| 1. |
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| 2. |
- Jarvius, Jonas, et al.
(författare)
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Digital Quantification using Amplified Single-Molecule Detection
- 2006
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Ingår i: Nature Methods. - 1548-7091 .- 1548-7105. ; 3:9, s. 725-727
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Tidskriftsartikel (refereegranskat)abstract
- We describe a scheme for biomolecule enumeration by converting nanometer-scale specific molecular recognition events mediated by rolling-circle amplification to fluorescent micrometer-sized DNA molecules amenable to discrete optical detection. Our amplified single-molecule detection (SMD) approach preserves the discrete nature of the molecular population, allowing multiplex detection and highly precise quantification of molecules over a dynamic range of seven orders of magnitude. We apply the method for sensitive detection and quantification of the bacterial pathogen Vibrio cholerae.
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| 3. |
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| 4. |
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| 5. |
- Melin, Jonas, et al.
(författare)
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Homogeneous amplified single-molecule detection : Characterization of key parameters
- 2007
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Ingår i: Analytical Biochemistry. - : Elsevier BV. - 0003-2697 .- 1096-0309. ; 368:2, s. 230-238
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Tidskriftsartikel (refereegranskat)abstract
- We recently presented a method that enables single-molecule enumeration by transforming specific molecular recognition events at nanometer dimensions to micrometer-sized DNA macromolecules. This transformation process is mediated by target-specific padlock probe ligation, followed by rolling circle amplification (RCA), resulting in the creation of one rolling circle product (RCP) for each recognized target. The transformation makes optical detection and quantification possible using standard fluorescence microscopy by counting the number of generated RCPs in a sample pumped through a microfluidic channel. In this study, we demonstrate that confocal volume definition is crucial to achieve high-precision measurements in the microfluidic quantification (coefficient of variance typically 3%). We further demonstrate that complementary sequence motifs between RCPs is only a weak inducer of aggregates and that all detection sites of the RCPs are occupied at detection oligonucleotide concentrations greater than 5 nM if hybridized in the proper buffer conditions. Therefore, the signal/noise ratio is limited by the number of detection sites. By increasing the density of detection sites in the RCP by a factor of 1.9, we show that the optical signal/noise level can be increased from 42 to 75.
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| 6. |
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| 7. |
- Melin, Jonas, et al.
(författare)
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Ligation-based molecular tools for lab-on-a-chip devices
- 2008
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Ingår i: New Biotechnology. - : Elsevier BV. - 1871-6784. ; 25:1, s. 42-8
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Tidskriftsartikel (refereegranskat)abstract
- Molecular diagnostics can offer early detection of disease, improved diagnostic accuracy, and qualified follow-up. Moreover, the use of microfluidic devices can in principle render these analyses quickly and user-friendly, placing them within the reach of the general practitioner and maybe even in households. However, the progress launching such devices has been limited so far. We propose that an important limiting factor has been the difficulty of establishing molecular assays suitable for microfabricated formats. The assays should be capable of monitoring a wide range of molecules, including genomic DNA, RNA and proteins with secondary modifications and interaction partners, and they must exhibit excellent sensitivity and specificity. We discuss these problems and describe a series of molecular tools that may present new opportunities for lab-on-a-chip devices at the point-of-care.
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| 8. |
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| 9. |
- Melin, Jonas, et al.
(författare)
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Thermoplastic microfluidic platform for single-molecule detection, cell culture and actuation
- 2005
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 77:22, s. 7122-30
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Tidskriftsartikel (refereegranskat)abstract
- We have developed a multipurpose microfluidic platform that allows for sensitive fluorescence detection on inexpensive disposable chips. The fabrication scheme involves rapid injection molding of thermoplastics, followed by silica deposition and covalent attachment of an unstructured flexible lid. This combines the virtues of elastomer technology with high-throughput compact disk injection molding. Using this technique, the time to produce 100 chips using a single master can be lowered from more than 1 week by standard PDMS technologies to only a couple hours. The optical properties of the fabricated chips were evaluated by studying individual fluorescence-labeled DNA molecules in a microchannel. Concatemeric DNA molecules were generated through rolling circle replication of circular DNA molecules, which were labeled by hybridization of fluorescence-tagged oligonucleotides. Rolling circle products (RCPs) were detected after as little as 5 min of DNA polymerization, and the RCPs in solution showed no tendency for aggregation. To illustrate the versatility of the platform, we demonstrate two additional applications: The flexible property of the lid was used to create a peristaltic pump generating a flow rate of 9 nL/s. Biocompatibility of the platform was illustrated by culturing Chinese hamster ovary cells for 7 days in the microfluidic channels.
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| 10. |
- Pinidiyaarachchi, Amalka, et al.
(författare)
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Digital image processing for multiplexing of single molecule detection
- 2005
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Ingår i: Medicinteknikdagarna.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Using padlock and proximity probing techniques, individual molecular identification events are converted to long DNA molecules, carrying repeated sequence motifs used for identification of the detected molecules. We show that identification events can be amplified using rolling circle replication, and randomly attached to a surface for repeated access by identification probes. Repeated hybridization with detection probes carrying fluorescing nano-crystals (quantum dots) of varying spectral properties opens the possibility to search for large numbers of different identification events simultaneously. Methods for digital image processing of the resulting multi-spectral data include spatial as well as spectral data clustering. Spatial data processing includes registration of images from repeated hybridization events as well as delineation of clustered reporter events. Spectral data processing and analysis includes classification of spectral data into groups of either pre-defined or unknown patterns representing different molecular identification events.
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| 11. |
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| 12. |
- Christensen, Jonas, 1963-, et al.
(författare)
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The Beautiful Risk of Collaborative and Interdisciplinary Research. A Challenging Collaborative and Critical Approachtoward Sustainable Learning Processes in Academic Profession
- 2021
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Ingår i: Sustainability. - Basel : MDPI. - 2071-1050. ; 13, s. 1-20
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we aim to identify and explore possibilities and challenges of academicinterdisciplinary capacities and ethos. The objective is that this knowledge could be used both infuture interdisciplinary research projects and in educational settings. We achieve this through selfreflectivelearning processes among a group of interdisciplinary scholars from four distinctly differentsubjects. The method used is an autoethnographic and empirical self-reflective approach to datacollection, analysis and deconstruction of professional learning processes. This also serves to establishresearch methodological trustworthiness and authenticity. The results show that interdisciplinarityis undervalued by grant-giving institutions and the academic system, in general. It also entailstime-consuming and risky research practices. However, interdisciplinary and collaborative researchcreates a more innovative and stimulating learning environment and enforces new ways of thinkingand doing, in ascertaining each individual’s knowledge and competences. We argue that a long-terminterdisciplinary and collaborative research process could enhance and raise a critical thinking andcreative consciousness among scholars, contributing to a more holistic, sustainable and socially robustlearning in research and higher education. Finally, we conclude that this academic interdisciplinarycapacity and ethos could be framed and enhanced by the notion of Challenge-Based Learning.
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| 13. |
- Christersson, Cecilia E., et al.
(författare)
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Challenge-Based Learning in Higher Education : A Malmö University Position Paper
- 2022
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Ingår i: International Journal of Innovative Teaching and Learning in Higher Education. - : IGI Global. - 2644-1624 .- 2644-1640. ; 3:1, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- Higher education institutions (HEIs) have a pivotal role in fulfilling the social dimension of sustainability and contributing to a complex changing society. To meet these challenges, Malmö University has in interdisciplinary groups researched the role of challenge-based learning (CBL) in relation to staff, students, disciplines, and stakeholders. This position paper is based on that work. Malmö University argues that with a CBL approach, HEIs will actively contribute to the building of a sustainable learning society through collaboration in education, research, and innovation. This paper theoretically explores the CBL approach as a collaborative learning exchange within HEIs and society at large. CBL is defined through eight key elements, clustered as entities of three domains: diversity and inclusion, co-creation and collaboration, and change agents and contextual challenges. These are discussed and empirically exemplified with the purpose to support designing, planning, and accomplishing CBL in teaching and learning in HE for a global learning society.
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| 14. |
- Dahlin, Anna M., 1979-, et al.
(författare)
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A genome-wide association study on medulloblastoma
- 2020
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Ingår i: Journal of Neuro-Oncology. - : Springer. - 0167-594X .- 1573-7373. ; 147:2, s. 309-315
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Medulloblastoma is a malignant embryonal tumor of the cerebellum that occurs predominantly in children. To find germline genetic variants associated with medulloblastoma risk, we conducted a genome-wide association study (GWAS) including 244 medulloblastoma cases and 247 control subjects from Sweden and Denmark.Methods: Genotyping was performed using Illumina BeadChips, and untyped variants were imputed using IMPUTE2.Results: Fifty-nine variants in 11 loci were associated with increased medulloblastoma risk (p < 1 × 10–5), but none were statistically significant after adjusting for multiple testing (p < 5 × 10–8). Thirteen of these variants were genotyped, whereas 46 were imputed. Genotyped variants were further investigated in a validation study comprising 249 medulloblastoma cases and 629 control subjects. In the validation study, rs78021424 (18p11.23, PTPRM) was associated with medulloblastoma risk with OR in the same direction as in the discovery cohort (ORT = 1.59, pvalidation = 0.02). We also selected seven medulloblastoma predisposition genes for investigation using a candidate gene approach: APC, BRCA2, PALB2, PTCH1, SUFU, TP53, and GPR161. The strongest evidence for association was found for rs201458864 (PALB2, ORT = 3.76, p = 3.2 × 10–4) and rs79036813 (PTCH1, ORA = 0.42, p = 2.6 × 10–3).Conclusion: The results of this study, including a novel potential medulloblastoma risk loci at 18p11.23, are suggestive but need further validation in independent cohorts.
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| 15. |
- Dahlin, Anna M., 1979-, et al.
(författare)
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Genetic Variants in the 9p21.3 Locus Associated with Glioma Risk in Children, Adolescents, and Young Adults : A Case-Control Study
- 2019
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Ingår i: Cancer Epidemiology, Biomarkers and Prevention. - : American Association for Cancer Research. - 1055-9965 .- 1538-7755. ; 28:7, s. 1252-1258
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Tidskriftsartikel (refereegranskat)abstract
- Background: Genome-wide association studies have identified germline genetic variants in 25 genetic loci that increase the risk of developing glioma in adulthood. It is not known if these variants increase the risk of developing glioma in children and adolescents and young adults (AYA). To date, no studies have performed genome-wide analyses to find novel genetic variants associated with glioma risk in children and AYA.Methods: We investigated the association between 8,831,628 genetic variants and risk of glioma in 854 patients diagnosed up to the age of 29 years and 3,689 controls from Sweden and Denmark. Recruitment of patients and controls was population based. Genotyping was performed using Illumina BeadChips, and untyped variants were imputed with IMPUTE2. We selected 41 established adult glioma risk variants for detailed investigation.Results: Three adult glioma risk variants, rs634537, rs2157719, and rs145929329, all mapping to the 9p21.3 (CDKN2B-AS1) locus, were associated with glioma risk in children and AYA. The strongest association was seen for rs634537 (odds ratioG = 1.21; 95% confidence interval = 1.09–1.35; P = 5.8 × 10−4). In genome-wide analysis, an association with risk was suggested for 129 genetic variants (P <1 × 10−5).Conclusions: Carriers of risk alleles in the 9p21.3 locus have an increased risk of glioma throughout life. The results from genome-wide association analyses require validation in independent cohorts.Impact: Our findings line up with existing evidence that some, although not all, established adult glioma risk variants are associated with risk of glioma in children and AYA. Validation of results from genome-wide analyses may reveal novel susceptibility loci for glioma in children and AYA.
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| 16. |
- Forzati, Marco, et al.
(författare)
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40-gb/s field transmission through 540 km ssmf using the aprz modulation format
- 2005
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Ingår i: Optics InfoBase Conference Papers. - : Optical Society of America. - 1557527849 - 9781557527844
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Konferensbidrag (refereegranskat)abstract
- We report the first field transmission experiment using the APRZ modulation format for 40-Gb/s transmission through 540 km SSMF, which confirms the improved nonlinear tolerance of APRZ. The optimum phase-modulation amplitude in this experiment is p/2.
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| 17. |
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| 18. |
- Foss-Skiftesvik, Jon, et al.
(författare)
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Multi-ancestry genome-wide association study of 4069 children with glioma identifies 9p21.3 risk locus
- 2023
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Ingår i: Neuro-Oncology. - : Oxford University Press. - 1522-8517 .- 1523-5866. ; 25:9, s. 1709-1720
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Although recent sequencing studies have revealed that 10% of childhood gliomas are caused by rare germline mutations, the role of common variants is undetermined and no genome-wide significant risk loci for pediatric central nervous system tumors have been identified to date.METHODS: Meta-analysis of 3 population-based genome-wide association studies comprising 4069 children with glioma and 8778 controls of multiple genetic ancestries. Replication was performed in a separate case-control cohort. Quantitative trait loci analyses and a transcriptome-wide association study were conducted to assess possible links with brain tissue expression across 18 628 genes.RESULTS: Common variants in CDKN2B-AS1 at 9p21.3 were significantly associated with astrocytoma, the most common subtype of glioma in children (rs573687, P-value of 6.974e-10, OR 1.273, 95% CI 1.179-1.374). The association was driven by low-grade astrocytoma (P-value of 3.815e-9) and exhibited unidirectional effects across all 6 genetic ancestries. For glioma overall, the association approached genome-wide significance (rs3731239, P-value of 5.411e-8), while no significant association was observed for high-grade tumors. Predicted decreased brain tissue expression of CDKN2B was significantly associated with astrocytoma (P-value of 8.090e-8).CONCLUSIONS: In this population-based genome-wide association study meta-analysis, we identify and replicate 9p21.3 (CDKN2B-AS1) as a risk locus for childhood astrocytoma, thereby establishing the first genome-wide significant evidence of common variant predisposition in pediatric neuro-oncology. We furthermore provide a functional basis for the association by showing a possible link to decreased brain tissue CDKN2B expression and substantiate that genetic susceptibility differs between low- and high-grade astrocytoma.
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| 19. |
- Franks, P. W., et al.
(författare)
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Technological readiness and implementation of genomic-driven precision medicine for complex diseases
- 2021
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Ingår i: Journal of Internal Medicine. - : Wiley. - 0954-6820 .- 1365-2796. ; 290:3, s. 602-620
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Forskningsöversikt (refereegranskat)abstract
- The fields of human genetics and genomics have generated considerable knowledge about the mechanistic basis of many diseases. Genomic approaches to diagnosis, prognostication, prevention and treatment - genomic-driven precision medicine (GDPM) - may help optimize medical practice. Here, we provide a comprehensive review of GDPM of complex diseases across major medical specialties. We focus on technological readiness: how rapidly a test can be implemented into health care. Although these areas of medicine are diverse, key similarities exist across almost all areas. Many medical areas have, within their standards of care, at least one GDPM test for a genetic variant of strong effect that aids the identification/diagnosis of a more homogeneous subset within a larger disease group or identifies a subset with different therapeutic requirements. However, for almost all complex diseases, the majority of patients do not carry established single-gene mutations with large effects. Thus, research is underway that seeks to determine the polygenic basis of many complex diseases. Nevertheless, most complex diseases are caused by the interplay of genetic, behavioural and environmental risk factors, which will likely necessitate models for prediction and diagnosis that incorporate genetic and non-genetic data.
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| 20. |
- Grindal, Mats, et al.
(författare)
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On the Testing Maturity of Software Producing Organizations
- 2006
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Ingår i: Proceedings of the 1st International Conference Testing : Academia & Industry Conference Practice And Research Techniques (TAIC PART), 29th-31st August, Cumberland Lodge, Windsor, UK.
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Konferensbidrag (refereegranskat)
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| 21. |
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| 22. |
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| 23. |
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| 24. |
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| 25. |
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| 26. |
- Hedsten, Karin, 1964, et al.
(författare)
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MEMS-based VCSEL beam steering using replicated polymer diffractive lens
- 2008
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Ingår i: Sensors and Actuators, A: Physical. - : Elsevier BV. - 0924-4247 .- 1873-3069. ; 142:1, s. 336-345
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Tidskriftsartikel (refereegranskat)abstract
- Abstract. This paper describes a fully integrated micro-optical system, in which dynamic angular control of the beam from a VCSEL (vertical cavity surface emitting laser) is realized by laterally moving a collimat¬ing diffractive lens in the light path. The lens is mounted on a translatable silicon stage, which consists of a frame with an opening for the light to traverse the lens and electro-statically driven comb actuators, by which the lateral movement is achieved. Devices implementing both 1D and 2D scanning have been fabricated and evaluated. Integration of the lens onto the translatable silicon stage is done using a newly developed fabrication process based on hot embossing of an amorphous fluorocarbon polymer. This fabrication process relies on a reversed-order protocol, where the structuring of the optical element precedes the silicon microstructuring. Assembly and packaging of the VCSEL-MOEMS system, using LTCC (low temperature cofired ceramic) technique, is also demonstrated. Optical evaluation of the system and beam steering function shows significant beam deflection for a relatively low driving voltage (~70 V).
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| 27. |
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| 28. |
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| 29. |
- Kundrat, J., et al.
(författare)
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GNPy : Lessons Learned and Future Plans [Invited]
- 2022
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Ingår i: 2022 European Conference on Optical Communication, ECOC 2022. - : Institute of Electrical and Electronics Engineers Inc.. - 9781957171159
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Konferensbidrag (refereegranskat)abstract
- We discuss the history, past challenges and future plans of GNPy, an open source project for simulating physical impairments in contemporary DWDM network. The paper describes the unique interaction among network operators, equipment vendors, and standard bodies, as well as challenges in implementing the digital twin of an optical network.
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| 30. |
- Lintzén, Nina, 1978-, et al.
(författare)
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Laboratory Investigation of Different Insulating Materials Used for Snow Storage
- 2019
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Ingår i: Journal of cold regions engineering. - : American Society of Civil Engineers (ASCE). - 0887-381X .- 1943-5495. ; 33:4
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Tidskriftsartikel (refereegranskat)abstract
- Storage of snow has become of increasing interest for the winter business industry. Covering a pile of snow with an insulating material protects the snow from heat transfer from the surroundings and reduces the melting. Storing snow enables ski resorts to set an opening date, and it can also be used to secure winter sports events that are dependent on snow. Cover materials that are commonly used as insulation are wood-based materials, such as sawdust, and textile materials and sheets. How efficiently a cover material functions as thermal insulation depends on the material characteristics and thickness of the insulating layer. In this study, results from a laboratory experiment are presented, which aimed at comparing different commonly used cover materials, as well as some other materials that have not previously been used as thermal insulation on snow. Different layer thicknesses were also investigated. The results show that the insulating capacity of sawdust is reduced with time. Despite degrading insulating properties with time, sawdust is still considered one of the best materials to use as insulation on snow, and it is also more efficient than the textile materials investigated in this study. Doubling the textile layers or adding a three-dimensional (3D) spacer textile, which implies adding a layer of air between the textile and the snow, reduces the snow melting. Water absorption, water transport, and evaporation of water affect the melting. In this work, evaporative cooling did not prove to reduce melting; therefore, it was not evident whether a textile material should be permeable. An interesting material used in the study was Quartzene, which absorbed all the melt water and protected the snow most efficiently of the materials tested.
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| 31. |
- Mahmoudian, Laili, et al.
(författare)
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Microchip electrophoresis for detection of circle-to-circle amplification products towards sensitive and rapid DNA analysis
- 2007
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Ingår i: Chemistry Letters. - 0366-7022 .- 1348-0715. ; 36:3, s. 396-397
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Tidskriftsartikel (refereegranskat)abstract
- A new method for fast and precise analysis of circle-to-circle amplification (C2CA) products by microchip electrophoresis has been developed. Stable C2CA products were produced by applying a new enzymatic step to C2CA. Detection was carried out within 55s with RSD of migration time of 3.6% (it = 6) enabling reproducibility and high speed. A real sample of bacterial pathogen (V. Cholerae) at single nucleotide level was detected successfully based on this method.
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| 32. |
- Mahmoudian, Laili, et al.
(författare)
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Microchip electrophoresis for specific gene detection of the pathogenic bacteria V. cholerae by circle-to-circle amplification
- 2008
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Ingår i: Analytical Sciences. - 0910-6340 .- 1348-2246. ; 24:3, s. 327-32
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Tidskriftsartikel (refereegranskat)abstract
- We have developed a new method for a fast and precise analysis of circle-to-circle amplification (C2CA) product for specific gene detection by microchip electrophoresis. In this method, we have added a new enzymatic step to the C2CA reaction, which could be carried out isothermally at 37 degrees C. Compared to the original single-stranded DNA, the double-stranded DNA that is produced by this enzymatic reaction is more reliable for analysis by microchip electrophoresis. C2CA product was detected within 55 s with high reproducibility by this method which was successfully applied to the detection of 10-ng genomic DNA of the pathogenic bacteria Vibrio. cholerae within 110 s. Purification was found to be an indispensable step for the analysis of the C2CA product of genomic DNA samples.
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| 33. |
- Melin, Jonas, et al.
(författare)
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Microreplication in a Silicon Processing Compatible Material
- 2005
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Ingår i: IEEE/LEOS Optical MEMS 2005: International Conference on Optical MEMS and Their Applications, Oulu, Finland, 1-4 August 2005. - 9780780392786 ; , s. 89-90
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Konferensbidrag (refereegranskat)abstract
- We present a novel fabrication process for the integration of polymer micro-optical elements on silicon. The process relies on a reverse order protocol based on embossing in an amorphous fluorocarbon polymer, Cytop™.
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| 34. |
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| 35. |
- Melin, Jonas, 1976-
(författare)
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Single-Molecule Detection and Optical Scanning in Miniaturized Formats
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In later years polymer replication techniques have become a frequently employed fabrication method for microfluidic and micro-optical devices. This thesis describes applications and further developments of microstructures replicated in polymer materials. A novel method for homogenous amplified single-molecule detection utilizing a microfluidic readout format is presented. The method enables enumeration of single biomolecules by transforming specific molecular recognition events at nanometer dimensions to micrometer-sized DNA macromolecules. This transformation process is mediated by target specific padlock probe ligation, followed by rolling circle amplification (RCA) resulting in the creation of one rolling circle product (RCP) for each recognized target. Throughout this transformation the discrete nature of the molecular population is preserved. By hybridizing a fluorescence-labeled DNA detection oligonucleotide to each repeated sequence of the RCP, a confined cluster of fluorophores is generated, which makes optical detection and quantification possible. Spectral multiplexing is also possible since the spectral profile of each RCP can be analyzed separately. The microfluidic data acquisition process is characterized in detail and conditions that allow for quantification limited only by Poisson sampling statistics is established. The molecular characteristics of RCPs in solution are also investigated.Furthermore a novel thermoplastic microfluidic platform is described. The platform allows for observation of the microchannels using high magnification optics and also offers the possibility of on-chip cell culture and the integration of mechanical actuators.A novel fabrication process for the integration of polymer micro-optical elements on silicon is presented. The process is used for fabrication of a micro-optical system consisting of a laser and a movable microlens making beam steering possible. Such a micro-scanning system could potentially be used for miniaturized biochemical analysis.
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| 36. |
- Melin, L G, et al.
(författare)
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Evaluation of four composite shear test methods by digital speckle strain mapping and fractographic analysis
- 2000
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Ingår i: Journal of composites technology & research. - 0884-6804 .- 1945-7537. ; 22:3, s. 161-172
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Tidskriftsartikel (refereegranskat)abstract
- Four methods to determine composite interlaminar shear strength (ILSS) are evaluated. In particular, the recently devised inclined double-notch shear test (IDNS) is compared with three existing and more established methods: the Iosipescu test, the short three-point bending test (S3PB) and the double-notch compression test (DNC). The uniformity of strain field in the test region in a real test situation-which is the crucial test method quality parameter-is investigated by strain mapping using digital speckle photography. The measured strain fields are compared with FE-calculated strains representing ideal conditions and both known advantages and drawbacks of the different methods are confirmed. The IDNS test produces the most uniform strain fields and also consistently high ILSS values. A fractographic analysis indicates shear separation over a major part of the fracture surfaces of all specimen types; typical shear cusps were found over about 80% of the IDNS fracture surface and in about 50% to 70% in the other specimens. For the Iosipescu tests, failure initiation could be ascribed to initiation in tension at defects. Experimentally determined stress-strain responses in shear exhibit a distinct variation among the different methods. For the best methods, a notable material softening was observed Drier to failure. Observed formation of shear cusps is believed to be the primary cause for this softening of the composite material studied here.
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| 37. |
- Melin, Niklas, 1978-, et al.
(författare)
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Measuring constitutive shear behavior of orthotropic composites and evaluation of the modified Iosipescu test
- 2006
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Ingår i: Composite structures. - : Elsevier BV. - 0263-8223 .- 1879-1085. ; 76:1-2, s. 106-115
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Tidskriftsartikel (refereegranskat)abstract
- The modified Iosipescu test uses a variable notch opening angle 0, depending on the material anisotropy and orientation, to accomplish even stress- and strain-fields in the test region. Constitutive shear properties can thus be measured more accurately, more completely, and with fewer sources of error. Here more materials and properties were studied, and a 3D optical strain- and displacement-monitoring system was used to evaluate and improve both the modified test and the novel fixture used here. It performed substantially better than the commonly used Wyoming fixture in terms of producing constant through specimen thickness conditions and preventing undesired specimen twisting. Additionally, loading-unloading behavior of two high-performance, essentially unidirectional, fiber composites was investigated to assess stiffness reduction, damage, localization, and irreversible strains. In the present of such, well controlled testing conditions are even more important.
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| 38. |
- Melin, Niklas, 1978-, et al.
(författare)
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Sensitivity to specimen imperfections of Ioisipescu shear for composite laminates
- 2007
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Ingår i: 16th International Conference on Composite Materials, ICCM-16. - 9784931136052
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The influence of imperfections in specimen geometry is studied for the Ioispescu test. With FE-analyses and experimental verifications, it is found that slight deviations from nominal geometry in the specimen gripping section may cause errors in measured/calculated strain levels by up to 100%, or even more. Unacceptably large errors may occur already for imperfections in the order of 0.01 mm. Most critical is the case when gripping surfaces are tilted towards each other, giving a stubbed conical shape of the cross section. A rhomboidal cross section does not cause as large front-to-back differences but produces uneven, skewed strain profiles. Numerical calculations show the severity of, and sensitivity to, such imperfections for both isotropic materials and orthotropic composites. And experiments with aluminum- and uniaxial carbon fiber composite specimens with controlled geometrical deviations verify, using in-situ strain field monitoring, that the same phenomena occur also in real experiments, and at comparable magnitudes.
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| 39. |
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| 40. |
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| 41. |
- Melin, Niklas, 1978-
(författare)
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The modified Iosipescu shear test for orthotropic materials
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- AbstractThe Iosipescu shear test, also known as asymmetric four point bending of a V-notched beam,is frequently used for measuring in-plane shear properties of composites. The ASTM standard(ASTM D-5379-05) regulates how the test is to be performed. It prescribes a notch openingangle of 90° independently of the material tested, although this has proven to produceinhomogenous strain distributions in the test region (between the notches) for orthotropicmaterials. Commonly, strain gauges are attached in the center of the test region where thedeviation from average strain is high. Thus, systematic errors in the measurement in the rangeof 10% or more may be introduced.The modified Iosipescu shear test, presented in this thesis, uses a variable notch opening angledepending on the material orthotropy and orientation to accomplish even stress- and strainfields in the test region. The variable notch opening angle accommodates both anisotropicmaterials and their orientation. Based on an elastic rescaling theory for orthotropic materials,the geometry was rescaled to recreate the same stress distribution in the test region as forisotropic materials. Specifically the notch opening angle was rescaled depending on theorthotropic ratio, the ratio of the two in-plane principal stiffnesses (Ex/Ey), to obtain theoptimal notch geometry. The rescaling procedure has been verified numerically with FEsimulationsand experimentally for several materials of different orthotropic ratio showingthat this was a very feasible method. Using a whole field optical measurement system duringtesting, significantly more homogenous strain fields were observed than for the standardspecimen geometry. Thus, there is no longer any need for correction factors, relying on FEsimulation,to obtain correct shear moduli. Constitutive shear properties and strength can thusbe more accurately measured, more completely and with fewer sources of error. Notablyhigher shear strengths at larger strains were also recorded compared to standard testing.The function of the new fixture was evaluated and compared with the standard Wyomingfixture. Combined in-situ 3D deformation measurements of both the new fixture and thespecimen showed that out of plane specimen deformation was very low and substantiallylower than the Wyoming fixture. Thus considerably lower parasitic stresses are introducedwith the new fixture.Recommendations regarding fastening of the specimen were determined based on simpleanalysis combined with FE-calculations and experiments. For both isotropic and orthotropic itwas found favorable if the clamp load used to hold the specimen and the expected net peakload and were set about equal. This reduces the risk of failure outside the test region bycrushing, brushing, splitting and etc. The same effects as shown in the FE-simulations werealso observed experimentally and of similar relative magnitude.Problems with differences in strains arising on the front and back face of the specimen duringtesting have been frequently reported in the literature. This is believed to stem from deviationsfrom nominal specimen geometry such as non-parallel and/or non-perpendicular boundingsurfaces. Three types of these combinations were evaluated numerically and the two mostsignificant were confirmed experimentally. The most critical geometrical deviation assessedwas a specimen with slightly conical cross section in the gripping region. For both isotropicand orthotropic materials, very small deviations from nominal geometry, caused unacceptablylarge errors in measurements of constitutive behavior
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| 42. |
- Michaud, Dominique S., et al.
(författare)
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Anthropometric Measures, Physical Activity, and Risk of Glioma and Meningioma in a Large Prospective Cohort Study
- 2011
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Ingår i: Cancer Prevention Research. - Philadelphia, PA : American Association for Cancer Research, Inc.. - 1940-6207 .- 1940-6215. ; 4:9, s. 1385-1392
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Tidskriftsartikel (refereegranskat)abstract
- Body fatness has been associated with increased risk of a number of hormone-dependent cancers. Recent studies suggest that body mass index (BMI) may be related to meningiomas, which are more common in women than men, and for which estrogens are believed to play a role. Using data from a large European propective cohort, 203 incident cases of meningioma and 340 cases of glioma were included in the analysis for measures of body fat, height, and physical activity among 380,775 participants. All analyses were conducted using Cox proportional hazards model and controlling for age, sex, country, and education. A 71% increase in risk of meningioma was observed among men and women in the top quartile of waist circumference (HR = 1.71, 95% CI = 1.08-2.73, P-trend = 0.01). A positive association was also observed for BMI and meningioma (HR = 1.48, 95% CI = 0.98-2.23, for BMI >= 30 compared with a BMI of 20-24.9, P-trend = 0.05). An association with height and meningioma was also suggestive (HR = 1.24, 95% 0.96-1.51, for each 10 cm increase). In contrast, no associations were observed for height and different measures of body fat and risk of glioma. Physical activity was not related to either type of brain tumors. Results from this study support an increase in risk of meningioma with higher body fatness among both men and women. No association was observed between anthropometric measures and risk of glioma. Cancer Prev Res; 4(9); 1385-92. (C) 2011 AACR.
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| 43. |
- Michaud, Dominique S, et al.
(författare)
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Coffee and tea intake and risk of brain tumors in the European prospective investigation into cancer and nutrition (EPIC) cohort study
- 2010
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Ingår i: American Journal of Clinical Nutrition. - : American Society for Nutrition. - 0002-9165 .- 1938-3207. ; 92:5, s. 1145-1150
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Tidskriftsartikel (refereegranskat)abstract
- Background: In a recent US cohort study, total coffee and tea consumption was inversely associated with risk of glioma, and experimental studies showed that caffeine can slow the invasive growth of glioblastoma.Objective: The objective was to examine the relation between coffee and tea intake and the risk of glioma and meningioma in a large European cohort study, the European Prospective Investigation into Cancer and Nutrition (EPIC).Design: Data on coffee and tea intake were collected from men and women recruited into the EPIC cohort study. Over an average of 8.5 y of follow-up, 343 cases of glioma and 245 cases of meningioma were newly diagnosed in 9 countries. We used Cox proportional hazards models to examine the relation between coffee and tea and brain tumors.Results: We observed no associations between coffee, tea, or combined coffee and tea consumption and risk of either type of brain tumor when using quantiles based on country-specific distributions of intake. However, a significant inverse association was observed for glioma risk among those consuming ≥100 mL coffee and tea per day compared with those consuming <100 mL/d (hazard ratio: 0.66; 95% CI: 0.44, 0.97; P = 0.03). The association was slightly stronger in men (hazard ratio: 0.59; 95% CI: 0.34, 1.01) than in women (hazard ratio: 0.74; 95% CI: 0.42, 1.31), although neither was statistically significant.Conclusions: In this large cohort study, we observed an inverse association between total coffee and tea consumption and risk of glioma that was consistent with the findings of a recent study. These findings, if further replicated in other studies, may provide new avenues of research on gliomas.
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| 44. |
- Michaud, Dominique S., et al.
(författare)
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Reproductive Factors and Exogenous Hormone Use in Relation to Risk of Glioma and Meningioma in a Large European Cohort Study
- 2010
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Ingår i: Cancer Epidemiology Biomarkers & Prevention. - 1538-7755 .- 1055-9965. ; 19:10, s. 2562-2569
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Tidskriftsartikel (refereegranskat)abstract
- Background: The etiologies of glioma and meningioma tumors are largely unknown. Although reproductive hormones are thought to influence the risk of these tumors, epidemiologic data are not supportive of this hypothesis; however, few cohort studies have published on this topic. We examined the relation between reproductive factors and the risk of glioma and meningioma among women in the European Prospective Investigation into Cancer and Nutrition (EPIC). Methods: After a mean of 8.4 years of follow-up, 193 glioma and 194 meningioma cases were identified among 276,212 women. Information on reproductive factors and hormone use was collected at baseline. Cox proportional hazard regression was used to determine hazard ratios (HR) and 95% confidence intervals (95% CI). Results: No associations were observed between glioma or meningioma risk and reproductive factors, including age at menarche, parity, age at first birth, menopausal status, and age at menopause. A higher risk of meningioma was observed among postmenopausal women who were current users of hormone replacement therapy (HR, 1.79; 95% CI, 1.18-2.71) compared with never users. Similarly, current users of oral contraceptives were at higher risk of meningioma than never users (HR, 3.61; 95% CI, 1.75-7.46). Conclusion: Our results do not support a role for estrogens and glioma risk. Use of exogenous hormones, especially current use, seems to increase meningioma risk. However, these findings could be due to diagnostic bias and require confirmation. Impact: Elucidating the role of hormones in brain tumor development has important implications and needs to be further examined using biological measurements. Cancer Epidemiol Biomarkers Prev; 19(10); 2562-9. (C) 2010 AACR.
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| 45. |
- Neumeister, Jonas, et al.
(författare)
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A modified Iosipescu Test for Anisotropic Composite Panels
- 2004
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Ingår i: 14th Internatonal Conference on Composite Materials, ICCM-14. ; , s. 121-129
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Konferensbidrag (refereegranskat)abstract
- The Iosipescu (V-notched beam) shear test for in-plane shear properties of composite panels was modified with respect to specimen geometry. The ASTM standard prescribes V notches with 90° opening angle, while the resulting stress field in the test region strongly depends on the material anisotropy. Thus, the test performance depends on actual material properties and material orientation relative to the test region. A variable notch opening angle was proposed to accomodate both material anisotropy and orientation.
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| 46. |
- Neumeister, Jonas, et al.
(författare)
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Specimen Clamping and Performance of the Iosipescu Shear Test Applied for Composite Materials
- 2007
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Ingår i: 16th International Conference on Composite Materials, ICCM-16. - 9784931136052
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Clamping and subsequent loading in shear of Ioispescu specimens is investigated. Combined stresses reach similar, or even higher, levels locally compared the nominal shear stress, both compressive and tensile. Especially for brittle materials, composites, and materials with anisotropic failure modes, these stresses may cause premature failure outside the test region and appropriate clamping levels become important. A clamping ratio (r) between clamping force and peak shear force is introduced, and it is shown that for quasi-isotropic failure modes, the overall lowest detrimental stresses are obtained for about r ∼ 1. It is further shown that loss of contact always occurs in one part of the clamping region unless r is in excess of 2.5-3. Near that loss of contact, high tensile stresses are obtained. Even with moderate r, there will be local plasticity or crushing etc due to high contact pressure near the end of the opposing gripping face. These findings are shown both numerically and experimentally using optical full field strain measurements.
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| 47. |
- Rohrmann, Sabine, et al.
(författare)
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Consumption of meat and dairy and lymphoma risk in the European Prospective Investigation into Cancer and Nutrition
- 2011
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Ingår i: International Journal of Cancer. - Geneve : Wiley. - 0020-7136 .- 1097-0215. ; 128:3, s. 623-634
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Tidskriftsartikel (refereegranskat)abstract
- The consumption of meat and other foods of animal origin is a risk factor for several types of cancer, but the results for lymphomas are inconclusive. Therefore, we examined these associations among 411,097 participants of the European Prospective Investigation into Cancer and Nutrition. During a median follow-up of 8.5 years, 1,334 lymphomas (1,267 non-Hodgkin lymphoma (NHL) and 67 Hodgkin lymphomas) were identified. Consumption of red and processed meat, poultry, milk and dairy products was assessed by dietary questionnaires. Cox proportional hazard regression was used to evaluate the association of the consumption of these food groups with lymphoma risk. Overall, the consumption of foods of animal origin was not associated with an increased risk of NHLS or HL, but the associations with specific subgroups of NHL entities were noted. A high intake of processed meat was associated with an increased risk of B-cell chronic lymphocytic leukemia (BCLL) [ relative risk (RR) per 50 g intake = 1.31, 95% confidence interval (CI) 1.06-1.63], but a decreased risk of follicular lymphomas (FL) (RR = 0.58; CI 0.38-0.89). A high intake of poultry was related to an increased risk of B-cell lymphomas (RR = 1.22; CI 1.05-1.42 per 10 g intake), FL (RR = 1.65; CI 1.18-2.32) and BCLL (RR = 1.54; CI 1.18-2.01) in the continuous models. In conclusion, no consistent associations between red and processed meat consumption and lymphoma risk were observed, but we found that the consumption of poultry was related to an increased risk of B-cell lymphomas. Chance is a plausible explanation of the observed associations, which need to be confirmed in further studies.
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| 48. |
- Schlehofer, B, et al.
(författare)
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Primary brain tumours and specific serum immunoglobulin E : a case-control study nested in the European prospective investigation into cancer and nutrition cohort
- 2011
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Ingår i: Allergy. European Journal of Allergy and Clinical Immunology. - : Wiley. - 0105-4538 .- 1398-9995. ; 66:11, s. 1434-1441
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: Background: Case-control studies suggest that patients with allergic diseases have a lower risk of developing glioma but not meningioma or schwannoma. However, those data can be differentially biased. Prospective studies with objective measurements of immunologic biomarkers, like immunoglobulin E (IgE), in blood obtained before cancer diagnosis could help to clarify whether an aetiological association exists. Methods: The present case-control study nested within the European Prospective Investigation into Cancer and Nutrition (EPIC) measured specific serum IgE as a biomarker for the most common inhalant allergens in 275 glioma, 175 meningioma and 49 schwannoma cases and 963 matched controls using the ImmunoCAP specific IgE test. Subjects with an IgE level ≥0.35 kUA/l (kilo antibody units per litre) were classified as sensitized by allergens. Odds ratios (OR) and 95% confidence intervals (CI) were estimated by adjusted conditional logistic regression models for each tumour subtype. The effect of dose-response relationship was assessed in five increasing IgE level categories to estimate P-values for trend. Results: The risk of glioma was inversely related to allergic sensitization (OR = 0.73; 95% CI 0.51-1.06), especially pronounced in women (OR = 0.53; 95% CI 0.30-0.95). In dose-response analyses, for high-grade glioma, the lowest OR was observed in sera with the highest IgE levels (P for trend = 0.04). No association was seen for meningioma and schwannoma. Conclusion: The results, based on serum samples prospectively collected in a cohort study, provide some support for the hypothesis that individuals with allergic sensitization are at reduced risk of glioma and confirm results from previous case-control studies.
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| 49. |
- Sjöström, Sara, et al.
(författare)
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Human immunoglobulin G levels of viruses and associated glioma risk
- 2011
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Ingår i: Cancer Causes and Control. - : Springer. - 0957-5243 .- 1573-7225. ; 22:9, s. 1259-1266
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Tidskriftsartikel (refereegranskat)abstract
- Few consistent etiological factors have been identified for primary brain tumors. Inverse associations to asthma and low levels of varicella-zoster virus, immunoglobulin (Ig) levels in prevalent cases have indicted a role for the immune system in the development of glioma. Because samples from prevalent cases of glioma could be influenced by treatments such as steroids and chemotherapy, we investigated pre-diagnostic samples from three large Scandinavian cohorts. To test the hypothesis that immune response levels to these viruses are associated etiologically with glioma risk, we investigated pre-diagnostic immunoglobulin levels for cytomegalovirus (CMV), varicella-zoster virus (VZV), adenovirus (Ad), and Epstein-Barr virus (EBV) including the nuclear antigen (EBNA1) using plasma samples from 197 cases of adult glioma and 394 controls collected from population-based cohorts in Sweden and Denmark. Low VZV IgG levels were marginally significantly more common in glioma cases than the controls (odds ratio (OR) = 0.68, 95% CI 0.41-1.13) for the fourth compared with the first quartile (p = 0.06 for trend). These results were more prominent when analyzing cases with blood sampling at least 2 years before diagnosis (OR = 0.63, 95% CI 0.37-1.08) (p = 0.03). No association with glioma risk was observed for CMV, EBV, and adenovirus.
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| 50. |
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