| 1. |
- Abadei, S., et al.
(författare)
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Microwave properties of tunable capacitors basee on magnetron sputtered ferroelectric Na0.5K0.5NbO3 film on low and high resistivity silicon substrates
- 2001
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Ingår i: Integrated Ferroelectrics. - : Informa UK Limited. - 1058-4587 .- 1607-8489. ; 39:1-4, s. 359-366
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this work, small signal DC voltage dependent dielectric permittivity, loss tangent, and tuneability of magnetron sputtered epitaxial Na0.5K0.5NO3 films are studied experimentally. (100)-oriented Na0.5K0.5NbO3 films are deposited onto SiO2-buffered CMOS grade low resistivity (p = 10-20 cm) and high resistivity (p = 15-45 kcm) silicon substrates. Planar capacitors with 2 or 4 m gaps between electrodes have been fabricated on top of ferroelectric films. These devices have been characterized in the frequency range 1.0 MHz to 50 GHz at temperatures 30 - 300K. Na0.5K0.5NbO3/SiO2/Si structures on high resistivity silicon substrate exhibit C-V performances typical for Metal-Insulator- Semiconductor (MIS) capacitors. At low frequencies, f 1.0 GHz, the large tuneability and large losses are associated with the MIS structure, while at higher microwave frequencies the tuneability is mainly associated with the ferroelectric, film. At 1.0 MHz and room temperature, the tuneability of Na0.5K0.5NbO3/SiO2/Si structures more than 90%, reducing to 10-15 % at 50 GHz. The losses decrease with increasing the DC bias and frequency. A Q-factor more than 15 at 50 GHz is observed. The dielectric permittivity of the Na0.5K0.5NbO3 film is in the range 50-150 at frequencies 0.045-50 GHz. On low resistivity substrate the performance of Na0.5K0.5NbO3 films is completely screened by the high losses in silicon, and the tuneability is negligible. © 2001 Taylor and Francis.
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| 4. |
- Ahlborg, Helene, 1980, et al.
(författare)
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Small-scale hydropower in Africa: Socio-technical designs for renewable energy in Tanzanian villages
- 2015
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Ingår i: Energy Research and Social Science. - : Elsevier BV. - 2214-6296. ; 5, s. 20-33
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we explore the process of economic change following the NGO-led implementation of a small-scale off-grid hydropower system in Tanzania. We examine how the implementing actor deals with economic challenges and local ownership in order to achieve sustainable electricity supply. The qualitative case study shows that the NGO, ACRA-CCS, has overcome a number of constraints, which are sometimes associated with donor funding. This has been achieved by having multiple donors, an integrated approach and a longer presence. The 'logic' of implementation included active enhancement of productive electricity use, community services and benefits. As a result of these actions, the customer base grew quickly, rather than it taking many years to develop. The case illustrates the process whereby an off-grid system becomes economically viable. Local ownership has led to the project becoming an arena for community collaboration and problem solving, and creating values such as effective load management and protection of infrastructure. We suggest that attention should be given to possible public private community partnerships (PPCPs)-involving communities as crucial partners. The choice of a socio-technical system perspective was fruitful and provided crucial insights into how different factors manifested, interacted and played out in practice.
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| 5. |
- Ahlström, Johan, 1969, et al.
(författare)
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Effect of strain gradient on the microstructure and mechanical properties of pearlitic steel
- 2019
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Ingår i: IOP Conference Series: Materials Science and Engineering. - 1757-8981 .- 1757-899X. ; 580:1
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Konferensbidrag (refereegranskat)abstract
- Pearlitic steels, with a combination of good strength and wear properties, are commonly used for railway rails. The passage of trains creates large shear strain gradients in the surface layer of rails. Knowledge of the microstructural evolution and material properties as related to the shear strain in this layer is therefore important for prediction both of crack evolution and fatigue life. A bi-axial torsion-compression machine was used to deform fully pearlitic R260 rail steel test bars to create a similar gradient structure. Uniaxial tension and compression tests were performed on these pre-deformed test bars to evaluate the mechanical properties of the material. The local microstructural parameters, such as thickness of the ferrite and cementite lamellae, the dislocation density in the ferrite lamellae, the interlamellar spacing and eth local hardness at different places across the diameter of the bars, as well as microstructural evolution across the radius, were characterized. An attempt to set up a correlation between the local microstructural parameters, hardness and the macro mechanical properties is made and discussed in the present study.
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| 6. |
- Ahlström, Johan
(författare)
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Vattenkemiska effekter vid kalkning av rinnande vatten : Baserad på provtagning 2010–2016 inom målvattendragsundersökningen och kalkeffektuppföljningen
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Kalkningen av försurade sjöar och vattendrag är en av de största miljövårdande insatserna som genomförts i Sverige. Sedan slutet på 1970-talet har närmare sex miljarder kronor av statliga och kommunala medel bekostat spridning av drygt fem miljoner ton kalk. Kalkningen är fortfarande omfattande och årligen sprids ungefär 100 000 ton kalk till en kostnad av 130 mnkr.Syftet med kalkningen är att höja pH-värdet i försurade sjöar och vattendrag till en nivå där det naturliga växt- och djurlivet inte påverkas negativt. De vattenkemiska målen baseras därför på toleransgränser för de djurarter som naturligt finns i vattenområdet.Kalkningen ska utformas och genomföras så att pH-målen inte underskrids, men även så att målen nås till så låga kostnader som möjligt. Kalkning av rinnande vatten är särskilt komplicerad. Inte minst gäller det den vattenkemiska uppföljningen som ställer stora krav på provtagningstidpunkt i förhållande till tillfällen när risken för att underskrida pH-målet är som störst. Denna utvärdering baseras delvis på kemidata från den ordinarie uppföljningen, delvis också på data från en nationell provtagning, målvattendragsundersökningen, som genomfördes under perioden 2010–2016.Rapporten har tagits fram av Havs- och vattenmyndigheten. Syftet är att redovisa i vilken utsträckning de vattenkemiska målen uppnås och hur effektivt kalkningen förmår höja pH och alkalinitet i förhållande till använd kalkdos. I rapporten identifieras faktorer i kalkningens genomförande som är avgörande för måluppfyllelse och kalkeffekt. Resultaten utgör ett viktigt underlag för en kommande uppdatering av den nuvarande vägledningen (Handbok för kalkning av sjöar och vattendrag 2010:2) samt för nästa nationella kalkningsplan.
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| 8. |
- Ahmed, M, et al.
(författare)
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Laminin α2 controls mouse and human stem cell behaviour during midbrain dopaminergic neuron development
- 2019
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Ingår i: Development (Cambridge, England). - : The Company of Biologists. - 1477-9129 .- 0950-1991. ; 146:16
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Tidskriftsartikel (refereegranskat)abstract
- The development of the central nervous system requires the coordination of proliferation and differentiation of neural stem cells. Here, we show that laminin alpha 2 (lm-α2) is a component of the midbrain dopaminergic (mDA) progenitor niche in the ventral midbrain (VM) and identify a concentration-dependent role for lm211 in regulating mDA progenitor proliferation and survival via distinct set of receptors. At high-concentrations, lm211 rich environments maintain mDA progenitors in a proliferative state via integrins α6β1 and α7β1. Whereas low concentrations of lm211 support mDA lineage survival via dystroglycan receptors. We confirmed our findings in vivo where, in the absence of lm-α2, the VM was smaller, with increased apoptosis, and the progenitor pool depleted through premature differentiation resulting in fewer mDA neurons. In examining mDA neuron subtype composition we found a reduction in later-born mDA neurons of the ventral tegmental area, which control a range of cognitive behaviours. Our results identify a novel role for lm in neural development and provide a possible mechanism for autism-like behaviours and brainstem hypoplasia seen in some patients with mutations of the human lm-α2 gene.
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| 9. |
- Ahmed, Mukhtar
(författare)
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Quantification of Climate Warming and Crop Management Impacts on Phenology of Pulses-Based Cropping Systems
- 2020
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Ingår i: International Journal Of Plant Production. - : Springer Science and Business Media LLC. - 1735-6814 .- 1735-8043. ; 15, s. 107-123
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Tidskriftsartikel (refereegranskat)abstract
- Climate warming is impacting the phenology, growth and productivity of diverse cropping systems at local, regional and global levels. Long-term observed chickpea-mungbean system (CMS) phenological changes were used for the determination of the relationship between crop practices, climate warming and phenology for the making strategies for CMS to minimize negative climate change impacts. Observed thermal trend from sowing to maturity was ranging from 0.82 to 1.15 degrees C decade(-1)for chickpea and 0.64 to 0.97 degrees C decade(-1)for mungbean during 1980-2018. Observed chickpea phenology stages was earlier for mean value of 7.04 (sowing; S), 6.76 (emergence; E), 4.31 (anthesis; A), 2.15 (maturity; M) days decade(-1), whereas chickpea phases were decreased averagely 2.73 (S-A), 2.16 (A-M), 4.89 (S-M) days decade(-1). Mungbean, 'S' 6.24, 'E' 5.97, 'A' 3.76, and 'M' 2.01 days decade(-1)were occurred earlier. Period of mungbean phenology phases were lessened with averaged 2.45 (S-A), 1.76 (S-M) and 4.23 (A-M) days decade(-1), respectively. Phenological stages and phases of both crops chickpea and mungbean correlated negatively with rising temperatures at all sites studied. By using CROPGRO-Chickpea and CROPGRO-Legume models for usual chickpea and mungbean cultivars at the sites for 38 years duration indicated that model predicted phenology stages were accelerated with thermal trend more as compared with observed stages. This showed that, during last decades, growing newly evolved cultivars of pulses having more thermal time requirement have significantly offset the increased temperature induced changes in chickpea (33%) and mungbean (20%) phenology. Therefore, for the mitigation of climate warming influences, newly evolved cultivars for CMS must be familiarized that need greater demand for degree days and having higher tolerance to temperature.
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| 10. |
- Aires, Filipe, et al.
(författare)
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Towards more realistic hypotheses for the information content analysis of cloudy/precipitating situations - Application to a hyperspectral instrument in the microwave
- 2019
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Ingår i: Quarterly Journal of the Royal Meteorological Society. - : Wiley. - 0035-9009 .- 1477-870X. ; 145:718, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- Information Content (IC) analysis can be used before an instrument is built to estimate its retrieval uncertainties and analyse their sensitivity to several factors. It is a very useful method to define/optimize satellite instruments. IC has shown its potential to compare instrument concepts in the infrared or the microwave. IC is based on some hypotheses such as the the Gaussian character of the radiative transfer (RT) and instrument errors, the first-guess errors (Gaussian character, std and correlation structure), or the linearization of the RT around a first guess. These hypotheses are easier to define for simple atmospheric situations. However, even in the clear-sky case, their complexity has never ceased to increase towards more realism, to optimize the assimilation of satellite measurements in numerical weather prediction (NWP) systems. In the cloudy/precipitating case, these hypotheses are even more difficult to define in a realistic way as many factors are still very difficult to quantify. In this study, several tools are introduced to specify more realistic IC hypotheses than the current practice. We focus on microwave observations as they are more pertinent for clouds and precipitation. Although not perfect, the proposed solutions are a new step towards more realistic IC assumptions of cloudy/precipitating scenes. A state-dependence of the RT errors is introduced, the first-guess errors have a more complex vertical structure, the IC is performed simultaneously on all the hydrometeors to take into account the contamination effect of the RT input uncertainties, and the IC is performed on a diversified set of cloudy/precipitating scenes with well-defined hydrometeor assumptions. The method presented in this study is illustrated using the HYperspectral Microwave Sensor (HYMS) instrument concept with channels between 6.9 and 874 GHz (millimetre and sub-millimetre regions). HYMS is considered as a potential next generation microwave sounder.
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