| 41. |
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| 42. |
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| 43. |
- Özdogan, Özgecan, et al.
(författare)
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Massive MIMO With Dual-Polarized Antennas
- 2023
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Ingår i: IEEE Transactions on Wireless Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 1536-1276 .- 1558-2248. ; 22:2, s. 1448-1463
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Tidskriftsartikel (refereegranskat)abstract
- This paper considers a single-cell massive MIMO (multiple-input multiple-output) system with dual-polarized antennas at both the base station and users. We study a channel model that includes the key practical aspects that arise when utilizing dual-polarization: channel cross-polar discrimination (XPD) and cross-polar correlations (XPC) at the transmitter and receiver. We derive the achievable uplink and downlink spectral efficiencies (SE) with and without successive interference cancellation (SIC) when using the linear minimum mean squared error (MMSE), zero-forcing (ZF), and maximum ratio (MR) combining/precoding schemes. The expressions depend on the statistical properties of the MMSE channel estimator obtained for the dual-polarized channel model. Closed-form uplink and downlink SE expressions for MR combining/precoding are derived. Using these expressions, we propose power-control algorithms that maximize the uplink and downlink sum SEs under uncorrelated fading but can be used to enhance performance also with correlated fading. We compare the SEs achieved in dual-polarized and uni-polarized setups numerically and evaluate the impact of XPD and XPC conditions. The simulations reveal that dual-polarized setups achieve 40-60% higher SEs and the gains remain also under severe XPD and XPC. Dual-polarized also systems benefit more from advanced signal processing that compensates for imperfections.
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| 44. |
- Özenci, Volkan
(författare)
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Immune regulation in multiple sclerosis : cytokines and metalloproteinases
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Immunological mechanisms play a central role in the pathogenesis sclerosis (MS). In this study two groups of related immune variables are cytokines and metalloproteinases (MMPs), which regulate each other's production and activation. Cytokines play key role in pathogenesis and treatments of Cytokines are regulatory proteins secreted by a variety of cells. The pleiotropic action of cytokines include numerous effects on cells of the immune modulating immune responses. Cytokine receptors are crucial for the net effect of cytokines. The balance between Th1 and Th2 type cytokines might determine whether the immune response in MS is detrimental or beneficial. MMPs are a group of endopeptidases that degrade extracellular pro mechanisms in the genesis of inflammatory demyelination, such as recruitment, blood-brain barrier breakdown and myelin destruction are con be MMP-dependent processes. Aims of the study: 1. To investigate the levels of cytokine secreting blood and cerebrospinal fluid mononuclear cells (MNC) in patients with MS and controls; 2. To define further the cytokine disbalance in MS by examining the levels of cytokine receptors that are important in the net effect of cytokine function; 3. To study the levels of blood and CSF MNC in MS expressing mRNA of MMPs and their inhibitors; and 4. To examine the effects of IFN-[beta] on cytokines and MMPs in MS. Results: MS is associated with increased numbers of IL-6 and TNF-[alpha] secreting blood MNC and decreased numbers of IL-10 secreting cells compared to healthy subjects. In CSF, similar numbers of IL-6 and IL-10 secreting cells were observed in patients with MS and other neurological diseases (OND). Patients with MS also had higher levels of MMP-3, MMP-9 and tissue inhibitor of metalloproteinases-1 (TIMP-1) mRNA expressing blood MNC compared to controls. When patients with MS examined before vs. during 1 year of treatment with IFN-[beta], treatment resulted in decreased numbers of IL-6 and TNF-[alpha] secreting MNC and of MMP-3 and MMP mRNA expressing MNC compared to pretreatment levels. On the contrary, numbers of IL-10 secreting MNC and TIMP-1 mRNA expressing MNC were augmented IFN-[beta] therapy. IL-12 is a key cytokine for the development of Th1 type of immune response. ELISPOT assays were adopted to detect IL-12 secreting cells. In intracellular staining of IL-12 was measured by flow cytometry. Numbers of secreting blood MNC correlated with IL-12 positive blood MNC detected by flow cytometry. Utilizing IL-12 ELISPOT assays, elevated numbers of IL-12 secreting blood MNC were observed after stimulation with TNF-[alpha], IFN-[gamma], LPS, LPS+TNF-[alpha] or LPS+IFN-[gamma] compared to cultures without stimulation. When patients with MS were compared with controls, no difference was observed for numbers of IL-12 secreting blood MNC. In contrast, levels of IL-12 receptor (R)[beta]1 and -02 expressing T cells are higher in MS compared to controls, suggesting an elevated net effect of IL-12 in MS. Conclusion: MS is associated with a disbalance of cytokines and of MMPs that may contribute to the pathogenesis of the disease. IFN-[beta] therapy seems to normalize altered levels of cytokines and MMPs observed in MS.
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| 45. |
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| 46. |
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| 47. |
- Hargreaves, D., et al.
(författare)
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- 2004
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Rapport (refereegranskat)
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| 48. |
- Aad, G., et al.
(författare)
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- 2011
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swepub:Mat__t (refereegranskat)
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| 49. |
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| 50. |
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