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- Buker, P., et al.
(författare)
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DO3SE modelling of soil moisture to determine ozone flux to forest trees
- 2012
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 12:12, s. 5537-5562
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Tidskriftsartikel (refereegranskat)abstract
- The DO3SE (Deposition of O-3 for Stomatal Exchange) model is an established tool for estimating ozone (O-3) deposition, stomatal flux and impacts to a variety of vegetation types across Europe. It has been embedded within the EMEP (European Monitoring and Evaluation Programme) photochemical model to provide a policy tool capable of relating the flux-based risk of vegetation damage to O-3 precursor emission scenarios for use in policy formulation. A key limitation of regional flux-based risk assessments has been the assumption that soil water deficits are not limiting O-3 flux due to the unavailability of evaluated methods for modelling soil water deficits and their influence on stomatal conductance (g(sto)), and subsequent O-3 flux. This paper describes the development and evaluation of a method to estimate soil moisture status and its influence on g(sto) for a variety of forest tree species. This DO3SE soil moisture module uses the Penman-Monteith energy balance method to drive water cycling through the soil-plant-atmosphere system and empirical data describing g(sto) relationships with pre-dawn leaf water status to estimate the biological control of transpiration. We trial four different methods to estimate this biological control of the transpiration stream, which vary from simple methods that relate soil water content or potential directly to g(sto), to more complex methods that incorporate hydraulic resistance and plant capacitance that control water flow through the plant system. These methods are evaluated against field data describing a variety of soil water variables, g(sto) and transpiration data for Norway spruce (Picea abies), Scots pine (Pinus sylvestris), birch (Betula pendula), aspen (Populus tremuloides), beech (Fagus sylvatica) and holm oak (Quercus ilex) collected from ten sites across Europe and North America. Modelled estimates of these variables show consistency with observed data when applying the simple empirical methods, with the timing and magnitude of soil drying events being captured well across all sites and reductions in transpiration with the onset of drought being predicted with reasonable accuracy. The more complex methods, which incorporate hydraulic resistance and plant capacitance, perform less well, with predicted drying cycles consistently underestimating the rate and magnitude of water loss from the soil. A sensitivity analysis showed that model performance was strongly dependent upon the local parameterisation of key model drivers such as the maximum g(sto), soil texture, root depth and leaf area index. The results suggest that the simple modelling methods that relate g(sto) directly to soil water content and potential provide adequate estimates of soil moisture and influence on g(sto) such that they are suitable to be used to assess the potential risk posed by O-3 to forest trees across Europe.
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- Hedman, E., et al.
(författare)
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Effectiveness of Internet-based cognitive behaviour therapy for panic disorder in routine psychiatric care
- 2013
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Ingår i: Acta Psychiatrica Scandinavica. - : Wiley. - 0001-690X .- 1600-0447. ; 128:6, s. 457-467
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Tidskriftsartikel (refereegranskat)abstract
- ObjectiveGuided Internet-based cognitive behaviour therapy (ICBT) for panic disorder has been shown to be efficacious in several randomized controlled trials. However, the effectiveness of the treatment when delivered within routine psychiatric care has not been studied. The aim of this study was to investigate the effectiveness of ICBT for panic disorder within the context of routine psychiatric care. MethodWe conducted a cohort study investigating all patients (n=570) who had received guided ICBT for panic disorder between 2007 and 2012 in a routine care setting at an out-patient psychiatric clinic providing Internet-based treatment. The primary outcome measure was the Panic Disorder Severity Scale-Self-report (PDSS-SR). ResultsParticipants made large improvements from screening and pretreatment assessments to posttreatment (Cohen's d range on the PDSS-SR=1.07-1.55). Improvements were sustained at 6-month follow-up. ConclusionThis study suggests that ICBT for panic disorder is as effective when delivered in a routine care context as in the previously published randomized controlled trials.
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- Lemme, Max C., 1970-, et al.
(författare)
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Gate-Activated Photoresponse in a Graphene p-n Junction
- 2011
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 11:10, s. 4134-4137
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Tidskriftsartikel (refereegranskat)abstract
- We study photodetection in graphene near a local electrostatic gate, which enables active control of the potential landscape and carrier polarity. We find that a strong photoresponse only appears when and where a p-n junction is formed, allowing on-off control of photodetection. Photocurrents generated near p-n junctions do not require biasing and can be realized using submicrometer gates. Locally modulated photoresponse enables a new range of applications for graphene-based photodetectors including, for example, pixilated infrared imaging with control of response on subwavelength dimensions.
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- Sjöström, Martin, et al.
(författare)
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Evaluation of MODIS gross primary productivity for Africa using eddy covariance data
- 2013
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Ingår i: Remote Sensing of Environment. - : Elsevier BV. - 0034-4257. ; 131, s. 275-286
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Tidskriftsartikel (refereegranskat)abstract
- MOD17A2 provides operational gross primary production (GPP) data globally at 1 km spatial resolution and 8-day temporal resolution. MOD17A2 estimates GPP according to the light use efficiency (LUE) concept assuming a fixed maximum rate of carbon assimilation per unit photosynthetically active radiation absorbed by the vegetation (epsilon(max)). Minimum temperature and vapor pressure deficit derived from meteorological data down-regulate epsilon(max) and constrain carbon assimilation. This data is useful for regional to global studies of the terrestrial carbon budget, climate change and natural resources. In this study we evaluated the MOD17A2 product and its driver data by using in situ measurements of meteorology and eddy covariance GPP for 12 African sites. MOD17A2 agreed well with eddy covariance GPP for wet sites. Overall, seasonality was well captured but MOD17A2 GPP was underestimated for the dry sites located in the Sahel region. Replacing the meteorological driver data derived from coarse resolution reanalysis data with tower measurements reduced MOD17A2 GPP uncertainties, however, the underestimations at the dry sites persisted. Inferred epsilon(max) calculated from tower data was higher than the epsilon(max) prescribed in MOD17A2. This, in addition to uncertainties in fraction of absorbed photosynthetically active radiation (FAPAR) explains some of the underestimations. The results suggest that improved quality of driver data, but primarily a readjustment of the parameters in the biome parameter look-up table (BPLUT) may be needed to better estimate GPP for African ecosystems in MOD17A2. (C) 2013 Elsevier Inc. All rights reserved.
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