Showing 1531 - 1540 of 2040 Items
The Importance of What We Care About: A Solidarity Approach to Resource Allocation
Date: 2020-01-01
Creator: Kristi A. Olson
Access: Open access
- At some point in your life, you will need to allocate resources among individuals, but how should you do so? One prominent suggestion is the envy test: the envy test is satisfied when and only when no one prefers someone else’s bundle. In Part I, I explain and then reject Tom Parr’s recent attempt to justify the envy test. Yet, like Parr, I believe the envy test captures something important. Thus, in Part II, I distinguish two approaches to resource allocation. Parr’s defense of the envy test assumes what I will call an individualist approach: what matters are each individual’s preferences. In lieu of the individualist approach, I endorse the solidarity approach: what matters are everyone’s preferences. After explaining the distinction, I show that the envy test—or at least something like it—can be defended using the solidarity approach even if it cannot be defended using the individualist approach.
Anthropogenic Impacts on Atmospheric Carbonyl Sulfide Since the 19th Century Inferred From Polar Firn Air and Ice Core Measurements
Date: 2020-08-27
Creator: M. Aydin
G. L. Britten
S. A. Montzka
C. Buizert
F., Primeau
V. Petrenko
M. B. Battle
M. R. Nicewonger
J. Patterson
B. Hmiel
E. S. Saltzman
Access: Open access
- Carbonyl sulfide (COS) was measured in firn air collected during seven different field campaigns carried out at four different sites in Greenland and Antarctica between 2001 and 2015. A Bayesian probabilistic statistical model is used to conduct multisite inversions and to reconstruct separate atmospheric histories for Greenland and Antarctica. The firn air inversions cover most of the 20th century over Greenland and extend back to the 19th century over Antarctica. The derived atmospheric histories are consistent with independent surface air time series data from the corresponding sites and the Antarctic ice core COS records during periods of overlap. Atmospheric COS levels began to increase over preindustrial levels starting in the 19th century, and the increase continued for much of the 20th century. Atmospheric COS peaked at higher than present-day levels around 1975 CE over Greenland and around 1987 CE over Antarctica. An atmosphere/surface ocean box model is used to investigate the possible causes of observed variability. The results suggest that changes in the magnitude and location of anthropogenic sources have had a strong influence on the observed atmospheric COS variability.
Formation of rarefaction waves in origami-based metamaterials
Date: 2016-04-15
Creator: H. Yasuda
C. Chong
E. G. Charalampidis
P. G. Kevrekidis
J., Yang
Access: Open access
- We investigate the nonlinear wave dynamics of origami-based metamaterials composed of Tachi-Miura polyhedron (TMP) unit cells. These cells exhibit strain softening behavior under compression, which can be tuned by modifying their geometrical configurations or initial folded conditions. We assemble these TMP cells into a cluster of origami-based metamaterials, and we theoretically model and numerically analyze their wave transmission mechanism under external impact. Numerical simulations show that origami-based metamaterials can provide a prototypical platform for the formation of nonlinear coherent structures in the form of rarefaction waves, which feature a tensile wavefront upon the application of compression to the system. We also demonstrate the existence of numerically exact traveling rarefaction waves in an effective lumped-mass model. Origami-based metamaterials can be highly useful for mitigating shock waves, potentially enabling a wide variety of engineering applications.
Captured segment exchange: A strategy for custom engineering large genomic regions in Drosophila melanogaster
Date: 2013-04-24
Creator: Jack R. Bateman
Michael F. Palopoli
Sarah T. Dale
Jennifer E. Stauffer
Anita L., Shah
Justine E. Johnson
Conor W. Walsh
Hanna Flaten
Christine M. Parsons
Access: Open access
- Site-specific recombinases (SSRs) are valuable tools for manipulating genomes. In Drosophila, thousands of transgenic insertions carrying SSR recognition sites have been distributed throughout the genome by several large-scale projects. Here we describe a method with the potential to use these insertions to make custom alterations to the Drosophila genome in vivo. Specifically, by employing recombineering techniques and a dual recombinase-mediated cassette exchange strategy based on the phiC31 integrase and FLP recombinase, we show that a large genomic segment that lies between two SSR recognition-site insertions can be "captured" as a target cassette and exchanged for a sequence that was engineered in bacterial cells. We demonstrate this approach by targeting a 50-kb segment spanning the tsh gene, replacing the existing segment with corresponding recombineered sequences through simple and efficient manipulations. Given the high density of SSR recognition-site insertions in Drosophila, our method affords a straightforward and highly efficient approach to explore gene function in situ for a substantial portion of the Drosophila genome. © 2013 by the Genetics Society of America.
Efficient and rapid identification of Candida albicans allelic status using SNP-RFLP
Date: 2009-11-01
Creator: Anja Forche
Musetta Steinbach
Judith Berman
Access: Open access
- Candida albicans is the most prevalent opportunistic fungal pathogen in the clinical setting, causing a wide spectrum of diseases ranging from superficial mucosal lesions to life-threatening deep-tissue infections. Recent studies provide strong evidence that C. albicans possesses an arsenal of genetic mechanisms promoting genome plasticity and that it uses these mechanisms under conditions of nutritional or antifungal drug stress. Two microarray-based methods, single nucleotide polymorphism (SNP) and comparative genome hybridization arrays, have been developed to study genome changes in C. albicans. However, array technologies can be relatively expensive and are not available to every laboratory. In addition, they often generate more data than needed to analyze specific genomic loci or regions. Here, we have developed a set of SNP-restriction fragment length polymorphism (RFLP) (or PCR-RFLP) markers, two per chromosome arm, for C. albicans. These markers can be used to rapidly and accurately detect large-scale changes in the C. albicans genome including loss of heterozygosity (LOH) at single loci, across chromosome arms or across whole chromosomes. Furthermore, skewed SNP-RFLP allelic ratios are indicative of trisomy at heterozygous loci. While less comprehensive than array-based approaches, we propose SNP-RFLP as an inexpensive, rapid, and reliable method to screen strains of interest for possible genome changes. © 2009 Federation of European Microbiological Societies.
Measurement of two-photon production of the χc2
Date: 1994-01-01
Creator: J. Dominick
S. Sanghera
V. Shelkov
T. Skwarnicki
R., Stroynowski
I. Volobouev
P. Zadorozhny
M. Artuso
D. He
M. Goldberg
N. Horwitz
R. Kennett
G. C. Moneti
F. Muheim
Y. Mukhin
S. Playfer
Y. Rozen
S. Stone
M. Thulasidas
G. Vasseur
G. Zhu
J. Bartelt
S. E. Csorna
Z. Egyed
V. Jain
P. Sheldon
D. S. Akerib
B. Barish
M. Chadha
S. Chan
D. F. Cowen
Access: Open access
- The CLEO II detector is used to search for the production of χc2 states in two-photon interactions. We use the signature χc2→γJ/ ψ→γl+l- with l=e,μ. Using 1.49 fb-1 of data taken with beam energies near 5.29 GeV, the two-photon width of the χc2 is determined to be Γ(χc2→γγ)=1.08±0.30(stat)±0.26(syst) keV, in agreement with predictions from perturbative QCD. © 1994 The American Physical Society.
Atmospheric abundance and global emissions of perfluorocarbons CF4, C2F6 and C3F8 since 1800 inferred from ice core, firn, air archive and in situ measurements
Date: 2016-09-21
Creator: Cathy M. Trudinger
Paul J. Fraser
David M. Etheridge
William T. Sturges
Martin K., Vollmer
Matt Rigby
Patricia Martinerie
Jens Mühle
David R. Worton
Paul B. Krummel
L. Paul Steele
Benjamin R. Miller
Johannes Laube
Francis S. Mani
Peter J. Rayner
Christina M. Harth
Emmanuel Witrant
Thomas Blunier
Jakob Schwander
Simon O'Doherty
Mark Battle
Access: Open access
- Perfluorocarbons (PFCs) are very potent and long-lived greenhouse gases in the atmosphere, released predominantly during aluminium production and semiconductor manufacture. They have been targeted for emission controls under the United Nations Framework Convention on Climate Change. Here we present the first continuous records of the atmospheric abundance of CF4 (PFC-14), C2F6 (PFC-116) and C3F8 (PFC-218) from 1800 to 2014. The records are derived from high-precision measurements of PFCs in air extracted from polar firn or ice at six sites (DE08, DE08-2, DSSW20K, EDML, NEEM and South Pole) and air archive tanks and atmospheric air sampled from both hemispheres. We take account of the age characteristics of the firn and ice core air samples and demonstrate excellent consistency between the ice core, firn and atmospheric measurements. We present an inversion for global emissions from 1900 to 2014. We also formulate the inversion to directly infer emission factors for PFC emissions due to aluminium production prior to the 1980s. We show that 19th century atmospheric levels, before significant anthropogenic influence, were stable at 34.1 ± 0.3 ppt for CF4 and below detection limits of 0.002 and 0.01 ppt for C2F6 and C3F8, respectively. We find a significant peak in CF4 and C2F6 emissions around 1940, most likely due to the high demand for aluminium during World War II, for example for construction of aircraft, but these emissions were nevertheless much lower than in recent years. The PFC emission factors for aluminium production in the early 20th century were significantly higher than today but have decreased since then due to improvements and better control of the smelting process. Mitigation efforts have led to decreases in emissions from peaks in 1980 (CF4) or early-to-mid-2000s (C2F6 and C3F8) despite the continued increase in global aluminium production; however, these decreases in emissions appear to have recently halted. We see a temporary reduction of around 15 % in CF4 emissions in 2009, presumably associated with the impact of the global financial crisis on aluminium and semiconductor production.
Measurement of the branching fraction for D+K-++
Date: 1994-01-01
Creator: R. Balest
K. Cho
M. Daoudi
W. T. Ford
D. R., Johnson
K. Lingel
M. Lohner
P. Rankin
J. G. Smith
J. P. Alexander
C. Bebek
K. Berkelman
K. Bloom
T. E. Browder
D. G. Cassel
H. A. Cho
D. M. Coffman
P. S. Drell
R. Ehrlich
P. Gaiderev
M. Garcia-Sciveres
B. Geiser
B. Gittelman
S. W. Gray
D. L. Hartill
B. K. Heltsley
C. D. Jones
S. L. Jones
J. Kandaswamy
N. Katayama
P. C. Kim
Access: Open access
- Using the CLEO II detector at the Cornell Electron Storage Ring we have measured the ratio of branching fractions, B(D+K-++)/(D0K-+)=2.350.160.16. Our recent measurement of scrB(D0K-+) then gives scrB(D+K-++)=(9.30.60.8)%. © 1994 The American Physical Society.
Isolation of nine microsatellite loci in Dolichogenidea homoeosomae (Hymenoptera) a parasitoid of the sunflower moth Homoeosoma electellum (Lepidoptera)
Date: 2006-03-01
Creator: Vladimir Douhovnikoff
Caterina Nerney
George K. Roderick
Craig H. Newton
Stephen C., Welter
Access: Open access
- Nine microsatellite loci were isolated from the insect Dolichogenidea homoeosomae (Hymenoptera: Braconidae), an important parasitoid of the sunflower moth Homosoeosoma electellum (Lepidoptera: Pyralidae), and assayed for polymorphism. All nine loci were polymorphic within the five populations tested, with two to 14 alleles per locus. Expected and observed heterozygosities ranged from 0.39 to 0.90 and 0.25 to 0.72 respectively. These are the first microsatellite primers developed for D. homeosomae and will be useful for studies of population dynamics and connectivity. © 2006 Blackwell Publishing Ltd.
Two measurements of B0B»0 mixing
Date: 1993-01-01
Creator: J. Bartelt
S. E. Csorna
Z. Egyed
V. Jain
P., Sheldon
D. S. Akerib
B. Barish
M. Chadha
S. Chan
D. F. Cowen
G. Eigen
J. S. Miller
C. O'Grady
J. Urheim
A. J. Weinstein
D. Acosta
M. Athanas
G. Masek
B. Ong
H. Paar
M. Sivertz
A. Bean
J. Gronberg
R. Kutschke
S. Menary
R. J. Morrison
S. Nakanishi
H. N. Nelson
T. K. Nelson
J. D. Richman
A. Ryd
Access: Open access
- We have measured the B0B»0 mixing probability, d, using a sample of 965 000 BB» pairs from (4S) decays. Counting dilepton events, we find d=0.1570.0160.018-0.021+0.028. Using tagged B0 events, we find d=0.1490.0230.0190.010. The first (second) error is statistical (systematic). The third error reflects a 15% uncertainty in the assumption, made in both cases, that charged and neutral B pairs contribute equally to dilepton events. We also obtain a limit on the CP impurity in the Bd0 system, Re(B0)<0.045 at 90% C.L. © 1993 The American Physical Society.