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- Poorter, Lourens, et al.
(författare)
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Wet and dry tropical forests show opposite successional pathways in wood density but converge over time
- 2019
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Ingår i: Nature Ecology & Evolution. - : Nature Publishing Group. - 2397-334X. ; 3:6, s. 928-934
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Tidskriftsartikel (refereegranskat)abstract
- Tropical forests are converted at an alarming rate for agricultural use and pastureland, but also regrow naturally through secondary succession. For successful forest restoration, it is essential to understand the mechanisms of secondary succession. These mechanisms may vary across forest types, but analyses across broad spatial scales are lacking. Here, we analyse forest recovery using 1,403 plots that differ in age since agricultural abandonment from 50 sites across the Neotropics. We analyse changes in community composition using species-specific stem wood density (WD), which is a key trait for plant growth, survival and forest carbon storage. In wet forest, succession proceeds from low towards high community WD (acquisitive towards conservative trait values), in line with standard successional theory. However, in dry forest, succession proceeds from high towards low community WD (conservative towards acquisitive trait values), probably because high WD reflects drought tolerance in harsh early successional environments. Dry season intensity drives WD recovery by influencing the start and trajectory of succession, resulting in convergence of the community WD over time as vegetation cover builds up. These ecological insights can be used to improve species selection for reforestation. Reforestation species selected to establish a first protective canopy layer should, among other criteria, ideally have a similar WD to the early successional communities that dominate under the prevailing macroclimatic conditions.
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| 2. |
- Bernal, Ximena E., et al.
(författare)
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Empowering Latina scientists
- 2019
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 363:6429, s. 825-826
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Luís Martins, Joana, 1984, et al.
(författare)
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Radiation emission in laser-wakefields driven by structured laser pulses with orbital angular momentum
- 2019
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- High-intensity X-ray sources are invaluable tools, enabling experiments at the forefront of our understanding of materials science, chemistry, biology, and physics. Laser-plasma electron accelerators are sources of high-intensity X-rays, as electrons accelerated in wakefields emit short-wavelength radiation due to betatron oscillations. While applications such as phasecontrast imaging with these betatron sources have already been demonstrated, others would require higher photon number and would benefit from increased tunability. In this paper we demonstrate, through detailed 3D simulations, a novel configuration for a laser-wakefield betatron source that increases the energy of the X-ray emission and also provides increased flexibility in the tuning of the X-ray photon energy. This is made by combining two Laguerre-Gaussian pulses with non-zero net orbital angular momentum, leading to a rotation of the intensity pattern, and hence, of the driven wakefields. The helical motion driven by the laser rotation is found to dominate the radiation emission, rather than the betatron oscillations. Moreover, the radius of this helical motion can be controlled through the laser spot size and orbital angular momentum indexes, meaning that the radiation can be tuned fully independently of the plasma parameters.
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| 4. |
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| 5. |
- Pereira, T., et al.
(författare)
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Randomized study of the effects of cocoa-rich chocolate on the ventricle–arterial coupling and vascular function of young, healthy adults
- 2019
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Ingår i: Nutrition. - : Elsevier BV. - 0899-9007. ; 63-64, s. 175-183
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: The aim of this study was to evaluate and explore the benefits of long-term dark chocolate intake in young, healthy adults by measuring cardiovascular function. Methods: A randomized study was conducted with 30 healthy participants ages 18 to 27 y. Half of the participants ingested a 20-g dose of lower cocoa chocolate (LCC; ∼55%; 12.6 ± 1.4 mg equivalent of epicatechin/g) and the others ingested a daily dose of 20 g of higher cocoa chocolate (HCC; ∼90%; 18.2 ± 2.6 mg equivalent of epicatechin/g). A baseline evaluation was performed before the participants started ingesting the assigned chocolate for a 30-d period, after which a final evaluation was performed. Each evaluation included heart ultrasonography, carotid-femoral pulse wave velocity (PWV) and carotid pulse wave analysis, flow-mediated slowing (FMS), and an analysis of the ventricular–arterial coupling (VAC), which reflects the matching between the aorta and the left ventricle (ratio of arterial elastance to left ventricle elastance). Results: The baseline evaluation presented similar values within normal range in both groups. The positive vascular effects were overall more distinct in the group eating the HCC. No structural modifications on the heart were found after the intervention, notwithstanding cardiac function was improved on certain functional parameters in the HCC group only. A statistically significant improvement was depicted over the brachial and central systolic and pulse pressures in the HCC group, and a trend for improvement in the reflected waves component (Aix) and the FMS was also observed in the HCC, but not in the LCC group. VAC parameters were similar at baseline between groups, but showed a significant improvement in the HCC group after intervention, increasing from 0.674 to 0.719 (P = 0.004), so that the post-intervention VAC was significantly higher in the HCC group than in the LCC group (P < 0.05). In addition, significant variation was observed in both groups regarding arterial and left ventricle elastances, stroke work, and potential energy, with greater mean differences identified in the HCC group. Conclusion: This study demonstrated that regular consumption of HCC has beneficial effects on the cardiovascular system in young, healthy adults, improving vascular function by reducing central brachial artery pressures and promoting vascular relaxation, and thus enhancing the matching of the arterial system with the left ventricle. © 2019 Elsevier Inc.
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