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  • 201.
    Blom, Hans
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Experimentell biomolekylär fysik.
    Chmyrov, Andriy
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Experimentell biomolekylär fysik.
    Hassler, Kai
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Experimentell biomolekylär fysik.
    Davis, L.M.
    Widengren, Jerker
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Experimentell biomolekylär fysik.
    Triplet-State Investigations of Fluorescent Dyes at Dielectric Interfaces Using Total Internal Reflection Fluorescence Correlation Spectroscopy2009Inngår i: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 113, nr 19, s. 5554-5566Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The triplet-state kinetics of several fluorescent dyes used in ultrasensitive fluorescence microscopy are investigated using total internal reflection fluorescence correlation spectroscopy (TIR-FCS). A theoretical outline of the correlation analysis and the physical aspects of evanescent excitation and fluorescence emission at dielectric interfaces are given. From this analysis, the rates of intersystem crossing and triplet decay are deduced for fluorescein, ATTO 488, rhodamine 110, rhodamine 123, and rhodamine 6G in aqueous buffer solutions. All investigated dyes show slightly higher triplet rates at the dielectric interface compared to bulk solution measurements. We attribute this enhancement to possible modifications of the dyes’ photophysical properties near a dielectric interface. In the case of rhodamine 6G, the impact of changes in the dye concentration, ionic strength of the solvent, and potassium iodide concentration are also investigated. This leads to a better understanding of the influences of dye−dye, dye−solvent, and dye−surface interactions on the increased triplet intersystem crossing and triplet decay rates. The study shows that analysis of triplet-state kinetics by TIR-FCS not only results in a better understanding of how the photophysical properties of the dyes are affected by the presence of an interface, but also provides a means for probing the microenvironment near dielectric interfaces.

  • 202.
    Blom, Hans
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Experimentell biomolekylär fysik.
    Hassler, Kai
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Experimentell biomolekylär fysik.
    Chmyrov, Andriy
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Experimentell biomolekylär fysik.
    Widengren, Jerker
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Experimentell biomolekylär fysik.
    Electrostatic Interactions of Fluorescent Molecules with Dielectric Interfaces Studied by Total Internal Reflection Fluorescence Correlation Spectroscopy2010Inngår i: International Journal of Molecular Sciences, ISSN 1422-0067, E-ISSN 1422-0067, Vol. 11, nr 2, s. 368-406Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Electrostatic interactions between dielectric surfaces and different fluorophoresused in ultrasensitive fluorescence microscopy are investigated using objective-based TotalInternal Reflection Fluorescence Correlation Spectroscopy (TIR-FCS). The interfacialdynamics of cationic rhodamine 123 and rhodamine 6G, anionic/dianionic fluorescein,zwitterionic rhodamine 110 and neutral ATTO 488 are monitored at various ionic strengthsat physiological pH. As analyzed by means of the amplitude and time-evolution of theautocorrelation function, the fluorescent molecules experience electrostatic attraction orrepulsion at the glass surface depending on their charges. Influences of the electrostaticinteractions are also monitored through the triplet-state population and triplet relaxationtime, including the amount of detected fluorescence or the count-rate-per-moleculeparameter. These TIR-FCS results provide an increased understanding of how fluorophoresare influenced by the microenvironment of a glass surface, and show a promising approachfor characterizing electrostatic interactions at interfaces.

  • 203.
    Blom, Hans
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Experimentell biomolekylär fysik.
    Kastrup, L.
    Eggeling, C.
    Fluorescence fluctuation spectroscopy in reduced detection volumes2006Inngår i: Current Pharmaceutical Biotechnology, ISSN 1389-2010, E-ISSN 1873-4316, Vol. 7, nr 1, s. 51-66Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Fluorescence fluctuation spectroscopy is a versatile technique applied to in vitro and in vivo investigations of biochemical processes Such as interactions, mobilities or densities with high specifity and sensitivity. The prerequisite of this dynamical fluorescence technique is to have, at a time, only few fluorescent molecules in the detection volume in order to generate significant fluorescence fluctuations. For Usual confocal fluorescence microscopy this amounts to a useful concentration in the nanomolar range. The concentration of many biomolecules in living cell or on cell membranes is, however, often quite high, usually in the micro- to the millimolar range. To allow fluctuation spectroscopy and track intracellular interaction or localization of single fluorescently labeled biomolecules ill Such crowded environments, development of detection volumes with nanoscale resolution is necessary. As diffraction prevents this in the case of light microscopy, new (non-invasive) optical concepts have been developed. In this mini-review article we present recent advancements, implemented to decrease the detection volume below that of normal fluorescence microscopy. Especially, their combination with fluorescence fluctuation spectroscopy is emphasized.

  • 204.
    Blom, Hans
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Experimentell biomolekylär fysik.
    Ronnlund, Daniel
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Experimentell biomolekylär fysik.
    Scott, Lena
    Spicarova, Zuzana
    Widengren, Jerker
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Experimentell biomolekylär fysik.
    Bondar, Alexander
    Aperia, Anita
    Brismar, Hjalmar
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Cellens fysik.
    Spatial distribution of Na+-K+-ATPase in dendritic spines dissected by nanoscale superresolution STED microscopy2011Inngår i: BMC neuroscience (Online), ISSN 1471-2202, E-ISSN 1471-2202, Vol. 12, s. 16-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: The Na+,K+-ATPase plays an important role for ion homeostasis in virtually all mammalian cells, including neurons. Despite this, there is as yet little known about the isoform specific distribution in neurons. Results: With help of superresolving stimulated emission depletion microscopy the spatial distribution of Na+,K+-ATPase in dendritic spines of cultured striatum neurons have been dissected. The found compartmentalized distribution provides a strong evidence for the confinement of neuronal Na+,K+-ATPase (alpha 3 isoform) in the postsynaptic region of the spine. Conclusions: A compartmentalized distribution may have implications for the generation of local sodium gradients within the spine and for the structural and functional interaction between the sodium pump and other synaptic proteins. Superresolution microscopy has thus opened up a new perspective to elucidate the nature of the physiological function, regulation and signaling role of Na+,K+-ATPase from its topological distribution in dendritic spines.

  • 205.
    Blom, Hans
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Cellens fysik. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Rönnlund, Daniel
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Experimentell biomolekylär fysik.
    Scott, L.
    Westin, L.
    Widengren, Jerker
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Experimentell biomolekylär fysik. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Aperia, A.
    Brismar, Hjalmar
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Cellens fysik. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Spatial Distribution of DARPP-32 in Dendritic Spines2013Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, nr 9, s. e75155-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The phosphoprotein DARPP-32 (dopamine and cyclic adenosine 3́, 5́-monophosphate-regulated phosphoprotein, 32 kDa) is an important component in the molecular regulation of postsynaptic signaling in neostriatum. Despite the importance of this phosphoprotein, there is as yet little known about the nanoscale distribution of DARPP-32. In this study we applied superresolution stimulated emission depletion microscopy (STED) to assess the expression and distribution of DARPP-32 in striatal neurons. Primary culture of striatal neurons were immunofluorescently labeled for DARPP-32 with Alexa-594 and for the dopamine D1 receptor (D1R) with atto-647N. Dual-color STED microscopy revealed discrete localizations of DARPP-32 and D1R in the spine structure, with clustered distributions in both head and neck. Dissected spine structures reveal that the DARPP-32 signal rarely overlapped with the D1R signal. The D1R receptor is positioned in an "aggregated" manner primarily in the spine head and to some extent in the neck, while DARPP-32 forms several neighboring small nanoclusters spanning the whole spine structure. The DARPP-32 clusters have a mean size of 52 +/- 6 nm, which is close to the resolution limit of the microscope and corresponds to the physical size of a few individual phosphoprotein immunocomplexes. Dissection of synaptic proteins using superresolution microscopy gives possibilities to reveal in better detail biologically relevant information, as compared to diffraction-limited microscopy. In this work, the dissected postsynaptic topology of the DARPP-32 phosphoprotein provides strong evidence for a compartmentalized and confined distribution in dendritic spines. The protein topology and the relatively low copy number of phosphoprotein provides a conception of DARPP-32's possibilities to fine-tune the regulation of synaptic signaling, which should have an impact on the performance of the neuronal circuits in which it is expressed.

  • 206.
    Blom, Hans
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Experimentell biomolekylär fysik.
    Rönnlund, Daniel
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Experimentell biomolekylär fysik.
    Scott, Lena
    Spicarova, Zuzana
    Rantanen, Ville
    Widengren, Jerker
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Experimentell biomolekylär fysik.
    Aperia, Anita
    Brismar, Hjalmar
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Cellens fysik.
    Nearest neighbor analysis of dopamine D1 receptors and Na plus -K plus -ATPases in dendritic spines dissected by STED microscopy2012Inngår i: Microscopy research and technique (Print), ISSN 1059-910X, E-ISSN 1097-0029, Vol. 75, nr 2, s. 220-228Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Protein localization in dendritic spines is the focus of intense investigations within neuroscience. Applications of super-resolution microscopy to dissect nanoscale protein distributions, as shown in this work with dual-color STED, generate spatial correlation coefficients having quite small values. This means that colocalization analysis to some extent looses part of its correlative impact. In this study we thus introduced nearest neighbor analysis to quantify the spatial relations between two important proteins in neurons, the dopamine D1 receptor and Na+,K+-ATPase. The analysis gave new information on how dense the D1 receptor and Na+,K+-ATPase constituting nanoclusters are located both with respect to the homogenous (self to same) and the heterogeneous (same to other) topology. The STED dissected nanoscale topologies provide evidence for both a joint as well as a separated confinement of the D1 receptor and the Na+,K+-ATPase in the postsynaptic areas of dendritic spines. This confined topology may have implications for generation of local sodium gradients and for structural and functional interactions modulating slow synaptic transmission processes. Microsc. Res. Tech., 2011.

  • 207.
    Blom, Hans
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Cellens fysik. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Widengren, Jerker
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Experimentell biomolekylär fysik.
    STED microscopy: towards broadened use and scope of applications2014Inngår i: Current opinion in chemical biology, ISSN 1367-5931, E-ISSN 1879-0402, Vol. 20, nr 1, s. 127-133Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    High resolution Stimulated Emission Depletion (STED) microscopy has been demonstrated for fundamental studies in cells, living tissue and organisms. Today, a major trend in the STED technique development is to make the instruments simpler and more user-friendly, without compromising performance. This has become possible by new low-cost, turn-key laser technology and by implementing specifically designed phase plates and polarization elements, extending and simplifying the shaping of the laser beam profiles. These simpler and cheaper realizations of STED are now becoming more broadly available. In parallel with the continuous development of sample preparation and fluorophore reporter molecules ultimately setting the limit of the image quality, contrast and resolution, we can thus expect a significant increase in the use of STED, in science as well as for clinical and drug development purposes.

  • 208.
    Blom, Hans
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Cellulär biofysik. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Widengren, Jerker
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Experimentell biomolekylär fysik.
    Stimulated Emission Depletion Microscopy2017Inngår i: Chemical Reviews, ISSN 0009-2665, E-ISSN 1520-6890, Vol. 117, nr 11, s. 7377-7427Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Despite its short history, diffraction-unlimited fluorescence microscopy techniques have already made a substantial imprint in the biological sciences. In this review, we describe how stimulated emission depletion (STED) imaging originally evolved, how it compares to other optical super-resolution imaging techniques, and what advantages it provides compared to previous golden-standards for biological microscopy, such as diffraction-limited optical microscopy and electron microscopy. We outline the prerequisites for successful STED imaging experiments, emphasizing the equally critical roles of instrumentation, sample preparation, and photophysics, and describe major evolving strategies for how to push the borders of STED imaging even further in life science. Finally, we provide examples of how STED nanoscopy can be applied, within three different fields with particular potential for STED imaging experiments: neuroscience, plasma membrane biophysics, and subcellular clinical diagnostics. In these areas, and in many more, STED imaging can be expected to play an increasingly important role in the future.

  • 209. Blom, M.
    et al.
    Reis, K.
    Nehru, V.
    Blom, Hans
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Cellens fysik. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Gad, A. K. B.
    Aspenström, P.
    RhoD is a Golgi component with a role in anterograde protein transport from the ER to the plasma membrane2015Inngår i: Experimental Cell Research, ISSN 0014-4827, E-ISSN 1090-2422, Vol. 333, nr 2, s. 208-219Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    RhoD is a member of the Rho GTPase family and it coordinates actin dynamics and membrane trafficking. Activation of RhoD results in formation of filopodia, dissolution of stress fibers, and the subsequent formation of short actin bundles. In addition, RhoD localizes to early endosomes and recycling endosomes, and has a regulatory role in endosome trafficking. In this study, we report on a function of RhoD in the regulation of Golgi homeostasis. We show that manipulation of protein and activation levels of RhoD, as well as of its binding partner WHAMM, result in derailed localization of Golgi stacks. Moreover, vesicle trafficking from the endoplasmic reticulum to the plasma membrane via the Golgi apparatus measured by the VSV-G protein is severely hampered by manipulation of RhoD or WHAMM. In summary, our studies demonstrate a novel role for this member of the Rho GTPases in the regulation of Golgi function.

  • 210. Blomqvist, M.
    et al.
    Pålsson, M.
    Blomster, O.
    Manneberg, Göran
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Fundamental-mode fiber-to-fiber coupling at high-power2009Inngår i: Solid State Lasers XVIII: Technology and Devices, SPIE - International Society for Optical Engineering, 2009, s. 71930F-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Fiber-to-fiber coupling between two different fibers is a state of the art technology. Products are available on the market where multimode fibers can be coupled with very low power loss, at very high powers (multi-kilowatt). We have, however, always been forced to accept a certain loss in beam quality, manifesting as an increase in the Beam Parameter Product (BPP). In fundamental-mode fiber-to-fiber coupling no beam quality is lost. We instead expect to have a certain power loss in the coupling. This paper addresses the problems in free-space fundamental-mode fiber-to-fiber coupling, including theoretical estimations of expected power loss, estimated demands on the stability of the optics as well as measured values on a fundamental mode fiber-to-fiber coupler. The theoretical calculations of the sensitivity of the coupling efficiency due to radial misalignment and defocus (longitudinal displacement) have been confirmed experimentally. Experimental results at 100 W laser power include 88% coupling efficiency using a large mode area fiber with mode-field diameter (MFD) of 18 μm and 75 % coupling efficiency using a single-mode fiber with MFD of 6.4 μm.

  • 211. Bode, M.
    et al.
    Freitag, I.
    Spiekermann, S.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Ultra-violet single frequency pulses with high averagepower using frequency converted passively Q-switched quasi-monolithic Nd:YAGring lasers2001Konferansepaper (Fagfellevurdert)
  • 212.
    Bogoni, Antonella
    et al.
    Scuola Super Sant Anna, I-56127 Pisa, Italy..
    Mecozzi, Antonio
    Univ Aquila, Dept Phys & Chem Sci, I-67100 Laquila, Italy..
    Okonkwo, Chigo M.
    Eindhoven Univ Technol, NL-5612 AZ Eindhoven, Netherlands..
    Plant, David V.
    McGill Univ, Dept Elect & Comp Engn, Montreal, PQ, Canada..
    Saitoh, Kunimasa
    Hokkaido Univ, Elect Engn, Sapporo, Hokkaido 0600814, Japan.;Hokkaido Univ, Grad Sch Engn, Sapporo, Hokkaido 0600814, Japan.;Hokkaido Univ, Grad Sch Informat Sci & Technol, Sapporo, Hokkaido 0600814, Japan..
    Wosinska, Lena
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik. KTH, Skolan för elektroteknik och datavetenskap (EECS), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Liu, Gordon Ning
    Huawei Technol Co Ltd, Shenzhen 518129, Peoples R China..
    Umbach, Andreas
    AUCCEPT Consulting GmbH, D-14055 Berlin, Germany..
    Charlet, Gabriel
    Huawei Paris Res Ctr, F-75002 Paris, France..
    Gaudino, Roberto
    Politecn Torino, Dipartimento Elettron & Telecomunicaz, I-10129 Turin, Italy..
    Foreword to the Special Issue on the 44th European Conference on Optical Communication (ECOC 2018)2019Inngår i: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 37, nr 5, s. 1450-1455Artikkel i tidsskrift (Annet vitenskapelig)
  • 213.
    Bokhari, Ramiz Ahmed
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Confocal Imaging and Analysis of Quantum Dots on living Cells2013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 214. Bolanos, Western
    et al.
    Carvajal, Joan J.
    Mateos, Xavier
    Cinta Pujol, Maria
    Thilmann, Nicky
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Lifante, Gines
    Aguilo, Magdalena
    Diaz, Francesc
    Epitaxial layers of KY1-x-yGdxLuy(WO4)(2) doped with Er3+ and Tm3+ for planar waveguide lasers2010Inngår i: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 32, nr 3, s. 469-474Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Here we show the results we obtained in the fabrication of planar wave guide lasers based on monoclinic double tungstates doped with Er3+ and Tm3+. We have successfully introduced these ions into the lattice matched KY0.59Gd0.19Lu0.22(WO4)(2) epitaxial layers grown on KY(WO4)(2) substrates without loss of optical quality and keeping a high refractive index contrast between the epitaxial layer and the substrate. We characterized the waveguiding properties of these epitaxial layers at lambda = 632.8 nm by dark modes spectroscopy, and we showed that these waveguides can support several TE and TM modes. Spectroscopic characterization of the active lanthanide ions in these crystals is also presented.

  • 215. Bolaños, W.
    et al.
    Carvajal, J.J.
    Mateos, X.
    Pujol, M.C.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Thilmann, Nicky
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Aguiló, M.
    Díaz, F.
    Fabrication and characterization of epitaxial layers of the KY1-x-yGdxLuy(WO4)2 system for waveguide lasers2009Konferansepaper (Fagfellevurdert)
  • 216. Bollampalli, V. P.
    et al.
    Harumi Yamashiro, L.
    Feng, X.
    Bierschenk, D.
    Gao, Y.
    Blom, Hans
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Cellens fysik. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Henriques-Normark, B.
    Nylén, S.
    Rothfuchs, A. G.
    BCG Skin Infection Triggers IL-1R-MyD88-Dependent Migration of EpCAMlow CD11bhigh Skin Dendritic cells to Draining Lymph Node During CD4+ T-Cell Priming2015Inngår i: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 11, nr 10, artikkel-id e1005206Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The transport of antigen from the periphery to the draining lymph node (DLN) is critical for T-cell priming but remains poorly studied during infection with Mycobacterium bovis Bacille Calmette-Guérin (BCG). To address this we employed a mouse model to track the traffic of Dendritic cells (DCs) and mycobacteria from the BCG inoculation site in the skin to the DLN. Detection of BCG in the DLN was concomitant with the priming of antigen-specific CD4+ T cells at that site. We found EpCAMlow CD11bhigh migratory skin DCs to be mobilized during the transport of BCG to the DLN. Migratory skin DCs distributed to the T-cell area of the LN, co-localized with BCG and were found in close apposition to antigen-specific CD4+ T cells. Consequently, blockade of skin DC traffic into DLN dramatically reduced mycobacterial entry into DLN and muted T-cell priming. Interestingly, DC and mycobacterial entry into the DLN was dependent on IL-1R-I, MyD88, TNFR-I and IL-12p40. In addition, we found using DC adoptive transfers that the requirement for MyD88 in BCG-triggered migration was not restricted to the migrating DC itself and that hematopoietic expression of MyD88 was needed in part for full-fledged migration. Our observations thus identify a population of DCs that contribute towards the priming of CD4+ T cells to BCG infection by transporting bacilli into the DLN in an IL-1R-MyD88-dependent manner and reveal both DC-intrinsic and -extrinsic requirements for MyD88 in DC migration.

  • 217. Bollampalli, V. P.
    et al.
    Yamashiro, L. H.
    Feng, X.
    Bierschenk, D.
    Gao, Y.
    Blom, Hans
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Henriques-Normark, B.
    Nylen, S.
    Rothfuchs, A. G.
    BCG skin infection triggers IL-1R-MyD88-dependent migration of EpCAM(low) CD11b(high) skin dendritic cells to draining lymph node during CD4(+) T-cell priming2016Inngår i: European Journal of Immunology, ISSN 0014-2980, E-ISSN 1521-4141, Vol. 46, s. 790-790Artikkel i tidsskrift (Annet vitenskapelig)
  • 218.
    Bondarenko, Artem
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Nonlinear dynamics of strongly-bound magnetic vortex pairs2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This work is a study of nonlinear phenomena in vertically stacked pairs of magnetic vortices. New dynamic regimes are uncovered with a decrease in the inter-vortex separation to below the lateral vortex-core size. These include linear, non-linear, and chaos dynamics of the coupled vortex cores, as well as core-core coupling/decoupling driven by resonant microwave fields. In addition to the direct advantages gained from the favorable symmetry of the system, which includes the fringing flux closure, new ways of exciting and controlling the motion of the vortex cores are shown. The dynamics of the vortex stack show promising improvements over those of a single vortex, in particular the characteristic speed of operation can be increased by an order of magnitude. The system therefore is viewed to have the potential for applications in data storage and oscillators.

    A combination of experimental, analytical, and numerical methods is used. A theoretical framework based on the quasiparticle Thiele-equation approach, extended to thermally driven dynamics by using the Monte Carlo method, is constructed and extensively tested experimentally and numerically. In-depth micromagnetic simulations are performed and show consistency with the results obtained analytically, both successfully validated against the measured data collected in a series of experiments on spin vortex pairs. Among these are microwave spectroscopy, transient dynamics, thermal decay, and pinning spectroscopy measurements.

    In particular, it is shown that the nonlinear frequency response of a two-vortex system exhibits a fold-over and an isolated rotational core-core resonance. A parametric inter-modal interaction is shown to induce hybrid dynamic regimes of the vortex-core oscillation when the system is subject to high excitation amplitudes.

    An intrinsic bi-stability of the core positions in the structure is found and investigated as a candidate for a memory element. The bi-stability is pronounced at lower temperatures. The rates of thermal switching were investigated in order to find the optimum operating DC-bias conditions.

    It is found that parametric interactions play a big role in the otherwise frustrated dynamics of essentially a 1D system. The parameters of the short excitation pulses for switching between the core-core states are optimized to achieve switching probabilities of over 90% in the experiment, with the pulses only a few nanoseconds long.

    Vortex pairs are demonstrated to be sensitive to the presence of defects in the ferromagnetic layers of the nanostructure. It is shown that the key factor in this sensitivity lies in the vortex' flux closure. Binding of a core-core pair to a defect is observed experimentally. A model is developed to describe the changes in the dynamical characteristics of the defect-pinned vortex pair. The capabilities of the model for characterizing magnetic and morphological defects in nanostructures are demonstrated.

  • 219.
    Bondarenko, Artem
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Holmgren, Erik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Koop, Björn C.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Descamps, Thomas
    KTH.
    Ivanov, B. A.
    Korenivski, Vladislav
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Stochastic dynamics of strongly-bound magnetic vortex pairs2017Inngår i: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 7, nr 5, artikkel-id 056007Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We demonstrate that strongly-bound spin-vortex pairs exhibit pronounced stochastic behaviour. Such dynamics is due to collective magnetization states originating from purely dipolar interactions between the vortices. The resulting thermal noise exhibits telegraph-like behaviour, with random switching between different oscillation regimes observable at room temperature. The noise in the system is further studied by varying the external field and observing the related changes in the frequency of switching and the probability for different magnetic states and regimes. Monte Carlo simulations are used to replicate and explain the experimental observations.

  • 220.
    Bondarenko, Artem
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Holmgren, Erik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Li, Zhong Wei
    Ivanov, B. A.
    Institute of Magnetism, National Academy of Science, 03142 Kiev, Ukraine; National University of Science and Technology “MISiS”, Moscow 119049, Russian Federation..
    Korenivski, Vladislav
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Chaotic dynamics in spin-vortex pairs2019Inngår i: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, artikkel-id 054402Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on spin-vortex pair dynamics measured at temperatures low enough to suppress stochastic core motion, thereby uncovering the highly nonlinear intrinsic dynamics of the system. Our analysis shows that the decoupling of the two vortex cores is resonant and can be enhanced by dynamic chaos. We detail the regions of the relevant parameter space, in which the various mechanisms of the resonant core-core dynamics are activated. We show that the presence of chaos can reduce the thermally induced spread in the decoupling time by up to two orders of magnitude.

  • 221.
    Bora, Tanujjal
    et al.
    Asian Inst Technol, Sch Engn & Technol, Ind Syst Engn, Nanotechnol, POB 4, Klongluang 12120, Pathumthani, Thailand..
    Dutta, Joydeep
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Plasmonic Photocatalyst Design: Metal-Semiconductor Junction Affecting Photocatalytic Efficiency2019Inngår i: Journal of Nanoscience and Nanotechnology, ISSN 1533-4880, E-ISSN 1533-4899, Vol. 19, nr 1, s. 383-388Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Silver-zinc oxide nanorods (Ag-ZnO NRs) and gold-zinc oxide nanorods (Au-ZnO NRs) plasmonic photocatalysts were fabricated by the deposition of Ag and Au nanoparticles on ZnO NRs. The photocatalysts were studied with electron microscopy, energy dispersive spectroscopy (EDS), UV-vis optical absorption and photoluminescence spectroscopy. The effect of type of metals on the ZnO surface on its photocatalytic activity under ultra violet (UV) as well as visible light excitation are investigated and their contribution towards enhanced photo-generated charge separation in terms of the type of junction (Ohmic or Schottky) the metal forms with the semiconductor are explained.

  • 222.
    Borg, Malin
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Ghattas, Elias
    KTH, Skolan för teknik och hälsa (STH). KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Syla, Ardian
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Graphical User Interface for Intermodulation Atomic Force Microscopyok.2011Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    In atomic force microscopy (AFM) a cantilever, with a sharp tip attached

    to its free end, is scanned over a surface. Forces from the surface aect

    the tip causing cantilever deection, which is registered by a detector. This

    information is then used to create a topographical image of the surface on

    nanoscale. We were a part of a project that developed a new type of AFM,

    namely intermodulation atomic force microscopy (IMAFM). It is based on

    dynamic AFM, but instead of one drive frequency, two or more frequencies

    are used. This generates more information from the sample. Our part in this

    project was to improve the software already in use. This will facilitate future

    simulations and experiments; and also utilize the available information in a

    new way.

  • 223.
    Borgani, Riccardo
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Probing nonlinear electrical properties at the nanoscale: Studies in multifrequency AFM2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Nanostructured materials promise great advances in diverse and active research fields such as energy harvesting and storage, corrosion prevention and high-density memories. Electrical characterization at the nanometer scale is key to understanding and optimizing the performance of these materials, and therefore central to the progress of nanotechnology. One of the most versatile tools for this purpose is the atomic force microscope (AFM), thanks to its ability to image surfaces with high spatial resolution.

    In this thesis we present several multifrequency techniques for AFM. Intermodulation electrostatic force microscopy (ImEFM) measures the potential of a surface with low noise and high spatial resolution. In contrast to traditionally available methods, ImEFM does not use a feedback-controlled bias to measure the surface potential, and is therefore suitable to measurements in liquid environments. Removing feedback allows the applied bias to be used for investigating charge injection and extraction on nanocomposite materials. Intermodulation conductive AFM (ImCFM) measures the current-voltage characteristic of a sample at every point of an AFM image. ImCFM is able to separate the galvanic and displacement contributions to the measured current, improving the measurement speed by four orders of magnitude compared to previously available methods. We finally demonstrate an alternative approach to pump-probe spectroscopy, which allows the AFM to measure electrical charge dynamics with a time resolution approaching the nanosecond range.

    These techniques are based on intermodulation spectroscopy, and they demonstrate the power and flexibility of measuring and analyzing nonlinear response in the frequency domain. The nonlinearity of the tip-surface force is used to concentrate response in a narrow band around the resonance of the AFM cantilever, where force measurement sensitivity is at the thermal limit. In this narrow band, we perform coherent measurements at multiple frequencies by exploiting the stability of a single reference oscillation. The power of the multifrequency approach is nicely demonstrated in a general method for measuring and compensating background forces, i.e. long-range linear forces that act on the body of the AFM probe. This compensation is necessary to reveal the the true force between the surface and the AFM tip. We show the effect of the compensation on soft polymer materials, where the background forces are typically strongest.

  • 224.
    Borgani, Riccardo
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Sensing photo-induced surface charges on OrganicPhoto-Voltaic materials using Atomic Force Microscopy2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 225.
    Borgani, Riccardo
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Forchheimer, Daniel
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Bergqvist, Jonas
    Thorén, Per-Anders
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Inganas, Olle
    Haviland, David B.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Intermodulation electrostatic force microscopy for imaging surface photo-voltage2014Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, nr 14, s. 143113-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We demonstrate an alternative to Kelvin Probe Force Microscopy for imaging surface potential. The open-loop, single-pass technique applies a low-frequency AC voltage to the atomic force microscopy tip while driving the cantilever near its resonance frequency. Frequency mixing due to the nonlinear capacitance gives intermodulation products of the two drive frequencies near the cantilever resonance, where they are measured with high signal to noise ratio. Analysis of this intermodulation response allows for quantitative reconstruction of the contact potential difference. We derive the theory of the method, validate it with numerical simulation and a control experiment, and we demonstrate its utility for fast imaging of the surface photo-voltage on an organic photovoltaic material.

  • 226.
    Borgani, Riccardo
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Gilzad Kohan, Mojtaba
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, 97187 Luleå, Sweden.
    Vomiero, Alberto
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, 97187 Luleå, Sweden.
    Haviland, David B.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Fast multifrequency measurement of nonlinear conductanceManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Low noise measurement of small currents in nanometer-scale junctions is of central importance to the characterization of novel high-performance devices and materials for applications ranging from energy harvesting and energy conversion to topological materials for quantum computers. The high resistance of these junctions and the stray capacitance of their measurement leads impose speed limitations (tens of seconds) on the traditional methods of measuring their nonlinear conductance, making detailed investigations of change with external fields or maps of variation over a surface impractical, if not impossible. Here we demonstrate fast (milliseconds) reconstruction of nonlinear current-voltage characteristics from phase-coherent multifrequency lock-in data using the inverse Fourier transform. The measurement technique allows for separation of the galvanic and displacement currents in the junction and easy cancellation of parasitic displacement current due to the measurement leads. We use the method to reveal nanometer-scale variations in the electrical transport properties of organic photovoltaic and semiconducting thin films. The method has broad applicability and its wide-spread implementation promises advancement in high-speed and high-resolution characterization for nanotechnology.

  • 227.
    Borgani, Riccardo
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Haviland, David B.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Intermodulation spectroscopy as an alternative to pump-probe for the measurement of fast dynamics at the nanometer scaleManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    We present an alternative approach to pump-probe spectroscopy for measuring fast charge dynamics with an atomic force microscope (AFM). Our approach is based on coherent multifrequency lock-in measurement of the intermodulation between a mechanical drive and an optical or electrical excitation. In response to the excitation, the charge dynamics of the sample is reconstructed by fitting a theoretical model to the measured frequency spectrum of the electrostatic force near resonance of the AFM cantilever. We discuss the time resolution, which in theory is limited only by the measurement time, but in practice is of order one nanosecond for standard cantilevers and imaging speeds. We verify the method with simulations and demonstrate it with a control experiment, achieving a time resolution of 20 ns in ambient conditions, limited by thermal noise.

  • 228.
    Borgani, Riccardo
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Haviland, David B.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Intermodulation spectroscopy as an alternative to pump-probe for the measurement of fast dynamics at the nanometer scale2019Inngår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 90, nr 1, artikkel-id 013705Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present an alternative approach to pump-probe spectroscopy for measuring fast charge dynamics with an atomic force microscope (AFM). Our approach is based on coherent multifrequency lock-in measurement of the intermodulation between a mechanical drive and an optical or electrical excitation. In response to the excitation, the charge dynamics of the sample is reconstructed by fitting a theoretical model to the measured frequency spectrum of the electrostatic force near resonance of the AFM cantilever. We discuss the time resolution, which in theory is limited only by the measurement time, but in practice is of order 1 ns for standard cantilevers and imaging speeds. We verify the method with simulations and demonstrate it with a control experiment, achieving a time resolution of 30 ns in ambient conditions, limited by thermal noise.

  • 229.
    Borgani, Riccardo
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Kohan, Mojtaba Gilzad
    Lulea Univ Technol, Dept Engn Sci & Math, SE-97187 Lulea, Sweden..
    Vomiero, Alberto
    Lulea Univ Technol, Dept Engn Sci & Math, SE-97187 Lulea, Sweden..
    Haviland, David B.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Fast Multifrequency Measurement of Nonlinear Conductance2019Inngår i: Physical Review Applied, E-ISSN 2331-7019, Vol. 11, nr 4, artikkel-id 044062Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We describe a phase-coherent multifrequency lock-in measurement technique that uses the inverse Fourier transform to reconstruct the nonlinear current-voltage characteristic of a nanoscale junction. The method provides separation of the galvanic and displacement currents in the junction and easy cancellation of the parasitic displacement current from the measurement leads. These two features allow us to overcome traditional limitations imposed by the low conductance of the junction and the high capacitance of the leads, thus providing an increase in measurement speed of several orders of magnitude. We demonstrate the method in the context of conductive atomic force microscopy, acquiring current-voltage characteristics at every pixel while scanning at standard imaging speed.

  • 230.
    Borgani, Riccardo
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Pallon, Love
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Haviland, David
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Local Charge Injection and Extraction on Surface-Modified Al2O3Nanoparticles in LDPE2016Inngår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 16, nr 9, s. 5934-5937, artikkel-id 10.1021/acs.nanolett.6b02920Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We use a recently developed scanning probe technique to image with high spatial resolution the injection and extraction of charge around individual surface-modified aluminum oxide nanoparticles embedded in a low-density polyethylene (LDPE) matrix. We find that the experimental results are consistent with a simple band structure model where localized electronic states are available in the band gap (trap states) in the vicinity of the nanoparticles. This work offers experimental support to a previously proposed mechanism for enhanced insulating properties of nanocomposite LDPE and provides a powerful experimental tool to further investigate such properties.

  • 231.
    Borgani, Riccardo
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Thorén, Per-Anders
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Forchheimer, Daniel
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Dobryden, Illia
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Sah, Si Mohamed
    KTH.
    Claesson, Per Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Haviland, David B.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Background-Force Compensation in Dynamic Atomic Force Microscopy2017Inngår i: Physical Review Applied, E-ISSN 2331-7019, Vol. 7, nr 6, artikkel-id 064018Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background forces are linear long-range interactions of the cantilever body with its surroundings that must be compensated for in order to reveal tip-surface force, the quantity of interest for determining material properties in atomic force microscopy. We provide a mathematical derivation of a method to compensate for background forces, apply it to experimental data, and discuss how to include background forces in simulation. Our method, based on linear-response theory in the frequency domain, provides a general way of measuring and compensating for any background force and it can be readily applied to different force reconstruction methods in dynamic AFM.

  • 232.
    Borlenghi, Simone
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Material- och nanofysik.
    Boman, Magnus
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Programvaruteknik och datorsystem, SCS. RISE SICS, Electrum 229, SE-16429 Kista, Sweden..
    Delin, Anna
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik. KTH, Centra, SeRC - Swedish e-Science Research Centre.
    Modeling reservoir computing with the discrete nonlinear Schrodinger equation2018Inngår i: Physical review. E, ISSN 2470-0045, E-ISSN 2470-0053, Vol. 98, nr 5, artikkel-id 052101Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We formulate, using the discrete nonlinear Schrodinger equation (DNLS), a general approach to encode and process information based on reservoir computing. Reservoir computing is a promising avenue for realizing neuromorphic computing devices. In such computing systems, training is performed only at the output level by adjusting the output from the reservoir with respect to a target signal. In our formulation, the reservoir can be an arbitrary physical system, driven out of thermal equilibrium by an external driving. The DNLS is a general oscillator model with broad application in physics, and we argue that our approach is completely general and does not depend on the physical realization of the reservoir. The driving, which encodes the object to be recognized, acts as a thermodynamic force, one for each node in the reservoir. Currents associated with these thermodynamic forces in turn encode the output signal from the reservoir. As an example, we consider numerically the problem of supervised learning for pattern recognition, using as a reservoir a network of nonlinear oscillators.

  • 233.
    Borlenghi, Simone
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Material- och nanofysik.
    Delin, Anna
    KTH, Centra, SeRC - Swedish e-Science Research Centre. KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Stochastic Thermodynamics of Oscillators' Networks2018Inngår i: Entropy, ISSN 1099-4300, E-ISSN 1099-4300, Vol. 20, nr 12, artikkel-id 992Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We apply the stochastic thermodynamics formalism to describe the dynamics of systems of complex Langevin and Fokker-Planck equations. We provide in particular a simple and general recipe to calculate thermodynamical currents, dissipated and propagating heat for networks of nonlinear oscillators. By using the Hodge decomposition of thermodynamical forces and fluxes, we derive a formula for entropy production that generalises the notion of non-potential forces and makes transparent the breaking of detailed balance and of time reversal symmetry for states arbitrarily far from equilibrium. Our formalism is then applied to describe the off-equilibrium thermodynamics of a few examples, notably a continuum ferromagnet, a network of classical spin-oscillators and the Frenkel-Kontorova model of nano friction.

  • 234. Borlenghi, Simone
    et al.
    Mahani, M. R.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Fangohr, Hans
    Franchin, M.
    Delin, Anna
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik. KTH, Centra, SeRC - Swedish e-Science Research Centre. Uppsala Univ, Sweden.
    Fransson, Jonas
    Micromagnetic simulations of spin-torque driven magnetization dynamics with spatially resolved spin transport and magnetization texture2017Inngår i: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, nr 9, artikkel-id 094428Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a simple and fast method to simulate spin-torque driven magnetization dynamics in nanopillar spin-valve structures. The approach is based on the coupling between a spin transport code based on random matrix theory and a micromagnetics finite-elements software. In this way the spatial dependence of both spin transport and magnetization dynamics is properly taken into account. Our results are compared with experiments. The excitation of the spin-wave modes, including the threshold current for steady-state magnetization precession and the nonlinear frequency shift of the modes are reproduced correctly. The giant magneto resistance effect and the magnetization switching also agree with experiment. The similarities with recently described spin-caloritronics devices are also discussed.

  • 235.
    Borysov, Stanislav
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik. KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Roudi, Yasser
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. The Kavli Institute for Systems Neuroscience, NTNU, Trondheim, Norway.
    Balatsky, Alexander V.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Institute for Materials Science, Los Alamos National Laboratory, Los Alamos, NM, United States.
    U.S. stock market interaction network as learned by the Boltzmann machine2015Inngår i: European Physical Journal B: Condensed Matter Physics, ISSN 1434-6028, E-ISSN 1434-6036, Vol. 88, nr 12, s. 1-14Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study historical dynamics of joint equilibrium distribution of stock returns in the U.S. stock market using the Boltzmann distribution model being parametrized by external fields and pairwise couplings. Within Boltzmann learning framework for statistical inference, we analyze historical behavior of the parameters inferred using exact and approximate learning algorithms. Since the model and inference methods require use of binary variables, effect of this mapping of continuous returns to the discrete domain is studied. The presented results show that binarization preserves the correlation structure of the market. Properties of distributions of external fields and couplings as well as the market interaction network and industry sector clustering structure are studied for different historical dates and moving window sizes. We demonstrate that the observed positive heavy tail in distribution of couplings is related to the sparse clustering structure of the market. We also show that discrepancies between the model’s parameters might be used as a precursor of financial instabilities.

  • 236.
    Borysov, Stanislav S.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik. KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm University, Sweden.
    Balatsky, Alexander V.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm University, Sweden.
    Cross-Correlation Asymmetries and Causal Relationships between Stock and Market Risk2014Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, nr 8, s. e105874-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study historical correlations and lead-lag relationships between individual stock risk (volatility of daily stock returns) and market risk (volatility of daily returns of a market-representative portfolio) in the US stock market. We consider the cross-correlation functions averaged over all stocks, using 71 stock prices from the Standard & Poor's 500 index for 1994-2013. We focus on the behavior of the cross-correlations at the times of financial crises with significant jumps of market volatility. The observed historical dynamics showed that the dependence between the risks was almost linear during the US stock market downturn of 2002 and after the US housing bubble in 2007, remaining at that level until 2013. Moreover, the averaged cross-correlation function often had an asymmetric shape with respect to zero lag in the periods of high correlation. We develop the analysis by the application of the linear response formalism to study underlying causal relations. The calculated response functions suggest the presence of characteristic regimes near financial crashes, when the volatility of an individual stock follows the market volatility and vice versa.

  • 237.
    Borysov, Stanislav S.
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Forchheimer, Daniel
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Haviland, David B.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Dynamic calibration of higher eigenmode parameters of a cantilever in atomic force microscopy by using tip-surface interactions2014Inngår i: Beilstein Journal of Nanotechnology, ISSN 2190-4286, Vol. 5, s. 1899-1904Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a theoretical framework for the dynamic calibration of the higher eigenmode parameters (stiffness and optical lever inverse responsivity) of a cantilever. The method is based on the tip-surface force reconstruction technique and does not require any prior knowledge of the eigenmode shape or the particular form of the tip-surface interaction. The calibration method proposed requires a single-point force measurement by using a multimodal drive and its accuracy is independent of the unknown physical amplitude of a higher eigenmode.

  • 238.
    Borysov, Stanislav S.
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Platz, Daniel
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    de Wijn, Astrid S.
    Forchheimer, Daniel
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Tolén, Eric A.
    Balatsky, Alexander V.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Haviland, David B.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Reconstruction of tip-surface interactions with multimodal intermodulation atomic force microscopy2013Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 88, nr 11, s. 115405-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We propose a theoretical framework for reconstructing tip-surface interactions using the intermodulation technique when more than one eigenmode is required to describe the cantilever motion. Two particular cases of bimodal motion are studied numerically: one bending and one torsional mode, and two bending modes. We demonstrate the possibility of accurate reconstruction of a two-dimensional conservative force field for the former case, while dissipative forces are studied for the latter.

  • 239. Bouchard, F.
    et al.
    de la Hoz, P.
    Björk, Gunnar
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Boyd, R. W.
    Grassl, M.
    Hradil, Z.
    Karimi, E.
    Klimov, A. B.
    Leuchs, G.
    Rehacek, J.
    Sanchez-Soto, L. L.
    Quantum metrology at the limit with extremal Majorana constellations2017Inngår i: Operator Theory: Advances and Applications, ISSN 1004-4469, E-ISSN 2334-2536, Vol. 4, nr 11, s. 1429-1432Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Quantum metrology allows for a tremendous boost in the accuracy of measurement of diverse physical parameters. The estimation of a rotation constitutes a remarkable example of this quantum-enhanced precision. The recently introduced Kings of Quantumness are especially germane for this task when the rotation axis is unknown, as they have a sensitivity independent of that axis and they achieve a Heisenberg-limit scaling. Here, we report the experimental realization of these states by generating up to 21-dimensional orbital angular momentum states of single photons, and confirm their high metrological abilities.

  • 240.
    Boucly, Anthony
    et al.
    Sorbonne Univ, CNRS UMR 7614, Lab Chim Phys Matiere & Rayonnement, 4 Pl Jussieu, F-75252 Paris 05, France..
    Rochet, Francois
    Sorbonne Univ, CNRS UMR 7614, Lab Chim Phys Matiere & Rayonnement, 4 Pl Jussieu, F-75252 Paris 05, France.;Synchrotron SOLEIL, BP 48, F-91192 Gif Sur Yvette, France..
    Arnoux, Quentin
    Sorbonne Univ, CNRS UMR 7614, Lab Chim Phys Matiere & Rayonnement, 4 Pl Jussieu, F-75252 Paris 05, France..
    Gallet, Jean-Jacques
    Sorbonne Univ, CNRS UMR 7614, Lab Chim Phys Matiere & Rayonnement, 4 Pl Jussieu, F-75252 Paris 05, France.;Synchrotron SOLEIL, BP 48, F-91192 Gif Sur Yvette, France..
    Bournel, Fabrice
    Sorbonne Univ, CNRS UMR 7614, Lab Chim Phys Matiere & Rayonnement, 4 Pl Jussieu, F-75252 Paris 05, France.;Synchrotron SOLEIL, BP 48, F-91192 Gif Sur Yvette, France..
    Tissot, Heloise
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Material- och nanofysik. Sorbonne Univ, CNRS UMR 7614, Lab Chim Phys Matiere & Rayonnement, 4 Pl Jussieu, F-75252 Paris 05, France.;Synchrotron SOLEIL, BP 48, F-91192 Gif Sur Yvette, France.
    Marry, Virginie
    Sorbonne Univ, CNRS UMR 8234, Physicochim Electrolyses & Nanosyst Interfaciaux, 4 Pl Jussieu, F-75252 Paris 05, France..
    Dubois, Emmanuelle
    Sorbonne Univ, CNRS UMR 8234, Physicochim Electrolyses & Nanosyst Interfaciaux, 4 Pl Jussieu, F-75252 Paris 05, France..
    Michot, Laurent
    Sorbonne Univ, CNRS UMR 8234, Physicochim Electrolyses & Nanosyst Interfaciaux, 4 Pl Jussieu, F-75252 Paris 05, France..
    Soft X-ray Heterogeneous Radiolysis of Pyridine in the Presence of Hydrated Strontium-Hydroxyhectorite and its Monitoring by Near-Ambient Pressure Photoelectron Spectroscopy2018Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, artikkel-id 6164Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The heterogeneous radiolysis of organic molecules in clays is a matter of considerable interest in astrochemistry and environmental sciences. However, little is known about the effects of highly ionizing soft X-rays. By combining monochromatized synchrotron source irradiation with in situ Near Ambient Pressure X-ray Photoelectron Spectroscopy (in the mbar range), and using the synoptic view encompassing both the gas and condensed phases, we found the water and pyridine pressure conditions under which pyridine is decomposed in the presence of synthetic Sr2+-hydroxyhectorite. The formation of a pyridine/water/Sr2+ complex, detected from the Sr 3d and N 1s core-level binding energies, likely presents a favorable situation for the radiolytic breaking of the O-H bond of water molecules adsorbed in the clay and the subsequent decomposition of the molecule. However, decomposition stops when the pyridine pressure exceeds a critical value. This observation can be related to a change in the nature of the active radical species with the pyridine loading. This highlights the fact that the destruction of the molecule is not entirely determined by the properties of the host material, but also by the inserted organic species. The physical and chemical causes of the present observations are discussed.

  • 241. Boudrioua, A.
    et al.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Moretti, P.
    Loulerque, C.
    Depth dependence of the second harmonic generationof ion implanted waveguides2000Konferansepaper (Fagfellevurdert)
  • 242. Boyko, A. A.
    et al.
    Kostyukova, N. Y.
    Badikov, V.
    Badikov, D.
    Panyutin, V.
    Shevyrdyaeva, G.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Marchev, G. M.
    Kolker, D. B.
    Petrov, V.
    Intracavity difference-frequency mixing of OPO signal and idler pulses in BaGa4Se72017Inngår i: Optics InfoBase Conference Papers, Optical Society of America, 2017, Vol. Part F41Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An overall quantum conversion efficiency of 7.8% is achieved by intracavity mixing the signal and idler of a 1.064-μm pumped Rb:PPKTP OPO in BaGa4Se7, generating >0.7 mJ pulse energy at ~7 μm and 100 Hz.

  • 243. Boyko, A. A.
    et al.
    Marchev, G. M.
    Petrov, V.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Kolker, D. B.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Kostyukova, N. Y.
    Intracavity-pumped, cascaded AgGaSe2 optical parametric oscillator tunable up to 18 μm2016Inngår i: Optics InfoBase Conference Papers, OSA - The Optical Society , 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We report on a AgGaSe2 optical parametric oscillator (OPO), intracavity pumped by the 1.85-μm signal pulses of a 1.064-μm pumped Rb:PPKTP OPO. It operates at 100 Hz with idler tunability from ~8 to 18 μm. 

  • 244. Boyko, A. A.
    et al.
    Marchev, G. M.
    Petrov, V.
    Pasiskevicius, Valdus
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Kolker, D. B.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Kostyukova, N. Y.
    Intracavity-pumped, cascaded Mid-IR optical parametric oscillator based on AgGaSe22015Inngår i: Advanced Solid State Lasers, ASSL 2015, Optical Society of America, 2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We report on an AgGaSe2 optical parametric oscillator (OPO), intracavity pumped by the 1.85-μm signal pulses from a 1.064-μm pumped Rb:PPKTP OPO. It operates at 100 Hz with idler tunability from 5.8 to 8.3 μm.

  • 245. Boyko, A.
    et al.
    Badikov, V.
    Shevyrdyaeva, G.
    Badikov, D.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Petrov, V.
    Intracavity-pumped, cascaded optical parametric oscillator based on BaGa2GeSe62018Inngår i: Optics InfoBase Conference Papers, Optics Info Base, Optical Society of America, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We employ the new chalcogenide crystal BaGa2GeSe6 for the first time for frequency down-conversion into the mid-IR, in an optical parametric oscillator (OPO), intracavity pumped by the signal wave of a 1.064-μm pumped Rb:PPKTP OPO. .

  • 246. Boyko, A.
    et al.
    Kostyukova, N.
    Guha, S.
    Schunemann, P. G.
    Marchev, G.
    Panyutin, V.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Kolker, D.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Petrov, V.
    Rb: PPKTP optical parametric oscillator with intracavity difference- frequency generation in temperature-tuned OPGaAs2017Inngår i: Optics InfoBase Conference Papers, OSA - The Optical Society , 2017Konferansepaper (Fagfellevurdert)
  • 247. Boyko, Andrey A.
    et al.
    Kostyukova, Nadezhda Y.
    Badikov, Valeriy
    Badikov, Dmitrii
    Panyutin, Vladimir
    Shevyrdyaeva, Galina
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Marchev, Georgi M.
    Kolker, Dmitry B.
    Petrov, Valentin
    Intracavity difference-frequency mixing of optical parametric oscillator signal and idler pulses in BaGa4Se72017Inngår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 56, nr 10, s. 2783-2786Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An overall quantum conversion efficiency of 7.8% is achieved by intracavity mixing the signal and idler of a 1.064 mu m pumped Rb: PPKTP optical parametric oscillator in BaGa4Se7. In this way, a pulse energy of similar to 0.71 mJ is generated at similar to 7 mu m for a repetition rate of 100 Hz. Tuning of the mid-IR radiation is demonstrated by heating of the Rb: PPKTP crystal.

  • 248. Boyko, Andrey A.
    et al.
    Kostyukova, Nadezhda Y.
    Marchev, Georgi M.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Kolker, Dmitry B.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Petrov, Valentin
    Rb:PPKTP optical parametric oscillator with intracavity difference-frequency generation in AgGaSe22016Inngår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 41, nr 12, s. 2791-2794Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A 1.064 mu m pumped Rb:PPKTP optical parametric oscillator (OPO) generates mid-IR radiation by intracavity mixing the resonant signal and idler waves in AgGaSe2. The similar to 6 ns pulses at similar to 7 mu m have an energy of 670 mu J at 100 Hz, equivalent to an average power of 67 mW. The overall quantum conversion efficiency from 1.064 mu m amounts to 8%, and the power conversion efficiency is 1.2%.

  • 249. Boyko, Andrey A.
    et al.
    Marchev, Georgi M.
    Petrov, Valentin
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Kolker, Dmitry B.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Kostyukova, Nadezhda Y.
    Intracavity-pumped, cascaded AgGaSe2 optical parametric oscillator tunable from 5.8 to 18 mu m2015Inngår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 23, nr 26, s. 33460-33465Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A AgGaSe2 nonlinear crystal placed in a coupled cavity is intracavity pumped by the similar to 1.85-mu m signal pulses of a 1.064-mu m pumped Rb: PPKTP doubly-resonant optical parametric oscillator (OPO) operating at a repetition rate of 100 Hz. Using two samples cut for type-I and II phase-matching, the overall idler tunability of the singly-resonant AgGeSe2 OPO covers an unprecedented spectral range from 5.8 to similar to 18 mu m in the mid-IR.

  • 250. Boyko, Andrey A.
    et al.
    Schunemann, Peter G.
    Guha, Shekhar
    Kostyukova, Nadezhda Y.
    Kolker, Dmitry B.
    Panyutin, Vladimir L.
    Marchev, Georgi M.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Zukauskas, Andrius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Mayorov, Fedor
    Petrov, Valentin
    Optical parametric oscillator pumped at similar to 1 mu m with intracavity mid-IR difference-frequency generation in OPGaAs2018Inngår i: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 8, nr 3, s. 549-554Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Intracavity difference-frequency generation (DFG) between signal and idler pulses is investigated in orientation-patterned GaAs inside the cavity of a similar to 1 mu m pumped nanosecond optical parametric oscillator (OPO). Using two different samples and temperature tuning in the non-critical configuration, tunability between 7 and 9.2 mu m is demonstrated. The superior thermo-mechanical properties of OPGaAs enabled also for the first time operation of this cascaded scheme at kilohertz (1-3 kHz) repetition rates reaching average powers similar to 10 mW in the mid-IR.

2345678 201 - 250 of 2643
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