| 1. |
- Chand, Damini, 1986, et al.
(author)
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Cell culture and Drosophila model systems define three classes of anaplastic lymphoma kinase mutations in neuroblastoma.
- 2013
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In: Disease models & mechanisms. - Cambridge, UK : The Company of Biologists. - 1754-8411 .- 1754-8403. ; 6:2, s. 373-82
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Journal article (peer-reviewed)abstract
- Neuroblastoma is a childhood extracranial solid tumor which is associated with a number of genetic changes. Included in these genetic alterations are mutations in the kinase domain of the Anaplastic Lymphoma Kinase (ALK) receptor tyrosine kinase (RTK), which have been found in both somatic and familial neuroblastoma. In order to treat patients accordingly required characterisation of these mutations in terms of their response to ALK tyrosine kinase inhibitors (TKIs). Here, we report the identification and characterisation of two novel neuroblastoma ALK mutations (A1099T and 1464STOP) which we have investigated together with several previously reported but uncharacterised ALK mutations (T1087I, D1091N, T1151M, M1166R, F1174I and A1234T). In order to understand the potential role of these ALK mutations in neuroblastoma progression we have employed cell culture based systems together with the model organism Drosophila as a readout for ligand-independent activity. Mutation of ALK at position F1174I generates a gain-of-function receptor capable of activating intracellular targets, such as ERK (extracellular signal regulated kinase) and STAT3 (signal transducer and activator of transcription 3) in a ligand independent manner. Analysis of these previously uncharacterised ALK mutants and comparison with ALK(F1174) mutants suggests that ALK mutations observed in neuroblastoma fall into three classes. These are: (i) gain-of-function ligand independent mutations such as ALK(F1174), (ii) kinase-dead ALK mutants, e.g. ALK(I1250T)(Schonherr et al 2011a) or (iii) ALK mutations which are ligand-dependent in nature. Irrespective of the nature of the observed ALK mutants, in every case the activity of the mutant ALK receptors could be abrogated by the ALK inhibitor crizotinib (PF-02341066, Xalkori), albeit with differing levels of sensitivity.
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| 2. |
- Sandström, Agneta, 1959-, et al.
(author)
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Cognitive deficits in relation to personality type and hypothalamic-pituitary-adrenal (HPA) axis dysfunction in women with stress-related exhaustion
- 2011
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In: Scandinavian Journal of Psychology. - Oxford : Wiley-Blackwell. - 0036-5564 .- 1467-9450. ; 52:1, s. 71-82
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Journal article (peer-reviewed)abstract
- Exhaustion caused by long-term work-related stress may cause cognitive dysfunction. We explored factors that may link chronic stress and cognitive impairment. Personality, psychiatric screening, and behavior were assessed by self-reporting measures in 20 female patients (mean age 39.3 years; range 26–53) with a preliminary diagnosis of stress-related exhaustion and in 16 healthy matched controls. Cognitive performance was investigated with a detailed neuropsychological test battery. Cortisol axis function was assessed by urinary and saliva collections of cortisol, dexamethasone suppression, Synacthen response, and corticotropin-releasing hormone (CRH) tests. Proinflammatory cytokines were measured. Hippocampal volumes were estimated by magnetic resonance imaging. Multivariate and univariate statistical methods were used to explore putative differences between groups and factors linked to cognitive impairment. Cognitive function clearly differed between groups, with decreased attention and visuospatial memory in the patient group, suggesting frontal cortex/medial temporal cortex-network dysfunction. Increased harm avoidance and persistence was present among patients, with lowered self-directedness linked to lower quality of life, increased anxious and depressive tendencies, and experiences of psychosocial stress. Attention was decreased with concomitantly impaired visuospatial memory. The pituitary (adrenocorticotropic hormone, ACTH) response to CRH was decreased in patients, with an increased cortisol/ACTH response to CRH. However, cortisol production rates, diurnal or dexamethasone-suppressed saliva cortisol levels, and the cortisol response to Synacthen were unaltered. Hippocampal volumes did not differ between groups. These findings suggest that cognitive dysfunction in stress-related exhaustion is linked to distinct personality traits, low quality of life, and a decreased ACTH response to CRH.
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| 3. |
- Frykholm, Erik, 1985-
(author)
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The relevance and assessment of limb muscle function in individuals with chronic obstructive pulmonary disease
- 2021
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Doctoral thesis (other academic/artistic)abstract
- Chronic obstructive pulmonary disease (COPD) is a disease that is characterised by persistent respiratory symptoms and airflow limitation. Consequences beyond the airways and lungs are common, and include limb muscle dysfunction. Limb muscle dysfunction is treated with exercise training, and should be preceded by assessments to individualise prescriptions. Guidelines recommend assessment of quadriceps strength, but limb muscle dysfunction affects more than strength. Other less investigated assessments may be of interest. During training, direct physiological (cardiorespiratory, metabolic, and biomechanical) and symptomatic responses are important, since they can affect training effectivity, and they may differ depending on whether arms or legs are used. The main aims of this thesis were to investigate the relevance of assessments of quadriceps function, feasibility and reliability of methods to assess quadriceps endurance, and to compare the direct physiological and symptomatic responses during arm and leg activities in people with COPD.Method: This thesis is based on four papers. These include one systematic review with a meta-analysis of studies comparing direct physiological and symptomatic responses to activities performed with the arms versus the legs, and three papers based on an international cross-sectional multicentre study investigating reliability, feasibility, and relevance of three leg extension assessments of quadriceps endurance. Relative and absolute reliability were determined via interclass correlation coefficient (ICC), coefficient of variation (CV %), and limits of agreement (LoA %) for measures of isokinetic total work, isokinetic fatigue index, isometric time to exhaustion, and isotonic repetitions to exhaustion. The relevance of the measures of quadriceps endurance and other quadriceps functions were determined by the association to functional capacity and physical activity with Pearson correlation analyses (r) and multiple linear regression models (R2, adjusted R2, Δ R2, and Δ adjusted R2).Results: Results from the meta-analyses show that leg-cycle ergometer resulted in greater tidal volume (137 mL), minute ventilation (4.8 L/min), and oxygen consumption (164 mL/min) compared to arm cycle ergometer, while symptomatic responses were similar. Physiological responses (e.g., minute ventilation and oxygen consumption) during arm compared to leg resistance training exercises were similar. Results from studies on functional activities depend on the type and intensity of the activity performed. Isokinetic total work was the measurement with the highest relative reliability (ICC = 0.98) and the smallest absolute reliability (e.g., CV% = 6.5). Isokinetic fatigue index, isometric, and isotonic measures demonstrated low-to-high relative reliability (ICC = 0.64, 0.88, 0.91), and absolute reliability was larger (e.g., CV% = 20.3, 14.9, and 15.8%). Participants performed better on the retest for isokinetic total work and isometric measurements (4.8 and 10%, p < 0.001). The feasibility was similar across protocols, with an average time consumption of< 7.5 minutes, limited perceived dyspnoea compared to leg fatigue, and no major adverse advents. The measures of quadriceps function had mostly similar (r = +/- 0.07–0.45) levels of correlations to the functional capacity and physical activity. In multiple regression analyses improved quadriceps power the models to predict functional capacity the most (Δ adjusted R2= 0.10, 0.15, adjusted R2 = 0.60, 0.39). Isotonic endurance was the only muscle function that improved all physical activity models (ΔR2 = 0.04–0.07, p < 0.05, R2 = 0.38–0.49).Conclusions: The results indicate that if the goal of an activity is to maximise physiological responses such as minute ventilation and oxygen consumption, activities involving the legs should be preferred. Symptomatic responses seems task and intensity dependent, which suggest that strategies used to reduce symptoms should be based on relative intensity. In the assessment of quadriceps endurance, isokinetic, isometric and isotonic protocols present low to very high relative reliability. Differences in reliability and the better performance at retest might reflect differences in ability to detect true change. Quadriceps power seems to be more relevant to functional capacity, and isotonic quadriceps endurance seems to be more relevant to physical activity.
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| 4. |
- Sandström, Jan
(composer, creator_code:cre_t)
-
Acqua Alta
- 2013
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Artistic work (peer-reviewed)abstract
- Stycke komponerat av Jan Sandström med text av Meena Alexander.Verket uruppfördes av renässansensemblen Serikon under ledninga av Erik Westberg vid konserten Acqua Alta i Luleå Domkyrka den 8:e februari 2013.Konserten stöds av Statens musikverk och Kulturrådet.
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| 5. |
- Sandström, Sven-Erik, 1956-, et al.
(author)
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Accurate approximation of the current on a smooth scatterer in 2D
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Other publication (other academic/artistic)abstract
- The integral equations of high frequency electromagnetic scattering can be solved by means of the method of moments. In the case of smooth scatterers, it is feasible to factorise the surface current into an oscillating part and a slowly varying part.In this study, a Fourier transform technique is used for accurate approx- imation of the oscillating part. The complex wave number and the cor- responding amplitudes for the decay in the shadow zone are extracted by means of an extension of the symmetric discrete Fourier transform. This approximation is used as an oscillatory scaling in the method of moments. Substantial improvement of the accuracy is obtained with a small number of basis functions for both convex and concave scatterers. The scatterers have a moderate variation in the curvature.
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| 6. |
- Sandström, Sven-Erik, 1956-
(author)
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An extension of the Fock current distribution functions
- 2012
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In: AEU - International Journal of Electronics and Communications. - : Elsevier BV. - 1434-8411 .- 1618-0399. ; 66:7, s. 540-546
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Journal article (peer-reviewed)abstract
- The standard Fock functions that are the point of departure for this study are used in diffraction theory to describe the surface current on perfectly conducting convex scatterers. They are fairly accurate near the shadow boundary and in the shadow. There is also a reformulation in terms of these functions that describes the field in the lit region. In this study, a uniform counterpart to these functions is obtained for cylindrical geometry by means of integral representations. The numerical aspects of the evaluation of these integrals are discussed. High accuracy is achieved, also for the lit region. Asymptotic approximations for the uniform functions are obtained in the high frequency limit. These expansions could provide the same accuracy as the integral representation inside the lit domain of the scatterer.
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| 7. |
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| 8. |
- Sandström, Sven-Erik, 1956-
(author)
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Implementation of FMCW radar at low frequencies
- 2020
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In: AEU - International Journal of Electronics and Communications. - : Elsevier. - 1434-8411 .- 1618-0399. ; 117, s. 1-4
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Journal article (peer-reviewed)abstract
- FMCW radar is a low power technique for distance measurement suitable for many applications. At low frequencies, FMCW (Frequency Modulated Contin- uous Wave) radar can penetrate shadow zones or complex media such as forest. The need for large bandwidth in the measurements may require the use of log periodic antennas. In this study, signal processing and calibration are imple- mented in Labview, in combination with a USRP (Universal Software Radio Peripheral). A USRP is a form of interface between the RF hardware and the computer. The total bandwidth and the resolution are increased by reusing the bandwidth of the USRP.
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| 9. |
- Sandström, Sven-Erik, 1956-
(author)
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On Sparsity Related to the Integral Equations of 2D Electromagnetic Scattering
- 2023
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In: Radio Science. - New York : John Wiley & Sons. - 0048-6604 .- 1944-799X. ; 58:4
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Journal article (peer-reviewed)abstract
- The integral equations of electromagnetic scattering are often solved with the Fast Multipole Method. If the application involves multiple excitations one could instead consider methods that separate factorization and solution. The cost of an elaborate factorization could then be compensated for by an efficient solution. An approach to obtain substantial sparsity in the solution step is considered here. By using the generality provided by the integral representation, the kernel is modified so as to create sparsity in the resulting linear system. In the two modifications that are described here there is an attempt to optimize the shape of the kernel with respect to sparsity and accuracy.
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| 10. |
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