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

Screening Out the SPAM: Using Suppressor Genetics to Identify Novel Effectors of Fertility

The biology and genetics of the nematode C. elegans makes it an attractive model organism for elucidating complex biological systems. For example, in many organisms the production of oocytes and sperm depends upon interactions between germline and somatic gonadal tissues. PAM-1, the C. elegans paralog of the human puromycin sensitive aminopeptidase, mediates a signaling pathway that participates in stimulating oocyte maturation. Mutations in pam-1 result in a reduced brood size and a dramatic increase in embryonic lethality. PAM-1 and its paralogs are conserved throughout eukaryota and participate in numerous signaling pathways. However, identification of the other components of these pathways has remained elusive. We have initiated a genetic suppressor screen to isolate and identify novel components of the PAM-1 signaling pathway. In several separate experiments, we have mutagenized over 90,000 nematode genomes and have screened the F2 generation of the mutagenized animals for alleles that suppress the pam-1 phenotype and result in a healthier and more fecund worm. From these screens we have isolated several suppressor alleles. Using classical genetic mapping techniques we have mapped one of these alleles, spam-1(akr1), to the right terminus of chromosome IV. We predict that these suppressor alleles represent novel genes in the pam-1 signaling pathway, and that identification of these suppressor alleles will provide some insight into the mechanisms that govern fertility in both C. elegans and humans

Genetic and Biochemical Analyses of Germ Cell Formation and Nuclear Division in Early Drosophila Embryos

Many genes in the fruit fly Drosophila show striking similarity to human genes. It is thus likely that understanding the cellular mechanisms in Drosophila will help to understand cellular processes in humans and may provide critical insight into the biological cause of human diseases. Our study focuses on the mechanisms of germ cell formation. In most organisms, germ cells are set aside from somatic cells early during development. Eventually primordial germ cells differentiate, form gonads, and become egg and sperm and thereby produce the next generation. Therefore, germ cells are the stem cells that give rise to a whole organism. To search for new genes directly involved in germ cell formation, we conducted a large mutant screen of the second chromosome\u27s right arm. As a result, we identified two alleles of a new gene involved in germline development. In addition, we isolated five alleles of another gene and showed that it acts in germ cell formation by properly distributing germ cell nuclei during their division and migration in early Drosophila embryos. Characterization of these new genes is underway and will be reported. Finally, we are in process of identifying metabolic energy-producing pathways that are mainly used for formation of germ cells. Understanding the mechanisms governing germ cell specification in Drosophila should contribute to our understanding of germline development in humans and may explain the origin of human germline disorders, namely germline cancers and infertility

Evolution of the Sibişel Shear Zone (South Carpathians): A study of its type locality near Răşinari (Romania) and tectonic implications

The Sibiel Shear Zone is a 1-3km wide, ductile shear zone located in the South Carpathian Mountains, Romania. In the Rsinari area, the ductile shear zone juxtaposes amphibolite facies rocks of the Lotru Metamorphic Suite against greenschist facies rocks of the Rauorul Cisndioarei Formation. The first represents the eroded remnants of Peri-Gondwanan arcs formed between the Neoproterozoic-Silurian (650-430Ma), regionally metamorphosed to amphibolite facies during the Variscan orogeny (350-320Ma). The second is composed of metasedimentary and metavolcanic Neoproterozoic-Ordovician (700-497Ma) assemblages of mafic to intermediate bulk composition also resembling an island arc metamorphosed during the Ordovician (prior to similar to 463Ma). Between these lie the epidote amphibolite facies mylonitic and ultramylonitic rocks of the Sibisel Formation, a tectonic melange dominated by mafic actinolite schists attenuated into a high strain ductile shear zone. Mineral Rb-Sr isochrons document the time of juxtaposition of the three domains during the Permian to Early Triassic (similar to 290-240Ma). Ductile shear sense indicators suggest a right lateral transpressive mechanism of juxtaposition; the Sibiel shear zone is a remnant Permo-Triassic suture between two Early Paleozoic Gondwanan terranes. A zircon and apatite U-Th/He age transect across the shear zone yields Alpine ages (54-90Ma apatite and 98-122Ma zircon); these data demonstrate that the exposed rocks were not subjected to Alpine ductile deformation. Our results have significant implications for the assembly of Gondwanan terranes and their docking to Baltica during Pangea's formation. Arc terranes free of Variscan metamorphism existed until the Early Triassic, emphasizing the complex tectonics of terrane amalgamation during the closure of Paleotethys.Romanian Executive Agency for Higher Education, Research, Development and Innovation [PN-II-ID-PCE-2011-3-0217, PN-II-ID-PCE-2011-3-0030]First published: 26 September 2016; 6 Month Embargo.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]

Phanerozoic amalgamation of the Alxa Block and North China Craton: Evidence from Paleozoic granitoids, U-Pb geochronology and Sr-Nd-Pb-Hf-O isotope geochemistry

The North China Craton (NCC) has been considered to be part of the supercontinent Columbia. The nature of the NCC western boundary, however, remains strongly disputed. A key question in this regard is whether or not the Alxa Block is a part of the NCC. It is located in the vicinity of the inferred boundary, and therefore could potentially resolve the issue of the NCC's relationship to the Columbia supercontinent. Some previous studies based on the Alxa Block's geological evolution and detrital zircon ages suggested that it is likely not a part of the NCC. The lack of evidence from key igneous rock units, however, requires further constraints on the tectonic affinity of the western NCC and Alxa Block and on the timing of their amalgamation.The North China Craton (NCC) has been considered to be part of the supercontinent Columbia. The nature of the NCC western boundary, however, remains strongly disputed. A key question in this regard is whether or not the Alxa Block is a part of the NCC. It is located in the vicinity of the inferred boundary, and therefore could potentially resolve the issue of the NCC's relationship to the Columbia supercontinent. Some previous studies based on the Alxa Block's geological evolution and detrital zircon ages suggested that it is likely not a part of the NCC. The lack of evidence from key igneous rock units, however, requires further constraints on the tectonic affinity of the western NCC and Alxa Block and on the timing of their amalgamation.The differences in whole rock Nd model ages and Pb isotope compositions of the Paleoproterozoic–Permian rocks in either side of the west fault of the Bayanwulashan–Diebusige complexes suggest that the Alxa Block is not a part of the NCC, and that the western boundary of the NCC is probably located on this fault. Furthermore, the linear distribution of the Early Paleozoic–Early Carboniferous granitoids, the high zircon δ18O values of the Late Silurian quartz diorites, the Early Devonian metamorphism and the foreland basin system formed during the collision between the Alxa Block and the NCC indicate that a Paleozoic cryptic suture zone likely existed in this area and records the amalgamation of the Alxa Block and North China Craton. Together with detrital zircon data, the initial collision was considered to have possibly occurred in Late Ordovician