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  • 1
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 10 August 2010, Vol.107(32), pp.14369-72
    Description: Flagellar motility, a mode of active motion shared by many prokaryotic species, is recognized as a key mechanism enabling population dispersal and resource acquisition in microbial communities living in marine, freshwater, and other liquid-replete habitats. By contrast, its role in variably hydrated habitats, where water dynamics result in fragmented aquatic habitats connected by micrometric films, is debated. Here, we quantify the spatial dynamics of Pseudomonas putida KT2440 and its nonflagellated isogenic mutant as affected by the hydration status of a rough porous surface using an experimental system that mimics aquatic habitats found in unsaturated soils. The flagellar motility of the model soil bacterium decreased sharply within a small range of water potential (0 to -2 kPa) and nearly ceased in liquid films of effective thickness smaller than 1.5 microm. However, bacteria could rapidly resume motility in response to periodic increases in hydration. We propose a biophysical model that captures key effects of hydration and liquid-film thickness on individual cell velocity and use a simple roughness network model to simulate colony expansion. Model predictions match experimental results reasonably well, highlighting the role of viscous and capillary pinning forces in hindering flagellar motility. Although flagellar motility seems to be restricted to a narrow range of very wet conditions, fitness gains conferred by fast surface colonization during transient favorable periods might offset the costs associated with flagella synthesis and explain the sustained presence of flagellated prokaryotes in partially saturated habitats such as soil surfaces.
    Keywords: Bacterial Physiological Phenomena -- Drug Effects ; Flagella -- Physiology ; Pseudomonas Putida -- Physiology ; Water -- Pharmacology
    ISSN: 00278424
    E-ISSN: 1091-6490
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  • 2
    Language: English
    In: Journal of Personality and Social Psychology, August, 2014, Vol.107(2), p.265(11)
    Description: Humans are motivated by a quest for significance that is threatened by the inevitability of death. However, individuals with interdependent self-construals, self-representations that reflect embeddedness with and connection to others, are able to extend themselves through time and space through their linkage to a larger social group. The present set of 5 experiments tested the hypotheses that individuals primed with an interdependent self-construal would fear death less and would be more willing to face harm for the sake of the group than individuals with an independent self-construal, that is, self-representations that reflect autonomy and independence from others ("I have self-control"). The results show that interdependent self-construals, compared to independent self-construals, attenuate death anxiety, reduce the avoidance of death, increase the approach to death-related stimuli, induce a greater willingness to become a martyr, and induce a greater willingness to sacrifice the self for other members of important groups
    Keywords: Fear Of Death -- Analysis ; Self-Construal -- Analysis
    ISSN: 0022-3514
    Source: Cengage Learning, Inc.
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  • 3
    Language: English
    In: Applied and Environmental Microbiology, 2012, Vol. 78(8), p.2936
    Description: Using a novel experimental system that allows control of the matric potential of an agar slab, we explored the hydration conditions under which swarming motility is possible. If there is recognition that this physical parameter is a key determinant of swarming, it is usually neither controlled nor measured rigorously but only manipulated through proxies, namely, the agar concentration and the drying time of "soft" agar plates (swarming plates). We contend that this not only obscures the biophysical mechanisms underlying swarming but also impedes a full assessment of its clinical and environmental significances. Our results indicate that swarming motility is restricted to a narrow range of high matric water potentials in the three pseudomonads tested (Pseudomonas sp. DSS73, Pseudomonas syringae B728a, and Pseudomonas aeruginosa PA14). The threshold below which no swarming was observed was about -0.45 kPa for the first and about -0.1 kPa for the latter two. Above the threshold, the expansion rate of DSS73 swarms increased exponentially with the matric potential. Mutants deficient in surfactant production were totally or partially unable to expand rapidly on the surface of the agar slab. Our results thus suggest that swarming motility in pseudomonads is restricted to (micro)sites where ambient humidity is very high (relative humidity of 〉99.99%). The spatiotemporal occurrence of such sites is limited in many types of terrestrial environments.
    Keywords: Water Microbiology ; Pseudomonas -- Physiology ; Water -- Chemistry;
    ISSN: 1098-5336
    ISSN: 10985336
    ISSN: 00992240
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  • 4
    Language: English
    In: Soil Biology and Biochemistry, December 2015, Vol.91, pp.258-267
    Description: The spatial ecology of soil microbial communities and their functioning is an understudied aspect of soil microbial ecology. Much of our understanding of the spatial organisation of microbial communities has been obtained at scales that are inappropriate for identifying how microbial functioning and spatial patterns are related. In order to reveal the spatial strategies of soil microorganisms, we measured the microscale spatial distribution of 6 exoenzyme activities (EEA) and related them to the catalytic potential of three soils. The relationship between EEA profiles and microbial community structure was also measured in soil aggregates. All the EEA exhibited scale-invariant spatial clustering. The extent of spatial clustering varied significantly among EEA, suggesting that microbial communities employ different spatial strategies when foraging for different elements. The dispersed distribution of alkaline phosphatase suggests that microorganisms invest more heavily in the acquisition of P. The EEA associated with the C and N cycles, but not the P cycle, were significantly affected by management practices in the loamy soil. A significant negative relationship between the extent of spatial clustering of EEA and the overall intensity of the EEA was identified in the two loamy soils, indicating that the microscale spatial ecology of microbial activity may have a significant impact on biogeochemical cycles. No relationship was found between microbial community structure and EEA profiles in aggregates. However, a number of negative relationships between the relative abundance of certain taxa and the most dispersed EEA (alkaline phosphatase and β-glucosidase) were found, suggesting that these taxa make the EEA products available by means other than the production of exoenzymes (e.g. solubilisation of phosphate through the production of organic acids).
    Keywords: Aggregate ; Dispersion ; Exoenzyme Activity ; Management Practices ; Micro-Scale ; Spatial Distribution ; Taxonomic Microarray ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 5
    Language: English
    In: Soil Biology and Biochemistry, 2015, Vol.90, p.122(17)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.soilbio.2015.08.003 Byline: Lasse L. Pedersen, Barth F. Smets, Arnaud Dechesne Abstract: Steep physiochemical gradients and diffusive limitation associated with microscale features such as cracks and pores make soil and sediments remarkably heterogeneous environments, which is reflected on many environmentally important processes. If we are to understand and attempt to control the ecology of the microorganisms which inhabit these environments we must not only characterize their inhabitants, but also the complex biogeochemical landscape they live in. This includes local concentrations of electron acceptors and donors, microbial metabolites and key physical and chemical parameters such as pH and soil structure. To this end, an array of techniques for collecting data at the microscale has been developed, deployed and refined, ranging from microsensor probes to planar sensors. This review provides a general reference for and a critical comparison of microscale techniques available to the fields of soil and sediment microbial ecology. Techniques are evaluated based on their ability to provide spatially resolved data at the microscale, with focus on performance characteristics, potential for repeated measurements, degree of physical disruption they create, and accessibility. Microscale studies have given us many insights, but we outline further progress needed to make the microscale toolkit more accessible and to extend the range of analytes that can be measured simultaneously, so that we may expand our knowledge of the complex environmental microscale heterogeneity and its impact on soil and sediment ecology and functioning. Author Affiliation: Department of Environmental Engineering, Technical University of Denmark, Kgs. Lyngby 2800, Denmark Article History: Received 13 February 2015; Revised 31 July 2015; Accepted 1 August 2015
    Keywords: Metabolites – Analysis ; Metabolites – Measurement ; Soil Microbiology – Analysis ; Soil Microbiology – Measurement ; Soils – Analysis ; Soils – Measurement ; Sensors – Analysis ; Sensors – Measurement ; Sediments (Geology) – Analysis ; Sediments (Geology) – Measurement
    ISSN: 0038-0717
    Source: Cengage Learning, Inc.
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  • 6
    Language: English
    In: Journal of Personality and Social Psychology, 2014, Vol.107(2), pp.265-275
    Description: Humans are motivated by a quest for significance that is threatened by the inevitability of death. However, individuals with interdependent self-construals, self-representations that reflect embeddedness with and connection to others, are able to extend themselves through time and space through their linkage to a larger social group. The present set of 5 experiments tested the hypotheses that individuals primed with an interdependent self-construal would fear death less and would be more willing to face harm for the sake of the group than individuals with an independent self-construal, that is, self-representations that reflect autonomy and independence from others (“I have self-control”). The results show that interdependent self-construals, compared to independent self-construals, attenuate death anxiety, reduce the avoidance of death, increase the approach to death-related stimuli, induce a greater willingness to become a martyr, and induce a greater willingness to sacrifice the self for other members of important groups.
    Keywords: Self-Construal ; Quest For Significance ; Martyrdom ; Self-Sacrifice ; Death Anxiety
    ISSN: 0022-3514
    E-ISSN: 1939-1315
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  • 7
    Language: English
    In: The Science of the Total Environment, Feb 15, 2014, Vol.472, p.90(9)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.scitotenv.2013.11.009 Byline: Annette E. Rosenbom, Philip J. Binning, Jens Aamand, Arnaud Dechesne, Barth F. Smets, Anders R. Johnsen Abstract: The potential for pesticide degradation varies greatly at the centimeter-scale in agricultural soil. Three dimensional numerical simulations were conducted to evaluate how such small-scale spatial heterogeneity may affect the leaching of the biodegradable pesticide 2-methyl-4-chlorophenoxyacetic acid (MCPA) in the upper meter of a variably-saturated, loamy soil profile. To incorporate realistic spatial variation in degradation potential, we used data from a site where 420 mineralization curves over 5 depths have been measured. Monod kinetics was fitted to the individual curves to derive initial degrader biomass values, which were incorporated in a reactive transport model to simulate heterogeneous biodegradation. Six scenarios were set up using COMSOL Multiphysics to evaluate the difference between models having different degrader biomass distributions (homogeneous, heterogeneous, or no biomass) and either matrix flow or preferential flow through a soil matrix with a wormhole. MCPA leached, within 250days, below 1m only when degrader biomass was absent and preferential flow occurred. Both biodegradation in the plow layer and the microbially active lining of the wormhole contributed to reducing MCPA-leaching below 1m. The spatial distribution of initial degrader biomass within each soil matrix layer, however, had little effect on the overall MCPA-leaching. Article History: Received 17 September 2013; Revised 1 November 2013; Accepted 1 November 2013
    Keywords: Leaching -- Analysis ; Loams -- Analysis ; Biodegradation -- Analysis
    ISSN: 0048-9697
    Source: Cengage Learning, Inc.
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  • 8
    Language: English
    In: The Lancet, 18 April 2015, Vol.385(9977), pp.1505-1505
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/S0140-6736(15)60744-9 Byline: Anne Marie Oudesluys-Murphy, Hester M Diderich, Mark Dechesne, Simone E Buitendijk Author Affiliation: (a) Leiden University Medical Centre, 2333 ZA Leiden, The Netherlands (b) Emergency Department, Medical Centre Haaglanden, The Hague, The Netherlands (c) LeidenUniversity -- Campus The Hague, The Hague, The Netherlands (d) Women's and Family Health, Leiden University Medical Centre, Leiden, The Netherlands
    Keywords: Medicine
    ISSN: 0140-6736
    E-ISSN: 1474-547X
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  • 9
    Language: English
    In: Soil Biology and Biochemistry, November 2015, Vol.90, pp.122-138
    Description: Steep physiochemical gradients and diffusive limitation associated with microscale features such as cracks and pores make soil and sediments remarkably heterogeneous environments, which is reflected on many environmentally important processes. If we are to understand and attempt to control the ecology of the microorganisms which inhabit these environments we must not only characterize their inhabitants, but also the complex biogeochemical landscape they live in. This includes local concentrations of electron acceptors and donors, microbial metabolites and key physical and chemical parameters such as pH and soil structure. To this end, an array of techniques for collecting data at the microscale has been developed, deployed and refined, ranging from microsensor probes to planar sensors. This review provides a general reference for and a critical comparison of microscale techniques available to the fields of soil and sediment microbial ecology. Techniques are evaluated based on their ability to provide spatially resolved data at the microscale, with focus on performance characteristics, potential for repeated measurements, degree of physical disruption they create, and accessibility. Microscale studies have given us many insights, but we outline further progress needed to make the microscale toolkit more accessible and to extend the range of analytes that can be measured simultaneously, so that we may expand our knowledge of the complex environmental microscale heterogeneity and its impact on soil and sediment ecology and functioning.
    Keywords: Microsensor ; Planar Sensor ; Optode ; Spatial ; Gradients ; Agriculture ; Chemistry
    ISSN: 0038-0717
    E-ISSN: 1879-3428
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  • 10
    Language: English
    In: Crime, Law and Social Change, 2011, Vol.55(4), pp.287-292
    Description: The present article considers deradicalization programs. It is observed that deradicalization is primarily a strategic tool, that it was already used in the 1970s, that it can occur spontaneously, and that is should be differentiated from physical disengagement. An evaluation of existing deradicalization programs lead to the propositions that 1) deradicalization programs in the area of right-wing extremism primarily focus on changing behavior not thoughts, that 2) currently there is insufficient insight in what motives people to deradicalize, and 3) that insights from psychology are still insufficiently used to increase effectiveness of deradicalization. Research can make an important contribution to optimize efficiency of deradicalization for counterterrorism purposes.
    ISSN: 0925-4994
    E-ISSN: 1573-0751
    Source: Springer Science & Business Media B.V.
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