20 research outputs found
Solstice PF Spray Cleaner (Aerosol) for Cleaning of LOX/GOX Components
No abstract availabl
The Origins of a Rich Absorption Line Complex in a Quasar at Redshift 3.45
We discuss the nature and origin of a rich complex of narrow absorption lines
in the quasar J102325.31+514251.0 at redshift 3.447. We measure nine C
IV(\lambda1548,1551) absorption line systems with velocities from -1400 to
-6200 km/s, and full widths at half minimum ranging from 16 to 350 km/s. We
also detect other absorption lines in these systems, including H I, C III, N V,
O VI, and Si IV. Lower ionisation lines are not present, indicating a generally
high degree of ionisation in all nine systems. The total hydrogen column
densities range from <=10^{17.2} to 10^{19.1}cm^{-2}. We examine several
diagnostics to estimate more directly the location and origin of each absorber.
Four of the systems can be attributed to a quasar-driven outflow based on line
profiles that are smooth and broad compared to thermal line widths. Several
systems also have other indicators of a quasar outflow origin, including
partial covering. Altogether there is direct evidence for 6 of the 9 systems
forming in a quasar outflow. Consistent with a near-quasar origin, eight of the
systems have metallicity values or lower limits in the range Z >= 1-8 Z_{sun}.
The lowest velocity system, which has an ambiguous location, also has the
lowest metallicity, Z <= 0.3 Z_{sun}, and might form in a non-outflow
environment farther from the quasar. Overall, however, this complex of narrow
absorption lines can be identified with a highly structured, multi-component
outflow from the quasar. The high metallicities are similar to those derived
for other quasars at similar redshifts and luminosities, and are consistent
with evolution scenarios wherein quasars appear after the main episodes of star
formation and metal enrichment in the host galaxies.Comment: 16 pages, 12 figures, Accepted to MNRAS, July 201
Metallicity and Far-Infrared Luminosity of High Redshift Quasars
We present the results of an exploratory study of broad line region (BLR)
metallicity in 34 2.2 < z < 4.6 quasars with far-infrared (FIR) luminosities
(L_FIR) from 10^13.4 to 10^12.1 L_\odot . Quasar samples sorted by L_FIR might
represent an evolutionary sequence if the star formation rates (SFRs) in quasar
hosts generally diminish across quasar lifetimes. We use rest-frame ultraviolet
spectra from the Sloan Digital Sky Survey to construct three composite spectra
sorted by L_FIR, corresponding to average SFRs of 4980, 2130 and 340 M_\odot
yr^-1 after correcting for a nominal quasar FIR contribution. The measured N V
{\lambda} 1240/C IV {\lambda} 1550 and Si IV {\lambda} 1397+O IV] {\lambda}
1402/C IV {\lambda} 1550 emission line ratios indicate super-solar BLR
metallicities in all three composites, with no evidence for a trend with the
star formation rate. The formal derived metallicities, Z ~ 5-9 Z_\odot , are
similar to those derived for the BLRs of other quasars at similar redshifts and
luminosities. These results suggest that the ongoing star formation in the host
is not responsible for the metal enrichment of the BLR gas. Instead, the BLR
gas must have been enriched before the visible quasar phase. These results for
high quasar metallicities, regardless of L_FIR, are consistent with evolution
scenarios wherein visibly bright quasars appear after the main episode(s) of
star formation and metal enrichment in the host galaxies. Finally, young
quasars, those more closely associated with a recent merger or a blowout of gas
and dust, may exhibit tracers of these events, such as redder continuum slopes
and higher incidence of narrow absorption lines. With the caveat of small
sample sizes, we find no relation between L_FIR and the reddening or the
incidence of absorption lines.Comment: 10 pages, 3 figures. Accepted to MNRAS, May 201
Diel activity patterns of two distinct populations of Aedes aegypti in Miami, FL and Brownsville, TX
The diel biting activity of Aedes (Stegomyia) aegypti (L) populations was extensively investigated in the early 1900s to gain more information on the biology of Ae. aegypti, and this information was used to devise effective approaches to controlling populations of this species and protect the human population from widespread arbovirus outbreaks. However, few contemporary studies are available regarding the diel activity patterns of Ae. aegypti. To assess the diel activity patterns of Ae. aegypti in southern Florida and Texas, we conducted 96-h uninterrupted mosquito collections once each month from May through November 2019 in Miami, Florida, and Brownsville, Texas, using BG-Sentinel 2 Traps. The overall diel activity pattern in both cities was bimodal with morning and evening peak activity between 7:00 and 8:00 and between 19:00 and 20:00. There were significant daily, monthly, seasonal, and site-specific differences in activity patterns, but these differences did not affect the overall peak activity times. These differences suggest daily, monthly, seasonal, and site-specific variations in human exposure to Ae. aegypti. Our observations can be used in planning and executing Ae. aegypti vector control activities in southern Florida and southern Texas, specifically those targeting the adult mosquito populations
Development and Flammability Testing of Magnesium Alloys for Space Applications
This project will be comparing the flammability of select lightweight Mg alloys for use in a simulated ISS environment. It will also be determining the factors that influence flammability of selected alloys in elevated oxygen, including the formation of an oxide layer. The significance of this work is that such alloys can reduce weight saving by up to 30%. This work is adding to knowledge base of lightweight Mg alloys for possible future applications, as no previous flammability testing of Mg alloys have been conducted at elevated oxygen concentrations
PENSAMIENTO CRÍTICO EN LA INVESTIGACIÓN CIENTÍFICA Y ACADÉMICA COLECCIÓN CIENTÍFICA EDUCACIÓN, EMPRESA Y SOCIEDAD
PENSAMIENTO CRÍTICO EN LA INVESTIGACIÓN CIENTÍFICA Y ACADÉMICA COLECCIÓN CIENTÍFICA EDUCACIÓN, EMPRESA Y SOCIEDAD Primera Edición 2023 Vol. 21 Editorial EIDEC Sello Editorial EIDEC (978-958-53018) NIT 900583173-1 ISBN: 978-628-95884-1-5 Formato: Digital PDF (Portable Document Format) DOI: https://doi.org/10.34893/e1150-3660-8721-s Publicación: Colombia Fecha Publicación: 13/09/2023 Coordinación Editorial Escuela Internacional de Negocios y Desarrollo Empresarial de Colombia – EIDEC Centro de Investigación Científica, Empresarial y Tecnológica de Colombia – CEINCET Red de Investigación en Educación, Empresa y Sociedad – REDIEES Revisión y pares evaluadores Centro de Investigación Científica, Empresarial y Tecnológica de Colombia – CEINCET Red de Investigación en Educación, Empresa y Sociedad – REDIEE
God of Compassion
1982/02/17. Share their experiences of working with refugees both in the U.S. and in other parts of the world. Director of Refugee and Relief Service, World Concern. Attorney for Salvadorian refugees