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- Araghi, Marzieh, et al.
(author)
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Use of moist oral snuff (snus) and pancreatic cancer : Pooled analysis of nine prospective observational studies
- 2017
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In: International Journal of Cancer. - : Wiley. - 0020-7136 .- 1097-0215. ; 141:4, s. 687-693
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Journal article (peer-reviewed)abstract
- While smoking is a well-established risk factor for pancreatic cancer, the effect of smokeless tobacco is less well understood. We used pooled individual data from the Swedish Collaboration on Health Effects of Snus Use to assess the association between Swedish snus use and the risk of pancreatic cancer. A total of 424,152 male participants from nine cohort studies were followed up for risk of pancreatic cancer through linkage to health registers. We used shared frailty models with random effects at the study level, to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) adjusted for confounding factors. During 9,276,054 person-years of observation, 1,447 men developed pancreatic cancer. Compared to never-snus use, current snus use was not associated with risk of pancreatic cancer (HR 0.96, 95% CI 0.83-1.11) after adjustment for smoking. Swedish snus use does not appear to be implicated in the development of pancreatic cancer in men. Tobacco smoke constituents other than nicotine or its metabolites may account for the relationship between smoking and pancreatic cancer. What's new? While smoking is a well-established risk factor for pancreatic cancer, the effect of smokeless tobacco is less well understood. Smokeless tobacco like snus yields lower exposure to tobacco carcinogens compared with smoking, because it does not undergo combustion, but delivers an equivalent dose of nicotine. Using pooled individual data from the Swedish Collaboration on Health Effects of Snus Use, here the authors show that Swedish snus use does not appear to be implicated in the development of pancreatic cancer in men. Tobacco smoke constituents other than nicotine or its metabolites may account for the relationship between smoking and pancreatic cancer.
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| 4. |
- Båth, Magnus, 1974, et al.
(author)
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Evaluation of the imaging properties of two generations of a CCD-based system for digital chest radiography.
- 2002
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In: Medical physics. - : Wiley. - 0094-2405. ; 29:10, s. 2286-97
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Journal article (peer-reviewed)abstract
- Two generations of a CCD-based detector system with lens-based optical coupling for digital chest radiography were evaluated in terms of presampling MTF, NPS, NEQ, DQE, linearity in response, and SNR over the detector area. Measurements were performed over a wide exposure range and at several different beam qualities. Neither the presampling MTF nor the DQE showed any general strong beam quality dependence, whereas the NPS and NEQ did when compared at specific entrance air kerma values. The exposure dependency for the DQE was found to be considerable, with the detectors showing low DQE at low exposures, and higher DQE at higher exposures. It was found that the second generation has been substantially improved compared to its predecessor regarding all the relevant parameters. The DQE(0) at an entrance air kerma of 5 microGy increased from 9% to 15%, mainly due to a better system gain (including optical coupling efficiency and matching of the energy of the emitted light photons to the sensitivity of the CCD camera). The first generation of detectors was found to have problems with bad peripheral resolution [MTF(muN/2) <0.1]. This problem was nonexistent for the second generation for which uniform resolution has been obtained [MTF(muN/2)=0.3]. A theoretical calculation of the DQE of two model systems similar to the ones evaluated was also performed, and the results were comparable to the experimentally determined data at high exposures. The model shows that both systems suffer from low optical coupling efficiency due to the large demagnification used. The main conclusion is that although the second generation has been improved, there is still a problem with low system gain leading to relatively modest DQE values, especially at low exposures.
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| 5. |
- Båth, Magnus, 1974, et al.
(author)
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Investigation of parameters concerning the modulation transfer function in digital radiography
- 2001
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In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X. ; 4320, s. 350-361
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Journal article (other academic/artistic)abstract
- The effects of the design of a radiographic system on the modulation transfer function (MTF) are studied with a specially developed computer program. The program simulates a digital radiographic system by using three parameters: sampling distance, sampling aperture, and the spread of the signal in the detector due to the interaction processes of the incoming photons. The signal spread is approximated by Gaussian distributions. The influence of the three parameters is studied on the presampling MTF and on the two extreme cases of the digital MTF: The maximum MTF and the minimum MTF. From theoretical data on the interaction processes, the resolution properties of an amorphous selenium flat-panel detector are simulated. The program is also used to simulate a measurement of the presampling MTF with the slit method, and the effect of the slit width on the measured presampling MTF is examined.
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| 7. |
- Båth, Magnus, 1974, et al.
(author)
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Method for determining the two-dimensional presampling modulation transfer function in digital radiography
- 2001
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In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X. ; 4320, s. 268-279
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Journal article (other academic/artistic)abstract
- In digital radiography, radial asymmetry may be present. The use of a one-dimensional representation of the resolution properties can therefore be questioned. Although measurements are often done in two orthogonal directions, there may be a need for a more detailed description. A method of measuring the two-dimensional presampling modulation transfer function (MTF) has therefore been developed. A finely sampled "disk spread function" is obtained by imaging an aperture mask, consisting of N2 circular holes arranged in an N×N manner in an opaque material, in such a way that each hole is positioned at a different phase relative to the sampling coordinates of the detector system. This spread function is resampled, extrapolated, Fourier transformed, and finally corrected for the finite hole size in order to obtain the presampling MTF. The method was tested on a computed radiography (CR) system through measurements with a prototype mask, consisting of 100 holes of radius 0.2 mm drilled in a lead alloy. The results were compared with measurements using the slit method, and were found to be consistent. Problems associated with the method, e.g. errors due to incorrect alignment of the holes in the aperture mask with the beam, and limitations due to the finite hole size, are discussed.
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| 9. |
- Gustafsson, Patrik, 1974-
(author)
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Frameworks for task design and technology integration in the mathematics classroom
- 2016
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Licentiate thesis (other academic/artistic)abstract
- In recent years many teachers and students have begun having good access to digital technology in their classrooms, and in the context of Sweden the majority of secondary schools are known as one-to-one schools, with students having their own computer or tablet. However, the mere presence of technology in the classroom is not a guarantee for improved teaching and learning. In fact, there is a challenge involved with integrating technology in the classroom and many teachers need support. Therefore, the aim of this thesis is to contribute to the knowledge about support for teachers integrating digital technology, especially a classroom response system (CRS), in the mathematics classroom. This is done by focusing on frameworks for CRS task design and technology integration. The thesis consists of two papers and a kappa. Both papers use data from a design research project including interventions in two cases. Paper I focuses on the development of design principles and task types for CRS tasks in a multiple-choice format aiming to engineer mathematical classroom discussions. The study generated three design principles, six task types, and 31 empirically evaluated tasks. The empirical evaluation shows that teachers consider the evaluated CRS tasks useful for engineering mathematical classroom discussions. Paper II focuses on exploring the potential of Ruthven’s (2009) SFCP framework as tool for analyzing empirical data in order to conceptualize and analyze teachers’ reasoning about critical aspects of technology integration in the mathematics classroom. The results show that the SFCP framework can be useful for capturing teachers’ reasoning about critical aspects of technology integration, but also that the framework does not capture teachers’ reasoning about students’ attitudes and behaviors. Therefore, the framework would benefit from taking into consideration students’ attitudes and behaviors, as these features are a challenge teachers need to deal with when integrating technology in the classroom. This thesis kappa, building on earlier research as well as the results and methods of its own papers, ends with an elaborated discussion on the challenges and support for teachers wanting to integrate CRS in their mathematics classroom.
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| 10. |
- Gustafsson, Patrik, 1974-
(author)
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Support for productive whole-class discussions in mathematics : Developing and exploring frameworks in the context of classroom response systems
- 2023
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Doctoral thesis (other academic/artistic)abstract
- In recent decades, research has stressed the importance of productive classroom discussions in high-quality mathematical instruction for all learners. However, after decades of attempts by professional development programs to support teachers in achieving these discussions, they are rarely reported on in the classroom context. Thus, there is still a need for support for teachers’ establishment of these discussions. One promising activity for achieving productive discussions involves using a classroom response system and implementing tasks in a multiple-choice format. However, there is little knowledge about whole-class discussions in secondary school mathematics using this approach. This thesis responds to this lack by contributing to knowledge about support for achieving productive whole-class discussions in mathematics using classroom response systems and multiple-choice tasks. The thesis particularly addresses knowledge about the key practices of constructing multiple-choice tasks and leading whole-class discussions. This is operationalized by applying an educational design research approach to 1) develop design principles for constructing tasks and a supplementary task type framework and further evaluate the potential of these design principles by characterizing whole-class discussions, and 2) explore frameworks for analyzing teachers’ leading of whole-class discussions and technology integration. In this work, data from interviews with teachers, reflection notes, and observations were used. The main results cover: characteristics of useful tasks in a multiple-choice format aiming at supporting teachers in achieving productive discussions; characteristics of whole-class discussions in the context of classroom response system in secondary school mathematics; the potential of applying the Structuring Features of Classroom Practice framework as an analytic tool to conceptualize and analyze teachers’ reasoning about classroom response system; and the suggestion of five new categories of teacher actions and enrichments of two existing categories in the redirecting, progressing and focusing framework. In the kappa of this thesis, these results are merged and discussed in relation to theories of ambitious mathematics instruction. The focus is on examining whether and how classroom response systems and multiple-choice tasks can support teachers in establishing this instruction. In summary, the main contributions of this thesis are: a tool for constructing multiple-choice tasks aimed at generating productive discussions in mathematics; an examination of analytical tools for analyzing teachers’ leading of whole-class discussions and technology integration; and suggestions for the development of these tools.
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