Thermal infrared data analyses of Meteor Crater, Arizona: Implications for Mars spaceborne data from the Thermal Emission Imaging System

Thermal infrared (TIR) data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument are used to identify the lithologic distribution of the Meteor Crater ejecta blanket and nearby (within ~3 km) region. This has many applications to the analysis of data from the Thermal Emission Imaging System (THEMIS) instrument that is currently in orbit at Mars. ASTER and THEMIS, whereas orbiting different planets, have similar spatial and spectral resolutions. THEMIS represents the highest spatial resolution (100 m) to date of the Martian surface, thereby allowing small (~ 1km) impact craters to be studied in detail for the first time. Meteor Crater serves as an analog for the many similar-sized impact sites on the surface of Mars. These sites are future research targets with THEMIS, and ASTER data of Meteor Crater provides ideal data and geologic landscape in preparation for future THEMIS investigations. Fieldwork at Meteor Crater yielded sample collection of the primary lithologies and an opportunity to validate previously-collected high-resolution (3.2 m), airborne Thermal Imaging Multispectral Scanner (TIMS) data. Laboratory thermal emission spectra were obtained for the samples collected. Deconvolution of ASTER TIR emissivity data were performed with image end-members and sample end-members. Comparisons of the spaceborne data to high-resolution airborne TIMS data were used to assess the validity of the ASTER end-member analyses. The ASTER image end-member analysis agreed well with the earlier TIMS end-member analysis where the effects of resolution degradation were accounted for. Laboratory spectra and mineral spectral libraries provided poor fits of deconvolution of multispectral TIR data. Lithologies with similar spectral signatures or with low areal abundances were difficult to identify.Using the same methodology as that applied to the ASTER TIR data of Meteor Crater, THEMIS TIR data of a small (~ 1 km) impact crater in Syrtis Major were analyzed. The crater's rim and ejecta blanket was found to contain larger particle sizes than the surrounding (ejecta-free) plain, indicating a young (fresh) impact age and little or no accumulation of dust. The composition of the rim, ejecta, and surrounding plain was determined to be basaltic. It is hoped that the work performed here will complement future investigations of fresh impact sites with THEMIS data that may be used to solve geologic questions such as 1.) the composition of ejecta blocks that represent pre-impact, underlying stratigraphy in high-albedo, dust-covered regions of Mars, 2.) the approximate age of impact, and 3.) regolith/dust thickness, which appears to be a factor of #2

Reductive coupling reactions of organosilanes for the monoselective C–F functionalization of trifluoromethylarenes

2022 Summer.Includes bibliographical references.The mono-selective defluorofunctionalization of trifluoromethylarenes is an emerging strategy to access ⍺,⍺-difluorobenzylic derivatives, which are difficult to access in a divergent manner. Fluorine incorporation is a common strategy employed during the optimization of potential pharmaceuticals in the drug discovery process. Much effort has been spent over the past few decades in developing fluorination methodologies, and the result has been tremendous growth in aryl and alkyl fluorination and trifluoromethylation reactions. On the other hand, methods to install other fluoroalkyl motifs are less developed. Due to the abundant availability of trifluoromethylarenes, mono-selective defluorofunctionalization reactions would be an ideal route to access ⍺,⍺-difluorobenzylic derivatives, which are becoming increasing examined in drug discovery settings. Chapter one will provide the necessary background to understand the context of the work described throughout the following chapters. First, there will be an overview of the importance of fluorine for the development of pharmaceutical compounds. Then there will be a brief summary of the different strategies that have been developed to achieve the trifluoromethylation of arenes as well as the common routes to access ⍺,⍺-difluorobenzylic compounds. Finally, a thorough discussion of the challenges and reported solutions to achieve mono-selective defluorofunctionalization of trifluoromethylarenes will be provided. Chapter two will describe the initial discovery, development, and mechanistic investigation of the defluoroallylation reaction reported by the Bandar group. This discovery led to the identification of a new strategy to achieve reductive coupling through the use of Lewis base activated organosilanes, which provides the basis for the reactions discovered and developed in chapters three and four. Chapter three will describe the discovery, development, and mechanistic investigation of a reductive coupling reaction of trifluoromethylarenes with formamides. This reaction generates a silylated hemiaminal product which is a valuable synthetic intermediate to access a broad scope of ⍺,⍺-difluorobenzylic derivatives. Mechanistic investigations support the generation of a ⍺,⍺-difluorobenzylsilane intermediate in the reaction. Isolated of the ⍺,⍺-difluorobenzylsilane and subsequent derivatizations further broaden the scope of transformations accessible via this reductive coupling process. Chapter four will describe the discovery and preliminary development of the mono-selective hydrodefluorination of trifluoromethylarenes using hydrosilanes activated by a Lewis basic catalyst. Two different catalytic systems are demonstrated that operate via different mechanisms, which provides access to different reaction scopes. A short discussion on the future work of this project will also be provided, where a junior graduate student is developing conditions to enable the mono-selective hydrodefluorination of electron-neutral trifluoromethylarenes

Fall Broccoli Cultivar Trial 2012-2013

This is a compilation of 30 research trial reports from four land-grant universities in the Midwestern United States. Crops include cantaloupe, pickling cucumber, pepper, potato, pumpkin, summer squash and zucchini, sweet corn, tomato, and watermelon. Somecrops were evaluated in high tunnels or hoophouses. Most trials evaluated different cultivars or varieties. One report addressed plant spacing for sweet corn and one addressed soil block for production of tomato seedlings. A list of vegetable seed sources and a list of other online sources of vegetable trial reports are also included

Soybean Canopy Gap Influence on Velvetleaf Seed Production

Gaps in the soybean row provide locations for velvetleaf (Abutilon theophrasti) plant growth. Gap width, and velvetleaf plant location within the gap, were investigated for effect on seed production. There was no significant difference in velvetleaf capsule production between plants that grew either centered in a gap or at the western end of a gap in east-west oriented soybean rows. Also, there was no difference in plant survival, emergence through the soybean canopy, flowering, locule number per capsule, or average seed weight of velvetleaf based on gap width. However, there was a difference in capsule production based on gap width. In 1999, seed capsule production increased from approximately 35 capsules plant-1 at 0 cm gap width to 140 capsules plant-1 in the 90 cm gap. In 2000, seed capsule production increased from approximately 9 capsules plant-1 at 0 cm gap width to 98 capsules plant-1 in the 90 cm gap. Seed production ranged from an estimate of 300 to 5900 seeds plant-1. As gap width in the soybean row increases, it becomes more important to monitor and control velvetleaf growth. It is even possible, however, to have significant velvetleaf seed production from plants that emerge in a 30 cm gap in the row

Banner News

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