83,145 Hits in 2.2 sec

R. Andrew Nelson

1953 Physics today  
Andrew Nelson, physicist in the geochemistry | and petrology branch of the Geological Survey, Depart- ment of the Interior at Bethesda, Maryland, died on May 10 at the age of 48.  ...  Nelson was one of the earliest to develop methods of surveying radioactivity from the air as a means of prospecting for uranium.  ... 
doi:10.1063/1.3061314 fatcat:zdqflgvw5beu7pzoh7zrortvle

: Angels of War . Andrew Pike, Hank Nelson, Gavan Daws

Karl G. Heider
1984 American Anthropologist  
A film by Andrew Pike, Hank Nelson, and Gavan Daws. 54 minutes, color. Purchase $750 (lsmm), $650 (video), rental $75. Also available in short version (34 minutes).  ...  One of the producers, Hank Nelson, a historian at the Australian National University, has written extensively about Papua New Guinea.  ... 
doi:10.1525/aa.1984.86.2.02a01110 fatcat:jlz6mbiqjjgflcklk4s663slei

Nelson Spencer (1918–2002)

Larry Brace, George Carignan, Tom Donahue, Andrew Nagy, Donald Hunten
2003 EOS  
For the individual Nelson Spencer PAGE 82 Nelson Spencer, former chief of the Laboratory for Atmospheres at NASA/Goddard Space Flight Center, died on 31 August 2002 in Bethesda, Maryland, at the age of  ...  He received the Michigan Fron tiersman Award in 1960, - LARRY BRACE, GEORGE CARIGNAN,TOM DONAHUE, AND ANDREW NAGY, University of Michigan, Ann Arbor; AND DONALD HUNTEN, University of Arizona,Springer  ... 
doi:10.1029/2003eo090008 fatcat:lgrtb4hcmbdgbh6xf2vac6j2ja

Towards Understanding Jovian Planet Migration [article]

Andrew F. Nelson
1999 arXiv   pre-print
Initial conditions The PPM code and initial conditions are very similar to those presented in Nelson et al. 1998 . We begin with a one M ⊙ protostar fixed to the origin of our coordinate system.  ... 
arXiv:astro-ph/9908147v1 fatcat:miluzqkcd5atpbenykrwpkgnme

A trans-acting long non-coding RNA represses flowering in Arabidopsis [article]

Yu Jin, Maxim Ivanov, Anna Nelson Dittrich, Andrew Nelson, Sebastian Marquardt
2021 bioRxiv   pre-print
Eukaryotic genomes give rise to thousands of long non-coding RNAs (lncRNAs), yet the purpose of lncRNAs remains largely enigmatic. Functional characterization of lncRNAs is challenging due to multiple orthogonal hypothesis for molecular activities of lncRNA loci. Here, we identified a flowering associated intergenic lncRNA (FLAIL) that represses flowering in Arabidopsis. An allelic series of flail loss-of-function mutants generated by CRISPR/Cas9 and T-DNA mutagenesis showed an early flowering
more » ... henotype. Gene expression analyses in flail mutants revealed differentially expressed genes linked to the regulation of flowering. A genomic rescue fragment of FLAIL introduced in flail mutants complemented gene expression defects and early flowering, consistent with trans-acting effects of the FLAIL RNA. Knock-down of FLAIL RNA levels using the artificial microRNA approach revealed an early flowering phenotype shared with genomic mutations, indicating a trans-acting role of FLAIL RNA in the repression of flowering time. Genome-wide detection of FLAIL-DNA interactions by ChIRP-seq suggested that FLAIL may directly bind genomic regions. FLAIL bound to genes involved in regulation of flowering that were differentially expressed in flail, consistent with the interpretation of FLAIL as a trans-acting lncRNA directly shaping gene expression. Our findings highlight FLAIL as a trans-acting lncRNA that affects flowering in Arabidopsis, likely through mediating transcriptional regulation of genes directly bound by FLAIL.
doi:10.1101/2021.11.15.468639 fatcat:qmsgwkrnznc2be3jyohxbewyni

Dynamics and Observational Appearance of Circumstellar Disks [article]

Andrew F. Nelson
1999 arXiv   pre-print
DYNAMICS AND OBSERVATIONAL APPEARANCE OF CIRCUMSTELLAR DISKS by Andrew Frederick Nelson A Dissertation Submitted to the Faculty of the DEPARTMENT OF PHYSICS In Partial Fulfillment of the Requirements  ...  My parents, Jim and Judy Nelson. My sister Margot and her husband Jeff. And my brother, Charlie. Hopefully someday soon there will be other additions.  ... 
arXiv:astro-ph/9908158v1 fatcat:navsv4sikranhbk3f4np5novgu

Nelson, Andrew, Alexander Rödlach, and Roos Willems (eds.): The Crux of Refugee Resettlement. Rebuilding Social Networks. Lanham: Lexington Books, 2019. 299 pp. ISBN 978-​1-​4985-​8889-​8. Price: $ 115.00

Alison B. Strang
2021 Anthropos: Internationale Zeitschrift für Völker- und Sprachenkunde  
Nelson points out that providing refugees with very short-term economic support pushes them into low-skilled, low-paid jobs and limits their access to language learning and other training and education  ...  These chapters (Nelson, Lumley-Sapanski, and Stadler) provide fascinating insight into the way different refugee communities mobilise their capital (cultural, personal and social) to achieve different  ... 
doi:10.5771/0257-9774-2021-1-263 fatcat:5i4kb2fpcfctphttkwui4rnu2m

A Resolution Requirement for Disk Simulations Modeling Collapse [article]

Andrew F. Nelson
2003 arXiv   pre-print
The statement that the physical model in Nelson et al. was insufficient is certainly valid (see e.g. Nelson et al. 2000) .  ...  Bate & Burkert (1997) arrived at a similar result for particle simulations: numerical instability could be suppressed by resolving Nelson Figure 1 .  ... 
arXiv:astro-ph/0301600v1 fatcat:fcyrcasc6jbjpnrfxr3cd4mldi

Gravitational instability in binary protoplanetary disks [article]

Lucio Mayer, Alan Boss, Andrew F. Nelson
2007 arXiv   pre-print
Numerical resolution Nelson (2000) smaller than that in Nelson (2000) in overdense regions forming during the simulation.  ...  Fig. 10 . 10 Temperature profiles of the disks in Nelson  ... 
arXiv:0705.3182v1 fatcat:jx5bp7jgqzhzjpgwyoywexs57i

A simple-rapid method to separate uranium, thorium, and protactinium for U-series age-dating of materials

Andrew W. Knight, Eric S. Eitrheim, Andrew W. Nelson, Steven Nelson, Michael K. Schultz
2014 Journal of Environmental Radioactivity  
Uranium-series dating techniques require the isolation of radionuclides in high yields and in fractions free of impurities. Within this context, we describe a novel-rapid method for the separation and purification of U, Th, and Pa. The method takes advantage of differences in the chemistry of U, Th, and Pa, utilizing a commercially-available extraction chromatographic resin (TEVA) and standard reagents. The elution behavior of U, Th, and Pa were optimized using liquid scintillation counting
more » ... niques and fractional purity was evaluated by alpha-spectrometry. The overall method was further assessed by isotope dilution alpha-spectrometry for the preliminary age determination of an ancient carbonate sample obtained from the Lake Bonneville site in western Utah (United States). Preliminary evaluations of the method produced elemental purity of greater than 99.99% and radiochemical recoveries exceeding 90% for U and Th and 85% for Pa. Excellent purity and yields (76% for U, 96% for Th and 55% for Pa) were also obtained for the analysis of the carbonate samples and the preliminary Pa and Th ages of about 39,000 years before present are consistent with 14 C-derived age of the material.
doi:10.1016/j.jenvrad.2014.02.010 pmid:24681438 pmcid:PMC5538884 fatcat:pfswpvyb2zdc7oygtejb5cpzcm

A radical approach to diverse meroterpenoids

Andrew Gomm, Adam Nelson
2020 Nature Chemistry  
A radical approach to diverse meroterpenoids Andrew Gomm and Adam Nelson* School of Chemistry and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK *Email: a.s.nelson  ... 
doi:10.1038/s41557-019-0414-7 pmid:31959961 fatcat:zxptnyuu7be27lqlikj7ltlrnu

Microbial range expansions on liquid substrates [article]

Severine Atis, Bryan T. Weinstein, Andrew W. Murray, David R. Nelson
2018 arXiv   pre-print
Despite the importance that fluid flow plays in transporting and organizing populations, few laboratory systems exist to systematically investigate the impact of advection on their spatial evolutionary dynamics. To address this problem, we study the morphology and genetic spatial structure of microbial colonies growing on the surface of a nutrient-laden fluid 10^4 to 10^5 times more viscous than water in Petri dishes, the extreme but finite viscosity inhibits undesired thermal convection and
more » ... ows populations to effectively live at the air-liquid interface due to capillary forces. We discover that S. cerevisiae (baker's yeast) growing on a viscous liquid behave like "active matter": they metabolically generate fluid flows many times larger than their unperturbed colony expansion speed, and that flow, in return, can dramatically impact their colony morphology and spatial population genetics. We show that yeast cells generate fluid flows by consuming surrounding nutrients and decreasing the local substrate density, leading to misaligned fluid pressure and density contours, which ultimately generates vorticity via a thresholdless baroclinic instability. Numerical simulations demonstrate that an intense vortex ring is produced below the colony's edge and quantitatively predict the observed flow. As the viscosity of the substrate is lowered and the self-induced flow intensifies, we observe three distinct morphologies: at the highest viscosity,compact circular colonies similar to those grown on hard agar plates except with a stretched regime of exponential expansion, intermediate viscosities give rise to compact colonies with "fingers" that are ripped away to break into smaller cell clusters, and at the lowest viscosity, the expanding colony breaks up into many genetically-diverse, mutually repelling, island-like fragments of yeast colonies.
arXiv:1812.09797v1 fatcat:clb5lvcf4zag7djjn6cj5yfsni

Evolutionary and biochemical analyses reveal conservation of the Brassicaceae telomerase ribonucleoprotein complex [article]

Kelly Dew-Budd, Julie Cheung, Anna Nelson-Dittrich, Kyle Palos, Evan S Forsythe, Andrew D.L. Nelson, Mark A Beilstein
2019 bioRxiv   pre-print
TRAP was performed as described fragment (TRF) length analyses were performed as described in Nelson et al. (2014) . In brief, Fig 3 ; 3 S2 Figure).  ... 
doi:10.1101/760785 fatcat:74buwbxxh5c2tjasrwgyxnuaw4

Spatially-constrained growth enhances conversional meltdown [article]

Maxim O. Lavrentovich, Mary E. Wahl, David R. Nelson, Andrew W. Murray
2015 bioRxiv   pre-print
Cells that mutate or commit to a specialized function (differentiate) often undergo conversions that are effectively irreversible. Slowed growth of converted cells can act as a form of selection, balancing unidirectional conversion to maintain both cell types at a steady-state ratio. However, when one-way conversion is insufficiently counterbalanced by selection, the original cell type will ultimately be lost, often with negative impacts on the population's overall fitness. The critical balance
more » ... between selection and conversion needed for preservation of unconverted cells and the steady-state ratio between cell types depends on the spatial circumstances under which cells proliferate. We present experimental data on a yeast strain engineered to undergo irreversible conversion: this synthetic system permits cell type-specific fluorescent labeling and exogenous variation of the relative growth and conversion rates. We find that populations confined to grow on a flat agar surface are more susceptible than their well-mixed counterparts to fitness loss via a conversion-induced "meltdown." We then present analytical predictions for growth in several biologically-relevant geometries -- well-mixed liquid media, radially-expanding two-dimensional colonies, and linear fronts in two dimensions -- by employing analogies to the directed percolation transition from non-equilibrium statistical physics. These simplified theories are consistent with the experimental results.
doi:10.1101/027292 fatcat:k63jjqddfrfvpahdpsalzrtyya

Aggregate Selection in Evolutionary Robotics [chapter]

Andrew L. Nelson, Edward Grant
2007 Studies in Computational Intelligence  
doi:10.1007/978-3-540-49720-2_4 fatcat:pvjv7jfawzcpzed6jhu2bcllya
« Previous Showing results 1 — 15 out of 83,145 results