| 1. |
- Aznar, MC, et al.
(författare)
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In vivo absorbed dose measurements in mammography using a new real-time luminescence technique
- 2005
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Ingår i: British Journal of Radiology. - : British Institute of Radiology. - 1748-880X .- 0007-1285. ; 78:928, s. 328-334
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Tidskriftsartikel (refereegranskat)abstract
- A dosimetry system based on radioluminescence (RL) and optically stimulated luminescence (OSL) from carbon doped aluminium oxide (Al2O3:C) crystals was developed for in vivo absorbed dose measurements in mammography. A small cylindrical crystal of Al2O3:C (diameter 0.48 mm and length 2 mm) was coupled to the end of a 1 mm diameter optical fibre cable. Owing to their small size and characteristic shape, these probes can be placed on the body surface in the field of view during the examination, without compromising the reading of the mammogram. Our new technique was tested with a mammography unit (Siemens Mammomat 3000) and screen-film technique over a range of clinically relevant X-ray energies. The results were compared with those obtained from an ionization chamber usually used for the determination of absorbed dose in mammography. The reproducibility of measurements was around 3% (1 standard deviation) at 4.5 mGy for both RL and OSL data. The dose response was found to be linear between 4.5 mGy and 30 mGy. The energy dependence of the system is around 18% between 23 kV and 35 kV. In vivo measurements were performed during three patient examinations. It was shown that entrance and exit doses could be measured. The presence of the small probes did not significantly interfere with the diagnostic quality of the images. Entrance doses estimated by RL/OSL results agreed within 3% with entrance surface dose values calculated from the ionization chamber measurements. These results indicate a considerable potential for use in routine control and in vivo dose measurements in mammography.
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| 2. |
- Belkheiri, Tallal, 1985, et al.
(författare)
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Effect of pH on Kraft Lignin Depolymerisation in Subcritical Water
- 2016
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 30:6, s. 4916-4924
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Tidskriftsartikel (refereegranskat)abstract
- Softwood kraft lignin was depolymerized using subcritical water (623 K and 25 MPa) in a continuous small pilot unit. ZrO2 and K2CO3 were used as catalysts, and phenol was used as capping agent to suppress repolymerization. The effect of pH was investigated by adding KOH in five steps to the feed. The yield of water-soluble organics increased with pH. The yield of bio-oil was also influenced by the pH and varied between 28 and 32 wt %. The char yield on the zirconia catalyst showed a minimum at pH 8.1. The yield of suspended solids was low at pH below 8.1 but increased at higher pH values. The oxygen content in the bio-oil was only 15 wt %, compared to about 26 wt % in the kraft lignin.
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| 3. |
- Belkheiri, Tallal, 1985, et al.
(författare)
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Hydrothermal liquefaction of kraft lignin in sub-critical water: the influence of the sodium and potassium fraction
- 2018
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Ingår i: Biomass Conversion and Biorefinery. - : Springer Science and Business Media LLC. - 2190-6815 .- 2190-6823. ; 8:3, s. 585-595
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Tidskriftsartikel (refereegranskat)abstract
- As a part of developing a hydrothermal liquefaction (HTL) process to valorise lignin, it is important to consider integration possibilities with existing infrastructures in order to obtain an overall positive economic impact. One obvious example is to integrate the HTL process with the kraft pulp mill: transport and storage costs is reduced, the temperature levels on process streams can be matched (energy integration) and the recovery/use of alkali can be made efficient. In this study, softwood kraft lignin was depolymerised using sub-critical water (623 K; 25 MPa) in a continuous, small pilot unit with a flow rate of 2 kg/h. ZrO2, K2CO3/KOH and Na2CO3/NaOH were used as catalytic system, and phenol as the capping agent. The influence of the ratio between sodium and potassium in the feed on the yield and composition of the product stream was investigated. The results showed that bio-oil, water-soluble organics (WSO) and char yields were not remarkably influenced by shifting the catalytic system from potassium to sodium. Moreover, the yields of most phenolic compounds did not change significantly when the sodium fraction was varied in the feed. The amounts of suspended solids in the bio-oil produced showed, however, a diminishing trend, (decrease from 10.8 to 3.8%) when the sodium fraction was increased in the feed, whilst the opposite trend was observed for the heavy oil, which increased from 24.6 to 37.6%.
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| 4. |
- Belkheiri, Tallal, 1985, et al.
(författare)
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Hydrothermal Liquefaction of Kraft Lignin in Subcritical Water: Influence of Phenol as Capping Agent
- 2018
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 32:5, s. 5923-5932
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Tidskriftsartikel (refereegranskat)abstract
- The depolymerization of LignoBoost Kraft lignin in subcritical water, i.e. hydrothermal liquefaction (HTL), was investigated using ZrO 2 , K 2 CO 3 , and KOH as catalysts in a fixed-bed reactor with recirculation. Focus was placed on the effect exerted by the concentration of the phenol in suppressing repolymerization, which is responsible for forming char. Feeds with various concentrations of phenol (2-10%) were investigated, and the results showed that phenol partially prevents repolymerization even at low concentrations. The bio-oil yield of (61.0 ± 2.7) % was fairly stable when the concentration of phenol was varied. In the case of the formation of char on the catalyst, the char yield revealed a weakly decreasing trend (14.6-12.3%) when the amount of phenol in the feed was increased. The results also showed that the phenolic monomers that are alkylated, such as o-/p-cresols, increased significantly with increasing concentrations of phenol, while aromatic compounds, based on a guaiacol ring structure, showed decreasing trends.
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| 5. |
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| 6. |
- Boye, Kristin, et al.
(författare)
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Sulfur flow in a soil-plant system-effects of long-term treatment history and soil properties
- 2010
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Ingår i: Plant and Soil. - : Springer Science and Business Media LLC. - 0032-079X .- 1573-5036. ; 334, s. 323-334
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Tidskriftsartikel (refereegranskat)abstract
- The influence of long-term treatment and soil type on sulfur (S) flow patterns within soil and from soil to plant was studied in a pot experiment with Italian rye grass (Lolium multiflorum cv. SW Fredrik) with (+S) or without (-S) added S. Soil samples were taken from two field treatments (farmyard manure (FYM) application or crop residue (CR) incorporation) at four sites with differing soil types within the Swedish long-term fertility experiment series. To follow gross processes, the initial soil sulfate pool was labeled with carrier-free H (2) (35) SO(4). The -S treatment resulted in visual symptoms of S deficiency, reduced biomass production and lower total S uptake by the rye grass. The isotopic measurements revealed that more than two thirds of the plant S was derived from non-labeled soil organic S, even in the + S treatment, and that all organic S pools (physically unprotected/protected and residual organic S) in the soil were involved in the S transformations. The long-term FYM treatment had resulted in higher S cycling rates and a slightly higher resistance to S deficiency than the CR treatment. The influence of soil type on S flow patterns was important, but probably only partly related to the soil S properties.
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| 7. |
- Bringselius, Louise, et al.
(författare)
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Vem ska bestämma? Dilemman kring effektivitetsrevisorns professionella utrymme - och riksrevisorns roll
- 2014
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Ingår i: Riksrevisionen 10 år: Granskning, ansvar, lärande. - 9789186949525
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Bokkapitel (populärvet., debatt m.m.)abstract
- Riksrevisionens första tio år har präglats av turbulens. En fråga som har vållat särskild debatt är inskränkningarna av effektivitetsrevisorns utrymme för självständigt utövande av det professionella omdömet. Detta kapitel ägnas åt den frågan. Det baseras på tio års nära forskning om Riksrevisionen. När myndigheten bildades valde riksrevisorerna att öka sitt eget inflytande över granskningarna, samtidigt som revisorns professionella utrymme i stället minskades. Ambitionen var att öka kvaliteten i granskningarna. Kritiken från revisorerna har varit omfattande och handlat om såväl minskad motivation som principiella avvägningar. Kapitlet visar hur frågan om det professionella utrymmet innebär en svår avvägning i dessa avseenden, men också hur det finns tydliga normer i INTOSAI:s riktlinjer och den internationella litteraturen kring revision, som stipulerar att revisorns professionella utrymme bör vara tämligen omfattande. Kapitlet argumenterar att en anledning till utvecklingen och konflikterna i frågan på Riksrevisionen kan vara oklarhet avseende riksrevisorernas roll. Dessa kan antingen vara tillsatta primärt för att säkra granskningens kvalitet eller primärt för att administrativt leda och utveckla verksamheten och dess relationer. Här finns tecken på diskrepans mellan riksrevisorernas egen syn och den syn som riksdagen ger uttryck för.
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| 8. |
- Dustler, Magnus, et al.
(författare)
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Breast compression in mammography: pressure distribution patterns
- 2012
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Ingår i: Acta Radiologica. - : SAGE Publications. - 1600-0455 .- 0284-1851. ; 53:9, s. 973-980
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Tidskriftsartikel (refereegranskat)abstract
- Background: Breast compression is important in mammography in order to improve image quality, better separate tissue components, and reduce absorbed dose to the breast. In this study we use a method to measure and visualize the distribution of pressure over a compressed breast in mammography. Purpose: To measure and describe the pressure distribution over the breast as a result of applied breast compression in mammography. Material and Methods: One hundred and three women aged 40.7-74.3 years (median, 48.9 years) invited for mammographic screening consented to take part in this study. They were subjected to two additional breast compressions of the left breast (standard force and approximately 50% reduction). Pressure images of the compressed breast were obtained using force sensing resistor (FSR) sensors placed underneath the compression plate. Subjects rated their experience of pain on a visual analogue scale (VAS). Results: Four pressure patterns were identified, fitting 81 of the 103 breasts, which were grouped accordingly. The remaining 22 breasts were found to correspond to a combination of any two patterns. Two groups (43 breasts) showed pressure mainly over the juxtathoracic part of the breast, had significantly greater breast thickness (P = 0.003) and had a lower mean pressure over dense tissue (P < 0.0001) than those with more evenly distributed pressure. Reducing compression force increased average breast thickness by 1.8 mm (P < 0.0001). Conclusion: The distribution of pressure differed greatly between breasts. In a large proportion of breasts the compression plate did not provide optimal compression of the breast, the compression force being absorbed in juxtathoracic structures.
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| 9. |
- Hemdal, Bengt, et al.
(författare)
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Can the average glandular dose in routine digital mammography screening be reduced? A pilot study using revised image quality criteria.
- 2005
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 114:1-3, s. 383-8
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Tidskriftsartikel (refereegranskat)abstract
- There is a need for tools that in a simple way can be used for the evaluation of image quality related to clinical requirements in mammography. The aim of this work was to adjust the present European image quality criteria to be relevant also for digital mammography images, and to use as simple and as few criteria as possible. A pilot evaluation of the new set of criteria was made with mammograms of 28 women from a General Electric Senographe 2000D full-field digital mammography system. One breast was exposed using the standard automatic exposure mode, the other using about half of that absorbed dose. Three experienced radiologists evaluated the images using visual grading analysis technique. The results indicate that the new quality criteria can be used for the evaluation of image quality related to clinical requirements in digital mammography in a simple way. The results also suggest that absorbed doses for the mammography system used may be substantially reduced.
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| 10. |
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