Cross-comparison of diagnostic and 0D modeling of a micro-hollow cathode discharge in the stationary regime in an Ar/N2 gas mixture

2021 ◽  
Author(s):  
Alice Remigy ◽  
Salima Kasri ◽  
Thibault Darny ◽  
Hiba Kabbara ◽  
Ludovic William ◽  
...  
Keyword(s):  
Hollow Cathode ◽  
Ultra Violet ◽  
Hollow Cathode Discharge ◽  
Tunable Diode Laser ◽  
Physical Parameters ◽  
Gas Mixture ◽  
High Electron ◽  
Experimental Conditions ◽  
Wide Range ◽  
Averaged Model

Abstract A micro-hollow cathode discharge (MHCD) operated in Ar/N2 gas mixture, working in the normal regime, was studied both experimentally and with a 0D (volume-averaged) model in this work. This source provides high electron densities (up to 1015 cm-3) at low injected power (1W). To understand the mechanisms leading to the production of N atoms, the densities of electrons, N atoms and argon metastable atoms (Ar*) were monitored over a wide range of experimental conditions. Electrons, N atoms and Ar* densities were probed by means of Optical Emission Spectroscopy (OES), Vacuum Ultra Violet Fourier Transform Spectroscopy (VUV FTS) and Tunable Diode Laser Absorption Spectroscopy (TDLAS), respectively. Measurements showed that using a smaller hole diameter enables to work with less injected power, while increasing the power density inside the hole and, subsequently, increasing the densities of excited species. Varying the percentage of N2 in the gas mixture highlighted that, up to 80%, the density of N atoms increases although the dissociation rate drops. Looking at the processes involved in the production of N atoms with the help of the 0D model, we found that at very low N2 fraction, N atoms are mostly produced through dissociative electron-ion recombination. However, adding more N2 decreases drastically the electron density. The density of N atoms does not drop thanks to the contribution of Ar* atoms, which are the main species dissociating N2 between 5 and 55% of N2 in the gas mixture. A reasonable agreement is found between the experiments and the model results. This study shows that, with this MHCD, it is possible to significantly modify the production of N atoms when modifying the physical parameters, making it particularly relevant for applications requiring a N atoms source, such as nitride deposition.

scholarly journals The λ 2530 band of NH

1936 ◽  
Vol 155 (884) ◽  
pp. 173-182 ◽  
Author(s):  
R. Winstanley Lunt ◽  
R. W. B. Pearse ◽  
E. C. W. Smith ◽  
Alfred Fowler
Keyword(s):  
Hollow Cathode ◽  
Band System ◽  
Ultra Violet ◽  
Hollow Cathode Discharge ◽  
System A ◽  
Previous Communication ◽  
Quartz Spectrograph

A previous communication by the authors described the use of a hollow cathode discharge in rapidly streaming ammonia for the excitation of a new band system of NH having its (0, 0) band at λ 4502. Observations of the spectrum obtained under these conditions have now been extended to the ultra-violet region. With an improved hollow cathode capable of carrying heavier currents, in addition to the well-known bands of the 3 Π → 3 ∑ and 1 Π → 1 ∆ systems of NH, a band is obtained at λ 2530 identical with that reported bx Hori. Hori used a 40 kV transformer discharge in a mixture of nitrogen and hydrogen between a wire and a cup-shaped electrode of tungsten, the cup containing sodium or lithium. The intensity of the band was extremely weak compared with that in the hollow cathode discharge, which is such that the band max be photographed on a Hilger E1 quartz spectrograph with exposures of from 1 to 2 hours. The examination of the band as seen under higher dispersion than that used by Hori confirms his assignment of the band to the molecule NH; it also allows the authors to correct certain details of Hori's analysis, and to relate the band to bands of NH which are already known. Table I contains all the lines measurable in the region of the band. The strong lines are nearly all accounted for by the P, Q, and R branches of the λ 2530 band, the (0, 0) band of the system. A number of the remaining weaker lines have been assigned to the P, Q, and R branches of the (1, 1) band, as indicated in italics in the table.

New cw laser lines in a noble gas mixture high voltage hollow cathode discharge

1978 ◽  
Vol 68 (3-4) ◽  
pp. 317-318 ◽  
Author(s):  
M. Jánossy ◽  
K. Rózsa ◽  
L. Csillag ◽  
J. Bergou
Keyword(s):  
High Voltage ◽  
Hollow Cathode ◽  
Noble Gas ◽  
Hollow Cathode Discharge ◽  
Gas Mixture ◽  
Cw Laser

scholarly journals Rotational analysis of the first negative band spectrum of oxygen

1938 ◽  
Vol 237 (783) ◽  
pp. 471-507 ◽  
Keyword(s):  
Hollow Cathode ◽  
High Frequency ◽  
Ultra Violet ◽  
Hollow Cathode Discharge ◽  
Rotational Structure ◽  
Band Spectrum ◽  
First Order ◽  
Negative Band ◽  
Quantum Numbers ◽  
Low Dispersion

The first negative bands of oxygen, A 6856, (0, 2), A 6419, (0, 1), A6026, (0, 0), A 5632, (1, 0) and A 5295, (2, 0) appear in the negative glow when a discharge is passed through oxygen at low pressure. Under low dispersion the bands appear very diffuse, but each exhibits on the long-wave side a well-defined head degraded to the violet, to which the wave-lengths given above refer, accompanied by a less well-defined head about 30 cm.-1 towards shorter wave-lengths. Though they have no state in common with the ultra-violet negative bands they are generally attributed to the O j molecule. References to earlier work are given by Frerichs (1926), who excited the spectrum with high intensity in a hollow-cathode discharge in oxygen and photographed it in the first order of a 21 ft. grating. In each band he found two branches, one of which formed the sharp head referred to above. On the basis of a combination relation between the branches he assigned vibrational quantum numbers to the bands. Bands additional to those given above have been discovered by Mulliken and Stevens (1933) and Bozoky and Schmid (1935). It was found by the latter workers that the bands given above, with the exception of A6856, were not single but formed the first band in each of the progressions v' — v" = — 1, 0, +1, +2, respectively. They excited the spectrum by a high-frequency discharge which seemed to have a lower effective temperature than the hollow.-cathode discharge, so that the rotational structure was not well developed and the later bands in each progression were not masked by the overlapping rotational structure of the first band

Strongly Coupled Redox-Linked Conformational Switching at the Active Site of the Non-Heme Iron-Dependent Dioxygenase, TauD

2019 ◽  
Author(s):  
Christopher John ◽  
Greg M. Swain ◽  
Robert P. Hausinger ◽  
Denis A. Proshlyakov
Keyword(s):  
Active Site ◽  
Structural Model ◽  
Heme Iron ◽  
Chemical Transformations ◽  
Experimental Conditions ◽  
Strongly Coupled ◽  
Non Heme Iron ◽  
Reversible Redox ◽  
Wide Range ◽  
Complex Structural

2-Oxoglutarate (2OG)-dependent dioxygenases catalyze C-H activation while performing a wide range of chemical transformations. In contrast to their heme analogues, non-heme iron centers afford greater structural flexibility with important implications for their diverse catalytic mechanisms. We characterize an <i>in situ</i> structural model of the putative transient ferric intermediate of 2OG:taurine dioxygenase (TauD) by using a combination of spectroelectrochemical and semi-empirical computational methods, demonstrating that the Fe (III/II) transition involves a substantial, fully reversible, redox-linked conformational change at the active site. This rearrangement alters the apparent redox potential of the active site between -127 mV for reduction of the ferric state and 171 mV for oxidation of the ferrous state of the 2OG-Fe-TauD complex. Structural perturbations exhibit limited sensitivity to mediator concentrations and potential pulse duration. Similar changes were observed in the Fe-TauD and taurine-2OG-Fe-TauD complexes, thus attributing the reorganization to the protein moiety rather than the cosubstrates. Redox difference infrared spectra indicate a reorganization of the protein backbone in addition to the involvement of carboxylate and histidine ligands. Quantitative modeling of the transient redox response using two alternative reaction schemes across a variety of experimental conditions strongly supports the proposal for intrinsic protein reorganization as the origin of the experimental observations.

Comparison of plasma characteristics of high-power pulsed sputtering glow discharge and hollow-cathode discharge

2020 ◽  
Vol 60 (1) ◽  
pp. 015501
Author(s):  
Shoki Abe ◽  
Katsuyuki Takahashi ◽  
Seiji Mukaigawa ◽  
Koichi Takaki ◽  
Ken Yukimura
Keyword(s):  
Glow Discharge ◽  
High Power ◽  
Hollow Cathode ◽  
Hollow Cathode Discharge ◽  
Plasma Characteristics

scholarly journals Low-Energy Electron Damage to Condensed-Phase DNA and Its Constituents

2021 ◽  
Vol 22 (15) ◽  
pp. 7879
Author(s):  
Yingxia Gao ◽  
Yi Zheng ◽  
Léon Sanche
Keyword(s):  
Condensed Phase ◽  
Genetic Material ◽  
High Energy ◽  
Dna Lesions ◽  
Low Energy ◽  
Experimental Investigations ◽  
Experimental Conditions ◽  
Strand Breaks ◽  
Sequence Of Events ◽  
Wide Range

The complex physical and chemical reactions between the large number of low-energy (0–30 eV) electrons (LEEs) released by high energy radiation interacting with genetic material can lead to the formation of various DNA lesions such as crosslinks, single strand breaks, base modifications, and cleavage, as well as double strand breaks and other cluster damages. When crosslinks and cluster damages cannot be repaired by the cell, they can cause genetic loss of information, mutations, apoptosis, and promote genomic instability. Through the efforts of many research groups in the past two decades, the study of the interaction between LEEs and DNA under different experimental conditions has unveiled some of the main mechanisms responsible for these damages. In the present review, we focus on experimental investigations in the condensed phase that range from fundamental DNA constituents to oligonucleotides, synthetic duplex DNA, and bacterial (i.e., plasmid) DNA. These targets were irradiated either with LEEs from a monoenergetic-electron or photoelectron source, as sub-monolayer, monolayer, or multilayer films and within clusters or water solutions. Each type of experiment is briefly described, and the observed DNA damages are reported, along with the proposed mechanisms. Defining the role of LEEs within the sequence of events leading to radiobiological lesions contributes to our understanding of the action of radiation on living organisms, over a wide range of initial radiation energies. Applications of the interaction of LEEs with DNA to radiotherapy are briefly summarized.

scholarly journals Review of the Upright Balance Assessment Based on the Force Plate

2021 ◽  
Vol 18 (5) ◽  
pp. 2696
Author(s):  
Baoliang Chen ◽  
Peng Liu ◽  
Feiyun Xiao ◽  
Zhengshi Liu ◽  
Yong Wang
Keyword(s):  
Postural Balance ◽  
Force Plate ◽  
Assessment Method ◽  
Balance Assessment ◽  
Experimental Conditions ◽  
Methodological Research ◽  
Assessment Tests ◽  
Wide Range ◽  
Foot Posture ◽  
Plate System

Quantitative assessment is crucial for the evaluation of human postural balance. The force plate system is the key quantitative balance assessment method. The purpose of this study is to review the important concepts in balance assessment and analyze the experimental conditions, parameter variables, and application scope based on force plate technology. As there is a wide range of balance assessment tests and a variety of commercial force plate systems to choose from, there is room for further improvement of the test details and evaluation variables of the balance assessment. The recommendations presented in this article are the foundation and key part of the postural balance assessment; these recommendations focus on the type of force plate, the subject’s foot posture, and the choice of assessment variables, which further enriches the content of posturography. In order to promote a more reasonable balance assessment method based on force plates, further methodological research and a stronger consensus are still needed.

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