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- Shelemin, A., et al.
(författare)
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Nucleation and Growth of Magnetron-Sputtered Ag Nanoparticles as Witnessed by Time-Resolved Small Angle X-Ray Scattering
- 2019
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Ingår i: Particle and Particle Systems Characterization. - : John Wiley & Sons. - 0934-0866 .- 1521-4117.
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Tidskriftsartikel (refereegranskat)abstract
- Kinetic aspects of the synthesis of Ag nanoparticles (NPs) by magnetron sputtering are studied by in situ and time‐resolved small angle X‐ray scattering (SAXS). Part of the NPs are found to become confined within a capture zone at 1–10 mm from the surface of the target and circumscribed by the plasma ring. Three regimes of the NP growth are identified: 1) early growth at which the average NP diameter rapidly increases to 90 nm; 2) cycling instabilities at which the SAXS signal periodically fluctuates either due to expelling of large NPs from the capture zone or due to the axial rotation of the NP cloud; and 3) steady‐state synthesis at which stable synthesis of the NPs is achieved. The NP confinement within the capture zone is driven by the balance of forces, the electrostatic force being dominant. On reaching the critical size, large NPs acquire an excessive charge and become expelled from the capture zone via the electrostatic interactions. As a result, significant NP deposits are formed on the inner walls of the aggregation chamber as well as in the central area of the target.
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- MacDougall, Andrew S., et al.
(författare)
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Widening global variability in grassland biomass since the 1980s
- 2024
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Ingår i: Nature Ecology & Evolution. - : Springer Nature. - 2397-334X.
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Tidskriftsartikel (refereegranskat)abstract
- Global change is associated with variable shifts in the annual production of aboveground plant biomass, suggesting localized sensitivities with unclear causal origins. Combining remotely sensed normalized difference vegetation index data since the 1980s with contemporary field data from 84 grasslands on 6 continents, we show a widening divergence in site-level biomass ranging from +51% to −34% globally. Biomass generally increased in warmer, wetter and species-rich sites with longer growing seasons and declined in species-poor arid areas. Phenological changes were widespread, revealing substantive transitions in grassland seasonal cycling. Grazing, nitrogen deposition and plant invasion were prevalent in some regions but did not predict overall trends. Grasslands are undergoing sizable changes in production, with implications for food security, biodiversity and carbon storage especially in arid regions where declines are accelerating.
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- Buitelaar, Jan K, et al.
(författare)
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A randomized, double-blind study of continuation treatment for attention-deficit/hyperactivity disorder after 1 year.
- 2007
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Ingår i: Biological Psychiatry. - : Elsevier BV. - 0006-3223. ; 61:5, s. 694-699
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The efficacy of atomoxetine in maintaining symptom response following 1 year of treatment was assessed in children and adolescents (n = 163) with DSM-IV defined attention-deficit/hyperactivity disorder (ADHD). METHODS: Subjects had previously responded to atomoxetine acutely and had completed 1 year of double-blind atomoxetine treatment. They were then randomly assigned in double-blind fashion to continued atomoxetine or placebo substitution for 6 months. RESULTS: Atomoxetine was superior to placebo in preventing relapse (Wilcoxon test, p = .008) and in maintaining symptom response (ADHD Rating Scale IV score, p < .001). Among subjects assigned to discontinuation, the magnitude of symptom return was generally to a level of severity less than that observed at study entry. CONCLUSIONS: Following 1 year of treatment with atomoxetine, continued treatment over the ensuing 6 months was associated with superior outcomes compared with placebo substitution. However, there was considerable variability between individuals in the magnitude of symptom return after drug discontinuation, suggesting that some subjects treated with atomoxetine for a year with good results may consolidate gains made during drug treatment and could benefit from a medication-free trial to assess the need for ongoing drug treatment.
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- Lundgren, Edvin, et al.
(författare)
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The surface oxide as a source of oxygen on Rh(111)
- 2005
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 144:SI, s. 367-372
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Tidskriftsartikel (refereegranskat)abstract
- The reduction of a thin surface oxide on the Rh(1 1 1) surface by CO is studied in situ by photoemission spectroscopy, scanning tunneling microscopy, and density functional theory. CO molecules are found not to adsorb on the surface oxide at a sample temperature of 100 K, in contrast to on the clean and chemisorbed oxygen covered surface. Despite this behavior, the surface oxide may still be reduced by CO, albeit in a significantly different fashion as compared to the reduction of a phase containing only chemisorbed on surface oxygen. The experimental observations combined with theoretical considerations concerning the stability of the surface oxide, result in a model of the reduction process at these pressures suggesting that the surface oxide behaves as a source of oxygen for the CO-oxidation reaction.
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