| 1. |
- Alam, Md. Minhaj, et al.
(author)
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Analysis of the stress raising action of flaws in laser clad deposits
- 2013
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In: Materials and Design. - : Elsevier BV. - 0261-3069 .- 0264-1275 .- 1873-4197. ; 46, s. 328-337
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Journal article (peer-reviewed)abstract
- Fatigue cracking of laser clad cylindrical and square section bars depends upon a variety of factors. This paper presents Finite Element Analysis (FEA) of the different macro stress fields generated as well as stress raisers created by laser cladding defects for four different fatigue load conditions. As important as the defect types are their locations and orientations, categorized into zero-, one- and two-dimensional defects. Pores and inclusions become critical close to surfaces. The performance of as-clad surfaces can be governed by the sharpness of surface notches and planar defects like hot cracks or lack-of-fusion (LOF) are most critical if oriented vertically, transverse to the bar axis. The combination of the macro stress field with the defect type and its position and orientation determines whether it is the most critical stress raiser. Based on calculated cases, quantitative and qualitative charts were developed as guidelines to visualize the trends of different combinations.
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| 2. |
- Kaplan, Alexander, et al.
(author)
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Stress raising in laser clad components depending on geometry and defects
- 2013
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In: 14th NOLAMP Conference. - Luleå : Luleå tekniska universitet. - 9789174396881 - 9789174396898 ; , s. 281-292
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Conference paper (other academic/artistic)abstract
- The fatigue life of laser clad components is basically determined by stress raisers, which arehere studied by Finite Element Analysis. Cylindrical and square section bars are compared foraxial, bending and torsional load conditions, which induces the macro-stress field withcorresponding stress peaks. Defects from laser cladding such as pores, cracks or the surfaceroughness superimpose additional stress raising action on this stress field. The geometricalposition and orientation of the defects has strong impact on the induced maximum stresslevel. For surface pores it is demonstrated by the fractography that their occurrence within acritical azimuthal range can initiate fatigue cracking. The different conditions of samplegeometry, load situations, materials and defects are compared and discussed. In particular,advanced illustration methods are applied for improved and generalized documentation andexplanation of the trends, both qualitatively and quantitatively. Guidelines are presented, inparticular emphasizing critical defects and situations, such as surface pores that are difficult todetect because of inclusions, or pores just underneath the surface that generate particularlyhigh stress.
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| 3. |
- Tuominen, J., et al.
(author)
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Fatigue behavior of laser clad round steel bars
- 2015
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In: Journal of laser applications. - : Laser Institute of America. - 1042-346X .- 1938-1387. ; 27:1
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Journal article (peer-reviewed)abstract
- Laser cladding is an overlay welding method to manufacture high performance, fusion bonded metal, and metal matrix composite coatings on metallic substrates with low dilution. Owing to steep thermal gradients, rapid solidification, and possible mismatch in coefficients of thermal expansion between the coating and the substrate, laser cladding induces large tensile residual stresses in coating layer, potentially affecting the service life of clad component under external load-induced stresses. In this study, four-point bending and torsion fatigue tests were conducted on relatively large round laser clad steel bars to determine the effect of laser cladding on fatigue strength. Quenched and tempered 42CrMo4 steel clad with Inconel 625 and S355 structural steel clad with Stellite 21 were subjected to various stress levels for relatively large number of cycles with and without postweld heat treatment (PWHT). The results indicated that Stellite 21 decreased the fatigue life of S355 at all the applied loads, whereas Inconel 625 increased the fatigue life of 42CrMo4 at high loads but decreased at low loads. Applied PWHT did not show any positive influence on fatigue life.
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| 4. |
- Alam, Md. Minhaj, et al.
(author)
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Surface pore initiated fatigue failure in laser clad components
- 2013
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In: Journal of laser applications. - : Laser Institute of America. - 1042-346X .- 1938-1387. ; 25:3
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Journal article (peer-reviewed)abstract
- A laser clad and machined cylindrical structural steel rod was fatigue tested under four-point bending load. The resulting fracture could be tracked back to a spherical surface pore in the Co-based coating. Due to an oxide inclusion, the pore was not identified by dye penetrant inspection. Two circular buckling strain patterns that were detected beside the pore at the surfaces after fracture confirm local plastic deformation prior to crack initiation. In order to calculate the stress field around the surface pore, linear elastic finite element analysis was carried out. For four-point bending load, a surface pore generally exceeds the maximum stress of a smooth rod as long as the pore is located within an azimuthal angle of ±55°, which was the case for the presented as well as for another pore initiated sample.
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| 5. |
- Vardelle, Armelle, et al.
(author)
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Erratum to The 2016 Thermal Spray Roadmap
- 2017
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In: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 26:5, s. 985-986
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Journal article (peer-reviewed)
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| 6. |
- Vardelle, Armelle, et al.
(author)
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The 2016 Thermal Spray Roadmap
- 2016
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In: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 25:8, s. 1376-1440
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Journal article (peer-reviewed)abstract
- Considerable progress has been made over the last decades in thermal spray technologies, practices and applications. However, like other technologies, they have to continuously evolve to meet new problems and market requirements. This article aims to identify the current challenges limiting the evolution of these technologies and to propose research directions and priorities to meet these challenges. It was prepared on the basis of a collection of short articles written by experts in thermal spray who were asked to present a snapshot of the current state of their specific field, give their views on current challenges faced by the field and provide some guidance as to the R&D required to meet these challenges. The article is divided in three sections that deal with the emerging thermal spray processes, coating properties and function, and biomedical, electronic, aerospace and energy generation applications. © 2016, ASM International.
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| 7. |
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| 8. |
- Adewumi, Oluseun, et al.
(author)
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Characterization of human embryonic stem cell lines by the International Stem Cell Initiative
- 2007
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In: Nature Biotechnology. - : Springer Science and Business Media LLC. - 1087-0156 .- 1546-1696. ; 25:7, s. 803-816
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Journal article (peer-reviewed)abstract
- The International Stem Cell Initiative characterized 59 human embryonic stem cell lines from 17 laboratories worldwide. Despite diverse genotypes and different techniques used for derivation and maintenance, all lines exhibited similar expression patterns for several markers of human embryonic stem cells. They expressed the glycolipid antigens SSEA3 and SSEA4, the keratan sulfate antigens TRA-1-60, TRA-1-81, GCTM2 and GCT343, and the protein antigens CD9, Thy1 (also known as CD90), tissue- nonspecific alkaline phosphatase and class 1 HLA, as well as the strongly developmentally regulated genes NANOG, POU5F1 (formerly known as OCT4), TDGF1, DNMT3B, GABRB3 and GDF3. Nevertheless, the lines were not identical: differences in expression of several lineage markers were evident, and several imprinted genes showed generally similar allele-specific expression patterns, but some gene-dependent variation was observed. Also, some female lines expressed readily detectable levels of XIST whereas others did not. No significant contamination of the lines with mycoplasma, bacteria or cytopathic viruses was detected.
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| 13. |
- Paloviita, P, et al.
(author)
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Small RNA expression and miRNA modification dynamics in human oocytes and early embryos
- 2021
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In: Genome research. - : Cold Spring Harbor Laboratory. - 1549-5469 .- 1088-9051. ; 31:8, s. 1474-
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Journal article (peer-reviewed)abstract
- Small noncoding RNAs (sRNAs) play important roles during the oocyte-to-embryo transition (OET), when the maternal phenotype is reprogrammed and the embryo genome is gradually activated. The transcriptional program driving early human development has been studied with the focus mainly on protein-coding RNAs, and expression dynamics of sRNAs remain largely unexplored. We profiled sRNAs in human oocytes and early embryos using an RNA-sequencing (RNA-seq) method suitable for low inputs of material. We show that OET in humans is temporally coupled with the transition from predominant expression of oocyte short piRNAs (os-piRNAs) in oocytes, to activation of microRNA (miRNA) expression in cleavage stage embryos. Additionally, 3′ mono- and oligoadenylation of miRNAs is markedly increased in zygotes. We hypothesize that this may modulate the function or stability of maternal miRNAs, some of which are retained throughout the first cell divisions in embryos. This study is the first of its kind elucidating the dynamics of sRNA expression and miRNA modification along a continuous trajectory of early human development and provides a valuable data set for in-depth interpretative analyses.
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| 14. |
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| 15. |
- Sepponen, K., et al.
(author)
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Steroidogenic factor 1 (NR5A1) induces multiple transcriptional changes during differentiation of human gonadal-like cells
- 2022
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In: Differentiation. - : Elsevier BV. - 0301-4681. ; 128:Nov-Dec, s. 83-100
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Journal article (peer-reviewed)abstract
- Nuclear receptor subfamily 5 group A member 1 (NR5A1) encodes steroidogenic factor 1 (SF1), a key regulatory factor that determines gonadal development and coordinates endocrine functions. Here, we have established a stem cell-based model of human gonadal development and applied it to evaluate the effects of NR5A1 during the transition from bipotential gonad to testicular cells. We combined directed differentiation of human induced pluripotent stem cells (46,XY) with activation of endogenous NR5A1 expression by conditionally-inducible CRISPR activation. The resulting male gonadal-like cells expressed several Sertoli cell transcripts, secreted anti-Müllerian hormone and responded to follicle-stimulating hormone by producing sex steroid intermediates. These characteristics were not induced without NR5A1 activation. A total of 2691 differentially expressed genetic elements, including both coding and non-coding RNAs, were detected immediately following activation of NR5A1 expression. Of those, we identified novel gonad-related putative NR5A1 targets, such as SCARA5, which we validated also by immunocytochemistry. In addition, NR5A1 activation was associated with dynamic expression of multiple gonad- and infertility-related differentially expressed genes. In conclusion, by combining targeted differentiation and endogenous activation of NR5A1 we have for the first time, been able to examine in detail the effects of NR5A1 in early human gonadal cells. The model and results obtained provide a useful resource for future investigations exploring the causative reasons for gonadal dysgenesis and infertility in humans. © 2022 The Authors
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