Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 109Citation - Scopus: 102Search for Heavy Narrow Dilepton Resonances in Pp Collisions at Root S=7 Tev and Root S=8 Tev(Elsevier Ltd., 2013) Karapınar, GülerAn updated search for heavy narrow resonances decaying to muon or electron pairs using the CMS detector is presented. Data samples from pp collisions at root s = 7 TeV and 8 TeV at the LHC, with integrated luminosities of up to 5.3 and 4.1 fb(-1), respectively, are combined. No evidence for a heavy narrow resonance is observed. The analysis of the combined data sets excludes, at 95% confidence level, a Sequential Standard Model Z '(SSM) resonance lighter than 2590 GeV, a superstring-inspired Z '(psi) lighter than 2260 GeV, and Kaluza-Klein gravitons lighter than 2390 (2030) GeV, assuming that the coupling parameter k/(M) over bar (Pl) is 0.10 (0.05). These are the most stringent limits to date. (C) 2013 CERN. Published by Elsevier B.V. All rights reserved.Article Citation - WoS: 7Citation - Scopus: 7Effects of Interedge Scattering on the Wigner Crystallization in Graphene Nanoribbons(American Physical Society, 2017) Modarresi, Mohsen; Güçlü, Alev DevrimWe investigate the effects of coupling between the two zigzag edges of graphene nanoribbons on the Wigner crystallization of electrons and holes using a combination of tight-binding, mean-field Hubbard and many-body configuration interaction methods. We show that the thickness of the nanoribbon plays a crucial role in the formation of Wigner crystal. For ribbon widths smaller than 16 Å, increased kinetic energy overcomes the long-range Coulomb repulsion and suppresses the Wigner crystallization. For wider ribbons up to 38 Å wide, strong Wigner localization is observed for an even number of electrons, revealing an even-odd effect also found in the Coulomb-blockade addition spectrum. Interedge correlations are found to be strong enough to allow simultaneous crystallization on both edges, although an applied electric field can decouple the two edges. Finally, we show that Wigner crystallization can also occur for holes, albeit weaker than for electrons.Article Citation - WoS: 56Citation - Scopus: 57Dynamic Nuclear Polarization of Spherical Nanoparticles(Royal Society of Chemistry, 2013) Akbey, Ümit; Altın, Burcu; Linden, Arne; Özçelik, Serdar; Gradzielski, Michael; Oschkinat, HartmutSpherical silica nanoparticles of various particle sizes (∼10 to 100 nm), produced by a modified Stoeber method employing amino acids as catalysts, are investigated using Dynamic Nuclear Polarization (DNP) enhanced Nuclear Magnetic Resonance (NMR) spectroscopy. This study includes ultra-sensitive detection of surface-bound amino acids and their supramolecular organization in trace amounts, exploiting the increase in NMR sensitivity of up to three orders of magnitude via DNP. Moreover, the nature of the silicon nuclei on the surface and the bulk silicon nuclei in the core (sub-surface) is characterized at atomic resolution. Thereby, we obtain unique insights into the surface chemistry of these nanoparticles, which might result in improving their rational design as required for promising applications, e.g. as catalysts or imaging contrast agents. The non-covalent binding of amino acids to surfaces was determined which shows that the amino acids not just function as catalysts but become incorporated into the nanoparticles during the formation process. As a result only three distinct Q-types of silica signals were observed from surface and core regions. We observed dramatic changes of DNP enhancements as a function of particle size, and very small particles (which suit in vivo applications better) were hyperpolarized with the best efficiency. Nearly one order of magnitude larger DNP enhancement was observed for nanoparticles with 13 nm size compared to particles with 100 nm size. We determined an approximate DNP penetration-depth (∼4.2 or ∼5.7 nm) for the polarization transfer from electrons to the nuclei of the spherical nanoparticles. Faster DNP polarization buildup was observed for larger nanoparticles. Efficient hyperpolarization of such nanoparticles, as achieved in this work, can be utilized in applications such as magnetic resonance imaging (MRI).Conference Object Citation - WoS: 1Citation - Scopus: 1Modification of Surface Morphology of Uhmwpe for Biomedical Implants(Materials Research Society, 2007) Öztarhan, Ahmet; Sokullu Urkaç, Emel; Kaya, Nusret; Yenigül, Mesut; Tıhmınlıoğlu, Funda; Ezdeşir, Ayhan; Zimmerman, Robert; Budak, Satılmış; Muntele, C.; Chhay, Bopha; Ila, Daryush; Oks, Efim; Nikolaev, Alexey; Tek, Zekai; Eltem, RenginUltra High Molecular Weight Polyethylene (UHMWPE) samples were implanted with metal and metal-gas hybrid ions (Ag, Ag+N, C+H, C+H+Ar, Ti+O) by using improved MEVVA Ion implantation technique [1,2]. An extraction voltage of 30 kV and influence of 1017 ions/cm2 were attempted in this experiment, to change their surface morphologies in order to understand the effect of ion implantation on the surface properties of UHMWPEs. Characterizations of the implanted samples with RBS , ATR - FTIR, spectra were compared with the un-implanted ones . Implanted and unimplanted samples were also thermally characterized by TGA and DSC. It was generally observed that C-H bond concentration seemed to be decreasing with ion implantation and the results indicated that the chain structure of UHMWPE were changed and crosslink density and polymer crystallinity were increased compared to unimplanted ones resulting in increased hardness. It was also observed that nano size cracks (approx.10nm) were significantly disappeared after Ag implantation, which also has an improved antibacterial effect. Contact angle measurements showed that wettability of samples increased with ion implantation. Results showed that metal and metal+gas hybrid ion implantation could be an effective way to improve the surface properties of UHMWPE to be used in hip and knee prosthesis.