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Sökning: WFRF:(Enquist K)

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  • Moles, A. T., et al. (författare)
  • Correlations between physical and chemical defences in plants : Tradeoffs, syndromes, or just many different ways to skin a herbivorous cat?
  • 2013
  • Ingår i: New Phytologist. - 0028-646X. ; 198:1, s. 252-263
  • Tidskriftsartikel (refereegranskat)abstract
    • Most plant species have a range of traits that deter herbivores. However, understanding of how different defences are related to one another is surprisingly weak. Many authors argue that defence traits trade off against one another, while others argue that they form coordinated defence syndromes. We collected a dataset of unprecedented taxonomic and geographic scope (261 species spanning 80 families, from 75 sites across the globe) to investigate relationships among four chemical and six physical defences. Five of the 45 pairwise correlations between defence traits were significant and three of these were tradeoffs. The relationship between species' overall chemical and physical defence levels was marginally nonsignificant (P = 0.08), and remained nonsignificant after accounting for phylogeny, growth form and abundance. Neither categorical principal component analysis (PCA) nor hierarchical cluster analysis supported the idea that species displayed defence syndromes. Our results do not support arguments for tradeoffs or for coordinated defence syndromes. Rather, plants display a range of combinations of defence traits. We suggest this lack of consistent defence syndromes may be adaptive, resulting from selective pressure to deploy a different combination of defences to coexisting species.
  • Chen, F., et al. (författare)
  • Reply to "comment on 'Ultrafast terahertz-field-driven ionic response in ferroelectric BaTiO3 ' "
  • 2018
  • Ingår i: Physical Review B. - American Physical Society. - 2469-9950. ; 97:22
  • Tidskriftsartikel (refereegranskat)abstract
    • In this reply to S. Durbin's comment on our original paper "Ultrafast terahertz-field-driven ionic response in ferroelectric BaTiO3," we concur that his final equations 8 and 9 more accurately describe the change in diffracted intensity as a function of Ti displacement. We also provide an alternative derivation based on an ensemble average over unit cells. The conclusions of the paper are unaffected by this correction.
  • Chen, F., et al. (författare)
  • Ultrafast terahertz-field-driven ionic response in ferroelectric BaTiO3
  • 2016
  • Ingår i: Physical Review B. - American Physical Society. - 1098-0121. ; 94:18
  • Tidskriftsartikel (refereegranskat)abstract
    • The dynamical processes associated with electric field manipulation of the polarization in a ferroelectric remain largely unknown but fundamentally determine the speed and functionality of ferroelectric materials and devices. Here we apply subpicosecond duration, single-cycle terahertz pulses as an ultrafast electric field bias to prototypical BaTiO3 ferroelectric thin films with the atomic-scale response probed by femtosecond x-ray-scattering techniques. We show that electric fields applied perpendicular to the ferroelectric polarization drive large-amplitude displacements of the titanium atoms along the ferroelectric polarization axis, comparable to that of the built-in displacements associated with the intrinsic polarization and incoherent across unit cells. This effect is associated with a dynamic rotation of the ferroelectric polarization switching on and then off on picosecond time scales. These transient polarization modulations are followed by long-lived vibrational heating effects driven by resonant excitation of the ferroelectric soft mode, as reflected in changes in the c-axis tetragonality. The ultrafast structural characterization described here enables a direct comparison with first-principles-based molecular-dynamics simulations, with good agreement obtained.
  • Moles, A. T., et al. (författare)
  • Putting plant resistance traits on the map : A test of the idea that plants are better defended at lower latitudes
  • 2011
  • Ingår i: New Phytologist. - 0028-646X. ; 191:3, s. 777-788
  • Tidskriftsartikel (refereegranskat)abstract
    • It has long been believed that plant species from the tropics have higher levels of traits associated with resistance to herbivores than do species from higher latitudes. A meta-analysis recently showed that the published literature does not support this theory. However, the idea has never been tested using data gathered with consistent methods from a wide range of latitudes. • We quantified the relationship between latitude and a broad range of chemical and physical traits across 301 species from 75 sites world-wide. • Six putative resistance traits, including tannins, the concentration of lipids (an indicator of oils, waxes and resins), and leaf toughness were greater in high-latitude species. Six traits, including cyanide production and the presence of spines, were unrelated to latitude. Only ash content (an indicator of inorganic substances such as calcium oxalates and phytoliths) and the properties of species with delayed greening were higher in the tropics. • Our results do not support the hypothesis that tropical plants have higher levels of resistance traits than do plants from higher latitudes. If anything, plants have higher resistance toward the poles. The greater resistance traits of high-latitude species might be explained by the greater cost of losing a given amount of leaf tissue in low-productivity environments. © 2011 New Phytologist Trust.
  • Stacey, Simon N, et al. (författare)
  • Ancestry-Shift Refinement Mapping of the C6orf97-ESR1 Breast Cancer Susceptibility Locus
  • 2010
  • Ingår i: PLoS Genetics. - Public Library of Science. - 1553-7404. ; 6:7
  • Tidskriftsartikel (refereegranskat)abstract
    • We used an approach that we term ancestry-shift refinement mapping to investigate an association, originally discovered in a GWAS of a Chinese population, between rs2046210[T] and breast cancer susceptibility. The locus is on 6q25.1 in proximity to the C6orf97 and estrogen receptor alpha (ESR1) genes. We identified a panel of SNPs that are correlated with rs2046210 in Chinese, but not necessarily so in other ancestral populations, and genotyped them in breast cancer case: control samples of Asian, European, and African origin, a total of 10,176 cases and 13,286 controls. We found that rs2046210[T] does not confer substantial risk of breast cancer in Europeans and Africans (OR = 1.04, P = 0.099, and OR = 0.98, P = 0.77, respectively). Rather, in those ancestries, an association signal arises from a group of less common SNPs typified by rs9397435. The rs9397435[G] allele was found to confer risk of breast cancer in European (OR = 1.15, P = 1.2x10(-3)), African (OR = 1.35, P = 0.014), and Asian (OR = 1.23, P = 2.9x10(-4)) population samples. Combined over all ancestries, the OR was 1.19 (P = 3.9x10(-7)), was without significant heterogeneity between ancestries (P-het = 0.36) and the SNP fully accounted for the association signal in each ancestry. Haplotypes bearing rs9397435[G] are well tagged by rs2046210[ T] only in Asians. The rs9397435[G] allele showed associations with both estrogen receptor positive and estrogen receptor negative breast cancer. Using early-draft data from the 1,000 Genomes project, we found that the risk allele of a novel SNP (rs77275268), which is closely correlated with rs9397435, disrupts a partially methylated CpG sequence within a known CTCF binding site. These studies demonstrate that shifting the analysis among ancestral populations can provide valuable resolution in association mapping.
  • Akter, Shaheda T., et al. (författare)
  • Failure envelope for interaction of stresses perpendicular to the grain with rolling shear stress in wood
  • 2018
  • Ingår i: 6th European Conference on Computational Mechanics (ECCM 6), 7th European Conference on Computational Fluid Dynamics (ECFD 7), 11 – 15 June 2018, Glasgow, UK.
  • Konferensbidrag (refereegranskat)abstract
    • The orthotropic material property in combination with ductility in compression, brittleness in shear and tension, very low shear modulus in radial-tangential (RT) plane etc. requires anisotropic stress failure criteria, as well as their evolution with increasing strains. Three- dimensional failure criteria have been proposed for this purpose, but their validation in the RT plane with interaction of rolling shear stresses has attracted less attention. Corresponding stress interactions are however important for modelling of engineered wood-based products under compression perpendicular to the grain when taking into account influence of the annual ring structure.The work aims at defining failure envelopes for stresses perpendicular to the grain with rolling shear stress interaction based on experimental investigations performed on Norway spruce. The experimental set-up was realized in a biaxial testing frame and consisted of stiff steel plates to transfer load from the testing machine to wood specimen. Mechanical grips prevented rotation and uplifting of the specimen in case of pure shear and tensile loading, respectively. In addition to conventional linear variable differential transformers, a digital image correlation system was used to measure strain fields on the surface of wood specimens and steel plates. Measurements of dog-bone shaped specimens were carried out along different stress interaction paths by displacement controlled loading.The experimental dataset was then compared with commonly used phenomenological failure criteria, namely Tsai-Hill, Tsai-Wu [1], Norris [2] and Hoffman, as well as with regression equations from previous works [3].Experiments revealed that the stress-strain relationship under compression, shear, and biaxial loading differs in radial and tangential directions. None of the three-dimensional stress failure criteria provided good prediction of experiments under compression and rolling shear, but experimental data was closer to the regression equation proposed in [3].
  • Andersson, Emma K, 1978-, et al. (författare)
  • Small molecule screening using a whole cell viral replication reporter gene assay identifies 2-{[2-(benzoylamino)benzoyl]amino}-benzoic acid as a novel anti-adenoviral compound
  • 2010
  • Ingår i: Antimicrobial Agents and Chemotherapy. - American society for microbiology. - 0066-4804. ; 54:9, s. 3871-3877
  • Tidskriftsartikel (refereegranskat)abstract
    • Adenovirus infections are widespread in society and are occasionally associated with severe, but rarely with life-threatening, disease in otherwise healthy individuals. In contrast, adenovirus infections present a real threat to immunocompromised individuals and can result in disseminated and fatal disease. The number of patients undergoing immunosuppressive therapy for solid organ or hematopoietic stem cell transplantation is steadily increasing, as is the number of AIDS patients, and this makes the problem of adenovirus infections even more urgent to solve. There is no formally approved treatment of adenovirus infections today, and existing antiviral agents evaluated for their anti-adenoviral effect give inconsistent results. We have developed a whole cell-based assay for high-throughput screening of potential anti-adenoviral compounds. The assay is unique in that it is based on a replication competent adenovirus type 11p GFP-expressing vector (RCAd11pGFP). This allows measurement of fluorescence changes as a direct result of RCAd11pGFP genome expression. Using this assay, we have screened 9,800 commercially available small organic compounds. Initially, we observed approximately 400 compounds that inhibited adenovirus expression in vitro by >/= 80% but only 24 were later confirmed as dose-dependent inhibitors of adenovirus. One compound in particular, 2-[[2-(benzoylamino)benzoyl]amino]-benzoic acid, turned out to be a potent inhibitor of adenovirus replication.
  • Babst, F., et al. (författare)
  • When tree rings go global: Challenges and opportunities for retro- and prospective insight
  • 2018
  • Ingår i: Quaternary Science Reviews. ; 197, s. 1-20
  • Tidskriftsartikel (refereegranskat)abstract
    • The demand for large-scale and long-term information on tree growth is increasing rapidly as environmental change research strives to quantify and forecast the impacts of continued warming on forest ecosystems. This demand, combined with the now quasi-global availability of tree-ring observations, has inspired researchers to compile large tree-ring networks to address continental or even global-scale research questions. However, these emergent spatial objectives contrast with paleo-oriented research ideas that have guided the development of many existing records. A series of challenges related to how, where, and when samples have been collected is complicating the transition of tree rings from a local to a global resource on the question of tree growth. Herein, we review possibilities to scale tree-ring data (A) from the sample to the whole tree, (B) from the tree to the site, and (C) from the site to larger spatial domains. Representative tree-ring sampling supported by creative statistical approaches is thereby key to robustly capture the heterogeneity of climate-growth responses across forested landscapes. We highlight the benefits of combining the temporal information embedded in tree rings with the spatial information offered by forest inventories and earth observations to quantify tree growth and its drivers. In addition, we show how the continued development of mechanistic tree-ring models can help address some of the non-linearities and feedbacks that complicate making inference from tree-ring data. By embracing scaling issues, the discipline of dendrochronology will greatly increase its contributions to assessing climate impacts on forests and support the development of adaptation strategies. © 2018 Elsevier Ltd
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