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- Andersson, Marit, et al.
(författare)
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A modified standard addition method in X-ray fluorescence spectrometry
- 1993
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Ingår i: Talanta. - 0039-9140 .- 1873-3573. ; 40:5, s. 669-674
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Tidskriftsartikel (refereegranskat)abstract
- A modified standard addition method for single element determination by X-ray fluorescence spectrometry has been studied. The attenuation properties of the standard added samples are kept constant by adding decreasing amounts of an attenuation modifier along with increasing amounts of a standard. In this way the standard addition curve will be a straight line in cases where the ordinary standard addition curve is non-linear, and linear regression can be used to evaluate the concentration of the analyte. Standard additions of oxides of a number of elements, with and without modifier, have been made to cellulose powder or a mixture of aluminium oxide and polyethylene as matrices in order to test the method. The method has been applied to the determination of zinc in fly-ash from a steel work and of iron in cement. The fly-ash contained about 5% of zinc and the cement samples between 2 and 5% of Fe(2)O(3). The results were compared with those obtained by ICP-AES after decomposition of samples in lithium tetraborate or lithium metaborate and dissolution of the melt in 10%(v/v) nitric acid. The results agreed within 2%, relative, for fly-ash and within 3-6%, relative, for cement samples.
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| 4. |
- Andersson, Marit, et al.
(författare)
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Determination of bromine, chlorine, sulphur and phosphorus in peat by X-ray fluorescence spectrometry combined with single-element and multi-element standard addition
- 1990
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Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 37:2, s. 185-191
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Tidskriftsartikel (refereegranskat)abstract
- Bromine (20-40 ppm), chlorine (200-500 ppm), sulphur (0.2-3%) and phosphorus (300-1000 ppm) in peat have been determined by X-ray fluorescence spectrometry (XRFS) combined with the standard-addition method. Chlorine, sulphur and phosphorus have also been determined by other methods and agreement between the results is good. Theoretical calculations based on the Sherman equation were made to validate the linearity of the standard-addition curves. A multi-element standard-addition technique has been tested with addition of all elements at the same time. The results for chlorine were high but after correction for the difference in attenuation coefficient between the sample and added compound the results agreed with those from single-element standard addition.
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- Andersson, Marit, et al.
(författare)
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Determination of lead in fly-ash from a garbage incinerator by atomic-absorption and x-ray fluorescence spectrometry
- 1988
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Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 35:5, s. 337-41
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Tidskriftsartikel (refereegranskat)abstract
- The lead content in fly-ash collected by an electrostatic precipitator has been determined by atomic-absorption spectrometry (AAS) after decomposition by four different leaching/dissolution techniques, and also determined by X-ray fluorescence spectrometry (XRFS) by the standard-addition method. The XRFS data were evaluated by non-linear regression since the standard additions affected the attenuation coefficient of the sample. Good agreement was obtained between the results obtained with AAS and XRFS. It is concluded that lead is quantitatively extracted by hot 1M nitric acid or treatment with hydrofluoric acid/nitric acid. Direct measurement of briquetted samples by XRFS is suggested for rapid monitoring of the lead content in fly-ash from garbage incineration.
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| 6. |
- Andersson, Marit, et al.
(författare)
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Determination of lead in household refuse fly-ash by X-ray fluorescence spectrometry and a modified standard-addition technique
- 1991
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Ingår i: Talanta. - 0039-9140 .- 1873-3573. ; 38:4, s. 385-390
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Tidskriftsartikel (refereegranskat)abstract
- Lead in fly-ash from a garbage incinerator has been determined by X-ray fluorescence spectrometry (XRFS) and a modified standard-addition method. To keep the attenuation properties of the spiked samples constant, decreasing amounts of an attenuation modifier [mercury (II) acetate] were added together with increasing amounts of the standard (lead nitrate). Linearity between fluorescence intensity and amount of lead was thus obtained, so the amount of lead in the sample could be evaluated by linear regression. The amount of modifier needed could be calculated from a simple expression. The method was validated by comparison with the results obtained by applying atomic-absorption spectrometry (AAS) to solutions made by leaching the fly-ash with strong acid. For 8 fly-ash samples, containing between 0.8 and 1.35% lead, the largest absolute difference between the two sets of results was 0.03%. Theoretical calculations based on a simplified version of the Sherman equation were performed to confirm the linearity of the modified standard-addition curves.
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- Hashemi, Payman, et al.
(författare)
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Agarose film coated glass slides for preparation of pH optical sensors
- 2007
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 121:2, s. 396-400
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Tidskriftsartikel (refereegranskat)abstract
- A method for preparation of optical sensors was developed by agarose film coating on aminosilanated glass slides. An optical pH sensor was accordingly prepared by epoxy activation of the agarose film, followed by chemical immobilization of Neutral Red dye. In an optimized coupling pH of 12 and a dye concentration of 10(-2) mol L-1 a pH sensor for a pH range of 2-8.5 was obtained. A theoretical equation was derived using the extended Henderson-Hasselbalch equation that reproduced the measured data well. The sensor was mounted in a flow cell and successfully applied for on-line pH measurements. The sensor responded rapidly to the pH changes with a response time of less than 2 min and reproducibility better than 0.40% (R.S.D.). In comparison to a stand-alone agarose membrane, the agarose coated glass slide showed better physical properties and easier handling and application but slightly slower response times. No evidence of leaching of the dye or any signal drift was observed.
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- Heverin, Maura, et al.
(författare)
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On the regulatory importance of 27-hydroxycholesterol in mouse liver
- 2017
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Ingår i: Journal of Steroid Biochemistry and Molecular Biology. - : Elsevier. - 0960-0760 .- 1879-1220. ; 169, s. 10-21
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Forskningsöversikt (refereegranskat)abstract
- 27-Hydroxycholesterol (27OH) is a strong suppressor of cholesterol synthesis and a weak activator of LXR in vitro. The regulatory importance of 27OH in vivo is controversial. Here we utilized male mice with increased levels of 27OH either due to increased production (CYP27A1 transgenic mice) or reduced metabolism (Cyp7b1-/- mice). We also used mice lacking 27OH due to a knockout of Cyp27a1. The latter mice were treated with cholic acid to compensate for reduced bile acid synthesis. The effects of the different levels of 27OH on Srebp- and other LXR-regulated genes in the liver were investigated. In the liver of CYP27tg mice we found a modest increase of the mRNA levels corresponding to the LXR target genes Cyp7b1 and Abca1. A number of other LXR-regulated genes were not affected. The effect on Abca1 mRNA was not seen in the liver of Cyp7b1-/- mice. There were little or no effects on cholesterol synthesis. In the liver of the Cyp27-/- mice treated with 0.025% cholic acid there was no significant effect of the knockout on the LXR target genes. In a previous work triple-knockout mice deficient in the biosynthesis of 24S-hydroxycholesterol, 25-hydroxycholesterol and 27OH were shown to have impaired response to dietary cholesterol, suggesting side-chain oxidized oxysterols to be mediators in cholesterol-induced effects on LXR target genes at a transcriptional level (Chen W. et al., Cell Metab. 5 (2007) 73-79). The hydroxylated oxysterol responsible for the effect was not defined. We show here that treatment of wildtype mice with dietary cholesterol under the same conditions as in the above study induced the LXR target genes Lpl, Abcg8 and Srebp1c in wild type mice but failed to activate the same genes in mice lacking 27-hydroxycholesterol due to a knockout of Cyp27. We failed to demonstrate the above effects at the protein level (Abcg8) or at the activity level (Lpl). The results suggest that 27OH is not an important regulator of Srebp- or LXR regulated genes under basal conditions in mouse liver. On the other hand 27OH appears to mediate cholesterol-induced effects on some LXR target genes at a transcriptional level under some in vivo conditions.
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| 11. |
- Lewin, Nongnit, et al.
(författare)
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Single Nucleotide Polymorphism and Cancer Risk, Tumour Recurrence, or Survival of Head and Neck Cancer Patients
- 2017
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Ingår i: Oncology. - : S. Karger AG. - 0030-2414 .- 1423-0232. ; 92, s. 161-169
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Tidskriftsartikel (refereegranskat)abstract
- Objective: This paper aims at studying the influence of single-nucleotide polymorphisms (SNPs) on cancer risk, tumor recurrence, and survival in head and neck (H&N) cancer patients. Methods: A total of 45 SNPs in 41 genes were investigated. A total of 174 Caucasian H&N cancer patients and 245 healthy blood donors were enrolled in the study. Results: Ten SNPs were associated with H&N cancer risk, but the identified SNPs differed among males and females. Some of the SNPs were related to immune response genes. The immune response gene SNPs were also related to survival. In particular, we noted that the tumor necrosis factor alpha (TNFα) rs1800629 could have an influence on cancer risk, tumor recurrence as well as survival. Conclusion: Genetic variation of the TNFα rs1800629 might be useful as a biomarker in clinical decision-making since it was found to be related to cancer risk, tumor recurrence, and survival of H&N cancer patients.
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| 12. |
- Olin, Anette, 1967, et al.
(författare)
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Enabling and constraining actions shaping a teacher-researcher collaboration
- 2013
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Ingår i: Paper presented within the symposium Using research insights to support teachers' learning and agency to teach science at the ESERA-conference, Larnaca, September 2-7, 2013..
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Konferensbidrag (refereegranskat)abstract
- This paper is inquiring a collaboration between a teacher team and researchers in improving science teaching using Clarke and Hollingsworth’s (2002) model of teacher professional growth. We focus this presentation on how the domain of consequences in terms of expected salient outcomes becomes the motor for a shared reflection in this collaboration. The collaboration is at the same time a vulnerable local project, which is shaped in the cross-fire of other projects. The empirical design includes a year-long series of teacher-researcher meetings, recorded by audio and sometimes video. The setting was that of a Swedish secondary school (ages 13-15). These meetings focused the planning and development of lessons within a specific school science area – the human body – making use of both teacher experience – for example in terms of different ways of conducting “good teaching” in this area – and research outcomes – for example the idea of organising purposes (Johansson and Wickman, 2011). The aim and outcome of the inquiry is 1) the explication of conditions for (un)successful collaborations between teachers and researchers, and 2) an understanding of what shapes the local practice and its current and future form. The use of the theory of practice architecture (Kemmis & Grootenboer, 2008) leads to an identification of key sayings, doings and relatings done within and between the meetings, and that together comprise the nexus of actions that make up the teacher-researcher practice. For example, we show some of the negotiations and renegotiations on the use of a diagnostic instrument, starting out from the external domain, changing from instrumental and summative to a powerful formative tool, having concrete meaning in the local domain of practice, and becoming a key doing relating the practice of the planning meetings to the practice of the classrooms.
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| 13. |
- Olin, Anette, 1967, et al.
(författare)
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Features of an Emerging Practice and Professional Development in a Science Teacher Team Collaboration with a Researcher Team
- 2016
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Ingår i: Journal of Science Teacher Education. - : Informa UK Limited. - 1046-560X .- 1573-1847. ; 27:6, s. 607-624
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Tidskriftsartikel (refereegranskat)abstract
- This study concerns teaching and learning development in science through collaboration between science teachers and researchers. At the core was the ambition to integrate research outcomes of science education—here ‘didactic models’—with teaching practice, aligned with professional development. The phase where the collaboration moves from initial establishment towards a stable practice is investigated. The study aims to identifying features of formation and exploring consequences for the character of contact between research and teaching. Specific questions are “What may be identified as actions and arrangements impacting the quality and continuation of the emerging practice?” and “What and in what ways may support teacher growth?” The analysis draws on practice architectures as a theoretical framework and specifically investigates the initial meetings as a practice-node for a new practice, empirically drawing on documented reflections on science teaching, primarily from meetings and communication. The results take the form of an analytical-narrative account of meetings that focused planning, enactment and reflection on teaching regarding the human body. We identify enabling actions such as collaborative work with concrete material from the classroom and arrangements such as the regular meetings and that the collaborative group had a core of shared competence—in science teaching and learning. Constraining were actions such as introducing research results with weak connection to practical action in the school practice and arrangements such as differences between school and university practice architectures and the general ‘oppression’ of teachers’ classroom practice. The discussion includes reflections on researchers’ roles and on a research and practice base for school development.
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