| 1. |
- Admass, Muluneh
(författare)
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3-D numerical modeling of flow and sediment transport in rivers
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The fully integrated 3-D, time dependant, hydrodynamic and sediment transport numerical model ECOMSED was used to simulate flow and sediment transport in rivers. ECOMSED was originally developed for large water bodies such as lakes and oceans and solves the primitive equations of RANS along with a second order turbulence model in an orthogonal curvilinear σ- coordinate system. The availability of the model as an open FORTRAN source code made modifications and addition of new models possible. A new bed load transport model was implemented in the code as well as improvements in treatment of river roughness parameterization, bed form effects, and automatic update of flow depth due to bed evolution. The model was applied to 1- km long reach of the River Klarälven, Sweden, where it bifurcates into two west and east channels. The water surface and the flow division in the channels were made in agreement with field data by spatially varying the roughness. However, the spatial distribution of the bed shear stress was not realistic. Improvements were made in the bottom boundary condition to represent the variable effects of bed forms on roughness depending on the flow regime and the flow depth. The improved model realistically reproduced the flow field as well as the sediment transport processes in the river Klarälven.
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| 2. |
- Admassie, Shimelis, et al.
(författare)
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Charge storage properties of biopolymer electrodes with (sub)tropical lignins
- 2014
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 16:45, s. 24681-24684
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Tidskriftsartikel (refereegranskat)abstract
- The electrochemical and charge storage properties of different lignins inside biopolymer electrodes were studied and correlated with the chemical variations of the lignins as indicated from the nuclear magnetic resonance (NMR) spectroscopic data. The varying fractions of monolignols were found to correlate with charge storage properties. It was found that as the sinapyl to guaiacyl (S/G) ratio increased both the specific capacitance and charge capacity increased considerably. This indicates that quinones generated on S-units can contribute more to charge storage in the biopolymer electrodes.
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| 3. |
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| 4. |
- Andersson, Lotta, et al.
(författare)
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Local early warning systems for drought - Could they add value to nationally disseminated seasonal climate forecasts?
- 2020
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Ingår i: Weather and Climate Extremes. - : ELSEVIER. - 2212-0947. ; 28
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Tidskriftsartikel (refereegranskat)abstract
- Limited application and use of forecast information restrict smallholder farmers ability to deal with drought in proactive ways. This paper explores the barriers that impede use and uptake of seasonal climate forecasts (SCF) in two pilot communities in Limpopo Province. Current interpretation, translation and mediation of national SCF to the local context is weak. A local early warning system (EWS) was developed that incorporated hydrological modelled information based on national SCF, locally monitored rainfall and soil moisture by a wireless sensor network, and signs from indigenous climate indicators. We assessed to what degree this local EWS could improve interpretation of SCF and increase understanding and uptake by farmers. Local extension staff and champion farmers were found to play important knowledge brokering roles that could be strengthened to increase trust of SCF. The local EWS provided added value to national SCF by involving community members in local monitoring, enacting knowledge interplay with indigenous knowledge and simplifying and tailoring SCF and hydrological information to the local context. It also helped farmers mentally prepare for upcoming conditions even if many do not currently have the adaptive mindsets, economic resources or pre-conditions to positively respond to SCF information.
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| 5. |
- Andersson, Lars-Magnus, 1968, et al.
(författare)
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Increased cerebrospinal fluid protein tau concentration in neuro-AIDS
- 1999
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Ingår i: J Neurol Sci. ; 171:2, s. 92-6
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: Assessment of cerebrospinal fluid (CSF) levels of protein tau in human immunodeficiency virus type 1 (HIV-1) infection. MATERIAL AND METHODS: CSF tau levels were analyzed in 52 HIV-1-infected patients, 37 of whom had no neurological symptoms, eight had aquired immunodeficiency syndrome (AIDS) dementia complex (ADC), and seven had AIDS with other neurological complications. RESULTS: A significantly higher mean CSF tau concentration was found in patients with ADC (380 pg/ml) compared with patients with neuroasymptomatic HIV-1 infection (120 pg/ml, P<0.01) and HIV-negative controls (150 pg/ml, P<0.05). No difference in CSF tau levels was found between patients with ADC and patients with AIDS with other neurological complications. CONCLUSION: CSF tau might be used as a biochemical marker for axonal degeneration and might be of use to identify HIV-1-infected patients with ADC and other neurological complications, but it cannot discriminate between ADC and other neurological complications in HIV-1-infection.
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| 6. |
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| 7. |
- Andersson, Martin, et al.
(författare)
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Fracture strength of glass chips for high-pressure microfluidics
- 2016
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 26:9
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Tidskriftsartikel (refereegranskat)abstract
- High-pressure microfluidics exposes new areas in chemistry. In this paper, the reliability of transparent borosilicate glass chips is investigated. Two designs of circular cavities are used for fracture strength tests, either 1.6 mm wide with rounded corners to the fluid inlets, or 2.0 mm wide with sharp inlet corners. Two kinds of tests are done, either short-term,e.g. pressurization to fracture at room temperature, or long-term, with fracture at constant pressurization for up to one week, in the temperature region 11–125 °C. The speed of crack fronts is measured using a high-speed camera. Results show fracture stresses in the range of 129 and 254 MPa for short-term measurements. Long-term measurements conclude the presences of a temperature and stress dependent delayed fracture. For a reliability ofone week at 11–38 °C, a pressure limit is found at the lower end of the short-term measurements, or 15% lower than the average. At 80 °C, this pressure limit is 45% lower. Crack speeds are measured to be 10−5 m s-1 during short-term fracture. These measurements are comparable with estimations based on slow crack growth and show that the growth affects the reliability of glass chips. This effect is strongly affected by high temperatures, thus lowers the operating window of high-pressure glass microfluidic devices.
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| 8. |
- Andersson, Maria, et al.
(författare)
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Interindividual differences in initial DNA repair capacity when evaluating H2O2-induced DNA damage in extended-term cultures of human lymphocytes using the comet assay
- 2007
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Ingår i: Cell Biology and Toxicology. - : Springer Science and Business Media LLC. - 0742-2091 .- 1573-6822. ; 23:6, s. 401-411
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Tidskriftsartikel (refereegranskat)abstract
- It has been suggested that extended-term cultures of human lymphocytes could be used as a complement to cell lines based on transformed cells when testing the genotoxicity of chemicals. To investigate whether the pattern of induced DNA damage and its subsequent repair differs significantly between cultures based on different blood donors, hydrogen peroxide (H2O2)-induced DNA damage was measured in cultures from four different subjects using the comet assay. The DNA damage was significantly increased in all cultures after 10 min exposure to 0.25 mmol/L H2O2, and there was a significant decrease in the H2O2-induced DNA damage in all cultures after 30 min of DNA repair. The level of damage varied between the different donors, especially after the repair. Using PCR and DNA sequencing, exon 5 of the p53 gene was sequenced in the lymphocytes from the donors with the lowest and highest residual damage. No such mutation was found. Mouse lymphoma L5178Y cells carrying the p53 mutation in exon 5 were included as a reference. These cells were found to be less sensitive toward the H2O2-induced DNA damage, and they were also found to have a rather low DNA repair capacity. The demonstrated variation in H2O2-induced DNA damage and DNA repair capacity between the cultures from the different subjects may be important from a risk assessment perspective, but is obviously not of decisive importance when it comes to the development of a routine assay for genotoxicity.
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| 9. |
- Andersson, Mauritz
(författare)
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Quantum Dynamics of Molecular Systems and Guided Matter Waves
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Quantum dynamics is the study of time-dependent phenomena in fundamental processes of atomic and molecular systems. This thesis focuses on systems where nature reveals its quantum aspect; e.g. in vibrational resonance structures, in wave packet revivals and in matter wave interferometry. Grid based numerical methods for solving the time-dependent Schrödinger equation are implemented for simulating time resolved molecular vibrations and to compute photo-electron spectra, without the necessity of diagonalizing a large matrix to find eigenvalues and eigenvectors.Pump-probe femtosecond laser spectroscopy on the sodium potassium molecule, showing a vibrational period of 450 fs, is theoretically simulated. We find agreement with experiment by inclusion of the finite length laser pulse and finite temperature effects.Complicated resonance structures observed experimentally in photo-electron spectra of hydrogen- and deuterium chloride is analyzed by a numerical computation of the spectra. The dramatic difference in the two spectra arises from non-adiabatic interactions, i.e. the interplay between nuclear and electron dynamics. We suggest new potential curves for the 32Σ+ and 42Σ+ states in HCI+.It is possible to guide slow atoms along magnetic potentials like light is guided in optical fibers. Quantum mechanics dictates that matter can show wave properties. A proposal for a multi mode matter wave interferometer on an atom chip is studied by solving the time-dependent Schrödinger equation in two dimensions. The results verifies a possible route for an experimental realization.An improved representation for wave functions using a discrete set of coherent states is presented. We develop a practical method for computing the expansion coefficients in this non-orthogonal set. It is built on the concept of frames, and introduces an iterative method for computing a representation of the identity operator. The phase-space localization property of the coherent states gives adaptability and better sampling efficiency.
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| 10. |
- Andersson, Ulf, 1963-
(författare)
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Working memory as a predictor of written arithmetical skills in children : The importance of central executive functions
- 2008
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Ingår i: British Journal of Educational Psychology. - 0007-0998 .- 2044-8279. ; 78:2, s. 181-203
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Tidskriftsartikel (refereegranskat)abstract
- Background. The study was conducted in an attempt to further our understanding of how working memory contributes to written arithmetical skills in children. Aim. The aim was to pinpoint the contribution of different central executive functions and to examine the contribution of the two subcomponents of children's written arithmetical skills. Sample and method. A total of 141 third- and fourth-graders were administered arithmetical tasks and measures of working memory, fluid IQ and reading. Regression analysis was used to examine the relationship between working memory and written arithmetical skills. Results. Three central executive measures (counting span, trail making and verbal fluency) and one phonological loop measure (Digit Span) were significant and predictors of arithmetical performance when the influence of reading, age and IQ was controlled for in the analysis. Conclusions. The present findings demonstrate that working memory, in general, and the central executive, in particular, contribute to children's arithmetical skills. It was hypothesized that monitoring and coordinating multiple processes, and accessing arithmetical knowledge from long-term memory, are important central executive functions during arithmetical performance. The contribution of the phonological loop and the central executive (concurrent processing and storage of numerical information) indicates that children aged 9-10 years primarily utilize verbal coding strategies during written arithmetical performance. © 2008 The British Psychological Society.
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