A Study of Polycyclic Aromatic Hydrocarbons During Combustion in an AFBC System

The purpose of this study was to develop the on-line method of analysis which leads to the study of polycyclic aromatic hydrocarbons (PAHs) during combustion in an atmospheric fluidized bed combustor (AFBC) system. The study of PAHs is important because they may be produced upon the combustion of coal. The US EPA prioritizes PAHs as major pollutants due to their mutagenic and carcinogenic effects. Standards of PAHs were analyzed by injection into the gas chromatograph-mass spectrometer (GC-MS). These standards were then analyzed using the on-line method. Two coals were burned in the AFBC system and effluent samples were collected. These were analyzed with the GC-MS to see if there were any PAHs or chlorobenzenes present

The Science Performance of JWST as Characterized in Commissioning

This paper characterizes the actual science performance of the James Webb Space Telescope (JWST), as determined from the six month commissioning period. We summarize the performance of the spacecraft, telescope, science instruments, and ground system, with an emphasis on differences from pre-launch expectations. Commissioning has made clear that JWST is fully capable of achieving the discoveries for which it was built. Moreover, almost across the board, the science performance of JWST is better than expected; in most cases, JWST will go deeper faster than expected. The telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies.Comment: 5th version as accepted to PASP; 31 pages, 18 figures; https://iopscience.iop.org/article/10.1088/1538-3873/acb29

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

Time series observations with the mid-infrared instrument (MIRI) on JWST

Time-variable phenomena such as transiting exoplanets will be a major science theme for the James Webb Space Telescope (JWST). For Guaranteed Time and Early Release Science Observations, over 500 hours of JWST time have been allocated to time series observations (TSOs) of transiting exoplanets. Several dedicated observing modes are available in the instrument suite, whose operations are specifically tailored to these challenging observations. MIRI, the only JWST instrument covering the wavelength range longwards of 5 mu m on JWST, will offer TSOs in two of its modes: the low resolution spectrometer, and the imager. In this paper we will describe these modes for MIRI, and discuss how they differ operationally from regular (non-TSO) observations. We will show performance estimates based on ground testing and modeling, discuss the most relevant detector effects for high precision (spectro-)photometry, and provide some guidelines for planning MIRI TSOs.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Evolutionary remodelling of N-terminal domain loops fine-tunes SARS-CoV-2 spike

The emergence of SARS-CoV-2 variants has exacerbated the COVID-19 global health crisis. Thus far, all variants carry mutations in the spike glycoprotein, which is a critical determinant of viral transmission being responsible for attachment, receptor engagement and membrane fusion, and an important target of immunity. Variants frequently bear truncations of flexible loops in the N-terminal domain (NTD) of spike; the functional importance of these modifications has remained poorly characterised. We demonstrate that NTD deletions are important for efficient entry by the Alpha and Omicron variants and that this correlates with spike stability. Phylogenetic analysis reveals extensive NTD loop length polymorphisms across the sarbecoviruses, setting an evolutionary precedent for loop remodelling. Guided by these analyses, we demonstrate that variations in NTD loop length, alone, are sufficient to modulate virus entry. We propose that variations in NTD loop length act to fine-tune spike; this may provide a mechanism for SARS-CoV-2 to navigate a complex selection landscape encompassing optimisation of essential functionality, immune driven antigenic variation and ongoing adaptation to a new host