Browsing by Subject "GROWTH"

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    Assessing phylogenetic relationships in extant heterosporous ferns (Salviniales), with a focus on Pilularia and Salvinia
    (Botanical Journal of the Linnean Society, 2008-08-01) Nagalingum, NS; Nowak, MD; Pryer, KM
    Heterosporous ferns (Salviniales) are a group of approximately 70 species that produce two types of spores (megaspores and microspores). Earlier broad-scale phylogenetic studies on the order typically focused on one or, at most, two species per genus. In contrast, our study samples numerous species for each genus, wherever possible, accounting for almost half of the species diversity of the order. Our analyses resolve Marsileaceae, Salviniaceae and all of the component genera as monophyletic. Salviniaceae incorporate Salvinia and Azolla; in Marsileaceae, Marsilea is sister to the clade of Regnellidium and Pilularia - this latter clade is consistently resolved, but not always strongly supported. Our individual species-level investigations for Pilularia and Salvinia, together with previously published studies on Marsilea and Azolla (Regnellidium is monotypic), provide phylogenies within all genera of heterosporous ferns. The Pilularia phylogeny reveals two groups: Group I includes the European taxa P. globulifera and P. minuta; Group II consists of P. americana, P. novae-hollandiae and P. novae-zelandiae from North America, Australia and New Zealand, respectively, and are morphologically difficult to distinguish. Based on their identical molecular sequences and morphology, we regard P. novae-hollandiae and P. novae-zelandiae to be conspecific; the name P. novae-hollandiae has nomenclatural priority. The status of P. americana requires further investigation as it consists of two geographically and genetically distinct North American groups and also shows a high degree of sequence similarity to P. novae-hollandiae. Salvinia also comprises biogeographically distinct units - a Eurasian group (S. natans and S. cucullata) and an American clade that includes the noxious weed S. molesta, as well as S. oblongifolia and S. minima. © 2008 The Linnean Society of London.
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    Can Results-Free Review Reduce Publication Bias? The Results and Implications of a Pilot Study
    (Comparative Political Studies, 2016-11) Findley, MG; Jensen, NM; Malesky, EJ; Pepinsky, TB
    © 2016, © The Author(s) 2016. In 2015, Comparative Political Studies embarked on a landmark pilot study in research transparency in the social sciences. The editors issued an open call for submissions of manuscripts that contained no mention of their actual results, incentivizing reviewers to evaluate manuscripts based on their theoretical contributions, research designs, and analysis plans. The three papers in this special issue are the result of this process that began with 19 submissions. In this article, we describe the rationale for this pilot, expressly articulating the practices of preregistration and results-free review. We document the process of carrying out the special issue with a discussion of the three accepted papers, and critically evaluate the role of both preregistration and results-free review. Our main conclusions are that results-free review encourages much greater attention to theory and research design, but that it raises thorny problems about how to anticipate and interpret null findings. We also observe that as currently practiced, results-free review has a particular affinity with experimental and cross-case methodologies. Our lack of submissions from scholars using qualitative or interpretivist research suggests limitations to the widespread use of results-free review.
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    Competing for global capital or local voters? The politics of business location incentives
    (Public Choice, 2015-09) Jensen, NM; Malesky, EJ; Walsh, M
    © 2015, Springer Science+Business Media New York. The competition for global capital has led to interjurisdictional competition between countries, states and cities as to who can offer the most attractive incentives to firms. In this study, we examine the domestic politics of this competition by focusing on incentive use in the United States from 1999 to 2012. We define incentives as the targeted tax deductions or exemptions that are used to lure businesses into a locality. Drawing on data from municipal incentive programs, we examine how electoral competition shapes the use and oversight of targeted incentives. We find evidence that cities with elected mayors provide larger incentives than non-elected city managers by taking advantage of exogeneity in the assignment of city government institutions and a database of over 2000 investment incentives from 2010 to 2012. We also find that elected mayors enjoy more lax oversight of incentive projects than their appointed counterparts. Our results have important implications for the study of interjurisdictional competition and the role of electoral institutions in shaping economic policy.
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    Earthworms modify plant biomass and nitrogen capture under conditions of soil nutrient heterogeneity and elevated atmospheric CO2 concentrations
    (Soil Biology and Biochemistry, 2014-01-01) García-Palacios, Pablo; Maestre, Fernando T; Bradford, Mark A; Reynolds, James F
    Earthworms modify the way roots respond to soil nutrient patchiness. However, few studies have evaluated the joint effects of earthworms and soil heterogeneity on plant community biomass and species dominance, and none of them have assessed the influence of different patch features and environmental conditions on such effects. We evaluated how soil nutrient heterogeneity, earthworms (Eisenia fetida), organic material quality (15N-labelled leaves and roots of contrasting C: N ratios) and elevated atmospheric CO2 concentrations (phytotron chambers) affected the resource-use strategy, biomass and species dominance of mixtures formed by Lolium perenne L. and Plantago lanceolata L. Soil heterogeneity decreased N capture from the organic material, especially in the presence of earthworms. Mixtures experienced a 26 and 36% decrease in shoot and root biomass when earthworms were added to the heterogeneous microcosms, but only with high quality organic material. The dominance of L. perenne was lower under conditions of elevated CO2, nutrient heterogeneity and earthworms. Our data suggest that earthworms can neutralize positive plant growth responses to soil heterogeneity by exacerbating decreases in the supply of N to the plant. Specifically, earthworms foraging for high quality patches may stimulate microbial N immobilization, translating into lower N capture by plants. Increases in casting activity under elevated CO2, and hence in microbial N immobilization, may also explain why earthworms modulated the effects of soil heterogeneity and CO2 concentrations on plant community structure. We show that earthworms, absent from most soil nutrient heterogeneity studies, mediate plant biomass responses to nutrient patchiness by affecting N capture. Future plant-foraging behaviour studies should consider the roles played by soil engineers such as earthworms, so that results can be better extrapolated to natural communities. © 2014 Elsevier Ltd.
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    Genome-wide CRISPR Screen to Identify Genes that Suppress Transformation in the Presence of Endogenous KrasG12D.
    (Scientific reports, 2019-11-20) Huang, Jianguo; Chen, Mark; Xu, Eric S; Luo, Lixia; Ma, Yan; Huang, Wesley; Floyd, Warren; Klann, Tyler S; Kim, So Young; Gersbach, Charles A; Cardona, Diana M; Kirsch, David G
    Cooperating gene mutations are typically required to transform normal cells enabling growth in soft agar or in immunodeficient mice. For example, mutations in Kras and transformation-related protein 53 (Trp53) are known to transform a variety of mesenchymal and epithelial cells in vitro and in vivo. Identifying other genes that can cooperate with oncogenic Kras and substitute for Trp53 mutation has the potential to lead to new insights into mechanisms of carcinogenesis. Here, we applied a genome-wide CRISPR/Cas9 knockout screen in KrasG12D immortalized mouse embryonic fibroblasts (MEFs) to search for genes that when mutated cooperate with oncogenic Kras to induce transformation. We also tested if mutation of the identified candidate genes could cooperate with KrasG12D to generate primary sarcomas in mice. In addition to identifying the well-known tumor suppressor cyclin dependent kinase inhibitor 2A (Cdkn2a), whose alternative reading frame product p19 activates Trp53, we also identified other putative tumor suppressors, such as F-box/WD repeat-containing protein 7 (Fbxw7) and solute carrier family 9 member 3 (Slc9a3). Remarkably, the TCGA database indicates that both FBXW7 and SLC9A3 are commonly co-mutated with KRAS in human cancers. However, we found that only mutation of Trp53 or Cdkn2a, but not Fbxw7 or Slc9a3 can cooperate with KrasG12D to generate primary sarcomas in mice. These results show that mutations in oncogenic Kras and either Fbxw7 or Slc9a3 are sufficient for transformation in vitro, but not for in vivo sarcomagenesis.
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    Importance of diameter control on selective synthesis of semiconducting single-walled carbon nanotubes.
    (ACS nano, 2014-08-11) Li, Jinghua; Ke, Chung-Ting; Liu, Kaihui; Li, Pan; Liang, Sihang; Finkelstein, Gleb; Wang, Feng; Liu, Jie
    The coexistence of semiconducting and metallic single-walled carbon nanotubes (SWNTs) during synthesis is one of the major bottlenecks that prevent their broad application for the next-generation nanoelectronics. Herein, we present more understanding and demonstration of the growth of highly enriched semiconducting SWNTs (s-SWNTs) with a narrow diameter distribution. An important fact discovered in our experiments is that the selective elimination of metallic SWNTs (m-SWNTs) from the mixed arrays grown on quartz is diameter-dependent. Our method emphasizes controlling the diameter distribution of SWNTs in a narrow range where m-SWNTs can be effectively and selectively etched during growth. In order to achieve narrow diameter distribution, uniform and stable Fe-W nanoclusters were used as the catalyst precursors. About 90% of as-prepared SWNTs fall into the diameter range 2.0-3.2 nm. Electrical measurement results on individual SWNTs confirm that the selectivity of s-SWNTs is ∼95%. The present study provides an effective strategy for increasing the purity of s-SWNTs via controlling the diameter distribution of SWNTs and adjusting the etchant concentration. Furthermore, by carefully comparing the chirality distributions of Fe-W-catalyzed and Fe-catalyzed SWNTs under different water vapor concentrations, the relationship between the diameter-dependent and electronic-type-dependent etching mechanisms was investigated.
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    Morphometric signals of population decline in diademed sifakas occupying degraded rainforest habitat in Madagascar.
    (Scientific reports, 2019-06-19) Irwin, Mitchell T; Samonds, Karen E; Raharison, Jean-Luc; Junge, Randall E; Mahefarisoa, Karine Lalaina; Rasambainarivo, Fidisoa; Godfrey, Laurie R; Glander, Kenneth E
    Anthropogenic habitat change can have varied impacts on primates, including both negative and positive outcomes. Even when behavioural shifts are seen, they may reflect decreased health, or simply behavioural flexibility; understanding this distinction is important for conservation efforts. This study examines habitat-related variation in adult and immature morphometrics among diademed sifakas (Propithecus diadema). We collected morphometric data from sifakas at Tsinjoarivo, Madagascar (19 years, 188 captures, 113 individuals). Captures spanned 12 groups, five within continuous forest ("CONT"), and seven in degraded fragments ("FRAG") where sifakas have lower nutritional intakes. Few consistent differences were found between CONT and FRAG groups. However, using home range quality as a covariate rather than a CONT/FRAG dichotomy revealed a threshold: the two FRAG groups in the lowest-quality habitat showed low adult mass and condition (wasting), and low immature mass and length (stunting). Though less-disturbed fragments apparently provide viable habitat, we suggest the sifakas in the most challenging habitats cannot evolve fast enough to keep up with such rapid habitat change. We suggest other long-lived organisms will show similar morphometric "warning signs" (wasting in adults, stunting in immatures); selected morphometric variables can thus be useful at gauging vulnerability of populations in the face of anthropogenic change.
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    The effect of market competition on bribery in emerging economies: An empirical analysis of Vietnamese firms
    (World Development, 2020-07-01) Malesky, EJ; Nguyen, TV; Bach, TN; Ho, BD
    © 2020 Elsevier Ltd Studies of firm bribery have not fully examined how market competition conditions the effects of social norms on firms’ bribe payments. We suggest that firms pay bribes to obtain abnormal rents and/or to conform to accepted rules of corruption. These motivations operate differently, depending on the level of market competition. Using data from an annual survey of 10,000 Vietnamese firms between 2006 and 2017, we find that in environments characterized by open competition, bribery is positively associated with long-standing norms in the business social context, while in closed-competition environments, bribe payments are functions of rents that accrue from uncertainty in policy-making.