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  • 124051. Yokoya, S.
    et al.
    Jönsson, Pär G.
    KTH, Superseded Departments, Metallurgy.
    Sasaki, K.
    Tada, K.
    Takagi, Shigeo
    KTH, Superseded Departments, Metallurgy.
    Iguchi, M.
    The effect of swirl flow in an immersion nozzle on the heat and fluid flow in a billet continuous casting mold2004In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 33, no 1, p. 22-28Article in journal (Refereed)
    Abstract [en]

    A numerical analysis and a water model study of the mold region of a billet continuous caster was performed with a novel injection concept using swirling flow in the pouring tube, to control the heat and mass transfer in the continuous casting mold. The following results were found: A weak impinging flow can be observed near the corner of the mold wall, which results in the promotion of uniform heat and mass transfer all around across the plane, particularly at the casting corner. An upward flow directed from the vicinity of the nozzle outlet to the meniscus can be observed near the corner of the upper part of the mold, which leads to the active heat and mass transfer into the meniscus. A uniform velocity and heat distribution can be obtained within a short distance of 200 mm downward from the outlet of the nozzle. Quite different mold flow patterns are observed between the divergent and straight immersion nozzles. Heat and mass transport in the mold using the divergent nozzle is much more reasonable than that using the straight nozzle.

  • 124052. Yokoya, S.
    et al.
    Takagi, S.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Hallgren, Line
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Kholmatov, Shavkat
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Tsukaguchi, Y.
    Swirling flow effect in immersion nozzle on control of heat and mass transport in casting teeming2006In: 2006 TMS Fall Extraction and Processing Division, 2006, p. 485-498Conference paper (Refereed)
    Abstract [en]

    With increasing requirement of steel productivity and quality in continuous casting in the conventional casting system using an immersion nozzle, it is very difficult to establish a reasonable molten flow pattern. In order to overcome this difficulty, we propose a new method of imparting swirling motion onto the flow in the immersion nozzle and to control the flow pattern in the mold. Following results have been obtained during the studies. For the case of slab continuous casting mold: High amplitudes of oscillation with a period of 10 to 15 seconds are observed in the outlet flow of the immersion nozzle and meniscus flow in the conventional casting system, while these phenomena are remarkably suppressed using swirling motion in the immersion nozzle, which leads to very calm and uniform flow pattern at the outlets of the immersion nozzle, in the mold and on the meniscus in the mold; For the case of billet continuous casting mold: (1) heat and mass transfer near the meniscus can be remarkably activated compared with a conventional straight type immersion nozzle without swirl, and (2) Quite different mold flow patterns are observed between the divergent and straight immersion nozzles. Heat and mass transport in the mold using the divergent nozzle is much more reasonable compared to that of straight nozzle. The findings, mentioned above, are very useful to control the flow pattern in the slab, and billet continuous casters. Such effectiveness of swirling flow in the SEN on the mold flow has been put into practical use. As a result, remarkable progress on the quality and production of continuous casting products has been observed in practical application.

  • 124053. Yokoyama, T.
    et al.
    Olsson, Mårten
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Izumi, S.
    Sakai, S.
    Investigation into the self-loosening behavior of bolted joint subjected to rotational loading2012In: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 23, p. 35-43Article in journal (Refereed)
    Abstract [en]

    The self-loosening mechanisms of a bolted joint subjected to a rotational load were investigated using three-dimensional FEM. A previous theory regarding the conditions of initiation and progress of loosening was verified. Loosening occurs if the relative rotation angle applied to the bolt reaches a critical value . Ξ cr and the thread surface undergoes a complete slip. In addition, loosening progresses if . T sl<. T w<. T st holds, where . T sl, . T st, and . T w are the loosening and the tightening torque of the thread surface, and the slip torque of the bearing surface, respectively. If above conditions hold, bolt tension decreases in proportion to the relative rotation angle of the bolt during complete thread-surface slip while bolt tension does not change during complete bearing-surface slip. If these conditions do not hold, loosening does not progress even if the thread or the bearing surface undergoes complete slip. In order to verify the above loosening mechanism, a loosening test was carried out. It was confirmed that the loosening progressed by the same mechanism as that shown by FEM.

  • 124054.
    Yoluk, Ozge
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Andersson, Magnus
    Lindahl, Erik
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Improved Comparative Models of Human Gabaar Ligand-Gated Ion Channels Based on Structural Dynamics of GluCl2013In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 104, no 2, p. 638A-638AArticle in journal (Other academic)
  • 124055.
    Yoluk, Ozge
    et al.
    KTH, Centres, Science for Life Laboratory, SciLifeLab. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Heusser, Stephanie
    SciLifeLab, Solna, Sweden.;Stockholm Univ, S-10691 Stockholm, Sweden..
    Andersson, Magnus
    KTH, Centres, Science for Life Laboratory, SciLifeLab. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Orellana, Laura
    KTH.
    Lindahl, Erik
    KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, Stockholm, Sweden..
    Gating Ritual: Simulations of Gating in Glutamate-Gated Chloride Channel2015In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 108, no 2, p. 431A-431AArticle in journal (Other academic)
  • 124056.
    Yoluk, Ozge
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics.
    Heusser, Stephanie
    Stockholm Univ, Biochem & Biophys, S-10691 Stockholm, Sweden..
    Pouya, Iman
    KTH, School of Engineering Sciences (SCI), Physics, Theoretical & Computational Biophysics.
    Howard, Rebecca
    Skidmore Coll, Chem, Saratoga Springs, Sweden..
    Klement, Göran
    Stockholm Univ, Biochem & Biophys, S-10691 Stockholm, Sweden..
    Lindahl, Erik
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics. Stockholm Univ, Biochem & Biophys, S-10691 Stockholm, SwedenStockholm Univ, Biochem & Biophys, S-10691 Stockholm, Sweden.
    Opening and Selectivity of the Glic Ligand-Gated Ion Channel can be Tuned by Mutation of Hydrophobic Residues in the Pore2015In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 108, no 2, p. 431A-431AArticle in journal (Other academic)
  • 124057.
    Yoluk, Ozge
    et al.
    KTH, Centres, Science for Life Laboratory, SciLifeLab. KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics.
    Lindahl, Erik
    KTH, Centres, Science for Life Laboratory, SciLifeLab. KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics. Stockholm Univ, Dept Biochem & Biophys, Ctr Biomembrane Res.
    Andersson, Magnus
    KTH, Centres, Science for Life Laboratory, SciLifeLab. KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics.
    Conformational Gating Dynamics in the GluCl Anion-Selective Chloride Channel2015In: ACS Chemical Neuroscience, ISSN 1948-7193, E-ISSN 1948-7193, Vol. 6, no 8, p. 1459-1467Article in journal (Refereed)
    Abstract [en]

    Cys-loop receptors are central to propagation of signals in the nervous system. The gating of the membrane-spanning pore is triggered by structural rearrangements in the agonist-binding site, located some so A away from the pore. A sequential conformational change, propagating from the ligand-binding site to the pore, has been proposed to govern gating in all Cys-loop receptors. Here, we identify structural and dynamic components of the conformational gating in the eukaryotic glutamate-gated chloride channel (GluCl) by means of molecular dynamics (MD) simulations with and without the L-glutamate agonist bound. A significant increase in pore opening and accompanying hydration is observed in the presence of glutamate. Potential of mean force calculations reveal that the barrier for ion passage drops from 15 kcal/mol to 5-10 kcal/mol with the agonist bound. This appears to be explained by agonist binding that leads to significant changes in the intersubunit hydrogen-bonding pattern, which induce a slight tilt of the extracellular domain relative to the transmembrane domain in the simulations. This rearrangement is subtle, but correspond to the direction of the quaternary twist observed as a key difference between open and closed X-ray structures. While the full reversible gating is still a much slower process, the observed structural dynamics sheds new light on the early stages of how the agonist influences the extracellular domain, how the extracellular domain interacts with the transmembrane domain, and how changes in the transmembrane domain alter the free energy of ion passage.

  • 124058.
    Yoluk, Ozge
    et al.
    KTH, Centres, Science for Life Laboratory, SciLifeLab. KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, Stockholm, Sweden..
    Orellana, L
    KTH.
    Lindahl, E
    KTH.
    Microsecond time-scale dynamics of the pentameric ligand-gated ion channels: a comparative study2015In: European Biophysics Journal, ISSN 0175-7571, E-ISSN 1432-1017, Vol. 44, p. S219-S219Article in journal (Other academic)
  • 124059.
    Yoluk, Özge
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Biological Physics.
    Elucidating the Gating Mechanism of Cys-Loop Receptors2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Cys-loop receptors are membrane proteins that are key players for the fast synaptic neurotransmission. Their ion transport initiates new nerve signals after activation by small agonist molecules, but this function is also highly sensitive to allosteric modulation by a number of compounds such as anesthetics, alcohol or anti-parasitic agents. For a long time, these modulators were believed to act primarily on the membrane, but the availability of high- resolution structures has made it possible to identify several binding sites in the transmembrane domains of the ion channels. It is known that ligand binding in the extracellular domain causes a conformational earthquake that interacts with the transmembrane domain, which leads to channel opening. The investigations carried out in this thesis aim at understanding the connection between ligand binding and channel opening.

    I present new models of the mammalian GABAA receptor based on the eukaryotic structure GluCl co-crystallized with an anti-parasitic agent, and show how these models can be used to study receptor-modulator interactions. I also show how removal of the bound modulator leads to gradual closing of the channel in molecular dynamics simulations. In contrast, simulations of the receptor with both the agonist and the modulator remain stable in an open-like conformation. This makes it possible to extract several key interactions, and I propose mechanisms for how the extracellular domain motion is initiated. The rapid increase in the number of cys-loop receptor structures the last few years has further made it possible to use principal component analysis (PCA) to create low-dimensional descriptions of the conformational landscape. By performing PCA on the crystal structure ensemble, I have been able to divide the structures into functional clusters and sample the transitions between them using various sampling methods.

    The studies presented in this thesis contribute to our understanding of the gating mechanism and the functional clustering of the cys-loop receptor structures, which both are important to design new allosteric modulator drugs that influence the channel function, in particular to treat neurological disorders.

  • 124060.
    Yoluk, Özge
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics. KTH, Centres, Science for Life Laboratory, SciLifeLab. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Brömstrup, Torben
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics. KTH, Centres, Science for Life Laboratory, SciLifeLab. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Bertaccini, Edward J.
    Trudell, James R.
    Lindahl, Erik
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics. KTH, Centres, Science for Life Laboratory, SciLifeLab. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Stabilization of the GluCl Ligand-Gated Ion Channel in the Presence and Absence of Ivermectin2013In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 105, no 3, p. 640-647Article in journal (Refereed)
    Abstract [en]

    Improving our understanding of the mechanisms and effects of anesthetics is a critically important part of neuroscience. The currently dominant theory is that anesthetics and similar molecules act by binding to Cys-loop receptors in the postsynaptic terminal of nerve cells and potentiate or inhibit their function. Although structures for some of the most important mammalian channels have still not been determined, a number of important results have been derived from work on homologous cationic channels in bacteria. However, partly due to the lack of a nervous system in bacteria, there are a number of questions about how these results relate to higher organisms. The recent determination of a structure of the eukaryotic chloride channel, GluCl, is an important step toward accurate modeling of mammalian channels, because it is more similar in function to human Cys-loop receptors such as GABA(A)R or GlyR. One potential issue with using GluCl to model other receptors is the presence of the large ligand ivermectin (IVM) positioned between all five subunits. Here, we have performed a series of microsecond molecular simulations to study how the dynamics and structure of GluCl change in the presence versus absence of IVM. When the ligand is removed, subunits move at least 2 angstrom closer to each other compared to simulations with IVM bound. In addition, the pore radius shrinks to 1.2 angstrom, all of which appears to support a model where IVM binding between subunits stabilizes an open state, and that the relaxed nonIVM conformations might be suitable for modeling other channels. Interestingly, the presence of IVM also has an effect on the structure of the important loop C located at the neurotransmitter-binding pocket, which might help shed light on its partial agonist behavior.

  • 124061.
    Yoluk, Özge
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics.
    Murail, Samuel
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics.
    Lindahl, Erik
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics. Center for Biomembrane Research.
    Simulations of Subunit Interactions in the C. Elegans GluCl Ligand-Gated2012In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 102, no 3, p. 472A-472AArticle in journal (Other academic)
  • 124062.
    Yoluk, Özge
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics.
    Orellana, Laura
    Bertaccini, Edward J.
    Trudell, James R.
    Lindahl, Erik
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics.
    Principal Components from Ligand-Gated Ion Channel Structures Enable Ensemble Studies of Microsecond-Scale Transitions2016In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 110, no 3, p. 454A-454AArticle in journal (Other academic)
  • 124063.
    Yoluk, Özge
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Riederer, Erika A.
    Andersson, Magnus
    Klement, Goran
    Trudell, James R.
    Bertaccini, Edward J.
    Howard, Rebecca J.
    Lindahl, Erik
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Contribution of Structural Elements to Activation and Allosteric Modulation in an Anionic Ligand-Gated Ion Channel2014In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 106, no 2, p. 547A-547AArticle in journal (Other academic)
  • 124064. Yong, C.
    et al.
    Jinyue, Yan
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Asian biofuel development at a crossroads2007In: Renewable Energy for Development, ISSN 1101-8267, Vol. 20, no 2, p. 6-7Article in journal (Refereed)
    Abstract [en]

    Some of the views on the development of Asian biofuel at a crossroad are discussed. Different strategic choice in technologies and market development can lead to different prospects for Asian biofuel development. Malaysia and Indonesia are expanding their palm oil cultivation in the hope of exporting at least 30% of the bio-diesel to the European countries. China is the third largest bioethanol produces in the world after Brazil and US. The reason behind the drastic increase of non-state-owned biofuels processors in China is the potential international demand, particularly for the European Union. Some of the Asian countries such as China, India, and the Philippines are trying to create or enlarge domestic markets by introducing a blending mandate to reduce the growing dependency on imported oil. India jatropha and pongamia strategies are intended to balance the disparity between urban and rural development and also to decrease oil imports.

  • 124065. Yong, C.
    et al.
    Johnson, Francis X.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy and Climate Studies, ECS.
    Sweden: greening the power market in a context of liberalization and nuclear ambivalence2008In: Promoting Sustainable Electricity in Europe / [ed] W. M. Lafferty och A. Ruud, Edward Elgar Publishing, 2008, p. 219-250Chapter in book (Refereed)
  • 124066. Yong, Ken-Tye
    et al.
    Qian, Jun
    Roy, Indrajit
    Lee, Hoon Hi
    Bergey, Earl J.
    Tramposch, Kenneth M.
    He, Sailing
    Swihart, Mark T.
    Maitra, Anirban
    Prasad, Paras N.
    Quantum rod bioconjugates as targeted probes for confocal and two-photon fluorescence imaging of cancer cells2007In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 7, no 3, p. 761-765Article in journal (Refereed)
  • 124067. Yong, Y. -S
    et al.
    Aravazhi, S.
    Vázquez-Córdova, S. A.
    Carvajal, J. J.
    Díaz, F.
    Herek, J. L.
    García-Blanco, S. M.
    Pollnau, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. University of Twente, Netherlands.
    Direct confocal lifetime measurements on rare-earth-doped media exhibiting radiation trapping2017In: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 7, no 2, p. 527-532Article in journal (Refereed)
    Abstract [en]

    Radiation trapping occurs in rare-earth-doped active media with strong spectral overlap of luminescence and ground-state absorption. It is demonstrated experimentally that a confocal measurement mitigates the influence of radiation trapping on the measured luminescence lifetime, hence allowing for direct extraction of the lifetime from the measured decay curves. The radiation trapping effect is largely suppressed by probing a small sample volume and rejecting the photons reemitted from the unpumped region. This non-destructive measurement method is applied to ytterbium (Yb3+) activated potassium double tungstate crystalline layers with Yb3+ concentrations ranging from 1.2 at.% up to 76 at.% (~8 × 1019 - 5 × 1021 cm-3). The measured lifetime values are comparable to the results reported for Yb3+-doped potassium double tungstate powder diluted in liquid.

  • 124068. Yong, Y. S.
    et al.
    Aravazhi, S.
    Vázquez-Córdova, S. A.
    García-Blanco, S. M.
    Pollnau, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    1050 dB/cm Gain in a 57.5at.% Yb-doped KGd(WO4)2 thin film at 981 nm2014In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2014Conference paper (Refereed)
  • 124069. Yong, Y. -S
    et al.
    Aravazhi, S.
    Vázquez-Córdova, S. A.
    Herek, J. L.
    García-Blanco, S. M.
    Pollnau, Markus
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Temperature dependence of transition cross sections in rare-earth-doped laser materials2017In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2017Conference paper (Refereed)
  • 124070. Yong, Y. -S
    et al.
    Aravazhi, S.
    Vázquez-Córdova, S. A.
    Herek, J. L.
    García-Blanco, S. M.
    Pollnau, Markus
    KTH, School of Engineering Sciences (SCI), Applied Physics. University of Twente, Netherlands.
    Temperature-dependent absorption and gain of ytterbium-doped potassium double tungstates for chip-scale amplifiers and lasers2017In: Integrated Optics: Devices, Materials, and  Technologies XXI, SPIE - International Society for Optical Engineering, 2017, Vol. 10106, article id 1010606Conference paper (Refereed)
    Abstract [en]

    Ytterbium-doped potassium rare-earth double tungstate thin films are excellent candidates for highly efficient waveguide lasers, as well as high-gain waveguide amplifiers, with a record-high optical gain per unit length of 935 dB/cm recently demonstrated. However, the spectroscopic properties of these highly ytterbium-doped thin films and, in particular, their temperature dependence are not well investigated. These characteristics are required for the understanding of the behavior of the fabricated optical devices and crucial for further device optimization. We experimentally determined the absorption cross-sections for a potassium ytterbium gadolinium double tungstate, KYb0.57Gd0.43(WO4)2, thin film grown lattice matched onto an undoped KY(WO4)2 substrate. At room temperature, the peak cross-section value at 981 nm and the overall absorption spectrum are very similar to those of Yb-doped bulk potassium double tungstate crystals, although Yb is now the dominating rare-earth content. The temperature-dependent study shows a significant decrease of the absorption cross-section values at 933 nm and 981 nm with increasing temperature. We verify theoretically that this is due to the temperature dependence of fractional populations in the individual Stark levels of the absorbing crystal-field multiplet, in combination with the linewidth broadening with increasing temperature. Further investigations suggest that the broadening of absorption linewidth at 981 nm originates in the intra-manifold relaxation between the two lowest Stark levels of the ground state. Finally, the implications of the spectroscopic findings on the operating characteristics of waveguide amplifiers are investigated. Amplifiers operating at 80 °C are expected to exhibit only 67% of the maximum theoretical gain at room temperature.

  • 124071. Yong, Yean-Sheng
    et al.
    Aravazhi, Shanmugam
    Vazquez-Cordova, Sergio A.
    Carjaval, Joan J.
    Diaz, Francesc
    Herek, Jennifer L.
    Garcia-Blanco, Sonia M.
    Pollnau, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Temperature-dependent absorption and emission of potassium double tungstates with high ytterbium content2016In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 24, no 23, p. 26825-26837Article in journal (Refereed)
    Abstract [en]

    We study the spectroscopic properties of thin films of potassium ytterbium gadolinium double tungstates, KYb0.57Gd0.43(WO4)(2), and potassium ytterbium lutetium double tungstates, KYb0.76Lu0.24(WO4)(2), specifically at the central absorption line near 981 nm wavelength, which is important for amplifiers and lasers. The absorption cross-section of both thin films is found to be similar to those of bulk potassium rare-earth double tungstates, suggesting that the crystalline layers retain their spectroscopic properties albeit having >50 at.% Yb3+ concentration. The influence of sample temperature is investigated and found to substantially affect the measured absorption cross-section. Since amplifiers and lasers typically operate above room temperature due to pump-induced heating, the temperature dependence of the peak-absorption cross-section of the KYb0.57Gd0.43(WO4)(2) is evaluated for the sample being heated from 20 degrees C to 170 degrees C, resulting in a measured reduction of peak-absorption cross-section at the transitions near 933 nm and 981 nm by similar to 40% and similar to 52%, respectively. It is shown that two effects, the change of Stark-level population and linewidth broadening due to intra-manifold relaxation induced by temperature-dependent electronphonon interaction, contribute to the observed behavior. The effective emission cross-sections versus temperature have been calculated. Luminescence-decay measurements show no significant dependence of the luminescence lifetime on temperature.

  • 124072.
    Yong, Yean-Sheng
    et al.
    Univ Twente, MESA Inst Nanotechnol, Opt Sci Grp, POB 217, NL-7500 AE Enschede, Netherlands..
    Aravazhi, Shanmugam
    Univ Twente, MESA Inst Nanotechnol, Integrated Opt Microsyst Grp, POB 217, NL-7500 AE Enschede, Netherlands..
    Vazquez-Cordova, Sergio A.
    Univ Twente, MESA Inst Nanotechnol, Opt Sci Grp, POB 217, NL-7500 AE Enschede, Netherlands..
    Herek, Jennifer L.
    Univ Twente, MESA Inst Nanotechnol, Opt Sci Grp, POB 217, NL-7500 AE Enschede, Netherlands..
    Garcia-Blanco, Sonia M.
    Univ Twente, MESA Inst Nanotechnol, Opt Sci Grp, POB 217, NL-7500 AE Enschede, Netherlands..
    Pollnau, Markus
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics. Univ Twente, MESA Inst Nanotechnol, Integrated Opt Microsyst Grp, POB 217, NL-7500 AE Enschede, Netherlands..
    Temperature Dependence of Transition Cross Sections in Rare-earth-doped Laser Materials2017In: 2017 CONFERENCE ON LASERS AND ELECTRO-OPTICS EUROPE & EUROPEAN QUANTUM ELECTRONICS CONFERENCE (CLEO/EUROPE-EQEC), IEEE , 2017Conference paper (Refereed)
  • 124073. Yong, Y.S.
    et al.
    Aravazhi, S.
    Vázquez-Córdova, S.A.
    García-Blanco, S.M.
    Pollnau, Markus
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Integrated Optical MicroSystems Group, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, Enschede, Netherlands.
    Highly Yb-doped KGd(WO4)2 thin-film amplifier2015In: CLEO: Science and Innovations 2015, Optical Society of America, 2015Conference paper (Refereed)
    Abstract [en]

    We report record-high small-signal gain of 1050 dB/cm at 981 nm wavelength in a KGd<inf>0.425</inf>Yb<inf>0.575</inf>(WO<inf>4</inf>)<inf>2</inf> thin film. The sensitivity of gain to the shift of beam-focus position, which is critical under non-waveguiding conditions, is investigated.

  • 124074. Yong, Z.
    et al.
    Gong, C.
    Dong, Y.
    Zhang, S.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang University.
    Broadband localized electric field enhancement produced by a single-element plasmonic nanoantenna2017In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 7, no 4, p. 2074-2080Article in journal (Refereed)
    Abstract [en]

    We propose a novel design of a broadband plasmonic nanoantenna, investigate it numerically using finite-difference time-domain methods, and explain its performance using the analysis of charge distribution in addition to a multipole expansion. The custom-designed single-element nanoantenna consists of a modified gold ring structure with a bowtie-shaped spike inside. In contrast to the spectral response of extinction, the broadband localized electric field intensity enhancement is achieved over a bandwidth of 850 nm in the near infrared spectrum. Up to 26- and 22-fold field enhancements near the bowtie spike are obtained at the peak and even in the dip region of the extinction spectrum, respectively. Moreover, the nanostructure exhibits high tunability of its spectral features by modifying the structural parameters. We further demonstrate that the proposed nanoantenna can provide broadband spontaneous emission rates and quantum efficiency enhancements when a low-quantum efficiency emitter is introduced.

  • 124075. Yong, Zhengdong
    et al.
    Zhang, Senlin
    Dong, Yongjiang
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Broadband Nanoantennas for Plasmon Enhanced Fluorescence and Raman Spectroscopies2015In: Progress In Electromagnetics Research, ISSN 1070-4698, E-ISSN 1559-8985, Vol. 153, p. 123-131Article in journal (Refereed)
    Abstract [en]

    We propose a novel design of broadband plasmonic nanoantenna that is suitable for fluorescence and Raman enhancement. The structure consists of a gold nanoring and bowties at the center. We numerically investigate the near field and far field performance by employing the finite-difference time-domain method. High Purcell enhancement and large SERS are demonstrated in a record wide spectral bandwidth of 700 nm based on a single emitter-antenna configuration. Moreover, unlike a traditional antenna design, the proposed nanoantenna has low heat generation and high field enhancement at the gap simultaneously when operating off resonance.

  • 124076. Yong, Zhengdong
    et al.
    Zhang, Senlin
    Gong, Chensheng
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang University, China.
    Narrow band perfect absorber for maximum localized magnetic and electric field enhancement and sensing applications2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 24063Article in journal (Refereed)
    Abstract [en]

    Plasmonics offer an exciting way to mediate the interaction between light and matter, allowing strong field enhancement and confinement, large absorption and scattering at resonance. However, simultaneous realization of ultra-narrow band perfect absorption and electromagnetic field enhancement is challenging due to the intrinsic high optical losses and radiative damping in metals. Here, we propose an all-metal plasmonic absorber with an absorption bandwidth less than 8 nm and polarization insensitive absorptivity exceeding 99%. Unlike traditional Metal-Dielectric-Metal configurations, we demonstrate that the narrowband perfect absorption and field enhancement are ascribed to the vertical gap plasmonic mode in the deep subwavelength scale, which has a high quality factor of 120 and mode volume of about 10(-4) x (lambda(res)/n)(3). Based on the coupled mode theory, we verify that the diluted field enhancement is proportional to the absorption, and thus perfect absorption is critical to maximum field enhancement. In addition, the proposed perfect absorber can be operated as a refractive index sensor with a sensitivity of 885 nm/RIU and figure of merit as high as 110. It provides a new design strategy for narrow band perfect absorption and local field enhancement, and has potential applications in biosensors, filters and nonlinear optics.

  • 124077.
    Yongfei, Ji
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Proton Coupled Hole Transfer for H2O and small organic molecules (CH3OH, HCOOH and HCOH) on AnataseTiO2(101) SurfaceManuscript (preprint) (Other academic)
  • 124078. Yoo, Eun Jeong
    et al.
    Ahlquist, Mårten
    Department of Chemistry, Skaggs Institute of Chemical Biology, Scripps Research Institute.
    Bae, Imhyuck
    Sharpless, K. Barry
    Fokin, Valery V.
    Chang, Sukbok
    Mechanistic studies on the Cu-catalyzed three-component reactions of sulfonyl azides, 1-alkynes and amines, alcohols, or water: Dichotomy via a common pathway2008In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 73, no 14, p. 5520-5528Article in journal (Refereed)
    Abstract [en]

    Combined analyses of experimental and computational studies on the Cu-catalyzed three-component reactions of sulfonyl azides, terminal alkynes and amines, alcohols, or water are described. A range of experimental data including product distribution ratio and trapping of key intermediates support the validity of a common pathway in the reaction of 1-alkynes and two distinct types of azides substituted with sulfonyl and aryl(alkyl) groups. The proposal that bimolecular cycloaddition reactions take place initially between triple bonds and sulfonyl azides to give N-sulfonyl triazolyl copper intermediates was verified by a trapping experiment. The main reason for the different outcome from reactions between sulfonyl and aryl(alkyl) azides is attributed to the lability of the N-sulfonyl triazolyl copper intermediates. These species are readily rearranged to another key intermediate, ketenimine, into which various nucleophiles such as amines, alcohols, or water add to afford the three-component coupled products: amidines, imidates, or amides, respectively. In addition, the proposed mechanistic framework is in good agreement with the obtained kinetics and competition studies. A computational study (B3LYP/LACV3P*+) was also performed confirming the proposed mechanistic pathway that the triazolyl copper intermediate plays as a branching point to dictate the product distribution.

  • 124079. Yoo, Eun Jeong
    et al.
    Ahlquist, Mårten
    Department of Chemistry, Building 201, Kemitorvet Technical University of Denmark.
    Kim, Seok Hwan
    Bae, Imhyuck
    Fokin, Valery V.
    Sharpless, K. Barry
    Chang, Sukbok
    Copper-catalyzed synthesis of N-sulfonyl-1,2,3-triazoles: Controlling selectivity2007In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 46, no 10, p. 1730-1733Article in journal (Refereed)
    Abstract [en]

    (Chemical Equation Presented) 4-Substituted 1-(N-sulfonyl)-1,2,3-triazoles are selectively obtained by using the Cu-catalyzed azide-alkyne cycloaddition reaction with sulfonyl azides. Performing the reaction at 0°C in chloroform in the presence of 2,6-lutidine and Cul as the catalyst effectively prevents the ketenimine pathway and provides convenient access to N-sulfonyltriazoles in good to excellent yields.

  • 124080.
    Yoo, Jaehyun
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Learning communication delay patterns for remotely controlled UAV networks2017In: IFAC PAPERSONLINE, Elsevier, 2017, Vol. 50, no 1, p. 13216-13221Conference paper (Refereed)
    Abstract [en]

    This paper deals with collaborative unmanned aerial vehicles (UAVs) that are remotely controlled from a cloud server. The main contribution is to apply machine learning technique to find a pattern of network-induced effects on maneuvers of UAVs, in order to compensate for time delays and packet losses in remote communication. As machine learning technique, a Gaussian process (GP) based approach is employed due to its computational simplicity and flexibility in modelling complex expressions using a small number of parameters. We combine a deterministic compensation for an enhanced GP model to overcome a problem of the lack of training data at the beginning of training phase. This is done by defining training data input as a set of delayed observation and the deterministic compensation term, and by training the GP on residual between the true state and the input set. The proposed algorithm is evaluated to collaborative trajectory tracking of two UAVs. Simulations are performed for various delays and tracking scenarios. It is shown that the better tracking results are achieved compared to a conventional linear compensation algorithm.

  • 124081.
    Yoo, Jaehyun
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Semi-Supervised Learning for Mobile Robot Localization using Wireless Signal Strengths2017In: 2017 INTERNATIONAL CONFERENCE ON INDOOR POSITIONING AND INDOOR NAVIGATION (IPIN), 2017Conference paper (Refereed)
    Abstract [en]

    This paper proposes a new semi-supervised machine learning for localization. It improves localization efficiency by reducing efforts needed to calibrate labeled training data by using unlabeled data, where training data come from received signal strengths of a wireless communication link. The main idea is to treat training data as spatio-temporal data. We compare the proposed algorithm with the state-of-art semi-supervised learning methods. The algorithms are evaluated for estimating the unknown location of a smartphone mobile robot. The experimental results show that the developed learning algorithm is the most accurate and robust to the varying amount of training data, without sacrificing the computation speed.

  • 124082.
    Yoo, Jaehyun
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Kim, Hyoun Jin
    Indoor Localization Without a Prior Map by Trajectory Learning From Crowdsourced Measurements2017In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 66, no 11, p. 2825-2835Article in journal (Refereed)
  • 124083.
    Yoo, Jaehyun
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Kim, H. J.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Path planning for remotely controlled UAVs using Gaussian process filter2017In: 17th International Conference on Control, Automation and Systems, ICCAS 2017, IEEE Computer Society, 2017, p. 477-482Conference paper (Refereed)
    Abstract [en]

    Most of the recent results in control of unmanned aerial vehicles (UAVs) have focused on motion stability and navigation in well-structured environments, without considering communication delay influences. In order to deal with time delays and packet losses in networked UAVs, this paper suggests a machine learning based Gaussian process (GP) filter for a path planning problem. The developed GP filter estimates the UAV states accurately given delayed observation by learning the pattern of network-induced effects on UAV maneuvers. We validate that the GP filter produces the lower error rate than Kalman filter by analyzing error covariances. The proposed algorithm is evaluated on a collaborative trajectory tracking task for two networked-UAVs and the better control performance is achieved.

  • 124084.
    Yoo, Jaehyun
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Kim, H. Jin
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Mapless Indoor Localization by Trajectory Learning from a Crowd2016In: 2016 INTERNATIONAL CONFERENCE ON INDOOR POSITIONING AND INDOOR NAVIGATION (IPIN), Institute of Electrical and Electronics Engineers (IEEE), 2016, article id 7743685Conference paper (Refereed)
    Abstract [en]

    This paper suggests a mapless indoor localization using wifi received signal strength (RSS) of a smartphone, collected by multiple people. A new trajectory learning algorithm by combining a dynamic time warping and a machine learning technique is proposed in order to generate an alternative map. Moreover, we combine particle filter and Gaussian process (GP) for the position estimation, because it can use the alternative map as the probabilistic function (the prior), and can use probabilistic relationship (the likelihood) between wifi RSSs and location. Field experimental results confirm the usefulness of our algorithm when the map is not available and robustness against outliers, in that the accuracy of the proposed localization is similar to that using the true map information.

  • 124085.
    Yoo, Jaehyun
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Lee, Seungjae
    Seoul Natl Univ, Dept Mech & Aerosp Engn, Seoul, South Korea..
    Kim, H. Jin
    Seoul Natl Univ, Dept Mech & Aerosp Engn, Seoul, South Korea..
    Johansson, Karl H.
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Trajectory generation for networked UAVs using online learning for delay compensation2017In: 1st Annual IEEE Conference on Control Technology and Applications, CCTA 2017, IEEE, 2017, p. 1941-1946Conference paper (Refereed)
    Abstract [en]

    This paper presents a trajectory generation mechanism based on machine learning for a network of unmanned aerial vehicles (UAVs). For delay compensation, we apply an online regression technique to learn a pattern of network-induced effects on UAV maneuvers. Due to online learning, the control system not only adapts to changes to the environment, but also maintains a fixed amount of training data. The proposed algorithm is evaluated on a collaborative trajectory tracking task for two UAVs. Improved tracking is achieved in comparison to a conventional linear compensation algorithm.

  • 124086.
    Yoo, Jaehyun
    et al.
    KTH, School of Electrical Engineering (EES). KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Molin, Adam
    Jafarian, Matin
    KTH, School of Education and Communication in Engineering Science (ECE). KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Esen, Hasan
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Event-triggered Model Predictive Control with Machine Learning for Compensation of Model Uncertainties2017In: 2017 IEEE 56th Annual Conference on Decision and Control, CDC 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 5463-5468Conference paper (Refereed)
    Abstract [en]

    As one of the extensions of model predictive control (MPC), event-triggered MPC takes advantage of the reduction of control updates. However, approaches to event-triggered MPCs may be subject to frequent event-triggering instants in the presence of large disturbances. Motivated by this, this paper suggests an application of machine learning to this control method in order to learn a compensation model for disturbance attenuation. The suggested method improves both event-triggering policy efficiency and control accuracy compared to previous approaches to event-triggered MPCs. We employ the radial basis function (RBF) kernel based machine learning technique. By the universial approximation property of the RBF, which imposes an upper bound on the training error, we can present the stability analysis of the learningaided control system. The proposed algorithm is evaluated by means of position control of a nonholonomic robot subject to state-dependent disturbances. Simulation results show that the developed method yields not only two times less event triggering instants, but also improved tracking performance.

  • 124087.
    Yoo, Jaehyun
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Nekouei, Ehsan
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Event-based Observer and MPC with Disturbance Attenuation using ERM Learning2018In: 2018 European Control Conference, ECC 2018, Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 1894-1899, article id 8550289Conference paper (Refereed)
    Abstract [en]

    This paper presents a learning-based approach for disturbance attenuation for a non-linear dynamical system with event-based observer and model predictive control (MPC). Using the empirical risk minimization (ERM) method, we can obtain a learning error bound which is function of the number of samples, learning parameters, and model complexity. It enables us to analyze the closed-loop stability in terms of the learning property, where the state estimation error by the ERM learning is guaranteed to be bounded. Simulation results underline the learning's capability, the control performance and the event-triggering efficiency in comparison to the conventional event-triggered control scheme.

  • 124088. Yoo, S. J. B.
    et al.
    Heritage, J. P.
    Hernandez, V. J.
    Scott, R. P.
    Cong, W.
    Fontaine, N. K.
    Broeke, R. G.
    Cao, J.
    Seo, S. W.
    Baek, J. H.
    Soares, F. M.
    Du, Y.
    Yang, C.
    Jiang, W.
    Aihara, K.
    Ding, Z.
    Kolner, B. H.
    Pham, Anh-Vu
    Lin, Shu
    Olsson, F.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Liou, K. Y.
    Chu, S. N. G.
    Hamm, R. A.
    Patel, B.
    Hobson, W. S.
    Lothian, J. R.
    Vatanapradit, S.
    Gruezke, L. A.
    Tsang, W. T.
    Shearn, M.
    Scherer, A.
    Spectral phase encoded time spread optical code division multiple access technology for next generation communication networks Invited2007In: Journal of Optical Networking, ISSN 1536-5379, Vol. 6, no 10, p. 1210-1227Article in journal (Refereed)
    Abstract [en]

    We overview and summarize the progress of the spectral phase encoded time spreading (SPECTS) optical code division multiple access (O-CDMA) technology. Recent progress included a demonstration of a 320 Gbit/s (32-user x 10 Gbit/s) all-optical passive optical network testbed based on the SPECTS O-CDMA technology and a theoretical prediction of the spectral efficiency at 100% and above. In particular, InP-based integrated photonics allows implementation of SPECTS O-CDMA transmitters and receivers monolithically integrated on a chip. The integrated InP chip technology not only allows robust and compact configurations for practical and low-cost O-CDMA network deployments but also offers code reconfigurations at rapid rates for secure communication applications.

  • 124089. Yoo, S. J. B.
    et al.
    Lourdudoss, Sebastian
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    InP photonic integrated circuits for optical communciations2008Conference paper (Refereed)
    Abstract [en]

    This paper describes photonic integration circuits (PICs) realized on the InP platform including high-speed mode locked lasers, arrayed waveguide gratings (AWGs), differential Mach-Zehnder optical switches (MZI), and high-speed amplitude and phase modulators. Selected area hydride vapor phase epitaxy (HVPE) and organometallic chemical vapor deposition (OMCVD) were used to realized planarized and passivated integration including active and passive elements. The integrated chips of various configurations were investigated for 'Optical Code Division Multiple Access (O-CDMA)', in local area networks, and for 'Optical Arbitrary Waveform Generation (OAWG),' in high-speed otptical communications.

  • 124090. Yoo, S. J.
    et al.
    Ismail, Mohammed
    A highly linear CMOS baseband chain for wideband wireless applications2004In: ETRI Journal, ISSN 1225-6463, E-ISSN 2233-7326, Vol. 26, no 5, p. 486-492Article in journal (Refereed)
    Abstract [en]

    The emergence of wide channel bandwidth wireless standards requires the use of a highly linear, wideband integrated CMOS baseband chain with moderate power consumption. In this paper, we present the design of highly linear, wideband active RC filters and a digitally programmable variable gain amplifier. To achieve a high unity gain bandwidth product with moderate power consumption, the feed-forward compensation technique is applied for the design of wideband active RC filters. Measured results from a 0.5 mum CMOS prototype baseband chain show a cutoff frequency of 10 MHz, a variable gain range of 33 dB, an in-band IIP3 of 13 dBV, and an input referred noise of 114 muVrms while dissipating 20 mW from a 3 V supply.

  • 124091. Yoo, T.
    et al.
    Khym, S.
    Lee, H.
    Chung, S.
    Department of Physics, Korea University.
    Lee, S.
    Liu, X.
    Furdyna, J. K.
    Asymmetry in the planar Hall resistance of Fe films grown on vicinal GaAs substrates2010In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 107, no 9Article in journal (Refereed)
    Abstract [en]

    We have investigated the Hall effects of the ferromagnetic Fe films grown on standard (001) and on vicinal (i.e., slightly tilted toward the [1 1- 0] direction) GaAs substrates at room temperature. While the symmetric hysteresis in the planar Hall resistance (PHR) is obtained from Fe film grown nominal (001) substrate, a significant asymmetry appeared in the Fe films grown on vicinal GaAs substrates. The asymmetry in the hysteresis of the PHR observed in the Fe film grown on vicinal surface originates from the switching of magnetization M between two easy axes while it is confined to the (001) crystal plane rather than to the film plane, thus involves both the planar Hall effect (PHE) and the anomalous Hall effect (AHE). The contribution of the AHE systematically increases as the tilted angle of the substrate increases. The asymmetric hysteresis of the PHR in the Fe films grown on the tilted substrate provides four distinct resistance states, which can be used for quaternary memory devices. © 2010 American Institute of Physics.

  • 124092. Yoo, T.
    et al.
    Khym, S.
    Yea, S. -Y
    Chung, S.
    Department of Physics, Korea University.
    Lee, S.
    Liu, X.
    Furdyna, J. K.
    Four discrete Hall resistance states in single-layer Fe film for quaternary memory devices2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 95, no 20Article in journal (Refereed)
    Abstract [en]

    We report the realization of four distinct magnetic states using single layers of Fe at room temperature. When the Fe film was grown on the vicinal surface of GaAs, the fourfold-symmetric magnetization along crystallographic direction give rise to four distinct Hall resistance values due to the different combination of planar and anomalous Hall effects for the given direction. Each Hall resistance state can be written reproducibly by the sequence of field pulses and was remained constant at the written state for more than 2 h, which brings the idea of a quaternary memory device much closer to practical implementation. © 2009 American Institute of Physics.

  • 124093.
    Yoon, Jungmin
    et al.
    Korea Adv Inst Sci & Technol, Canc Metastasis Control Ctr, Dept Biol Sci, Daejeon 34141, South Korea..
    Kim, Seung Joong
    Univ Calif San Francisco, Calif Inst Quantitat Biosci, Dept Bioengn & Therapeut Sci, Dept Pharmaceut Chem, San Francisco, CA 94158 USA..
    An, Sojin
    Univ Michigan, Sch Med, Dept Biol Chem, 1150 W Med Ctr Dr,SPC 5606, Ann Arbor, MI 48109 USA..
    Cho, Saehyun
    Korea Adv Inst Sci & Technol, Canc Metastasis Control Ctr, Dept Biol Sci, Daejeon 34141, South Korea..
    Leitner, Alexander
    ETH, Inst Mol Syst Biol, Dept Biol, CH-8093 Zurich, Switzerland..
    Jung, Taeyang
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Structural Biotechnology. Karolinska Inst, Dept Biosci & Nutr, SE-14157 Stockholm, Sweden; Korea Adv Inst Sci & Technol, Canc Metastasis Control Ctr, Dept Biol Sci, Daejeon 34141, South Korea.
    Aebersold, Ruedi
    ETH, Inst Mol Syst Biol, Dept Biol, CH-8093 Zurich, Switzerland.;Univ Zurich, Fac Sci, Zurich, Switzerland..
    Hebert, Hans
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Structural Biotechnology. Karolinska Inst, Dept Biosci & Nutr, SE-14157 Stockholm, Sweden.
    Cho, Uhn-Soo
    Univ Michigan, Sch Med, Dept Biol Chem, 1150 W Med Ctr Dr,SPC 5606, Ann Arbor, MI 48109 USA..
    Song, Ji-Joon
    Korea Adv Inst Sci & Technol, Canc Metastasis Control Ctr, Dept Biol Sci, Daejeon 34141, South Korea..
    Integrative Structural Investigation on the Architecture of Human Importin4_Histone H3/1-14_Asf1a Complex and Its Histone H3 Tail Binding2018In: Journal of Molecular Biology, ISSN 0022-2836, E-ISSN 1089-8638, Vol. 430, no 6, p. 822-841Article in journal (Refereed)
    Abstract [en]

    Importin4 transports histone H3/H4 in complex with Asf1a to the nucleus for chromatin assembly. Importin4 recognizes the nuclear localization sequence located at the N-terminal tail of histones. Here, we analyzed the structures and interactions of human Importin4, histones and Asf1a by cross-linking mass spectrometry, X-ray crystallography, negative-stain electron microscopy, small-angle X-ray scattering and integrative modeling. The cross-linking mass spectrometry data showed that the C-terminal region of Importin4 was extensively cross-linked with the histone H3 tail. We determined the crystal structure of the C-terminal region of Importin4 bound to the histone H3 peptide, thus revealing that the acidic patch in Importin4 accommodates the histone H3 tail, and that histone H3 Lys14 contributes to the interaction with Importin4. In addition, we show that Asf1a modulates the binding of histone H3/H4 to Importin4. Furthermore, the molecular architecture of the Importin4_histone H3/H4_Asf1a complex was produced through an integrative modeling approach. Overall, this work provides structural insights into how Importin4 recognizes histones and their chaperone complex.

  • 124094. Yoon, K. H.
    et al.
    Noh, J. S.
    Kwon, C. H.
    Muhammed, Mamoun
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Photocatalytic behavior of TiO2 thin films prepared by sol-gel process2006In: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 95, no 1, p. 79-83Article in journal (Refereed)
    Abstract [en]

    Titanium dioxide solution was prepared via sol-gel process with and without acetyl acetone (AcAc). The formation of the anatase phase in the thin films using AcAc was initiated at 300 degrees C while the anatase phase in the thin films without using AcAc began to appear at 100 degrees C. Surface roughness of the TiO2 films using and without using AcAc ranged from 0.414 to 3.08 nm and from 3.72 to 5.35 nm, respectively. Photocatalytic decomposition rate examined by methylene blue solution showed 80% at 400 degrees C and 88% at 600 degrees C for the TiO2 thin films using AcAc. On the other hand, the photocatalytic decomposition rate of the TiO2 thin films without using AcAc showed 80% at 100 degrees C and 97% at 400 degrees C, respectively. At the temperature above 400 degrees C, the photocatalytic activity decreased due to appearance of the rutile phase. Comparison between the TiO2 thin films showing the maximum photocatalytic activity revealed that the TiO2 thin film without using AcAc showed 10% higher photocatalytic decomposition rate from the initial 10 to 120 min as compared with the TiO2 thin film using AcAc, which was closely related to the formation of the anatase phase and the surface roughness.

  • 124095. Yoon, Y. J.
    et al.
    Chung, S. J.
    Lee, H. J.
    Lee, S.
    An, S. Y.
    Liu, X.
    Furdyna, J. K.
    Effect of p-type buffer layer on the properties of GaMnAs ferromagnetic semiconductors2004In: Journal of the Korean Physical Society, ISSN 0374-4884, E-ISSN 1976-8524, Vol. 45, no SUPPL., p. S720-S723Article in journal (Refereed)
    Abstract [en]

    We have studied the magnetic and transport properties of Ga 1-xMn xAs epilayers grown either on undoped or on p-type doped GaAs buffer layer. The temperature dependence of the resistivity at zero magnetic field reveals that the Curie temperature (T C) in the Ga 1-xMn xAs layer grown on p-type doped GaAs buffer is slightly higher than that observed in the layer grown on undoped GaAs buffer. The magnetic and transport properties of the two samples show significant differences when they are placed in a magnetic field. In SQUID measurements, the Ga 1-xMn xAs layer grown on p-type buffer shows a larger coercive field and much slower decay of remanent magnetization than the layer grown on undoped buffer. This robust magnetic behavior observed in the doped sample is discussed in terms of the increase of free carrier concentration in the system arising from p-type doping in the buffer layer.

  • 124096. Yordanova, E.
    et al.
    Voros, Z.
    Varsani, A.
    Graham, D. B.
    Norgren, C.
    Khotyaintsev, Yu. V.
    Vaivads, A.
    Eriksson, E.
    Nakamura, R.
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Marklund, Göran
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Ergun, R. E.
    Magnes, W.
    Baumjohann, W.
    Fischer, D.
    Plaschke, F.
    Narita, Y.
    Russell, C. T.
    Strangeway, R. J.
    Le Contel, O.
    Pollock, C.
    Torbert, R. B.
    Giles, B. J.
    Burch, J. L.
    Avanov, L. A.
    Dorelli, J. C.
    Gershman, D. J.
    Paterson, W. R.
    Lavraud, B.
    Saito, Y.
    Electron scale structures and magnetic reconnection signatures in the turbulent magnetosheath2016In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 43, no 12, p. 5969-5978Article in journal (Refereed)
    Abstract [en]

    Collisionless space plasma turbulence can generate reconnecting thin current sheets as suggested by recent results of numerical magnetohydrodynamic simulations. The Magnetospheric Multiscale (MMS) mission provides the first serious opportunity to verify whether small ion-electron-scale reconnection, generated by turbulence, resembles the reconnection events frequently observed in the magnetotail or at the magnetopause. Here we investigate field and particle observations obtained by the MMS fleet in the turbulent terrestrial magnetosheath behind quasi-parallel bow shock geometry. We observe multiple small-scale current sheets during the event and present a detailed look of one of the detected structures. The emergence of thin current sheets can lead to electron scale structures. Within these structures, we see signatures of ion demagnetization, electron jets, electron heating, and agyrotropy suggesting that MMS spacecraft observe reconnection at these scales.

  • 124097.
    Yosef Nezhad Arya, Nessa
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Concrete Structures.
    Second-order FE Analysis of Axial Loaded Concrete Members According to Eurocode 22015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A nonlinear finite element analysis was performed for an axial loaded reinforced concrete column subjected to biaxial bending taking into account second-order effects. According to Eurocode there are two ways to take second-order effects into consideration: nonlinear FE analysis and hand calculation based on the simplified methods explained in Eurocode 2. Since simulating this kind of structures in ABAQUS is difficult, several simulations were made to find the correct model with satisfying accuracy.

    The nonlinear analysis focused on material modelling of concrete and its nonlinear behaviour. The simulation took into consideration the inelastic behaviour of concrete along with the confinement effect from transverse reinforcement.

    The finite element model was verified by comparing the obtained results from FEA to the results from a benchmark experiment. The mean values needed for simulating the FE model was derived from the mean compressive strength of concrete. After verification, another FE model using design parameters was analysed and the results were compared to the results from calculations based on simplified methods according to Eurocode 2 to see how much they agreed with each other. In a parametric study, the effect of eccentricity, compressive and tensile strength of concrete, fracture energy, modulus of elasticity, column cross-section dimension and length, steel yield stress and stirrup spacing were studied.

    A comparison between outcomes from the simplified methods and ABAQUS, calculated with design parameters showed that the bearing capacity from FE analysis was 21-34 % higher than the one obtained with the simplified methods. It is recommended that in further studies, analyse different slender reinforced concrete column with different L/h with FE-simulation to investigate if FEA always gives a more accurate result. For this case, and probably for columns with complex geometries, a finite element analysis is a better choice. 

  • 124098. Yosef, Nir
    et al.
    Käll, Lukas
    KTH, School of Biotechnology (BIO), Gene Technology.
    From sequence to structure to networks2008In: Genome Biology, ISSN 1465-6906, E-ISSN 1474-760X, Vol. 9, no 11Article in journal (Refereed)
    Abstract [en]

    A report on the 7th European Conference on Computational Biology (ECCB), Cagliari, Italy, 22-26 September 2008.

  • 124099.
    Yosef, Sonia
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management.
    Sommer, Julia
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management.
    High Yield – A Late Bloomer’s Time To Shine?2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Real estate companies are capital intense and bank loans represent the most common source of funding. However, the years following the latest financial crisis resulted in difficult terms and expensive bank loans, which cleared a path for alternative sources of funding. Small and me-dium-sized real estate companies displayed a particular interest in corporate bonds and ever since then the real estate sector have been overrepresented on the Swedish corporate bond mar-ket. Despite the growth during the past years, the Swedish market still appears to be underde-veloped compared to other countries. However, several trends are now indicating that High Yield is on the rise. New regulations that are currently being implemented will increase the costs for banks further and consequently make bank loans even more expensive. Simultane-ously, the current low interest-rate environment and volatile stock markets are increasing de-mand for High Yield alternatives among retail and institutional investors. This study investi-gates the High Yield market for small and medium-sized real estate companies and is built upon eleven interviews with professionals. It concludes that the market is underdeveloped because there has been no previous demand for it. Swedish banks and companies have traditionally had a synergetic relationship while investors relied on saving accounts and equities. The situation today is different; investors are demanding High Yield investments and the segment will most probably increase in the future. Real estate companies are positive to bonds and wish to increase the current ratio of their debt portfolio. There are however several barriers for continued growth, such as lack of knowledge, transparency, liquidity as well as fair pricing in the market. In the current state, corporate bond investments are suitable only for professional investors. The ex-emption is High Net Worth Individuals, who buy and hold, which are particularly suited for smaller corporate bonds.

  • 124100.
    Yosef, Sonia
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management.
    Sommer, Julia
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management.
    High Yield – Tid Att Blomstra?: En studie av den svenska företagsobligationsmarknaden för små och medelstora fastighetsföretag2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
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