Surface-catalyzed recombination into excited electronic, vibrational, rotational, and kinetic energy states: A review

Laboratory experiments in which recombined CO, CO2, D2O, OH, N2, H2, and O2 molecules desorb from surfaces in excited internal and translational states are briefly reviewed. Unequilibrated distributions predominate from the principally catalytic metal substrates so far investigated. Mean kinetic energies have been observed up to approx. 3x, and in some cases less than, wall-thermal; the velocity distributions generally vary with emission angle, with non-Lambertian particle fluxes. The excitation state populations are found to depend on surface impurities, in an as yet unexplained way

Infrared emission from desorbed NO2(*) and NO(*)

Infrared photons from the radiative cascade accompany both the gas phase NO2 continuum chemiluminescence (which originates from its 2B2 and 2B1 states) and the NO beta bands. When these upper electronic states are excited by recombination/desorption at surfaces of low Earth orbiting spacecraft, similar IR emission spectrums will be observed. The principal NO2 features (other than the long wavelength tail of its electronic transitions) are the nu sub 3 fundamental sequence near 6.2 microns and nu sub 1 + nu sub 3 intercombination bands near 3.6 microns; NO would emit the delta v=1 and delta v=2 systems above 5.3 and 2.7 microns. Because of the long radiative lifetimes of the upper vibrational states, the infrared radiances in projections parallel to the vehicle surface (which we estimate) are substantially less than those of the visible and ultraviolet glows

The NO-NO2 system at laboratory surfaces

Experiments on formation and excitation of NO2 and NO molecules at (and near) laboratory surfaces of varying degrees of characterization are reviewed. On some transition metals NO is desorbed in the B sub 2 pi state, from which it radiates the familiar beta (B yields x) bands. In contrast while an ONO intermediate is inferred from isotope interchange measurements on platinum, neither ground state nor excited NO2 has been found to be desorbed under the relatively limited number of laboratory conditions so far investigated

Gaseous optical contamination of the spacecraft environment: A review

Interactions between the ambient atmosphere and orbiting spacecraft, sounding rockets, and suborbital vehicles, and with their effluents, give rise to optical (extreme UV to LWIR) foreground radiation which constitutes noise that raises the detection threshold for terrestrial and celestial radiations, as well as military targets. Researchers review the current information on the on-orbit optical contamination. Its source species are created in interaction processes that can be grouped into three categories: (1) Reactions in the gas phase between the ambient atmosphere and desorbates and exhaust; (2) Reactions catalyzed by exposed ram surfaces, which occur spontaneously even in the absence of active material releases from the vehicles; and (3) Erosive excitative reactions with exposed bulk (organic) materials, which have recently been identified in the laboratory though not as yet observed on spacecraft. Researchers also assess the effect of optical pumping by earthshine and sunlight of both reaction products and effluents

Photometric analysis of a space shuttle water venting

Presented here is a preliminary interpretation of a recent experiment conducted on Space Shuttle Discovery (Mission STS 29) in which a stream of liquid supply water was vented into space at twilight. The data consist of video images of the sunlight-scattering water/ice particle cloud that formed, taken by visible light-sensitive intensified cameras both onboard the spacecraft and at the AMOS ground station near the trajectory's nadir. This experiment was undertaken to study the phenomenology of water columns injected into the low-Earth orbital environment, and to provide information about the lifetime of ice particles that may recontact Space Shuttle orbits later. The findings about the composition of the cloud have relevance to ionospheric plasma depletion experiments and to the dynamics of the interaction of orbiting spacecraft with the environment

Fundamentos de la epidemiología genómica, lecciones aprendidas de la enfermedad por coronavirus (COVID-19) y nuevas direcciones

La pandemia de la enfermedad por coronavirus 2019 (COVID-19) fue una de las principales causas de muerte en todo el mundo en 2020. La enfermedad es causada por el coronavirus 2 (SARS-CoV-2), un virus de ARN de la subfamilia Orthocoronavirinae relacionado con otros 2 coronavirus clínicamente relevantes, SARS-CoV y MERS-CoV. Al igual que otros coronavirus y varios otros virus, el SARS-CoV-2 se originó en los murciélagos. Sin embargo, a diferencia de otros coronavirus, el SARS-CoV-2 resultó en una pandemia devastadora. La pandemia de SARS-CoV-2 continúa, debido a la evolución viral que conduce a variantes más transmisibles e inmunes evasivas. Tecnologías como la secuenciación genómica, ha impulsado el cambio de la epidemiología sindrómica a la molecular, y promete una mejor comprensión de las variantes. La pandemia de COVID-19 ha expuesto obstáculos críticos que deben abordarse para desarrollar la ciencia de las pandemias. Gran parte del progreso se está aplicando en el mundo desarrollado. Sin embargo, persisten las barreras para el uso de la epidemiología molecular en los países de ingresos bajos y medianos (LMIC), incluida la falta de logística para equipos y reactivos y la falta de capacitación en análisis. Revisamos la literatura de epidemiología molecular para comprender sus orígenes desde la epidemia de SARS (2002-2003) hasta los eventos de influenza y la pandemia actual de COVID-19. Abogamos por una mejor vigilancia genómica del SARS-CoV y por comprender la diversidad de patógenos en posibles huéspedes zoonóticos. Este trabajo requerirá capacitación en computación filogenética y de alto rendimiento para mejorar los análisis del origen y la propagación de patógenos. Los objetivos generales son comprender y reducir el riesgo de zoonosis a través de la colaboración interdisciplinaria y la reducción de las barreras logísticas

The Early Reception of Pliny the Younger in Tertullian of Carthage and Eusebius of Caesarea

In 1967 Alan Cameron published a landmark article in this journal, ‘The fate of Pliny's Letters in the late Empire’. Opposing the traditional thesis that the letters of Pliny the Younger were only rediscovered in the mid to late fifth century by Sidonius Apollinaris, Cameron proposed that closer attention be paid to the faint but clear traces of the letters in the third and fourth centuries. On the basis of well-observed intertextual correspondences, Cameron proposed that Pliny's letters were being read by the end of the fourth century at the latest. That article now seems the vanguard of a rise in scholarly interest in Pliny's late-antique reception. But Cameron also noted the explicit attention given to the letters by two earlier commentators—Tertullian of Carthage, in the late second to early third century, and Eusebius of Caesarea, in the early fourth. The use of Pliny in these two earliest commentators, in stark contrast to their later successors, has received almost no subsequent attention