| 1. |
- Aevarsson, Arnthór, et al.
(author)
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Going to extremes - a metagenomic journey into the dark matter of life
- 2021
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In: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 1574-6968. ; 368:12
-
Research review (peer-reviewed)abstract
- The Virus-X-Viral Metagenomics for Innovation Value-project was a scientific expedition to explore and exploit uncharted territory of genetic diversity in extreme natural environments such as geothermal hot springs and deep-sea ocean ecosystems. Specifically, the project was set to analyse and exploit viral metagenomes with the ultimate goal of developing new gene products with high innovation value for applications in biotechnology, pharmaceutical, medical, and the life science sectors. Viral gene pool analysis is also essential to obtain fundamental insight into ecosystem dynamics and to investigate how viruses influence the evolution of microbes and multicellular organisms. The Virus-X Consortium, established in 2016, included experts from eight European countries. The unique approach based on high throughput bioinformatics technologies combined with structural and functional studies resulted in the development of a biodiscovery pipeline of significant capacity and scale. The activities within the Virus-X consortium cover the entire range from bioprospecting and methods development in bioinformatics to protein production and characterisation, with the final goal of translating our results into new products for the bioeconomy. The significant impact the consortium made in all of these areas was possible due to the successful cooperation between expert teams that worked together to solve a complex scientific problem using state-of-the-art technologies as well as developing novel tools to explore the virosphere, widely considered as the last great frontier of life.
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| 2. |
- Agnarsson, Björn, et al.
(author)
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Influence of initial surface reconstruction on nitridation of Al2O3 (0001) using low pressure ammonia
- 2007
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In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 101:1, s. 013519-
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Journal article (peer-reviewed)abstract
- The purpose of this study is to investigate the effect of initial surface reconstruction on the nitridation process of Al2O3 (0001). This was done by exposing differently reconstructed sapphire substrates at different temperatures to low pressure ammonia (NH3). Structural and chemical analysis were carried out using low-electron energy diffraction and x-ray photoelectron spectroscopy. The experiments revealed that using low pressure ammonia (P-NH3 < 1 X 10(-5) Torr), no nitridation takes place on (1x1) unreconstructed surfaces. However, when the unreconstructed surface starts to change to a (root 31 x root 31) R +/- 9 degrees reconstructed surface, with increasing substrate temperature, the nitridation becomes successful. When using the initially reconstructed surface, the nitridation is successful even from the lowest temperature used. These results suggest that the initial surface reconstruction has a major effect on the nitridation process. This kinetic behavior has not been reported before, with most nitridation studies mainly focusing on the effect of surface temperature on the resulting surface morphology, rather than the actual kinetics of the process itself.
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| 3. |
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| 4. |
- Cabral, Diogo, et al.
(author)
-
Electrical and thermal performance evaluation of symmetric truncated C-PVT trough solar collectors with vertical bifacial receivers
- 2018
-
In: Solar Energy. - : Elsevier Ltd. - 0038-092X .- 1471-1257. ; 174, s. 683-690
-
Journal article (peer-reviewed)abstract
- One way to reduce solar collectors’ production costs is to use concentrators that increase the output per photovoltaic cell. Concentrating collectors re-direct solar radiation that passes through an aperture into an absorber/receiver. Symmetrical truncated non-tracking C-PVT trough collectors based on a parabola and compound parabolic concentrator (CPC) geometries have been developed. The collector type has a central vertical bifacial (fin) receiver and it was optimized for lower latitudes. In this paper, the electrical and thermal performance of symmetric truncated non-tracking low concentrator PVT solar collectors with vertical bifacial receivers is analysed, through a numerical ray-tracing model software and a multi-paradigm numerical computing environment. A thermal (quasi-dynamic testing method for liquid heating collectors described in the international standard for solar thermal collectors ISO 9806:2013) and electrical performance models were implemented to evaluate the design concepts. The evaluation was made for heating Domestic Hot Water for a Single Family House in Fayoum (Egypt), where CPC geometries with a concentration factor of 1.6 achieved 8 to 13%rel higher energy yields (in kWh/m2/year) than the Pure Parabola geometries.
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| 5. |
- Cabral, Diogo, et al.
(author)
-
Experimental investigation of a CPVT collector coupled with a wedge PVT receiver
- 2021
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In: Solar Energy. - : Elsevier. - 0038-092X .- 1471-1257. ; 215, s. 335-345
-
Journal article (peer-reviewed)abstract
- This paper presents an experimental investigation of a photovoltaic-thermal solar collector (commonly known as PVT) that generates both electricity and heat from the same gross area. PVT solar collectors, in theory, achieve higher combined electrical and heat yields. Additionally, PVT enables a thermal coupling between PV cells and a heat transfer cooling medium. Electrical and thermal outdoor testing measurements have been performed on alow concentration PVT solar collector based on a parabolic reflector geometry with a wedge PVT receiver. Several outdoor experiments have been carried out and presented, such as daily instantaneous electrical and thermal performance efficiency diagrams, as well as optical efficiency charts. Moreover, an electrical IncidenceAngle Modifier (for both transversal and longitudinal directions) assessment has been performed and presented. Furthermore, an overall heat loss coefficient of 4.1 W/m2.◦C has been attained. A measured thermal optical and electrical efficiency of 59% and 8% have been achieved, respectively. Additionally, the placement of the wedge receiver shown to be very sensitive to high incidence angles, as the electrical transversal Incidence AngleModifier factor decreases significantly after reaching its electrical peak efficiency at 10◦.
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| 6. |
- Cabral, Diogo, et al.
(author)
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Performance Evaluation of Non-Uniform Illumination on a Transverse Bifacial PVT Receiver in Combination with a CPC Geometry
- 2019
-
In: Solar Energy. - : Elsevier BV. - 0038-092X .- 1471-1257. ; 194, s. 696-708
-
Journal article (peer-reviewed)abstract
- PVT collectors co-generate electricity and heat from the same gross area, thus achieving higher combined heat and electric yields. A comprehensive evaluation has been carried out on non-uniform solar irradiation profile distributions on four symmetric low concentration CPC PVT (LCPVT) solar collector design concepts. Additionally, an electrical and thermal performance evaluation of symmetric truncated LCPVT solar collectors based on a CPC reflector geometry with a central transverse bifacial PVT receiver has been carried out, through a numerical ray-tracing model software and a multi-paradigm numerical computing environment software. A simplified thermal (quasi-dynamic testing method for liquid heating collectors described in the international standard for solar thermal collectors ISO 9806:2017) and electrical performance models were employed to evaluate the LCPVT design concepts. The evaluation was carried out for heating Domestic Hot Water (DHW) for a Single Family House (SFH) in Fayoum (Egypt), where energy yields between 351 and 391 kWh/m2/year have been achieved. The non-uniform solar irradiation assessment showed that the PV cells are exposed to high levels of radiation due to the specific reflector geometry. Furthermore, the study showed that the CPC geometries are very sensitive to the shading effect, as partial shadowing is substantial for high incidence angles.
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| 7. |
- Cabral, Diogo, et al.
(author)
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Ray tracing simulations of a novel low concentrator PVT solar collector for low latitudes
- 2017
-
In: ISES Solar World Congress 2017 - IEA SHC International Conference on Solar Heating and Cooling for Buildings and Industry 2017, Proceedings. - Freiburg, Germany : International Solar Energy Society. - 9783981465976 ; , s. 1068-1079
-
Conference paper (peer-reviewed)abstract
- One way to reduce solar collector's production costs is to use concentrators that increase the output per photovoltaic cell. Concentrating collectors re-direct solar radiation that passes through an aperture into an absorber. The current study evaluates electrical performance of symmetric C-PVT solar collectors with a vertical bifacial receiver, through a numerical ray tracing model software, Tonatiuh. Several designs have been analysed, such as the Pure Parabola (PP) and MaReCo CPC geometries, both symmetric. Parameters such as concentration factor, electrical performance, transversal and longitudinal IAM (Incidence Angle Modifier), the influence of optical elements and influence of the length of the reflector in the shadow effect have been studied for different geometries. The simulations were performed for Mogadishu, Somalia and showed good results for the Pure Parabola collector (PPc) annual received energy, 379 and 317 kWh/m2/year for a focal length of 15 e 30 mm, respectively. A symmetrical double MaReCo CPC collector has been simulated with the annual received energy of 315 kWh/m2/year. The addition of the optical elements will decrease the annual received energy of the PPc by around 11.5%, where the optical properties (7.1%) and glass (4.1%) have the biggest impact in the annual received energy. Overall, symmetric geometries proved to be the most suitable geometries for low latitudes applications, being the geometry f1 (focal length of 15 mm) the best one.
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| 8. |
- Cabral, Diogo, PhD, 1990-
(author)
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Reflector Optimization for Low Concentration Photovoltaic-Thermal Solar Collectors
- 2022
-
Doctoral thesis (other academic/artistic)abstract
- The alarming new global warming and increasing awareness related to climate change (mainly due to the high emissions of carbon dioxide) in recent decades linked all nations into a common cause, which requires ambitious efforts to combat climate change by adapting energy systems to its effects.The knowledge gain presented in this dissertation establishes the foundations for the development of a more efficient concentrating photovoltaic-thermal (PVT) solar collector. The presented work provides decision-makers with a broader, more detailed performance assessment of concentrating PVT solar collectors.A critical issue for concentrating PVT solar collectors lies in the respective reflector shape, which will determine, to some extent, the overall performance of the CPVT collector. Therefore, several symmetrical reflector design concepts were designed and optimized through Monte Carlo ray-tracing software. With the support of a MATLAB script, a simulation test methodology has been developed and optimized, allowing a more thorough analysis of the results regarding the viability of the different reflector shapes, which established the compound parabolic collector (CPC) to be the most appropriate reflector geometry for PVT solar collectors.Moreover, CPC-PVT solar collectors (based on the findings described above) were designed, built and outdoor tested (under steady-state method guidelines) for their thermal and electrical peak efficiencies, heat losses and incidence angle modifier (IAM) coefficients.The developments achieved in this dissertation significantly enhanced the annual performance of CPC-CPVT solar collectors, which closes the efficiency/performance gap between mature technologies such as PV modules or ST collectors.
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| 9. |
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| 10. |
- Cornelissen, Johannes H C, et al.
(author)
-
Global negative vegetation feedback to climate warming responses of leaf litter decomposition rates in cold biomes
- 2007
-
In: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 10:7, s. 619-627
-
Journal article (peer-reviewed)abstract
- Whether climate change will turn cold biomes from large long-term carbon sinks into sources is hotly debated because of the great potential for ecosystem-mediated feedbacks to global climate. Critical are the direction, magnitude and generality of climate responses of plant litter decomposition. Here, we present the first quantitative analysis of the major climate-change-related drivers of litter decomposition rates in cold northern biomes worldwide.Leaf litters collected from the predominant species in 33 global change manipulation experiments in circum-arctic-alpine ecosystems were incubated simultaneously in two contrasting arctic life zones. We demonstrate that longer-term, large-scale changes to leaf litter decomposition will be driven primarily by both direct warming effects and concomitant shifts in plant growth form composition, with a much smaller role for changes in litter quality within species. Specifically, the ongoing warming-induced expansion of shrubs with recalcitrant leaf litter across cold biomes would constitute a negative feedback to global warming. Depending on the strength of other (previously reported) positive feedbacks of shrub expansion on soil carbon turnover, this may partly counteract direct warming enhancement of litter decomposition.
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| 11. |
- Etherden, Nicholas, et al.
(author)
-
Shading losses for different types of residential PV systems and its city-wide impact on PV potential
- 2019
-
In: Proceedings of Solar Integration Workshop Dublin 2019.
-
Conference paper (other academic/artistic)abstract
- Power optimiser are becoming increasingly popular in residential photovoltaic installations. Besides monitoring and safety advantages the power optimise can increase production under partial shading conditions due to the individual maximum power point tracking performed independently for each panel. This study quantifies the production gains with power optimisers through both empirical and theoretical city-wide simulations. Empirical measurements on adjacent string and optimiser PV systems showed that shading losses from a tree decreased from 17% to 13 %. A study of 1100 single family houses in an urban suburb showed that 2/3 of the houses would have a gain with optimisers above 20 kWh/kWp and year.
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| 12. |
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| 13. |
- Francisco Contero, Jose, et al.
(author)
-
The impact of shading in the performance of three different solar PV systems
- 2017
-
In: PROCEEDINGS OF THE 11TH ISES EUROSUN 2016 CONFERENCE. - Freiburg, Germany : INTL SOLAR ENERGY SOC. ; , s. 1168-1179
-
Conference paper (peer-reviewed)abstract
- Partial shading decreases the performance of PV modules due to the series connection between the solar cells. In the recent years, several new technologies have emerged within the photovoltaics field to mitigate the effect of shading in the performance of the PV modules. For an accurate assessment of the performance of these devices, it is required to evaluate them comparatively in different circumstances. Three systems with six series-connected PV modules (each containing 60 cells) have been installed at the University of Gavle. System One comprises a string inverter system with 6 PV modules; System Two features a DC-DC optimizer per panel and a string inverter; System Three incorporates three micro inverters for six modules. A major conclusion of this study was that under partial shading of one (or more) modules both System Two (DC-DC optimizers) and System Three (micro inverters) perform considerably better than System One (string inverter), as long as the Impp of the shadowed module is lower than the Impp of the unshaded string It is also important that the Vmpp in the shaded module is higher than the lowest allowed voltage of the DC-DC optimizer or module inverter. The economic implications of the usage of these devices were also analyzed.
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| 14. |
- Gallardo-Saavedra, Sara, et al.
(author)
-
Simulation, validation and analysis of shading effects on a PV system
- 2018
-
In: Solar Energy. - : Elsevier. - 0038-092X .- 1471-1257. ; 170, s. 828-839
-
Journal article (peer-reviewed)abstract
- A simulation program for calculating the IV-curve for series connected PV-modules during partial shadowing has been developed and experimentally validated. The software used for modelling the modules is LTspice IV. The validation has been done by means of a comparative analysis using the experimental results obtained in a set of tests performed on the mono-crystalline modules of the Gävle University's laboratory in Sweden. Experimental measurements were carried out in two groups. The first group is a string of six modules with bypass diodes while the second one corresponds to a single PV module. The simulation results of both groups demonstrated a remarkable agreement with the experimental data, which means that the designed model can be used for simulating the influence of shading on the power of a string. The model has been used for analysing the performance of strings of PV modules with shadows and the benefits of installing DC-DC optimizers or module inverters, that minimise the impact of shading, have been investigated.
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| 15. |
- Gomes, João, 1979-, et al.
(author)
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Defining an Annual Energy Output Ratio between Solar Thermal Collectors and Photovoltaic Modules
- 2022
-
In: Energies. - : MDPI. - 1996-1073. ; 15:15
-
Journal article (peer-reviewed)abstract
- Photovoltaics (PV) and Solar Thermal (ST) collectors are sometimes competitors, as investment capacity, energy demand, and roof space are limited. Therefore, a ratio that quantifies the difference in annual energy output between ST and PV for different locations is useful. A market survey assessing the average price and performance both in 2013 and 2021 was conducted, showing a factor of 3 cell price decrease combined with a 20% efficiency increase, while ST showed negligible variation. Winsun simulations were conducted, and the results were plotted on the world map. Despite variations due to local climate, the ratio of energy production (ST/PV) increases at lower latitudes mainly due to (a) higher air temperature increasing ST output but decreasing the PV output; (b) solar radiation reducing ST efficiency to zero while having a minor impact on PV efficiency. The ratio was calculated for several ST operating temperatures. For latitudes lower than 66 degrees, the ratio of a flat plate at 50 degrees C to a PV module ranges from 1.85 to 4.46, while the ratio between a vacuum tube at 50 degrees C and a PV module ranges from 3.05 to 4.76. This ratio can support the decision between installing ST or PV while combining different factors such as energy value, system complexity, and installation cost.
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| 16. |
- Gomes, João, 1979-
(author)
-
Development of Concentrating Photovoltaic-Thermal Solar Collectors
- 2021
-
Doctoral thesis (other academic/artistic)abstract
- Fossil fuels have greatly improved human living standards and saved countless lives. However, today, their continued use threatens human survival, as CO2 levels rise at an unprecedented pace to levels never seen during human existenceon earth.This thesis aims at gathering knowledge on solar energy in general and photovoltaic thermal (PVT) and concentrating photovoltaic thermal (C-PVT) in particular. This thesis establishes several key research questions for PVTs and C-PVT collectors and attempts to answer them.A comprehensive market study of solar thermal (ST), photovoltaic (PV) and PVT was conducted to obtain prices and performance. Simulations of the energy output around the world were conducted. A ratio between ST and PV annual output was defined to serve as a tool for comparison and plotted on a world map.A key issue for PVT collectors is how to encapsulate the solar cells in a way that, amongst other things, protects the cell from the thermal expansion of the receiver, has a high transparency, and insulates electrically while at the same time conducts the heat to the receiver. In order to be useful, this analysis must also consider the impacts on the production processes. Several prototypes were constructed, a test methodology was created, and the analysis of the results enabled several conclusions on the validity of the different silicon encapsulations methods.This thesis relies heavily on collector testing with 30 different prototypes of C-PVTs being designed and constructed. Most testing was conducted using steady state method but quasi dynamic was also carried out. From this work, several guidelines were created for the design of collectors in terms of reflector geometry, cell size, string configuration, encapsulation method and several other design aspects. These analyses were complemented with thermal simulations (COMSOL & ANSYS), string layout (LT SPICE) and evaluation of existing installations. Two novel design ideas came from this thesis work, which the author will patent in the coming year. Additionally, raytracing work has been conducted and a new reflector geometry more appropriate for C-PVTs has been found to significantly improve the annual performance. Finally, the current and future position of PVTs in the global energy market is discussed.
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| 17. |
- Gustafsson, Mattias, 1972-
(author)
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Energy efficiency measures in the built environment - some aspects to consider in Sweden
- 2018
-
Doctoral thesis (other academic/artistic)abstract
- The traditional energy system as we know it today will change in the future. There is a worldwide concern about the global warming situation and there are different actions implemented to limit the consequences from, mainly, the use of fossil fuels.In this thesis, multi-unit apartment buildings have been simulated according to how the global CO2 emissions change when different energy efficiency measures are implemented. The simulated buildings have also been used to investigate how the calculated energy efficiency of a building according to Swedish building regulations varies depending on which technology for heating is used in the building and if the building has a solar PV installation or solar thermal system. When the energy efficiency of a building is calculated accord-ing to Swedish building regulations, this thesis shows that heat pumps are a favored technology compared to district heating. Another result is that electric-ity use/production within the investigated district heating system is the most important factor to consider when minimizing global CO2 emissions.This thesis also investigates how the configuration of electric meters owned by the distribution system operator affects the monitored amount of self-consumed and produced excess electricity. Finally, four local low-voltage distri-bution networks were simulated when a future charging scenario of electric vehicles was implemented.If a single-family house installs a solar PV installation, this thesis reveals that the configuration of the electric meter is important for the monitored amount of self-consumed electricity. This thesis also shows that the investigated low-voltage distribution networks can handle future power demand from electric vehicles and a high share of solar PV installations, but rural low-volt-age distribution networks will need to be reinforced or rebuilt to manage the investigated future scenarios.
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| 18. |
- Hagström, A. L., et al.
(author)
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An iterative approach to determine the refractive index of 3D printed 60GHz PLA lenses
- 2018
-
In: Proceedings of the 14th Loughborough Antennas and Propagation Conference (LAPC 2018). - Piscataway, N.J. : IEEE. - 9781785619694
-
Conference paper (peer-reviewed)abstract
- This paper describes an iterative approach to determine quasi-optical properties of standard 3D printer filament material to, in an inexpensive and fast way, construct focusing lenses for millimetre wave systems. Results from three lenses with different focal lengths are shown and discussed. The real part of the permittivity at 60GHz for polylactic acid (PLA) is in this paper determined to be εr=2.74. © 2018 Institution of Engineering and Technology. All rights reserved.
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| 19. |
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| 20. |
- Hjorth, Martin, et al.
(author)
-
Thalidomide and dexamethasone vs. bortezomib and dexamethasone for melphalan refractory myeloma: a randomized study.
- 2012
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In: European journal of haematology. - : Wiley. - 0902-4441 .- 1600-0609. ; 88:6, s. 485-496
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Journal article (other academic/artistic)abstract
- Objectives: Thalidomide and bortezomib have been frequently used for second-line therapy in patients with myeloma relapsing after or refractory to initial melphalan-based treatment, but no randomized trials have been published comparing these two treatment alternatives. Methods: Thalidomide- and bortezomib-naïve patients with melphalan refractory myeloma were randomly assigned to low-dose thalidomide + dexamethasone (Thal-Dex) or bortezomib + dexamethasone (Bort-Dex). At progression on either therapy, the patients were offered crossover to the alternative drug combination. An estimated 300 patients would be needed for the trial to detect a 50% difference in median PFS between the treatment arms. Results: After inclusion of 131 patients, the trial was prematurely closed because of low accrual. Sixty-seven patients were randomized to Thal-Dex and 64 to Bort-Dex. Progression-free survival was similar (median, 9.0 months for Thal-Dex and 7.2 for Bort-Dex). Response rate was similar (55% for Thal-Dex and 63% for Bort-Dex), but time to response was shorter (P < 0.05) and the VGPR rate higher (P < 0.01) for Bort-Dex. Time-to-other treatment after crossover was similar (median, 13.2 months for Thal-Dex and 11.2 months for Bort-Dex), as was overall survival (22.8 months for Thal-Dex and 19.0 for Bort-Dex). Venous thromboembolism was seen in seven patients and cerebrovascular events in four patients in the Thal-Dex group. Severe neuropathy, reactivation of herpes virus infections, and mental depression were more frequently observed in the Bort-Dex group. In the quality-of-life analysis, no difference was noted for physical function, pain, and global quality of life. Fatigue and sleep disturbances were significantly more prevalent in the Bort-Dex group. Conclusions: Thalidomide (50–100 mg daily) in combination with dexamethasone seems to have an efficacy comparable with that of bortezomib and dexamethasone in melphalan refractory myeloma. However, the statistical strength of the results in this study is limited by the low number of included patients.
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| 21. |
- Hoffman, Tove, et al.
(author)
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Association between guilds of birds in the African-Western Palaearctic region and the tick species Hyalomma rufipes, one of the main vectors of Crimean-Congo hemorrhagic fever virus.
- 2022
-
In: Microorganisms. - : MDPI AG. - 2076-2607. ; 10
-
Journal article (peer-reviewed)abstract
- The migratory behavior of wild birds contributes to the geographical spread of ticks and their microorganisms. In this study, we aimed to investigate the dispersal and co-occurrence of Francisella and spotted fever group Rickettsia (SFGR) in ticks infesting birds migrating northward in the African-Western Palaearctic region (AWPR). Birds were trapped with mist nests across the Mediterranean basin during the 2014 and 2015 spring migration. In total, 575 ticks were collected from 244 birds. We screened the ticks for the species Francisella tularensis, the genus Francisella, and SFGR by microfluidic real-time PCR. Confirmatory analyses and metagenomic sequencing were performed on tick samples that putatively tested positive for F. tularensis during initial screenings. Hyalomma rufipes was the most common tick species and had a high prevalence of Francisella, including co-occurrence of Francisella and SFGR. Metagenomic analysis of total DNA extracted from two H. rufipes confirmed the presence of Francisella, Rickettsia, and Midichloria. Average nucleotide identity and phylogenetic inference indicated the highest identity of the metagenome-assembled genomes to a Francisella-like endosymbiont (FLE), Rickettsia aeschlimannii, and Midichloria mitochondrii. The results of this study suggest that (i) FLE- and SFGR-containing ticks are dispersed by northbound migratory birds in the AWPR, (ii) H. rufipes likely is not involved in transmission of F. tularensis in the AWPR, and (iii) a dual endosymbiosis of FLEs and Midichloria may support some of the nutritional requirements of H. rufipes.
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| 22. |
- Hornestam, Björn, et al.
(author)
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Intravenously administered digoxin in patients with acute atrial fibrillation : a population pharmacokinetic/pharmacodynamic analysis based on the Digitalis in Acute Atrial Fibrillation trial
- 2003
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In: European Journal of Clinical Pharmacology. - : Springer Science and Business Media LLC. - 0031-6970 .- 1432-1041. ; 58:11, s. 747-755
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Journal article (peer-reviewed)abstract
- OBJECTIVE: Atrial fibrillation is commonly treated with intravenously administered digoxin. The main objective of this study was to investigate the relationship between plasma concentration of digoxin and heart rate. SUBJECTS AND METHODS: Plasma concentrations of digoxin were analysed in 105 patients allocated to digoxin therapy in the Digitalis in Acute Atrial Fibrillation (DAAF) trial. A pharmacokinetic/pharmacodynamic (PK/PD) model for the relationship among digoxin dose, plasma concentration and heart rate in patients remaining in atrial fibrillation was constructed using non-linear, mixed-effect modelling. One hundred and twenty-two placebo-treated patients were included as a control group. In 56 patients, one late sample at 16 h after the first dose of digoxin was obtained while in 49 patients an early sample at 0.25-0.5 h and a late sample 16 h after the first dose were obtained. Heart rate was measured at 0, 2, 6, 12 and 16 h after inclusion, with data from 98, 89, 67, 56 and 53 patients available at each time point, respectively. RESULTS: A two-compartment model best described the time course of digoxin concentrations in plasma. Digoxin and creatinine clearance correlated strongly and mean plasma concentration of digoxin at 16 h was within recommended levels (1.6+/-1.0 nM). The decrease in heart rate in placebo-treated patients was, on average, 0.5 beats/min (bpm) per hour. In patients on digoxin, a linear relationship between the estimated digoxin concentration at the effect site and the drop-in heart rate was found. The half-life for the digoxin distribution to the effect compartment was approximately 3.8 h. The degree of reduction was related to the initial heart rate and patients with higher heart rate had a more pronounced decrease. The model predicted that a digoxin concentration of 1 nM at the effect site reduces heart rate by 9.4%. CONCLUSION: A PK/PD model for the relationship between the plasma concentration of digoxin, the estimated concentration at the effect site and the reduction in heart rate during atrial fibrillation could be defined using a population pharmacokinetic approach. Our data indicate that a more aggressive dosing regimen of digoxin may be more effective in terms of heart rate reduction.
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| 23. |
- Lundin, Magnus, et al.
(author)
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Compton scattering from the deuteron and extracted neutron polarizabilities
- 2003
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In: Physical Review Letters. - 1079-7114. ; 90:19
-
Journal article (peer-reviewed)abstract
- Differential cross sections for Compton scattering from the deuteron were measured at MAX-Lab for incident photon energies of 55 and 66 MeV at nominal laboratory angles of 45degrees, 125degrees, and 135degrees. Tagged photons were scattered from liquid deuterium and detected in three NaI spectrometers. By comparing the data with theoretical calculations in the framework of a one-boson-exchange potential model, the sum and the difference of the isospin-averaged nucleon polarizabilities, alpha(N) + beta(N) = 17.4 +/- 3.7 and alpha(N) - beta(N) = 6.4 +/- 2.4 (in units of 10(-4) fm(3)), have been determined. By combining the latter with the global-averaged value for alpha(p) - beta(p) and using the predictions of the Baldin sum rule for the sum of the nucleon polarizabilities, we have obtained values for the neutron electric and magnetic polarizabilities of alpha(n) = 8.8 +/- 2.4(total) +/- 3.0(model) and beta(n) = 6.5 -/+ 2.4(total) -/+ 3.0(model), respectively.
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| 24. |
- Mattsson, Magnus, 1964-, et al.
(author)
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Fältstudie av två metoder för energieffektivisering av äldre fönster – fönsterfilmer testade med hotbox-teknik
- 2020
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Reports (other academic/artistic)abstract
- Föreliggande studie har undersökt två typer av fönsterfilmer som avser förbättra fönster avseende energi- och komfortaspekter. Filmerna utgörs av tunn självhäftande plast med högteknologisk strålningsreflekterande beläggning. Framför allt har en ny typ av värmeisolerande film (här kallad ”Energifilm”) testats, vilken främst syftar till att minska värmeförlusten genom fönstret mot ett kallare uteklimat. Energifilmen har i detta projekt provats i fält med den s.k. hotbox-metoden, varvid ett 2-glasfönsters värmeförlust kunnat mätas på plats i en verklig, kulturhistorisk byggnad – Rådhuset i Gävle. Hotbox-metoden används normalt i laboratoriemiljö och ett viktigt syfte med projektet har varit att utvärdera metoden i fält. Förutom energifilmen provades även solreflekterande film (”Solfilm”), vilken främst avser minska transmission av strålningsvärme från direkt solljus. Studien innefattar även antikvariska och estetiska aspekter på applicering av fönsterfilmer, där byggnadsantikvarier anlitats för subjektiv bedömning. Resultaten pekar på att hotbox-metoden är användbar i fält, om än ganska mödosam att få på plats rent praktiskt. Mätresultaten indikerar att montage av Energifilm minskar värmetransporten (U-värdet) genom fönstrets glasade del med ca 31 % om filmen placeras på någon av glasytorna i spalten mellan glasen, medan minskningen blir ca 19 % vid placering på insidan av innerglaset. Placering i spalten tycks därmed effektivast när så är möjligt; det minskar också risken för kondens och kallras längs fönstrets insida. Rent ekonomiskt tycks det emellertid svårt att räkna hem någon vinst genom investering i vare sig Energifilm eller Solfilm. Montage av Solfilm tenderar tvärtom att öka energikostnaderna. Termisk buffring i den tunga rådhusbyggnaden bidrar till att hålla nere den värmeökning som kan ske vid mycket solinstrålning och internvärme; Solfilm torde komma bättre till pass i lättare byggnader. Rådhusbyggnaden var även försedd med mekanisk behovsstyrd ventilation, med möjlighet till ganska höga ventilationsflöden för kylning; i byggnader utan sådant system kommer Solfilm till bättre nytta. Både energi- och Solfilm förbättrar dock den termiska komforten, både avseende kyla och värme, särskilt för personer som befinner sig i närheten av fönstren. Så, snarare än minskade kostnader torde det vara komfort- och/eller miljöskäl som kan motivera investering i fönsterfilmerna. Fönsterfilmerna medförde minskad ljustransmittans (-16 % för Energifilm; -22 % för Solfilm) och viss (måttlig) färgförändring vid vissa ljusförhållanden och betraktelsevinklar. Överlag fick de studerade fönsterfilmerna emellertid tämligen hög acceptans av byggnadsantikvarierna, men man noterade att noggrannhet vid montaget är mycket viktigt. Montage av filmerna demonstrerades också gå förhållandevis snabbt och medföra liten störning på verksamheten i lokalerna under installation. Filmerna kan också klippas till att passa t.ex. krökta bågar, och de medför inte någon ökad belastning (tyngd) för fönstret, i jämförelse med andra metoder som innebär komplettering med ett extra glas på bågen. Test av borttagning av 3 år gammal Energifilm visade att detta kunde göras utan att skada fönster-glasen, men det synes tveksamt att montera filmerna på riktigt tunna, ömtåliga glas, då sådana riskerar gå sönder vid borttagning av filmen, som ändå noterades sitta tämligen hårt fast.
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| 29. |
- Spanos, Elias, et al.
(author)
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Cardioprotection of the enkephalin analog Eribis peptide 94 in a rat model of ischemia and reperfusion is highly dependent on dosing regimen and timing of administration
- 2015
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In: European Journal of Pharmacology. - : Elsevier BV. - 0014-2999. ; 747, s. 1-6
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Journal article (peer-reviewed)abstract
- Eribis Peptide 94 (EP94) is an enkephalin analog with cardioprotective properties in ischemia and reperfusion. The aim of the present study was to define the optimal timing and dosing of the administration of EP94 during ischemia and reperfusion in a rat model. 172 anesthetized and mechanically ventilated male Sprague-Dawley rats were randomly assigned to different administration protocols of EP94 and subjected to 30 or 40min of coronary artery occlusion followed by 2h of reperfusion. EP94 was administered intravenously at different doses and time intervals. Area at risk (AAR) and infarct size (IS) were determined by staining with Evans Blue (EB) and Triphenyl tetrazolium chloride (TTC), respectively. EP94 reduced IS/AAR when administered as a double bolus (0.5µg/kg per dose), whereas single (1μg/kg) or triple boluses (0.5μg/kg per dose) did not confer any protection. Reduction of IS/AAR was of highest magnitude if EP94 was administered 5 and 0min before the 30min ischemic period (47% reduction, P<0.05), with declining cardioprotective effect with later administration during ischemia. When EP94 was administered after 15 and 20min of a 40-min ischemic period, reduction of IS/AAR was of the same magnitude as when given after 5 and 10min of a 30-min ischemic period. It is concluded that EP94 confers cardioprotection after double bolus administration. The effects are highly dependent on the timing of administration in relation to ischemia and reperfusion. Time of reperfusion from drug administration seems to be more critical than the total duration of ischemia.
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| 30. |
- Svensson, Elin M., et al.
(author)
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Pharmacokinetic Interactions for Drugs with a Long Half-Life-Evidence for the Need of Model-Based Analysis
- 2016
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In: AAPS Journal. - : Springer Science and Business Media LLC. - 1550-7416. ; 18:1, s. 171-179
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Journal article (peer-reviewed)abstract
- Pharmacokinetic drug-drug interactions (DDIs) can lead to undesired drug exposure, resulting in insufficient efficacy or aggravated toxicity. Accurate quantification of DDIs is therefore crucial but may be difficult when full concentration-time profiles are problematic to obtain. We have compared non-compartmental analysis (NCA) and model-based predictions of DDIs for long half-life drugs by conducting simulation studies and reviewing published trials, using antituberculosis drug bedaquiline (BDQ) as a model compound. Furthermore, different DDI study designs were evaluated. A sequential design mimicking conducted trials and a population pharmacokinetic (PK) model of BDQ and the M2 metabolite were utilized in the simulations where five interaction scenarios from strong inhibition (clearance fivefold decreased) to strong induction (clearance fivefold increased) were evaluated. In trial simulations, NCA systematically under-predicted the DDIs' impact. The bias in average exposure was 29-96% for BDQ and 20-677% for M2. The model-based analysis generated unbiased predictions, and simultaneous fitting of metabolite data increased precision in DDI predictions. The discrepancy between the methods was also apparent for conducted trials, e.g., lopinavir/ritonavir was predicted to increased BDQ exposure 22% by NCA and 188% by model-based methods. In the design evaluation, studies with parallel designs were considered and shown to generally be inferior to sequential/cross-over designs. However, in the case of low inter-individual variability and no informative metabolite data, a prolonged parallel design could be favored. Model-based analysis for DDI assessments is preferable over NCA for victim drugs with a long half-life and should always be used when incomplete concentration-time profiles are part of the analysis.
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| 31. |
- Wallhagen, Marita, tekn dr, docent, 1979-, et al.
(author)
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Viewpoints on Environmental Assessment of Building Certification Method - Miljöbyggnad
- 2021
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In: Urban Transition - Perspectives on Urban Systems and Environments. - : IntechOpen.
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Book chapter (peer-reviewed)abstract
- Production, management, use, and end-of-life of buildings has a large impact on climate change. Therefore, environmental targets are set to lower the greenhouse gas (GHG) emissions from the building sector. To reach these targets building regulation and voluntary environmental assessment methods (EAMs) that evaluate and certify the building's environmental impact are put forward as tools to push the building sector towards lower GHG emissions. In Sweden, building design is governed by building regulations and the dominant EAM is ‘Miljöbyggnad’ (MB) (“Environmental building”). Today, more than 1900 buildings have been certified by MB and it has influenced the building and property sector. In this chapter the potential impact MB and the linked Swedish building regulations have on building performance, energy use and GHG emissions, will be reviewed and discussed. The analysis investigates several of the MB’s indicators, evaluate to what degree EAMs can influence the design of the building and the energy system to lower the energy use and GHG emissions based on material choices. The analysis presents important aspects that may influence the design of the building and its energy system and what challenges and possibilities the indicators, criteria and regulations can have on buildings and climate change. In addition, some modification and suggestion for improvements are presented.
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| 32. |
- Westbury, L. D., et al.
(author)
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Recent sarcopenia definitions-prevalence, agreement and mortality associations among men: Findings from population-based cohorts
- 2023
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In: Journal of Cachexia Sarcopenia and Muscle. - : Wiley. - 2190-5991 .- 2190-6009. ; 14:1, s. 565-575
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Journal article (peer-reviewed)abstract
- BackgroundThe 2019 European Working Group on Sarcopenia in Older People (EWGSOP2) and the Sarcopenia Definitions and Outcomes Consortium (SDOC) have recently proposed sarcopenia definitions. However, comparisons of the performance of these approaches in terms of thresholds employed, concordance in individuals and prediction of important health-related outcomes such as death are limited. We addressed this in a large multinational assembly of cohort studies that included information on lean mass, muscle strength, physical performance and health outcomes. MethodsWhite men from the Health Aging and Body Composition (Health ABC) Study, Osteoporotic Fractures in Men (MrOS) Study cohorts (Sweden, USA), the Hertfordshire Cohort Study (HCS) and the Sarcopenia and Physical impairment with advancing Age (SarcoPhAge) Study were analysed. Appendicular lean mass (ALM) was ascertained using DXA; muscle strength by grip dynamometry; and usual gait speed over courses of 2.4-6 m. Deaths were recorded and verified. Definitions of sarcopenia were as follows: EWGSOP2 (grip strength <27 kg and ALM index <7.0 kg/m(2)), SDOC (grip strength <35.5 kg and gait speed <0.8 m/s) and Modified SDOC (grip strength <35.5 kg and gait speed <1.0 m/s). Cohen's kappa statistic was used to assess agreement between original definitions (EWGSOP2 and SDOC). Presence versus absence of sarcopenia according to each definition in relation to mortality risk was examined using Cox regression with adjustment for age and weight; estimates were combined across cohorts using random-effects meta-analysis. ResultsMean (SD) age of participants (n = 9170) was 74.3 (4.9) years; 5929 participants died during a mean (SD) follow-up of 12.1 (5.5) years. The proportion with sarcopenia according to each definition was EWGSOP2 (1.1%), SDOC (1.7%) and Modified SDOC (5.3%). Agreement was weak between EWGSOP2 and SDOC (kappa = 0.17). Pooled hazard ratios (95% CI) for mortality for presence versus absence of each definition were EWGSOP2 [1.76 (1.42, 2.18), I-2: 0.0%]; SDOC [2.75 (2.28, 3.31), I-2: 0.0%]; and Modified SDOC [1.93 (1.54, 2.41), I-2: 58.3%]. ConclusionsThere was low prevalence and poor agreement among recent sarcopenia definitions in community-dwelling cohorts of older white men. All indices of sarcopenia were associated with mortality. The strong relationship between sarcopenia and mortality, regardless of the definition, illustrates that identification of appropriate management and lifecourse intervention strategies for this condition is of paramount importance.
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- Äbelö, Angela, et al.
(author)
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Gastric acid secretion in the dog : a mechanism-based pharmacodynamic model for histamine stimulation and irreversible inhibition by omeprazole
- 2002
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In: Journal of Pharmacokinetics and Pharmacodynamics. - 1567-567X .- 1573-8744. ; 29:4, s. 365-382
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Journal article (peer-reviewed)abstract
- A mechanism-based pharmacodynamic model was used to describe the inhibitory effect by omeprazole on gastric acid secretion measured after histamine stimulation in the dog. The model identifies parameters that are related to the physiological system, the histamine stimulation, and the irreversible effect of omeprazole on the H+, K(+)-ATPase enzyme. Four different experiments with omeprazole (Exps. 1-4) and two placebo experiments were performed in each of the four Heidenhain pouch dogs used. For placebo and experiments 1-3, saline or omeprazole 0.81 mumol/kg was infused during 3 hr with measurements of histamine-stimulated gastric acid secretion in two periods of 3.5-6.5 hr, one period starting just before the omeprazole infusion and a second later period up to 29 hr post infusion. In experiment 4, 0.18 mumol/kg of omeprazole was infused for 22.5 min and gastric juice was collected for 5 hr post infusion. The response data was well described by the model. Similar parameter estimates were obtained by three different analysis methods; naïve pooling, two-stage method and nonlinear mixed effects modeling. The elimination rate constant for the H+, K(+)-ATPase enzyme, kout, was estimated to be 0.040 hr-1, corresponding to a half-life of about 17 hr. This rate constant determines the duration of omeprazole inhibition after long-term exposure. For short-term omeprazole exposure the duration is determined by the rate constant for transfer of enzymes from active to resting state, estimated to be 1.88 hr-1. The second-order rate constant for histamine stimulation was estimated to be 0.064 hr-1 per histamine concentration unit and the maximum acid secretion was estimated to be 5.0 mmol H+/30 min. The second-order rate constant for the irreversible binding of omeprazole to H+, K(+)-ATPase, kome, was estimated to be 2.39 L/mumol.hr. By modeling the histamine-induced baseline response simultaneously with active treatment, predictions of the response are possible not only following different dosing regimens of omeprazole, but also following different degrees of histamine stimulation.
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| 35. |
- Äbelö, Angela, et al.
(author)
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Pharmacodynamic modelling of reversible gastric acid pump inhibition in dog and man
- 2001
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In: European Journal of Pharmaceutical Sciences. - 0928-0987 .- 1879-0720. ; 14:4, s. 339-346
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Journal article (peer-reviewed)abstract
- H 335/25, a 4-amino quinoline, belongs to a new class of reversible gastric acid pump inhibitors. A potential advantage of such drugs over the irreversible proton pump inhibitors (PPIs) is better control over the effect-time profile. Dose escalation studies were performed to characterize the effect on acid secretion in dogs (n=24) and healthy male subjects (n=12). The effect-time profile was delayed compared to the concentration-time profile. A model-based approach, using non-linear mixed effects modelling, was applied to quantify and elucidate the mechanism for the delayed effect. Three different models were investigated: (1) a slow equilibration preceding the formation of drug-enzyme complex, modelled by an effect-compartment, (2) a slow equilibration between free drug, free enzyme and drug-enzyme complex, described by a kinetic binding model, and (3) a delay between enzyme inhibition and the measured response, described by an indirect response model. Model 2 was shown to be superior to models 1 and 3, for both dog and human data. The dissociation rate constant, k(off), was estimated to be 0.85 and 0.88 h and the calculated equilibration constant, K(d), was 160 and 250 nM in dog and man, respectively. Simulations of the predicted time-course of the effect beyond the 4-5-h observation period was similar for the three models.
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