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| 2. |
- Power, M. J., et al.
(författare)
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Changes in fire regimes since the Last Glacial Maximum : an assessment based on a global synthesis and analysis of charcoal data
- 2008
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Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 30:7-8, s. 887-907
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Tidskriftsartikel (refereegranskat)abstract
- Fire activity has varied globally and continuously since the last glacial maximum (LGM) in response to long-term changes in global climate and shorter-term regional changes in climate, vegetation, and human land use. We have synthesized sedimentary charcoal records of biomass burning since the LGM and present global maps showing changes in fire activity for time slices during the past 21,000 years (as differences in charcoal accumulation values compared to pre-industrial). There is strong broad-scale coherence in fire activity after the LGM, but spatial heterogeneity in the signals increases thereafter. In North America, Europe and southern South America, charcoal records indicate less-than-present fire activity during the deglacial period, from 21,000 to ∼11,000 cal yr BP. In contrast, the tropical latitudes of South America and Africa show greater-than-present fire activity from ∼19,000 to ∼17,000 cal yr BP and most sites from Indochina and Australia show greater-than-present fire activity from 16,000 to ∼13,000 cal yr BP. Many sites indicate greater-than-present or near-present activity during the Holocene with the exception of eastern North America and eastern Asia from 8,000 to ∼3,000 cal yr BP, Indonesia and Australia from 11,000 to 4,000 cal yr BP, and southern South America from 6,000 to 3,000 cal yr BP where fire activity was less than present. Regional coherence in the patterns of change in fire activity was evident throughout the post-glacial period. These complex patterns can largely be explained in terms of large-scale climate controls modulated by local changes in vegetation and fuel load.
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| 4. |
- Fisher, Rosie A., et al.
(författare)
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Vegetation demographics in Earth System Models : A review of progress and priorities
- 2018
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 24:1, s. 35-54
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Forskningsöversikt (refereegranskat)abstract
- Numerous current efforts seek to improve the representation of ecosystem ecology and vegetation demographic processes within Earth System Models (ESMs). These developments are widely viewed as an important step in developing greater realism in predictions of future ecosystem states and fluxes. Increased realism, however, leads to increased model complexity, with new features raising a suite of ecological questions that require empirical constraints. Here, we review the developments that permit the representation of plant demographics in ESMs, and identify issues raised by these developments that highlight important gaps in ecological understanding. These issues inevitably translate into uncertainty in model projections but also allow models to be applied to new processes and questions concerning the dynamics of real-world ecosystems. We argue that stronger and more innovative connections to data, across the range of scales considered, are required to address these gaps in understanding. The development of first-generation land surface models as a unifying framework for ecophysiological understanding stimulated much research into plant physiological traits and gas exchange. Constraining predictions at ecologically relevant spatial and temporal scales will require a similar investment of effort and intensified inter-disciplinary communication.
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| 5. |
- Grossmann, Igor, et al.
(författare)
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Insights into the accuracy of social scientists' forecasts of societal change
- 2023
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Ingår i: Nature Human Behaviour. - : Springer Nature. - 2397-3374. ; 7, s. 484-501
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Tidskriftsartikel (refereegranskat)abstract
- How well can social scientists predict societal change, and what processes underlie their predictions? To answer these questions, we ran two forecasting tournaments testing the accuracy of predictions of societal change in domains commonly studied in the social sciences: ideological preferences, political polarization, life satisfaction, sentiment on social media, and gender-career and racial bias. After we provided them with historical trend data on the relevant domain, social scientists submitted pre-registered monthly forecasts for a year (Tournament 1; N = 86 teams and 359 forecasts), with an opportunity to update forecasts on the basis of new data six months later (Tournament 2; N = 120 teams and 546 forecasts). Benchmarking forecasting accuracy revealed that social scientists' forecasts were on average no more accurate than those of simple statistical models (historical means, random walks or linear regressions) or the aggregate forecasts of a sample from the general public (N = 802). However, scientists were more accurate if they had scientific expertise in a prediction domain, were interdisciplinary, used simpler models and based predictions on prior data. How accurate are social scientists in predicting societal change, and what processes underlie their predictions? Grossmann et al. report the findings of two forecasting tournaments. Social scientists' forecasts were on average no more accurate than those of simple statistical models.
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| 6. |
- Ciray, H N, et al.
(författare)
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Presence and localization of connexins 43 and 26 in cell cultures derived from myometrial tissues from nonpregnant and pregnant women and from leiomyomas
- 2000
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Ingår i: American Journal of Obstetrics and Gynecology. - 0002-9378 .- 1097-6868. ; 182:4, s. 926-930
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE:Our objective was to study the appearance and distribution of connexins 43 and 26 in various human myometrial cell cultures.STUDY DESIGN:Scrape loading, Western blotting, and immunohistochemical techniques were applied to cultured cells derived from myometrial tissues obtained from nonpregnant and pregnant women (upper and lower uterine segments) and from leiomyomas (tumor and analogous myometrial tissues).RESULTS:Scrape loading revealed the presence of metabolic coupling in all tissues. Indirect immunohistochemical studies showed membrane localization of connexin 43 in all myometrial cultures. Western blots and indirect immunohistochemical studies showed the presence and localization of the connexin 26 protein and associated gap junctions in tissues from myomas and from nonpregnant and pregnant women except for those derived from the upper segment of the pregnant uterus.CONCLUSION:These results show that human myometrial cultures express various gap junction proteins and that there are regional differences in expression of connexins in tissues from pregnant women.
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| 7. |
- Sawyer, Jordan C., et al.
(författare)
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Reactions of C+ + Cl-, Br-, and I--A comparison of theory and experiment
- 2019
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 151:24
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Tidskriftsartikel (refereegranskat)abstract
- Rate constants for the reactions of C+ + Cl-, Br-, and I- were measured at 300 K using the variable electron and neutral density electron attachment mass spectrometry technique in a flowing afterglow Langmuir probe apparatus. Upper bounds of <10(-8) cm(3) s(-1) were found for the reaction of C+ with Br- and I-, and a rate constant of 4.2 +/- 1.1 x 10(-9) cm(3) s(-1) was measured for the reaction with Cl-. The C+ + Cl- mutual neutralization reaction was studied theoretically from first principles, and a rate constant of 3.9 x 10(-10) cm(3) s(-1), an order of magnitude smaller than experiment, was obtained with spin-orbit interactions included using a semiempirical model. The discrepancy between the measured and calculated rate constants could be explained by the fact that in the experiment, the total loss of C+ ions was measured, while the theoretical treatment did not include the associative ionization channel. The charge transfer was found to take place at small internuclear distances, and the spin-orbit interaction was found to have a minor effect on the rate constant.
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| 8. |
- Scherer, SW, et al.
(författare)
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Human chromosome 7: DNA sequence and biology
- 2003
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Ingår i: Science (New York, N.Y.). - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 300:5620, s. 767-772
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Tidskriftsartikel (refereegranskat)abstract
- DNA sequence and annotation of the entire human chromosome 7, encompassing nearly 158 million nucleotides of DNA and 1917 gene structures, are presented. To generate a higher order description, additional structural features such as imprinted genes, fragile sites, and segmental duplications were integrated at the level of the DNA sequence with medical genetic data, including 440 chromosome rearrangement breakpoints associated with disease. This approach enabled the discovery of candidate genes for developmental diseases including autism.
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| 9. |
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| 10. |
- Von Eggers, Jordan M., et al.
(författare)
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Environmental filtering governs consistent vertical zonation in sedimentary microbial communities across disconnected mountain lakes
- 2024
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Ingår i: Environmental Microbiology. - : John Wiley & Sons. - 1462-2912 .- 1462-2920. ; 26:3
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Tidskriftsartikel (refereegranskat)abstract
- Subsurface microorganisms make up the majority of Earth's microbial biomass, but ecological processes governing surface communities may not explain community patterns at depth because of burial. Depth constrains dispersal and energy availability, and when combined with geographic isolation across landscapes, may influence community assembly. We sequenced the 16S rRNA gene of bacteria and archaea from 48 sediment cores across 36 lakes in four disconnected mountain ranges in Wyoming, USA and used null models to infer assembly processes across depth, spatial isolation, and varying environments. Although we expected strong dispersal limitations across these isolated settings, community composition was primarily shaped by environmental selection. Communities consistently shifted from domination by organisms that degrade organic matter at the surface to methanogenic, low-energy adapted taxa in deeper zones. Stochastic processes—like dispersal limitation—contributed to differences among lakes, but because these effects weakened with depth, selection processes ultimately governed subsurface microbial biogeography.
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