Compact ion sources are widely used in plasma thrusters, thin film deposition, ion implantation, and so on. This study fabricated a compact surface flashover ion source with titanium thin films deposited on alumina substrates as electrodes. The fabrication process, phase composition analysis, ion current and ion current distribution, and mass-to-charge composition of the compact surface flashover ion source are presented in this article. The phase composition analysis revealed that the phase composition of the electrodes was not affected after more than 200 discharges; however, the discharge changed the diffraction peak intensity ratio. A parallel-plate electrode and 9-tip probe array were used to measure the total ion current and ion current distribution. The experimental results confirm the excellent discharge stability of the ion source, and the uniformity of the ion current at different positions. By measuring the mass-to-charge composition, it was found that the main composition of ions was Ti $^{\text{i}+}$ . In the initial discharge period, the dominant ion species were Ti $^{{\text{3}+}}$ and Ti $^{{\text{4}+}}$ . At a later period, the dominant ion species were Ti $^{{\text{1}+}}$ and Ti $^{{\text{2}+}}$ . The results can be useful in the development of novel compact ion sources.
Oral antibiotics such as metronidazole, vancomycin and fidaxomicin are therapies of choice for Clostridium difficile infection. Several important mechanisms for C. difficile antibiotic resistance have been described, including the acquisition of antibiotic resistance genes via the transfer of mobile genetic elements, selective pressure in vivo resulting in gene mutations, altered expression of redox-active proteins, iron metabolism, and DNA repair, as well as via biofilm formation. This update summarizes new information published since 2010 on phenotypic and genotypic resistance mechanisms in C. difficile and addresses susceptibility test methods and other strategies to counter antibiotic resistance of C. difficile.
The work mechanism of the Penning ion source is introduced in this paper.The research process of the invention,development and application of the Penning ion source is reviewed.And the domestic and overseas developments are introduced in detail separately.Then the application of Penning ion source,especially in well-logging,is concerned.Finally,the shortage of the domestic research work,the further work of theories and experiments are discussed.
Background: Clostridioides difficile resistant to macrolide-lincosamide-streptogramin B (MLS B ) has not been reported in China. Methods: In a cross-sectional study in two tertiary hospitals, C. difficile isolates from stool specimens from community-onset, hospital-associated diarrheal patients were analyzed for toxin genes, genotype, and antibiotic resistance, and the patients' clinical charts were reviewed. Results: A total of 190 (15.2%) isolates (102 A + B + and 88 A − B + ) from 1250 community acquired (CA) patients were recovered and all were susceptible to vancomycin and metronidazole. High-level resistance (minimum inhibitory concentration > 128 mg/L) to erythromycin and clindamycin was recorded in 77.9% and 88.4% of the tested isolates, respectively. Furthermore, 89.3% (159/178) of the isolates resistant to MLS B carried the erythromycin resistance methylase gene ( ermB ). The statistically significant factors associated with C. difficile infection (CDI) induced by A − B + isolates with MLS B resistance included a severity score of > 2 (odds ratio [95% confidence interval], 7.43 [2.31– 23.87]) and platelet count (cells × 10 9 cells/L) < 100 [5.19 (1.58– 17.04)]. The proportion of A − B + increased with enhanced CDI severity ( x 2 = 21.62, P < 0.001), which was significantly higher than that of ermB -positive A + B + in severity score of 4 ( x 2 = 8.61, P = 0.003). The average severity score of ermB -positive isolates was significantly higher than that of ermB -negative isolates in A − B + ( Z = − 2.41, P = 0.016). Conclusion: The ermB -positive A − B + C. difficile with MLS B resistance is described for the first time as a potential epidemic clone inducing severe CDI in CA diarrheal patients in Eastern China. Keywords: Clostridioides difficile , molecular characteristic, macrolide-lincosamide-streptogramin B resistance
sequence type (ST) 35 has been found in humans and animals worldwide. However, its genomic epidemiology and clonal transmission have not been explored in detail. In this study, 176
The deuterium plasma parameters of a miniature Penning discharge ion source have been measured by a single probe. Electron temperature and electron density can be acquired from the I-V curves. The results show that electron temperature increases and electron density decreases with the probe tip departing from the centre of plasma area. Meanwhile, both electron temperature and electron density increase with increase in discharge current. Electron temperature is about 1.8 ~ 7.1 eV and electron density is about 2.7 χ 10 14 - 3.7 χ 10 15 m -3 , when the distance between the probe tip and the centre of plasma area varies from 1 to 6 mm. Electron temperature is about 5.7 - 12.5 eV and electron density is about 6.7 χ 10 14 - 2.2 χ 10 15 m -3 , when discharge current varies from 50 to 200 μA. The results can provide useful information for the design and operation of Penning ion sources.
Penning-type ion source performance for neutron generator applications is characterized partly by the atomic ion fraction. A miniature Penning ion source has been fabricated to investigate the atomic ion fraction of the deuterium plasma by a mass-energy analyer. The energy for the mass settings of 2 and 4, corresponding to D + and D 2+ ions respectively, show Guass distributions. The results show that the atomic ion fraction could vary from 2.26% to 5.63% by changing the pressure, the anode voltage and the discharge current. The results can provide useful information for the choosing of the discharge conditions.
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