| 1. |
- Aydin, Osman, et al.
(author)
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EU FP7 INFSO-ICT-317669 METIS, D4.2 Final report on trade-off investigations
- 2014
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Reports (other academic/artistic)abstract
- Research activities in METIS WP4 include several aspects related to the network-level of future wireless communication networks. Thereby, a large variety of scenarios is considered and solutions are proposed to serve the needs envisioned for the year 2020 and beyond. This document provides vital findings about several trade-offs that need to be leveraged when designing future network-level solutions. In more detail, it elaborates on the following trade-offs:• Complexity vs. Performance improvement• Centralized vs. Decentralized• Long time-scale vs. Short time-scale• Information Interflow vs. Throughput/Mobility enhancement• Energy Efficiency vs. Network Coverage and CapacityOutlining the advantages and disadvantages in each trade-off, this document serves as a guideline for the application of different network-level solutions in different situations and therefore greatly assists in the design of future communication network architectures.
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| 2. |
- Pedersen, Torbjorn O., et al.
(author)
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Endothelial microvascular networks affect gene-expression profiles and osteogenic potential of tissue-engineered constructs
- 2013
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In: STEM CELL RES THER. - : Springer Science and Business Media LLC. - 1757-6512. ; 4, s. 52-
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Journal article (peer-reviewed)abstract
- Introduction: A major determinant of the potential size of cell/scaffold constructs in tissue engineering is vascularization. The aims of this study were twofold: first to determine the in vitro angiogenic and osteogenic geneexpression profiles of endothelial cells (ECs) and mesenchymal stem cells (MSCs) cocultured in a dynamic 3D environment; and second, to assess differentiation and the potential for osteogenesis after in vivo implantation. Methods: MSCs and ECs were grown in dynamic culture in poly(L-lactide-co-1,5-dioxepan-2-one) (poly(LLA-co-DXO)) copolymer scaffolds for 1 week, to generate three-dimensional endothelial microvascular networks. The constructs were then implanted in vivo, in a murine model for ectopic bone formation. Expression of selected genes for angiogenesis and osteogenesis was studied after a 1-week culture in vitro. Human cell proliferation was assessed as expression of ki67, whereas a-smooth muscle actin was used to determine the perivascular differentiation of MSCs. Osteogenesis was evaluated in vivo through detection of selected markers, by using real-time RT-PCR, alkaline phosphatase (ALP), Alizarin Red, hematoxylin/eosin (HE), and Masson trichrome staining. Results: The results show that endothelial microvascular networks could be generated in a poly(LLA-co-DXO) scaffold in vitro and sustained after in vivo implantation. The addition of ECs to MSCs influenced both angiogenic and osteogenic gene-expression profiles. Furthermore, human ki67 was upregulated before and after implantation. MSCs could support functional blood vessels as perivascular cells independent of implanted ECs. In addition, the expression of ALP was upregulated in the presence of endothelial microvascular networks. Conclusions: This study demonstrates that copolymer poly(LLA-co-DXO) scaffolds can be prevascularized with ECs and MSCs. Although a local osteoinductive environment is required to achieve ectopic bone formation, seeding of MSCs with or without ECs increases the osteogenic potential of tissue-engineered constructs.
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| 3. |
- Pedersen, Torbjorn O., et al.
(author)
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Mesenchymal stem cells induce endothelial cell quiescence and promote capillary formation
- 2014
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In: Stem Cell Research & Therapy. - : Springer Science and Business Media LLC. - 1757-6512. ; 5, s. 23-
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Journal article (peer-reviewed)abstract
- Introduction: Rapid establishment of functional blood vessels is a prerequisite for successful tissue engineering. During vascular development, endothelial cells (ECs) and perivascular cells assemble into a complex regulating proliferation of ECs, vessel diameter and production of extracellular matrix proteins. The aim of this study was to evaluate the ability of mesenchymal stem cells (MSCs) to establish an endothelial-perivascular complex in tissue-engineered constructs comprising ECs and MSCs. Methods: Primary human ECs and MSCs were seeded onto poly(L-lactide-co-1,5-dioxepan-2-one) (poly(LLA-co-DXO)) scaffolds and grown in dynamic culture before subcutaneous implantation in immunocompromised mice for 1 and 3 weeks. Cellular activity, angiogenic stimulation and vascular assembly in cell/scaffold constructs seeded with ECs or ECs/MSCs in a 5:1 ratio was monitored with real-time RT-PCR, ELISA and immunohistochemical microscopy analysis. Results: A quiescent phenotype of ECs was generated, by adding MSCs to the culture system. Decreased proliferation of ECs, in addition to up-regulation of selected markers for vascular maturation was demonstrated. Baseline expression of VEGFa was higher for MSCs compared with EC (P < 0.001), with subsequent up-regulated VEGFa-expression for EC/MSC constructs before (P < 0.05) and after implantation (P < 0.01). Furthermore, an inflammatory response with CD11b + cells was generated from implantation of human cells. At the end of the 3 week experimental period, a higher vascular density was shown for both cellular constructs compared with empty control scaffolds (P < 0.01), with the highest density of capillaries being generated in constructs comprising both ECs and MSCs. Conclusions: Induction of a quiescent phenotype of ECs associated with vascular maturation can be achieved by co-seeding with MSCs. Hence, MSCs can be appropriate perivascular cells for tissue-engineered constructs.
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| 4. |
- Sun, Yang, 1983-, et al.
(author)
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Degradable amorphous scaffolds with enhanced mechanical properties and homogeneous cell distribution produced by a three-dimensional fiber deposition method
- 2012
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In: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 100A:10, s. 2739-2749
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Journal article (peer-reviewed)abstract
- The mechanical properties of amorphous, degradable, and highly porous poly(lactide-co-caprolactone) structures have been improved by using a 3D fiber deposition (3DF) method. Two designs of 3DF scaffolds, with 45 degrees and 90 degrees layer rotation, were printed and compared with scaffolds produced by a salt-leaching method. The scaffolds had a porosity range from 64% to 82% and a high interconnectivity, measured by micro-computer tomography. The 3DF scaffolds had 89 times higher compressive stiffness and 35 times higher tensile stiffness than the salt-leached scaffolds. There was a distinct decrease in the molecular weight during printing as a consequence of the high temperature. The chain microstructure was, however, not affected; the glass transition temperature and the decomposition temperature were constant. Human OsteoBlast-like cells were cultured in vitro and the cell morphology and distribution were observed by scanning electron microscopy and fluorescence microscopy. The cell distribution on the 3DF scaffolds was more homogeneous than the salt-leached scaffolds, suggesting that 3DF scaffolds are more suitable as porous biomaterials for tissue engineering. These results show that it is possible to design and optimize the properties of amorphous polymer scaffolds. The 3DF method produce amorphous degradable poly(lactide-co-caprolactone) that are strong and particularly suitable for cell proliferation.
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| 5. |
- Sun, Yang, et al.
(author)
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Surfactant as a Critical Factor When Tuning the Hydrophilicity in Three-Dimensional Polyester-Based Scaffolds : Impact of Hydrophilicity on Their Mechanical Properties and the Cellular Response of Human Osteoblast-Like Cells
- 2014
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 15:4, s. 1259-1268
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Journal article (peer-reviewed)abstract
- In tissue engineering, the hydrophilicity of porous scaffolds is essential and influences protein and cell adhesion as well as nutrient diffusion into the scaffold. The relative low hydrophilicity of degradable polyesters, which limits diffusion of nutrients, is a major drawback in large porous scaffolds of these materials when used for bone tissue engineering and repair of critical size defects. Designing porous biodegradable polymer scaffolds with improved hydrophilicity, while maintaining their mechanical, thermal, and degradation properties is therefore of clinical interest. Here, surfactants were used to tune the hydrophilicity and material properties. A total of 3-20% (w/w) of surfactant, polysorbate 80 (Tween 80), was used as an additive in poly(L-lactide-co-1,5-diozepan-2-one) [poly(LLA-co-DXO)] and poly(L-lactide)-co-(epsilon-caprolactone) [poly(LLA-co-CL)] scaffolds. A significantly decreased water contact angle was recorded for all the blends and the crystallinity, glass transition temperature and crystallization temperature were reduced with increased amounts of surfactant. Copolymers with the addition of 3% Tween 80 had comparable mechanical properties as the pristine copolymers. However, the E-modulus and tensile stress of copolymers decreased significantly with the addition of 10 and 20% Tween 80. Initial cell response of the material was evaluated by seeding human osteoblast-like cells (HOB) on the scaffolds. The addition of 3% Tween 80 did not significantly influence cell attachment or proliferation, while 20% Tween 80 significantly inhibited osteoblast proliferation. RT-PCR results showed that 3% Tween 80 stimulated mRNA expression of alkaline phosphatase (ALP), osteoprotegerin (OPG), and bone morphogenetic protein-2 (BMP-2).
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| 6. |
- Xing, Zhe, et al.
(author)
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Biological Effects of Functionalizing Copolymer Scaffolds with Nanodiamond Particles
- 2013
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In: Tissue Engineering. Part A. - : Mary Ann Liebert. - 1937-3341 .- 1937-335X. ; 19:15-16, s. 1783-1791
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Journal article (peer-reviewed)abstract
- Significant evidence has indicated that poly(L-lactide)-co-(epsilon-caprolactone) [(poly(LLA-co-CL)] scaffolds could be one of the suitable candidates for bone tissue engineering. Oxygen-terminated nanodiamond particles (n-DP) were combined with poly(LLA-co-CL) and revealed to be positive for cell growth. In this study, we evaluated the influence of poly(LLA-co-CL) scaffolds modified by n-DP on attachment, proliferation, differentiation of bone marrow stromal cells (BMSCs) in vitro, and on bone formation using a sheep calvarial defect model. BMSCs were seeded on either poly(LLA-co-CL)-or n-DP-coated scaffolds and incubated for 1 h. Scanning electron microscopy (SEM) and fluorescence microscopy were used in addition to protein and DNA measurements to evaluate cellular attachment on the scaffolds. To determine the effect of n-DP on proliferation of BMSCs, cell/scaffold constructs were harvested after 3 days and evaluated by Bicinchoninic Acid (BCA) protein assay and SEM. In addition, the osteogenic differentiation of cells grown for 2 weeks on the various scaffolds and in a dynamic culture condition was evaluated by real-time RT-PCR. Unmodified and modified scaffolds were implanted into the calvaria of six-year-old sheep. The expression of collagen type I (COL I) and bone morphogenetic protein-2 (BMP-2) after 4 weeks as well as the formation of new bone after 12 and 24 weeks were analyzed by immunohistochemistry and histology. Scaffolds modified with n-DP supported increased cell attachment and the mRNA expression of osteopontin (OPN), bone sialoprotein (BSP), and BMP-2 were significantly increased after 2 weeks of culture. The BMSCs had spread well on the various scaffolds investigated after 3 days in the study with no significant difference in cell proliferation. Furthermore, the in vivo data revealed more positive staining of COLI and BMP-2 in relation to the n-DP-coated scaffolds after 4 weeks and presented more bone formation after 12 and 24 weeks. n-DP modification significantly increased cell attachment and differentiation of BMSCs on poly(LLA-co-CL) scaffolds in vitro and enhanced bone formation in vivo.
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| 7. |
- Yu, Jin-Tao, et al.
(author)
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Cyclotricatechylene based porous crystalline material : Synthesis and applications in gas storage
- 2012
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In: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 22:12, s. 5369-5373
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Journal article (peer-reviewed)abstract
- An undulated two-dimensional CTC-based covalent organic framework, CTC-COF, was synthesized through solvothermal reaction for the first time. This mesoporous material stacks in an eclipsed mode in the microcrystalline state. CTC-COF has a surface area of 1710 m(2) g(-1), with a pore width of 2.26 nm calculated by the NL-DFT modelling. The bowl-shaped core unit led to a larger surface area than its analogue, COF-5 constructed by planar subunits. This material has higher low pressure hydrogen uptake than other 2D COFs with similar structures, and even close to the 3D COF materials.
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| 8. |
- Yutao, Sui, 1984, et al.
(author)
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Performance study of fixed and moving relays for vehicular users with multi-cell handover under co-channel interference
- 2013
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In: IEEE International Conference on Connected Vehicles and Expo. ; , s. 514-520
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Conference paper (peer-reviewed)abstract
- In this paper, we investigate the power outage probability (OP) of a vehicular user equipment (VUE) device served by half-duplex decode-and-forward relay nodes (RNs) under co-channel interference. Both moving RNs (MRNs) and fixed RNs (FRNs) are studied, and compared with the baseline, base station (BS) to VUE direct transmission. In order to understand the benefit for vehicular users served by an RN, we consider practical channel models for different involved links as well as the impact of handover (HO) between the BS and the RNs. For an accurate comparison, we present a comprehensive framework to optimize the HO parameters, as well as we numerically optimize the FRN position which minimizes the average power OP at the VUE. FRN shows its advantage to serve its nearby VUEs. However, when vehicular penetration loss is moderate to high, MRN assisted transmission greatly outperforms transmission assisted by an FRN as well as direct transmission. Hence, the use of MRNs is very promising for improving the quality-of-service (QoS) of VUEs in future mobile communication systems.
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