| 1. |
- Adjeiwaah, Mary, 1980-, et al.
(författare)
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Dosimetric Impact of MRI Distortions : A Study on Head and Neck Cancers
- 2019
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Ingår i: International Journal of Radiation Oncology, Biology, Physics. - : Elsevier. - 0360-3016 .- 1879-355X. ; 103:4, s. 994-1003
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To evaluate the effect of magnetic resonance (MR) imaging (MRI) geometric distortions on head and neck radiation therapy treatment planning (RTP) for an MRI-only RTP. We also assessed the potential benefits of patient-specific shimming to reduce the magnitude of MR distortions for a 3-T scanner.Methods and Materials: Using an in-house Matlab algorithm, shimming within entire imaging volumes and user-defined regions of interest were simulated. We deformed 21 patient computed tomography (CT) images with MR distortion fields (gradient nonlinearity and patient-induced susceptibility effects) to create distorted CT (dCT) images using bandwidths of 122 and 488 Hz/mm at 3 T. Field parameters from volumetric modulated arc therapy plans initially optimized on dCT data sets were transferred to CT data to compute a new plan. Both plans were compared to determine the impact of distortions on dose distributions.Results: Shimming across entire patient volumes decreased the percentage of voxels with distortions of more than 2 mm from 15.4% to 2.0%. Using the user-defined region of interest (ROI) shimming strategy, (here the Planning target volume (PTV) was the chosen ROI volume) led to increased geometric for volumes outside the PTV, as such voxels within the spinal cord with geometric shifts above 2 mm increased from 11.5% to 32.3%. The worst phantom-measured residual system distortions after 3-dimensional gradient nonlinearity correction within a radial distance of 200 mm from the isocenter was 2.17 mm. For all patients, voxels with distortion shifts of more than 2 mm resulting from patient-induced susceptibility effects were 15.4% and 0.0% using bandwidths of 122 Hz/mm and 488 Hz/mm at 3 T. Dose differences between dCT and CT treatment plans in D-50 at the planning target volume were 0.4% +/- 0.6% and 0.3% +/- 0.5% at 122 and 488 Hz/mm, respectively.Conclusions: The overall effect of MRI geometric distortions on data used for RTP was minimal. Shimming over entire imaging volumes decreased distortions, but user-defined subvolume shimming introduced significant errors in nearby organs and should probably be avoided.
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| 2. |
- Aid, Graham, 1980-, et al.
(författare)
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Expanding roles for the Swedish waste management sector in interorganizational resource management
- 2017
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Ingår i: Resources, Conservation and Recycling. - : Elsevier BV. - 0921-3449 .- 1879-0658. ; 124, s. 85-97
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Tidskriftsartikel (refereegranskat)abstract
- Several waste management (WM) professionals see an ongoing shift in the focus of the industry, from that of atransport and treatment sector to that of a more integrated sustainable service provision and material productionsector. To further develop such transitional ambitions, WM organizations are increasingly looking toward interorganizationalresource network concepts (such as the circular economy and industrial symbiosis) as models ofhow they would like to create new value together with their customers and partners.This article aims to take a step in addressing uncertainties behind such transitions by analyzing barriers forinter-organizational resource management and in turn uncovering some potential opportunities and risks ofnovel offerings from the WM sector. Obstacles for developing innovative inter-organizational resource networkshave been identified based on studies of implementing industrial symbiosis networks. Subsequently, managingexecutives from Swedish private and public WM organizations were interviewed regarding the sector’s capacityto overcome such barriers – opportunities and risks of providing new resource management services – and howtheir organizations might approach the role of actively facilitating more resource efficient regions.Eco-Industrial park management and contracting out holistic resource management are some areas in whichthe respondents see WM organizations offering new services. In relation to such approaches, various risks (e.g.being cut out of investment benefits, or unstable supply) and opportunities (e.g. new markets and enhancedsustainability profiles) were identified. Additionally, it was seen that WM companies would need to makesubstantial changes to their business approach, becoming less dependent on flows of mixed materials forexample, if they are to become even more central value chain actors. To strengthen such approaches, it was seenthat the sector will need to find methods to strategically build strong, long term partnerships, expand upon andtake advantage of available knowledge resources (i.e. best practice technologies and regional material flows),and explore new business models (i.e. stockpiling, park management, or waste minimization). Additionally,working with sector representatives to argue for a more balanced market conditions next to primary productionshould assist the viability of new offerings in the wider market.
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| 3. |
- Almquist, Joachim, 1980, et al.
(författare)
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Overexpressing cell systems are a competitive option to primary adipocytes when predicting in vivo potency of dual GPR81/GPR109A agonists
- 2018
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Ingår i: European Journal of Pharmaceutical Sciences. - : Elsevier BV. - 0928-0987 .- 1879-0720. ; 114, s. 155-165
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Tidskriftsartikel (refereegranskat)abstract
- Mathematical models predicting in vivo pharmacodynamic effects from in vitro data can accelerate drug discovery, and reduce costs and animal use. However, data integration and modeling is non-trivial when more than one drug-target receptor is involved in the biological response. We modeled the inhibition of non-esterified fatty acid release by dual G-protein-coupled receptor 81/109A (GPR81/GPR109A) agonists in vivo in the rat, to estimate the in vivo EC50 values for 12 different compounds. We subsequently predicted those potency estimates using EC 50 values obtained from concentration-response data in isolated primary adipocytes and cell systems overexpressing GPR81 or GPR109A in vitro. A simple linear regression model based on data from primary adipocytes predicted the in vivo EC50 better than simple linear regression models based on in vitro data from either of the cell systems. Three models combining the data from the overexpressing cell systems were also evaluated: two piecewise linear models defining logical OR- and AND-circuits, and a multivariate linear regression model. All three models performed better than the simple linear regression model based on data from primary adipocytes. The OR-model was favored since it is likely that activation of either GPR81 or GPR109A is sufficient to deactivate the cAMP pathway, and thereby inhibit non-esterified fatty acid release. The OR-model was also able to predict the in vivo selectivity between the two receptors. Finally, the OR-model was used to predict the in vivo potency of 1651 new compounds. This work suggests that data from the overexpressing cell systems are sufficient to predict in vivo potency of GPR81/GPR109A agonists, an approach contributing to faster and leaner drug discovery.
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| 4. |
- Apler, Anna, 1980-, et al.
(författare)
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Distribution and dispersal of metals in contaminated fibrous sediments of industrial origin
- 2019
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Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 215, s. 470-481
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Tidskriftsartikel (refereegranskat)abstract
- Industrial emissions can impact aquatic environments and unregulated discharges from pulp and paper factories have resulted in deposits of cellulose fiber along the Swedish coast. These deposits are contaminated by metals, but due to their unique fibrous character the extent of sorption and dispersal of the metals is unclear. Fibrous sediments were sampled at two sites in the Ångermanälven river estuary, Sweden. The partitioning of metals between the sediment, pore water and bottom water was investigated and the degree of bioavailability was evaluated. The levels of metals in the sediment were high in fibrous or offshore samples, depending on the metal, whereas the levels of dissolved metals in pore water were low or below the limit of quantification. Partition coefficients (KD) showed that sorption to the sediment was stronger at one of the fibrous sites, possibly related to the type and size of organic matter. Undisturbed bottom water samples contained low levels of both dissolved and particle bound metals, but when comparing measured metal concentrations to threshold values of ecological status and ecotoxicological assessment criteria, both sediments and bottom water may be detrimental to living organisms. In-situ re-suspension experiments showed that the concentrations of particle bound metals increased whereas the dissolved concentrations decreased. The analyzed metals are probably retained by the solid phases of the fibrous sediment or adsorbed to particles in the water, reducing their bioavailability.
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| 5. |
- Azhar, Shoaib, 1980-, et al.
(författare)
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Extraction of hemicelluloses from fiberized spruce wood
- 2015
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 117, s. 19-24
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Tidskriftsartikel (refereegranskat)abstract
- A novel mechanical pre-treatment method was used to separate the wood chips into fiber bundles in order to extract high molecular weight wood polymers. The mechanical pre-treatment involved chip compression in a conical plug-screw followed by defibration in a fiberizer. The fiberized wood was treated with hot water at various combinations of time and temperature in order to analyze the extraction yield of hemicelluloses at different conditions. Nearly 6 mg/g wood of galactoglucomannan was obtained at 90◦C/120min which was about three times more than what could be extracted from wood chips. The extracted carbohydrates had molecular weight ranging up to 60 kDa. About 10% of each of the extracted material had a molecular weight above 30 kDa. The extraction liquor could also be reused for consecutive extractions with successive increase in the extraction yield of hemicelluloses.
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| 6. |
- Beijer, Kristina, 1980-, et al.
(författare)
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Azoles additively inhibit cytochrome P450 1 (EROD) and 19 (aromatase) in rainbow trout (Oncorhynchus mykiss)
- 2018
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Ingår i: Aquatic Toxicology. - : Elsevier BV. - 0166-445X .- 1879-1514. ; 198, s. 73-81
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Tidskriftsartikel (refereegranskat)abstract
- Antifungal azoles are widely used in medicine, agriculture, and material protection and several antifungal azoles have been found in environmental samples. Although these compounds were designed to inhibit fungal enzymes such as lanosterol-14-demethylase (cytochrome P450 (CYP) 51), it is well established that the inhibitory actions of azoles are not specific for fungal CYP isozymes.We refined a gill filament assay to determine the inhibition of CYP1, measured as reduced 7-ethoxyresorufin-O-deethylase (EROD) activity, in rainbow trout (Oncorhynchus mykiss) gill tissue ex vivo. The advantage of this method is that both induction and inhibition of EROD are performed ex vivo. Among thirteen azoles studied, the five that caused the strongest inhibition of gill EROD activity at a concentration of 5 μM were selected for concentration–response assessment. These compounds (bifonazole, clotrimazole, imazalil, miconazole, and prochloraz) showed IC50 values ranging from 0.1 to 1.5 μM. CYP19 (aromatase) inhibition was measured using microsomes from rainbow trout brains. Concentration-response curves for CYP19 inhibition were determined for letrozole, bifonazole, clotrimazole, imazalil, miconazole and prochloraz, which gave IC50 values ranging from 0.02 to 3.3 μM. It was further found that mixtures of the five most potent azoles reduced both CYP1 and 19 catalytic activity in an additive fashion (IC50 = 0.7 μM and 0.6 μM, in the respective assay). Bifonazole (IC50 = 0.1 μM) is not previously known to inhibit CYP1 activity.The additive inhibition of CYP1 and CYP19 catalytic activity is an important finding of the present study. We conclude that this additive action of azoles could mediate adverse impacts on CYP regulated physiological functions in environmentally exposed fish.
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| 7. |
- Eynian, Mahdi, 1980-
(författare)
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In-process identification of modal parameters using dimensionless relationships in milling chatter
- 2019
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Ingår i: International journal of machine tools & manufacture. - : Elsevier BV. - 0890-6955 .- 1879-2170. ; 143, s. 49-62
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Tidskriftsartikel (refereegranskat)abstract
- Machining parameters needed for stable, high-performance high-speed machining could be found using mathematical models that need accurate measurements of modal parameters of the machining system. In-process modal parameters, however, can slightly differ from those measured offline and this can limit the applicability of simple measurement methods such as impact hammer tests. To study and extract the in-process modal parameters, mathematical models are used to define two key dimensionless parameters and establish their relationships with each other and the modal parameters. Based on these relationships, the modal parameters are extracted using two analytical methods, the two-point method (TPM), and the regression method (RM). As shown with experimental studies, the RM extracts the modal parameters successfully and while being much faster than the existing iteration-based methods, it provides stability lobe predictions that match well the experimental results. Furthermore, it is noted that the natural frequency parameter is estimated with much better relative precision compared to the damping ratio and the modal stiffness parameters. © 2019 Elsevier Ltd
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| 8. |
- Eynian, Mahdi, 1980-
(författare)
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Vibration frequencies in stable and unstable milling
- 2015
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Ingår i: International journal of machine tools & manufacture. - : Elsevier BV. - 0890-6955 .- 1879-2170. ; 90, s. 44-49
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Tidskriftsartikel (refereegranskat)abstract
- Vibration frequencies in machining may be employed for calculation of natural frequencies of the dominant modes in chatter and selection of chatter-free spindle speeds with large material removal rates. In this approach, it is important to investigate the relationship between the vibration frequencies, the natural frequencies, spindle speeds and depth of cuts for both stable and unstable cutting conditions. In this paper, the dominant poles of the closed loop time delay differential equation of a milling operation are calculated by successive sectioning of the complex plane and using Cauchy's argument principle. Vibration frequency and damping ratio of the closed loop machining system for each cutting condition is calculated based on the position of the dominant pole on the complex plane which provides 3D plots of the vibration frequency and closed loop damping ratio over any range of depth of cuts and spindle speeds. Finally, the findings of the analytical approach are compared to a machining experiment and a time domain simulation and differences and similarities in their predictions are discussed.
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| 9. |
- Gerlee, Philip, 1980, et al.
(författare)
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Travelling wave analysis of a mathematical model of glioblastoma growth
- 2016
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Ingår i: Mathematical Biosciences. - : Elsevier BV. - 0025-5564 .- 1879-3134. ; 276, s. 75-81
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we analyse a previously proposed cell-based model of glioblastoma (brain tumour) growth, which is based on the assumption that the cancer cells switch phenotypes between a proliferative and motile state (Gerlee and Nelander, PLoS Comp. Bio., 8(6) 2012). The dynamics of this model can be described by a system of partial differential equations, which exhibits travelling wave solutions whose wave speed depends crucially on the rates of phenotypic switching. We show that under certain conditions on the model parameters, a closed form expression of the wave speed can be obtained, and using singular perturbation methods we also derive an approximate expression of the wave front shape. These new analytical results agree with simulations of the cell-based model, and importantly show that the inverse relationship between wave front steepness and speed observed for the Fisher equation no longer holds when phenotypic switching is considered.
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| 10. |
- Gosens, Jorrit, 1980
(författare)
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Natural resource endowment is not a strong driver of wind or PV development
- 2017
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Ingår i: Renewable Energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 113, s. 1007-1018
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Tidskriftsartikel (refereegranskat)abstract
- Natural resources have previously been included in analyses explaining differences between renewable energy deployment across countries or subnational regions. Most previous analyses used resource volumes, or rough proxies for these, and results have been inconclusive. This study uses panel data analysis, with indicators of both the quality and quantity of natural resources, and analyses effects on wind and PV development by comparing countries of the world, and provinces or states of China, Germany, and the US. Either measure of natural resources has limited explanatory power on differences in wind or PV development between countries. Resource quality, not quantity, has a more consistent, positive effect when comparing states or provinces of China, Germany and the US. Still, plenty of countries, states or provinces with relatively poor quality natural resources have managed relatively high levels of wind or PV development, and vice versa. The only exceptions are the US wind power market and the Chinese PV market, where development is more strongly correlated with natural resources. The conclusion is that natural resources are a small part in a larger set of drivers, and that low quality natural resources do not preclude developing relatively high market shares of wind or PV power.
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