3,024 research outputs found
Astromaterials Curation Online Resources for Principal Investigators
The Astromaterials Acquisition and Curation office at NASA Johnson Space Center curates all of NASA's extraterrestrial samples, the most extensive set of astromaterials samples available to the research community worldwide. The office allocates ~1500 individual samples to researchers and students each year and has served the planetary research community for 45+ years. The Astromaterials Curation office provides access to its sample data repository and digital resources to support the research needs of sample investigators and to aid in the selection and request of samples for scientific study. These resources can be found on the Astromaterials Acquisition and Curation website at https://curator.jsc.nasa.gov. To better serve our users, we have engaged in several activities to enhance the data available for astromaterials samples, to improve the accessibility and performance of the website, and to address user feedback. We havealso put plans in place for continuing improvements to our existing data products
Ancient metabolisms of a thermophilic subseafloor bacterium
© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Smith, A. R., Mueller, R., Fisk, M. R., & Colwell, F. S. Ancient metabolisms of a thermophilic subseafloor bacterium. Frontiers in Microbiology, 12, (2021): 764631, https://doi.org/10.3389/fmicb.2021.764631.The ancient origins of metabolism may be rooted deep in oceanic crust, and these early metabolisms may have persisted in the habitable thermal anoxic aquifer where conditions remain similar to those when they first appeared. The WoodâLjungdahl pathway for acetogenesis is a key early biosynthetic pathway with the potential to influence ocean chemistry and productivity, but its contemporary role in oceanic crust is not well established. Here, we describe the genome of a novel acetogen from a thermal suboceanic aquifer olivine biofilm in the basaltic crust of the Juan de Fuca Ridge (JdFR) whose genome suggests it may utilize an ancient chemosynthetic lifestyle. This organism encodes the genes for the complete canonical WoodâLjungdahl pathway, but is potentially unable to use sulfate and certain organic carbon sources such as lipids and carbohydrates to supplement its energy requirements, unlike other known acetogens. Instead, this organism may use peptides and amino acids for energy or as organic carbon sources. Additionally, genes involved in surface adhesion, the import of metallic cations found in Fe-bearing minerals, and use of molecular hydrogen, a product of serpentinization reactions between water and olivine, are prevalent within the genome. These adaptations are likely a reflection of local environmental micro-niches, where cells are adapted to life in biofilms using ancient chemosynthetic metabolisms dependent on H2 and iron minerals. Since this organism is phylogenetically distinct from a related acetogenic group of Clostridiales, we propose it as a new species, Candidatus Acetocimmeria pyornia.Metagenome sequencing was made possible by the Deep Carbon Observatory Census of Deep Life supported by the Alfred P. Sloan Foundation and was performed at the Marine Biological Laboratory (Woods Hole, MA, United States). This work was funded by NASA grant NNX08AO22G and a graduate fellowship from the NSF Center for Dark Energy Biosphere Investigations. The flow cells were funded under J0972A from the U.S. Science Support Program of Joint Oceanographic Institutions
Using Design Interventions to Develop Communication Solutions for Integrated Pest Management
Iowa State Universityâs (ISU) Integrated Pest Management (IPM) program partnered with the ISU College of Design (COD) to use Design Thinking and other practical design methodologies and theories to identify and develop approaches to address IPM extension and communication issues. ISU IPM met with agriculture industry, program colleagues, and ISU COD faculty to discuss IPM-related needs in agriculture and to determine the programâs primary challenges. ISU COD faculty developed a two-semester course for undergraduate students, allocating various resources to solve these challenges. Undergraduates in the course, as the primary agents and problem solvers, developed various strategies the IPM program and its colleagues could implement. A model of interdisciplinary collaboration was developed, where design and science may function as equal partners in a design education setting. In our collaboration, the partners bought into a design-led process-based methodology that began with identifying IPM communication needs. This project resulted in unique design interventions to communicate IPM to stakeholders and the public, as well as created a model for interdisciplinary cooperation that can be exported to fields outside of agriculture and IPM
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Distributions of Extracellular Peptidases Across Prokaryotic Genomes Reflect Phylogeny and Habitat
Proteinaceous compounds are abundant forms of organic nitrogen in soil and aquatic ecosystems, and the rate of protein depolymerization, which is accomplished by a diverse range of microbial secreted peptidases, often limits nitrogen turnover in the environment. To determine if the distribution of secreted peptidases reflects the ecological and evolutionary histories of different taxa, we analyzed their distribution across prokaryotic lineages. Peptidase gene sequences of 147 archaeal and 2,191 bacterial genomes from the MEROPS database were screened for secretion signals, resulting in 55,072 secreted peptidases belonging to 148 peptidase families. These data, along with their corresponding 16S rRNA sequences, were used in our analysis. Overall, Bacteria had a much wider collection of secreted peptidases, higher average numbers of secreted peptidases per genome, and more unique peptidase families than Archaea. We found that the distribution of secreted peptidases corresponded to phylogenetic relationships among Bacteria and Archaea and often segregated according to microbial lifestyles, suggesting that the secreted peptidase complements of microbial taxa are optimized for the environmental microhabitats they occupy. Our analyses provide the groundwork for examining the specific functional role of families of secreted peptidases in relationship to the organisms and the corresponding environments in which they function
Kantowski-Sachs String Cosmologies
We present new exact solutions of the low-energy-effective-action string
equations with both dilaton and axion fields non-zero. The
background universe is of Kantowski-Sachs type. We consider the possibility of
a pseudoscalar axion field () that can be either time or
space dependent. The case of time-dependent reduces to that of a stiff
perfect-fluid cosmology. For space-dependent there is just one non-zero
time-space-space component of the axion field , and this corresponds to a
distinguished direction in space which prevents the models from isotropising.
Also, in the latter case, both the axion field and its tensor potential
() are dependent on time and space yet the energy-momentum tensor remains
time-dependent as required by the homogeneity of the cosmological model.Comment: 23 pages, REVTEX, 6 figures available on reques
Absence of Persistent Magnetic Oscillations in Type-II Superconductors
We report on a numerical study intended to examine the possibility that
magnetic oscillations persist in type II superconductors beyond the point where
the pairing self-energy exceeds the normal state Landau level separation. Our
work is based on the self-consistent numerical solution for model
superconductors of the Bogoliubov-deGennes equations for the vortex lattice
state. In the regime where the pairing self-energy is smaller than the
cyclotron energy, magnetic oscillations resulting from Landau level
quantization are suppressed by the broadening of quasiparticle Landau levels
due to the non-uniform order parameter of the vortex lattice state, and by
splittings of the quasiparticle bands. Plausible arguments that the latter
effect can lead to a sign change of the fundamental harmonic of the magnetic
oscillations when the pairing self-energy is comparable to the cyclotron energy
are shown to be flawed. Our calculations indicate that magnetic oscillations
are strongly suppressed once the pairing self-energy exceeds the Landau level
separation.Comment: 7 pages, revtex, 7 postscript figure
The influence of collective neutrino oscillations on a supernova r-process
Recently, it has been demonstrated that neutrinos in a supernova oscillate
collectively. This process occurs much deeper than the conventional
matter-induced MSW effect and hence may have an impact on nucleosynthesis. In
this paper we explore the effects of collective neutrino oscillations on the
r-process, using representative late-time neutrino spectra and outflow models.
We find that accurate modeling of the collective oscillations is essential for
this analysis. As an illustration, the often-used "single-angle" approximation
makes grossly inaccurate predictions for the yields in our setup. With the
proper multiangle treatment, the effect of the oscillations is found to be less
dramatic, but still significant. Since the oscillation patterns are sensitive
to the details of the emitted fluxes and the sign of the neutrino mass
hierarchy, so are the r-process yields. The magnitude of the effect also
depends sensitively on the astrophysical conditions - in particular on the
interplay between the time when nuclei begin to exist in significant numbers
and the time when the collective oscillation begins. A more definitive
understanding of the astrophysical conditions, and accurate modeling of the
collective oscillations for those conditions, is necessary.Comment: 27 pages, 10 figure
Reshuffling the OPE: Delocalized Operator Expansion
A generalization of the operator product expansion for Euclidean correlators
of gauge invariant QCD currents is presented. Each contribution to the modified
expansion, which is based on a delocalized multipole expansion of a
perturbatively determined coefficient function, sums up an infinite series of
local operators. On a more formal level the delocalized operator expansion
corresponds to an optimal choice of basis sets in the dual spaces which are
associated with the interplay of perturbative and nonperturbative N-point
correlations in a distorted vacuum. A consequence of the delocalized expansion
is the running of condensates with the external momentum. Phenomenological
evidence is gathered that the gluon condensate, often being the leading
nonperturbative parameter in the OPE, is indeed a function of resolution.
Within a model calculation of the nonperturbative corrections to the ground
state energy of a heavy quarkonium system it is shown exemplarily that the
convergence properties are better than those of the OPE. Potential applications
of the delocalized operator expansion in view of estimates of the violation of
local quark-hadron duality are discussed.Comment: Talk given at conference Continuous advances in QCD 2002 /
Arkadyfest, Minneapolis; 16 pages, 4 figure
Familial Alzheimer's Disease Mutations in PSEN1 Lead to Premature Human Stem Cell Neurogenesis
Mutations in presenilin 1 (PSEN1) or presenilin 2 (PSEN2), the catalytic subunit of Îł-secretase, cause familial Alzheimerâs disease (fAD). We hypothesized that mutations in PSEN1 reduce Notch signaling and alter neurogenesis. Expression data from developmental and adult neurogenesis show relative enrichment of Notch and Îł-secretase expression in stem cells, whereas expression of APP and ÎČ-secretase is enriched in neurons. We observe premature neurogenesis in fAD iPSCs harboring PSEN1 mutations using two orthogonal systems: cortical differentiation in 2D and cerebral organoid generation in 3D. This is partly driven by reduced Notch signaling. We extend these studies to adult hippocampal neurogenesis in mutation-confirmed postmortem tissue. fAD cases show mutation-specific effects and a trend toward reduced abundance of newborn neurons, supporting a premature aging phenotype. Altogether, these results support altered neurogenesis as a result of fAD mutations and suggest that neural stem cell biology is affected in aging and disease
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Chloroflexi CL500-11 Populations That Predominate Deep-Lake Hypolimnion Bacterioplankton Rely on Nitrogen-Rich Dissolved Organic Matter Metabolism and Câ Compound Oxidation
The Chloroflexi CL500-11 clade contributes a large proportion of the bacterial biomass in the oxygenated hypolimnia of deep lakes worldwide, including the world's largest freshwater system, the Laurentian Great Lakes. Traits that allow CL500-11 to thrive and its biogeochemical role in these environments are currently unknown. Here, we found that a CL500-11 population was present mostly in offshore waters along a transect in ultraoligotrophic Lake Michigan (a Laurentian Great Lake). It occurred throughout the water column in spring and only in the hypolimnion during summer stratification, contributing up to 18.1% of all cells. Genome reconstruction from metagenomic data suggested an aerobic, motile, heterotrophic lifestyle, with additional energy being gained through carboxidovory and methylovory. Comparisons to other available streamlined freshwater genomes revealed that the CL500-11 genome contained a disproportionate number of cell wall/capsule biosynthesis genes and the most diverse spectrum of genes involved in the uptake of dissolved organic matter (DOM) substrates, particularly peptides. In situ expression patterns indicated the importance of DOM uptake and protein/peptide turnover, as well as type I and type II carbon monoxide dehydrogenase and flagellar motility. Its location in the water column influenced its gene expression patterns the most. We observed increased bacteriorhodopsin gene expression and a response to oxidative stress in surface waters compared to its response in deep waters. While CL500-11 carries multiple adaptations to an oligotrophic lifestyle, its investment in motility, its large cell size, and its distribution in both oligotrophic and mesotrophic lakes indicate its ability to thrive under conditions where resources are more plentiful. Our data indicate that CL500-11 plays an important role in nitrogen-rich DOM mineralization in the extensive deep-lake hypolimnion habitat
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