| 1. |
- Lindgren, Anders E. G., et al.
(författare)
-
Total Synthesis of the Resveratrol Oligomers (+/-)-Ampelopsin B and (+/-)-E-Viniferin
- 2016
-
Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; :3, s. 426-429
-
Tidskriftsartikel (refereegranskat)abstract
- The total synthesis of the resveratrol dimers (+/-)-ampelopsin B and (+/-)-E-viniferin is reported. Highlights of the approach include the use of cyclopropylmethyl groups to protect aromatic alcohols. This group allows an acid promoted three-step, one-pot deprotection-epimerization-cyclization of an advanced intermediate to give (+/-)-ampelopsin B. An important advantage with our strategy is the possibility of synthesizing analogs to these natural products to further study the chemistry and biology of resveratrol oligomers.
|
|
| 2. |
|
|
| 3. |
- Nordqvist, Emelie, et al.
(författare)
-
Deferred imitation, associative memory and communication in 14-month-old children
- 2015
-
Konferensbidrag (refereegranskat)abstract
- The presentation will build on two recent studies that combine behavioral observations of memory (deferred imitation, DI), electrophysiological (Event-Related Potentials, ERP) measures of associative memory and parental reports of language in 14-monthsold children. In both studies, an ERP (Nc) response indicating associative memory as well as a correlation between Nc and DI was observed. Further analysis revealed strong individual variability: The clearest relationship with ERP was noted for the subgroup of children performing non-optimally on the DI tasks. In addition, we also found a statistically significant correlation between parental report of receptive language and our ERP measure of associative memory.
|
|
| 4. |
- Nordqvist, Emelie, et al.
(författare)
-
The relationship between deferred imitation, associative memory, and communication in 14-months-old children. Behavioral and electrophysiological indices
- 2015
-
Ingår i: Frontiers in Psychology. - : Frontiers. - 1664-1078. ; 6:260
-
Tidskriftsartikel (refereegranskat)abstract
- The present study combines behavioral observations of memory (deferred imitation, DI, after a brief delay of 30 min and after a long delay of 2-3 weeks) and electrophysiological (event-related potentials, ERPs) measures of associative memory, as well as parental reports of non-verbal and verbal communication in sixteen 14-months-old children. Results show that for DI, the children remembered the stimulus after the brief but not after the long delay. There was a clear electrophysiological response indicating associative memory. Furthermore, a correlation between DI and ERR suggests that both measures of memory (DI and associative memory) tap into similar mechanisms in 14months-old children. There was also a statistically significant relation between parental report of receptive (verbal) language and the ERP, showing an association between receptive language skills and associative memory.
|
|
| 5. |
- Andersson, C. David, et al.
(författare)
-
Benefits of statistical molecular design, covariance analysis, and reference models in QSAR : a case study on acetylcholinesterase
- 2015
-
Ingår i: Journal of Computer-Aided Molecular Design. - : Springer Science and Business Media LLC. - 0920-654X .- 1573-4951. ; 29:3, s. 199-215
-
Tidskriftsartikel (refereegranskat)abstract
- Scientific disciplines such as medicinal- and environmental chemistry, pharmacology, and toxicology deal with the questions related to the effects small organic compounds exhort on biological targets and the compounds' physicochemical properties responsible for these effects. A common strategy in this endeavor is to establish structure-activity relationships (SARs). The aim of this work was to illustrate benefits of performing a statistical molecular design (SMD) and proper statistical analysis of the molecules' properties before SAR and quantitative structure-activity relationship (QSAR) analysis. Our SMD followed by synthesis yielded a set of inhibitors of the enzyme acetylcholinesterase (AChE) that had very few inherent dependencies between the substructures in the molecules. If such dependencies exist, they cause severe errors in SAR interpretation and predictions by QSAR-models, and leave a set of molecules less suitable for future decision-making. In our study, SAR- and QSAR models could show which molecular sub-structures and physicochemical features that were advantageous for the AChE inhibition. Finally, the QSAR model was used for the prediction of the inhibition of AChE by an external prediction set of molecules. The accuracy of these predictions was asserted by statistical significance tests and by comparisons to simple but relevant reference models.
|
|
| 6. |
- Arja, Katriann, et al.
(författare)
-
Synthesis and Characterization of Novel Fluoro-glycosylated Porphyrins that can be Utilized as Theranostic Agents
- 2018
-
Ingår i: ChemistryOpen. - : Wiley-VCH Verlagsgesellschaft. - 2191-1363. ; 7:7, s. 495-503
-
Tidskriftsartikel (refereegranskat)abstract
- Small molecules with modalities for a variety of imaging techniques as well as therapeutic activity are essential, as such molecules render opportunities to simultaneously conduct diagnosis and targeted therapy, so called theranostics. In this regard, glycoporphyrins have proven useful as theranostic agents towards cancer, as well as noncancerous conditions. Herein, the synthesis and characterization of heterobifunctional glycoconjugated porphyrins with two different sugar moieties, a common monosaccharide at three sites, and a 2-fluoro-2-deoxy glucose (FDG) moiety at the fourth site are presented. The fluoro-glycoconjugated porphyrins exhibit properties for multimodal imaging and photodynamic therapy, as well as specificity towards cancer cells. We foresee that our findings might aid in the chemical design of heterobifunctional glycoconjugated porphyrins that could be utilized as theranostic agents.
|
|
| 7. |
- Bartoschek, Michael, et al.
(författare)
-
Spatially and functionally distinct subclasses of breast cancer-associated fibroblasts revealed by single cell RNA sequencing
- 2018
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9:1
-
Tidskriftsartikel (refereegranskat)abstract
- Cancer-associated fibroblasts (CAFs) are a major constituent of the tumor microenvironment, although their origin and roles in shaping disease initiation, progression and treatment response remain unclear due to significant heterogeneity. Here, following a negative selection strategy combined with single-cell RNA sequencing of 768 transcriptomes of mesenchymal cells from a genetically engineered mouse model of breast cancer, we define three distinct subpopulations of CAFs. Validation at the transcriptional and protein level in several experimental models of cancer and human tumors reveal spatial separation of the CAF subclasses attributable to different origins, including the peri-vascular niche, the mammary fat pad and the transformed epithelium. Gene profiles for each CAF subtype correlate to distinctive functional programs and hold independent prognostic capability in clinical cohorts by association to metastatic disease. In conclusion, the improved resolution of the widely defined CAF population opens the possibility for biomarker-driven development of drugs for precision targeting of CAFs.
|
|
| 8. |
- Blomberg, Frida, et al.
(författare)
-
Emotional arousal and lexical specificity modulate response times differently depending on ear of presentation in a dichotic listening task
- 2015
-
Ingår i: The Mental Lexicon. - : John Benjamins Publishing Company. - 1871-1340 .- 1871-1375. ; 10:2, s. 221-246
-
Tidskriftsartikel (refereegranskat)abstract
- We investigated possible hemispheric differences in the processing of four different lexical semantic categories: SPECIFIC (e.g. bird), GENERAL (e.g. animal), ABSTRACT (e.g. advice), and EMOTIONAL (e.g. love). These wordtypes were compared using a dichotic listening paradigm and a semantic category classification task. Response times (RTs) were measured when participants classified testwords as concrete or abstract. In line with previous findings, words were expected to be processed faster following right-ear presentation. However, lexical specificity and emotional arousal were predicted to modulate response times differently depending on the ear of presentation. For left-ear presentation, relatively faster RTs were predicted for SPECIFIC and EMOTIONAL words as opposed to GENERAL and ABSTRACT words. An interaction of ear and wordtype was found. For right-ear presentation, RTs increased as testwords’ imageability decreased along the span SPECIFIC–GENERAL–EMOTIONAL–ABSTRACT. In contrast, for left ear presentation, EMOTIONAL words were processed fastest, while SPECIFIC words gave rise to long RTs on par with those for ABSTRACT words. Thus, the prediction for EMOTIONAL words presented in the left ear was borne out, whereas the prediction for SPECIFIC words was not. This might be related to previously found differences in processing of stimuli at a global or local level.
|
|
| 9. |
- Blomberg, Frida, et al.
(författare)
-
Lexical specificity, imageability and emotional arousal modulate the N400 and the N700
- 2016
-
Ingår i: 8th Annual Meeting of the Society for the Neurobiology of Language. SNL 2016. ; , s. 207-207
-
Konferensbidrag (refereegranskat)abstract
- Introduction: The event-related potential (ERP) componentN400 as well as a later effect, often labeled ‘N700’ haverepeatedly been shown to increase for concrete as compared to abstract words (Barber, Otten, Kousta, & Vigliocco, 2013; Gullick, Mitra, & Coch, 2013; Kounios & Holcomb, 1994; Nittono, Suehiro, & Hori, 2002; West & Holcomb, 2000). In addition, pseudowords elicit greater N400s than real words (Lau, Phillips, & Poeppel, 2008). Previous interpretations of the N400 as indexing contextual integration or alternatively, activation of semantic features in long-term memory, do notfully explain the combination of these differences. The present study compared ERPs in the N400 and N700 time-windows for PSEUDOWORDS (e.g. ‘danalod’) and four noun categories differing in specificity and imageability: (SPECIFIC, e.g. ‘squirrel’, GENERAL, e.g. ‘animal’, EMOTIONAL, e.g. ‘happiness’ and ABSTRACT, e.g. ‘tendency’).Methods: EEGwas recorded from 32 scalp electrodes and response times were measured while 35 healthy, right-handed native Swedish speakers (age 20-37) performed an imageability rating (IR) task and a lexical decision (LD) task. The stimuli were 160 written nouns, 40 each of the above-mentioned semantic categories, and 160 phonologically legal pseudowords. Statistical comparisons of ERPs in the N400 (300-500 ms post-stimulus onset) and N700 (500-800 ms post-stimulus onset) time-windows were carried out using within-subjects ANOVAs.Results: In the LD task, N400 amplitudes increasedin the order EMOTIONAL < ABSTRACT < GENERAL < SPECIFIC < PSEUDOWORD. A largely similar pattern wasfound in the IR task as well as in the N700 time-window ofboth tasks. N400 and N700 effects were found for SPECIFIC-GENERAL test words also when they were matched for imageability, indicating that something other than imageabilityper se was driving the effects.Conclusion: The pattern of ERPamplitudes seen in the present study could be explained by a model which assumes that words with larger numbers of associated words in the mental lexicon yield smaller N400s, for example abstract as compared to concrete words and real words as compared to pseudowords. The fact that N400 andN700 effects were found for SPECIFIC-GENERAL test wordseven when they were matched for imageability indicates that other factors, possibly related to hierarchical semantic relationsbetween concrete noun categories, drive the effect. In line withthe suggested model, this might be explained by superordinate GENERAL nouns having a larger number of lexical associates than SPECIFIC nouns.References:Barber, H. A., Otten, L. J., Kousta, S.-T., & Vigliocco, G. (2013). Brain and Language, 125(1), 47–53.Gullick, M. M., Mitra, P., & Coch, D. (2013). Psychophysiology, 50(5), 431–440.Kounios, J., & Holcomb, P. J. (1994). Journal of Experimental Psychology: Learning, Memory, and Cognition, 20(4), 804–823.Lau, E. F., Phillips, C., & Poeppel, D. (2008). Nature Reviews Neuroscience, 9(12), 920–933.Nittono, H., Suehiro, M., & Hori, T. (2002). International Journal of Psychophysiology, 1–11.West, W. C., & Holcomb, P. J. (2000). Journal of Cognitive Neuroscience, 12(6), 1024–1037.
|
|
| 10. |
|
|
| 11. |
- Bogoeva, Vanya, et al.
(författare)
-
Ruthenium porphyrin-induced photodamage in bladder cancer cells
- 2016
-
Ingår i: Photodiagnosis and Photodynamic Therapy. - : ELSEVIER SCIENCE BV. - 1572-1000 .- 1873-1597. ; 14
-
Tidskriftsartikel (refereegranskat)abstract
- Photodynamic therapy (PDT) is a noninvasive treatment for solid malignant and flat tumors. Light activated sensitizers catalyze photochemical reactions that produce reactive oxygen species which can cause cancer cell death. In this work we investigated the photophysical properties of the photosensitizer ruthenium(II) porphyrin (RuP), along with its PDT efficiency onto rat bladder cancer cells (AY27). Optical spectroscopy verified that RuP is capable to activate singlet oxygen via blue and red absorption bands and inter system crossing (ISC) to the triplet state. In vitro experiments on AY27 indicated increased photo-toxicity of RuP (20 mu M, 1811 incubation) after cell illumination (at 435 nm), as a function of blue light exposure. Cell survival fraction was significantly reduced to 14% after illumination of 20 mu M RuP with 15.6 J/cm(2), whereas the "dark toxicity" of 20 mu M RuP was 17%. Structural and morphological changes of cells were observed, due to RuP accumulation, as well as light-dependent cell death was recorded by confocal microscopy. Flow cytometry verified that PDT-RuP (50 mu M) triggered significant photo-induced cellular destruction with a photoxicity of (93% +/- 0.9%). Interestingly, the present investigation of RuP-PDT showed that the dominating mode of cell death is necrosis. RuP "dark toxicity" compared to the conventional chemotherapeutic drug cisplatin was higher, both evaluated by the MIT assay (24 h). In conclusion, the present investigation shows that RuP with or without photoactivation induces cell death of bladder cancer cells. (C) 2016 Elsevier B.V. All rights reserved.
|
|
| 12. |
- Chateau, Denis, et al.
(författare)
-
Long Distance Enhancement of Nonlinear Optical Properties Using Low Concentration of Plasmonic Nanostructures in Dye Doped Monolithic Sol-Gel Materials.
- 2016
-
Ingår i: Advanced Functional Materials. - Weinheim : Wiley. - 1616-301X .- 1616-3028. ; 26:33
-
Tidskriftsartikel (refereegranskat)abstract
- Monolithic sol-gel silica composites incorporating platinum-based chromophores and various types of gold nanoparticles (AuNPs) are prepared and polished to high optical quality. Their photophysical properties are investigated. The glass materials show well-defined localized surface plasmon resonance (SPR) absorbance from the visible to NIR. No redshifts of the AuNP plasmon absorption peaks due to the increase in nanoparticle doping concentration are observed in the glasses, proving that no or very small SPR coupling effects occur between the AuNPs. At 600 nm excitation, but not at 532 nm, the AuNPs improve the nonlinear absorption performance of glasses codoped with 50 × 10−3 m of a Pt-acetylide chromophore. The glasses doped with lower concentrations of AuNPs (2-5 μm average distance) and 50 × 10−3 m in chromophore, show a marked improvement in nonlinear absorption, with no or only small improvement for the more highly AuNP doped glasses. This study shows the importance of excitation wavelength and nanoparticle concentration for composite systems employing AuNPs to improve two-photon absorption of chromophores. [ABSTRACT FROM AUTHOR]
|
|
| 13. |
- Djerf, Henrik, et al.
(författare)
-
Cost-effectiveness of revascularization in patients with intermittent claudication.
- 2018
-
Ingår i: The British journal of surgery. - : Oxford University Press (OUP). - 1365-2168 .- 0007-1323. ; 105:13, s. 1742-1748
-
Tidskriftsartikel (refereegranskat)abstract
- Revascularization is a treatment option for patients with intermittent claudication. However, there is a lack of evidence to support its long-term benefits and cost-effectiveness. The aim of this study was to compare the cost-effectiveness of revascularization and best medical therapy (BMT) with that of BMT alone.Data were used from the IRONIC (Invasive Revascularization Or Not in Intermittent Claudication) RCT where consecutive patients with mild-to-severe intermittent claudication owing to aortoiliac or femoropopliteal disease were allocated to either BMT alone (including a structured, non-supervised exercise programme) or to revascularization together with BMT. Inpatient and outpatient costs were obtained prospectively over 24 months of follow-up. Mean improvement in quality-adjusted life-years (QALYs) was calculated based on responses to the EuroQol Five Dimensions EQ-5D-3 L™ questionnaire. Cost-effectiveness was assessed as the cost per QALY gained.A total of 158 patients were randomized, 79 to each group. The mean cost per patient in the BMT group was €1901, whereas it was €8280 in the group treated with revascularization in addition to BMT, with a cost difference of €6379 (95 per cent c.i. €4229 to 8728) per patient. Revascularization in addition to BMT resulted in a mean gain in QALYs of 0·16 (95 per cent c.i. 0·06 to 0·24) per patient, giving an incremental cost-effectiveness ratio of €42 881 per QALY.The costs associated with revascularization together with BMT in patients with intermittent claudication were about four times higher than those of BMT alone. The incremental cost-effectiveness ratio of revascularization was within the accepted threshold for public willingness to pay according to the Swedish National Guidelines, but exceeded that of the UK National Institute for Health and Care Excellence guidelines.
|
|
| 14. |
|
|
| 15. |
- Dumanski, Jan P., et al.
(författare)
-
Smoking is associated with mosaic loss of chromosome Y
- 2015
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 347:6217, s. 81-83
-
Tidskriftsartikel (refereegranskat)abstract
- Tobacco smoking is a risk factor for numerous disorders, including cancers affecting organs outside the respiratory tract. Epidemiological data suggest that smoking is a greater risk factor for these cancers in males compared to females. This observation, together with the fact that males have a higher incidence of and mortality from most non-sex-specific cancers, remains unexplained. Loss of chromosome Y (LOY) in blood cells is associated with increased risk of nonhematological tumors. We demonstrate here that smoking is associated with LOY in blood cells in three independent cohorts [TwinGene: odds ratio (OR) = 4.3, 95% CI = 2.8-6.7; ULSAM: OR = 2.4, 95% CI = 1.6-3.6; and PIVUS: OR = 3.5, 95% CI = 1.4-8.4] encompassing a total of 6014 men. The data also suggest that smoking has a transient and dose-dependent mutagenic effect on LOY status. The finding that smoking induces LOY thus links a preventable risk factor with the most common acquired human mutation.
|
|
| 16. |
- Ekblad, Torun, et al.
(författare)
-
Identification of Poly(ADP-Ribose) Polymerase Macrodomain Inhibitors Using an AlphaScreen Protocol
- 2018
-
Ingår i: SLAS Discovery. - : Sage Publications. - 2472-5560 .- 2472-5552. ; 23:4, s. 353-362
-
Tidskriftsartikel (refereegranskat)abstract
- Macrodomains recognize intracellular adenosine diphosphate (ADP)-ribosylation resulting in either removal of the modification or a protein interaction event. Research into compounds that modulate macrodomain functions could make important contributions. We investigated the interactions of all seven individual macrodomains of the human poly(ADP-ribose) polymerase (PARP) family members PARP9, PARP14, and PARP15 with five mono-ADP-ribosylated (automodified) ADP-ribosyltransferase domains using an AlphaScreen assay. Several mono-ADP-ribosylation-dependent interactions were identified, and they were found to be in the micromolar affinity range using surface plasmon resonance (SPR). We then focused on the interaction between PARP14 macrodomain-2 and the mono-ADP-ribosylated PARP10 catalytic domain, and probed a similar to 1500-compound diverse library for inhibitors of this interaction using AlphaScreen. Initial hit compounds were verified by concentration-response experiments using AlphaScreen and SPR, and they were tested against PARP14 macrodomain-2 and -3. Two initial hit compounds and one chemical analog each were further characterized using SPR and microscale thermophoresis. In conclusion, our results reveal novel macrodomain interactions and establish protocols for identification of inhibitors of such interactions.
|
|
| 17. |
- Ekblad, Torun, et al.
(författare)
-
Towards small molecule inhibitors of mono-ADP-ribosyltransferases
- 2015
-
Ingår i: European Journal of Medicinal Chemistry. - : Elsevier BV. - 0223-5234 .- 1768-3254. ; 95, s. 546-551
-
Tidskriftsartikel (refereegranskat)abstract
- Protein ADP-ribosylation is a post-translational modification involved in DNA repair, protein degradation, transcription regulation, and epigenetic events. Intracellular ADP-ribosylation is catalyzed predominantly by ADP-ribosyltransferases with diphtheria toxin homology (ARTDs). The most prominent member of the ARTD family, poly(ADP-ribose) polymerase-1 (ARTD1/PARP1) has been a target for cancer drug development for decades. Current PARP inhibitors are generally non-selective, and inhibit the mono-ADP-ribosyltransferases with low potency. Here we describe the synthesis of acylated amino benzamides and screening against the mono-ADP-ribosyltransferases ARTD7/PARP15, ARTD8/PARP14, ARTD10/PARP10, and the poly-ADP-ribosyltransferase ARTD1/PARP1. The most potent compound inhibits ARTD10 with sub-micromolar IC50.
|
|
| 18. |
- Gidlund, Henrik, et al.
(författare)
-
Road surface photometric characterisation and its impact on energy savings
- 2019
-
Ingår i: Coatings. - : MDPI AG. - 2079-6412. ; 9:5
-
Tidskriftsartikel (refereegranskat)abstract
- How road surfaces reflect light in space is a physical characteristic that plays a key role in the design of road lighting installations: by European Standards the average luminance is the target quantity to assure the required safety conditions of the motorized road traffic. Lighting systems are designed (luminous flux installed per kilometre) to comply with the above requirement, starting from reference values of road surfaces reflection published in an old scientific document. These data are obsolete and not representative of current road surfaces, but they are still used to design current LED lighting systems. European Community funded a SURFACE project to provide to EU standard organization new traceable reference data, representative of current road surfaces used in EU. The paper presents the data collections and the impact on road lighting of using available old reference data versus SURFACE collected data of current road surfaces. Results highlight advantages in using bright pavements as well the need for introducing systems for flux control in road lighting installation to compensate for the discrepancies between current reference data and actual road surface data.
|
|
| 19. |
- Giummarella, Nicola, et al.
(författare)
-
Lignin Prepared by Ultrafiltration of Black Liquor : Investigation of Solubility, Viscosity, and Ash Content
- 2016
-
Ingår i: BioResources. - : North Carolina State University. - 1930-2126. ; 11:2, s. 3494-3510
-
Tidskriftsartikel (refereegranskat)abstract
- Technical lignin, which can be potentially obtained in large amounts as a by-product from kraft pulping, represents a potential resource for manufacturing fuels and chemicals. Upgrading of lignin, by lowering its molecular weight, is a valuable alternative to precipitation from black liquor, which occurs in the Lignoboost process. The solubility properties of Lignoboost lignin and filtered lignin in a number of technically feasible solvents were compared, and it was found that both lignins were dissolved in similar solvents. With the exception of furfural, the best lignin solvents generally were organic solvents miscible with water, such as methanol. It was possible to dissolve more filtered lignin in higher concentrations than Lignoboost lignin; additionally, the viscosities of the filtered lignin solutions were also considerably lower than those of Lignoboost lignin, especially at higher concentrations. Methods for non-organic component removal from filtrated lignin were tested, and it was concluded that several cold acidic treatments after dewatering can lower the ash content to values below 0.5% by weight.
|
|
| 20. |
- Grönholm, Erik, et al.
(författare)
-
Predominance of caudate nucleus lesions in acute ischemic stroke patients with impairments in language and speech
- 2016
-
Ingår i: European Journal of Neurology. - : Wiley. - 1351-5101 .- 1468-1331. ; 23:1, s. 148-153
-
Tidskriftsartikel (refereegranskat)abstract
- Background and purpose. Whereas traditional views of language processing in the brain have assumed that the language function is concentrated to a limited number of cortical areas (Broca’s and Wernicke’s areas), current knowledge points at a much more complex system of language and speech processing involving many brain areas, both cortical and subcortical. The purpose of the current study was to make an unbiased assessment of which cerebral areas are affected in first-ever acute ischemic stroke patients identified as having language and speech impairments according to the National Institute of Health Stroke Scale (NIHSS). Methods. Data from thirty-four patients with language and speech impairments, with a score of 1-3 on item 9 on the NIHSS, following ischemic stroke was collected from the Lund Stroke Register. MRI images acquired up to 20 days after stroke onset were used to create an overlap lesion image using MRIcron software. Results. The classical language areas, Wernicke’s and Broca’s area, were affected in less than one fourth of the patients. The most frequently affected region was a subcortical region - the left caudate nucleus and the adjacent corona radiata. Conclusions. These findings contribute to the growing body of evidence that the basal ganglia have a crucial role in the control over language and speech processing.
|
|
| 21. |
- Gustafsson, Håkan, et al.
(författare)
-
Visualization of oxidative stress in ex vivo biopsies using electron paramagnetic resonance imaging
- 2015
-
Ingår i: Magnetic Resonance in Medicine. - : Wiley. - 0740-3194 .- 1522-2594. ; 73:4, s. 1682-1691
-
Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: The purpose of this study was to develop an X-Band electron paramagnetic resonance imaging protocol for visualization of oxidative stress in biopsies.METHODS: The developed electron paramagnetic resonance imaging protocol was based on spin trapping with the cyclic hydroxylamine spin probe 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine and X-Band EPR imaging. Computer software was developed for deconvolution and back-projection of the EPR image. A phantom containing radicals of known spatial characteristic was used for evaluation of the developed protocol. As a demonstration of the technique electron paramagnetic resonance imaging of oxidative stress was performed in six sections of atherosclerotic plaques. Histopathological analyses were performed on adjoining sections.RESULTS: The developed computer software for deconvolution and back-projection of the EPR images could accurately reproduce the shape of a phantom of known spatial distribution of radicals. The developed protocol could successfully be used to image oxidative stress in six sections of the three ex vivo atherosclerotic plaques.CONCLUSIONS: We have shown that oxidative stress can be imaged using a combination of spin trapping with the cyclic hydroxylamine spin probe cyclic hydroxylamine spin probe 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine and X-Band EPR imaging. A thorough and systematic evaluation on different types of biopsies must be performed in the future to validate the proposed technique. Magn Reson Med, 2014.
|
|
| 22. |
- Hägglund, Maria, Lektor, 1975-, et al.
(författare)
-
Världsbäst på eHälsa kräver internationellt samarbete
- 2017
-
Ingår i: Svenska dagbladet. - Stockholm, Sweden : Svenska Dagbladet AB & Co.. - 1101-2412.
-
Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Det är glädjande att myndigheter nu äntligen tittar mer på internationellt delade detaljerade dokumentationsmodeller för innehåll i journaler. Vi hoppas att de ger tillräckligt kraftfulla och tydliga budskap så att de upphandlande vårdgivarna också ser vikten av detta. Om vi ska bli världsbäst på eHälsa krävs internationellt samarbete, skriver flera forskare i medicinsk informatik.
|
|
| 23. |
|
|
| 24. |
- Iacomussi, P, et al.
(författare)
-
Metrology of Road Surface for Smart Lighting
- 2017
-
Ingår i: PROCEEDINGSOF THE LUX EUROPA 2017 European Lighting Conference. - Ljubljana. - 9789619373347 ; , s. 103-107
-
Konferensbidrag (refereegranskat)abstract
- The knowledge of the luminance coefficient q or of the reduced luminance coefficient r of road surface is an unavoidable requirement for designing road lighting installations able to assure adequate road luminance for visual conditions, energy consumption and traffic safety according to standard requirements. Unfortunately q available data refers to measurements made during the seventies with no traceability or measurement uncertainty. In the last 40 years the road surfaces pavements evolved as well the road lighting sources and luminaires. EMPIR project SURFACE will provide validated, optimised and reliable geometrical conditions for the measurement of q as well as reference data representative of current road pavements and future needs, as support of the European Standardisation process, CIE and European Metrology infrastructure.
|
|
| 25. |
|
|
| 26. |
- Jonsson, Kenneth, et al.
(författare)
-
Traffic compensated luminance estimation
- 2015
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Active control of street light sources based on sensor data is desired to meet requirements on traffic safety and environmental protection. In this report, we summarise the results of a research study focusing on some of the fundamental problems occurring when performing real-world sensor measurements for lighting control. In particular, we present results on the impact of traffic and the relationship between sensor angle and measured road surface luminance. Moreover, we present a comparison between different approaches to estimating the veiling luminance in tunnel lighting applications.
|
|
| 27. |
- Julin, Bettina, et al.
(författare)
-
Association between sociodemographic determinants and health outcomes in individuals with type 2 diabetes in Sweden
- 2018
-
Ingår i: Diabetes/Metabolism Research Reviews. - : Wiley. - 1520-7552 .- 1520-7560. ; 34:4, s. -9
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Concurrent multifactorial treatment is needed to reduce consequent risks of diabetes, yet most studies investigating the relationship between sociodemographic factors and health outcomes have focused on only one risk factor at a time. Swedish health care is mainly tax-funded, thus providing an environment that should facilitate equal health outcomes in patients, independent of background, socioeconomic status or health profile. This study aimed at investigating the association between several sociodemographic factors and diabetes-related health outcomes represented by HbA1c , systolic blood pressure, LDL cholesterol, predicted 5-year risk of cardiovascular disease as well as statin use.METHODS: This large retrospective registry-study was based on patient-level data from individuals diagnosed with type 2 diabetes mellitus during 2010-2011 (n = 416,228) in any of seven Swedish regions (~65% of the Swedish population). Health equity in diabetes care was analyzed through multivariate regression analyses on intermediary outcomes (HbA1c , systolic blood pressure, LDL), predicted 5-year risk of cardiovascular disease and process (i.e. statin use) after one-year follow-up, adjusting for several sociodemographic factors.RESULTS: We observed differences in intermediary risk measures, predicted 5-year risk of cardiovascular disease as well as process dependent on place of birth, sex, age, education and social setting, despite Sweden's articulated vision of equal health care.CONCLUSIONS: Diabetes patients' health was associated with sociodemographic prerequisites. In addition to demographics (age, sex) and disease history; educational level, marital status and region of birth are important factors to consider when benchmarking health outcomes, e.g. average HbA1c level, between organizational units or between different administrative regions.
|
|
| 28. |
- Lilja, Mikael, et al.
(författare)
-
Determinants of HbA1c in patients with type 1 diabetes in seven Swedish county councils
- 2015
-
Ingår i: Diabetologia. - : Springer. - 0012-186X .- 1432-0428. ; 58:Suppl. 1 Abstr. 278, s. S140-S141
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Background and aims: In order to make fair comparisons between the results of different health care providers, proper consideration of the casemix of the populations they serve is important. HbA1c is often used as a metric to indicate the quality of diabetes care, it is therefore of value to determine what patient characteristics affect this outcome. As part of the ongoing National Collaboration for Value Based Reimbursement and Monitoring Systems, we therefore set out to investigate what factors are associated with HbA1c in a large retrospective cohort of persons with type 1 diabetes.Materials and methods: This was a retrospective register study where we analyzed persons 18 years or older, with a health care contact and a diagnosis of diabetes during 2010-11 in the administrative systems of seven Swedish county councils (Dalarna, Jämtland Härjedalen, Skåne, Stockholm, Uppsala, Västra Götaland and Östergötland), covering ~70% of the Swedish population and linked this data to data from the National Diabetes Register, socioeconomic data from Statistics Sweden and data on filled prescriptions from the Prescribed Drug Register. We estimated a random effect model on HbA1c after one year of follow-up, including socioeconomic, demographic and clinical factors.Results: Based on a complete case approach, 13 396 patients were analyzed. Women had on average higher HbA1c than men. Blood sugar control seemed to be better with higher age. Of the socioeconomic factors, higher education was associated with lower levels of HbA1c, as was being married. By contrast, we found no association between HbA1c and being born outside the EU.Ahistory (previous 2 years) of diabetes related complications were associated with higher levels of HbA1c, which is likely due to high levels of HbA1c being an indicator of what is causing the complications in the first place. The exception to this pattern was patients with renal failure.Conclusion: Apart from obvious demographic factors such as age and gender as well as disease history, educational and civil status are important factors to take into consideration when comparing obtained HbA1c levels between health care providers. This also raises the question of the need for additional focus on education directed towards these groups to facilitate improved diabetes management.
|
|
| 29. |
- Lilledahl, Magnus B., et al.
(författare)
-
Combined imaging of oxidative stress and microscopic structure reveals new features in human atherosclerotic plaques
- 2015
-
Ingår i: Journal of Biomedical Optics. - : Society of Photo-optical Instrumentation Engineers (SPIE). - 1083-3668 .- 1560-2281. ; 20:2, s. 020503-
-
Tidskriftsartikel (refereegranskat)abstract
- Human atherosclerotic samples collected by carotid endarterectomy were investigated using electronic paramagnetic resonance imaging (EPRI) for visualization of reactive oxygen species, and nonlinear optical microscopy (NLOM) to study structural features. Regions of strong EPRI signal, indicating a higher concentration of reactive oxygen species and increased inflammation, were found to colocalize with regions dense in cholesterol crystals as revealed by NLOM.
|
|
| 30. |
- Lindgren, Anders, 1985-
(författare)
-
Synthesis of Small Molecules Targeting ADP-Ribosyltransferases and Total Synthesis of Resveratrol Based Natural Products
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Diphtheria Toxin-like ADP-RibosyltransferasesThe Human ADP-ribosyl transferases (ARTDs) are a group of poorly studied enzymes which are believed to be involved in e.g. DNA repair, protein degradation, transcription regulation and cell death. Medicinal chemistry programmes aimed at developing selective inhibitors of these ARTDs were initiated. A suitable starting compound for one of these enzymes, ARTD3, was found by screening a library of NAD-mimics using a thermal shift assay. A virtual screening protocol was instead developed in order to find novel inhibitors of ARTD7, 8, and 10. The hit compounds were then further developed into selective inhibitors of the corresponding ARTDs by systematically varying different structural features using a combination of synthetic organic chemistry, computational chemistry and structural biology. Compounds were initially characterized using differential scanning fluorimetry which was later replaced with an enzymatic assay to obtain IC50 values. Biotinylated analogs were also synthesized in an attempt to develop an AlphaScreen assay. A selective ARTD3 inhibitor was ultimately identified and found to delay DNA repair in cells after γ-irradiation. These compounds are potentially valuable tools for elucidating the biological role of the poorly characterized ARTD-family of proteins.Total Synthesis of Resveratrol Based Natural ProductsThe polyphenolic natural product (-)-hopeaphenol was found to inhibit the type III secretion system present in certain gram-negative bacteria. (-)-Hopeaphenol is a tetramer of resveratrol and in order to investigate whether the entire structure was essential for inhibition two resveratrol dimers, ε-viniferin and ampelopsin B, were synthesized using a flexible and divergent synthetic route. Highlights of the synthetic strategy include the use of cyclopropylmethyl protecting groups, allowing an acid mediated three-step-one-pot deprotection-epimerization-cyclization of an advanced intermediate to form ampelopsin B. All previously reported syntheses of these two natural products include a dimerization of resveratrol which severly limits the possibilities to synthesize structural analogs. This new strategy enables the synthesis of a wide variety of analogs to ε-viniferin and ampelopsin B.
|
|
| 31. |
- Lindgren, Erik, et al.
(författare)
-
Nondestructive Evaluation with Laser Ultrasound of Powder Bed Fusion Printed Metal Parts
- 2019
-
Konferensbidrag (refereegranskat)abstract
- Introduction/PurposeMany of the main advantages of 3D printing metal components, for example the possibility to manufacture components of high geometriccomplexity in small series, typically make the nondestructive quality control difficult and resource intense. A number of published studies haveproposed in-process quality control of the component, as it is built layer by layer, as a possible general approach solution to this difficulty. Previousstudies have also indicated that the non-contact nondestructive testing method laser ultrasound might be an applicable method to conduct such anin-process nondestructive evaluation of 3D printed components.MethodsIn this work laser ultrasonic nondestructive evaluation of both electron beam and laser beam powder bed fusion printed metal parts isdemonstrated. Nickel-base and Stainless Steel samples are evaluated both from a machined surface and, in order to simulate the in-process setup,from the as-printed top surface.ResultsThe laser ultrasonic evaluation results are compared to results from other material characterization methods. Designed artificial defects as well asprocess material anomalies could be detected with the proposed laser ultrasonic evaluation, both when the evaluation was performed from the asprintedtop surface as well as from the machined surface.ConclusionsWe conclude that laser ultrasound can be utilized to detect material anomalies of interest in powder bed fusion printed metal parts. Furtherresearch is required in order to better understand and improve the capability and reliability of the nondestructive evaluation method.
|
|
| 32. |
- Lindgren, Karl-Oskar, 1976-, et al.
(författare)
-
Access to education and political candidacy : Lessons from school openings in Sweden
- 2019
-
Ingår i: Economics of Education Review. - : Elsevier. - 0272-7757 .- 1873-7382. ; 69, s. 138-148
-
Tidskriftsartikel (refereegranskat)abstract
- How does availability of education affect who becomes a political representative? Theorists have pointed out that access to education is a key to a well-functioning democracy, but few empirical studies have examined how changes in the access to education influence the chances of becoming a politician. In this paper, we analyze the effects of a large series of school openings in Sweden during the early 20th century, which provided adolescents with better access to secondary education. We use administrative data pertaining to the entire Swedish population born between 1916 and 1945. According to our empirical results, the opening of a new lower secondary school in a municipality increased the baseline probability of running for political office by 10–20%, and the probability of holding office by 20–30%.
|
|
| 33. |
|
|
| 34. |
- Lindgren, Karl-Oskar, 1976-, et al.
(författare)
-
Enhancing Electoral Equality: Can Education Compensate for Family Background Differences in Voting Participation?
- 2019
-
Ingår i: American Political Science Review. - 0003-0554 .- 1537-5943. ; 113:1, s. 108-122
-
Tidskriftsartikel (refereegranskat)abstract
- © 2018 American Political Science Association. It is well documented that voter turnout is lower among persons who grow up in families from a low socioeconomic status compared with persons from high-status families. This paper examines whether reforms in education can help reduce this gap. We establish causality by exploiting a pilot scheme preceding a large reform of Swedish upper secondary education in the early 1990s, which gave rise to exogenous variation in educational attainment between individuals living in different municipalities or born in different years. Similar to recent studies employing credible identification strategies, we fail to find a statistically significant average effect of education on political participation. We move past previous studies, however, and show that the reform nevertheless contributed to narrowing the voting gap between individuals of different social backgrounds by raising turnout among those from low socioeconomic status households. The results thus square well with other recent studies arguing that education is particularly important for uplifting politically marginalized groups.
|
|
| 35. |
|
|
| 36. |
|
|
| 37. |
|
|
| 38. |
- Lindgren, Lars-Erik, 1956-, et al.
(författare)
-
Nondestructive Evaluation with Laser Ultrasound of Powder Bed Fusion Printed Metal
- 2019
-
Konferensbidrag (refereegranskat)abstract
- Many of the main advantages of 3D printing metal components, for example the possibility to manufacture parts of high geometric complexity in small series, typically make the nondestructive quality control difficult and resource intense. A number of published studies have proposed in-process nondestructive evaluation of the printed material, as it is built layer by layer, as a possible general approach solution to this difficulty. Previous studies have also indicated that the non-contact nondestructive testing method laser ultrasound might be an applicable method to conduct such an in-process nondestructive evaluation of 3D printed parts. Potential pros of such an ultrasonic based evaluation, as compared to more process monitoring like approaches (e.g. acoustic emission from the printing process) would for example be increased defect characterization capabilities.In this work laser ultrasonic nondestructive evaluation of both electron beam and laser beam powder bed fusion printed metal is demonstrated. Nickel-base and Stainless Steel samples are evaluated both from a machined surface and, in order to simulate the in-process setup, from the as-printed top surface.The laser ultrasonic evaluation results are then compared to results from other material characterization methods, such as light optical microscopy and X-ray inspection. Designed artificial defects as well as process material anomalies could be detected with the proposed laser ultrasonic evaluation. In some cases material defects could be detected also when the laser ultrasonic evaluation was performed from the as-printed top surface.Our results are similar to other studies that have been reported on the subject: laser ultrasound can be utilized to detect material anomalies of interest in powder bed fusion printed metal material. Further research is required in order to better understand and improve the capability and reliability of the nondestructive evaluation method.
|
|
| 39. |
- Lindgren, Lars-Erik, et al.
(författare)
-
Towards predictive simulations of machining
- 2016
-
Ingår i: Comptes rendus. Mecanique. - : Elsevier BV. - 1631-0721 .- 1873-7234. ; 344:4-5, s. 284-295
-
Tidskriftsartikel (refereegranskat)abstract
- Machining simulations are challenging with respect to both numerical issues and physical phenomena occurring during machining. The latter are mainly related to the description of the bulk material behaviour (plasticity) and surface properties (friction and wear). The aim of this paper is to present what is required for predictive models, depending on their scopes, as well as the needed developments for the future. The paper includes a short review of selected works that are relevant for this purpose as well as conclusions based on our own experience
|
|
| 40. |
- Lindgren, Mikael, 1963-, et al.
(författare)
-
CHARACTERIZATION OF REFLECTIVITY AND GEOMETRY FOR SOFT CAR TARGETS
- 2019
-
Ingår i: Proceedings of the 29th Session of the CIE. - Wien. - 9783902842749 ; , s. 1753-1767
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper reports on results from a study of characteristics for 3D soft surrogate vehicle targets. Such targets are used extensively for testing and verification of optical sensor systems for Advanced Driver Assistance Systems and Automated Driving. However, the influence of wear-and-tear on the vehicle target is not well known. Consequently, no clear requirement exists on how many collisions a soft target can be exposed to before it no longer performs well.Important characteristics for optical sensor systems are surface reflectance in the relevant wavelength range and geometry of the soft target. We report on measurements of spectral reflectivity and geometry performed before, during and after an accelerated ageing campaign involving 100 rear-end collisions at 50 km/h. The reflectivity was found to change very little while the geometry was strongly affected.
|
|
| 41. |
- Lindgren, Mikael, 1963-, et al.
(författare)
-
Characterization of visual and IR reflectivity for soft car targets
- 2018
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Advanced Driver Assistance Systems (ADAS) and Automated Driving (AD) vehicles rely heavily on optical sensors. Extensive testing of optical sensors is required and typically performed at test tracks like AstaZero. Soft surrogate targets are used for safety reasons, but the optical characteristics of surrogate targets may differ considerably from that of real vehicles. During tests the quality of the soft surrogate targets deteriorates due to repeated impacts and reassembly of the targets, and there is a need for methods to secure the quality of the soft surrogate targets over time.RISE has conducted a project together with Volvo Cars and Veoneer to develop and validate accurate and repeatable measurement methods of the optical characteristics of 3D soft car targets. The goal is to support international standardisation (ISO) with standard methods enabling future verification and calibration of optical characteristics of active safety 3D soft car targets.The poster presents results from optical measurements on soft car targets and real cars, performed in the project. One target was subjected to 100 rear-end collisions during which the reflectivity was measured.
|
|
| 42. |
- Lindgren, Mikael, 1963, et al.
(författare)
-
Traffic compensated luminance estimation
- 2015
-
Ingår i: 28th CIE Session, 28 jun - 4 jul 2015 Manchester UK.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
|
|
| 43. |
- Lindgren, Ola, et al.
(författare)
-
The Effect of Radioiodine Treatment on TRAb, Anti-TPO, and Anti-TG in Graves' Disease
- 2019
-
Ingår i: European Thyroid Journal. - : Bioscientifica. - 2235-0640 .- 2235-0802. ; 8:2, s. 64-69
-
Tidskriftsartikel (refereegranskat)abstract
- Background: In Graves' disease (GD), immunocompetent cells infiltrate thyroid tissue with release of TSH-receptor antibodies (TRAb), and radioiodine treatment is known to elicit an immune response with an increase in TRAb. Objectives: The aim was to study if all patients treated with radioiodine respond with a release of TRAb, anti-thyroperoxidase (anti-TPO), and anti-thyroglobulin (anti-TG). Methods: This is a prospective observational study. GD patients (n = 131) were admitted for treatment with radioiodine. Thyroid antibodies were measured before and 3 months after iodine-131 treatment. Results: After 3 months, a fold change > 1.1 was found in 66% of the GD patients, while the remaining 34% did not have a change or decrease in in TRAb. Anti-TPO and anti-TG also increased; the former showed an increase in 73% and the latter of 52%, while 27 and 48% decreased/were unchanged. A significant positive correlation was found between TRAb and anti-TPO, but not between TRAb and anti-TG. In the group with an increase in TRAb, the median fold change was 5.1, but there were no additional effects of tobacco smoking. The proportion of females below the median age (51.5 years) was significantly higher in the group that increased in TRAb compared to the one that decreased/was unchanged (66 vs. 34%). Conclusions: Treatment with radioiodine elicits an increase in thyroid antibodies, but not in all GD patients. The proportion of responders varied and was affected by age, resulting in a stronger immune response at younger age. However, there were no additional effects of smoking.
|
|
| 44. |
|
|
| 45. |
- Lunden, Hampus, et al.
(författare)
-
An optical power limiting and ultrafast photophysics investigation of a series of multi-branched heavy atom substituted fluorene molecules
- 2019
-
Ingår i: Inorganics. - : MDPI AG. - 2304-6740. ; 7:10
-
Tidskriftsartikel (refereegranskat)abstract
- A common molecular design paradigm for optical power limiting (OPL) applications is to introduce heavy atoms that promote intersystem crossing and triplet excited states. In order to investigate this effect, three multi-branched fluorene molecules were prepared where the central moiety was either an organic benzene unit, para-dibromobenzene, or a platinum(II)-alkynyl unit. All three molecules showed good nanosecond OPL performance in solution. However, only the dibromobenzene and Pt-alkynyl compounds showed strong microsecond triplet excited state absorption (ESA). To investigate the photophysical cause of the OPL, especially for the fully organic molecule, photokinetic measurements including ultrafast pump-probe spectroscopy were performed. At nanosecond timescales, the ESA of the organic molecule was larger than the two with intersystem crossing (ISC) promoters, explaining its good OPL performance. This points to a design strategy where the singlet-state ESA is balanced with the ISC rate to increase OPL performance at the beginning of a nanosecond pulse.
|
|
| 46. |
- Lunden, Hampus, et al.
(författare)
-
Dispersion and self-orientation of gold nanoparticles in sol-gel hybrid silica - optical transmission properties
- 2015
-
Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry. - 2050-7526 .- 2050-7534. ; 3:5, s. 1026-1034
-
Tidskriftsartikel (refereegranskat)abstract
- Silica-based hybrid materials doped with gold nanoparticles (AuNPs) of different shapes were prepared with an adapted sol-gel technology (using MTEOS) and polished to high optical quality. Both spherical (23 and 45 nm in diameter) and bipyramidal (36, 50 and 78 nm in length) AuNPs were prepared and used as dopants. The AuNPs were functionalized with a novel silicone polymer for compatibilization with the sol-gel medium. The glass materials showed well defined localized surface plasmon resonance (SPR) absorbance from the visible to NIR. No redshifts in the spectra, due to the increase in doping concentration, were observed in the glasses, proving that no or very small SPR coupling effects occur. Spectroscopic Muller Matrix Ellipsometry showed that the shorter bipyramidal AuNPs (36 and 50 nm in length) have a clear preferred orientation in the MTEOS matrix, i.e. a tendency to be oriented with their long axis in the plane parallel to the glass surfaces. Dispersions of AuNPs have proven to be good optical power limiters that depend on particle size and geometry. The solid-state glass materials showed good optical power limiting at 532 nm for nanosecond pulses, which did not depend on the size or geometry of the AuNPs. In contrast to the observation at 532 nm, at 600 nm no optical limiting effect was observed. In these solids, as for dispersions of AuNPs, the optical limiting response is caused by scattering.
|
|
| 47. |
- Lundén, H., et al.
(författare)
-
Efficient reverse saturable absorption of sol-gel hybrid plasmonic glasses
- 2017
-
Ingår i: Optical materials (Amsterdam). - Amsterdam : Elsevier. - 0925-3467 .- 1873-1252. ; 69, s. 134-140
-
Tidskriftsartikel (refereegranskat)abstract
- Monolithic silica sol-gel glasses doped with platinum(II) acetylide complexes possessing respectively four or six phenylacetylene units (PE2-CH2OH and PE3-CH2OH) in combination with various concentrations of spherical and bipyramidal gold nanoparticles (AuNPs) known to enhance non-linear optical absorption, were prepared and polished to high optical quality. The non-linear absorption of the glasses was measured and compared to glasses doped solely with AuNPs, a platinum(II) acetylide with shorter delocalized structure, or combinations of both. At 532 nm excitation wavelength the chromophore inhibited the non-linear scattering previously found for glasses only doped with AuNPs. The measured non-linear absorption was attributed to reverse saturable absorption from the chromophore, as previously reported for PE2-CH2OH/AuNP glasses. At 600 nm strong nonlinear absorption was observed for the PE3-CH2OH/AuNPs glasses, also attributed to reverse saturable absorption. But contrary to previous findings for PE2-CH2OH/AuNPs, no distinct enhancement of the non-linear absorption for PE3-CH2OH/AuNPs was observed. A numerical population model for PE3-CH2OH was used to give a qualitative explanation of this difference. A stronger linear absorption in PE3-CH2OH would cause the highly absorbing triplet state to populate quicker during the leading edge of the laser pulse and this would in turn reduce the influence from two-photon absorption enhancement from AuNPs.
|
|
| 48. |
- Lundén, Hampus, et al.
(författare)
-
How to assess good candidate molecules for self-activated optical power limiting
- 2018
-
Ingår i: Optical Engineering. - : SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS. - 0091-3286 .- 1560-2303. ; 57:3
-
Tidskriftsartikel (refereegranskat)abstract
- Reverse saturable absorbers have shown great potential to attenuate laser radiation. Good candidate molecules and various particles have successfully been incorporated into different glass matrices, enabling the creation of self-activated filters against damaging laser radiation. Although the performance of such filters has been impressive, work is still ongoing to improve the performance in a wider range of wavelengths and pulse widths. The purpose of this tutorial is, from an optical engineering perspective, to give an understanding of the strengths and weaknesses of this class of smart materials, how relevant photophysical parameters are measured and influence system performance and comment on the pitfalls in experimental evaluation of materials. A numerical population model in combination with simple physical formulas is used to demonstrate system behavior from a performance standpoint. Geometrical reasoning shows the advantage of reverse saturable absorption over nonlinear scattering due to a fraction of scattered light being recollected by imaging system optics. The numerical population model illustrates the importance of the optical power limiting performance during the leading edge of a nanosecond pulse, which is most strongly influenced by changes in the two-photon absorption cross section and the triplet linear absorption cross section for a modeled Pt-acetylide. This tutorial not only targets optical engineers evaluating reverse saturable absorbing materials but also aims to assist researchers with a chemistry background working on optical power limiting materials. We also present photophysical data for a series of coumarins that can be useful for the determination of quantum yields and two-photon cross sections and show examples of characterization of molecules with excited triplet states. (c) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE).
|
|
| 49. |
- Lundén, Hampus
(författare)
-
Nonlinear materials for optical power limiting : characterization and modelling
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High power laser pulses can be a threat to optical sensors, including the human eye. Traditionally this threat has been alleviated by colour filters that block radiation in chosen wavelength ranges. Colour filters’ main drawback is that they block radiation regardless of it being useful or damaging, information is lost for wavelengths at which the filter is active. Protecting the entire wavelength range of a sensor would block or strongly attenuate the radiation needed for the operation of the sensor.Sol-gel glasses highly doped with optically non-linear chromophores have previously shown high optical quality in combination with efficient optical power limiting (OPL) through reverse saturable absorption (RSA). These filters transmit visible light unless the light fluence is above a certain threshold. A key design consideration of laser protection filters is linear absorption in relation to the threshold level. A high linear absorption means that the user’s view is degraded by the filter.To model the photokinetics of RSA chromophores, the five-level population model is widely used. It consists of three singlet and two triplet levels. Model parameters relevant for OPL performance include linear absorption cross-sections, two-photon absorption (2PA) cross-sections, lifetimes, quantum yields and inter-system-crossing (ISC) times. The dominant design paradigm is to have a highly absorbing and long-lived triplet state that is quickly populated by ISC during the beginning of a laser pulse.To simultaneously achieve a lower threshold and linear absorption a vast number of materials for self-activated filters were evaluated, either as bulk glasses or solutions. An f/5 setup was used to evaluate their OPL performance while several photophysical measurements were performed to gain an understanding of system behaviour. The first three series of methyltriethoxysilane (MTEOS) Sol-Gel glasses were doped with gold nanoparticles either solely, or with one of two Pt-acetylide chromophores. One with shorter conjugated ligands, the second with similar but longer conjugated ligands. Finally, a series of multi-branched fluorene chromophores were evaluated in solution. Their central moiety was either an organic benzene unit or an ISC promoter in the form of para-dibromobenzene or a platinum(II)-alkynyl unit.For the gold nanoparticle doped glasses, the lower performance Pt-acetylide with short ligands had its OPL threshold lowered at 600nm while the glasses doped with only gold nanoparticles showed no OPL at all. Secondly, the enhancement was most pronounced for very low gold nanoparticle concentrations. While gold nanoparticles alone showed good OPL performance at 532 nm, at this wavelength neither Pt-acetylide showed an obvious OPL enhancement beyond linear absorption losses from codoping with gold nanoparticles.The improved OPL performance at 600 nm was attributed to stronger 2PA, by electric field enhancement from the gold nanoparticles. The lack of detectable OPL improvement for 532 nm and for the higher performance Pt-Acetylide chromophore with long ligands were qualitatively explained by a lower sensitivity to 2PA on system performance. A degraded performance from linear absorption by excess nanoparticles in front of the focus explained the weakening of the enhancement at higher gold nanoparticle concentrations.All three fluorene chromophores, including the chromophore without a central ISC promoter, showed broadband OPL through the visible spectrum. The OPL performance of the two chromophores with ISC promoters was expected considering their transient absorption at microsecond time-scales. For the fluorene chromophore without an ISC-promoter, ultra-fast transient absorption was used to identify singlet excited state absorption as the source of the OPL performance.Both of these series of experiments demonstrate how a simplistic view of simply increasing desired photophysical parameters, e.g. effective 2PA cross-section or ISC quantum yield, do not always result in a noticeable increase in system performance. By employing numerical population models it was possible to identify which parameters had the highest impact on OPL performance.
|
|
| 50. |
- Lundén, Hampus
(författare)
-
Sol-Gel Glasses Doped with Pt-Acetylides and Gold Nanoparticles for Enhanced Optical Power Limiting
- 2017
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- High power laser pulses can be a threat to sensors, including the human eye. Traditionally this threat has been alleviated by colour filters that blocks radiation in chosen wavelength ranges. Colour filters’ main drawback is that they block radiation regardless of it being useful or damaging, information is removed for wavelengths at which the filter protect. Protecting the entire wavelength range of a sensor would block or strongly attenuate the radiation needed for the operation of the sensor.Sol-gel glasses highly doped with Pt-Acetylide chromophores have previously shown high optical quality in combination with efficient optical power limiting through reverse saturable absorption1. These filters will transmit visible light unless the light fluence is above a certain threshold. A key design consideration of laser protection filters is linear absorption in relation to threshold level. By increasing chromophore concentration the threshold is lowered at the expense of higher linear absorption. This means that the user’s view is degraded through the filter.Adding small amounts of gold nanoparticles to the glasses resulted in an increase in optical power limiting performance. The optimal concentration of gold nanoparticles corresponded to a mean particle distance of several micrometers. The work in this licentiate thesis is about the characterization and explanation of this effect.The glasses investigated in this work were MTEOS Sol-Gel glasses doped with either only gold nanoparticles of varying shape and concentration, 50mM of PE2-CH2OH codoped with gold nanoparticles or 50mM of PE3-CH2OH codoped with gold nanoparticles. The glasses only doped with gold nanoparticles showed high optical power limiting performance at 532nm laser wavelength, but no optical power limiting at the fluences tested at 600nm. The PE2-CH2OH glasses codoped with gold nanoparticles showed an enhancement of optical power limiting at 600nm for the low gold nanoparticle concentration glasses. The enhancement was weakened or not present for higher concentrations. A similar enhancement above noise level for the PE3-CH2OH glasses was not found.A population model is used to give a qualitative explanation of the findings. The improvement in optical power limiting performance for the PE2-CH2OH glasses is explained by the gold nanoparticles helping to more quickly populate the highly absorbing triplet state during the rising edge of the laser pulse by enhancing two-photon absorption. The lack of any marked enhancement for the PE3-CH2OH glasses is explained by the PE3-CH2OH chromophore already being of sufficiently high performance to quickly populate the highly absorbing triplet state during the rising edge of the laser pulse. Further work is necessary to validate this model against other chromophores and improving its quantitative predictive power.
|
|
