Radio-frequency plasma potential variations originating from capacitive coupling from the coil antenna in inductively coupled plasmas

Includes bibliographical references (page 3434).The radio-frequency plasma potential in a stove top inductively coupled plasma source is measured by a capacitive probe. The experimental results are compared to a crude circuit model which accounts for capacitive coupling between the rf coil and the bulk plasma. The capacitive coupling model has three terms: the dielectric window capacitance, the sheath capacitance between the dielectric window and the bulk plasma, and the bulk plasma to ground sheath capacitance. The crude circuit model predictions are verified by quantitative comparison with the measured rf plasma potential in the bulk argon plasma at pressures from 1 to 20 mTorr and radio-frequency (13.56MHz) plasma power levels from 60 to 1000 W. Finally, the measured ion energy spectrum, as determined by a retarding potential analyzer, agrees with rf plasma potential measurements over the entire range of experimental conditions

Molecular Hydrogen and [FeII] in Active Galactic Nuclei

(Abridge) Near-infrared spectroscopy is used to study the kinematics and excitation mechanisms of the H2 and [FeII] gas in a sample of AGN. The H2 lines are unresolved in all objects in which they were detected while the [FeII] lines have widths implying gas velocities of up to 650 km/s. This suggests that, very likely, the H2 and [FeII] emission does not originate from the same parcel of gas. Molecular H2 were detected in 90% of the sample, including PG objects, indicating detectavel amounts of molecular material even in objects with low levels of circumnuclear starburst activity. The data favors thermal excitation for the H2 lines. Indeed, in NGC3227, Mrk766, NGC4051 and NGC4151, the molecular emission is found to be purely thermal. This result is also confirmed by the rather similar vibrational and rotational temperatures in the objects for which they were derived. [FeII] lines are detected in all of the AGN. The [FeII] 1.254mu/Pa-beta ratio is compatible with excitation of the [FeII] by the active nucleus, but in Mrk 766 it implies a stellar origin. A correlation between H2/Br-gamma and [FeII]/Pa-beta is found. We confirm that it is a useful diagnostic tool in the NIR to separate emitting line objects by their level of nuclear activity. X-ray excitation models are able to explain the observed H2 and part of the [FeII] emission. Most likely, a combination of X-ray heating, shocks driven by the radio jet, and circumnuclear star formation contributes, in different proportions, to the H2 and [FeII] emission. In most of our spectra, the [FeII] 1.257mu/1.644mu ratio is found to be 30% lower than the intrinsic value based on current atomic data. This implies either than the extinction towards the [FeII] emitting clouds is very similar in most objects or there are possible inaccuracies in the A-values in the [FeII] transitions.Comment: 18 pages, 6 figures, Accepted for publication in Astronomy & Astrophysic

Supports to Improve Academic Outcomes With Racially and Ethnically Minoritized Youth: A Review of Research

For decades, racially and ethnically minoritized youth have been subject to unequal distributions of access and opportunity in school, leading to inequities in academic outcomes. Educators require knowledge and skills to provide relevant instruction and create a more supportive, effective classroom environment. This systematic review includes 24 qualitative and quantitative studies in which researchers investigated a culturally responsive classroom intervention or practice to promote academic outcomes for racially and ethnically minoritized youth. Within these studies, authors described several approaches to promote academic success: (a) developing authentic partnerships with families, (b) using effective pedagogy with students’ culture infused, and (c) accessing rigorous professional development. In addition, studies were assessed for methodological quality, and qualitative works met design standards more often than the quantitative studies reviewed. Implications include the need for additional research to inform comprehensive support for educators to design effective instructional environments for all students, especially those who have historically encountered systemic barriers in school