2+(B) is predicted to be generated mainly through successive processes of Penning ionization by helium metastables and electron-impact excitation of N2+(X), the latter is most responsible for the density decrease of N2+(B) because much more N2+(X) is converted to N4+(X) as the increase of N2 fraction. Also, the electron density and electron temperature decrease with the discharge mode transition. [ABSTRACT FROM AUTHOR]

Nitric oxide NO is one of the major targets for environmental monitoring, but the existing NO sensors are limited by their low sensitivity and narrow test range. Here, a NO gas sensor employing multiwalled carbon nanotubes (MWCNTs) was fabricated, and its properties in NO-N2 mixture were investigated from both emission and ionization. The current I e passing through the nanotubes cathode was found to decrease with increasing NO concentration and increase linearly in different slopes with the extracting voltage U e. It is shown that the Schottky barrier of the MWCNTs calculated by I e increased with NO concentration due to the adsorption of NO gas, which restrained the electron emission and consequently weakened the ionization. The positive ion currents I c passing through the collecting electrode at different voltages of U e were found to monotonically decrease with increasing NO concentration, which was induced by both of the reduced electron emission and the consumption of the two excited metastable states N2(A³u +) and N2(a'¹u -) by NO. The sensor exhibited high sensitivity at the low temperature of 30 °C. The calculated conductivity was found to be able to take place of Ic for NO detection in a wide voltage range of 80-150 V U e. [ABSTRACT FROM AUTHOR]

We present in this paper how oxygen additive impacts on the cold atmospheric-pressure helium plasmas by means of a one-dimensional fluid model. For the oxygen concentration [O2] > -0.1%, the influence of oxygen on the electron characteristics and the power dissipation becomes important, e.g., the electron density, the electron temperature in sheath, the electron-coupling power, and the sheath width decreasing by 1.6 to 16 folds with a two-log increase in [O2] from 0.1% to 10%. Also the discharge mode evolves from the y mode to the a mode. The reactive oxygen species are found to peak in the narrow range of [O2] = 0.4%-0.9% in the plasmas, similar to their power-coupling values. This applies to their wall fluxes except for those of O* and O2". These two species have very short lifetimes, thus only when generated in boundary layers within several micrometers next to the electrode can contribute to the fluxes. The dominant reactive oxygen species and the corresponding main reactions are schematically presented, and their relations are quantified for selected applications. [ABSTRACT FROM AUTHOR]

The atmospheric pressure dielectric barrier discharge in helium is a pulsed discharge in nature and the moment of maximum species densities is almost consistent with peak discharge current density. In this paper, a one-dimensional fluid model is used to investigate the temporal structure of plasma species in an atmospheric He-N2 dielectric barrier discharge (DBD). It is demonstrated that there exist microsecond delays of the moments of the maximum electron and ion densities from the peak of discharge current density. These time delays are caused by a competition between the electron impact and Penning ionizations, modulated by the N2 level in the plasma-forming gas. Besides, significant electron wall losses lead to the DBD being more positively charged and, with a distinct temporal separation in the peak electron and cation densities, the plasma is characterized with repetitive bursts of net positive charges. The temporal details of ionic and reactive plasma species may provide a new idea for some biological processes. [ABSTRACT FROM AUTHOR]

Recently, much attention has been paid to SF6-CO2 mixtures as one of substitutes for pure SF6 gas. In this paper, the dielectric breakdown properties of hot SF6-CO2 mixtures are investigated at temperatures of 300-3500K and pressures of 0.01-1.0 MPa. Under the assumptions of local thermodynamic equilibrium and local chemical equilibrium, the equilibrium compositions of hot SF6-CO2 mixtures with different CO2 proportions are obtained based on Gibbs free energy minimization. The cross sections for interactions between electrons and neutral species are presented. Some unknown ionization cross sections are determined theoretically using Deutsch-Märk (DM) formalism based on quantum chemistry. Two-term Boltzmann equation is adopted to calculate the electron energy distribution function, reduced ionization coefficient, reduced attachment coefficient, and reduced effective ionization coefficient. Then the reduced critical electric field strength of mixtures, corresponding to dielectric breakdown performances, is determined when the generation and loss of electrons are balanced. Finally, the influences of temperature, pressure, and CO2 proportion on the reduced critical electric field strength are studied. It is found that a large percentage of CO2 can obviously reduce concentrations of high-energy electrons. At temperatures above 1750 K, an addition of CO2 to SF6 gas can enhance dielectric breakdown performances. However, at low temperatures, too much CO2 added into mixtures can reduce dielectric breakdown abilities. In addition, increasing gas pressure can improve dielectric breakdown performances. But the influence will be no more significant if pressure is over 0.8 MPa. [ABSTRACT FROM AUTHOR]

We synthesize ZnO butterfly single wing scales (SWSs) directly templated from original individual SWSs. A 20° departure of the light incidence may drastically reduce the reflectance intensity by ten times. This work helps clarify the mechanism in butterfly replica optical properties, which are hotly being discussed at present. [ABSTRACT FROM AUTHOR]

The application of cold atmospheric plasma jet in cancer treatment has received extensive attention. Research on the spatial distribution of the anticancer effects induced by plasma jet is of great significance for further promoting its clinical application. Here, based on two-dimensional monolayer cells and three-dimensional (3D) multicellular tumor spheroids, the distributions of anticancer effects induced by He plasma jet irradiation on tumor tissue were studied in detail. It was found that the effective anticancer area of the plasma jet was affected by the gas flow rate. Further studies showed that the plasma jet caused physical damage in the central region of the anticancer area and induced apoptosis in the peripheral region due to the reactive oxygen species (ROS) generated by the plasma jet. In addition, the anticancer results on 3D multicellular tumor spheroids indicated that the apoptosis rate and the anticancer depth of the plasma jet were different at different distances from the plasma-irradiated spot. This study could help us better understand the actual anticancer effects of a plasma jet on living tumor tissues, and it may provide beneficial information for optimizing the plasma jet treatment method in future clinical applications. [ABSTRACT FROM AUTHOR]