| 1. |
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| 2. |
- Ahnesjö, Anders, et al.
(författare)
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The IMRT information process-mastering the degrees of freedom in external beam therapy
- 2006
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Ingår i: Physics in Medicine and Biology. - 0031-9155 .- 1361-6560. ; 51:13, s. R381-402
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Tidskriftsartikel (refereegranskat)abstract
- The techniques and procedures for intensity-modulated radiation therapy (IMRT) are reviewed in the context of the information process central to treatment planning and delivery of IMRT. A presentation is given of the evolution of the information based radiotherapy workflow and dose delivery techniques, as well as the volume and planning concepts for relating the dose information to image based patient representations. The formulation of the dose shaping process as an optimization problem is described. The different steps in the calculation flow for determination of machine parameters for dose delivery are described starting from the formulation of optimization objectives over dose calculation to optimization procedures. Finally, the main elements of the quality assurance procedure necessary for implementing IMRT clinically are reviewed.
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| 3. |
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| 4. |
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| 5. |
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| 6. |
- Bagampadde, Umaru, et al.
(författare)
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Characterization of chemical reactivity of liquid antistripping additives using potentiometric titration and FTIR spectroscopy
- 2006
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 20:5, s. 2174-2180
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Tidskriftsartikel (refereegranskat)abstract
- Chemical reactivity of two liquid antistripping additives mixed with two bitumens of diverse acid numbers was evaluated. Additives present in the blends were detected by use of potentiometric titration and infrared spectroscopy. Tests were done at dosages of 0, 0.5, 1.0, and 2.0%; storage temperatures of 25, 100, 140, and 150 degrees C; and storage times of 1, 24, and 72 h. At 0.5% dosage, close to typical field values, the more basic additive mixed with bitumen of high acid number almost ceased to be detected after 24 h of storage at 140 degrees C. The less basic additive could be detected beyond these conditions, irrespective of the bitumen used. At higher dosages, reactions with the bitumens were found to be more pronounced with the more basic additive. The reactions between the additives and bitumens studied seemed to be higher in the bitumen with higher acid number, irrespective of the dosage. Statistical analysis indicated that all the parameters studied significantly affected change in amount of additives detected in the blends. A correlation was established between potentiometric titration and infrared spectroscopy in detecting amine additives. This correlation notwithstanding, infrared spectroscopy was found to not be a good tool for measuring amines in the blends, especially at low concentrations.
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| 7. |
- Bagampadde, Umaru, et al.
(författare)
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Classical and contemporary aspects of stripping in bituminous mixtures
- 2004
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Ingår i: International Journal on Road Materials and Pavement Design. - 1468-0629 .- 2164-7402. ; 5:1, s. 7-45
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Tidskriftsartikel (refereegranskat)abstract
- Stripping or removal of bitumen from an aggregate because of water penetrating into the interface causes many pavements to fail. Stripping has been existent since the advent of paving technology. It causes functional weakening of pavements leading to costly repairs. This state-of-the-art paper deals with important concepts of stripping as, bitumen chemistry and rheology, aggregate properties (chemical and mineralogical composition, surface texture, morphology, porosity, etc), traffic, water properties, construction practices (mixing, placement and in-service drainage) and nature of antistripping additives. Adhesion of bitumen onto aggregate is explained based on theories like mechanistic tenacity, molecular orientation, chemical reaction, and thermodynamic balance of interfacial forces. Stripping is elucidated using several mechanisms namely, displacement, detachment, spontaneous emulsification, bitumen film rupture, water pore pressure, hydraulic scouring, chemical disbanding, microbial activity, osmosis; and blistering and pitting. Attendant theories to the mechanisms are explained. Moisture sensitivity test methods emerged are described and discussed. The large number of tests that have evolved shows the importance of the phenomenon of stripping. Remedial measures which include use of antistripping additives, careful selection of hot mix component materials, good construction practice, and others have been proposed for use in practice.
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| 8. |
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| 9. |
- Bagampadde, Umaru, et al.
(författare)
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Impact of bitumen and aggregate composition on stripping in bituminous mixtures
- 2006
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Ingår i: Materials and Structures. - : Springer Science and Business Media LLC. - 1359-5997 .- 1871-6873. ; 39:287, s. 303-315
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Tidskriftsartikel (refereegranskat)abstract
- The impact of bitumen and aggregate composition on stripping was investigated using four bitumens and four aggregates. Moisture sensitivity was assessed based on retained resilient modulus and tensile strength ratio (MRR and TSR, respectively). The results indicate that mixtures from the bitumen with a high acid number exhibited high resilient modulus and tensile strength in the dry condition for all the aggregates. In wet condition, this conclusion did also hold except for one aggregate. Regarding penetration grade, mixtures made with lower penetration grade bitumen exhibited higher resilient modulus and tensile strength, in dry and wet conditions, than those of higher penetration grade. Bitumen characteristics like acid number, penetration grade and molecular size distribution did not influence moisture sensitivity. Mixtures with aggregates containing alkali metals (sodium and potassium) exhibited relatively high moisture sensitivity, regardless of the bitumen used. In contrast, indications of moisture sensitivity were not apparent in mixtures made with aggregates containing calcium, magnesium and iron. Data analysis revealed that variability in moisture sensitivity is attributed to aggregate rather than bitumen. No significant interaction effect between bitumen and aggregate was found on moisture sensitivity. The results indicated good correlation between MRR and TSR in ranking mixtures for stripping.
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| 10. |
- Bagampadde, Umaru, et al.
(författare)
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Influence of aggregate chemical and mineralogical composition on stripping in bituminous mixtures
- 2005
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Ingår i: The international journal of pavement engineering. - : Informa UK Limited. - 1029-8436 .- 1477-268X. ; 6:4, s. 229-239
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Tidskriftsartikel (refereegranskat)abstract
- The influence of aggregate chemical and mineralogical composition on moisture sensitivity was investigated using 11 aggregates from typical tropical and temperate climates and one bitumen. Mix design and compaction were based on Swedish Road 94 hot mix base specifications and moisture damage was determined using resilient modulus and tensile strength ratios. As much as practically possible, air voids, gradation, compaction level, bitumen content and curing were controlled. Mixtures from aggregates containing sodium and potassium exhibited relatively high moisture sensitivity. The converse was apparent for aggregates with calcium, magnesium and iron. No significant correlation was observed between the strength ratios and contents of Al2O3 and SiO2. Stripping was generally high for aggregates with quartz and alkali feldspars, although one aggregate with practically 100% quartz showed low moisture sensitivity. Statistical analysis showed good correlation between resilient modulus and tensile strength ratios.
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| 11. |
- Bagampadde, Umaru, 1969-
(författare)
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Investigations on moisture damage-related behaviour of bituminous materials
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This doctoral thesis presents results of literature review on classical and contemporary aspects of stripping, as well as experimental investigations on moisture damage as influenced by bituminous materials. Previous research in the area of moisture damage was reviewed and synthesized into a state-of-the-art. Important parameters linked to moisture sensitivity, like bituminous material characteristics, dynamic loads from heavy vehicles, environmental factors, construction practice and nature of anti-stripping additives, are presented. The state-of-the-art in current test methods is summarized and given. The experimental work involved investigations of the influence of bitumen and aggregate composition on water susceptibility. The influence of aggregate mineralogy and chemistry was evaluated using eleven aggregates and one bitumen, followed by studying the interactive effect of four bitumens and four aggregates. Moisture sensitivity was evaluated in accordance with (EN 12697-12:2003) for conditioning, ASTM D 4123 for resilient modulus determination, and (EN 12697-23:2003) for indirect tensile strength testing. Furthermore, thermal stability of two liquid amine anti-stripping additives mixed with two bitumens of varied acidity was investigated using potentiometric titration and Fourier Transform Infrared (FTIR) Spectroscopy. Lastly, a technique based on Fourier Transform Infrared Spectroscopy-Attenuated Total Reflectance (FTIR-ATR) was developed and used for studying transport of water across thin bitumen films, as well as stripping at bitumen/substrate interfaces. Bitumens from different sources and three substrates (silicon, germanium and zinc selenide crystals) were used. Based on the results obtained, it was concluded that aggregates containing sodium and potassium in alkali feldspars generally showed high moisture sensitivity. In contrast, presence of calcium, magnesium and iron was associated with aggregates with low moisture sensitivity. Contrary to several previous findings, one aggregate with practically 100% quartz exhibited low moisture sensitivity. No linear relationship between moisture sensitivity and the contents of SiO2 and Al2O3 in the aggregates studied was established. Results of the interactive influence of bitumen and aggregate composition showed that high acid and low penetration bitumens exhibited high dry strength for all the aggregates studied. On the other hand, for a given bitumen, the wet strengths were found to be aggregate specific. The results of tests on thermal stability of amine additives showed that usefulness of these additives reduces considerably, when the more alkaline additive was mixed with the high acid bitumen, followed by storing the blends under pronounced conditions of time and temperature (24 hours and 140ºC, or more, in this study). Much less interaction occurred when the less alkaline additive was blended with the low acid bitumen. Even if a correlation was found between the results of potentiometric titration and Fourier Transform Infrared spectroscopy, the latter was not considered good enough at detecting amine additives, especially at low dosages. The technique based on FTIR-ATR developed in this study distinguished between good and bad bitumens with regard to stripping. The effectiveness of amine-based additives in reducing stripping was also shown by the method. Three likely processes occurred during the test, namely water diffusion, film break, and displacement (stripping) of bitumen from the substrate surface. The results also indicated that the diffusion process of water into the bitumen/substrate interface does not obey Fick’s law.
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| 12. |
- Benedek, Hunor, et al.
(författare)
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Strategies for quality assurance of intensity modulated radiation therapy
- 2015
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Ingår i: 8TH INTERNATIONAL CONFERENCE ON 3D RADIATION DOSIMETRY (IC3DDOSE). - : Institute of Physics (IOP). ; 573, s. 012015-012015
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Konferensbidrag (refereegranskat)abstract
- In late 2011 The Swedish Society of Radiation Physics formed a working group to concentrate on the Quality Assurance of modern radiation therapy techniques. The given task was to identify and summarise the different QA strategies in Sweden and also the international recommendations. This was used to formulate recommendations for practical guidelines within Sweden. In this paper a brief summery of the group's work is presented. All the Swedish radiation therapy centres do a pre treatment verification measurement as QA for every new IMRT and VMAT plan. Physicists do it and they believe it to be time consuming. A general standpoint from all the centres was that new guidelines and legislation is needed to allow QA that does not require a measurement. Based on various international publications and recommendations the working group has presented two strategies, one where all new plans are checked through measurement and one where no measurement is needed. The measurement-based strategy is basically the same as the one used today with an extended machine QA part. The other presented strategy is process oriented where all the different parts of the treatment chain are checked separately. The final report can be found in Swedish on http://www.radiofysik.org.
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| 13. |
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| 14. |
- Blomquist, Erik, et al.
(författare)
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Positive correlation between occlusion rate and nidus size of proton beam treated brain arteriovenous malformations (AVMs)
- 2016
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Ingår i: Acta Oncologica. - 0284-186X .- 1651-226X. ; 55:1, s. 105-112
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Proton beam radiotherapy of arteriovenous malformations (AVM) in the brain has been performed in Uppsala since 1991. An earlier study based on the first 26 patients concluded that proton beam can be used for treating large and medium sized AVMs that were considered difficult to treat with photons due to the risk of side effects. In the present study we analyzed the result from treating the subsequent 65 patients.MATERIAL AND METHODS: A retrospective review of the patients' medical records, treatment protocols and radiological results was done. Information about gender, age, presenting symptoms, clinical course, the size of AVM nidus and rate of occlusion was collected. Outcome parameters were the occlusion of the AVM, clinical outcome and side effects.RESULTS: The rate of total occlusion was overall 68%. For target volume 0-2cm(3) it was 77%, for 3-10 cm(3) 80%, for 11-15 cm(3) 50% and for 16-51 cm(3) 20%. Those with total regress of the AVM had significantly smaller target volumes (p < 0.009) higher fraction dose (p < 0.001) as well as total dose (p < 0.004) compared to the rest. The target volume was an independent predictor of total occlusion (p = 0.03). There was no difference between those with and without total occlusion regarding mean age, gender distribution or symptoms at diagnosis. Forty-one patients developed a mild radiation-induced brain edema and this was more common in those that had total occlusion of the AVM. Two patients had brain hemorrhages after treatment. One of these had no effect and the other only partial occlusion from proton beams. Two thirds of those presenting with seizures reported an improved seizure situation after treatment.CONCLUSION: Our observations agree with earlier results and show that proton beam irradiation is a treatment alternative for brain AVMs since it has a high occlusion rate even in larger AVMs.
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| 15. |
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| 16. |
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| 17. |
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| 18. |
- Edwards, Ylva, et al.
(författare)
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Influence of commercial waxes and polyphosphoric acid on bitumen and asphalt concrete performance at low and medium temperatures
- 2006
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Ingår i: Materials and Structures. - : Springer Science and Business Media LLC. - 1359-5997 .- 1871-6873. ; 39:7, s. 725-737
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Tidskriftsartikel (refereegranskat)abstract
- The influence of adding four types of commercial wax and one polyphosphoric acid to a non-waxy bitumen was investigated with regard to binder and asphalt concrete mixture performance. Binder properties were determined using dynamic shear rheometer (DSR), bending beam rheometer, force ductilometer and various conventional test methods. Asphalt concrete performance was investigated using tensile stress restrained specimen test (TSRST), creep test at -25 degrees C, dynamic creep test at 40 degrees C and complex modulus test at 0, 10 and 20 degrees C. Totally eleven binders and eight asphalt mixtures were investigated. TSRST fracture temperatures of the asphalt mixtures were marginally influenced by the addition of any of the additives, and significant physical hardening of the binders, observed by BBR testing, could not be established using TSRST. Also in creep testing of asphalt mixtures at -25 degrees C, recorded effects were less pronounced compared to binder testing. In dynamic creep testing, the smallest permanent strains were recorded for the asphalt mixtures containing FT-paraffin or montan wax, indicating better resistance to rutting. Adding polyethylene wax or polyphosphoric acid to the non-waxy bitumen used, showed considerable positive stiffening effects on the binder at medium and higher temperatures. However, this increase in stiffness could not be shown in dynamic creep testing (at 40 degrees C) of asphalt concrete mixtures containing these additives.
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| 19. |
- Edwards, Ylva, et al.
(författare)
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Influence of commercial waxes on bitumen aging properties
- 2005
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 19:6, s. 2519-2525
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Tidskriftsartikel (refereegranskat)abstract
- Aging properties of wax-modified 160/220 bitumens and the influence of wax on these properties were evaluated using dynamic mechanical analysis (DMA), bending beam rheometer (BBR) analysis, force ductility testing, Fourier transform infrared (FTIR) spectroscopy, and thin-layer chromatography (TLC-FID). The binders were aged by means of the rolling thin-film oven test (RTFOT) and a pressure aging vessel (PAV). It was observed that aging resulted in oxidation of the bitumen (increase in carbonyl absorbance and in resin and/or asphaltene content by TLC-FID.) Changes in rheological properties of aged wax-modified binders depended on the base bitumen as well as on the type and amount of wax additive. Aging increased the complex modulus as well as elasticity, indicated by a decrease in phase angle at medium temperatures. For the polyethylene wax (PW)-modified binders, originally showing a large decrease in phase angle at higher temperature, this decrease was markedly reduced by aging, indicating network damage. Results and aging indexes obtained in this study indicate no or marginally positive influence of wax on bitumen aging properties.
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| 20. |
- Edwards, Ylva, 1948-
(författare)
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Influence of waxes on bitumen and asphalt concrete mixture performance
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This doctoral thesis consists of a literature review, presented in two papers, and another six papers describing experimental studies of the influence of different kinds of wax and polyphosporic acid on bitumen and asphalt concrete mixture properties. The literature review should give an extensive description of the field of knowledge concerning wax in bitumen. Effects of wax in crude oil, bitumen and asphalt concrete as well as test methods for studying these effects are described. Theories behind possible mechanisms are also discussed, and commercial wax as additive to bitumen for different purposes included. The experimental parts comprise laboratory studies involving totally five 160/220 penetration base bitumens from different sources, two isolated bitumen waxes, five commercial waxes and one polyphosphoric acid. Asphalt concrete slabs, containing base or modified bitumen were prepared and tested. Binder properties were evaluated using different types of laboratory equipment, such as dynamic shear rheometer (DSR), bending beam rheometer (BBR), differential scanning calorimeter (DSC), force ductilometer, as well as equipment for determining conventional parameters like penetration, softening point, viscosity, and Fraass breaking point. Fourier Transform Infrared (FTIR) spectroscopy and Thin Layer Chromatography (TLC-FID) were used for chemical characterization. The binders were aged by means of the rolling thin film oven test (RTFOT) and pressure ageing vessel (PAV) in combination. Asphalt concrete properties were evaluated at low temperatures using the tensile strain restrained specimen test (TSRST) and creep test at -25°C. Dynamic creep testing was performed at 40°C, as well as complex modulus tests between 0 and 20°C. Binder test results indicated that the magnitude and type of effect on bitumen rheology depend on the bitumen itself, type of crystallizing fraction in the bitumen and/or type and amount of additive used. Bitumen composition was found to be of decisive importance. Adding polyethylene wax or polyphosphoric acid, especially to a non-waxy 160/220 penetration grade bitumen, showed no or positive effects on the rheological behaviour at low temperatures (decrease in stiffness) as well as medium and high temperatures (increase in complex modulus and decrease in phase angle). However, the corresponding positive effects could not be shown in dynamic creep testing (at 40°C) of asphalt concrete mixtures containing these modified binders. Adding FT-paraffin decreased the physical hardening index for all bitumens. Also polyethylene wax and montan wax showed this effect for some bitumens. Slack wax showed a large increasing effect on physical hardening, and polyphosphoric acid none or a minor negative effect. No correlation between physical hardening index (PHI) and wax content by DSC was found in this study, involving both natural bitumen wax and commercial wax. Addition of the commercial waxes used showed no or marginally positive influence on bitumen ageing properties for the bitumens and test conditions used. Comparing asphalt mixture test results to the corresponding binder test results, the effects on asphalt mixtures from adding commercial wax or polyphosphoric acid were less evident. Significant binder physical hardening by BBR could not be confirmed by TSRST.
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| 21. |
- Edwards, Ylva, et al.
(författare)
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Rheological effects of commercial waxes and polyphosphoric acid in bitumen 160/220 : low temperature performance
- 2006
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 85:7-8, s. 989-997
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Tidskriftsartikel (refereegranskat)abstract
- Effects of adding three commercial waxes and a polyphosphoric acid to three bitumens of 160/220 penetration grade were studied using different types of laboratory equipment, such as dynamic shear rheometer (DSR), bending beam rheometer (BBR), differential scanning calorimeter (DSC), force ductilometer (FD) as well as equipment for determining conventional parameters like penetration, softening point and Fraass breaking point. The paper deals with low-temperature effects, which could influence the thermal cracking resistance of asphalt concrete pavements. The results show that magnitude and type of effect on bitumen rheology depend on the bitumen itself as well as type and amount of additive used. Bitumen composition was found to be of decisive importance. Adding polyethylene wax or polyphosphoric acid, especially to nonwaxy 160/220-penetration grade bitumen, showed positive effects on the rheological behaviour at low temperatures.
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| 22. |
- Edwards, Ylva, et al.
(författare)
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Rheological effects of commercial waxes and polyphosphoric acid in bitumen 160/220 : High and medium temperature performance
- 2007
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Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618 .- 1879-0526. ; 21:10, s. 1899-1908
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Tidskriftsartikel (refereegranskat)abstract
- The effects of adding three commercial waxes and a polyphosphoric acid to three bitumens of 160/220 penetration grade were studied using different types of laboratory equipment, such as Dynamic Shear Rheometer (DSR), Differential Scanning Calorimeter (DSC), Force Ductilometer (FD) as well as equipment for determining conventional parameters like penetration, softening point and Fraass breaking point. The paper deals with effects at medium and high in-service temperatures likely to affect the rutting performance of an asphalt concrete pavement. The results show that magnitude and type of effect on bitumen theology depend on the bitumen as well as type and amount of additive used. Bitumen composition was found to be of decisive importance. Adding polyethylene wax or polyphosphoric acid especially to a non-waxy bitumen, showed considerable positive effects on the theological behaviour at medium and higher temperatures.
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| 23. |
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| 24. |
- Edwards, Ylva, et al.
(författare)
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Wax in bitumen : Part 1: Classifications and General Aspects
- 2005
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Ingår i: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 6:3, s. 281-309
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Tidskriftsartikel (refereegranskat)abstract
- Wax in bitumen has for a long time been of great interest, particularly regarding effects on bitumen quality and methods for determining wax content. Opinions about wax in bitumen have varied over the years and sometimes been contradictory. The findings of a literature study are presented in two companion papers. The main intention of the study was to give an extensive description ofthe field of knowledge concerning wax in bitumen. In this paper, classifications and general aspects on effects of wax in crude oil and bitumen are described. Theories behind possible mechanisms are also discussed, and commercial wax as additive to bitumen for different purposes described. Effects of wax are influenced by chemical composition and rheological properties of the bitumen, amount of wax in the bitumen as well as chemical composition and crystalline structure of the wax. The effect of wax on bitumen is linked to its crystallinity and melting properties. The temperature range of application as well as the definition of wax in bitumen is also of great importance. The presence of large wax crystals (macrocrystalline wax) in bitumen is considered to be most problematic. However, waxes in bitumen generally are microcrystalline and/or amorphous and can contain branched, alicyclic and aromatic components with heteroatoms, which renders crystallization considerably more difficult.
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| 25. |
- Edwards, Ylva, et al.
(författare)
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Wax in bitumen : Part II: Characterization and Effects
- 2005
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Ingår i: International Journal on Road Materials and Pavement Design. - : Informa UK Limited. - 1468-0629 .- 2164-7402. ; 6:4, s. 439-468
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Tidskriftsartikel (refereegranskat)abstract
- A large number of different methods for isolating and characterizing wax in bitumen, as well as for determination of wax content, have been used over the years. The methods used for determining wax content all give different results for one and the same bitumen, which has caused problems for many years. Through different types of phase transition, wax in bitumen influences bitumen properties to a larger or minor extent. In some cases, such an influence may give rise to negative effects like increased sensitivity to cracking or plastic deformation in asphalt concrete pavements. In other cases, wax may even show positive effects on bitumen, such as increased stiffness at higher temperatures, leading to improved resistance to rutting. This paper is the second of two companion papers discussing the field of knowledge concerning wax in bitumen. In the first paper, classifications and general aspects on effects of wax in crude oil and bitumen are described.
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| 26. |
- Ekblad, Jonas, et al.
(författare)
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Influence of mica content on time domain reflectometry and soil-water characteristic curve of coarse granular materials
- 2008
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Ingår i: ASTM geotechnical testing journal. - 0149-6115 .- 1945-7545. ; 31:4, s. 321-333
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Tidskriftsartikel (refereegranskat)abstract
- Elevated fractions of free mica particles in unbound granular materials, used in road constructions, are believed to reduce bearing capacity and influence the hydraulic behavior of the road structure. The objective of this investigation was to study the influence of mica content on the soil water characteristic curve and the dielectric response measured by time domain reflectometry, for coarse granular (maximum particle size 63 mm) materials. Increased fraction of mica was achieved by partly replacing the base crushed rock material smaller than 4 mm, by pure muscovite mica of similar grading, thereby keeping the overall particle size distribution unchanged. Acquired results indicated that, given equal matric suction, the water retention capacity increased with increased amount of mica. Concerning the time domain reflectometry measurements, no influence of mica content could be detected. Determined water contents required adjustment because of the nonlinear distribution of water in the sample.
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| 27. |
- Ekblad, Jonas, et al.
(författare)
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Influence of water and mica content on resilient properties of coarse granular materials
- 2008
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Ingår i: The international journal of pavement engineering. - : Informa UK Limited. - 1029-8436 .- 1477-268X. ; 9:3, s. 215-227
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Tidskriftsartikel (refereegranskat)abstract
- Elevated amounts of free mica particles in unbound granular materials used in road construction are believed to detrimentally influence bearing capacity. The objective of presented work was to investigate the influence of mica content on resilient properties of coarse granular material (maximum particle size 63mm) under varying water contents. The test scheme comprised triaxial tests, using constant confining pressures, at incrementally raised water contents up to practically full saturation. Increased mica content was achieved by replacing a part of the base material grading smaller than 4mm, with an equal amount of pure muscovite mica of similar grading, hence keeping the overall particle size distribution unchanged. Generally, resilient modulus decreased with increased mica content and elevated water contents caused reduction in stiffness. In relative terms, the reduction in resilient modulus caused by water decreased with increased mica content.
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| 28. |
- Ekblad, Jonas, 1966-
(författare)
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Influence of Water on Coarse Granular Road Material Properties
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Even though the practical experience of using coarse unbound granular materials is extensive, detailed knowledge on the mechanical and hydraulic behavior is to a large extent lacking. Regarding influence of water on mechanical properties, this is even more pronounced. The main objective of this work was to investigate the influence of water on behavior and properties of coarse granular materials. The study comprises measurements of resilient properties, soil-water characteristic curve and influence of water content on dielectric properties measured by the use of time domain reflectometry (TDR). The work described herein comprised two test series in terms of materials: firstly, a series where the grading was changed and secondly, a series where the influence of increased contents of free mica was studied. To measure resilient response, triaxial testing, using sample size of 500 mm diameter and 1000 mm height, was performed mainly using constant confining pressures. Tests were performed at incrementally varying water contents up to almost full saturation. Dielectric response and matric suction of compacted specimens were measured in a steel box at varying water content. Results from the first series indicated that the influence of water content on resilient properties depends on the material grading. The coarsest grading, containing least fines, experienced only a small reduction when brought close to saturation. Specimens with an increased amount of fines and more even distribution responded with a substantial loss of resilient modulus upon increased water content. It also appeared as water content increased, the specimens became more dilative. From the second series, generally, resilient modulus decreased with increased mica content and furthermore, elevated water contents caused reduction in stiffness. However, in relative terms, the reduction in resilient modulus caused by water decreased with increased mica content. The soil-water characteristic curves are influenced by grading coefficient and mica content; retentive capacity increases with decreased grading coefficient and increases with increased amount of mica. Volumetric water content as a function of apparent relative permittivity was fitted using a third-degree polynomial. Although, determined relationships deviated from Topp's (1980) relationship. Detailed information on the work is given in five enclosed papers.
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| 29. |
- Ekblad, Jonas, et al.
(författare)
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Influence of water on resilient properties of coarse granular materials
- 2006
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Ingår i: International Journal on Road Materials and Pavement Design. - 1468-0629 .- 2164-7402. ; 7:3, s. 369-404
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this work was to investigate influence of water on resilient properties of a coarse (maximum particle size 90 mm) granular material using various gradings. Triaxial testing, using large-size samples (diameter 500 mm and height 1000 mm) and constant confining pressures, was performed at varying water content up to practically full saturation. Time Domain Reflectometry (TDR) was used to monitor transient in-sample water contents. Evaluation comprised resilient modulus and Poisson ratio in terms of total stresses, although the results were also discussed in the context of effective stresses. The coarsest grading experienced only a small reduction in resilient modulus when brought close to saturation, while specimens with an increased amount of fines and more even distribution responded with a substantial loss of resilient modulus upon increased water content. It also appeared that, as water content increased, the specimens became more dilative (increase in Poisson ratio).
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| 30. |
- Ekblad, Jonas, et al.
(författare)
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Time domain reflectometry measurements and soil-water characteristic curves of coarse granular materials used in road pavements
- 2007
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Ingår i: Canadian geotechnical journal (Print). - 0008-3674 .- 1208-6010. ; 44:7, s. 858-872
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Tidskriftsartikel (refereegranskat)abstract
- Coarse granular materials are used extensively in road construction. Bearing capacity can be affected by the water content in the layers of these materials. The ability to estimate water content and to infer water movements is therefore important. The purpose of the work described herein was to determine soil-water characteristic curves and the relationship between relative apparent permittivity and volumetric water content for coarse (maximum particle size 90 mm) granular materials having various gradations. The relative apparent permittivity was measured with the aid of time-domain reflectometry (TDR), and the concurrent matric suction was measured with a tensiometer. Samples were prepared in a steel box and were heavily compacted, and TDR probes and a tensiometer cup were buried within the matrix. The variation in volumetric water content with apparent relative permittivity was found to deviate from the Topp et al. relationship. Soil-water characteristic curves were described using the Brooks-Corey and van Genuchten models. A pronounced hysteresis between wetting and drying paths was observed. For the low water retention coarse materials, measurements of water content might, in general, require correction because of the nonlinear distribution of water in the sample.
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| 34. |
- Ekblad, Jonas, et al.
(författare)
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Water in coarse granular materials : Resilient and retentive properties
- 2008
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Ingår i: Adv. Transp. Geotech. - Proc. Int. Conf. Transp. Geotech.. - : CRC PRESS-TAYLOR & FRANCIS GROUP. - 9780415475907 ; , s. 117-123, s. 117-
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Konferensbidrag (refereegranskat)abstract
- Granular material is, perhaps the most common construction material used in civil engineering, being an important constituent in road constructions, railways, embankments, foundations, buildings etc. This paper presents results from triaxial testing, at various water contents using constant confining pressure, of two different continuously graded granular materials with maximum particle size 90 mm and 63 mm, respectively. Furthermore, water retention properties of the unbound materials are presented and examples of water distributions in a common construction are shown. From the results presented, it can be concluded that increased water contents cause a reduction in resilient modulus and an increase in strain ratio. The distribution of water content in the vertical direction is highly nonlinear and the degree of saturation in the unbound layers of a road construction depends to a large degree on the level of the water table.
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| 40. |
- Isacsson, Ulf, et al.
(författare)
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A method to separate the rectum from the prostate during proton beam radiotherapy of prostate cancer patients
- 2010
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Ingår i: Acta Oncologica. - : Informa UK Limited. - 0284-186X .- 1651-226X. ; 49:4, s. 500-505
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Tidskriftsartikel (refereegranskat)abstract
- The use of protons for curative treatment of prostate cancer is increasing, either as a single treatment modality or in combination with conventional radiotherapy. The proximity between prostate (target) and rectum (organ at risk) often leads to a compromise between dose to target and organ at risk. Material and methods. The present study describes a method where the distance between prostate and rectum is increased by retraction of the rectum in dorsal direction. Comparative treatment plans with and without retraction of the rectum in the same patients have been studied. Nine patients with biopsy proven, localised adenocarcinoma of the prostate were studied. A cylindrical rod of Perspex was inserted into the rectum. This device allows the rectum to be retracted posteriorly. The patients were given a proton boost of 20 Gy in four fractions of 5 Gy in addition to a conventional photon beam treatment to a dose of 50 Gy in 25 fractions of 2 Gy. Results. Comparative treatment planning shows that the treatment plan with rectal retraction significantly reduces (p < 0.01) the volume of the rectal wall receiving high doses (equal to 70 Gy in 2 Gy fractions) in all patients. Conclusions. The proton boost treatment with retraction of rectum during treatment decreases the rectal dose substantially. This is expected to reduce rectal side effects.
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| 47. |
- Isacsson, Ulf
(författare)
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Comparative treatment planning in external radiotherapy of malignant tumours : Potential gains using protons
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- It is well known that protons have physical characteristics superior to conventional radiation qualities in external beam radiotherapy. The primary aim of this work is to determine if the physical advantages also may lead to clinical advantages. A second aim is to evaluate the treatment planning algorithms incorporated into a 3D treatment planning system, used in the prediction, Helax-TMSTM. The potential benefits of using protons instead of conventional radiation qualities is evaluated by comparing treatment plans. Dose-response models of tumour control probability (TCP) and normal tissue complication probability (NTCP) were used to predict the treatment outcome for the different plans. Uncertainties in the results were studied in sensitivity analyses.Comparative studies were performed in four different tumour types, locally advanced rectal cancer, a paraspinal tumour, oesophageal cancer and left-sided node-positive breast cancer. Advantages with protons were seen in all cases, but the advantages were of different size.Proton therapy in patients with oesophageal carcinoma increases the TCP from 6 to 49% if a risk of 1% in the spinal cord and a total NTCP for the two lungs equivalent to a one-sided pulmectomy is allowed. This gain is relatively insensitive to variations, within reasonable limits, in the dose-response parameters.Proton therapy reduces the risk for cardiac mortality and radiation pneumonitis to almost zero when treating node-positive left-sided breast cancer after breast-conserving surgery.The evaluation of the treatment planning algorithms shows that pencil kernel algorithms are required in order to accurately calculate dose distributions in heterogeneous patient volumes. The scattering phenomenon in the vicinity of interfaces between different materials is modelled. The magnitude of the effect is underestimated (less than 1%) due to the inherent approximations.
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