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- Janhäll, Sara, 1965-, et al.
(författare)
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Release of carbon nanotubes during combustion of polymer nanocomposites in a pilot-scale facility for waste incineration
- 2021
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Ingår i: NanoImpact. - : Elsevier BV. - 2452-0748. ; 24
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposites, formed by incorporating nanoparticles into a matrix of standard materials, are increasing on the market. Little focus has been directed towards safe disposal and recycling of these new materials even though the disposal has been identified as a phase of the products' life cycle with a high risk of uncontrolled emissions of nanomaterials. In this study, we investigate if the carbon nanotubes (CNTs), when used as a filler in two types of polymers, are fully destructed in a pilot-scale combustion unit designed to mimic the combustion under waste incineration. The two polymer nanocomposites studied, polycarbonate (PC) with CNT and high-density polyethylene (HDPE) with CNT, were incinerated at two temperatures where the lower temperature just about fulfilled the European waste incineration directive while the upper was chosen to be on the safe side of fulfilling the directive. Particles in the flue gas were sampled and analysed with online and offline instrumentation along with samples of the bottom ash. CNTs could be identified in the flue gas in all experiments, although present to a greater extent when the CNTs were introduced in PC as compared to in HDPE. In the case of using PC as polymer matrix, CNTs were identified in 3–10% of the analysed SEM images while for HDPE in only ~0.5% of the images. In the case of PC, the presence of CNTs decreased with increasing bed temperature (from 10% to 3% of the images). The CNTs identified were always in bundles, often coated with remnants of the polymer, forming particles of ~1–4 μm in diameter. No CNTs were identified in the bottom ash, likely explained by the difference in time when the bottom ash and fly ash are exposed to high temperatures (~hours compared to seconds) in the pilot facility. The results suggest that the residence time of the fly ash in the combustion zone is not long enough to allow full oxidation of the CNTs. Thus, the current regulation on waste incineration (requiring a residence time of the flue gas >850 °C during at least 2 s) may not be enough to obtain complete destruction of CNTs in polymer composites. Since several types of CNTs are known to be toxic, we stress the need for further investigation of the fate and toxicity of CNTs in waste treatment processes.
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| 2. |
- Kataria, Bharti, 1955-, et al.
(författare)
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Learning effects in visual grading assessment of model-based reconstruction algorithms in abdominal Computed Tomography
- 2023
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Ingår i: EUROPEAN JOURNAL OF RADIOLOGY OPEN. - : Elsevier BV. - 2352-0477. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Images reconstructed with higher strengths of iterative reconstruction algorithms may impair radi-ologists' subjective perception and diagnostic performance due to changes in the amplitude of different spatial frequencies of noise. The aim of the present study was to ascertain if radiologists can learn to adapt to the unusual appearance of images produced by higher strengths of Advanced modeled iterative reconstruction al-gorithm (ADMIRE). Methods: Two previously published studies evaluated the performance of ADMIRE in non-contrast and contrast -enhanced abdominal CT. Images from 25 (first material) and 50 (second material) patients, were reconstructed with ADMIRE strengths 3, 5 (AD3, AD5) and filtered back projection (FBP). Radiologists assessed the images using image criteria from the European guidelines for quality criteria in CT. To ascertain if there was a learning effect, new analyses of data from the two studies was performed by introducing a time variable in the mixed -effects ordinal logistic regression model. Results: In both materials, a significant negative attitude to ADMIRE 5 at the beginning of the viewing was strengthened during the progress of the reviews for both liver parenchyma (first material:-0.70, p < 0.01, second material:-0.96, p < 0.001) and overall image quality (first material:-0.59, p < 0.05, second materi-al::-1.26, p < 0.001). For ADMIRE 3, an early positive attitude for the algorithm was noted, with no significant change over time for all criteria except one (overall image quality), where a significant negative trend over time (-1.08, p < 0.001) was seen in the second material.Conclusions: With progression of reviews in both materials, an increasing dislike for ADMIRE 5 images was apparent for two image criteria. In this time perspective (weeks or months), no learning effect towards accepting the algorithm could be demonstrated.
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| 4. |
- Rydberg, Tomas, 1962, et al.
(författare)
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Emissions of additives from plastics in the societal material stock – a case study for Sweden
- 2012
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Ingår i: Handbook of Environmental Chemistry. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1867-979X. ; 18, s. 253-264, s. 253-264
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Estimating the size of the problems related to release, fate, exposure and effects from the human use of chemical substances in materials and consumer products is daunting. More than 100,000 chemical substances are in commercial use and a reasonable description of their existence in, and release from, plastic polymers, glues, paints, fibres, lubricants etc. comprise a big challenge. Here we report the initial results from a generic emission model that has been developed and applied to estimate emissions of a set of organic chemicals from products. The scope of the study was to estimate emissions from products containing plastic materials during their average lifetime within the geographical boundaries of Sweden. The results show that approximately 2% of the plastic additives are emitted annually. Plasticisers, flame retardants, organic pigments and stabilizers are the use categories of additives that are emitted in the largest quantities. Until now, the method has only been used to estimate emissions of additives from plastic materials, but it is believed to also be applicable to other materials.
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