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Sökning: WFRF:(Larsson Torbjörn) > (2010-2014)

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1.
  • Alrutz, Marie, et al. (författare)
  • Projektledning
  • 2013
  • Bok (populärvet., debatt m.m.)abstract
    • Projektledning är ett yrke med egen certifiering. Det pågår en spännande utveckling inom området och det blir allt viktigare att hålla sig ajour med utvecklingen.Det övergripande målet med den här handboken är att vara en ständigt aktuell heltäckande bok om projektar­bete. Innehållsmässigt täcker den både frågor som har med struktur och styrning att göra och frågor om ledning av människor och mänskliga processer i grupp. Kompetens inom projekt byggs av både kunskap och erfarenhet. Vi följer kontinuerligt aktuell forskning inom dessa områden och bjuder in intressanta forskare att medverka som författare. Vi skildrar verkliga projekt och låter erfarenheterna få plats, både de bästa erfarenheterna och de utmaningar som man tagit sig igenom.Handboken är levande och det innebär att artiklar tas bort för att ge plats för nya, i takt med att den uppdateras fortlöpande.
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2.
  • Amankwah, Henry, et al. (författare)
  • A maximum flow formulation of a multi-period open-pit mining problem
  • 2014
  • Ingår i: Operational Research. - : Springer Berlin/Heidelberg. - 1109-2858 .- 1866-1505. ; 14:1, s. 1-10
  • Tidskriftsartikel (refereegranskat)abstract
    • We consider the problem of finding an optimal mining sequence for an open pit during a number of time periods subject to only spatial and temporal precedence constraints. This problem is of interest because such constraints are generic to any open-pit scheduling problem and, in particular, because it arises as a Lagrangean relaxation of an open-pit scheduling problem. We show that this multi-period open-pit mining problem can be solved as a maximum flow problem in a time-expanded mine graph. Further, the minimum cut in this graph will define an optimal sequence of pits. This result extends a well-known result of J.-C. Picard from 1976 for the open-pit mine design problem, that is, the single-period case, to the case of multiple time periods.
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3.
  • Amankwah, Henry, 1969- (författare)
  • Mathematical Optimization Models and Methods for Open-Pit Mining
  • 2011
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Open-pit mining is an operation in which blocks from the ground are dug to extract the ore contained in them, and in this process a deeper and deeper pit is formed until the mining operation ends. Mining is often a highly complex industrial operation, with respect to both technological and planning aspects. The latter may involve decisions about which ore to mine and in which order. Furthermore, mining operations are typically capital intensive and long-term, and subject to uncertainties regarding ore grades, future mining costs, and the market prices of the precious metals contained in the ore. Today, most of the high-grade or low-cost ore deposits have already been depleted, and to obtain sufficient profitability in mining operations it is therefore today often a necessity to achieve operational efficiency with respect to both technological and planning issues.In this thesis, we study the open-pit design problem, the open-pit mining scheduling problem, and the open-pit design problem with geological and price uncertainty. These problems give rise to (mixed) discrete optimization models that in real-life settings are large scale and computationally challenging.The open-pit design problem is to find an optimal ultimate contour of the pit, given estimates of ore grades, that are typically obtained from samples in drill holes, estimates of costs for mining and processing ore, and physical constraints on mining precedence and maximal pit slope. As is well known, this problem can be solved as a maximum flow problem in a special network. In a first paper, we show that two well known parametric procedures for finding a sequence of intermediate contours leading to an ultimate one, can be interpreted as Lagrangian dual approaches to certain side-constrained design models. In a second paper, we give an alternative derivation of the maximum flow problem of the design problem.We also study the combined open-pit design and mining scheduling problem, which is the problem of simultaneously finding an ultimate pit contour and the sequence in which the parts of the orebody shall be removed, subject to mining capacity restrictions. The goal is to maximize the discounted net profit during the life-time of the mine. We show in a third paper that the combined problem can also be formulated as a maximum flow problem, if the mining capacity restrictions are relaxed; in this case the network however needs to be time-expanded.In a fourth paper, we provide some suggestions for Lagrangian dual heuristic and time aggregation approaches for the open-pit scheduling problem. Finally, we study the open-pit design problem under uncertainty, which is taken into account by using the concept of conditional value-atrisk. This concept enables us to incorporate a variety of possible uncertainties, especially regarding grades, costs and prices, in the planning process. In real-life situations, the resulting models would however become very computationally challenging.
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4.
  • Amankwah, Henry, et al. (författare)
  • Open-pit mining with uncertainty : A conditional value-at-risk approach
  • 2013
  • Ingår i: Optimization Theory, Decision Making, and Operations Research Applications. - New York : Springer. - 9781461451334 - 9781461451341 ; , s. 117-139
  • Konferensbidrag (refereegranskat)abstract
    • The selection of a mine design is based on estimating net present values of all possible, technically feasible mine plans so as to select the one with the maximum value. It is a hard task to know with certainty the quantity and quality of ore in the ground. This geological uncertainty and also the future market behavior of metal prices and foreign exchange rates, which are always uncertain, make mining a high risk business. Value-at-Risk (VaR) is a measure that is used in financial decisions to minimize the loss caused by inadequate monitoring of risk. This measure does, however, have certain drawbacks such as lack of consistency, nonconvexity, and nondifferentiability. Rockafellar and Uryasev [J. Risk 2, 21-41 (2000)] introduce the Conditional Value-at-Risk (CVaR) measure as an alternative to the VaR measure. The CVaR measure gives rise to a convex optimization problem. An optimization model that maximizes expected return while minimizing risk is important for the mining sector as this will help make better decisions on the blocks of ore to mine at a particular point in time. We present a CVaR approach to the uncertainty involved in open-pit mining. We formulate investment and design models for the open-pit mine and also give a nested pit scheduling model based on CVaR. Several numerical results based on our models are presented by using scenarios from simulated geological and market uncertainties.
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5.
  • Bruce, Carl, et al. (författare)
  • Preparation and evaluation of a block copolymer compatibilizer for biocomposite applications
  • 2012
  • Konferensbidrag (refereegranskat)abstract
    • In this study, the concept of using a free polymer as a compatibilzer in biocomposite applications has been evaluated with focus on the polymer poly(ɛ-caprolactone) (PCL), commonly used in conventional grafting onto/from cellulose. A block copolymer consisting of PCL and a shorter segment of poly(di(methylamino)ethyl methacrylate) (PDMAEMA) was made combining ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). The length of the PDMAEMA-part was kept constant, and the PCL-part was varied in three different lengths, yielding three separate block copolymers. As a final step, the PDMAEMA-part was quaternized, which resulted in cationically charged chains –polyelectrolytes. The charged part could then be used as an electrostatic linker allowing the PDMAEMA-PCL copolymer to be adsorbed onto negatively charged cellulose model surfaces. Finally, these cellulose model surfaces were evaluated regarding for example amount of polymer adsorbed and hydrophobic character, investigated with techniques such as quartz crystal microbalance (QCM) and contact angle measurements.
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6.
  • Bäck, Henry, et al. (författare)
  • Den svenska politiken : Strukturer, processer och resultat
  • 2011. - 3
  • Bok (övrigt vetenskapligt/konstnärligt)abstract
    • I boken ges en bred översikt över statsskicket och politiken. Med utgångspunkt i stats- och samhällsvetenskaplig forskning beskrivs och analyseras staten, EU, kommuner och landsting. Läs mer Det politiska systemet gör det möjligt att fatta gemensamma beslut och skrida till gemensam handling i samhället. Till skillnad från andra system för gemensamt handlande verkar politiken genom att använda makt. För att kunna fånga maktutövningen i ett politiskt system krävs analytiska instrument i form av samhällsvetenskaplig teori. I boken behandlas särskilt det politiska systemets inbyggda kontrollmekanismer och den politiska processen. Formandet av den offentliga politiken illustreras med några centrala politikområden i den moderna svenska politiken. Här beskrivs och analyseras både det formella normativa ramverket och "hur det verkligen går till". För att begripa dagens svenska politik behöver vi kunna göra jämförelser i både tid och rum, och därför anläggs ett historiskt perspektiv och görs utblickar på andra länder.Stig Montin, docent i statsvetenskap vid Örebro universitet
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8.
  • Daneva (Mitradjieva), Maria, et al. (författare)
  • A Comparison of Feasible Direction Methods for the Stochastic Transportation Problem
  • 2010
  • Ingår i: Computational optimization and applications. - : Springer Science and Business Media LLC. - 0926-6003 .- 1573-2894. ; 46:3, s. 451-466
  • Tidskriftsartikel (refereegranskat)abstract
    • The feasible direction method of Frank and Wolfe has been claimed to be efficient for solving the stochastic transportation problem. While this is true for very moderate accuracy requirements, substantially more efficient algorithms are otherwise diagonalized Newton and conjugate Frank–Wolfe algorithms, which we describe and evaluate. Like the Frank–Wolfe algorithm, these two algorithms take advantage of the structure of the stochastic transportation problem. We also introduce a Frank–Wolfe type algorithm with multi-dimensional search; this search procedure exploits the Cartesian product structure of the problem. Numerical results for two classic test problem sets are given. The three new methods that are considered are shown to be superior to the Frank–Wolfe method, and also to an earlier suggested heuristic acceleration of the Frank–Wolfe method.
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9.
  • Falkmer, Marita, et al. (författare)
  • Recognition of facially expressed emotions and visual search strategies in adults with Asperger syndrome
  • 2011
  • Ingår i: RES AUTISM SPECTR DISORD. - : Elsevier BV. - 1750-9467 .- 1878-0237. ; 5:1, s. 210-217
  • Tidskriftsartikel (refereegranskat)abstract
    • Can the disadvantages persons with Asperger syndrome frequently experience with reading facially expressed emotions be attributed to a different visual perception, affecting their scanning patterns? Visual search strategies, particularly regarding the importance of information from the eye area, and the ability to recognise facially expressed emotions were compared between 24 adults with Asperger syndrome and their matched controls. While wearing a head mounted eye tracker, the participants viewed 12 pairs of photos of faces. The first photo in each pair was cut up into puzzle pieces. Six of the 12 puzzle pieced photos had the eyes bisected. The second photo showed a happy, an angry and a surprised face of the same person as in the puzzle pieced photo. Differences in visual search strategies between the groups were established. Adults with Asperger syndrome had greater difficulties recognizing these basic emotions than controls. The distortion of the eye area affected the ability to identify emotions even more negatively for participants with Asperger syndrome.
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10.
  • Falkmer, Marita, et al. (författare)
  • The influences of static and interactive dynamic facial stimuli on visual strategies in persons with Asperger syndrome
  • 2011
  • Ingår i: Research in Autism Spectrum Disorders. - : Elsevier BV. - 1750-9467 .- 1878-0237. ; 5:2, s. 935-940
  • Tidskriftsartikel (refereegranskat)abstract
    • Several studies, using eye tracking methodology, suggest that different visual strategies in persons with autism spectrum conditions, compared with controls, are applied when viewing facial stimuli. Most eye tracking studies are, however, made in laboratory settings with either static (photos) or non-interactive dynamic stimuli, such as video clips. Whether or not these results are transferable to a "real world" dialogue situation remains unclear. In order to examine the consistency of visual strategies across conditions, a comparison of two static conditions and an interactive dynamic "real world" condition, in 15 adults with Asperger syndrome and 15 matched controls, was made using an eye tracker. The static stimuli consisted of colour photos of faces, while a dialogue between the participants and the test leader created the interactive dynamic condition. A within-group comparison showed that people with AS, and their matched controls, displayed a high degree of stability in visual strategies when viewing faces, regardless of the facial stimuli being static or real, as in the interactive dynamic condition. The consistency in visual strategies within the participants suggests that results from studies with static facial stimuli provide important information on individual visual strategies that may be generalized to "real world" situations.
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11.
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12.
  • Forslid, Torbjörn, et al. (författare)
  • Att förhandla litterärt värde : Sami Said och Väldigt sällan fin
  • 2013
  • Ingår i: Tidskrift för litteraturvetenskap. - 1104-0556 .- 2001-094X. ; 43:3-4, s. 121-134
  • Tidskriftsartikel (refereegranskat)abstract
    • This article aims to highlight how literary value is constructed today: how it is created and negotiated. It seeks to develop a perspective that considers the manifold and complex value-negotiation process. In accordance with Barbara Herrnstein Smith, the article argues that literary value is generated by a constant and continuous series of negotiations between production and sale: the institutions, groups of readers, and individuals who are part of the value-making process. A number of different values circulate among different stakeholders – trade, educational, aesthetic, personal, and so on – and the negotiations take place in accordance with the dictates of the respective needs, interests, and resources of these stakeholders. While Barbara Herrnstein Smith’s theories on literary value remain influential, they have rarely been tested empirically. The basic premise of the article is that the process of value creation has to be discussed from new perspectives based on empirical research. The article presents a case study of the Swedish author Sami Said’s literary debut – the critically acclaimed Väldigt sällan fin – and the negotiation process before and after its publication. The fact that Said was unknown at the time of his debut most likely foregrounded the visible negotiation of literary value in his case, but we believe that the process can be seen as an example of a continual and on-going practise in the literary sphere as a whole. The analysis shows that different agents claimed values and positions both in relation to the book and to each other. For example, marketing and publishing paratexts emphasised values of knowledge, institutionalised literary criticism valued the aesthetic qualities of the novel, while readers writing on the Internet took a more emotional and subjective position. The valuation also went back-and-forth between reading the novel as expressing a particular, non-Swedish experience with biographical overtones, and understanding it as manifesting universal existential values.
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13.
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14.
  • Gunnarsson, Anna-Karin, et al. (författare)
  • Increased energy intake in hip fracture patients affects nutritional biochemical markers
  • 2012
  • Ingår i: Scandinavian Journal of Surgery. - 1457-4969 .- 1799-7267. ; 101:3, s. 204-210
  • Tidskriftsartikel (refereegranskat)abstract
    • Background and Aims: We have previously shown that nutritional guidelines decreased the incidence of pressure ulcers in hip fracture patients. In the present study, we evaluate whether the nutritional biochemical markers S-IGF-1 (Insulin-like Growth Factor 1), S-Transthyretin and S-Albumin are affected by patients' energy intake, and whether the markers are useful as predictors of postoperative complications. Material and Methods: Quasi-experimental design, with one intervention and one control group, as well as pre- and post-study measurements. Eighty-eight hip fracture patients were included: 42 in the control group and 46 in the intervention group. The control group received regular nutritional support pre- and postoperatively, while the intervention group received nutritional support that followed new, improved clinical guidelines from admission to five days postoperatively. S-Albumin, S-Transthyretin, C-Reactive Protein (S-CRP) and S-IGF-1 were analysed at admission and five days postoperatively as well as complications like pressure ulcer and infection. Results: The intervention group had a significantly higher energy intake; for example, 1636 kcal versus 852 kcal postoperative day 1. S-IGF-1 levels decreased significantly in the control group, while no decrease in the intervention group. S-Albumin and S-Transthyretin decreased and S-CRP increased significantly in both groups, indicating that those markers were not affected short-term by a high-energy intake. There was no correlation between short-term postoperative complications and S-IGF-1, S-Transthyretin or S-Albumin at admission. Conclusion: The results of our study showed that S-IGF-1 can be used as a short-term nutritional biochemical marker, as it was affected by a five-day high-energy regimen. However, neither S-IGF-1, S-Transthyretin or S-Albumin were useful in predicting postoperative complications within five days postoperatively.
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15.
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16.
  • Helmersson-Karlqvist, Johanna, et al. (författare)
  • Serum MMP-9 and TIMP-1 concentrations and MMP-9 activity during surgery-induced inflammation in humans
  • 2012
  • Ingår i: Clinical Chemistry and Laboratory Medicine. - : Walter de Gruyter GmbH. - 1434-6621 .- 1437-4331. ; 50:6, s. 1115-1119
  • Tidskriftsartikel (refereegranskat)abstract
    •  Background: Matrix metalloproteinase 9 (MMP-9) and the endogenous inhibitor to MMP-9, tissue inhibitor of metalloproteinase 1 (TIMP-1), have important roles in tissue remodelling and are implicated in a number of diseases related to inflammation. The time course in activation and formation of MMPs and TIMPs during an inflammatory reaction is not fully known. This study investigates MMP-9 and TIMP-1 concentrations and MMP-9 activity at different time points after major surgery when a state of noticeable inflammation is expected. Methods: Serum MMP-9 and TIMP-1 concentrations and MMP-9 activity were analysed preoperatively and 4 and 30 days postoperatively in patients undergoing elective surgery (coronary artery bypass n=21; orthopaedic surgery, n=29). Results: Serum TIMP-1 and MMP-9 activity increased significantly 4 days after surgery (p<0.05 and p<0.01, respectively) and decreased again 30 days after surgery (p<0.01, respectively, compared to 4 days after surgery). Serum MMP-9 increased significantly 4 days after surgery (p<0.05) and was still high 30 days after surgery (p<0.01 compared to before surgery). The calculated MMP-9/TIMP-1 ratio was increased 30 days after surgery compared to before surgery (p<0.01). Conclusions: The inflammatory state induced by elective surgery is associated with increased TIMP-1 response and MMP-9 activity in serum within a few days which may be of importance for the postoperative heeling process. The further increase in MMP-9 concentrations at day 30 postoperative did not result in increased MMP-9 activity. Serum MMP-9 concentrations or the calculated MMP-9/TIMP-1 ratio do not entirely represent MMP-9 activity during surgery-induced inflammation.
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17.
  • Holm, Åsa, et al. (författare)
  • A linear programming model for optimizing HDR brachytherapy dose distributions with respect to mean dose in the DVH-tail
  • 2013
  • Ingår i: Medical physics (Lancaster). - : American Association of Physicists in Medicine. - 0094-2405. ; 40:8
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: Recent research has shown that the optimization model hitherto used in high-dose-rate (HDR) brachytherapy corresponds weakly to the dosimetric indices used to evaluate the quality of a dose distribution. Although alternative models that explicitly include such dosimetric indices have been presented, the inclusion of the dosimetric indices explicitly yields intractable models. The purpose of this paper is to develop a model for optimizing dosimetric indices that is easier to solve than those proposed earlier. less thanbrgreater than less thanbrgreater thanMethods: In this paper, the authors present an alternative approach for optimizing dose distributions for HDR brachytherapy where dosimetric indices are taken into account through surrogates based on the conditional value-at-risk concept. This yields a linear optimization model that is easy to solve, and has the advantage that the constraints are easy to interpret and modify to obtain satisfactory dose distributions. less thanbrgreater than less thanbrgreater thanResults: The authors show by experimental comparisons, carried out retrospectively for a set of prostate cancer patients, that their proposed model corresponds well with constraining dosimetric indices. All modifications of the parameters in the authors model yield the expected result. The dose distributions generated are also comparable to those generated by the standard model with respect to the dosimetric indices that are used for evaluating quality. less thanbrgreater than less thanbrgreater thanConclusions: The authors new model is a viable surrogate to optimizing dosimetric indices and quickly and easily yields high quality dose distributions.
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18.
  • Holm, Åsa (författare)
  • Dose Plan Optimization in HDR Brachytherapy using Penalties : Properties and Extensions
  • 2011
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • High dose-rate (HDR) brachytherapy is a specific type of radiotherapy used to treat tumours of for example the cervix, prostate, and breasts. In HDR brachytherapy applicators are implanted into or close to the tumour volume. A radioactive source is moved through these applicators and stops at certain positions, known as dwell points. For each patient an anatomy-based dose plan is created that decides for example where to place the applicators, which dwell points to use, and for how long. The aim when creating a dose plan is to deliver an as high dose as possible to the tumour while simultaneously keeping the dose to the surrounding healthy organs as low as possible.In order to improve the quality of dose plans mathematical optimization methods are today used in clinical practice. Usually one solves a linear penalty model that minimizes a weighted deviation from dose intervals provided by a physician. In this thesis we study certain properties and alterations of this model.One interesting property of the model that we study is the distribution of the basic variables. We show that due to the distribution of these variables only a limited number of dwell positions can be used. Since relatively few dwell positions are used some of the corresponding dwell times have to be long in order for the desired overall dose level to be reached. These long dwell times have been observed in clinical practice and are considered to be a problem.Another property that we study is the correlation between the objective value of the linear penalty model and dose-volume parameters used for evaluation of dose plans. We show that the correlation is weak, which implies that optimizing the linear penalty model does not give a solution to the correct problem.Some alternative models are also considered. One that includes into the optimization the decision of where to place the applicators, when HDR brachytherapy is applied for prostate cancer, and one that reduces the long dwell times by using piecewise linear penalties. The solutions to both models show significant improvements.
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19.
  • Holm, Åsa, et al. (författare)
  • Impact of Using Linear Optimization Models in Dose Planning for HDR Brachytherapy
  • 2012
  • Ingår i: Medical physics (Lancaster). - : American Association of Physicists in Medicine. - 0094-2405. ; 39:2, s. 1021-1028
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: Dose plans generated with optimization models hitherto used in HDR brachytherapy have shown a tendency to yield longer dwell times than manually optimized plans. Concern has been raised for the corresponding undesired hot spots and various methods to mitigate these have been developed. The hypotheses of this work are a) that one cause for the long dwell times is the use of objective functions comprising simple linear penalties and b) that alternative penalties, being piecewise linear, would lead to reduced length of individual dwell times.Methods: The characteristics of the linear penalties and the piecewise linear penalties are analysed mathematically. Experimental comparisons between the two types of penalties are carried out retrospectively for a set of prostate cancer patients.Results: While most dose-volume parameters do not differ significantly between the two types of penalties significant changes can be seen in the dwell times. On the average, total dwell times were reduced by 4.2%, with a reduction of maximum dwell times by 30%, using the alternative penalties.Conclusion: The use of linear penalties in optimization models for HDR brachytherapy is one cause for undesired longer dwell times appearing in mathematically optimized plans. By introducing alternative penalties significant reduction in dwell times can be achieved for HDR brachytherapy dose plans. Although various constraints as to reduce the long dwell times have been developed our finding is of fundamental interest in showing the shape of the objective function to be one reason for their appearance.
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20.
  • Holm, Åsa (författare)
  • Mathematical Optimization of HDR Brachytherapy
  • 2013
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • One out of eight deaths throughout the world is due to cancer. Developing new treatments and improving existing treatments is hence of major importance. In this thesis we have studied how mathematical optimization can be used to improve an existing treatment method: high-dose-rate (HDR) brachytherapy.HDR brachytherapy is a radiation modality used to treat tumours of for example the cervix, prostate, breasts, and skin. In HDR brachytherapy catheters are implanted into or close to the tumour volume. A radioactive source is moved through the catheters, and by adjusting where the catheters are placed, called catheter positioning, and how the source is moved through the catheters, called the dwelling time pattern, the dose distribution can be controlled.By constructing an individualized catheter positioning and dwelling time pattern, called dose plan, based on each patient's anatomy, it is possible to improve the treatment result. Mathematical optimization has during the last decade been used to aid in creating individualized dose plans. The dominating optimization model for this purpose is a linear penalty model. This model only considers the dwelling time pattern within already implanted catheters, and minimizes a weighted deviation from dose intervals prescribed by a physician.In this thesis we show that the distribution of the basic variables in the linear penalty model implies that only dwelling time patterns that have certain characteristics can be optimal. These characteristics cause troublesome inhomogeneities in the plans, and although various measures for mitigating these are already available, it is of fundamental interest to understand their cause.We have also shown that the relationship between the objective function of the linear penalty model and the measures commonly used for evaluating the quality of the dose distribution is weak. This implies that even if the model is solved to optimality there is no guarantee that the generated plan is optimal with respect to clinically relevant objectives, or even near-optimal. We have therefore constructed a new model for optimizing the dwelling time pattern. This model approximates the quality measures by the concept conditional value-at-risk, and we show that the relationship between our new model and the quality measures is strong. Furthermore, the new model generates dwelling time patterns that yield high-quality dose distributions.Combining optimization of the dwelling time pattern with optimization of the catheter positioning yields a problem for which it is rarely possible to find a proven optimal solution within a reasonable time frame. We have therefore developed a variable neighbourhood search heuristic that outperforms a state-of-the-art optimization software (CPLEX). We have also developed a tailored branch-and-bound algorithm that is better at improving the dual bound than a general branch-and-bound algorithm. This is a step towards the development of a method that can find proven optimal solutions to the combined problem within a reasonable time frame.
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21.
  • Holm, Åsa, et al. (författare)
  • Study of the Relationship Between Dosimetric Indices and Linear Penalties in Dose Distribution Optimization for HDR Prostate Brachytherapy
  • 2013
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Purpose: Most clinical software for optimizing dwelling time patterns is based on a linear penalty model. The quality of a dose distribution generated by the dwelling time pattern is, however, evaluated through a number of dosimetric indices. The purpose of this article is to investigate the relationship between the linear penalty model and the dosimetric indices.Method and Materials: Data sets from three patients, previously treated for prostate cancer with HDR brachytherapy as a boost to external beam therapy, were used for this study, and for each of them 300 random dwelling time patterns were generated. The relationship between the linear penalty model and the dosimetric indices were studied both by the Pearson’s product moment correlation coefficient between the objective function value of the linear penalty model and the values of the dosimetric indices, and by scatter-grams.Results: For one of the three patients we found a clear connection between the linear penalty model and the values of the dosimetric indices, but not for the other two. For the two patients without a clear connection there where some dosimetric indices that actually improved with deteriorating objective function value.Conclusion: The dwelling time pattern found by using the linear penalty model does not correspond to the optimal dose distribution with respect to dosimetric indices.
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22.
  • Holmberg, Daniel, et al. (författare)
  • Reducing scanning time to 50% for In-111 pentetreotide SPECT when using model-based compensation
  • 2012
  • Ingår i: 2012 IEEE nuclear science symposium and medical imaging conference record (NSS/MIC). - : IEEE. - 9781467320306 - 9781467320283 ; , s. 2946-2949
  • Konferensbidrag (refereegranskat)abstract
    • In In-111-pentetreotide SPECT, it can be difficult to detect small tumors because of high noise levels and low spatial resolution. The aim of this study was to perform optimization of tumor detection in the liver, with regards to the acquisition and reconstruction protocol for In-111-pentetreotide SPECT with model-based compensation included in the OSEM reconstruction. We were also interested in the effect of performing the examination in half of the time or with half the administered activity. Image reconstruction without model-based compensation was also included for comparison. The study concentrates on the acquired number of projections and the subset size in the OSEM reconstruction, and evaluates contrast as a function of noise for a range of OSEM iterations. The raw-data projections are produced using Monte Carlo simulations of a patient-like anthropomorphic phantom with realistic In-111 pentetreotide uptake, including spherical tumors in the liver. Two collimators are evaluated, the extended low-energy general-purpose (ELEGP) and the medium-energy general-purpose (MEGP) collimator. ELEGP proved to be a better collimator when using model-based compensation. The results also indicate that a relatively low number of subsets is advantageous, and that 60 projection angles or even lower is a better choice than 120. For both collimators the time-reduced scan including model-based compensation was better compared to the full-time reconstructions without model-based compensation.
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23.
  • Larsson, Anders, et al. (författare)
  • Life style intervention in moderately overweight individuals is associated with decreased levels of cathepsins L and S in plasma
  • 2014
  • Ingår i: Annals of Clinical and Laboratory Science. - : The Association of Clinical Scientists. - 0091-7370 .- 1550-8080. ; 44:3, s. 283-285
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Adipose tissue cells produce cathepsins L and S, which have proatherogenic effects. Obesity is strongly linked to atherogenesis, cardiovascular morbidity, and mortality. OBJECTIVE: The aim of the present study was to see if life style interventions/weight reduction could decrease cathepsin L and S levels in blood plasma. METHOD: Study subjects (n=31) were recruited to a life style intervention program aiming at increased physical activity, more healthy eating habits, and weight reduction for most of the participants. Blood samples were collected at inclusion and after 4 and 8 weeks. RESULTS: Cathepsin L was significantly reduced at 4 weeks (p<0.0001) and 8 weeks (p=0.0004). A similar reduction was also seen for cathepsin S at 4 weeks (p=0.03) and 8 weeks (p=0.008). No significant change in fractalkine values was observed at 4 weeks (p=0.58), but a significant increase was apparent at 8 weeks (p=0.0002). CONCLUSION: The intervention program resulted in significant reductions of cathepsin L and S levels in plasma after 4 and 8 weeks of intervention.
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24.
  • Larsson, Anders, et al. (författare)
  • Lifestyle intervention is associated with decreased concentrations of circulating pentraxin 3 independent of CRP decrease
  • 2013
  • Ingår i: Upsala Journal of Medical Sciences. - : Uppsala Medical Society. - 0300-9734 .- 2000-1967. ; 118:3, s. 165-168
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives. Pentraxin 3 (PTX3) is an acute phase marker, which is produced at the site of infection or inflammation in contrast to CRP that is mainly synthesized by the liver. The aim of the present study was to see if lifestyle interventions/weight loss would lead to decreased blood plasma concentrations of PTX3. Methods. Study subjects (n = 31) were recruited to a lifestyle intervention program aiming at increased physical activity, improved eating habits, and weight loss. High-sensitivity C-reactive protein (CRP) and PTX3 methods were used for analysis of CRP and PTX3 in plasma samples collected at inclusion and after 4 and 8 weeks of treatment. Results. Wilcoxon paired samples test showed a significant decrease in PTX3 concentrations from 2068 pg/mL at start to 2007 pg/mL at 4 weeks (P = 0.002) and 1748 pg/mL at 8 weeks (P = 0.003). The PTX3 decrease was not significantly correlated with a corresponding decrease in CRP or weight reduction. Conclusions. The lifestyle intervention program resulted in a significant reduction of circulating concentrations of pentraxin 3 already after 4 and 8 weeks of treatment.
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25.
  • Larsson, Anne, et al. (författare)
  • Optimal contrast as a function of noise for Butterworth filtering of 111 In-pentetreotide SPECT when using model-based compensation
  • 2013
  • Ingår i: 2013 IEEE NUCLEAR SCIENCE SYMPOSIUM AND MEDICAL IMAGING CONFERENCE (NSS/MIC). - 9781479905348
  • Konferensbidrag (refereegranskat)abstract
    • In 111 In-pentetreotide SPECT, it can be difficult to detect small tumors because of low spatial resolution and high noise levels. For an efficient cancer treatment, it is however important to detect the tumors at an early stage. The aim of this study was to perform optimization of Butterworth post-filtering of In-111-pentetreotide SPECT, with regard to small tumor detection in the liver. All images were reconstructed with model-based OSEM reconstruction. Two collimators are evaluated, the extended low-energy general-purpose (ELEGP) and the medium-energy general-purpose (MEGP) collimator. The raw-data projection images are produced using Monte Carlo simulations of an anthropomorphic phantom with realistic In-111-pentetreotide uptake, including seven spherical tumors in the liver. Evaluation was performed using tumor contrast as a function of background noise. According to the results, the detection of the smallest tumors is facilitated by not applying a filter. For somewhat larger tumors, a Butterworth filter of critical frequencies of 0.5-0.6 cm(-1) and an order of 10-12 is more appropriate. ELEGP proved to be better than MEGP for small tumor detection. The study is a continuation of a previous project where collimator choice, acquisition time, number of projection angles and OSEM settings were studied for the same geometry.
  •  
26.
  • Larsson, Anders, et al. (författare)
  • Weight reduction is associated with decreased CRP levels
  • 2013
  • Ingår i: Clinical Laboratory. - 1433-6510. ; 59:9-10, s. 1135-1138
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Obesity is very costly for society and weight reduction is important to reduce obesity related dis-eases. We have evaluated the effect of weight reduction on CRP values to see if high sensitivity CRP could be used to provide persons on life style intervention programs with positive feedback.Methods: Study subjects (n = 26) were recruited to a life style intervention program aiming for weight loss among the laboratory staff at Uppsala University Hospital, Sweden. Blood samples for high sensitivity CRP were collect-ed at inclusion and after 4 weeks. Body composition was estimated by measurements performed on an inexpensive bioimpedance analyzer.Results: CRP reduction was significantly associated with weight reduction after four weeks (p = 0.00005) and eight weeks (p = 0.0002). Data from the bioimpedance analyzer were not useful on an individual level.Conclusions: High sensitivity CRP could be used to provide positive feedback in workplace weight reduction pro-grams.
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27.
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28.
  • Larsson, Karin, et al. (författare)
  • Novel antigen design for the generation of antibodies to G-protein-coupled receptors
  • 2011
  • Ingår i: JIM - Journal of Immunological Methods. - : Elsevier BV. - 0022-1759 .- 1872-7905. ; 370:1-2, s. 14-23
  • Tidskriftsartikel (refereegranskat)abstract
    • Antibodies are important tools for the study of G-protein-coupled receptors, key proteins in cellular signaling. Due to their large hydrophobic membrane spanning regions and often very short loops exposed on the surface of the cells, generation of antibodies able to recognize the receptors in the endogenous environment has been difficult. Here, we describe an antigen-design method where the extracellular loops and N-terminus are combined to a single antigen for generation of antibodies specific to three selected GPCRs: NPY5R, B2ARN and GLP1R. The design strategy enabled straightforward antigen production and antibody generation. Binding of the antibodies to intact receptors was analyzed using flow cytometry and immunofluorescence based confocal microscopy on A-431 cells overexpressing the respective GPCR. The antibody-antigen interactions were characterized using epitope mapping, and the antibodies were applied in immunohistochemical staining of human tissues. Most of the antibodies showed specific binding to their respective overexpressing cell line but not to the non-transfected cells, thus indicating binding to their respective target receptor. The epitope mapping showed that sub-populations within the purified antibody pool recognized different regions of the antigen. Hence, the genetic combination of several different epitopes enables efficient generation of specific antibodies with potential use in several applications for the study of endogenous receptors.
  •  
29.
  • Larsson, Lisa, 1984, et al. (författare)
  • Continuing Cooling Performance Investigation of a Rear Mounted Cooling Package for Heavy Vehicles
  • 2011
  • Ingår i: SAECommercial Vehicles 2011, 13-14 September, Chicago, USA. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International.
  • Konferensbidrag (refereegranskat)abstract
    • This investigation is a continuing analysis of cooling performance and aerodynamic properties of a rear mounted cooling module on a semi generic commercial vehicle, which was carried out by Larsson, Löfdahl and Wiklund [1]. In the previous study two designs of the cooling package installation were positioned behind the rear wheelhouse and the results were compared to a front mounted cooling module. The investigation was mainly focused on a critical cooling situation occurring at lower vehicle speeds for a distribution vehicle. The conclusion from the study was that the cooling performance for one of the rear mounted installation was favorable compared to the front mounted cooling package. This was mainly due to the low vehicle speed, the high fan speed and to fewer obstacles around the cooling module resulting in a lower system restriction within the installation. The main purpose with the present investigation was to determine the power needed to overcome the aerodynamic drag together with the power needed by the fan to obtain a specific cooling performance at a higher vehicle speed. One front and three rear mounted cooling package installations with a vehicle operating at 90 km/h were included in the analysis. The study the vehicle geometry was modified to be able to implement the changes for the rear cooling module installations. The design of the air inlet, air outlet and the duct in front of and after the cooling package were changed for the rear mounted cooling package installation to improve the airflow and as a result the cooling performance. The investigation was performed by the use of Computational Fluid Dynamics. It was found that the total power required due to aerodynamic drag and fan operation to obtain a specific cooling performance was reduced for two of the rear mounted compared to the front mounted cooling module. Even though the fan for these installations required more power, the total power needed by the vehicle was decreased due to a lower aerodynamic resistance. The total power demand was decreased by 1.9 kW for one of the rear mounted installations compared to the front mounted cooling package. Furthermore it was established that the design of the air inlet for a rear mounted cooling package was important to obtain a low total power demand, a high mass flow of air through the cooling module and to obtain an uniform flow over the heat exchangers. For a critical driving situation due to cooling performance, occurring at lower vehicle speeds, the rear mounted cooling packages were also favorable due to cooling performance compared to the front mounted cooling module installation. This was mainly due to the lower system resistance and higher static fan efficiency received for these installations. To increase the cooling performance and decrease the required power even more the air inlet, the fan choice and the duct geometry can be further developed.
  •  
30.
  • Larsson, Lisa, 1984, et al. (författare)
  • Cooling Performance Investigation of a Rear Mounted Cooling Package for Heavy Vehicles
  • 2011
  • Ingår i: SAE World Congress 2011, 12-14 April, Detroit, USA. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International.
  • Konferensbidrag (refereegranskat)abstract
    • The aim of the study was to investigate the cooling performance of two cooling package positions for distribution vehicles by using Computational Fluid Dynamics. The first cooling package was positioned in the front of the vehicle, behind the grill and the second position was at the rear of the vehicle. Each case was evaluated by its cooling performance for a critical driving situation and its aerodynamic drag at 90 km/h, where the largest challenge of an alternative position is the cooling air availability. The geometry used was a semi-generic commercial vehicle, based on a medium size distribution truck with a heat rejection value set to a fixed typical level at maximum power for a 13 litre Euro 6 diesel engine. The heat exchangers included in the study were the air conditioning condenser, the charge air cooler and the radiator.It was found that the main problem with the rear mounted cooling installation was the combination of the fan and the geometry after the fan. The combination of these parameters for the rear mounted cooling module resulted in a high system restriction and low cooling performance values. To obtain the same cooling performance as the front mounted installation the fan had to rotate 23 % faster, corresponding to 86 % more power for the fan, for a maximum power driving situation. For the rearward installation it was seen that the drag was reduced and no recirculation was present at low velocities as it was for the frontal positioned cooling module. Thereafter the duct after the fan for the rear mounted position was removed and the cooling performance became better than the front positioned cooling module. The conclusions made from the study were that the rearward positioned cooling module was an advantage at lower vehicle velocities, at higher speeds the air inlet has to be redesigned to obtain a more uniform airflow over the heat exchangers as well as obtaining higher cooling performance, and that the combination of the fan and its environment must be carefully matched. Though, this study was based on distribution vehicles mainly operating at lower velocities.
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31.
  • Larsson, Lisa, 1984, et al. (författare)
  • Yaw- and Trailer Dependence for Rear-Mounted Cooling Installations for Heavy Vehicles
  • 2012
  • Ingår i: American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FEDSM. - 0888-8116. - 9780791844755 ; 1:PARTS A AND B, s. 31-40
  • Konferensbidrag (refereegranskat)abstract
    • Due to stricter emissions legislation and increasing fuel prices vehicle efficiency must be improved. A trend that has been seen in recent years is increased engine power for heavy vehicles. Different exhaust gas after-treatment systems have also been introduced to be able to meet the emission demands. Though, these implementations do not only affect the engine power and the emission levels, they also tend to increase the cooling demand. Therefore, the cooling performance for vehicles has to be increased. At the same time the cooling installation in the front of the vehicle accounts for a substantial part of the total aerodynamic resistance of the vehicle. To reduce the fuel consumption the grill in the front could be covered and the cooling module could be relocated elsewhere. This would decrease the aerodynamic resistance; but a more frequent fan operation would most likely be needed to achieve the same cooling performance in different driving conditions.This paper presents a comparative study of front-mounted and rear-mounted cooling package installations, using three different configurations for the rear installation on a rigid truck. For each case the cooling performance, fan demand and aerodynamic resistance were compared for different operating conditions at both lower and higher vehicle speeds and engine loads. The study was based on Computational Fluid Dynamics (CFD), where the simulations were performed in zero and five-degree yaw conditions, with and without a trailer added behind the truck. It was seen that a relocation of the cooling module has a potential for fuel savings at higher vehicle speeds, due to the reduction in power to overcome the aerodynamic resistance. At lower vehicle speeds the cooling performance was increased since a lower system restriction was observed for the rear-mounted configurations. Results also showed that both the cooling performance and the aerodynamic drag was affected by the yawed air condition and when adding a trailer behind the truck. The mass airflow was increased when the air was directed towards the air intake, while it was decreased when the air intake was positioned at the leeward side of the vehicle. When the trailer was added behind the vehicle less air entered the cooling module at a higher vehicle speed. But for the critical cooling situation the trailer did not affect the amount of air entering the cooling module.
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32.
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33.
  • Larsson, Per A., 1980-, et al. (författare)
  • Improved barrier films of cross-linked cellulose nanofibrils: a microscopy study
  • 2014
  • Ingår i: Green materials. - : Thomas Telford Ltd.. - 2049-1220 .- 2049-1239. ; 2:4, s. 163-168
  • Tidskriftsartikel (refereegranskat)abstract
    • It is highly desirable to replace gas barriers of aluminium and non-renewable plastics in order to lower our ecological footprint. One interesting candidate is films made from cellulose nanofibrils (CNFs), which after cross-linking have been shown to have competitive barrier properties even at a high relative humidity (80% RH). This work presents studies at even higher relative humidity (90% RH) and microscopic studies of what happens when unmodified and cross-linked CNF films are exposed to water. The microscopy techniques used were scanning electron microscopy of dry and wet cross-sections of films after freeze-drying and atomic force microscopy in the dry state and in the wet state shortly after wetting. Both techniques clearly revealed that the cross-links prevent the CNFs from separating from each other and hence prevent the films from swelling, so that the free-volume-sensitive gas permeability is maintained at a low level.
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34.
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35.
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36.
  • Larsson, Sylvia, et al. (författare)
  • Fuel pellets from lodge pole pine first thinnings
  • 2012
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Stemwood and whole trees of lodgepole pine (Pinus contorta Dougl. var. latifolia L.) were evaluated asraw materials for fuel pellets in a pilot scale pelletizing study. Pellet and pelletizing properties were measured andmodeled in an experimental design where raw material moisture content (%), die channel length (mm), and storage time(days) were varied. Additionally, ash contents (%), extractive contents (%), and ash melting temperatures (°C) wereanalyzed. For both assortments, raw material moisture content was positively correlated to pellet bulk density anddurability (range 9-13%, wet base). Both assortments had ash contents below 0.7%, and thus, fulfilled the demands forclass A1 pellets.
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37.
  • Larsson, Sylvia, et al. (författare)
  • Temperature controlled feed layer formation in biofuel pellet production
  • 2012
  • Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 94, s. 81-85
  • Tidskriftsartikel (refereegranskat)abstract
    • A pilot scale pelletizing system (capacity: 300 kg/h) with integrated die temperature control was built and evaluated using reed canary grass as a model raw material. A pelletizing series was performed using a full factorial design having independent factors such as die temperature (35-65 C), raw material moisture content (12-15% w.b.), and raw material temperature/steam conditioning (0-2 kg/h), with continuous or discontinuous feed layer formation as responses. Die temperature was the most influential parameter on feed layer formation and was negatively correlated to continuous feed layer formation. An immediate response, changing discontinuous production patterns into continuous was experienced when die temperature was lowered by the temperature control system. Further, a partial least squares discriminant analysis model, using the experimentally varied parameters, predicted continuous or discontinuous feed layer formation with 100% accuracy. Thus, die temperature control can be considered as a fast and efficient method for overcoming feed layer losses in pelletizing.
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38.
  • Larsson, Sylvia, et al. (författare)
  • Temperature patterns in large scale wood pellet silo storage
  • 2012
  • Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 92, s. 322-327
  • Tidskriftsartikel (refereegranskat)abstract
    • Over a 7 month period, temperatures were monitored in six large scale (approximately 4500 metric tons) silos for wood pellet storage. Each silo had 124 temperature sensors mounted on cables for an even distribution within the volume. During the study, silos were charged and discharged several times, creating different scenarios. Under certain circumstances, pellet temperatures increased vertically from bottom to top in an additive way, and temperatures around 65-70 degrees C were reached at the top of the silos. At some occasions, temperatures were increasing uncontrollably and silos were emptied due to the risk of fire. In an additive scenario, a maximum heat front velocity of 12 cm/h and a maximum temperature increment for a specific sensor of 2.4 degrees C/h was found. To avoid condensation of moisture from the ventilation air on stored pellets fan operation is suggested to be controlled by a dew point algorithm. (C) 2011 Elsevier Ltd. All rights reserved.
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39.
  • Larsson, Torbjörn, et al. (författare)
  • Allocation of Link Flow Detectors for Origin-Destination Matrix Estimation-A Comparative Study
  • 2010
  • Ingår i: COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING. - : Wiley. - 1093-9687 .- 1467-8667. ; 25:2, s. 116-131
  • Tidskriftsartikel (refereegranskat)abstract
    • Origin-destination (OD) matrices are essential for various analyses in the field of traffic planning, and they are often estimated from link flow observations. We compare methods for allocating link flow detectors to a traffic network with respect to the quality of the estimated OD-matrix. First, an overview of allocation methods proposed in the literature is presented. Second, we construct a controlled experimental environment where any allocation method can be evaluated, and compared to others, in terms of the quality of the estimated OD-matrix. Third, this environment is used to evaluate and compare three fundamental allocation methods. Studies are made on the Sioux Falls network and on a network modeling the city of Linkoping. Our conclusion is, that the most commonly studied approach for detector allocation, maximizing the coverage of OD-pairs, seems to be unfavorable for the quality of the estimated OD-matrix.
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40.
  • Larsson, Torbjörn, et al. (författare)
  • Ergodic convergence in subgradient optimization - with application to simplicial decomposition of convex programs
  • 2012
  • Ingår i: Contemporary Mathematics. - Providence, Rhode Island : American Mathematical Society. - 0271-4132 .- 1098-3627. ; 568, s. 159-186
  • Tidskriftsartikel (refereegranskat)abstract
    • When non-smooth, convex minimization problems are solved by subgradient optimization methods, the subgradients used will in general not accumulate to subgradients that verify the optimality of a solution obtained in the limit. It is therefore not a straightforward task to monitor the progress of subgradient methods in terms of the approximate fulfilment of optimality conditions. Further, certain supplementary information, such as convergent estimates of Lagrange multipliers and convergent lower bounds on the optimal objective value, is not directly available in subgradient schemes. As a means of overcoming these weaknesses in subgradient methods, we introduced in LPS96b, LPS96c, and LPS98 the computation of an ergodic (averaged) sequence of subgradients. Specifically, we considered a non-smooth, convex program solved by a conditional subgradient optimization scheme with divergent series step lengths, and showed that the elements of the ergodic sequence of subgradients in the limit fulfil the optimality conditions at the optimal solution, to which the sequence of iterates converges. This result has three important implications. The first is the finite identification of active constraints at the solution obtained in the limit. The second is the establishment of the convergence of ergodic sequences of Lagrange multipliers; this result enables sensitivity analyses for solutions obtained by subgradient methods. The third is the convergence of a lower bounding procedure based on an ergodic sequence of affine underestimates of the objective function; this procedure also provides a proper termination criterion for subgradient optimization methods. This article contributes first an overview of results and applications found in LPS96b, LPS96c, and LPS98 pertaining to the generation of ergodic sequences of subgradients generated within a subgradient scheme. It then presents an application of these results to that of the first instance of a simplicial decomposition algorithm for convex and non-smooth optimization problems.
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41.
  • Larsson, Torbjörn, et al. (författare)
  • Subben's checklist and the quality of articles in OR
  • 2014
  • Ingår i: ORbit. ; :23, s. 6-7
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • This short article presents two itemed lists that may be a helping hand during the assessment of a scientific article in the field of mathematical optimization/operations research, be it your own, a Master's or PhD student's, or even a paper that you are refereeing for a journal or a conference. The first list (“Subben’s checklist”) describes necessary ingredients of a complete article, while the second list provides criteria for assessing the quality/scientific value of an article.
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42.
  • Larsson, Torbjörn, et al. (författare)
  • Subben’s checklist and the quality of articles in OR
  • 2014
  • Ingår i: ORbit. - 1601-8893. ; 23, s. 6-7
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • In ORbit 23, we brought a small article by TorbjörnLarsson and Michael Patriksson about “Subben’schecklist”. We now revisit the topic in more depth.
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43.
  • Lemne, Marja, 1947- (författare)
  • För långt från regeringen – och för nära : Expertgruppen ESO:s födelse, levnad och död
  • 2010
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The purpose of this dissertation has been to undertake a broad case study of ESO based on the theories of power, thereby analysing what happens in the political administrative system when an organisation as ESO is established with the somewhat untraditional task to question the programmes, performance, organisation and costs of the public sector. The following is discussed in this study. Firstly, the tension and interaction between politicians, civil servants and experts in the Administration is analysed, highlighting the problems of classifying an individual as consistently belonging to one of the three categories – individuals to a considerable part alternated between the role of politician and that of civil servant or expert. Nevertheless the study seems to indicate that individuals linked to the Ministry of Finance tended to dominate in the internal deliberations of ESO. Secondly, the importance of ESO as an instrument in the hands of the Ministry of Finance in the internal power struggle between different segments of the public sector is analysed – showing the problems of being identified as belonging to the Ministry of Finance while officially being at the service of the government as whole. Thirdly, the ambivalent role of ESO on the external arena is stressed. Although being an administrative agency controlled by the government, its primary functions of delivering critical assessment of on-going public policies made it, in practise, into a useful tool of the political opposition in its criticism of the government. Another conclusion is that the decision to establish the expert group as well as the one to close it down was politically initiated – on both occasions opposed to by the officials.
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44.
  • Lestander, Torbjörn, et al. (författare)
  • Near infrared image analysis for online identification and separation of wood chips with elevated levels of extractives
  • 2012
  • Ingår i: Journal of Near Infrared Spectroscopy. - : SAGE Publications. - 0967-0335 .- 1751-6552. ; 20, s. 591-599
  • Tidskriftsartikel (refereegranskat)abstract
    • Forest-based biorefinery feedstocks are usually broken up into wood chips prior to any form of processing. These wood chips have a complex and highly variable composition, although they may look identical to an inexperienced observer. Some chips have high contents of valuable extractives. Therefore, it would be desirable to separate such chips that are rich in extractives. Various fractions of pine and spruce wood were used to acquire near infrared 11000-2498 nm) hyperspectral images in order to explore the usefulness of multivariate image analysis for detection and separation purposes. Multivariate modelling by image principal component analysis detected large variations in extractive content among wood chips of different biomass types, for example, sapwood, heartwood and knotwood. The extractive parts could be classified in the images and their content could be reasonably well predicted. Partial least squares (PLS) regression models could be made between collected spectra and measured extractive contents. These worked better for milled and homogenised bulk samples than for average image spectra. Regression coefficients showed that the C-H bonds in the spectra were responsible for the validity of the models. The average image PLS models could be used to make prediction images showing the location of the regions with high extractive content in knotwood. The results indicate that extremely rapid spectral-based fractionation could be used to separate tailored biomass streams of wood chips.
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45.
  • Li, Jingjing, et al. (författare)
  • Selection of affibody molecules to the ligand-binding site of the insulin-like growth factor-1 receptor
  • 2010
  • Ingår i: Biotechnology and applied biochemistry. - : Wiley. - 0885-4513 .- 1470-8744. ; 55, s. 99-109
  • Tidskriftsartikel (refereegranskat)abstract
    • Affibody molecules binding to the site of hormone interaction in IGF-IR (insulin-like growth factor-I receptor) were successfully selected by phage-display technology employing a competitive-elution strategy during biopanning, whereby release of receptor-bound phagemids was accomplished by competition with IGFI (insulin-like growth factor-I). In non-competitive selections, the elution of receptor-bound phagemids was performed by imidazole or low-pH incubation, which also resulted in the isolation of affibody molecules that could bind to the receptor. An ELISA-based assay showed that the affibody molecules generated by IGF-I competition during elution, in addition to affibody molecules generated in the noncompetitive selections, could compete with IGF-I for binding to the receptor. The affinities of the isolated variants to IGF-IR-overexpressing MCF-7 cells were determined and ranged from high nanomolar to 2.3 nM. The most promising variant, Z(4;40), was shown to recognize IGF- IR efficiently in several different contexts: in analyses based on flow cytometry, fluorescence microscopy and receptor pull-down from cell extracts. In addition, when Z, was added to the medium of MCF-7 cells that were dependent on IGF-I for efficient growth, it was found to have a dose-dependent growth-inhibitory effect on the cells. Applications of affibody-based reagents for quantitative and qualitative analyses of IGF- I R status, as well as applications of affibody-based reagents for therapy, are discussed.
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46.
  • Lindmark, Torbjörn, 1966- (författare)
  • Samhällskunskapslärares ämneskonceptioner
  • 2013
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In this thesis, I will discuss subject conceptions among social studies teachers who work in upper secondary schools. The aim of this study is to investigate and analyse subject conceptions among social studies teachers and their relationship to the teachers’ personal background. Subject conceptions can be expressed in both planned and realized teaching, which are analysed in this study. The questions posed are: What subject conceptions are expressed in the social studies teachers’ descriptions of their teaching? Are there any relationships between the teachers’ personal background and the subject conceptions they express? Which subject conceptions are manifested in written tests and exercises? This study consists of three empirical sub-studies. The first sub-study is based on a questionnaire with 60 social studies teachers in upper secondary schools in two counties in Sweden. The second sub-study is based on in-depth interviews with eight social studies teachers who expressed different subject conceptions in the questionnaire. The last sub-study is based on a document analysis of 28 written tests and examinations that were collected from the interviewed teachers. The theoretical framework of this study consists of structuration, class, gender and didactic theories.Some conclusions can be drawn from this study. There are different subject conceptions among the social studies teachers. I have found four typical subject conceptions, which I have called the fact-and-concept–focused, value-focused, analysis-focused and citizenship-focused subject conceptions. The study also shows that the teachers’ personal background has a relationship with their subject conceptions, to a certain degree. Gender and the combination of subjects in the teachers’ academic exams are related to the subject conceptions that the teachers express. Also, internal framing factors, like social background, political views and years in the profession, and external frame factors, like steering documents, textbooks, current news events and the students’ interests and needs, influence the teachers’ subject understanding to different extents. The study also shows that there are differences between the subject conceptions, which are shown in the teachers’ descriptions of their teachings and their assessment materials. The majority of the teachers in the study expressed the citizenship-focused subject conception in the questionnaire, while the written tests and examinations are dominated by fact-and-concept–focused and analysis-focused questions. One conclusion drawn from the empirical results is that code, classification and framing vary among the different conceptions of the subject social studies.
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47.
  • Lundberg, Kristian (författare)
  • Effect Oriented Planning in Military Mission Support Systems : Models and Heuristic Approaches
  • 2013
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Today there are many aspects of model based planning, probably much more than for just 20 years ago. Today data is not the problem, data is everywhere, but the big issue is to understand how to gain advantage of data in decision making - a growing focus is now on modeling!This work is devoted to this task and can be seen as a three part study. First a general problem of multi-resource routing with sequence dependent costs is studied both in terms of models, as well as the development of methods to solve this class of problems efficiently. Sequence dependent costs among resources arise in situations where for instance, one resource is allocated to a task which influence another task and makes that easier in the sense that it can be conducted to a lower cost or shorter time or some other measured effort. This is a useful building block in military decision making when making plans for troops, attacks or missions in general.The next part is founded by Vinnova via the research project “Effect Oriented Planning in Dynamic Scenarios”, and deals with a military ground attack problem with simultaneous attacks against a plurality of targets. This part deals with the difficulties of the attacker-defender problem which is modeled in a Nonlinear Mixed Integer Programming formulation. Suggestions are given how to refine and transform this into robust solution methods.The last part, also included in the Vinnova research project, deals with mission support modeling of Air to Ground missions including multiple aircrafts and a plurality of targets. In this case, sequencing is most important and a strong effort has been put in the understanding and transformation of the problem into models and methods.In these last two parts implementations of models and heuristics as well as computer runs and simulations, originates from the work in [19] and [20] which has been an invaluable contribution to this work.The results are very promising where fast execution and sufficient planning accuracy have drawn the attention as a foundation for future work and research in model based decision making applicable to industry needs and ambitions.
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48.
  • Manner, Sophie, et al. (författare)
  • Asymmetric baker's yeast reductions of bridgehead-substituted bicyclo[2.2.2]octane-2,6-dione derivatives followed by conversion into catalytically active BODOLs for the diethylzinc addition to benzaldehyde.
  • 2010
  • Ingår i: Tetrahedron. - : Elsevier Ltd.. - 0957-4166 .- 1362-511X. ; 21:11-12, s. 1374-1381
  • Tidskriftsartikel (refereegranskat)abstract
    • 4-Substituted bicyclo[2.2.2]octane-2,6-diones I [R = acetyl, benzyl, allyl, etc.] have been synthesized and tested as substrates in the enantioselective redn. with baker's yeast to give the corresponding hydroxy ketones II [R = acetyl, benzyl, allyl, etc.]. It was found that the deriv. bearing a TIPSO group at the 4-position was not reduced at all while that with a TBDMSO group gave 87% yield and 46% ee. Other 4-oxy functionalized derivs. were reduced with varying yields (36-87%) and ees (10-82%). The best result was obtained for the 4-Oallyl deriv. (80% yield, 82% ee). The hydroxy ketones carrying the benzyloxy and allyloxy groups at the 4-position were converted into the corresponding BODOLs III [R = allyl, benzyl], which were tested as catalysts in the diethylzinc addn. to benzaldehyde. In this reaction the ees were 90% and 89%, resp., which showed that BODOLs substituted at the 4-position are essentially as good catalysts in this reaction as those bearing a hydrogen. [on SciFinder(R)]
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49.
  • Mähler, Emma, et al. (författare)
  • Detecting small liver tumors with In-111-Pentetreotide SPECT-A Collimator study based on Monte Carlo simulations
  • 2012
  • Ingår i: IEEE Transactions on Nuclear Science. - : IEEE. - 0018-9499 .- 1558-1578. ; 59:1, s. 47-53
  • Tidskriftsartikel (refereegranskat)abstract
    • In In-111- pentetreotide single-photon emission computed tomography (SPECT), the tumor-to-background-uptake ratio is generally high. The noise is, however, also usually on a high level, and in combination with the low spatial resolution of SPECT, this may lead to difficulties in the detection of small tumors. This is especially the case in regions with a relatively high background activity, such as in the liver, which is a common region for somatostatin-positive metastases. Visually detecting the small tumors is important for a successful treatment of the cancer disease. In this paper, we compare three different parallel-hole collimators for In-111-pentetreotide SPECT regarding contrast as a function of image noise for a phantom simulating small tumors in liver background. The corresponding contrast-to-noise ratios are also presented. All raw-data projections are produced using Monte Carlo simulations. The collimators are of type low-energy general-purpose (LEGP), extended LEGP (ELEGP), and medium-energy general-purpose (MEGP). Reconstructions were performed with OSEM both with and without model-based compensation. Of the investigated collimators, the ELEGP collimator proved to be the most optimal for the smallest tumors, both with and without model-based compensation included in the reconstruction. It is also shown that model-based compensation outperforms the conventional reconstruction technique.
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50.
  • Ndengo Rugengamanzi, Marcel, 1964- (författare)
  • Term structure estimation based on a generalized optimization framework
  • 2013
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The current work is devoted to estimating the term structure of interest rates based on a generalized optimization framework. To x the ideas of the subject, we introduce representations of the term structure as they are used in nance: yield curve, discount curve and forward rate curve.Yield curves are used in empirical research in nance and macroeconomic to support nancial decisions made by governments and/or private nancial institutions. When governments (or nancial corporations) need fundings, they issue to the public (i.e. the market) debt securities (bills, bonds, notes, etc ) which are sold at the discount rate at the settlement date and promise the face value of the security at the redemption date, known as maturity date. Bills, notes and bonds are usually sold with maximum maturity of 1 year, 10 years and 30 years respectively.Let us assume that the government issues to the market zero-coupon bonds, which provide a single payment at maturity of each bond. To determine the price of the security at time of settlement, a single discount factor is used. Thus, the yield can be dened as the discount rate which makes the present value of the security issued (the zero-coupon bond) equal to its initial price. The yield curve describes the relationship between a particular yield and a bond's maturity. In general, given a certain number of bonds with dierent time to maturity, the yield curve will describe the one-to-one relationship between the bond yields and their corresponding time to maturity. For a realistic yield curve, it is important to use only bonds from the same class of issuer or securities having the same degree of liquidity when plotting the yields.Discount factors, used to price bonds, are functions of the time to maturity. Given that yields are positive, these functions are assumed to be monotonically decreasing as the time to maturity increases. Thus, a discount curve is simply the graph of discount factors for dierent maturities associated with dierent securities.Another useful curve uses the forward rate function which can be deduced from both the discount factor and the yield function. The forward rate is the rate of return for an investment that is agreed upon today but which starts at some time in the future and provides payment at some time in the future as well. When forward rates are used, the resulting curve is referred to as the forward rate curve. Thus, any of these curves, that is, the yield curve, the discount curve or the forward rate curve, can be used to represent what is known as the term structure of interest rate. The shapes that the term structure of interest rates can assume include upward sloping, downward sloping,  atness or humped, depending on the state of the economy. When the expectations of market participants are incorporated in the construction of these curves representing the term structure, their shapes capture and summarize the cost of credit and risks associated with every security traded.However, constructing these curves and the choice of an appropriate representation of the term structure to use is not a straightforward task. This is due to the complexity of the market data, precisely, the scarcity of zero-coupon bonds which constitutes the backbone of the term structure. The market often provides coupons alongside market security prices for a small number of maturities. This implies that, for the entire maturity spectrum, yields can not be observed on the market. Based on available market data, yields must be estimated using traditional interpolation methods. To this end, polynomial splines as well as parsimonious functions are the methods mostly used by nancial institutions and in research in nance. However, it is observed in literature that these methods suer from the shape constraints which cause them to produce yield curves that are not realistic with respect to the market observations. Precisely, the yield curves produced by these methods are characterized by unrealistic t of the market data, either in the short end or in the long end of the term structure of interest rate.To ll the gap, the current research models the yield curve using a generalized optimization framework. The method is not shape constrained, which implies that it can adapt to any shape the yield curve can take across the entire maturity spectrum. While estimating the yield curve using this method in comparison with traditional methods on the Swedish and US markets, it is shown that any other traditional method used is a special case of the generalized optimization framework. Moreover, it is shown that, for a certain market consistency, the method produces lower variances than any of the traditional methods tested. This implies that the method produces forward rate curve of higher quality compared to the existing traditional methods.Interest rate derivatives are instruments whose prices depend or are derived from the price of other instruments. Derivatives instruments that are extensively used include the forward rate agreement (FRA) contracts where forward rate is used and the interest rate swap (IRS) where LIBOR rate is used as  oating rate. These instruments will only be used to build up the term structure of interest rates. Since the liquidity crisis in 2007, it is observed that discrepancies in basis spread between interest rates applied to dierent interest rate derivatives have grown so large that a single discount curve is no longer appropriate to use for pricing securities consistently. It has been suggested that the market needs new methods for multiple yield curves estimation to price securities consistently with the market. As a response, the generalized optimization framework is extended to a multiple yield curves estimation. We show that, unlike the cubic spline for instance, which is among the mostly used traditional method, the generalized framework can produce multiple yield curves and tenor premium curves that are altogether smooth and realistic with respect to the market observations.U.S. Treasury market is, by size and importance, a leading market which is considered as benchmark for most xed-income securities that are traded worldwide. However, existing U.S. Treasury yield curves that are used in the market are of poor quality since they have been estimated by traditional interpolation methods which are shape constrained. This implies that the market prices they imply contain lots of noise and as such, are not safe to use. In this work, we use the generalized optimization framework to estimate high-quality forward rates for the U.S. Treasury yield curve. Using ecient frontiers, we show that the method can produce low pricing error with low variance as compared to the least squares methods that have been used to estimate U.S. Treasury yield curves.We nally use the high-quality U.S. Treasury forward rate curve estimated by the generalized optimization framework as input to the essentially ane model to capture the randomness property in interest rates and the time-varying term premium. This premium is simply a compensation that is required for additional risks that investors are exposed to. To determine optimal investment in the U.S. Treasury market, a two-stage stochastic programming model without recourse is proposed, which model borrowing, shorting and proportional transaction cost. It is found that the proposed model can provide growth of wealth in the long run. Moreover, its Sharpe ratio is better than the market index and its Jensen's alpha is positive. This implies that the Stochastic Programming model proposed can produce portfolios that perform better than the market index.
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