3,909 research outputs found
Cognition and Economic Outcomes in the Health and Retirement Survey
Dimensions of cognitive skills are potentially important but often neglected determinants of the central economic outcomes that shape overall well-being over the life course. There exists enormous variation among households in their rates of wealth accumulation, their holdings of financial assets, and the relative risk in their chosen asset portfolios that have proven difficult to explain by conventional demographic factors, the amount of bequests they receive or anticipating giving, and the level of economic resources of the household. These may be cognitively demanding decisions at any age but especially so at older ages. This research examines the association of cognitive skills with wealth, wealth growth, and wealth composition for people in their pre and post-retirement years.
Ariel - Volume 4 Number 2
Editors
David A. Jacoby
Eugenia Miller
Tom Williams
Associate Editors
Paul Bialas
Terry Burt
Michael Leo
Gail Tenikat
Editor Emeritus and Business Manager
Richard J. Bonnano
Movie Editor
Robert Breckenridge
Staff
Richard Blutstein
Mary F. Buechler
Steve Glinks
Len Grasman
Alice M. Johnson
J. D. Kanofsky
Tom Lehman
Dave Mayer
Bernie Odd
Structural characteristics of positionally-disordered lattices: relation to the first sharp diffraction peak in glasses
Positional disorder has been introduced into the atomic structure of certain
crystalline lattices, and the orientationally-averaged structure factor S(k)
and pair-correlation function g(r) of these disordered lattices have been
studied. Analytical expressions for S(k) and g(r) for Gaussian positional
disorder in 2D and 3D are confirmed with precise numerical simulations. These
analytic results also have a bearing on the unsolved Gauss circle problem in
mathematics. As the positional disorder increases, high-k peaks in S(k) are
destroyed first, eventually leaving a single peak, that with the lowest-k
value. The pair-correlation function for lattices with such high levels of
positional disorder exhibits damped oscillations, with a period equal to the
separation between the furthest-separated (lowest-k) lattice planes. The last
surviving peak in S(k) is, for example for silicon and silica, at a wavevector
nearly identical to that of the experimentally-observed first sharp diffraction
peak (FSDP) in the amorphous phases of those materials. Thus, for these
amorphous materials at least, the FSDP can be regarded as arising from
scattering from atomic configurations equivalent to the single family of
positionally-disordered local Bragg planes having the furthest separation.Comment: v2: changes in response to referees' comments: Figure 2 made more
readable, improved discussion of height of peaks in S(k), other minor changes
4 pages, 3 figures, submitted to Physical Review
Mixing and Matching Genes of Marine and Terrestrial Origin in the Biosynthesis of the Mupirocin Antibiotics
With growing understanding of the underlying pathways of polyketide biosynthesis, along with the continual expansion of the synthetic biology toolkit, it is becoming possible to rationally engineer and fine-tune the polyketide biosynthetic machinery for production of new compounds with improved properties such as stability and/or bioactivity. However, engineering the pathway to the thiomarinol antibiotics has proved challenging. Here we report that genes from a marine Pseudoalternomonas sp. producing thiomarinol can be expressed in functional form in the biosynthesis of the clinically important antibiotic mupirocin from the soil bacterium Pseudomonas fluorescens. It is revealed that both pathways employ the same unusual mechanism of tetrahydropyran (THP) ring formation and the enzymes are cross compatible. Furthermore, the efficiency of downstream processing of 10,11-epoxy versus 10,11-alkenic metabolites are comparable. Optimisation of the fermentation conditions in an engineered strain in which production of pseudomonic acid A (with the 10,11-epoxide) is replaced by substantial titres of the more stable pseudomonic acid C (with a 10,11-alkene) pave the way for its development as a more stable antibiotic with wider applications than mupirocin
Exploiting Carbonyl Groups to Control Intermolecular Rhodium-Catalyzed Alkene and Alkyne Hydroacylation
Readily available Ī²-carbonyl-substituted aldehydes are shown to be exceptional substrates for Rh-catalyzed intermolecular alkene and alkyne hydroacylation reactions. By using cationic rhodium catalysts incorporating bisphosphine ligands, efficient and selective reactions are achieved for Ī²-amido, Ī²-ester, and Ī²-keto aldehyde substrates, providing a range of synthetically useful 1,3-dicarbonyl products in excellent yields. A correspondingly broad selection of alkenes and alkynes can be employed. For alkyne substrates, the use of a catalyst incorporating the Ampaphos ligand triggers a regioselectivity switch, allowing both linear and branched isomers to be prepared with high selectivity in an efficient manner. Structural data, confirming aldehyde chelation, and a proposed mechanism are provided
Cessation of biomechanical stretch model of C2C12 cells models myocyte atrophy and anaplerotic changes in metabolism using non-targeted metabolomics analysis
Studies of skeletal muscle disuse, either in patients on bed rest or experimentally in animals (immobilization), have demonstrated that decreased protein synthesis is common, with transient parallel increases in protein degradation. Muscle disuse atrophy involves a process of transition from slow to fast myosin fiber types. A shift toward glycolysis, decreased capacity for fat oxidation, and substrate accumulation in atrophied muscles have been reported, as has accommodation of the liver with an increased gluconeogenic capacity. Recent studies have modeled skeletal muscle disuse by using cyclic stretch of differentiated myotubes (C2C12), which mimics the loading pattern of mature skeletal muscle, followed by cessation of stretch. We utilized this model to determine the metabolic changes using non-targeted metabolomics analysis of the media. We identified increases in amino acids resulting from protein degradation (largely sarcomere) that occurs with muscle atrophy that are involved in feeding the Krebās cycle through anaplerosis. Specifically, we identified increased alanine/proline metabolism (significantly elevated proline, alanine, glutamine, and asparagine) and increased Ī±-ketoglutaric acid, the proposed Krebās cycle intermediate being fed by the alanine/proline metabolic anaplerotic mechanism. Additionally, several unique pathways not clearly delineated in previous studies of muscle unloading were seen, including: 1) elevated keto-acids derived from branched chain amino aicds (i.e. 2-ketoleucine and 2-keovaline), which feed into a metabolic pathway supplying acetyl-CoA and 2-hydroxybutyrate (also significantly increased); and 2) elevated guanine, an intermediate of purine metabolism, was seen at 12 hours unloading. Given the interest in targeting different aspects of the ubiquitin proteasome system to inhibit protein degradation, this C2C12 system may allow the identification of direct and indirect alterations in metabolism due to anaplerosis or through other yet to be identified mechanisms using a non-targeted metabolomics approach
Recent Applications of Space Weather Research to NASA Space Missions
Marshall Space Flight Center s Space Environments Team is committed to applying the latest research in space weather to NASA programs. We analyze data from an extensive set of space weather satellites in order to define the space environments for some of NASA s highest profile programs. Our goal is to ensure that spacecraft are designed to be successful in all environments encountered during their missions. We also collaborate with universities, industry, and other federal agencies to provide analysis of anomalies and operational impacts to current missions. This presentation is a summary of some of our most recent applications of space weather data, including the definition of the space environments for the initial phases of the Space Launch System (SLS), acquisition of International Space Station (ISS) frame potential variations during geomagnetic storms, and Nascap-2K charging analyses
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