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C4F7N and C5F10O are the most promising SF6 alternatives as eco-friendly insulating gaseous mediums in electrical engineering.

During the arc breaking process of high-voltage circuit breaker, the eco-friendly SF6-alternative gases will inevitably decompose and generate various decomposition products. In some cases, it will contain solid by-products such as solid carbon, which will have a deterioration effect on the electrical insulation performance of the equipment. It has been found that adding a proper amount of O2 can effectively inhibit the formation of solid carbon. In this paper, based on the improved Gibbs free energy minimization method, a calculation model considering the solid decomposition products was established, and the arc plasma composition of CO2/O2 mixtures with the new eco-friendly gases, such as C4F7N, C5F10O, HFO-1234ze(E) and HFO-1336mzz(E), in LTE state was calculated. The change of decomposition products with the initial O2 ratio is studied, and the criterion expression of inhibiting solid carbon formation is obtained. We also applied the method to the calculation of other SF6-alternative gases containing sulfur atoms such as NSF3 and CF3SO2F. Finally, we showed that solid carbon can be inhibited when proper molecule formula is satisfied. This work may provide a new idea for further exploring the potential SF6-alternative gases.

Background Treatment options for refractory metastatic colorectal cancer (mCRC) were limited. Anlotinib is a novel multitarget tyrosine kinase inhibitor. ALTER0703 study was conducted to assess efficacy and safety of anlotinib for patients with refractory mCRC. Materials and Methods This was a multicenter, double-blinded, placebo-controlled, randomized phase III trial involving 33 hospitals in China. Patients had taken at least two lines of therapies were 2:1 randomized to receive oral anlotinib (12 mg/day; days 1–14; 21 days per cycle) or placebo, plus best supportive care. Randomization was stratified by previous VEGF-targeting treatments and time from diagnosis to metastases. The primary endpoint was overall survival (OS). The secondary endpoints were progression-free survival (PFS), objective response rate (ORR), disease control rate (DCR), quality of life (QoL), and safety. Results A total of 419 patients (anlotinib: 282; placebo: 137) were treated from December 2014 to August 2016. The median PFS was improved in anlotinib group (4.1 months; 95% confidence interval [CI], 3.4–4.5) over placebo group (1.5 months; 95% CI, 1.4–1.5), with a hazard ratio (HR) of 0.34 (95% CI, 0.27–0.43; p < .0001). However, median OS was similar between two groups (8.6 months; 95% CI, 7.8–9.7 vs. 7.2 months; 95% CI, 6.2–8.8; HR, 1.02; p = .870). Improvements of ORR and DCR were observed in anlotinib over placebo. The most common grade ≥ 3 anlotinib related adverse events were hypertension (20.92%), increased γ-GT (7.09%), and hand-foot skin reaction (6.38%). Conclusion Anlotinib was tolerated in Chinese patients with refractory mCRC. Although OS did not reach significant difference, anlotinib still provided clinical benefits by substantially prolonged PFS in these patients. Implications for Practice In this randomized clinical trial that included 419 patients with refractory metastatic colorectal cancer, substantial prolonged in progression-free survival was noted in patients who received anlotinib compared with those given placebo. Improvements on objective response rate and disease control rate was also observed in anlotinib group. However, overall survival was similar between the two groups. In a word, in third-line or above treatment of Chinese patients with refractory metastatic colorectal cancer, anlotinib provided clinical benefit by significantly prolonged progression-free survival.

P-glycoprotein (P-gp) efflux assay is an integral part of discovery screening, especially for drugs requiring brain penetration as P-gp efflux ratio (ER) inversely correlates with brain exposure. However, significant variability in P-gp ER generated across cell lines can lead to misclassification of a P-gp substrate and subsequently disconnect with brain exposure data. We hypothesized that the ER depends on P-gp protein expression level in the in vitro assay. Quantitative proteomics and immunofluorescence staining were utilized to characterize P-gp protein expression and localization in four recombinant cell lines, over-expressing human or mouse P-gp isoforms, followed by functional evaluation. Efflux data generated in each cell line was compared against available rodent brain distribution data. The results suggested that the cell line with highest P-gp expression (hMDCK-MDR1 sourced from NIH) led to greatest dynamic range for efflux; thus, proving to be the most sensitive model to predict brain penetration. Cell lines with lower P-gp expression exhibited the greatest tendency for compound-dependent in vitro efflux saturation leading to false negative results. Ultimately, P-gp kinetics were characterized using a compartmental model to generate system-independent parameters to resolve such discrepancy. This study highlights the need for careful choice of well characterized P-gp in vitro tools and utility of modeling techniques to enable appropriate interpretation of the data.

The perfluoronitrile C4F7N is considered a promising SF6-alternative in high-voltage gas-insulated apparatus, thanks to its high dielectric strength and low global warming potential. However, a complete and consistent set of electron-neutral collision cross-sections of C4F7N is still lacking, which hinders relevant plasma modeling. In this contribution, the available electron-neutral collision cross-sections of C4F7N are first compiled and assessed. The initial cross-sections are adjusted iteratively by the electron swarm method to determine a complete and self-consistent cross-section set of C4F7N for the first time. The set is validated by a systematic comparison of electron swarm parameters between Boltzmann equation analysis and experimental measurements in pure C4F7N as well as C4F7N/N2 and C4F7N/Ar mixtures. The proposed cross-section set of C4F7N will be made available to the community in the LXCat database. It will be of particular importance for applications with an emphasis on the discharge mechanisms of this novel gas.

Clearance (CL) prediction remains a significant challenge in drug discovery, especially when complex processes such as drug transporters are involved. The present work explores various in vitro to in vivo extrapolation (IVIVE) approaches to predict hepatic CL driven by uptake transporters in rat. Broadly, two different IVIVE methods using suspended rat hepatocytes were compared: initial uptake CL (PSu,inf) and intrinsic metabolic CL (CLint,met) corrected by unbound hepatocytes to medium partition coefficient (Kpuu). Kpuu was determined by temperature method (Temp Kpuu,ss), homogenization method (Hom Kpuu,ss), and initial rate method (Kpuu,V0). In addition, the impact of bovine serum albumin (BSA) on each of these methods was investigated. Twelve compounds, which are known substrates of organic anion-transporting polypeptides representing diverse chemical matter, were selected for these studies. As expected, CLint,met alone significantly underestimated hepatic CL for all the test compounds. Overall, predicted hepatic CL using PSu,inf with BSA, Hom Kpuu,ss with BSA, and Temp Kpuu,ss showed the most robust correlation with in vivo rat hepatic CL. Adding BSA improved hepatic CL prediction for selected compounds when using the PSu,inf and Hom Kpuu,ss methods, with minimal impact on the Temp Kpuu,ss and Kpuu,V0 methods. None of the IVIVE approaches required an empirical scaling factor. These results suggest that supplementing rat hepatocyte suspension with BSA may be essential in drug discovery research for novel chemical matters to improve CL prediction. SIGNIFICANCE STATEMENT: The current investigation demonstrates that hepatocyte uptake assay supplemented with 4% bovine serum albumin is a valuable tool for estimating unbound hepatic uptake clearance (CL) and Kpuu. Based upon the extended clearance concept, direct extrapolation from these in vitro parameters significantly improved the overall hepatic CL prediction for organic anion-transporting polypeptide substrates in rat. This study provides a practical in vitro to in vivo extrapolation strategy for predicting transporter-mediated hepatic CL in early drug discovery.

In this paper, a calculation method is proposed to predict the dielectric strength (DS) of gases and the DS of some promising SF 6 alternative gases and their mixtures is further evaluated by DC breakdown tests. The calculation method is based on the density functional theory (DFT), so that the DS of the gases can be obtained by only calculating their molecular parameters, including the average static electronic polarizability and adiabatic ionization energy. The paper also presents the DC breakdown strength of the C 4 F 7 N, C 5 F 10 O, and HFO-type gases, and it is found that the experimental DS values are in good agreement with the calculated values. In addition, DC breakdown tests for gas mixtures are also conducted and their synergistic effect is discussed in detail. The results show that the DS of C 4 F 7 N mixed gases is equivalent to that of pure SF 6 gas even under high pressures, indicating their potential applications in HV electrical equipment. The DS of C 5 F 10 O mixed gas is slightly lower than that of C 4 F 7 N mixed gas. Compared with CO 2 , mixing with air brings stronger synergistic effect in C 5 F 10 O and C 4 F 7 N in our experiment. The DS of HFO mixture is substantially less than that of SF 6 because of the weak synergistic effect when mixed with CO 2 or N 2 . This paper presents an effective method to evaluate DS of SF 6 alternative gases and the results are useful for their future engineering applications.

This paper addresses the prediction of microparticle-initiated breakdown in mm-scaled air gaps which has a transition Pd value of about 200 Pa.m. Predictions by Townsend theory and streamer inception are compared with experimental measurements and the results indicate that the Townsend theory is in better agreement. Based on this method, the breakdown voltage of an air gap with a single microparticle is calculated and drops quasi-linearly with its radius at a decay factor about 35 V/μm. The relative reduction rates of U b caused by single r m =10 and 100 μm microparticle reaches 3.1 and 37.3%, respectively. However once r m =10 μm microparticles cluster, the reduction rate rises to 7.2 and 35.5%. This provides a prediction method to assess the effects of microparticles on gas breakdown, especially in mm-scaled gap with transition Pd value and contributes to development of insulation performance.

In order to study the characteristic of the electrical explosion of copper and aluminum powders, a multilayer generator was designed, an experimental system was set up, and the parameters of metal powder electrical explosion were measured and analyzed. The results show that the duration of the electrical explosion process increases significantly due to the addition of metal powder. The duration of aluminum powder electrical explosion jet flow is ~86.36 ms due to its self-sustained combustion, which releases a large amount of energy, and a small fraction of aluminum powder particles is not burned. The duration of copper powder electrical explosion jet flow is ~15.84 ms, and most of the copper powder particles are in the solid state. The current pause process is absent; instead, the first discharge process is connected to the second discharge process. The effect of copper powder on the first discharge process is greater than that of aluminum powder. Furthermore, the ignition ability of copper powder electrical explosion to solid propellant is stronger than that of aluminum powder in a closed bomb experiment. These results are indubitably meaningful for the application of metal powder electrical explosion and ignition of solid propellant in an electrothermal chemical gun.

The C 4 F 7 N/CO 2 gas mixture has attracted much attention due to its excellent insulation property and eco-friendly character. In order to evaluate the feasibility of its application in DC GIL, this paper focuses on the surface charging characteristics of spacers under DC stress in the C 4 F 7 N/CO 2 mixture. First, the DC insulation strength was tested under uniform field. The results show that the critical dielectric strength of pure C 4 F 7 N is more than twice that of SF 6 and the dielectric strength of 15%∼20% C 4 F 7 N/CO 2 mixture is equivalent to that of SF 6 . Next, the surface charge measurement of spacers was performed in C 4 F 7 N/CO 2 mixtures, which reveals that the surface charge density decreases slightly with the increase of C 4 F 7 N content. However, the surface charging level in 25% C 4 F 7 N/CO 2 mixture is still much higher than that in SF 6 . It is found that most of the surface charge stems from partial discharges (PDs) near the flange. The PD measurement shows that in SF 6 , there are more PDs with low magnitude, but much less PDs with high magnitude compared to that in the 15%∼25% C 4 F 7 N/CO 2 mixtures. It is the different PD behaviors between C 4 F 7 N/CO 2 mixtures and SF 6 that lead to their different surface charging characteristics.

An experimental and numerical study of the plasma instabilities in an electrical exploding cylindrical Al liner is reported. The Al liner 3 mm in diameter and 10 μm in thickness is exploded at the Qin-1 facility (450 ns, 400 kA). Various diagnostics, such as multi-frame laser shadowgraphy, an x-ray framing camera, and an x-ray backlighting system are developed. The different imaging systems are sensitive to plasma of different areal densities based on the comparison between the experiments and simulation, which reveal the dynamics of the exploding liner in more detail. The laser shadow images show the low-density plasma (∼1–2 × 10−4 g cm−2) at the edge of the liner, and both the amplitude and wavelength of the plasma instabilities increase over time, which are considered to be magnetohydrodynamic (MHD) instabilities rather than electrothermal instabilities. During the ablation of the liner, quasi-periodic azimuthally correlated striations are directly observed in extreme ultraviolet (EUV) self-emission images. Meanwhile, the vertical filaments, which are electrothermal instabilities for plasma under the condition of ∂η/∂T < 0, are also observed in EUV self-emission images. The x-ray backlighting images of the exploding liner are obtained by placing an X-pinch load on the current-return path to serve as an x-ray point source (∼1 ns, ∼10 μm). The x-ray backlighting results show the behavior of the high-density plasma (∼1.89 × 10−3 g cm−2), which includes the transition from electrothermal to MHD instabilities. Finally, we realized a 2D MHD simulation of the exploding liner under experimental conditions, which shows good agreement with the results of the experimental perturbation.

Electrical wire explosion (EWE) has been extensively studied as an efficient source of underwater shock waves (SWs), with potential applications in electrohydraulic forming, reservoir stimulation, etc. The amplitude, impulse and energy of EWE shock waves are, however, limited by the energy storage of the power source, which is sometimes technically difficult or very expensive to increase, for example in a deep and narrow wellbore. In these situations, it is possible to further enhance the SWs by additional energetic materials that can be ignited by the EWE plasmas. The concept is quite alike the bridge wire detonator, but in this case the EWE operates with much higher current, and the energetic materials of much lower sensitivity, such as ammonium perchlorate /aluminum mixture (AP /Al), AP /Al /nitromethane mixture, CuO /Al /nitromethane mixture, can be directly ignited. The SW of this hybrid load contains a high amplitude, short-pulse EWE component generated by EWE and detonation of energetic materials, and a relatively low amplitude, long-pulse component generated by the combustion of energetic materials (mainly Al) behind the detonation wave front. This approach provides a practical compromise among limited energy storage, strong shock waves, and safe usage of explosives. In this talk, we present experimental results and engineering applications of this hybrid SW load, including the EWE characteristics in a powdered and muddy Al-based energetic material, physical process of the ignition, combustion and SW formation, the SW characteristics, the SW generator with automatic load feeding, and finally applications in enhanced recovery of coal bed methane. The promises and challenges in this SW-based dynamic reservoir stimulation technique will also be discussed.

Laser induced breakdown spectroscopy (LIBS) can be used to analyze hazardous samples and samples in remotely accessible or hazardous environments without handling the sample or exposing the analyst to hazards. Thus, nuclear engineering applications became one of the fast-growing fields of LIBS 1,2 In this paper, we report the development of the LIBS systems in the nuclear power plant applications.

The gas mixture CO2–O2 has been considered as an insulation and arc-quenching medium in gas-insulated switchgears. In this paper, the dielectric breakdown properties of CO2–O2 mixtures at different O2 concentrations and gas pressures were studied theoretically by considering ion kinetics in a spatial–temporal growth avalanche model. A kinetic scheme that includes all the main reactions likely to occur in CO2–O2 mixtures is presented. An improved method to calculate the dielectric strength of the gas mixture is developed, based on an avalanche model that considers both spatial growth and temporal processes. Next, the reaction rates of ionization, attachment, detachment and ion conversion, the effective ionization Townsend coefficient αeff/N, and reduced critical electric field strength ( E/N) cr in CO2–O2 mixtures at different mixing ratios and gas pressures are analyzed in detail. Finally, a pulsed Townsend experiment is performed to verify the validity and accuracy of the calculation method. Based on this, one detachment reaction rate is modified to yield more accurate results. Better consistency between the results and the experimental values supports the validity of the kinetic system, reaction rates, and the improved calculation method.

Underwater electrical wire explosion (UEWE) is an efficient source of underwater shock waves (SWs). In order to efficiently simulate the interaction between the UEWE SW and structures, a coupled model that includes the electric circuit, the exploding wire and the surrounding water is established based on user-subroutines provided by the commercial explicit dynamics software ANSYS AUTODYN. The modeling starts from room temperature by using the tabular wide-range metal equation of state (EOS) and conductivity data. Experimental validation is performed with copper wires exploded by a μs-timescale pulsed discharge. The numerical results show satisfactory consistency with experiments in terms of the current and voltage waveforms, the wire expansion trajectory, the evolution of SW front, the interaction between SW and electrodes and the SW pressure profiles. The main discrepancy lies in the SW amplitude that is ∼20% higher in the calculation and the possible reasons are discussed in detail. Based on this approach and with proper modifications to the metal EOS and conductivity data, the interaction between UEWE SWs and structures can be efficiently modeled in 2D and 3D for practical applications.