| 1. |
- Nilsson, J, et al.
(författare)
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Variation in the content of glucosinolates, hydroxycinnamic acids, carotenoids, total antioxidant capacity and low-molecular-weight carbohydrates in Brassica vegetables
- 2006
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Ingår i: Journal of the Science of Food and Agriculture. - : Wiley. - 1097-0010 .- 0022-5142. ; 86:4, s. 528-538
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Tidskriftsartikel (refereegranskat)abstract
- Bioactive compounds were investigated in genotypes (cauliflower 10, white cabbage 10, curly kale 1) and plant parts of the three crops. The content of most of the major glucosinolates glucobrassicin, sinigrin and glucoiberin differed significantly between cultivars. Samples harvested in 2000 had higher amounts of several glucosinolates than samples from 1999. Within cauliflower the buds of the floret had 1.5 to 2.5-fold higher concentration of glucobrassicin and 4-methoxyglucobrassicin than the stalk. In white cabbage several glucosinolates had their highest content in the outer leaves (up to 2-fold higher). Upper leaves of curly kale contained 5-fold more of total glucosinolates than lower leaves. Chlorogenic acid was the dominating hydroxycinnamate in curly kale, which also contained at least ten times more of carotenoids (mainly lutein) than white cabbage. Total antioxidant capacity (TAC) assayed with the FRAP method was 0.76 (0.06) mu mol/g fw (mean (SD)) in water-soluble and 0.32 (0.04) in water-insoluble extracts of cauliflower which was 62-68% higher than in white cabbage. Curly kale contained 6.4 and 6.1 mu mol/g fw TAC in water-soluble and water-insoluble extracts. TAC did not differ between plant parts. Progoitrin and 4-hydroxyglucobrassicin were correlated to water-soluble TAC in white cabbage, probably reflecting a variation in other compounds. Cauliflower contained less glucose, fructose and sorbitol but more sucrose than white cabbage. Curly kale had lower contents of glucose (similar to 2 times), fructose (similar to 4-S times) and sucrose (20 and 36 times, respectively) than cauliflower and white cabbage, while inositol was only found in curly kale. Storage of white cabbage reduced the amount of sorbitol and sucrose. The study shows that cultivar, plant part and storage affect the content of bioactive compounds in Brassica vegetables. The variation between years, as in cauliflower, is due to environmental factors. Since the cultivar ranking order was rather stable for several components the data could provide a basis for the selection of cultivars optimised for valuable health components for fresh market consumption. (c) 2005 Society of Chemical Industry.
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| 2. |
- Abdalmoaty, Mohamed, 1986-
(författare)
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Learning Stochastic Nonlinear Dynamical Systems Using Non-stationary Linear Predictors
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The estimation problem of stochastic nonlinear parametric models is recognized to be very challenging due to the intractability of the likelihood function. Recently, several methods have been developed to approximate the maximum likelihood estimator and the optimal mean-square error predictor using Monte Carlo methods. Albeit asymptotically optimal, these methods come with several computational challenges and fundamental limitations.The contributions of this thesis can be divided into two main parts. In the first part, approximate solutions to the maximum likelihood problem are explored. Both analytical and numerical approaches, based on the expectation-maximization algorithm and the quasi-Newton algorithm, are considered. While analytic approximations are difficult to analyze, asymptotic guarantees can be established for methods based on Monte Carlo approximations. Yet, Monte Carlo methods come with their own computational difficulties; sampling in high-dimensional spaces requires an efficient proposal distribution to reduce the number of required samples to a reasonable value.In the second part, relatively simple prediction error method estimators are proposed. They are based on non-stationary one-step ahead predictors which are linear in the observed outputs, but are nonlinear in the (assumed known) input. These predictors rely only on the first two moments of the model and the computation of the likelihood function is not required. Consequently, the resulting estimators are defined via analytically tractable objective functions in several relevant cases. It is shown that, under mild assumptions, the estimators are consistent and asymptotically normal. In cases where the first two moments are analytically intractable due to the complexity of the model, it is possible to resort to vanilla Monte Carlo approximations. Several numerical examples demonstrate a good performance of the suggested estimators in several cases that are usually considered challenging.
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| 3. |
- Alenlöv, Johan, et al.
(författare)
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Particle-Based Adaptive-Lag Online Marginal Smoothing in General State-Space Models
- 2019
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Ingår i: IEEE Transactions on Signal Processing. - : IEEE. - 1053-587X .- 1941-0476. ; 67:21, s. 5571-5582
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Tidskriftsartikel (refereegranskat)abstract
- We present a novel algorithm, an adaptive-lag smoother, approximating efficiently, in an online fashion, sequences of expectations under the marginal smoothing distributions in general state-space models. The algorithm evolves recursively a bank of estimators, one for each marginal, in resemblance with the so-called particle-based, rapid incremental smoother (PaRIS). Each estimator is propagated until a stopping criterion, measuring the fluctuations of the estimates, is met. The presented algorithm is furnished with theoretical results describing its asymptotic limit and memory usage.
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| 4. |
- Betancourt, Lazaro Hiram, et al.
(författare)
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The hidden story of heterogeneous B-raf V600E mutation quantitative protein expression in metastatic melanoma—association with clinical outcome and tumor phenotypes
- 2019
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Ingår i: Cancers. - : MDPI AG. - 2072-6694. ; 11:12
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Tidskriftsartikel (refereegranskat)abstract
- In comparison to other human cancer types, malignant melanoma exhibits the greatest amount of heterogeneity. After DNA-based detection of the BRAF V600E mutation in melanoma patients, targeted inhibitor treatment is the current recommendation. This approach, however, does not take the abundance of the therapeutic target, i.e., the B-raf V600E protein, into consideration. As shown by immunohistochemistry, the protein expression profiles of metastatic melanomas clearly reveal the existence of inter-and intra-tumor variability. Nevertheless, the technique is only semi-quantitative. To quantitate the mutant protein there is a fundamental need for more precise techniques that are aimed at defining the currently non-existent link between the levels of the target protein and subsequent drug efficacy. Using cutting-edge mass spectrometry combined with DNA and mRNA sequencing, the mutated B-raf protein within metastatic tumors was quantitated for the first time. B-raf V600E protein analysis revealed a subjacent layer of heterogeneity for mutation-positive metastatic melanomas. These were characterized into two distinct groups with different tumor morphologies, protein profiles and patient clinical outcomes. This study provides evidence that a higher level of expression in the mutated protein is associated with a more aggressive tumor progression. Our study design, comprised of surgical isolation of tumors, histopathological characterization, tissue biobanking, and protein analysis, may enable the eventual delineation of patient responders/non-responders and subsequent therapy for malignant melanoma.
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| 5. |
- Betancourt, Lazaro Hiram, et al.
(författare)
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The human melanoma proteome atlas-Defining the molecular pathology
- 2021
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Ingår i: Clinical and Translational Medicine. - : Wiley. - 2001-1326. ; 11:7, s. 1-20
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Tidskriftsartikel (refereegranskat)abstract
- The MM500 study is an initiative to map the protein levels in malignant melanoma tumor samples, focused on in-depth histopathology coupled to proteome characterization. The protein levels and localization were determined for a broad spectrum of diverse, surgically isolated melanoma tumors originating from multiple body locations. More than 15,500 proteoforms were identified by mass spectrometry, from which chromosomal and subcellular localization was annotated within both primary and metastatic melanoma. The data generated by global proteomic experiments covered 72% of the proteins identified in the recently reported high stringency blueprint of the human proteome. This study contributes to the NIH Cancer Moonshot initiative combining detailed histopathological presentation with the molecular characterization for 505 melanoma tumor samples, localized in 26 organs from 232 patients.
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| 6. |
- Bizjajeva, Svetlana, et al.
(författare)
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Antithetic sampling for sequential Monte Carlo methods with application to state-space models
- 2016
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Ingår i: Annals of the Institute of Statistical Mathematics. - : Springer Berlin/Heidelberg. - 0020-3157 .- 1572-9052. ; 68:5, s. 1025-1053
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we cast the idea of antithetic sampling, widely used in standard Monte Carlo simulation, into the framework of sequential Monte Carlo methods. We propose a version of the standard auxiliary particle filter where the particles are mutated blockwise in such a way that all particles within each block are, first, offspring of a common ancestor and, second, negatively correlated conditionally on this ancestor. By deriving and examining the weak limit of a central limit theorem describing the convergence of the algorithm, we conclude that the asymptotic variance of the produced Monte Carlo estimates can be straightforwardly decreased by means of antithetic techniques when the particle filter is close to fully adapted, which involves approximation of the so-called optimal proposal kernel. As an illustration, we apply the method to optimal filtering in state-space models.
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| 7. |
- Boström, Lena, 1960-, et al.
(författare)
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Digital visualisering i skolan : Mittuniversitetets slutrapport från förstudien
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Den här studiens syfte har varit tvåfaldigt, nämligen att testa alternativa lärmetoder via ett digitalt läromedel i matematik i en kvasiexperimentell studie samt att tillämpa metoder av användarupplevelser för interaktiva visualiseringar, och därigenom öka kunskapen kring hur upplevd kvalitet beror på använd teknik. Pilotstudien sätter också fokus på flera angelägna områden inom skolutveckling både regionalt och nationellt samt viktiga aspekter när det gäller kopplingen teknik, pedagogik och utvärderingsmetoder inom “den tekniska delen”. Det förra handlar om sjunkande matematikresultat i skolan, praktiknära skolforskning, stärkt digital kompetens, visualisering och lärande samt forskning om visualisering och utvärdering. Den senare svarar på frågor om vilka tekniska lösningar som tidigare använts och med vilket syfte har de skapats samt hur visualiseringar har utvärderats enligt läroböcker och i forskningslitteratur. När det gäller elevernas resultat, en av de stora forskningsfrågorna i studien, så fann vi inga signifikanta skillnader mellan traditionell undervisning och undervisning med visualiseringsläromedlet (3D). Beträffande elevers attityder till matematikmomentet kan konstateras att i kontrollgruppen för årskurs 6 förbättrades attityden signifikans, men inte i klass 8. Gällande flickors och pojkars resultat och attityder kan vi konstatera att flickorna i båda klasserna hade bättre förkunskaper än pojkarna samt att i årskurs 6 var flickorna mer positiva till matematikmomentet än pojkarna i kontrollgruppen. Därutöver kan vi inte skönja några signifikanta skillnader. Andra viktiga rön i studien var att provkonstruktionen inte var optimal samt att tiden för provgenomförande har stor betydelse när på dagen det genomfördes. Andra resultat resultaten i den kvalitativa analysen pekar på positiva attityder och beteenden från eleverna vid arbetet med det visuella läromedlet. Elevernas samarbete och kommunikation förbättrades under lektionerna. Vidare pekade lärarna på att med 3D-läromedlet gavs större möjligheter till att stimulera flera sinnen under lärprocessen. En tydlig slutsats är att 3D-läromedlet är ett viktigt komplement i undervisningen, men kan inte användas helt självt. Vi kan varken sälla oss till de forskare som anser att 3D-visualisering är överlägset som läromedel för elevers resultat eller till de forskare som varnar för dess effekter för elevers kognitiva överbelastning. Våra resultat ligger mer i linje med de slutsatser Skolforskningsinstitutet (2017) drar, nämligen att undervisning med digitala läromedel i matematik kan ha positiva effekter, men en lika effektiv undervisning kan möjligen designas på andra sätt. Däremot pekar resultaten i vår studie på ett flertal störningsmoment som kan ha påverkat möjliga resultat och behovet av god teknologin och välutvecklade programvaror. I studien har vi analyserat resultaten med hjälp av två övergripande ramverk för integrering av teknikstöd i lärande, SAMR och TPACK. Det förra ramverket bidrog med en taxonomi vid diskussionen av hur väl teknikens möjligheter tagits tillvara av läromedel och i läraktiviteter, det senare för en diskussion om de didaktiska frågeställningarna med fokus på teknikens roll. Båda aspekterna är högaktuella med tanke på den ökande digitaliseringen i skolan. Utifrån tidigare forskning och denna pilotstudie förstår vi att det är viktigt att designa forskningsmetoderna noggrant. En randomisering av grupper vore önskvärt. Prestandamått kan också vara svåra att välja. Tester där personer får utvärdera användbarhet (usability) och användarupplevelse (user experience, UX) baserade på både kvalitativa och kvantitativa metoder blir viktiga för själva användandet av tekniken, men det måste till ytterligare utvärderingar för att koppla tekniken och visualiseringen till kvaliteten i lärandet och undervisningen. Flera metoder behövs således och det blir viktigt med samarbete mellan olika ämnen och discipliner.
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| 8. |
- Byungura, Jean Claude, 1979-
(författare)
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Improving IT Integration for Higher Education Institutional Performance : Towards a Contextualised IT-Institutional Alignment Model
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The integration of information technology (IT) into service delivery is currently seen as an innovative strategy to support the modernising of universities worldwide. However, in some institutions in developing countries, including Rwanda, IT has failed to add the intended value to university services, despite huge associated investments in IT. Consequently, IT-organisational alignment continues to be a primary concern for university managers. This alignment is viewed in terms of its strategic, socio-cultural, and technological dimensions. For effective IT-institutional alignment, several antecedents (alignment practices) for creating an appropriate fit between IT and organisations have been suggested in the literature. However, several studies exploring IT alignment focused mainly on general business companies, and similar research with an emphasis on higher education institutions is still scarce. Therefore, the aim of this research was twofold: firstly, it attempted to understand the process of IT integration into universities; and secondly, to propose a contextual model for IT-institutional alignment within a higher education context. A design science research methodology (DSRM) was applied in this research, using surveys and case studies as research strategies. Preliminary findings at the exploration phase of this research indicated a strong misalignment between IT and the university services caused by the lack of clearly defined alignment practices. Furthermore, as the research main outcome, an IT-Institutional Alignment Model (ITIAM) was proposed after reaching an understanding of the current state and challenges related to IT integration into teaching, learning, research and university administration. This model includes 44 alignment practices, related to both technical and non-technical dimensions. These alignment practices were clustered under six categories: (1) Communication, (2) Structure/Governance, (3) Technology Scope, (4) Competence/Value Measurement, (5) Skills, and (6) Partnership. Alignment practices related to institutional structure and governance, skills and communication were found to have a strong positive influence on the institutional performance, as compared to those related to competence and value measurement, partnership, and technology scope. Based on the research findings, the proposed ITIAM, which was iteratively tested and evaluated using case study institutions, was found to be a relevant tool for guiding the implementation of IT systems towards the improvement of institutional performance. Hence, this thesis makes a theoretical contribution by applying the concept of IT alignment within a higher education context and by documenting the empirically tested contextual alignment practices as conveyed in the ITIAM Model. Additionally, as a practical implication, the results can serve as a reference for an effective IT integration process in university services and for how to improve performance through effective use of IT in teaching, learning, research and educational management.
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| 9. |
- Cardoso, Gabriel, et al.
(författare)
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BR-SNIS : Bias Reduced Self-Normalized Importance Sampling
- 2022
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Ingår i: Advances in Neural Information Processing Systems 35 - 36th Conference on Neural Information Processing Systems, NeurIPS 2022. - : Neural Information Processing Systems Foundation.
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Konferensbidrag (refereegranskat)abstract
- Importance Sampling (IS) is a method for approximating expectations under a target distribution using independent samples from a proposal distribution and the associated importance weights. In many applications, the target distribution is known only up to a normalization constant, in which case self-normalized IS (SNIS) can be used. While the use of self-normalization can have a positive effect on the dispersion of the estimator, it introduces bias. In this work, we propose a new method, BR-SNIS, whose complexity is essentially the same as that of SNIS and which significantly reduces bias without increasing the variance. This method is a wrapper in the sense that it uses the same proposal samples and importance weights as SNIS, but makes clever use of iterated sampling-importance resampling (i-SIR) to form a bias-reduced version of the estimator. We furnish the proposed algorithm with rigorous theoretical results, including new bias, variance and high-probability bounds, and these are illustrated by numerical examples.
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| 10. |
- Cardoso, Gabriel, et al.
(författare)
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Particle-based, Rapid Incremental Smoother Meets Particle Gibbs
- 2023
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Ingår i: Statistica sinica. - : Institute of Statistical Science. - 1017-0405 .- 1996-8507. ; :1
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Tidskriftsartikel (refereegranskat)abstract
- The particle-based, rapid incremental smoother (PARIS) is a sequential Monte Carlo technique allowing for efficient online approximation of expectations of additive functionals under Feynman–Kac path distributions. Under weak assumptions, the algorithm has linear computational complexity and limited memory requirements. It also comes with a number of non-asymptotic bounds and convergence results. However, being based on self-normalised importance sampling, the PARIS estimator is biased; its bias is inversely proportional to the number of particles but has been found to grow linearly with the time horizon under appropriate mixing conditions. In this work, we propose the Parisian particle Gibbs (PPG) sampler, whose complexity is essentially the same as that of the PARIS and which significantly reduces the bias for a given computational complexity at the price of a modest increase in the variance. This method is a wrapper in the sense that it uses the PARIS algorithm in the inner loop of particle Gibbs to form a bias-reduced version of the targeted quantities. We substantiate the PPG algorithm with theoretical results, including new bounds on bias and variance as well as deviation inequalities. We illustrate our theoretical results with numerical experiments supporting our claims.
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