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Alan K. Soper - One of the best experts on this subject based on the ideXlab platform.

  • Freezing of Aqueous Solutions and Chemical Stability of Amorphous Pharmaceuticals: Water Clusters Hypothesis.
    Journal of pharmaceutical sciences, 2018
    Co-Authors: Evgenyi Shalaev, Alan K. Soper, J. Axel Zeitler, Satoshi Ohtake, Christopher J. Roberts, Michael J. Pikal, Elena V. Boldyreva
    Abstract:

    Abstract Molecular mobility has been traditionally invoked to explain physical and chemical stability of diverse pharmaceutical systems. Although the molecular mobility concept has been credited with creating a scientific basis for stabilization of amorphous pharmaceuticals and biopharmaceuticals, it has become increasingly clear that this approach represents only a partial description of the underlying fundamental principles. An additional mechanism is proposed herein to address 2 key questions: (1) the existence of unfrozen water (i.e., partial or complete freezing inhibition) in aqueous solutions at subzero temperatures and (2) the role of water in the chemical stability of amorphous pharmaceuticals. These apparently distant phenomena are linked via the concept of water clusters. In particular, freezing inhibition is associated with the confinement of water clusters in a solidified matrix of an amorphous solute, with nanoscaled water clusters being observed in aqueous glasses using Wide-Angle Neutron Scattering. The chemical instability is suggested to be directly related to the catalysis of proton transfer by water clusters, considering that proton transfer is the key elementary reaction in many chemical processes, including such common reactions as hydrolysis and deamidation.

  • Water in a Soft Confinement: Structure of Water in Amorphous Sorbitol
    The journal of physical chemistry. B, 2016
    Co-Authors: Evgenyi Shalaev, Alan K. Soper
    Abstract:

    The structure of water in 70 wt % sorbitol–30 wt % water mixture is investigated by Wide-Angle Neutron Scattering (WANS) as a function of temperature. WANS data are analyzed using empirical potential structure refinement to obtain the site–site radial distribution functions (RDFs). Orientational structure of water is represented using OW–OW–OW triangles distributions and a tetrahedrality parameter, q, while water–water correlation function is used to estimate size of water clusters. Water structure in the sorbitol matrix is compared with that of water confined in nanopores of MCM41. The results indicate the existence of voids in the sorbitol matrix with the length scale of approximately 5 A, which are filled by water. At 298 K, positional water structure in these voids is similar to that of water in MCM41, whereas there is a difference in the tetrahedral (orientational) arrangement. Cooling to 213 K strengthens tetrahedrality, with the orientational order of water in sorbitol becoming similar to that of c...

  • Water in a Soft Confinement: Structure of Water in Amorphous Sorbitol B
    The Journal of Physical Chemistry, 2016
    Co-Authors: Evgenyi Shalaev, Alan K. Soper
    Abstract:

    The structure of water in 70 wt % sorbitol–30 wt % water mixture is investigated by Wide-Angle Neutron Scattering (WANS) as a function of temperature. WANS data are analyzed using empirical potential structure refinement to obtain the site–site radial distribution functions (RDFs). Orientational structure of water is represented using OW–OW–OW triangles distributions and a tetrahedrality parameter, q, while water–water correlation function is used to estimate size of water clusters. Water structure in the sorbitol matrix is compared with that of water confined in nanopores of MCM41. The results indicate the existence of voids in the sorbitol matrix with the length scale of approximately 5 A, which are filled by water. At 298 K, positional water structure in these voids is similar to that of water in MCM41, whereas there is a difference in the tetrahedral (orientational) arrangement. Cooling to 213 K strengthens tetrahedrality, with the orientational order of water in sorbitol becoming similar to that of confined water in MCM41 at 210 K, whereas further cooling to 100 K does not introduce any additional changes in the tetrahedrality. The results obtained allow us to propose, for the first time, that such confinement of water in a sorbitol matrix is the main reason for the lack of ice formation in this system.

  • Solute-solute correlation in aqueous solution of tetramethylurea
    Physica B-condensed Matter, 1997
    Co-Authors: S. Ansell, László Cser, T. Grósz, G. Jancsó, Pál Jóvári, Alan K. Soper
    Abstract:

    Abstract The HH radial distribution function obtained by of a Wide-Angle Neutron Scattering experiment on a 2 molar aqueous solution of tetramethylurea at 10°C using the isotope substitution method is reported.

  • Neutron Scattering from hydrogenous polymers
    Physica B-condensed Matter, 1992
    Co-Authors: B. Rosi-schwartz, Geoffrey R. Mitchell, Alan K. Soper
    Abstract:

    Abstract We report a wide angle Neutron Scattering experiment on atactic polystyrene, performed on the novel SANDALS diffractometer at the pulsed Neutron facility ISIS (UK). Results for samples of both totally deuterated and totally hydrogenated polystyrene are presented and compared with predictions from statistical models for the chain configuration. SANDALS enormous potential for the investigation of hydrogenated organic materials is presented.

Masakatsu Misawa - One of the best experts on this subject based on the ideXlab platform.

  • Structure of Poly(vinyl alcohol) Gels Studied by Wide- and Small-Angle Neutron Scattering
    Macromolecules, 1994
    Co-Authors: Toshiji Kanaya, Michihiro Furusaka, Masatoshi Ohkura, Keisuke Kaji, Masakatsu Misawa
    Abstract:

    The structure of poly(vinyl alcohol) (PVA) gels formed in a mixture of deuterated DMSO and heavy water at 23°C has been investigated. It was directly confirmed from the Wide-Angle Neutron Scattering measurements that cross-linking points or junction points in the gels are crystallites. In the small-angle Scattering measurements, it was found that the Scattering intensity I(Q) decreases with Q according to the -4th power law (Porod's law) in the Q range above 0.05 A -1 where Q=4π sin θ/λ (2θ and λ are Scattering angle and wavelength of Neutron, respectively), suggesting that the surface of the crystallites has a clear boundary

  • Small angle Neutron Scattering from poly(vinyl alcohol) gels
    Physica B-condensed Matter, 1992
    Co-Authors: Toshiji Kanaya, Michihiro Furusaka, Masatoshi Ohkura, Keisuke Kaji, Masakatsu Misawa, Hitoshi Yamaoka, George D. Wignall
    Abstract:

    Abstract Structural studies have been performed on poly(vinyl alcohol)(PVA) gels formed in mixtures of dimethylsulfoxide and water at 23°C by means of small angle and wide angle Neutron Scattering techniques in a wide Q range of 0.003–10A-1.

Michihiro Furusaka - One of the best experts on this subject based on the ideXlab platform.

  • Wide-Angle Neutron Scattering STUDY OF THERMAL DENATURATION OF LYSOZYME
    Physica B-condensed Matter, 1997
    Co-Authors: Mitsuhiro Hirai, Shigeki Arai, Hiroki Iwase, Toshiharu Takizawa, Shigeru Shimizu, Michihiro Furusaka
    Abstract:

    Abstract Many studies of folding-unfolding transition of protein have been carried out for the clarification of the fundamental biological problem of protein folding, namely, how a polypeptide chain attains its native conformation. Although one of the approaches to solve protein-folding mechanisms is evidently to follow denaturation processes of protein, there is little direct evidence showing intramolecular structural changes under thermal perturbation. By using a Wide-Angle Neutron-Scattering spectrometer, we have monitored the thermal denaturation process of hen egg-white lysozyme at different pH under the unaggregative condition. The present results show that the temperature elevation gradually induces an intramolecular structural fluctuation prior to a main transition of the tertiary structure without accompanying significant heat absorption, and the multiplicity in the thermal transition observed suggests the presence of hierarchic stability depending on the structural hierarchy which would characterize an energetic landscape of folding-unfolding transition of protein.

  • Mesoscopic structure of SiC fibers by Neutron and x-ray Scattering
    Journal of Materials Research, 1996
    Co-Authors: Kentaro Suzuya, Michihiro Furusaka, Noboru Watanabe, Makoto Osawa, Kiyohito Okamura, Kaoru Shibata, Tomoaki Kamiyama, Kenji Suzuki
    Abstract:

    Mesoscopic structures of SiC fibers produced from polycarbosilane by different methods were studied by diffraction and small-angle Scattering of Neutrons and x-rays. Microvoids of a size of 4–10 Å in diameter have been observed for the first time by Neutron Scattering in a medium momentum transfer range ( Q = 0.1–1.0 Å^−1). The size and the volume fraction of β–SiC particles were determined for fibers prepared at different heat-treatment temperatures. The results show that Wide-Angle Neutron Scattering measurements are especially useful for the study of the mesoscopic structure of multicomponent materials.

  • Structure of Poly(vinyl alcohol) Gels Studied by Wide- and Small-Angle Neutron Scattering
    Macromolecules, 1994
    Co-Authors: Toshiji Kanaya, Michihiro Furusaka, Masatoshi Ohkura, Keisuke Kaji, Masakatsu Misawa
    Abstract:

    The structure of poly(vinyl alcohol) (PVA) gels formed in a mixture of deuterated DMSO and heavy water at 23°C has been investigated. It was directly confirmed from the Wide-Angle Neutron Scattering measurements that cross-linking points or junction points in the gels are crystallites. In the small-angle Scattering measurements, it was found that the Scattering intensity I(Q) decreases with Q according to the -4th power law (Porod's law) in the Q range above 0.05 A -1 where Q=4π sin θ/λ (2θ and λ are Scattering angle and wavelength of Neutron, respectively), suggesting that the surface of the crystallites has a clear boundary

  • Small angle Neutron Scattering from poly(vinyl alcohol) gels
    Physica B-condensed Matter, 1992
    Co-Authors: Toshiji Kanaya, Michihiro Furusaka, Masatoshi Ohkura, Keisuke Kaji, Masakatsu Misawa, Hitoshi Yamaoka, George D. Wignall
    Abstract:

    Abstract Structural studies have been performed on poly(vinyl alcohol)(PVA) gels formed in mixtures of dimethylsulfoxide and water at 23°C by means of small angle and wide angle Neutron Scattering techniques in a wide Q range of 0.003–10A-1.

Toshiji Kanaya - One of the best experts on this subject based on the ideXlab platform.

  • Micro- and mesoscopic structure of poly(vinyl alcohol) gels determined by Neutron and light Scattering
    Supramolecular Science, 1998
    Co-Authors: Toshiji Kanaya, Masatoshi Ohkura, Hiroki Takeshita, Yuichi Nishikoji, Koji Nishida, Keisuke Kaji
    Abstract:

    Abstract We studied the structure of poly(vinyl alcohol) (PVA) gels formed in mixtures of dimethyl sulfoxide (DMSO) and water using several Scattering techniques such as Wide-Angle Neutron Scattering (WANS), small-angle Neutron Scattering (SANS), ultra-small-angle Neutron Scattering (U-SANS) and light Scattering (LS) to cover a very wide Q range from 10 -4 to 10 A -1 . The WANS measurements have revealed that the cross-linking points of the gels are crystallites, and the size and its distribution have been evaluated by the SANS measurements. The SANS results have also shown that the structure observed in the low Q range below 10 -2  A -1 is dominated by a liquid–liquid-phase separation. The early stage of the phase separation has been studied in detail using the time-resolved LS technique, while the late stage has been investigated by the U-SANS technique because the LS measurements cannot access the opaque samples. On the basis of the results, we present a quantitative sketch of the structure of the PVA gel.

  • Structure of Poly(vinyl alcohol) Gels Studied by Wide- and Small-Angle Neutron Scattering
    Macromolecules, 1994
    Co-Authors: Toshiji Kanaya, Michihiro Furusaka, Masatoshi Ohkura, Keisuke Kaji, Masakatsu Misawa
    Abstract:

    The structure of poly(vinyl alcohol) (PVA) gels formed in a mixture of deuterated DMSO and heavy water at 23°C has been investigated. It was directly confirmed from the Wide-Angle Neutron Scattering measurements that cross-linking points or junction points in the gels are crystallites. In the small-angle Scattering measurements, it was found that the Scattering intensity I(Q) decreases with Q according to the -4th power law (Porod's law) in the Q range above 0.05 A -1 where Q=4π sin θ/λ (2θ and λ are Scattering angle and wavelength of Neutron, respectively), suggesting that the surface of the crystallites has a clear boundary

  • Small angle Neutron Scattering from poly(vinyl alcohol) gels
    Physica B-condensed Matter, 1992
    Co-Authors: Toshiji Kanaya, Michihiro Furusaka, Masatoshi Ohkura, Keisuke Kaji, Masakatsu Misawa, Hitoshi Yamaoka, George D. Wignall
    Abstract:

    Abstract Structural studies have been performed on poly(vinyl alcohol)(PVA) gels formed in mixtures of dimethylsulfoxide and water at 23°C by means of small angle and wide angle Neutron Scattering techniques in a wide Q range of 0.003–10A-1.

Andrzej Burian - One of the best experts on this subject based on the ideXlab platform.

  • The atomic scale structure of saccharose-based carbons
    Philosophical Magazine, 2017
    Co-Authors: N. Woźnica, Henry E. Fischer, ᴌ. Hawełek, S. Duber, Veijo Honkimäki, Mirosława Pawlyta, A. Bulou, Andrzej Burian
    Abstract:

    AbstractActivated carbons (ACs) have a wide range of applications, in which the largely expanded specific surface plays a major role. The question of their structure came back to the limelight with the discovery of nanotubes fullerenes, which suggested that curved surfaces may be present in their structure and which incorporates well into the ideas of ACs porous structure. The source of those curved surfaces is atomic defects present inside the in-plane graphitic honeycomb lattice. Such defects have a crucial influence on the macroscopic morphology as well as physical properties of the material. The activated carbon (AC) in this work was derived from carbonised saccharose by activation with NaOH. Both materials – before and after activation were investigated. The main methods used in this study are wide angle Neutron Scattering and wide angle X-ray Scattering combined with computer simulations. Confirmation of the proposed structures was sought with high-resolution transmission electron microscopy and Ram...

  • The atomic scale structure of graphene powder studied by Neutron and X-ray diffraction
    Journal of Applied Crystallography, 2015
    Co-Authors: Natalia Woznica, Henry E. Fischer, Lukasz Hawelek, I. I. Bobrinetskiy, Andrzej Burian
    Abstract:

    The structure of graphene obtained by chemical exfoliation of graphite via the oxidation/reduction procedure has been determined using Wide-Angle Scattering of Neutrons and X-rays combined with computer simulations based on classical molecular dynamics (MD). A comparison of results obtained from Wide-Angle Neutron Scattering (WANS) with the D4 Neutron diffractometer dedicated for liquids and amorphous materials (Institute Laue–Langevin in Grenoble) and from Wide-Angle X-ray Scattering (WAXS) with the laboratory Rigaku-Denki D/MAX RAPID II diffractometer has shown that both techniques provide data of a good quality that can be used to derive precise and valuable structural information about graphene. To obtain detailed structural information, the paracrystal formalism has been used along with MD simulations. The MD simulations were performed at 300 K with second-generation reactive empirical bond order potential for atoms lying in the same layer and the Lennard–Jones potential for interlayer interactions. The proposed models consist of three-layered systems, 36 A in diameter, in which mono-vacancy, di-vacancy and Stone–Thrower–Wales types of defects are introduced. The reported results show that the WANS and WAXS methods together with the MD simulations contribute to a detailed description of the graphene materials, including the presence of topological defects, which is important as their structure at the atomic scale dramatically affects their electrical and mechanical properties.

  • Paracrystalline nature of saccharose- and anthracene-based carbons studied by Wide-Angle Scattering
    2003
    Co-Authors: A. Szczygielska, Andrzej Burian, John C. Dore, S. Duber, Alex C. Hannon
    Abstract:

    A series of porous carbon materials, produced by pyrolysis of saccharose and anthracene and heat treated at 1000°C, 1800°C and 2600°C has been studied by Wide-Angle Neutron Scattering. The Neutron data were collected at Rutheford Appleton Laboratory (RAL). The data were recorded in the Scattering vector range from 0 to 60 Å-1 which enabled them to be converted to a real-space representation via the Fourier transform. The structure of these carbons has been described in terms of a model based on disordered, graphite-like layers with very weak interlayer correlations. At higher temperatures the anthracene-based carbon transforms into graphite while the carbon produced from saccharose remains disordered. The graphitization process has been studied in detail by careful analysis of the diffraction data in real and reciprocal space.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

  • Structural studies of carbon nanotubes by Wide-Angle Neutron Scattering
    International Conference on Solid State Crystals '98: Epilayers and Heterostructures in Optoelectronics and Semiconductor Technology, 1999
    Co-Authors: Andrzej Burian, John C. Dore, Henry E. Fischer, Jeremy Sloan, A. Szczygielska
    Abstract:

    In this paper structural studies on multiwall carbon nanotubes by Wide-Angle Neutron Scattering are reported. Analysis of the Neutron Scattering data in both reciprocal and real space and a comparison with the graphite and turbostatic carbon data shows the perfect hexagonal structure within a single graphene sheet and short-range graphite-like interlayer correlation in multiwalled carbon nanotubes. As the interatomic distances increase a systematic departure from the perfect graphitic structure is observed.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

  • Structural studies of multiwall carbon nanotubes by Neutron diffraction
    Physical Review B, 1999
    Co-Authors: Andrzej Burian, John C. Dore, Henry E. Fischer, Jeremy Sloan
    Abstract:

    We report on structural studies of multiwall carbon nanotubes by Wide-Angle Neutron Scattering up to a maximum Scattering vector Q(max) = 166 nm(-1). The derived reduced radial distribution functions of the nanotubes are compared to those determined for graphite and turbostratic carbon, providing evidence that the stacking pattern of graphene tubules in multiwall carbon nanotubes is intermediate between those of the other two carbon forms. The (002) and (004) peaks of the nanotubes appear at smaller angles than graphite, yielding the intertubule spacing of 0.341 nm. At small length scales (less than or similar to 0.5 nm) the nanotube structure resembles that of graphite, including graphitelike interlayer correlations for at least a few adjacent layers. Beyond this range, a systematic decrease in peak amplitudes and deviation from the graphite structure is observed. [S0163-1829(99)06903-9].