To study the size-resolved characteristics of airborne bacterial community composition, diversity, and abundance, outdoor aerosol samples were analysed by 16S rRNA gene-targeted quantitative PCR and ...amplicon sequencing with Illumina MiSeq. The samples were collected using size-resolved samplers between August and October 2016, at a suburban site in Toyama City and an urban site in Yokohama City, Japan. The bacterial communities were found to be dominated by Actinobacteria, Firmicutes, and Proteobacteria. At the genus level, we found a high abundance of human skin-associated bacteria, such as Propionibacterium, Staphylococcus, and Corynebacterium, in the urban site. Whereas, a high abundance of bacteria associated with soil and plants, such as Methylobacterium and Sphingomonas, was observed in the suburban site. Furthermore, our data revealed a shift in the bacterial community structure, diversity, and abundance of total bacteria at a threshold of 1.1-µm diameter. Interestingly, we observed that Legionella spp., the causal agents of legionellosis in humans, were mainly detected in > 2.1 µm coarse particles. Our data indicate that local environmental factors including built environments could influence the outdoor airborne bacterial community at each site. These results provide a basis for understanding the size-resolved properties of bacterial community composition, diversity, and abundance in outdoor aerosol samples and their potential influence on human health.
We have developed an atomic model for calculating the polarization state of the Lyman-α line in plasma caused by anisotropic electron collision excitations. The model assumes a nonequilibrium state ...of the electron temperature between the directions parallel (T‖) and perpendicular (T⊥) to the magnetic field. A simplified assumption on the formation of an excited state population in the model is justified by detailed analysis of population flows regarding the upper state of the Lyman-α transition with the help of collisional-radiative model calculations. Calculation results give the polarization degree of several percent under typical conditions in the edge region of a magnetically confined fusion plasma. It is also found that the relaxation of polarization due to collisional averaging among the magnetic sublevels is effective in the electron density region considered. An analysis of the experimental data measured in the Large Helical Device gives T⊥/T‖=7.6 at the expected Lyman-α emission location outside the confined region. The result is derived with the absolute polarization degree of 0.033, and T⊥=32 eV and ne=9.6×1018m−3 measured by the Thomson scattering diagnostic system.
We have measured the emission line spectra of neutral helium (21P - 31D, 667.8 nm) in a poloidal cross-section of the plasma in the Large Helical Device (LHD). The measurement has been made from two ...different observation ports with 40 lines-of-sight each. A tomographic analysis was done to derive the line intensity distribution, using the Hopfield Neural Network method with the Phillips-Tikhonov regularization term. The algorithm was expanded to incorporate Zeeman splittings, a feature prominently evident in the measured spectra, providing information on the position of the emission. The results revealed a concentrated radiation distribution near the X-points and on the divertor legs, specifically those connected to the inboard side divertor plates. We have confirmed that reconstructed images are available even when the analysis is performed solely with data from one of the two observation ports. This suggests the potential applicability of our approach under highly limited options for observation port arrangements. By reconstructing the line emission distribution only using the π peak signals, we show that our method can estimate the vertical emission positions from the Zeeman effect. The robustness of our new method was also checked.
In this study, eight emission lines in the visible wavelength range of neutral helium were used to diagnose the electron density and temperature of the Large Helical Device (LHD) helium plasma ...instead of the conventional three-line method. The collisional-radiative (CR) model for low-pressure helium plasma was revised to include the optical escape factors for spontaneous transition from the n1P states to the ground state so that the influence of the absorption effect under optically thick conditions could be considered. The developed algorithm was based on fitting the number densities of eight excited states obtained using optical emission spectroscopy (OES). The electron density, electron temperature, ground-state density, and optical escape factors were selected as the fitting parameters. The objective function was set as the summation of the residual errors between the number densities measured in the experiment and those calculated using the revised model. A regularization term was introduced for the optical escape factor and optimized through bias and variance analyses. The results show that the agreement between the number density calculated by the algorithm and its counterpart measured in the experiment was generally improved compared to the method using three lines.
A novel rovibrationally resolved collisional-radiative model of molecular hydrogen that includes 4,133 rovibrational levels for electronic states whose united atom principal quantum number is below ...six is developed. The rovibrational X 1 Σ g + population distribution in a SlimCS fusion demo detached divertor plasma is investigated by solving the model time dependently with an initial 300 K Boltzmann distribution. The effective reaction rate coefficients of molecular assisted recombination and of other processes in which atomic hydrogen is produced are calculated using the obtained time-dependent population distribution.
Full vertical profiles of visible bremsstrahlung continuum have been measured for diagnostics of effective ion charge, Zeff , with parallel optical fiber arrays at horizontally elongated plasma cross ...section in the Large Helical Device (LHD). Measured bremsstrahlung profiles were asymmetric due to non-uniform bremsstrahlung emissions located in the stochastic magnetic field layer. Then, the Zeff profile analysis has been done only for a magnetic configuration with relatively thin stochastic magnetic field layer, i.e. for plasmas at magnetic axis position of Rax = 3.60 m. The effect of the non-uniform bremsstrahlung emission disappears in the lower half profile at Rax = 3.60 m, while the Zeff profile analysis is extremely difficult in other magnetic configurations due to the presence of the non-uniform bremsstrahlung emission over the entire vertical profile from top to bottom. To improve the difficult situation in the Zeff diagnostic the fan array optical fiber system was newly installed at vertically elongated plasma cross section for full horizontal profile measurement. It is found that the non-uniform bremsstrahlung emissions disappear from the signal and the observed bremsstrahlung profile is almost symmetric between inboard and outboard radial profiles. The analysis on the Zeff profile has been carried out based on the plasma equilibrium database in LHD, TSMAP. A preliminary result is obtained in high-density discharges, which shows a flat Zeff profile and values of Zeff ∼ 1.
Two dimensional turbulence observed in the linear magnetized device PANTA is studied using a visible high speed camera system. When the fluctuation component are decomposed with Fourier-Bessel ...expansion, complex density fluctuations are recognized as the superposition of the several mode having low mode number, e.g., m = 1, 2, and 3. The phase relations between waves indicate that they are non-linearly coupled.
We have recently incorporated the occupation probability formalism (OPF) in the simulation model C. Stehlé and S. Jacquemot, Astron. Astrophys. 271, 348 (1993) to have a smooth transition from ...discrete lines to continuum spectrum in the wavelength range near the Balmer series limit. We have analyzed spectra measured for the hydrogen pellet ablation cloud in the Large Helical Device with the revised model, and have found that the electron density in the ablation cloud has a close correlation with the electron temperature of the background plasma. This type of correlation is first confirmed in the present analysis and should give a new insight in the simulation studies of pellet ablation for the magnetically confined fusion plasma.
Tungsten (W) is one of the major impurities in ITER and future DEMO reactors. However, diagnosing ion density, temperature, and spatial distribution for tungsten ions in low charge states such as ...W17+-W27+ is difficult due to a lack of spectral line data. In this study, we observed tungsten Unresolved Transition Array (UTA) spectra around W20+ in Large Helical Device. Furthermore, the emission spectra of tungsten ions ranging from W19+-W23+ were also measured using Compact electron Beam Ion Trap (CoBIT). Two spectral peaks were detected in the CoBIT experimental setup. Subsequently, these peaks were theoretically identified as 5s-5p and 5p3/2-5d transitions using Flexible Atomic Code (FAC). The identified peaks are useful for impurity diagnostics of ITER edge plasma.
Fast ion diagnostic is one of the most crucial plasma diagnostics for nuclear fusion investigation. A new diagnostic method for fast ions has been proposed using visible spectra of 3He produced by a ...deuteron-deuteron reaction. This diagnostic method has a better energy resolution than methods using neutron/γ-ray and is superior to conventional spectroscopy in measuring high energy (MeV order) ions. This diagnostic method has been predicted using numerical analysis for ITER, but no verification experiments have been performed yet. In this study, we examined the measurability of this diagnostic method in the large helical device (LHD) deuterium plasma. Although very dependent on the measurement geometry and the spectrometer performance, it may be possible to measure the fast 3He visible spectrum.
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