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  • 301.
    Dong, Hanwu
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). South China Agricultural University, China.
    Huang, Cunke
    Moser, David
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). EURAC Research, Italy.
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zhu, Min
    Structure and stability of high pressure synthesized MgTM2H6 (TM = Zr, Nb) hydrides2015In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 96, p. 237-248Article in journal (Refereed)
    Abstract [en]

    The structure of two isomorphous high pressure synthesized metal hydrides MgZr2H6 and MgNb2H6 is described in the R-3m space group with the hexagonal unit cells a = 3.3592(2) angstrom, c = 25.131(3) angstrom and a = 3.2901(9) angstrom, c = 23.09(1) angstrom, respectively (Z = 3). The metal atom structures were refined from powder XRD data, with Mg in the 3a site (0, 0, 0,) and Zr and Nb in the 6c site (0, 0, z) with the only refineable atomic parameter z = 0.225 and z = 0.220, respectively. As only a minute sample could be produced in the anvil cell, a conventional structural determination with neutron diffraction on a deuterated sample could not be made. Instead formation energies of the all proposed structural models were calculated using density functional theory (DFT) for accessing the most stable structure of the lowest energy level. The measured lattice parameters and the refined atomic positional parameters from the powder X-ray diffraction pattern were reproduced well by the OFT calculation. The hydrogen atoms were found to fully occupy an octahedral site coordinated by 3Mg and 3Zr atoms, a tetrahedral site coordinated by 4Zr atoms and another tetrahedral site coordinated by 3Mg and 1Zr atoms. Chemical, mechanical and dynamical stabilities of the MgZr2H6 structure were further discussed based on a chemical potential equilibrium diagram constructed from the calculated formation energies, calculated elastic constants and phonon spectra respectively. It is also shown that a high pressure increases the stability of the new hydrides.

  • 302.
    Dong, Hanwu
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kiros, Yohannes
    Noreus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    An air-metal hydride battery using MmNi(3.6)Mn(0.4)Al(0.3)Co(0.7) in the anode and a perovskite in the cathode2010In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 35, no 9, p. 4336-4341Article in journal (Refereed)
    Abstract [en]

    Hydrogen storage alloy MmNi(3.6)Mn(0.4)Al(0.3)Co(0.7) (MH) was tested as anode material in a metal hydride-air cell. The cathode was a non-noble metal air electrode based on a mixture of perovskite and pyrolyzed macrocycles on carbon. Polarization and discharge capacities of the electrodes were measured and compared at 22 degrees C and 40 degrees C using air or oxygen at the cathode. Discharge capacity reaching 330 mAh/g MH with pure oxygen at 40 degrees C and 305 mAh/g MH with air at 22 degrees C were obtained. Power densities and/or energy densities were found to significantly depend on the increase of the electrode kinetics on both the ORR (oxygen reduction reaction) and HOR (hydrogen oxidation reaction). However, for air electrode, an increase of oxygen concentration by using pure oxygen gas plays a more important role than an 18 degrees C temperature increase. (C) 2010 Professor T. Nejat Veziroglu.

  • 303. Dong, Yihui
    et al.
    Ji, Xiaoyan
    Laaksonen, Aatto
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Nanjing Tech University, China; Uppsala University, Sweden; Petru Poni Institute of Macromolecular Chemistry, Romania.
    Cao, Wei
    An, Rong
    Lu, Linghong
    Lu, Xiaohua
    Determination of the small amount of proteins interacting with TiO2 nanotubes by AFM-measurement2019In: Biomaterials, ISSN 0142-9612, E-ISSN 1878-5905, Vol. 192, p. 368-376Article in journal (Refereed)
    Abstract [en]

    Detecting the small amounts of proteins interacting effectively with the solid film electrodes surface still remains a challenge. To address this, in this work, a new approach was proposed by the combination of the adhesion forces and the molecular interaction measured with AFM. Cytochrome c (Cyt C) interacting effectively with TiO2 nanotube arrays (TNAs) was chosen as a probe. The amounts of Cyt C molecules interacting effectively on TNAs surface (C-TNA) range from 5.5x10(-12) to 7.0x10(-12) mol/cm(2) (68.2-86.8 ng/cm(2)) and they are comparable with the values obtained by the electrochemistry method in the literature, in evidence of the accuracy of this AFM-based approach. The reliability of the proposed approach was further verified by conducting Surface Enhanced Raman Scattering (SERS) measurements and estimating the enhancement factor (EF). This interaction-based AFM approach can be used to accurately obtain the small amounts of adsorbed substances on the solid film electrodes surface in the applications such as biosensors, biocatalysis, and drug delivery, etc.

  • 304. Dosis, Ioannis
    et al.
    Kamarianos, Athanasios
    Athanasiadou, Maria
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Athanassiadis, Ioannis
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Karamanlis, Xanthippos
    Polybrominated diphenyl ethers (PBDEs) in marine sediment of Thermaikos Gulf, Greece2011In: International Journal of Environmental Analytical Chemistry, ISSN 0306-7319, E-ISSN 1029-0397, Vol. 91, no 12, p. 1151-1165Article in journal (Refereed)
    Abstract [en]

    Polybrominated diphenyl ether (PBDE) concentrations were determined in marine sediment samples collected from 7 different locations around Thermaikos Gulf in north Greece. PBDEs were detected in all sampling sites and their average total concentration (Sigma PBDEs) ranged from 0.26 to 4.92 ng g(-1) d.w. Concentrations were an order of magnitude higher in locations outlining the inner part of the Gulf, which were also closer to industrial areas, sewage treatment plant discharges, the city's harbour and landfill area. These findings suggest pollution in the aquatic ecosystem from industrial and urban activities in the area. Congener profiles exhibit predominance of BDE-209, while concentrations of other PBDE congeners were usually lower, when compared to similar studies from other countries globally, indicating that Thermaikos Gulf is among the low-polluted areas. Statistical analysis showed significant differences among the higher polluted sampling stations. Statistically significant differences also existed between sampling stations with high and low PBDE concentrations. Correlations between congeners suggested local contamination sources; however, specific point sources of pollution were not established.

  • 305.
    Dowaidar, Moataz
    et al.
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Abdelhamid, Hani Nasser
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hällbrink, Mattias
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Freimann, Krista
    Kurrikof, Kaido
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Langel, Ülo
    Stockholm University, Faculty of Science, Department of Neurochemistry. University of Tartu, Estonia.
    Magnetic Nanoparticle Assisted Self-assembly of Cell Penetrating Peptides-Oligonucleotides Complexes for Gene Delivery2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 9159Article in journal (Refereed)
    Abstract [en]

    Magnetic nanoparticles (MNPs, Fe3O4) incorporated into the complexes of cell penetrating peptides (CPPs)-oligonucleotides (ONs) promoted the cell transfection for plasmid transfection, splice correction, and gene silencing efficiencies. Six types of cell penetrating peptides (CPPs; PeptFect220 (denoted PF220), PF221, PF222, PF223, PF224 and PF14) and three types of gene therapeutic agents (plasmid (pGL3), splicing correcting oligonucleotides (SCO), and small interfering RNA (siRNA) were investigated. Magnetic nanoparticles incorporated into the complexes of CPPs-pGL3, CPPs-SCO, and CPPs-siRNA showed high cell biocompatibility and efficiently transfected the investigated cells with pGL3, SCO, and siRNA, respectively. Gene transfer vectors formed among PF14, SCO, and MNPs (PF14-SCO-MNPs) showed a superior transfection efficiency (up to 4-fold) compared to the noncovalent PF14-SCO complex, which was previously reported with a higher efficiency compared to commercial vector called Lipofectamine™2000. The high transfection efficiency of the new complexes (CPPs-SCO-MNPs) may be attributed to the morphology, low cytotoxicity, and the synergistic effect of MNPs and CPPs. PF14-pDNA-MNPs is an efficient complex for in vivo gene delivery upon systemic administration. The conjugation of CPPs-ONs with inorganic magnetic nanoparticles (Fe3O4) may open new venues for selective and efficient gene therapy.

  • 306.
    Dowaidar, Moataz
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Abdelhamid, Hani Nasser
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Assuit University, Egypt.
    Hällbrink, Mattias
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Langel, Ülo
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Chitosan enhances gene delivery of oligonucleotide complexes with magnetic nanoparticles–cell-penetrating peptide2018In: Journal of biomaterials applications, ISSN 0885-3282, E-ISSN 1530-8022, Vol. 33, no 3, p. 392-401Article in journal (Refereed)
    Abstract [en]

    Gene-based therapies, including the delivery of oligonucleotides, offer promising methods for the treatment of cancer cells. However, they have various limitations including low efficiency. Herein, cell-penetrating peptides (CPPs)-conjugated chitosan-modified iron oxide magnetic nanoparticles (CPPs-CTS@MNPs) with high biocompatibility as well as high efficiency were tested for the delivery of oligonucleotides such as plasmid pGL3, splice correction oligonucleotides, and small-interfering RNA. A biocompatible nanocomposite, in which CTS@MNPs was incorporated in non-covalent complex with CPPs-oligonucleotide, is developed. Modifying the surface of magnetic nanoparticles with cationic chitosan-modified iron oxide improved the performance of magnetic nanoparticles-CPPs for oligonucleotide delivery. CPPs-CTS@MNPs complexes enhance oligonucleotide transfection compared to CPPs@MNPs or CPPs. The hydrophilic character of CTS@MNPs improves complexation with plasmid pGL3, splice correction oligonucleotides, and small-interfering RNA payload, which consequently resulted in not only strengthening the colloidal stability of the constructed complex but also improving their biocompatibility. Transfection using PF14-splice correction oligonucleotides-CTS@MNPs showed sixfold increase of the transfection compared to splice correction oligonucleotides-PF14 that showed higher transfection than the commercially available lipid-based vector Lipofectamine™ 2000. Nanoscaled CPPs-CTS@MNPs comprise a new family of biomaterials that can circumvent some of the limitations of CPPs or magnetic nanoparticles.

  • 307.
    Dowaidar, Moataz
    et al.
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Abdelhamid, Hani Nasser
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hällbrink, Mattias
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Langel, Ülo
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Graphene oxide nanosheets in complex with cell penetrating peptides for oligonucleotides delivery2017In: Biochimica et Biophysica Acta - General Subjects, ISSN 0304-4165, E-ISSN 1872-8006, Vol. 1861, no 9, p. 2334-2341Article in journal (Refereed)
    Abstract [en]

    A new strategy for gene transfection using the nanocarrier of cell penetrating peptides (CPPs; PepFect14 (PF14) or PepFect14 (PF14) (PF221)) in complex with graphene oxide (GO) is reported. GO complexed with CPPs and plasmid (pGL3), splice correction oligonucleotides (SCO) or small interfering RNA (siRNA) are performed. Data show adsorption of CPPs and oligonucleotides on the top of the graphenic lamellar without any observed change of the particle size of GO. GO mitigates the cytotoxicity of CPPs and improves the material biocompatibility. Complexes of GO-pGL3-CPPs (CPPs; PF14 or PF221) offer 2.1–2.5 fold increase of the cell transfection compared to pGL3-CPPs (CPPs; PF14 or PF221). GO-SCO-PF14 assemblies effectively transfect the cells with an increase of > 10–25 fold compared to the transfection using PF14. The concentration of GO plays a significant role in the material nanotoxicity and the transfection efficiency. The results open a new horizon in the gene treatment using CPPs and offer a simple strategy for further investigations.

  • 308. Duan, Lele
    et al.
    Wang, Lei
    Inge, A. Ken
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Fischer, Andreas
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sun, Licheng
    Insights into Ru-Based Molecular Water Oxidation Catalysts: Electronic and Noncovalent-Interaction Effects on Their Catalytic Activities2013In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 52, no 14, p. 7844-7852Article in journal (Refereed)
    Abstract [en]

    A series of Ru-bda water oxidation catalysts [Ru(bda)L-2] (H(2)bda = 2,2'-bipyridine-6,6'-dicarboxylic acid; L = [HNEt3][3-SO3-pyridine], 1; 4-(EtOOC)-pyridine, 2; 4-bromopyridine, 3; pyridine, 4; 4-methoxypyridine, 5; 4-(Me2N)-pyridine, 6; 4-[Ph(CH2)(3)]-pyridine, 7) were synthesized with election-donating/-withdrawing groups and hydro-philic/hydrophobic groups in the axial ligands. These complexes were characterized by H-1 NMR spectroscopy, high-resolution mass spectrometry, elemental analysis, and electrochemistry. In addition, complexes 1 and 6 were further identified by single crystal X-ray crystallography, revealing a highly distorted octahedral configuration of the Ru coordination sphere. All of these complexes are highly active toward Ce-IV-driven (Ce-IV = Ce(NH4)(2)(NO3)(6)) water oxidation with oxygen evolution rates up to 119 mols of O-2 per mole of catalyst per second. Their structure-activity relationship was investigated. Electron-withdrawing and noncovalent interactions (attraction) exhibit positive effect on the catalytic activity of Ru-bda catalysts.

  • 309. Duarte-Salles, Talita
    et al.
    von Stedingk, Hans
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    Granum, Berit
    Gutzkow, Kristine B.
    Rydberg, Per
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    Törnqvist, Margareta
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    Mendez, Michelle A.
    Brunborg, Gunnar
    Brantsaeter, Anne Lise
    Meltzer, Helle Margrete
    Alexander, Jan
    Haugen, Margaretha
    Dietary Acrylamide Intake during Pregnancy and Fetal Growth-Results from the Norwegian Mother and Child Cohort Study (MoBa)2013In: Journal of Environmental Health Perspectives, ISSN 0091-6765, E-ISSN 1552-9924, Vol. 121, no 3, p. 374-379Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Acrylamide has shown developmental and reproductive toxicity in animals, as well as neurotoxic effects in humans with occupational exposures. Because it is widespread in food and can pass through the human placenta, concerns have been raised about potential developmental effects of dietary exposures in humans. OBJECTIVES: We assessed associations of prenatal exposure to dietary acrylamide with small for gestational age (SGA) and birth weight. METHODS: This study included 50,651 women in the Norwegian Mother and Child Cohort Study (MoBa). Acrylamide exposure assessment was based on intake estimates obtained from a food frequency questionnaire (FFQ), which were compared with hemoglobin (Hb) adduct measurements reflecting acrylamide exposure in a subset of samples (n = 79). Data on infant birth weight and gestational age were obtained from the Medical Birth Registry of Norway. Multivariable regression was used to estimate associations between prenatal acrylamide and birth outcomes. RESULTS: Acrylamide intake during pregnancy was negatively associated with fetal growth. When women in the highest quartile of acrylamide intake were compared with women in the lowest quartile, the multivariable-adjusted odds ratio (OR) for SGA was 1.11 (95% CI: 1.02, 1.21) and the coefficient for birth weight was -25.7 g (95% CI: -35.9, -15.4). Results were similar after excluding mothers who smoked during pregnancy. Maternal acrylamide-and glycidamide-Hb adduct levels were correlated with estimated dietary acrylamide intakes (Spearman correlations = 0.24; 95% CI: 0.02, 0.44; and 0.48; 95% CI: 0.29, 0.63, respectively). CONCLUSIONS: Lowering dietary acrylamide intake during pregnancy may improve fetal growth.

  • 310. Dyachenko, O G
    et al.
    Istomin, S Y
    Fedotov, M M
    Antipov, E V
    Svensson, Gunnar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nygren, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Holm, W
    Structure and properties of Ba6 − xLnxNb10O30, Ln = La, Ce and Nd compounds1997In: Materials research bulletin, ISSN 0025-5408, E-ISSN 1873-4227, Vol. 32, no 4, p. 409-419Article in journal (Refereed)
    Abstract [en]

    Ba6 − xLnxNb10O30 compounds, Ln = La, Ce and Nd, with a tetragonal tungsten bronze-type structure have been synthesized and were characterized by X-ray powder diffraction and EDS analysis. The homogeneity regions of the obtained compounds were found to be 0 ≤ x ≤ 2 for La, and 0 ≤ x ≤ 1.5 for Ce and Nd. The crystal structures of Ba5LaNb10O30 and Ba4La2Nb10O30 were refined using X-ray powder diffraction data. Refinement indicated the presence of vacancies in the positions. This observation was supported by oxidation studies of the La-substituted compounds. The temperature dependence of the normalized resistivity of the compounds showed a nonmetallic behavior. The increase in the ratio with decreasing temperature is less distinct for the phases with the higher concentration of rare-earth cation.

  • 311.
    Eden, Mattias
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Physical Chemistry.
    Grins, Jekabs
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Inorganic Chemistry.
    Jansson, Kjell
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Al and O substitutions in BaS-phases, Ba2AlxSi12-xN16-xO2+x: A TEM, XRD and solid-state NMR study2008In: Solid State Sciences, ISSN 1293-2558, E-ISSN 1873-3085, Vol. 10, no 1, p. 50-60Article in journal (Refereed)
    Abstract [en]

    In a series of Ba-based oxonitrido-silicate S-phases (Ba2AlxSi12-xN16-xO2+x) spanning a compositional range up to x approximate to 3, we examine the incorporation of Al and O by Si-29 and Al-27 magic-angle spinning (MAS) solid state nuclear magnetic resonance (NMR) and Al-27 triple-quantum MAS (3QMAS). The 3QMAS spectra reveal Al-27 signals from two distinct structural environments, assigned to AlN4 or AlN3O tetrahedra, respectively, and with their relative amounts depending on the S-phase substitution parameter x. Si-29 NMR show variable fractions of SiN4 and SiN3O environments. The NMR results accord overall with a structural substitution model for which O enters at one crystallographic position (occupied according to N4-xOx), in conjunction with a random Al for Si substitution at two distinct crystallographic positions. This leads to S-phase frameworks built from SiN4, SiN3O, AlN4 and AlN3O tetrahedra.

  • 312.
    Edén, Mattias
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Al-27 NMR Studies of Aluminosilicate Glasses2015In: Annual Reports on NMR Spectroscopy / [ed] Webb, GA, San Diego: Elsevier, 2015, Vol. 86, p. 237-331Chapter in book (Refereed)
    Abstract [en]

    Aluminosilicate glasses are of great geological and technological importance. Significant efforts have been spent for enhancing the insight into their structures, where magic-angle-spinning (MAS) NMR that exploits the spin-5/2 27Al as probe nucleus constitutes one widely utilized option. We review the application of basic 27Al NMR experimentation for studying primarily the short-range (less than or similar to 0.3 nm) structure of aluminosilicate glasses, emphasizing practical aspects of performing MAS and triple-quantum MAS NMR experiments, as well as options for data analysis to extract 27Al NMR parameters and quantifying AlOp populations. We illustrate the strengths and weaknesses of routine 27Al NMR for investigating aluminosilicate glasses, including its development over time. While parts of the text apply generally to MAS NMR targeting half-integer spins as structural probes in crystalline as well as amorphous materials, the focus remains on 27Al NMR applications to aluminosilicate glasses, whose basic structural features are outlined together with a survey of the most central research problems in the field. By providing both in-depth discussions about the building blocks of aluminosilicate glasses while assuming a modest background knowledge of the reader about MAS NMR and glass structure, we hope that the presentation will appeal to a broad audience, encompassing both experienced researchers in solid-state NMR or glass structures, as well as to beginners in either area.

  • 313.
    Edén, Mattias
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    The split network analysis for exploring composition-structure correlations in multi-component glasses: I. Rationalizing bioactivity-composition trends of bioglasses2011In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 357, no 6, p. 1595-1602Article in journal (Refereed)
    Abstract [en]

    We present a strategy, referred to as “split network” analysis, for assessing the average network polymerization (r(F)) and mean number of bridging oxygen (BO) atoms ( (N) over bar (F)(BO)) for each individual network former F in multi-component oxide-based glasses, primarily targeting those involving Al, B, P and Si. This requires a priori knowledge about the parameters (r(F), (N) over bar (F)(BO)) of all network builders, but one, whose values are deduced by the split network procedure. We illustrate split-network concepts for establishing composition/structure/bioactivity correlations in Na-Ca-Si-P-O glasses. The cooperating influences on the bioactivity from the average polymerization degree of the silicate network and the amounts of orthophosphate and sodium ions are discussed.

  • 314.
    Edén, Mattias
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Two-dimensional MAS NMR correlation protocols involving double-quantum filtering of quadrupolar spin-pairs2010In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 204, no 1, p. 99-110Article in journal (Refereed)
    Abstract [en]

    Three two-dimensional (2D) NMR homonuclear correlation techniques invoking double-quantum (2Q) filtration of the central transitions of half-integer spins are evaluated numerically and experimentally. They correlate directly detected single-quantum (1Q) coherences in the t(2) domain with either of 1Q, two-spin 2Q or single-spin multiple-quantum coherence-evolutions in the indirect (t(1)) dimension. We employ experimental Na-23 and Al-22 NMR on sodium sulfite and the natural mineral sillimanite (SiAl2O5), in conjunction with simulated 2D spectra from pairs of dipolar-recoupled spins-3/2 and 5/2 at different external magnetic fields, to compare the correlation strategies from the viewpoints of 2D spectral resolution, signal sensitivity, implementational aspects and their relative merits for establishing internuclear proximities and quadrupolar tensor orientations.

  • 315.
    Edén, Mattias
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zeeman Truncation in NMR. I. The Role of Operator Commutation2015In: Concepts in magnetic resonance. Bridging education and research, ISSN 1546-6086, E-ISSN 1552-5023, Vol. 43, no 4, p. 91-108Article in journal (Refereed)
    Abstract [en]

    Hamiltonians are of pivotal importance for describing and analyzing NMR experiments. However, the exact spin Hamiltonian operators are in practice not utilized, but merely a simplified form referred to either as the secular, Zeeman-truncated, or high-field Hamiltonian. It results after accounting for the dominating role of the Zeeman interaction relative to all other, much smaller NMR interactions, such as chemical shifts, through-bond, or through-space spin-spin couplings. In this article and the following one, we introduce the Zeeman truncation process to newcomers to NMR by thoroughly reviewing the options available for reducing the full Hamiltonian of a spin interaction to its Zeeman-truncated counterpart. The present paper considers time-independent Hamiltonians, where we discuss the criteria for performing truncation, highlighting the role of operator commutation by a simple formalism that is equivalent to application of lowest-order static perturbation theory. The validity of the approximations are illustrated by examining the explicit matrix representations of the exact and Zeeman truncated Hamiltonians, considering the NMR interactions relevant for systems of interacting spin-1/2 nuclei.

  • 316.
    Edén, Mattias
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zeeman Truncation in NMR. II. Time Averaging in the Rotating Frame2015In: Concepts in magnetic resonance. Bridging education and research, ISSN 1546-6086, E-ISSN 1552-5023, Vol. 43, no 4, p. 109-126Article in journal (Refereed)
    Abstract [en]

    The truncation of NMR interactions by the Zeeman Hamiltonian is here examined from a different perspective than that of our previous article [Concepts Magn. Reson., vol. 43A, pages 91-108 (2015)]: a Zeeman-truncated Hamiltonian is arranged by transforming the initially stationary operator of the NMR interaction into the rotating frame, followed by a time-averaging procedure over one Larmor period ( 2/0). We review the concept of an interaction frame, with focus on the rotating frame relevant for the Zeeman interaction, as well as the time-averaging procedure and the criteria for application of the resulting stationary Hamiltonian. A decisive advantage of this approach is its suitability for truncating time-dependent Hamiltonians, such as that of a radio-frequency (RF) field. Various options for reducing the time-dependent RF Hamiltonian into its stationary form are contrasted and thoroughly discussed. The role of Zeeman truncation is illustrated by examining the rotating-frame RF Hamiltonian associated with both on-resonance and off-resonance irradiation, where the time-independent operator character allows for applying the approximation strategies reviewed in our previous article.

  • 317.
    Edén, Mattias
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Sundberg, Peter
    Stålhandske, Christina
    The split network analysis for exploring composition-structure correlations in multi-component glasses: II. Multinuclear NMR studies of alumino-borosilicates and glass-wool fibers2011In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 357, no 6-7, p. 1587-1594Article in journal (Refereed)
    Abstract [en]

    The preceding part [M. Eden, J. Non.-Cryst. Solids, 357, (2011) 1595-1602] introduced the “split network” strategy for estimating the network polymerization degree (r(A)) and mean number of bridging oxygen (BO) atoms ((N) over bar (A)(BO)) for a network former A, given that these parameters are known for all other network builders in the multi-component oxide glass. However, as the detailed ordering of BO and non-bridging oxygen (NBO) species is often difficult to assess experimentally, we summarize some “rules of thumb” for predicting the coordination number and tendency to accept NBO ions for Al(3+), B(3+), Si(4+) and P(5+) cations: they are helpful in scenarios devoid of experimental data. Using the parameters r and (N) over bar (BO), we present expressions for the BO/NBO distributions among tetrahedrally coordinated cations, as predicted from the binary and random models. Multinuclear (11)B, (27)Al and (29)Si solid-state NMR is exploited to derive the split network representations of a set of Na-Ca-(Al)-(B)-Si-O glasses. These results are subsequently used to gain structural insight into two commercial glass-wool fibers that constitute alumino-borosilicate networks modified by Na(+), K(+), Ca(2+) and Mg(2+) ions.

  • 318. Efthimiopoulos, Ilias
    et al.
    Benson, Daryn E.
    Konar, Sumit
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nylén, Johanna
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Svensson, Gunnar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Häussermann, Ulrich
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Liebig, Stefan
    Ruschewitz, Uwe
    Vazhenin, Grigory V.
    Loa, Ingo
    Hanfland, Michael
    Syassen, Karl
    Structural transformations of Li2C2 at high pressures2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 6, article id 064111Article in journal (Refereed)
    Abstract [en]

    Structural changes of Li2C2 under pressure were studied by synchrotron x-ray diffraction in a diamond anvilcell under hydrostatic conditions and by using evolutionary search methodology for crystal structure prediction.We show that the high-pressure polymorph of Li2C2, which forms from the Immm ground-state structure (Z = 2)at around 15 GPa, adopts an orthorhombic Pnma structure with Z = 4. Acetylide C2 dumbbells characteristic ofImmm Li2C2 are retained in Pnma Li2C2. The structure of Pnma Li2C2 relates closely to the anticotunnite-typestructure. C2 dumbbell units are coordinated by nine Li atoms, as compared to eight in the antifluorite structureof Immm Li2C2. First-principles calculations predict a transition of Pnma Li2C2 at 32 GPa to a topologicallyidentical phase with a higher Cmcm symmetry. The coordination of C2 dumbbell units by Li atoms is increasedto 11. The structure of Cmcm Li2C2 relates closely to the Ni2 In-type structure. It is calculated that Cmcm Li2C2becomes metallic at pressures above 40 GPa. In experiments, however, Pnma Li2C2 is susceptible to irreversibleamorphization.

  • 319. Egorov, A. V.
    et al.
    Brodskaya, E. N.
    Laaksonen, Aatto
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Uppsala University, Sweden.
    The Effect of Single-Atomic Ions on the Melting of Microscopic Ice Particles According to Molecular Dynamics Data2018In: Colloid Journal of the Russian Academy of Science, ISSN 1061-933X, E-ISSN 1608-3067, Vol. 80, no 5, p. 484-491Article in journal (Refereed)
    Abstract [en]

    Molecular dynamics simulation of microscopic ice particles containing Ca2+, F-, Cl-, Na+, and Li+ ions has been performed in the temperature range of 20-200 K. For all the systems under consideration, phase and structural transformations accompanying their heating have been studied in detail, and the melting points have been determined. The main attention has been focused on the determination of the mechanisms of the effect of ions on the phase state of microcrystals.

  • 320. Egorov, Andrei V.
    et al.
    Lyubartsev, Alexander P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Laaksonen, Aatto
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Molecular Dynamics Simulation Study of Glycerol-Water Liquid Mixtures2011In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 115, no 49, p. 14572-14581Article in journal (Refereed)
    Abstract [en]

    To study the effects of water on conformational dynamics of polyalcohols, Molecular Dynamics simulations of glycerol water liquid mixtures have been carried out at different concentrations: 42.9 and 60.0 wt 96 of glycerol, respectively. On the basis of the analysis of backbone conformer distributions, it is found that the surrounding water molecules have a large impact on the populations of the glycerol conformers. While the local structure of water in the liquid mixture is surprisingly close to that in pure liquid water, the behavior of glycerols can be divided into three different categories where roughly 25% of them occur in a structure similar to that in pure liquid of glycerol, ca. 25% of them exist as monomers, solvated by water, and the remaining 50% of glycerols in the mixture form H-bonded strings as. remains of the glycerol H-bond network. The typical glycerol H-bond network still exists even at the lower concentration of 40 wt % of glycerol. The microheterogeneity of water glycerol mixtures is analyzed using time-averaged distributions of the sizes of the water aggregates. At 40 wt % of glycerol, the cluster sizes from 3 to 10 water molecules are observed. The increase of glycerol content causes a depletion of clusters leading to smaller 3-5 molecule clusters domination. Translational diffusion coefficients have been calculated to study the dynamical behavior of both glycerol and water molecules. Rotational-reorientational motion is studied both in overall and in selected substructures on the basis of time correlation functions. Characteristic time scales for different motional modes are deduced on the basis of the calculated correlation times. The general conclusion is that the presence of water increases the overall mobility of glycerol, while glycerol slows the mobility of water.

  • 321.
    Eklöf, Daniel
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mysterious SiB3: Identifying the relation between a- and b-SiB3Manuscript (preprint) (Other academic)
  • 322.
    Eklöf, Daniel
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Structure-property investigation of ZnSb, ZnAs, and SiB3: - binary semiconductors with electron poor framework structures2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In today’s society, where energy conservation and green energy are buzz words, new scientific discoveries in green energy harvesting is key. This work focuses on materials capable of recycling low value thermal energy. Low value thermal energy, waste heat, is for free, and can be transformed into valuable electricity via thermoelectric technology. A thermoelectric device cleanly converts heat into electricity through the Seebeck effect. Thermoelectric devices can play an important role in satisfying the future global need for efficient energy management, however, the primary barrier of improving thermoelectric devices is the materials themselves.

    The aim of this thesis is to identify new compositions and structures for thermoelectric materials. In particular, the concept of “electron poor framework semiconductors” is explored. Electron Poor Framework Semiconductors (EPFS) are materials at the border between metals and non-metals, which often show intricate and unique structures with complex bonding schemes. Generally, constituting elements should be from group 12(II) (Zn, Cd), 13(III) (B, Al, Ga, In), 14(IV) (Si, Ge, Sn, Pb), 15(V) (Sb, Bi), and 16(VI) (Te), i.e. elements which have a similar electronegativity (between 1.5-2.0). All EPFS materials have in common highly complex crystal structures, which are thought to be a consequence of their electron-poor bonding patterns. EPFS materials have an intrinsically very low – glass like - lattice thermal conductivity. The focus of this thesis is on combinations of group 12(II) (Zn) with 16 (V) (As, Sb), and 13(III) (B) with 14(IV) (Si).

    ZnSb possesses a simple structure with 8 formula units in an orthorhombic unit cell, it is considered a stoichiometric compound without noticeable structural disorder. In this thesis ZnSb is used as a model system to establish more broadly structure–property correlations in Sb based EPFS materials.

    ZnSb was established to possess an impurity band that determines electrical transport properties up to 300–400 K. Doping of ZnSb with Ag seems to enhance the impurity band by increasing the number of acceptor states and improving charge carrier density by two orders of magnitude. ZT values of Ag doped ZnSb are found to exceed 1 at 350 K. The origin of the low thermal conductivity of ZnSb was traced back to a multitude of localized low energy optic modes, acting as Einstein-like rattling modes.

    ZnAs was accessed through high pressure synthesis. The compound is isostructural to ZnSb and possess an indirect band gap of 0.9 eV, which is larger than that for ZnSb (0.5 eV). The larger band gap is attributed to the higher polarity of Zn-As bonds. The electrical resistivity of ZnAs is higher and the Seebeck coefficient is lower compared to ZnSb. However, ZnAs and ZnSb exhibit similarly low lattice thermal conductivity, although As is considerably lighter than Sb. This was explained by their similar bonding properties.

    Lastly, the longstanding mystery of SiB3 phases was resolved. The formation of metastable and disordered α-SiB3-x is fast and thus kinetically driven, whereas formation of stable β-SiB3 is slow and not quantitative unless high pressure conditions are applied. This thesis work established reproducible synthesis routes for both materials. The fast kinetics can be exploited for simultaneous synthesis and sintering of α -SiB3-x specimens in a SPS device. It is suggested that α -SiB3-x represents a promising refractory thermoelectric material.

  • 323.
    Eklöf, Daniel
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Fischer, A.
    Wu, Y.
    Scheidt, E. -W
    Scherer, W.
    Häussermann, Ulrich
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Transport properties of the ii v semiconductor znsb2013In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 1, no 4, p. 1407-1414Article in journal (Refereed)
    Abstract [en]

    The intermetallic compound ZnSb is an electron poor (II-V) semiconductor with interesting thermoelectric properties. Electrical resistivity, thermopower and thermal conductivity were measured on single crystalline and various polycrystalline specimens. The work establishes the presence of impurity band conduction as an intrinsic phenomenon of ZnSb. The impurity band governs electrical transport properties at temperatures up to 300-400 K after which ZnSb becomes an intrinsic conductor. Furthermore this work establishes an inherently low lattice thermal conductivity of ZnSb, which is comparable to the state-of-the- art thermoelectric material PbTe. It is argued that the impurity band relates to the presence of Zn defects and the low thermal conductivity to the electron-poor bonding properties of ZnSb.

  • 324. Eklöf-Österberg, Carin
    et al.
    Nedumkandathil, Reji
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Häussermann, Ulrich
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Jaworski, Aleksander
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Pell, Andrew J.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Tyagi, Madhusudan
    Jalarvo, Niina H.
    Frick, Bernhard
    Faraone, Antonio
    Karlsson, Maths
    Dynamics of Hydride Ions in Metal Hydride-Reduced BaTiO3 Samples Investigated with Quasielastic Neutron Scattering2019In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, no 4, p. 2019-2030Article in journal (Refereed)
    Abstract [en]

    Perovskite-type oxyhydrides, BaTiO3-xHx, have been recently shown to exhibit hydride-ion (H-) conductivity at elevated temperatures, but the underlying mechanism of hydride-ion conduction and how it depends on temperature and oxygen vacancy concentration remains unclear. Here, we investigate, through the use of quasielastic neutron scattering techniques, the nature of the hydride-ion dynamics in three metal hydride-reduced BaTiO3 samples that are characterized by the simultaneous presence of hydride ions and oxygen vacancies. Measurements of elastic fixed window scans upon heating reveal the presence of quasielastic scattering due to hydride-ion dynamics for temperatures above ca. 200 K. Analyses of quasielastic spectra measured at low (225 and 250 K) and high (400-700 K) temperature show that the dynamics can be adequately described by established models of jump diffusion. At low temperature, <= 250 K, all of the models feature a characteristic jump distance of about 2.8 angstrom, thus of the order of the distance between neighboring oxygen atoms or oxygen vacancies of the perovskite lattice and a mean residence time between successive jumps of the order of 0.1 ns. At higher temperatures, >400 K, the jump distance increases to about 4 angstrom, thus of the order of the distance between next-nearest neighboring oxygen atoms or oxygen vacancies, with a mean residence time of the order of picoseconds. A diffusion constant D was computed from the data measured at low and high temperatures, respectively, and takes on values of about 0.4 X 10(-6) cm(-2) s(-1) at the lowest applied temperature of 225 K and between ca. 20 X 10(-6) and 100 X 10(-6) cm(-2) s(-1) at temperatures between 400 and 700 K. Activation energies E-a were derived from the measurements at high temperatures and take on values of about 0.1 eV and show a slight increase with increasing oxygen vacancy concentration.

  • 325. Eldesouky, A.
    et al.
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Svengren, Henrik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Attallah, M. M.
    Salem, H. G.
    Effect of grain size reduction of AA2124 aluminum alloy powder compacted by spark plasma sintering2014In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 609, p. 215-221Article in journal (Refereed)
    Abstract [en]

    Nanocrystalline (Average grain size similar to 200 nm) bulk AA2124 alloy was produced through high energy ball milling of microcrystalline powder followed by spark plasma sintering (SPS) at 480 degrees C with a holding time of 10 min. The effect of initial particle and grain size on the microstructural evolution as well as on the relative density and mechanical properties of the specimens consolidated through SPS and hot pressing (HP) at the same temperature for 60 min was investigated for ball milled nano-powders (NP), as well as as-received micro-powders (MP). Results showed that the NP specimens consolidated with SPS had the highest microhardness values compared to the other specimens despite not achieving full densification. On the other hand, a general increase in density, hardness, and compressive strength was observed for all SPS consolidates compared to HP. The presence of aluminum oxide and its influence on the consolidation process as well as the resulting mechanical properties of the bulk specimens is also discussed. (C) 2014 The Authors. Published by Elsevier B.V.

  • 326.
    Elias-Wolff, Federico
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lindén, Martin
    Lyubartsev, Alexander P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Brandt, Erik G.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Curvature sensing by cardiolipin in simulated buckled membranes2019In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 15, no 4, p. 792-802Article in journal (Refereed)
    Abstract [en]

    Cardiolipin is a non-bilayer phospholipid with a unique dimeric structure. It localizes to negative curvature regions in bacteria and is believed to stabilize respiratory chain complexes in the highly curved mitochondrial membrane. Cardiolipin's localization mechanism remains unresolved, because important aspects such as the structural basis and strength for lipid curvature preferences are difficult to determine, partly due to the lack of efficient simulation methods. Here, we report a computational approach to study curvature preferences of cardiolipin by simulated membrane buckling and quantitative modeling. We combine coarse-grained molecular dynamics with simulated buckling to determine the curvature preferences in three-component bilayer membranes with varying concentrations of cardiolipin, and extract curvature-dependent concentrations and lipid acyl chain order parameter profiles. Cardiolipin shows a strong preference for negative curvatures, with a highly asymmetric chain order parameter profile. The concentration profiles are consistent with an elastic model for lipid curvature sensing that relates lipid segregation to local curvature via the material constants of the bilayers. These computations constitute new steps to unravel the molecular mechanism by which cardiolipin senses curvature in lipid membranes, and the method can be generalized to other lipids and membrane components as well.

  • 327.
    Elías-Wolff, Federico
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lindén, Martin
    Lyubartsev, Alexander P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Brandt, Erik G.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Computing Curvature Sensitivity of Biomolecules in Membranes by Simulated Buckling2018In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 14, no 3, p. 1643-1655Article in journal (Refereed)
    Abstract [en]

    Membrane curvature sensing, where the binding free energies of membrane-associated molecules depend on the local membrane curvature, is a key factor to modulate and maintain the shape and organization of cell membranes. However, the microscopic mechanisms are not well understood, partly due to absence of efficient simulation methods. Here, we describe a method to compute the curvature dependence of the binding free energy of a membrane associated probe molecule that interacts with a buckled membrane, which has been created by lateral compression of a flat bilayer patch. This buckling approach samples a wide range of curvatures in a single simulation, and anisotropic effects can be extracted from the orientation statistics. We develop an efficient and robust algorithm to extract the motion of the probe along the buckled membrane surface, and evaluate its numerical properties by extensive sampling of three coarse-grained model systems: local lipid density in a curved environment for single-component bilayers, curvature preferences of individual lipids in two-component membranes, and curvature sensing by a homotrimeric transmembrane protein. The method can be used to complement experimental data from curvature partition assays and provides additional insight into mesoscopic theories and molecular mechanisms for curvature sensing.

  • 328.
    Elías-Wolff, Federico
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lindén, Martin
    Lyubartsev, Alexander P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Brandt, Erik G.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Curvature sensing by cardiolipin in simulated buckled membranesIn: Article in journal (Refereed)
  • 329. Emam, Hossam E.
    et al.
    Abdelhamid, Hani Nasser
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Assuit University, Egypt.
    Abdelhameed, Reda M.
    Self-cleaned photoluminescent viscose fabric incorporated lanthanide-organic framework (Ln-MOF)2018In: Dyes and pigments, ISSN 0143-7208, E-ISSN 1873-3743, Vol. 159, p. 491-498Article in journal (Refereed)
    Abstract [en]

    Photoluminescent textiles emitted light in ultraviolet (UV)-radiation region has advanced a variety of applications including military and police clothes. The current study reports the preparation of photoluminescent viscose fabrics incorporated lanthanide metal-organic framework (Ln-MOF) and their applications for self-cleaning. In situ growth of Ln (Eu3+, Tb3+) MOF into viscose fabrics were achieved using Ln (NO3)(3) and 1,2,4,5-benzenetetracarboxylic dianhydride as organic ligand. The in-growth Ln-MOF within fabrics were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscope, energy dispersive X-ray, and fluorescence spectroscopy. Under the UV lamb (345 nm), Eu-MOF@viscose fabric and Tb-MOF@viscose fabric visually emitted red and green color, respectively. The excitation-emission spectra showed the spectra for the D-5(0)-> F-7(0.4) transitions and D-5(4)-> F-7(5) transitions in case of Eu-MOF and Tb-MOF@viscose fabrics, respectively. The photoluminescent properties of Ln-MOF@viscose fabrics were enhanced after reactive dying process. The self-cleaning functions of Ln-MOF@viscose fabrics were estimated through studying the photo-degradation of Rhodamine B (RhB) dye over the fabrics. After 120 min irradiation time, the photo-degradation of RhB dye was 85-97%, indicating high performance of Ln-MOF@viscose fabric. The materials are promising for advanced applications including protective clothing, textile-based sensors, smart tagging and tickets.

  • 330.
    Engelbrecht, Leon
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Stellenbosch University, South Africa; University of Cagliari, Italy.
    Mocci, Francesca
    Laaksonen, Aatto
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Uppsala University, Sweden.
    Koch, Klaus R.
    Pt-195 NMR and Molecular Dynamics Simulation Study of the Solvation of [PtCl6](2-) in Water-Methanol and Water-Dimethoxyethane Binary Mixtures2018In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 57, no 19, p. 12025-12037Article in journal (Refereed)
    Abstract [en]

    The experimental Pt-195 NMR chemical shift, delta((195) Pt), of the [PtCl6](2-) anion dissolved in binary mixtures of water and a fully miscible organic solvent is extremely sensitive to the composition of the mixture at room temperature. Significantly nonlinear delta(Pt-195) trends as a function of solvent composition are observed in mixtures of water-methanol, or ethylene glycol, 2methoxyethanol, and 1,2-dimethoxyethane (DME). The extent of the deviation from linearity of the delta((195) Pt) trend depends strongly on the nature of the organic component in these solutions, which broadly suggests preferential solvation of the [PtCl6](2-) anion by the organic molecule. This simplistic interpretation is based on an accepted view pertaining to monovalent cations in similar binary solvent mixtures. To elucidate these phenomena in detail, classical molecular dynamics computer simulations were performed for [PtCl6](2-) in water-methanol and water-DME mixtures using the anionic charge scaling approach to account for the effect of electronic dielectric screening. Our simulations suggest that the simplistic model of preferential solvation of [PtCl6](2-) by the organic component as inferred from nonlinear delta(Pt-195) trends is not entirely accurate, particularly for water-DME mixtures. The delta(Pt-195) trend in these mixtures levels off for high DME mole fractions, which results from apparent preferential location of [PtCl6](2-) anions at the borders of water-rich regions or clusters within these inherently micro-heterogeneous mixtures. By contrast in water-methanol mixtures, apparently less pronounced mixed solvent micro-heterogeneity is found, suggesting the experimental delta(Pt-195) trend is consistent with a more moderate preferential solvation of [PtCl6](2-) anions. This finding underlines the important role of solvent-solvent interactions and micro-heterogeneity in determining the solvation environment of [PtCl6](2-) anions in binary solvent mixtures, probed by highly sensitive Pt-195 NMR. The notion that preferential solvation of [PtCl6](2-) results primarily from competing ion-solvent interactions as generally assumed for monatomic ions, may not be appropriate in general.

  • 331.
    Engström, Karin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Gustafson, Karl P. J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Shakeri, Mozaffar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Co-immobilization of an Enzyme and a Metal into the Compartments of Mesoporous Silica for Cooperative Tandem Catalysis: An Artificial Metalloenzyme2013In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 52, no 52, p. 14006-14010Article in journal (Refereed)
    Abstract [en]

    Surpassing nature: A hybrid catalyst in which Candida antarctica lipase B and a nanopalladium species are co-immobilized into the compartments of mesoporous silica is presented. The metal nanoparticles and the enzyme are in close proximity to one another in the cavities of the support. The catalyst mimics a metalloenzyme and was used for dynamic kinetic resolution of a primary amine in high yield and excellent enantioselectivity.

  • 332.
    Erbing, Elis
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Vazquez-Romero, Ana
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bermejo Gómez, Antonio
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Platero-Prats, Ana E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Carson, Fabian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Tolstoy, Päivi
    Martín-Matute, Belén
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    General, Simple, and Chemoselective Catalysts for the Isomerization of Allylic Alcohols: The Importance of the Halide Ligand2016In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, no 44, p. 15659-15663Article in journal (Refereed)
    Abstract [en]

    Remarkably simple Ir-III catalysts enable the isomerization of primary and sec-allylic alcohols under very mild reaction conditions. X-ray absorption spectroscopy (XAS) and mass spectrometry (MS) studies indicate that the catalysts, with the general formula [Cp*Ir-III], require a halide ligand for catalytic activity, but no additives or additional ligands are needed.

  • 333. Eremina, R. M.
    et al.
    Gavrilova, T. P.
    Guenther, A.
    Wang, Z.
    Lortz, R.
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Berger, H.
    von Nidda, H. A. Krug
    Deisenhofer, J.
    Loidl, A.
    Magnetization and specific heat of the dimer system CuTe(2)O(5)2011In: European Physical Journal B: Condensed Matter Physics, ISSN 1434-6028, E-ISSN 1434-6036, Vol. 84, no 3, p. 391-395Article in journal (Refereed)
    Abstract [en]

    We report on magnetization and specific heat measurements on single-crystalline CuTe(2)O(5). The experimental data are directly compared to theoretical results for two different spin structures, namely an alternating spin-chain and a two-dimensional (2D) coupled dimer model, obtained by Das et al. [Phys. Rev. B 77, 224437 (2008)]. While the analysis of the specific heat does not allow to distinguish between the two models, the magnetization data is in good agreement with the 2D coupled dimer model.

  • 334.
    Eriksson, Lars
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Grins, Jekabs
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Svensson, Gunnar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    DFT predictions of Prussian Blue structures2018In: DFT predictions of Prussian Blue structures, 2018Conference paper (Refereed)
  • 335.
    Eriksson, Lars
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Melcher, Charles L.
    Eriksson, Marita
    Rothfuss, Harold
    Grazioso, Ron
    Aykac, Mehmet
    Design Considerations of Phoswich Detectors for High Resolution Positron Emission Tomography2009In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 56, no 1, p. 182-188Article in journal (Refereed)
    Abstract [en]

    A way to improve the spatial resolution in positron emission tomography (PET) is to determine the depth-of-interaction (DOI) in the detector. A way to achieve this is to use the phoswich approach, a detector with two or more layers of different scintitlators. The layer identification is done by using differences in scintillation decay time and pulse shape discrimination techniques. The advantages of the concept have been demonstrated in the HRRT high resolution PET system using a LSO/LYSO combination giving a high spatial resolution uniformity of around 2.5 mm within a larger part of the imaged volume. A phoswich combination that lately has received attention is LuAP/LSO or LuYAP/LSO. The suggestions come from the Crystal Clear Collaboration and there is a patent application for its use in PET. This particular combination of phoswich may, however, have a complication since both LuAP and LuYAP emit in the excitation band of LSO, thus making the functionality more complex. In the present paper we have looked into this and suggested different ways to overcome potential drawbacks.

  • 336.
    Eriksson, Lars
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Methyl 3-O-alpha-L-fucopyranosyl alpha-D-galactopyranoside: a synchrotron study2012In: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 68, p. o528-U1770Article in journal (Refereed)
    Abstract [en]

    The title compound, C13H24O10 is the methyl glycoside of a structural element alpha-L-Fucp-(1 -> 3)-alpha-D-Galp making up two thirds of the repeating unit in the capsular polysaccharide of Klebsiella K63. The conformation of the title compound is described by the glycosidic torsion angles phi(H) = 55 (1)degrees and psi H = -24 (1)degrees. The hydroxymethyl group in the galactose residue is present in the gauche-trans conformation. In the crystal, O-H center dot center dot center dot O hydrogen bonds connect the disaccharide units into chains along the a-axis direction and further hydrogen bonds cross-link the chains.

  • 337.
    Eriksson, Lars
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Methyl 3-O-α-l-fucopyranosyl β-d-glucopyranoside tetrahydrate2012In: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 68, p. o3180-o3181Article in journal (Refereed)
    Abstract [en]

    The title compound, C13H24O10·4H2O, is the methyl glycoside of a disaccharide structural element present in the backbone of the capsular polysaccharide from Klebsiella K1, which contains only three sugars and a substituent in the polysaccharide repeating unit. The conformation of the title disaccharide is described by the glycosidic torsion angles ϕH = 51.1 (1)° and ψH = 25.8 (1)°. In the crystal, a number of O—HO hydrogen bonds link the methyl glycoside and water mol­ecules, forming a three-dimensional network. One water mol­ecule is disordered over two positions with occupancies of 0.748 (4) and 0.252 (4).

  • 338.
    Eriksson, Mirva
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Spark Plasma Sintering Enhancing Grain Sliding, Deformation and Grain Size Control: Studies of the Systems Ti, Ti/TiB2, Na0.5 K0.5 NbO3, and Hydroxyapatite2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The unique features of the Spark plasma sintering (SPS) were used to investigate the sintering and deformation behaviour of titanium and titanium–titanium diboride composites, and to control the sintering and grain growth of ferroelectric Na0.5K0.5NbO3 (NKN) and of hydroxyapatite (HAp). In the SPS the samples experience a temperature different from that recorded by the thermocouple (pyrometer) used and this temperature difference has been estimated for Ti and NKN.

     

    Sintering and deformation of titanium was investigated. Increasing heating rate and/or pressure shifted the sintering to lower temperatures, and the sintering and deformation rates changed when the α→β phase transition temperature was passed. Fully dense Ti/TiB2 composites were prepared. The Ti/TiB2 composites could be deformed at high temperatures, but the hardness decreased due to the formation of TiB. 

     

    The kinetic windows within which it is possible to obtain fully dense NKN and HAp ceramics and simultaneously avoid grain growth are defined. Materials have a threshold temperature above which rapid and abnormal grain growth takes place. The abnormal grain growth of NKN is due to a small shift in the stoichiometry, which in turn impairs the ferroelectric properties. Fully transparent HAp nanoceramics was prepared, and between 900 and 1050 oC elongated grains are formed, while above 1050 oC abnormal grain growth takes place.NKN samples containing grains of the sizes 0.35–0.6 µm yielded optimum ferroelectric properties, i.e. a high remanent polarization (Pr = 30 µC/cm2) and high piezoelectric constant (d33= 160 pC/N). The ferroelectric domain structure was studied, and all grains exhibited a multi-domain type of structure.

  • 339.
    Eriksson, Mirva
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Liu, Yi
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Hu, Jiangfeng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Gao, Lian
    State Key Lab of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai.
    Nygren, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Transparent hydroxyapatite nanoceramics by high pressure spark plasma sintering at the minimized sintering temperatureManuscript (preprint) (Other academic)
    Abstract [en]

    For direct observation of the bio-interfacial reactions with improved spatial and temporal resolution by confocal microscopy transparent hydroxyapatite nanoceramics are demanded. The aim of the present study was to, through detailed kinetics study and micostructural characterization, define a processing window within which transparent HAp nanoceramics can be produced by spark plasma sintering of dry powders.  A lab-made hydrothermally processed bulky powder composed of loosely aggregated nanorods and a commercial granulated-powder composed of irregular shaped nanorods were tested.  The use of a high pressure cell allows the application of pressure up to 500 MPa. It was found that applying of high pressure is beneficial for widen up the processing window for attaining dense HAp ceramics with nano grained microstructure. The high transparency of HAp nanoceramics obtained in this study is ascribed to the high density and homogeneous nano-structure achieved besides the unique intrinsic optical properties of the HAp crystal, i.e. its low refractive index and very small birefringence. Achieving full densification at the minimized sintering temperature allows for the first time the preparation of transparent HAp nanoceramics with stoichiometric composition, i.e. avoiding the loss of water that commonly encountered  during the conventional ways of sintering.

  • 340.
    Eriksson, Mirva
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Liu, Yi
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hu, Jiangfeng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gao, Lian
    Nygren, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Shen, Zhijian James
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Transparent hydroxyapatite ceramics with nanograin structure prepared by high pressure spark plasma sintering at the minimized sintering temperature2011In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 31, no 9, p. 1533-1540Article in journal (Refereed)
    Abstract [en]

    A hydrothermally processed bulky powder composed of loosely aggregated nano-sized rods was consolidated by spark plasma sintering. The use of a high pressure cell allows the application of pressure up to 500 MPa. It was found that applying of high pressure is beneficial for widening up the kinetic window for attaining dense HAp nanoceramics. The high transparency of HAp nanoceramics obtained in this study is ascribed to the high density and homogeneous nano-grained structure achieved besides the unique intrinsic optical properties of the HAp crystal itself, i.e. its low refractive index and very small birefringence. Achieving full densification at the minimized sintering temperature allows for the first time the preparation of transparent HAp nanoceramics with stoichiometric composition, i.e. avoiding the loss of structural water that commonly takes place during the conventional ways of sintering.

  • 341.
    Eriksson, Mirva
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Radwan, Mohamed
    Shen, Zhijian James
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Spark plasma sintering of wc, cemented carbide and functional graded materials2013In: International journal of refractory metals & hard materials, ISSN 0958-0611, E-ISSN 2213-3917, ISSN 0263-4368, Vol. 36, p. 31-37Article in journal (Refereed)
    Abstract [en]

    Spark plasma sintering (SPS) is an extremely fast solidification technique for compounds that are difficult to sinter within the material group's metals, ceramics, or composites thereof. SPS uses a uniaxial pressure and a very rapid heating cycle to consolidate these materials. The heating is generated by Joule effect when a strong, pulsed electric current passes the conductive graphite die and also through the sample, if conductive. Cemented carbides (hard metals) are mostly used for metal cutting and drilling, wood cutting or rock drilling tools and are consolidated either by pressureless sintering (PLS), hot pressing (HP), or hot isostatic pressing (HIP). With SPS the main benefit is the ability to control the WC grain size due to the short sintering times at high temperature. In addition, unwished reactions between WC and cobalt to form other phases are minimized. By SPS the amount of cobalt can be reduced towards zero in fully dense WC materials. With this technique it is easy to prepare gradient materials where a ductile weldable metal can be joined with the cemented carbide part.

  • 342.
    Eriksson, Mirva
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Salamon, David
    Nygren, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Spark plasma sintering and deformation of Ti-TiB2 composites.2008In: Materials Science & Engineering, A: Structural Materials: Properties, Microstructure and Processing, ISSN 0921-5093, Vol. 1-2, no A475, p. 101-104Article in journal (Refereed)
    Abstract [en]

    Spark plasma sintering (SPS) was used to investigate the densification and deformation behaviour of Ti–TiB2 composites. Fully densified samples were prepared with Ti addition larger than 5%. The prepared composites can be deformed under compression at 1700 °C to achieve a strain of 50% without cracking. At lower temperatures, cracks were initiated due to low ductility of TiB2 and low content of Ti. During the sintering and deformation, TiB is formed via a reaction between Ti and TiB2. To elucidate the formation mechanism of TiB in the SPS process, reactive sintering of TiB using element precursors was also performed. Fully dense samples were prepared but it was not possible to prepare pure uniphase TiB. The reactive sintering resulted in the formation of TiB and TiB2 mixtures at low temperatures and a mixture of TiB2 and Ti3B4 at high temperature

  • 343.
    Eriksson, Mirva
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Yan, Haixue
    School of Engineering and Materials Science, Queen Mary University of London,.
    Nygren, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Reece, Mike J
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Low temperature consolidated lead-free ferroelectric niobateceramics with improved electrical properties2010In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 25, no 2, p. 240-247Article in journal (Refereed)
    Abstract [en]

    There is a concerted effort to develop lead-free piezoelectric ceramics. ((Na0.5K0.5)NbO3 based ceramics have good electrical properties, and are a potential replacement material for lead zirconate titanate piezoelectric ceramics. In this work a commercial powder based on (Na0.5K0.5)NbO3 with an initial particle size of 260 nm was consolidated by plasma sintering (SPS). To avoid volatilization, high mechanical pressures were used to minimize the densification temperature. It was found that under a uniaxial pressure of 100 MPa, fully densified compacts can be prepared at 850. Ceramics densified at such a low temperature demonstrate an unusually high remanent polarization (30 mC/cm2) and high d33 (146 pC/N). The improved ferroelectric properties are ascribed to the homogeneous, dense, and submicron grained microstructure achieved.

  • 344.
    Eriksson, Mirva
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Yan, Haixue
    School of Engineering and Materials Science and Nanoforce Technology Ltd, Queen Mary University of London, London, United Kingdom.
    Viola, Giuseppe
    School of Engineering and Materials Science and Nanoforce Technology Ltd, Queen Mary University of London, London, United Kingdom.
    Ning, Huanpo
    School of Engineering and Materials Science and Nanoforce Technology Ltd, Queen Mary University of London, London, United Kingdom.
    Gruner, Daniel
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Nygren, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Reece, Mike
    School of Engineering and Materials Science and Nanoforce Technology Ltd, Queen Mary University of London, London, United Kingdom.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Department of Materials Chemistry.
    Effect of grain size on ferroelectric domain and electrical properties of submicron sized sodium potassium niobate ceramicsManuscript (preprint) (Other (popular science, discussion, etc.))
    Abstract [en]

    Piezoelectric ceramics of the composition Na0.5K0.5NbO3 (NKN) with grain sizes in the range of 0.2 - 1 mm were fabricated by Spark Plasma Sintering using normal pressure dies and a high pressure cell designed for pressures up to 500 MPa  with the purpose of investigating the effect of grain size on domain structures and electrical properties. Optimized processing conditions enabled ceramics of high densities (>99.5%TD) to be made at T≥850°C. It was found that domain size decreases with decreasing grain size and that non-180° ferroelectric domains walls were still visible in 200 nm sized grains. The room temperature dielectric constant firstly increased with decreasing grain size and then decreased in the low grain size regime. The materials with finer grain size displayed a broad ferro-paraelectric phase transition and a depression of the dielectric maximum at the Curie point. They also displayed an increase in the coercive field and approximately unchanged remnant polarization. The material sintered at 850°C represents a very good candidate for lead-free piezoelectric applications, because of its high piezoelectric constant (d33 = 160±2 pC/N).

  • 345.
    Eriksson, Mirva
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Yan, Haixue
    Viola, Giuseppe
    Ning, Huanpo
    Grunér, Daniel
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nygren, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Reece, Mike J.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ferroelectric Domain Structures and Electrical Properties of Fine-Grained Lead-Free Sodium Potassium Niobate Ceramics2011In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 94, no 10, p. 3391-3396Article in journal (Refereed)
    Abstract [en]

    Piezoelectric ceramics of the composition Na(0.5)K(0.5)NbO(3) (NKN) with grain sizes in the range of 0.2-1 mu m were fabricated by spark plasma sintering. Ferroelectric domain size decreases with decreasing grain size and non-180 degrees ferroelectric domains walls were still visible in 200 nm sized grains. The Curie point of the ceramics was grain size independent. This suggests that the critical grain size for a single domain single grain structure for NKN is <200 nm. Optimized processing conditions enabled ceramics of high densities (>99.5% theoretical density) to be made at T >= 850 degrees C. For the dense ceramics (grain size >= 350 nm), the room temperature dielectric constant and coercive field increased with decreasing grain size. The remnant polarization was grain size independent. The material sintered at 850 degrees C is a very good candidate for lead-free piezoelectric applications because of its high piezoelectric constant (d(33) = 160 +/- 2 pC/N).

  • 346.
    Eriksson, Sune
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Chemistry.
    Karlsson, Patrik
    Törnqvist, Margareta
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    Measurement of evaporated acrylamide during heat treatment of food and other biological materials2007In: LWT – Food Science and Technology, ISSN 0023-6438, Vol. 40, no 7, p. 706-712Article in journal (Refereed)
    Abstract [en]

    It is established that acrylamide could be formed during heating of food products. In the present work we have studied whether the formed acrylamide could evaporate from food at elevated temperatures used in cooking (>160 °C) or used in determination of dry matter in laboratory analysis (ca. 105 °C). It was demonstrated that acrylamide evaporates from food samples during both cooking and temperatures used for drying. Up to ca. 4 μg/m3 could be measured above the fry pan during frying of potato. In parallel we have also studied whether acrylamide could be formed and evaporate during the elevated temperatures of 65–130 °C used for dry matter determinations in other types of samples containing biological material, like agricultural and environmental samples. It was found that acrylamide is formed during conditions for drying of soil, sediment and silage samples, as well as cereals, animal feed, etc. After drying, levels of acrylamide up to about 100 μg/kg were found, e.g. in samples of sediment and sludge. The measurements showed in the food, agricultural and environmental samples tested a minor fraction, roughly estimated to be 0.15–7.2% of the formed acrylamide evaporates at the used elevated temperatures.

  • 347.
    Ermilova, Inna
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Modeling of biomembranes: from computational toxicology to simulations of neurodegenerative diseases2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    It was known from the middle of the last century that a cell-membrane is a lipid bilayer. Since that time a large number of experimental studies has been done in order to see how a certain molecule can penetrate through a membrane. Due to the complexity of laboratory experiments computational chemistry became a convenient tool for investigations involving this process. In a real life a compound has to pass through several membranes of different chemical composition before reaching the actual target. Such a diversity in constitution gives a various selectivity to cell-membranes: some molecules will penetrate through them and others will not. That is why the development and a choice of suitable models for lipid bilayers are important steps in such a research. In this thesis new all-atomistic models for polyunsaturated phospholipids in cis conformations have been derived and added to the SLipids force field. After a successful force field validation, the new lipid models were used in molecular dynamics and well-tempered metadynamics simulations of several problems, such as toxicity of hydroxylated polybrominated diphenyl ethers (OH-PBDE), behavior of cholesterol in various membranes, an aggregation of amyloid-β (Aβ) peptides. The significance of the presence of lipid unsaturation has been demonstrated by all computations. 2’-OH-BDE68 (ortho) showed the affinity to saturated lipid bilayer, but had more conformational variations in the center of the unsaturated membrane. Cholesterol did not exhibit the preference to polynsaturated lipid bilayers from free energy calculations, but the diversity in orientations of this molecule, depending on its locations was observed. The behavior of Aβ peptides was dependent on membrane saturation as well. The insertion of Aβ peptides was detected in lipid bilayers containing higher amounts of polyunsaturated phospholipids, while in systems with more saturated membranes amyloids aggregated on membrane surfaces. Moreover, a comparison of simulations for quadro- and mono-component lipid bilayers showed that the membrane built of 18:0-22:6 PC can serve as a good model for the ’healthy’ tissue of a human brain. Also the lipid bilayer built of 14:0-14:0 PC exhibited similar features as the quadro-lipid membrane representing the brain tissue affected by Alzheimer’s disease. Good agreement of some computational results with available experimental findings demonstrated the applicability of computer simulations to real life problems.

  • 348.
    Ermilova, Inna
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lyubartsev, Alexander
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Modelling of interactions between Aβ(25-35) peptide and phospholipid bilayers: effects of cholesterol and lipid saturation2019In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084Article in journal (Refereed)
  • 349.
    Ermilova, Inna
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lyubartsev, Alexander P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Cholesterol in phospholipid bilayers: positions and orientations inside membranes with different unsaturation degrees2019In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 15, no 1, p. 78-93Article in journal (Refereed)
    Abstract [en]

    Cholesterol is an essential component of all animal cell membranes and plays an important role in maintaining the membrane structure and physical–chemical properties necessary for correct cell functioning. The presence of cholesterol is believed to be responsible for domain formation (lipid rafts) due to different interactions of cholesterol with saturated and unsaturated lipids. In order to get detailed atomistic insight into the behaviour of cholesterol in bilayers composed of lipids with varying degrees of unsaturation, we have carried out a series of molecular dynamics simulations of saturated and polyunsaturated lipid bilayers with different contents of cholesterol, as well as well-tempered metadynamics simulations with a single cholesterol molecule in these bilayers. From these simulations we have determined distributions of cholesterol across the bilayer, its orientational properties, free energy profiles, and specific interactions of molecular groups able to form hydrogen bonds. Both molecular dynamics and metadynamics simulations showed that the most unsaturated bilayer with 22:6 fatty acid chains shows behaviour which is most different from other lipids. In this bilayer, cholesterol is relatively often found in a “flipped” configuration with the hydroxyl group oriented towards the membrane middle plane. This bilayer has also the highest (least negative) binding free energy among liquid phase bilayers, and the lowest reorientation barrier. Furthermore, cholesterol molecules in this bilayer are often found to form head-to-tail contacts which may lead to specific clustering behaviour. Overall, our simulations support ideas that there can be a subtle interconnection between the contents of highly unsaturated fatty acids and cholesterol, deficiency or excess of each of them is related to many human afflictions and diseases.

  • 350.
    Ermilova, Inna
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lyubartsev, Alexander P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Extension of the Slipids Force Field to Polyunsaturated Lipids2016In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 120, no 50, p. 12826-12842Article in journal (Refereed)
    Abstract [en]

    The all-atomic force field Slipids (Stockholm Lipids) for lipid bilayers simulations has been extended to polyunsaturated lipids. Following the strategy adopted in the development of previous versions of the Slipids force field, the parametrization was essentially based on high-level ab initio calculations. Atomic charges and torsion angles related to polyunsaturated lipid tails were parametrized using structures of dienes molecules. The new parameters of the force field were validated in simulations of bilayers composed of seven polyunsaturated lipids. An overall good agreement was found with available experimental data on the areas per lipids, volumetric properties of bilayers, deuterium order parameters, and scattering form factors. Furthermore, simulations of bilayers consisting of highly polyunsaturated lipids and cholesterol molecules have been carried out. The majority of cholesterol molecules were found in a position parallel to bilayer normal with the hydroxyl group directed to the membrane surface, while a small fraction of cholesterol was found in the bilayer center parallel to the membrane plane. Furthermore, a tendency of cholesterol molecules to form chain-like clusters in polyunsaturated bilayers was qualitatively observed.

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