Showing 331 - 340 of 722 Items
The (Far) Backstory of the U.S.-Colombia Free Trade Agreement
Date: 2013-10-10
Creator: Stephen Meardon
Access: Open access
- In two pairs of episodes, first in 1824 and 1846 and then in 1892 and 1935, similar U.S.-Colombia trade agreements or their enabling laws were embraced first by protectionists and then by free traders. The history of the episodes supports the view that although political institutions exist to curb de facto political power, such power may be wielded to undo the institutions’ intended effects. The doctrinal affinities and interests of political actors are more decisive determinants of the free-trade or protectionist orientation of trade agreements than the agreements’ texts or legal superstructures. The long delay from signing to passage of the current U.S.-Colombia Free Trade Agreement is another case in point.
Formation of oral and pharyngeal dentition in teleosts depends on differential recruitment of retinoic acid signaling
Date: 2010-09-01
Creator: Yann Gibert
Laure Bernard
Melanie Debiais-Thibaud
Franck Bourrat
Jean Stephane, Joly
Karen Pottin
Axel Meyer
Sylvie Retaux
David W. Stock
William R. Jackman
Pawat Seritrakul
Gerrit Begemann
Vincent Laudet
Access: Open access
- One of the goals of evolutionary developmental biology is to link specific adaptations to changes in developmental pathways. The dentition of cypriniform fishes, which in contrast to many other teleost fish species possess pharyngeal teeth but lack oral teeth, provides a suitable model to study the development of feeding adaptations. Here, we have examined the involvement of retinoic acid (RA) in tooth development and show that RA is specifically required to induce the pharyngeal tooth developmental program in zebrafish. Perturbation of RA signaling at this stage abolished tooth induction without affecting the development of tooth-associated ceratobranchial bones. We show that this inductive event is dependent on RA synthesis from aldh1a2 in the ventral posterior pharynx. Fibroblast growth factor (FGF) signaling has been shown to be critical for tooth induction in zebrafish, and its loss has been associated with oral tooth loss in cypriniform fishes. Pharmacological treatments targeting the RA and FGF pathways revealed that both pathways act independently during tooth induction. In contrast, we find that in Mexican tetra and medaka, species that also possess oral teeth, both oral and pharyngeal teeth are induced independently of RA. Our analyses suggest an evolutionary scenario in which the gene network controlling tooth development obtained RA dependency in the lineage leading to the cypriniforms. The loss of pharyngeal teeth in this group was cancelled out through a shift in aldh1a2 expression, while oral teeth might have been lost ultimately due to deficient RA signaling in the oral cavity. © FASEB.
Oakeshott, Berlin, and liberalism
Date: 2003-01-01
Creator: Paul Franco
Access: Open access
- This article compares the political philosophies of Michael Oakeshott and Isaiah Berlin, probably the two most important political philosophers in postwar Britain, who, strangely, had very little to do with one another during their illustrious careers. The article focuses on their respective critiques of rationalism and theories of liberal pluralism, arguing that Oakeshott provides the more consistent and philosophically satisfying account in both instances.
Modelling ecosystem services in terrestrial systems
Date: 2010-07-22
Creator: Erik J. Nelson
Gretchen C. Daily
Access: Open access
- Over the past few decades, a multi-disciplinary research community has documented the goods and services provided by ecosystems in specific sites scattered across the world. This research community has now begun to focus on creating methods and tools for mapping and valuing the ecosystem services produced on any landscape in the world. We describe some of these methods and tools and how they calculate and express ecosystem service provision and value on landscapes. We also describe methods for predicting landscape change. These predictions can be used by multi-ecosystem service models to assess potential changes and trade-offs in ecosystem service provision and values into the future. © 2010 Faculty of 1000 Ltd.
Who benefits? How interest-convergence shapes benefit-sharing and indigenous rights to sustainable livelihoods in Russia
Date: 2020-11-01
Creator: Maria S. Tysiachniouk
Laura A. Henry
Svetlana A. Tulaeva
Leah S. Horowitz
Access: Open access
- The paper examines interactions of oil companies and reindeer herders in the tundra of the Russian Arctic. We focus on governance arrangements that have an impact on the sustainability of oil production and reindeer herding. We analyze a shift in benefit-sharing arrangements between oil companies and Indigenous Nenets reindeer herders in Nenets Autonomous Okrug (NAO), Russia, as an evolution of the herders’ rights, defined as the intertwined co-production of legal processes, ideologies, and power relations. Semi-structured interviews, participant observation, and document analysis demonstrate that in NAO, benefit-sharing shifted from paternalism (dependent on herders’ negotiation skills) to company-centered social responsibility (formalized compensation rules). This shift was enabled by the adoption of a formal methodology for calculating income lost due to extractive projects and facilitated by the regional government’s efforts to develop reindeer-herding. While laws per se did not change, herders’ ability to access compensation and markets increased. This paper shows that even when ideologies of indigeneity are not influential, the use of existing laws and convergence of the government’s and Indigenous groups’ economic interests may shift legal processes and power relations toward greater rights for Indigenous groups.
Levels of DNA polymorphism vary with mating system in the nematode genus Caenorhabditis
Date: 2002-01-01
Creator: Andrew Graustein
John M. Caspar
James R. Walters
Michael F. Palopoli
Access: Open access
- Self-fertilizing species often harbor less genetic variation than cross-fertilizing species, and at least four different models have been proposed to explain this trend. To investigate further the relationship between mating system and genetic variation, levels of DNA sequence polymorphism were compared among three closely related species in the genus Caenorhabditis: two self-fertilizing species, Caenorhabditis elegans and C. briggsae, and one cross-fertilizing species, C. remanei. As expected, estimates of silent site nucleotide diversity were lower in the two self-fertilizing species. For the mitochondrial genome, diversity in the selfing species averaged 42% of diversity in C. remanei. Interestingly, the reduction in genetic variation was much greater for the nuclear than for the mitochondrial genome. For two nuclear genes, diversity in the selfing species averaged 6 and 13% of diversity in C. remanei. We argue that either population bottlenecks or the repeated action of natural selection, coupled with high levels of selfing, are likely to explain the observed reductions in species-wide genetic diversity.
Exuberant and inhibited toddlers: Stability of temperament and risk for problem behavior
Date: 2008-03-01
Creator: Cynthia A. Stifter
Samuel Putnam
Laudan Jahromi
Access: Open access
- Temperament, effortful control, and problem behaviors at 4.5 years were assessed in 72 children classified as exuberant, inhibited, and low reactive as 2-year-olds. Exuberant toddlers were more positive, socially responsive to novel persons, less shy, and rated as having more problem behaviors, including externalizing and internalizing behaviors, than other children as preschoolers. Two forms of effortful control, the ability to delay a response and the ability to produce a subdominant response, were associated with fewer externalizing behaviors, whereas expressing more negative affect (relative to positive/neutral affect) when disappointed was related to more internalizing behaviors. Interaction effects implicated high levels of unregulated emotion during disappointment as a risk factor for problem behaviors in exuberant children. © 2008 Cambridge University Press.
A database and synthesis of northern peatland soil properties and Holocene carbon and nitrogen accumulation
Date: 2014-09-01
Creator: Julie Loisel
Zicheng Yu
David W. Beilman
Philip Camill
Jukka, Alm
Matthew J. Amesbury
David Anderson
Sofia Andersson
Christopher Bochicchio
Keith Barber
Lisa R. Belyea
Joan Bunbury
Frank M. Chambers
Daniel J. Charman
François De Vleeschouwer
Barbara Fiałkiewicz-Kozieł
Access: Open access
- Here, we present results from the most comprehensive compilation of Holocene peat soil properties with associated carbon and nitrogen accumulation rates for northern peatlands. Our database consists of 268 peat cores from 215 sites located north of 45°N. It encompasses regions within which peat carbon data have only recently become available, such as the West Siberia Lowlands, the Hudson Bay Lowlands, Kamchatka in Far East Russia, and the Tibetan Plateau. For all northern peatlands, carbon content in organic matter was estimated at 42 ± 3% (standard deviation) for Sphagnum peat, 51 ± 2% for non-Sphagnum peat, and at 49 ± 2% overall. Dry bulk density averaged 0.12 ± 0.07 g/cm3, organic matter bulk density averaged 0.11 ± 0.05 g/cm3, and total carbon content in peat averaged 47 ± 6%. In general, large differences were found between Sphagnum and non-Sphagnum peat types in terms of peat properties. Time-weighted peat carbon accumulation rates averaged 23 ± 2 (standard error of mean) g C/m2/yr during the Holocene on the basis of 151 peat cores from 127 sites, with the highest rates of carbon accumulation (25–28 g C/m2/yr) recorded during the early Holocene when the climate was warmer than the present. Furthermore, we estimate the northern peatland carbon and nitrogen pools at 436 and 10 gigatons, respectively. The database is publicly available at https://peatlands.lehigh.edu.
A new data set for estimating organic carbon storage to 3 m depth in soils of the northern circumpolar permafrost region
Date: 2013-12-23
Creator: G. Hugelius
J. G. Bockheim
P. Camill
B. Elberling
G., Grosse
J. W. Harden
K. Johnson
T. Jorgenson
C. D. Koven
P. Kuhry
G. Michaelson
U. Mishra
J. Palmtag
J. O'Donnell
L. Schirrmeister
E. A.G. Schuur
Access: Open access
- High-latitude terrestrial ecosystems are key components in the global carbon cycle. The Northern Circumpolar Soil Carbon Database (NCSCD) was developed to quantify stocks of soil organic carbon (SOC) in the northern circumpolar permafrost region (a total area of 18.7 × 106 km2). The NCSCD is a geographical information system (GIS) data set that has been constructed using harmonized regional soil classification maps together with pedon data from the northern permafrost region. Previously, the NCSCD has been used to calculate SOC storage to the reference depths 0–30 cm and 0–100 cm (based on 1778 pedons). It has been shown that soils of the northern circumpolar permafrost region also contain significant quantities of SOC in the 100–300 cm depth range, but there has been no circumpolar compilation of pedon data to quantify this deeper SOC pool and there are no spatially distributed estimates of SOC storage below 100 cm depth in this region. Here we describe the synthesis of an updated pedon data set for SOC storage (kg C m−2) in deep soils of the northern circumpolar permafrost regions, with separate data sets for the 100–200 cm (524 pedons) and 200–300 cm (356 pedons) depth ranges. These pedons have been grouped into the North American and Eurasian sectors and the mean SOC storage for different soil taxa (subdivided into Gelisols including the sub-orders Histels, Turbels, Orthels, permafrost-free Histosols, and permafrost-free mineral soil orders) has been added to the updated NCSCDv2. The updated version of the data set is freely available online in different file formats and spatial resolutions that enable spatially explicit applications in GIS mapping and terrestrial ecosystem models. While this newly compiled data set adds to our knowledge of SOC in the 100–300 cm depth range, it also reveals that large uncertainties remain. Identified data gaps include spatial coverage of deep (> 100 cm) pedons in many regions as well as the spatial extent of areas with thin soils overlying bedrock and the quantity and distribution of massive ground ice.©Author(s) 2013.
Scattering equations and BCJ relations for gauge and gravitational amplitudes with massive scalar particles
Date: 2014-09-01
Creator: Stephen G. Naculich
Access: Open access
- Abstract: We generalize the scattering equations to include both massless and massive particles. We construct an expression for the tree-level n-point amplitude with n − 2 gluons or gravitons and a pair of massive scalars in arbitrary spacetime dimension as a sum over the (n − 3)! solutions of the scattering equations, à la Cachazo, He, and Yuan. We derive the BCJ relations obeyed by these massive amplitudes.