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  • 251. Seiboth, Frank
    et al.
    Schropp, Andreas
    Scholz, Maria
    Wittwer, Felix
    Rödel, Christian
    Wünsche, Martin
    Ullsperger, Tobias
    Nolte, Stefan
    Rahomäki, Jussi
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Parfeniukas, Karolis
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Giakoumidis, Stylianos
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vogt, Ulrich
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Wagner, Ulrich
    Rau, Christoph
    Boesenberg, Ulrike
    Garrevoet, Jan
    Falkenberg, Gerald
    Galtier, Eric C.
    Ja Lee, Hae
    Nagler, Bob
    Schroer, Christian G.
    Perfect X-ray focusing via fitting corrective glasses to aberrated optics2017Ingår i: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Due to their short wavelength, X-rays can in principle be focused down to a few nanometres and below. At the same time, it is this short wavelength that puts stringent requirements on X-ray optics and their metrology. Both are limited by today’s technology. In this work, we present accurate at wavelength measurements of residual aberrations of a refractive X-ray lens using ptychography to manufacture a corrective phase plate. Together with the fitted phase plate the optics shows diffraction-limited performance, generating a nearly Gaussian beam profile with a Strehl ratio above 0.8. This scheme can be applied to any other focusing optics, thus solving the X-ray optical problem at synchrotron radiation sources and X-ray free-electron lasers.

  • 252.
    Selin, Mårten
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    3D X-ray microscopy: image formation, tomography and instrumentation2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Tomografi i mjukröntgenmikroskopi är en ny teknik för att få ut kvantitativ strukturell 3D information om celler. Dess styrka jämfört med andra tekniker är att den kan avbilda intakta celler i deras nära naturliga tillstånd med ett par 10 nm upplösning, utan omfattande preparering. Dock är metoderna för att rekonstruera 3D-data beroende av algoritmer som antar projektionsdata, vilket bilderna i allmänhet inte är på grund av avbildningsystemens begränsade skärpedjup. För att få ut den fulla potentialen av tomografi i röntgenmikroskopi behövs en ökad förståelse för avbildningsprocessen.

    Denna avhandling behandlar zonplatte-baserad röntgenmikroskopi för biologisk avbildning och den nödvändiga teorin för en numerisk implementering av en avbildningsmodell i 3D. En ny rekonstruktionsmetod föreslås som förbättrar upplösningen i rekonstruktionen för ett tomografiskt avbildat objekt. Detta visas i simuleringar och experiment. Slutligen omfattar denna avhandling arbete på Stockholms mjukröntgenmikroskop, inklusive en uppgradering av röntgenkällan som ger oöverträffad ljusstyrka för ett kompakt system. Denna uppgradering möjliggör högkvalitativ avbildning av celler i deras nästan naturliga tillstånd med endast 10 sekunders exponering.

  • 253.
    Selin, Mårten
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Bertilson, Michael
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Nilsson, Daniel
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    von Hofsten, Olov
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vogt, Ulrich
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    DiffractX: A Simulation Toolbox for Diffractive X-ray Optics2011Ingår i: 10TH INTERNATIONAL CONFERENCE ON X-RAY MICROSCOPY / [ed] McNulty, I; Eyberger, C; Lai, B, American Institute of Physics (AIP), 2011, Vol. 1365, s. 341-344Konferensbidrag (Refereegranskat)
    Abstract [en]

    X-ray wavefront propagation is a powerful technique when simulating the performance of x-ray optical components. Using various numerical methods, interesting parameters such as focusing capability and efficiency can be investigated. Here we present the toolbox DiffractX, implemented in MATLAB. It contains many different wave propagation methods for the simulation of diffractive x-ray optics, including Fresnel propagation, the finite difference method (FDM), the thin object approximation, the rigorous coupled wave theory (RCWT), and the finite element method (FEM). All tools are accessed through a graphical interface, making the design of simulations fast and intuitive, even for users with little or no programming experience. The tools have been utilized to characterize realistic as well as idealized optical components. This will aid further developments of diffractive x-ray optics.

  • 254.
    Selin, Mårten
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Fogelqvist, Emelie
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Holmberg, Anders
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Guttmann, Peter
    Vogt, Ulrich
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    3D simulation of the image formation in soft x-ray microscopes2014Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 22, nr 25, s. 30756-30768Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In water-window soft x-ray microscopy the studied object is typically larger than the depth of focus and the sample illumination is often partially coherent. This blurs out-of-focus features and may introduce considerable fringing. Understanding the influence of these phenomena on the image formation is therefore important when interpreting experimental data. Here we present a wave-propagation model operating in 3D for simulating the image formation of thick objects in partially coherent soft x-ray microscopes. The model is compared with present simulation methods as well as with experiments. The results show that our model predicts the image formation of transmission soft x-ray microscopes more accurately than previous models.

  • 255.
    Selin, Mårten
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Fogelqvist, Emelie
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Werner, Stephan
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Tomographic reconstruction in soft x-ray microscopy using focus-stack back-projection2015Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 40, nr 10, s. 2201-2204Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tomographic reconstruction in soft x-ray microscopy is a powerful technique for obtaining high-resolution 3D images of biological samples. However, the depth of focus of such zone-plate-based microscopes is typically shorter than the thickness of many relevant biological objects, challenging the validity of the projection assumption used in conventional reconstruction algorithms. In order to make full use of the soft x-ray microscopes' high resolution, the tomographic reconstruction needs to take the depth of focus into account. Here we present a method to achieve high resolution in the full sample when the depth of focus is short compared to the sample thickness. The method relies on the back-projection of focus-stacked image data from x-ray microscopy. We demonstrate the method on theoretical and experimental data.

  • 256.
    Shaglwf, Zaid
    et al.
    Univ Southampton, Fac Engn & Phys Sci, Sch Engn, Southampton SO17 1BJ, Hants, England..
    Hammarström, Björn
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Laila, Dina Shona
    Coventry Univ, Sch Mech Aerosp & Automot, Coventry CV1 5FB, W Midlands, England..
    Hill, Martyn
    Univ Southampton, Fac Engn & Phys Sci, Sch Engn, Southampton SO17 1BJ, Hants, England..
    Glynne-Jones, Peter
    Univ Southampton, Fac Engn & Phys Sci, Sch Engn, Southampton SO17 1BJ, Hants, England..
    Acoustofluidic particle steering2019Ingår i: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 145, nr 2, s. 945-955Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Steering micro-objects using acoustic radiation forces is challenging for several reasons: resonators tend to create fixed force distributions that depend primarily on device geometry, and even when using switching schemes, the forces are hard to predict a priori. In this paper an active approach is developed that measures forces from a range of acoustic resonances during manipulation using a computer controlled feedback loop based in MATLAB, with a microscope camera for particle imaging. The arrangement uses a planar resonator where the axial radiation force is used to hold particles within a levitation plane. Manipulation is achieved by summing the levitation frequency with an algorithmically chosen second resonance frequency, which creates lateral forces derived from gradients in the kinetic energy density of the acoustic field. Apart from identifying likely resonances, the system does not require a priori knowledge of the structure of the acoustic force field created by each resonance. Manipulation of 10 mu m microbeads is demonstrated over 100 s mu m. Manipulation times are of order 10 s for paths of 200 mu m length. The microfluidic device used in this work is a rectangular glass capillary with a 6 mm wide and 300 mu m high fluid chamber.

  • 257.
    Shaker, Kian
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Larsson, Jakob C.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Quantitative predictions in small-animal X-ray fluorescence tomography2019Ingår i: Biomedical Optics Express, ISSN 2156-7085, E-ISSN 2156-7085, Vol. 10, nr 8, s. 3773-3788, artikel-id 364926Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    X-ray fluorescence (XRF) tomography from nanoparticles (NPs) shows promise for high-spatial-resolution molecular imaging in small-animals. Quantitative reconstruction algorithms aim to reconstruct the true distribution of NPs inside the small-animal, but so far there has been no feasible way to predict signal levels or evaluate the accuracy of reconstructions in realistic scenarios. Here we present a GPU-based computational model for small-animal XRF tomography. The unique combination of a highly accelerated Monte Carlo tool combined with an accurate small-animal phantom allows unprecedented realistic full-body simulations. We use this model to simulate our experimental system to evaluate the quantitative performance and accuracy of our reconstruction algorithms on large-scale organs as well as mm-sized tumors. Furthermore, we predict the detection limits for sub-mm tumors at realistic NP concentrations. The computational model will be a valuable tool for optimizing next-generation experimental arrangements and reconstruction algorithms.

  • 258.
    Skoglund Lindberg, Peter Anders
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Electron-Impact Liquid-Jet Water-Window X-ray Sources2010Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This Thesis describes the development and characterization of a soft x-ray liquidjet-anode electron-impact source. With a water-jet target the primary emission is the O Kα line at 525 eV. This is close to the lower edge of the water-window, a spectral region lacking simple laboratory sources. In the hard x-ray regime electronimpact microfocus sources have matured and are simple, stable, reliable, and inexpensive. It would be beneficial if this source concept could be used also for soft x-ray generation.  

    Spectral measurements of a 120 W, 30 keV electron beam focused on a 20 μm water jet show an x-ray intensity of up to 3.2 × 1012 ph/(s×sr×line). Combined with source size measurements up to 50 W a maximum brightness of 3.5 × 109 ph/(s×μm2×sr×line) is reported. This makes the brightness comparable to the compact discharge-plasma sources presently used for soft x-ray microscopy. The source appears to be scalable another order of magnitude which would make the brightness equal to that of the laser-plasma sources.

     

  • 259.
    Skoglund, Peter
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lundström, Ulf
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vogt, Ulrich
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    High-brightness water-window electron-impact liquid-jet microfocus source2010Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, nr 8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate stable high-brightness operation of an electron-impact water-jet-anode soft x-ray source. A 30 kV, 7.8 W electron beam is focused onto a 20 mu m diameter jet resulting in water-window oxygen line emission at 525 eV/2.36 nm with a brightness of 3.0x10(9) ph/(sx mu m(2)xsrxline). Monte Carlo-based modeling shows good quantitative agreement with the experiments. The source has potential to increase the x-ray power and brightness by another 1-2 orders of magnitude and fluid-dynamical jet instabilities is determined to be the most important limiting factor. The source properties make it an attractive alternative for table-top x-ray microscopy.

  • 260.
    Skoglund, Peter
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lundström, Ulf
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vogt, Ulrich
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Takman, Per
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Electron-Impact Water-Jet Microfocus Source for Water-Window Microscopy2011Ingår i: 10th International Conference on X-Ray Microscopy / [ed] McNulty, I; Eyberger, C; Lai, B, 2011, Vol. 1365, s. 152-155Konferensbidrag (Refereegranskat)
    Abstract [en]

    We demonstrate high-brightness operation of an electron-impact water-jet-anode soft x-ray source with an increased power loading of 15 times compared to our previously published results, with a corresponding increase in similar to 525-eV x-ray intensity of 6.4 times. This has been accomplished by improving the vacuum pumping system and the electron focusing optics, and increasing the liquid-jet velocity. The source now operates up to 120-W e-beam power and at a 525-eV brightness of 3.5x10(9) ph/(sx mu m(2)xsrxline). The source concept has potential to increase the x-ray brightness by another order of magnitude by optimizing the e-beam focusing and upgrading the power supply. Currently, spot enlargement with increased power is determined to be the most important limiting factor.

  • 261.
    Smith, Arlene
    et al.
    National university of Ireland, Galway.
    Burvall, Anna
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Dainty, Christopher
    National University of Ireland, Galway.
    Partial spatial coherence in an excimer-laser lithographic imaging system2010Ingår i: OPTICAL MICROLITHOGRAPHY XXIII / [ed] Mircea V. Dusa; Will Conley, SPIE - International Society for Optical Engineering, 2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    We have recently explored the Elementary Function method, previously presented by Wald et al (Proc. SPIE 59621G, 2005), and we have demonstrated under what circumstances this method can be used to reduce the propagation calculations of partially coherent light to two dimensions. In this paper, we examine the methods used to measure the spatial coherence of a light source in the literature. We present a method based on work previously shown by Mejia et al (Opt Comm 273 (428-434), 2007) which uses an array of pinholes with one degree of redundancy. We discuss the design of the pinhole array and present the results of some simulations.

  • 262.
    Smith, Arlene
    et al.
    National University of Irelend, Galway.
    Burvall, Anna
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Dainty, Christopher
    National University of Ireland, Galway.
    Partially coherent image computation using elementary functions2009Ingår i: Optical Microlithography XXII / [ed] Harry J. Levinson; Mircea V. Dusa, SPIE - International Society for Optical Engineering, 2009Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    It is well-known that calculations of the propagation of partially coherent light, such as those required for the calculation of two-dimensional image intensities, involve four-dimensional functions. Recently, Wald et al [Proc SPIE, 59621G, 2005] outlined a method for reducing the four-dimensional problem to a purely twodimensional one. Instead of an exact modal expansion of the mutual coherence function or cross-spectral density, an approximate expansion is used, into what we call elementary functions. In this paper, rules of thumb are developed for fast and efficient computation of the image intensity in a simple partially coherent lithographic imaging system.

  • 263.
    Spah, Alexander
    et al.
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Pathak, Harshad
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Kim, Kyung Hwan
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Perakis, Fivos
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Mariedahl, Daniel
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Amann-Winkel, Katrin
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Sellberg, Jonas A.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lee, Jae Hyuk
    Pohang Accelerator Lab, Pohang 37673, Gyeongbuk, South Korea..
    Kim, Sangsoo
    Pohang Accelerator Lab, Pohang 37673, Gyeongbuk, South Korea..
    Park, Jaehyun
    Pohang Accelerator Lab, Pohang 37673, Gyeongbuk, South Korea..
    Nam, Ki Hyun
    Pohang Accelerator Lab, Pohang 37673, Gyeongbuk, South Korea..
    Katayama, Tetsuo
    Japan Synchrotron Radiat Res Inst, Kouto 1-1-1, Sayo, Hyogo 6795198, Japan..
    Nilsson, Anders
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Apparent power-law behavior of water's isothermal compressibility and correlation length upon supercooling2019Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 21, nr 1, s. 26-31Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The isothermal compressibility and correlation length of supercooled water obtained from small-angle X-ray scattering (SAXS) were analyzed by fits based on an apparent power-law in the temperature range from 280 K down to the temperature of maximum compressibility at 229 K. Although the increase in thermodynamic response functions is not towards a critical point, it is still possible to obtain an apparent power law all the way to the maximum values with best-fit exponents of gamma = 0.40 +/- 0.01 for the isothermal compressibility and nu = 0.26 +/- 0.03 for the correlation length. The ratio between these exponents is close to a value of approximate to 0.5, as expected for a critical point, indicating the proximity of a potential second critical point. Comparison of gamma obtained from experiment with molecular dynamics simulations on the iAMOEBA water model shows that it would be located at pressures in the neighborhood of 1 kbar. The high value and sharpness of the compressibility maximum observed in the experiment are not reproduced by any of the existing classical water models, thus inviting further development of simulation models of water.

  • 264. Stankevic, Tomas
    et al.
    Engblom, Christer
    Langlois, Florent
    Alves, Filipe
    Lestrade, Alain
    Jobert, Nicolas
    Cauchon, Gilles
    Vogt, Ulrich
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Kubsky, Stefan
    Interferometric characterization of rotation stages for X-ray nanotomography2017Ingår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 88, nr 5, artikel-id 053703Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The field of three-dimensional multi-modal X-ray nanoimaging relies not only on high-brilliance X-rays but also on high-precision mechanics and position metrology. Currently available state-of-the-art linear and rotary drives can provide 3D position accuracy within tens to hundreds of nm, which is often insufficient for high resolution imaging with nanofocused X-ray beams. Motion errors are especially troublesome in the case of rotation drives and their correction is more complicated and relies on the metrology grade reference objects. Here we present a method which allows the characterisation and correction of the radial and angular errors of the rotary drives without the need for a highly accurate metrology object. The method is based on multi-probe error separation using fiber-laser interferometry and uses a standard cylindrical sample holder as a reference. The obtained runout and shape measurements are then used to perform the position corrections using additional drives. We demonstrate the results of the characterization for a piezo-driven small rotation stage. The error separation allowed us to measure the axis runout to be approximately +/-1.25 mu m, and with active runout compensation this could be reduced down to +/-42 nm.

  • 265.
    Stollberg, Heide
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Compact Soft X-Ray Microscopy: Image Processing and Instrumentation2006Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Soft x-ray microscopy is a powerful technique for natural-contrast, high-resolution imaging of organic materials. This Thesis describes new instrumentational and new image-processing methods to improve the image quality of the compact x-ray microscope at the Biomedical & X-Ray Physics division at KTH. The microscope is based on a laser-plasma source combined with different condenser optics, either multilayer mirrors or zone plates. Imaging is performed by micro zone plates. The microscope works in the water window (\lambda = 2.3-4.4 nm), where the attenuation lengths of oxygen and carbon differ strongly, providing high natural contrast for carbon-containing specimens in an aqueous environment.

    By optimizing the properties of the laser-plasma source and fabricating multilayer mirrors with high, uniform reflectivity, the performance of the microscope's illumination system could be improved and exposure times decreased significantly to about 2 min for imaging dry samples and 5 min for imaging wet samples. For imaging of wet samples, a wet-specimen chamber was developed, which is vacuum-compatible. Since it is horizontally mounted in the microscope, it offers advantages for investigations in polymer and soil science.

    To improve the quality of images taken by the compact x-ray microscope an image-restoration algorithm was developed. Denoising is performed by a filtering algorithm based on the discrete wavelet transform. This algorithm shows advantages compared to Fourier-based algorithms, since the filtering of spatial frequencies is done locally. An improvement in exposure time by a factor of about 2 could be realized without loss of image information.

    To stimulate experiments on functional imaging in x-ray microscopy an image-analysis algorithm for identifying colloidal-gold particles was developed. This algorithm is based on a combination of a threshold with respect to the local absorption and a shape discrimination, realized by fitting a Gaussian profile to the potential particles. The algorithm was evaluated and optimized on images taken by the transmission x-ray microscope at BESSY II. The size-selective identification and localization of single gold particles down to a diameter of 50 nm was demonstrated.

  • 266.
    Stollberg, Heide
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Guttmann, Peter
    Institut für Röntgenphysik, Georg-August-Universität Göttingen, Berlin.
    Takman, Per
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Size-selective colloidal-gold localization in transmission x-ray microscopy2007Ingår i: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818, Vol. 225, nr 1, s. 80-87Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Colloidal gold is a useful marker for functional-imaging experiments in transmission X-ray microscopy. Due to the low contrast of gold particles with small diameters it is necessary to develop a powerful algorithm to localize the single gold particles. The presented image-analysis algorithm for identifying colloidal gold particles is based on the combination of a threshold with respect to the local absorption and shape discrimination, realized by fitting a Gaussian profile to the identified regions of interest. The shape discrimination provides the possibility of size-selective identification and localization of single colloidal gold particles down to a diameter of 50 nm. The image-analysis algorithm, therefore, has potential for localization studies of several proteins simultaneously and for localization of fiducial markers in X-ray tomography.

  • 267.
    Stollberg, Heide
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Yulin, Sergiy
    Fraunhofer-Institut fur Angewandte Optik und Feinmechanik, Jena.
    Takman, Per
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    High-reflectivity Cr/Sc multilayer condenser for compact soft x-ray microscopy2006Ingår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 77, nr 12, s. 123101-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The condenser is a critical component in compact water-window x-ray microscopes as it influences the exposure time via its efficiency and the resolution via its numerical aperture. Normal-incidence multilayer mirrors can reach large geometrical collection efficiencies and match the numerical aperture of the zone plate but require advanced processing for high total reflectivity. In the present article we demonstrate large-diameter normal-incidence spherical Cr/Sc multilayer condensers with high and uniform reflectivity. Dc-magnetron sputtering was used to deposit 300 bilayers of Cr/Sc with a predetermined d-spacing matching the lambda=3.374 nm operating wavelength on spherical substrates. The mirrors show a uniform reflectivity of similar to 3% over the full 58 mm diameter condenser area. With these mirrors an improvement in exposure time by a factor of 10 was achieved, thereby improving the performance of the compact x-ray microscope significantly.

  • 268.
    Svennebring, Jessica
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Ultrasonic Handling of Living Cells in Microfluidic Systems2009Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Microfluidic chips have become a powerful tool in research where biological cells are processed and/or analyzed. One method for contactless cell manipulation in microfluidic chips that has gained an increasing amount of attention the last decade is ultrasonic standing wave (USW) technology. This Thesis explores the biocompatibility of USW technology applied to microfluidic chips, and presents a novel USW-based method for serial processing and accurate characterization of living cells.

    The biocompatibility has been investigated by measuring the proliferation rate of cells after they had been trapped and aggregated inside a chip by ultrasound. No negative influence was observed after continuous exposure to 0.85 MPa pressure amplitudes for up to 75 min. Furthermore, the heat generation in the fluid channel caused by the ultrasound has been measured and used in a regulation scheme where the temperature can be controlled around any relevant temperature (e.g. 37‰) with ±0.1‰ accuracy for more than 12 hours. The proliferation rate and temperature investigations suggest that USW technology applied to microfluidic chips is a biocompatiblemethod useful for long-term handling of living cells.

    We have introduced a new concept of contactless ultrasonic ”caging” of single cells or small aggregates of cells. These cages are channel segments in the microfluidic chips that are geometrically designed to resonate at one or several actuation frequencies. The actuation is performed remotely by up to five external frequency specific wedge transducers, where each transducer produces a localized and spatially confined standing wave with a specific orientation of its corresponding radiation force field. By multi-frequency actuation, sophisticated and flexible force fields are realized by both overlapping and separated single fields. The Thesis describes two different cages: A sub-mm ”micro-cage” for tree-dimensional manipulationof single cells, and a 5-mm ”mini-cage” for selective retention of small cell aggregates (up to approx. 10^3 cells) from a continuously feeding sample flow. Finally,our microfluidic chips were also designed to be compatible with high-resolution optical microscopy. We have demonstrated sub-μm-resolution confocal fluorescence and trans-illumination microscopy imaging of ultrasonically caged living cells.

  • 269.
    Svennebring, Jessica
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Manneberg, Otto
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Wiklund, Martin
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Dynamic flow cytometry in an acousto-optic microfluidic chip2008Ingår i: 12th International Conference on Miniaturized Systems for Chemistry and Life Sciences - The Proceedings of MicroTAS 2008 Conference, Chemical and Biological Microsystems Society , 2008, s. 1175-1177Konferensbidrag (Refereegranskat)
    Abstract [en]

    A microfluidic ultrasonic manipulation system is used for controlled selection, re-tention and optical characterization of individual particles or cells. The system is based on a chip-integrated focused ultrasonic resonator that is actuated on either one or both of two different frequencies. Particles are pre-aligned, and either bypassed through or injected and retained in the focused resonator, depending on the actuation mode. Dynamic flow cytometry is demonstrated by real-time optical monitoring of controlled numbers of retained and positioned cells or beads.

  • 270.
    Svennebring, Jessica
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Manneberg, Otto
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Wiklund, Martin
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Gentle cell handling using ultrasonic standing waves in a chip-based perfusion system for cell characterization and on-chip cultivation2007Konferensbidrag (Refereegranskat)
  • 271.
    Svennebring, Jessica
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Manneberg, Otto
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Iranmanesh, Ida
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Wiklund, Martin
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Ultrasonic manipulation in microfluidic systems: Selective cell handling and characterization2009Konferensbidrag (Övrigt vetenskapligt)
  • 272.
    Svennebring, Jessica
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Manneberg, Otto
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Skafte-Pedersen, Peder
    Bruus, Henrik
    Wiklund, Martin
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Selective bioparticle retention and characterization in a chip-integrated confocal ultrasonic cavity2009Ingår i: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 103, s. 323-328Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate selective retention and positioning of cells or other bioparticles by ultrasonic manipulation in a microfluidic expansion chamber during microfluidic perfusion. The chamber is designed as a confocal ultrasonic resonator for maximum confinement of the ultrasonic force field at the chamber center, where the cells are trapped. We investigate the resonant modes in the expansion chamber and its connecting inlet channel by theoretical modeling and experimental verification during no-flow conditions. Furthermore, by triple-frequency ultrasonic actuation during continuous microfluidic sample feeding, a set of several manipulation functions performed in series is demonstrated: sample bypass-injection-aggregation and retention-positioning. Finally, we demonstrate transillumination microscopy imaging Of Ultrasonically trapped COS-7 cell aggregates.

  • 273.
    Svennebring, Jessica
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Manneberg, Otto
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Wiklund, Martin
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Gentle retention of cells in a focusing ultrasonic resonator integrated in a chip-based perfusion system for cell characterization and on-chip cultivation2007Konferensbidrag (Refereegranskat)
  • 274.
    Svennebring, Jessica
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Manneberg, Otto
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Wiklund, Martin
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Temperature regulation during ultrasonic manipulation for long-term cell handling in a microfluidic chip2007Ingår i: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 17, s. 2469-2474Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Regulation by the use of ultrasonic standing wave technology in a microfluidic chip. The system is based on a microfabricated silicon structure sandwiched between two glass layers, and an external ultrasonic transducer using a refractive wedge placed on top of the chip for efficient coupling of ultrasound into the microchannel. The chip is fully transparent and compatible with any kind of high-resolution optical microscopy. The temperature regulation method uses calibration data of the temperature increase due to the ultrasonic actuation for determining the temperature of the surrounding air and microscope table, controlled by a warm-air heating unit and a heatable mounting frame. The heating methods are independent of each other, resulting in a flexible choice of ultrasonic actuation voltage and flow rate for different cell and particle manipulation purposes. Our results indicate that it is possible to perform stable temperature regulation with an accuracy of the order of +/- 0.1 degrees C around any physiologically relevant temperature (e.g., 37 degrees C) with high temporal stability and repeatability. The purpose is to use ultrasound for long-term cell and/or particle handling in a microfluidic chip while controlling and maintaining the biocompatibility of the system.

  • 275.
    Svensson, Björn
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik. KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Cederström, Björn
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik. KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Aslund, Magnus
    Lundqvist, Mats
    Teleman, Max
    Variable height multi-slit collimator and optimized image reconstruction in a photon-counting system for digital mammography2011Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 648, s. S216-S219Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have investigated a pre-breast collimator able to operate at variable heights for a photon-counting scanned multi-slit mammography system. A prototype system was built and used to evaluate how different collimator heights combined with optimized collimator slit widths affect dose efficiency and scan time. Moreover, new image construction software which takes into account the sub-pixel shift of each detector line was implemented and evaluated. With maintained scan time a collimator 79 mm above patient support improved dose efficiency for a 100 mu m disc by 12% and by 22% for a scan time extended by 10%. For image reconstruction and the same disc size a dose efficiency improvement of 32% +/- 9% was measured indicating a higher gain than expected. (c) 2010 Elsevier B.V. All rights reserved.

  • 276.
    Takman, Per A. C.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Stollberg, Heide
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Johansson, Göran A.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Holmberg, Anders
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lindblom, Magnus
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Sub 30-nm resolution compact x-ray microscopy2006Ingår i: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818Artikel i tidskrift (Övrigt vetenskapligt)
  • 277.
    Takman, Per
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Stollberg, Heide
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Johansson, Göran A.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Holmberg, Anders
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lindblom, Magnus
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    High-resolution compact x-ray microscopy2007Ingår i: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818, Vol. 226, nr 2, s. 175-181Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate compact full-field soft X-ray transmission microscopy with sub 60-nm resolution operating at λ= 2.48 nm. The microscope is based on a 100-Hz regenerative liquid-nitrogen-jet laser-plasma source in combination with a condenser zone plate and a micro-zone plate objective for high-resolution imaging onto a 2048 × 2048 pixel CCD detector. The sample holder is mounted in a helium atmosphere and allows imaging of both dry and wet specimens. The microscope design enables fast sample switching and the sample can be pre-aligned using a visible-light microscope. High-quality images can be acquired with exposure times of less than 5 min. We demonstrate the performance of the microscope using both dry and wet samples.

  • 278.
    Takman, Per
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vogt, Ulrich
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Towards compact x-ray microscopy with liquid-nitrogen-jet laser-plasma source2006Ingår i: Proceedings of 8th International Conference on X-ray Microscopy, 2006, s. 12-14Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this contribution we present source properties and design considerations for a compact x-ray microscope operating in the water-window spectral region at 2.48 nm. The microscope will use a liquid-nitrogen-jet laser-plasma source with sufficient brightness, uniformity, stability and reliability for microscopy operation. The source is quantitatively characterized by calibrated slitgrating spectroscopy and zone-plate imaging to determine absolute photon numbers and source size and stability. Calculations including sources parameters as well as characteristics of available x-ray optics indicate that high-quality microscope images can be obtained with exposure times in the range of few minutes.

  • 279. Tellefsen, G.
    et al.
    Liljeborg, Anders V G
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Johannsen, A.
    Johannsen, G.
    The role of the toothbrush in the abrasion process2011Ingår i: International Journal of Dental Hygiene, ISSN 1601-5029, E-ISSN 1601-5037, Vol. 9, nr 4, s. 284-290Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Aim: To evaluate the relative abrasivity of different toothbrushes both qualitatively and quantitatively. Materials and Methods: Acrylic plates were exposed to brushing in a brushing machine with ten different toothbrushes with water alone and with a toothpaste. The results were evaluated using a profilometer after one and 6 h of brushing (corresponding to 2000 and 12 000 double strokes, respectively). A surface roughness value (Ra-value) and also a volume loss value were calculated from the profilometer measurements. These values were then compared to each other. Results: The results showed that brushing with water alone caused less abrasion than when a toothpaste was added. Six-hour brushing with water caused less abrasion than 1 h with a toothpaste. The number of filaments or filament diameter influenced the results in various ways. When brushing with water, the harder toothbrush (Jordan Medium) caused more abrasion (higher Ra-value), but when adding the toothpaste, the softer toothbrush (Jordan soft) caused more abrasion after 12 000 double strokes. Conclusion: Besides supporting the fact that a toothpaste is needed to create a significant abrasion, this study also showed that a softer toothbrush can cause as much and in some cases more abrasion than harder ones. When conducting abrasivity studies, it is important to look at both the quantitative and qualitative aspect of abrasivity.

  • 280. Thieme, J.
    et al.
    Sedlmair, J.
    Gleber, S-C
    Bertilson, Michael
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Von Hofsten, Olov
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Takman, Per
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    High-resolution imaging of soil colloids in aqueous media with a compact soft X-ray microscope2009Ingår i: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 186, s. 012107-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Colloids play an important role when describing parameters of and processes within soils, sediments or aquifers due to their abundance and their high specific surface area. It is of great importance to visualize the morphology of the structures formed by these particles as close as possible to environmental conditions. With X-ray microscopy colloids from the environment can be imaged directly in aqueous media with high spatial resolution. We demonstrate the first use of a compact laboratory x-ray microscope for studies of colloids from the environment, namely aqueous suspensions of clays and soils. The microscope is based on a high-brightness laser-produced-plasma X-ray source, a multilayer mirror and diffractive optics. The experiments show that such compact X-ray microscopes are reaching the image quality and operational maturity to make a significant impact in fields like environmental sciences.

  • 281. Thuering, T.
    et al.
    Zhou, Tunhe
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lundström, Ulf
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Burvall, Anna
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Rutishauser, S.
    David, C.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Stampanoni, M.
    X-ray grating interferometry with a liquid-metal-jet source2013Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, nr 9, s. 091105-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A liquid-metal-jet X-ray tube is used in an X-ray phase-contrast microscope based on a Talbot type grating interferometer. With a focal spot size in the range of a few microns and a photon flux of similar to 10(12) photons/s x sr, the brightness of such a source is approximately one order of magnitude higher than for a conventional microfocus source. For comparison, a standard microfocus source was used with the same grating interferometer, showing significantly increased visibility for the liquid-metal-jet arrangement. Together with the increased flux, this results in improved signal-to-noise ratio.

  • 282. Tolmachev, Vladimir
    et al.
    Hofström, Camilla
    KTH, Skolan för bioteknologi (BIO), Molekylär Bioteknologi (stängd 20130101).
    Malmberg, Jennie
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Ahlgren, Sara
    Orlova, Anna
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Gräslund, Torbjorn
    KTH.
    HEHEHE: a new chelator for [Tc-99m(CO)(3)](+)-labeling assembling His(6)-tag in protein purification2010Ingår i: Nuclear Medicine and Biology, ISSN 0969-8051, E-ISSN 1872-9614, Vol. 37, nr 6, s. 698-698Artikel i tidskrift (Övrigt vetenskapligt)
  • 283.
    Tuohimaa, Tomi
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Liquid-Jet-Target Microfocus X-Ray Sources: Electron Guns, Optics and Phase-Contrast Imaging2008Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This Thesis describes the development of an electron-impact microfocus x-ray source and its application for phase-contrast imaging. The source is based on a novel, liquid-jet target concept. Stable and continuous operation can be achieved at substantially higher electron-beam power densities than conventional solid target based systems. The maximum x-ray brightness can potentially be increased by a factor of 10-1000, which would provide significantly improved performance in applications such as imaging. In order to reach the high x-ray brightness, comparable performance from the electron gun is needed. A LaB6-cathode-based electron gun is analyzed in terms of achievable e-beam brightness and beam quality and is found capable to deliver power densities in the 10-100 MW/mm2 range using optimized electro-optics. A proof-of-principle microfocus source has been developed. Experiments show that the liquid-metal-jet target can be operated at more than an order of magnitude higher e-beam power densities than modern solid-metal targets. This brightness enhancement has been utilized to acquire in-line phase-contrast images of weakly absorbing objects. The source potentially enables the application of high-resolution phase-contrast x-ray imaging with short exposure times in clinics and laboratories.

    Different liquid-jet-target materials have been tested. The Sn-jet (Ka=25.3 keV) could be suitable for mammography, whereas the Ga-jet ((Ka=9.2 keV) may be utilized for x-ray diffraction studies. In addition, a non-metallic methanol jet has been the demonstrated in stable x-ray operation. All materials and compounds found in liquid form can, thus, potentially be used for electron-impact liquid-jet-target x-ray generation.

    Scaling to higher e-beam power density and x-ray brightness levels is discussed and is determined to be feasible. Potential difficulties, such as debris emission and instabilities of the x-ray emission spot, are investigated in some detail. Larger and/or faster jets could overcome the present limitations because of their inherently higher heat load capacities. Dynamic-similarity experiments show that liquid jets can in principle be operated in a stable manner at much higher speeds than previously shown.

  • 284.
    Tuohimaa, Tomi
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Ewald, Johannes
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Schlie, Moritz Gustav
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Fernandez-Varea, J. M.
    Facultat de Física (ECM), Universitat de Barcelona.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vogt, Ulrich
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    A microfocus x-ray source based on a nonmetal liquid-jet anode2008Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, nr 23, s. 233509-1-233509-3Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate stable operation of a nonmetallic anode in an electron-impact x-ray source. A high-brightness electron beam is focused on a similar to 70 m/s speed, similar to 10 mu m diameter methanol jet producing stable x-ray emission with peak spectral brightness at similar to 5.4 x 10(5) photons/(s x mu m(2) x sr x 0.1% BW). The jet is fully evaporated in the interaction point. The shape of a simulated spectrum using Monte Carlo methods shows good agreement with experimental data, and the theoretical brightness values give an upper limit for the achievable x-ray emission from jets with very high velocities. Using this anode concept, all compounds and elements found in liquid form are potentially usable for x-ray generation.

  • 285.
    Tuohimaa, Tomi
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Otendal, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    High-intensity electron beam for liquid-metal-jet anode hard x-ray generation2005Ingår i: Proceedings of SPIE, the International Society for Optical Engineering, ISSN 0277-786X, E-ISSN 1996-756X, Vol. 5918Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on our progress towards the experimental realization of a liquid-metal-jet-anode x-ray source with high brightness. We have previously shown that this electron-impact source has potential for very high x-ray brightness by combining small-spot high-flux operation of the electron beam with high-speed operation of the regenerative liquid-metal-jet anode. In the present paper we review the system and describe theoretical calculations for improving the 50 kV, 600 W electron-beam focussing to ∼30 μm spot size. With such a system the power density on the liquid-metal-jet would be ∼400 kW/mm 2, i.e., more than an order of magnitude higher than the power density on a state-of-the-art rotating anode.

  • 286.
    Tuohimaa, Tomi
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Otendal, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Phase-contrast x-ray imaging with a liquid-metal-jet-anode microfocus source2007Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, nr 7, s. 074104-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Phase-contrast methods increase contrast, detail, and selectivity in x-ray imaging. Present compact x-ray sources do not provide the necessary spatial coherence with sufficient power to allow the laboratory-scale high-resolution phase-contrast imaging with adequate exposure times. In this letter, the authors demonstrate phase-contrast imaging with few-micron detail employing a compact similar to 6.5 mu m spot liquid-metal-jet-anode high-brightness microfocus source. The 40 W source is operated at more than ten times higher electron-beam power density than present microfocus sources and is shown to provide sufficient spatial coherence as well as scalability to high power, thereby enabling the application of phase-contrast x-ray imaging with short exposure times in clinics and laboratories.

  • 287.
    Twengström, William
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    High-resolution biomedical phase-contrast tomography2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Förbättrad tredimensionell biomedicinsk avbildning kan ge en bättre förståelse av vävnadsstruktur, tillväxt och sjukdomar. De flesta av dagens avbildningstekniker som ger cellulär upplösning är baserade på synligt eller infrarött ljus. Dessa metoder kan inte avbilda mer än en millimeter ner i vävnad. Därför kan inte större prov avbildas i sin helhet utan att snittas. Tekniker som vanligen används för att avbilda större prover ger inte tillräcklig kontrast och upplösning för att avbilda strukturer av cellulär storlek i mjuk vävnad. Det finns ett behov av nya avbildningsmetoder som kan fylla utrymmet mellan befintliga metoder. Av praktiska skäl föredras att använda kompakt utrustning, för att möjliggöra nära koppling till annan forskning och tillämpningar. Dessutom, minimerade förberedelser av proven reducerar både arbetsinsatsen och tiden tills resultaten är klara.

    I den här doktorsavhandlingen har propagationsbaserad faskontrast- \mbox{tomografi} med metallstråleröntgenkällor undersökts för högupplöst tredimensionell avbildning. Genom att använda faskontrast kan kontrasten för strukturer av cellulär storlek i mjukvävnad ökas markant jämfört med absoption, även i större prover. Den höga upplösningen hänger på användandet av en röntgenkälla med liten emissionsspot, men även med hög effekt för att hålla exponeringstider korta.

    Den här doktorsavhandlingen handlar om att utveckla och optimera experimetella metoder och bildrekonstruktionsalgoritmer. En ny metod för att ta bort ringartefakter utvecklades och testades, och en jämförelse av flermaterials-fasrekonstruktion gjordes. Förbättringarna ger bättre kontrast och upplösning, men minskar också brus och artefakter. Den förbättrade bildkvaliteten visas i några biomedicinska tillämpningar. Det visas att metoden kan avbilda 5 µm stora myofibriller i hela zebrafiskar trots den lilla storleken och låga kontrasten hos myofibriller. En högupplöst tomografi av en mus kan göras snabbt genom att använda en specialiserad högeffektskälla. Bildkvaliteten i tomografier av både mänskliga kranskärl och en mummifierad mänsklig hand är tillräcklig för att analysera vävnader och strukturer av cellulär storlek, vilket är något som skulle kunna kallas virtuell histologi.

  • 288.
    Twengström, William
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Persson, Jonas
    Szekely, Laszlo
    Hertz, Hans
    KTH, Skolan för teknikvetenskap (SCI), Fysik. KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik. KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Cellular-resolution 3D virtual histology of human coronary arteries using x-ray phase tomography2018Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, artikel-id 11014Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High-spatial-resolution histology of coronary artery autopsy samples play an important role for understanding heart disease such as myocardial infarction. Unfortunately, classical histology is often destructive, has thick slicing, requires extensive sample preparation, and is time-consuming. X-ray micro-CT provides fast nondestructive 3D imaging but absorption contrast is often insufficient, especially for observing soft-tissue features with high resolution. Here we show that propagation-based x-ray phase-contrast tomography has the resolution and contrast to image clinically relevant soft-tissue features in intact coronary artery autopsy samples with cellular resolution. We observe microscopic lipid-rich plaques, individual adipose cells, ensembles of few foam cells, and the thin fibrous cap. The method relies on a small-spot laboratory x-ray microfocus source, and provides high-spatial resolution in all three dimensions, fast data acquisition, minimum sample distortion and requires no sample preparation.

  • 289.
    Uhlén, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Nanofabrication of Zone Plates for Hard X-Ray Free-Electron Lasers2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This Thesis describes the development of hard X-ray zone plates intended for focusing radiation at X-ray free-electron lasers (XFELs). XFELs provide unprecedented brightness and zone plates which are put in the intense X-ray beam are at risk of being damaged. Therefore, it is crucial to perform damage tests in order to design zone plates which can survive the XFEL beam.

    Zone plates are diffractive nanofocusing optics and are regularly used at high brightness synchrotron beamlines in the soft and hard X-ray regime. The resolution of a zone plate is proportional to its outermost zonewidth and thus depends on the smallest feature that can be fabricated. State-of-the-art nanofabrication processes developed for zone plates are able to produce zonewidths down to 10 nm. However, for hard X-rays, the zone plates need to be of sufficient thickness to efficiently focus the radiation. Thus, the limit in the fabrication of hard X-ray zone plates lies in the high aspect-ratios. This Thesis describes two processes developed for high aspect-ratio nanostructuring. The first process uses tungsten as diffractive material. Aspect-ratios up to 1:15 have been accomplished. Furthermore, a mounting method of a central stop directly on the zone plate is also presented. The other fabrication process uses diamond, in which aspect-ratios of 1:30 have been demonstrated. Both processes rely on thin-film deposition techniques, electron-beam lithography, and reactive ion etching. Thanks to the materials’ excellent thermal properties these types of zone plates should be suitable for XFEL applications. Tungsten and diamond diffractive optics have been tested at an XFEL at Stanford (LCLS), and damage investigations were performed in order to determine the maximum fluence that could be imposed on the optics before degradation occured. The conclusion of these damage tests is that tungsten and diamond diffractive optics can survive the XFEL beam and could potentially be used in beamline experiments relying on nanofocused X-ray beams. Finally in this Thesis, characterization of two zone plates using an interferometer is presented, where it is also shown that the interferometric method can be used to pin-point beamline instabilities.

  • 290.
    Uhlén, Fredrik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lindqvist, Sandra
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Nilsson, Daniel
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Reinspach, Julia
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vogt, Ulrich
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Holmberg, Anders
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    New diamond nanofabrication process for hard x-ray zone plates2011Ingår i: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 29, nr 6, s. 06FG03-1-06FG03-4Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The authors report on a new tungsten-hardmask-based diamond dry-etch process for fabricating diamond zone plate lenses with a high aspect ratio. The tungsten hardmask is structured by electron-beam lithography, together with Cl2/O2 and SF6/O2 reactive ion etching in a trilayer resist-chromium-tungsten stack. The underlying diamond is then etched in an O2 plasma. The authors demonstrate excellent-quality diamond gratings with half-pitch down to 80 nm and a height of 2.6 μm, as well as zone plates with a 75 μm diameter and 100 nm outermost zone width. The diffraction efficiency of the zone plates is measured to 14.5% at an 8 keV x-ray energy, and the imaging properties were investigated in a scanning microscope arrangement showing sub-100-nm resolution. The imaging and thermal properties of these lenses make them suitable for use with high-brightness x-ray free-electron laser sources.

  • 291.
    Uhlén, Fredrik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Nilsson, Daniel
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Holmberg, Anders
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Schroer, C. G.
    Seiboth, F.
    Patommel, J.
    Meier, V.
    Hoppe, R.
    Schropp, A.
    Lee, H. J.
    Nagler, B.
    Galtier, E.
    Krzywinski, J.
    Sinn, H.
    Vogt, Ulrich
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Damage investigation on tungsten and diamond diffractive optics at a hard x-ray free-electron laser2013Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 21, nr 7, s. 8051-8061Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Focusing hard x-ray free-electron laser radiation with extremely high fluence sets stringent demands on the x-ray optics. Any material placed in an intense x-ray beam is at risk of being damaged. Therefore, it is crucial to find the damage thresholds for focusing optics. In this paper we report experimental results of exposing tungsten and diamond diffractive optics to a prefocused 8.2 keV free-electron laser beam in order to find damage threshold fluence levels. Tungsten nanostructures were damaged at fluence levels above 500 mJ/cm(2). The damage was of mechanical character, caused by thermal stress variations. Diamond nanostructures were affected at a fluence of 59 000 mJ/cm(2). For fluence levels above this, a significant graphitization process was initiated. Scanning Electron Microscopy (SEM) and mu-Raman analysis were used to analyze exposed nanostructures.

  • 292.
    Uhlén, Fredrik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Nilsson, Daniel
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Rahomäki, Jussi
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Belova, Liubov
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Schroer, Christian G.
    Seiboth, Frank
    Holmberg, Anders
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vogt, Ulrich
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Nanofabrication of tungsten zone plates with integrated platinum central stop for hard X-ray applications2014Ingår i: Microelectronic Engineering, ISSN 0167-9317, E-ISSN 1873-5568, Vol. 116, s. 40-43Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a nanofabrication process for producing tungsten zone plates used in hard X-ray applications including a method of integrating a high-energy absorbing central stop with the optic. Tungsten zone plates are structured with electron-beam lithography and subsequent reactive ion etching. The central stop originates from a platinum wire. It is cut to dimension by focused ion beam etching, and afterwards attached to the zone plate center using ion beam induced deposition of platinum. A zone plate with integrated central stop will simplify alignment in hard X-ray scanning microscope arrangements where the 0th order light must be eliminated. The focusing performance of the zone plate device was investigated by scanning coherent diffraction imaging (ptychography) at 8 keV photon energy. We could demonstrate a diffraction-limited focus size of 53 nm diameter full-width-at-half-maximum. Tungsten zone plates with integrated central stops show promising results for use in hard X-ray microscopes at high-brightness facilities.

  • 293.
    Uhlén, Fredrik
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Rahomäki, Jussi
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Nilsson, Daniel
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Seiboth, Frank
    Sanz, Claude
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Wagner, Ulrich
    Rau, Christoph
    Schroer, Christian G.
    Vogt, Ulrich
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Ronchi test for characterization of X-ray nanofocusing optics and beamlines2014Ingår i: Journal of Synchrotron Radiation, ISSN 0909-0495, E-ISSN 1600-5775, Vol. 21, s. 1105-1109Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A Ronchi interferometer for hard X-rays is reported in order to characterize the performance of the nanofocusing optics as well as the beamline stability. Characteristic interference fringes yield qualitative data on present aberrations in the optics. Moreover, the visibility of the fringes on the detector gives information on the degree of spatial coherence in the beamline. This enables the possibility to detect sources of instabilities in the beamline like vibrations of components or temperature drift. Examples are shown for two different nanofocusing hard X-ray optics: a compound refractive lens and a zone plate.

  • 294.
    Unsbo, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Device and method for demonstrating optical effects2008Patent (Övrig (populärvetenskap, debatt, mm))
  • 295. van der Mooren, M.
    et al.
    Rosén, R.
    Franssen, L.
    Lundström, Linda
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Piers, P.
    Degradation of visual performance with increasing levels of retinal stray light2016Ingår i: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 57, nr 13, s. 5443-5448Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    PURPOSE. To quantify the effect of induced stray light on halo size, luminance threshold, and contrast sensitivity. METHODS. Retinal stray light was induced in five healthy subjects using different photographic filters. The stray light induced ranged from levels observed in intraocular lenses (IOLs) with glistenings (low) to cataract level (high). The visual impact was measured for halo size, luminance detection threshold, and contrast sensitivity with and without a glare source. RESULTS. The amount of retinal stray light induced by the different filters was similar when measured using the psychophysical method and the optical bench method. Low amounts of induced stray light cause the halo size to increase by 21%, the luminance detection threshold to increase by 156%, and contrast sensitivity to decrease by 10% to 21% dependent on spatial frequency and presence of a glare source. The visual impact percentages for high amounts of induced stray light were, respectively, 76%, 2130%, and 30% to 49%. In the presence of a glare source, contrast sensitivity losses were larger and shifted to lower spatial frequencies. CONCLUSIONS. Low levels of retinal stray light can cause significant increases in halo sizes, elevations in luminance detection thresholds, and reductions in contrast sensitivity whether or not a glare source is present.

  • 296.
    Van der Mooren, Marrie
    et al.
    AMO Groningen BV, Res & Dev, Groningen, Netherlands..
    Rosen, Robert
    AMO Groningen BV, Res & Dev, Groningen, Netherlands..
    Franssen, Luuk
    AMO Groningen BV, Res & Dev, Groningen, Netherlands..
    Lundström, Linda
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Piers, Patricia A.
    AMO Groningen BV, Res & Dev, Groningen, Netherlands..
    Prediction of contrast sensitivity in the presence of glare2017Ingår i: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 58, nr 8Artikel i tidskrift (Övrigt vetenskapligt)
  • 297. Van der Mooren, Marrie
    et al.
    Steinert, Roger F.
    Tyson, Farrell
    Rosen, Robert
    Lundström, Linda
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Piers, Patricia A.
    Understanding visual complaints of two intraocular lens explant cases2015Ingår i: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 56, nr 7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

     Purpose 

    In two different cases, multifocal intraocular lenses (MFIOLs) were explanted due to visual complications related to the presence of micro-vacuoles in the optic body. These micro-vacuoles cause straylight, which resulted in complaints of hazy and blurry vision. The purpose of this study is to objectively measure and systematically quantify the visual impact of this straylight. The study will thereby give a better understanding of the origin of reported visual complaints when micro-vacuoles are present.

     Methods 

    The amount of straylight in the two explanted MFIOLs was measured using an in-vitro setup and quantified using the scattering parameter s. To determine the impact of straylight on vision, photographic filters characterized in the same in-vitro setup were used to induce straylight on five subjects. Four different psychophysical visual tests were used: halo size, luminance detection with a glare source, and contrast sensitivity (CS) with and without the presence of glare. For all tests, the impact was modeled as a linear interpolation of the logarithm of the test score against the logarithm of the scattering parameter, log(s).

     Results 

    The straylight measured by the in-vitro setup was 6 deg2/sr for case 1 and 4 deg2/sr for case 2. Assuming a base straylight level of 1.1 log(s), the induced increase for the two patients was 0.17 log(s) and 0.12 log(s) respectively.<br /> The impact for the visual tests per unit of log(s) was the following: for halo size, 0.55 log(degrees)/log(s); for luminance detection 2.72 log(cd/m2)/log(s); for CS without glare, 0.33 log(CS)/log(s); and for CS with glare, 0.58 log(CS)/log(s). The induced straylight for the two explanted MFIOLs therefore corresponds to an increase of halo size of 24% and 16%, a luminance detection threshold increase of 190% and 112%, a contrast sensitivity decrease of 12% and 9% without a glare source, and a contrast sensitivity decrease of 20% and 9% with a glare source.

     Conclusions 

    In the explanted MFIOLs we could objectively measure straylight. This straylight corresponds psychophysically to increases in halo size, loss of luminance sensitivity and decrease in contrast sensitivity. Among the visual tests, measurement of luminance detection showed the highest sensitivity.

  • 298.
    Vanherberghen, Bruno
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Cellens fysik.
    Manneberg, Otto
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Christakou, Athanasia
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Frisk, Thomas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Cellens fysik.
    Ohlin, Mathias
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Önfelt, Björn
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Cellens fysik.
    Wiklund, Martin
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Ultrasound-controlled cell aggregation in a multi-well chip2010Ingår i: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 10, nr 20, s. 2727-2732Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate a microplate platform for parallelized manipulation of particles or cells by frequency-modulated ultrasound. The device, consisting of a silicon-glass microchip and a single ultrasonic transducer, enables aggregation, positioning and high-resolution microscopy of cells distributed in an array of 100 microwells centered on the microchip. We characterize the system in terms of temperature control, aggregation and positioning efficiency, and cell viability. We use time-lapse imaging to show that cells continuously exposed to ultrasound are able to divide and remain viable for at least 12 hours inside the device. Thus, the device can be used to induce and maintain aggregation in a parallelized fashion, facilitating long-term microscopy studies of, e.g., cell-cell interactions.

  • 299.
    Vanherberghen, Bruno
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Cellens fysik.
    Manneberg, Otto
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Christakou, Athanasia
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Cellens fysik.
    Frisk, Thomas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Cellens fysik.
    Önfelt, Björn
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Cellens fysik.
    Wiklund, Martin
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Highly parallelized cell aggregation by ultrasound for studies of immune cell interaction2009Konferensbidrag (Övrigt vetenskapligt)
  • 300.
    Venkataraman, Abinaya Priya
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vision Beyond the Fovea: Evaluation and Stimuli Properties2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Denna forskning handlar om att utvärdera synen i periferin. Vår perifera syn är ovärderlig i det dagliga livet. Målsättningen med denna avhandling är dels att utveckla metoder speciellt lämpade för perifer synutvärdering och dels att mäta hur olika synfunktioner varierar över synfältet. Resultaten har tillämpning både inom synrehabilitering för personer med centraltsynfältsbortfall och inom närsynthetsforskning.

    Adaptiv psykofysisk metodologi baserad på Bayesiansk statistik användes vid all utvärdering av det perifera seendet. Vi implementerade en rutin för tidseffektiv mätning av perifer kontrastkänslighet och verifierade den ut till 30° i synfältet. Den perifera synen utvärderades för olika egenskaper hos objektet: skärpa, rörelse, riktning och utbredning. Skärpan kontrollerades med hjälp av adaptiv optik och/eller glasögonkorrektion speciellt anpassad för den perifera synvinkeln. Vi fann att många periferasynfunktioner förbättras av optisk korrektion, särskilt för personer med centralt synfältsbortfall. Vi hittade även förbättringar i periferkontrastkänslighet för låga ortsfrekvenser när objektet modulerades med hastigheter mellan 5 och 10 Hz, vilket gäller både normalseende och personer med centralt synfältsbortfall. I periferin är det lättare att se linjer som är orienterade parallellt med synfältsmeridianen. Vi har visat att denna riktningsbias gäller både för upplösning och detektion i periferin, även när de asymmetriska optiska felen minimeras. För bästa mätnoggrannhet rekommenderar vi därför att använda randmönster som ligger snett relativt synfältsmeridianen. Denna riktningsbias skulle även kunna påverka hur den perifera bildkvalitén inverkar på utvecklingen av närsynthet. Ytterligare ett bevis för att perifer syn kan påverka den centrala synfunktionen är att, när objektets utbredning ökades, uppfattade personen det som mindre suddigt.

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