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  • 251. Häggström, Lennart
    et al.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Ahniyaz, Anwar
    Nordblad, Per
    Ericsson, Tore
    Kamali, Saeed
    Mössbauer and magnetization studies of iron oxide nanocrystals2008In: Hyperfine Interactions, ISSN 0304-3843, E-ISSN 1572-9540, Vol. 189, p. 49-53Article in journal (Refereed)
    Abstract [en]

    Monodisperse iron oxide nanocrystals have been produced following nonhydrolytic, thermal decomposition routes. Spherically shaped particles with diameter of 4 and 12 nm and cubic shaped particles with an edge length of 9 nm have been studied. The particles have been shown to consist of mainly maghemite. A reduction of the saturation magnetic hyperfine field is observed for the 4 nm particles as compared to the corresponding bulk value. The anisotropy energy determined from the temperature variation of the magnetic hyperfine field was strongly enhanced for the 4 nm particles.

  • 252.
    Hälldahl, Lars
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Inorganic Chemistry.
    Studies of reactions occurring in the AUC-process: from UF₆ to sintered UO₂ pellets1985Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This study has been carried out to investigate the influence of process parameters upon the material characteristics during the conversion of UFg to UO2 powder, and the importance of variation in these charcteristics for the final quality of the sintered pellets. The first process step is a precipitation of ammonium uranyl carbonate (AUC) from UFg, ammonia and carbon dioxide. In this step the most important characteristic is the particle size distribution, which is determined by the concentration of the reacting species and by the temperature.

    The reducing capacity of the atmosphere, the heating rate and the final temperature influence the specific surface area, the stoichiometry and the crystallite size, obtained in the reduction of AUC to UO2 powder.

    The studies also reveal that the reaction path from AUC to UO2 is very complex. Intermediates such as amorphous UO3, CÏ-UO3, uranium oxide hydrates, U4O9 and U30g can under certain conditions exist, transiently during this operation. The reaction path actually followed very strongly influences the powder characteristics.

    Methods to study sinterability and sintering kinetics have also been employed. Quasi-isothermal dilatometry (QID), has been used to find the rate controlling mechanism in the initial stage of sintering, and to evaluate the activation energy in the different atmospheres and diffusion coefficients.

    Full-scale experiments have verified the findings; coarse, inactive powders accumulate high defect concentations during pressing, leading to a relatively high defect frequency after sintering. Finer powders, which are still coarser than a certain minimum, however give the strongest green pellets with the best sinterablity. This type of powders also yields high quality sintered pellets with low defect frequencies.

  • 253. Häusserman, Ulrich
    et al.
    Söderberg, Karin
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Norrestam, Rolf
    Comparative Study of the High-Pressure Behaviour of As, Sb, and Bi2002In: Journal of the American Chemical Society, ISSN 1520-5126, Vol. 124, p. 15359-15367Article in journal (Refereed)
  • 254. Häussermann, Ulrich
    et al.
    Degtyareva, Olga
    Mikhaylushkin, A.
    Söderberg, Karin
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Simak, S.I.
    McMahon, M.I.
    Nelmes, M.I.
    Norrestam, Rolf
    Alloys Bi1-xSbx under High-Pressure2004In: Physical Review B, ISSN 1098-0121, Vol. 69, p. 134203-1 - 134203-10Article in journal (Refereed)
  • 255. Häussermann, Ulrich
    et al.
    Lind, Hanna
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Lidin, Sven
    Structure and bonding principles of stackings (Bi2Se3)m(Bi2)n: a challenging family of materialsManuscript (Other academic)
  • 256.
    Högberg, Carl-Johan
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Molecular Dynamics Investigations of Structure and Dynamics of Lipid Bilayers and Associated Anesthetics2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Detailed understanding of lipid bilayers are of tremendous importance due to their role in many biological processes. This Thesis focuses on structural and dynamical properties of lipid bilayers and their interactions with locally acting anesthetics, studied by Molecular Dynamics simulations.

    The effect of dehydration of a lipid bilayer is a biologically important phenomenon which was investigated by detailed examination of a number of structural and dynamical lipid parameters at different levels of hydration. The result shows that whereas the structural properties of the bilayer only moderately depend on the degree of hydration, the dynamics of the system is affected very strongly.

    Related to changes in the bilayer caused by hydration are structural and dynamical changes caused by the presence of anesthetics. Lidocaine is a common, locally acting anesthetic that interacts with lipid bilayers. The difference in position, orientation and diffusional behavior for charged and uncharged lidocaine was examined. The overall results indicate a rather restricted motion, determined by the lipids for the charged lidocaine, whereas the uncharged molecules are more free to diffuse in the lateral direction, as well as able to cross the bilayer.

    For membrane associated anesthetics, the effect on the bilayer electrostatic potential when introducing anesthetic compounds could contribute to the anesthetic effect. When the change in electrostatic potential and headgroup orientation was examined, both properties were found to be changed by charged as well as uncharged lidocaine. Surprisingly, the potentials in the middle part of the bilayer were almost the same for the charged and uncharged form of lidocaine. The suggested explanation for this is that the uncharged lidocaine gives a significant contribution to the electrostatic potential due to its orientation.

    Knowledge about the three dimensional structure and structural changes of the lipids in a bilayer is an important biological question. The validity of a method based on the additive potential and maximum entropy model applied to a lipid bilayer was investigated by comparing distributions for two torsion angles extracted from simulations with their corresponding distributions received from the combined model. The results indicates that this new method could be used as a tool for interpretation of experimental data in bilayer systems.

    For better correspondence with experiment, a calibration of the CHARMM force field was conducted by changing interactions in the lipid tails and charges in the lipid head group. With these new parameters, the simulations gave a fraction of gauche conformations in the lipid tails close to the experimentally determined value, and a very good experimental agreement for the area per lipid, electron density, X-ray structure factor, and NMR order parameters.

  • 257.
    Högberg, Carl-Johan
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Lyubartsev, Alexander
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Effect of local anesthetic lidocaine on electrostatic properties of a lipid bilayer2007In: Biophysical JournalArticle in journal (Refereed)
  • 258.
    Högberg, Carl-Johan
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry. Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Physical Chemistry.
    Lyubartsev, Alexander
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Physical Chemistry.
    Effect of Local Anesthetic Lidocaine on Electrostatic Properties of a Lipid Bilayer2008In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 94, p. 525-531Article in journal (Refereed)
    Abstract [en]

    The influence of local anesthetic lidocaine on electrostatic properties of a lipid membrane bilayer was studied by molecular dynamics simulations. The electrostatic dipole potential, charge densities, and orientations of the headgroup angle have been examined in presence of different amounts of charged or uncharged forms of lidocaine. Important differences of the membrane properties caused by the presence of the both forms of lidocaine are presented and discussed. Our simulations have shown that both charged and uncharged lidocaine cause almost the same increase of the dipole electrostatic potential in the middle of membrane though for different reasons. The increase, being about 90 mV for 9 mol % of lidocaine and 220 mV for 28 mol% of lidocaine, is of the size which may affect the functioning of voltage-gated ion channels.

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  • 259.
    Högberg, Carl-Johan
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Maliniak, Arnold
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Lyubartsev, Alexander
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Dynamical and structural properties of charged and uncharged lidocaine in a lipid bilayer2007In: Biophysical Chemistry, Vol. 125, p. 416-424Article in journal (Refereed)
  • 260.
    Högberg, Carl-Johan
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Physical Chemistry.
    Nikitin, Alexei
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Physical Chemistry.
    Lyubartsev, Alexander
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Physical Chemistry.
    Modification of the CHARMM force field for DMPC lipid bilayer2008In: Journal of Computational Chemistry, ISSN 0192-8651, E-ISSN 1096-987X, Vol. 29, no 14, p. 2359-2369Article in journal (Refereed)
    Abstract [en]

    The CHARMM force field for DMPC lipids was modified in order to improve agreement with experiment for a number of important properties of hydrated lipid bilayer. The modification consists in introduction of a scaling factor 0.83 for 1-4 electrostatic interactions (between atoms separated by three covalent bonds), which provides correct transgauche ratio in the alkane tails, and recalculation of the headgroup charges on the basis of HF/6-311(d,p) ab-initio computations. Both rigid TIP3P and flexible SPC water models were used with the new lipid model, showing similar results. The new model in a 75 ns simulation has shown a correct value of the area per lipid at zero surface tension, as well as good agreement with the experiment for the electron density, structure factor, and order parameters, including those in the headgroup part of lipids.

  • 261.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hammar, Peter
    Vesely, Jan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramón
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Department of Physical, Inorganic and Structural Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Organocatalytic asymmetric hydrophosphination of alpha,beta-unsaturated aldehydes: Development, mechanism and DFT calculations2008In: Advanced Synthesis & Catalysis, ISSN 1615-4150, Vol. 350, no 11-12, p. 1875-1884Article in journal (Refereed)
  • 262.
    Ibrahem, Ismail
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramón
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Vesely, Jan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hammar, Peter
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Himo, Fahmi
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Enantioselective organocatalytic hydrophosphination of alpha,beta-unsaturated aldehydes2007In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 46, p. 4507-4510Article in journal (Refereed)
  • 263.
    Iftekhar, Shahriar
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Grins, Jekabs
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Svensson, Gunnar
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Lööf, J.
    Jarmar, T.
    Botton, G.
    Andrei, C.
    Engqvist, H.
    Phase formation of CaAl2O4 from CaCO3-Al2O3 powder mixtures2008In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 28, no 4, p. 747-756Article in journal (Refereed)
    Abstract [en]

    Calcium aluminate is the main constituent in calcium aluminate cements, used in a wide range of applications in construction and mining industries and recently also as biomedical implant. In applications that demand very precise reaction features, such as the biomedical ones, the phase purity is of very high importance.

    In this paper the formation of CaAl2O4 from CaCO3–Al2O3 powder mixtures has been studied, varying holding times between 1 and 40 h and temperatures between 1300 and 1500 °C. Phase formation was studied in samples both quenched from the holding temperatures and in samples slowly cooled. Samples were characterized by X-ray powder diffraction (XRPD), using Guinier-Hägg film data and the Rietveld method, and scanning (SEM) and transmission (TEM) electron microscopy. Samples for TEM with very high site accuracy were produced using focused ion beam microscopy.

    In addition to CA (CaAl2O4) the samples contained major amounts of CA2 (CaAl4O7), C12A7 (Ca12Al14O33) and minor amounts of un-reacted A (Al2O3). Trace amounts of C3A (Ca3Al2O6) were observed only for samples heated to 1500 °C. The amount of the Ca-rich phase C12A7 was found to decrease with time as it reacts with A and, to a less degree, CA2 to form CA. In agreement with previous studies the amount of CA2 formed decreases comparatively slowly with time. Its un-reactivity is due to that it is concentrated in isolated porous regions of sizes up to 100 μm. The formation of the Ca aluminates is found to be in response to local equilibriums within small inhomogeneous regions, with no specific phase acting as an intermediate phase. Samples quenched from 1500 °C were found to contain smaller amounts of poorly crystallized phases. A reaction between C and A takes place already at 900 °C, forming a meta-stable orthorhombic modification of CA. The orthorhombic unit cell with a = 8.732(2) Å, b = 8.078(2) Å, c = √3·a = 15.124(4) Å was verified by electron diffraction, revealing frequent twinning and disorder of the crystallites.

  • 264.
    Iftekhar, Shahriar
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Leonova, E.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Edén, Mattias
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Structural Characterizations of Lanthanum Aluminosilicate Glasses by 27Al and 29Si Solid State NMR2009In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 355, no 43-44, p. 2165-2174Article in journal (Refereed)
    Abstract [en]

    We investigate the network structures of LaSiAlO glasses by 29Si magic-angle-spinning (MAS) nuclear magnetic resonance (NMR). Their compositions span most of the glass-forming region of the ternary La2O3Al2O3SiO2 system at 1600 °C. The 29Si NMR resonances narrow and become progressively deshielded when Al substitutes for Si in the network, as well as for increasing La-content of the glass, which leads to network depolymerization. We compare experimental and calculated center of gravities of the 29Si NMR peaks, the latter generated from different simplified models for the distributions of Al and Si as well as bridging oxygen (BO) and non-bridging oxygen (NBO) atoms over the networks. The data do not permit accurate quantifications and may only be interpreted in limiting scenarios. However, they indicate that both distributions are essentially randomized, implying a clear deviation of the Al/Si ordering from that according to a Loewenstein Al-avoidance, coupled with a nearly uniform partitioning of the NBO atoms between Al and Si tetrahedra.

  • 265.
    Istomin, Sergey Ya.
    et al.
    Chemical Department, Moscow State University.
    Grippa, Alexander Yu.
    Chemical Department, Moscow State University.
    D'yachenko, Oleg G.
    Chemical Department, Moscow State University.
    Antipov, Eugeny V.
    Chemical Department, Moscow State University.
    Svensson, Gunnar
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Tholence, Jean L.
    LEPES, CNRS, BP 166, 38042 Grenoble Cedex 9, France.
    A new superconducting sulfide—'EuNb2S5'1998In: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 300, p. 67-70Article in journal (Refereed)
    Abstract [en]

    A new low-temperature superconducting (Tc≈3 K) niobium sulfide ‘EuNb2S5' with a hexagonal structure (a=3.3556(8) Å, c=23.440(9) Å) was synthesized from a mixture of EuS, Nb(m) and S in evacuated and sealed silica tubes, heated at 1100°C for 48 h. This superconductor was characterized by EDX analysis, X-ray powder and electron diffraction studies. Electron diffraction revealed the presence of a supercell: asuper=bsuper=√7×a.

  • 266.
    Ivanov, Sergei
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Path Integral studies of quantum systems at finite temperatures2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents and develops the path integral simulation techniques in application to small quantum systems at finite temperatures. The first goal is to obtain exact thermodynamic expressions for systems of noninteracting

    The rest and the major part of the thesis is dedicated to the development and testing of Bead-Fourier path integral molecular dynamics. Although, path integral molecular dynamics as well as path integral Monte Carlo are well

    First, molecular dynamics under Bead-Fourier scheme was developed and tested on the examples of quantum harmonic oscillator and Hydrogen atom. The main attention was paid to ergodicity problems. Then we addressed the question,

    Later, the formalism for identical particles was developed.

    Finally, the question of molecular dynamics efficacy was raised. It was shown, that formalisms for identical and distinguishable particles, both, can be reformulated into a more efficient ones, providing all dynamical variables

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  • 267.
    Ivanov, Sergei
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Lyubartsev, Alexander
    Bead-Fourier path integral molecular dynamics for identical particles2005In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 123, p. 034105-Article in journal (Other academic)
    Abstract [en]

    The Bead-Fourier path integral molecular dynamics technique introduced earlier [ S. D. Ivanov, A. P. Lyubartsev, and A. Laaksonen, Phys. Rev. E 67 066710 (2003) ] is applied for simulation of electrons in the simplest molecules: molecular hydrogen, helium atom, and their ions. Special attention is paid to the correct description of electrons in the core region of a nucleus. In an attempt to smooth the Coulomb potential at small distances, a recipe is suggested. The simulation results are in excellent agreement with the analytical solution for the “harmonic helium atom”, as well as with the vibrational potential of the H2 molecule and He ionization energies. It is demonstrated, that the Bead-Fourier path integral molecular dynamics technique is able to provide the accuracy required for the description of electron structure and chemical bonds in cases when electron exchange effects need not be taken into account.

  • 268.
    Ivanov, Sergei
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Lyubartsev, Alexander
    Simulations of one- and two-electron systems by Bead-Fourier path integral molecular dynamics2005In: Journal of Chemical Physics, ISSN 0021-9606, Vol. 123, p. 034105-Article in journal (Refereed)
  • 269.
    Ivanov, Sergei
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Lyubartsev, Alexander
    Laaksonen, Aatto
    Bead-Fourier path integral molecular dynamics2003In: Physical Review E, ISSN 1539-3755, Vol. 67, p. 066710-Article in journal (Refereed)
  • 270. Izquierdo-Barba, Isabel
    et al.
    Arcos, Daniel
    Sakamoto, Yasuhiro
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Lopez-Noriega, Adolfo
    Vallet-Regi, Maria
    High-performance mesoporous bioceramics mimicking bone mineralization2008In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 20, no 9, p. 3191-3198Article in journal (Refereed)
    Abstract [en]

    The preparation of bioceramics with ordered mesoporous structures is of importance for biomedical technology, for the design of bone and dental grafts with regeneration purposes. Here we demonstrate that hexagonal mesoporous SiO2-CaO-P2O5 bioglasses (MBG) with high calcium content are the first known bioceramics that exhibit amorphous calcium phosphate (ACP)-octacalcium phosphate (OCP)-calcium deficient carbonatehydroxyapatite (CDHA) maturation as biomineralization governing mechanism in simulated body fluid (SBF), similarly to the in vivo biomineralization process. The unique characteristics of hexagonal MBGs lead to a local acid pH at the bioceramic surface that allows the formation of metastable OCP. Besides, 3D cubic MBG has been also synthesized, exhibiting higher surface area and porosity. The 3D reconstruction carried out by electron microscopy evidence a 3D bicontinuous network comprising a pair of rods mutually intertwined, creating the pore system available in three dimensions. This 3D pore system provides not only high surface area and porosity but also easier interchange of ions, increasing mass transport and diffusion processes. The final result is that 3D cubic MBGs exhibit an accelerated bioactivity behavior, forming a bonelike apatite phase on the surface, I h after coming into contact with SBF.

  • 271.
    Izquierdo-Barba, Isabel
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Kupferschmidt, Natalia
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Schmidtchen, Artur
    Malmsten, Martin
    Vallet-Regí, Maria
    Incorporation of antimicrobial compounds in mesoporous silica film monolith2009In: Biomaterials, ISSN 0142-9612, E-ISSN 1878-5905, Vol. 30, no 29, p. 5729-5736Article in journal (Refereed)
    Abstract [en]

    : Incorporation of the antimicrobial peptide LL-37 (LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES), as well as low molecular weight antimicrobial chlorhexidine, into mesoporous silica was obtained using an EISA one-pot synthesis method. FTIR confirmed efficient encapsulation of both LL-37 and chlorhexidine into mesoporous silica, while XRD and TEM showed that antimicrobial agent incorporation can be achieved without greatly affecting the structure of the mesoporous silica. The modified mesoporous silica released LL-37 and chlorhexidine slowly, reaching maximum release after about 200 h. The release rate could also be controlled through incorporation of SH groups in the pore walls, adding to pore hydrophobicity and reducing the release rate by about 50% compared to the unmodified mesoporous silica. Mesoporous silica containing either LL-37 or chlorhexidine displayed potent bactericidal properties against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. While chlorhexidine-loaded mesoporous silica displayed an accompanying high toxicity, as judged from hemolysis, LDH release, and MTT assay, the corresponding material containing LL-37 showed very low toxicity by all these assays, comparable to that observed for mesoporous silica in the absence of antibacterial drug, as well as to the negative controls in the respective assays. Mesoporous silica containing LL-37 therefore holds potential as an implantable material or a surface coating for such materials, as it combines potent bactericidal action with low toxicity, important features for controlling implant-related infections, e.g., for multi-resistant pathogens or for cases where access to the infection site of systemically administered antibiotics is limited due to collagen capsule formation or other factors.

     

  • 272.
    Jalilehvand, Farideh
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Leung, Bonnie O.
    Izadifard, Maryam
    Damian, Emiliana
    Mercury(II) Cysteine Complexes in Alkaline Aqueous Solution2006In: Inorganic Chemistry, Vol. 45, no 1, p. 66 -73Article in journal (Refereed)
  • 273.
    Jansson, Jennie L. M.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Maliniak, Arnold
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Conformational Dynamics of Oligosaccharides: NMR Techniques and Computer Simulations2006In: NMR Spectroscopy and Computer Modeling of Carbohydrates: Recent Advances / [ed] Johannes F. G Vliegenthar & Robert J. Woods, American Chemical Society (ACS), 2006, p. 20-39Chapter in book (Refereed)
    Abstract [en]

    NMR spectroscopy techniques in conjunction with molecular dynamics simulations facilitate description of conformation and dynamics of oligosaccharides in solution. Herein we describe approaches based on hetero-nuclear carbon-proton spin-spin coupling constants useful for assessing conformational preferences at the glycosidic linkage, exemplified for á-cyclodextrin. Furthermore, we utilize hetero-nuclear carbon-proton residual dipolar couplings together with molecular dynamics simulations in the analysis of the conformational dynamics of the milk oligosaccharide Lacto-N-neotetraose.

  • 274. Jesudason, C.G.
    et al.
    Lyubartsev, Alexander
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Laaksonen, Aatto
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Conformational characteristics of single flexible polyelectrolyte chain2009In: The European Physical Journal E Soft matter, ISSN 1292-8941, E-ISSN 1292-895X, Vol. 30, p. 341-350Article in journal (Refereed)
    Abstract [en]

    The behavior of a flexible anionic chain of 150 univalent and negatively charged beads connected by harmonic-like potential interactions with each other in the presence of equal number of positive and free counterions, observed in molecular dynamics simulations with Langevin thermostat, is described in a temperature range from 0.1 to 10.0 in reduced units. The total and Coulombic energies, radial distribution functions, radii of gyration, end-to-end distances of the chain are depicted. Our results turned out to be qualitatively similar to the results obtained earlier for a lattice polyelectrolyte model, including temperature maximum of the polyelectrolyte chain and internal phase transition which seems to occur abruptly at low temperatures for all the systems studied, judging from the shape of end-to end distance, gyration radius and energy profiles.

  • 275. Jiang, Q. H.
    et al.
    Ma, J.
    Lin, Y. H.
    Nan, Ce-Wen
    Shi, Z.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Multiferroic properties of Bi0.87La0.05Tb0.08FeO3 ceramics prepared by spark plasma sintering2007In: Applied Physics Letters, Vol. 91, no 2, p. 022914/1-022914/3Article in journal (Refereed)
  • 276. Jiang, Qinghui
    et al.
    Lin, Yuanhua
    Nan, Ce-Wen
    Zhijian, Shen
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Grins, Jekabs
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Esmaeilzadeh, Saeid
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Hoeche, Thomas
    Ferroelectric and ferromagnetic properties of hot-pressed Bi0.95-xLa0.05TbxFeO3 ceramics2007In: Journal of the American Ceramic Society, Vol. 90, no 2, p. 608-613Article in journal (Refereed)
  • 277. Jiang, S. W.
    et al.
    Matsukawa, T.
    Tanaka, Satoshi
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Uematsu, K.
    Formation of bubbles in aqueous alumina slurries2007In: Journal of European Ceramics Society, Vol. 27, p. 879-885Article in journal (Refereed)
  • 278. Jiang, S. W.
    et al.
    Nakamura, S.
    Tanaka, Satoshi
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Uematsu, K.
    A new air-drying forming of alumina ceramics using high solid-loaded slurries with addition of glycerol2007In: Journal of Materials Research, Vol. 22, p. 244-248Article in journal (Refereed)
  • 279. Jin, H
    et al.
    Che, S
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Sakamoto, Y
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Qiu, H
    Mesoporous Silica Microstructures Engineered by Self-assembling of Lipid Molecule2008In: Chemistry A European Journal, Vol. 14, p. 6413-6420Article in journal (Refereed)
  • 280.
    Johansson, Mikael
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Purse, Byron W.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Terasak, Osamu
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Aerobic Oxidations Catalyzed by Zeolite-Encapsulated Cobalt Salophen2008In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 350, no 11-12, p. 1807-1815Article in journal (Refereed)
    Abstract [en]

    Cobalt salophen was encapsulated in a series of zeolites with a wide variation of the silicon-to-aluminium atomic ratio and with different cations. The zeolite-cobalt salophen catalysts were prepared using the “ship-in-a-bottle technique” where the complex was synthesized in the super cage of the zeolite and therefore locked into the pocket. The encapsulated catalysts were then tested in the aerobic oxidation of hydroquinone to p-benzoquinone; the best encapsulated catalyst was shown to be an efficient electron-transfer mediator in a palladium-catalyzed aerobic oxidative carbocyclization.

  • 281. Johansson, Olof
    et al.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Lomoth, Reiner
    Pd-catalyzed siarylation of aniline –a qay to a non-linear bis(terpyridyl) ligand providing increased electronic communication2008In: Dalton Transactions, p. 3649-3651Article in journal (Refereed)
  • 282.
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    A critical survey of the grain refining mechanisms of aluminium1993Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the present work, several possible interpretations of the grain refining mechanisms of aluminium castings after additions of titanium and boron are compared with the results of critical test experiments. The presence of B does not seem to affect the binary Al-Ti phase diagram close to the A1 comer, except for formation of boride phase. It is shown by powder X-ray diffraction and by energy dispersive X-ray spectrometry that the (Ali_xTix)B2 solid solubility is unlimited.

    At hypoperitectic additions of Al-Ti-B (<0.15wt%Ti) both calculations and experiments give evidence that TiAlj dissolves within one minute at a contact temperature of 775°C. From the experimental results it seems clear that the dominating mechanism is heterogeneous nucléation on boride particles. At hyperperitectic concentrations (>0.15wt%Ti) TiAl3 can act as the nucleating phase; in the presence of boron a preperitectic reaction can occur. The experiments show that this reaction is precipitation of supersaturated a-Al.

    The presence of potent nucleating particles is not the only prerequisite for successful grain refinement; an undercooling that may be caused by the presence of alloying elements is also necessary in order to create a driving force for growth. It is found that the constitutional contributions from various alloying elements are additive at low concentrations.

    Zr is reported to poison the effect of Al-Ti-B grain refiners. It is found that this poisoning effect occurs at hyperperitectic Zr concentrations (>0.11wt%). Precipitation of the solid solution phase (Ti j_xZrx)Al3 is found to consume enough Ti to decrease the growth restricting effect so much that the grain size is influenced.

  • 283.
    Johnsson, Mats
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Lemmens, Peter
    Perovskites and thin films - crystallography and chemistry2008In: Journal of Physics: Condensed Matter, Vol. 20, p. 264001 (6pp)-Article in journal (Refereed)
  • 284.
    Johnsson, Mats
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Törnroos, K. W.
    Zinc selenium oxochloride, b-Zn2(SeO3)Cl2, a synthetic polymorph of the mineral Sophiite2007In: Acta Crystallographica, Vol. C63, p. i34-i36Article in journal (Refereed)
  • 285.
    Jonsson, K. Hanna M.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Methyl 4-O-benzoyl-2,3-O-isopropylidene-a-L-rhamnopyranoside2006In: Acta Crystallographica Section C: Crystal Structure Communications, ISSN 0108-2701, E-ISSN 1600-5759, Vol. 62, no 8, p. o447-o449Article in journal (Refereed)
    Abstract [en]

    The title compound, C17H22O6, having an ester group at O4 of the hexopyranosyl sugar residue shows for the exo-cyclic C=O bond a conformation that is eclipsed to the C4-H4 bond. The two related torsion angles are denoted by syn and cis conformations. The q1 torsion angle (H4-C4-O4-C10) is indicated to have a similar conformation in solution as analyzed by NMR spectroscopy and a Karplus-type relationship.

  • 286. Jäger, Michael
    et al.
    Johansson, Olof
    Bergquist, Jonas
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Synthesis and Characterization of 2,6-Di(quinolin-8-yl)pyridines. New Ligands for Bistridentate RuII Complexes with s Luminescent Lifetimes2007In: Journal of Organic Chemistry, Vol. 72, no 26, p. 10227-10230Article in journal (Refereed)
  • 287.
    Kadir, Abdulkarim
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Noreus, Dag
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Structural determination of NaAl2Ga2 intermetallic compound having the ThCr2Si2 type structure.2009In: Journal of Alloys and Compounds, Vol. 477, no 1-2, p. 149-151Article in journal (Refereed)
    Abstract [en]

    NaAl2Ga2 intermetallic compound has been synthesized by direct combination of the elements in the atomic ratio Na:Ga:Al = 1:2:2. Guinier–Hägg X-ray and neutron powder diffraction determined a ThCr2Si2 type structure for the new compound with tetragonal unit cell axis a = 4.1817(5) and c = 11.388(2) Å.

  • 288.
    Kadir, Abdulkarim
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    A new synthetic route to Mg2Na2NiH6 where a [NiH4] complex is for the first time stabilized by alkali metal counterions2007In: Inorganic Chemisty, Vol. 46, p. 2220-2223Article in journal (Refereed)
  • 289. Kaga, H.
    et al.
    Kinemuch, Y.
    Tanaka, Satoshi
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Makiya, A.
    Kato, Z.
    Uematsu, K.
    Watari, K.
    Fabrication of c-axis oriented higher manganese silicide by a high-magnetic-field and its thermoelectric properties2007In: Journal of Materials Research, Vol. 22, p. 2917-2923Article in journal (Refereed)
  • 290. Kaga, H.
    et al.
    Kinemuch, Y.
    Yilmaz, Y.
    Watari, K.
    Nakano, H.
    Tanaka, Satoshi
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Makiya, A.
    Kato, Z.
    Uematsu, K.
    Orientation dependence of transport property and microstructural characterization of Al-doped ZnO ceramics2007In: Acta Materialia, Vol. 55, p. 4753-4757Article in journal (Refereed)
  • 291. Kamba, S.
    et al.
    Nuzhnyy, D.
    Vanek, P.
    Savinov, M.
    Knizek, K.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Santava, E.
    Maca, K.
    Sadowski, M.
    Petzelt, J.
    Optic soft mode behavior in quantum paraelectric EuTiO32007In: Los Alamos National Laboratory, Preprint Archive, Condensed Matter, Vol. 1-4Article in journal (Refereed)
  • 292. Katcho, Nebil A.
    et al.
    Urones-Garrote, Esteban
    Avila-Brande, David
    Gómez-Herrero, Adrian
    Urbonaite, Sigita
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Csillag, Stefan
    Lomba, Enrique
    Agulló-Rueda, Fernando
    Landa-Canovas, Angel R.
    Otero-Díaz, L. Carlos
    Carbon hollow nanospheres from chlorination of ferrocene2007In: Chemistry of Materials, ISSN 0897-4756, Vol. 19, p. 2304 -2309Article in journal (Refereed)
  • 293. Kaynak, Filiz Betűl
    et al.
    Gökhan Kelek, Nesrin
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Salgin Gökşen, Umut
    Molecular structure of 2-methylamino-5-[(5-methyl-2-benzoxazolinone-3-yl)methyl]-1,3,4-thiadiazole dihydrophosphate: a combined X-ray crystallographic and ab initio study2008In: Structural Chemistry, Vol. 19, p. 757-764Article in journal (Refereed)
  • 294. Kerkau, Alexander
    et al.
    Grüner, Daniel
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Ormeci, Alim
    Site Occupation Reversal in the C14 Laves Phase Nb(Cr1-xCox)22009In: Zeitschrift für Anorganische und Allgemeines Chemie, ISSN 0044-2313, E-ISSN 1521-3749, Vol. 635, no 4-5, p. 637-648Article in journal (Refereed)
    Abstract [en]

    The C14 phase Nb(Cr1-xCox)(2) forms within a broad homogencity range of 0.127(3) <= x <= 0.937(8) at 1100 degrees C. The distribution of chromium and cobalt atoms on the crystallographic positions 2a and 6h has been studied by a single crystal structure analysis and a statistical mechanics approach using energies from firs-principles full potential electronic structure calculations. For the first time a preferential occupation of the minority component of the 2a site has been observed. The calculations support a preferential site occupation with a reversal close to equal chromium and cobalt content

  • 295. Kessler, VG
    et al.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Johansson, C
    Ahniyaz, A
    Seisenbaeva, GA
    Häggström, S
    Kamali, S
    Nordblad, P
    Preparation of iron oxide nanocrystals by surfactant-free or oleic acid-assisted thermal decomposition of a Fe(III) alkoxide2008In: Journal of Magnetism and Magnetic Materials, Vol. 320, p. 781-787Article in journal (Refereed)
  • 296. Khasanova, Nellie R.
    et al.
    Van Tandeloo, Gustaaf
    Lebedev, Oleg I.
    Amelinx, S.
    Grippa, Alexander Yu
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Abakumov, Artiom M.
    Istomin, Sergey Ya.
    D'yachenko, Oleg G.
    Antipov, Eugeny V.
    A New Structure Type of the Ternary Sulfide Eu1.3Nb1.9S52002In: Journal of Solid State Chemistry, ISSN 1095-726X, Vol. 164, no 2, p. 345-353Article in journal (Refereed)
    Abstract [en]

    The structure model for the Eu1.3Nb1.9S5 compound is determined based on high-resolution electron microscopy evidence. This compound crystallizes in a hexagonal unit cell with a=8.8732(8) Å and c=23.45(1) Å. Its structure is built up as an alternating sequence of trigonal-prismatic NbS2 layers of formula [Nb7S14] and [Nb(Eu3S4)2] slabs along the c-direction. In the [Nb(Eu3S4)2] block the stacking of two close-packed (Eu3S4) layers creates octahedral interstices formed by S atoms; these cavities are occupied by Nb cations. The model is compared with structures of other Eu-containing niobium sulfides, such as Eu0.167NbS2 and the misfit compound [(EuS)1.5]1.15NbS2.

  • 297. Knee, Christopher S.
    et al.
    Lindberg, Fredrik
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Khan, Nasima
    Svensson, Gunnar
    Svedlindh, Peter
    Rundlöf, Håkan
    Eriksson, Sten G.
    Börjesson, Lars
    Influence of oxygen defects on the structure and magnetic properties of Sr1-xBixCoO3-y (0.1 ≤ x ≤ 0.2) supercell perovskites2006In: Chemistry of Materials, ISSN 1520-5002, Vol. 18, no 5, p. 1354 - 1364Article in journal (Refereed)
  • 298. Kocsis, L.
    et al.
    Mink, Janos
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Inorganic Chemistry.
    Jalilehvand, F.
    Laffin, L. J.
    Berkesi, O.
    Hajba, L.
    Vibrational spectroscopic study of the hydrated platinum(II), palladium(II) and cis-diammineplatinum(II) ions in acidic aqueous solutions2009In: Journal of Raman Spectroscopy, ISSN 0377-0486, E-ISSN 1097-4555, Vol. 40, no 5, p. 481-490Article in journal (Refereed)
    Abstract [en]

    Mid infrared, far-infrared and Raman spectroscopic studies, combined with force field analyses, were performed for the 1 hydrated platinum(II) and palladium(II) ions and cis-diammineplatinum(II) complex in acidic aqueous solutions. Simplified Density Functional Theory (DFT) calculations were made for the equatorial plane of the platinum complexes. Careful subtraction of solvent spectra allowed a number of 'internal' modes of coordinated H2O and NH3 to be determined as weak residual bands. The [Pt(OH2)(6)](2+) and [cis-Pt(NH3)(2)(OH2)(4)](2+) complexes were found to be six-coordinated with four ligands strongly bound in an equatorial plane. The assignments of the vibrational modes in the equatorial plane could be performed on the basis of the experimental observations and by comparison with metal-ligand vibrations of square-planar complexes, aided by normal coordinate calculations. For the weakly coordinated axial aqua ligands, the low wavenumber range and the polarizibility properties allowed the assignments of the bands at about 365 and 325 cm(-1) to the stretching modes of one short and one longer Pt - O* bound to axial aqua ligands, respectively. A similar picture with even less strongly bound axial water molecules emerges from Raman spectroscopy data for the hydrated palladium(II) ion, [Pd(OH2)(6)](2+). The results are consistent with a description of the [Pt(OH2)(6)](2+) and [Pd(OH2)(6)](2+) aqua ions in C-4v symmetry, and with the [cis-Pt(NH3)(2)(OH2)(4)](2+) complex in the Cs point group, and also in qualitative agreement with the structures devised from previous extended X-ray absorption fine structure (EXAFS) measurements.

  • 299.
    Kovács, Helena
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Physical Chemistry.
    Interactions and dynamics of small molecules in liquid mixtures: as studied by nuclear spin relaxation and computer simulations1990Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The present thesis concerns the interactions and dynamics of various types of smallmolecules in their liquid mixtures. The relationship between nuclear magneticrelaxation experiments, Molecular Dynamics simulations and dynamic models isexplored.Multinuclear magnetic relaxation was determined over the whole concentration rangein the components of the following binary mixtures: D^)-DMSO-dg, CD3CN-CDCI3 andCH3CN-H2O. Carbon-13 relaxation was measured in 1 mol% of sucrose and amethylated disaccharide in a 2:1 mixture of D2O-DMSO-dg, at variable temperatureoutside the extreme narrowing region. Nitrogen-14 relaxation was measured in 1 mol%of CHgCN in ^O-CHglCHg^OH as a function of the solvent mixture composition. Therotational correlation times were deduced from the relaxation rates. Self-diffusioncoefficients were also reported for the components of the CD3CN-CDCI3 system.Computer simulations were performed using the Molecular Dynamics method, and datacollected for the binary mixtures of CHgCN-CHClj and CH3CN-H2O over the wholeconcentration range. Radial distribution functions, pairwise interaction energies, andtime autocorrelation functions for the linear velocity, angular velocity andreorientation were reported.The NMR and MD-simulations data are not only directly compared, they are also usedto evaluate the applicability of diverse motional models. If a linear correlation withviscosity exists, the macroscopic hydrodynamic model is tested, possibly whileincluding some corrections for the molecular shape and boundary. However, this modelis seldom even seemingly correct for the small molecules of the present studies. Thediffusion model, where small angular displacements are assumed, is qualitativelyadequate in many cases. Nevertheless, some of the rotations are shown to be too far in theinertial limit to follow the diffusion model. The extended diffusion model, although itallows for rotations of arbitrary size, fails to describe the rotational motions in theacetonitrile/chloroform mixtures. The overall and internal motions of the twodisaccharides are described by the rotational diffusion model. A tentative attempt ismade to apply the continuum model of dielectric friction to acetonitrile in the mixedsolvent of water and 1-propanol.

  • 300.
    Kowalewski, Jozef
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Aski, Sahar Nikkhou
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Quinuclidine complex with α-cyclodextrin: a diffusion and 13C NMR relaxation study2008In: Magnetic Resonance in Chemistry, Vol. 46, p. 261-267Article in journal (Refereed)
    Abstract [en]

    The stability of an inclusion complex of quinuclidine with α-cyclodextrin in solution was investigated by NMR measurements of the translational diffusion coefficient. A 1:1 stoichiometry model yielded an association constant of 35 ± 3 M-1. The guest molecules exchange rapidly between the host cavity and the bulk solution. The reorientational dynamics of the guest and host molecules was studied using carbon-13 NMR relaxation at two magnetic fields. The relaxation of the host nuclei showed very little dependence on the guest–host concentration ratio, while the 13C spins in quinuclidine were sensitive to the solution composition. Using mole-fraction data, it was possible to extract the relaxation parameters for the bound and free form of quinuclidine. Relaxation rates of the guest molecule, free in solution, were best described by an axially symmetric model, while the data of the complex species were analysed using the Lipari–Szabo method. Applying the axially symmetric model to the complexed quinuclidine indicated that the anisotropy of its reorientation in the bound form was increased.

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