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  • 251.
    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 tomography2019Inngår i: Biomedical Optics Express, ISSN 2156-7085, E-ISSN 2156-7085, Vol. 10, nr 8, s. 3773-3788, artikkel-id 364926Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 252.
    Skoglund Lindberg, Peter Anders
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Electron-Impact Liquid-Jet Water-Window X-ray Sources2010Licentiatavhandling, med artikler (Annet vitenskapelig)
    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.

     

  • 253.
    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 source2010Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, nr 8Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 254.
    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 Microscopy2011Inngår i: 10th International Conference on X-Ray Microscopy / [ed] McNulty, I; Eyberger, C; Lai, B, 2011, Vol. 1365, s. 152-155Konferansepaper (Fagfellevurdert)
    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.

  • 255.
    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 system2010Inngår i: OPTICAL MICROLITHOGRAPHY XXIII / [ed] Mircea V. Dusa; Will Conley, SPIE - International Society for Optical Engineering, 2010Konferansepaper (Fagfellevurdert)
    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.

  • 256.
    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 functions2009Inngår i: Optical Microlithography XXII / [ed] Harry J. Levinson; Mircea V. Dusa, SPIE - International Society for Optical Engineering, 2009Konferansepaper (Annet vitenskapelig)
    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.

  • 257.
    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 supercooling2019Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 21, nr 1, s. 26-31Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 258. 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 nanotomography2017Inngår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 88, nr 5, artikkel-id 053703Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 259.
    Stollberg, Heide
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Compact Soft X-Ray Microscopy: Image Processing and Instrumentation2006Doktoravhandling, med artikler (Annet vitenskapelig)
    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.

  • 260.
    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 microscopy2007Inngår i: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818, Vol. 225, nr 1, s. 80-87Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 261.
    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 microscopy2006Inngår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 77, nr 12, s. 123101-Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 262.
    Svennebring, Jessica
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Ultrasonic Handling of Living Cells in Microfluidic Systems2009Doktoravhandling, med artikler (Annet vitenskapelig)
    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.

  • 263.
    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 chip2008Inngår 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. 1175-1177Konferansepaper (Fagfellevurdert)
    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.

  • 264.
    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 cultivation2007Konferansepaper (Fagfellevurdert)
  • 265.
    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 characterization2009Konferansepaper (Annet vitenskapelig)
  • 266.
    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 cavity2009Inngår i: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 103, s. 323-328Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 267.
    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 cultivation2007Konferansepaper (Fagfellevurdert)
  • 268.
    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 chip2007Inngår i: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 17, s. 2469-2474Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 269.
    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 mammography2011Inngår 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-S219Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 270.
    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 microscopy2006Inngår i: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818Artikkel i tidsskrift (Annet vitenskapelig)
  • 271.
    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 microscopy2007Inngår i: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818, Vol. 226, nr 2, s. 175-181Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 272.
    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 source2006Inngår i: Proceedings of 8th International Conference on X-ray Microscopy, 2006, s. 12-14Konferansepaper (Fagfellevurdert)
    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.

  • 273. 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 process2011Inngår i: International Journal of Dental Hygiene, ISSN 1601-5029, E-ISSN 1601-5037, Vol. 9, nr 4, s. 284-290Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 274. 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 microscope2009Inngår i: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 186, s. 012107-Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 275. 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 source2013Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, nr 9, s. 091105-Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 276. 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 purification2010Inngår i: Nuclear Medicine and Biology, ISSN 0969-8051, E-ISSN 1872-9614, Vol. 37, nr 6, s. 698-698Artikkel i tidsskrift (Annet vitenskapelig)
  • 277.
    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 Imaging2008Doktoravhandling, med artikler (Annet vitenskapelig)
    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.

  • 278.
    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 anode2008Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, nr 23, s. 233509-1-233509-3Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 279.
    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 generation2005Inngår i: Proceedings of SPIE, the International Society for Optical Engineering, ISSN 0277-786X, E-ISSN 1996-756X, Vol. 5918Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 280.
    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 source2007Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, nr 7, s. 074104-Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 281.
    Twengström, William
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    High-resolution biomedical phase-contrast tomography2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Improved three-dimensional biomedical imaging can give a better understanding of tissue structure, growth and diseases. Most present imaging techniques that provide cellular spatial resolution are based on visible or infrared light. These methods cannot image deeper than a millimeter into tissue. Consequently, larger samples cannot be completely imaged without sectioning. Techniques that are typically used to image larger samples don't provide sufficient contrast and resolution to image cellular-sized features in soft tissues. There is a need for new imaging methods that can fill the gap between present methods. For practical reasons, compact equipment is preferred, to enable close connection to other research and applications. Furthermore, minimized sample preparation both reduces the work needed and the time until results are ready.

    In this Thesis, propagation-based phase-contrast tomography with liquid-metal-jet x-ray sources has been investigated for high-resolution three-dimensional biomedical imaging. By using phase contrast, the contrast for cellular-sized features in soft tissue is vastly increased compared to absorption, also in larger samples. The high resolution relies on using an x-ray source with small emission spot, but also with high power to keep exposure times reasonable.

    This Thesis is about developing and optimizing experimental methods and image reconstruction algorithms. A new method to remove ring artifacts was developed and tested, and a comparison of multi-material phase-retrieval algorithms was made. The improvements provide better contrast and resolution, as well as reduce noise and artifacts. The improved image quality is demonstrated in a few biomedical applications. It is shown that the method can image 5 µm large myofibrils in whole-body zebrafish, despite the small size and low contrast of myofibrils. A high-resolution tomography of a mouse can be done fast by using a specialized high-power source. The image quality in tomographies of both human coronary arteries and a mummified human hand is sufficient to analyze the tissues and cellular-sized features, which is something that could be called virtual histology. 

  • 282.
    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 tomography2018Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, artikkel-id 11014Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 283.
    Uhlén, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Nanofabrication of Zone Plates for Hard X-Ray Free-Electron Lasers2015Doktoravhandling, med artikler (Annet vitenskapelig)
    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.

  • 284.
    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 plates2011Inngår i: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 29, nr 6, s. 06FG03-1-06FG03-4Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 285.
    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 laser2013Inngår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 21, nr 7, s. 8051-8061Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 286.
    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 applications2014Inngår i: Microelectronic Engineering, ISSN 0167-9317, E-ISSN 1873-5568, Vol. 116, s. 40-43Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 287.
    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 beamlines2014Inngår i: Journal of Synchrotron Radiation, ISSN 0909-0495, E-ISSN 1600-5775, Vol. 21, s. 1105-1109Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 288.
    Unsbo, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Device and method for demonstrating optical effects2008Patent (Annet (populærvitenskap, debatt, mm))
  • 289. 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 light2016Inngår i: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 57, nr 13, s. 5443-5448Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 290.
    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 glare2017Inngår i: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 58, nr 8Artikkel i tidsskrift (Annet vitenskapelig)
  • 291. 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 cases2015Inngår i: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 56, nr 7Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 292.
    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 chip2010Inngår i: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 10, nr 20, s. 2727-2732Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 293.
    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 interaction2009Konferansepaper (Annet vitenskapelig)
  • 294.
    Venkataraman, Abinaya Priya
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vision Beyond the Fovea: Evaluation and Stimuli Properties2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This research is about evaluating vision in the periphery. Peripheral vision is of fundamental importance in the performance of our everyday activities. The aim of this thesis is to develop methods suitable for the evaluation of peripheral vision and to assess how different visual functions vary across the visual field. The results have application both within the field of visual rehabilitation of people with central visual field loss (CFL)and as well as in myopia research.

    All methods for assessing peripheral vision were implemented with adaptive psychophysical algorithms based on Bayesian statistics. A routine for time-efficient evaluation of peripheral contrast sensitivity was implemented and verified for measurements out to 30° in the visual field. Peripheral vision was evaluated for different properties of the stimuli: sharpness, motion, orientation, and extent. Optical quality was controlled using adaptive optics and/or corrective spectacles specially adapted for the peripheral viewing angle. We found that many peripheral visual functions improved with optical correction, especially in people with CFL. We also found improvements in peripheral contrast sensitivity for low spatial frequencies when stimuli drifted at 5 to 10 Hz; this applies both for people with normal vision and those with CFL. In the periphery, it is easier to see lines that are oriented parallel with respect to the visual field meridian. We have shown that this directional bias is present for both resolution and detection tasks in the periphery, even when the asymmetric optical errors are minimized. For accurate evaluation of peripheral vision, we therefore recommend using gratings that are oriented oblique to the visual  field meridian. The directional bias may have implications in how peripheral image quality affects myopia progression. Another proof that peripheral vision can influence central visual function is the fact that, when the stimulus extent was increased beyond the fovea, the blur in the stimulus was less noticeable.

  • 295.
    Venkataraman, Abinaya Priya
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lewis, Peter
    Unsbo, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lundström, Linda
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Peripheral contrast sensitivity for drifting stimuliManuskript (preprint) (Annet vitenskapelig)
  • 296. Venkataraman, Abinaya Priya
    et al.
    Lundström, Linda
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lewis, Peter
    Unsbo, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Peripheral resolution and contrast sensitivity: Effects of stimulus drift2017Inngår i: Vision Research, ISSN 0042-6989, E-ISSN 1878-5646, s. 145-149Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Optimal temporal modulation of the stimulus can improve foveal contrast sensitivity. This study evaluates the characteristics of the peripheral spatiotemporal contrast sensitivity function in normal-sighted subjects. The purpose is to identify a temporal modulation that can potentially improve the remaining peripheral visual function in subjects with central visual field loss. High contrast resolution cut-off for grating stimuli with four temporal frequencies (0, 5, 10 and 15 Hz drift) was first evaluated in the 10° nasal visual field. Resolution contrast sensitivity for all temporal frequencies was then measured at four spatial frequencies between 0.5 cycles per degree (cpd) and the measured stationary cut-off. All measurements were performed with eccentric optical correction. Similar to foveal vision, peripheral contrast sensitivity is highest for a combination of low spatial frequency and 5–10 Hz drift. At higher spatial frequencies, there was a decrease in contrast sensitivity with 15 Hz drift. Despite this decrease, the resolution cut-off did not vary largely between the different temporal frequencies tested. Additional measurements of contrast sensitivity at 0.5 cpd and resolution cut-off for stationary (0 Hz) and 7.5 Hz stimuli performed at 10, 15, 20 and 25° in the nasal visual field also showed the same characteristics across eccentricities.

  • 297.
    Venkataraman, Abinaya Priya
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lundström, Linda
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Winter, Simon
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Unsbo, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik. Royal Inst Technol, KTH, Biomed & Xray Phys, Stockholm, Sweden..
    Small and Large Field Blur Adaptation: Foveal and Peripheral Contrast Sensitivity Changes2014Inngår i: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 55, nr 13Artikkel i tidsskrift (Annet vitenskapelig)
  • 298.
    Venkataraman, Abinaya Priya
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Papadogiannis, Petros
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Romashchenko, Dmitry
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Winter, Simon
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Unsbo, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lundström, Linda
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Peripheral resolution and contrast sensitivity: effects of monochromatic and chromatic aberrations2019Inngår i: Optical Society of America. Journal A: Optics, Image Science, and Vision, ISSN 1084-7529, E-ISSN 1520-8532, Vol. 36, nr 4, s. B52-B57Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Correction and manipulation of peripheral refractive errors are indispensable for people with central vision loss and in optical interventions for myopia control. This study investigates further enhancements of peripheral vision by compensating for monochromatic higher-order aberrations (with an adaptive optics system) and chromatic aberrations (with a narrowband green filter, 550 nm) in the 20 degrees nasal visual field. Both high-contrast detection cutoff and contrast sensitivity improved with optical correction. This improvement was most evident for gratings oriented perpendicular to the meridian due to asymmetric optical errors. When the natural monochromatic higher-order aberrations are large, resolution of 10% contrast oblique gratings can also be improved with correction of these errors. Though peripheral vision is mainly limited by refractive errors and neural factors, higher-order aberration correction beyond conventional refractive errors can still improve peripheral vision under certain circumstances.

  • 299.
    Venkataraman, Abinaya Priya
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Radhakrishnan, A.
    Dorronsoro, C.
    Lundström, Linda
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Marcos, S.
    Role of parafovea in blur perception2017Inngår i: Vision Research, ISSN 0042-6989, E-ISSN 1878-5646, Vol. 138, s. 59-65Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The blur experienced by our visual system is not uniform across the visual field. Additionally, lens designs with variable power profile such as contact lenses used in presbyopia correction and to control myopia progression create variable blur from the fovea to the periphery. The perceptual changes associated with varying blur profile across the visual field are unclear. We therefore measured the perceived neutral focus with images of different angular subtense (from 4° to 20°) and found that the amount of blur, for which focus is perceived as neutral, increases when the stimulus was extended to cover the parafovea. We also studied the changes in central perceived neutral focus after adaptation to images with similar magnitude of optical blur across the image or varying blur from center to the periphery. Altering the blur in the periphery had little or no effect on the shift of perceived neutral focus following adaptation to normal/blurred central images. These perceptual outcomes should be considered while designing bifocal optical solutions for myopia or presbyopia.

  • 300.
    Venkataraman, Abinaya Priya
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Radhakrishnan, Aiswaryah
    Dorronsoro, Carlos
    Lundström, Linda
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Marcos, Susana
    Effect of parafovea on blur perceptionManuskript (preprint) (Annet vitenskapelig)
345678 251 - 300 of 352
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