Chlorine atom densities in the (3p5)2P1/2o(3{\rm p}^{5})^{2} {\rm P}_{1/2}^{\rm o} excited spin–orbit state measured by two-photon absorption laser-induced fluorescence in a chlorine inductively coupled plasma

International audienceChlorine atom densities in the spinorbit excited state were measured by two-photon absorption laser-induced fluorescence (TALIF) in an inductively coupled plasma discharge in pure Cl2. The atoms were excited by two photons at 235.702 nm to the state and detected by fluorescence to the (4s) 4P5/2 state at 726 nm. The population of this state relative to that in the ground state, was determined from the relative TALIF signal intensity from the two states, combined with new calculations of the two-photon absorption cross-sections. was found to increase continuously with radio-frequency power (50500 W), whereas with Cl2 pressure (590 mTorr) it passes through a maximum at 10 mTorr, reaching ~30% at 500 W. This maximum corresponds to the maximum of electron density in the discharge. Combining this density ratio measurement with previous measurements of the absolute ground state chlorine atom density [1] allows the absolute spin-orbit excited state density to be estimated. A significant fraction of the total chlorine atom density is in this excited state which should be included in plasma chemistry models

Absorption and transport of deuterium-substituted 2 R,4\u2032R,8\u2032R-\u3b1-tocopherol in human lipoproteins

Oral administration of a single dose of tri- or hexadeuterium substituted 2 R,4\u2032R,8\u2032R-\u3b1-tocopheryl acetate (d3- or d6-\u3b1-T-Ac) to humans was used to follow the absorption and transport of vitamin E in plasma lipoproteins. Three hr after oral administration of d3-\u3b1-T-Ac (15 mg) to 2 subjects, plasma levels of d3-\u3b1-T were detectable; these increased up to 10 hr, reached a plateau at 24 hr, then decreased. Following administration of d6-\u3b1-T-Ac (15-16 mg) to 2 subjects, the percentage of deuterated tocopherol relative to the total tocopherol in chylomicrons increased more rapidly than the corresponding percentage in whole plasma. Chylomicrons and plasma lipoproteins were isolated from 2 additional subjects following administration of d3-\u3b1-T-Ac (140 or 60 mg). The percentage of deuterated tocopherol relative to the total tocopherol increased most rapidly in chylomicrons, then in very low density lipoproteins (VLDL), followed by essentially identical increases in low and high density lipoproteins (LDL and HDL, respectively) and lastly, in the red blood cells. This pattern of appearance of deuterated tocopherol is consistent with the concept that newly absorbed vitamin E is secreted by the intestine into chylomicrons; subsequently, chylomicron remnants are taken up by the liver from which the vitamin E is secreted in VLDL. The metabolism of VLDL in the circulation results in the simultaneous delivery of vitamin E into LDL and HDL. \ua9 1988 American Oil Chemists' Society.Peer reviewed: YesNRC publication: Ye

On-line monitoring of microbial fuel cells operated with pulse-width modulated electrical load

This study describes application of an equivalent circuit model (ECM) for on-line monitoring of microbial fuel cells (MFCs). ECM analytical solutions were derived for MFCs operated with pulse-width modulated electrical load connection at high and low frequencies. These analytical solutions were used to develop an on-line procedure for estimating MFC internal resistance, internal capacitance and open circuit voltage. The proposed parameter estimation and monitoring procedure was used to follow MFC startup performance as well as its performance at various organic loads. A comparison of ESM-based on-line estimations with conventional polarization tests confirmed feasibility of the proposed approach.Peer reviewed: YesNRC publication: Ye

Numerical experiment to estimate the validity of negative ion diagnostic using photo-detachment combined with Langmuir probing

International audienceThis paper presents a critical assessment of the theory of photo-detachment diagnostic method used to probe the negative ion density and electronegativity α = n-/ne. In this method, a laser pulse is used to photo-detach all negative ions located within the electropositive channel (laser spot region). The negative ion density is estimated based on the assumption that the increase of the current collected by an electrostatic probe biased positively to the plasma is a result of only the creation of photo-detached electrons. In parallel, the background electron density and temperature are considered as constants during this diagnostics. While the numerical experiments performed here show that the background electron density and temperature increase due to the formation of an electrostatic potential barrier around the electropositive channel. The time scale of potential barrier rise is about 2 ns, which is comparable to the time required to completely photo-detach the negative ions in the electropositive channel (∼3 ns). We find that neglecting the effect of the potential barrier on the background plasma leads to an erroneous determination of the negative ion density. Moreover, the background electron velocity distribution function within the electropositive channel is not Maxwellian. This is due to the acceleration of these electrons through the electrostatic potential barrier. In this work, the validity of the photo-detachment diagnostic assumptions is questioned and our results illustrate the weakness of these assumptions