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  • 1.
    Andersson, AS
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Kalska, B
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Jonsson, P
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
    Haggstrom, L
    Nordblad, P
    Tellgren, R
    Thomas, JO
    The magnetic structure and properties of rhombohedral Li3Fe2(PO4)(3)2000In: JOURNAL OF MATERIALS CHEMISTRY, ISSN 0959-9428, Vol. 10, no 11, p. 2542-2547Article in journal (Refereed)
    Abstract [en]

    Magnetic susceptibility measurements indicate that rhombohedral Li3Fe2(PO4)(3), obtained by ion exchange of monoclinic Na3Fe2(PO4)(3), exhibits a paramagnetic to antiferromagnetic transition at T-N approximate to 27 K. Curie-Weiss-like behaviour is observ

  • 2.
    Andersson, AS
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Thomas, JO
    Physics, Department of Physics.
    Kalska, B
    Haggstrom, L
    Thermal stability of LiFePO4-based cathodes2000In: ELECTROCHEMICAL AND SOLID STATE LETTERS, ISSN 1099-0062, Vol. 3, no 2, p. 66-68Article in journal (Refereed)
    Abstract [en]

    The capacity and cyclability of solid-state synthesized LiFePO4-based laminate cells of type <Li \ liq. el. \ LiFePO4> have been studied at 23, 40, and 60 degrees C. Larger capacities were obtained for cells cycled at the elevated temperatures. No evidenc

  • 3.
    Broddefalk, A
    et al.
    INORGANIC CHEMISTRY. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
    James, P
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Liu, HP
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Kalska, B
    Andersson, Y
    Granberg, P
    Nordblad, P
    Haggstrom, L
    Eriksson, I
    Structural and magnetic properties of (Fe1-xMnx)3P (x < 0.25)2000In: PHYSICAL REVIEW B, ISSN 1098-0121, Vol. 61, no 1, p. 413-421Article in journal (Refereed)
    Abstract [en]

    Structural and magnetic properties of (Fe1-xMnx)(3)P compounds have been investigated by means of x-ray and neutron diffraction experiments, magnetization measurements, Mossbauer experiments, and first principles calculations. The Curie temperature of the

  • 4.
    Haggstrom, L
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    James, P
    Chemistry, Department of Chemistry.
    Eriksson, O
    Liu, HP
    Trosko, M
    Szymanski, K
    Dobrzynski, L
    Hyperfine interaction study of (Fe1-xCox)(3)P compounds2000In: PHYSICAL REVIEW B, ISSN 1098-0121, Vol. 61, no 10, p. 6798-6804Article in journal (Refereed)
    Abstract [en]

    The magnetic and ordering properties of (Fe1-xCox)(3)P (x=0, 0.1, 0.2, and 0.33) compounds have been studied by Fe-57 Mossbauer technique. These investigations show that Co preferentially substitutes Fe in two out of three metal sites. Variations of the m

  • 5.
    Karlsson, Leif
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    Keane, Michael P
    Berger, Rolf
    Chemistry, Department of Chemistry. Oorganisk kemi.
    An XPS-study of isostructural multinary thallium copper chalcogenides1990In: Journal of the Less-Common Metals, Vol. 166, p. 353-365Article in journal (Refereed)
  • 6.
    Liu, HP
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. INORGANIC CHEMISTRY.
    Colarieti-Tosti, M
    Physics, Department of Physics.
    Broddefalk, A
    Technology, Department of Materials Science.
    Andersson, Y
    Lidstrom, E
    Eriksson, O
    On the structural polymorphism of CePt2Sn2: experiment and theory2000In: JOURNAL OF ALLOYS AND COMPOUNDS, ISSN 0925-8388, Vol. 306, no 1-2, p. 30-39Article in journal (Refereed)
    Abstract [en]

    Samples of the heavy fermion compound CePt2Sn2 with varying compositions have been synthesised and examined from room temperature up to the melting point. Two crystallographic structures of the intermetallic alloy CePt2Sn2 were observed and they were syst

  • 7.
    Lu, J
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Hugosson, H
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Eriksson, Olle
    Nordström, Lars
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Chemical vapour deposition of molybdenum carbides: aspects of phase stability2000In: THIN SOLID FILMS, ISSN 0040-6090, Vol. 370, no 1-2, p. 203-212Article in journal (Refereed)
    Abstract [en]

    Thin films of different molybdenum carbides (delta-MoC1-x, gamma'-MoC1-x and Mo2C) have been deposited from a gas mixture of MoCl5/H-2/C2H4 at 800 degrees C by CVD. The H-2 content in the vapour has a strong influence on the phase composition and microstr

  • 8.
    Razifar, Pasha
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Centre for Image Analysis. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis.
    Lubberink, Mark
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Schneider, Harald
    Långström, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Bengtsson, Ewert
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Centre for Image Analysis. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis.
    Bergström, Mats
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience.
    Non-isotropic noise correlation in PET data reconstructed by FBP but not by OSEM demonstrated using auto-correlation function2005In: Bio Medical Central (BMC): Medical Imaging, Vol. 5, no 3Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Positron emission tomography (PET) is a powerful imaging technique with the potential of obtaining functional or biochemical information by measuring distribution and kinetics of radiolabelled molecules in a biological system, both in vitro and in vivo. PET images can be used directly or after kinetic modelling to extract quantitative values of a desired physiological, biochemical or pharmacological entity. Because such images are generally noisy, it is essential to understand how noise affects the derived quantitative values. A pre-requisite for this understanding is that the properties of noise such as variance (magnitude) and texture (correlation) are known. METHODS: In this paper we explored the pattern of noise correlation in experimentally generated PET images, with emphasis on the angular dependence of correlation, using the autocorrelation function (ACF). Experimental PET data were acquired in 2D and 3D acquisition mode and reconstructed by analytical filtered back projection (FBP) and iterative ordered subsets expectation maximisation (OSEM) methods. The 3D data was rebinned to a 2D dataset using FOurier REbinning (FORE) followed by 2D reconstruction using either FBP or OSEM. In synthetic images we compared the ACF results with those from covariance matrix. The results were illustrated as 1D profiles and also visualized as 2D ACF images. RESULTS: We found that the autocorrelation images from PET data obtained after FBP were not fully rotationally symmetric or isotropic if the object deviated from a uniform cylindrical radioactivity distribution. In contrast, similar autocorrelation images obtained after OSEM reconstruction were isotropic even when the phantom was not circular. Simulations indicated that the noise autocorrelation is non-isotropic in images created by FBP when the level of noise in projections is angularly variable. Comparison between 1D cross profiles on autocorrelation images obtained by FBP reconstruction and covariance matrices produced almost identical results in a simulation study. CONCLUSION: With asymmetric radioactivity distribution in PET, reconstruction using FBP, in contrast to OSEM, generates images in which the noise correlation is non-isotropic when the noise magnitude is angular dependent, such as in objects with asymmetric radioactivity distribution. In this respect, iterative reconstruction is superior since it creates isotropic noise correlations in the images.

  • 9.
    Razifar, Pasha
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Centre for Image Analysis. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis.
    Sandström, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Schneider, Harald
    Långström, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Maripuu, Enn
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Bengtsson, Ewert
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Centre for Image Analysis. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis.
    Bergström, Mats
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience.
    Noise correlation in PET, CT, SPECT and PET/CT data evaluated using autocorrelation function: a phantom study on data, reconstructed using FBP and OSEM.2005In: Bio Medical Central (BMC): Medical Imaging, Vol. 5, no 5Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Positron Emission Tomography (PET), Computed Tomography (CT), PET/CT and Single Photon Emission Tomography (SPECT) are non-invasive imaging tools used for creating two dimensional (2D) cross section images of three dimensional (3D) objects. PET and SPECT have the potential of providing functional or biochemical information by measuring distribution and kinetics of radiolabelled molecules, whereas CT visualizes X-ray density in tissues in the body. PET/CT provides fused images representing both functional and anatomical information with better precision in localization than PET alone.Images generated by these types of techniques are generally noisy, thereby impairing the imaging potential and affecting the precision in quantitative values derived from the images. It is crucial to explore and understand the properties of noise in these imaging techniques. Here we used autocorrelation function (ACF) specifically to describe noise correlation and its non-isotropic behaviour in experimentally generated images of PET, CT, PET/CT and SPECT. METHODS: Experiments were performed using phantoms with different shapes. In PET and PET/CT studies, data were acquired in 2D acquisition mode and reconstructed by both analytical filter back projection (FBP) and iterative, ordered subsets expectation maximisation (OSEM) methods. In the PET/CT studies, different magnitudes of X-ray dose in the transmission were employed by using different mA settings for the X-ray tube. In the CT studies, data were acquired using different slice thickness with and without applied dose reduction function and the images were reconstructed by FBP. SPECT studies were performed in 2D, reconstructed using FBP and OSEM, using post 3D filtering. ACF images were generated from the primary images, and profiles across the ACF images were used to describe the noise correlation in different directions. The variance of noise across the images was visualised as images and with profiles across these images. RESULTS: The most important finding was that the pattern of noise correlation is rotation symmetric or isotropic, independent of object shape in PET and PET/CT images reconstructed using the iterative method. This is, however, not the case in FBP images when the shape of phantom is not circular. Also CT images reconstructed using FBP show the same non-isotropic pattern independent of slice thickness and utilization of care dose function. SPECT images show an isotropic correlation of the noise independent of object shape or applied reconstruction algorithm. Noise in PET/CT images was identical independent of the applied X-ray dose in the transmission part (CT), indicating that the noise from transmission with the applied doses does not propagate into the PET images showing that the noise from the emission part is dominant. The results indicate that in human studies it is possible to utilize a low dose in transmission part while maintaining the noise behaviour and the quality of the images. CONCLUSION: The combined effect of noise correlation for asymmetric objects and a varying noise variance across the image field significantly complicates the interpretation of the images when statistical methods are used, such as with statistical estimates of precision in average values, use of statistical parametric mapping methods and principal component analysis. Hence it is recommended that iterative reconstruction methods are used for such applications. However, it is possible to calculate the noise analytically in images reconstructed by FBP, while it is not possible to do the same calculation in images reconstructed by iterative methods. Therefore for performing statistical methods of analysis which depend on knowing the noise, FBP would be preferred.

  • 10.
    Wirde, M
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    Gelius, U
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
    Nyholm, L
    Chemistry, Department of Chemistry.
    Self-assembled monolayers of cystamine and cysteamine on gold studied by XPS and voltammetry1999In: LANGMUIR, ISSN 0743-7463, Vol. 15, no 19, p. 6370-6378Article in journal (Refereed)
    Abstract [en]

    The formation of self-assembled chemisorbed layers of cystamine, cysteamine, and 4-aminothiophenol on gold has been studied by XPS and voltammetry. These compounds, often used in the preparation of biosensors and modified electrodes, are shown to yield surface coverages of approximately 80% of that of a octadecanethiol monolayer within 5 min in millimolar aqueous and ethanolic solutions. The results of the XPS experiments reveal that a shoulder on the S 2p(3/2) peak (situated at 162.1 eV) develops at 161.3 eV upon increasing the adsorption time from minutes to 1 week and that the initial rate of formation of the shoulder is higher for cystamine than for cysteamine. This shoulder is believed to be due to the presence of a sulfur species with a higher coordination number with respect to gold. Increased adsorption times also give rise to increased amounts of oxidized carbon and sulfur in the films. The oxidation of the sulfur in the thiols results in a detachment of the molecules from the gold surface, as indicated by XPS experiments with different takeoff angles. The main N 1s peak for cystamine is shifted toward higher binding energies for increasing adsorption times while two prominent nitrogen peaks are generally seen for cysteamine. For cysteamine, increasing adsorption times result in an increase of the main nitrogen component at the higher binding energy, yielding an apparent shift in the nitrogen peak with time similar to that seen for cystamine. Possible explanations for these experimental findings are discussed. Cystamine, cysteamine, and 4-aminothiophenol films on gold are shown to be irreversibly oxidized in the gold oxide formation region. On the basis of evaluation of the oxidation charge, surface coverages of approximately 1 x 10(-9) mol/cm(2) were obtained for adsorption times between 5 min and 1 week.

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