52 research outputs found
Diversity and distribution of cytochrome oxidase I (COI) haplotypes of the brown marmorated stink bug, Halyomorpha halys Stål (Hemiptera, Pentatomidae), along the eastern front of its invasive range in Eurasia
The arrival, establishment and pest status of Halyomorpha halys in Europe and non-native countries in Asia have been well-documented, with thorough characterisation of the genetic diversity and occurrence of cytochrome oxidase I (COI) haplotypes in Switzerland, France, Hungary, Italy and Greece. However, a number of gaps exist in terms of the characterisation of the haplotype diversity and occurrence of H. halys along the invasion front that covers eastern Europe, western and central Asia. To contribute towards filling this gap, the COI haplotype diversity and distribution were investigated for H. halys collected in Serbia, Ukraine, Russia, Georgia and Kazakhstan. A total of 646 specimens were analysed and five haplotypes were found (H1, H3, H8, H33 and H80). Haplotype H1 was present in all five countries investigated and was the only haplotype detected amongst > 500 specimens collected from Ukraine, Russia and Georgia. H1 (82%) was the dominant haplotype found in Kazakhstan, alongside H3 (18%). In contrast to the low or no diversity observed in these four countries, Serbia had higher haplotype diversity and was represented by five haplotypes. Although H3 was dominant (47%) in Serbia, H1 was also prevalent (40%); the remaining haplotypes (H8, H33 and H80) were minor contributors (1–11%) to the haplotype composition. The results are discussed in context with other known populations in neighbouring countries and patterns of haplotype diversity indicate the movement of successful invasive populations in Europe to generate secondary invasions along the eastern front of the invasion in Eurasia. Possible scenarios regarding the spread of particular haplotypes in these regions are discussed, along with suggestions for future research to fill existing gaps
Collisional kinetics of non-uniform electric field, low-pressure, direct-current discharges in H
A model of the collisional kinetics of energetic hydrogen atoms, molecules,
and ions in pure H discharges is used to predict H emission
profiles and spatial distributions of emission from the cathode regions of
low-pressure, weakly-ionized discharges for comparison with a wide variety of
experiments. Positive and negative ion energy distributions are also predicted.
The model developed for spatially uniform electric fields and current densities
less than A/m is extended to non-uniform electric fields, current
densities of A/m, and electric field to gas density ratios MTd at 0.002 to 5 Torr pressure. (1 Td = V m and 1 Torr =
133 Pa) The observed far-wing Doppler broadening and spatial distribution of
the H emission is consistent with reactions among H, H,
H, and H ions, fast H atoms, and fast H molecules, and with
reflection, excitation, and attachment to fast H atoms at surfaces. The
H excitation and H formation occur principally by collisions of
fast H, fast H, and H with H. Simplifications include using a
one-dimensional geometry, a multi-beam transport model, and the average
cathode-fall electric field. The H emission is linear with current
density over eight orders of magnitude. The calculated ion energy distributions
agree satisfactorily with experiment for H and H, but are only in
qualitative agreement for H and H. The experiments successfully modeled
range from short-gap, parallel-plane glow discharges to beam-like,
electrostatic-confinement discharges.Comment: Submitted to Plasmas Sources Science and Technology 8/18/201
Excessive hydrogen and deuterium Balmer lines broadening in a hollow cathode glow discharges
Results of a Doppler spectroscopy study of hydrogen and deuterium
Balmer lines in the stainless steel and copper hollow cathode glow
discharge, operated in pure hydrogen, deuterium and mixtures of inert gases
with hydrogen, are reported. For all gases and gas mixtures plasma
observations perpendicular to electric field revealed the excessively large
Doppler broadening. By changing mode of glow discharge operation, the
Doppler broadened line profiles in helium-hydrogen mixture are recorded
parallel to the discharge electric field as well. The excessively broadened
part of the H line profile is shifted towards blue or red
wavelength by changing the direction of electric field vector. The presence
of large excessive Balmer lines broadening in pure hydrogen and in its gas
mixture with neon as well as shifting of the excessively broadened part of
line profile by means of electric field is in contradiction with the
resonance transfer model proposed by Mills et al. in several publications,
see e.g. [IEEE Trans. Plasma Sci. 31, 338 (2003)].
Excessive Doppler broadening of the H
A comparative study of the radial intensity distribution
of the excessively Doppler broadened hydrogen Hα line in a hollow
cathode (HC) glow discharge operated in hydrogen and argon-hydrogen gas
mixtures with stainless steel (SS) and titanium (Ti) cathode is reported.
The main interest of this work is focused on the dependence of radial
distribution upon cathode material and cathode surface composition. The
analysis of experimental radial distributions and results obtained from
H+↦ metal surface interaction simulation combined with available
data for H ↦ metal target interaction explains the difference between SS
and Ti cathodes. These results explain also the important role of metal
hydrides at the cathode surface for discharge-HC interaction. The influence
of the hollow cathode temperature on the radial distribution of the
excessively broadened Hα line and on the emission of Ar I and Ar
II lines from discharge in argon-hydrogen gas mixture are also
investigated. The increase of the excessive Doppler broadened part of the
Hα line profile with HC temperature is always detected. The
intensity of Ar I and Ar II lines is also used to examine the influence of
small admixtures of hydrogen in argon
Ne I spectral line shapes in Grimm-type glow discharge
We report the results of five Ne I line shapes study in an abnormal Grimm-type glow discharge operating in neon. The spectral lines were observed along the axis of a cylindrical glow discharge parallel (side-on) and perpendicular (end-on) to the cathode surface. The side-on spectra showed a spectral line shift and sometimes a simultaneous shift and split in the cathode fall region of the glow discharge. The results of the measured line shift with the available data for the dc Stark effect were used to estimate the electric field strength in the cathode fall region of the glow discharge. The end-on recorded line profiles showed up to 30% larger half-widths than the side-on recorded line profiles from the negative glow. This effect is a result of the superposition of line emission in the cathode fall region under the influence of the dc Stark effect on the line profile from the negative glow. In addition, wavy features at the far wing in the direction of dc Stark shift were detected. All observed phenomena related to end-on line shapes in Grimm discharge were related quantitatively to the dc Stark effect in the cathode fall region and plasma line broadening in the negative glow region
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